Effects of shearing on biogas production and microbial community structure during anaerobic digestion with recuperative thickening.

Science.gov (United States)

Yang, Shufan; Phan, Hop V; Bustamante, Heriberto; Guo, Wenshan; Ngo, Hao H; Nghiem, Long D

2017-06-01

Recuperative thickening can intensify anaerobic digestion to produce more biogas and potentially reduce biosolids odour. This study elucidates the effects of sludge shearing during the thickening process on the microbial community structure and its effect on biogas production. Medium shearing resulted in approximately 15% increase in biogas production. By contrast, excessive or high shearing led to a marked decrease in biogas production, possibly due to sludge disintegration and cell lysis. Microbial analysis using 16S rRNA gene amplicon sequencing showed that medium shearing increased the evenness and diversity of the microbial community in the anaerobic digester, which is consistent with the observed improved biogas production. By contrast, microbial diversity decreased under either excessive shearing or high shearing condition. In good agreement with the observed decrease in biogas production, the abundance of Bacteroidales and Syntrophobaterales (which are responsible for hydrolysis and acetogenesis) decreased due to high shearing during recuperative thickening. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Effect of addition of different nano-clays on the fumed silica-polyethylene glycol based shear-thickening fluids

Science.gov (United States)

Singh, Mansi; Mehta, Rajeev; Verma, Sanjeev K.; Biswas, Ipsita

2018-01-01

A comparative study of the rheology of shear thickening suspensions of 20% fumed silica in polyethylene glycol (PEG200) with different nano clays as additives has been done. The nano-clays used are montmorillonite (MMT), Closite15A, Kaolin and Halloysite clay. The objective was to study the effect of relatively cost-effective clays as a partial substitute of silica. Specifically, the effect of type, concentration, temperature and frequency were considered. The results indicate that the shear thickening properties of Closite15A as additive in temperature ranges of 25 °C-45 °C performs the best and Halloysite performs best at higher (55 °C) and lower temperatures (5, 15 °C). The elasticity effects in dynamic experiments were markedly enhanced by Halloysite clay addition. Addition of MMT, however, led to insignificant enhancement in critical viscosity in steady-state as well as dynamic state-rheology. Interestingly, shear thickening fluid (STF) with all clay except MMT was stable after storing for more than a month. These findings indicate that the introduction of nano-clay as additives is a promising and cost effective method for enhancing the STF behavior which can be utilized in high impact resistant (about 3000% strain and 300 rad s-1 frequency) applications.

Disentangling the role of hydrodynamic and frictional forces in a shear-thickening suspension

Science.gov (United States)

Cohen, Itai

2015-03-01

Who among us has not spent countless hours squeezing, rubbing, and smushing gooey substances like, tooth paste, silly putty, corn starch, and even bodily fluids between our fingers? If we could magnify our view and look deep within the substances we are handling what structures would we find? How, do these structures lead to the fascinating mechanical properties that we experience on the scale of our fingers. In this talk I will address the phenomenon of shear thickening in which the viscosity of a suspension increases with increasing shear rate. I will describe recent measurements we have made using a newly developed confocal rheoscope that, for the first time, experimentally visualize the hydrodynamically induced particle clusters. Such clusters have been implicated in continuous shear thickening. It remains controversial as to whether thickening in such suspensions also arises from frictional interactions between particles. The distinct contributions of frictional and hydrodynamic forces are typically difficult to measure independently using conventional techniques. Here, I will describe our approach for using both bulk rheometry techniques and our confocal rheoscope to disentangle their contributions to the total stress response.

Rheological characteristics of cold thickened beverages containing xanthan gum-based food thickeners used for dysphagia diets.

Science.gov (United States)

Cho, Hyun M; Yoo, Byoungseung

2015-01-01

Cold beverages are commonly thickened with commercial gum-based food thickeners for consumption by patients with dysphagia. In this study, the rheological properties of a thickened water and five thickened beverages (orange juice, apple juice, grape juice, whole milk, and a sport drink) that were prepared with four commercial instant xanthan gum-based thickeners (coded A-D) were investigated at a 3% thickener concentration. All thickened samples showed high shear-thinning behavior with yield stress at the serving temperature of 8°C. The magnitudes of apparent viscosity (ηa,50), consistency index (K), storage modulus (G'), and loss modulus (G'') of the thickened beverages, except for water, with food thickener A were significantly higher compared with other thickeners (B, C, and D) (Pbeverages were observed at 1-hour storage, and at longer times their K values, except for milk, remained approximately constant. Rheological parameters demonstrated statistically significant differences in flow and dynamic behaviors between the cold thickened beverages prepared with the xanthan gum-based food thickeners (Pfood thickener, and storage time. In particular, appropriately selecting a commercial food thickener for preparing thickened beverages seems to be of importance for managing dysphagia. Copyright © 2015 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.

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

Science.gov (United States)

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

2017-05-01

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

Stab Resistance of Shear Thickening Fluid (STF)-Kevlar Composites for Body Armor Applications

National Research Council Canada - National Science Library

Egres Jr., R. G; Decker, M. J; Halbach, C. J; Lee, Y. S; Kirkwood, J. E; Kirwood, K. M; Wagner, N. J; Wetzel, E. D

2004-01-01

The stab resistance of shear thickening fluid (STF)-Kevlar and STF-Nylon fabric composites are investigated and found to exhibit significant improvements over neat fabric targets of equivalent areal density...

Nonlinear damping for vibration isolation of microsystems using shear thickening fluid

Science.gov (United States)

Iyer, S. S.; Vedad-Ghavami, R.; Lee, H.; Liger, M.; Kavehpour, H. P.; Candler, R. N.

2013-06-01

This work reports the measurement and analysis of nonlinear damping of micro-scale actuators immersed in shear thickening fluids (STFs). A power-law damping term is added to the linear second-order model to account for the shear-dependent viscosity of the fluid. This nonlinear model is substantiated by measurements of oscillatory motion of a torsional microactuator. At high actuation forces, the vibration velocity amplitude saturates. The model accurately predicts the nonlinear damping characteristics of the STF using a power-law index extracted from independent rheology experiments. This result reveals the potential to use STFs as adaptive, passive dampers for vibration isolation of microelectromechanical systems.

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

Science.gov (United States)

2012-01-19

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

Laminar flow of a shear-thickening fluid in a 90∘ pipe bend

Science.gov (United States)

Marn, Jure; Ternik, Primož

2006-05-01

The non-Newtonian fluid flow in a sharp 90∘ curved pipe is studied numerically to obtain the pressure loss coefficient prompted by disagreement between the existing empirical correlations and results obtained by computer codes. This disagreement results from presumption of fully developed flow throughout the curvature (correlations) while the actual flow is partially developed for the Newtonian and sharp 90∘ curved bend non-Newtonian flows, and fully developed for slightly bent 90∘ curvature non-Newtonian flow. The Quadratic model is employed to accommodate the shear-thickening behavior of an electrostatic ash and water mixture. Numerical results are obtained for different values of Reynolds number. Finally, results for local pressure loss coefficient are compared with values obtained for the Power law rheological model.

Boundary Effects and Shear Thickening of Colloidal Suspensions: A study based on measurement of Suspension Microstructure

Science.gov (United States)

Perera, M. Tharanga D.

Microstructure is key to understanding rheological behaviors of flowing particulate suspensions. During the past decade, Stokesian Dynamics simulations have been the dominant method of determining suspension microstructure. Structure results obtained numerically reveal that an anisotropic structure is formed under high Peclet (Pe) number conditions. Researchers have used various experimental techniques such as small angle neutron scattering (SANS) and light scattering methods to validate microstructure. This work outlines an experimental technique based on confocal microscopy to study microstructure of a colloidal suspension in an index-matched fluid flowing in a microchannel. High resolution scans determining individual particle locations in suspensions 30-50 vol % yield quantitative results of the local microstructure in the form of the pair distribution function, g(r). From these experimentally determined g(r), the effect of shear rate, quantified by the Peclet number as a ratio of shear and Brownian stress, on the suspension viscosity and normal stress follow that seen in macroscopic rheological measurements and simulations. It is generally believed that shear thickening behavior of colloidal suspensions is driven by the formation of hydroclusters. From measurements of particle locations, hydroclusters are identified. The number of hydroclusters grows exponentially with increasing Pe, and the onset of shear thickening is driven by the increase in formation of clusters having 5-8 particles. At higher Pe, we notice the emergence of 12 or more particle clusters. The internal structure of these hydroclusters has been investigated, and there is some evidence that particles internal to hydroclusters preferentially align along the 45° and 135° axis. Beyond observations of bulk suspension behavior, the influence of boundaries on suspension microstructure is also investigated. Experiments were performed for suspensions flowing over smooth walls, made of glass

Shear thickening in suspensions: the lubricated-to-frictional contact scenario

Science.gov (United States)

Morris, Jeffrey

2017-11-01

Suspensions of solid particles in viscous liquids can vary from low-viscosity liquids to wet granular materials or soft solids depending on the solids loading and the forces acting between particles. When the particles are very concentrated, these mixtures are ''dense suspensions.'' Dense suspensions often exhibit shear thickening, an increase in apparent viscosity as the shear rate is increased. In its most extreme form, order of magnitude increases in viscosity over such a narrow range in shear rate occur that the term discontinuous shear thickening (DST) is applied. DST is particularly striking as it occurs in the relatively simple case of nearly hard spheres in a Newtonian liquid, and is found to take place for submicron particles in colloidal dispersions to much larger particle corn starch dispersions. We focus on simulations of a recently developed ``lubricated-to-frictional'' rheology in which the interplay of viscous lubrication, repulsive surface forces, and contact friction between particle surfaces provides a scenario to explain DST. Our simulation method brings together elements of the discrete-element method from granular flow with a simplified Stokesian Dynamics, and can rationalize not only the abrupt change in properties with imposed shear rate (or shear stress), but also the magnitude of the change. The large change in properties is associated with the breakdown of lubricating films between particles, with activation of Coulomb friction between particles. The rate dependence is caused by the shearing forces driving particles to contact, overwhelming conservative repulsive forces between surfaces; the repulsive forces are representative of colloidal stabilization by surface charge or steric effects, e.g. due to adsorbed polymer. The results of simulation are compared to developments by other groups, including a number of experimental studies and a theory incorporating the same basic elements as the simulation. The comparison to experiments of the

Rheological characterization of modified foodstuffs with food grade thickening agents

Science.gov (United States)

Reyes-Ocampo, I.; Aguayo-Vallejo, JP; Ascanio, G.; Córdova-Aguilar, MS

2017-01-01

This work describes a rheological characterization in terms of shear and extensional properties of whole milk, modified with food grade thickening agents (xanthan and carboxymethyl cellulose) with the purpose of being utilized in dysphagia treatment. Shear viscosity of the thickened fluids (2% wt. of xanthan and CMC) were measured in a stress-controlled rheometer and for extensional viscosity, a custom-built orifice flowmeter was used, with elongation rates from 20 to 3000 s-1. Such elongation-rate values represent the entire swallowing process, including the pharyngeal and esophageal phases. The steady-state shear and extensional flow curves were compared with the flow curve of a pudding consistency BaSO4 suspension (α=05), typically used as a reference fluid for the specialized commercial dysphagia products. The modified fluids presented non-Newtonian behavior in both, shear and extensional flows, and the comparison with the reference fluid show that the thickened milk prepared here, can be safely used for consumption by patients with severe dysphagia.

Giant deviation of a relaxation time from generalized Newtonian theory in discontinuous shear thickening suspensions

Science.gov (United States)

Maharjan, Rijan; Brown, Eric

2017-12-01

We investigated the transient relaxation of a discontinuous shear thickening (DST) suspension of cornstarch in water. We performed two types of relaxation experiments starting from a steady shear in a parallel-plate rheometer, followed either by stopping the top plate rotation and measuring the transient torque relaxation or by removing the torque on the plate and measuring the transient rotation of the tool. We found that at low effective weight fraction ϕeffmodel. The regime where the relaxation was inconsistent with the generalized Newtonian model was the same where we found positive normal stress during relaxation, and in some cases we found an oscillatory response, suggestive of a solidlike structure consisting of a system-spanning contact network of particles. This regime also corresponds to the same packing fraction range where we consistently found discontinuous shear thickening in rate-controlled, steady-state measurements. The relaxation time in this range scales with the inverse of the critical shear rate at the onset of shear thickening, which may correspond to a contact relaxation time for nearby particles in the structure to flow away from each other. In this range, the relaxation time was the same in both stress- and rate-controlled relaxation experiments, indicating the relaxation time is more intrinsic than an effective viscosity in this range and is needed in addition to the steady-state viscosity function to describe transient flows. The discrepancy between the measured relaxation times and the generalized Newtonian prediction was found to be as large as four orders of magnitude, and extrapolations diverge in the limit as ϕeff→ϕc as the generalized Newtonian prediction approaches 0. This quantitative discrepancy indicates the relaxation is not controlled by the dissipative terms in the constitutive relation. At the highest weight fractions, the relaxation time scales were measured to be on the order of ˜1 s. The fact that this time scale is

Design and testing of a rotational brake with shear thickening fluids

Science.gov (United States)

Tian, Tongfei; Nakano, Masami

2017-03-01

A rotational brake working with shear thickening fluid (STF) was designed and tested in this study. With the optimisation in design, most of the STF in the brake can receive the same shear rate when the brake rotates. The parts of this brake were fabricated with a 3D printer and then assembled manually. Three types of STFs with various carrier fluids and different particles were fabricated and tested with a rheometer. Then the brake with each STF was separately tested with the rheometer. The estimated and measured torques as a function of the angular velocity fit each other well. The stability of the rotational STF brake was investigated in repeated tests, which proved the function of the brake for a long time.

The rheology of concentrated dispersions: structure changes and shear thickening in experiments and computer simulations

NARCIS (Netherlands)

Boersma, W.H.; Laven, J.; Stein, H.N.; Moldenaers, P.; Keunings, R.

1992-01-01

The flow-induced changes in the microstructure and rheol. of very concd., shear thickening dispersions are studied. Results obtained for polystyrene sphere dispersions are compared with previous data and computer simulations to give better insight into the processes occurring in the dispersions. [on

Sensory and rheological characteristics of thickened liquids differing concentrations of a xanthan gum-based thickener.

Science.gov (United States)

Kim, Hyeri; Hwang, Han-Im; Song, Ki-Won; Lee, Jeehyun

2017-12-01

The objectives of this study were to develop and compare sensory characteristics of beverages and soups thickened with different concentrations of a xanthan gum-based thickener, and to examine, using rheological measurement, whether the viscosity of the thickened liquids conformed to the recommendations of the National Dysphagia Diet (NDD) Task Force. Beverages tested included water, apple juice, orange juice, soymilk, and Yakult. The thickening agent was added to samples at concentrations of 1, 2, or 3%. Addition of the thickening agent had a significant effect on the appearance, texture, and starchy flavor, which were evaluated by descriptive sensory evaluation. The reference standards of viscosity used in sensory descriptive analysis could be useful to practitioners who have to make dysphagia diets and need to learn to make them properly. In rheological measurement, viscosity of thickened liquids in stationary state would be perceived as higher compared to that while swallowing, because of the shear thinning property. This could lead to noncompliance of the medical advice or malnutrition. It is necessary to determine optimal proportion of xanthan gum-based thickener or uncover alternatives, which have shear thinning properties lower than those of xanthan gum, for the acceptance of dysphagia patients. There was no pudding-like viscosity as classified by NDD, when prepared following instructions. Future studies should include higher concentrations of thickener to find out the concentration of the thickener resulting in pudding-like viscosity as recommended by NDD. When a manufacturer modifies or develops a xanthan gum-based thickener, findings from this study can be utilized to understand sensory and rheological characteristics of thickened liquid. For practitioners who have to make dysphagia diets, the reference standards of viscosity used in sensory descriptive analysis could be helpful for deciding the viscosity level of thickened liquids based only on visual

Effect of the yarn pull-out velocity of shear thickening fluid-impregnated Kevlar fabric on the coefficient of friction

Energy Technology Data Exchange (ETDEWEB)

Aikarami, Sh [Dept. of Mechanical and Aerospace Engineering, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Kordani, N. [Dept. of Mechanical Engineering, University of Mazandaran, Mazandaran (Iran, Islamic Republic of); Sadough, Vanini A. [Dept. of Mechanical Engineering, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Amiri, H. [Technical Campus, Tehran South Branch, Islamic Azad University, Tehran(Iran, Islamic Republic of)

2016-08-15

This study explains the yarn pull-out process behavior of woven fabrics in relation to their mechanical properties. Empirical research on the relationship between the yarn pull-out behavior and fabric properties are evaluated, along with a detailed comparison of friction between the fabric fibers in static and dynamic modes. Samples are tested in three modes, namely, neat, dissolved liquid, and silica particle- based Shear thickening fluid (STF)-treated fabric. Accordingly, the presence of STF increases friction between the fabrics and the warp and weft yarns, as well as prevents the displacement of the yarns. Increased friction also leads to an increase in the energy absorption of the yarn pull-out process. In this research, the pull-out test has been performed at three different velocities: 50, 250 and 500 mm/min. Results show that increases in the pull-out velocity increase the pull-out force of the neat and dissolved liquid samples. By contrast, the behavior is completely opposite in the STF-treated sample. Comparing the yarn pull-out values indicates that the STF-treated samples have the highest value, which is approximately three times higher than that of the neat sample.

Effect of the yarn pull-out velocity of shear thickening fluid-impregnated Kevlar fabric on the coefficient of friction

International Nuclear Information System (INIS)

Aikarami, Sh; Kordani, N.; Sadough, Vanini A.; Amiri, H.

2016-01-01

This study explains the yarn pull-out process behavior of woven fabrics in relation to their mechanical properties. Empirical research on the relationship between the yarn pull-out behavior and fabric properties are evaluated, along with a detailed comparison of friction between the fabric fibers in static and dynamic modes. Samples are tested in three modes, namely, neat, dissolved liquid, and silica particle- based Shear thickening fluid (STF)-treated fabric. Accordingly, the presence of STF increases friction between the fabrics and the warp and weft yarns, as well as prevents the displacement of the yarns. Increased friction also leads to an increase in the energy absorption of the yarn pull-out process. In this research, the pull-out test has been performed at three different velocities: 50, 250 and 500 mm/min. Results show that increases in the pull-out velocity increase the pull-out force of the neat and dissolved liquid samples. By contrast, the behavior is completely opposite in the STF-treated sample. Comparing the yarn pull-out values indicates that the STF-treated samples have the highest value, which is approximately three times higher than that of the neat sample

The rheology of shear thickening fluid (STF) and the dynamic performance of an STF-filled damper

International Nuclear Information System (INIS)

Zhang, X Z; Li, W H; Gong, X L

2008-01-01

This paper presents a study of the rheological properties of shear thickening fluid (STF) and its application as a damper. The STF samples, with different weight fractions, were prepared by dispersing nanosized silica particles in a solvent. By using a parallel-plate rheometer, both steady-state and dynamic experiments were carried out to investigate the rheological properties of STFs. Experimental results indicated that these suspensions show an abrupt increase in complex viscosity beyond a critical dynamic shear rate, as well as this increase being reversible. Working with the fabricated STF materials, a prototype damper was fabricated and its dynamic performances were experimentally evaluated. An equivalent linear model through effective elastic stiffness and viscous damping was developed to address both the damping and the stiffness capabilities of the damper. Also, a mathematical model was developed to investigate working mechanisms of STF-based devices

On the effectiveness of incorporating shear thickening fluid with fumed silica particles in hip protectors

Science.gov (United States)

Haris, A.; Goh, B. W. Y.; Tay, T. E.; Lee, H. P.; Rammohan, A. V.; Tan, V. B. C.

2018-01-01

The objective of this research is to develop a smart hip protector by incorporating shear thickening fluid (STF) into conventional foam hip protectors. The shear thickening properties of fumed silica particles dispersed in liquid polyethylene glycol (PEG) were determined from rheological tests. Dynamic drop tests, using a 4 kg drop platen at 0.5 m drop height, were conducted to study how STF improves energy absorption as compared to unfilled foam and PEG filled foam. The results show that PEG filled foam reduces the mean peak force transmitted by a further 55% and mean peak displacement by 32.5% as compared to the unfilled foam; the STF filled foam further reduces mean peak force and displacement by 15% and 41% respectively when compared to the PEG filled foam. At a displacement of 22 mm, the STF filled foam absorbs 7.4 times more energy than the PEG filled foam. The results of varying the drop mass and drop height show that the energy absorbed per unit displacement for STF filled foam is always higher than that of PEG filled foam. Finally, the effectiveness of a prototype of hip protector made from 15 mm thick STF filled foam in preventing hip fractures was studied under two different loading conditions: distributed load (plate drop test) and concentrated load (ball drop test). The results of the plate and ball drop tests show that among all hip protectors tested in this study, only the prototype can reduce the mean peak impact force to be lower than the force required to fracture a hip bone (3.1 kN) regardless of the type of loading. Moreover, the peak force of the prototype is about half of this value, suggesting thinner prototype could have been used instead. These findings show that STF is effective in improving the performance of hip protectors.

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

Energy Technology Data Exchange (ETDEWEB)

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

2014-11-01

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

RHEOLOGICAL CHARACTERIZATION OF COFFEEFLAVORED YOGURT WITH DIFFERENT TYPES OF THICKENER

Directory of Open Access Journals (Sweden)

Thiago Rocha dos Santos MATHIAS

2011-12-01

Full Text Available Yogurt is a functional food that has great demand due to the consumer’s search for a healthier diet. In order to expand the consumer market of this product, many flavors are available, satisfying the most varied preferences. Besides the taste attribute, consistency and viscosity of yogurt are some of the main factors involved in product quality and acceptance. Therefore, this work is a study of the influence of concentration of thickener in coffee-flavored yogurt. The thickener agent used was gelatin. The rheological behavior (flow and viscosity curves of yogurts with and without addition of gelatin was compared with commercial yogurt, which contains another type of thickener (locust bean gum in its formulation. The flow and viscosity curves were obtained from rotational rheometer Thermo Haake Mars, with a range of shear rate from 0.02 to 100 s-1 (rising curve and 100 to 0.02 s-1 (descendent curve at a total time of 20 minutes. Hysteresis was determined as the area between the curves and adjusted to the models of Bingham, Casson, Herschel-Bulkley and Ostwald-de-Waele. Were also carried out tests of thixotropy, by measuring the viscosity as a function of time at a constant rate of 100 s-1 for 10 minutes. These curves were adjusted by the Weltman model. All samples showed pseudoplastic and thixotropic behavior. The Herschel-Bulkley model was the best fit to the three samples tested. The Weltman’s model well described the thixotropy tests, except for the sample of commercial yogurt. The use of gelatin as a thickener showed protective character, reducing the structural break of the gel.

Direct Shear Behavior of Fiber Reinforced Concrete Elements

Directory of Open Access Journals (Sweden)

Hussein Al-Quraishi

2018-01-01

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

Complex, multilayered azimuthal anisotropy beneath Tibet: evidence for co-existing channel flow and pure-shear crustal thickening

Science.gov (United States)

Agius, Matthew R.; Lebedev, Sergei

2017-09-01

Of the two debated, end-member models for the late-Cenozoic thickening of Tibetan crust, one invokes 'channel flow' (rapid viscous flow of the mid-lower crust, driven by topography-induced pressure gradients and transporting crustal rocks eastward) and the other 'pure shear' (faulting and folding in the upper crust, with viscous shortening in the mid-lower crust). Deep-crustal deformation implied by each model is different and would produce different anisotropic rock fabric. Observations of seismic anisotropy can thus offer a discriminant. We use broad-band phase-velocity curves-each a robust average of tens to hundreds of measurements-to determine azimuthal anisotropy in the entire lithosphere-asthenosphere depth range and constrain its amplitude. Inversions of the differential dispersion from path pairs, region-average inversions and phase-velocity tomography yield mutually consistent results, defining two highly anisotropic layers with different fast-propagation directions within each: the middle crust and the asthenosphere. In the asthenosphere beneath central and eastern Tibet, anisotropy is 2-4 per cent and has an NNE-SSW fast-propagation azimuth, indicating flow probably driven by the NNE-ward, shallow-angle subduction of India. The distribution and complexity of published shear wave splitting measurements can be accounted for by the different anisotropy in the mid-lower crust and asthenosphere. The estimated splitting times that would be accumulated in the crust alone are 0.25-0.8 s; in the upper mantle-0.5-1.2 s, depending on location. In the middle crust (20-45 km depth) beneath southern and central Tibet, azimuthal anisotropy is 3-5 and 4-6 per cent, respectively, and its E-W fast-propagation directions are parallel to the current extension at the surface. The rate of the extension is relatively low, however, whereas the large radial anisotropy observed in the middle crust requires strong alignment of mica crystals, implying large finite strain and

Shear behavior of reinforced Engineered Cementitious Composites (ECC) beams

DEFF Research Database (Denmark)

Paegle, Ieva; Fischer, Gregor

2010-01-01

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

Influence of Base Oil Polarity on the Transient Shear Flow of Biodegradable Lubricating Greases

Directory of Open Access Journals (Sweden)

Martin Fiedler

2015-09-01

Full Text Available The scope of this study is to elucidate the physical mechanisms influencing the transient flow behavior of lubricating greases based on biogenic oleochemicals from a polarity point of view. This includes the mutually interacting influence of base oil polarity and thickening agents on the rheologically-measured mechanical structural degradation in transient shear flow. Due to the high temperature dependence of Keesom forces in the background of polar-active bond mechanisms, the analysis of the transient flow response as a function of temperature allows to attribute the observed influences to differences in base oil polarity. In general, clay-thickened greases show a greater tendency to be rheologically influenced by base oil polarities than soap-thickened lubricating greases.

