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Sample records for shear band development

  1. Development of shear bands in amorphous-crystalline metallic alloys

    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

  2. Development of local shear bands and orientation gradients in fcc polycrystals

    Beaudoin, A.J. Jr.; Mecking, H.; Kocks, U.F.

    1995-01-01

    A finite element formulation which derives constitutive response from crystal plasticity theory is used to examine localized deformation in fcc polycrystals. The polycrystals are simple, idealized arrangements of grains. Localized deformations within individual grains lead to the development of domains that are separated by boundaries of high misorientation. Shear banding is seen to occur on a microscopic scale of grain dimensions. The important consequences of these simulations are that the predicted local inhomogeneities are meeting various requirements which make them possible nucleation sites for recrystallization

  3. Room Temperature Shear Band Development in Highly Twinned Wrought Magnesium AZ31B Sheet

    Scott, Jon; Miles, Michael; Fullwood, David; Adams, Brent; Khosravani, Ali; Mishra, Raja K.

    2013-01-01

    Failure mechanisms were studied in wrought AZ31B magnesium alloy after forming under different strain paths. Optical micrographs were used to observe the shear band formation and regions of high twin density in samples strained under uniaxial, biaxial, and plane strain conditions. Interrupted testing at 4 pct effective strain increments, until failure, was used to observe the evolution of the microstructure. The results showed that shear bands, with a high percentage of twinned grains, appeared early in the samples strained under biaxial or plane strain tension. These bands are similar to those seen in uniaxial tension specimens just prior to failure where the uniaxial tensile ductility was much greater than that observed for plane strain or biaxial tension conditions. A forming limit diagram for AZ31B, which was developed from the strain data, showed that plane strain and biaxial tension had very similar limit strains; this contrasts with materials like steel or aluminum alloys, which typically have greater ductility in biaxial tension compared to plane strain tension.

  4. Experimental study on the adiabatic shear bands

    Affouard, J.

    1984-07-01

    Four martensitic steels (Z50CDV5 steel, 28CND8 steel, 35NCDV16 steel and 4340 steel) with different hardness between 190 and 600 Hsub(B) (Brinell hardness), have been studied by means of dynamic compressive tests on split Hopkinson pressure bar. Microscopic observations show that the fracture are associated to the development of adiabatic shear bands (except 4340 steel with 190 Hsub(B) hardness). By means of tests for which the deformation is stopped at predetermined levels, the measurement of shear and hardness inside the band and the matrix indicates the chronology of this phenomenon: first the localization of shear, followed by the formation of adiabatic shear band and ultimatly crack initiation and propagation. These results correlated with few simulations by finite elements have permitted to suggest two mecanisms of deformation leading to the formation of adiabatic shear bands in this specific test [fr

  5. The dynamics of a shear band

    Giarola, Diana; Capuani, Domenico; Bigoni, Davide

    2018-03-01

    A shear band of finite length, formed inside a ductile material at a certain stage of a continued homogeneous strain, provides a dynamic perturbation to an incident wave field, which strongly influences the dynamics of the material and affects its path to failure. The investigation of this perturbation is presented for a ductile metal, with reference to the incremental mechanics of a material obeying the J2-deformation theory of plasticity (a special form of prestressed, elastic, anisotropic, and incompressible solid). The treatment originates from the derivation of integral representations relating the incremental mechanical fields at every point of the medium to the incremental displacement jump across the shear band faces, generated by an impinging wave. The boundary integral equations (under the plane strain assumption) are numerically approached through a collocation technique, which keeps into account the singularity at the shear band tips and permits the analysis of an incident wave impinging a shear band. It is shown that the presence of the shear band induces a resonance, visible in the incremental displacement field and in the stress intensity factor at the shear band tips, which promotes shear band growth. Moreover, the waves scattered by the shear band are shown to generate a fine texture of vibrations, parallel to the shear band line and propagating at a long distance from it, but leaving a sort of conical shadow zone, which emanates from the tips of the shear band.

  6. The brittle-viscous-plastic evolution of shear bands in the South Armorican Shear Zone

    Bukovská, Zita; Jeřábek, Petr; Morales, Luiz F. G.; Lexa, Ondrej; Milke, Ralf

    2014-05-01

    Shear bands are microscale shear zones that obliquely crosscut an existing anisotropy such as a foliation. The resulting S-C fabrics are characterized by angles lower than 45° and the C plane parallel to shear zone boundaries. The S-C fabrics typically occur in granitoids deformed at greenschist facies conditions in the vicinity of major shear zones. Despite their long recognition, mechanical reasons for localization of deformation into shear bands and their evolution is still poorly understood. In this work we focus on microscale characterization of the shear bands in the South Armorican Shear Zone, where the S-C fabrics were first recognized by Berthé et al. (1979). The initiation of shear bands in the right-lateral South Armorican Shear Zone is associated with the occurrence of microcracks crosscutting the recrystallized quartz aggregates that define the S fabric. In more advanced stages of shear band evolution, newly formed dominant K-feldspar, together with plagioclase, muscovite and chlorite occur in the microcracks, and the shear bands start to widen. K-feldspar replaces quartz by progressively bulging into the grain boundaries of recrystallized quartz grains, leading to disintegration of quartz aggregates and formation of fine-grained multiphase matrix mixture. The late stages of shear band development are marked by interconnection of fine-grained white mica into a band that crosscuts the original shear band matrix. In its extremity, the shear band widening may lead to the formation of ultramylonites. With the increasing proportion of shear band matrix from ~1% to ~12%, the angular relationship between S and C fabrics increases from ~30° to ~40°. The matrix phases within shear bands show differences in chemical composition related to distinct evolutionary stages of shear band formation. The chemical evolution is well documented in K-feldspar, where the albite component is highest in porphyroclasts within S fabric, lower in the newly formed grains within

  7. Introduction to the viewpoint set on shear bands

    Hutchinson, J.W.

    1984-01-01

    Recent work aimed at improving our understanding of shear banding and flow localization as modes of deformation and failure is summarized in the six viewpoint articles which follow. For the most part, the emphasis here is on the observation and analysis of shear banding in metals, but active efforts are also underway to understand the role of shear bands in the deformation and failure of soils and rocks. There is a tendency to regard shear bands as a failure mode, as indeed they often are. But extensive straining under highly constrained conditions such as rolling can give rise to profuse flow localization into shear bands which can be regarded as microscopic in the sense that their extent is on the scale of the grains rather than the overall dimensions of the block of material being deformed. Hatherly and Malin describe in detail the observation of such bands and emphasize that they should be considered as a mode of deformation under these circumstances. They relate the formation of the bands to microstructural aspects and discuss their role in the development of recrystallization textures. It will be clear from reading the articles in this viewpoint set that the beginnings of a quantitative theory of shear banding is in place. Continued progress will require parallel developments in constitutive theory and experimental observation. Moreover, basic questions remain to be explored related to the spatial development of the shear bands, their mutual interaction, their development into a failure mode, and how these are influenced by factors such as overall deformational constraint, rate of straining, and temperature

  8. Focus: Nucleation kinetics of shear bands in metallic glass.

    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.

  9. A Shear Banding Model for Penetration Calculations

    2000-04-01

    mechanism of strength reduction to zero within a shear band in three different steels, includ- ing AISI 4340 with RHC 44, which is reasonably similar to RHA...TECH LIB CHINA LAKE CA 93555-6001 CDR NAVAL SUR WAR CTR C S COFFEY PPARK FZERILLI CODE 4140 R K GARRET JR JMCKIRGAN TECH LIB 101 STRAUSS AVE

  10. Discrete Analysis of Damage and Shear Banding in Argillaceous Rocks

    Dinç, Özge; Scholtès, Luc

    2018-05-01

    A discrete approach is proposed to study damage and failure processes taking place in argillaceous rocks which present a transversely isotropic behavior. More precisely, a dedicated discrete element method is utilized to provide a micromechanical description of the mechanisms involved. The purpose of the study is twofold: (1) presenting a three-dimensional discrete element model able to simulate the anisotropic macro-mechanical behavior of the Callovo-Oxfordian claystone as a particular case of argillaceous rocks; (2) studying how progressive failure develops in such material. Material anisotropy is explicitly taken into account in the numerical model through the introduction of weakness planes distributed at the interparticle scale following predefined orientation and intensity. Simulations of compression tests under plane-strain and triaxial conditions are performed to clarify the development of damage and the appearance of shear bands through micromechanical analyses. The overall mechanical behavior and shear banding patterns predicted by the numerical model are in good agreement with respect to experimental observations. Both tensile and shear microcracks emerging from the modeling also present characteristics compatible with microstructural observations. The numerical results confirm that the global failure of argillaceous rocks is well correlated with the mechanisms taking place at the local scale. Specifically, strain localization is shown to directly result from shear microcracking developing with a preferential orientation distribution related to the orientation of the shear band. In addition, localization events presenting characteristics similar to shear bands are observed from the early stages of the loading and might thus be considered as precursors of strain localization.

  11. Strain gradient drives shear banding in metallic glasses

    Tian, Zhi-Li; Wang, Yun-Jiang; Chen, Yan; Dai, Lan-Hong

    2017-09-01

    Shear banding is a nucleation-controlled process in metallic glasses (MGs) involving multiple temporal-spatial scales, which hinders a concrete understanding of its structural origin down to the atomic scale. Here, inspired by the morphology of composite materials, we propose a different perspective of MGs as a hard particle-reinforced material based on atomic-scale structural heterogeneity. The local stable structures indicated by a high level of local fivefold symmetry (L5FS) act as hard "particles" which are embedded in the relatively soft matrix. We demonstrate this concept by performing atomistic simulations of shear banding in CuZr MG. A shear band is prone to form in a sample with a high degree of L5FS which is slowly quenched from the liquid. An atomic-scale analysis on strain and the structural evolution reveals that it is the strain gradient effect that has originated from structural heterogeneity that facilitates shear transformation zones (STZs) to mature shear bands. An artificial composite model with a high degree of strain gradient, generated by inserting hard MG strips into a soft MG matrix, demonstrates a great propensity for shear banding. It therefore confirms the critical role strain gradient plays in shear banding. The strain gradient effect on shear banding is further quantified with a continuum model and a mechanical instability analysis. These physical insights might highlight the strain gradient as the hidden driving force in transforming STZs into shear bands in MGs.

  12. Dilatancy induced ductile-brittle transition of shear band in metallic glasses

    Zeng, F.; Jiang, M. Q.; Dai, L. H.

    2018-04-01

    Dilatancy-generated structural disordering, an inherent feature of metallic glasses (MGs), has been widely accepted as the physical mechanism for the primary origin and structural evolution of shear banding, as well as the resultant shear failure. However, it remains a great challenge to determine, to what degree of dilatation, a shear banding will evolve into a runaway shear failure. In this work, using in situ acoustic emission monitoring, we probe the dilatancy evolution at the different stages of individual shear band in MGs that underwent severely plastic deformation by the controlled cutting technology. A scaling law is revealed that the dilatancy in a shear band is linearly related to its evolution degree. A transition from ductile-to-brittle shear bands is observed, where the formers dominate stable serrated flow, and the latter lead to a runaway instability (catastrophe failure) of serrated flow. To uncover the underlying mechanics, we develop a theoretical model of shear-band evolution dynamics taking into account an atomic-scale deformation process. Our theoretical results agree with the experimental observations, and demonstrate that the atomic-scale volume expansion arises from an intrinsic shear-band evolution dynamics. Importantly, the onset of the ductile-brittle transition of shear banding is controlled by a critical dilatation.

  13. Shear banding, discontinuous shear thickening, and rheological phase transitions in athermally sheared frictionless disks

    Vâgberg, Daniel; Olsson, Peter; Teitel, S.

    2017-05-01

    We report on numerical simulations of simple models of athermal, bidisperse, soft-core, massive disks in two dimensions, as a function of packing fraction ϕ , inelasticity of collisions as measured by a parameter Q , and applied uniform shear strain rate γ ˙. Our particles have contact interactions consisting of normally directed elastic repulsion and viscous dissipation, as well as tangentially directed viscous dissipation, but no interparticle Coulombic friction. Mapping the phase diagram in the (ϕ ,Q ) plane for small γ ˙, we find a sharp first-order rheological phase transition from a region with Bagnoldian rheology to a region with Newtonian rheology, and show that the system is always Newtonian at jamming. We consider the rotational motion of particles and demonstrate the crucial importance that the coupling between rotational and translational degrees of freedom has on the phase structure at small Q (strongly inelastic collisions). At small Q , we show that, upon increasing γ ˙, the sharp Bagnoldian-to-Newtonian transition becomes a coexistence region of finite width in the (ϕ ,γ ˙) plane, with coexisting Bagnoldian and Newtonian shear bands. Crossing this coexistence region by increasing γ ˙ at fixed ϕ , we find that discontinuous shear thickening can result if γ ˙ is varied too rapidly for the system to relax to the shear-banded steady state corresponding to the instantaneous value of γ ˙.

  14. Microstructural evolution of a model, shear-banding micellar solution during shear startup and cessation.

    López-Barrón, Carlos R; Gurnon, A Kate; Eberle, Aaron P R; Porcar, Lionel; Wagner, Norman J

    2014-04-01

    We present direct measurements of the evolution of the segmental-level microstructure of a stable shear-banding polymerlike micelle solution during flow startup and cessation in the plane of flow. These measurements provide a definitive, quantitative microstructural understanding of the stages observed during flow startup: an initial elastic response with limited alignment that yields with a large stress overshoot to a homogeneous flow with associated micellar alignment that persists for approximately three relaxation times. This transient is followed by a shear (kink) band formation with a flow-aligned low-viscosity band that exhibits shear-induced concentration fluctuations and coexists with a nearly isotropic band of homogenous, highly viscoelastic micellar solution. Stable, steady banding flow is achieved only after approximately two reptation times. Flow cessation from this shear-banded state is also found to be nontrivial, exhibiting an initial fast relaxation with only minor structural relaxation, followed by a slower relaxation of the aligned micellar fluid with the equilibrium fluid's characteristic relaxation time. These measurements resolve a controversy in the literature surrounding the mechanism of shear banding in entangled wormlike micelles and, by means of comparison to existing literature, provide further insights into the mechanisms driving shear-banding instabilities in related systems. The methods and instrumentation described should find broad use in exploring complex fluid rheology and testing microstructure-based constitutive equations.

  15. Edge-Induced Shear Banding in Entangled Polymeric Fluids.

    Hemingway, Ewan J; Fielding, Suzanne M

    2018-03-30

    Despite decades of research, the question of whether solutions and melts of highly entangled polymers exhibit shear banding as their steady state response to a steadily imposed shear flow remains controversial. From a theoretical viewpoint, an important unanswered question is whether the underlying constitutive curve of shear stress σ as a function of shear rate γ[over ˙] (for states of homogeneous shear) is monotonic, or has a region of negative slope, dσ/dγ[over ˙]<0, which would trigger banding. Attempts to settle the question experimentally via velocimetry of the flow field inside the fluid are often confounded by an instability of the free surface where the sample meets the outside air, known as "edge fracture." Here we show by numerical simulation that in fact even only very modest edge disturbances-which are the precursor of full edge fracture but might well, in themselves, go unnoticed experimentally-can cause strong secondary flows in the form of shear bands that invade deep into the fluid bulk. Crucially, this is true even when the underlying constitutive curve is monotonically increasing, precluding true bulk shear banding in the absence of edge effects.

  16. Dilatant shear band formation and diagenesis in calcareous, arkosic sandstones, Vienna Basin (Austria)

    Lommatzsch, Marco; Exner, Ulrike; Gier, Susanne; Grasemann, Bernhard

    2015-01-01

    The present study examines deformation bands in calcareous arkosic sands. The investigated units can be considered as an equivalent to the Matzen field in the Vienna Basin (Austria), which is one of the most productive oil reservoirs in central Europe. The outcrop exposes carbonate-free and carbonatic sediments of Badenian age separated by a normal fault. Carbonatic sediments in the hanging wall of the normal fault develop dilation bands with minor shear displacements (< 2 mm), whereas carbonate-free sediments in the footwall develop cataclastic shear bands with up to 70 cm displacement. The cataclastic shear bands show a permeability reduction up to 3 orders of magnitude and strong baffling effects in the vadose zone. Carbonatic dilation bands show a permeability reduction of 1-2 orders of magnitude and no baffling structures. We distinguished two types of deformation bands in the carbonatic units, which differ in deformation mechanisms, distribution and composition. Full-cemented bands form as dilation bands with an intense syn-kinematic calcite cementation, whereas the younger loose-cemented bands are dilatant shear bands cemented by patchy calcite and clay minerals. All analyzed bands are characterized by a porosity and permeability reduction caused by grain fracturing and cementation. The changed petrophysical properties and especially the porosity evolution are closely related to diagenetic processes driven by varying pore fluids in different diagenetic environments. The deformation band evolution and sealing capacity is controlled by the initial host rock composition. PMID:26300577

  17. B(M1) values in the band-crossing of shears bands in 197Pb

    Krücken, R.; Cooper, J. R.; Beausang, C. W.; Novak, J. R.; Dewald, A.; Klug, T.; Kemper, G.; von Brentano, P.; Carpenter, M.; Wiedenhöver, I.

    We present details of the band crossing mechanism of shears bands using the example of 197Pb. Absolute reduced matrix elements B(M1) were determined by means of a RDM lifetime measurement in one of the shears bands in 197Pb. The experiment was performed using the New Yale Plunger Device (NYPD) in conjunction with the Gammasphere array. Band mixing calculations on the basis of the semi-classical model of the shears mechanism are used to describe the transition matrix elements B(M1) and energies throughout the band-crossing regions. Good agreement with the data was obtained and the detailed composition of the states in the shears band are discussed.

  18. Experimental study of shear bands formation in a granular material

    Nguyen Thai Binh

    2017-01-01

    Full Text Available We present an experimental investigation of the formation of shear bands in a granular sample submitted to a biaxial test. Our principal result is the direct observation of the bifurcation at the origin of the localization process in the material. At the bifurcation, the shear band is spatially extended: we observe a breaking of symmetry without any sudden localization of the deformation in a narrow band. Our work thus allows to clearly distinguish different phenomena: bifurcation which is a ponctual event which occurs before the peak, localization which is a process that covers a range of deformation of several percents during which the peak occurs and finally stationary shear bands which are well-defined permanent structures that can be observed at the end of the localization process, after the peak.

  19. Shear bands as growing instabilities in viscoanelastic media with memory

    Marina Dolfin

    2013-09-01

    Full Text Available In this paper we investigate the critical conditions under which a small perturbation in an homogeneous continuum can possibly grows into a shear band instability. In particular, we analyze from a thermodynamical viewpoint the phenomenon of shear bands in viscoanelastic media with memory. It is emphasized, in the scientific literature, that the specific adopted rheology strongly affects the results so that a special attention has to be paid, also for engineering purposes, to the accuracy of the rheological model. Several well-known rheological model (for instance the so called Maxwell or Jeffreys media are particular cases of the general model we adopt in the paper to analyze shear bands. Instability conditions, giving rise to shear bands formation, are obtained by introducing small perturbations around an homogeneous deformation into the system of differential equations governing the problem of homogeneous deformations in the considered continuous medium; as a result a non-homogeneous linear dynamical system is obtained whose stability is analyzed. A research perspective in view of a possible comparison with experimental results is proposed; in particular the simple methodology proposed in the paper should be applied in view of using the phenomenon of the initiation of shear bands to calculate the thermomechanical coefficients of real materials.

  20. Numerical simulation of systems of shear bands in ductile metal with inclusions

    Plohr, JeeYeon N., E-mail: jplohr@lanl.gov; Plohr, Bradley J. [Los Alamos National Laboratory, Theoretical Division, Los Alamos, NM 87545 (United States)

    2016-02-15

    We develop a method for numerical simulations of high strain-rate loading of mesoscale samples of ductile metal with inclusions. Because of its small-scale inhomogeneity, the composite material is prone to localized shear deformation (adiabatic shear bands). This method employs the Generalized Method of Cells of Paley and Aboudi [Mech. Materials, vol. 14, pp. 127–139, 1992] to ensure that the micro mechanical behavior of the metal and inclusions is reflected properly in the behavior of the composite at the mesoscale. To find the effective plastic strain rate when shear bands are present, we extend and apply the analytic and numerical analysis of shear bands of Glimm, Plohr, and Sharp [Mech. Materials, vol. 24, pp. 31–41, 1996]. Our tests of the method focus on the stress/strain response in uniaxial-strain flow, both compressive and tensile, of depleted uranium metal containing silicon carbide inclusions. We use the Preston-Tonks-Wallace viscoplasticity model [J. Appl. Phys., vol. 93, pp. 211–220, 2003], which applies to the high strain-rate regime of an isotropic viscoplastic solid. In results, we verify the elevated temperature and thermal softening at shear bands in our simulations of pure DU and DU/SiC composites. We also note that in composites, due the asymmetry caused by the inclusions, shear band form at different times in different subcells. In particular, in the subcells near inclusions, shear band form much earlier than they do in pure DU.

  1. Numerical simulation of systems of shear bands in ductile metal with inclusions

    JeeYeon N. Plohr

    2016-02-01

    Full Text Available We develop a method for numerical simulations of high strain-rate loading of mesoscale samples of ductile metal with inclusions. Because of its small-scale inhomogeneity, the composite material is prone to localized shear deformation (adiabatic shear bands. This method employs the Generalized Method of Cells of Paley and Aboudi [Mech. Materials, vol. 14, pp. 127–139, 1992] to ensure that the micro mechanical behavior of the metal and inclusions is reflected properly in the behavior of the composite at the mesoscale. To find the effective plastic strain rate when shear bands are present, we extend and apply the analytic and numerical analysis of shear bands of Glimm, Plohr, and Sharp [Mech. Materials, vol. 24, pp. 31–41, 1996]. Our tests of the method focus on the stress/strain response in uniaxial-strain flow, both compressive and tensile, of depleted uranium metal containing silicon carbide inclusions. We use the Preston-Tonks-Wallace viscoplasticity model [J. Appl. Phys., vol. 93, pp. 211–220, 2003], which applies to the high strain-rate regime of an isotropic viscoplastic solid. In results, we verify the elevated temperature and thermal softening at shear bands in our simulations of pure DU and DU/SiC composites. We also note that in composites, due the asymmetry caused by the inclusions, shear band form at different times in different subcells. In particular, in the subcells near inclusions, shear band form much earlier than they do in pure DU.

  2. Structural mechanisms of formation of adiabatic shear bands

    Mikhail Sokovikov

    2016-10-01

    Full Text Available The paper focuses on the experimental and theoretical study of plastic deformation instability and localization in materials subjected to dynamic loading and high-velocity perforation. We investigate the behavior of samples dynamically loaded during Hopkinson-Kolsky pressure bar tests in a regime close to simple shear conditions. Experiments were carried out using samples of a special shape and appropriate test rigging, which allowed us to realize a plane strain state. Also, the shear-compression specimens proposed in were investigated. The lateral surface of the samples was investigated in a real-time mode with the aid of a high-speed infra-red camera CEDIP Silver 450M. The temperature field distribution obtained at different time made it possible to trace the evolution of plastic strain localization. Use of a transmission electron microscope for studying the surface of samples showed that in the regions of strain localization there are parts taking the shape of bands and honeycomb structure in the deformed layer. The process of target perforation involving plug formation and ejection was investigated using a high-speed infra-red camera. A specially designed ballistic set-up for studying perforation was used to test samples in different impulse loading regimes followed by plastic flow instability and plug ejection. Changes in the velocity of the rear surface at different time of plug ejection were analyzed by Doppler interferometry techniques. The microstructure of tested samples was analyzed using an optical interferometer-profilometer and a scanning electron microscope. The subsequent processing of 3D deformation relief data enabled estimation of the distribution of plastic strain gradients at different time of plug formation and ejection. It has been found that in strain localization areas the subgrains are elongated taking the shape of bands and undergo fragmentation leading to the formation of super-microcrystalline structure, in which the

  3. The possible mass region for shears bands and chiral doublets

    Meng, J [Institute of Physical and Chemical Research, Wako, Saitama (Japan); Frauendorf, S

    1998-03-01

    The Tilted Axis Cranking (TAC) theory is reviewed. The recent progress of TAC for triaxial deformed nuclei is reported. More emphasis has been paid to the new discovered phenomena - chiral doublets and their explanation. The possible mass region for the shears bands and chiral doublets and their experimental signature are discussed. (author)

  4. Spontaneous formation of densely packed shear bands of rotating fragments.

    Åström, J A; Timonen, J

    2012-05-01

    Appearance of self-similar space-filling ball bearings has been suggested to provide the explanation for seismic gaps, shear weakness, and lack of detectable frictional heat formation in mature tectonic faults (shear zones). As the material in a shear zone fractures and grinds, it could be thought to eventually form a conformation that allows fragments to largely roll against each other without much sliding. This type of space-filling "ball bearing" can be constructed artificially, but so far how such delicate structures may appear spontaneously has remained unexplained. It is demonstrated here that first-principles simulations of granular packing with fragmenting grains indeed display spontaneous formation of shear bands with fragment conformations very similar to those of densely packed ball bearings.

  5. Numerical simulation of systems of shear bands in ductile metal with inclusions

    Plohr, Jeeyeon

    2017-06-01

    We develop a method for numerical simulations of high strain-rate loading of mesoscale samples of ductile metal with inclusions. Because of its small-scale inhomogeneity, the composite material is prone to localized shear deformation. This method employs the Generalized Method of Cells to ensure that the micro mechanical behavior of the metal and inclusions is reflected properly in the behavior of the composite at the mesoscale. To find the effective plastic strain rate when shear bands are present, we extend and apply the analytic and numerical analysis of shear bands of Glimm, Plohr, and Sharp. Our tests of the method focus on the stress/strain response in uniaxial-strain flow, both compressive and tensile, of depleted uranium metal containing silicon carbide inclusions. In results, we verify the elevated temperature and thermal softening at shear bands in our simulations of pure DU and DU/SiC composites. We also note that in composites, due the asymmetry caused by the inclusions, shear band form at different times in different subcells. In particular, in the subcells near inclusions, shear band form much earlier than they do in pure DU.

  6. Adiabatic shear banding and scaling laws in chip formation with application to cutting of Ti-6Al-4V

    Molinari, A.; Soldani, X.; Miguélez, M. H.

    2013-11-01

    The phenomenon of adiabatic shear banding is analyzed theoretically in the context of metal cutting. The mechanisms of material weakening that are accounted for are (i) thermal softening and (ii) material failure related to a critical value of the accumulated plastic strain. Orthogonal cutting is viewed as a unique configuration where adiabatic shear bands can be experimentally produced under well controlled loading conditions by individually tuning the cutting speed, the feed (uncut chip thickness) and the tool geometry. The role of cutting conditions on adiabatic shear banding and chip serration is investigated by combining finite element calculations and analytical modeling. This leads to the characterization and classification of different regimes of shear banding and the determination of scaling laws which involve dimensionless parameters representative of thermal and inertia effects. The analysis gives new insights into the physical aspects of plastic flow instability in chip formation. The originality with respect to classical works on adiabatic shear banding stems from the various facets of cutting conditions that influence shear banding and from the specific role exercised by convective flow on the evolution of shear bands. Shear bands are generated at the tool tip and propagate towards the chip free surface. They grow within the chip formation region while being convected away by chip flow. It is shown that important changes in the mechanism of shear banding take place when the characteristic time of shear band propagation becomes equal to a characteristic convection time. Application to Ti-6Al-4V titanium are considered and theoretical predictions are compared to available experimental data in a wide range of cutting speeds and feeds. The fundamental knowledge developed in this work is thought to be useful not only for the understanding of metal cutting processes but also, by analogy, to similar problems where convective flow is also interfering with

  7. Analyzing shear band formation with high resolution X-ray diffraction

    Pagan, Darren C.; Obstalecki, Mark; Park, Jun-Sang; Miller, Matthew P.

    2018-04-01

    Localization of crystallographic slip into shear bands during uniaxial compression of a copper single crystal is studied using very far-field high-energy diffraction microscopy (vff-HEDM). Diffracted intensity was collected in-situ as the crystal deformed using a unique mobile detector stage that provided access to multiple diffraction peaks with high-angular resolution. From the diffraction data, single crystal orientation pole figures (SCPFs) were generated and are used to track the evolution of the distribution of lattice orientation that develops as slip localizes. To aid the identification of 'signatures' of shear band formation and analyze the SCPF data, a model of slip-driven lattice reorientation within shear bands is introduced. Confidence is built in conclusions drawn from the SCPF data about the character of internal slip localization through comparisons with strain fields on the sample surface measured simultaneously using digital image correlation. From the diffraction data, we find that the active slip direction and slip plane are not directly aligned with the orientation of the shear bands that formed. In fact, by extracting the underlying slip system activity from the SCPF data, we show that intersecting shear bands measured on the surface of the sample arise from slip primarily on the same underlying single slip system. These new vff-HEDM results raise significant questions on the use of surface measurements for slip system activity estimation. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  8. Shear banding in large strain plasticity - Influence of specimen dimensions

    Mucha, Marzena; Wcisło, Balbina; Pamin, Jerzy

    2018-01-01

    The paper deals with numerical analysis of shear banding which occurs in an elongated rectangular plate for a large strain elastic-plastic material model. It is focused on the influence of plate size proportions and finite element mesh density on numerical results. The discussion is limited to isothermal conditions and ideal plasticity. First a plain strain case is computed for different lengths of the plate, then simulations are repeated for plane stress for which different thicknesses of the plate are considered. Most of the computations are performed for three finite element meshes to verify discretization sensitivity of the results. The simulations are performed using AceGen and AceFEM packages for Wolfram Mathematica.

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

    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.

  10. Density changes in shear bands of a metallic glass determined by correlative analytical transmission electron microscopy

    Rösner, Harald, E-mail: rosner@uni-muenster.de [Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Strasse 10, D-48149 Münster (Germany); Peterlechner, Martin [Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Strasse 10, D-48149 Münster (Germany); Kübel, Christian [Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology (INT), Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany); Karlsruhe Nano Micro Facility (KNMF), Karlsruhe Institute of Technology (KIT), D-76344 Eggenstein-Leopoldshafen (Germany); Schmidt, Vitalij [Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Strasse 10, D-48149 Münster (Germany); Wilde, Gerhard [Institut für Materialphysik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Strasse 10, D-48149 Münster (Germany); Institute of Nanochemistry and Nanobiology, School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444 (China)

    2014-07-01

    Density changes between sheared zones and their surrounding amorphous matrix as a result of plastic deformation in a cold-rolled metallic glass (melt-spun Al{sub 88}Y{sub 7}Fe{sub 5}) were determined using high-angle annular dark-field (HAADF) detector intensities supplemented by electron-energy loss spectroscopy (EELS), energy-dispersive X-ray (EDX) and nano-beam diffraction analyses. Sheared zones or shear bands were observed as regions of bright or dark contrast arising from a higher or lower density relative to the matrix. Moreover, abrupt contrast changes from bright to dark and vice versa were found within individual shear bands. We associate the decrease in density mainly with an enhanced free volume in the shear bands and the increase in density with concomitant changes of the mass. This interpretation is further supported by changes in the zero loss and Plasmon signal originating from such sites. The limits of this new approach are discussed. - Highlights: • We describe a novel approach for measuring densities in shear bands of metallic glasses. • The linear relation of the dark-field intensity I/I{sub 0} and the mass thickness ρt was used. • Individual shear bands showed abrupt contrast changes from bright to dark and vice versa. • Density changes ranging from about −10% to +6% were found for such shear bands. • Mixtures of amorphous/medium range ordered domains were found within the shear bands.

  11. Experimental Investigation of Adiabatic Shear Banding at Different Impact Velocities

    1993-01-01

    plasticity and ASB’s is the Double-notch Shear specimen, it has been decided to use this concept in shear testing at medium and high strain rates...is the Double-notch Shear specimen. it has been decided to use this concept in shear testing at medium and high strain rates. Originally, Campbell...7] C. Fressengeas, Analyse dynamique 61asto-viscoplastique de l’h6tdrogdndit6 de la ddforma- tion plastique de cisalllement, Proc. Int. Conf. on

  12. Atomistic simulation study of the shear-band deformation mechanism in Mg-Cu metallic glasses

    Bailey, Nicholas; Schiøtz, Jakob; Jacobsen, Karsten Wedel

    2006-01-01

    We have simulated plastic deformation of a model Mg-Cu metallic glass in order to study shear banding. In uniaxial tension, we find a necking instability occurs rather than shear banding. We can force the latter to occur by deforming in plane strain, forbidding the change of length in one...... of the transverse directions. Furthermore, in most of the simulations a notch is used to initiate shear bands, which lie at a 45 degrees angle to the tensile loading direction. The shear bands are characterized by the Falk and Langer local measure of plastic deformation D-min(2), averaged here over volumes...... observe a slight decrease in density, up to 1%, within the shear band, which is consistent with notions of increased free volume or disorder within a plastically deforming amorphous material....

  13. Modeling of Metallic Glass Matrix Composites Under Compression: Microstructure Effect on Shear Band Evolution

    Jiang, Yunpeng; Qiu, Kun; Sun, Longgang; Wu, Qingqing

    2018-01-01

    The relationship among processing, microstructure, and mechanical performance is the most important for metallic glass matrix composites (MGCs). Numerical modeling was performed on the shear banding in MGCs, and the impacts of particle concentration, morphology, agglomerate, size, and thermal residual stress were revealed. Based on the shear damage criterion, the equivalent plastic strain acted as an internal state variable to depict the nucleation, growth, and coalescence of shear bands. The element deletion technique was employed to describe the process of transformation from shear band to micro-crack. The impedance effect of particle morphology on the propagation of shear bands was discussed, whereby the toughening mechanism was clearly interpreted. The present work contributes to the subsequent strengthening and toughening design of MGCs.

  14. Ordering fluctuations in a shear-banding wormlike micellar system

    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...

  15. Shear Strains, Strain Rates and Temperature Changes in Adiabatic Shear Bands

    1980-05-01

    X14A. It has been found that when bainitic and martensitic steels are sheared adiabatically, a layer of material within ths shear zone is altezed and...Sooiety for Metals, Metals Park, Ohio, 1978, pp. 148-0. 21 TABLE II SOLID-STATE TRANSFORMATIONS IN BAINITIC STEEL TRANSFORMATION TRANSFORMATION...shear, thermoplastic, plasticity, plastic deformation, armor, steel IL AnSRACT ( -=nba asoa.tm a naeoesM iN faity by bleak n bet/2972 Experiments

  16. The Formation and Evolution of Shear Bands in Plane Strain Compressed Nickel-Base Superalloy

    Bin Tang

    2018-02-01

    Full Text Available The formation and evolution of shear bands in Inconel 718 nickel-base superalloy under plane strain compression was investigated in the present work. It is found that the propagation of shear bands under plane strain compression is more intense in comparison with conventional uniaxial compression. The morphology of shear bands was identified to generally fall into two categories: in “S” shape at severe conditions (low temperatures and high strain rates and “X” shape at mild conditions (high temperatures and low strain rates. However, uniform deformation at the mesoscale without shear bands was also obtained by compressing at 1050 °C/0.001 s−1. By using the finite element method (FEM, the formation mechanism of the shear bands in the present study was explored for the special deformation mode of plane strain compression. Furthermore, the effect of processing parameters, i.e., strain rate and temperature, on the morphology and evolution of shear bands was discussed following a phenomenological approach. The plane strain compression attempt in the present work yields important information for processing parameters optimization and failure prediction under plane strain loading conditions of the Inconel 718 superalloy.

  17. Fourier band-power E/B-mode estimators for cosmic shear

    Becker, Matthew R.; Rozo, Eduardo

    2016-01-20

    We introduce new Fourier band-power estimators for cosmic shear data analysis and E/B-mode separation. We consider both the case where one performs E/B-mode separation and the case where one does not. The resulting estimators have several nice properties which make them ideal for cosmic shear data analysis. First, they can be written as linear combinations of the binned cosmic shear correlation functions. Secondly, they account for the survey window function in real-space. Thirdly, they are unbiased by shape noise since they do not use correlation function data at zero separation. Fourthly, the band-power window functions in Fourier space are compact and largely non-oscillatory. Fifthly, they can be used to construct band-power estimators with very efficient data compression properties. In particular, we find that all of the information on the parameters Ωm, σ8 and ns in the shear correlation functions in the range of ~10–400 arcmin for single tomographic bin can be compressed into only three band-power estimates. Finally, we can achieve these rates of data compression while excluding small-scale information where the modelling of the shear correlation functions and power spectra is very difficult. Given these desirable properties, these estimators will be very useful for cosmic shear data analysis.

  18. Microstructural evolution in adiabatic shear bands of copper at high strain rates: Electron backscatter diffraction characterization

    Tang Lin; Chen Zhiyong; Zhan Congkun; Yang Xuyue; Liu Chuming; Cai Hongnian

    2012-01-01

    The microstructural evolution of adiabatic shear bands in annealed copper with different large strains at high strain rates has been investigated by electron backscatter diffraction. The results show that mechanical twinning can occur with minimal contribution to shear localization under dynamic loading. Elongated ultrafine grains with widths of 100–300 nm are observed during the evolution of the adiabatic shear bands. A rotational dynamic recrystallization mechanism is proposed to explain the formation of the elongated ultrafine grains. - Highlights: ► The microstructural evolution of ASB is studied by electron backscatter diffraction. ► Twinning can occur in ASB while the contribution to shear localization is slight. ► Elongated ultrafine grains are observed during the evolution process of ASB. ► A possible mechanism is proposed to explain the microstructure evolution of ASB.

  19. Adiabatic shear bands as predictors of strain rate in high speed machining of ramax-2

    Zeb, M.A.; Irfan, M.A.; Velduis, A.C.

    2008-01-01

    Shear band formation was studied in the chips obtained by turning of stainless steel- Ramax-2 (AISI 420F). The machining was performed on a CNC lathe using a PVD (Physical Vapor Deposition) cutting tool insert. The cutting speeds ranged from 50 m/ min to 250 m/min. Dry cutting conditions were employed. At cutting speeds higher than 30 m/mill, the chip did not remain intact with the workpiece using quick stop device. It was difficult to get the chip root SEM (Scanning Electron Microscope) micrographs at further higher speeds. Therefore, the width of the shear bands was used as the predictor of the strain rates involved at various cutting speeds. The results showed that the strain rates are quite in agreement with the amount of strain rate found during machining of such types of stainless steels. It was also observed that shear band density increased with increasing cutting speed. (author)

  20. The effects of buoyancy on shear-induced melt bands in a compacting porous medium

    Butler, S. L.

    2009-03-01

    It has recently been shown [Holtzman, B., Groebner, N., Zimmerman, M., Ginsberg, S., Kohlstedt, D., 2003. Stress-driven melt segregation in partially molten rocks. Geochem. Geophys. Geosyst. 4, Art. No. 8607; Holtzman, B.K., Kohlstedt, D.L., 2007. Stress-driven melt segregation and strain partitioning in partially molten rocks: effects of stress and strain. J. Petrol. 48, 2379-2406] that when partially molten rock is subjected to simple shear, bands of high and low porosity are formed at a particular angle to the direction of instantaneous maximum extension. These have been modeled numerically and it has been speculated that high porosity bands may form an interconnected network with a bulk, effective permeability that is enhanced in a direction parallel to the bands. As a result, the bands may act to focus mantle melt towards the axis of mid-ocean ridges [Katz, R.F., Spiegelman, M., Holtzman, B., 2006. The dynamics of melt and shear localization in partially molten aggregates. Nature 442, 676-679]. In this contribution, we examine the combined effects of buoyancy and matrix shear on a deforming porous layer. The linear theory of Spiegelman [Spiegelman, M., 1993. Flow in deformable porous media. Part 1. Simple analysis. J. Fluid Mech. 247, 17-38; Spiegelman, M., 2003. Linear analysis of melt band formation by simple shear. Geochem. Geophys. Geosyst. 4, doi:10.1029/2002GC000499, Article 8615] and Katz et al. [Katz, R.F., Spiegelman, M., Holtzman, B., 2006. The dynamics of melt and shear localization in partially molten aggregates. Nature 442, 676-679] is generalized to include both the effects of buoyancy and matrix shear on a deformable porous layer with strain-rate dependent rheology. The predictions of linear theory are compared with the early time evolution of our 2D numerical model and they are found to be in excellent agreement. For conditions similar to the upper mantle, buoyancy forces can be similar to or much greater than matrix shear-induced forces. The

  1. Effects of texture on shear band formation in plane strain tension/compression and bending

    Kuroda, M.; Tvergaard, Viggo

    2007-01-01

    In this study, effects of typical texture components observed in rolled aluminum alloy sheets on shear band formation in plane strain tension/compression and bending are systematically studied. The material response is described by a generalized Taylor-type polycrystal model, in which each grain ...... shear band formation in bent specimens is compared to that in the tension/compression problem. Finally, the present results are compared to previous related studies, and the efficiency of the present method for materials design in future is discussed....

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

    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

  3. Analysis of shear band instabilities in sintered metals

    Redanz, Pia; Tvergaard, Viggo

    1999-01-01

    of a material instability. The elastic plastic behaviour of the material is represented by a material model, which combines the Gurson model, relevant to rather low porosities, with the FKM model, developed for high porosity powder compacts. Predictions are shown for various levels of initial porosity...

  4. Staircase bands in 105,107,109Ag: fingerprint of interplay between shears mechanism and collective rotation

    Das, B.; Rather, Niyaz; Datta, P.

    2015-01-01

    Shears mechanism in weakly deformed nuclei has been firmly established by numerous experimental observations since its inception by S. Fruaendorf in early nineties. On the contrary, the scope of Shears mode of excitation in moderately deformed nuclei is a less explored territory. The Shears mechanism is primarily identified in bands having strong M1 transitions with increasing energies as well as falling B(M1) rates as a function of angular momentum. On the other hand, the presence of M1 energy staggering in odd and odd-odd nuclei indicates that the signature is a good quantum number which corresponds to collective rotation. It is interesting to note that nuclei near Z=50 shell closure are moderately deformed as well as Shears structure develop at higher excitation with quasi-particles alignment. To be specific, the moderately deformed Ag nuclei are good candidates for such study as the high spin states are predominantly generated by the valance neutrons in low-Ω orbitals of h 11/2 and the valance protons in high-Ω orbitals of g 9/2 which forms a Shears structure

  5. Effect of pre-existing shear bands on the tensile mechanical properties of a bulk metallic glass

    Cao, Q.P.; Liu, J.W.; Yang, K.J.; Xu, F.; Yao, Z.Q.; Minkow, A.; Fecht, H.J.; Ivanisenko, J.; Chen, L.Y.; Wang, X.D.; Qu, S.X.; Jiang, J.Z.

    2010-01-01

    Bulk Zr 64.13 Cu 15.75 Ni 10.12 Al 10 metallic glass has been rolled at room temperature in two different directions, and the dependences of microstructure and tensile mechanical property on the degree of deformation and rolling directions have been investigated. No deformation-induced crystallization occurs except for shear bands. Shear band formation in conjugated directions is achieved in the specimen rolled in two directions, while rolling in one direction induces shear band formation only in a single direction. Pre-existing properly spaced soft inhomogeneities can stabilize shear bands and lead to tensile plastic strain, and the efficient intersection of shear bands in conjugated directions results in work-hardening behavior, which is further confirmed by in situ tensile scanning electron microscopic observation. Based on the experimental results obtained in two different specimen geometries and finite element analysis, it is deduced that a normal-stress-modified maximum shear stress criterion rather than a shear plane criterion can describe the conditions for the formation of shear bands in uniaxial tension.

  6. Analytical solution for shear bands in cold-rolled 1018 steel

    Voyiadjis, George Z.; Almasri, Amin H.; Faghihi, Danial; Palazotto, Anthony N.

    2012-06-01

    Cold-rolled 1018 (CR-1018) carbon steel has been well known for its susceptibility to adiabatic shear banding under dynamic loadings. Analysis of these localizations highly depends on the selection of the constitutive model. To deal with this issue, a constitutive model that takes temperature and strain rate effect into account is proposed. The model is motivated by two physical-based models: the Zerilli and Armstrong and the Voyiadjis and Abed models. This material model, however, incorporates a simple softening term that is capable of simulating the softening behavior of CR-1018 steel. Instability, localization, and evolution of adiabatic shear bands are discussed and presented graphically. In addition, the effect of hydrostatic pressure is illustrated.

  7. IR thermographic observation and shear bands plasticity analysis in Fe-based metallic glass

    Bouzakher, B.; Benameur, T.; Sidhom, H.

    2009-01-01

    Infrared thermography observation and in situ atomic force microscopy characterization were carried out to investigate the mechanical damage processes at the edge-notch region of large ribbons of Fe 78 Si 10 B 12 metallic glass. An obvious thermoelastic and inelastic degradation phenomenon was observed ahead at the notched region of the specimens, which probably result from free volume accumulation process and shear band activity during plane stress solicitations. Moreover, AFM topographic and frictional analysis of changes in the crack path during stable crack propagation regime revealed a periodic morphology evolution, formation of nanoscale damage cavity in the range of 20-140 nm and a maximum temperature rise ahead of the pre-crack tip was found in the order of 1.5 deg. C. The nanometer scaled shear offset, discreteness and shear bands density were determined. While these key parameters play a role in observing a large plastic zone in front of the crack, however they are unable to explain the distinct intrinsic ductility of some monolithic metallic glasses. A general Mohr-Coulomb-type constitutive description was used to deduce analytic expressions for prediction of the variation of hydrostatic component of the applied stress to the shear stress ratio as function of Poisson's ratio.

  8. High-Strain Rate Failure Modeling Incorporating Shear Banding and Fracture

    2017-11-22

    High Strain Rate Failure Modeling Incorporating Shear Banding and Fracture The views, opinions and/or findings contained in this report are those of...SECURITY CLASSIFICATION OF: 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 13. SUPPLEMENTARY NOTES 12. DISTRIBUTION AVAILIBILITY STATEMENT 6. AUTHORS...Report as of 05-Dec-2017 Agreement Number: W911NF-13-1-0238 Organization: Columbia University Title: High Strain Rate Failure Modeling Incorporating

  9. Microstructure evolution associated with adiabatic shear bands and shear band failure in ballistic plug formation in Ti-6Al-4V targets

    Murr, L.E.; Ramirez, A.C.; Gaytan, S.M.; Lopez, M.I.; Martinez, E.Y.; Hernandez, D.H.; Martinez, E.

    2009-01-01

    The microstructures and microstructure evolution associated with adiabatic shear band (ASB) formation in ballistic plugging in thick (2.5 cm) Ti-6Al-4V targets impacted by cylindrical, 4340 steel projectiles (2.0 cm in height) at impact velocities ranging from 633 m/s to 1027 m/s (just above the ballistic limit) were investigated by optical and transmission electron microscopy. ASB width increased from 10 μm to 21 μm as the velocity increased. ASB evolution was accompanied by the evolution of dark deformation bands composed of α' martensite platelets which increased in density with increasing impact velocity. The corresponding Vickers microindentation hardness also increased from HV 619 to HV 632 in contrast to the surrounding matrix microindentation hardness of HV 555. These deformation bands were not necessarily precursors to ASB formation. The ASB average Vickers microindentation hardness was essentially constant at HV 645, a 16% increase over the matrix. This constant microindentation hardness was characterized by a consistent DRX grain structure which varied from equiaxed, defect-free grains (∼2 μm diameter) to heavily dislocated, equiaxed grains. Cracks nucleating and propagating within the ABSs were observed to increase from 8% to 87% of the ASB length with increasing impact velocity.

  10. Numerical Simulation of Adiabatic Shear Bands in Ti-6Al-4V Alloy Due to Fragment Impact

    Fermen-Coker, Muege

    2004-01-01

    ... and lethality technologies for the Army's Future Combat Systems. Onset and propagation of adiabatic shear bands are investigated both experimentally and computationally by studying the ballistic impact of 20-mm steel fragments against Ti-6Al-4V plates...

  11. All you need is shape: Predicting shear banding in sand with LS-DEM

    Kawamoto, Reid; Andò, Edward; Viggiani, Gioacchino; Andrade, José E.

    2018-02-01

    This paper presents discrete element method (DEM) simulations with experimental comparisons at multiple length scales-underscoring the crucial role of particle shape. The simulations build on technological advances in the DEM furnished by level sets (LS-DEM), which enable the mathematical representation of the surface of arbitrarily-shaped particles such as grains of sand. We show that this ability to model shape enables unprecedented capture of the mechanics of granular materials across scales ranging from macroscopic behavior to local behavior to particle behavior. Specifically, the model is able to predict the onset and evolution of shear banding in sands, replicating the most advanced high-fidelity experiments in triaxial compression equipped with sequential X-ray tomography imaging. We present comparisons of the model and experiment at an unprecedented level of quantitative agreement-building a one-to-one model where every particle in the more than 53,000-particle array has its own avatar or numerical twin. Furthermore, the boundary conditions of the experiment are faithfully captured by modeling the membrane effect as well as the platen displacement and tilting. The results show a computational tool that can give insight into the physics and mechanics of granular materials undergoing shear deformation and failure, with computational times comparable to those of the experiment. One quantitative measure that is extracted from the LS-DEM simulations that is currently not available experimentally is the evolution of three dimensional force chains inside and outside of the shear band. We show that the rotations on the force chains are correlated to the rotations in stress principal directions.

  12. Effect of microstructure on the nucleation and initiation of adiabatic shear bands (ASBs) during impact

    Boakye Yiadom, Solomon, E-mail: boakyeys@cc.umanitoba.ca; Khaliq Khan, Abdul, E-mail: abdulkhaliq.khan@umanitoba.ca; Bassim, Nabil, E-mail: nabil.bassim@ad.umanitoba.ca

    2014-10-06

    While instability may occur homogenously during plastic deformation, the formation of adiabatic shear band (ASBs) does not follow a homogenous instability during impact. Geometrical stress concentration sites and/or microstructural inhomogeneities result in the nucleation and initiation of shear strain localization. In this study, initial microstructural inhomogeneity was found to produce nucleation sites for the initiation of ASBs. It was observed that double misfit interfaces and boundary layers with random arrangement of atomic columns are formed around precipitated carbides and they increase the volume fraction of dislocation sources within the specimens. The AISI 4340 steel specimens which were tempered at the lowest temperature had smaller precipitated carbides with high aspect ratios densely distributed within the matrix and were easily susceptible to the formation of ASBs. As the tempering temperature increased, the relative sizes of the carbides increased with a corresponding reduction in their aspect ratios and their distribution density within the matrix and thus were more resistant to the formation of ASBs. In this study, it is demonstrated that the intersection of an activated dislocation source with the direction of maximum shear (regions of stress concentrations) within the specimens during impact, is a necessary condition for the point of intersection to act as a possible site for the nucleation of ASBs, depending on the rate of dislocation generation, local strain and strain rate. At a constant carbide volume fraction, the higher susceptibility of the tempered specimens to the initiation of ASBs is attributed to the volume fraction of the points of intersection between activated dislocation sources and direction of maximum shear during impact. Additionally, the smaller carbides, with their higher aspect ratios and distribution densities, accentuate the effect of strain gradients and the microstructural inhomogeneities associated with the tempered

  13. A numerical model for adiabatic shear bands with application to a thick-walled cylinder in 304 stainless steel

    Liu, Mingtao; Li, Yongchi; Hu, Xiuzhang; Hu, Haibo

    2014-01-01

    The formation of an adiabatic shear band (ASB) experiences three stages: stable plastic flow, nucleation and a fluid-like stage. For different stages, the microstructures of the material undergo great changes. The mechanical behavior of the material in each stage has its own unique characteristics. To describe these characteristics, a multi-stage model for the shear band is proposed. For the stable plastic flow stage, a modified adiabatic J–C constitutive relationship is used. For the nucleation stage, the effects of work hardening and temperature softening are described by a power function of plastic strain. A Newtonian fluid model is used for the fluid-like stage. The formation of a shear band is an instability process. Various defects in the material are perturbation sources, which change the local yield stress. To describe the disturbances, a probability factor is introduced into the macroscopic constitutive relationship. The yield stress in the material is assumed to obey a Gaussian distribution. The multi-stage model combined with a probability factor is applied to simulate the rupture of thick-walled cylinder in 304 Stainless Steel (304SS). A close agreement is found between the simulation and experimental results, such as the failure mechanism, shear band spacing and propagating velocity of the shear band. By combining the experimental results with the simulation results, the importance of the nucleation stage is emphasized. (paper)

  14. Metallurgical analysis of a failed maraging steel shear screw used in the band separation system of a satellite launch vehicle

    S.V.S. Narayana Murty

    2016-10-01

    Full Text Available Maraging steels have excellent combination of strength and toughness and are extensively used for a variety of aerospace applications. In one such critical application, this steel was used to fabricate shear screws of a stage separation system in a satellite launch vehicle. During assembly preparations, one of the shear screws which connected the separation band and band end block has failed at the first thread. Microstructural analysis revealed that the crack originated from the root of the thread and propagated in an intergranular mode. The failure is attributed to combined effect of stress and corrosion leading to stress corrosion cracking.

  15. Compressive failure model for fiber composites by kink band initiation from obliquely aligned, shear-dislocated fiber breaks

    Bai, J.; Phoenix, S.L. [Cornell University, Ithaca, NY (United States). Dept. of Theoretical and Applied Mechanics

    2005-04-01

    Predicting compressive failure of a unidirectional fibrous composite is a longstanding and challenging problem that we study from a new perspective. Motivated by previous modelling of tensile failure as well as experimental observations on compressive failures in single carbon fibers, we develop a new micromechanical model for the compressive failure process in unidirectional, planar composites. As the compressive load is increased, random fiber failures are assumed to occur due to statistically distributed flaws, analogous to what occurs in tension. These breaks are often shear-mode failures with slanted surfaces that induce shear dislocations, especially when they occur in small groups aligned obliquely. Our model includes interactions of dislocated and neighboring intact fibers through a system of fourth-order, differential equations governing transverse deformation, and also allows for local matrix plastic yielding and debonding from the fiber near and within the dislocation arrays. Using the Discrete Fourier Transform method, we find a 'building-block' analytical solution form, which naturally embodies local length scales of fiber microbuckling and instability. Based on the influence function, superposition approach, a computationally efficient scheme is developed to model the evolution of fiber and matrix stresses. Under increasing compressive strain the simulations show that matrix yielding and debonding crucially lead to large increases in bending strains in fibers next to small groups of obliquely aligned, dislocated breaks. From the paired locations of maximum fiber bending in flanking fibers, the triggering of an unstable kink band becomes realistic. The geometric features of the kink band, such as the fragment lengths and orientation angles, will depend on the fiber and matrix mechanical and geometric properties. In carbon fiber-polymer matrix systems our model predicts a much lower compressive failure stress than obtained from Rosen

  16. The formation of PSB-like shear bands in cyclically deformed ultrafine grained copper processed by ECAP

    Wu, S.D.; Wang, Z.G.; Jiang, C.B.; Li, G.Y.; Alexandrov, I.V.; Valiev, R.Z

    2003-06-15

    Cyclic deformation was performed on ultrafine grained copper processed by ECAP. Shear bands (SBs) and adjacent microstructures were investigated using electron channeling contrast in scanning electron microscope. The possible formation mechanism of SB was discussed based on the characteristic distribution of defects introduced by ECAP.

  17. Experimental Study of the Composition and Structure of Granular Media in the Shear Bands Based on the HHC-Granular Model

    Guang-jin Wang

    2014-01-01

    Full Text Available The researchers cannot control the composition and structure of coarse grained soil in the indoor experiment because the granular particles of different size have the characteristics of random distribution and no sorting. Therefore, on the basis of the laboratory tests with the coarse grained soil, the HHC-Granular model, which could simulate the no sorting and random distribution of different size particles in the coarse-grained soil, was developed by use of cellular automata method. Meanwhile, the triaxial numerical simulation experiments of coarse grained soil were finished with the different composition and structure soil, and the variation of shear strength was discussed. The results showed that the internal friction angle was likely to reduce with the increasing of gravel contents in the coarse-grained soil, but the mean internal friction angle significantly increased with the increment of gravel contents. It indicated that the gravel contents of shear bands were the major factor affecting the shear strength.

  18. In vivo wall shear measurements within the developing zebrafish heart.

    R Aidan Jamison

    Full Text Available Physical forces can influence the embryonic development of many tissues. Within the cardiovascular system shear forces resulting from blood flow are known to be one of the regulatory signals that shape the developing heart. A key challenge in investigating the role of shear forces in cardiac development is the ability to obtain shear force measurements in vivo. Utilising the zebrafish model system we have developed a methodology that allows the shear force within the developing embryonic heart to be determined. Accurate wall shear measurement requires two essential pieces of information; high-resolution velocity measurements near the heart wall and the location and orientation of the heart wall itself. We have applied high-speed brightfield imaging to capture time-lapse series of blood flow within the beating heart between 3 and 6 days post-fertilization. Cardiac-phase filtering is applied to these time-lapse images to remove the heart wall and other slow moving structures leaving only the red blood cell movement. Using particle image velocimetry to calculate the velocity of red blood cells in different regions within the heart, and using the signal-to-noise ratio of the cardiac-phase filtered images to determine the boundary of blood flow, and therefore the position of the heart wall, we have been able to generate the necessary information to measure wall shear in vivo. We describe the methodology required to measure shear in vivo and the application of this technique to the developing zebrafish heart. We identify a reduction in shear at the ventricular-bulbar valve between 3 and 6 days post-fertilization and demonstrate that the shear environment of the ventricle during systole is constantly developing towards a more uniform level.

  19. In vivo wall shear measurements within the developing zebrafish heart.

    Jamison, R Aidan; Samarage, Chaminda R; Bryson-Richardson, Robert J; Fouras, Andreas

    2013-01-01

    Physical forces can influence the embryonic development of many tissues. Within the cardiovascular system shear forces resulting from blood flow are known to be one of the regulatory signals that shape the developing heart. A key challenge in investigating the role of shear forces in cardiac development is the ability to obtain shear force measurements in vivo. Utilising the zebrafish model system we have developed a methodology that allows the shear force within the developing embryonic heart to be determined. Accurate wall shear measurement requires two essential pieces of information; high-resolution velocity measurements near the heart wall and the location and orientation of the heart wall itself. We have applied high-speed brightfield imaging to capture time-lapse series of blood flow within the beating heart between 3 and 6 days post-fertilization. Cardiac-phase filtering is applied to these time-lapse images to remove the heart wall and other slow moving structures leaving only the red blood cell movement. Using particle image velocimetry to calculate the velocity of red blood cells in different regions within the heart, and using the signal-to-noise ratio of the cardiac-phase filtered images to determine the boundary of blood flow, and therefore the position of the heart wall, we have been able to generate the necessary information to measure wall shear in vivo. We describe the methodology required to measure shear in vivo and the application of this technique to the developing zebrafish heart. We identify a reduction in shear at the ventricular-bulbar valve between 3 and 6 days post-fertilization and demonstrate that the shear environment of the ventricle during systole is constantly developing towards a more uniform level.

  20. The Effect of Displacement Mode of Rigid Retaining Walls on Shearing Bands by Active Earth Pressure

    A. Sekkel

    2013-10-01

    Full Text Available This work treats the physical modeling of failure mechanisms by active earth pressure. This last is developed by retaining wall movement. A lot of research showed that wall displacement has a significant effect on active earth pressure. A good comprehension of active earth pressure phenomenon and its failure mechanisms help us to better conceive retaining walls. The conception of a small-scale model allowed the realization of active earth pressure tests, while displacing the mobile wall toward the outside of the massif. The studied material is that of Schneebeli; light two-dimensional material made of cylindrical plastic rollers, simulating granular non-cohesive soil. The evolution of shearing zones under continuous and discontinuous displacement modes of mobile walls by correlation pictures allows the investigation of the localization of deformations and failure mechanisms.

