WorldWideScience

Sample records for dynamic rheological studies

  1. Comparative study of sea ice dynamics simulations with a Maxwell elasto-brittle rheology and the elastic-viscous-plastic rheology in NEMO-LIM3

    Science.gov (United States)

    Raulier, Jonathan; Dansereau, Véronique; Fichefet, Thierry; Legat, Vincent; Weiss, Jérôme

    2017-04-01

    Sea ice is a highly dynamical environment characterized by a dense mesh of fractures or leads, constantly opening and closing over short time scales. This characteristic geomorphology is linked to the existence of linear kinematic features, which consist of quasi-linear patterns emerging from the observed strain rate field of sea ice. Standard rheologies used in most state-of-the-art sea ice models, like the well-known elastic-viscous-plastic rheology, are thought to misrepresent those linear kinematic features and the observed statistical distribution of deformation rates. Dedicated rheologies built to catch the processes known to be at the origin of the formation of leads are developed but still need evaluations on the global scale. One of them, based on a Maxwell elasto-brittle formulation, is being integrated in the NEMO-LIM3 global ocean-sea ice model (www.nemo-ocean.eu; www.elic.ucl.ac.be/lim). In the present study, we compare the results of the sea ice model LIM3 obtained with two different rheologies: the elastic-viscous-plastic rheology commonly used in LIM3 and a Maxwell elasto-brittle rheology. This comparison is focused on the statistical characteristics of the simulated deformation rate and on the ability of the model to reproduce the existence of leads within the ice pack. The impact of the lead representation on fluxes between ice, atmosphere and ocean is also assessed.

  2. Analogy between dynamics of thermo-rheological and piezo-rheological pendulums

    Energy Technology Data Exchange (ETDEWEB)

    Hedrih, K [Faculty of Mechanical Engineering University of Nis, Mathematical Institute SANU, ul. Vojvode Tankosic 3/V/22, 18000-Nis (Serbia)], E-mail: katica@masfak.ni.ac.yu, E-mail: khedrih@eunet.yu

    2008-02-15

    The constitutive stress-strain relations of the standard thermo-rheological and piezo-rheological hereditary element in differential form as well as in two different integro-differential forms are defined. The considered problem of a thermo-rheological hereditary discrete system nonlinear dynamics in the form of thermo-rheological double pendulum system with coupled pendulums gets the significance of two constrained bodies in plane motion problem, as a problem important for studying a sensor dynamics or actuator dynamics in active structure dynamics. System of the averaged equations in the first approximation for amplitudes and phases are derived and qualitatively analyzed. Analogy between nonlinear dynamics of the double pendulum systems with thermo-rheological and piezo-rheological properties between pendulums is pointed out.

  3. Studies on fish and pork paste gelation by dynamic rheology and circular dichroism.

    Science.gov (United States)

    Liu, R; Zhao, S-M; Xiong, S-B; Xie, B-J; Liu, H-M

    2007-09-01

    The muscle paste of fish, pork, and their mixtures were prepared to study the gelling characteristics by dynamic rheological measurement. The gelation mechanisms of muscle paste were also investigated by circular dichroism. Gel formation of fish paste occurred in 2 steps of 5 to 35 and 51 to 90 degrees C respectively, while pork paste mainly in 1 step of 49 to 72 degrees C. Gel formation was relative to the alpha-helix unfolding of myosin, which responded the melting temperatures of 40 and 50 degrees C for fish myosin and 50 and 60 degrees C for pork myosin, respectively. Alpha-helix unfolding of myosin was beneficial for gel formation. During gel formation, G' of muscle paste was linearly related to alpha-helical content of myosin. The interactions of fish and pork proteins at high temperature (>35 degrees C) could change the gel forming characteristics of muscle paste. Mixed paste exhibited a similar gelation pattern to individual fish paste with 2 visible increases in G'. Addition of pork could suppress the breakdown of fish gel structure at approximately 50 degrees C. Mixing pork and silver carp in a certain ratio could improve the gel properties of silver carp products.

  4. Rheology and dynamics of colloidal superballs.

    Science.gov (United States)

    Royer, John R; Burton, George L; Blair, Daniel L; Hudson, Steven D

    2015-07-28

    Recent advances in colloidal synthesis make it possible to generate a wide array of precisely controlled, non-spherical particles. This provides a unique opportunity to probe the role that particle shape plays in the dynamics of colloidal suspensions, particularly at higher volume fractions, where particle interactions are important. We examine the role of particle shape by characterizing both the bulk rheology and micro-scale diffusion in a suspension of pseudo-cubic silica superballs. Working with these well-characterized shaped colloids, we can disentangle shape effects in the hydrodynamics of isolated particles from shape-mediated particle interactions. We find that the hydrodynamic properties of isolated superballs are marginally different from comparably sized hard spheres. However, shape-mediated interactions modify the suspension microstructure, leading to significant differences in the self-diffusion of the superballs. While this excluded volume interaction can be captured with a rescaling of the superball volume fraction, we observe qualitative differences in the shear thickening behavior of moderately concentrated superball suspensions that defy simple rescaling onto hard sphere results. This study helps to define the unknowns associated with the effects of shape on the rheology and dynamics of colloidal solutions.

  5. A dynamic rheological model for thin-film lubrication

    Institute of Scientific and Technical Information of China (English)

    Zhang Xiang-Jun; Huang Ying; Guo Yan-Bao; Tian Yu; Meng Yong-Gang

    2013-01-01

    In this study,the effects of the non-Newtonian rheological properties of the lubricant in a thin-film lubrication regime between smooth surfaces were investigated.The thin-film lubrication regime typically appears in Stribeck curves with a clearly observable minimum coefficient of friction (COF) and a low-COF region,which is desired for its lower energy dissipation.A dynamic rheology of the lubricant from the hydrodynamic lubrication regime to the thin-film lubrication regime was proposed based on the convected Maxwell constitutive equation.This rheology model includes the increased relaxation time and the yield stress of the confined lubricant thin film,as well as their dependences on the lubricant film thickness.The Deborah number (De number) was adopted to describe the liquid-solid transition of the confined lubricant thin film under shearing.Then a series of Stribeck curves were calculated based on Tichy's extended lubrication equations with a perturbation of the De number.The results show that the minimum COF points in the Stribeck curve correspond to a critical De number of 1.0,indicating a liquid-to-solid transition of the confined lubricant film.Furthermore,the two proposed parameters in the dynamic rheological model,namely negative slipping length b (indicating the lubricant interfacial effect) and the characteristic relaxation time λ0,were found to determine the minimum COF and the width of the low-COF region,both of which were required to optimize the shape of the Stribeck curve.The developed dynamic rheological model interprets the correlation between the rheological and interfacial properties of lubricant and its lubrication behavior in the thin-film regime.

  6. A hybrid molecular dynamics study on the non-Newtonian rheological behaviors of shear thickening fluid.

    Science.gov (United States)

    Chen, Kaihui; Wang, Yu; Xuan, Shouhu; Gong, Xinglong

    2017-07-01

    To investigate the microstructural evolution dependency on the apparent viscosity in shear-thickening fluids (STFs), a hybrid mesoscale model combined with stochastic rotation dynamics (SRD) and molecular dynamics (MD) is used. Muller-Plathe reverse perturbation method is adopted to analyze the viscosities of STFs in a two-dimensional model. The characteristic of microstructural evolution of the colloidal suspensions under different shear rate is studied. The effect of diameter of colloidal particles and the phase volume fraction on the shear thickening behavior is investigated. Under low shear rate, the two-atom structure is formed, because of the strong particle attractions in adjacent layers. At higher shear rate, the synergetic pair structure extends to layered structure along flow direction because of the increasing hydrodynamics action. As the shear rate rises continuously, the layered structure rotates and collides with other particles, then turned to be individual particles under extension or curve string structure under compression. Finally, at the highest shear rate, the strings curve more severely and get into two-dimensional cluster. The apparent viscosity of the system changes from shear-thinning behavior to the shear-thickening behavior. This work presents valuable information for further understanding the shear thickening mechanism.

  7. Rheology via nonequilibrium molecular dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Hoover, W.G.

    1982-10-01

    The equilibrium molecular dynamics formulated by Newton, Lagrange, and Hamilton has been modified in order to simulate rheologial molecular flows with fast computers. This modified Nonequilibrium Molecular Dynamics (NEMD) has been applied to fluid and solid deformations, under both homogeneous and shock conditions, as well as to the transport of heat. The irreversible heating associated with dissipation could be controlled by carrying out isothermal NEMD calculations. The new isothermal NEMD equations of motion are consistent with Gauss' 1829 Least-Constraint principle as well as certain microscopic equilibrium and nonequilibrium statistical formulations due to Gibbs and Boltzmann. Application of isothermal NEMD revealed high-frequency and high-strain-rate behavior for simple fluids which resembled the behavior of polymer solutions and melts at lower frequencies and strain rates. For solids NEMD produces plastic flows consistent with experimental observations at much lower strain rates. The new nonequilibrium methods also suggest novel formulations of thermodynamics in nonequilibrium systems and shed light on the failure of the Principle of Material Frame Indifference.

  8. Dynamic hysteresis in the rheology of complex fluids.

    Science.gov (United States)

    Puisto, Antti; Mohtaschemi, Mikael; Alava, Mikko J; Illa, Xavier

    2015-04-01

    Recently, rheological hysteresis has been studied systematically in a wide range of complex fluids combining global rheology and time-resolved velocimetry. In this paper we present an analysis of the roles of the three most fundamental mechanisms in simple-yield-stress fluids: structure dynamics, viscoelastic response, and spatial flow heterogeneities, i.e., time-dependent shear bands. Dynamical hysteresis simulations are done analogously to rheological ramp-up and -down experiments on a coupled model which incorporates viscoelasticity and time-dependent structure evolution. Based on experimental data, a coupling between hysteresis measured from the local velocity profiles and that measured from the global flow curve has been suggested. According to the present model, even if transient shear banding appears during the shear ramps, in typical narrow-gap devices, only a small part of the hysteretic response can be attributed to heterogeneous flow. This results in decoupling of the hysteresis measured from the local velocity profiles and the global flow curve, demonstrating that for an arbitrary time-dependent rheological response this proposed coupling can be very weak.

  9. Dynamics and Rheology of Soft Colloidal Glasses

    KAUST Repository

    Wen, Yu Ho

    2015-01-20

    © 2015 American Chemical Society. The linear viscoelastic (LVE) spectrum of a soft colloidal glass is accessed with the aid of a time-concentration superposition (TCS) principle, which unveils the glassy particle dynamics from in-cage rattling motion to out-of-cage relaxations over a broad frequency range 10-13 rad/s < ω < 101 rad/s. Progressive dilution of a suspension of hairy nanoparticles leading to increased intercenter distances is demonstrated to enable continuous mapping of the structural relaxation for colloidal glasses. In contrast to existing empirical approaches proposed to extend the rheological map of soft glassy materials, i.e., time-strain superposition (TSS) and strain-rate frequency superposition (SRFS), TCS yields a LVE master curve that satis fies the Kramers-Kronig relations which interrelate the dynamic moduli for materials at equilibrium. The soft glassy rheology (SGR) model and literature data further support the general validity of the TCS concept for soft glassy materials.

  10. Liquid rheology study on refined rapeseed oil

    Institute of Scientific and Technical Information of China (English)

    刘其梅; 罗迎社; 殷水平; 陈胜铭; 张党权; 彭万喜

    2008-01-01

    The rapeseed oil extracted from the mature seeds was purified by refining processing,and the rheological characteristic analysis of the viscosity and dynamic shear rate at gradient temperatures was made.The result shows that at 20,40,60 and 80 ℃ respectively,when the shear rate gradually rises,the torque increases accordingly but its viscosity does not vary distinctly.The result suggests that when rapeseed oil is used as the raw of edible oils and industries,the working procedures at high temperature will not influence its rheological characteristic distinctly.

  11. [Molecular Dynamics of Self-assembling and Rheology of Superhelical Structure of Protofiber of Spider Web].

    Science.gov (United States)

    Shaitan, K V; Orshanskiy, I A

    2015-01-01

    In this study we suggested a dynamics simulation for the formation of protofiber of spider web nanofiber. It was shown that a bundle of parallel polyalanine β-strands of sufficient length is arranged through self-assembly into a stable right-handed super helix. By numerical analysis we investigated the rheological properties and provided in nonlinear regime a generalization of the model of Singer for description of the rheological behaviour of super helix.

  12. Evolution of nano-rheological properties of Nafion¯ thin films during pH modification by strong base treatment: A static and dynamic force spectroscopy study

    Science.gov (United States)

    Eslami, Babak; López-Guerra, Enrique A.; Raftari, Maryam; Solares, Santiago D.

    2016-04-01

    Addition of a strong base to Nafion® proton exchange membranes is a common practice in industry to increase their overall performance in fuel cells. Here, we investigate the evolution of the nano-rheological properties of Nafion thin films as a function of the casting pH, via characterization with static and dynamic, contact and intermittent-contact atomic force microscopy (AFM) techniques. The addition of KOH causes non-monotonic changes in the viscoelastic properties of the films, which behave as highly dissipative, softer materials near neutral pH values, and as harder, more elastic materials at extreme pH values. We quantify this behavior through calculation of the temporal evolution of the compliance and the glassy compliance under static AFM measurements. We complement these observations with dynamic AFM metrics, including dissipated power and virial (for intermittent-contact-mode measurements), and contact resonance frequency and quality factor (for dynamic contact-mode measurements). We explain the non-monotonic material property behavior in terms of the degree of ionic crosslinking and moisture content of the films, which vary with the addition of KOH. This work focuses on the special case study of the addition of strong bases, but the observed mechanical property changes are broadly related to water plasticizing effects and ionic crosslinking, which are also important in other types of films.

  13. DYNAMIC RHEOLOGICAL BEHAVIOR OF POLYPROPYLENE FILLED WITH ULTRA-FINE POWDERED RUBBER PARTICLES

    Institute of Scientific and Technical Information of China (English)

    Qiang Zheng; Yan-xia Cao; Miao Du

    2004-01-01

    Dynamic rheological characteristics of polypropylene (PP) filled with ultra-fine full-vulcanized powdered rubber (UFPR) composed of styrene-butadiene copolymer were studied through dynamic rheological measurements on an Advanced Rheometric Expansion System (ARES). A specific viscoelastic phenomenon, i.e. "the second plateau", appeared at low frequencies, and exhibits a certain dependence on the amount of rubber particles and the dispersion state in the matrix. This phenomenon is attributed to the formation of aggregation structure of rubber particles. The analyses of Cole-Cole diagrams of the dynamic viscoelastic functions suggest that the heterogeneity of the composites is enhanced on increasing both particle content and temperature.

  14. Relationship between dynamic recrystallization, grain size distribution and rheology

    NARCIS (Netherlands)

    Heege, Johannes Hendrik ter

    2002-01-01

    The solid state flow behavior (rheology) of materials constituting the Earth’s mantle and crust is of key importance in controlling the dynamics of large scale geodynamic processes, such as mantle convection, subduction, mountain building and basin formation. Flow laws that are calibrated using

  15. Relationship between dynamic recrystallization, grain size distribution and rheology

    NARCIS (Netherlands)

    Heege, Johannes Hendrik ter

    2002-01-01

    The solid state flow behavior (rheology) of materials constituting the Earth’s mantle and crust is of key importance in controlling the dynamics of large scale geodynamic processes, such as mantle convection, subduction, mountain building and basin formation. Flow laws that are calibrated using l

  16. Rheological studies of polysaccharides for skin scaffolds.

    Science.gov (United States)

    Almeida, Nalinda; Mueller, Anja; Hirschi, Stanley; Rakesh, Leela

    2014-05-01

    Polysaccharide hydrogels are good candidates for skin scaffolds because of their inherent biocompatibility and water transport properties. In the current study, hydrogels were made from a mixture of four polysaccharides: xanthan gum, konjac gum, iota-carrageenan, and kappa-carrageenan. Gel formation, strength, and structure of these polysaccharides were studied using rheological and thermal techniques. All gel samples studied were strong gels at all times because of the gradual water loss. However, after 12 h of storage, elastic (G') and loss (G'') moduli of hydrogel mixture containing all the ingredients is of one to two orders of magnitude greater than that of mixtures not containing either xanthan gum or iota-carrageenan, which confirmed the varied levels of gel strength. This is mainly due to the rate of water loss in each of these mixtures, resulting in gels of varying structures and dynamic moduli over a period of time. Iota-carrageenan and xanthan gum differ in their effect on gel strength and stability in combination with konjac gum and kappa-carrageenan.

  17. Advances and expectations of study on wood rheology

    Institute of Scientific and Technical Information of China (English)

    马远荣; 罗迎社; 李贤军

    2008-01-01

    By studying and summarizing the characteristics of wood rheology,the mathematic models of creep and mechano-sorptive creep of wood were analyzed.Rheology behaviors in process,especially drying stress and deformation set were discussed.Application of wood rheology in woodcraft process was elaborated and the research prospects and orientation were forecasted.

  18. Structure, dynamics, and rheology of concentrated dispersions of poly(ethylene glycol)-grafted colloids

    OpenAIRE

    Zackrisson, Malin; Stradner, Anna; Schurtenberger, Peter; Bergenholtz, Johan

    2006-01-01

    A comprehensive experimental study of the dynamics and rheology of concentrated aqueous dispersions of poly(ethylene glycol)-grafted colloidal spheres is reported. The study focuses on good solvent conditions, for which excluded-volume interactions dominate. At high concentrations a glass transition is evident from the nondecaying component of the intensity correlation function measured with three-dimensional dynamic light scattering. Results for the linear viscoelastic and steady shear rheol...

  19. Elongational Viscosity Rheological Parameter Study

    Science.gov (United States)

    1982-06-01

    can prepare a simple table of collapse ratios as a function of prts.-orc ±t,.s. ii Table. Collapse Ratios as a Function of Pressure Ratios (i = 1.4...that were used in this study were all water soluble polyrner systems. The two polymers used were carboxymethylcellulose (CMC) 40U t

  20. Transient, nonlinear rheology of reversible colloidal gels by dynamic simulation

    Science.gov (United States)

    Landrum, Benjamin; Russel, William; Zia, Roseanna

    2014-11-01

    We study the nonlinear rheology of reversible colloidal gels via dynamic simulation as they undergo age- and flow-induced structural evolution, with a view toward understanding and predicting transient behaviors such as multi-step and delayed yield. The gel is formed from 750,000 Brownian spheres interacting via hard-sphere repulsion and O(kT) short-range attraction, where thermal fluctuations are strong enough to allow continued structural rearrangement in the absence of flow. During startup of imposed strain rate, the transition to steady state is characterized by one or more ``overshoots'' in the stress which suggest initial yield, formation of a stronger gel, and subsequent yield of the new gel. When subjected to step-shear stress, the microstructure undergoes limited creep, followed by viscous flow. This macroscopic ``delayed flow'' is consistent with previously proposed models of competition between breakage and formation of particle bonds among static load-bearing structures. Our findings suggest, however, that the load-bearing structures evolve, and that the gel's resistance to delayed failure depends upon this structural evolution and reinforcement. We put forth a micro-mechanical model of stress gradient-driven particle transport that captures this macroscopic behavior.

  1. Predicting dynamics and rheology of blood flow: A comparative study of multiscale and low-dimensional models of red blood cells

    Science.gov (United States)

    Pan, Wenxiao; Fedosov, Dmitry A.; Caswell, Bruce; Karniadakis, George Em

    2011-01-01

    We compare the predictive capability of two mathematical models for red blood cells (RBCs) focusing on blood flow in capillaries and arterioles. Both RBC models as well as their corresponding blood flows are based on the dissipative particle dynamics (DPD) method, a coarse-grained molecular dynamics approach. The first model employs a multiscale description of the RBC (MS-RBC), with its membrane represented by hundreds or even thousands of DPD-particles connected by springs into a triangular network in combination with out-of-plane elastic bending resistance. Extra dissipation within the network accounts for membrane viscosity, while the characteristic biconcave RBC shape is achieved by imposition of constraints for constant membrane area and constant cell volume. The second model is based on a low-dimensional description (LD-RBC) constructed as a closed torus-like ring of only 10 large DPD colloidal particles. They are connected into a ring by worm-like chain (WLC) springs combined with bending resistance. The LD-RBC model can be fitted to represent the entire range of nonlinear elastic deformations as measured by optical-tweezers for healthy and for infected RBCs in malaria. MS-RBCs suspensions model the dynamics and rheology of blood flow accurately for any vessel size but this approach is computationally expensive for vessel diameters above 100 microns. Surprisingly, the much more economical suspensions of LD-RBCs also capture the blood flow dynamics and rheology accurately except for small-size vessels comparable to RBC diameter. In particular, the LD-RBC suspensions are shown to properly capture the experimental data for the apparent viscosity of blood and its cell-free layer (CFL) in tube flow. Taken together, these findings suggest a hierarchical approach in modeling blood flow in the arterial tree, whereby the MS-RBC model should be employed for capillaries and arterioles below 100 microns, the LD-RBC model for arterioles, and the continuum description for

  2. Study of rheological behaviour of wines

    Science.gov (United States)

    Trávníček, Petr; Burg, Patrik; Krakowiak-Bal, Anna; Junga, Petr; Vítěz, Tomáš; Ziemiańczyk, Urszula

    2016-10-01

    This study deals with rheological properties of various wine varieties. Samples of the following wines were used for this experiment: André, Cabernet Moravia, Laurot, Saint Laurent, Gruner Veltliner, Pinot Blanc, Müller Thurgau, and Riesling Italico. These samples were obtained from wine produced from the grapes collected in the Czech Republic (Morava region, subregion Velke Pavlovice). In the first phase, the chemical composition of the samples was determined. The following chemical parameters were determined: total acidity, pH, content of the alcohol, reduced sugars, free SO2, total SO2, and volatile acids. In the second phase of the study, the physical properties of the samples were determined and the samples of the wines were subjected to rheological tests. These tests consisted in determination of apparent viscosity in relation to temperature, hysteresis loop tests, and apparent viscosity related to time. The dependence of the shear rate on the shear stress was described with the Herschel-Bulkley mathematical model. The experiment yielded the following findings: seven out of the eight samples behaved as non-Newtonian fluids at low temperature (5°C); non-Newtonian behaviour was changed into Newtonian at the temperature higher than 10°C; non-Newtonian behaviour was characterised as thixotropic behaviour; the degree of thixotropy is relatively small and reaches 1.85 Pa s-1 ml-1.

  3. Dynamic rupture in a damage-breakage rheology model

    Science.gov (United States)

    Lyakhovsky, Vladimir; Ben-Zion, Yehuda; Ilchev, Assen; Mendecki, Aleksander

    2016-08-01

    We present a thermodynamically based formulation for modelling dynamic rupture processes in the brittle crust using a continuum damage-breakage rheology. The model combines aspects of a continuum viscoelastic damage framework for brittle solids with a continuum breakage mechanics for granular flow within dynamically generated slip zones. The formulation accounts for the density of distributed cracking and other internal flaws in damaged rocks with a scalar damage parameter, and addresses the grain size distribution of a granular phase in the slip zone with a breakage parameter. A dynamic brittle instability is associated with a critical level of damage in the solid, leading to loss of convexity of the solid strain energy, localization and transition to a granular phase associated with lower energy level. The continuum damage-breakage rheology model treats the localization to a slip zone at the onset of dynamic rupture and post-failure recovery process as phase transitions between solid and granular states. The model generates sub- and supershear rupture velocities and pulse-type ruptures seen also in frictional models, and additional important features such as strong dynamic changes of volumetric strain near the rupture front and diversity of nucleation mechanisms. The propagation of rupture front and slip accumulation at a point are correlated with sharp dynamic dilation followed by a gradual decay to a level associated with the final volumetric change associated with the granular phase transition in the slipping zone. The local brittle failure process associated with the solid-granular transition is expected to produce isotropic radiation in addition to the deviatoric terms. The framework significantly extends the ability to model brittle processes in complex geometrical structures and allows analysing the roles of gouge thickness and other parameters on nucleation, rupture and radiation characteristics.

  4. Predicting dynamics and rheology of blood flow: A comparative study of multiscale and low-dimensional models of red blood cells.

    Science.gov (United States)

    Pan, Wenxiao; Fedosov, Dmitry A; Caswell, Bruce; Karniadakis, George Em

    2011-09-01

    We compare the predictive capability of two mathematical models for red blood cells (RBCs) focusing on blood flow in capillaries and arterioles. Both RBC models as well as their corresponding blood flows are based on the dissipative particle dynamics (DPD) method, a coarse-grained molecular dynamics approach. The first model employs a multiscale description of the RBC (MS-RBC), with its membrane represented by hundreds or even thousands of DPD-particles connected by springs into a triangular network in combination with out-of-plane elastic bending resistance. Extra dissipation within the network accounts for membrane viscosity, while the characteristic biconcave RBC shape is achieved by imposition of constraints for constant membrane area and constant cell volume. The second model is based on a low-dimensional description (LD-RBC) constructed as a closed torus-like ring of only 10 large DPD colloidal particles. They are connected into a ring by worm-like chain (WLC) springs combined with bending resistance. The LD-RBC model can be fitted to represent the entire range of nonlinear elastic deformations as measured by optical-tweezers for healthy and for infected RBCs in malaria. MS-RBCs suspensions model the dynamics and rheology of blood flow accurately for any vessel size but this approach is computationally expensive for vessel diameters above 100μm. Surprisingly, the much more economical suspensions of LD-RBCs also capture the blood flow dynamics and rheology accurately except for small-size vessels comparable to RBC diameter. In particular, the LD-RBC suspensions are shown to properly capture the experimental data for the apparent viscosity of blood and its cell-free layer (CFL) in tube flow. Taken together, these findings suggest a hierarchical approach in modeling blood flow in the arterial tree, whereby the MS-RBC model should be employed for capillaries and arterioles below 100μm, the LD-RBC model for arterioles, and the continuum description for arteries.

  5. Exploring the relationship between nanoscale dynamics and macroscopic rheology in natural polymer gums.

    Science.gov (United States)

    Grein-Iankovski, Aline; Riegel-Vidotti, Izabel C; Simas-Tosin, Fernanda F; Narayanan, Suresh; Leheny, Robert L; Sandy, Alec R

    2016-11-23

    We report a study connecting the nanoscale and macroscale structure and dynamics of Acacia mearnsii gum as probed by small-angle X-ray scattering (SAXS), X-ray photon correlation spectroscopy (XPCS) and rheology. Acacia gum, in general, is a complex polysaccharide used extensively in industry. Over the analyzed concentration range (15 to 30 wt%) the A. mearnsii gum is found to have a gel-like linear rheology and to exhibit shear thinning flow behavior under steady shear. The gum solutions exhibited a steadily increasing elastic modulus with increasing time after they were prepared and also the emergence of shear thickening events within the shear thinning behavior, characteristic of associative polymers. XPCS measurements using gold nanoparticles as tracers were used to explore the microscopic dynamics within the biopolymer gels and revealed a two-step relaxation process with a partial decay at inaccessibly short times, suggesting caged motion of the nanoparticles, followed by a slow decay at later delay times. Non-diffusive motion evidenced by a compressed exponential line shape and an inverse relationship between relaxation time and wave vector characterizes the slow dynamics of A. mearnsii gum gels. Surprisingly, we have determined that the nanometer-scale mean square displacement of the nanoparticles showed a close relationship to the values predicted from the macroscopic elastic properties of the material, obtained through the rheology experiments. Our results demonstrate the potential applicability of the XPCS technique in the natural polymers field to connect their macroscale properties with their nanoscale structure and dynamics.

  6. INVESTIGATION OF STRUCTURE AND PROPERTIES FOR POLYMER SYSTEMS BASED ON DYNAMIC RHEOLOGICAL APPROACHES

    Institute of Scientific and Technical Information of China (English)

    Qiang Zheng; Min Zuo

    2005-01-01

    The dynamic rheological measurements have been a preferred approach to the characterization of the structure and properties for multi-component or multi-phase polymer systems, due to its sensitive response to changes of structure for these heterogeneous polymers. In the present article, recent progresses in the studies on dynamic theology for heterogeneous polymer systems including polymeric composites filled with inorganic particles, thermo-oxidized polyolefins, phaseseparated polymeric blends and functional polymers with the scaling and percolation behavior are reviewed, mainly depending on the results by the authors' group. By means of rheological measurements, not only some new fingerprints responsible for the evolution of morphology and structure concerning these polymer systems are obtained, the corresponding results are also significant for the design and preparation of novel polymer-based composites and functional materials.

  7. Dynamic analysis of electro- and magneto-rheological fluid dampers using duct flow models

    Science.gov (United States)

    Esteki, Kambiz; Bagchi, Ashutosh; Sedaghati, Ramin

    2014-03-01

    Magneto-rheological (MR) and electro-rheological (ER) fluid dampers provide a semi-active control mechanism for suppressing vibration responses of a structure. MR and ER fluids change their viscosity under the influence of magnetic and electrical fields, respectively, which facilitates automatic control when these fluids are used in damping devices. The existing models, namely the phenomenological models for simulating the behavior of MR and ER dampers, rely on various parameters determined experimentally by the manufacturers for each damper configuration. It is of interest to develop mechanistic models of these dampers which can be applied to various configurations so that their fundamental characteristics can be studied to develop flexible design solutions for smart structures. This paper presents a formulation for dynamic analysis of electro-rheological (ER) and magneto-rheological (MR) fluid dampers in flow and mix mode configurations under harmonic and random excitations. The procedure employs the vorticity transport equation and the regularization function to deal with the unsteady flow and nonlinear behavior of ER/MR fluid in general motion. The finite difference method has been used to solve the governing differential equations. Using the developed approach, the damping force of ER/MR dampers can be calculated under any type of excitation.

  8. Tear Film Dynamics: the roles of complex structure and rheology

    Science.gov (United States)

    Dey, Mohar; Feng, James; Vivek, Atul S.; Dixit, Harish N.; Richhariya, Ashutosh

    2016-11-01

    Ocular surface infections such as microbial and fungal keratitis are among leading causes of blindness in the world. A thorough understanding of the pre-corneal tear film dynamics is essential to comprehend the role of various tear layer components in the escalation of such ocular infections. The pre-corneal tear film comprises of three layers of complex fluids, viz. the innermost mucin layer, a hydrophilic protective cover over the sensitive corneal epithelium, the intermediate aqueous layer that forms the bulk of the tear film and is often embedded with large number of bio-polymers either in the form of soluble mucins or pathogens, and finally the outermost lipid layer that stabilizes the film by decreasing the air/tear film interfacial tension. We have developed a comprehensive mathematical model to describe such a film by incorporating the effects of the non-uniform mucin distribution along with the complex rheology of the aqueous layer with/without pathogens, Marangoni effects from the lipid layer and the slip effects at the base of the tear film. A detailed linear stability analysis and a fully non-linear solution determine the break up time (BUT) of such a tear film. We also probe the role of the various components of the pre-corneal tear film in the dynamics of rupture.

  9. A fully dynamic magneto-rheological fluid damper model

    Science.gov (United States)

    Jiang, Z.; Christenson, R. E.

    2012-06-01

    Control devices can be used to dissipate the energy of a civil structure subjected to dynamic loading, thus reducing structural damage and preventing failure. Semiactive control devices have received significant attention in recent years. The magneto-rheological (MR) fluid damper is a promising type of semiactive device for civil structures due to its mechanical simplicity, inherent stability, high dynamic range, large temperature operating range, robust performance, and low power requirements. The MR damper is intrinsically nonlinear and rate-dependent, both as a function of the displacement across the MR damper and the command current being supplied to the MR damper. As such, to develop control algorithms that take maximum advantage of the unique features of the MR damper, accurate models must be developed to describe its behavior for both displacement and current. In this paper, a new MR damper model that includes a model of the pulse-width modulated (PWM) power amplifier providing current to the damper, a proposed model of the time varying inductance of the large-scale 200 kN MR dampers coils and surrounding MR fluid—a dynamic behavior that is not typically modeled—and a hyperbolic tangent model of the controllable force behavior of the MR damper is presented. Validation experimental tests are conducted with two 200 kN large-scale MR dampers located at the Smart Structures Technology Laboratory (SSTL) at the University of Illinois at Urbana-Champaign and the Lehigh University Network for Earthquake Engineering Simulation (NEES) facility. Comparison with experimental test results for both prescribed motion and current and real-time hybrid simulation of semiactive control of the MR damper shows that the proposed MR damper model can accurately predict the fully dynamic behavior of the large-scale 200 kN MR damper.

  10. Analyses of Dynamic Rheological Behavior of Polymer Melt Based on Novel Experimental Equipment and Procedures

    Institute of Scientific and Technical Information of China (English)

    LIU Yuejun; QU Jinping; CAO Xianwu; SHI Pu

    2005-01-01

    By introducing a vibrating force field into the extrusion process of polymer melt, an experimental equipment of constant velocity type dynamic rheometer of capillary (CVDRC) was designed. A set of experimental procedures was established, by which the dynamic rheological parameters of polymer can be acquired, and a set of data management methods to undergo time-domain or frequency-domain analysis was set up for dynamic rheological data of polymer melt. Meantime, the characterization formula of polymer melt's rheological behavior in a vibrating force field was set up. The instantaneous value of capillary entry pressure, capillary volume flow rate and their phase difference were measured and analyzed, and the melt apparent viscosity, which describes the rheological behavior of polymer melt in a vibrating force field, was obtained.

  11. Rheological study of chitosan in solution;Estudo reologico de quitosana em solucao

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Italo Guimaraes Medeiros da; Alves, Keila dos Santos; Balaban, Rosangela de Carvalho, E-mail: balaban@supercabo.com.b [Universidade Federal do Rio Grande do Norte (UFRN), Natal, RN (Brazil). Dept. de Quimica

    2009-07-01

    Chitosan is an abundant biopolymer with remarkable physicochemical and biological properties, usually employed in a wide range of applications. It acts as a cationic polyelectrolyte in aqueous acid solutions, leading to unique characteristics. In this work, chitosan was characterized by {sup 1}H NMR and its rheological behavior were studied as function of chitosan sample, shear rate, polymer concentration, ionic strength, time and temperature. In order to calculate rheological parameters and to understand the macromolecular dynamic in solution, the Otswald-de Waele model was fitted. (author)

  12. Morphological, rheological and electrochemical studies ofpoly(ethylene oxide) electrolytes containing fumed silicananoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Jiangbing; Kerr, John B.; Duan, Robert G.; Han, Yongbong

    2003-06-01

    In this paper, the rheology and crystallization of composite Poly(Ethylene Oxide) (PEO) electrolytes were studied by dynamic mechanical analysis, DSC and polarized light microscopy. The effects of fumed silica nanoparticles on the conductivities of the polymer electrolytes at temperatures above and below their melting point were measured and related to their rheology and crystallization behavior, respectively. The electrolyte/electrode interfacial properties and cycling performances of the composite polymer electrolytes in Li/Li cells are also discussed. The measured electrochemical properties were found to depend heavily on the operational environments and sample processing history.

  13. DYNAMIC RHEOLOGICAL ANALYSIS AS A SENSITIVE METHOD FOR ANALYZING STRUCTURAL CHANGES DURING THERMO-OXIDATION OF POLYOLEFIN ELASTOMERS

    Institute of Scientific and Technical Information of China (English)

    Zheng-hong Guo; Zheng-ping Fang

    2009-01-01

    Dynamic rheological analysis and Fourier transform infrared spectroscopy (P'TIR) were used to study the effects of thermo-oxidation on the viscoelasticity and microstructure of polyolefin elastomers (POE).It was found that dynamic storage modulus (G') and dynamic loss modulus (G') at low frequency region can sensitively reflect the change of microstructure of POE,which can be seen through the "second plateau" appeared in G' versus co plots at low frequencies.The frequency dependence of loss tangent (tanδ) measured under different frequency sweeps showed that the thermo-oxidative behaviors of POE relied on the holding time.The dynamic rheology test was found to be a sensitive technique for analyzing the structural changes during thermo-oxidation of polymers.

  14. Study of the rheological properties of oil

    Energy Technology Data Exchange (ETDEWEB)

    Jewulski, J.

    1979-01-01

    The author describes industrial research into the process of disturbing the thixotropic structure of oil in well L-3 during constant oil coagulation inside the ''Rheostat'' rotating cylindrical viscosity meter. This oil, containing paraffin, has a high viscosity and corresponds to the chemical classification for pseudo water plastic thixotropic flowing liquid. This research was conducted at temperatures of 15,20,25, and 30 degrees C. The final time period is determined for the disintegration of the oil structure, during which almost no indicator changes are detected by industrial metering devices. This process of disintegration was viewed by the author as a breakdown of the thixotropic structure during the given rate of coagulation. Metering results were approximated and found to be most significant in non-stationary processes over a relatively short period of time. The rheological curve is then often replaced by a straight angle. This article also examines certain factors in the transport of such oil and trunklines and the resulting effects upon that oil's rheological composition.

  15. Evolution of nano-rheological properties of Nafion{sup ®} thin films during pH modification by strong base treatment: A static and dynamic force spectroscopy study

    Energy Technology Data Exchange (ETDEWEB)

    Eslami, Babak; López-Guerra, Enrique A.; Raftari, Maryam; Solares, Santiago D., E-mail: ssolares@gwu.edu [Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC 20052 (United States)

    2016-04-28

    Addition of a strong base to Nafion{sup ®} proton exchange membranes is a common practice in industry to increase their overall performance in fuel cells. Here, we investigate the evolution of the nano-rheological properties of Nafion thin films as a function of the casting pH, via characterization with static and dynamic, contact and intermittent-contact atomic force microscopy (AFM) techniques. The addition of KOH causes non-monotonic changes in the viscoelastic properties of the films, which behave as highly dissipative, softer materials near neutral pH values, and as harder, more elastic materials at extreme pH values. We quantify this behavior through calculation of the temporal evolution of the compliance and the glassy compliance under static AFM measurements. We complement these observations with dynamic AFM metrics, including dissipated power and virial (for intermittent-contact-mode measurements), and contact resonance frequency and quality factor (for dynamic contact-mode measurements). We explain the non-monotonic material property behavior in terms of the degree of ionic crosslinking and moisture content of the films, which vary with the addition of KOH. This work focuses on the special case study of the addition of strong bases, but the observed mechanical property changes are broadly related to water plasticizing effects and ionic crosslinking, which are also important in other types of films.

  16. Estimating Rheological Parameters of Anhydrite from Folded Evaporite sequences: Implications for Internal Dynamics of Salt Structure

    Science.gov (United States)

    Adamuszek, Marta; Dabrowski, Marcin; Schmalholz, Stefan M.; Urai, Janos L.; Raith, Alexander

    2015-04-01

    Salt structures have been identified as a potential target for hydrocarbon, CO2, or radioactive waste storage. The most suitable locations for magazines are considered in the thick and relatively homogeneous rock salt layers. However, salt structures often consist of the evaporite sequence including rock salt intercalated with other rock types e.g.: anhydrite, gypsum, potassium and magnesium salt, calcite, dolomite, or shale. The presence of such heterogeneities causes a serious disturbance in the structure management. Detailed analysis of the internal architecture and internal dynamics of the salt structure are crucial for evaluating them as suitable repositories and also their long-term stability. The goal of this study is to analyse the influence of the presence of anhydrite layers on the internal dynamics of salt structures. Anhydrite is a common rock in evaporite sequences. Its physical and mechanical properties strongly differ from the properties of rock salt. The density of anhydrite is much higher than the density of salt, thus anhydrite is likely to sink in salt causing the disturbance of the surrounding structures. This suggestion was the starting point to the discussion about the long-term stability of the magazines in salt structures [1]. However, the other important parameter that has to be taken into account is the viscosity of anhydrite. The high viscosity ratio between salt and anhydrite can restrain the layer from sinking. The rheological behaviour of anhydrite has been studied in laboratory experiments [2], but the results only provide information about the short-term behaviour. The long-term behaviour can be best predicted using indirect methods e.g. based on the analysis of natural structures that developed over geological time scale. One of the most promising are fold structures, the shape of which is very sensitive to the rheological parameters of the deforming materials. Folds can develop in mechanically stratified materials during layer

  17. Effect of oil type and fatty acid composition on dynamic and steady shear rheology of vegetable oils.

    Science.gov (United States)

    Yalcin, Hasan; Toker, Omer Said; Dogan, Mahmut

    2012-01-01

    In this study, effect of fatty acid composition on dynamic and steady shear rheology of oils was studied. For this aim, different types of vegetable oils (soybean, sunflower, olive, hazelnut, cottonseed and canola), were used. Rheological properties of oil samples were identified by rheometer (Thermo-Haake) at 25°C and fatty acid composition of oils was determined by GC (Agilent 6890). Steady shear rheological properties of oil samples were measured at shear rate range of 0.1-100 s⁻¹. Viscosity of olive, hazelnut, cottonseed, canola, soybean and sunflower was 61.2 mPa.s, 59.7 mPa.s, 57.3 mPa.s, 53.5 mPa.s, 48.7 mPa.s and 48.2 mPa.s, respectively. There was a significant difference between viscosity of oils except soybean and sunflower. As a result it was seen that there was a correlation between viscosity and monounsaturated (R=0.89), polyunsaturated (R=-0.97) fatty acid composition of oils, separately. Equation was found to predict viscosity of the oils based on mono and polyunsaturation composition of oils. In addition the dynamic rheological properties of oils were also examined. G', G'' and tan δ (G''/G') values were measured at 0.3 Pa (in viscoelastic region) and 0.1-1 Hz. As a result of multiple regression analysis another equations were found between tan δ, viscosity and polyunsaturated fatty acids.

  18. The dynamics of polymer bridge formation and disruption and its effect on the bulk rheology of suspensions.

    Science.gov (United States)

    Bhosale, Prasad S; Berg, John C

    2012-12-11

    Bridge-flocculated colloidal gels are used in many important processes and products such as gel casting for advanced ceramics, precursor inks for 3D printing, and waste treatment strategies. An important aspect of polymer bridged gels that makes them excellent candidates for these applications is the precise control it affords for control of rheological properties. Recent studies have shown that adhesion between bridged surfaces increases with time as the number of polymer bridges formed grows. However, the consequences of the dynamics of these processes toward bulk rheological properties have not been studied. Here we investigate the link between the dynamics of polymer bridging and disruption and bulk rheology in dense colloidal silica particle suspensions flocculated by polyethylene oxide (PEO). Microscale pull-off force measurements using atomic force microscope (AFM) show that upon repeated disruption and establishment of bridged contact, the adhesion between the surfaces is reduced. During contact disruption, the polymer chains bridging the two surfaces are stretched leading to chain scission. On the re-establishment of contact, these fragmented polymer chains are unable to fully re-establish the adhesion. Macroscale measurements using oscillatory rheology show that this reduced adhesion results in reduction of both the storage modulus and the yield stress. If the slurry is subjected to high shear for long periods, polymer chain scission is amplified, and the fragmented polymer chains are unable to bridge the particles again, resulting in free-flowing slurries.

  19. Rheology and deep tectonics

    Directory of Open Access Journals (Sweden)

    G. Ranalli

    1997-06-01

    Full Text Available The distribution of the rheological properties of the lithosphere in space, and their variations in time, have a profound effect on the resulting tectonic deformation. A classical way of estimating these properties makes use of rheological profiles (strength envelopes. Although rheological profiles are based on assumptions and approximations which limit their resolving power, they are an efficient first-order tool for the study of lithosphere rheology, and their application clarifies the dynamics of tectonic processes. Two examples of the interaction of rheology and tectonics are discussed, namely, the post-orogenic relaxation of Moho topography (which is an additional factor to be considered in tectonic inversion, and the strength control on the level of necking in extension (which may lead to apparent local isostasy at passive continental margins and in sedimentary basins.

  20. EFFECT OF INCORPORATING STARCH/SILICA COMPOUND FILLERS INTO UNCURED SSBR ON ITS DYNAMIC RHEOLOGICAL PROPERTIES

    Institute of Scientific and Technical Information of China (English)

    Hong Li; Yihu Song; Qiang Zheng

    2008-01-01

    The dynamic rheological properties of a composite composed of solution-polymerized styrene butadiene rubber (SSBR) filled with starch/silica (SiO2) compound fillers were studied by means of temperature,frequency and strain sweeps,respectively,and the influence of the starch content in the compound fillers (SCCF) on the rheological behaviors was discussed.It is found from frequency sweeps that a maximum of loss tangent (tanδ) appears at 20 rad/s,which is independent of SCCF.G' of the composites decreases whereas tanδ and critical strain (γc) of Payne effect increase with increasing SCCF.The reasons for these are believed to be that both SiO2 and starch could form filler networks due to interaction of hydrogen bounding between them,and the interactions between SiO2 and SSBR are stronger than those between starch and SSBR.Moreover,increasing SCCF in the compound fillers is in favor of improving the stability of the filler networks.Furthermore,tanδ values at 0℃ and 60℃ representing the properties for the wet traction and the rolling resistance of SSBR composites respectively can be improved by partial replacing SiO2 with starch.However,the reinforcement effect of starch to SSBR is weaker than that of SiO2 due to starch agglomeration.

  1. Dynamic and shear stress rheological properties of guar galactomannans and its hydrolyzed derivatives.

    Science.gov (United States)

    Hussain, Majid; Bakalis, Serafim; Gouseti, Ourania; Zahoor, Tahir; Anjum, Faqir Muhammad; Shahid, Muhammad

    2015-01-01

    Guar galactomannan from seed of Cyamopsis tetragonolobus was hydrolyzed using acid (HCl), base [Ba(OH)2] and enzyme (mannanase) method to obtain depolymerized substances with possible functional applications as soluble dietary fiber. Rheological behavior of crude, purified, and depolymerized guar gum solutions was studied at 25 °C, using shear stress and dynamic oscillatory measurements, performed with controlled stress rheometer Bohlin CVO (Malvern Instruments) fitted with cone-and-plate geometry. The various guar gums solutions with different viscosities exhibited shear-thinning behavior at high shear rate and Newtonian behavior at low shear rate. At low shear rate, sigma crude guar gum (SCGG), crude guar gum (CGG), acid hydrolyzed guar gum (AHGG) and enzyme hydrolyzed guar gum (EHGG) exhibited viscosities of 18.59, 1.346, 0.149 and 0.022 Pas, respectively. Oscillatory experiments (G", G') of gums solutions showed typical behavior of weak viscoelastic gel. All investigated guar gums were further used for glucose bio-accessibility using a novel in vitro small intestinal model (SIM). All gums solutions resulted in 20% reduction in simulated glucose absorption, indicating a non-significant functionality difference between various guar gums. So, it can be concluded that hydrolyzed guar gums without disturbing their rheological and physiological behavior would be useful for incorporation in various food products as soluble dietary fiber.

  2. Effects of non-linear rheology on the electrospinning process: a model study

    CERN Document Server

    Pontrelli, Giuseppe; Coluzza, Ivan; Pisignano, Dario; Succi, Sauro

    2014-01-01

    We develop an analytical bead-spring model to investigate the role of non-linear rheology on the dynamics of electrified jets in the early stage of the electrospinning process. Qualitative arguments, parameter studies as well as numerical simulations, show that the elongation of the charged jet filament is significantly reduced in the presence of a non-zero yield stress. This may have beneficial implications for the optimal design of future electrospinning experiments.

  3. Studies on the Pasting and Rheology of Rice Starch with Different Protein Residual

    OpenAIRE

    Lin, Qinlu; Xiao, Huaxi; Li, Lihui; Yu, Fengxiang; Tian, Wei

    2010-01-01

    International audience; Indica rice starch and japonica rice starch were used in the study. The protein contents of the two rice variety were respectively 0.43%, 0.62%, 0.84%, 1.08%, 1.25%. The pasting and rheological properties of samples were determined with Rapid Visco Analyzer and dynamic rheometer. The results indicated that, with the increase of protein content, the peak viscosity, breakdown viscosity and final viscosity of rice starch paste decreased, the setback viscosity increased an...

  4. Rheology and FTIR studies of model waxy crude oils with relevance to gelled pipeline restart

    Energy Technology Data Exchange (ETDEWEB)

    Magda, J.J.; Guimeraes, K.; Deo, M.D. [Utah Univ., Salt Lake City, UT (United States). Dept. of Chemical Engineering; Venkatesan, R.; Montesi, A. [Chevron Energy Technology Co., Houston, TX (United States)

    2008-07-01

    Gels composed of wax crystals may sometimes form when crude oils are transported in pipelines when ambient temperatures are low. The gels may stop the pipe flow, making it difficult or even impossible to restart the flow without breaking the pipe. Rheology and FTIR techniques were used to study the problem and to characterize transparent model waxy crude oils in pipeline flow experiments. These model oils were formulated without any highly volatile components to enhance the reproducibility of the rheology tests. Results were presented for the time- and temperature-dependent rheology of the model waxy crude oils as obtained in linear oscillatory shear and in creep-recovery experiments. The model oils were shown to exhibit many of the rheological features reported for real crude oils, such as 3 distinct apparent yield stresses, notably static yield stress, dynamic yield stress, and elastic-limit yield stress. It was concluded that of the 3, the static yield stress value, particularly its time dependence, can best be used to predict the restart behaviour observed for the same gel in model pipelines.

  5. The influence of effusion rate and rheology on lava flow dynamics and morphology: A case study from the 1971 and 1988-1990 eruptions at Villarrica and Lonquimay volcanoes, Southern Andes of Chile

    Science.gov (United States)

    Castruccio, Angelo; Contreras, María Angélica

    2016-11-01

    We analyzed two historical lava flows from the Southern Andes of Chile: The lava flows from the 1971 Villarrica volcano eruption and the 1988-1990 Lonquimay volcano eruption. The 1971 lava flow has a volume of 2.3 × 107 m3, a maximum length of 16.5 km and was emplaced in two days, with maximum effusion rates of 800 m3/s. The lava has a mean width of 150 m and thicknesses that decrease from 10 to 12 m at 5 km from the vent to 5-8 m at the flow front. The morphology is mainly 'a'ā. The 1988-1990 lava flow has a volume of 2.3 × 108 m3, a maximum length of 10.2 km and was emplaced in 330 days, with peak effusion rates of 80 m3/s. The flow has a mean width of 600 m and thicknesses that increase from 10 to 15 m near the vent to > 50 m at the front. The morphology varies from 'a'ā in proximal sectors to blocky in the rest of the flow. We modelled the advance rate and thickness of these flows assuming two possible dynamical regimes: An internal rheology regime modelled as a Herschel-Bulkley (HB) fluid and a Yield Strength in the Crust (YSC) regime. We compared our results with the widely used Newtonian and Bingham rheologies. Our results indicate that the 1971 flow can be modelled either by the HB, Bingham or Newtonian rheologies using a single temperature, while the 1988-1990 flow was controlled by the YSC regime. Our analysis and comparison of models shows that care should be taken when modelling a lava flow, as different rheologies and assumptions can reach the same results in terms of advance rate and flow thickness. These examples suggest that the crustal strength should be taken into account in any model of lava flow advance.

  6. Studies on Rheological Properties of Konjac-tea Drink

    Institute of Scientific and Technical Information of China (English)

    PANG Jie; XU Qiu-lan; SUN Yu-jing; ZHANG Fu-sheng; TIAN Shi-ping

    2003-01-01

    Konjac black tea(sugar-free) and konjac glucomannan(KGM) solution were studied by using rheometer,refractometer etc.The relationship between their rheological properties and temperature or concentration was discussed in detail.The results showed that viscosity was significantly affected by temperature and concentration;and pH stability of Konjac-tea was related to the molecular property of KGM.

  7. Microbiological and rheological studies on Portuguese kefir grains

    OpenAIRE

    Pintado, Manuela E.; Silva, J. A. Lopes da; Fernandes, Paulo B.; Malcata, F. Xavier; Hogg, Tim A.

    1996-01-01

    Part of the data presented in this paper was included in a poster entitled Studies on kefir grains: microbiological characterization, biomass increase rate, and rheology of the polysaccharide produced, which was presented at the Prof. Nicolau van Uden Portuguese Symposium of Applied Microbiology and Biotechnology – First Symposium on Yeasts, February 1993, Luso, Portugal. The native bacteria and yeasts present in Portuguese kefir grains stored under four distinct sets of environmenta...

  8. A Multiscale Red Blood Cell Model with Accurate Mechanics, Rheology, and Dynamics

    Science.gov (United States)

    Fedosov, Dmitry A.; Caswell, Bruce; Karniadakis, George Em

    2010-01-01

    Abstract Red blood cells (RBCs) have highly deformable viscoelastic membranes exhibiting complex rheological response and rich hydrodynamic behavior governed by special elastic and bending properties and by the external/internal fluid and membrane viscosities. We present a multiscale RBC model that is able to predict RBC mechanics, rheology, and dynamics in agreement with experiments. Based on an analytic theory, the modeled membrane properties can be uniquely related to the experimentally established RBC macroscopic properties without any adjustment of parameters. The RBC linear and nonlinear elastic deformations match those obtained in optical-tweezers experiments. The rheological properties of the membrane are compared with those obtained in optical magnetic twisting cytometry, membrane thermal fluctuations, and creep followed by cell recovery. The dynamics of RBCs in shear and Poiseuille flows is tested against experiments and theoretical predictions, and the applicability of the latter is discussed. Our findings clearly indicate that a purely elastic model for the membrane cannot accurately represent the RBC's rheological properties and its dynamics, and therefore accurate modeling of a viscoelastic membrane is necessary. PMID:20483330

  9. [Study of relationship between the onset time of sudden deafness and blood rheology].

    Science.gov (United States)

    Chen, Xiu-Mei; Zhang, Qing-Quan; Xie, Guang

    2007-03-01

    To investigate the correlation of the onset time of sudden deafness and blood rheology using a large-scale retrospective study. One hundred and ninety-eight patients of sudden deafness were examined with blood rheology and compared with 60 healthy people. Thirty patients were as subjects to study the circadian of blood rheology in order to search whether the blood rheology of morning was the highest. By divided 24 hours into twelve groups, each group contained two hours. Then the 198 patients were separated into twelve groups according to the time of onset. The blood rheology of each group was analyzed and compared with each other to observe which group was the highest. Most blood rheology index of the patients were higher than that of the healthy people. The onset time in most of the patients was during 4 am-8 am, but 45 patients during 4 am-6 am and 40 patients during 6 am-8 am. By analyzing and comparing the blood rheology of each group, the results showed that the blood rheology index in the group of 4 am-8 am was highest. And the blood rheology index of sudden deafness was highest in the morning. There was a close relation between blood rheology and sudden deafness. The peak time of onset was 4 am-8 am, and the patients whose blood rheology were the highest should be more predisposed to sudden deafness than the other patients.

  10. Nonlinear Dynamics Analysis of the Semiactive Suspension System with Magneto-Rheological Damper

    Directory of Open Access Journals (Sweden)

    Hailong Zhang

    2015-01-01

    Full Text Available This paper examines dynamical behavior of a nonlinear oscillator which models a quarter-car forced by the road profile. The magneto-rheological (MR suspension system has been established, by employing the modified Bouc-Wen force-velocity (F-v model of magneto-rheological damper (MRD. The possibility of chaotic motions in MR suspension is discovered by employing the method of nonlinear stability analysis. With the bifurcation diagrams and corresponding Lyapunov exponent (LE spectrum diagrams detected through numerical calculation, we can observe the complex dynamical behaviors and oscillating mechanism of alternating periodic oscillations, quasiperiodic oscillations, and chaotic oscillations with different profiles of road excitation, as well as the dynamical evolutions to chaos through period-doubling bifurcations, saddle-node bifurcations, and reverse period-doubling bifurcations.

  11. Changes in cytoskeletal dynamics and nonlinear rheology with metastatic ability in cancer cell lines

    Science.gov (United States)

    Coughlin, Mark F.; Fredberg, Jeffrey J.

    2013-12-01

    Metastatic outcome is impacted by the biophysical state of the primary tumor cell. To determine if changes in cancer cell biophysical properties facilitate metastasis, we quantified cytoskeletal biophysics in well-characterized human skin, bladder, prostate and kidney cell line pairs that differ in metastatic ability. Using magnetic twisting cytometry with optical detection, cytoskeletal dynamics was observed through spontaneous motion of surface bound marker beads and nonlinear rheology was characterized through large amplitude forced oscillations of probe beads. Measurements of cytoskeletal dynamics and nonlinear rheology differed between strongly and weakly metastatic cells. However, no set of biophysical parameters changed systematically with metastatic ability across all cell lines. Compared to their weakly metastatic counterparts, the strongly metastatic kidney cancer cells exhibited both increased cytoskeletal dynamics and stiffness at large deformation which are thought to facilitate the process of vascular invasion.

  12. Study of the rheological behavior of chocolate and margarine [abstract

    Directory of Open Access Journals (Sweden)

    Debaste, F.

    2010-01-01

    Full Text Available In the food industry, the production process is often established in an empirical way, according to rules of good practice. These methods present gaps, in particular at the level of the production regularity. To model and optimize the processes, it is highly useful to determine the physico-chemical properties of the product. In this work, chocolate and margarine are studied, both aiming direct industrial application but also aiming a general enhancement of rheological mechanism understanding. Indeed, the chocolate is a suspension of solid particles in cocoa butter and the margarine is a water-in-oil emulsion. Rheological behavior of those fluids is therefore relying on different key phenomena. In this work the flow behavior of both products is characterized and a mathematical model describing the rheological behavior of chocolate is developed. For chocolate, the goal is to model the tempering process. To establish the rheological behavior of chocolate, viscosity measurements were realized in a SEARLE VT550 viscometer using a bob and cup geometry. To build the mathematical law, general tests following the International Office of Cocoa, Chocolate and Sugar Confectionery (IOCCC recommended method (Servais et al., 2004 were performed. The obtained rheogram shows that the chocolate has a slightly thixotropic behavior. More focus is set on a smaller range of shear rate important for the industrial application (Debaste et al., 2008. Measures for various temperatures and various quantities of cocoa butter were realized. The results show a classical shear-thinning behavior. Further, a statistical analysis of the results was made to determine the parameters of a power-law describing this behavior. It appears that temperature and cocoa butter fraction have no influence on the exponent but well on the consistency parameter. For margarine, the goal is to model the flow in resting tubes, the last step in the industrial production (Herman et al., 2008. To

  13. Study on the rheology of subducting slabs

    Institute of Scientific and Technical Information of China (English)

    ZANG; Shaoxian

    2001-01-01

    [1]Jiao Jiujiu, Grey hydrogeologic system analysis and time series model, Survey Science and Technology (in Chinese), 1987,(10): 39-43.[2]Li Shuwen, Wang Baolai, Xiao Guoqiang, A compound model of grey and periodic scrape and its application in groundwater prediction, Journal of Hebei Institute of Architectural Science & Technology (in Chinese), 1992, (3): 246-251.[3]Wang Qingyin, Li Shuwen, Grey distributed parameter model and groundwater analog, Journal of Hebei Institute of Architectural Science & Technology (in Chinese), 1992, (3): 66-70.[4]Guo Chunqing, Xia Riyuan, Liu Zhenglin, Gray Systematic Theory and Methodological Study of Krast Groundwater Resources Evaluation (in Chinese), Beijing: Geological Publishing House, 1993, 3-60.[5]Wang Qingyin, Liu Kaidi, The Mathematical Method of Grey Systematic Theory and Its Application (in Chinese), Chengdu: Publishing House of Southwestern China University of Communication, 1990, 23-27.[6]Wang Qingyin, Wu Heqing, The concept of grey number and its property, in Proceedings of NAFIPS98, USA, 1998,45-49.[7]Givoli, D., Doukhovni, I., Finite element programming approach for contact problems with geometrical nonlinearity, Computers and Structures, 1996, (8): 31-41.[8]Li Shuwen, Wang Zhiqiang, Wu Qiang, The superiority of storage-centered finite element method in solving seepage problem, Coal Geology and Exploration (in Chinese), 1999, (5): 46-49.

  14. Linear low-density polyethylene/silica micro- and nanocomposites: dynamic rheological measurements and modelling

    Directory of Open Access Journals (Sweden)

    2010-02-01

    Full Text Available Linear low-density polyethylene (LLDPE based composites were prepared by melt compounding with 1, 2, 3 and 4 vol% of various kinds of amorphous silicon dioxide (SiO2 micro- and nanoparticles. Dynamic rheological tests in parallel plate configuration were conducted in order to detect the role of the filler morphology on the rheological behaviour of the resulting micro- and nanocomposites. A strong dependence of the rheological parameters from the filler surface area was highlighted, with a remarkable enhancement of the storage shear modulus (G′ and of the viscosity (η in fumed silica nanocomposites and in precipitated silica microcomposites, while glass microbeads only marginally affected the rheological properties of the LLDPE matrix. This result was explained considering the formation of a network structure arising from particle-particle interactions due to hydrogen bonding between silanol groups. A detailed analysis of the solid like behaviour for the filled samples at low frequencies was conducted by fitting viscosity data with a new model, based on a modification of the original De Kee-Turcotte expression performed in order to reach a better modelling of the high-frequency region.

  15. Semi-brittle rheology and ice dynamics in DynEarthSol3D

    Science.gov (United States)

    Logan, Liz C.; Lavier, Luc L.; Choi, Eunseo; Tan, Eh; Catania, Ginny A.

    2017-01-01

    We present a semi-brittle rheology and explore its potential for simulating glacier and ice sheet deformation using a numerical model, DynEarthSol3D (DES), in simple, idealized experiments. DES is a finite-element solver for the dynamic and quasi-static simulation of continuous media. The experiments within demonstrate the potential for DES to simulate ice failure and deformation in dynamic regions of glaciers, especially at quickly changing boundaries like glacier termini in contact with the ocean. We explore the effect that different rheological assumptions have on the pattern of flow and failure. We find that the use of a semi-brittle constitutive law is a sufficient material condition to form the characteristic pattern of basal crevasse-aided pinch-and-swell geometry, which is observed globally in floating portions of ice and can often aid in eroding the ice sheet margins in direct contact with oceans.

  16. Rheology study of supercritically extracted tea-oil

    Institute of Scientific and Technical Information of China (English)

    张党权; 陈胜铭; 彭万喜; 刘其梅; 谷振军; 樊绍刚; 邓顺阳

    2008-01-01

    The rheological analysis on dynamic shear rate-viscosity relationship of tea-oil extracted from tea-oil tree seeds by supercritical extraction method was carried out at gradient temperatures and constant shear rate,respectively.The results show that at 20,40,60 and 80 ℃,once the shear rate increases gradually,the torque enlarges correspondingly,while the viscosity shows little difference.However,at the constant shear rate,the rising temperature results in a steady downtrend on tea-oil viscosity.This results reveal that tea-oil viscosity is not closely correlated with shear rate at constant temperature,yet negatively correlated with temperature at constant shear rate.

  17. Study Of Hydration Kinetics and Rheological Behaviour of Guar Gum

    Directory of Open Access Journals (Sweden)

    K.Nandhini Venugopal

    2010-01-01

    Full Text Available Guar galactomannan is a plant polysaccharide with extensive pplications in food, paper, textile and petroleum industries. The main advantages for using guar are its low cost, easy availability and capacity to form viscous solutions and gels at low concentration. Additionally, chain architecture of guar galactomannan can be selectively modified to tailor properties of guar formulations and open up new opportunities for guar usage.The parameters such as hydration of guar, intrinsic viscosity measurements for determining the molecular weight of guar, rheological properties of guar were studied.

  18. A rheological study of behavior of polymer-bitumen blends

    Energy Technology Data Exchange (ETDEWEB)

    Djonlagic, J. [Belgrade Univ. (Yugoslavia). Faculty of Technology and Metallurgy; Dunjic, B. [Belgrade Univ. (Yugoslavia). Faculty of Technology and Metallurgy; Javanovic, J.A. [Belgrade Univ. (Yugoslavia). Faculty of Technology and Metallurgy

    1996-12-01

    The influence of the elastomer such as SBS and SBR and their mixtures on the structure and rheological properties of blown bitumen B 65 blends, was studied. The crude oil denoted as SEB (Soviet Export Blend) was used to obtain the B 65 sample. (orig./HS) [Deutsch] Es wurde die Wirkung der SBR- und SBS-Elastomere und ihrer Mischungen, auf die Struktur und die rheologischen Eigenschaften des aus geblasenem Bitumen B 65 hergestellten Polymer-Bitumens (PmB), untersucht. Die B 65 Probe stammte aus dem Erdoel SEB (Soviet Export Blend). (orig./HS)

  19. Rheological and structural studies of carboxymethyl derivatives of chitosan

    Energy Technology Data Exchange (ETDEWEB)

    Winstead, Cherese; Katagumpola, Pushpika [Delaware State University, Department of Chemistry, 1200 N. Dupont Highway, Dover, DE 19901 (United States)

    2014-05-15

    The degrees of substitution of chitosan derivatives were varied and the viscoelastic behavior of these biopolymer solutions was studied using rheology. Chitosan is a cationic copolymer of glucosamine and N-acetylglucosamine obtained by alkaline deacetylation of chitin. Due to its inherent non-toxicity, biocompatibility, and biodegradability, chitosan has gained much interest. However, the poor solubility of the biopolymer in water and most common organic solvents limits its applications. Therefore, the focus of this work is the chemical modification of chitosan via carboxymethylation as well as studying the viscoelastic behavior of these polymer solutions. Varying degrees of substitution (DS) of carboxymethyl chitosan derivatives were synthesized by treating chitosan with monochloroacetic acid under alkylated medium varying the reaction time and temperature. The effect of degree of substitution on the rheology of these polymer solutions was studied as a function of concentration. The viscosity of chitosan derivatives sharply increased with increase in degree of substitution. G' and G' dependence on strain and angular frequency were studied and were found to exhibit predominantly viscous behavior. Additional characterization of the derivatized products were further studied using Fourier transform infrared (FT-IR), {sup 1}H Nuclear Magnetic Resonance ({sup 1}H NMR) spectroscopy, X-ray diffraction (XRD), and thermal gravimetric analysis as well as differential scanning calorimetry (DSC). Degree of substitution (DS) was calculated by titrimetric method.

  20. Rheological and structural studies of carboxymethyl derivatives of chitosan

    Science.gov (United States)

    Winstead, Cherese; Katagumpola, Pushpika

    2014-05-01

    The degrees of substitution of chitosan derivatives were varied and the viscoelastic behavior of these biopolymer solutions was studied using rheology. Chitosan is a cationic copolymer of glucosamine and N-acetylglucosamine obtained by alkaline deacetylation of chitin. Due to its inherent non-toxicity, biocompatibility, and biodegradability, chitosan has gained much interest. However, the poor solubility of the biopolymer in water and most common organic solvents limits its applications. Therefore, the focus of this work is the chemical modification of chitosan via carboxymethylation as well as studying the viscoelastic behavior of these polymer solutions. Varying degrees of substitution (DS) of carboxymethyl chitosan derivatives were synthesized by treating chitosan with monochloroacetic acid under alkylated medium varying the reaction time and temperature. The effect of degree of substitution on the rheology of these polymer solutions was studied as a function of concentration. The viscosity of chitosan derivatives sharply increased with increase in degree of substitution. G' and G" dependence on strain and angular frequency were studied and were found to exhibit predominantly viscous behavior. Additional characterization of the derivatized products were further studied using Fourier transform infrared (FT-IR), 1H Nuclear Magnetic Resonance (1H NMR) spectroscopy, X-ray diffraction (XRD), and thermal gravimetric analysis as well as differential scanning calorimetry (DSC). Degree of substitution (DS) was calculated by titrimetric method.

  1. Non-Newtonian behavior observed via dynamic rheology for various particle types in energetic materials and simulant composites

    Science.gov (United States)

    Choi, Jong Han; Lee, Sangmook; Lee, Jae Wook

    2017-02-01

    The rheological properties of polymer composites highly filled with different filler materials were examined using a stress-controlled rheometer with a parallel-plate configuration, for particle characterization of the filler materials in plastic (polymer) bonded explosive (PBX). Ethylene vinyl acetate (EVA) with dioctyl adipate (DOA) was used as the matrix phase, which was shown to exhibit Newtonian-like behavior. The dispersed phase consisted of one of two energetic materials, i.e., explosive cyclotrimethylene trinitramine (RDX) or cyclotetramethylene tetranitramine (HMX), or a simulant (Dechlorane) in a bimodal size distribution. Before the test, preshearing was conducted to identify the initial condition of each sample. All examined filled polymer specimens exhibited yield stress and shear-thinning behavior over the investigated frequency range. The complex viscosity dependence on the dynamic oscillation frequency was also fitted using an appropriate rheological model, suggesting the model parameters. Furthermore, the temperature dependency of the different filler particle types was determined for different filler volume fractions. These comparative studies revealed the influence of the particle characteristics on the rheological properties of the filled polymer.

  2. Nonequilibrium molecular dynamics simulation of the rheology of linear and branched alkanes

    Energy Technology Data Exchange (ETDEWEB)

    Cui, S.T.; Cummings, P.T.; Cochran, H.D.; Moore, J.D.; Gupta, S.A. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemical Engineering]|[Oak Ridge National Lab., TN (United States). Chemical Technology Div.