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

Science.gov (United States)

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

2018-01-01

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

Study on reinforced lightweight coconut shell concrete beam behavior under shear

International Nuclear Information System (INIS)

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

2013-01-01

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

Structure of a shear-thickening polysaccharide extracted from the New Zealand black tree fern, Cyathea medullaris.

Science.gov (United States)

Wee, May S M; Matia-Merino, Lara; Carnachan, Susan M; Sims, Ian M; Goh, Kelvin K T

2014-09-01

A shear-thickening water-soluble polysaccharide was purified from mucilage extracted from the fronds of the New Zealand black tree fern (Cyathea medullaris or 'mamaku' in Māori) and its structure characterised. Constituent sugar analysis by three complementary methods, combined with linkage analysis (of carboxyl reduced samples) and 1H and 13C nuclear magnetic resonance spectroscopy (NMR) revealed a glucuronomannan comprising a backbone of 4-linked methylesterified glucopyranosyl uronic acid and 2-linked mannopyranosyl residues, branched at O-3 of 45% and at both O-3 and O-4 of 53% of the mannopyranosyl residues with side chains likely comprising terminal xylopyranosyl, terminal galactopyranosyl, non-methylesterified terminal glucopyranosyl uronic acid and 3-linked glucopyranosyl uronic acid residues. The weight-average molecular weight of the purified polysaccharide was ∼1.9×10(6) Da as determined by size-exclusion chromatography coupled with multi-angle laser light scattering (SEC-MALLS). The distinctive rheological properties of this polysaccharide are discussed in relation to its structure. Copyright © 2014 Elsevier B.V. All rights reserved.

Shear-wave dynamic behavior using two different orientations

International Nuclear Information System (INIS)

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

2007-01-01

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

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

Science.gov (United States)

Panizza, P.; Courbin, L.; Cristobal, G.; Rouch, J.; Narayanan, T.

2003-05-01

We investigate the effect of shear flow on a lamellar-sponge phase-separating fluid when subjected to shear flow. We show the existence of two different steady states (droplets and ribbons structures) whose nature does not depend on the way to reach the two-phase unstable region of the phase diagram (temperature quench or stirring). The transition between ribbons and droplets is shear thickening and its nature strongly depends on what dynamical variable is imposed. If the stress is fixed, flow visualization shows the existence of shear bands at the transition, characteristic of coexistence in the cell between ribbons and droplets. In this shear-banding region, the viscosity oscillates. When the shear rate is fixed, no shear bands are observed. Instead, the transition exhibits a hysteretic behavior leading to a structural bi-stability of the phase-separating fluid under flow.

Shear strength behavior of geotextile/geomembrane interfaces

Directory of Open Access Journals (Sweden)

Belén M. Bacas

2015-12-01

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

Time-dependent behavior of rough discontinuities under shearing conditions

Science.gov (United States)

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

2018-02-01

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

Seismic behavior of reinforced concrete shear walls

International Nuclear Information System (INIS)

Wang, F.; Gantenbein, F.

1989-01-01

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

Tribological characteristic enhancement effects by polymer thickened oil in lubricated sliding contacts

Science.gov (United States)

Pratomo, Ariawan Wahyu; Muchammad, Tauviqirrahman, Mohammad; Jamari, Bayuseno, Athanasius P.

2016-04-01

Polymer thickened oils are the most preferred materials for modern lubrication applications due to their high shear. The present paper explores a lubrication mechanism in sliding contact lubricated with polymer thickened oil considering cavitation. Investigations are carried out by using a numerical method based on commercial CFD (computational fluid dynamic) software ANSYS for fluid flow phenomenon (Fluent) to assess the tribological characteristic (i.e. hydrodynamic pressure distribution) of lubricated sliding contact. The Zwart-Gerber-Belamri model for cavitation is adopted in this simulation to predict the extent of the full film region. The polymer thickened oil is characterized as non-Newtonian power-law fluid. The simulation results show that the cavitation lead lower pressure profile compared to that without cavitation. In addition, it is concluded that the characteristic of the lubrication performance with polymer thickened oil is strongly dependent on the Power-law index of lubricant.

Behavior of Reinforced Concrete Membrane Elements Subjected to Bidirectional Shear Loads

OpenAIRE

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

2013-01-01

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

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

Science.gov (United States)

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

2018-01-01

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

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

Science.gov (United States)

Labib, Moheb

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

Shear behavior of concrete beams externally prestressed with Parafil ropes

Directory of Open Access Journals (Sweden)

A.H. Ghallab

2013-03-01

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

Seismic behavior of semi-supported steel shear walls

DEFF Research Database (Denmark)

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

2012-01-01

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

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

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Simon Heru Prassetyo

2017-08-01

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

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

DEFF Research Database (Denmark)

Paegle, Ieva; Fischer, Gregor

2016-01-01

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

PEG and Thickeners: A Critical Interaction Between Polyethylene Glycol Laxative and Starch-Based Thickeners.

Science.gov (United States)

Carlisle, Brian J; Craft, Garrett; Harmon, Julie P; Ilkevitch, Alina; Nicoghosian, Jenik; Sheyner, Inna; Stewart, Jonathan T

2016-09-01

Clinicians commonly encounter dysphagia and constipation in a skilled nursing population. Increasing the viscosity of liquids, usually with a starch- or xanthan gum-based thickener, serves as a key intervention for patients with dysphagia. We report a newly identified and potentially dangerous interaction between polyethylene glycol 3350 laxative (PEG) and starch-thickened liquids. A patient requiring nectar-thickened liquids became constipated, and medical staff prescribed PEG for constipation. His nurse observed that the thickened apple juice immediately thinned to near-water consistency when PEG was added. She obtained the same results with thickened water and coffee. We quantified this phenomenon by isothermal rotational rheology. Results confirmed a precipitous loss of thickening when PEG was added to starch-based thickeners but not with xanthan gum-based thickeners. Clinicians and front-line staff should be aware of this potentially critical interaction between PEG- and starch-based thickeners. Although confirmatory studies are needed, our preliminary data suggest that PEG may be compatible with xanthan gum-- based thickeners. Copyright © 2016 AMDA – The Society for Post-Acute and Long-Term Care Medicine. All rights reserved.

Evaluation of composite shear walls behavior (parametric study

Directory of Open Access Journals (Sweden)

Ali Nikkhoo

2017-11-01

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

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

Directory of Open Access Journals (Sweden)

Alhamad Siyam

2017-01-01

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

Behaviors of Polymer Additives Under EHL and Influences of Interactions Between Additives on Friction Modification

Science.gov (United States)

Sakurai, T.

1984-01-01

Polymer additives have become requisite for the formulation of multigrade engine oils. The behavior of polymethacrylate (PMA)-thickened oils as lubricants in concentrated contacts under nominal rolling and pure sliding conditions was investigated by conventional optical interferometry. The PMA thickened oils behaved differently from the base oil in the formation of elastohydrodynamic (EHL) films. The higher the elastohydrodynamic molecular weight of the PMA contained in the lubricant, the thinner was the oil film under EHL conditions. The film thickness of shear-degraded PMA-thickened oils was also investigated. The behavior of graphite particles dispersed in both the base oil and the PMA-thickened oil was studied under pure sliding by taking photomicrographs. Many kinds of additives are contained in lubricating oil and the interactions between additives are considered. The interactions of zinc-organodithiophosphates (ZDP) with other additives is discussed.

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

Science.gov (United States)

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

2017-09-01

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

A Novel Model for the Entire Settling-Thickening Process in a Secondary Settling Tank.

Science.gov (United States)

He, Zhijiang; Zhang, Yuankai; Wang, Hongchen; Qi, Lu; Yin, Xunfei; Zhang, Xiaojun; Wen, Yang

2016-12-01

  Sludge settling and thickening occur simultaneously in secondary settling tanks (SSTs). The ability to accurately calculate the settling and thickening capacity of activated sludge was of great importance. Despite extensive studies on the development of settling velocity models for use with SSTs, these models have not been applied due to the difficulty in calibrating the related parameters. Additionally, there have been some studies of the thickening behavior of the activated sludge in SSTs. In this study, a novel settling and thickening model for activated sludge was developed, and the model was validated using experimental data (R2 = 0.830 to 0.963, p settling and thickening behavior of the activated sludge in an SST. The application of these models requires only one critical parameter, namely, the stirred sludge volume index SSVI3.5, which is readily available in a water resource recovery facility.

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

Science.gov (United States)

Cui, Zhenlu

2011-03-01

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

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

Science.gov (United States)

Kumar, Amit; Higdon, Jonathan J L

2010-11-01

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

Shear layer characteristics of supersonic free and impinging jets

Science.gov (United States)

Davis, T. B.; Kumar, R.

2015-09-01

The initial shear layer characteristics of a jet play an important role in the initiation and development of instabilities and hence radiated noise. Particle image velocimetry has been utilized to study the initial shear layer development of supersonic free and impinging jets. Microjet control employed to reduce flow unsteadiness and jet noise appears to affect the development of the shear layer, particularly near the nozzle exit. Velocity field measurements near the nozzle exit show that the initially thin, uncontrolled shear layer develops at a constant rate while microjet control is characterized by a rapid nonlinear thickening that asymptotes downstream. The shear layer linear growth rate with microjet control, in both the free and the impinging jet, is diminished. In addition, the thickened shear layer with control leads to a reduction in azimuthal vorticity for both free and impinging jets. Linear stability theory is used to compute unstable growth rates and convection velocities of the resultant velocity profiles. The results show that while the convection velocity is largely unaffected, the unstable growth rates are significantly reduced over all frequencies with microjet injection. For the case of the impinging jet, microjet control leads to near elimination of the impingement tones and an appreciable reduction in broadband levels. Similarly, for the free jet, significant reduction in overall sound pressure levels in the peak radiation direction is observed.

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-07-15

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

Time Independent Fluids

Science.gov (United States)

Collyer, A. A.

1973-01-01

Discusses theories underlying Newtonian and non-Newtonian fluids by explaining flow curves exhibited by plastic, shear-thining, and shear-thickening fluids and Bingham plastic materials. Indicates that the exact mechanism governing shear-thickening behaviors is a problem of further study. (CC)

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

Science.gov (United States)

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

2017-12-07

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

Importance of Tensile Strength on the Shear Behavior of Discontinuities

Science.gov (United States)

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

2012-05-01

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

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

Science.gov (United States)

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

2018-06-01

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

Modeling of Mesoscale Variability in Biofilm Shear Behavior.

Directory of Open Access Journals (Sweden)

Pallab Barai

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2013-06-15

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

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

Directory of Open Access Journals (Sweden)

Qiyun Qiao

2017-12-01

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

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

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K. Abubakri

2016-10-01

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

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

Science.gov (United States)

Hashemnejad, Seyed Meysam; Kundu, Santanu

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

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

Science.gov (United States)

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

2018-02-01

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

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

Science.gov (United States)

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

2017-11-01

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

Thickening the outer margins of the Tibetan Plateau: The role of crustal shortening

Science.gov (United States)

Lease, R. O.; Burbank, D. W.

2012-12-01

One of the most direct consequences of the collision of two buoyant continents is large-scale crustal thickening that results in the upward and outward growth of high terrain. As the stronger Indian continent has collided with weaker Asia over at least the past 50 Myr, widespread crustal thickening has occurred over an area that is approximately 2.5 million km^2 at present. The resultant Tibetan crust is the thickest observed on Earth today with an average thickness of 65 km and a maximum that may reach 90 km in places. The mechanisms by which Tibetan crust has thickened, however, as well as the timing and distribution of these mechanisms across the plateau, remain debatable. Two of the most popular mechanisms for thickening the crust beneath the margins of the Tibetan Plateau are: 1) pure shear with faulting and folding in the upper crust and horizontal shortening below; and 2) flow and inflation of lower or middle crust without significant shortening of the upper crust. To help discriminate between the relative contributions of these two mechanisms, well-constrained estimates of upper crustal shortening are needed. Here we document the Cenozoic shortening budget across the northeastern Tibetan Plateau margin near 36°N 102.5°E with several 100- to 145-km-long balanced cross sections. Thermochronological and magnetostratigraphic data indicate that modest NNE-SSW shortening began in middle Eocene time, shortly after initial India-Asia collision. Accelerated east-west shortening, however, did not commence until ~35 Myr later. A five-fold acceleration in shortening rates in middle Miocene-to-Recent time accounts for more than half of the total Cenozoic crustal shortening and thickening in this region. Overall, the balanced cross sections indicate 11 ± 2 % east-west shortening since middle Miocene time, and ~9 ± 2 % NNE-SSW shortening between middle Eocene and middle Miocene times. Given the present-day crustal thickness of 56 ± 4 km in northeastern Tibet, crustal

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

Science.gov (United States)

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

2013-10-23

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

Sensory texture analysis of thickened liquids during ingestion.

Science.gov (United States)

Chambers, Edgar; Jenkins, Alicia; Mertz Garcia, Jane

2017-12-01

Practitioners support the use of thickened liquids for many patients with disordered swallowing. Although physical measures have highlighted differences among products there are questions about the ability of the measures to fully explain the sensory texture effects during swallowing of thickened liquids. This study used a trained sensory panel to describe the textural aspects of liquids during ingestion and swallowing. The lexicon was able to characterize differences in beverages, thickeners, and thickness levels with the most important attribute being viscosity, which loaded heavily in the almost one-dimensional space that resulted from the sensory analysis of these beverages. Other effects, such as slipperiness provided some minimal additional information on the products. Trained sensory panelists were shown to be useful in the measurement of differences in thickened liquid products prescribed for patients with dysphagia. They were able to differentiate products based on perceived differences related to flow speed, viscosity, and other parameters suggesting their use in further studies of swallowing behavior and for development of products for disordered swallowing should be considered. Understanding how these variables might relate to clinical decision making about product selection or modification to best meet the nutritional needs of a person with disordered swallowing could be helpful. This is especially true given the difficulties in measuring texture instrumentally in these products. © 2017 Wiley Periodicals, Inc.

Effect of rock joint roughness on its cyclic shear behavior

Directory of Open Access Journals (Sweden)

S.M. Mahdi Niktabar

2017-12-01

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

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

International Nuclear Information System (INIS)

Maruta, M.; Yamazaki, M.

1993-01-01

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

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

International Nuclear Information System (INIS)

Gao, Wei; Wang, Xingzhe

2016-01-01

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

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

Directory of Open Access Journals (Sweden)

Joo-Won Kang

2013-10-01

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

Interfacial Shear Strength and Adhesive Behavior of Silk Ionomer Surfaces.

Science.gov (United States)

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

2017-09-11

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

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

Directory of Open Access Journals (Sweden)

Floriana Petrone

2014-07-01

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

Experimental study on concrete shear wall behavior under seismic loading

International Nuclear Information System (INIS)

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

1991-01-01

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

Thickened infant formula: What to know

NARCIS (Netherlands)

Salvatore, Silvia; Savino, Francesco; Singendonk, Maartje; Tabbers, Merit; Benninga, Marc A.; Staiano, Annamaria; Vandenplas, Yvan

2018-01-01

This study aimed to provide an overview of the characteristics of thickened formulas to aid health care providers manage infants with regurgitations. The indications, properties, and efficacy of different thickening agents and thickened formulas on regurgitation and gastroesophageal reflux in

Rheological State Diagrams for Rough Colloids in Shear Flow.

Science.gov (United States)

Hsiao, Lilian C; Jamali, Safa; Glynos, Emmanouil; Green, Peter F; Larson, Ronald G; Solomon, Michael J

2017-10-13

To assess the role of particle roughness in the rheological phenomena of concentrated colloidal suspensions, we develop model colloids with varying surface roughness length scales up to 10% of the particle radius. Increasing surface roughness shifts the onset of both shear thickening and dilatancy towards lower volume fractions and critical stresses. Experimental data are supported by computer simulations of spherical colloids with adjustable friction coefficients, demonstrating that a reduction in the onset stress of thickening and a sign change in the first normal stresses occur when friction competes with lubrication. In the quasi-Newtonian flow regime, roughness increases the effective packing fraction of colloids. As the shear stress increases and suspensions of rough colloids approach jamming, the first normal stresses switch signs and the critical force required to generate contacts is drastically reduced. This is likely a signature of the lubrication films giving way to roughness-induced tangential interactions that bring about load-bearing contacts in the compression axis of flow.

Rheological State Diagrams for Rough Colloids in Shear Flow

Science.gov (United States)

Hsiao, Lilian C.; Jamali, Safa; Glynos, Emmanouil; Green, Peter F.; Larson, Ronald G.; Solomon, Michael J.

2017-10-01

To assess the role of particle roughness in the rheological phenomena of concentrated colloidal suspensions, we develop model colloids with varying surface roughness length scales up to 10% of the particle radius. Increasing surface roughness shifts the onset of both shear thickening and dilatancy towards lower volume fractions and critical stresses. Experimental data are supported by computer simulations of spherical colloids with adjustable friction coefficients, demonstrating that a reduction in the onset stress of thickening and a sign change in the first normal stresses occur when friction competes with lubrication. In the quasi-Newtonian flow regime, roughness increases the effective packing fraction of colloids. As the shear stress increases and suspensions of rough colloids approach jamming, the first normal stresses switch signs and the critical force required to generate contacts is drastically reduced. This is likely a signature of the lubrication films giving way to roughness-induced tangential interactions that bring about load-bearing contacts in the compression axis of flow.

Ribbon phase in a phase-separated lyotropic lamellar-sponge mixture under shear flow

Science.gov (United States)

Cristobal, G.; Rouch, J.; Panizza, P.; Narayanan, T.

2001-07-01

We report the effect of shear flow on a phase-separated system composed of lyotropic lamellar (Lα) and sponge (L3) phases in a mixture of brine, surfactant, and cosurfactant. Optical microscopy, small-angle light, and x-ray scattering measurements are consistent with the existence of a steady state made of multilamellar ribbonlike structures aligned in the flow direction. At high shear rates, these ribbonlike structures become unstable and break up into monodisperse droplets resulting in a shear-thickening transition.

Complex rheological behaviors of loach (Misgurnus anguillicaudatus) skin mucus

International Nuclear Information System (INIS)

Wang, Xiang; Su, Heng; Lv, Weiyang; Du, Miao; Song, Yihu; Zheng, Qiang

2015-01-01

The functions and structures of biological mucus are closely linked to rheology. In this article, the skin mucus of loach (Misgurnus anguillicaudatus) was proved to be a weak hydrogel susceptible to shear rate, time, and history, exhibiting: (i) Two-region breakdown of its gel structure during oscillatory strain sweep; (ii) rate-dependent thickening followed by three-region thinning with increased shear rate, and straight thinning with decreased shear rate; and (iii) time-dependent rheopexy at low shear rates, and thixotropy at high shear rates. An interesting correlation between the shear rate- and time-dependent rheological behaviors was also revealed, i.e., the rheopexy-thixotropy transition coincided with the first-second shear thinning region transition. Apart from rheology, a structure of colloidal network was observed in loach skin mucus using transmission electron microscopy. The complex rheology was speculated to result from inter- and intracolloid structural alterations. The unique rheology associated with the colloidal network structure, which has never been previously reported in vertebrate mucus, may play a key role in the functions (e.g., flow, reannealing, lubrication, and barrier) of the mucus

Complex rheological behaviors of loach (Misgurnus anguillicaudatus) skin mucus

Energy Technology Data Exchange (ETDEWEB)

Wang, Xiang, E-mail: 11229036@zju.edu.cn; Su, Heng, E-mail: shtdyso@163.com; Lv, Weiyang, E-mail: 3090103369@zju.edu.cn; Du, Miao, E-mail: dumiao@zju.edu.cn; Song, Yihu, E-mail: s-yh0411@zju.edu.cn; Zheng, Qiang, E-mail: zhengqiang@zju.edu.cn [MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

2015-01-15

The functions and structures of biological mucus are closely linked to rheology. In this article, the skin mucus of loach (Misgurnus anguillicaudatus) was proved to be a weak hydrogel susceptible to shear rate, time, and history, exhibiting: (i) Two-region breakdown of its gel structure during oscillatory strain sweep; (ii) rate-dependent thickening followed by three-region thinning with increased shear rate, and straight thinning with decreased shear rate; and (iii) time-dependent rheopexy at low shear rates, and thixotropy at high shear rates. An interesting correlation between the shear rate- and time-dependent rheological behaviors was also revealed, i.e., the rheopexy-thixotropy transition coincided with the first-second shear thinning region transition. Apart from rheology, a structure of colloidal network was observed in loach skin mucus using transmission electron microscopy. The complex rheology was speculated to result from inter- and intracolloid structural alterations. The unique rheology associated with the colloidal network structure, which has never been previously reported in vertebrate mucus, may play a key role in the functions (e.g., flow, reannealing, lubrication, and barrier) of the mucus.

Sensory characteristics of liquids thickened with commercial thickeners to levels specified in the International Dysphagia Diet Standardization Initiative (IDDSI) framework.

Science.gov (United States)

Ong, Jane Jun-Xin; Steele, Catriona M; Duizer, Lisa M

2018-06-01

Sensory characteristics are important for the acceptance of thickened liquids, but those of liquids thickened to the new standards put forth by the International Dysphagia Diet Standardization Initiative (IDDSI) are unknown. This research sought to identify and rate the perception of important sensory properties of liquids thickened to levels specified in the IDDSI framework. Samples were made with water, with and without added barium sulfate, and were thickened with a cornstarch or xanthan gum based thickener. Samples were characterized using projective mapping/ultra-flash profiling to identify important sample attributes, and then with trained descriptive analysis panels to characterize those attributes in non-barium and barium thickened liquids. Three main groups of attributes were observed. Taste and flavor attributes decreased in intensity with increasing thickener. Thickener specific attributes included graininess and chalkiness for the cornstarch thickened samples, and slipperiness for the xanthan gum samples. Within the same type of thickener, ratings of thickness-related attributes (perceived viscosity, adhesiveness, manipulation, and swallowing) at different IDDSI levels were significantly different from each other. However, in non-barium samples, cornstarch samples were perceived as thicker than xanthan gum samples even though they had similar apparent viscosities at 50 s -1 . On the other hand, the two thickeners had similar perceived thickness in the barium samples even though the apparent viscosities of cornstarch samples were higher than those of the xanthan gum samples. In conclusion, IDDSI levels can be distinguished based on sensory properties, but these properties may be affected by the type of thickener and medium being thickened.

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

International Nuclear Information System (INIS)

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

2010-01-01

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

Study of cement pastes rheological behavior using dynamic shear rheometer

Directory of Open Access Journals (Sweden)

J. E. S. L. Teixeira

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

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

International Nuclear Information System (INIS)

Ahmad, S.; Bukhari, I.A.

2007-01-01

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

Dynamic behavior and functional integrity tests on RC shear walls

International Nuclear Information System (INIS)

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

1991-01-01

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

Strain transformation between tectonic extrusion and crustal thickening in the growth of the Tibetan Plateau

Science.gov (United States)

Liu, M.; Li, Y.; Sun, Y.; Shen, X.

