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Sample records for shear thinning behavior

  1. Shear thinning behaviors in magmas

    Science.gov (United States)

    Vetere, F. P.; Cassetta, M.; Perugini, D.

    2017-12-01

    Studies on magma rheology are of fundamental importance to understanding magmatic processes from depth to surface. Since viscosity is one of the most important parameter controlling eruption mechanisms, as well as lava flow emplacement, a comprehensive knowledge on the evolution of magma viscosities during crystallization is required. We present new viscosity data on partly crystalized basalt, andesite and analogue lavas comparable to those erupted on Mercury's northern volcanic plains. High-temperature viscosity measurements were performed using a rotational Anton Paar RheolabQC viscometer head at the PVRG labs, in Perugia (Italy) (http://pvrg.unipg.it). The relative proportion of phases in each experimental run were determined by image analysis on BS-SEM images at different magnifications; phases are glasses, clinopyroxene, spinel, plagioclase for the basalt, plagioclase and spinel for the andesite and pure enstatite and clinopyroxenes, for the analogue Mercury's composition. Glass and crystalline fractions determined by image analysis well correlate with compositions of residual melts. In order to constrain the viscosity (η) variations as a function of crystallinity, shear rate (γ) was varied from 0.1 to 5 s-1. Viscosity vs. time at constant temperature shows a typical S-shape curve. In particular, for basaltic composition η vary from 3.1-3.8 Pa s [log η] at 1493 K and crystallinity of 19 area % as γ vary from 1.0 to 0.1 s-1; the andesite viscosity evolution is 3.2 and 3.7 Pa s [log η] as γ varies from 1 to 0.1 at 1493 K and crystal content of 17 area %; finally, Mercury's analogue composition was investigated at different temperature ranging from 1533 to 1502 K (Vetere et al., 2017). Results, for γ = 0.1, 1.0 and 5.0 s-1, show viscosity variation between 2.7-4.0, 2.5-3.4 and 2.0-3.0 [log η inPa s] respectively while crystallinity vary from 9 to 27 (area %). As viscosity decreases as shear rate increases, these data points to a shear thinning behaviour

  2. Shear thinning behavior of monolayer liquid lubricant films measured by fiber wobbling method

    International Nuclear Information System (INIS)

    Hamamoto, Y; Itoh, S; Fukuzawa, K; Zhang, H

    2010-01-01

    It is essential to clarify mechanical properties of monolayer lubricant films coated on magnetic disks under shearing motion for designing future hard disk drives with ultra-low flying height. Many of previous researchers reported that strong shear rate dependence of viscoelasticity was one of the typical phenomena observed with molecularly thin liquid films. However, it has not been clarified whether or not perfluoropolyether (PFPE) lubricant films, which are used for the head-disk interface (HDI) lubrication, show shear thinning behavior under actual HDI conditions. In this study, we used the fiber wobbling method that can achieve both highly-sensitive shear force measurement and precise gap control and measured shear rate dependence of viscoelastic properties of monolayer PFPE films coated on the magnetic disk. Our experimental results showed that shear thinning does occur at high shear rate ranged from 10 2 to 10 6 s -1 .

  3. Calanoid Copepod Behavior in Thin Layer Shear Flows: Freshwater Versus Marine

    Science.gov (United States)

    Skipper, A. N.; Webster, D. R.; Yen, J.

    2015-11-01

    Marine copepods have been shown to behaviorally respond to vertical gradients of horizontal velocity and aggregate around thin layers. The current study addresses whether a freshwater copepod from an alpine lake demonstrates similar behavior response. Hesperodiaptomus shoshone is often the greatest biomass in alpine lakes and is the dominant zooplankton predator within its environment. The hypothesis is that H. shoshone responds to vertical gradients of horizontal velocity, which are associated with river outflows from alpine lakes, with fine-scale changes in swimming kinematics. The two calanoid copepods studied here, H. shoshone (freshwater) and Calanus finmarchicus(marine), are of similar size (2 - 4 mm), have similar morphologies, and utilize cruising as their primary swimming mode. The two animals differ not only in environment, but also in diet; H. shoshone is a carnivore, whereas C. finmarchicusis an herbivore. A laminar, planar jet (Bickley) was used in the laboratory to simulate a free shear flow. Particle image velocimetry (PIV) quantified the flow field. The marine species changed its swimming behavior significantly (increased swimming speed and turning frequency) and spent more time in the layer (40% vs. 70%) from control to treatment. In contrast, the freshwater species exhibited very few changes in either swimming behavior or residence time. Swimming kinematics and residence time results were also similar between males and females. Unlike the marine copepod, the results suggest the environmental flow structure is unimportant to the freshwater species.

  4. Designing shear-thinning

    Science.gov (United States)

    Nelson, Arif Z.; Ewoldt, Randy H.

    2017-11-01

    Design in fluid mechanics often focuses on optimizing geometry (airfoils, surface textures, microfluid channels), but here we focus on designing fluids themselves. The dramatically shear-thinning ``yield-stress fluid'' is currently the most utilized non-Newtonian fluid phenomenon. These rheologically complex materials, which undergo a reversible transition from solid-like to liquid-like fluid flow, are utilized in pedestrian products such as paint and toothpaste, but also in emerging applications like direct-write 3D printing. We present a paradigm for yield-stress fluid design that considers constitutive model representation, material property databases, available predictive scaling laws, and the many ways to achieve a yield stress fluid, flipping the typical structure-to-rheology analysis to become the inverse: rheology-to-structure with multiple possible materials as solutions. We describe case studies of 3D printing inks and other flow scenarios where designed shear-thinning enables performance remarkably beyond that of Newtonian fluids. This work was supported by Wm. Wrigley Jr. Company and the National Science Foundation under Grant No. CMMI-1463203.

  5. Shear Resistance Variations in Experimentally Sheared Mudstone Granules: A Possible Shear-Thinning and Thixotropic Mechanism

    Science.gov (United States)

    Hu, Wei; Xu, Qiang; Wang, Gonghui; Scaringi, Gianvito; Mcsaveney, Mauri; Hicher, Pierre-Yves

    2017-11-01

    We present results of ring shear frictional resistance for mudstone granules of different size obtained from a landslide shear zone. Little rate dependency of shear resistance was observed in sand-sized granules in any wet or dry test, while saturated gravel-sized granules exhibited significant and abrupt reversible rate-weakening (from μ = 0.6 to 0.05) at about 2 mm/s. Repeating resistance variations occurred also under constant shear displacement rate. Mudstone granules generate mud as they are crushed and softened. Shear-thinning and thixotropic behavior of the mud can explain the observed behavior: with the viscosity decreasing, the mud can flow through the coarser soil pores and migrate out from the shear zone. This brings new granules into contact which produces new mud. Thus, the process can start over. Similarities between experimental shear zones and those of some landslides in mudstone suggest that the observed behavior may play a role in some landslide kinematics.

  6. Rheology of polyaniline-dinonylnaphthalene disulfonic acid (DNNDSA) montmorillonite clay nanocomposites in the sol state: shear thinning versus pseudo-solid behavior.

    Science.gov (United States)

    Garai, Ashesh; Nandi, Arun K

    2008-04-01

    The melt rheology of polyaniline (PANI)-dinonylnaphthalenedisulfonic acid (DNNDSA) gel nanocomposites (GNCs) with organically modified (modified with cetyl trimethylammonium bromide)-montmorillonite (om-MMT) clay has been studied for three different clay concentrations at the temperature range 120-160 degrees C. Field emission scanning electron microscopy (FE-SEM), wide angle X-ray scattering (WAXS), differential scanning calorimetry (DSC) and dc-conductivity data (approximately 10(-3) S/cm) indicate that the PANI-DNNDSA melt is in sol state and it is not de-doped at that condition. The WAXS data indicate that in GNC-1 sol clay tactoids are in exfoliated state but in the other sols they are in intercalated state. The zero shear viscosity (eta0), storage modulus (G') and loss modulus (G") increase than that of pure gel in the GNCs. The pure sol and the sols of gel nanocomposites (GNCs) exhibit Newtonian behavior for low shear rate (clay concentration and the power law index (n) decreases with increase in clay concentration in the GNCs indicating increased shear thinning for the clay addition. Thus the sols of om-clay nanocomposites of PANI-DNNDSA system are easily processible. The storage modulus (G') of GNC sols are higher than that of pure PANI-DNNDSA sol, GNC1 sol shows a maximum of 733% increase in storage modulus and the percent increase decreases with increase in temperature. Exfoliated nature of clay tactoids has been attributed for the above dramatic increase of G'. The PANI-DNNDSA sol nanocomposites behave as a pseudo-solid at higher frequency where G' and loss modulus (G") show a crossover point in the frequency sweep experiment at a fixed temperature. The crossover frequency decreases with increase in clay concentration and it increases with increase in temperature for GNC sols. The pseudo-solid behavior has been explained from jamming or network formation of clay tactoids under shear. A probable explanation of the two apparently contradictory phenomena

  7. Shear thinning and shear thickening of a confined suspension of vesicles

    Science.gov (United States)

    Nait Ouhra, A.; Farutin, A.; Aouane, O.; Ez-Zahraouy, H.; Benyoussef, A.; Misbah, C.

    2018-01-01

    Widely regarded as an interesting model system for studying flow properties of blood, vesicles are closed membranes of phospholipids that mimic the cytoplasmic membranes of red blood cells. In this study we analyze the rheology of a suspension of vesicles in a confined geometry: the suspension, bound by two planar rigid walls on each side, is subject to a shear flow. Flow properties are then analyzed as a function of shear rate γ ˙, the concentration of the suspension ϕ , and the viscosity contrast λ =ηin/ηout , where ηin and ηout are the fluid viscosities of the inner and outer fluids, respectively. We find that the apparent (or effective viscosity) of the suspension exhibits both shear thinning (decreasing viscosity with shear rate) or shear thickening (increasing viscosity with shear rate) in the same concentration range. The shear thinning or thickening behaviors appear as subtle phenomena, dependant on viscosity contrast λ . We provide physical arguments on the origins of these behaviors.

  8. Onset of shear thinning in glassy liquids: Shear-induced small reduction of effective density.

    Science.gov (United States)

    Furukawa, Akira

    2017-01-01

    We propose a simple mechanism for describing the onset of shear thinning in a high-density glassy liquid. In a shear flow, along the compression axis, the overlap between neighboring particles is more enhanced than that at equilibrium, meaning that the "effective" size is reduced along this axis. On the other hand, along the extension axis perpendicular to the compression axis, the average structural configurations are stretched, but it does not indicate the expansion of the "effective" size itself. This asymmetric shear flow effect for particles results in a small reduction of the "effective" density. Because, in glass-forming liquids, the structural relaxation time τ_{α} strongly depends on the density ρ, even a very small reduction of the effective density should lead to a significant decrease of the relaxation time under shear flow. We predict that the crossover shear rate from Newtonian to non-Newtonian flow behaviors is given by γ[over ̇]_{c}=[ρ(∂τ_{α}/∂ρ)]^{-1}, which can be much smaller than 1/τ_{α} near the glass transition point. It is shown that this prediction is consistent with the results of molecular dynamics simulations.

  9. Investigation of Shear-Thinning Behavior on Film Thickness and Friction Coefficient of Polyalphaolefin Base Fluids With Varying Olefin Copolymer Content

    Energy Technology Data Exchange (ETDEWEB)

    Zolper, Thomas J.; He, Yifeng; Delferro, Massimiliano; Shiller, Paul; Doll, Gary; LotfizadehDehkordi, Babak; Ren, Ning; Lockwood, Frances; Marks, Tobin J.; Chung, Yip-Wah; Greco, Aaron; Erdemir, Ali; Wang, Qian

    2016-08-11

    This study investigates the rheological properties, elastohydrodynamic (EHD) film-forming capability, and friction coefficients of low molecular mass poly-alpha-olefin (PAO) base stocks with varying contents of high molecular mass olefin copolymers (OCPs) to assess their shear stability and their potential for energy-efficient lubrication. Several PAO-OCP mixtures were blended in order to examine the relationship between their additive content and tribological performance. Gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy were used to characterize the molecular masses and structures, respectively. Density, viscosity, EHD film thickness, and friction were measured at 303 K, 348 K, and 398 K. Film thickness and friction were studied at entrainment speeds relevant to the boundary, mixed, and full-film lubrication regimes. The PAO-OCP mixtures underwent temporary shear-thinning resulting in decreases in film thickness and hydrodynamic friction. These results demonstrate that the shear characteristics of PAO-OCP mixtures can be tuned with the OCP content and provide insight into the effects of additives on EHD characteristics.

  10. Thermal convection of viscoelastic shear-thinning fluids

    International Nuclear Information System (INIS)

    Albaalbaki, Bashar; Khayat, Roger E; Ahmed, Zahir U

    2016-01-01

    The Rayleigh–Bénard convection for non-Newtonian fluids possessing both viscoelastic and shear-thinning behaviours is examined. The Phan-Thien–Tanner (PTT) constitutive equation is implemented to model the non-Newtonian character of the fluid. It is found that while the shear-thinning and viscoelastic effects could annihilate one another for the steady roll flow, presence of both behaviours restricts the roll stability limit significantly compared to the cases when the fluid is either inelastic shear-thinning or purely viscoelastic with constant viscosity. (paper)

  11. Swimming efficiency in a shear-thinning fluid

    Science.gov (United States)

    Nganguia, Herve; Pietrzyk, Kyle; Pak, On Shun

    2017-12-01

    Micro-organisms expend energy moving through complex media. While propulsion speed is an important property of locomotion, efficiency is another factor that may determine the swimming gait adopted by a micro-organism in order to locomote in an energetically favorable manner. The efficiency of swimming in a Newtonian fluid is well characterized for different biological and artificial swimmers. However, these swimmers often encounter biological fluids displaying shear-thinning viscosities. Little is known about how this nonlinear rheology influences the efficiency of locomotion. Does the shear-thinning rheology render swimming more efficient or less? How does the swimming efficiency depend on the propulsion mechanism of a swimmer and rheological properties of the surrounding shear-thinning fluid? In this work, we address these fundamental questions on the efficiency of locomotion in a shear-thinning fluid by considering the squirmer model as a general locomotion model to represent different types of swimmers. Our analysis reveals how the choice of surface velocity distribution on a squirmer may reduce or enhance the swimming efficiency. We determine optimal shear rates at which the swimming efficiency can be substantially enhanced compared with the Newtonian case. The nontrivial variations of swimming efficiency prompt questions on how micro-organisms may tune their swimming gaits to exploit the shear-thinning rheology. The findings also provide insights into how artificial swimmers should be designed to move through complex media efficiently.

  12. Injectable shear-thinning nanoengineered hydrogels for stem cell delivery

    DEFF Research Database (Denmark)

    Thakur, Ashish; Jaiswal, Manish K.; Peak, Charles W.

    2016-01-01

    -thinning characteristics, and enhanced mechanical stiffness, elastomeric properties, and physiological stability. The shear-thinning characteristics of nanocomposite hydrogels are investigated for human mesenchymal stem cell (hMSC) delivery. The hMSCs showed high cell viability after injection and encapsulated cells......Injectable hydrogels are investigated for cell encapsulation and delivery as they can shield cells from high shear forces. One of the approaches to obtain injectable hydrogels is to reinforce polymeric networks with high aspect ratio nanoparticles such as two-dimensional (2D) nanomaterials. 2D...... showed a circular morphology. The proposed shear-thinning nanoengineered hydrogels can be used for cell delivery for cartilage tissue regeneration and 3D bioprinting....

  13. Performance of a Polymer Flood with Shear-Thinning Fluid in Heterogeneous Layered Systems with Crossflow

    Directory of Open Access Journals (Sweden)

    Kun Sang Lee

    2011-08-01

    Full Text Available Assessment of the potential of a polymer flood for mobility control requires an accurate model on the viscosities of displacement fluids involved in the process. Because most polymers used in EOR exhibit shear-thinning behavior, the effective viscosity of a polymer solution is a highly nonlinear function of shear rate. A reservoir simulator including the model for the shear-rate dependence of viscosity was used to investigate shear-thinning effects of polymer solution on the performance of the layered reservoir in a five-spot pattern operating under polymer flood followed by waterflood. The model can be used as a quantitative tool to evaluate the comparative studies of different polymer flooding scenarios with respect to shear-rate dependence of fluids’ viscosities. Results of cumulative oil recovery and water-oil ratio are presented for parameters of shear-rate dependencies, permeability heterogeneity, and crossflow. The results of this work have proven the importance of taking non-Newtonian behavior of polymer solution into account for the successful evaluation of polymer flood processes. Horizontal and vertical permeabilities of each layer are shown to impact the predicted performance substantially. In reservoirs with a severe permeability contrast between horizontal layers, decrease in oil recovery and sudden increase in WOR are obtained by the low sweep efficiency and early water breakthrough through highly permeable layer, especially for shear-thinning fluids. An increase in the degree of crossflow resulting from sufficient vertical permeability is responsible for the enhanced sweep of the low permeability layers, which results in increased oil recovery. It was observed that a thinning fluid coefficient would increase injectivity significantly from simulations with various injection rates. A thorough understanding of polymer rheology in the reservoir and accurate numerical modeling are of fundamental importance for the exact estimation

  14. Seismic behavior of reinforced concrete shear walls

    International Nuclear Information System (INIS)

    Wang, F.; Gantenbein, F.

    1989-01-01

    Reinforced concrete shear walls have an important contribution to building stiffness. So, it is necessary to know their behavior under seismic loads. The ultimate behavior study of shear walls subjected to dynamic loadings includes: - a description of the nonlinear global model based on cyclic static tests, - nonlinear time history calculations for various forcing functions. The comparison of linear and nonlinear results shows important margins related to the ductility when the bandwidth of the forcing function is narrow and centred on the wall natural frequency

  15. Imaging the Microscopic Structure of Shear Thinning and Thickening Colloidal Suspensions

    KAUST Repository

    Cheng, X.

    2011-09-01

    The viscosity of colloidal suspensions varies with shear rate, an important effect encountered in many natural and industrial processes. Although this non-Newtonian behavior is believed to arise from the arrangement of suspended particles and their mutual interactions, microscopic particle dynamics are difficult to measure. By combining fast confocal microscopy with simultaneous force measurements, we systematically investigate a suspension\\'s structure as it transitions through regimes of different flow signatures. Our measurements of the microscopic single-particle dynamics show that shear thinning results from the decreased relative contribution of entropic forces and that shear thickening arises from particle clustering induced by hydrodynamic lubrication forces. This combination of techniques illustrates an approach that complements current methods for determining the microscopic origins of non-Newtonian flow behavior in complex fluids.

  16. Numerical Investigation of the Performance of Kenics Static Mixers for the Agitation of Shear Thinning Fluids

    OpenAIRE

    A. Mahammedi; H. Ameur; A. Ariss

    2017-01-01

    The laminar flow of non-Newtonian fluids through a Kenics static mixer is investigated by using the CFD (Computational Fluid Dynamics) tool. The working fluids have a shear thinning behavior modeled by the Ostwald De Waele law. We focus on the effect of Reynolds number, fluid properties, twist angle and blade pitch on the flow characteristics and energy cost. The pressure drop information obtained from the simulations was compared to several experimental correlations and data available in the...

  17. Study of shear thickening behavior in colloidal suspensions

    Directory of Open Access Journals (Sweden)

    N Maleki Jirsaraee

    2015-01-01

    Full Text Available We studied the shear thickening behavior of the nano silica suspension (silica nanoparticles 12 nm in size suspended in ethylene glycol under steady shear. The critical shear rate for transition into shear thickening phase was determined at different concentrations and temperatures. The effect of temperature and concentration was studied on the shear thickening behavior. In silica suspension, it was observed that all the samples had a transition into shear thickening phase and also by increasing the temperature, critical shear rate increased and viscosity decreased. Our observations showed that movement in silica suspension was Brownian and temperature could cause a delay in transition into shear thickening phase. Yet, we observed that increasing the concentration would decrease critical shear rate and increase viscosity. Increasing temperature increased Brownian forces and increasing concentration increased hydrodynamic forces, confirming the contrast between these two forces for transition into shear thickening phase for the suspensions containing nano particles

  18. Turbulent characteristics of shear-thinning fluids in recirculating flows

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, A.S. [Inst. Superior de Engenharia do Porto (Portugal). Dept. de Engenharia Quimica; Pinho, F.T. [Centro de Estudos de Fenomenos de Transporte, Departamento de Engenharia Mecanica e Gestao Industrial, Faculdade de Engenharia da Universidade do Porto, Rua dos Bragas, 4050-123 Porto (Portugal)

    2000-03-01

    A miniaturised fibre optic laser-Doppler anemometer was used to carry out a detailed hydrodynamic investigation of the flow downstream of a sudden expansion with 0.1-0.2% by weight shear-thinning aqueous solutions of xanthan gum. Upstream of the sudden expansion the pipe flow was fully-developed and the xanthan gum solutions exhibited drag reduction with corresponding lower radial and tangential normal Reynolds stresses, but higher axial Reynolds stress near the wall and a flatter axial mean velocity profile in comparison with Newtonian flow. The recirculation bubble length was reduced by more than 20% relative to the high Reynolds number Newtonian flow, and this was attributed to the occurrence further upstream of high turbulence for the non-Newtonian solutions, because of advection of turbulence and earlier high turbulence production in the shear layer. Comparisons with the measurements of Escudier and Smith (1999) with similar fluids emphasized the dominating role of inlet turbulence. The present was less anisotropic, and had lower maximum axial Reynolds stresses (by 16%) but higher radial turbulence (20%) than theirs. They reported considerably longer recirculating bubble lengths than we do for similar non-Newtonian fluids and Reynolds numbers. (orig.)

  19. Shear behavior of reinforced Engineered Cementitious Composites (ECC) beams

    DEFF Research Database (Denmark)

    Paegle, Ieva; Fischer, Gregor

    2010-01-01

    This paper describes an experimental investigation of the shear behavior of beams consisting of steel reinforced Engineered Cementitious Composites (ECC). Based on the strain hardening and multiple cracking behavior of ECC, this study investigates the extent to which ECC can improve the shear...... capacity of beams loaded primarily in shear and if ECC can partially or fully replace the conventional transverse steel reinforcement in beams. However, there is a lack of understanding of how the fibers affect the shear carrying capacity and deformation behavior of structural members if used either...

  20. Extrusion Bioprinting of Shear-Thinning Gelatin Methacryloyl Bioinks.

    Science.gov (United States)

    Liu, Wanjun; Heinrich, Marcel A; Zhou, Yixiao; Akpek, Ali; Hu, Ning; Liu, Xiao; Guan, Xiaofei; Zhong, Zhe; Jin, Xiangyu; Khademhosseini, Ali; Zhang, Yu Shrike

    2017-06-01

    Bioprinting is an emerging technique for the fabrication of 3D cell-laden constructs. However, the progress for generating a 3D complex physiological microenvironment has been hampered by a lack of advanced cell-responsive bioinks that enable bioprinting with high structural fidelity, particularly in the case of extrusion-based bioprinting. Herein, this paper reports a novel strategy to directly bioprint cell-laden gelatin methacryloyl (GelMA) constructs using bioinks of GelMA physical gels (GPGs) achieved through a simple cooling process. Attributed to their shear-thinning and self-healing properties, the GPG bioinks can retain the shape and form integral structures after deposition, allowing for subsequent UV crosslinking for permanent stabilization. This paper shows the structural fidelity by bioprinting various 3D structures that are typically challenging to fabricate using conventional bioinks under extrusion modes. Moreover, the use of the GPG bioinks enables direct bioprinting of highly porous and soft constructs at relatively low concentrations (down to 3%) of GelMA. It is also demonstrated that the bioprinted constructs not only permit cell survival but also enhance cell proliferation as well as spreading at lower concentrations of the GPG bioinks. It is believed that such a strategy of bioprinting will provide many opportunities in convenient fabrication of 3D cell-laden constructs for applications in tissue engineering, regenerative medicine, and pharmaceutical screening. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Initial postbuckling analysis of elastoplastic thin-shear structures

    Science.gov (United States)

    Carnoy, E. G.; Panosyan, G.

    1984-01-01

    The design of thin shell structures with respect to elastoplastic buckling requires an extended analysis of the influence of initial imperfections. For conservative design, the most critical defect should be assumed with the maximum allowable magnitude. This defect is closely related to the initial postbuckling behavior. An algorithm is given for the quasi-static analysis of the postbuckling behavior of structures that exhibit multiple buckling points. the algorithm based upon an energy criterion allows the computation of the critical perturbation which will be employed for the definition of the critical defect. For computational efficiency, the algorithm uses the reduced basis technique with automatic update of the modal basis. The method is applied to the axisymmetric buckling of cylindrical shells under axial compression, and conclusions are given for future research.

  2. Direct Shear Behavior of Fiber Reinforced Concrete Elements

    Directory of Open Access Journals (Sweden)

    Hussein Al-Quraishi

    2018-01-01

    Full Text Available Improving the accuracy of load-deformation behavior, failure mode, and ultimate load capacity for reinforced concrete members subjected to in-plane loadings such as corbels, wall to foundation connections and panels need shear strength behavior to be included. Shear design in reinforced concrete structures depends on crack width, crack slippage and roughness of the surface of cracks. This paper illustrates results of an experimental investigation conducted to investigate the direct shear strength of fiber normal strength concrete (NSC and reactive powder concrete (RPC. The tests were performed along a pre-selected shear plane in concrete members named push-off specimens. The effectiveness of concrete compressive strength, volume fraction of steel fiber, and shear reinforcement ratio on shear transfer capacity were considered in this study. Furthermore, failure modes, shear stress-slip behavior, and shear stress-crack width behavior were also presented in this study. Tests’ results showed that volume fraction of steel fiber and compressive strength of concrete in NSC and RPC play a major role in improving the shear strength of concrete. As expectedly, due to dowel action, the shear reinforcement is the predominant factor in resisting the shear stress. The shear failure of NSC and RPC has the sudden mode of failure (brittle failure with the approximately linear behavior of shear stress-slip relationship till failure. Using RPC instead of NSC with the same amount of steel fibers in constructing the push-off specimen result in high shear strength. In NSC, shear strength influenced by the three major factors; crack surface friction, aggregate interlock and steel fiber content if present. Whereas, RPC has only steel fiber and cracks surface friction influencing the shear strength. Due to cementitious nature of RPC in comparisons with NSC, the RPC specimen shows greater cracks width. It is observed that the Mattock model gives very satisfactory

  3. Behavior of Tilted Angle Shear Connectors

    Science.gov (United States)

    Khorramian, Koosha; Maleki, Shervin; Shariati, Mahdi; Ramli Sulong, N. H.

    2015-01-01

    According to recent researches, angle shear connectors are appropriate to transfer longitudinal shear forces across the steel-concrete interface. Angle steel profile has been used in different positions as L-shaped or C-shaped shear connectors. The application of angle shear connectors in tilted positions is of interest in this study. This study investigates the behaviour of tilted-shaped angle shear connectors under monotonic loading using experimental push out tests. Eight push-out specimens are tested to investigate the effects of different angle parameters on the ultimate load capacity of connectors. Two different tilted angles of 112.5 and 135 degrees between the angle leg and steel beam are considered. In addition, angle sizes and lengths are varied. Two different failure modes were observed consisting of concrete crushing-splitting and connector fracture. By increasing the size of connector, the maximum load increased for most cases. In general, the 135 degrees tilted angle shear connectors have a higher strength and stiffness than the 112.5 degrees type. PMID:26642193

  4. Behavior of Tilted Angle Shear Connectors.

    Directory of Open Access Journals (Sweden)

    Koosha Khorramian

    Full Text Available According to recent researches, angle shear connectors are appropriate to transfer longitudinal shear forces across the steel-concrete interface. Angle steel profile has been used in different positions as L-shaped or C-shaped shear connectors. The application of angle shear connectors in tilted positions is of interest in this study. This study investigates the behaviour of tilted-shaped angle shear connectors under monotonic loading using experimental push out tests. Eight push-out specimens are tested to investigate the effects of different angle parameters on the ultimate load capacity of connectors. Two different tilted angles of 112.5 and 135 degrees between the angle leg and steel beam are considered. In addition, angle sizes and lengths are varied. Two different failure modes were observed consisting of concrete crushing-splitting and connector fracture. By increasing the size of connector, the maximum load increased for most cases. In general, the 135 degrees tilted angle shear connectors have a higher strength and stiffness than the 112.5 degrees type.

  5. Evaluation of composite shear walls behavior (parametric study

    Directory of Open Access Journals (Sweden)

    Ali Nikkhoo

    2017-11-01

    Full Text Available Composite shear walls which are made of a layer of steel plate with a concrete cover in one or both sides of the steel plate, are counted as the third generation of the shear walls. Nowadays, composite shear walls are widely utilized in building new resisting structures as well as rehabilitating of the existing structures in earthquake-prone countries. Despite of its advantages, use of the composite shear walls is not yet prevalent as it demands more detailed appropriate investigation. Serving higher strength, flexibility and better energy absorption, while being more economical are the main advantages of this system which has paved its path to be used in high-rise buildings, structural retrofit and reservoir tanks. In this research, channel shear connectors are utilized to connect the concrete cover to the steel plate. As a key parameter, variation in the distance of shear connectors and their arrangement on the behavior of composite shear walls has been scrutinized. In addition, the shear stiffness, flexibility, out of plane displacement and the energy absorption of the structural system has been explored. For this purpose, several structural models with different shear distances and arrangements have been investigated. The obtained results reveal that with increase in shear connectors’ distance, the wall stiffness would reduce while its lateral displacement increases up to eighty percent While the out of plane displacement of the steel plate will reduce up to three times.

  6. Origins of the anomalous stress behavior in charged colloidal suspensions under shear.

    Science.gov (United States)

    Kumar, Amit; Higdon, Jonathan J L

    2010-11-01

    Numerical simulations are conducted to determine microstructure and rheology of sheared suspensions of charged colloidal particles at a volume fraction of ϕ=0.33. Over broad ranges of repulsive force strength F0 and Péclet number Pe, dynamic simulations show coexistence of ordered and disordered stable states with the state dependent on the initial condition. In contrast to the common view, at low shear rates, the disordered phase exhibits a lower viscosity (μ(r)) than the ordered phase, while this behavior is reversed at higher shear rates. Analysis shows the stress reversal is associated with different shear induced microstructural distortions in the ordered and disordered systems. Viscosity vs shear rate data over a wide range of F0 and Pe collapses well upon rescaling with the long-time self-diffusivity. Shear thinning viscosity in the ordered phase scaled as μ(r)∼Pe(-0.81) at low shear rates. The microstructural dynamics revealed in these studies explains the anomalous behavior and hysteresis loops in stress data reported in the literature.

  7. Experimental study on concrete shear wall behavior under seismic loading

    International Nuclear Information System (INIS)

    Gantenbein, F.; Queval, J.C.; Epstein, A.; Dalbera, J.

    1991-01-01

    An experimental program has been undertaken on the dynamic behavior of shear walls with and without openings. The experimental set-up, the test program and the main results will be detailed in the paper

  8. Shear behavior of concrete beams externally prestressed with Parafil ropes

    Directory of Open Access Journals (Sweden)

    A.H. Ghallab

    2013-03-01

    Full Text Available Although extensive work has been carried out investigating the use of external prestressing system for flexural strengthening, a few studies regarding the shear behavior of externally prestressed beams can be found. Five beams, four of them were externally strengthened using Parafil rope, were loaded up to failure to investigate the effect of shear span/depth ratio, external prestressing force and concrete strength on their shear behavior. Test results showed that the shear span to depth ratio has a significant effect on both the shear strength and failure mode of the strengthened beams and the presence of external prestressing force increased the ultimate load of the tested beams by about 75%. Equations proposed by different codes for both the conventional reinforced concrete beams and for ordinary prestressed beams were used to evaluate the obtained experimental results. In general, codes equations showed a high level of conservatism in predicting the shear strength of the beams. Also, using the full strength rather than half of the concrete shear strength in the Egyptian code PC-method improves the accuracy of the calculated ultimate shear strength.

  9. Determining shear modulus of thin wood composite materials using a cantilever beam vibration method

    Science.gov (United States)

    Cheng Guan; Houjiang Zhang; John F. Hunt; Haicheng Yan

    2016-01-01

    Shear modulus (G) of thin wood composite materials is one of several important indicators that characterizes mechanical properties. However, there is not an easy method to obtain this value. This study presents the use of a newly developed cantilever beam free vibration test apparatus to detect in-plane G of thin wood composite...

  10. Shear-wave dynamic behavior using two different orientations

    International Nuclear Information System (INIS)

    Ghassem Alaskari, M. K.; Hashemi, S. J.

    2007-01-01

    For laterally complex media, it may be more suitable to take a different orientation of the displacement vector of Shear-waves. This may change the sign of several imaginary reflections and conversion coefficients to be used in reservoir characterization and Amplitude Versus Offset analysis or modeling. In this new convention the positive direction of the displacement vector of reflected Shear-waves is chosen to the left of ray tangent (in the direction of wave propagation). Therefore, the definition of the displacement vector of shear-waves can be used properly even for very complicated media. Finally the shear-wave dynamic behavior of a reservoir zone can be illustrated for laterally varying structures in terms of the amplitude variation and phase behavior using this new orientation

  11. Time-dependent behavior of rough discontinuities under shearing conditions

    Science.gov (United States)

    Wang, Zhen; Shen, Mingrong; Ding, Wenqi; Jang, Boan; Zhang, Qingzhao

    2018-02-01

    The mechanical properties of rocks are generally controlled by their discontinuities. In this study, the time-dependent behavior of rough artificial joints under shearing conditions was investigated. Based on Barton’s standard profile lines, samples with artificial joint surfaces were prepared and used to conduct the shear and creep tests. The test results showed that the shear strength of discontinuity was linearly related to roughness, and subsequently an empirical equation was established. The long-term strength of discontinuity can be identified using the inflection point of the isocreep-rate curve, and it was linearly related to roughness. Furthermore, the ratio of long-term and instantaneous strength decreased with the increase of roughness. The shear-stiffness coefficient increased with the increase of shear rate, and the influence of shear rate on the shear stiffness coefficient decreased with the decrease of roughness. Further study of the mechanism revealed that these results could be attributed to the different time-dependent behavior of intact and joint rocks.

  12. Effect of rock joint roughness on its cyclic shear behavior

    Directory of Open Access Journals (Sweden)

    S.M. Mahdi Niktabar

    2017-12-01

    Full Text Available Rock joints are often subjected to dynamic loads induced by earthquake and blasting during mining and rock cutting. Hence, cyclic shear load can be induced along the joints and it is important to evaluate the shear behavior of rock joint under this condition. In the present study, synthetic rock joints were prepared with plaster of Paris (PoP. Regular joints were simulated by keeping regular asperity with asperity angles of 15°–15° and 30°–30°, and irregular rock joints which are closer to natural joints were replicated by keeping the asperity angles of 15°–30° and 15°–45°. The sample size and amplitude of roughness were kept the same for both regular and irregular joints which were 298 mm × 298 mm × 125 mm and 5 mm, respectively. Shear test was performed on these joints using a large-scale direct shear testing machine by keeping the frequency and amplitude of shear load under constant cyclic condition with different normal stress values. As expected, the shear strength of rock joints increased with the increases in the asperity angle and normal load during the first cycle of shearing or static load. With the increase of the number of shear cycles, the shear strength decreased for all the asperity angles but the rate of reduction was more in case of high asperity angles. Test results indicated that shear strength of irregular joints was higher than that of regular joints at different cycles of shearing at low normal stress. Shearing and degradation of joint asperities on regular joints were the same between loading and unloading, but different for irregular joints. Shear strength and joint degradation were more significant on the slope of asperity with higher angles on the irregular joint until two angles of asperities became equal during the cycle of shearing and it started behaving like regular joints for subsequent cycles.

  13. Interfacial Shear Strength and Adhesive Behavior of Silk Ionomer Surfaces.

    Science.gov (United States)

    Kim, Sunghan; Geryak, Ren D; Zhang, Shuaidi; Ma, Ruilong; Calabrese, Rossella; Kaplan, David L; Tsukruk, Vladimir V

    2017-09-11

    The interfacial shear strength between different layers in multilayered structures of layer-by-layer (LbL) microcapsules is a crucial mechanical property to ensure their robustness. In this work, we investigated the interfacial shear strength of modified silk fibroin ionomers utilized in LbL shells, an ionic-cationic pair with complementary ionic pairing, (SF)-poly-l-glutamic acid (Glu) and SF-poly-l-lysine (Lys), and a complementary pair with partially screened Coulombic interactions due to the presence of poly(ethylene glycol) (PEG) segments and SF-Glu/SF-Lys[PEG] pair. Shearing and adhesive behavior between these silk ionomer surfaces in the swollen state were probed at different spatial scales and pressure ranges by using functionalized atomic force microscopy (AFM) tips as well as functionalized colloidal probes. The results show that both approaches were consistent in analyzing the interfacial shear strength of LbL silk ionomers at different spatial scales from a nanoscale to a fraction of a micron. Surprisingly, the interfacial shear strength between SF-Glu and SF-Lys[PEG] pair with partially screened ionic pairing was greater than the interfacial shear strength of the SF-Glu and SF-Lys pair with a high density of complementary ionic groups. The difference in interfacial shear strength and adhesive strength is suggested to be predominantly facilitated by the interlayer hydrogen bonding of complementary amino acids and overlap of highly swollen PEG segments.

  14. Seismic behavior of semi-supported steel shear walls

    DEFF Research Database (Denmark)

    Jahanpour, A.; Jönsson, J.; Moharrami, H.

    2012-01-01

    During the recent past decade semi-supported steel shear walls (SSSW) have been introduced as an alternative to the traditional type of steel plate shear walls. In this system the shear wall does not connect directly to the main columns of the building frame; instead it is connected to a pair...... of secondary columns that do not carry vertical gravity loads. In this paper, the interaction between the wall plate and the surrounding frame is investigated experimentally for typical SSSW systems in which the wall-frame has a bending-dominant behavior. Based on the possible storey failure mechanisms...... a simple method is proposed for design of the floor beams. A quasi static cyclic experimental study has been performed in order to investigate the collapse behavior of the wall-plate and surrounding frame. Furthermore the test setup has been developed in order to facilitate standardized cyclic tests...

  15. Importance of Tensile Strength on the Shear Behavior of Discontinuities

    Science.gov (United States)

    Ghazvinian, A. H.; Azinfar, M. J.; Geranmayeh Vaneghi, R.

    2012-05-01

    In this study, the shear behavior of discontinuities possessing two different rock wall types with distinct separate compressive strengths was investigated. The designed profiles consisted of regular artificial joints molded by five types of plaster mortars, each representing a distinct uniaxial compressive strength. The compressive strengths of plaster specimens ranged from 5.9 to 19.5 MPa. These specimens were molded considering a regular triangular asperity profile and were designed so as to achieve joint walls with different strength material combinations. The results showed that the shear behavior of discontinuities possessing different joint wall compressive strengths (DDJCS) tested under constant normal load (CNL) conditions is the same as those possessing identical joint wall strengths, but the shear strength of DDJCS is governed by minor joint wall compressive strength. In addition, it was measured that the predicted values obtained by Barton's empirical criterion are greater than the experimental results. The finding indicates that there is a correlation between the joint roughness coefficient (JRC), normal stress, and mechanical strength. It was observed that the mode of failure of asperities is either pure tensile, pure shear, or a combination of both. Therefore, Barton's strength criterion, which considers the compressive strength of joint walls, was modified by substituting the compressive strength with the tensile strength. The validity of the modified criterion was examined by the comparison of the predicted shear values with the laboratory shear test results reported by Grasselli (Ph.D. thesis n.2404, Civil Engineering Department, EPFL, Lausanne, Switzerland, 2001). These comparisons infer that the modified criterion can predict the shear strength of joints more precisely.

  16. Shear strength behavior of geotextile/geomembrane interfaces

    Directory of Open Access Journals (Sweden)

    Belén M. Bacas

    2015-12-01

    Full Text Available This paper aims to study the shear interaction mechanism of one of the critical geosynthetic interfaces, the geotextile/geomembrane, typically used for lined containment facilities such as landfills. A large direct shear machine is used to carry out 90 geosynthetic interface tests. The test results show a strain softening behavior with a very small dilatancy (<0.5 mm and nonlinear failure envelopes at a normal stress range of 25–450 kPa. The influences of the micro-level structure of these geosynthetics on the macro-level interface shear behavior are discussed in detail. This study has generated several practical recommendations to help professionals to choose what materials are more adequate. From the three geotextiles tested, the thermally bonded monofilament exhibits the best interface shear strength under high normal stress. For low normal stress, however, needle-punched monofilaments are recommended. For the regular textured geomembranes tested, the space between the asperities is an important factor. The closer these asperities are, the better the result achieves. For the irregular textured geomembranes tested, the nonwoven geotextiles made of monofilaments produce the largest interface shear strength.

  17. EMHD micro-pumping of a non-conducting shear-thinning fluid under EDL phenomena

    International Nuclear Information System (INIS)

    Gaikwad, Harshad; Borole, Chetan; Basu, Dipankar N.; Mondal, Pranab K.

    2016-01-01

    The Electro-Magneto-Hydrodynamic (EMHD) pumping of a binary fluid system constituted by one non-conducting shear-thinning fluid (top layer) by exploiting the transverse momentum exchange through the interfacial viscous shearing effect from a conducting Newtonian fluid layer (bottom layer) in a microfluidic channel is investigated. An externally applied electric field drives the conducting fluid layer under the influence of an applied magnetic field as well. The study reveals that the volume transport of shear-thinning fluid gets augmented for low magnetic field strength, higher electrical double layer (EDL) effect, low viscosity ratio and moderate potential ratio. It is also established that the volumetric flow rate reduces significantly for the higher magnetic field strength. (author)

  18. Instabilities of convection patterns in a shear-thinning fluid between plates of finite conductivity

    Science.gov (United States)

    Varé, Thomas; Nouar, Chérif; Métivier, Christel

    2017-10-01

    Rayleigh-Bénard convection in a horizontal layer of a non-Newtonian fluid between slabs of arbitrary thickness and finite thermal conductivity is considered. The first part of the paper deals with the primary bifurcation and the relative stability of convective patterns at threshold. Weakly nonlinear analysis combined with Stuart-Landau equation is used. The competition between squares and rolls, as a function of the shear-thinning degree of the fluid, the slabs' thickness, and the ratio of the thermal conductivity of the slabs to that of the fluid is investigated. Computations of heat transfer coefficients are in agreement with the maximum heat transfer principle. The second part of the paper concerns the stability of the convective patterns toward spatial perturbations and the determination of the band width of the stable wave number in the neighborhood of the critical Rayleigh number. The approach used is based on the Ginzburg-Landau equations. The study of rolls stability shows that: (i) for low shear-thinning effects, the band of stable wave numbers is bounded by zigzag instability and cross-roll instability. Furthermore, the marginal cross-roll stability boundary enlarges with increasing shear-thinning properties; (ii) for high shear-thinning effects, Eckhaus instability becomes more dangerous than cross-roll instability. For square patterns, the wave number selection is always restricted by zigzag instability and by "rectangular Eckhaus" instability. In addition, the width of the stable wave number decreases with increasing shear-thinning effects. Numerical simulations of the planform evolution are also presented to illustrate the different instabilities considered in the paper.

  19. Bias of shear wave elasticity measurements in thin layer samples and a simple correction strategy.

    Science.gov (United States)

    Mo, Jianqiang; Xu, Hao; Qiang, Bo; Giambini, Hugo; Kinnick, Randall; An, Kai-Nan; Chen, Shigao; Luo, Zongping

    2016-01-01

    Shear wave elastography (SWE) is an emerging technique for measuring biological tissue stiffness. However, the application of SWE in thin layer tissues is limited by bias due to the influence of geometry on measured shear wave speed. In this study, we investigated the bias of Young's modulus measured by SWE in thin layer gelatin-agar phantoms, and compared the result with finite element method and Lamb wave model simulation. The result indicated that the Young's modulus measured by SWE decreased continuously when the sample thickness decreased, and this effect was more significant for smaller thickness. We proposed a new empirical formula which can conveniently correct the bias without the need of using complicated mathematical modeling. In summary, we confirmed the nonlinear relation between thickness and Young's modulus measured by SWE in thin layer samples, and offered a simple and practical correction strategy which is convenient for clinicians to use.

  20. Shear thickening behavior of nanoparticle suspensions with carbon nanofillers

    Energy Technology Data Exchange (ETDEWEB)

    Sha, Xiaofei; Yu, Kejing, E-mail: yukejing@gmail.com; Cao, Haijian; Qian, Kun [Ministry of Education, Jiangnan University, Key Laboratory of Eco-textiles (China)

    2013-07-15

    Suspensions comprised of silica nanoparticle (average diameter: 650 nm) and carbon nanofillers dispersed in polyethylene glycol were prepared and investigated. Rheological measurement demonstrated that the mixed suspensions showed a non-Newtonian flow profile, and the shear thickening effect was enhanced by the addition of carbon nanotubes (CNTs) (main range of diameter: 10-20 nm; length: 5-15 {mu}m; purity: >97 wt%) and graphene nanoplatelets (GNs) (average diameter: >50 nm; average length: 20 {mu}m; purity: >92 wt%). It suggested that better the aggregation effect of dispersed particles was, the more significant the shear thickening effect achieved. The results also revealed that the formation of large nanomaterials clusters could be suitable to explain the phenomena. Furthermore, the trend of shear thickening behavior of the silica suspension with CNTs was more striking than that of GNs. The physical reactions between those multi-dispersed phases had been described by the schematic illustrations in papers. Otherwise, a model was built to explain these behaviors, which could be attributed to the unique structures and inherent properties of these two different nanofillers. And the morphologies of the shear thickening fluid which were examined by transmission electron microscopy confirmed this mechanism.

  1. Droplet breakup driven by shear thinning solutions in a microfluidic T-junction

    Science.gov (United States)

    Chiarello, Enrico; Gupta, Anupam; Mistura, Giampaolo; Sbragaglia, Mauro; Pierno, Matteo

    2017-12-01

    Droplet-based microfluidics turned out to be an efficient and adjustable platform for digital analysis, encapsulation of cells, drug formulation, and polymerase chain reaction. Typically, for most biomedical applications, the handling of complex, non-Newtonian fluids is involved, e.g., synovial and salivary fluids, collagen, and gel scaffolds. In this study, we investigate the problem of droplet formation occurring in a microfluidic T-shaped junction, when the continuous phase is made of shear thinning liquids. At first, we review in detail the breakup process, providing extensive, side-by-side comparisons between Newtonian and non-Newtonian liquids over unexplored ranges of flow conditions and viscous responses. The non-Newtonian liquid carrying the droplets is made of Xanthan solutions, a stiff, rodlike polysaccharide displaying a marked shear thinning rheology. By defining an effective Capillary number, a simple yet effective methodology is used to account for the shear-dependent viscous response occurring at the breakup. The droplet size can be predicted over a wide range of flow conditions simply by knowing the rheology of the bulk continuous phase. Experimental results are complemented with numerical simulations of purely shear thinning fluids using lattice Boltzmann models. The good agreement between the experimental and numerical data confirm the validity of the proposed rescaling with the effective Capillary number.

  2. Aspiration of human neutrophils: effects of shear thinning and cortical dissipation.

    Science.gov (United States)

    Drury, J L; Dembo, M

    2001-12-01

    It is generally accepted that the human neutrophil can be mechanically represented as a droplet of polymeric fluid enclosed by some sort of thin slippery viscoelastic cortex. Many questions remain however about the detailed rheology and chemistry of the interior fluid and the cortex. To address these quantitative issues, we have used a finite element method to simulate the dynamics of neutrophils during micropipet aspiration using various plausible assumptions. The results were then systematically compared with aspiration experiments conducted at eight different combinations of pipet size and pressure. Models in which the cytoplasm was represented by a simple Newtonian fluid (i.e., models without shear thinning) were grossly incapable of accounting for the effects of pressure on the general time scale of neutrophil aspiration. Likewise, models in which the cortex was purely elastic (i.e., models without surface viscosity) were unable to explain the effects of pipet size on the general aspiration rate. Such models also failed to explain the rapid acceleration of the aspiration rate during the final phase of aspiration nor could they account for the geometry of the neutrophil during various phases of aspiration. Thus, our results indicate that a minimal mechanical model of the neutrophil needs to incorporate both shear thinning and surface viscosity to remain valid over a reasonable range of conditions. At low shear rates, the surface dilatation viscosity of the neutrophil was found to be on the order of 100 poise-cm, whereas the viscosity of the interior cytoplasm was on the order of 1000 poise. Both the surface viscosity and the interior viscosity seem to decrease in a similar fashion when the shear rate exceeds approximately 0.05 s(-1). Unfortunately, even models with both surface viscosity and shear thinning studied are still not sufficient to fully explain all the features of neutrophil aspiration. In particular, the very high rate of aspiration during the

  3. Modeling of Mesoscale Variability in Biofilm Shear Behavior.

    Directory of Open Access Journals (Sweden)

    Pallab Barai

    Full Text Available Formation of bacterial colonies as biofilm on the surface/interface of various objects has the potential to impact not only human health and disease but also energy and environmental considerations. Biofilms can be regarded as soft materials, and comprehension of their shear response to external forces is a key element to the fundamental understanding. A mesoscale model has been presented in this article based on digitization of a biofilm microstructure. Its response under externally applied shear load is analyzed. Strain stiffening type behavior is readily observed under high strain loads due to the unfolding of chains within soft polymeric substrate. Sustained shear loading of the biofilm network results in strain localization along the diagonal direction. Rupture of the soft polymeric matrix can potentially reduce the intercellular interaction between the bacterial cells. Evolution of stiffness within the biofilm network under shear reveals two regimes: a initial increase in stiffness due to strain stiffening of polymer matrix, and b eventual reduction in stiffness because of tear in polymeric substrate.

  4. Collective Behavior of Amoebae in Thin Films

    Science.gov (United States)

    Bae, Albert

    2005-03-01

    We have discovered new aspects of social behavior in Dictyostelium discoideum by culturing high density colonies in liquid media depleted of nutrients in confined geometries by using three different preparations: I. thin (15-40um thick) and II. ultrathin (behavior of cells despite flattening that increased their areas by over an order of magnitude. We also observed that the earliest synchronized response of cells following the onset of starvation, a precursor to aggregation, was hastened by reducing the thickness of the aqueous culture layer. We were surprised to find that the threshold concentration for aggregation was raised by thin film confinement when compared to bulk behavior. Finally, both the ultra thin and microfluidic preparations reveal, with new clarity, vortex states of aggregation.

  5. Dynamic behavior and functional integrity tests on RC shear walls

    International Nuclear Information System (INIS)

    Akino, Kinji; Nasuda, Toshiaki; Shibata, Akenori.

    1991-01-01

    A project consisting of seven subprojects has been conducted to study the dynamic behavior and functional integrity of reinforced concrete (RC) shear walls in reactor buildings. The objective of this project is to obtain the data to improve and prepare the seismic analysis code regarding the nonlinear structural behavior and integrity of reactor buildings during and after earthquakes. The project started in April, 1986, and will end in March, 1994. Seven subprojects are strain rate test, damping characteristic test, ultimate state response test and the verification test for the test of restoring force characteristics regarding dynamic restoring force characteristics and damping performance; the restoring force characteristic test on the shear walls with openings; and pull-out strength test and the test on air leakage through concrete cracks regarding the functional integrity. The objectives of respective subprojects, the test models and the interim results are reported. Three subprojects have been completed by March, 1990. The results of these projects will be used for the overall evaluation. The strain rate test showed that the ultimate strength of shear walls increased with strain rate. A formula for estimating air flow through the cracks in walls was given by the leakage test. (K.I.)

  6. Glass transition memorized by the enthalpy-entropy compensation in the shear thinning of supercooled metallic liquids

    Science.gov (United States)

    Zhang, Meng; Liu, Lin

    2018-06-01

    To unravel the true nature of glass transition, broader insights into glass forming have been gained by examining the stress-driven glassy systems, where strong shear thinning, i.e. a reduced viscosity under increasing shear rate, is encountered. It is argued that arbitrarily small stress-driven shear rates would ‘melt’ the glass and erase any memory of its thermal history. In this work, we report a glass transition memorized by the enthalpy-entropy compensation in strongly shear-thinned supercooled metallic liquids, which coincides with the thermal glass transition in both the transition temperature and the activation Gibbs free energy. Our findings provide distinctive insights into both glass forming and shear thinning, and enrich current knowledge on the ubiquitous enthalpy-entropy compensation empirical law in condensed matter physics.

  7. Detecting Psychopathy from Thin Slices of Behavior

    Science.gov (United States)

    Fowler, Katherine A.; Lilienfeld, Scott O.; Patrick, Christopher J.

    2009-01-01

    This study is the first to demonstrate that features of psychopathy can be reliably and validly detected by lay raters from "thin slices" (i.e., small samples) of behavior. Brief excerpts (5 s, 10 s, and 20 s) from interviews with 96 maximum-security inmates were presented in video or audio form or in both modalities combined. Forty raters used…

  8. Study of cement pastes rheological behavior using dynamic shear rheometer

    Directory of Open Access Journals (Sweden)

    J. E. S. L. Teixeira

    Full Text Available Concrete, in its fresh state, has flow characteristics that are crucial to its proper launch and densification. These characteristics are usually measured through empirical testing as the slump test, but this test does not quantify completely the material behavior. Since this material is characterized as a Bingham fluid, it is essential the study of its rheological behavior to verify its properties even in fresh state. The use of classical rheology has been employed by the scientific community to obtain rheological parameters determinants to characterize this material, such as yield stress, plastic viscosity and evolution of shear stress to shear rate. Thus, this present study aims to determine the rheological behavior of different cement pastes produced with cement CP III 40 RS, varying between them the hydration periods (20 and 60 min, the water-cement ratio (0.40, 0.45 and 0.50 and the use or not of additive. Samples were assayed by flow test to determine the rheological parameters showing the effect of the variables mentioned above in these parameters.

  9. Nonlinear shear behavior of rock joints using a linearized implementation of the Barton–Bandis model

    Directory of Open Access Journals (Sweden)

    Simon Heru Prassetyo

    2017-08-01

    Full Text Available Experiments on rock joint behaviors have shown that joint surface roughness is mobilized under shearing, inducing dilation and resulting in nonlinear joint shear strength and shear stress vs. shear displacement behaviors. The Barton–Bandis (BB joint model provides the most realistic prediction for the nonlinear shear behavior of rock joints. The BB model accounts for asperity roughness and strength through the joint roughness coefficient (JRC and joint wall compressive strength (JCS parameters. Nevertheless, many computer codes for rock engineering analysis still use the constant shear strength parameters from the linear Mohr–Coulomb (M−C model, which is only appropriate for smooth and non-dilatant joints. This limitation prevents fractured rock models from capturing the nonlinearity of joint shear behavior. To bridge the BB and the M−C models, this paper aims to provide a linearized implementation of the BB model using a tangential technique to obtain the equivalent M−C parameters that can satisfy the nonlinear shear behavior of rock joints. These equivalent parameters, namely the equivalent peak cohesion, friction angle, and dilation angle, are then converted into their mobilized forms to account for the mobilization and degradation of JRC under shearing. The conversion is done by expressing JRC in the equivalent peak parameters as functions of joint shear displacement using proposed hyperbolic and logarithmic functions at the pre- and post-peak regions of shear displacement, respectively. Likewise, the pre- and post-peak joint shear stiffnesses are derived so that a complete shear stress-shear displacement relationship can be established. Verifications of the linearized implementation of the BB model show that the shear stress-shear displacement curves, the dilation behavior, and the shear strength envelopes of rock joints are consistent with available experimental and numerical results.

  10. Study on reinforced lightweight coconut shell concrete beam behavior under shear

    International Nuclear Information System (INIS)

    Gunasekaran, K.; Annadurai, R.; Kumar, P.S.

    2013-01-01

    Highlights: • Coconut shell used as aggregate in concrete production. • Coconut shell concrete beam behavior studied under shear. • Coconut shell concrete beam behavior are compared with control concrete beams. - Abstract: Lightweight concrete has been produced using crushed coconut shell as coarse aggregate. The shear behavior of reinforced concrete beam made with coconut shell is analyzed and compared with the normal control concrete. Eight beams, four with coconut shell concrete and four with normal control concrete were fabricated and tested. Study includes the structural shear behavior, shear capacity, cracking behavior, deflection behavior, ductility, strains in concrete and in reinforcement. It was observed that the shear behavior of coconut shell concrete is comparable to that of other lightweight concretes. The results of concrete compression strain and steel tension strain showed that coconut shell concrete is able to achieve its full strain capacity under shear loadings. However, the failure zones of coconut shell concrete were larger than for control concrete beams

  11. Effect of shear span-to-depth ratio on the shear behavior of BFRP-RC deep beams

    Directory of Open Access Journals (Sweden)

    Alhamad Siyam

    2017-01-01

    Full Text Available This study investigates the shear behavior of deep concrete beams reinforced with basalt fiber reinforced polymer (BFRP bars for flexure without web reinforcements. The experimental testing performed herein consisted of a total of 4 short beams, three of which were reinforced with BFRP and one beam was reinforced with steel bars. The primary test variable was the shear-span-to-effective-depth ratio (a/d and its influence on the beams’ mid-span deflections, shear capacity, load-deformation relationships and the failure modes.

  12. Structural performance of new thin-walled concrete sandwich panel system reinforced with bfrp shear connectors

    DEFF Research Database (Denmark)

    Hodicky, Kamil; Hulin, Thomas; Schmidt, Jacob Wittrup

    2013-01-01

    This paper presents a new thin-walled concrete sandwich panel system reinforced with basalt fiber-reinforced plastic (BFRP) with optimum structural performances and a high thermal resistance developed by Connovate and Technical University of Denmark. The shear connecting system made of a BFRP grid...... is described and provides information on the structural design with its advantages. Experimental and numerical investigations of the BFRP connecting systems were performed. The experimental program included testing of small scale specimens by applying shear (push-off) loading and semi-full scale specimens...... on finite element modelling showed that the developed panel system meets the objectives of the research and is expected to have promising future....

  13. Behavior of Reinforced Concrete Membrane Elements Subjected to Bidirectional Shear Loads

    OpenAIRE

    Labib, M.; Moslehy, Y.; Ayoub, A.

    2013-01-01

    The shear design and behavior of a typical membrane reinforced concrete (RC) element has been extensively studied in the past several decades. Such design requires knowledge of the constitutive behavior of RC elements subjected to a shear stress acting along its plane (in-plane shear). These constitutive models were accurately derived from experimental test data on representative RC panel elements. The true behavior of many large, complex structures, however, involves interaction between the ...

  14. Loading direction-dependent shear behavior at different temperatures of single-layer chiral graphene sheets

    Science.gov (United States)

    Zhao, Yang; Dong, Shuhong; Yu, Peishi; Zhao, Junhua

    2018-06-01

    The loading direction-dependent shear behavior of single-layer chiral graphene sheets at different temperatures is studied by molecular dynamics (MD) simulations. Our results show that the shear properties (such as shear stress-strain curves, buckling strains, and failure strains) of chiral graphene sheets strongly depend on the loading direction due to the structural asymmetry. The maximum values of both the critical buckling shear strain and the failure strain under positive shear deformation can be around 1.4 times higher than those under negative shear deformation. For a given chiral graphene sheet, both its failure strain and failure stress decrease with increasing temperature. In particular, the amplitude to wavelength ratio of wrinkles for different chiral graphene sheets under shear deformation using present MD simulations agrees well with that from the existing theory. These findings provide physical insights into the origins of the loading direction-dependent shear behavior of chiral graphene sheets and their potential applications in nanodevices.

  15. Shear-Rate-Dependent Behavior of Clayey Bimaterial Interfaces at Landslide Stress Levels

    Science.gov (United States)

    Scaringi, Gianvito; Hu, Wei; Xu, Qiang; Huang, Runqiu

    2018-01-01

    The behavior of reactivated and first-failure landslides after large displacements is controlled by the available shear resistance in a shear zone and/or along slip surfaces, such as a soil-bedrock interface. Among the factors influencing the resistance parameter, the dependence on the shear rate can trigger catastrophic evolution (rate-weakening) or exert a slow-down feedback (rate-strengthening) upon stress perturbation. We present ring-shear test results, performed under various normal stresses and shear rates, on clayey soils from a landslide shear zone, on its parent lithology and other lithologies, and on clay-rock interface samples. We find that depending on the materials in contact, the normal stress, and the stress history, the shear-rate-dependent behaviors differ. We discuss possible models and underlying mechanisms for the time-dependent behavior of landslides in clay soils.

  16. Research Status on Bonding Behavior of Prefabricated Concrete Shear Wall

    Science.gov (United States)

    Wang, Donghui; Liu, Xudong; Wang, Sheng; Li, Shanshan

    2018-03-01

    Prefabricated shear wall structure adapts to the development and requirements of China’s residential industrialization. The key to the prefabricated concrete shear wall structure is the connection between the prefabricated members, where the reliability of the connection of the concrete joint is related to the overall performance and seismic effect of the structure. In this paper, the microstructures of the joint surface and shear properties are analysed, and the formula for calculating the shear strength of the joint is obtained.

  17. Non-Newtonian behavior and molecular structure of Cooee bitumen under shear flow

    DEFF Research Database (Denmark)

    Lemarchand, Claire; Bailey, Nicholas; Daivis, Peter

    2015-01-01

    The rheology and molecular structure of a model bitumen (Cooee bitumen) under shear are investigated in the non-Newtonian regime using non-equilibrium molecular dynamics simulations. The shear viscosity, normal stress differences, and pressure of the bitumen mixture are computed at different shear...... rates and different temperatures. The model bitumen is shown to be a shear-thinning fluid at all temperatures. In addition, the Cooee model is able to reproduce experimental results showing the formation of nanoaggregates composed of stacks of flat aromatic molecules in bitumen. These nanoaggregates...

  18. Thin liquid films with time-dependent chemical reactions sheared by an ambient gas flow

    Science.gov (United States)

    Bender, Achim; Stephan, Peter; Gambaryan-Roisman, Tatiana

    2017-08-01

    Chemical reactions in thin liquid films are found in many industrial applications, e.g., in combustion chambers of internal combustion engines where a fuel film can develop on pistons or cylinder walls. The reactions within the film and the turbulent outer gas flow influence film stability and lead to film breakup, which in turn can lead to deposit formation. In this work we examine the evolution and stability of a thin liquid film in the presence of a first-order chemical reaction and under the influence of a turbulent gas flow. Long-wave theory with a double perturbation analysis is used to reduce the complexity of the problem and obtain an evolution equation for the film thickness. The chemical reaction is assumed to be slow compared to film evolution and the amount of reactant in the film is limited, which means that the reaction rate decreases with time as the reactant is consumed. A linear stability analysis is performed to identify the influence of reaction parameters, material properties, and environmental conditions on the film stability limits. Results indicate that exothermic reactions have a stabilizing effect whereas endothermic reactions destabilize the film and can lead to rupture. It is shown that an initially unstable film can become stable with time as the reaction rate decreases. The shearing of the film by the external gas flow leads to the appearance of traveling waves. The shear stress magnitude has a nonmonotonic influence on film stability.

  19. Effect of shear-thinning behaviour on liquid-liquid plug flow in microchannels

    Science.gov (United States)

    Roumpea, Evangelia; Chinaud, Maxime; Weheliye, Weheliye Hashi; Angeli, Panagiota; Kahouadji, Lyes; Matar, Omar K.

    2016-11-01

    The present work investigates the dynamics of plug formation of shear-thinning solutions in a 200 μm microchannel using a two-colour micro-PIV system. Measurements, including phase-averaged velocity fields, have been conducted both at the T-junction inlet and the main channel to enhance understanding of non-Newtonian liquid-liquid flows. Two aqueous glycerol solutions containing xanthan gum are used as the non-Newtonian fluids while 5 cSt silicone oil is the Newtonian phase. The current experimental results revealed a pronounced impact of the xanthan gum (shear-thinning behaviour) on the flow pattern transition boundaries, and enhance the fluid flowrates where plug flow occurred. The addition of polymer resulted also in different hydrodynamic characteristics such as a bullet-shaped plug and an increased film thickness between the plug and the wall. In the present work, the technique allows to capture the velocity field of both phases simultaneously. Experimental results are compared with the numerical simulations provided by the code BLUE. Project funded under the UK Engineering and Physical Sciences Research Council (EPSRC) Programme Grant MEMPHIS.

  20. Critical behavior of ferromagnetic Ising thin films

    International Nuclear Information System (INIS)

    Cossio, P.; Mazo-Zuluaga, J.; Restrepo, J.

    2006-01-01

    In the present work, we study the magnetic properties and critical behavior of simple cubic ferromagnetic thin films. We simulate LxLxd films with semifree boundary conditions on the basis of the Monte Carlo method and the Ising model with nearest neighbor interactions. A Metropolis dynamics was implemented to carry out the energy minimization process. For different film thickness, in the nanometer range, we compute the temperature dependence of the magnetization, the magnetic susceptibility and the fourth order Binder's cumulant. Bulk and surface contributions of these quantities are computed in a differentiated fashion. Additionally, according to finite size scaling theory, we estimate the critical exponents for the correlation length, magnetic susceptibility, and magnetization. Results reveal a strong dependence of critical temperature and critical exponents on the film thickness. The obtained critical exponents are finally compared to those reported in literature for thin films

  1. Phenomenological interpretation of the shear behavior of reinforced Engineered Cementitious Composite beams

    DEFF Research Database (Denmark)

    Paegle, Ieva; Fischer, Gregor

    2016-01-01

    This paper describes an experimental investigation of the shear behavior of beams consisting of steel Reinforced Engineered Cementitious Composites (R/ECC). This study investigates and quantifies the effect of ECC's strain hardening and multiple cracking behavior on the shear capacity of beams...

  2. Influence of shear cutting parameters on the fatigue behavior of a dual-phase steel

    Science.gov (United States)

    Paetzold, I.; Dittmann, F.; Feistle, M.; Golle, R.; Haefele, P.; Hoffmann, H.; Volk, W.

    2017-09-01

    The influence of the edge condition of car body and chassis components made of steel sheet on fatigue behavior under dynamic loading presents a major challenge for automotive manufacturers and suppliers. The calculated lifetime is based on material data determined by the fatigue testing of specimens with polished edges. Prototype components are often manufactured by milling or laser cutting, whereby in practice, the series components are produced by shear cutting due to its cost-efficiency. Since the fatigue crack in such components usually starts from a shear cut edge, the calculated and experimental determined lifetime will vary due to the different conditions at the shear cut edges. Therefore, the material data determined with polished edges can result in a non-conservative component design. The aim of this study is to understand the relationship between the shear cutting process and the fatigue behavior of a dual-phase steel sheet. The geometry of the shear cut edge as well as the depth and degree of work hardening in the shear affected zone can be adjusted by using specific shear cutting parameters, such as die clearance and cutting edge radius. Stress-controlled fatigue tests of unnotched specimens were carried out to compare the fatigue behavior of different edge conditions. By evaluating the results of the fatigue experiments, influential shear cutting parameters on fatigue behavior were identified. It was possible to assess investigated shear cutting strategies regarding the fatigue behavior of a high-strength steel DP800.

  3. Interfacial shear behavior of composite flanged concrete beams

    Directory of Open Access Journals (Sweden)

    Moataz Awry Mahmoud

    2014-08-01

    Full Text Available Composite concrete decks are commonly used in the construction of highway bridges due to their rapid constructability. The interfacial shear transfer between the top slab and the supporting beams is of great significance to the overall deck load carrying capacity and performance. Interfacial shear capacity is directly influenced by the distribution and the percentage of shear connectors. Research and design guidelines suggest the use of two different approaches to quantify the required interfacial shear strength, namely based on the maximum compressive forces in the flange at mid span or the maximum shear flow at the supports. This paper investigates the performance of flanged reinforced concrete composite beams with different shear connector’s distribution and reinforcing ratios. The study incorporated both experimental and analytical programs for beams. Key experimental findings suggest that concentrating the connectors at the vicinity of the supports enhances the ductility of the beam. The paper proposes a simple and straight forward approach to estimate the interfacial shear capacity that was proven to give good correlation with the experimental results and selected code provisions. The paper presents a method to predict the horizontal shear force between precast beams and cast in-situ slabs.

  4. Structural behavior of human lumbar intervertebral disc under direct shear.

    Science.gov (United States)

    Schmidt, Hendrik; Häussler, Kim; Wilke, Hans-Joachim; Wolfram, Uwe

    2015-03-18

    The intervertebral disc (IVD) is a complex, flexible joint between adjacent vertebral bodies that provides load transmission while permitting movements of the spinal column. Finite element models can be used to help clarify why and how IVDs fail or degenerate. To do so, it is of importance to validate those models against controllable experiments. Due to missing experimental data, shear properties are not used thus far in validating finite element models. This study aimed to investigate the structural shear properties of human lumbar IVDs in posteroanterior (PA) and laterolateral (LL) loading directions. Fourteen lumbar IVDs (median age: 49 years) underwent direct shear in PA and LL loading directions. A custom-build shear device was used in combination with a materials testing machine to load the specimens until failure. Shear stiffness, ultimate shear force and displacement, and work to failure were determined. Each specimen was tested until complete or partial disruption. Median stiffness in PA direction was 490 N/mm and in LL direction 568 N/mm. Median ultimate shear force in the PA direction was 2,877 N and in the LL direction 3,199 N. Work to failure was 12 Nm in the PA and 9 Nm in the LL direction. This study was an experiment to subject IVDs to direct shear. The results could help us to understand the structure and function of IVDs with regard to mechanical spinal stability, and they can be used to validate finite element models of the IVD.

  5. Flow behavior at different shear rates for dry powders

    NARCIS (Netherlands)

    Singh, A.; Singh, A.; Luding, Stefan; Nürnberg Messe GmbH,

    2010-01-01

    Using Discrete Element Simulations (DEM), an effort is made to study the so called “Split bottom ring shear cell” where a slow, quasi-static deformation leads to wide shear bands. Density, velocity and deformation gradients as well as structure and stress tensors, can be computed by a single

  6. Panel and planar experimental shear behavior of wood panels ...

    African Journals Online (AJOL)

    Panel shear strength along the thickness and planar shear along the length of wood panels laminated softwood oriented OSB 10 mm thick, conditioned at different moisture contents (anhydrous medium, ambient temperature and humid medium) was measured on standardized test specimens, cut in half lengthwise panel ...

  7. Reverse flow and vortex breakdown in a shear-thinning fluid

    International Nuclear Information System (INIS)

    Cabeza, C; Sarasua, G; Barrere, N; Marti, A C

    2011-01-01

    The effect of polymer concentration on the development of reverse secondary flow and vortex breakdown was studied using a viscoelastic solution of polyacrlylamide in water. The fluid was contained in cylindrical containers of two different radii, the top end wall of which rotated at a varying speed, thus, imparting a circulating motion to the fluid. Whereas using a newtonian fluid, streamlines will occupy the entire container, the flow of a shear-thinning fluid may divide into two cells of opposite circulating motion. The curve of critical Reynolds and elasticity numbers (Re, E) values corresponding to the development of reverse flow was obtained over a wide range of Re values. Vortex breakdown was found to occur at extremely low Re values.

  8. Modelling secondary instability of co-current a thin gas-sheared film

    Energy Technology Data Exchange (ETDEWEB)

    Vozhakov, I S; Cherdantsev, A V; Arkhipov, D G, E-mail: vozhakov@gmail.com [Kutateladze Institute of Thermophysics, Novosibirsk (Russian Federation)

    2016-12-15

    Recent experimental works found the existence of two types of waves on the surface of gas-sheared thin films. Slower short-living ‘secondary waves’ appear due to the instability of the rear slopes of faster long-living ‘primary waves’. In this paper, modelling of spatiotemporal evolution of liquid film in such kind of flows is performed using relatively simple theoretical models. The modelling results are directly compared with the experimental data. It is found that the phenomenon of secondary waves generation at the rear slopes of the primary waves is reproduced by the model. This allows us to reduce the number of hypotheses which explain the mechanism responsible for such instability. Recommendations for future theoretical investigations are proposed. (paper)

  9. Modelling secondary instability of co-current a thin gas-sheared film

    International Nuclear Information System (INIS)

    Vozhakov, I S; Cherdantsev, A V; Arkhipov, D G

    2016-01-01

    Recent experimental works found the existence of two types of waves on the surface of gas-sheared thin films. Slower short-living ‘secondary waves’ appear due to the instability of the rear slopes of faster long-living ‘primary waves’. In this paper, modelling of spatiotemporal evolution of liquid film in such kind of flows is performed using relatively simple theoretical models. The modelling results are directly compared with the experimental data. It is found that the phenomenon of secondary waves generation at the rear slopes of the primary waves is reproduced by the model. This allows us to reduce the number of hypotheses which explain the mechanism responsible for such instability. Recommendations for future theoretical investigations are proposed. (paper)

  10. Buoyant miscible displacement flow of shear-thinning fluids: Experiments and Simulations

    Science.gov (United States)

    Ale Etrati Khosroshahi, Seyed Ali; Frigaard, Ian

    2017-11-01

    We study displacement flow of two miscible fluids with density and viscosity contrast in an inclined pipe. Our focus is mainly on displacements where transverse mixing is not significant and thus a two-layer, stratified flow develops. Our experiments are carried out in a long pipe, covering a wide range of flow-rates, inclination angles and viscosity ratios. Density and viscosity contrasts are achieved by adding Glycerol and Xanthan gum to water, respectively. At each angle, flow rate and viscosity ratio are varied and density contrast is fixed. We identify and map different flow regimes, instabilities and front dynamics based on Fr , Re / Frcosβ and viscosity ratio m. The problem is also studied numerically to get a better insight into the flow structure and shear-thinning effects. Numerical simulations are completed using OpenFOAM in both pipe and channel geometries and are compared against the experiments. Schlumberger, NSERC.