    1998-03-01

    Liquid alkanes in the molecular weight range of C{sub 20}-C{sub 40} are the main constituents of lubricant basestocks, and their rheological properties are therefore of great concern in industrial lubricant applications. Using massively parallel supercomputers and an efficient parallel algorithm, the authors have carried out systematic studies of the rheological properties of a variety of model liquid alkanes ranging from linear to singly branched and multiply branched alkanes. They aim to elucidate the relationship between the molecular architecture and the viscous behavior. Nonequilibrium molecular dynamics simulations have been carried out for n-decane (C{sub 10}H{sub 22}), n-hexadecane (C{sub 16}H{sub 34}), n-tetracosane (C{sub 24}H{sub 50}), 10-n-hexylnonadecane (C{sub 25}H{sub 52}), and squalane (2, 6, 10, 15, 19, 23-hexamethyltetracosane, C{sub 30}H{sub 62}). At a high strain rate, the viscosity shows a power-law shear thinning behavior over several orders of magnitude in strain rate, with exponents ranging from {minus}0.33 to {minus}0.59. The power-law shear thinning is shown to be closely related to the ordering of the molecules. The molecular architecture is shown to have a significant influence on the power-law exponent. At a low strain rate, the viscosity behavior changes to a Newtonian plateau, whose accurate determination has been elusive in previous studies. The molecular order in this regime is essentially that of the equilibrium system, a signature of the linear response. The Newtonian plateau is verified by independent equilibrium molecular dynamics simulations using the Green-Kubo method. The reliable determination of the Newtonian viscosity from nonequilibrium molecular simulation permits us to calculate the viscosity index for squalane. The viscosity index is a widely used property to characterize the lubricant`s temperature performance, and the studies represent the first approach toward its determination by molecular simulation.

  3. Study on the Rheological Property of Cassava Starch Adhesives

    Directory of Open Access Journals (Sweden)

    Junjun Liu

    2014-03-01

    Full Text Available The main goal of this study was to use cassava starch in the production of environmentally sound adhesives. ‘Three-formaldehyde glue’ pollutes the environment and harms to human health strongly, which widely used for wood-based panels preparation. Environment-friendly cassava starch adhesives were prepared using method of oxidation-gelatinization, insteading of the three formaldehyde glue. The effects of the quality ratio of starch and water, temperature and shear rate on the apparent viscosity of the adhesive were studied. The rheological eigenvalue of apparent viscosity was studied through nonlinear regression. The results showed that the apparent viscosity of cassava starch adhesives decreased with the increasing of temperature; the apparent viscosity decreased slowly with the increasing of rotor speed; the phenomenon of shear thinning appeared within cassava starch adhesives which was pseudo-plastic fluids. Cassava starch adhesives with characteristics of non-toxic, no smell and pollution could be applied in interior and upscale packaging.

  4. Different Applications of Rheological Techniques in Studies of Physical Gels

    DEFF Research Database (Denmark)

    Hvidt, Søren

    . Rheological techniques are used extensively in studies of physical gels and gelation. In the lecture some of the common techniques used in studies of gels will be addressed. Small amplitude oscillatory measurements are the most common type of measurement performed, and such measurements allow a determination......Physical gels are of both great scientific and practical interest. The cytoplasm of cells, which consists of a complex physical gel of protein filaments, is important for most of the cellular processes including cell division and cell motility. Nature has developed this complex system......-forming biopolymers. Physical gels are also used in the paint industry to minimize sedimentation. Delayed and controlled drug release is of importance in the pharmaceutical industry, and one way to obtain this control is to hide active components in physical gels. Two excellent reviews cover many aspects...

  5. Rheology of Supramolecular Polymers

    DEFF Research Database (Denmark)

    Shabbir, Aamir

    efficient processes or biomedical areas. Design and development of supramolecular polymers using ionic, hydrogen bonding or transition metal complexes with tailored properties requires deep understanding of dynamics both in linear and non-linear deformations. While linear rheology is important to understand......) hydrogen bonding polymers, and (b) ionic bonding polymers (hereafter termed as ionomers). We study linear and non-linear rheology fora model system of entangled pure poly(n-butyl acrylate), PnBA, homopolymer andfour poly(acrylic acid), PnBA-PAA, copolymers with varying AA side groups synthesizedvia...

  6. An Evaluation of Magneto Rheological Dampers for Controlling Gun Recoil Dynamics

    Directory of Open Access Journals (Sweden)

    Mehdi Ahmadian

    2001-01-01

    Full Text Available The application of magneto rheological dampers for controlling recoil dynamics is examined, using a recoil demonstrator that includes a single-shot 50 caliber BMG rifle action and a MR damper. The demonstrator is selected such that it can adequately represent the velocities that commonly occur in weapons with a recoil system, and can be used for collecting data for analyzing the effects of MR dampers on recoil dynamics. The MR damper is designed so that it can work effectively at the large velocities commonly occurring in gun recoil, and also be easily adjusted to reasonably optimize the damper performance for the recoil demonstrator. The test results show that it is indeed possible to design and use MR dampers for recoil applications, which subject the damper to relative velocities far larger than the applications that such dampers have commonly been used for (i.e., vehicle applications. Further, the results indicate that the recoil force increases and the recoil stroke decreases nonlinearly with an increase in the damping force. Also of significance is the fact that the adjustability of MR dampers can be used in a closed-loop system such that the large recoil forces that commonly occur upon firing the gun are avoided and, simultaneously, the recoil stroke is reduced. This study points to the need for several areas of research including establishing the performance capabilities for MR dampers for gun recoil applications in an exact manner, and the potential use of such dampers for a fire out of battery recoil system.

  7. Rheological study of chitosan and its blends: An overview

    Directory of Open Access Journals (Sweden)

    Esam A. El-hefian

    2010-06-01

    Full Text Available Chitosan, a modified natural carbohydrate polymer derived from carapaces of crabs and shrimps, has received a great deal of attention for its applications in diverse fields owing to its biodegradability, biocompatibility, non-toxicity and anti-bacterial property. The wide-ranging applications involve a broad spectrum of characterisation techniques and rheology represents one technique of growing importance in this field. This paper is an attempt to review the latest development in the rheology of chitosan, either on its own or associated with other materials, including the parameters that strongly influence its rheological behaviour such as concentration, pH and temperature.

  8. Rheology of a vesicle suspension with finite concentration: a numerical study.

    Science.gov (United States)

    Thiébaud, Marine; Misbah, Chaouqi

    2013-12-01

    Vesicles, closed membranes made of a bilayer of phospholipids, are considered as a biomimetic system for the mechanics of red blood cells. The understanding of their dynamics under flow and their rheology is expected to help the understanding of the behavior of blood flow. We conduct numerical simulations of a suspension of vesicles in two dimensions at a finite concentration in a shear flow imposed by countertranslating rigid bounding walls by using an appropriate Green's function. We study the dynamics of vesicles, their spatial configurations, and their rheology, namely, the effective viscosity η(eff). A key parameter is the viscosity contrast λ (the ratio between the viscosity of the encapsulated fluid over that of the suspending fluid). For small enough λ, vesicles are known to exhibit tank treading (TT), while at higher λ they exhibit tumbling (TB). We find that η(eff) decreases in the TT regime, passes a minimum at a critical λ=λ(c), and increases in the TB regime. This result confirms previous theoretical and numerical works performed in the extremely dilute regime, pointing to the robustness of the picture even in the presence of hydrodynamic interactions. Our results agree also with very recent numerical simulations performed in three dimensions both in the dilute and more concentrated regime. This points to the fact that dimensionality does not alter the qualitative features of η(eff). However, they disagree with recent simulations in two dimensions. We provide arguments about the possible sources of this disagreement.

  9. Rheological study of the mixture of acetaminophen and polyethylene oxide for hot-melt extrusion application.

    Science.gov (United States)

    Suwardie, Herman; Wang, Peng; Todd, David B; Panchal, Viral; Yang, Min; Gogos, Costas G

    2011-08-01

    There is a growing interest of extrusion drug and polymer together to manufacture various solid dosages. In those cases, the drug's release profiles are greatly affected by the miscibility of two materials. The goal of this study is to test the drug's solubility in molten polymer and obtain the mixture's rheological properties for the purpose of optimizing the extrusion process. The dynamic and steady viscosities of APAP-PEO mixture were determined using oscillatory and capillary rheometers. The curves of viscosity vs. drug loading generally have a "V" shape, and the minimal point gives the APAP's solubility in PEO. The test results suggest that different dynamic methods lead to essentially the same solubility data. At high shear rates, the mixtures show shear thinning behavior and the viscosity becomes less sensitive to the drug loading. In other words, it is desirable to use a low shear rate in order to deduce the drug's solubility in polymer from the viscosity data. On the other hand, viscosity data at high shear rates are more representative of the materials' rheological properties during extrusion.

  10. Rheological study of chitosan and its blends: An overview

    OpenAIRE

    EL-HEFIAN, Esam A.

    2010-01-01

    Chitosan, a modified natural carbohydrate polymer derived from carapaces of crabs and shrimps, has received a great deal of attention for its applications in diverse fields owing to its biodegradability, biocompatibility, non-toxicity and anti-bacterial property. The wide-ranging applications involve a broad spectrum of characterisation techniques and rheology represents one technique of growing importance in this field. This paper is an attempt to review the latest development in the rheolog...

  11. Numerical experiments on the dynamics of channelised lava flows at Mount Cameroon volcano with the FLOWGO thermo-rheological model

    Science.gov (United States)

    Wantim, M. N.; Kervyn, M.; Ernst, G. G. J.; del Marmol, M. A.; Suh, C. E.; Jacobs, P.

    2013-03-01

    As for many other effusive volcanoes, Mount Cameroon (MC) is a volcano for which only limited information exists on lava flow properties and emplacement dynamics for recent eruptions. This study provides new quantitative constraints for rheological and dynamic characteristics of lava flow effusion for the 1982 and 2000 eruptive events, used to calibrate the FLOWGO thermo-rheological model for these lava flows. The FLOWGO 1-D physical model is used to simulate down-flow evolution of the geometry and rheology of channel-contained cooling-limited lava flows. Morphometric data from historical lava flows were acquired from the field, e.g. channel geometry, levee and background slope, in order to estimate lava yield strength, velocity and effusion rate. Lava density and viscosity were also estimated from compositional data and laboratory methods. To account for uncertainty in the input rheological and geometrical data, three end-member scenarios were used to bracket the potential range in lava channel initial dimension, initial lava temperature and phenocryst content. For each of these scenarios, two crustal growth models were used: one assuming strong insulation due to lava flow surface crusting, the other a much lower crusting rate. Twelve numerical simulations were made per flow and the results were compared against the channel geometry, microlite content, yield strength and viscosity estimates from field and laboratory investigations. Best-fit models where obtained for both the 1982 and 2000 lava flows using a low rate of surface crusting, high initial temperature and low phenocryst content. Model-predicted lengths were within 5% of the actual lengths. Modelled mean effusion rates for the 1982 (52-64 m3 s- 1) and 2000 (10 m3 s- 1) flows closely matched field data derived estimations (26-68 and 9.5 m3 s- 1 respectively). FLOWGO model results are highly sensitive to initial channel dimensions, phenocryst content and the FLOWGO model is unable to reproduce the observed

  12. Lithospheric Rheology Constrained by Loading of the Hawaiian Islands and its Implications for the Dynamics of Plate Tectonics

    Science.gov (United States)

    Zhong, S.; Watts, A. B.

    2013-12-01

    Lithospheric rheology is important for understanding crustal and lithospheric dynamics, and the conditions for plate tectonics. For example, numerical modeling studies suggest that plate tectonics emerge from the dynamics of mantle convection when a small coefficient of friction (significantly to match the observations, together with frictional coefficient in the range from 0.1 to 0.7. However, the small coefficient of friction weakens the shallow part of the lithosphere so much that it causes the minima in strain rate and stress to occur at too large depths to be consistent with the depth distribution of seismicity at Hawaii. Our results therefore suggest that the coefficient of friction is between 0.25 and 0.7. Finally, maximum lithospheric stress under Hawaiian loads is about 100-200 MPa for models that match the observations, and this stress may be viewed as the largest lithospheric stress on the Earth.

  13. Chocolate rheology

    Directory of Open Access Journals (Sweden)

    Estela Vidal Gonçalves

    2010-12-01

    Full Text Available Rheology is the science that studies the deformation and flow of solids and fluids under the influence of mechanical forces. The rheological measures of a product in the stage of manufacture can be useful in quality control. The microstructure of a product can also be correlated with its rheological behavior allowing for the development of new materials. Rheometry permits attainment of rheological equations applied in process engineering, particularly unit operations that involve heat and mass transfer. Consumer demands make it possible to obtain a product that complies with these requirements. Chocolate industries work with products in a liquid phase in conching, tempering, and also during pumping operations. A good design of each type of equipment is essential for optimum processing. In the design of every process, it is necessary to know the physical characteristics of the product. The rheological behavior of chocolate can help to know the characteristics of application of the product and its consumers. Foods are generally in a metastable state. Their texture depends on the structural changes that occur during processing. Molten chocolate is a suspension with properties that are strongly affected by particle characteristics including not only the dispersed particles but also the fat crystals formed during chocolate cooling and solidification. Chocolate rheology is extensively studied, and it is known that chocolate texture and stability is strongly affected by the presence of specific crystals

  14. Rheological-dynamical continuum damage model for concrete under uniaxial compression and its experimental verification

    Directory of Open Access Journals (Sweden)

    Milašinović Dragan D.

    2015-01-01

    Full Text Available A new analytical model for the prediction of concrete response under uniaxial compression and its experimental verification is presented in this paper. The proposed approach, referred to as the rheological-dynamical continuum damage model, combines rheological-dynamical analogy and damage mechanics. Within the framework of this approach the key continuum parameters such as the creep coefficient, Poisson’s ratio and damage variable are functionally related. The critical values of the creep coefficient and damage variable under peak stress are used to describe the failure mode of the concrete cylinder. The ultimate strain is determined in the post-peak regime only, using the secant stress-strain relation from damage mechanics. The post-peak branch is used for the energy analysis. Experimental data for five concrete compositions were obtained during the examination presented herein. The principal difference between compressive failure and tensile fracture is that there is a residual stress in the specimens, which is a consequence of uniformly accelerated motion of load during the examination of compressive strength. The critical interpenetration displacements and crushing energy are obtained theoretically based on the concept of global failure analysis. [Projekat Ministarstva nauke Republike Srbije, br. ON 174027: Computational Mechanics in Structural Engineering i br. TR 36017: Utilization of by-products and recycled waste materials in concrete composites for sustainable construction development in Serbia: Investigation and environmental assessment of possible applications

  15. Mantle dynamics in super-Earths: Post-perovskite rheology and self-regulation of viscosity

    Science.gov (United States)

    Tackley, P. J.; Ammann, M.; Brodholt, J. P.; Dobson, D. P.; Valencia, D.

    2013-07-01

    The discovery of extra-solar "super-Earth" planets with sizes up to twice that of Earth has prompted interest in their possible lithosphere and mantle dynamics and evolution. Simple scalings suggest that super-Earths are more likely than an equivalent Earth-sized planet to be undergoing plate tectonics. Generally, viscosity and thermal conductivity increase with pressure while thermal expansivity decreases, resulting in lower convective vigour in the deep mantle, which, if extralopated to the largest super-Earths might, according to conventional thinking, result in no convection in their deep mantles due to the very low effective Rayleigh number. Here we evaluate this. First, as the mantle of a super-Earth is made mostly of post-perovskite we here extend the density functional theory (DFT) calculations of post-perovskite activation enthalpy of to a pressure of 1 TPa, for both slowest diffusion (upper-bound rheology) and fastest diffusion (lower-bound rheology) directions. Along a 1600 K adiabat the upper-bound rheology would lead to a post-perovskite layer of a very high (˜1030 Pa s) but relatively uniform viscosity, whereas the lower-bound rheology leads to a post-perovskite viscosity increase of ˜7 orders of magnitude with depth; in both cases the deep mantle viscosity would be too high for convection. Second, we use these DFT-calculated values in statistically steady-state numerical simulations of mantle convection and lithosphere dynamics of planets with up to ten Earth masses. The models assume a compressible mantle including depth-dependence of material properties and plastic yielding induced plate-like lithospheric behaviour. Results confirm the likelihood of plate tectonics for planets with Earth-like surface conditions (temperature and water) and show a self-regulation of deep mantle temperature. The deep mantle is not adiabatic; instead feedback between internal heating, temperature and viscosity regulates the temperature such that the viscosity has the

  16. External and internal gelation of pectin solutions: microscopic dynamics versus macroscopic rheology

    Science.gov (United States)

    Secchi, E.; Munarin, F.; Alaimo, M. D.; Bosisio, S.; Buzzaccaro, S.; Ciccarella, G.; Vergaro, V.; Petrini, P.; Piazza, R.

    2014-11-01

    Pectin is a natural biopolymer that forms, in the presence of divalent cations, ionic-bound gels typifying a large class of biological gels stabilized by non-covalent cross-links. We investigate and compare the kinetics of formation and aging of pectin gels obtained either through external gelation via perfusion of free Ca2+ ions, or by internal gelation due to the supply of the same ions from the dissolution of CaCO3 nanoparticles. The microscopic dynamics obtained with photon correlation imaging, a novel optical technique that allows obtaining the microscopic dynamics of the sample while retaining the spatial resolution of imaging techniques, is contrasted with macroscopic rheological measurements at constant strain. Pectin gelation is found to display peculiar two-stage kinetics, highlighted by non-monotonic growth in time of both microscopic correlations and gel mechanical strength. These results are compared to those found for alginate, another biopolymer extensively used in food formulation.

  17. External and internal gelation of pectin solutions: microscopic dynamics versus macroscopic rheology.

    Science.gov (United States)

    Secchi, E; Munarin, F; Alaimo, M D; Bosisio, S; Buzzaccaro, S; Ciccarella, G; Vergaro, V; Petrini, P; Piazza, R

    2014-11-19

    Pectin is a natural biopolymer that forms, in the presence of divalent cations, ionic-bound gels typifying a large class of biological gels stabilized by non-covalent cross-links. We investigate and compare the kinetics of formation and aging of pectin gels obtained either through external gelation via perfusion of free Ca(2+) ions, or by internal gelation due to the supply of the same ions from the dissolution of CaCO3 nanoparticles. The microscopic dynamics obtained with photon correlation imaging, a novel optical technique that allows obtaining the microscopic dynamics of the sample while retaining the spatial resolution of imaging techniques, is contrasted with macroscopic rheological measurements at constant strain. Pectin gelation is found to display peculiar two-stage kinetics, highlighted by non-monotonic growth in time of both microscopic correlations and gel mechanical strength. These results are compared to those found for alginate, another biopolymer extensively used in food formulation.

  18. Carboxymethylation of Cassia angustifolia seed gum: synthesis and rheological study.

    Science.gov (United States)

    Rajput, Gaurav; Pandey, I P; Joshi, Gyanesh

    2015-03-06

    The seeds of Cassia angustifolia are a rich source of galactomannan gum. The seed gums possess a wide variety of industrial applications. To utilize C. angustifolia seed gum for broader industrial applications, the carboxymethyl-Cassia angustifolia seed gum (CM-CAG) was synthesized. The gum was etherified with sodium monochloroacetate (SMCA) in a methanol-water system in presence of alkali (NaOH) at different reaction conditions. The variables studied includes alkali concentration, SMCA concentration, methanol:water ratio, liquor:gum ratio, reaction temperature and time. The extent of carboxymethylation was determined as degree of substitution (DS). The optimum conditions for preparing CM-CAG (DS=0.474) comprised 0.100 mol of NaOH, 0.05 mol of SMCA, 80% of methanol:water ratio (as % methanol) and liquor:gum ratio (v/w) of 10:1 at 75 °C for 60 min using 0.03 mol (as AGU) of CAG. Rheological studies showed CM-CAG to exhibit non-Newtonian pseudoplastic behaviour, relatively high viscosity, cold water solubility and solution stability. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Physics of Hard Sphere Experiment: Scattering, Rheology and Microscopy Study of Colloidal Particles

    Science.gov (United States)

    Cheng, Z.-D.; Zhu, J.; Phan, S.-E.; Russel, W. B.; Chaikin, P. M.; Meyer, W. V.

    2002-01-01

    The Physics of Hard Sphere Experiment has two incarnations: the first as a scattering and rheology experiment on STS-83 and STS-94 and the second as a microscopy experiment to be performed in the future on LMM on the space station. Here we describe some of the quantitative and qualitative results from previous flights on the dynamics of crystallization in microgravity and especially the observed interaction of growing crystallites in the coexistance regime. To clarify rheological measurements we also present ground based experiments on the low shear rate viscosity and diffusion coefficient of several hard sphere experiments at high volume fraction. We also show how these experiments will be performed with confocal microscopy and laser tweezers in our lab and as preparation for the phAse II experiments on LMM. One of the main aims of the microscopy study will be the control of colloidal samples using an array of applied fields with an eye toward colloidal architectures. Temperature gradients, electric field gradients, laser tweezers and a variety of switchable imposed surface patterns are used toward this control.

  20. Rheological control on the AD 472 Pollena eruption dynamics (Somma-Vesuvius)

    Science.gov (United States)

    Vona, Alessandro; Romano, Claudia; Giordano, Guido; Sulpizio, Roberto; Campagnola, Silvia; De Benedetti, Arnaldo Angelo

    2016-04-01

    The 472 AD Pollena sub-Plinian eruption of Vesuvius was characterized by three main eruptive phases. Pulsatory eruptive dynamics were driven by magmatic fragmentation of a phonolitic (L1) to tephri-phonolitic magma (L8) during Phases I and II, whereas phreatomagmatic fragmentation dominated Phase III. In order to investigate magma dynamics, we integrated field data on the physical properties (column height, mass discharge rate) with a detailed chemico-textural analysis of the fall-out products (L1-L8), and with laboratory measurements of the phonolite (L1) and tephriphonolite (L8) multiphase rheology. The fall deposits mainly consist of crystal-bearing pumice (L1) or scoria (L2 to L8) lapilli. Gaussian Vesicle Volume Distributions (VVDs) indicate a single and rapid event of bubble nucleation and growth (Vesicle Number Density, VND = 107-109 cm-3). Cristallinity is constituted by dominant leucite and clinopyroxene and increases with stratigraphic height. The amount of H2O initially dissolved in the magma (1.7-3.6 wt% by Raman spectroscopy on Cpx-hosted melt inclusions) decreases from L1 to L8 layer. Anhydrous melt viscosity of the two end-member compositions was measured at high T (1000° C isothermal (T= 1150 - 1190 ° C) crystallization experiments in a concentric cylinder set-up. The measured effect of crystals is in good agreement with literature models and the results can be extended to estimate natural magma rheology. During the first part of the eruption (L1 - L3), despite a decrease in H2O, the column height increases from 12 to 17 km, possibly related to a change of conduit/vent geometry. The following phases are characterized by relatively steady conditions, while the highest eruptive energy is reached at level L8 (20 km column height) despite its lowest silica content. Textural analyses indicate that the crystal content reaches almost maximum packing (φ = 0.48) in L8 and accordingly bulk viscosity increases by 2 orders of magnitude. We suggest that the

  1. Studies on Rheology of E-printing Inks by μ-PIV in Microchannels

    Science.gov (United States)

    Jang, Young-Sik; Song, Simon

    2009-11-01

    Using printing technologies for electronic circuits, such as antennas for radio frequency identification (RFID) chips, has been paid attention to recently in order to reduce production costs. In general, E-printing inks used for printed electronics have non-Newtonian properties because they contain metallic particles. Thus, it is important to investigate rheological behaviors of E-printing inks and suggest proper rheological models for developing printing devices for printed electronics. Also, the rheological models are necessary to accurately predict ink behaviors using CFD. However, classic methods to study rheological models are somewhat irrelevant since they require the mass consumption of expensive E-printing inks. Thus, to study rheological models suitable for commercial E-printing inks, we use microfluidic chips that only requires nascent E-printing inks. We measured flow velocities using μPIV and pressure drops along the microchannel to determine a relationship between stress and strain rate of ink flows. We found that the E-printing inks exhibit shear-thinning behaviors. In the presentation, we will propose rheology models suitable for the E-printing inks.

  2. Mathematical model of microbicidal flow dynamics and optimization of rheological properties for intra-vaginal drug delivery: Role of tissue mechanics and fluid rheology.

    Science.gov (United States)

    Anwar, Md Rajib; Camarda, Kyle V; Kieweg, Sarah L

    2015-06-25

    Topically applied microbicide gels can provide a self-administered and effective strategy to prevent sexually transmitted infections (STIs). We have investigated the interplay between vaginal tissue elasticity and the yield-stress of non-Newtonian fluids during microbicide deployment. We have developed a mathematical model of tissue deformation driven spreading of microbicidal gels based on thin film lubrication approximation and demonstrated the effect of tissue elasticity and fluid yield-stress on the spreading dynamics. Our results show that both elasticity of tissue and yield-stress rheology of gel are strong determinants of the coating behavior. An optimization framework has been demonstrated which leverages the flow dynamics of yield-stress fluid during deployment to maximize retention while reaching target coating length for a given tissue elasticity.

  3. Rheological study of polypropylene irradiated with polyfunctional monomers

    Science.gov (United States)

    Otaguro, H.; Rogero, S. O.; Yoshiga, A.; Lima, L. F. C. P.; Parra, D. F.; Artel, B. W. H.; Lugão, A. B.

    2007-12-01

    The aim of this paper is to investigate the rheological properties of polypropylene (PP) modified by ionization radiation (gamma rays) in the presence of two different monomers. The samples were mixed in a twin-screw extruder with ethylene glycol dimethacrylate (EGDMA) or trimethylolpropane trimethacrylate (TMPTMA) with concentration in the range of 0.5-5.0 mmol. After that, they were irradiated with 20 kGy dose of gamma radiation. The structural modification of polypropylene was analyzed in the melt state by measuring melt flow rate (MFR), η* (complex viscosity) and G' (storage modulus) in the angular frequency range of 10 -1 to 3 × 10 2 rad s -1. From the oscillatory rheology data, one could obtain the values of η0 (zero shear viscosity) that would be related to the molar mass. All results were discussed with respect to the crosslinking and degradation process that occur in the post-reactor treatment to produce controlled rheology polypropylene. The resulting polymeric materials were submitted the cytotoxicity in vitro test by neutral red uptake methodology with NCTC L 929 cell line from American Type Culture Collection bank. All modified PP samples presented no cytotoxicity.

  4. A nonlinear kinematic and dynamic modeling of Macpherson suspension systems with a magneto-rheological damper

    Science.gov (United States)

    Dutta, Saikat; Choi, Seung-Bok

    2016-03-01

    It is well known that Macpherson strut suspension systems are widely used in light and medium weight vehicles. The performance of these suspension systems can be enriched by incorporating magneto-rheological (MR) dampers and an appropriate dynamic model is required in order to find out the ride comfort and other performances properly in the sense of practical environment conditions. Therefore, in this work the kinematic and dynamic modeling of Macpherson strut suspension system with MR damper is presented and its responses are evaluated. The governing equations are formulated using the kinematic properties of the suspension system and adopting Lagrange’s equation. In the formulation of the model, both the rotation of the wheel assembly and the lateral stiffness of the tire are considered to represent the nonlinear characteristic of Macpherson type suspension system. The formulated mathematical model is then compared with equivalent conventional quarter car suspension model and the different dynamic responses such as the displacement of the sprung mass are compared to emphasize the effectiveness of the proposed model. Additionally, in this work the important kinematic properties of suspension system such as camber angle, king-pin angle and track width alteration, which cannot be obtained from conventional quarter car suspension model, are evaluated in time and frequency domains. Finally, vibration control responses of the proposed suspension system are presented in time and frequency domains which are achieved from the semi-active sky-hook controller.

  5. Examination of the rheological properties of stirred joghurt during the long-term storage by using dynamic oscillation method

    Directory of Open Access Journals (Sweden)

    Milica Vilušić

    2003-07-01

    Full Text Available In this work the rheological properties of stirred yoghurt during the longterm storage at 4 and 8°C were investigated. The optimal quantity of additives, in order to increase dry matter content (whole milk powder and whey protein-lactalbumin, was preliminary determined and the fermentation was performed. During 42 days, i.e., 1st, 7th, 14th, 21st, 28th, 35th and 42nd day of storage of stirred yoghurt, in refrigerator at 4 and 8°C, the changes of pH value, acidity and rheological properties by using of dynamic oscillation method were observed. Results of this work indicated that an addition of whole milk powder and whey protein have an influence on rheological properties of stirred yoghurt. The long-term storage of stirred yoghurt and the results of dynamic oscilations showed permanently higher G’storage (elasticity modulus, where elastic properties of viscoelastic products dominate, in comparison with the G” loss (viscosity modulus. Increased moduls of elasticy and viscosity, as function of time, permanently occurs at pH value 4.00 and lower, as an indication of alteration of long casein chains in the coagulum structure. Different temperatures of storage had no influence on changes of rheological properties of examinated types of stirred yoghur. The relation of above mentioned moduls of elasticy and viscosity kept the same increasing tendency.

  6. Rheological Predictions of Network Systems Swollen with Entangled Solvent

    Science.gov (United States)

    2014-04-01

    solvent was previously studied experimentally. In this article, we use the discrete slip-link model to predict its linear and nonlinear rheology ...Model parameters are obtained from the dynamic modulus data of pure solvent. Network rheology predictions also require an estimate of the fraction and...Triangle Park, NC 27709-2211 rheology ;polymer properties;gels, networks;mathematical modeling;multiscale modeling REPORT DOCUMENTATION PAGE 11. SPONSOR

  7. Rheological control on the dynamics of explosive activity in the 2000 summit eruption of Mt. Etna

    Directory of Open Access Journals (Sweden)

    D. Giordano

    2010-02-01

    Full Text Available In the period from January to June 2000 Mt. Etna exhibited an exceptional explosive activity characterised by a succession of 64 Strombolian and fire-fountaining episodes from the summit South-East crater. Textural analysis of the eruptive products reveals that the magma associated with the Strombolian phases had a much larger crystal content >55 vol% with respect to the magma discharged during the fire-fountain phases (~35 vol%. Rheological modelling shows that the crystal-rich magma falls in a region beyond a critical crystal content where the small addition of solid particles causes an exponential increase of the effective magma viscosity. When implemented into the modelling of steady magma ascent dynamics, the large crystal content of the Strombolian eruption phases results in a one order of magnitude decrease of mass flow-rate, and in the onset of conditions where small heterogeneities in the solid fraction carried by the magma translate into highly unsteady eruption dynamics. Therefore, we argue that crystallization on top of the magmatic column during the intermediate phases when magma was not discharged caused the conditions to shift from fire-fountain to Strombolian activity. The numerical simulations also provide a consistent interpretation of the association between fire-fountain activity and emergence of lava flows from the crater flanks.

  8. Rheological control on the dynamics of explosive activity in the 2000 summit eruption of Mt. Etna

    Directory of Open Access Journals (Sweden)

    D. Giordano

    2010-07-01

    Full Text Available In the period from January to June 2000 Mt. Etna exhibited an exceptional explosive activity characterized by a succession of 64 Strombolian and fire-fountaining episodes from the summit South-East Crater. Textural analysis of the eruptive products reveals that the magma associated with the Strombolian phases had a much larger crystal content (>55 vol% with respect to the magma discharged during the fire-fountain phases (~35 vol%. Rheological modelling shows that the crystal-rich magma falls in a region beyond a critical crystal content where small addition of solid particles causes an exponential increase of the effective magma viscosity. When implemented into the modeling of steady magma ascent dynamics (as assumed for the fire-fountain activity, a large crystal content as the one found for products of Strombolian eruption phases results in a one order of magnitude decrease of mass flow-rate, and in the onset of conditions where small heterogeneities in the solid fraction carried by the magma translate into highly unsteady eruption dynamics. We argue that crystallization on top of the magmatic column during the intermediate phases when magma was not discharged favoured conditions corresponding to Strombolian activity, with fire-fountain activity resuming after removal of the highly crystalline top. The numerical simulations also provide a consistent interpretation of the association between fire-fountain activity and emergence of lava flows from the crater flanks.

  9. The effect of rheological approximations on the dynamics and topography in 3D subduction-collision models

    Science.gov (United States)

    Pusok, Adina E.; Kaus, Boris J. P.; Popov, Anton A.

    2016-04-01

    Most of the major mountain belts and orogenic plateaus are found within the overlying plate of active or fossil subduction and/or collision zones. Moreover, they evolve differently from one another as the result of specific combinations of surface and mantle processes. These differences arise for several reasons, such as different rheological properties, different amounts of regional isostatic compensation, and different mechanisms by which forces are applied to the convergent plates. Previous 3D geodynamic models of subduction/collision processes have used various rheological approximations, making numerical results difficult to compare, since there is no clear image on the extent of these approximations on the dynamics. Here, we employ the code LaMEM to perform high-resolution long-term 3D simulations of subduction/continental collision in an integrated lithospheric and upper-mantle scale model. We test the effect of rheological approximations on mantle and lithosphere dynamics in a geometrically simplified model setup that resembles a tectonic map of the India-Asia collision zone. We use the "sticky-air" approach to allow for the development of topography and the dynamics of subduction and collision is entirely driven by slab-pull (i.e. "free subduction"). The models exhibit a wide range of behaviours depending on the rheological law employed: from linear to temperature-dependent visco-elasto-plastic rheology that takes into account both diffusion and dislocation creep. For example, we find that slab dynamics varies drastically between end member models: in viscous approximations, slab detachment is slow following a viscous thinning, while for a non-linear visco-elasto-plastic rheology, slab detachment is relatively fast, inducing strong mantle flow in the slab window. We also examine the stress states in the subducting and overriding plates and topography evolution in the upper plate, and we discuss the implications on lithosphere dynamics at convergent margins

  10. HDPE/纳米SiO2杂化材料的动态流变行为研究%The Study of the Dynamic Rheological Behavior of the HDPE/Nano-SiO2 Hybrid Materials

    Institute of Scientific and Technical Information of China (English)

    施海华; 周井隆; 龚方红; 熊煦; 刘春林; 陶国良

    2011-01-01

    Vinyl trimethoxysilane (VTMS) was grafted to the chain of the high density-polyethylene (HDPE) via melt grafting reaction. The tetraethoxysilane (TEOS) which acts as precursor was mixed with grafted HDPE,and then the HDPE/SiO2 hybrid materials were prepared by sol-gel process. The dynamic rheological behavior of the prepared high density-polyethylene/nano-silica hybrid composites was investigated by plate rheometer.Experimental results show that the complex viscosity (η*) of the composites increases with increasing the content of SiO2. When the SiO2 content of the hybrid composite reaches 1.2%, its complex viscosity η* increases suddenly and the shear thinning behavior appears. In the low frequency region, both the curves of the storage module G' vs. frequency ω and loss module G" vs. ω of the HDPE/SiO2 appear a second flat; and on the curve of the strain γ vs. storage module G', there appears two linear viscoelastic sections. These phenomena can be attributed to the links between the nano-SiO2 particles and polymer matrix in the hybrid system by chemical bonds and the uniform distribution of the nano-SiO2 particles; while when the nano-SiO2 content reaches 1.2%, the "solid-like" behavior may occur between the particles.%通过熔融接枝反应将乙烯基三甲氧基硅烷(VTMS)接枝到高密度聚乙烯(HDPE)分子链上,以四乙氧基硅烷(TEOS)为前驱体,加入接枝的HDPE中,通过溶胶-凝胶法(Sol-Gel)制备了HDPE/SiO2杂化材料,使用平板流变仪研究了纳米SiO2对HDPE/纳米SiO2杂化材料的动态流变行为的影响.结果表明,当SiO2含量达到1.2%时,复数黏度η*发生突变,并出现强烈的剪切变稀:低频区,储能模量G'、损耗模量G"出现第二平台;对应的应变y-G'曲线上,体系出现两段线性粘弹区域.这些现象表明由于杂化体系中纳米SiO2粒子与基体聚合物间通过化学键链接,并且均匀分布,在纳米粒子的含量达到1.2%时,粒子间就

  11. Experimental study on the rheological behaviour of coal ash slurries

    Directory of Open Access Journals (Sweden)

    Assefa K.M.

    2015-12-01

    Full Text Available Extensive experimental investigations were carried out to evaluate the rheological behaviour of fly ash (FA slurry without and with the addition of bottom ash (BA and BA slurry without and with the addition of FA. The FA slurries exhibited Bingham behaviour at solid mass concentrations ranging from 60–65% and mixing proportions from 10– 40%. A substantial reduction in yield stress was observed except for mixing proportion of 40% on which the yield stress and viscosity were increased drastically for all solid concentrations. Hence, it can be concluded that the yield stress and viscosity of FA slurry were very much influenced by adding BA up to the mixing proportion of 30%. The rheological behaviour of BA slurries with and without the addition of FA in proportions of 10–50% was investigated and exhibited Newtonian behaviours for solid mass concentrations ranging from 30–50% without and with the addition of FA. The viscosity increases with increasing the solid concentrations and proportion of FA. Based on these experimental data, a correlation was developed to predict the relative viscosity of BA slurries as a function of solid volume fraction and FA mass proportion of 0–50% and the RMSE and R2 values showed good agreement between the experimental and the predicted data.

  12. Study of the influential factors on the rheological behavior of adhesive mortar available in the market

    Directory of Open Access Journals (Sweden)

    M. R. M. M. Costa

    Full Text Available Rheology studies the deformation and flow of matter and seeks to describe the deformations of material depending on the time they are exposed to mechanical actions. This paper proposes to understand the behavior of fresh mortar adhesives in Squeeze Flow tests based on rheological characterization of different commercial compositions. In the tests, flow of material results from the application of a compressive load on the sample in the fresh state which causes displacement due to stresses generated during radial shear flow. We performed further physical characterizations of mortars and viscosity on material passing the through a sieve with a 0.075 mm sieve opening with the objective of basing the analysis of the results obtained from Squeeze Flow tests. It was observed that the mortars studied showed differences in rheological behavior, probably resulting from synergistic action of some of the composition parameters, especially the particle size distribution and particle morphology.

  13. Study of the rheological properties of a fermentation broth of the fungus Beauveria bassiana in a bioreactor under different hydrodynamic conditions.

    Science.gov (United States)

    Núñez-Ramírez, Diola Marina; Medina-Torres, Luis; Valencia-López, José Javier; Calderas, Fausto; López Miranda, Javier; Medrano-Roldán, Hiram; Solís-Soto, Aquiles

    2012-11-01

    Fermentation with filamentous fungi in a bioreactor is a complex dynamic process that is affected by flow conditions and the evolution of the rheological properties of the medium. These properties are mainly affected by the biomass concentration and the morphology of the fungus. In this work, the rheological properties of a fermentation with the fungus Beauveria bassiana under different hydrodynamic conditions were studied and the rheological behavior of this broth was simulated through a mixture of carboxymethyl cellulose sodium and cellulose fibers (CMCNa-SF). The bioreactor was a 10 L CSTR tank operated at different stir velocities. Rheological results were similar at 100 and 300 rpm for both systems. However, there was a significant increase in the viscosity accompanied by a change in the consistence index, calculated according to the power law model, for both systems at 800 rpm. The systems exhibited shear-thinning behavior at all stir velocities, which was determined with the power law model. The mixing time was observed to increase as the cellulose content in the system increased and, consequently, the efficiency of mixing diminished. These results are thought to be due to the rheological and morphological similarities of the two fungal systems. These results will help in the optimization of scale-up production of these fungi.

  14. A study on the rheological properties of recycled rubber-modified asphalt mixtures.

    Science.gov (United States)

    Karacasu, Murat; Okur, Volkan; Er, Arzu

    2015-01-01

    Using waste rubber in asphalt mixes has become a common practice in road construction. This paper presents the results of a study on the rheological characteristics of rubber-modified asphalt (RMA) concrete under static and dynamic loading conditions. A number of static and dynamic creep tests were conducted on RMA mix specimens with different rubber sizes and contents, and a series of resonant column tests were conducted to evaluate the shear modulus and damping values. To simulate the stress-strain response of traffic-induced loading, the measurements were taken for different confining pressures and strain levels. The results of the study indicated that rubber modification increases stiffness and damping ratio, making it a very attractive material for use in road construction. However the grain size of the rubber is very important. Although RMA may cost up to 100% more than regular asphalt, the advantages it brings, such as an increased service life of the road and proper waste utilization contributing to a more sustainable infrastructure, may justify the added cost.

  15. A Study on the Rheological Properties of Recycled Rubber-Modified Asphalt Mixtures

    Directory of Open Access Journals (Sweden)

    Murat Karacasu

    2015-01-01

    Full Text Available Using waste rubber in asphalt mixes has become a common practice in road construction. This paper presents the results of a study on the rheological characteristics of rubber-modified asphalt (RMA concrete under static and dynamic loading conditions. A number of static and dynamic creep tests were conducted on RMA mix specimens with different rubber sizes and contents, and a series of resonant column tests were conducted to evaluate the shear modulus and damping values. To simulate the stress-strain response of traffic-induced loading, the measurements were taken for different confining pressures and strain levels. The results of the study indicated that rubber modification increases stiffness and damping ratio, making it a very attractive material for use in road construction. However the grain size of the rubber is very important. Although RMA may cost up to 100% more than regular asphalt, the advantages it brings, such as an increased service life of the road and proper waste utilization contributing to a more sustainable infrastructure, may justify the added cost.

  16. A Computational Study of the Rheology and Structure of Surfactant Covered Droplets

    Science.gov (United States)

    Maia, Joao; Boromand, Arman

    Using different types of surface-active agents are ubiquitous in different industrial applications ranging from cosmetic and food industries to polymeric nano-composite and blends. This allows to produce stable multiphasic systems like foams and emulsions whose stability and shelf-life are directly determined by the efficiency and the type of the surfactant molecules. Moreover, presence and self-assembly of these species on an interface will display complex dynamics and structural evolution under different processing conditions. Analogous to bulk rheology of complex systems, surfactant covered interfaces will response to an external mechanical forces or deformation differently depends on the molecular configuration and topology of the system constituents. Although the effect of molecular configuration of the surface-active molecules on the planar interfaces has been studied both experimentally and computationally, it remains challenging from both experimental and computational aspects to track efficiency and effectiveness of different surfactant molecules with different molecular geometries on curved interfaces. Using Dissipative Particle Dynamics, we have studies effectiveness and efficiency of different surfactant molecules on a curved interface in equilibrium and far from equilibrium. Interfacial tension is calculated for linear and branched surfactant with different hydrophobic and hydrophilic tail and head groups with different branching densities. Deformation parameter and Taylor plots are obtained for individual surfactant molecules under shear flow.

  17. STUDIES ON STRUCTURE AND PHASE BEHAVIOR OF MULTICOMPONENT POLYMERS THROUGH RHEOLOGICAL TESTS

    Institute of Scientific and Technical Information of China (English)

    Min Zuo; Qiang Zheng; Wan-jie Wang

    2007-01-01

    Rheological measurement has been a preferred approach to the characterization of the structure and phase behaviors for multi-component/multi-phase polymer systems, due to its sensitive response to the changes of structure for these heterogeneous polymers. In the present article, recent progresses in the studies on rheology for heterogeneous polymer systems including phase-separated polymeric blends and block copolymers are reviewed, mainly depending on the results by the authors' research group. By means of rheological measurements, not only some new fingerprints responsible for the evolution of morphology and structure concerning these polymer systems are obtained, also the corresponding results are significant for design and preparation of novel polymeric structural materials and functional materials.

  18. Blood rheology using a Brownian dynamics simulation of bead spring ring with a constant area

    Science.gov (United States)

    Lopez, Rogelio

    Coronary artery disease is epidemic in the western world. Occlusive vascular disease, when considered in terms of total incidence rather than separated to organ involvement, is the leading human's health hazard. A better understanding of occlusive vascular disease is so important that does not need to be justified. Blood theological properties are important factors in the occurrence and onset development of these diseases and may help in a rational approach to predictive and anticipatory therapies. Blood is a suspension of red blood cells (RBC) and therefore has a complex flow behavior. This research presents a Brownian dynamics (BD) model that captures the complex rheological behavior of blood; a three-bead-spring ring with a holonomic constant area constraint is being used to model the RBC in a dilute Newtonian solvent. The BD model has been used in simulations of RBCs to generate the RBC configuration. The stress tensor or momentum flux tensor is obtained as an ensemble average over molecular configurations by Giesekus expression of the stress calculator. This stress calculator makes it possible to obtain the RBC rheological properties of the model blood suspension under different flow conditions: homogeneous simple shear flow, elongational flow, inception of a steady shear flow, stress relaxation after cessation of steady shear flow and flow within narrow vessels by considering the blood microstructure scale process. The model's main results obtained for the specified flows are as follows: (a) Simulations in steady shear flow in an unbounded space the dilute blood suspension model expresses both shear thinning behavior for the viscosity and first normal stress coefficient. (b) In steady elongational flow, the elongational viscosity of the dilute blood suspension increases when the elongational rate increases. (c) Stress growth upon inception of steady shear flow; increasing shear rates does the shear stress approach its steady state monotonically. (d) Stress

  19. Study of rheological, viscoelastic and vulcanization behavior of sponge EPDM/NR blended nano- composites

    Science.gov (United States)

    Arshad Bashir, M.; Shahid, M.; Ahmed, Riaz; Yahya, A. G.

    2014-06-01

    In this research paper the effect of blending ratio of natural rubber (NR) with Ethylene Propylene Diene Monomer (EPDM) were investigated. Different samples of EPDM/NR ratio were prepared to study the variation of NR in EPDM on rheology, curing characteristics, tangent δ, and viscosity variation during vulcanization of sponge nano composites.The main aim of present research is to develop elastomeric based sponge composites with the blending ratio of base elastomers along with the carbon nano particles for high energy absorbing and damping applications. The curing characteristics, rheology and viscoelastic nature of the composite is remarkably influenced with the progressive blending ratio of the base elastomeric matrix.

  20. A study of the kinetic, dielectric, and rheological properties of thermosetting resins used in pultruded polymer composites

    Science.gov (United States)

    Shanku, Reshma

    A comprehensive analysis has been conducted of the curing behavior of AOC VIBRINRTM E-606-6 (medium reactivity isophthalic), E-964 (high reactivity isophthalic), and P-341 (highest reactivity) polyester resins, and Shell EPON 9310 resin/EPON 9360 curing agent/EPON 537 accelerator resin system using calorimetric, dielectric, and rheological methods. The unsaturated polyester resins were cured with two different catalysts at three levels of concentration. Calorimetry and dielectrometry were employed to obtain polyester resin curing properties for the resin formulations studied. Rheological characterization of selected polyester resin formulations and the EPON 9310 resin system were also conducted. Kinetic parameters for all resin formulations were determined using a differential scanning calorimeter (DSC) by dynamic and isothermal methods. The dynamic and isothermal kinetic parameters obtained were used to generate heat flow values which were compared to the experimental DSC heat flow recorded; kinetic parameters that accurately modeled the pultrusion process were selected. The kinetic parameters were used in a numerical model to predict temperatures and degrees of cure under pultrusion processing conditions. The results obtained from the in-situ dielectric tests conducted on the pultruder in the Composites Material Laboratory at the University of Mississippi were compared to the degree of cure predictions from the numerical model and the experimental degree of cure from calorimetric analysis. Prior to the in-situ pultrusion studies, small quantities of resin formulations were tested for their dielectric cure properties when heated in an oven simulating pultrusion processing temperatures and rate of heating. This technique allowed small quantities of resins to be tested for degrees of cure. It was determined that such screening tests can be effectively conducted and can aid in pultrusion process planning. Complex viscosity profiles until gelation were generated for

  1. Using Microfluidic Device to Study Rheological Properties of Heavy Oil

    CERN Document Server

    Keshmiri, Kiarash; Tchoukov, Plamen; Huang, Haibo; Nazemifard, Neda

    2016-01-01

    In this study, capillary-driven flow of different pure liquids and diluted bitumen samples were studied using microfluidic channel (width of 30 um and depth of 9 um). Capillary filling kinetics of liquids as a function of time were evaluated and compared with theoretical predictions. For pure liquids including water, toluene, hexane, and methanol experimental results agreed well with theoretical predictions. However, for bitumen samples, as concentration of bitumen increased the deviation between theoretical and experimental results became larger. The higher deviation for high concentrations (i.e. above 30%) can be due to the difference between dynamic contact angle and bulk contact angle. Microchannels are suitable experimental devices to study the flow of heavy oil and bitumen in porous structure such as those of reservoirs.

  2. Physical characteristics of conditioned anaerobic digested sludge - A fractal,transient and dynamic rheological viewpoint

    Institute of Scientific and Technical Information of China (English)

    Yili Wang; Emilie Dieude-Fauvel; Steven K Dentel

    2011-01-01

    The changes in the physical characteristics of unconditioned and conditioned anaerobic digested sludge (ADS) biosolids,such as capillary suction time (CST),yield stress,average size and fractal dimensions,were investigated through a CST test,transient and dynamic rheological test and image analysis.The results showed that the optimum polymer dose range was observed when CST or its reciprocal value was employed as an indicator.There were good correlations between the yield stresses determined from both a controlled shear stress test and a strain amplitude sweep test.The yield stress and storage modulus (G') increased as the polymer dose increased in most cases.A frequency sweep test revealed that polymer conditioning could extend the frequency sweep ranges for their elastic behaviors over viscous behaviors as well as the gel-like structure in the linear viscoelastic range.These results implied that more deformation energy was stored in this rigid structure,and that elastic behavior became increasingly dominant with the addition of the polymer in most cases.In addition,both the average sizes and two-dimensional fractal dimensions for conditioned ADS biosolids presented a similar up-climax-down variation trend as the polymer doses increased,whereas the critical polymer doses at the highest average sizes or two-dimensional fractal dimensions,were different.Correlation analysis revealed that the conditioned ADS dewaterability was not correlated with the yield stresses,while the average sizes or the two-dimensional fractal dimensions for conditioned ADS biosolids could be taken as the indication parameters for ADS dewaterability.

  3. Influence of extrusion rate and magma rheology on the growth of lava domes: Insights from particle-dynamics modeling

    Science.gov (United States)

    Husain, Taha; Elsworth, Derek; Voight, Barry; Mattioli, Glen; Jansma, Pamela

    2014-09-01

    Lava domes are structures that grow by the extrusion of viscous silicic or intermediate composition magma from a central volcanic conduit. Repeated cycles of growth are punctuated by collapse, as the structure becomes oversized for the strength of the composite magma that rheologically stiffens and strengthens at its surface. Here we explore lava dome growth and failure mechanics using a two-dimensional particle-dynamics model. The model follows the evolution of fractured lava, with solidification driven by degassing induced crystallization of magma. The particle-dynamics model emulates the natural development of dome growth and rearrangement of the lava dome which is difficult in mesh-based analyses due to mesh entanglement effects. The deformable talus evolves naturally as a frictional carapace that caps a ductile magma core. Extrusion rate and magma rheology together with crystallization temperature and volatile content govern the distribution of strength in the composite structure. This new model is calibrated against existing observational models of lava dome growth. Results show that the shape and extent of the ductile core and the overall structure of the lava dome are strongly controlled by the infusion rate. The effects of extrusion rate on magma rheology are sensitive to material stiffness, which in turn is a function of volatile content and crystallinity. Material stiffness and material strength are key model parameters which govern magma rheology and subsequently the morphological character of the lava dome and in turn stability. Degassing induced crystallization causes material stiffening and enhances material strength reflected in non-Newtonian magma behavior. The increase in stiffness and strength of the injected magma causes a transition in the style of dome growth, from endogenous expansion of a ductile core, to stiffer and stronger intruding material capable of punching through the overlying material and resulting in the development of a spine or

  4. Rheological properties of soil: a review

    Science.gov (United States)

    Zhu, Guangli; Zhu, Long; Yu, Chao

    2017-05-01

    Recently rheological methods have been applied to investigate the mechanical properties of soil micro-structure. Rheological techniques have a number of quantitative physically based measurements and offer a better understanding of how soil micro-structure behaves when subject to stress. Rheological material is refers to deformation properties similar to the solid and flow properties similar to the liquid of bound water and colloidal substances under stress. Soil rheology is divided into fluid rheology and plasticity rheology. Fluid rheology is produced by rheological material. Plasticity rheology mainly refers to the sliding and peristaltic between soil solid particles under shear stress. It is generally believed that the soft soil rheology mainly belongs to fluid rheology, while the rheology of sand and other coarse grained soil mainly belongs to plasticity rheology. Thus, rheology mechanisms of soft soil and sand are different. This paper introduces the methods of the research progress on the rheology of soil, in the soil rheological mechanism, rheological model and rheological numerical aspects of the research at home and abroad were summarized and analysed, discussed the problems existed in related research, and puts forward some suggestions for the future study on the rheology of soil.

  5. Superplasticity of metals: phenomenology based on rheological properties and structural dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Smirnov, O.M. [Moscow State Steel and Alloys Inst. (Russian Federation). Lab. of Superplastic Mater. Deformation

    1997-12-31

    Fine structure superplasticity (FSSP), high strain rate superplasticity (HSRSP) and phase transformation superplasticity (PTSP) as well as superplastic-like behaviour of some natural and industrial materials evidently belong to the same type of rheological behaviour i.e. non-linear viscoplastic flow. Temperature map has been proposed as a base for rheological analysis of various types of superplastic and superplastic-like flow of metallic materials. A phenomenological model has been developed to describe deformation of polycrystalline materials at elevated temperatures in a wide range of strain rates with respect to structure evolution during deformation. Rheological analysis of FSSP, HSRSP and PTSP materials along with a slurry during rheocasting shows similarities and peculiarities of superplastic and superplastic-like behaviour. The value of apparent viscosity seems to be an informative index for estimation of rheological and physical state of grain boundaries as a viscous phase and of polycrystalline material as a whole. A new process of impulse bulk forming is presented to show unique possibility of joining in one process two stages of a regular superplastic technology, i.e. preparation of ultrafine grain structure followed by HSRSP deformation. (orig.) 37 refs.

  6. Dynamic Rheological Characterization of A Thermotropic Liquid Crystalline Poly (aryl ether ketone)

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The rheometrics ARES rheometer was applied to determining the rheological behavior of a thermotropic liquid crystalline poly (aryl ether ketone). The viscosity of the material decreases with increasing temperature, reaching a minimum in the nematic state, then slightly increases with further raising the temperature in the biphase.

  7. Rheology of organoclay suspension

    CSIR Research Space (South Africa)

    Hato, MJ

    2011-05-01

    Full Text Available -1 Colloid & Polymer Science Volume 289, Number 10, 1119-1125, DOI: 10.1007/s00396-011-2438-4 Rheology of organoclay suspension Mpitloane Joseph Hato, Ke Zhang, Suprakas Sinha Ray and Hyoung Jin Choi Abstract We have studied the rheological...

  8. Dose-dependent collagen cross-linking of rabbit scleral tissue by blue light and riboflavin treatment probed by dynamic shear rheology.

    Science.gov (United States)

    Schuldt, Carsten; Karl, Anett; Körber, Nicole; Koch, Christian; Liu, Qing; Fritsch, Anatol W; Reichenbach, Andreas; Wiedemann, Peter; Käs, Josef A; Francke, Mike; Iseli, Hans Peter

    2015-08-01

    To determine the visco-elastic properties of isolated rabbit scleral tissue and dose-dependent biomechanical and morphological changes after collagen cross-linking by riboflavin/blue light treatment. Scleral patches from 87 adult albino rabbit eyes were examined by dynamic shear rheology. Scleral patches were treated by riboflavin and different intensities of blue light (450 nm), and the impact on the visco-elastic properties was determined by various rheological test regimes. The relative elastic modulus was calculated from non-treated and corresponding treated scleral patches, and treatments with different blue light intensities were compared. Shear rheology enables us to study the material properties of scleral tissue within physiological relevant parameters. Cross-linking treatment increased the viscous as well as the elastic modulus and changed the ratio of the elastic versus viscous proportion in scleral tissue. Constant riboflavin application combined with different blue light intensities from 12 mW/cm(2) up to 100 mW/cm(2) increased the relative elastic modulus of scleral tissue by factors up to 1.8. Further enhancement of the applied light intensity caused a decline of the relative elastic modulus. This might be due to destructive changes of the collagen bundle structure at larger light intensities, as observed by histological examination. Collagen cross-linking by riboflavin/blue light application increases the biomechanical stiffness of the sclera in a dose-dependent manner up to certain light intensities. Therefore, this treatment might be a suitable therapeutic approach to stabilize the biomechanical properties of scleral tissue in cases of pathological eye expansion. © 2014 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

  9. Rheological analysis of bitumens dy dynamic shear rheometer : effect of thermical history on the results

    OpenAIRE

    MOUILLET, V; LAPALU, L; PLANCHE, JP; DURRIEU, F

    2004-01-01

    In order to prevent binder-related pavement failures, it is very important to be able to characterize the performances of bituminous binders that play an essential role in the construction and reinforcement of pavements. However, because of its specific and complex composition, bitumen is a visco-elastic material whose intrinsic rheological properties depend upon the temperature and the loading time. One way to characterize this particular behaviour is to measure the response of the material ...

  10. Rheological Study of Batter Dough for Yorkshire Pudding Production

    Science.gov (United States)

    Migliori, M.; Gabriele, D.; Baldino, N.; Lupi, F. R.; de Cindio, B.

    2008-07-01

    Batter dough are widely used in manufacturing of baked goods having different texture characteristics. The analysis of "liquid-like" properties of these systems allows the control of product shape and consistency during production, because of the flow pattern definition. This work deals with "batter" for "Yorkshire Pudding" production, having a characteristic shape mainly due to the combination of shear flow and bubble expansion during baking. Some of mechanical properties can be controlled by varying the recipe as normally done during industrial production. Dynamic measurement and viscosity data at some characteristic temperatures are reported in the view of supporting the modeling of the shape variation under shear flow and bubble expansion.

  11. Dynamics of associative polymer solutions: Capillary break-up, jetting and rheology

    Science.gov (United States)

    Sharma, Vivek; Serdy, James G.; Threfall-Holmes, Phil; McKinley, Gareth H.

    2011-11-01

    Associative polymer solutions are used in extensively in the formulations for water-borne paints, food, inks, cosmetics, etc to control the rheology and processing behavior of multi-component dispersions. These complex dispersions are processed and used over a broad range of shear and extensional rates. Furthermore, the commercially relevant formulations use dilute solutions of associative polymers, which have low viscosity and short relaxation times, and hence their non-Newtonian response is not apparent in a conventional rheometer. In this talk, we explore several methods for systematically exploring the linear and nonlinear solution rheology of associative polymer dispersions, including: fractional model description of physical gelation, high frequency oscillatory tests at frequencies up to 10 kHz, microfluidic shear rheometry at deformation rates up to 1000000 /s and the influence of transient extensional rheology in the jet breakup. We show that high deformation rates can be obtained in jetting flows, and the growth and evolution of instability during jetting and break-up of these viscoelastic fluids shows the influence of both elasticity and extensibility.

  12. Structure of Sodium Carboxymethyl Cellulose Aqueous Solutions: A SANS and Rheology Study

    Science.gov (United States)

    Lopez, Carlos G; Rogers, Sarah E; Colby, Ralph H; Graham, Peter; Cabral, João T

    2015-01-01

    We report a small angle neutron scattering (SANS) and rheology study of cellulose derivative polyelectrolyte sodium carboxymethyl cellulose with a degree of substitution of 1.2. Using SANS, we establish that this polymer is molecularly dissolved in water with a locally stiff conformation with a stretching parameter. We determine the cross sectional radius of the chain ( 3.4 Å) and the scaling of the correlation length with concentration (ξ = 296 c−1/2Å for c in g/L) is found to remain unchanged from the semidilute to concentrated crossover as identified by rheology. Viscosity measurements are found to be in qualitative agreement with scaling theory predictions for flexible polyelectrolytes exhibiting semidilute unentangled and entangled regimes, followed by what appears to be a crossover to neutral polymer concentration dependence of viscosity at high concentrations. Yet those higher concentrations, in the concentrated regime defined by rheology, still exhibit a peak in the scattering function that indicates a correlation length that continues to scale as. © 2014 The Authors. Journal of Polymer Science Part B: Polymer Physics Published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 492–501 PMID:26709336

  13. Rheological Behavior of Immiscible PS/LDPE Blends: A Comparative Study of the Palierne Emulsion Model

    Directory of Open Access Journals (Sweden)

    Chatchai KUNYAWUT

    2015-02-01

    Full Text Available The rheological behavior of polystyrene (PS/low density polyethylene (LDPE blends have been investigated. Blends with 10, 20 and 30 wt% LDPE were prepared using a co-rotating twin-screw extruder at a melt mixing temperature of 180°C. SEM micrographs revealed that all blends exhibited droplet-type dispersion morphology. Rheological measurements were performed at the same temperature as the mixing temperature. The complex viscosity of the blends laid between those of the PS and the LDPE and decreased with increasing LDPE concentration. The plots of tand of blends with 10 and 20 wt% LDPE suggested that the elasticity of these blends was comparable to that of the pure PS. By contrast, the elasticity behavior of the blend with 30 wt% LDPE was shown to be similar to that of LDPE. Palierne model predictions were in very good agreement with the experimental data for the blends having 10 and 20 wt% LDPE. For the 30 wt% LDPE blend, agreement with the prediction and the experimental data was not as good. Within the frequency range of the rheological measurements, the second plateau at low frequency which results from an increase of the elasticity was not observed in any of the blends studied. This is expected to be due to the long relaxation times of the relatively large LDPE droplets of these blends.

  14. Impact of the composition of polysaccharide composite gels on small molecules diffusion: A rheological and NMR study

    OpenAIRE

    2010-01-01

    The gelation mechanism of carrageenan depends on the amount and nature of the polysaccharide, and is cation sensitive. From a rheological approach, this specificity leads to different textural properties. In composite gels with carrageenans, starch and sucrose, the presence of κ/κ2-carrageenan, even at low levels, has an impact on textural and structural properties. In this study, rheological and diffusion NMR measurements were performed on composite gels to probe gel structure at the macro- ...

  15. Experimental study on the rheological behaviour of debris flow

    Directory of Open Access Journals (Sweden)

    A. Scotto di Santolo

    2010-12-01

    Full Text Available A model able to describe all the processes involved in a debris flow can be very complex owing to the sudden changing of the material that turns from solid into liquid state. The two phases of the phenomenon are analysed separately referring to soil mechanics procedures with regard to the trigger phase, and to an equivalent fluid for the post-failure phase. The present paper is devoted to show the experimental results carried out to evaluate the behaviour assumed by a pyroclastic-derived soil during the flow. A traditional fluid tool has been utilized: a standard rotational rheometer equipped with two different geometries. The soils tested belong to deposits that cover the slopes of the Campania region, Italy, often affected by debris flows. The influence of solid concentration Cv and grain size distribution was tested: the soils were destructurated, sieved and mixed with water starting from the in situ porosity. All material mixtures showed a non-Newtonian fluid behaviour with a yield stress τy that increases with a solid volumetric concentration and decreases for an increase of sand fraction. The experimental data were fitted with standard model for fluids. A simple relation between Cv and τy was obtained. The yield stress seems to be a key parameter for describing and predicting the post-failure behaviour of debris flows. These results suggest that in the field a small change in solid fraction, due to rainfall, will cause a slight decrease of the static yield stress, readily inducing a rapid flow which will stop only when the dynamic yield stress is reached, namely on a much smoother slope. This can explain the in situ observed post-failure behaviour of debris flows, which are able to flow over very long distances even on smooth slopes.

  16. An Experimental Study on the Dynamic Characteristics of Vehicle Semi-active Seat Suspension with Magneto-rheological Damper%汽车磁流变半主动座椅悬架动态特性的试验研究

    Institute of Scientific and Technical Information of China (English)

    寇发荣

    2015-01-01

    For further improving vehicle ride comfort,a magneto-rheological damper for vehicle semi-active seat suspension is developed with its damping characteristic test conducted. After analyzing its force bearing condi-tion, a dynamics model for vehicle semi-active seat suspension is built, a corresponding skyhook control strategy is devised, and a simulation is performed on the skyhook control of seat under both random and sinusoidal excitation inputs. Meanwhile a physical prototype of semi-active seat suspension with magneto-rheological damper and its test bench system are developed with corresponding bench test carried out. The results indicate that the results of simu-lation basically well agree with test data and the magneto-rheological damper developed has a good damping control-lability. Compared to original passive seat suspension, the dynamic performances of vehicle semi-active seat with magneto-rheological damper are improved by some 30% with a significant effect of vibration attenuation.%为进一步提高汽车的乘坐舒适性,研发了一种汽车座椅半主动悬架用磁流变减振器,并对其进行阻尼特性试验,通过分析其受力情况,建立了汽车半主动座椅悬架动力学模型,设计了用于座椅磁流变半主动悬架的天棚控制策略,并在随机和正弦激励输入下进行了座椅天棚控制仿真计算,试制了磁流变半主动座椅物理样机及试验台架系统,开展了磁流变半主动座椅悬架的台架试验研究。结果表明,理论仿真和试验结果基本吻合,磁流变减振器阻尼可控性好;相对于被动座椅悬架,采用磁流变半主动座椅悬架后,座椅动态性能改善了30%左右,磁流变半主动座椅悬架减振效果显著。

  17. Summary of rheological studies related to HWVP slurries

    Energy Technology Data Exchange (ETDEWEB)

    Lanning, D.D.; Smith, P.A.; Terrones, G.; Larson, D.E.

    1996-02-01

    Numerous studies (Section 8) have,addressed the Theological properties of simulated process slurries at the Savannah River Laboratory for the Defense Waste Processing Facility and at Pacific Northwest Laboratory`(PNL) for the Hanford Waste Vitrification Plant (HWVP). These studies were reviewed to summarize existing data applicable to HWVP design. The reviewers determined that the existing data provide important information on the effects of feed variability, solids loading, temperature, formating, pH, and scale-up. However, these data cannot serve as a basis for fundamental slurry transport calculations because data are not reported in sufficient detail over a range of shear rates and in appropriate terms to be sufficient for transport calculations.

  18. Cyclic Macromolecules: Dynamics and Nonlinear Rheology, Final Report DOE Award # DE-FG02-05ER46218, Texas Tech University

    Energy Technology Data Exchange (ETDEWEB)

    McKenna, Gregory B.; Grubbs, Robert H.; Kornfield, Julia A.

    2012-04-25

    The work described in the present report had the original goal to produce large, entangled, ring polymers that were uncontaminated by linear chains and to characterize by rheological methods the dynamics of these rings. While the work fell short of this specific goal, the outcomes of the research performed under support from this grant provided novel macromolecular synthesis methods, new separation methods for ring and linear chains, and novel rheological data on bottle brush polymers, wedge polymers and dendron-based ring molecules. The grant funded a total of 8 archival manuscripts and one patent, all of which are attached to the present report.

  19. Different Applications of Rheological Techniques in Studies of Physical Gels

    DEFF Research Database (Denmark)

    Hvidt, Søren

    -forming biopolymers. Physical gels are also used in the paint industry to minimize sedimentation. Delayed and controlled drug release is of importance in the pharmaceutical industry, and one way to obtain this control is to hide active components in physical gels. Two excellent reviews cover many aspects...... of the elastic storage modulus, G’, and loss modulus, G”, as a function of e.g. frequency, temperature, or time. Two other techniques, which can be very useful for studies of gels, are creep and relaxation measurements. These techniques, which allow determinations of the compliance and the relaxation modulus...... importance in many applications. When a gel is deformed with increasing strain or strain amplitudes most gels eventually rupture. The yield stress denotes the maximum stress gels can withstand. Different ways of determining yield stress will be illustrated. Oscillatory measurements only allow determinations...

  20. Rheologic studies on middle ear effusions and their mucus glycoproteins.

    Science.gov (United States)

    FitzGerald, J E; Green, G G; Birchall, J P; Pearson, J P

    1989-04-01

    The properties of pooled thick and thin middle ear effusions, from children with otitis media with effusion, were studied by viscometry. Mucus glycoproteins were responsible for effusion viscosity. Their percentage by weight in thick and thin effusions was 25% and 8.2%, respectively. N-acetylcysteine and 0.2 mol/L of mercaptoethanol caused a 39% viscosity drop in a 5-mg/mL glycoprotein solution, whereas S-carboxymethylcysteine had no effect. Treatment of thick effusions with 0.2 mol/L of mercaptoethanol initially caused a viscosity decrease followed by a gradual increase. Higher reducing agent concentrations (0.5 mol/L) caused a more rapid decrease followed by a rapid increase, presumably by causing nonspecific aggregation of reduced protein molecules. These results suggest that the concentration of and the time that a mucolytic is in the middle ear would be of prime importance in achieving the desired decrease in viscosity.