2017-12-01

The Indo-Eurasian continental collision since 50 Ma has thickened the crust to raise the Himalayan-Tibetan Plateau and driven lateral extrusion of Asian lithospheric blocks to affect Cenozoic tectonics in central and east Asia. The relative roles of crustal thickening and tectonic extrusion, and the strain partitioning between them over time and space, remain controversial. We have analyzed the strain rates using GPS velocities, and correlated the results with vertical motion derived from precise leveling. We found that tectonic extrusion largely transforms to crustal thickening near the margins of the Tibetan Plateau. Near the NW margin of the Tibetan Plateau, the shear stain transforms to compressive strain, consistent with neotectonic studies that indicate crustal shortening and uplift. Around the SE margin, shear stain largely terminates in the southern Yunnan province of China. The present-day crustal motion in SE Tibetan Plateau can be well explained by gravitational spreading without invoking plate-edge push as envisioned in the tectonic extrusion model. Using data collected from local seismic arrays, we derived receiver functions to image the lithospheric structures across the Tibetan Plateau and the Alashan block to its north and the Ordos block to its east. Our results indicate that the mantle lithosphere of these bounding Asian blocks has not been reworked by Tibetan tectonics; instead they have acted as restrictive walls to the growing Tibetan Plateau. Our finite element modeling shows that crustal deformation along the margins of the Tibetan Plateau are consistent with the notion that the east- and southeastward extrusion of the Tibetan lithosphere is largely confined to the Tibetan Plateau because of the restrictive bounding blocks of the Asian lithosphere. Thus the tectonic impact of the Indo-Eurasian collision on the Cenozoic Asian tectonics may not be as extensive as previously thought.

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

NARCIS (Netherlands)

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

2017-01-01

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

Influence of particle size on the low and high strain rate behavior of dense colloidal dispersions of nanosilica

Energy Technology Data Exchange (ETDEWEB)

Asija, Neelanchali; Chouhan, Hemant; Gebremeskel, Shishay Amare; Bhatnagar, Naresh, E-mail: nareshb@mech.iitd.ac.in [Indian Institute of Technology Delhi, Mechanical Engineering Department (India)

2017-01-15

Shear thickening is a non-Newtonian flow behavior characterized by the increase in apparent viscosity with the increase in applied shear rate, particularly when the shear rate exceeds a critical value termed as the critical shear rate (CSR). Due to this remarkable property of shear-thickening fluids (STFs), they are extensively used in hip protection pads, protective gear for athletes, and more recently in body armor. The use of STFs in body armor has led to the development of the concept of liquid body armor. In this study, the effect of particle size is explored on the low and high strain rate behavior of nanosilica dispersions, so as to predict the efficacy of STF-aided personal protection systems (PPS), specifically for ballistic applications. The low strain rate study was conducted on cone and plate rheometer, whereas the high strain rate characterization of STF was conducted on in-house fabricated split Hopkinson pressure bar (SHPB) system. Spherical nanosilica particles of three different sizes (100, 300, and 500 nm) as well as fumed silica particles of four different specific surface areas (Aerosil A-90, A-130, A-150, and A-200), respectively, were used in this study. The test samples were prepared by dispersing nanosilica particles in polypropylene glycol (PPG) using ultrasonic homogenization method. The low strain rate studies aided in determining the CSR of the synthesized STF dispersions, whereas the high strain rate studies explored the impact-resisting ability of STFs in terms of the impact toughness and the peak stress attained during the impact loading of STF in SHPB testing.

Echocardiography: pericardial thickening and constrictive pericarditis.

Science.gov (United States)

Schnittger, I; Bowden, R E; Abrams, J; Popp, R L

1978-09-01

A total of 167 patients with pericardial thickening noted on M node echocardiography were studied retrospectively. After the echocardiogram, 72 patients underwent cardiac surgery, cardiac catheterization or autopsy for various heart diseases; 96 patients had none of these procedures. In 49 patients the pericardium was directly visualized at surgery or autopsy; 76 percent of these had pericardial thickening or adhesions. In another 8 percent, pericardial adhesions were absent, but no comment had been made about the appearance of the pericardium itself. In the remaining 16 percent, no comment had been made about the pericardium or percardial space. Cardiac catheterization in 64 patients revealed 24 with hemodynamic findings of constrictive pericarditis or effusive constrictive disease. Seven echocardiographic patterns consistent with pericardial adhesions or pericardial thickening are described and related when possible to the subsequent findings at heart surgery or autopsy. The clinical diagnoses of 167 patients with pericardial thickening are presented. The hemodynamic diagnosis of constrictive pericardial disease was associated with the echocardiographic finding of pericardial thickening, but there were no consistent echocardiographic patterns of pericardial thickening diagnostic of constriction. However, certain other echocardiographic abnormalities of left ventricular posterior wall motion and interventricular septal motion and a high E-Fo slope were suggestive of constriction.

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

DEFF Research Database (Denmark)

Li, Jingqing; Guan, Peipei; Zhang, Yao

2014-01-01

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

Multichannel thickener of flotation tailings

Energy Technology Data Exchange (ETDEWEB)

Kondratenko, A F; Shuliko, A N; Zinchenko, A F

1983-04-01

A multichannel thickener of flotation tailings developed by Ukrniiugleobogashchenie is described. Tailings with solid content ranging from 40 to 60 g/l are mixed with flocculation reagents (quantity ratio from 60 to 70 g/l) in a turbulent mixer: waste water with tailings fed to the mixer is divided into three streams, flocculation reagents are batched in stages with each water stream. After turbulent mixing, water, tailings and reagent are fed to the settling chamber. Settling chamber (dimensions 2.4 x 1.5 x 1.0 m) is divided into a number of channels by settling surfaces of 0.35 m/sup 2/ each, inclined at an angle of 55 degrees. Distance between the surfaces is 50 mm. The thickener has a total settling surface of 18.7 m/sup 2/. Water with tailings flows upwards, cleaned water is removed by a separating system and settled tailings move downward and accumulate in the compacting chamber (dimensions 1.5 x 1.5 x 0.9 m). From the compacting chamber thickened slurry with solid content from 90 to 150 g/l is removed by a hydraulic system. During performance testing in some plants preparing coal difficult to wash, thickening efficiency amounted to 100%. The results of performance testing are shown in two tables. Factors which influence thickener productivity are evaluated. (In Russian)

Behavior of Tilted Angle Shear Connectors

Science.gov (United States)

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

2015-01-01

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

Behavior of Tilted Angle Shear Connectors.

Directory of Open Access Journals (Sweden)

Koosha Khorramian

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

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

International Nuclear Information System (INIS)

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

2013-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2013-10-15

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

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

OpenAIRE

Cuenca Asensio, Estefanía

2013-01-01

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

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

Science.gov (United States)

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

2014-08-01

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

[Residual pleural thickening in tuberculous pleuritis. Associated factors

Science.gov (United States)

Ruiz, E; Alegre, J; Alemán, C; Vizcaya, S; Armadans, L; Segura, R M; Andreu, J; Iglesias, D; Fernández de Sevilla, T

2000-10-01

To study the factors related to the development of residual pleural thickening in pleural tuberculosis. We studied 39 patients with tuberculous pleural effusion. A chest X-ray was taken of each patient at the end of treatment. The patients' medical histories, pleural fluid findings and diagnostic chest films were evaluated. Residual pleural thickening was defined as thickening that was visibly greater than 2 mm in the lower side portion of the chest film. Residual pleural thickening developed in 26% of patients and was found mainly in men (RR = 3.86). In no patients with Löwenstein-Jensen cultures positive for Mycobacterium tuberculosis did pleural complications develop. Residual pleural thickening is a common complication of tuberculous pleural effusion. Residual pleural thickening in tuberculous pleurisy occurs more often in men and older patients, and in cases in which pleural liquid culture is negative for M. tuberculosis.

Effect of Time and Temperature on Thickened Infant Formula.

Science.gov (United States)

Gosa, Memorie M; Dodrill, Pamela

2017-04-01

Unlike adult populations, who primarily depend on liquids for hydration alone, infants rely on liquids to provide them with hydration and nutrition. Speech-language pathologists working within pediatric medical settings often identify dysphagia in patients and subsequently recommend thickened liquids to reduce aspiration risk. Caregivers frequently report difficulty attempting to prepare infant formula to the prescribed thickness. This study was designed to determine (1) the relationship between consistencies in modified barium swallow studies and thickened infant formulas and (2) the effects of time and temperature on the resulting thickness of infant formula. Prepackaged barium consistencies and 1 standard infant formula that was thickened with rice cereal and with 2 commercially available thickening agents were studied. Thickness was determined via a line spread test after various time and temperature conditions were met. There were significant differences between the thickened formula and barium test consistencies. Formula thickened with rice cereal separated over time into thin liquid and solid residue. Formula thickened with a starch-based thickening agent was thicker than the desired consistency immediately after mixing, and it continued to thicken over time. The data from this project suggest that nectar-thick and honey-thick infant formulas undergo significant changes in flow rates within 30 minutes of preparation or if refrigerated and then reheated after 3 hours. Additional empirical evidence is warranted to determine the most reliable methods and safest products for thickening infant formula when necessary for effective dysphagia management.

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-02-08

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

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

International Nuclear Information System (INIS)

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

1995-01-01

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

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

DEFF Research Database (Denmark)

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

2013-01-01

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

Non-traumatic Thickening of the Anterior Cruciate Ligament

Energy Technology Data Exchange (ETDEWEB)

Oh, Hyun Jun; Park, Jin Gyoon; Song, Sang Gook [Chonnam National University Hospital, Gwangju (Korea, Republic of)

2009-08-15

To describe the magnetic resonance (MR) imaging findings of non-traumatic thickening of the anterior cruciate ligament (ACL) and to evaluate the associated lesions. Between January 2003 and August 2005, 44 knees of 44 patients who had thickened ACLs on MR images and had no history of knee trauma were analyzed retrospectively. The normal thickness of the ACL was measured on axial T2-weighted images of 40 healthy adult knees. The MR imaging findings of the thickened ACLs and associated lesions were analyzed. In 40 cases of healthy knees, the thickness of the proximal ACL was 3-6 mm. In 44 cases of non-traumatic thickening of the ACL, the thickness of the proximal ACL was 8-14 mm. There was an increased signal intensity and ill-defined border in all cases of thickened ACLs, linear low-signal intensity fibers parallel to the long axis of the thickened ACL (celery stalk appearance) in 24 cases, and entrapment in 10 cases. With respect to associated lesions, there was osteoarthritis in 40 cases, meniscal tears in 42 cases, and degeneration of the posterior cruciate ligament in 7 cases. Non-traumatic thickening of the ACL was associated with osteoarthritis and meniscal tears in almost all cases and showed increased signal intensity and ill-defined borders simulating acute ligamentous tears

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

OpenAIRE

Abubakri, K.; Veladi, H.

2016-01-01

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

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

Directory of Open Access Journals (Sweden)

Ahmed Ibrahim

2016-12-01

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

Non-Newtonian particulate flow simulation: A direct-forcing immersed boundary-lattice Boltzmann approach

Science.gov (United States)

Amiri Delouei, A.; Nazari, M.; Kayhani, M. H.; Kang, S. K.; Succi, S.

2016-04-01

In the current study, a direct-forcing immersed boundary-non-Newtonian lattice Boltzmann method (IB-NLBM) is developed to investigate the sedimentation and interaction of particles in shear-thinning and shear-thickening fluids. In the proposed IB-NLBM, the non-linear mechanics of non-Newtonian particulate flows is detected by combination of the most desirable features of immersed boundary and lattice Boltzmann methods. The noticeable roles of non-Newtonian behavior on particle motion, settling velocity and generalized Reynolds number are investigated by simulating benchmark problem of one-particle sedimentation under the same generalized Archimedes number. The effects of extra force due to added accelerated mass are analyzed on the particle motion which have a significant impact on shear-thinning fluids. For the first time, the phenomena of interaction among the particles, such as Drafting, Kissing, and Tumbling in non-Newtonian fluids are investigated by simulation of two-particle sedimentation and twelve-particle sedimentation. The results show that increasing the shear-thickening behavior of fluid leads to a significant increase in the kissing time. Moreover, the transverse position of particles for shear-thinning fluids during the tumbling interval is different from Newtonian and the shear-thickening fluids. The present non-Newtonian particulate study can be applied in several industrial and scientific applications, like the non-Newtonian sedimentation behavior of particles in food industrial and biological fluids.

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

Directory of Open Access Journals (Sweden)

Nur Yazdani

2016-01-01

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

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

Science.gov (United States)

Kim, Daehyeon; Ha, Sungwoo

2014-02-07

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

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

Directory of Open Access Journals (Sweden)

Abu-Bakre Abdelmoneim Elamin Mohamad

2016-08-01

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

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

Directory of Open Access Journals (Sweden)

Yurisman

2010-11-01

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

The development and application of high-capacity thickening techniques

International Nuclear Information System (INIS)

Ji Zhenwan; Song Yuejie

1995-01-01

On the basis of sedimentation theory and comparison between the high-capacity and conventional thickening techniques, the authors analyse the ways to increase capacity and to improve technological parameters of thickeners, describes the construction features, development, application, automatic control and test installations of high-capacity thickeners at home and abroad

Interfacial shear behavior of composite flanged concrete beams

Directory of Open Access Journals (Sweden)

Moataz Awry Mahmoud

2014-08-01

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

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

Directory of Open Access Journals (Sweden)

Rafea Flaih Hassan

2018-02-01

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

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

International Nuclear Information System (INIS)

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

2007-01-01

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

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

International Nuclear Information System (INIS)

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

2013-01-01

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

Color doppler sonography in thickened gallbladder wall

International Nuclear Information System (INIS)

Han, Sang Suk; Choi, Seok Jin; Seo, Chang Hae; Eun, Choong Ki

1996-01-01

The thickening of the gallbladder wall is a valuable finding for the diagnosis of cholecystitis, but may be seen in non-cholecystic disease as well as in acute or chronic cholecystitis. The purpose of this study is to determine the value of color Doppler sonography in differentiating the causes of thickened gallbladder wall. Ninety eight patients with thickened gallbladder wall(more than 3mm) which was not due to gallbladder cancer were prospectively evaluated with color Doppler sonography. Sixty-six cases, confirmed by pathologic reports and clinical records, were analyzed for correlation between thickened gallbladder wall and color flow signal according to the underlying causes. Of the 66 patients, 28 cases were cholecystitis and 38 cases had non-cholecystic causes such as liver cirrhosis, ascites, hepatitis, pancreatitis, renal failure, and hypoalbuminemia. Of the 28 patients with cholecystitis(12 acute, 16 chronic), 23(82%) had color Doppler flow signals in the thickened gallbladder wall. Of the 38 patients with non-cholecystic causes, eight(21%) had color Doppler flow signals. There was a statistically significant difference of color Doppler flow signals between the cholecystitis and non-cholecystic groups(p=0.0001). No significant difference of color Doppler flow signals was found between cases of acute and chronic cholecystitis. Of the 23 patients with color Doppler flow signals in 28 cases of cholecystitis, 18(78.3%) showed a linear pattern and five(21.7%) showed a spotty pattern. Of the eight patients with color Doppler flow signals in the 38 non-cholecystic cases, four(50%) showed a linear pattern and four(50%) showed a spotty pattern. In cholecystitis, a linear color Doppler flow signal pattern is a much more frequent finding than a spotty pattern. Color Doppler sonography is a useful and adequate method for determining whether a thickened gallbladder wall is the result of cholecystitis or has non-cholecystic causes

Formulation of lubricating grease using Beeswax thickener

Science.gov (United States)

Suhaila, N.; Japar, A.; Aizudin, M.; Aziz, A.; Najib Razali, Mohd

2018-04-01

The issues on environmental pollution has brought the industries to seek the alternative green solutions for lubricating grease formulation. The significant challenges in producing modified grease are in which considering the chosen thickener as one of the environmental friendly material. The main purposes of the current research were to formulate lubricant grease using different types of base oils and to study the effect of thickener on the formulated lubricant grease. Used oil and motor oil were used as the base oils for the grease preparation. Beeswax and Damar were used as thickener and additive. The grease is tested based on its consistency, stability and oil bleeding. The prepared greases achieved grease consistency of grade 2 and 3 except for grease with unfiltered used oil. Grease formulated with used oil and synthetic oil tend to harden and loss its lubricating ability under high temperature compared to motor oil’ grease. Grease modification using environmental friendly thickener were successfully formulated but it is considered as a low temperature grease as the beeswax have low melting point of 62°C-65°C.

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

Directory of Open Access Journals (Sweden)

Daehyeon Kim

2014-02-01

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

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

Science.gov (United States)

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

2018-05-01

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

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

Directory of Open Access Journals (Sweden)

Ammar N. HANOON

2014-12-01

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

Thickened cortical bones in congenital neutropenia

International Nuclear Information System (INIS)

Boechat, M.I.; Gormley, L.S.; O'Laughlin, B.J.

1987-01-01

Congenital neutropenia is an uncommon entity which may be familial and has a wide spectrum of clinical expression. Three sisters with the severe form of the disease, that suffered from recurrent infections which lead to their demise are described. Review of their radiographs revealed the presence of cortical thickening of the bones. Although several syndroms with different bone abnormalities have been reported associated with neutropenia, the radiographic finding of thickened cortex in children with congenital neutropenia has not been previously described. (orig.)

Thickened cortical bones in congenital neutropenia

Energy Technology Data Exchange (ETDEWEB)

Boechat, M.I.; Gormley, L.S.; O' Laughlin, B.J.

1987-02-01

Congenital neutropenia is an uncommon entity which may be familial and has a wide spectrum of clinical expression. Three sisters with the severe form of the disease, that suffered from recurrent infections which lead to their demise are described. Review of their radiographs revealed the presence of cortical thickening of the bones. Although several syndroms with different bone abnormalities have been reported associated with neutropenia, the radiographic finding of thickened cortex in children with congenital neutropenia has not been previously described.

Non-homogeneous flow profiles in sheared bacterial suspensions

Science.gov (United States)

Samanta, Devranjan; Cheng, Xiang

Bacterial suspensions under shear exhibit interesting rheological behaviors including the remarkable ``superfluidic'' state with vanishing viscosity at low shear rates. Theoretical studies have shown that such ``superfluidic'' state is linked with non-homogeneous shear flows, which are induced by coupling between nematic order of active fluids and hydrodynamics of shear flows. However, although bulk rheology of bacterial suspensions has been experimentally studied, shear profiles within bacterial suspensions have not been explored so far. Here, we experimentally investigate the flow behaviors of E. coli suspensions under planar oscillatory shear. Using confocal microscopy and PIV, we measure velocity profiles across gap between two shear plates. We find that with increasing shear rates, high-concentration bacterial suspensions exhibit an array of non-homogeneous flow behaviors like yield-stress flows and shear banding. We show that these non-homogeneous flows are due to collective motion of bacterial suspensions. The phase diagram of sheared bacterial suspensions is systematically mapped as functions of shear rates an bacterial concentrations. Our experiments provide new insights into rheology of bacterial suspensions and shed light on shear induced dynamics of active fluids. Chemical Engineering and Material Science department.

The diagnostic significance of thickening of extrapleural fat

International Nuclear Information System (INIS)

Zhao Weifeng; Pan Jixu; Liu Fugeng

1999-01-01

Objective: To determine the role of thickening of extrapleural fat (EPF) in the diagnosis of pleural and/or para-pleural lung disease. Methods: 166 patients with pleural and/or para-pleural lung disease were studied by CT. Any EPF demonstrated would be near the diseased area, its thickness, and CT number were measured and compared with the CT number of the subcutaneous fat. The anterior thoracic wall of 50 normal subjects were also observed for the normal EPF appearances. Results: In normal group 28(56%) cases showed EPF, its thickness being 1-2 mm. In patient group 106(63.9%) cases showed EPF, among these 88 cases showed the thickness of EPF>2 mm. The mean thickness of the thickened EPF was 5.6 mm. Its mean CT number was -90.3 HU. Higher than that of the subcutaneous fat, the latter's mean CT number was -116.8HU. In this group, the causative disease included radiation lung injury, empyema, chronic lung tuberculosis, thickened and calcified pleura, calcified tuberculoma and lung injury, empyema, chronic lung tuberculosis, thickened and calcified pleura, calcified tuberculoma and lung fibrosis. In the remaining 18 cases, the thickness of EPF was less than 2 mm. No EPF was demonstrated in the other 60 patients. In the latter group the disease included carcinomatous effusion, pleural transudates, peripheral lung caner, thickened pleura, pleural metastasis, tuberculous pleural effusion, acute pneumonia and pleural fibroma. Conclusions: The thickening of EPF was mostly seen in chronic inflammatory and tuberculous diseases. This sign was helpful in differential diagnosis of pleural and/or parapleural lung disease

Predicting Shear Transformation Events in Metallic Glasses

Science.gov (United States)

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

2018-03-01

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

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

Science.gov (United States)

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

2017-11-22

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

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

International Nuclear Information System (INIS)

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

1995-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-04-13

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

Non-aqueous slurries used as thickeners

Energy Technology Data Exchange (ETDEWEB)

Hatfield, J C

1982-04-07

A non-aqueous slurry is described that is suitable for use as a thickener or viscosifier in oil or gas drilling, fracturing, flow diversion completion or workover fluids. The slurry comprises a water-soluble cellulose ether polymer, a water-insoluble liquid hydrocarbon, a non-ionic surfactant having an HLB of from 7 to 14, and an organo modified clay. There also is described a process for thickening or viscosifying a drilling, fracturing, flow diversion, completion or workover fluid. The use of the slurry prevents bumping during addition to aqueous fluids. (27 claims)

Flocking particles in a non-Newtonian shear thickening fluid

Science.gov (United States)

Mucha, Piotr B.; Peszek, Jan; Pokorný, Milan

2018-06-01

We prove the existence of strong solutions to the Cucker–Smale flocking model coupled with an incompressible viscous non-Newtonian fluid with the stress tensor of a power–law structure for . The fluid part of the system admits strong solutions while the solutions to the CS part are weak. The coupling is performed through a drag force on a periodic spatial domain . Additionally, we construct a Lyapunov functional determining the large time behavior of solutions to the system.

Characterization of oils sands thickened tailings

Energy Technology Data Exchange (ETDEWEB)

Scott, J.D.; Jeeravipoolvarn, S.; Donahue, R.; Ozum, B. [Alberta Univ., Edmonton, AB (Canada). Dept. of Civil and Environmental Engineering

2008-07-01

This presentation discussed the characterization of oils sands thickened tailings. The problem statement was defined as the fact that many laboratory procedures to characterize fine tailings do not take into account the extraction process, and instead use standardized laboratory tests. The purpose of this presentation was to demonstrate how different extraction processes affect the fine tailings geotechnical properties and water chemistry. Properties that were characterized included particle size analysis from hydrometer-sieve tests; per cent clay from methylene blue tests; per cent clay from mineralogy tests; Atterberg limits; water chemistry; and morphology by scanning electron microscopy. The presentation discussed the origin of fines (silt and clay) in tailings; where fine particles come from; tailings materials; mineralogy of tailings; the hydrometer-sieve test on fine tailings and thickened tailings; and the methylene blue test. It was concluded that the great majority of clay minerals in the tailings come from the clay-shale discontinuous seams and layers. For thickened tailings, the dispersed and non-dispersed hydrometer tests show considerable difference in the amount of clay size material. tabs., figs.

Late extensional shear zones and associated recumbent folds in the Alpujarride subduction complex, Betic Cordillera, southern Spain

Energy Technology Data Exchange (ETDEWEB)

Orozco, M.; Alonso-Chaves, F.; Platt, J.

2017-11-01

The existence in the Alpujarride Complex (Betic Cordillera, southern Spain) of a relatively continuous extensional event (following crustal thickening) is based on detailed structural studies and is consistent with the P-T paths and geochronological data established for the Alpujarride rocks. According to our research, the Alpujarride Complex contains two large-scale shear zones accommodating early Miocene extension. The shear zones contain km-scale recumbent folds, some with sheath fold geometry, and megaboudinage structures, and are closely associated with detachment faults. Large-scale folds and boudins cause dome-like undulations in the detachments, which are inferred to overlap in time with the deformation in the shear zones. One shear zone in the eastern part of the orogen is top-N; the other, in the western part, is top-E. The change in the shear direction may represent a temporal evolution in the direction of shear, possibly related to a change in the subduction direction in space and time.

Late extensional shear zones and associated recumbent folds in the Alpujarride subduction complex, Betic Cordillera, southern Spain

International Nuclear Information System (INIS)

Orozco, M.; Alonso-Chaves, F.; Platt, J.

2017-01-01

The existence in the Alpujarride Complex (Betic Cordillera, southern Spain) of a relatively continuous extensional event (following crustal thickening) is based on detailed structural studies and is consistent with the P-T paths and geochronological data established for the Alpujarride rocks. According to our research, the Alpujarride Complex contains two large-scale shear zones accommodating early Miocene extension. The shear zones contain km-scale recumbent folds, some with sheath fold geometry, and megaboudinage structures, and are closely associated with detachment faults. Large-scale folds and boudins cause dome-like undulations in the detachments, which are inferred to overlap in time with the deformation in the shear zones. One shear zone in the eastern part of the orogen is top-N; the other, in the western part, is top-E. The change in the shear direction may represent a temporal evolution in the direction of shear, possibly related to a change in the subduction direction in space and time.