  11. Empirical resistive-force theory for slender biological filaments in shear-thinning fluids

    Science.gov (United States)

    Riley, Emily E.; Lauga, Eric

    2017-06-01

    Many cells exploit the bending or rotation of flagellar filaments in order to self-propel in viscous fluids. While appropriate theoretical modeling is available to capture flagella locomotion in simple, Newtonian fluids, formidable computations are required to address theoretically their locomotion in complex, nonlinear fluids, e.g., mucus. Based on experimental measurements for the motion of rigid rods in non-Newtonian fluids and on the classical Carreau fluid model, we propose empirical extensions of the classical Newtonian resistive-force theory to model the waving of slender filaments in non-Newtonian fluids. By assuming the flow near the flagellum to be locally Newtonian, we propose a self-consistent way to estimate the typical shear rate in the fluid, which we then use to construct correction factors to the Newtonian local drag coefficients. The resulting non-Newtonian resistive-force theory, while empirical, is consistent with the Newtonian limit, and with the experiments. We then use our models to address waving locomotion in non-Newtonian fluids and show that the resulting swimming speeds are systematically lowered, a result which we are able to capture asymptotically and to interpret physically. An application of the models to recent experimental results on the locomotion of Caenorhabditis elegans in polymeric solutions shows reasonable agreement and thus captures the main physics of swimming in shear-thinning fluids.

  12. Evaluation of Thin Kevlar-Epoxy Fabric Panels Subjected to Shear Loading

    Science.gov (United States)

    Baker, Donald J.

    1996-01-01

    The results of an analytical and experimental investigation of 4-ply Kevlar-49-epoxy panels loaded by in-plane shear are presented. Approximately one-half of the panels are thin-core sandwich panels and the other panels are solid-laminate panels. Selected panels were impacted with an aluminum sphere at a velocity of either 150 or 220 ft/sec. The strength of panels impacted at 150 ft/sec was not reduced when compared to the strength of the undamaged panels, but the strength of panels impacted at 220 ft/sec was reduced by 27 to 40 percent. Results are presented for panels that were cyclically loaded from a load less than the buckling load to a load in the postbuckling load range. The thin-core sandwich panels had a lower fatigue life than the solid panels. The residual strength of the solid and sandwich panels cycled more than one million cycles exceeded the baseline undamaged panel strengths. The effect of hysteresis in the response of the sandwich panels is not significant. Results of a nonlinear finite element analysis conducted for each panel design are presented.

  13. Effect of coating thickness on interfacial shear behavior of zirconia-coated sapphire fibers in a polycrystalline alumina matrix

    International Nuclear Information System (INIS)

    Hellmann, J.R.; Chou, Y.S.

    1995-01-01

    The effect of zirconia (ZrO 2 ) interfacial coatings on the interfacial shear behavior in sapphire reinforced alumina was examined in this study. Zirconia coatings of thicknesses ranging from 0.15 to 1.45 μm were applied to single crystal sapphire (Saphikon) fibers using a particulate loaded sol dipping technique. After calcining at 1,100 C in air, the coated fibers were incorporated into a polycrystalline alumina matrix via hot pressing. Interfacial shear strength and sliding behavior of the coated fibers was examined using thin-slice indentation fiber pushout and pushback techniques. In all cases, debonding and sliding occurred at the interface between the fibers and the coating. The coatings exhibited a dense microstructure and led to a higher interfacial shear strength (> 240 MPa) and interfacial sliding stress (> 75 MPa) relative to previous studies on the effect of a porous interphase on interfacial properties. The interfacial shear strength decreased with increasing fiber coating thickness (from 389 ± 59 to 241 ± 43 MPa for 0.15 to 1.45 microm thick coatings, respectively). Sliding behavior exhibited load modulation with increasing displacement during fiber sliding which is characteristic of fiber roughness-induced stick-slip. The high interfacial shear strengths and sliding stresses measured in this study, as well as the potentially strength degrading surface reconstruction observed on the coated fibers after hot pressing and heat treatment, indicate that dense zirconia coatings are not suitable candidates for optimizing composite toughness and strength in the sapphire fiber reinforced alumina system

  14. Cyclic behavior of low rise concrete shear walls containing recycled coarse and fine aggregates

    NARCIS (Netherlands)

    Qiao, Qiyun; Cao, Wanlin; Qian, Zhiwei; Li, Xiangyu; Zhang, Wenwen; Liu, Wenchao

    2017-01-01

    In this study, the cyclic behaviors of low rise concrete shear walls using recycled coarse or fine aggregates were investigated. Eight low rise Recycled Aggregates Concrete (RAC) shear wall specimens were designed and tested under a cyclic loading. The following parameters were varied:

  15. Experimental and numerical models of three-dimensional gravity-driven flow of shear-thinning polymer solutions used in vaginal delivery of microbicides.

    Science.gov (United States)

    Kheyfets, Vitaly O; Kieweg, Sarah L

    2013-06-01

    HIV/AIDS is a growing global pandemic. A microbicide is a formulation of a pharmaceutical agent suspended in a delivery vehicle, and can be used by women to protect themselves against HIV infection during intercourse. We have developed a three-dimensional (3D) computational model of a shear-thinning power-law fluid spreading under the influence of gravity to represent the distribution of a microbicide gel over the vaginal epithelium. This model, accompanied by a new experimental methodology, is a step in developing a tool for optimizing a delivery vehicle's structure/function relationship for clinical application. We compare our model with experiments in order to identify critical considerations for simulating 3D free-surface flows of shear-thinning fluids. Here we found that neglecting lateral spreading, when modeling gravity-induced flow, resulted in up to 47% overestimation of the experimental axial spreading after 90 s. In contrast, the inclusion of lateral spreading in 3D computational models resulted in rms errors in axial spreading under 7%. In addition, the choice of the initial condition for shape in the numerical simulation influences the model's ability to describe early time spreading behavior. Finally, we present a parametric study and sensitivity analysis of the power-law parameters' influence on axial spreading, and to examine the impact of changing rheological properties as a result of dilution or formulation conditions. Both the shear-thinning index (n) and consistency (m) impacted the spreading length and deceleration of the moving front. The sensitivity analysis showed that gels with midrange m and n values (for the ranges in this study) would be most sensitive (over 8% changes in spreading length) to 10% changes (e.g., from dilution) in both rheological properties. This work is applicable to many industrial and geophysical thin-film flow applications of non-Newtonian fluids; in addition to biological applications in microbicide drug delivery.

  16. FRP-RC Beam in Shear: Mechanical Model and Assessment Procedure for Pseudo-Ductile Behavior

    Directory of Open Access Journals (Sweden)

    Floriana Petrone

    2014-07-01

    Full Text Available This work deals with the development of a mechanics-based shear model for reinforced concrete (RC elements strengthened in shear with fiber-reinforced polymer (FRP and a design/assessment procedure capable of predicting the failure sequence of resisting elements: the yielding of existing transverse steel ties and the debonding of FRP sheets/strips, while checking the corresponding compressive stress in concrete. The research aims at the definition of an accurate capacity equation, consistent with the requirement of the pseudo-ductile shear behavior of structural elements, that is, transverse steel ties yield before FRP debonding and concrete crushing. For the purpose of validating the proposed model, an extended parametric study and a comparison against experimental results have been conducted: it is proven that the common accepted rule of assuming the shear capacity of RC members strengthened in shear with FRP as the sum of the maximum contribution of both FRP and stirrups can lead to an unsafe overestimation of the shear capacity. This issue has been pointed out by some authors, when comparing experimental shear capacity values with the theoretical ones, but without giving a convincing explanation of that. In this sense, the proposed model represents also a valid instrument to better understand the mechanical behavior of FRP-RC beams in shear and to calculate their actual shear capacity.

  17. Strength and behavior in shear of reinforced concrete deep beams under dynamic loading conditions

    Energy Technology Data Exchange (ETDEWEB)

    Adhikary, Satadru Das [School of Civil and Environmental Engineering, Nanyang Technological University, 639798 (Singapore); Li, Bing, E-mail: cbli@ntu.edu.sg [School of Civil and Environmental Engineering, Nanyang Technological University, 639798 (Singapore); Fujikake, Kazunori [Department of Civil and Environmental Engineering, National Defense Academy, Yokosuka 239 8686 (Japan)

    2013-06-15

    Highlights: ► Effects of wider range of loading rates on dynamic shear behavior of RC deep beams. ► Experimental investigation of RC deep beam with and without shear reinforcements. ► Verification of experimental results with truss model and FE simulation results. ► Empirical equations are proposed to predict the dynamic increase factor of maximum resistance. -- Abstract: Research on reinforced concrete (RC) deep beams has seen considerable headway over the past three decades; however, information on the dynamic shear strength and behavior of RC deep beams under varying rates of loads remains limited. This paper describes the experimental results of 24 RC deep beams with and without shear reinforcements under varying rates of concentrated loading. Results obtained serve as useful data on shear resistance, failure patterns and strain rates corresponding to varying loading rates. An analytical truss model approach proves its efficacy in predicting the dynamic shear resistance under varying loading rates. Furthermore, three-dimensional nonlinear finite element (FE) model is described and the simulation results are verified with the experimental results. A parametric study is then conducted to investigate the influence of longitudinal reinforcement ratio, transverse reinforcement ratio and shear span to effective depth ratio on shear behavior. Subsequently, two empirical equations were proposed by integrating the various parameters to assess the dynamic increase factor (DIF) of maximum resistance under varying rates of concentrated loading.

  18. ON SHEAR BEHAVIOR OF STRUCTURAL ELEMENTS MADE OF STEEL FIBER REINFORCED CONCRETE

    OpenAIRE

    Cuenca Asensio, Estefanía

    2013-01-01

    Cuenca Asensio, E. (2012). ON SHEAR BEHAVIOR OF STRUCTURAL ELEMENTS MADE OF STEEL FIBER REINFORCED CONCRETE [Tesis doctoral no publicada]. Universitat Politècnica de València. doi:10.4995/Thesis/10251/18326. Palancia

  19. Characteristics of Asperity Damage and Its Influence on the Shear Behavior of Granite Joints

    Science.gov (United States)

    Meng, Fanzhen; Zhou, Hui; Wang, Zaiquan; Zhang, Chuanqing; Li, Shaojun; Zhang, Liming; Kong, Liang

    2018-02-01

    Surface roughness significantly affects the shear behavior of rock joints; thus, studies on the asperity damage characteristics and its influence on the shear behavior of joints are extremely important. In this paper, shear tests were conducted on tensile granite joints; asperity damage was evaluated based on acoustic emission (AE) events; and the influence of asperity damage on joint shear behavior was analyzed. The results indicated that the total AE events tended to increase with normal stress. In addition, the asperity damage initiation shear stress, which is defined as the transition point from slow growth to rapid growth in the cumulative events curve, was approximately 0.485 of the peak shear strength regardless of the normal stress. Moreover, 63-85% of the AE events were generated after the peak shear stress, indicating that most of the damage occurred in this stage. Both the dilation and the total AE events decreased with shear cycles because of the damage inflicted on asperities during the previous shear cycle. Two stages were observed in the normal displacement curves under low normal stress, whereas three stages (compression, dilation and compression again) were observed at a higher normal stress; the second compression stage may be caused by tensile failure outside the shear plane. The magnitude of the normal stress and the state of asperity are two important factors controlling the post-peak stress drop and stick-slip of granite joints. Serious deterioration of asperities will stop stick-slip from recurring under the same normal stress because the ability to accumulate energy is decreased. The AE b-value increases with the number of shear cycles, indicating that the stress concentration inside the fault plane is reduced because of asperity damage; thus, the potential for dynamic disasters, such as fault-slip rockbursts, will be decreased.

  20. Pore scale simulations for the extension of the Darcy-Forchheimer law to shear thinning fluids

    Science.gov (United States)

    Tosco, Tiziana; Marchisio, Daniele; Lince, Federica; Boccardo, Gianluca; Sethi, Rajandrea

    2014-05-01

    Flow of non-Newtonian fluids through porous media at high Reynolds numbers is often encountered in chemical, pharmaceutical and food as well as petroleum and groundwater engineering and in many other industrial applications (1 - 2). In particular, the use of shear thinning polymeric solutions has been recently proposed to improve colloidal stability of micro- and nanoscale zerovalent iron particles (MZVI and NZVI) for groundwater remediation. In all abovementioned applications, it is of paramount importance to correctly predict the pressure drop resulting from non-Newtonian fluid flow through the porous medium. For small Reynolds numbers, usually up to 1, typical of laboratory column tests, the extended Darcy law is known to be applicable also to non Newtonian fluids, provided that all non-Newtonian effects are lumped together into a proper viscosity parameter (1,3). For higher Reynolds numbers (eg. close to the injection wells) non linearities between pressure drop and flow rate arise, and the Darcy-Forchheimer law holds for Newtonian fluids, while for non-Newtonian fluids, it has been demonstrated that, at least for simple rheological models (eg. power law fluids) a generalized Forchheimer law can be applied, even if the determination of the flow parameters (permeability K, inertial coefficient β, and equivalent viscosity) is not straightforward. This work (co-funded by European Union project AQUAREHAB FP7 - Grant Agreement Nr. 226565) aims at proposing an extended formulation of the Darcy-Forchheimer law also for shear-thinning fluids, and validating it against results of pore-scale simulations via computational fluid dynamics (4). Flow simulations were performed using Fluent 12.0 on four different 2D porous domains for Newtonian and non-Newtonian fluids (Cross, Ellis and Carreau models). The micro-scale flow simulation results are analyzed in terms of 'macroscale' pressure drop between inlet and outlet of the model domain as a function of flow rate. The

  1. A study on shear behavior of R/C beams subjected to long-term heating

    International Nuclear Information System (INIS)

    Maruta, M.; Yamazaki, M.

    1993-01-01

    In nuclear power plants, many structural members are subjected to long term heating. There are few experimental data available on the behavior especially in shear of reinforced concrete (R/C) members subjected to long term heating. This paper describes a study aimed at experimentally determining the shear behavior of R/C members in nuclear power plant facilities following sustained heating at high temperatures

  2. Constitutive Behavior of Reinforced Concrete Membrane Elements under Tri-directional Shear

    Science.gov (United States)

    Labib, Moheb

    The two-dimensional behavior of typical reinforced concrete (RC) structures has been extensively studied in the past several decades by investigating the constitutive behavior of full-scale reinforced concrete elements subjected to a bi-axial state of stress. In order to understand the true behavior of many large complex structures, the goal of this investigation is to develop new constitutive relationships for RC elements subjected to tri-directional shear stresses. Recently, additional out-of-plane jacks were installed on the panel tester at University of Houston so that concrete elements could be subjected to tri-directional shear stresses. This upgrade makes the panel tester the only one of its kind in the US that is capable of applying such combinations of stresses on full-scale reinforced concrete elements. This dissertation presents the details of the mounting and installation of the additional hydraulic jacks on the universal panel tester. The experimental program includes a series of seven reinforced concrete elements subjected to different combinations of in-plane and out-of-plane shear stresses. Increasing the applied out-of-plane shear stresses reduced the membrane shear strength of the elements. The effect of applying out-of-plane shear stresses on the in-plane shear strength was represented by modifying the softening coefficient in the compression stress strain curve of concrete struts. The modified model was able to capture the behavior and the ultimate capacity of the tested elements. The effect of the in-plane shear reinforcement ratio on the interaction between in-plane and out-of-plane shear stresses was evaluated. The model was implemented in the Finite Element package FEAP and was used to predict the ultimate capacity of many structures subjected to a combination of in-plane and out-of-plane shear stresses. The results of the analytical model were used to develop simplified design equations for members subjected to bi-directional shear loads

  3. Shear Behavior Models of Steel Fiber Reinforced Concrete Beams Modifying Softened Truss Model Approaches.

    Science.gov (United States)

    Hwang, Jin-Ha; Lee, Deuck Hang; Ju, Hyunjin; Kim, Kang Su; Seo, Soo-Yeon; Kang, Joo-Won

    2013-10-23

    Recognizing that steel fibers can supplement the brittle tensile characteristics of concrete, many studies have been conducted on the shear performance of steel fiber reinforced concrete (SFRC) members. However, previous studies were mostly focused on the shear strength and proposed empirical shear strength equations based on their experimental results. Thus, this study attempts to estimate the strains and stresses in steel fibers by considering the detailed characteristics of steel fibers in SFRC members, from which more accurate estimation on the shear behavior and strength of SFRC members is possible, and the failure mode of steel fibers can be also identified. Four shear behavior models for SFRC members have been proposed, which have been modified from the softened truss models for reinforced concrete members, and they can estimate the contribution of steel fibers to the total shear strength of the SFRC member. The performances of all the models proposed in this study were also evaluated by a large number of test results. The contribution of steel fibers to the shear strength varied from 5% to 50% according to their amount, and the most optimized volume fraction of steel fibers was estimated as 1%-1.5%, in terms of shear performance.

  4. Shear Behavior Models of Steel Fiber Reinforced Concrete Beams Modifying Softened Truss Model Approaches

    Directory of Open Access Journals (Sweden)

    Joo-Won Kang

    2013-10-01

    Full Text Available Recognizing that steel fibers can supplement the brittle tensile characteristics of concrete, many studies have been conducted on the shear performance of steel fiber reinforced concrete (SFRC members. However, previous studies were mostly focused on the shear strength and proposed empirical shear strength equations based on their experimental results. Thus, this study attempts to estimate the strains and stresses in steel fibers by considering the detailed characteristics of steel fibers in SFRC members, from which more accurate estimation on the shear behavior and strength of SFRC members is possible, and the failure mode of steel fibers can be also identified. Four shear behavior models for SFRC members have been proposed, which have been modified from the softened truss models for reinforced concrete members, and they can estimate the contribution of steel fibers to the total shear strength of the SFRC member. The performances of all the models proposed in this study were also evaluated by a large number of test results. The contribution of steel fibers to the shear strength varied from 5% to 50% according to their amount, and the most optimized volume fraction of steel fibers was estimated as 1%–1.5%, in terms of shear performance.

  5. Adiabatic shear behaviors in rolled and annealed pure titanium subjected to dynamic impact loading

    Energy Technology Data Exchange (ETDEWEB)

    Kuang, Lianjun; Chen, Zhiyong, E-mail: czysh@netease.com; Jiang, Yanghui; Wang, Zhiming; Wang, Renke; Liu, Chuming

    2017-02-08

    The hat-shaped samples cut from rolled and annealed titanium plates were prepared to explore the adiabatic shear behaviors subjected to high-strain-rate deformation operated via Split Hopkinson Pressure Bar. The dynamic shear response calculation reveals that dynamic deformation processes of both state samples can be divided in similar three stages but rolled sample shows a higher susceptibility of adiabatic shear localization compared with the annealed one. Optical microscopy and electronic backscatter diffraction technique (EBSD) were used to systematically analyze the microstructure and texture characteristics. The results show that adiabatic shear bands form in both state samples and rotational dynamic recrystallization (RDRX) occurs within shear area and results in the formation of ultrafine equiaxed grains. Furthermore, ultrafine equiaxed grains within adiabatic shear bands have the same texture feature that <11–20> direction and {10-10} plane parallel to macro local shear direction and shear plane respectively. In the deformation region around the shear band, {10–12} <–1011> tensile and {11–22} <11-2-3> compressive two types twins are observed in both state samples and {10–12} <–1011> tensile twins are more frequently observed in rolled sample. In the rolled sample, {10–12} <–1011> tensile twins are more likely to happen in the hat-brim side than the hat-body side due to the difference of stress state in two sides.

  6. Failure Behavior of Elbows with Local Wall Thinning

    Science.gov (United States)

    Lee, Sung-Ho; Lee, Jeong-Keun; Park, Jai-Hak

    Wall thinning defect due to corrosion is one of major aging phenomena in carbon steel pipes in most plant industries, and it results in reducing load carrying capacity of the piping components. A failure test system was set up for real scale elbows containing various simulated wall thinning defects, and monotonic in-plane bending tests were performed under internal pressure to find out the failure behavior of them. The failure behavior of wall-thinned elbows was characterized by the circumferential angle of thinned region and the loading conditions to the piping system.

  7. Comprehensive Die Shear Test of Silicon Packages Bonded by Thermocompression of Al Layers with Thin Sn Capping or Insertions

    Directory of Open Access Journals (Sweden)

    Shiro Satoh

    2018-04-01

    Full Text Available Thermocompression bonding for wafer-level hermetic packaging was demonstrated at the lowest temperature of 370 to 390 °C ever reported using Al films with thin Sn capping or insertions as bonding layer. For shrinking the chip size of MEMS (micro electro mechanical systems, a smaller size of wafer-level packaging and MEMS–ASIC (application specific integrated circuit integration are of great importance. Metal-based bonding under the temperature of CMOS (complementary metal-oxide-semiconductor backend process is a key technology, and Al is one of the best candidates for bonding metal in terms of CMOS compatibility. In this study, after the thermocompression bonding of two substrates, the shear fracture strength of dies was measured by a bonding tester, and the shear-fractured surfaces were observed by SEM (scanning electron microscope, EDX (energy dispersive X-ray spectrometry, and a surface profiler to clarify where the shear fracture took place. We confirmed two kinds of fracture mode. One mode is Si bulk fracture mode, where the die shear strength is 41.6 to 209 MPa, proportionally depending on the area of Si fracture. The other mode is bonding interface fracture mode, where the die shear strength is 32.8 to 97.4 MPa. Regardless of the fracture modes, the minimum die shear strength is practical for wafer-level MEMS packaging.

  8. Rheo-SAXS investigation of shear-thinning behaviour of very anisometric repulsive disc-like clay suspensions.

    Science.gov (United States)

    Philippe, A M; Baravian, C; Imperor-Clerc, M; De Silva, J; Paineau, E; Bihannic, I; Davidson, P; Meneau, F; Levitz, P; Michot, L J

    2011-05-18

    Aqueous suspensions of swelling clay minerals exhibit a rich and complex rheological behaviour. In particular, these repulsive systems display strong shear-thinning at very low volume fractions in both the isotropic and gel states. In this paper, we investigate the evolution with shear of the orientational distribution of aqueous clay suspensions by synchrotron-based rheo-SAXS experiments using a Couette device. Measurements in radial and tangential configurations were carried out for two swelling clay minerals of similar morphology and size, Wyoming montmorillonite and Idaho beidellite. The shear evolution of the small angle x-ray scattering (SAXS) patterns displays significantly different features for these two minerals. The detailed analysis of the angular dependence of the SAXS patterns in both directions provides the average Euler angles of the statistical effective particle in the shear plane. We show that for both samples, the average orientation is fully controlled by the local shear stress around the particle. We then apply an effective approach to take into account multiple hydrodynamic interactions in the system. Using such an approach, it is possible to calculate the evolution of viscosity as a function of shear rate from the knowledge of the average orientation of the particles. The viscosity thus recalculated almost perfectly matches the measured values as long as collective effects are not too important in the system.

  9. Rheo-SAXS investigation of shear-thinning behaviour of very anisometric repulsive disc-like clay suspensions

    International Nuclear Information System (INIS)

    Philippe, A M; Baravian, C; Imperor-Clerc, M; De Silva, J; Davidson, P; Paineau, E; Bihannic, I; Michot, L J; Meneau, F; Levitz, P

    2011-01-01

    Aqueous suspensions of swelling clay minerals exhibit a rich and complex rheological behaviour. In particular, these repulsive systems display strong shear-thinning at very low volume fractions in both the isotropic and gel states. In this paper, we investigate the evolution with shear of the orientational distribution of aqueous clay suspensions by synchrotron-based rheo-SAXS experiments using a Couette device. Measurements in radial and tangential configurations were carried out for two swelling clay minerals of similar morphology and size, Wyoming montmorillonite and Idaho beidellite. The shear evolution of the small angle x-ray scattering (SAXS) patterns displays significantly different features for these two minerals. The detailed analysis of the angular dependence of the SAXS patterns in both directions provides the average Euler angles of the statistical effective particle in the shear plane. We show that for both samples, the average orientation is fully controlled by the local shear stress around the particle. We then apply an effective approach to take into account multiple hydrodynamic interactions in the system. Using such an approach, it is possible to calculate the evolution of viscosity as a function of shear rate from the knowledge of the average orientation of the particles. The viscosity thus recalculated almost perfectly matches the measured values as long as collective effects are not too important in the system.

  10. Field Test of Enhanced Remedial Amendment Delivery Using a Shear-Thinning Fluid

    Energy Technology Data Exchange (ETDEWEB)

    Truex, Michael J.; Vermeul, Vincent R.; Adamson, David; Oostrom, Martinus; Zhong, Lirong; Mackley, Rob D.; Fritz, Brad G.; Horner, Jacob A.; Johnson, Timothy C.; Thomle, Jonathan N.; Newcomer, Darrell R.; Johnson, Christian D.; Rysz, Michal; Wietsma, Thomas W.; Newell, Charles J.

    2015-03-01

    Heterogeneity of hydraulic properties in aquifers may lead to contaminants residing in lower-permeability zones where it is difficult to deliver remediation amendments using conventional injection processes. The focus of this effort is to examine use of a shear-thinning fluid (STF) to improve the uniformity of remedial amendment distribution within a heterogeneous aquifer. Previous studies have demonstrated the significant potential of STFs for improving remedial amendment delivery in heterogeneous aquifers, but quantitative evaluation of these improvements from field applications are lacking. A field-scale test was conducted that compares data from successive injection of a tracer in water followed by injection of a tracer in a STF to evaluate the impact of the STF on tracer distribution uniformity in the presence of permeability contrasts within the targeted injection zone. Data from tracer breakthrough at multiple depth-discrete monitoring intervals and electrical resistivity tomography showed that inclusion of STF in the injection solution slowed movement in high-permeability pathways, improved delivery of amendment to low-permeability materials, and resulted in better uniformity in injected fluid distribution within the targeted treatment zone.

  11. Cyclic Behavior of Low Rise Concrete Shear Walls Containing Recycled Coarse and Fine Aggregates.

    Science.gov (United States)

    Qiao, Qiyun; Cao, Wanlin; Qian, Zhiwei; Li, Xiangyu; Zhang, Wenwen; Liu, Wenchao

    2017-12-07

    In this study, the cyclic behaviors of low rise concrete shear walls using recycled coarse or fine aggregates were investigated. Eight low rise Recycled Aggregates Concrete (RAC) shear wall specimens were designed and tested under a cyclic loading. The following parameters were varied: replacement percentages of recycled coarse or fine aggregates, reinforcement ratio, axial force ratio and X-shaped rebars brace. The failure characteristics, hysteretic behavior, strength and deformation capacity, strain characteristics and stiffness were studied. Test results showed that the using of the Recycled Coarse Aggregates (RCA) and its replacement ratio had almost no influence on the mechanical behavior of the shear wall; however, the using of Recycled Fine Aggregates (RFA) had a certain influence on the ductility of the shear wall. When the reinforcement ratio increased, the strength and ductility also increased. By increasing the axial force ratio, the strength increased but the ductility decreased significantly. The encased brace had a significant effect on enhancing the RAC shear walls. The experimental maximum strengths were evaluated with existing design codes, it was indicated that the strength evaluation of the low rise RAC shear walls can follow the existing design codes of the conventional concrete shear walls.

  12. Cyclic Behavior of Low Rise Concrete Shear Walls Containing Recycled Coarse and Fine Aggregates

    Directory of Open Access Journals (Sweden)

    Qiyun Qiao

    2017-12-01

    Full Text Available In this study, the cyclic behaviors of low rise concrete shear walls using recycled coarse or fine aggregates were investigated. Eight low rise Recycled Aggregates Concrete (RAC shear wall specimens were designed and tested under a cyclic loading. The following parameters were varied: replacement percentages of recycled coarse or fine aggregates, reinforcement ratio, axial force ratio and X-shaped rebars brace. The failure characteristics, hysteretic behavior, strength and deformation capacity, strain characteristics and stiffness were studied. Test results showed that the using of the Recycled Coarse Aggregates (RCA and its replacement ratio had almost no influence on the mechanical behavior of the shear wall; however, the using of Recycled Fine Aggregates (RFA had a certain influence on the ductility of the shear wall. When the reinforcement ratio increased, the strength and ductility also increased. By increasing the axial force ratio, the strength increased but the ductility decreased significantly. The encased brace had a significant effect on enhancing the RAC shear walls. The experimental maximum strengths were evaluated with existing design codes, it was indicated that the strength evaluation of the low rise RAC shear walls can follow the existing design codes of the conventional concrete shear walls.

  13. Shear effects on crystallization behaviors and structure transitions of isotactic poly-1-butene

    DEFF Research Database (Denmark)

    Li, Jingqing; Guan, Peipei; Zhang, Yao

    2014-01-01

    Different melt pre-shear conditions were applied to isotactic poly-1-butene (iP-1-B) and the effect on the crystallization behaviors and the crystalline structure transitions of iP-1-B were investigated. The polarized optical microscope observations during isothermal crystallization process...... revealed that the applied melt pre-shear within the experimental range could enhance the nucleation of crystal II and accelerate the diameter growth of the formed spherulites. If the applied melt pre-shear rate was large enough, Shish-Kebabs structure could be formed. After the isothermal crystallization...... was formed in the melt pre-sheared iP-1-B samples. Further investigations were applied with synchrotron radiation instruments. Wide angle X-ray scattering (WAXS) and small angle X-ray scattering (SAXS) after the crystal transition showed that the applied melt pre-shear could result in orientated fine...

  14. Stress in closed thin-walled tubes of single box subjected by shear forces and application to airfoils

    Directory of Open Access Journals (Sweden)

    Zebbiche Toufik

    2014-09-01

    Full Text Available The presented work is to develop a numerical computation program to determine the distribution of the shear stress to shear in closed tubes with asymmetric single thin wall section with a constant thickness and applications to airfoils and therefore determining the position and value of the maximum stress. In the literature, there are exact analytical solutions only for some sections of simple geometries such as circular section. Hence our interest is focused on the search of approximate numerical solutions for more complex sections used in aeronautics. In the second stage the position of the shear center is determined so that the section does not undergo torsion. The analytic function of the boundary of the airfoil is obtained by using the cubic spline interpolation since it is given in the form of tabulated points.

  15. Bulk Shear-Wave Transduction Experiments Using Magnetostrictive Transducers with a Thin Fe-Co Alloy Patch

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jae Ha; Cho, Seung Hyun; Ahn, Bong Young; Kwon, Hyu Sang [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of)

    2010-08-15

    Recently, the results of many studies have clarified the successful performance of magnetostrictive transducers in which a ferromagnetic patch is used for the transduction of guided shear waves; this is because a thin ferromagnetic patch with strong magnetostriction is very useful for generating and detecting shear wave. This investigation deals with bulk shear wave transduction by means of magnetostriction; on the other hand, the existing studies have been focused on guided shear waves. A modular transducer was developed: this transducer comprised a coil, magnets, and a thin ferromagnetic patch that was made of Fe-Co alloy. Some experiments were conducted to verify the performance of the developed transducer. Radiation directivity pattern of the developed transducer was obtained, and a test to detect the damage on a side drill hole of a steel block specimen was carried out. From the results of these tests, the good performance of the transducer for nondestructive testing was verified on the basis of the signal-to-noise ratio and narrow beam directivity.

  16. Bubble formation in shear-thinning fluids: Laser image measurement and a novel correlation for detached volume

    Directory of Open Access Journals (Sweden)

    Fan Wenyuan

    2017-01-01

    Full Text Available A laser image system has been established to quantify the characteristics of growing bubbles in quiescent shear-thinning fluids. Bubble formation mechanism was investigated by comparing the evolutions of bubble instantaneous shape, volume and surface area in two shear-thinning liquids with those in Newtonian liquid. The effects of solution mass concentration, gas chamber volume and orifice diameter on bubble detachment volume are discussed. By dimensional analysis, a single bubble volume detached within a moderate gas flowrate range was developed as a function of Reynolds number ,Re, Weber number, We, and gas chamber number, Vc, based on the orifice diameter. The results reveal that the generated bubble presents a slim shape due to the shear-thinning effect of the fluid. Bubble detachment volume increases with the solution mass concentration, gas chamber volume and orifice diameter. The results predicted by the present correlation agree better with the experimental data than the previous ones within the range of this paper.

  17. Development of Test Method for Simple Shear and Prediction of Hardening Behavior Considering the Branchings Effect

    International Nuclear Information System (INIS)

    Kim, Dongwook; Bang, Sungsik; Kim, Minsoo; Lee, Hyungyil; Kim, Naksoo

    2013-01-01

    In this study we establish a process to predict hardening behavior considering the Branchings effect for zircaloy-4 sheets. When a metal is compressed after tension in forming, the yield strength decreases. For this reason, the Branchings effect should be considered in FE simulations of spring-back. We suggested a suitable specimen size and a method for determining the optimum tightening torque for simple shear tests. Shear stress-strain curves are obtained for five materials. We developed a method to convert the shear load-displacement curve to the effective stress-strain curve with Fea. We simulated the simple shear forward/reverse test using the combined isotropic/kinematic hardening model. We also investigated the change of the load-displacement curve by varying the hardening coefficients. We determined the hardening coefficients so that they follow the hardening behavior of zircaloy-4 in experiments

  18. Development of Test Method for Simple Shear and Prediction of Hardening Behavior Considering the Branchings Effect

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dongwook; Bang, Sungsik; Kim, Minsoo; Lee, Hyungyil; Kim, Naksoo [Sogang Univ., Seoul (Korea, Republic of)

    2013-10-15

    In this study we establish a process to predict hardening behavior considering the Branchings effect for zircaloy-4 sheets. When a metal is compressed after tension in forming, the yield strength decreases. For this reason, the Branchings effect should be considered in FE simulations of spring-back. We suggested a suitable specimen size and a method for determining the optimum tightening torque for simple shear tests. Shear stress-strain curves are obtained for five materials. We developed a method to convert the shear load-displacement curve to the effective stress-strain curve with Fea. We simulated the simple shear forward/reverse test using the combined isotropic/kinematic hardening model. We also investigated the change of the load-displacement curve by varying the hardening coefficients. We determined the hardening coefficients so that they follow the hardening behavior of zircaloy-4 in experiments.

  19. A study on shear behavior of reinforced concrete beams subjected to long-term heating

    International Nuclear Information System (INIS)

    Maruta, M.; Yamazaki, M.; Miyashita, T.

    1995-01-01

    A study has been undertaken to determine the shear behavior of reinforced concrete members in nuclear power plant facilities following sustained heating to high temperatures. A total of nine specimens was tested. The parameters of the tests were (1) heating temperature (65, 90 and 175 C) and (2) heating period (1, 3, 6 or 12 months). Different combinations of these parameters were employed, and the shear strength deterioration rate was evaluated. The test results were confirmed by a non-linear finite element analysis. The relationship between the concrete compressive strengths, which varied from heating face to upper portion, and the shear strength in specimens was evaluated. (orig.)

  20. A thin rivulet or ridge subject to a uniform transverse shear stress at its free surface due to an external airflow

    KAUST Repository

    Sullivan, J. M.; Paterson, C.; Wilson, S. K.; Duffy, B. R.

    2012-01-01

    We use the lubrication approximation to analyze three closely related problems involving a thin rivulet or ridge (i.e., a two-dimensional droplet) of fluid subject to a prescribed uniform transverse shear stress at its free surface due

  1. Enhanced In Situ Chemical Oxidation Using Surfactants and Shear Thinning Fluids

    Science.gov (United States)

    Hauswirth, S.; Sadeghi, S.; Cerda, C. C.; Espinoza, I.; Schultz, P. B.; Miller, C. T.

    2017-12-01

    In situ chemical oxidation (ISCO) is an attractive approach for the remediation of recalcitrant contaminants, due to the fact that target compounds are degraded in place, precluding the need for ex situ treatment or disposal. However, field applications of ISCO approaches have been plagued by "rebound" of contaminant concentrations in groundwater weeks to months after treatment. The cause of rebound at a given site may vary, but is typically associated with back-diffusion from finer grained, low permeability units or the presence of non-aqueous phase liquids (NAPLs) that are incompletely degraded during treatment. Modifications to traditional ISCO methods have been proposed to overcome these challenges, including the use of shear-thinning polymers to improve delivery of oxidants to low permeability units and the addition of surfactants to improve dissolution of contaminants from NAPLs. In this work, we investigate the application of these approaches to the oxidation of manufactured gas plant (MGP) tars—NAPLs composed primarily of polycyclic aromatic hydrocarbons (PAHs). We conducted experiments to determine the mutual impact of each chemical component on the physical and chemical properties of the overall system. Specifically, experiments were designed to: determine the kinetics and overall effectiveness of contaminant-oxidant reactions for multiple oxidant-activator combinations; screen several common surfactants in terms of their ability to increase MGP tar solubility and their compatibility with oxidant systems; measure the impact of oxidants and surfactants on the rheology of several common polymer additives; and assess the effect of surfactants and polymers on the consumption of oxidants/activators and on the kinetics of contaminant-oxidant reactions. The results of this work provide insight into the chemical and physical mechanisms associated with enhanced ISCO approaches and an improved basis with which to model and design ISCO applications at both the lab

  2. Effect of mid-thickness rebar mesh on the behavior and punching shear strength of interior slab–column connection

    Directory of Open Access Journals (Sweden)

    Ahmed Ibrahim

    2016-12-01

    The obtained results indicate that, the proposed shear reinforcement system has a positive effect in the enhancement of both the punching shear capacity and the strain energy of interior slab–column connection of both normal and high strength concrete. The general finite element software ANSYS can be used successfully to simulate the punching shear behavior of reinforced concrete flat plates.

  3. Analysis of the Shear Behavior of Stubby Y-Type Perfobond Rib Shear Connectors for a Composite Frame Structure.

    Science.gov (United States)

    Kim, Sang-Hyo; Kim, Kun-Soo; Lee, Do-Hoon; Park, Jun-Seung; Han, Oneil

    2017-11-22

    Shear connectors are used in steel beam-concrete slabs of composite frame and bridge structures to transfer shear force according to design loads. The existing Y-type perfobond rib shear connectors are designed for girder slabs of composite bridges. Therefore, the rib and transverse rebars of the conventional Y-type perfobond rib shear connectors are extremely large for the composite frames of building structures. Thus, this paper proposes stubby Y-type perfobond rib shear connectors, redefining the existing connectors, for composite frames of building structures; these were used to perform push-out tests. These shear connectors have relatively small ribs compared to the conventional Y-type perfobond rib shear connectors. To confirm the shear resistance of these stubby shear connectors, we performed an experiment by using transverse rebars D13 and D16. The results indicate that these shear connectors have suitable shear strength and ductility for application in composite frame structures. The shear strengths obtained using D13 and D16 were not significantly different. However, the ductility of the shear connectors with D16 was 45.1% higher than that of the shear connectors with D13.

  4. Shear and Rapeseed Oil Addition Affect the Crystal Polymorphic Behavior of Milk Fat

    DEFF Research Database (Denmark)

    Kaufmann, Niels; Kirkensgaard, Jacob Judas Kain; Andersen, Ulf

    2013-01-01

    The effect of shear on the crystallization kinetics of anhydrous milk fat (AMF) and blends with 20 and 30 % w/w added rapeseed oil (RO) was studied. Pulse 1H NMR was used to follow the a to b0 polymorphic transition. The NMR method was confirmed and supported by SAXS/WAXS experiments. Samples were...... faster in the presence of RO allowing more room for the conformational changes to occur. Final SFC decreased with increasing RO content. Shear applied in 20 and 30 % blends caused the destruction of b0-related 3L structure leaving only 2L packing. In AMF and statically crystallized samples, both 3L and 2......L packing existed. Shear did not affect the amount of b crystals formed. The study shows that both shear and RO affect the polymorphic behavior of milk fat, and that 1H NMR is able to detect polymorphic transition in blends with up to 30 % w/w RO....

  5. Thinning Approximation for Two-Dimensional Scattering Patterns from Coarse-Grained Polymer Melts under Shear Flow

    Science.gov (United States)

    Hagita, Katsumi; Murashima, Takahiro; Takano, Hiroshi; Kawakatsu, Toshihiro

    2017-12-01

    We proposed a thinning approximation (TA) for estimation of the two-dimensional (2D) wide-angle scattering patterns from Kremer-Grest polymer melts under shear. In the TA, extra particles are inserted at the middle of bonds for fine-graining of the coarse-grained polymers. For the case without the TA, spots corresponding to the orientation of bonds at a high shear rate are difficult to observe because the bond length of successive particles is comparable to the distance between neighboring particles. With the insertion of the extra particles, a ring pattern originating from the neighboring particles can be moved to a wide-angle region. Thus, we can observe the spots at high shear rates. We also examined the relationship between 2D scattering patterns and the Weissenberg number, which is defined as the product of the shear rate and the longest relaxation time. It is confirmed that the relationship for coarse-grained polymers with the TA is consistent with that of the all-atomistic model of polyethylene.

  6. Fatigue life assessment of thin-walled welded joints under non-proportional load-time histories by the shear stress rate integral approach

    Directory of Open Access Journals (Sweden)

    A. Bolchoun

    2016-10-01

    Full Text Available Fatigue life tests under constant and variable amplitude loadings were performed on the tube-tube thin-walled welded specimens made of magnesium (AZ31 and AZ61 alloys. The tests included pure axial, pure torsional and combined in-phase and out-of-phase loadings with the load ratio  RR " ", " " 1  . For the tests with variable amplitude loads a Gaußdistributed loading spectrum with S L 4 5 10  cycles was used. Since magnesium welds show a fatigue life reduction under out-of-phase loads, a stress-based method, which takes this behavior into account, is proposed. The out-of-phase loading results in rotating shear stress vectors in the section planes, which are not orthogonal to the surface. This fact is used in order to provide an out-of-phase measure of the load. This measure is computed as an area covered by the shear stress vectors in all planes over a certain time interval, its computation involves the shear stress and the shear stress rate vectors in the individual planes. Fatigue life evaluation for the variable amplitudes loadings is performed using the Palmgren-Miner linear damage accumulation, whereas the total damage of every cycle is split up into two components: the amplitude component and the out-of-phase component. In order to compute the two components a modification of the rainflow counting method, which keeps track of the time intervals, where the cycles occur, must be used. The proposed method also takes into account different slopes of the pure axial and the pure torsional Wöhler-line by means of a Wöhler-line interpolation for combined loadings

  7. Alloy-dependent deformation behavior of highly ductile nanocrystalline AuCu thin films

    International Nuclear Information System (INIS)

    Lohmiller, Jochen; Spolenak, Ralph; Gruber, Patric A.

    2014-01-01

    Nanocrystalline thin films on compliant substrates become increasingly important for the development of flexible electronic devices. In this study, nanocrystalline AuCu thin films on polyimide substrate were tested in tension while using a synchrotron-based in situ testing technique. Analysis of X-ray diffraction profiles allowed identifying the underlying deformation mechanisms. Initially, elastic and microplastic deformation is observed, followed by dislocation-mediated shear band formation, and eventually macroscopic crack formation. Particularly the influence of alloy composition, heat-treatment, and test temperature were investigated. Generally, a highly ductile behavior is observed. However, high Cu concentrations, annealing, and/or large plastic strains lead to localized deformation and hence reduced ductility. On the other hand, enhanced test temperature allows for a delocalized deformation and extended ductility

  8. Meshless Solution of the Problem on the Static Behavior of Thin and Thick Laminated Composite Beams

    Science.gov (United States)

    Xiang, S.; Kang, G. W.

    2018-03-01

    For the first time, the static behavior of laminated composite beams is analyzed using the meshless collocation method based on a thin-plate-spline radial basis function. In the approximation of a partial differential equation by using a radial basis function, the shape parameter has an important role in ensuring the numerical accuracy. The choice of a shape parameter in the thin plate spline radial basis function is easier than in other radial basis functions. The governing differential equations are derived based on Reddy's third-order shear deformation theory. Numerical results are obtained for symmetric cross-ply laminated composite beams with simple-simple and cantilever boundary conditions under a uniform load. The results found are compared with available published ones and demonstrate the accuracy of the present method.

  9. Alloy-dependent deformation behavior of highly ductile nanocrystalline AuCu thin films

    Energy Technology Data Exchange (ETDEWEB)

    Lohmiller, Jochen [Karlsruhe Institute of Technology, Institute for Applied Materials, P.O. Box 3640, 76021 Karlsruhe (Germany); Laboratory for Nanometallurgy, Department of Materials, ETH Zurich, Wolfgang-Pauli-Str. 10, 8093 Zurich (Switzerland); Spolenak, Ralph [Laboratory for Nanometallurgy, Department of Materials, ETH Zurich, Wolfgang-Pauli-Str. 10, 8093 Zurich (Switzerland); Gruber, Patric A., E-mail: patric.gruber@kit.edu [Karlsruhe Institute of Technology, Institute for Applied Materials, P.O. Box 3640, 76021 Karlsruhe (Germany)

    2014-02-10

    Nanocrystalline thin films on compliant substrates become increasingly important for the development of flexible electronic devices. In this study, nanocrystalline AuCu thin films on polyimide substrate were tested in tension while using a synchrotron-based in situ testing technique. Analysis of X-ray diffraction profiles allowed identifying the underlying deformation mechanisms. Initially, elastic and microplastic deformation is observed, followed by dislocation-mediated shear band formation, and eventually macroscopic crack formation. Particularly the influence of alloy composition, heat-treatment, and test temperature were investigated. Generally, a highly ductile behavior is observed. However, high Cu concentrations, annealing, and/or large plastic strains lead to localized deformation and hence reduced ductility. On the other hand, enhanced test temperature allows for a delocalized deformation and extended ductility.

  10. Investigation of the Behavior of Steel Shear Walls Using Finite Elements Analysis

    Directory of Open Access Journals (Sweden)

    K. Abubakri

    2016-10-01

    Full Text Available Currently, steel shear walls are considered by engineers as an economic method against lateral loads imposed by wind and earthquake in tall structures. Accordingly, there is a growing need to develop accurate methods alongside approximation methods to estimate the behavior of these structural elements. The finite element technique is one of the strongest numerical methods in analysis of solid mechanics problems. Finite element analysis however requires high technical knowledge of the behavioral models of materials. Therefore, it is less used by designers for certain structural elements such as steel shear walls. This study examines the failure mechanism of steel shear walls using finite elements analysis and validates this modeling by comparing the results with experimental studies.

  11. Effects of Particle Size on the Shear Behavior of Coarse Grained Soils Reinforced with Geogrid

    Directory of Open Access Journals (Sweden)

    Daehyeon Kim

    2014-02-01

    Full Text Available In order to design civil structures that are supported by soils, the shear strength parameters of soils are required. Due to the large particle size of coarse-grained soils, large direct shear tests should be performed. In this study, large direct shear tests on three types of coarse grained soils (4.5 mm, 7.9 mm, and 15.9 mm were performed to evaluate the effects of particle size on the shear behavior of coarse grained soils with/without geogrid reinforcements. Based on the direct shear test results, it was found that, in the case of no-reinforcement, the larger the maximum particle size became, the larger the friction angle was. Compared with the no-reinforcement case, the cases reinforced with either soft geogrid or stiff geogrid have smaller friction angles. The cohesion of the soil reinforced with stiff geogrid was larger than that of the soil reinforced with soft geogrid. The difference in the shear strength occurs because the case with a stiff geogrid has more soil to geogrid contact area, leading to the reduction in interlocking between soil particles.

  12. Effects of Particle Size on the Shear Behavior of Coarse Grained Soils Reinforced with Geogrid.

    Science.gov (United States)

    Kim, Daehyeon; Ha, Sungwoo

    2014-02-07

    In order to design civil structures that are supported by soils, the shear strength parameters of soils are required. Due to the large particle size of coarse-grained soils, large direct shear tests should be performed. In this study, large direct shear tests on three types of coarse grained soils (4.5 mm, 7.9 mm, and 15.9 mm) were performed to evaluate the effects of particle size on the shear behavior of coarse grained soils with/without geogrid reinforcements. Based on the direct shear test results, it was found that, in the case of no-reinforcement, the larger the maximum particle size became, the larger the friction angle was. Compared with the no-reinforcement case, the cases reinforced with either soft geogrid or stiff geogrid have smaller friction angles. The cohesion of the soil reinforced with stiff geogrid was larger than that of the soil reinforced with soft geogrid. The difference in the shear strength occurs because the case with a stiff geogrid has more soil to geogrid contact area, leading to the reduction in interlocking between soil particles.

  13. The non-monotonic shear-thinning flow of two strongly cohesive concentrated suspensions

    OpenAIRE

    Buscall, Richard; Kusuma, Tiara E.; Stickland, Anthony D.; Rubasingha, Sayuri; Scales, Peter J.; Teo, Hui-En; Worrall, Graham L.

    2014-01-01

    The behaviour in simple shear of two concentrated and strongly cohesive mineral suspensions showing highly non-monotonic flow curves is described. Two rheometric test modes were employed, controlled stress and controlled shear-rate. In controlled stress mode the materials showed runaway flow above a yield stress, which, for one of the suspensions, varied substantially in value and seemingly at random from one run to the next, such that the up flow-curve appeared to be quite irreproducible. Th...

  14. End Effects in Rotational Viscometry I. No-Slip Shear-Thinning Samples in the Z40 DIN Sensor.

    Czech Academy of Sciences Publication Activity Database

    Wein, Ondřej; Večeř, Marek; Havlica, Jaromír

    2007-01-01

    Roč. 46, 5 (2007) , s. 765-772 ISSN 0035-4511. [Annual Rheology Conference AERC 2006 /3./. Crete, 27.04.2006-29.04.2006] R&D Projects: GA ČR(CZ) GA104/04/0826; GA ČR GP104/06/P287; GA ČR GP104/05/P554 Institutional research plan: CEZ:AV0Z40720504 Keywords : rotational couette flow * shear-thinning fluids * end effects Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.110, year: 2007

  15. Effect of shear span, concrete strength and strrup spacing on behavior of pre-stressed concrete beams

    International Nuclear Information System (INIS)

    Ahmad, S.; Bukhari, I.A.

    2007-01-01

    The shear strength of pre-stressed concrete beams is one of the most important factors to be considered in their design. The available data on shear behavior of pre-tensioned prestressed concrete beams is very limited. In this experimental study, pre-tensioned prestressed concrete I-beams are fabricated with normal and high- strength concretes, varying stirrup spacing and shear span-to-depth ratios. 1Wenty one I-beam specimens that are 300 mm deep and 3745-4960mm long are tested up to failure while deflections, cracking pattern, cracking and failure loads were recorded. The research results are compared with ACI 318-02 and Structure Analysis Program, Response 2000. It was observed that with the decrease in concrete strength, failure mode of prestressed concrete beams changes from flexure shear to web shear cracking for values of shear span-to-depth ratio less than 4.75. Increase in stirrup spacing decreased the effectiveness of stirrups in transmitting shear across crack as a result of which failure mode is changed to web shear cracking especially for beams with lower values of shear span-to-depth ratios. ACI code underestimates the shear carrying capacity of prestressed concrete beams with lower values of shear span- to-depth ratios. Response 2000 can be used more effectively in predicting shear behavior of normal strength prestressed concrete beams. (author)

  16. Effect of Carreau-Yasuda rheological parameters on subcritical Lapwood convection in horizontal porous cavity saturated by shear-thinning fluid

    Science.gov (United States)

    Khechiba, Khaled; Mamou, Mahmoud; Hachemi, Madjid; Delenda, Nassim; Rebhi, Redha

    2017-06-01

    The present study is focused on Lapwood convection in isotropic porous media saturated with non-Newtonian shear thinning fluid. The non-Newtonian rheological behavior of the fluid is modeled using the general viscosity model of Carreau-Yasuda. The convection configuration consists of a shallow porous cavity with a finite aspect ratio and subject to a vertical constant heat flux, whereas the vertical walls are maintained impermeable and adiabatic. An approximate analytical solution is developed on the basis of the parallel flow assumption, and numerical solutions are obtained by solving the full governing equations. The Darcy model with the Boussinesq approximation and energy transport equations are solved numerically using a finite difference method. The results are obtained in terms of the Nusselt number and the flow fields as functions of the governing parameters. A good agreement is obtained between the analytical approximation and the numerical solution of the full governing equations. The effects of the rheological parameters of the Carreau-Yasuda fluid and Rayleigh number on the onset of subcritical convection thresholds are demonstrated. Regardless of the aspect ratio of the enclosure and thermal boundary condition type, the subcritical convective flows are seen to occur below the onset of stationary convection. Correlations are proposed to estimate the subcritical Rayleigh number for the onset of finite amplitude convection as a function of the fluid rheological parameters. Linear stability of the convective motion, predicted by the parallel flow approximation, is studied, and the onset of Hopf bifurcation, from steady convective flow to oscillatory behavior, is found to depend strongly on the rheological parameters. In general, Hopf bifurcation is triggered earlier as the fluid becomes more and more shear-thinning.

  17. Steady shear characteristic and behavior of magneto-thermo-elasticity of isotropic MR elastomers

    International Nuclear Information System (INIS)

    Gao, Wei; Wang, Xingzhe

    2016-01-01

    The magneto-thermo-elastic steady shear behaviors of isotropic smart composites of silicon rubber matrix randomly filled with ferromagnetic particles, commonly referred to as magnetorheological (MR) elastomers, are investigated experimentally and theoretically in the present study. The strip specimens of the MR elastomer composite with different ferromagnetic particle concentrations are fabricated and implemented for lap-shear tests under both magnetic and thermal fields. It is illustrated that the magneto-thermo-elastic shear modulus of the MR elastomer is markedly enhanced with the volume fraction of ferromagnetic particles and the applied external magnetic field, while the shear modulus is decreased with the environment temperature. To qualitatively elucidate the magneto-thermo-elastic shear performance of this kind of magnetic smart composites, a modified constitutive of hyperelasticity is suggested taking into account the influence of magnetic field and temperature on the magnetic potential energy and strain energy. The theoretical modeling predictions on the stress–strain behaviors for different applied magnetic fields and environment temperatures are compared to experimental observations to demonstrate a good agreement. (paper)

  18. Thin slices of child personality: Perceptual, situational, and behavioral contributions.

    Science.gov (United States)

    Tackett, Jennifer L; Herzhoff, Kathrin; Kushner, Shauna C; Rule, Nicholas

    2016-01-01

    The present study examined whether thin-slice ratings of child personality serve as a resource-efficient and theoretically valid measurement of child personality traits. We extended theoretical work on the observability, perceptual accuracy, and situational consistency of childhood personality traits by examining intersource and interjudge agreement, cross-situational consistency, and convergent, divergent, and predictive validity of thin-slice ratings. Forty-five unacquainted independent coders rated 326 children's (ages 8-12) personality in 1 of 15 thin-slice behavioral scenarios (i.e., 3 raters per slice, for over 14,000 independent thin-slice ratings). Mothers, fathers, and children rated children's personality, psychopathology, and competence. We found robust evidence for correlations between thin-slice and mother/father ratings of child personality, within- and across-task consistency of thin-slice ratings, and convergent and divergent validity with psychopathology and competence. Surprisingly, thin-slice ratings were more consistent across situations in this child sample than previously found for adults. Taken together, these results suggest that thin slices are a valid and reliable measure to assess child personality, offering a useful method of measurement beyond questionnaires, helping to address novel questions of personality perception and consistency in childhood. (c) 2016 APA, all rights reserved).

  19. Investigation of the Behavior of Steel Shear Walls Using Finite Elements Analysis

    OpenAIRE

    Abubakri, K.; Veladi, H.

    2016-01-01

    Currently, steel shear walls are considered by engineers as an economic method against lateral loads imposed by wind and earthquake in tall structures. Accordingly, there is a growing need to develop accurate methods alongside approximation methods to estimate the behavior of these structural elements. The finite element technique is one of the strongest numerical methods in analysis of solid mechanics problems. Finite element analysis however requires high technical knowledge of the behavior...

  20. Development of a structural model for the nonlinear shear deformation behavior of a seismic isolator

    International Nuclear Information System (INIS)

    Lee, Jae Han; Koo, Gyeong Hoi; Yoo, Bong

    2002-02-01

    The seismic excitation test results of an isolated test structure for artificial time history excitation are summarized for structure models of the isolated structure and isolation bearing. To simulate the response characteristic of isolated structure, shear hysteresis curves of isolators are analyzed. A simple analysis model is developed representing the actual dynamic behaviors of the test model, and the seismic responses using the simple model of the isolated structure and structure models, which are developed such as linear and bilinear models for isolators, are performed and compared with those of the seismic tests. The developed bilinear model is well applicable only to large shear strain area of LLRB

  1. Quasi-static and dynamic forced shear deformation behaviors of Ti-5Mo-5V-8Cr-3Al alloy

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhiming; Chen, Zhiyong, E-mail: czysh@netease.com; Zhan, Congkun; Kuang, Lianjun; Shao, Jianbo; Wang, Renke; Liu, Chuming

    2017-04-13

    The mechanical behavior and microstructure characteristics of Ti-5Mo-5V-8Cr-3Al alloy were investigated with hat-shaped samples compressed under quasi-static and dynamic loading. Compared with the quasi-static loading, a higher shear stress peak and a shear instability stage were observed during the dynamic shear response. The results showed that an adiabatic shear band consisting of ultrafine equiaxed grains was only developed in the dynamic specimen, while a wider shear region was formed in the quasi-static specimen. The microhardness measurements revealed that shear region in the quasi-static specimen and adiabatic shear band in the dynamic specimen exhibited higher hardness than that of adjacent regions due to the strain hardening and grain refining, respectively. A stable orientation, in which the crystallographic {110} planes and <111> directions were respectively parallel to the shear plane and shear direction, developed in both specimens. And the microtexture of the adiabatic shear band was more well-defined than that of the shear region in the quasi-static specimen. Rotational dynamic recrystallization mechanism was suggested to explain the formation of ultrafine equiaxed grains within the adiabatic shear band by thermodynamic and kinetic calculations.

  2. A Conceptual Model for Shear-Induced Phase Behavior in Crystallizing Cocoa Butter

    International Nuclear Information System (INIS)

    Mazzanti, G.; Guthrie, S.; Marangoni, A.; Idziak, S.

    2007-01-01

    We propose a conceptual model to explain the quantitative data from synchrotron X-ray diffraction experiments on the shear-induced phase behavior of cocoa butter, the main structural component of chocolate. We captured two-dimensional diffraction patterns from cocoa butter at crystallization temperatures of 17.5, 20.0, and 22.5 o C under shear rates from 45 to 1440 s -1 and under static conditions. From the simultaneous analysis of the integrated intensity, correlation length, lamellar thickness, and crystalline orientation, we postulate a conceptual model to provide an explanation for the distribution of phases II, IV, V, and X and the kinetics of the process. As previously proposed in the literature, we assume that the crystallites grow layer upon layer of slightly different composition. The shear rate and temperature applied define these compositions. Simultaneously, the shear and temperature define the crystalline interface area available for secondary nucleation by promoting segregation and affecting the size distribution of the crystallites. The combination of these factors (composition, area, and size distribution) favors dramatically the early onset of phase V under shear and determines the proportions of phases II, IV, V, and X after the transition. The experimental observations, the methodology used, and the proposed explanation are of fundamental and industrial interest, since the structural properties of crystalline networks are determined by their microstructure and polymorphic crystalline state. Different proportions of the phases will thus result in different characteristics of the final material

  3. Behavior of an MBT waste in monotonic triaxial shear tests

    International Nuclear Information System (INIS)

    Bhandari, Athma Ram; Powrie, William

    2013-01-01

    Highlights: ► We studied the stress–strain–strength characteristics of an MBT waste. ► Rate of mobilization of strength with strain depends on initial density. ► Image analysis technique was used to determine whole-specimen displacement fields. ► Initial mode of deformation of a loose specimen is one-dimensional compression. ► Reinforcing elements enhance the resistance to lateral and volumetric deformation. - Abstract: Legislation in some parts of the world now requires municipal solid waste (MSW) to be processed prior to landfilling to reduce its biodegradability and hence its polluting potential through leachate and fugitive emission of greenhouse gases. This pre-processing may be achieved through what is generically termed mechanical–biological-treatment (MBT). One of the major concerns relating to MBT wastes is that the strength of the material may be less than for raw MSW, owing to the removal of sheet, stick and string-like reinforcing elements during processing. Also, the gradual increase in mobilized strength over strains of 30% or so commonly associated with unprocessed municipal solid waste may not occur with treated wastes. This paper describes a series of triaxial tests carried out to investigate the stress–strain–strength characteristics of an MBT waste, using a novel digital image analysis technique for the determination of detailed displacement fields over the whole specimen. New insights gained into the mechanical behavior of MBT waste include the effect of density on the stress–strain response, the initial 1-D compression of lightly consolidated specimens, and the likely reinforcing effect of small sheet like particles remaining in the waste

  4. Experimental investigations into the shear behavior of self-compacting RC beams with and without shear reinforcement

    Directory of Open Access Journals (Sweden)

    Ammar N. HANOON

    2014-12-01

    Full Text Available Self-compacting concrete (SCC is a new generation of high-performance concrete, known for its excellent deformability and high resistance to segregation and bleeding. Nonetheless, SCC may be incapable of resisting shear because the shear resistance mechanisms of this concrete are uncertain, especially the aggregate interlock mechanism. This uncertainty is attributed to the fact that SCC contains a smaller amount of coarse aggregates than normal concrete (NC does. This study focuses on the shear strength of self-compacting reinforced concrete (RC beams with and without shear reinforcement. A total of 16 RC beam specimens was manufactured and tested in terms of shear span-to-depth ratio and flexural and shear reinforcement ratio. The test results were compared with those of the shear design equations developed by ACI, BS, CAN and NZ codes. Results show that an increase in web reinforcement enhanced cracking strength and ultimate load. Shear-tension failure was the control failure in all tested beams.

  5. Large strain deformation behavior of polymeric gels in shear- and cavitation rheology

    Science.gov (United States)

    Hashemnejad, Seyed Meysam; Kundu, Santanu

    Polymeric gels are used in many applications including in biomedical and in food industries. Investigation of mechanical responses of swollen polymer gels and linking that to the polymer chain dynamics are of significant interest. Here, large strain deformation behavior of two different gel systems and with different network architecture will be presented. We consider biologically relevant polysaccharide hydrogels, formed through ionic and covalent crosslinking, and physically associating triblock copolymer gels in a midblock selective solvent. Gels with similar low-strain shear modulus display distinctly different non-linear rheological behavior in large strain shear deformation. Both these gels display strain-stiffening behavior in shear-deformation prior to macroscopic fracture of the network, however, only the alginate gels display negative normal stress. The cavitation rheology data show that the critical pressure for cavitation is higher for alginate gels than that observed for triblock gels. These distinctly different large-strain deformation behavior has been related to the gel network structure, as alginate chains are much stiffer than the triblock polymer chains.

  6. Living bacteria rheology: Population growth, aggregation patterns, and collective behavior under different shear flows

    Science.gov (United States)

    Patrício, P.; Almeida, P. L.; Portela, R.; Sobral, R. G.; Grilo, I. R.; Cidade, T.; Leal, C. R.

    2014-08-01

    The activity of growing living bacteria was investigated using real-time and in situ rheology—in stationary and oscillatory shear. Two different strains of the human pathogen Staphylococcus aureus—strain COL and its isogenic cell wall autolysis mutant, RUSAL9—were considered in this work. For low bacteria density, strain COL forms small clusters, while the mutant, presenting deficient cell separation, forms irregular larger aggregates. In the early stages of growth, when subjected to a stationary shear, the viscosity of the cultures of both strains increases with the population of cells. As the bacteria reach the exponential phase of growth, the viscosity of the cultures of the two strains follows different and rich behaviors, with no counterpart in the optical density or in the population's colony-forming units measurements. While the viscosity of strain COL culture keeps increasing during the exponential phase and returns close to its initial value for the late phase of growth, where the population stabilizes, the viscosity of the mutant strain culture decreases steeply, still in the exponential phase, remains constant for some time, and increases again, reaching a constant plateau at a maximum value for the late phase of growth. These complex viscoelastic behaviors, which were observed to be shear-stress-dependent, are a consequence of two coupled effects: the cell density continuous increase and its changing interacting properties. The viscous and elastic moduli of strain COL culture, obtained with oscillatory shear, exhibit power-law behaviors whose exponents are dependent on the bacteria growth stage. The viscous and elastic moduli of the mutant culture have complex behaviors, emerging from the different relaxation times that are associated with the large molecules of the medium and the self-organized structures of bacteria. Nevertheless, these behaviors reflect the bacteria growth stage.

  7. Effect of length of thinning area on the failure behavior of carbon steel pipe containing a defect of wall thinning

    International Nuclear Information System (INIS)

    Kim, Jin Weon; Park, Chi Yong

    2003-01-01

    The present study performed pipe failure tests using 102 mm-Sch. 80 carbon steel pipe with various simulated wall thinning defects, to investigate the effect of axial length of wall thinning and internal pressure on the failure behavior of pipe thinned by flow accelerated corrosion (FAC). The tests were conducted under loading conditions of four-point bending with and without internal pressure. The results showed that a failure mode of pipe with a defect depended on the magnitude of internal pressure and axial thinning length as well as stress type and thinning depth and circumferential angle. Both load carrying capability (LCC) and deformation capability (DC) were depended on stress type in the thinning area and dimensions of thinning defect. For applying tensile stress to the thinned area, the dependence of LCC on the axial length of wall thinning was determined by circumferential thinning angle, and the DC was proportionally increased with increase in axial length of wall thinning regardless of the circumferential angle. For applying compressive stress to thinned area, however, the LCC was decreased with increase in axial length of the thinned area. Also, the effect of internal pressure on failure behavior was characterized by failure mode of thinned pipe, and it promoted crack occurrence and mitigated a local buckling of the thinned area

  8. The effect of dry shear aligning of nanotube thin films on the photovoltaic performance of carbon nanotube-silicon solar cells.

    Science.gov (United States)

    Stolz, Benedikt W; Tune, Daniel D; Flavel, Benjamin S

    2016-01-01

    Recent results in the field of carbon nanotube-silicon solar cells have suggested that the best performance is obtained when the nanotube film provides good coverage of the silicon surface and when the nanotubes in the film are aligned parallel to the surface. The recently developed process of dry shear aligning - in which shear force is applied to the surface of carbon nanotube thin films in the dry state, has been shown to yield nanotube films that are very flat and in which the surface nanotubes are very well aligned in the direction of shear. It is thus reasonable to expect that nanotube films subjected to dry shear aligning should outperform otherwise identical films formed by other processes. In this work, the fabrication and characterisation of carbon nanotube-silicon solar cells using such films is reported, and the photovoltaic performance of devices produced with and without dry shear aligning is compared.

  9. Settling of isolated particles and of suspensions in a shear-thinning medium; Sedimentation de particules isolees et de suspensions en milieu rheofluidifiant

    Energy Technology Data Exchange (ETDEWEB)

    Daugan, S.

    2002-11-01

    After drawing up a balance sheet of current knowledge of settling of particles and suspensions in Newtonian and non Newtonian fluids, we introduce the characterisation of the fluid-particles system and especially the shear-thinning behavior of Xanthan solutions. This experimental study is organised into two parts. First of all, we study the settling behavior of a few particles falling along their line of centres. The conditions for particles aggregation with respect to the rheological properties of the suspending fluid are systematically reported. To that extent, rheological relaxation experiments are performed. Once aggregated, the particles velocities are much more important that the velocity of a single one. We show that a simple model, based on the Newtonian case, allows to predict the position and the velocity of each particle with respect to the initial separation distance between them. The second part of this work is devoted to the study of the settling behavior of spherical and monodisperse particles suspensions according to the particles volume fraction, the polymer concentration of the suspending fluid and the geometry of the sedimenting cell. From a model giving the particle volume fraction as a function of the luminous intensity transmitted by the suspension, we show that three regimes of different kinetics occur. During the second regime, the particle volume fraction decreases exponentially with time and the observed phenomena are very fast. Finally, we study the spatial structuration of the suspension and we link it to the topography of the sediment obtained at the end of the sedimentation. (author)

  10. Exact solutions for oscillatory shear sweep behaviors of complex fluids from the Oldroyd 8-constant framework

    Science.gov (United States)

    Saengow, Chaimongkol; Giacomin, A. Jeffrey

    2018-03-01

    In this paper, we provide a new exact framework for analyzing the most commonly measured behaviors in large-amplitude oscillatory shear flow (LAOS), a popular flow for studying the nonlinear physics of complex fluids. Specifically, the strain rate sweep (also called the strain sweep) is used routinely to identify the onset of nonlinearity. By the strain rate sweep, we mean a sequence of LAOS experiments conducted at the same frequency, performed one after another, with increasing shear rate amplitude. In this paper, we give exact expressions for the nonlinear complex viscosity and the corresponding nonlinear complex normal stress coefficients, for the Oldroyd 8-constant framework for oscillatory shear sweeps. We choose the Oldroyd 8-constant framework for its rich diversity of popular special cases (we list 18 of these). We evaluate the Fourier integrals of our previous exact solution to get exact expressions for the real and imaginary parts of the complex viscosity, and for the complex normal stress coefficients, as functions of both test frequency and shear rate amplitude. We explore the role of infinite shear rate viscosity on strain rate sweep responses for the special case of the corotational Jeffreys fluid. We find that raising η∞ raises the real part of the complex viscosity and lowers the imaginary. In our worked examples, we thus first use the corotational Jeffreys fluid, and then, for greater accuracy, we use the Johnson-Segalman fluid, to describe the strain rate sweep response of molten atactic polystyrene. For our comparisons with data, we use the Spriggs relations to generalize the Oldroyd 8-constant framework to multimode. Our generalization yields unequivocally, a longest fluid relaxation time, used to assign Weissenberg and Deborah numbers to each oscillatory shear flow experiment. We then locate each experiment in the Pipkin space.

  11. Self-organization behaviors of shear bands in 7075 T73 and annealed aluminum alloy

    International Nuclear Information System (INIS)

    Yang, Y.; Li, D.H.; Zheng, H.G.; Li, X.M.; Jiang, F.

    2009-01-01

    The self-organization behaviors of multiple adiabatic shear bands (ASBs) in the 7075 T73 aluminum alloy were investigated by means of the thick-walled cylinder (TWC) technique. Shear bands first nucleate at the inner boundary of the aluminum alloy tube and propagate along the maximum shear stress direction in the spiral trajectory. On the cross section of the specimen, shear bands distribute either in the clockwise or the anticlockwise direction. The number of ASBs in the clockwise direction is roughly twice that in the anticlockwise direction. However, the 7075 annealed alloy does not generate any shear band under the same experimental conditions. Numerical simulation with coupled thermo-mechanical analysis was carried out to investigate the evolution mechanism of adiabatic shear bands. Both uniform and non-uniform finite element models were created. The simulation results of the non-uniform model are in better agreement with those of the experiment. In the non-uniform case, the spacing between ASBs is larger than that of the uniform model, and most of the ASBs prefer to propagate in the clockwise direction. For the first time, two types of particles (second phase), hard particles and soft particles, are separately introduced into the metal matrix in the non-uniform model to simulate their effects on the self-organization of ASBs. The soft particles reduce the time required for ASBs nucleation. Stress collapse first occurs at the region where the soft particles are located and most of the ASBs pass through these soft particles. However, ASBs propagate along the paths that are adjacent to the hard particles instead of passing through them. As experimental observations, there is no shear band nucleating in the annealed alloy in simulation. Under the same conditions, the energy barrier for the formation of ASBs in the annealed aluminum alloy is about 2.5 times larger than that in the T73 alloy, which means that the adiabatic shearing is less likely to nucleate in the

  12. Flexural and Shear Behavior of RC Concrete Beams Reinforced with Fiber Wire Mesh

    Directory of Open Access Journals (Sweden)

    Rafea Flaih Hassan

    2018-02-01

    Full Text Available This work aims to study  the effect of using fiber wire mesh on the flexural and shear properties of RC concrete beams. Six reinforced concrete beams (120*180*1220mm were tested under two load points. Fiber wire mesh was applied with two manners, first one is three layers as U shape around the section of the beam, the second one is four layers around overall section of beam. The test results indicated that using of fiber wire mesh as additional reinforcement can increase the ultimate load of about (1.85-3.58% in the case of flexural and (17.7-23.7% in case of shear. Also,  results showed that an increasing in  first cracking  load is obtained from  (42.8-85.7% in case of flexural and from (41.2-76.5% in case of shear. Also the shear behavior of beams becomes more ductile when the fiber wire mesh was used in beams. The cracks of shrinkage was disappeared when the fiber wire mesh surround the section of the beam. 