  1. Atomic structure of shear bands in Cu64Zr36 metallic glasses studied by molecular dynamics simulations

    Feng, Shidong; Qi, Li; Wang, Limin; Pan, Shaopeng; Ma, Mingzhen; Zhang, Xinyu; Li, Gong; Liu, Riping

    2015-01-01

    Graphical abstract: Figure shows that atoms in the shear band (SB) moved desultorily compared with those in the matrix. These atoms seriously interacted with each other similar to the grain boundary in crystalline materials. Figuratively, if these atoms wanted to “pass” the shear band, they should arrange their irritations. However, stress concentrations and high energy were observed in SB, which resulted in instability in the deformation process and finally led to a disastrously brittle fracture. - Abstract: Molecular dynamics simulations on the atomic structure of shear bands (SBs) in Cu 64 Zr 36 metallic glasses are presented. Results show that the atoms in the SB move desultorily, in contrast to those in the matrix. The saturated degree of bonded pairs considering the “liquid-like” character of SB quantitatively provides important details in extending earlier studies on SBs. Zr-centered 〈0, 2, 8, 5〉 clusters exhibit strong spatial correlations and tendency to connect with each other in short-range order. The 〈0, 2, 8, 5〉 cluster-type medium-range order is the main feature inside the SB relative to the matrix. The fractal results demonstrate the planar-like fashion of the 〈0, 2, 8, 5〉 network in SB, forming an interpenetrating solid-like backbone. Such heterogeneous structure provides a fundamental structural perspective of mechanical instability in SB

  2. Studies of Shear Band Velocity Using Spatially and Temporally Resolved Measurements of Strain During Quasistatic Compression of Bulk Metallic Glass

    Wright, W J; Samale, M; Hufnagel, T; LeBlanc, M; Florando, J

    2009-06-15

    We have made measurements of the temporal and spatial features of the evolution of strain during the serrated flow of Pd{sub 40}Ni{sub 40}P{sub 20} bulk metallic glass tested under quasistatic, room temperature, uniaxial compression. Strain and load data were acquired at rates of up to 400 kHz using strain gages affixed to all four sides of the specimen and a piezoelectric load cell located near the specimen. Calculation of the displacement rate requires an assumption about the nature of the shear displacement. If one assumes that the entire shear plane displaces simultaneously, the displacement rate is approximately 0.002 m/s. If instead one assumes that the displacement occurs as a localized propagating front, the velocity of the front is approximately 2.8 m/s. In either case, the velocity is orders of magnitude less than the shear wave speed ({approx}2000 m/s). The significance of these measurements for estimates of heating in shear bands is discussed.

  3. X-Band RF Gun Development

    Vlieks, A.E.

    2012-01-01

    In support of the MEGa-ray program at LLNL and the High Gradient research program at SLAC, a new X-band multi-cell RF gun is being developed. This gun, similar to earlier guns developed at SLAC for Compton X-ray source program, will be a standing wave structure made of 5.5 cells operating in the pi mode with copper cathode. This gun was designed following criteria used to build SLAC X-band high gradient accelerating structures. It is anticipated that this gun will operate with surface electric fields on the cathode of 200 MeV/m with low breakdown rate. RF will be coupled into the structure through a final cell with symmetric duel feeds and with a shape optimized to minimize quadrupole field components. In addition, geometry changes to the original gun, operated with Compton X-ray source, will include a wider RF mode separation, reduced surface electric and magnetic fields.

  4. Development of a shear force measurement dummy for seat comfort.

    Seong Guk Kim

    Full Text Available Seat comfort is one of the main factors that consumers consider when purchasing a car. In this study, we develop a dummy with a shear-force sensor to evaluate seat comfort. The sensor has dimensions of 25 mm × 25 mm × 26 mm and is made of S45C. Electroless nickel plating is employed to coat its surface in order to prevent corrosion and oxidation. The proposed sensor is validated using a qualified load cell and shows high accuracy and precision (measurement range: -30-30 N; sensitivity: 0.1 N; linear relationship: R = 0.999; transverse sensitivity: <1%. The dummy is manufactured in compliance with the SAE standards (SAE J826 and incorporates shear sensors into its design. We measure the shear force under four driving conditions and at five different speeds using a sedan; results showed that the shear force increases with speed under all driving conditions. In the case of acceleration and deceleration, shear force significantly changes in the lower body of the dummy. During right and left turns, it significantly changes in the upper body of the dummy.

  5. Development of a shear force measurement dummy for seat comfort.

    Kim, Seong Guk; Ko, Chang-Yong; Kim, Dong Hyun; Song, Ye Eun; Kang, Tae Uk; Ahn, Sungwoo; Lim, Dohyung; Kim, Han Sung

    2017-01-01

    Seat comfort is one of the main factors that consumers consider when purchasing a car. In this study, we develop a dummy with a shear-force sensor to evaluate seat comfort. The sensor has dimensions of 25 mm × 25 mm × 26 mm and is made of S45C. Electroless nickel plating is employed to coat its surface in order to prevent corrosion and oxidation. The proposed sensor is validated using a qualified load cell and shows high accuracy and precision (measurement range: -30-30 N; sensitivity: 0.1 N; linear relationship: R = 0.999; transverse sensitivity: <1%). The dummy is manufactured in compliance with the SAE standards (SAE J826) and incorporates shear sensors into its design. We measure the shear force under four driving conditions and at five different speeds using a sedan; results showed that the shear force increases with speed under all driving conditions. In the case of acceleration and deceleration, shear force significantly changes in the lower body of the dummy. During right and left turns, it significantly changes in the upper body of the dummy.

  6. The effect of liquid phase separation on the Vickers microindentation shear bands evolution in a Fe-based bulk metallic glass

    Askari-Paykani, M. [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, North Kargar Street, Tehran 11356-4563 (Iran, Islamic Republic of); Nili Ahmadabadi, M., E-mail: nili@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, North Kargar Street, Tehran 11356-4563 (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Seiffodini, A. [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, North Kargar Street, Tehran 11356-4563 (Iran, Islamic Republic of); Yazd University, Department of Material Science and Engineering, Yazd 84196 (Iran, Islamic Republic of)

    2013-11-15

    The Vickers microindentation experiments and associated plastic deformation in as-cast and annealed (Fe{sub 0.9}Ni{sub 0.1}){sub 77}Mo{sub 5}P{sub 9}C{sub 7.5}B{sub 1.5} bulk metallic glass was conducted. In addition to the bulk indentation behavior, the shear band morphology underneath the Vickers microindenter was examined by employing the bonded interface technique. Microstructural characterization revealed that a liquid phase separation occurred during melting process. Atomic force microscopy of the glassy matrix of the as-cast specimen reveals the composition inhomogeneity induced by the liquid phase separation. This effect generates shear band branching or deflection during the shear band propagation. For the bulk indentation, the trends in the hardness vs. indentation load were found related to the pressure sensitive index and the phase separation process simultaneously. The results show that the as-cast as well as the annealed specimens are deformed through semi-circular and radial shear bands. In addition, in the partially crystalized specimen, the change in the properties and microstructure of the BMG induced by the partial crystallization treatment and phase separation process resulted in tertiary shear bands formation.

  7. Lifetimes near the bandhead of a shears band in 198Pb

    Kruecken, R.; Kruecken, R.; Clark, R.M.; Deleplanque, M.A.; Diamond, R.M.; Fallon, P.; Lee, I.Y.; Macchiavelli, A.O.; Schmid, G.J.; Stephens, F.S.; Vetter, K.; Dewald, A.; Peusquens, R.; Brentano, P. von; Hauschild, K.

    1998-01-01

    Subpicosecond lifetimes of states near the bandhead of an M1 band in 198 Pb have been measured with the recoil-distance Doppler-shift technique using the Gammasphere array and the Cologne plunger. The deduced B(M1) values are in agreement with the predictions of the tilted axis cranking (TAC) model. Their spin dependence continues the trend set by recently published B(M1) values for the high spin states in this band. The emerging picture gives strong support to the concept of open-quotes magnetic rotation,close quotes an alternative mode for the generation of rotational spectra in nuclei. copyright 1998 The American Physical Society

  8. Shear-peel strength comparison of orthodontic band cements including novel calcium silicate

    Leo, Mariantonietta; Løvschall, Henrik

    calcium silicate with fluoride and fast-setting, Glass ionomer, and Zinc phosphate cement, used for luting of orthodontic bands on molars kept one month in phosphate buffering solution (PBS). Materials and methods: The roots of 35 extracted human molars were embedded in acryl. Three groups were allocated....... An orthodontic band (AO) was fitted on the free crown. Each group of the teeth (n>10) was cemented with novel calcium silicate (Protooth), Glass ionomer (Orthocem), or Zinc phosphate (DeTrey Zinc). The cements were mixed according to the manufacturers instructions. Samples were stored at 37ºC in humid chamber...... Silicate (Protooth) and Zinc phosphate cement (DeTrey Zinc) were significantly higher than Glass ionomer cement (Orthocem) when looking for the force (N, p

  9. Characterization of adiabatic shear bands in the zirconium alloy impacted by split Hopkinson pressure bar at a strain rate of 6000 s−1

    Zou, D.L.; Luan, B.F.; Liu, Q.; Chai, L.J.; Chen, J.W.

    2012-01-01

    The adiabatic shear bands formed in the zirconium alloy impacted by split Hopkinson pressure bar at a strain rate of about 6000 s −1 were characterized systemically by means of a high resolution field emission scanning electron microscope equipped with electron backscatter diffraction probe. The results show that the transformed bands were distinguished on the cross-section view of the impacted specimens, and the ultrafine and equiaxed grains formed in the transformed bands were confirmed. The gradient variation of the grains across the transformed bands from the boundary to the center of the bands was observed, and the grains at the center of the transformed bands were finer than other zones. Based on the characterization of the deformed microstructure adjacent to the transformed bands, the formation mechanism of the ultrafine and equiaxed grains in the transformed bands was revealed, and the rotational dynamic recrystallization mechanism should be responsible for the formation of the ultrafine and equiaxed grains in the transformed bands. According to the collection of the cumulative misorientation at different strain levels, the formation and evolution process of the ultrafine and equiaxed grains in the transformed bands were speculated. The microhardness measurements show that high microhardness value in the transformed bands was obtained because of the grain refining, and the large standard deviation of the microhardness at the center of the transformed bands was confirmed due to the gradient microstructural distribution in the bands.

  10. Development of softcopy environment for primary color banding visibility assessment

    Min, Byungseok; Pizlo, Zygmunt; Allebach, Jan P.

    2008-01-01

    Fine-pitch banding is one of the most unwanted artifacts in laser electrophotographic (EP) printers. It is perceived as a quasiperiodic fluctuation in the process direction. Therefore, it is essential for printer vendors to know how banding is perceived by humans in order to improve print quality. Monochrome banding has been analyzed and assessed by many researchers; but there is no literature that deals with the banding of color laser printers as measured from actual prints. The study of color banding is complicated by the fact that the color banding signal is physically defined in a three-dimensional color space, while banding perception is described in a one-dimensional sense such as more banding or less banding. In addition, the color banding signal arises from the independent contributions of the four primary colorant banding signals. It is not known how these four distinct signals combine to give rise to the perception of color banding. In this paper, we develop a methodology to assess the banding visibility of the primary colorant cyan based on human visual perception. This is our first step toward studying the more general problem of color banding in combinations of two or more colorants. According to our method, we print and scan the cyan test patch, and extract the banding profile as a one dimensional signal so that we can freely adjust the intensity of banding. Thereafter, by exploiting the pulse width modulation capability of the laser printer, the extracted banding profile is used to modulate a pattern consisting of periodic lines oriented in the process direction, to generate extrinsic banding. This avoids the effect of the halftoning algorithm on the banding. Furthermore, to conduct various banding assessments more efficiently, we also develop a softcopy environment that emulates a hardcopy image on a calibrated monitor, which requires highly accurate device calibration throughout the whole system. To achieve the same color appearance as the hardcopy

  11. Shear bands and anisotropy of the mechanical properties of an MA2-1pch magnesium alloy after equal-channel angular pressing

    Serebryany, V. N.; Khar'kova, M. A.; D'yakonov, G. S.; Kopylov, V. I.; Dobatkin, S. V.

    2017-10-01

    Effect of structure and texture on the anisotropy of the mechanical properties of the MA2-1pch magnesium alloy subjected to equal-channel angular pressing and subsequent annealing has been studied in two mutually perpendicular planes Y and X (along and across the pressing direction). The anisotropy of the mechanical properties is shown to be due to various orientations of shear bands and various types of texture inside the bands and outside them in planes X and Y.

  12. Development of Shear Connections in Steelconcrete Composite Structures

    Biegus, Antoni; Lorenc, Wojciech

    2015-03-01

    Different types of shear connectors and modelling techniques are presented. Basic research conducted or presented after year 2000 is taken into consideration, following the idea of concrete dowel implemented in the form of perfobond strip at the beginning of the 1980s by F. Leonhardt. The latest research in the field of continuous shear connectors applied in bridges is highlited with special focus at the composite dowel shear connection, as it seems to be the most modern solution being strongly introduced to the industry. Final shape of composite dowel shear connection is presented.

  13. Synergistic effects of the safety factor and shear flows on development of internal transport barriers in reversed shear plasmas

    Wang, A.K.; Dong, J.Q.; Qu, W.X.; Qiu, X.M.

    2002-01-01

    A new suppression mechanism of turbulent transport, characteristic of the synergism between safety factor and shear flows, is proposed to explain the internal transport barriers (ITBs) observed in neutral-beam-heated tokamak discharges with reversed magnetic shear. It is shown that the evolution of turbulent transport with the strength of the suppression mechanism reproduces the basic features of the formation and development of ITBs observed in experiments. In addition, the present analyses predict the possibility of global ion and electron heat transport barriers

  14. Magnetic structure of deformation-induced shear bands in amorphous Fe{sub 80}B{sub 16}Si{sub 4} observed by magnetic force microscopy

    Brown, G.W. [Center for Materials Science, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Hawley, M.E. [Materials Science and Technology Division, (MST-8), Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Markiewicz, D.J. [Department of Chemistry, Princeton University, Princeton, New Jersey 08544 (United States); Spaepen, F.; Barth, E.P. [Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States)

    1999-04-01

    Processing-induced magnetic structures in amorphous metallic alloys are of interest because of their impact on the performance of materials used in electric device applications. Plastic deformation associated with cutting or bending the material to the desired shape occurs through the formation of shear bands. The stress associated with these shear bands induces magnetic domains that can lead to power losses through interaction with the fields and currents involved in normal device operation. These domains have been studied previously using a variety of techniques capable of imaging magnetic domain structures. In an effort to better characterize and understand these issues, we have applied atomic and magnetic force microscopy to these materials to provide three-dimensional nanometer-scale topographic resolution and micrometer-scale magnetic resolution. {copyright} {ital 1999 American Institute of Physics.}

  15. The occurrence of shear banding in a millimeter scale (12-bar3)[634] grain of an Al-4.5% Mg alloy during plane strain compression

    Chapelle, David; Darrieulat, Michel

    2003-01-01

    The appearance of localization in shear bands during plane strain compression (PSC) of an Al-4.5% Mg alloy is investigated, with emphasis on a millimeter scale S-orientated grain in the longitudinal section of the specimen, upon which a gold microgrid was deposited. In order to justify this focus, attention is also paid on smaller grains of other areas. The microgrid technique allows the local strain field at various steps of deformation to be followed and in-plane components to be plotted over the selected region. Electron back scattered diffraction analysis was also used to gain an insight into the crystallography of local lattice rotations. One can then predict the potentially activated slip systems according to the Schmid law with Taylor's hypothesis, and assert the initial crystallographic feature of shear banding. This provides the opportunity to gain a more complete understanding, assuming a grain scale effect, of the mechanisms involved in the occurrence of shear banding in this alloy, and to reveal its influence on the rolling texture

  16. Model Development for MODIS Thermal Band Electronic Crosstalk

    Chang, Tiejun; Wu, Aisheng; Geng, Xu; Li, Yonghonh; Brinkman, Jake; Keller, Graziela; Xiong, Xiaoxiong

    2016-01-01

    MODerate-resolution Imaging Spectroradiometer (MODIS) has 36 bands. Among them, 16 thermal emissive bands covering a wavelength range from 3.8 to 14.4 m. After 16 years on-orbit operation, the electronic crosstalk of a few Terra MODIS thermal emissive bands developed substantial issues that cause biases in the EV brightness temperature measurements and surface feature contamination. The crosstalk effects on band 27 with center wavelength at 6.7 m and band 29 at 8.5 m increased significantly in recent years, affecting downstream products such as water vapor and cloud mask. The crosstalk effect is evident in the near-monthly scheduled lunar measurements, from which the crosstalk coefficients can be derived. The development of an alternative approach is very helpful for independent verification.In this work, a physical model was developed to assess the crosstalk impact on calibration as well as in Earth view brightness temperature retrieval. This model was applied to Terra MODIS band 29 empirically to correct the Earth brightness temperature measurements. In the model development, the detectors nonlinear response is considered. The impact of the electronic crosstalk is assessed in two steps. The first step consists of determining the impact on calibration using the on-board blackbody (BB). Due to the detectors nonlinear response and large background signal, both linear and nonlinear coefficients are affected by the crosstalk from sending bands. The second step is to calculate the effects on the Earth view brightness temperature retrieval. The effects include those from affected calibration coefficients and the contamination of Earth view measurements. This model links the measurement bias with crosstalk coefficients, detector non-linearity, and the ratio of Earth measurements between the sending and receiving bands. The correction of the electronic cross talk can be implemented empirically from the processed bias at different brightness temperature. The implementation

  17. Experimental investigation of edge sheared flow development and configuration effects in the TJ-II stellarator

    Pedrosa, M.A.; Hidalgo, C.; Alonso, A.; Calderon, E.; Orozco, O.; Pablos, J.L. de

    2005-01-01

    Experimental results have shown that the generation of spontaneous perpendicular sheared flow (i.e. the naturally occurring shear layer) requires a minimum plasma density or gradient in the TJ-II stellarator. This finding has been observed by means of multiple plasma diagnostics, including probes, fast cameras, reflectometry and HIBP. The obtained shearing rate of the naturally occurring shear layer results in general comparable to the one observed during biasing-improved confinement regimes. It has been found that there is a coupling between the onset of sheared flow development and an increase in the level of plasma edge fluctuations pointing to turbulence as the main ingredient of the radial electric field drive; once the shear flow develops the level of turbulence tends to decrease. The link between the development of sheared flows and plasma density in TJ-II has been observed in different magnetic configurations and plasma regimes. Preliminary results show that the threshold density value depends on the iota value and on the magnetic ripple (plasma volume). Recent experiments carried out in the LHD stellarator have shown that edge sheared flows are also affected by the magnitude of edge magnetic ripple: the threshold density to trigger edge sheared flows increases with magnetic ripple . Those results have been interpreted as an evidence of the importance of neoclassical effect in the physics of ExB sheared flows. For some TJ-II magnetic configurations with higher edge iota (ι/2π≥ 1.8) there is a sharp increase in the edge density gradient simultaneous to a strong reduction of fluctuations and transport and a slight increase of the shearing rate and perpendicular rotation (≥2 km/s) as density increases above the threshold. The role of the edge ripple, the presence of edge rational surfaces and properties of turbulent transport are considered as possible ingredients to explain the spontaneous development of edge sheared flows in TJ-II. (author)

  18. Broad band tunable dye laser development

    Lee, Jong Min; Kim, Jung Bog; Kim, Sung Ho; Go, Do Kyung; Lim, Chang Hwan; Rho, Si Pyo; Song, Kyu Seok; Lee, Byung Cheol; Rhi, Jong Hoon; Han, Jae Min; Cha, Hyung Ki; Cha, Byung Hun; Jeong, Do Yung; Han, Jae Min; Jung, Yeu Chang; Im, Ho; Yoo, Choon Sun; Jung, Byung Ik; Seok, Gum Sook

    1992-12-01

    The technical goal and objectives are the development of a tunable laser which can be tuned from UV to near IR and commercialization for uses in various fields. Two kinds of resonators are developed. User can select one resonator and change into the other without changing other parts. GIM type has a linewidth of 5GHz which is able to be used usually, and SLM type is very narrow linewidth of less than 1GHz. Each system can have one or two amplifiers depending on output power or cost. High stability and safety, cost-down, and modules into about 30 components have been tried. We hope that this laser can help developments in researches of university, industry, and institute. (Author)

  19. Development of Shear Capacity Prediction Model for FRP-RC Beam without Web Reinforcement

    Md. Arman Chowdhury

    2016-01-01

    Full Text Available Available codes and models generally use partially modified shear design equation, developed earlier for steel reinforced concrete, for predicting the shear capacity of FRP-RC members. Consequently, calculated shear capacity shows under- or overestimation. Furthermore, in most models some affecting parameters of shear strength are overlooked. In this study, a new and simplified shear capacity prediction model is proposed considering all the parameters. A large database containing 157 experimental results of FRP-RC beams without shear reinforcement is assembled from the published literature. A parametric study is then performed to verify the accuracy of the proposed model. Again, a comprehensive review of 9 codes and 12 available models is done, published back from 1997 to date for comparison with the proposed model. Hence, it is observed that the proposed equation shows overall optimized performance compared to all the codes and models within the range of used experimental dataset.

  20. Development of in-situ rock shear test under low compressive to tensile normal stress

    Nozaki, Takashi; Shin, Koichi

    2003-01-01

    The purpose of this study is to develop an in-situ rock shear testing method to evaluate the shear strength under low normal stress condition including tensile stress, which is usually ignored in the assessment of safety factor of the foundations for nuclear power plants against sliding. The results are as follows. (1) A new in-situ rock shear testing method is devised, in which tensile normal stress can be applied on the shear plane of a specimen by directly pulling up a steel box bonded to the specimen. By applying the counter shear load to cancel the moment induced by the main shear load, it can obtain shear strength under low normal stress. (2) Some model tests on Oya tuff and diatomaceous mudstone have been performed using the developed test method. The shear strength changed smoothly from low values at tensile normal stresses to higher values at compressive normal stresses. The failure criterion has been found to be bi-linear on the shear stress vs normal stress plane. (author)

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

    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

  2. Development history of crimp shear tools. Item D11 Decommissioning Group

    Farmer, A.K.

    1988-02-01

    This report gives information on the continuing development of a range of crimp/shear tools aimed at separating items of radioactive plant, eg, gloveboxes, from a variety of service pipelines which could also be internally contaminated. (author)

  3. Development of Personalized Urination Recognition Technology Using Smart Bands

    Sung-Jong Eun

    2017-04-01

    Full Text Available Purpose This study collected and analyzed activity data sensed through smart bands worn by patients in order to resolve the clinical issues posed by using voiding charts. By developing a smart band-based algorithm for recognizing urination activity in patients, this study aimed to explore the feasibility of urination monitoring systems. Methods This study aimed to develop an algorithm that recognizes urination based on a patient’s posture and changes in posture. Motion data was obtained from a smart band on the arm. An algorithm that recognizes the 3 stages of urination (forward movement, urination, backward movement was developed based on data collected from a 3-axis accelerometer and from tilt angle data. Real-time data were acquired from the smart band, and for data corresponding to a certain duration, the absolute value of the signals was calculated and then compared with the set threshold value to determine the occurrence of vibration signals. In feature extraction, the most essential information describing each pattern was identified after analyzing the characteristics of the data. The results of the feature extraction process were sorted using a classifier to detect urination. Results An experiment was carried out to assess the performance of the recognition technology proposed in this study. The final accuracy of the algorithm was calculated based on clinical guidelines for urologists. The experiment showed a high average accuracy of 90.4%, proving the robustness of the proposed algorithm. Conclusions The proposed urination recognition technology draws on acceleration data and tilt angle data collected via a smart band; these data were then analyzed using a classifier after comparative analyses with standardized feature patterns.

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

    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

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

    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.

  6. The development of a tensile-shear punch correlation for yield properties of model austenitic alloys

    Hankin, G.L.; Faulkner, R.G. [Loughborough Univ. (United Kingdom); Hamilton, M.L.; Garner, F.A. [Pacific Northwest National Lab., Richland, WA (United States)

    1997-08-01

    The effective shear yield and maximum strengths of a set of neutron-irradiated, isotopically tailored austentic alloys were evaluated using the shear punch test. The dependence on composition and neutron dose showed the same trends as were observed in the corresponding miniature tensile specimen study conducted earlier. A single tensile-shear punch correlation was developed for the three alloys in which the maximum shear stress or Tresca criterion was successfully applied to predict the slope. The correlation will predict the tensile yield strength of the three different austenitic alloys tested to within {+-}53 MPa. The accuracy of the correlation improves with increasing material strength, to within {+-} MPa for predicting tensile yield strengths in the range of 400-800 MPa.

  7. The development of a tensile-shear punch correlation for yield properties of model austenitic alloys

    Hankin, G.L.; Faulkner, R.G.; Hamilton, M.L.; Garner, F.A.

    1997-01-01

    The effective shear yield and maximum strengths of a set of neutron-irradiated, isotopically tailored austentic alloys were evaluated using the shear punch test. The dependence on composition and neutron dose showed the same trends as were observed in the corresponding miniature tensile specimen study conducted earlier. A single tensile-shear punch correlation was developed for the three alloys in which the maximum shear stress or Tresca criterion was successfully applied to predict the slope. The correlation will predict the tensile yield strength of the three different austenitic alloys tested to within ±53 MPa. The accuracy of the correlation improves with increasing material strength, to within ± MPa for predicting tensile yield strengths in the range of 400-800 MPa

  8. Electronic materials with a wide band gap: recent developments

    Detlef Klimm

    2014-09-01

    Full Text Available The development of semiconductor electronics is reviewed briefly, beginning with the development of germanium devices (band gap Eg = 0.66 eV after World War II. A tendency towards alternative materials with wider band gaps quickly became apparent, starting with silicon (Eg = 1.12 eV. This improved the signal-to-noise ratio for classical electronic applications. Both semiconductors have a tetrahedral coordination, and by isoelectronic alternative replacement of Ge or Si with carbon or various anions and cations, other semiconductors with wider Eg were obtained. These are transparent to visible light and belong to the group of wide band gap semiconductors. Nowadays, some nitrides, especially GaN and AlN, are the most important materials for optical emission in the ultraviolet and blue regions. Oxide crystals, such as ZnO and β-Ga2O3, offer similarly good electronic properties but still suffer from significant difficulties in obtaining stable and technologically adequate p-type conductivity.

  9. Development of L-band pillbox RF window

    Takeuchi, Y.; Fukuda, S.; Hisamatsu, H.; Saito, Y.; Takahashi, A.

    1994-01-01

    A pillbox RF output window was developed for the L-band pulsed klystron for the Japanese Hadron Project (JHP) 1-GeV proton linac. The window was designed to withstand a peak RF power of 6 MW, where the pulse width is 600 μsec and the repetition rate is 50 Hz. A high power model was fabricated using an alumina ceramic which has a low loss tangent of 2.5x10 -5 . A high power test was successfully performed up to a 113 kW RF average power with a 4 MW peak power, a 565 μsec pulse width and a 50 Hz repetition rate. By extrapolating the data of this high power test, the temperature rise of the ceramic is estimated low enough at the full RF power of 6 MW. Thus this RF window is expected to satisfy the specifications of the L-band Klystron. (author)

  10. Development of Method for X-band Weather Radar Calibration

    Nielsen, Jesper Ellerbæk; Thorndahl, Søren Liedtke; Rasmussen, Michael R.

    2013-01-01

    Calibration of the X-band LAWR (Local Area Weather Radar) is traditionally based on an assumed linear relation between the LAWRradar output and the rainfall intensity. However, closer inspections of the data reveal that the validity of this linear assumption is doubtful. Previous studies of this ......Calibration of the X-band LAWR (Local Area Weather Radar) is traditionally based on an assumed linear relation between the LAWRradar output and the rainfall intensity. However, closer inspections of the data reveal that the validity of this linear assumption is doubtful. Previous studies...... of this type of weather radar have also illustrated that the radar commonly has difficulties in estimating high rain rates. Therefore, a new radar–rainfall transformation model and a calibration method have been developed. The new method is based on nonlinear assumptions and is aimed at describing the whole...

  11. Experimental investigation of edge sheared flow development and configuration effects in the TJ-II stellarator

    Pedrosa, M. A.; Hidalgo, C.; Alonso, A.; Calderon, E.; Orozco, R. O.; Pablos, J. L. de

    2005-07-01

    It is well known the importance of the shear as a stabilizing mechanism to control plasma fluctuations in magnetically confined plasmas [1]. It has been clearly established that Ex B shear stabilization mechanisms are an important piece for the improvement of confinement on fusion devices. In particular both edge and core transport barriers are related to a large increase in the Ex B sheared flow. As a consequence clarifying the driving mechanisms of sheared flow in fusion plasmas is a main issue. The existence of parallel and perpendicular sheared flows at the plasma edge, and the interplay between them in different plasma conditions has been studied in the TJ-II [2]. Recent experiments carried out by means of different approaches in the TJ-II stellarator have shown that the generation of spontaneous edge perpendicular sheared flow can be externally controlled by means of plasma density with good reproducibility and reliability [3, 4]. Although experimentally the plasma density has been used as an external control knob, it would be more appropriate to characterize experimental results in terms of edge plasma gradient (e.g. ion saturation current gradient) [3]. It has also been found that there exists a coupling between the onset of sheared flow development and an increase in the level of plasma edge turbulence; once sheared flow is fully developed the level of fluctuations and turbulent transport slightly decreases whereas edge gradients and plasma density increase. It has been experimentally established that the minimum plasma density (or/and minimum level of plasma turbulence) essential for the development of the shear layer depends on the plasma magnetic configuration [5, 6]. For some plasma magnetic configurations with high iota value a sheared flow-induced regime with characteristics resembling those of an improved confinement one has been found. The similarity in the structure of the velocity shear layer and in the turbulence characteristics [7] in different

  12. Development of generalized correlation equation for the local wall shear stress

    Jeon, Yu Mi; Bae, Jun Ho; Park, Joo Hwan

    2010-01-01

    The pressure drop characteristics for a fuel channel are essential for the design and reliable operation of a nuclear reactor. Over several decades, analytical methods have been developed to predict the friction factor in the fuel bundle flows. In order to enhance the accuracy of prediction for the pressure drop in a rod bundle, the influences of a channel wall and the local shear stress distribution should be considered. Hence, the correlation equation for a local shear stress distribution should be developed in order to secure an analytical solution for the friction factor of a rod bundle. For a side subchannel, which has the influence of the channel wall, the local shear stress distribution is dependent on the ratio of wall to diameter (W/D) as well as the ratio of pitch to diameter (P/D). In the case that W/D has the same value with P/D, the local shear stress distribution can be simply correlated with the function of angular position for each value of P/D. While, in the case that W/D has the different value with P/D, the correlation equation should be developed for each case of P/D and W/D. Hence, in the present study, the generalized correlation equation of a local shear stress distribution is developed for a side subchannel in the case that W/D has the different value with P/D

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

    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

  14. Development of Generalized Correlation Equation for the Local Wall Shear Stress

    Jeon, Yu Mi; Park, Ju Hwan

    2010-06-01

    The pressure drop characteristics for a fuel channel are essential for the design and reliable operation of a nuclear reactor. Over several decades, analytical methods have been developed to predict the friction factor in the fuel bundle flows. In order to enhance the accuracy of prediction for the pressure drop in a rod bundle, the influences of a channel wall and the local shear stress distribution should be considered. Therefore, the correlation equation for a local wall shear stress distribution should be developed in order to secure an analytical solution for the friction factor of a rod bundle. For a side subchannel, which has the influence of the channel wall, the local wall shear stress distribution is dependent on the ratio of wall to diameter (W/D) as well as the ratio of pitch to diameter (P/D). In the case that W/D has the same value with P/D, the local shear stress distribution can be simply correlated with the function of angular position for each value of P/D. While in the case where W/D has a different value than P/D, the correlation equation should be developed for each case of P/D and W/D. Therefore, in the present study, the generalized correlation equation of the local wall shear stress distribution was developed for a side subchannel in the case where W/D has a different value than P/D. Consequently, the generalized correlation equation of a local wall shear stress distribution can be represented by the equivalent pitch to diameter ratio, P'/D for the case that P/D and W/D had a different value

  15. A mathematical model for fluid shear-sensitive 3D tissue construct development.

    Liu, Dan; Chua, Chee-Kai; Leong, Kah-Fai

    2013-01-01

    This research studies dynamic culture for 3D tissue construct development with computational fluid dynamics. It proposes a mathematical model to evaluate the impact of flow rates and flow shear stress on cell growth in 3D constructs under perfusion. The modeling results show that dynamic flow, even at flow rate as low as 0.002 cm/s, can support much better mass exchange, higher cell number, and more even cell and nutrient distribution compared to static culture. Higher flow rate can further improve nutrient supply and mass exchange in the construct, promoting better nutritious environment and cell proliferation compared to lower flow rate. In addition, consideration of flow shear stress predicts much higher cell number in the construct compared to that without shear consideration. While the nutrient can dominate shear stress in influencing cell proliferation, the shear effect increases with flow rate. The proposed model helps tissue engineers better understand the cell-flow relationship at the molecular level during dynamic culture.

  16. Effects of earthquake induced rock shear on containment system integrity. Laboratory testing plan development

    Read, Rodney S.

    2011-07-01

    This report describes a laboratory-scale testing program plan to address the issue of earthquake induced rock shear effects on containment system integrity. The document contains a review of relevant literature from SKB covering laboratory testing of bentonite clay buffer material, scaled analogue tests, and the development of related material models to simulate rock shear effects. The proposed testing program includes standard single component tests, new two-component constant volume tests, and new scaled analogue tests. Conceptual drawings of equipment required to undertake these tests are presented along with a schedule of tests. The information in this document is considered sufficient to engage qualified testing facilities, and to guide implementation of laboratory testing of rock shear effects. This document was completed as part of a collaborative agreement between SKB and Nuclear Waste Management Organization (NWMO) in Canada

  17. Effects of earthquake induced rock shear on containment system integrity. Laboratory testing plan development

    Read, Rodney S. (RSRead Consulting Inc. (Canada))

    2011-07-15

    This report describes a laboratory-scale testing program plan to address the issue of earthquake induced rock shear effects on containment system integrity. The document contains a review of relevant literature from SKB covering laboratory testing of bentonite clay buffer material, scaled analogue tests, and the development of related material models to simulate rock shear effects. The proposed testing program includes standard single component tests, new two-component constant volume tests, and new scaled analogue tests. Conceptual drawings of equipment required to undertake these tests are presented along with a schedule of tests. The information in this document is considered sufficient to engage qualified testing facilities, and to guide implementation of laboratory testing of rock shear effects. This document was completed as part of a collaborative agreement between SKB and Nuclear Waste Management Organization (NWMO) in Canada

  18. Alternative Shear Panel Configurations for Light Wood Construction. Development, Seismic Performance, and Design Guidance

    Wilcoski, James; Fischer, Chad; Allison, Tim; Malach, Kelly Jo

    2002-04-01

    Shear panels are used in light wood construction to resist lateral loads resulting from earthquakes or strong winds. These panels are typically made of wooden sheathing nailed to building frame members, but this standard panel design interferes with the installation of sheet insulation. A non-insulated shear panel conducts heat between the building interior and exterior wasting considerable amounts of energy. Several alternative shear panel designs were developed to avoid this insulation-mounting problem and sample panels were tested according to standard cyclic test protocols. One of the alternative designs consisted of diagonal steel straps nailed directly to the structural framing. Several others consisted of sheathing nailed to 2 x 4 framing then set into a larger 2 x 6 structural frame in such a way that no sheathing protruded beyond the edge of the 2 x 6 members. Also samples of industry-standard shear panels were constructed and tested in order to establish a performance baseline. Analytical models were developed to size test panels and predict panel behavior. A procedure was developed for establishing design capacities based on both test data and established baseline panel design capacity. The behavior of each panel configuration is documented and recommended design capacities are presented.

  19. IHEP S-band 45 MW pulse power klystron development

    Dong Dong; Zhou Zusheng; Zhang Liang; Li Gangying; Tian Shuangmin

    2006-01-01

    S-band 45 MW pulse power klystron has been developed in the Institute of High Energy Physics (IHEP) for the Beijing Electron Positron Collider (BEPC) upgrade projects (BEPC-II). This new klystron has 5 cavities in its RF-beam interaction and single RF output window, and the RF output power is 45 MW at 310 kV, the gain is 50 dB, the efficiency 40%. The manufacturing, training and testing of a prototype klystron has been finished in IHEP and RF power 45 MW at 300 kV has been reached. The testing results show that all the parameters of the 45 MW klystron reach the design goal. (authors)

  20. Development of L-band, 10MW multi beam klystron

    Irikura, M.; Miyake, S.; Yano, A.; Kazakov, S.; Larionov, A.; Teryaev, V.; Chin, Y.H.

    2004-01-01

    A 10-MW, L-band multi beam klystron (MBK) for TESLA linear collider and TESLA XFEL has been under development at Toshiba Electron Tubes and Devices Co., Ltd. (TETD) in collaboration with KEK. The TESLA requires pulsed klystrons capable of 10 MW output power at 1300 MHz with 1.5 ms pulse length and a repetition rate of 10 pps. The MBK with 6 low-perveance beams in parallel enables us to operate at lower cathode voltage with higher efficiency. The design work has been accomplished and the fabrication is under way. We are going to start conditioning and testing of prototype no.0 in the middle of July 2004. The design overview will be presented. (author)

  1. Wide-band coherent receiver development for enhanced surveillance

    Simpson, M.L.; Richards, R.K.; Hutchinson, D.P.

    1998-03-01

    Oak Ridge National Laboratory (ORNL) has been developing advanced coherent IR heterodyne receivers for plasma diagnostics in fusion reactors for over 20 years. Recent progress in wide band IR detectors and high speed electronics has significantly enhanced the measurement capabilities of coherent receivers. In addition, developments in new HgCdTe and quantum well IR photodetector (QWIP) focal plane arrays are providing the possibility of both active and passive coherent imaging. In this paper the authors discuss the implications of these new enabling technologies to the IR remote sensing community for enhanced surveillance. Coherent receivers, as opposed to direct or thermal detection, provide multiple dimensions of information about a scene or target in a single detector system. Combinations of range, velocity, temperature, and chemical species information are all available from a coherent heterodyne receiver. They present laboratory data showing measured noise equivalent power (NEP) of new QWIP detectors with heterodyne bandwidths greater than 7 GHz. For absorption measurements, a wide band coherent receiver provides the capability of looking between CO 2 lines at off-resonance peaks and thus the measurement of lines normally inaccessible with conventional heterodyne or direct detection systems. Also described are differential absorption lidar (DIAL) and Doppler laboratory measurements using an 8 x 8 HgCdTe focal plane array demonstrating the snapshot capability of coherent receiver detector arrays for enhanced chemical plume and moving hardbody capture. Finally they discuss a variety of coherent receiver configurations that can suppress (or enhance) sensitivity of present active remote sensing systems to speckle, glint, and other measurement anomalies

  2. Effect of Different Loading Conditions on the Nucleation and Development of Shear Zones Around Material Heterogeneities

    Rybacki, E.; Nardini, L.; Morales, L. F.; Dresen, G.

    2017-12-01

    Rock deformation at depths in the Earth's crust is often localized in high temperature shear zones, which occur in the field at different scales and in a variety of lithologies. The presence of material heterogeneities has long been recognized to be an important cause for shear zones evolution, but the mechanisms controlling initiation and development of localization are not fully understood, and the question of which loading conditions (constant stress or constant deformation rate) are most favourable is still open. To better understand the effect of boundary conditions on shear zone nucleation around heterogeneities, we performed a series of torsion experiments under constant twist rate (CTR) and constant torque (CT) conditions in a Paterson-type deformation apparatus. The sample assemblage consisted of copper-jacketed Carrara marble hollow cylinders with one weak inclusion of Solnhofen limestone. The CTR experiments were performed at maximum bulk strain rates of 1.8-1.9*10-4 s-1, yielding shear stresses of 19-20 MPa. CT tests were conducted at shear stresses between 18.4 and 19.8 MPa resulting in shear strain rates of 1-2*10-4 s-1. All experiments were run at 900 °C temperature and 400 MPa confining pressure. Maximum bulk shear strains (γ) were ca. 0.3 and 1. Strain localized within the host marble in front of the inclusion in an area termed process zone. Here grain size reduction is intense and local shear strain (estimated from markers on the jackets) is up to 8 times higher than the applied bulk strain, rapidly dropping to 2 times higher at larger distance from the inclusion. The evolution of key microstructural parameters such as average grain size and average grain orientation spread (GOS, a measure of lattice distortion) within the process zone, determined by electron backscatter diffraction analysis, differs significantly as a function of loading conditions. Both parameters indicate that, independent of bulk strain and distance from the inclusion, the

  3. Development of a Control Banding Tool for Nanomaterials

    Riediker, M.; Ostiguy, C.; Triolet, J.; Troisfontaine, P.; Vernez, D.; Bourdel, G.; Thieriet, N.; Cadène, A.

    2012-01-01

    Control banding (CB) can be a useful tool for managing the potential risks of nanomaterials. The here proposed CB, which should be part of an overall risk control strategy, groups materials by hazard and emission potential. The resulting decision matrix proposes control bands adapted to the risk potential levels and helps define an action plan. If this plan is not practical and financially feasible, a full risk assessment is launched. The hazard banding combines key concepts of nanomaterial t...

  4. Development of a Shear Deformable Element Using the Absolute Nodal Coordinate Formulation

    Omar, Mohamed

    2000-01-01

    .... The effect of the shear deformation is accounted for without the need for introducing Timoshenko's shear coefficient By using the absolute coordinates, the nonlinear strain-displacement relationships...

  5. Development of X-band klystron technology at SLAC

    Caryotakis, G.

    1997-05-01

    The SLAC design for a 1-TeV collider (NLC) requires klystrons with a performance which is well beyond the state-of-the-art for microwave tubes in the United States or abroad. The electrical specifications for the NLC klystrons are not fully established, but they are approximately as follows: Frequency, 11.4 GHz; Peak Power, 75 MW; Pulse Length, 1.5 μs; Repetition Rate, 180 Hz; Gain, 50 dB; Efficiency, (including beam focusing) 50%. SLAC is in the seventh year of a program to develop these klystrons. The choice of X-band as the operating frequency, along with the sheer size of the NLC, have resulted in some new, most demanding standards for the klystrons which may power this future machine. These are related to the overall efficiency required, to the high rf gradients that must be supported at the output circuit without vacuum breakdown, and to the manufacturing cost of the 5,000-10,000 klystrons needed for the collider

  6. Development of a Control Banding Tool for Nanomaterials

    M. Riediker

    2012-01-01

    Full Text Available Control banding (CB can be a useful tool for managing the potential risks of nanomaterials. The here proposed CB, which should be part of an overall risk control strategy, groups materials by hazard and emission potential. The resulting decision matrix proposes control bands adapted to the risk potential levels and helps define an action plan. If this plan is not practical and financially feasible, a full risk assessment is launched. The hazard banding combines key concepts of nanomaterial toxicology: translocation across biological barriers, fibrous nature, solubility, and reactivity. Already existing classifications specific to the nanomaterial can be used “as is.” Otherwise, the toxicity of bulk or analogous substances gives an initial hazard band, which is increased if the substance is not easily soluble or if it has a higher reactivity than the substance. The emission potential bands are defined by the nanomaterials' physical form and process characteristics. Quantities, frequencies, and existing control measures are taken into account during the definition of the action plan. Control strategies range from room ventilation to full containment with expert advice. This CB approach, once validated, can be easily embedded in risk management systems. It allows integrating new toxicity data and needs no exposure data.

  7. Nucleation and thickening of shear bands in nano-scale twin/matrix lamellae of a Cu-Al alloy processed by dynamic plastic deformation

    Hong, C.S.; Tao, N.R.; Huang, Xiaoxu

    2010-01-01

    dislocation structure (DDS) into a nano-sized (sub)grain structure (NGS). On the two sides of a core region, two transition layers (TRLs) exist where the T/M lamellae experienced much less shear strain. The interface boundaries separating the core region and the TRLs are characterized by very large shear...

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

    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.

  9. Development and validation of the downhole freestanding shear device (DFSD) for measuring the dynamic properties of clay.

    2008-12-01

    The Downhole Freestanding Shear Device (DFSD) is an innovative tool developed for in situ measurement of dynamic : properties (modulus and damping) of clay soils over a broad range of strains. The device essentially performs : laboratory-quality tors...

  10. Development of an omni-directional shear horizontal mode magnetostrictive patch transducer

    Liu, Zenghua; Hu, Yanan; Xie, Muwen; Fan, Junwei; He, Cunfu; Wu, Bin

    2018-04-01

    The fundamental shear horizontal wave, SH0 mode, has great potential in defect detection and on-line monitoring with large scale and high efficiency in plate-like structures because of its non-dispersive characteristics. Aiming at consistently exciting single SH0 mode in plate-like structures, an omni-directional shear horizontal mode magnetostrictive patch transducer (OSHM-MPT) is developed on the basis of magnetostrictive effect. It consists of four fan-shaped array elements and corresponding plane solenoid array (PSA) coils, four fan-shaped permanent magnets and a circular nickel patch. The experimental results verify that the developed transducer can effectively produce the single SH0 mode in an aluminum plate. The frequency response characteristics of this developed transducer are tested. The results demonstrate that the proposed OSHM-MPT has a center frequency of 300kHz related to the distance between adjacent arc-shaped steps of the PSA coils. Furthermore, omni-directivity of this developed transducer is tested. The results demonstrate that the developed transducer has a high omnidirectional consistency.

  11. Development of the L-band superconducting cavity system

    Ota, T.; Kakutani, N.; Sukenobu, S. [Toshiba Corp., Yokohama, Kanagawa (JP)] [and others

    2000-02-01

    R and D activities on superconducting cavities in 1998 at TOSHIBA are presented. An L-band single-cell niobium cavity with four ports on the beam pipes was fabricated in our company and tested at KEK. The cryostat and refrigerator system for the cavity were designed and fabricated. The cryostat installed the cavity was tested in low temperature. R and D of hydroforming to fabricate seamless cavities is also presented. (author)

  12. Development of the L-band superconducting cavity system

    Ota, T.; Kakutani, N.; Sukenobu, S.

    2000-01-01

    R and D activities on superconducting cavities in 1998 at TOSHIBA are presented. An L-band single-cell niobium cavity with four ports on the beam pipes was fabricated in our company and tested at KEK. The cryostat and refrigerator system for the cavity were designed and fabricated. The cryostat installed the cavity was tested in low temperature. R and D of hydroforming to fabricate seamless cavities is also presented. (author)

  13. Development of at-wavelength metrology using grating-based shearing interferometry at Diamond Light Source

    Wang, Hongchang; Berujon, Sebastien; Sawhney, Kawal

    2013-01-01

    The grating-based shearing interferometer has been established and further developed on B16 at Diamond Light Source. The beamline performances of both an X-ray plane mirror and a compound refractive lens (CRL) have been investigated using this technique. The slope error of the X-ray mirror was retrieved from the wavefront phase gradient, which was measured using two different processing schemes: phase stepping and moiré fringe analysis. The interferometer has demonstrated a high sensitivity with sub-microradian accuracy. Some of the advantages, disadvantages and limitations for the two approaches will also be presented.

  14. Development of at-wavelength metrology using grating-based shearing interferometry at Diamond Light Source

    Wang, Hongchang; Berujon, Sebastien; Sawhney, Kawal

    2013-03-01

    The grating-based shearing interferometer has been established and further developed on B16 at Diamond Light Source. The beamline performances of both an X-ray plane mirror and a compound refractive lens (CRL) have been investigated using this technique. The slope error of the X-ray mirror was retrieved from the wavefront phase gradient, which was measured using two different processing schemes: phase stepping and moiré fringe analysis. The interferometer has demonstrated a high sensitivity with sub-microradian accuracy. Some of the advantages, disadvantages and limitations for the two approaches will also be presented.

  15. Development of Shear Deformable Laminated Shell Element and Its Application to ANCF Tire Model

    2015-04-24

    Sharp, R. S. and Crocombe, A. D., 2012, "Normal and Shear Forces in the Contact Patch of a Braked Racing Tyre . Part 2: Development of a Physical Tyre ...The University of Iowa 2312 Seamans Center Iowa City, IA 52242 Paramsothy Jayakumar US Army TARDEC 6501 E. 11 Mile Road Warren, MI 48397-5000...PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) US Army RDECOM-TARDEC,6501 E. 11 Mile Road

  16. Development of an in-situ banking shear test method; Moritsuchi no gen'ichi sendan shikenho no kaihatsu

    Nishikata, U. [Kansai Electric Power Co. Inc., Osaka (Japan)

    1998-12-10

    Development was made on a simplified site-use single face shear testing device and a test method that can perform in-situ and direct measurement during construction on shear strength of coarse particle materials having large diameters. The test device consists of shear frames embedded in the in-situ ground bed, a weight for vertical loading, and a traction device to load horizontal force. In the test, prescribed rolling compaction is performed by a vibration roller which presses in the shear frames into unwound banking by using a four-piece vibration roller. Crushed stones are piled on cells of the shear frames to the same height. The specified weight is placed thereon via a loading plate, which is used as the vertical load. The shear force is loaded by horizontally pulling chains connected to the shear frames by using the traction device, and is measured by a load cell. The vertical displacement is measured by two vertical displacement meters, and the horizontal displacement by one horizontal displacement meter. A verification test is continuing using the test device. Four cases with different vertical stresses can be tested in about one day. (NEDO)

  17. Predicting development of undrained shear strength in soft oil sands tailings

    Masala, S. [Klohn Crippen Berger, Calgary, AB (Canada); Matthews, J. [Shell Canada Ltd., Calgary, AB (Canada)

    2010-07-01

    This PowerPoint presentation discussed a method of predicting the development of undrained shear strength in soft oil sands tailings. Phenomenology charts of oil sands tailings ponds were used to present the suspension, density, stresses and hydrostatic behaviour of tailings. Sedimentation and consolidation processes were discussed. The charts demonstrated how the tailings slurry settles and consolidates, releases water and dissipates pore pressures. The slurry then develops intergranular stresses and increases in density. The increases correlate with increased resistance to deformation and decreased compressibility and hydraulic conductivity. A critical state soil mechanics (CSSM) was used to characterize the soft oil sands tailings. Undrained strength was determined using the concept of the undrained strength ratio (USR). The USR was determined using traditional geotechnical investigation methods. Settling of the non-consolidated (NC) soil deposits was simulated using the finite strain consolidation theory. The model was based on the premise that current effective stresses control undrained shear strength in the NC deposits. Case studies were used to demonstrate the predictive framework. tabs, figs.

  18. Development of K-Basin High-Strength Homogeneous Sludge Simulants and Correlations Between Unconfined Compressive Strength and Shear Strength

    Onishi, Yasuo; Baer, Ellen BK; Chun, Jaehun; Yokuda, Satoru T.; Schmidt, Andrew J.; Sande, Susan; Buchmiller, William C.

    2011-02-20

    K-Basin sludge will be stored in the Sludge Transport and Storage Containers (STSCs) at an interim storage location on Central Plateau before being treated and packaged for disposal. During the storage period, sludge in the STSCs may consolidate/agglomerate, potentially resulting in high-shear-strength material. The Sludge Treatment Project (STP) plans to use water jets to retrieve K-Basin sludge after the interim storage. STP has identified shear strength to be a key parameter that should be bounded to verify the operability and performance of sludge retrieval systems. Determining the range of sludge shear strength is important to gain high confidence that a water-jet retrieval system can mobilize stored K-Basin sludge from the STSCs. The shear strength measurements will provide a basis for bounding sludge properties for mobilization and erosion. Thus, it is also important to develop potential simulants to investigate these phenomena. Long-term sludge storage tests conducted by Pacific Northwest National Laboratory (PNNL) show that high-uranium-content K-Basin sludge can self-cement and form a strong sludge with a bulk shear strength of up to 65 kPa. Some of this sludge has 'paste' and 'chunks' with shear strengths of approximately 3-5 kPa and 380-770 kPa, respectively. High-uranium-content sludge samples subjected to hydrothermal testing (e.g., 185 C, 10 hours) have been observed to form agglomerates with a shear strength up to 170 kPa. These high values were estimated by measured unconfined compressive strength (UCS) obtained with a pocket penetrometer. Due to its ease of use, it is anticipated that a pocket penetrometer will be used to acquire additional shear strength data from archived K-Basin sludge samples stored at the PNNL Radiochemical Processing Laboratory (RPL) hot cells. It is uncertain whether the pocket penetrometer provides accurate shear strength measurements of the material. To assess the bounding material strength and

  19. Computed and experimental interactions between eddy structure and dispersed particles in developing free shear layers

    Buckingham, A.C.; Siekhaus, W.J.; Keller, J.O.; Ellzey, J.; Hubbard, G.; Daily, J.W.

    1982-01-01

    We are investigating the interactive process between turbulent flow and dispersed phase particles. We are focusing on the mechanisms that appear to result in a reduction of local turbulent intensity and a corresponding reduction in wall heat transfer and subsequent wall erosion in turbulent solid propellant combustion flow. We apply computational simulations and physical experiments specialized to a developing free shear layer over a rearward facing step and over a parallel splitter plate. The flow configuration evolves in a two-dimensional, steady, combustion and non-combustion turbulent free shear mixing region, with and without particle additives. The computational simulations combine three basic components: gas phase Navier-Stokes solutions, Lagrange particle field solutions and a Monte Carlo technique for the random encounters, forces and accelerations between the two fields. We concentrate here on relatively large sized additive particles (of the order of tens of microns to 100 microns mean diameter). We examine their apparent influence in breaking up the larger, energy bearing eddy structures into smaller structures which are more readily dissipated

  20. Shear machines

    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.)

  1. Development of a metal-clad advanced composite shear web design concept

    Laakso, J. H.

    1974-01-01

    An advanced composite web concept was developed for potential application to the Space Shuttle Orbiter main engine thrust structure. The program consisted of design synthesis, analysis, detail design, element testing, and large scale component testing. A concept was sought that offered significant weight saving by the use of Boron/Epoxy (B/E) reinforced titanium plate structure. The desired concept was one that was practical and that utilized metal to efficiently improve structural reliability. The resulting development of a unique titanium-clad B/E shear web design concept is described. Three large scale components were fabricated and tested to demonstrate the performance of the concept: a titanium-clad plus or minus 45 deg B/E web laminate stiffened with vertical B/E reinforced aluminum stiffeners.

  2. The development for C-band whole sealed vacuum accelerating tuber

    Zhou Wenzhen; Zhang Xiangyang; Ding Shulin; Hu Jinquan; Yang Zhenyuan

    1999-01-01

    S-Band standing wave electron linacs have got wide-ranging application for industry nondestructive testing and formed varied kinds of products. X-band electron linac for NDT has been developed by Schonberg Company USA in 1985. Because of bigger structure of S-band linac and difficult machining of X-Band linac, an C-band portable linac for NDT has been developed in CIAE at present, a whole sealed vacuum accelerating tuber will be given here. It consists of 4 cavities, the phase velocity of the first two cavities is 0.5 and 0.9, respectively, and that of the second two cavities is 1. The high power testing proved that the design of the accelerating tuber is good for 1.5 MeV electron linac for NDT

  3. Evaluation of a metal shear web selectively reinforced with filamentary composites for space shuttle application. Phase 1 summary report: Shear web design development

    Laakso, J. H.; Zimmerman, D. K.

    1972-01-01

    An advanced composite shear web design concept was developed for the Space Shuttle orbiter main engine thrust beam structure. Various web concepts were synthesized by a computer-aided adaptive random search procedure. A practical concept is identified having a titanium-clad + or - 45 deg boron/epoxy web plate with vertical boron/epoxy reinforced aluminum stiffeners. The boron-epoxy laminate contributes to the strength and stiffness efficiency of the basic web section. The titanium-cladding functions to protect the polymeric laminate parts from damaging environments and is chem-milled to provide reinforcement in selected areas. Detailed design drawings are presented for both boron/epoxy reinforced and all-metal shear webs. The weight saving offered is 24% relative to all-metal construction at an attractive cost per pound of weight saved, based on the detailed designs. Small scale element tests substantiate the boron/epoxy reinforced design details in critical areas. The results show that the titanium-cladding reliably reinforces the web laminate in critical edge load transfer and stiffener fastener hole areas.

  4. Development of banded microstructure in 34CrNiMo6 steel

    A. Nagode

    2016-07-01

    Full Text Available In this paper the development of a banded microstructure in hot-rolled 34CrNiMo6 steel which consisted of bainitic and martensitic bands is explained. The chemical compositions of the bands were measured with energy dispersive x-ray spectroscopy (EDS, which showed that the martensitic bands contained more alloying elements (Mn, Cr, Mo, Si than bainitic bands. By using Oberhoffer reagent, the segregations of phosphorus were also revealed. These phosphorus segregations coincided with the positive segregations of the alloying elements. The continuous cooling transformation (CCT diagrams of steel were calculated. They confirmed the formation of martensite in positive segregations and the formation of bainite in negative segregations.

  5. RRI-GBT MULTI-BAND RECEIVER: MOTIVATION, DESIGN, AND DEVELOPMENT

    Maan, Yogesh; Deshpande, Avinash A.; Chandrashekar, Vinutha; Chennamangalam, Jayanth; Rao, K. B. Raghavendra; Somashekar, R.; Ezhilarasi, M. S.; Sujatha, S.; Kasturi, S.; Sandhya, P.; Duraichelvan, R.; Amiri, Shahram; Aswathappa, H. A.; Sarabagopalan, G.; Ananda, H. M.; Anderson, Gary; Bauserman, Jonah; Beaudet, Carla; Bloss, Marty; Barve, Indrajit V.

    2013-01-01

    We report the design and development of a self-contained multi-band receiver (MBR) system, intended for use with a single large aperture to facilitate sensitive and high time-resolution observations simultaneously in 10 discrete frequency bands sampling a wide spectral span (100-1500 MHz) in a nearly log-periodic fashion. The development of this system was primarily motivated by need for tomographic studies of pulsar polar emission regions. Although the system design is optimized for the primary goal, it is also suited for several other interesting astronomical investigations. The system consists of a dual-polarization multi-band feed (with discrete responses corresponding to the 10 bands pre-selected as relatively radio frequency interference free), a common wide-band radio frequency front-end, and independent back-end receiver chains for the 10 individual sub-bands. The raw voltage time sequences corresponding to 16 MHz bandwidth each for the two linear polarization channels and the 10 bands are recorded at the Nyquist rate simultaneously. We present the preliminary results from the tests and pulsar observations carried out with the Robert C. Byrd Green Bank Telescope using this receiver. The system performance implied by these results and possible improvements are also briefly discussed.

  6. RRI-GBT MULTI-BAND RECEIVER: MOTIVATION, DESIGN, AND DEVELOPMENT

    Maan, Yogesh; Deshpande, Avinash A.; Chandrashekar, Vinutha; Chennamangalam, Jayanth; Rao, K. B. Raghavendra; Somashekar, R.; Ezhilarasi, M. S.; Sujatha, S.; Kasturi, S.; Sandhya, P.; Duraichelvan, R.; Amiri, Shahram; Aswathappa, H. A.; Sarabagopalan, G.; Ananda, H. M. [Raman Research Institute, Bangalore (India); Anderson, Gary; Bauserman, Jonah; Beaudet, Carla; Bloss, Marty [National Radio Astronomy Observatory, P.O. Box 2, Green Bank, WV (United States); Barve, Indrajit V. [Indian Institute of Astrophysics, Bangalore (India); and others

    2013-01-15

    We report the design and development of a self-contained multi-band receiver (MBR) system, intended for use with a single large aperture to facilitate sensitive and high time-resolution observations simultaneously in 10 discrete frequency bands sampling a wide spectral span (100-1500 MHz) in a nearly log-periodic fashion. The development of this system was primarily motivated by need for tomographic studies of pulsar polar emission regions. Although the system design is optimized for the primary goal, it is also suited for several other interesting astronomical investigations. The system consists of a dual-polarization multi-band feed (with discrete responses corresponding to the 10 bands pre-selected as relatively radio frequency interference free), a common wide-band radio frequency front-end, and independent back-end receiver chains for the 10 individual sub-bands. The raw voltage time sequences corresponding to 16 MHz bandwidth each for the two linear polarization channels and the 10 bands are recorded at the Nyquist rate simultaneously. We present the preliminary results from the tests and pulsar observations carried out with the Robert C. Byrd Green Bank Telescope using this receiver. The system performance implied by these results and possible improvements are also briefly discussed.