Studies of food thickeners in Nigeria for contamination by ...

African Journals Online (AJOL)

Jane

2011-08-10

Aug 10, 2011 ... Food thickeners or thickening agents are used in food to absorb the fluid of the ... used in beverages, gravies, sauces and stews. The use of food ... Furthermore, it has also not been possible to develop effective management.

Dynamic localization and shear-induced hopping of particles: A way to understand the rheology of dense colloidal dispersions

International Nuclear Information System (INIS)

Jiang, Tianying; Zukoski, Charles F.

2014-01-01

For decades, attempts have been made to understand the formation of colloidal glasses and gels by linking suspension mechanics to particle properties where details of size, shape, and spatial dependencies of pair potentials present a bewildering array of variables that can be manipulated to achieve observed properties. Despite the range of variables that control suspension properties, one consistent observation is the remarkably similarity of flow properties observed as particle properties are varied. Understanding the underlying origins of the commonality in those behaviors (e.g., shear-thinning with increasing stress, diverging zero shear rate viscosity with increasing volume fraction, development of a dynamic yield stress plateau with increases in volume faction or strength of attraction, development of two characteristic relaxation times probed in linear viscoelasticity, the creation of a rubbery plateau modulus at high strain frequencies, and shear-thickening) remains a challenge. Recently, naïve mode coupling and dynamic localization theories have been developed to capture collective behavior giving rise to formation of colloidal glasses and gels. This approach characterizes suspension mechanics of strongly interacting particles in terms of sluggish long-range particle diffusion modulated by varying particle interactions and volume fraction. These theories capture the scaling of the modulus with the volume fraction and strength of interparticle attraction, the frequency dependence of the moduli at the onset of the gel/glass transition, together with the divergence of the zero shear rate viscosity and cessation of diffusivity for hard sphere systems as close packing is approached. In this study, we explore the generality of the predictions of dynamic localization theory for systems of particles composed of bimodal particle size distributions experiencing weak interactions. We find that the mechanical properties of these suspensions are well captured within

Dynamic localization and shear-induced hopping of particles: A way to understand the rheology of dense colloidal dispersions

Energy Technology Data Exchange (ETDEWEB)

Jiang, Tianying; Zukoski, Charles F., E-mail: czukoski@illinois.edu [Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801 (United States)

2014-09-01

For decades, attempts have been made to understand the formation of colloidal glasses and gels by linking suspension mechanics to particle properties where details of size, shape, and spatial dependencies of pair potentials present a bewildering array of variables that can be manipulated to achieve observed properties. Despite the range of variables that control suspension properties, one consistent observation is the remarkably similarity of flow properties observed as particle properties are varied. Understanding the underlying origins of the commonality in those behaviors (e.g., shear-thinning with increasing stress, diverging zero shear rate viscosity with increasing volume fraction, development of a dynamic yield stress plateau with increases in volume faction or strength of attraction, development of two characteristic relaxation times probed in linear viscoelasticity, the creation of a rubbery plateau modulus at high strain frequencies, and shear-thickening) remains a challenge. Recently, naïve mode coupling and dynamic localization theories have been developed to capture collective behavior giving rise to formation of colloidal glasses and gels. This approach characterizes suspension mechanics of strongly interacting particles in terms of sluggish long-range particle diffusion modulated by varying particle interactions and volume fraction. These theories capture the scaling of the modulus with the volume fraction and strength of interparticle attraction, the frequency dependence of the moduli at the onset of the gel/glass transition, together with the divergence of the zero shear rate viscosity and cessation of diffusivity for hard sphere systems as close packing is approached. In this study, we explore the generality of the predictions of dynamic localization theory for systems of particles composed of bimodal particle size distributions experiencing weak interactions. We find that the mechanical properties of these suspensions are well captured within

The Measurement of Thickened Liquids Used for the Management of Dysphagia

Science.gov (United States)

Nicholson, T. M.; Torley, P. J.; Cichero, J. A. Y.

2008-07-01

Dysphagia is a condition where a person has difficulty in swallowing. This can lead to reduced dietary intake, dehydration and malnutrition and also aspiration of material into the lungs and asphyxiation. Using thickened fluids slow the act of swallowing and by doing so enhance safe swallowing. A common method of thickening drinks is to use a powdered thickener, but this can lead to problems in ensuring that the consistency of the degree of thickening appropriate to an individual is maintained by those making up the fiuids. There is also no assurance that the thickness of thickened liquids is consistent across commercial manufacturers. In this field viscosity is typically measured using a Line Spread Test, with the resulting viscosities being described by such terms as nectar- honey- or pudding-thick. This test is prone to many variations in operating conditions and so cannot provide accurate reproducible data. In this paper we have used conventional rheology (dynamic oscillatory using a couette cell) to provide quantitative measurement of the development in thickness of various beverages as a function of time. It was found fruit juices typically required less thickener and milk more to achieve the same thickness, but that the degree of thickening varied non-linearly with addition level.

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

International Nuclear Information System (INIS)

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

2009-01-01

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

Significance of appendiceal thickening in association with typhlitis in pediatric oncology patients

International Nuclear Information System (INIS)

McCarville, M.B.; Thompson, J.; Adelman, C.S.; Lee, M.O.; Li, C.; Alsammarae, D.; Rao, B.N.; May, M.V.; Jones, S.C.; Sandlund, J.T.

2004-01-01

Background: The management of pediatric oncology patients with imaging evidence of appendiceal thickening is complex because they are generally poor surgical candidates and often have confounding clinical findings. Objective: We sought to determine the significance of appendiceal thickening in pediatric oncology patients who also had typhlitis. Specifically, we evaluated the impact of this finding on the duration of typhlitis, its clinical management, and outcome. Materials and methods: From a previous review of the management of typhlitis in 90 children with cancer at our institution, we identified 4 with imaging evidence of appendiceal thickening. We compared colonic wall measurements, duration of typhlitis symptoms, management, and outcome of patients with appendiceal thickening and typhlitis to patients with typhlitis alone. Results: There was no significant difference in duration of typhlitis symptoms between patients with typhlitis only (15.6 ± 1.2 days) and those with typhlitis and appendiceal thickening (14.5 ± 5.8 days; P = 0.9). Two patients with appendiceal thickening required surgical treatment for ischemic bowel, and two were treated medically. Only one patient in the typhlitis without appendiceal thickening group required surgical intervention. There were no deaths in children with appendiceal thickening; two patients died of complications of typhlitis alone. (orig.)

Final Research Performance Report - Small Molecular Associative Carbon Dioxide (CO₂) Thickeners for Improved Mobility Control

Energy Technology Data Exchange (ETDEWEB)

Enick, Robert M. [Univ. of Pittsburgh, PA (United States)

2017-12-31

The initial objective of this project was to promote the application of a CO₂ thickener for improved mobility control during CO₂ EOR based on solubility tests, viscosity tests, and core floods. Ultimately, it was demonstrated that the CO₂-soluble polymeric thickeners are much better suited for use a CO₂-soluble conformance control agents for diverting the flow of CO₂ away from thief zones. Our team generated several effective small molecule CO₂ thickeners with ARPA-e funding. Unfortunately, none of these small molecule thickeners could dissolve in CO₂ without the addition of unacceptably large amounts of hexane or toluene as a co-solvent Therefore none were viable candidates for the core flooding studies associated with NETL award. Therefore during the entire core flood testing program associated with this NETL award, our team used only the most promising polymeric CO₂ thickener, a polyfluoroacrylate (PFA). In order to produce an environmentally benign polymer, the monomer used to make the new polymers used in this study was a fluoroacrylate that contains only six fluorinated carbons. We verified CO₂ solubility with a phase behavior cell. The thickening potential of all polymer samples was substantiated with a falling ball viscometer and a falling cylinder viscometer at Pitt. Two different viscometers were used to determine the increase in CO₂ viscosity that could be achieved via the dissolution of PFA. Praxair, which has an interest in thickening CO₂ for pilot EOR projects and for waterless hydraulic fracturing, agreed to measure the viscosity of CO₂-PFA solutions at no cost to the project. Falling cylinder viscometery was conducted at Pitt in our windowed high pressure phase behavior cell. Both apparatuses indicated that at very low shear rates the CO₂ viscosity increased by a factor of roughly 3.5 when 1wt% PFA was

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

International Nuclear Information System (INIS)

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

2002-02-01

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

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

KAUST Repository

Wafai, Husam

2016-09-20

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

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

Science.gov (United States)

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

2008-06-01

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

Computer-aided detection of bladder wall thickening in CT urography (CTU)

Science.gov (United States)

Cha, Kenny H.; Hadjiiski, Lubomir M.; Chan, Heang-Ping; Caoili, Elaine M.; Cohan, Richard H.; Weizer, Alon Z.; Gordon, Marshall N.; Samala, Ravi K.

2018-02-01

We are developing a computer-aided detection system for bladder cancer in CT urography (CTU). Bladder wall thickening is a manifestation of bladder cancer and its detection is more challenging than the detection of bladder masses. We first segmented the inner and outer bladder walls using our method that combined deep-learning convolutional neural network with level sets. The non-contrast-enhanced region was separated from the contrast-enhanced region with a maximum-intensity-projection-based method. The non-contrast region was smoothed and gray level threshold was applied to the contrast and non-contrast regions separately to extract the bladder wall and potential lesions. The bladder wall was transformed into a straightened thickness profile, which was analyzed to identify regions of wall thickening candidates. Volume-based features of the wall thickening candidates were analyzed with linear discriminant analysis (LDA) to differentiate bladder wall thickenings from false positives. A data set of 112 patients, 87 with wall thickening and 25 with normal bladders, was collected retrospectively with IRB approval, and split into independent training and test sets. Of the 57 training cases, 44 had bladder wall thickening and 13 were normal. Of the 55 test cases, 43 had wall thickening and 12 were normal. The LDA classifier was trained with the training set and evaluated with the test set. FROC analysis showed that the system achieved sensitivities of 93.2% and 88.4% for the training and test sets, respectively, at 0.5 FPs/case.

Aplicação de um Modelo Reológico Não-Linear em Sistemas Poliméricos Dilatantes Application of Non-Linear Rheological Model to Shear-Tickening Polymeric Systems

Directory of Open Access Journals (Sweden)

Rômulo F. Navarro

2002-01-01

Full Text Available A dilatância é um comportamento reológico comum a vários sistemas poliméricos embora não ocorra em polímeros puros. Existem várias teorias aplicáveis à explicação desse fenômeno e alguns modelos matemáticos para o ajuste de dados experimentais de quatro de suas seis formas de ocorrência. Neste trabalho é dado enfoque à dilatância antecedida por um comportamento newtoniano e sucedida pelo comportamento pseudoplástico. Para ajustar dados constantes da literatura para sistemas desse tipo, é apresentado um modelo híbrido e não-linear. Para o teste do modelo foram utilizados dados existentes na literatura para solução de alfa,ômega poli(t-butilestireno em óleo mineral e suspensão de partículas do copolímero de estireno com acrilato de metila em solução aquosa de poli(ácido acrílico. O modelo proposto apresenta boa concordância com os dados experimentais.Shear-thickening (dilatant behavior is common in several polymeric systems, but not in pure polymers. There are many theories that can be used to describe shear-thickening and some mathematical models that fit experimental data of three of its six types: dilatant, newtonian-dilatant, newtonian-dilatant-pseudoplastic, viscoplastic-dilatant, pseudoplastic-dilatant and newtonian-pseudoplastic-newtonian-dilatant sequences. This work deals with the behavior of newtonian-dilatant-pseudoplastic sequence behavior and proposes a hybrid, non-linear and viscous model to fit the experimental data from systems that present such rheological behavior. The systems under investigation were: a solution of alpha,omega poly(t-butylstyrene in a mineral oil (3g/dl (sample 1 and b suspension of styrene -- methyl acrylate copolymer (S-co-MA particles (15% vol. in a poly(acrylic acid (PAA (1% wt and water solution (sample 2. The proposed model agrees with the experimental data analysed.

Shear-induced phase changes in mixtures

International Nuclear Information System (INIS)

Romig, K.D.; Hanley, H.J.M.

1986-01-01

A thermodynamic theory to account for the behavior of liquid mixtures exposed to a shear is developed. One consequence of the theory is that shear-induced phase changes are predicted. The theory is based on a thermodynamics that includes specifically the shear rate in the formalism and is applied to mixtures by a straightforward modification of the corresponding states, conformalsolution approach. The approach is general but is used here for a mixture of Lennard-Jones particles with a Lennard-Jones equation of state as a reference fluid. The results are discussed in the context of the Scott and Van Konynenberg phase classification. It is shown that the influence of a shear does affect substantially the type of the phase behavior. Results from the model mixture are equated loosely with those from real polymeric liquids

The receptor-like kinase AtVRLK1 regulates secondary cell wall thickening.

Science.gov (United States)

Huang, Cheng; Zhang, Rui; Gui, Jinshan; Zhong, Yu; Li, Laigeng

2018-04-20

During the growth and development of land plants, some specialized cells, such as tracheary elements, undergo secondary cell wall thickening. Secondary cell walls contain additional lignin, compared with primary cell walls, thus providing mechanical strength and potentially improving defenses against pathogens. However, the molecular mechanisms that initiate wall thickening are unknown. In this study, we identified an Arabidopsis thaliana leucine-rich repeat receptor-like kinase, encoded by AtVRLK1 (Vascular-Related RLK 1), that is specifically expressed in cells undergoing secondary cell wall thickening. Suppression of AtVRLK1expression resulted in a range of phenotypes that included retarded early elongation of the inflorescence stem, shorter fibers, slower root growth, and shorter flower filaments. In contrast, upregulation of AtVRLK1 led to longer fiber cells, reduced secondary cell wall thickening in fiber and vessel cells, and defects in anther dehiscence. Molecular and cellular analyses showed that downregulation of AtVRLK1 promoted secondary cell wall thickening and upregulation of AtVRLK1 enhanced cell elongation and inhibited secondary cell wall thickening. We propose that AtVRLK1 functions as a signaling component in coordinating cell elongation and cell wall thickening during growth and development. {copyright, serif} 2018 American Society of Plant Biologists. All rights reserved.

Relation between wall shear stress and carotid artery wall thickening MRI versus CFD

DEFF Research Database (Denmark)

Cibis, Merih; Potters, Wouter V.; Selwaness, Mariana

2016-01-01

Wall shear stress (WSS), a parameter associated with endothelial function, is calculated by computational fluid dynamics (CFD) or phase-contrast (PC) MRI measurements. Although CFD is common in WSS (WSSCFD) calculations, PC-MRI-based WSS (WSSMRI) is more favorable in population studies; since...... it is straightforward and less time consuming. However, it is not clear if WSSMRI and WSSCFD show similar associations with vascular pathology. Our aim was to test the associations between wall thickness (WT) of the carotid arteries and WSSMRI and WSSCFD. The subjects (n=14) with an asymptomatic carotid plaque who...... underwent MRI scans two times within 4 years of time were selected from the Rotterdam Study. We compared WSSCFD and WSSMRI at baseline and follow-up. Baseline WSSMRI and WSSCFD values were divided into 3 categories representing low, medium and high WSS tertiles. WT of each tertile was compared by a one...

Research Status on Bonding Behavior of Prefabricated Concrete Shear Wall

Science.gov (United States)

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

2018-03-01

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

Viscosity of Dysphagia-Oriented Cold-Thickened Beverages: Effect of Setting Time at Refrigeration Temperature

Science.gov (United States)

Kim, Sung-Gun; Yoo, Byoungseung

2015-01-01

Background: Although extensive literature is available on the viscosity of thickened beverages with food thickeners, no attempt has been made to study the effect of setting time on the viscosity of pudding-like cold-thickened beverages with xanthan gum (XG)-based thickeners by using a rheometer. In particular, it is of considerable practical…

Structural behavior of human lumbar intervertebral disc under direct shear.

Science.gov (United States)

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

2015-03-18

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

Breast disease with skin thickening: differential diagnosis with mammography and ultrasonography

Energy Technology Data Exchange (ETDEWEB)

Shin, Young Rok; Kim, Hak Hee; Cha, Eun Suk; Park, Hye Seong; Kim, Ki Tae; Shinn, Kyung Sub [The Catholic University of Korea College of Medicine, Seoul (Korea, Republic of)

1999-02-01

Diffuse skin thickening of the breast is produced by lymphedema usually secondary to obstruction of the axillary lymphatics. On physical examination, the affected breast is, due to increased fluid content, larger, heavier, and of higher overall density. Mammography reveals an increased coarse reticular pattern. Thickening of the skin can have many causes. It may be a result of tumor invasion or a tumor in the dermal lymphatics ; or because of lymphatic congestion through obstruction of lymphatic drainage within the breast, in the axilla, or centrally in the mediastinum. Further causes may be congestive heart failure, benign inflammation, primary skin processes such as psoriasis, or systemic diseases which involve the skin. Mammographic appearance is known to be nonspecific. Ultrasound can demonstrate skin thickening directly, but despite some reports suggesting that the cause of skin thickening can be inferred from the results of ultrasound, this is not usually of practical importance. The purpose of this study is to review the causes of skin thickening of the breast and to use mammography and US to differentiate the causes.

A Comparison of the Viscosities of Thickened Liquids for Pediatric Dysphagia.

Science.gov (United States)

Wijesinghe, Ranjith; Clifton, Mekale; Tarlton, Morgan; Heinsohn, Erica; Ewing, Mary

It has been reported that Speech Language Pathologists in different facilities across the nation use a variety of thickening agents and recipes as therapeutic measures for infants and children diagnosed with dysphagia. Limited research has been completed in this area. Viscosity was tested to determine the thickness of each thickening agent mixed with infant formula. The values were then compared to the National Dysphagia Diet liquid levels to determine which thickening agent resulted in the desired viscosity levels. The thickeners were mixed with common infant formulas and soy formulas to determine if the type of formula impacted the viscosity. The main goal was to determine if the assumed thickness level (viscosity) of prescribed thickened liquids was actually being met. This topic is of high concern because of its impact on the safety and well-being of clients with dysphagia. A viscometer was used to collect the viscosity levels. Commercially available formulas selected for this study. The final results of our investigation will be presented during the APS meeting. This work is supported by a Ball State University Immersive Learning Grant.

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-07-15

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

Synthesis and Evaluation of CO2 Thickeners Designed with Molecular Modeling

Energy Technology Data Exchange (ETDEWEB)

Robert Enick; Erick Beckman; J. Karl Johnson

2009-08-31

The objective of this research was to use molecular modeling techniques, coupled with our prior experimental results, to design, synthesize and evaluate inexpensive, non-fluorous carbon dioxide thickening agents. The first type of thickener that was considered was associating polymers. Typically, these thickeners are copolymers that contain a highly CO{sub 2}-philic monomer, and a small concentration of a CO{sub 2}-phobic associating monomer. Yale University was solely responsible for the synthesis of a second type of thickener; small, hydrogen bonding compounds. These molecules have a core that contains one or more hydrogen-bonding groups, such as urea or amide groups. Non-fluorous, CO{sub 2}-philic functional groups were attached to the hydrogen bonding core of the compound to impart CO{sub 2} stability and macromolecular stability to the linear 'stack' of these compounds. The third type of compound initially considered for this investigation was CO{sub 2}-soluble surfactants. These surfactants contain conventional ionic head groups and composed of CO{sub 2}-philic oligomers (short polymers) or small compounds (sugar acetates) previously identified by our research team. Mobility reduction could occur as these surfactant solutions contacted reservoir brine and formed mobility control foams in-situ. The vast majority of the work conducted in this study was devoted to the copolymeric thickeners and the small hydrogen-bonding thickeners; these thickeners were intended to dissolve completely in CO{sub 2} and increase the fluid viscosity. A small but important amount of work was done establishing the groundwork for CO{sub 2}-soluble surfactants that reduced mobility by generating foams in-situ as the CO{sub 2}+surfactant solution mixed with in-situ brine.

Structural evolution of the Irtysh Shear Zone: implication for the Late Paleozoic amalgamation of multiple arc systems in Central Asia

Science.gov (United States)

Li, Pengfei; Sun, Min; Rosenbaum, Gideon

2015-04-01

The NW-SE Irtysh Shear Zone represents a major tectonic boundary in the Central Asian Orogenic Belt, recording the amalgamation history between the peri-Siberian orogenic system and the Kazakhstan orogenic system. The structural evolution and geodynamics of this shear zone is still poorly documented. Here we present new structural data complemented by chronological data in an attempt to unravel the geodynamic significance of the Irtysh Shear Zone in the context of accretion history of the Central Asian Orogenic Belt. Our results show three episodes of deformation for the shear zone. D1 foliation is locally recognized in low strain area and recorded by garnet inclusions, whereas D2 is represented by a sub-horizontal fabric and related NW-SE lineation. D3 is characterized by a transpersonal deformation event, to form a series of NW-SE mylonitic belts with sinistral kinematics, and to overprint D2 fabric forming regional-scale NW-SE upright folds. A paragneiss sample from the shear zone yielded the youngest detrital zircon peaks in the late Carboniferous, placing a maximum age constraint on the deformation, which overlaps in time with the late Paleozoic collision between the Chinese Altai and the intraoceanic arc system of the East Junggar and West Junggar. We interpret three episodes of deformation to represent orogenic thickening (D1), collapse (D2) and thickening (D3) in response to this collisional event. Sinistral shearing (D3) together with the coeval dextral shearing in the Tianshan accommodate eastward extrusion of the Kazakhstan orogenic system during the late Paleozoic amalgamation of the Central Asian Orogenic Belt. Acknowledgements: This study was financially supported by the Major Basic Research Project of the Ministry of Science and Technology of China (Grant: 2014CB440801), Hong Kong Research Grant Council (HKU705311P and HKU704712P), National Science Foundation of China (41273048, 41273012) and a HKU CRCG grant. The work is a contribution of the Joint

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

Science.gov (United States)

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

2018-01-01

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

Shear-induced morphology transition and microphase separation in a lamellar phase doped with clay particles.

Science.gov (United States)

Nettesheim, Florian; Grillo, Isabelle; Lindner, Peter; Richtering, Walter

2004-05-11

We report on the influence of shear on a nonionic lamellar phase of tetraethyleneglycol monododecyl ether (C12E4) in D2O containing clay particles (Laponite RD). The system was studied by means of small-angle light scattering (SALS) and small-angle neutron scattering (SANS) under shear. The SANS experiments were conducted using a H2O/D2O mixture of the respective scattering length density to selectively match the clay scattering. The rheological properties show the familiar shear thickening regime associated with the formation of multilamellar vesicles (MLVs) and a shear thinning regime at higher stresses. The variation of viscosity is less pronounced as commonly observed. In the shear thinning regime, depolarized SALS reveals an unexpectedly strong variation of the MLV size. SANS experiments using the samples with lamellar contrast reveal a change in interlamellar spacing of up to 30% at stresses that lead to MLV formation. This change is much more pronounced than the change observed, when shear suppresses thermal bilayer undulations. Microphase separation occurs, and as a consequence, the lamellar spacing decreases drastically. The coincidence of the change in lamellar spacing and the onset of MLV formation is a strong indication for a morphology-driven microphase separation.

Texture Adaption in Dysphagia: Acceptability Differences Between Thickened and Naturally Thick Beverages.

Science.gov (United States)

Gerschke, Marco; Seehafer, Peggy

The aim of the study was to investigate differences in the acceptability between thickened and naturally viscous beverages. This was an exploratory, cross-sectional study. One hundred twenty-eight healthy volunteers rated overall liking/disliking of a selection of each of three thickened drinks and three beverages of natural viscosity pre- and postconsumption. Mean ratings were subjected to statistical analysis done with t tests. Although all naturally thick beverages evoked good expectations, there were significant differences in expected acceptance of thickened fluids concerning the kind of beverage. Postconsumption of naturally thick beverages were rated significantly better than thickened. The findings suggest an alternative offer of naturally thick drinks and waiver of thickening water when viscosity adaption is needed. The sufficient and safe oral fluid intake in dysphagia requires compliance to dietetic recommendations. Naturally thick beverages can contribute to increase the appeal of texture-modified diet.

Experimental study of a shear wall with numerous small openings

International Nuclear Information System (INIS)

Sotomura, K.; Murazumi, Y.; Yoshizaki, S.; Ezaki, T.