  1. An Analytical Study of Fire Out of Battery Using Magneto Rheological Dampers

    Directory of Open Access Journals (Sweden)

    Mehdi Ahmadian

    2002-01-01

    Full Text Available The application of magneto rheological dampers for controlling the dynamics of a fire out-of-battery recoil system is examined, using a dynamic simulation of a 105mm cannon. Upon providing a brief background on MR dampers and fire out-of-battery dynamics, we will describe the simulation model, along with some of the results obtained from the model. The simulation results show that although conventional hydraulic recoil dampers can be designed and tuned to control fire out-of-battery dynamics as effectively as MR dampers, they are not able to perform well when firing faults are encountered. The results show that MR dampers are able to adapt to the firing faults such as pre-fire, hang-fire, and misfire and provide "soft recoil" under all firing conditions. The inability of conventional hydraulic dampers to adapt to the firing faults can yield recoil dynamics that seriously jeopardize the performance of the gun. Therefore, the results presented here show that MR dampers may provide an enabling technology in achieving fire out-of-battery under all firing conditions.

  2. A Novel Method of Mechanical Oxidation of CNT for Polymer Nanocomposite Application: Evaluation of Mechanical, Dynamic Mechanical, and Rheological Properties

    Directory of Open Access Journals (Sweden)

    Priyanka Pandey

    2014-01-01

    Full Text Available A new approach of oxidation of carbon nanotubes has been used to oxidize the CNTs. A comparative aspect of the mechanical oxidation and acid oxidation process has been established. FTIR analysis and titration method have shown the higher feasibility of the mechanical oxidation method to oxidize the CNTs. Comparatively less damage to the CNTs has been observed in case of mechanically oxidized as compared to acid oxidized CNTs. The mechanical properties of the nanocomposites reinforced with the acid oxidized CNT (ACNT and mechanically oxidized CNTs (McCNT were analyzed and relatively higher properties in the nanocomposites reinforced with McCNT were noticed. The less degree of entanglement in the McCNTs was noticed as compared to ACNTs. The dynamic mechanical analysis of the nanocomposites revealed much improved load transfer capability in the McCNT reinforced composites. Further, the rheological properties of the nanocomposites revealed the higher performance of McCNT reinforced composites.

  3. Viscosity changes in hyaluronic acid: Irradiation and rheological studies

    Energy Technology Data Exchange (ETDEWEB)

    Daar, Eman [Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom)], E-mail: e.daar@surrey.ac.uk; King, L.; Nisbet, A. [Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Thorpe, R.B. [Fluids and Systems Centre, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Bradley, D.A. [Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom)

    2010-04-15

    Hyaluronic acid (HA) is a significant component of the extracellular matrix (ECM), particular interest being shown herein in synovial fluid. The present study aims to investigate the degrading effects of X-ray radiation on HA at radiotherapy doses. Measurements of viscosity and shear stresses on HA solutions have been made at different shear rates using various types of viscometer for different concentrations in the range 0.01-1% w/v of HA. The HA has been subjected to doses of 6 MV photon radiation ranging from 0 to 20 Gy, the major emphasis being on doses below 5 Gy. It is found that there is a dose-dependent relationship between viscosity and shear rate, viscosity reducing with radiation dose, this being related to polymer scissions via the action of radiation-induced free radicals. The dependency appears to become weaker at higher concentrations, possibly due to the contribution to viscosity from polymer entanglement becoming dominant over that from mean molecular weight. Present results, for HA solutions in the concentration range 0.01% to 1% w/v, show reduced viscosity with dose over the range 0-4 Gy, the latter covering the dose regime of interest in fractionated radiotherapy. The work also shows agreement with previous Raman microspectrometry findings by others, the possible bond alterations being defined by comparison with available published data.

  4. Rheological principles of development hetero-modulus and hetero-viscous complex materials with extreme dynamic strength

    Science.gov (United States)

    Gömze, L. A.; Gömze, L. N.

    2017-02-01

    Materials with different crystalline and morphological compositions have different chemical, physical, mechanical and rheological properties, including wear protection, melting temperature, module of elasticity and viscosity. Examining the material structures and behaviors of differentceramic bodies and CMCs under high speed collisions in several years the authors have understood the advantages of hetero-modulus and hetero-viscous complex material systems to absorb and dissipate the kinetic energy of objects during high speed collisions. Applying the rheo-mechanical principles the authors successfully developed a new family of hetero-modulus and hetero-viscous alumina matrix composite materials with extreme mechanical properties including dynamic strength. These new corundum-matrix composite materials reinforced with Si2ON 2, Si3N4 , SiAlON and AlN submicron and nanoparticles have excellent dynamic strength during collisions with high density metallic bodies with speeds about 1000 m/sec or more. At the same time in the alumina matrix composites can be observed a phase transformation of submicron and nanoparticles of alpha and beta silicone-nitride crystals into cubicc-Si3N4 diamond-like particles can be observed, when the high speed collision processes are taken place in vacuum or oxygen-free atmosphere. Using the rheological principles and the energy engorgement by fractures, heating and melting of components the authors successfully developed several new hetero-modulus, hetero-viscous and hetero-plastic complex materials. These materials generally are based on ceramic matrixes and components having different melting temperatures and modules of elasticity from low values like carbon and light metals (Mg, Al, Ti, Si) up to very high values like boride, nitride and carbide ceramics. Analytical methods applied in this research were scanning electron microscopy, X-ray diffractions and energy dispersive spectrometry. Digital image analysis was applied to microscopy

  5. Rheological behaviors of Graphitic oxide/Sodium alginate dispersions

    Institute of Scientific and Technical Information of China (English)

    张庆旭

    2015-01-01

    One kind of the carbonaceous materials with high performance was chosen to prepare dispersions of GO/SA. The influence of GO contents on rheological properties of SA solution was studied with rotational rheometer under different test conditions. Steady rheological results showed that the solutions exhibited shear-thinning behaviors. The viscosities decreased with the increasing of shear rates. Dynamic rheological results showed that both SA solutions and SA/GO suspensions exhibited liquid-like behaviors. Moreover indicate that incorporation of small amounts GO can significantly increase the G' and G'' of SA spinning solution, reflecting good dispersion of GO nanolayers in SA solution, which was proved by Cole-Cole curves.

  6. Study on Theoretical Modeling of Semi-Active Electro-Rheological Fluid Damper

    Institute of Scientific and Technical Information of China (English)

    饶柱石; 傅志方; 张华良

    2003-01-01

    This paper emphases on analyzing and investigating the mechanical behavior of electro-rheological fluid (ERF) semi-active damper. Theoretical model was developed to describe the relationship between electric field and the resistance force of ERF flowing through two parallel plane electrodes. In the model, the pressure drop along electrodes was supposed to consist of two parts: one related with viscosity and the other related with dynamic yield shear stress. The concept of yield stress in fluence factor was developed inderiving the theoretical formula for calculating the pressure drop in the damper. The influences of some other factors, such as, nonideal Newtonian fluid and temperature have also been taken into account. Numerical and experimental work have been performed to prove the validity of the proposed model. The comparison of both results shows that the developed model is quite effective and practicable.

  7. Purification of cress seed (Lepidium sativum) gum: A comprehensive rheological study

    DEFF Research Database (Denmark)

    Razmkhah, Somayeh; Razavi, Seyed Mohammad Ali; Mohammadifar, Mohammad Amin

    2016-01-01

    In this paper, the effects of different purification methods (ethanol (sample E), isopropanol (sample I) and ethanol-isopropanol (sample EI)) on intrinsic viscosity, steady and dynamic rheological properties of cress seed gum were investigated. The gum dispersions exhibited viscoelastic properties......, the storage modulus (G′) was higher than the loss modulus (G″), and mechanical spectra of the crude and purified cress seed gums were classified as weak gels. The purified samples had stronger and more elastic network structure than the crude gum (CSG) and the gel network got stronger along the series of I......, EI and E. All the gum dispersions indicated shear-thinning behavior and the viscosity of the samples followed the order of E > EI > I > CSG. Herschel-Bulkley model was the best model to describe steady shear flow behavior and Arrhenius-type model was also applied to describe the effect of temperature...

  8. Study of Rheological Properties of Bituminous Binders in Middle and High Temperatures

    Directory of Open Access Journals (Sweden)

    Remišová Eva

    2016-05-01

    Full Text Available The bitumen binders in road pavements are exposed traffic loading effect at different climatic conditions. A resistance to these stresses depends on bitumen properties as well. The paper presents rheological properties (G*, δ, ν* determined and compared for four bituminous binders (unmodified and polymer modified bitumen at temperature 46 – 60 (80 °C and dynamic viscosity at temperature 130 – 190 °C (Brookfield viscometer. On the basis of viscosity results it is possible to set optimal production and compaction temperatures. Elastic and viscous behavior of binder in the middle temperature is determined in rheometers. The higher value of complex modulus, the stiffer bitumen binder is able to resist deformation. The greater content of elastic components (e.g. polymer in bitumen varies mainly elastic-viscous properties of primary bitumen.

  9. Experimental study and modeling of the rheology and hydraulics in the foam drilling; Estudos experimentais e modelagem da reologia e da hidraulica na perfuracao com espuma

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Andre L.; Sa, Carlos H.M. de; Lourenco, Affonso M.F.; S. Junior, Valter [PETROBRAS, S.A, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas]. E-mails: aleibsohn@cenpes.petrobras.com.br; chsa@cenpes.petrobras.com.br; affonso-lourenco@utulsa.edu; vsj@cenpes.petrobras.com.br

    2000-07-01

    This article describes the extense experimental effort for analyzing the foam stability and rheological properties for application as light drilling fluid. The study considered the influence of the foaming and concentration on the foam rheology and the gas volumetric fraction on the foam rheological properties. Simple correlations were proposed for quantification of the experimental behaviour. Field tests were performed to evaluate one of the foaming agents analyzed in laboratory by using 16 combinations of the gas-fluid flow.

  10. Performance of maleated castor oil based plasticizer on rubber: rheology and curing characteristic studies

    Science.gov (United States)

    Indrajati, I. N.; Dewi, I. R.

    2017-07-01

    The objective of this study was to evaluate the performance of maleated castor oil (MACO) as plasticizer on natural rubber (NR), ethylene propylene diene monomer (EPDM), and nitrile butadiene rubber (NBR). The parameter studied were involving rheological, curing and swelling properties. The MACOs were prepared by an esterification reaction between castor oil (CO) and maleic anhydride (MAH) with the help of xylene as water entrainer to improve water removal. Resulting oils then applied as a plasticizer in each of those rubbers within a fixed loading of 5 phr. Comparison has been made to evaluate the performance of MACO and conventional plasticizer (paraffinic oil for NR and EPDM, DOP for NBR) on each rubber. Rheology, curing characteristic and swelling of each rubber were studied. The results showed that rubber (NR/EPDM/NBR) plasticized with MACO had given similar flow characteristic to conventional plasticizers. MACO exhibited slow curing, confirmed by higher t90, but the scorch safety was of the same magnitude. MAH loading tended to decrease the flow properties and curing rate, while scorch time (ts2) was independent.

  11. Shear rheology and in-vitro release kinetic study of apigenin from lyotropic liquid crystal.

    Science.gov (United States)

    Fan, Jun; Liu, Feng; Wang, Zhongni

    2016-01-30

    Apigenin is a flavonoid compound with diverse pharmacological functions which could develop health benefit products, but its formulation is hampered by its poor water solubility and bioavailability. In this paper, in order to overcome these difficulties, apigenin was encapsulated in LLC formed by polyoxyethylene-10-oleyl ether (Brij 97) and sodium deoxycholate (NaDC) mixtures. The hexagonal liquid crystalline phase (H) and the cubic liquid crystalline phase (C) were found in this system. The shear rheology was used to study the structure change with temperature. It was shown that C3 (Brij 97-NaDC/IPM-PEG400/H2O=36:9:55) was C at low temperature. But above 35.6°C, the matrix of C3 completely transformed to polymer solution. The matrix of H3 was H (Brij 97-NaDC:IPM-PEG 400:H2O=50:9:41) below 50°C, but the structural strength change was obvious. Vitro release experiment was used to study drug release kinetics. It was indicated that apigenin encapsulated in LLC conformed to the concentration diffusion model, and cumulative percentage of apigenin released from C3 and H3 had corresponding relationship with the shear rheology at different temperatures. Copyright © 2015. Published by Elsevier B.V.

  12. Optical and rheological study of gamma irradiated rare-earth nanoparticle based ferrofluids

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Nibedita [Nanoscience and Soft Matter Laboratory, Department of Physics, Tezpur University, PO Napaam, Tezpur 784 028, Assam (India); Mohanta, Dambarudhar, E-mail: best@tezu.ernet.in [Nanoscience and Soft Matter Laboratory, Department of Physics, Tezpur University, PO Napaam, Tezpur 784 028, Assam (India); Department of Physics, School of Engineering and Applied Sciences, Harvard University, MA 02138 (United States); Saha, Abhijit [UGC-DAE Consortium for Scientific Research, Kolkata Centre, III/LB-8 Bidhannagar, Kolkata 700 098 (India)

    2012-12-01

    Highlights: Black-Right-Pointing-Pointer Gd{sub 2}O{sub 3} nanoparticle based ferrofluids have been produced with ethanol as carrier medium. Black-Right-Pointing-Pointer PL emission show improvement in defect related emission with {gamma}-irradiation dose. Black-Right-Pointing-Pointer The ferrofluids show shear thinning behavior with bi-exponential decay characteristics. Black-Right-Pointing-Pointer Fast and slow components are found to increase with irradiation dose. - Abstract: The present work reports on the optical and rheological properties of unexposed and gamma irradiated rare-earth (RE) oxide nanoparticle-based ferrofluids (FF). The ferrofluids were prepared by dispersing surfactant coated gadolinium oxide (Gd{sub 2}O{sub 3}) nanoparticles in ethanol medium and later on subjected to energetic gamma irradiation (1.25 MeV) at select doses. As predicted from transmission electron microscopy and X-ray diffraction (XRD) studies, the synthesized nanoparticles are of {approx}7 nm size which crystallize into cubic crystal structure. The photoluminescence response reveals creation of defect states on nanoparticle surfaces when FFs are subjected to gamma irradiation. Whereas, rheology measurements showed unusual shear thinning behavior of the ferrofluids. The flow behavior of all the samples can be correlated to the bi-exponential decay curve fitting which reveals that decay phenomenon is governed by two independent mechanism: fast and slow events. The variation of the decay parameter with irradiation dose is attributed to the creation of point defects and weakening of inter nanoparticle bonding.

  13. Effect of annealing temperature on gelatinization of rice starch suspension as studied by rheological and thermal measurements.

    Science.gov (United States)

    Tsutsui, Kazumi; Katsuta, Keiko; Matoba, Teruyoshi; Takemasa, Makoto; Nishinari, Katsuyoshi

    2005-11-16

    The effect of annealing temperature (Ta) on the rheological behavior of 10 wt % rice starch suspension was investigated by the dynamic viscoelasticity, the differential scanning calorimetry (DSC), and the amount of leached out amylose and the swelling ratio of starch suspension. The rheological behaviors of the annealed samples are classified into three types in terms of Ta: Ta1, 48 and 55 degrees C, which are much lower than the gelatinization temperature, Tgel (=62 degrees C); Ta2, 58, 60, and 62 degrees C, which are almost the same as Tgel; and Ta3, 65, 68, 70, and 73 degrees C, which are much higher than Tgel. For the samples annealed at Ta2, the onset temperature of the storage and the loss moduli, G' and G'', increased with increasing T(a), and G' and G" in the temperature range from 65 to 90 degrees C gradually increased though smaller than those for the nonannealed sample, the control. This can be understood by the partial gelatinization; i.e., the leached out amylose prevents further amylose from leaching out. The rheological property of the samples annealed at Ta1 is not so different from that of the control, and the samples annealed at Ta3 are almost gelatinized. The rheological behavior of starch suspension can be controlled by Ta.

  14. Regime of aggregate structures and magneto-rheological characteristics of a magnetic rod-like particle suspension: Monte Carlo and Brownian dynamics simulations

    Science.gov (United States)

    Okada, Kazuya; Satoh, Akira

    2017-09-01

    In the present study, we address a suspension composed ferromagnetic rod-like particles to elucidate a regime change in the aggregate structures and the magneto-rheological characteristics. Monte Carlo simulations have been employed for investigating the aggregate structures in thermodynamic equilibrium, and Brownian dynamics simulations for magneto-rheological features in a simple shear flow. The main results obtained here are summarized as follows. For the case of thermodynamic equilibrium, the rod-like particles aggregate to form thick chain-like clusters and the neighboring clusters incline in opposite directions. If the external magnetic field is increased, the thick chain-like clusters in the magnetic field direction grow thicker by adsorbing the neighboring clusters that incline in the opposite direction. Hence, a significant phase change in the particle aggregates is not induced by an increase in the magnetic field strength. For the case of a simple shear flow, even a weak shear flow induces a significant regime change from the thick chain-like clusters of thermodynamic equilibrium into wall-like aggregates composed of short raft-like clusters. A strong external magnetic field drastically changes these aggregates into wall-like aggregates composed of thick chain-like clusters rather than the short raft-like clusters. The internal structure of these aggregates is not strongly influenced by a shear flow, and the formation of the short raft-like clusters is maintained inside the aggregates. The main contribution to the net viscosity is the viscosity component due to magnetic particle-particle interaction forces in relation to the present volumetric fraction. Hence, a larger magnetic interaction strength and also a stronger external magnetic field give rise to a larger magneto-rheological effect. However, the dependence of the viscosity on these factors is governed in a complex manner by whether or not the wall-like aggregates are composed mainly of short raft

  15. Protein conformational transitions at the liquid-gas interface as studied by dilational surface rheology.

    Science.gov (United States)

    Noskov, Boris A

    2014-04-01

    Experimental results on the dynamic dilational surface elasticity of protein solutions are analyzed and compared. Short reviews of the protein behavior at the liquid-gas interface and the dilational surface rheology precede the main sections of this work. The kinetic dependencies of the surface elasticity differ strongly for the solutions of globular and non-globular proteins. In the latter case these dependencies are similar to those for solutions of non-ionic amphiphilic polymers and have local maxima corresponding to the formation of the distal region of the surface layer (type I). In the former case the dynamic surface elasticity is much higher (>60 mN/m) and the kinetic dependencies are monotonical and similar to the data for aqueous dispersions of solid nanoparticles (type II). The addition of strong denaturants to solutions of bovine serum albumin and β-lactoglobulin results in an abrupt transition from the type II to type I dependencies if the denaturant concentration exceeds a certain critical value. These results give a strong argument in favor of the preservation of the protein globular structure in the course of adsorption without any denaturants. The addition of cationic surfactants also can lead to the non-monotonical kinetic dependencies of the dynamic surface elasticity indicating destruction of the protein tertiary and secondary structures. The addition of anionic surfactants gives similar results only for the protein solutions of high ionic strength. The influence of cationic surfactants on the local maxima of the kinetic dependencies of the dynamic surface elasticity for solutions of a non-globular protein (β-casein) differs from the influence of anionic surfactants due to the heterogeneity of the charge distribution along the protein chain. In this case one can use small admixtures of ionic surfactants as probes of the adsorption mechanism. The effect of polyelectrolytes on the kinetic dependencies of the dynamic surface elasticity of protein

  16. Interaction of pepsin-[C16mim]Br system: interfacial dilational rheology and conformational studies.

    Science.gov (United States)

    Huang, Tian; Cao, Chong; Liu, Zi-lin; Li, Yang; Du, Feng-pei

    2014-09-21

    The interfacial rheological property is closely related to the stabilities of foams and emulsions, yet there have been limited studies on the interaction between proteins with ionic liquid-type imidazolium surfactants at the decane-water interface as well as in the bulk. Herein, we investigated the interfacial and bulk properties of pepsin (PEP) and an ionic liquid (IL), 1-hexadecyl-3-methylimidazolium bromide, [C(16)mim]Br. The interfacial pressure and dilational rheology studies were performed to describe the formation of [C(16)mim]Br-pepsin complexes. The influence of the oscillating frequency and the bulk concentration of [C(16)mim]Br on the dilational properties were explored. The conformational changes were studied by monitoring the fluorescence and far UV-CD spectra. The results reveal that the globular structure of pepsin is one of the decisive factors controlling the nature of the interfacial film. The monotonous increase in the dilational elastic modulus of pepsin-[C(16)mim]Br solutions with the surface age indicates that no loops and tails had formed. Interestingly, with an increase in the concentration of [C(16)mim]Br, the εd-c curve first passes through a plateau value due to steric hindrance and the electrostatic barrier of already absorbed tenacious pepsin-[C(16)mim]Br complexes. With the further addition of [C(16)mim]Br, the remarkable decrease in dilational elastic modulus indicates that the compact structure is destroyed gradually. The results of the fluorescence spectra and far UV-CD spectra confirm that [C(16)mim]Br did not produce perceptible changes in pepsin at the concentrations studied in the dilational experiment. Possible schematic programs of the pepsin-[C(16)mim]Br interaction model at the interface and in bulk phase are proposed.

  17. Effect of high hydrostatic pressure and high dynamic pressure on stability and rheological properties of model oil-in-water emulsions

    Science.gov (United States)

    Bigikocin, Erman; Mert, Behic; Alpas, Hami

    2011-09-01

    Both static and dynamic high pressure applications provide interesting modifications in food structures which lead to new product formulations. In this study, the effects of two different treatments, high hydrostatic pressure (HHP) and high dynamic pressure (HDP), on oil-in-water emulsions were identified and compared. Microfluidization was selected from among the HDP homogenization techniques. The performance of each process was analyzed in terms of rheological modifications and emulsion stability improvements compared with the coarse emulsions. The stability of the emulsions was determined comparatively by using an analytical photo-centrifuge device employing novel analysis technology. Whey protein isolate (WPI) in combination with a food polysaccharide (xanthan gum, guar gum or locust bean gum) were used as emulsifying and stabilizing ingredients. The effective disruption of oil droplets and the degradation of polysaccharides by the shear forces under high pressure in HDP microfluidization yielded finer emulsions with lower viscosities, leading to distinctive improvements in emulsion stability. On the other hand, improvements in stability obtained with HHP treatment were due to the thickening of the emulsions mainly induced by protein unfolding. The corresponding increases in viscosity were intensified in emulsion formulations containing higher oil content. Apart from these, HHP treatment was found to be relatively more contributive to the enhancements in viscoelastic properties.

  18. The numerical study of the influence of rheological parameters stratified flows characteristics in cable dies

    Science.gov (United States)

    Kozitsyna, M. V.; Trufanova, N. M.

    2017-01-01

    Today the process of coextrusion is the most technological in the cable production with cross-linked polyethylene, composed of two or more layers of polymeric insulation. Since the covering technology is a simultaneous imposition of all necessary layers (two semiconducting shields on the insulation and conductor and one - on insulation), the main focus of this study is the analysis of significance of various factors influence on stratified flows characteristics. This paper has considered the flow of two abnormally viscous liquids in the cable head. The problem has been solved through a three-dimensional statement by applying the finite element method in the Ansys software package. The influence has been estimated by varying the rheological properties of materials to create all necessary layers thickness.

  19. A preliminary study on the rheological properties of human ejaculate and changes during liquefaction

    Institute of Scientific and Technical Information of China (English)

    Yong-DeShi; Lan-FengPan; Fei-KunYang; Si-QiWang

    2004-01-01

    Aim: To study the changes in rheological properties, namely the parameters of the hysteresis loops and yield stress versus time for human semen after ejaculation. Methods: Ejaculates were obtained from volunteers and immediately put into the test cup of a Brookfield Programmable DV- 11 Rheometer, by which the hysteresis loops and yield stress were determined. Results: (1) Yield stress values dropped down from more than 3000 mPa to 60 mPa inabout 5 minutes after ejaculation; (2) The shape of the hysteresis loops of shear stress versus shear rate was changed from the counter-clockwise direction, that enclosed a large area, into the clockwise direction, that enclosed a very small area. Conclusion: Human ejaculate originally possesses semi-solid or visco-elastic body behavior and in 5 minutes after liquefaction, it becomes a thixotropic fluid or shearing thinning fluid with very low viscosity. (Asian J Androl 2004 Dec; 6: 299-304)

  20. Rheological and mechanical study of regenerated cellulose/multi-walled carbon nanotube composites

    Science.gov (United States)

    Shao, Wei; Wang, Shuxia; Liu, Hui; Wu, Jimin; Huang, Min; Ma, Wenjing; Huang, Chaobo

    2016-09-01

    Regenerated cellulose (RC)-based composites reinforced with multi-walled carbon nanotubes (MWCNTs) were prepared by a facile casting method. The morphology and microstructure of the fabricated composites were characterized using transmission electron microscopy, Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. Thermogravimetry and derivative thermogravimetric analysis were conducted to investigate the effect of MWCNTs on the thermal behaviors of the RC. The results showed that the introduction of MWCNTs enhanced the thermal stability of the RC. Moreover, the effect of the dispersion state of MWCNTs in microcrystalline cellulose/ZnCl2 solutions with varying MWCNT loadings was studied by rheological tests. The mechanical properties of composite films were remarkably improved compared to those of pure RC film. Specifically, the composite film containing 3 wt% of MWCNTs exhibits a 123% enhancement in tensile strength and a 163% enhancement in the Young’s modulus compared with the pure RC film.

  1. Hierarchical cross-linking in physical alginate gels: a rheological and dynamic light scattering investigation

    Science.gov (United States)

    Larobina, Domenico; Cipelletti, Luca

    We investigate the dynamics of alginate gels, an important class of biopolymer-based viscoelastic materials, by combining mechanical tests and non-conventional, time-resolved light scattering methods. Two relaxation modes are observed upon applying a compressive or shear stress. Dynamic light scattering and diffusive wave spectroscopy measurements reveal that these modes are associated with discontinuous rearrangement events that restructure the gel network via anomalous, non-diffusive microscopic dynamics. We show that these dynamics are due to both thermal activation and internal stress stored during gelation and propose a scenario where a hierarchy of cross-links with different life times is responsible for the observed complex behavior. Measurements at various temperatures and sample ages are presented to support this scenario.

  2. Study on the Rheological Properties and Constitutive Model of Shenzhen Mucky Soft Soil

    Directory of Open Access Journals (Sweden)

    Huang Wei

    2014-07-01

    Full Text Available In order to obtain the basic parameters of numerical analysis about the time-space effect of the deformation occurring in Shenzhen deep soft-soil foundation pit, a series of triaxial consolidated-undrained shear rheology tests on the peripheral mucky soft soil of a deep foundation pit support were performed under different confining pressures. The relations between the axial strain of the soil and time, as well as between the pore-water pressure of the soil and time, were achieved, meanwhile on the basis of analyzing the rheological properties of the soil, the relevant rheological models were built. Analysis results were proved that the rheology of Shenzhen mucky soft soil was generally viscous, elastic, and plastic, and had a low yield stress between 90 and 150 kPa. The increase in pore-water pressure made the rheological time effect of the mucky soft soil more remarkable. Thus, the drainage performance in practical engineering should be improved to its maximum possibility extent to decrease the soft-soil rheological deformation. Lastly, a six-component extended Burgers model was employed to fit the test results and the parameters of the model were determined. Findings showed that the extended Burgers model could satisfactorily simulate the various rheological stages of the mucky soft soil. The constitutive model and the determination of its parameters can be served as a foundation for the time-space effect analysis on the deformation of deep soft-soil foundation pits.

  3. Experimental study on the rheologic behavior of debris flow material in the Campania region, Italy

    Science.gov (United States)

    Scotto di Santolo, A.; Evangelista, A.; Pellegrino, A.

    2009-04-01

    The rheologic behavior of the natural material collected in the source area of debris flows occurred in the Campania region has been investigated. Several studies have been carried out on the conditions leading to the triggering of landslides. Less information is available on the transition between soil behavior and fluid behavior. In this work the rheologic flow behavior of the suspension of these materials in distilled water has been investigated with a standard viscosimeter (AR 2000ex TA Instruments) at different solid volumetric concentrations Cv (20, 30 and 40%). The materials tested were taken from the source area of three debris flows occurred in the mountainsides of the Northwestern Campania region (Southern Italy): Nocera, Salerno (March 2005) material A in the following; Monteforte Irpino, Avellino (May 1998) material B; Astroni, Naples (December 2005) material C. The soil type regards the most recent pyroclastic deposits deriving from the volcanic activity of mount Somma/Vesuvius (comprising the Sorrento Penisula and the mountains of Sarno-Quindici) for materials A and B. For material C, the soil type regards the most recent pyroclastic deposits deriving from the volcanic activity of the Phlegrean Fields (part of the city of Naples). For each solid volumetric concentration Cv, two kinds of tests have been performed: test on fine particle suspension (maximum diameter of 0.1 mm); test on large particle suspension (maximum diameter of 0.5 mm). The principal result is that the flow behavior is almost the same for all pyroclastic deposits: the materials behave like a Non-Newtonian fluid with a threshold shear stress (yield stress). The shear stress increases with increase of shear strain in the range analyzed (1< γ י

  4. Effects of stress conditions on rheological properties of granular soil in large triaxial rheology laboratory tests

    Institute of Scientific and Technical Information of China (English)

    陈晓斌; 张家生; 刘宝琛; 唐孟雄

    2008-01-01

    In order to study the rheological properties of red stone granular soil,a series of rheological experiments were executed on large tri-axial rheological apparatus.Under 100,200 and 300 kPa confining stress conditions,the rheological tests were carried out.These experiment results showed that the stress conditions,especially the stress level were the critical influencing factors of the rheological deformation properties.Under the low stress level(S=0.1),the granular soil showed the elastic properties,and there was no obvious rheological deformation.Under the middle stress level(0.2rheological properties.However,under the high stress level(S>0.8) creep curves showed the non-linear viscous plastic rheological properties.Especially,under the stress level of S=1.0,the accelerated rheological phase of creep curves occurred at early time with a trend of failure.The stress level had obvious effects on the final rheological deformation of the soil sample,and the final rheological deformation increments nonlinearly increased with stress level.The final rheological deformation increment and step was little under low stress level,while it became large under high stress level,which showed the nonlinearly rheological properties of the granular soil.The confining pressure also had direct effects on final rheological deformation,and the final rheological deformation linearly increased with confining pressure increments.

  5. A rheological study of hydrophobic-surface-active polymer systems structuration; Etude rheologique de la structuration de systemes polymere hydrophobe-tensioactif

    Energy Technology Data Exchange (ETDEWEB)

    Heinrich, E.

    1997-01-29

    This work deals with the study of the rheology and the structuration of hydrophobic polymer and surfactant systems. The used associative polymers are acrylamide/nonyl methacrylate copolymers and the surfactant is nonionic. They are particularly used for hydrocarbons extraction techniques as drilling (drilling fluids) or wells cementation. The studied materials are first characterized by different analytic techniques. This preliminary stage of the work gives a good insight of the physico-chemical parameters of the systems. The effect of surfactant was shown by studying the variation of Newtonian viscosity as a function of surfactant concentration. This yields bell curves, whose maximum determines the critical aggregation concentration (cac). The hydrophobic effect is analysed in different polymer concentration regimes, in quasi-static conditions, and under shear. The study of the dynamic visco-elasticity of semi-dilute solutions allows to observe the effect of the hydrophobic associations on the relaxation time of the chains. The system can be described as a superposition of two networks of junctions: the network of physical entanglements and a second one formed by the hydrophobic links. Phenomena of structuration have been observed at room temperature for surfactant concentrations close to the cac. The increase of viscosity or elastic modulus can be 3 to 4 orders of magnitude. The effect of the temperature on the structure of the systems is studied as well. The rheological characterization of the Sol-Gel transition is developed and the rheological behavior of the solutions in a structured state shows a critical stress for rupture of the structure. Microscopic observations of the birefringence of the solutions display the existence of lamellar vesicles, which leads to the following assumption: the formation of big spherulites create a rigidification of the macromolecular network. (author) 190 refs.

  6. Preparation of Nitrocellulose Gel Based on Phase Separation in Ternary System and Study on Its Dynamic Rheological Characteristics%三元体系相分离制备硝化纤维素凝胶及其动态流变性的研究

    Institute of Scientific and Technical Information of China (English)

    张云华; 邵自强

    2015-01-01

    The nitrocellulose (NC)gels were prepared from a ternary system NC/acetone/ethanol by solvent evapo-ration induced phase separation.The response degrees of the gel to external stimuli (such as strain,frequency,tem-perature)were investigated by linear rheological methods.Dynamic rheological characteristics of NC gels were stud-ied.Results show that the final morphologies of NC gels are influenced by mass ratios of the initial solvent/non-sol-vent (acetone/ethanol)and NC contents.The effect of changing initial acetone/ethanol ratios on the dynamic rheo-logical characteristics of the NC gels is different from the effect of changing NC contents.With increasing the ace-tone content,the volume of the NC gel prepared decreases,the NC content in the gel increases,the storage modulus (G′)and loss modulus (G″)of NC gels increase as well as the critical strain value (γc )decreases with increasing the NC content in the gels,whereas the value of G′and G″first increase and then decrease with increasing the NC con-tent in the gels when the mass ratio of acetone/ethanol is 2∶3.The values of G′and G″of all NC gels over the en-tire temperature scanning are basically unchanged,indicating that the interactions among NC chains and between NC/solvent can not be disrupted upon heating to higher temperatures.%通过溶剂蒸发引发相分离从硝化纤维素/丙酮/乙醇三元体系中制备出硝化纤维素凝胶,采用线性流变学方法考察凝胶对外界刺激(如应变、频率、温度)的响应程度,研究了凝胶的动态流变性能。结果表明,溶剂/非溶剂(丙酮/乙醇)质量比或硝化纤维素含量影响最终硝化纤维素凝胶的形貌,改变溶剂比例与硝化纤维素含量对硝化纤维素凝胶的动态流变性能的影响不同,增加丙酮含量,制备出的硝化纤维素凝胶体积减小,凝胶中硝化纤维素的含量增加,储能模量 G′和损耗模量 G″增加,临界应变(γc

  7. 地震动力学:震源分布与岩石圈流变特性%EARTHQUAKE DYNAMICS: SOURCE DISTRIBUTION WITH RESPECT TO LITHOSPHERIC RHEOLOGY

    Institute of Scientific and Technical Information of China (English)

    陈胜早

    2007-01-01

    Earthquake source distribution strongly depends on temperature and pressure conditions of the tectonic environments. Focal mechanism complicates the temperature-pressure conditions of the lower stability transition at the brittle-ductile transition boundary of the continental crust, a transition from velocity weakening (seismic) to velocity strengthening (non-seismic). Plate boundary associated earthquakes such as interface and intraslab events are studied on a platform of lithospheric rheology and crust-mantle dynamics. Brittle friction bears dynamic constraints on depth distribution of subduction interface earthquakes. Deep earthquakes, including subduction intraslab events, are not well explained by frictional shearing mechanism, for which a candidate mechanism appears to be associated with solid-solid phase transition at high pressure and temperature conditions where a brittle rupture or frictional processes may not be plausible. Rheological properties relevant to physics of earthquake focus and source depth distribution are critically reviewed based on theoretical and experimental research.%地震震源分布强烈依赖于构造环境的温度和压力条件.震源机制可使大陆地壳脆性-韧性转换带(下部稳定性过渡边界)的温压条件复杂化.该过渡边界伴随速度弱化作用(有震活动)向速度强化作用(无震活动)的转化.在岩石圈流变和壳幔动力学的基础上研究了与板块边界有关的地震活动,包括板缘地震和俯冲板片地震.俯冲带板缘地震的深度分布受约于脆性摩擦动力机制,而摩擦剪切机制不能满意地解释深震活动,包括俯冲板片地震.这是因为深震震源机制可能与高压、高温条件下的固一固相变有关,而用脆性破裂或摩擦作用来解释就不近合理.以理论与实验研究为依据,本文对与震源物理和震源分布有关的岩石圈流变特性进行了较为深入的论述.

  8. 1H NMR and Rheological Studies of the Calcium Induced Gelation Process in Aqueous Low Methoxyl Pectin Solutions

    Science.gov (United States)

    Dobies, M.; Kuśmia, S.; Jurga, S.

    2006-07-01

    The 1H NMR relaxometry in combination with water proton spin-spin relaxation time measurements and rheometry have been applied to study the ionic gelation of 1% w/w aqueous low methoxyl pectin solution induced by divalent Ca2+ cations from a calcium chloride solution. The model-free approach to the analysis of 1H NMR relaxometry data has been used to separate the information on the static (β) and dynamic () behaviour of the systems tested. The 1H NMR results confirm that the average mobility of both water and the pectin molecules is largely dependent on the concentration of the cross-linking agent. The character of this dependency (β, and T2 vs. CaCl2 concentration) is consistent with the two-stage gelation process of low methoxyl pectin, in which the formation of strongly linked dimer associations (in the range of 0-2.5 mM CaCl2) is followed by the appearance of weak inter-dimer aggregations (for CaCl2≥ 3.5 mM). The presence of the weak gel structure for the sample with 3.5 mM CaCl2 has been confirmed by rheological measurements. Apart from that, the T1 and T2 relaxation times have been found to be highly sensitive to the syneresis phenomenon, which can be useful to monitor the low methoxyl pectin gel network stability.

  9. Combined rheological and ultrasonic study of alginate and pectin gels near the sol-gel transition.

    Science.gov (United States)

    Audebrand, Michel; Kolb, Max; Axelos, Monique A V

    2006-10-01

    The sol-gel transition of biopolymer mixtures has been investigated by rheological and ultrasonic measurements. A scaling analysis of the data was performed for both types of measurements. A gel time was determined from rheology for the pure pectin samples, and the data could be fitted to a universal scaling form near the transition point. Its critical exponents are in good agreement with the predictions of scalar percolation theory. In addition, the ultrasonic signal of the pectin samples close to the transition was analyzed in terms of a high-frequency scaling approach for the attenuation and the velocity. For the alginate samples and the mixtures, for which the gel point cannot be determined reliably from rheology, the ultrasonic measurements were analyzed using the same scaling form as for the pectin sample, thus providing a method for estimating the gel point, even in the absence of rheological data.

  10. Rheology and Morphology of a Trachybasaltic Lava Flow: a Case Study from the Cima Volcanic Field (CA)

    Science.gov (United States)

    Soldati, A.; Beem, J. R.; Robertson, T.; Gomez, F. G.; Whittington, A. G.

    2015-12-01

    Subliquidus rheology of a trachybasaltic lava was measured in the laboratory for the first time. Field observations of the parent flow focused on surface morphology characterization, which was later quantified in terms of surface roughness. The studied lava flow was emitted during the Holocene by a monogenetic cinder cone in the Cima Volcanic Field (CA). Surface morphology transitions from smooth pahoehoe ropes near the vent to jagged `a`a blocks over the majority of the flow. A variety of 2 m2 outcrops were photographed using a hand-held DSLR camera, and their surface texture was reconstructed with photogrammetry. The roughness of each outcrop, effectively described by the standard deviation between the real photogrammetric point cloud and the best-fitting surface, was quantified at different spatial scales, ranging from 0.5 cm to 200 m. We found that the roughness of the flow increases linearly as spatial resolution decreases, with a slope break corresponding to the average size of the outcrop lava blocks. The rheology of Cima lavas was determined by concentric cylinder viscometry in the 1220 °C to 1160 °C temperature range. The obtained rheological flow curves indicate a Bingham rheology, with clearly detected yield strength ranging from 25 Pa at the higher temperatures up to 650 Pa at the lower temperatures. Plagioclase crystallization begins at 1170 °C, likely playing a key role in promoting yield strength escalation. Viscosity increases by one order of magnitude (from 94 to 1116 Pa·s) over the 60 °C span of cooling considered, remaining consistently lower than most basaltic melts due to the high alkali content (6 wt%). The rheological and morphological results are being integrated, in order to assess if it is possible to identify the rheological fingerprint of the active flow on the preserved flow morphology. The composition-dependence of the morphological pahoehoe to `a`a transition in a rheological map is being assessed by comparing our results to

  11. RHEOLOGY OF CHICKPEA PROTEIN CONCENTRATE DISPERSIONS

    Directory of Open Access Journals (Sweden)

    Aurelia Ionescu

    2011-12-01

    Full Text Available Chickpea proteins are used as ingredients in comminuted sausage products and many oriental textured foods. Rheological behaviour of chickpea protein concentrate was studied using a controlled stress rheometer. The protein dispersion prepared with phosphate buffer at pH 7.0 presented non-Newtonian shear thinning behaviour and rheological data well fitted to the Sisko, Carreau and Cross models. The viscoelastic properties of the chickpea protein suspensions were estimated by measuring the storage and loss moduli in oscillatory frequency conditions (0.1-10 Hz at 20°C. Moreover, thermally induced gelation of the chickpea proteins (16, 24 and 36% was studied at pH 7.0 and 4.5 in the temperature range 50 to 100oC and salt concentration ranging from 0 to 1 M. Gelling behaviour was quantified by means of dynamic rheological measurements. Gels formation was preceded by the decrease of storage modulus and loss moduli, coupled with the increase of the phase angle (delta. The beginning of thermal gelation was influenced by protein concentration, pH and salt level. In all studied cases, storage modulus increased rapidly in the temperature range 70-90°C. All rheological parameters measured at 90°C were significantly higher at pH 4.5 compared to pH 7.0.

  12. Rheological Behavior for Mica-filled Polypropylene Composite Melts

    Institute of Scientific and Technical Information of China (English)

    Yan Xia CAO; Miao DU; Qiang ZHENG

    2004-01-01

    The study on rheological properties of a series of mica-filled polypropylene ( PP ) composites was carried out. The influence of surface-treatment of mica particles on dynamic rheological behavior of the composites were dealt with. The viscosity ( η ) and dynamic modulus ( G′ ) of the composite melts were higher than those of PP matrix, especially those for systems treated with silane, which was attributed to the interfacial adhesion enhancement. However, surface-treatment of mica by titanate resulted in lower η and G′, as compared with the treatment by silane. The reason for this is believed to be the formation of the mono-molecular layer on the mica surface.

  13. Comprehensive study of rheological and surface properties of the selected slag system in the context of its internal structure

    Directory of Open Access Journals (Sweden)

    L. Řeháčková

    2016-10-01

    Full Text Available Rheological (dynamic viscosity, flow curves and surface properties (surface tension of real slag system were experimentally investigated. Measurements of dynamic viscosity were performed with use of the high-temperature viscometer Anton Paar FRS 1 600. The method of sessile drop was used for measurement of surface tension. Surface tension and dynamic viscosity were measured in the temperature interval from 1 200 to 1 600 °C. The structural characteristics of the selected samples were determined by X-ray diffraction (XRD. The samples for given analysis were prepared by quench cooling. Experimentally determined values of dynamic viscosity and surface tension were compared with the results of X-ray diffraction phase analysis.

  14. Determination of heat-set gelation capacity of a quinoa protein isolate (Chenopodium quinoa) by dynamic oscillatory rheological analysis.

    Science.gov (United States)

    Kaspchak, Elaine; Oliveira, Marco Aurelio Schüler de; Simas, Fernanda Fogagnoli; Franco, Célia Regina Cavicchiolo; Silveira, Joana Léa Meira; Mafra, Marcos Rogério; Igarashi-Mafra, Luciana

    2017-10-01

    This work aimed to study the influence of pH (3.5 and 7.0) and CaCl2 and MgCl2 addition on heat-set gelation of a quinoa protein isolate at 10% and 15% (w/w). The protein isolate obtained was composed mainly of 11S globulin as was observed by electrophoresis and mass spectrometry analysis. Heat-set gelation occurred at both pH values studied. Nevertheless, the gels formed at pH 3.5 were more viscoelastic and denser than those formed at pH 7.0, that was coarser and presented syneresis. The CaCl2 and MgCl2 addition increased the gel strength during rheological analysis at pH 3.5, possibly due to the formation of fiber-like connections in the gel network. At pH 7.0, the divalent salts resulted in weaker gels formed by agglomerates, suggesting a neutralization of the protein surface charges. The differences in quinoa protein gelation were attributed to solubility, and the flexibility of proteins secondary structure at the pH studied. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Injectable silica-permanganate gel as a slow-release MnO4(-) source for groundwater remediation: rheological properties and release dynamics.

    Science.gov (United States)

    Yang, S; Oostrom, M; Truex, M J; Li, G; Zhong, L

    2016-02-01

    Injectable slow-release permanganate gels (ISRPGs), formed by mixing aqueous KMnO4 solution with fumed silica powders, may have potential applications in remediating chlorinated solvent plumes in groundwater. A series of batch, column, and two-dimensional (2-D) flow cell experiments has been completed to characterize the ISRPG and study the release of permanganate (MnO4(-)) under a variety of conditions. The experiments have provided information on ISRPG rheology, MnO4(-) release dynamics and distribution in porous media, and trichloroethene (TCE) destruction by the ISRPG-released oxidant. The gel possesses shear thinning characteristics, resulting in a relatively low viscosity during mixing, and facilitating subsurface injection and distribution. Batch tests clearly showed that MnO4(-) diffused out from the ISRPG into water. During this process, the gel did not dissolve or disperse into water, but rather maintained its initial shape. Column experiments demonstrated that MnO4(-) release from the ISRPG lasted considerably longer than that from an aqueous solution. In addition, due to the longer release duration, TCE destruction by ISRPG-released MnO4(-) was considerably more effective than that when MnO4(-) was delivered using aqueous solution injection. In the 2-D flow cell experiments, it was demonstrated that ISRPGs released a long-lasting, low-concentration MnO4(-) plume potentially sufficient for sustainable remediation in aquifers.

  16. Mantle Dynamics in Super-Earths: Post-Perovskite Rheology and Self-Regulation of Viscosity

    CERN Document Server

    Tackley, Paul J; Brodholt, John P; Dobson, David P; Valencia, Diana

    2012-01-01

    Simple scalings suggest that super-Earths are more likely than an equivalent Earth-sized planet to be undergoing plate tectonics. Generally, viscosity and thermal conductivity increase with pressure while thermal expansivity decreases, resulting in lower convective vigor in the deep mantle. According to conventional thinking, this might result in no convection in a super-Earth's deep mantle. Here we evaluate this. First, we here extend the density functional theory (DFT) calculations of post-perovskite activation enthalpy of to a pressure of 1 TPa. The activation volume for diffusion creep becomes very low at very high pressure, but nevertheless for the largest super-Earths the viscosity along an adiabat may approach 1030 Pa s in the deep mantle. Second, we use these calculated values in numerical simulations of mantle convection and lithosphere dynamics of planets with up to ten Earth masses. The models assume a compressible mantle including depth-dependence of material properties and plastic yielding induce...

  17. 5th European Rheology Conference

    CERN Document Server

    1998-01-01

    Global sustainable development of the world economy requires better understanding and utilization of natural recourses. In this endeavor rheology has an indispensable role. The Rheology Conferences are therefore always an important event for science and technology. The Fifth European Rheology Conference, held from September 6 to 11 in the Portoro-z, Slovenia, will be the first AlI-European rheology meeting after the formal constitution of the European Society ofRheology. As such it will be a special historical event. At this meeting the European Society of Rheology will introduce the Weissenberg Medal, to be bestowed every four years to an individual for hislhers contribution to the field of Rheology. The recipient ofthe first award will be professor G. Marrucci ofthe Universita degli Studi di Napoli, Italy. Two mini Symposia will be part of the Conference. The first, on Industrial Rheology, will commemorate the late professor G. Astarita. The second will honor the eightieth birthday of professor N.W. Tschoeg...

  18. Evolution of rheologically heterogeneous salt structures: a case study from the northeast of the Netherlands

    Directory of Open Access Journals (Sweden)

    A F. Raith

    2015-07-01

    Full Text Available At the first order salt structures are controlled by the low flow strength of evaporites and by the tectonic boundary conditions. Rheological contrasts within an evaporite body have an important effect on the evolution of the internal structure of salt, but how this mechanical layering affects salt deformation at different scales is not well known. The potassium–magnesium salts (K-Mg salts carnallite and bischofite are prime examples of layers with much lower effective viscosity than rock salt: their low viscosity presents serious drilling hazards but also allows squeeze solution mining. In contrast, anhydrite and carbonate layers (stringers in salt are much stronger than halite. In this study, we used high-resolution 3-D seismic and well data to study the evolution of the Veendam and Slochteren salt pillows at the southern boundary of the Groningen High, northern Netherlands. Here the rock salt layers contain both the mechanically stronger Zechstein III Anhydrite–Carbonate stringer and the weaker K-Mg salts, providing an example of extreme rheological heterogeneities in salt structures. The internal structure of the two salt pillows shows areas in which the K-Mg salt-rich ZIII 1b layer is much thicker than elsewhere, in combination with a complexly ruptured and folded ZIII Anhydrite–Carbonate stringer. Thickness maps of supra-salt sediments and well data are used to infer the initial depositional architecture of the K-Mg salts and their deformation history. Results suggest that active faulting and the resulting depressions of the Zechstein surface above a Rotliegend graben caused the local accumulation of bittern brines and precipitation of the thick K-Mg salts. During the first phase of salt flow and withdrawal from the Veendam area, under differential loading by Buntsandstein sediments, the ZIII stringer was boudinaged while the lens of Mg salts remained relatively undeformed. This was followed by a convergence stage, when the K-Mg salt

  19. Studies on rheology and microbiological evaluation of hydrotropically gelled starch as topical vehicle for terbinafine hydrochloride

    Directory of Open Access Journals (Sweden)

    Rao Kovur

    2008-01-01

    Full Text Available The present study was aimed for the development and evaluation of hydrotropic starch gels of terbinafine hydrochloride which is an allylamine derivative of antifungal agent was formulated by using corn starch and sodium salicylate as hydrotropic salt. The gels were prepared in presence and absence of propylene glycol. The prepared gels were evaluated for in vitro drug release, rheological behavior and microbial studies. The degree of increase in the drug diffusion was found to be in order corn starch gel with propylene glycol was greater than corn starch gel without propylene glycol. The microbial studies were carried out in soya bean casein digest medium with Candida albicans as test organisms and were found to be 22.86 ± 0.58 and 20.22 ± 0.65 mm for TCSG (IV and TCS (III, respectively. All the gels exhibited shear thinning. The rheogram indicated that the gel systems are pseudoplastic and exhibited thixotropy. The added propylene glycol has not appreciably altered the apparent viscosity values.

  20. A preliminary study on the lithospheric thermal-rheological structure of the East Qinling orogenic belt

    Institute of Scientific and Technical Information of China (English)

    CHENG Shunyou; ZHANG Guowei; DIAO Bo; GUO Anlin; YU Xiangni

    2007-01-01

    This paper considers the lithospheric rheological structure of the East Qinling orogenic belt to explore its geodynamics. The lithospheric rheological structure was calculated by the constraints of the lithospheric temperature structure. The thermal-rheological stratification structures of the lithosphere in the East Qinling orogenic belt present different features from each other within different tectonic units. The hinterland fault-bounded fold zone (HLZ) and the North Qinling thick-skinned imbricated thrust zone (NQL) in the northern half part of the Qinling orogen, with a tempera-ture of 305℃ for the Moho boundary, are characterized by "cold" geotherm, thickened lithosphere and the model C for rheological stratification structure. The South Qinling tectonic zone (SQL), with a mean temperature of 642℃ and a high temperature of 826℃ for the Moho boundary, has obvious features with the model H of"hot" geotherm, thinned lithosphere and intensive rheological behavior within moderate-lower crust and top of the upper mantle. During post-orogenesis, the NQL, being the convergent frontal region of continental subduction beneath the Qinling orogen by both the North China craton (NC) and Yangtze craton (YZ), is in a coexistence period of a dominantly thickened lithosphere and an initial delamination, and the SQL, proba-bly under pluming, has been developing new delamination and underplating and partial melting within the crust in its axel area and recycling for mass and energy (in the forms of heat transfer and convection) between the crust and mantle.

  1. STUDYING THE EFFECT OF SWEETENERS ON RHEOLOGICAL PROPERTIES OF CHOCOLATE MASS

    Directory of Open Access Journals (Sweden)

    Chernykh I. A.

    2016-10-01

    Full Text Available Chocolate products with reduced calories are becoming increasingly popular among consumers and producers. One method of producing chocolate with low calorie content is some replacement with alternative sucrose sugar substitutes. We have investigated the effect of various bulk sweeteners (maltitol, isomalt and erythritol with different particle size, divided into three intervals (106-53, 53-38, and 38-20 microns on the rheological properties of molten chocolate. It was found, that the model of the Herschel-Bulkley is better than others, it describes the real rheological properties of the chocolate mass. It is established, that because of maltitol, it affects the rheological properties of chocolate just as sucrose and thus it may be a good alternative. The use of isomalt causes higher plastic viscosity of the chocolate mass and maltitol improves the fluidity of the chocolate mass, significantly more than other bulk sweeteners. Changing the particle size leads to a change in the plastic viscosity and yield point. Differences in the rheological properties of chocolate with different bulk sugar substitutes have been caused by differences in the volume fraction of solids and the distribution of particle size. When replacing sucrose to improve the rheological properties of the chocolate, we have to select sweeteners with large particle size, but sweeteners particle size should be small enough to result in chocolate with good organoleptic properties

  2. Rheological characterization and stability study of an emulsion made with a dairy by-product enriched with omega-3 fatty acids

    Directory of Open Access Journals (Sweden)

    Angela María Ormaza ZAPATA

    2015-03-01

    Full Text Available This study involved a rheological characterization of a W/O emulsion manufactured on a pilot scale using omega-3 fatty acids as part of the oil phase and butter milk as the emulsifier. Polyunsaturated omega-3 fatty acids are essential to prevent cardiovascular diseases, improve pulmonary function and also form part of the neurological structure. Buttermilk is a by-product of the dairy industry and has a high organic load which possesses surfactant properties and constitutes a good substitute for conventional emulsifiers in the food industry. The microstructural nature of the emulsion was characterized from the viscoelastic parameters and mechanical spectra. The linear viscoelastic range was determined, from which the maximum stress that the emulsion could withstand from the processing conditions without altering its microstructure was established. In addition, the storage stability of the emulsion was studied to instrumentally predict the rheological behaviour before sensory destabilization of the emulsion was observed. At the frequencies used, a significant decrease in dynamic viscoelastic parameters was periodically observed (G 'and G'', showing a structural change during storage. Furthermore, a coalescence phenomenon was observed after 18 months. The formulation with added omega-3 fatty acids and buttermilk provided a basis for obtaining a functional food as well as adding value to an industrial by-product.

  3. Rheological studies of the gelation of deacetylated gellan gum (Gelrite) in physiological conditions.

    Science.gov (United States)

    Paulsson, M; Hägerström, H; Edsman, K

    1999-10-01

    Gels have been successfully used to increase the mucosal contact time and hence the bioavailability of nasal and ophthalmic formulations. The use of in situ gelling polymers requires a rapid sol-gel transition that produces a strong gel for an optimal contact time. In this study, the rheological behaviour of deacetylated gellan gum (Gelrite) was analysed in order to better understand the reasons for the good performance in humans. Thermal scans were used to study gel formation and other changes in the structure of the samples when the macromolecular and ionic contents were altered. The effect the different ions in tear fluid (Na+, K+, Ca2+) had on the gel strength and the consequences of dilution due to the ocular protective mechanisms were examined. Na+ was found to be the most important gel-promoting ion in vivo. It was also found that gels are formed in tear fluid even when the concentration of Gelrite) is only 0.1%. Samples with concentrations of Gelrite of 0.5-1% do not require more ions than 10-25% of those in tear fluid to form gels. These two findings can partly explain the good performance of Gelrite in vivo. Gels with a high elastic modulus can thus be formed even though dilution of instilled drops takes place.

  4. Rheological study to test a new formulation of silk screen paint

    Directory of Open Access Journals (Sweden)

    Palmonari, C.

    2000-10-01

    Full Text Available A study was carried out to evaluate a new formulation of silk screen paint developed with the objective of changing the traditional, expensive milling process as well as replacing the organic milling medium with a water-based solution. The new and traditional formulations are compared on the basis of their rheological properties. Some oscillatory tests were found to be useful to study milling conditions that simulate the industrial preparation process.

    Se ha llevado a cabo un estudio para evaluar una nueva fórmula de pasta serigráifca desarrollada con el objetivo de cambiar el proceso tradicional de molienda cuyo coste es más elevado y para reemplazar el vehículo serigráfico de molienda orgánico por uno acuoso. Las dos fórmulas, la nueva y la tradicional, se han comparado en función de sus propiedades reológicas. Las mediciones en régimen oscilatorio han resultado muy útiles para obtener las condiciones de molienda en laboratorio que mejor simularan las condiciones a nivel industrial.

  5. Effect of Rheology on Mantle Dynamics and Plate Tectonics in Super-Earths

    Science.gov (United States)

    Tackley, P. J.; Ammann, M. W.; Brodholt, J. P.; Dobson, D. P.; Valencia, D. C.

    2011-12-01

    The discovery of extra-solar "super-Earth" planets with sizes up to twice that of Earth has prompted interest in their possible lithosphere and mantle dynamics and evolution. Simple scalings [1,2] suggest that super-Earths are more likely than an equivalent Earth-sized planet to be undergoing plate tectonics. Generally, viscosity and thermal conductivity increase with pressure while thermal expansivity decreases, resulting in lower convective vigor in the deep mantle, which, if extralopated to the largest super-Earths might, according to conventional thinking, result a very low effective Rayleigh number in their deep mantles and possibly no convection there. Here we evaluate this. (i) As the mantle of a super-Earth is made mostly of post-perovskite we here extend the density functional theory (DFT) calculations of post-perovskite activation enthalpy of [3] to a pressure of 1 TPa. The activation volume for diffusion creep becomes very low at very high pressure, but nevertheless for the largest super-Earths the viscosity along an adiabat may approach 10^30 Pa s in the deep mantle, which would be too high for convection. (ii) We use these DFT-calculated values in numerical simulations of mantle convection and lithosphere dynamics of planets with up to ten Earth masses. The models assume a compressible mantle including depth-dependence of material properties and plastic yielding induced plate-like lithospheric behavior, solved using StagYY [4]. Results confirm the likelihood of plate tectonics and show a novel self-regulation of deep mantle temperature. The deep mantle is not adiabatic; instead internal heating raises the temperature until the viscosity is low enough to facilitate convective loss of the radiogenic heat, which results in a super-adiabatic temperature profile and a viscosity increase with depth of no more than ~3 orders of magnitude, regardless of what is calculated for an adiabat. It has recently been argued [5] that at very high pressures, deformation

  6. Studies on the rheology and oxygen mass transfer in the clavulanic acid production by Streptomyces clavuligerus

    Directory of Open Access Journals (Sweden)

    E. R. Gouveia

    2000-12-01

    Full Text Available In the present work rheological characteristics and volumetric oxygen transfer coefficient (kLa were investigated during batch cultivations of Streptomyces clavuligerus NRRL 3585 for production of clavulanic acid. The experimental rheological data could be adequately described in terms of the power law model and logistic equation. Significant changes in the rheological parameters consistency index (K and flow behavior index (n were observed with the fermentation evolution. Interesting correlations between the consistency index (K/biomass concentration (C X and the flow behavior index (n/biomass concentration were proposed. Volumetric oxygen mass transfer coefficient (kLa was determined by the gas balance method. Classical correlation relating the volumetric oxygen mass transfer coefficient to the operating conditions, physical and to transport properties, including apparent viscosity (muap, could be applied to the experimental results.

  7. An experimental approach to the study of the rheology behaviour of synthetic bone calcium phosphate cements

    Energy Technology Data Exchange (ETDEWEB)

    Friberg, J.; Fernandez, E.; Sarda, S.; Nilsson, M.; Ginebra, M.P.; Planell, J.A. [Universidad Politecnica de Catalunya, Barcelona (Spain). Dept. of Materials Science and Metallurgical Engineering; Martinez, S. [Barcelona Univ. (Spain). Mineralogia i Recursos Minerals

    2001-07-01

    Calcium phosphate cements were developed to fit surgical needs in biomedical fields such as odontology or traumatology. Nowadays, a broad field of new applications have been found for this kind of materials. Drug delivery systems, tissue-engineering scaffolds and osteoporotic bone filling applications are some of the new fields that are being benefited with these materials. Looking at both, commercial and new experimental calcium phosphate cements it is found that {alpha}-tricalcium phosphate is the main reactive powder responsible for the setting and the hardening of the cement. Thus, it is important to know how {alpha}-tricalcium phosphate affects injectability of these cements. The aim of this study was to investigate the rheological behaviour of {alpha}-tricalcium phosphate slurries in order to know how the cement injectability should be modified. Factors such as liquid to powder ratio, particle size of the main reactive powder and the addition of dispersants have been considered. The results showed that viscosity decreased when particle size of reactant was increased and when liquid to powder ratio was increased. It was also found that a minimum of viscosity exists at an optimum value of the weight percentage of dispersant. (orig.)

  8. Rheology, microrheology and structure of soft materials

    Science.gov (United States)

    Oppong, Felix K.

    We study the relationship between the bulk rheological properties and the micron-scale structure and rheology of different types of soft materials. The materials studied are Laponite, a colloidal clay suspension; Carbopol, a dispersion of microgel particles; hydroxyethyl cellulose, a linear polymer solution; and hydrophobically modified hydroxyethyl cellulose, an associative polymer. Bulk properties are measured using conventional shear rheometry. The micron-scale measurements are performed using techniques based on multiple particle tracking and dynamic light scattering. From the thermal motion of suspended tracer particles, we obtain information about the local structure and viscoelastic properties of the materials. We investigate the evolution of Laponite from a liquid to a gel and find that the process is length-scale dependent. We study the properties of Carbopol as a function of microgel concentration and find that as concentration increases, a jamming transition occurs which is related to the onset of yield stress on the bulk scale. We compare the viscoelastic properties of hydroxyethylcellulose and its associative derivative and observe that the hydrophobic interactions in the latter lead to much slower dynamics than in the unmodified polymer. A study of the stress relaxation in hydroxyethylcellulose showed that it depended on both the wait time after the application and removal of a large strain and on the type and magnitude of the deformation applied. Our work exploits the unique ability of microrheological techniques to probe both the rheology and structure of soft materials on the microscopic scale, which enables a better understanding of the relationship between bulk scale properties and microscopic structure in these systems. Keywords. Rheology, microrheology, soft materials, particle tracking, dynamic light scattering, viscoelasticity, yield stress, gelation, polymers.

  9. Numerical study of jumps formed in free-surface flows down an incline : influence of the fluid rheology

    Science.gov (United States)

    Naaim, Mohamed; Faug, Thierry

    2017-04-01

    The discontinuities in height and velocity, namely jumps, formed in free-surface flows are important processes in geophysics, for instance when they are formed during the interaction of avalanche-flows with protection structures. The present study investigates steady state jumps formed in free-surface flows with the help of numerical simulations based on depth-averaged equations. A control constant mass discharge is supplied to an incline. By imposing a difference in basal friction between a upper part of the chute bottom and a lower part of the chute bottom, a supercritical flow is produced upstream while a subcritical flow appears downstream. The transition between both gives birth to a jump located at the transition between the two portions of the chute with different basal friction. Different constitutive equations are tested (laminar, turbulent, local granular rheology, Voellmy, Herschel Bulkley), thus allowing us to quantify the influence of the fluid rheology on the jump properties : position, geometry and size.

  10. Capillary rise of a non-Newtonian power law liquid: impact of the fluid rheology and dynamic contact angle.

    Science.gov (United States)

    Digilov, Rafael M

    2008-12-02

    The impact of non-Newtonian behavior and the dynamic contact angle on the rise dynamics of a power law liquid in a vertical capillary is studied theoretically and experimentally for quasi-steady-state flow. An analytical solution for the time evolution of the meniscus height is obtained in terms of a Gaussian hypergeometric function, which in the case of a Newtonian liquid reduces to the Lucas-Washburn equation modified by the dynamic contact angle correction. The validity of the solution is checked against experimental data on the rise dynamics of a shear-thinning cmc solution in a glass microcapillary, and excellent agreement is found.

  11. Rheological properties of rennet-induced skim milk gels.

    NARCIS (Netherlands)

    Zoon, P.

    1988-01-01

    The rheological properties of rennet-induced skim milk gels, which are viscoelastic materials, were studied under various conditions.Dynamic and stress relaxation experiments were performed at small deformations of the gel network, whereas constant stress (creep) experiments were performed at large

  12. Rheological properties of soybean protein isolate gels containing emulsion droplets

    NARCIS (Netherlands)

    Kim, K.H.; Renkema, J.M.S.; Vliet, van T.

    2001-01-01

    Rheological properties of soybean protein gels containing various volume fractions oil droplets have been studied at small and large deformations. Dynamic viscoelastic properties of soybean protein isolate gels were determined as a function of the volume fraction of oil droplets stabilised by the sa

  13. Studying bacterial hydrophobicity and biofilm formation at liquid-liquid interfaces through interfacial rheology and pendant drop tensiometry.

    Science.gov (United States)

    Rühs, P A; Böcker, L; Inglis, R F; Fischer, P

    2014-05-01

    Bacterial adsorption to interfaces is a key factor in biofilm formation. One major limitation to understanding biofilm formation and development is the accurate measurement of bacterial cell adhesion to hydrophobic interfaces. With this study, bacterial attachment and biofilm growth over time at water-oil interface was monitored through interfacial rheology and tensiometry. Five model bacteria (Pseudomonas putida KT2442, Pseudomonas putida W2, Salmonella typhimurium, Escherichia coli, and Bacillus subtilis) were allowed to adsorb at the water-oil interface either in their non-growing or growing state. We found that we were able to observe the initial kinetics of bacterial attachment and the transient biofilm formation at the water-oil interface through interfacial rheology and tensiometry. Electrophoretic mobility measurements and bacterial adhesion to hydrocarbons (BATH) tests were performed to characterize the selected bacteria. To validate interfacial rheology and tensiometry measurements, we monitored biofilm formation utilizing both confocal laser scanning microscopy and light microscopy. Using this combination of techniques, we were able to observe the elasticity and tension development over time, from the first bacterial attachment up to biofilm formation. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Rheological profiling of organogels prepared at critical gelling concentrations of natural waxes in a triacylglycerol solvent

    OpenAIRE

    Patel, Ashok; Babaahmadifooladi, Mehrnoosh; Lesaffer, Ans; Dewettinck, Koen

    2015-01-01

    The aim of this study was to use a detailed rheological characterization to gain new insights into the gelation behavior of natural waxes. To make a comprehensive case, six natural waxes (differing in the relative proportion of chemical components: hydrocarbons, fatty alcohols, fatty acids, and wax esters) were selected as organogelators to gel high-oleic sunflower oil. Flow and dynamic rheological properties of organogels prepared at critical gelling concentrations (Cg) of waxes were studied...

  15. Rheological properties of Cubic colloidal suspensions

    Science.gov (United States)

    Boromand, Arman; Maia, Joao

    2016-11-01

    Colloidal and non-colloidal suspensions are ubiquitous in many industrial application. There are numerous studies on these systems to understand and relate their complex rheological properties to their microstructural evolution under deformation. Although most of the experimental and simulation studies are centered on spherical particles, in most of the industrial applications the geometry of the colloidal particles deviate from the simple hard sphere and more complex geometries exist. Recent advances in microfabrication paved the way to fabricate colloidal particles with complex geometries for applications in different areas such as drug delivery where the fundamental understanding of their dynamics has remained unexplored. In this study, using dissipative particle dynamics, we investigate the rheological properties of cubic (superball) particles which are modeled as the cluster of core-modified DPD particles. Explicit representation of solvent particles in the DPD scheme will conserve the full hydrodynamic interactions between colloidal particles. Rheological properties of these cubic suspensions are investigated in the dilute and semi-dilute regimes. The Einstein and Huggins coefficients for these particles with different superball exponent will be calculate which represent the effect of single particle's geometry and multibody interactions on viscosity, respectively. The response of these suspensions is investigated under simple shear and oscillatory shear where it is shown that under oscillation these particles tend to form crystalline structure giving rise to stronger shear-thinning behavior recently measured experimentally.

  16. Rheology and density of glucose syrup and honey: Determining their suitability for usage in analogue and fluid dynamic models of geological processes

    Science.gov (United States)

    Schellart, W. P.

    2011-06-01

    Analogue models of lithospheric deformation and fluid dynamic models of mantle flow mostly use some kind of syrup such as honey or glucose syrup to simulate the low-viscosity sub-lithospheric mantle. This paper describes detailed rheological tests and density measurements of three brands of glucose syrup and three brands of honey. Additional tests have been done for one brand of glucose syrup that was diluted with water to various degrees (2%, 5% and 10% by weight). The rheological tests have been done to test the effect of shear strain, shear rate and temperature on the dynamic viscosity of the syrup. The results show that the viscosity of all glucose syrups and honeys is independent of shear strain (i.e. no strain hardening or softening). The viscosity of the glucose syrups is independent of shear rate (γ˙), i.e. linear-viscous or Newtonian, in the range γ˙=10-4-10 s with stress exponents that are almost identical to one ( n = 0.995-1.004). All the honeys show a very weak, but consistent, decrease in viscosity with increasing shear rate of 7-14% from 10 -3 to 10 0 s -1 and have stress exponents more distinct from one ( n = 1.007-1.026). All syrups have a viscosity that is strongly dependent on temperature in the range 0-50 °C, where viscosity decreases with increasing temperature. Such decrease can be fitted with exponential and Arrhenius functions, with the latter giving the best results. Furthermore, the viscosity of glucose syrup decreases approximately exponentially with increasing water content. Oscillation tests indicate that the rheology of all the syrups is entirely dominated by viscous behaviour and not by elastic behaviour at frequencies of 10 -3-10 2 Hz. Finally, the density investigations show that the density of glucose syrup and honey decreases approximately linearly with increasing temperature in the range 10-70 °C, with coefficients of thermal volumetric expansion at 20 °C of 3.89-3.95 × 10 -4 °C -1 and 4.57-4.81 × 10 -4 °C -1 for

  17. PREFACE: Rheology and Elasticity Studies at Ultra-High Pressures and Temperatures

    Science.gov (United States)

    Liu, Haozhe; Wenk, Hans-Rudolf; Duffy, Thomas S.