  7. Component development for X-band above 100 MW

    Fowkes, W.R.; Callin, R.S.; Studzinski, M.

    1991-05-01

    The requirement for some of the components described in this paper began with the Relativistic Klystron program done in collaboration with LLNL and LBL. This effort culminated in a klystron operating at 11.4 GHz delivering 330 MW into a pair of high-gradient accelerating structures. The electron beam for this klystron was formed in a 1 MeV induction linac at a very low duty cycle. The subsequent RF source development work at SLAC for the Next Linear Collider utilized some of these components, and required further and new development of others, work reliably at higher average power. 6 refs., 6 figs., 1 tab

  8. Development of a Skewed Pipe Shear Connector for Precast Concrete Structures.

    Kim, Sang-Hyo; Choi, Jae-Gu; Park, Sejun; Lee, Hyunmin; Heo, And Won-Ho

    2017-05-13

    Joint connection methods, such as shear key and loop bar, improve the structural performance of precast concrete structures; consequently, there is usually decreased workability or constructional efficiency. This paper proposes a high-efficiency skewed pipe shear connector. To resist shear and pull-out forces, the proposed connectors are placed diagonally between precast concrete segments and a cast-in-place concrete joint part on a girder. Design variables (such as the pipe diameter, length, and insertion angle) have been examined to investigate the connection performance of the proposed connector. The results of our testing indicate that the skewed pipe shear connectors have 50% higher ductility and a 15% higher ratio of maximum load to yield strength as compared to the corresponding parameters of the loop bar. Finite element analysis was used for validation. The resulting validation indicates that, compared to the loop bar, the skewed pipe shear connector has a higher ultimate shear and pull-out resistance. These results indicate that the skewed pipe shear connector demonstrates more idealized behavior than the loop bar in precast concrete structures.

  9. In situ monitoring of localized shear stress and fluid flow within developing tissue constructs by Doppler optical coherence tomography

    Jia, Yali; Bagnaninchi, Pierre O.; Wang, Ruikang K.

    2008-02-01

    Mechanical stimuli can be introduced to three dimensional (3D) cell cultures by use of perfusion bioreactor. Especially in musculoskeletal tissues, shear stress caused by fluid flow generally increase extra-cellular matrix (ECM) production and cell proliferation. The relationship between the shear stress and the tissue development in situ is complicated because of the non-uniform pore distribution within the cell-seeded scaffold. In this study, we firstly demonstrated that Doppler optical coherence tomography (DOCT) is capable of monitoring localized fluid flow and shear stress in the complex porous scaffold by examining their variation trends at perfusion rate of 5, 8, 10 and 12 ml/hr. Then, we developed the 3D porous cellular constructs, cell-seeded chitosan scaffolds monitored during several days by DOCT. The fiber based fourier domain DOCT employed a 1300 nm superluminescent diode with a bandwidth of 52 nm and a xyz resolution of 20×20×15 μm in free space. This setup allowed us not only to assess the cell growth and ECM deposition by observing their different scattering behaviors but also to further investigate how the cell attachment and ECM production has the effect on the flow shear stress and the relationship between flow rate and shear stress in the developing tissue construct. The possibility to monitor continuously the constructs under perfusion will easily indicate the effect of flow rate or shear stress on the cell viability and cell proliferation, and then discriminate the perfusion parameters affecting the pre-tissue formation rate growth.

  10. Development of simple band-spectral pyranometer and quantum meter using photovoltaic cells and bandpass filters

    Bilguun, Amarsaikhan, E-mail: bilguun@pes.ee.tut.ac.jp; Nakaso, Tetsushi; Harigai, Toru; Suda, Yoshiyuki; Takikawa, Hirofumi, E-mail: takikawa@ee.tut.ac.jp [Toyohashi University of Technology, 1-1 Habarigaoka, Tempaku, Toyohashi 441-8580 (Japan); Tanoue, Hideto [Kitakyushu National College of Technology, 5-20-1, Kokuraminami, Kitakyushu, Fukuoka 802-0985 (Japan)

    2016-02-01

    In recent years, greenhouse automatic-control, based on the measurement of solar irradiance, has been attracting attention. This control is an effective method for improving crop production. In the agricultural field, it is necessary to measure Photon Flux Density (PFD), which is an important parameter in the promotion of plant growth. In particular, the PFD of Photosynthetically Active Radiation (PAR, 400-700 nm) and Plant Biologically Active Radiation (PBAR, 300-800 nm) have been discussed in agricultural plant science. The commercial quantum meter (QM, PAR meter) can only measure Photosynthetically Photon Flux Density (PPFD) which is the integrated PFD quantity on the PAR wavelength. In this research, a band-spectral pyranometer or quantum meter using PVs with optical bandpass filters for dividing the PBAR wavelength into 100 nm bands (five independent channels) was developed. Before field testing, calibration of the instruments was carried out using a solar simulator. Next, a field test was conducted in three differing weather conditions such as clear, partly cloudy and cloudy skies. As a result, it was found that the response rate of the developed pyranometer was faster by four seconds compared with the response rate of the commercial pyranometer. Moreover, the outputs of each channel in the developed pyranometer were very similar to the integrated outputs of the commercial spectroradiometer. It was confirmed that the solar irradiance could be measured in each band separately using the developed band-spectral pyranometer. It was indicated that the developed band-spectral pyranometer could also be used as a PV band-spectral quantum meter which is obtained by converting the band irradiance into band PFD.

  11. Development of simple band-spectral pyranometer and quantum meter using photovoltaic cells and bandpass filters

    Bilguun, Amarsaikhan; Nakaso, Tetsushi; Harigai, Toru; Suda, Yoshiyuki; Takikawa, Hirofumi; Tanoue, Hideto

    2016-02-01

    In recent years, greenhouse automatic-control, based on the measurement of solar irradiance, has been attracting attention. This control is an effective method for improving crop production. In the agricultural field, it is necessary to measure Photon Flux Density (PFD), which is an important parameter in the promotion of plant growth. In particular, the PFD of Photosynthetically Active Radiation (PAR, 400-700 nm) and Plant Biologically Active Radiation (PBAR, 300-800 nm) have been discussed in agricultural plant science. The commercial quantum meter (QM, PAR meter) can only measure Photosynthetically Photon Flux Density (PPFD) which is the integrated PFD quantity on the PAR wavelength. In this research, a band-spectral pyranometer or quantum meter using PVs with optical bandpass filters for dividing the PBAR wavelength into 100 nm bands (five independent channels) was developed. Before field testing, calibration of the instruments was carried out using a solar simulator. Next, a field test was conducted in three differing weather conditions such as clear, partly cloudy and cloudy skies. As a result, it was found that the response rate of the developed pyranometer was faster by four seconds compared with the response rate of the commercial pyranometer. Moreover, the outputs of each channel in the developed pyranometer were very similar to the integrated outputs of the commercial spectroradiometer. It was confirmed that the solar irradiance could be measured in each band separately using the developed band-spectral pyranometer. It was indicated that the developed band-spectral pyranometer could also be used as a PV band-spectral quantum meter which is obtained by converting the band irradiance into band PFD.

  12. Development of simple band-spectral pyranometer and quantum meter using photovoltaic cells and bandpass filters

    Bilguun, Amarsaikhan; Nakaso, Tetsushi; Harigai, Toru; Suda, Yoshiyuki; Takikawa, Hirofumi; Tanoue, Hideto

    2016-01-01

    In recent years, greenhouse automatic-control, based on the measurement of solar irradiance, has been attracting attention. This control is an effective method for improving crop production. In the agricultural field, it is necessary to measure Photon Flux Density (PFD), which is an important parameter in the promotion of plant growth. In particular, the PFD of Photosynthetically Active Radiation (PAR, 400-700 nm) and Plant Biologically Active Radiation (PBAR, 300-800 nm) have been discussed in agricultural plant science. The commercial quantum meter (QM, PAR meter) can only measure Photosynthetically Photon Flux Density (PPFD) which is the integrated PFD quantity on the PAR wavelength. In this research, a band-spectral pyranometer or quantum meter using PVs with optical bandpass filters for dividing the PBAR wavelength into 100 nm bands (five independent channels) was developed. Before field testing, calibration of the instruments was carried out using a solar simulator. Next, a field test was conducted in three differing weather conditions such as clear, partly cloudy and cloudy skies. As a result, it was found that the response rate of the developed pyranometer was faster by four seconds compared with the response rate of the commercial pyranometer. Moreover, the outputs of each channel in the developed pyranometer were very similar to the integrated outputs of the commercial spectroradiometer. It was confirmed that the solar irradiance could be measured in each band separately using the developed band-spectral pyranometer. It was indicated that the developed band-spectral pyranometer could also be used as a PV band-spectral quantum meter which is obtained by converting the band irradiance into band PFD

  13. A Reactor Development Scenario for the FUZE Shear-flow Stabilized Z-pinch

    McLean, H. S.; Higginson, D. P.; Schmidt, A.; Tummel, K. K.; Shumlak, U.; Nelson, B. A.; Claveau, E. L.; Golingo, R. P.; Weber, T. R.

    2016-10-01

    We present a conceptual design, scaling calculations, and a development path for a pulsed fusion reactor based on the shear-flow-stabilized Z-pinch device. Experiments performed on the ZaP device have demonstrated stable operation for 40 us at 150 kA total discharge current (with 100 kA in the pinch) for pinches that are 1cm in diameter and 100 cm long. Scaling calculations show that achieving stabilization for a pulse of 100 usec, for discharge current 1.5 MA, in a shortened pinch 50 cm, results in a pinch diameter of 200 um and a reactor plant Q 5 for reasonable assumptions of the various system efficiencies. We propose several key intermediate performance levels in order to justify further development. These include achieving operation at pinch currents of 300 kA, where Te and Ti are calculated to exceed 1 keV, 700 kA where fusion power exceeds pinch input power, and 1 MA where fusion energy per pulse exceeds input energy per pulse. This work funded by USDOE ARPAe ALPHA Program and performed under the auspices of Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-697801.

  14. C-band RF-system development for e{sup +}e{sup -} linear collider

    Shintake, T.; Akasaka, N.; Matsumoto, H. [High Energy Accelerator Research Organization, Tsukuba, Ibaraki (Japan); Oh, J.S.; Yoshida, M.; Watanabe, K.; Ohkubo, Y.; Yonezawa, H.; Baba, H.

    1998-11-01

    Hardware R and D on the C-band (5712 MHz) RF-system for an electron/positron linear collider started in 1996 at KEK. During two years R and D, we have developed a 50-MW C-band klystron (TOSHIBA E3746), a 'Smart Modulator', a traveling-wave resonator (TWR) and a cold model of the rf-pulse compressor. A C-band accelerating structure, which uses the choke-mode cavity, is under development. Its HOM damping performance will be tested using short-bunch beams of ASSET beam-line at SLAC in this year. The C-band system is able to accelerate a high-current beam at an accelerating gradient higher than that in a conventional S-band system, therefore, there will be various applications in the future beside the linear collider. For example, we can build an injector for a SR-ring and for various physics experiments within a short site-length. Additionally, since the C-band components are compact, it has a big potentiality to be widely used in various medical and industrial applications, such as an electron-beam radiotherapy machine, or a compact non-destructive X-ray imaging system. (author)

  15. A Reactor Development Scenario for the FuZE Sheared-Flow Stabilized Z-pinch

    McLean, Harry S.; Higginson, D. P.; Schmidt, A.; Tummel, K. K.; Shumlak, U.; Nelson, B. A.; Claveau, E. L.; Forbes, E. G.; Golingo, R. P.; Stepanov, A. D.; Weber, T. R.; Zhang, Y.

    2017-10-01

    We present a conceptual design, scaling calculations, and development path for a pulsed fusion reactor based on a flow-stabilized Z-pinch. Experiments performed on the ZaP and ZaP-HD devices have largely demonstrated the basic physics of sheared-flow stabilization at pinch currents up to 100 kA. Initial experiments on the FuZE device, a high-power upgrade of ZaP, have achieved 20 usec of stability at pinch current 100-200 kA and pinch diameter few mm for a pinch length of 50 cm. Scaling calculations based on a quasi-steady-state power balance show that extending stable duration to 100 usec at a pinch current of 1.5 MA and pinch length of 50 cm, results in a reactor plant Q 5. Future performance milestones are proposed for pinch currents of: 300 kA, where Te and Ti are calculated to exceed 1-2 keV; 700 kA, where DT fusion power would be expected to exceed pinch input power; and 1 MA, where fusion energy per pulse exceeds input energy per pulse. This work funded by USDOE ARPA-E and performed under the auspices of Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-734770.

  16. Effects of plasticization and shear stress on phase structure development and properties of soy protein blends.

    Chen, Feng; Zhang, Jinwen

    2010-11-01

    In this study, soy protein concentrate (SPC) was used as a plastic component to blend with poly(butylene adipate-co-terephthalate) (PBAT). Effects of SPC plasticization and blend composition on its deformation during mixing were studied in detail. Influence of using water as the major plasticizer and glycerol as the co-plasticizer on the deformation of the SPC phase during mixing was explored. The effect of shear stress, as affected by SPC loading level, on the phase structure of SPC in the blends was also investigated. Quantitative analysis of the aspect ratio of SPC particles was conducted by using ImageJ software, and an empirical model predicting the formation of percolated structure was applied. The experimental results and the model prediction showed a fairly good agreement. The experimental results and statistic analysis suggest that both SPC loading level and its water content prior to compounding had significant influences on development of the SPC phase structure and were correlated in determining the morphological structures of the resulting blends. Consequently, physical and mechanical properties of the blends greatly depended on the phase morphology and PBAT/SPC ratio of the blends.

  17. Development of Wearable Sheet-Type Shear Force Sensor and Measurement System that is Insusceptible to Temperature and Pressure.

    Toyama, Shigeru; Tanaka, Yasuhiro; Shirogane, Satoshi; Nakamura, Takashi; Umino, Tokio; Uehara, Ryo; Okamoto, Takuma; Igarashi, Hiroshi

    2017-07-31

    A sheet-type shear force sensor and a measurement system for the sensor were developed. The sensor has an original structure where a liquid electrolyte is filled in a space composed of two electrode-patterned polymer films and an elastic rubber ring. When a shear force is applied on the surface of the sensor, the two electrode-patterned films mutually move so that the distance between the internal electrodes of the sensor changes, resulting in current increase or decrease between the electrodes. Therefore, the shear force can be calculated by monitoring the current between the electrodes. Moreover, it is possible to measure two-dimensional shear force given that the sensor has multiple electrodes. The diameter and thickness of the sensor head were 10 mm and 0.7 mm, respectively. Additionally, we also developed a measurement system that drives the sensor, corrects the baseline of the raw sensor output, displays data, and stores data as a computer file. Though the raw sensor output was considerably affected by the surrounding temperature, the influence of temperature was drastically decreased by introducing a simple arithmetical calculation. Moreover, the influence of pressure simultaneously decreased after the same calculation process. A demonstrative measurement using the sensor revealed the practical usefulness for on-site monitoring.

  18. Shear localization and microstructure in coarse grained beta titanium alloy

    Wang, Bingfeng, E-mail: biw009@ucsd.edu [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan (China); School of Materials Science and Engineering, Central South University, Changsha, Hunan (China); Department of Mechanical and Aerospace Engineering, University of California, San Diego, United States of America (United States); Key Lab of Nonferrous Materials, Ministry of Education, Central South University, Changsha, Hunan (China); Wang, Xiaoyan [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan (China); School of Materials Science and Engineering, Central South University, Changsha, Hunan (China); Li, Zezhou [Department of Mechanical and Aerospace Engineering, University of California, San Diego, United States of America (United States); Ma, Rui [School of Materials Science and Engineering, Central South University, Changsha, Hunan (China); Zhao, Shiteng [Department of Mechanical and Aerospace Engineering, University of California, San Diego, United States of America (United States); Xie, Fangyu [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan (China); School of Materials Science and Engineering, Central South University, Changsha, Hunan (China); Zhang, Xiaoyong [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan (China)

    2016-01-15

    Adiabatic shear localization plays an important role in the deformation and failure of the coarse grained beta titanium alloy Ti-5 Al-5 Mo-5 V-1 Cr-1 Fe with grain size about 1 mm at high strain rate deformation. Hat shaped specimens with different nominal shear strains are used to induce the formation of shear bands under the controlled shock-loading experiments. The true stress in the specimens can reach about 1040 MPa where the strain is about 1.83. The whole shear localization process lasts about 35 μs. The microstructures within the shear band are investigated by optical microscopy, scanning electron microscopy / electron backscatter diffraction, and transmission electron microscopy. The results show that the width of the shear bands decreases with increasing nominal shear strain, and the grains in the transition region near the shear band are elongated along the shear band, and the core of the shear band consists of the ultrafine deformed grains with width of 0.1 μm and heavy dislocations. With the aims of accommodating the imposed shear strain and maintaining neighboring grain compatibility, the grain subdivision continues to take place within the band. A fiber texture is formed in the core of the shear band. The calculated temperature rise in the shear band can reach about 722 K. Dynamic recovery is responsible for the formation of the microstructure in coarse grained beta titanium alloy.

  19. Development of kink bands in granodiorite: Effect of mechanical heterogeneities, fault geometry, and friction

    Chheda, T. D.; Nevitt, J. M.; Pollard, D. D.

    2014-12-01

    the shortening is accommodated by more kinking. Analysis of these parameters also gives us an insight concerning the kilometer-scale kink band in the Mount Abbot Quadrangle, where the Rosy Finch Shear Zone may provide the mechanical heterogeneity that is necessary to cause kinking.

  20. Shear Elasticity and Shear Viscosity Imaging in Soft Tissue

    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

  1. C-Band Airport Surface Communications System Standards Development, Phase I

    Hall, Edward; Isaacs, James; Zelkin, Natalie; Henriksen. Steve

    2010-01-01

    This document is being provided as part of ITT's NASA Glenn Research Center Aerospace Communication Systems Technical Support (ACSTS) contract NNC05CA85C, Task 7: "New ATM Requirements--Future Communications, C-Band and L-Band Communications Standard Development." The proposed future C-band (5091- to 5150-MHz) airport surface communication system, referred to as the Aeronautical Mobile Airport Communications System (AeroMACS), is anticipated to increase overall air-to-ground data communications systems capacity by using a new spectrum (i.e., not very high frequency (VHF)). Although some critical services could be supported, AeroMACS will also target noncritical services, such as weather advisory and aeronautical information services as part of an airborne System Wide Information Management (SWIM) program. AeroMACS is to be designed and implemented in a manner that will not disrupt other services operating in the C-band. This report defines the AeroMACS concepts of use, high-level system requirements, and architecture; the performance of supporting system analyses; the development of AeroMACS test and demonstration plans; and the establishment of an operational AeroMACS capability in support of C-band aeronautical data communications standards to be advanced in both international (International Civil Aviation Organization, ICAO) and national (RTCA) forums. This includes the development of system parameter profile recommendations for AeroMACS based on existing Institute of Electrical and Electronics Engineering (IEEE) 802.16e- 2009 standards

  2. Observation and modeling of mixing-layer development in high-energy-density, blast-wave-driven shear flow

    Di Stefano, C. A.; Kuranz, C. C.; Klein, S. R.; Drake, R. P.; Malamud, G.; Henry de Frahan, M. T.; Johnsen, E.; Shimony, A.; Shvarts, D.; Smalyuk, V. A.; Martinez, D.

    2014-01-01

    In this work, we examine the hydrodynamics of high-energy-density (HED) shear flows. Experiments, consisting of two materials of differing density, use the OMEGA-60 laser to drive a blast wave at a pressure of ∼50 Mbar into one of the media, creating a shear flow in the resulting shocked system. The interface between the two materials is Kelvin-Helmholtz unstable, and a mixing layer of growing width develops due to the shear. To theoretically analyze the instability's behavior, we rely on two sources of information. First, the interface spectrum is well-characterized, which allows us to identify how the shock front and the subsequent shear in the post-shock flow interact with the interface. These observations provide direct evidence that vortex merger dominates the evolution of the interface structure. Second, simulations calibrated to the experiment allow us to estimate the time-dependent evolution of the deposition of vorticity at the interface. The overall result is that we are able to choose a hydrodynamic model for the system, and consequently examine how well the flow in this HED system corresponds to a classical hydrodynamic description

  3. Application of Ring Shear Testing to Optimize Pharmaceutical Formulation and Process Development of Solid Dosage Forms

    Søgaard, Søren Vinter; Pedersen, Troels; Allesø, Morten

    This study investigates how shear and wall friction tests performed at small stresses can be applied to predict critical flow properties of powders, such as flow patterns and arching tendencies, in pharmaceutical manufacturing operations. The study showed that this approach is a promising method...

  4. Linear and nonlinear development of m=0 instability in a diffuse Bennett Z-pinch equilibrium with sheared axial flow

    Paraschiv, I.; Bauer, B. S.; Lindemuth, I. R.; Makhin, V.

    2010-01-01

    The effect of sheared axial flow on the Z-pinch sausage instability has been examined with two-dimensional magnetohydrodynamic simulations. Diffuse Bennett equilibria in the presence of axial flows with parabolic and linear radial profiles have been considered, and a detailed study of the linear and nonlinear development of small perturbations from these equilibria has been performed. The consequences of both single-wavelength and random-seed perturbations were calculated. It was found that sheared flows changed the internal m=0 mode development by reducing the linear growth rates, decreasing the saturation amplitude, and modifying the instability spectrum. High spatial frequency modes were stabilized to small amplitudes and only long wavelengths continued to grow. Full stability was obtained for supersonic plasma flows.

  5. Development of III-Sb Quantum Dot Systems for High Efficiency Intermediate Band Solar Cells

    Huffaker, Diana [Univ. of California, Los Angeles, CA (United States); Hubbard, Seth [Rochester Inst. of Technology, NY (United States); Norman, Andrew [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2015-07-31

    This project aimed to develop solar cells that can help reduce cost per watt. This work focused on developing solar cells that utilize quantum dot (QD) nanomaterials to provide multijunction solar cell efficiency at the cost of single junction solar cell. We focused on a novel concept known as intermediate band solar cells (IBSC) where an additional energy band is inserted in a single solar cell to accommodate sub-bandgap photons absorption which otherwise are lost through transmission. The additional energy band can be achieved by growing QDs within a solar cell p-n junction. Though numerous studies have been conducted to develop such QD systems, very small improvements in solar energy conversion efficiency have been reported. This is mainly due to non-optimal material parameters such as band gap, band offset etc. In this work, we identified and developed a novel QD material system that meets the requirements of IBSC more closely than the current state-of-the-art technology. To achieve these goals, we focused on three important areas of solar cell design: band structure calculations of new materials, efficient device design for high efficiency, and development of new semiconductor materials. In this project, we focused on III-Sb materials as they possess a wide range of energy bandgaps from 0.2 eV to 2eV. Despite the difficulty involved in realizing these materials, we were successfully developed these materials through a systematic approach. Materials studied in this work are AlAsSb (Aluminum Arsenide Antimonide), InAlAs (Indium Aluminum Arsenide) and InAs (Indium Arsenide). InAs was used to develop QD layers within AlAsSb and InAlAs p-n junctions. As the QDs have very small volume, up to 30 QD layers been inserted into the p-n junction to enhance light absorption. These QD multi-stack devices helped in understanding the challenges associated with the development of quantum dot solar cells. The results from this work show that the quantum dot solar cells indeed

  6. Facebook Band Director's Group: Member Usage Behaviors and Perceived Satisfaction for Meeting Professional Development Needs

    Rickels, David A.; Brewer, Wesley D.

    2017-01-01

    The purpose of this study was to investigate participation in a Facebook social media community known as Band Director's Group (BDG) through examination of members' demographic profiles, self-reported usage behaviors, and perceptions about how group activity satisfies their professional development needs. Respondents to an online survey (n = 336)…

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

    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...

  8. Development of C-band Accelerating Section for SuperKEKB

    Kamitani, T; Ikeda, M; Kakihara, K; Ohsawa, S; Oogoe, T; Sugimura, T; Takatomi, T; Yamaguchi, S; Yokoyama, K

    2004-01-01

    For the luminosity upgrade of the present KEK B-factory to SuperKEKB, the injector linac has to increase the positron acceleration energy from 3.5 to 8.0 GeV. In order to double the acceleration field gradient from 21 to 42 MV/m, design studies on C-band accelerator module has started in 2002. First prototype 1-m long accelerating section has been fabricated based upon a design which is half scale of the present S-band section. High power test of the C-band section has been performed at a test stand and later at an accelerator module in the KEKB injector linac. In a beam acceleration test, a field gradient of 41 MV/m is achieved with 43 MW RF power from a klystron. This paper report on the recent status of the high-power test and also the development of a second prototype section.

  9. Development of narrow-band fluorescence index for the detection of aflatoxin contaminated corn

    Yao, Haibo; Hruska, Zuzana; Kincaid, Russell; Ononye, Ambrose; Brown, Robert L.; Bhatnagar, Deepak; Cleveland, Thomas E.

    2011-06-01

    Aflatoxin is produced by the fungus Aspergillus flavus when the fungus invades developing corn kernels. Because of its potent toxicity, the levels of aflatoxin are regulated by the Food and Drug Administration (FDA) in the US, allowing 20 ppb (parts per billion) limits in food, and feed intended for interstate commerce. Currently, aflatoxin detection and quantification methods are based on analytical tests. These tests require the destruction of samples, can be costly and time consuming, and often rely on less than desirable sampling techniques. Thus, the ability to detect aflatoxin in a rapid, non-invasive way is crucial to the corn industry in particular. This paper described how narrow-band fluorescence indices were developed for aflatoxin contamination detection based on single corn kernel samples. The indices were based on two bands extracted from full wavelength fluorescence hyperspectral imagery. The two band results were later applied to two large sample experiments with 25 g and 1 kg of corn per sample. The detection accuracies were 85% and 95% when 100 ppb threshold was used. Since the data acquisition period is significantly lower for several image bands than for full wavelength hyperspectral data, this study would be helpful in the development of real-time detection instrumentation for the corn industry.

  10. Development of Flexible Extremities Protection utilizing Shear Thickening Fluid/Fabric Composites

    2012-01-19

    The influence of Interparticle Interactions and Hydrodynamic Forces on Shear Thickening in Concentrated Colloidal Dispersions and Slurries 10...Armor Using Fumed SiO2 Nanoparticles Dispersed into Polyethylene Glycol (PEG) through Sonic Cavitation , NSTI-Nanotech 2006. 2006/05/07 00:00:00...for a wide variety of suspensions such as clay–water [17], calcium carbonate–water [18], polystyrene spheres in silicon oil [19], iron particles in

  11. Development of a wall-shear-stress sensor and measurements in mini-channels with partial blockages

    Afara, Samer; Medvescek, James; Mydlarski, Laurent; Baliga, Bantwal R.; MacDonald, Mark

    2014-05-01

    The design, construction, operation and validation of a wall-shear-stress sensor, and measurements obtained using this sensor in air flows downstream of partial blockages in a mini-channel are presented. The sensor consisted of a hot wire mounted over a small rectangular slot and operated using a constant-temperature anemometer. It was used to investigate flows similar to those within the mini-channels inside notebook computers. The overall goal of the present work was to develop a sensor suitable for measurements of the wall-shear stress in such flows, which can be used to validate corresponding numerical simulations, as the latter are known to be often surprisingly inaccurate. To this end, measurements of the wall-shear stress, and the corresponding statistical moments and power spectral densities, were obtained at different distances downstream of the partial blockage, with blockage ratios of 39.7, 59.2, and 76.3 %. The Reynolds number (based on average velocity and hydraulic diameter) ranged from 100 to 900. The results confirmed the presence of unsteadiness, separation, reattachment, and laminar-turbulent transition in the ostensibly laminar flow of air in mini-channels with partial blockages. The present results demonstrate why accurate numerical predictions of cooling air flows in laptop and notebook computers remain a challenging task.

  12. Development of new pedestal temperature models with self-consistent magnetic shear and safety factor in BALDUR and JETTO codes

    Suwanna, S.; Onjun, T.; Wongpan, P.; Parail, V.; Poolyarat, N.; Picha, R.

    2009-01-01

    Full text: A formation of a steep pressure gradient region near the plasma edge, called the pedestal, is a main reason for an improved performance in H-mode plasma. In this work, new pedestal temperature models are developed based on different theoretical-based width concepts: flow shear stabilization width concept, magnetic and flow shear stabilization width concept, and diamagnetic stabilization width concept. In the BALDUR code, each pedestal width model is combined with a ballooning mode pressure gradient model to predict the pedestal temperature, which is a boundary condition needed to predict plasma profiles. In the JETTO code, an anomalous transport is suppressed within the pedestal region, which results in a formation of a steep pressure gradient region. The pedestal width is predicted using these theoretically based width concepts. The plasma profiles in the pedestal region are limited by ELM crashes, which can be triggered either by ballooning modes or by peeling modes, depending on which instability is destabilized first. It is found in the BALDUR simulations that the simulated pedestal temperature profiles agree well with experimental data in the region close to the pedestal, but show larger deviation in the core region. In a preliminary investigation, these models agree reasonably well with experiments, yielding overall RMS less than 20%. Furthermore, the model based flow shear stabilization matches very well data from both DIII-D and JET, while the model based on magnetic and flow shear stabilization over-predicts results from JET and under-predicts those from DIII-D. Other statistical analyses such a calculation of offset values, ratios of predicted pedestal (resp. core) temperatures to those from experiments are performed. (author)

  13. Development and testing of Band 10 receivers for the ALMA project

    Uzawa, Y., E-mail: y.uzawa@nao.ac.jp [National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Fujii, Y.; Gonzalez, A.; Kaneko, K.; Kroug, M.; Kojima, T.; Kuroiwa, K.; Miyachi, A. [National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Saito, S.; Makise, K.; Wang, Z. [National Institute of Information and Telecommunications Technology, 588-2 Iwaoka, Iwaoka-cho, Kobe, Hyogo 651-2492 (Japan); Asayama, S. [Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago (Chile)

    2013-11-15

    Highlights: •The ALMA Band 10 (787–950 GHz) SIS receivers have been developed. •The complex conductivity of NbTiN was measured by a THz-TDS for the mixer design. •Tens of Band 10 receivers have been produced and their performance was quite well. •The best achieved receiver noise temperature was 125 K corresponding to 3hf/k{sub B}. •Band 10 receiver installed in the ALMA antenna captured astronomical signals. -- Abstract: The production model of a dual polarization heterodyne receiver for the Atacama Large Millimeter/submillimteter Array (ALMA) telescope has been developed to operate in the 787–950 GHz frequency band. The receiver uses two double sideband (DSB) waveguide mixers with Nb/AlOx/Nb tunnel junctions and NbTiN/SiO{sub 2}/Al microstrip tuning circuits on quartz substrate. A terahertz time domain spectrometer was used to characterize our NbTiN film for the tuning circuit design, which revealed that the complex conductivity of the film is described by the Mattis-Bardeen theory including a finite scattering time of 15 fs and a superconducting gap with a gap ratio 2Δ/k{sub B}T{sub C} ∼ 4.0. Tens of these receivers (out of the total production number of 73) have been successfully produced, and their performance is well within the stringent ALMA requirements. The best achieved DSB receiver noise temperature is 125 K, corresponding to about 3hf/k{sub B} for 4 K operation. One of Band 10 receivers has successfully been installed in the ALMA antenna for a test observation.

  14. Development and testing of Band 10 receivers for the ALMA project

    Uzawa, Y.; Fujii, Y.; Gonzalez, A.; Kaneko, K.; Kroug, M.; Kojima, T.; Kuroiwa, K.; Miyachi, A.; Saito, S.; Makise, K.; Wang, Z.; Asayama, S.

    2013-01-01

    Highlights: •The ALMA Band 10 (787–950 GHz) SIS receivers have been developed. •The complex conductivity of NbTiN was measured by a THz-TDS for the mixer design. •Tens of Band 10 receivers have been produced and their performance was quite well. •The best achieved receiver noise temperature was 125 K corresponding to 3hf/k B . •Band 10 receiver installed in the ALMA antenna captured astronomical signals. -- Abstract: The production model of a dual polarization heterodyne receiver for the Atacama Large Millimeter/submillimteter Array (ALMA) telescope has been developed to operate in the 787–950 GHz frequency band. The receiver uses two double sideband (DSB) waveguide mixers with Nb/AlOx/Nb tunnel junctions and NbTiN/SiO 2 /Al microstrip tuning circuits on quartz substrate. A terahertz time domain spectrometer was used to characterize our NbTiN film for the tuning circuit design, which revealed that the complex conductivity of the film is described by the Mattis-Bardeen theory including a finite scattering time of 15 fs and a superconducting gap with a gap ratio 2Δ/k B T C ∼ 4.0. Tens of these receivers (out of the total production number of 73) have been successfully produced, and their performance is well within the stringent ALMA requirements. The best achieved DSB receiver noise temperature is 125 K, corresponding to about 3hf/k B for 4 K operation. One of Band 10 receivers has successfully been installed in the ALMA antenna for a test observation

  15. Design of an X-band accelerating structure using a newly developed structural optimization procedure

    Huang, Xiaoxia [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Fang, Wencheng; Gu, Qiang [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Zhao, Zhentang, E-mail: zhaozhentang@sinap.ac.cn [Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); University of Chinese Academy of Sciences, Beijing 100049 (China)

    2017-05-11

    An X-band high gradient accelerating structure is a challenging technology for implementation in advanced electron linear accelerator facilities. The present work discusses the design of an X-band accelerating structure for dedicated application to a compact hard X-ray free electron laser facility at the Shanghai Institute of Applied Physics, and numerous design optimizations are conducted with consideration for radio frequency (RF) breakdown, RF efficiency, short-range wakefields, and dipole/quadrupole field modes, to ensure good beam quality and a high accelerating gradient. The designed X-band accelerating structure is a constant gradient structure with a 4π/5 operating mode and input and output dual-feed couplers in a racetrack shape. The design process employs a newly developed effective optimization procedure for optimization of the X-band accelerating structure. In addition, the specific design of couplers providing high beam quality by eliminating dipole field components and reducing quadrupole field components is discussed in detail.

  16. Shape fabric development in rigid clast populations under pure shear: The influence of no-slip versus slip boundary conditions

    Mulchrone, Kieran F.; Meere, Patrick A.

    2015-09-01

    Shape fabrics of elliptical objects in rocks are usually assumed to develop by passive behavior of inclusions with respect to the surrounding material leading to shape-based strain analysis methods belonging to the Rf/ϕ family. A probability density function is derived for the orientational characteristics of populations of rigid ellipses deforming in a pure shear 2D deformation with both no-slip and slip boundary conditions. Using maximum likelihood a numerical method is developed for estimating finite strain in natural populations deforming for both mechanisms. Application to a natural example indicates the importance of the slip mechanism in explaining clast shape fabrics in deformed sediments.

  17. Development of an ultrasonic shear reflection technique to monitor the crystallization of cocoa butter.

    Rigolle, Annelien; Foubert, Imogen; Hettler, Jan; Verboven, Erik; Demuynck, Ruth; Van Den Abeele, Koen

    2015-09-01

    The quasi-isothermal crystallization process of cocoa butter was monitored by an ultrasonic shear reflection technique utilizing a custom-built experimental set-up in a temperature controlled environment. To facilitate the interpretation of the measurement results, the propagation of shear waves was first theoretically studied in different configurations of gas, liquid or solid layers with varying thickness for the case of normal incidence, yielding theoretical equations of the shear wave reflection coefficient (swRC) for different layering conditions. The typical experimentally observed pattern of the swRC during quasi-isothermal cocoa butter crystallization was subsequently linked to the theoretical equations. The remarkable oscillatory damped response in the swRC as function of the crystallization time could be explained by constructive and destructive interference of a first reflection at the boundary between a plexiglass delay line and the crystallized cocoa butter and a second reflection occurring at the interface between crystallized and liquid substance. This hypothesis was supported by the excitation frequency dependence of the oscillations. The quality of the fit of the theoretical model to the experimental results was very good and also the reproducibility between different independent measurements was acceptable. Finally, measurements at different temperatures (18°C and 20°C) suggested that the technique was able to detect differences in crystallization behavior, as measurements at 18°C displayed faster oscillations compared to measurements at 20°C. Moreover, this was also confirmed by the theoretical model, as a higher value of the crystallization rate parameter K, exhibited more rapid oscillations. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. The Development of Layered Photonic Band Gap Structures Using a Micro-Transfer Molding Technique

    Kevin Jerome Sutherland

    2001-01-01

    Photonic band gap (PBG) crystals are periodic dielectric structures that manipulate electromagnetic radiation in a manner similar to semiconductor devices manipulating electrons. Whereas a semiconductor material exhibits an electronic band gap in which electrons cannot exist, similarly, a photonic crystal containing a photonic band gap does not allow the propagation of specific frequencies of electromagnetic radiation. This phenomenon results from the destructive Bragg diffraction interference that a wave propagating at a specific frequency will experience because of the periodic change in dielectric permitivity. This gives rise to a variety of optical applications for improving the efficiency and effectiveness of opto-electronic devices. These applications are reviewed later. Several methods are currently used to fabricate photonic crystals, which are also discussed in detail. This research involves a layer-by-layer micro-transfer molding ((mu)TM) and stacking method to create three-dimensional FCC structures of epoxy or titania. The structures, once reduced significantly in size can be infiltrated with an organic gain media and stacked on a semiconductor to improve the efficiency of an electronically pumped light-emitting diode. Photonic band gap structures have been proven to effectively create a band gap for certain frequencies of electro-magnetic radiation in the microwave and near-infrared ranges. The objective of this research project was originally two-fold: to fabricate a three dimensional (3-D) structure of a size scaled to prohibit electromagnetic propagation within the visible wavelength range, and then to characterize that structure using laser dye emission spectra. As a master mold has not yet been developed for the micro transfer molding technique in the visible range, the research was limited to scaling down the length scale as much as possible with the current available technology and characterizing these structures with other methods

  19. The Development of Layered Photonic Band Gap Structures Using a Micro-Transfer Molding Technique

    Sutherland, Kevin Jerome [Iowa State Univ., Ames, IA (United States)

    2001-01-01

    Photonic band gap (PBG) crystals are periodic dielectric structures that manipulate electromagnetic radiation in a manner similar to semiconductor devices manipulating electrons. Whereas a semiconductor material exhibits an electronic band gap in which electrons cannot exist, similarly, a photonic crystal containing a photonic band gap does not allow the propagation of specific frequencies of electromagnetic radiation. This phenomenon results from the destructive Bragg diffraction interference that a wave propagating at a specific frequency will experience because of the periodic change in dielectric permitivity. This gives rise to a variety of optical applications for improving the efficiency and effectiveness of opto-electronic devices. These applications are reviewed later. Several methods are currently used to fabricate photonic crystals, which are also discussed in detail. This research involves a layer-by-layer micro-transfer molding ({mu}TM) and stacking method to create three-dimensional FCC structures of epoxy or titania. The structures, once reduced significantly in size can be infiltrated with an organic gain media and stacked on a semiconductor to improve the efficiency of an electronically pumped light-emitting diode. Photonic band gap structures have been proven to effectively create a band gap for certain frequencies of electro-magnetic radiation in the microwave and near-infrared ranges. The objective of this research project was originally two-fold: to fabricate a three dimensional (3-D) structure of a size scaled to prohibit electromagnetic propagation within the visible wavelength range, and then to characterize that structure using laser dye emission spectra. As a master mold has not yet been developed for the micro transfer molding technique in the visible range, the research was limited to scaling down the length scale as much as possible with the current available technology and characterizing these structures with other methods.

  20. Adiabatic shear localization in ultrafine grained 6061 aluminum alloy

    Wang, Bingfeng, E-mail: biw009@ucsd.edu [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Department of Mechanical and Aerospace Engineering, University of California, San Diego (United States); State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan (China); Key Lab of Nonferrous Materials, Ministry of Education, Central South University, Changsha 410083 (China); Ma, Rui; Zhou, Jindian [School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Li, Zezhou; Zhao, Shiteng [Department of Mechanical and Aerospace Engineering, University of California, San Diego (United States); Huang, Xiaoxia [School of Materials Science and Engineering, Central South University, Changsha 410083 (China)

    2016-10-15

    Localized shear is an important mode of deformation; it leads to catastrophic failure with low ductility, and occurs frequently during high strain-rate deformation. The hat-shaped specimen has been successfully used to generate shear bands under controlled shock-loading tests. The microstructure in the forced shear band was characterized by optical microscopy, microhardness, and transmission electron microscopy. The true flow stress in the shear region can reach 800 MPa where the strain is about 2.2. The whole shear localization process lasts for about 100 μs. The shear band is a long and straight band distinguished from the matrix by boundaries. It can be seen that the grains in the boundary of the shear band are highly elongated along the shear direction and form the elongated cell structures (0.2 µm in width), and the core of the shear band consists of a number of recrystallized equiaxed grains with 0.2−0.3 µm in diameters, and the second phase particles distribute in the boundary of the ultrafine equiaxed new grains. The calculated temperature in the shear band can reach about 667 K. Finally, the formation of the shear band in the ultrafine grained 6061 aluminum alloy and its microstructural evolution are proposed.

  1. A state-of-the-art anisotropic rock deformation model incorporating the development of mobilised shear strength

    Noor, M. J. Md; Jobli, A. F.

    2018-04-01

    Currently rock deformation is estimated using the relationship between the deformation modulus Em and the stress-strain curve. There have been many studies conducted to estimate the value of Em. This Em is basically derived from conducting unconfined compression test, UCS. However, the actual stress condition of the rock in the ground is anisotropic stress condition where the rock mass is subjected to different confining and vertical pressures. In addition, there is still no empirical or semi-empirical framework that has been developed for the prediction of rock stress-strain response under anisotropic stress condition. Arock triaxial machine GCTS Triaxial RTX-3000 has been deployed to obtain the anisotropic stress-strain relationship for weathered granite grade II from Rawang, Selangor sampled at depth of 20 m and subjected to confining pressure of 2 MPa, 7.5 MPa and 14 MPa. The developed mobilised shear strength envelope within the specimen of 50 mm diameter and 100 mm height during the application of the deviator stress is interpreted from the stress-strain curves. These mobilised shear strength envelopes at various axial strains are the intrinsic property and unique for the rock. Once this property has been established then it is being used to predict the stress-strain relationship at any confining pressure. The predicted stress-strain curves are compared against the curves obtained from the tests. A very close prediction is achieved to substantiate the applicability of this rock deformation model. This is a state-of-the art rock deformation theory which characterise the deformation base on the applied load and the developed mobilised shear strength within the rock body.

  2. Development of small C-band standing-wave accelerator structure

    Miura, S.; Takahashi, A.; Hisanaga, N.; Sekido, H.; Yoshizumi, A.

    2000-01-01

    We have newly developed a compact C-band (5712 MHz) standing-wave accelerator for the medical product/waste sterilization applications. The accelerator consists of an electron gun operating at 25 kV DC followed by a single-cell pre-buncher and 3-cell buncher section, and 11-cell of the side-coupled standing-wave accelerating structure. The total length including the electron gun is about 600 mm. The first high-power test was performed in March 2000, where the accelerator successively generated the electron beam of 9 MeV energy and 160 mA peak-current at 3.8 MW RF input power. Mitsubishi Heavy Industry starts to serve the sterilization systems using C-band accelerator reported here, and also supplies the accelerator components for the medical oncology applications. (author)

  3. Development and Application of integrated monitoring platform for the Doppler Weather SA-BAND Radar

    Zhang, Q.; Sun, J.; Zhao, C. C.; Chen, H. Y.

    2017-10-01

    The doppler weather SA-band radar is an important part of modern meteorological observation methods, monitoring the running status of radar and the data transmission is important.This paper introduced the composition of radar system and classification of radar data,analysed the characteristics and laws of the radar when is normal or abnormal. Using Macromedia Dreamweaver and PHP, developed the integrated monitoring platform for the doppler weather SA-band radar which could monitor the real-time radar system running status and important performance indicators such as radar power,status parameters and others on Web page,and when the status is abnormal it will trigger the audio alarm.

  4. Development of an S-band cavity Beam Position Monitor for ATF2

    Heo, A.; Kim, E.-S.; Kim, H.; Son, D.; Honda, Y.; Tauchi, T.

    2013-04-01

    We have developed an S-band cavity Beam Position Monitor (BPM) in order to measure the position of an electron beam in the final focus area at ATF2, which is the test facility for the final focus design for the International Linear Collider (ILC). The lattice of the ILC Beam Delivery System (BDS) has been modified, requiring a larger physical aperture of 40 mm in the final focus area. The beam orbit measurement in this area is now covered with high resolution S-Band cavity BPMs. In this paper we summarize the design of the cavity BPM and the first experimental results. The calibration slopes were measured as 0.87 counts/μm in the x-coordinate direction and 1.16 counts/μm in the y-coordinate direction.

  5. What are the factors that affect band 5 nurses' career development and progression?

    Balls, Paula

    Continuing professional development (CPD) and career progression opportunities have been linked with job satisfaction and intent to remain in nursing. To provide an insight into band 5 registered nurses' perceptions of development opportunities and their ability to change posts. A hermeneutic phenomenological approach was used, collecting data through semi structured interviews with six RNs. Seven themes emerged, including the thirst for knowledge and the importance of structured learning and career advice. Barriers to career development were perceived as the working environment and the trust not enabling and facilitating development through funding and release time. Ward and team culture can inhibit career development and progression by failing to nurture staff and promote self confidence. In addition, organisational changes can facilitate career mobility.

  6. Plasticity Approach to Shear Design

    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....

  7. FaCT phase-I evaluation on the advanced aqueous reprocessing process (2). Development of mechanical disassembly and short stroke shearing systems for FBR fuel reprocessing

    Takeuchi, Masayuki; Kitagaki, Toru; Higuchi, Hidetoshi; Fukushima, Mineo; Washiya, Tadahiro; Kobayashi, Tsuguyuki

    2011-01-01

    JAEA promotes a development of an advanced head-end process in FaCT project. We selected mechanical cutting method for disassembly process and short stroke method for shearing process. In the FaCT phase-I, the criteria was set for decision about the innovative technology and some fundamental performances of the innovative technology such as precision, speed, durability, operation performance and system concept were discussed by the engineering test and design work. We designed and fabricated an engineering-scale test device for mechanical disassembly and short stroke shearing and have carried out the engineering tests using simulated fuel assemblies. As a part of the engineering test results, the effects of cutting conditions on the durability of cutting tool and cutting stability were discussed. Also, the reduction of magazine width is effective to improve the precision of sheared pin length, and the bundle of simulated fuel pins were successfully sheared to 10 ± 5mm, which is a target for the sheared pin length. The criteria for the mechanical disassembly technology and the short stroke shearing technology were satisfied, so we judged that the development of innovative technologies has worth going on for the next phase in the FaCT project. (author)

  8. Development of a rocking R/C shear wall system implementing repairable structural fuses

    Parsafar, Saeed; Moghadam, Abdolreza S.

    2017-09-01

    In the last decades, the concept of earthquake resilient structural systems is becoming popular in which the rocking structure is considered as a viable option for buildings in regions of high seismicity. To this end, a novel wall-base connection based on the " repairable structure" approach is proposed and evaluated. The proposed system is made of several steel plates and high strength bolts act as a friction connection. To achieve the desired rocking motion in the proposed system, short-slotted holes are used in vertical directions for connecting the steel plates to the shear wall (SW). The experimental and numerical studies were performed using a series of displacement control quasi-static cyclic tests on a reference model and four different configurations of the proposed connection installed at the wall corners. The seismic response of the proposed system is compared to the conventional SW in terms of energy dissipation and damage accumulation. In terms of energy dissipation, the proposed system depicted better performance with 95% more energy dissipation capability compared to conventional SW. In terms of damage accumulation, the proposed SW system is nearly undamaged compared to the conventional wall system, which was severely damaged at the wall-base region. Overall, the introduced concept presents a feasible solution for R/C structures when a low-damage design is targeted, which can improve the seismic performance of the structural system significantly.

  9. Towards a new tool to develop a 3-D shear-wave velocity model from converted waves

    Colavitti, Leonardo; Hetényi, György

    2017-04-01

    The main target of this work is to develop a new method in which we exploit converted waves to construct a fully 3-D shear-wave velocity model of the crust. A reliable 3-D model is very important in Earth sciences because geological structures may vary significantly in their lateral dimension. In particular, shear-waves provide valuable complementary information with respect to P-waves because they usually guarantee a much better correlation in terms of rock density and mechanical properties, reducing the interpretation ambiguities. Therefore, it is fundamental to develop a new technique to improve structural images and to describe different lithologies in the crust. In this study we start from the analysis of receiver functions (RF, Langston, 1977), which are nowadays largely used for structural investigations based on passive seismic experiments, to map Earth discontinuities at depth. The RF technique is also commonly used to invert for velocity structure beneath single stations. Here, we plan to combine two strengths of RF method: shear-wave velocity inversion and dense arrays. Starting from a simple 3-D forward model, synthetic RFs are obtained extracting the structure along a ray to match observed data. During the inversion, thanks to a dense stations network, we aim to build and develop a multi-layer crustal model for shear-wave velocity. The initial model should be chosen simple to make sure that the inversion process is not influenced by the constraints in terms of depth and velocity posed at the beginning. The RFs inversion represents a complex problem because the amplitude and the arrival time of different phases depend in a non-linear way on the depth of interfaces and the characteristics of the velocity structure. The solution we envisage to manage the inversion problem is the stochastic Neighbourhood Algorithm (NA, Sambridge, 1999a, b), whose goal is to find an ensemble of models that sample the good data-fitting regions of a multidimensional parameter

  10. The genesis of adiabatic shear bands

    Landau, P.; Osovski, S.; Venkert, A.; Gärtnerová, Viera; Rittel, D.

    2016-01-01

    Roč. 6, Nov (2016), s. 1-6, č. článku 37226. ISSN 2045-2322 R&D Projects: GA ČR GBP108/12/G043 Institutional support: RVO:68378271 Keywords : mechanical engineering * mechanical properties * metals and alloys * phase transitions and critical phenomena Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 4.259, year: 2016

  11. Large Eddy Simulation of Spatially Developing Turbulent Reacting Shear Layers with the One-Dimensional Turbulence Model

    Hoffie, Andreas Frank

    Large eddy simulation (LES) combined with the one-dimensional turbulence (ODT) model is used to simulate spatially developing turbulent reacting shear layers with high heat release and high Reynolds numbers. The LES-ODT results are compared to results from direct numerical simulations (DNS), for model development and validation purposes. The LES-ODT approach is based on LES solutions for momentum and pressure on a coarse grid and solutions for momentum and reactive scalars on a fine, one-dimensional, but three-dimensionally coupled ODT subgrid, which is embedded into the LES computational domain. Although one-dimensional, all three velocity components are transported along the ODT domain. The low-dimensional spatial and temporal resolution of the subgrid scales describe a new modeling paradigm, referred to as autonomous microstructure evolution (AME) models, which resolve the multiscale nature of turbulence down to the Kolmogorv scales. While this new concept aims to mimic the turbulent cascade and to reduce the number of input parameters, AME enables also regime-independent combustion modeling, capable to simulate multiphysics problems simultaneously. The LES as well as the one-dimensional transport equations are solved using an incompressible, low Mach number approximation, however the effects of heat release are accounted for through variable density computed by the ideal gas equation of state, based on temperature variations. The computations are carried out on a three-dimensional structured mesh, which is stretched in the transverse direction. While the LES momentum equation is integrated with a third-order Runge-Kutta time-integration, the time integration at the ODT level is accomplished with an explicit Forward-Euler method. Spatial finite-difference schemes of third (LES) and first (ODT) order are utilized and a fully consistent fractional-step method at the LES level is used. Turbulence closure at the LES level is achieved by utilizing the Smagorinsky

  12. New developed cylindrical TM010 mode EPR cavity for X-band in vivo tooth dosimetry.

    Guo Junwang

    Full Text Available EPR tooth in vivo dosimetry is an attractive approach for initial triage after unexpected nuclear events. An X-band cylindrical TM010 mode resonant cavity was developed for in vivo tooth dosimetry and used in EPR applications for the first time. The cavity had a trapezoidal measuring aperture at the exact position of the cavity's cylindrical wall where strong microwave magnetic field H1 concentrated and weak microwave electric field E1 distributed. Theoretical calculations and simulations were used to design and optimize the cavity parameters. The cavity features were evaluated by measuring DPPH sample, intact incisor samples embed in a gum model and the rhesus monkey teeth. The results showed that the cavity worked at designed frequency and had the ability to make EPR spectroscopy in relative high sensitivity. Sufficient modulation amplitude and microwave power could be applied into the aperture. Radiation induced EPR signal could be observed remarkably from 1 Gy irradiated intact incisor within only 30 seconds, which was among the best in scan time and detection limit. The in vivo spectroscopy was also realized by acquiring the radiation induced EPR signal from teeth of rhesus monkey whose teeth was irradiated by dose of 2 Gy. The results suggested that the cavity was sensitive to meet the demand to assess doses of significant level in short time. This cavity provided a very potential option for the development of X-band in vivo dosimetry.

  13. Development of tearing instability in a current sheet forming by sheared incompressible flow

    Tolman, Elizabeth A.; Loureiro, Nuno F.; Uzdensky, Dmitri A.

    2018-02-01

    Sweet-Parker current sheets in high Lundquist number plasmas are unstable to tearing, suggesting they will not form in physical systems. Understanding magnetic reconnection thus requires study of the stability of a current sheet as it forms. Formation can occur due to sheared, sub-Alfvénic incompressible flows which narrow the sheet. Standard tearing theory (Furth et al. Phys. Fluids, vol. 6 (4), 1963, pp. 459-484, Rutherford, Phys. Fluids, vol. 16 (11), 1973, pp. 1903-1908, Coppi et al. Fizika Plazmy, vol. 2, 1976, pp. 961-966) is not immediately applicable to such forming sheets for two reasons: first, because the flow introduces terms not present in the standard calculation; second, because the changing equilibrium introduces time dependence to terms which are constant in the standard calculation, complicating the formulation of an eigenvalue problem. This paper adapts standard tearing mode analysis to confront these challenges. In an initial phase when any perturbations are primarily governed by ideal magnetohydrodynamics, a coordinate transformation reveals that the flow compresses and stretches perturbations. A multiple scale formulation describes how linear tearing mode theory (Furth et al. Phys. Fluids, vol. 6 (4), 1963, pp. 459-484, Coppi et al. Fizika Plazmy, vol. 2, 1976, pp. 961-966) can be applied to an equilibrium changing under flow, showing that the flow affects the separable exponential growth only implicitly, by making the standard scalings time dependent. In the nonlinear Rutherford stage, the coordinate transformation shows that standard theory can be adapted by adding to the stationary rates time dependence and an additional term due to the strengthening equilibrium magnetic field. Overall, this understanding supports the use of flow-free scalings with slight modifications to study tearing in a forming sheet.

  14. Breaking Sound Barriers: New Perspectives on Effective Big Band Development and Rehearsal

    Greig, Jeremy; Lowe, Geoffrey

    2014-01-01

    Jazz big band is a common extra-curricular musical activity in Western Australian secondary schools. Jazz big band offers important fundamentals that can help expand a student's musical understanding. However, the teaching of conventions associated with big band jazz has often been haphazard and can be daunting and frightening, especially for…

  15. Design and development of low level S-Band RF control system for IRFEL injector LINAC

    Mohania, Praveen; Mahawar, Ashish; Singh, Adarsh Pratap; Namdeo, Rajkumar; Baxy, Deodatta; Shrivastava, Purushottam

    2015-01-01

    A low level RF system has been designed and developed for phase and amplitude stabilization of S- Band microwave power being fed to fundamental buncher cavity and the injector LINAC structure of the Infra Red Free Electron Laser being developed at RRCAT Indore. The system uses analog phase shifters and voltage variable attenuators to control the phase and amplitude respectively, the control voltages for phase shifters and attenuators are generated using a 12 Bit ADC and is software controlled. The system has a slow feedback to correct phase and amplitude drifts occurring due to thermal variations and a fast feed forward mechanism to vary amplitude and phase of the output pulse to compensate beam loading and to shape the klystron output power. The present paper describes the design aspects of the LLRF system. (author)

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

    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.

  17. K-Band Phased Array Developed for Low- Earth-Orbit Satellite Communications

    Anzic, Godfrey

    1999-01-01

    Future rapid deployment of low- and medium-Earth-orbit satellite constellations that will offer various narrow- to wide-band wireless communications services will require phased-array antennas that feature wide-angle and superagile electronic steering of one or more antenna beams. Antennas, which employ monolithic microwave integrated circuits (MMIC), are perfectly suited for this application. Under a cooperative agreement, an MMIC-based, K-band phased-array antenna is being developed with 50/50 cost sharing by the NASA Lewis Research Center and Raytheon Systems Company. The transmitting array, which will operate at 19 gigahertz (GHz), is a state-of-the-art design that features dual, independent, electronically steerable beam operation ( 42 ), a stand-alone thermal management, and a high-density tile architecture. This array can transmit 622 megabits per second (Mbps) in each beam from Earth orbit to small Earth terminals. The weight of the total array package is expected to be less than 8 lb. The tile integration technology (flip chip MMIC tile) chosen for this project represents a major advancement in phased-array engineering and holds much promise for reducing manufacturing costs.

  18. Design and development of permanent magnet based focusing lens for J-Band Klystron

    Singh, Kumud; Itteera, Janvin; Ukarde, Priti; Malhotra, Sanjay; Taly, Y.K., E-mail: kumuds@barc.gov.in [Control Instrumentation Division, Bhabha Atomic Research Centre, Mumbai (India); Bandyopadhay, Ayan; Meena, Rakesh; Rawat, Vikram; Joshi, L.M [Microwave Tubes Division, Central Electronics Engineering Research Institute, Pilani (India)

    2014-07-01

    Applying permanent magnet technology to beam focusing in klystrons can reduce their power consumption and increase their reliability of operation. Electromagnetic design of the beam focusing elements, for high frequency travelling wave tubes, is very critical. The magnitude and profile of the magnetic field need to match the optics requirement from beam dynamics studies. The rise of the field from cathode gun region to the uniform field region (RF section) is important as the desired transition from zero to peak axial field must occur over a short axial distance. Confined flow regime is an optimum choice to minimize beam scalloping but demands an axial magnetic field greater than 2 - 3 times the Brillouin flow field. This necessitates optimization in the magnet design achieve high magnetic field within given spatial constraints. Electromagnetic design and simulations were done using 3D Finite element method (FEM) analysis software. A permanent magnet based focusing lens for a miniature J-Band klystron has been designed and developed at Control Instrumentation Division, BARC. This paper presents the design, simulation studies, beam transmission and RF tests results for J Band klystron with permanent magnet focusing lens. (author)

  19. Automatic Earthquake Shear Stress Measurement Method Developed for Accurate Time- Prediction Analysis of Forthcoming Major Earthquakes Along Shallow Active Faults

    Serata, S.