1981-01-01

Many small openings for piping and ducts are usually required in the shear walls for PWR nuclear power plant. It is generally believed that such openings oadversely affect the strength and stiffness of shear walls. However, little information is available concerning the behavior of walls with numerous small openings. Therefore, tests using wall specimens and an analysis using an FEM program were carried out to investigate this behavior. Main findings are as follows: 1) The ultimate strength of a shear wall with numerous small openings may be obtained by using the effective area at the critical cross section of the shear wall. 2) Shear walls with openings can be restored to the same shear strength and stiffness as shear walls without openings by diagonal reinforcement. (orig./HP)

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

International Nuclear Information System (INIS)

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

2006-01-01

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

Distinguishing benign from malignant gallbladder wall thickening using FDG-PET

International Nuclear Information System (INIS)

Oe, Ai; Kawabe, Joji; Torii, Kenji

2006-01-01

Because thickening of the gallbladder wall is observed not only in patients with gallbladder cancer but also in those with benign diseases such as chronic cholecystitis and gallbladder adenomyosis, it is difficult to distinguish between benign and malignant gallbladder wall thickening by conventional techniques of diagnostic imaging such as computed tomography (CT), magnetic resonance imaging (MRI), and abdominal ultrasonography (US). In the present study, we attempted to distinguish between benign and malignant gallbladder wall thickening by means of fluorine-18-fluorodeoxyglucose (FDG)-Positron emission tomography (PET). FDG-PET was performed in 12 patients with gallbladder wall thickening detected by CT or US, to determine whether it was benign or malignant. Emission scans were taken, beginning 45 minutes after intravenous administration of FDG, and standardized uptake value (SUV) was calculated as an indicator of glucose metabolism. Of the 12 patients, 4 showed positive uptake of FDG in the gallbladder wall. Of these 4 patients, 3 had gallbladder cancer. The remaining one, who had chronic cholecystitis, had false-positive findings. The other 8 patients had negative uptake of FDG in the gallbladder wall. Two of these 8 underwent surgical resection, which yielded a diagnosis of chronic cholecystitis. The other 6 patients exhibited no sign of gallbladder malignancy and have been followed without active treatment. FDG-PET appears able to distinguish between benign and malignant gallbladder wall thickening. (author)

Magnetorheological dampers in shear mode

International Nuclear Information System (INIS)

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

2008-01-01

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

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

Science.gov (United States)

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

2014-02-01

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

[Effect of food thickener on disintegration and dissolution of magnesium oxide tablets].

Science.gov (United States)

Tomita, Takashi; Goto, Hidekazu; Yoshimura, Yuya; Tsubouchi, Yoshiko; Nakanishi, Rie; Kojima, Chikako; Yoneshima, Mihoko; Yoshida, Tadashi; Tanaka, Katsuya; Sumiya, Kenji; Kohda, Yukinao

2015-01-01

It has been reported that magnesium oxide tablets are excreted in a non-disintegrated state in the stool of patients when the tablets are administered after being immersed in a food thickener. Therefore we examined whether immersion in a food thickener affects the pharmacological effect in patients taking magnesium oxide tablets, and whether immersion affects its disintegration and solubility. The mean dosage (1705 mg/d) was higher for patients who took tablets after immersion in a food thickener than for those who took non-immersed tablets (1380 mg/d). The disintegration time and dissolution rate of the immersed tablets were lower than those of non-immersed tablets in vitro. Furthermore, components that constitute the food thickener and differences in composition concentrations differentially affect the disintegration and solubility of magnesium oxide tablets. This suggests that commercially available food thickeners are likely to be associated with changes in the degradation of magnesium oxide tablets, and they therefore should be carefully used in certain clinical situations.

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

African Journals Online (AJOL)

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

Nonlinear interaction of Rayleigh--Taylor and shear instabilities

International Nuclear Information System (INIS)

Finn, J.M.

1993-01-01

Results on the nonlinear behavior of the Rayleigh--Taylor instability and consequent development of shear flow by the shear instability [Phys. Fluids B 4, 488 (1992)] are presented. It is found that the shear flow is generated at sufficient amplitude to reduce greatly the convective transport. For high viscosity, the time-asymptotic state consists of an equilibrium with shear flow and vortex flow (with islands, or ''cat's eyes''), or a relaxation oscillation involving an interplay between the shear instability and the Rayleigh--Taylor instability in the presence of shear. For low viscosity, the dominant feature is a high-frequency nonlinear standing wave consisting of convective vortices localized near the top and bottom boundaries. The localization of these vortices is due to the smaller shear near the boundary regions. The convective transport is largest around these convective vortices near the boundary and there is a region of good confinement near the center. The possible relevance of this behavior to the H mode and edge-localized modes (ELM's) in the tokamak edge region is discussed

Gallbladder wall thickening: MR imaging and pathologic correlation with emphasis on layered pattern

International Nuclear Information System (INIS)

Jung, S.E.; Lee, J.M.; Hahn, S.T.; Lee, K.; Rha, S.E.; Choi, B.G.; Kim, E.K.

2005-01-01

The aim of this study was to correlate MR findings of gallbladder wall thickening with pathologic findings on the basis of the layered pattern and to evaluate the diagnostic value of MR imaging in gallbladder disease. We retrospectively evaluated the source images of HASTE sequences for MR cholangiography in 144 patients with gallbladder wall thickening. The layered pattern of thickened wall was classified into four patterns. Type 1 shows two layers with a thin hypointense inner layer and thick hyperintense outer layer. Type 2 has two layers of ill-defined margin. Type 3 shows multiple hyperintense cystic spaces in the wall. Type 4 shows diffuse nodular thickening without layering. MR findings of a layered pattern of thickened gallbladder were well correlated with histopathology. Chronic cholecystitis matched to type 1, acute cholecystitis corresponded to type 2, adenomyomatosis showed type 3, and the gallbladder carcinomas showed type 4. All four layered patterns were associated with PPV of 73% or greater, sensitivity of 92% or greater and specificity of 95% or greater. Our results indicate that MR findings of gallbladder wall thickening are characteristic in each entity and correlate well with pathologic findings. The classification of the layered pattern may be valuable for interpreting thickened gallbladder wall. (orig.)

Flow behavior at different shear rates for dry powders

NARCIS (Netherlands)

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

2010-01-01

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

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

Science.gov (United States)

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

2016-10-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-10-15

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

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

International Nuclear Information System (INIS)

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

2016-01-01

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

Process for the preparation of a thickened explosive slurry

Energy Technology Data Exchange (ETDEWEB)

1972-10-25

A process is described for the preparation of a thickened explosive slurry, substantially aqueous. The composition consists essentially of a suspension of an inorganic oxygen salt for furnishing oxygen in a fluid matrix. This fluid matrix consists of a lower aliphatic glycol (ethylene, diethylene, propylene, dipropylene) thickened with one of the polysaccharides (glucose, mannose, galactose) or mixtures of them. The composition should have a density below 1.8 g per cu cm. (5 claims)

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

DEFF Research Database (Denmark)

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

2010-01-01

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

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

Science.gov (United States)

Ucar, Taner; Merter, Onur

2018-01-01

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

EFFECT OF THICKENERS ON THE TEXTURE OF STIRRED YOGURT

Directory of Open Access Journals (Sweden)

D. GONÇALVEZ

2009-03-01

Full Text Available

The effect of the addition of gelatin and starch on the rheological properties of sweetened plain stirred yogurt was studied by manufacturing six samples: two with gelatin (3000 and 6000 ppm, three with starch (1000, 5000, 10000 ppm and a sample without thickener (control. Rheological characterization of the samples was performed using a coaxial cylinder Haake VT500 viscometer. Yield stress ( and hysteresis were also determined. Syneresis (% was measured by centrifugation at 1100 rpm for 10 minutes. Sensory characterization was performed with a panel of trained sensory assessors, who evaluated the following texture attributes: viscosity, ropiness, creaminess and mouthfeel. All samples showed thixotropic and pseudoplastic behaviour. Since the upward curve did not fit a unique model, it was divided in two regions. The first one fitted Herschel-Bulkley’s model. The addition of gelatine decreased flow behaviour index (n, whereas yield stress significantly increased with the addition of both thickeners. Gelatine was more efficient in reducing syneresis than starch. The addition of thickeners significantly increased all the studied sensory texture attributes. Non-oral and oral parameters were highly correlated witch each other and witch rheological parameters. KEYWORDS: Yogurt; texture; thickeners.

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

Directory of Open Access Journals (Sweden)

Reza Bemanian

2016-03-01

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

Anomalous transport due to shear-Alfven waves

International Nuclear Information System (INIS)

Lee, W.W.; Chance, M.S.; Okuda, H.

1980-10-01

The behavior of shear-Alfven eigenmodes and the accompanied anomalous transport have been investigated. In the particle simulation, equilibrium thermal fluctuations associated with the eigenmodes have been observed to nullify the zeroth-order shear near the rational surface through the induced second-order eddy current, and, in turn, give rise to the formation of magnetic islands which cause rapid electron energy transport in the region. The theoretical verification of the observed behavior is discussed

Temperature-dependent residual shear strength characteristics of smectite-rich landslide soils

Science.gov (United States)

Shibasaki, Tatsuya; Matsuura, Sumio; Okamoto, Takashi

2015-04-01

behaviors were also recognized during cooling-event tests. Shear stress fluctuations, which were obtained by 1 Hz data sampling, showed that shear behavior characteristically changed in response to temperature conditions. Stick-slip behavior prevailed under room temperature conditions, whereas shear behavior gradually changed into stable sliding behavior as temperature decreased. SEM (Scanning Electric Microscope) observation on shear surfaces indicated that silt- and sand-size asperities in the vicinity of the shear surface influence the occurrence of stick-slip behavior. It is also characteristically noted that rod-shaped smectitic clays, here called "roll", developed on shear surfaces and are arrayed densely perpendicular to the shearing direction in a micrometer scale. We assume that these rolls are probably rotating slowly within shear zone and acting as a lubricant which affects the temperature-dependent frictional properties of the shearing plane. These experimental results show that residual strength characteristics of smectite-rich soils are sensitive to temperature conditions. Our findings imply that if slip surface soils contain a high fraction of smectite, a decrease in ground temperature can lead to lowered shear resistance of the slip surface and triggering of slow landslide movement.

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

Science.gov (United States)

Kim, JunHee; You, Young-Chan

2015-03-03

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

The life of phi: the development of phi thickenings in roots of the orchids of the genus Miltoniopsis.

Science.gov (United States)

Idris, Nurul A; Collings, David A

2015-02-01

Phi thickenings, bands of secondary wall thickenings that reinforce the primary wall of root cortical cells in a wide range of species, are described for the first time in the epiphytic orchid Miltoniopsis. As with phi thickenings found in other plants, the phi thickenings in Miltoniopsis contain highly aligned cellulose running along the lengths of the thickenings, and are lignified but not suberized. Using a combination of histological and immunocytochemical techniques, thickening development can be categorized into three different stages. Microtubules align lengthwise along the thickening during early and intermediate stages of development, and callose is deposited within the thickening in a pattern similar to the microtubules. These developing thickenings also label with the fluorescently tagged lectin wheat germ agglutinin (WGA). These associations with microtubules and callose, and the WGA labeling, all disappear when the phi thickenings are mature. This pattern of callose and WGA deposition show changes in the thickened cell wall composition and may shed light on the function of phi thickenings in plant roots, a role for which has yet to be established.

Pumping evaluations with paste tailings thickened close to the surface disposal area

OpenAIRE

Wennberg, Thord; Sellgren, Anders

2007-01-01

An elevated location of a paste thickener on a ridge close to the disposal area is considered at a Swedish iron ore mine. About 0.7 Mtonnes of thickened tailings are planned to be layered as paste in the vicinity of the thickener over several years with pipeline lengths of up to 900 m after about 20 years. In order to clarify the pipeline pumping characteristics of the tailings product for volumetric solids concentration from 40 to 50%, experiments in loop systems with pipeline inner diameter...

Thrusting and transpressional shearing in the Pan-African nappe southwest El-Sibai core complex, Central Eastern Desert, Egypt

Science.gov (United States)

El-Wahed, Mohamed A. Abd.

2008-01-01

The Wadi El-Shush area in the Central Eastern Desert (CED) of Egypt is occupied by the Sibai core complex and its surrounding Pan-African nappe complex. The sequence of metamorphic and structural events in the Sibai core complex and the enveloping Pan-African nappe can be summarized as follows: (1) high temperature metamorphism associated with partial melting of amphibolites and development of gneissic and migmatitic rocks, (2) between 740 and 660 Ma, oblique island arc accretion resulted in Pan-African nappe emplacement and the intrusion of syn-tectonic gneissic tonalite at about 680 ± 10 Ma. The NNW-SSE shortening associated with oblique island arc accretion produced low angle NNW-directed thrusts and open folds in volcaniclastic metasediments, schists and isolated serpentinite masses (Pan-African nappe) and created NNE-trending recumbent folds in syn-tectonic granites. The NNW-SSE shortening has produced imbricate structures and thrust duplexes in the Pan-African nappe, (3) NE-ward thrusting which deformed the Pan-African nappe into SW-dipping imbricate slices. The ENE-WSW compression event has created NE-directed thrusts, folded the NNW-directed thrusts and produced NW-trending major and minor folds in the Pan-African nappe. Prograde metamorphism (480-525 °C at 2-4.5 kbar) was synchronous with thrusting events, (4) retrograde metamorphism during sinistral shearing along NNW- to NW-striking strike-slip shear zones (660-580 Ma), marking the external boundaries of the Sibai core complex and related to the Najd Fault System. Sinistral shearing has produced steeply dipping mylonitic foliation and open plunging folds in the NNW- and NE-ward thrust planes. Presence of retrograde metamorphism supports the slow exhumation of Sibai core complex under brittle-ductile low temperature conditions. Arc-accretion caused thrusting, imbrication and crustal thickening, whereas gravitational collapse of a compressed and thickened lithosphere initiated the sinistral movement

Evaluating interfacial shear stresses in composite hollo

Directory of Open Access Journals (Sweden)

Aiham Adawi

2016-09-01

Full Text Available Analytical evaluation of the interfacial shear stresses for composite hollowcore slabs with concrete topping is rare in the literature. Adawi et al. (2014 estimated the interfacial shear stiffness coefficient (ks that governs the behavior of the interface between hollowcore slabs and the concrete topping using push-off tests. This parameter is utilized in this paper to provide closed form solutions for the differential equations governing the behavior of simply supported composite hollowcore slabs. An analytical solution based on the deformation compatibility of the composite section and elastic beam theory, is developed to evaluate the shear stresses along the interface. Linear finite element modeling of the full-scale tests presented in Adawi et al. (2015 is also conducted to validate the developed analytical solution. The proposed analytical solution was found to be adequate in estimating the magnitude of horizontal shear stress in the studied composite hollowcore slabs.

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

Science.gov (United States)

Saengow, Chaimongkol; Giacomin, A. Jeffrey

2018-03-01

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

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

Science.gov (United States)

Garai, Ashesh; Nandi, Arun K

2008-04-01

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

Sheared Electroconvective Instability

Science.gov (United States)

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

2012-11-01

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

Focus: Nucleation kinetics of shear bands in metallic glass.

Science.gov (United States)

Wang, J Q; Perepezko, J H

2016-12-07

The development of shear bands is recognized as the primary mechanism in controlling the plastic deformability of metallic glasses. However, the kinetics of the nucleation of shear bands has received limited attention. The nucleation of shear bands in metallic glasses (MG) can be investigated using a nanoindentation method to monitor the development of the first pop-in event that is a signature of shear band nucleation. The analysis of a statistically significant number of first pop-in events demonstrates the stochastic behavior that is characteristic of nucleation and reveals a multimodal behavior associated with local spatial heterogeneities. The shear band nucleation rate of the two nucleation modes and the associated activation energy, activation volume, and site density were determined by loading rate experiments. The nucleation activation energy is very close to the value that is characteristic of the β relaxation in metallic glass. The identification of the rate controlling kinetics for shear band nucleation offers guidance for promoting plastic flow in metallic glass.

Shear thinning behaviors in magmas

Science.gov (United States)

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

2017-12-01

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

Gelation under shear

Energy Technology Data Exchange (ETDEWEB)

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

1995-12-31

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

3D cardiac wall thickening assessment for acute myocardial infarction

Science.gov (United States)

Khalid, A.; Chan, B. T.; Lim, E.; Liew, Y. M.

2017-06-01

Acute myocardial infarction (AMI) is the most severe form of coronary artery disease leading to localized myocardial injury and therefore irregularities in the cardiac wall contractility. Studies have found very limited differences in global indices (such as ejection fraction, myocardial mass and volume) between healthy subjects and AMI patients, and therefore suggested regional assessment. Regional index, specifically cardiac wall thickness (WT) and thickening is closely related to cardiac function and could reveal regional abnormality due to AMI. In this study, we developed a 3D wall thickening assessment method to identify regional wall contractility dysfunction due to localized myocardial injury from infarction. Wall thickness and thickening were assessed from 3D personalized cardiac models reconstructed from cine MRI images by fitting inscribed sphere between endocardial and epicardial wall. The thickening analysis was performed in 5 patients and 3 healthy subjects and the results were compared against the gold standard 2D late-gadolinium-enhanced (LGE) images for infarct localization. The notable finding of this study is the highly accurate estimation and visual representation of the infarct size and location in 3D. This study provides clinicians with an intuitive way to visually and qualitatively assess regional cardiac wall dysfunction due to infarction in AMI patients.

Effect of Human Saliva on the Consistency of Thickened Drinks for Individuals with Dysphagia

Science.gov (United States)

Vallons, Katleen J. R.; Helmens, Harold J.; Oudhuis, A. A. C. M.

2015-01-01

Background: Thickening of foods and fluids is commonly used in the management of dysphagia to reduce the risk of aspiration. The use of starch-based thickeners is established. However, the use of gums in thickeners is gaining interest as they are resistant to salivary amylase, which may promote safer swallowing. Aims: To compare the effect of…

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

Science.gov (United States)

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

2015-11-01

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

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

International Nuclear Information System (INIS)

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

1993-09-01

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

Autocrine role of vascular IL-15 in intimal thickening

International Nuclear Information System (INIS)

Cercek, Miha; Matsumoto, Michiaki; Li, Hongyan; Chyu, K.-Y.; Peter, Ashok; Shah, Prediman K.; Dimayuga, Paul C.

2006-01-01

Interleukin 15 (IL-15) is a pro-inflammatory cytokine that modulates T cell recruitment and activation, independent of antigen. It has been detected in human atherosclerotic plaques and atherosclerotic plaques of apoE-/- mice. IL-15 regulates fractalkine (FKN)-CX3CR1 chemokine signaling which is involved in atherogenesis and promotes SMC proliferation. We investigated the role of IL-15 in intimal thickening after arterial injury. Treatment of serum-stimulated SMC with IL-15 in vitro attenuated proliferation and suppressed CX3CR1 and FKN mRNA expression. The role of endogenous IL-15 in vivo was investigated in injured carotid arteries of mice. Periadventitial arterial injury resulted in increased IL-15 expression in the media and neointima, paralleled by increased IL-15 receptor α expression. Blockade of endogenous IL-15 increased intimal thickening. FKN and CX3CR1 expression increased after injury and were further augmented after IL-15 blockade. These data suggest that endogenous IL-15 attenuated intimal thickening after arterial injury. The potential mechanism of action is suppression of CX3CR1 signaling

A comparative ultrastructural study of pit membranes with plasmodesmata associated thickenings in four angiosperm species.

Science.gov (United States)

Rabaey, David; Lens, Frederic; Huysmans, Suzy; Smets, Erik; Jansen, Steven

2008-11-01

Recent micromorphological observations of angiosperm pit membranes have extended the number and range of taxa with pseudo-tori in tracheary elements. This study investigates at ultrastructural level (TEM) the development of pseudo-tori in the unrelated Malus yunnanensis, Ligustrum vulgare, Pittosporum tenuifolium, and Vaccinium myrtillus in order to determine whether these plasmodesmata associated thickenings have a similar developmental pattern across flowering plants. At early ontogenetic stages, the formation of a primary thickening was observed, resulting from swelling of the pit membrane in fibre-tracheids and vessel elements. Since plasmodesmata appear to be frequently, but not always, associated with these primary pit membrane thickenings, it remains unclear which ultrastructural characteristics control the formation of pseudo-tori. At a very late stage during xylem differentiation, a secondary thickening is deposited on the primary pit membrane thickening. Plasmodesmata are always associated with pseudo-tori at these final developmental stages. After autolysis, the secondary thickening becomes electron-dense and persistent, while the primary thickening turns transparent and partially or entirely dissolves. The developmental patterns observed in the species studied are similar and agree with former ontogenetic studies in Rosaceae, suggesting that pseudo-tori might be homologous features across angiosperms.

Simulations of Granular Particles Under Cyclic Shear

Science.gov (United States)

Royer, John; Chaikin, Paul

2012-02-01

We perform molecular dynamics (MD) simulations of spherical grains subjected to cyclic, quasi-static shear in a 3D parallelepiped shear cell. This virtual shear cell is constructed out of rough, bumpy walls in order to minimize wall-induced ordering and has an open top surface to allow the packing to readily dilate or compact. Using a standard routine for MD simulations of frictional grains, we simulate over 1000 shear cycles, measuring grain displacements, the local packing density and changes in the contact network. Varying the shear amplitude and the friction coefficient between grains, we map out a phase diagram for the different types of behavior exhibited by these sheared grains. With low friction and high enough shear, the grains can spontaneously order into densely packed crystals. With low shear and increasing friction the packing remains disordered, yet the grains arrange themselves into configurations which exhibit limit cycles where all grains return to the same position after each full shear cycle. At higher shear and friction there is a transition to a diffusive state, where grains continue rearrange and move throughout the shear cell.

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

Directory of Open Access Journals (Sweden)

Tohid Akhlaghi

2014-01-01

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

Novel CO{sub 2}-thickeners for improved mobility control

Energy Technology Data Exchange (ETDEWEB)

Enick, Dr. Robert M.; Beckman, Dr. Eric J.; Hamilton, Dr. Andrew

2000-02-02

The objective of this study was to design, synthesize, and characterize thickening agents for dense carbon dioxide and to evaluate their solubility and viscosity-enhancing potential in CO{sub 2}. Previously, fluoroacrylate homopolymers and fluorinated telechelic ionomers were shown to increase the viscosity of carbon dioxide by a factor of 3--4 at concentrations of 2--3 at concentrations of 4--5 wt%. This report details the findings for several new types of carbon dioxide thickening candidates. Hydrocarbon-fluorocarbon random copolymers, sulfonated hydrocarbon-fluorocarbon random copolymers, semifluorinated trialkyltin fluorides and small hydrogen-bounding compounds were evaluated.

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

DEFF Research Database (Denmark)

Lemarchand, Claire; Bailey, Nicholas; Daivis, Peter

2015-01-01

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

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

International Nuclear Information System (INIS)

1974-06-01

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

Control of cracking in R.C. Structures: Numerical simulation of a squat shear wall

NARCIS (Netherlands)

Damoni, C.; Belletti, B.; Lilliu, G.

2013-01-01

In this paper the behavior of a squat shear wall subjected to monotonic shear loading is investigated. The study fits into the experimental program driven by CEOS.fr on modeling of the behavior of the tested mocks-ups (monotonic and cycling loading-under prevented or free shrinkage). The shear wall

Effect of FRP on the Energy Absorbed by Steel Shear Walls with Openings

Directory of Open Access Journals (Sweden)

Mojtaba Ghasemzadeh

2015-06-01

Full Text Available It’s for more than three decades that Steel Shear Walls are being used as lateral load resisting system. Definitely,the actual behavior of steel shear walls can be assessed using experimental results. However, solve many of phenomenon like this one should be done using mathematical and theoretical methods due to their special characteristics such as high expenses, lack of laboratory facilities and time limitations. In this study, the behavior of steel plate shear walls with openings in a one-story frame were evaluated and compared in various conditions. For this purpose, different values ​​for the opening in shear wall was considered and exposed to lateral displacement in ABAQUS as a comprehensive finite element software. Then, the impact of FRP arrangement on shear wall was evaluated to represent the structural behavior under various conditions. Result shows that, use of FRP sheets as parallel layers on both sides of shear wall has the best response on energy absorption, so that performance of the model was better than shear wall fully covered with FRP.