    2006-06-01

    One of the major goals of geophysical research is to understand deformation in the deep Earth. The COMPRES (Consortium for Materials Properties Research in Earth Sciences) workshop on `Rheology and Elasticity Studies at Ultra-High Pressures and Temperatures' was held on 21-23 October 2005 at the Advanced Photon Source, Argonne National Laboratory, organized by Haozhe Liu, Hans-Rudolf Wenk and Thomas S Duffy, and provided an opportunity to assemble more than 50 scientists from six countries. Experts in diamond anvil cell (DAC) design, large-volume high-pressure apparatus and data analysis defined the current state of ultra-high pressure deformation studies and explored initiatives to push the technological frontier. The DAC, when used in radial diffraction geometry, emerges as a powerful tool for investigation of plasticity and elasticity of materials at high pressures. More information regarding this workshop can be found at the website: http://www.hpcat.aps.anl.gov/Hliu/Workshop/Index1.htm. In this special issue of Journal of Physics: Condensed Matter, 17 manuscripts review the state-of-the-art and we hope they will stimulate researchers to participate in this field and take it forward to a new level. A major incentive for high-pressure research has been the need of geophysicists to understand composition, physical properties and deformation in the deep Earth in order to interpret the macroscopically observed seismic anisotropy. In the mantle and core, materials deform largely in a ductile manner at low stresses and strain rates. From observational inferences and experiments at lower pressures, it is considered plausible that deformation occurs in the field of dislocation creep or diffusion creep and deformation mechanisms depend in a complex way on stress, strain rate, pressure, temperature, grain size and hydration state. With novel apparatus such as the rotational Drickamer press or deformation DIA (D-DIA) multianvil apparatus, large volumes (approximately 10

  18. Osteoarthritic synovial fluid rheology and correlations with protein concentration.

    Science.gov (United States)

    Madkhali, Anwar; Chernos, Michael; Grecov, Dana; Kwok, Ezra

    2016-11-09

    Osteoarthritis is a common, localized joint disease that causes pain, stiffness and reduced mobility. Osteoarthritis is particularly common in the knees. The effects of osteoarthritis on the rheology of synovial fluid in the knees are not fully understood and consequently require further study. The purpose of this study is to investigate the effects of protein content on synovial fluid shear rheology. A secondary study outcome will include study of the temperature dependence of synovial fluid behaviour. 38 osteoarthritic synovial fluid samples were studied under shear flow. Shear properties were correlated with protein concentration. Viscosupplement was used as a comparison and to verify measurement reliability. The effects of temperature were investigated at 20, 29 and 37°C. Shear rheological properties were found to vary widely between samples, however all samples demonstrated clear non-Newtonian shear thinning behaviour. In general viscoelastic properties were lower in osteoarthritic samples than previously studied healthy synovial fluid. A moderate correlation was observed between synovial fluid dynamic moduli at a frequency of 2.5 Hz and protein concentration. Temperature was found to affect the rheology of osteoarthritic synovial fluid and was fitted with the Arrhenius model. Increased protein concentration has been correlated with decreased shear rheological parameters. Temperature dependence of synovial fluid was also demonstrated and modelled for use in Part 2 of this article.

  19. Rheological behavior, chemical and physical characterization of soybean and cottonseed methyl esters submitted to thermal oxidation process

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Adriano Sant' ana; Silva, Flavio Luiz Honorato da; Lima, Ezenildo Emanuel de; Carvalho, Maria Wilma N.C. [Universidade Federal de Campina Grande (CCT/UFCG), PB (Brazil). Centro de Ciencia e Tecnologia; Dantas, Hemeval Jales; Farias, Paulo de Almeida [Universidade Federal de Campina Grande (CTRN/UFCG), PB (Brazil). Centro de Tecnologia e Recursos Naturais

    2008-07-01

    In this study the effect of antioxidant terc-butylhydroxyanisol (BHA) on the oxidative stability of soybean and cottonseed methyl esters subjected to thermal degradation at 100 deg C was studied. Soybean and cottonseed methyl esters specific mass, dynamic viscosity and rheological behavior were evaluated. According to results, antioxidant degraded samples specific mass and dynamic viscosity did not showed alterations, remaining statistically equal. Soybean and cottonseed methyl esters showed a Newtonian rheological behavior and degraded samples without adding BHA showed rheological behavior alterations. (author)

  20. Rheological behavior, chemical and physical characterization of soybean and cottonseed methyl esters submitted to thermal oxidation process

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Adriano Sant' ana; Silva, Flavio Luiz Honorato da; Lima, Ezenildo Emanuel de; Carvalho, Maria Wilma N.C. [Universidade Federal de Campina Grande (CCT/UFCG), PB (Brazil). Centro de Ciencia e Tecnologia; Dantas, Hemeval Jales; Farias, Paulo de Almeida [Universidade Federal de Campina Grande (CTRN/UFCG), PB (Brazil). Centro de Tecnologia e Recursos Naturais

    2008-07-01

    In this study the effect of antioxidant terc-butylhydroxyanisol (BHA) on the oxidative stability of soybean and cottonseed methyl esters subjected to thermal degradation at 100 deg C was studied. Soybean and cottonseed methyl esters specific mass, dynamic viscosity and rheological behavior were evaluated. According to results, antioxidant degraded samples specific mass and dynamic viscosity did not showed alterations, remaining statistically equal. Soybean and cottonseed methyl esters showed a Newtonian rheological behavior and degraded samples without adding BHA showed rheological behavior alterations. (author)

  1. An experimental study on semi-brittle and plastic rheology of Panzhihua gabbro

    Institute of Scientific and Technical Information of China (English)

    HE; Changrong(何昌荣); ZHOU; Yongsheng(周永胜); SANG; Zunan(桑祖南)

    2003-01-01

    We have carried out a systematic experimental study on semi-brittle and plastic deformation of fine-grained Panzhihua gabbro under dry condition with temperature range of 700-1100℃, confining pressure of 450-500 MPa, and strain rate of 1×10-4-3.1×10-6 s-1, using a triaxial testing system with a Griggs type solid medium pressure vessel. In terms of the parameters in the flow law and microstructure after deformation, the rate-dependent deformation can be categorized into three modes: (i) In temperature range of 700-800℃, the deformation is accommodated by semi-brittle flow, with activation energy Q = 612 ± 12 kJ/mol, and stress exponent n = 14.6. The deformation in microscopic scale corresponds to the dislocation glide accompanied with microfracturing. (ii) In temperature range of 900-950℃, the predominant deformation mechanisms in this phase are mechanical twinning and dislocation glide, with activation energy Q =720 ± 61 kJ/mol, and stress exponent n = 6.4. (iii) In temperature range of 1000-1150℃, the major deformation mechanisms are dislocation glide and dislocation climb with minor processes of partial melting, with activation energy Q = 699 ± 55 kJ/mol and stress exponent n = 4.1. The microstructure and deformation mechanism of our experiments are comparable to the results of clinopyroxene and diabase as observed in previous studies. The flow stress of a mafic lower crust is calculated based on the rheological parameters of dry fine-grained gabbro, which implies that a lower curst with mafic granulite may be brittle, and it is possible to fracture and produce frictional slips. This may be an important implication for earthquake nucleation in the lower crust.

  2. Unifying suspension and granular rheology.

    Science.gov (United States)

    Boyer, François; Guazzelli, Élisabeth; Pouliquen, Olivier

    2011-10-28

    Using an original pressure-imposed shear cell, we study the rheology of dense suspensions. We show that they exhibit a viscoplastic behavior similarly to granular media successfully described by a frictional rheology and fully characterized by the evolution of the friction coefficient μ and the volume fraction ϕ with a dimensionless viscous number I(v). Dense suspension and granular media are thus unified under a common framework. These results are shown to be compatible with classical empirical models of suspension rheology and provide a clear determination of constitutive laws close to the jamming transition.

  3. Dynamic rheological, microstructural and physicochemical properties of blend fish protein recovered from kilka (Clupeonella cultriventris) and silver carp (Hypophthalmichthys molitrix) by the pH-shift process or washing-based technology.

    Science.gov (United States)

    Abdollahi, Mehdi; Rezaei, Masoud; Jafarpour, Ali; Undeland, Ingrid

    2017-08-15

    This study aimed to evaluate how blending pH-shift produced protein isolates from gutted kilka (Clupeonella cultriventris) and silver carp (Hypophthalmichthys molitrix) affected dynamic rheological and chemical properties of the proteins as well as microstructural and physico-mechanical properties of produced gels. Studied variables were protein solubilization pH (acid vs. alkaline) and blending step (before or after protein precipitation). Comparisons were made with conventionally washed minces from kilka and silver carp fillets; either alone or after blending. Rheological studies revealed that blending alkali-produced protein isolates before precipitation resulted in rapid increase of G' reflecting the formation of intermolecular protein-protein interactions with higher rate. Furthermore, blending of alkali-produced protein isolates and washed minces, respectively, of kilka and silver carp improved physico-mechanical properties of the resultant gels compared to pure kilka proteins. However, the pH-shift method showed higher efficacy in development of blend surimi at the same blending ratio compared to the conventional washing. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. [Blood rheologic disorders in patients with polycythemia vera and their correction by therapeutic erythrocytapheresis].

    Science.gov (United States)

    Likhovetskaia, Z M; Prigozhina, T A; Gorbunova, N A; Kalinin, N N; Petrov, M M

    1989-11-01

    The rheologic blood properties were studied in patients with polycythemia vera (PV) before and after erythrocytapheresis. The patients with PV showed a complex of hemorheologic disorders (high blood viscosity at different rates of deviation, intensified red blood cell aggregation, decreased deformability of these cells) found to be implicated in the disease pathogenesis. Erythrocytapheresis promoted the improvement of the rheologic characteristics such as dynamic blood viscosity and the red blood cell aggregation ratio.

  5. Effect of Thermal History on Rheological Properties of Partially Hydrolyzed Polyacrylamide/Anionic Surfactant SDS Complex Systems

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The effects of thermal history on the rheological properties of partially hydrolyzed polyacrylamide/ sodium dodecyl sulfate complex aqueous solutions have been studied using both steady shear and dynamic temperature sweep characterizations. An abnormal rheological behavior was found that dynamic moduli of the aqueous solutions increased, while the viscosity decreased after thermal treatment, which could help to gain insight into the micro-phase evolution of the polymer/surfactant complex aqueous solutions and its dependence on temperature.

  6. Solid Character of Membrane Ceramides: A Surface Rheology Study of Their Mixtures with Sphingomyelin

    Science.gov (United States)

    Catapano, Elisa R.; Arriaga, Laura R.; Espinosa, Gabriel; Monroy, Francisco; Langevin, Dominique; López-Montero, Iván

    2011-01-01

    The compression and shear viscoelasticities of egg-ceramide and its mixtures with sphingomyelin were investigated using oscillatory surface rheology performed on Langmuir monolayers. We found high values for the compression and shear moduli for ceramide, compatible with a solid-state membrane, and extremely high surface viscosities when compared to typical fluid lipids. A fluidlike rheological behavior was found for sphingomyelin. Lateral mobilities, measured from particle tracking experiments, were correlated with the monolayer viscosities through the usual hydrodynamic relationships. In conclusion, ceramide increases the solid character of sphingomyelin-based membranes and decreases their fluidity, thus drastically decreasing the lateral mobilities of embedded objects. This mechanical behavior may involve important physiological consequences in biological membranes containing ceramides. PMID:22261061

  7. Studies of the Rheological Behavior of Polypropylene/Polyamide-6 Blend by Capillary Rheometer

    Institute of Scientific and Technical Information of China (English)

    YIN Cui-yu; SHEN Xin-yuan

    2002-01-01

    The rheological behavior of blend, e.g. polypropylene,PP, with polyamide - 6, PA6, has been investigated.Results show that this blend is a pseudo plastic fluid and the amount of PA6 seems to be a dominator to influence all rheological properties. In addition to the expected influence by temperature generally for polymer, it has been found the amount of PA6 is valid in a range, e.g. 0-20% corresponding to the PP amount, i.e. in this range, the larger the PA6 added, the larger is the nonNewtonian index, n, and this is obviously especially for PP/PA6 blend with the high shear stress.

  8. Dispersion and rheological studies of Y–PSZ tape casting slurry

    Indian Academy of Sciences (India)

    K G Vasantha Kumari; K Sasidharan; M Sapna; Raghu Natarajan

    2005-04-01

    Different solvent systems in combination with three different dispersants were tried to find out the suitable solvent–dispersant combination, which give optimum dispersion of PSZ. Based on sedimentation, viscosity and rheology characteristics, zeotropic ethanol : xylene with a ratio of 50 : 50 along with 0.5 wt% phosphate ester was found to be the best solvent and dispersant combination. Optimized tape casting slurry was prepared using PEG 600 and BBP as plasticizers and PVB as the binder. Cyclohexanone was used as the homogenizer. The optimized slurry composition with 58% solid loading exhibited shear-thinning pseudoplastic rheological behaviour. Y–PSZ tapes of ∼ 50 m thickness free from visible defects were cast with a green tape density of 55%.

  9. STUDYING THE EFFECT OF SWEETENERS ON RHEOLOGICAL PROPERTIES OF CHOCOLATE MASS

    OpenAIRE

    Chernykh I. A.; Krasin P. S.; Kalmanovich S. A.; Krasina I. B.

    2016-01-01

    Chocolate products with reduced calories are becoming increasingly popular among consumers and producers. One method of producing chocolate with low calorie content is some replacement with alternative sucrose sugar substitutes. We have investigated the effect of various bulk sweeteners (maltitol, isomalt and erythritol) with different particle size, divided into three intervals (106-53, 53-38, and 38-20 microns) on the rheological properties of molten chocolate. It was found, that the model ...

  10. Rheological Studies Dedicated to the Development of a Novel Injectable Polymeric Blend for Viscosupplementation Treatment

    OpenAIRE

    2016-01-01

    Viscosupplementation is an intra-articular symptomatic treatment of mild osteoarthritis. The treatment involves the injection of high-molecular-weight hyaluronan (HA), and especially of cross-linked HA to restore the lubricating and cushioning properties of the synovial fluid. This work involves the development of a novel viscosupplementation fluid based on amidated carboxymethylcellulose and obtained by blending the soluble polymer with its crosslinked derivative. Rheological analyses car...

  11. Rheology measurements of a biomass slurry: an inter-laboratory study

    Energy Technology Data Exchange (ETDEWEB)

    Stickel, Jonathan J. [National Renewable Energy Laboratory, National Bioenergy Center, Golden, CO (United States); Knutsen, Jeffrey S.; Liberatore, Matthew W. [Colorado School of Mines, Department of Chemical Engineering, Golden, CO (United States); Luu, Wing; Bousfield, Douglas W. [University of Maine, Department of Chemical and Biological Engineering, Orono, ME (United States); Klingenberg, Daniel J.; Root, Thatcher W.; Ehrhardt, Max R.; Monz, Thomas O. [University of Wisconsin, Department of Chemical and Biological Engineering and Rheology Research Center, Madison, WI (United States); Scott, C. Tim [U.S. Forest Service Forest Products Laboratory, Madison, WI (United States)

    2009-12-15

    The conversion of biomass, specifically lignocellulosic biomass, into fuels and chemicals has recently gained national attention as an alternative to the use of fossil fuels. Increasing the concentration of the biomass solids during biochemical conversion has a large potential to reduce production costs. These concentrated biomass slurries have highly viscous, non-Newtonian behavior that poses several technical challenges to the conversion process. A collaborative effort to measure the rheology of a biomass slurry at four separate laboratories has been undertaken. A comprehensive set of rheological properties were measured using several different rheometers, flow geometries, and experimental methods. The tendency for settling, water evaporation, and wall slip required special care when performing the experiments. The rheological properties were measured at different concentrations up to 30% insoluble solids by mass. The slurry was found to be strongly shear-thinning, to be viscoelastic, and to have a significant concentration-dependent yield stress. The elastic modulus was found to be almost an order of magnitude larger than the loss modulus and weakly dependent on frequency. The techniques and results of this work will be useful to characterize other biomass slurries and in the design of biochemical conversion processing steps that operate at high solids concentrations. (orig.)

  12. Rheology measurements of a biomass slurry: an inter-laboratory study

    Energy Technology Data Exchange (ETDEWEB)

    Stickel, Jonathan J.; Knutsen, Jeffrey S.; Liberatore, Matthew W.; Luu, Wing; Bousfield, Douglas W.; Klingenberg, Daniel J.; Scott, C. Tim; Root, Thatcher W.; Ehrhardt, Max R.; Monz, Thomas O.

    2009-09-02

    The conversion of biomass, specifically lignocellulosic biomass, into fuels and chemicals has recently gained national attention as an alternative to the use of fossil fuels. Increasing the concentration of the biomass solids during biochemical conversion has a large potential to reduce production costs. These concentrated biomass slurries have highly viscous, non-Newtonian behavior that poses several technical challenges to the conversion process. A collaborative effort to measure the rheology of a biomass slurry at four separate laboratories has been undertaken. A comprehensive set of rheological properties were measured using several different rheometers, flow geometries, and experimental methods. The tendency for settling, water evaporation, and wall slip required special care when performing the experiments. The rheological properties were measured at different concentrations up to 30% insoluble solids by mass. The slurry was found to be strongly shear-thinning, to be viscoelastic, and to have a significant concentration-dependent yield stress. The elastic modulus was found to be almost an order of magnitude larger than the loss modulus and weakly dependent on frequency. The techniques and results of this work will be useful to characterize other biomass slurries and in the design of biochemical conversion processing steps that operate at high solids concentrations.

  13. Rheological characterization of dental waxes

    OpenAIRE

    Zhang, Kehao

    2004-01-01

    Objectives The purpose of this study was to evaluate the rheological behaviour of new experimental dental waxes in dependent on temperature. Material and method Seven experimental dental waxes, provided by Dentaurum GmbH, were tested. No.018 was chosen as a control. Rheological experiments were performed at different temperatures using a Paar Physica Rheometer UDS200 equiped with a parallel plate cell. The temperature was regulated with a Peltier system (TEK130P) and a thermostat un...

  14. Rheology of semiflexible bundle networks with transient linkers.

    Science.gov (United States)

    Müller, Kei W; Bruinsma, Robijn F; Lieleg, Oliver; Bausch, Andreas R; Wall, Wolfgang A; Levine, Alex J

    2014-06-13

    We present a theoretical and computational analysis of the rheology of networks made up of bundles of semiflexible filaments bound by transient cross-linkers. Such systems are ubiquitous in the cytoskeleton and can be formed in vitro using filamentous actin and various cross-linkers. We find that their high-frequency rheology is characterized by a scaling behavior that is quite distinct from that of networks of the well-studied single semiflexible filaments. This regime can be understood theoretically in terms of a length-scale-dependent bending modulus for bundles. Next, we observe new dissipative dynamics associated with the shear-induced disruption of the network at intermediate frequencies. Finally, at low frequencies, we encounter a region of non-Newtonian rheology characterized by power-law scaling. This regime is dominated by bundle dissolution and large-scale rearrangements of the network driven by equilibrium thermal fluctuations.

  15. Investigations of Physical and Rheological Properties of Aged Rubberised Bitumen

    Directory of Open Access Journals (Sweden)

    Asim Hassan Ali

    2013-01-01

    Full Text Available Several road pavement distresses are related to rheological bitumen properties. Rutting and fatigue cracking are the major distresses that lead to permanent failures in pavement construction. Influence of crumb rubber modifier (CRM on rheological properties of bitumen binder such as improvement of high and intermediate temperatures is investigated in the binder’s fatigue and rutting resistance through physical-rheological changes in this research. The bitumen binders were aged by rolling thin film oven (RTFOT to simulate short-term aging and pressure aging vessel (PAV to simulate long-term aging. The effects of aging on the rheological and physical properties of bitumen binders were studied conducting dynamic shear rheometer test (DSR, Brookfield viscometer test, softening point test, and penetration test. The results showed that the use of rubberised bitumen binder reduces the aging effect on physical and rheological properties of the bitumen binder as illustrated through lower aging index of viscosity, lower aging index of , and an increase in with crumb rubber modifier content increasing, indicating that the crumb rubber might improve the aging resistance of rubberised bitumen binder. In addition, the results showed that the softening point increment ( and penetration aging ratio (PAR of the rubberised bitumen binder decreased significantly due to crumb rubber modification. Furthermore, the higher crumb rubber content, the lower after PAV aging, which led to higher resistance to fatigue cracking bitumen.

  16. Study the nature of changes in the dynamic viscosity of milk and fruit products

    Directory of Open Access Journals (Sweden)

    A. N. Ostrikov

    2013-01-01

    Full Text Available The variation of the dynamic viscosity of dairy products and fruit puree with the free run-off on the vertical wall of the vacuum chamber with a two-stage vacuum evaporation was studied. The effect of evaporation temperature and product moisture on the rheological properties of milk and fruit blends was investigated.

  17. Cluster Morphology-Polymer Dynamics Correlations in Sulfonated Polystyrene Melts: Computational Study

    Science.gov (United States)

    Agrawal, Anupriya; Perahia, Dvora; Grest, Gary S.

    2016-04-01

    Reaching exceptionally long times up to 500 ns in equilibrium and nonequilibrium molecular dynamics simulations studies, we have attained a fundamental molecular understanding of the correlation of ionomer clusters structure and multiscale dynamics, providing new insight into one critical, long-standing challenge in ionic polymer physics. The cluster structure in melts of sulfonated polystyrene with Na+ and Mg2 + counterions are resolved and correlated with the dynamics on multiple length and time scales extracted from measurements of the dynamic structure factor and shear rheology. We find that as the morphology of the ionic clusters changes from ladderlike for Na+ to disordered structures for Mg2 + , the dynamic structure factor is affected on the length scale corresponding to the ionic clusters. Rheology studies show that the viscosity for Mg2 + melts is higher than for Na+ ones for all shear rates, which is well correlated with the larger ionic clusters' size for the Mg2 + melts.

  18. The effects of excipients on protein aggregation during agitation: an interfacial shear rheology study.

    Science.gov (United States)

    Liu, Lu; Qi, Wei; Schwartz, Daniel K; Randolph, Theodore W; Carpenter, John F

    2013-08-01

    We investigated the effects of excipients in solutions of keratinocyte growth factor 2 (KGF-2) on protein aggregation during agitation as well as on interfacial shear rheology at the air-water interface. Samples were incubated with or without agitation, and in the presence or absence of the excipients heparin, sucrose, or polysorbate 80 (PS80). The effect of excipients on the extent of protein aggregation was determined by UV-visible spectroscopy and micro-flow imaging. Interfacial shear rheology was used to detect the gelation time and strength of protein gels at the air-water interface. During incubation, protein particles of size ≥1 μm and insoluble aggregates formed faster for KGF-2 solutions subjected to agitation. Addition of either heparin or sucrose promoted protein aggregation during agitation. In contrast, PS80 substantially inhibited agitation-induced KGF-2 aggregation but facilitated protein particulate formation in quiescent solutions. The combination of PS80 and heparin or sucrose completely prevented protein aggregation during both nonagitated and agitated incubations. Interfacial rheological measurements showed that KGF-2 in buffer alone formed an interfacial gel within a few minutes. In the presence of heparin, KGF-2 interfacial gels formed too quickly for gelation time to be determined. KGF-2 formed gels in about 10 min in the presence of sucrose. The presence of PS80 in the formulation inhibited gelation of KGF-2. Furthermore, the interfacial gels formed by the protein in the absence of PS80 were reversible when PS80 was added to the samples after gelation. Therefore, there is a correspondence between formulations that exhibited interfacial gelation and formulations that exhibited agitation-induced aggregation. Copyright © 2013 Wiley Periodicals, Inc.

  19. Study of rheological properties in modified random propylene-ethylene copolymer

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Sivelton G.; Otaguro, Harumi; Lima, Luis F.C.P.; Lugao, Ademar B. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Quimica e Meio Ambiente], E-mail: sgsantos@ipen.br; Artel, Beatriz W.H. [Empresa Brasileira de Radiacao Ltda (EMBRARAD), Cotia, SP (Brazil)

    2007-07-01

    The random copolymer of propylene and ethylene (RP) presents exceptional transparency and brightness; possess low transference of odor and flavor showing better relation of rigidity/impact than homopolymer of polypropylene (PP). Due to the existence of units of ethylene this copolymer has distinct characteristics than PP of the same melt flow rate, improving its processability and allowing the use in processes such as: injection and blow molding and thermoforming of the plates. In the case of the thermoforming, the melt conventional polypropylene has the tendency to collapse during the process. It is well known, that the incorporation of a second monomer diminishes drastically the melting point of the sample up to 5 deg C changing its rheological characteristic and processing conditions. Therefore, the aim of the present work is to modify the random copolymer of propylene-ethylene with melt flow of 10 g/10 min and check its properties. In this process gamma irradiation technique was used to induce chemical changes in RP in the presence of Tri-allyl-cyanurate (TAC), with concentration ranging from 0 to 5.0 mmol/100 g of the pure resin. All samples had been characterized adequately with respect to rheological properties as: viscosity at low shear rate, storage and loss modulus, as well as, the evaluation of molecular mass distribution from zero shear viscosity value ({eta}0). The improvements in the rheological properties and processability had been evaluated in term of its performance during the thermoforming vacuum process. The modified samples showed a good performance during the thermoforming process. This behavior was observed exactly when the monomer concentration increase, except in the case of 5.0 mmol, where the sample tores during thermoforming, probably due to the high degree of ramification and branching in polymer chain. (author)

  20. Experimental Studies on High-Frequency Performance of the Inverse Control Magneto-Rheological Damper

    Institute of Scientific and Technical Information of China (English)

    DU Xiuli; LIAO Weizhang; NIU Dongxu

    2006-01-01

    Severe vibration of underground structures may be induced under blast loads.According to the characteristics of the explosion-induced ground shock wave,a new-type damper,inverse control magneto-rheological(MR) damper was designed to control the vibration.The high-frequency performance test of the MR damper was carried out on the small shaking table.It is shown that the performance can be modeled by use of the modified Bouc-Wen model,and the pa rameters of the model keep stable in the range of 15-50 Hz.

  1. Experimental study of oil-water interface layers dilatation rheological properties

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Oil-water interface layers dilatation rheological properties have been measured with the liquid-liquid interface film pressure measurement apparatus, which was based on the principles of Langmuir film balance. Experimental results show that it is possible to form the interface-associ- ated material caused by the attraction of the dispersion forces at the pure alkane-water interface. The type of material is sensitive to the interfacial pressure. Under the influence of the interfacial pressure, the stability of the interface associated materials decreases with the increase of the number of alkane carbons.

  2. Role of Yield Stress in Magma Rheology

    Science.gov (United States)

    Kurokawa, A.; Di Giuseppe, E.; Davaille, A.; Kurita, K.

    2012-04-01

    Magmas are essentially multiphase material composed of solid crystals, gaseous bubbles and silicate liquids. They exhibit various types of drastic change in rheology with variation of mutual volumetric fractions of the components. The nature of this variable rheology is a key factor in controlling dynamics of flowing magma through a conduit. Particularly the existence of yield stress in flowing magma is expected to control the wall friction and formation of density waves. As the volumetric fraction of solid phase increases yield stress emerges above the critical fraction. Several previous studies have been conducted to clarify this critical value of magmatic fluid both in numerical simulations and laboratory experiments ([Lejeune and Pascal, 1995], [Saar and Manga 2001], [Ishibashi and Sato 2010]). The obtained values range from 13.3 to 40 vol%, which display wide variation and associated change in rheology has not been clarified well. In this presentation we report physical mechanism of emergence of yield stress in suspension as well as the associated change in the rheology based on laboratory experiments using analog material. We utilized thermogel aqueous suspension as an analog material of multiphase magma. Thermogel, which is a commercial name for poly(N-isopropyl acrylamide) (PNIPAM) undergoes volumetric phase change at the temperature around 35C:below this temperature the gel phase absorbs water and swells while below this it expels water and its volume shrinks. Because of this the volumetric fraction of gel phase systematically changes with temperature and the concentration of gel powder. The viscosity measured at lower stress drastically decreases across this phase change with increasing temperature while the viscosity at higher stress does not exhibit large change across the transition. We have performed a series of rheological measurements focusing on the emergence of yield stress on this aqueous suspension. Since the definition of yield stress is not

  3. Nanoemulsion-based gel formulation of diclofenac diethylamine: design, optimization, rheological behavior and in vitro diffusion studies.

    Science.gov (United States)

    Hamed, Rania; Basil, Marwa; AlBaraghthi, Tamadur; Sunoqrot, Suhair; Tarawneh, Ola

    2016-12-01

    Chronic oral administration of the non-steroidal anti-inflammatory drug, diclofenac diethylamine (DDEA), is often associated with gastrointestinal ulcers and bleeding. As an alternative to oral administration, a nanoemulsion-based gel (NE gel) formulation of DDEA was developed for topical administration. An optimized formulation for the o/w nanoemulsion of oil, surfactant and cosurfactant was selected based on nanoemulsion mean droplet size, clarity, stability, and flowability, and incorporated into the gelling agent Carbopol® 971P. Rheological studies of the DDEA NE gel were conducted and compared to those of conventional DDEA gel and emulgel. The three gels exhibited an elastic behavior, where G' dominated G″ at all frequencies, indicating the formation of strong gels. NE gel exhibited higher G' values than conventional gel and emulgel, which indicated the formation of a stronger gel network. Strat-M® membrane, a synthetic membrane with diffusion characteristics that are well correlated to human skin, was used for the in vitro diffusion studies. The release of DDEA from conventional gel, emulgel and NE gel showed a controlled release pattern over 12 h, which was consistent with the rheological properties of the gels. DDEA release kinetics from the three gels followed super case II transport as fitted by Korsmeyer-Peppas model.

  4. AN EXPERIMENTAL STUDY ON THE RHEOLOGICAL PROPERTIES OF CONDITIONED MUNICIPAL ACTIVATED SLUDGE

    Directory of Open Access Journals (Sweden)

    SALAM K. AL-DAWERY

    2017-01-01

    Full Text Available This research work was focused on the rheological characteristics of conditioned fresh activated sludge using TA rheometer HR-2. The effect of cationic polyelectrolyte conditioner has been investigated for floc size, surface properties and yield stress at different pH values in a comparative fashion. Our approach was to reveal the effect of polymer on the municipal activated sludge with high organic contents up to 80%. The results indicated an improvement of 50% in settling properties by addition polyelectrolyte up to 4 mg/g solid/l. Rheological data analysis showed that responses of shear stress - shear rate were found to be closest to Bingham model and gave almost similar and smaller k values of average 6.2×10-3. The results of shear creep indicated that all sludge samples have less rigid structures with no reconstruction behavior. The optical analyses of the samples indicated that the floc sizes were increased with successive addition of polyelectrolyte. The increase of floc sizes caused large stresses especially for solution with pH=9. As the flocculation accorded despite the negative zeta potential, this phenomenon can be referred to that interparticles hydrogen bridging was governing flocculation rather than charge neutralization. Also, during the experiment, bacterial growth showed an adaption despite the conditioning with polyelectrolyte.

  5. Characterization and rheological study of the galactomannan extracted from seeds of Cassia grandis.

    Science.gov (United States)

    Albuquerque, Priscilla B S; Barros, Wilson; Santos, Gustavo R C; Correia, Maria T S; Mourão, Paulo A S; Teixeira, José A; Carneiro-da-Cunha, Maria G

    2014-04-15

    Galactomannan extracted from seeds of Cassia grandis with 0.1M NaCl, followed by ethanol precipitation, presented a yield of 36 ± 8%. The polysaccharide has a constant mannose/galactose ratio (2.44:1). Methylation analysis, one and two dimensional NMR spectroscopy confirmed that the polysaccharide has a central core composed of 4-linked β-mannose units, with branches of galactose, linked to the carbohydrate core through α(1-6) linkage. The amorphous nature of the galactomannan was confirmed by X-ray diffraction. Rheological characterization exhibited Newtonian plateaus followed by shear-thinning zones characteristic of polymer solutions up to 1.5% (w/v) and above this value the system exhibited yield stress associated with a weak gel. Adjusting stress-strain curves confirmed a 1.6% (w/v) as the galactomannan concentration value for the sol-gel transition. These results indicate that the galactomannan extracted from C. grandis seeds presents rheological characteristics suitable for applications in pharmaceutical, biomedical, cosmetic and food industries.

  6. Studies on cure kinetics and rheological properties of difunctional epoxy/polysulfone blend system

    Energy Technology Data Exchange (ETDEWEB)

    Park, S.J.; Kim, H.C.; Lee, J.R. [Korean Research Institue of Chemical Technology, Taejeon (Korea)

    2001-03-01

    In this work, the cure kinetics and rheological properties of difunctional epoxy (diglycidylether of bisphenol A, DGEBA)/polysulfone (PSF) blends were investigated using differential scanning calorimeter and rheometer. From the DSC results of the blends, the temperature of the exothermic peak and cure activation energy (E{sub a}) using a half-width method were increased with increasing the PSF content to neat epoxy resin up to 30 wt%. However, a marginal decrease in the blend system was shown in E{sub a}. The conversion ({alpha}) and conversion rate (da/dt) were decreased as the content of PSF increases. Rheological properties of the blend system were investigated under isothermal condition using a rheometer. Cross-linking activation energy (E{sub c}) was determined from the Arrhenius equation based on gel time and curing temperature. As a result, the E-c showed a similar behavior with E{sub a}, which could be resulted from high viscosity of PSF and the phase separation between DGEBA and PSF. (author). 26 refs., 10 figs.

  7. Studies on the rheological and gelatinization characteristics of waxy wheat flour.

    Science.gov (United States)

    Zhang, Huanxin; Zhang, Wei; Xu, Chunzhong; Zhou, Xing

    2014-03-01

    The chemical composition, rheological and gelatinization characteristics of waxy wheat flour were investigated. Compared with wheat flour, waxy wheat flour has lower protein (9.52%), amylase (1.02%) and higher crude starch (73.19%) contents. Because of its different chemical composition, waxy wheat flour exhibited some better processing characteristics (water-holding capacity, dough development time, extensibility, swelling power and setback) than normal wheat flour. It also exhibited some defects in rheological characteristics, including a higher degree of softening, a lower Farinograph quality number and smaller resistance to extensibility ratio. Differential scanning calorimetry results showed that waxy wheat flour gelatinized at higher onset (To=60.9 °C), peak (Tp=64.9 °C), conclusion (Tc=73.6 °C) temperatures and required more energy (ΔH=7.6J/g) to melt gelatinized starch gels. The results of this investigation indicated that blending waxy wheat flour with normal flour is a promising way to improve product quality in baked foods and to prolong the shelf-life of these products. Copyright © 2013 Elsevier B.V. All rights reserved.

  8. Study on Rheological Behavior of Begonia Juices%海棠汁的流变特性研究

    Institute of Scientific and Technical Information of China (English)

    丁仕强

    2012-01-01

    LVDV-Ⅲ+ type rheometer was used to study the rheological characteristics of crabapple juice at different temperatures and Gabriel sugar content Results showed that the apparent viscosity and shear stress of crabapple juice increased with the increase of shear rate. Along with the increase of the shear rate, a slightly upward trends in apparent viscosity was found. Crabapple juice showed the basic fluid rheological properties of inflation plastic. Fittly the experimental curves with Herschel-Bulkley equation showed that the R2 values was above 0.99.%采用LVDV-Ⅲ+型流变仪对不同温度、百利糖度下的海棠汁的流变特性进行研究,研究发现海棠汁随着剪切速率增大,表现粘度逐渐增大,剪切应力随之增大;同时随着剪切速率的逐渐增大,表观粘度大小的变化趋势较小但表现出较微的上升趋势.海棠汁流变特性符合胀塑性流体的基本特征,通过Herschel-Bulkley方程拟合,相关系数R2都在0.99以上,并就方程中参数的变化进行了解释说明.

  9. Rheology of the Active Cell Cortex in Mitosis.

    Science.gov (United States)

    Fischer-Friedrich, Elisabeth; Toyoda, Yusuke; Cattin, Cedric J; Müller, Daniel J; Hyman, Anthony A; Jülicher, Frank

    2016-08-09

    The cell cortex is a key structure for the regulation of cell shape and tissue organization. To reach a better understanding of the mechanics and dynamics of the cortex, we study here HeLa cells in mitosis as a simple model system. In our assay, single rounded cells are dynamically compressed between two parallel plates. Our measurements indicate that the cortical layer is the dominant mechanical element in mitosis as opposed to the cytoplasmic interior. To characterize the time-dependent rheological response, we extract a complex elastic modulus that characterizes the resistance of the cortex against area dilation. In this way, we present a rheological characterization of the cortical actomyosin network in the linear regime. Furthermore, we investigate the influence of actin cross linkers and the impact of active prestress on rheological behavior. Notably, we find that cell mechanics values in mitosis are captured by a simple rheological model characterized by a single timescale on the order of 10 s, which marks the onset of fluidity in the system. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  10. Shape Effect of Crushed Sand Filler on Rheology: A Preliminary Experimental and Numerical Study

    DEFF Research Database (Denmark)

    Spangenberg, Jon; Cepuritis, Rolands; Hovad, Emil

    2016-01-01

    was quantified with the slump flow test (i.e. mini cone). The shape effect was isolated in the experiments by the use of non overlapping bimodal particle distributions of cement particles with a number average diameter of approximate to 0.01 mm and filler particles with a number average diameter of approximate...... classification, and had length/thickness (L/T) aspect ratios of 2.00 and 1.82, respectively. The particles were characterized with X-ray micro-computed tomography, coupled with spherical harmonic analysis to mathematically describe the full 3-D shape of the particles, while the rheological performance...... to 0.1 mm. The two filler types were tested with a range of chi-values (volume of cement divided by total volume of solids). The flowability of the matrix increased with decreasing aspect ratios of the filler. However, the chi-value at which the maximum volume fraction threshold was obtained varied...

  11. Surface rheology and interface stability.

    Energy Technology Data Exchange (ETDEWEB)

    Yaklin, Melissa A.; Cote, Raymond O.; Moffat, Harry K.; Grillet, Anne Mary; Walker, Lynn; Koehler, Timothy P.; Reichert, Matthew D. (Carnegie Mellon University, Pittsburgh, PA); Castaneda, Jaime N.; Mondy, Lisa Ann; Brooks, Carlton, F.

    2010-11-01

    We have developed a mature laboratory at Sandia to measure interfacial rheology, using a combination of home-built, commercially available, and customized commercial tools. An Interfacial Shear Rheometer (KSV ISR-400) was modified and the software improved to increase sensitivity and reliability. Another shear rheometer, a TA Instruments AR-G2, was equipped with a du Nouey ring, bicone geometry, and a double wall ring. These interfacial attachments were compared to each other and to the ISR. The best results with the AR-G2 were obtained with the du Nouey ring. A Micro-Interfacial Rheometer (MIR) was developed in house to obtain the much higher sensitivity given by a smaller probe. However, it was found to be difficult to apply this technique for highly elastic surfaces. Interfaces also exhibit dilatational rheology when the interface changes area, such as occurs when bubbles grow or shrink. To measure this rheological response we developed a Surface Dilatational Rheometer (SDR), in which changes in surface tension with surface area are measured during the oscillation of the volume of a pendant drop or bubble. All instruments were tested with various surfactant solutions to determine the limitations of each. In addition, foaming capability and foam stability were tested and compared with the rheology data. It was found that there was no clear correlation of surface rheology with foaming/defoaming with different types of surfactants, but, within a family of surfactants, rheology could predict the foam stability. Diffusion of surfactants to the interface and the behavior of polyelectrolytes were two subjects studied with the new equipment. Finally, surface rheological terms were added to a finite element Navier-Stokes solver and preliminary testing of the code completed. Recommendations for improved implementation were given. When completed we plan to use the computations to better interpret the experimental data and account for the effects of the underlying bulk

  12. Experimental studies on elastic and rheological properties of amphibolites at high pressure and high temperature

    Institute of Scientific and Technical Information of China (English)

    HUANG; Xiaoge(黄晓葛); BAI; Wuming(白武明); HU; Jianmin(胡健民)

    2003-01-01

    Laboratory measurements of compressional-wave velocities and rheological properties are carried out on natural amphibolites collected from Chencai, Zhejiang Province at high pressures and high temperatures. The experiments of elastic wave velocity find that the compressional-wave velocities travel faster along the lineation(X-direction) within the foliation plane than those normal to the foliation (Z-direction). The velocity anisotropies are high for the amphibolites at 550℃ and pressure of 800 MPa or 600 MPa. Furthermore, the values of anisotropy and average velocity are respectively 7.83% and 6.77km/s for the samples with fine grain size, 9.77% and 6.64km/s for the samples with medium grain size. With increasing temperature at high static pressure, the wave velocities spreading along three structure directions in the samples all start to drop from 750℃ up. The rheological experiments also find that there is a marked strength reduction from 750℃ to 800℃ although the flow strength gradually decreases with increasing temperature for the fine-grained amphibolite at a confining pressure of 500 MPa and strain rate of 1×10-4s-1. Based on the results of microcopy observations, electronic probe analyses and infrared spectra analyses for some samples, the reduction of flow strength and wave velocity may be due to partial melting of amphibole above 750℃. In addition, the rock deformations undergo from localized brittle fracture, semi-brittle deformation (cataclastic flow or semi-brittle faulting, semi-brittle flow) to homogeneous crystal-plastic flow from 600℃ to 1000℃, confining pressure of 500 MPa and strain rate of 1×10-4s-1.

  13. Rheological Behavior of the Matrixes of Bauxite-Based Castables

    Institute of Scientific and Technical Information of China (English)

    Ye Fangbao; Rigaud M.; LIU Xinhong; ZHONG Xiangchong

    2003-01-01

    Rheology of castables is greatly affected and controlled by rheological behavior of their matrix. In this work, the rheological properties of bauxite-based castable matrix have been studied. The effects of super-fine silica and alumina addition, water/cement ratio, dispersants and bauxite particle-size on viscosity, shear rate and shear stress of the slurries have been investigated. Based on these results, the range of optimum composition of the matrix with good rheological behavior has been obtained.

  14. Rheological Characterization of Unusual DWPF Slurry Samples (U)

    Energy Technology Data Exchange (ETDEWEB)

    Koopman, D. C.

    2005-09-01

    A study was undertaken to identify and clarify examples of unusual rheological behavior in Defense Waste Processing Facility (DWPF) simulant slurry samples. Identification was accomplished by reviewing sludge, Sludge Receipt and Adjustment Tank (SRAT) product, and Slurry Mix Evaporator (SME) product simulant rheological results from the prior year. Clarification of unusual rheological behavior was achieved by developing and implementing new measurement techniques. Development of these new methods is covered in a separate report, WSRC-TR-2004-00334. This report includes a review of recent literature on unusual rheological behavior, followed by a summary of the rheological measurement results obtained on a set of unusual simulant samples. Shifts in rheological behavior of slurries as the wt. % total solids changed have been observed in numerous systems. The main finding of the experimental work was that the various unusual DWPF simulant slurry samples exhibit some degree of time dependent behavior. When a given shear rate is applied to a sample, the apparent viscosity of the slurry changes with time rather than remaining constant. These unusual simulant samples are more rheologically complex than Newtonian liquids or more simple slurries, neither of which shows significant time dependence. The study concludes that the unusual rheological behavior that has been observed is being caused by time dependent rheological properties in the slurries being measured. Most of the changes are due to the effect of time under shear, but SB3 SME products were also changing properties while stored in sample bottles. The most likely source of this shear-related time dependence for sludge is in the simulant preparation. More than a single source of time dependence was inferred for the simulant SME product slurries based on the range of phenomena observed. Rheological property changes were observed on the time-scale of a single measurement (minutes) as well as on a time scale of hours

  15. THE RHEOLOGICAL PROPERTIES AND OUTBURST MECHANISM OF GASEOUS COAL

    Institute of Scientific and Technical Information of China (English)

    何学秋; 周世宁; 林柏泉

    1991-01-01

    Coal and methane outburst is one of the harmful disasters in coal mines. We have studied the rheological properties of gaseous coal in laboratory and obtained its rheological fracture principle. This principle can better explain and describe the outburst mechanism of gaseous coal. Thereby a rheological hypothesis of coal and methane outburst is put forward in this paper.

  16. Rheological behavior study of a clay-polymer mixture: effects of the polymer addition; Etude du comportement rheologique de melanges argiles - polymeres. Effets de l'ajout de polymeres

    Energy Technology Data Exchange (ETDEWEB)

    Benchabane, A

    2006-11-15

    The aim of the present work is to establish a bibliographical synthesis on the microstructure, the colloidal and rheological characterization of bentonite suspensions with and without polymer/surfactant addition; to lead to a rheological characterization of clay-additive mixtures and to understand the interaction between the clay particles and polymer/surfactants. Different experimental measurements: rheology, particle sizing, and x-ray diffraction were used to study the rheological character of the water-bentonite-anionic additive mixtures (CMC, SDS, xanthane) as well as the nature of the particle-particle interactions and particle-additive. The modeling part led to the adoption of Tiu and Boger's model to predict the thixotropy of the bentonite suspensions without additive. Thus, a new model is proposed with physical parameters for a better correlation of the rheological behavior of the various studied mixtures. (author)

  17. Rheology of Model Dough Formulation

    Science.gov (United States)

    Desai, Kiran; Lele, Smita; Lele, Ashish

    2008-07-01

    Dough is generally considered a viscoelastic material, and its elasticity is attributed to the hydrated gluten matrix. Since starch is a major constituent of flour (˜70 wt% on dry basis) we may expect it to contribute to dough rheology in a non-trivial manner. Considering dough to belong to the generic class of soft solid materials, we use the Strain-Rate Frequency Superposition (SRFS) technique to study rheology of various model dough compositions in which the starch/gluten ratio is systematically varied from 100/0 to 0/100. We find that for compositions containing 0-25% gluten the SRFS superposition principle works well, while for compositions containing greater than 25% gluten the quality of SRFS mastercurves deteriorates gradually. Thus we propose that starch particles contribute substantially to the rheology of dough containing up to 25% gluten.

  18. Rheology and flocculation of polymer-modified microfibrillated cellulose suspensions

    OpenAIRE

    Karppinen, Anni

    2014-01-01

    In this thesis, the rheology and flocculation of microfibrillated cellulose (MFC) suspensionswas modified using different cationic and anionic polymers and surface modification. For this purpose, MFC suspensions were studied simultaneously with a dynamic rotational rheometer and two imaging methods. The flocculation tendency of the suspensions was mainly evaluated using photographing through a transparent rheometer cup, and for some suspensions, optical coherence tomography (OCT), which gives...

  19. Rheology of complex fluid-fluid interfaces: a unified approach based on nonequilibrium thermodynamics

    NARCIS (Netherlands)

    Sagis, L.M.C.

    2010-01-01

    Surface rheological properties affect the dynamics of vesicles, nanoparticles, emulsion droplets, foam bubbles, polymer microcapsules, liquid jets, living cells, lung avioli, thin liquid films, and many other multiphase systems. Surface rheology is therefore relevant for a wide range of disciplines

  20. Rheology of complex fluid-fluid interfaces: a unified approach based on nonequilibrium thermodynamics

    NARCIS (Netherlands)

    Sagis, L.M.C.

    2010-01-01

    Surface rheological properties affect the dynamics of vesicles, nanoparticles, emulsion droplets, foam bubbles, polymer microcapsules, liquid jets, living cells, lung avioli, thin liquid films, and many other multiphase systems. Surface rheology is therefore relevant for a wide range of disciplines

  1. Rheological properties of asphalt mixtures containing various fibers

    Institute of Scientific and Technical Information of China (English)

    叶群山; 吴少鹏; 陈筝; 刘至飞

    2008-01-01

    Rheological characteristics of fiber-modified asphalt mixture were investigated.Cellulous fiber,polyester fiber and mineral fiber were used as additives for asphalt mixture,and the dosages were 0.3%,0.3%,0.4%,respectively.Dynamic modulus test using superpave simple performance tester(SPT) was adopted to study the dynamic modulus and phase angle for the control mixture and fiber-modified ones at various temperatures and frequencies.Test results show that the rheological properties can be improved significantly by the addition of various fibers.The dynamic modulus increases with the increase of frequency,and the phase angle decreases with the increase of frequency.When various fibers are used,the dynamic modulus increases and phase angle decreases at each frequency.This indicates that the stiffness and the elastic portion of fiber-modified asphalt mixtures can be enhanced when various fibers are used,which results in the change of viscoelastic properties of mixtures.The creep test results show that the total strain and the permanent strain of asphalt mixtures during load-unload cycle can be significantly reduced,which results in the improvement of resistance to permanent deformation for asphalt mixtures containing various fiber additives.The Burgers model can be employed effectively to illustrate the rheological properties of fiber modified asphalt mixtures.

  2. A disc-type magneto-rheologic fluid damper

    Institute of Scientific and Technical Information of China (English)

    祝长生

    2003-01-01

    A disc-type magneto-rheological fluid damper operating in shear mode is proposed in this paper,which is based on the special characteristics of the magneto-rheological (MR) fluid with rapid, reversible and dramatic change in its rheological properties by the application of an external magnetic field. The magneticfield of the disc-type MR fluid damper is analysed by the finite element method ; the controllability of the disctype MR fluid damper on the dynamic behaviour of a rotor system ; and the effectiveness of the disc-type MR fluid damper in controlling the vibration of a rotor system, are studied in a flexible rotor system with an over-hung disc. It is shown that the magnetic flux density of the disc-type MR fluid damper in the working areas can significantly change with the applied current in the coil ; and that the dynamic behavior of the disc-type MR fluid damper can be varied by the application of an external magnetic field produced by a low voltage electromagnetic coil. The disc-type MR fluid damper can significantly change the dynamic characteristics of a rotor system, provided that the location of the disk-type MR fluid damper is carefully chosen. The disc-type MR fluid damper is a new actuator with good dynamic characteristics for rotating machinery.

  3. A disc-type magneto-rheologic fluid damper

    Institute of Scientific and Technical Information of China (English)

    祝长生

    2003-01-01

    A disc-type magneto-rheological fluid damper operating in shear mode is proposed in this paper, which is based on the special characteristics of the magneto-rheological (MR) fluid with rapid, reversible and dramatic change in its rheological properties by the application of an external magnetic field. The magnetic field of the disc-type MR fluid damper is analysed by the finite element method; the controllability of the disc-type MR fluid damper on the dynamic behaviour of a rotor system; and the effectiveness of the disc-type MR fluid damper in controlling the vibration of a rotor system, are studied in a flexible rotor system with an over-hung disc. It is shown that the magnetic flux density of the disc-type MR fluid damper in the working areas can significantly change with the applied current in the coil; and that the dynamic behavior of the disc-type MR fluid damper can be varied by the application of an external magnetic field produced by a low voltage electromagnetic coil. The disc-type MR fluid damper can significantly change the dynamic characteristics of a rotor system, provided that the location of the disk-type MR fluid damper is carefully chosen. The disc-type MR fluid damper is a new actuator with good dynamic characteristics for rotating machinery.

  4. Rheology of Rice Flour Dough with Gum Arabic: Small and Large-Deformation Studies, Sensory Assessment and Modeling.

    Science.gov (United States)

    Shanthilal, J; Bhattacharya, Suvendu

    2015-08-01

    The absence of gluten protein makes the rice flour doughs difficult to handle when flattened/sheeted products are to be prepared. The rheological, sensory and microstructural changes in rice flour doughs having gum Arabic (0% to 5%, w/w) and moisture contents (44% to 50%) were studied for improving the dough handling characteristics. Rheological parameters like storage modulus (G') and complex viscosity (η*) decreased with an increase in moisture content while loss angle (δ) increased. A power-law type equation was suitable to relate angular frequency (ω) with G', G", and η* (0.814 ≤ r ≤ 0.999, P ≤ 0.01). An increase in gum and moisture contents increased δ from 6.9° to 15.5° but decreased the energy required for compression/flattening. The 6-element spring-dashpot model was suitable (r ≥ 0.991, P ≤ 0.01) for creep curves. The sensory panel had the opinion that dough with a low to moderate hardness between 3 and 4, and stickiness of ≤ 3.5 was suitable for the purpose of flattening in relation to the preparation of sheeted/flattened products; the appropriate condition for dough formulation was with the moisture and gum contents of 47.0% to 47.9% and 1.55% to 2.25%, respectively to offer the desirability index between 0.50 and 0.52. The microstructure of the rice flour dough in the absence of gum Arabic appeared to possess loosely bound flour particles. The presence of gum provided a coating on flour particles to yield dough having good cohesive microstructure. © 2015 Institute of Food Technologists®

  5. Shear rheology of mixed protein adsorption layers vs their structure studied by surface force measurements.

    Science.gov (United States)

    Danov, Krassimir D; Kralchevsky, Peter A; Radulova, Gergana M; Basheva, Elka S; Stoyanov, Simeon D; Pelan, Eddie G

    2015-08-01

    The hydrophobins are proteins that form the most rigid adsorption layers at liquid interfaces in comparison with all other investigated proteins. The mixing of hydrophobin HFBII with other conventional proteins is expected to reduce the surface shear elasticity and viscosity, E(sh) and η(sh), proportional to the fraction of the conventional protein. However, the experiments show that the effect of mixing can be rather different depending on the nature of the additive. If the additive is a globular protein, like β-lactoglobulin and ovalbumin, the surface rigidity is preserved, and even enhanced. The experiments with separate foam films indicate that this is due to the formation of a bilayer structure at the air/water interface. The more hydrophobic HFBII forms the upper layer adjacent to the air phase, whereas the conventional globular protein forms the lower layer that faces the water phase. Thus, the elastic network formed by the adsorbed hydrophobin remains intact, and even reinforced by the adjacent layer of globular protein. In contrast, the addition of the disordered protein β-casein leads to softening of the HFBII adsorption layer. Similar (an even stronger) effect is produced by the nonionic surfactant Tween 20. This can be explained with the penetration of the hydrophobic tails of β-casein and Tween 20 between the HFBII molecules at the interface, which breaks the integrity of the hydrophobin interfacial elastic network. The analyzed experimental data for the surface shear rheology of various protein adsorption layers comply with a viscoelastic thixotropic model, which allows one to determine E(sh) and η(sh) from the measured storage and loss moduli, G' and G″. The results could contribute for quantitative characterization and deeper understanding of the factors that control the surface rigidity of protein adsorption layers with potential application for the creation of stable foams and emulsions with fine bubbles or droplets. Copyright © 2014

  6. Rheology in Pharmaceutical Sciences

    DEFF Research Database (Denmark)

    Aho, Johanna; Hvidt, Søren; Baldursdottir, Stefania

    2016-01-01

    Rheology is the science of flow and deformation of matter. Particularly gels and non-Newtonian fluids, which exhibit complex flow behavior, are frequently encountered in pharmaceutical engineering and manufacturing, or when dealing with various in vivo fluids. Therefore understanding rheology...... is important, and the ability to use rheological characterization tools is of great importance for any pharmaceutical scientist involved in the field. Flow can be generated by shear or extensional deformations, or a combination of both. This chapter introduces the basics of both shear and extensional rheology...

  7. Dynamic and steady: shear rheological properties of xanthan and guar gums dispersed in yellow passion fruit pulp (Passiflora edulis f. flavicarpa

    Directory of Open Access Journals (Sweden)

    I. C. F Moraes

    2011-09-01

    Full Text Available Yellow passion fruit pulp is unstable, presenting phase separation that can be avoided by the addition of hydrocolloids. For this purpose, xanthan and guar gum [0.3, 0.7 and 1.0% (w/w] were added to yellow passion fruit pulp and the changes in the dynamic and steady - shear rheological behavior evaluated. Xanthan dispersions showed a more pronounced pseudoplasticity and the presence of yield stress, which was not observed in the guar gum dispersions. Cross model fitting to flow curves showed that the xanthan suspensions also had higher zero shear viscosity than the guar suspensions, and, for both gums, an increase in temperature led to lower values for this parameter. The gums showed different behavior as a function of temperature in the range of 5 - 35ºC. The activation energy of the apparent viscosity was dependent on the shear rate and gum concentration for guar, whereas for xanthan these values only varied with the concentration. The mechanical spectra were well described by the generalized Maxwell model and the xanthan dispersions showed a more elastic character than the guar dispersions, with higher values for the relaxation time. Xanthan was characterized as a weak gel, while guar presented a concentrated solution behavior. The simultaneous evaluation of temperature and concentration showed a stronger influence of the polysaccharide concentration on the apparent viscosity and the G' and G" moduli than the variation in temperature.

  8. Simple rheology of mixed proteins

    Science.gov (United States)

    Mixing different proteins to form strong gel networks for food applications may create synergistic increases in viscoelasticity that cannot be achieved with a single protein. In this study, small amplitude oscillatory shear analyses were used to investigate the rheology of calcium caseinate (CC), e...

  9. Rheology of Lignocellulose Suspensions and Impact of Hydrolysis: A Review.

    Science.gov (United States)

    Nguyen, Tien Cuong; Anne-Archard, Dominique; Fillaudeau, Luc

    2015-01-01

    White biotechnologies have several challenges to overcome in order to become a viable industrial process. Achieving highly concentrated lignocellulose materials and releasing fermentable substrates, with controlled kinetics in order to regulate micro-organism activity, present major technical and scientific bottlenecks. The degradation of the main polymeric fractions of lignocellulose into simpler molecules is a prerequisite for an integrated utilisation of this resource in a biorefinery concept. The characterisation methods and the observations developed for rheology, morphology, etc., that are reviewed here are strongly dependent on the fibrous nature of lignocellulose, are thus similar or constitute a good approach to filamentous culture broths. This review focuses on scientific works related to the study of the rheological behaviour of lignocellulose suspensions and their evolution during biocatalysis. In order to produce the targeted molecules (synthon), the lignocellulose substrates are converted by enzymatic degradation and are then metabolised by micro-organisms. The dynamics of the mechanisms is limited by coupled phenomena between flow, heat and mass transfers in regard to diffusion (within solid and liquid phases), convection (mixing, transfer coefficients, homogeneity) and specific inhibitors (concentration gradients). As lignocellulose suspensions consist of long entangled fibres for the matrix of industrial interest, they exhibit diverse and complex properties linked to this fibrous character (rheological, morphological, thermal, mechanical and biochemical parameters). Among the main variables to be studied, the rheological behaviour of such suspensions appears to be determinant for process efficiency. It is this behaviour that will determine the equipment to be used and the strategies applied (substrate and biocatalysis feed, mixing, etc.). This review provides an overview of (i) the rheological behaviour of fibrous materials in suspension, (ii) the

  10. Rheological characteristics of synthetic road binders

    Energy Technology Data Exchange (ETDEWEB)

    Gordon D. Airey; Musarrat H. Mohammed; Caroline Fichter [University of Nottingham, Nottingham (United Kingdom)

    2008-08-15

    This paper deals with the synthesis of polymer binders from monomers that could in future be derived from renewable resources. These binders consist of polyethyl acrylate (PEA) of different molecular weight, polymethyl acrylate (PMA) and polybutyl acrylate (PBA), which were synthesised from ethyl acrylate, methyl acrylate and butyl acrylate, respectively, by atom transfer radical polymerization (ATRP). The fundamental rheological properties of these binders were determined by means of a dynamic shear rheometer (DSR) using a combination of temperature and frequency sweeps. The results indicate that PEA has rheological properties similar to that of 100/150 penetration grade bitumen, PMA similar rheological properties to that of 10/20 penetration grade bitumen, while PBA, due to its highly viscous nature and low complex modulus, cannot be used on its own as an asphalt binder. The synthetic binders were also combined with conventional penetration grade bitumen to produce a range of bitumen-synthetic polymer binder blends. These blends were batched by mass in the ratio of 1:1 or 3:1 and subjected to the same DSR rheological testing as the synthetic binders. The blends consisting of a softer bitumen (70/100 pen or 100/150 pen) with a hard synthetic binder (PMA) tended to be more compatible and therefore stable and produced rheological properties that combined the properties of the two components. The synthetic binders and particularly the extended bitumen samples (blends) produced rheological properties that showed similar characteristics to elastomeric SBS PMBs. 30 refs., 12 figs., 2 tabs.

  11. Studying the rheological properties and the influence of drag reduction on a waxy crude oil in pipeline flow

    Directory of Open Access Journals (Sweden)

    M.H. Hassanean

    2016-03-01

    The rheological behaviors of tested waxy crude oil were studied at different temperatures (varies from 67 to 102 °F and different DRA concentrations (10, 20, 30, 40, and 50 ppm. The results showed that at all constant DRA concentrations, the viscosity highly decreased until 80 °F (above pour point by 15 °F. However, by increasing the DRA concentration, the viscosity is increased at temperatures lower than 80 °F. This is because the DRA is a high molecular weight polymer which participates in increasing viscosity by increasing its concentration. After 80 °F, the DRA concentration has an insignificant effect on viscosity. So the effect of the DRA is not in reducing viscosity but mainly in reducing the degree of turbulence energy. The field studies were performed at a normal temperature of tested pipeline sections (100 °F. The tested DRA has an improving effect on reducing the pressure drop of pipeline which leads to reduction in crude oil pumping energy or an increase in the pipeline capacity with a high efficiency of the DRA.

  12. The helicopter dynamic stability analysis in hover condition using magneto-rheological dampers%悬停状态带磁流变减摆器直升机的动稳定性分析

    Institute of Scientific and Technical Information of China (English)

    卫丽君; 李书

    2012-01-01

    Magneto-rheological damper model suitable for helicopter air resonance and momentum theory model of hover condition involving momentum theory were built in this paper. The equations of the two models with the dynamic equations of helicopter rotor/body coupling were solved by Simulink time domain simulation method to obtain the helicopter dynamic stability influenced by Magneto-rheological damper and compared the blade flapping and lagging impacted by Magneto-rheological dampers under different voltages. It could be conclude that under a certain voltage, Magneto-rheological damper was not influenced by duel-frequent excitation, and was good at restraining the helicopter air resonance.%建立了适用于直升机悬停状态动稳定性的磁流变减摆器模型,悬停状态下动力入流模型采用动量理论模型,与直升机旋翼/机体耦合动力学方程组联立,采用Simulink时域仿真的方法计算得到磁流变减摆器对悬停状态下直升机动稳定的影响,对比了不同电压下磁流变减摆器对桨叶挥舞摆振运动的影响.结果表明:对于磁流变减摆器,施加不同电压可得到不同的阻尼力,该性质可以抑制直升机悬停状态动不稳定性.

  13. Study and rheological characterization of various bone ash porcelain formulations; Estudo e caracterizacao reologica de diferentes formulacoes de porcelana de cinza de ossos

    Energy Technology Data Exchange (ETDEWEB)

    Carus, L.A.; Bento, L.; Braganca, S.R., E-mail: laucarus@gmail.com [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Programa de Pos-Graduacao em Engenharia de Minas, Metalurgica e de Materiais

    2012-07-01

    The bone ash porcelain is a widely accepted product on the market because their qualities such as high strength and whiteness, to differ from common table porcelains. Its traditional formulation comes from an English recipe, consisting of 25% of kaolin, 25% of feldspar and 50% of bovine bone ash. In some studies, this proportion is adapted to regional conditions, optimizing the formulation according to the raw materials available. In this study, the rheological behavior of bone porcelain suspensions, in which the flux feldspar is partially substituted by an alternative flux (espudomenio, wollastonite and glass). The results show that the rheological behavior of porcelain is affected by the size, shape, surface area and particle size distribution of particles in suspension.

  14. Rheology v.2 theory and applications

    CERN Document Server

    Eirich, Frederick

    1958-01-01

    Rheology: Theory and Applications, Volume II deals with the specific rheological subjects, such as deformational behavior in relation to the classic subjects and topics of rheology. This volume is divided into 13 chapters. Considerable chapters are devoted to the theory and aspects of viscoelastic and relaxation phenomena, as well as the applied theory concerning substances related to these phenomena, including elastomers, gelatins, and fibers. Other chapters cover the general principles of geological deformations derived from the study of less """"immobile"""" objects. The remaining chapt

  15. Attenuation of seismic waves and the universal rheological model of the Earth's mantle

    Science.gov (United States)

    Birger, B. I.

    2007-08-01

    Analysis of results of laboratory studies on creep of mantle rocks, data on seismic wave attenuation in the mantle, and rheological micromechanisms shows that the universal, i.e., relevant to all time scales, rheological model of the mantle can be represented as four rheological elements connected in series. These elements account for elasticity, diffusion rheology, high temperature dislocation rheology, and low temperature dislocation rheology. The diffusion rheology element is described in terms of a Newtonian viscous fluid. The high temperature dislocation rheology element is described by the rheological model previously proposed by the author. This model is a combination of a power-law non-Newtonian fluid model for stationary flows and the linear hereditary Andrade model for flows associated with small strains. The low temperature dislocation rheology element is described by the linear hereditary Lomnitz model.

  16. The Impact of Blood Rheology on Drug Transport in Stented Arteries: Steady Simulations

    Science.gov (United States)

    Vijayaratnam, Pujith R. S.; O’Brien, Caroline C.; Reizes, John A.; Barber, Tracie J.; Edelman, Elazer R.

    2015-01-01

    Background and Methods It is important to ensure that blood flow is modelled accurately in numerical studies of arteries featuring drug-eluting stents due to the significant proportion of drug transport from the stent into the arterial wall which is flow-mediated. Modelling blood is complicated, however, by variations in blood rheological behaviour between individuals, blood’s complex near-wall behaviour, and the large number of rheological models which have been proposed. In this study, a series of steady-state computational fluid dynamics analyses were performed in which the traditional Newtonian model was compared against a range of non-Newtonian models. The impact of these rheological models was elucidated through comparisons of haemodynamic flow details and drug transport behaviour at various blood flow rates. Results Recirculation lengths were found to reduce by as much as 24% with the inclusion of a non-Newtonian rheological model. Another model possessing the viscosity and density of blood plasma was also implemented to account for near-wall red blood cell losses and yielded recirculation length increases of up to 59%. However, the deviation from the average drug concentration in the tissue obtained with the Newtonian model was observed to be less than 5% in all cases except one. Despite the small sensitivity to the effects of viscosity variations, the spatial distribution of drug matter in the tissue was found to be significantly affected by rheological model selection. Conclusions/Significance These results may be used to guide blood rheological model selection in future numerical studies. The clinical significance of these results is that they convey that the magnitude of drug uptake in stent-based drug delivery is relatively insensitive to individual variations in blood rheology. Furthermore, the finding that flow separation regions formed downstream of the stent struts diminish drug uptake may be of interest to device designers. PMID:26066041

  17. A numerical study of the effects of fluid rheology and stroke kinematics on flagellar swimming in complex fluids

    Science.gov (United States)

    Li, Chuanbin; Guy, Robert; Thomases, Becca

    2016-11-01

    It is observed in experiments that as the fluid rheology is changed, Chlamydomonas reinhardtii exhibits changes in both flagellar kinematics and the swimming speed. To understand this phenomenon, we develop a computational model of the swimmer, using flagellar strokes fit from experimental data. We conduct numerical simulations by changing strokes and fluid rheology independently to dissect the effects of these two factors. We discover that stroke patterns extracted from viscoelastic fluids generate much lower stress and have higher efficiency at the cost of lower swimming speed. We also discover that higher fluid elasticity hinders swimming for a fixed stroke pattern.

  18. Evaluation of rheological behavior of 10W40 lubricant containing hybrid nano-material by measuring dynamic viscosity

    Science.gov (United States)

    Ahmadi Nadooshan, Afshin; Hemmat Esfe, Mohammad; Afrand, Masoud

    2017-08-01

    In the present paper, the dynamic viscosity of 10W40 lubricant containing hybrid nano-materials has been examined. Hybrid nano-materials were composed of 90% of silica (SiO2) with 20-30 nm mean particle size and 10% of multi-walled carbon nanotubes (MWCNTs) with inner diameter of 2-6 nm and outer diameter of 5-20 nm. Nano-lubricant samples were prepared by two-step method with solid volume fractions of 0.05%, 0.1%, 0.25%, 0.5%, 0.75% and 1%. Dynamic viscosity of the samples was measured at temperatures between 5 and 55 °C and at shear rates of 666.5 s-1 up to 11,997 s-1. Experimental results indicated that the nano-lubricant had non-Newtonian behavior at all temperatures, while 10w40 oil was non-Newtonian only at high temperatures. With the use of the curve fitting technique of experimental data, power law and consistency indexes were obtained; furthermore, these coefficients were assessed by shear stress and viscosity diagram.