  13. Flexural and Shear Behavior of FRP Strengthened AASHTO Type Concrete Bridge Girders

    Directory of Open Access Journals (Sweden)

    Nur Yazdani

    2016-01-01

    Full Text Available Fiber-reinforced polymers (FRP are being increasingly used for the repair and strengthening of deteriorated or unsafe concrete structures, including structurally deficient concrete highway bridges. The behavior of FRP strengthened concrete bridge girders, including failure modes, failure loads, and deflections, can be determined using an analytical finite element modeling approach, as outlined in this paper. The differences in flexural versus shear FRP strengthening and comparison with available design guidelines are also beneficial to design professionals. In this paper, a common AASHTO type prestressed concrete bridge girder with FRP wrapping was analyzed using the ANSYS FEM software and the ACI analytical approach. Both flexural and shear FRP applications, including vertical and inclined shear strengthening, were examined. Results showed that FRP wrapping can significantly benefit concrete bridge girders in terms of flexure/shear capacity increase, deflection reduction, and crack control. The FRP strength was underutilized in the section selected herein, which could be addressed through decrease of the amount of FRP and prestressing steel used, thereby increasing the section ductility. The ACI approach produced comparable results to the FEM and can be effectively and conveniently used in design.

  14. Experimental study on the shear behavior of the interface between cushion materials and the concrete raft

    Science.gov (United States)

    Li, Yaokun; Han, Xiaolei; Galal, Khaled; Ji, Jing

    2018-01-01

    Cushion is a layer of granular materials between the raft and the ground. The shear behavior of the interface between the cushion and the raft may influence the seismic performance of the superstructure. In order to quantify such influences, horizontal shear tests on the interfaces between different cushion materials and concrete raft under monotonic and cyclic loading were carried out. The vertical pressure P v, material type and cushion thickness h c were taken as variables. Conclusions include: 1) under monotonic loading, P v is the most significant factor; the shear resistance P hmax increases as P v increases, but the normalized factor of resistance μ n has an opposite tendency; 2) for the materials used in this study, μ n varies from 0.40 to 0.70, the interface friction angle δ s varies from 20° to 35°, while u max varies from 3 mm to 15 mm; 3) under cyclic loading, the interface behavior can be abstracted as a "three-segment" back-bone curve, the main parameters include μ n, the displacement u 1 and stiffness K 1 of the elastic stage, the displacement u 2 and stiffness K 2 of the plastic stage; 4) by observation and statistical analysis, the significance of different factors, together with values of K 1, K 2 and μ n have been obtained.

  15. Simulation of shear plugging through thin plates using the GRIM Eulerian hydrocode

    Science.gov (United States)

    Church, P.; Cornish, R.; Cullis, I.; Lynch, N.

    2000-03-01

    Ballistic experiments have been performed using aluminum spheres against 10-mm rolled homogenous armour (RHA), MARS270, MARS300, and titanium alloy plates to investigate the influence of the plugging mechanism on material properties. The experiments have measured the threshold for plug mass and velocity as well as the recovered aluminum sphere mass over a range of velocities. Some of the experiments have been simulated using the in-house second generation Eulerian hydrocode GRIM. The calculations feature advanced material algorithms derived from interrupted tensile testing techniques and a triaxial failure model derived from notched tensile tests over a range of strain rates and temperatures. The effect of mesh resolution on the results has been investigated and understood. The simulation results illustrate the importance of the constitutive model in the shear localization process and the subsequent plugging phenomena. The stress triaxiality is seen as the dominant feature in controlling the onset and subsequent propagation of the crack leading to the shear plug. The simulations have demonstrated that accurate numerics coupled with accurate constitutive and fracture algorithms can successfully reproduce the observed experimental features. However, extrapolation of the fracture data leads to the simulations overpredicting the plug damage. The reasons for this are discussed.

  16. Shear-induced Long Range Order in Diblock Copolymer Thin Films

    Science.gov (United States)

    Ding, Xuan; Russell, Thomas

    2007-03-01

    Shear is a well-established means of aligning block copolymer micro-domains in bulk; cylinder-forming block copolymers respond by orienting cylinder axes parallel to the flow direction, and macroscopic specimens with near-single-crystal texture can be obtained. A stepper motor is a brushless, synchronous electric motor that can divide a full rotation into a large number of steps. With the combination of a stepper motor and several gear boxes in our experiment, we can control the rotating resolution to be as small as 1 x10-4 degree/step. Also, with the help of a customized computer program we can control the motor speed in a very systematical way. By changing parameters such as the weight (or the uniform pressure) and the lateral force we can carry on experiment to examine the effect of lateral shear on different polymer systems such as PS-b-PEO (large χ) and PS-b-P2VP (small χ).

  17. A Shear Horizontal Waveguide Technique for Monitoring of High Temperature Pipe Thinning

    International Nuclear Information System (INIS)

    Cheong, Yongmoo; Kim, Hongpyo; Lee, Duckhyun

    2014-01-01

    An ultrasonic thickness measurement method is a well-known and most commonly used non-destructive testing technique for wall thickness monitoring of a piping or plate. However, current commonly available ultrasonic transducers cannot withstand high temperatures of, above 200 .deg. C. Currently, the variation of wall thickness of the pipes is determined by a portable ultrasonic gauge during plant shutdowns. This manual ultrasonic method reveals several disadvantages: inspections have to be performed during shutdowns with the possible consequences of prolonging down time and increasing production losses, insulation has to be removed and replaced for each manual measurement, and scaffolding has to be installed to inaccessible areas, resulting in considerable cost for intervention. In addition, differences of the measurement conditions such as examiner, temperature, and couplant could result in measurement errors. It has been suggested that a structural health monitoring approach with permanently installed ultrasonic thickness gauges could have substantial benefits over current practices. In order to solve those fundamental problems occurring during the propagation of ultrasound at high temperature, a shear horizontal waveguide technique for wall thickness monitoring at high temperatures is developed. A dry clamping device without a couplant for the acoustic contact between waveguide and pipe surface was designed and fabricated. The shear horizontal waveguides and clamping device result in an excellent S/N ratio and high accuracy of measurement with long exposure in an elevated temperature condition. A computer program for on-line monitoring of the pipe thickness at high temperature for a long period of time was developed. The system can be applied to monitor the FAC in carbon steel piping in a nuclear power plant after a verification test for a long period of time

  18. Shear Tests and Calculation of Shear Resistance with the PC Program RFEM from Thin Partition Walls of Brick in Old Buildings

    Directory of Open Access Journals (Sweden)

    Korjenic Sinan

    2015-11-01

    Full Text Available This paper is about the shear capacity of partition walls in old buildings based on shear tests which were carried out under real conditions in an existing building. There were experiments conducted on different floors and in each case, the maximum recordable horizontal force and the horizontal displacement of the respective mortar were measured. At the same time material studies and material investigations were carried out in the laboratory. The material parameters were used for the calculation of the precise shear capacity of each joint. In the shear tests, the maximum displacement of a mortar joint was determined at a maximum of two to four millimetres. Furthermore, no direct linear relationship between the theoretical load (wall above it and the shear stress occurred could be detected in the analysis of the experiment, as it was previously assumed.

  19. Shear Tests and Calculation of Shear Resistance with the PC Program RFEM from Thin Partition Walls of Brick in Old Buildings

    Science.gov (United States)

    Korjenic, Sinan; Nowak, Bernhard; Löffler, Philipp; Vašková, Anna

    2015-11-01

    This paper is about the shear capacity of partition walls in old buildings based on shear tests which were carried out under real conditions in an existing building. There were experiments conducted on different floors and in each case, the maximum recordable horizontal force and the horizontal displacement of the respective mortar were measured. At the same time material studies and material investigations were carried out in the laboratory. The material parameters were used for the calculation of the precise shear capacity of each joint. In the shear tests, the maximum displacement of a mortar joint was determined at a maximum of two to four millimetres. Furthermore, no direct linear relationship between the theoretical load (wall above it) and the shear stress occurred could be detected in the analysis of the experiment, as it was previously assumed.

  20. Nanomechanical Behavior of High Gas Barrier Multilayer Thin Films.

    Science.gov (United States)

    Humood, Mohammad; Chowdhury, Shahla; Song, Yixuan; Tzeng, Ping; Grunlan, Jaime C; Polycarpou, Andreas A

    2016-05-04

    Nanoindentation and nanoscratch experiments were performed on thin multilayer films manufactured using the layer-by-layer (LbL) assembly technique. These films are known to exhibit high gas barrier, but little is known about their durability, which is an important feature for various packaging applications (e.g., food and electronics). Films were prepared from bilayer and quadlayer sequences, with varying thickness and composition. In an effort to evaluate multilayer thin film surface and mechanical properties, and their resistance to failure and wear, a comprehensive range of experiments were conducted: low and high load indentation, low and high load scratch. Some of the thin films were found to have exceptional mechanical behavior and exhibit excellent scratch resistance. Specifically, nanobrick wall structures, comprising montmorillonite (MMT) clay and polyethylenimine (PEI) bilayers, are the most durable coatings. PEI/MMT films exhibit high hardness, large elastic modulus, high elastic recovery, low friction, low scratch depth, and a smooth surface. When combined with the low oxygen permeability and high optical transmission of these thin films, these excellent mechanical properties make them good candidates for hard coating surface-sensitive substrates, where polymers are required to sustain long-term surface aesthetics and quality.

  1. Shear-thickening behavior of Fe-ZSM5 zeolite slurry and its removal with alumina/boehmites

    Science.gov (United States)

    Liu, Xiao-guang; Li, Yan; Xue, Wen-dong; Sun, Jia-lin; Tang, Qian

    2018-06-01

    A cryogenic scanning electron microscopy (cryo-SEM) technique was used to explore the shear-thickening behavior of Fe-ZSM5 zeolite pastes and to discover its underlying mechanism. Bare Fe-ZSM5 zeolite samples were found to contain agglomerations, which may break the flow of the pastes and cause shear-thickening behaviors. However, the shear-thickening behaviors can be eliminated by the addition of halloysite and various boehmites because of improved particle packing. Furthermore, compared with pure Fe-ZSM5 zeolite samples and its composite samples with halloysite, the samples with boehmite (Pural SB or Disperal) additions exhibited network structures in their cryo-SEM images; these structures could facilitate the storage and release of flow water, smooth paste flow, and avoid shear-thickening. By contrast, another boehmite (Versal 250) formed agglomerations rather than network structures after being added to the Fe-ZSM5 zeolite paste and resulted in shear-thickening behavior. Consequently, the results suggest that these network structures play key roles in eliminating the shear-thickening behavior.

  2. Cooling of a microchannel with thin evaporating liquid film sheared by dry gas flow

    Science.gov (United States)

    Kabova, Yu O.; Kuznetsov, V. V.

    2017-11-01

    A joint motion of thin liquid film and dry gas in a microchannel is investigated numerically at different values of initial concentration of the liquid vapor in the gas phase, taking into account the evaporation process. Major factors affecting the temperature distribution in the liquid and the gas phases are as follows: transfer of heat by liquid and gas flows, heat loses due to evaporation, diffusion heat exchange. Comparisons of the numerical results for the case of the dry gas and for the case of equilibrium concentration of vapor in the gas have been carried out. It is shown that use of dry gas enhances the heat dissipation from the heater. It is found out that not only intense evaporation occurs near the heating areas, but also in both cases vapor condensation takes place below the heater in streamwise direction.

  3. Brownian dynamics simulations of an order-disorder transition in sheared sterically stabilized colloidal suspensions

    International Nuclear Information System (INIS)

    Rigos, A.A.; Wilemski, G.

    1992-01-01

    The shear thinning behavior of a sterically stabilized nonaqueous colloidal suspension was investigated using nonequilibrium Brownian dynamics simulations of systems with 108 and 256 particles. At a volume fraction of 0.4, the suspension is thixotropic: it has a reversible shear thinning transition from a disordered state to an ordered, lamellar state with triangularly packed strings of particles. The time scale for the transition is set by the free particle diffusion constant. For the smaller system, the transition occurs gradually with increasing shear rate. For the larger system, the transition is sharp and discontinuous shear thinning is found. 34 refs., 9 figs., 1 tab

  4. The Feasibility of Structural Health Monitoring Using the Fundamental Shear Horizontal Guided Wave in a Thin Aluminum Plate

    Directory of Open Access Journals (Sweden)

    Jorge Franklin Mansur Rodrigues Filho

    2017-05-01

    Full Text Available Structural health monitoring (SHM is emerging as an essential tool for constant monitoring of safety-critical engineering components. Ultrasonic guided waves stand out because of their ability to propagate over long distances and because they can offer good estimates of location, severity, and type of damage. The unique properties of the fundamental shear horizontal guided wave (SH0 mode have recently generated great interest among the SHM community. The aim of this paper is to demonstrate the feasibility of omnidirectional SH0 SHM in a thin aluminum plate using a three-transducer sparse array. Descriptions of the transducer, the finite element model, and the imaging algorithm are presented. The image localization maps show a good agreement between the simulations and experimental results. The SH0 SHM method proposed in this paper is shown to have a high resolution and to be able to locate defects within 5% of the true location. The short input signal as well the non-dispersive nature of SH0 leads to high resolution in the reconstructed images. The defect diameter estimated using the full width at half maximum was 10 mm or twice the size of the true diameter.

  5. Adjustable rheology of fumed silica dispersion in urethane prepolymers: Composition-dependent sol and gel behaviors and energy-mediated shear responses

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Zhong, E-mail: 11329038@zju.edu.cn; Song, Yihu, E-mail: s-yh0411@zju.edu.cn; Wang, Xiang, E-mail: 11229036@zju.edu.cn; Zheng, Qiang, E-mail: zhengqiang@zju.edu.cn [MOE Key Laboratory of Macromolecule Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

    2015-07-15

    Variation of colloidal and interfacial interactions leads to a microstructural diversity in fumed silica dispersions exhibiting absolutely different sol- or gel-like rheological responses. In this study, fumed silicas with different surface areas (200–400 m{sup 2}/g) and surface characteristics (hydrophilic or hydrophobic) are dispersed into moisture-cured polyurethane. The microstructures investigated using transmission electron microscope are associated perfectly with three different rheological behaviors: (i) Sols with well-dispersed silica aggregates, (ii) weak gels with agglomerate-linked networks, and (iii) strong gels with concentrated networks of large agglomerates. Though sols and gels are well distinguished by shear thickening or sustained thinning response through steady shear flow test, it is interesting that the sols and weak gels exhibit a uniform modulus plateau-softening-hardening-softening response with increasing dynamic strain at frequency 10 rad s{sup −1} while the strong gels show a sustained softening beyond the linear regime. Furthermore, the onset of softening and hardening can be normalized: The two softening are isoenergetic at mechanical energies of 0.3 J m{sup −3} and 10 kJ m{sup −3}. On the other hand, the hardening is initiated by a critical strain of 60%. The mechanisms involved in the generation of the sol- and the gel-like dispersions and their structural evolutions during shear are thoroughly clarified in relation to the polyols, the characteristic and content of silica and the curing catalysts.

  6. Unified model to predict flexural shear behavior of externally bonded RC beams

    International Nuclear Information System (INIS)

    Colotti, V.; Spadea, G.; Swamy, R.N.

    2006-01-01

    Structural strengthening with externally bonded reinforcement is now recognized as a cost-effective, structurally sound and practically efficient method of rehabilitating deteriorating and damaged reinforced concrete beams. There is now an urgent need to develop a sound engineering basis which can predict the failure loads of all such strengthened beams in a reliable and consistent manner. Existing models to predict the behavior at ultimate of strengthened beams suffer from many limitations and weaknesses. This paper presents a unified global model, based on the Strut-and-Tie approach, to predict the failure loads of reinforced concrete beams strengthened for flexure and/or shear. This structural model is based on rational engineering principles, considers all the possible failure modes, and incorporates the load transfer mechanism bond to reflect the debonding phenomena which has a dominant influence on the failure process of plated beams. The model is validated against about 200 strengthened beam test reported in the literature and failing in flexure and/or shear, involving a large number of structural variables and steel, carbon and glass fiber reinforced polymer laminates as reinforcing medium. (author)

  7. Effect of Vertically Propagating Shear Waves on Seismic Behavior of Circular Tunnels

    Directory of Open Access Journals (Sweden)

    Tohid Akhlaghi

    2014-01-01

    Full Text Available Seismic design loads for tunnels are characterized in terms of the deformations imposed on the structure by surrounding ground. The free-field ground deformations due to a seismic event are estimated, and the tunnel is designed to accommodate these deformations. Vertically propagating shear waves are the predominant form of earthquake loading that causes the ovaling deformations of circular tunnels to develop, resulting in a distortion of the cross sectional shape of the tunnel lining. In this paper, seismic behavior of circular tunnels has been investigated due to propagation of shear waves in the vertical direction using quasi-static analytical approaches as well as numerical methods. Analytical approaches are based on the closed-form solutions which compute the forces in the lining due to equivalent static ovaling deformations, while the numerical method carries out dynamic, nonlinear soil-structure interaction analysis. Based on comparisons made, the accuracy and reliability of the analytical solutions are evaluated and discussed. The results show that the axial forces determined using the analytical approaches are in acceptable agreement with numerical analysis results, while the computed bending moments are less comparable and show significant discrepancies. The differences between the analytical approaches are also investigated and addressed.

  8. Behavior of Shear Link of WF Section with Diagonal Web Stiffener of Eccentrically Braced Frame (EBF of Steel Structure

    Directory of Open Access Journals (Sweden)

    Yurisman

    2010-11-01

    Full Text Available This paper presents results of numerical and experimental study of shear link behavior, utilizing diagonal stiffener on web of steel profile to increase shear link performance in an eccentric braced frame (EBF of a steel structure system. The specimen is to examine the behavior of shear link by using diagonal stiffener on web part under static monotonic and cyclic load. The cyclic loading pattern conducted in the experiment is adjusted according to AISC loading standards 2005. Analysis was carried out using non-linear finite element method using MSC/NASTRAN software. Link was modeled as CQUAD shell element. Along the boundary of the loading area the nodal are constraint to produce only one direction loading. The length of the link in this analysis is 400mm of the steel profile of WF 200.100. Important parameters considered to effect significantly to the performance of shear link have been analyzed, namely flange and web thicknesses, , thickness and length of web stiffener, thickness of diagonal stiffener and geometric of diagonal stiffener. The behavior of shear link with diagonal web stiffener was compared with the behavior of standard link designed based on AISC 2005 criteria. Analysis results show that diagonal web stiffener is capable to increase shear link performance in terms of stiffness, strength and energy dissipation in supporting lateral load. However, differences in displacement ductility’s between shear links with diagonal stiffener and shear links based on AISC standards have not shown to be significant. Analysis results also show thickness of diagonal stiffener and geometric model of stiffener to have a significant influence on the performance of shear links. To perform validation of the numerical study, the research is followed by experimental work conducted in Structural Mechanic Laboratory Center for Industrial Engineering ITB. The Structures and Mechanics Lab rotary PAU-ITB. The experiments were carried out using three test

  9. Asymptotic behavior of local dipolar fields in thin films

    Energy Technology Data Exchange (ETDEWEB)

    Bowden, G.J., E-mail: gjb@phys.soton.ac.uk [School of Physics and Astronomy, University of Southampton, SO17 1BJ (United Kingdom); Stenning, G.B.G., E-mail: Gerrit.vanderlaan@diamond.ac.uk [Magnetic Spectroscopy Group, Diamond Light Source, Didcot OX11 0DE (United Kingdom); Laan, G. van der, E-mail: gavin.stenning@stfc.ac.uk [ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Didcot OX11 0QX (United Kingdom)

    2016-10-15

    A simple method, based on layer by layer direct summation, is used to determine the local dipolar fields in uniformly magnetized thin films. The results show that the dipolar constants converge ~1/m where the number of spins in a square film is given by (2m+1){sup 2}. Dipolar field results for sc, bcc, fcc, and hexagonal lattices are presented and discussed. The results can be used to calculate local dipolar fields in films with either ferromagnetic, antiferromagnetic, spiral, exponential decay behavior, provided the magnetic order only changes normal to the film. Differences between the atomistic (local fields) and macroscopic fields (Maxwellian) are also examined. For the latter, the macro B-field inside the film is uniform and falls to zero sharply outside, in accord with Maxwell boundary conditions. In contrast, the local field for the atomistic point dipole model is highly non-linear inside and falls to zero at about three lattice spacing outside the film. Finally, it is argued that the continuum field B (used by the micromagnetic community) and the local field B{sub loc}(r) (used by the FMR community) will lead to differing values for the overall demagnetization energy. - Highlights: • Point-dipolar fields in uniformly magnetized thin films are characterized by just three numbers. • Maxwell's boundary condition is partially violated in the point-dipole approximation. • Asymptotic values of point dipolar fields in circular monolayers scale as π/r.

  10. A thin rivulet or ridge subject to a uniform transverse shear stress at its free surface due to an external airflow

    KAUST Repository

    Sullivan, J. M.

    2012-01-01

    We use the lubrication approximation to analyze three closely related problems involving a thin rivulet or ridge (i.e., a two-dimensional droplet) of fluid subject to a prescribed uniform transverse shear stress at its free surface due to an external airflow, namely a rivulet draining under gravity down a vertical substrate, a rivulet driven by a longitudinal shear stress at its free surface, and a ridge on a horizontal substrate, and find qualitatively similar behaviour for all three problems. We show that, in agreement with previous numerical studies, the free surface profile of an equilibrium rivulet/ridge with pinned contact lines is skewed as the shear stress is increased from zero, and that there is a maximum value of the shear stress beyond which no solution with prescribed semi-width is possible. In practice, one or both of the contact lines will de-pin before this maximum value of the shear stress is reached, and so we consider situations in which the rivulet/ridge de-pins at one or both contact lines. In the case of de-pinning only at the advancing contact line, the rivulet/ridge is flattened and widened as the shear stress is increased from its critical value, and there is a second maximum value of the shear stress beyond which no solution with a prescribed advancing contact angle is possible. In contrast, in the case of de-pinning only at the receding contact line, the rivulet/ridge is thickened and narrowed as the shear stress is increased from its critical value, and there is a solution with a prescribed receding contact angle for all values of the shear stress. In general, in the case of de-pinning at both contact lines there is a critical "yield" value of the shear stress beyond which no equilibrium solution is possible and the rivulet/ridge will evolve unsteadily. In the Appendix, we show that an equilibrium rivulet/ridge with prescribed flux/area is quasi-statically stable to two-dimensional perturbations. © 2012 American Institute of Physics.

  11. Optical emission, vibrational feature, and shear-thinning aspect of Tb3+-doped Gd2O3 nanoparticle-based novel ferrofluids irradiated by gamma photons

    Science.gov (United States)

    Paul, Nibedita; Hazarika, Samiran; Saha, Abhijit; Mohanta, Dambarudhar

    2013-10-01

    The present work reports on the spectroscopic and rheological properties of un-exposed and gamma (γ-) irradiated rare earth (RE) oxide nanoparticle-based ferrofluids (FFs). The FFs were produced by dispersing surfactant coated terbium (Tb3+)-doped gadolinium oxide (Gd2O3) nanoparticles in the ethanol medium and later on they were subjected to energetic γ-irradiation (1.25 MeV) at select doses (97 Gy and 2.635 kGy). The synthesized RE oxide nanoparticles were of ˜7 nm size and having a cubic crystal structure, as predicted from transmission electron microscopy and x-ray diffraction studies. Fourier transformed infra-red (FT-IR) spectra showed an adequate blue shift of the Gd-O vibrational stretching mode from a wavenumber value of ˜558 cm-1, for the un-irradiated sample to a value of ˜540 cm-1 corresponding to the irradiated sample (2.635 kGy). In contrast, photoluminescence spectra have revealed modification of defect states along with Tb3+ assisted radiative transitions. The rheology measurements have illustrated unusual shear thinning behavior of the FFs, with an apparently improved power index (s) value from 0.34 to 0.50, obtained for increasing γ-dose cases. The variation of the decay parameter with irradiation dose, as predicted from the nature of apparent viscosity curves, is attributed to the defect formation, role of impurity ions (Tb3+), and weakening of inter nanoparticle bonding. The unusual properties of the novel RE oxide based FFs may find scope in sealing and shielding elements in the radiation environment including accelerator and other related zones.

  12. Molecular dynamics simulations indicate that deoxyhemoglobin, oxyhemoglobin, carboxyhemoglobin, and glycated hemoglobin under compression and shear exhibit an anisotropic mechanical behavior.

    Science.gov (United States)

    Yesudasan, Sumith; Wang, Xianqiao; Averett, Rodney D

    2018-05-01

    We developed a new mechanical model for determining the compression and shear mechanical behavior of four different hemoglobin structures. Previous studies on hemoglobin structures have focused primarily on overall mechanical behavior; however, this study investigates the mechanical behavior of hemoglobin, a major constituent of red blood cells, using steered molecular dynamics (SMD) simulations to obtain anisotropic mechanical behavior under compression and shear loading conditions. Four different configurations of hemoglobin molecules were considered: deoxyhemoglobin (deoxyHb), oxyhemoglobin (HbO 2 ), carboxyhemoglobin (HbCO), and glycated hemoglobin (HbA 1C ). The SMD simulations were performed on the hemoglobin variants to estimate their unidirectional stiffness and shear stiffness. Although hemoglobin is structurally denoted as a globular protein due to its spherical shape and secondary structure, our simulation results show a significant variation in the mechanical strength in different directions (anisotropy) and also a strength variation among the four different hemoglobin configurations studied. The glycated hemoglobin molecule possesses an overall higher compressive mechanical stiffness and shear stiffness when compared to deoxyhemoglobin, oxyhemoglobin, and carboxyhemoglobin molecules. Further results from the models indicate that the hemoglobin structures studied possess a soft outer shell and a stiff core based on stiffness.

  13. Adhesion behavior of endothelial progenitor cells to endothelial cells in simple shear flow

    Science.gov (United States)

    Gong, Xiao-Bo; Li, Yu-Qing; Gao, Quan-Chao; Cheng, Bin-Bin; Shen, Bao-Rong; Yan, Zhi-Qiang; Jiang, Zong-Lai

    2011-12-01

    The adhesion of endothelial progenitor cells (EPCs) on endothelial cells (ECs) is one of the critical physiological processes for the regenesis of vascular vessels and the prevention of serious cardiovascular diseases. Here, the rolling and adhesion behavior of EPCs on ECs was studied numerically. A two-dimensional numerical model was developed based on the immersed boundary method for simulating the rolling and adhesion of cells in a channel flow. The binding force arising from the catch bond of a receptor and ligand pair was modeled with stochastic Monte Carlo method and Hookean spring model. The effect of tumor necrosis factor alpha (TNF- α) on the expression of the number of adhesion molecules in ECs was analyzed experimentally. A flow chamber system with CCD camera was set up to observe the top view of the rolling of EPCs on the substrate cultivated with ECs. Numerical results prove that the adhesion of EPC on ECs is closely related to membrane stiffness of the cell and shear rate of the flow. It also suggests that the adhesion force between EPC and EC by P-selectin glycoprotein ligand-1 only is not strong enough to bond the cell onto vessel walls unless contributions of other catch bond are considered. Experimental results demonstrate that TNF- α enhanced the expressions of VCAM, ICAM, P-selectin and E-selectin in ECs, which supports the numerical results that the rolling velocity of EPC on TNF- α treated EC substrate decreases obviously compared with its velocity on the untreated one. It is found that because the adhesion is affected by both the rolling velocity and the deformability of the cell, an optimal stiffness of EPC may exist at a given shear rate of flow for achieving maximum adhesion rates.

  14. 2010 Thin Film & Small Scale Mechanical Behavior Gordon Research Conference

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Thomas Balk

    2010-07-30

    Over the past decades, it has been well established that the mechanical behavior of materials changes when they are confined geometrically at least in one dimension to small scale. It is the aim of the 2010 Gordon Conference on 'Thin Film and Small Scale Mechanical Behavior' to discuss cutting-edge research on elastic, plastic and time-dependent deformation as well as degradation mechanisms like fracture, fatigue and wear at small scales. As in the past, the conference will benefit from contributions from fundamental studies of physical mechanisms linked to material science and engineering reaching towards application in modern applications ranging from optical and microelectronic devices and nano- or micro-electrical mechanical systems to devices for energy production and storage. The conference will feature entirely new testing methodologies and in situ measurements as well as recent progress in atomistic and micromechanical modeling. Particularly, emerging topics in the area of energy conversion and storage, such as material for batteries will be highlighted. The study of small-scale mechanical phenomena in systems related to energy production, conversion or storage offer an enticing opportunity to materials scientists, who can provide new insight and investigate these phenomena with methods that have not previously been exploited.

  15. An experimental study on the flexural and shear behavior of steel plate concrete—reinforced concrete connected structures

    International Nuclear Information System (INIS)

    Hwang, K.M.; Lee, K.J.; Yang, H.J.; Kim, W.K.

    2013-01-01

    Highlights: ► This paper confirmed the structural behavior of the connection plane between a RC and a SC member. ► Out-of-plane flexural load tests verified the appropriateness of the ductile non-contact splice length. ► The test results for the in-plane shear load showed the needlessness of horizontal bars in the SC member. ► In order to consider dynamic loads such as earthquakes, cyclic loading tests were carried out. ► Numerical analysis was carried out to verify test results and its results was compared with them. -- Abstract: This paper describes an experimental study on the structural behavior of the joint plane between a RC (reinforced concrete) wall and a SC (steel plate concrete) wall under out-of-plane flexural loads and in-plane shear loads. L- and I-shaped test specimens were produced to efficiently assess the flexural and shear behavior of the structures. In order to consider dynamic loads such as earthquakes, cyclic loading tests were carried out. The out-of-plane flexural test conducted on the short development length L-shaped specimen with a non-contact splice length exhibited a ductile failure mode that surpassed the nominal strength, verifying the validity of the splice length used in its design. The in-plane shear test was conducted on two I-shaped specimens varying the compositional presence of horizontal bars in the SC member. The test results showed that the capacity of the specimens was more than their nominal strength regardless of the compositional presence of horizontal bars. The shear friction tests of the RC–SC member connection conducted on the other L-shaped specimen caused the failure of the SC member and verified a shear resistance of at least 85.5% compared to the theoretical value

  16. On the appearance of vorticity and gradient shear bands in wormlike micellar solutions of different CPCl/salt systems

    Energy Technology Data Exchange (ETDEWEB)

    Mütze, Annekathrin, E-mail: muetzea@ethz.ch; Heunemann, Peggy; Fischer, Peter [ETH Zürich, Institute of Food, Nutrition and Health, Schmelzbergstrasse 9, 8092 Zürich (Switzerland)

    2014-11-01

    Wormlike micellar salt/surfactant solutions (X-salicylate, cetylpyridinium chloride) are studied with respect to the applied shear stress, concentration, temperature, and composition of the counterions (X = lithium, sodium, potassium, magnesium, and calcium) of the salicylate salt solute to determine vorticity and gradient shear bands. A combination of rheological measurements, laser technique, video analysis, and rheo-small-angle neutron scattering allow for a detailed exploration of number and types of shear bands. Typical flow curves of the solutions show Newtonian, shear-thinning, and shear-thickening flow behavior. In the shear-thickening regime, the solutions show vorticity and gradient shear bands simultaneously, in which vorticity shear bands dominate the visual effect, while gradient shear bands always coexist and predominate the rheological response. It is shown that gradient shear bands change their phases (turbid, clear) with the same frequency as the shear rate oscillates, whereas vorticity shear bands change their phases with half the frequency of the shear rate. Furthermore, we show that with increasing molecular mass of the counterions the number of gradient shear bands increases, while the number of vorticity shear bands remains constant. The variation of temperature, shear stress, concentration, and counterions results in a predictable change in the rheological behavior and therefore allows adjustment of the number of vorticity shear bands in the shear band regime.

  17. Experimental Validation of the Transverse Shear Behavior of a Nomex Core for Sandwich Panels

    Science.gov (United States)

    Farooqi, M. I.; Nasir, M. A.; Ali, H. M.; Ali, Y.

    2017-05-01

    This work deals with determination of the transverse shear moduli of a Nomex® honeycomb core of sandwich panels. Their out-of-plane shear characteristics depend on the transverse shear moduli of the honeycomb core. These moduli were determined experimentally, numerically, and analytically. Numerical simulations were performed by using a unit cell model and three analytical approaches. Analytical calculations showed that two of the approaches provided reasonable predictions for the transverse shear modulus as compared with experimental results. However, the approach based upon the classical lamination theory showed large deviations from experimental data. Numerical simulations also showed a trend similar to that resulting from the analytical models.

  18. Failure mode and fracture behavior evaluation of pipes with local wall thinning subjected to bending load

    International Nuclear Information System (INIS)

    Ahn, Seok Hwan; Nam, Ki Woo; Kim, Seon Jin; Kim, Jin Hwan; Kim, Hyun Soo; Do, Jae Yoon

    2003-01-01

    Fracture behaviors of pipes with local wall thinning are very important for the integrity of nuclear power plant. In pipes of energy plants, sometimes, the local wall thinning may result from severe Erosion-Corrosion (E/C) damage. However, the effects of local wall thinning on strength and fracture behaviors of piping system were not well studied. In this paper, the monotonic bending tests were performed of full-scale carbon steel pipes with local wall thinning. A monotonic bending load was applied to straight pipe specimens by four-point loading at ambient temperature without internal pressure. From the tests, fracture behaviors and fracture strength of locally thinned pipe were manifested systematically. The observed failure modes were divided into four types; ovalization, crack initiation/growth after ovalization, local buckling and crack initiating/growth after local buckling. Also, the strength and the allowable limit of piping system with local wall thinning were evaluated

  19. Resistivity behavior of optimized PbTiO3 thin films prepared by spin coating method

    Science.gov (United States)

    Nurbaya, Z.; Wahid, M. H.; Rozana, M. D.; Alrokayan, S. A. H.; Khan, H. A.; Rusop, M.

    2018-05-01

    Th is study presents the resistivity behavior of PbTiO3 thin films which were prepared towards metal-insulator-metal capacitor device fabrication. The PbTiO3 thin films were prepared through sol-gel spin coating method that involved various deposition parameters that is (1) different molar concentration of PbTiO3 solutions, (2) various additional PbAc-content in PbTiO3 solutions, and (3) various annealing temperature on PbTiO3 thin films. Hence, an electrical measurement of current versus voltage was done to determine the resistivity behavior of PbTiO3 thin films.

  20. Thermoluminescent behavior of diamond thin films exposed to ultraviolet radiation

    International Nuclear Information System (INIS)

    Barboza F, M.; Gastelum, S.; Melendrez, R.; Chernov, V.; Bernal, R.; Cruz V, C.; Brown, F.

    2002-01-01

    In this work the thermoluminescent properties of diamond thin films are discussed which are grown up through the chemical vapor method exposed to ultraviolet radiation of 200-280 nm. The films with thickness 3, 6, 9, 12, 180 and 500 microns were grown up using a precursor gas formed of H 2 -CH 4 -CO excited through microwave energy or hot filament.The structure and morphology of the films were examined through scanning electron microscopy, indicating the formation of different diamond polycrystal structures which depend on the type of heating of the precursor gas used as well as the film dimensions. In general, the brilliance curve depends on the sample and the wavelength of the irradiation ultraviolet light, however it presents clearly thermoluminescence bands in 148, 160, 272, 304, 320 and 324 C degrees. The maximum of the thermoluminescence efficiency is obtained for the case of sample exposure with light of 214 nm. The sample of 500 microns is what exhibits greater thermoluminescent efficiency of those studied samples. The thermoluminescent behavior in function of radiation dose presents regions of linearity and supra linearity for higher and small doses respectively. The disappearance of the thermoluminescent signal depends on the characteristics of the film and it can reach until a 30 % of loss before to reach the stability. (Author)

  1. Dynamic behavior of tuning fork shear-force structures in a SNOM system

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Fengli [Department of Engineering Mechanics, AML, CNMM, Tsinghua University, Beijing 100084 (China); Li, Xide, E-mail: lixide@tsinghua.edu.cn [Department of Engineering Mechanics, AML, CNMM, Tsinghua University, Beijing 100084 (China); Wang, Jia [State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instruments, Tsinghua University, Beijing 100084 (China); Fu, Yu [Temasek Laboratories, Nanyang Technological University, 50 Nanyang Drive, 637553 (Singapore)

    2014-07-01

    Piezoelectric tuning fork shear-force structures are widely used as a distance control unit in a scanning near-field optical microscopy. However, the complex dynamic behavior among the micro-tuning forks (TFs), optical fiber probes, and the probe–surface interactions is still a crucial issue to achieve high-resolution imaging or near-field interaction inspections. Based on nonlinear beam tension-bending vibration theory, vibration equations in both longitudinal and lateral directions have been established when the TF structure and the optical fiber are treated as deformable structures. The relationship of the probe–surface interaction induced by Van der Waals force has been analyzed and the corresponding numerical results used to describe the vibrational behavior of the probe approaching the sample surface are obtained. Meanwhile, the viscous resistance of the liquid film on the sample surface has also been investigated using linear beam-bending vibration theory. Experiments testing the interaction between the probe and the water film on a single crystal silicon wafer have been carried out and the viscous resistance of the water film was estimated using the established equations. Finally, to use the TF-probe structure as a force sensor, the relation between the dynamic response of the TF-probe system and an external force on the probe tip was obtained. - Highlights: • Nonlinear vibration equation is established for a deformable tuning fork probe assembly. • Probe–sample interactions induced by Van der Waals force and viscous resistance are investigated. • The viscous resistance between the probe and the water film is estimated using testing results.

  2. Effects of the cooling rate on the shear behavior of continuous glass fiber/impact polypropylene composites (GF-IPP)

    KAUST Repository

    Wafai, Husam

    2016-09-20

    Fiber-reinforced composites with improved dissipation of energy during impact loading have recently been developed based on a polypropylene copolymer commonly called impact polypropylene (IPP). Composites made of IPP reinforced with glass fibers (GF) are particularly attractive to the automotive industry due to their low cost and good impact resistance. In such composites, the cooling rate varies depending on processing techniques and manufacturing choices. Here, we study the effects of the cooling rate of GF-IPP composites on shear behavior, which is critical in impact applications, using [±45]s monotonic and cyclic (load/unload) tensile specimens. The specimens were manufactured under a wide range of cooling rates (3 °C/min, 22 °C/min, 500–1000 °C/min). Mainly dominated by the properties of the matrix, the global shear behavior of GF-IPP composites differed considerably with respect to the cooling rate. However, the performance of the fiber-matrix interface (chemically modified) appeared to be unaffected by the range of cooling rates used in this study. We found that the cooling rate has a minor effect on the rate of damage accumulation, while it strongly modifies the shear-activated rate-dependant viscoelastic behavior. © 2016 Elsevier Ltd

  3. Dynamic behavior of dual cross-linked nanoparticle networks under oscillatory shear

    International Nuclear Information System (INIS)

    Iyer, Balaji V S; Yashin, Victor V; Balazs, Anna C

    2014-01-01

    Via computer simulations, we investigate the linear and nonlinear viscoelastic response of polymer grafted nanoparticle networks subject to oscillatory shear at different amplitudes and frequencies. The individual nanoparticles are composed of a rigid spherical core and a corona of grafted polymers that encompass reactive end groups. With the overlap of the coronas on adjacent particles, the reactive end groups form permanent or labile bonds, and thus form a ‘dual cross-linked’ network. The existing labile bonds between particles can break and reform depending on the bond rupture rate, extent of deformation and the frequency of oscillation. We study how the viscoelastic behavior of the material depends on the energy of the labile bonds and identify the network characteristics that give rise to the observed viscoelastic response. We observe that with an increase in labile bond energy, the storage modulus increases while the loss modulus shows a more complex response depending on the labile bond energy. Specifically, in the case of the samples with the weaker labile bonds, the loss modulus increases monotonically, while for the samples with the stronger labile bonds, the loss modulus exhibits a minimum with an increase in frequency. We show that an increase in the storage modulus corresponds to an enhancement in the average number of bonds in the samples and the characteristics of the loss modulus depend on both the bond kinetics and the mobility of the particles in the network. Furthermore, we determine that the effective contribution of the bonds to the storage modulus decreases with increase in strain amplitude. In particular, while bond formation at small amplitude drives an increase in storage modulus, at large amplitudes it promotes clustering and formation of voids leading to strain softening. Our simulations provide a mesoscopic picture of how the nature of labile bonds affects the performance of cross-linked polymer-grafted nanoparticle networks. (paper)

  4. Isotropic-nematic transition in shear flow: State selection, coexistence, phase transitions, and critical behavior

    Science.gov (United States)

    Olmsted, Peter D.; Goldbart, Paul M.

    1992-10-01

    Macroscopic fluid motion can have dramatic consequences near the isotropic-nematic transition in fluids of nematogens. We explore some of these consequences using both deterministic and stochastic descriptions involving coupled hydrodynamic equations of motion for the nematic order parameter and fluid velocity fields. By analyzing the deterministic equations of motion we identify the locally stable states of homogeneous nematic order and strain rate, thus determining the homogeneous nonequilibrium steady states which the fluid may adopt. By examining inhomogeneous steady states we construct the analog of a first-order phase boundary, i.e., a line in the nonequilibrium phase diagram spanned by temperature and applied stress, at which nonequilibrium states may coexist, and which terminates in a nonequilibrium analog of a critical point. From an analysis of the nematic order-parameter discontinuity across the coexistence line, along with properties of the interface between homogeneous states, we extract the analog of classical equilibrium critical behavior near the nonequilibrium critical point. We develop a theory of fluctuations about biaxial nonequilibrium steady states by augmenting the deterministic description with noise terms, to simulate the effect of thermal fluctuations. We use this description to discuss the scattering of polarized light by order-parameter fluctuations near the nonequilibrium critical point and also in weak shear flow near the equilibrium phase transition. We find that fluids of nematogens near an appropriate temperature and strain rate exhibit the analog of critical opalescence, the intensity of which is sensitive to the polarizations of the incident and scattered light, and to the precise form of the critical mode.

  5. Derivation of energy-based base shear force coefficient considering hysteretic behavior and P-delta effects

    Science.gov (United States)

    Ucar, Taner; Merter, Onur

    2018-01-01

    A modified energy-balance equation accounting for P-delta effects and hysteretic behavior of reinforced concrete members is derived. Reduced hysteretic properties of structural components due to combined stiffness and strength degradation and pinching effects, and hysteretic damping are taken into account in a simple manner by utilizing plastic energy and seismic input energy modification factors. Having a pre-selected yield mechanism, energy balance of structure in inelastic range is considered. P-delta effects are included in derived equation by adding the external work of gravity loads to the work of equivalent inertia forces and equating the total external work to the modified plastic energy. Earthquake energy input to multi degree of freedom (MDOF) system is approximated by using the modal energy-decomposition. Energy-based base shear coefficients are verified by means of both pushover analysis and nonlinear time history (NLTH) analysis of several RC frames having different number of stories. NLTH analyses of frames are performed by using the time histories of ten scaled ground motions compatible with elastic design acceleration spectrum and fulfilling duration/amplitude related requirements of Turkish Seismic Design Code. The observed correlation between energy-based base shear force coefficients and the average base shear force coefficients of NLTH analyses provides a reasonable confidence in estimation of nonlinear base shear force capacity of frames by using the derived equation.

  6. Evaluation of Nonlinear Behavior of Dual Steel Frame-Shear Wall System by a Group of Real Earthquakes

    Directory of Open Access Journals (Sweden)

    Reza Bemanian

    2016-03-01

    Full Text Available Dual system of steel moment frame and steel plate shear wall has many advantages in comparison to the other systems. Since the last four decades the dual system has been used more frequently in new and existing structures. the steel shear wall has many advantages such as high ductility, strength, stiffness and it has light weight, it consequent reduce lateral forces and time efficiency in contracture procedure. The aim of this study is to evaluate the seismic performance of the dual steel frame steel plate shear wall system in comparison with the moment resisting frame using nonlinear dynamic analysis. A dual System of Steel Moment frame and steel Plate shear walls system and a moment resisting frame is chosen a frame of four stories building were designed by used existing code. The height of each floor is 3.5 m. Seismic behavior of frame evaluate using nonlinear dynamic analysis. For this purpose a set of seven earthquake ground motions were appropriately selected and applied to the systems. Interstory drift ratio, input energy, distribution frames responses in height were compared for the systems under two different hazard level of ground motion and the results were analyzed.

  7. Creep Behavior in Interlaminar Shear of a SiC/SiC Ceramic Composite with a Self-healing Matrix

    Science.gov (United States)

    Ruggles-Wrenn, M. B.; Pope, M. T.

    2014-02-01

    Creep behavior in interlaminar shear of a non-oxide ceramic composite with a multilayered matrix was investigated at 1,200 °C in laboratory air and in steam environment. The composite was produced via chemical vapor infiltration (CVI). The composite had an oxidation inhibited matrix, which consisted of alternating layers of silicon carbide and boron carbide and was reinforced with laminated Hi-Nicalon™ fibers woven in a five-harness-satin weave. Fiber preforms had pyrolytic carbon fiber coating with boron carbide overlay applied. The interlaminar shear properties were measured. The creep behavior was examined for interlaminar shear stresses in the 16-22 MPa range. Primary and secondary creep regimes were observed in all tests conducted in air and in steam. In air and in steam, creep run-out defined as 100 h at creep stress was achieved at 16 MPa. Larger creep strains were accumulated in steam. However, creep strain rates and creep lifetimes were only moderately affected by the presence of steam. The retained properties of all specimens that achieved run-out were characterized. Composite microstructure, as well as damage and failure mechanisms were investigated.

  8. Composite Behavior of a Novel Insulated Concrete Sandwich Wall Panel Reinforced with GFRP Shear Grids: Effects of Insulation Types.

    Science.gov (United States)

    Kim, JunHee; You, Young-Chan

    2015-03-03

    A full-scale experimental program was used in this study to investigate the structural behavior of novel insulated concrete sandwich wall panels (SWPs) reinforced with grid-type glass-fiber-reinforced polymer (GFRP) shear connectors. Two kinds of insulation-expanded polystyrene (EPS) and extruded polystyrene (XPS) with 100 mm thickness were incased between the two concrete wythes to meet the increasing demand for the insulation performance of building envelope. One to four GFRP shear grids were used to examine the degree of composite action of the two concrete wythes. Ten specimens of SWPs were tested under displacement control subjected to four-point concentrated loads. The test results showed that the SWPs reinforced with GFRP grids as shear connectors developed a high degree of composite action resulting in high flexural strength. The specimens with EPS foam exhibited an enhanced load-displacement behavior compared with the specimens with XPS because of the relatively stronger bond between insulation and concrete. In addition, the ultimate strength of the test results was compared to the analytical prediction with the mechanical properties of only GRFP grids. The specimens with EPS insulation presented higher strength-based composite action than the ones with XPS insulation.

  9. Effect of boundary conditions on the strength and deformability of replicas of natural fractures in welded tuff: Comparison between predicted and observed shear behavior using a graphical method

    International Nuclear Information System (INIS)

    Wibowo, J.; Amadei, B.; Sture, S.; Robertson, A.B.

    1993-09-01

    Four series of cyclic direct-shear experiments were conducted on several replicas of three natural fractures and a laboratory-developed tensile fracture of welded tuff from Yucca Mountain to test the graphical load-displacement analysis method proposed by Saeb (1989) and Amadei and Saeb (1990). Based on the results of shear tests conducted on several joint replicas under different levels of constant normal load ranging between 0.6 and 25.6 kips (2.7 and 113.9 kN), the shear behavior of joint replicas under constant normal stiffness ranging between 14.8 and 187.5 kips/in. (25.9 and 328.1 kN/cm) was predicted by using the graphical method. The predictions were compared to the results of actual shear tests conducted for the same range of constant normal stiffness. In general, a good agreement was found between the predicted and the observed shear behavior

  10. Study on the application of shear-wave elastography to thin-layered media and tubular structure: Finite-element analysis and experiment verification

    Science.gov (United States)

    Jang, Jun-keun; Kondo, Kengo; Namita, Takeshi; Yamakawa, Makoto; Shiina, Tsuyoshi

    2016-07-01

    Shear-wave elastography (SWE) enables the noninvasive and quantitative evaluation of the mechanical properties of human soft tissue. Generally, shear-wave velocity (C S) can be estimated using the time-of-flight (TOF) method. Young’s modulus is then calculated directly from the estimated C S. However, because shear waves in thin-layered media propagate as guided waves, C S cannot be accurately estimated using the conventional TOF method. Leaky Lamb dispersion analysis (LLDA) has recently been proposed to overcome this problem. In this study, we performed both experimental and finite-element (FE) analyses to evaluate the advantages of LLDA over TOF. In FE analysis, we investigated why the conventional TOF is ineffective for thin-layered media. In phantom experiments, C S results estimated using the two methods were compared for 1.5 and 2% agar plates and tube phantoms. Furthermore, it was shown that Lamb waves can be applied to tubular structures by extracting lateral waves traveling in the long axis direction of the tube using a two-dimensional window. Also, the effects of the inner radius and stiffness (or shear wavelength) of the tube on the estimation performance of LLDA were experimentally discussed. In phantom experiments, the results indicated good agreement between LLDA (plate phantoms of 2 mm thickness: 5.0 m/s for 1.5% agar and 7.2 m/s for 2% agar; tube phantoms with 2 mm thickness and 2 mm inner radius: 5.1 m/s for 1.5% agar and 7.0 m/s for 2% agar; tube phantoms with 2 mm thickness and 4 mm inner radius: 5.3 m/s for 1.5% agar and 7.3 m/s for 2% agar) and SWE measurements (bulk phantoms: 5.3 m/s ± 0.27 for 1.5% agar and 7.3 m/s ± 0.54 for 2% agar).

  11. Shear Behavior of Corrugated Steel Webs in H Shape Bridge Girders

    Directory of Open Access Journals (Sweden)

    Qi Cao

    2015-01-01

    Full Text Available In bridge engineering, girders with corrugated steel webs have shown good mechanical properties. With the promotion of composite bridge with corrugated steel webs, in particular steel-concrete composite girder bridge with corrugated steel webs, it is necessary to study the shear performance and buckling of the corrugated webs. In this research, by conducting experiment incorporated with finite element analysis, the stability of H shape beam welded with corrugated webs was tested and three failure modes were observed. Structural data including load-deflection, load-strain, and shear capacity of tested beam specimens were collected and compared with FEM analytical results by ANSYS software. The effects of web thickness, corrugation, and stiffening on shear capacity of corrugated webs were further discussed.

  12. Viscoelasticity and nonlinear simple shear flow behavior of an entangled asymmetric exact comb polymer solution

    KAUST Repository

    Snijkers, F.; Kirkwood, K. M.; Vlassopoulos, D.; Leal, L. G.; Nikopoulou, A.; Hadjichristidis, Nikolaos; Coppola, S.

    2016-01-01

    We report upon the characterization of the steady-state shear stresses and first normal stress differences as a function of shear rate using mechanical rheometry (both with a standard cone and plate and with a cone partitioned plate) and optical rheometry (with a flow-birefringence setup) of an entangled solution of asymmetric exact combs. The combs are polybutadienes (1,4-addition) consisting of an H-skeleton with an additional off-center branch on the backbone. We chose to investigate a solution in order to obtain reliable nonlinear shear data in overlapping dynamic regions with the two different techniques. The transient measurements obtained by cone partitioned plate indicated the appearance of overshoots in both the shear stress and the first normal stress difference during start-up shear flow. Interestingly, the overshoots in the start-up normal stress difference started to occur only at rates above the inverse stretch time of the backbone, when the stretch time of the backbone was estimated in analogy with linear chains including the effects of dynamic dilution of the branches but neglecting the effects of branch point friction, in excellent agreement with the situation for linear polymers. Flow-birefringence measurements were performed in a Couette geometry, and the extracted steady-state shear and first normal stress differences were found to agree well with the mechanical data, but were limited to relatively low rates below the inverse stretch time of the backbone. Finally, the steady-state properties were found to be in good agreement with model predictions based on a nonlinear multimode tube model developed for linear polymers when the branches are treated as solvent.

  13. Viscoelasticity and nonlinear simple shear flow behavior of an entangled asymmetric exact comb polymer solution

    KAUST Repository

    Snijkers, F.

    2016-03-31

    We report upon the characterization of the steady-state shear stresses and first normal stress differences as a function of shear rate using mechanical rheometry (both with a standard cone and plate and with a cone partitioned plate) and optical rheometry (with a flow-birefringence setup) of an entangled solution of asymmetric exact combs. The combs are polybutadienes (1,4-addition) consisting of an H-skeleton with an additional off-center branch on the backbone. We chose to investigate a solution in order to obtain reliable nonlinear shear data in overlapping dynamic regions with the two different techniques. The transient measurements obtained by cone partitioned plate indicated the appearance of overshoots in both the shear stress and the first normal stress difference during start-up shear flow. Interestingly, the overshoots in the start-up normal stress difference started to occur only at rates above the inverse stretch time of the backbone, when the stretch time of the backbone was estimated in analogy with linear chains including the effects of dynamic dilution of the branches but neglecting the effects of branch point friction, in excellent agreement with the situation for linear polymers. Flow-birefringence measurements were performed in a Couette geometry, and the extracted steady-state shear and first normal stress differences were found to agree well with the mechanical data, but were limited to relatively low rates below the inverse stretch time of the backbone. Finally, the steady-state properties were found to be in good agreement with model predictions based on a nonlinear multimode tube model developed for linear polymers when the branches are treated as solvent.

  14. An investigation on vulnerability assessment of steel structures with thin steel shear wall through development of fragility curves

    OpenAIRE

    Mohsen Gerami; Saeed Ghaffari; Amir Mahdi Heidari Tafreshi

    2017-01-01

    Fragility curves play an important role in damage assessment of buildings. Probability of damage induction to the structure against seismic events can be investigated upon generation of afore mentioned curves. In current research 360 time history analyses have been carried out on structures of 3, 10 and 20 story height and subsequently fragility curves have been adopted. The curves are developed based on two indices of inter story drifts and equivalent strip axial strains of the shear wall. T...

  15. Investigating the crystal growth behavior of biodegradable polymer blend thin films using in situ atomic force microscopy

    CSIR Research Space (South Africa)

    Malwela, T

    2014-01-01

    Full Text Available This article reports the crystal growth behavior of biodegradable polylactide (PLA)/poly[(butylene succinate)-co-adipate] (PBSA) blend thin films using atomic force microscopy (AFM). Currently, polymer thin films have received increased research...

  16. A new model of cavern diameter based on a validated CFD study on stirring of a highly shear-thinning fluid.

    Science.gov (United States)

    Story, Anna; Jaworski, Zdzisław

    2017-01-01

    Results of numerical simulations of momentum transfer for a highly shear-thinning fluid (0.2% Carbopol) in a stirred tank equipped with a Prochem Maxflo T type impeller are presented. The simulation results were validated using LDA data and both tangential and axial force measurements in the laminar and early transitional flow range. A good agreement between the predicted and experimental results of the local fluid velocity components was found. From the predicted and experimental values of both tangential and axial forces, the power number, Po , and thrust number, Th , were also calculated. Values of the absolute relative deviations were below 4.0 and 10.5%, respectively, for Po and Th , which confirms a satisfactory agreement with experiments. An intensive mixing zone, known as cavern, was observed near the impeller. In this zone, the local values of fluid velocity, strain rate, Metzner-Otto coefficient, shear stress and intensity of energy dissipation were all characterized by strong variability. Based on the results of experimental study a new model using non-dimensional impeller force number was proposed to predict the cavern diameter. Comparative numerical simulations were also carried out for a Newtonian fluid (water) and their results were similarly well verified using LDA measurements, as well as experimental power number values.

  17. Applying the behavioral economics principle of unit price to DRO schedule thinning.

    Science.gov (United States)

    Roane, Henry S; Falcomata, Terry S; Fisher, Wayne W

    2007-01-01

    Within the context of behavioral economics, the ratio of response requirements to reinforcer magnitude is called unit price. In this investigation, we yoked increases in reinforcer magnitude with increases in intervals of differential reinforcement of other behavior (DRO) to thin DRO intervals to a terminal value.

  18. Applying the Behavioral Economics Principle of Unit Price to DRO Schedule Thinning

    Science.gov (United States)

    Roane, Henry S.; Falcomata, Terry S.; Fisher, Wayne W.

    2007-01-01

    Within the context of behavioral economics, the ratio of response requirements to reinforcer magnitude is called "unit price." In this investigation, we yoked increases in reinforcer magnitude with increases in intervals of differential reinforcement of other behavior (DRO) to thin DRO intervals to a terminal value. (Contains 1 figure.)

  19. Rheological Behavior of Tomato Fiber Suspensions Produced by High Shear and High Pressure Homogenization and Their Application in Tomato Products

    Science.gov (United States)

    Sun, Ping; Adhikari, Benu P.; Li, Dong

    2018-01-01

    This study investigated the effects of high shear and high pressure homogenization on the rheological properties (steady shear viscosity, storage and loss modulus, and deformation) and homogeneity in tomato fiber suspensions. The tomato fiber suspensions at different concentrations (0.1%–1%, w/w) were subjected to high shear and high pressure homogenization and the morphology (distribution of fiber particles), rheological properties, and color parameters of the homogenized suspensions were measured. The homogenized suspensions were significantly more uniform compared to unhomogenized suspension. The homogenized suspensions were found to better resist the deformation caused by external stress (creep behavior). The apparent viscosity and storage and loss modulus of homogenized tomato fiber suspension are comparable with those of commercial tomato ketchup even at the fiber concentration as low as 0.5% (w/w), implying the possibility of using tomato fiber as thickener. The model tomato sauce produced using tomato fiber showed desirable consistency and color. These results indicate that the application of tomato fiber in tomato-based food products would be desirable and beneficial. PMID:29743890

  20. Study of the Relation between the Resonance Behavior of Thickness Shear Mode (TSM Sensors and the Mechanical Characteristics of Biofilms

    Directory of Open Access Journals (Sweden)

    Pedro Castro

    2017-06-01

    Full Text Available This work analyzes some key aspects of the behavior of sensors based on piezoelectric Thickness Shear Mode (TSM resonators to study and monitor microbial biofilms. The operation of these sensors is based on the analysis of their resonance properties (both resonance frequency and dissipation factor that vary in contact with the analyzed sample. This work shows that different variations during the microorganism growth can be detected by the sensors and highlights which of these changes are indicative of biofilm formation. TSM sensors have been used to monitor in real time the development of Staphylococcus epidermidis and Escherichia coli biofilms, formed on the gold electrode of the quartz crystal resonators, without any coating. Strains with different ability to produce biofilm have been tested. It was shown that, once a first homogeneous adhesion of bacteria was produced on the substrate, the biofilm can be considered as a semi-infinite layer and the quartz sensor reflects only the viscoelastic properties of the region immediately adjacent to the resonator, not being sensitive to upper layers of the biofilm. The experiments allow the microrheological evaluation of the complex shear modulus (G* = G′ + jG″ of the biofilm at 5 MHz and at 15 MHz, showing that the characteristic parameter that indicates the adhesion of a biofilm for the case of S. epidermidis and E. coli, is an increase in the resonance frequency shift of the quartz crystal sensor, which is connected with an increase of the real shear modulus, related to the elasticity or stiffness of the layer. In addition both the real and the imaginary shear modulus are frequency dependent at these high frequencies in biofilms.

  1. Thermodynamical fluctuations and critical behavior in weakly disordered YBCO thin and ultra-thin films

    International Nuclear Information System (INIS)

    Lesueur, J.; Aprili, M.; Degoy, S.; Chambonnet, D.; Keller, D.

    1996-01-01

    The specific role of disorder in the transport properties of YBCO has been investigated, using both light-ion irradiation of thin films to finely tune the amount of atomic disorder, and ultra-thin films grown to study possible dimensional effects. For weak disorder, the samples display a resistive transition typical of the mean-field paraconductive regime of a homogeneous media, well described by the Lawrence and Doniach model for layered superconductors. As the disorder increases, two effects take place. First, the c-axis coherence length becomes shorter, leading to a more anisotropic material, as shown by the excess conductivity above T c . Second, an incipient granularity is revealed, leading to a less sharper transition, which is analyzed within the random 3D XY critical model for the paracoherence transition. Two main results are derived: an experimental test of the Ginzburg criteria for the paracoherence transition, and a new fluctuation regime in nanometric grain size superconductors

  2. Effect of shear stress on electromagnetic behaviors in superconductor-ferromagnetic bilayer structure

    Science.gov (United States)

    Yong, Huadong; Zhao, Meng; Jing, Ze; Zhou, Youhe

    2014-09-01

    In this paper, the electromagnetic response and shielding behaviour of superconductor-ferromagnetic bilayer structure are studied. The magnetomechanical coupling in ferromagnetic materials is also considered. Based on the linear piezomagnetic coupling model and anti-plane shear deformation, the current density and magnetic field in superconducting strip are obtained firstly. The effect of shear stress on the magnetization of strip is discussed. Then, we consider the magnetic cloak for superconductor-ferromagnetic bilayer structure. The magnetic permeability of ferromagnetic material is obtained for perfect cloaking in uniform magnetic field with magnetomechanical coupling in ferromagnet. The simulation results show that the electromagnetic response in superconductors will change by applying the stress only to the ferromagnetic material. In addition, the performance of invisibility of structure for non-uniform field will be affected by mechanical stress. It may provide a method to achieve tunability of superconducting properties with mechanical loadings.

  3. Shear-mode Crack Initiation Behavior in the Martensitic and Bainitic Microstructures

    Directory of Open Access Journals (Sweden)

    Wada Kentaro

    2018-01-01

    Full Text Available Fully reversed torsional fatigue tests were conducted to elucidate the behaviour of shear-mode crack initiation and propagation in one martensitic and two bainitic steels. The relationship between the crack initiation site and microstructure was investigated by means of an electron backscatter diffraction (EBSD technique. From the S-N diagram, two notable results were obtained: (i the shear-mode crack was initiated on the prior austenitic grain boundary in martensitic steel, while in bainitic steels, the crack was initiated along the {110} plane; one of the slip planes of bcc metals, and (ii the torsional fatigue limit of lower bainitic steel with finer grains was 60 MPa higher than that of upper bainitic steel with coarser grains even though the hardnesses were nearly equivalent. The mechanism determining the torsional fatigue strength in these steels is discussed from the viewpoint of microstructure morphology.

  4. Cell behaviors on micro-patterned porous thin films

    International Nuclear Information System (INIS)

    Phong, Ho Quoc; Wang Shuling; Wang, Meng-Jiy

    2010-01-01

    Thin polymer films with patterned surfaces have drawn tremendous attention in manufacturing advanced electronic, mechanical devices and in biomaterials due to the advantageous properties such as mechanical strength, chemical resistance and optic transparency. The applications can be extended to the fields such as catalysts, antireflection coatings, template for inorganic growth masks, and substrates for cell culturing providing the patterned surface containing micron-sized features. Various methods have been used to fabricate polymers with micro-patterned surfaces such as photolithographic, ink-jet printing, nonsolvent, spin coating in a dry environment, self-organization, and the condensation of monodisperse water droplet on the polymer solution. The physiological functions of mature cells depend on the microenvironment/niche surrounding which can provide proper factors to regulate cell proliferation and differentiation. While designing appropriate scaffolds for tissue engineering, the microstructure is one of the most important factors to be considered. In this work, a facile single-step phase separation method was used to create micro-patterned polymer thin films with concaves or convexes with sizes ranged from 7 to 70 μm. The effects of water content, casting volume and the addition of surfactant on the distribution of pores and substrate morphology were examined. Moreover, detailed observations of fibroblast cells on the micro-patterned thin films were presented to compare and elucidate the roles of surface micro-features and chemical functionalities.

  5. Interaction between depolarization effects, interface layer, and fatigue behavior in PZT thin film capacitors

    Science.gov (United States)

    Böttger, U.; Waser, R.

    2017-07-01

    The existence of non-ferroelectric regions in ferroelectric thin films evokes depolarization effects leading to a tilt of the P(E) hysteresis loop. The analysis of measured hysteresis of lead zirconate titanate (PZT) thin films is used to determine a depolarization factor which contains quantitative information about interfacial layers as well as ferroelectrically passive zones in the bulk. The derived interfacial capacitance is smaller than that estimated from conventional extrapolation techniques. In addition, the concept of depolarization is used for the investigation of fatigue behavior of PZT thin films indicating that the mechanism of seed inhibition, which is responsible for the effect, occurs in the entire film.

  6. An investigation on vulnerability assessment of steel structures with thin steel shear wall through development of fragility curves

    Directory of Open Access Journals (Sweden)

    Mohsen Gerami

    2017-02-01

    Full Text Available Fragility curves play an important role in damage assessment of buildings. Probability of damage induction to the structure against seismic events can be investigated upon generation of afore mentioned curves. In current research 360 time history analyses have been carried out on structures of 3, 10 and 20 story height and subsequently fragility curves have been adopted. The curves are developed based on two indices of inter story drifts and equivalent strip axial strains of the shear wall. Time history analysis is carried out in Perform 3d considering 10 far field seismograms and 10 near fields. Analysis of low height structures revealed that they are more vulnerable in accelerations lower than 0.8 g in near field earthquakes because of higher mode effects. Upon the generated fragility curves it was observed that middle and high structures have more acceptable performance and lower damage levels compared to low height structures in both near and far field seismic hazards.

  7. Experimental and Numerical Analysis of the Compressive and Shear Behavior for a New Type of Self-Insulating Concrete Masonry System

    Directory of Open Access Journals (Sweden)

    Abu-Bakre Abdelmoneim Elamin Mohamad

    2016-08-01

    Full Text Available The developed study aimed at investigating the mechanical behavior of a new type of self-insulating concrete masonry unit (SCMU. A total of 12 full-grouted wall assemblages were prepared and tested for compression and shear strength. In addition, different axial stress ratios were used in shear tests. Furthermore, numerical models were developed to predict the behavior of grouted specimens using simplified micro-modeling technique. The mortar joints were modeled with zero thickness and their behavior was applied using the traction–separation model of the cohesive element. The experimental results revealed that the shear resistance increases as the level of precompression increases. A good agreement between the experimental results and numerical models was observed. It was concluded that the proposed models can be used to deduct the general behavior of grouted specimens.

  8. STICK AND SLIP BEHAVIOR OF CONFINED OLIGOMER MELTS UNDER SHEAR - A MOLECULAR-DYNAMICS STUDY

    NARCIS (Netherlands)

    MANIAS, E; HADZIIOANNOU, G; BITSANIS, [No Value; TENBRINKE, G

    1993-01-01

    The flow behaviour of melts of short chains, confined in molecularly thin Couette flow geometries, is studied with molecular-dynamics simulations. The effect of wall attraction and confinement on the density and velocity profiles is analysed. In these highly inhomogeneous films, a strong correlation

  9. Nonlinear current-voltage behavior in PZT thin films

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Mi; Zhang, Weikang; Zhang, Zebin; Li, Shida; Zhang, Ping; Lan, Kuibo [Tianjin University, School of Electrical and Information Engineering, Tianjin (China)

    2017-05-15

    In this paper, Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} (PZT) thin films were prepared by sol-gel synthesis and characterized by X-ray diffraction, field emission scanning electron microscopy and current-voltage measurements. Here, we demonstrate that in addition to the outstanding ferroelectric and dielectric properties, the PZT films also have remarkably nonlinear current-voltage characteristics. Considering the contact of semi-conductive grains in the PZT films, a double Schottky barrier (DSB) model may be responsible for such phenomena. The test results show that with the decrease of annealing temperature and the increase of the film thickness, the threshold voltages (V{sub th}) increase obviously. The maximum V{sub th} value of 60.95 V and the minimum value of 6.9 V in our experiments were obtained from the five-layered samples annealed at 600 C and the two-layered samples annealed at 700 C, respectively. As a result, PZT thin film may lead to efficient switching and sensing devices. (orig.)

  10. Orientation-dependent microstructure and shear flow behavior of extruded Mg–Li–Zn alloys

    Energy Technology Data Exchange (ETDEWEB)

    Karami, M.; Mahmudi, R., E-mail: mahmudi@ut.ac.ir

    2015-06-11

    The microstructural and textural evolutions together with the orientation dependencies of mechanical properties of the extruded Mg–6Li–1Zn (LZ61), Mg–8Li–1Zn (LZ81) and Mg–12Li–1Zn (LZ121) alloys were investigated. The shear punch testing (SPT) method was employed to evaluate the room- and high-temperature (200–300 °C) mechanical anisotropy of the extruded materials. Microstructural analysis revealed that, despite a great discontinuous dynamic recrystallization (DDRX) occurred in the extrusion direction (ED) and normal direction (ND), the microstructural anisotropy was observed in all extruded materials, the effect which was more pronounced in the LZ81 alloy by developing banded structure in the ND condition. Textural studies in both hcp LZ61 and LZ81-α phase showed a fiber-type texture with the basal planes being parallel to the ED after extrusion. For the LZ81 alloy, however, the interfering presence of β phase affects the LZ81-α-phase texture by reducing the intensity of the maximum orientations of the basal and prismatic planes. Similar weakened bimodal type texture was formed in the bcc-structured LZ81-β phase, where some <110> poles were located parallel to the ED along with developing some other poles of a fiber-type character. It was also found that the abnormal grain growth might have been encouraged by the strong texture developed in the extruded LZ121 alloy. The SPT results indicated that the texture-dependent hcp LZ61 alloy showed higher shear strength in the ND condition than the ED condition, caused by the texture strengthening effect. As the Li content and deformation temperature increase, the texture dependence of strength properties, and thus, the mechanical anisotropy, decrease so that the LZ121-ND sample showed lower shear strength than the ED specimen due to the greater grain sizes achieved in the ND condition.

  11. An experimental investigation of the seismic behavior of semi-supported steel shear walls

    DEFF Research Database (Denmark)

    Jahanpour, Alireza; Jönsson, Jeppe; Moharrami, H.

    2010-01-01

    . These half scale models represent an intermediate storey in a multi-storey steel frame. Hysteresis loops traced from the load deflection curves of these tests have an “S” shape and dissipate energy well. The system has an acceptable level of ductility, which enables its use as a lateral earthquake load......A semi-supported steel shear wall (SSSW) has been developed in the recent decade, the steel wall is connected to secondary columns that do not carry vertical loads and are used to enable the plate to enter into the post buckling region and develop a tension field. Theoretical research...

  12. Elastic behavior and onset of cracking in cement composite plates reinforced by perforated thin steel sheets

    Science.gov (United States)

    Aronchik, V.

    1996-03-01

    Thin cement mortar plates reinforced by perforated thin steel sheets have been tested in four-point flexure loading. Six kinds of sheet reinforcement and to additional ones (for control) were used. Perforated sheets of the Daugavpils Factory of Machinery Chains differed by their thickness (0.6-1.8 mm), shape (round, rectangular, oval, "dumbbell"), and mark of steel (St. 08, 50, 70). Dimensions of plantes were 100×20×2 cm. Cements-sand mortar with a 1∶2 ratio of cement PZ35 and river sand of 3 mm grains was used as a matrix. Control specimens of similar dimensions and matrix were reinforced by wire cages and meshes (ferrocement). The testing was performed using an UMM-5 testing machine. Maximum deflection (at the midspan), tension, and shear strains were recorded. The expeimental data are presented in tables and graphs. The testing results showed that the elasticity modulus of material was in good agreement with the "admixture rule;" an onset of cracking for all types (excluding one) practically did not differ from reference samples; the mode of fracture in typical cases included an adhesion failure and significant shear strains. In one case the limit of the tension strength of the reinforcement was achieved.

  13. Evaluation of Steel Shear Walls Behavior with Sinusoidal and Trapezoidal Corrugated Plates

    Directory of Open Access Journals (Sweden)

    Emad Hosseinpour

    2015-01-01

    Full Text Available Reinforcement of structures aims to control the input energy of unnatural and natural forces. In the past four decades, steel shear walls are utilized in huge constructions in some seismic countries such as Japan, United States, and Canada to lessen the risk of destructive forces. The steel shear walls are divided into two types: unstiffened and stiffened. In the former, a series of plates (sinusoidal and trapezoidal corrugated with light thickness are used that have the postbuckling field property under overall buckling. In the latter, steel profile belt series are employed as stiffeners with different arrangement: horizontal, vertical, or diagonal in one side or both sides of wall. In the unstiffened walls, increasing the thickness causes an increase in the wall capacity under large forces in tall structures. In the stiffened walls, joining the stiffeners to the wall is costly and time consuming. The ANSYS software was used to analyze the different models of unstiffened one-story steel walls with sinusoidal and trapezoidal corrugated plates under lateral load. The obtained results demonstrated that, in the walls with the same dimensions, the trapezoidal corrugated plates showed higher ductility and ultimate bearing compared to the sinusoidal corrugated plates.