Rheological behavior of water-ash mixtures from Sakurajima and Ontake volcanoes: implications for lahar flow dynamics

Science.gov (United States)

Kurokawa, Aika K.; Ishibashi, Hidemi; Miwa, Takahiro; Nanayama, Futoshi

2018-06-01

Lahars represent one of the most serious volcanic hazards, potentially causing severe damage to the surrounding environment, not only immediately after eruption but also later due to rainfall or snowfall. The flow of a lahar is governed by volcanic topography and its rheological behavior, which is controlled by its volume, microscale properties, and the concentration of particles. However, the effects of particle properties on the rheology of lahars are poorly understood. In this study, viscosity measurements were performed on water-ash mixtures from Sakurajima and Ontake volcanoes. Samples from Sakurajima show strong and simple shear thinning, whereas those from Ontake show viscosity fluctuations and a transition between shear thinning and shear thickening. Particle analysis of the volcanic ash together with a theoretical analysis suggests that the rheological difference between the two types of suspension can be explained by variations in particle size distribution and shape. In particular, to induce the complex rheology of the Ontake samples, coexistence of two particle size groups may be required since two independent behaviors, one of which follows the streamline (Stokes number St << 1, inertial number I < 0.001) and the other shows a complicated motion ( St 1, I 0.001), compete against each other. The variations in the spatial distribution of polydisperse particles, and the time dependence of this feature which generates apparent rheological changes, indicate that processes related to microscale particle heterogeneities are important in understanding the flow dynamics of lahars and natural polydisperse granular-fluid mixtures in general.

Numerical modeling of cracking pattern's influence on the dynamic response of thickened tailings disposals: a periodic approach

Science.gov (United States)

Ferrer, Gabriel; Sáez, Esteban; Ledezma, Christian

2018-01-01

Copper production is an essential component of the Chilean economy. During the extraction process of copper, large quantities of waste materials (tailings) are produced, which are typically stored in large tailing ponds. Thickened Tailings Disposal (TTD) is an alternative to conventional tailings ponds. In TTD, a considerable amount of water is extracted from the tailings before their deposition. Once a thickened tailings layer is deposited, it loses water and it shrinks, forming a relatively regular structure of tailings blocks with vertical cracks in between, which are then filled up with "fresh" tailings once the new upper layer is deposited. The dynamic response of a representative column of this complex structure made out of tailings blocks with softer material in between was analyzed using a periodic half-space finite element model. The tailings' behavior was modeled using an elasto-plastic multi-yielding constitutive model, and Chilean earthquake records were used for the seismic analyses. Special attention was given to the liquefaction potential evaluation of TTD.

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

Science.gov (United States)

Furukawa, Akira

2017-01-01

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

A simple empirical model for the clarification-thickening process in wastewater treatment plants.

Science.gov (United States)

Zhang, Y K; Wang, H C; Qi, L; Liu, G H; He, Z J; Fan, H T

2015-01-01

In wastewater treatment plants (WWTPs), activated sludge is thickened in secondary settling tanks and recycled into the biological reactor to maintain enough biomass for wastewater treatment. Accurately estimating the activated sludge concentration in the lower portion of the secondary clarifiers is of great importance for evaluating and controlling the sludge recycled ratio, ensuring smooth and efficient operation of the WWTP. By dividing the overall activated sludge-thickening curve into a hindered zone and a compression zone, an empirical model describing activated sludge thickening in the compression zone was obtained by empirical regression. This empirical model was developed through experiments conducted using sludge from five WWTPs, and validated by the measured data from a sixth WWTP, which fit the model well (R² = 0.98, p settling was also developed. Finally, the effects of denitrification and addition of a polymer were also analysed because of their effect on sludge thickening, which can be useful for WWTP operation, e.g., improving wastewater treatment or the proper use of the polymer.

Shear wave propagation in piezoelectric-piezoelectric composite layered structure

Directory of Open Access Journals (Sweden)

Anshu Mli Gaur

Full Text Available The propagation behavior of shear wave in piezoelectric composite structure is investigated by two layer model presented in this approach. The composite structure comprises of piezoelectric layers of two different materials bonded alternatively. Dispersion equations are derived for propagation along the direction normal to the layering and in direction of layering. It has been revealed that thickness and elastic constants have significant influence on propagation behavior of shear wave. The phase velocity and wave number is numerically calculated for alternative layer of Polyvinylidene Difluoride (PVDF and Lead Zirconate Titanate (PZT-5H in composite layered structure. The analysis carried out in this paper evaluates the effect of volume fraction on the phase velocity of shear wave.

Steady shear viscosity of stirred yoghurts with varying ropiness

NARCIS (Netherlands)

van Marle, M.E.; van Marle, M.E.; van den Ende, Henricus T.M.; de Kruif, C.G.; de Kruif, C.G.; Mellema, J.

1999-01-01

Stirred yogurt was viewed as a concentrated dispersion of aggregates consisting of protein particles. The steady-shear behavior of three types of stirred yogurt with varying ropiness was investigated experimentally. To describe the shear-dependent viscosity, a microrheological model was used which

A Comparative Study Between Modified Starch and Xanthan Gum Thickeners in Post-Stroke Oropharyngeal Dysphagia.

Science.gov (United States)

Vilardell, N; Rofes, L; Arreola, V; Speyer, R; Clavé, P

2016-04-01

Thickeners are used in post-stroke oropharyngeal dysphagia (OD) as a compensatory therapeutic strategy against aspirations. To compare the therapeutic effects of modified starch (MS) and xanthan gum (XG) thickeners on swallow safety and efficacy in chronic post-stroke OD patients using clinical and videofluoroscopic (VFS) assessment. Patients were studied by clinical assessment (volume-viscosity swallow test, V-VST) and VFS using 3 volumes (5, 10, 20 mL) and 3 viscosities (liquid, nectar and spoon thick), comparing MS and XG. We studied 122 patients (46MS, 76XG). (A) V-VST showed that both thickeners similarly improved safety of swallow. Prevalence of safe swallowing significantly increased with enhanced viscosity (P < 0.001 vs liquid), MS: 47.83 % at liquid, 84.93 % at nectar and 92.96 % at spoon thick; XG: 55.31 % at liquid, 77.78 % at nectar and 97.84 % at spoon thick. Patients on MS reported higher prevalence of pharyngeal residue at spoon-thick viscosities. (B) VFS: increasing bolus viscosity with either thickener increased prevalence of safe swallows (P < 0.001 vs liquid), MS: 30.25 % liquid, 61.07 % nectar and 92.64 % spoon thick; XG: 29.12 % liquid, 71.30 % nectar and 89.91 % spoon thick. Penetration-aspiration scale score was significantly reduced with increased viscosity with both thickeners. MS increased oral and pharyngeal residues at nectar and spoon-thick viscosities but XG did not. Timing of airway protection mechanisms and bolus velocity were not affected by either thickener. Increasing bolus viscosity with MS and XG thickeners strongly and similarly improved safety of swallow in chronic post-stroke OD by a compensatory mechanism; in contrast only MS thickeners increased oropharyngeal residue.

Shear strength of palm oil clinker concrete beams

International Nuclear Information System (INIS)

Mohammed, Bashar S.; Foo, W.L.; Hossain, K.M.A.; Abdullahi, M.

2013-01-01

Highlights: ► Palm oil clinker can be used as lightweight aggregate for the production of structural concrete. ► The palm oil clinker concrete can be classified as lightweight concrete. ► Full scale reinforced palm oil clinker concrete beams without shear reinforcement were tested. ► The CSA based design equation can be used for the prediction of shear capacity with a limit. - Abstract: This paper presents experimental results on the shear behavior of reinforced concrete beams made of palm oil clinker concrete (POCC). Palm oil clinker (POC) is a by-product of palm oil industry and its utilization in concrete production not only solves the problem of disposing this solid waste but also helps to conserve natural resources. Seven reinforced POCC beams without shear reinforcement were fabricated and their shear behavior was tested. POCC has been classified as a lightweight structural concrete with air dry density less than 1850 kg/m 3 and a 28-day compressive strength more than 20 MPa. The experimental variables which have been considered in this study were the POCC compressive strength, shear span–depth ratio (a/d) and the ratio of tensile reinforcement (ρ). The results show that the failure mode of the reinforced POCC beam is similar to that of conventional reinforced concrete beam. In addition, the shear equation of the Canadian Standard Association (CSA) can be used in designing reinforced POCC beam with ρ ⩾ 1. However, a 0.5 safety factor should be included in the formula for ρ < 1

An analysis of a joint shear model for jointed media with orthogonal joint sets

International Nuclear Information System (INIS)

Koteras, J.R.

1991-10-01

This report describes a joint shear model used in conjunction with a computational model for jointed media with orthogonal joint sets. The joint shear model allows nonlinear behavior for both joint sets. Because nonlinear behavior is allowed for both joint sets, a great many cases must be considered to fully describe the joint shear behavior of the jointed medium. An extensive set of equations is required to describe the joint shear stress and slip displacements that can occur for all the various cases. This report examines possible methods for simplifying this set of equations so that the model can be implemented efficiently form a computational standpoint. The shear model must be examined carefully to obtain a computationally efficient implementation that does not lead to numerical problems. The application to fractures in rock is discussed. 5 refs., 4 figs

Test and lower bound modeling of keyed shear connections in RC shear walls

DEFF Research Database (Denmark)

Sørensen, Jesper Harrild; Herfelt, Morten Andersen; Hoang, Linh Cao

2018-01-01

This paper presents an investigation into the ultimate behavior of a recently developed design for keyed shear connections. The influence of the key depth on the failure mode and ductility of the connection has been studied by push-off tests. The tests showed that connections with larger key...

[Analysis of thickening polysaccharides by the improved diethyldithioacetal derivatization method].

Science.gov (United States)

Akiyama, Takumi; Yamazaki, Takeshi; Tanamoto, Kenichi

2011-01-01

The identification test for thickening polysaccharides containing neutral saccharides and uronic acids was investigated by GC analysis of constituent monosaccharides. The reported method, in which monosaccharides were converted to diethyldithioacetal derivatives with ethanethiol followed by trimethylsilylation, was improved in terms of operability and reproducibility of GC/MS analysis. The suitability of the improved diethyldithioacetal derivatization method was determined for seven thickening polysaccharides, i.e., carob bean gum, guar gum, karaya gum, gum arabic, gum ghatti, tragacanth gum and peach gum. The samples were acid-hydrolyzed to form monosaccharides. The hydrolysates were derivatized and analyzed with GC/FID. Each sugar derivative was detected as a single peak and was well separated from others on the chromatograms. The amounts of constituent monosaccharides in thickening polysaccharides were successfully estimated. Seven polysaccharides were distinguished from each other on the basis of constituent monosaccharides. Further examination of the time period of hydrolysis of polysaccharides using peach gum showed that the optimal times were not the same for all monosaccharides. A longer time was needed to hydrolyze glucuronic acid than neutral saccharides. The findings suggest that hydrolysis time may sometimes affect the analytical results on composition of constituent monosaccharides in polysaccharides.

Microstructural changes in thickened corpus callosum in children: contribution of magnetic resonance diffusion tensor imaging

Energy Technology Data Exchange (ETDEWEB)

Merlini, Laura; Anooshiravani, Mehrak; Kanavaki, Aikaterini; Hanquinet, Sylviane [University of Geneva Children' s Hospital, Pediatric Radiology Unit, Geneva (Switzerland)

2015-06-15

Thickened corpus callosum is a rare finding and its pathophysiology is not well known. An anomalous supracallosal bundle has been depicted by fiber tracking in some cases but no diffusion tensor imaging metrics of thickened corpus callosum have been reported. To use diffusion tensor imaging (DTI) in cases of thickened corpus callosum to help in understanding its clinical significance. During a 7-year period five children (ages 6 months to 15 years) with thickened corpus callosum were studied. We determined DTI metrics of fractional anisotropy (FA), mean diffusivity, and axial (λ1) and radial (λ2, λ3) diffusivity and performed 3-D fiber tracking reconstruction of the thickened corpus callosum. We compared our results with data from the literature and 24 age-matched controls. Brain abnormalities were seen in all cases. All children had at least three measurements of corpus callosum thickness above the 97th percentile according to age. In all children 3-D fiber tracking showed an anomalous supracallosal bundle and statistically significant decrease in FA (P = 0.003) and λ1 (P = 0.001) of the corpus callosum compared with controls, but no significant difference in mean diffusivity and radial diffusivity. Thickened corpus callosum was associated with abnormal bundles, suggesting underlying axonal guidance abnormality. DTI metrics suggested abnormal fiber compactness and density, which may be associated with alterations in cognition. (orig.)

A New Thickener for CO2 Anhydrous Fracturing Fluid

Directory of Open Access Journals (Sweden)

Zhang Jian

2015-01-01

Full Text Available CO2 dry fracturing technology is well-known for its advantages. Little water is used in this technology, which is able to ease the pressure of consumption on water resources. Many abroad theoretical researches, laboratory experiments and field tests have been taken to explore the yield mechanism, the adaptability and the technology of pure liquid CO2 fracturing. These achievements have been applied to a variety of reservoirs transformation and improven the effectiveness of stimulation treatment in a degree. The researches and studies in the domestic didn’t get popular until recent years. Thus, this article firstly introduces the main development and application about pure CO2 anhydrous fracturing technology, and sums up the effect and evaluation of its fluid through application examples both in the domestic and abroad. However, although this technology has many excellent qualities, but systematic studies indicate that its proppant-carrying capacity is less competitive because of the low viscosity of pure CO2 liquid and other reasons. In a consequence, it is necessary to develop an appropriate thickener for CO2 anhydrous fracturing fluid to improve its carrying capacity. Then this article describes some studies of previous scholars about CO2 thickener. Then we put forward our own research ideas and transform it into actual experiments. Thanks to the valid performances of these tests, we successfully develop a thickener X and cosolvent B.

Analysis of abnormally thickened endometrial patterns on transvaginal sonography

International Nuclear Information System (INIS)

Lee, Myung Sook; Cho, Hyeun Cha

1999-01-01

To determine whether the transvaginal sonographic appearance of the thickened endometrium can help to predict the underlying endometrial pathologic process. The sonogram reports of fall 41 pre- and 21 postmenopausal women who underwent transvaginal sonogram were retrospectively analyzed. The women undergoing estrogen replacement therapy, tamoxifen therapy or having abnormal cervical cytology were excluded from this study. The analysis of sonographic and histologic results was performed in all patients. Three distinct sonographic patterns were encountered. Type I consisted of heterogeneous endometrial thickening with internal hypoechoic areas (normal [n=4], polyp [n=1] and cancer [n=4] in premenopausal women and cancer [n=4] in postmenopausal women). Type II consisted of echogenic endometrial thickening with or without tiny cysts (normal[n=5], and hyperplasia [n=7] in premenopausal women and normal [n=4], polyp [n=2], and hyperplasia [n=1] in postmenopausal women). Type III consisted of localized well defined endoluminal lesion (normal [n=1], polyp [n=14], hyperplasia [n=1], cancer [n=1], and submucosal mass [n=3] in premenopausal women and normal [n=4], polyp [n=2],submucosal mass [n=3], and hematoma [n=1] in postmenopausal women). The measurement of the endometrial thickness combined with analysis of sonographic echo patterns may be helpful in prediction and differentiation of endometrial disease in pre- and postmenopausal women. Also it can contribute to avoiding unnecessary D and C.

Production and properties of a thickener with ability of suspending sand

Energy Technology Data Exchange (ETDEWEB)

Qin, B.; Wang, D.; Li, Z.; Chen, J. [China University of Mining and Technology, Xuzhou (China). School of Mineral and Safety Engineering

2006-06-15

To overcome the shortcomings of pouring sands, a thickener with the ability to suspend sands was developed. It is mixed with sands to form densified slurry, and can insure the sands against deposition, jamming pipelines and dehydration. The chemical structure of the thickener is introduced in this paper and the production process is studied. The main processes include immersion, decomposition, dilution and addition of additives. In order to produce a thickener with high viscosity to suspend sands, key factors must be controlled in each process: the immersion time is 2 h; the mass fraction of formaldehyde is 0.01% and mass of NaCO{sub 3} accounts for 15% of dry material; the water temperature is 65{sup o}C in summer and 72{sup o}C in winter and the decomposition time is 2 h in the reaction; the densified decomposition solution should be diluted to 1% mass fraction; the additives of calcium ions and pH indicators must be added to the diluted liquid; the mass fraction of CaCl{sub 2} is 0.048% and the pH value of the solution is 7.5. The thickener is a gel with three-dimensional network structure, a liquid with non-Newtonian behaviour and the characteristics of pseudo-plastic material, a solution with little resistance and the ability to revive its oral primary viscosity. It has been successfully applied in Shendong Mines and has great value and wide-spread prospective use. 10 refs., 6 figs.

Vertical structures in vibrated wormlike micellar solutions

Science.gov (United States)

Epstein, Tamir; Deegan, Robert

2008-11-01

Vertically vibrated shear thickening particulate suspensions can support a free-standing interfaces oriented parallel to gravity. We find that shear thickening worm-like micellar solutions also support such vertical interfaces. Above a threshold in acceleration, the solution spontaneously accumulates into a labyrinthine pattern characterized by a well-defined vertical edge. The formation of vertical structures is of interest because they are unique to shear-thickening fluids, and they indicate the existence of an unknown stress bearing mechanism.

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

Science.gov (United States)

Chaharlang, Mahmood; Samavati, Vahid

2015-08-01

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

Design and implementation of a shearing apparatus for the experimental study of shear displacement in rocks

Science.gov (United States)

Moore, Johnathan; Crandall, Dustin; Gill, Magdalena; Brown, Sarah; Tennant, Bryan

2018-04-01

Fluid flow in the subsurface is not well understood in the context of "impermeable" geologic media. This is especially true of formations that have undergone significant stress fluctuations due to injection or withdrawal of fluids that alters the localized pressure regime. When the pressure regime is altered, these formations, which are often already fractured, move via shear to reduce the imbalance in the stress state. While this process is known to happen, the evolution of these fractures and their effects on fluid transport are still relatively unknown. Numerous simulation and several experimental studies have been performed that characterize the relationship between shearing and permeability in fractures; while many of these studies utilize measurements of fluid flow or the starting and ending geometries of the fracture to characterize shear, they do not characterize the intermediate stages during shear. We present an experimental apparatus based on slight modifications to a commonly available Hassler core holder that allows for shearing of rocks, while measuring the hydraulic and mechanical changes to geomaterials during intermediate steps. The core holder modification employs the use of semi-circular end caps and structural supports for the confining membrane that allow for free movement of the sheared material while preventing membrane collapse. By integrating this modified core holder with a computed tomography scanner, we show a new methodology for understanding the interdependent behavior between fracture structure and flow properties during intermediate steps in shearing. We include a case study of this device function which is shown here through shearing of a fractured shale core and simultaneous observation of the mechanical changes and evolution of the hydraulic properties during shearing.

Shear Behavior of Corrugated Steel Webs in H Shape Bridge Girders

Directory of Open Access Journals (Sweden)

Qi Cao

2015-01-01

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

A mathematical model for batch and continuous thickening of flocculent suspensions in vessels with varying section

Energy Technology Data Exchange (ETDEWEB)

Buerger, R.; Damasceno, J.J.R.; Karlesen, K.H.

2001-10-01

The phenomenological theory of continuous thickening of flocculated suspensions in an ideal cylindrical thickener is extended to vessels having varying cross-section, including divergent or convergent conical vessels. The purpose of this contribution is to draw attention to the corresponding mathematical model, whose key ingredient is a strongly degenerate parabolic partial differential equation. For ideal (non-flocculated) suspensions, which do not form co compressible sediments, the mathematical model reduces to the kinematic approach by Anestis, who developed a method of construction of exact solution by the method of characteristics. The difficulty lies in the fact that characteristics and iso-concentration lines, unlike the conventional Kynch model for cylindrical vessels, do not coincide, and one has to resort to numerical methods to simulate the thickening process. A numerical algorithm is presented and employed for simulations of continuous thickening. Implications of the mathematical model are also demonstrated by steady-state calculations, which lead to new possibilities in thickener design. (author)

The theoretical shear strength of fcc crystals under superimposed triaxial stress

Energy Technology Data Exchange (ETDEWEB)

Cerny, M., E-mail: cerny.m@fme.vutbr.cz [Institute of Engineering Physics, Faculty of Mechanical Engineering, Brno University of Technology, Technicka 2, CZ-616 69 Brno (Czech Republic); Pokluda, J. [Institute of Engineering Physics, Faculty of Mechanical Engineering, Brno University of Technology, Technicka 2, CZ-616 69 Brno (Czech Republic)

2010-05-15

The influence of a triaxial stress applied normally to shear planes and shear direction during affine shear deformation of face-centered cubic crystals on the theoretical shear strength is studied for the <112-bar >{l_brace}111{r_brace} shear system using first-principles methods. The applied relaxation procedure guarantees that the modeled system is subjected to a superposition of shear, normal and in-plane stresses with individually adjustable in-plane and normal stress values. The theoretical shear strengths of individual elements prove to be qualitatively different functions of the superimposed stresses. In the special case of hydrostatic loading, however, these functions are qualitatively uniform. This behavior is discussed in terms of the electronic structure.

Modeling of shear wall buildings

Energy Technology Data Exchange (ETDEWEB)

Gupta, A K [North Carolina State Univ., Raleigh (USA). Dept. of Civil Engineering

1984-05-01

Many nuclear power plant buildings, for example, the auxiliary building, have reinforced concrete shear walls as the primary lateral load resisting system. Typically, these walls have low height to length ratio, often less than unity. Such walls exhibit marked shear lag phenomenon which would affect their bending stiffness and the overall stress distribution in the building. The deformation and the stress distribution in walls have been studied which is applicable to both the short and the tall buildings. The behavior of the wall is divided into two parts: the symmetric flange action and the antisymmetry web action. The latter has two parts: the web shear and the web bending. Appropriate stiffness equations have been derived for all the three actions. These actions can be synthesized to solve any nonlinear cross-section. Two specific problems, that of lateral and torsional loadings of a rectangular box, have been studied. It is found that in short buildings shear lag plays a very important role. Any beam type formulation which either ignores shear lag or includes it in an idealized form is likely to lead to erroneous results. On the other hand a rigidity type approach with some modifications to the standard procedures would yield nearly accurate answers.

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

Science.gov (United States)

Toubia, Elias Anis

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

Discrete Analysis of Damage and Shear Banding in Argillaceous Rocks

Science.gov (United States)

Dinç, Özge; Scholtès, Luc

2018-05-01

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

Detection, modeling and matching of pleural thickenings from CT data towards an early diagnosis of malignant pleural mesothelioma

Science.gov (United States)

Chaisaowong, Kraisorn; Kraus, Thomas

2014-03-01

Pleural thickenings can be caused by asbestos exposure and may evolve into malignant pleural mesothelioma. While an early diagnosis plays the key role to an early treatment, and therefore helping to reduce morbidity, the growth rate of a pleural thickening can be in turn essential evidence to an early diagnosis of the pleural mesothelioma. The detection of pleural thickenings is today done by a visual inspection of CT data, which is time-consuming and underlies the physician's subjective judgment. Computer-assisted diagnosis systems to automatically assess pleural mesothelioma have been reported worldwide. But in this paper, an image analysis pipeline to automatically detect pleural thickenings and measure their volume is described. We first delineate automatically the pleural contour in the CT images. An adaptive surface-base smoothing technique is then applied to the pleural contours to identify all potential thickenings. A following tissue-specific topology-oriented detection based on a probabilistic Hounsfield Unit model of pleural plaques specify then the genuine pleural thickenings among them. The assessment of the detected pleural thickenings is based on the volumetry of the 3D model, created by mesh construction algorithm followed by Laplace-Beltrami eigenfunction expansion surface smoothing technique. Finally, the spatiotemporal matching of pleural thickenings from consecutive CT data is carried out based on the semi-automatic lung registration towards the assessment of its growth rate. With these methods, a new computer-assisted diagnosis system is presented in order to assure a precise and reproducible assessment of pleural thickenings towards the diagnosis of the pleural mesothelioma in its early stage.

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

Science.gov (United States)

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

2014-05-01

microcracks and nearly absent in matrix grains in the well developed C bands. The chemical variation between primary and secondary new-formed micas was clearly identified by the Mg-Ti-Na content. The microstructural analysis documents a progressive decrease in quartz grain size and increasing interconnectivity of K-feldspar and white mica towards more mature shear bands. The contact-frequency analysis demonstrates that the phase distribution in shear bands tends to evolve from quartz aggregate distribution via randomization to K-feldspar aggregate distribution. The boundary preferred orientation is absent in quartz-quartz contacts either inside of outside the C bands, while it changes from random to parallel to the C band for the K-feldspar and and K-feldspar-quartz boundaries. The lack of crystallographic preferred orientation of the individual phases in the mixed matrix of the C planes suggests a dominant diffusion-assisted grain boundary sliding deformation mechanism. In the later stages of shear band development, the deformation is accommodated by crystal plasticity of white mica in micaceous bands. The crystallographic and microstructural data thus indicate two important switches in deformation mechanisms, from (i) brittle to Newtonian viscous behavior in the initial stages of shear band evolution and from (ii) Newtonian viscous to power law in the later evolutionary stages. The evolution of shear bands in the South Armorican Shear Zone thus document the interplay between deformation mechanisms and chemical reactions in deformed granitoids.