  19. Microgravity Foam Structure and Rheology

    Science.gov (United States)

    Durian, Douglas J.

    1997-01-01

    To exploit rheological and multiple-light scattering techniques, and ultimately microgravity conditions, in order to quantify and elucidate the unusual elastic character of foams in terms of their underlying microscopic structure and dynamics. Special interest is in determining how this elastic character vanishes, i.e. how the foam melts into a simple viscous liquid, as a function of both increasing liquid content and shear strain rate. The unusual elastic character of foams will be quantified macroscopically by measurement of the shear stress as a function of static shear strain, shear strain rate, and time following a step strain; such data will be analyzed in terms of a yield stress, a static shear modulus, and dynamical time scales. Microscopic information about bubble packing and rearrangement dynamics, from which these macroscopic non-Newtonian properties presumably arise, will be obtained non-invasively by novel multiple-light scattering diagnostics such as Diffusing-Wave Spectroscopy (DWS). Quantitative trends with materials parameters, such as average bubble size, and liquid content, will be sought in order to elucidate the fundamental connection between the microscopic structure and dynamics and the macroscopic rheology.

  20. Investigation of rheological properties of TPS modified bitumen

    Institute of Scientific and Technical Information of China (English)

    刘全涛; 吴少鹏; 刘聪慧; 王金刚

    2008-01-01

    Rheological properties of the virgin bitumen and TPS modified bitumen binders with several percentages of TPS additives were studied.All TPS modified bituminous binders were prepared on a laboratory scale.Dynamic shear rheometer(DSR) strain sweep test was made to measure the linear viscoelasticity areas of various bitumen binders at -20-70 ℃,then temperature sweep test and frequency sweep test were made in the linear viscoelasticity areas.Complex modulus master curves were drawn to analyze and compare various bitumen binders’ rheological properties.Based on the test results,the ideal percentage of TPS additive was brought forward.The results show that TPS modified bitumen binders have more excellent properties at high,medium and low temperatures compared with original bitumen.The dosages of TPS additive are vital to their properties.

  1. Rheological Characterization of Ethanolamine Gel Propellants

    Science.gov (United States)

    V. S Jyoti, Botchu; Baek, Seung Wook

    2016-07-01

    Ethanolamine is considered to be an environmentally friendly propellant system because it has low toxicity and is noncarcinogenic in nature. In this article, efforts are made to formulate and prepare ethanolamine gel systems, using pure agarose and hybrids of paired gelling agents (agarose + polyvinylpyrrolidine (PVP), agarose + SiO2, and PVP + SiO2), that exhibit a measurable yield stress, thixotropic behavior under shear rate ranges of 1-1,000 s-1 and a viscoelastic nature. To achieve these goals, multiple rheological experiments (including flow and dynamic studies) are performed. In this article, results are presented from experiments measuring the apparent viscosity, yield stress, thixotropy, dynamic strain, frequency sweep, and tan δ behaviors, as well as the effects of the test temperature, in the gel systems. The results show that the formulated ethanolamine gels are thixotropic in nature with yield stress between 30 and 60 Pa. The apparent viscosity of the gel decreases as the test temperature increases, and the apparent activation energy is the lowest for the ethanolamine-(PVP + SiO2) gel system. The dynamic rheology study shows that the type of gellant, choice of hybrid gelling materials and their concentration, applied frequencies, and strain all vitally affect the viscoelastic properties of the ethanolamine gel systems. In the frequency sweep experiment, the ethanolamine gels to which agarose, agarose + PVP, and agarose + SiO2 were added behave like linear frequency-dependent viscoelastic liquids, whereas the ethanolamine gel to which PVP + SiO2 was added behaves like a nearly frequency-independent viscoelastic solid. The variation in the tan δ of these gelled propellants as a function of frequency is also discussed.

  2. Crust rheology, slab detachment and topography

    Science.gov (United States)

    Duretz, T.; Gerya, T. V.

    2012-04-01

    The collision between continents following the closure of an ocean can lead to the subduction of continental crust. The introduction of buoyant crust within subduction zones triggers the development of extensional stresses in slabs which eventually result in their detachment. The dynamic consequences of slab detachment affects the development of topography, the exhumation of high-pressure rocks and the geodynamic evolution of collision zones. We employ two-dimensional thermo-mechanical modelling in order to study the importance of crustal rheology on the evolution of spontaneous subduction-collision systems and the occurrence of slab detachment. The modelling results indicate that varying the rheological structure of the crust can results in a broad range of collisional evolutions involving slab detachment, delamination (associated to slab rollback), or the combination of both mechanisms. By enhancing mechanical coupling at the Moho, a strong crust leads to the deep subduction of the crust (180 km). These collisions are subjected to slab detachment and subsequent coherent exhumation of the crust accommodated by eduction (inversion of subduction sense) and thrusting. In these conditions, slab detachment promotes the development of a high (> 4.5 km) and narrow (delamination of the lithosphere, preventing slab detachment to occur. Further shortening leads to buckling and thickening of the crust resulting in the development of topographic bulging on the lower plate. Collisions involving rheologically layered crust are characterised by a decoupling level at mid-crustal depths. These initial condition favours the delamination of the upper crust as well as the deep subduction of the lower crust. These collisions are thus successively affected by delamination and slab detachment and both processes contribute to the exhumation of the subducted crust. A wide (> 200 km) topographic plateau develops as the results of the buoyant extrusion of the upper crust onto the foreland

  3. Effect of Mantle Rheology on Viscous Heating induced during Ice Sheet Cycles

    Science.gov (United States)

    Huang, Pingping; Wu, Patrick; van der Wal, Wouter

    2017-04-01

    little more irregular than that from uniform viscosity model. However, peak heating in the VM5a model is as big as 22.5 times that of the chondritic radiogenic heating, and is much bigger than that from linear rheology with uniform viscosity (3.95 times the chondritic radiogenic heating), non-linear rheology model (10.14 times) and composite rheology model (10.04 times). Applications of viscous heating will also be discussed. References Hanyk, L., Matyska, C., & Yuen, D. A. (2005). Short time-scale heating of the Earth's mantle by ice-sheet dynamics. Earth, planets and space, 57(9), 895-902. Wu, P. (2004). Using commercial finite element packages for the study of earth deformations, sea levels and the state of stress. Geophysical Journal International, 158(2), 401-408. Van der Wal, W., P. Wu, H. Wang & M.G. Sideris, (2010). Sea levels and uplift rate from composite rheology in glacial isostatic adjustment modeling, J. Geod., J. Geod., 50:38-48. Peltier, W., Argus, D., and Drummond, R. (2015). Space geodesy constrains ice age terminal deglaciation: The global ICE-6GC (VM5a) model. Journal of Geophysical Research: Solid Earth, 120(1): 450-487

  4. Rheological properties of wormlike micelles formed in the sodium oleate/trisodium phosphate aqueous solution

    Institute of Scientific and Technical Information of China (English)

    Yong Qiang Ji; Wei Shan Wang; Gan Zuo Li; Li Qiang Zheng

    2008-01-01

    Aqueous solution of anionic surfactant,sodium oleate (NaOA),was studied by means of steady-state shear rheology and dynamic oscillatory technique.The system of NaOA/Na3PO4 showed high viscosity,strong viscoelasticity and good ability of countering Ca2+,Mg2+.The Maxwell model and Cole-Cole plot were applied to study the dynamic viscoelasticity of wormlike micelles.The microstructures of the wormlike micelles were characterized by FF-TEM.

  5. Rheological phenomena in focus

    CERN Document Server

    Boger, DV

    1993-01-01

    More than possibly any other scientific discipline, rheology is easily visualized and the relevant literature contains many excellent photographs of unusual and often bizarre phenomena. The present book brings together these photographs for the first time. They are supported by a full explanatory text. Rheological Phenomena in Focus will be an indispensable support manual to all those who teach rheology or have to convince colleagues of the practical relevance of the subject within an industrial setting. For those who teach fluid mechanics, the book clearly illustrates the difference be

  6. Theory of rheology

    Science.gov (United States)

    Hutton, J. F.

    1973-01-01

    The structure of the modern theory of rheology is discussed to show the assumptions and limitations. Rheology is discussed as a branch of continuum mechanics to determine the relationships between stress, strain, and strain rate which will give a closer representation of lubricant properties than the Newtonian flow equation. Rheology is also investigated as a branch of chemical physics. Consideration is limited to those theories of nonpolymeric and polymeric fluids which can represent viscoelasticity in terms of identifiable and measureable molecular characteristics. The possibility that elastic liquids may rupture in shear and linear tension analogous to the failure of solids is proposed.

  7. Transient rheology of stimuli responsive hydrogels: Integrating microrheology and microfluidics

    Science.gov (United States)

    Sato, Jun

    Stimuli-responsive hydrogels have diverse potential applications in the field of drug delivery, tissue engineering, agriculture, cosmetics, gene therapy, and as sensors and actuators due to their unique responsiveness to external signals, such as pH, temperature, and ionic strength. Understanding the responsiveness of hydrogel structure and rheology to these stimuli is essential for designing materials with desirable performance. However, no instrumentation and well-defined methodology are available to characterize the structural and rheological responses to rapid solvent changes. In this thesis, a new microrheology set-up is described, which allows us to quantitatively measure the transient rheological properties and microstructure of a variety of solvent-responsive complex fluids. The device was constructed by integrating particle tracking microrheology and microfluidics and offers unique experimental capabilities for performing solvent-reponse measurements on soft fragile materials without applying external shear forces. Transient analysis methods to quantitatively obtain rheological properties were also constructed, and guidelines for the trade-off between statistical validity and temporal resolution were developed to accurately capture physical transitions. Employing the new device and methodology, we successfully quantified the transient rheological and microstructural responses during gel formation and break-up, and viscosity changes of solvent-responsive complex fluids. The analysis method was expanded for heterogeneous samples, incorporating methods to quantify the microrheology of samples with broad distributions of individual particle dynamics. Transient microrheology measurements of fragile, heterogeneous, self-assembled block copolypeptide hydrogels revealed that solvent exchange via convective mixing and dialysis can lead to significantly different gel properties and that commonly applied sample preparation protocols for the characterization of soft

  8. Graphene networks and their influence on free-volume properties of graphene-epoxidized natural rubber composites with a segregated structure: rheological and positron annihilation studies.

    Science.gov (United States)

    He, Canzhong; She, Xiaodong; Peng, Zheng; Zhong, Jieping; Liao, Shuangquan; Gong, Wei; Liao, Jianhe; Kong, Lingxue

    2015-05-14

    Epoxidized natural rubber-graphene (ENR-GE) composites with segregated GE networks were successfully fabricated using the latex mixing combined in situ reduced technology. The rheological behavior and electrical conductivity of ENR-GE composites were investigated. At low frequencies, the storage modulus (G') became frequency-independent suggesting a solid-like rheological behavior and the formation of GE networks. According to the percolation theory, the rheological threshold of ENR-GE composites was calculated to be 0.17 vol%, which was lower than the electrical threshold of 0.23 vol%. Both percolation thresholds depended on the evolution of the GE networks in the composites. At low GE concentrations (<0.17 vol%), GE existed as individual units, while a "polymer-bridged GE network" was constructed in the composites when GE concentrations exceeded 0.17 vol%. Finally, a "three-dimensional GE network" with percolation conductive paths was formed with a GE concentration of 0.23 vol%, where a remarkable increase in the conductivity of ENR-GE composites was observed. The effect of GE on the atom scale free-volume properties of composites was further studied by positron annihilation lifetime spectroscopy and positron age momentum correlation measurements. The motion of ENR chains was retarded by the geometric confinement of "GE networks", producing a high-density interfacial region in the vicinity of GE nanoplatelets, which led to a lower ortho-positronium lifetime intensity and smaller free-volume hole size.

  9. Are Thermoresponsive Microgels Model Systems for Concentrated Colloidal Suspensions? A Rheology and Small-Angle Neutron Scattering Study

    NARCIS (Netherlands)

    Stieger, M.A.; Pedersen, J.S.; Lindner, P.; Richtering, W.

    2004-01-01

    The structure of concentrated temperature-sensitive poly(N-isopropylacrylamide) (PNiPAM) microgel suspensions has been investigated employing rheology and small-angle neutron scattering (SANS). A previously described model expression for the particle form factor Pinho(q) is extended by a model hard

  10. Rheological study of chitosan/polyol-phosphate systems: influence of the polyol part on the thermo-induced gelation mechanism.

    Science.gov (United States)

    Supper, Stephanie; Anton, Nicolas; Seidel, Nina; Riemenschnitter, Marc; Schoch, Christian; Vandamme, Thierry

    2013-08-13

    Thermo-sensitive gelling systems, like chitosan/polyol-phosphate, are candidates with a high potential for the design of biodegradable drug delivery systems, notably for in situ forming depots. They consist of stable and low viscosity aqueous solutions, liquid at room temperature, which turn into a gel state upon an increase of temperature (e.g., after subcutaneous administration). This technology enables a sustained release of potentially encapsulated active substances. Despite these thermo-gelling solutions being widely studied for the development of parenteral drug delivery systems, most commonly using β-glycerophosphate (β-GP) as gelling agent, the mechanism inducing the gelation and the role of the polyol part in this mechanism has not been clearly elucidated. To investigate the mechanism of the gelation process, comprehensive rheological studies were performed, comparing different chitosan/polyol-phosphate systems varying in the chemical structure of the polyol parts of the gelling agents. As reference, β-GP was compared to glucose-1-phosphate (G1-P) and glucose-6-phosphate (G6-P) and to a polyol-free phosphate salt, Na2HPO4, as well. Frequency sweep experiments at different temperatures or different gelling agent concentrations, temperature, and time sweep tests were performed as complementary experimental approaches. The results disclosed significant trends with widespread implications, establishing a relationship between the chemical structure of the polyol part and the macroscopic gelling behavior of the solutions, that is, transition temperature, gelation time, and gel strength. The new results presented in this study show that increasing the size of the polyol part prevents the interactions between the chitosan chains, strongly influencing the gelling process.

  11. On shear rheology of gel propellants

    Energy Technology Data Exchange (ETDEWEB)

    Rahimi, Shai; Peretz, Arie [RAFAEL, MANOR Propulsion and Explosive Systems Division, Haifa (Israel); Natan, Benveniste [Faculty of Aerospace Engineering, Technion - Israel Institute of Technology, Haifa (Israel)

    2007-04-15

    Selected fuel, oxidizer and simulant gels were prepared and rheologically characterized using a rotational rheometer. For fuel gelation both organic and inorganic gellants were utilized, whereas oxidizers and simulants were gelled with addition of silica and polysaccharides, respectively. The generalized Herschel-Bulkley constitutive model was found to most adequately represent the gels studied. Hydrazine-based fuels, gelled with polysaccharides, were characterized as shear-thinning pseudoplastic fluids with low shear yield stress, whereas inhibited red-fuming nitric acid (IRFNA) and hydrogen peroxide oxidizers, gelled with silica, were characterized as yield thixotropic fluids with significant shear yield stress. Creep tests were conducted on two rheological types of gels with different gellant content and the results were fitted by Burgers-Kelvin viscoelastic constitutive model. The effect of temperature on the rheological properties of gel propellant simulants was also investigated. A general rheological classification of gel propellants and simulants is proposed. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  12. Rheology of Structured Oils

    Science.gov (United States)

    Kelbaliev, G. I.; Rasulov, S. R.; Rzaev, A. G.; Mustafaeva, G. R.

    2017-07-01

    Rheological models of structured oils are proposed and compared with available experimental data on oils from different deposits. It is shown that structured oils can possess properties of Bingham and power-law non-Newtonian fluids.

  13. Rheology of waxy oils

    Energy Technology Data Exchange (ETDEWEB)

    Alicke, Alexandra A.; Marchesini, Flavio H.; Mendes, Paulo R. de Souza [Pontificia Universidade Catolica do Rio de Janeiro (PUC-Rio), RJ (Brazil)], e-mails: fhmo@puc-rio.br, pmendes@puc-rio.br; Ziglio, Claudio [Petrobras Research Center, Rio de Janeiro, RJ (Brazil)], e-mail: ziglio@petrobras.com.br

    2010-07-01

    It is well known that below the crystallization temperature the rheology of waxy oils changes from Newtonian to an extremely complex non-Newtonian behavior, which is shear-rate and temperature-history dependent. Along the last decades a lot of effort has been put into obtaining reliable rheological measurements from different oils so as to understand the yielding of waxy oils as well as the effects of shear and temperature histories on rheological properties, such as viscosity, yield stress, storage and loss moduli. In this paper we examine in detail the related literature, discussing the main reasons for some disagreements concerning the history effects on the flow properties of waxy oils. In addition, we performed temperature ramps and stress-amplitude-sweep tests and compared the results obtained with the main trends observed, highlighting the effects of cooling and shear on the microstructure and consequently on the rheological properties of these oils. (author)

  14. Polyelectrolytes thermodynamics and rheology

    CERN Document Server

    P M, Visakh; Picó, Guillermo Alfredo

    2014-01-01

    This book discusses current development of theoretical models and experimental findings on the thermodynamics of polyelectrolytes. Particular emphasis is placed on the rheological description of polyelectrolyte solutions and hydrogels.

  15. 胶原溶液流变性能的研究%Study on rheological behaviors of collagen

    Institute of Scientific and Technical Information of China (English)

    肖世维; 林海; 但卫华

    2012-01-01

    以纯化猪皮为原料提取胶原,配制不同浓度胶原溶液研究其流变性能,采用幂律方程拟合流动曲线,拟合程度非常高,以黏流活化能分析了黏度对温度的依赖性。讨论了胶原溶液浓度、剪切速率、温度对其黏度的影响。结果表明,该胶原溶液具有假塑性流体特征,浓度越高,非牛顿指数n越小,假塑性越强,黏度随剪切速率增大而下降的程度越明显。相同剪切速率下,温度升高,各浓度胶原溶液黏度下降。浓度越高,黏流活化能越大,对温度越敏感。%In this study,the rheological behaviors of collagen solutions prepared with collagen extracted from pigskin were studied at different concentration.By means of fitting the Ostwald de Wale model and based on the good fitting degree,the dependence of viscosity on collagen concentration,temperature and shear rates was analyzed.Results revealed that this collagen solution has pseudo-plastic behavior.And the concentration of solutions increased,the value of non-Newton index get smaller,the pseudo-plastic behavior appeared more obviously.Viscosity of different concentration declined increasingly with increasing shear rate and temperature.The higher concentration it is,the higher viscosity it has,the larger the value of Eη is and the more sensitive it is to temperature.

  16. Rheology of Superplastic Ceramics

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Constitutive equation of rheglogy describing a phenomenological level of superplastic deformation as functional correlation between tensor components of stress and strain rate has been analyzed for the case of superplastic ceramic flow. Rheological properties of material are taken into account by means of scalar rheological coefficients of shear and volume viscosity, which are functions of temperature, effective stress (or strain rate) and density of material.

  17. Novel design of a self powered and self sensing magneto-rheological damper

    Science.gov (United States)

    Meftahul Ferdaus, Mohammad; Rashid, M. M.; Bhuiyan, M. M. I.; Muthalif, Asan Gani Bin Abdul; Hasan, M. R.

    2013-12-01

    Magneto-rheological (MR) dampers are semi-active control devices and use MR fluids. Magneto-rheological dampers have successful applications in mechatronics engineering, civil engineering and numerous areas of engineering. At present, traditional MR damper systems, require a isolated power supply and dynamic sensor. This paper presents the achievability and accuracy of a self- powered and self-sensing magneto-rheological damper using harvested energy from the vibration and shock environment in which it is deployed and another important part of this paper is the increased yield stress of the Magneto rheological Fluids. Magneto rheological fluids using replacement of glass beads for Magnetic Particles to surge yield stress is implemented here. Clearly this shows better result on yield stress, viscosity, and settling rate. Also permanent magnet generator (PMG) is designed and attached to a MR damper. For evaluating the self-powered MR damper's vibration mitigating capacity, an Engine Mount System using the MR damper is simulated. The ideal stiffness of the PMG for the Engine Mount System (EMS) is calculated by numerical study. The vibration mitigating performance of the EMS employing the self-powered & self sensing MR damper is theoretically calculated and evaluated in the frequency domain.

  18. Oral texture perception in relation to rheology for mayonnaise

    NARCIS (Netherlands)

    Terpstra, M.E.J.; Janssen, A.M.; Linden, van der E.; Wijk, de R.A.

    2004-01-01

    Sensory attributes of commercial mayonnaises have been correlated to rheological curves to obtain those measuring conditions that reflect the oral perception of specific (texture) attributes. Correlations are found mainly with data from flow curve measurements and from dynamic stress measurements

  19. The failure of the Stava Valley tailings dams (Northern Italy): numerical analysis of the flow dynamics and rheological properties

    National Research Council Canada - National Science Library

    Pirulli, Marina; Barbero, Monica; Marchelli, Maddalena; Scavia, Claudio

    2017-01-01

    .... The traditional geotechnical assessment of tailings facilities has mainly concentrated on the stability of tailings dams, while relatively few studies have investigated the flow of tailings released after dam failure...

  20. In situ rheology of yeast biofilms.

    Science.gov (United States)

    Brugnoni, Lorena I; Tarifa, María C; Lozano, Jorge E; Genovese, Diego

    2014-01-01

    The aim of the present work was to investigate the in situ rheological behavior of yeast biofilms growing on stainless steel under static and turbulent flow. The species used (Rhodototula mucilaginosa, Candida krusei, Candida kefyr and Candida tropicalis) were isolated from a clarified apple juice industry. The flow conditions impacted biofilm composition over time, with a predominance of C. krusei under static and turbulent flow. Likewise, structural variations occurred, with a tighter appearance under dynamic flow. Under turbulent flow there was an increase of 112 μm in biofilm thickness at 11 weeks (p rheology and contribute to a thin body of knowledge about fungal biofilm formation.

  1. RHEOLOGIC BEHAVIOR OF PASTRY CREAMS

    OpenAIRE

    Camelia Vizireanu; Aurelia Ionescu; Daniela Istrati; Felicia Dima

    2012-01-01

    The increased social and economic importance of ready–made food production, together with the complexity of production technology, processing, handling and acceptance of these fragile and perishable products requires extensive knowledge of their physical properties. Viscoelastic properties play an important role in the handling and quality attributes of creams.Our study was to investigate the rheological properties of different confectionary creams, by scanning the field of shear rates at con...

  2. Effect of in situ exopolysaccharide production on physicochemical, rheological, sensory, and microstructural properties of the yogurt drink ayran: an optimization study based on fermentation kinetics.

    Science.gov (United States)

    Yilmaz, M T; Dertli, E; Toker, O S; Tatlisu, N B; Sagdic, O; Arici, M

    2015-03-01

    Exopolysaccharide (EPS)-producing starter cultures are preferred for the manufacture of fermented milk products to improve rheological and technological properties. However, no clear correlation exists between EPS production and the rheological and technological properties of fermented milk products such as the yogurt drink ayran. In this study, 4 different strain conditions (EPS- and EPS+ Streptococcus thermophilus strains) were tested as a function of incubation temperature (32, 37, or 42°C) and time (2, 3, or 4 h) to determine the effect of culture type and in situ EPS production on physicochemical, rheological, sensory, and microstructural properties of ayran. Furthermore, we assessed the effect of fermentation conditions on amounts of EPS production by different EPS-producing strains during ayran production. A multifactorial design of response surface methodology was used to model linear, interaction, and quadratic effects of these variables on steady shear rheological properties of ayran samples and in situ EPS production levels. The physicochemical and microbiological characteristics of ayran samples altered depending on incubation conditions and strain selection. Steady shear tests showed that ayran samples inoculated with EPS+ strains exhibited pseudoplastic flow behavior. Production of ayran with EPS- strain (control sample) resulted in the lowest apparent viscosity values (η50), whereas those produced with the combination of 2 EPS+ strains yielded ayran with notably increased η50 values. We concluded that incubation time was the variable with the greatest effect on η50, consistency coefficient (K), and flow behavior index (n) values. In situ EPS production was also affected by these conditions during ayran fermentation in which strain-specific metabolism conditions were found to be the most important factor for EPS production. In addition, these findings correlated the amount of in situ EPS produced with the rheological properties of ayran. Scanning

  3. Modeling of rheological properties for entangled polymer systems

    Science.gov (United States)

    Banerjee, Nilanjana

    The study of entangled polymer rheology both in the field of medicine and polymer processing has their major importance. Mechanical properties of biomolecules are studied in order to better understand cellular behavior. Similarly, industrial processing of polymers needs thorough understanding of rheology so as to improve process techniques. Work in this dissertation has been organized into three major sections. Firstly, numerical/analytical models are reviewed for describing rheological properties and mechanical behaviors of cytoskeleton. The cytoskeleton models are classified into categories according to the length scales of the phenomena of interest. The main principles and characteristics of each model are summarized and discussed by comparison with each other, thus providing a systematic understanding of biopolymer network modeling. Secondly, a new constitutive "toy" Mead-Banerjee-Park (MBP) model is developed for monodisperse entangled polymer systems, by introducing the idea of a configuration dependent friction coefficient (CDFC) and entanglement dynamics (ED) into the MLD "toy" model. The model is tested against experimental data in steady and transient extensional and shear flows. The model simultaneously captures the monotonic thinning of the extensional flow curve of polystyrene (PS) melts and the extension hardening found in PS solutions. Thirdly, the monodisperse MBP model is accordingly modified into polydisperse MBP "toy" constitutive model to predict the nonlinear viscoelastic material properties of model polydisperse systems. The polydisperse MBP toy model accurately predicts the material properties in the forward direction for transient uniaxial extension and transient shear flow.

  4. Extension velocity partitioning, rheological crust-mantle and intra-crustal decoupling and tectonically inherited structures: consequences for continental rifting dynamics.

    Science.gov (United States)

    Wang, Kun; Mezri, Leila; Burov, Evgueni; Le Pourhiet, Laetitia

    2015-04-01

    We implemented series of systematic thermo-mechanical numerical models testing the importance of the rheological structure and extension rate partitioning for continental rift evolution. It is generally assumed that styles of continental rifting are mainly conditioned by the initial integrated strength of the lithosphere. For example, strong plates are expected to undergo extension in narrow rifting mode, while weak lithospheres would stretch in wide rifting mode. However, we show that this classification is largely insufficient because the notion of the integrated strength ignores the internal rheological structure of the lithosphere that may include several zones of crust-mantle or upper-crust-intermediate (etc) crust decoupling. As well, orogenic crusts characterizing most common sites of continental extension may exhibit inverted lithological sequences, with stronger and denser formerly lower crustal units on top of weaker and lighter upper crustal units. This all may result in the appearance of sharp rheological strength gradients and presence of decoupling zones, which may lead to substantially different evolution of the rift system. Indeed, strong jump-like contrasts in the mechanical properties result in mechanical instabilities while mechanical decoupling between the competent layers results in overall drop of the flexural strength of the system and may also lead to important horizontal flow of the ductile material. In particular, the commonly inferred concept of level of necking (that assumes the existence of a stationary horizontal stretching level during rifting) looses its sense if necking occurs at several distinct levels. In this case, due to different mechanical strength of the rheological layers, several necking levels develop and switch from one depth to another resulting in step-like variations of rifting style and accelerations/decelerations of subsidence during the active phase of rifting. During the post-rifting phase, initially decoupled

  5. Experimental constraints on the rheology, eruption, and emplacement dynamics of analog lavas comparable to Mercury's northern volcanic plains

    Science.gov (United States)

    Vetere, F.; Rossi, S.; Namur, O.; Morgavi, D.; Misiti, V.; Mancinelli, P.; Petrelli, M.; Pauselli, C.; Perugini, D.

    2017-07-01

    We present new viscosity measurements of a synthetic silicate system considered an analogue for the lava erupted on the surface of Mercury. In particular, we focus on the northern volcanic plains (NVP), which correspond to the largest lava flows on Mercury and possibly in the Solar System. High-temperature viscosity measurements were performed at both superliquidus (up to 1736 K) and subliquidus conditions (1569-1502 K) to constrain the viscosity variations as a function of crystallinity (from 0 to 28%) and shear rate (from 0.1 to 5 s-1). Melt viscosity shows moderate variations (4-16 Pa s) in the temperature range of 1736-1600 K. Experiments performed below the liquidus temperature show an increase in viscosity as shear rate decreases from 5 to 0.1 s-1, resulting in a shear thinning behavior, with a decrease in viscosity of 1 log unit. The low viscosity of the studied composition may explain the ability of NVP lavas to cover long distances, on the order of hundreds of kilometers in a turbulent flow regime. Using our experimental data we estimate that lava flows with thickness of 1, 5, and 10 m are likely to have velocities of 4.8, 6.5, and 7.2 m/s, respectively, on a 5° ground slope. Numerical modeling incorporating both the heat loss of the lavas and its possible crystallization during emplacement allows us to infer that high effusion rates (>10,000 m3/s) are necessary to cover the large distances indicated by satellite data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft.

  6. Studying microstructural dynamics of complex fluids with particle tracking microrheology

    Science.gov (United States)

    Breedveld, Victor

    2004-11-01

    Over the last decade, particle tracking microrheology has matured as a new tool for complex fluids research. The main advantages of microrheology over traditional macroscopic rheometry are: the required sample size is extremely small ( ˜ 1 microliter); local viscoelastic properties in a sample can be probed with high spatial resolution ( ˜1-10 micrometer); and the sample is not disturbed by moving rheometer parts. I will present two examples of recent work in my group that highlight how these characteristics can be exploited to acquire unique information about the microstructure of complex fluids. First, we have studied protein unfolding. Traditionally, protein unfolding is studied with spectroscopic techniques (circular dichroism, NMR, fluorescence). Although viscosity has been listed in textbooks as a suitable technique, few -if any- quantitative rheological studies of unfolding have been reported, mainly due to technical difficulties. With microrheology, we have been able to quantify the size of the folded and unfolded protein, as well as the Gibbs free energy of unfolding, for aqueous bovine serum albumine solutions upon addition of urea as a denaturant. The results are in excellent agreement with literature data. Secondly, we have developed new technology for studying the microstructural dynamics of solvent-responsive complex fluids. In macroscopic rheometry it is virtually impossible to change solvent composition and measure the rheological response of a sample. By integrating microfluidics and microrheology we have been able to overcome this barrier: due to the micrometer lengthscales in microfluidiv devices, diffusive timescales in a dialysis set-up become short enough to achieve rapid and reversible changes in sample composition, without affecting the concentration of macromolecular components. Our dialysis cell for microrheology is a unique tool for studying the dynamics of structural and rheological changes induced by solvent composition. I will

  7. The study of rheological behavior and safety metrics of natural biopolymers

    OpenAIRE

    ASYAKINA L.K.; DOLGANYUK V.F.; BELOVA D.D.; PERAL M.M.; L. S. Dyshlyuk

    2016-01-01

    Traditionally, plastics are made from artificial synthetic polymers. These polymers have an unnatural structure, that’s why they are not biodegradable. Based on the latest advances in polymers structure studies, the article sets forward new biodegradable materials highly competitive with base plastic. Biodegradable films were received by fill-and-drain method from agar-agar, carrageenan and hydroxypropyl methylcellulose with glycerol, used as a plasticizer. Various compositions of biodegradab...

  8. Formulation development and rheological studies of palatable cefetamet pivoxil hydrochloride dry powder suspension

    Directory of Open Access Journals (Sweden)

    G Divakar

    2011-05-01

    Full Text Available Background and the purpose of the study: Because of its intense bitter taste and susceptibility to moisture Cefetamet Pivoxil (CPH is presently available only in the form of tablet. The aim of this study was to develop taste masked CPH dry powder suspension. Methods: Methods employed for formulations were: a Film coating of CPH using Eudragit E100 and subsequent adsorption on different carriers such as spray-dried lactose, sodium starch glycolate and spry-dried mannitol and b Complexation of CPH with three different ion exchange resins viz; indion 234, amberlite IRP64 and amberlite IRP69. Results: Taste evaluation as recognized by volunteers revealed that coating with eudragit E100 and subsequent adsorption on different carriers do not mask the bitter taste of the drug. Suspensions prepared using amberlite IRP64 and amberlite IRP69 were extremely palatable with no bitter after taste. They showed pseudoplastic flow behavior and were too viscous even after shearing for sufficient duration of time and exhibited poor pourability. The suspension made with indion 234 was palatable with slight or no bitter after taste. It demonstrated plastic flow with negligible thixotropy. It had moderate viscosity at rest and could be poured after a reasonable amount of shaking. CPH dry powder suspensions were very unstable under different conditions except under refrigeration. A 5% degradation of drug was occurred in reconstituted suspension in 4 days period when stored at room temperature. Conclusion: Dry powder suspension prepared with indion 234 with 5% overages was stable even after 4th day of reconstitution and palatable with slight or no bitter after taste

  9. A study of the rheology of planar granular flow of dumbbells using discrete element method simulations

    Science.gov (United States)

    Mandal, Sandip; Khakhar, D. V.

    2016-10-01

    Granular materials handled in industries are typically non-spherical in shape and understanding the flow of such materials is important. The steady flow of mono-disperse, frictional, inelastic dumbbells in two-dimensions is studied by soft sphere, discrete element method simulations for chute flow and shear cell flow. The chute flow data are in the dense flow regime, while the shear cell data span a wide range of solid fractions. Results of a detailed parametric study for both systems are presented. In chute flow, increase in the aspect ratio of the dumbbells results in significant slowing of the flow at a fixed inclination and in the shear cell it results in increase in the shear stress and pressure for a fixed shear rate. The flow is well-described by the μ-I scaling for inertial numbers as high as I = 1, corresponding to solid fractions as low as ϕ = 0.3, where μ is the effective friction (the ratio of shear stress to pressure) and I is the inertial number (a dimensionless shear rate scaled with the time scale obtained from the local pressure). For a fixed inertial number, the effective friction increases by 60%-70% when aspect ratio is increased from 1.0 (sphere) to 1.9. At low values of the inertial number, there is little change in the solid fraction with aspect ratio of the dumbbells, whereas at high values of the inertial number, there is a significant increase in solid fraction with increase in aspect ratio. The dense flow data are well-described by the Jop-Forterre-Pouliquen model [P. Jop et al., Nature 441, 727-730 (2006)] with the model parameters dependent on the dumbbell aspect ratio. The variation of μ with I over the extended range shows a maximum in the range I ∈ (0.4, 0.5), while the solid fraction shows a faster than linear decrease with inertial number. A modified version of the JFP model for μ(I) and a power law model for ϕ(I) is shown to describe the combined data over the extended range of I.

  10. Characterization of green rHDPE biocomposites filled with natural filler: Rheological and thermal studies

    Science.gov (United States)

    Lim, B. Y.; Voon, C. H.; Adawiah Mahmod, R.

    2016-11-01

    Palm kernel shell filled recycled high density polyethylene (rHDPE/PKS) biocomposites were produced in order to reduce the waste product from palm oil production. The biocomposites at various filler loading were prepared by melt mixing at 180 °C. Ultra Plast TP0' was selected as coupling agent in rHDPE/PKS biocomposites, in order to modify the properties of biocomposites. It was found that the higher filler loading had reduced the melt flow index (MFI) values. However, with the increasing of testing temperature from 180 to 210 °C, the MFI values of the biocomposites were increased. The presence of Ultra Plast TP01was capable to increase MFI values of the biocomposites. The thermal studies showed that thermal stability of the biocomposites was affected by PKS loading and coupling agent. Though the thermal stability of biocomposites was reduced by PKS, it can be improved by Ultra Plast TP01. Hence, Ultra Plast TP01 can serve as an effective coupling agent for rHDPE/PKS.

  11. Study of rheological behavior and miscibility of epoxidized natural rubber modified neoprene

    Science.gov (United States)

    Chiu, Hsien-Tang; Tsai, Peir-An; Cheng, Tzu-Chi

    2006-02-01

    The Mooney viscosity, curing rates, vulcanization behavior, and the relationship between molecular motion of epoxidized natural rubber (ENR) and neoprene (CR) blends at different blending ratios have been studied. The experimental results of ENR/CR blends show that the Mooney viscosity decreased gradually. Plasticization was most pronounced at an ENR/CR ratio of 75/25 and is thus the easiest to process. Owing to the ring opening of the epoxy group of ENR, the rate of crosslink formation is much faster than that of CR at higher temperature. The vulcanized rate increased with increasing ENR content. The results indicated that 175 °C and 5 min were the optimum processing conditions for ENR/CR blends. The DMA spectra showed a single damping peak for the ENR/CR blends, which suggests that ENR and CR are miscible. As seen in the Arrhenius plot of frequency against T g, the activation energy increased with increasing ENR contents. This suggests the existence of interpenetration of these two rubber molecular networks.

  12. Post-seismic stress relaxation with a linear transient rheology

    Directory of Open Access Journals (Sweden)

    Antonio Piersanti

    2010-05-01

    Full Text Available We performed an analysis of post-seismic stress relaxation, taking into account generalized linear rheologies. We compared the stress field (and its derived functions obtained with a classical Maxwell rheology with that obtained with a transient Burgers body. From a set of synthetic case studies, we have revealed quantitative and qualitative differences both in relaxation times and in local stress values when a transient rheology is introduced. As a practical application, we modeled the time evolution of the Coulomb failure function following the 2009 L'Aquila earthquake, and we show that a transient rheology can lead to non-monotonic time dependence.

  13. Rheological behaviour of wheat glutens at small and large deformations. Comparison of two glutens differing in bread making potential

    NARCIS (Netherlands)

    Janssen, A. M.; vanVliet, T; Vereijken, JM

    The rheological characteristics of hydrated cv. Obelisk and Katepwa glutens, with poor and good baking potential, respectively, were studied at small and large deformations. Dynamic (oscillatory) measurements at small deformations over a frequency range of 0.03 to 3 rad/s showed that cv. Katepwa

  14. Competitive adsorption from mixed hen egg-white lysozyme/surfactant solutions at the air-water interface studied by tensiometry, ellipsometry, and surface dilational rheology.

    Science.gov (United States)

    Alahverdjieva, V S; Grigoriev, D O; Fainerman, V B; Aksenenko, E V; Miller, R; Möhwald, H

    2008-02-21

    The competitive adsorption at the air-water interface from mixed adsorption layers of hen egg-white lysozyme with a non-ionic surfactant (C10DMPO) was studied and compared to the mixture with an ionic surfactant (SDS) using bubble and drop shape analysis tensiometry, ellipsometry, and surface dilational rheology. The set of equilibrium and kinetic data of the mixed solutions is described by a thermodynamic model developed recently. The theoretical description of the mixed system is based on the model parameters for the individual components.

  15. Effect of Thickener Type on the Rheological Properties of Hot Thickened Soups Suitable for Elderly People with Swallowing Difficulty

    Science.gov (United States)

    Kim, Sung-Gun; Yoo, Whachun; Yoo, Byoungseung

    2014-01-01

    Flow and dynamic rheological properties of hot thickened soups for consumption by the elderly people with swallowing difficulty (dysphagia) were investigated at a serving temperature of 60°C. In this study, sea mustard soup (SMS) and dried pollock soup (DPS), which have been widely known as favorable hot soups provided in a domestic hospitals and nursing homes for dysphagic patients, were thickened with four commercial xanthan gum (XG)-based food thickeners (coded A~D) marketed in Korea. Thickened soups prepared with different thickeners showed high shear-thinning flow behaviors (n=0.15~0.21). Apparent viscosity (ηa,50), consistency index (K), storage modulus (G′), and loss modulus (G″) demonstrated differences in rheological behaviors between the XG-based thickeners. The magnitudes of G′ were much higher than those of G″ over the entire range of frequency (ω) with the high dependence on ω, showing the rheological behavior similar to a weak gel. In general, all rheological parameter values of thickened DPS samples were higher when compared to the thickened SMS samples. These results indicate that flow and dynamic rheological properties of hot thickened soups containing commercial XG-based thickeners are strongly dependent on the type of thickener and soup. PMID:25580403

  16. Effects of mucokinetic drugs on rheological properties of reconstituted human nasal mucus.

    Science.gov (United States)

    Rhee, C S; Majima, Y; Cho, J S; Arima, S; Min, Y G; Sakakura, Y

    1999-01-01

    To investigate the effects of mucokinetic drugs on the rheological properties of human nasal mucus in patients with chronic sinusitis. We reconstituted human nasal mucus obtained from 74 patients with chronic sinusitis and determined the effects of 4 mucokinetic drugs, including acetylcysteine, deoxynuclease I, 2% sodium bicarbonate, and a combination product containing tyloxapol (Alevaire), on rheological properties of reconstituted human nasal mucus (RHNM). We used 5% RHNM dissolved in phosphate-buffered solution as the optimal buffer and concentration of RHNM for the study because it showed a viscoelastic response similar to that of freshly collected nasal mucus from patients with chronic sinusitis. Four experiments were performed to determine the influence of each drug on dynamic viscosity and elasticity of 5% RHNM. Distilled water was used as a control. Acetylcysteine and deoxynuclease I significantly decreased both dynamic viscosity and elastic modulus, while distilled water had no effect on rheological properties of 5% RHNM in vitro. Alevaire significantly reduced both dynamic viscosity and elastic modulus. Sodium bicarbonate significantly reduced elastic modulus but not dynamic viscosity. Reduction of elastic modulus by Alevaire was significantly greater than that by sodium bicarbonate, while there was no difference in reduction of dynamic viscosity between them. Our results indicate that RHNM may be useful for studying the topical effects of various drugs on nasal mucus from patients with chronic sinusitis.

  17. Effects of Inertia on the Steady-Shear Rheology of Disordered Solids

    Science.gov (United States)

    Nicolas, Alexandre; Barrat, Jean-Louis; Rottler, Jörg

    2016-02-01

    We study the finite-shear-rate rheology of disordered solids by means of molecular dynamics simulations in two dimensions. By systematically varying the damping strength ζ in the low-temperature limit, we identify two well-defined flow regimes, separated by a thin (temperature-dependent) crossover region. In the overdamped regime, the athermal rheology is governed by the competition between elastic forces and viscous forces, whose ratio gives the Weissenberg number Wi ∝ζ γ ˙; the macroscopic stress Σ follows the frequently encountered Herschel-Bulkley law Σ =Σ0+k √{Wi } , with yield stress Σ0>0 . In the underdamped (inertial) regime, dramatic changes in the rheology are observed for low damping: the flow curve becomes nonmonotonic. This change is not caused by longer-lived correlations in the particle dynamics at lower damping; instead, for weak dissipation, the sample heats up considerably due to, and in proportion to, the driving. By thermostating more or less underdamped systems, we are able to link quantitatively the rheology to the kinetic temperature and the shear rate, rescaled with Einstein's vibration frequency.

  18. How does inertia affect the steady-shear rheology of disordered solids?

    Science.gov (United States)

    Rottler, Joerg; Barrat, Jean-Louis; Nicolas, Alexandre

    We study the finite-shear-rate rheology of disordered solids with molecular dynamics simulations in two dimensions. By systematically varying the damping strength ζ, we identify two well defined flow regimes, separated by a thin crossover region. In the overdamped regime, the athermal rheology is governed by the competition between elastic forces and viscous forces, whose ratio gives the Weissenberg number Wi ζ γ ˙ the macroscopic stress Σ follows the frequently encountered Herschel-Bulkley law Σ =Σ0 + k√{ Wi} , with yield stress Σ0 > 0 . In the underdamped (inertial) regime, dramatic changes in the rheology are observed for low damping: the flow curve becomes nonmonotonic. This change is not caused by longer-lived correlations in the particle dynamics at lower damping; instead, for weak dissipation, the sample heats up considerably and proportional to the driving. By thermostatting more or less underdamped systems, we are able to link quantitatively the rheology to the kinetic temperature Tk, while the damping strength enters only indirectly by setting Tk.

  19. Rheological Properties Study of PSM/PP Composite%PSM/PP复合材料的流变性能研究

    Institute of Scientific and Technical Information of China (English)

    彭少贤; 李龙; 赵西坡; 敖卫; 黄亚琼

    2011-01-01

    The rheological behavior of PSM/PP composite were studied by die rheometer. The influences of extrusion moulding temperature, shear rate, mass fraction of LPP and PP chain branching on the rheological behavior of PSM were investigated. The results showed that the rheological curves obeyed pseudo-plastic law during 140 ~ 170℃, 0 ~ 103s-1, and apparent viscosity descend along with the increase of temperature and shear rate and the declining rate was less. The curves transformed to Newton section when the temperature was over 170℃. The apparent viscosity of PSM/SCBPP blend was lower than that of PSM/LPP, and the apparent viscosity of PSM/LCBPP blend was higher than that of PSM/LPP. Finally, shear rate sensitivity of PSM was lower than that of PP.%应用毛细管流变仪研究了可塑性淀粉生物基材料(PSM)/聚丙烯(PP)体系的流变学性质.讨论了挤出成型温度、剪切速率、线性聚丙烯(LPP)含量和PP支链结构对PSM流动性能的影响.结果表明:140~170℃,0~103 s-1下流动曲线具假塑性流体特点;表观黏度随温度、剪切速率增加而降低,黏度随剪切速率下降逐渐减少;170℃后曲线有向牛顿型流体变化的趋势;PSM/短支链PP (SCBPP)比PSM/LPP的表观黏度低,PSM/长支链PP( LCB-PP)比PSM/LPP的表观黏度高;PSM对剪切速率的敏感性低于PP.

  20. Studying Dynamics in Business Networks

    DEFF Research Database (Denmark)

    Andersen, Poul Houman; Anderson, Helen; Havila, Virpi;

    1998-01-01

    This paper develops a theory on network dynamics using the concepts of role and position from sociological theory. Moreover, the theory is further tested using case studies from Denmark and Finland...

  1. High pressure rheology of gas hydrate formed from multiphase systems using modified Couette rheometer

    Science.gov (United States)

    Pandey, Gaurav; Linga, Praveen; Sangwai, Jitendra S.

    2017-02-01

    Conventional rheometers with concentric cylinder geometries do not enhance mixing in situ and thus are not suitable for rheological studies of multiphase systems under high pressure such as gas hydrates. In this study, we demonstrate the use of modified Couette concentric cylinder geometries for high pressure rheological studies during the formation and dissociation of methane hydrate formed from pure water and water-decane systems. Conventional concentric cylinder Couette geometry did not produce any hydrates in situ and thus failed to measure rheological properties during hydrate formation. The modified Couette geometries proposed in this work observed to provide enhanced mixing in situ, thus forming gas hydrate from the gas-water-decane system. This study also nullifies the use of separate external high pressure cell for such measurements. The modified geometry was observed to measure gas hydrate viscosity from an initial condition of 0.001 Pa s to about 25 Pa s. The proposed geometries also possess the capability to measure dynamic viscoelastic properties of hydrate slurries at the end of experiments. The modified geometries could also capture and mimic the viscosity profile during the hydrate dissociation as reported in the literature. The present study acts as a precursor for enhancing our understanding on the rheology of gas hydrate formed from various systems containing promoters and inhibitors in the context of flow assurance.

  2. Activated Sludge Rheology

    DEFF Research Database (Denmark)

    Ratkovich, Nicolas Rios; Horn, Willi; Helmus, Frank

    2013-01-01

    Rheological behaviour is an important fluid property that severely impacts its flow behaviour and many aspects related to this. In the case of activated sludge, the apparent viscosity has an influence on e.g. pumping, hydrodynamics, mass transfer rates, sludge-water separation (settling and filtr...

  3. Rheology of concentrated biomass

    Science.gov (United States)

    J.R. Samaniuk; J. Wang; T.W. Root; C.T. Scott; D.J. Klingenberg

    2011-01-01

    Economic processing of lignocellulosic biomass requires handling the biomass at high solids concentration. This creates challenges because concentrated biomass behaves as a Bingham-like material with large yield stresses. Here we employ torque rheometry to measure the rheological properties of concentrated lignocellulosic biomass (corn stover). Yield stresses obtained...

  4. A study on the effects of three types of deflocculants and the increase in the pH on the rheological behavior of nano carbon suspensions.

    Science.gov (United States)

    Salehpour, Z; Mirhabibi, A R; Javadpour, J; Aghababazadeh, R; Brydson, R

    2009-07-01

    In this study, the rheological behavior of carbon black suspension with different amounts of three deflocculants (Dispex G40, Dispex N40 and CMC) has been investigated. As the rheological behavior of carbon black is markedly dependent on pH, the effect of the increase in pH has been studied. Dispex G40 and Sodium carboxymethycellulose (CMC), are effective in promoting complete deflocculation of carbon black suspensions with 20, 30 and 40 wt% solids concentrations for Dispex G40, and 40 wt% for CMC. 40 wt% suspensions containing Dispex N40 exhibit a yield stress at all levels of deflocculant investigated. However, a minimum in the extrapolated yield stress and apparent viscosity curve indicates that there is an optimum deflocculation level. The addition of alkali enhances the deflocculating power of CMC and Dispex G40, reducing any existing yield stress to zero. However, it would appear that Dispex N40 is desorbed when the pH is increased as rapid coagulation of the system is apparent, arising from a reduction in the repulsive forces.

  5. Yielding behavior and temperature-induced on-field oscillatory rheological studies in a novel MR suspension containing polymer-capped Fe3Ni alloy microspheres

    Science.gov (United States)

    Arief, Injamamul; Mukhopadhyay, P. K.

    2017-05-01

    Magnetic Bimetallic alloy nanoparticles of 3d elements are known for their tunable shape, size and magnetic anisotropy and find extensive applications ranging from magneto-mechanical to biomedical devices. This paper reports the polyol-mediated synthesis of Fe-rich polyacrylic acid (PAA)-Fe3Ni alloyed microspheres and its morphological and structural characterizations with scanning electron microscopy and X-ray diffraction studies. Magnetorheological fluid was prepared by dispersing the 10 vol% microparticles in silicone oil. The room temperature viscoelastic characterization of the fluid was performed under different magnetic fields. The field-dependent yield stresses were scaled using Klingenberg model and found that static yield stress was more accurately described by an M3 dependence, where M is particle magnetization. We proposed a multipolar contribution and ascertained the fact that simple dipolar description was insufficient to describe the trend in a complex rheological fluid. Temperature-dependent oscillatory rheological studies under various fields were also investigated. This demonstrated a strong temperature-induced thinning effect. The temperature-thinning in complex moduli and viscosity were more pronounced for the samples at higher magnetic field owing to quasi-solid behavior.

  6. The effect of structural properties on rheological behaviour of starches in binary dimethyl sulfoxide-water solutions

    Science.gov (United States)

    Ptaszek, Paweł; Dziubiński, Marek; Grzesik, N. Mirosław; Liszka-Skoczylas, Marta

    2017-01-01

    This research study analysed the rheological properties of potato amylose and potato amylopectin in binary solutions of the following water and dimethyl sulfoxide concentrations: 90% DMSO (1), 80% DMSO (2) and 50% DMSO (3), with preparation methodology involving the dissolution at the temperature of 98°C. The studies of dynamic light scattering on the biopolymer coils and the determination of main relaxation times of the solutions were carried out. For the amylose solutions, the fast relaxation phenomena are predominant. The results of the quality tests of the hysteresis loop showed, that the amylose solutions in the solvents (1) and (2) are rheologically stable and shear-thickened. The amylose solutions in solvents (3) reveal oscillatory alterations of viscosity in the time. Amylopectin solutions are characterized by 80% share of slow relaxation phenomena, very low diffusion coefficients and hydrodynamic radii in the range of 2000 nm. The amylopectin solutions are rheologically unstable. PMID:28152071

  7. The effect of structural properties on rheological behaviour of starches in binary dimethyl sulfoxide-water solutions.

    Science.gov (United States)

    Ptaszek, Anna; Ptaszek, Paweł; Dziubiński, Marek; Grzesik, N Mirosław; Liszka-Skoczylas, Marta

    2017-01-01

    This research study analysed the rheological properties of potato amylose and potato amylopectin in binary solutions of the following water and dimethyl sulfoxide concentrations: 90% DMSO (1), 80% DMSO (2) and 50% DMSO (3), with preparation methodology involving the dissolution at the temperature of 98°C. The studies of dynamic light scattering on the biopolymer coils and the determination of main relaxation times of the solutions were carried out. For the amylose solutions, the fast relaxation phenomena are predominant. The results of the quality tests of the hysteresis loop showed, that the amylose solutions in the solvents (1) and (2) are rheologically stable and shear-thickened. The amylose solutions in solvents (3) reveal oscillatory alterations of viscosity in the time. Amylopectin solutions are characterized by 80% share of slow relaxation phenomena, very low diffusion coefficients and hydrodynamic radii in the range of 2000 nm. The amylopectin solutions are rheologically unstable.

  8. The effects of cryopreservation on red blood cell rheologic properties

    NARCIS (Netherlands)

    Henkelman, Sandra; Lagerberg, Johan W. M.; Graaff, Reindert; Rakhorst, Gerhard; van Oeveren, Willem

    2010-01-01

    BACKGROUND: In transfusion medicine, frozen red blood cells (RBCs) are an alternative for liquid-stored RBCs. Little is known about the rheologic properties (i.e., aggregability and deformability) of thawed RBCs. In this study the rheologic properties of high-glycerol frozen RBCs and postthaw stored

  9. TRIMETHYLSILYLATED SILICA AS RHEOLOGY MODIFIER FOR SILICONE RESINS

    Institute of Scientific and Technical Information of China (English)

    Wei Huang; Ying Huang; Yunzhao Yu

    2000-01-01

    Trimethylsilylated silica was synthesized through hydrolytic condensation of tetraethoxysilane followed by trimethylsilylation. Rheological properties of the silicone resin with trimethylsilylated silica as modifier were studied. It turned out that the particle size of silica was important to the rheological behavior of the modified resin. Trimethylsilylated silica of medium particle size shows the strongest tendency of forming physical network in the resin.

  10. Research on the rheological properties of pesticide suspension concentrate

    Institute of Scientific and Technical Information of China (English)

    谭成侠; 沈德隆; 翁建全; 陈庆悟; 刘会君; 袁其亮

    2004-01-01

    This study reports research on pesticide suspension rheology and a new rheological parameter, the relative value of approach, which has great advantage for judging the physical stability of a pesticide suspension concentrate. Experiments showed that the system can form stable dispersions when the value of the relative value of approach (Sr) is less than 0.1.

  11. Studies on rheological property of coating for handling container bottom%集装箱箱底涂料流变性能的研究

    Institute of Scientific and Technical Information of China (English)

    陈东初; 刘娅莉

    2001-01-01

    The purpose of this study was to improve the rheological propertyof thick anticorrosive coatings. Varied thixotropic agents with different weight percent were added in anticorrosive coating. It proved that thixotropic agent consists of 2 weight percent modified polyamide and 1 weight percent bentonite has the best result. Viscosities of the coating at different rate of shear were tested, and Casson equation between coating viscosity and rate of shear was derived. The results show that the addition of thixotropic agent improves the rheological property of coating for handling container bottom obviously.%为提高厚防腐涂层的流变性能,在涂料中加入不同种类及含量的触变剂,优选出最佳触变剂,即2%改性聚酰胺和1%膨润土。通过不同剪切速率下的涂料粘度的测量,推导出Casson公式。结果表明,触变剂的加入能满足集装箱底涂料对流变性的要求。

  12. Understanding rheological hysteresis in soft glassy materials.

    Science.gov (United States)

    Radhakrishnan, Rangarajan; Divoux, Thibaut; Manneville, Sébastien; Fielding, Suzanne M

    2017-03-01

    Motivated by recent experimental studies of rheological hysteresis in soft glassy materials, we study numerically strain rate sweeps in simple yield stress fluids and viscosity bifurcating yield stress fluids. Our simulations of downward followed by upward strain rate sweeps, performed within fluidity models and the soft glassy rheology model, successfully capture the experimentally observed monotonic decrease of the area of the rheological hysteresis loop with sweep time in simple yield stress fluids, and the bell shaped dependence of hysteresis loop area on sweep time in viscosity bifurcating fluids. We provide arguments explaining these two different functional forms in terms of differing tendencies of simple and viscosity bifurcating fluids to form shear bands during the sweeps, and show that the banding behaviour captured by our simulations indeed agrees with that reported experimentally. We also discuss the difference in hysteresis behaviour between inelastic and viscoelastic fluids. Our simulations qualitatively agree with the experimental data discussed here for four different soft glassy materials.

  13. Analysis of the Magnetic Field Influence on the Rheological Properties of Healthy Persons Blood

    Directory of Open Access Journals (Sweden)

    Anna Marcinkowska-Gapinska

    2013-01-01

    Full Text Available The influence of magnetic field on whole blood rheological properties remains a weakly known phenomenon. An in vitro analysis of the magnetic field influence on the rheological properties of healthy persons blood is presented in this work. The study was performed on blood samples taken from 25 healthy nonsmoking persons and included comparative analysis of the results of both the standard rotary method (flow curve measurement and the oscillatory method known also as the mechanical dynamic analysis, performed before and after exposition of blood samples to magnetic field. The principle of the oscillatory technique lies in determining the amplitude and phase of the oscillations of the studied sample subjected to action of a harmonic force of controlled amplitude and frequency. The flow curve measurement involved determining the shear rate dependence of blood viscosity. The viscoelastic properties of the blood samples were analyzed in terms of complex blood viscosity. All the measurements have been performed by means of the Contraves LS40 rheometer. The data obtained from the flow curve measurements complemented by hematocrit and plasma viscosity measurements have been analyzed using the rheological model of Quemada. No significant changes of the studied rheological parameters have been found.

  14. Analysis of the magnetic field influence on the rheological properties of healthy persons blood.

    Science.gov (United States)

    Marcinkowska-Gapinska, Anna; Nawrocka-Bogusz, Honorata

    2013-01-01

    The influence of magnetic field on whole blood rheological properties remains a weakly known phenomenon. An in vitro analysis of the magnetic field influence on the rheological properties of healthy persons blood is presented in this work. The study was performed on blood samples taken from 25 healthy nonsmoking persons and included comparative analysis of the results of both the standard rotary method (flow curve measurement) and the oscillatory method known also as the mechanical dynamic analysis, performed before and after exposition of blood samples to magnetic field. The principle of the oscillatory technique lies in determining the amplitude and phase of the oscillations of the studied sample subjected to action of a harmonic force of controlled amplitude and frequency. The flow curve measurement involved determining the shear rate dependence of blood viscosity. The viscoelastic properties of the blood samples were analyzed in terms of complex blood viscosity. All the measurements have been performed by means of the Contraves LS40 rheometer. The data obtained from the flow curve measurements complemented by hematocrit and plasma viscosity measurements have been analyzed using the rheological model of Quemada. No significant changes of the studied rheological parameters have been found.

  15. Rheological behaviour of irradiated wound dressing poly(vinyl pyrrolidone) hydrogels

    Science.gov (United States)

    Lugão, Ademar B.; Rogero, Sizue O.; Malmonge, Sônia M.

    2002-03-01

    The use of hydrogels as biomaterials has increased lately. Poly(vinyl pyrrolidone) (PVP) is an example of polymer hydrogels applied for the synthesis of hydrogel to be used in different biomedical applications. This paper describes a study on rheological properties of PVP hydrogels obtained by gamma radiation techniques. PVP hydrogels were obtained by gamma radiation of PVP water solutions with different radiation doses. It was studied the influence of additives such as poly(ethylene glycol) (PEG), poly(ethylene oxide) (PEO) and glycerol on the rheological behaviour of the gel. The rheological behaviour of hydrogel samples was characterized by measuring the shear storage modulus ( G') under dynamic shear loading. Besides this, sterility and cytotoxicity tests were performed. The study on rheological behaviour of hydrogels showed that G' of PVP gels change according to the additive used. Glycerol increases the fluidity of the gel. The influence of PEG depends on the amount and on its molecular mass. The increase on PEG amount and molecular mass cause a decrease of G' and an increase in the crosslinking density of PVP hydrogel network. The use of high molecular weight PEO allows the increase of the elasticity of the PVP gels.

  16. Rheological behavior and dynamic mechanical properties of nano-copper powder/PP composite material%纳米铜粉/PP复合材料的流变性能及动态力学性能研究

    Institute of Scientific and Technical Information of China (English)

    徐德增; 赵婷; 刘智超; 白麓楠; 郭静

    2012-01-01

    将纳米铜粉经硅烷偶联剂KH550处理后,按不同的配比与聚丙烯(PP)混合,经螺杆挤压制得纳米铜粉/PP复合材料,研究了纳米铜粉在PP复合材料中的分散性以及PP复合材料的流变性能和动态力学性能.结果表明:经改性后的纳米铜粉均匀分散在PP中;纳米铜粉/PP复合材料为非牛顿假塑性流体;在低剪切速率下,复合材料熔体的黏度高于纯PP的,随着纳米铜粉的含量增加,复合材料体系的表观黏度增大,高剪切速率时,纳米铜粉的添加量对复合材料的流动性能影响较小;当复合材料体系中纳米铜粉的质量分数小于或等于0.5%时,其熔体流动性能提高,储能模量小于纯PP的,当纳米铜粉质量分数大于0.5%时,其储能模量提高并高于纯PP的.%Nano-copper powder/polypropylene (PP) composite material was prepared by blending PP and nano-copper powder modified with silane coupling agent KH550 at different ratios prior to screw extrusion. The dispersion of nano-copper powder in PP composite material was studied, as were the rheological behavior and dynamic mechanical properties of PP composite material. The results showed that nano-copper powder uniformly dispersed in PP matrix after modification; nano-copper powder/PP composite material was non-Newtonian pseudoplastic fluid; the viscosity of the composite material melt was higher than that of pure PP at low shearing rate; the apparent viscosity of the composite material system was increased with the addition of nano-copper powder; the addition of nano-copper powder had a slight effect on the rheological behavior of composite material at high shearing rate; the flowability of the composite material melt was improved, the storage modulus was lower than that of pure PP when the addition of nano-copper powder was not more than 0. 5% by mass fraction in the composite material system; and the storage modulus was higher than that of pure PP when the mass fraction of nano

  17. Effects of rheology and viscosity of biobased adhesives on bonding performance

    Science.gov (United States)

    Rheology is the science of deformation and flow of the matter due to the application of a force. Most rheological tests involve applying a force to a material and measuring its flow or change in shape. Rheological characterization is useful to study the flowability and viscoelastic properties of adh...

  18. Evaluation of the rheological behavior of asphaltic binder modified with zeolite material

    Energy Technology Data Exchange (ETDEWEB)

    Silveira, E.M. da; Sant' ana, Hosiberto B.; Soares, Sandra A.; Soares, Jorge B. [Federal University of Ceara, Fortaleza, CE (Brazil)

    2008-07-01

    Several new processes have been developed to reduce mixing and compaction temperatures of hot mix asphalt without sacrificing the quality of the resulting pavement. One of these processes utilizes the zeolite, a crystalline hydrated aluminum silicate. A laboratory study was conducted to determine the applicability of zeolite to improve the rheological and chemical behavior of an asphaltic binder. The synthetic asphaltic binder was produced with different zeolite contents (0,1; 0.3; and 0.5% w/w) by wet process. The rheological and chemical behavior was verified by Dynamic Shear Rheometer and Infrared Spectroscopy, respectively. The zeolite's chemical composition and morphology was studied by Dispersive X-ray Spectroscopy (EDX). Additionally, the scanning electron microscope (SEM) was utilized to establish the zeolite elemental composition. The results showed that investigated zeolite was classified as a sodium aluminum silicate and it was able to modify the rheological properties of the neat asphalt binder. The G*/sin{delta} parameter was affected by the zeolite presence, indicating better performance for the binders with zeolite. The results show that synthetic binders can partly replicate the rheological properties of conventional AB. Comparable complex modulus values was obtained. No significant difference was found in viscoelastic response, given by the phase angles as a function of both temperature and frequency. (author)

  19. RHEOLOGY FEATURE OF SIMPLE METAL MELT

    Institute of Scientific and Technical Information of China (English)

    C.J. Sun; H.R. Geng; Y.S. Shen; X.Y. Teng; Z.X. Yang

    2007-01-01

    The rheology feature of Sb, Bi melt and alloys was studied using coaxial cylinder high-temperature viscometer. The results showed that the curve of torsion-rotational speed for Sb melt presents a linear relation in all measured temperature ranges, whereas for the Bi melt, the curve presents obvious non-Newtonian feature within the low temperature range and at relative high shear stress. The rheology feature of Sb80Bi20 and Sb20Bi80, alloy melts was well correlated with that of Sb and Bi, respectively. It is considered that the rheology behavior of Sb melt plays a crucial role in Sb80Bi20, alloy and that of Bi melt plays a crucial role in Sb20Bi80 alloy.

  20. Cytoskeletal dynamics

    DEFF Research Database (Denmark)

    Bendix, Pól Martin

    2015-01-01

    I worked with reconstitutted contractile acto-myosin systems containing mainly actin, actin cross-linkers and myosin motors. Contractility and rheology of such systems was studied using confocal microscopy and rheology....

  1. Linear and Nonlinear Rheology Combined with Dielectric Spectroscopy of Hybrid Polymer Nanocomposites for Semiconductive Applications

    Science.gov (United States)

    Kádár, Roland; Abbasi, Mahdi; Figuli, Roxana; Rigdahl, Mikael; Wilhelm, Manfred

    2017-01-01

    The linear and nonlinear oscillatory shear, extensional and combined rheology-dielectric spectroscopy of hybrid polymer nanocomposites for semiconductive applications were investigated in this study. The main focus was the influence of processing conditions on percolated poly(ethylene-butyl acrylate) (EBA) nanocomposite hybrids containing graphite nanoplatelets (GnP) and carbon black (CB). The rheological response of the samples was interpreted in terms of dispersion properties, filler distortion from processing, filler percolation, as well as the filler orientation and distribution dynamics inside the matrix. Evidence of the influence of dispersion properties was found in linear viscoelastic dynamic frequency sweeps, while the percolation of the nanocomposites was detected in nonlinearities developed in dynamic strain sweeps. Using extensional rheology, hybrid samples with better dispersion properties lead to a more pronounced strain hardening behavior, while samples with a higher volume percentage of fillers caused a drastic reduction in strain hardening. The rheo-dielectric time-dependent response showed that in the case of nanocomposites containing only GnP, the orientation dynamics leads to non-conductive samples. However, in the case of hybrids, the orientation of the GnP could be offset by the dispersing of the CB to bridge the nanoplatelets. The results were interpreted in the framework of a dual PE-BA model, where the fillers would be concentrated mainly in the BA regions. Furthermore, better dispersed hybrids obtained using mixing screws at the expense of filler distortion via extrusion processing history were emphasized through the rheo-dielectric tests. PMID:28336857

  2. Linear and Nonlinear Rheology Combined with Dielectric Spectroscopy of Hybrid Polymer Nanocomposites for Semiconductive Applications.

    Science.gov (United States)

    Kádár, Roland; Abbasi, Mahdi; Figuli, Roxana; Rigdahl, Mikael; Wilhelm, Manfred

    2017-01-24

    The linear and nonlinear oscillatory shear, extensional and combined rheology-dielectric spectroscopy of hybrid polymer nanocomposites for semiconductive applications were investigated in this study. The main focus was the influence of processing conditions on percolated poly(ethylene-butyl acrylate) (EBA) nanocomposite hybrids containing graphite nanoplatelets (GnP) and carbon black (CB). The rheological response of the samples was interpreted in terms of dispersion properties, filler distortion from processing, filler percolation, as well as the filler orientation and distribution dynamics inside the matrix. Evidence of the influence of dispersion properties was found in linear viscoelastic dynamic frequency sweeps, while the percolation of the nanocomposites was detected in nonlinearities developed in dynamic strain sweeps. Using extensional rheology, hybrid samples with better dispersion properties lead to a more pronounced strain hardening behavior, while samples with a higher volume percentage of fillers caused a drastic reduction in strain hardening. The rheo-dielectric time-dependent response showed that in the case of nanocomposites containing only GnP, the orientation dynamics leads to non-conductive samples. However, in the case of hybrids, the orientation of the GnP could be offset by the dispersing of the CB to bridge the nanoplatelets. The results were interpreted in the framework of a dual PE-BA model, where the fillers would be concentrated mainly in the BA regions. Furthermore, better dispersed hybrids obtained using mixing screws at the expense of filler distortion via extrusion processing history were emphasized through the rheo-dielectric tests.

  3. Rheological behaviour of lahar flow

    Science.gov (United States)

    Lafarge, N.; Chambon, G.; Thouret, J. C.; Laigle, D.