    2006-12-01

    The Serata Stressmeter has been developed to measure and monitor earthquake shear stress build-up along shallow active faults. The development work made in the past 25 years has established the Stressmeter as an automatic stress measurement system to study timing of forthcoming major earthquakes in support of the current earthquake prediction studies based on statistical analysis of seismological observations. In early 1982, a series of major Man-made earthquakes (magnitude 4.5-5.0) suddenly occurred in an area over deep underground potash mine in Saskatchewan, Canada. By measuring underground stress condition of the mine, the direct cause of the earthquake was disclosed. The cause was successfully eliminated by controlling the stress condition of the mine. The Japanese government was interested in this development and the Stressmeter was introduced to the Japanese government research program for earthquake stress studies. In Japan the Stressmeter was first utilized for direct measurement of the intrinsic lateral tectonic stress gradient G. The measurement, conducted at the Mt. Fuji Underground Research Center of the Japanese government, disclosed the constant natural gradients of maximum and minimum lateral stresses in an excellent agreement with the theoretical value, i.e., G = 0.25. All the conventional methods of overcoring, hydrofracturing and deformation, which were introduced to compete with the Serata method, failed demonstrating the fundamental difficulties of the conventional methods. The intrinsic lateral stress gradient determined by the Stressmeter for the Japanese government was found to be the same with all the other measurements made by the Stressmeter in Japan. The stress measurement results obtained by the major international stress measurement work in the Hot Dry Rock Projects conducted in USA, England and Germany are found to be in good agreement with the Stressmeter results obtained in Japan. Based on this broad agreement, a solid geomechanical

  20. Development of cataclastic foliation in deformation bands in feldspar-rich conglomerates of the Rio do Peixe Basin, NE Brazil

    Nicchio, Matheus A.; Nogueira, Francisco C. C.; Balsamo, Fabrizio; Souza, Jorge A. B.; Carvalho, Bruno R. B. M.; Bezerra, Francisco H. R.

    2018-02-01

    In this work we describe the deformation mechanisms and processes that occurred during the evolution of cataclastic deformation bands developed in the feldspar-rich conglomerates of the Rio do Peixe Basin, NE Brazil. We studied bands with different deformation intensities, ranging from single cm-thick tabular bands to more evolved clustering zones. The chemical identification of cataclastic material within deformation bands was performed using compositional mapping in SEM images, EDX and XRD analyses. Deformation processes were identified by microstructural analysis and by the quantification of comminution intensity, performed using digital image processing. The deformation bands are internally non homogeneous and developed during five evolutionary stages: (1) moderate grain size reduction, grain rotation and grain border comminution; (2) intense grain size reduction with preferential feldspar fragmentation; (3) formation of subparallel C-type slip zones; (4) formation of S-type structures, generating S-C-like fabric; and (5) formation of C‧-type slip zones, generating well-developed foliation that resembles S-C-C‧-type structures in a ductile environment. Such deformation fabric is mostly imparted by the preferential alignment of intensely comminuted feldspar fragments along thin slip zones developed within deformation bands. These processes were purely mechanical (i.e., grain crushing and reorientation). No clays or fluids were involved in such processes.

  1. Progress on the development of NbZr Radio frequency band reject filters

    Hudak, J.J.; Alper, M.; Cotte, D.; Gardner, C.G.; Harvey, A.

    1983-01-01

    This chapter reports on the design and testing of a tunable superconducting filter element fabricated from Nb25%Zr having a transition temperature of 11 K. The filter element will serve as a component in a multielement filter bank to be cooled to less than 10 K by a two stage Gifford-McMahon refrigerator. A radio frequency (RF) interference rejection system composed of a set of tunable superconducting filter elements is being developed to supplement conventional interference rejection tehcniques. The thermal loading performance of the 8.5 K Gifford-McMahon refrigerator is found to exceed 2 watts at 10 K on the second stage with a 10 watt loading on the first stage. A superconducting filter bank consisting of tunable narrow band RF filters applied to strong interfering signals can be used to match the dynamic range of the RF signal environment to that of the receiving system

  2. Development of GaInNAsSb alloys: Growth, band structure, optical properties and applications

    Harris, James S. Jr.; Kudrawiec, R.; Yuen, H.B.; Bank, S.R.; Bae, H.P.; Wistey, M.A.; Jackrel, D.; Pickett, E.R.; Sarmiento, T.; Goddard, L.L.; Lordi, V.; Gugov, T.

    2007-01-01

    In the past few years, GaInNAsSb has been found to be a potentially superior material to both GaInNAs and InGaAsP for communications wavelength laser applications. It has been observed that due to the surfactant role of antimony during epitaxy, higher quality material can be grown over the entire 1.2-1.6 μm range on GaAs substrates. In addition, it has been discovered that antimony in GaInNAsSb also works as a constituent that significantly modifies the valence band. These findings motivated a systematic study of GaInNAsSb alloys with widely varying compositions. Our recent progress in growth and materials development of GaInNAsSb alloys and our fabrication of 1.5-1.6 μm lasers are discussed in this paper. We review our recent studies of the conduction band offset in (Ga,In) (N,As,Sb)/GaAs quantum wells and discuss the growth challenges of GaInNAsSb alloys. Finally, we report record setting long wavelength edge emitting lasers and the first monolithic VCSELs operating at 1.5 μm based on GaInNAsSb QWs grown on GaAs. Successful development of GaInNAsSb alloys for lasers has led to a much broader range of potential applications for this material including: solar cells, electroabsorption modulators, saturable absorbers and far infrared optoelectronic devices and these are also briefly discussed in this paper. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Development of Electromagnetic Band Gap Structures in the Perspective of Microstrip Antenna Design

    Md. Shahidul Alam

    2013-01-01

    Full Text Available Electromagnetic band gap (EBG technology has become a significant breakthrough in the radio frequency (RF and microwave applications due to their unique band gap characteristics at certain frequency ranges. Since 1999, the EBG structures have been investigated for improving performances of numerous RF and microwave devices utilizing the surface wave suppression and the artificial magnetic conductor (AMC properties of these special type metamaterial. Issues such as compactness, wide bandwidth with low attenuation level, tunability, and suitability with planar circuitry all play an important role in the design of EBG structures. Remarkable efforts have been undertaken for the development of EBG structures to be compatible with a wide range of wireless communication systems. This paper provides a comprehensive review on various EBG structures such as three-, two-, and one-dimensional (3D, 2D, and 1D EBG, mushroom and uniplanar EBG, and their successive advancement. Considering the related fabrication complexities, implementation of vialess EBG is an attractive topic for microwave engineers. For microstrip antennas, EBG structures are used in diversified ways, which of course found to be effective except in some cases. The EBG structures are also successfully utilized in antenna arrays for reducing the mutual coupling between elements of the array. Current challenges and limitations of the typical microstrip antennas and different EBG structures are discussed in details with some possible suggestions. Hopefully, this survey will guide to increasing efforts towards the development of more compact, wideband, and high-efficient uniplanar EBG structures for performance enhancement of antenna and other microwave devices.

  4. Development of GaInNAsSb alloys: Growth, band structure, optical properties and applications

    Harris, James S. Jr.; Kudrawiec, R.; Yuen, H.B.; Bank, S.R.; Bae, H.P.; Wistey, M.A.; Jackrel, D.; Pickett, E.R.; Sarmiento, T.; Goddard, L.L.; Lordi, V.; Gugov, T. [Solid State and Photonics Laboratory, Stanford University, CIS-X 328, Via Ortega, Stanford, California 94305-4075 (United States)

    2007-08-15

    In the past few years, GaInNAsSb has been found to be a potentially superior material to both GaInNAs and InGaAsP for communications wavelength laser applications. It has been observed that due to the surfactant role of antimony during epitaxy, higher quality material can be grown over the entire 1.2-1.6 {mu}m range on GaAs substrates. In addition, it has been discovered that antimony in GaInNAsSb also works as a constituent that significantly modifies the valence band. These findings motivated a systematic study of GaInNAsSb alloys with widely varying compositions. Our recent progress in growth and materials development of GaInNAsSb alloys and our fabrication of 1.5-1.6 {mu}m lasers are discussed in this paper. We review our recent studies of the conduction band offset in (Ga,In) (N,As,Sb)/GaAs quantum wells and discuss the growth challenges of GaInNAsSb alloys. Finally, we report record setting long wavelength edge emitting lasers and the first monolithic VCSELs operating at 1.5 {mu}m based on GaInNAsSb QWs grown on GaAs. Successful development of GaInNAsSb alloys for lasers has led to a much broader range of potential applications for this material including: solar cells, electroabsorption modulators, saturable absorbers and far infrared optoelectronic devices and these are also briefly discussed in this paper. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. Mechanisms of fine extinction band development in vein quartz: new insights from correlative light and electron microscopy

    Derez, Tine; Van Der Donck, Tom; Plümper, Oliver; Muchez, Philippe; Pennock, Gill; Drury, Martyn R.; Sintubin, Manuel

    2017-07-01

    Fine extinction bands (FEBs) (also known as deformation lamellae) visible with polarized light microscopy in quartz consist of a range of nanostructures, inferring different formation processes. Previous transmission electron microscopy studies have shown that most FEB nanostructures in naturally deformed quartz are elongated subgrains formed by recovery of dislocation slip bands. Here we show that three types of FEB nanostructure occur in naturally deformed vein quartz from the low-grade metamorphic High-Ardenne slate belt (Belgium). Prismatic oriented FEBs are defined by bands of dislocation walls. Dauphiné twin boundaries present along the FEB boundaries probably formed after FEB formation. In an example of two sub-rhombohedral oriented FEBs, developed as two sets in one grain, the finer FEB set consists of elongated subgrains, similar to FEBs described in previous transmission electron microscopy studies. The second wider FEB set consists of bands with different dislocation density and fluid-inclusion content. The wider FEB set is interpreted as bands with different plastic strain associated with the primary growth banding of the vein quartz grain. The nanometre-scale fluid inclusions are interpreted to have formed from structurally bounded hydroxyl groups that moreover facilitated formation of the elongate subgrains. Larger fluid inclusions aligned along FEBs are explained by fluid-inclusion redistribution along dislocation cores. The prismatic FEB nanostructure and the relation between FEBs and growth bands have not been recognized before, although related structures have been reported in experimentally deformed quartz.

  6. Localization in inelastic rate dependent shearing deformations

    Katsaounis, Theodoros

    2016-09-18

    Metals deformed at high strain rates can exhibit failure through formation of shear bands, a phenomenon often attributed to Hadamard instability and localization of the strain into an emerging coherent structure. We verify formation of shear bands for a nonlinear model exhibiting strain softening and strain rate sensitivity. The effects of strain softening and strain rate sensitivity are first assessed by linearized analysis, indicating that the combined effect leads to Turing instability. For the nonlinear model a class of self-similar solutions is constructed, that depicts a coherent localizing structure and the formation of a shear band. This solution is associated to a heteroclinic orbit of a dynamical system. The orbit is constructed numerically and yields explicit shear localizing solutions. © 2016 Elsevier Ltd

  7. Localization in inelastic rate dependent shearing deformations

    Katsaounis, Theodoros; Lee, Min-Gi; Tzavaras, Athanasios

    2016-01-01

    Metals deformed at high strain rates can exhibit failure through formation of shear bands, a phenomenon often attributed to Hadamard instability and localization of the strain into an emerging coherent structure. We verify formation of shear bands for a nonlinear model exhibiting strain softening and strain rate sensitivity. The effects of strain softening and strain rate sensitivity are first assessed by linearized analysis, indicating that the combined effect leads to Turing instability. For the nonlinear model a class of self-similar solutions is constructed, that depicts a coherent localizing structure and the formation of a shear band. This solution is associated to a heteroclinic orbit of a dynamical system. The orbit is constructed numerically and yields explicit shear localizing solutions. © 2016 Elsevier Ltd

  8. Deformation bands in porous sandstones their microstructure and petrophysical properties

    Torabi, Anita

    2007-12-15

    Deformation bands are commonly thin tabular zones of crushed or reorganized grains that form in highly porous rocks and sediments. Unlike a fault, typically the slip is negligible in deformation bands. In this dissertation the microstructure and petrophysical properties of deformation bands have been investigated through microscopy and numerical analysis of experimental and natural examples. The experimental work consists of a series of ring-shear experiments performed on porous sand at 5 and 20 MPa normal stresses and followed by microscopic examination of thin sections from the sheared samples. The results of the ring-shear experiments and comparison of them to natural deformation bands reveals that burial depth (level of normal stress in the experiments) and the amount of shear displacement during deformation are the two significant factors influencing the mode in which grains break and the type of shear zone that forms. Two end-member types of experimental shear zones were identified: (a) Shear zones with diffuse boundaries, which formed at low levels of normal stress and/or shear displacement; and (b) Shear zones with sharp boundaries, which formed at higher levels of normal stress and/or shear displacement. Our interpretation is that with increasing burial depth (approximately more than one kilometer, simulated in the experiments by higher levels of normal stress), the predominant mode of grain fracturing changes from flaking to splitting; which facilitates the formation of sharp-boundary shear zones. This change to grain splitting increases the power law dimension of the grain size distribution (D is about 1.5 in sharp boundary shear zones). Based on our observations, initial grain size has no influence in the deformation behavior of the sand at 5 MPa normal stresses. A new type of cataclastic deformation band is described through outcrop and microscopic studies; here termed a 'slipped deformation band'. Whereas previously reported cataclastic

  9. Role of symmetry-breaking induced by Er × B shear flows on developing residual stresses and intrinsic rotation in the TEXTOR tokamak

    Xu, Y.; Shesterikov, I.; Berte, M.; Dumortier, P.; Van Schoor, M.; Vergote, M.; Hidalgo, C.; Krämer-Flecken, A.; Koslowski, R.

    2013-01-01

    Direct measurements of residual stress (force) have been executed at the edge of the TEXTOR tokamak using multitip Langmuir and Mach probes, together with counter-current NBI torque to balance the existing toroidal rotation. Substantial residual stress and force have been observed at the plasma boundary, confirming the existence of a finite residual stress as possible mechanisms to drive the intrinsic toroidal rotation. In low-density discharges, the residual stress displays a quasi-linear dependence on the local pressure gradient, consistent with theoretical predictions. At high-density shots the residual stress and torque are strongly suppressed. The results show close correlation between the residual stress and the E r × B flow shear rate, suggesting a minimum threshold of the E × B flow shear required for the k ∥ symmetry breaking. These findings provide the first experimental evidence of the role of E r × B sheared flows in the development of residual stresses and intrinsic rotation. (letter)

  10. The importance of strain localisation in shear zones

    Bons, Paul D.; Finch, Melanie; Gomez-Rivas, Enrique; Griera, Albert; Llorens, Maria-Gema; Steinbach, Florian; Weikusat, Ilka

    2016-04-01

    The occurrence of various types of shear bands (C, C', C'') in shear zones indicate that heterogeneity of strain is common in strongly deformed rocks. However, the importance of strain localisation is difficult to ascertain if suitable strain markers are lacking, which is usually the case. Numerical modelling with the finite-element method has so far not given much insight in the development of shear bands. We suggest that this is not only because the modelled strains are often not high enough, but also because this technique (that usually assumes isotropic material properties within elements) does not properly incorporate mineral deformation behaviour. We simulated high-strain, simple-shear deformation in single- and polyphase materials with a full-field theory (FFT) model coupled to the Elle modelling platform (www.elle.ws; Lebensohn 2001; Bons et al. 2008). The FFT-approach simulates visco-plastic deformation by dislocation glide, taking into account the different available slip systems and their critical resolved shear stresses in relations to the applied stresses. Griera et al. (2011; 2013) have shown that this approach is particularly well suited for strongly anisotropic minerals, such as mica and ice Ih (Llorens 2015). We modelled single- and polyphase composites of minerals with different anisotropies and strengths, roughly equivalent to minerals such as ice Ih, mica, quartz and feldspar. Single-phase polycrystalline aggregates show distinct heterogeneity of strain rate, especially in case of ice Ih, which is mechanically close to mica (see also Griera et al. 2015). Finite strain distributions are heterogeneous as well, but the patterns may differ from that of the strain rate distribution. Dynamic recrystallisation, however, usually masks any strain and strain rate localisation (Llorens 2015). In case of polyphase aggregates, equivalent to e.g. a granite, we observe extensive localisation in both syn- and antithetic shear bands. The antithetic shear bands

  11. The effect of non-uniform mass loading on the linear, temporal development of particle-laden shear layers

    Senatore, Giacomo [Department of Aerospace Engineering, Universita di Pisa, Pisa 56122 (Italy); Davis, Sean; Jacobs, Gustaaf, E-mail: gjacobs@mail.sdsu.edu [Department of Aerospace Engineering and Engineering Mechanics, San Diego State University, San Diego, 92182 California (United States)

    2015-03-15

    The effect of non-uniformity in bulk particle mass loading on the linear development of a particle-laden shear layer is analyzed by means of a stochastic Eulerian-Eulerian model. From the set of governing equations of the two-fluid model, a modified Rayleigh equation is derived that governs the linear growth of a spatially periodic disturbance. Eigenvalues for this Rayleigh equation are determined numerically using proper conditions at the co-flowing gas and particle interface locations. For the first time, it is shown that non-uniform loading of small-inertia particles (Stokes number (St) <0.2) may destabilize the inviscid mixing layer development as compared to the pure-gas flow. The destabilization is triggered by an energy transfer rate that globally flows from the particle phase to the gas phase. For intermediate St (1 < St < 10), a maximum stabilizing effect is computed, while at larger St, two unstable modes may coexist. The growth rate computations from linear stability analysis are verified numerically through simulations based on an Eulerian-Lagrangian (EL) model based on the inviscid Euler equations and a point particle model. The growth rates found in numerical experiments using the EL method are in very good agreement with growth rates from the linear stability analysis and validate the destabilizing effect induced by the presence of particles with low St.

  12. Study on shear properties of coral sand under cyclic simple shear condition

    Ji, Wendong; Zhang, Yuting; Jin, Yafei

    2018-05-01

    In recent years, the ocean development in our country urgently needs to be accelerated. The construction of artificial coral reefs has become an important development direction. In this paper, experimental studies of simple shear and cyclic simple shear of coral sand are carried out, and the shear properties and particle breakage of coral sand are analyzed. The results show that the coral sand samples show an overall shear failure in the simple shear test, which is more accurate and effective for studying the particle breakage. The shear displacement corresponding to the peak shear stress of the simple shear test is significantly larger than that corresponding to the peak shear stress of the direct shear test. The degree of particle breakage caused by the simple shear test is significantly related to the normal stress level. The particle breakage of coral sand after the cyclic simple shear test obviously increases compared with that of the simple shear test, and universal particle breakage occurs within the whole particle size range. The increasing of the cycle-index under cyclic simple shear test results in continuous compacting of the sample, so that the envelope curve of peak shearing force increases with the accumulated shear displacement.

  13. Development of an ultra wide band microwave radar based footwear scanning system

    Rezgui, Nacer Ddine; Bowring, Nicholas J.; Andrews, David A.; Harmer, Stuart W.; Southgate, Matthew J.; O'Reilly, Dean

    2013-10-01

    At airports, security screening can cause long delays. In order to speed up screening a solution to avoid passengers removing their shoes to have them X-ray scanned is required. To detect threats or contraband items hidden within the shoe, a method of screening using frequency swept signals between 15 to 40 GHz has been developed, where the scan is carried out whilst the shoes are being worn. Most footwear is transparent to microwaves to some extent in this band. The scans, data processing and interpretation of the 2D image of the cross section of the shoe are completed in a few seconds. Using safe low power UWB radar, scattered signals from the shoe can be observed which are caused by changes in material properties such as cavities, dielectric or metal objects concealed within the shoe. By moving the transmission horn along the length of the shoe a 2D image corresponding to a cross section through the footwear is built up, which can be interpreted by the user, or automatically, to reveal the presence of concealed threat within the shoe. A prototype system with a resolution of 6 mm or less has been developed and results obtained for a wide range of commonly worn footwear, some modified by the inclusion of concealed material. Clear differences between the measured images of modified and unmodified shoes are seen. Procedures for enhancing the image through electronic image synthesis techniques and image processing methods are discussed and preliminary performance data presented.

  14. Developments in dynamic MR elastography for in vitro biomechanical assessment of hyaline cartilage under high-frequency cyclical shear.

    Lopez, Orlando; Amrami, Kimberly K; Manduca, Armando; Rossman, Phillip J; Ehman, Richard L

    2007-02-01

    The design, construction, and evaluation of a customized dynamic magnetic resonance elastography (MRE) technique for biomechanical assessment of hyaline cartilage in vitro are described. For quantification of the dynamic shear properties of hyaline cartilage by dynamic MRE, mechanical excitation and motion sensitization were performed at frequencies in the kilohertz range. A custom electromechanical actuator and a z-axis gradient coil were used to generate and image shear waves throughout cartilage at 1000-10,000 Hz. A radiofrequency (RF) coil was also constructed for high-resolution imaging. The technique was validated at 4000 and 6000 Hz by quantifying differences in shear stiffness between soft ( approximately 200 kPa) and stiff ( approximately 300 kPa) layers of 5-mm-thick bilayered phantoms. The technique was then used to quantify the dynamic shear properties of bovine and shark hyaline cartilage samples at frequencies up to 9000 Hz. The results demonstrate that one can obtain high-resolution shear stiffness measurements of hyaline cartilage and small, stiff, multilayered phantoms at high frequencies by generating robust mechanical excitations and using large magnetic field gradients. Dynamic MRE can potentially be used to directly quantify the dynamic shear properties of hyaline and articular cartilage, as well as other cartilaginous materials and engineered constructs. (c) 2007 Wiley-Liss, Inc.

  15. Effect of a shear modified Gurson model on damage development in a FSW tensile specimen

    Nielsen, Kim Lau; Tvergaard, Viggo

    2009-01-01

    For a friction stir welded aluminum plate the resistance to ductile failure is studied by analyzing tensile test specimens cut out across the weldline. As the stress triaxiality is rather low in these tests, the Gurson material model is not expected to give a very accurate description of the void......, such that the damage parameter does not really represent the void volume fraction. Various amounts of the additional damage evolution are compared with predictions of the original Gurson model. The analyses are carried out for different yield stress profiles transverse to the weld and for different specimen widths....... It is found that the modification does provide additional damage development in the friction stir weld, which may help to fit experimental data. But the suggested modification depends strongly on the overall stress state, and may have a too strong effect in some cases where the stress triaxiality is rather...

  16. Development of technical means for directional hydraulic fracturing with shearing loading of borehole walls

    Rybalkin, LA; Patutin, AV; Patutin, DV

    2018-03-01

    During the process of mineral deposits’ mining one of the most important conditions for safe and economically profitable work of a mining enterprise is obtaining timely information on the stress state of the developed massif. One of the most common methods of remote study of the geomechanical state of the rock massif is hydraulic fracturing of the formation. Directional hydraulic fracturing is a type of the method employed to form cracks across production wells. This technology was most widely used in the gas industry to extract gas from shale formations. In mining, this technology is used to set up filtration screens, to integrate degassing, to soften the hard roof of coal seams. Possible practical appliance is the expansion of the application field of this technology to intensify the production of viscous oil, to leach non-ferrous metals, to create in the rock massif anti-filtration screens for various purposes, as well as to measure stresses acting along the wells.

  17. Development of wide band digital receiver for atmospheric radars using COTS board based SDR

    Yasodha, Polisetti; Jayaraman, Achuthan; Thriveni, A.

    2016-07-01

    Digital receiver extracts the received echo signal information, and is a potential subsystem for atmospheric radar, also referred to as wind profiling radar (WPR), which provides the vertical profiles of 3-dimensional wind vector in the atmosphere. This paper presents the development of digital receiver using COTS board based Software Defined Radio technique, which can be used for atmospheric radars. The developmental work is being carried out at National Atmospheric Research Laboratory (NARL), Gadanki. The digital receiver consists of a commercially available software defined radio (SDR) board called as universal software radio peripheral B210 (USRP B210) and a personal computer. USRP B210 operates over a wider frequency range from 70 MHz to 6 GHz and hence can be used for variety of radars like Doppler weather radars operating in S/C bands, in addition to wind profiling radars operating in VHF, UHF and L bands. Due to the flexibility and re-configurability of SDR, where the component functionalities are implemented in software, it is easy to modify the software to receive the echoes and process them as per the requirement suitable for the type of the radar intended. Hence, USRP B210 board along with the computer forms a versatile digital receiver from 70 MHz to 6 GHz. It has an inbuilt direct conversion transceiver with two transmit and two receive channels, which can be operated in fully coherent 2x2 MIMO fashion and thus it can be used as a two channel receiver. Multiple USRP B210 boards can be synchronized using the pulse per second (PPS) input provided on the board, to configure multi-channel digital receiver system. RF gain of the transceiver can be varied from 0 to 70 dB. The board can be controlled from the computer via USB 3.0 interface through USRP hardware driver (UHD), which is an open source cross platform driver. The USRP B210 board is connected to the personal computer through USB 3.0. Reference (10 MHz) clock signal from the radar master oscillator

  18. A non-linear procedure for the numerical analysis of crack development in beams failing in shear

    P. Bernardi

    2016-01-01

    Full Text Available In this work, a consistent formulation for the representation of concrete behavior before and after cracking has been implemented into a non-linear model for the analysis of reinforced concrete structures, named 2D-PARC. Several researches have indeed pointed out that the adoption of an effective modeling for concrete, combined with an accurate failure criterion, is crucial for the correct prediction of the structural behavior, not only in terms of failure load, but also with reference to a realistic representation of crack initiation and development. This last aspect is particularly relevant at serviceability conditions in order to verify the fulfillment of structural requirements provided by Design Codes, which limit the maximum crack width due to appearance and durability issues. In more details, a constitutive model originally proposed by Ottosen and based on non-linear elasticity has been here incorporated into 2D-PARC in order to improve the numerical efficiency of the adopted algorithm, providing at the same time an accurate prediction of the structural response. The effectiveness of this procedure has been verified against significant experimental results available in the technical literature and relative to reinforced concrete beams without stirrups failing in shear, which represent a problem of great theoretical and practical importance in the field of structural engineering. Numerical results have been compared to experimental evidences not only in terms of global structural response (i.e. applied load vs. midspan deflection, but also in terms of crack pattern evolution and maximum crack widths.

  19. Development and feasibility of a wearable infant wrist band for the objective measurement of physical activity using accelerometery.

    Prioreschi, Alessandra; Nappey, Thomas; Westgate, Kate; Olivier, Patrick; Brage, Soren; Micklesfield, Lisa Kim

    2018-01-01

    It is important to be able to reliably and feasibly measure infant and toddler physical activity in order to determine adherence to current physical activity guidelines and effects on early life development, growth and health. This study aimed to describe the development of an infant wearable wrist-worn band for the measurement of physical activity; to determine the feasibility of the device data for observational measurement of physical activity and to determine the caregiver reported acceptability of the infant wearable wrist band. After various iterations of prototypes and piloting thereof, a final wearable band was designed to fit an Axivity AX3 monitor. Mother and infant/toddler (aged 3-24 months) pairs ( n  = 152) were recruited, and mothers were asked for their child to wear the band with enclosed monitor at all times for 1 week (minimum 3 days). Feasibility was assessed by determining technical reliability of the data, as well as wear time and compliance according to requirements for observational measurement. Acceptability was assessed via questionnaire. Technical reliability of the Axivity AX3 monitors in this age group was good. After excluding days that did not have at least 15 h of wear time, only 2% of participants had less than three valid days of data remaining, and 4% of participants had no data (due to device loss or data loss). Therefore, 94% of participants were compliant, having three or more days of wear with at least 15 h of wear per day, thus providing enough valid data for observational measurement. The majority (60%) of mothers reported being "very happy" with the safety of the device, while only 8% were "a little worried". A large majority (86%) of mothers stated that the band attracted attention from others, although this was mostly attributed to curiosity about the function of the band. Most (80%) of participants rated the comfort of the band as "comfortable", and 10% rated it as "very comfortable". The infant wearable band

  20. Development of a Polarized Electron Gun Based on an S-Band PWT Photoinjector

    Clendenin, J E; Yu, D; Newsham, D; Luo, Y; Smirnov, A

    2003-01-01

    An RF polarized electron gun utilizing the unique features of an integrated, plane-wave-transformer (PWT) photoelectron injector [1] is being developed by DULY Research Inc. in collaboration with SLAC. Modifications to a DULY S-band device [2] include: a re-design of the photocathode/RF backplane interface to accommodate a GaAs cathode; change in the design of the vacuum ports to provide 10-11 Torr operation; the inclusion of a load-lock photocathode replacement system to allow for reactivation and cessation of the GaAs photocathode in a vacuum; and alteration of the magnet field coils to make room for the load-lock. The use of a stainless steel outer tank and cooling rods without copper plating may also provide better vacuum performance at the expense of diminished Q factor. The effectiveness of both the standard cooling rods and synthetic diamond heat sinks for disk cooling is investigated for future linear collider applications operating at a rep rate of 180 Hz and a bunch charge of 2 nC.

  1. S-band 300 W pulsed solid state microwave amplifier development for driving high power klystrons for electron accelerators

    Mohania, Praveen; Shrivastava, Purushottam; Hannurkar, P.R.

    2005-01-01

    S-Band Microwave electron accelerators like microtrons and linear accelerators need pulsed microwaves from few megawatts to tens of megawatts to accelerator the electrons to desired energy and intensity. Klystron tube based driver amplifiers were used to drive the high power klystrons, which need microwave power from few tens of watts to 1 kW depending on tube output power and gain. A endeavour was initiated at Centre for Advanced Technology to develop state of art solid state S-band microwave amplifiers indigenously to drive the klystron tubes. A modular design approach was used and individual modules up to 160 W power levels were developed and tested. Finally combining 160 W modules will give up to 300 W output power. Several more modules can be combined to achieve even high power levels. Present paper describes the developmental efforts of 300 W S-band solid-state amplifiers and related microwave technologies. (author)

  2. Development of a system for measuring wall shear stress in blood vessels using magnetic resonance imaging and computational fluid dynamics

    Yoshida, Keita; Nagao, Taisuke; Okada, Kouji; Miyazaki, Shohei; Yang, Xiaomei; Yamazaki, Youichi; Murase, Kenya

    2008-01-01

    We developed a system for measuring the wall shear stress (WSS) in blood vessels using magnetic resonance imaging (MRI) and computational fluid dynamics (CFD). The time-dependent velocity at the center of the blood vessel was measured by phase-contrast MRI and was approximated by finite Fourier series, which was used for generating the velocity profile at the inlet for the boundary condition to the CFD method. To validate the CFD method, we compared the WSS obtained by the CFD method with the theoretical value in a straight cylinder with various radii for both steady and pulsatile flows. We also investigated the dependence of the WSS on the inlet velocity profile incorporated into the CFD method. For steady flow, there was a good agreement between the WSS obtained by the CFD method and the theoretical value. For pulsatile flow, there was a relatively good agreement between them when the radius of the cylinder was 2.5 mm and the inlet velocity profile was given by the Womersley solution for fully developed pulsatile flow in a straight circular cylinder. When the radius of the cylinder was 5 mm and/or the inlet velocity profile was assumed to be parabolic, large differences were observed between them, suggesting that the assumption of fully developed flow does not hold true in these cases. In human studies, the vortex due to the secondary blood flow in the carotid arterial sinus was clearly observed. The WSS in the bifurcation was the highest, while that in the carotid arterial sinus was the smallest. In conclusion, the system presented here appears to be useful for measuring the WSS in blood vessels and for analyzing the cause and/or extent of atherosclerosis, and our results suggest that the inlet velocity profile should be carefully considered. (author)

  3. Development of an X-Band 50 MW Multiple Beam Klystron

    Song, Liqun; Ferguson, Patrick; Ives, R. Lawrence; Miram, George; Marsden, David; Mizuhara, Max

    2003-12-01

    Calabazas Creek Research, Inc. is developing an X-band 50 MW multiple beam klystron (MBK) on a DOE SBIR Phase II grant. The electrical design and preliminary mechanical design were completed on the Phase I. This MBK consists of eight discrete klystron circuits driven by eight electron beams located symmetrically on a circle with a radius of 6.3 cm. Each beam operates at 190 kV and 66 A. The eight beam electron gun is in development on a DOE SBIR Phase II grant. Each circuit consists of an input cavity, two gain cavities, three penultimate cavities, and a three cavity output circuit operating in the PI/2 mode. Ring resonators were initially proposed for the complete circuit; however, low beam — wave interaction resulted in the necessity to use discrete cavities for all eight circuits. The input cavities are coupled via hybrid waveguides to ensure constant drive power amplitude and phase. The output circuits can either be combined using compact waveguide twists driving a TE01 high power window or combined into a TM04 mode converter driving the same TE01 window. The gain and efficiency for a single circuit has been optimized using KLSC, a 2 1/2D large signal klystron code. Simulations for a single circuit predict an efficiency of 53% for a single output cavity and 55% for the three cavity output resonator. The total RF output power for this MBK is 55 MW. During the Phase II emphasis will be given to cost reduction techniques resulting in a robust — high efficient — long life high power amplifier.

  4. Development of an X-Band 50 MW Multiple Beam Klystron

    Song Liqun; Ferguson, Patrick; Ives, R. Lawrence; Miram, George; Marsden, David; Mizuhara, Max

    2003-01-01

    Calabazas Creek Research, Inc. is developing an X-band 50 MW multiple beam klystron (MBK) on a DOE SBIR Phase II grant. The electrical design and preliminary mechanical design were completed on the Phase I. This MBK consists of eight discrete klystron circuits driven by eight electron beams located symmetrically on a circle with a radius of 6.3 cm. Each beam operates at 190 kV and 66 A. The eight beam electron gun is in development on a DOE SBIR Phase II grant. Each circuit consists of an input cavity, two gain cavities, three penultimate cavities, and a three cavity output circuit operating in the PI/2 mode. Ring resonators were initially proposed for the complete circuit; however, low beam -- wave interaction resulted in the necessity to use discrete cavities for all eight circuits. The input cavities are coupled via hybrid waveguides to ensure constant drive power amplitude and phase. The output circuits can either be combined using compact waveguide twists driving a TE01 high power window or combined into a TM04 mode converter driving the same TE01 window. The gain and efficiency for a single circuit has been optimized using KLSC, a 2 1/2D large signal klystron code. Simulations for a single circuit predict an efficiency of 53% for a single output cavity and 55% for the three cavity output resonator. The total RF output power for this MBK is 55 MW. During the Phase II emphasis will be given to cost reduction techniques resulting in a robust - high efficient - long life high power amplifier

  5. A Piezoelectric Shear Stress Sensor

    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. An underwater shear compactor

    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)

  7. Parameterization of sheared entrainment in a well-developed CBL. Part I: Evaluation of the scheme through large-eddy simulations

    Liu, Peng; Sun, Jianning; Shen, Lidu

    2016-10-01

    The entrainment flux ratio A e and the inversion layer (IL) thickness are two key parameters in a mixed layer model. A e is defined as the ratio of the entrainment heat flux at the mixed layer top to the surface heat flux. The IL is the layer between the mixed layer and the free atmosphere. In this study, a parameterization of A e is derived from the TKE budget in the firstorder model for a well-developed CBL under the condition of linearly sheared geostrophic velocity with a zero value at the surface. It is also appropriate for a CBL under the condition of geostrophic velocity remaining constant with height. LESs are conducted under the above two conditions to determine the coefficients in the parameterization scheme. Results suggest that about 43% of the shear-produced TKE in the IL is available for entrainment, while the shear-produced TKE in the mixed layer and surface layer have little effect on entrainment. Based on this scheme, a new scale of convective turbulence velocity is proposed and applied to parameterize the IL thickness. The LES outputs for the CBLs under the condition of linearly sheared geostrophic velocity with a non-zero surface value are used to verify the performance of the parameterization scheme. It is found that the parameterized A e and IL thickness agree well with the LES outputs.

  8. Morphological Development of Melt Crystallized Poly(propylene oxide) by In Situ AFM: Formation of Banded Spherulites

    Beekmans, L.G.M.; Hempenius, Mark A.; Vancso, Gyula J.

    2004-01-01

    The morphology of poly(propylene oxide) (PPO) crystals grown from the melt was investigated. The spherulites of the optically pure S polymers displayed a regular pattern of concentric rings as observed by polarizing optical microscopy, while the stereocopolymer developed irregularly banded, or

  9. "School Banding": Principals' Perspectives of Teacher Professional Development in the School-Based Management Context

    Lee, Daphnee Hui Lin; Chiu, Chi Shing

    2017-01-01

    Purpose: The purpose of this paper is to explore how principals' leadership approaches to teacher professional development arise from school banding and may impact upon teacher professional capital and student achievement. Design/methodology/approach: The case study is situated within the context of school-based management, comprising reflective…

  10. Design and Development of Mixed-Metal Oxide Photocatalysts: the Band Engineering Approach

    Boltersdorf, Jonathan Andrew

    The design and development of mixed-metal oxides incorporating Ag(I), Pb(II), Sn(II), and Bi(III), i.e., with filled d10 or d10s2 electron configurations, have yielded new approaches to tune optical and photocatalytic properties for solar energy conversion. My research efforts in the area of solid-state photochemistry have focused on utilizing flux-mediated ion-exchange methods in conjunction with the band engineering approach to synthesize new materials for solar energy driven total water splitting. Layered perovskite phases and the polysomatic family of tantalate/niobate structures, with the general formula Am+ ( n+1)/mB(3 n+1)O(8n +3) (A = Na, Ag; B = Ta, Nb), have received increasing attention owing to their synthetic flexibility, tunable optical band gaps, and photocatalytic activities for total water splitting. Structures in the family of A m+ (n+1)/ mB(3n +1)O(8n+3) structures are based on the stacking of pentagonal bipyramidal layers, where n defines the average thickness (1 ≤ n ≤ 2) of the BO7 layers that alternate with isolated BO6 octahedra surrounded by A-site cations. Synthetic limitations in the discovery of new phases within the layered perovskites and the Am + (n+1)/mB(3 n+1)O(8n +3) structural families can be addressed with the aid of a metal-salt solvent, known as the molten-salt flux method. The flux synthetic route requires the use of an inorganic salt heated above its melting temperature in order to serve as a solvent system for crystallization. Molten fluxes allow for synthetic modification of particle characteristics and can enable the low temperature stabilization of new compositions and phases with limited stability using ion-exchange reactions (e.g., PbTa4O11, AgLaNb 2O7). Solid-state and flux-mediated exchange methods were utilized in order to synthetically explore and investigate the layered perovskites ALaNb2O7, AA2Nb3O 10, A'2La2Ti3O10 (A' = Rb, Ag; A = Ca, Sr), the Am+ (n+1)/mB 3n+1O(8 n+3) structural family (Am + = Na(I), Ag

  11. Multifractal spectra in shear flows

    Keefe, L. R.; Deane, Anil E.

    1989-01-01

    Numerical simulations of three-dimensional homogeneous shear flow and fully developed channel flow, are used to calculate the associated multifractal spectra of the energy dissipation field. Only weak parameterization of the results with the nondimensional shear is found, and this only if the flow has reached its asymptotic development state. Multifractal spectra of these flows coincide with those from experiments only at the range alpha less than 1.

  12. Band structure of semiconductors

    Tsidilkovski, I M

    2013-01-01

    Band Structure of Semiconductors provides a review of the theoretical and experimental methods of investigating band structure and an analysis of the results of the developments in this field. The book presents the problems, methods, and applications in the study of band structure. Topics on the computational methods of band structure; band structures of important semiconducting materials; behavior of an electron in a perturbed periodic field; effective masses and g-factors for the most commonly encountered band structures; and the treatment of cyclotron resonance, Shubnikov-de Haas oscillatio

  13. Development of an eight-band theory for quantum dot heterostructures

    Pokatilov, E.P.; Fonoberov, V.A.; Fomin, V.; Devreese, J.T.

    2001-01-01

    We derive a nonsymmetrized eight-band effective-mass Hamiltonian for quantum dot heterostructures (QDH's) in Burt's envelope-function representation. The 8*8 radial Hamiltonian and the boundary conditions for the Schrodinger equation are obtained for spherical QDH's. Boundary conditions for

  14. Developments in the chemistry and band gap engineering of donor-acceptor substituted conjugated polymers

    Mullekom, van H.A.M.; Vekemans, J.A.J.M.; Havinga, E.E.; Meijer, E.W.

    2001-01-01

    This paper reviews the tools to manipulate and minimize the band gap of conjugated (co)polymers. The effects of minimization of the bond length alternation and of the incorporation of donor-K-acceptor units are discussed in particular. A systematic study of a series of alternating donor-acceptor

  15. Localization, Weakening and Fluid-rock Coupling Mechanisms in Gypsum: Development and Initial Data From a New, Combined, Rotary Shear and Acoustic Emission Apparatus.

    Benson, P. M.; Pozzi, G.; Guerin-Marthe, S.; De Paola, N.; Nielsen, S. B.; Tomas, R.

    2017-12-01

    We present initial pilot data from a newly developed apparatus designed to measure Acoustic Emissions (AE) during the shear of fault gouges to 25 MPa normal stress and up to a maximum speed of 1 m/s, simulating dynamic earthquake processes. The sample assembly consists of a titanium-vanadium alloy (Ti-alloy, Ti90Al6V4) anvil fitted with 6 ports on the lower (stationary) section for AE sensors that record the activity of the shearing occurring in the gouge layer above. AE data are amplified from between 6 to 70 dB and recorded to disk continuously at a sampling rate of 10 MHz; calibration tests with Teflon shims confirm that the machine noise is negligible. Gouge thicknesses of approximately 2 mm are used, confined with a Teflon ring. Here we focus on Gypsum gouge from the Volterra region of Italy, sieved to give a constant gouge range of between 63 to 90 micrometers. Mechanical data show the onset of weakening after a slip of 1-3 cm for velocities of v = 100 to 1 cm s-1 respectively. Microstructural observations reveal a shear zone bounded by sharp mirror surfaces, and the development of a dehydration front, which is likely to have produced small pockets of water. We also record a characteristic `pulsing' AE signal generated after shearing is arrested, manifested as a series of energy spikes occurring at regular intervals. However, these signals are only generally seen for shear tests conducted on gypsum gouges (not in anhydrite) at 10cm per second or higher. Taken together, we interpret these observations as evidence that the initial shearing generated a thin slip zone that heats up rapidly, generating the dehydration front. Once motion ceases, pockets of trapped pressurized water combined with thermal stress generates distributed micro-fracturing detected as an initial swarm of high energy AE, and allows fluids to vent in pulses to the ambient atmosphere. An initial seismic -b value analysis of the continuous AE waveform also supports these initial findings.

  16. Development of intermediate-scale structure at different altitudes within an equatorial plasma bubble: Implications for L-band scintillations

    Bhattacharyya, A.; Kakad, B.; Gurram, P.; Sripathi, S.; Sunda, S.

    2017-01-01

    An important aspect of the development of intermediate-scale length (approximately hundred meters to few kilometers) irregularities in an equatorial plasma bubble (EPB) that has not been considered in the schemes to predict the occurrence pattern of L-band scintillations in low-latitude regions is how these structures develop at different heights within an EPB as it rises in the postsunset equatorial ionosphere due to the growth of the Rayleigh-Taylor instability. Irregularities at different heights over the dip equator map to different latitudes, and their spectrum as well as the background electron density determine the strength of L-band scintillations at different latitudes. In this paper, VHF and L-band scintillations recorded at different latitudes together with theoretical modeling of the scintillations are used to study the implications of this structuring of EPBs on the occurrence and strength of L-band scintillations at different latitudes. Theoretical modeling shows that while S4 index for scintillations on a VHF signal recorded at an equatorial station may be >1, S4 index for scintillations on a VHF signal recorded near the crest of the equatorial ionization anomaly (EIA) generally does not exceed the value of 1 because the intermediate-scale irregularity spectrum at F layer peak near the EIA crest is shallower than that found in the equatorial F layer peak. This also explains the latitudinal distribution of L-band scintillations. Thus, it is concluded that there is greater structuring of an EPB on the topside of the equatorial F region than near the equatorial F layer peak.

  17. Steady shear rate rheology of suspensions, as described by the gaint floc model

    Stein, H.N.; Laven, J.

    2001-01-01

    The break-down of a particle network by shear is described as the development of shear planes: a region able to withstand low shear stresses may break down under a larger stress; thus with increasing shear stress and shear rate, the mutual distance (A) between successive shear planes decreases

  18. Four-dimensional characterization of thrombosis in a live-cell, shear-flow assay: development and application to xenotransplantation.

    Donald G Harris

    Full Text Available Porcine xenografts are a promising source of scarce transplantable organs, but stimulate intense thrombosis of human blood despite targeted genetic and pharmacologic interventions. Current experimental models do not enable study of the blood/endothelial interface to investigate adhesive interactions and thrombosis at the cellular level under physiologic conditions. The purpose of this study was to develop and validate a live-cell, shear-flow based thrombosis assay relevant to general thrombosis research, and demonstrate its potential in xenotransplantation applications.Confluent wild-type (WT, n = 48 and Gal transferase knock-out (GalTKO, which resist hyperacute rejection; n = 11 porcine endothelia were cultured in microfluidic channels. To mimic microcirculatory flow, channels were perfused at 5 dynes/cm2 and 37°C with human blood stained to fluorescently label platelets. Serial fluorescent imaging visualized percent surface area coverage (SA, for adhesion of labeled cells and total fluorescence (a metric of clot volume. Aggregation was calculated by the fluorescence/SA ratio (FR. WT endothelia stimulated diffuse platelet adhesion (SA 65 ± 2% and aggregation (FR 120 ± 1 a.u., indicating high-grade thrombosis consistent with the rapid platelet activation and consumption seen in whole-organ lung xenotransplantation models. Experiments with antibody blockade of platelet aggregation, and perfusion of syngeneic and allo-incompatible endothelium was used to verify the biologic specificity and validity of the assay. Finally, with GalTKO endothelia thrombus volume decreased by 60%, due primarily to a 58% reduction in adhesion (P < 0.0001 each; importantly, aggregation was only marginally affected (11% reduction, P < 0.0001.This novel, high-throughput assay enabled dynamic modeling of whole-blood thrombosis on intact endothelium under physiologic conditions, and allowed mechanistic characterization of endothelial and platelet interactions. Applied to

  19. Fifty years of shear zones

    Graham, Rodney

    2017-04-01

    We are here, of course, because 1967 saw the publication of John Ramsay's famous book. Two years later a memorable field trip from Imperial College to the Outer Hebrides saw John on a bleak headland on the coast of North Uist where a relatively undeformed metadolerite within Lewisian (Precambrian) gneisses contained ductile shear zones with metamorphic fabrics in amphibolite facies. One particular outcrop was very special - a shear zone cutting otherwise completely isotropic, undeformed metadolerite, with an incremental foliation starting to develop at 45° to the deformation zone, and increasing in intensity as it approached the shear direction. Here was proof of the process of simple shear under ductile metamorphic conditions - the principles of simple shear outlined in John Ramsay's 1967 book clearly visible in nature, and verified by Ramsay's mathematical proofs in the eventual paper (Ramsay and Graham, 1970). Later work on the Lewisian on the mainland of Scotland, in South Harris, in Africa, and elsewhere applied Ramsay's simple shear principles more liberally, more imprecisely and on larger scale than at Caisteal Odair, but in retrospect it documented what seems now to be the generality of mid and lower crustal deformation. Deep seismic reflection data show us that on passive margins hyper-stretched continental crust (whether or not cloaked by Seaward Dipping Reflectors) seems to have collapsed onto the mantle. Crustal faults mostly sole out at or above the mantle - so the Moho is a detachment- an 'outer marginal detachment', if you like, and, of course, it must be a ductile shear. On non-volcanic margins this shear zone forms the first formed ocean floor before true sea floor spreading gets going to create real oceanic crust. Gianreto Manatschal, Marcel Lemoine and others realised that the serpentinites described in parts of the Alps are exposed remnants of this ductile shear zone. Associated ophicalcite breccias tell of sea floor exposure, while high

  20. Self-contained pipe cutting shear. Innovative technology summary report

    1998-11-01

    The US Department of Energy (DO) is in the process of decontaminating and decommissioning (D and D) many of its nuclear facilities throughout the country. Facilities have to be dismantled and demolition waste must be sized into manageable pieces for handling and disposal. Typically, the facilities undergoing D and D are contaminated, either chemically, radiologically, or both. In its D and D work, the DOE was in need of a tool capable of cutting steel and stainless steel pipe up to 6.4 cm in diameter. The self-contained pipe cutting shear was developed by Lukas Hydraulic GmbH and Co. KG to cut pipes up to 6.4 cm (2.5 in.) in diameter. This tool is a portable, hand-held hydraulic shear that is powered by a built-in rechargeable battery or a portable auxiliary rechargeable battery. Adding to its portability, it contains no hydraulic fluid lines or electrical cords, making it useful in congested areas or in areas with no power. Both curved and straight blades can be attached, making it adaptable to a variety of conditions. This tool is easy to set up, operates quietly, and cuts through pipes quickly. It is especially useful on contaminated pipes, as it crimps the ends while cutting and produces no residual cuttings. This shear is a valuable alternative to baseline technologies such as portable band saws, electric hacksaws, and other hydraulic shears. Costs using the innovative shear for cutting 2.5 cm (1-in.) pipe, for example, are comparable to costs using a conventional shear, approximately 80% of portable bandsaw costs and half of electric hacksaw costs

  1. Development of two U.H.F. band resonators for application to CO2 laser electro-optical modulation

    Egan, M.G.; Blanc, P.; Sexton, M.C.

    1980-01-01

    The purpose of this report is to describe the design and testing of two U.H.F. band resonators destined for use in the linear electro-optical modulator of the CO 2 Laser Rapid Interferometer diagnostic at present under development for the WEGA Tokamak. The resonators take the form of a re-entrant coaxial line cavity and an interdigital line filter, both of which possess the regions of high electric field necessary to activate the linear electro-optical effect

  2. Influence of macroscopic shear deformation on polygonization and recrystallization of molybdenum crystals

    Larikov, L.N.; Belyakova, M.N.; Maksimenko, E.A.; Mudruk, P.V.

    1984-01-01

    The effect of shear bands on polygonization and recrystallization is studied on molybdenum monocrystals deformed by compression. A sharp bend of the lattice is shown to be a structural condition necessary for arising the shear step. Internal stress relaxation strongly changes kinetics of softening processes in compressed molybdenum crystals: it slows down polygonization under low-temperature heating (below 700 deg C) and accelerates it under high-temperature heating (higher 1000 deg C). Under the effect of relaxation of internal streses recrystallization in the investigated crystals is similar to dynamical: recrystallized grains are distorted and they have a developed substructure

  3. Development of the C-Band BPM System for ATF2

    Lyapin, A; Wing, M; Shin, S; Honda, Y; Tauchi, T; Terunuma, N; Heo, A; Kim, E; Kim, K; Ainsworth, R C E; Boogert, S T; Boorman, G; Molloy, S; McCormick, D; Nelson, J; White, G; Ward, D

    2010-01-01

    The ATF2 international collaboration is intending to demonstrate nanometre beam sizes required for the future Linear Colliders. An essential part of the beam diagnostics needed to achieve that goal is the high resolution cavity beam position monitors (BPMs). In this paper we report on the C-band system consisting of 32 BPMs spread over the whole length of the new ATF2 extraction beamline. We discuss the design of the BPMs and electronics, main features of the DAQ system, and the first operational experience with these BPMs.

  4. Development of a High-Stability Microstrip-based L-band Radiometer for Ocean Salinity Measurements

    Pellerano, Fernando A.; Horgan, Kevin A.; Wilson, William J.; Tanner, Alan B.

    2004-01-01

    The development of a microstrip-based L-band Dicke radiometer with the long-term stability required for future ocean salinity measurements to an accuracy of 0.1 psu is presented. This measurement requires the L-band radiometers to have calibration stabilities of less than or equal to 0.05 K over 2 days. This research has focused on determining the optimum radiometer requirements and configuration to achieve this objective. System configuration and component performance have been evaluated with radiometer test beds at both JPL and GSFC. The GSFC testbed uses a cryogenic chamber that allows long-term characterization at radiometric temperatures in the range of 70 - 120 K. The research has addressed several areas including component characterization as a function of temperature and DC bias, system linearity, optimum noise diode injection calibration, and precision temperature control of components. A breadboard radiometer, utilizing microstrip-based technologies, has been built to demonstrate this long-term stability.

  5. Two-stage structural development of a Paleozoic auriferous shear zone at the Globe-Progress deposit, Reefton, New Zealand

    Milham, L.; Craw, D.

    2009-01-01

    The Globe-Progress gold deposit at Reefton is hosted in a curvilinear mineralised zone that cuts Paleozoic Greenland Group basement metagreywackes. Two discrete phases of mineralisation have resulted in the formation of five different ore types along the shear. An initial phase of mineralisation formed hydrothermal quartz veins and associated Au, As, and S enrichment, with low-grade mineralised host rock. These quartz veins and mineralised host rocks form the outer regions of the mineralised zone. A second hydrothermal phase introduced Sb, Au, As, and S during brittle shear deformation focused on the pre-existing mineralised rocks. This deformation and mineralisation resulted in the formation of metre-scale cataclasite ore and quartz breccia from mineralised host rock and hydrothermal quartz veins, respectively. Cataclasite was derived from argillite layers in the host rock, from which Na, Fe, and Mg have been leached during mineralisation; Al, Ti, and Cr have been conserved; and there has been minor enrichment in Sr, Pb, Zn, and Cu. No quartz was added to the cataclasite or quartz breccia during mineralisation, but some quartz recrystallisation occurred locally, and quartz clasts were physically incorporated into the cataclasite during deformation. The presence of euhedral sulfides in the cataclasite (40% of total sulfides), late-stage undeformed stibnite veins infilling breccia (1-5 cm 3 scale), and undeformed free gold in quartz breccia, imply that the second phase of mineralisation persisted both during and after cataclasis and brecciation. Antimony deposition is greatest in the central cataclasite, up to 6 wt%, and locally in the quartz breccia where stibnite veins are present. Concentrations of Sb decrease with distance from the shear zone. The second, Sb-rich phase of mineralisation in the Globe-Progress deposit resembles similar Sb-rich overprints in the correlative Victorian goldfield of Australia. (author). 38 refs., 10 figs., 1 tab.

  6. Bending and Shear Stresses Developed by the Instantaneous Arrest of the Root of a Moving Cantilever Beam

    Stowell, Elbridge, Z; Schwartz, Edward B; Houbolt, John C

    1945-01-01

    A theoretical and experimental investigation has been made of the behavior of a cantilever beam in transverse motion when its root is suddenly brought to rest. Equations are given for determining the stresses, the deflections, and the accelerations that arise in the beam as a result of the impact. The theoretical equations, which have been confirmed experimentally, reveal that, at a given percentage of the distance from root to tip, the bending stresses for a particular mode are independent of the length of the beam, whereas the shear stresses vary inversely with the length.

  7. Flow behavior at different shear rates for dry powders

    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

  8. High Resolution Shear Profile Measurements in Entangled Polymers

    Hayes, Keesha A.; Buckley, Mark R.; Cohen, Itai; Archer, Lynden A.

    2008-01-01

    spanning a wide range of molecular weights and number of entanglements (8≤Z≤56), but reveal large differences between the imposed and measured shear rates. These findings disagree with recent reports that shear banding is a characteristic flow response

  9. Development of C-band High-Power Mix-Mode RF Window

    Michizono, S; Matsumoto, T; Nakao, K; Takenaka, T

    2004-01-01

    High power c-band (5712 MHz) rf system (40 MW, 2 μs, 50 Hz) is under consideration for the electron-linac upgrade aimed for the super KEKB project. An rf window, which isolates the vacuum and pass the rf power, is one of the most important components for the rf system. The window consists of a ceramic disk and a pill-box housing. The mix-mode rf window is designed so as to decrease the electric field on the periphery of the ceramic disk. A resonant ring is assembled in order to examine the high-power transmission test. The window was tested up to the transmission power of 160 MW. The rf losses are also measured during the rf operation.

  10. Development of L-band niobium superconducting RF cavities with high accelerating field

    Saito, Kenji; Noguchi, Shuichi; Ono, Masaaki; Kako, Eiji; Shishido, Toshio; Matsuoka, Masanori; Suzuki, Takafusa; Higuchi, Tamawo.

    1994-01-01

    Superconducting RF cavity is a candidate for the TeV energy e + /e - linear collider of next generation if the accelerating field is improved to 25-30 MV/m and much cost down is achieved in cavity fabrication. Since 1990, KEK has continued R and D of L-band niobium superconducting cavities focusing on the high field issue. A serious problem like Q-degradation due to vacuum discharge came out on the way, however, it has been overcome and presently all of cavities which were annealed at 1400degC achieved the accelerating field of >25 MV/m with enough Qo value. Recent results on single cell cavities are described in this paper. (author)

  11. Development of the C-band (5712 MHz) 50 MW class PPM klystron (2)

    Matsumoto, H.; Shintake, T.; Ohkubo, Y.; Taoka, H.; Ohhashi, K.; Kakuno, K.

    2001-01-01

    Hot isostatic pressing (HIP) technique has been firstly applied to fabricate a magnetic circuit in a PPM klystron. Simply stacking disks of the magnetic stainless-steel (Mag-SUS) and oxygen-free-copper (OFC) alternatively, and processing in a HIP vessel filled with pressurised Ar-gas at 1200-kgf/cm 2 and temperature of 800degC for 2 hours, they were bonded in one block with diffusion bonding. No brazing-alloys were used in this process. After machining the rf-cavities and beam drift-tube on the bonded PPM stack, they were assembled together in one body by means of conventional brazing method. The C-band PPM klystron based on this technique was fabricated in the course of the Linear Collider R and D. Out-put power of 37 MW was generated with 2.5-μsec pulse width and 50 pps repetition rate. (author)

  12. Development of a new code to solve hydro-mechanical coupling, shear failure and tensile failure due to hydraulic fracturing operations.

    María Gómez Castro, Berta; De Simone, Silvia; Carrera, Jesús

    2016-04-01

    Nowadays, there are still some unsolved relevant questions which must be faced if we want to proceed to the hydraulic fracturing in a safe way. How much will the fracture propagate? This is one of the most important questions that have to be solved in order to avoid the formation of pathways leading to aquifer targets and atmospheric release. Will the fracture failure provoke a microseismic event? Probably this is the biggest fear that people have in fracking. The aim of this work (developed as a part of the EU - FracRisk project) is to understand the hydro-mechanical coupling that controls the shear of existing fractures and their propagation during a hydraulic fracturing operation, in order to identify the key parameters that dominate these processes and answer the mentioned questions. This investigation focuses on the development of a new C++ code which simulates hydro-mechanical coupling, shear movement and propagation of a fracture. The framework employed, called Kratos, uses the Finite Element Method and the fractures are represented with an interface element which is zero thickness. This means that both sides of the element lie together in the initial configuration (it seems a 1D element in a 2D domain, and a 2D element in a 3D domain) and separate as the adjacent matrix elements deform. Since we are working in hard, fragile rocks, we can assume an elastic matrix and impose irreversible displacements in fractures when rock failure occurs. The formulation used to simulate shear and tensile failures is based on the analytical solution proposed by Okada, 1992 and it is part of an iterative process. In conclusion, the objective of this work is to employ the new code developed to analyze the main uncertainties related with the hydro-mechanical behavior of fractures derived from the hydraulic fracturing operations.