Feed thickener for infants up to six months of age with gastro-oesophageal reflux.

Science.gov (United States)

Kwok, T'ng Chang; Ojha, Shalini; Dorling, Jon

2017-12-05

Gastro-oesophageal reflux (GOR) is common in infants, and feed thickeners are often used to manage it in infants as they are simple to use and perceived to be harmless. However, conflicting evidence exists to support the use of feed thickeners. To evaluate the use of feed thickeners in infants up to six months of age with GOR in terms of reduction in a) signs and symptoms of GOR, b) reflux episodes on pH probe monitoring or intraluminal impedance or a combination of both, or c) histological evidence of oesophagitis. We used the standard search strategy of the Cochrane Neonatal Review Group to search the Cochrane Central Register of Controlled Trials (CENTRAL 2016, Issue 2), MEDLINE via PubMed (1966 to 22 November 2016), Embase (1980 to 22 November 2016), and CINAHL (1982 to 22 November 2016). We also searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles for randomised controlled trials. We included randomised controlled trials if they examined the effects of feed thickeners as compared to unthickened feeds (no treatment or placebo) in treating GOR in term infants up to six months of age or six months of corrected gestational age for those born preterm. Two review authors independently identified eligible studies from the literature search. Two review authors independently performed data extraction and quality assessments of the eligible studies. Differences in opinion were resolved by discussion with a third review author, and consensus was reached among all three review authors. We used the GRADE approach to assess the quality of the evidence. Eight trials recruiting a total of 637 infants met the inclusion criteria for the systematic review. The infants included in the review were mainly formula-fed term infants. The trials were of variable methodological quality. Formula-fed term infants with GOR on feed thickeners had nearly two fewer episodes of regurgitation per day (mean difference -1.97 episodes per day

Pectinous cell wall thickenings formation - A common defense strategy of plants to cope with Pb.

Science.gov (United States)

Krzesłowska, Magdalena; Rabęda, Irena; Basińska, Aneta; Lewandowski, Michał; Mellerowicz, Ewa J; Napieralska, Anna; Samardakiewicz, Sławomir; Woźny, Adam

2016-07-01

Lead, one of the most abundant and hazardous trace metals affecting living organisms, has been commonly detected in plant cell walls including some tolerant plants, mining ecotypes and hyperaccumulators. We have previously shown that in tip growing Funaria sp. protonemata cell wall is remodeled in response to lead by formation of thickenings rich in low-methylesterified pectins (pectin epitope JIM5 - JIM5-P) able to bind metal ions, which accumulate large amounts of Pb. Hence, it leads to the increase of cell wall capacity for Pb compartmentalization. Here we show that diverse plant species belonging to different phyla (Arabidopsis, hybrid aspen, star duckweed), form similar cell wall thickenings in response to Pb. These thickenings are formed in tip growing cells such as the root hairs, and in diffuse growing cells such as meristematic and root cap columella cells of root apices in hybrid aspen and Arabidopsis and in mesophyll cells in star duckweed fronds. Notably, all analyzed cell wall thickenings were abundant in JIM5-P and accumulated high amounts of Pb. In addition, the co-localization of JIM5-P and Pb commonly occurred in these cells. Hence, cell wall thickenings formed the extra compartment for Pb accumulation. In this way plant cells increased cell wall capacity for compartmentalization of this toxic metal, protecting protoplast from its toxicity. As cell wall thickenings occurred in diverse plant species and cell types differing in the type of growth we may conclude that pectinous cell wall thickenings formation is a widespread defense strategy of plants to cope with Pb. Moreover, detection of natural defense strategy, increasing plant cell walls capacity for metal accumulation, reveals a promising direction for enhancing plant efficiency in phytoremediation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Airway wall thickening and emphysema show independent familial aggregation in chronic obstructive pulmonary disease

DEFF Research Database (Denmark)

Patel, Bipen D; Coxson, Harvey O; Pillai, Sreekumar G

2008-01-01

RATIONALE: It is unclear whether airway wall thickening and emphysema make independent contributions to airflow limitation in chronic obstructive pulmonary disease (COPD) and whether these phenotypes cluster within families. OBJECTIVES: To determine whether airway wall thickening and emphysema (1...... to airflow obstruction in COPD. These phenotypes show independent aggregation within families of individuals with COPD, suggesting that different genetic factors influence these disease processes....... the severity of airway wall thickening and emphysema. MEASUREMENTS AND MAIN RESULTS: A total of 3,096 individuals were recruited to the study, of whom 1,159 (519 probands and 640 siblings) had technically adequate high-resolution computed tomography scans without significant non-COPD-related thoracic disease...

Water-bearing explosives thickened with a partially hydrolyzed acrylamide polymer

Energy Technology Data Exchange (ETDEWEB)

Lyerly, W.M.

1971-11-23

Thickened water-bearing explosives are provided which do not segregate and are water-resistant over a wide range of viscosities. Preferred compositions have a unique combination of pourability and fluidity coupled with resistance to water and segregation which makes them particularly suitable in small diameter holes and in holes partially filled with water. Accordingly, water-bearing explosive compositions also are provided which consist of inorganic oxidizing salt, fuel, and water, which improvement consists of thickening the compositions with the combination of polyacrylamide and cross-linked galactomannan. The weight ratio of the polyacrylamide to galactomanan is from about ratio 0.1:1 to 10:1, and preferably 1:1 to 5:1. (1 claim)

Notes on hyperscaling violating Lifshitz and shear diffusion

Science.gov (United States)

Kolekar, Kedar S.; Mukherjee, Debangshu; Narayan, K.

2017-07-01

We explore in greater detail our investigations of shear diffusion in hyperscaling violating Lifshitz theories in Phys. Lett. B 760, 86 (2016), 10.1016/j.physletb.2016.06.046. This adapts and generalizes the membrane-paradigm-like analysis of Kovtun, Son, and Starinets for shear gravitational perturbations in the near horizon region given certain self-consistent approximations, leading to the shear diffusion constant on an appropriately defined stretched horizon. In theories containing a gauge field, some of the metric perturbations mix with some of the gauge field perturbations and the above analysis is somewhat more complicated. We find a similar near-horizon analysis can be obtained in terms of new field variables involving a linear combination of the metric and the gauge field perturbation resulting in a corresponding diffusion equation. Thereby as before, for theories with Lifshitz and hyperscaling violating exponents z , θ satisfying z <4 -θ in four bulk dimensions, our analysis here results in a similar expression for the shear diffusion constant with power-law scaling with temperature suggesting universal behavior in relation to the viscosity bound. For z =4 -θ , we find logarithmic behavior.

Oil sands thickened froth treatment tailings exhibit acid rock drainage potential during evaporative drying.

Science.gov (United States)

Kuznetsov, Petr; Kuznetsova, Alsu; Foght, Julia M; Siddique, Tariq

2015-02-01

Bitumen extraction from oil sands ores after surface mining produces different tailings waste streams: 'froth treatment tailings' are enriched in pyrite relative to other streams. Tailings treatment can include addition of organic polymers to produce thickened tailings (TT). TT may be further de-watered by deposition into geotechnical cells for evaporative drying to increase shear strength prior to reclamation. To examine the acid rock drainage (ARD) potential of TT, we performed predictive analyses and laboratory experiments on material from field trials of two types of thickened froth treatment tailings (TT1 and TT2). Acid-base accounting (ABA) of initial samples showed that both TT1 and TT2 initially had net acid-producing potential, with ABA values of -141 and -230 t CaCO₃ equiv. 1000 t(-1) of TT, respectively. In long-term kinetic experiments, duplicate ~2-kg samples of TT were incubated in shallow trays and intermittently irrigated under air flow for 459 days to simulate evaporative field drying. Leachates collected from both TT samples initially had pH~6.8 that began decreasing after ~50 days (TT2) or ~250 days (TT1), stabilizing at pH~2. Correspondingly, the redox potential of leachates increased from 100-200 mV to 500-580 mV and electrical conductivity increased from 2-5 dS m(-1) to 26 dS m(-1), indicating dissolution of minerals during ARD. The rapid onset and prolonged ARD observed with TT2 is attributed to its greater pyrite (13.4%) and lower carbonate (1.4%) contents versus the slower onset of ARD in TT1 (initially 6.0% pyrite and 2.5% carbonates). 16S rRNA gene pyrosequencing analysis revealed rapid shift in microbial community when conditions became strongly acidic (pH~2) favoring the enrichment of Acidithiobacillus and Sulfobacillus bacteria in TT. This is the first report showing ARD potential of TT and the results have significant implications for effective management of pyrite-enriched oil sands tailings streams/deposits. Copyright © 2014

Origins of Shear Jamming for Frictional Grains

Science.gov (United States)

Wang, Dong; Zheng, Hu; Ren, Jie; Dijksman, Joshua; Bares, Jonathan; Behringer, Robert

2016-11-01

Granular systems have been shown to be able to behave like solids, under shear, even when their densities are below the critical packing fraction for frictionless isotropic jamming. To understand such a phenomena, called shear jamming, the question we address here is: how does shear bring a system from a unjammed state to a jammed state, where the coordination number, Z, is no less than 3, the isotropic jamming point for frictional grains? Since Z can be used to distinguish jammed states from unjammed ones, it is vital to understand how shear increases Z. We here propose a set of three particles in contact, denoted as a trimer, as the basic unit to characterize the deformation of the system. Trimers, stabilized by inter-grain friction, fail under a certain amount of shear and bend to make extra contacts to regain stability. By defining a projection operator of the opening angle of the trimer to the compression direction in the shear, O, we see a systematically linear decrease of this quantity with respect to shear strain, demonstrating the bending of trimers as expected. In addition, the average change of O from one shear step to the next shows a good collapse when plotted against Z, indicating a universal behavior in the process of shear jamming. We acknowledge support from NSF DMR1206351, NASA NNX15AD38G, the William M. Keck Foundation and a RT-MRSEC Fellowship.

Asbestos-related diffuse pleural thickening.

Science.gov (United States)

Fujimoto, Nobukazu; Kato, Katsuya; Usami, Ikuji; Sakai, Fumikazu; Tokuyama, Takeshi; Hayashi, Seiji; Miyamoto, Kenji; Kishimoto, Takumi

2014-01-01

The clinical features of asbestos-related diffuse pleural thickening (DPT) remain unclear. To clarify the association between radiological findings of DPT and respiratory function. Medical data from patients with asbestos-related DPT were collected, including their history of occupational or neighborhood asbestos exposure, initial symptoms, modified Medical Research Council dyspnea grade, smoking history, radiological findings, and respiratory function test results. There were 106 DPT patients between 2005 and 2010 [i.e. 103 men (97.2%) and 3 women (2.8%)]. The median age at diagnosis was 69 years (range 46-88). Patient occupations related to asbestos exposure included: asbestos product manufacturing (n = 17); the shipbuilding industry (n = 14); the construction industry (n = 13); heat insulation work (n = 12); plumbing, asbestos spraying, and electrical work (n = 7 each), and transportation and demolition work (n = 4 each). The median duration of asbestos exposure was 25 years (range 2-54), and the median latency period before the onset of DPT was 46 years (range 25-66). Involvement of the costophrenic angle (CPA) was also negatively correlated with the percent vital capacity (%VC; r = -0.448, p < 0.01). Pleural thickness and the craniocaudal and horizontal extension of pleural thickening, as determined by chest computed tomography (CT), were also negatively correlated with %VC (r = -0.226, p < 0.05; r = -0.409, p < 0.01, and r = -0.408, p < 0.01, respectively). DPT develops after a long latency period following occupational asbestos exposure and causes marked respiratory dysfunction. The extension of DPT should be evaluated by chest CT, and chest X-ray would be important for the evaluation of the involvement of the CPA.

Potential effect of skull thickening on the associations between cognition and brain atrophy in ageing.

Science.gov (United States)

Aribisala, Benjamin Segun; Royle, Natalie A; Valdés Hernández, Maria C; Murray, Catherine; Penke, Lars; Gow, Alan; Maniega, Susana Muñoz; Starr, John M; Bastin, Mark; Deary, Ian; Wardlaw, Joanna

2014-09-01

intracranial volume (ICV) is commonly used as a marker of premorbid brain size in neuroimaging studies as it is thought to remain fixed throughout adulthood. However, inner skull table thickening would encroach on ICV and could mask actual brain atrophy. we investigated the effect that thickening might have on the associations between brain atrophy and cognition. the sample comprised 57 non-demented older adults who underwent structural brain MRI at mean age 72.7 ± 0.7 years and were assessed on cognitive ability at mean age 11 and 73 years. Principal component analysis was used to derive factors of general cognitive ability (g), information processing speed and memory from the recorded cognitive ability data. The total brain tissue volume and ICV with (estimated original ICV) and without (current ICV) adjusting for the effects of inner table skull thickening were measured. General linear modelling was used to test for associations. all cognitive ability variables were significantly (P skull thickening (g: η(2) = 0.177, speed: η(2) = 0.264 and memory: η(2) = 0.132). After accounting for skull thickening, only speed was significantly associated with percentage total brain volume in ICV (η(2) = 0.085, P = 0.034), not g or memory. not accounting for skull thickening when computing ICV can distort the association between brain atrophy and cognitive ability in old age. Larger samples are required to determine the true effect. © The Author 2014. Published by Oxford University Press on behalf of the British Geriatrics Society. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Shear Elasticity and Shear Viscosity Imaging in Soft Tissue

Science.gov (United States)

Yang, Yiqun

In this thesis, a new approach is introduced that provides estimates of shear elasticity and shear viscosity using time-domain measurements of shear waves in viscoelastic media. Simulations of shear wave particle displacements induced by an acoustic radiation force are accelerated significantly by a GPU. The acoustic radiation force is first calculated using the fast near field method (FNM) and the angular spectrum approach (ASA). The shear waves induced by the acoustic radiation force are then simulated in elastic and viscoelastic media using Green's functions. A parallel algorithm is developed to perform these calculations on a GPU, where the shear wave particle displacements at different observation points are calculated in parallel. The resulting speed increase enables rapid evaluation of shear waves at discrete points, in 2D planes, and for push beams with different spatial samplings and for different values of the f-number (f/#). The results of these simulations show that push beams with smaller f/# require a higher spatial sampling rate. The significant amount of acceleration achieved by this approach suggests that shear wave simulations with the Green's function approach are ideally suited for high-performance GPUs. Shear wave elasticity imaging determines the mechanical parameters of soft tissue by analyzing measured shear waves induced by an acoustic radiation force. To estimate the shear elasticity value, the widely used time-of-flight method calculates the correlation between shear wave particle velocities at adjacent lateral observation points. Although this method provides accurate estimates of the shear elasticity in purely elastic media, our experience suggests that the time-of-flight (TOF) method consistently overestimates the shear elasticity values in viscoelastic media because the combined effects of diffraction, attenuation, and dispersion are not considered. To address this problem, we have developed an approach that directly accounts for all

Shear machines

International Nuclear Information System (INIS)

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

1980-01-01

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

Discrimination between pleural thickening and minimal pleural effusion using color Doppler chest ultrasonography

OpenAIRE

Hasan, Ali A.; Makhlouf, Hoda A.; Mohamed, Alaa R.M.

2013-01-01

Background: The discrimination of pleural thickening from minimal pleural effusion may be difficult as both lesions appear as anechoic on grayscale ultrasound, hence, free of “echoes” does not confirm the presence of pleural fluid. Aim of this study: To evaluate the value of color Doppler ultrasound in differentiating minimal pleural effusion that could be aspirated from pleural thickening and to compare it with grayscale ultrasound. Patients and methods: This analytic cross-sectional s...

Finite Element Analysis of Reinforced Concrete Beam-Column Connections with Governing Joint Shear Failure Mode

Directory of Open Access Journals (Sweden)

M.A. Najafgholipour

Full Text Available Abstract Reinforced concrete (RC beam-column connections especially those without transverse reinforcement in joint region can exhibit brittle behavior when intensive damage is concentrated in the joint region during an earthquake event. Brittle behavior in the joint region can compromise the ductile design philosophy and the expected overall performance of structure when subjected to seismic loading. Considering the importance of joint shear failure influences on strength, ductility and stability of RC moment resisting frames, a finite element modeling which focuses on joint shear behavior is presented in this article. Nonlinear finite element analysis (FEA of RC beam-column connections is performed in order to investigate the joint shear failure mode in terms of joint shear capacity, deformations and cracking pattern. A 3D finite element model capable of appropriately modeling the concrete stress-strain behavior, tensile cracking and compressive damage of concrete and indirect modeling of steel-concrete bond is used. In order to define nonlinear behavior of concrete material, the concrete damage plasticity is applied to the numerical model as a distributed plasticity over the whole geometry. Finite element model is then verified against experimental results of two non-ductile beam-column connections (one exterior and one interior which are vulnerable to joint shear failure. The comparison between experimental and numerical results indicates that the FE model is able to simulate the performance of the beam-column connections and is able to capture the joint shear failure in RC beam-column connections.

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

Science.gov (United States)

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

2016-05-01

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

Thickening agent for flood water in secondary recovery of oil and for other aqueous salt solutions

Energy Technology Data Exchange (ETDEWEB)

Roth, H H

1966-04-14

Alkenyl-aromatic polymer sulfonates are good thickeners for some aqueous solutions, but addition of salts to such solutions reduces the desirable viscosity. High-molecular, water-soluble alkenyl-aromatic polymers which carry sulfonic acid or sulfonate groups substituted at the aromatic nuclei yield thickened solutions (e.g., for waterflooding) which are not influenced by the presence of water-soluble salts. Such polymers are derivatives of polyvinyltoluene, alone or in combination with about 5% acrylonitrile. It was also found that such thickening agents are less adsorbed on the rock matrix in a waterflood formation. (1 claim)

A new dedicated finite element for push-over analysis of reinforced concrete shear wall systems

Directory of Open Access Journals (Sweden)

Delal Doğru ORMANCI

2016-06-01

Full Text Available In this study, a finite element which has been analyzed based on anisotropic behavior of reinforced shear walls is developed. Element stiffness matrices were varied based on whether the element is in the tension or the compression zone of the cross-section. Nonlinear behavior of reinforced shear wall model is investigated under horizontal loads. This behavior is defined with a similar approach to plastic hinge assumption in frame structures that the finite element behaves lineer elastic between joints and plastic deformations are concentrated on joints as vertical plastic displacements. According to this acceptance, plastic behavior of reinforced shear wall occurs when the vertical strain reaches elastic strain limit. In the definition of finite element, displacement functions are chosen considering that the partition of shear walls just at floor levels, are enough for solution. Results of this study are compared with the solution obtained from a different computer programme and experimental results.

Seismic cycle feedbacks in a mid-crustal shear zone

Science.gov (United States)

Melosh, Benjamin L.; Rowe, Christie D.; Gerbi, Christopher; Smit, Louis; Macey, Paul

2018-07-01

Mid-crustal fault rheology is controlled by alternating brittle and plastic deformation mechanisms, which cause feedback cycles that influence earthquake behavior. Detailed mapping and microstructural observations in the Pofadder Shear Zone (Namibia and South Africa) reveal a lithologically heterogeneous shear zone core with quartz-rich mylonites and ultramylonites, plastically overprinted pseudotachylyte and active shear folds. We present evidence for a positive feedback cycle in which coseismic grain size reduction facilitates active shear folding by enhancing competency contrasts and promoting crystal plastic flow. Shear folding strengthens a portion of a shear zone by limb rotation, focusing deformation and promoting plastic flow or brittle slip in resulting areas of localized high stress. Using quartz paleopiezometry, we estimate strain and slip rates consistent with other studies of exhumed shear zones and modern plate boundary faults, helping establish the Pofadder Shear Zone as an ancient analogue to modern, continental-scale, strike-slip faults. This feedback cycle influences seismicity patterns at the scale of study (10s of meters) and possibly larger scales as well, and contributes to bulk strengthening of the brittle-plastic transition on modern plate boundary faults.

Comparison of observed rheological properties of hard wheat flour dough with predictions of the Giesekus-Leonov, White-Metzner and Phan-Thien Tanner models

Science.gov (United States)

Dhanasekharan, M.; Huang, H.; Kokini, J. L.; Janes, H. W. (Principal Investigator)

1999-01-01

The measured rheological behavior of hard wheat flour dough was predicted using three nonlinear differential viscoelastic models. The Phan-Thien Tanner model gave good zero shear viscosity prediction, but overpredicted the shear viscosity at higher shear rates and the transient and extensional properties. The Giesekus-Leonov model gave similar predictions to the Phan-Thien Tanner model, but the extensional viscosity prediction showed extension thickening. Using high values of the mobility factor, extension thinning behavior was observed but the predictions were not satisfactory. The White-Metzner model gave good predictions of the steady shear viscosity and the first normal stress coefficient but it was unable to predict the uniaxial extensional viscosity as it exhibited asymptotic behavior in the tested extensional rates. It also predicted the transient shear properties with moderate accuracy in the transient phase, but very well at higher times, compared to the Phan-Thien Tanner model and the Giesekus-Leonov model. None of the models predicted all observed data consistently well. Overall the White-Metzner model appeared to make the best predictions of all the observed data.

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

Science.gov (United States)

Plohr, Jeeyeon

2017-06-01

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

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

Science.gov (United States)

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

2017-05-01

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

Three-dimensional shear transformation zone dynamics model for amorphous metals

International Nuclear Information System (INIS)

Homer, Eric R; Schuh, Christopher A

2010-01-01

A fully three-dimensional (3D) mesoscale modeling framework for the mechanical behavior of amorphous metals is proposed. The model considers the coarse-grained action of shear transformation zones (STZs) as the fundamental deformation event. The simulations are controlled through the kinetic Monte Carlo algorithm and the mechanical response of the system is captured through finite-element analysis, where STZs are mapped onto a 3D finite-element mesh and are allowed to shear in any direction in three dimensions. Implementation of the technique in uniaxial creep tests over a wide range of conditions validates the model's ability to capture the expected behaviors of an amorphous metal, including high temperature flow conforming to the expected constitutive law and low temperature localization in the form of a nascent shear band. The simulation results are combined to construct a deformation map that is comparable to experimental deformation maps. The flexibility of the modeling framework is illustrated by performing a contact test (simulated nanoindentation) in which the model deforms through STZ activity in the region experiencing the highest shear stress

Atomic simulation of bcc niobium Σ5〈001〉{310} grain boundary under shear deformation

International Nuclear Information System (INIS)

Huang, Bo-Wen; Shang, Jia-Xiang; Liu, Zeng-Hui; Chen, Yue

2014-01-01

The shear behaviors of grain boundaries are investigated using molecular dynamics simulations. The Σ5〈001〉{310} symmetric tilt grain boundary (GB) of body-centered cubic (bcc) Nb is investigated and the simulations are conducted under a series of shear directions at a wide range of temperatures. The results show that the GB shearing along [13 ¯ 0], which is perpendicular to the tilt axis, has a coupled motion behavior. The coupling factor is predicted using Cahn’s model. The critical stress of the coupling motion is found to decrease exponentially with increasing temperature. The GB under shear deformation along the [001 ¯ ] direction, which is parallel to the tilt axis, has a pure sliding behavior at most of the temperatures investigated. The critical stress of sliding is found to be much larger than that of the coupled motion at the same temperature. At very low temperatures, pure sliding is not observed, and dislocation nucleating and extending is found on GBs. We observed mixed behaviors when the shear direction is between [13 ¯ 0] and [001 ¯ ]. The transition region between GB coupled motion and pure sliding is determined. If the shear angles between the shear direction and the tilt axis are larger than a certain value, the GB has a coupled motion behavior similar to the [13 ¯ 0] direction. A GB with a shear angle smaller than the critical angle exhibits mixed mechanisms at low temperatures, such as dislocation, atomic shuffle and GB distortion, whereas for the [001 ¯ ]-like GB pure sliding is the dominating mechanism at high temperatures. The stresses to activate the coupling and gliding motions are analyzed for shear deformations along different directions at various temperatures

Crestal Sinus Augmentation in the Presence of Severe Sinus Mucosal Thickening: A Report of 3 Cases.