    2012-04-01

    Lahars are mixtures of water and debris flowing down the flanks of volcanoes. These flows generally occur after heavy rainfalls and carry sediments deposited by volcanic eruptions. They are among the most destructive volcanic phenomena, and were responsible, in the 20th century, for 40% of the fatalities associated with volcanic eruptions worldwide. However, the mechanical behaviour and the propagation of these particular debris flows still remain poorly understood. In the frame of the research project Laharisk, Mount Semeru in Java (Indonesia) was chosen as a test site to monitor lahar activity and flows properties owing to the frequent occurrence of lahars on its flanks during the monsoon rainy period. Two observation stations, situated 510 m apart, were installed in the Curah Lengkong Valley on the southeast flank of Semeru volcano. The relatively straight and box-shaped channel between the two stations represents a natural flume well suited to study the hydraulics of the flows. Both stations are equipped with video cameras, pore-pressure and load sensors, AFM geophones, and one broad-band seismometer to measure the evolution over time of lahar flow height, speed, and discharge. Bucket samples are also directly taken in the flows at regular time-intervals in order to provide sediment concentration and grain-size distribution. The rheological behaviour of the material is studied through laboratory vane tests at constant imposed shear rate conducted on the fine-sized fraction (independent of the shear rate. In addition, the friction coefficient increases with sediment concentration. At the scale of the flow, the rheology of the material can also be investigated through the relationship between flow height and discharge in control sections. The obtained relationship has the form of a power law, and is also indicative of a frictional mechanical behaviour. Here also, the concentration appears as an important parameter controlling the rheological behavior of flow

  4. Characterization of the interaction between chitosan and inorganic sodium phosphates by means of rheological and optical microscopy studies.

    Science.gov (United States)

    Casettari, Luca; Cespi, Marco; Palmieri, Giovanni Filippo; Bonacucina, Giulia

    2013-01-16

    The physicochemical and rheological properties of chitosan and two different inorganic sodium phosphate dispersions (NaH(2)PO(4) and Na(3)PO(4)) were investigated in order to elucidate the role of different factors, such as ratios between polymer and sodium inorganic phosphates, different pHs and storage stability, on the gelling properties of chitosan. This was deemed opportune since physico-chemical characterizations of chitosan in the literature often appear incomplete and questionable. We also compared the elastic modulus values of the different chitosan/inorganic phosphate systems and examined their behaviour through optical microscopy analyses. The most efficient formulations that showed a thermogelling capacity with a significant gel transition behaviour after 24h were the NaH(2)PO(4)/chitosan and Na(3)PO(4)/chitosan systems at ratio 2 and pH 7.0. These results confirmed the importance of the pH value and ratio selection for the final systems.

  5. Orientation and Relaxation of Polymer-clay Solutions Studied by Rheology and Small-angle Neutron Scattering

    Energy Technology Data Exchange (ETDEWEB)

    Malwitz, M. M. [Louisiana State University; Butler, Paul D [ORNL; Porcar, L. [National Institute of Standards and Technology (NIST); Angelette, D. P. [Louisiana State University; Schmidt, G. [National Institute of Standards and Technology (NIST)

    2004-01-01

    The influence of shear on viscoelastic solutions of poly(ethylene oxide) (PEO) and clay [montmorillonite, i.e., Cloisite NA+ (CNA)] was investigated with rheology and small-angle neutron scattering (SANS). The steady-state viscosity and SANS were used to measure the shear-induced orientation and relaxation of the polymer and clay platelets. Anisotropic scattering patterns developed at much lower shear rates than in pure clay solutions. The scattering anisotropy saturated at low shear rates, and the CNA clay platelets aligned with the flow, with the surface normal parallel to the gradient direction. The cessation of shear led to partial and slow randomization of the CNA platelets, whereas extremely fast relaxation was observed for laponite (LRD) platelets. These PEO-CNA networklike solutions were compared with previously reported PEO-LRD networks, and the differences and similarities, with respect to the shear orientation, relaxation, and polymer-clay interactions, were examined.

  6. Rheological and DSC study of sol-gel transition in aqueous dispersions of industrially important polymers and colloids

    Energy Technology Data Exchange (ETDEWEB)

    Nishinari, K. [Osaka City Univ. (Japan). Dept. of Food and Nutrition

    1997-12-01

    Gelation kinetics, mechanical spectra, thermal scanning rheology (TSR), and differential scanning calorimetry (DSC) in aqueous solutions of gelling polymers and colloids such as seaweed polysaccharides (agarose, carrageenans), microbial polysaccharides (gellan, curdlan), plant polysaccharides (methylcellulose), globular proteins (casein, glycinin, {beta}-conglycinin), fibrous proteins (gelatin, fibrin), and polyvinyl alcohol, which are related to foods, cosmetics, biomedical and pharmaceutical applications, are described. Some gelation processes at a constant temperature have been treated successfully by an equation of first order kinetics or by other modified equations, and the molecular mechanism of gel formation is discussed briefly. For water-soluble polymers, the criterion of the gel or sol based on the frequency dependence of storage and loss moduli gives valuable informations. TSR and DSC are complementary, and the combination of these methods has been proved to be useful. (orig.) 81 refs.

  7. Vinpocetine and Pyritinol: A New Model for Blood Rheological Modulation in Cerebrovascular Disorders—A Randomized Controlled Clinical Study

    Directory of Open Access Journals (Sweden)

    Hayder M. Alkuraishy

    2014-01-01

    Full Text Available Blood and plasma viscosity are the major factors affecting blood flow and normal circulation. Whole blood viscosity is mainly affected by plasma viscosity, red blood cell deformability/aggregation and hematocrit, and other physiological factors. Thirty patients (twenty males + ten females with age range 50–65 years, normotensive with history of cerebrovascular disorders, were selected according to the American Heart Stroke Association. Blood viscosity and other rheological parameters were measured after two-day abstinence from any medications. Dual effects of vinpocetine and pyritinol exhibit significant effects on all hemorheological parameters (P0.05. Therefore, joint effects of vinpocetine and pyritinol improve blood and plasma viscosity in patients with cerebrovascular disorders.

  8. Rheology and Relaxation Timescales of ABA Triblock Polymer Gels

    Science.gov (United States)

    Peters, Andrew; Lodge, Timothy

    When dissolved in a midblock selective solvent, ABA polymers form gels composed of aggregated end block micelles bridged by the midblocks. While much effort has been devoted to the study of the structure of these systems, the dynamics of these systems has received less attention. We examine the underlying mechanism of shear relaxation of ABA triblock polymer gels, especially as a function of chain length, composition, and concentration. Recent work using time-resolved small-angle neutron scattering of polystyrene (PS)-block-poly(ethylene-alt-propylene) (PEP) in squalane has elucidated many aspects of the dynamics of diblock chain exchange. By using rheology to study bulk relaxation phenomena of the triblock equivalent, PS-PEP-PS, we apply the knowledge gained from the chain exchange studies to bridge the gap between the molecular and macroscopic relaxation phenomena in PS-PEP-PS triblock gels.

  9. Becker and Lomnitz rheological models: A comparison

    Science.gov (United States)

    Mainardi, Francesco; Spada, Giorgio

    2012-07-01

    The viscoelastic material functions for the Becker and the Lomnitz rheological models, sometimes employed to describe the transient flow of rocks, are studied and compared. Their creep functions, which are known in a closed form, share a similar time dependence and asymptotic behavior. This is also found for the relaxation functions, obtained by solving numerically a Volterra equation of the second kind. We show that the two rheologies constitute a clear example of broadly similar creep and relaxation patterns associated with neatly distinct retardation spectra, for which analytical expressions are available.

  10. Rheological Properties of Asphalt Modified by Supramolecular UV Resistant Material-LDHs

    Institute of Scientific and Technical Information of China (English)

    WANG Jinshan; WU Shaopeng; HAN Jun; LIU Xing

    2012-01-01

    Dynamic rheological properties of asphalt modified by Supramolecular UV resistant material-layered double hydroxides(LDHs) was studied by means of the dynamic shear rheometer (DSR) test.Two typical base asphalts were chosen and modified by 2 different LDHs contents.DSR tests were performed on the original samples,samples after exposed to outdoor and samples after the artificial accelerated UV aging tests respectively to analyze the rheological properties.It is found that when the LDHs content is between 3wt% and 5wt% of asphalt weight,the high temperature performance and fatigue resistant property of the modified asphalt become better,the UV aging resistance properties are improved.

  11. Rheological and physical properties of spray-dried mucilage obtained from Hylocereus undatus cladodes.

    Science.gov (United States)

    García-Cruz, E E; Rodríguez-Ramírez, J; Méndez Lagunas, L L; Medina-Torres, L

    2013-01-02

    This study examines the rheological behavior of reconstituted spray-dried mucilage isolated from the cladodes of pitahaya (Hylocereus undatus), the effects of concentration and its relationship with physical properties were analyzed in reconstituted solutions. Drying process optimization was carried out through the surface response method, utilizing a factorial 2(3) design with three central points, in order to evaluate yield and rheological properties. The reconstituted mucilage exhibited non-Newtonian shear-thinning behavior, which adequately fit the Cross model (R(2)>0.95). This dynamic response suggests a random coil configuration. The steady-shear viscosity and dynamic response are suitably correlated through the Cox-Merz rule, confirming the mucilage's stability of flow. Analysis of the physical properties of the mucilage (Tg, DTP, and particle morphology) explains the shear-thinning behavior. Copyright © 2012 Elsevier Ltd. All rights reserved.

  12. Influence of Antioxidant-Enhanced Polymers in Bitumen Rheology and Bituminous Concrete Mixtures Mechanical Performance

    Directory of Open Access Journals (Sweden)

    Samer Dessouky

    2015-01-01

    Full Text Available This paper evaluates the effect of polymer enhancement with antioxidant in the rheological properties of bitumen and mechanical properties of bituminous concrete mixture (BCM. In this study, two antioxidant-enhanced polymers were utilized in mitigating bitumen hardening due to aging. The rheological testing consists of temperature sweep using Dynamic Shear Rheometer at various aging conditions. Critical stiffness temperature data from the sweep test suggested that enhanced polymer exhibits less long-term hardening and brittleness compared to standard polymer. The mechanical testing consists of dynamic modulus, indirect tensile, flow number, and beam fatigue tests on BCM exposed to short-term aging. Hamburg wheel tracking test was also performed to assess moisture-damage susceptibility. It is found that the enhanced-polymer BCM exhibited higher modulus, higher tensile strength ratio, improved rutting resistance, lower moisture-damage susceptibility, and slightly increased fatigue life as compared to standard-polymer BCM.

  13. Influence of MR damper modeling on vehicle dynamics

    Science.gov (United States)

    de-J Lozoya-Santos, Jorge; Morales-Menendez, Ruben; Ramirez-Mendoza, Ricardo A.; Vivas-Lopez, Carlos A.

    2013-12-01

    The influence of magneto-rheological damper modeling in vehicle dynamics analysis is studied. Several tests using CarSim™ compare a four-corner controlled semi-active suspension for two different magneto-rheological damper models. The magneto-rheological damper characteristics were identified from experimental data. A model-free controller discards the influence of control and emphasizes the compliance of the magneto-rheological damper model; the characteristics of the vehicle index performance considered were comfort, road holding, handling, roll and suspension deflection. The comparison for magneto-rheological damper dynamics and semi-active suspension covers the automotive bandwidth. The results show that high precision of a magneto-rheological damper model as an isolated feature is not enough. The magneto-rheological damper model, as a component of a vehicle suspension, needs to simulate with passive precision and variable damping forces. The findings exhibit the requisite of accurate models for evaluation of semi-active control systems in classic tests. The lack of the friction component in a magneto-rheological damper model leads to an overestimation in handling and stability.

  14. Molecular water motions of skim milk powder solutions during acidification studied by 17O and 1H nuclear magnetic resonance and rheology

    DEFF Research Database (Denmark)

    Møller, S M; Whittaker, A. K.; Stokes, J. R.

    2011-01-01

    The molecular motion of water was studied in glucono-δ-lactone-acidified skim milk powder (SMP) solutions with various pH values and dry matter contents. NMR relaxometry measurements revealed that lowering the pH in SMP solutions affected 17O and 1HT2 relaxation rates almost identically. Conseque......The molecular motion of water was studied in glucono-δ-lactone-acidified skim milk powder (SMP) solutions with various pH values and dry matter contents. NMR relaxometry measurements revealed that lowering the pH in SMP solutions affected 17O and 1HT2 relaxation rates almost identically....... Consequently, the present study indicates that the proteins present in the samples do not affect the 1H relaxation behavior markedly, even at relatively high SMP concentrations (1525%). Comparison of rheological measurements and NMR measurements suggested that the collapse of k-casein during acidification...

  15. Rheology in lubrication

    Science.gov (United States)

    Cheng, H. S.

    1973-01-01

    The rheological effects on lubrication are discussed. The types of lubrication considered are thick film hydrodynamic lubrication and thin film elastohydrodynamic lubrication. The temperature-viscosity, viscoelastic, shear-thinning, and normal stess effects on the lubrication of journal bearings are analyzed. A graph of the pressure distribution of viscoelastic liquids in journal bearings is provided. Mathematical models are developed to define the effects of various properties of the lubricants on friction reduction.

  16. Blood rheology and aging

    OpenAIRE

    Oğuz K. Başkurt; Simmonds, Michael J. ; Meiselman, Herbert J.

    2013-01-01

    Journal of Geriatric Cardiology (2013) 10: 291301 ©2013 JGC All rights reserved; www.jgc301.com http://www.jgc301.com; | Journal of Geriatric Cardiology Review  Open Access  Blood rheology and aging Michael J. Simmonds1, Herbert J. Meiselman2, Oguz K. Baskurt3 1Heart Foundation Research Centre, Griffith Health Institute, Griffith University, Gold Coast, QLD 4222, Australia 2Department of Physiology and Biophysics, Keck School of Medicine, University of S...

  17. Blood rheology in marine mammals

    Directory of Open Access Journals (Sweden)

    Michael Castellini

    2010-12-01

    Full Text Available The field of blood oxygen transport and delivery to tissues has been studied by comparative physiologists for many decades. Within this general area, the particular differences in oxygen delivery between marine and terrestrial mammals has focused mainly on oxygen supply differences and delivery to the tissues under low blood flow diving conditions. Yet, the study of the inherent flow properties of the blood itself (hemorheology is rarely discussed when addressing diving. However, hemorheology is important to the study of marine mammals because of the critical nature of the oxygen stores that are carried in the blood during diving periods. This review focuses on the essential elements of hemorheology, how they are defined and on fundamental rheological applications to marine mammals. While the comparative rationale used throughout the review is much broader than the particular problems associated with diving, the basic concepts focus on how changes in the flow properties of whole blood would be critical to oxygen delivery during diving. This review introduces the reader to most of the major rheological concepts that are relevant to the unique and unusual aspects of the diving physiology of marine mammals.

  18. Mixture Effect on the Dilatation Rheology of Asphaltenes-Laden Interfaces.

    Science.gov (United States)

    Liu, Fang; Darjani, Shaghayegh; Akhmetkhanova, Nelya; Maldarelli, Charles; Banerjee, Sanjoy; Pauchard, Vincent

    2017-02-28

    Asphaltenes are a solubility class of crude oils comprising polyaromatic and heterocyclic molecules with different interfacial activities. The previously neglected effects of compositional mixture on dilatational rheology are discussed in the light of diffusional relaxation models. It is demonstrated that the reported deviations from the Lucassen-van den Tempel model for a single-component solution could largely originate from a distribution in adsorption coefficients within the asphaltenes class. This particularly applies to the peculiar gel point rheology previously ascribed to asphaltenes cross-linking at the interface. Furthermore, an extensive bibliographical review shows that asphaltenes dilatational rheology data always verify the main features of diffusional relaxation, including a decrease in modulus at high bulk concentrations and phase shift values always lower than 45°. Using diffusional relaxation concepts, the reanalysis of the most extensive dataset so far confirmed recently published studies, showing that asphaltenes exhibit a unique equation of state (EOS) irrespective of adsorption conditions. This EOS proves to be very similar for bitumen and petroleum asphaltenes. Finally, a numerical application of a binary diffusional model proved efficient to capture both dynamic interfacial tension and dilatational rheology, with the same parameters. It appears that a minority of asphaltenes (less than 10%) have a much stronger interfacial activity than the bulk of them, as previously demonstrated by fractionation. These results open up the need for a reinterpretation of the physical mechanisms of asphaltenes adsorption in terms of classical amphiphilic behavior, with a potential impact on emulsion breaking and enhanced oil recovery strategies.

  19. Experiments on Paint Rheology

    Science.gov (United States)

    Hartranft, Thomas J.; Settles, Gary S.

    1998-11-01

    We seek a better understanding of the atomization of paints for purposes of limiting the environmental impact of spray painting. However, to do so one must confront both the shear and extensional rheology of mobile non-Newtonian fluids whose very composition is often complex and even unknown. A conventional Couette rheometer yields data on paint shear behavior, but no commercial instrument is available to measure the extensional viscosity, which is believed to govern ligamentary breakup in spray painting. Here a converging-flow extensional rheometer has been built for this purpose. Flow rate and orifice pressure drop are measured and related to the rheological properties of the fluid. At first, experience was gained by visualizing in this device the flow of clear aqueous solutions of both Newtonian (glycerol) and non-Newtonian (polyacrylamide) thickeners. Commercial latex and marine paints were then tested, with the goal of characterizing their extensional behavior and the hope that they might be replaceable by simpler aqueous rheological "substitute" fluids insofar as their atomization behavior is concerned. (Research supported by the US Navy via the Penn State Applied Research Laboratory.)

  20. Theoretical studies of combustion dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Bowman, J.M. [Emory Univ., Atlanta, GA (United States)

    1993-12-01

    The basic objectives of this research program are to develop and apply theoretical techniques to fundamental dynamical processes of importance in gas-phase combustion. There are two major areas currently supported by this grant. One is reactive scattering of diatom-diatom systems, and the other is the dynamics of complex formation and decay based on L{sup 2} methods. In all of these studies, the authors focus on systems that are of interest experimentally, and for which potential energy surfaces based, at least in part, on ab initio calculations are available.

  1. Dynamical behavior of disordered spring networks

    OpenAIRE

    Yucht, M. G.; Sheinman, M.; Broedersz, C. P.

    2013-01-01

    We study the dynamical rheology of spring networks with a percolation model constructed by bond dilution in a two-dimensional triangular lattice. Hydrodynamic interactions are implemented by a Stokesian viscous coupling between the network nodes and a uniformly deforming liquid. Our simulations show that in a critical connectivity regime, these systems display weak power law rheology in which the complex shear modulus scales with frequency as G^* ~ (i * omega)^Delta where Delta = 0.41, in dis...

  2. Particle size dependent rheological property in magnetic fluid

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jie; Pei, Lei; Xuan, Shouhu, E-mail: xuansh@ustc.edu.cn; Yan, Qifan; Gong, Xinglong, E-mail: gongxl@ustc.edu.cn

    2016-06-15

    The influence of the particle size on the rheological property of magnetic fluid was studied both by the experimental and computer simulation methods. Firstly, the magnetic fluids were prepared by dispersing Fe{sub 3}O{sub 4} nanospheres with size varied from 40 nm to 100 nm and 200 nm in the solution. Then, the rheological properties were investigated and it was found that the relative magnetorheological effects increased with increasing the particle size. Finally, the molecular dynamic simulation was used to analyze the mechanical characteristics of the magnetic fluid and the chain-like model agreed well with the experimental result. The authentic chain-like structure observed by a microscope agreed with the simulation results. The three particles composed of the similar cluster nanostructure, thus they exhibited similar magnetic property. To this end, the unique assembling microstructures was the origination of the mechanical difference. And it was found that the higher MR (magnetorheological) effects of the large particle based magnetic fluid was originated from the stronger assembling microstructure under the applying magnetic field. - Highlights: • 40 nm, 100 nm and 200 nm Fe{sub 3}O{sub 4} nanospheres were dispersed in water. • The magnetorheological effect increased with increasing the particle sizes. • Molecular dynamic simulation was used in this article.

  3. In situ thermal characterization of cooling/crystallizing lavas during rheology measurements and implications for lava flow emplacement

    Science.gov (United States)

    Kolzenburg, S.; Giordano, D.; Cimarelli, C.; Dingwell, D. B.

    2016-12-01

    Transport properties of natural silicate melts at super-liquidus temperatures are reasonably well understood. However, migration and transport of silicate melts in the Earth's crust and at its surface generally occur at sub-liquidus temperatures and in settings where the melts undergo crystallization under various cooling and/or decompression conditions. In such dynamic situations the occurrence of processes such as the release of latent heat during phase changes, viscous heating, thermal advection and -inertia, and changing heat capacity, all represent potential influences on the state, and thereby on the physico-chemical behavior of the system. To date, rheological data at sub-liquidus temperatures are scarce and cooling-rate dependent, disequilibrium rheological data are virtually absent. In fact, no in situ thermal characterization of liquid or multiphase mixtures during rheological experiments, under either static or dynamic thermal conditions has been presented to date. Here we describe a new experimental setup for in situ thermal characterization of cooling/crystallizing lavas during viscosity measurement at temperatures up to 1600 °C. We use this device to recover in situ, real-time, observations of the combined rheological and thermal evolution of natural, re-melted lava samples during the transient disequilibrium conditions characteristic of lava flows and shallow crustal magma migration and storage systems in nature. We present the calibration procedure and the method employed to recover the thermal evolution of an experimental sample during flow in varying shear regimes, assess the experimental uncertainty and show the ability of the apparatus to measure the release of latent heat of crystallization during transient rheological experiments. We further report the results from a first experimental study on the rheological and thermal evolution of a basaltic lava undergoing continuous cooling at a series of different cooling rates and discuss the

  4. Rheology of nanofluids: a review.

    Science.gov (United States)

    Wang, Liang; Chen, Haisheng; Witharana, Sanjeeva

    2013-11-01

    The rheological behavior of nanofluids published in recent research papers and the relevant patents are reviewed in this article. Effects of various factors such as preparation, nanoparticle and base fluid properties, concentration, temperature, surface charge, and aggregation etc. on the rheological behavior of nanofluids are discussed. Brownian motion and nanoparticle aggregation are found to be the major mechanisms for rheological properties of nanofluids compared to the micro-sized suspensions. The importance of microstructure as means of understanding the mechanisms behind the rheological and heat transfer behavior of nanofluids is also disclosed.

  5. The rheology of crystal-rich magmas (Kuno Award Lecture)

    Science.gov (United States)

    Huber, Christian; Aldin Faroughi, Salah; Degruyter, Wim

    2016-04-01

    The rheology of magmas controls not only eruption dynamics but also the rate of transport of magmas through the crust and to a large extent the rate of magma differentiation and degassing. Magma bodies stalled in the upper crust are known to spend most of their lifespan above the solidus at a high crystal content (Cooper and Kent, 2014; Huber et al., 2009), where the probability of melt extraction (crystal fractionation) is the greatest (Dufek and Bachmann, 2010). In this study, we explore a new theoretical framework to study the viscosity of crystal bearing magmas. Since the seminal work of A. Einstein and W. Sutherland in the early 20th century, it has been shown theoretically and tested experimentally that a simple self-similar behavior exist between the relative viscosity of dilute (low crystal content) suspensions and the particle volume fraction. The self-similar nature of that relationship is quickly lost as we consider crystal fractions beyond a few volume percent. We propose that the relative viscosity of crystal-bearing magmas can be fully described by two state variables, the intrinsic viscosity and the crowding factor (a measure of the packing threshold in the suspension). These two state variables can be measured experimentally under different conditions, which allows us to develop closure relationships in terms of the applied shear stress and the crystal shape and size distributions. We build these closure equations from the extensive literature on the rheology of synthetic suspensions, where the nature of the particle shape and size distributions is better constrained and apply the newly developed model to published experiments on crystal-bearing magmas. We find that we recover a self-similar behavior (unique rheology curve) up to the packing threshold and show that the commonly reported break in slope between the relative viscosity and crystal volume fraction around the expected packing threshold is most likely caused by a sudden change in the state

  6. The Lubricity and Rheological Properties of Magnetorheological Fluids

    Directory of Open Access Journals (Sweden)

    Nowiński Emil

    2016-10-01

    Full Text Available The article presents results of tribological research carried on four ball tester and dynamic rheometer for different magnetorheological fluids. The wear test was conducted with and without magnetic field. The dynamic rheology measurement was done at wide range of velocity. The inteligent fluids differed from each other by an amount of solid phase and kind of base liquid.

  7. RHEOLOGIC BEHAVIOR OF PASTRY CREAMS

    Directory of Open Access Journals (Sweden)

    Camelia Vizireanu

    2012-03-01

    Full Text Available The increased social and economic importance of ready–made food production, together with the complexity of production technology, processing, handling and acceptance of these fragile and perishable products requires extensive knowledge of their physical properties. Viscoelastic properties play an important role in the handling and quality attributes of creams.Our study was to investigate the rheological properties of different confectionary creams, by scanning the field of shear rates at constant temperature and frequency, angular frequency scanning at small deformations and quantification of rheological changes during application of deformation voltages. The creams tested were made in the laboratory using specific concentrates as fine powders, marketed by the company “Dr. Oetker” compared with similar creams based on traditional recipes and techniques. Following the researches conducted we could conclude that both traditional creams and the instant ones are semi fluid food products with pseudoplastic and thixotropic shear flow behavior, with structural viscosity. Instant and traditional creams behaved as physical gels with links susceptible to destruction, when subjected to deformation forces.

  8. Rheological evolution of subducting slabs

    Science.gov (United States)

    Hirth, G.

    2016-12-01

    The mechanical behavior of subducting lithosphere depends on both the rheological evolution of the slab and how the slab is modified prior to subduction. Geophysical data demonstrate that the combination of thermal evolution and deformation lead to alteration of the slab at both mid-ocean ridges and the outer rise of subduction zones. In addition, the locations of earthquakes in these locations are generally consistent with both extrapolation of laboratory data that constrain the depth to the brittle-plastic transition, and deformation mechanisms inferred from microstructural analysis of mantle rocks recovered from the oceanic lithosphere. However, the frictional properties of both mantle aggregates and their alteration products suggest that linking the location of lithospheric earthquakes to regions that become hydrothermally altered is not straightforward. Furthermore, the inferred link between the location of intermediate-depth seismicity and the conditions of dehydration reactions is challenged by laboratory studies on dehydration embrittlement. In this presentation, I will introduce these apparent discrepancies; provide some possible resolutions for them based on scaling of laboratory data and discuss the implications for how an integrated understanding of slab rheology informs our understanding of the mechanical and geochemical evolution of the slab.

  9. RHEOLOGY OF CONCENTRATED SOLUTIONS OF HYPERBRANCHED POLYESTERS

    Science.gov (United States)

    The solution rheology of different generations of hyperbranched polyesters in N-methyl-2- pyrrolidinone (NMP) solvent was examined in this study. The solutions exhibited Newtonian behavior over a wide range of polyester concentrations. Also, the relative viscosities of poly(amido...

  10. RHEOLOGY OF CONCENTRATED SOLUTIONS OF HYPERBRANCHED POLYESTERS

    Science.gov (United States)

    The solution rheology of different generations of hyperbranched polyesters in N-methyl-2- pyrrolidinone (NMP) solvent was examined in this study. The solutions exhibited Newtonian behavior over a wide range of polyester concentrations. Also, the relative viscosities of poly(amido...

  11. Rheology and structure of milk protein gels

    NARCIS (Netherlands)

    Vliet, van T.; Lakemond, C.M.M.; Visschers, R.W.

    2004-01-01

    Recent studies on gel formation and rheology of milk gels are reviewed. A distinction is made between gels formed by aggregated casein, gels of `pure` whey proteins and gels in which both casein and whey proteins contribute to their properties. For casein' whey protein mixtures, it has been shown th

  12. Rheology and structure of milk protein gels

    NARCIS (Netherlands)

    Vliet, van T.; Lakemond, C.M.M.; Visschers, R.W.

    2004-01-01

    Recent studies on gel formation and rheology of milk gels are reviewed. A distinction is made between gels formed by aggregated casein, gels of `pure` whey proteins and gels in which both casein and whey proteins contribute to their properties. For casein' whey protein mixtures, it has been shown

  13. Geodynamic inversion to constrain the nonlinear rheology of the lithosphere

    Science.gov (United States)

    Baumann, Tobias; Kaus, Boris

    2015-04-01

    A common method to determine the strength of the lithosphere is through estimating its effective elastic thickness from the coherence between gravity and topography. This method assumes a priori that the lithosphere is a thin elastic plate floating on a viscous mantle. Whereas this seems to work well with oceanic plates, it has given controversial results in continental collision zones. Usually, continental collisions zones are well-studied areas for which additional geophysical datasets such as receiver functions and seismic tomography exist that constrain the geometry of the lithosphere and often show that it is rather complex. Yet, lithospheric geometry by itself is insufficient to understand the dynamics of the lithosphere, as this also requires knowledge of the rheology of the lithosphere. Experimental results show significant variability between various rock types and there are large uncertainties in extrapolating laboratory values to nature, which leaves room for speculation. An independent approach is thus required to better understand the rheology and dynamics of the lithosphere in collision zones. Our method combines numerical thermo-mechanical forward models of the present-day lithosphere with a massively parallel Bayesian inversion approach. The geometry of the forward models is part of the a priori knowledge and is constructed from seismological data. We jointly invert topography, gravity, horizontal and vertical surface velocities to constrain the unknown rheological material parameters of the forward models in a probabilistic sense. The model rheology is described with experimentally determined viscous creep laws and other parameters describing the plastic behaviour. As viscosity is temperature dependent, the temperature structure of the forward models is parameterised as well. We apply the method to cross-sections of the India-Asia collision system. In this case, we deal with 17 to 20 model parameters, which requires solving up to 2 × 106 forward

  14. Rheological behaviors of doughs reconstituted from wheat gluten and starch.

    Science.gov (United States)

    Yang, Yanyan; Song, Yihu; Zheng, Qiang

    2011-08-01

    Hydrated starch-gluten reconstituted doughs were prepared and dynamic rheological tests of the reconstituted doughs were performed using dynamic strain and dynamic frequency sweep modes. Influence of starch/gluten ratio on rheological behaviors of the reconstituted doughs was investigated. The results showed that the reconstituted doughs exhibited nonlinear rheological behavior with increasing strain. The mechanical spectra revealed predominantly elastic characteristics in frequency range from 10(-1) rad s(-1) to 10(2) rad s(-1). Cole-Cole functions were applied to fit the mechanical spectra to reveal the influence of starch/gluten ratio on Plateau modulus and longest relaxation time of the dough network. The time-temperature superposition principle was applicable to a narrow temperature range of 25°C ~40°C while it failed at 50°C due to swelling and gelatinization of the starch.

  15. Rheological profile of boron nitride–ethylene glycol nanofluids

    Energy Technology Data Exchange (ETDEWEB)

    Żyła, Gaweł, E-mail: gzyla@prz.edu.pl [Department of Physics, Rzeszów University of Technology, Rzeszów (Poland); Witek, Adam; Gizowska, Magdalena [Department of Nanotechnology, Institute of Ceramics and Building Materials, Warsaw (Poland)

    2015-01-07

    The paper presents the complete rheological profile of boron nitride (BN)–ethylene glycol (EG) nanofluids. Nanofluids have been produced by two-step method on the basis of commercially available powder of plate-like grains of nanometrical thickness. Viscoelastic structure has been determined in oscillatory measurements at a constant frequency and temperature. Viscosity and flow curves for these materials have been measured. Studies have shown that the Carreau model can be used for the modeling of dynamic viscosity curves of the material. The samples were tested for the presence of thixotropy. The dependence of viscosity on temperature was also examined. The effect of temperature on the dynamic viscosity of BN-EG nanofluids can be modelled with the use of Vogel-Fulcher-Tammann expression.

  16. Wide frequency rheological modeling of crosslinked polyacrylamide gels

    CERN Document Server

    Abidine, Yara; Michel, Richard; Duperray, Alain; Palade, Liviu Iulian; Verdier, Claude

    2013-01-01

    Gels are known to behave as viscoelastic materials but only a small amount of data is usually provided in the glassy transition. Results concerning the dynamic moduli G′ and G′′ are presented here using AFM in contact oscillatory mode and show good agreement with classical rheological data. Different gels are studied with increasing polymer concentration. G0N, the plateau modulus, is measured at low frequencies, but interestingly another one, G1, is found at high frequencies. A model based on fractional derivatives is proposed, covering the whole frequency range. The relaxation spectrum is recovered, and the physical parameters contain interesting information about the local dynamics of crosslinks.

  17. Study on the rheological properties and volatile release of cold-set emulsion-filled protein gels.

    Science.gov (United States)

    Mao, Like; Roos, Yrjö H; Miao, Song

    2014-11-26

    Emulsion-filled protein gels (EFP gels) were prepared through a cold-set gelation process, and they were used to deliver volatile compounds. An increase in the whey protein isolate (WPI) content from 4 to 6% w/w did not show significant effect on the gelation time, whereas an increase in the oil content from 5 to 20% w/w resulted in an earlier onset of gelation. Gels with a higher WPI content had a higher storage modulus and water-holding capacity (WHC), and they presented a higher force and strain at breaking, indicating that a more compact gel network was formed. An increase in the oil content contributed to gels with a higher storage modulus and force at breaking; however, this increase did not affect the WHC of the gels, and gels with a higher oil content became more brittle, resulting in a decreased strain at breaking. GC headspace analysis showed that volatiles released at lower rates and had lower air-gel partition coefficients in EFP gels than those in ungelled counterparts. Gels with a higher WPI content had lower release rates and partition coefficients of the volatiles. A change in the oil content significantly modified the partition of volatiles at equilibrium, but it produced a minor effect on the release rate of the volatiles. The findings indicated that EFP gels could be potentially used to modulate volatile release by varying the rheological properties of the gel.

  18. STUDY ON THE CAPILLARY RHEOLOGICAL PROPERTIES OF POLYETHYLENE%几种聚乙烯毛细管流变性能的研究

    Institute of Scientific and Technical Information of China (English)

    阳范文; 赵治国; 何浏炜

    2011-01-01

    采用高压毛细管流变仪研究了聚乙烯(PE)在225℃和250℃下的流变行为.结果表明,PE的粘度随着剪切速率的增加而降低,相同结构PE的粘度随熔体流动速率(MFR)的增加而降低;在同一温度和剪切速率下,当MFR相当时茂金属线性低密度聚乙烯(PE-MLLD)的粘度最大、线性低密度聚乙烯(PE-LLD)次之、低密度聚乙烯(PE-LD)最小;MFR相同的PE-MLLD,密度越高粘度越大;对于MFR相近、密度不同的PE-LLD,粘度更依赖于MFR的大小.%The rheological properties of polyethylene were studied by Haake rheological tester, the difference of apparent viscosity for different polyethylene between 225℃ and 250℃ were discussed. The results showed that the apparent viscosity decreased with increase of shear rate, the apparent viscosity of polyethylene with same structure decreased with increase of MFR. When the temperature and shear rate remained unchanged, the apparent viscosity of PE-MLLD was higher than that of PE-LLD, PE-LLD was higher than that of PE-LD. For PE-MLLD with nearly MFR, the apparent viscosity of PE-MLLD increased with increase of density. For PELLD with nearly MFR and different density, the apparent viscosity of PE-LLD had more influence than MFR.

  19. Transport analogy for segregation and granular rheology

    Science.gov (United States)

    Liu, Siying; McCarthy, Joseph J.

    2017-08-01

    Here, we show a direct connection between density-based segregation and granular rheology that can lead to insight into both problems. Our results exhibit a transition in the rate of segregation during simple shear that occurs at I ˜0.5 and mimics a coincident regime change in flow rheology. We propose scaling arguments that support a packing fraction criterion for this transition that can both explain our segregation results as well as unify existing literature studies of granular rheology. By recasting a segregation model in terms of rheological parameters, we establish an approach that not only collapses results for a wide range of conditions, but also yields a direct relationship between the coordination number z and the segregation velocity. Moreover, our approach predicts the precise location of the observed regime change or saturation. This suggests that it is possible to rationally design process operating conditions that lead to significantly lower segregation extents. These observations can have a profound impact on both the study of granular flow or mixing as well as industrial practice.

  20. Impact of Rheology on Meltblown Polymer Nanofibers

    Science.gov (United States)

    Tan, Dawud H.; Ellison, Christopher J.; Bates, Frank S.; Macosko, Christopher W.

    2008-07-01

    Melt blowing, a commercialized polymer processing technique, is used to produce a majority of nonwoven fiber products. It utilizes a stream of hot air to attenuate an extruded polymer strand into a fiber that is typically larger than 1 μm in diameter. Recently, our group has demonstrated the capability of melt blowing various polymers into defect-free fibers with an average diameter of several hundred nanometers by using a lab scale melt blowing device designed after a typical commercial instrument. However, surface tension-driven instabilities are observed when the smallest fibers are generated, resulting in droplets dispersed in the fiber mat. We hypothesize that altering the rheological properties of polymer may either delay or suppress these instabilities. In this study, the rheology has been studied systematically by melt blowing bidisperse polymeric blends obtained by mixing low and high molecular weight polymer. The associated changes in the rheological properties and the effect of rheology on the average and the width of the fiber diameter distribution will be highlighted.

  1. An Introduction to Rheology with an Emphasis on Application to Dispersions

    Science.gov (United States)

    Motyka, Andrea L.

    1996-04-01

    Rheology is the study of the flow and deformation of matter. This interdisciplinary field encompasses many different types of materials and applications, both in academia and industry. One of the most challenging and practical areas in which technical strides have been made is dispersion chemistry. Rheology can be used to characterize not only flow properties of a material, but also structural features. This introduction is intended to help newcomers to the field to comprehend, relatively quickly, the practical nature of rheological information and to recognize the impact of the type of internal structure on rheological properties. This article describes dispersions well-suited to rheological study and the types of interparticle forces responsible for their internal structure. The fundamental terms and concepts of rheology are explained using practical examples to illustrate how rheological techniques distinguish dispersions in terms of both flow properties and structural features.

  2. DEVELOPMENT OF TEST PROTOCOLS FOR THE ANALYSIS OF MAGNETO-RHEOLOGICAL PROPERTIES OF FIELD-RESPONSIVE BITUMINOUS BINDERS

    Directory of Open Access Journals (Sweden)

    Ezio Santagata

    2014-01-01

    Full Text Available Magneto-rheological fluids are materials that exhibit a significant change in their rheological properties in the presence of a magnetic field. Because of such a field-dependent behavior, they can act as smart materials in applications in which changeable performances are desired. In road pavement engineering, the use of bitumen-based magneto-rheological fluids may open innovative scenarios related to the construction of smart pavement sections and to the investigation of damage mechanisms in binders and mixtures. The research work presented in this study explored magneto-rheological properties of several field-responsive bituminous binders obtained from two different base bitumens combined with multi-wall carbon nanotubes and powder iron. The experimental program included oscillatory shear loading tests at different temperatures, performed in the strain controlled mode by means of a dynamic shear rheometer equipped with a magneto-rheological device. The investigation was carried out with the specific goal of identifying critical issues which should be taken into account in materials preparation, testing procedures and data analysis. Undesired overheating of specimens during testing was identified and taken into account for a correct interpretation of experimental data. Thus, while the field-sensitivity of carbon nanotubes was found to be negligible as a result of the magnetic shielding action of bitumen, it was shown that powder iron can significantly affect the magneto-rheological properties of bituminous binders when employed in sufficiently high amounts. Moreover, obtained results indicated that selection of base bitumen is a key factor in designing bituminous-based smart materials. Practical implications which derive from the study are mainly relative to the fine-tuning of laboratory characterization procedures which should necessarily overcome current limitations in temperature regulation and magnetic field generation. Experimental data

  3. A rheological and microscopical characterization of biocompatible ferrofluids

    Energy Technology Data Exchange (ETDEWEB)

    Nowak, J., E-mail: johannes.nowak@tu-dresden.de [Chair of Magnetofluiddynamics, Measuring and Automation Technology, Technische Universität Dresden, 01069 Germany (Germany); Wolf, D. [Triebenberg Laboratory, Technische Universität Dresden, 01328 Germany (Germany); Odenbach, S. [Chair of Magnetofluiddynamics, Measuring and Automation Technology, Technische Universität Dresden, 01069 Germany (Germany)

    2014-03-15

    There is an increasing interest in suspensions of magnetic nanoparticles in the biomedical area. Those ferrofluids are e.g. used for magnetic resonance imaging and emerging research focuses on employing the fluids for magnetic drug targeting or magnetic particle heating as a potential treatment for cancer. For these applications the knowledge of the suspensions' thermophysical properties is of major interest to guarantee a safe and effective application. Therefore the flow behavior cannot be neglected as it might significantly influence the execution of the aforementioned applications. In this experimental study two biocompatible ferrofluids were investigated. Rheological measurements were carried out using rotational rheometry. To allow an interpretation of the fluids' behavior the microscopic make-up was investigated using dynamic light scattering and transmission electron microscopy. Measurements of diluted ferrofluids were carried out as a first step to simulate the rheological behavior reflecting the concentration of magnetic nanoparticles found in blood flow for most biomedical applications of such fluids. The detected strong effects show the potential to significantly influence application and handling of the biocompatible ferrofluids in the medical area and should therefore be taken into account for further research as well as for the application of such fluids. - Highlights: • The rheology of biocompatible multicore ferrofluids is influenced by magnetic fields. • The flow curves can be described by the Herschel–Bulkley model. • A connection between the magnetoviscous effect and the particle size is found. • The strong magnetoviscous effect exists even if the fluids are diluted. • The connection between the effect and the dilution is mathematically described.

  4. Molecule-Based Rheology Switching

    NARCIS (Netherlands)

    Paulusse, Jos M.J.; Sijbesma, Rint P.

    2006-01-01

    Sound-activated switching: The rheological behavior of fluids can be affected by external stimuli, as demonstrated by electrochemically and photochemically induced changes in viscosity and sol–gel transitions. Recently, ultrasound has emerged as a novel rheology switch for supramolecular polymers an

  5. Up-to-date progress of study on rheological properties of monolithic refractories%不定形耐火材料流变性研究新进展

    Institute of Scientific and Technical Information of China (English)

    王战民; 曹喜营; 王守业; 陈卢; 冯海霞; 李少飞; 刘晋学; 李再耕

    2012-01-01

    Some research achievements on Theological behaviour of monolithic refractories accomplished by our group were briefly reviewed in present paper. Rheological properties of the vibrating type castables and coating mixes were analyzed and discussed by means of the newly developed castable viscometer and Brookfield viscometer equipped with moving up-down rotor, respectively. Relationship between rheological parameters and installation properties of castables with or without microsilica containing was studied and discussed. Rheological properties of AI2O3-SiC-SiO2-C self-flow castables as a function of flocculants addition were also illuminated. Suggestions on further researches on rheology of monolithic refractories were proposed.%总结了近期不定形耐火材料流变性研究方面的一些新进展,包括新的流变性研究试验方法、流变性的评价方法、浇注料的流变性和流动性之间的关系,以及絮凝剂对浇注料流变性的影响,并提出了今后进行不定形耐火材料流变性研究的建议.

  6. Lithospheric thermal-rheological structures of the continental margin in the northern South China Sea

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Thermal structures of three deep seismic profiles in the continental margin in the northern South China Sea are calculated, their "thermal" lithospheric thicknesses are evaluated based on the basalt dry solidus, and their rheological structures are evaluated with linear frictional failure criterion and power-law creep equation. "Thermal" lithosphere is about 90 km in thickness in shelf area, and thins toward the slope, lowers to 60-65 km in the lower slope, ocean crust and Xisha Trough. In the mid-west of the studied area, the lithospheric rheological structure in shelf area and Xisha Islands is of four layers: brittle, ductile, brittle and ductile. Because of uprising of heat mantle and thinning of crust and lithosphere in Xisha Trough, the bottom of the upper brittle layer is only buried at 16 km. In the eastern area, the bottom of the upper brittle layer in the north is buried at 20 km or so, while in lower slope and ocean crust, the rheological structure is of two layers of brittle and ductile, and crust and uppermost mantle form one whole brittle layer whose bottom is buried at 30-32 km. Analyses show that the characteristics of rheological structure accord with the seismic result observed. The character of rheological stratification implies that before the extension of the continent margin, there likely was a ductile layer in mid-lower crust. The influence of the existence of ductile layer to the evolution of the continent margin and the different extensions of ductile layer and brittle layer should not be overlooked. Its thickness, depth and extent in influencing continent margin's extension and evolution should be well evaluated in building a dynamic model for the area.

  7. Morphology and rheology in filamentous cultivations.

    Science.gov (United States)

    Wucherpfennig, T; Kiep, K A; Driouch, H; Wittmann, C; Krull, R

    2010-01-01

    Because of their metabolic diversity, high production capacity, secretion efficiency, and capability of carrying out posttranslational modifications, filamentous fungi are widely exploited as efficient cell factories in the production of metabolites, bioactive substances, and native or heterologous proteins, respectively. There is, however, a complex relationship between the morphology of these microorganisms, transport phenomena, the viscosity of the cultivation broth, and related productivity. The morphological characteristics vary between freely dispersed mycelia and distinct pellets of aggregated biomass, every growth form having a distinct influence on broth rheology. Hence, the advantages and disadvantages for mycelial or pellet cultivation have to be balanced out carefully. Because of the still inadequate understanding of the morphogenesis of filamentous microorganisms, fungal morphology is often a bottleneck of productivity in industrial production. To obtain an optimized production process, it is of great importance to gain a better understanding of the molecular and cell biology of these microorganisms as well as the relevant approaches in biochemical engineering. In this chapter, morphology and growth of filamentous fungi are described, with special attention given to specific problems as they arise from fungal growth forms; growth and mass transfer in fungal biopellets are discussed as an example. To emphasize the importance of the flow behavior of filamentous cultivation broths, an introduction to rheology is also given, reviewing important rheological models and recent studies concerning rheological parameters. Furthermore, current knowledge on morphology and productivity in relation to the environom is outlined in the last section of this review. Copyright 2010 Elsevier Inc. All rights reserved.

  8. Aggregate of nanoparticles: rheological and mechanical properties

    Directory of Open Access Journals (Sweden)

    Wang Yu

    2011-01-01

    Full Text Available Abstract The understanding of the rheological and mechanical properties of nanoparticle aggregates is important for the application of nanofillers in nanocompoistes. In this work, we report a rheological study on the rheological and mechanical properties of nano-silica agglomerates in the form of gel network mainly constructed by hydrogen bonds. The elastic model for rubber is modified to analyze the elastic behavior of the agglomerates. By this modified elastic model, the size of the network mesh can be estimated by the elastic modulus of the network which can be easily obtained by rheology. The stress to destroy the aggregates, i.e., the yield stress (σy , and the elastic modulus (G' of the network are found to be depended on the concentration of nano-silica (ϕ, wt.% with the power of 4.02 and 3.83, respectively. Via this concentration dependent behavior, we can extrapolate two important mechanical parameters for the agglomerates in a dense packing state (ϕ = 1: the shear modulus and the yield stress. Under large deformation (continuous shear flow, the network structure of the aggregates will experience destruction and reconstruction, which gives rise to fluctuations in the viscosity and a shear-thinning behavior.

  9. Rheology of Emulsion-Filled Gels Applied to the Development of Food Materials

    Directory of Open Access Journals (Sweden)

    Ivana M. Geremias-Andrade

    2016-08-01

    Full Text Available Emulsion-filled gels are classified as soft solid materials and are complex colloids formed by matrices of polymeric gels into which emulsion droplets are incorporated. Several structural aspects of these gels have been studied in the past few years, including their applications in food, which is the focus of this review. Knowledge of the rheological behavior of emulsion-filled gels is extremely important because it can measure interferences promoted by droplets or particle inclusion on the textural properties of the gelled systems. Dynamic oscillatory tests, more specifically, small amplitude oscillatory shear, creep-recovery tests, and large deformation experiments, are discussed in this review as techniques present in the literature to characterize rheological behavior of emulsion-filled gels. Moreover, the correlation of mechanical properties with sensory aspects of emulsion-filled gels appearing in recent studies is discussed, demonstrating the applicability of these parameters in understanding mastication processes.

  10. PS/LLDPE原位增容及合金的热性能与动态流变行为%In-Situ Compatibilization, Thermal Properties and Dynamic Rheological Behavior of PS/LLDPE Blends

    Institute of Scientific and Technical Information of China (English)

    徐建平; 刘涛涛

    2011-01-01

    Polystyrene(PS) and linear low density polyethylene(LLDP) blends were in-situ compatibilized by the Friedel-Crafts alkylation reaction, and the blends were characterized via Fourier transform infrared spectroscopy analysis, thermal gravimetric analysis and dynamic rheology. The results show that adding 0.4% AlCl3 to PS/LLDPE (80/20, mass ratio)blends can help to produce more PS-g-LLDPE copolymer, and the grafting-percent-ratio is high to 30.9%. The mechanical properties of the compatibilized blends are improved notably compared to that of the mechanical blends, for example, the tensile strength is increased from 14.1 MPa to 20.0 MPa and its elongation at break increases from 4.2% to 12.1%. The thermogravimetric analysis shows the temperature of maximum rate of degradation of the compatibilized blends is raised 11 ℃. The dynamic rheological properties show that at the low frequency (ω) range, the dynamic storage modulus (G′), loss modulus (G") and complex viscosity (η*) of the blends by in-situ compatibilization are higher than of the mechanical blends, while the loss tangent (tanδ) is lower than of mechanical blends.%用傅立叶红外光谱、热失重分析、动态流变等方法研究了聚苯乙烯(PS)/线型低密度聚乙烯(LLDPE)大分子之间的Friedel-Crafts烷基化反应.结果表明,在PS/LLDPE(质量比80/20)共混物中加入0.4%的AlCl,有利于生成较多LLDPE-g-PS接枝物,其接枝百分比达30.9%,与简单共混体系相比,增容体系力学性能得到明显提高,其拉伸强度从14.1 MPa提高至20.0 MPa,断裂伸长率从4.2%提高至12.1%;热重分析显示,其最大分解速率温度提高ll℃;动态流变行为显示,在低频率(ω)区域,原位增容合金的动态储能模量(G')、损耗模量(G")和复数黏度(η)高于简单共混物,损耗正切(tanδ)低于简单共混物.

  11. 3-D rheologic model of earthquake preparation (Ⅲ): Precursor field

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    On the basis of the theory of viscoelastic displacement and strain field for the three-dimensional rheologic model of earthquake preparation, this paper mainly studies the theoretical solution of precursor field for the three-dimensional rheologic model of earthquake preparation. We derive the viscoelastic analytical expressions of the ground tilt, underground water level, earth resistivity at an arbitrary point (x, y, z) in the rheologic medium, and analyzed the earth resistivity preliminarily, providing a certain theoretical basis for the precursor analysis of seismogenic process.

  12. Sensory and rheological properties of Polish commercial mayonnaise.

    Science.gov (United States)

    Juszczak, Lesław; Fortuna, Teresa; Kośla, Aneta

    2003-08-01

    Sensory and rheological analyses were performed to compare seven commercial mayonnaises having various fat contents and containing, or not, thickening and stabilizing agents. It was found that mayonnaise samples differed in their sensory and rheological properties. The samples with a higher fat content scored higher in sensory analysis than the low-fat ones. The mayonnaises studied showed non-Newtonian, pseudoplastic flow with yield stress and thixotropy. All mayonnaises, although to a different degree, exhibited a decrease in the apparent viscosity at constant shear. The mayonnaise samples which contained thickeners and stabilizers had a greater rheological stability.

  13. Rheological profiling of organogels prepared at critical gelling concentrations of natural waxes in a triacylglycerol solvent.

    Science.gov (United States)

    Patel, Ashok R; Babaahmadi, Mehrnoosh; Lesaffer, Ans; Dewettinck, Koen

    2015-05-20

    The aim of this study was to use a detailed rheological characterization to gain new insights into the gelation behavior of natural waxes. To make a comprehensive case, six natural waxes (differing in the relative proportion of chemical components: hydrocarbons, fatty alcohols, fatty acids, and wax esters) were selected as organogelators to gel high-oleic sunflower oil. Flow and dynamic rheological properties of organogels prepared at critical gelling concentrations (Cg) of waxes were studied and compared using drag (stress ramp and steady flow) and oscillatory shear (stress and frequency sweeps) tests. Although, none of the organogels satisfied the rheological definition of a "strong gel" (G″/G' (ω) ≤ 0.1), on comparing the samples, the strongest gel (highest critical stress and dynamic, apparent, and static yield stresses) was obtained not with wax containing the highest proportion of wax esters alone (sunflower wax, SFW) but with wax containing wax esters along with a higher proportion of fatty alcohols (carnauba wax, CRW) although at a comparatively higher Cg (4%wt for latter compared to 0.5%wt for former). As expected, gel formation by waxes containing a high proportion of lower melting fatty acids (berry, BW, and fruit wax, FW) required a comparatively higher Cg (6 and 7%wt, respectively), and in addition, these gels showed the lowest values for plateau elastic modulus (G'LVR) and a prominent crossover point at higher frequency. The gelation temperatures (TG'=G″) for all the studied gels were lower than room temperature, except for SFW and CRW. The yielding-type behavior of gels was evident, with most gels showing strong shear sensitivity and a weak thixotropic recovery. The rheological behavior was combined with the results of thermal analysis and microstructure studies (optical, polarized, and cryo-scanning electron microscopy) to explain the gelation properties of these waxes.

  14. Drop dynamics on a stretched viscoelastic filament: An experimental study

    Science.gov (United States)

    Peixinho, Jorge; Renoult, Marie-Charlotte; Crumeyrolle, Olivier; Mutabazi, Innocent

    2016-11-01

    Capillary pressure can destabilize a thin liquid filament during breakup into a succession of drops. Besides, the addition of a linear, high molecular weight, flexible and soluble polymer is enough to modify the morphology of this instability. In the time period preceding the breakup, the development of beads-on-a-string structures where drops are connected by thin threads is monitored. The drops dynamics involve drop formation, drop migration and drop coalescence. Experiments using a high-speed camera on stretched bridges of viscoelastic polymeric solutions were conducted for a range of viscosities and polymer concentrations. The rheological properties of the solutions are also quantified through conventional shear rheology and normal stress difference. The overall goal of this experimental investigation is to gain more insight into the formation and time evolution of the drops. The project BIOENGINE is co-financed by the European Union with the European regional development fund and by the Normandie Regional Council.

  15. Investigation of rheological properties of mixtures of soft ice cream

    Directory of Open Access Journals (Sweden)

    L. V. Golubeva

    2012-01-01

    Full Text Available The paper presents the study of the rheological properties of multicomponent mixtures for soft ice cream enriched with various stabilizers to facilitate evaluation and selection of the optimal mixture.

  16. Using Ultrasound to Measure Mud Rheological Properties

    Science.gov (United States)

    Maa, P. Y. P. Y.; Kwon, J. I.; Park, K. S.

    2015-12-01

    In order to predict the dynamic responses of newly consolidated cohesive sediment beds, a better understanding of the material rheological properties (bulk density, ρ, kinematic viscosity, ν, and shear modulus, G, assuming mud is a simple Voigt viscoelastic model) of these sediment beds is needed. An acoustic approach that uses a commercially available 250 kHz shear wave transducer and tone-burst waves has been developed to measure those properties. This approach uses a 86.3 mm long delay-line (DL) to separate the generated pressure and shear waves, and measures the reflected shear waves as well as the reflected pressure waves caused at the interface between the delay line and the mud to interpret these properties. By using materials (i.e., air, water, olive oil, and honey) with available rheological properties to establish a calibration relationship between the information carried by the measured reflected waves and those given material properties, the mud properties as well as thνe change of these properties during consolidation can be interpreted. Using jelly pudding as a check, a value of G ≈ 12310 N/m2 and ν ≈ 5 x 10-5 m2/s were estimated. For the consolidating kaolinite bed (with zero salinity and initial suspended sediment concentration about 420 g/cm3), the measurements show that the shear modulus developed after about 40 hours and approached a value on the order of 15000 N/m2 after about 100 hours. The initial kinematic viscosity was about 5 x 10-4 m2/s, and it decreased slowly with time and approached a low plateau between 10-6 and 10-7 m2/s after 300 hours. The measured bulk density showed a small increasing rate during the entire consolidation period, except at a short period between 80 and 90 hours after consolidation. Results from this study suggest a promising approach for developing an in-situ instrument to measure mud properties, as well as many other materials in other industries.

  17. Rheology of cubic particles suspended in a Newtonian fluid.

    Science.gov (United States)

    Cwalina, Colin D; Harrison, Kelsey J; Wagner, Norman J

    2016-05-18

    Many real-world industrial processes involve non-spherical particles suspended in a fluid medium. Knowledge of the flow behavior of these suspensions is essential for optimizing their transport properties and designing processing equipment. In the present work, we explore and report on the rheology of concentrated suspensions of cubic-shaped colloidal particles under steady and dynamic shear flow. These suspensions exhibit a rich non-Newtonian rheology that includes shear thickening and normal stress differences at high shear stresses. Scalings are proposed to connect the material properties of these suspensions of cubic particle to those measured for suspensions of spherical particles. Negative first normal stress differences indicate that lubrication hydrodynamic forces dominate the stress in the shear-thickened state. Accounting for the increased lubrication hydrodynamic interactions between the flat surfaces of the cubic particles allows for a quantitative comparison of the deviatoric stress in the shear-thickened state to that of spherical particles. New semi-empirical models for the viscosity and normal stress difference coefficients are presented for the shear-thickened state. The results of this study indicate that cubic particles offer new and unique opportunities to formulate colloidal dispersions for field-responsive materials.

  18. Rheological properties of a {gamma}-Fe{sub 2}O{sub 3} paraffin-based ferrofluid

    Energy Technology Data Exchange (ETDEWEB)

    Masoud Hosseini, S.; Fazlali, Alireza [Department of Chemical Engineering, Faculty of Engineering, Arak University, Arak (Iran, Islamic Republic of); Ghasemi, E., E-mail: eghasemi@iust.ac.i [Institute of Color Science and Technology (ICST), 1668814811 Tehran (Iran, Islamic Republic of); Ahmadi Moghaddam, H.; Salehi, M. [Institute of Color Science and Technology (ICST), 1668814811 Tehran (Iran, Islamic Republic of)

    2010-12-15

    A stable {gamma}-Fe{sub 2}O{sub 3} paraffin-based ferrofluid was prepared via high energy milling. The magnetic particles were characterized using X-ray diffraction, dynamic light scattering and vibrating sample magnetometer techniques. The rheological properties of the ferrofluid were studied using a standard rotating rheometer. The magnetoviscous effect and thixotropy in the ferrofluid were studied. The formation and destruction of magnetically induced structures and the interactions of nanoparticles and aggregates are discussed.

  19. Rheology and physical-chemical characteristics of the solutions of the medicines

    Science.gov (United States)

    Urakov, A.; Urakova, N.

    2015-04-01

    In the laboratory studied the dynamics of rheology of water solutions with plasma- inflammatory and antiseptic funds when mixing them with blood, plasma and pus under the influence of the following physical and chemical factors of local interaction: gravity, specific gravity, temperature, relative viscosity, internal pressure, sparkling water, total concentration of the ingredients, surface activity, volume of acid and osmotic activity of medicines. Found that the rheology of biological liquids improve hyperthermic, highly alkaline and highly carbonated solution medicines. For the dilution of pus, dense festering mass of sulfur plugs and tear stones invited to apply heated to +39 - +42°C with aqueous solution of 0.5 - 3% hydrogen peroxide and 0.5 - 10% sodium bicarbonate saturated with carbon dioxide to excess pressure 0.2 ATM.

  20. Rheological effects of commercial waxes and polyphosphoric acid in bitumen 160/220 low temperature performance

    Energy Technology Data Exchange (ETDEWEB)

    Ylva Edwards; Yuksel Tasdemir; Ulf Isacsson [Royal Institute of Technology (KTH), Stockholm (Sweden). Division of Highway Engineering

    2006-05-15

    Effects of adding three commercial waxes and a polyphosphoric acid to three bitumens of 160/220 penetration grade were studied using different types of laboratory equipment, such as dynamic shear rheometer (DSR), bending beam rheometer (BBR), differential scanning calorimeter (DSC), force ductilometer (FD) as well as equipment for determining conventional parameters like penetration, softening point and Fraass breaking point. The paper deals with low-temperature effects, which could influence the thermal cracking resistance of asphalt concrete pavements. The results show that magnitude and type of effect on bitumen rheology depend on the bitumen itself as well as type and amount of additive used. Bitumen composition was found to be of decisive importance. Adding polyethylene wax or polyphosphoric acid, especially to non-waxy 160/220-penetration grade bitumen, showed positive effects on the rheological behaviour at low temperatures. 24 refs., 6 figs., 5 tabs.

  1. The effect of epoxidized soybean oil on mechanical and rheological properties of poly(butylene succinate)/lignin via vane extruder

    Science.gov (United States)

    Liu, Huanyu; Huang, Zhaoxia; Qu, Jinping; Meng, Cong

    2016-03-01

    Epoxidized Soybean Oil (ESO) have been used as the compatilizer in the Poly (butylene succinate)/lignin (PBS/lignin) composites. Compatibilized composites were fabricated by a novel vane extruder (VE) which can generate global and dynamic elongational flow. The effects of ESO on the mechanical, rheological properties and morphology of PBS/lignin were studied. The results indicated that the use of ESO had plasticizing effect on the matrix PBS while the addition reduced tensile strength. From SEM micrographs it could be clearly observed that there was a better interfacial adhesion between lignin and matrix. Meanwhile, rheological tests showed the incorporation of ESO improved its Newtonian behavior and can enhance PBS's flexibility.

  2. Photoacoustic and photothermal cytometry for monitoring multiple blood rheology parameters in vivo

    Science.gov (United States)

    Galanzha, Ekaterina I.; Zharov, Vladimir P.

    2012-01-01

    Alterations of blood rheology (hemorheology) are important for the early diagnosis, prognosis, and prevention of many diseases, including myocardial infarction, stroke, sickle cell anemia, thromboembolism, trauma, inflammation, and malignancy. However, real-time in vivo monitoring of hemorheological status using multiple parameters over long periods of time has not been reported. Here we describe the capability of label-free photoacoustic (PA) and photothermal (PT) flow cytometry in detection and imaging modes for dynamic monitoring of rheological parameters in circulating blood. We show that this integrated platform can simultaneously measure the main rheological parameters and may improve their diagnostic value. Using phenomenological approaches, we analyze correlations of PT and PA signal characteristics in the dynamic modes with red blood cell (RBC) aggregation, deformability, shape (e.g., as in sickle cells), intracellular hemoglobin distribution, individual cell velocity, flux of RBCs, and likely shear rate. Proof of concept is demonstrated in ex vivo and in vivo tests, including high-speed PT imaging of RBC shape in pathological conditions and identification of sickle cells in a mouse model of human sickle cell disease. These studies revealed the potential of this new platform integrating PT, PA, and conventional optical techniques for translation to use in humans using safe, portable, laser-based medical devices for point-of-care screening of disease progression and therapy efficiency. PMID:21948731

  3. The Rheology of Concentrated Suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Andreas Acrivos

    2004-09-07

    Research program on the rheological properties of flowing suspensions. The primary purpose of the research supported by this grant was to study the flow characteristics of concentrated suspensions of non-colloidal solid particles and thereby construct a comprehensive and robust theoretical framework for modeling such systems quantitatively. At first glance, this seemed like a modest goal, not difficult to achieve, given that such suspensions were viewed simply as Newtonian fluids with an effective viscosity equal to the product of the viscosity of the suspending fluid times a function of the particle volume fraction. But thanks to the research findings of the Principal Investigator and of his Associates, made possible by the steady and continuous support which the PI received from the DOE Office of Basic Energy Sciences, the subject is now seen to be more complicated and therefore much more interesting in that concentrated suspensions have been shown to exhibit fascinating and unique rheological properties of their own that have no counterpart in flowing Newtonian or even non-Newtonian (polymeric) fluids. In fact, it is generally acknowledged that, as the result of these investigations for which the PI received the 2001 National Medal of Science, our understanding of how suspensions behave under flow is far more detailed and comprehensive than was the case even as recently as a decade ago. Thus, given that the flow of suspensions plays a crucial role in many diverse physical processes, our work has had a major and lasting impact in a subject having both fundamental as well as practical importance.

  4. Rheology, processing, and mechanical properties of thermoplastic/graphite fiber composites

    Energy Technology Data Exchange (ETDEWEB)

    Scobbo, J.J. Jr.

    1989-01-01

    Various cause and effect relations between the rheology, processing and mechanical properties of poly(ether ether ketone) (PEEK) and poly(arylene sulfide) (PAS) matrix composites were studied. The test methods and characterization schemes used emphasize novel techniques for characterizing composites that have not been used previously. A dynamic mechanical analyzer has been modified and used to characterize transition temperatures of the neat matrix resins and the 60 volume percent continuous graphite fiber reinforced composites. Transitions related to local order may have been found in PEEK at 380{degree}C and PAS at 345{degree}C. Transitions such as these have not been reported previously using dynamic mechanical analysis. Basic rheological behavior of the resins has been studied using dynamic mechanical analysis. Similar dynamic tests were performed on PEEK and PAS matrix unidirectional prepreg tape-based laminates. Tests were performed for the first time in simple shear with the matrix in the melt state. Simple shear deformation is of interest because it represents flow behavior of laminated composites in processing operations such as thermoforming. A simple model of resin layers between fibrous plates describes the observed behavior. A bending mode dynamic test has been developed to determine laminate softening temperatures. This test has been shown to be beneficial in the characterization of composite elastic properties at room temperature. The test requires less material and labor than other more common mechanical property tests. Processing studies were conducted where the radiative heating of laminates was simulated to determine optimum thermoforming cycle times.

  5. RHEOLOGICAL PROPERTIES OF VISCOUS DEBRIS FLOWS IN THE JIANGJIA RAVINE, YUNNAN, CHINA

    Institute of Scientific and Technical Information of China (English)

    Yuyi WANG; Chyandeng JAN; Changzhi LI; Wenliang HAN

    2001-01-01

    The rheological properties of natural debris flow are studied using experimental data obtained from a rheometer built by the authors. The present study is aimed to address the rheological properties of viscous debris flow at low shear rate. It is found that overstress effect and shear-rate-thinning phenomenon characterize the viscous debris flow in the Jiangjia Ravine, China. Results obtained from this study are believed to lay the foundation for further study on the theory of debris flow rheology.

  6. Finite element modelling of rheological and penetration characteristics of curing PMMA bone cement in total hip replacement

    OpenAIRE

    2006-01-01

    This thesis is concerned with the study of the rheological properties of PMMA bone cement that is used as a grout for bone and prosthesis in THR and TKR Interdigitation of bone cement through porous cancellous bone depends on the rheological characteristics of bone cement and porosity of the cancellous bone. The rheological characteristics of the bone cement are thus an important factor effecting the optimum penetration of bone cement through cancellous bone. In this project the rheologic...

  7. Non-Newtonian versus numerical rheology: Practical impact of shear-thinning on the prediction of stable and unstable flows in intracranial aneurysms.

    Science.gov (United States)

    Khan, M O; Steinman, D A; Valen-Sendstad, K

    2017-07-01

    Computational fluid dynamics (CFD) shows promise for informing treatment planning and rupture risk assessment for intracranial aneurysms. Much attention has been paid to the impact on predicted hemodynamics of various modelling assumptions and uncertainties, including the need for modelling the non-Newtonian, shear-thinning rheology of blood, with equivocal results. Our study clarifies this issue by contextualizing the impact of rheology model against the recently demonstrated impact of CFD solution strategy on the prediction of aneurysm flow instabilities. Three aneurysm cases were considered, spanning a range of stable to unstable flows. Simulations were performed using a high-resolution/accuracy solution strategy with Newtonian and modified-Cross rheology models and compared against results from a so-called normal-resolution strategy. Time-averaged and instantaneous wall shear stress (WSS) distributions, as well as frequency content of flow instabilities and dome-averaged WSS metrics, were minimally affected by the rheology model, whereas numerical solution strategy had a demonstrably more marked impact when the rheology model was fixed. We show that point-wise normalization of non-Newtonian by Newtonian WSS values tended to artificially amplify small differences in WSS of questionable physiological relevance in already-low WSS regions, which might help to explain the disparity of opinions in the aneurysm CFD literature regarding the impact of non-Newtonian rheology. Toward the goal of more patient-specific aneurysm CFD, we conclude that attention seems better spent on solution strategy and other likely "first-order" effects (eg, lumen segmentation and choice of flow rates), as opposed to "second-order" effects such as rheology. Copyright © 2016 John Wiley & Sons, Ltd.

  8. Rheology and texture of doughs: applications on wheat and corn

    Directory of Open Access Journals (Sweden)

    Eduardo Rodríguez Sandoval

    2010-04-01

    Full Text Available A dough made of maylacceou materials shows a viscoelastic behavior, its macroestructural behavior depends on processing conditions, its constitutents and the interaction among them. Studies on dough rheology and texture are useful and important for applications that include ingredient specifications, quality control, product design and adaptation of new processing technologies. This work is a review of rheological and textural principles, testing methods and characteristics of wheat and com doughs.