  13. Improving band-to-band tunneling in a tunneling carbon nanotube field effect transistor by multi-level development of impurities in the drain region

    Naderi, Ali; Ghodrati, Maryam

    2017-12-01

    In this paper, in order to improve the performance of a tunneling carbon nanotube field effect transistor (T-CNTFET) a new structure is proposed using multi-level impurity distribution along the drain region. The new T-CNTFET structure consists of six parts in the drain with stepwise doping distribution. The impurities on the drain side are n -type and the length of each region is 5nm. Electronic features of the proposed structure are simulated by the solution of Poisson and Schrödinger equations and the self-consistent method using Non-equilibrium Green's Function (NEGF). Simulation results show that the proposed structure reduces the band curvature near the drain-channel connection and widens the tunneling barrier. As a result, band-to-band tunneling and the OFF current are reduced and the ON/OFF current ratio increases in comparison with the conventional structure. In summary, by improving the subthreshold swing parameters, delay time, power delay product ( PDP and cut-off frequency compared to the conventional structure, the proposed structure can be considered as a proper candidate for digital applications with high speed and low power dissipation.

  14. Shear-induced chaos

    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

  15. Shear-induced chaos

    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.

  16. Semiconductor laser shearing interferometer

    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

  17. Non-homogeneous flow profiles in sheared bacterial suspensions

    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.

  18. Modeling combined tension-shear failure of ductile materials

    Partom, Y

    2014-01-01

    Failure of ductile materials is usually expressed in terms of effective plastic strain. Ductile materials can fail by two different failure modes, shear failure and tensile failure. Under dynamic loading shear failure has to do with shear localization and formation of adiabatic shear bands. In these bands plastic strain rate is very high, dissipative heating is extensive, and shear strength is lost. Shear localization starts at a certain value of effective plastic strain, when thermal softening overcomes strain hardening. Shear failure is therefore represented in terms of effective plastic strain. On the other hand, tensile failure comes about by void growth under tension. For voids in a tension field there is a threshold state of the remote field for which voids grow spontaneously (cavitation), and the material there fails. Cavitation depends on the remote field stress components and on the flow stress. In this way failure in tension is related to shear strength and to failure in shear. Here we first evaluate the cavitation threshold for different remote field situations, using 2D numerical simulations with a hydro code. We then use the results to compute examples of rate dependent tension-shear failure of a ductile material.

  19. Direct numerical simulations of temporally developing hydrocarbon shear flames at elevated pressure: effects of the equation of state and the unity Lewis number assumption

    Korucu, Ayse; Miller, Richard

    2016-11-01

    Direct numerical simulations (DNS) of temporally developing shear flames are used to investigate both equation of state (EOS) and unity-Lewis (Le) number assumption effects in hydrocarbon flames at elevated pressure. A reduced Kerosene / Air mechanism including a semi-global soot formation/oxidation model is used to study soot formation/oxidation processes in a temporarlly developing hydrocarbon shear flame operating at both atmospheric and elevated pressures for the cubic Peng-Robinson real fluid EOS. Results are compared to simulations using the ideal gas law (IGL). The results show that while the unity-Le number assumption with the IGL EOS under-predicts the flame temperature for all pressures, with the real fluid EOS it under-predicts the flame temperature for 1 and 35 atm and over-predicts the rest. The soot mass fraction, Ys, is only under-predicted for the 1 atm flame for both IGL and real gas fluid EOS models. While Ys is over-predicted for elevated pressures with IGL EOS, for the real gas EOS Ys's predictions are similar to results using a non-unity Le model derived from non-equilibrium thermodynamics and real diffusivities. Adopting the unity Le assumption is shown to cause misprediction of Ys, the flame temperature, and the mass fractions of CO, H and OH.

  20. Predicting Shear Transformation Events in Metallic Glasses

    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.

  1. Shear strength of non-shear reinforced concrete elements

    Hoang, Cao linh

    1997-01-01

    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.Proposals have been made on how the derived standard solutions may be applied to more complicated cases, such as continuous beams, beams......The report deals with the shear strength of statically indeterminate reinforced concrete beams without shear reinforcement. Solutions for a number of beams with different load and support conditions have been derived by means of the crack sliding model developed by Jin- Ping Zhang.This model...

  2. The TRICLOBS Dynamic Multi-Band Image Data Set for the Development and Evaluation of Image Fusion Methods.

    Alexander Toet

    Full Text Available The fusion and enhancement of multiband nighttime imagery for surveillance and navigation has been the subject of extensive research for over two decades. Despite the ongoing efforts in this area there is still only a small number of static multiband test images available for the development and evaluation of new image fusion and enhancement methods. Moreover, dynamic multiband imagery is also currently lacking. To fill this gap we present the TRICLOBS dynamic multi-band image data set containing sixteen registered visual (0.4-0.7μm, near-infrared (NIR, 0.7-1.0μm and long-wave infrared (LWIR, 8-14μm motion sequences. They represent different military and civilian surveillance scenarios registered in three different scenes. Scenes include (military and civilian people that are stationary, walking or running, or carrying various objects. Vehicles, foliage, and buildings or other man-made structures are also included in the scenes. This data set is primarily intended for the development and evaluation of image fusion, enhancement and color mapping algorithms for short-range surveillance applications. The imagery was collected during several field trials with our newly developed TRICLOBS (TRI-band Color Low-light OBServation all-day all-weather surveillance system. This system registers a scene in the Visual, NIR and LWIR part of the electromagnetic spectrum using three optically aligned sensors (two digital image intensifiers and an uncooled long-wave infrared microbolometer. The three sensor signals are mapped to three individual RGB color channels, digitized, and stored as uncompressed RGB (false color frames. The TRICLOBS data set enables the development and evaluation of (both static and dynamic image fusion, enhancement and color mapping algorithms. To allow the development of realistic color remapping procedures, the data set also contains color photographs of each of the three scenes. The color statistics derived from these photographs

  3. Formation of structural steady states in lamellar/sponge phase-separating fluids under shear flow

    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.

  4. Development of new S-band RF window for stable high-power operation in linear accelerator RF system

    Joo, Youngdo; Lee, Byung-Joon; Kim, Seung-Hwan; Kong, Hyung-Sup; Hwang, Woonha; Roh, Sungjoo; Ryu, Jiwan

    2017-09-01

    For stable high-power operation, a new RF window is developed in the S-band linear accelerator (Linac) RF systems of the Pohang Light Source-II (PLS-II) and the Pohang Accelerator Laboratory X-ray Free-Electron Laser (PAL-XFEL). The new RF window is designed to mitigate the strength of the electric field at the ceramic disk and also at the waveguide-cavity coupling structure of the conventional RF window. By replacing the pill-box type cavity in the conventional RF window with an overmoded cavity, the electric field component perpendicular to the ceramic disk that caused most of the multipacting breakdowns in the ceramic disk was reduced by an order of magnitude. The reduced electric field at the ceramic disk eliminated the Ti-N coating process on the ceramic surface in the fabrication procedure of the new RF window, preventing the incomplete coating from spoiling the RF transmission and lowering the fabrication cost. The overmoded cavity was coupled with input and output waveguides through dual side-wall coupling irises to reduce the electric field strength at the waveguide-cavity coupling structure and the possibility of mode competitions in the overmoded cavity. A prototype of the new RF window was fabricated and fully tested with the Klystron peak input power, pulse duration and pulse repetition rate of 75 MW, 4.5 μs and 10 Hz, respectively, at the high-power test stand. The first mass-produced new RF window installed in the PLS-II Linac is running in normal operation mode. No fault is reported to date. Plans are being made to install the new RF window to all S-band accelerator RF modules of the PLS-II and PAL-XFEL Linacs. This new RF window may be applied to the output windows of S-band power sources like Klystron as wells as the waveguide windows of accelerator facilities which operate in S-band.

  5. Design and development of a 6 MW peak, 24 kW average power S-band klystron

    Joshi, L.M.; Meena, Rakesh; Nangru, Subhash; Kant, Deepender; Pal, Debashis; Lamba, O.S.; Jindal, Vishnu; Jangid, Sushil Kumar, E-mail: joslm@rediffmail.com [Central Electronics Engineering Research Institute, Council of Scientific and Industrial Research, Pilani (India); Chakravarthy, D.P.; Dixit, Kavita [Bhabha Atomic Research Centre, Mumbai (India)

    2011-07-01

    A 6 MW peak, 24 kW average power S-band Klystron is under development at CEERI, Pilani under an MoU between BARC and CEERI. The design of the klystron has been completed. The electron gun has been designed using TRAK and MAGIC codes. RF cavities have been designed using HFSS and CST Microwave Studio while the complete beam wave interaction simulation has been done using MAGIC code. The thermal design of collector and RF window has been done using ANSYS code. A Gun Collector Test Module (GCTM) was developed before making actual klystron to validate gun perveance and thermal design of collector. A high voltage solid state pulsed modulator has been installed for performance valuation of the tube. The paper will cover the design aspects of the tube and experimental test results of GCTM and klystron. (author)

  6. Commissioning of indigenous microwave test facility for development and pilot production of 2 MW S-band magnetrons

    Shrivastava, Purushottam; Wanmode, Y.D.; Hannurkar, P.R.; Prasad, Sharda

    2005-01-01

    To have self reliance in the field of microwave devices and to have consistent supply of pulsed magnetrons for the Indian accelerator programme. CAT initiated development of 2 MW S-Band pulsed magnetrons in collaboration with CEERI, Pilani. The design, development and testing of the microwave test facilities for ageing. conditioning and performance testing of Indian magnetrons, was successfully done by CAT indigenously. After the rigorous testing. the test facility was shifted, installed and commissioned at CEERI, Pilani by CAT. Over a period of 10 years, nine prototypes were aged and tested, two magnetrons were life tested and five magnetrons under production programme have been successfully conditioned and tested. Testing of more numbers is underway. The system details. commissioning aspects are discussed, results are shown. (author)

  7. Design and development of a 6 MW peak, 24 kW average power S-band klystron

    Joshi, L.M.; Meena, Rakesh; Nangru, Subhash; Kant, Deepender; Pal, Debashis; Lamba, O.S.; Jindal, Vishnu; Jangid, Sushil Kumar; Chakravarthy, D.P.; Dixit, Kavita

    2011-01-01

    A 6 MW peak, 24 kW average power S-band Klystron is under development at CEERI, Pilani under an MoU between BARC and CEERI. The design of the klystron has been completed. The electron gun has been designed using TRAK and MAGIC codes. RF cavities have been designed using HFSS and CST Microwave Studio while the complete beam wave interaction simulation has been done using MAGIC code. The thermal design of collector and RF window has been done using ANSYS code. A Gun Collector Test Module (GCTM) was developed before making actual klystron to validate gun perveance and thermal design of collector. A high voltage solid state pulsed modulator has been installed for performance valuation of the tube. The paper will cover the design aspects of the tube and experimental test results of GCTM and klystron. (author)

  8. Development of nanometer resolution C-Band radio frequency beam position monitors in the Final Focus Test Beam

    Slaton, T.; Mazaheri, G.

    1998-08-01

    Using a 47 GeV electron beam, the Final Focus Test Beam (FFTB) produces vertical spot sizes around 70 nm. These small beam sizes introduce an excellent opportunity to develop and test high resolution Radio Frequency Beam Position Monitors (RF-BPMs). These BPMs are designed to measure pulse to pulse beam motion (jitter) at a theoretical resolution of approximately 1 nm. The beam induces a TM 110 mode with an amplitude linearly proportional to its charge and displacement from the BPM's (cylindrical cavity) axis. The C-band (5,712 MHz) TM 110 signal is processed and converted into beam position for use by the Stanford Linear Collider (SLC) control system. Presented are the experimental procedures, acquisition, and analysis of data demonstrating resolution of jitter near 25 nm. With the design of future e + e - linear colliders requiring spot sizes close to 3 nm, understanding and developing RF-BPMs will be essential in resolving and controlling jitter

  9. Ku Band Phased Array Feed Development for Surface Water Ocean Topography Mission

    National Aeronautics and Space Administration — The purpose of this project is to design components essential to the development of phased arrays and phased array feeds for use in remote sensing. Specifically the...

  10. Development of an S-band high-power pillbox-type RF window

    Miura, A.; Matsumoto, H.

    1992-01-01

    We report on the development of RF windows used to handle a high transmission power up to 110 MW for the Japan Linear Collider. A detailed simulation on multipactoring has been carried out. The results were compared with cathode-luminescence on the surface of alumina RF windows experimentally observed with power transmission up to 200 MW. (Author) 10 refs., 9 figs

  11. Photonic integration and components development for a Ku-band phased array antenna system

    Marpaung, D.A.I.; Zhuang, L.; Burla, M.; Roeloffzen, C.G.H.; Noharet, Bertrand; Wang, Qin; Beeker, W.P.; Beeker, Willem; Leinse, Arne; Heideman, Rene

    2011-01-01

    In this paper the development of a phased array antenna system using a photonic beamformer is reported. The paper emphasizes on the photonic integration between two main components of the beamformer, namely the photonic beamformer chip and the electroabsorption modulator array. System level

  12. Shear zones between rock units with no relative movement

    Koyi, Hemin; Schmeling, Harro; Burchardt, Steffi

    2013-01-01

    Shear zones are normally viewed as relatively narrow deformation zones that accommodate relative displacement between two "blocks" that have moved past each other in opposite directions. This study reports localized zones of shear between adjacent blocks that have not moved past each other. Such ...... given credit for and may be responsible for some reverse kinematics reported in shear zones....... or wakes, elongated bodies (vertical plates or horizontal rod-like bodies) produce tabular shear zones or wakes. Unlike conventional shear zones across which shear indicators usually display consistent symmetries, shear indicators on either side of the shear zone or wake reported here show reverse...... kinematics. Thus profiles exhibit shear zones with opposed senses of movement across their center-lines or -planes.We have used field observations and results from analytical and numerical models to suggest that examples of wakes are the transit paths that develop where denser blocks sink within salt...

  13. Development of Coatings for Radar Absorbing Materials at X-band

    Kumar, Abhishek; Singh, Samarjit

    2018-03-01

    The present review gives a brief account on some of the technical features of radar absorbing materials (RAMs). The paper has been presented with a concentrated approach towards the material aspects for achieving enhanced radar absorption characteristics for its application as a promising candidate in stealth technology and electromagnetic interference (EMI) minimization problems. The effect of metal particles doping/dispersion in the ferrites and dielectrics has been discussed for obtaining tunable radar absorbing characteristics. A short theoretical overview on the development of absorber materials, implementation of genetic algorithm (GA) in multi-layering and frequency selective surfaces (FSSs) based multi-layer has also been presented for the development of radar absorbing coatings for achieving better absorption augmented with broadband features in order to counter the radar detection systems.

  14. Remote Sensing Wind and Wind Shear System.

    Contents: Remote sensing of wind shear and the theory and development of acoustic doppler; Wind studies; A comparison of methods for the remote detection of winds in the airport environment; Acoustic doppler system development; System calibration; Airport operational tests.

  15. Development of a new concept automatic frequency controller for an ultrasmall C-band linear accelerator guide

    Kamino, Yuichiro; Tsukuda, Kazuhiro; Kokubo, Masaki; Miura, Sadao; Hirai, Etsuro; Hiraoka, Masahiro; Ishikawa, Junzo

    2007-01-01

    We are developing a four-dimensional, image-guided radiotherapy system with a gimbaled x-ray head. The system has pursuing irradiation capability in addition to precise irradiation capability, owing to its agile x-ray head. The moving x-ray head requires a very small C-band accelerator guide. The heat intensity of the accelerator guide is much higher than that of conventional S-band medical linear accelerators. The resonance frequency varies over almost 1.0 MHz with a thermal time constant of about 30 s. An automatic frequency controller (AFC) is employed to compensate for this variation in resonance frequency. Furthermore, we noted that fast AFC response is important for step-and-shoot intensity modulation radiotherapy (IMRT), in which the beam is turned on and off frequently. Therefore, we invented a digital AFC, based on a new concept, to provide effective compensation for the thermal characteristics of the accelerator guide and to ensure stable and optimized x-ray treatment. An important aspect of the performance of the AFC is the capture-frequency range over which the AFC can seek, lock on to, and track the resonance frequency. The conventional, analog AFC used in S-band medical linear accelerators would have a capture-frequency range of about 0.9 MHz, if applied to our accelerator guide, and would be inappropriate. Conversely, our new AFC has a capture-frequency range of 24 MHz, which is well suited to our accelerator guide. The design concept behind this new AFC has been developed and verified. A full prototype system was constructed and tested on an existing accelerator guide at the rated x-ray output (500 cGy/min) of our radiotherapy system, with a pulse-repetition frequency of 300 Hz. The AFC acquired the resonance frequency of the accelerator guide within 0.15 s after beam-on, and provided stable tracking and adjustment of the frequency of the microwave source to the resonance frequency of the accelerator guide. With a planned improvement of the

  16. Development of an automatic frequency control system for an X-band (=9300 MHz) RF electron linear accelerator

    Cha, Sungsu, E-mail: sscha@kaeri.re.kr [Nuclear Data Center, Korea Atomic Energy Research Institute (KAERI), Daejeon 34057 (Korea, Republic of); Kim, Yujong; Lee, Byung Cheol [Nuclear Data Center, Korea Atomic Energy Research Institute (KAERI), Daejeon 34057 (Korea, Republic of); Park, Hyung Dal [Radiation Technology eXcellence(RTX), Daejeon 34025 (Korea, Republic of); Lee, Seung Hyun [Department of Energy Science, Sungkyunkwan University(SKKU), Suwon 16419 (Korea, Republic of); Buaphad, Pikad [Nuclear Data Center, Korea Atomic Energy Research Institute (KAERI), Daejeon 34057 (Korea, Republic of); Radiation Technology eXcellence(RTX), Daejeon 34025 (Korea, Republic of); Accelerator and Nuclear Fusion Physical Engineering, University of Science and Technology(UST), Daejeon 34113 (Korea, Republic of)

    2017-05-21

    KAERI is developing a 6 MeV X-band radio frequency (RF) electron linear accelerator for medical purposes. The proposed X-band accelerator consists of an e-gun, an accelerating structure, two solenoid magnets, two steering magnets, a magnetron, a modulator, and an automatic frequency control (AFC) system. The accelerating structure of the component consists of oxygen-free high-conductivity copper (OFHC). Therefore, the ambient temperature changes the volume, and the resonance frequency of the accelerating structure also changes. If the RF frequency of a 9300 MHz magnetron and the resonance frequency of the accelerating structure do not match, it can degrade the performance. That is, it will decrease the output power, lower the beam current, decrease the X-ray dose rate, increase the reflection power, and result in unstable operation of the accelerator. Accelerator operation should be possible at any time during all four seasons. To prevent humans from being exposed to radiation when it is operated, the accelerator should also be operable through remote monitoring and remote control. Therefore, the AFC system is designed to meet these requirements; it is configured based on the concept of a phase-locked loop (PLL) model, which includes an RF section, an intermediate frequency (IF) [1-3] section, and a local oscillator (LO) section. Some resonance frequency controllers use a DC motor, chain, and potentiometer to store the position and tune the frequency [4,5]. Our AFC system uses a step motor to tune the RF frequency of the magnetron. The maximum tuning turn number of our magnetron frequency tuning shaft is ten. Since the RF frequency of our magnetron is 9300±25 MHz, it gives 5 MHz (∵±25 MHz/10 turns → 50 MHz/10 turns =5 MHz/turn) frequency tuning per turn. The rotation angle of our step motor is 0.72° per step and the total step number per one rotation is 360°/0.72°=500 steps. Therefore, the tuning range per step is 10 kHz/step (=5 MHz per turn/500 steps per

  17. Development of an automatic frequency control system for an X-band (=9300 MHz) RF electron linear accelerator

    Cha, Sungsu; Kim, Yujong; Lee, Byung Cheol; Park, Hyung Dal; Lee, Seung Hyun; Buaphad, Pikad

    2017-05-01

    KAERI is developing a 6 MeV X-band radio frequency (RF) electron linear accelerator for medical purposes. The proposed X-band accelerator consists of an e-gun, an accelerating structure, two solenoid magnets, two steering magnets, a magnetron, a modulator, and an automatic frequency control (AFC) system. The accelerating structure of the component consists of oxygen-free high-conductivity copper (OFHC). Therefore, the ambient temperature changes the volume, and the resonance frequency of the accelerating structure also changes. If the RF frequency of a 9300 MHz magnetron and the resonance frequency of the accelerating structure do not match, it can degrade the performance. That is, it will decrease the output power, lower the beam current, decrease the X-ray dose rate, increase the reflection power, and result in unstable operation of the accelerator. Accelerator operation should be possible at any time during all four seasons. To prevent humans from being exposed to radiation when it is operated, the accelerator should also be operable through remote monitoring and remote control. Therefore, the AFC system is designed to meet these requirements; it is configured based on the concept of a phase-locked loop (PLL) model, which includes an RF section, an intermediate frequency (IF) [1-3] section, and a local oscillator (LO) section. Some resonance frequency controllers use a DC motor, chain, and potentiometer to store the position and tune the frequency [4,5]. Our AFC system uses a step motor to tune the RF frequency of the magnetron. The maximum tuning turn number of our magnetron frequency tuning shaft is ten. Since the RF frequency of our magnetron is 9300±25 MHz, it gives 5 MHz (∵±25 MHz/10 turns → 50 MHz/10 turns =5 MHz/turn) frequency tuning per turn. The rotation angle of our step motor is 0.72° per step and the total step number per one rotation is 360°/0.72°=500 steps. Therefore, the tuning range per step is 10 kHz/step (=5 MHz per turn/500 steps per

  18. Development of an automatic frequency control system for an X-band (=9300 MHz) RF electron linear accelerator

    Cha, Sungsu; Kim, Yujong; Lee, Byung Cheol; Park, Hyung Dal; Lee, Seung Hyun; Buaphad, Pikad

    2017-01-01

    KAERI is developing a 6 MeV X-band radio frequency (RF) electron linear accelerator for medical purposes. The proposed X-band accelerator consists of an e-gun, an accelerating structure, two solenoid magnets, two steering magnets, a magnetron, a modulator, and an automatic frequency control (AFC) system. The accelerating structure of the component consists of oxygen-free high-conductivity copper (OFHC). Therefore, the ambient temperature changes the volume, and the resonance frequency of the accelerating structure also changes. If the RF frequency of a 9300 MHz magnetron and the resonance frequency of the accelerating structure do not match, it can degrade the performance. That is, it will decrease the output power, lower the beam current, decrease the X-ray dose rate, increase the reflection power, and result in unstable operation of the accelerator. Accelerator operation should be possible at any time during all four seasons. To prevent humans from being exposed to radiation when it is operated, the accelerator should also be operable through remote monitoring and remote control. Therefore, the AFC system is designed to meet these requirements; it is configured based on the concept of a phase-locked loop (PLL) model, which includes an RF section, an intermediate frequency (IF) [1-3] section, and a local oscillator (LO) section. Some resonance frequency controllers use a DC motor, chain, and potentiometer to store the position and tune the frequency [4,5]. Our AFC system uses a step motor to tune the RF frequency of the magnetron. The maximum tuning turn number of our magnetron frequency tuning shaft is ten. Since the RF frequency of our magnetron is 9300±25 MHz, it gives 5 MHz (∵±25 MHz/10 turns → 50 MHz/10 turns =5 MHz/turn) frequency tuning per turn. The rotation angle of our step motor is 0.72° per step and the total step number per one rotation is 360°/0.72°=500 steps. Therefore, the tuning range per step is 10 kHz/step (=5 MHz per turn/500 steps per

  19. Implementation on Landsat Data of a Simple Cloud Mask Algorithm Developed for MODIS Land Bands

    Oreopoulos, Lazaros; Wilson, Michael J.; Varnai, Tamas

    2010-01-01

    This letter assesses the performance on Landsat-7 images of a modified version of a cloud masking algorithm originally developed for clear-sky compositing of Moderate Resolution Imaging Spectroradiometer (MODIS) images at northern mid-latitudes. While data from recent Landsat missions include measurements at thermal wavelengths, and such measurements are also planned for the next mission, thermal tests are not included in the suggested algorithm in its present form to maintain greater versatility and ease of use. To evaluate the masking algorithm we take advantage of the availability of manual (visual) cloud masks developed at USGS for the collection of Landsat scenes used here. As part of our evaluation we also include the Automated Cloud Cover Assesment (ACCA) algorithm that includes thermal tests and is used operationally by the Landsat-7 mission to provide scene cloud fractions, but no cloud masks. We show that the suggested algorithm can perform about as well as ACCA both in terms of scene cloud fraction and pixel-level cloud identification. Specifically, we find that the algorithm gives an error of 1.3% for the scene cloud fraction of 156 scenes, and a root mean square error of 7.2%, while it agrees with the manual mask for 93% of the pixels, figures very similar to those from ACCA (1.2%, 7.1%, 93.7%).

  20. Shear deformation-induced anisotropic thermal conductivity of graphene.

    Cui, Liu; Shi, Sanqiang; Wei, Gaosheng; Du, Xiaoze

    2018-01-03

    Graphene-based materials exhibit intriguing phononic and thermal properties. In this paper, we have investigated the heat conductance in graphene sheets under shear-strain-induced wrinkling deformation, using equilibrium molecular dynamics simulations. A significant orientation dependence of the thermal conductivity of graphene wrinkles (GWs) is observed. The directional dependence of the thermal conductivity of GWs stems from the anisotropy of phonon group velocities as revealed by the G-band broadening of the phonon density of states (DOS), the anisotropy of thermal resistance as evidenced by the G-band peak mismatch of the phonon DOS, and the anisotropy of phonon relaxation times as a direct result of the double-exponential-fitting of the heat current autocorrelation function. By analyzing the relative contributions of different lattice vibrations to the heat flux, we have shown that the contributions of different lattice vibrations to the heat flux of GWs are sensitive to the heat flux direction, which further indicates the orientation-dependent thermal conductivity of GWs. Moreover, we have found that, in the strain range of 0-0.1, the anisotropy ratio of GWs increases monotonously with increasing shear strain. This is induced by the change in the number of wrinkles, which is more influential in the direction perpendicular to the wrinkle texture. The findings elucidated here emphasize the utility of wrinkle engineering for manipulation of nanoscale heat transport, which offers opportunities for the development of thermal channeling devices.

  1. The development of the larval nervous system, musculature and ciliary bands of Pomatoceros lamarckii (Annelida: heterochrony in polychaetes

    Shimeld Sebastian M

    2006-10-01

    Full Text Available Abstract Background To understand the evolution of animals it is essential to have taxon sampling across a representative spread of the animal kingdom. With the recent rearrangement of most of the Bilateria into three major clades (Ecdysozoa, Lophotrochozoa and Deuterostomia it has become clear that the Lophotrochozoa are relatively poorly represented in our knowledge of animal development, compared to the Ecdysozoa and Deuterostomia. We aim to contribute towards redressing this balance with data on the development of the muscular, nervous and ciliary systems of the annelid Pomatoceros lamarckii (Serpulidae. We compare our data with other lophotrochozoans. Results P. lamarckii develops locomotory and feeding structures that enable it to become a swimming, planktotrophic larva within 24 hours. Formation of the trochophore includes development of a prototroch, metatroch and neurotroch, development of apical and posterior nervous elements at similar times, and development of musculature around the ciliary bands and digestive tract prior to development of any body wall muscles. The adult nervous and muscular systems are essentially preformed in the late larva. Interestingly, the muscular systems of the larvae and juvenile worms do not include the circular muscles of the body wall, which are considered to be plesiomorphic for annelids, although the possibility that circular muscles develop after these stages cannot be ruled out at this point. Conclusion A comparison between polychaetes shows variability in the timing (heterochrony of development of body wall muscles and elements of the nervous system. These heterochronies are one route for evolution of different life history strategies, such as adaptations to feeding requirements.

  2. Development of ultra pure germanium epi layers for blocked impurity band far infrared detectors

    Lutz, M.P.

    1991-05-01

    The main goals of this paper are: (1) To develop a low-pressure CVD (LPCVD) process that allows epitaxial growth at lower temperatures. Lower temperatures will allow the achievement of a sharp dopant profile at the substrate/epi-layer interface. Less out-diffusion from the substrate would allow the use of thinner epitaxial layers, which would lead to a larger depletion width in the photoactive region. LPCVD also avoids, to a great extent, gas-phase nucleation, which would cause Ge particulates to fall onto the wafer surface during growth. (2) To reduce high levels of oxygen and copper present at the wafer interface, as observed by secondary ion mass spectroscopy (SIMS). In order to achieve high-quality epitaxial layers, it is imperative that the substrate surface be of excellent quality. (3) To make and test detectors, after satisfactory epitaxial layers have been made

  3. The effect of pressure and shear on tissue viability of human skin in relation to the development of pressure ulcers: a systematic review.

    Hoogendoorn, Iris; Reenalda, Jasper; Koopman, Bart F J M; Rietman, Johan S

    2017-08-01

    Pressure ulcers are a significant problem in health care, due to high costs and large impact on patients' life. In general, pressure ulcers develop as tissue viability decreases due to prolonged mechanical loading. The relation between load and tissue viability is highly influenced by individual characteristics. It is proposed that measurements of skin blood flow regulation could provide good assessment of the risk for pressure ulcer development, as skin blood flow is essential for tissue viability. . Therefore, the aim of this systematic review is to gain insight in the relation between mechanical load and the response of the skin and underlying tissue to this loading measured in-vivo with non-invasive techniques. A systematic literature search was performed to identify articles analysing the relation between mechanical load (pressure and/or shear) and tissue viability measured in-vivo. Two independent reviewers scored the methodological quality of the 22 included studies. Methodological information as well as tissue viability parameters during load application and after load removal were extracted from the included articles and used in a meta-analysis. Pressure results in a decrease in skin blood flow parameters, compared to baseline; showing a larger decrease with higher magnitudes of load. The steepness of the decrease is mostly dependent on the anatomical location. After load removal the magnitude of the post-reactive hyperaemic peak is related to the magnitude of pressure. Lastly, shear in addition to pressure, shows an additional negative effect, but the effect is less apparent than pressure on skin viability. Copyright © 2017 Tissue Viability Society. Published by Elsevier Ltd. All rights reserved.

  4. Development and evaluation of automated systems for detection and classification of banded chromosomes: current status and future perspectives

    Wang Xingwei; Zheng Bin; Wood, Marc; Li Shibo; Chen Wei; Liu Hong

    2005-01-01

    Automated detection and classification of banded chromosomes may help clinicians diagnose cancers and other genetic disorders at an early stage more efficiently and accurately. However, developing such an automated system (including both a high-speed microscopic image scanning device and related computer-assisted schemes) is quite a challenging and difficult task. Since the 1980s, great research efforts have been made to develop fast and more reliable methods to assist clinical technicians in performing this important and time-consuming task. A number of computer-assisted methods including classical statistical methods, artificial neural networks and knowledge-based fuzzy logic systems, have been applied and tested. Based on the initial test using limited datasets, encouraging results in algorithm and system development have been demonstrated. Despite the significant research effort and progress made over the last two decades, computer-assisted chromosome detection and classification systems have not been routinely accepted and used in clinical laboratories. Further research and development is needed

  5. Development and evaluation of automated systems for detection and classification of banded chromosomes: current status and future perspectives

    Wang Xingwei [Center for Bioengineering and School of Electrical and Computer Engineering, University of Oklahoma, OK (United States); Zheng Bin [Department of Radiology, University of Pittsburgh Medical Center, Pittsburgh, PA (United States); Wood, Marc [Center for Bioengineering and School of Electrical and Computer Engineering, University of Oklahoma, OK (United States); Li Shibo [Department of Pediatrics, University of Oklahoma Medical Center, Oklahoma City, OK (United States); Chen Wei [Department of Physics and Engineering, University of Central Oklahoma, Edmond, OK (United States); Liu Hong [Center for Bioengineering and School of Electrical and Computer Engineering, University of Oklahoma, OK (United States)

    2005-08-07

    Automated detection and classification of banded chromosomes may help clinicians diagnose cancers and other genetic disorders at an early stage more efficiently and accurately. However, developing such an automated system (including both a high-speed microscopic image scanning device and related computer-assisted schemes) is quite a challenging and difficult task. Since the 1980s, great research efforts have been made to develop fast and more reliable methods to assist clinical technicians in performing this important and time-consuming task. A number of computer-assisted methods including classical statistical methods, artificial neural networks and knowledge-based fuzzy logic systems, have been applied and tested. Based on the initial test using limited datasets, encouraging results in algorithm and system development have been demonstrated. Despite the significant research effort and progress made over the last two decades, computer-assisted chromosome detection and classification systems have not been routinely accepted and used in clinical laboratories. Further research and development is needed.

  6. Development of optical inspection system of L-band SRF cavity

    Tajima, Yujiro; Iwashita, Yoshihisa; Hayano, Hitoshi

    2008-01-01

    The International Linear Collider (ILC) will require about 15,000 1.3 GHz superconducting radio frequency (SRF) accelerating cavities with high accelerating gradient (>35 MV/m) in its main linac. The high yield (80%) of successful high gradient cavities is necessary. Both of the yield and the accelerating gradient of SRF cavities does not reach the required level at present. We think that the gradient of the SRF cavities is limited by irregularities on the interior surface of the cavities, for example, fine dusts (1μm), balls (100μm) and pits (100μm): electrons emitted from the fine dusts by the tunnel effect are accelerated in the electric field, and consume the stored energy of the cavities (Field Emission). The balls and pits cause a breakdown by a magnetic field enhancement or a thermal current concentration (Thermal Breakdown). To prevent these problems the interior surface are treated by polishing and rinsing. The relation between the surface states and the gradient limitations, however, is still not clarified. To study the relation, we are developing an optical inspection system of the interior surface. (author)

  7. Developing the Infrared PAH Emission Bands Into Calibrated Probes of Astrophysical Conditions with The NASA Ames PAH IR Spectroscopic Database

    Boersma, Christiaan

    We propose to quantitatively calibrate the PAH band strength ratios that have been traditionally used as qualitative proxies of PAH properties and linking PAH observables with local astrophysical conditions, thus developing PAHs into quantitative probes of astronomical environments. This will culminate in a toolbox (calibration charts) that can be used by PAH experts and non-PAH experts alike to unlock the information hidden in PAH emission sources that are part of the Spitzer and ISO archives. Furthermore, the proposed work is critical to mine the treasure trove of information JWST will return as it will capture, for the first time, the complete mid-infrared (IR) PAH spectrum with fully resolved features, through a single aperture, and along single lines-of-sight; making it possible to fully extract the information contained in the PAH spectra. In short, the work proposed here represents a major step in enabling the astronomical PAH model to reach its full potential as a diagnostic of the physical and chemical conditions in objects spanning the Universe. Polycyclic aromatic hydrocarbons (PAHs), a common and important reservoir of accessible carbon across the Universe, play an intrinsic part in the formation of stars, planets and possibly even life itself. While most PAH spectra appear quite similar, they differ in detail and contain a wealth of untapped information. Thanks to recent advances in laboratory studies and computer-based calculations of PAH spectra, the majority of which have been made at NASA Ames, coupled with the astronomical modeling tools we have developed, we can interpret the spectral details at levels never before possible. This enables us to extract local physical conditions and track subtle changes in these conditions at levels previously impossible. Building upon the tools and paradigms developed as part of the publicly available NASA Ames PAH IR Spectroscopic Database (PAHdb; www.astrochem.org/pahdb/), the purpose of our proposed research is

  8. Friction of Shear-Fracture Zones

    Riikilä, T. I.; Pylväinen, J. I.; Åström, J.

    2017-12-01

    A shear fracture of brittle solids under compression undergoes a substantial evolution from the initial microcracking to a fully formed powder-filled shear zone. Experiments covering the entire process are relatively easy to conduct, but they are very difficult to investigate in detail. Numerically, the large strain limit has remained a challenge. An efficient simulation model and a custom-made experimental device are employed to test to what extent a shear fracture alone is sufficient to drive material to spontaneous self-lubrication. A "weak shear zone" is an important concept in geology, and a large number of explanations, specific for tectonic conditions, have been proposed. We demonstrate here that weak shear zones are far more general, and that their emergence only demands that a microscopic, i.e., fragment-scale, stress relaxation mechanism develops during the fracture process.

  9. Evaluation of size dependent design shear strength of reinforced ...

    to the development of the size dependent models on the shear strength in ... predict the diagonal cracking strength and the ultimate shear strength of RC ... ing strength of normal beams was by Zsutty (1968) based on the data base available without .... The comparison of the calculated shear strength of the beams is shown.

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

    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.

  11. Development of nanometer resolution C-Band radio frequency beam position monitors in the Final Focus Test Beam

    Slaton, T.; Mazaheri, G. [Stanford Univ., CA (US). Stanford Linear Accelerator Center; Shintake, T. [National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)

    1998-08-01

    Using a 47 GeV electron beam, the Final Focus Test Beam (FFTB) produces vertical spot sizes around 70 nm. These small beam sizes introduce an excellent opportunity to develop and test high resolution Radio Frequency Beam Position Monitors (RF-BPMs). These BPMs are designed to measure pulse to pulse beam motion (jitter) at a theoretical resolution of approximately 1 nm. The beam induces a TM{sub 110} mode with an amplitude linearly proportional to its charge and displacement from the BPM's (cylindrical cavity) axis. The C-band (5,712 MHz) TM{sub 110} signal is processed and converted into beam position for use by the Stanford Linear Collider (SLC) control system. Presented are the experimental procedures, acquisition, and analysis of data demonstrating resolution of jitter near 25 nm. With the design of future e{sup +}e{sup -} linear colliders requiring spot sizes close to 3 nm, understanding and developing RF-BPMs will be essential in resolving and controlling jitter.

  12. Experimental study of shear rate dependence in perpetually sheared granular matter

    Liu, Sophie Yang; Guillard, François; Marks, Benjy; Rognon, Pierre; Einav, Itai

    2017-06-01

    We study the shear behaviour of various granular materials by conducting novel perpetual simple shear experiments over four orders of magnitude of relatively low shear rates. The newly developed experimental apparatus employed is called "3D Stadium Shear Device" which is an extended version of the 2D Stadium Shear Device [1]. This device is able to provide a non-radial dependent perpetual shear flow and a nearly linear velocity profile between two oppositely moving shear walls. Using this device, we are able to test a large variety of granular materials. Here, we demonstrate the applicability of the device on glass beads (diameter 1 mm, 3 mm, and 14 mm) and rice. We particularly focus on studying these materials at very low inertial number I ranging from 10-6 to 10-2. We find that, within this range of I, the friction coefficient μ of glass beads has no shear rate dependence. A particularly appealing observation comes from testing rice, where the attainment of critical state develops under much longer duration than in other materials. Initially during shear we find a value of μ similar to that found for glass beads, but with time this value decreases gradually towards the asymptotic critical state value. The reason, we believe, lies in the fact that rice grains are strongly elongated; hence the time to achieve the stable μ is primarily controlled by the time for particles to align themselves with respect to the shear walls. Furthermore, the initial packing conditions of samples also plays a role in the evolution of μ when the shear strain is small, but that impact will eventually be erased after sufficient shear strain.

  13. Experimental study of shear rate dependence in perpetually sheared granular matter

    Liu Sophie Yang

    2017-01-01

    Full Text Available We study the shear behaviour of various granular materials by conducting novel perpetual simple shear experiments over four orders of magnitude of relatively low shear rates. The newly developed experimental apparatus employed is called “3D Stadium Shear Device” which is an extended version of the 2D Stadium Shear Device [1]. This device is able to provide a non-radial dependent perpetual shear flow and a nearly linear velocity profile between two oppositely moving shear walls. Using this device, we are able to test a large variety of granular materials. Here, we demonstrate the applicability of the device on glass beads (diameter 1 mm, 3 mm, and 14 mm and rice. We particularly focus on studying these materials at very low inertial number I ranging from 10−6 to 10−2. We find that, within this range of I, the friction coefficient μ of glass beads has no shear rate dependence. A particularly appealing observation comes from testing rice, where the attainment of critical state develops under much longer duration than in other materials. Initially during shear we find a value of μ similar to that found for glass beads, but with time this value decreases gradually towards the asymptotic critical state value. The reason, we believe, lies in the fact that rice grains are strongly elongated; hence the time to achieve the stable μ is primarily controlled by the time for particles to align themselves with respect to the shear walls. Furthermore, the initial packing conditions of samples also plays a role in the evolution of μ when the shear strain is small, but that impact will eventually be erased after sufficient shear strain.

  14. Development of a shear-force scanning near-field cathodoluminescence microscope for characterization of nanostructures' optical properties.

    Bercu, N B; Troyon, M; Molinari, M

    2016-09-01

    An original scanning near-field cathodoluminescence microscope for nanostructure characterization has been developed and successfully tested. By using a bimorph piezoelectric stack both as actuator and detector, the developed setup constitutes a real improvement compared to previously reported SEM-based solutions. The technique combines a scanning probe and a scanning electron microscope in order to simultaneously offer near-field cathodoluminescence and topographic images of the sample. Share-force topography and cathodoluminescence measurements on GaN, SiC and ZnO nanostructures using the developed setup are presented showing a nanometric resolution in both topography and cathodoluminescence images with increased sensitivity compared to classical luminescence techniques. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

  15. Development of an Age Band on the ManuVis for 3-Year-Old Children with Visual Impairments.

    Reimer, A M; Barsingerhorn, A D; Overvelde, A; Nijhuis-Van der Sanden, M W G; Boonstra, F N; Cox, R F A

    2017-08-01

    To compare fine motor performance of 3-year-old children with visual impairment with peers having normal vision, to provide reference scores for 3-year-old children with visual impairment on the ManuVis, and to assess inter-rater reliability. 26 children with visual impairment (mean age: 3 years 7 months (SD 3 months); 17 boys) and 28 children with normal vision (mean age: 3 years 7 months (SD 4 months); 14 boys) participated in the study. The ManuVis age band for 3-year-old children comprised two one-handed tasks, two two-handed tasks, and a pre-writing task. Children with visual impairment needed more time on all tasks (p children with normal vision (p Children aged 42-47 months performed significantly faster on two tasks and had better total scores than children aged 36-41 months (p children is appropriate to assess fine motor skills, and is sensitive to differences between children with visual impairment and normal vision and between half-year age groups. Reference scores are provided for 3-year-old children with visual impairment to identify delayed fine motor development.

  16. Investigation of grapevine photosynthesis using hyperspectral techniques and development of hyperspectral band ratio indices sensitive to photosynthesis.

    Ozelkan, Emre; Karaman, Muhittin; Candar, Serkan; Coskun, Zafer; Ormeci, Cankut

    2015-01-01

    The photosynthetic rate of 9 different grapevines were analyzed with simultaneous photosynthesis and spectroradiometric measurements on 08.08.2012 (veraison) and 06.09.2012 (harvest). The wavelengths and spectral regions, which most properly express photosynthetic rate, were determined using correlation and regression analysis. In addition, hyperspectral band ratio (BR) indices sensitive to photosynthesis were developed using optimum band ratio (OBRA) method. The relation of BR results with photosynthesis values are presented with the correlation matrix maps created in this study. The examinations were performed for both specific dates (i.e., veraison and harvest) and also in aggregate (i.e., correlation between total spectra and photosynthesis data). For specific dates wavelength based analysis, the photosynthesis were best determined with -0.929 correlation coefficient (r) 609 nm of yellow region at veraison stage, and -0.870 at 641 nm of red region at harvest stage. For wavelength based aggregate analysis, 640 nm of red region was found to be correlated with 0.921 and -0.867 r values respectively and red edge (RE) (695 nm) was found to be correlated with -0.922 and -0.860 r values, respectively. When BR indices results were analyzed with photosynthetic values for specific dates, -0.987 r with R8../R, at veraison stage and -0.911 r with R696/R944 at harvest stage were found most correlated. For aggregate analysis of BR, common BR presenting great correlation with photosynthesis for both measurements was found to be R632/R971 with -0.974, -0.881 r values, respectively and other R610/R760 with -0.976, -0.879 r values. The final results of this study indicate that the proportion of RE region to a region with direct or indirect correlation with photosynthetic provides information about rate of photosynthesis. With the indices created in this study, the photosynthesis rate of vineyards can be determined using in-situ hyperspectral remote sensing. The findings of this

  17. Phase Field Theory and Analysis of Pressure-Shear Induced Amorphization and Failure in Boron Carbide Ceramic

    John D. Clayton

    2014-07-01

    Full Text Available A nonlinear continuum phase field theory is developed to describe amorphization of crystalline elastic solids under shear and/or pressure loading. An order parameter describes the local degree of crystallinity. Elastic coefficients can depend on the order parameter, inelastic volume change may accompany the transition from crystal to amorphous phase, and transitional regions parallel to bands of amorphous material are penalized by interfacial surface energy. Analytical and simple numerical solutions are obtained for an idealized isotropic version of the general theory, for an element of material subjected to compressive and/or shear loading. Solutions compare favorably with experimental evidence and atomic simulations of amorphization in boron carbide, demonstrating the tendency for structural collapse and strength loss with increasing shear deformation and superposed pressure.

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

    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.

  19. Coexistence and transition between shear zones in slow granular flows.

    Moosavi, Robabeh; Shaebani, M Reza; Maleki, Maniya; Török, János; Wolf, Dietrich E; Losert, Wolfgang

    2013-10-04

    We report experiments on slow granular flows in a split-bottom Couette cell that show novel strain localization features. Nontrivial flow profiles have been observed which are shown to be the consequence of simultaneous formation of shear zones in the bulk and at the boundaries. The fluctuating band model based on a minimization principle can be fitted to the experiments over a large variation of morphology and filling height with one single fit parameter, the relative friction coefficient μ(rel) between wall and bulk. The possibility of multiple shear zone formation is controlled by μ(rel). Moreover, we observe that the symmetry of an initial state, with coexisting shear zones at both side walls, breaks spontaneously below a threshold value of the shear velocity. A dynamical transition between two asymmetric flow states happens over a characteristic time scale which depends on the shear strength.

  20. High Resolution Shear Profile Measurements in Entangled Polymers

    Hayes, Keesha A.

    2008-11-17

    We use confocal microscopy and particle image velocimetry to visualize motion of 250-300 nm. fluorescent tracer particles in entangled polymers subject to a rectilinear shear flow. Our results show linear velocity profiles in polymer solutions spanning a wide range of molecular weights and number of entanglements (8≤Z≤56), but reveal large differences between the imposed and measured shear rates. These findings disagree with recent reports that shear banding is a characteristic flow response of entangled polymers, and instead point to interfacial slip as an important source of strain loss. © 2008 The American Physical Society.

  1. Health Promotion Outcomes of a Newly Developed Elastic Band Exercise Program for Older Adults in the Community: A Pilot Test.

    Chan, Shu-Ya; Kuo, Chang-Chih; Chen, Kuei-Min; Tseng, Wei-Shyuan; Huang, Hsin-Ting; Li, Chun-Huw

    2016-06-01

    Studies indicate that the incidence of disease, the mortality rate, and medical costs are significantly higher in people aged 65 years and over who do not engage in physical activities than in their peers who do engage in these activities. Therefore, promoting appropriate physical activity among older adults in the community is essential to delaying the health implications of aging. This pilot test was developed to assess the effectiveness of a newly developed Senior Elastic Band (SEB) exercise program on the health of older adults in community care stations. A quasiexperimental design was used. A convenience sample of 20 participants from a community care station was recruited. The SEB intervention included three phases (warm-up, aerobic motion, and static stretching) and was conducted three times per week, 40 minutes per session for 1 month. Twelve health indicators in three categories (functional fitness, self-perceived health status, and sleep quality) were examined before and immediately after 1 month of SEB exercises. Participants showed improved performance at the end of the 1-month study for the following indicators: lung capacity, cardiopulmonary fitness, upper and lower body flexibilities, upper limb muscle power, lower limb muscle endurance, and self-perceived physical health status (all ps exercise program shows preliminary and promising effects on improving the health of older adults in a community care station. Healthcare professionals who work with older adults living in the community may consider the SEB exercise program as a health promotion modality to recommend and implement with this population. However, we recommend further testing the long-term effects of this program on a larger population.

  2. Shear-wave velocity characterization of the USGS Hawaiian strong-motion network on the Island of Hawaii and development of an NEHRP site-class map

    Wong, Ivan G.; Stokoe, Kenneth; Cox, Brady R.; Yuan, Jiabei; Knudsen, Keith L.; Terra, Fabia; Okubo, Paul G.; Lin, Yin-Cheng

    2011-01-01

    To assess the level and nature of ground shaking in Hawaii for the purposes of earthquake hazard mitigation and seismic design, empirical ground-motion prediction models are desired. To develop such empirical relationships, knowledge of the subsurface site conditions beneath strong-motion stations is critical. Thus, as a first step to develop ground-motion prediction models for Hawaii, spectral-analysis-of-surface-waves (SASW) profiling was performed at the 22 free-field U.S. Geological Survey (USGS) strong-motion sites on the Big Island to obtain shear-wave velocity (VS) data. Nineteen of these stations recorded the 2006 Kiholo Bay moment magnitude (M) 6.7 earthquake, and 17 stations recorded the triggered M 6.0 Mahukona earthquake. VS profiling was performed to reach depths of more than 100 ft. Most of the USGS stations are situated on sites underlain by basalt, based on surficial geologic maps. However, the sites have varying degrees of weathering and soil development. The remaining strong-motion stations are located on alluvium or volcanic ash. VS30 (average VS in the top 30 m) values for the stations on basalt ranged from 906 to 1908 ft/s [National Earthquake Hazards Reduction Program (NEHRP) site classes C and D], because most sites were covered with soil of variable thickness. Based on these data, an NEHRP site-class map was developed for the Big Island. These new VS data will be a significant input into an update of the USGS statewide hazard maps and to the operation of ShakeMap on the island of Hawaii.

  3. Kink bands in thrust regime: Examples from Srinagar–Garhwal area ...

    Srinagar–Garhwal; kink bands; paleostress; shearing along kink planes; Himalaya; North Almora Thrust. J. Earth Syst. Sci. 120, No. 5, October 2011, pp. 939–948 ..... The α>β geometry observed in kink bands suggest towards shearing as a common phenomenon along the kink planes. (Anderson 1964). Since considerable ...

  4. Recent progress in shear punch testing

    Hamilton, M.L.; Toloczko, M.B.; Lucas, G.E.

    1994-09-01

    The shear punch test was developed in response to the needs of the materials development community for small-scale mechanical properties tests. Such tests will be of great importance when a fusion neutron simulation device is built, since such a device is expected to have a limited irradiation volume. The shear punch test blanks a circular disk from a fixed sheet metal specimen, specifically a TEM disk. Load-displacement data generated during the test can be related to uniaxial tensile properties such as yield and ultimate strength. Shear punch and tensile tests were performed at room temperature on a number of unirradiated aluminum, copper, vanadium, and stainless steel alloys and on several irradiated aluminum alloys. Recent results discussed here suggest that the relationship between shear punch strength and tensile strength varies with alloy class, although the relationship determined for the unirradiated condition remains valid for the irradiated aluminum alloys

  5. Evaluating interfacial shear stresses in composite hollo

    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.

  6. Study of the relation of the band at 3595 CM{sup -1} in FTIR spectrum of natural quartz with color development by gamma irradiation

    Silva, Helena Cristina M.; Lameiras, Fernando S., E-mail: helenacrisms@gmail.com, E-mail: fsl@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2015-07-01

    Brazil is a major producer of gemological quartz as smoky quartz, morion, citrine, amethyst, and prasiolite. Due to its abundance, hardness, and color varieties, quartz is used in jewelry industry. However, very often quartz is found in nature colorless or with faint colors, which requires exposure to ionizing radiation for color enhancement or development. Not all quartz can develop color. Chromophore chemical elements must be present in suitable proportions for color development after irradiation and heating. Infrared spectrometry is used to separate the quartz that can develop colors from the ones that cannot. Bands in infrared spectrum can indicate the presence and relative contents of chromophore chemical elements, such as aluminum, iron, lithium, sodium, and hydrogen. Some samples of colorless quartz show a band at 3595 cm{sup -1} whose origin is yet not assigned. Samples of quartz with a prominent band at 3595 cm{sup -1} were exposed to gamma rays and heating to observe its behavior. From the statistical point of view, no modification was observed on the position and amplitude of this band after irradiation up 75 kGy and heating to 300-330 deg C. This study should be completed with samples of different origins and higher doses, as well as chemical analyses of trace chemical elements in the samples. (author)

  7. Development and Validation of a Classification System to Identify High-Grade Dysplasia and Esophageal Adenocarcinoma in Barrett's Esophagus Using Narrow-Band Imaging

    Sharma, Prateek; Bergman, Jacques J. G. H. M.; Goda, Kenichi; Kato, Mototsugu; Messmann, Helmut; Alsop, Benjamin R.; Gupta, Neil; Vennalaganti, Prashanth; Hall, Matt; Konda, Vani; Koons, Ann; Penner, Olga; Goldblum, John R.; Waxman, Irving

    2016-01-01

    Although several classification systems have been proposed for characterization of Barrett's esophagus (BE) surface patterns based on narrow-band imaging (NBI), none have been widely accepted. The Barrett's International NBI Group (BING) aimed to develop and validate an NBI classification system for

  8. Study of the relation of the band at 3595 CM-1 in FTIR spectrum of natural quartz with color development by gamma irradiation

    Silva, Helena Cristina M.; Lameiras, Fernando S.

    2015-01-01

    Brazil is a major producer of gemological quartz as smoky quartz, morion, citrine, amethyst, and prasiolite. Due to its abundance, hardness, and color varieties, quartz is used in jewelry industry. However, very often quartz is found in nature colorless or with faint colors, which requires exposure to ionizing radiation for color enhancement or development. Not all quartz can develop color. Chromophore chemical elements must be present in suitable proportions for color development after irradiation and heating. Infrared spectrometry is used to separate the quartz that can develop colors from the ones that cannot. Bands in infrared spectrum can indicate the presence and relative contents of chromophore chemical elements, such as aluminum, iron, lithium, sodium, and hydrogen. Some samples of colorless quartz show a band at 3595 cm -1 whose origin is yet not assigned. Samples of quartz with a prominent band at 3595 cm -1 were exposed to gamma rays and heating to observe its behavior. From the statistical point of view, no modification was observed on the position and amplitude of this band after irradiation up 75 kGy and heating to 300-330 deg C. This study should be completed with samples of different origins and higher doses, as well as chemical analyses of trace chemical elements in the samples. (author)

  9. Shear melting and high temperature embrittlement: theory and application to machining titanium.

    Healy, Con; Koch, Sascha; Siemers, Carsten; Mukherji, Debashis; Ackland, Graeme J

    2015-04-24

    We describe a dynamical phase transition occurring within a shear band at high temperature and under extremely high shear rates. With increasing temperature, dislocation deformation and grain boundary sliding are supplanted by amorphization in a highly localized nanoscale band, which allows for massive strain and fracture. The mechanism is similar to shear melting and leads to liquid metal embrittlement at high temperature. From simulation, we find that the necessary conditions are lack of dislocation slip systems, low thermal conduction, and temperature near the melting point. The first two are exhibited by bcc titanium alloys, and we show that the final one can be achieved experimentally by adding low-melting-point elements: specifically, we use insoluble rare earth metals (REMs). Under high shear, the REM becomes mixed with the titanium, lowering the melting point within the shear band and triggering the shear-melting transition. This in turn generates heat which remains localized in the shear band due to poor heat conduction. The material fractures along the shear band. We show how to utilize this transition in the creation of new titanium-based alloys with improved machinability.

  10. Performance review of an indigenously developed high power test stand built for the Indian S-band 5 MW pulsed klystron development

    Shrivastava, Purushottam; Baxy, D.; Mulchandani, J.; Hannurkar, P.R.; Joshi, L.M.

    2003-01-01

    CAT took up development of 5 MW S-Band klystrons indigenously in collaboration with CEERI Pilani. The development of klystron prototype is completed. These klystrons are very crucial devices, for energizing the 10-20 MeV electron accelerators, which are developed in the country for various industrial, medical and scientific applications. A test station has been developed indigenously at CAT for these klystrons. It consists of a 12 MW peak power 130 kV klystron pulse modulator, a 1 : 10 pulse transformer, 130 kV high voltage deck having high voltage pulse divider, pulse current transformer as well indigenously built klystron socket, filament supplies, klystron support structure and pulse transformer oil tank. After development/rigorous testing the test stand was shifted to CEERI and was installed and commissioned there by CAT. Gun collector test module and prototypes of the 5 MW klystron were tested, aged and conditioned at high power using this test stand. The details of the system / test results are discussed

  11. Adiabatic Shear Bands in Simple and Dipolar Viscoplastic Materials

    1991-08-01

    d Engineering Mechanics. University of Missouri-Holla. Holla. MO 65401-0249. C S.A Mace -r. Germam .Maxirr. Cork. - DrucK GmbH Carl-i -0&sset7«v...iaxirn Gorki - Druck GmoH Car:- -Ossietzk^ -Str 30 11 7400 Auenöurs I _LL 1+ Xf . . M „ .,Mqon ACTA MECHANICA Acta Mechamca 86, .31—.1...points 13, 14, 15 and 17 becomes clear from the results plotted in Fig. 3d . The plots of the temperature rise at other points con- sidered are not

  12. Yielding and shear banding in soft glassy materials

    Fall, A.; Paredes, J.; Bonn, D.

    2010-01-01

    Yield stress fluids have proven difficult to characterize, and a reproducible determination of the yield stress is difficult. We study two types of yield stress fluids (YSF) in a single system: simple and thixotropic ones. This allows us to show that simple YSF are simply a special case of

  13. Comparative analysis of miRNA expression during the development of insects of different metamorphosis modes and germ-band types.

    Ylla, Guillem; Piulachs, Maria-Dolors; Belles, Xavier

    2017-10-11

    Do miRNAs contribute to specify the germ-band type and the body structure in the insect embryo? Our goal was to address that issue by studying the changes in miRNA expression along the ontogeny of the German cockroach Blattella germanica, which is a short germ-band and hemimetabolan species. We sequenced small RNA libraries representing 11 developmental stages of B. germanica ontogeny (with especial emphasis on embryogenesis) and the changes in miRNA expression were examined. Data were compared with equivalent data for two long germ-band holometabolan species Drosophila melanogaster and Drosophila virilis, and the short germ-band holometabolan species Tribolium castaneum. The identification of B. germanica embryo small RNA sequences unveiled miRNAs not detected in previous studies, such as those of the MIR-309 family and 54 novel miRNAs. Four main waves of miRNA expression were recognized (with most miRNA changes occurring during the embryonic stages): the first from day 0 to day 1 of embryogenesis, the second during mid-embryogenesis (days 0-6), the third (with an acute expression peak) on day 2 of embryonic development, and the fourth during post-embryonic development. The second wave defined the boundaries of maternal-to-zygotic transition, with maternal mRNAs being cleared, presumably by Mir-309 and associated scavenger miRNAs. miRNAs follow well-defined patterns of expression over hemimetabolan ontogeny, patterns that are more diverse during embryonic development than during the nymphal stages. The results suggest that miRNAs play important roles in the developmental transitions between the embryonic stages of development (starting with maternal loading), during which they might influence the germ-band type and metamorphosis mode.

  14. Adiabatic shear localization in a near beta Ti–5Al–5Mo–5 V–1Cr–1Fe alloy

    Wang, Bingfeng, E-mail: biw009@ucsd.edu [School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan (China); Key Lab of Nonferrous Materials, Ministry of Education, Central South University, Changsha 410083, Hunan (China); Department of Mechanical and Aerospace Engineering, University of California, San Diego (United States); Sun, Jieying; Wang, Xiaoyan; Fu, Ao [School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan (China)

    2015-07-15

    Adiabatic shear localization plays an important role in the deformation and failure of near beta Ti–5Al–5Mo–5 V–1Cr–1Fe alloy used in aircraft's gear at high rate deformation. Hat shaped specimens with different nominal shear strains are used to induce the formation of an adiabatic shear band under controlled shock-loading experiments. When the nominal shear strain is about 0.68, unstable shear deformation of the alloy emerges after the true flow stress reaches 1100 MPa, the first vibration peak during the split Hopkinson pressure bar testing, and the whole process lasts about 62 μs. The microstructures within the shear band in the Ti–5Al–5Mo–5V–1Cr–1Fe alloy are investigated by means of optical microscopy, scanning electron microscopy and transmission electron microscopy. Phase transformation occurs in the shear band when the nominal shear strain increases to 0.68. A number of equiaxed grains with sizes 50–200 nm and alpha″-phase are in the center of the shear band. Kinetic calculations indicate that during the deformation process, the recrystallized nanosized grains can be formed in the shear band by way of the subgrain boundaries rotation, and the alpha″ phase transformation start after the subgrain boundaries rotated to 30°.