  14. Dissolution behavior of irradiated mixed oxide fuel with short stroke shearing for fast reactor reprocessing

    International Nuclear Information System (INIS)

    Ikeuchi, Hirotomo; Sano, Yuichi; Shibata, Atsuhiro; Koizumi, Tsutomu; Washiya, Tadahiro

    2013-01-01

    An efficient dissolution process was established for future reprocessing in which mixed-oxide (MOX) fuels with high plutonium contents and dissolver solution with high heavy-metal (HM) concentrations (more than 500 g dm -3 ) will be treated. This dissolution process involves short stroke shearing of fuels (∼10 mm in length). The dissolution kinetics of irradiated MOX fuels and the effects of the Pu content, HM concentration, and fuel form on the dissolution rate were investigated. Irradiated fuel was found to dissolve as 10 2 -10 3 times fast as non-irradiated fuel, but the rate decreased with increasing Pu content. Kinetic analysis based on the fragmentation model, which considers the penetration and diffusion of nitric acid through fuel matrices prior to chemical reaction, indicated that the dissolution rate of irradiated fuel was affected not only by the volume ratio of liquid to solid (L/S ratio) but also by the exposed surface area per unit mole of nitric acid (A/m ratio). The penetration rate of nitric acid is expected to be decreased at high HM concentrations by a reduction in the L/S ratio, but enhanced by shearing the fuel pieces with short strokes and thus enlarging the A/m ratio. (author)

  15. Investigation of Asphalt Mixture Creep Behavior Using Thin Beam Specimens

    International Nuclear Information System (INIS)

    Zofka, Adam; Marasteanu, Mihai; Turos, Mugur

    2008-01-01

    The asphalt pavement layer consists of two or more lifts of compacted asphalt mixture; the top of the layer is also exposed to aging, a factor that significantly affects the mixture properties. The current testing specifications use rather thick specimens that cannot be used to investigate the gradual change in properties with pavement depth. This paper investigates the feasibility of using the 3-point bending test with thin asphalt mixture beams (127x12.7x6.35 mm) to determine the low-temperature creep compliance of the mixtures. Several theoretical and semi-empirical models, from the theory of composites, are reviewed and evaluated using numerical and experimental data. Preliminary results show that this method can be used for low-temperature mixture characterization but several crucial factors need further inspection and interpretation

  16. Theoretical study of the flow in a fluid damper containing high viscosity silicone oil: Effects of shear-thinning and viscoelasticity

    Science.gov (United States)

    Syrakos, Alexandros; Dimakopoulos, Yannis; Tsamopoulos, John

    2018-03-01

    The flow inside a fluid damper where a piston reciprocates sinusoidally inside an outer casing containing high-viscosity silicone oil is simulated using a finite volume method, at various excitation frequencies. The oil is modeled by the Carreau-Yasuda (CY) and Phan-Thien and Tanner (PTT) constitutive equations. Both models account for shear-thinning, but only the PTT model accounts for elasticity. The CY and other generalised Newtonian models have been previously used in theoretical studies of fluid dampers, but the present study is the first to perform full two-dimensional (axisymmetric) simulations employing a viscoelastic constitutive equation. It is found that the CY and PTT predictions are similar when the excitation frequency is low, but at medium and higher frequencies, the CY model fails to describe important phenomena that are predicted by the PTT model and observed in experimental studies found in the literature, such as the hysteresis of the force-displacement and force-velocity loops. Elastic effects are quantified by applying a decomposition of the damper force into elastic and viscous components, inspired from large amplitude oscillatory shear theory. The CY model also overestimates the damper force relative to the PTT model because it underpredicts the flow development length inside the piston-cylinder gap. It is thus concluded that (a) fluid elasticity must be accounted for and (b) theoretical approaches that rely on the assumption of one-dimensional flow in the piston-cylinder gap are of limited accuracy, even if they account for fluid viscoelasticity. The consequences of using lower-viscosity silicone oil are also briefly examined.

  17. Damage Behaviors and Compressive Strength of Toughened CFRP Laminates with Thin Plies Subjected to Transverse Impact Loadings

    Science.gov (United States)

    Yokozeki, Tomohiro; Aoki, Yuichiro; Ogasawara, Toshio

    It has been recognized that damage resistance and strength properties of CFRP laminates can be improved by using thin-ply prepregs. This study investigates the damage behaviors and compressive strength of CFRP laminates using thin-ply and standard prepregs subjected to out-of-plane impact loadings. CFRP laminates used for the evaluation are prepared using the standard prepregs, thin-ply prepregs, and combinations of the both. Weight-drop impact test and post-impact compression test of quasi-isotropic laminates are performed. It is shown that the damage behaviors are different between the thin-ply and the standard laminates, and the compression-after-impact strength is improved by using thin-ply prepregs. Effects of the use of thin-ply prepregs and the layout of thin-ply layers on the damage behaviors and compression-after-impact properties are discussed based on the experimental results.

  18. Study on Mechanical Behavior of Thin-walled Member during Precision Straightening Process

    Directory of Open Access Journals (Sweden)

    Ben Guan

    2014-09-01

    Full Text Available This paper introduces the mechanical behavior of precise straightening thin-walled members systematically. As a result of its cross section characteristics of the thin-walled members, traditional straightening theory does not work well in the straightening process of this kind of metal bar stock. Considering the stress evolvement of section during the straightening process, a model was built to analysis the straightening process like thin-walled member with great section height. By making a thorough analysis of the straightening process, the section deformation law and the relationship between sectional distortion and straightening parameters has been mastered. An analytical model was built for macroscopic energetics parameters of the straightening process and the parameters was optimized based on this model. Then loading mode of thin-walled member straightening was discussed.

  19. Injectable Shear-Thinning CaSO4/FGF-18-Incorporated Chitin-PLGA Hydrogel Enhances Bone Regeneration in Mice Cranial Bone Defect Model.

    Science.gov (United States)

    Sivashanmugam, A; Charoenlarp, Pornkawee; Deepthi, S; Rajendran, Arunkumar; Nair, Shantikumar V; Iseki, Sachiko; Jayakumar, R

    2017-12-13

    For craniofacial bone regeneration, shear-thinning injectable hydrogels are favored over conventional scaffolds because of their improved defect margin adaptability, easier handling, and ability to be injected manually into deeper tissues. The most accepted method, after autografting, is the use of recombinant human bone morphogenetic protein-2 (BMP-2); however, complications such as interindividual variations, edema, and poor cost-efficiency in supraphysiological doses have been reported. The endogenous synthesis of BMP-2 is desirable, and a molecule which induces this is fibroblast growth factor-18 (FGF-18) because it can upregulate the BMP-2 expression  by supressing noggin. We developed a chitin-poly(lactide-co-glycolide) (PLGA) composite hydrogel by regeneration chemistry and then incorporated CaSO 4 and FGF-18 for this purpose. Rheologically, a 7-fold increase in the elastic modulus was observed in the CaSO 4 -incorporated chitin-PLGA hydrogels as compared to the chitin-PLGA hydrogel. Shear-thinning Herschel-Bulkley fluid nature was observed for both hydrogels. Chitin-PLGA/CaSO 4 gel showed sustained release of FGF-18. In vitro osteogenic differentiation showed an enhanced alkaline phosphatase (ALP) expression in the FGF-18-containing chitin-PLGA/CaSO 4 gel when compared to cells alone. Further, it was confirmed by studying the expression of osteogenic genes [RUNX2, ALP, BMP-2, osteocalcin (OCN), and osteopontin (OPN)], immunofluorescence staining of BMP-2, OCN, and OPN, and alizarin red S staining. Incorporation of FGF-18 in the hydrogel increased the endothelial cell migration. Further, the regeneration potential of the prepared hydrogels was tested in vivo, and longitudinal live animal μ-CT was performed. FGF-18-loaded chitin-PLGA/CaSO 4 showed early and almost complete bone healing in comparison with chitin-PLGA/CaSO 4 , chitin-PLGA/FGF-18, chitin-PLGA, and sham control systems, as confirmed by hematoxylin and eosin and osteoid tetrachrome stainings

  20. Rheometry-PIV of shear-thickening wormlike micelles.

    Science.gov (United States)

    Marín-Santibañez, Benjamín M; Pérez-Gonzalez, José; de Vargas, Lourdes; Rodríguez-Gonzalez, Francisco; Huelsz, Guadalupe

    2006-04-25

    The shear-thickening behavior of an equimolar semidilute aqueous solution of 40 mM/L cetylpyridinium chloride and sodium salicylate was studied in this work by using a combined method of rheometry and particle image velocimetry (PIV). Experiments were conducted at 27.5 degrees C with Couette, vane-bob, and capillary rheometers in order to explore a wide shear stress range as well as the effect of boundary conditions and time of flow on the creation and destruction of shear-induced structures (SIS). The use of the combined method of capillary rheometry with PIV allowed the detection of fast spatial and temporal variations in the flow kinematics, which are related to the shear-thickening behavior and the dynamics of the SIS but are not distinguished by pure rheometrical measurements. A rich-in-details flow curve was found for this solution, which includes five different regimes. Namely, at very low shear rates a Newtonian behavior was found, followed by a shear thinning one in the second regime. In the third, shear banding was observed, which served as a precursor of the SIS and shear-thickening. The fourth and fifth regimes in the flow curve were separated by a spurtlike behavior, and they clearly evidenced the existence of shear-thickening accompanied by stick-slip oscillations at the wall of the rheometer, which subsequently produced variations in the shear rate under shear stress controlled flow. Such a stick-slip phenomenon prevailed up to the highest shear stresses used in this work and was reflected in asymmetric velocity profiles with spatial and temporal variations linked to the dynamics of creation and breakage of the SIS. The presence of apparent slip at the wall of the rheometer provides an energy release mechanism which leads to breakage of the SIS, followed by their further reformation during the stick part of the cycles. In addition, PIV measurements allowed the detection of apparent slip at the wall, as well as mechanical failures in the bulk of the

  1. Rheological Investigation on the Effect of Shear and Time Dependent Behavior of Waxy Crude Oil

    Directory of Open Access Journals (Sweden)

    Japper-Jaafar A.

    2014-07-01

    Full Text Available Rheological measurements are essential in transporting crude oil, especially for waxy crude oil. Several rheological measurements have been conducted to determine various rheological properties of waxy crude oil including the viscosity, yield strength, wax appearance temperature (WAT, wax disappearance temperature (WDT, storage modulus and loss modulus, amongst others, by using controlled stress rheometers. However, a procedure to determine the correct parameters for rheological measurements is still unavailable in the literature. The paper aims to investigate the effect of shear and time dependent behaviours of waxy crude oil during rheological measurements. It is expected that the preliminary work could lead toward a proper rheological measurement guideline for reliable rheological measurement of waxy crude oil.

  2. Experimental investigation into the seismic behavior of nuclear power plant shear wall structures

    International Nuclear Information System (INIS)

    Kenneally, R.M.; Burns, J.J. Jr.

    1988-01-01

    Nuclear power plant structures are designed to resist large earthquakes. However, as new data are obtained on earthquake activity throughout the United States, plant design earthquake levels have increased. The U.S. Nuclear Regulatory Commission is sponsoring an analytical-experimental research program to obtain information on the strucutral response of nuclear power plant shear wall strucutres subjected to earthquake motions within and beyond their design basis. Using different size scale models constructed with microconcrete and prototypical concrete this research has demonstrated consistent results for measured values of stiffness at load levels within the design basis. Furthermore, the values are well below the theoretical stiffnesses calculated from an uncracked cross-section strength-of-materials approach. Current program emphasis is to assess the credibility of previous experimental work by beginning to resolve the 'stiffness difference' issue. (orig.)

  3. Dynamic behavior of a rotating delaminated composite beam including rotary inertia and shear deformation effects

    Directory of Open Access Journals (Sweden)

    Ramazan-Ali Jafari-Talookolaei

    2015-09-01

    Full Text Available A finite element (FE model is developed to study the free vibration of a rotating laminated composite beam with a single delamination. The rotary inertia and shear deformation effects, as well as the bending–extension, bending–twist and extension–twist coupling terms are taken into account in the FE model. Comparison between the numerical results of the present model and the results published in the literature verifies the validity of the present model. Furthermore, the effects of various parameters, such as delamination size and location, fiber orientation, hub radius, material anisotropy and rotating speed, on the vibration of the beam are studied in detail. These results provide useful information in the study of the free vibration of rotating delaminated composite beams.

  4. Comportamiento al corte de hormigones reforzado con fibras de acero Shear behavior of steel fiber reinforced concretes

    Directory of Open Access Journals (Sweden)

    Sergio Carmona Malatesta

    2009-01-01

    Full Text Available En este artículo se presentan los resultados de un estudio experimental a cerca de la influencia de la incorporación de fibras de acero en el comportamiento del hormigón frente a esfuerzos de corte, medidos utilizando el ensayo JSCE - SF6, modificado. Usando los resultados de los ensayos realizados se evalúa La capacidad de disipación de energía del hormigón durante la rotura o tenacidad del hormigón reforzado con fibras en función del contenido y tipo de Fibra utilizada. Con los resultados obtenidos, se puede concluir que la incorporación de fibras como refuerzo al esfuerzo de corte aumenta la ductilidad del hormigón, permitiendo mayores deformaciones que un hormigón convencional. Se observa que la capacidad de absorber energía de los hormigones, cuantificada a través de la tenacidad absoluta, se incrementa más de tres veces cuando se incorporar fibras y no se tienen roturas frágiles. Por lo tanto, la incorporación de fibras como refuerzo es una buena solución para mejorar la respuesta del hormigón ante solicitaciones de corte. Por otra parte, se demuestra que el ensayo de corte propuesto por la recomendación japonesa JSCE-SF6, levemente modificada, entrega resultados coherentes y reproducibles, permitiendo cuantificar diferentes propiedades del hormigón reforzado con fibras sometido a solicitaciones de corte.This paper presents the results of an experimental research on influence of steel fibers on shear behavior of concrete, using modified JSCE - SF6 test. The tests results are used to evaluate the energy dissipation capacity of concrete during failure or fiber reinforced concrete toughness, in terms of amount and type of fibers. With the results, it can be concluded that the addition of fibers as shear reinforcement influence significantly the ductility of concrete. The results show that the absorption energy capacity of concrete, measured by mean of absolute toughness, increase 3 times when concrete is reinforced with

  5. Anomalous behavior of the diffusion coefficient in thin active films

    International Nuclear Information System (INIS)

    Basu, Abhik; Joanny, Jean-Francois; Prost, Jacques; Jülicher, Frank

    2012-01-01

    Inspired by recent experiments in cell biology, we elucidate the visco-elastic properties of an active gel by studying the dynamics of a small tracer particle inside it. In a stochastic hydrodynamic approach for an active gel of finite thickness L, we calculate the mean square displacement of a particle. These particle displacements are governed by fluctuations in the velocity field. We characterize the short-time behavior when the gel is a solid as well as the limit of long times when the gel becomes a fluid and the particle shows simple diffusion. Active stresses together with local polar order give rise to velocity fluctuations that lead to characteristic behaviors of the diffusion coefficient that differ fundamentally from those found in a passive system: the diffusion coefficient can depend on system size and diverges as L approaches an instability threshold. Furthermore, the diffusion coefficient becomes independent of the particle size in this case. (paper)

  6. Shear machines

    International Nuclear Information System (INIS)

    Astill, M.; Sunderland, A.; Waine, M.G.

    1980-01-01

    A shear machine for irradiated nuclear fuel elements has a replaceable shear assembly comprising a fuel element support block, a shear blade support and a clamp assembly which hold the fuel element to be sheared in contact with the support block. A first clamp member contacts the fuel element remote from the shear blade and a second clamp member contacts the fuel element adjacent the shear blade and is advanced towards the support block during shearing to compensate for any compression of the fuel element caused by the shear blade (U.K.)

  7. Web buckling behavior under in-plane compression and shear loads for web reinforced composite sandwich core

    Science.gov (United States)

    Toubia, Elias Anis

    Sandwich construction is one of the most functional forms of composite structures developed by the composite industry. Due to the increasing demand of web-reinforced core for composite sandwich construction, a research study is needed to investigate the web plate instability under shear, compression, and combined loading. If the web, which is an integral part of the three dimensional web core sandwich structure, happens to be slender with respect to one or two of its spatial dimensions, then buckling phenomena become an issue in that it must be quantified as part of a comprehensive strength model for a fiber reinforced core. In order to understand the thresholds of thickness, web weight, foam type, and whether buckling will occur before material yielding, a thorough investigation needs to be conducted, and buckling design equations need to be developed. Often in conducting a parametric study, a special purpose analysis is preferred over a general purpose analysis code, such as a finite element code, due to the cost and effort usually involved in generating a large number of results. A suitable methodology based on an energy method is presented to solve the stability of symmetrical and specially orthotropic laminated plates on an elastic foundation. Design buckling equations were developed for the web modeled as a laminated plate resting on elastic foundations. The proposed equations allow for parametric studies without limitation regarding foam stiffness, geometric dimensions, or mechanical properties. General behavioral trends of orthotropic and symmetrical anisotropic plates show pronounced contribution of the elastic foundation and fiber orientations on the buckling resistance of the plate. The effects of flexural anisotropy on the buckling behavior of long rectangular plates when subjected to pure shear loading are well represented in the model. The reliability of the buckling equations as a design tool is confirmed by comparison with experimental results

  8. Plastic collapse behavior for thin tube with two parallel cracks

    International Nuclear Information System (INIS)

    Moon, Seong In; Chang, Yoon Suk; Kim, Young Jin; Lee, Jin Ho; Song, Myung Ho; Choi, Young Hwan; Kim, Joung Soo

    2004-01-01

    The current plugging criterion is known to be too conservative for some locations and types of defects. Many defects detected during in-service inspection take on the form of multiple cracks at the top of tube sheet but there is no reliable plugging criterion for the steam generator tubes with multiple cracks. Most of the previous studies on multiple cracks are confined to elastic analyses and only few studies have been done on the steam generator tubes failed by plastic collapse. Therefore, it is necessary to develop models which can be used to estimate the failure behavior of steam generator tubes with multiple cracks. The objective of this study is to verify the applicability of the optimum local failure prediction models proposed in the previous study. For this, plastic collapse tests are performed with the tube specimens containing two parallel through-wall cracks. The plastic collapse load of the steam generator tubes containing two parallel through-wall cracks are also estimated by using the proposed optimum global failure model and the applicability is investigated by comparing the estimated results with the experimental results. Also, the interaction effect between two cracks was evaluated to explain the plastic collapse behavior

  9. Influence of temperature, concentration and shear rate on the rheological behavior of malay apple (Syzygium malaccense juice

    Directory of Open Access Journals (Sweden)

    Pedro Henrique Santos

    Full Text Available Summary The aim of this study was to evaluate the rheological behavior of malay apple, a traditional Amazonian fruit with high bioactive properties, at different temperatures and soluble solids concentrations. The experiments were carried out in a Brookfield R/S Plus rheometer with concentric cylinders geometry. Power Law, Herschel-Bulkley, Mizrahi-Berk, and Sisko rheological models were fitted to the experimental data. The malay apple juice (pulp and skin showed a pseudoplastic behavior for all temperatures and concentrations with flow behavior indexes lower than 1. The temperature effect on the samples’ apparent viscosity was analyzed by the Arrhenius equation. The activation energy increased with a decrease in the soluble solids concentration, showing that the lower the concentration, the greater the temperature influence on the apparent viscosity. The soluble solids effect was described by the exponential equation. The exponential factor increased with the temperature increasing, showing that the higher the temperature, the greater the effect of the soluble solids concentration on samples’ apparent viscosity. Finally, a triparametric mathematical model combining temperature, concentration, and shear rate was proposed aiming to evaluate its effects on the samples’ apparent viscosity and has accurately adjusted to the data with high correlation index R2.

  10. Simulation of shear thickening in attractive colloidal suspensions.

    Science.gov (United States)

    Pednekar, Sidhant; Chun, Jaehun; Morris, Jeffrey F

    2017-03-01

    The influence of attractive forces between particles under conditions of large particle volume fraction, ϕ, is addressed using numerical simulations which account for hydrodynamic, Brownian, conservative and frictional contact forces. The focus is on conditions for which a significant increase in the apparent viscosity at small shear rates, and possibly the development of a yield stress, is observed. The high shear rate behavior for Brownian suspensions has been shown in recent work [R. Mari, R. Seto, J. F. Morris and M. M. Denn PNAS, 2015, 112, 15326-15330] to be captured by the inclusion of pairwise forces of two forms, one a contact frictional interaction and the second a repulsive force often found in stabilized colloidal dispersions. Under such conditions, shear thickening is observed when shear stress is comparable to the sum of the Brownian stress, kT/a 3 , and a characteristic stress based on the combination of interparticle force, i.e. σ ∼ F 0 /a 2 with kT the thermal energy, F 0 the repulsive force scale and a the particle radius. At sufficiently large ϕ, this shear thickening can be very abrupt. Here it is shown that when attractive interactions are present with the noted forces, the shear thickening is obscured, as the viscosity shear thins with increasing shear rate, eventually descending from an infinite value (yield stress conditions) to a plateau at large stress; this plateau is at the same level as the large-shear rate viscosity found in the shear thickened state without attractive forces. It is shown that this behavior is consistent with prior observations in shear thickening suspensions modified to be attractive through depletion flocculation [V. Gopalakrishnan and C. F. Zukoski J. Rheol., 2004, 48, 1321-1344]. The contributions of the contact, attractive, and hydrodynamics forces to the bulk stress are presented, as are the contact networks found at different attractive strengths.

  11. Computer simulation of the anomalous elastic behavior of thin films and superlattices

    International Nuclear Information System (INIS)

    Wolf, D.

    1992-10-01

    Atomistic simulations are reviewed that elucidate the causes of the anomalous elastic behavior of thin films and superlattices (the so-called supermodulus effect). The investigation of free-standing thin films and of superlattices of grain boundaries shows that the supermodulus effect is not an electronic but a structural interface effect intricately connected with the local atomic disorder at the interfaces. The consequent predictions that (1) coherent strained-layer superlattices should show the smallest elastic anomalies and (2) the introduction of incoherency at the interfaces should enhance all anomalies are validated by simulations of dissimilar-material superlattices. 38 refs, 10 figs

  12. Vibrational behavior of adaptive aircraft wing structures modelled as composite thin-walled beams

    Science.gov (United States)

    Song, O.; Librescu, L.; Rogers, C. A.

    1992-01-01

    The vibrational behavior of cantilevered aircraft wings modeled as thin-walled beams and incorporating piezoelectric effects is studied. Based on the converse piezoelectric effect, the system of piezoelectric actuators conveniently located on the wing yield the control of its associated vertical and lateral bending eigenfrequencies. The possibility revealed by this study enabling one to increase adaptively the eigenfrequencies of thin-walled cantilevered beams could play a significant role in the control of the dynamic response and flutter of wing and rotor blade structures.

  13. Optical and structural behaviors of crosslinked polyvinyl alcohol thin films

    Science.gov (United States)

    Pandit, Subhankar; Kundu, Sarathi

    2018-04-01

    Polyvinyl Alcohol (PVA) has excellent properties like uniaxial tensile stress, chemical resistance, biocompatibility, etc. The properties of PVA further can be tuned by crosslinking process. In this work, a simple heat treatment method is used to find out the optimum crosslinking of PVA and the corresponding structural and optical responses are explored. The PVA crosslinking is done by exposing the films at different temperatures and time intervals. The optical property of pure and heat treated PVA films are investigated by UV-Vis absorption and photoluminescence emission spectroscopy and structural modifications are studied by Fourier Transform Infrared Spectroscopy (FTIR). The absorption peaks of pure PVA are observed at ≈ 280 and 335 nm and the corresponding emission is observed at ≈ 424 nm. The pure PVA showed modified optical behaviors after the heat treatment. In addition, dipping the PVA films in hot water (85°C) for nearly 20 minutes also show impact on both structural and optical properties. From FTIR spectroscopy, the changes in vibrational band positions confirm the structural modifications of PVA films.

  14. Non-ohmic transport behavior in ultra-thin gold films

    International Nuclear Information System (INIS)

    Alkhatib, A.; Souier, T.; Chiesa, M.

    2011-01-01

    Highlights: → C-AFM study on ultra-thin gold films. → Connection between ultra-thin film morphology and lateral electrical transport. → Transition between ohmic and non-ohmic behavior. → Electrical transition correlation to the film structure continuity. → Direct and indirect tunneling regimes related to discontinuous structures. - Abstract: Structure and local lateral electrical properties of Au films of thicknesses ranging from 10 to 140 nm are studied using conductive atomic force microscopy. Comparison of current maps taken at different thicknesses reveals surprising highly resistive regions (10 10 -10 11 Ω), the density of which increases strongly at lower thickness. The high resistivity is shown to be directly related to discontinuities in the metal sheet. Local I-V curves are acquired to show the nature of electrical behavior relative to thickness. Results show that in Au films of higher thickness the electrical behavior is ohmic, while it is non-ohmic in highly discontinuous films of lower thickness, with the transition happening between 34 and 39 nm. The non-ohmic behavior is explained with tunneling occurring between separated Au islands. The results explain the abrupt increase of electrical resistivity at lower thin film thicknesses.

  15. Transient behaviors of ZnO thin films on a transparent, flexible polyethylene terephthalate substrate

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yong Jun [Department of Nano-Physics, Gachon University, 1342 Seongnamdaero, Sujeong-gu, Seongnam-si, Gyeonggi-do 461-701 (Korea, Republic of); Lee, Ho Seok [Department of Materials Science and Engineering, Korea University, 5-1 Anam-dong, Seongbuk-gu, Seoul 136-713 (Korea, Republic of); Noh, Jin-Seo, E-mail: jinseonoh@gachon.ac.kr [Department of Nano-Physics, Gachon University, 1342 Seongnamdaero, Sujeong-gu, Seongnam-si, Gyeonggi-do 461-701 (Korea, Republic of)

    2016-03-31

    Thickness-dependent electrical, structural, and optical properties of zinc oxide (ZnO) thin films on polyethylene terephthalate (PET) substrates have been investigated in the very thin thickness range of 20 to 120 nm. In this thickness range, the electrical resistance of ZnO film increased with an increase in film thickness. This unusual transition behavior was explained in terms of structural evolution from Zn-phase-incorporating non-crystalline ZnO to hexagonal-structured ZnO. A critical thickness for the full development of hexagonal ZnO crystal was estimated at approximately 80 nm in this study. ZnO thin films on PET substrates exhibit a high optical transmittance of > 70% and good endurance to bending cycles over the measured thickness range. The results of this study indicate that a trade-off should be sought between structural, electrical, optical, and mechanical properties for practical applications of very thin ZnO films on organic substrates. - Highlights: • Very thin ZnO films were sputter-deposited on the PET substrate. • The ZnO film resistance increases with an increase in film thickness until saturation. • Hexagonal crystal structures gradually develop with increasing film thickness. • A Zn phase appears in a 20-nm-thick ZnO film. • ZnO films show high optical transmittance of > 80% and good endurance to bending.

  16. Transient behaviors of ZnO thin films on a transparent, flexible polyethylene terephthalate substrate

    International Nuclear Information System (INIS)

    Kim, Yong Jun; Lee, Ho Seok; Noh, Jin-Seo

    2016-01-01

    Thickness-dependent electrical, structural, and optical properties of zinc oxide (ZnO) thin films on polyethylene terephthalate (PET) substrates have been investigated in the very thin thickness range of 20 to 120 nm. In this thickness range, the electrical resistance of ZnO film increased with an increase in film thickness. This unusual transition behavior was explained in terms of structural evolution from Zn-phase-incorporating non-crystalline ZnO to hexagonal-structured ZnO. A critical thickness for the full development of hexagonal ZnO crystal was estimated at approximately 80 nm in this study. ZnO thin films on PET substrates exhibit a high optical transmittance of > 70% and good endurance to bending cycles over the measured thickness range. The results of this study indicate that a trade-off should be sought between structural, electrical, optical, and mechanical properties for practical applications of very thin ZnO films on organic substrates. - Highlights: • Very thin ZnO films were sputter-deposited on the PET substrate. • The ZnO film resistance increases with an increase in film thickness until saturation. • Hexagonal crystal structures gradually develop with increasing film thickness. • A Zn phase appears in a 20-nm-thick ZnO film. • ZnO films show high optical transmittance of > 80% and good endurance to bending.

  17. The impact of voxel size-based inaccuracies on the mechanical behavior of thin bone structures.

    Science.gov (United States)

    Maloul, Asmaa; Fialkov, Jeffrey; Whyne, Cari

    2011-03-01

    Computed tomography (CT)-based measures of skeletal geometry and material properties have been widely used to develop finite element (FE) models of bony structures. However, in the case of thin bone structures, the ability to develop FE models with accurate geometry derived from clinical CT data presents a challenge due to the thinness of the bone and the limited resolution of the imaging devices. The purpose of this study was to quantify the impact of voxel size on the thickness and intensity values of thin bone structure measurements and to assess the effect of voxel size on strains through FE modeling. Cortical bone thickness and material properties in five thin bone specimens were quantified at voxel sizes ranging from 16.4 to 488 μm. The measurements derived from large voxel size scans showed large increases in cortical thickness (61.9-252.2%) and large decreases in scan intensity (12.9-49.5%). Maximum principal strains from FE models generated using scans at 488 μm were decreased as compared to strains generated at 16.4 μm voxel size (8.6-64.2%). A higher level of significance was found in comparing intensity (p = 0.0001) vs. thickness (p = 0.005) to strain measurements. These findings have implications in developing methods to generate accurate FE models to predict the biomechanical behavior of thin bone structures.

  18. Influence of shear forces on the aggregation and sedimentation behavior of cerium dioxide (CeO{sub 2}) nanoparticles under different hydrochemical conditions

    Energy Technology Data Exchange (ETDEWEB)

    Lv, Bowen; Wang, Chao; Hou, Jun, E-mail: hhuhjyhj@126.com; Wang, Peifang, E-mail: pfwang2005@hhu.edu.cn; Miao, Lingzhan; Li, Yi; Ao, Yanhui; Yang, Yangyang; You, Guoxiang; Xu, Yi [Hohai University, Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education (China)

    2016-07-15

    This study contributed to a better understanding of the behavior of nanoparticles (NPs) in dynamic water. First, the aggregation behavior of CeO{sub 2} NPs at different pH values in various salt solutions was examined to determine the appropriate hydrochemical conditions for hydrodynamics study. Second, the aggregation behavior of CeO{sub 2} NPs under different shear forces was investigated at pH 4 and ionic strength 0 in various salt solutions to find out whether shear forces could influence the stability of the nanoparticles and if yes, how. Also, five-stage sedimentation tests were conducted to understand the influence of shear stress on the vertical distribution of CeO{sub 2} NPs in natural waters. The aggregation test showed that the shear force could increase the collision efficiency between NPs during aggregation and cause a relatively large mass of NPs to remain in suspension. Consequently, the nanoparticles had a greater possibility of continued aggregation. The sedimentation test under static conditions indicated that a large mass of NPs (>1000 nm) sink to the bottom layer, leaving only small aggregates dispersed in the upper or middle layer of the solution. However, later sedimentation studies under stirring conditions demonstrated that shear forces can disrupt this stratification phenomenon. These results suggest that shear forces can influence the spatial distribution of NPs in natural waters, which might lead to different toxicities of CeO{sub 2} NPs to aquatic organisms distributed in the different water layers. This study contributes to a better understanding of nanomaterial toxicology and provides a way for further research.Graphical Abstract.

  19. Origin of shear thickening in semidilute wormlike micellar solutions and evidence of elastic turbulence

    International Nuclear Information System (INIS)

    Marín-Santibáñez, Benjamín M.; Pérez-González, José; Rodríguez-González, Francisco

    2014-01-01

    The origin of shear thickening in an equimolar semidilute wormlike micellar solution of cetylpyridinium chloride and sodium salicylate was investigated in this work by using Couette rheometry, flow visualization, and capillary Rheo-particle image velocimetry. The use of the combined methods allowed the discovery of gradient shear banding flow occurring from a critical shear stress and consisting of two main bands, one isotropic (transparent) of high viscosity and one structured (turbid) of low viscosity. Mechanical rheometry indicated macroscopic shear thinning behavior in the shear banding regime. However, local velocimetry showed that the turbid band increased its viscosity along with the shear stress, even though barely reached the value of the viscosity of the isotropic phase. This shear band is the precursor of shear induced structures that subsequently give rise to the average increase in viscosity or apparent shear thickening of the solution. Further increase in the shear stress promoted the growing of the turbid band across the flow region and led to destabilization of the shear banding flow independently of the type of rheometer used, as well as to vorticity banding in Couette flow. At last, vorticity banding disappeared and the flow developed elastic turbulence with chaotic dynamics

  20. Enhancement of room temperature ferromagnetic behavior of rf sputtered Ni-CeO_2 thin films

    International Nuclear Information System (INIS)

    Murugan, R.; Vijayaprasath, G.; Mahalingam, T.; Ravi, G.

    2016-01-01

    Highlights: • Ni-CeO_2 thin films deposited by using rf Magnetron sputtering with different concentrations of Ni. • Deposited thin films have single crystalline and uniform surface morphology. • Photoluminescence and micro-Raman spectra were interpreted for Ni-CeO_2 thin films. • XPS spectra confirmed Ni ions were present in the doped CeO_2 thin films. • Ni ions induced ferromagnetic behavior of Ni-CeO_2 films were confirmed through VSM. - Abstract: Ni-doped CeO_2 thin films were prepared under Ar"+ atmosphere on glass substrates using rf magnetron sputtering. To assess the properties of the prepared thin films, the influence of various amounts of Ni dopant on structural, morphological, optical, vibrational, compositional and magnetic properties of the CeO_2 films were studied by using X-Ray diffraction (XRD), atomic force microscope (AFM), photoluminescence (PL), micro-Raman, X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). XRD patterns for all the samples revealed the expected CeO_2 cubic fluorite-type structure and Ni ions were uniformly distributed in the samples. AFM images of the prepared samples indicate high dense, columnar structure with uniform distribution of CeO_2. Room-temperature photoluminescence (PL) and micro-Raman spectroscopic studies revealed an increase of oxygen vacancies with higher concentration of Ni in CeO_2. XPS results confirm the presence of Ni_2_p, O_1_s and Ce and depict that cerium is present as both Ce"4"+ and Ce"3"+ oxidation states in Ce_1_−_xNi_xO_2 (x = 15%) thin film. Field dependent magnetization measurements revealed a paramagnetic behavior for pure CeO_2, while a ferromagnetic behavior appeared when Ni is doped in CeO_2 films. Doping dependent magnetization measurements suggest that the observed ferromagnetism is due to the presence of metallic Ni clusters with nanometric size and broad size distribution.

  1. Steady shear flow properties of Cordia myxa leaf gum as a function of concentration and temperature.

    Science.gov (United States)

    Chaharlang, Mahmood; Samavati, Vahid

    2015-08-01

    The steady shear flow properties of dispersions of Cordia myxa leaf gum (CMLG) were determined as a function of concentration (0.5-2.5%, w/w), and temperature (10-50 °C). The CMLG dispersions exhibited strong shear-thinning behavior at all concentrations and temperatures. The Power-law (Ostwald-Waele's) and Herschel-Bulkley models were employed to characterize flow behavior of CMLG solutions at 0.1-100 s(-1) shear rate. Non-Newtonian shear-thinning behavior was observed at all temperatures and concentrations. While increase in temperature decreased the viscosity and increased the flow behavior indices, adverse effect was obtained by increasing the concentration. The Power-law model was found the best model to describe steady shear flow behavior of CMLG. The pseudoplasticity of CMLG increased markedly with concentration. An Arrhenius-type model was also used to describe the effect of temperature. The activation energy (Ea) appeared in the range of 5.972-18.104 kJ/mol, as concentration increased from 0.5% to 2.5%, at a shear rate of 10 s(-1). Copyright © 2015 Elsevier B.V. All rights reserved.

  2. 2012 THIN FILM AND SMALL SCALE MECHANICAL BEHAVIOR GRS/GRC, JULY 21-27, 2012

    Energy Technology Data Exchange (ETDEWEB)

    Balk, Thomas

    2012-07-27

    The mechanical behavior of materials with small dimension(s) is of both fundamental scientific interest and technological relevance. The size effects and novel properties that arise from changes in deformation mechanism have important implications for modern technologies such as thin films for microelectronics and MEMS devices, thermal and tribological coatings, materials for energy production and advanced batteries, etc. The overarching goal of the 2012 Gordon Research Conference on "Thin Film and Small Scale Mechanical Behavior" is to discuss recent studies and future opportunities regarding elastic, plastic and time-dependent deformation, as well as degradation and failure mechanisms such as fatigue, fracture and wear. Specific topics of interest include, but are not limited to: fundamental studies of physical mechanisms governing small-scale mechanical behavior; advances in test techniques for materials at small length scales, such as nanotribology and high-temperature nanoindentation; in-situ mechanical testing and characterization; nanomechanics of battery materials, such as swelling-induced phenomena and chemomechanical behavior; flexible electronics; mechanical properties of graphene and carbon-based materials; mechanical behavior of small-scale biological structures and biomimetic materials. Both experimental and computational work will be included in the oral and poster presentations at this Conference.

  3. Triaxial shear behavior of a cement-treated sand–gravel mixture

    Directory of Open Access Journals (Sweden)

    Younes Amini

    2014-10-01

    Full Text Available A number of parameters, e.g. cement content, cement type, relative density, and grain size distribution, can influence the mechanical behaviors of cemented soils. In the present study, a series of conventional triaxial compression tests were conducted on a cemented poorly graded sand–gravel mixture containing 30% gravel and 70% sand in both consolidated drained and undrained conditions. Portland cement used as the cementing agent was added to the soil at 0%, 1%, 2%, and 3% (dry weight of sand–gravel mixture. Samples were prepared at 70% relative density and tested at confining pressures of 50 kPa, 100 kPa, and 150 kPa. Comparison of the results with other studies on well graded gravely sands indicated more dilation or negative pore pressure in poorly graded samples. Undrained failure envelopes determined using zero Skempton's pore pressure coefficient (A¯=0 criterion were consistent with the drained ones. Energy absorption potential was higher in drained condition than undrained condition, suggesting that more energy was required to induce deformation in cemented soil under drained state. Energy absorption increased with increase in cement content under both drained and undrained conditions.

  4. Microstructure and mechanical behavior of a shape memory Ni-Ti bi-layer thin film

    Energy Technology Data Exchange (ETDEWEB)

    Mohri, Maryam [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe (Germany); Nili-Ahmadabadi, Mahmoud, E-mail: nili@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, University of Tehran, Tehran (Iran, Islamic Republic of); Ivanisenko, Julia [Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe (Germany); Schwaiger, Ruth [Karlsruhe Institute of Technology, Institute for Applied Materials, 76021 Karlsruhe (Germany); Hahn, Horst; Chakravadhanula, Venkata Sai Kiran [Karlsruhe Institute of Technology, Institute of Nanotechnology, 76021 Karlsruhe (Germany)

    2015-05-29

    Two different single-layers and a bi-layer Ni-Ti thin films with chemical compositions of Ni{sub 45}Ti{sub 50}Cu{sub 5}, Ni{sub 50.8}Ti{sub 49.2} and Ni{sub 50.8}Ti{sub 49.2}/Ni{sub 45}Ti{sub 50}Cu{sub 5} (numbers indicate at.%) determined by energy dispersive X-ray spectroscopy were deposited on Si (111) substrates using DC magnetron sputtering. The structures, surface morphology and transformation temperatures of annealed thin films at 500 °C for 15 min and 1 h were studied using grazing incidence X-ray diffraction, transmission electron microscopy (TEM), atomic force microscopy and differential scanning calorimetry (DSC), respectively. Nanoindentation was used to characterize the mechanical properties. The DSC and X-ray diffraction results indicated the austenitic structure of the Ni{sub 50.8}Ti{sub 49.2} and martensitic structure of the Ni{sub 45}Ti{sub 50}Cu{sub 5} thin films while the bi-layer was composed of austenitic and martensitic thin films. TEM study revealed that copper encourages crystallization in the bi-layer such that crystal structure containing nano-precipitates in the Ni{sub 45}Ti{sub 50}Cu{sub 5} layer was detected after 15 min annealing while the Ni{sub 50.8}Ti{sub 49.2} layer crystallized after 60 min at 500 °C. Furthermore, after annealing at 500 °C for 15 min, a precipitate free zone and thin layer amorphous were observed closely to the interface in the top layer. The bi-layer was completely crystallized at 500 °C for 1 h and the orientation of the Ni-rich precipitates indicated a stress gradient in the bi-layer. The bi-layer thin film showed different transformation temperatures and mechanical behavior from the single-layers. The developed bi-layer has different phase transformation temperatures, the higher temperatures of shape memory effect and lower temperature of pseudo-elastic behavior compared to the single-layers. Also, the bi-layer thin film exhibited a combined pseudo-elastic behavior and shape memory effect with a reduced

  5. Influence of helium atoms on the shear behavior of the fiber/matrix interphase of SiC/SiC composite

    Science.gov (United States)

    Jin, Enze; Du, Shiyu; Li, Mian; Liu, Chen; He, Shihong; He, Jian; He, Heming

    2016-10-01

    Silicon carbide has many attractive properties and the SiC/SiC composite has been considered as a promising candidate for nuclear structural materials. Up to now, a computational investigation on the properties of SiC/SiC composite varying in the presence of nuclear fission products is still missing. In this work, the influence of He atoms on the shear behavior of the SiC/SiC interphase is investigated via Molecular Dynamics simulation following our recent paper. Calculations are carried out on three dimensional models of graphite-like PyC/SiC interphase and amorphous PyC/SiC interphase with He atoms in different regions (the SiC region, the interface region and the PyC region). In the graphite-like PyC/SiC interphase, He atoms in the SiC region have little influence on the shear strength of the material, while both the shear strength and friction strength may be enhanced when they are in the PyC region. Low concentration of He atoms in the interface region of the graphite-like PyC/SiC interphase increases the shear strength, while there is a reduction of shear strength when the He concentration is high due to the switch of sliding plane. In the amorphous PyC/SiC interphase, He atoms can cause the reduction of the shear strength regardless of the regions that He atoms are located. The presence of He atoms may significantly alter the structure of SiC/SiC in the interface region. The influence of He atoms in the interface region is the most significant, leading to evident shear strength reduction of the amorphous PyC/SiC interphase with increasing He concentration. The behaviors of the interphases at different temperatures are studied as well. The dependence of the shear strengths of the two types of interphases on temperatures is studied as well. For the graphite-like PyC/SiC interphase, it is found strongly related to the regions He atoms are located. Combining these results with our previous study on pure SiC/SiC system, we expect this work may provide new insight

  6. Influence of helium atoms on the shear behavior of the fiber/matrix interphase of SiC/SiC composite

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Enze [State Nuclear Power Research Institute, Beijing, 100029 (China); Du, Shiyu, E-mail: dushiyu@nimte.ac.cn [Engineering Laboratory of Specialty Fibers and Nuclear Energy Materials, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang, 315201 (China); Li, Mian [Engineering Laboratory of Specialty Fibers and Nuclear Energy Materials, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang, 315201 (China); Liu, Chen [Beijing Research Institute of Chemical Engineering and Metallurgy (China); He, Shihong [State Nuclear Power Research Institute, Beijing, 100029 (China); Engineering Laboratory of Specialty Fibers and Nuclear Energy Materials, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang, 315201 (China); He, Jian [Center for Translational Medicine, Department of Biotechnology, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023 (China); He, Heming, E-mail: heheming@snptc.com.cn [State Nuclear Power Research Institute, Beijing, 100029 (China)

    2016-10-15

    Silicon carbide has many attractive properties and the SiC/SiC composite has been considered as a promising candidate for nuclear structural materials. Up to now, a computational investigation on the properties of SiC/SiC composite varying in the presence of nuclear fission products is still missing. In this work, the influence of He atoms on the shear behavior of the SiC/SiC interphase is investigated via Molecular Dynamics simulation following our recent paper. Calculations are carried out on three dimensional models of graphite-like PyC/SiC interphase and amorphous PyC/SiC interphase with He atoms in different regions (the SiC region, the interface region and the PyC region). In the graphite-like PyC/SiC interphase, He atoms in the SiC region have little influence on the shear strength of the material, while both the shear strength and friction strength may be enhanced when they are in the PyC region. Low concentration of He atoms in the interface region of the graphite-like PyC/SiC interphase increases the shear strength, while there is a reduction of shear strength when the He concentration is high due to the switch of sliding plane. In the amorphous PyC/SiC interphase, He atoms can cause the reduction of the shear strength regardless of the regions that He atoms are located. The presence of He atoms may significantly alter the structure of SiC/SiC in the interface region. The influence of He atoms in the interface region is the most significant, leading to evident shear strength reduction of the amorphous PyC/SiC interphase with increasing He concentration. The behaviors of the interphases at different temperatures are studied as well. The dependence of the shear strengths of the two types of interphases on temperatures is studied as well. For the graphite-like PyC/SiC interphase, it is found strongly related to the regions He atoms are located. Combining these results with our previous study on pure SiC/SiC system, we expect this work may provide new insight

  7. Influence of helium atoms on the shear behavior of the fiber/matrix interphase of SiC/SiC composite

    International Nuclear Information System (INIS)

    Jin, Enze; Du, Shiyu; Li, Mian; Liu, Chen; He, Shihong; He, Jian; He, Heming

    2016-01-01

    Silicon carbide has many attractive properties and the SiC/SiC composite has been considered as a promising candidate for nuclear structural materials. Up to now, a computational investigation on the properties of SiC/SiC composite varying in the presence of nuclear fission products is still missing. In this work, the influence of He atoms on the shear behavior of the SiC/SiC interphase is investigated via Molecular Dynamics simulation following our recent paper. Calculations are carried out on three dimensional models of graphite-like PyC/SiC interphase and amorphous PyC/SiC interphase with He atoms in different regions (the SiC region, the interface region and the PyC region). In the graphite-like PyC/SiC interphase, He atoms in the SiC region have little influence on the shear strength of the material, while both the shear strength and friction strength may be enhanced when they are in the PyC region. Low concentration of He atoms in the interface region of the graphite-like PyC/SiC interphase increases the shear strength, while there is a reduction of shear strength when the He concentration is high due to the switch of sliding plane. In the amorphous PyC/SiC interphase, He atoms can cause the reduction of the shear strength regardless of the regions that He atoms are located. The presence of He atoms may significantly alter the structure of SiC/SiC in the interface region. The influence of He atoms in the interface region is the most significant, leading to evident shear strength reduction of the amorphous PyC/SiC interphase with increasing He concentration. The behaviors of the interphases at different temperatures are studied as well. The dependence of the shear strengths of the two types of interphases on temperatures is studied as well. For the graphite-like PyC/SiC interphase, it is found strongly related to the regions He atoms are located. Combining these results with our previous study on pure SiC/SiC system, we expect this work may provide new insight

  8. Diode behavior in ultra-thin low temperature ALD grown zinc-oxide on silicon

    Directory of Open Access Journals (Sweden)

    Nazek El-Atab

    2013-10-01

    Full Text Available A thin-film ZnO(n/Si(p+ heterojunction diode is demonstrated. The thin film ZnO layer is deposited by Atomic Layer Deposition (ALD at different temperatures on a p-type silicon substrate. Atomic force microscopy (AFM AC-in-Air method in addition to conductive AFM (CAFM were used for the characterization of ZnO layer and to measure the current-voltage characteristics. Forward and reverse bias n-p diode behavior with good rectification properties is achieved. The diode with ZnO grown at 80°C exhibited the highest on/off ratio with a turn-on voltage (VON ∼3.5 V. The measured breakdown voltage (VBR and electric field (EBR for this diode are 5.4 V and 3.86 MV/cm, respectively.

  9. Adding thin-ideal internalization and impulsiveness to the cognitive-behavioral model of bulimic symptoms.

    Science.gov (United States)

    Schnitzler, Caroline E; von Ranson, Kristin M; Wallace, Laurel M

    2012-08-01

    This study evaluated the cognitive-behavioral (CB) model of bulimia nervosa and an extension that included two additional maintaining factors - thin-ideal internalization and impulsiveness - in 327 undergraduate women. Participants completed measures of demographics, self-esteem, concern about shape and weight, dieting, bulimic symptoms, thin-ideal internalization, and impulsiveness. Both the original CB model and the extended model provided good fits to the data. Although structural equation modeling analyses suggested that the original CB model was most parsimonious, hierarchical regression analyses indicated that the additional variables accounted for significantly more variance. Additional analyses showed that the model fit could be improved by adding a path from concern about shape and weight, and deleting the path from dieting, to bulimic symptoms. Expanding upon the factors considered in the model may better capture the scope of variables maintaining bulimic symptoms in young women with a range of severity of bulimic symptoms. Copyright © 2012 Elsevier Ltd. All rights reserved.

  10. Scaling behavior of mixed-state hall effect in MgB2 thin films

    International Nuclear Information System (INIS)

    Jung, Soon-Gil; Seong, W.K.; Kang, W.N.; Choi, Eun-Mi; Kim, Heon-Jung; Lee, Sung-Ik; Kim, Hyeong-Jin; Kim, H.C.

    2006-01-01

    The Hall resistivity (ρ xy ) and the longitudinal resistivity (ρ xx ) in c-axis-oriented superconducting MgB 2 thin films have been investigated in extended fields up to 18T. We have observed a scaling behavior between the Hall resistivity and the longitudinal resistivity, ρ xy =Aρ xx β , where the exponent (β) is observed to be independent of the temperatures and the magnetic fields. For a wide magnetic field region from 1 to 18T and a wide temperature region from 10 to 28K, a universal power law with β=2.0+/-0.1 was observed in c-axis-oriented MgB 2 thin films. These results can be well interpreted by using recent models

  11. Soil behavior under earthquake loading conditions. In situ impulse test for determination of shear modulus for seismic response analyses. Progress report

    International Nuclear Information System (INIS)

    1974-06-01

    Progress is reported in the determination of the best methods of evaluation and prediction of soil behavior of potential nuclear power plant sites under seismic loading conditions. Results are reported of combined experimental and analytical studies undertaken to continue development of an in situ impulse test for determination of the soil shear modulus. Emphasis of the field work was directed toward making the field measurements at frequent depth intervals and at shear strains in the strong motion earthquake range. Emphasis of the analytical work was aimed toward supporting the field effort through processing and evaluation of the experimental test results combined with additional calculations required to gain insight into data interpretation and the in situ test setup itself. Continuing studies to evaluate free field soil behavior under earthquake loading conditions are discussed. (U.S.)

  12. Influence of type-I fimbriae and fluid shear stress on bacterial behavior and multicellular architecture of early Escherichia coli biofilms at single-cell resolution.

    Science.gov (United States)

    Wang, Liyun; Keatch, Robert; Zhao, Qi; Wright, John A; Bryant, Clare E; Redmann, Anna L; Terentjev, Eugene M

    2018-01-12

    Biofilm formation on abiotic surfaces in food and medical industry can cause severe contamination and infection, yet how biological and physical factors determine cellular architecture of early biofilms and bacterial behavior of the constituent cells remains largely unknown. In this study we examine the specific role of type-I fimbriae in nascent stages of biofilm formation and the response of micro-colonies to environmental flow shear at single-cell resolution. The results show that type-I fimbriae are not required for reversible adhesion from plankton, but critical for irreversible adhesion of Escherichia coli ( E.coli ) MG1655 forming biofilms on polyethylene terephthalate (PET) surfaces. Besides establishing a firm cell-surface contact, the irreversible adhesion seems necessary to initiate the proliferation of E.coli on the surface. After application of shear stress, bacterial retention is dominated by the 3D architecture of colonies independent of the population and the multi-layered structure could protect the embedded cells from being insulted by fluid shear, while cell membrane permeability mainly depends on the biofilm population and the duration time of the shear stress. Importance Bacterial biofilms could lead to severe contamination problems in medical devices and food processing equipment. However, biofilms are usually studied at a rough macroscopic level, thus little is known about how individual bacterial behavior within biofilms and multicellular architecture are influenced by bacterial appendages (e.g. pili/fimbriae) and environmental factors during early biofilm formation. We apply Confocal Laser Scanning Microscopy (CLSM) to visualize E.coli micro-colonies at single-cell resolution. Our findings suggest that type-I fimbriae are vital to the initiation of bacterial proliferation on surfaces and that the responses of biofilm architecture and cell membrane permeability of constituent bacteria to fluid shear stress are different, which are

  13. The Shear Strength and Fracture Behavior of Sn-Ag- xSb Solder Joints with Au/Ni-P/Cu UBM

    Science.gov (United States)

    Lee, Hwa-Teng; Hu, Shuen-Yuan; Hong, Ting-Fu; Chen, Yin-Fa

    2008-06-01

    This study investigates the effects of Sb addition on the shear strength and fracture behavior of Sn-Ag-based solders with Au/Ni-P/Cu underbump metallization (UBM) substrates. Sn-3Ag- xSb ternary alloy solder joints were prepared by adding 0 wt.% to 10 wt.% Sb to a Sn-3.5Ag alloy and joining them with Au/Ni-P/Cu UBM substrates. The solder joints were isothermally stored at 150°C for up to 625 h to study their microstructure and interfacial reaction with the UBM. Single-lap shear tests were conducted to evaluate the mechanical properties, thermal resistance, and failure behavior. The results show that UBM effectively suppressed intermetallic compound (IMC) formation and growth during isothermal storage. The Sb addition helped to refine the Ag3Sn compounds, further improving the shear strength and thermal resistance of the solders. The fracture behavior evolved from solder mode toward the mixed mode and finally to the IMC mode with increasing added Sb and isothermal storage time. However, SnSb compounds were found in the solder with 10 wt.% Sb; they may cause mechanical degradation of the solder after long-term isothermal storage.

  14. Excited waves in shear layers

    Science.gov (United States)

    Bechert, D. W.

    1982-01-01

    The generation of instability waves in free shear layers is investigated. The model assumes an infinitesimally thin shear layer shed from a semi-infinite plate which is exposed to sound excitation. The acoustical shear layer excitation by a source further away from the plate edge in the downstream direction is very weak while upstream from the plate edge the excitation is relatively efficient. A special solution is given for the source at the plate edge. The theory is then extended to two streams on both sides of the shear layer having different velocities and densities. Furthermore, the excitation of a shear layer in a channel is calculated. A reference quantity is found for the magnitude of the excited instability waves. For a comparison with measurements, numerical computations of the velocity field outside the shear layer were carried out.

  15. Evaluation of Nonlinear Behavior of Dual Steel Frame-Shear Wall System by a Group of Real Earthquakes

    OpenAIRE

    Reza Bemanian; Hamzeh Shakib

    2016-01-01

    Dual system of steel moment frame and steel plate shear wall has many advantages in comparison to the other systems. Since the last four decades the dual system has been used more frequently in new and existing structures. the steel shear wall has many advantages such as high ductility, strength, stiffness and it has light weight, it consequent reduce lateral forces and time efficiency in contracture procedure. The aim of this study is to evaluate the seismic performance of the dual steel fra...

  16. Tensile and fatigue behaviors of printed Ag thin films on flexible substrates

    International Nuclear Information System (INIS)

    Sim, Gi-Dong; Won, Sejeong; Lee, Soon-Bok

    2012-01-01

    Flexible electronics using nanoparticle (NP) printing has been highlighted as a key technology enabling eco-friendly, low-cost, and large-area fabrication. For NP-based printing to be used as a successive alternative to photolithography and vacuum deposition, stretchability and long term reliability must be considered. This paper reports the stretchability and fatigue behavior of 100 nm thick NP-based silver thin films printed on polyethylene-terephthalate substrate and compares it to films deposited by electron-beam evaporation. NP-based films show stretchability and fatigue life comparable to evaporated films with intergranular fracture as the dominant failure mechanism.

  17. Tensile and fatigue behaviors of printed Ag thin films on flexible substrates

    Science.gov (United States)

    Sim, Gi-Dong; Won, Sejeong; Lee, Soon-Bok

    2012-11-01

    Flexible electronics using nanoparticle (NP) printing has been highlighted as a key technology enabling eco-friendly, low-cost, and large-area fabrication. For NP-based printing to be used as a successive alternative to photolithography and vacuum deposition, stretchability and long term reliability must be considered. This paper reports the stretchability and fatigue behavior of 100 nm thick NP-based silver thin films printed on polyethylene-terephthalate substrate and compares it to films deposited by electron-beam evaporation. NP-based films show stretchability and fatigue life comparable to evaporated films with intergranular fracture as the dominant failure mechanism.

  18. Deformation behavior of Cu bicrystals with the Σ9(110)(221) symmetric tilt grain boundary under pure shear studied by atomistic simulation method

    International Nuclear Information System (INIS)

    Wan Liang; Wang Shaoqing

    2010-01-01

    The deformation behavior of Cu bicrystals with the symmetric tilt grain boundary (STGB) under pure shear has been studied by atomistic simulation method with the embedded atom method (EAM) interatomic potentials. By using an energy minimization method, it shows that there are two optimized structures of this grain boundary (GB) which correspond to two local energy minima on the potential energy surface of the GB. The structure with lower energy is the stable one while the other is a metastable structure. The pure shear process of the bicrystals at ambient temperature has been studied by molecular dynamics (MD) simulation method. The simulated results indicate that there are three structure transformation modes of this GB depending on the shear direction: (1) pure GB sliding; (2) GB atomic shuffling accompanied by dislocation emission from GB; (3) GB migration coupled GB sliding, namely, GB coupling motion. In addition, an analysis of the structure evolution of the GB shows that, there are two mechanisms for GB coupling motion depending on the shear direction. One is the collective motion of GB atoms and the other is structure transformation realized by uncorrelated atomic shuffling processes. The former mechanism can induce structure transition of GB between the stable one and the metastable one, while the latter introduces faceting of the GB. (authors)

  19. Thermal dewetting behavior of polystyrene composite thin films with organic-modified inorganic nanoparticles.

    Science.gov (United States)

    Kubo, Masaki; Takahashi, Yosuke; Fujii, Takeshi; Liu, Yang; Sugioka, Ken-ichi; Tsukada, Takao; Minami, Kimitaka; Adschiri, Tadafumi

    2014-07-29

    The thermal dewetting of polystyrene composite thin films with oleic acid-modified CeO2 nanoparticles prepared by the supercritical hydrothermal synthesis method was investigated, varying the nanoparticle concentration (0-30 wt %), film thickness (approximately 50 and 100 nm), and surface energy of silanized silicon substrates on which the composite films were coated. The dewetting behavior of the composite thin films during thermal annealing was observed by an optical microscope. The presence of nanoparticles in the films affected the morphology of dewetting holes, and moreover suppressed the dewetting itself when the concentration was relatively high. It was revealed that there was a critical value of the surface energy of the substrate at which the dewetting occurred. In addition, the spatial distributions of nanoparticles in the composite thin films before thermal annealing were investigated using AFM and TEM. As a result, we found that most of nanoparticles segregated to the surface of the film, and that such distributions of nanoparticles contribute to the stabilization of the films, by calculating the interfacial potential of the films with nanoparticles.

  20. Silicon wafer wettability and aging behaviors: Impact on gold thin-film morphology

    KAUST Repository

    Yang, Xiaoming; Zhong, Zhaowei; Diallo, Elhadj; Wang, Zhihong; Yue, Weisheng

    2014-01-01

    This paper reports on the wettability and aging behaviors of the silicon wafers that had been cleaned using a piranha (3:1 mixture of sulfuric acid (H2SO4, 96%) and hydrogen peroxide (H2O 2, 30%), 120 °C), SC1 (1:1:5 mixture of NH4OH, H 2O2 and H2O, at 80°C) or HF solution (6 parts of 40% NH4F and 1 part of 49% HF, at room temperature) solution, and treated with gaseous plasma. The silicon wafers cleaned using the piranha or SC1 solution were hydrophilic, and the water contact angles on the surfaces would increase along with aging time, until they reached the saturated points of around 70°. The contact angle increase rate of these wafers in a vacuum was much faster than that in the open air, because of loss of water, which was physically adsorbed on the wafer surfaces. The silicon wafers cleaned with the HF solution were hydrophobic. Their contact angle decreased in the atmosphere, while it increased in the vacuum up to 95°. Gold thin films deposited on the hydrophilic wafers were smoother than that deposited on the hydrophobic wafers, because the numerous oxygen groups formed on the hydrophilic surfaces would react with gold adatoms in the sputtering process to form a continuous thin film at the nucleation stage. The argon, nitrogen, oxygen gas plasma treatments could change the silicon wafer surfaces from hydrophobic to hydrophilic by creating a thin (around 2.5 nm) silicon dioxide film, which could be utilized to improve the roughness and adhesion of the gold thin film. © 2014 Elsevier Ltd. All rights reserved.

  1. Silicon wafer wettability and aging behaviors: Impact on gold thin-film morphology

    KAUST Repository

    Yang, Xiaoming

    2014-10-01

    This paper reports on the wettability and aging behaviors of the silicon wafers that had been cleaned using a piranha (3:1 mixture of sulfuric acid (H2SO4, 96%) and hydrogen peroxide (H2O 2, 30%), 120 °C), SC1 (1:1:5 mixture of NH4OH, H 2O2 and H2O, at 80°C) or HF solution (6 parts of 40% NH4F and 1 part of 49% HF, at room temperature) solution, and treated with gaseous plasma. The silicon wafers cleaned using the piranha or SC1 solution were hydrophilic, and the water contact angles on the surfaces would increase along with aging time, until they reached the saturated points of around 70°. The contact angle increase rate of these wafers in a vacuum was much faster than that in the open air, because of loss of water, which was physically adsorbed on the wafer surfaces. The silicon wafers cleaned with the HF solution were hydrophobic. Their contact angle decreased in the atmosphere, while it increased in the vacuum up to 95°. Gold thin films deposited on the hydrophilic wafers were smoother than that deposited on the hydrophobic wafers, because the numerous oxygen groups formed on the hydrophilic surfaces would react with gold adatoms in the sputtering process to form a continuous thin film at the nucleation stage. The argon, nitrogen, oxygen gas plasma treatments could change the silicon wafer surfaces from hydrophobic to hydrophilic by creating a thin (around 2.5 nm) silicon dioxide film, which could be utilized to improve the roughness and adhesion of the gold thin film. © 2014 Elsevier Ltd. All rights reserved.

  2. Reversed-phase thin-layer chromatography behavior of aldopentose derivatives

    Directory of Open Access Journals (Sweden)

    Malbaša Radomir V.

    2012-01-01

    Full Text Available Quantitative structure-retention relationships (QSRR have been used to study the chromatographic behavior of some aldopentose. The behavior of aldopentose derivatives was investigated by means of the reversed-phase thin-layer chromatography (RP TLC on the silica gel impregnated with paraffin oil stationary phases. Binary mixtures of methanol-water, acetone-water and dioxane-water were used as mobile phases. Retention factors, RM0, corresponding to zero percent organic modifier in the aqueous mobile phase was determined. Lipophilicity C0 was calculated as the ratio of the intercept and slope values. There was satisfactory correlation between them and log P values calculated using different theoretical procedures. Some of these correlations offer very good predicting models, which are important for a better understanding of the relationships between chemical structure and retention. The study showed that the hydrophobic parameters RM0 and C0 can be used as a measures of lipophilicity of investigated compounds.

  3. Axial Crushing Behaviors of Thin-Walled Corrugated and Circular Tubes - A Comparative Study

    Science.gov (United States)

    Reyaz-Ur-Rahim, Mohd.; Bharti, P. K.; Umer, Afaque

    2017-10-01

    With the help of finite element analysis, this research paper deals with the energy absorption and collapse behavior with different corrugated section geometries of hollow tubes made of aluminum alloy 6060-T4. Literature available experimental data were used to validate the numerical models of the structures investigated. Based on the results available for symmetric crushing of circular tubes, models were developed to investigate corrugated thin-walled structures behavior. To study the collapse mechanism and energy absorbing ability in axial compression, the simulation was carried in ABAQUS /EXPLICIT code. In the simulation part, specimens were prepared and axially crushed to one-fourth length of the tube and the energy diagram of crushing force versus axial displacement is shown. The effect of various parameters such as pitch, mean diameter, corrugation, amplitude, the thickness is demonstrated with the help of diagrams. The overall result shows that the corrugated section geometry could be a good alternative to the conventional tubes.

  4. Nanotribological Behavior of Carbon Based Thin Films: Friction and Lubricity Mechanisms at the Nanoscale

    Directory of Open Access Journals (Sweden)

    Costas A. Charitidis

    2013-04-01

    Full Text Available The use of materials with very attractive friction and wear properties has raised much attention in research and industrial sectors. A wide range of tribological applications, including rolling and sliding bearings, machining, mechanical seals, biomedical implants and microelectromechanical systems (MEMS, require thin films with high mechanical strength, chemical inertness, broad optical transparency, high refractive index, wide bandgap excellent thermal conductivity and extremely low thermal expansion. Carbon based thin films like diamond, diamond-like carbon, carbon nitride and cubic boron nitride known as “super-hard” material have been studied thoroughly as the ideal candidate for tribological applications. In this study, the results of experimental and simulation works on the nanotribological behavior of carbon films and fundamental mechanisms of friction and lubricity at the nano-scale are reviewed. The study is focused on the nanomechanical properties and analysis of the nanoscratching processes at low loads to obtain quantitative analysis, the comparison obtain quantitative analysis, the comparison of their elastic/plastic deformation response, and nanotribological behavior of the a-C, ta-C, a-C:H, CNx, and a-C:M films. For ta-C and a-C:M films new data are presented and discussed.

  5. Conductivity behavior of very thin gold films ruptured by mass transport in photosensitive polymer film

    Energy Technology Data Exchange (ETDEWEB)

    Linde, Felix; Sekhar Yadavalli, Nataraja; Santer, Svetlana [Department of Experimental Physics, Institute for Physics and Astronomy, University of Potsdam, 14476 Potsdam (Germany)

    2013-12-16

    We report on conductivity behavior of very thin gold layer deposited on a photosensitive polymer film. Under irradiation with light interference pattern, the azobenzene containing photosensitive polymer film undergoes deformation at which topography follows a distribution of intensity, resulting in the formation of a surface relief grating. This process is accompanied by a change in the shape of the polymer surface from flat to sinusoidal together with a corresponding increase in surface area. The gold layer placed above deforms along with the polymer and ruptures at a strain of 4%. The rupturing is spatially well defined, occurring at the topographic maxima and minima resulting in periodic cracks across the whole irradiated area. We have shown that this periodic micro-rupturing of a thin metal film has no significant impact on the electrical conductivity of the films. We suggest a model to explain this phenomenon and support this by additional experiments where the conductivity is measured in a process when a single nanoscopic scratch is formed with an AFM tip. Our results indicate that in flexible electronic materials consisting of a polymer support and an integrated metal circuit, nano- and micro cracks do not alter significantly the behavior of the conductivity unless the metal is disrupted completely.

  6. Pronounced prefronto-temporal cortical thinning in schizophrenia: Neuroanatomical correlate of suicidal behavior?

    Science.gov (United States)

    Besteher, Bianca; Wagner, Gerd; Koch, Kathrin; Schachtzabel, Claudia; Reichenbach, Jürgen R; Schlösser, Ralf; Sauer, Heinrich; Schultz, C Christoph

    2016-10-01

    Schizophrenia is characterized by increased mortality for which suicidality is the decisive factor. An analysis of cortical thickness and folding to further elucidate neuroanatomical correlates of suicidality in schizophrenia has not yet been performed. We searched for relevant brain regions with such differences between patients with suicide-attempts, patients without any suicidal thoughts and healthy controls. 37 schizophrenia patients (14 suicide-attempters and 23 non-suicidal) and 50 age- and gender-matched healthy controls were included. Suicidality was documented through clinical interview and chart review. All participants underwent T1-weighted MRI scans. Whole brain node-by-node cortical thickness and folding were estimated (FreeSurfer Software) and compared. Additionally a three group comparison for prefrontal regions-of-interest was performed in SPSS using a multifactorial GLM. Compared with the healthy controls patients showed a typical pattern of cortical thinning in prefronto-temporal regions and altered cortical folding in the right medial temporal cortex. Patients with suicidal behavior compared with non-suicidal patients demonstrated pronounced (psuicidal patients with non-suicidal patients significant (psuicidal behaviour in schizophrenia. We identified cortical thinning in a network strongly involved in regulation of impulsivity, emotions and planning of behaviour in suicide attempters, which might lead to neuronal dysregulation in this network and consequently to a higher risk of suicidal behavior. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. A Laboratory Investigation on Shear Strength Behavior of Sandy Soil: Effect of Glass Fiber and Clinker Residue Content

    Directory of Open Access Journals (Sweden)

    Bouaricha Leyla

    2017-12-01

    Full Text Available A study was undertaken to investigate the shear strength parameters of treated sands reinforced with randomly distributed glass fibers by carrying out direct shear test after seven days curing periods. Firstly, we studied the fiber content and fiber length effect on the peak shear strength on samples. The second part gives a parametric analysis on the effect of glass fiber and clinker residue content on the shear strength parameters for two types of uniform Algerian sands having different particle sizes (Chlef sand and Rass sand with an average relative density Dr = 50%. Finally, the test results show that the combination of glass fiber and clinker residue content can effectively improve the shear strength parameters of soil in comparison with unreinforced soil. For instance, there is a significant gain for the cohesion and friction angle of reinforced sand of Chlef. Compared to unreinforced sand, the cohesion for sand reinforced with different ratios of clinker residue increased by 4.36 to 43.08 kPa for Chlef sand and by 3.1 to 28.64 kPa for Rass sand. The feature friction angles increased from 38.73° to 43.01° (+4.28°, and after the treatment, clinker residue content of soil evaluated to 5% (WRC = 5%.

  8. A Laboratory Investigation on Shear Strength Behavior of Sandy Soil: Effect of Glass Fiber and Clinker Residue Content

    Science.gov (United States)

    Bouaricha, Leyla; Henni, Ahmed Djafar; Lancelot, Laurent

    2017-12-01

    A study was undertaken to investigate the shear strength parameters of treated sands reinforced with randomly distributed glass fibers by carrying out direct shear test after seven days curing periods. Firstly, we studied the fiber content and fiber length effect on the peak shear strength on samples. The second part gives a parametric analysis on the effect of glass fiber and clinker residue content on the shear strength parameters for two types of uniform Algerian sands having different particle sizes (Chlef sand and Rass sand) with an average relative density Dr = 50%. Finally, the test results show that the combination of glass fiber and clinker residue content can effectively improve the shear strength parameters of soil in comparison with unreinforced soil. For instance, there is a significant gain for the cohesion and friction angle of reinforced sand of Chlef. Compared to unreinforced sand, the cohesion for sand reinforced with different ratios of clinker residue increased by 4.36 to 43.08 kPa for Chlef sand and by 3.1 to 28.64 kPa for Rass sand. The feature friction angles increased from 38.73° to 43.01° (+4.28°), and after the treatment, clinker residue content of soil evaluated to 5% (WRC = 5%).

  9. Friction and wear behavior of nitrogen-doped ZnO thin films deposited via MOCVD under dry contact

    Directory of Open Access Journals (Sweden)

    U.S. Mbamara

    2016-06-01

    Full Text Available Most researches on doped ZnO thin films are tilted toward their applications in optoelectronics and semiconductor devices. Research on their tribological properties is still unfolding. In this work, nitrogen-doped ZnO thin films were deposited on 304 L stainless steel substrate from a combination of zinc acetate and ammonium acetate precursor by MOCVD technique. Compositional and structural studies of the films were done using Rutherford Backscattering Spectroscopy (RBS and X-ray Diffraction (XRD. The frictional behavior of the thin film coatings was evaluated using a ball-on-flat configuration in reciprocating sliding under dry contact condition. After friction test, the flat and ball counter-face surfaces were examined to assess the wear dimension and failure mechanism. Both friction behavior and wear (in the ball counter-face were observed to be dependent on the crystallinity and thickness of the thin film coatings.

  10. Creep behavior in interlaminar shear of a Hi-Nicalon™/SiC–B4C composite at 1200 °C in air and in steam

    International Nuclear Information System (INIS)

    Ruggles-Wrenn, M.B.; Pope, M.T.; Zens, T.W.

    2014-01-01

    Creep behavior in interlaminar shear of a non-oxide ceramic composite with a multilayered matrix was investigated at 1200 °C in laboratory air and in steam environment. The composite was produced via chemical vapor infiltration (CVI). The composite had an oxidation inhibited matrix, which consisted of alternating layers of silicon carbide and boron carbide and was reinforced with laminated Hi-Nicalon™ fibers woven in a five-harness-satin weave. Fiber preforms had pyrolytic carbon fiber coating with boron carbon overlay applied. The interlaminar shear properties were measured. The creep behavior was examined for interlaminar shear stresses in the 16–22 MPa range. Primary and secondary creep regimes were observed in all tests conducted in air and in steam. In air and in steam, creep run-out defined as 100 h at creep stress was achieved at 16 MPa. Similar creep strains were accumulated in air and in steam. Furthermore, creep strain rates and creep lifetimes were only moderately affected by the presence of steam. The retained properties of all specimens that achieved run-out were characterized. Composite microstructure, as well as damage and failure mechanisms were investigated. The tested specimens were also examined using electron probe microanalysis (EPMA) with wavelength dispersive spectroscopy (WDS). Analysis of the fracture surfaces revealed significant surface oxidation, but only trace amounts of boron and carbon. Cross sectional analysis showed increasing boron concentration in the specimen interior

  11. Computer Simulation Study of Collective Phenomena in Dense Suspensions of Red Blood Cells under Shear

    CERN Document Server

    Krüger, Timm

    2012-01-01

    The rheology of dense red blood cell suspensions is investigated via computer simulations based on the lattice Boltzmann, the immersed boundary, and the finite element methods. The red blood cells are treated as extended and deformable particles immersed in the ambient fluid. In the first part of the work, the numerical model and strategies for stress evaluation are discussed. In the second part, the behavior of the suspensions in simple shear flow is studied for different volume fractions, particle deformabilities, and shear rates. Shear thinning behavior is recovered. The existence of a shear-induced transition from a tumbling to a tank-treading motion is demonstrated. The transition can be parameterized by a single quantity, namely the effective capillary number. It is the ratio of the suspension stress and the characteristic particle membrane stress. At the transition point, a strong increase in the orientational order of the red blood cells and a significant decrease of the particle diffusivity are obser...