  9. Rheology of the gelation process of silica gel

    OpenAIRE

    Filho, O. K.; Aegerter, Michel A.

    1988-01-01

    The rheology of silica sols prepared from mixtures of tetramethoxysilane (TMOS)-methanol-water under basic neutral conditions has been studied at 25, 40 and 60 ° C during the gelation process. The sols show non-Newtonian pseudoplastic behavior from the time of preparation with the appearance of yield stress near the gelation point. The results are analysed using rheological equations of state and the concept of the point of gelation is discussed. For neutral sols an apparent activation energy...

  10. Estudo reológico do vinho branco clarificado por membrana cerâmica = Rheological study of white wine clarified by ceramic membrane

    Directory of Open Access Journals (Sweden)

    Ricardo Cardoso de Oliveira

    2006-07-01

    Full Text Available Os processos de separação por membranas em fluxo tangencial têm se mostrado como uma alternativa em substituição as técnicas clássicas de filtração. Isso tem ocorrido pois esses processos eliminam os resíduos gerados pelo método convencional e combinam a clarificação, estabilização e a esterilização em uma operação contínua de filtração. Neste trabalho, teve-se como objetivo estudar o comportamento reológico do vinho branco submetido a uma clarificação com membrana cerâmica de diâmetro médio de poros de 0,05 μm a 2 bar e 20ºC nas amostras de alimentado, permeado e retido. Obteve-se uma considerável redução na turbidez e não foi constatada variação significativa nas demais análises físico-químicas realizadas a ponto de descaracterizar o vinho obtido. Notou-se nas amostras de alimentado, retido e permeado o comportamento reológico de fluído newtoniano.Membrane filtration is emerging as a rather promising technology for this purpose due to its ability to perform wine clarification/filtration/hygienization in one single step of continuous operation. This study aimed to evaluate the performance of a ceramic membrane with 0,05 mm at 2bar and 20ºC in the clarification of the white wine, and also to evaluate the rheology behavior ofwine in the samples of feed, permeated and retained. A great reduction in the turbidy was obtained and there was no significant variation in the other physical chemistry analyses accomplished to the point of affecting the features of the obtained wine. It was noticed that in the samples of feed, retained and permeated the rheological behavior of Newtonian fluid.

  11. Cooling of a channeled lava flow with non-Newtonian rheology: crust formation and surface radiance

    Directory of Open Access Journals (Sweden)

    Stefano Santini

    2011-12-01

    Full Text Available We present here the results from dynamical and thermal models that describe a channeled lava flow as it cools by radiation. In particular, the effects of power-law rheology and of the presence of bends in the flow are considered, as well as the formation of surface crust and lava tubes. On the basis of the thermal models, we analyze the assumptions implicit in the currently used formulae for evaluation of lava flow rates from satellite thermal imagery. Assuming a steady flow down an inclined rectangular channel, we solve numerically the equation of motion by the finite-volume method and a classical iterative solution. Our results show that the use of power-law rheology results in relevant differences in the average velocity and volume flow rate with respect to Newtonian rheology. Crust formation is strongly influenced by power-law rheology; in particular, the growth rate and the velocity profile inside the channel are strongly modified. In addition, channel curvature affects the flow dynamics and surface morphology. The size and shape of surface solid plates are controlled by competition between the shear stress and the crust yield strength: the degree of crust cover of the channel is studied as a function of the curvature. Simple formulae are currently used to relate the lava flow rate to the energy radiated by the lava flow as inferred from satellite thermal imagery. Such formulae are based on a specific model, and consequently, their validity is subject to the model assumptions. An analysis of these assumptions reveals that the current use of such formulae is not consistent with the model.

  12. Study on effect of rheological on stress and deformation of sand-gravel-fill dam%流变对面板砂砾石坝应力变形的影响研究

    Institute of Scientific and Technical Information of China (English)

    李阳; 任亮; 王瑞骏; 荆慧斌; 牛文龙; 郭兰春

    2014-01-01

    为研究砂砾石料流变对面板砂砾石坝应力变形的影响规律,在对砂砾石料的流变机理及其分析方法进行分析与选择的基础上,以某高面板砂砾石坝为例,运用三维有限元法,按不考虑砂砾石料流变效应和考虑砂砾石流变效应两种计算方案,分别进行其应力变形的三维有限元计算,然后通过对计算方案所获计算结果的对比分析,系统总结砂砾石料流变对面板砂砾石坝应力变形的影响规律。结果表明:砂砾石料流变使得坝体的应力变形呈现逐渐增大的趋势;流变对于坝体向上游水平位移的影响最大,对坝体向下游水平位移和坝体竖向位移的影响次之,对面板挠度和面板顺坡向应力的影响则相对较小。因此,在实际面板砂砾石坝工程设计中,考虑砂砾石料的流变效应是十分必要的。%The paper studied the law of influence of sand-gravel-fill rheology on stress deformation of CFRD.By means of analyzing and selecting the rheological mechanism and rheological analysis of the sand-gravel-fill,and combining with the engineering practice of concrete face sand-gravel-fill dam ,and u-sing three-dimensional nonlinear finite element method , the paper analyzed the effect of rheological on stress and deformation of the dam and used two calculation program of considering sand-gravel rheological effects or not .It then analyzed and compared the the results of two calculation program , and systematically summarized the effect of rheological on stress and deformation of dam .The results show that the rheology makes the stress and deformation of dam and the panel shows a tendency of increase .The effect of rheolo-gy on the displacement of upstream of dam is greater , and that on downstream and vertical displacement is lesser.The effect on panel deflection and panel stress along downslope is very small .Therefore, it is necessary to consider the rheological effect of sand

  13. Rheological and structural properties of differently acidified and renneted milk gels.

    Science.gov (United States)

    Liu, X T; Zhang, H; Wang, F; Luo, J; Guo, H Y; Ren, F Z

    2014-01-01

    In this study we assessed the rheological and structural properties of differently acidified and renneted milk gels by controlling pH value and renneting extent. Skim milk were exactly renneted to 4 extents (20, 35, 55, and 74%) and then direct acidified to the desired pH (4.8, 5.0, 5.2, 5.5, 5.8, and 6.2), respectively. Rheological properties were assessed by dynamic rheological measurements, structural properties were studied by spontaneous whey separation and confocal laser scanning micrograph, and protein interactions were studied by dissociation test. Results showed that minimally renneted milk samples (20 and 35%) formed weak gels with low storage modulus, and the acidification range within which gels could form was narrow (pH ≤ 5.2). Highly renneted milk samples formed more gels with high storage modulus. The results of this study revealed that acidification determined the structural properties of highly renneted milk gels. As pH increased from 5.0 to 6.2, highly renneted milk gels had lower loss tangent, decreased spontaneous syneresis, and smaller pores. For both the low and high rennetings, divalent calcium bonds contributed less at low pH than at high pH. In conclusion, renneting increased the pH range suitable for gel formation; acidification determined the spontaneous syneresis and microstructure of highly renneted milk gels.

  14. Role of interfacial rheological properties in oil field chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Lakatos-Szabo, J.; Lakatos, I.; Kosztin, B.

    1996-12-31

    Interfacial rheological properties of different Hungarian crude oil/water systems were determined in wide temperature and shear rate range and in presence of inorganic electrolytes, tensides, alkaline materials and polymers. The detailed laboratory study definitely proved that the interfacial rheological properties are extremely sensitive parameters towards the chemical composition of inmiscible formation liquids. Comparison and interpretation of the interfacial rheological properties may contribute significantly to extension of the weaponry of the reservoir characterization, better understanding of the displacement mechanism, development of the more profitable EOR/IOR methods, intensification of the surface technologies, optimization of the pipeline transportation and improvement of the refinery operations. It was evidenced that the interfacial rheology is an efficient and powerful detection technique, which may enhance the knowledge on formation, structure, properties and behaviour of interfacial layers. 17 refs., 18 figs., 2 tabs.

  15. Oral texture perception in relation to rheology for mayonnaise

    NARCIS (Netherlands)

    Terpstra, M.E.J.; Janssen, A.M.; Linden, van der E.; Wijk, de R.A.

    2004-01-01

    Sensory attributes of commercial mayonnaises have been correlated to rheological curves to obtain those measuring conditions that reflect the oral perception of specific (texture) attributes. Correlations are found mainly with data from flow curve measurements and from dynamic stress measurements ou

  16. Some advances in crude oil rheology and its application

    Institute of Scientific and Technical Information of China (English)

    张劲军; 柳歆

    2008-01-01

    Waxy crude oil exhibits complex shear-and-thermal-history-dependent non-Newtonian behaviors.In the past 10 years,driven by the petroleum industry,crude oil rheology has been an active field.Studies on crude oil rheology have been passing a way from simply relying on rheological measurements,through quantitative experimental simulation of shear and thermal history effects in pipelining,to recent development of correlation between flow properties and shear and thermal history.Currently,the study is toward quantitative inquiry of relations between the rheological behaviors and micro-structures of wax crystals as well as oil compositions.Advances achieved by the author’ team are summarized,including simulation of the thermal and shear history effects,correlations and computation of flow properties,fractal characterization of morphology and structure of wax crystals,relations of rheological behaviors to fractal dimension and oil compositions,and the most successful example of the application of rheology in crude oil pipelining.Future studies are prospected.

  17. Injectable Silica–Permanganate Gel as a Slow-Release MnO4- Source for Groundwater Remediation. Rheological Properties and Release Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Shuo; Oostrom, Martinus; Truex, Michael J.; Li, G.; Zhong, Lirong

    2016-01-12

    Injectable slow-release permanganate gel (ISRPG), formed by mixing KMnO4 solution with fumed silica powder, may have a potential application in remediating chlorinated solvent plumes in groundwater. A series of batch, column, and flow cell experiments has been completed to test the gel behavior under a variety of conditions. The experiments have provided information on ISRPG rheology, permanganate (MnO4- ) release dynamics and distribution, and trichloroethene (TCE) degradation by ISRPG-released oxidant. The gel possesses remarkable shear thinning characteristics, resulting in a relative low viscosity during mixing, and facilitating its subsurface injection and distribution. Batch tests revealed that MnO4- was diffused out from ISRPG into water while the gel did not dissolve or disperse into water but maintained its initial shape. Column experiments showed that MnO4- release from ISRPG lasted considerably longer than the release from aqueous solution. TCE degradation by ISRPG-released MnO4- was much more effective than that when MnO4- was delivered using aqueous solution injection. In two-dimensional flow cell experiments, it was demonstrated that ISRPG slowly released a long-lasting low concentration MnO4- plume sufficient for remediation and sustainable in an aquifer for a long period of time.

  18. Networking and rheology of concentrated clay suspensions "matured" in mineral medicinal water.

    Science.gov (United States)

    Aguzzi, Carola; Sánchez-Espejo, Rita; Cerezo, Pilar; Machado, José; Bonferoni, Cristina; Rossi, Silvia; Salcedo, Inmaculada; Viseras, César

    2013-09-10

    This work studied the influence of "maturation" conditions (time and agitation) on aggregation states, gel structure and rheological behaviour of a special kind of pharmaceutical semisolid products made of concentrated clay suspensions in mineral medicinal water. Maturation of the samples was carried out in distilled and sulphated mineral medicinal water, both in static conditions (without agitation) and with manual stirring once a week, during a maximum period of three months. At the measured pH interval (7.5-8.0), three-dimensional band-type networks resulting from face/face contacts were predominant in the laminar (disc-like) clay suspensions, whereas the fibrous (rod-like) particles formed micro-aggregates by van der Waals attractions. The high concentration of solids in the studied systems greatly determined their behaviour. Rod-like sepiolite particles tend to align the major axis in aggregates promoted by low shearing maturation, whereas aggregates of disc-like smectite particles did not have a preferential orientation and their complete swelling required long maturation time, being independent of stirring. Maturation of both kinds of suspensions resulted in improved rheological properties. Laminar clay suspensions became more structured with time, independently from static or dynamic maturation conditions, whereas for fibrous clay periodic agitation was also required. Rheological properties of the studied systems have been related to aggregation states and networking mechanisms, depending on the type of clay minerals constituents. Physical stability of the suspensions was not impaired by the specific composition of the Graena medicinal water.

  19. 新型可降解聚碳酸亚丙酯的动态流变性能%Dynamic Rheological Properties of Novel Biodegradable Poly(Propylene Carbonate) Plastics

    Institute of Scientific and Technical Information of China (English)

    石璞; 钟苗苗; 陈浪; 刘跃军

    2015-01-01

    The solvent residue, thermal stability and dynamic rheological properties of industrial grade Poly (propylene carbonate) (PPC) were characterized by Gas Chromatography (GC), Thermal Gravimetric analysis (TG), Rotational Rheom-eter and Melt Index Meter. The GC results showed that PPC contained 1.281wt%residual monomer propylene oxide. The TG results indicated poor processing thermal stability of PPC. The rotation rheological results further revealed poor processing thermal stability of PPC. The degradation of PPC was more intensified for great heat because of huge amounts of energy consumed in the friction processing of between the molecular chain. Therefore, the shear rate should not be too great for preventing serious degradation in characterization. The results of melt index indicated that under the requirements of the conventional processing, PPC had proper fluidity when the processing temperature reached 180℃. PPC manufacturers should reduce the molecular weight with the narrowing of molecular weight distribution to improve material flow and thus greatly reduce the difficulty in processing.%利用气相色谱(GC)仪、热重分析(TG)仪、旋转流变仪和熔融指数仪等,研究了工业级聚碳酸亚丙酯(PPC)的溶剂残留、热稳定性能和动态流变性能。GC结果表明,工业级PPC含有质量分数为1.281%的残留环氧丙烷单体;TG及旋转流变测试结果表明,材料的加工热稳定性能较差。同时,加工过程中分子链之间的摩擦内耗能极大,产热量极大,更易加剧其降解。因此,加工的剪切速率不可太大,否则降解严重。熔融指数测试结果表明:从常规加工的要求看,加工温度需要达到180℃才有合适的流动性。基于所得研究结果,建议生产厂商考虑适当减小PPC的分子量,并使其相对分子量分布变窄,以提高材料的流动性,这样可极大降低PPC的加工难度。

  20. Size-dependent rheology of type-I collagen networks.

    Science.gov (United States)

    Arevalo, Richard C; Urbach, Jeffrey S; Blair, Daniel L

    2010-10-20

    We investigate the system size-dependent rheological response of branched type I collagen gels. When subjected to a shear strain, the highly interconnected mesh dynamically reorients, resulting in overall stiffening of the network. When a continuous shear strain is applied to a collagen network, we observe that the local apparent modulus, in the strain-stiffening regime, is strongly dependent on the gel thickness. In addition, we demonstrate that the overall network failure is determined by the ratio of the gel thickness to the mesh size. These findings have broad implications for cell-matrix interactions, the interpretation of rheological tissue data, and the engineering of biomimetic scaffolds.

  1. A Comparative Study of Partial Replacement of Wheat Flour with Whey and Soy Protein on Rheological Properties of Dough and Cookie Quality

    Directory of Open Access Journals (Sweden)

    Xiaozhi Tang

    2017-01-01

    Full Text Available The development of wheat-based foods that are enriched with proteins is increasingly popular. The purpose of this study was to compare the effects of partial replacement of wheat flour with whey and soy proteins (0–30% on the rheological properties of dough and cookie-making quality. The incorporation of whey protein (WP diluted the concentration of gluten, leading to an increase in dough development time (MDT and breakdown torque and a decrease in stability time (MST and minimum torque (MMT. The gelation of WP during the heat treatment increased dough peak torque (MPT, G′, and G′′. As a contrast, the addition of soy protein (SP increased dough MST, MDT, and MMT. The aggregation of SP helped increase G′ and decrease tan δ of the dough in oscillatory shear tests. The weak gelling effects and higher water absorption of SP decreased MPT, G′, and G′′ of the dough during heat treatment. With SP, the spread ratio of cookies first decreased from 6.39 to 5.66 and then increased to 6.86, and the overall acceptability scores ranged from 6.62 to 7.02, indicating that the formed soy protein network helped maintain the dough structure for obtaining an improvement in the quality of bakery products.

  2. An experimental study of convective heat transfer, friction, and rheology for non-Newtonian fluids: Polymer solutions, suspensions of fibers, and suspensions of particulates

    Science.gov (United States)

    Matthys, E. F.

    The convective heat transfer, friction, and rheological properties of various types of nonNewtonian fluid in circular tube flows were investigated. If an apparent Reynolds number is used and if the temperature and degradation effects are properly taken into account, the reduced turbulent friction and heat transfer results, respectively, are then shown to be well correlated by the same expressions for different fluids, regardless of the nature of the fluids and whether they are shear-thinning or shear-thickening. This representation can also separate the reductions in turbulent heat transfer and friction that are induced by viscoelasticity from those induced by pseudoplasticity. Polyacrylamide solutions inducing asymptotic and intermediate drag reduction regimes were investigated over a broad range of Reynolds numbers. A kerosene-based antimisting polymer solution was also studied. Suspensions of bentonite of various concentrations were investigated in laminar and turbulent regimes, and the results for fully developed and entrance flows were well correlated by Newtonian relationships when an adequate wall viscosity concept was used.

  3. The Nonlinear Rheology of Electrorheological Fluids

    Science.gov (United States)

    Martin, James E.

    1998-03-01

    When a colloidal suspension is exposed to a uniaxial electric field the polarized particles chain along field lines causing a macroscopic "solidification" of the fluid, the basis of the so-called electrorheological (ER) effect. Likewise, in a rotating electric field particles form sheets in the plane of the field, which we call the rotary ER effect. Both of these fluids exhibit a nonlinear, shear thinning rheology, due to shear-induced structural relaxations. Because the fluid stress can be controlled by the applied field, a number of applications are possible, including electromechanical actuators, clutches, and active vibration dampers. To design these devices, and to develop effective control loop algorithms, it is necessary to understand the strongly nonlinear rheology of these fluids. We have used time-resolved, two-dimensional light scattering on a concentrated colloidal silica fluid in steady and oscillatory shear to demonstrate that the fragmentation and aggregation of chain-like particle microstructures is the cause of flow nonlinearities. We show that the light scattering is an indirect measure of the fluid stress. These observations form the basis of a kinetic chain model we developed to describe the nonlinear dynamics of the microstructures in ER fluids in nonstationary shear flows. Understanding the microstructural dynamics then leads us to a theory of the macroscopic rheology of these fluids in nonstationary, low Reynolds number flows. Finally, we have conducted extensive large-scale (1000-10000 particles) simulations of these fluids in steady and oscillatory shear, and will compare these results to theory and experiment.

  4. Impact of Water on Rheological Behavior of Polyurethane Glues

    Directory of Open Access Journals (Sweden)

    Laiveniece Laura

    2016-06-01

    Full Text Available Gluing of wood with great moisture content has challenge of water interaction with glue to give unwanted changes in glue properties and formed bond-line. Rheological measurements of polyurethane glues are sufficiently effective method to understand the polymer curing process and viscoelastic properties. Gel formation point is important parameter for a glue from the point of its application. When glue reaches the gel formation point, its viscosity drastically increases so that it could not properly wet the wood and it can result in poor bonds. One-component moisture curing polyurethane glues require water molecules for the polyadditional reaction. When water is involved in the curing reaction, it reacts with the isocyanate groups of glue and can lead to the formation of excessive carbon dioxide and thus can lead to glue penetration out of bond-line, additional backpressure. The dynamic viscoelastic parameters such as complex dynamic viscosity (ή, phase angle (δ, elastic storage modulus (G”, the viscous loss modulus (G” of two kinds of polyurethane glues depending on added water amount (from 0.9% to 10.0% at a constant frequency and deformation (oscillation mode were determined using rheometer. The aim of the present study was to investigate impact of added water on rheological behavior of polyurethane glues. At the end of this study it was concluded that tested glues indicated various behavior depending on chemical composition and added water content. Gel formation point is higher in case of GlueI. However, gel formation time was higher in case of GlueII and was not dependent on added water content. Gel formation time was faster for GlueII. Nevertheless, faster formed gel is stronger than longer formed gel of GlueI.

  5. Rheological behaviour of heated potato starch dispersions

    Science.gov (United States)

    Juszczak, L.; Witczak, M.; Ziêba, T.; Fortuna, T.

    2012-10-01

    The study was designed to investigate the rheological properties of heated potato starch dispersions. Water suspensions of starch were heated at 65, 80 or 95°C for 5, 15, 30 or 60 min. The dispersions obtained were examined for granule size distribution and rheology. It was found that the starch dispersions significantly differed in both respects. The mean diameters of starch granules were largest for the dispersion heated at 65°C and smallest for that heated at 95°C. As the heating temperature was raised, the yield stresses and consistency coefficients decreased, while the flow behaviour indexes and Casson plastic viscosities increased. There were also differences in the viscoelastic properties of the dispersions: for those heated at 65°C the storage and loss moduli increased with heating time whereas for those heated at 80°C both moduli decreased.

  6. Introduction to Rheology for Ultrasonic Engineers

    Science.gov (United States)

    Ueda, Takanobu

    2008-05-01

    Here, I introduce the fundamental concept and methodology of rheology measurement especially to researchers in the field of ultrasonic engineering. Althogh we consider the material as fluid and characterize it in terms of viscosity accompanied by its complex part representing elasticity, ultrasonic spectroscopy regards the material as solid with elasticity, which determines ultrasonic velocity. Although these two research fields have contrary viewpoints, they share the purpose of the study, that is, to characterize the mechanical properties of the material as a function of frequency or shear rate and to reveal its mechanism and structure at the molecular level. In this paper, I show the basic methods of rheology measurement and analysis in relation to ultrasonic technology.

  7. Nonlinear rheology of entangled polymers at turning point.

    Science.gov (United States)

    Wang, Shi-Qing

    2015-02-28

    Thanks to extensive observations of strain localization upon startup or after stepwise shear, a conceptual framework for nonlinear rheology of entangled polymers appears to have emerged that has led to discovery of many new phenomena, which were not previously predicted by the standard tube model. On the other hand, the published theoretical and experimental attempts to test the limits of the tube model have largely demonstrated that the most experimental data appear consistent with the tube-model based theoretical calculations. Therefore, the field of nonlinear rheology of entangled polymers is at a turning point and is thus a rather crucial area in which further examinations are needed. In particular, more molecular dynamics simulations are needed to delineate the detailed molecular mechanisms for the various nonlinear rheological phenomena.

  8. Molecular rheological analysis on binary blends of perfluoropolyether lubricants

    Science.gov (United States)

    Seung Chung, Pil; Hari Vemuri, Sesha; Park, Sejoon; Jhon, Myung S.

    2014-05-01

    The molecular rheology of PFPE becomes critically important in designing optimal lubricants that control the friction/wear and air-bearing by tuning elastic or viscous shear/elongation deformations, which affect the performance and reliability of the hard disk drive. In this paper, we examine the rheological responses of nano blended PFPEs including storage (elastic) and loss (viscous) moduli (G' and G″), by monitoring the time-dependent-stress-strain relationship via non-equilibrium molecular dynamics simulations. By introducing binary blend of nonfunctional and functional PFPEs, we control the degree of liquid/solid-like behavior using the rheology as a complementary tool for design criteria by tuning molecular conformation and diffusion with nano blend ratio.

  9. Rheology of fractal networks

    CERN Document Server

    Patricio, Pedro; Duarte, Jorge; Januario, Cristina

    2015-01-01

    We investigate the rheology of a fractal network, in the framework of the linear theory of viscoelasticity. We identify each segment of the network with a simple Kelvin-Voigt element, with a well defined equilibrium length. The final structure retains the elastic characteristics of a solid or a gel. By considering a very simple regular self-similar structure of segments in series and in parallel, in 1, 2 or 3 dimensions, we are able to express the viscoelasticity of the network as an effective generalised Kelvin-Voigt model with a power law spectrum of retardation times, $\\phi\\sim\\tau^{\\alpha-1}$. We relate the parameter $\\alpha$ with the fractal dimension of the gel. In some regimes ($0<\\alpha<1$), we recover the weak power law behaviours of the elastic and viscous moduli with the angular frequencies, $G'\\sim G''\\sim w^\\alpha$, that occur in a variety of soft materials, including living cells. In other regimes, we find different and interesting power laws for $G'$ and $G''$.

  10. Rheological approach to targeting phenomena of lipoplexes.

    Science.gov (United States)

    Sun, Yan

    2011-12-01

    Lipoplexes, the complexes of plasmid DNA with cationic lipids, are considered as an attractive alternative to viral delivery systems. However, synthesized lipoplexes showed several limitations including insufficient transfection, low reproducibility and low stability. Here we attempt to delineate the relationships between the synthesis process, morphology (e.g., shape and liquid crystal structure), and the transfection efficiency of lipoplexes with rheological technology. Mini-capillary viscometers with automatic measurement and control components were designed and used to study the morphology of lipoplexes at a macroscopical scale. In such a dilute macromolecule suspension system, the shape factor of lipoplex was correlated with the viscosity measurement. The results showed that the shape factors of lipoplexes were different with various molecular structures of cationic lipid and helper lipid. A quantitative relation was set up between the shape factors and the length of DNA/polyelectrolytes, which may help better explain lipoplexes formation. To improve the stability and reproducibility of lipoplexes, an incubation period was suggested before the use of lipoplex. A rheological method was introduced to fix the hydromechanical parameters so that the entire preparation and incubation process was carried out consistently. A laminar flow incubation environment was showed suitable for lipoplex preparation and helped improve lipoplex stability and minimize aggregation. Other flow incubations, such as turbulent flow or impinging flow, were more complicated and further study is necessary to fully understand them. In brief, the rheological methods can help reveal the mechanisms of lipoplex formation and advance the rational design of lipoplexes for pharmaceutical applications.

  11. Evolution of the rheological structure of Mars

    Science.gov (United States)

    Azuma, Shintaro; Katayama, Ikuo

    2017-01-01

    The evolution of Mars has been greatly influenced by temporal changes in its rheological structure, which may explain the difference in tectonics between Mars and Earth. Some previous studies have shown the rheological structures of Mars calculated from the flow law of rocks and the predicted thermal structure. However, the Peierls mechanism, which is the dominant deformation mechanism at relatively low temperature, and the evolution of water reservoirs on Mars were not considered in such studies. In this paper, we apply the Peierls mechanism to refine the rheological structure of Mars to show a new history of the planet that considers the most recent reports on its evolution of water reservoirs. Considering the Peierls creep and the evolution of water reservoirs, we attempt to explain why the tectonics of Mars is inactive compared with that of Earth. On early Mars, the lithospheric thickness inferred from the brittle-ductile transition was small, and the lithospheric strength was low ( 200-300 MPa) under wet conditions at 4 Gya. This suggests that plate boundaries could have developed on the early "wet" Mars, which is a prerequisite for the operation of plate tectonics. Our results also imply that the lithospheric strength had significantly increased in the Noachian owing to water loss. Therefore, plate tectonics may have ceased or could no longer be initiated on Mars. At the least, the tectonic style of Mars would have dramatically changed during the Noachian.[Figure not available: see fulltext.

  12. Study on effects of pH and salt on the rheological properties of CMC%pH及盐对CMC流变特性的影响研究

    Institute of Scientific and Technical Information of China (English)

    吴伟都; 王雅琼; 朱慧; 李言郡; 施文蓉

    2012-01-01

    The effect of citric acid and lactic acid on the basis of different pH on the rheological properties of CMC solution were studied with the method of monofactorial five-level variance analysis.The results show that different acid has no significant effect on the zero-shearing viscosity,viscosity,viscosity damping,elasticity modulus,viscous modulus and dynamic viscosity as well on the level when α equals to 0.05.When pH was below 6,other properties declined obviously except viscosity damping,while pH was greater than 6(included),pH had no visible effect on all the properties.Meanwhile,the effect of different concentration of sodium citrate and sodium tripolyphosphate on the rheological properties of CMC solution were also studied.The results show that on the level when α equals to 0.05,the concentration of sodium citrate had significant effect on other properties except viscosity damping and that of sodium tripolyphosphate had significant effect on other properties except viscosity damping and viscoelasticity ratio,while there was no difference between sodium citrate and sodium tripolyphosphate.In addition,zero-shearing viscosity,viscosity,dynamic viscosity,elasticity modulus and viscous modulus highly correlate to the concentration of salt and a series of equations are obtained by the way of equation fitting.%应用单因素五水平方差分析法,研究柠檬酸及乳酸不同pH对CMC溶液流变特性的影响。结果表明,在α=0.05水平不同酸对零剪切黏度、黏度、黏度衰减、弹性模量、黏性模量及复合黏度无明显差异;pH≥6时pH对各特性指标无明显影响,pH〈6时随pH下降除黏度衰减减弱外,其余各特性指标出现明显下降。另外,应用单因素六水平方差分析法研究不同柠檬酸钠及不同三聚磷酸钠含量对CMC流变特性的影响,结果表明,在α=0.05水平不同柠檬酸钠浓度除黏度衰减外对其余指标有明显影响,不同三聚磷酸钠浓度除黏度衰减及损耗

  13. The rheology of icy satellites

    Science.gov (United States)

    Sammis, C. G.

    1984-01-01

    High-temperature creep in orthoenstatite under conditions of controlled oxygen fugacity was studied. It was found that creep was conttrolled by the extremely thin layer of SiO2 which wetted the grain boundaries. Slight reduction of the (Mg, Fe)SiO3 enstatite during hot pressing produced microscopic particles of Fe and the thin film of intergranular SiO2. This result highlights another complication in determining the flow properties of iron bearing silicates which constitute the bulk of terrestrial planets and moons. The Phenomenon may be important in the ductile formation of any extraterrestrial body which is formed in a reducing environment. The rheology of dirty ice was studied. This involves micromechanical modeling of hardening phenomena due to contamination by a cosmic distribution of silicate particles. The larger particles are modeled by suspension theory. In order to handle the distribution of particles sizes, the hardening is readed as a critical phenomenon, and real space renormalization group techniques are used. Smaller particles interact directly with the dislocations. The particulate hardening effect was studied in metals. The magnitude of such hardening in ice and the defect chemistry of ice are studied to assess the effects of chemical contamination by methane, ammonia, or other likely contaminants.

  14. Numerical analysis of rheological and tribological behavior influence on 16MnCr5 forging fibering

    Science.gov (United States)

    Gavrus, A.; Pintilie, D.; Nedelcu, R.

    2016-10-01

    The present research work is focus on the influence of the rheological constitutive equation and friction law formulation on 16MnCr5 forging fibering. Numerical analysis using FE Forge® and Abaqus code show the importance of the rheological softening terms on the metals fibers morphology and position coordinate. Calibration of friction law and sensitivity of softening parameters corresponding to a Hansel-Spittel rheological equation have been studied.

  15. Rheological behaviour of egg white and egg yolk from different poultry specimen

    Science.gov (United States)

    Kumbár, V.; Nedomová, Š.; Votava, J.; Buchar, J.

    2017-01-01

    The main goal of this study is differences in rheological behaviour of hen (ISA BROWN), goose (Anser anser f. domestica) and Japanese quail (Coturnix japonica) egg white and egg yolk. The rheological behaviour of egg white and egg yolk was studied using a concentric cylinder viscometer. Rheological behaviour was pseudoplastic and flow curves were fitted by the Herschel-Bulkley model and Ostwald-de Waele model with high values of coeficients of determination R2. The meaning of rheological parameters on friction factors during flow of egg white and egg yolk in real tube has been shown. Preliminary information on time-dependent behaviour of tested liquids has been also obtained.

  16. Effect of Ultraviolet Aging on Rheology and Chemistry of LDH-Modified Bitumen

    OpenAIRE

    Xing Liu; Shaopeng Wu; Gang Liu; Liping Li

    2015-01-01

    Layered double hydroxides (LDHs) are an ultravioletlight (UV)-resistant material. In this study, two types of LDHs (Mg-Al-LDHs and Zn-Al-LDHs) were applied to modify bitumen by melt-blending. The effect of ultraviolet aging on the rheology and chemistry of LDH-modified bitumen was studied by means of dynamic shear rheometer (DSR), thin-layer chromatography with flame ionization detection (TLC-FID), Fourier transform infrared spectroscopy (FTIR), and Ultraviolet-Visible (UV-Vis) spectrophotome...

  17. Properties of starch-polyglutamic acid (PGA) graft copolymer prepared by microwave irradiation - Fourier transform infrared spectroscopy (FTIR) and rheology studies

    Science.gov (United States)

    The rheological properties of waxy starch-'-polygutamic acid (PGA) graft copolymers were investigated. Grafting was confirmed by FTIR spectroscopy. The starch-PGA copolymers absorbed water and formed gels, which exhibited concentration-dependent viscoelastic solid properties. Higher starch-PGA conce...

  18. Variation and trends in dough rheological properties and flour quality in 330 Chinese wheat varieties

    Directory of Open Access Journals (Sweden)

    Xiushi Yang

    2014-08-01

    Full Text Available The objective of this study was to investigate variation and trends in dough rheological properties and flour quality traits in 330 Chinese wheat varieties. The dough rheological properties of development time (DT, stability time (ST, and farinograph quality number (FQN were evaluated, as well as the flour quality traits of protein (PC, wet gluten content (WGC, and sedimentation value (SV. The coefficients of variation of DT (40.5%, ST (58.1%, and FQN (42.4% were higher than those of PC (9.1%, WGC (10.1%, and SV (15.3%. Normal distributions were observed for the flour quality indices but not for the rheological parameters. SV was strongly correlated with the three rheological parameters and accordingly might be used as a primary indicator for dough rheological property evaluation. Our results showed that there has been marked improvement in dough rheological properties for Chinese wheat varieties released since 1986, while flour quality has remained stable.

  19. Laser speckle micro rheology for micro-mechanical mapping of bio-materials (Conference Presentation)

    Science.gov (United States)

    Hajjarian Kashany, Zeinab; Ahn, Shawn; Tavakoli Nia, Hadi; Tshikudi, Diane M.; Grodzinsky, Alan; Jain, Rakesh K.; Nadkarni, Seemantini K.

    2016-03-01

    Laser speckle Micro-rheology (LSM) is a novel optical tool for evaluating the viscoelastic properties of biomaterials. In LSM, a laser beam illuminates the specimen and scattered rays are collected through an objective by a high-speed CMOS camera. The self-interference of light rays forms a fluctuating speckle pattern captured by the CMOS sensor. Spatio-temporal correlation analysis of speckle images provides the intensity autocorrelation function, g2(t), for individual pixels. Next, the mean square displacements (MSD) of Brownian particles are deduced and substituted in the generalized Stokes-Einstein relation (GSER) to yield a 2D map of viscoelastic modulus, |G*(ω)|. To compare the accuracy, sensitivity, and dynamic range of LSM measurements with standard mechanical testing methods, homogeneous polyethylene glycol (PEG), agarose, and polyacrylamide (PA) gels, of assorted viscoelastic properties were fabricated and evaluated using LSM, shear rheology, and indentation-mode atomic force microscopy (AFM). Results showed a statistically significant, strong correlation between G* values measured by LSM and shear rheology (R=0.94, pscale stiffness patterns were tested using LSM. The reconstructed |G*| maps illustrated the high sensitivity of LSM in resolving mechanical heterogeneities below 100 microns. These findings demonstrate the competent accuracy and sensitivity of LSM measurements. Moreover, the non-contact nature of LSM provides a major advantage over mechanical tests, making it suitable for in vivo studies in future.

  20. Rheological and microstructural properties of porcine myofibrillar protein-lipid emulsion composite gels.

    Science.gov (United States)

    Wu, Mangang; Xiong, Youling L; Chen, Jie; Tang, Xueyan; Zhou, Guanghong

    2009-01-01

    The objective of the study was to investigate the role of emulsified fat (lard) and oil (peanut oil) in the rheology and microstructure of porcine myofibrillar protein (MP) gels. Heat-induced composite gels were prepared from 2% MP with 0% to 15% pre-emulsified lipids at 0.6 M NaCl, pH 6.2. Dynamic rheological testing upon temperature sweeping (20 to 80 degrees C at 2 degrees C/min) showed substantial increases in G' (an elastic modulus) of MP sols/gels with the addition of emulsions. Gel hardness was markedly enhanced (P or=10% emulsions, and the composite gel with 15% lard was 33% more rigid (P gels by 28% to 44% (P gel structure filled with protein-coated fat/oil globules that interacted with the protein matrix via disulfide bonds. The results indicated that both physical and chemical forces contributed to the enhancements in the rheology, moisture retention, and lipid stabilization in the MP-emulsion composite gels.

  1. Effect of pH on the rheological response of reconstituted gastric mucin

    Directory of Open Access Journals (Sweden)

    Jonathan Argenis Caicedo

    2015-08-01

    Full Text Available The rheological response of reconstituted gastric mucin was studied by time dependent rheological experiments as function of pH. Mucin concentrations of 5% and 10% were prepared in buffer dispersions at pH of 1.15, 2.00, 2.55, 4.00 and 7.67.  The isoelectric point was identified by z-potential between pH 2.00 to 2.55. Dynamic light scattering showed that as pH reduced, a second population of larger mucin aggregates was formed indicating the presence of new structures. Steady shear rheological measurements reflected the pseudoplastic behavior of mucin dispersions and the effect of concentration on viscosity. Creep-recovery measurements were performed on the regenerated mucus at different levels of pH. By creep, it was possible to determine the values of zero-shear-viscosity of mucin suspensions, with higher precision and in a lower experimental time than steady shear measurements. Additionally, it was found that at pH ~1.15, the viscosity of the mucus increased to high values, which is an indicative of a gel-like structure. By recovery experiments, it was possible to find that even the very low viscosities the mucin suspensions at pH ~1.15 possessed a defined elastic character. By the use of a four-element mechanistic viscoelastic model, it was concluded that this elasticity underwent retardation due to the combined effect of viscous and elastic responses.

  2. Mechanical, morphological and rheological properties of polyamide 6/organo-montmorillonite nanocomposites

    Directory of Open Access Journals (Sweden)

    2007-02-01

    Full Text Available Polyamide (PA6 nanocomposites containing 4wt% organo-montmorillonite (OMMT were melt-compounded followed by injection molding. The mechanical properties of the PA6/OMMT nanocomposites were studied through tensile and flexural tests. The rheological behaviour of the nanocomposites was determined by plate/plate rheological measurements. Attempts were made to trace the rheological parameters that reliably reflect the observed changes in the clay dispersion. X-ray diffraction (XRD and atomic force microscopy (AFM were used to characterize the exfoliation and dispersion of the OMMT in the PA6 matrix. The thermal properties of PA6/OMMT nanocomposite were characterized by Dynamic Mechanical Thermal Analysis (DMTA. The tensile modulus and strength of the PA6 was increased in the presence of OMMT. The flexural strength of PA6/OMMT was approximately doubled compared to the tensile strength value. The significant enhancement of both tensile and flexural strength was attributed to the delaminated clay formation. XRD and AFM results revealed the formation of PA6 nanocomposites as the OMMT was successfully exfoliated.

  3. PHYSICOCHEMICAL AND RHEOLOGICAL CHARACTERIZATION OF AVOCADO OILS

    Directory of Open Access Journals (Sweden)

    Tamara de Souza Jorge

    2015-08-01

    Full Text Available Avocado oil is rich in bioactive compounds, which can improve human health by acting as an antioxidant. It may be extracted from different varieties of avocado, such as Margarida and Hass varieties, each of them with particular characteristics. Aiming to evaluate the differences between them, avocado fruits and pulps from these were analyzed according to their physicochemical characteristics. After extracted, the oils had their bioactive characteristics studied and rheological behavior determined through a rotational rheometer. They were then compared to commercial avocado oil. The fruits of Margarida variety had greater size, higher weight (664.51 g, and higher pulp yield (72.19% than Hass variety, which showed higher lipid content (65.29 g/100 g dry basis. The commercial oil showed less primary oxidative degradation, whereas Margarida variety had a lower level of secondary degradation products as well as a higher content of bioactive compounds, such as phytosterols (999.60 mg/kg and tocopherols (36.73 mg/kg. The rheological behaviors of both oils were appropriately described through Newton model, with R2 > 0.999 for all temperatures. By an Arrhenius type equation, it was verified that Hass's rheological parameters are more influenced by temperature than Margarida and commercial oil, presenting activation energy of 33.6 kJ/mol.

  4. Rheology of nanocrystalline cellulose aqueous suspensions.

    Science.gov (United States)

    Shafiei-Sabet, Sadaf; Hamad, Wadood Y; Hatzikiriakos, Savvas G

    2012-12-11

    The rheological properties and microstructure of nanocrystalline cellulose (NCC) aqueous suspensions have been investigated at different concentrations. The suspension is isotropic up to 3 wt %, and phase separates to liquid crystalline and isotropic domains at higher concentrations where the samples exhibit a fingerprint texture and the viscosity profile shows a three-region behavior, typical of liquid crystals. The suspension behaves as a rheological gel at even higher concentrations where the viscosity profile shows a single shear thinning behavior over the whole range of shear rates investigated. The effects of ultrasound energy and temperature on the rheological properties and structure of these suspensions were studied using polarized optical microscopy and rheometry. Our results indicate that the amount of applied ultrasound energy affects the microstructure of the suspensions and the pitch of the chiral nematic domains. The viscosity profile is changed significantly at low shear rates, whereas the viscosity of biphasic suspensions at intermediate and high shear rates decreased with increasing temperature. This suggests that, between 30 and 40 °C, structural rearrangement takes place. At higher concentrations of about 10 wt %, the temperature has no significant effect on viscosity; however, a marked increase in viscosity has been observed at around 50 °C. Finally, the Cox-Merz rule was found to fail after a critical concentration, thereby implying significant structural formation. This critical concentration is much higher for sonicated compared to unsonicated suspensions.

  5. Linear and Nonlinear Rheology Combined with Dielectric Spectroscopy of Hybrid Polymer Nanocomposites for Semiconductive Applications

    Directory of Open Access Journals (Sweden)

    Roland Kádár

    2017-01-01

    Full Text Available The linear and nonlinear oscillatory shear, extensional and combined rheology-dielectric spectroscopy of hybrid polymer nanocomposites for semiconductive applications were investigated in this study. The main focus was the influence of processing conditions on percolated poly(ethylene-butyl acrylate (EBA nanocomposite hybrids containing graphite nanoplatelets (GnP and carbon black (CB. The rheological response of the samples was interpreted in terms of dispersion properties, filler distortion from processing, filler percolation, as well as the filler orientation and distribution dynamics inside the matrix. Evidence of the influence of dispersion properties was found in linear viscoelastic dynamic frequency sweeps, while the percolation of the nanocomposites was detected in nonlinearities developed in dynamic strain sweeps. Using extensional rheology, hybrid samples with better dispersion properties lead to a more pronounced strain hardening behavior, while samples with a higher volume percentage of fillers caused a drastic reduction in strain hardening. The rheo-dielectric time-dependent response showed that in the case of nanocomposites containing only GnP, the orientation dynamics leads to non-conductive samples. However, in the case of hybrids, the orientation of the GnP could be offset by the dispersing of the CB to bridge the nanoplatelets. The results were interpreted in the framework of a dual PE-BA model, where the fillers would be concentrated mainly in the BA regions. Furthermore, better dispersed hybrids obtained using mixing screws at the expense of filler distortion via extrusion processing history were emphasized through the rheo-dielectric tests.

  6. Fault rheology beyond frictional melting.

    Science.gov (United States)

    Lavallée, Yan; Hirose, Takehiro; Kendrick, Jackie E; Hess, Kai-Uwe; Dingwell, Donald B

    2015-07-28

    During earthquakes, comminution and frictional heating both contribute to the dissipation of stored energy. With sufficient dissipative heating, melting processes can ensue, yielding the production of frictional melts or "pseudotachylytes." It is commonly assumed that the Newtonian viscosities of such melts control subsequent fault slip resistance. Rock melts, however, are viscoelastic bodies, and, at high strain rates, they exhibit evidence of a glass transition. Here, we present the results of high-velocity friction experiments on a well-characterized melt that demonstrate how slip in melt-bearing faults can be governed by brittle fragmentation phenomena encountered at the glass transition. Slip analysis using models that incorporate viscoelastic responses indicates that even in the presence of melt, slip persists in the solid state until sufficient heat is generated to reduce the viscosity and allow remobilization in the liquid state. Where a rock is present next to the melt, we note that wear of the crystalline wall rock by liquid fragmentation and agglutination also contributes to the brittle component of these experimentally generated pseudotachylytes. We conclude that in the case of pseudotachylyte generation during an earthquake, slip even beyond the onset of frictional melting is not controlled merely by viscosity but rather by an interplay of viscoelastic forces around the glass transition, which involves a response in the brittle/solid regime of these rock melts. We warn of the inadequacy of simple Newtonian viscous analyses and call for the application of more realistic rheological interpretation of pseudotachylyte-bearing fault systems in the evaluation and prediction of their slip dynamics.

  7. Vibrational spectroscopy to support the link between rheology and continuous twin-screw melt granulation on molecular level: A case study.

    Science.gov (United States)

    Monteyne, Tinne; Heeze, Liza; Oldörp, Klaus; Vervaet, Chris; Remon, Jean-Paul; De Beer, Thomas

    2016-06-01

    Twin screw hot melt granulation (TSHMG) is an innovative and continuous drug formulation process allowing granulation of moisture sensitive drugs. However, due to the lack of experience and in-depth process understanding, this technique is not yet widely used. During the TSHMG process, the microstructure of the granules is generated and modified and strongly depends on the flow behavior of the material. Hence, rheology might be a suitable tool to simulate and examine this process. However, chemical interactions of the material are influencing the physical properties leading to the microstructure. In this research project it is spectroscopically investigated whether the heat applied in a rheometer induces the same molecular effects as these occurring during TSHMG of the model formulation caffeine anhydrous/Soluplus®. Hence, it is evaluated whether rheology can be used as a simulation tool to improve the understanding of the material behavior at molecular level during continuous melt granulation. Therefore, in-line Raman spectroscopy is executed during TSHMG and in situ Fourier Transform Infra-red (FTIR) during oscillatory rheological experiments. The results from the in-line Raman monitoring revealed polymorph transition of caffeine anhydrous during twin screw melt granulation with Soluplus® which is stimulated depending on the binder concentration and/or granulation temperature. A correlation was seen between the FTIR spectra obtained during the rheological temperature ramp and the in-line collected Raman spectra during the melt granulation runs. The polymorphic conversion of caffeine anhydrous could be detected in the same temperature range with both techniques, proving the comparability of plate-plate rheometry and hot melt granulation (HMG) for this case with the used parameter settings. Process simulation using rheology combined with in situ FTIR seems a promising approach to increase process understanding and to facilitate binder and parameter selection for

  8. [Development of technology, of rheological and biopharmaceutical properties of new gel].

    Science.gov (United States)

    Mekhralieva, S Dzh

    2013-04-01

    The purpose of this research is the development of technology for preparation of hydrogel Glysotrical and study its rheological and biopharmaceutical characteristics. Based on gel-forming chitosan, PEG-400, glycerol and Tween-80 a new composition of hydrogel - Glysotrical was developed. Rheological properties of Glysotrical, as well as biopharmaceutical properties of artificial (cellophane) and natural membrane (chicken and pork skin) were investigated by dialysis. Rheological properties of different concentrations of chitosan solution and gel Glysotrical prepared on their basis were studied. It was determined that gel derived from the 5% solution of chitosan meets the technological requirements (pH-5,5-6,0, melting point-75,0±1,07°C, dynamic viscosity - 890,6 ± 3,57 cps). Rheological properties of the hydrogel Glysotrical, prepared on the basis of a multi-component composition in different temperatures (20, 40, 60°C) were identified. It was found that shear of helium drug (458 H/m2, 355 H/m2) at 20° and 40°C is lower, and the value of dynamic viscosity (912spz, 602spz) higher than that of chitosan gel; the hydrogel is stable at 20° and 40°C. High kinetic activity of hydrogel with Tween-80 is observed. During 5 hours membrane maximum quantity of routine diffusion from helium mass into dialysate in cellophane is 57,54 ±0,51%; in normal skin chicken - 20,04±0,55%; in the skin of chicken treated with 2% citric acid - 23,14±0,45%; normal pig skin - 12,64±0,09%; in the skin of pigs, treated with acid - 15,08± 0,11%. The study showed that the gel Glysotrical at 10-22°C is maintained for 2 years. Physico-chemical, rheological, technological and biopharmaceutical research showed that 4% gel Glysotrical was good in treatment of dermatological diseases.

  9. Atomic dynamics of alumina melt: A molecular dynamics simulation study

    Directory of Open Access Journals (Sweden)

    S.Jahn

    2008-03-01

    Full Text Available The atomic dynamics of Al2O3 melt are studied by molecular dynamics simulation. The particle interactions are described by an advanced ionic interaction model that includes polarization effects and ionic shape deformations. The model has been shown to reproduce accurately the static structure factors S(Q from neutron and x-ray diffraction and the dynamic structure factor S(Q,ω from inelastic x-ray scattering. Analysis of the partial dynamic structure factors shows inelastic features in the spectra up to momentum transfers, Q, close to the principal peaks of partial static structure factors. The broadening of the Brillouin line widths is discussed in terms of a frequency dependent viscosity η(ω.

  10. Extraction of passion fruit seed oil using supercritical CO2: a study of mass transfer and rheological property by Bayesian inference

    Directory of Open Access Journals (Sweden)

    Cardoso de Oliveira, R.

    2013-09-01

    Full Text Available The extraction of oil from passion fruit seeds using supercritical CO2 was studied. Experimental data were obtained for extraction conducted at 15, 20 and 25 MPa; at temperatures of 40 and 50 °C with CO2 flow rates of 1.5 and 3.0 mL min–1. An increase in the pressure, temperature and CO2 flow rate increased the yield. The maximum extraction yield obtained was 18.5%. The mass transfer coefficients for passion fruit oil were found to be 8.496 3 10-5 s-1 at 25 MPa, 50 °C and 3 mL s–1 CO2 flow rate. Dilatant fluid behavior was observed in all tests of the rheological study.Se ha estudiado la extracción de aceite de semillas de frutos de la pasión con CO2 supercrítico. Los datos experimentales se obtuvieron para una extracción llevada a cabo a 15, 20 y 25 MPa; a temperaturas de 40 y 50 °C y a flujos de CO2 de 1,5 y 3,0 mL min–1. Un incremento de la presión, la temperatura y del flujo de CO2 aumentó el rendimiento. El máximo rendimiento de la extracción obtenida fue de 18,5%. Los coeficientes de transferencia de masa para el aceite de fruta de la pasión encontrados fueron 8,496 3 10-5 s–1 a 25 MPa, 50 °C y 3 mL s–1 de flujo de CO2. Se observó un comportamiento de fluido dilatante en todos los ensayos reológicos.

  11. 紫甘薯浓缩汁的流变特性研究%Study on the Rheological Properties of Concentrated Purple Sweet Potato juice

    Institute of Scientific and Technical Information of China (English)

    张涛; 吕晓玲; 李津; 杨雪吟

    2012-01-01

    Rheological properties of Purple Sweet Potato concentrated juice were studied at different temperature(25 ℃,50 ℃,75 ℃) and different concentration(10°Brix,20°Brix,30°Brix,40°Brix,50°Brix,60°Brix) by the rheometer CV-Ⅲ+.The results showed that within the study of temperature and concentration framework,the purple sweet potato concentrated juice was the Newtonian fluid;Through regression analysis showed that: the effect of temperature on viscosity could be described by Arrhenius type equation,the effect of concentration on viscosity could be described by an Index type equation;and the equation used to describe combined effect of temperature and concentration on viscosity of concentrated purple sweet potato juice was established.%采用CV-Ⅲ+型数字流变仪对不同温度(25℃,50℃,75℃)和不同浓度(10°Brix,20°Brix,30°Brix,40°Brix,50°Brix,60°Brix)下的紫甘薯浓缩汁的流变特性进行了研究,结果表明:在所研究的温度和浓度范围内,紫甘薯浓缩汁为牛顿流体;回归分析表明,温度对粘度的影响符合Arrhenius方程,浓度对粘度的影响可以用指数方程更准确的表示,并依此推导并验证了温度和浓度对紫甘薯浓缩汁粘度综合影响的方程模型。

  12. Rheological Behavior of Xanthan Gum Solution Related to Shear Thinning Fluid Delivery for Subsurface Remediation

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Lirong; Oostrom, Martinus; Truex, Michael J.; Vermeul, Vincent R.; Szecsody, James E.

    2013-01-15

    Xanthan gum, a biopolymer, forms shear thinning fluids which can be used as delivery media to improve the distribution of remedial amendments injected into heterogeneous subsurface environments. The rheological behavior of the shear thinning solution needs to be known to develop an appropriate design for field injection. In this study, the rheological properties of xanthan gum solutions were obtained under various chemical and environmental conditions relevant to delivery of remedial amendments to groundwater. Higher xanthan concentration raised the absolute solution viscosity and increased the degree of shear thinning. Addition of remedial amendments (e.g., phosphate, sodium lactate, ethyl lactate) caused the dynamic viscosity of xanthan gum to decrease, but the solutions maintained shear-thinning properties. Use of simple salt (e.g. Na+, Ca2+) to increase the solution ionic strength also decreased the dynamic viscosity of xanthan and the degree of shear thinning, although the effect is a function of xanthan gum concentration and diminished as the xanthan gum concentration was increased. At high xanthan concentration, addition of salt to the solution increased dynamic viscosity. In the absence of sediments, xanthan gum solutions maintain their viscosity properties for months. However, xanthan gum solutions were shown to lose dynamic viscosity over a period of days to weeks when contacted with saturated site sediment. Loss of viscosity is attributed to physical and biodegradation processes.

  13. Researches on thermal and rheological properties of cream- and vegetable spread

    Directory of Open Access Journals (Sweden)

    A. N. Ostrikov

    2016-01-01

    Full Text Available Researches of thermal and rheological properties of cream- and vegetable spread are necessary for the scientific substantiation of their obtaining process, namely mixing and crystallization processes. As the object of research, we chose a cream- and vegetable spread, with the following composition: peanut butter 10%; wheat germ oil 10%; linseed oil 20%; butter 59.8%; emulsifier 0.2%. With the data obtained in the course of research of the rheological properties of cream- and vegetable spread, one can subsequently generate recommendations for optimization of technological modes of production. In particular, one can solve problems of intensification of hydro-mechanical and thermal processes by carrying them out at such a temperature and speed when the maximum preservation of the produced product structure will be achieved. Determination of thermal characteristics was carried out in the apparatus for the study of thermal and rheological properties of viscoelastic liquids Coesfeld RT-1394H. Rheological researches of cream- and vegetable spread were carried out on a series of viscometers SV-10 and PB-8m. The graphs of spread dynamic viscosity dependence on the temperature, and the dependence of the effective viscosity of the spread and vegetable oils on the shear rate were built according to experimental data. The data obtained is rational to choose the equipment for processing and production of cream- and vegetable spread, to simulate processes taking place in the production process, to solve problems of intensification of thermal and hydro-mechanical processes reasonably, by conducting the production process at temperatures that do not cause the destruction of the product structure.

  14. PP/HDPE共混体系毛细管流变性能研究%Study of Capillary Rheological Properties of PP/HDPE Blends

    Institute of Scientific and Technical Information of China (English)

    陶国良; 刘涌; 廖华勇; 纪波印; 李靖

    2012-01-01

    用毛细管流变仪对以马来酸酐接枝聚丙烯(PP-g-MAH)为相容剂的聚丙烯/高密度聚乙烯(PP/HDPE)共混体系的流变性能进行研究.研究发现,PP/HDPE共混体系属于假塑性流体:随着剪切速率的增加,表观黏度下降:PP-g-MAH的加入降低了共混体系的表观粘度:HDPE与PP的非牛顿指数在低剪切速事区与适宜强度下适用于幂律方程的经验公式;HDPE与PP共混后,HDPE含量越低,体系出现壁面滑移的临界剪切速率越高,可加工性能越好.%The rhealogical properties of PP/HDPE blends which was combined by PP-g-MAH ,were studied by capiiiary rheometer. The results show thai the rheological behavior of PP/HDPE blends is non-Newtonian fluid. With the increase of shear rate, the apparent viscosity drops. The apparent viscosity of the blends reduce with the added of PP-g-MAH. For the non-Newtonian index, the power law is applicable to HDPE and PP, white in low shear rate and the temperature is suitable. The critical shear rate in wall slip of PP/HDPE blends increases while the content of HDPE reduce. The property of process performance is better.

  15. Rheology of Biopolymer Solutions and Gels

    OpenAIRE

    David R. Picout; Ross-Murphy, Simon B.

    2003-01-01

    Rheological techniques and methods have been employed for many decades in the characterization of polymers. Originally developed and used on synthetic polymers, rheology has then found much interest in the field of natural (bio) polymers. This review concentrates on introducing the fundamentals of rheology and on discussing the rheological aspects and properties of the two major classes of biopolymers: polysaccharides and proteins. An overview of both their solution properties (dilute to semi...

  16. Rheology of Biopolymer Solutions and Gels

    Directory of Open Access Journals (Sweden)

    David R. Picout

    2003-01-01

    Full Text Available Rheological techniques and methods have been employed for many decades in the characterization of polymers. Originally developed and used on synthetic polymers, rheology has then found much interest in the field of natural (bio polymers. This review concentrates on introducing the fundamentals of rheology and on discussing the rheological aspects and properties of the two major classes of biopolymers: polysaccharides and proteins. An overview of both their solution properties (dilute to semi-dilute and gel properties is described.

  17. Rheological Properties of Aging Thermosensitive Suspensions

    NARCIS (Netherlands)

    Purnomo, E.H; van den Ende, Henricus T.M.; Mellema, J.; Mugele, Friedrich Gunther

    2007-01-01

    Aging observed in soft glassy materials inherently affects the rheological properties of these systems and has been described by the soft glassy rheology (SGR) model [S. M. Fielding et al., J. Rheol. 44, 323 (2000)]. In this paper, we report the measured linear rheological behavior of

  18. The role of protein content on the steady and oscillatory shear rheology of model synovial fluids.

    Science.gov (United States)

    Zhang, Z; Barman, S; Christopher, G F

    2014-08-28

    Recent studies have debated the role of protein content on the bulk rheology of synovial fluid; in particular, it has been questioned if proteins aggregate or interact with hyaluronic acid in synovial fluid to enhance bulk rheology, or if observed effects were due to systematic measurement error caused by interfacial rheology, stemming from protein adsorption to the interface. Utilizing several techniques to ensure results reflect only bulk rheology, an examination of the role of bovine serum albumin and γ-globulin on model synovial fluid rheology has been undertaken. When interfacial rheology caused by protein adsorption to the interface is abrogated, the bulk rheology of a model synovial fluid composed of bovine serum albumin, γ-globulin, and hyaluronic acid is found to be dominated solely by the hyaluronic acid over a wide range of shear rates, strains and frequencies. These results show that the previously reported enhanced rheological properties of model synovial fluids are solely due to interfacial rheology and not from any type of protein aggregation/interaction in bulk solution.

  19. Local Rheology of Human Neutrophils Investigated Using Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Yong J. Lee, Dipika Patel, Soyeun Park

    2011-01-01

    Full Text Available During the immune response, neutrophils display localized mechanical events by interacting with their environment through the micro-vascular transit, trans-endothelial, and trans-epithelial migration. Nano-mechanical studies of human neutrophils on localized nano-domains could provide the essential information for understanding their immune responsive functions. Using the Atomic Force Microscopy (AFM - based micro-rheology, we have investigated rheological properties of the adherent human neutrophils on local nano-domains. We have applied the modified Hertz model to obtain the viscoelastic moduli from the relatively thick body regions of the neutrophils. In addition, by using more advanced models to account for the substrate effects, we have successfully characterized the rheological properties of the thin leading and tail regions as well. We found a regional difference in the mechanical compliances of the adherent neutrophils. The central regions of neutrophils were significantly stiffer (1,548 ± 871 Pa than the regions closer to the leading edge (686 ± 801 Pa, while the leading edge and the tail (494 ± 537 Pa regions were mechanically indistinguishable. The frequency-dependent elastic and viscous moduli also display a similar regional difference. Over the studied frequency range (100 to 300 Hz, the complex viscoelastic moduli display the partial rubber plateau behavior where the elastic moduli are greater than the viscous moduli for a given frequency. The non-disparaging viscous modulus indicates that the neutrophils display a viscoelastic dynamic behavior rather than a perfect elastic behavior like polymer gels. In addition, we found no regional difference in the structural damping coefficient between the leading edge and the cell body. Thus, we conclude that despite the lower loss and storage moduli, the leading edges of the human neutrophils display partially elastic properties similar to the cell body. These results suggest that the

  20. Toothpaste microstructure and rheological behaviors including aging and partial rejuvenation

    Science.gov (United States)

    Liu, Zhiwei; Liu, Lei; Zhou, Huan; Wang, Jiali; Deng, Linhong

    2015-08-01

    Toothpastes are mainly composed of a dense suspension of abrasive substances, flavors, and therapeutic ingredients in a background liquid of humectants and water, and usually exhibit complex rheological behaviors. However, the relationship between the rheology and microstructure of toothpaste remains to be studied. In this paper, three commonly used toothpastes, namely Colgate, Darlie and Yunnan Baiyao (Ynby), were qualitatively and quantitatively studied as soft glassy materials. We found that although the three toothpastes generally behaved in similar fashion in terms of rheology, each particular one was distinct from others in terms of the quantitative magnitude of the rheologcial properties including thixotropy, creep and relaxation, yield stress, and power-law dependence of modulus on frequency. In addition, the history-dependent effects were interpreted in terms of aging and rejuvenation phenomena, analogous to those existing in glassy systems, and Ynby seemed to result in greater extent of aging and rejuvenation as compared to the other two. All these differences in toothpaste rheology may well be attributed to the different microscopic network microstructures as observed in this study. Therefore, this study provides first evidence of microstructurebased rheological behaviors of toothpaste, which may be useful for optimizing its composition, manufacturing processing as well as end-user applications.

  1. Shear History Extensional Rheology Experiment II (SHERE II) Microgravity Rheology with Non-Newtonian Polymeric Fluids

    Science.gov (United States)

    Jaishankar, Aditya; Haward, Simon; Hall, Nancy Rabel; Magee, Kevin; McKinley, Gareth

    2012-01-01

    The primary objective of SHERE II is to study the effect of torsional preshear on the subsequent extensional behavior of filled viscoelastic suspensions. Microgravity environment eliminates gravitational sagging that makes Earth-based experiments of extensional rheology challenging. Experiments may serve as an idealized model system to study the properties of lunar regolith-polymeric binder based construction materials. Filled polymeric suspensions are ubiquitous in foods, cosmetics, detergents, biomedical materials, etc.

  2. Rheological studies of PMMA-PVC based polymer blend electrolytes with LiTFSI as doping salt.

    Directory of Open Access Journals (Sweden)

    Chiam-Wen Liew

    Full Text Available In this research, two systems are studied. In the first system, the ratio of poly (methyl methacrylate (PMMA and poly (vinyl chloride (PVC is varied, whereas in the second system, the composition of PMMA-PVC polymer blends is varied with dopant salt, lithium bis (trifluoromethanesulfonyl imide (LiTFSI with a fixed ratio of 70 wt% of PMMA to 30 wt% of PVC. Oscillation tests such as amplitude sweep and frequency sweep are discussed in order to study the viscoelastic properties of samples. Elastic properties are much higher than viscous properties within the range in the amplitude sweep and oscillatory shear sweep studies. The crossover of G' and G'' is absent. Linear viscoelastic (LVE range was further determined in order to perform the frequency sweep. However, the absence of viscous behavior in the frequency sweep indicates the solid-like characteristic within the frequency regime. The viscosity of all samples is found to decrease as shear rate increases.

  3. Comparative spectroscopic and rheological studies on crude and purified soluble barley and oat ß-glucan preparations

    DEFF Research Database (Denmark)

    Mikkelsen, Mette Skau; Jespersen, Birthe P Møller; Møller, Birger Lindberg;

    2010-01-01

    on exact β-glucan content regardless of amount and composition of α-glucan impurities was found for both OBG and BBG. This study suggests that the structural characteristics of the β-glucan polymers such as molar mass are of greater functional importance than the presence of lager amounts of starch/α-dextrins...

  4. Thermal-rheological structure of the lithosphere beneath two types of basins in eastern and western China

    Institute of Scientific and Technical Information of China (English)

    王良书; 李成; 刘福田; 李华; 卢华复; 刘绍文

    2000-01-01

    After calculating thermal-rheological properties of the lithosphere in the Northern Jiangsu basin, the Bohaiwan basin as well as the Jiyang depression in the east and Tarim basin in the west of China, this paper analyzes the relationship between thermal-rheological structures and tectonic evolution of the two types of basins. The results show that the thermal-rheoiogical structures of the lithosphere directly reflect the dynamic processes. Under different dynamic environments, the style of basin formation and the differences in basin evolution are closely related to the dynamic properties of the lithosphere indicated by thermal-rheological structures.

  5. Reconciling laboratory and observational models of mantle rheology in geodynamic modelling

    Science.gov (United States)

    King, Scott D.

    2016-10-01

    Experimental and geophysical observations constraining mantle rheology are reviewed with an emphasis on their impact on mantle geodynamic modelling. For olivine, the most studied and best-constrained mantle mineral, the tradeoffs associated with the uncertainties in the activation energy, activation volume, grain-size and water content allow the construction of upper mantle rheology models ranging from nearly uniform with depth to linearly increasing from the base of the lithosphere to the top of the transition zone. Radial rheology models derived from geophysical observations allow for either a weak upper mantle or a weak transition zone. Experimental constraints show that wadsleyite and ringwoodite are stronger than olivine at the top of the transition zone; however the uncertainty in the concentration of water in the transition zone precludes ruling out a weak transition zone. Both observational and experimental constraints allow for strong or weak slabs and the most promising constraints on slab rheology may come from comparing inferred slab geometry from seismic tomography with systematic studies of slab morphology from dynamic models. Experimental constraints on perovskite and ferropericlase strength are consistent with general feature of rheology models derived from geophysical observations and suggest that the increase in viscosity through the top of the upper mantle could be due to the increase in the strength of ferropericlase from 20-65 GPa. The decrease in viscosity in the bottom half of the lower mantle could be the result of approaching the melting temperature of perovskite. Both lines of research are consistent with a high-viscosity lithosphere, a low viscosity either in the upper mantle or transition zone, and high viscosity in the lower mantle, increasing through the upper half of the lower mantle and decreasing in the bottom half of the lower mantle, with a low viscosity above the core. Significant regions of the mantle, including high

  6. Deformation above mobile substrates, salt rheology and spatial distribution of salt structures: A 3D seismic study of the Permian southern North Sea

    Science.gov (United States)

    Hernandez, Karina; Mitchell, Neil; Huuse, Mads

    2016-04-01

    At ~255 Ma, cycles of evaporation of seawater led to deposition of evaporites including halite (rock salt) in the North Sea Basin. After later burial by denser sediments, the salt beds rose as pillows and diapirs. Assuming mobilization is due to Rayleigh-Taylor gravitational instability of heavy fluid (sediments) overlying light fluid (salts), theory suggests that the spacing between diapirs should be proportional to the original thickness of the salt layer. For example, a description of the theory in Turcotte and Schubert (1982) predicts structure wavelength to be 2.6 times the salt thickness. Previous research has explored mobilization of salt deposits assuming they have uniform rheology. However, this is not justified as halite rheology varies with temperature, grain size and pore brine content. Furthermore, evaporitic sequences contain various minerals besides halite (e.g., anhydrite, gypsum), which have different rheological properties. 3D seismic and well data reveal the internal structure of salt beds. The data have allowed characterization of structure wavelengths and salt thickness, so that the impact of internal composition and other properties on halokinetic behaviour can be assessed.

  7. Rheological Study Of The Mixture Of Acetaminophen And Polyethylene Oxide For Hot-Melt Extrusion Application (PREPRINT)

    Science.gov (United States)

    2011-01-01

    effect . The edge effect becomes more severe as the shear rate increases [9]. The maximum torque for the oscillatory rheom- eter used in this study is...1500 g cm, while the edge effect is often manifested by the sudden drop of the torque. The viscosity in a capillary flow is calculated using following...application, Eur. J. Pharm. Biopharm. (2011), doi:10.1016/j.ejpb.2011.03.013The shear rate for the oscillatory rheometer is limited by the torque and edge

  8. Bottlebrush Polymers: Synthesis, Rheology, and Self-Assembly

    Science.gov (United States)

    Dalsin, Samuel J.