  15. Shear-induced phase changes in mixtures

    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

  16. New Method for the Development of Plasmonic Metal-Semiconductor Interface Layer: Polymer Composites with Reduced Energy Band Gap

    Shujahadeen B. Aziz

    2017-01-01

    Full Text Available Silver nanoparticles within a host polymer of chitosan were synthesized by using in situ method. Ultraviolet-visible spectroscopy was then carried out for the prepared chitosan : silver triflate (CS : AgTf samples, showing a surface plasmonic resonance (SPR peak at 420 nm. To prepare polymer composites with reduced energy band gap, different amounts of alumina nanoparticles were incorporated into the CS : AgTf solution. In the present work, the results showed that the reduced silver nanoparticles and their adsorption on wide band gap alumina (Al2O3 particles are an excellent approach for the preparation of polymer composites with small optical band gaps. The optical dielectric loss parameter has been used to determine the band gap experimentally. The physics behind the optical dielectric loss were interpreted from the viewpoint of quantum mechanics. From the quantum-mechanics viewpoint, optical dielectric loss was also found to be a complex equation and required lengthy numerical computation. From the TEM investigation, the adsorption of silver nanoparticles on alumina has been observed. The optical micrograph images showed white spots (silver specks with different sizes on the surface of the films. The second semicircle in impedance Cole-Cole plots was found and attributed to the silver particles.

  17. Effect of hot band grain size on development of textures and magnetic properties in 2.0% Si non-oriented electrical steel sheet

    Lee, K.M. [Department of Materials Science and Engineering, Korea University, 5-1, Anam-dong, Sungbuk-Gu, Seoul 136-701 (Korea, Republic of); Huh, M.Y., E-mail: myhuh@korea.ac.kr [Department of Materials Science and Engineering, Korea University, 5-1, Anam-dong, Sungbuk-Gu, Seoul 136-701 (Korea, Republic of); Lee, H.J.; Park, J.T.; Kim, J.S. [Electrical Steel Sheet Research Group, Technical Research Laboratories, POSCO, Goedong-dong, Pohang (Korea, Republic of); Shin, E.J. [Korea Atomic Energy Research Institute, Neutron Science Division, Daejeon 305-353 (Korea, Republic of); Engler, O. [Hydro Aluminium Rolled Products GmbH, Research and Development Bonn, P.O. Box 2468, D-53014 Bonn (Germany)

    2015-12-15

    The effect of hot band grain size on the development of crystallographic texture and magnetic properties in non-oriented electrical steel sheet was studied. After cold rolling the samples with different initial grain sizes displayed different microstructures and micro-textures but nearly identical macro-textures. The homogeneous recrystallized microstructure and micro-texture in the sample having small grains caused normal continuous grain growth. The quite irregular microstructure and micro-texture in the recrystallized sample with large initial grain size provided a preferential growth of grains in 〈001〉//ND and 〈113〉//ND which were beneficial for developing superior magnetic properties. - Highlights: • We produced hot bands of electrical steel with different grain size but same texture. • Hot band grain size strongly affected cold rolling and subsequent annealing textures. • Homogeneous recrystallized microstructure caused normal continuous grain growth. • Irregular recrystallized microstructure led to selective growth of <001>//ND grains. • Hot band with large grains was beneficial for superior magnetic properties.

  18. Deformation bands in porous carbonate grainstones: Field and laboratory observations

    Cilona, A.; Baud, P.; Tondi, E.; Agosta, F.; Vinciguerra, S.; Rustichelli, A.; Spiers, C.J.

    2012-01-01

    Recent field-based studies documented deformation bands in porous carbonates; these structures accommodate volumetric and/or shear strain by means of pore collapse, grain rotation and/or sliding. Microstructural observations of natural deformation bands in carbonates showed that, at advanced stages

  19. Effect of periodic fluctuation of soil particle rotation resistance on interface shear behaviour

    Ebrahimian, Babak; Noorzad, Asadollah

    2010-01-01

    The interface behaviour between infinite extended narrow granular layer and bounding structure is numerically investigated using finite element method. The micro-polar (Cosserat) continuum approach within the framework of elasto-plasticity is employed to remove the numerical difficulties caused by strain-softening of materials in classical continuum mechanics. Mechanical properties of cohesionless granular soil are described with Lade's model enhanced with polar terms including Cosserat rotations, curvatures and couple stresses via mean grain diameter as the internal length. The main attention of paper is laid on the influence of spatial periodic fluctuation of rotation resistance of soil particles interlocked with the surface of bounding structure on evolution and location of shear band developed inside granular body. The finite element results demonstrate that the location and evolution of shear localization in granular body is strongly affected by prescribed non-uniform micro-polar kinematic boundary conditions along the interface.

  20. Confocal microscopy of colloidal dispersions in shear flow using a counter-rotating cone-plate shear cell

    Derks, Didi; Wisman, Hans; Blaaderen, Alfons van; Imhof, Arnout

    2004-01-01

    We report on novel possibilities for studying colloidal suspensions in a steady shear field in real space. Fluorescence confocal microscopy is combined with the use of a counter-rotating cone-plate shear cell. This allows imaging of individual particles in the bulk of a sheared suspension in a stationary plane. Moreover, this plane of zero velocity can be moved in the velocity gradient direction while keeping the shear rate constant. The colloidal system under study consists of rhodamine labelled PMMA spheres in a nearly density and refractive index matched mixture of cyclohexylbromide and cis-decalin. We show measured flow profiles in both the fluid and the crystalline phase and find indications for shear banding in the case of a sheared crystal. Furthermore, we show that, thanks to the counter-rotating principle of the cone-plate shear cell, a layer of particles in the bulk of a sheared crystalline suspension can be imaged for a prolonged time, with the result that their positions can be tracked

  1. C-Band Airport Surface Communications System Standards Development. Phase II Final Report. Volume 2: Test Bed Performance Evaluation and Final AeroMACS Recommendations

    Hall, Edward; Magner, James

    2011-01-01

    This report is provided as part of ITT s NASA Glenn Research Center Aerospace Communication Systems Technical Support (ACSTS) contract NNC05CA85C, Task 7: New ATM Requirements-Future Communications, C-Band and L-Band Communications Standard Development and was based on direction provided by FAA project-level agreements for New ATM Requirements-Future Communications. Task 7 included two subtasks. Subtask 7-1 addressed C-band (5091- to 5150-MHz) airport surface data communications standards development, systems engineering, test bed and prototype development, and tests and demonstrations to establish operational capability for the Aeronautical Mobile Airport Communications System (AeroMACS). Subtask 7-2 focused on systems engineering and development support of the L-band digital aeronautical communications system (L-DACS). Subtask 7-1 consisted of two phases. Phase I included development of AeroMACS concepts of use, requirements, architecture, and initial high-level safety risk assessment. Phase II builds on Phase I results and is presented in two volumes. Volume I is devoted to concepts of use, system requirements, and architecture, including AeroMACS design considerations. Volume II (this document) describes an AeroMACS prototype evaluation and presents final AeroMACS recommendations. This report also describes airport categorization and channelization methodologies. The purposes of the airport categorization task were (1) to facilitate initial AeroMACS architecture designs and enable budgetary projections by creating a set of airport categories based on common airport characteristics and design objectives, and (2) to offer high-level guidance to potential AeroMACS technology and policy development sponsors and service providers. A channelization plan methodology was developed because a common global methodology is needed to assure seamless interoperability among diverse AeroMACS services potentially supplied by multiple service providers.

  2. C-Band Airport Surface Communications System Standards Development. Phase II Final Report. Volume 1: Concepts of Use, Initial System Requirements, Architecture, and AeroMACS Design Considerations

    Hall, Edward; Isaacs, James; Henriksen, Steve; Zelkin, Natalie

    2011-01-01

    This report is provided as part of ITT s NASA Glenn Research Center Aerospace Communication Systems Technical Support (ACSTS) contract NNC05CA85C, Task 7: New ATM Requirements-Future Communications, C-Band and L-Band Communications Standard Development and was based on direction provided by FAA project-level agreements for New ATM Requirements-Future Communications. Task 7 included two subtasks. Subtask 7-1 addressed C-band (5091- to 5150-MHz) airport surface data communications standards development, systems engineering, test bed and prototype development, and tests and demonstrations to establish operational capability for the Aeronautical Mobile Airport Communications System (AeroMACS). Subtask 7-2 focused on systems engineering and development support of the L-band digital aeronautical communications system (L-DACS). Subtask 7-1 consisted of two phases. Phase I included development of AeroMACS concepts of use, requirements, architecture, and initial high-level safety risk assessment. Phase II builds on Phase I results and is presented in two volumes. Volume I (this document) is devoted to concepts of use, system requirements, and architecture, including AeroMACS design considerations. Volume II describes an AeroMACS prototype evaluation and presents final AeroMACS recommendations. This report also describes airport categorization and channelization methodologies. The purposes of the airport categorization task were (1) to facilitate initial AeroMACS architecture designs and enable budgetary projections by creating a set of airport categories based on common airport characteristics and design objectives, and (2) to offer high-level guidance to potential AeroMACS technology and policy development sponsors and service providers. A channelization plan methodology was developed because a common global methodology is needed to assure seamless interoperability among diverse AeroMACS services potentially supplied by multiple service providers.

  3. Keyed shear joints

    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...

  4. Sheared Electroconvective Instability

    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.

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

    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

  6. Edge Sheared Flows and Blob Dynamics

    Myra, J.; D' Ippolito, D.; Russell, D., E-mail: jrmyra@lodestar.com [Lodestar Research Corporation, Boulder (United States); Davis, W. M.; Zweben, S. [Princeton Plasma Physics Laboratory, Princeton (United States); Terry, J.; LaBombard, B. [Massachusetts Institute of Technology, Cambridge (United States)

    2012-09-15

    Full text: A study of sheared flows in the edge and scrape-off layer (SOL) and their interaction with blob-filaments is presented. Edge sheared flows are believed to be important for the L-H, and H-L transitions. Blob generation and dynamics impacts both the (near-separatrix) scrape-off-layer (SOL) width critical for power handling in the divertor, and the interaction of plasma in the far SOL with plasma-facing components. These topics are critical for ITER and future devices. A fluid-based 2D curvature-interchange model embedded in the SOLT code is employed to study these issues. Sheared binormal flows both regulate the power flux crossing the separatrix and control the character of emitted turbulence structures such as blob-filaments. At a critical power level (depending on parameters) the laminar flows containing intermittent, but bound, structures give way to full-blown blob emissions signifying a transition from quasi-diffusive to convective transport. In order to diagnose sheared flows in experiments and assess their interaction with blobs, a blob-tracking algorithm has been developed and applied to both NSTX and Alcator C-Mod data. Blob motion and ellipticity can be affected by sheared flows, and are diagnosed and compared with seeded blob simulations. A picture of the interaction of blobs and sheared flows is emerging from advances in the theory and simulation of edge turbulence, combined with ever-improving capabilities for edge diagnostics and their analysis. (author)

  7. Absorption band Q model for the earth

    Anderson, D.L.; Given, J.W.

    1982-01-01

    Body wave, surface wave, and normal mode data are used to place constraints on the frequency dependence of Q in the mantle. With a simple absorption band model it is possible to satisfy the shear sensitive data over a broad frequency range. The quality factor Q/sub s/(ω) is proportional to ω/sup α/ in the band and to ω and ω -1 at higher and lower frequencies, respectively, as appropriate for a relaxation mechanism with a spectrum of relaxation time. The parameters of the band are Q(min) = 80, α = 0.15, and width, 5 decades. The center of the band varies from 10 1 seconds in the upper mantle, to 1.6 x 10 3 seconds in the lower mantle. The shift of the band with depth is consistent with the expected effects of temperature, pressure and stress. High Q, regions of the mantle are attributed to a shift of the absorption band to longer periods. To satisfy the gravest fundamental spheroidal modes and the ScS data, the absorption band must shift back into the short-period seismic band at the base of the mantle. This may be due to a high temperature gradient or high shear stresses. A preliminary attempt is also made to specify bulk dissipation in the mantle and core. Specific features of the absorption band model are low Q in the body wave band at both the top and the base of the mantle, low Q for long-period body waves in the outer core, an inner core Q 2 that increases with period, and low Q/sub p//Q/sub s/ at short periods in the middle mantel. The short-period Q/sub s/ increases rapidly at 400 km and is relatively constant from this depth to 2400 km. The deformational Q of the earth at a period of 14 months is predicted to be 463

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

    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.

  9. Shear strength of non-shear reinforced concrete elements

    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. Spurious Shear in Weak Lensing with LSST

    Chang, C.; Kahn, S.M.; Jernigan, J.G.; Peterson, J.R.; AlSayyad, Y.; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Gibson, R.R.; Gilmore, K.; Grace, E.; Hannel, M.; Hodge, M.A.; Jee, M.J.; Jones, L.; Krughoff, S.; Lorenz, S.; Marshall, P.J.; Marshall, S.; Meert, A.

    2012-09-19

    The complete 10-year survey from the Large Synoptic Survey Telescope (LSST) will image {approx} 20,000 square degrees of sky in six filter bands every few nights, bringing the final survey depth to r {approx} 27.5, with over 4 billion well measured galaxies. To take full advantage of this unprecedented statistical power, the systematic errors associated with weak lensing measurements need to be controlled to a level similar to the statistical errors. This work is the first attempt to quantitatively estimate the absolute level and statistical properties of the systematic errors on weak lensing shear measurements due to the most important physical effects in the LSST system via high fidelity ray-tracing simulations. We identify and isolate the different sources of algorithm-independent, additive systematic errors on shear measurements for LSST and predict their impact on the final cosmic shear measurements using conventional weak lensing analysis techniques. We find that the main source of the errors comes from an inability to adequately characterise the atmospheric point spread function (PSF) due to its high frequency spatial variation on angular scales smaller than {approx} 10{prime} in the single short exposures, which propagates into a spurious shear correlation function at the 10{sup -4}-10{sup -3} level on these scales. With the large multi-epoch dataset that will be acquired by LSST, the stochastic errors average out, bringing the final spurious shear correlation function to a level very close to the statistical errors. Our results imply that the cosmological constraints from LSST will not be severely limited by these algorithm-independent, additive systematic effects.

  11. Development and studies of Cd_1_−_xMg_xTe thin films with varying band gaps to understand the Mg incorporation and the related material properties

    Palomera, Roger C.; Martínez, Omar S.; Pantoja-Enriquez, J.; Mathews, N.R.; Reyes-Banda, Martín G.; Krishnan, B.; Mathew, X.

    2017-01-01

    Highlights: • Cd_1_−_xMg_xTe films with band gap in the range 1.47–2.41 eV is obtained. • Cd substitution by Mg was confirmed with SIMS and XPS analysis. • Cd_1_−_xMg_xTe films maintained CdTe structural features but with higher band gap. • Mg incorporation in CdTe inhibited grain growth. - Abstract: In this paper we report a systematic work involving the development of Cd_1_−_xMg_xTe thin films by co-evaporation of CdTe and Mg. The evaporation rate of both materials were adjusted to obtain ternary films of varying stoichiometry and hence the band gap. We have deposited films with band gap ranging from 1.47 to 2.41 eV. The films were characterized for structural, morphological, optical, opto-electronic, and spectroscopic properties. The film stoichiometry was studied across the thickness using SIMS data. SEM images showed that the grain size has a dependence on Mg content in the film, which inhibits the grain growth. The structural parameters showed a systematic dependence on Mg content in the film, however, there was no noticeable change in the XRD reflections with respect that of pure CdTe for lower concentrations of Mg. XPS analysis shed light on the incorporation of Mg further supporting the band gap variations observed with the UV–Vis spectroscopic studies. The photoresponse of the film was affected by Mg incorporation. Prototype devices of the type Cd_1_−_XMg_xTe/CdS were fabricated and the results are discussed.

  12. Shear localization in a mature mylonitic rock analog during fast slip

    Takahashi, M.; van den Ende, M. P. A.; Niemeijer, A. R.; Spiers, C. J.

    2017-02-01

    Highly localized slip zones developed within ductile shear zones, such as pseudotachylyte bands occurring within mylonitic fabric rocks, are frequently interpreted as evidence for earthquake nucleation and/or propagation within the ductile regime. To understand brittle/frictional shear localization processes in ductile shear zones and to relate these to earthquake nucleation and propagation, we performed tests with large changes in velocity on a brine-saturated, 80:20 (wt %) mixture of halite and muscovite gouge after forming a mature mylonitic structure through frictional-viscous flow. The direct effect a on shear strength that occurs in response to an instantaneous upward velocity-step is an important parameter in determining the nature of seismic rupture nucleation and propagation. We obtained reproducible results regarding low-velocity mechanical behavior compared with previous work, but also obtained new insights into effects of sudden increases in slip velocity on localization and strength evolution, at velocities above a critical velocity Vc (˜20 μm/s). We found that once a ductile, mylonitic structure has developed in a shear zone, subsequent cataclastic deformation is consistently localized in a narrow zone. This switch to localized deformation is controlled by the imposed velocity and becomes most apparent at velocities above Vc. In addition, the direct effect drops rapidly when the velocity exceeds Vc. This implies that slip can accelerate toward seismic velocities almost instantly and without much loss of fracture energy, once Vc is exceeded. Obtaining a measure for Vc in natural faults is therefore of key importance for understanding earthquake nucleation and propagation in the brittle-ductile transitional regime.

  13. Structure in sheared supercooled liquids: Dynamical rearrangements of an effective system of icosahedra.

    Pinney, Rhiannon; Liverpool, Tanniemola B; Royall, C Patrick

    2016-12-21

    We consider a binary Lennard-Jones glassformer whose super-Arrhenius dynamics are correlated with the formation of particles organized into icosahedra under simple steady state shear. We recast this glassformer as an effective system of icosahedra [Pinney et al., J. Chem. Phys. 143, 244507 (2015)]. From the observed population of icosahedra in each steady state, we obtain an effective temperature which is linearly dependent on the shear rate in the range considered. Upon shear banding, the system separates into a region of high shear rate and a region of low shear rate. The effective temperatures obtained in each case show that the low shear regions correspond to a significantly lower temperature than the high shear regions. Taking a weighted average of the effective temperature of these regions (weight determined by region size) yields an estimate of the effective temperature which compares well with an effective temperature based on the global mesocluster population of the whole system.

  14. Experiments on sheet metal shearing

    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...

  15. Shear flow stabilization of the hydromagnetic Rayleigh-Taylor instability

    Roderick, N.F.; Shumlak, U.; Douglas, M.; Peterkin, R.E. Jr.; Ruden, E.

    1997-01-01

    Numerical simulations have indicated that shear flow may help stabilize the hydromagnetic Rayleigh-Taylor instability in imploding plasma z-pinches. A simple extension to a model presented in Chandrasekhar has been developed to study the linear stability of incompressible plasma subjected to both a shear flow and acceleration. The model has been used to investigate the stability plasma implosion schemes using externally imposed velocity shear which develops from the plasma flow itself. Specific parameters were chosen to represent plasma implosions driven by the Saturn and PBFA-Z, pulsed power generators at Sandia National Laboratories. Results indicate a high shear is necessary to stabilize the z-pinch implosions studied

  16. CAT LIDAR wind shear studies

    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. Development of high power X-band semiconductor microwave switch for pulse compression systems of future linear colliders

    Fumihiko Tamura

    2002-06-01

    Full Text Available We describe concepts for high power semiconductor rf switches, designed to handle signals at X-band with power level near 100 MW. We describe an abstract design methodology and derive a general scaling law for these switches. We also present a design and experimental work of a switch operating at the TE_{01} mode in overmoded circular waveguides. The switch is composed of an array of tee junction elements that have a p-i-n diode array window in the third arm.

  18. Gelation under shear

    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.

  19. Forflytning: shear og friktion

    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...

  20. Experimental Research on Boundary Shear Stress in Typical Meandering Channel

    Chen, Kai-hua; Xia, Yun-feng; Zhang, Shi-zhao; Wen, Yun-cheng; Xu, Hua

    2018-06-01

    A novel instrument named Micro-Electro-Mechanical System (MEMS) flexible hot-film shear stress sensor was used to study the boundary shear stress distribution in the generalized natural meandering open channel, and the mean sidewall shear stress distribution along the meandering channel, and the lateral boundary shear stress distribution in the typical cross-section of the meandering channel was analysed. Based on the measurement of the boundary shear stress, a semi-empirical semi-theoretical computing approach of the boundary shear stress was derived including the effects of the secondary flow, sidewall roughness factor, eddy viscosity and the additional Reynolds stress, and more importantly, for the first time, it combined the effects of the cross-section central angle and the Reynolds number into the expressions. Afterwards, a comparison between the previous research and this study was developed. Following the result, we found that the semi-empirical semi-theoretical boundary shear stress distribution algorithm can predict the boundary shear stress distribution precisely. Finally, a single factor analysis was conducted on the relationship between the average sidewall shear stress on the convex and concave bank and the flow rate, water depth, slope ratio, or the cross-section central angle of the open channel bend. The functional relationship with each of the above factors was established, and then the distance from the location of the extreme sidewall shear stress to the bottom of the open channel was deduced based on the statistical theory.

  1. In-silico experiments on characteristic time scale at a shear-free gas-liquid interface in fully developed turbulence

    Nagaosa, Ryuichi [Research Center for Compact Chemical System (CCS), AIST, 4-2-1 Nigatake, Miyagino, Sendai 983-8551 (Japan); Handler, Robert A, E-mail: ryuichi.nagaosa@aist.go.jp [Department of Mechanical Engineering, Texas A and M University, College Station, TX 77843-3123 (United States)

    2011-12-22

    The purpose of this study is to model scalar transfer mechanisms in a fully developed turbulence for accurate predictions of the turbulent scalar flux across a shear-free gas-liquid interface. The concept of the surface-renewal approximation (Dankwerts, 1951) is introduced in this study to establish the predictive models for the interfacial scalar flux. Turbulent flow realizations obtained by a direct numerical simulation technique are employed to prepare details of three-dimensional information on turbulence in the region very close to the interface. Two characteristic time scales at the interface have been examined for exact prediction of the scalar transfer flux. One is the time scale which is reciprocal of the root-mean-square surface divergence, T{sub {gamma}} = ({gamma}{gamma}){sup -1/2}, where {gamma} is the surface divergence. The other time scale to be examined is T{sub S} = {Lambda}/V, where {Lambda} is the zero-correlation length of the surface divergence as the interfacial length scale, and V is the root-mean-square velocity fluctuation in the streamwise direction as the interfacial velocity scale. The results of this study suggests that T{sub {gamma}} is slightly unsatisfactory to correlate the turbulent scalar flux at the gas-liquid interface based on the surface-renewal approximation. It is also found that the proportionality constant appear to be 0.19, which is different with that observed in the laboratory experiments, 0.34 (Komori, Murakami, and Ueda, 1989). It is concluded that the time scale, T{sub {gamma}}, is considered a different kind of the time scale observed in the laboratory experiments. On the other hand, the present in-silico experiments indicate that T{sub s} predicts the turbulent scalar flux based on the surface-renewal approximation in a satisfactory manner. It is also elucidated that the proportionality constant for T{sub s} is approximately 0.36, which is very close to that found by the laboratory experiments. This fact shows

  2. In-silico experiments on characteristic time scale at a shear-free gas-liquid interface in fully developed turbulence

    Nagaosa, Ryuichi; Handler, Robert A

    2011-01-01

    The purpose of this study is to model scalar transfer mechanisms in a fully developed turbulence for accurate predictions of the turbulent scalar flux across a shear-free gas-liquid interface. The concept of the surface-renewal approximation (Dankwerts, 1951) is introduced in this study to establish the predictive models for the interfacial scalar flux. Turbulent flow realizations obtained by a direct numerical simulation technique are employed to prepare details of three-dimensional information on turbulence in the region very close to the interface. Two characteristic time scales at the interface have been examined for exact prediction of the scalar transfer flux. One is the time scale which is reciprocal of the root-mean-square surface divergence, T γ = (γγ) −1/2 , where γ is the surface divergence. The other time scale to be examined is T S = Λ/V, where Λ is the zero-correlation length of the surface divergence as the interfacial length scale, and V is the root-mean-square velocity fluctuation in the streamwise direction as the interfacial velocity scale. The results of this study suggests that T γ is slightly unsatisfactory to correlate the turbulent scalar flux at the gas-liquid interface based on the surface-renewal approximation. It is also found that the proportionality constant appear to be 0.19, which is different with that observed in the laboratory experiments, 0.34 (Komori, Murakami, and Ueda, 1989). It is concluded that the time scale, T γ , is considered a different kind of the time scale observed in the laboratory experiments. On the other hand, the present in-silico experiments indicate that T s predicts the turbulent scalar flux based on the surface-renewal approximation in a satisfactory manner. It is also elucidated that the proportionality constant for T s is approximately 0.36, which is very close to that found by the laboratory experiments. This fact shows that the time scale T s appears to be essentially the same as the time scale

  3. Shear Roll Mill Reactivation

    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

  4. Microstructural characteristics of adiabatic shear localization in a metastable beta titanium alloy deformed at high strain rate and elevated temperatures

    Zhan, Hongyi, E-mail: h.zhan@uq.edu.au [Centre for Advanced Materials Processing and Manufacture, School of Mechanical and Mining Engineering, The University of Queensland, St Lucia, Queensland 4072 (Australia); Zeng, Weidong [State Key Laboratory of Solidification Processing, School of Materials, Northwestern Polytechnical University, Xi' an 710072 (China); Wang, Gui [Centre for Advanced Materials Processing and Manufacture, School of Mechanical and Mining Engineering, The University of Queensland, St Lucia, Queensland 4072 (Australia); Defence Material Technology Centre, Level 2, 24 Wakefield St, Hawthorn, VIC 3122 (Australia); Kent, Damon [School of Science and Engineering, University of the Sunshine Coast, Sippy Downs, Queensland 4575 (Australia); Dargusch, Matthew [Centre for Advanced Materials Processing and Manufacture, School of Mechanical and Mining Engineering, The University of Queensland, St Lucia, Queensland 4072 (Australia); Defence Material Technology Centre, Level 2, 24 Wakefield St, Hawthorn, VIC 3122 (Australia)

    2015-04-15

    The microstructural evolution and grain refinement within adiabatic shear bands in the Ti6554 alloy deformed at high strain rates and elevated temperatures have been characterized using transmission electron microscopy. No stress drops were observed in the corresponding stress–strain curve, indicating that the initiation of adiabatic shear bands does not lead to the loss of load capacity for the Ti6554 alloy. The outer region of the shear bands mainly consists of cell structures bounded by dislocation clusters. Equiaxed subgrains in the core area of the shear band can be evolved from the subdivision of cell structures or reconstruction and transverse segmentation of dislocation clusters. It is proposed that dislocation activity dominates the grain refinement process. The rotational recrystallization mechanism may operate as the kinetic requirements for it are fulfilled. The coexistence of different substructures across the shear bands implies that the microstructural evolution inside the shear bands is not homogeneous and different grain refinement mechanisms may operate simultaneously to refine the structure. - Graphical abstract: Display Omitted - Highlights: • The microstructure within the adiabatic shear band was characterized by TEM. • No stress drops were observed in the corresponding stress–strain curve. • Dislocation activity dominated the grain refinement process. • The kinetic requirements for rotational recrystallization mechanism were fulfilled. • Different grain refinement mechanisms operated simultaneously to refine the structure.

  5. Deformation of footwall rock of Phulad Shear Zone, Rajasthan ...

    Phulad Shear Zone (PSZ) of Delhi Fold Belt in Rajasthan is a northeasterly striking ductile shear zone with a well developed mylonitic foliation (035/70E) and a downdip stretching lineation. The deformation in the PSZ has developed in a transpressional regime with thrusting sense of movement. The northeastern unit, i.e. ...

  6. Development of wide-band, time and energy resolving, optical photon detectors with application to imaging astronomy

    Miller, A.J.; Cabrera, B.; Romani, R.W.; Figueroa-Feliciano, E.; Nam, S.W.; Clarke, R.M.

    2000-01-01

    Superconducting transition edge sensors (TESs) are showing promise for the wide-band spectroscopy of individual photons from the mid-infrared (IR), through the optical, and into the near ultraviolet (UV). Our TES sensors are ∼20 μm square, 40 nm thick tungsten (W) films with a transition temperature of about 80 mK. We typically attain an energy resolution of 0.15 eV FWHM over the optical range with relative timing resolution of 100 ns. Single photon events with sub-microsecond risetimes and few microsecond falltimes have been achieved allowing count rates in excess of 30 kHz per pixel. Additionally, tungsten is approximately 50% absorptive in the optical (dropping to 10% in the IR) giving these devices an intrinsically high quantum efficiency. These combined traits make our detectors attractive for fast spectrophotometers and photon-starved applications such as wide-band, time and energy resolved astronomical observations. We present recent results from our work toward the fabrication and testing of the first TES optical photon imaging arrays

  7. Compaction bands in shale revealed through digital volume correlation of time-resolved X-ray tomography scans

    McBeck, J.; Kobchenko, M.; Hall, S.; Tudisco, E.; Cordonnier, B.; Renard, F.

    2017-12-01

    Previous studies have identified compaction bands primarily within sandstones, and in fewer instances, within other porous rocks and sediments. Using Digital Volume Correlation (DVC) of X-ray microtomography scans, we find evidence of localized zones of high axial contraction that form tabular structures sub-perpendicular to maximum compression, σ1, in Green River shale. To capture in situ strain localization throughout loading, two shale cores were deformed in the HADES triaxial deformation apparatus installed on the X-ray microtomography beamline ID19 at the European Synchrotron Radiation Facility. In these experiments, we increase σ1 in increments of two MPa, with constant confining pressure (20 MPa), until the sample fails in macroscopic shear. After each stress step, a 3D image of the sample inside the rig is acquired at a voxel resolution of 6.5 μm. The evolution of lower density regions within 3D reconstructions of linear attenuation coefficients reveal the development of fractures that fail with some opening. If a fracture produces negligible dilation, it may remain undetected in image segmentation of the reconstructions. We use the DVC software TomoWarp2 to identify undetected fractures and capture the 3D incremental displacement field between each successive pair of microtomography scans acquired in each experiment. The corresponding strain fields reveal localized bands of high axial contraction that host minimal shear strain, and thus match the kinematic definition of compaction bands. The bands develop sub-perpendicular to σ1 in the two samples in which pre-existing bedding laminations were oriented parallel and perpendicular to σ1. As the shales deform plastically toward macroscopic shear failure, the number of bands and axial contraction within the bands increase, while the spacing between the bands decreases. Compaction band development accelerates the rate of overall axial contraction, increasing the mean axial contraction throughout the sample

  8. Strain localization band width evolution by electronic speckle pattern interferometry strain rate measurement

    Guelorget, Bruno [Institut Charles Delaunay-LASMIS, Universite de technologie de Troyes, FRE CNRS 2848, 12 rue Marie Curie, B.P. 2060, 10010 Troyes Cedex (France)], E-mail: bruno.guelorget@utt.fr; Francois, Manuel; Montay, Guillaume [Institut Charles Delaunay-LASMIS, Universite de technologie de Troyes, FRE CNRS 2848, 12 rue Marie Curie, B.P. 2060, 10010 Troyes Cedex (France)

    2009-04-15

    In this paper, electronic speckle pattern interferometry strain rate measurements are used to quantify the width of the strain localization band, which occurs when a sheet specimen is submitted to tension. It is shown that the width of this band decreases with increasing strain. Just before fracture, this measured width is about five times wider than the shear band and the initial sheet thickness.

  9. Specific features of the occurrence, development, and re-compaction of spall and shear fractures in spherically-convergent shells made of unalloyed iron and some steels under their spherical explosive loading

    Kozlov, E.A.; Brichikov, S.A.; Gorbachev, D.M.; Brodova, I.G.; Yablonskikh, T.I.

    2007-01-01

    Results of comparative metallographic examination of recovered shells exposed to explosive loading in two modes (with and without a heavy casing confining explosion products scatter) are presented. The shells were made of high-purity and technical-grade unalloyed iron with the initial grain size 250 and 125 μm, steel 30KhGSA in delivery state and quenched up to HR C 35...40, austenitic stainless steel 12Kh18N10T. The heavy casing used in experiments is demonstrated to ensure a rather compact convergence of shells destroyed at high radii. In the described comparative experiments, one managed to compile the 12Kh18N10T steel shell, after it was spalled at high radii and exposed to shear fracture and spallation layer fragmentation at medium radii, into a compact sphere but failed to do the same with the 30KhGSA quenched steel shell after it was fractured according to spall and shear mechanisms at high and medium radii. Polar zones of this steel shell have obvious undercompressed areas due to significant dissipative losses to overcome the shear strength. Occurrence, development, and re-compaction of spall and shear fractures in spherically-convergent shells made of materials, which were already carefully investigated in 1D- and 2D-geometry experiments, were systematically studied in order to verify and validate new physical models of dynamic fractures, as well as up-to-date used in 1D-, 2D- and 3D-numerical algorithms [ru

  10. Development of transformation bands in TiNi SMA for various stress and strain rates studied by a fast and sensitive infrared camera

    Pieczyska, E A; Kulasinski, K; Tobushi, H

    2013-01-01

    TiNi shape memory alloy (SMA) was subjected to tension at various strain rates for stress- and strain-controlled tests. The nucleation, development and saturation of the stress-induced martensitic transformation were investigated, based on the specimen temperature changes, measured by a fast and sensitive infrared camera. It was found that the initial, macroscopically homogeneous phase transformation occurs at the same stress level for all strain rates applied, regardless of the loading manner, while the stress of the localized transformation increases with the strain rate. At higher strain rate, a more dynamic course of the transformation process was observed, revealed in the creation of numerous fine transformation bands. An inflection point was noticed on the stress–strain curve, dividing the transformation range into two stages: the first heterogeneous, where transformation bands nucleate and evolve throughout the sample; the second, where the bands overlap, related to significant temperature increase and an upswing region of the curve. In the final part of the SMA loading a decrease of the average sample temperature revealed the saturation stage of the transformation. It was also observed that nucleation of the localized martensitic forward transformation takes place in the weakest area of the sample in both approaches, whereas the reverse transformation always initiates in its central part. (paper)

  11. C/NOFS Satellite Electric Field and Plasma Density Observations of Plasma Instabilities Below the Equatorial F-Peak -- Evidence for Approximately 500 km-Scale Spread-F "Precursor" Waves Driven by Zonal Shear Flow and km-Scale, Narrow-Banded Irregularities

    Pfaff, R.; Freudenreich, H.; Klenzing, J.; Liebrecht, C.; Valladares, C.

    2011-01-01

    As solar activity has increased, the ionosphere F-peak has been elevated on numerous occasions above the C/NOFS satellite perigee of 400km. In particular, during the month of April, 2011, the satellite consistently journeyed below the F-peak whenever the orbit was in the region of the South Atlantic anomaly after sunset. During these passes, data from the electric field and plasma density probes on the satellite have revealed two types of instabilities which had not previously been observed in the C/NOFS data set (to our knowledge): The first is evidence for 400-500km-scale bottomside "undulations" that appear in the density and electric field data. In one case, these large scale waves are associated with a strong shear in the zonal E x B flow, as evidenced by variations in the meridional (outward) electric fields observed above and below the F-peak. These undulations are devoid of smaller scale structures in the early evening, yet appear at later local times along the same orbit associated with fully-developed spread-F with smaller scale structures. This suggests that they may be precursor waves for spread-F, driven by a collisional shear instability, following ideas advanced previously by researchers using data from the Jicamarca radar. A second new result (for C/NOFS) is the appearance of km-scale irregularities that are a common feature in the electric field and plasma density data that also appear when the satellite is below the F -peak at night. The vector electric field instrument on C/NOFS clearly shows that the electric field component of these waves is strongest in the zonal direction. These waves are strongly correlated with simultaneous observations of plasma density oscillations and appear both with, and without, evidence of larger-scale spread-F depletions. These km-scale, quasi-coherent waves strongly resemble the bottomside, sinusoidal irregularities reported in the Atmosphere Explorer satellite data set by Valladares et al. [JGR, 88, 8025, 1983

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

    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.

  13. Piezoelectric energy harvesting through shear mode operation

    Malakooti, Mohammad H; Sodano, Henry A

    2015-01-01

    Piezoelectric materials are excellent candidates for use in energy harvesting applications due to their high electromechanical coupling properties that enable them to convert input mechanical energy into useful electric power. The electromechanical coupling coefficient of the piezoelectric material is one of the most significant parameters affecting energy conversion and is dependent on the piezoelectric mode of operation. In most piezoceramics, the d 15 piezoelectric shear coefficient is the highest coefficient compared to the commonly used axial and transverse modes that utilize the d 33 and the d 31 piezoelectric strain coefficients. However, complicated electroding methods and challenges in evaluating the performance of energy harvesting devices operating in the shear mode have slowed research in this area. The shear deformation of a piezoelectric layer can be induced in a vibrating sandwich beam with a piezoelectric core. Here, a model based on Timoshenko beam theory is developed to predict the electric power output from a cantilever piezoelectric sandwich beam under base excitations. It is shown that the energy harvester operating in the shear mode is able to generate ∼50% more power compared to the transverse mode for a numerical case study. Reduced models of both shear and transverse energy harvesters are obtained to determine the optimal load resistance in the system and perform an efficiency comparison between two models with fixed and adaptive resistances. (paper)

  14. High strength semi-active energy absorbers using shear- and mixedmode operation at high shear rates

    Becnel, Andrew C.

    This body of research expands the design space of semi-active energy absorbers for shock isolation and crash safety by investigating and characterizing magnetorheological fluids (MRFs) at high shear rates ( > 25,000 1/s) under shear and mixed-mode operation. Magnetorheological energy absorbers (MREAs) work well as adaptive isolators due to their ability to quickly and controllably adjust to changes in system mass or impact speed while providing fail-safe operation. However, typical linear stroking MREAs using pressure-driven flows have been shown to exhibit reduced controllability as impact speed (shear rate) increases. The objective of this work is to develop MREAs that improve controllability at high shear rates by using pure shear and mixed shear-squeeze modes of operation, and to present the fundamental theory and models of MR fluids under these conditions. A proof of concept instrument verified that the MR effect persists in shear mode devices at shear rates corresponding to low speed impacts. This instrument, a concentric cylinder Searle cell magnetorheometer, was then used to characterize three commercially available MRFs across a wide range of shear rates, applied magnetic fields, and temperatures. Characterization results are presented both as flow curves according to established practice, and as an alternate nondimensionalized analysis based on Mason number. The Mason number plots show that, with appropriate correction coefficients for operating temperature, the varied flow curve data can be collapsed to a single master curve. This work represents the first shear mode characterization of MRFs at shear rates over 10 times greater than available with commercial rheometers, as well as the first validation of Mason number analysis to high shear rate flows in MRFs. Using the results from the magnetorheometer, a full scale rotary vane MREA was developed as part of the Lightweight Magnetorheological Energy Absorber System (LMEAS) for an SH-60 Seahawk helicopter

  15. Localization and Instability in Sheared Granular Materials: Role of Pore Fluids and Non-monotonic Rate Dependent Rheology

    Ma, X.; Elbanna, A. E.; Kothari, K.

    2017-12-01

    Fault zone dynamics hold the key to resolving many outstanding geophysical problems including the heat flow paradox, discrepancy between fault static and dynamic strength, and energy partitioning. Most fault zones that generate tectonic events are gouge filled and fluid saturated posing the need for formulating gouge-specific constitutive models that capture spatially heterogeneous compaction and dilation, non-monotonic rate dependence, and transition between localized and distributed deformation. In this presentation, we focus primarily on elucidating microscopic underpinnings for shear banding and stick-slip instabilities in sheared saturated granular materials and explore their implications for earthquake dynamics. We use a non-equilibrium thermodynamics model, the Shear Transformation Zone theory, to investigate the dynamics of strain localization and its connection to stability of sliding in the presence and absence of pore fluids. We also consider the possible influence of self-induced mechanical vibrations as well as the role of external acoustic vibrations as analogue for triggering by a distant event. For the dry case, our results suggest that at low and intermediate strain rates, persistent shear bands develop only in the absence of vibrations. Vibrations tend to fluidize the granular network and de-localize slip at these rates. Stick-slip is only observed for rough grains and it is confined to the shear band. At high strain rates, stick-slip disappears and the different systems exhibit similar stress-slip response. Changing the vibration intensity, duration or time of application alters the system response and may cause long-lasting rheological changes. The presence of pore fluids modifies the stick slip pattern and may lead to both loss and development of slip instability depending on the value of the confining pressure, imposed strain rate and hydraulic parameters. We analyze these observations in terms of possible transitions between rate

  16. Bolt Shear Force Sensor

    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

  17. Shear reinforced beams in autoclaved aerated concrete

    Cornelius, Thomas

    2010-01-01

    Shear behaviour in concrete materials is very well documented, for normal density concrete materials. In this paper results of various tests on low density concrete materials like aerated autoclaved concrete (in the following denoted aircrete) will be presented and analyzed for different combinat....... Codes for designing prefabricated reinforced components of aircrete structures have adopted these recently developed approaches.......Shear behaviour in concrete materials is very well documented, for normal density concrete materials. In this paper results of various tests on low density concrete materials like aerated autoclaved concrete (in the following denoted aircrete) will be presented and analyzed for different...

  18. In-situ tracer tests and models developed to understand flow paths in a shear zone at the Grimsel Test Site, Switzerland

    Blechschmidt, I.; Martin, A. J.

    2012-12-01

    The Grimsel Test Site (www.grimsel.com) is an international underground research laboratory excavated at a depth of 450m below the surface in the crystalline Aare Massif of southern Switzerland in 1984. It is operated and owned by the National Cooperative for the Disposal of Radioactive Waste of Switzerland (NAGRA) which is the organization responsible for managing and researching the geological disposal of all types of radioactive wastes originating in Switzerland. One experiment, the Colloid Formation and Migration test (CFM*), is an ongoing in-situ migration test started in 2004 to study colloid facilitated transport behavior of radionuclides through a shear zone. The importance of colloid transport in the context of a radioactive waste repository is that it provides a mechanism for potentially enhancing the advective transport of radionuclides. The montmorillonite clays that are planned to be used as an engineered barrier around the radioactive waste in many repository concepts may be a source of such colloids under specific hydraulic and/or chemical boundary conditions. The CFM project includes an integrated programme of field testing, laboratory studies and modelling/interpretation. The field tests are performed in a shear zone where the natural outflow has been controlled by a tunnel packer system and flow is monitored with an array of boreholes drilled for CFM and previous experiments at the site. The flow field is controlled by a low-rate extraction from a surface packer. The controlled low-rate extraction creates a region of low hydraulic gradients and fluid velocity within the shear zone, suitable for study under repository-relevant or other geo-resource relevant conditions. Here we present a summary of the migration tracer tests carried out so far to understand the hydraulic properties and transport characteristics of the shear zone using both stable and radioactive (Na-22, Cs-137, Ba-133, Th-232, Np-237, Am-243, Pu-242) tracers as well as colloids, and

  19. The development of blue ice moraines from englacial debris bands as detected by GPR, Mt Achernar, central Transantarctic Mountains, Antarctica

    Kassab, C.; Lindback, K.; Pettersson, R.; Licht, K.; Graly, J. A.; Kaplan, M. R.

    2016-12-01

    Blue ice moraines cover a small percentage of Antarctica, but can contain a significant record of ice sheet dynamics and climate over multiple glacial cycles. Previous work has focused on the temporal and provenance record contained within these moraines and less on mechanisms by which such deposits form and their temporal evolution. In order to create a conceptual model of their formation, >25 km of ground penetrating radar transects at 25 and 100 MHz frequencies were collected at the Mt Achernar moraine adjacent to Law Glacier. Here, ice ablation causes debris bands to emerge and deliver sediment to the surface. Most transects were collected perpendicular to the ice-moraine margin, and extend from the actively flowing Law Glacier ice to a distance of 2 km into the moraine. The 25 and 100 MHz transects penetrate to a depth of 200 m and 60 m respectively and reveal a relatively complex internal stratigraphy. Closest to the ice-moraine margin, stratigraphy is not well resolved due to a high amount of clutter. Steeply dipping parallel reflections first emerge 400m away from the ice margin and dip toward Law Glacier. These reflections continue inwards to 1450m, where the reflections become more closely spaced. Hummocky topography and parallel ridge/trough topography dominate the geomorphic expression. The hummocky topography corresponds to the region where reflections are not well resolved. The ridges are interpreted to be debris bands that are emerging at the surface, similar to those along the margin of the Law Glacier where debris is newly emerging. The reflections in the GPR transects indicate that debris is transported from depth to the surface of the ice where it accumulates forming the Mt Achernar moraine. It appears that the various reflection patterns correspond to unique surface geomorphic expressions. The reflections also indicate that at least the first 2 km of debris rich buried ice in the moraine can be linked to the actively flowing Law Glacier

  20. Congenital Constriction Band Syndrome

    Rajesh Gupta, Fareed Malik, Rishabh Gupta, M.A.Basit, Dara Singh

    2008-01-01

    Congenital constriction bands are anomalous bands that encircle a digit or an extremity. Congenitalconstriction band syndrome is rare condition and is mostly associated with other musculoskeletaldisorders.We report such a rare experience.

  1. Starch-zein beldns formed by shear flow

    Habeych Narvaez, E.A.; Dekkers, B.; Goot, van der A.J.; Boom, R.M.

    2008-01-01

    A newly in-house developed shearing device was used to explore the formation of new types of microstructures in concentrated starch¿zein blends. The device allowed processing of the biopolymer blends under homogeneous, simple shear flow conditions. Water and glycerol were added as plasticizers.

  2. Wind Shear Characteristics at Central Plains Tall Towers (presentation)

    Schwartz, M.; Elliott, D.

    2006-06-05

    The objectives of this report are: (1) Analyze wind shear characteristics at tall tower sites for diverse areas in the central plains (Texas to North Dakota)--Turbines hub heights are now 70-100 m above ground and Wind measurements at 70-100+ m have been rare. (2) Present conclusions about wind shear characteristics for prime wind energy development regions.

  3. Wind Shear Systems Implementation Plan, Benefit/Cost Study.

    1980-08-01

    not. Accordingly, the three self contained Wind Shear Systems currently being marketed by avionics manufacturers are considered to have lower relative... RESEARC { AND I’iVEIOPMEN1 The FAA research ni d development ffort has taken a threefold appro,,ch to the vind sh#ear problem. Ore. approach was to

  4. Experimental investigation of separated shear layer from a leading ...

    Shear layer development over a thick flat plate with a semi-circular leading edge is investigated for a range of angles of attack under different pressure gradients for a Reynolds number of 2.44×105 (based on chord and free-stream velocity). The characteristics of the separated shear layer are very well documented through ...

  5. Dynamic Shear Deformation and Failure of Ti-6Al-4V and Ti-5Al-5Mo-5V-1Cr-1Fe Alloys.

    Ran, Chun; Chen, Pengwan

    2018-01-05

    To study the dynamic shear deformation and failure properties of Ti-6Al-4V (Ti-64) alloy and Ti-5Al-5Mo-5V-1Cr-1Fe (Ti-55511) alloy, a series of forced shear tests on flat hat shaped (FHS) specimens for the two investigated materials was performed using a split Hopkinson pressure bar setup. The evolution of shear deformation was monitored by an ultra-high-speed camera (Kirana-05M). Localized shear band is induced in the two investigated materials under forced shear tests. Our results indicate that severe strain localization (adiabatic shear) is accompanied by a loss in the load carrying capacity, i.e., by a sudden drop in loading. Three distinct stages can be identified using a digital image correlation technique for accurate shear strain measurement. The microstructural analysis reveals that the dynamic failure mechanisms for Ti-64 and Ti-55511 alloys within the shear band are of a cohesive and adhesive nature, respectively.

  6. Excited waves in shear layers

    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.

  7. Designing shear-thinning

    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.

  8. Dual-band infrared camera

    Vogel, H.; Schlemmer, H.

    2005-10-01

    Every year, numerous accidents happen on European roads due to bad visibility (fog, night, heavy rain). Similarly, the dramatic aviation accidents of year 2001 in Milan and Zurich have reminded us that aviation safety is equally affected by reduced visibility. A dual-band thermal imager was developed in order to raise human situation awareness under conditions of reduced visibility especially in the automotive and aeronautical context but also for all transportation or surveillance tasks. The chosen wavelength bands are the Short Wave Infrared SWIR and the Long Wave Infrared LWIR band which are less obscured by reduced visibility conditions than the visible band. Furthermore, our field tests clearly show that the two different spectral bands very often contain complementary information. Pyramidal fusion is used to integrate complementary and redundant features of the multi-spectral images into a fused image which can be displayed on a monitor to provide more and better information for the driver or pilot.

  9. Inductive shearing of drilling pipe

    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.

  10. Magnetorheological dampers in shear mode

    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

  11. Band Subset Selection for Hyperspectral Image Classification

    Chunyan Yu

    2018-01-01

    Full Text Available This paper develops a new approach to band subset selection (BSS for hyperspectral image classification (HSIC which selects multiple bands simultaneously as a band subset, referred to as simultaneous multiple band selection (SMMBS, rather than one band at a time sequentially, referred to as sequential multiple band selection (SQMBS, as most traditional band selection methods do. In doing so, a criterion is particularly developed for BSS that can be used for HSIC. It is a linearly constrained minimum variance (LCMV derived from adaptive beamforming in array signal processing which can be used to model misclassification errors as the minimum variance. To avoid an exhaustive search for all possible band subsets, two numerical algorithms, referred to as sequential (SQ and successive (SC algorithms are also developed for LCMV-based SMMBS, called SQ LCMV-BSS and SC LCMV-BSS. Experimental results demonstrate that LCMV-based BSS has advantages over SQMBS.

  12. Tolerance Evaluation of Poloidal Shear Keys for ITER TF Coil

    Fu Youkun; Neil, M.; Cees Jong

    2006-01-01

    There are 18 ITER Toroidal Field (TF) Coils. Unlike the other ITER coils, these coils are structurally linked. These links consist of friction between the coil legs in the central vault formed by the inner straight legs of the coils, four outer inter-coil structures (OIS) and one inner inter-coil structure (IIS). The OIS consists essentially of bands around all 18 coils to provide shear support by forming shear panels with the coil case, and the IIS consists of poloidal circular keys placed directly between the coil cases. Global analysis of the 'perfect' coil shape has shown high stresses in the IIS, in the poloidal keyways. Optimization has successfully reduced these stresses to acceptable values as regards the expected fatigue resistance. However it is necessary to confirm that the stresses are still acceptable when realistic values of geometry variations are included (i.e. the effect of coil and case tolerances). Because of the extensive mechanical links between coils the poloidal key stresses can also be affected by tolerances elsewhere in the case. As the first step in assessment of the possible variations in stresses, a substructure technique is being used to develop a local model of the key region. The result of geometry variations between individual coils is a loss in the 18 fold symmetry used to simplify previous analyses. With the new and optimized model it should be possible to relax the 18-fold symmetry, but a full analysis of all 18 coils is still not possible. Systematic ways of representing the tolerance variation in the finite element model have been developed so that parametric studies can be undertaken without a full reconstruction of the model. (author)

  13. Functional Polymer Opals and Porous Materials by Shear-Induced Assembly of Tailor-Made Particles.

    Gallei, Markus

    2018-02-01

    Photonic band-gap materials attract enormous attention as potential candidates for a steadily increasing variety of applications. Based on the preparation of easily scalable monodisperse colloids, such optically attractive photonic materials can be prepared by an inexpensive and convenient bottom-up process. Artificial polymer opals can be prepared by shear-induced assembly of core/shell particles, yielding reversibly stretch-tunable materials with intriguing structural colors. This feature article highlights recent developments of core/shell particle design and shear-induced opal formation with focus on the combination of hard and soft materials as well as crosslinking strategies. Structure formation of opal materials relies on both the tailored core/shell architecture and the parameters for polymer processing. The emphasis of this feature article is on elucidating the particle design and incorporation of addressable moieties, i.e., stimuli-responsive polymers as well as elaborated crosslinking strategies for the preparation of smart (inverse) opal films, inorganic/organic opals, and ceramic precursors by shear-induced ordering. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Shear strength of non-shear reinforced concrete elements

    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...

  15. Proceedings of the 4th KEK mechanical engineering workshop. Research and development on the technology of the X-band accelerator fabrication

    Ueno, Kenji

    2003-10-01

    The fourth KEK Mechanical Engineering Workshop was held on April 17, 2003. The main subject was ''The Research and Development on the Technology of the X-band Accelerator Fabrication'', which is a part of the collaboration work of Accelerator Laboratory, ACC and Mechanical Engineering Center, MEC based on the joint X-band accelerator research of KEK and SLAC. The main topic of study in FY 2002 was the problem analysis, and seeking its counter-measures about pitting generated over the inner-surface of the accelerator cavities through high field tests. Therefore, to analyze and develop counter-measures for these pittings, manufacturing of several kinds of test accelerators and conducting analytical tests for the surface of cells have been mainly undertaken by ACC and MEC. On the other hand, basic studies of the cutting and bonding processes have shown effective results for the future production process through corroboration work with academic and industrial fields. Related scientists and engineers from various fields participated in this workshop and presented their works. As a keynote speech, Prof. Hitoshi Yamamoto, belonging to Tohoku University, presented ''The physics on linear collider'', and Assistant Prof. Nobukazu Toge, belonging to ACC of KEK, presented ''The Linear Collider Accelerator''. Also, as an invitation speech, former Prof. Nobuteru Hitomi, former Head of MEC, who was the originator of this workshop, and one of the leaders in X-band accelerator fabrication, presented ''The promotion and survey of fabrication technology on X-band accelerator''. These speeches were very instructive, and presented a chance to think about the direction of R and D in our project. Twenty-four papers, ten from KEK, including the keynote speech, seven from universities and seven from industrial companies, were presented and discussed ardently. Among the discussion, there was an opinion that a fast pace to establish mass-production technology is a major requirement for the

  16. Development of an Internally-Calibrated Wide-Band Airborne Microwave Radiometer to Provide High-Resolution Wet-Tropospheric Path Delay Measurements for SWOT (HAMMR - High-frequency Airborne Microwave and Millimeter-wave Radiometer)

    National Aeronautics and Space Administration — Development of an Internally-Calibrated Wide-Band Airborne Microwave Radiometer to Provide High-Resolution Wet-Tropospheric Path Delay Measurements for SWOT (HAMMR -...

  17. Exploring the relationship between cortical GABA concentrations, auditory gamma-band responses and development in ASD: Evidence for an altered maturational trajectory in ASD.

    Port, Russell G; Gaetz, William; Bloy, Luke; Wang, Dah-Jyuu; Blaskey, Lisa; Kuschner, Emily S; Levy, Susan E; Brodkin, Edward S; Roberts, Timothy P L

    2017-04-01

    Autism spectrum disorder (ASD) is hypothesized to arise from imbalances between excitatory and inhibitory neurotransmission (E/I imbalance). Studies have demonstrated E/I imbalance in individuals with ASD and also corresponding rodent models. One neural process thought to be reliant on E/I balance is gamma-band activity (Gamma), with support arising from observed correlations between motor, as well as visual, Gamma and underlying GABA concentrations in healthy adults. Additionally, decreased Gamma has been observed in ASD individuals and relevant animal models, though the direct relationship between Gamma and GABA concentrations in ASD remains unexplored. This study combined magnetoencephalography (MEG) and edited magnetic resonance spectroscopy (MRS) in 27 typically developing individuals (TD) and 30 individuals with ASD. Auditory cortex localized phase-locked Gamma was compared to resting Superior Temporal Gyrus relative cortical GABA concentrations for both children/adolescents and adults. Children/adolescents with ASD exhibited significantly decreased GABA+/Creatine (Cr) levels, though typical Gamma. Additionally, these children/adolescents lacked the typical maturation of GABA+/Cr concentrations and gamma-band coherence. Furthermore, children/adolescents with ASD additionally failed to exhibit the typical GABA+/Cr to gamma-band coherence association. This altered coupling during childhood/adolescence may result in Gamma decreases observed in the adults with ASD. Therefore, individuals with ASD exhibit improper local neuronal circuitry maturation during a childhood/adolescence critical period, when GABA is involved in configuring of such circuit functioning. Provocatively a novel line of treatment is suggested (with a critical time window); by increasing neural GABA levels in children/adolescents with ASD, proper local circuitry maturation may be restored resulting in typical Gamma in adulthood. Autism Res 2017, 10: 593-607. © 2016 International Society for

  18. Origin of Shear Stability and Compressive Ductility Enhancement of Metallic Glasses by Metal Coating

    Sun, B. A.; Chen, S. H.; Lu, Y. M.; Zhu, Z. G.; Zhao, Y. L.; Yang, Y.; Chan, K. C.; Liu, C. T.

    2016-01-01

    Metallic glasses (MGs) are notorious for the poor macroscopic ductility and to overcome the weakness various intrinsic and extrinsic strategies have been proposed in past decades. Among them, the metal coating is regarded as a flexible and facile approach, yet the physical origin is poorly understood due to the complex nature of shear banding process. Here, we studied the origin of ductile enhancement in the Cu-coating both experimentally and theoretically. By examining serrated shear events and their stability of MGs, we revealed that the thin coating layer plays a key role in stopping the final catastrophic failure of MGs by slowing down shear band dynamics and thus retarding its attainment to a critical instable state. The mechanical analysis on interplay between the coating layer and shear banding process showed the enhanced shear stability mainly comes from the lateral tension of coating layer induced by the surface shear step and the bonding between the coating layer and MGs rather than the layer thickness is found to play a key role in contributing to the shear stability. PMID:27271435

  19. Shear-driven phase transformation in silicon nanowires.

    Vincent, L; Djomani, D; Fakfakh, M; Renard, C; Belier, B; Bouchier, D; Patriarche, G

    2018-03-23

    We report on an unprecedented formation of allotrope heterostructured Si nanowires by plastic deformation based on applied radial compressive stresses inside a surrounding matrix. Si nanowires with a standard diamond structure (3C) undergo a phase transformation toward the hexagonal 2H-allotrope. The transformation is thermally activated above 500 °C and is clearly driven by a shear-stress relief occurring in parallel shear bands lying on {115} planes. We have studied the influence of temperature and axial orientation of nanowires. The observations are consistent with a martensitic phase transformation, but the finding leads to clear evidence of a different mechanism of deformation-induced phase transformation in Si nanowires with respect to their bulk counterpart. Our process provides a route to study shear-driven phase transformation at the nanoscale in Si.

  20. Electrostatic and magnetic fluctuations in the proximity of the velocity shear layer in the TJ-I Tokamak

    Garcia-Cortes, I.; Pedrosa, M.A.; Hidalgo, C.

    1992-01-01

    The structure of the electrostatic and magnetic turbulence changes in the proximity of the naturally velocity shear layer in the TJ-I tokamak. A decorrelation in the broad-band magnetic fluctuations and a decreasing in the density fluctuation levels have been observed in the proximity (scrape-off layer side) of the shear layer. The results are interpreted in terms of turbulence characteristics modified by sheared poloidal flows or/and magnetic configuration. (author) 8 fig. 16 ref

  1. Simulation of shear thickening in attractive colloidal suspensions.

    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.

  2. Magnetic field reconnexion in a sheared field

    Ugai, M.