  12. Diffusion barrier characteristics and shear fracture behaviors of eutectic PbSn solder/electroless Co(W,P) samples

    International Nuclear Information System (INIS)

    Pan, Hung-Chun; Hsieh, Tsung-Eong

    2012-01-01

    Highlights: ► Diffusion barrier features, activation energies of IMC growth and mechanical behaviors of electroless Co(W,P)/PbSn joints. ► Amorphous Co(W,P) is a sacrificial- plus stuffed-type barrier while polycrystalline Co(W,P) is a sacrificial-type barrier. ► Ductile mode dominates the failure of Co(W,P)/PbSn joints. ► Phosphorus content of Co(W,P) is crucial to the barrier capability and microstructure evolution at Co(W,P)/PbSn interface. ► Diffusion barrier capability is governed by the nature of chemical bonds, rather than the crystallinity of materials. - Abstract: Diffusion barrier characteristics, activation energy (E a ) of IMC growth and bonding properties of amorphous and polycrystalline electroless Co(W,P) (termed as α-Co(W,P) and poly-Co(W,P)) to eutectic PbSn solder are presented. Intermetallic compound (IMC) spallation and an nano-crystalline P-rich layer were observed in PbSn/α-Co(W,P) samples subjected to liquid-state aging at 250 °C. In contrast, IMCs resided on the P-rich layer in PbSn/α-Co(W,P) samples subjected to solid-state aging at 150 °C. Thick IMCs neighboring to an amorphous W-rich layer was seen in PbSn/poly-Co(W,P) samples regardless of the aging type. α-Co(W,P) was found to be a sacrificial- plus stuffed-type barrier while poly-Co(W,P) is mainly a sacrificial-type barrier. The values of E a 's for PbSn/α-Co(W,P) and PbSn/poly-Co(W,P) systems were 338.6 and 167.5 kJ/mol, respectively. Shear test revealed the ductile mode dominates the failure in both α- and poly-Co(W,P) samples. Analytical results indicated the high P content in electroless layer might enhance the barrier capability but degrade the bonding strength.

  13. Chemical controls on fault behavior: weakening of serpentinite sheared against quartz-bearing rocks and its significance for fault creep in the San Andreas system

    Science.gov (United States)

    Moore, Diane E.; Lockner, David A.

    2013-01-01

    The serpentinized ultramafic rocks found in many plate-tectonic settings commonly are juxtaposed against crustal rocks along faults, and the chemical contrast between the rock types potentially could influence the mechanical behavior of such faults. To investigate this possibility, we conducted triaxial experiments under hydrothermal conditions (200-350°C), shearing serpentinite gouge between forcing blocks of granite or quartzite. In an ultramafic chemical environment, the coefficient of friction, µ, of lizardite and antigorite serpentinite is 0.5-0.6, and µ increases with increasing temperature over the tested range. However, when either lizardite or antigorite serpentinite is sheared against granite or quartzite, strength is reduced to µ ~ 0.3, with the greatest strength reductions at the highest temperatures (temperature weakening) and slowest shearing rates (velocity strengthening). The weakening is attributed to a solution-transfer process that is promoted by the enhanced solubility of serpentine in pore fluids whose chemistry has been modified by interaction with the quartzose wall rocks. The operation of this process will promote aseismic slip (creep) along serpentinite-bearing crustal faults at otherwise seismogenic depths. During short-term experiments serpentine minerals reprecipitate in low-stress areas, whereas in longer experiments new Mg-rich phyllosilicates crystallize in response to metasomatic exchanges across the serpentinite-crustal rock contact. Long-term shear of serpentinite against crustal rocks will cause the metasomatic mineral assemblages, which may include extremely weak minerals such as saponite or talc, to play an increasingly important role in the mechanical behavior of the fault. Our results may explain the distribution of creep on faults in the San Andreas system.

  14. The interaction of two spheres in a simple-shear flow of complex fluids

    Science.gov (United States)

    Firouznia, Mohammadhossein; Metzger, Bloen; Ovarlez, Guillaume; Hormozi, Sarah

    2017-11-01

    We study the interaction of two small freely-moving spheres in a linear flow field of Newtonian, shear thinning and yield stress fluids. We perform a series of experiments over a range of shear rates as well as different shear histories using an original apparatus and with the aid of conventional rheometry, Particle Image Velocimetry and Particle Tracking Velocimetry. Showing that the non-Newtonian nature of the suspending fluid strongly affects the shape of particle trajectories and the irreversibility. An important point is that non-Newtonian effects can be varied and unusual. Depending on the shear rate, nonideal shear thinning and yield stress suspending fluids might show elasticity that needs to be taken into account. The flow field around one particle is studied in different fluids when subjected to shear. Then using these results to explain the two particle interactions in a simple-shear flow we show how particle-particle contact and non-Newtonian behaviors result in relative trajectories with fore-aft asymmetry. Well-resolved velocity and stress fields around the particles are presented here. Finally, we discuss how the relative particle trajectories may affect the microstructure of complex suspensions and consequently the bulk rheology. NSF (Grant No. CBET-1554044-CAREER).

  15. Crystallization characteristic and scaling behavior of germanium antimony thin films for phase change memory.

    Science.gov (United States)

    Wu, Weihua; Zhao, Zihan; Shen, Bo; Zhai, Jiwei; Song, Sannian; Song, Zhitang

    2018-04-19

    Amorphous Ge8Sb92 thin films with various thicknesses were deposited by magnetron sputtering. The crystallization kinetics and optical properties of the Ge8Sb92 thin films and related scaling effects were investigated by an in situ thermally induced method and an optical technique. With a decrease in film thickness, the crystallization temperature, crystallization activation energy and data retention ability increased significantly. The changed crystallization behavior may be ascribed to the smaller grain size and larger surface-to-volume ratio as the film thickness decreased. Regardless of whether the state was amorphous or crystalline, the film resistance increased remarkably as the film thickness decreased to 3 nm. The optical band gap calculated from the reflection spectra increases distinctly with a reduction in film thickness. X-ray diffraction patterns confirm that the scaling of the Ge8Sb92 thin film can inhibit the crystallization process and reduce the grain size. The values of exponent indices that were obtained indicate that the crystallization mechanism experiences a series of changes with scaling of the film thickness. The crystallization time was estimated to determine the scaling effect on the phase change speed. The scaling effect on the electrical switching performance of a phase change memory cell was also determined. The current-voltage and resistance-voltage characteristics indicate that phase change memory cells based on a thinner Ge8Sb92 film will exhibit a higher threshold voltage, lower RESET operational voltage and greater pulse width, which implies higher thermal stability, lower power consumption and relatively lower switching velocity.

  16. The order-to-disorder transition behavior of PS-b-P2VP thin film system

    Science.gov (United States)

    Ahn, Hyungju; Ryu, Du

    2013-03-01

    We investigated the transition behavior such as the order-to-disorder transition (ODT) for symmetric poly(styrene)-block-poly(2-vinly pridine) (PS-b-P2VP) using SAXS and GISAXS for block copolymer bulks and films. The bulk transition temperature of PS-b-P2VP was significantly influenced by the interfacial interactions in thin films, leading to the different transition temperature. From these results, we will discuss about the interfacial interaction effects on the phase behaviors in bulks and thin films system of PS-b-P2VP.

  17. Behavior of Hollow Thin Welded Tubes Filled with Sand Slag Concrete

    Directory of Open Access Journals (Sweden)

    Noureddine Ferhoune

    2016-01-01

    Full Text Available This paper presents the axial bearing capacity of thin welded rectangular steel stubs filled with concrete sand. A series of tests was conducted to study the behavior of short composite columns under axial compressive load; the cross section dimensions were 100 × 70 × 2 mm. A total of 20 stubs have been tested, as follows: 4 hollow thin welded tubes were tested to axial and eccentric load compression, 4 were filled with ordinary concrete appointed by BO columns, 6 were filled with concrete whose natural sand was completely substituted by a crystallized sand slag designated in this paper by BSI, and 6 were tucked in concrete whose natural sand was partially replaced by a crystallized sand slag called BSII. The main parameters studied are the height of the specimen (300 mm–500 mm, eccentricity of load and type of filling concrete. Based on test results obtained, it is confirmed that the length of the tubes has a considerable effect on the bearing capacity and the failure mode. In all test tubes, fracture occurred by the convex local buckling of steel section due to the outward thrust of the concrete; it was observed that the sand concrete improves the bearing capacity of tubes compounds compared to those filled with ordinary concrete.

  18. Improved polymer thin-film wetting behavior through nanoparticle segregation to interfaces

    International Nuclear Information System (INIS)

    Krishnan, R S; Mackay, M E; Duxbury, P M; Hawker, C J; Asokan, Suba; Wong, Michael S; Goyette, Rick; Thiyagarajan, P

    2007-01-01

    We report a systematic study of improved wetting behavior for thin polymer films containing nanoparticles, as a function of nanoparticle size and concentration, the energy of the substrate and the dielectric properties of the nanoparticles. An enthalpy matched system consisting of polystyrene nanoparticles in linear polystyrene is used to show that nanoparticles are uniformly distributed in the film after spin coating and drying. However, on annealing the film above its bulk glass transition temperature these nanoparticles segregate strongly to the solid substrate. We find that for a wide range of film thicknesses and nanoparticle sizes, a substrate coverage of nanoparticles of approximately a monolayer is required for dewetting inhibition. Cadmium selenide quantum dots also inhibit dewetting of polystyrene thin films, again when a monolayer is present. Moreover, TEM microscopy images indicate that CdSe quantum dots segregate primarily to the air interface. Theoretical interpretation of these phenomena suggests that gain of linear chain configurational entropy promotes segregation of nanoparticles to the solid substrate, as occurs for polystyrene nanoparticles; however, for CdSe nanoparticles this is offset by surface energy or enthalpic terms which promote segregation of the nanoparticles to the air interface

  19. Anomalous degradation behaviors under illuminated gate bias stress in a-Si:H thin film transistor

    International Nuclear Information System (INIS)

    Tsai, Ming-Yen; Chang, Ting-Chang; Chu, Ann-Kuo; Hsieh, Tien-Yu; Lin, Kun-Yao; Wu, Yi-Chun; Huang, Shih-Feng; Chiang, Cheng-Lung; Chen, Po-Lin; Lai, Tzu-Chieh; Lo, Chang-Cheng; Lien, Alan

    2014-01-01

    This study investigates the impact of gate bias stress with and without light illumination in a-Si:H thin film transistors. It has been observed that the I–V curve shifts toward the positive direction after negative and positive gate bias stress due to interface state creation at the gate dielectric. However, this study found that threshold voltages shift negatively and that the transconductance curve maxima are anomalously degraded under illuminated positive gate bias stress. In addition, threshold voltages shift positively under illuminated negative gate bias stress. These degradation behaviors can be ascribed to charge trapping in the passivation layer dominating degradation instability and are verified by a double gate a-Si:H device. - Highlights: • There is abnormal V T shift induced by illuminated gate bias stress in a-Si:H thin film transistors. • Electron–hole pair is generated via trap-assisted photoexcitation. • Abnormal transconductance hump is induced by the leakage current from back channel. • Charge trapping in the passivation layer is likely due to the fact that a constant voltage has been applied to the top gate

  20. Relationships among the Microstructure, Mechanical Properties, and Fatigue Behavior in Thin Ti6Al4V

    Directory of Open Access Journals (Sweden)

    Y. Fan

    2016-01-01

    Full Text Available The microstructures of Ti6Al4V are complex and strongly affect its mechanical properties and fatigue behavior. This paper investigates the role of microstructure on mechanical and fatigue properties of thin-section Ti6Al4V sheets, with the aim of reviewing the effects of microstructure on fatigue properties where suboptimal microstructures might result following heat treatment of assemblies that may not be suited to further annealing, for example, following laser welding. Samples of Ti6Al4V sheet were subjected to a range of heat treatments, including annealing and water quenching from temperatures ranging from 650°C to 1050°C. Micrographs of these samples were inspected for microstructure, and hardness, 0.2% proof stress, elongation, and fracture strength were measured and attributed back to microstructure. Fractography was used to support the findings from microstructure and mechanical analyses. The strength ranking from high to low for the microstructures of thin Ti6Al4V sheets observed in this study is as follows: acicular α′ martensite, Widmanstätten, bimodal, and equiaxed microstructure. The fatigue strength ranking from high to low is as follows: equiaxed, bimodal, Widmanstätten, and acicular α′ martensite microstructure.

  1. Nonlinear photocurrent-intensity behavior of amorphous InZnO thin film transistors

    Science.gov (United States)

    Lu, Huiling; Zhou, Xiaoliang; Liang, Ting; Zhang, Letao; Zhang, Shengdong

    2018-01-01

    The photocurrent (IPH) of amorphous InZnO thin film transistors in the off-state is investigated as a function of incident optical power (P). The results show that IPH exhibits a nonlinear dependence on P. Additionally, the dependence of IPH on P exhibits a strong photon energy (hυ)-dependent feature. When P is relatively low, IPH is shown to be proportional to Pγ, where γ is greater than 1. The γ > 1 behavior may be ascribed to the source-barrier-lowering effect due to the accumulation of photo-induced positive charges at the source side. When P is relatively high, while IPH remains proportional to Pγ under the incident light with hυ larger than the optical bandgap (Eg) of a-IZO, it turns to increase at an exponential rate with P if hυ of the incident light is smaller than the Eg. The exponential increase in IPH is attributed to the source-barrier-thinning effect, which leads to a significantly enhanced tunneling current.

  2. Relative viscosity of emulsions in simple shear flow: Temperature, shear rate, and interfacial tension dependence

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Se Bin; Lee, Joon Sang [Dept. of Mechanical Engineering, Yonsei Unversity, Seoul (Korea, Republic of)

    2015-08-15

    We simulate an emulsion system under simple shear rates to analyze its rheological characteristics using the lattice Boltzmann method (LBM). We calculate the relative viscosity of an emulsion under a simple shear flow along with changes in temperature, shear rate, and surfactant concentration. The relative viscosity of emulsions decreased with an increase in temperature. We observed the shear-thinning phenomena, which is responsible for the inverse proportion between the shear rate and viscosity. An increase in the interfacial tension caused a decrease in the relative viscosity of the decane-in-water emulsion because the increased deformation caused by the decreased interfacial tension significantly influenced the wall shear stress.

  3. Effect of divalent ions on the optical emission behavior of protein thin films

    Energy Technology Data Exchange (ETDEWEB)

    Bhowal, Ashim Chandra, E-mail: ashimbhowal111@gmail.com; Kundu, Sarathi [Physical Sciences Division, Institute of Advanced Study in Science and Technology, Vigyan Path, Paschim Boragaon, Garchuk, Guwahati, Assam 781035 (India)

    2016-05-06

    Photoluminescence behaviors of proteinthin film, bovine serum albumin (BSA) have been studied in the presence of three divalent ions (Mg{sup 2+}, Ca{sup 2+} and Ba{sup 2+}) at different temperatures using fluorescence spectroscopy. Film thickness and morphology have been studied using atomic force microscopy. Variation of different physicochemical parameters like temperature, solvent polarity, pH, ionic strength, substrate binding etc. can make conformational changes in the protein structure and hence influences the emission behavior.In thin film conformation of BSA, dynamic quenching behavior has beenidentified in the presence of all the three divalent ions at pH≈ 5.5. Depending upon the charge density of the divalent ions interaction with protein molecules modifies and as a result quenching efficiency varies. Also after heat treatment, conformation of the protein molecules changes and as a result the quenching efficiency enhances than that of the unheated films. Studies on such protein-ion interactions and conformational variation may explore various functions of protein when it will adsorb on soft surfaces like membranes, vesicles, etc.

  4. Molecular Weight Effects on the Glass Transition and Confinement Behavior of Polymer Thin Films.

    Science.gov (United States)

    Xia, Wenjie; Hsu, David D; Keten, Sinan

    2015-08-01

    Nanoscale polymer thin films exhibit strong confinement effects on Tg arising from free surfaces. However, the coupled influence of molecular weight (MW) and surface effects on Tg is not well understood for low MW film systems below the entanglement length. Utilizing atomistically informed coarse-grained molecular dynamics simulations for poly(methyl methacrylate) (PMMA), it is demonstrated that the decrease in free-standing film Tg with respect to bulk is more significant for low MW compared to high MW systems. Investigation of the local interfacial properties reveals that the increase in the local free volume near the free surface is greater for low MW, explaining the MW dependence of Tg -confinement behaviors. These findings corroborate recent experiments on low MW films, and highlight the relationship between nanoconfinement phenomena and local free volume effects arising from free surfaces. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Influence of irradiation on the switching behavior in PZT thin films

    International Nuclear Information System (INIS)

    Baturin, I.; Menou, N.; Shur, V.; Muller, C.; Kuznetsov, D.; Hodeau, J.-L.; Sternberg, A.

    2005-01-01

    Spatially nonuniform imprint behavior induced by X-ray synchrotron, electron and neutron irradiation has been investigated in sol-gel Pb(Zr,Ti)O 3 thin films. The analysis of the switching current data reveals the strong influence of irradiation on the switching current shape. The obtained effects have been explained as a result of acceleration of the bulk screening process induced by irradiation. It was shown that the spatial distribution of the internal bias field is determined by the domain structure existing during irradiation. The changes in the structural characteristics during fatigue cycling have been reveled by high resolution synchrotron X-ray diffraction experiments on (1 1 1)-oriented PZT-based capacitors with a composition in the morphotropic region. From both ex situ and in situ measurements, microstructural changes with cyclic switching during fatigue have been evidenced and correlated with the evolution of the switching characteristics

  6. Collective magnetic behaviors of Fe-Ag nanostructured thin films above the percolation limit

    International Nuclear Information System (INIS)

    Alonso, J.; Fdez-Gubieda, M. L.; Barandiaran, J. M.; Svalov, A.; Sarmiento, G.; Fernandez Barquin, L.; Pedro, I. de; Orue, I.

    2009-01-01

    The magnetic behavior of sputtered and pulsed laser deposited (PLD) Fe x Ag 100-x thin films with 27≤x≤55 has been studied by means of ac and dc magnetic measurements. Sputtered samples present a continuous decrease in the magnetization, down to 310 K for x=30, where a magnetic transition into a superparamagnetic state with the presence of dipolar interactions is observed. The ac susceptibility measurements indicate that this transition resembles that of three dimensional glassy systems. Sputtered samples with higher concentration of Fe present a similar but slower thermal evolution of magnetization. PLD samples with x≥50 show a Curie-Weiss-type transition above ∼200 K triggered by direct exchange interactions. As the temperature decreases, the system behaves like a ferromagnet and below ∼75 K, a transition into a cluster-glass state appears. As the composition decreases, these phenomena vanish

  7. Experimental procedure for the characterization of cyclic behavior from very thin plate specimens

    International Nuclear Information System (INIS)

    Maury, A.; Moulin, D.

    1983-01-01

    Many investigators, including those involved in the INTERNATIONAL BENCHMARK PROJECT ON SIMPLIFIED METHODS FOR ELEVATED TEMPERATURE DESIGN AND ANALYSIS - PROBLEM II, have tried to reproduce experimentally observed behavior by inelastic calculations. Unfortunately, the material characteristics used in the computer code were established from monotonic tensile tests performed with specimens extracted from the plate product itself (1.45 mm thick) employed to construct the ratchetting specimen. It now appears that the cyclic behavior of the material is much more relevant to the phenomenon observed. Hence the need to make this kind of characterization. Nevertheless, the practical problem is to produce cyclic stresses, i.e. tensile and compressive stresses, with very thin specimens. The main difficulty is to prevent the buckling effect. A new special device set up for this particular purpose is described here. The solution adopted was to create uniformly distributed alternative pure bending stresses in the thin plate specimen. Bending moments were produced by two end-grips fixed to the specimen, and these grips were mounted on a conventional test-machine which was displacement-controlled. To reduce tensile and compressive membrane stresses inside the specimen, the grips had two parallel axles of rotation. The forces produced by the machine and the displacements of a number of points of the specimen were continuously recorded during the test, so that cyclically stabilized, bending moments could be evaluated easily for each curvature variation imposed. The very first cyclic experimental data obtained, at room temperature, for the material of the sodium test specimen, a 316 type stainless steel, are presented. It may be noted that the simple specimens were very easy to prepare and hence inexpensive. (orig.)

  8. Compressive pre-stress effects on magnetostrictive behaviors of highly textured Galfenol and Alfenol thin sheets

    Directory of Open Access Journals (Sweden)

    Julia R. Downing

    2017-05-01

    Full Text Available Fe-Ga (Galfenol and Fe-Al (Alfenol are rare-earth-free magnetostrictive alloys with mechanical robustness and strong magnetoelastic coupling. Since highly textured Galfenol and Alfenol thin sheets along orientations have been developed with magnetostrictive performances of ∼270 ppm and ∼160 ppm, respectively, they have been of great interest in sensor and energy harvesting applications. In this work, we investigate stress-dependent magnetostrictive behaviors in highly textured rolled sheets of NbC-added Fe80Al20 and Fe81Ga19 alloys with a single (011 grain coverage of ∼90%. A compact fixture was designed and used to introduce a uniform compressive pre-stress to those thin sheet samples along a [100] direction. As compressive pre-stress was increased to above 100 MPa, the maximum observed magnetostriction increased 42% in parallel magnetostriction along the stress direction, λ//, in highly textured (011 Fe81Ga19 thin sheets for a compressive pre-stress of 60 MPa. The same phenomena were observed for (011 Fe80Al20 (maximum increase of 88% with a 49 MPa compressive stress. This trend is shown to be consistent with published results on the effect of pre-stress on magnetostriction in rods of single crystal and textured polycrystalline Fe-Ga alloy of similar compositions, and single crystal data gathered using our experimental set up. Interestingly, the saturating field (Hs does not vary with pre-stresses, while the saturating field in rod-shaped samples of Fe-Ga increases with an increase of pre-stress. This suggests that for a range of compressive pre-stresses, thin sheet samples have larger values of d33 transduction coefficients and susceptibility than rod-shaped samples of similar alloy compositions, and hence they should provide performance benefits when used in sensor and actuator device applications. Thus, we discuss potential reasons for the unexpected trends in Hs with pre-stress, and present preliminary results from tests conducted

  9. Steady-shear rheological properties of graphene-reinforced epoxy resin for manufacturing of aerospace composite films

    Science.gov (United States)

    Clausi, Marialaura; Santonicola, M. Gabriella; Laurenzi, Susanna

    2016-05-01

    The aim of this work is to analyze the steady-shear rheological behavior and the absolute viscosity of epoxy matrix reinforced with graphene nanoplatelets (xGnP) before cure. Three different grades of xGnP (grades C, M and H) were dispersed homogenously at different weight percentages (wt%) into the epoxy matrix, ranging from 0.5 to 5 wt%. It is found that nanocomposite fluids with xGnP-C exhibit a Newtonian behavior at shear rate in the range 0.1-100 s-1, conversely, nanocomposite fluids with xGnP of grade M and H exhibit a shear-thinning behavior with the increase of nanoplatelet loading. Results from this analysis indicate how the steady shear rheological properties of the nano-reinforced polymer fluids depend on the geometrical characteristics of the graphene nanoplatelets.

  10. Strain-induced alignment and phase behavior of blue phase liquid crystals confined to thin films.

    Science.gov (United States)

    Bukusoglu, Emre; Martinez-Gonzalez, Jose A; Wang, Xiaoguang; Zhou, Ye; de Pablo, Juan J; Abbott, Nicholas L

    2017-12-06

    We report on the influence of surface confinement on the phase behavior and strain-induced alignment of thin films of blue phase liquid crystals (BPs). Confining surfaces comprised of bare glass, dimethyloctadecyl [3-(trimethoxysilyl)propyl] ammonium chloride (DMOAP)-functionalized glass, or polyvinyl alcohol (PVA)-coated glass were used with or without mechanically rubbing to influence the azimuthal anchoring of the BPs. These experiments reveal that confinement can change the phase behavior of the BP films. For example, in experiments performed with rubbed-PVA surfaces, we measured the elastic strain of the BPs to change the isotropic-BPII phase boundary, suppressing formation of BPII for film thicknesses incommensurate with the BPII lattice. In addition, we observed strain-induced alignment of the BPs to exhibit a complex dependence on both the surface chemistry and azimuthal alignment of the BPs. For example, when using bare glass surfaces causing azimuthally degenerate and planar anchoring, BPI oriented with (110) planes of the unit cell parallel to the contacting surfaces for thicknesses below 3 μm but transitioned to an orientation with (200) planes aligned parallel to the contacting surfaces for thicknesses above 4 μm. In contrast, BPI aligned with (110) planes parallel to confining surfaces for all other thicknesses and surface treatments, including bare glass with uniform azimuthal alignment. Complementary simulations based on minimization of the total free energy (Landau-de Gennes formalism) confirmed a thickness-dependent reorientation due to strain of BPI unit cells within a window of surface anchoring energies and in the absence of uniform azimuthal alignment. In contrast to BPI, BPII did not exhibit thickness-dependent orientations but did exhibit orientations that were dependent on the surface chemistry, a result that was also captured in simulations by varying the anchoring energies. Overall, the results in this paper reveal that the orientations

  11. Dynamic behavior of transport in normal and reversed shear plasmas with internal barriers in JT-60U

    International Nuclear Information System (INIS)

    Neudatchin, Sergi V.; Takizuka, Tomonori; Shirai, Hiroshi; Fujita, Takaaki; Isayama, Akihiko; Kamada, Yutaka; Koide, Yoshihiko

    2001-12-01

    Transport evolution in normal shear (NrS) and reversed shear (RS) JT-60U tokamak plasmas with internal transport barrier (ITB) is described as a combination of various fast and slow time scale processes. Abrupt in time (ms time scale) and wide in space (∼0.3 of minor radius) variations of electron and ion heat diffusivities χ e,i (δχ e,i ), which are called ITB-events and seen as simultaneous rise and decay of electron and ion temperatures in two spatial zones, are found for weak ITBs in both NrS and RS plasmas. Profiles of δχ e in RS plasmas with strong ITBs are usually localized near ITB foot inside smaller space region. The maximum of the heat flux variation is located near position of the minimum of safety factor in various RS plasmas, and variation is extended in positive shear region. Inward and outward heat pulse propagations created by the jump of χ e and the sawtooth-like crash are analyzed. Small values of χ e and the absence of heat pinch are found inside strong ITBs. Another non-local abrupt variations of χ e inside most of the plasma volume, including significant part of weak ITB inside RS zone of RS plasmas, are seen at the ELM-induced H-L transition and the L-H recovery. (author)

  12. Shearing and compression behavior of end-grafted polyelectrolyte brushes with mono- and trivalent counterions: a molecular dynamics simulation

    International Nuclear Information System (INIS)

    Cao, Qianqian; Zuo, Chuncheng; Li, Lujuan; He, Hongwei

    2010-01-01

    We investigate polyelectrolytes end-grafted on two apposing walls using molecular dynamics simulation techniques. Monovalent and trivalent counterions are explicitly treated. Under normal compression, the osmotic pressure is examined in detail by decomposing it into various virial terms. It has been found that at small wall separations the increase in the osmotic pressure can be ascribed to the increase in the short-range virial term. At large wall separations, a negative osmotic pressure is observed in trivalent systems. Moreover, we study the effect of lateral shear on the density profiles of monomers and counterions, the net charge distribution, the local pressure tensor, the degree of interpenetration and the friction coefficient. At large shear ratios, the electrostatic interactions are weakened at the interface between two brushes. It is worth noting that although the magnitudes of the normal and shear stress components for the trivalent case are significantly lesser than those for the monovalent case, the friction coefficient is larger in the trivalent systems

  13. Shear bond strength and enamel fracture behavior of ceramic brackets Fascination® and Fascination®2.

    Science.gov (United States)

    Gittner, Robert; Müller-Hartwich, Ralf; Engel, Sylvia; Jost-Brinkmann, Paul-Georg

    2012-01-01

    The purpose of this study was to compare the shear bond strength and incidence of enamel fractures of the ceramic brackets Fascination® and Fascination®2. A total of 360 teeth (180 first upper bicuspids and 180 lower incisors) were stored in 96% ethanol, while 360 other teeth (180 first upper bicuspids and 180 lower incisors) were stored in 0.1% thymol. All 720 teeth were bonded one-half each with Fascination® and Fascination®2 brackets using three different adhesives and three different light curing units. The teeth were debonded with a debonding-device according to DIN EN ISO 10477 using a universal testing machine with a crosshead speed of 1 mm per minute. The enamel surface was then examined stereomicroscopically (10x and 40x magnification). The non-parametric Mann-Whitney U test was used, since the data were not normally distributed. The Fascination®2 brackets provided significantly lower shear bond strength than Fascination® brackets (p = 0.003). Fascination® brackets demonstrated significantly fewer, smaller enamel fractures than Fascination®2 brackets (p = 0.012). The lower shear bond strength of the Fascination®2 brackets is clinically acceptable, but our study's experimental design did not enable us to prove whether this is clinically associated with a lower risk of enamel fracture.

  14. Effectiveness of mechanical thinning and prescribed burning on fire behavior in Pinus nigra forests in NE Spain.

    Science.gov (United States)

    Piqué, Míriam; Domènech, Rut

    2018-03-15

    Fuel treatments can mitigate present and future impacts of climate change by reducing fire intensity and severity. In recent years, Pinus nigra forests in the Mediterranean basin have been dramatically affected by the new risk of highly intense and extreme fires and its distribution area has been reduced. New tools are necessary for assessing the management of these forests so they can adapt to the challenges to come. Our main goal was to evaluate the effects of different fuel treatments on Mediterranean Pinus nigra forests. We assessed the forest response, in terms of forest structure and fire behavior, to different intensities of low thinning treatments followed by different slash prescriptions (resulting in: light thinning and lop and scatter; light thinning and burn; heavy thinning and lop and scatter; heavy thinning and burn; and, untreated control). Treatments that used fire to decrease the resulting slash were the most effective for reducing active crown fires decreasing the rate of spread and flame length more than 89%. Low thinning had an effect on torching potential, but there was no difference between intensities of thinning. Only an outcoming crown fire could spread actively if it was sustained by a high-enough constant wind speed and enough surface fuel load. Overall, treatments reduce fire intensity and treated areas have a more homogenous fire behavior response than untreated areas. This provides opportunities to extinguish the fire and reduce the probability of trees dying from the fire. It would be helpful to include ecological principles and fire behavior criteria in silvicultural treatment guidelines in order to perform more efficient management techniques in the future. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Effect of local wall thinning on the collapse behavior of pipe elbows subjected to a combined internal pressure and in-plane bending load

    International Nuclear Information System (INIS)

    Kim, Jin-Weon; Na, Man-Gyun; Park, Chi-Yong

    2008-01-01

    The objective of this study was to investigate the effect of local wall thinning on the collapse behavior of pipe elbows subjected to a combined internal pressure and in-plane bending load. This study evaluated the global deformation behavior and collapse moment of the elbows, which contained various types of local wall-thinning defects at their intrados or extrados, using three-dimensional elastic-plastic finite element analysis. The analysis results showed that the global deformation behavior of locally wall-thinned elbows was largely governed by the mode of the bending and the elbow geometry rather than the wall-thinning parameters, except for elbows with considerably large and deep wall thinning that showed plastic instabilities induced by local buckling and plastic collapsing in the thinned area. The reduction in the collapse moment with wall-thinning depth was considerable when local buckling occurred in the thinned areas, whereas the effect of the thinning depth was small when ovalization occurred. The effects of the circumferential thinning angle and thinning length on the collapse moment of elbows were not major for shallow wall-thinning cases. For deeper wall-thinning cases, however, their effects were significant and the dependence of collapse moment on the axial thinning length was governed by the stress type applied to the wall-thinned area. Typically, the reduction in the collapse moment due to local wall thinning was clearer when the thinning defect was located at the intrados rather than the extrados, and it was apparent for elbows with larger bend radius

  16. Influence of Normal and Shear Stress on the Hydraulic Transmissivity of Thin Cracks in a Tight Quartz Sandstone, a Granite, and a Shale

    Science.gov (United States)

    Rutter, Ernest H.; Mecklenburgh, Julian

    2018-02-01

    Transmissivity of fluids along fractures in rocks is reduced by increasing normal stress acting across them, demonstrated here through gas flow experiments on Bowland shale, and oil flow experiments on Pennant sandstone and Westerly granite. Additionally, the effect of imposing shear stress at constant normal stress was determined, until frictional sliding started. In all cases, increasing shear stress causes an accelerating reduction of transmissivity by 1 to 3 orders of magnitude as slip initiated, as a result of the formation of wear products that block fluid pathways. Only in the case of granite, and to a lesser extent in the sandstone, was there a minor amount of initial increase of transmissivity prior to the onset of slip. These results cast into doubt the commonly applied presumption that cracks with high resolved shear stresses are the most conductive. In the shale, crack transmissivity is commensurate with matrix permeability, such that shales are expected always to be good seals. For the sandstone and granite, unsheared crack transmissivity was respectively 2 and 2.5 orders of magnitude greater than matrix permeability. For these rocks crack transmissivity can dominate fluid flow in the upper crust, potentially enough to permit maintenance of a hydrostatic fluid pressure gradient in a normal (extensional) faulting regime.

  17. Magnetorheological dampers in shear mode

    International Nuclear Information System (INIS)

    Wereley, N M; Cho, J U; Choi, Y T; Choi, S B

    2008-01-01

    In this study, three types of shear mode damper using magnetorheological (MR) fluids are theoretically analyzed: linear, rotary drum, and rotary disk dampers. The damping performance of these shear mode MR dampers is characterized in terms of the damping coefficient, which is the ratio of the equivalent viscous damping at field-on status to the damping at field-off status. For these three types of shear mode MR damper, the damping coefficient or dynamic range is derived using three different constitutive models: the Bingham–plastic, biviscous, and Herschel–Bulkley models. The impact of constitutive behavior on shear mode MR dampers is theoretically presented and compared

  18. Semiconductor- to metallic-like behavior in Bi thin films on KCl substrate

    International Nuclear Information System (INIS)

    Bui, Thanh Nhan; Raskin, Jean-Pierre; Hackens, Benoit

    2016-01-01

    Bi thin films, with a thickness of 100 nm, are deposited by electron-beam evaporation on a freshly cleaved (100) KCl substrate. The substrate temperature during film growth (T_d_e_p) ranges from room temperature up to 170 °C. Films deposited at room temperature exhibit a maze-like microstructure typical of the rhombohedral (110) texture, as confirmed by X-ray diffraction. For T_d_e_p above 80 °C, a different microstructure appears, characterized by concentric triangular shapes corresponding to the trigonal (111) texture. Temperature dependence of the resistivity shows a transition from a semiconductor-like behavior for films deposited at room temperature to a metallic-like behavior for T_d_e_p above 80 °C. From magnetoresistance measurements between room temperature and 1.6 K, we extract the electron and hole mobilities, concentrations, and mean free paths, which allow to draw a complete picture of the transport properties of both types of films.

  19. Morphology and growth behavior of O_2-free chemical bath deposited ZnS thin films

    International Nuclear Information System (INIS)

    Jet Meitzner, K.; Tillotson, Brock M.; Siedschlag, Amanda T.; Moore, Frederick G.; Kevan, Stephen D.; Richmond, Geraldine L.

    2015-01-01

    We investigate the role of reagent concentrations and ambient O_2 on the morphology and growth behavior of ZnS thin films grown with the chemical bath deposition method. We investigate the role of substrate on film morphology, and find significant differences between films deposited on SiO_2 versus Si. The films are also sensitive to dissolved O_2 in the bath, as it causes a layer of SiO_2 to form at the ZnS/Si interface during deposition. Degassing of solutions and an N_2 atmosphere are effective to minimize this oxidation, allowing deposition of ZnS films directly onto Si. Under these conditions, we examine film properties as they relate to reagent bath concentrations. As the reagent concentrations are decreased, both the film roughness and growth rate decrease linearly. We also observe deformation and shifting of X-ray diffraction peaks that increases with decreasing reagent concentrations. The shifts are characteristic of lattice compression (caused by the substitution of oxygen for sulfur), and the deformation is characteristic of distortion of the lattice near crystal grain interfaces (caused by tensile stress from interatomic forces between neighboring crystal grains). At the weakest concentrations, the low roughness suggests a mixed growth mode in which both clusters and individual ZnS nanocrystallites contribute to film growth. With increasing reagent concentrations, the growth mode shifts and becomes dominated by deposition of clusters. - Highlights: • We deposit ZnS thin films by chemical bath deposition in an O_2-free environment. • The O_2-free environment is effective to minimize oxidation of the Si substrate. • The dominant growth mechanism changes with reagent concentrations. • Film morphology and composition change with reagent concentrations. • X-ray diffraction reveals tensile stress between ZnS crystal grains.

  20. Long-Term Bending Creep Behavior of Thin-Walled CFRP Tendon Pretensioned Spun Concrete Poles

    Directory of Open Access Journals (Sweden)

    Giovanni P. Terrasi

    2014-07-01

    Full Text Available This paper discusses the long-term behavior of a series of highly-loaded, spun concrete pole specimens prestressed with carbon fiber-reinforced polymer (CFRP tendons, which were subjected to outdoor four-point bending creep tests since 1996 in the frame of collaboration with the Swiss precast concrete producer, SACAC (Società Anonima Cementi Armati Centrifugati. The 2 m span cylindrical beams studied are models for lighting poles produced for the last 10 years and sold on the European market. Five thin-walled pole specimens were investigated (diameter: 100 mm; wall-thickness: 25–27 mm. All specimens were produced in a pretensioning and spinning technique and were prestressed by pultruded CFRP tendons. Initially, two reference pole specimens were tested in quasi-static four-point bending to determine the short-term failure moment and to model the short-term flexural behavior. Then, three pole specimens were loaded to different bending creep moments: while the lowest loaded specimen was initially uncracked, the second specimen was loaded with 50% of the short-term bending failure moment and exhibited cracking immediately after load introduction. The highest loaded pole specimen sustained a bending moment of 72% of the short-term bending failure moment for 16.5 years before failing in July 2013, due to the bond failure of the tendons, which led to local crushing of the high-performance spun concrete (HPSC. Besides this, long-term monitoring of the creep tests has shown a limited time- and temperature-dependent increase of the deflections over the years, mainly due to the creep of the concrete. A concrete creep-based model allowed for the calculation of the long-term bending curvatures with reasonable accuracy. Furthermore, the pole specimens showed crack patterns that were stable over time and minimal slippage of the tendons with respect to the pole’s end-faces for the two lower load levels. The latter proves the successful and durable

  1. Shear behavior of thermoformed woven-textile thermoplastic prepregs: An analysis combining bias-extension test and X-ray microtomography

    Science.gov (United States)

    Gassoumi, M.; Rolland du Roscoat, S.; Casari, P.; Dumont, P. J. J.; Orgéas, L.; Jacquemin, F.

    2017-10-01

    Thermoforming allows the manufacture of structural parts for the automotive and aeronautical domains using long fiber thermoplastic prepregs with short cycle times. During this operation, several sheets of molten prepregs are stacked and subjected to large macroscale strains, mainly via in-plane shear, out-of-plane consolidation or dilatation, and bending of the fibrous reinforcement. These deformation modes and the related meso and microstructure evolutions are still poorly understood. However, they can drastically alter the end-use macroscale properties of fabricated parts. To better understand these phenomena, bias extension tests were performed using specimens made of several stacked layers of glass woven fabrics and polyamide matrix. The macroscale shear behavior of these prepregs was investigated at various temperatures. A multiscale analysis of deformed samples was performed using X-ray microtomography images of the deformed specimens acquired at two different spatial resolutions. The low-resolution images were used to analyze the deformation mechanisms and the structural characteristics of prepregs at the macroscale and bundle scales. It was possible to analyze the 3D shapes of deformed samples and, in particular, the spatial variations of their thickness so as to quantify the out-of-plane dilatancy or consolidation phenomena induced by the in-plane shear of prepregs. At a lower scale, the analysis of the high-resolution images showed that these mechanisms were accompanied by the growth of pores and the deformation of fiber bundles. The orientation of the fiber bundles and its through-thickness evolution were measured along the weft and warp directions in the deformed samples, allowing the relevance of geometrical models currently used to analyze bias extension tests to be discussed. Results can be used to enhance the current rheological models for the prediction of thermoforming of thermoplastic prepregs.

  2. Oxidation behavior of arc evaporated Al-Cr-Si-N thin films

    Energy Technology Data Exchange (ETDEWEB)

    Tritremmel, Christian; Daniel, Rostislav; Mitterer, Christian; Mayrhofer, Paul H.; Lechthaler, Markus; Polcik, Peter [Christian Doppler Laboratory for Advanced Hard Coatings, Department of Physical Metallurgy and Materials Testing, Montanuniversitaet Leoben, Franz-Josef-Strasse 18, A-8700 Leoben (Austria); Christian Doppler Laboratory for Application Oriented Coating Development, Department of Physical Metallurgy and Materials Testing, Montanuniversitaet Leoben, Franz-Josef-Strasse 18, A-8700 Leoben (Austria); OC Oerlikon Balzers AG, Iramali 18, LI-9496 Balzers (Liechtenstein); PLANSEE Composite Materials GmbH, Siebenbuergerstrasse 23, D-86983 Lechbruck am See (Germany)

    2012-11-15

    The impact of Al and Si on the oxidation behavior of Al-Cr-(Si)-N thin films synthesized by arc evaporation of powder metallurgically prepared Al{sub x}Cr{sub 1-x} targets with x = Al/(Al + Cr) of 0.5, 0.6, and 0.7 and (Al{sub 0.5}Cr{sub 0.5}){sub 1-z}Si{sub z} targets with Si contents of z = 0.05, 0.1, and 0.2 in N{sub 2} atmosphere was studied in detail by means of differential scanning calorimetry, thermogravimetric analysis (TGA), x-ray diffraction, and Raman spectroscopy. Dynamical measurements in synthetic air (up to 1440 Degree-Sign C) revealed the highest onset temperature of pronounced oxidation for nitride coatings prepared from the Al{sub 0.4}Cr{sub 0.4}Si{sub 0.2} target. Isothermal TGA at 1100, 1200, 1250, and 1300 Degree-Sign C highlight the pronounced improvement of the oxidation resistance of Al{sub x}Cr{sub 1-x}N coatings by the addition of Si. The results show that Si promotes the formation of a dense coating morphology as well as a dense oxide scale when exposed to air.

  3. Anisotropic ferromagnetic behaviors in highly orientated epitaxial NiO-based thin films

    Directory of Open Access Journals (Sweden)

    Yu-Jun Zhang

    2015-07-01

    Full Text Available Antiferromagnetic materials attract a great amount of attention recently for promising antiferromagnet-based spintronics applications. NiO is a conventional antiferromagnetic semiconductor material and can show ferromagnetism by doping other magnetic elements. In this work, we synthesized epitaxial Fe-doped NiO thin films on SrTiO3 substrates with various crystal orientations by pulsed laser deposition. The room-temperature ferromagnetism of these films is anisotropic, including the saturated magnetization and the coercive field. The anisotropic magnetic behaviors of Fe-doped NiO diluted magnetic oxide system should be closely correlated to the magnetic structure of antiferromagnetic NiO base. Within the easy plane of NiO, the coercive field of the films becomes smaller, and larger coercive field while tested out of the easy plane of NiO. The saturated magnetization anisotropy is due to different strain applied by different substrates. These results lead us to more abundant knowledge of the exchange interactions in this conventional antiferromagnetic system.

  4. Size effects in electrical behavior of high-Tc thin-film bridges

    International Nuclear Information System (INIS)

    Afanasyev, A.S.; Gubankov, V.N.; Divin, Y.Y.

    1991-01-01

    This paper reports on the size effects in electrical characteristics of polycrystalline YBa 2 Cu 3 O 7-x thin-film bridges studied in the temperature range 4-300K. It is shown, that at T > T c the decrease of bridge widths w from 200 to 10 μm leads to the increase of resistance R in several times and to the change in R □ (T) behavior □ from metallic type to activation type. At □ T approx-lt T c the R □ (w) values exponentially increased when the width w was decreased under some definite size L. At T c the index I c (T) ∼ (T - T) α changed from 3 to 1 if bridge width was decreased. Experimental data are discussed within the model, which takes into account large-scale percolation processes in the system of different intergrain Josephson junctions, where characteristic length L 0 of critical subnetwork is much larger than the grain size

  5. Flame retardant behavior of polyelectrolyte-clay thin film assemblies on cotton fabric.

    Science.gov (United States)

    Li, Yu-Chin; Schulz, Jessica; Mannen, Sarah; Delhom, Chris; Condon, Brian; Chang, Sechin; Zammarano, Mauro; Grunlan, Jaime C

    2010-06-22

    Cotton fabric was treated with flame-retardant coatings composed of branched polyethylenimine (BPEI) and sodium montmorillonite (MMT) clay, prepared via layer-by-layer (LbL) assembly. Four coating recipes were created by exposing fabric to aqueous solutions of BPEI (pH 7 or 10) and MMT (0.2 or 1 wt %). BPEI pH 10 produces the thickest films, while 1 wt % MMT gives the highest clay loading. Each coating recipe was evaluated at 5 and 20 bilayers. Thermogravimetric analysis showed that coated fabrics left as much as 13% char after heating to 500 degrees C, nearly 2 orders of magnitude more than uncoated fabric, with less than 4 wt % coming from the coating itself. These coatings also reduced afterglow time in vertical flame tests. Postburn residues of coated fabrics were examined with SEM and revealed that the weave structure and fiber shape in all coated fabrics were preserved. The BPEI pH 7/1 wt % MMT recipe was most effective. Microcombustion calorimeter testing showed that all coated fabrics reduced the total heat release and heat release capacity of the fabric. Fiber count and strength of uncoated and coated fabric are similar. These results demonstrate that LbL assembly is a relatively simple method for imparting flame-retardant behavior to cotton fabric. This work lays the foundation for using these types of thin film assemblies to make a variety of complex substrates (foam, fabrics, etc.) flame resistant.

  6. Phase behavior of diblock copolymer/star-shaped polymer thin film mixtures.

    Science.gov (United States)

    Zhao, Junnan; Sakellariou, Georgios; Green, Peter F

    2016-05-07

    We investigated the phase behavior of thin film, thickness h≈ 100 nm, mixtures of a polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer with star-shaped polystyrene (SPS) molecules of varying functionalities f, where 4 ≤f≤ 64, and molecular weights per arm Marm. The miscibility of the system and the surface composition varied appreciably with Marm and f. For large values of Marm, regardless of f, the miscibility of the system was qualitatively similar to that of linear chain PS/PS-b-P2VP mixtures - the copolymer chains aggregate to form micelles, each composed of an inner P2VP core and PS corona, which preferentially segregate to the free surface. On the other hand, for large f and small Marm, SPS molecules preferentially resided at the free surface. Moreover, blends containing SPS molecules with the highest values of f and lowest values of Marm were phase separated. These observations are rationalized in terms of competing entropic interactions and the dependence of the surface tension of the star-shaped molecules on Marm and f.

  7. Tensile and shear fracture behavior of fiber reinforced plastics at 77K irradiated by various radiation sources

    International Nuclear Information System (INIS)

    Humer, K.; Weber, H.W.; Tschegg, E.K.; Gerstenberg, H.

    1993-08-01

    Influence of radiation damage (gamma, electron, neutron) on mechanical properties of fiber reinforced plastics (FRPs) has been investigated. Different types of FRPs (two or three dimensional E-, S- or T-glass fiber reinforcement, epoxy or bismaleimide resin) have been irradiated at room temperature with 2 MeV electrons and 6O Co γ-rays up to 1.8 x 1 0 8 Gy as well as with different reactor spectra up to a fast neutron fluence of 5 x lO 22 m -2 (E > 0.1 MeV). Tensile and intralaminar shear tests were carried out on the irradiated samples at 77 K. Some samples were irradiated at 5 K and tested at 77 K with and without an annealing cycle to room temperature. Results on the influence of these radiation conditions and of warm-up cycles on the mechanical properties of FRPs are compared and discussed

  8. Tensile and shear fracture behavior of fiber reinforced plastics at 77K irradiated by various radiation sources

    Energy Technology Data Exchange (ETDEWEB)

    Humer, K.; Weber, H.W. [Atominstitut der Oesterreichischen Hochschulen, Vienna (Austria); Tschegg, E.K. [Technische Univ., Vienna (Austria). Inst. fuer Angewandte und Technische Physik; Egusa, Shigenori [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment; Birtcher, R.C. [Argonne National Lab., IL (United States); Gerstenberg, H. [Technische Univ. Muenchen, Garching (Germany). Fakultaet fuer Physik

    1993-08-01

    Influence of radiation damage (gamma, electron, neutron) on mechanical properties of fiber reinforced plastics (FRPs) has been investigated. Different types of FRPs (two or three dimensional E-, S- or T-glass fiber reinforcement, epoxy or bismaleimide resin) have been irradiated at room temperature with 2 MeV electrons and {sup 6O}Co {gamma}-rays up to 1.8 {times} 1 0{sup 8} Gy as well as with different reactor spectra up to a fast neutron fluence of 5 {times} lO{sup 22} m{sup {minus}2} (E > 0.1 MeV). Tensile and intralaminar shear tests were carried out on the irradiated samples at 77 K. Some samples were irradiated at 5 K and tested at 77 K with and without an annealing cycle to room temperature. Results on the influence of these radiation conditions and of warm-up cycles on the mechanical properties of FRPs are compared and discussed.

  9. Mesoscopic Simulations of the Phase Behavior of Aqueous EO 19 PO 29 EO 19 Solutions Confined and Sheared by Hydrophobic and Hydrophilic Surfaces

    KAUST Repository

    Liu, Hongyi; Li, Yan; Krause, Wendy E.; Pasquinelli, Melissa A.; Rojas, Orlando J.

    2012-01-01

    The MesoDyn method is used to investigate associative structures in aqueous solution of a nonionic triblock copolymer consisting of poly(propylene oxide) capped on both ends with poly(ethylene oxide) chains. The effect of adsorbing (hydrophobic) and nonadsorbing (hydrophilic) solid surfaces in contact with aqueous solutions of the polymer is elucidated. The macromolecules form self-assembled structures in solution. Confinement under shear forces is investigated in terms of interfacial behavior and association. The formation of micelles under confinement between hydrophilic surfaces occurs faster than in bulk aqueous solution while layered structures assemble when the polymers are confined between hydrophobic surfaces. Micelles are deformed under shear rates of 1 μs -1 and eventually break to form persistent, adsorbed layered structures. As a result, surface damage under frictional forces is prevented. Overall, this study indicates that aqueous triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) (Pluronics, EO mPO nEO m) act as a boundary lubricant for hydrophobic surfaces but not for hydrophilic ones. © 2011 American Chemical Society.

  10. Mesoscopic Simulations of the Phase Behavior of Aqueous EO 19 PO 29 EO 19 Solutions Confined and Sheared by Hydrophobic and Hydrophilic Surfaces

    KAUST Repository

    Liu, Hongyi

    2012-01-25

    The MesoDyn method is used to investigate associative structures in aqueous solution of a nonionic triblock copolymer consisting of poly(propylene oxide) capped on both ends with poly(ethylene oxide) chains. The effect of adsorbing (hydrophobic) and nonadsorbing (hydrophilic) solid surfaces in contact with aqueous solutions of the polymer is elucidated. The macromolecules form self-assembled structures in solution. Confinement under shear forces is investigated in terms of interfacial behavior and association. The formation of micelles under confinement between hydrophilic surfaces occurs faster than in bulk aqueous solution while layered structures assemble when the polymers are confined between hydrophobic surfaces. Micelles are deformed under shear rates of 1 μs -1 and eventually break to form persistent, adsorbed layered structures. As a result, surface damage under frictional forces is prevented. Overall, this study indicates that aqueous triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) (Pluronics, EO mPO nEO m) act as a boundary lubricant for hydrophobic surfaces but not for hydrophilic ones. © 2011 American Chemical Society.

  11. [Weight control behaviors in dieting adolescent girls and their relation to body dissatisfaction and obsession with thinness].

    Science.gov (United States)

    Contreras, M Liliana A; Morán, Javier K; Frez, Scarlett H; Lagos, Carola O; Marín, María Paz F; de los Ángeles Pinto B, María; Suzarte, Érika A

    2015-01-01

    Obsession with thinness and body dissatisfaction can lead adolescents to follow unsupervised diets, which could result in risky weight control behaviors such as fasting, vomiting, use of diuretics and laxatives. The aim of the current study is to examine weight control behaviors in dieting adolescents and relate them to body dissatisfaction (BD) and obsession with thinness (OT). A cross-sectional study was conducted on 439 adolescents from Valparaiso public schools to investigate risky weight control behaviors due to BD and OT scales from the Eating Disorders Inventory-2 (EDI-2), comparing restrained eaters and non-restrained eaters. A total of 43% adolescents had followed a weight loss diet without medical supervision. The dieters had higher BD and OT values. Moderate to severe food restriction, based on expert judgment, was observed in 29.6%, and differences in the presence and severity of purging behaviors were found between the 2 groups. One third of the adolescents studied followed diets without professional supervision and had higher BD and OT values, as well as risky weight control behaviors. Overweight and obese adolescents followed more restrictive diets and developed riskier weight control behaviors. Copyright © 2015. Publicado por Elsevier España, S.L.U.

  12. Gelation under shear

    Energy Technology Data Exchange (ETDEWEB)

    Butler, B.D.; Hanley, H.J.M.; Straty, G.C. [National Institute of Standards and Technology, Boulder, CO (United States); Muzny, C.D. [Univ. of Colorado, Boulder, CO (United States)

    1995-12-31

    An experimental small angle neutron scattering (SANS) study of dense silica gels, prepared from suspensions of 24 nm colloidal silica particles at several volume fractions {theta} is discussed. Provided that {theta}{approx_lt}0.18, the scattered intensity at small wave vectors q increases as the gelation proceeds, and the structure factor S(q, t {yields} {infinity}) of the gel exhibits apparent power law behavior. Power law behavior is also observed, even for samples with {theta}>0.18, when the gel is formed under an applied shear. Shear also enhances the diffraction maximum corresponding to the inter-particle contact distance of the gel. Difficulties encountered when trying to interpret SANS data from these dense systems are outlined. Results of computer simulations intended to mimic gel formation, including computations of S(q, t), are discussed. Comments on a method to extract a fractal dimension characterizing the gel are included.

  13. Critical behavior of ferromagnetic La0.7Sr0.3CoO3 thin films

    International Nuclear Information System (INIS)

    Schwarz, T.

    2007-07-01

    The present thesis concentrates on the critical behavior of ferromagnetic La 0.7 Sr 0.3 CoO 3 thin films (LSCO) close to the magnetic phase transition. The LSCO thin films were prepared by pulsed laser deposition and optimized with respect to their structural and magnetic properties. For the characterization of the structural and magnetic characteristics various methods were used. By means of X-ray diffraction and electron microscopy the crystallinity and microstructure of the epitaxial films were examined, respectively. The analysis of the chemical composition was accomplished by Rutherford backscattering and energy dispersive X-ray diffraction (EDX). Parallel to the investigations of the LSCO films a low-temperature measuring system for electrical measurements in magnetic fields up to 8 T in a temperature range from 1.5 K to 300 K was developed and built up including the necessary control and measuring software. The central point of this work was dedicated to the characterization of the magnetic characteristics of the LSCO films. In comparison, single crystals and polycrystalline bulk samples were also available. At these samples temperature-dependent and isothermal magnetization measurements were accomplished by a SQUID magnetometer. To determine the critical behavior of the samples the critical exponents of the susceptibility and the spontaneous magnetization in the proximity of the ferromagnetic phase transition were determined. For the exact determination of the critical exponents from the experimental data an evaluation routine in Matlab on basis of the Arrott representation method was used. In addition to the investigations of the critical behavior, electrical transportation measurements and neutron reflection measurements with spin-polarized neutrons were performed. The investigations of this work show that, in contrast to the critical behavior of single-crystal LSCO volume samples where a three-dimensional Heisenberg behavior could be observed, the

  14. Investigation of Deterioration Behavior of Hysteretic Loops in Nonlinear Static Procedure Analysis of Concrete Structures with Shear Walls

    International Nuclear Information System (INIS)

    Ghodrati Amiri, G.; Amidi, S.; Khorasani, M.

    2008-01-01

    In the recent years, scientists developed the seismic rehabilitation of structures and their view points were changed from sufficient strength to the performance of structures (Performance Base Design) to prepare a safe design. Nonlinear Static Procedure analysis (NSP) or pushover analysis is a new method that is chosen for its speed and simplicity in calculations. 'Seismic Rehabilitation Code for Existing Buildings' and FEMA 356 considered this method. Result of this analysis is a target displacement that is the base of the performance and rehabilitation procedure of the structures. Exact recognition of that displacement could develop the workability of pushover analysis. In these days, Nonlinear Dynamic Analysis (NDP) is only method can exactly apply the seismic ground motions. In this case because it consumes time, costs very high and is more difficult than other methods, is not applicable as much as NSP. A coefficient used in NSP for determining the target displacement is C2 (Stiffness and Strength Degradations Coefficient) and is applicable for correcting the errors due to eliminating the stiffness and strength degradations in hysteretic loops. In this study it has been tried to analysis three concrete frames with shear walls by several accelerations that scaled according to FEMA 273 and FEMA 356. These structures were designed with Iranian 2800 standard (vers.3). Finally after the analyzing by pushover method and comparison results with dynamic analysis, calculated C2 was comprised with values in rehabilitation codes

  15. Study on viscosity of conventional and polymer modified asphalt binders in steady and dynamic shear domain

    Science.gov (United States)

    Saboo, Nikhil; Singh, Bhupendra; Kumar, Praveen; Vikram, Durgesh

    2018-02-01

    This study focuses on evaluating the flow behavior of conventional and polymer modified asphalt binders in steady- and dynamic-shear domain, for a temperature range of 20-70 °C, using a Dynamic Shear Rheometer (DSR). Steady-shear viscosity and frequency sweep tests were carried out on two conventional (VG 10 and VG 30) and two polymer (SBS and EVA) modified asphalt binders. Applicability of the Cox-Merz principle was evaluated and complex viscosity master curves were analyzed at five different reference temperatures. Cross model was used to simulate the complex viscosity master curves at different temperatures. It was found that asphalt binders exhibited shear-thinning behavior at all the test temperatures. The critical shear rate increased with increase in temperature and was found to be lowest for plastomeric modified asphalt binder. The Cox-Merz principle was found to be valid in the zero-shear viscosity (ZSV) domain and deviated at higher frequency/shear rate for all the binders. Results from the study indicated that the ratio of ZSV can be successfully used as shift factors for construction of master curves at different reference temperatures. Cross model was found to be suitable in simulating the complex viscosity master curves at all the test temperatures. Analysis of model parameters indicated that a strong relationship exists between ZSV and the critical shear rate. ZSV and critical shear rate varied exponentially with temperature. This relationship was used to propose a simple equation for assessing the shift factors for construction of master curves.

  16. Poole-Frenkel behavior in amorphous oxide thin-film transistors prepared on SiOC

    International Nuclear Information System (INIS)

    Oh, Teresa

    2014-01-01

    The electron behavior in amorphous indium-gallium-zinc-oxide thin film transistors (a-IGZO TFTs) depends on the polar characteristics of SiOC, which is used as a gate dielectric. The properties of the interface between the semiconductor and SiOC were defined by using a Schottky contact with a low potential barrier and Poole-Frenkel contacts with a high potential barrier. The leakage current of SiOC, which was used as a gate insulator, decreased at the Poole-Frenkel contacts because of the high potential barrier. The ambipolar properties in the field effect transistor were observed to depend on the various characteristics of SiOC, which ranged from its behaving as an ideal insulator or as a material with a high dielectric constant. The resistance of the a-IGZO channel changed from positive to negative at SiOC, which had the lowest polarity. As to the conduction due to the diffusion current, the mobility increased with increasing carrier concentrations. However, the drift carrier conduction was related to the reduced mobility at higher carrier concentrations. The performance of the transistors was enhanced by the tunneling and the diffusion currents Rather than by the drift current caused by trapping. The Schottky contact and the Poole-Frenkel (PF) contacts at an interface between the IGZO channel and the SiOC were defined according to the heights of potential barriers caused by the depletion layer. The leakage current was very low about 10 -12 A at SiOC with PF contacts because of the height of potential barrier was double that with a Schottky contact because the tunneling conductance due to the diffusion current originated from the PF contacts of non-polar SiOC.

  17. Poole-Frenkel behavior in amorphous oxide thin-film transistors prepared on SiOC

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Teresa [Cheongju University, Cheongju (Korea, Republic of)

    2014-05-15

    The electron behavior in amorphous indium-gallium-zinc-oxide thin film transistors (a-IGZO TFTs) depends on the polar characteristics of SiOC, which is used as a gate dielectric. The properties of the interface between the semiconductor and SiOC were defined by using a Schottky contact with a low potential barrier and Poole-Frenkel contacts with a high potential barrier. The leakage current of SiOC, which was used as a gate insulator, decreased at the Poole-Frenkel contacts because of the high potential barrier. The ambipolar properties in the field effect transistor were observed to depend on the various characteristics of SiOC, which ranged from its behaving as an ideal insulator or as a material with a high dielectric constant. The resistance of the a-IGZO channel changed from positive to negative at SiOC, which had the lowest polarity. As to the conduction due to the diffusion current, the mobility increased with increasing carrier concentrations. However, the drift carrier conduction was related to the reduced mobility at higher carrier concentrations. The performance of the transistors was enhanced by the tunneling and the diffusion currents Rather than by the drift current caused by trapping. The Schottky contact and the Poole-Frenkel (PF) contacts at an interface between the IGZO channel and the SiOC were defined according to the heights of potential barriers caused by the depletion layer. The leakage current was very low about 10{sup -12} A at SiOC with PF contacts because of the height of potential barrier was double that with a Schottky contact because the tunneling conductance due to the diffusion current originated from the PF contacts of non-polar SiOC.

  18. Thin Slices of Athletes' Nonverbal Behavior Give Away Game Location: Testing the Territoriality Hypothesis of the Home Game Advantage.

    Science.gov (United States)

    Furley, Philip; Schweizer, Geoffrey; Memmert, Daniel

    2018-01-01

    The present research investigated whether perceivers could detect who is playing at home or away in soccer matches based on thin slices of professional (Experiment 1) and amateur (Experiment 3) athletes' nonverbal behavior prior to the match and whether perceivers rated athletes playing at home relatively higher on behavioral dimensions (Experiments 2 and 3) linked to territoriality. In Experiment 1 ( N = 80), participants watched short videos depicting soccer players prior to a UEFA Champions League match and rated whether athletes were more likely to be playing at home or away. In Experiment 2 (two groups N = 102 and N = 101), perceivers rated these videos in terms of assertiveness, dominance, and aggression. In Experiment 3, we replicated the procedure of Experiments 1 and 2 with different stimulus material from amateur soccer ( N = 112). Participants could significantly differentiate between home playing and away playing athletes (Experiment 1: d = 0.44 and Experiment 3: d = 1.07). Experiments 2 and 3 showed that perceivers rated professional and amateur soccer players higher on assertiveness ( d = 0.34-0.63), dominance ( d = 0.20-0.55), and aggression ( d = 0.16-0.49) when playing at home compared to playing away. Findings are supportive of evolutionary accounts of nonverbal behavior, ecological approaches to person perception, and the thin slices of behavior hypothesis by demonstrating that humans change their nonverbal behavior depending on game location. We discuss the relevance of the present findings for the home advantage in sports.

  19. Sheared Electroconvective Instability

    Science.gov (United States)

    Kwak, Rhokyun; Pham, Van Sang; Lim, Kiang Meng; Han, Jongyoon

    2012-11-01

    Recently, ion concentration polarization (ICP) and related phenomena draw attention from physicists, due to its importance in understanding electrochemical systems. Researchers have been actively studying, but the complexity of this multiscale, multiphysics phenomenon has been limitation for gaining a detailed picture. Here, we consider electroconvective(EC) instability initiated by ICP under pressure-driven flow, a scenario often found in electrochemical desalinations. Combining scaling analysis, experiment, and numerical modeling, we reveal unique behaviors of sheared EC: unidirectional vortex structures, its size selection and vortex propagation. Selected by balancing the external pressure gradient and the electric body force, which generates Hagen-Poiseuille(HP) flow and vortical EC, the dimensionless EC thickness scales as (φ2 /UHP)1/3. The pressure-driven flow(or shear) suppresses unfavorably-directed vortices, and simultaneously pushes favorably-directed vortices with constant speed, which is linearly proportional to the total shear of HP flow. This is the first systematic characterization of sheared EC, which has significant implications on the optimization of electrodialysis and other electrochemical systems.

  20. Bending and Shear Behavior of Pultruded Glass Fiber Reinforced Polymer Composite Beams With Closed and Open Sections

    Science.gov (United States)

    Estep, Daniel Douglas

    Several advantages, such as high strength-to-weight ratio, high stiffness, superior corrosion resistance, and high fatigue and impact resistance, among others, make FRPs an attractive alternative to conventional construction materials for use in developing new structures as well as rehabilitating in-service infrastructure. As the number of infrastructure applications using FRPs grows, the need for the development of a uniform Load and Resistance Factor Design (LRFD) approach, including design procedures and examples, has become paramount. Step-by-step design procedures and easy-to-use design formulas are necessary to assure the quality and safety of FRP structural systems by reducing the possibility of design and construction errors. Since 2008, the American Society of Civil Engineers (ASCE), in coordination with the American Composites Manufacturers Association (ACMA), has overseen the development of the Pre-Standard for Load and Resistance Factor Design (LRFD) of Pultruded Fiber Reinforced Polymer (FRP) Structures using probability-based limit states design. The fifth chapter of the pre-standard focuses on the design of members in flexure and shear under different failure modes, where the current failure load prediction models proposed within have been shown to be highly inaccurate based on experimental data and evaluation performed by researchers at the West Virginia University Constructed Facilities Center. A new prediction model for determining the critical flexural load capacity of pultruded GFRP square and rectangular box beams is presented within. This model shows that the type of failure can be related to threshold values of the beam span-to-depth ratio (L/h) and total flange width-to-thickness ratio (bf /t), resulting in three governing modes of failure: local buckling failure in the compression flange (4 ≤ L/h < 6), combined strain failure at the web-flange junction (6 ≤ L/h ≤ 10), and bending failure in the tension flange (10 < L/h ≤ 42

  1. Superhydrophilic Thin-Film Composite Forward Osmosis Membranes for Organic Fouling Control: Fouling Behavior and Antifouling Mechanisms

    KAUST Repository

    Tiraferri, Alberto

    2012-10-16

    This study investigates the fouling behavior and fouling resistance of superhydrophilic thin-film composite forward osmosis membranes functionalized with surface-tailored nanoparticles. Fouling experiments in both forward osmosis and reverse osmosis modes are performed with three model organic foulants: alginate, bovine serum albumin, and Suwannee river natural organic matter. A solution comprising monovalent and divalent salts is employed to simulate the solution chemistry of typical wastewater effluents. Reduced fouling is consistently observed for the superhydrophilic membranes compared to control thin-film composite polyamide membranes, in both reverse and forward osmosis modes. The fouling resistance and cleaning efficiency of the functionalized membranes is particularly outstanding in forward osmosis mode where the driving force for water flux is an osmotic pressure difference. To understand the mechanism of fouling, the intermolecular interactions between the foulants and the membrane surface are analyzed by direct force measurement using atomic force microscopy. Lower adhesion forces are observed for the superhydrophilic membranes compared to the control thin-film composite polyamide membranes. The magnitude and distribution of adhesion forces for the different membrane surfaces suggest that the antifouling properties of the superhydrophilic membranes originate from the barrier provided by the tightly bound hydration layer at their surface, as well as from the neutralization of the native carboxyl groups of thin-film composite polyamide membranes. © 2012 American Chemical Society.

  2. Superhydrophilic thin-film composite forward osmosis membranes for organic fouling control: fouling behavior and antifouling mechanisms.

    Science.gov (United States)

    Tiraferri, Alberto; Kang, Yan; Giannelis, Emmanuel P; Elimelech, Menachem

    2012-10-16

    This study investigates the fouling behavior and fouling resistance of superhydrophilic thin-film composite forward osmosis membranes functionalized with surface-tailored nanoparticles. Fouling experiments in both forward osmosis and reverse osmosis modes are performed with three model organic foulants: alginate, bovine serum albumin, and Suwannee river natural organic matter. A solution comprising monovalent and divalent salts is employed to simulate the solution chemistry of typical wastewater effluents. Reduced fouling is consistently observed for the superhydrophilic membranes compared to control thin-film composite polyamide membranes, in both reverse and forward osmosis modes. The fouling resistance and cleaning efficiency of the functionalized membranes is particularly outstanding in forward osmosis mode where the driving force for water flux is an osmotic pressure difference. To understand the mechanism of fouling, the intermolecular interactions between the foulants and the membrane surface are analyzed by direct force measurement using atomic force microscopy. Lower adhesion forces are observed for the superhydrophilic membranes compared to the control thin-film composite polyamide membranes. The magnitude and distribution of adhesion forces for the different membrane surfaces suggest that the antifouling properties of the superhydrophilic membranes originate from the barrier provided by the tightly bound hydration layer at their surface, as well as from the neutralization of the native carboxyl groups of thin-film composite polyamide membranes.

  3. Spin Speed and Duration Dependence of TiO2 Thin Films pH Sensing Behavior

    Directory of Open Access Journals (Sweden)

    Muhammad AlHadi Zulkefle

    2016-01-01

    Full Text Available Titanium dioxide (TiO2 thin films were applied as the sensing membrane of an extended-gate field-effect transistor (EGFET pH sensor. TiO2 thin films were deposited by spin coating method and the influences of the spin speed and spin duration on the pH sensing behavior of TiO2 thin films were investigated. The spin coated TiO2 thin films were connected to commercial metal-oxide-semiconductor field-effect transistor (MOSFET to form the extended gates and the MOSFET was integrated in a readout interfacing circuit to complete the EGFET pH sensor system. For the spin speed parameter investigation, the highest sensitivity was obtained for the sample spun at 3000 rpm at a fixed spinning time of 60 s, which was 60.3 mV/pH. The sensitivity was further improved to achieve 68 mV/pH with good linearity of 0.9943 when the spin time was 75 s at the speed of 3000 rpm.

  4. Influences of overload on low cycle fatigue behaviors of elbow pipe with local wall thinning

    International Nuclear Information System (INIS)

    Sato, Kyohei; Ogino, Kanako; Takahashi, Koji; Ando, Kotoji; Urabe, Yoshio

    2011-01-01

    Low cycle fatigue tests were conducted using 100A elbow pipe specimens with or without local wall thinning. Local wall thinning was machined on the inside of the extrados of test elbows to simulate metal loss due to flow-accelerated corrosion or liquid droplet impingement erosion. Low cycle fatigue tests were carried out under displacement control with an inner pressure of 9 MPa. To simulate seismic events, low cycle fatigue tests were carried out on elbow pipe subjected to cyclic overloads. Regardless of local wall thinning, fatigue life of overload pipe was not so different from that of the non-overload pipe in appearance. Miner's rule can be applied to evaluate fatigue life of the elbow pipes with and without wall thinning, even if overload is applied. (author)

  5. Electrochemical Behavior of TiO2 Nanoparticle Doped WO3 Thin Films

    Directory of Open Access Journals (Sweden)

    Suvarna R. Bathe

    2014-01-01

    Full Text Available Nanoparticle TiO2 doped WO3 thin films by pulsed spray pyrolysis technique have been studied on fluorine tin doped (FTO and glass substrate. XRD shows amorphous nature for undoped and anatase phase of TiO2 having (101 plane for nanoparticle TiO2 doped WO3 thin film. SEM shows microfibrous reticulated porous network for WO3 with 600 nm fiber diameter and nanocrystalline having size 40 nm for TiO2 nanoparticle doped WO3 thin film. TiO2 nanoparticle doped WO3 thin film shows ~95% reversibility due to may be attributed to nanocrystalline nature of the film, which helpful for charge insertion and deinsertion process. The diffusion coefficient for TiO2 nanoparticle doped WO3 film is less than undoped WO3.

  6. Modeling the influence of the seeding layer on the transition behavior of a ferroelectric thin film

    International Nuclear Information System (INIS)

    Oubelkacem, A.; Essaoudi, I.; Ainane, A.; Saber, M.; Dujardin, F.

    2011-01-01

    The transition properties of a ferroelectric thin film with seeding layers were studied using the effective field theory with a probability distribution technique that accounts for the self-spin correlation functions. The effect of interaction parameters for the seeding layer on the phase diagram was also examined. We calculated the critical temperature and the polarization of the ferroelectric thin film for different seeding layer structures. We found that the seeding layer can greatly increase the Curie temperature and the polarization.

  7. Thin slices of friendship: do non-verbal behaviors predict first impressions during getting acquainted interactions?

    OpenAIRE

    Urgancı, Betül

    2017-01-01

    Cataloged from PDF version of article. Thesis (M.S.): Bilkent University, Department of Psychology, İhsan Doğramacı Bilkent University, 2017. Includes bibliographical references (leaves 28-32). Does a very brief observation of a person predict first impressions? Prior research has shown that these brief observations, called thin slices, predict many psychological outcomes such as individual performance. However, there is a not much research investigating whether thin slices predict f...