    Bottlebrush polymers are comb-like molecules with a high density of side chains grafted along a central backbone. Due to their unique conformational properties, bottlebrush polymers have become attractive candidates for developing new photonic bandgap materials, nanotubes and nanowires, or drug delivery vehicles, to name a few. This dissertation primarily investigates the rheological properties and self-assembly behavior of bottlebrush polymer molecules made using a variety of different polymerization routes. A considerable portion of the work is directed towards the linear rheology of model, polyolefin-based bottlebrush polymers with independently varied branch and backbone lengths. These studies demonstrate how the tight spacing between branch points effectively precludes backbone entanglement in the polymer melts, but it does not inhibit the formation of entanglements among the branched side chains. Furthermore, the relaxation profiles reveal transient scaling behavior in which the dynamics transition from Zimm-like to Rouse-like at increasing relaxation times. These results highlight the distinct conformational character of bottlebrushes at different length scales. The latter parts of this work report on the self-assembly behavior of bottlebrush diblock polymers composed of atactic polypropylene and polystyrene side chains. The diblock samples are analyzed using small-angle X-ray scattering and atomic force microscopy. Nearly all of the samples display strong segregation between the two blocks, owing to the large molar mass of typical bottlebrush polymers. Consequently, only one experimental sample displays an accessible order-disorder transition temperature. The strong segregation is also shown to affect the ability of large bottlebrush diblocks to readily achieve well-ordered nanostructures by self-assembly. Finally, results of the most symmetric (by volume fraction) diblock samples are compared with predictions of a newly developed self-consistent field

  9. Examination of rheological properties of aqueous solutions of sodium caseinate

    Directory of Open Access Journals (Sweden)

    Jolanta Gawałek

    2012-12-01

    Full Text Available Application of sodium caseinate as a functional additive in manufacturing processes requires production of its concentrated aqueous solutions which, in industrial conditions, presents a number of difficulties. In order to develop an effective and optimal industrial process of mixing – manufacturing a concentrated solution of sodium caseinate, it is essential to know rheological properties in a definite range of concentrations changing in the course of the dissolving process. The material for investigations was typical commercial sodium caseinate in the form of dry powder manufactured in Poland from acid casein using the method of extrusion. The objective of the undertaken empirical studies was the assessment of the impact of the concentration on rheological properties of sodium caseinate concentrates. Investigations were carried out for five concentrates manufactured in a mixer equipped in a mechanical agitator at concentrations ranging X (% Î (2.5¸12.5 and changing mass proportions of sodium caseinate in the aqueous solution as follows: GS/G (kgS·kg-1 = 0.025. On the basis of the obtained research results, classical flow curves were plotted for individual concentrates. The determined values of viscosity and density of the examined solutions were correlated in the form of h = f(GS/G and r = f(GS/G dependencies which were used during the determination of classical characteristics of mixing forces essential for the assessment of energetic expenditures required to manufacture concentrates in a mixer equipped in a mechanical agitator. The density of the examined concentrates increased in a way directly proportional, while the dynamic viscosity coefficient increased exponentially together with the increase of sodium caseinate concentration. Sodium caseinate concentrates exhibited Newtonian character in the examined range of concentrations.

  10. Rheological measurements on artifical muds

    NARCIS (Netherlands)

    De Wit, P.J.

    1992-01-01

    The rheological behaviour of three artificial muds was determined using a rotational viscometer. First some characteristics of the viscometer used were rneasured. For want of an appropriate calibration tluid, the viscosity of demineralized water was determined. The result agreed very well with what

  11. RHEOLOGICAL ASPECTS OF MULTILAYER MATERIALS

    Directory of Open Access Journals (Sweden)

    V. V. Artemchuk

    2010-11-01

    Full Text Available The issues related to renewal of worn-out parts of a rolling stock with the layered coatings are considered in the article. In developing a mathematical model of wearing a multilayer material as an object of rheology certain assumptions, which enable using the methods of mechanics and mechanics of continuous medium, are done.

  12. Molecular dynamics studies of entangled polymer chains

    NARCIS (Netherlands)

    Bulacu, Monica Iulia

    2008-01-01

    The thesis presents three molecular dynamics studies of polymeric ensembles in which the chain entanglement plays the major role in the internal dynamics of the system. A coarse-grained model is used for representing the polymer chains as strings of beads connected by finite-extensible springs. In a

  13. Effect of alcohol-acid modification on physicochemical, rheological and morphological properties of glutinous rice starch.

    Science.gov (United States)

    Gope, Sangeeta; Samyor, Duyi; Paul, Atanu Kumar; Das, Amit Baran

    2016-12-01

    In the present study chemical modification of glutinous rice starch was carried out using 1-Buatnol-hydrochloric acid with varying time and temperature. The changes in physico-chemical, dynamic rheological and morphological properties of starch during hydrolysis was investigated. There was a significant increase in water solubility of starch due to modification; however, swelling and sedimentation value decrease after modification. The peak, hold and final viscosity of modified starches were decreased significantly as compared to native starch. Thermal properties and dynamic rheological properties of rice starch were changed with the change in time and temperature during modification. The storage (G') modulus, loss (G″) modulus, dynamic viscosity (η') and complex viscosity (η*) of modified starches were varied significantly. Analysis of microstructure revealed that the hydrolysis altered morphology of starch granules. The hydrolysis was affected the surface properties and granule size of rice starch. These results suggested that 1-butanol-HCl hydrolysis of glutinous rice starch can be a preferred way of modification.

  14. Green synthesis of silver nanoparticles using green tea leaves: Experimental study on the morphological, rheological and antibacterial behaviour

    Science.gov (United States)

    Nakhjavani, Maryam; Nikkhah, V.; Sarafraz, M. M.; Shoja, Saeed; Sarafraz, Marzieh

    2017-10-01

    In this paper, silver nanoparticles are produced via green synthesis method using green tea leaves. The introduced method is cost-effective and available, which provides condition to manipulate and control the average nanoparticle size. The produced particles were characterized using x-ray diffraction, scanning electron microscopic images, UV visualization, digital light scattering, zeta potential measurement and thermal conductivity measurement. Results demonstrated that the produced samples of silver nanoparticles are pure in structure (based on the x-ray diffraction test), almost identical in terms of morphology (spherical and to some extent cubic) and show longer stability when dispersed in deionized water. The UV-visualization showed a peak in 450 nm, which is in accordance with the previous studies reported in the literature. Results also showed that small particles have higher thermal and antimicrobial performance. As green tea leaves are used for extracting the silver nanoparticles, the method is eco-friendly. The thermal behaviour of silver nanoparticle was also analysed by dispersing the nanoparticles inside the deionized water. Results showed that thermal conductivity of the silver nano-fluid is higher than that of obtained for the deionized water. Activity of Ag nanoparticles against some bacteria was also examined to find the suitable antibacterial application for the produced particles.

  15. STUDIES ON APPARENT KINETICS AND RHEOLOGICAL BEHAVIOR OF EPOXY/ACRYLATE IPNS AS VACUUM PRESSURE IMPREGNATION RESINS

    Institute of Scientific and Technical Information of China (English)

    Jing-kuan Duan; Chonung Kim; Ping-kai Jiang

    2009-01-01

    The apparent kinetics and cure behavior of novel interpenetrating polymer networks (IPNs) based on cycloaliphatic epoxy resin (CER) and tri-functional acrylate have been investigated by means of differential scanning calorimetry (DSC) and Fourier transform infrared spectrosccpy (FT-IR). The results of DSC measurements show that the curing reaction of the TMPTMA component is much earlier than that of the CER component, which can lead to the formation of the IPNs. In contrast to neat anhydride-CER system, the anhydride-CER/TMPTMA systems exhibit relatively lower curing temperatures. The activation energy for initiating the reaction of the anhydride-CER system slightly increases, whereas the activation energy for propagating the reaction markedly reduces during the full IPNs formation. The FF-IR spectroscopic changes are interpreted in terms of curing mechanism of CER and TMPTMA components. The extent of reaction is calculated from FT-IR absorption bands, which depends on the reactive group concentration. The experimental results of FT-IR measurements are in good agreements with those of DSC measurements. The theological behavior of anhydride-CER/TMPTMA systems during IPNs formation is studied in this paper. It is confirmed that the introduction of TMPTMA monomer into anhydride-epoxy resin has significant effects on the theological behavior of the system.

  16. Analysis of the Rheological Behaviour of Selected Semi-Solid Slag Systems in Blast Furnace Flow Conditions

    Directory of Open Access Journals (Sweden)

    Migas P.

    2015-04-01

    Full Text Available The rheological properties of liquid and semi-solid systems of slag and hot metal in a blast furnace are extremely important from the perspective of their dripping in the unit. The rheological nature and the values of the dynamic viscosity coefficient of liquid and semi-solid phases - slag and hot metal - determine the permeability of the zones in which those systems exist. The modelling of dripping processes and e.g. static and dynamic holding/retention of liquid in the bed, requires an accurate description of the rheological behaviour of slag and iron systems. Determining the liquid flow through the lump bed of the blast furnace is based on the assumption that liquids in the unit in the whole range of their occurrence are similar to a Newtonian ideal liquid. This study presents an analysis of the findings of high-temperature rheometric measurements of CaO-SiO2-Al2O3-MgO systems, liquid, semi-solid slags of the blast furnace type doped with TiO2 and solids in the form of TiN. The tests were performed within a temperature range of 1310-1490°C. Also measurement results for glycerol solutions with concentrations of 86% and 100% at the ambient temperature, simulating blast furnace slags with various contents of solids - PC, anthracite - are presented.

  17. Research on rheological properties of micro-fine grouting cement

    Institute of Scientific and Technical Information of China (English)

    管学茂; 王雨利; 杨雷

    2003-01-01

    This article studies the influence of the fineness of cement, fly ash(FA), its composite admixture and the amount and way mixed with superplasticizer on the rheological properties of micro-fine cement(MC). By means of modern instruments and technologies (such as XRD, SEM, laser granulometer and superficial-potential apparatus etc.), the article studies the mineral compositions, the appearance character of grains, particle size distribution and superficial potential of FA and its composite materials. And through that, the reducing mechanism of FA is thoroughly analyzed. The study shows that FA and its composite admixture are excellent components which can effectively improve the rheological properties of micro-fine cement, and that the superplasticizer has a saturation point and the mixing way of it has a great influence on the rheological properties.

  18. Effects of polyethyleneimine adsorption on rheology of bentonite suspensions

    Indian Academy of Sciences (India)

    A Alemdar; N Öztekin; F B Erim; Ö I Ece; N Güngör

    2005-06-01

    The influence of the cationic polymer, polyethyleneimine polymer (PEI) on the flow behaviour of bentonite suspensions (2%, w/w), was studied. XRD, zeta potential and adsorption studies were done together with rheological measurements. The addition of PEI at concentration ranges of 10-5–4.5 g/l and their rheological properties and stability of bentonite suspensions were studied. The adsorption rates for the bentonite suspensions are very fast. The XRD results showed that the PEG molecules did not intercalate into the layers of the clay.

  19. Factors That Influence the Extensional Rheological Property of Saliva.

    Science.gov (United States)

    Vijay, Amrita; Inui, Taichi; Dodds, Michael; Proctor, Gordon; Carpenter, Guy

    2015-01-01

    The spinnbarkeit of saliva reflects the ability of saliva to adhere to surfaces within the mouth, thereby serving as a protective role and aiding in lubrication. Therefore, alterations in the extensional rheology of saliva may result in the loss in adhesiveness or the ability to bind onto surfaces. Mucin glycoproteins and their structures are known to be important factors for the extensional rheological properties of saliva. The conformation of mucin depends on factors such as pH and ionic strength. Chewing is one of the main stimuli for salivary secretion but creates significant sheer stress on the salivary film which could influence mouthfeel perceptions. The current study investigates the possible factors which affect the extensional rheological properties of saliva by comparing submandibular/sublingual saliva with different oral stimuli within the same group of subjects. Unstimulated and stimulated saliva (chew, smell and taste) salivas were collected primarily from submandibular/sublingual glands. The saliva samples were measured for Spinnbarkeit followed by the measuring mucin, total protein, total calcium and bicarbonate concentrations. The results indicated correlations between rheological properties and mucin/ion concentrations. However, chewing stimulated submandibular/sublingual saliva is shown to have significantly lower Spinnbarkeit, but factors such as mucin, protein and calcium concentrations did not account for this variation. Analysis of the concentration of bicarbonate and pH appears to suggest that it has a prominent effect on extensional rheology of saliva.

  20. Factors That Influence the Extensional Rheological Property of Saliva.

    Directory of Open Access Journals (Sweden)

    Amrita Vijay

    Full Text Available The spinnbarkeit of saliva reflects the ability of saliva to adhere to surfaces within the mouth, thereby serving as a protective role and aiding in lubrication. Therefore, alterations in the extensional rheology of saliva may result in the loss in adhesiveness or the ability to bind onto surfaces. Mucin glycoproteins and their structures are known to be important factors for the extensional rheological properties of saliva. The conformation of mucin depends on factors such as pH and ionic strength. Chewing is one of the main stimuli for salivary secretion but creates significant sheer stress on the salivary film which could influence mouthfeel perceptions. The current study investigates the possible factors which affect the extensional rheological properties of saliva by comparing submandibular/sublingual saliva with different oral stimuli within the same group of subjects. Unstimulated and stimulated saliva (chew, smell and taste salivas were collected primarily from submandibular/sublingual glands. The saliva samples were measured for Spinnbarkeit followed by the measuring mucin, total protein, total calcium and bicarbonate concentrations. The results indicated correlations between rheological properties and mucin/ion concentrations. However, chewing stimulated submandibular/sublingual saliva is shown to have significantly lower Spinnbarkeit, but factors such as mucin, protein and calcium concentrations did not account for this variation. Analysis of the concentration of bicarbonate and pH appears to suggest that it has a prominent effect on extensional rheology of saliva.

  1. Factors That Influence the Extensional Rheological Property of Saliva

    Science.gov (United States)

    Vijay, Amrita; Inui, Taichi; Dodds, Michael; Proctor, Gordon; Carpenter, Guy

    2015-01-01

    The spinnbarkeit of saliva reflects the ability of saliva to adhere to surfaces within the mouth, thereby serving as a protective role and aiding in lubrication. Therefore, alterations in the extensional rheology of saliva may result in the loss in adhesiveness or the ability to bind onto surfaces. Mucin glycoproteins and their structures are known to be important factors for the extensional rheological properties of saliva. The conformation of mucin depends on factors such as pH and ionic strength. Chewing is one of the main stimuli for salivary secretion but creates significant sheer stress on the salivary film which could influence mouthfeel perceptions. The current study investigates the possible factors which affect the extensional rheological properties of saliva by comparing submandibular/sublingual saliva with different oral stimuli within the same group of subjects. Unstimulated and stimulated saliva (chew, smell and taste) salivas were collected primarily from submandibular/sublingual glands. The saliva samples were measured for Spinnbarkeit followed by the measuring mucin, total protein, total calcium and bicarbonate concentrations. The results indicated correlations between rheological properties and mucin/ion concentrations. However, chewing stimulated submandibular/sublingual saliva is shown to have significantly lower Spinnbarkeit, but factors such as mucin, protein and calcium concentrations did not account for this variation. Analysis of the concentration of bicarbonate and pH appears to suggest that it has a prominent effect on extensional rheology of saliva. PMID:26305698

  2. Rheological study of an hydrate slurry as secondary two-phase refrigerant. Experimental results and modelling; Etude rheologique d'une suspension d'hydrates en tant que fluide frigoporteur diphasique: resultats experimentaux et modelisation

    Energy Technology Data Exchange (ETDEWEB)

    Darbouret, M.

    2005-12-15

    Secondary two-phase fluids are suspensions of solid crystals. Thanks to the melting latent heat, they present a great interest for cold transportation. Moreover, they are a mean of reducing the amount of classical refrigerant. In the refrigeration field, ice slurries are already used. The goal is now to extend this technology to other temperature ranges suitable for other applications like freezing or air-conditioning. For an air-conditioning application, a TBAB (Tetra-Butyl-Ammonium Bromide) aqueous solution is studied. Under atmospheric pressure and for positive temperatures, this solution crystallizes into ice-like compounds named 'hydrates'. First, the physical properties of the aqueous solution and its crystallisation conditions were studied. Two different types of hydrates can appear. The goal of the experimental set-up is to study the rheological behaviour of two-phase fluids. Slurries are made in brushed-surface heat exchanger and pumped into pipes where flow rates and pressure drops are measured. The rheological behaviour of TBAB hydrates slurries can be described using a Bingham fluid model. We highlight that the two rheological parameters, which are the apparent viscosity and the yield shear stress, depend on the volume fraction of crystal of course, but also on the hydrate type, and on the initial concentration of the solution. The yield shear stress is interpreted as the consequence of the Van der Waals inter-particle interaction forces. Finally, possible stratification effects are modelled with a finite difference method. The principle is to calculate particle concentration and velocity profiles following the flow of the slurry. Calculations are validated with experimental velocity profiles published by P. Reghem (2002). This model underlines the influence of the particle distribution in the pipe on pressure drops. (author)

  3. Effects of chemical and enzymatic modification on dough rheology and biscuit characteristics

    DEFF Research Database (Denmark)

    Pedersen, Lene; Kaack, Karl; Bergsøe, Merete Norsker

    2005-01-01

    The effect of addition of sodium meta-bisulfite and a commercial protease on dough rheological properties and biscuit characteristics was studied on 7 biscuit wheat cultivars. Sodium meta-bisulfite (SMS) (360 mg/kg flour) or protease (300 mg/kg flour) was added to semisweet biscuit dough. Rheolog...

  4. Rheology as a tool for evaluation of melt processability of innovative dosage forms

    DEFF Research Database (Denmark)

    Aho, Johanna Maaria; Boetker, Johan P; Baldursdottir, Stefania

    2015-01-01

    for the process simulations which are also becoming increasingly important. The authors aim to give an overview to the basics of rheology and summarize examples of the studies where rheology has been utilized in setting up or evaluating extrusion processes. Furthermore, examples of different experimental set...

  5. Rheological behaviour of latexes in-can and during film drying

    NARCIS (Netherlands)

    Molenaar, F.; Svanholm, T.; Toussaint, A.

    1997-01-01

    In-can rheology was studied for sixteen model acrylate latexes and a commercial vinyl/acrylate copolymer latex. Following the model of Quemada, the shear thinning behaviour, the effects of latex neutralisation and the copolymer composition could be described. Furthermore, the rheological effects of

  6. Categorization of rheological scaling models for particle gels applied to casein gels

    NARCIS (Netherlands)

    Mellema, M.; Opheusden, van J.H.J.; Vliet, van T.

    2002-01-01

    Rennet-induced casein gels made from skim milk were studied rheologically. A scaling model or framework for describing the rheological behavior of gels is discussed and used for classification of the structure of casein gels. There are two main parameters in the model that describe the number of def

  7. Rheological behavior of oxide nanopowder suspensions

    Science.gov (United States)

    Cinar, Simge

    Ceramic nanopowders offer great potential in advanced ceramic materials and many other technologically important applications. Because a material's rheological properties are crucial for most processing routes, control of the rheological behavior has drawn significant attention in the recent past. The control of rheological behavior relies on an understanding of how different parameters affect the suspension viscosities. Even though the suspension stabilization mechanisms are relatively well understood for sub-micron and micron size particle systems, this knowledge cannot be directly transferred to nanopowder suspensions. Nanopowder suspensions exhibit unexpectedly high viscosities that cannot be explained with conventional mechanisms and are still a topic of investigation. This dissertation aims to establish the critical parameters governing the rheological behavior of concentrated oxide nanopowder suspensions, and to elucidate the mechanisms by which these parameters control the rheology of these suspensions. Aqueous alumina nanopowders were chosen as a model system, and the findings were extrapolated to other oxide nanopowder systems such as zirconia, yttria stabilized zirconia, and titania. Processing additives such as fructose, NaCl, HCl, NaOH, and ascorbic acid were used in this study. The effect of solids content and addition of fructose on the viscosity of alumina nanopowder suspensions was investigated by low temperature differential scanning calorimetry (LT-DSC), rheological, and zeta potential measurements. The analysis of bound water events observed in LT-DSC revealed useful information regarding the rheological behavior of nanopowder suspensions. Because of the significance of interparticle interactions in nanopowder suspensions, the electrostatic stabilization was investigated using indifferent and potential determining ions. Different mechanisms, e.g., the effect of the change in effective volume fraction caused by fructose addition and electrostatic

  8. 可注射磷酸钙骨水泥的流变性能研究%Study on the Rheological Properties of Injectable Calcium Phosphate Cement

    Institute of Scientific and Technical Information of China (English)

    陈芳萍; 刘昌胜

    2012-01-01

    The influence of additives on the theological properties of injectable calcium phosphate cement (ICPC) was investigated with an advanced expansion system rheometer. During the measurement of steady rheological properties, the viscosity, shear stress, and thixotropy were detected. During dynamic oscillation testing, the viscoelastic response of the ICPC under forced oscillation and the internal structure were unvailled. The results indicated that the ICPC showed both plastic and thixotropic behavior with little effect by additives. The introduction of these water-soluble polymers improved the viscosity and thixotropy of the ICPC, which are conducive to the stability of the whole system. These additives improve the recoverability and stability of the ICPC network after being sheared, in which xanthan gum and chitosan were the most obvious. On this basis, the time to form a gel was assessed to be in the range of 2 563 ~ 2 600 s for xanthan gum-ICPC system. In addition, with the increasing of xanthan gum contents, the thixotropic loop area of ICPC enlarged, but the for- mation of network structure was not stable under high shear condition.%采用高级流变扩展系统研究了添加剂种类及其含量对可注射磷酸钙骨水泥(ICPC)流变特性的影响。采用稳态流动实验表征浆体的静态粘度,用触变环面积、应力降低率和屈服应力表征ICPC浆体的触变性,并进行动态频率扫描和动态时间扫描实验动态监测ICPC的粘、弹、塑性变化规律以及水化反应过程流变参数的依时性。结果表明:添加剂并不改变ICPC的粘弹性。水溶性高分子化合物的加入提高了ICPC的粘度和触变性,利于整个体系的稳定;添加剂不同程度上提高了ICPC剪切后的网络结构恢复能力和稳定性,尤其以黄原胶和几丁糖最为明显。在此基础上,评估了加入黄原胶后ICPC形成凝胶的时间,约为2563~2600s。此外,随着黄原胶含量的增加

  9. INVESTIGATION OF RHEOLOGICAL PROPERTIES OF MODIFIED BITUMEN

    Directory of Open Access Journals (Sweden)

    Erofeev Vladimir Trofimovich

    2016-08-01

    Full Text Available At the present time the most widely used type of road pavement is asphalt-concrete pavement produced on the basis of oil bitumen. One of the efficient ways to increase the quality and durability of asphalt-concrete pavement is modification of bitumen. Though Russian specialists still don’t have the global view of the ideal and real asphalt cement, the requirements to its quality and durability indicators in the composition of road structure haven’t yet formed. The authors present the investigation results of the properties of oil asphalt cement containing 0.5-2.0% of modifier “Olazol”. The physical, mechanical and rheological properties of the modified bitumen are determined. The dependences of the dynamic viscosity of the modified bitumen from the quantity of introduced modifier, shear rate and reheat temperature are analyzed.

  10. [The dynamics of changes in rheological properties of oral fluid in patients with different levels of oral hygiene, using removable dentures].

    Science.gov (United States)

    Mikhaylenko, T N; Ernestyuk, A M; Rozhko, N M

    2014-12-01

    The issue of changing the physical and physico-chemical characteristics of oral fluid and their dependence on the level of oral hygiene in patients with removable dentures, requires further study. Therefore, in 86 individuals with 138 removable dentures, and 34 patients who are dentally and somatically healthy, we have had studied the parameters of viscosity, velocity of salivation, pH and concentration of mucin. According to the results of the factor analysis, it was determined that 78.6% of the studied parameters were indicators of hygienic condition of oral cavity. On the basis of significant difference and the strength and direction of correlation between the studied parameters and values of the integral index of oral hygiene, it was found, that in patients without somatic pathology with proper oral hygiene, we observed the growth of the rate of salivation and pH(c1), and in case of improper hygienic condition - reducing rate of salivation and increasing concentration of mucin. In case of the presence of somatic pathology, with an improvement of oral hygiene, the growth of pH(c1) and reducing of concentration of mucin was observed. The deterioration of oral hygiene level led to the increase of the rate of viscosity and the reduction of the salivation rate.

  11. RHEOLOGICAL BEHAVIOR OF KAOLIN TOUGHENED POLYPROPYLENE COMPOSITES

    Institute of Scientific and Technical Information of China (English)

    OU Yuchun; FANG Xiaoping; FENG Yupeng

    1997-01-01

    The relation between the rheological behavior and various interfacial properties of Kaolin rigid particle toughened polypropylene(PP/Kaolin) composites were studied by means of parallel-plate rheometer, melt flow rate apparatus, scanning electron microscopy (SEM) and other testing methods. The results show that addition of interfacial modifier to PP/Kaolin composites is advantageous to homogeneous dispersion of filler in PP matrix,formation of flexible interlayer between Kaolin particles and PP matrix and improvement of the melt processibility of the composites.

  12. RHEOLOGICAL BEHAVIOR OF EPOXY RESIN WATERBORNE DISPERSIONS

    Institute of Scientific and Technical Information of China (English)

    Zhen-zhong Yang; Yuan-ze Xu; De-lu Zhao

    2001-01-01

    The waterborne dispersions of epoxy resin were prepared by the phase inversion emulsification technique.Rheological behavior and its relationship with the structural change of the systems were studied. It was shown that the concentrated dispersions were highly viscoelastic and pseudoplastic, which was attributed to the formation of a physical network among the waterborne particles via hydrogen bond. The dilute dispersions were Newtonian fluids. The discrete clusters composed of small waterborne particles were found in diluted dispersions. With increasing solid content, there existed a structural transition via percolation through a cluster-cluster aggregation mode to form the physical network, which was qualitatively evidenced by the TEM morphologies.``

  13. The Panel Study of Income Dynamics (PSID)

    Data.gov (United States)

    U.S. Department of Health & Human Services — The Panel Study of Income Dynamics (PSID) began in 1968 with a nationally representative sample of over 18,000 individuals living in 5,000 families in the United...

  14. Size-Dependent Rheology of Type-I Collagen Networks

    OpenAIRE

    Arevalo, Richard C.; Urbach, Jeffrey S.; Blair, Daniel L.

    2010-01-01

    We investigate the system size dependent rheological response of branched type I collagen gels. When subjected to a shear strain, the highly interconnected mesh dynamically reorients, resulting in overall stiffening of the network. When a continuous shear strain is applied to a collagen network, we observe that the local apparent modulus, in the strain-stiffening regime, is strongly dependent on the gel thickness. In addition, we demonstrate that the overall network failure is determined by t...

  15. Effect of host-rock rheology on dyke shape, thickness and magma overpressure

    Science.gov (United States)

    Vachon, Rémi; Hieronymus, Christoph F.

    2017-03-01

    The size and thickness of dykes is of fundamental importance for volcano dynamics because dykes are the primary path for magma transport, and because large numbers of dykes often comprise a major proportion of the volcanic edifice and of the underlying crust. Standard elastic models predict dyke geometry to be elliptic in cross-section for constant overpressure and uniform host-rock properties, whereas observations show that dyke thickness is typically more nearly constant with a sharp taper at the ends. Moreover, the predicted overpressures required to inflate dykes in a purely elastic medium are often significantly higher (>150 MPa and up to 2 GPa) than those estimated by other means (about 1-50 MPa). In this study, we use 2-D finite element models to test whether other host-rock rheologies lead to more realistic dyke shapes and overpressures. We examine three different rheologies, each of which is affected by the presence of the dyke itself: (1) elasticity with reduced moduli in regions of low pressure or tension; (2) elastoplasticity with plastic failure in the high-stress regions surrounding the dyke tips; (3) viscoelasticity with a viscosity decrease due to heating by the dyke. We use rheological parameters obtained from laboratory experiments whenever possible, and assume static conditions for the final dyke shape. We find that all three rheologies tend to make the dyke more rectangular relative to the elliptical dykes of the linearly elastic models. The change in shape is due to enhanced deformation in the high-stress zone surrounding the dyke tip. We also find that the overpressure required to inflate an initially thin dyke to a given thickness is reduced for all three rheologies. The greatest decrease in overpressure by a factor of about 0.1 is observed for the elastoplastic model, and for the viscoelastic model if the dyke intrudes into moderately pre-heated host-rock. We discuss our results with respect to dyke observations from Rum Island (Scotland

  16. 魔芋葡甘聚糖/威兰胶体系流变性能研究%Study on the rheological properties of KGM/WG blending system

    Institute of Scientific and Technical Information of China (English)

    温成荣; 潘娟; 庞杰

    2014-01-01

    The rheological properties of KGM/WG blending system were studied. The results showed that the viscosity of KGM/WG compound system decreased with the increase of shear rate,exhibiting a typical pseudoplastic. KGM/WG compound system was highly concentration-dependent as the higher concentration led to more obvious increase in viscosity. Compared with the pure KGM,the rheological properties and thermal stability of the compound system was obvious improved with adding a certain amount of WG. The sample KW8 had stronger intermolecular forces and the best rheological properties.%本文主要对魔芋葡甘聚糖/威兰胶(KGM/WG)共混体系的流变性能进行了研究,结果表明:不管是单一多糖还是KGM/WG共混体系,黏度均随剪切速率的增加而逐渐下降,呈现为假塑性流体;KGM/WG共混体系表现出很强的浓度依赖性,浓度越高,黏度越高;相比于单一KGM,添加一定量的WG,共混体系的流变性能和热稳定性能明显提高;KW8共混体系多糖分子间存在较强的作用力,流变性能最佳。

  17. Estudo do comportamento reológico das argilas bentoníticas de Cubati, Paraíba, Brasil Rheological behavior study of bentonite clays from Cubati, Paraíba, Brazil

    Directory of Open Access Journals (Sweden)

    R. R. Menezes

    2009-12-01

    Full Text Available O estado da Paraíba possui jazidas de bentonitas utilizadas comercialmente para uma vasta gama de setores tecnológicos. No entanto, esses jazimentos estão se exaurindo, após dezenas de anos de exploração. Assim, este trabalho tem por objetivo dar prosseguimento à caracterização de argilas bentoníticas de Cubati, PB, estudando o comportamento reológico das dispersões argila-água de modo avaliar seu desempenho para fluidos de perfuração de poços de petróleo base água. As amostras estudadas foram secas a 60 ºC e determinou-se sua capacidade de troca de cátions. As argilas foram transformadas em sódica por tratamento com Na2CO3 e em seguida realizou-se o estudo do comportamento reológico das dispersões. As viscosidades, aparente e plástica, o volume de filtrado, os parâmetros reológicos do fluido e a sua força gel foram determinados. Os resultados evidenciaram que cada amostra apresenta um teor ótimo de carbonato de sódio e que as dispersões argila-água possuem um comportamento pseudo-plástico e tixotrópico. Duas amostras apresentam potencial para utilização como agentes viscosificantes para fluidos de perfuração.The bentonites of the state of Paraíba, Brazil, are commercially used in numerous technological sectors, particularly in oil drilling muds. However, these bentonite deposits are becoming exhausted due to several years of exploitation. Thus, the aim of this work was continue the characterization of the bentonites from Cubati, Paraíba, studying the rheological behavior of water-clay suspensions, evaluating their viability to be used in oil drilling muds. The samples were dried at 60 ºC and, their cation exchange capacity was determined. The natural bentonite clays were transformed in sodium bentonite by addition of concentrated Na2CO3 solution, then the suspensions rheological study was performed. The apparent and plastic viscosities, water loss, rheological parameters and the gel force were determined

  18. TLA 改性沥青的高温流变性能研究%Research on the Temperature Rheological Properties of TLA Modified Asphalt

    Institute of Scientific and Technical Information of China (English)

    杨娥

    2012-01-01

      This paper applies dynamic mechanical analysis method to study the dynamic rheological properties of common asphalt and TLA modified asphalt in high -temperature; and measures the temperature and frequency pa -rameters of the dynamic rheological properties within a certain range ; and analyses the impact of the variation of the rheological properties of asphalt TLA through the analysis of different dosage TLA modified asphalt dynamic per -formance parameters.The results show that: after adding TLA increased asphalt complex modulus , phase angle de-creases while asphalt rutting factor increases .%  采用动态力学分析方法对基质沥青和 TLA 改性沥青的高温动态流变性能进行研究,测定了一定温度和频率范围内的动态流变性能参数,并通过分析 TLA 掺量不同的改性沥青的动态性能参数变化规律来分析 TLA 对沥青的流变性能的影响,结果表明:加入 TLA 后沥青复数模量增大,相位角减小,沥青的车辙因子相应增大。

  19. Effect of Ultraviolet Aging on Rheology and Chemistry of LDH-Modified Bitumen

    Directory of Open Access Journals (Sweden)

    Xing Liu

    2015-08-01

    Full Text Available Layered double hydroxides (LDHs are an ultravioletlight (UV-resistant material. In this study, two types of LDHs (Mg-Al-LDHs and Zn-Al-LDHs were applied to modify bitumen by melt-blending. The effect of ultraviolet aging on the rheology and chemistry of LDH-modified bitumen was studied by means of dynamic shear rheometer (DSR, thin-layer chromatography with flame ionization detection (TLC-FID, Fourier transform infrared spectroscopy (FTIR, and Ultraviolet-Visible (UV-Vis spectrophotometry to reveal the mechanisms of action for LDHs and bitumen. The results showed that within the UV spectra (220–400 nm, the reflectance of Zn-Al-LDHs was larger than that of Mg-Al-LDHs. These two LDHs have different influences on the performance of bitumen. Mg-Al-LDHs had a more obvious influence on the physical and dynamic rheological properties of bitumen than Zn-Al-LDHs. Zn-Al-LDHs improved the UV-aging resistance of bitumen more. The reason can be that the reflectance of the Zn-Al-LDHs to the UV light is larger than that of the Mg-Al-LDHs. The Zn-Al-LDH-modified bitumen had more potential to improve the UV-aging resistance during the service life of asphalt pavement.

  20. Rheological Properties of Enzymatically Isolated Tomato Fruit Cuticle.

    Science.gov (United States)

    Petracek, P. D.; Bukovac, M. J.

    1995-10-01

    Rheological properties were determined for cuticular membranes (CMs) enzymatically isolated from mature tomato (Lycopersicon esculentum Mill. cv Pik Red) fruit. The cuticle responded as a viscoelastic polymer in stress-strain studies. Both CM and dewaxed CM expanded and became more elastic and susceptible to fracture when hydrated, suggesting that water plasticized the cuticle. Dewaxing of the CM caused similar changes in elasticity and fracturing, indicating that wax may serve as a supporting filler in the cutin matrix. Exposure of the cuticle to the surfactant Triton X-100 did not significantly affect its rheological properties.

  1. Microscale rheology of a soft glassy material close to yielding.

    Science.gov (United States)

    Jop, Pierre; Mansard, Vincent; Chaudhuri, Pinaki; Bocquet, Lydéric; Colin, Annie

    2012-04-06

    Using confocal microscopy, we study the flow of a model soft glassy material: a concentrated emulsion. We demonstrate the micro-macro link between in situ measured movements of droplets during the flow and the macroscopic rheological response of a concentrated emulsion, in the form of scaling relationships connecting the rheological "fluidity" with local standard deviation of the strain-rate tensor. Furthermore, we measure correlations between these local fluctuations, thereby extracting a correlation length which increases while approaching the yielding transition, in accordance with recent theoretical predictions. © 2012 American Physical Society

  2. SUMMARY OF 2009 RHEOLOGY MODIFIER PROGRAM

    Energy Technology Data Exchange (ETDEWEB)

    Hansen, E.

    2009-12-08

    The overall objective of the EM-31 Rheological Modifiers and Wetting Agents program is to utilize commercially available rheology modifiers to increase the solids fraction of radioactive sludge based waste streams, resulting in an increase in throughput and decreasing the overall processing time. The program first investigates the impact of rheology modifiers on slurry simulants and then utilizes the most effective rheology modifiers on radioactive slurries. The work presented in this document covers the initial investigation of rheology modifier testing with simulants. This task is supported by both the Savannah River National Laboratory (SRNL) and Pacific Northwest National Laboratory (PNNL). The SRNL EM-31 task, for this year, was to investigate the use of rheology modifiers on simulant Defense Waste Processing Facility (DWPF) melter feeds. The task is to determine, based on the impact of the rheology modifier, if there are rheology modifiers that could reduce the water content of the slurry going to the DWPF melter, hence increasing the melt rate by decreasing the water loading. The rheology modifier in essence would allow a higher solids content slurry to have the same type of rheology or pumpability of a lower solids slurry. The modifiers selected in this report were determined based on previous modifiers used in high level waste melter feed simulants, on-going testing performed by counterparts at PNNL, and experiences gain through use of modifiers in other Department of Energy (DOE) processes such as grout processing. There were 12 rheology modifiers selected for testing, covering both organic and inorganic types and they were tested at four different concentrations for a given melter feed. Five different DWPF melter feeds were available and there was adequate material in one of the melter feeds to increase the solids concentration, resulting in a total of six simulants for testing. The mass of melter feed available in each simulant was not adequate for

  3. Molecular Rheology of Complex Fluids

    DEFF Research Database (Denmark)

    Huang, Qian; Rasmussen, Henrik Koblitz

    The processing of polymer materials is highly governed by its rheology, and influences the properties of the final product. For example, a recurring problem is instability in extrusion that leads to imperfect plastic parts. The ability to predict and control the rheological behavior of polymer......–state viscosity between melts and solutions is still an open question. Branched polymer melts have more complex molecular structures. A stress maximum during the start–up of uniaxial extensional flow was reported in 1979 for a low–density polyethylene (LDPE) melt. Subsequently observations of a steady stress......) linear polystyrene melts and solutions; 2) the bidisperse and polydisperse linear polystyrene melts; 3) the NMMD branched polystyrene melts; and 4) the polydisperse branched polyethylene melts. The experimental results are also compared with some developing theoretical models. Finally, to ensure...

  4. Structural rheology of a model ointment.

    Science.gov (United States)

    Pena, L E; Lee, B L; Stearns, J F

    1994-06-01

    A model ointment consisting of white petrolatum, mineral oil and microcrystalline wax was studied using rheology, microscopy and thermal techniques. Rheograms studied over a temperature range of 25-40 degrees C indicated that the overall rheogram shape changed little as the temperature increased. However, two inflections gradually disappeared as the temperature increased. Thermal optical analysis showed that the temperature range over which these inflection disappeared correlated with the melting transition of the components forming the secondary structure. Another series of rheograms obtained from ointments with different combinations of the raw materials showed the rheology of the ointment is primarily controlled by the white petrolatum and mineral oil and that the microcrystalline wax acts to build-up the structure by incorporating itself into the existing white petrolatum structure. Thermal optical analysis of comelts of the raw materials proved that the ointment network structure is essentially a recombination of the naturally occurring components in differing ratios. The knowledge obtained from these studies is applied to a discussion of the thermal and mechanical stresses encountered in the filling operation.

  5. Structural analysis of gluten-free doughs by fractional rheological model

    Science.gov (United States)

    Orczykowska, Magdalena; Dziubiński, Marek; Owczarz, Piotr

    2015-02-01

    This study examines the effects of various components of tested gluten-free doughs, such as corn starch, amaranth flour, pea protein isolate, and cellulose in the form of plantain fibers on rheological properties of such doughs. The rheological properties of gluten-free doughs were assessed by using the rheological fractional standard linear solid model (FSLSM). Parameter analysis of the Maxwell-Wiechert fractional derivative rheological model allows to state that gluten-free doughs present a typical behavior of viscoelastic quasi-solid bodies. We obtained the contribution dependence of each component used in preparations of gluten-free doughs (either hard-gel or soft-gel structure). The complicate analysis of the mechanical structure of gluten-free dough was done by applying the FSLSM to explain quite precisely the effects of individual ingredients of the dough on its rheological properties.

  6. Correlation between rheological behavior and structure of multi-component polymer systems

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Rheological measurement has been an effective method to characterize the structure and properties for multiphase/multi-component polymers, owing to its sensitivity to the structure change of hetero geneous systems. In this article, recent progress in the studies on the morphology/structure and rheological properties of heterogeneous systems is summarized, mainly reporting the findings of the authors and their collaborators, involving the correlation between the morphology and viscoelastic relaxation of LCST-type polymer blends, the microstructure and linear/nonlinear viscoelastic behavior of block copolymers, time scaling of shear-induced crystallization and rheological response of polyolefins, and the relationship between the structure/properties and rheological behavior of filled polymer blends. It is suggested that a thorough understanding of the characteristic rheological response to the morphology/structure evolution of multiphase/multi-component polymers facilitates researchers' optimizing the morphology/structure and ultimate mechanical properties of polymer materials.

  7. Rheological Behavior of Bauxite-Based SiC-Containing Castables

    Institute of Scientific and Technical Information of China (English)

    YE Fangbao; M. Rigaud; LIU Xinhong; ZHONG Xiangchong

    2004-01-01

    Low cement (LC) and ultra-low cement (ULC)bauxite-SiC castables are important and high performance monolithic refiactories andthey have been widely used iniron-making and incinerator linings. In this work, rheo-logical behavior of LC and ULC bauxite-based SiC-contain-ing castables has been studied, including the effects of SiC content and cement content on rheological properties of thecastables. The results show that with an increase of SiC and cement content, rheological properties of the castablesdeteriorate. On the other hand, moderate amounts of SiC(4% ~ 8% ) and of calcium aluminate cement (2% ~4% ) have very slight influence on rheological properties,(i. e. when the castables are sheared their torque andyield torque only slightly increase with the shearing speed). The rheological characteristics of the castables fol-low Bingham fiuid and always show shear thinning behav-ior.

  8. Correlation between rheological behavior and structure of multi-component polymer systems

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Rheological measurement has been an effective method to characterize the structure and properties for multiphase/multi-component polymers, owing to its sensitivity to the structure change of hetero- geneous systems. In this article, recent progress in the studies on the morphology/structure and rheological properties of heterogeneous systems is summarized, mainly reporting the findings of the authors and their collaborators, involving the correlation between the morphology and viscoelastic relaxation of LCST-type polymer blends, the microstructure and linear/nonlinear viscoelastic behavior of block copolymers, time scaling of shear-induced crystallization and rheological response of poly- olefins, and the relationship between the structure/properties and rheological behavior of filled polymer blends. It is suggested that a thorough understanding of the characteristic rheological response to the morphology/structure evolution of multiphase/multi-component polymers facilitates researchers’ op- timizing the morphology/structure and ultimate mechanical properties of polymer materials.

  9. Nonlinear dynamics in the study of birdsong

    Science.gov (United States)

    Mindlin, Gabriel B.

    2017-09-01

    Birdsong, a rich and complex behavior, is a stellar model to understand a variety of biological problems, from motor control to learning. It also enables us to study how behavior emerges when a nervous system, a biomechanical device and the environment interact. In this review, I will show that many questions in the field can benefit from the approach of nonlinear dynamics, and how birdsong can inspire new directions for research in dynamics.

  10. Dynamic study of milling low depth channels

    Directory of Open Access Journals (Sweden)

    Rosca Dorin Mircea

    2017-01-01

    Full Text Available This paper presents a study of dynamic aspects of the milling cutters used in particular case of low depth channels. A new calculation method was developed, taking into account the high variations of cutting forces during milling small depth channels with peripheral cutting tools. A new formula was established for the minimal value of channel depth that allows cutting process to be performed in conditions of dynamic stability.

  11. Dynamic rheology of food protein networks

    Science.gov (United States)

    Small amplitude oscillatory shear analyses of samples containing protein are useful for determining the nature of the protein matrix without damaging it. Elastic modulus, viscous modulus, and loss tangent (the ratio of viscous modulus to elastic modulus) give information on the strength of the netw...

  12. Cine CT technique for dynamic airway studies

    Energy Technology Data Exchange (ETDEWEB)

    Ell, S.R.; Jolles, H.; Keyes, W.D.; Galvin, J.R.

    1985-07-01

    The advent of cine CT scanning with its 50-msec data acquisition time promises a much wider range of dynamic CT studies. The authors describe a method for dynamic evaluation of the extrathoracic airway, which they believe has considerable potential application in nonfixed upper-airway disease, such as sleep apnea and stridor of unknown cause. Conventional CT is limited in such studies by long data acquisition time and can be used to study only prolonged maneuvers such as phonation. Fluoroscopy and digital subtraction studies are limited by relatively high radiation dose and inability to image all wall motions simultaneously.

  13. Quantitative predictions of the μ(I rheology in 2D and 3D granular column collapse: scaling laws and quasi-static vs. inertial regimes

    Directory of Open Access Journals (Sweden)

    Valette Rudy

    2017-01-01

    Full Text Available We introduce an accurate numerical method for the computation of 2D and 3D granular collapse under gravity flows using the μ(I rheology. We show that this rheology can capture the two experimentally observed types of spreading and the corresponding scaling laws, and we provide an accurate sensitivity analysis to rheological constants. Finally, we underline the role of time-dependency on the spreading dynamics.

  14. Study of mechanical, rheological and thermal properties of nanocomposite HMSPP (high melt strength polypropylene) with Brazilian bentonite; Estudo das propriedades mecanicas, reologicas e termicas de nanocomposito de HMSPP (polipropileno com alta resistencia do fundido) com uma bentonita brasileira

    Energy Technology Data Exchange (ETDEWEB)

    Fermino, Danilo Marin

    2011-07-01

    This work concerns to the study of the mechanical, thermal and rheological behavior of the nano composite HMSPP - Polypropylene High Melt Strength (obtained at a dose of 12.5 kGy) and a bentonite clay Brazilian Paraiba, known as 'Chocolate' in concentrations of 5 and 10% by weight, comparison of to one American Clay, Cloisite 20A nanocomposite was done. Agent compatibilizer polypropylene-graft, known as maleic anhydride (PP-g-AM) was addict 3% concentration thought technique melt intercalation using a twin-screw extruder and the specimens were prepared by injection process. The mechanical behavior was evaluated by strength, flexural strength and impact tests. The thermal behavior was evaluated by the techniques of differential scanning calorimetry (DSC) and thermogravimetry (TGM). The rheological behavior was evaluated in rheometer. The morphology of the nanocomposites was studied by the technique of scanning electron microscopy (SEM). The organophilic bentonite and the nanocomposites were characterized by X-ray diffraction (XRD) and infrared (FTIR). (author)

  15. Estudo do efeito da temperatura sobre o comportamento reológico das polpas de gabiroba e goiaba = Study of temperature effect on rheological behavior of gabiroba and guava pulps

    Directory of Open Access Journals (Sweden)

    Ricardo Cardoso de Oliveira

    2011-01-01

    Full Text Available Neste trabalho um estudo sobre o comportamento reológico das polpas degabiroba e goiaba foi estudado na faixa de temperatura de 20 – 35ºC. As medidas reológicas foram feitas em rêometro Brookfield equipados com cilindro coaxial. Os reogramas foram ajustados a partir dos dados experimentais para os modelos de Ostwald de Waale, Bingham e Herschell-Buckley pela metodologia Bayesiana. Para ambas as polpas foram verificadas o comportamento pseudoplástico e sendo a pseudoplasticidade maior em baixas temperaturas. Considerando o modelo de Ostwald de Waale, a viscosidade aparente e o índice deconsistência diminuíram com o aumento da temperatura ao passo que índice de comportamento aumentou com o aumento de temperatura.In this work a study on the rheological behavior of the guava and gabiroba pulp were studied in temperature range from 20 – 35ºC. The rheological measurements were made in Brookfield rheometer equipped with coaxial cylinder. The rheograms were adjusted from the experimental data for the models of Ostwald de Waale, Bingham andHerschell-Buckley by Bayesian methodology. For both the pulps the pseudo plastic behavior was found, and pseudo plasticity was bigger at low temperatures. Considering the Ostwald de Waale model, the viscosity and consistency index decreased with the rising of the temperature while index of behavior increased with the rising of the temperature.

  16. Couple analysis on strength reduction theory and rheological mechanism for slope stability

    Institute of Scientific and Technical Information of China (English)

    刘子振; 言志信; 段建

    2008-01-01

    Considering the rheological properties of rock and soil body,and exploiting the merit of strength reduction technique,a theory of couple analysis is brought forward on the basis of strength reduction theory and rheological properties.Then,the concept and the calculation procedure of the safety factor are established at different time.Making use of finite element software ANSYS,the most dangerous sliding surface of the slope can be obtained through the strength reduction technique.According to the dynamic safety factor based on rheological mechanism,a good forecasting could be presented to prevent and cure the landslide.The result shows that the couple analysis reveals the process of the slope failure with the time and the important influence on the long-term stability due to the rheological parameters.

  17. Study on Rheology Behavior of Wood-Plastic Composites%木塑复合材料转矩流变性研究

    Institute of Scientific and Technical Information of China (English)

    徐冬梅; 张琳; 刘太闯; 袁晓龙; 曾长春

    2013-01-01

    Rheology behaviors of PVC,PP and PE-HD based wood-plastic composites were investigated by torque rheometer. The results show that wood powder content is the primary factor affecting rheology behavior. With the increase of wood powder content,the maximum torsional and equilibrium torque are improved,while fluidity is decreased. Processing fluidity of composite can be improved by adding coupling agent,compatibilizer and lubricant.%用转矩流变仪分别研究了聚氯乙烯、聚丙烯、高密度聚乙烯基木塑复合材料的转矩流变行为。结果表明,木粉用量是影响复合材料流变性的主要因素,随着木粉用量的增加,木塑复合材料的最大扭矩和平衡扭矩都提高,导致体系的流动性变差;采用偶联剂处理木粉和加入增容剂有助于改善体系的流动性;加入润滑剂也有利于熔体的流动。

  18. Rheological properties of isotropic magnetorheological elastomers featuring an epoxidized natural rubber

    Science.gov (United States)

    Azhani Yunus, Nurul; Amri Mazlan, Saiful; Ubaidillah; Choi, Seung-Bok; Imaduddin, Fitrian; Aziz, Siti Aishah Abdul; Khairi, Muntaz Hana Ahmad

    2016-10-01

    This study presents principal field-dependent rheological properties of magnetorheological elastomers (MREs) in which an epoxidized natural rubber (ENR) is adopted as a matrix (in short, we call it ENR-based MREs). The isotropic ENR-based MRE samples are fabricated by mixing the ENR compound with carbonyl iron particles (CIPs) with different weight percentages. The morphological properties of the samples are firstly analysed using the microstructure assessment. The influences of the magnetic field on the viscoelastic properties of ENR-based MREs are then examined through the dynamic test under various excitation frequencies. The microstructure of MRE samples exhibits a homogeneous distribution of CIPs in the ENR matrix. The dramatic increment of storage modulus, loss modulus and loss tangent of the ENR-based MREs are also observed from the field-dependent rheological test. This directly demonstrates that the stiffness and damping properties of the samples can be adjusted by the magnetic field. It is also seen that the CIP content, exciting frequency and the magnetic field essentially influence the dynamic properties of the ENR-based MREs. The strong correlation between the magnetization and the magneto-induced storage modulus could be used as a useful guidance in synthesizing the ENR-based MREs for certain applications.

  19. Rheological characterization of a gel produced using human blood plasma and alginate mixtures.

    Science.gov (United States)

    Malagón-Romero, Dionisio; Hernández, Nicolás; Cardozo, Carmen; Godoy-Silva, Rubén D

    2014-06-01

    Human blood plasma is a material used to generate tissue equivalents due to presence of fibrinogen. However, gels formed using human blood plasma has weak mechanical properties. In this study, different mixtures of sodium alginate and blood plasma were performed and evaluated. By determining ζ potential can be established the stability of the plasma-alginate mixture and by dynamic rheology can determine the most suitable parameters for the gelation of the above mixtures, when calcium chloride is used as a crosslinker. Experimental results evidence an increment in ζ potential at alginate concentrations of 0.8% and 1.6% with a resulting pseudoplastic behavior of evaluated mixtures, which described the homogenization of the mixture. On the other hand, mixtures were gelled by using aspersion of calcium chloride and characterized by dynamic rheology. Solid behavior is dominant in all range of frequency sweep test between 0.1Hz and 100Hz. Finally, the ultimate tensile strength of a gel reach 6.36938±0.24320kPa, which is enough for manual handling of the gel. Between the tasks of the gel would be used for cell entrapment, for controlled release of drugs or in the manufacture of wound dressings.

  20. Rheological Evaluation of Polymer Modiifed Asphalt Binders

    Institute of Scientific and Technical Information of China (English)

    WANG Lan; CHANG Chunqing

    2015-01-01

    The microstructure and dynamic rheological characteristics of asphalt containing different polymer modifiers (crumb rubber, styrene-butadiene-styrene and crumb rubber mix with styrene-butadiene-styrene) at mid and high service temperature levels were investigated by using scanning electron microscopy(SEM), dynamic shear rheometer(DSR) and repeat creep test. The main objective of the investigation was to rank the modifiers based on their effect on performance characteristics of asphalt under service conditions. To evaluate the effect of different modiifers on the viscoelastic response of asphalt, the temperature and frequency dependences of the dynamic viscoelastic properties were compared. The mid-temperature fatigue resistance and high-temperature rutting resistance of three polymer modiifed asphalts were evaluated to predict their ifeld performance in roads. Based on the current results, an improved rutting factor was proposed to determine the rutting resistance of asphalt pavements. In addition, the viscous stiffness (Gv), deifned as the reciprocal of viscous compliance, was used to evaluate the high-temperature deformation resistance of asphalt mixtures. The experimental results indicate that the asphalt containing crumb rubber only shows superior performance at mid and high service temperatures in all three modiifed asphalt binders due to the action of the crumb rubber.

  1. Thermophysical and Rheological Properties of Imidazolium-Based Ionic Liquids: The Effect of Aliphatic versus Aromatic Functionality

    Science.gov (United States)

    Tao, Ran; Xue, Lianjie; Tamas, George; Quitevis, Edward; Simon, Sindee

    2014-03-01

    As a material class, ionic liquids possess attractive properties and have a wide range of potential uses. In this work, a series of imidazolium-based ionic liquids with the same carbon number varying from aliphatic to aromatic functionalities are investigated. The effects of cation symmetry and larger aromatic polycyclic functionality are studied. The thermal properties, including the glass transition temperature, melting temperature, and decomposition temperature, are characterized, and the density and the ionic conductivity are measured as a function of temperature. Rheological studies are performed using both steady-state and dynamic shear modes. The Cox-Merz relationship between the steady shear viscosity and the dynamic viscosity is examined. The temperature dependence of viscosity is described by the Vogel-Fulcher-Tammann equation and the dynamic fragility is calculated for each ionic liquid and compared to the fragility obtained from calorimetry. Master curves of dynamic shear responses are also constructed and will be discussed.

  2. Rheology v.3 theory and applications

    CERN Document Server

    Eirich, Frederick

    1960-01-01

    Rheology: Theory and Applications, Volume 3 is a collection of articles contributed by experts in the field of rheology - the science of deformation and flow. This volume is composed of specialized chapters on the application of normal coordinate analysis to the theory of high polymers; principles of rheometry; and the rheology of cross-linked plastics, poly electrolytes, latexes, inks, pastes, and clay. Also included are a series of technological articles on lubrication, spinning, molding, extrusion, and adhesion and a survey of the general features of industrial rheology. Materials scientist

  3. “安全流变-突变”理论对心理危机干预的理论探讨%A Study on Theory of Safety Rheology and Mutation for Psychological Crisis Intervention

    Institute of Scientific and Technical Information of China (English)

    张金健; 朱正中

    2015-01-01

    Theory of Safety Rheology and Mutation is the essential law of the safety evolution process of things,and it provides a new theoretical perspective for the study of psychology.To analyze the process of psychological crisis from its e-mergence to develop ment based on the Theory of Safety Rheology and Mutation can provide a useful reference for university psychological crisis intervention.%“安全流变—突变”理论作为事物安全演化过程的本质规律,为心理学研究提供了一个新的理论视角。文章运用“安全流变—突变”理论诠释心理危机从产生到发生的变化过程,此对高校心理危机干预工作提供有益借鉴。

  4. Study on some rheological parameters of water and clay basis drilling fluids additivated with industrial sodium silicate; Estudo de alguns parametros reologicos de fluidos de perfuracao a base de agua e argila aditivados com silicato de sodio industrial

    Energy Technology Data Exchange (ETDEWEB)

    Amorim, Luciana Viana [Universidade Federal, Campina Grande, PB (Brazil). Engenharia de Processos]. E-mail: lucianaa@labdes.ufpb.br; Viana, Josiane Dantas; Farias, Kassie Vieira [Universidade Federal, Campina Grande, PB (Brazil). Dept. de Engenharia de Materiais]. E-mail: josianedantas@bol.com.br; kassievieira@bol.com.br; Franca, Kepler Borges; Lira, Helio de Lucena; Ferreira, Heber Carlos [Universidade Federal, Campina Grande, PB (Brazil). Dept. de Eng. Quimica]. E-mail: kepler@labdes.ufpb.br; helio@dema.ufpb.br; heber@dema.ufpb.br

    2003-07-01

    The aim of this work is to study some rheological parameters of water based oil well drilling fluids and bentonite clay from Boa Vista, PB, treated with industrial sodium silicate. It were selected there samples of natural polycationic bentonite clays and four industrial sodium bentonite clays. The natural clays were treated with concentrated Na{sub 2}CO{sub 3} solution. The drilling fluids were prepared with concentration of 4.86% w/w, according to PETROBRAS norms, and additivated with four different concentration of industrial sodium silicate. After 24 hours of cure, it were measured apparent viscosity (AV) and plastic viscosity (PV) by using a Fann 35A viscosimeter and water loss (WL) by using a Fann filter press. The results showed a change in the rheology of the drilling fluids. The drilling fluids prepared with industrialized clays showed a decrease in AV and an increase in WL. For the drilling fluids prepared with natural clays treated with Na{sub 2}CO{sub 3}, it was observed a decrease in AV and WL and an increase in PV. Also, it was observed a change in the drilling fluids state from flocculated-gel to a partially flocculated. (author)

  5. Rheological properties of magneto-responsive copolymer gels

    NARCIS (Netherlands)

    An, H.

    2012-01-01

    New magneto rheological systems that respond mechanically to external homogeneous magnetic fields, namely, physically cross-linked magneto rheological (MR) gels, were synthesized and investigated. Various aspects of the rheological behavior were considered such as linear viscoelastic response for va

  6. Ultrasound image velocimetry for rheological measurements

    Science.gov (United States)

    Gurung, A.; Haverkort, J. W.; Drost, S.; Norder, B.; Westerweel, J.; Poelma, C.

    2016-09-01

    Ultrasound image velocimetry (UIV) allows for the non-intrusive measurement of a wide range of flows without the need for optical transparency. In this study, we used UIV to measure the local velocity field of a model drilling fluid that exhibits yield stress flow behavior. The radial velocity profile was used to determine the yield stress and the Herschel-Bulkley model flow index n and the consistency index k. Reference data were obtained using the conventional offline Couette rheometry. A comparison showed reasonable agreement between the two methods. The discrepancy in model parameters could be attributed to inherent differences between the methods, which cannot be captured by the three-parameter model used. Overall, with a whole flow field measurement technique such as UIV, we were able to quantify the complex rheology of a model drilling fluid. These preliminary results show that UIV can be used as a non-intrusive diagnostic for in situ, real-time measurement of complex opaque flow rheology.

  7. Rheological properties of ternary mixtures of yellow fruits - doi: 10.4025/actascitechnol.v35i3.16096

    Directory of Open Access Journals (Sweden)

    Charles Windson Isidoro Haminiuk

    2013-06-01

    Full Text Available In this work, the rheological behaviour of ternary mixtures of orange juice, pineapple and mango pulps was studied using response surface methodology. The flow curves were adequately described by the Herschel–Bulkley rheological model. All the ternary mixtures studied presented a change in the rheological parameters with an increase in temperature, and the majority of the formulations were shear-thinning fluids. The rheological responses were influenced by different pulp proportions and different temperatures (20 or 60oC. The quadratic and cubic models used to fit the responses were considered suitable owing to the high values of the coefficient of determination.  

  8. Research on the rheological properties of pesticide suspension concentrate

    Institute of Scientific and Technical Information of China (English)

    潭成侠; 沈德隆; 翁建全; 陈庆悟; 刘会君; 袁其亮

    2004-01-01

    This study reports research on pesticide suspension rheology and a new rheologicaI parameter, the relative value of approach, which has great advantage for judging the physical stability of a pesticide suspension concentrate. Experiments showed that the system can form stable dispersions when the value of the relative value of approach (St) is less than 0.1.

  9. The rheological and fracture properties of Gouda cheese

    NARCIS (Netherlands)

    Luyten, H.

    1988-01-01

    The rheological and fracture behaviour of Gouda cheese was studied. Methods for determining these properties of visco-elastic materials are described. Application of the theory of fracture mechanics, after modification and expansion, to visco-elastic materials with a

  10. Formation, structure and rheological properties of soy protein gels.

    NARCIS (Netherlands)

    Renkema, J.M.S.

    2001-01-01

    Keywords: soy protein isolate, glycinin,β-conglycinin, heat denaturation, gelation, network structure, rheology, permeability measurements, microscopy, pH, ionic strength, emulsified oil dropletsThis study was performed to understand the factors determining heat-induced formation an

  11. Dark chocolate’s compositional effects revealed by oscillatory rheology

    NARCIS (Netherlands)

    van der Vaart, K.; Depypere, F.; De Graef, V.; Schall, P.; Fall, A.; Bonn, D.; Dewettinck, K.

    2013-01-01

    In this study, two types of oscillatory shear rheology are applied on dark chocolate with varying volume fraction, particle size distribution, and soy lecithin concentration. The first, a conventional strain sweep, allows for the separation of the elastic and viscous properties during the yielding.

  12. Concentrated whey protein particle dispersions: Heat stability and rheological properties

    NARCIS (Netherlands)

    Saglam, D.; Venema, P.; Vries, de R.J.; Shi, J.; Linden, van der E.

    2013-01-01

    In this work heat stability and rheological properties of concentrated whey protein particle dispersions in different dispersing media are studied. Whey protein particles (protein content ~20% w/v) having an average size of a few microns were formed using a combination of two-step emulsification and

  13. Differential Rheology Among ABO Blood Group System In Nigerians

    African Journals Online (AJOL)

    Official Publication of the African Association of Physiological Sciences ... alterations in membrane and cytoskeletal properties that could affect the rheology of blood. This study was therefore .... microcirculation and acute organ dysfunction (Oguz and Herbert ..... Ajayi et al. Robert E. and Marx D.D.S. (2001): Platelet-Rich.

  14. RHEOLOGICAL ASPECTS OF MUCIN-CONTAINING SOLUTIONS AND SALIVA SUBSTITUTES

    NARCIS (Netherlands)

    HOLTERMAN, HJ; WATERMAN, HA; BLOM, C; SGRAVENMADE, FJ; Mellema, J.

    1992-01-01

    In this study rheological properties of aqueous solutions of mucin, albumin and mucin-albumin have been investigated in search for saliva substitutes. They were compared with commercially available saliva substitutes on the one hand and natural human saliva on the other hand. For the latter a few me

  15. Dynamic melt flow of nanocomposites based on poly-epsilon-caprolactam

    DEFF Research Database (Denmark)

    Utracki, Leszek; Lyngaae-Jørgensen, Jørgen

    2002-01-01

    The dynamic flow behavior of polyamide-6 (PA-6) and a nanocomposite (PNC) based on it was studied. The latter resin contained 2 wt% of organoclay. The two materials were blended in proportions of 0, 25, 50, 75, and 100 wt% PNC. The dynamic shear rheological properties of well-dried specimens were...

  16. An empirical study of dynamic graph algorithms

    Energy Technology Data Exchange (ETDEWEB)

    Alberts, D. [Freie Universitaet Berlin (Germany); Cattaneo, G. [Universita di Salerno (Italy); Italiano, G.F. [Universita Ca Forscari di Venezia (Italy)

    1996-12-31

    We conduct an empirical study on some dynamic graph algorithms which where developed recently. The following implementations were tested and compared with simple algorithms: dynamic connectivity, and dynamic minimum 1 spanning tree based on sparsification by Eppstein et al.; dynamic connectivity based on a very recent paper by Henzinger and King. In our experiments, we considered both random and non-random inputs. Moreover, we present a simplified variant of the algorithm by Henzinger and King, which for random inputs was always faster than the original implementation. Indeed, this variant was among the fastest implementations for random inputs. For non-random inputs, sparsification was the fastest algorithm for small sequences of updates; for medium and large sequences of updates, the original algorithm by Henzinger and King was faster. Perhaps one of the main practical results of this paper is that our implementations of the sophisticated dynamic graph algorithms were faster than simpler algorithms for most practical values of the graph parameters, and competitive with simpler algorithms even in case of very small graphs (say graphs with less than a dozen vertices and edges). From the theoretical point of view, we analyze the average case running time of sparsification and prove that the logarithmic overhead for simple sparsification vanishes for dynamic random graphs.

  17. Rheological benchmark of silicone oils used for analog modeling of short- and long-term lithospheric deformation

    Science.gov (United States)

    Rudolf, Michael; Boutelier, David; Rosenau, Matthias; Schreurs, Guido; Oncken, Onno

    2016-08-01

    Analog models of tectonic processes at various scales commonly use silicone polymers to simulate viscous flow in the lower crust and mantle. To achieve dynamic similarity with the natural prototype and to improve comparability between analog models, better knowledge of the rheology of commonly used silicones is required. In this study, we present a rheological benchmark of silicones used in various laboratories. Rheometric tests, including rotational and oscillatory tests, were performed and the viscoelastic behavior of silicone is quantitatively described. We found that silicone oils show a transition from Newtonian viscous to power-law, shear thinning behavior around shear rates of 10- 2 to 10- 1 s- 1. The viscosity of chemically similar silicones varied between 2 and 3 × 104 Pa s. Maxwell relaxation times are about 0.1-0.2 s. Such a behavior is able to mimic slow to fast deformation mechanisms in the ductile regime, such as diffusion and dislocation creep as well as viscoelastic relaxation processes. Temperature and aging effects are verified, but can be considered minor with respect to the uncertainty in rheological properties in the natural prototype. Nevertheless, to assure comparability between models and proper scaling the exact properties and conditions should be reported.

  18. Rheological and functional properties of composite sweet potato - wheat dough as affected by transglutaminase and ascorbic acid.

    Science.gov (United States)

    Ndayishimiye, Jean Bernard; Huang, Wei-Ning; Wang, Feng; Chen, Yong-Zheng; Letsididi, Rebaone; Rayas-Duarte, Patricia; Ndahetuye, Jean Baptiste; Tang, Xiao-Juan

    2016-02-01

    Effect of transglutaminase (TGM) and ascorbic acid (AA) on composite sweet potato - wheat dough functional and rheological properties was studied. Partial substitution of wheat flour with sweet potato flour at the level of 20 % significantly (P ≤ 0.05) reduced glutenin, gliadin, dough stability, protein weakening, storage modulus (G') and viscous modulus (G″). Mixolab revealed that both TGM and AA treated dough had stability and protein weakening closed to wheat dough (control), with TGM treated dough having the highest values. TGM Introduced new cross-link bonds as shown by the change of amino acid concentration, leading to an increase in storage modulus (G') and viscous modulus (G″), with G' being higher at all levels of TGM concentration. The opposite was observed for composite dough treated with AA as measured by controlled - stress rheometer. TGM treatment increased glutenin and gliadin content. Compared with the control, dough treated with AA exhibited high molecular weight of polymers than TGM treated dough. The results indicate that the TGM and AA modification of the mixolab and dynamic rheological characteristics (G' and G″) dependent on the changes of GMP, glutenin, gliadin and protein weakening in the composite dough. TGM and AA treatment could improve functional and rheological properties of sweet potato - wheat dough to levels that might be achieved with normal wheat bread. However, it's extremely important to optimize the concentrations of both additives to obtain the optimum response.

  19. VUV studies of molecular photofragmentation dynamics

    Energy Technology Data Exchange (ETDEWEB)

    White, M.G. [Brookhaven National Laboratory, Upton, NY (United States)

    1993-12-01

    State-resolved, photoion and photoelectron methods are used to study the neutral fragmentation and ionization dynamics of small molecules relevant to atmospheric and combustion chemistry. Photodissociation and ionization are initiated by coherent VUV radiation and the fragmentation dynamics are extracted from measurements of product rovibronic state distributions, kinetic energies and angular distributions. The general aim of these studies is to investigate the multichannel interactions between the electronic and nuclear motions which determine the evolution of the photoexcited {open_quotes}complex{close_quotes} into the observed asymptotic channels.

  20. In vivo Dynamic Studies of Brain Metabolism

    Institute of Scientific and Technical Information of China (English)

    LUO Xuechun; JIANG Yufeng; ZHANG Riqing

    2005-01-01

    Nuclear magnetic resonance (NMR) can noninvasively monitor intracellular concentrations and kinetic properties of numerous inorganic and organic compounds. A 31P NMR surface coil was used in vivo to dynamically measure phosphocreatine (PCr), adenosine triphosphate (ATP), and intracellular inorganic phosphate (Pi) levels in mouse brain during ischemia-reperfusion to study the damage of cerebral tissues caused by ischemia and effects of herbs on cerebral energy metabolism during ischemia-reperfusion. The study provides dynamic brain energy metabolism data during different periods. The data show that some herbs more rapidly increase the PCr level during the recovery phase than in the control group.