    1981-01-01

    A nonlinear development of the Petschek mode in a sheared magnetic field where there is a field component Bsub(z) along an X line is numerically studied. It is found that finite-amplitude intermediate waves, adjacent to the slow shock, may eventually stand in the quasi-steady configuration; on the other hand, the fundamental characteristics of the Petschek-mode development are scarcely influenced, either qualitatively or quantitatively, by the Bsub(z) field. (author)

  3. Analysis of Shear Stress and Energy Consumption in a Tubular Airlift Membrane System

    Ratkovich, Nicolas Rios; Chan, C.C.V.; Berube, P.R.

    2011-01-01

    of fouling by imposing high shear stress near the surface of the membrane. Previously, shear stress histograms (SSH) have been introduced to summarize results from an experimental setup developed to investigate the shear stress imposed on the surface of a membrane under different two-phase flow conditions...

  4. Effects of different aging statuses and strain rate on the adiabatic shear susceptibility of 2195 aluminum–lithium alloy

    Yang, Y.; Tan, G.Y.; Chen, P.X.; Zhang, Q.M.

    2012-01-01

    The adiabatic shear susceptibility of 2195 aluminum–lithium alloy was investigated by means of split Hopkinson pressure bar. The stress collapse in true stress–true strain curves and true stress–time curves was observed. The adiabatic shear susceptibility of different aging statuses and strain rate were discussed by means of metallography observation. The critical strain, stress collapse time and formation energy of adiabatic shear bands were compared. The results show that different aging statuses and strain rate have significant influences on adiabatic shear behaviors of 2195 aluminum–lithium alloy. The peak-aged specimen has the highest adiabatic shearing susceptibility, while the under-aged specimen has the least adiabatic shear susceptibility. The susceptibility of adiabatic shearing increases with the increases of strain rate.

  5. Effects of different aging statuses and strain rate on the adiabatic shear susceptibility of 2195 aluminum-lithium alloy

    Yang, Y. [School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan (China); State Key Laboratory of Explosion Science and Technology, Beijing 100081 (China); Tan, G.Y., E-mail: yangyanggroup@163.com [School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan (China); Chen, P.X. [School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan (China); Zhang, Q.M. [State Key Laboratory of Explosion Science and Technology, Beijing 100081 (China)

    2012-06-01

    The adiabatic shear susceptibility of 2195 aluminum-lithium alloy was investigated by means of split Hopkinson pressure bar. The stress collapse in true stress-true strain curves and true stress-time curves was observed. The adiabatic shear susceptibility of different aging statuses and strain rate were discussed by means of metallography observation. The critical strain, stress collapse time and formation energy of adiabatic shear bands were compared. The results show that different aging statuses and strain rate have significant influences on adiabatic shear behaviors of 2195 aluminum-lithium alloy. The peak-aged specimen has the highest adiabatic shearing susceptibility, while the under-aged specimen has the least adiabatic shear susceptibility. The susceptibility of adiabatic shearing increases with the increases of strain rate.

  6. The DSS-14 C-band exciter

    Rowan, D. R.

    1989-01-01

    The development and implementation of a C-band exciter for use with the Block IV Receiver-Exciter Subsystem at Deep Space Station 14 (DSS-14) has been completed. The exciter supplements the standard capabilities of the Block IV system by providing a drive signal for the C-band transmitter while generating coherent translation frequencies for C-band (5-GHz) to S-band (2.2- to 2.3-GHz) Doppler extraction, C-band to L-band (1.6-GHz) zero delay measurements, and a level calibrated L-band test signal. Exciter functions are described, and a general explanation and description of the C-band uplink controller is presented.

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

    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.

  8. Development of the high-power THz spectroscopy and imaging systems on the basis of an S-band compact electron LINAC

    Kuroda, R.; Taira, Y.; Tanaka, M.; Toyokawa, H.; Yamada, K.; Kumaki, M.; Tachibana, M.; Sakaue, K.; Washio, M.

    2014-01-01

    The high-power terahertz time-domain spectroscopy (THz-TDS) and imaging systems have been developed on the basis of an S-band compact electron linac at AIST. Such high-power THz source is strongly expected for inspection of dangerous materials in the homeland security field. The high-power THz radiations are generated in two methods with the high-brightness ultra-short electron bunch. One is THz coherent synchrotron radiation (THz-CSR) for THz imaging applications. The other is THz coherent transition radiation (THz-CTR) for the THz spectroscopy. The THz-CTR time-domain spectroscopy (TDS) has been constructed with the EO sampling method and demonstrated in freq. range between 0.1-2 THz. The absorption measurements of drug samples have been successfully performed in atmosphere. In this symposium, we will describe details of the THz-CTR-TDS and imaging experiments and a future plan of the THz applications. (author)

  9. Development of a NEHRP site classification map of Chiang Mai city, Thailand, based on shear-wave velocity using the MASW technique

    Thitimakorn, Thanop

    2013-08-01

    To account for site amplification and seismic hazard mapping, the shear-wave velocity (Vs) profile to a depth of 30 m (Vs (30)) is an important parameter and can be used to calculate the ground motion for specific site conditions. In this study, the near-surface Vs profiles of soils were collected at 44 sites in Chiang Mai city using the multi-channel analysis of surface-wave technique. The Vs of each tested location was average weighted to Vs (30) based on the National Earthquake Hazards Reduction Program (NEHRP) criteria. The average Vs (30) value of the alluvium soils was about 362 m s-1, which falls between NEHRP site classes C and D. The average Vs (30) values of flood plain, fluvial clay and natural levee soils (at 300, 299 and 311 m s-1, respectively) all equated to NEHRP class D. The colluvial deposits in the north-western part of the city were mainly composed of gravel, coarse sand and rock fragments, and were assigned to class C (average Vs (30) of 412 m s-1). Soils with lower Vs values will experience higher earthquake ground shaking than those of the bedrock. Accordingly the major part of Chiang Mai city may experience substantial ground shaking due to the amplification in the soft soils.

  10. Solid State KA-Band, Solid State W-Band and TWT Amplifiers, Phase I

    National Aeronautics and Space Administration — Phase I of the proposal describes plans to develop a state of the art transmitter for the W-Band and KA -Band Cloud Radar system. Our focus will be concentrated in...

  11. Band Structure Characteristics of Nacreous Composite Materials with Various Defects

    Yin, J.; Zhang, S.; Zhang, H. W.; Chen, B. S.

    2016-06-01

    Nacreous composite materials have excellent mechanical properties, such as high strength, high toughness, and wide phononic band gap. In order to research band structure characteristics of nacreous composite materials with various defects, supercell models with the Brick-and-Mortar microstructure are considered. An efficient multi-level substructure algorithm is employed to discuss the band structure. Furthermore, two common systems with point and line defects and varied material parameters are discussed. In addition, band structures concerning straight and deflected crack defects are calculated by changing the shear modulus of the mortar. Finally, the sensitivity of band structures to the random material distribution is presented by considering different volume ratios of the brick. The results reveal that the first band gap of a nacreous composite material is insensitive to defects under certain conditions. It will be of great value to the design and synthesis of new nacreous composite materials for better dynamic properties.

  12. Shear Zone-Hosted Base Metal Mineralization near Abraha ...

    Tadesse

    of Arabia; B) Plan view of northern Ethiopia showing the roads and position ... within NE trending shear zone in the basement rocks with well developed alterations ...... country rocks and transported to the sites of deposition i.e. structural weak.

  13. Development and performance test of a new high power RF window in S-band PLS-II LINAC

    Hwang, Woon-Ha; Joo, Young-Do; Kim, Seung-Hwan; Choi, Jae-Young; Noh, Sung-Ju; Ryu, Ji-Wan; Cho, Young-Ki

    2017-12-01

    A prototype of RF window was developed in collaboration with the Pohang Accelerator Laboratory (PAL) and domestic companies. High power performance tests of the single RF window were conducted at PAL to verify the operational characteristics for its application in the Pohang Light Source-II (PLS-II) linear accelerator (Linac). The tests were performed in the in-situ facility consisting of a modulator, klystron, waveguide network, vacuum system, cooling system, and RF analyzing equipment. The test results with Stanford linear accelerator energy doubler (SLED) have shown no breakdown up to 75 MW peak power with 4.5 μs RF pulse width at a repetition rate of 10 Hz. The test results with the current operation level of PLS-II Linac confirm that the RF window well satisfies the criteria for PLS-II Linac operation.

  14. Turbulent shear layers in confining channels

    Benham, Graham P.; Castrejon-Pita, Alfonso A.; Hewitt, Ian J.; Please, Colin P.; Style, Rob W.; Bird, Paul A. D.

    2018-06-01

    We present a simple model for the development of shear layers between parallel flows in confining channels. Such flows are important across a wide range of topics from diffusers, nozzles and ducts to urban air flow and geophysical fluid dynamics. The model approximates the flow in the shear layer as a linear profile separating uniform-velocity streams. Both the channel geometry and wall drag affect the development of the flow. The model shows good agreement with both particle image velocimetry experiments and computational turbulence modelling. The simplicity and low computational cost of the model allows it to be used for benchmark predictions and design purposes, which we demonstrate by investigating optimal pressure recovery in diffusers with non-uniform inflow.

  15. Development of FeCoB/Graphene Oxide based microwave absorbing materials for X-Band region

    Das, Sukanta; Chandra Nayak, Ganesh; Sahu, S.K.; Oraon, Ramesh

    2015-01-01

    This work explored the microwave absorption capability of Graphene Oxide and Graphene Oxide coated with FeCoB for stealth technology. Epoxy based microwave absorbing materials were prepared with 30% loading of Graphene Oxide, FeCoB alloy and Graphene Oxide coated with FeCoB. Graphene Oxide and FeCoB were synthesized by Hummer's and Co-precipitation methods, respectively. The filler particles were characterized by FESEM, XRD and Vibrating Sample Magnetometer techniques. Permittivity, permeability and reflection loss values of the composite absorbers were measured with vector network analyzer which showed a reflection loss value of −7.86 dB, at 10.72 GHz, for single layered Graphene Oxide/Epoxy based microwave absorbers which can be correlated to the absorption of about 83.97% of the incident microwave energy. Reflection loss value of FeCoB/Epoxy based microwave absorber showed −13.30 dB at 11.67 GHz, which corresponded to maximum absorption of 93.8%. However, reflection loss values of Graphene Oxide coated with FeCoB/Epoxy based single-layer absorber increased to −22.24 dB at 12.4 GHz which corresponds to an absorption of 99% of the incident microwave energy. - Highlights: • FeCoB coated Graphene Oxide (GO) was synthesized by co-precipitation method. • GO, FeCoB and GO@FeCoB based microwave absorbers were developed with Epoxy matrix. • GO and FeCoB/Epoxy absorbers showed −7.86 & −13.30 dB reflection loss, respectively. • Maximum Reflection loss of −22.24 dB was achieved with GO@FeCoB/Epoxy absorber

  16. Test and lower bound modeling of keyed shear connections in RC shear walls

    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...

  17. SEDflume - High Shear Stress Flume

    Federal Laboratory Consortium — The U.S. Army Corps of Engineers High Shear Stress flume (SEDflume) is designed for estimating erosion rates of fine-grained and mixed fine/coarse grained sediments...

  18. Motional Effect on Wall Shear Stresses

    Kock, Samuel Alberg; Torben Fründ, Ernst; Yong Kim, Won

    Atherosclerosis is the leading cause of death and severe disability. Wall Shear Stress (WSS), the stress exerted on vessel walls by the flowing blood is a key factor in the development of atherosclerosis. Computational Fluid Dynamics (CFD) is widely used for WSS estimations. Most CFD simulations...... are based on static models to ease computational burden leading to inaccurate estimations. The aim of this work was to estimate the effect of vessel wall deformations (expansion and bending) on WSS levels....

  19. Size effects in shear interfaces

    GARNIER, J

    2001-01-01

    In physical modelling (centrifuge tests, calibration chambers, laboratory tests), the size of the soil particles may not be negligible when compared to the dimensions of the models. Size effects may so disturb the response of the models and the experimental data obtained on these cannot be extended to true scale conditions. Different tests have been performed to study and quantify the size effects that may happen in shear interfaces between soils and structures : modified shear box tests, pul...

  20. Shear Alfven waves in tokamaks

    Kieras, C.E.

    1982-12-01

    Shear Alfven waves in an axisymmetric tokamak are examined within the framework of the linearized ideal MHD equations. Properties of the shear Alfven continuous spectrum are studied both analytically and numerically. Implications of these results in regards to low frequency rf heating of toroidally confined plasmas are discussed. The structure of the spatial singularities associated with these waves is determined. A reduced set of ideal MHD equations is derived to describe these waves in a very low beta plasma

  1. Reward banding to determine reporting rate of recovered mourning dove bands

    Tomlinson, R.E.

    1968-01-01

    Reward bands placed on the other leg of certain regularly banded immature mourning doves (Zenaidura macroura) were used to develop information on reporting rates of recovered dove bands. Reports from 15 widely separated sections of the United States showed considerable variation in recovery rate of doves both with and without reward bands. The overall percentages of banded doves that were reported as recovered were 9.69% for those with reward bands and 3.83% for controls. The bandreporting rate for states influenced by publicity was 66%; that for states not influenced was 32%.

  2. Coherent structures in compressible free-shear-layer flows

    Aeschliman, D.P.; Baty, R.S. [Sandia National Labs., Albuquerque, NM (United States). Engineering Sciences Center; Kennedy, C.A.; Chen, J.H. [Sandia National Labs., Livermore, CA (United States). Combustion and Physical Sciences Center

    1997-08-01

    Large scale coherent structures are intrinsic fluid mechanical characteristics of all free-shear flows, from incompressible to compressible, and laminar to fully turbulent. These quasi-periodic fluid structures, eddies of size comparable to the thickness of the shear layer, dominate the mixing process at the free-shear interface. As a result, large scale coherent structures greatly influence the operation and efficiency of many important commercial and defense technologies. Large scale coherent structures have been studied here in a research program that combines a synergistic blend of experiment, direct numerical simulation, and analysis. This report summarizes the work completed for this Sandia Laboratory-Directed Research and Development (LDRD) project.

  3. Stimulated bioluminescence by fluid shear stress associated with pipe flow

    Cao Jing; Wang Jiangan; Wu Ronghua, E-mail: caojing981@126.com [Col. of Electronic Eng., Naval University of Engineering, Wuhan 430033 (China)

    2011-01-01

    Dinoflagellate can be stimulated bioluminescence by hydrodynamic agitation. Two typical dinoflagellate (Lingulodinium polyedrum and Pyrocystis noctiluca) was choosed to research stimulated bioluminescence. The bioluminescence intensity and shear stress intensity were measured using fully developed pipe flow. There is shear stress threshold to agitate organism bioluminescence. From these experiment, the response thresholds of the stimulated bioluminscence always occurred in laminar flows at a shear stress level of 0.6-3 dyn/cm{sup 2}. At the same time, the spectral characteristc of dinoflagellate was recorded, the wavelength of them is about 470nm, and the full width at half maximum is approximate 30nm.

  4. Study of magnetorheological fluids at high shear rates

    Wang, Xiaojie; Gordaninejad, Faramarz [University of Nevada, Department of Mechanical Engineering, Reno, NV (United States)

    2006-08-15

    The tunable rheological properties of magnetorheological (MR) materials at high shear rates are studied using a piston-driven flow-mode-type rheometer. The proposed method provides measurement of the apparent viscosity and yield stress of MR fluids for a shear rate range of 50 to 40,000 s{sup -1}. The rheological properties of a commercial MR fluid, as well as a newly developed MR polymeric gel, and a ferrofluid-based MR fluid are investigated. The results for apparent viscosity and dynamic and static shear stresses under different applied magnetic fields are reported. (orig.)

  5. Weak lensing Study in VOICE Survey I: Shear Measurement

    Fu, Liping; Liu, Dezi; Radovich, Mario; Liu, Xiangkun; Pan, Chuzhong; Fan, Zuhui; Covone, Giovanni; Vaccari, Mattia; Amaro, Valeria; Brescia, Massimo; Capaccioli, Massimo; De Cicco, Demetra; Grado, Aniello; Limatola, Luca; Miller, Lance; Napolitano, Nicola R.; Paolillo, Maurizio; Pignata, Giuliano

    2018-06-01

    The VST Optical Imaging of the CDFS and ES1 Fields (VOICE) Survey is a Guaranteed Time program carried out with the ESO/VST telescope to provide deep optical imaging over two 4 deg2 patches of the sky centred on the CDFS and ES1 pointings. We present the cosmic shear measurement over the 4 deg2 covering the CDFS region in the r-band using LensFit. Each of the four tiles of 1 deg2 has more than one hundred exposures, of which more than 50 exposures passed a series of image quality selection criteria for weak lensing study. The 5σ limiting magnitude in r- band is 26.1 for point sources, which is ≳1 mag deeper than other weak lensing survey in the literature (e.g. the Kilo Degree Survey, KiDS, at VST). The photometric redshifts are estimated using the VOICE u, g, r, i together with near-infrared VIDEO data Y, J, H, Ks. The mean redshift of the shear catalogue is 0.87, considering the shear weight. The effective galaxy number density is 16.35 gal/arcmin2, which is nearly twice the one of KiDS. The performance of LensFit on such a deep dataset was calibrated using VOICE-like mock image simulations. Furthermore, we have analyzed the reliability of the shear catalogue by calculating the star-galaxy cross-correlations, the tomographic shear correlations of two redshift bins and the contaminations of the blended galaxies. As a further sanity check, we have constrained cosmological parameters by exploring the parameter space with Population Monte Carlo sampling. For a flat ΛCDM model we have obtained Σ _8 = σ _8(Ω _m/0.3)^{0.5} = 0.68^{+0.11}_{-0.15}.

  6. Flexible Micropost Arrays for Shear Stress Measurement

    Wohl, Christopher J.; Palmieri, Frank L.; Hopkins, John W.; Jackson, Allen M.; Connell, John W.; Lin, Yi; Cisotto, Alexxandra A.

    2015-01-01

    Increased fuel costs, heightened environmental protection requirements, and noise abatement continue to place drag reduction at the forefront of aerospace research priorities. Unfortunately, shortfalls still exist in the fundamental understanding of boundary-layer airflow over aerodynamic surfaces, especially regarding drag arising from skin friction. For example, there is insufficient availability of instrumentation to adequately characterize complex flows with strong pressure gradients, heat transfer, wall mass flux, three-dimensionality, separation, shock waves, and transient phenomena. One example is the acoustic liner efficacy on aircraft engine nacelle walls. Active measurement of shear stress in boundary layer airflow would enable a better understanding of how aircraft structure and flight dynamics affect skin friction. Current shear stress measurement techniques suffer from reliability, complexity, and airflow disruption, thereby compromising resultant shear stress data. The state-of-the-art for shear stress sensing uses indirect or direct measurement techniques. Indirect measurements (e.g., hot-wire, heat flux gages, oil interferometry, laser Doppler anemometry, small scale pressure drag surfaces, i.e., fences) require intricate knowledge of the studied flow, restrictive instrument arrangements, large surface areas, flow disruption, or seeding material; with smaller, higher bandwidth probes under development. Direct measurements involve strain displacement of a sensor element and require no prior knowledge of the flow. Unfortunately, conventional "floating" recessed components for direct measurements are mm to cm in size. Whispering gallery mode devices and Fiber Bragg Gratings are examples of recent additions to this type of sensor with much smaller (?m) sensor components. Direct detection techniques are often single point measurements and difficult to calibrate and implement in wind tunnel experiments. In addition, the wiring, packaging, and installation

  7. L-band brightness temperature disaggregation for use with S-band and C-band radiometer data for WCOM

    Yao, P.; Shi, J.; Zhao, T.; Cosh, M. H.; Bindlish, R.

    2017-12-01

    There are two passive microwave sensors onboard the Water Cycle Observation Mission (WCOM), which includes a synthetic aperture radiometer operating at L-S-C bands and a scanning microwave radiometer operating from C- to W-bands. It provides a unique opportunity to disaggregate L-band brightness temperature (soil moisture) with S-band C-bands radiometer data. In this study, passive-only downscaling methodologies are developed and evaluated. Based on the radiative transfer modeling, it was found that the TBs (brightness temperature) between the L-band and S-band exhibit a linear relationship, and there is an exponential relationship between L-band and C-band. We carried out the downscaling results by two methods: (1) downscaling with L-S-C band passive measurements with the same incidence angle from payload IMI; (2) downscaling with L-C band passive measurements with different incidence angle from payloads IMI and PMI. The downscaling method with L-S bands with the same incident angle was first evaluated using SMEX02 data. The RMSE are 2.69 K and 1.52 K for H and V polarization respectively. The downscaling method with L-C bands is developed with different incident angles using SMEX03 data. The RMSE are 2.97 K and 2.68 K for H and V polarization respectively. These results showed that high-resolution L-band brightness temperature and soil moisture products could be generated from the future WCOM passive-only observations.

  8. Shear dilatancy and acoustic emission in dry and saturated granular materials

    Brodsky, E. E.; Siman-Tov, S.

    2017-12-01

    Shearing of granular materials plays a strong role in naturally sheared systems as landslides and faults. Many works on granular flows have concentrated on dry materials, but relatively little work has been done on water saturated sands. Here we experimentally investigate dry versus saturated quartz-rich sand to understand the effect of the fluid medium on the rheology and acoustic waves emission of the sheared sand. The sand was sheared in a rotary shear rheometer under applied constant normal stress boundary at low (100 µm/s) to high (1 m/s) velocities. Mechanical, acoustic data and deformation were continuously recorded and imaged. For dry and water saturated experiments the granular volume remains constant for low shear velocities ( 10-3 m/s) and increases during shearing at higher velocities ( 1 m/s). Continuous imaging of the sheared sand show that the steady state shear band thickness is thicker during the high velocity steps. No significant change observed in the shear band thickness between dry and water saturated experiments. In contrast, the amount of dilation during water saturated experiments is about half the value measured for dry material. The measured decrease cannot be explained by shear band thickness change as such is not exist. However, the reduced dilation is supported by our acoustic measurements. In general, the event rate and acoustic event amplitudes increase with shear velocity. While isolated events are clearly detected during low velocities at higher the events overlap, resulting in a noisy signal. Although detection is better for saturated experiments, during the high velocity steps the acoustic energy measured from the signal is lower compared to that recorded for dry experiments. We suggest that the presence of fluid suppresses grain motion and particles impacts leading to mild increase in the internal pressure and therefore for the reduced dilation. In addition, the viscosity of fluids may influence the internal pressure via

  9. Practical Weak-lensing Shear Measurement with Metacalibration

    Sheldon, Erin S. [Brookhaven National Laboratory, Bldg. 510, Upton, NY 11973 (United States); Huff, Eric M. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109 (United States)

    2017-05-20

    Metacalibration is a recently introduced method to accurately measure weak gravitational lensing shear using only the available imaging data, without need for prior information about galaxy properties or calibration from simulations. The method involves distorting the image with a small known shear, and calculating the response of a shear estimator to that applied shear. The method was shown to be accurate in moderate-sized simulations with galaxy images that had relatively high signal-to-noise ratios, and without significant selection effects. In this work we introduce a formalism to correct for both shear response and selection biases. We also observe that for images with relatively low signal-to-noise ratios, the correlated noise that arises during the metacalibration process results in significant bias, for which we develop a simple empirical correction. To test this formalism, we created large image simulations based on both parametric models and real galaxy images, including tests with realistic point-spread functions. We varied the point-spread function ellipticity at the five-percent level. In each simulation we applied a small few-percent shear to the galaxy images. We introduced additional challenges that arise in real data, such as detection thresholds, stellar contamination, and missing data. We applied cuts on the measured galaxy properties to induce significant selection effects. Using our formalism, we recovered the input shear with an accuracy better than a part in a thousand in all cases.

  10. Estimated strength of shear keys in concrete dams

    Curtis, D.D. [Hatch Energy, Niagara Falls, ON (Canada); Lum, K.K.Y. [BC Hydro, Burnaby, BC (Canada)

    2008-07-01

    BC Hydro requested that Hatch Energy review the seismic stability of Ruskin Dam which was constructed in 1930 at Hayward Lake in British Columbia. The concrete gravity dam is founded nearly entirely on rock in a narrow valley. The vertical joints between blocks are keyed and grouted. The strength of the shear keys was assessed when a non-linear finite element model found that significant forces were being transferred laterally to the abutments during an earthquake. The lateral transfer of loads to the abutment relies on the strength of the shear keys. The dynamic finite element analysis was used to determine the stability of the dam. A review of the shear strength measurements reported in literature showed that the measurements compared well to those obtained by BC Hydro from cores taken from Ruskin Dam. The cohesive strength obtained using the Griffith failure criteria was also in good agreement with both sets of measurements. A simple ultimate shear strength equation was developed using the Mohr-Coulomb failure criteria to determine combined cohesive and frictional strength of shear keys. Safety factors of 2.0 for static loads and 1.5 for seismic loads were proposed to reduce the ultimate strength to allowable values. It was concluded that given the relatively high shear strength established for the shear keys, the abutment rock or dam/abutment contact will control the amount of load which can arch to the abutments. 8 refs., 4 tabs., 5 figs.

  11. Nonlinear interaction of Rayleigh--Taylor and shear instabilities

    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

  12. Experimental observation of shear thickening oscillation

    Nagahiro, Shin-ichiro; Nakanishi, Hiizu; Mitarai, Namiko

    2013-01-01

    We report experimental observations of the shear thickening oscillation, i.e. the spontaneous macroscopic oscillation in the shear flow of severe shear thickening fluid. Using a density-matched starch-water mixture, in the cylindrical shear flow of a few centimeters flow width, we observed...

  13. Design of a side-band-separating heterodyne mixer for band 9 of ALMA

    Baryshev, AM; Kooi, J; Mena, FR; Lodewijk, CRJ; Wild, W

    2005-01-01

    A side-band-separating (SBS) heterodyne mixer has been designed for the Atacama Large Millimeter Array (ALMA) 602-720 GHz band, as it will present a great improvement over the current double-side-band configuration under development at the moment. Here we present design details and the results of

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

    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.

  15. Critical Velocity for Shear Localization in A Mature Mylonitic Rock Analogue

    Takahashi, M.; van den Ende, M.; Niemeijer, A. R.; Spiers, C. J.

    2016-12-01

    Highly localized slip zones, seen within ductile shear zones developed in nature, such as pseudotachylite bands occurring within mylonites, are widely recognized as evidence for earthquake nucleation and/or propagation within and overprinting the ductile regime. To understand brittle/frictional localization processes in ductile shear zones and to connect these to earthquake nucleation and propagation processes, we performed large velocity step-change tests on a brine-saturated, 80:20 (wt. %) halite and muscovite gouge mixture, after forming a mature mylonitic structure through pressure solution creep at low-velocity. The sharp increase in sliding strength that occurs in response to an instantaneous upward velocity-step (direct effect) is an important parameter in determining the potential for and nature of seismic rupture nucleation. We obtained reproducible results regarding low velocity mechanical behavior compared with previous work of Niemeijer and Spiers, [2006], but also obtained new insights into the effects of sudden increases in slip velocity on localization and strength evolution, at velocities above a specific critical velocity Vc ( 20 μm/sec). We found that once a ductile, mylonitic structure has developed in a shear zone, subsequent cataclastic deformation at high velocity (> Vc) is consistently localized in a narrow zone characterized by fine grains of halite aligned in arrays between foliated muscovite Due to this intense localization, structures presumably developed under low velocity conditions were still preserved in large parts of the gouge body. This switch to localized deformation is controlled by the imposed velocity, and becomes most apparent at velocities over Vc. In addition, the direct effect a decreases rapidly when the velocity exceeds Vc. This implies that slip can localize and accelerate towards seismic velocities more or less instantly once Vc is exceeded. Obtaining a measure for Vc in natural faults is therefore of key importance

  16. Shear layer characteristics of supersonic free and impinging jets

    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.

  17. Effects of ExB velocity shear and magnetic shear on turbulence and transport in magnetic confinement devices

    Burrell, K.H.

    1996-11-01

    One of the scientific success stories of fusion research over the past decade is the development of the ExB shear stabilization model to explain the formation of transport barriers in magnetic confinement devices. This model was originally developed to explain the transport barrier formed at the plasma edge in tokamaks after the L (low) to H (high) transition. This concept has the universality needed to explain the edge transport barriers seen in limiter and divertor tokamaks, stellarators, and mirror machines. More recently, this model has been applied to explain the further confinement improvement from H (high)-mode to VH (very high)-mode seen in some tokamaks, where the edge transport barrier becomes wider. Most recently, this paradigm has been applied to the core transport barriers formed in plasmas with negative or low magnetic shear in the plasma core. These examples of confinement improvement are of considerable physical interest; it is not often that a system self-organizes to a higher energy state with reduced turbulence and transport when an additional source of free energy is applied to it. The transport decrease that is associated with ExB velocity shear effects also has significant practical consequences for fusion research. The fundamental physics involved in transport reduction is the effect of ExB shear on the growth, radial extent and phase correlation of turbulent eddies in the plasma. The same fundamental transport reduction process can be operational in various portions of the plasma because there are a number ways to change the radial electric field Er. An important theme in this area is the synergistic effect of ExB velocity shear and magnetic shear. Although the ExB velocity shear appears to have an effect on broader classes of microturbulence, magnetic shear can mitigate some potentially harmful effects of ExB velocity shear and facilitate turbulence stabilization

  18. Deformation bands, early markers of tectonic activity in front of a fold-and-thrust belt: Example from the Tremp-Graus basin, southern Pyrenees, Spain

    Robert, Romain; Robion, Philippe; Souloumiac, Pauline; David, Christian; Saillet, Elodie

    2018-05-01

    Strain localization in a porous calcarenite facies of the Aren formation in the Tremp basin was studied. This Maastrichtian syn-tectonic formation exposed in front of the Boixols thrust, in the Central South Pyrenean Zone, hosts bedding perpendicular deformation bands. These bands are organized in two major band sets, striking East-West and N-020 respectively. Both populations formed during early deformation stages linked to the growth of the fold and thrust. A magnetic fabric study (Anisotropy of Magnetic Susceptibility, AMS) was carried out to constrain the shortening direction responsible for the deformation bands development during the upper Cretaceous-Paleocene N-S contraction in the region, which allowed us to define populations of Pure Compaction Bands (PCB) and Shear Enhanced Compaction Bands (SECB) regarding their orientations compared to the shortening direction. Both sets are formed by cataclastic deformation, but more intense in the case of SECBs, which are also thinner than PCBs. The initial pore space is both mechanically reduced and chemically filled by several cementation phases. We propose a geomechanical model based on the regional context of layer parallel shortening, thrusting and strike-slip tectonics considering the burial history of the formation, in order to explain the development of both types of bands at remarkably shallow depths.

  19. Double-Lap Shear Test For Honeycomb Core

    Nettles, Alan T.; Hodge, Andrew J.

    1992-01-01

    Double-lap test measures shear strength of panel made of honeycomb core with 8-ply carbon-fiber/epoxy face sheets. Developed to overcome three principal disadvantages of prior standard single-lap shear test: specimen had to be more than 17 in. long; metal face sheets had to be used; and test introduced torque, with consequent bending and peeling of face sheets and spurious tensile or compressive loading of honeycomb.

  20. Focusing of Shear Shock Waves

    Giammarinaro, Bruno; Espíndola, David; Coulouvrat, François; Pinton, Gianmarco

    2018-01-01

    Focusing is a ubiquitous way to transform waves. Recently, a new type of shock wave has been observed experimentally with high-frame-rate ultrasound: shear shock waves in soft solids. These strongly nonlinear waves are characterized by a high Mach number, because the shear wave velocity is much slower, by 3 orders of magnitude, than the longitudinal wave velocity. Furthermore, these waves have a unique cubic nonlinearity which generates only odd harmonics. Unlike longitudinal waves for which only compressional shocks are possible, shear waves exhibit cubic nonlinearities which can generate positive and negative shocks. Here we present the experimental observation of shear shock wave focusing, generated by the vertical motion of a solid cylinder section embedded in a soft gelatin-graphite phantom to induce linearly vertically polarized motion. Raw ultrasound data from high-frame-rate (7692 images per second) acquisitions in combination with algorithms that are tuned to detect small displacements (approximately 1 μ m ) are used to generate quantitative movies of gel motion. The features of shear shock wave focusing are analyzed by comparing experimental observations with numerical simulations of a retarded-time elastodynamic equation with cubic nonlinearities and empirical attenuation laws for soft solids.

  1. Modeling of shear wall buildings

    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.

  2. Role of E x B Shear and Magnetic Shear in the Formation of Transport Barriers in DIII-D

    Burrell, K.H.

    2005-01-01

    Development of the E x B shear stabilization model to explain the formation of transport barriers in magnetic confinement devices is a major achievement of fusion research. This concept has the universality needed to explain the H-mode edge transport barriers seen in limiter and divertor tokamaks, stellarators, and mirror machines; the broader edge transport barrier seen in VH-mode plasmas; and the core transport barriers formed in tokamaks with low or negative magnetic shear. These examples of confinement improvement are of considerable physical interest; it is not often that a system self-organizes to reduce transport when an additional source of free energy is applied to it. The transport decrease associated with E x B velocity shear is also of great practical benefit to fusion research. The fundamental physics involved in transport reduction is the effect of E x B shear on the growth, radial extent, and phase correlation of turbulent eddies in the plasma. The same basic transport reduction process can be operational in various portions of the plasma because there are a number of ways to change the radial electric field E r . An important theme in this area is the synergistic effect of E x B velocity shear and magnetic shear. Although the E x B velocity shear appears to have an effect on broader classes of microturbulence, magnetic shear can mitigate some potentially harmful effects of E x B velocity shear and facilitate turbulence stabilization. The experimental results on DIII-D and other devices are generally consistent with the basic theoretical models

  3. Shear-induced aggregation or disaggregation in edible oils: Models, computer simulation, and USAXS measurements

    Townsend, B.; Peyronel, F.; Callaghan-Patrachar, N.; Quinn, B.; Marangoni, A. G.; Pink, D. A.

    2017-12-01

    The effects of shear upon the aggregation of solid objects formed from solid triacylglycerols (TAGs) immersed in liquid TAG oils were modeled using Dissipative Particle Dynamics (DPD) and the predictions compared to experimental data using Ultra-Small Angle X-ray Scattering (USAXS). The solid components were represented by spheres interacting via attractive van der Waals forces and short range repulsive forces. A velocity was applied to the liquid particles nearest to the boundary, and Lees-Edwards boundary conditions were used to transmit this motion to non-boundary layers via dissipative interactions. The shear was created through the dissipative forces acting between liquid particles. Translational diffusion was simulated, and the Stokes-Einstein equation was used to relate DPD length and time scales to SI units for comparison with USAXS results. The SI values depended on how large the spherical particles were (250 nm vs. 25 nm). Aggregation was studied by (a) computing the Structure Function and (b) quantifying the number of pairs of solid spheres formed. Solid aggregation was found to be enhanced by low shear rates. As the shear rate was increased, a transition shear region was manifested in which aggregation was inhibited and shear banding was observed. Aggregation was inhibited, and eventually eliminated, by further increases in the shear rate. The magnitude of the transition region shear, γ˙ t, depended on the size of the solid particles, which was confirmed experimentally.

  4. Constitutive Curve and Velocity Profile in Entangled Polymers during Start-Up of Steady Shear Flow

    Hayes, Keesha A.

    2010-05-11

    Time-dependent shear stress versus shear rate, constitutive curve, and velocity profile measurements are reported in entangled polymer solutions during start-up of steady shear flow. By combining confocal microscopy and particle image velocimetry (PIV), we determine the time-dependent velocity profile in polybutadiene and polystyrene solutions seeded with fluorescent 150 nm silica and 7.5 μm melamine particles. By comparing these profiles with time-dependent constitutive curves obtained from experiment and theory, we explore the connection between transient nonmonotonic regions in the constitutive curve for an entangled polymer and its susceptibility to unstable flow by shear banding [Adams et al. Phys. Rev. Lett. 2009, 102, 067801-4]. Surprisingly, we find that even polymer systems which exhibit transient, nonmonotonic shear stress-shear rate relationships in bulk rheology experiments manifest time-dependent velocity profiles that are decidedly linear and show no evidence of unstable flow. We also report that interfacial slip plays an important role in the steady shear flow behavior of entangled polymers at shear rates above the reciprocal terminal relaxation time but has little, if any, effect on the shape of the velocity profile. © 2010 American Chemical Society.

  5. Alfven eigenmodes in shear reversed plasmas

    Breizman, B.N.; Berk, H.L.; Pekker, M.S.; Sharapov, S.E.; Hawkes, N.C.; Borba, D.N.; Pinches, S.D.

    2003-01-01

    Experiments on JT-60U and JET have shown that plasma configurations with shear reversal are prone to the excitation of unusual Alfven Eigenmodes by energetic particles. These modes emerge outside the TAE frequency gap, where one might expect them to be strongly damped. The modes often appear in bunches and they exhibit a quasi-periodic pattern of predominantly upward frequency sweeping (Alfven Cascades) as the safety factor q changes in time. This work presents a theory that explains the key features of the observed unusual modes including their connection to TAE's as well as the modifications of TAE's themselves near the shear reversal point. The developed theory has been incorporated into a reduced numerical model and verified with full geometry codes. JET experimental data on Alfven spectroscopy have been simulated to infer the mode numbers and the evolution of q min in the discharge. This analysis confirms the values of q that characterize the internal transport barrier triggering in reversed shear plasmas. (author)

  6. Wave anisotropy of shear viscosity and elasticity

    Rudenko, O. V.; Sarvazyan, A. P.

    2014-11-01

    The paper presents the theory of shear wave propagation in a "soft solid" material possessing anisotropy of elastic and dissipative properties. The theory is developed mainly for understanding the nature of the low-frequency acoustic characteristics of skeletal muscles, which carry important diagnostic information on the functional state of muscles and their pathologies. It is shown that the shear elasticity of muscles is determined by two independent moduli. The dissipative properties are determined by the fourth-rank viscosity tensor, which also has two independent components. The propagation velocity and attenuation of shear waves in muscle depend on the relative orientation of three vectors: the wave vector, the polarization vector, and the direction of muscle fiber. For one of the many experiments where attention was distinctly focused on the vector character of the wave process, it was possible to make a comparison with the theory, estimate the elasticity moduli, and obtain agreement with the angular dependence of the wave propagation velocity predicted by the theory.

  7. FEM Simulation of Incremental Shear

    Rosochowski, Andrzej; Olejnik, Lech

    2007-01-01

    A popular way of producing ultrafine grained metals on a laboratory scale is severe plastic deformation. This paper introduces a new severe plastic deformation process of incremental shear. A finite element method simulation is carried out for various tool geometries and process kinematics. It has been established that for the successful realisation of the process the inner radius of the channel as well as the feeding increment should be approximately 30% of the billet thickness. The angle at which the reciprocating die works the material can be 30 deg. . When compared to equal channel angular pressing, incremental shear shows basic similarities in the mode of material flow and a few technological advantages which make it an attractive alternative to the known severe plastic deformation processes. The most promising characteristic of incremental shear is the possibility of processing very long billets in a continuous way which makes the process more industrially relevant

  8. SHEAR ACCELERATION IN EXPANDING FLOWS

    Rieger, F. M. [ZAH, Institut für Theoretische Astrophysik, Universität Heidelberg, Philosophenweg 12, D-69120 Heidelberg (Germany); Duffy, P., E-mail: frank.rieger@mpi-hd.mpg.de, E-mail: peter.duffy@ucd.ie [University College Dublin, Belfield, Dublin 4 (Ireland)

    2016-12-10

    Shear flows are naturally expected to occur in astrophysical environments and potential sites of continuous non-thermal Fermi-type particle acceleration. Here we investigate the efficiency of expanding relativistic outflows to facilitate the acceleration of energetic charged particles to higher energies. To this end, the gradual shear acceleration coefficient is derived based on an analytical treatment. The results are applied to the context of the relativistic jets from active galactic nuclei. The inferred acceleration timescale is investigated for a variety of conical flow profiles (i.e., power law, Gaussian, Fermi–Dirac) and compared to the relevant radiative and non-radiative loss timescales. The results exemplify that relativistic shear flows are capable of boosting cosmic-rays to extreme energies. Efficient electron acceleration, on the other hand, requires weak magnetic fields and may thus be accompanied by a delayed onset of particle energization and affect the overall jet appearance (e.g., core, ridge line, and limb-brightening).

  9. Temperature and shear rate characteristics of electrorheological gel applied to a clutch

    Koyanagi, K; Takata, Y; Motoyoshi, T; Oshima, T; Kakinuma, Y; Anzai, H; Sakurai, K

    2013-01-01

    This investigation reports the physical characteristics of electrorheological (ER) gels, which are a type of functional material having controlled surface friction. We previously developed slip clutches using ER gels sandwiched between electrodes, and verified their responses and controllability. We newly report the temperature and shear rate characteristics of ER gel in this study because the input and output electrodes of the clutch continuously slip past each other. While the temperature of ER gels increased when energized, the shear stress hardly changed. Instead, wearing and adaptation to the electrode affect the property. The shear rate hardly affected the shear stress in the high-shear-rate region. Conversely, the shear stress depended on the shear rate in the lower region.

  10. Computerized lateral-shear interferometer

    Hasegan, Sorin A.; Jianu, Angela; Vlad, Valentin I.

    1998-07-01

    A lateral-shear interferometer, coupled with a computer for laser wavefront analysis, is described. A CCD camera is used to transfer the fringe images through a frame-grabber into a PC. 3D phase maps are obtained by fringe pattern processing using a new algorithm for direct spatial reconstruction of the optical phase. The program describes phase maps by Zernike polynomials yielding an analytical description of the wavefront aberration. A compact lateral-shear interferometer has been built using a laser diode as light source, a CCD camera and a rechargeable battery supply, which allows measurements in-situ, if necessary.

  11. Fade Mitigation Techniques at Ka-Band

    Dissanayake, Asoka (Editor)

    1996-01-01

    Rain fading is the dominant propagation impairment affecting Ka-band satellite links and rain fade mitigation is a key element in the design of Ka-band satellite networks. Some of the common fade mitigation techniques include: power control, diversity, adaptive coding, and resource sharing. The Advanced Communications Technology Satellite (ACTS) provides an excellent opportunity to develop and test Ka-band rain impairment amelioration techniques. Up-link power control and diversity are discussed in this paper.

  12. Shear Stress-Relative Slip Relationship at Concrete Interfaces

    Keun-Hyeok Yang

    2016-01-01

    Full Text Available This study develops a simple and rational shear stress-relative slip model of concrete interfaces with monolithic castings or smooth construction joints. In developing the model, the initial shear cracking stress and relative slip amount at peak stress were formulated from a nonlinear regression analysis using test data for push-off specimens. The shear friction strength was determined from the generalized equations on the basis of the upper-bound theorem of concrete plasticity. Then, a parametric fitting analysis was performed to derive equations for the key parameters determining the shapes of the ascending and descending branches of the shear stress-relative slip curve. The comparisons of predictions and measurements obtained from push-off tests confirmed that the proposed model provides superior accuracy in predicting the shear stress-relative slip relationship of interfacial shear planes. This was evidenced by the lower normalized root mean square error than those in Xu et al.’s model and the CEB-FIB model, which have many limitations in terms of the roughness of the substrate surface along an interface and the magnitude of equivalent normal stress.

  13. Wide Band to ''Double Band'' upgrade

    Kasper, P.; Currier, R.; Garbincius, P.; Butler, J.

    1988-06-01

    The Wide Band beam currently uses electrons obtained from secondary photon conversions to produce the photon beam incident on the experimental targets. By transporting the positrons produced in these conversions as well as the electrons it is possible to almost double the number of photons delivered to the experiments per primary beam proton. 11 figs

  14. Numerical Analysis of Fully Developed Laminar Flow in Trapezoidal and Sinusoidal Grooves with Shear Stress at the Liquid-Vapor Interface

    Thomas, Scott

    2000-01-01

    .... A computer model was developed using a finite difference solution which finds the mean velocity, Poiseuille number, and volumetric flow rate in terms of the groove geometry, meniscus contact angle...

  15. Mesoscale modeling of amorphous metals by shear transformation zone dynamics

    Homer, Eric R.; Schuh, Christopher A.

    2009-01-01

    A new mesoscale modeling technique for the thermo-mechanical behavior of metallic glasses is proposed. The modeling framework considers the shear transformation zone (STZ) as the fundamental unit of deformation, and coarse-grains an amorphous collection of atoms into an ensemble of STZs on a mesh. By employing finite element analysis and a kinetic Monte Carlo algorithm, the modeling technique is capable of simulating glass processing and deformation on time and length scales greater than those usually attainable by atomistic modeling. A thorough explanation of the framework is presented, along with a specific two-dimensional implementation for a model metallic glass. The model is shown to capture the basic behaviors of metallic glasses, including high-temperature homogeneous flow following the expected constitutive law, and low-temperature strain localization into shear bands. Details of the effects of processing and thermal history on the glass structure and properties are also discussed.

  16. Prompt and delayed spectroscopy of At203 : Observation of a shears band and a 29/2+ isomeric state

    Auranen, K.; Uusitalo, J.; Juutinen, S.; Badran, H.; Defranchi Bisso, F.; Cox, D.; Grahn, T.; Greenlees, P. T.; Herzáň, A.; Jakobsson, U.; Julin, R.; Konki, J.; Leino, M.; Lightfoot, A.; Mallaburn, M. J.; Neuvonen, O.; Pakarinen, J.; Papadakis, P.; Partanen, J.; Rahkila, P.; Sandzelius, M.; Sarén, J.; Scholey, C.; Sorri, J.; Stolze, S.; Wang, Y. K.

    2018-02-01

    Using fusion-evaporation reactions, a gas-filled recoil separator, recoil-gating technique and recoil-isomer decay tagging technique we have extended the level scheme of At-203 (N = 118) significantly. We have observed an isomeric [tau = 14.1(3) mu s] state with a spin and parity of 29/2(+). The isomeric state is suggested to originate from the pi(h(9/2)) circle times |Po-202; 11(-)> coupling, and it is depopulated through 286 keV E2 and 366 keV E3 transitions. In addition, we have observed a cascade of magnetic-dipole transitions which is suggested to be generated by the shears mechanism.

  17. Fracture transmissivity as a function of normal and shear stress: first results in Opalinus Clay

    Cuss, R.J.; Milodowski, A.; Noy, D.J.; Harrington, J.F.

    2010-01-01

    -test analysis has shown that the passage of fluid along the fracture surface has not been radially from the centre of the sample equally in all directions, but has focused along zones with one being strongly aligned with the direction of shear. Shear banding was also observed on part of the fracture surface. The first experiment has clearly shown the relationship of normal load and fracture transmissivity. It has also shown the complex development of transmissivity during active shear. The experimental results clearly show that fracture transmissivity is not a constant and that complex histories of transport mechanisms result, maybe signifying fault valve behaviour. This will have significant impact on modelling the EDZ and estimates of the transport properties in this highly complex and significant zone. (authors)

  18. Atomic mechanism of shear localization during indentation of a nanostructured metal

    Sansoz, F.; Dupont, V.

    2007-01-01

    Shear localization is an important mode of deformation in nanocrystalline metals. However, it is very difficult to verify the existence of local shear planes in nanocrystalline metals experimentally. Sharp indentation techniques may provide novel opportunities to investigate the effect of shear localization at different length scales, but the relationship between indentation response and atomic-level shear band formation has not been fully addressed. This paper describes an effort to provide direct insight on the mechanism of shear localization during indentation of nanocrystalline metals from atomistic simulations. Molecular statics is performed with the quasi-continuum method to simulate the indentation of single crystal and nanocrystalline Al with a sharp cylindrical probe. In the nanocrystalline regime, two grain sizes are investigated, 5 nm and 10 nm. We find that the indentation of nanocrystalline metals is characterized by serrated plastic flow. This effect seems to be independent of the grain size. Serration in nanocrystalline metals is found to be associated with the formation of shear bands by sliding of aligned interfaces and intragranular slip, which results in deformation twinning

  19. Amniotic constriction bands

    ... Supplements Videos & Tools Español You Are Here: Home → Medical Encyclopedia → Amniotic band sequence URL of this page: //medlineplus.gov/ency/ ... birth. The baby should be delivered in a medical center that has specialists experienced in caring for babies ... or partial loss of function of a body part. Congenital bands affecting large parts of the body cause the ...

  20. Grouted Connections with Shear Keys

    Pedersen, Ronnie; Jørgensen, M. B.; Damkilde, Lars

    2012-01-01

    This paper presents a finite element model in the software package ABAQUS in which a reliable analysis of grouted pile-to-sleeve connections with shear keys is the particular purpose. The model is calibrated to experimental results and a consistent set of input parameters is estimated so that dif...... that different structural problems can be reproduced successfully....

  1. Meniscal shear stress for punching.

    Tuijthof, Gabrielle J M; Meulman, Hubert N; Herder, Just L; van Dijk, C Niek

    2009-01-01

    Experimental determination of the shear stress for punching meniscal tissue. Meniscectomy (surgical treatment of a lesion of one of the menisci) is the most frequently performed arthroscopic procedure. The performance of a meniscectomy is not optimal with the currently available instruments. To design new instruments, the punching force of meniscal tissue is an important parameter. Quantitative data are unavailable. The meniscal punching process was simulated by pushing a rod through meniscal tissue at constant speed. Three punching rods were tested: a solid rod of Oslash; 3.00 mm, and two hollow tubes (Oslash; 3.00-2.60 mm) with sharpened cutting edges of 0.15 mm and 0.125 mm thick, respectively. Nineteen menisci acquired from 10 human cadaveric knee joints were punched (30 tests). The force and displacement were recorded from which the maximum shear stress was determined (average added with three times the standard deviation). The maximum shear stress for the solid rod was determined at 10.2 N/mm2. This rod required a significantly lower punch force in comparison with the hollow tube having a 0.15 mm cutting edge (plt;0.01). The maximum shear stress for punching can be applied to design instruments, and virtual reality training environments. This type of experiment is suitable to form a database with material properties of human tissue similar to databases for the manufacturing industry.

  2. Centrifuges and inertial shear forces

    Loon, van J.J.W.A.; Folgering, H.T.E.; Bouten, C.V.C.; Smit, T.H.

    2004-01-01

    Centrifuges are often used in biological studies for 1xg control samples in space flight microgravity experiments as well as in ground based research. Using centrifugation as a tool to generate an Earth like acceleration introduces unwanted inertial shear forces to the sample. Depending on the

  3. Shear wave velocity structure of northern and North-Eastern Ethiopia

    Kebede, F.; Mammo, T.; Panza, G.F.; Vuan, A.; Costa, G.

    1995-10-01

    The non-linear inversion technique known as hedgehog is utilized to define the average crustal structure of North and North-Eastern Ethiopia. To accomplish the task a two dimensional frequency-time analysis is performed to obtain Rayleigh wave group velocity dispersion curves. Six earthquakes recorded by the broad-band digital seismograph installed at the Geophysical Observatory of Addis Ababa University are utilized. The crustal structure between the Gulf of Tadjura (western Gulf of Aden) and Addis Ababa crossing southern Afar (path I) can be approximated by a total thickness of about 22 km with average S-wave velocity in the range 2.3 - 3.9 km/s. The crust-mantle transition is poorly developed at greater depths and the shear wave velocity ranges from 4.0 km/s to 4.3 km/s. If the effect of the plateau part is taken into account the average total crustal thickness is found to be less than 18 km and the average S-wave velocity varies in the range 2.4 - 3.9 km/s. The low shear wave velocity under the Afar crust is consistent with the result of other geophysical studies. For path II, which passes through the border of the Western Ethiopian plateau, the average crustal structure is found to be approximated by a thickness of about 40 km and average S-wave velocity between 3.0 km/s and 3.9 km/s. The crust overlies a lithospheric mantle with a shear wave velocity in the range 4.1-4.4 km/s. (author). 37 refs, 11 figs, 4 tabs

  4. An experimental investigation for external RC shear wall applications

    Kaltakci, M. Y.; Ozturk, M.; Arslan, M. H.

    2010-09-01

    The strength and rigidity of most reinforced concrete (RC) buildings in Turkey, which are frequently hit by destructive earthquakes, is not at a sufficient level. Therefore, the result of earthquakes is a significant loss of life and property. The strengthening method most commonly preferred for these type of RC buildings is the application of RC infilled walls (shear walls) in the frame openings of the building. However, since the whole building has to be emptied and additional heavy costs arise during this type of strengthening, users prefer not to strengthen their buildings despite the heavy risk they are exposed to. Therefore, it is necessary to develop easier-to-apply and more effective methods for the rapid strengthening of housing and the heavily-used public buildings which cannot be emptied during the strengthening process (such as hospitals and schools). This study empirically analyses the different methods of a new system which can meet this need. In this new system, named "external shear wall application", RC shear walls are applied on the external surface of the building, along the frame plane rather than in the building. To this end, 7 test samples in 1/2 and 1/3 geometrical scale were designed to analyse the efficiency of the strengthening technique where the shear wall leans on the frame from outside of the building (external shear wall application) and of the strengthening technique where a specific space is left between the frame and the external shear wall by using a coupling beam to connect elements (application of external shear wall with coupling beam). Test results showed that the maximum lateral load capacity, initial rigidity and energy dissipation behaviours of the samples strengthened with external shear wall were much better than those of the bare frames.

  5. An experimental investigation for external RC shear wall applications

    M. Y. Kaltakci

    2010-09-01

    Full Text Available The strength and rigidity of most reinforced concrete (RC buildings in Turkey, which are frequently hit by destructive earthquakes, is not at a sufficient level. Therefore, the result of earthquakes is a significant loss of life and property. The strengthening method most commonly preferred for these type of RC buildings is the application of RC infilled walls (shear walls in the frame openings of the building. However, since the whole building has to be emptied and additional heavy costs arise during this type of strengthening, users prefer not to strengthen their buildings despite the heavy risk they are exposed to. Therefore, it is necessary to develop easier-to-apply and more effective methods for the rapid strengthening of housing and the heavily-used public buildings which cannot be emptied during the strengthening process (such as hospitals and schools. This study empirically analyses the different methods of a new system which can meet this need. In this new system, named "external shear wall application", RC shear walls are applied on the external surface of the building, along the frame plane rather than in the building. To this end, 7 test samples in 1/2 and 1/3 geometrical scale were designed to analyse the efficiency of the strengthening technique where the shear wall leans on the frame from outside of the building (external shear wall application and of the strengthening technique where a specific space is left between the frame and the external shear wall by using a coupling beam to connect elements (application of external shear wall with coupling beam. Test results showed that the maximum lateral load capacity, initial rigidity and energy dissipation behaviours of the samples strengthened with external shear wall were much better than those of the bare frames.

  6. Nanoscale dislocation shear loops at static equilibrium and finite temperature

    Dang, Khanh; Capolungo, Laurent; Spearot, Douglas E.

    2017-12-01

    Atomistic simulations are used to determine the resolved shear stress necessary for equilibrium and the resulting geometry of nanoscale dislocation shear loops in Al. Dislocation loops with different sizes and shapes are created via superposition of elemental triangular dislocation displacement fields in the presence of an externally imposed shear stress. First, a bisection algorithm is developed to determine systematically the resolved shear stress necessary for equilibrium at 0 K. This approach allows for the identification of dislocation core structure and a correlation between dislocation loop size, shape and the computed shear stress for equilibrium. It is found, in agreement with predictions made by Scattergood and Bacon, that the equilibrium shape of a dislocation loop becomes more circular with increasing loop size. Second, the bisection algorithm is extended to study the influence of temperature on the resolved shear stress necessary for stability. An approach is presented to compute the effective lattice friction stress, including temperature dependence, for dislocation loops in Al. The temperature dependence of the effective lattice friction stress can be reliably computed for dislocation loops larger than 16.2 nm. However, for dislocation loops smaller than this threshold, the effective lattice friction stress shows a dislocation loop size dependence caused by significant overlap of the stress fields on the interior of the dislocation loops. Combined, static and finite temperature atomistic simulations provide essential data to parameterize discrete dislocation dynamics simulations.

  7. Modeling Shear Induced Von Willebrand Factor Binding to Collagen

    Dong, Chuqiao; Wei, Wei; Morabito, Michael; Webb, Edmund; Oztekin, Alparslan; Zhang, Xiaohui; Cheng, Xuanhong

    2017-11-01

    Von Willebrand factor (vWF) is a blood glycoprotein that binds with platelets and collagen on injured vessel surfaces to form clots. VWF bioactivity is shear flow induced: at low shear, binding between VWF and other biological entities is suppressed; for high shear rate conditions - as are found near arterial injury sites - VWF elongates, activating its binding with platelets and collagen. Based on parameters derived from single molecule force spectroscopy experiments, we developed a coarse-grain molecular model to simulate bond formation probability as a function of shear rate. By introducing a binding criterion that depends on the conformation of a sub-monomer molecular feature of our model, the model predicts shear-induced binding, even for conditions where binding is highly energetically favorable. We further investigate the influence of various model parameters on the ability to predict shear-induced binding (vWF length, collagen site density and distribution, binding energy landscape, and slip/catch bond length) and demonstrate parameter ranges where the model provides good agreement with existing experimental data. Our results may be important for understanding vWF activity and also for achieving targeted drug therapy via biomimetic synthetic molecules. National Science Foundation (NSF),Division of Mathematical Sciences (DMS).

  8. Compressibility effects in the shear layer over a rectangular cavity

    Beresh, Steven J.; Wagner, Justin; Casper, Katya Marie

    2016-10-26

    we studied the influence of compressibility on the shear layer over a rectangular cavity of variable width in a free stream Mach number range of 0.6–2.5 using particle image velocimetry data in the streamwise centre plane. As the Mach number increases, the vertical component of the turbulence intensity diminishes modestly in the widest cavity, but the two narrower cavities show a more substantial drop in all three components as well as the turbulent shear stress. Furthermore, this contrasts with canonical free shear layers, which show significant reductions in only the vertical component and the turbulent shear stress due to compressibility. The vorticity thickness of the cavity shear layer grows rapidly as it initially develops, then transitions to a slower growth rate once its instability saturates. When normalized by their estimated incompressible values, the growth rates prior to saturation display the classic compressibility effect of suppression as the convective Mach number rises, in excellent agreement with comparable free shear layer data. The specific trend of the reduction in growth rate due to compressibility is modified by the cavity width.

  9. Displacement-length scaling of brittle faults in ductile shear.

    Grasemann, Bernhard; Exner, Ulrike; Tschegg, Cornelius

    2011-11-01

    Within a low-grade ductile shear zone, we investigated exceptionally well exposed brittle faults, which accumulated antithetic slip and rotated into the shearing direction. The foliation planes of the mylonitic host rock intersect the faults approximately at their centre and exhibit ductile reverse drag. Three types of brittle faults can be distinguished: (i) Faults developing on pre-existing K-feldspar/mica veins that are oblique to the shear direction. These faults have triclinic flanking structures. (ii) Wing cracks opening as mode I fractures at the tips of the triclinic flanking structures, perpendicular to the shear direction. These cracks are reactivated as faults with antithetic shear, extend from the parent K-feldspar/mica veins and form a complex linked flanking structure system. (iii) Joints forming perpendicular to the shearing direction are deformed to form monoclinic flanking structures. Triclinic and monoclinic flanking structures record elliptical displacement-distance profiles with steep displacement gradients at the fault tips by ductile flow in the host rocks, resulting in reverse drag of the foliation planes. These structures record one of the greatest maximum displacement/length ratios reported from natural fault structures. These exceptionally high ratios can be explained by localized antithetic displacement along brittle slip surfaces, which did not propagate during their rotation during surrounding ductile flow.