  8. Experimental assessment and numerical modeling of the nonlinear behavior of the masonry shear walls under in-plane cyclic loading considering the brickwork-setting effect

    Directory of Open Access Journals (Sweden)

    Amir Hossein Karimi

    2017-08-01

    Full Text Available In this article, the main purpose is nonlinear analysis of the cyclic behavior of the masonry shear walls including brickwork setting using finite element method. Three different brickwork-settings including running bond style, herringbone style and Zarbi style (herreh style were investigated. To this end, the walls (in dimension of 195×1500×1720 mm were tested in the laboratory and then were simulated using macro modeling method by Abaqus software, and their hysteretic curves was drawn. The concrete damaged plasticity criteria in the Abaqus software is a model used in this research.In this method, the main failure mechanisms of fracture are cracking in tension and crushing in compression. The macro modeling method was used for numerical assessment of the masonry walls. After numerical modeling and drawing hysteretic curves and contrasting them with laboratory results, it was proven that the concrete damaged plasticity model, which is behavioral model for simulating concrete material, can be used for modeling masonry materials under seismic loading. However, this model cannot be used to simulate pinching effect in hysteretic curve drawn from seismic loading. The envelope curve resulted from the numerical analysis of all three brickwork layouts had a good agreement with the results of the laboratory tests, but in Hysteretic curve of Herringbone style and Zarbi style the pinching effect did not match experimental results

  9. Experimental Studies on the Behavior of a Newly-Developed Type of Self-Insulating Concrete Masonry Shear Wall under in-Plane Cyclic Loading

    Directory of Open Access Journals (Sweden)

    Abu-Bakre Abdelmoneim Elamin Mohamad

    2017-04-01

    Full Text Available This study aimed to investigate the inelastic behavior of a newly-developed type of self-insulating concrete masonry shear wall (SCMSW under in-plane cyclic loading. The new masonry system was made from concrete blocks with special configurations to provide a stronger bond between units than ordinary concrete masonry units. A total of six fully-grouted SCMSWs were prepared with different heights (1.59 to 5.78 m and different vertical steel configurations. The developed masonry walls were tested under in-plane cyclic loading and different constant axial load ratios. In addition, the relationship between the amount of axial loading, the amount of the flexural reinforcement and the wall aspect ratios and the nonlinear hysteretic response of the SCMSW was evaluated. The results showed that the lateral load capacity of SCMSW increases with the amount of applied axial load and the amount of vertical reinforcement. However, the lateral load capacity decreases as the wall aspect ratio increases. The existence of the boundary elements at the SCMSW ends increases the ductility and the lateral load capacity. Generally, the SCMSW exhibited predominantly flexural behavior. These results agreed with those reported in previous research for walls constructed with ordinary units.

  10. The effect of grain and pore sizes on the mechanical behavior of thin Al films deposited under different conditions

    International Nuclear Information System (INIS)

    Ben-David, E.; Landa, M.; Janovská, M.; Seiner, H.; Gutman, O.; Tepper-Faran, T.; Shilo, D.

    2015-01-01

    This paper presents a comprehensive study of the relationships between deposition conditions, microstructure and mechanical behavior in thin aluminum films commonly used in micro and nano-devices. A particular focus is placed on the effect of porosity, which is present in all thin films deposited by evaporation or sputtering techniques. The influences of the deposition temperature on the grain size, pore size and crystallographic texture were characterized by X-ray diffraction and scanning electron microscopy. The mechanical behavior of the films was investigated using four different methods. Each method is suitable for characterizing different properties and for testing the material at different length scales. Nanoindentation was used to study hardness at the level of individual grains; resonant ultrasound spectroscopy was used to measure the elastic moduli and porosity; and bulge and tensile tests were used to study released films under biaxial and uniaxial tensions. Our results demonstrate that even low porosities may have tremendous effects on the mechanical properties and that different methods allow the capture of different aspects of these effects. Therefore, a combination of several methods is required to obtain a comprehensive understanding of the mechanical behavior of a film. It is also shown that porosity with different pore size leads to very different effects on the mechanical behavior

  11. Predicting Shear Transformation Events in Metallic Glasses

    Science.gov (United States)

    Xu, Bin; Falk, Michael L.; Li, J. F.; Kong, L. T.

    2018-03-01

    Shear transformation is the elementary process for plastic deformation of metallic glasses, the prediction of the occurrence of the shear transformation events is therefore of vital importance to understand the mechanical behavior of metallic glasses. In this Letter, from the view of the potential energy landscape, we find that the protocol-dependent behavior of shear transformation is governed by the stress gradient along its minimum energy path and we propose a framework as well as an atomistic approach to predict the triggering strains, locations, and structural transformations of the shear transformation events under different shear protocols in metallic glasses. Verification with a model Cu64 Zr36 metallic glass reveals that the prediction agrees well with athermal quasistatic shear simulations. The proposed framework is believed to provide an important tool for developing a quantitative understanding of the deformation processes that control mechanical behavior of metallic glasses.

  12. Diode-like behavior of I–V curves of CoFe–(Al–O)/Si(100) granular thin films

    Energy Technology Data Exchange (ETDEWEB)

    Tuan Anh, Nguyen [ITIMS, Hanoi University of Science and Technology (HUST), Hanoi 10000 (Viet Nam); Hanoi Community College (HCC), Trung Kinh, Cau giay, Hanoi 10000 (Viet Nam); Van Cuong, Giap [ITIMS, Hanoi University of Science and Technology (HUST), Hanoi 10000 (Viet Nam); HungYen University of Technology and Education (UTEHY), Khoai chau, Hung Yen 39000 (Viet Nam); Anh Tuan, Nguyen, E-mail: tuanna@itims.edu.vn [ITIMS, Hanoi University of Science and Technology (HUST), Hanoi 10000 (Viet Nam)

    2015-01-15

    In this study, the electrical performance of (Co{sub 70}Fe{sub 30}){sub x}(Al–O){sub 1−x} (where x=0.1 and 0.3) granular thin films sputtered on Si(1 0 0) substrates, which were subsequently annealing at 350 °C for 1 h in vacuum, was investigated. The millimeter-sized samples were installed in an in-plane lateral Ag electrode configuration on the surface. The current–voltage (I–V) characteristics were measured in bias voltages of approximately ±7 V. The I–V curves demonstrated the so-called large Coulomb gaps and diode-like asymmetric behavior similar to a Zener diode-type rectification. This remarkable behavior was evaluated using the most suitable transport models. Results suggest that an effective magnetic diode could be fabricated from millimeter-sized magnetic granular thin films. - Highlights: • The granular MTJ systems can induce a strong collective Coulomb blockage effect. • Isolated magnetic nanoparticles can form asymmetric nano-double barrier MTJ chains. • Discrete system can induce diode-like rectification as a molecular electronic rectifier. • Irreversible cotunneling through nano-double barrier MTJ chains yields rectification. • Magnetic tunnel diodes can be created simply from the granular MTJ-type thin films.

  13. Prediction of Tensile Behavior of UHSFRC Considering the Flow Field in the Placing Dominated by Shear Flow

    Directory of Open Access Journals (Sweden)

    Joon-Shik Moon

    2018-01-01

    Full Text Available Considering the case of fabricating a UHSFRC (ultra-high strength fiber-reinforced concrete beam with the method of one end placing and self-flowing to the other end, it was intended to simulate the variation of the fiber orientation distribution according to the flow distance and the variation of the resultant tensile behaviors. Then the validity of the simulation approach was shown by comparing the simulated results with experimental ones. A three-point bending test with a notched beam was adopted for the experiment and a finite element analysis was performed to obtain the simulated results for the bending test considering the flow-dependent tensile behavior of the UHSFRC. From the simulation for the fiber orientation distribution according to the flow distance, it could be found that the major change in the fiber orientation distribution took place within a short flow distance and most of the fibers became nearly aligned to the flow direction. After some flow distance, there was a not-so-remarkable variation in the fiber orientation distribution that could influence the tensile behavior of the composite. For this flow region, the consistent flexural test results, regardless of flow distance, demonstrate the reliability of the simulation.

  14. Prediction of Tensile Behavior of UHSFRC Considering the Flow Field in the Placing Dominated by Shear Flow.

    Science.gov (United States)

    Moon, Joon-Shik; Kang, Su-Tae

    2018-01-26

    Considering the case of fabricating a UHSFRC (ultra-high strength fiber-reinforced concrete) beam with the method of one end placing and self-flowing to the other end, it was intended to simulate the variation of the fiber orientation distribution according to the flow distance and the variation of the resultant tensile behaviors. Then the validity of the simulation approach was shown by comparing the simulated results with experimental ones. A three-point bending test with a notched beam was adopted for the experiment and a finite element analysis was performed to obtain the simulated results for the bending test considering the flow-dependent tensile behavior of the UHSFRC. From the simulation for the fiber orientation distribution according to the flow distance, it could be found that the major change in the fiber orientation distribution took place within a short flow distance and most of the fibers became nearly aligned to the flow direction. After some flow distance, there was a not-so-remarkable variation in the fiber orientation distribution that could influence the tensile behavior of the composite. For this flow region, the consistent flexural test results, regardless of flow distance, demonstrate the reliability of the simulation.

  15. Crystallization and atomic diffusion behavior of high coercive Ta/Nd-Fe-B/Ta-based permanent magnetic thin film

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Na; Zhang, Xiao; You, Caiyin; Fu, Huarui [Xi' an University of Technology, School of Materials Science and Engineering, Xi' an (China); Shen, Qianlong [Logistics University of People' s Armed Police Force, Tianjin (China)

    2017-06-15

    A high coercivity of about 20.4 kOe was obtained through post-annealing the sputtered Ta/Nd-Fe-B/Ta-based permanent magnetic thin films. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses were performed to investigate the crystallization and atomic diffusion behaviors during post-annealing. The results show that the buffer and capping Ta layers prefered to intermix with Fe and B atoms, and Nd tends to be combined with O atoms. The preferred atomic combination caused the appearance of the soft magnetic phase of Fe-Ta-B, resulting in a kink of the second quadratic magnetic hysteresis loop. The preferred atomic diffusion and phase formation of the thin films were well explained in terms of the formation enthalpy of the various compounds. (orig.)

  16. A study of growth and thermal dewetting behavior of ultra-thin gold films using transmission electron microscopy

    Directory of Open Access Journals (Sweden)

    Sudheer

    2017-07-01

    Full Text Available The growth and solid-state dewetting behavior of Au thin films (0.7 to 8.4 nm deposited on the formvar film (substrate by sputtering technique have been studied using transmission electron microscopy. The size and number density of the Au nanoparticles (NPs change with an increase in the film thickness (0.7 to 2.8 nm. Nearly spherical Au NPs are obtained for 6 nm show capability to be used as an irreversible temperature sensor with a sensitivity of ∼0.1 CAF/°C. It is observed that annealing affects the crystallinity of the Au grains in the films. The electron diffraction measurement also shows annealing induced morphological evolution in the percolated Au thin films (≥3 nm during solid-state dewetting and recrystallization of the grains.

  17. Relaxorlike dielectric behavior in Ba0.7Sr0.3TiO3 thin films

    Science.gov (United States)

    Zednik, Ricardo J.; McIntyre, Paul C.; Baniecki, John D.; Ishii, Masatoshi; Shioga, Takeshi; Kurihara, Kazuaki

    2007-03-01

    We present the results of a systematic dielectric study for sputter deposited barium strontium titanate thin film planar capacitors measured over a wide temperature range of 20-575K for frequencies between 1kHz and 1MHz. Our observations of dielectric loss peaks in the temperature and frequency domains cannot be understood in the typical framework of intrinsic phonon losses. We find that the accepted phenomenological Curie-von Schweidler dielectric behavior (universal relaxation law) in our barium strontium titanate films is only applicable over a narrow temperature range. An excellent fit to the Vogel-Fulcher expression suggests relaxorlike behavior in these films. The activation energy of the observed phenomenon suggests that oxygen ion motion play a role in the apparent relaxor behavior, although further experimental work is required to test this hypothesis.

  18. Weakly sheared active suspensions: hydrodynamics, stability, and rheology.

    Science.gov (United States)

    Cui, Zhenlu

    2011-03-01

    We present a kinetic model for flowing active suspensions and analyze the behavior of a suspension subjected to a weak steady shear. Asymptotic solutions are sought in Deborah number expansions. At the leading order, we explore the steady states and perform their stability analysis. We predict the rheology of active systems including an activity thickening or thinning behavior of the apparent viscosity and a negative apparent viscosity depending on the particle type, flow alignment, and the anchoring conditions, which can be tested on bacterial suspensions. We find remarkable dualities that show that flow-aligning rodlike contractile (extensile) particles are dynamically and rheologically equivalent to flow-aligning discoid extensile (contractile) particles for both tangential and homeotropic anchoring conditions. Another key prediction of this work is the role of the concentration of active suspensions in controlling the rheological behavior: the apparent viscosity may decrease with the increase of the concentration.

  19. Physical–chemical and biological behavior of an amorphous calcium phosphate thin film produced by RF-magnetron sputtering

    International Nuclear Information System (INIS)

    Santos, Euler A. dos; Moldovan, Simona; Mateescu, Mihaela; Faerber, Jacques; Acosta, Manuel; Pelletier, Hervé; Anselme, Karine; Werckmann, Jacques

    2012-01-01

    This work evaluates the thermal reactivity and the biological reactivity of an amorphous calcium phosphate thin film produced by radio frequency (RF) magnetron sputtering onto titanium substrates. The analyses showed that the sputtering conditions used in this work led to the deposition of an amorphous calcium phosphate. The thermal treatment of this amorphous coating in the presence of H 2 O and CO 2 promoted the formation of a carbonated HA crystalline coating with the entrance of CO 3 2− ions into the hydroxyl HA lattice. When immersed in culture medium, the amorphous and carbonated coatings exhibited a remarkable instability. The presence of proteins increased the dissolution process, which was confirmed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses. Moreover, the carbonated HA coating induced precipitation independently of the presence of proteins under dynamic conditions. Despite this surface instability, this reactive calcium phosphate significantly improved the cellular behavior. The cell proliferation was higher on the Ticp than on the calcium phosphate coatings, but the two coatings increased cellular spreading and stress fiber formation. In this sense, the presence of reactive calcium phosphate coatings can stimulate cellular behavior. - Highlights: ► Functionalization of Ti with reactive CaP thin film by RF-magnetron sputtering. ► De-hydroxylation facilitating the insertion of CO 3 2− into the HA lattice. ► High surface reactivity in the presence of culture medium. ► Cell behavior improved by the presence of reactive films.

  20. The influence of polymer architectures on the dewetting behavior of thin polymer films: from linear chains to ring chains.

    Science.gov (United States)

    Wang, Lina; Xu, Lin; Liu, Binyuan; Shi, Tongfei; Jiang, Shichun; An, Lijia

    2017-05-03

    The dewetting behavior of ring polystyrene (RPS) film and linear polystyrene (LPS) film on silanized Si substrates with different grafting densities and PDMS substrate was investigated. Results showed that polymer architectures greatly influenced the dewetting behavior of the thin polymer film. On the silanized Si substrate with 69% grafting density, RPS chains exhibited stronger adsorption compared with LPS chains, and as a result the wetting layer formed more easily. For LPS films, with a decreased annealing temperature, the stability of the polymer film changed from non-slip dewetting via apparent slip dewetting to apparently stable. However, for RPS films, the polymer film stability switched from apparent slip dewetting to apparently stable. On the silanized Si substrate with 94% grafting density, the chain adsorption became weaker and the dewetting processes were faster than that on the substrate with 69% grafting density at the same experimental temperature for both the LPS and RPS films. Moreover, on the PDMS substrate, LPS films always showed non-slip dewetting, while the dewetting kinetics of RPS films switched from non-slip dewetting to slip dewetting behaviour. Forming the wetting layer strongly influenced the stability and dewetting behavior of the thin polymer films.

  1. Microstructure, elastic deformation behavior and mechanical properties of biomedical β-type titanium alloy thin-tube used for stents.

    Science.gov (United States)

    Tian, Yuxing; Yu, Zhentao; Ong, Chun Yee Aaron; Kent, Damon; Wang, Gui

    2015-05-01

    Cold-deformability and mechanical compatibility of the biomedical β-type titanium alloy are the foremost considerations for their application in stents, because the lower ductility restricts the cold-forming of thin-tube and unsatisfactory mechanical performance causes a failed tissue repair. In this paper, β-type titanium alloy (Ti-25Nb-3Zr-3Mo-2Sn, wt%) thin-tube fabricated by routine cold rolling is reported for the first time, and its elastic behavior and mechanical properties are discussed for the various microstructures. The as cold-rolled tube exhibits nonlinear elastic behavior with large recoverable strain of 2.3%. After annealing and aging, a nonlinear elasticity, considered as the intermediate stage between "double yielding" and normal linear elasticity, is attributable to a moderate precipitation of α phase. Quantitive relationships are established between volume fraction of α phase (Vα) and elastic modulus, strength as well as maximal recoverable strain (εmax-R), where the εmax-R of above 2.0% corresponds to the Vα range of 3-10%. It is considered that the "mechanical" stabilization of the (α+β) microstructure is a possible elastic mechanism for explaining the nonlinear elastic behavior. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Metallic behavior of NiS thin film under the structural, optical, electrical and ab initio investigation frameworks

    Energy Technology Data Exchange (ETDEWEB)

    Boughalmi, R. [Unité de physique des dispositifs à semi-conducteurs, Faculté des sciences de Tunis, Tunis El Manar University, 2092 Tunis (Tunisia); Rahmani, R. [Laboratoire de Physique des Couches Minces et Matériaux pour l' Electronique (LPC2ME). Département de physique, Faculté des Sciences, Université d' Oran Es-Sénia, Oran (Algeria); Département de physique, Université des Sciences et de la Technologie d' Oran- Mohamed-Boudiaf, Oran (Algeria); Boukhachem, A., E-mail: abdelwaheb.boukhachem@laposte.net [Unité de physique des dispositifs à semi-conducteurs, Faculté des sciences de Tunis, Tunis El Manar University, 2092 Tunis (Tunisia); Amrani, B.; Driss-Khodja, K. [Laboratoire de Physique des Couches Minces et Matériaux pour l' Electronique (LPC2ME). Département de physique, Faculté des Sciences, Université d' Oran Es-Sénia, Oran (Algeria); Amlouk, M. [Unité de physique des dispositifs à semi-conducteurs, Faculté des sciences de Tunis, Tunis El Manar University, 2092 Tunis (Tunisia)

    2015-08-01

    Nickel sulfide (NiS) thin films were deposited on the glass substrates by spray pyrolysis at 250 °C using an aqueous solution which contains nickel chloride hexahydrate and thiourea as precursors. X-ray diffraction analysis confirms that the hexagonal structure is being part of P6{sub 3}/mmc space group of the deposited films with (100) preferred orientation and lattice parameters a = 3.441 Å and c = 5.320 Å. The optical properties, investigated through transmittance and reflectance measurements reveal that the direct band gap energy (Eg) is around 0.55 eV. The electrical study shows a metallic behavior of the current II-VI binary compound. This behavior regarding NiS II-VI binary sulfide was confirmed by numerical studies based on the density functional theory (DFT) were adopted. The ground state quantities, such as lattice parameter, bulk modulus and its pressure derivative as well as the elastic constants were obtained. The values are consistent with the stability of hexagonal structure. The band structure and the states densities of such material were studied. The results show that there is an agreement between experimental and simulation. - Highlights: • NiS thin films are synthesized by Spray pyrolysis. • NiS is a low band gap compound. • These films have interesting electrical properties showing a metallic behavior. • Computational study confirms the electrical measurements.

  3. Structural predictor for nonlinear sheared dynamics in simple glass-forming liquids.

    Science.gov (United States)

    Ingebrigtsen, Trond S; Tanaka, Hajime

    2018-01-02

    Glass-forming liquids subjected to sufficiently strong shear universally exhibit striking nonlinear behavior; for example, a power-law decrease of the viscosity with increasing shear rate. This phenomenon has attracted considerable attention over the years from both fundamental and applicational viewpoints. However, the out-of-equilibrium and nonlinear nature of sheared fluids have made theoretical understanding of this phenomenon very challenging and thus slower to progress. We find here that the structural relaxation time as a function of the two-body excess entropy, calculated for the extensional axis of the shear flow, collapses onto the corresponding equilibrium curve for a wide range of pair potentials ranging from harsh repulsive to soft and finite. This two-body excess entropy collapse provides a powerful approach to predicting the dynamics of nonequilibrium liquids from their equilibrium counterparts. Furthermore, the two-body excess entropy scaling suggests that sheared dynamics is controlled purely by the liquid structure captured in the form of the two-body excess entropy along the extensional direction, shedding light on the perplexing mechanism behind shear thinning.

  4. Structural predictor for nonlinear sheared dynamics in simple glass-forming liquids

    Science.gov (United States)

    Ingebrigtsen, Trond S.; Tanaka, Hajime

    2018-01-01

    Glass-forming liquids subjected to sufficiently strong shear universally exhibit striking nonlinear behavior; for example, a power-law decrease of the viscosity with increasing shear rate. This phenomenon has attracted considerable attention over the years from both fundamental and applicational viewpoints. However, the out-of-equilibrium and nonlinear nature of sheared fluids have made theoretical understanding of this phenomenon very challenging and thus slower to progress. We find here that the structural relaxation time as a function of the two-body excess entropy, calculated for the extensional axis of the shear flow, collapses onto the corresponding equilibrium curve for a wide range of pair potentials ranging from harsh repulsive to soft and finite. This two-body excess entropy collapse provides a powerful approach to predicting the dynamics of nonequilibrium liquids from their equilibrium counterparts. Furthermore, the two-body excess entropy scaling suggests that sheared dynamics is controlled purely by the liquid structure captured in the form of the two-body excess entropy along the extensional direction, shedding light on the perplexing mechanism behind shear thinning.

  5. The effects of thinning and similar stand treatments on fire behavior in Western forests.

    Science.gov (United States)

    Russell T. Graham; Alan E. Harvey; Theresa B. Jain; Jonalea R. Tonn

    1999-01-01

    In the West, thinning and partial cuttings are being considered for treating millions of forested acres that are overstocked and prone to wildfire. The objectives of these treatments include tree growth redistribution, tree species regulation, timber harvest, wildlife habitat improvement, and wildfire-hazard reduction. Depending on the forest type and its structure,...

  6. Autophobicity and layering behavior of thin liquid-crystalline polymer films.

    NARCIS (Netherlands)

    Wielen, van der M.W.J.; Cohen Stuart, M.A.; Fleer, G.J.

    1998-01-01

    The stability against breaking-up of thin spin-coated films of liquid-crystalline polymers depends on the film thickness and annealing temperature. This study concerns side-chain liquid-crystalline polymers, based on alternating copolymers of maleic anhydride and mesogenic alkenes. The mesogenic

  7. Crystal plasticity based modeling of time and scale dependent behavior of thin films

    NARCIS (Netherlands)

    Erturk, I.; Gao, K.; Bielen, J.A.; Dommelen, van J.A.W.; Geers, M.G.D.

    2013-01-01

    The micro and sub-micro scale dimensions of the components of modern high-tech products pose challenging engineering problems that require advanced tools to tackle them. An example hereof is time dependent strain recovery, here referred to as anelasticity, which is observed in metallic thin film

  8. Indentation-Induced Mechanical Deformation Behaviors of AlN Thin Films Deposited on c-Plane Sapphire

    International Nuclear Information System (INIS)

    Jian, Sh.R.; Juang, J.Y.

    2012-01-01

    The mechanical properties and deformation behaviors of AlN thin films deposited on c-plane sapphire substrates by helicon sputtering method were determined using the Berkovich nano indentation and cross-sectional transmission electron microscopy (XTEM). The load-displacement curves show the 'pop-ins' phenomena during nano indentation loading, indicative of the formation of slip bands caused by the propagation of dislocations. No evidence of nano indentation-induced phase transformation or cracking patterns was observed up to the maximum load of 80 mN, from either XTEM or atomic force microscopy (AFM) of the mechanically deformed regions. Instead, XTEM revealed that the primary deformation mechanism in AlN thin films is via propagation of dislocations on both basal and pyramidal planes. Furthermore, the hardness and Young's modulus of AlN thin films estimated using the continuous contact stiffness measurements (CSMs) mode provided with the nanoindenter are 16.2 GPa and 243.5 GPa, respectively.

  9. Effect of oxygen on the thermomechanical behavior of tantalum thin films during the β-α phase transformation

    International Nuclear Information System (INIS)

    Knepper, Robert; Stevens, Blake; Baker, Shefford P.

    2006-01-01

    Tantalum thin films were prepared in the metastable β phase, and their thermomechanical behaviors were investigated in situ in an ultrahigh vacuum environment. Controlled levels of oxygen were incorporated into the films either during deposition, by surface oxidation after deposition, or during thermomechanical testing. The transformation from the β phase to the stable α phase takes place in conjunction with a distinct increase in tensile stress. The thermomechanical behavior is strongly affected by the amount of oxygen to which the film is exposed and the method of exposure. Increasing oxygen content inhibits the phase transformation, requiring higher temperatures to reach completion. It is shown that the phase transformation takes place by a nucleation and growth process that is limited by growth. Changes in the activation energy for the phase transformation due to solute drag are estimated as a function of oxygen content and the mechanisms behind the stress evolution are elucidated

  10. Simulations of Granular Particles Under Cyclic Shear

    Science.gov (United States)

    Royer, John; Chaikin, Paul

    2012-02-01

    We perform molecular dynamics (MD) simulations of spherical grains subjected to cyclic, quasi-static shear in a 3D parallelepiped shear cell. This virtual shear cell is constructed out of rough, bumpy walls in order to minimize wall-induced ordering and has an open top surface to allow the packing to readily dilate or compact. Using a standard routine for MD simulations of frictional grains, we simulate over 1000 shear cycles, measuring grain displacements, the local packing density and changes in the contact network. Varying the shear amplitude and the friction coefficient between grains, we map out a phase diagram for the different types of behavior exhibited by these sheared grains. With low friction and high enough shear, the grains can spontaneously order into densely packed crystals. With low shear and increasing friction the packing remains disordered, yet the grains arrange themselves into configurations which exhibit limit cycles where all grains return to the same position after each full shear cycle. At higher shear and friction there is a transition to a diffusive state, where grains continue rearrange and move throughout the shear cell.

  11. Study of tensile test behavior of austenitic stainless steel type 347 seamless thin-walled tubes in cold worked condition

    Energy Technology Data Exchange (ETDEWEB)

    Terui, Clarice, E-mail: clarice.terui@marinha.mil.br [Centro Tecnológico da Marinha em São Paulo (CINA/CTMSP), Iperó, SP (Brazil). Centro Industrial Nuclear da Marinha; Lima, Nelson B. de, E-mail: nblima@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNE-SP), Sao Paulo, SP (Brazil)

    2017-07-01

    These austenitic stainless steel type 347 seamless thin-walled tubes are potential candidates to be used in fuel elements of nuclear power plants (as PWR - Pressurized Water Reactor). So, their metallurgical condition and mechanical properties, as the tensile strength and yield strength, normally are very restrict in demanding project and design requirements. Several full size tensile tests at room temperature and high temperature (315 deg C) were performed in these seamless tubes in cold-worked condition. The results of specified tensile and yield strengths were achieved but the elongation of the tube, in the geometry of the component, could not be measured at high temperature due to unconventional mode of rupture (helical mode without separation of parts). The average value of elongation was obtained from stress-strain curves of hot tensile tests and was around 5%. The results obtained in this research show that this behavior of the full size tensile test samples of thin-walled tube (wall thickness less than 0.5 mm) in high temperature (315°C) is due to the combination of the manufacturing process, the material (crystallographic structure and chemical composition) and the final geometry of the component. In other words, the strong crystallographic texture of material induced by tube drawing process in addition with the geometry of the component are responsible for the behavior in hot uniaxial tensile tests. (author)

  12. Effects of LP-MOCVD prepared TiO2 thin films on the in vitro behavior of gingival fibroblasts

    International Nuclear Information System (INIS)

    Cimpean, Anisoara; Popescu, Simona; Ciofrangeanu, Cristina M.; Gleizes, Alain N.

    2011-01-01

    We report on the in vitro response of human gingival fibroblasts (HGF-1 cell line) to various thin films of titanium dioxide (TiO 2 ) deposited on titanium (Ti) substrates by low pressure metal-organic chemical vapor deposition (LP-MOCVD). The aim was to study the influence of film structural parameters on the cell behavior comparatively with a native-oxide covered titanium specimen, this objective being topical and interesting for materials applications in implantology. HGF-1 cells were cultured on three LP-MOCVD prepared thin films of TiO 2 differentiated by their thickness, roughness, transversal morphology, allotropic composition and wettability, and on a native-oxide covered Ti substrate. Besides traditional tests of cell viability and morphology, the biocompatibility of these materials was evaluated by fibronectin immunostaining, assessment of cell proliferation status and the zymographic evaluation of gelatinolytic activities specific to matrix metalloproteinases secreted by cells grown in contact with studied specimens. The analyzed surfaces proved to influence fibronectin fibril assembly, cell proliferation and capacity to degrade extracellular matrix without considerably affecting cell viability and morphology. The MOCVD of TiO 2 proved effective in positively modifying titanium surface for medical applications. Surface properties playing a crucial role for cell behavior were the wettability and, secondarily, the roughness, HGF-1 cells preferring a moderately rough and wettable TiO 2 coating.

  13. Leakage current behavior in lead-free ferroelectric (K,Na)NbO3-LiTaO3-LiSbO3 thin films

    Science.gov (United States)

    Abazari, M.; Safari, A.

    2010-12-01

    Conduction mechanisms in epitaxial (001)-oriented pure and 1 mol % Mn-doped (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.1,Sb0.06)O3 (KNN-LT-LS) thin films on SrTiO3 substrate were investigated. Temperature dependence of leakage current density was measured as a function of applied electric field in the range of 200-380 K. It was shown that the different transport mechanisms dominate in pure and Mn-doped thin films. In pure (KNN-LT-LS) thin films, Poole-Frenkel emission was found to be responsible for the leakage, while Schottky emission was the dominant mechanism in Mn-doped thin films at higher electric fields. This is a remarkable yet clear indication of effect of 1 mol % Mn on the resistive behavior of such thin films.

  14. Two-phase behavior in strained thin films of hole-doped manganites

    OpenAIRE

    Biswas, Amlan; Rajeswari, M.; Srivastava, R. C.; Li, Y. H.; Venkatesan, T.; Greene, R. L.; Millis, A. J.

    1999-01-01

    We present a study of the effect of biaxial strain on the electrical and magnetic properties of thin films of manganites. We observe that manganite films grown under biaxial compressive strain exhibit island growth morphology which leads to a non-uniform distribution of the strain. Transport and magnetic properties of these films suggest the coexistence of two different phases, a metallic ferromagnet and an insulating antiferromagnet. We suggest that the high strain regions are insulating whi...

  15. Complex rheological behaviors of loach (Misgurnus anguillicaudatus) skin mucus

    International Nuclear Information System (INIS)

    Wang, Xiang; Su, Heng; Lv, Weiyang; Du, Miao; Song, Yihu; Zheng, Qiang

    2015-01-01

    The functions and structures of biological mucus are closely linked to rheology. In this article, the skin mucus of loach (Misgurnus anguillicaudatus) was proved to be a weak hydrogel susceptible to shear rate, time, and history, exhibiting: (i) Two-region breakdown of its gel structure during oscillatory strain sweep; (ii) rate-dependent thickening followed by three-region thinning with increased shear rate, and straight thinning with decreased shear rate; and (iii) time-dependent rheopexy at low shear rates, and thixotropy at high shear rates. An interesting correlation between the shear rate- and time-dependent rheological behaviors was also revealed, i.e., the rheopexy-thixotropy transition coincided with the first-second shear thinning region transition. Apart from rheology, a structure of colloidal network was observed in loach skin mucus using transmission electron microscopy. The complex rheology was speculated to result from inter- and intracolloid structural alterations. The unique rheology associated with the colloidal network structure, which has never been previously reported in vertebrate mucus, may play a key role in the functions (e.g., flow, reannealing, lubrication, and barrier) of the mucus

  16. Complex rheological behaviors of loach (Misgurnus anguillicaudatus) skin mucus

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiang, E-mail: 11229036@zju.edu.cn; Su, Heng, E-mail: shtdyso@163.com; Lv, Weiyang, E-mail: 3090103369@zju.edu.cn; Du, Miao, E-mail: dumiao@zju.edu.cn; Song, Yihu, E-mail: s-yh0411@zju.edu.cn; Zheng, Qiang, E-mail: zhengqiang@zju.edu.cn [MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

    2015-01-15

    The functions and structures of biological mucus are closely linked to rheology. In this article, the skin mucus of loach (Misgurnus anguillicaudatus) was proved to be a weak hydrogel susceptible to shear rate, time, and history, exhibiting: (i) Two-region breakdown of its gel structure during oscillatory strain sweep; (ii) rate-dependent thickening followed by three-region thinning with increased shear rate, and straight thinning with decreased shear rate; and (iii) time-dependent rheopexy at low shear rates, and thixotropy at high shear rates. An interesting correlation between the shear rate- and time-dependent rheological behaviors was also revealed, i.e., the rheopexy-thixotropy transition coincided with the first-second shear thinning region transition. Apart from rheology, a structure of colloidal network was observed in loach skin mucus using transmission electron microscopy. The complex rheology was speculated to result from inter- and intracolloid structural alterations. The unique rheology associated with the colloidal network structure, which has never been previously reported in vertebrate mucus, may play a key role in the functions (e.g., flow, reannealing, lubrication, and barrier) of the mucus.

  17. Shear zone nucleation and deformation transient: effect of heterogeneities and loading conditions in experimentally deformed calcite

    Science.gov (United States)

    Morales, L. F. G.; Rybacki, E.; Dresen, G. H.; Kilian, R.

    2015-12-01

    In the Earth's middle to lower crust, strain is frequently localized along ductile shear zones, which commonly nucleate at structural and material heterogeneities. To investigate shear zone nucleation and development due to heterogeneities, we performed constant strain-rate (CSR) and constant stress (CS) simple shear (torsion) deformation experiments on Carrara marble samples containing weak (limestone) inclusions. The experiments were conducted in a Paterson-type gas deformation apparatus at 900 °C temperature and 400 MPa confining pressure and maximum bulk shear strains of 3. Peak shear stress was about 20 MPa for all the samples, followed by smooth weakening and steady state behavior. The strain is predominantly localized in the host marble within the process zone in front of the inclusion, defined by a zone of intense grain size reduction due to dynamic recrystallization. In CS tests a narrow shear zone developed in front of the inclusion, whereas in CSR experiments the deformation is more heterogeneously distributed, up to g=3.. In the later, secondary foliations oblique to the process zone and alternating thin, high-strain layers are common. In samples deformed at the same shear strain (g=1), the average recrystallized grain size in the process zone is similar for CS and CSR conditions. Crystallographic preferred orientation (CPO) measurements shows that different grain sizes have slightly different CPO patterns. CPO strength varies for different grain sizes, with a CPO strength peak between 40-50 μm, decreasing progressively within smaller grain size, but with secondary peaks for different coarse-grained sizes. Our observations suggest that the initial formation and transient deformation of shear zones is strongly affected by loading conditions.

  18. Transient Droplet Behavior and Droplet Breakup during Bulk and Confined Shear Flow in Blends with One Viscoelastic Component: Experiments, Modelling and Simulations

    Science.gov (United States)

    Cardinaels, Ruth; Verhulst, Kristof; Renardy, Yuriko; Moldenaers, Paula

    2008-07-01

    The transient droplet deformation and droplet orientation after inception of shear, the shape relaxation after cessation of shear and droplet breakup during shear, are microscopically studied, both under bulk and confined conditions. The studied blends contain one viscoelastic Boger fluid phase. A counter rotating setup, based on a Paar Physica MCR300, is used for the droplet visualisation. For bulk shear flow, it is shown that the droplet deformation during startup of shear flow and the shape relaxation after cessation of shear flow are hardly influenced by droplet viscoelasticity, even at moderate to high capillary and Deborah numbers. The effects of droplet viscoelasticity only become visible close to the critical conditions and a novel break-up mechanism is observed. Matrix viscoelasticity has a more pronounced effect, causing overshoots in the deformation and significantly inhibiting relaxation. However, different applied capillary numbers prior to cessation of shear flow, with the Deborah number fixed, still result in a single master curve for shape retraction, as in fully Newtonian systems. The long tail in the droplet relaxation can be qualitatively described with a phenomenological model for droplet deformation, when using a 5-mode Giesekus model for the fluid rheology. It is found that the shear flow history significantly affects the droplet shape evolution and the breakup process in blends with one viscoelastic component. Confining a droplet between two plates accelerates the droplet deformation kinetics, similar to fully Newtonian systems. However, the increased droplet deformation, due to wall effects, causes the steady state to be reached at a later instant in time. Droplet relaxation is less sensitive to confinement, leading to slower relaxation kinetics only for highly confined droplets. For the blend with a viscoelastic droplet, a non-monotonous trend is found for the critical capillary number as a function of the confinement ratio. Finally

  19. Transient Droplet Behavior and Droplet Breakup during Bulk and Confined Shear Flow in Blends with One Viscoelastic Component: Experiments, Modelling and Simulations

    International Nuclear Information System (INIS)

    Cardinaels, Ruth; Verhulst, Kristof; Moldenaers, Paula; Renardy, Yuriko

    2008-01-01

    The transient droplet deformation and droplet orientation after inception of shear, the shape relaxation after cessation of shear and droplet breakup during shear, are microscopically studied, both under bulk and confined conditions. The studied blends contain one viscoelastic Boger fluid phase. A counter rotating setup, based on a Paar Physica MCR300, is used for the droplet visualisation. For bulk shear flow, it is shown that the droplet deformation during startup of shear flow and the shape relaxation after cessation of shear flow are hardly influenced by droplet viscoelasticity, even at moderate to high capillary and Deborah numbers. The effects of droplet viscoelasticity only become visible close to the critical conditions and a novel break-up mechanism is observed. Matrix viscoelasticity has a more pronounced effect, causing overshoots in the deformation and significantly inhibiting relaxation. However, different applied capillary numbers prior to cessation of shear flow, with the Deborah number fixed, still result in a single master curve for shape retraction, as in fully Newtonian systems. The long tail in the droplet relaxation can be qualitatively described with a phenomenological model for droplet deformation, when using a 5-mode Giesekus model for the fluid rheology. It is found that the shear flow history significantly affects the droplet shape evolution and the breakup process in blends with one viscoelastic component. Confining a droplet between two plates accelerates the droplet deformation kinetics, similar to fully Newtonian systems. However, the increased droplet deformation, due to wall effects, causes the steady state to be reached at a later instant in time. Droplet relaxation is less sensitive to confinement, leading to slower relaxation kinetics only for highly confined droplets. For the blend with a viscoelastic droplet, a non-monotonous trend is found for the critical capillary number as a function of the confinement ratio. Finally

  20. Deformation and failure response of 304L stainless steel SMAW joint under dynamic shear loading

    International Nuclear Information System (INIS)

    Lee, Woei-Shyan; Cheng, J.-I.; Lin, C.-F.

    2004-01-01

    The dynamic shear deformation behavior and fracture characteristics of 304L stainless steel shielded metal arc welding (SMAW) joint are studied experimentally with regard to the relations between mechanical properties and strain rate. Thin-wall tubular specimens are deformed at room temperature under strain rates in the range of 8 x 10 2 to 2.8 x 10 3 s -1 using a torsional split-Hopkinson bar. The results indicate that the strain rate has a significant influence on the mechanical properties and fracture response of the tested SMAW joints. It is found that the flow stress, total shear strain to failure, work hardening rate and strain rate sensitivity all increase with increasing strain rate, but that the activation volume decreases. The observed dynamic shear deformation behavior is modeled using the Kobayashi-Dodd constitutive law, and it is shown that the predicted results are in good agreement with the experimental data. Fractographic analysis using scanning electron microscopy reveals that the tested specimens all fracture within their fusion zones, and that the primary failure mechanism is one of the extensive localized shearing. The fracture surfaces are characterized by the presence of many dimples. A higher strain rate tends to reduce the size of the dimples and to increase their density. The observed fracture features are closely related to the preceding flow behavior

  1. Microalga propels along vorticity direction in a shear flow

    Science.gov (United States)

    Chengala, Anwar; Hondzo, Miki; Sheng, Jian

    2013-05-01

    Using high-speed digital holographic microscopy and microfluidics, we discover that, when encountering fluid flow shear above a threshold, unicellular green alga Dunaliella primolecta migrates unambiguously in the cross-stream direction that is normal to the plane of shear and coincides with the local fluid flow vorticity. The flow shear drives motile microalgae to collectively migrate in a thin two-dimensional horizontal plane and consequently alters the spatial distribution of microalgal cells within a given suspension. This shear-induced algal migration differs substantially from periodic rotational motion of passive ellipsoids, known as Jeffery orbits, as well as gyrotaxis by bottom-heavy swimming microalgae in a shear flow due to the subtle interplay between torques generated by gravity and viscous shear. Our findings could facilitate mechanistic solutions for modeling planktonic thin layers and sustainable cultivation of microalgae for human nutrition and bioenergy feedstock.

  2. Bipolar and unipolar resistive switching behaviors of sol–gel-derived SrTiO3 thin films with different compliance currents

    International Nuclear Information System (INIS)

    Tang, M H; Wang, Z P; Zeng, Z Q; Xu, X L; Wang, G Y; Zhang, L B; Xiao, Y G; Yang, S B; Jiang, B; Li, J C; He, J

    2011-01-01

    The SrTiO 3 (STO) thin films on a Pt/Ti/SiO 2 /Si substrate were synthesized using a sol–gel method to form a metal–insulator–metal structure. This device shows the bipolar resistance switching (BRS) behavior for a compliance current I cc of less than 0.1 mA but exhibits soft breakdown at a higher level of compliance current. A transition from the BRS behavior to the stable unipolar resistive switching behavior (URS) was also observed. We found that the BRS behavior may be controlled by the structure interface while the URS behavior is likely bulk controlled. Our study indicates that the external compliance current is a key factor in resistance switching phenomenon of STO thin films

  3. Hysteresis loop behaviors of ferroelectric thin films:A Monte Carlo simulation study

    Institute of Scientific and Technical Information of China (English)

    C. M. Bedoya-Hincapi´e; H. H. Ortiz-´Alvarez; E. Restrepo-Parra; J. J. Olaya-Fl´orez; J. E. Alfonso

    2015-01-01

    The ferroelectric response of bismuth titanate Bi4Ti3O12 (BIT) thin film is studied through a Monte Carlo simulation of hysteresis loops. The ferroelectric system is described by using a Diffour Hamiltonian with three terms: the electric field applied in the z direction, the nearest dipole–dipole interaction in the transversal (x–y) direction, and the nearest dipole–dipole interaction in the direction perpendicular to the thin film (the z axis). In the sample construction, we take into consideration the dipole orientations of the monoclinic and orthorhombic structures that can appear in BIT at low temperature in the ferroelectric state. The effects of temperature, stress, and the concentration of pinned dipole defects are assessed by using the hysteresis loops. The results indicate the changes in the hysteresis area with temperature and stress, and the asymmetric hysteresis loops exhibit evidence of the imprint failure mechanism with the emergence of pinned dipolar defects. The simulated shift in the hysteresis loops conforms to the experimental ferroelectric response.

  4. Material Behavior Based Hybrid Process for Sheet Draw-Forging Thin Walled Magnesium Alloys

    International Nuclear Information System (INIS)

    Sheng, Z.Q.; Shivpuri, R.

    2005-01-01

    Magnesium alloys are conventionally formed at the elevated temperatures. The thermally improved formability is sensitive to the temperature and strain rate. Due to limitations in forming speeds, tooling strength and narrow processing windows, complex thin walled parts cannot be made by traditional warm drawing or hot forging processes. A hybrid process, which is based on the deformation mechanism of magnesium alloys at the elevated temperature, is proposed that combines warm drawing and hot forging modes to produce an aggressive geometry at acceptable forming speed. The process parameters, such as temperatures, forming speeds etc. are determined by the FEM modeling and simulation. Sensitivity analysis under the constraint of forming limits of Mg alloy sheet material and strength of tooling material is carried out. The proposed approach is demonstrated on a conical geometry with thin walls and with bottom features. Results show that designed geometry can be formed in about 8 seconds, this cannot be formed by conventional forging while around 1000s is required for warm drawing. This process is being further investigated through controlled experiments

  5. Hysteresis loop behaviors of ferroelectric thin films: A Monte Carlo simulation study

    Science.gov (United States)

    M. Bedoya-Hincapié, C.; H. Ortiz-Álvarez, H.; Restrepo-Parra, E.; J. Olaya-Flórez, J.; E. Alfonso, J.

    2015-11-01

    The ferroelectric response of bismuth titanate Bi4Ti3O12 (BIT) thin film is studied through a Monte Carlo simulation of hysteresis loops. The ferroelectric system is described by using a Diffour Hamiltonian with three terms: the electric field applied in the z direction, the nearest dipole-dipole interaction in the transversal (x-y) direction, and the nearest dipole-dipole interaction in the direction perpendicular to the thin film (the z axis). In the sample construction, we take into consideration the dipole orientations of the monoclinic and orthorhombic structures that can appear in BIT at low temperature in the ferroelectric state. The effects of temperature, stress, and the concentration of pinned dipole defects are assessed by using the hysteresis loops. The results indicate the changes in the hysteresis area with temperature and stress, and the asymmetric hysteresis loops exhibit evidence of the imprint failure mechanism with the emergence of pinned dipolar defects. The simulated shift in the hysteresis loops conforms to the experimental ferroelectric response. Project sponsored by the research departments of the Universidad Nacional de Colombia DIMA and DIB under Project 201010018227-“Crecimiento y caracterización eléctrica y estructural de películas delgadas de BixTiyOz producidas mediante Magnetrón Sputtering” and Project 12920-“Desarrollo teóricoexperimental de nanoestructuras basadas en Bismuto y materiales similares” and “Bisnano Project.”

  6. Picosecond laser pulse-driven crystallization behavior of SiSb phase change memory thin films

    International Nuclear Information System (INIS)

    Huang Huan; Li Simian; Zhai Fengxiao; Wang Yang; Lai Tianshu; Wu Yiqun; Gan Fuxi

    2011-01-01

    Highlights: → We reported crystallization dynamics of a novel SiSb phase change material. → We measured optical constants of as-deposited and irradiated SiSb areas. → Optical properties of as-deposited and irradiated SiSb thin film were compared. → Crystallization of irradiated SiSb was confirmed by using AFM and micro-Raman spectra. → The heat conduction effect of lower metal layer of multi-layer films was studied. - Abstract: Transient phase change crystallization process of SiSb phase change thin films under the irradiation of picosecond (ps) laser pulse was studied using time-resolved reflectivity measurements. The ps laser pulse-crystallized domains were characterized by atomic force microscope, Raman spectra and ellipsometrical spectra measurements. A reflectivity contrast of about 15% can be achieved by ps laser pulse-induced crystallization. A minimum crystallization time of 11 ns was achieved by a low-fluence single ps laser pulse after pre-irradiation. SiSb was shown to be very promising for fast phase change memory applications.

  7. Ordering fluctuations in a shear-banding wormlike micellar system

    DEFF Research Database (Denmark)

    Angelico, R.; Rossi, C. Oliviero; Ambrosone, L.

    2010-01-01

    We present a first investigation about the non-linear flow properties and transient orientational-order fluctuations observed in the shear-thinning lecithin–water–cyclohexane wormlike micellar system at a concentration near to the zero-shear isotropic–nematic phase transition. From rheological...

  8. Polarization fluctuation behavior of lanthanum substituted Bi{sub 4}Ti{sub 3}O{sub 12} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Ni; Xiang, Ping-Hua, E-mail: phxiang@ee.ecnu.edu.cn; Zhang, Yuan-Yuan; Wu, Xing; Tang, Xiao-Dong; Yang, Ping-Xiong; Duan, Chun-Gang; Chu, Jun-Hao [Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, Shanghai 200241 (China)

    2015-09-14

    Polarization fluctuation behavior of lanthanum substituted Bi{sub 4}Ti{sub 3}O{sub 12} (Bi{sub 4−x}La{sub x}Ti{sub 3}O{sub 12}, BLT) ferroelectric thin films has been examined. Remnant polarization exhibits an initial increase (P{sub up}, 1–10{sup 6} cycles) and a subsequent decrease (P{sub down}, 10{sup 6}–10{sup 9} cycles) with switching cycles, whereas the dielectric constant exhibits a continuous decrease. By careful investigations on the effect of switching frequency and annealing atmosphere on the polarization fluctuation characteristics, we propose that this polarization fluctuation characteristic of BLT films is attributed to the competition between domain pinning and passive layer growing effect, due to the redistribution of oxygen vacancy related defect under external applied field. P{sub up} behavior is dominated by the unpinning of pinned domain, while P{sub down} behavior is dominated by the reduction of applied field on BLT bulk layer, due to the growing of the passive layer between BLT and Pt electrode. By assuming the dielectric constant and initial thickness of passive layer, the passive layer was estimated to be about 2–5 times thicker than the initial state after 10{sup 9} cycling.

  9. Surface Behavior of Rhodamin and Tartrazine on Silica-Cellulose Sol-Gel Surfaces by Thin Layer Elution

    Directory of Open Access Journals (Sweden)

    Surjani Wonorahardjo

    2016-05-01

    Full Text Available Physical and chemical interactions are the principles for different types of separation systems as the equillibrium dynamics on surface plays a key-role. Surface modification is a way for selective separation at interfaces. Moreover, synthesis of gel silica by a sol-gel method is preferred due to the homogeneity and surface feature easily controlled. Cellulose can be added in situ to modified the silica features during the process. Further application for to study interaction of rhodamin and tartrazine in its surface and their solubilities in mobile phase explains the possibility for their separation. This paper devoted to evaluate the surface behavior in term of adsorption and desorption of tartrazine and rhodamin on silica-cellulose thin layer in different mobile phase. Some carrier liquids applied such as methanol, acetone, n-hexane and chloroform. The result proves tartrazine and rhodamin is separated and have different behavior in different mobile phase. The retardation factors (Rf of the mixtures suggest complexity behavior on silica-cellulose surface.

  10. Electronic and atomic structures of Ti1-xAlxN thin films related to their damage behavior

    International Nuclear Information System (INIS)

    Tuilier, M.-H.; Pac, M.-J.; Girleanu, M.; Covarel, G.; Arnold, G.; Louis, P.; Rousselot, C.; Flank, A.-M.

    2008-01-01

    Ti and Al K-edge x-ray absorption spectroscopy is used to investigate the electronic structure of Ti 1-x Al x N thin films deposited by reactive magnetron sputtering. The experimental near edge spectra of TiN and AlN are interpreted in the light of unoccupied density of state band structure calculations. The comparison of the structural parameters derived from x-ray absorption fine structure and x-ray diffraction reveals segregation between Al-rich and Ti-rich domains within the Ti 1-x Al x N films. Whereas x-ray diffraction probes only the crystallized domains, the structural information derived from extended x-ray absorption fine structure analysis turns on both crystalline and grain boundaries. The results are discussed by considering the damage behavior of the films depending on the composition

  11. Light-induced hysteresis and recovery behaviors in photochemically activated solution-processed metal-oxide thin-film transistors

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Jeong-Wan; Park, Sung Kyu, E-mail: yhkim76@skku.edu, E-mail: skpark@cau.ac.kr [School of Electrical and Electronics Engineering, Chung-Ang University, Seoul 156-756 (Korea, Republic of); Kim, Yong-Hoon, E-mail: yhkim76@skku.edu, E-mail: skpark@cau.ac.kr [School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2014-07-28

    In this report, photo-induced hysteresis, threshold voltage (V{sub T}) shift, and recovery behaviors in photochemically activated solution-processed indium-gallium-zinc oxide (IGZO) thin-film transistors (TFTs) are investigated. It was observed that a white light illumination caused negative V{sub T} shift along with creation of clockwise hysteresis in electrical characteristics which can be attributed to photo-generated doubly ionized oxygen vacancies at the semiconductor/gate dielectric interface. More importantly, the photochemically activated IGZO TFTs showed much reduced overall V{sub T} shift compared to thermally annealed TFTs. Reduced number of donor-like interface states creation under light illumination and more facile neutralization of ionized oxygen vacancies by electron capture under positive gate potential are claimed to be the origin of the less V{sub T} shift in photochemically activated TFTs.

  12. Investigation of Physical Properties and Electrochemical Behavior of Nitrogen-Doped Diamond-Like Carbon Thin Films

    Directory of Open Access Journals (Sweden)

    Rattanakorn Saensak

    2014-03-01

    Full Text Available This work reports characterizations of diamond-like carbon (DLC films used as electrodes for electrochemical applications. DLC thin films are prepared on glass slides and silicon substrates by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD using a gas mixture of methane and hydrogen. In addition, the DLC films are doped with nitrogen in order to reduce electrical resistivity. Compared to the undoped DLC films, the electrical resistivity of nitrogen-doped (N-doped DLC films is decreased by three orders of magnitude. Raman spectroscopy and UV/Vis spectroscopy analyses show the structural transformation in N-doped DLC films that causes the reduction of band gap energy. Contact angle measurement at N-doped DLC films indicates increased hydrophobicity. The results obtained from the cyclic voltammetry measurements with Fe(CN63-/Fe(CN64- redox species exhibit the correlation between the physical properties and electrochemical behavior of DLC films.

  13. Combined experimental and theoretical investigations of the photoluminescent behavior of Ba(Ti, Zr)O3 thin films

    International Nuclear Information System (INIS)

    Cavalcante, L.S.; Gurgel, M.F.C.; Paris, E.C.; Simoes, A.Z.; Joya, M.R.; Varela, J.A.; Pizani, P.S.; Longo, E.

    2007-01-01

    The correlation between experimental data and theoretical calculations have been investigated to explain the photoluminescence at room temperature of Ba(Ti 0.75 Zr 0.25 )O 3 (BTZ) thin films prepared by the polymeric precursor method. The degree of structural order-disorder was investigated by X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet-visible absorption spectroscopy and photoluminescence (PL) measurements. First-principles quantum mechanical calculations based on density functional theory (B3LYP level) were employed to study the electronic structure of ordered and deformed asymmetric models. The electronic properties are analyzed and the relevance of the present theoretical and experimental results on the PL behavior is discussed. The presence of localized electronic levels and a charge gradient in the band gap due to a break in symmetry, are responsible for the PL in disordered BTZ lattice

  14. Multiple collinear magnetic arrangements in thin Mn films supported on Fe(001). Antiferromagnetic versus ferromagnetic behavior

    International Nuclear Information System (INIS)

    Martinez, E.; Vega, A.; Robles, R.; Vazquez de Parga, A.L.

    2005-01-01

    We present a theoretical study of the magnetic properties of thin Mn films of 6 and 7 monolayers supported on Fe(001). The ab-initio tight binding linear muffin tin orbital (TB-LMTO) method was used to investigate the competition between ferromagnetic (F) and antiferromagnetic (AF) couplings within the system. We found several collinear magnetic solutions that may coexist at room temperature. The most stable configurations are characterized by AF coupling between the surface and subsurface Mn layers together with F coupling between Mn and Fe at the interface. The ground state arrangements for the 6 and 7 Mn films display opposite sign of the surface magnetic moment relative to the Fe substrate. The implications of these results in the possible onset of non-collinear magnetism when a step is present at the interface are discussed in comparison with Cr/Fe systems where non-collinear magnetism has been recently reported

  15. The wet corrosion of molybdenum thin film. Part I: Behavior at 25 C

    International Nuclear Information System (INIS)

    De Rosa, L.; Tomachuk, C.R.; Mitton, D.B.; Saiello, S.; Bellucci, F.; Springer, J.

    2004-01-01

    The corrosion and passivation behaviour of molybdenum thin films obtained by Physical Vapor Deposition (PVD) was investigated in aerated chloride and sulfate solutions at different pH values. Open circuit potential (ocp) measurements, polarisation experiments and electrochemical impedance spectroscopy (EIS) were employed. The experimental results suggest that the metal surface is covered by a passive film; however, corrosion still occurs. For the samples assessed during the current research, the acidic electrolytes tended to be less corrosive; however, a limited passive region was associated with the most basic sulfate or chloride solution. The effect of the pH was found to be more pronounced than the effect of the ion (chloride or sulfate). (Abstract Copyright [2004], Wiley Periodicals, Inc.)

  16. Programmable diode/resistor-like behavior of nanostructured vanadium pentoxide xerogel thin film.

    Science.gov (United States)

    Wan, Zhenni; Darling, Robert B; Anantram, M P

    2015-11-11

    Electrical properties of a Cr/V2O5/Cr structure are investigated and switching of the device due to electrochemical reactions is observed at low bias (resistor (reverse sweep first). The switching is irreversible and persistent, lasting for more than one month. By performing environmental tests, we prove that water molecules in the atmosphere and intercalated in the xerogel film are involved in the electrochemical reactions. It is proposed that an interfacial layer with reduced oxidation state forms at the Cr/V2O5 interface, and creates a higher Schottky barrier due to rise of electron affinity. Different interfacial layer thicknesses in forward and reverse first sweeps are responsible for different I-V characteristics in subsequent sweeps. The results suggest future applications of these V2O5 thin films in low-power read-only memory devices and diode-resistor networks.

  17. The effects of "thin ideal" media on women's body image concerns and eating-related intentions: the beneficial role of an autonomous regulation of eating behaviors.

    Science.gov (United States)

    Mask, Lisa; Blanchard, Céline M

    2011-09-01

    The present study examines the protective role of an autonomous regulation of eating behaviors (AREB) on the relationship between trait body dissatisfaction and women's body image concerns and eating-related intentions in response to "thin ideal" media. Undergraduate women (n=138) were randomly assigned to view a "thin ideal" video or a neutral video. As hypothesized, trait body dissatisfaction predicted more negative affect and size dissatisfaction following exposure to the "thin ideal" video among women who displayed less AREB. Conversely, trait body dissatisfaction predicted greater intentions to monitor food intake and limit unhealthy foods following exposure to the "thin ideal" video among women who displayed more AREB. Copyright © 2011 Elsevier Ltd. All rights reserved.

  18. Modeling of shear wall buildings

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, A K [North Carolina State Univ., Raleigh (USA). Dept. of Civil Engineering

    1984-05-01

    Many nuclear power plant buildings, for example, the auxiliary building, have reinforced concrete shear walls as the primary lateral load resisting system. Typically, these walls have low height to length ratio, often less than unity. Such walls exhibit marked shear lag phenomenon which would affect their bending stiffness and the overall stress distribution in the building. The deformation and the stress distribution in walls have been studied which is applicable to both the short and the tall buildings. The behavior of the wall is divided into two parts: the symmetric flange action and the antisymmetry web action. The latter has two parts: the web shear and the web bending. Appropriate stiffness equations have been derived for all the three actions. These actions can be synthesized to solve any nonlinear cross-section. Two specific problems, that of lateral and torsional loadings of a rectangular box, have been studied. It is found that in short buildings shear lag plays a very important role. Any beam type formulation which either ignores shear lag or includes it in an idealized form is likely to lead to erroneous results. On the other hand a rigidity type approach with some modifications to the standard procedures would yield nearly accurate answers.

  19. Elastic behavior of a red blood cell with the membrane's nonuniform natural state: equilibrium shape, motion transition under shear flow, and elongation during tank-treading motion.

    Science.gov (United States)

    Tsubota, Ken-Ichi; Wada, Shigeo; Liu, Hao

    2014-08-01

    Direct numerical simulations of the mechanics of a single red blood cell (RBC) were performed by considering the nonuniform natural state of the elastic membrane. A RBC was modeled as an incompressible viscous fluid encapsulated by an elastic membrane. The in-plane shear and area dilatation deformations of the membrane were modeled by Skalak constitutive equation, while out-of-plane bending deformation was formulated by the spring model. The natural state of the membrane with respect to in-plane shear deformation was modeled as a sphere ([Formula: see text]), biconcave disk shape ([Formula: see text]) and their intermediate shapes ([Formula: see text]) with the nonuniformity parameter [Formula: see text], while the natural state with respect to out-of-plane bending deformation was modeled as a flat plane. According to the numerical simulations, at an experimentally measured in-plane shear modulus of [Formula: see text] and an out-of-plane bending rigidity of [Formula: see text] of the cell membrane, the following results were obtained. (i) The RBC shape at equilibrium was biconcave discoid for [Formula: see text] and cupped otherwise; (ii) the experimentally measured fluid shear stress at the transition between tumbling and tank-treading motions under shear flow was reproduced for [Formula: see text]; (iii) the elongation deformation of the RBC during tank-treading motion from the simulation was consistent with that from in vitro experiments, irrespective of the [Formula: see text] value. Based on our RBC modeling, the three phenomena (i), (ii), and (iii) were mechanically consistent for [Formula: see text]. The condition [Formula: see text] precludes a biconcave discoid shape at equilibrium (i); however, it gives appropriate fluid shear stress at the motion transition under shear flow (ii), suggesting that a combined effect of [Formula: see text] and the natural state with respect to out-of-plane bending deformation is necessary for understanding details of the

  20. Thermodynamic properties, hysteresis behavior and stress-strain analysis of MgH2 thin films, studied over a wide temperature range

    NARCIS (Netherlands)

    Pivak, Y.; Schreuders, H.; Dam, B.

    2012-01-01

    Using hydrogenography, we investigate the thermodynamic parameters and hysteresis behavior in Mg thin films capped by Ta/Pd, in a temperature range from 333 K to 545 K. The enthalpy and entropy of hydride decomposition, ?Hdes = ?78.3 kJ/molH2, ?Sdes = ?136.1 J/K molH2, estimated from the Van't Hoff

  1. Improved behavior of cooper-amine complexes during thermal annealing for conductive thin film synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Ayag, Kevin Ray; Panama, Gustavo; Paul, Shrabani; Kim, Hong Doo [Dept. of Advanced Materials Engineering for Information and Electronics, Kyung Hee University, Yongin (Korea, Republic of)

    2017-02-15

    Previous studies successfully produced conductive thin films from organo-metallic-compounds-based inks. Some inks like those made from copper salt and amines, however, tend to move during thermal annealing and, thus, affect the conductive pattern on the substrate. In this study, conductive inks were synthesized by forming complexes of copper with amines and/or blended amines. To build-up an organo-metallic framework and preserve the pattern throughout the annealing period, diamine was added to the complex in different proportions. The prepared inks were coated on glass substrate and were annealed on a hot plate at 170°C under the gaseous mixture of formic acid and alcohol for 5 min. The metallic film was observed to retain the original pattern of the ink during and after annealing. Adhesion on the substrate was also improved. Inks with blended amines produced films with lower resistivities. The lowest electrical resistivity recorded was 4.99 μΩ cm, three times that of bulk copper.

  2. Origins of Shear Jamming for Frictional Grains

    Science.gov (United States)

    Wang, Dong; Zheng, Hu; Ren, Jie; Dijksman, Joshua; Bares, Jonathan; Behringer, Robert

    2016-11-01

    Granular systems have been shown to be able to behave like solids, under shear, even when their densities are below the critical packing fraction for frictionless isotropic jamming. To understand such a phenomena, called shear jamming, the question we address here is: how does shear bring a system from a unjammed state to a jammed state, where the coordination number, Z, is no less than 3, the isotropic jamming point for frictional grains? Since Z can be used to distinguish jammed states from unjammed ones, it is vital to understand how shear increases Z. We here propose a set of three particles in contact, denoted as a trimer, as the basic unit to characterize the deformation of the system. Trimers, stabilized by inter-grain friction, fail under a certain amount of shear and bend to make extra contacts to regain stability. By defining a projection operator of the opening angle of the trimer to the compression direction in the shear, O, we see a systematically linear decrease of this quantity with respect to shear strain, demonstrating the bending of trimers as expected. In addition, the average change of O from one shear step to the next shows a good collapse when plotted against Z, indicating a universal behavior in the process of shear jamming. We acknowledge support from NSF DMR1206351, NASA NNX15AD38G, the William M. Keck Foundation and a RT-MRSEC Fellowship.

  3. Joint model to simulate inelastic shear behavior of poorly detailed exterior and interior beam-column connections reinforced with deformed bars under seismic excitations

    International Nuclear Information System (INIS)

    Sharma, Akanshu; Reddy, G.R.; Vaze, K.K.; Ghosh, A.K.; Kushwaha, H.S.; Eligehausen, Rolf

    2009-12-01

    A model for predicting the nonlinear shear behaviour of reinforced concrete beam column joints based on principal stresses reaching limits is proposed. The joint model proposes shear springs for the column region and rotational spring for the beam region of the joint. This is based on the actual displacement behaviour of the shear buildings. The spring characteristics are calculated based on well-known principal of mechanics using the principal stresses as the failure criteria. The model reasonably accurately predicts the shear behaviour of the joint and also can consider the effect of axial loads on the column. The model does not need any special element or special program for implementation and can be used for nonlinear static pushover analysis of RC framed structures giving due consideration to joint deformations. The model is therefore extremely useful for practical displacement based analysis of old RC buildings where the joints were not designed and detailed as per current codal requirements, invariably making them the weakest link in the structure. The background theory, assumptions followed and the complete formulations for generating the joint characteristics are given in this report. The model is validated with experimental results of tests on exterior and interior beam-column connections given in the published literature having substandard detailing using deformed bars. (author)

  4. Modeling the instability behavior of thin film devices: Fermi Level Pinning

    Science.gov (United States)

    Moeini, Iman; Ahmadpour, Mohammad; Gorji, Nima E.

    2018-05-01

    We investigate the underlying physics of degradation/recovery of a metal/n-CdTe Schottcky junction under reverse or forward bias stressing conditions. We used Sah-Noyce-Shockley (SNS) theory to investigate if the swept of Fermi level pinning at different levels (under forward/reverse bias) is the origin of change in current-voltage characteristics of the device. This theory is based on Shockley-Read-Hall recombination within the depletion width and takes into account the interface defect levels. Fermi Level Pinning theory was primarily introduced by Ponpon and developed to thin film solar cells by Dharmadasa's group in Sheffield University-UK. The theory suggests that Fermi level pinning at multiple levels occurs due to high concentration of electron-traps or acceptor-like defects at the interface of a Schottky or pn junction and this re-arranges the recombination rate and charage collection. Shift of these levels under stress conditions determines the change in current-voltage characteristics of the cell. This theory was suggested for several device such as metal/n-CdTe, CdS/CdTe, CIGS/CdS or even GaAs solar cells without a modeling approach to clearly explain it's physics. We have applied the strong SNS modeling approach to shed light on Fermi Level Pinning theory. The modeling confirms that change in position of Fermi Level and it's pining in a lower level close to Valence band increases the recombination and reduces the open-circuit voltage. In contrast, Fermi Level pinning close to conduction band strengthens the electric field at the junction which amplifies the carrier collection and boosts the open-circuit voltage. This theory can well explain the stress effect on device characteristics of various solar cells or Schottky junctions by simply finding the right Fermi level pinning position at every specific stress condition.

  5. Non-homogeneous flow profiles in sheared bacterial suspensions

    Science.gov (United States)

    Samanta, Devranjan; Cheng, Xiang

    Bacterial suspensions under shear exhibit interesting rheological behaviors including the remarkable ``superfluidic'' state with vanishing viscosity at low shear rates. Theoretical studies have shown that such ``superfluidic'' state is linked with non-homogeneous shear flows, which are induced by coupling between nematic order of active fluids and hydrodynamics of shear flows. However, although bulk rheology of bacterial suspensions has been experimentally studied, shear profiles within bacterial suspensions have not been explored so far. Here, we experimentally investigate the flow behaviors of E. coli suspensions under planar oscillatory shear. Using confocal microscopy and PIV, we measure velocity profiles across gap between two shear plates. We find that with increasing shear rates, high-concentration bacterial suspensions exhibit an array of non-homogeneous flow behaviors like yield-stress flows and shear banding. We show that these non-homogeneous flows are due to collective motion of bacterial suspensions. The phase diagram of sheared bacterial suspensions is systematically mapped as functions of shear rates an bacterial concentrations. Our experiments provide new insights into rheology of bacterial suspensions and shed light on shear induced dynamics of active fluids. Chemical Engineering and Material Science department.

  6. Semiconductor laser shearing interferometer

    International Nuclear Information System (INIS)

    Ming Hai; Li Ming; Chen Nong; Xie Jiaping

    1988-03-01

    The application of semiconductor laser on grating shearing interferometry is studied experimentally in the present paper. The method measuring the coherence of semiconductor laser beam by ion etching double frequency grating is proposed. The experimental result of lens aberration with semiconductor laser shearing interferometer is given. Talbot shearing interferometry of semiconductor laser is also described. (author). 2 refs, 9 figs

  7. Microstructural, thermal and mechanical behavior of co-sputtered binary Zr–Cu thin film metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Apreutesei, M. [MATEIS Laboratory-INSA de Lyon, Bât. B. Pascal, 7 Avenue Jean Capelle, 69621 Villeurbanne Cedex (France); Steyer, P., E-mail: philippe.steyer@insa-lyon.fr [MATEIS Laboratory-INSA de Lyon, Bât. B. Pascal, 7 Avenue Jean Capelle, 69621 Villeurbanne Cedex (France); Joly-Pottuz, L. [MATEIS Laboratory-INSA de Lyon, Bât. B. Pascal, 7 Avenue Jean Capelle, 69621 Villeurbanne Cedex (France); Billard, A. [LERMPS-UTBM, Site de Montbéliard, 90010 Belfort Cédex (France); Qiao, J.; Cardinal, S. [MATEIS Laboratory-INSA de Lyon, Bât. B. Pascal, 7 Avenue Jean Capelle, 69621 Villeurbanne Cedex (France); Sanchette, F. [LASMIS-UTT, UMR CNRS 6279, 12 rue Marie Curie, CS 42060, 10004 Troyes Cedex (France); Pelletier, J.M.; Esnouf, C. [MATEIS Laboratory-INSA de Lyon, Bât. B. Pascal, 7 Avenue Jean Capelle, 69621 Villeurbanne Cedex (France)

    2014-06-30

    Bulk metallic glasses have attracted considerable attention over the last decades for their outstanding mechanical features (high strength, super-elasticity) and physico-chemical properties (corrosion resistance). Recently, some attempts to assign such original behavior from bulk materials to modified surfaces have been reported in the literature based on multicomponent alloys. In this paper we focused on the opportunity to form a metallic glass coating from the binary Zr–Cu system using a magnetron co-sputtering physical vapor deposition process. The composition of the films can be easily controlled by the relative intensities applied to both pure targets, which made possible the study of the whole Zr–Cu system (from 13.4 to 85.0 at.% Cu). The chemical composition of the films was obtained by energy dispersive X-ray spectroscopy, and their microstructure was characterized by scanning and transmission electron microscopy. The thermal stability of the films was deduced from an in situ X-ray diffraction analysis (from room temperature up to 600 °C) and correlated with the results of the differential scanning calorimetry technique. Their mechanical properties were determined by nanoindentation experiments. - Highlights: • We reported deposition of Zr-Cu thin film metallic glasses by co-sputtering • Films were XRD-amorphous in a wide composition range (33.3 – 85.0 at.% Cu) • Microstructure investigation revealed some local nanodomains • We examined the thermal stability by means of in situ X-ray diffraction • Nanoindentation was used to obtained mechanical properties of thin films.

  8. Investigation of the Effect of Residual Stress Gradient on the Wear Behavior of PVD Thin Films

    Science.gov (United States)

    Tlili, B.; Nouveau, C.; Guillemot, G.; Besnard, A.; Barkaoui, A.

    2018-02-01

    The control of residual stresses has been seldom investigated in multilayer coatings dedicated to improvement of wear behavior. Here, we report the preparation and characterization of superposed structures composed of Cr, CrN and CrAlN layers. Nano-multilayers CrN/CrAlN and Cr/CrN/CrAlN were deposited by Physical Vapor Deposition (PVD) onto Si (100) and AISI4140 steel substrates. The Cr, CrN and CrAlN monolayers were developed with an innovative approach in PVD coatings technologies corresponding to deposition with different residual stresses levels. Composition and wear tracks morphologies of the coatings were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, atomic force microscopy, x-ray photoelectron spectroscopy, energy-dispersive x-ray spectroscopy, x-ray diffraction and 3D-surface analyzer. The mechanical properties (hardness, residual stresses and wear) were investigated by nanoindentation, interferometry and micro-tribometry (fretting-wear tests). Observations suggest that multilayer coatings are composed mostly of nanocrystalline. The residual stresses level in the films has practically affected all the physicochemical and mechanical properties as well as the wear behavior. Consequently, it is demonstrated that the coating containing moderate stresses has a better wear behavior compared to the coating developed with higher residual stresses. The friction contact between coated samples and alumina balls shows also a large variety of wear mechanisms. In particular, the abrasive wear of the coatings was a combination of plastic deformation, fine microcracking and microspallation. The application of these multilayers will be wood machining of green wood.

  9. Effect of different nickel precursors on capacitive behavior of electrodeposited NiO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kore, R. M.; Ghadge, T. S.; Ambare, R. C.; Lokhande, B. J., E-mail: bjlokhande@yahoo.com [School of Physical Sciences, Solapur University, Solapur-413 255, M.S. (India)

    2016-04-13

    In the present study, the effect of nickel precursors containing different anions like nitrate, chloride and sulphate on the morphology and pseudocapacitance behavior of NiO is investigated. The NiO samples were prepared by using a potentiondynamic electrodeposition technique in the three electrode cell. Cyclic voltammetry technique was exploited for potentiodynamic deposition of the films. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), etc. The XRD reveals the cubic crystal structure for all samples. The SEM micrograph shows nanoflakelike, up grown nanoflakes and honeycomb like nanostructured morphologies for nitrate, chloride and sulphate precursors respectively. The capacitive behavior of these samples was recorded using cyclic voltammetry (CV), charge-discharge and electrochemical impedance spectroscopy (EIS) in 1 M KOH electrolyte. The specific capacitance values of NiO samples obtained using CV for nitrate, chloride and sulphate precursors were 136, 214 and 893 Fg{sup −1} respectively, at the scan rate of 5 mVs{sup −1}. The charge discharge study shows high specific energy for the sample obtained from sulphate (23.98 Whkg{sup −1}) as compared to chloride (9.67 Whkg{sup −1}) and nitrate (4.9 Whkg{sup −1}), whereas samples of cholride (13.9 kWkg{sup −1} and nitrate (10.5 kWkg{sup −1}) shows comparatively more specific power than samples obtained from sulphate (7.6 kWkg{sup −1}). The equivalent series resistance of NiO samples observed from EIS study are 1.34, 1.29 and 1.27 Ω respectively for nitrate, chloride and sulphate precursors. These results emphasizes that the samples obtained from sulphate precursors provides very low impedance through honeycomb like nanostructured morphology which supports good capacitive behavior of NiO.

  10. The effects of xenon ion irradiation on the photoluminesce behavior of poly(p-cresolformaldeyde)/diazonaphtoquinone thin films

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Irene T.S. [Depto. de Quimica Analitica e Inorganica, Instituto de Quimica e Geociencias, UFPel, Capao do Leao s/n, 96010-900, Pelotas, RS (Brazil)], E-mail: irene@ufpel.edu.br; Zawislak, F.C.; Balzaretti, Naira [Instituto de Fisica, UFRGS, Caixa Postal 15051, 91501-970 Porto Alegre (Brazil); Samios, D. [Instituto de Quimica, UFRGS, 91501-970 Porto Alegre (Brazil); Sias, U. [Centro Federal de Educacao Tecnologica de Pelotas, 96015-360 Pelotas (Brazil)

    2007-10-15

    In the present paper, we investigate the origin of photoluminescence (PL) and the changes in the optical properties: refractive index and absorption coefficient, in poly(p-cresolformaldeyde) and diazonaphtoquinone thin films irradiated with Xe ions. Films 400 nm thick have been irradiated with 800 keV Xe{sup 2+} ions in a fluence range from 10{sup 13} to 6 x 10{sup 15} Xe cm{sup -2}. The structural modifications were followed by the techniques of nuclear reaction analysis, elastic recoil detection analysis, Rutherford backscattering, Fourier transform infrared and Raman spectroscopies. The PL behavior was characterised with 488 nm excitation wavelength. The pristine films show emission with maxima of the main bands located at 635, 720 and 830 nm. For fluences up to 10{sup 14} Xe cm{sup -2}, the photoluminescence intensity increases with the irradiation fluence. The chain mobility lowering, characterized by the crosslinked structure, explains this behavior in organic systems. Other possible contribution for increasing of PL intensity, at these fluences, is the presence of oxygen trapped in the polymer chains by the dangling bonds. At intermediate and higher fluences, the photoluminescence starts to decrease. At fluences higher than 10{sup 14} Xe cm{sup -2}, irreversible changes of the organic structure occur and they are characterized by large losses of oxygen and hydrogen, transforming the material into amorphous carbon films. The loss of photoluminescent behavior is associated with the light absorption characteristics of the amorphous carbon structure. This conclusion is supported by the observed increase of the refractive indexes and absorption coefficients, obtained in the infrared region, as well as by the Raman results. Also, the effect of irradiation modifying the refractive index in the infrared region suggests the application of these films as waveguide in this region of wavelength.

  11. Nanometer-thin TiO2 enhances skeletal muscle cell phenotype and behavior

    Directory of Open Access Journals (Sweden)

    Ishizaki K

    2011-10-01

    Full Text Available Ken Ishizaki*, Yoshihiko Sugita*, Fuminori Iwasa, Hajime Minamikawa, Takeshi Ueno, Masahiro Yamada, Takeo Suzuki, Takahiro OgawaLaboratory for Bone and Implant Sciences, The Jane and Jerry Weintraub Center for Reconstructive Biotechnology, Division of Advanced Prosthodontics, Biomaterials and Hospital Dentistry, UCLA School of Dentistry, Los Angeles, CA, USA*Authors contributed equally to this workBackground: The independent role of the surface chemistry of titanium in determining its biological properties is yet to be determined. Although titanium implants are often in contact with muscle tissue, the interaction of muscle cells with titanium is largely unknown. This study tested the hypotheses that the surface chemistry of clinically established microroughened titanium surfaces could be controllably varied by coating with a minimally thin layer of TiO2 (ideally pico-to-nanometer in thickness without altering the existing topographical and roughness features, and that the change in superficial chemistry of titanium is effective in improving the biological properties of titanium.Methods and results: Acid-etched microroughened titanium surfaces were coated with TiO2 using slow-rate sputter deposition of molten TiO2 nanoparticles. A TiO2 coating of 300 pm to 6.3 nm increased the surface oxygen on the titanium substrates in a controllable manner, but did not alter the existing microscale architecture and roughness of the substrates. Cells derived from rat skeletal muscles showed increased attachment, spread, adhesion strength, proliferation, gene expression, and collagen production at the initial and early stage of culture on 6.3 nm thick TiO2-coated microroughened titanium surfaces compared with uncoated titanium surfaces.Conclusion: Using an exemplary slow-rate sputter deposition technique of molten TiO2 nanoparticles, this study demonstrated that titanium substrates, even with microscale roughness, can be sufficiently chemically modified to

  12. The impact of exposure to images of ideally thin models in TV commercials on eating behavior: an experimental study with women diagnosed with bulimia nervosa.

    Science.gov (United States)

    Rühl, Ilka; Legenbauer, Tanja; Hiller, Wolfgang

    2011-09-01

    This study investigates whether eating behavior in women with diagnosed bulimia nervosa is influenced by prior exposure to images of ideally thin models. Twenty-six participants diagnosed with bulimia nervosa (BN) and 30 normal controls (NC) were exposed to body-related and neutral TV commercials; then food that typically triggers binge eating was provided, and the amount of food eaten was measured. No significant difference for food intake between NC and BN could be found, but food intake for BN was predicted by the degree of thoughts related to eating behaviors during exposure to the thin ideal. No impact of general body image or eating pathology on food intake could be found. The results emphasize the importance of action-relevance of dysfunctional cognitions for the maintenance of eating-disordered behaviors in women with bulimia nervosa, when exposed to eating-disorder-specific triggers. Copyright © 2011 Elsevier Ltd. All rights reserved.

  13. Structural and photodegradation behaviors of Fe{sup 3+}-doping TiO{sub 2} thin films prepared by a sol–gel spin coating

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Huey-Jiuan; Yang, Tien-Syh [Department of Materials Science and Engineering, National United University, 1 Lien-Da, Kung-Ching Li, Miao-Li 36003, Taiwan (China); Wang, Moo-Chin, E-mail: mcwang@kmu.edu.tw [Department of Fragrance and Cosmetic Science, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung 80782, Taiwan (China); Hsi, Chi-Shiung, E-mail: chsi@nuu.edu.tw [Department of Materials Science and Engineering, National United University, 1 Lien-Da, Kung-Ching Li, Miao-Li 36003, Taiwan (China)

    2014-10-15

    Highlights: • Pure and various Fe{sup 3+}-doped TiO{sub 2} thin films have been successfully fabricated. • The phase of all thin films was single phase of anatase TiO{sub 2} when calcined at 823 K. • The crystallinity of TiO{sub 2} thin films decreased as Fe{sup 3+}-doping increased. • The photodegradation of each sample increased as the irradiation time increased. • The photodegradation increased as Fe{sup 3+}-doping increased at a fixed irradiation time. - Abstract: Pure and various Fe{sup 3+}-doping TiO{sub 2} thin films have been successfully fabricated on glass substrate prepared by a sol–gel spin coating route. The structural and photodegradation behavior of these films after calcined at various temperatures for 1 h were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectrum and degradation of 1.0 × 10{sup −5} M methylene blue solution. When all thin films after calcined at 823 K for 1 h, the crystalline phase are comprised only contained single phase of anatase TiO{sub 2}. The crystallinity of various Fe{sup 3+}-doping TiO{sub 2} thin films decreases with Fe{sup 3+}-doping concentration increased. The PL intensity of all thin films also decreases with Fe{sup 3+}-doping concentration increased. When all various Fe{sup 3+}-doping TiO{sub 2} thin films after calcined at 823 K for 1 h, the photodegradation of each sample increases with irradiation time increased. Moreover, the photodegradation also increases with Fe{sup 3+}-doping concentration increased when fixed at constant irradiation time.

  14. Electrochemical behavior of thin anodic oxide films on Zircaloy-4: Role of the mobile defects

    International Nuclear Information System (INIS)

    Salot, R.; Lefebvre-Joud, F.; Baroux, B.

    1996-01-01

    The first stages of the electrochemical oxidation of Zircaloy-4 are investigated using simple electrochemical tests and modeling the passive film modifications occurring as a result of contact with the electrolyte. Variations in electrode potential (open-circuit conditions) or current density (potentiodynamic scans) can be simply explained by a high field (F ∼ 10 6 V/cm) assisted passive film growth. Under open-circuit conditions, this field does not vary with exposure time (in the 2 h to 48 h range). The minimum electric field for the onset of high-field behavior is also evaluated and found smaller than the theoretical value which can be explained by a variation in the concentration of mobile defects throughout the film. Measurements of the electrode potential decay after a potentiodynamic scan confirm this model, allowing interpretation of the film modification as a combination of two separate phenomena: film growth under a high electric field and point defect annihilation

  15. Unusual ZFC and FC magnetic behavior in thin Co multi-layered structure

    Energy Technology Data Exchange (ETDEWEB)

    Ben-Dor, Oren; Yochelis, Shira [Department of Applied Physics, Center of Nanoscience and Nanotechnology, Hebrew University, Jerusalem 91904 (Israel); Felner, Israel [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Paltiel, Yossi [Department of Applied Physics, Center of Nanoscience and Nanotechnology, Hebrew University, Jerusalem 91904 (Israel)

    2017-04-15

    The observation of unusual magnetic phenomena in a Ni -based magnetic memory device ( O. Ben-Dor et al., 2013) encouraged us to conduct a systematic research on Co based multi-layered structure which contains a α-helix L polyalanine (AHPA-L) organic compound. The constant Co thickness is 7 nm and AHPA-L was also replaced by non-chiral 1-Decanethiol organic molecules. Both organic compounds were chemisorbed on gold by a thiol group. The dc magnetic field (H) was applied parallel and perpendicular to the surface layers. The perpendicular direction is the easy magnetization axis and along this orientation only, the zero-field-cooled (ZFC) plots exhibit a pronounced peak around 55–58 K. This peak is suppressed in the second ZFC and field-cooled (FC) runs performed shortly after the virgin ZFC one. Thus, around the peak position ZFC>FC a phenomenon seldom observed. This peak reappears after measuring the same material six months later. This behavior appears in layers with the non-chiral 1-Decanethiol and it is very similar to that obtained in sulfur doped amorphous carbon. The peak origin and the peculiar ZFC>FC case are qualitatively explained. - Highlights: • FC curve crosses ZFC curve in a 7 nm Co and thiol-based organic molecules multi-layered structure. • The ZFC>FC phenomena occurs for H perpendicular along the easy axis. • This phenomenon disappears in the second FC-ZFC run performed shortly after. • The unusual behavior reappears after six months.

  16. Shear-induced phase changes in mixtures

    International Nuclear Information System (INIS)

    Romig, K.D.; Hanley, H.J.M.

    1986-01-01

    A thermodynamic theory to account for the behavior of liquid mixtures exposed to a shear is developed. One consequence of the theory is that shear-induced phase changes are predicted. The theory is based on a thermodynamics that includes specifically the shear rate in the formalism and is applied to mixtures by a straightforward modification of the corresponding states, conformalsolution approach. The approach is general but is used here for a mixture of Lennard-Jones particles with a Lennard-Jones equation of state as a reference fluid. The results are discussed in the context of the Scott and Van Konynenberg phase classification. It is shown that the influence of a shear does affect substantially the type of the phase behavior. Results from the model mixture are equated loosely with those from real polymeric liquids

  17. Evaluating interfacial shear stresses in composite hollo

    Directory of Open Access Journals (Sweden)

    Aiham Adawi

    2016-09-01

    Full Text Available Analytical evaluation of the interfacial shear stresses for composite hollowcore slabs with concrete topping is rare in the literature. Adawi et al. (2014 estimated the interfacial shear stiffness coefficient (ks that governs the behavior of the interface between hollowcore slabs and the concrete topping using push-off tests. This parameter is utilized in this paper to provide closed form solutions for the differential equations governing the behavior of simply supported composite hollowcore slabs. An analytical solution based on the deformation compatibility of the composite section and elastic beam theory, is developed to evaluate the shear stresses along the interface. Linear finite element modeling of the full-scale tests presented in Adawi et al. (2015 is also conducted to validate the developed analytical solution. The proposed analytical solution was found to be adequate in estimating the magnitude of horizontal shear stress in the studied composite hollowcore slabs.

  18. Experimental study of a shear wall with numerous small openings

    International Nuclear Information System (INIS)

    Sotomura, K.; Murazumi, Y.; Yoshizaki, S.; Ezaki, T.

    1981-01-01

    Many small openings for piping and ducts are usually required in the shear walls for PWR nuclear power plant. It is generally believed that such openings oadversely affect the strength and stiffness of shear walls. However, little information is available concerning the behavior of walls with numerous small openings. Therefore, tests using wall specimens and an analysis using an FEM program were carried out to investigate this behavior. Main findings are as follows: 1) The ultimate strength of a shear wall with numerous small openings may be obtained by using the effective area at the critical cross section of the shear wall. 2) Shear walls with openings can be restored to the same shear strength and stiffness as shear walls without openings by diagonal reinforcement. (orig./HP)

  19. Behavior of a Spontaneously Arising Human Retinal Pigment Epithelial Cell Line Cultivated on Thin Alginate Film.

    Science.gov (United States)

    Najafabadi, Hoda Shams; Soheili, Zahra-Soheila; Ganji, Shahla Mohammad

    2015-01-01

    A cell line spontaneously derived from human retinal pigment epithelium (hRPE) was cultured on alginate film gelatinized with different concentrations of neurobasal cell culture medium (NCCM) to assess its growth and morphological behavior on this naturally occurring polysaccharide. Neonatal human globes were used to isolate hRPE cells. They were cultured in Dulbecco's modified Eagle's-medium-and-Ham's-F12-medium-(DMEM/F12) supplemented with 10% fetal bovine serum (FBS). Cultures were continuously studied using phase contrast microscopy. After the nineth passage, cells were characterized through immunocytochemical analysis for Oct4, Chx10, and Pax6 and Ki67 markers. In each well of a 6-well microplate, 1 and 2% weight/volume (w/v) alginate in deionized water was added and gelatinized using 1× and 10× NCCM. hRPE cells were cultured at a density of 2 × 105 cells/well in alginate-coated microplates. After 5 days, hRPE colonies were harvested and re-plated on polystyrene substrates. Morphology and growth of hRPE cultures were determined during the next 2 weeks. The first few passages of the cultures were purely hRPE cells that revealed typical morphological features of the pigmented epithelium. They made spaces, devoid of cells, between hRPE cell monolayer and fill in the unoccupied spaces. They grew faster than native RPE cells and rapidly overgrew. Immunocytochemical test revealed that the founded cells expressed Chx10, Pax6, Ki67 and Oct4. The hRPE cells survived unlimitedly on alginate film and formed giant adjoining colonies. After re-plating, hRPE colonies adhered quickly on polystyrene and displayed native hRPE morphological features. Alginate film can support the survival and growth of hRPE cells and induce the cells to re-organize in tissue-like structures.

  20. Transverse vibrations of shear-deformable beams using a general higher order theory

    Science.gov (United States)

    Kosmatka, J. B.

    1993-01-01

    A general higher order theory is developed to study the static and vibrational behavior of beam structures having an arbitrary cross section that utilizes both out-of-plane shear-dependent warping and in-plane (anticlastic) deformations. The equations of motion are derived via Hamilton's principle, where the full 3D constitutive relations are used. A simplified version of the general higher-order theory is also presented for beams having an arbitrary cross section that includes out-of-plane shear deformation but assumes that stresses within the cross section and in-plane deformations are negligible. This simplified model, which is accurate for long to moderately short wavelengths, offers substantial improvements over existing higher order theories that are limited to beams with thin rectangular cross sections. The current approach will be very useful in the study of thin-wall closed-cell beams such as airfoil-type sections where the magnitude of shear-related cross-sectional warping is significant.

  1. Effect of the Volume Fraction of Jute Fiber on the Interlaminar Shear Stress and Tensile Behavior Characteristics of Hybrid Glass/Jute Fiber Reinforced Polymer Composite Bar for Concrete Structures

    Directory of Open Access Journals (Sweden)

    Chan-Gi Park

    2016-01-01

    Full Text Available Hybrid glass/jute fiber reinforced polymer (HGJFRP composite bars were manufactured for concrete structures, and their interlaminar shear stress and tensile performance were evaluated. HGJFRP composite bars were manufactured using a combination of pultrusion and braiding processes. Jute fiber was surface-treated with a silane coupling agent. The mixing ratio of the fiber to the vinyl ester used in the HGJFRP composite bars was 7 : 3. Jute fiber was used to replace glass fiber in proportions of 0, 30, 50, 70, and 100%. The interlaminar shear stress decreased as the proportion of jute fiber increased. Fractures appeared due to delamination between the surface-treated component and the main part of the HGJFRP composite bar. Tensile load-strain curves with 50% jute fiber exhibited linear behavior. With a jute fiber volume fraction of 70%, some plastic deformation occurred. A jute fiber mixing ratio of 100% resulted in a display of linear elastic brittle behavior from the fiber; however, when the surface of the fiber was coated with poly(vinyl acetate, following failure, the jute fiber exhibited partial load resistance. The tensile strength decreased as the jute fiber content increased; however, the tensile strength did not vary linearly with jute fiber content.

  2. Optical, structural and electrochromic behavior studies on nanocomposite thin film of aniline, o-toluidine and WO3

    Science.gov (United States)

    Najafi-Ashtiani, Hamed; Bahari, Ali

    2016-08-01

    In the field of materials for electrochromic (EC) applications much attention was paid to the derivatives of aniline. We report on the optical, structural and electrochromic properties of electrochromic thin film based on composite of WO3 nanoparticles and copolymer of aniline and o-toluidine prepared by electrochemical polymerization method on fluorine doped tin oxide (FTO) coated glass. The thin film was studied by X-ray diffraction (XRD) and Fourier transforms infrared (FTIR) spectroscopy. The morphology of prepared thin film was characterized by field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and the thermal gravimetric analysis (TGA) as well. The optical spectra of nanocomposite thin film were characterized in the 200-900 nm wavelength range and EC properties of nanocomposite thin film were studied by cyclic voltammetry (CV). The calculation of optical band gaps of thin film exhibited that the thin film has directly allowed transition with the values of 2.63 eV on first region and 3.80 eV on second region. Dispersion parameters were calculated based on the single oscillator model. Finally, important parameters such as dispersion energy, oscillator energy and lattice dielectric constant were determined and compared with the data from other researchers. The nonlinear optical properties such as nonlinear optical susceptibility, nonlinear absorption coefficient and nonlinear refractive index were extracted. The obtained results of nanocomposite thin film can be useful for the optoelectronic applications.

  3. On shear rheology of gel propellants

    Energy Technology Data Exchange (ETDEWEB)

    Rahimi, Shai; Peretz, Arie [RAFAEL, MANOR Propulsion and Explosive Systems Division, Haifa (Israel); Natan, Benveniste [Faculty of Aerospace Engineering, Technion - Israel Institute of Technology, Haifa (Israel)

    2007-04-15

    Selected fuel, oxidizer and simulant gels were prepared and rheologically characterized using a rotational rheometer. For fuel gelation both organic and inorganic gellants were utilized, whereas oxidizers and simulants were gelled with addition of silica and polysaccharides, respectively. The generalized Herschel-Bulkley constitutive model was found to most adequately represent the gels studied. Hydrazine-based fuels, gelled with polysaccharides, were characterized as shear-thinning pseudoplastic fluids with low shear yield stress, whereas inhibited red-fuming nitric acid (IRFNA) and hydrogen peroxide oxidizers, gelled with silica, were characterized as yield thixotropic fluids with significant shear yield stress. Creep tests were conducted on two rheological types of gels with different gellant content and the results were fitted by Burgers-Kelvin viscoelastic constitutive model. The effect of temperature on the rheological properties of gel propellant simulants was also investigated. A general rheological classification of gel propellants and simulants is proposed. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  4. Shear failure of granular materials

    Science.gov (United States)

    Degiuli, Eric; Balmforth, Neil; McElwaine, Jim; Schoof, Christian; Hewitt, Ian

    2012-02-01

    Connecting the macroscopic behavior of granular materials with the microstructure remains a great challenge. Recent work connects these scales with a discrete calculus [1]. In this work we generalize this formalism from monodisperse packings of disks to 2D assemblies of arbitrarily shaped grains. In particular, we derive Airy's expression for a symmetric, divergence-free stress tensor. Using these tools, we derive, from first-principles and in a mean-field approximation, the entropy of frictional force configurations in the Force Network Ensemble. As a macroscopic consequence of the Coulomb friction condition at contacts, we predict shear failure at a critical shear stress, in accordance with the Mohr-Coulomb failure condition well known in engineering. Results are compared with numerical simulations, and the dependence on the microscopic geometric configuration is discussed. [4pt] [1] E. DeGiuli & J. McElwaine, PRE 2011. doi: 10.1103/PhysRevE.84.041310

  5. Structural, nanomechanical and variable range hopping conduction behavior of nanocrystalline carbon thin films deposited by the ambient environment assisted filtered cathodic jet carbon arc technique

    Energy Technology Data Exchange (ETDEWEB)

    Panwar, O.S., E-mail: ospanwar@mail.nplindia.ernet.in [Polymorphic Carbon Thin Films Group, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi - 110 012 (India); Rawal, Ishpal; Tripathi, R.K. [Polymorphic Carbon Thin Films Group, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi - 110 012 (India); Srivastava, A.K. [Electron and Ion Microscopy, Sophisticated and Analytical Instruments, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi - 110 012 (India); Kumar, Mahesh [Ultrafast Opto-Electronics and Tetrahertz Photonics Group, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi - 110 012 (India)

    2015-04-15

    Highlights: • Nanocrystalline carbon thin films are grown by filtered cathodic jet carbon arc process. • Effect of gaseous environment on the properties of carbon films has been studied. • The structural and nanomechanical properties of carbon thin films have been studied. • The VRH conduction behavior in nanocrystalline carbon thin films has been studied. - Abstract: This paper reports the deposition and characterization of nanocrystalline carbon thin films by filtered cathodic jet carbon arc technique assisted with three different gaseous environments of helium, nitrogen and hydrogen. All the films are nanocrystalline in nature as observed from the high resolution transmission electron microscopic (HRTEM) measurements, which suggests that the nanocrystallites of size ∼10–50 nm are embedded though out the amorphous matrix. X-ray photoelectron spectroscopic studies suggest that the film deposited under the nitrogen gaseous environment has the highest sp{sup 3}/sp{sup 2} ratio accompanied with the highest hardness of ∼18.34 GPa observed from the nanoindentation technique. The film deposited under the helium gaseous environment has the highest ratio of the area under the Raman D peak to G peak (A{sub D}/A{sub G}) and the highest conductivity (∼2.23 S/cm) at room temperature, whereas, the film deposited under the hydrogen environment has the lowest conductivity value (2.27 × 10{sup −7} S/cm). The temperature dependent dc conduction behavior of all the nanocrystalline carbon thin films has been analyzed in the light of Mott’s variable range hopping (VRH) conduction mechanism and observed that all the films obey three dimension VRH conduction mechanism for the charge transport.

  6. Fluid Effects on Shear Waves in Finely Layered Porous Media

    International Nuclear Information System (INIS)

    Berryman, J G

    2004-01-01

    Although there are five effective shear moduli for any layered VTI medium, one and only one effective shear modulus for the layered system contains all the dependence of pore fluids on the elastic or poroelastic constants that can be observed in vertically polarized shear waves. Pore fluids can increase the magnitude the shear energy stored by this modulus by a term that ranges from the smallest to the largest shear moduli of the VTI system. But, since there are five shear moduli in play, the increase in shear energy overall is reduced by a factor of about 5 in general. We can therefore give definite bounds on the maximum increase of shear modulus, being about 20% of the permitted range, when gas is fully replaced by liquid. An attendant increase of density (depending on porosity and fluid density) by approximately 5 to 10% partially offsets the effect of this shear modulus increase. Thus, an increase of shear wave speed on the order of 5 to 10% is shown to be possible when circumstances are favorable - i.e., when the shear modulus fluctuations are large (resulting in strong anisotropy), and the medium behaves in an undrained fashion due to fluid trapping. At frequencies higher than seismic (such as sonic and ultrasonic waves for well-logging or laboratory experiments), short response times also produce the requisite undrained behavior and, therefore, fluids also affect shear waves at high frequencies by increasing rigidity

  7. Annealing effect on the bipolar resistive switching behaviors of BiFeO3 thin films on LaNiO3-buffered Si substrates

    International Nuclear Information System (INIS)

    Chen Xinman; Zhang Hu; Ruan Kaibin; Shi Wangzhou

    2012-01-01

    Highlights: ► Annealing effect on the bipolar resistive switching behaviors of BiFeO 3 thin films with Pt/BiFeO 3 /LNO was reported. ► Rectification property was explained from the asymmetrical contact between top and bottom interfaces and the distinct oxygen vacancy density. ► The modification of Schottky-like barrier was suggested to be responsible for the resistance switching behaviors of Pt/BiFeO 3 /LNO devices. - Abstract: We reported the annealing effect on the electrical behaviors of BiFeO 3 thin films integrated on LaNiO 3 (LNO) layers buffered Si substrates by sol–gel spin-coating technique. All the BiFeO 3 thin films exhibit the reversible bipolar resistive switching behaviors with Pt/BiFeO 3 /LNO configuration. The electrical conduction mechanism of the devices was dominated by the Ohmic conduction in the low resistance state and trap-controlled space charged limited current in the high resistance state. Good diode-like rectification property was observed in device with BiFeO 3 film annealed at 500 °C, but vanished in device with BiFeO 3 film annealed at 600 °C. This was attributed to the asymmetrical contact between top and bottom interfaces as well as the distinct oxygen vacancy density verified by XPS. Furthermore, the modification of Schottky-like barrier due to the drift of oxygen vacancies was suggested to be responsible for the resistance switching behaviors of Pt/BiFeO 3 /LNO devices.

  8. Significant questions in thin liquid film heat transfer

    International Nuclear Information System (INIS)

    Bankoff, S.G.

    1994-01-01

    Thin liquid films appear in many contexts, such as the cooling of gas turbine blade tips, rocket engines, microelectronics arrays, and hot fuel element surfaces in hypothetical nuclear reactor accidents. Apart from these direct cooling applications of thin liquid layers, thin films form a crucial element in determining the allowable heat flux limits in boiling. This is because the last stages of dryout almost invariably involve the rupture of a residual liquid film, either as a microlayer underneath the bubbles, or a thin annular layer in a high-quality burnout scenario. The destabilization of these thin films under the combined actions of shear stress, evaporation, and thermocapillary effects is quite complex. The later stages of actual rupture to form dry regions, which then expand, resulting in possible overheating, are even more complex and less well understood. However, significant progress has been made in understanding the behavior of these thin films, which are subject to competing instabilities prior to actual rupture. This will be reviewed briefly. Recent work on the advance, or recession, of contact lines will also be described briefly, and significant questions that still remain to be answered will be discussed. 68 refs., 7 figs

  9. Control of cracking in R.C. Structures: Numerical simulation of a squat shear wall

    NARCIS (Netherlands)

    Damoni, C.; Belletti, B.; Lilliu, G.

    2013-01-01

    In this paper the behavior of a squat shear wall subjected to monotonic shear loading is investigated. The study fits into the experimental program driven by CEOS.fr on modeling of the behavior of the tested mocks-ups (monotonic and cycling loading-under prevented or free shrinkage). The shear wall

  10. Improvement of a wall thinning rate model for liquid droplet impingement erosion. Implementation of liquid film thickness model with consideration of film behavior

    International Nuclear Information System (INIS)

    Morita, Ryo

    2014-01-01

    Liquid droplet impingement erosion (LDI) is defined as an erosion phenomenon caused by high-speed droplet attack in a steam flow. Pipe wall thinning by LDI is sometimes observed in a steam piping system of a power plant. As LDI usually occurs very locally and is difficult to detect, predicting LDI location is required for safe operation of power plant systems. Therefore, we have involved in the research program to develop prediction tools that will be used easily in actual power plants. Our previous researches developed a thinning rate evaluation model due to LDI (LDI model) and the evaluation system of the thinning rate and the thinning shape within a practically acceptable time (LDI evaluation system). Though the LDI model can include a cushioning effect of liquid film which is generated on the material surface by droplet impingement as an empirical equation with fluid parameter, the liquid film thickness is not clarified due to complex flow condition. In this study, to improve the LDI model and the LDI evaluation system, an analytical model of the liquid film thickness was proposed with consideration of the liquid film flow behavior on the material surface. The mass balance of the liquid film was considered, and the results of CFD calculations and existing researches were applied to obtain the liquid film thickness in this model. As a result of the LDI evaluation of the new LDI model with liquid film model, improvement of the LDI model was achieved. (author)

  11. Examining shear processes during magma ascent

    Science.gov (United States)

    Kendrick, J. E.; Wallace, P. A.; Coats, R.; Lamur, A.; Lavallée, Y.

    2017-12-01

    Lava dome eruptions are prone to rapid shifts from effusive to explosive behaviour which reflects the rheology of magma. Magma rheology is governed by composition, porosity and crystal content, which during ascent evolves to yield a rock-like, viscous suspension in the upper conduit. Geophysical monitoring, laboratory experiments and detailed field studies offer the opportunity to explore the complexities associated with the ascent and eruption of such magmas, which rest at a pivotal position with regard to the glass transition, allowing them to either flow or fracture. Crystal interaction during flow results in strain-partitioning and shear-thinning behaviour of the suspension. In a conduit, such characteristics favour the formation of localised shear zones as strain is concentrated along conduit margins, where magma can rupture and heal in repetitive cycles. Sheared magmas often record a history of deformation in the form of: grain size reduction; anisotropic permeable fluid pathways; mineral reactions; injection features; recrystallisation; and magnetic anomalies, providing a signature of the repetitive earthquakes often observed during lava dome eruptions. The repetitive fracture of magma at ( fixed) depth in the conduit and the fault-like products exhumed at spine surfaces indicate that the last hundreds of meters of ascent may be controlled by frictional slip. Experiments on a low-to-high velocity rotary shear apparatus indicate that shear stress on a slip plane is highly velocity dependent, and here we examine how this influences magma ascent and its characteristic geophysical signals.

  12. The Effects of Thin and Heavy Media Images on Overweight and Underweight Consumers: Social Comparison Processes and Behavioral Implications

    OpenAIRE

    Smeesters, Dirk; Mussweiler, Thomas

    2010-01-01

    textabstractThis study examines how advertisements containing thin or heavy models influence the self‐esteem of overweight, normal, and underweight consumers. Previous research has mainly examined the influences of variations of the comparison standard on self‐evaluative outcomes, whereas we examine how the relative position of the self on the comparison dimension may moderate these effects. Three studies manipulated the size (thin vs. heavy) and extremity of the size (moderate vs. extreme) o...

  13. Emergence of non-Fermi liquid behaviors in 5d perovskite SrIrO{sub 3} thin films: Interplay between correlation, disorder, and spin-orbit coupling

    Energy Technology Data Exchange (ETDEWEB)

    Biswas, Abhijit [Department of Physics, POSTECH, Pohang 790-784 (Korea, Republic of); Kim, Ki-Seok [Department of Physics, POSTECH, Pohang 790-784 (Korea, Republic of); Institute of Edge of Theoretical Science (IES), POSTECH, Pohang 790-784 (Korea, Republic of); Jeong, Yoon H., E-mail: yhj@postech.ac.kr [Department of Physics, POSTECH, Pohang 790-784 (Korea, Republic of)

    2016-02-15

    We investigate the effects of compressive strain on the electrical resistivity of 5d iridium based perovskite SrIrO{sub 3} by depositing epitaxial films of thickness 35 nm on various substrates such as GdScO{sub 3} (110), DyScO{sub 3} (110), and SrTiO{sub 3} (001). Surprisingly, we find anomalous transport behaviors as expressed by ρ∝T{sup ε} in the temperature dependent resistivity, where the temperature exponent ε evolves continuously from 4/5 to 1 and to 3/2 with an increase of compressive strain. Furthermore, magnetoresistance always remains positive irrespective of resistivity upturns at low temperatures. These observations imply that the delicate interplay between correlation and disorder in the presence of strong spin-orbit coupling is responsible for the emergence of the non-Fermi liquid behaviors in 5d perovskite SrIrO{sub 3} thin films. We offer a theoretical framework for the interpretation of the experimental results. - Highlights: • We studied the effect of compressive strain on the perovskite SrIrO{sub 3} thin films. • We revealed non-Fermi liquid behaviors in the transport properties. • Irrespective of weak localization effects, magnetoresistance remains positive. • Mott-Anderson-Griffiths scenario is proposed to account for the NFL behaviors.

  14. The brittle-viscous-plastic evolution of shear bands in the South Armorican Shear Zone

    Science.gov (United States)

    Bukovská, Zita; Jeřábek, Petr; Morales, Luiz F. G.; Lexa, Ondrej; Milke, Ralf

    2014-05-01

    microcracks and nearly absent in matrix grains in the well developed C bands. The chemical variation between primary and secondary new-formed micas was clearly identified by the Mg-Ti-Na content. The microstructural analysis documents a progressive decrease in quartz grain size and increasing interconnectivity of K-feldspar and white mica towards more mature shear bands. The contact-frequency analysis demonstrates that the phase distribution in shear bands tends to evolve from quartz aggregate distribution via randomization to K-feldspar aggregate distribution. The boundary preferred orientation is absent in quartz-quartz contacts either inside of outside the C bands, while it changes from random to parallel to the C band for the K-feldspar and and K-feldspar-quartz boundaries. The lack of crystallographic preferred orientation of the individual phases in the mixed matrix of the C planes suggests a dominant diffusion-assisted grain boundary sliding deformation mechanism. In the later stages of shear band development, the deformation is accommodated by crystal plasticity of white mica in micaceous bands. The crystallographic and microstructural data thus indicate two important switches in deformation mechanisms, from (i) brittle to Newtonian viscous behavior in the initial stages of shear band evolution and from (ii) Newtonian viscous to power law in the later evolutionary stages. The evolution of shear bands in the South Armorican Shear Zone thus document the interplay between deformation mechanisms and chemical reactions in deformed granitoids.

  15. Haptic Edge Detection Through Shear

    Science.gov (United States)

    Platkiewicz, Jonathan; Lipson, Hod; Hayward, Vincent

    2016-03-01

    Most tactile sensors are based on the assumption that touch depends on measuring pressure. However, the pressure distribution at the surface of a tactile sensor cannot be acquired directly and must be inferred from the deformation field induced by the touched object in the sensor medium. Currently, there is no consensus as to which components of strain are most informative for tactile sensing. Here, we propose that shape-related tactile information is more suitably recovered from shear strain than normal strain. Based on a contact mechanics analysis, we demonstrate that the elastic behavior of a haptic probe provides a robust edge detection mechanism when shear strain is sensed. We used a jamming-based robot gripper as a tactile sensor to empirically validate that shear strain processing gives accurate edge information that is invariant to changes in pressure, as predicted by the contact mechanics study. This result has implications for the design of effective tactile sensors as well as for the understanding of the early somatosensory processing in mammals.

  16. Development of shear bands in amorphous-crystalline metallic alloys

    International Nuclear Information System (INIS)

    Pozdnyakov, V.A.

    2004-01-01

    A theoretical study is made into conditions of shear band evolution in amorphous-crystalline alloys with various morphological types of structural constituents. The condition of shear band evolution in thin amorphous alloys in the interior of the crystalline matrix is obtained. It is shown that a scale effect exists which manifests itself in suppression of the process of localized plastic flow with amorphous alloy thickness decreasing down to the limit. The analysis of the condition for shear band evolution in an amorphous alloy with nanocrystalline inclusions is accomplished. The relationship of a critical stress of shear band evolution to a volume fraction of disperse crystal inclusions is obtained. A consideration is also given to the evolution of shear bands in the material containing amorphous and crystalline areas of micro meter size. For the alloy with the structure of this type conditions for propagation of localized flows by a relay race type mechanism are determined [ru

  17. Shear flows induced by nonlinear evolution of double tearing modes

    International Nuclear Information System (INIS)

    Wang Zhengxiong; Kishimoto, Y.; Li, J. Q.; Wang Xiaogang; Dong, J. Q.

    2008-01-01

    Shear flows induced by nonlinear evolution of double tearing modes are investigated in a resistive magnetohydrodynamic model with slab geometry. It is found that intensive and thin poloidal shear flow layers are generated in the magnetic island region driven by coupled reconnection process at both rational surfaces. The structure of the flow layers keeps evolving after the merging of magnetic separatrices and forms a few narrow vortices along the open field lines in the final stage of magnetic reconnection. The effects of the distance between both rational surfaces and the initial magnetic shear on the nonlinear evolution of the plasma flows are also taken into consideration and the relevant mechanism is discussed

  18. A sensitive dynamic viscometer for measuring the complex shear modulus in a steady shear flow using the method of orthogonal superposition

    NARCIS (Netherlands)

    Zeegers, J.C.H.; Zeegers, Jos; van den Ende, Henricus T.M.; Blom, C.; Altena, E.G.; Beukema, Gerrit J.; Beukema, G.J.; Mellema, J.

    1995-01-01

    A new instrument to carry out complex viscosity measurements in equilibrium and in a steady shear flow has been developed. A small amplitude harmonic excitation is superimposed orthogonally to the steady shear rate component. It is realized by a thin-walled cylinder, which oscillates in the axial

  19. Photoelectrochemical behavior of Al{sub x}In{sub 1−x}N thin films grown by plasma-assisted dual source reactive evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Alizadeh, M., E-mail: alizadeh_kozerash@yahoo.com; Ganesh, V.; Pandikumar, A.; Goh, B.T.; Azianty, S.; Huang, N.M.; Rahman, S.A., E-mail: saadah@um.edu.my

    2016-06-15

    In this work the dependence of photoelectrochemical (PEC) behavior of Al{sub x}In{sub 1−x}N (0.48 ≤x ≤ 0.66) thin films grown by plasma-assisted dual source reactive evaporation, on the plasma dynamics and the alloys properties was studied. The influence of nitrogen flow rate on the compositional, morphological, structural and optical properties of the as-prepared films were investigated using X-ray photoelectron spectroscopy (XPS), Field emission scanning electron microscopy (FESEM), micro Raman spectroscopy and UV–vis spectroscopy. The PEC study of the as-grown Al{sub x}In{sub 1−x}N thin films targeted for water splitting application were performed in the presence of simulated solar irradiation of AM 1.5G (100 mW/cm{sup 2}). The PEC results revealed that the photocurrent for the Al{sub x}In{sub 1−x}N thin film grown at nitrogen flow rate of 80 sccm is ∼10-fold higher than the dark current. From the Mott–Schottky (MS) plots it was deduced that by increasing N{sub 2} flow rate up to 80 sccm, the flat band potential shifts toward more negative values. The good photoelectrochemical behavior of Al{sub x}In{sub 1−x}N thin films showed that this material could be a potential candidate for PEC water splitting. - Highlights: • Al{sub x}In{sub 1−x}N films were grown by Plasma-aided dual source reactive evaporation. • Effect of nitrogen flow rate on the films properties was investigated. • The band gap of the films decreased from 2.33 to 1.92 eV. • A good photoelectrochemical behavior of the Al{sub x}In{sub 1−x}N thin films was shown. • The photocurrent for the Al{sub 0.55}In{sub 0.45}N films is ∼10-fold higher than dark current.

  20. Nanomagnetic behavior of fullerene thin films in Earth magnetic field in dark and under polarization light influences.

    Science.gov (United States)

    Koruga, Djuro; Nikolić, Aleksandra; Mihajlović, Spomenko; Matija, Lidija

    2005-10-01

    In this paper magnetic fields intensity of C60 thin films of 60 nm and 100 nm thickness under the influence of polarization lights are presented. Two proton magnetometers were used for measurements. Significant change of magnetic field intensity in range from 2.5 nT to 12.3 nT is identified as a difference of dark and polarization lights of 60 nm and 100 nm thin films thickness, respectively. Specific power density of polarization light was 40 mW/cm2. Based on 200 measurement data average value of difference between magnetic intensity of C60 thin films, with 60 nm and 100 nm thickness, after influence of polarization light, were 3.9 nT and 9.9 nT respectively.

  1. Deformation behavior of Re alloyed Mo thin films on flexible substrates: In situ fragmentation analysis supported by first-principles calculations.

    Science.gov (United States)

    Jörg, Tanja; Music, Denis; Hauser, Filipe; Cordill, Megan J; Franz, Robert; Köstenbauer, Harald; Winkler, Jörg; Schneider, Jochen M; Mitterer, Christian

    2017-08-07

    A major obstacle in the utilization of Mo thin films in flexible electronics is their brittle fracture behavior. Within this study, alloying with Re is explored as a potential strategy to improve the resistance to fracture. The sputter-deposited Mo 1-x Re x films (with 0 ≤ x ≤ 0.31) were characterized in terms of structural and mechanical properties, residual stresses as well as electrical resistivity. Their deformation behavior was assessed by straining 50 nm thin films on polyimide substrates in uniaxial tension, while monitoring crack initiation and propagation in situ by optical microscopy and electrical resistance measurements. A significant toughness enhancement occurs with increasing Re content for all body-centered cubic solid solution films (x ≤ 0.23). However, at higher Re concentrations (x > 0.23) the positive effect of Re is inhibited due to the formation of dual-phase films with the additional close packed A15 Mo 3 Re phase. The mechanisms responsible for the observed toughness behavior are discussed based on experimental observations and electronic structure calculations. Re gives rise to both increased plasticity and bond strengthening in these Mo-Re solid solutions.

  2. Behavior of thin-walled beams made of advanced composite materials and incorporating non-classical effects

    Science.gov (United States)

    Librescu, Liviu; Song, Ohseop

    1991-11-01

    Several results concerning the refined theory of thin-walled beams of arbitrary closed cross-section incorporating nonclassical effects are presented. These effects are related both with the exotic properties characterizing the advanced composite material structures and the nonuniform torsional model. A special case of the general equations is used to study several problems of cantilevered thin-walled beams and to assess the influence of the incorporated effects. The results presented in this paper could be useful toward a more rational design of aeronautical or aerospace constructions, as well as of helicopter or tilt rotor blades constructed of advanced composite materials.

  3. Shear induced structures of soft colloids: Rheo-SANS experiments on kinetically frozen PEP-PEO diblock copolymer micelles

    International Nuclear Information System (INIS)

    Stellbrink, J; Lonetti, B; Rother, G; Willner, L; Richter, D

    2008-01-01

    We investigated the effect of external steady shear on dilute to concentrated solutions of PEP-PEO diblock copolymer micelles (soft colloids). The degree of softness in terms of particle interactions (intermolecular softness) and deformability of the individual particle (intramolecular softness) was varied by changing the ratio between hydrophobic and hydrophilic blocks from symmetric (1:1, hard sphere-like) to very asymmetric (1:20, star-like). We performed in situ rheology and small angle neutron scattering experiments (Rheo-SANS) to relate macroscopic flow properties to microscopic structural changes. The rheology data qualitatively show the same behavior for both types of micelles: (i) a divergence of the zero shear viscosity η 0 at a critical concentration φ c approximately following a Vogel-Fulcher-Tammann law and (ii) close to this liquid-solid transition a shear rate dependent viscosity which can be described by the Carreau function with an asymptotic power law η(γ-dot) ∼ γ-dot -0.4 starting at a critical shear rate γ-dot c . Rheo-SANS experiments in the liquid phase close to φ c were extended into the strong shear thinning region for both types of micelles at φ/φ c ∼0.8 and γ-dot red =γ-dot/γ-dot c approx. 10. In our Rheo-SANS data we observe a rather controversial influence of external shear on the structural properties of the two different micellar systems. With increasing shear rate the symmetric, hard sphere-like micelles show a decreasing structure factor S(Q) but a shear rate independent interparticle distance. The asymmetric, star-like micelles show an increase in S(Q) and an increase of the interparticle distance, both in the flow and vorticity direction. This unexpected behavior can be rationalized by a shear induced elongation and tilt of the star-like micelles along the flow direction as predicted by recent MD simulations (Ripoll et al 2006 Phys. Rev. Lett. 96 188302)

  4. Steady shear viscosity of stirred yoghurts with varying ropiness

    NARCIS (Netherlands)

    van Marle, M.E.; van Marle, M.E.; van den Ende, Henricus T.M.; de Kruif, C.G.; de Kruif, C.G.; Mellema, J.

    1999-01-01

    Stirred yogurt was viewed as a concentrated dispersion of aggregates consisting of protein particles. The steady-shear behavior of three types of stirred yogurt with varying ropiness was investigated experimentally. To describe the shear-dependent viscosity, a microrheological model was used which

  5. Shear Elasticity and Shear Viscosity Imaging in Soft Tissue

    Science.gov (United States)

    Yang, Yiqun

    In this thesis, a new approach is introduced that provides estimates of shear elasticity and shear viscosity using time-domain measurements of shear waves in viscoelastic media. Simulations of shear wave particle displacements induced by an acoustic radiation force are accelerated significantly by a GPU. The acoustic radiation force is first calculated using the fast near field method (FNM) and the angular spectrum approach (ASA). The shear waves induced by the acoustic radiation force are then simulated in elastic and viscoelastic media using Green's functions. A parallel algorithm is developed to perform these calculations on a GPU, where the shear wave particle displacements at different observation points are calculated in parallel. The resulting speed increase enables rapid evaluation of shear waves at discrete points, in 2D planes, and for push beams with different spatial samplings and for different values of the f-number (f/#). The results of these simulations show that push beams with smaller f/# require a higher spatial sampling rate. The significant amount of acceleration achieved by this approach suggests that shear wave simulations with the Green's function approach are ideally suited for high-performance GPUs. Shear wave elasticity imaging determines the mechanical parameters of soft tissue by analyzing measured shear waves induced by an acoustic radiation force. To estimate the shear elasticity value, the widely used time-of-flight method calculates the correlation between shear wave particle velocities at adjacent lateral observation points. Although this method provides accurate estimates of the shear elasticity in purely elastic media, our experience suggests that the time-of-flight (TOF) method consistently overestimates the shear elasticity values in viscoelastic media because the combined effects of diffraction, attenuation, and dispersion are not considered. To address this problem, we have developed an approach that directly accounts for all

  6. Fundamental study on a thin-film ae sensor for measurement of behavior of a multi-pad contact slider

    NARCIS (Netherlands)

    Imai, S.; Burger, G.J.; Lammerink, Theodorus S.J.; Fluitman, J.H.J.

    To study the fundamental dynamic characteristics of a multi-pad slider for contact recording, we developed a thin-film piezoelectric acoustic emission array sensor on an Si-suspension with an array pattern similar to that of contact pads. Experiments showed that the sensitivity of the sensor is

  7. A study for anticorrosion and tribological behaviors of thin/thick diamond-like carbon films in seawater

    Science.gov (United States)

    Ye, Yewei; Jia, Shujuan; Zhang, Dawei; Liu, Wei; Zhao, Haichao

    2018-03-01

    The thin and thick diamond-like carbon (DLC) films were prepared by unbalanced magnetron sputtering technique on 304L stainless steels and (100) silicon wafers. Microstructure, mechanical, corrosion and tribological properties were systematically investigated by SEM, Raman, nanoindenter, scratch tester, modulab electrochemical workstation and R-tec multifunctional tribological tester. Results showed that the adhesion force presented a descending trend with the growth in soaking time. The adhesion force of the thin DLC film with high residual compressive stress (‑3.72 GPa) was higher than that of the thick DLC film (‑2.96 GPa). During the corrosion test, the thick DLC film showed a higher impendence and a lower corrosion current density than the thin DLC film, which is attributed to the barrier action of large thickness. Compared to bare 304L substrate, the friction coefficients and wear rates of DLC films in seawater were obviously decreased. Meanwhile, the thin DLC film with ideal residual compressive stress, super adhesion force and good plastic deformation resistance revealed an excellent anti-wear ability in seawater.

  8. The Effects of Thin and Heavy Media Images on Overweight and Underweight Consumers: Social Comparison Processes and Behavioral Implications

    NARCIS (Netherlands)

    D.H.R.V. Smeesters (Dirk); T. Mussweiler (Thomas)

    2010-01-01

    textabstractThis study examines how advertisements containing thin or heavy models influence the self‐esteem of overweight, normal, and underweight consumers. Previous research has mainly examined the influences of variations of the comparison standard on self‐evaluative outcomes, whereas we examine

  9. Investigation on the oxidation behavior of AlCrVxN thin films by means of synchrotron radiation and influence on the high temperature friction

    Science.gov (United States)

    Tillmann, Wolfgang; Kokalj, David; Stangier, Dominic; Paulus, Michael; Sternemann, Christian; Tolan, Metin

    2018-01-01

    Friction minimization is an important topic which is pursued in research and industry. In addition to the use of lubricants, friction-reducing oxide phases can be utilized which occur during. These oxides are called Magnéli phases and especially vanadium oxides exhibit good friction reducing properties. Thereby, the lubrication effect can be traced back to oxygen deficiencies. AlCrN thin films are being used as coatings for tools which have to withstand high temperatures. A further improvement of AlCrN thin films concerning their friction properties is possible by incorporation of vanadium. This study analyzes the temperature dependent oxidation behavior of magnetron sputtered AlCrVN thin films with different vanadium contents up to 13.5 at.-% by means of X-ray diffraction and X-ray absorption near-edge spectroscopy. Up to 400 °C the coatings show no oxidation. A higher temperature of 700 °C leads to an oxidation and formation of Magnéli phases of the coatings with vanadium contents above 10.7 at.-%. Friction coefficients, measured by ball-on-disk test are correlated with the oxide formation in order to figure out the effect of vanadium oxides. At 700 °C a decrease of the friction coefficient with increasing vanadium content can be observed, due to the formation of VO2, V2O3 and the Magnéli phase V4O7.

  10. Comportamento da palha de cana-de-açúcar submetida ao corte por meio de ensaios de bancada Behavior of sugarcane trash submitted to shearing in laboratory conditions

    Directory of Open Access Journals (Sweden)

    Aloisio Bianchini

    2004-12-01

    Full Text Available Do ponto de vista da engenharia, poucos trabalhos a respeito do corte de restos culturais têm sido publicados, sendo escassas, portanto, as informações sobre o assunto. Sendo assim, este trabalho objetivou-se, estudar o comportamento da palha da cana-de-açúcar quanto ao corte, em função de sua umidade, espessura de sua camada e do ângulo oblíquo da lâmina. Para a coleta de dados foram utilizados um transdutor de força, acoplado á base das lâminas, e um sistema automático de coleta de dados, que trabalhou com taxa de aquisição de 9600 Hz. Os resultados demonstraram diferença significativa na força requerida quando se varia o ângulo oblíquo da lâmina e tendência linear desta força, com o aumento da quantidade de palha, entre 4 e 16 t ha-1. Verificou-se, também, que o requerimento de força e a demanda de energia, quando se variou a umidade da palha, apresentaram comportamento exponencial sendo que, acima de 28%, em base seca, as diferenças para a força de corte requerida e para a demanda de energia passaram a não ser mais significativas. A força máxima de corte apresentou tendência linear e inversamente proporcional ao ângulo oblíquo da lâmina.From an engineering standpoint, few papers on crop residue shearing have been published, especially with respect to sugarcane and information on the subject is scarce. Therefore, the objective of this work was to study the behavior of sugarcane trash submitted to shearing, as a function of its moisture content, thickness of trash layer and the oblique angle of the blade. A strength transducer, connected to the base of the blades and to an automatic data logger, was utilized to collect data, working at an acquisition rate of 9600 Hz. Results showed significant differences in the required strength when the oblique angle of the blade is changed, and a linear trend with the amount of trash between 4 and 16 t ha-1. The strength requirement and the energy demand showed an

  11. Shear of ordinary and elongated granular mixtures

    Science.gov (United States)

    Hensley, Alexander; Kern, Matthew; Marschall, Theodore; Teitel, Stephen; Franklin, Scott

    2015-03-01

    We present an experimental and computational study of a mixture of discs and moderate aspect-ratio ellipses under two-dimensional annular planar Couette shear. Experimental particles are cut from acrylic sheet, are essentially incompressible, and constrained in the thin gap between two concentric cylinders. The annular radius of curvature is much larger than the particles, and so the experiment is quasi-2d and allows for arbitrarily large pure-shear strains. Synchronized video cameras and software identify all particles and track them as they move from the field of view of one camera to another. We are particularly interested in the global and local properties as the mixture ratio of discs to ellipses varies. Global quantities include average shear rate and distribution of particle species as functions of height, while locally we investigate the orientation of the ellipses and non-affine events that can be characterized as shear transformational zones or possess a quadrupole signature observed previously in systems of purely circular particles. Discrete Element Method simulations on mixtures of circles and spherocylinders extend the study to the dynamics of the force network and energy dissipated as the system evolves. Supported by NSF CBET #1243571 and PRF #51438-UR10.

  12. Thin Layer Sensory Cues Affect Antarctic Krill Swimming Kinematics

    Science.gov (United States)

    True, A. C.; Webster, D. R.; Weissburg, M. J.; Yen, J.

    2013-11-01

    A Bickley jet (laminar, planar free jet) is employed in a recirculating flume system to replicate thin shear and phytoplankton layers for krill behavioral assays. Planar laser-induced fluorescence (LIF) and particle image velocimetry (PIV) measurements quantify the spatiotemporal structure of the chemical and free shear layers, respectively, ensuring a close match to in situ hydrodynamic and biochemical conditions. Path kinematics from digitized trajectories of free-swimming Euphausia superba examine the effects of hydrodynamic sensory cues (deformation rate) and bloom level phytoplankton patches (~1000 cells/mL, Tetraselamis spp.) on krill behavior (body orientation, swimming modes and kinematics, path fracticality). Krill morphology is finely tuned for receiving and deciphering both hydrodynamic and chemical information that is vital for basic life processes such as schooling behaviors, predator/prey, and mate interactions. Changes in individual krill behavior in response to ecologically-relevant sensory cues have the potential to produce population-scale phenomena with significant ecological implications. Krill are a vital trophic link between primary producers (phytoplankton) and larger animals (seabirds, whales, fish, penguins, seals) as well as the subjects of a valuable commercial fishery in the Southern Ocean; thus quantifying krill behavioral responses to relevant sensory cues is an important step towards accurately modeling Antarctic ecosystems.

  13. Emergence of non-Fermi liquid behaviors in 5d perovskite SrIrO3 thin films: Interplay between correlation, disorder, and spin-orbit coupling

    Science.gov (United States)

    Biswas, Abhijit; Kim, Ki-Seok; Jeong, Yoon H.

    2016-02-01

    We investigate the effects of compressive strain on the electrical resistivity of 5d iridium based perovskite SrIrO3 by depositing epitaxial films of thickness 35 nm on various substrates such as GdScO3 (110), DyScO3 (110), and SrTiO3 (001). Surprisingly, we find anomalous transport behaviors as expressed by ρ∝Tε in the temperature dependent resistivity, where the temperature exponent ε evolves continuously from 4/5 to 1 and to 3/2 with an increase of compressive strain. Furthermore, magnetoresistance always remains positive irrespective of resistivity upturns at low temperatures. These observations imply that the delicate interplay between correlation and disorder in the presence of strong spin-orbit coupling is responsible for the emergence of the non-Fermi liquid behaviors in 5d perovskite SrIrO3 thin films. We offer a theoretical framework for the interpretation of the experimental results.

  14. Measurement of the dynamic behavior of thin poly(N-isopropylacrylamide) hydrogels and their phase transition temperatures measured using reflectometric interference spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Okada, Fuminori [Konica Minolta, INC. (Japan); Akiyama, Yoshikatsu, E-mail: akiyama.yoshikatsu@twmu.ac.jp, E-mail: akiyama.yoshikatsu@abmes.twmu.ac.jp; Kobayashi, Jun [Tokyo Women’s Medical University (TWIns), Institute of Advanced Biomedical Engineering and Science (Japan); Ninomiya, Hidetaka [Konica Minolta, INC. (Japan); Kanazawa, Hideko [Keio University, Faculty of Pharmacy (Japan); Yamato, Masayuki; Okano, Teruo [Tokyo Women’s Medical University (TWIns), Institute of Advanced Biomedical Engineering and Science (Japan)

    2015-03-15

    Temperature-responsive cell culture surfaces prepared by modifying tissue-culture polystyrene with nanoscale poly(N-isopropylacrylamide) (PIPAAm) hydrogels are widely used as intelligent surfaces for the fabrication of various cell sheets that change with temperature. In this work, the characteristics of nanoscale PIPAAm hydrogels were phenomenologically elucidated on the basis of time-dependent surface evaluations under conditions of changing temperature. Because the dynamic characteristics of the nanoscale hydrogel did not exhibit good performance, the nanoscale PIPAAm hydrogel was analyzed by monitoring its temperature-dependent dynamic swelling/deswelling changes using reflectometric interference spectroscopy (RIfS) on an instrument equipped with a microfluidic system. RIfS measurements under ambient atmosphere provided the precise physical thickness of the dry PIPAAm hydrogel (6.7 nm), which agreed with the atomic force microscopy results (6.6 nm). Simulations of the reflectance spectra revealed that changes in the wavelength of the minimum reflectance (Δλ) were attributable to the changes in the refractive index of the thin PIPAAm hydrogel induced by a temperature-dependent volume phase transition. The temperature-dependent Δλ change was used to monitor the swelling/deswelling behavior of the nanoscale PIPAAm hydrogel. In addition, the phase transition temperature of the thin PIPAAm hydrogel under aqueous conditions was also determined to be the inflection point of the plot of the change in Δλ as a function of temperature. The dynamic behavior of a thin PIPAAm hydrogel chemically deposited on a surface was readily analyzed using a new analytical system with RIfS and microfluidic devices.

  15. Investigation of corrosion behavior of nitrogen doped and platinum/ruthenium doped diamond-like carbon thin films in Hank's solution

    International Nuclear Information System (INIS)

    Khun, N.W.; Liu, E.

    2011-01-01

    Undoped (DLC), nitrogen-doped (N-DLC) and platinum/ruthenium doped diamond-like carbon (PtRu-DLC) thin films were deposited on p-Si (100) substrates using a DC magnetron sputtering deposition system. The chemical composition, bonding structure, surface morphology and adhesion strength of the films were characterized using X-ray photoelectron spectroscopy (XPS), micro-Raman spectroscopy, atomic force microscopy (AFM) and micro-scratch test, respectively. The corrosion behavior of the films in a Hank's solution was investigated using potentiodynamic polarization test. The corrosion results revealed that the PtRu-DLC film had the highest corrosion potential among the films used in this study. Highlights: → DLC thin films were deposited on Si substrates via dc magnetron sputtering. → Some DLC films were doped with N and/or Pt/Ru. → The film corrosion behavior was studied in a Hank solution with polarization test. → The PtRu-DLC film showed the highest corrosion potential among the films studied.

  16. Investigation of corrosion behavior of nitrogen doped and platinum/ruthenium doped diamond-like carbon thin films in Hank's solution

    Energy Technology Data Exchange (ETDEWEB)

    Khun, N.W.; Liu, E., E-mail: MEJLiu@ntu.edu.sg

    2011-10-10

    Undoped (DLC), nitrogen-doped (N-DLC) and platinum/ruthenium doped diamond-like carbon (PtRu-DLC) thin films were deposited on p-Si (100) substrates using a DC magnetron sputtering deposition system. The chemical composition, bonding structure, surface morphology and adhesion strength of the films were characterized using X-ray photoelectron spectroscopy (XPS), micro-Raman spectroscopy, atomic force microscopy (AFM) and micro-scratch test, respectively. The corrosion behavior of the films in a Hank's solution was investigated using potentiodynamic polarization test. The corrosion results revealed that the PtRu-DLC film had the highest corrosion potential among the films used in this study. Highlights: {yields} DLC thin films were deposited on Si substrates via dc magnetron sputtering. {yields} Some DLC films were doped with N and/or Pt/Ru. {yields} The film corrosion behavior was studied in a Hank solution with polarization test. {yields} The PtRu-DLC film showed the highest corrosion potential among the films studied.

  17. Mechanical properties and local mobility of atactic-polystyrene films under constant-shear deformation

    NARCIS (Netherlands)

    Hudzinskyy, D.; Michels, M.A.J.; Lyulin, A.V.

    2012-01-01

    We have performed molecular-dynamics simulations of atactic polystyrene thin films to study the effect of shear rate, pressure, and temperature on the stress-strain behaviour, the relevant energetic contributions and non-affine displacements of polymer chains during constant-shear deformation. Under

  18. Temperature behavior of electrical properties of high-k lead-magnesium-niobium titanate thin-films

    Energy Technology Data Exchange (ETDEWEB)

    Chen Wenbin, E-mail: cwb0201@163.com [Electromechanical Engineering College, Guilin University of Electronic Technology (China); McCarthy, Kevin G. [Department of Electrical and Electronic Engineering, University College Cork (Ireland); Copuroglu, Mehmet; O' Brien, Shane; Winfield, Richard; Mathewson, Alan [Tyndall National Institute, University College Cork (Ireland)

    2012-05-01

    This paper reports on the temperature dependence of the electrical properties of high-k lead-magnesium-niobium titanate thin films processed with different compositions (with and without nanoparticles) and with different annealing temperatures (450 Degree-Sign C and 750 Degree-Sign C). These characterization results support the ongoing investigation of the material's electrical properties which are necessary before the dielectric can be used in silicon-based IC applications.

  19. The effect of grain and pore sizes on the mechanical behavior of thin Al films deposited under different conditions

    Czech Academy of Sciences Publication Activity Database

    Ben-David, E.; Landa, Michal; Janovská, Michaela; Seiner, Hanuš; Gutman, O.; Tepper-Faran, T.; Shilo, D.

    2015-01-01

    Roč. 87, April (2015), s. 321-331 ISSN 1359-6454 Grant - others:Rada Programu interní podpory projektů mezinárodní spolupráce AV ČR(CZ) M100761203 Program:M Institutional support: RVO:61388998 Keywords : thin films * mechanical properties * tensile tests * bulge tests * porosity Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 5.058, year: 2015 http://www.sciencedirect.com/science/article/pii/S1359645414009677

  20. Processing behaviors of thin-film pentacene and benzene-1,4-diboronic acid in supercritical carbon dioxide

    International Nuclear Information System (INIS)

    Ngo, Truc T.; Keegan, James E.; George, Robert D.

    2011-01-01

    This research investigates the feasibility of using supercritical carbon dioxide (scCO 2 ) as a green solvent for processing organic thin film semiconductor, such as pentacene, and a potential molecular modifier for use in electronic device applications. Benzene-1,4-diboronic acid (BDBA) was selected as a molecular modifier in this work due to its electron deficient nature, which can potentially enhance pentacene's physical, chemical or electronic properties by changing its structure in the solid state. In this study, the solubilities of BDBA and pentacene in scCO 2 are measured as individual compounds and as co-solutes, at 313 K, using ultraviolet (UV) spectroscopy. Methanol co-solvent effects on solubility have also been characterized for each compound. The results show that BDBA is insoluble in pure scCO 2 up to 1.82 × 10 7 Pa. However, with a small amount of methanol added to the mixture, BDBA becomes soluble in solution with a solubility of 3.81 × 10 −4 mol/l at 9.00 × 10 6 -Pa-pressure. In contrast, pentacene is only soluble in scCO 2 at pressures above 1.10 × 10 7 Pa, and its solubility is decreased upon addition of methanol due to the non-polar nature of pentacene. When a pentacene thin film is treated with BDBA in scCO 2 /methanol solution, BDBA sorption is observed at pressures as low as 8.80 × 10 6 Pa. Based on these results, it is concluded that treatment of pentacene thin films in scCO 2 is a promising approach that can be optimized for BDBA and other similar molecular modifiers, to produce multi-component organic thin film devices.

  1. Design and implementation of a shearing apparatus for the experimental study of shear displacement in rocks

    Science.gov (United States)

    Moore, Johnathan; Crandall, Dustin; Gill, Magdalena; Brown, Sarah; Tennant, Bryan

    2018-04-01

    Fluid flow in the subsurface is not well understood in the context of "impermeable" geologic media. This is especially true of formations that have undergone significant stress fluctuations due to injection or withdrawal of fluids that alters the localized pressure regime. When the pressure regime is altered, these formations, which are often already fractured, move via shear to reduce the imbalance in the stress state. While this process is known to happen, the evolution of these fractures and their effects on fluid transport are still relatively unknown. Numerous simulation and several experimental studies have been performed that characterize the relationship between shearing and permeability in fractures; while many of these studies utilize measurements of fluid flow or the starting and ending geometries of the fracture to characterize shear, they do not characterize the intermediate stages during shear. We present an experimental apparatus based on slight modifications to a commonly available Hassler core holder that allows for shearing of rocks, while measuring the hydraulic and mechanical changes to geomaterials during intermediate steps. The core holder modification employs the use of semi-circular end caps and structural supports for the confining membrane that allow for free movement of the sheared material while preventing membrane collapse. By integrating this modified core holder with a computed tomography scanner, we show a new methodology for understanding the interdependent behavior between fracture structure and flow properties during intermediate steps in shearing. We include a case study of this device function which is shown here through shearing of a fractured shale core and simultaneous observation of the mechanical changes and evolution of the hydraulic properties during shearing.

  2. Anomalous transport due to shear-Alfven waves

    International Nuclear Information System (INIS)

    Lee, W.W.; Chance, M.S.; Okuda, H.

    1980-10-01

    The behavior of shear-Alfven eigenmodes and the accompanied anomalous transport have been investigated. In the particle simulation, equilibrium thermal fluctuations associated with the eigenmodes have been observed to nullify the zeroth-order shear near the rational surface through the induced second-order eddy current, and, in turn, give rise to the formation of magnetic islands which cause rapid electron energy transport in the region. The theoretical verification of the observed behavior is discussed

  3. The influence of a brittle Cr interlayer on the deformation behavior of thin Cu films on flexible substrates: Experiment and model

    International Nuclear Information System (INIS)

    Marx, Vera M.; Toth, Florian; Wiesinger, Andreas; Berger, Julia; Kirchlechner, Christoph; Cordill, Megan J.; Fischer, Franz D.; Rammerstorfer, Franz G.; Dehm, Gerhard

    2015-01-01

    Thin metal films deposited on polymer substrates are used in flexible electronic devices such as flexible displays or printed memories. They are often fabricated as complicated multilayer structures. Understanding the mechanical behavior of the interface between the metal film and the substrate as well as the process of crack formation under global tension is important for producing reliable devices. In the present work, the deformation behavior of copper films (50–200 nm thick), bonded to polyimide directly or via a 10 nm chromium interlayer, is investigated by experimental analysis and computational simulations. The influence of the various copper film thicknesses and the usage of a brittle interlayer on the crack density as well as on the stress magnitude in the copper after saturation of the cracking process are studied with in situ tensile tests in a synchrotron and under an atomic force microscope. From the computational point of view, the evolution of the crack pattern is modeled as a stochastic process via finite element based cohesive zone simulations. Both, experiments and simulations show that the chromium interlayer dominates the deformation behavior. The interlayer forms cracks that induce a stress concentration in the overlying copper film. This behavior is more pronounced in the 50 nm than in the 200 nm copper films

  4. Keyed shear joints

    DEFF Research Database (Denmark)

    Hansen, Klaus

    This report gives a summary of the present information on the behaviour of vertical keyed shear joints in large panel structures. An attemp is made to outline the implications which this information might have on the analysis and design of a complete wall. The publications also gives a short...

  5. An underwater shear compactor

    International Nuclear Information System (INIS)

    Biver, E.; Sims, J.

    1997-01-01

    This paper, originally presented at the WM'96 Conference in Tucson Arizona, describes a concept of a specialised decommissioning tool designed to operate underwater and to reduce the volume of radioactive components by shearing and compacting. The shear compactor was originally conceived to manage the size reduction of a variety of decommissioned stainless steel tubes stored within a reactor fuel cooling pond and which were consuming a substantial volume of the pond. The main objective of this tool was to cut the long tubes into shorter lengths and to compact them into a flat rectangular form which could be stacked on the pond floor, thus saving valuable space. The development programme, undertaken on this project, investigated a wide range of factors which could contribute to an extended cutting blade performance, ie: materials of construction, cutting blade shape and cutting loads required, shock effects, etc. The second phase was to review other aspects of the design, such as radiological protection, cutting blade replacement, maintenance, pond installation and resultant wall loads, water hydraulics, collection of products of shearing/compacting operations, corrosion of the equipment, control system, operational safety and the ability of the equipment to operate in dry environments. The paper summarises the extended work programme involved with this shear compactor tool. (author)

  6. On the behaviour of gelled fibre suspensions in steady shear

    Energy Technology Data Exchange (ETDEWEB)

    Wolf, Bettina [Unilever Corporate Research, Bedford (United Kingdom); University of Nottingham, Division of Food Sciences, Loughborough (United Kingdom); White, Duncan; Melrose, John R.; Frith, William J. [Unilever Corporate Research, Bedford (United Kingdom)

    2007-03-15

    The shear rheological properties of suspensions of gelled agar fibres in a low viscosity Newtonian matrix fluid were investigated. Two classes of fibres, low aspect ratio fibres and high aspect ratio fibres with an aspect ratio of the order of 10 and 100 respectively were included in the investigations. For all fibre phase volumes investigated, from as low as 0.01 upwards, the flow curves are characterised by an apparent yield stress followed by shear-thinning which was independent of the fibre aspect ratio. Based on our analysis of the flow curves, we conclude that the high aspect ratio fibres behave like flexible threads in contrast to the low aspect ratio fibres whose high shear relative viscosity is successfully described by a relation for long rigid rods. These findings are supported by flow visualisation using an optical shearing stage coupled to a light microscope. (orig.)

  7. Investigating Direct Links between Depression, Emotional Control, and Physical Punishment with Adolescent Drive for Thinness and Bulimic Behaviors, Including Possible Moderation by the Serotonin Transporter 5-HTTLPR Polymorphism.

    Science.gov (United States)

    Rozenblat, Vanja; Ryan, Joanne; Wertheim, Eleanor H; King, Ross; Olsson, Craig A; Krug, Isabel

    2017-01-01

    Objectives: To examine the relationship between psychological and social factors (depression, emotional control, sexual abuse, and parental physical punishment) and adolescent drive for Thinness and Bulimic behaviors in a large community sample, and to investigate possible genetic moderation. Method: Data were drawn from the Australian Temperament Project (ATP), a population-based cohort study that has followed a representative sample of 2443 participants from infancy to adulthood across 16 waves since 1983. A subsample of 650 participants (50.2% female) of Caucasian descent who provided DNA were genotyped for a serotonin transporter promoter polymorphism ( 5-HTTLPR ). Adolescent disordered eating attitudes and behaviors were assessed using the Bulimia and Drive for Thinness scales of the Eating Disorder Inventory-2 (15-16 years). Depression and emotional control were examined at the same age using the Short Mood and Feelings Questionnaire, and an ATP-devised measure of emotional control. History of sexual abuse and physical punishment were assessed retrospectively (23-24 years) in a subsample of 467 of those providing DNA. Results: EDI-2 scores were associated with depression, emotional control, and retrospectively reported parental physical punishment. Although there was statistically significant moderation of the relationship between parental physical punishment and bulimic behaviors by 5-HTTLPR ( p = 0.0048), genotypes in this subsample were not in Hardy-Weinberg Equilibrium. No other G×E interactions were significant. Conclusion: Findings from this study affirm the central importance of psychosocial processes in disordered eating patterns in adolescence. Evidence of moderation by 5-HTTLPR was not conclusive; however, genetic moderation observed in a subsample not in Hardy-Weinberg Equilibrium warrants further investigation.