  10. Displacement–length scaling of brittle faults in ductile shear

    Grasemann, Bernhard; Exner, Ulrike; Tschegg, Cornelius

    2011-01-01

    Within a low-grade ductile shear zone, we investigated exceptionally well exposed brittle faults, which accumulated antithetic slip and rotated into the shearing direction. The foliation planes of the mylonitic host rock intersect the faults approximately at their centre and exhibit ductile reverse drag. Three types of brittle faults can be distinguished: (i) Faults developing on pre-existing K-feldspar/mica veins that are oblique to the shear direction. These faults have triclinic flanking structures. (ii) Wing cracks opening as mode I fractures at the tips of the triclinic flanking structures, perpendicular to the shear direction. These cracks are reactivated as faults with antithetic shear, extend from the parent K-feldspar/mica veins and form a complex linked flanking structure system. (iii) Joints forming perpendicular to the shearing direction are deformed to form monoclinic flanking structures. Triclinic and monoclinic flanking structures record elliptical displacement–distance profiles with steep displacement gradients at the fault tips by ductile flow in the host rocks, resulting in reverse drag of the foliation planes. These structures record one of the greatest maximum displacement/length ratios reported from natural fault structures. These exceptionally high ratios can be explained by localized antithetic displacement along brittle slip surfaces, which did not propagate during their rotation during surrounding ductile flow. PMID:26806996

  11. Imaging off-plane shear waves with a two-dimensional phononic crystal lens

    Chiang Chenyu; Luan Pigang

    2010-01-01

    A two-dimensional flat phononic crystal (PC) lens for focusing off-plane shear waves is proposed. The lens consists of a triangular lattice hole-array, embedded in a solid matrix. The self-collimation effect is employed to guide the shear waves propagating through the lens along specific directions. The Dirichlet-to-Neumann maps (DtN) method is employed to calculate the band structure of the PC, which can avoid the problems of bad convergence and fake bands automatically in the void-solid PC structure. When the lens is illuminated by the off-plane shear waves emanating from a point source, a subwavelength image appears in the far-field zone. The imaging characteristics are investigated by calculating the displacement fields explicitly using the multiple scattering method, and the results are in good agreement with the ray-trace predictions. Our results may provide insights for designing new phononic devices.

  12. Multiple band structure in 156Er

    Sunyar, A.W.; Der Mateosian, E.; Kistner, O.C.; Johnson, A.; Lumpkin, A.H.; Thieberger, P.

    1976-01-01

    The 142 Nd( 18 O,4n) 156 Er reaction at 90-95 MeV was used to study 156 Er high-spin states to spin 24. In addition to the background ground-state band, two well developed off-spin side bands, one of each parity, were observed. (Auth.)

  13. Microscopic Characterization of Tensile and Shear Fracturing in Progressive Failure in Marble

    Cheng, Yi; Wong, Louis Ngai Yuen

    2018-01-01

    Compression-induced tensile and shear fractures were reported to be the two fundamental fracture types in rock fracturing tests. This study investigates such tensile and shear fracturing process in marble specimens containing two different flaw configurations. Observations first reveal that the development of a tensile fracture is distinct from shear fracture with respect to their nucleation, propagation, and eventual formation in macroscale. Second, transgranular cracks and grain-scale spallings become increasingly abundant in shear fractures as loading increases, which is almost not observed in tensile fractures. Third, one or some dominant extensional microcracks are commonly observed in the center of tensile fractures, while such development of microcracks is almost absent in shear fractures. Microcracks are generally of a length comparable to grain size and distribute uniformly within the damage zone of the shear fracture. Fourth, the width of densely damaged zone in the shear fracture is nearly 10 times of that in the tensile fracture. Quantitative measurement on microcrack density suggests that (1) microcrack density in tensile and shear fractures display distinct characteristics with increasing loading, (2) transgranular crack density in the shear fracture decreases logarithmically with the distance away from the shear fracture center, and (3) whatever the fracture type, the anisotropy can only be observed for transgranular cracks with a large density, which partially explains why microcrack anisotropy usually tends to be unobvious until approaching peak stress in specimens undergoing brittle failure. Microcracking characteristics observed in this work likely shed light to some phenomena and conclusions generalized in seismological studies.

  14. Deformation localization at the tips of shear fractures: An analytical approach

    Misra, Santanu

    2011-04-01

    Mechanical heterogeneities are important features in rocks which trigger deformation localization in brittle, ductile or brittle-ductile modes during deformation. In a recent study Misra et al. (2009) have investigated these different processes of deformation localization at the tips of pre-existing planar shear fractures. The authors identified four mechanisms of deformation, ranging from brittle to ductile, operating at the crack tips. Mechanism A: brittle deformation is the dominant process that forms a pair of long tensile fractures at the two crack tips. Mechanism B: nature of deformation is mixed where the tensile fractures grow to a finite length with incipient plastic deformation at the tips. Mechanism C: mixed mode deformation characterized by dominating macro-scale shear bands, and short, opened-out tensile fissures. Mechanism D: localization of plastic bands in the form of a pair of shear bands at each tip without any discernible brittle fracturing. The transition of the mechanisms is a function of orientation ( α) of the crack with respect to the bulk compression direction and the finite length ( l) of the crack. The aim of this study is to present a theoretical analysis to account for the variability of deformation localization in the vicinity of pre-existing shear cracks considering an elastic-plastic rheological model. The analysis calculates the principal tensile stress ( σ1) and the second stress invariant ( I2) of the stress field at the fracture tip to explain the transition from Mechanism A (tensile fracturing) to Mechanism D (ductile strain). The results show that σ1 at the fracture tip increases non-linearly with increasing α and Ar (aspect ratio of the shear crack), and assumes a large value when α > 50 o, promoting tensile fractures. On the other hand, I2 is a maximum at α < 45°, resulting in nucleation of ductile shear bands.

  15. The microstructure and rheology of a model, thixotropic nanoparticle gel under steady shear and large amplitude oscillatory shear (LAOS)

    Min Kim, Jung; Kate Gurnon, A.; Wagner, Norman J.; Eberle, Aaron P. R.; Porcar, Lionel

    2014-01-01

    The microstructure-rheology relationship for a model, thermoreversible nanoparticle gel is investigated using a new technique of time-resolved neutron scattering under steady and time-resolved large amplitude oscillatory shear (LAOS) flows. A 21 vol. % gel is tested with varying strength of interparticle attraction. Shear-induced structural anisotropy is observed as butterfly scattering patterns and quantified through an alignment factor. Measurements in the plane of flow show significant, local anisotropy develops with alignment along the compressional axis of flow, providing new insights into how gels flow. The microstructure-rheology relationship is analyzed through a new type of structure-Lissajous plot that shows how the anisotropic microstructure is responsible for the observed LAOS response, which is beyond a response expected for a purely viscous gel with constant structure. The LAOS shear viscosities are observed to follow the “Delaware-Rutgers” rule. Rheological and microstructural data are successfully compared across a broad range of conditions by scaling the shear rate by the strength of attraction, providing a method to compare behavior between steady shear and LAOS experiments. However, important differences remain between the microstructures measured at comparatively high frequency in LAOS experiments and comparable steady shear experiments that illustrate the importance of measuring the microstructure to properly interpret the nonlinear, dynamic rheological response

  16. The microstructure and rheology of a model, thixotropic nanoparticle gel under steady shear and large amplitude oscillatory shear (LAOS)

    Min Kim, Jung; Kate Gurnon, A.; Wagner, Norman J., E-mail: wagnernj@udel.edu [Department of Chemical and Biomolecular Engineering and Center for Neutron Science, University of Delaware, Newark, Delaware 19716 (United States); Eberle, Aaron P. R. [NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Porcar, Lionel [NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 and Institut Laue-Langevin, BP 156, F-38042 Grenoble Cedex 9 (France)

    2014-09-01

    The microstructure-rheology relationship for a model, thermoreversible nanoparticle gel is investigated using a new technique of time-resolved neutron scattering under steady and time-resolved large amplitude oscillatory shear (LAOS) flows. A 21 vol. % gel is tested with varying strength of interparticle attraction. Shear-induced structural anisotropy is observed as butterfly scattering patterns and quantified through an alignment factor. Measurements in the plane of flow show significant, local anisotropy develops with alignment along the compressional axis of flow, providing new insights into how gels flow. The microstructure-rheology relationship is analyzed through a new type of structure-Lissajous plot that shows how the anisotropic microstructure is responsible for the observed LAOS response, which is beyond a response expected for a purely viscous gel with constant structure. The LAOS shear viscosities are observed to follow the “Delaware-Rutgers” rule. Rheological and microstructural data are successfully compared across a broad range of conditions by scaling the shear rate by the strength of attraction, providing a method to compare behavior between steady shear and LAOS experiments. However, important differences remain between the microstructures measured at comparatively high frequency in LAOS experiments and comparable steady shear experiments that illustrate the importance of measuring the microstructure to properly interpret the nonlinear, dynamic rheological response.

  17. Effect of Re on stacking fault nucleation under shear strain in Ni by atomistic simulation

    Liu Zheng-Guang; Wang Chong-Yu; Yu Tao

    2014-01-01

    The effect of Re on stacking fault (SF) nucleation under shear strain in Ni is investigated using the climbing image nudged elastic band method with a Ni—Al—Re embedded-atom-method potential. A parameter (ΔE sf b ), the activation energy of SF nucleation under shear strain, is introduced to evaluate the effect of Re on SF nucleation under shear strain. Calculation results show that ΔE sf b decreases with Re addition, which means that SF nucleation under shear strain in Ni may be enhanced by Re. The atomic structure observation shows that the decrease of ΔE sf b may be due to the expansion of local structure around the Re atom when SF goes through the Re atom. (rapid communication)

  18. Ideal MHD stability properties of pressure-driven modes in low shear tokamaks

    Manickam, J.; Pomphrey, N.; Todd, A.M.M.

    1987-03-01

    The role of shear in determining the ideal MHD stability properties of tokamaks is discussed. In particular, we assess the effects of low shear within the plasma upon pressure-driven modes. The standard ballooning theory is shown to break down, as the shear is reduced and the growth rate is shown to be an oscillatory function of n, the toroidal mode number, treated as a continuous parameter. The oscillations are shown to depend on both the pressure and safety-factor profiles. When the shear is sufficiently weak, the oscillations can result in bands of unstable n values which are present even when the standard ballooning theory predicts complete stability. These instabilities are named ''infernal modes.'' The occurrence of these instabilities at integer n is shown to be a sensitive function of q-axis, raising the possibility of a sharp onset as plasma parameters evolve. 20 refs., 31 figs

  19. Strengthening of Shear Walls

    Hansen, Christian Skodborg

    The theory for concrete structures strengthened with fiber reinforced polymer materials has been developing for approximately two decades, and there are at the present time numerous guidelines covering strengthening of many commonly encountered structural building elements. Strengthening of in...... that describes a unit width strip of a strengthened disk. The unit width strip is named a strengthened concrete tension member and contains a single tensile crack and four debonding cracks. Analysis of the member results in closed form expressions for the load-crack opening relationship. Further analysis...... of the response, results in the ability to determine and characterize the two-way crack propagation, i.e. the relationship between tensile cracking in the concrete and interface debonding between strengthening and concrete. Using the load-crack opening relationship from the strengthened concrete tension member...

  20. Shear behaviour of reinforced phyllite concrete beams

    Adom-Asamoah, Mark; Owusu Afrifa, Russell

    2013-01-01

    Highlights: ► Phyllite concrete beams often exhibited shear with anchorage bond failure. ► Different shear design provisions for reinforced phyllite beams are compared. ► Predicted shear capacity of phyllite beams must be modified by a reduction factor. -- Abstract: The shear behaviour of concrete beams made from phyllite aggregates subjected to monotonic and cyclic loading is reported. First diagonal shear crack load of beams with and without shear reinforcement was between 42–58% and 42–92% of the failure loads respectively. The phyllite concrete beams without shear links had lower post-diagonal cracking shear resistance compared to corresponding phyllite beams with shear links. As a result of hysteretic energy dissipation, limited cyclic loading affected the stiffness, strength and deformation of the phyllite beams with shear reinforcement. Generally, beams with and without shear reinforcement showed anchorage bond failure in addition to the shear failure due to high stress concentration near the supports. The ACI, BS and EC codes are conservative for the prediction of phyllite concrete beams without shear reinforcement but they all overestimate the shear strength of phyllite concrete beams with shear reinforcement. It is recommended that the predicted shear capacity of phyllite beams reinforced with steel stirrups be modified by a reduction factor of 0.7 in order to specify a high enough safety factor on their ultimate strength. It is also recommended that susceptibility of phyllite concrete beams to undergo anchorage bond failure is averted in design by the provision of greater anchorage lengths than usually permitted.

  1. Band parameters of phosphorene

    Lew Yan Voon, L C; Wang, J; Zhang, Y; Willatzen, M

    2015-01-01

    Phosphorene is a two-dimensional nanomaterial with a direct band-gap at the Brillouin zone center. In this paper, we present a recently derived effective-mass theory of the band structure in the presence of strain and electric field, based upon group theory. Band parameters for this theory are computed using a first-principles theory based upon the generalized-gradient approximation to the density-functional theory. These parameters and Hamiltonian will be useful for modeling physical properties of phosphorene. (paper)

  2. Infrared diffuse interstellar bands

    Galazutdinov, G. A.; Lee, Jae-Joon; Han, Inwoo; Lee, Byeong-Cheol; Valyavin, G.; Krełowski, J.

    2017-05-01

    We present high-resolution (R ˜ 45 000) profiles of 14 diffuse interstellar bands in the ˜1.45 to ˜2.45 μm range based on spectra obtained with the Immersion Grating INfrared Spectrograph at the McDonald Observatory. The revised list of diffuse bands with accurately estimated rest wavelengths includes six new features. The diffuse band at 15 268.2 Å demonstrates a very symmetric profile shape and thus can serve as a reference for finding the 'interstellar correction' to the rest wavelength frame in the H range, which suffers from a lack of known atomic/molecular lines.

  3. Band parameters of phosphorene

    Lew Yan Voon, L. C.; Wang, J.; Zhang, Y.

    2015-01-01

    Phosphorene is a two-dimensional nanomaterial with a direct band-gap at the Brillouin zone center. In this paper, we present a recently derived effective-mass theory of the band structure in the presence of strain and electric field, based upon group theory. Band parameters for this theory...... are computed using a first-principles theory based upon the generalized-gradient approximation to the density-functional theory. These parameters and Hamiltonian will be useful for modeling physical properties of phosphorene....

  4. A sensitive dynamic viscometer for measuring the complex shear modulus in a steady shear flow using the method of orthogonal superposition

    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

  5. Spatial bandwidth enlargement and field enhancement of shear horizontal waves in finite graded piezoelectric layered media

    Xu, Yanlong

    2015-09-01

    Shear horizontal (SH) wave propagation in finite graded piezoelectric layered media is investigated by transfer matrix method. Different from the previous studies on SH wave propagation in completely periodic layered media, calculations on band structure and transmission in this paper show that the graded layered media possess very large band gaps. Harmonic wave simulation by finite element method (FEM) confirms that the reason of bandwidth enlargement is that waves within the band gap ranges are spatially enhanced and stopped by the corresponding graded units. The study suggests that the graded structure possesses the property of manipulating elastic waves spatially, which shows potential applications in strengthening energy trapping and harvesting. © 2015.

  6. Dependence of Shear and Concentration on Fouling in a Membrane Bioreactor with Rotating Membrane Discs

    Jørgensen, Mads Koustrup; Pedersen, Malene Thostrup; Christensen, Morten Lykkegaard

    2014-01-01

    Rotating ceramic membrane discs were fouled with lab-scale membrane bioreactors (MBR) sludge. Sludge filtrations were performed at varying rotation speeds and in different concentric rings of the membranes on different sludge concentrations. Data showed that the back transport expressed by limiting...... flux increased with rotation speed and distance from membrane center as an effect of shear. Further, the limiting flux decreased with increasing sludge concentration. A model was developed to link the sludge concentration and shear stress to the limiting flux. The model was able to simulate the effect...... of shear stress and sludge concentration on the limiting flux. The model was developed by calculating the shear rate at laminar flow regime at different rotation speeds and radii on the membrane. Furthermore, through the shear rate and shear stress, the non-Newtonian behavior of MBR sludge was addressed...

  7. Ultra-Wideband Optical Modulation Spectrometer (OMS) Development: Study of the Optical Setup of a Wide-Band Optical Modulation Spectrometer

    Tolls, Volker; Stringfellow, Guy (Technical Monitor)

    2001-01-01

    The purpose of this study is to advance the design of the optical setup for a wide-band Optical Modulation Spectrometer (OMS) for use with astronomical heterodyne receiver systems. This report describes the progress of this investigation achieved from March until December 2001.

  8. Development of Seasonal BRDF Models to Extend the Use of Deep Convective Clouds as Invariant Targets for Satellite SWIR-Band Calibration

    Rajendra Bhatt

    2017-10-01

    Full Text Available Tropical deep convective clouds (DCC are an excellent invariant target for vicarious calibration of satellite visible (VIS and near-infrared (NIR solar bands. The DCC technique (DCCT is a statistical approach that collectively analyzes all identified DCC pixels on a monthly basis. The DCC reflectance in VIS and NIR spectrums is mainly a function of cloud optical depth, and provides a stable monthly statistical mode. However, for absorption shortwave infrared (SWIR bands, the monthly DCC response is found to exhibit large seasonal cycles that make the implementation of the DCCT more challenging at these wavelengths. The seasonality assumption was tested using the SNPP-VIIRS SWIR bands, with up to 50% of the monthly DCC response temporal variation removed through deseasonalization. In this article, a monthly DCC bidirectional reflectance distribution function (BRDF approach is proposed, which is found to be comparable to or can outperform the effects of deseasonalization alone. To demonstrate that the SNPP-VIIRS DCC BRDF can be applied to other JPSS VIIRS imagers in the same 13:30 sun-synchronous orbit, the VIIRS DCC BRDF was applied to Aqua-MODIS. The Aqua-MODIS SWIR band DCC reflectance natural variability is reduced by up to 45% after applying the VIIRS-based monthly DCC BRDFs.

  9. Shear instability of a gyroid diblock copolymer

    Eskimergen, Rüya; Mortensen, Kell; Vigild, Martin Etchells

    2005-01-01

    -induced destabilization is discussed in relation to analogous observations on shear-induced order-to-order and disorder-to-order transitions observed in related block copolymer systems and in microemulsions. It is discussed whether these phenomena originate in shear-reduced fluctuations or shear-induced dislocations....

  10. Insulation interlaminar shear strength testing with compression and irradiation

    McManamy, T.J.; Brasier, J.E.; Snook, P.

    1989-01-01

    The Compact Ignition Tokamak (CIT) project identified the need for research and development for the insulation to be used in the toroidal field coils. The requirements included tolerance to a combination of high compression and shear and a high radiation dose. Samples of laminate-type sheet material were obtained from commercial vendors. The materials included various combinations of epoxy, polyimide, E-glass, S-glass, and T-glass. The T-glass was in the form of a three-dimensional weave. The first tests were with 50 x 25 x 1 mm samples. These materials were loaded in compression and then to failure in shear. At 345-MPa compression, the interlaminar shear strength was generally in the range of 110 to 140 MPa for the different materials. A smaller sample configuration was developed for irradiation testing. The data before irradiation were similar to those for the larger samples but approximately 10% lower. Limited fatigue testing was also performed by cycling the shear load. No reduction in shear strength was found after 50,000 cycles at 90% of the failure stress. Because of space limitations, only three materials were chosen for irradiation: two polyimide systems and one epoxy system. All used boron-free glass. The small shear/compression samples and some flexure specimens were irradiated to 4 x 10 9 and 2 x 10 10 rad in the Advanced Technology Reactor at Idaho National Engineering Laboratory. A lead shield was used to ensure that the majority of the dose was from neutrons. The shear strength with compression before and after irradiation at the lower dose was determined. Flexure strength and the results from irradiation at the higher dose level will be available in the near future. 7 refs., 7 figs., 2 tabs

  11. CSF oligoclonal banding - slideshow

    ... this page: //medlineplus.gov/ency/presentations/100145.htm CSF oligoclonal banding - series—Normal anatomy To use the ... 5 out of 5 Overview The cerebrospinal fluid (CSF) serves to supply nutrients to the central nervous ...

  12. Decay of superdeformed bands

    Carpenter, M.P.; Khoo, T.L.; Lauritsen, T.

    1995-01-01

    One of the major challenges in the study of superdeformation is to directly connect the large number of superdeformed bands now known to the yrast states. In this way, excitation energies, spins and parities can be assigned to the levels in the second well which is essential to establish the collective and single-particle components of these bands. This paper will review some of the progress which has been made to understand the decay of superdeformed bands using the new arrays including the measurement of the total decay spectrum and the establishment of direct one-step decays from the superdeformed band to the yrast line in 194 Hg. 42 refs., 5 figs

  13. Laparoscopic gastric banding

    ... eat by making you feel full after eating small amounts of food. After surgery, your doctor can adjust the band ... You will feel full after eating just a small amount of food. The food in the small upper pouch will ...

  14. Sheared flow layer formation in tokamak plasmas with reversed magnetic shear

    Dong, J.Q.; Long, Y.X.; Mou, Z.Z.; Zhang, J.H.; Li, J.Q.

    2005-01-01

    Sheared flow layer (SFL) formation due to magnetic energy release through tearing-reconnections in tokamak plasmas is investigated. The characteristics of the SFLs created in the development of double tearing mode, mediated by electron viscosity in configurations with non-monotonic safety factor q profiles and, therefore, two rational flux surfaces of same q value, are analyzed in detail as an example. Quasi-linear simulations demonstrate that the sheared flows induced by the mode have desirable characteristics (lying at the boundaries of the magnetic islands), and sufficient levels required for internal transport barrier (ITB) formation. A possible correlation of the SFLs with experimental observations, that double transport barrier structures are preferentially formed in proximity of the two rational surfaces, is also proffered. (author)

  15. Statistical Model of Extreme Shear

    Larsen, Gunner Chr.; Hansen, Kurt Schaldemose

    2004-01-01

    In order to continue cost-optimisation of modern large wind turbines, it is important to continously increase the knowledge on wind field parameters relevant to design loads. This paper presents a general statistical model that offers site-specific prediction of the probability density function...... by a model that, on a statistically consistent basis, describe the most likely spatial shape of an extreme wind shear event. Predictions from the model have been compared with results from an extreme value data analysis, based on a large number of high-sampled full-scale time series measurements...... are consistent, given the inevitabel uncertainties associated with model as well as with the extreme value data analysis. Keywords: Statistical model, extreme wind conditions, statistical analysis, turbulence, wind loading, statistical analysis, turbulence, wind loading, wind shear, wind turbines....

  16. Shear failure of granular materials

    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

  17. Shear horizontal wave excitation and reception with shear horizontal piezoelectric wafer active sensor (SH-PWAS)

    Kamal, A; Giurgiutiu, V

    2014-01-01

    This article discusses shear horizontal (SH) guided-waves that can be excited with shear type piezoelectric wafer active sensor (SH-PWAS). The paper starts with a review of state of the art SH waves modelling and their importance in non-destructive evaluation (NDE) and structural health monitoring (SHM). The basic piezoelectric sensing and actuation equations for the case of shear horizontal piezoelectric wafer active sensor (SH-PWAS) with electro-mechanical coupling coefficient d 35 are reviewed. Multiphysics finite element modelling (MP-FEM) was performed on a free SH-PWAS to show its resonance modeshapes. The actuation mechanism of the SH-PWAS is predicted by MP-FEM, and modeshapes of excited structure are presented. The structural resonances are compared with experimental measurements and showed good agreement. Analytical prediction of SH waves was performed. SH wave propagation experimental study was conducted between different combinations of SH-PWAS and regular in-plane PWAS transducers. Experimental results were compared with analytical predictions for aluminium plates and showed good agreement. 2D wave propagation effects were studied by MP-FEM. An analytical model was developed for SH wave power and energy. The normal mode expansion (NME) method was used to account for superpositioning multimodal SH waves. Modal participation factors were presented to show the contribution of every mode. Power and energy transfer between SH-PWAS and the structure was analyzed. Finally, we present simulations of our developed wave power and energy analytical models. (paper)

  18. Structural Evolution of a Warm Frontal Precipitation Band During GCPEx

    Colle, Brian A.; Naeger, Aaron; Molthan, Andrew; Nesbitt, Stephen

    2015-01-01

    A warm frontal precipitation band developed over a few hours 50-100 km to the north of a surface warm front. The 3-km WRF was able to realistically simulate band development, although the model is somewhat too weak. Band genesis was associated with weak frontogenesis (deformation) in the presence of weak potential and conditional instability feeding into the band region, while it was closer to moist neutral within the band. As the band matured, frontogenesis increased, while the stability gradually increased in the banding region. Cloud top generating cells were prevalent, but not in WRF (too stable). The band decayed as the stability increased upstream and the frontogenesis (deformation) with the warm front weakened. The WRF may have been too weak and short-lived with the band because too stable and forcing too weak (some micro issues as well).

  19. Haptic Edge Detection Through Shear

    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.

  20. Development of an S-band cavity-type beam position monitor for a high power THz free-electron laser

    Noh, Seon Yeong; Kim, Eun-San, E-mail: eskim1@knu.ac.kr; Hwang, Ji-Gwang; Heo, A.; Won, Jang Si [Department of Physics, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Vinokurov, Nikolay A.; Jeong, Young UK, E-mail: yujung@kaeri.re.kr; Hee Park, Seong; Jang, Kyu-Ha [WCI Center for Quantum-Beam-based Radiation Research, Korea Atomic Energy Research Institute, 989-111 Daedeok-Daero, Yuseong-gu, Daejeon (Korea, Republic of)

    2015-01-15

    A cavity-type beam position monitor (BPM) has been developed for a compact terahertz (THz) free-electron laser (FEL) system and ultra-short pulsed electron Linac system at the Korea Atomic Energy Research Institute (KAERI). Compared with other types of BPMs, the cavity-type BPM has higher sensitivity and faster response time even at low charge levels. When electron beam passes through the cavity-type BPM, it excites the dipole mode of the cavity of which amplitude depends linearly on the beam offset from the center of the cavity. Signals from the BPM were measured as a function of the beam offset by using an oscilloscope. The microtron accelerator for the KAERI THz FEL produces the electron beam with an energy of 6.5 MeV and pulse length of 5 μs with a micropulse of 10-20 ps at the frequency of 2.801 GHz. The macropulse beam current is 40 mA. Because the microtron provides multi-bunch system, output signal would be the superposition of each single bunch. So high output signal can be obtained from superposition of each single bunch. The designed position resolution of the cavity-type BPM in multi-bunch is submicron. Our cavity-type BPM is made of aluminum and vacuum can be maintained by indium sealing without brazing process, resulting in easy modification and cost saving. The resonance frequency of the cavity-type BPM is 2.803 GHz and the cavity-type BPM dimensions are 200 × 220 mm (length × height) with a pipe diameter of 38 mm. The measured position sensitivity was 6.19 (mV/mm)/mA and the measured isolation between the X and Y axis was −39 dB. By measuring the thermal noise of system, position resolution of the cavity-type BPM was estimated to be less than 1 μm. In this article, we present the test results of the S-band cavity-type BPM and prove the feasibility of the beam position measurement with high resolution using this device.

  1. Development of an S-band cavity-type beam position monitor for a high power THz free-electron laser

    Noh, Seon Yeong; Kim, Eun-San; Hwang, Ji-Gwang; Heo, A.; won Jang, Si; Vinokurov, Nikolay A.; Jeong, Young UK; Hee Park, Seong; Jang, Kyu-Ha

    2015-01-01

    A cavity-type beam position monitor (BPM) has been developed for a compact terahertz (THz) free-electron laser (FEL) system and ultra-short pulsed electron Linac system at the Korea Atomic Energy Research Institute (KAERI). Compared with other types of BPMs, the cavity-type BPM has higher sensitivity and faster response time even at low charge levels. When electron beam passes through the cavity-type BPM, it excites the dipole mode of the cavity of which amplitude depends linearly on the beam offset from the center of the cavity. Signals from the BPM were measured as a function of the beam offset by using an oscilloscope. The microtron accelerator for the KAERI THz FEL produces the electron beam with an energy of 6.5 MeV and pulse length of 5 μs with a micropulse of 10-20 ps at the frequency of 2.801 GHz. The macropulse beam current is 40 mA. Because the microtron provides multi-bunch system, output signal would be the superposition of each single bunch. So high output signal can be obtained from superposition of each single bunch. The designed position resolution of the cavity-type BPM in multi-bunch is submicron. Our cavity-type BPM is made of aluminum and vacuum can be maintained by indium sealing without brazing process, resulting in easy modification and cost saving. The resonance frequency of the cavity-type BPM is 2.803 GHz and the cavity-type BPM dimensions are 200 × 220 mm (length × height) with a pipe diameter of 38 mm. The measured position sensitivity was 6.19 (mV/mm)/mA and the measured isolation between the X and Y axis was -39 dB. By measuring the thermal noise of system, position resolution of the cavity-type BPM was estimated to be less than 1 μm. In this article, we present the test results of the S-band cavity-type BPM and prove the feasibility of the beam position measurement with high resolution using this device.

  2. CFD simulation of estimating critical shear stress for cleaning flat ...

    Sumit Kawale

    2017-11-22

    Nov 22, 2017 ... Jet impingement; wall shear stress; cleaning of flat plate; turbulence model; critical shear stress; ... On comparing the theoretical predictions with wall shear ... distance and Reynolds number on peak value of local shear stress ...

  3. Broad-band near-field ground motion simulations in 3-dimensional scattering media

    Imperatori, W.

    2012-12-06

    The heterogeneous nature of Earth\\'s crust is manifested in the scattering of propagating seismic waves. In recent years, different techniques have been developed to include such phenomenon in broad-band ground-motion calculations, either considering scattering as a semi-stochastic or purely stochastic process. In this study, we simulate broad-band (0–10 Hz) ground motions with a 3-D finite-difference wave propagation solver using several 3-D media characterized by von Karman correlation functions with different correlation lengths and standard deviation values. Our goal is to investigate scattering characteristics and its influence on the seismic wavefield at short and intermediate distances from the source in terms of ground motion parameters. We also examine scattering phenomena, related to the loss of radiation pattern and the directivity breakdown. We first simulate broad-band ground motions for a point-source characterized by a classic ω2 spectrum model. Fault finiteness is then introduced by means of a Haskell-type source model presenting both subshear and super-shear rupture speed. Results indicate that scattering plays an important role in ground motion even at short distances from the source, where source effects are thought to be dominating. In particular, peak ground motion parameters can be affected even at relatively low frequencies, implying that earthquake ground-motion simulations should include scattering also for peak ground velocity (PGV) calculations. At the same time, we find a gradual loss of the source signature in the 2–5 Hz frequency range, together with a distortion of the Mach cones in case of super-shear rupture. For more complex source models and truly heterogeneous Earth, these effects may occur even at lower frequencies. Our simulations suggests that von Karman correlation functions with correlation length between several hundred metres and few kilometres, Hurst exponent around 0.3 and standard deviation in the 5–10 per cent

  4. Continuous shear - a method for studying material elements passing a stationary shear plane

    Lindegren, Maria; Wiwe, Birgitte; Wanheim, Tarras

    2003-01-01

    circumferential groove. Normally shear in metal forming processes is of another nature, namely where the material elements move through a stationary shear zone, often of small width. In this paper a method enabling the simulation of this situation is presented. A tool for continuous shear has beeen manufactured...... and tested with AlMgSil and copper. The sheared material has thereafter been tested n plane strain compression with different orientation concerning the angle between the shear plane and the compression direction....

  5. Combined Ideal and Kinetic Effects on Reversed Shear Alfven Eigenmodes

    Gorelenkov, N.N.; Kramer, G.J.; Nazikian, R.

    2011-01-01

    A theory of Reversed Shear Alfven Eigenmodes (RSAEs) is developed for reversed magnetic field shear plasmas when the safety factor minimum, qmin, is at or above a rational value. The modes we study are known sometimes as either the bottom of the frequency sweep or the down sweeping RSAEs. We show that the ideal MHD theory is not compatible with the eigenmode solution in the reversed shear plasma with qmin above integer values. Corrected by special analytic FLR condition MHD dispersion of these modes nevertheless can be developed. Large radial scale part of the analytic RSAE solution can be obtained from ideal MHD and expressed in terms of the Legendre functions. The kinetic equation with FLR effects for the eigenmode is solved numerically and agrees with the analytic solutions. Properties of RSAEs and their potential implications for plasma diagnostics are discussed.

  6. Combined ideal and kinetic effects on reversed shear Alfven eigenmodes

    Gorelenkov, N. N.; Kramer, G. J.; Nazikian, R.

    2011-01-01

    A reversed shear Alfven eigenmodes (RSAEs) theory has been developed for reversed magnetic field shear plasmas when the safety factor minimum, q min , is at or above a rational value. The modes we study are known sometimes as either the bottom of the frequency sweep or the down sweeping RSAEs. We show that, strictly speaking, the ideal MHD theory is not compatible with the eigenmode solution in the reversed shear plasma with q min above integer values. Corrected by a special analytic finite Larmor radius (FLR) condition, MHD dispersion of these modes nevertheless can be developed. Numerically, MHD structure can serve as a good approximation for the RSAEs.The large radial scale part of the analytic RSAE solution can be obtained from ideal MHD and expressed in terms of the Legendre functions. The kinetic equation with FLR effects for the eigenmode is solved numerically and agrees with the analytic solutions. Properties of RSAEs and their potential implications for plasma diagnostics are discussed.

  7. Simulations of Granular Particles Under Cyclic Shear

    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.

  8. Design proposal for ultimate shear strength of tapered steel plate girders

    A. Bedynek

    2017-03-01

    Full Text Available Numerous experimental and numerical studies on prismatic plate girders subjected to shear can be found in the literature. However, the real structures are frequently designed as non-uniform structural elements. The main objective of the research is the development of a new proposal for the calculation of the ultimate shear resistance of tapered steel plate girders taking into account the specific behaviour of such members. A new mechanical model is presented in the paper and it is used to show the differences between the behaviour of uniform and tapered web panels subjected to shear. EN 1993-1-5 design specifications for the determination of the shear strength for rectangular plates are improved in order to assess the shear strength of tapered elements. Numerical studies carried out on tapered steel plate girders subjected to shear lead to confirm the suitability of the mechanical model and the proposed design expression.

  9. Heavy metal contents in growth bands of Porites corals: Record of anthropogenic and human developments from the Jordanian Gulf of Aqaba

    Al-Rousan, Saber A.; Al-Shloul, Rashid N.; Al-Horani, Fuad A.; Abu-Hilal, Ahmad H.

    2007-01-01

    In order to assess pollutants and impact of environmental changes in the coastal region of the Jordanian Gulf of Aqaba, concentrations of six metals were traced through variations in 5 years growth bands sections of recent Porties coral skeleton. X-radiography showed annual growth band patterns extending back to the year 1925. Baseline metal concentrations in Porites corals were established using 35 years-long metal record from late Holocene coral (deposited in pristine environment) and coral from reef that is least exposed to pollution in the marine reserve in the Gulf of Aqaba. The skeleton samples of the collected corals were acid digested and analyzed for their Cd, Cu, Fe, Mn, Pb and Zn content using Flame Atomic Absorption Spectrophotometer (FAAS). All metal profiles (except Fe and Zn) recorded the same metal signature from recent coral (1925-2005) in which low steady baseline levels were displayed in growth bands older than 1965, similar to those obtained from fossil and unpolluted corals. Most metals showed dramatic increase (ranging from 17% to 300%) in growth band sections younger than 1965 suggesting an extensive contamination of the coastal area since the mid sixties. This date represents the beginning of a period that witnessed increasing coastal activities, constructions and urbanization. This has produced a significant reduction in coral skeletal extension rates. Results from this study strongly suggest that Porites corals have a high tendency to accumulate heavy metals in their skeletons and therefore can serve as proxy tools to monitor and record environmental pollution (bioindicators) in the Gulf of Aqaba

  10. Heavy metal contents in growth bands of Porites corals: Record of anthropogenic and human developments from the Jordanian Gulf of Aqaba

    Al-Rousan, Saber A. [Marine Science Station, University of Jordan and Yarmouk University, P.O. Box 195, Aqaba 77110 (Jordan)], E-mail: s.rousan@ju.edu.jo; Al-Shloul, Rashid N. [Department of Earth and Environmental Science, Faculty of Science, Yarmouk University, Irbid 21163 (Jordan); Al-Horani, Fuad A. [Marine Science Station, University of Jordan and Yarmouk University, P.O. Box 195, Aqaba 77110 (Jordan); Abu-Hilal, Ahmad H. [Department of Earth and Environmental Science, Faculty of Science, Yarmouk University, Irbid 21163 (Jordan)

    2007-12-15

    In order to assess pollutants and impact of environmental changes in the coastal region of the Jordanian Gulf of Aqaba, concentrations of six metals were traced through variations in 5 years growth bands sections of recent Porties coral skeleton. X-radiography showed annual growth band patterns extending back to the year 1925. Baseline metal concentrations in Porites corals were established using 35 years-long metal record from late Holocene coral (deposited in pristine environment) and coral from reef that is least exposed to pollution in the marine reserve in the Gulf of Aqaba. The skeleton samples of the collected corals were acid digested and analyzed for their Cd, Cu, Fe, Mn, Pb and Zn content using Flame Atomic Absorption Spectrophotometer (FAAS). All metal profiles (except Fe and Zn) recorded the same metal signature from recent coral (1925-2005) in which low steady baseline levels were displayed in growth bands older than 1965, similar to those obtained from fossil and unpolluted corals. Most metals showed dramatic increase (ranging from 17% to 300%) in growth band sections younger than 1965 suggesting an extensive contamination of the coastal area since the mid sixties. This date represents the beginning of a period that witnessed increasing coastal activities, constructions and urbanization. This has produced a significant reduction in coral skeletal extension rates. Results from this study strongly suggest that Porites corals have a high tendency to accumulate heavy metals in their skeletons and therefore can serve as proxy tools to monitor and record environmental pollution (bioindicators) in the Gulf of Aqaba.

  11. Use of the shearing interferometry for dense inhomogeneous plasma diagnostics

    Zakharenkov, Yu.A.; Sklizkov, G.V.; Shikanov, A.S.

    1980-01-01

    Investigated is a possibility of applying the shearing interferometry for diagnostics of a dense inhomogeneous laser plasma which makes it possible to measure the electron density without losses in accuracy near the critical surface. A shearing interferogram is formed upon interference of two identical images of the object under study shifted at some fixed distance. The value of the interference band deflection inside phase inhomogeneity depends on the gradient of the index of refraction in the direction of shift. It has been found that for studying the inner region of the laser plasma a small shift should be used, and for the external one - a large one. The version of a radial shift interferometry is shown to be optimum. For the inner region of the interferogram the error of the electron density restoration does not exceed 10%, and for the external one the error is comparable with that for the version of standard interferometry. A systematic analysis of the optimum type interferometers shows advantages of shearing interferometers. The maximum electron density recorded in experiments makes up approximately equal to 10 20 cm -3 , which is 3-5 times higher than the corresponding value obtained by a standard double-slit type interferometer at equal limiting parameters of the optical system applied

  12. High Efficiency Traveling-Wave Tube Power Amplifier for Ka-Band Software Defined Radio on International Space Station-A Platform for Communications Technology Development

    Simons, Rainee N.; Force, Dale A.; Kacpura, Thomas J.

    2013-01-01

    The design, fabrication and RF performance of the output traveling-wave tube amplifier (TWTA) for a space based Ka-band software defined radio (SDR) is presented. The TWTA, the SDR and the supporting avionics are integrated to forms a testbed, which is currently located on an exterior truss of the International Space Station (ISS). The SDR in the testbed communicates at Ka-band frequencies through a high-gain antenna directed to NASA s Tracking and Data Relay Satellite System (TDRSS), which communicates to the ground station located at White Sands Complex. The application of the testbed is for demonstrating new waveforms and software designed to enhance data delivery from scientific spacecraft and, the waveforms and software can be upgraded and reconfigured from the ground. The construction and the salient features of the Ka-band SDR are discussed. The testbed is currently undergoing on-orbit checkout and commissioning and is expected to operate for 3 to 5 years in space.

  13. Borehole Shear Device Phase II Development.

    1982-02-01

    FIGURE 8 ITEM QUANTITY DESCRIPTION B1 1 Torque/Normal Load Transducer - First Extension Coupling. B2 1 Torque/Normal Load Transducer - Gauge Tube. B3 I...235, type RFN 7012. Supplier - Ringfeder Limited, Forum Drive, Midland Indus- trial Estate, Rugby , Warwickshire CV21 iNT, UK. FB 1 Expanding Friction...Midland Industrial Estate, Rugby , Warwickshire CV21 INT, UK. GF 2 Deep Groove Ball Bearing (upper support bearing), 80 x 100 x 10. Supplier - SKF ref

  14. Research Advances on Fabricated Shear Wall System

    Liu, Xudong; Wang, Donghui; Wang, Sheng; Zhai, Yu

    2018-03-01

    With the rapid development of the construction industry, building energy consumption has been increasing, has become a problem that can not be ignored. It is imperative to develop energy-saving buildings. A new type of prefabricated shear wall is assembled and partially assembled by prefabricated parts, and some concrete is spliced together. The new structure has good integrity, seismic resistance and excellent energy saving and environmental protection performance. It reduces building energy consumption to a great extent. Therefore, the design method, manufacturing process, site assembly process and key technical problems of the system are discussed. For the construction industry gradually entered the energy conservation, environmental protection, safety and durability of sustainable development laid the foundation.

  15. Full L-S Band Telemetry System

    Jensen, Michael

    2001-01-01

    Recent changes in spectrum availability as well as higher demands for spectrum have motivated the development of telemetry transmit systems capable of fully operating over both L and S telemetry bands...

  16. Full L-S Band Telemetry System

    Jensen, Michael

    2003-01-01

    Recent changes in spectrum availability as well as higher demands for spectrum have motivated the development of telemetry transmit systems capable of fully operating over both L and S telemetry bands...

  17. Full L-S Band Telemetry System

    Jensen, Michael

    2002-01-01

    Recent changes in spectrum availability as well as higher demands for spectrum have motivated the development of telemetry transmit systems capable of fully operating over both L and S telemetry bands...

  18. Wind Shear Identification with the Retrieval Wind of Doppler Wearth Radar

    Zhou, S.; Cui, Y.; Zheng, H.; Zhang, T.

    2018-05-01

    A new method, which based on the wind field retrieval algorithm of Volume Velocity Process (VVP), has been used to identified the intensity of wind shear occurred in a severe convection process in Guangzhou. The intensity of wind shear's strength shown that new cells would be more likely to generate in areas where the magnitude generally larger than 3.0 m/(s*km). Moreover, in the areas of potential areas of rainfall, the wind shear's strength would larger than 4.5 m/(s*km). This wind shear identify method is very helpful to forecasting severe convections' moving and developments.

  19. Thermal conductivity of graphene nanoribbons under shear deformation: A molecular dynamics simulation

    Zhang, Chao; Hao, Xiao-Li; Wang, Cui-Xia; Wei, Ning; Rabczuk, Timon

    2017-01-01

    Tensile strain and compress strain can greatly affect the thermal conductivity of graphene nanoribbons (GNRs). However, the effect of GNRs under shear strain, which is also one of the main strain effect, has not been studied systematically yet. In this work, we employ reverse nonequilibrium molecular dynamics (RNEMD) to the systematical study of the thermal conductivity of GNRs (with model size of 4 nm × 15 nm) under the shear strain. Our studies show that the thermal conductivity of GNRs is not sensitive to the shear strain, and the thermal conductivity decreases only 12–16% before the pristine structure is broken. Furthermore, the phonon frequency and the change of the micro-structure of GNRs, such as band angel and bond length, are analyzed to explore the tendency of thermal conductivity. The results show that the main influence of shear strain is on the in-plane phonon density of states (PDOS), whose G band (higher frequency peaks) moved to the low frequency, thus the thermal conductivity is decreased. The unique thermal properties of GNRs under shear strains suggest their great potentials for graphene nanodevices and great potentials in the thermal managements and thermoelectric applications. PMID:28120921

  20. Amphibious Shear Velocity Structure of the Cascadia Subduction Zone

    Janiszewski, H. A.; Gaherty, J. B.; Abers, G. A.; Gao, H.

    2017-12-01

    The amphibious Cascadia Initiative crosses the coastline of the Cascadia subduction zone (CSZ) deploying seismometers from the Juan de Fuca ridge offshore to beyond the volcanic arc onshore. This allows unprecedented seismic imaging of the CSZ, enabling examination of both the evolution of the Juan de Fuca plate prior to and during subduction as well as the along strike variability of the subduction system. Here we present new results from an amphibious shear velocity model for the crust and upper mantle across the Cascadia subduction zone. The primary data used in this inversion are surface-wave phase velocities derived from ambient-noise Rayleigh-wave data in the 10 - 20 s period band, and teleseismic earthquake Rayleigh wave phase velocities in the 20 - 160 s period band. Phase velocity maps from these data reflect major tectonic structures including the transition from oceanic to continental lithosphere, Juan de Fuca lithosphere that is faster than observations in the Pacific for oceanic crust of its age, slow velocities associated with the accretionary prism, the front of the fast subducting slab, and the Cascades volcanic arc which is associated with slower velocities in the south than in the north. Crustal structures are constrained by receiver functions in the offshore forearc and onshore regions, and by active source constraints on the Juan de Fuca plate prior to subduction. The shear-wave velocities are interpreted in their relationships to temperature, presence of melt or hydrous alteration, and compositional variation of the CSZ.

  1. [Gastric band erosion: Alternative management].

    Echaverry-Navarrete, Denis José; Maldonado-Vázquez, Angélica; Cortes-Romano, Pablo; Cabrera-Jardines, Ricardo; Mondragón-Pinzón, Erwin Eduardo; Castillo-González, Federico Armando

    2015-01-01

    Obesity is a public health problem, for which the prevalence has increased worldwide at an alarming rate, affecting 1.7 billion people in the world. To describe the technique employed in incomplete penetration of gastric band where endoscopic management and/or primary closure is not feasible. Laparoscopic removal of gastric band was performed in five patients with incomplete penetrance using Foley catheterization in the perforation site that could lead to the development of a gastro-cutaneous fistula. The cases presented include a leak that required surgical lavage with satisfactory outcome, and one patient developed stenosis 3 years after surgical management, which was resolved endoscopically. In all cases, the penetration site closed spontaneously. Gastric band erosion has been reported in 3.4% of cases. The reason for inserting a catheter is to create a controlled gastro-cutaneous fistula, allowing spontaneous closure. Various techniques have been described: the totally endoscopic, hybrid techniques (endoscopic/laparoscopic) and completely laparoscopic. A technique is described here that is useful and successful in cases where the above-described treatments are not viable. Copyright © 2015. Published by Masson Doyma México S.A.

  2. A new confined high pressure rotary shear apparatus: preliminary results

    Faulkner, D.; Coughlan, G.; Bedford, J. D.

    2017-12-01

    The frictional properties of fault zone materials, and their evolution during slip, are of paramount importance for determining the earthquake mechanics of large tectonic faults. Friction is a parameter that is difficult to determine from seismological methods so much of our understanding comes from experiment. Rotary shear apparatuses have been widely used in experimental studies to elucidate the frictional properties of faults under realistic earthquake slip velocities (0.1-10 m/s) and displacements (>20 m). However one technical limitation of rotary shear experiments at seismic slip rates has been the lack of confinement. This has led to a limit on the normal stress (due to the strength of the forcing blocks) and also a lack of control of measurements of the pore fluid pressure. Here we present the first preliminary results from a rotary shear apparatus that has been developed to attempt to address this issue. The new fully confined ring shear apparatus has a fast-acting servo-hydraulic confining pressure system of up to 200 MPa and a servo-controlled upstream and downstream pore pressure system of up to 200 MPa. Displacement rates of 0.01μ/s to 2 m/s can be achieved. Fault gouge samples can therefore be sheared at earthquake speed whilst being subject to pressures typically associated with the depth of earthquake nucleation.

  3. Ultra wide band antennas

    Begaud, Xavier

    2013-01-01

    Ultra Wide Band Technology (UWB) has reached a level of maturity that allows us to offer wireless links with either high or low data rates. These wireless links are frequently associated with a location capability for which ultimate accuracy varies with the inverse of the frequency bandwidth. Using time or frequency domain waveforms, they are currently the subject of international standards facilitating their commercial implementation. Drawing up a complete state of the art, Ultra Wide Band Antennas is aimed at students, engineers and researchers and presents a summary of internationally recog

  4. Statistical Model of Extreme Shear

    Hansen, Kurt Schaldemose; Larsen, Gunner Chr.

    2005-01-01

    In order to continue cost-optimisation of modern large wind turbines, it is important to continuously increase the knowledge of wind field parameters relevant to design loads. This paper presents a general statistical model that offers site-specific prediction of the probability density function...... by a model that, on a statistically consistent basis, describes the most likely spatial shape of an extreme wind shear event. Predictions from the model have been compared with results from an extreme value data analysis, based on a large number of full-scale measurements recorded with a high sampling rate...

  5. Shear Strength Measurement Benchmarking Tests for K Basin Sludge Simulants

    Burns, Carolyn A.; Daniel, Richard C.; Enderlin, Carl W.; Luna, Maria; Schmidt, Andrew J.

    2009-06-10

    Equipment development and demonstration testing for sludge retrieval is being conducted by the K Basin Sludge Treatment Project (STP) at the MASF (Maintenance and Storage Facility) using sludge simulants. In testing performed at the Pacific Northwest National Laboratory (under contract with the CH2M Hill Plateau Remediation Company), the performance of the Geovane instrument was successfully benchmarked against the M5 Haake rheometer using a series of simulants with shear strengths (τ) ranging from about 700 to 22,000 Pa (shaft corrected). Operating steps for obtaining consistent shear strength measurements with the Geovane instrument during the benchmark testing were refined and documented.

  6. Upward swimming of a sperm cell in shear flow.

    Omori, Toshihiro; Ishikawa, Takuji

    2016-03-01

    Mammalian sperm cells are required to swim over long distances, typically around 1000-fold their own length. They must orient themselves and maintain a swimming motion to reach the ovum, or egg cell. Although the mechanism of long-distance navigation is still unclear, one possible mechanism, rheotaxis, was reported recently. This work investigates the mechanism of the rheotaxis in detail by simulating the motions of a sperm cell in shear flow adjacent to a flat surface. A phase diagram was developed to show the sperm's swimming motion under different shear rates, and for varying flagellum waveform conditions. The results showed that, under shear flow, the sperm is able to hydrodynamically change its swimming direction, allowing it to swim upwards against the flow, which suggests that the upward swimming of sperm cells can be explained using fluid mechanics, and this can then be used to further understand physiology of sperm cell navigation.

  7. Handedness in shearing auxetics creates rigid and compliant structures

    Lipton, Jeffrey Ian; MacCurdy, Robert; Manchester, Zachary; Chin, Lillian; Cellucci, Daniel; Rus, Daniela

    2018-05-01

    In nature, repeated base units produce handed structures that selectively bond to make rigid or compliant materials. Auxetic tilings are scale-independent frameworks made from repeated unit cells that expand under tension. We discovered how to produce handedness in auxetic unit cells that shear as they expand by changing the symmetries and alignments of auxetic tilings. Using the symmetry and alignment rules that we developed, we made handed shearing auxetics that tile planes, cylinders, and spheres. By compositing the handed shearing auxetics in a manner inspired by keratin and collagen, we produce both compliant structures that expand while twisting and deployable structures that can rigidly lock. This work opens up new possibilities in designing chemical frameworks, medical devices like stents, robotic systems, and deployable engineering structures.

  8. Seismic behavior of semi-supported steel shear walls

    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...

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

    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.

  10. Mean wall-shear stress measurements using the micro-pillar shear-stress sensor MPS3

    Große, S; Schröder, W

    2008-01-01

    A new sensor to measure the mean turbulent wall-shear stress in turbulent flows is described. The wall-shear stress sensor MPS 3 has been tested in a well-defined fully developed turbulent pipe flow at Reynolds numbers Re b based on the bulk velocity U b and the pipe diameter D in the range of Re b = 10 000–20 000. The results demonstrate a convincing agreement of the mean wall-shear stress obtained with the new sensor technique with analytical and experimental results from the literature. The sensor device consists of a flexible micro-pillar that extends from the wall into the viscous sublayer. Bending due to the exerting fluid forces, the pillar-tip deflection serves as a measure for the local wall-shear stress. The sensor concept, calibration techniques, the achievable accuracy and error estimates, the fields of application and the sensor limits will be discussed. Furthermore, a first estimate of the pillar dynamic response will be derived showing the potential of the sensor to also measure the turbulent fluctuating wall-shear stress

  11. Spatial bandwidth enlargement and field enhancement of shear horizontal waves in finite graded piezoelectric layered media

    Xu, Yanlong

    2015-01-01

    Shear horizontal (SH) wave propagation in finite graded piezoelectric layered media is investigated by transfer matrix method. Different from the previous studies on SH wave propagation in completely periodic layered media, calculations on band structure and transmission in this paper show that the graded layered media possess very large band gaps. Harmonic wave simulation by finite element method (FEM) confirms that the reason of bandwidth enlargement is that waves within the band gap ranges are spatially enhanced and stopped by the corresponding graded units. The study suggests that the graded structure possesses the property of manipulating elastic waves spatially, which shows potential applications in strengthening energy trapping and harvesting. - Highlights: • Shear horizontal wave propagation in finite graded piezoelectric layered media is investigated by transfer matrix method. • Calculations on band structure and transmission show that the graded layered media possess very large band gaps. • Finite element method confirms that waves in band gaps are spatially enhanced and stopped by the graded units. • The study suggests that the graded structure possesses the property of manipulating elastic waves spatially

  12. The Relationship between Elastic Properties and Shear Fabric in Clay-Rich Fault Gouge

    Kenigsberg, A.; Saffer, D. M.; Riviere, J.; Ryan, K. L.; Marone, C.

    2016-12-01

    The low mechanical strength of major crustal faults remains a fundamental problem in geophysics and earthquake mechanics. Although both clay abundance and shear fabric are known as key controls on the frictional weakening of faults, the detailed links between fabric, elastic properties, composition, and fault strength remain poorly understood. This gap in information is in part because data are lacking to fully characterize the evolution of gouge microstructures and elastic properties during shearing. Here, we use seismic wave propagation to probe gouge ultrasonic and elastic properties, as a proxy for the development of shear fabrics. We report on a suite of direct shear experiments that include ultrasonic wave transmission to monitor compressional and shear wave velocities (Vp, Vs), during progressive shear of synthetic, clay-rich fault gouge. In order to better understand when and how clay grain alignment and nano-coatings begin to dominate the affect of shear fabric and local gouge density on elastic properties and shear strength, we studied a suite of synthetic gouges composed of Ca-montmorillonite and quartz ranging from 0-100% clay. Our laboratory experiments document friction coefficients (μ) ranging from 0.21 for gouges composed of 100% smectite to 0.62 for 100% quartz, with μ decreasing as clay content increases. We find that Vp and Vs increases as shear progresses and porosity decreases. Ongoing analyses of ultrasonic waves will assess variations of Vp, Vs, and elastic moduli throughout shear and as a function of gouge composition. We anticipate that these variations will be linked to formation of fabric elements observed via microstructural analysis, and will be indicative of whether quartz or clay is dominating how the fabrics form. Finally, we expect that clay content will be the dominant factor controlling shear fabric evolution and, consequently, the key control on the evolution of elastic properties with shear.

  13. Characterizing shear properties of fine-grained subgrade soils under large capacity construction equipment

    Anochie-Boateng, Joseph

    2010-06-01

    Full Text Available properties including friction angle and cohesion for strength properties and shear modulus of the soil at three moisture states. Mohr-Coulomb failure models were developed together with shear modulus correlations for the soil sample. These models can be used...

  14. Dynamic evolution of shear - extensional tectonics in South China and uranium resource exploration strategic analysis

    Fang Shiyi; Tao Zhijun; Han Qiming

    2012-01-01

    A variety of multi- types, multi-level, multi-era shear - extensional tectonics in south China is developed, the main form of shear-extensional tectonics, and developmental characteristics and metallogenic geodynamic evolution is discovered, and thus uranium resource exploration strategic analysis is conducted

  15. Optimization of multiplane ?PIV for wall shear stress and wall topography characterization

    Rossi, M.; Lindken, R.; Westerweel, J.

    2009-01-01

    Multiplane ?PIV can be utilized to determine the wall shear stress and wall topology from the measured flow over a structured surface. A theoretical model was developed to predict the measurement error for the surface topography and shear stress, based on a theoretical analysis of the precision in

  16. High fluid shear strain causes injury in silver shark: Preliminary implications for Mekong hydropower turbine design

    Baumgartner, L. J. [New South Wales Department of Primary Industries, Narrandera Fisheries Centre, Narrandera NSW Australia; Institute of Land, Water and Society, Charles Sturt University, Albury NSW Australia; Thorncraft, G. [Faculty of Agriculture, Forestry and Fisheries, National University of Laos, Vientiane Lao People’s Democratic Republic; Phonekhampheng, O. [Faculty of Agriculture, Forestry and Fisheries, National University of Laos, Vientiane Lao People’s Democratic Republic; Boys, C. [New South Wales Department of Primary Industries, Port Stephens Fisheries Institute, Nelson Bay NSW Australia; Navarro, A. [Institute of Land, Water and Society, Charles Sturt University, Albury NSW Australia; Robinson, W. [Institute of Land, Water and Society, Charles Sturt University, Albury NSW Australia; Brown, R. [Pacific Northwest National Laboratory, Richland WA USA; Deng, Z. D. [Pacific Northwest National Laboratory, Richland WA USA

    2017-02-09

    Fluid shear arises when two bodies of water, travelling at different velocities, intersect. Fish entrained at the interface of these two water masses will experience shear stress; which can be harmful. The stress magnitude is dependent on waterbody mass and velocity; with the fish impact largely related to body size. Elevated shear stress occurs where rapidly flowing water passes near spillways, across screens, within turbine draft tubes or other passage routes. A flume was used to determine critical tolerances of silver shark (Balantiocheilos melanopterus) to different shear stress rates generated by a high velocity jet. Fish experienced higher levels of injury and mortality as shear stress was increased. Excessive shear forces had damaging impacts on fish. Mortality occurred at shear levels higher that 600/s. It is important that developers should attempt to model potential shear profiles expected during turbine passage in selected designs. These data will be critical to determine potential impacts on fish. If the likelihood of adverse impact is high, then alternative designs which have lower shear stress could be explored.

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

    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.

  18. Shear-induced transitions in a ternary polymeric system

    Zvelindovsky, AV; Sevink, GJA; Fraaije, JGEM

    The first three-dimensional simulation of shear-induced phase transitions in a polymeric system has been performed. The method is based on dynamic density-functional theory. The pathways between a bicontinuous phase with developing gyroid mesostructure and a lamellar/cylinder phase coexistence are

  19. Nonlinear analysis of shear deformable beam-columns partially ...

    In this paper, a boundary element method is developed for the nonlinear analysis of shear deformable beam-columns of arbitrary doubly symmetric simply or multiply connected constant cross section, partially supported on tensionless Winkler foundation, undergoing moderate large deflections under general boundary ...

  20. Analytical modeling for heat transfer in sheared flows of nanofluids

    Ferrari, C.; Kaoui, B.; L'vov, V.S.; Procaccia, I.; Rudenko, O.; Thije Boonkkamp, ten J.H.M.; Toschi, F.

    2012-01-01

    We developed a model for the enhancement of the heat flux by spherical and elongated nanoparticles in sheared laminar flows of nanofluids. Besides the heat flux carried by the nanoparticles, the model accounts for the contribution of their rotation to the heat flux inside and outside the particles.