  8. Investigating Direct Links between Depression, Emotional Control, and Physical Punishment with Adolescent Drive for Thinness and Bulimic Behaviors, Including Possible Moderation by the Serotonin Transporter 5-HTTLPR Polymorphism

    Directory of Open Access Journals (Sweden)

    Vanja Rozenblat

    2017-08-01

    Full Text Available Objectives: To examine the relationship between psychological and social factors (depression, emotional control, sexual abuse, and parental physical punishment and adolescent drive for Thinness and Bulimic behaviors in a large community sample, and to investigate possible genetic moderation.Method: Data were drawn from the Australian Temperament Project (ATP, a population-based cohort study that has followed a representative sample of 2443 participants from infancy to adulthood across 16 waves since 1983. A subsample of 650 participants (50.2% female of Caucasian descent who provided DNA were genotyped for a serotonin transporter promoter polymorphism (5-HTTLPR. Adolescent disordered eating attitudes and behaviors were assessed using the Bulimia and Drive for Thinness scales of the Eating Disorder Inventory-2 (15–16 years. Depression and emotional control were examined at the same age using the Short Mood and Feelings Questionnaire, and an ATP-devised measure of emotional control. History of sexual abuse and physical punishment were assessed retrospectively (23–24 years in a subsample of 467 of those providing DNA.Results: EDI-2 scores were associated with depression, emotional control, and retrospectively reported parental physical punishment. Although there was statistically significant moderation of the relationship between parental physical punishment and bulimic behaviors by 5-HTTLPR (p = 0.0048, genotypes in this subsample were not in Hardy–Weinberg Equilibrium. No other G×E interactions were significant. Conclusion: Findings from this study affirm the central importance of psychosocial processes in disordered eating patterns in adolescence. Evidence of moderation by 5-HTTLPR was not conclusive; however, genetic moderation observed in a subsample not in Hardy–Weinberg Equilibrium warrants further investigation.

  9. Shear strength of non-shear reinforced concrete elements

    DEFF Research Database (Denmark)

    Hoang, Cao linh

    1997-01-01

    The paper deals with the plastic shear strength of non shear reinforced T-beams.The influence of an un-reinforced flange on the shear capacity is investigated by considering a failure mechanism involving crack sliding in the web and a kind of membrane action over an effective width of the flange...

  10. Effect of aluminum addition on the optical, morphology and electrical behavior of spin coated zinc oxide thin films

    Directory of Open Access Journals (Sweden)

    Amit Kumar Srivastava

    2011-09-01

    Full Text Available Aluminum-doped ZnO thin films of high optical transmittance (∼ 84-100% and low resistivity (∼ 2.3x10-2 Ωcm have been prepared on glass substrate by the spin coating and subsequent annealing at 500°C for 1h in air or vacuum. Effect of aluminum doping and annealing environment on morphology, optical transmittance and electrical resistivity of ZnO thin films has been studied with possible application as a transparent electrode in photovoltaic. The changes occurring due to aluminum addition include reduction in grain size, root mean square roughness, peak-valley separation, and sheet resistance with improvement in the optical transmittance to 84-100% in the visible range. The origin of low electrical resistivity lies in increase in i electron concentration following aluminum doping (being trivalent, formation of oxygen vacancies due to vacuum annealing, filling of cation site with additional zinc at solution stage itself and ii carrier mobility.

  11. Unique rheological behavior of chitosan-modified nanoclay at highly hydrated state.

    Science.gov (United States)

    Liang, Songmiao; Liu, Linshu; Huang, Qingrong; Yam, Kit L

    2009-04-30

    This work attempts to explore the dynamic and steady-state rheological properties of chitosan modified clay (CMCs) at highly hydrated state. CMCs with different initial chitosan/clay weight ratios (s) were prepared from pre-exfoliated clay via electrostatic adsorption process. Thermogravimetric analysis and optical microscopy were used to determine the adsorbed content of chitosan (m) in CMCs and the microstructure of CMCs at highly hydrated state, respectively. Dynamic rheological results indicate that both stress-strain behavior and moduli of CMCs exhibit strong dependence on m. Shear-thinning behavior for all of CMCs is observed and further confirmed by steady-state shear test. Interestingly, two unique transitions, denoted as a small peak region of the shear viscosity for CMCs with m > 2.1% and a sharp drop region of the shear viscosity for CMCs with m shear rate range of about 10 < gamma < 40 and 0.2 < gamma < 0.5 s(- 1), respectively. Further, analysis on the recovery of CMCs at rest after underwent a preshearing process was performed with an emphasis to explain the presence of these unique transitions. Thixotropic effect was observed in CMCs and showed strong dependence on m and the preshearing history. Failure to Cox-Merz rule of the rheological behavior of CMCs suggests that some preferential orientation of the initial quiescent random arrangement of CMCs particles or their tactoids occurs under the applied shearing.

  12. Experiments on sheet metal shearing

    OpenAIRE

    Gustafsson, Emil

    2013-01-01

    Within the sheet metal industry, different shear cutting technologies are commonly used in several processing steps, e.g. in cut to length lines, slitting lines, end cropping etc. Shearing has speed and cost advantages over competing cutting methods like laser and plasma cutting, but involves large forces on the equipment and large strains in the sheet material.Numerical models to predict forces and sheared edge geometry for different sheet metal grades and different shear parameter set-ups a...

  13. Test and lower bound modeling of keyed shear connections in RC shear walls

    DEFF Research Database (Denmark)

    Sørensen, Jesper Harrild; Herfelt, Morten Andersen; Hoang, Linh Cao

    2018-01-01

    This paper presents an investigation into the ultimate behavior of a recently developed design for keyed shear connections. The influence of the key depth on the failure mode and ductility of the connection has been studied by push-off tests. The tests showed that connections with larger key...

  14. Tensile stress-dependent fracture behavior and its influences on photovoltaic characteristics in flexible PbS/CdS thin-film solar cells.

    Science.gov (United States)

    Lee, Seung Min; Yeon, Deuk Ho; Mohanty, Bhaskar Chandra; Cho, Yong Soo

    2015-03-04

    Tensile stress-dependent fracture behavior of flexible PbS/CdS heterojunction thin-film solar cells on indium tin oxide-coated polyethylene terephthalate (PET) substrates is investigated in terms of the variations of fracture parameters with applied strains and their influences on photovoltaic properties. The PbS absorber layer that exhibits only mechanical cracks within the applied strain range from ∼0.67 to 1.33% is prepared by chemical bath deposition at different temperatures of 50, 70, and 90 °C. The PbS thin films prepared at 50 °C demonstrate better mechanical resistance against the applied bending strain with the highest crack initiating bending strain of ∼1.14% and the lowest saturated crack density of 0.036 μm(-1). Photovoltaic properties of the cells depend on the deposition temperature and the level of applied tensile stress. The values of short-circuit current density and fill factor are dramatically reduced above a certain level of applied strain, while open-circuit voltage is nearly maintained. The dependency of photovoltaic properties on the progress of fractures is understood as related to the reduced fracture energy and toughness, which is limitedly controllable by microstructural features of the absorber layer.

  15. Rheological behavior and constitutive equations of heterogeneous titanium-bearing molten slag

    Science.gov (United States)

    Jiang, Tao; Liao, De-ming; Zhou, Mi; Zhang, Qiao-yi; Yue, Hong-rui; Yang, Song-tao; Duan, Pei-ning; Xue, Xiang-xin

    2015-08-01

    Experimental studies on the rheological properties of a CaO-SiO2-Al2O3-MgO-TiO2-(TiC) blast furnace (BF) slag system were conducted using a high-temperature rheometer to reveal the non-Newtonian behavior of heterogeneous titanium-bearing molten slag. By measuring the relationships among the viscosity, the shear stress and the shear rate of molten slags with different TiC contents at different temperatures, the rheological constitutive equations were established along with the rheological parameters; in addition, the non-Newtonian fluid types of the molten slags were determined. The results indicated that, with increasing TiC content, the viscosity of the molten slag tended to increase. If the TiC content was less than 2wt%, the molten slag exhibited the Newtonian fluid behavior when the temperature was higher than the critical viscosity temperature of the molten slag. In contrast, the molten slag exhibited the non-Newtonian pseudoplastic fluid characteristic and the shear thinning behavior when the temperature was less than the critical viscosity temperature. However, if the TiC content exceeded 4wt%, the molten slag produced the yield stress and exhibited the Bingham and plastic pseudoplastic fluid behaviors when the temperature was higher and lower than the critical viscosity temperature, respectively. When the TiC content increased further, the yield stress of the molten slag increased and the shear thinning phenomenon became more obvious.

  16. CAT LIDAR wind shear studies

    Science.gov (United States)

    Goff, R. W.

    1978-01-01

    The studies considered the major meteorological factors producing wind shear, methods to define and classify wind shear in terms significant from an aircraft perturbation standpoint, the significance of sensor location and scan geometry on the detection and measurement of wind shear, and the tradeoffs involved in sensor performance such as range/velocity resolution, update frequency and data averaging interval.

  17. Synaptic behaviors of thin-film transistor with a Pt/HfO x /n-type indium–gallium–zinc oxide gate stack

    Science.gov (United States)

    Yang, Paul; Park, Daehoon; Beom, Keonwon; Kim, Hyung Jun; Kang, Chi Jung; Yoon, Tae-Sik

    2018-07-01

    We report a variety of synaptic behaviors in a thin-film transistor (TFT) with a metal-oxide-semiconductor gate stack that has a Pt/HfO x /n-type indium–gallium–zinc oxide (n-IGZO) structure. The three-terminal synaptic TFT exhibits a tunable synaptic weight with a drain current modulation upon repeated application of gate and drain voltages. The synaptic weight modulation is analog, voltage-polarity dependent reversible, and strong with a dynamic range of multiple orders of magnitude (>104). This modulation process emulates biological synaptic potentiation, depression, excitatory-postsynaptic current, paired-pulse facilitation, and short-term to long-term memory transition behaviors as a result of repeated pulsing with respect to the pulse amplitude, width, repetition number, and the interval between pulses. These synaptic behaviors are interpreted based on the changes in the capacitance of the Pt/HfO x /n-IGZO gate stack, the channel mobility, and the threshold voltage that result from the redistribution of oxygen ions by the applied gate voltage. These results demonstrate the potential of this structure for three-terminal synaptic transistor using the gate stack composed of the HfO x gate insulator and the IGZO channel layer.

  18. Synaptic behaviors of thin-film transistor with a Pt/HfO x /n-type indium-gallium-zinc oxide gate stack.

    Science.gov (United States)

    Yang, Paul; Park, Daehoon; Beom, Keonwon; Kim, Hyung Jun; Kang, Chi Jung; Yoon, Tae-Sik

    2018-07-20

    We report a variety of synaptic behaviors in a thin-film transistor (TFT) with a metal-oxide-semiconductor gate stack that has a Pt/HfO x /n-type indium-gallium-zinc oxide (n-IGZO) structure. The three-terminal synaptic TFT exhibits a tunable synaptic weight with a drain current modulation upon repeated application of gate and drain voltages. The synaptic weight modulation is analog, voltage-polarity dependent reversible, and strong with a dynamic range of multiple orders of magnitude (>10 4 ). This modulation process emulates biological synaptic potentiation, depression, excitatory-postsynaptic current, paired-pulse facilitation, and short-term to long-term memory transition behaviors as a result of repeated pulsing with respect to the pulse amplitude, width, repetition number, and the interval between pulses. These synaptic behaviors are interpreted based on the changes in the capacitance of the Pt/HfO x /n-IGZO gate stack, the channel mobility, and the threshold voltage that result from the redistribution of oxygen ions by the applied gate voltage. These results demonstrate the potential of this structure for three-terminal synaptic transistor using the gate stack composed of the HfO x gate insulator and the IGZO channel layer.

  19. Influences of Shear History and Infilling on the Mechanical Characteristics and Acoustic Emissions of Joints

    Science.gov (United States)

    Meng, Fanzhen; Zhou, Hui; Wang, Zaiquan; Zhang, Liming; Kong, Liang; Li, Shaojun; Zhang, Chuanqing

    2017-08-01

    Filled joints, which are characterized by high deformability and low shear strength, are among the most critical discontinuities in rock mass and may be sheared repeatedly when subject to cyclic loading. Shear tests were carried out on tension splitting joints, with soil and granular cement mortar particles used as infillings, and the effects of the shear history on the mechanical behavior and acoustic emission (AE) of clean and filled joints were studied. The maximum strength in the subsequent shears was approximately 60% of the peak strength of the first shear for a clean joint, and the friction angle degraded from 63° to 45° after the first shear. The maximum shear strength of the filled joints was lower than 35% of the peak strength of the clean joint under the same normal stress. The change in the shear strength of filled joints with the number of shearing cycles was closely related to the transformation of the shear medium. Rolling friction occurred and the shear strength was low for the granular particle-filled joint, but the strength was elevated when the particles were crushed and sliding friction occurred. The AEs were significantly reduced during the second shear for the clean joint, and the peak AEs were mainly obtained at or near the turning point of the shear stress curve for the filled joint. The AEs were the highest for the cement particle-filled joint and lowest for the dry soil-filled joint; when subjected to repeated shears, the AEs were more complex because of the continuous changes to the shear medium. The evolution of the AEs with the shear displacement can accurately reflect the shear failure mechanism during a single shear process.

  20. Effect of working pressure on corrosion behavior of nitrogen doped diamond-like carbon thin films deposited by DC magnetron sputtering.

    Science.gov (United States)

    Khun, N W; Liu, E

    2011-06-01

    Nitrogen doped diamond-like carbon thin films were deposited on highly conductive p-silicon(100) substrates using a DC magnetron sputtering deposition system by varying working pressure in the deposition chamber. The bonding structure, adhesion strength, surface roughness and corrosion behavior of the films were investigated by using X-ray photoelectron spectroscopy, micro-Raman spectroscopy, micro-scratch test, atomic force microscopy and potentiodynamic polarization test. A 0.6 M NaCl electrolytic solution was used for the corrosion tests. The optimum corrosion resistance of the films was found at a working pressure of 7 mTorr at which a good balance between the kinetics of the sputtered ions and the surface mobility of the adatoms promoted a microstructure of the films with fewer porosities.

  1. Rectifying Behavior of Aligned ZnO Nano rods on Mg0.3Zn0.7O Thin Film Template

    International Nuclear Information System (INIS)

    Salina Muhamad; Suriani Abu Bakar; Mohamad Hafiz Mamat; Rafidah Ahmad; Mohamad Rusop

    2011-01-01

    Rectifying behavior more than 3 orders of aligned zinc oxide (ZnO) nano rods grown on Mg 0.3 Zn 0.7 O thin film template using chemical bath deposition method was observed, giving a barrier height of 0.75 eV, and the ideality factor achieved was almost 6, which was analyzed using thermionic emission theory. Field emission scanning electron microscope (FESEM) images revealed that the grown ZnO was in hexagonal shape, uniformly distributed and in vertically aligned form. The crystallinity of the sample being studied using X-ray diffraction (XRD), where the highest peak was found at (002) phase, confirming that high crystallinity of ZnO was attained. The effect of metal/semiconductor junction between metal and aligned ZnO nano rods was discussed in further details. (author)

  2. Modeling and characterization of the low frequency noise behavior for amorphous InGaZnO thin film transistors in the subthreshold region

    Science.gov (United States)

    Cai, Minxi; Yao, Ruohe

    2017-10-01

    An analytical model of the low-frequency noise (LFN) for amorphous InGaZnO (a-IGZO) thin film transistors (TFTs) in the subthreshold region is developed. For a-IGZO TFTs, relations between the device noise and the subgap defects are characterized based on the dominant multiple trapping and release (MTR) mechanism. The LFN is considered to be contributed from trapping/detrapping of carriers both into the border traps and the subgap density of states (DOS). It is revealed that the LFN behavior of a-IGZO TFTs in the subthreshold region is significantly influenced by the distribution of tail states, where MTR process prevails. The 1/f α (with α < 1) spectrum of the drain current noise is also related to the characteristic temperature of the tail states. The new method is introduced to calculate the LFN of devices by extracting the LFN-related DOS parameters from the current-voltage characteristics.

  3. ANALYSIS ON THE BEHAVIOR OF PRECIPITATES IN ULTRA-THIN HOT STRIP OF PLAIN LOW CARBON STEEL PRODUCED BY COMPACT STRIP PRODUCTION

    Institute of Scientific and Technical Information of China (English)

    H. Yu; Y.L. Kang; H.B. Dong; D.L. Liu; J. Fu

    2002-01-01

    This paper investigated the mechanism of precipitation and its influence upon prop-erties of ultra-thin hot strips of low carbon steel produced by CSP techniques usingexperiment and thermodynamics theory. The experimental results show that thereare lots of fine and dispersive precipitates in microstructures. By analysis, most ofaluminum nitrides are in grains, while coexisted precipitates of MnS are along grainboundaries. Coexisted precipitates compose cation-vacancy type oxides such as Al2O3in the core, while MnS is at the fringe of surface. The precipitation behavior of AlNand MnS in the hot strip is studied by thermodynamic calculation. At last, implica-tions between strengthening effect and techniques are analyzed using obtained solubilityproducts.

  4. Drop Weight Impact Behavior of Al-Si-Cu Alloy Foam-Filled Thin-Walled Steel Pipe Fabricated by Friction Stir Back Extrusion

    Science.gov (United States)

    Hangai, Yoshihiko; Nakano, Yukiko; Utsunomiya, Takao; Kuwazuru, Osamu; Yoshikawa, Nobuhiro

    2017-02-01

    In this study, Al-Si-Cu alloy ADC12 foam-filled thin-walled stainless steel pipes, which exhibit metal bonding between the ADC12 foam and steel pipe, were fabricated by friction stir back extrusion. Drop weight impact tests were conducted to investigate the deformation behavior and mechanical properties of the foam-filled pipes during dynamic compression tests, which were compared with the results of static compression tests. From x-ray computed tomography observation, it was confirmed that the fabricated foam-filled pipes had almost uniform porosity and pore size distributions. It was found that no scattering of the fragments of collapsed ADC12 foam occurred for the foam-filled pipes owing to the existence of the pipe surrounding the ADC12 foam. Preventing the scattering of the ADC12 foam decreases the drop in stress during dynamic compression tests and therefore improves the energy absorption properties of the foam.

  5. The effects of polymer molecular weight on filament thinning and drop breakup in microchannels

    International Nuclear Information System (INIS)

    Arratia, P E; Cramer, L-A; Gollub, J P; Durian, D J

    2009-01-01

    We investigate the effects of fluid elasticity on the dynamics of filament thinning and drop breakup processes in a cross-slot microchannel. Elasticity effects are examined using dilute aqueous polymeric solutions of molecular weight (MW) ranging from 1.5x10 3 to 1.8x10 7 . Results for polymeric fluids are compared to those for a viscous Newtonian fluid. The shearing or continuous phase that induces breakup is mineral oil. All fluids possess similar shear-viscosity (∼0.2 Pa s) so that the viscosity ratio between the oil and aqueous phases is close to unity. Measurements of filament thickness as a function of time show different thinning behavior for the different aqueous fluids. For Newtonian fluids, the thinning process shows a single exponential decay of the filament thickness. For low MW fluids (10 3 , 10 4 and 10 5 ), the thinning process also shows a single exponential decay, but with a decay rate that is slower than for the Newtonian fluid. The decay time increases with polymer MW. For high MW (10 6 and 10 7 ) fluids, the initial exponential decay crosses over to a second exponential decay in which elastic stresses are important. We show that the decay rate of the filament thickness in this exponential decay regime can be used to measure the steady extensional viscosity of the fluids. At late times, all fluids cross over to an algebraic decay which is driven mainly by surface tension.

  6. Etching behavior of poly (vinylidene fluoride) thin films irradiated with ion beams. Effect of irradiated ions and pretreatment

    International Nuclear Information System (INIS)

    Yamaki, Tetsuya; Rohani, Rosiah; Koshikawa, Hiroshi; Takahashi, Shuichi; Hasegawa, Shin; Asano, Masaharu; Maekawa, Yasunari; Voss, Kay-Obbe; Neumann, Reinhard

    2008-01-01

    Poly (vinylidene fluoride) thin films irradiated with four kinds of ion beams were exposed to a 9M KOH aqueous solution after their storage in air for 30 or 90 days at different temperatures. According to the conductometry, the heating at 120degC was found to enhance the etch rate in the latent track without changing that in the bulk, thereby enabling us to obtain very high etching sensitivity for the preparation of nano-sized through-pores. The formation of hydroperoxides during this pretreatment should facilitate the introduction of the etching agent to improve etchability. Additionally, the irradiation of higher-LET ions, causing each track to contain more activated sites (like radicals), was preferable to achieve high sensitivity of the etching. (author)

  7. Corrosion behavior of aluminum doped diamond-like carbon thin films in NaCl aqueous solution.

    Science.gov (United States)

    Khun, N W; Liu, E

    2010-07-01

    Aluminum doped diamond-like carbon (DLC:Al) thin films were deposited on n-Si(100) substrates by co-sputtering a graphite target under a fixed DC power (650 W) and an aluminum target under varying DC power (10-90 W) at room temperature. The structure, adhesion strength and surface morphology of the DLC:Al films were characterized by X-ray photoelectron spectroscopy (XPS), micro-scratch testing and atomic force microscopy (AFM), respectively. The corrosion performance of the DLC:Al films was investigated by means of potentiodynamic polarization testing in a 0.6 M NaCl aqueous solution. The results showed that the polarization resistance of the DLC:Al films increased from about 18 to 30.7 k(omega) though the corrosion potentials of the films shifted to more negative values with increased Al content in the films.

  8. Forflytning: shear og friktion

    DEFF Research Database (Denmark)

    2005-01-01

    friktion). Formålet med filmprojektet er: At give personalet i Apopleksiafsnittet viden om shear og friktion, så det motiveres til forebyggelse. Mål At udarbejde et enkelt undervisningsmateriale til bed-side-brug Projektbeskrivelse (resume) Patienter med apopleksi er særligt udsatte for tryksår, fordi de...... ofte er immobile, har svært ved at opretholde en god siddestilling eller ligger tungt i sengen som følger efter apopleksien Hvis personalet bruger forkert lejrings-og forflytningsteknik, udsættes patienterne for shear og friktion. Målgruppen i projektet er de personer, der omgås patienterne, dvs...

  9. Thermodynamic Properties, Hysteresis Behavior and Stress-Strain Analysis of MgH2 Thin Films, Studied over a Wide Temperature Range

    Directory of Open Access Journals (Sweden)

    Yevheniy Pivak

    2012-06-01

    Full Text Available Using hydrogenography, we investigate the thermodynamic parameters and hysteresis behavior in Mg thin films capped by Ta/Pd, in a temperature range from 333 K to 545 K. The enthalpy and entropy of hydride decomposition, ∆Hdes = −78.3 kJ/molH2, ∆Sdes = −136.1 J/K molH2, estimated from the Van't Hoff analysis, are in good agreement with bulk results, while the absorption thermodynamics, ∆Habs = −61.6 kJ/molH2, ∆Sabs = −110.9 J/K molH2, appear to be substantially affected by the clamping of the film to the substrate. The clamping is negligible at high temperatures, T > 523 K, while at lower temperatures, T < 393 K, it is considerable. The hysteresis at room temperature in Mg/Ta/Pd films increases by a factor of 16 as compared to MgH2 bulk. The hysteresis increases even further in Mg/Pd films, most likely due to the formation of a Mg-Pd alloy at the Mg/Pd interface. The stress–strain analysis of the Mg/Ta/Pd films at 300–333 K proves that the increase of the hysteresis occurs due to additional mechanical work during the (de-hydrogenation cycle. With a proper temperature correction, our stress–strain analysis quantitatively and qualitatively explains the hysteresis behavior in thin films, as compared to bulk, over the whole temperature range.

  10. Shear Roll Mill Reactivation

    Science.gov (United States)

    2012-09-13

    pneumatically operated paste dumper and belt conveyor system, the loss in weight feeder system, the hydraulically operated shear roll mill, the pellet...out feed belt conveyor , and the pack out system comprised of the metal detector, scale, and pack out empty and full drum roller conveyors . Page | 4...feed hopper and conveyor supplying the loss in weight feeder were turned on, and it was verified that these items functioned as designed . The

  11. Large-Amplitude Long-Wave Instability of a Supersonic Shear Layer

    Science.gov (United States)

    Messiter, A. F.

    1995-01-01

    For sufficiently high Mach numbers, small disturbances on a supersonic vortex sheet are known to grow in amplitude because of slow nonlinear wave steepening. Under the same external conditions, linear theory predicts slow growth of long-wave disturbances to a thin supersonic shear layer. An asymptotic formulation is given here which adds nonzero shear-layer thickness to the weakly nonlinear formulation for a vortex sheet. Spatial evolution is considered, for a spatially periodic disturbance having amplitude of the same order, in Reynolds number, as the shear-layer thickness. A quasi-equilibrium inviscid nonlinear critical layer is found, with effects of diffusion and slow growth appearing through nonsecularity condition. Other limiting cases are also considered, in an attempt to determine a relationship between the vortex-sheet limit and the long-wave limit for a thin shear layer; there appear to be three special limits, corresponding to disturbances of different amplitudes at different locations along the shear layer.

  12. Observation of Droplet Size Oscillations in a Two-Phase Fluid under Shear Flow

    Science.gov (United States)

    Courbin, Laurent; Panizza, Pascal; Salmon, Jean-Baptiste

    2004-01-01

    Experimental observations of droplet size sustained oscillations are reported in a two-phase flow between a lamellar and a sponge phase. Under shear flow, this system presents two different steady states made of monodisperse multilamellar droplets, separated by a shear-thinning transition. At low and high shear rates, the droplet size results from a balance between surface tension and viscous stress, whereas for intermediate shear rates it becomes a periodic function of time. A possible mechanism for such kinds of oscillations is discussed.

  13. In situ observations of crack arrest and bridging by nanoscale twins in copper thin films

    International Nuclear Information System (INIS)

    Kim, Seong-Woong; Li Xiaoyan; Gao Huajian; Kumar, Sharvan

    2012-01-01

    In situ tensile experiments in a transmission electron microscope revealed that micro-cracks in ultrafine grained, free-standing, thin copper foils containing nanoscale twins initiated in matrix domains separated by the twins and then arrested at twin boundaries as twin boundary sliding proceeded. The adjacent microcracks eventually coalesced through shear failure of the bridging twins. To investigate the atomic mechanism of this rarely seen nanoscale crack bridging behavior, molecular dynamics simulations were performed to show that during crack propagation twin boundaries are impinged upon by numerous dislocations from the plastically deforming matrix. These dislocations react at the interface and evolve into substantially impenetrable dislocation walls that strongly confine crack nucleation and resist crack propagation, leading to the experimentally observed crack bridging behavior. The present results raise an approach to significantly toughening polycrystalline thin films by incorporating nanoscale twin structures into individual grains that serve as crack bridging ligaments.

  14. Unique self-assembly behavior of a triblock copolymer and fabrication of catalytically active gold nanoparticle/polymer thin films at the liquid/liquid interface

    International Nuclear Information System (INIS)

    Shang, Ke; Geng, Yuanyuan; Xu, Xingtao; Wang, Changwei; Lee, Yong-Ill; Hao, Jingcheng; Liu, Hong-Guo

    2014-01-01

    Gold nanoparticle-doped poly(2-vinylpyridine)-block-polystyrene-block-poly(2-vinylpyridine) (P2VP-b-PS-b-P2VP) thin films were prepared at the planar liquid/liquid interface between the chloroform solution of the polymer and aqueous solution of HAuCl 4 . Transmission electron microscopic (TEM) investigations revealed that foam films composed of microcapsules as well as one-dimensional belts were formed, and numerous Au nanoparticles were incorporated in the walls of the microcapsules and the nanobelts. The walls and the belts have layered structure. The formation mechanism of the foams and the belts was attributed to adsorption of the polymer molecules, combination of the polymer molecules with AuCl 4 − ions, microphase separation and self-assembly of the composite molecules at the interface. This microstructure is different apparently from those formed in solutions, in casting or spin-coating thin films and at the air/water interface of this triblock copolymer, reflecting unique self-assembly behavior at the liquid/liquid interface. This microstructure is also different from those formed by homo-P2VP and P4VP-b-PS-b-P4VP at the liquid/liquid interface, indicating the effects of molecular structures on the self-assembly behaviors of the polymers. After further treatment by UV-light irradiation and KBH 4 aqueous solution, the gold species were reduced completely, as indicated by UV–vis spectra and X-ray photoelectron spectra (XPS). Thermogravimetric analysis indicated that the composite films have high thermal stability, and the content of gold was estimated to be about 9.1%. These composite films exhibited high catalytic activity for the reduction of 4-nitrophenol by KBH 4 in aqueous solutions. - Highlights: • P2VP-b-PS-b-P2VP formed microcapsules and nanobelts at the liquid/liquid interface. • Its self-assembly behavior differs from P4VP-b-PS-b-P4VP at the interface. • This behavior also differs from those in solution, in film and at air/water interface

  15. Unique self-assembly behavior of a triblock copolymer and fabrication of catalytically active gold nanoparticle/polymer thin films at the liquid/liquid interface

    Energy Technology Data Exchange (ETDEWEB)

    Shang, Ke; Geng, Yuanyuan; Xu, Xingtao [Key Laboratory for Colloid and Interface Chemistry of Education Ministry, Shandong University, Jinan 250100 (China); Wang, Changwei [Environmental Monitoring Center of Shandong Province, Jinan 250013 (China); Lee, Yong-Ill [Anastro Laboratory, Department of Chemistry, Changwon National University, Changwon 641-773 (Korea, Republic of); Hao, Jingcheng [Key Laboratory for Colloid and Interface Chemistry of Education Ministry, Shandong University, Jinan 250100 (China); Liu, Hong-Guo, E-mail: hgliu@sdu.edu.cn [Key Laboratory for Colloid and Interface Chemistry of Education Ministry, Shandong University, Jinan 250100 (China)

    2014-07-01

    Gold nanoparticle-doped poly(2-vinylpyridine)-block-polystyrene-block-poly(2-vinylpyridine) (P2VP-b-PS-b-P2VP) thin films were prepared at the planar liquid/liquid interface between the chloroform solution of the polymer and aqueous solution of HAuCl{sub 4}. Transmission electron microscopic (TEM) investigations revealed that foam films composed of microcapsules as well as one-dimensional belts were formed, and numerous Au nanoparticles were incorporated in the walls of the microcapsules and the nanobelts. The walls and the belts have layered structure. The formation mechanism of the foams and the belts was attributed to adsorption of the polymer molecules, combination of the polymer molecules with AuCl{sub 4}{sup −} ions, microphase separation and self-assembly of the composite molecules at the interface. This microstructure is different apparently from those formed in solutions, in casting or spin-coating thin films and at the air/water interface of this triblock copolymer, reflecting unique self-assembly behavior at the liquid/liquid interface. This microstructure is also different from those formed by homo-P2VP and P4VP-b-PS-b-P4VP at the liquid/liquid interface, indicating the effects of molecular structures on the self-assembly behaviors of the polymers. After further treatment by UV-light irradiation and KBH{sub 4} aqueous solution, the gold species were reduced completely, as indicated by UV–vis spectra and X-ray photoelectron spectra (XPS). Thermogravimetric analysis indicated that the composite films have high thermal stability, and the content of gold was estimated to be about 9.1%. These composite films exhibited high catalytic activity for the reduction of 4-nitrophenol by KBH{sub 4} in aqueous solutions. - Highlights: • P2VP-b-PS-b-P2VP formed microcapsules and nanobelts at the liquid/liquid interface. • Its self-assembly behavior differs from P4VP-b-PS-b-P4VP at the interface. • This behavior also differs from those in solution, in film and

  16. Habituation/Fatigue behavior of a synapse memristor based on IGZO-HfO2 thin film.

    Science.gov (United States)

    Jiang, Ran; Ma, Pengfei; Han, Zuyin; Du, Xianghao

    2017-08-24

    A synaptic memristor based on IGZO and oxygen-deficient HfO 2 films has been demonstrated. The memristor exhibits a fatigue response to a monotonic stimulus of voltage pulses, which is analogous to the habituation behavior of biological memory. The occurrence of habituation is nearly simultaneous with the transition from short-term memory to long-term memory. The movement and redistribution of oxygen species with the assistance of polarization in HfO 2 layer are responsible for the above results. The observation of habituation behavior proves the potential prospect of memristor on the mimic of biological neuron.

  17. Structures and shear response of lipid monolayers

    International Nuclear Information System (INIS)

    Dutta, P.; Ketterson, J.B.

    1993-02-01

    This report discusses our work during the last 3 years using x-ray diffraction and shear measurements to study lipid monolayers (membranes). The report is divided into: (1) structure: phase diagram of saturated fatty acid Langmuir monolayers, effect of head group interactions, studies of transferred monolayers (LB films); (2) mechanical properties: fiber=optic capillary wave probe and centrosymmetric trough, mechanical behavior of heneicosanoic acid monolayer phases

  18. High strength semi-active energy absorbers using shear- and mixedmode operation at high shear rates

    Science.gov (United States)

    Becnel, Andrew C.

    crew seat. Characterization tests were carried out on the LMEAS using a 40 vol% MRF used in the previous magnetorheometer tests. These were analyzed using both flow curves and apparent viscosity vs. Mason number diagrams. The nondimensionalized Mason number analysis resulted in data for all conditions of temperature, fluid composition, and shear rate, to collapse onto a single characteristic or master curve. Significantly, the temperature corrected Mason number results from both the bench top magnetorheometer and full scale rotary vane MREA collapse to the same master curve. This enhances the ability of designers of MRFs and MREAs to safely and effectively apply characterization data collected in low shear rate, controlled temperature environments to operational environments that may be completely different. Finally, the Searle cell magnetorheometer was modified with an enforced eccentricity to work in both squeeze and shear modes simultaneously to achieve so called squeeze strengthening of the working MRF, thereby increasing the apparent yield stress and the specific energy absorption. By squeezing the active MR fluid, particles undergo compression-assisted aggregation into stronger, more robust columns which resist shear better than single chains. A hybrid model describing the squeeze strengthening behavior is developed, and recommendations are made for using squeeze strengthening to improve practical MREA devices.

  19. Plasticity Approach to Shear Design

    DEFF Research Database (Denmark)

    Hoang, Cao Linh; Nielsen, Mogens Peter

    1998-01-01

    The paper presents some plastic models for shear design of reinforced concrete beams. Distinction is made between two shear failure modes, namely web crushing and crack sliding. The first mentioned mode is met in beams with large shear reinforcement degrees. The mode of crack sliding is met in non......-shear reinforced beams as well as in lightly shear reinforced beams. For such beams the shear strength is determined by the recently developed crack sliding model. This model is based upon the hypothesis that cracks can be transformed into yield lines, which have lower sliding resistance than yield lines formed...... in uncracked concrete. Good agree between theory and tests has been found.Keywords: dsign, plasticity, reinforced concrete, reinforcement, shear, web crushing....

  20. Rheological Behavior of Bentonite-Polyester Dispersions

    Science.gov (United States)

    Abu-Jdayil, Basim; Al-Omari, Salah Addin

    2013-07-01

    The rheological behavior of a bentonite clay dispersed in unsaturated polyester was investigated. The effects of the solid content and particle size on the steady and transient rheological properties of the dispersions were studied. In addition, two types of bentonite with different Na+/Ca+2 ratio were used in this study. The Herschel-Bulkley and the Weltman models were used to describe the apparent viscosity of the bentonite-polyester composite in relation to the shear rate and shearing time. The bentonite-polyester dispersions were found to exhibit both Newtonian and non-Newtonian behavior. The transition from a Newtonian to a Bingham plastic and then to a shear-thinning material with a yield stress was found to depend on the solid concentration, the particle size, and the type of bentonite. At a low solid content, the apparent viscosity of the bentonite dispersion increased linearly with solid concentration. But a dramatic increase in the apparent viscosity beyond a solid content of 20 wt.% was observed. On the other hand, a thixotropic behavior was detected in bentonite-polyester dispersions with a high solid content and a low particle size. However, this behavior was more pronounced in dispersions with a high Na+/Ca+2 ratio.

  1. Stoichiometry behavior of TaN, TaCN and TaC thin films produced by magnetron sputtering

    International Nuclear Information System (INIS)

    Vargas, M.; Castillo, H.A.; Restrepo-Parra, E.; De La Cruz, W.

    2013-01-01

    Thin films were synthesized in a magnetron sputtering system using a target of Ta with 99.99% purity and silicon substrates (1 1 1). The gases used for the film growth were (Ar + N 2 ), (Ar + CH 4 + N 2 ) and (Ar + CH 4 ) mixtures for TaN, TaCN and TaC, respectively. The substrate temperature increased from room temperature to 500 °C. The chemical composition and bonding configuration were examined using X-ray photoelectron spectroscopy (XPS), revealing Ta-N, Ta-C-N, Ta-C and C-C bonds. Moreover, the crystallographic structure was analyzed using X-ray diffraction (XRD), indicating the presence of (1 1 1) and (2 0 0) planes belonging to a face-centered cubic structure. The stoichiometry variation dependence on the CH 4 and N 2 flow was analyzed, and the influence of the substrate temperature on the coatings was investigated. Finally, scanning electron microscopy (SEM) was used to determine the evolution on the grain formation in the coatings as the substrate temperature increased.

  2. Stoichiometry behavior of TaN, TaCN and TaC thin films produced by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Vargas, M. [Centro de Nanociencia y Nanotecnología, Universidad Nacional Autónoma de México, A.P. 2681, C.P. 22860, Ensenada, B.C. (Mexico); Castillo, H.A. [Centro de Enseñanza Técnica y Superior, CETYS Universidad, Campus Tijuana, Tijuana, B.C. (Mexico); Restrepo-Parra, E., E-mail: erestrepopa@unal.edu.co [Universidad Nacional de Colombia Sede Medellín Colombia, Facultad de Minas, Manizales (Colombia); De La Cruz, W. [Centro de Nanociencia y Nanotecnología, Universidad Nacional Autónoma de México, A.P. 2681, C.P. 22860, Ensenada, B.C. (Mexico)

    2013-08-15

    Thin films were synthesized in a magnetron sputtering system using a target of Ta with 99.99% purity and silicon substrates (1 1 1). The gases used for the film growth were (Ar + N{sub 2}), (Ar + CH{sub 4} + N{sub 2}) and (Ar + CH{sub 4}) mixtures for TaN, TaCN and TaC, respectively. The substrate temperature increased from room temperature to 500 °C. The chemical composition and bonding configuration were examined using X-ray photoelectron spectroscopy (XPS), revealing Ta-N, Ta-C-N, Ta-C and C-C bonds. Moreover, the crystallographic structure was analyzed using X-ray diffraction (XRD), indicating the presence of (1 1 1) and (2 0 0) planes belonging to a face-centered cubic structure. The stoichiometry variation dependence on the CH{sub 4} and N{sub 2} flow was analyzed, and the influence of the substrate temperature on the coatings was investigated. Finally, scanning electron microscopy (SEM) was used to determine the evolution on the grain formation in the coatings as the substrate temperature increased.

  3. Characterization and gas-sensing behavior of an iron oxide thin film prepared by atomic layer deposition

    International Nuclear Information System (INIS)

    Aronniemi, Mikko; Saino, J.; Lahtinen, J.

    2008-01-01

    In this work we investigate an iron oxide thin film grown with atomic layer deposition for a gas sensor application. The objective is to characterize the structural, chemical, and electrical properties of the film, and to demonstrate its gas-sensitivity. The obtained scanning electron microscopy and atomic force microscopy results indicate that the film has a granular structure and that it has grown mainly on the glass substrate leaving the platinum electrodes uncovered. X-ray diffraction results show that iron oxide is in the α-Fe 2 O 3 (hematite) phase. X-ray photoelectron spectra recorded at elevated temperature imply that the surface iron is mainly in the Fe 3+ state and that oxygen has two chemical states: one corresponding to the lattice oxygen and the other to adsorbed oxygen species. Electric conductivity has an activation energy of 0.3-0.5 eV and almost Ohmic current-voltage dependency. When exposed to O 2 and CO, a typical n-type response is observed

  4. Seismic cycle feedbacks in a mid-crustal shear zone

    Science.gov (United States)

    Melosh, Benjamin L.; Rowe, Christie D.; Gerbi, Christopher; Smit, Louis; Macey, Paul

    2018-07-01

    Mid-crustal fault rheology is controlled by alternating brittle and plastic deformation mechanisms, which cause feedback cycles that influence earthquake behavior. Detailed mapping and microstructural observations in the Pofadder Shear Zone (Namibia and South Africa) reveal a lithologically heterogeneous shear zone core with quartz-rich mylonites and ultramylonites, plastically overprinted pseudotachylyte and active shear folds. We present evidence for a positive feedback cycle in which coseismic grain size reduction facilitates active shear folding by enhancing competency contrasts and promoting crystal plastic flow. Shear folding strengthens a portion of a shear zone by limb rotation, focusing deformation and promoting plastic flow or brittle slip in resulting areas of localized high stress. Using quartz paleopiezometry, we estimate strain and slip rates consistent with other studies of exhumed shear zones and modern plate boundary faults, helping establish the Pofadder Shear Zone as an ancient analogue to modern, continental-scale, strike-slip faults. This feedback cycle influences seismicity patterns at the scale of study (10s of meters) and possibly larger scales as well, and contributes to bulk strengthening of the brittle-plastic transition on modern plate boundary faults.

  5. Shear Adhesion of Tapered Nanopillar Arrays.

    Science.gov (United States)

    Cho, Younghyun; Minsky, Helen K; Jiang, Yijie; Yin, Kaiyang; Turner, Kevin T; Yang, Shu

    2018-04-04

    Tapered nanopillars with various cross sections, including cone-shaped, stepwise, and pencil-like structures (300 nm in diameter at the base of the pillars and 1.1 μm in height), are prepared from epoxy resin templated by nanoporous anodic aluminum oxide (AAO) membranes. The effect of pillar geometry on the shear adhesion behavior of these nanopillar arrays is investigated via sliding experiments in a nanoindentation system. In a previous study of arrays with the same geometry, it was shown that cone-shaped nanopillars exhibit the highest adhesion under normal loading while stepwise and pencil-like nanopillars exhibit lower normal adhesion strength due to significant deformation of the pillars that occurs with increasing indentation depth. Contrary to the previous studies, here, we show that pencil-like nanopillars exhibit the highest shear adhesion strength at all indentation depths among three types of nanopillar arrays and that the shear adhesion increases with greater indentation depth due to the higher bending stiffness and closer packing of the pencil-like nanopillar array. Finite element simulations are used to elucidate the deformation of the pillars during the sliding experiments and agree with the nanoindentation-based sliding measurements. The experiments and finite element simulations together demonstrate that the shape of the nanopillars plays a key role in shear adhesion and that the mechanism is quite different from that of adhesion under normal loading.

  6. Measurement of the temperature-dependent threshold shear-stress of red blood cell aggregation.

    Science.gov (United States)

    Lim, Hyun-Jung; Nam, Jeong-Hun; Lee, Yong-Jin; Shin, Sehyun

    2009-09-01

    Red blood cell (RBC) aggregation is becoming an important hemorheological parameter, which typically exhibits temperature dependence. Quite recently, a critical shear-stress was proposed as a new dimensional index to represent the aggregative and disaggregative behaviors of RBCs. The present study investigated the effect of the temperature on the critical shear-stress that is required to keep RBC aggregates dispersed. The critical shear-stress was measured at various temperatures (4, 10, 20, 30, and 37 degrees C) through the use of a transient microfluidic aggregometry. The critical shear-stress significantly increased as the blood temperature lowered, which accorded with the increase in the low-shear blood viscosity with the lowering of the temperature. Furthermore, the critical shear-stress also showed good agreement with the threshold shear-stress, as measured in a rotational Couette flow. These findings assist in rheologically validating the critical shear-stress, as defined in the microfluidic aggregometry.

  7. Nonlinear interaction of Rayleigh--Taylor and shear instabilities

    International Nuclear Information System (INIS)

    Finn, J.M.

    1993-01-01

    Results on the nonlinear behavior of the Rayleigh--Taylor instability and consequent development of shear flow by the shear instability [Phys. Fluids B 4, 488 (1992)] are presented. It is found that the shear flow is generated at sufficient amplitude to reduce greatly the convective transport. For high viscosity, the time-asymptotic state consists of an equilibrium with shear flow and vortex flow (with islands, or ''cat's eyes''), or a relaxation oscillation involving an interplay between the shear instability and the Rayleigh--Taylor instability in the presence of shear. For low viscosity, the dominant feature is a high-frequency nonlinear standing wave consisting of convective vortices localized near the top and bottom boundaries. The localization of these vortices is due to the smaller shear near the boundary regions. The convective transport is largest around these convective vortices near the boundary and there is a region of good confinement near the center. The possible relevance of this behavior to the H mode and edge-localized modes (ELM's) in the tokamak edge region is discussed

  8. Shear layer characteristics of supersonic free and impinging jets

    Science.gov (United States)

    Davis, T. B.; Kumar, R.

    2015-09-01

    The initial shear layer characteristics of a jet play an important role in the initiation and development of instabilities and hence radiated noise. Particle image velocimetry has been utilized to study the initial shear layer development of supersonic free and impinging jets. Microjet control employed to reduce flow unsteadiness and jet noise appears to affect the development of the shear layer, particularly near the nozzle exit. Velocity field measurements near the nozzle exit show that the initially thin, uncontrolled shear layer develops at a constant rate while microjet control is characterized by a rapid nonlinear thickening that asymptotes downstream. The shear layer linear growth rate with microjet control, in both the free and the impinging jet, is diminished. In addition, the thickened shear layer with control leads to a reduction in azimuthal vorticity for both free and impinging jets. Linear stability theory is used to compute unstable growth rates and convection velocities of the resultant velocity profiles. The results show that while the convection velocity is largely unaffected, the unstable growth rates are significantly reduced over all frequencies with microjet injection. For the case of the impinging jet, microjet control leads to near elimination of the impingement tones and an appreciable reduction in broadband levels. Similarly, for the free jet, significant reduction in overall sound pressure levels in the peak radiation direction is observed.

  9. Measurement of viscosity of slush at high shear rates

    OpenAIRE

    小林, 俊一; 川村, 公之; 津川, 圭一; 和泉, 薫; Kobayashi, Shun'ichi; Kawamura, Kimiyuki; Tugawa, Keiichi; Izumi, Kaoru

    1988-01-01

    Measurements of viscosity of slush were carried out using a method of flow along an inclined smooth surface in a 0℃cold room. The method was used to get the values of viscosity under high shear rates (25 and 75s^). From our experiments two important results were obtained: 1) the viscosity of slush decreases with increasing shear rates; 2) The fluid behavior is pseudoplastic that the values of non-Newtonian index of viscosity were less than unity.

  10. Shear-induced chaos

    International Nuclear Information System (INIS)

    Lin, Kevin K; Young, Lai-Sang

    2008-01-01

    Guided by a geometric understanding developed in earlier works of Wang and Young, we carry out numerical studies of shear-induced chaos in several parallel but different situations. The settings considered include periodic kicking of limit cycles, random kicks at Poisson times and continuous-time driving by white noise. The forcing of a quasi-periodic model describing two coupled oscillators is also investigated. In all cases, positive Lyapunov exponents are found in suitable parameter ranges when the forcing is suitably directed

  11. Shear-induced chaos

    Science.gov (United States)

    Lin, Kevin K.; Young, Lai-Sang

    2008-05-01

    Guided by a geometric understanding developed in earlier works of Wang and Young, we carry out numerical studies of shear-induced chaos in several parallel but different situations. The settings considered include periodic kicking of limit cycles, random kicks at Poisson times and continuous-time driving by white noise. The forcing of a quasi-periodic model describing two coupled oscillators is also investigated. In all cases, positive Lyapunov exponents are found in suitable parameter ranges when the forcing is suitably directed.

  12. Bolt Shear Force Sensor

    Science.gov (United States)

    2015-03-12

    0030] FIG. 7 is an isometric view of a deformable ring of the bolt shear force sensor of the present invention with an optical Attorney Docket No...102587 9 of 19 fiber having Bragg gratings wound around the ring; [0031] FIG. 8 is an isometric view of the deformable ring with wire strain... strength . [0047] Once the joint is subjected to an external load (see force arrows “F” and “F/2”); any frictional resistance to slip is overcome and

  13. The dynamic behavior of thin-film ionic transition metal complex-based light-emitting electrochemical cells

    Energy Technology Data Exchange (ETDEWEB)

    Meier, Sebastian B., E-mail: sebastian.meier@belectric.com, E-mail: wiebke.sarfert@siemens.com [Department of Materials Science VI: Materials for Electronics and Energy Technology, Friedrich-Alexander-University of Erlangen-Nuremberg, 91058 Erlangen (Germany); Siemens AG, Corporate Technology, CT RTC MAT IEC-DE, 91058 Erlangen (Germany); Hartmann, David; Sarfert, Wiebke, E-mail: sebastian.meier@belectric.com, E-mail: wiebke.sarfert@siemens.com [Siemens AG, Corporate Technology, CT RTC MAT IEC-DE, 91058 Erlangen (Germany); Winnacker, Albrecht [Department of Materials Science VI: Materials for Electronics and Energy Technology, Friedrich-Alexander-University of Erlangen-Nuremberg, 91058 Erlangen (Germany)

    2014-09-14

    Light-emitting electrochemical cells (LECs) have received increasing attention during recent years due to their simple architecture, based on solely air-stabile materials, and ease of manufacture in ambient atmosphere, using solution-based technologies. The LEC's active layer offers semiconducting, luminescent as well as ionic functionality resulting in device physical processes fundamentally different as compared with organic light-emitting diodes. During operation, electrical double layers (EDLs) form at the electrode interfaces as a consequence of ion accumulation and electrochemical doping sets in leading to the in situ development of a light-emitting p-i-n junction. In this paper, we comment on the use of impedance spectroscopy in combination with complex nonlinear squares fitting to derive key information about the latter events in thin-film ionic transition metal complex-based light-emitting electrochemical cells based on the model compound bis-2-phenylpyridine 6-phenyl-2,2´-bipyridine iridium(III) hexafluoridophosphate ([Ir(ppy)₂(pbpy)][PF₆]). At operating voltages below the bandgap potential of the ionic complex used, we obtain the dielectric constant of the active layer, the conductivity of mobile ions, the transference numbers of electrons and ions, and the thickness of the EDLs, whereas the transient thickness of the p-i-n junction is determined at voltages above the bandgap potential. Most importantly, we find that charge transport is dominated by the ions when carrier injection from the electrodes is prohibited, that ion movement is limited by the presence of transverse internal interfaces and that the width of the intrinsic region constitutes almost 60% of the total active layer thickness in steady state at a low operating voltage.

  14. Inductive shearing of drilling pipe

    Science.gov (United States)

    Ludtka, Gerard M.; Wilgen, John; Kisner, Roger; Mcintyre, Timothy

    2016-04-19

    Induction shearing may be used to cut a drillpipe at an undersea well. Electromagnetic rings may be built into a blow-out preventer (BOP) at the seafloor. The electromagnetic rings create a magnetic field through the drillpipe and may transfer sufficient energy to change the state of the metal drillpipe to shear the drillpipe. After shearing the drillpipe, the drillpipe may be sealed to prevent further leakage of well contents.

  15. Laser reflection method for determination of shear stress in low density transitional flows

    Science.gov (United States)

    Sathian, Sarith P.; Kurian, Job

    2006-03-01

    The details of laser reflection method (LRM) for the determination of shear stress in low density transitional flows are presented. The method is employed to determine the shear stress due to impingement of a low density supersonic free jet issuing out from a convergent divergent nozzle on a flat plate. The plate is smeared with a thin oil film and kept parallel to the nozzle axis. For a thin oil film moving under the action of aerodynamic boundary layer, the shear stress at the air-oil interface is equal to the shear stress between the surface and air. A direct and dynamic measurement of the oil film slope generated by the shear force is done using a position sensing detector (PSD). The thinning rate of the oil film is directly measured which is the major advantage of the LRM. From the oil film slope history, calculation of the shear stress is done using a three-point formula. The range of Knudsen numbers investigated is from 0.028 to 0.516. Pressure ratio across the nozzle varied from 3,500 to 8,500 giving highly under expanded free jets. The measured values of shear, in the overlapping region of experimental parameters, show fair agreement with those obtained by force balance method and laser interferometric method.

  16. Incorporation of amphiphilic ruthenium(II) ammine complexes into Langmuir-Blodgett thin films with switchable quadratic nonlinear optical behavior.

    Science.gov (United States)

    Boubekeur-Lecaque, Leïla; Coe, Benjamin J; Harris, James A; Helliwell, Madeleine; Asselberghs, Inge; Clays, Koen; Foerier, Stijn; Verbiest, Thierry

    2011-12-19

    Nine nonlinear optical (NLO) chromophores with pyridinium electron acceptors have been synthesized by complexing new proligands with {Ru(II)(NH(3))(5)}(2+) electron-donor centers. The presence of long alkyl/fluoroalkyl chain substituents imparts amphiphilic properties, and these cationic complexes have been characterized as their PF(6)(-) salts by using various techniques including electronic absorption spectroscopy and cyclic voltammetry. Each complex shows three reversible/quasireversible redox processes; a Ru(III/II) oxidation and two ligand-based reductions. The energies of the intense visible d → π* metal-to-ligand charge-transfer (MLCT) absorptions correlate to some extent with the ligand reduction potentials. (1)H NMR spectroscopy also provides insights into the relative electron-withdrawing strengths of the new ligands. Single crystal X-ray structures have been determined for two of the proligand salts and one complex salt, [Ru(II)(NH(3))(5)(4-C(16)H(33)PhQ(+))]Cl(3)·3.25H(2)O (PhQ(+) = N-phenyl-4,4'-bipyridinium), showing centrosymmetric packing structures in each case. The PF(6)(-) analogue of the latter complex has been used to deposit reproducibly high-quality, multilayered Langmuir-Blodgett (LB) thin films. These films show a strong second harmonic generation (SHG) response from a 1064 nm laser; their MLCT absorbance increases linearly with the number of layers (N) and I(2ω)/I(ω)(2) (I(2ω) = intensity at 532 nm; I(ω) = intensity at 1064 nm) scales quadratically with N, consistent with homogeneous deposition. LB films on indium tin oxide (ITO)-coated glass show electrochemically induced switching of the SHG response, with a decrease in activity of about 50% on Ru(II) → Ru(III) oxidation. This effect is reversible, but reproducible over only a few cycles before the signal from the Ru(II) species diminishes. This work extrapolates our original solution studies (Coe, B. J. et al. Angew. Chem., Int. Ed.1999, 38, 366) to the first demonstration of

  17. Behavior of Electrochemically Prepared CuInSe2 as Photovoltaic Absorber in thin Film Solar Cells

    International Nuclear Information System (INIS)

    Guillen, C; Martinez, M.A.; Dona, J. M.; Herrero, J; Gutierrez, M. T.

    2000-01-01

    Two different objectives have been pursued in the present investigation: 1) optimization of the CuInSe, preparation parameters from electrodeposited precursors, and 2) evaluation of their photovoltaic behavior by preparing and enhancing Mo/CuInSe,/CdS/TCO devices. When Cu-In-Se precursors are directly electrodeposited, the applied potential fit is essential to improve the photovoltaic performance. Suitable absorbers have been also obtained by evaporating an In layer onto electrodeposited Cu-Se precursors. In this case, the substrate temperature during evaporation determines the CuInSe, quality. Similar results have been reached by substituting typical Mo-coated glass substrates by flexible Mo foils. Different TCO tested (ZnO and ITO) have been found equivalent as front electrical contact in the devices. Solar cell performance can be improved by annealing in air at 200 degree centigree. (Author) 46 refs

  18. Shear strength of non-shear reinforced concrete elements

    DEFF Research Database (Denmark)

    Hoang, Cao linh

    1997-01-01

    The paper deals with the shear strength of prestressed hollow-core slabs determined by the theory of plasticity. Two failure mechanisms are considered in order to derive the solutions.In the case of sliding failure in a diagonal crack, the shear strength is determined by means of the crack sliding...

  19. Enhancement of shear strength and ductility for reinforced concrete wide beams due to web reinforcement

    Directory of Open Access Journals (Sweden)

    M. Said

    2013-12-01

    Full Text Available The shear behavior of reinforced concrete wide beams was investigated. The experimental program consisted of nine beams of 29 MPa concrete strength tested with a shear span-depth ratio equal to 3.0. One of the tested beams had no web reinforcement as a control specimen. The flexure mode of failure was secured for all of the specimens to allow for shear mode of failure. The key parameters covered in this investigation are the effect of the existence, spacing, amount and yield stress of the vertical stirrups on the shear capacity and ductility of the tested wide beams. The study shows that the contribution of web reinforcement to the shear capacity is significant and directly proportional to the amount and spacing of the shear reinforcement. The increase in the shear capacity ranged from 32% to 132% for the range of the tested beams compared with the control beam. High grade steel was more effective in the contribution of the shear strength of wide beams. Also, test results demonstrate that the shear reinforcement significantly enhances the ductility of the wide beams. In addition, shear resistances at failure recorded in this study are compared to the analytical strengths calculated according to the current Egyptian Code and the available international codes. The current study highlights the need to include the contribution of shear reinforcement in the Egyptian Code requirements for shear capacity of wide beams.

  20. Influence of structural disorder on low-temperature behavior of penetration depth in electron-doped high-TC thin films

    International Nuclear Information System (INIS)

    Lanfredi, A.J.C.; Sergeenkov, S.; Araujo-Moreira, F.M.

    2006-01-01

    To probe the influence of structural disorder on low-temperature behavior of magnetic penetration depth, λ(T), in electron-doped high-T C superconductors, a comparative study of high-quality Pr 1.85 Ce 0.15 CuO 4 (PCCO) and Sm 1.85 Ce 0.15 CuO 4 (SCCO) thin films is presented. The λ(T) profiles are extracted from conductance-voltage data using a highly-sensitive home-made mutual-inductance technique. The obtained results confirm a d-wave pairing mechanism in both samples (with nodal gap parameter Δ 0 /k B T C =2.0 and 2.1 for PCCO and SCCO films, respectively), substantially modified by impurity scattering (which is more noticeable in less homogeneous SCCO films) at the lowest temperatures. More precisely, Δλ(T)=λ(T)-λ(0) is found to follow the Goldenfeld-Hirschfeld interpolation formulae Δλ(T)/λ(0)=AT 2 /(T+T 0 ) with T 0 =ln(2)k B Γ 1/2 Δ 0 1/2 being the crossover temperature which demarcates pure and impure scattering processes (T 0 /T C =0.13 and 0.26 for PCCO and SCCO films, respectively). The value of the extracted impurity scattering rate Γ correlates with the quality of our samples and is found to be much higher in less homogeneous films with lower T C

  1. Temperature-dependent leakage current behavior of epitaxial Bi0.5Na0.5TiO3-based thin films made by pulsed laser deposition

    Science.gov (United States)

    Hejazi, M. M.; Safari, A.

    2011-11-01

    This paper discusses the electrical conduction mechanisms in a 0.88 Bi0.5Na0.5TiO3-0.08 Bi0.5K0.5TiO3-0.04 BaTiO3 thin film in the temperature range of 200-350 K. The film was deposited on a SrRuO3/SrTiO3 substrate by pulsed laser deposition technique. At all measurement temperatures, the leakage current behavior of the film matched well with the Lampert's triangle bounded by three straight lines of different slopes. The relative location of the triangle sides varied with temperature due to its effect on the density of charge carriers and un-filled traps. At low electric fields, the ohmic conduction governed the leakage mechanism. The calculated activation energy of the trap is 0.19 eV implying the presence of shallow traps in the film. With increasing the applied field, an abrupt increase in the leakage current was observed. This was attributed to a trap-filling process by the injected carriers. At sufficiently high electric fields, the leakage current obeyed the Child's trap-free square law suggesting the space charge limited current was the dominant mechanism.

  2. Investigating degradation behavior of InGaZnO thin-film transistors induced by charge-trapping effect under DC and AC gate bias stress

    International Nuclear Information System (INIS)

    Hsieh, Tien-Yu; Chang, Ting-Chang; Chen, Te-Chih; Tsai, Ming-Yen; Chen, Yu-Te

    2013-01-01

    This paper investigates the degradation mechanism of amorphous InGaZnO thin-film transistors under DC and AC gate bias stress. Comparing the degradation behavior at equal accumulated effective stress time, more pronounced threshold voltage shift under AC positive gate bias stress in comparison with DC stress indicates extra electron-trapping phenomenon that occurs in the duration of rising/falling time in pulse. Contrarily, illuminated AC negative gate bias stress exhibits much less threshold voltage shift than DC stress, suggesting that the photo-generated hole does not have sufficient time to drift to the interface of IGZO/gate insulator and causes hole-trapping under AC operation. Since the evolution of threshold voltage fits the stretched-exponential equation well, the different degradation tendencies under DC/AC stress can be attributed to the different electron- and hole-trapping efficiencies, and this is further verified by varying pulse waveform. - Highlights: ► Static and dynamic gate bias stresses are imposed on InGaZnO TFTs. ► Dynamic positive gate bias induces more pronounced threshold voltage shift. ► Static negative-bias illumination stress induces more severe threshold voltage shift. ► Evolution of threshold voltage fits the stretched-exponential equation well

  3. Behavior of Sn atoms in GeSn thin films during thermal annealing: Ex-situ and in-situ observations

    Science.gov (United States)

    Takase, Ryohei; Ishimaru, Manabu; Uchida, Noriyuki; Maeda, Tatsuro; Sato, Kazuhisa; Lieten, Ruben R.; Locquet, Jean-Pierre

    2016-12-01

    Thermally induced crystallization processes for amorphous GeSn thin films with Sn concentrations beyond the solubility limit of the bulk crystal Ge-Sn binary system have been examined by X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, and (scanning) transmission electron microscopy. We paid special attention to the behavior of Sn before and after recrystallization. In the as-deposited specimens, Sn atoms were homogeneously distributed in an amorphous matrix. Prior to crystallization, an amorphous-to-amorphous phase transformation associated with the rearrangement of Sn atoms was observed during heat treatment; this transformation is reversible with respect to temperature. Remarkable recrystallization occurred at temperatures above 400 °C, and Sn atoms were ejected from the crystallized GeSn matrix. The segregation of Sn became more pronounced with increasing annealing temperature, and the ejected Sn existed as a liquid phase. It was found that the molten Sn remains as a supercooled liquid below the eutectic temperature of the Ge-Sn binary system during the cooling process, and finally, β-Sn precipitates were formed at ambient temperature.

  4. Focus: Nucleation kinetics of shear bands in metallic glass.

    Science.gov (United States)

    Wang, J Q; Perepezko, J H

    2016-12-07

    The development of shear bands is recognized as the primary mechanism in controlling the plastic deformability of metallic glasses. However, the kinetics of the nucleation of shear bands has received limited attention. The nucleation of shear bands in metallic glasses (MG) can be investigated using a nanoindentation method to monitor the development of the first pop-in event that is a signature of shear band nucleation. The analysis of a statistically significant number of first pop-in events demonstrates the stochastic behavior that is characteristic of nucleation and reveals a multimodal behavior associated with local spatial heterogeneities. The shear band nucleation rate of the two nucleation modes and the associated activation energy, activation volume, and site density were determined by loading rate experiments. The nucleation activation energy is very close to the value that is characteristic of the β relaxation in metallic glass. The identification of the rate controlling kinetics for shear band nucleation offers guidance for promoting plastic flow in metallic glass.

  5. A Piezoelectric Shear Stress Sensor

    Science.gov (United States)

    Kim, Taeyang; Saini, Aditya; Kim, Jinwook; Gopalarathnam, Ashok; Zhu, Yong; Palmieri, Frank L.; Wohl, Christopher J.; Jiang, Xiaoning

    2016-01-01

    In this paper, a piezoelectric sensor with a floating element was developed for shear stress measurement. The piezoelectric sensor was designed to detect the pure shear stress suppressing effects of normal stress generated from the vortex lift-up by applying opposite poling vectors to the: piezoelectric elements. The sensor was first calibrated in the lab by applying shear forces and it showed high sensitivity to shear stress (=91.3 +/- 2.1 pC/Pa) due to the high piezoelectric coefficients of PMN-33%PT (d31=-1330 pC/N). The sensor also showed almost no sensitivity to normal stress (less than 1.2 pC/Pa) because of the electromechanical symmetry of the device. The usable frequency range of the sensor is 0-800 Hz. Keywords: Piezoelectric sensor, shear stress, floating element, electromechanical symmetry

  6. Effects of a Thin Ru-Doped PVP Interface Layer on Electrical Behavior of Ag/n-Si Structures

    Science.gov (United States)

    Badali, Yosef; Nikravan, Afsoun; Altındal, Şemsettin; Uslu, İbrahim

    2018-03-01

    The aim of this study is to improve the electrical property of Ag/n-Si metal-semiconductor (MS) structure by growing an Ru-doped PVP interlayer between Ag and n-Si using electrospinning technique. To illustrate the utility of the Ru-doped PVP interface layer, current-voltage (I-V) characteristics of Ag/n-Si (MS) and Ag/Ru-doped PVP/n-Si metal-polymer-semiconductor (MPS) structures was carried out. In addition, the main electrical parameters of the fabricated Ag/Ru-doped PVP/n-Si structures were investigated as a function of frequency and electric field using impedance spectroscopy method (ISM). The capacitance-voltage (C-V) plot showed an anomalous peak in the depletion region due to the special density distribution of interface traps/states (D it /N ss) and interlayer. Both the values of series resistance (R s) and N ss were drawn as a function of voltage and frequency between 0.5 kHz and 5 MHz at room temperature and they had a peak behavior in the depletion region. Some important parameters of the sample such as the donor concentration atoms (N D), Fermi energy (E F ), thickness of the depletion region (W D), barrier height (Φ B0 ) and R s were determined from the C -2 versus V plot for each frequency. The values of N D , W D , Φ B0 and R s were changed from 1 × 1015 cm-3, 9.61 × 10-5 cm, 0.94 eV and 19,055 Ω (at 0.5 kHz) to 0.13 × 1015 cm-3, 27.4 × 10-4 cm, 1.04 eV and 70 Ω (at 5 MHz), respectively. As a result of the experiments, it is observed that the change in electrical parameters becomes more effective at lower frequencies due to the N ss and their relaxation time (τ), dipole and surface polarizations.

  7. Formation of structural steady states in lamellar/sponge phase-separating fluids under shear flow

    Science.gov (United States)

    Panizza, P.; Courbin, L.; Cristobal, G.; Rouch, J.; Narayanan, T.

    2003-05-01

    We investigate the effect of shear flow on a lamellar-sponge phase-separating fluid when subjected to shear flow. We show the existence of two different steady states (droplets and ribbons structures) whose nature does not depend on the way to reach the two-phase unstable region of the phase diagram (temperature quench or stirring). The transition between ribbons and droplets is shear thickening and its nature strongly depends on what dynamical variable is imposed. If the stress is fixed, flow visualization shows the existence of shear bands at the transition, characteristic of coexistence in the cell between ribbons and droplets. In this shear-banding region, the viscosity oscillates. When the shear rate is fixed, no shear bands are observed. Instead, the transition exhibits a hysteretic behavior leading to a structural bi-stability of the phase-separating fluid under flow.

  8. The theoretical shear strength of fcc crystals under superimposed triaxial stress

    Energy Technology Data Exchange (ETDEWEB)

    Cerny, M., E-mail: cerny.m@fme.vutbr.cz [Institute of Engineering Physics, Faculty of Mechanical Engineering, Brno University of Technology, Technicka 2, CZ-616 69 Brno (Czech Republic); Pokluda, J. [Institute of Engineering Physics, Faculty of Mechanical Engineering, Brno University of Technology, Technicka 2, CZ-616 69 Brno (Czech Republic)

    2010-05-15

    The influence of a triaxial stress applied normally to shear planes and shear direction during affine shear deformation of face-centered cubic crystals on the theoretical shear strength is studied for the <112-bar >{l_brace}111{r_brace} shear system using first-principles methods. The applied relaxation procedure guarantees that the modeled system is subjected to a superposition of shear, normal and in-plane stresses with individually adjustable in-plane and normal stress values. The theoretical shear strengths of individual elements prove to be qualitatively different functions of the superimposed stresses. In the special case of hydrostatic loading, however, these functions are qualitatively uniform. This behavior is discussed in terms of the electronic structure.

  9. Shearing single crystal magnesium in the close-packed basal plane at different temperatures

    Science.gov (United States)

    Han, Ming; Li, Lili; Zhao, Guangming

    2018-05-01

    Shear behaviors of single crystal magnesium (Mg) in close-packed (0001) basal plane along the [ 1 bar 2 1 bar 0 ], [ 1 2 bar 10 ], [ 10 1 bar 0 ] and [ 1 bar 010 ] directions were studied using molecular dynamics simulations via EAM potential. The results show that both shear stress-strain curves along the four directions and the motion path of free atoms during shearing behave periodic characteristics. It reveals that the periodic shear displacement is inherently related to the crystallographic orientation in single crystal Mg. Moreover, different temperatures in a range from 10 to 750 K were considered, demonstrating that shear modulus decreases with increasing temperatures. The results agree well with the MTS model. It is manifested that the modulus is independent with the shear direction and the size of the atomic model. This work also demonstrates that the classical description of shear modulus is still effective at the nanoscale.

  10. Refined shear correction factor for very thick simply supported and uniformly loaded isosceles right triangular auxetic plates

    International Nuclear Information System (INIS)

    Lim, Teik-Cheng

    2016-01-01

    For moderately thick plates, the use of First order Shear Deformation Theory (FSDT) with a constant shear correction factor of 5/6 is sufficient to take into account the plate deflection arising from transverse shear deformation. For very thick plates, the use of Third order Shear Deformation Theory (TSDT) is preferred as it allows the shear strain distribution to be varied through the plate thickness. Therefore no correction factor is required in TSDT, unlike FSDT. Due to the complexity involved in TSDT, this paper obtains a more accurate shear correction factor for use in FSDT of very thick simply supported and uniformly loaded isosceles right triangular plates based on the TSDT. By matching the maximum deflections for this plate according to FSDT and TSDT, a variable shear correction factor is obtained. Results show that the shear correction factor for the simplified TSDT, i.e. 14/17, is least accurate. The commonly adopted shear correction factor of 5/6 in FSDT is valid only for very thin or highly auxetic plates. This paper provides a variable shear correction for FSDT deflection that matches the plate deflection by TSDT. This variable shear correction factor allows designers to justify the use of a commonly adopted shear correction factor of 5/6 even for very thick plates as long as the Poisson’s ratio of the plate material is sufficiently negative. (paper)

  11. Effect of temperature on the rheological properties with shear stress limit of iron oxide nanoparticle modified bentonite drilling muds

    Directory of Open Access Journals (Sweden)

    Ahmed S. Mohammed

    2017-09-01

    Full Text Available In this study, the effect of temperature on the rheological properties and weight loss of a water based bentonite drilling mud modified with iron oxide nanoparticle (nanoFe2O3 was investigated. The bentonite contents in the drilling muds were varied up to 6% by the weight of water and temperature was varied from 25 °C to 85 °C. The nanoFe2O3 content was varied between 0 and 1% by the weight of the drilling mud to modify the rheological properties of the drilling mud. The nanoFe2O3 and bentonite clay were characterized using the X-ray diffraction analysis (XRD and thermal gravimetric analysis (TGA. In the TGA study, the total weight loss at 800 °C for the bentonite decreased from 13% to 1.16%, a 91% reduction when the bentonite clay was mixed with 1% of nanoFe2O3. The results also showed that 1% of nanoFe2O3 increased the rheological properties of the drilling mud. The nanoFe2O3 modification increased the yield stress (τo and plastic viscosity (PV by 45–200% and 20–105% respectively based on the bentonite content and temperature of the drilling mud. The shear thinning behavior of the bentonite drilling mud with and without nanoFe2O3 has been quantified using the hyperbolic model and compared with three parameters Herschel–Bulkley model. The results showed that the hyperbolic model predicted the shear thinning relationship between the shear stress and shear strain rate of the nanoFe2O3 modified bentonite drilling mud very well. Also the hyperbolic model has a maximum shear stress limit whereas the Herschel–Bulkley model did not have a limit on the maximum shear stress. Based on the hyperbolic model the maximum shear stress for the 2%, 4% and 6% bentonite drilling muds without nanoFe2O3 at room temperature were 25 Pa, 35 Pa and 51 Pa respectively. The maximum shear stress for the 2%, 4% and 6% bentonite drilling muds modified with 1% nanoFe2O3 at 25 °C were 59 Pa, 84 Pa and 140 Pa respectively, hence an increase of 135–175

  12. A Novel Geometry for Shear Test Using Axial Tensile Setup

    Directory of Open Access Journals (Sweden)

    Sibo Yuan

    2018-05-01

    Full Text Available This paper studies a novel geometry for the in-plane shear test performed with an axial electromechanical testing machine. In order to investigate the influence of the triaxiality rate on the mechanical behavior, different tests will be performed on the studied material: simple tensile tests, large tensile tests and shear tests. For the whole campaign, a common equipment should be employed to minimize the impact of the testing device. As a consequence, for the shear tests, the geometry of the specimen must be carefully designed in order to adapt the force value and make it comparable to the one obtained for the tensile tests. Like most of the existing shear-included tensile test specimens, the axial loading is converted to shear loading at a particular region through the effect of geometry. A symmetric shape is generally preferred, since it can restrict the in-plane rotation of the shear section, keep shear increasing in a more monotonic path and double the force level thanks to the two shear zones. Due to the specific experimental conditions, such as dimensions of the furnace and the clamping system, the position of the extensometer or the restriction of sheet thickness (related to the further studies of size effect at mesoscale and hot temperature, several geometries were brought up and evaluated in an iterative procedure via finite element simulations. Both the numerical and experimental results reveal that the final geometry ensures some advantages. For instance, a relatively low triaxiality in the shear zone, limited in-plane rotation and no necking are observed. Moreover, it also prevents any out-of-plane displacement of the specimen which seems to be highly sensitive to the geometry, and presents a very limited influence of the material and the thickness.

  13. Ionic liquid nanotribology