Science.gov (United States)

Fang, Yiqin; An, Xueyin; Jeong, Seung-Mi; Choi, Byung-Ho

2018-06-01

In the presence of severe sinus mucosal thickening, the ostium can be blocked when the sinus membrane is lifted, causing drainage disturbances and sinusitis. Here, we present 3 cases in which maxillary sinus floor elevation was performed using a crestal approach in the presence of severe sinus mucosal thickening (>10 mm). The effects of maxillary sinus floor elevation using the crestal approach technique on sinus mucosal thickening and bone formation in the sinus were evaluated using cone beam computed tomography. None of the patients exhibited an increase in sinus membrane thickness. No complications were encountered during the follow-up periods, and bone formation was observed around the implants at the sinus floor. All implants were functioning successfully. Maxillary sinus floor elevation using the crestal approach technique in the presence of severe sinus mucosal thickening allows for minimally invasive sinus grafting and simultaneous implant placement and does not increase sinus membrane thickness.

Automatic airway-artery analysis on lung CT to quantify airway wall thickening and bronchiectasis

DEFF Research Database (Denmark)

Perez-Rovira, Adria; Kuo, Wieying; Petersen, Jens

2016-01-01

Purpose: Bronchiectasis and airway wall thickening are commonly assessed in computed tomography (CT) by comparing the airway size with the size of the accompanying artery. Thus, in order to automate the quantification of bronchiectasis and wall thickening following a similar principle......, and pairs airway branches with the accompanying artery, then quantifies airway wall thickening and bronchiectasis by measuring the wall-artery ratio (WAR) and lumen and outer wall airway-artery ratio (AAR). Measurements that do not use the artery size for normalization are also extracted, including wall...... area percentage (WAP), wall thickness ratio (WTR), and airway diameters. Results: The method was thoroughly evaluated using 8000 manual annotations of airway-artery pairs from 24 full-inspiration pediatric CT scans (12 diseased and 12 controls). Limits of agreement between the automatically...

The microstructure and rheology of a model, thixotropic nanoparticle gel under steady shear and large amplitude oscillatory shear (LAOS)

International Nuclear Information System (INIS)

Min Kim, Jung; Kate Gurnon, A.; Wagner, Norman J.; Eberle, Aaron P. R.; Porcar, Lionel

2014-01-01

The microstructure-rheology relationship for a model, thermoreversible nanoparticle gel is investigated using a new technique of time-resolved neutron scattering under steady and time-resolved large amplitude oscillatory shear (LAOS) flows. A 21 vol. % gel is tested with varying strength of interparticle attraction. Shear-induced structural anisotropy is observed as butterfly scattering patterns and quantified through an alignment factor. Measurements in the plane of flow show significant, local anisotropy develops with alignment along the compressional axis of flow, providing new insights into how gels flow. The microstructure-rheology relationship is analyzed through a new type of structure-Lissajous plot that shows how the anisotropic microstructure is responsible for the observed LAOS response, which is beyond a response expected for a purely viscous gel with constant structure. The LAOS shear viscosities are observed to follow the “Delaware-Rutgers” rule. Rheological and microstructural data are successfully compared across a broad range of conditions by scaling the shear rate by the strength of attraction, providing a method to compare behavior between steady shear and LAOS experiments. However, important differences remain between the microstructures measured at comparatively high frequency in LAOS experiments and comparable steady shear experiments that illustrate the importance of measuring the microstructure to properly interpret the nonlinear, dynamic rheological response

The microstructure and rheology of a model, thixotropic nanoparticle gel under steady shear and large amplitude oscillatory shear (LAOS)

Energy Technology Data Exchange (ETDEWEB)

Min Kim, Jung; Kate Gurnon, A.; Wagner, Norman J., E-mail: wagnernj@udel.edu [Department of Chemical and Biomolecular Engineering and Center for Neutron Science, University of Delaware, Newark, Delaware 19716 (United States); Eberle, Aaron P. R. [NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Porcar, Lionel [NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 and Institut Laue-Langevin, BP 156, F-38042 Grenoble Cedex 9 (France)

2014-09-01

The microstructure-rheology relationship for a model, thermoreversible nanoparticle gel is investigated using a new technique of time-resolved neutron scattering under steady and time-resolved large amplitude oscillatory shear (LAOS) flows. A 21 vol. % gel is tested with varying strength of interparticle attraction. Shear-induced structural anisotropy is observed as butterfly scattering patterns and quantified through an alignment factor. Measurements in the plane of flow show significant, local anisotropy develops with alignment along the compressional axis of flow, providing new insights into how gels flow. The microstructure-rheology relationship is analyzed through a new type of structure-Lissajous plot that shows how the anisotropic microstructure is responsible for the observed LAOS response, which is beyond a response expected for a purely viscous gel with constant structure. The LAOS shear viscosities are observed to follow the “Delaware-Rutgers” rule. Rheological and microstructural data are successfully compared across a broad range of conditions by scaling the shear rate by the strength of attraction, providing a method to compare behavior between steady shear and LAOS experiments. However, important differences remain between the microstructures measured at comparatively high frequency in LAOS experiments and comparable steady shear experiments that illustrate the importance of measuring the microstructure to properly interpret the nonlinear, dynamic rheological response.

Subclinical leaflet thickening and stent frame geometry in self-expanding transcatheter heart valves

DEFF Research Database (Denmark)

Fuchs, Andreas; De Backer, Ole; Brooks, Matthew

2017-01-01

AIMS: This study aimed to assess the potential relationship between subclinical leaflet thickening and stent frame geometry in patients who underwent aortic valve replacement with a self-expanding transcatheter heart valve (THV). METHODS AND RESULTS: Seventy-five patients with a self-expanding THV....... CONCLUSIONS: Regional THV stent frame underexpansion is associated with an increased risk of leaflet thickening. Post-dilatation of self-expanding THV as well as a supra-annular valve position seem to reduce the occurrence of this phenomenon....

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

Science.gov (United States)

Moore, Diane E.; Lockner, David A.

2013-01-01

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

Inexpensive CO2 Thickening Agents for Improved Mobility Control of CO2 Floods

Energy Technology Data Exchange (ETDEWEB)

Robert Enick; Eric Beckman; Andrew Hamilton

2005-08-31

The objective of this research was the design, synthesis and evaluation of inexpensive, non-fluorous carbon dioxide thickening agents. We followed the same strategy employed in the design of fluorinated CO{sub 2} polymeric thickeners. First, a highly CO{sub 2}-philic, hydrocarbon-based monomer was to be identified. Polymers or oligomers of this monomer were then synthesized. The second step was to design a CO{sub 2}-thickener based on these CO{sub 2}-philic polymers. Two types of thickeners were considered. The first was a copolymer in which the CO{sub 2}-philic monomer was combined with a small proportion of CO{sub 2}-phobic associating groups that could cause viscosity-enhancing intermolecular interactions to occur. The second was a small hydrogen-bonding compound with urea groups in the core to promote intermolecular interactions that would cause the molecules to 'stack' in solution while the arms were composed of the CO{sub 2}-philic oligomers. Although we were not able to develop a viable thickener that exhibited high enough CO{sub 2} solubility at EOR MMP conditions to induce a viscosity increase, we made significant progress in our understanding of CO{sub 2}-soluble compounds that can be used in subsequent studies to design CO{sub 2}-soluble thickeners or CO{sub 2}-soluble surfactant-based foaming agents. These findings are detailed in this final report. In summary, we assessed many polymers and verified that the most CO{sub 2}-soluble oxygenated hydrocarbon polymer is poly(vinyl acetate), PVAc. This is primarily due to the presence of both ether and carbonyl oxygens associated with acetate-rich compounds. In addition to polymers, we also made small acetate-rich molecules that were also capable of associating in solution via the inclusion of hydrogen-bonding groups in hopes of forming viscosity-enhancing macromolecules. Despite the presence of multiple acetate groups in these compounds, which can impart incredible CO{sub 2}-solubility to many

Shear viscosity enhancement in water–nanoparticle suspensions

International Nuclear Information System (INIS)

Balasubramanian, Ganesh; Sen, Swarnendu; Puri, Ishwar K.

2012-01-01

Equilibrium molecular dynamics simulations characterize the increase in the shear viscosity of water around a suspended silicon dioxide nanoparticle. Water layering on the solid surface decreases the fraction of adjacent fluid molecules that are more mobile and hence less viscous, thereby increasing the shear viscosity. The contribution of the nanoparticle surface area to this rheological behavior is identified and an empirical model that accounts for it is provided. The model successfully reproduces the shear viscosity predictions from previous experimental measurements as well as our simulations. -- Highlights: ► Layering of water on the solid surfaces increases the fraction of less mobile molecules adjacent to them. ► A nondimensional parameter predicts of viscosity enhancement due to particle shape, volume fraction. ► Model predictions agree with the results of atomistic simulations and experimental measurements.

Pelvis dilatation and mucosal thickening of transplanted kidney: comparative study of resistive index and ultrasonographic finding

International Nuclear Information System (INIS)

Kim, Myung Joon; Yoo, Hyung Sik; Lee, Jong Tae; Kim, Yu Seun; Park, Ki Il

1992-01-01

Diagnostic ability of duplex Doppler ultrasonography relying on resistive index is limited when clinical symptoms and signs of rejection are subtle or renal dysfunction is caused by other conditions such as urinary tract infection. To investigate the significance in the changes of renal pelvis, a combined analysis of resistive index and ultrasonographic findings in cases of renal pelvis dilatation and mucosal thickening was undertaken. A mean resistive index was calculated from Doppler measurements of the main, segmental and interlobar arteries. The cause of mucosal thickening was retrospectively analysed using the clinical and laboratory findings. Twenty three cases of renal pelvis dilatation and 17 cases of mucosal thickening were found in a total of 159 renal transplantation cases. In 14 of the 23 cases with renal pelvis dilatation, renal function was normal and their mean resistive index was 0.64 ± 0.04. Pelvis and ureter dilatation caused by ureteral stenosis or compression was demonstrated in 6 cases and their mean resistive index (0.72 ± 0.05) was increased. Mucosal thickening of renal pelvis was found in 7 of 32 cases with acute injection and in 2 of 13 cases with chronic rejection, but their mean resistive index was not different from that of the cases without pelvic mucosal changes. Three cases of acute rejection associated with urinary tract infection and 2 cases of chronic rejection in whom resistive indices were indeterminate, but mucosal thickening of the renal pelvis was prominent at ultrasonography. In renal transplant patients having indeterminate resistive index and mucosal thickening of the renal pelvis, ultrasonographic features must be correlated with the clinical and laboratory findings for an accurate diagnosis and treatment of renal dysfunction

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

Science.gov (United States)

Becnel, Andrew C.

crew seat. Characterization tests were carried out on the LMEAS using a 40 vol% MRF used in the previous magnetorheometer tests. These were analyzed using both flow curves and apparent viscosity vs. Mason number diagrams. The nondimensionalized Mason number analysis resulted in data for all conditions of temperature, fluid composition, and shear rate, to collapse onto a single characteristic or master curve. Significantly, the temperature corrected Mason number results from both the bench top magnetorheometer and full scale rotary vane MREA collapse to the same master curve. This enhances the ability of designers of MRFs and MREAs to safely and effectively apply characterization data collected in low shear rate, controlled temperature environments to operational environments that may be completely different. Finally, the Searle cell magnetorheometer was modified with an enforced eccentricity to work in both squeeze and shear modes simultaneously to achieve so called squeeze strengthening of the working MRF, thereby increasing the apparent yield stress and the specific energy absorption. By squeezing the active MR fluid, particles undergo compression-assisted aggregation into stronger, more robust columns which resist shear better than single chains. A hybrid model describing the squeeze strengthening behavior is developed, and recommendations are made for using squeeze strengthening to improve practical MREA devices.

Inelastic deformations of fault and shear zones in granitic rock

International Nuclear Information System (INIS)

Wilder, D.G.

1986-02-01

Deformations during heating and cooling of three drifts in granitic rock were influenced by the presence of faults and shear zones. Thermal deformations were significantly larger in sheared and faulted zones than where the rock was jointed, but neither sheared nor faulted. Furthermore, thermal deformations in faulted or sheared rock were not significantly recovered during subsequent cooling, thus a permanent deformation remained. This inelastic response is in contrast with elastic behavior identified in unfaulted and unsheared rock segments. A companion paper indicates that deformations in unsheared or unfaulted rock were effectively modeled as an elastic response. We conclude that permanent deformations occurred in fractures with crushed minerals and fracture filling or gouge materials. Potential mechanisms for this permanent deformation are asperity readjustments during thermal deformations, micro-shearing, asperity crushing and crushing of the secondary fracture filling minerals. Additionally, modulus differences in sheared or faulted rock as compared to more intact rock would result in greater deformations in response to the same thermal loads

Multiscale mechanical integrity of human supraspinatus tendon in shear after elastin depletion.

Science.gov (United States)

Fang, Fei; Lake, Spencer P

2016-10-01

Human supraspinatus tendon (SST) exhibits region-specific nonlinear mechanical properties under tension, which have been attributed to its complex multiaxial physiological loading environment. However, the mechanical response and underlying multiscale mechanism regulating SST behavior under other loading scenarios are poorly understood. Furthermore, little is known about the contribution of elastin to tendon mechanics. We hypothesized that (1) SST exhibits region-specific shear mechanical properties, (2) fiber sliding is the predominant mode of local matrix deformation in SST in shear, and (3) elastin helps maintain SST mechanical integrity by facilitating force transfer among collagen fibers. Through the use of biomechanical testing and multiphoton microscopy, we measured the multiscale mechanical behavior of human SST in shear before and after elastase treatment. Three distinct SST regions showed similar stresses and microscale deformation. Collagen fiber reorganization and sliding were physical mechanisms observed as the SST response to shear loading. Measures of microscale deformation were highly variable, likely due to a high degree of extracellular matrix heterogeneity. After elastase treatment, tendon exhibited significantly decreased stresses under shear loading, particularly at low strains. These results show that elastin contributes to tendon mechanics in shear, further complementing our understanding of multiscale tendon structure-function relationships. Copyright © 2016 Elsevier Ltd. All rights reserved.

A study on plate anchor detailing systems of shear re-bar

International Nuclear Information System (INIS)

Tsurumaki, S.; Ujiie, K.; Nishikawa, T.; Kitayama, K.

1995-01-01

For shell walls and base slabs in reactor buildings, besides a large amount of main bars, numerous shear re-bars have been employed to resist to out-of-plane force. As a result , detailing work involving shear re-bar is extremely involved. For example, the employed re-bar anchor method differs from the ordinary methods in which, a end of shear re-bar with 135-degrees hook or with anchor plate type and another re-bar end with 90-degrees hook are used. However the structural characteristics in members using shear re-bar of the bolt-mounted anchor plate have not yet been examined. A test was performed to confirm the effects of anchor methods for shear re-bars on shearing behavior of members. This paper describes the test plan, method and results. (author). 12 figs., 7 tabs

[Effect of Food Thickeners on the Disintegration, Dissolution, and Drug Activity of Rapid Oral-disintegrating Tablets].

Science.gov (United States)

Tomita, Takashi; Kohda, Yukinao; Kudo, Kenzo

2018-01-01

　For patients with dysphagia in medical facilities and nursing homes, food thickeners are routinely used to aid the ingestion of medicines such as tablets. However, some types of thickeners affect the disintegration and dissolution of tablets, such as rapidly-disintegrating magnesium oxide tablets and donepezil hydrochloride orally disintegrating tablets. Additionally, delayed disintegration and dissolution of tablets affect a drug's efficacy. As an example, with Voglibose orally disintegrating tablets, marked differences are observed in changes in glucose levels during glucose tolerance testing. When using food thickeners to aid tablet ingestion, it is therefore necessary to select a product that has little effect on drug disintegration, dissolution, and activity.

Haptic Edge Detection Through Shear

Science.gov (United States)

Platkiewicz, Jonathan; Lipson, Hod; Hayward, Vincent

2016-03-01

Most tactile sensors are based on the assumption that touch depends on measuring pressure. However, the pressure distribution at the surface of a tactile sensor cannot be acquired directly and must be inferred from the deformation field induced by the touched object in the sensor medium. Currently, there is no consensus as to which components of strain are most informative for tactile sensing. Here, we propose that shape-related tactile information is more suitably recovered from shear strain than normal strain. Based on a contact mechanics analysis, we demonstrate that the elastic behavior of a haptic probe provides a robust edge detection mechanism when shear strain is sensed. We used a jamming-based robot gripper as a tactile sensor to empirically validate that shear strain processing gives accurate edge information that is invariant to changes in pressure, as predicted by the contact mechanics study. This result has implications for the design of effective tactile sensors as well as for the understanding of the early somatosensory processing in mammals.

Influence of thickening of the inner skull table on intracranial volume measurement in older people.

Science.gov (United States)

Royle, N A; Hernández, M C Valdés; Maniega, S Muñoz; Arabisala, B S; Bastin, M E; Deary, I J; Wardlaw, J M

2013-07-01

It is generally assumed that intracranial volume (ICV) remains constant after peaking in early adulthood. Thus ICV is used as a 'proxy' for original brain size when trying to estimate brain atrophy in older people in neuroimaging studies. However, physiological changes in the skull, such as thickening of the frontal inner table, are relatively common in older age and will reduce ICV. The potential influence that inner table skull thickening may have on ICV measurement in old age has yet to be investigated. We selected 60 (31 males, 29 females) representative older adults aged 71.1-74.3years from a community-dwelling ageing cohort, the Lothian Birth Cohort 1936. A semi-automatically derived current ICV measurement obtained from high resolution T1-weighted volume scans was compared to the estimated original ICV by excluding inner skull table thickening using expert manual image processing. Inner table skull thickening reduced ICV from an estimated original 1480.0ml to a current 1409.1ml, a median decrease of 7.3% (Z=-6.334; pestimated original ICV is required for research into brain ageing. Copyright © 2013 Elsevier Inc. All rights reserved.

Glomerular parietal epithelial cell activation induces collagen secretion and thickening of Bowman's capsule in diabetes.

Science.gov (United States)

Holderied, Alexander; Romoli, Simone; Eberhard, Jonathan; Konrad, Lukas A; Devarapu, Satish K; Marschner, Julian A; Müller, Susanna; Anders, Hans-Joachim

2015-03-01

The metabolic and hemodynamic alterations in diabetes activate podocytes to increase extracellular matrix (ECM) production, leading to thickening of the glomerular basement membrane (GBM). We hypothesized that diabetes would activate parietal epithelial cells (PECs) in a similar manner and cause thickening of Bowman's capsules. Periodic acid Schiff staining of human kidney biopsies of 30 patients with diabetic nephropathy (DN) revealed a significantly thicker Bowman's capsule as compared with 20 non-diabetic controls. The average thickness was 4.55±0.21 μm in the group of patients with DN compared with 2.92±0.21 μm in the group of non-diabetic controls (PBowman's capsule showed strong association with CD44-positive PECs. In summary, metabolic alterations in diabetes activate PECs to increase the expression and secretion of Bowman's capsule proteins. This process may contribute to the thickening of the Bowman's capsule, similar to the thickening of the GBM that is driven by activated podocytes. These data may also imply that activated PECs contribute to ECM production once they migrate to the glomerular tuft, a process resulting in glomerular scaring, for example, in diabetic glomerulosclerosis.

Fluid Effects on Shear Waves in Finely Layered Porous Media

International Nuclear Information System (INIS)

Berryman, J G

2004-01-01

Although there are five effective shear moduli for any layered VTI medium, one and only one effective shear modulus for the layered system contains all the dependence of pore fluids on the elastic or poroelastic constants that can be observed in vertically polarized shear waves. Pore fluids can increase the magnitude the shear energy stored by this modulus by a term that ranges from the smallest to the largest shear moduli of the VTI system. But, since there are five shear moduli in play, the increase in shear energy overall is reduced by a factor of about 5 in general. We can therefore give definite bounds on the maximum increase of shear modulus, being about 20% of the permitted range, when gas is fully replaced by liquid. An attendant increase of density (depending on porosity and fluid density) by approximately 5 to 10% partially offsets the effect of this shear modulus increase. Thus, an increase of shear wave speed on the order of 5 to 10% is shown to be possible when circumstances are favorable - i.e., when the shear modulus fluctuations are large (resulting in strong anisotropy), and the medium behaves in an undrained fashion due to fluid trapping. At frequencies higher than seismic (such as sonic and ultrasonic waves for well-logging or laboratory experiments), short response times also produce the requisite undrained behavior and, therefore, fluids also affect shear waves at high frequencies by increasing rigidity

Study on the shear transfer of reinforced concrete at elevated temperature

International Nuclear Information System (INIS)

Ishida, Hiroaki; Kanazu, Tsutomu

1989-01-01

Reinforced concrete structures in nuclear power stations, such as a containment vessel and structural members supporting a reactor vessel, are designed assuming that they may be subjected to elevated temperature. In the design code, it is specified that the temperature of concrete must not exceed the limitation, and thermal effect shall be taken into account. In this study, the shearing test using Mattock type specimens was performed to investigate into the shear behavior of the reinforced concrete subjected to elevated temperature. The test parameters studied in this program were the reinforcement ratio in a shear plane, the compressive stress normal to a shear plane and temperature. The maximum shearing load of the specimens heated to 200 degC was about 10-20 % lower than that at normal temperature, but nearly equal to that of the specimens heated to 100 degC. The equation for evaluating the shearing strength ratio was proposed. The cracking width and slip at maximum shearing load increased as temperature rose. Up to 200 degC, the same relation existed between interface shear transfer rigidity and cracking width. (K.I.)

Experimental Characteristics of Dry Stack Masonry under Compression and Shear Loading

Directory of Open Access Journals (Sweden)

Kun Lin

2015-12-01

Full Text Available The behavior of dry stack masonry (DSM is influenced by the interaction of the infill with the frame (especially the joints between bricks, which requires further research. This study investigates the compression and shear behaviors of DSM. First, a series of compression tests were carried out on both masonry prism with mortar (MP_m and DSM prism (MP_ds. The failure mode of each prism was determined. Different from the MP_m, the stress-strain relationship of the MP_ds was characterized by an upward concavity at the initial stage. The compression strength of the MP_ds was slightly reduced by 15%, while the elastic modulus was reduced by over 62%. In addition, 36 shear-compression tests were carried out under cyclic loads to emphasize the influence of various loads on the shear-compression behavior of DSM. The results showed that the Mohr-Coulomb friction law adequately represents the failure of dry joints at moderate stress levels, and the varying friction coefficients under different load amplitudes cannot be neglected. The experimental setup and results are valuable for further research.

Experimental Characteristics of Dry Stack Masonry under Compression and Shear Loading.

Science.gov (United States)

Lin, Kun; Totoev, Yuri Zarevich; Liu, Hongjun; Wei, Chunli

2015-12-12

The behavior of dry stack masonry (DSM) is influenced by the interaction of the infill with the frame (especially the joints between bricks), which requires further research. This study investigates the compression and shear behaviors of DSM. First, a series of compression tests were carried out on both masonry prism with mortar (MP_m) and DSM prism (MP_ds). The failure mode of each prism was determined. Different from the MP_m, the stress-strain relationship of the MP_ds was characterized by an upward concavity at the initial stage. The compression strength of the MP_ds was slightly reduced by 15%, while the elastic modulus was reduced by over 62%. In addition, 36 shear-compression tests were carried out under cyclic loads to emphasize the influence of various loads on the shear-compression behavior of DSM. The results showed that the Mohr-Coulomb friction law adequately represents the failure of dry joints at moderate stress levels, and the varying friction coefficients under different load amplitudes cannot be neglected. The experimental setup and results are valuable for further research.

Reproducibility of an automatic quantitation of regional myocardial wall motion and systolic thickening on gated Tc-99m-MIBI myocardial SPECT

International Nuclear Information System (INIS)

Paeng, Jin Chul; Lee, Dong Soo; Cheon, Gi Jeong; Kim, Yu Kyeong; Chung, June Key; Lee, Myung Chul

2000-01-01

The aim of this study is to investigate the reproducibility of the quantitative assessment of segmental wall motion and systolic thickening provided by an automatic quantitation algorithm. Tc-99m-MIBI gated myocardial SPECT with dipyridamole stress was performed in 31 patients with known or suspected coronary artery disease (4 with single, 6 with two, 11 with triple vessel disease; ejection fraction 51±14%) twice consecutively in the same position. Myocardium was divided into 20 segments. Segmental wall motion and systolic thickening were calculated and expressed in mm and % increase respectively, using AutoQUANT TM software. The reproducibility of this quantitative measurement of wall motion and thickening was tested. Correlations between repeated measurements on consecutive gated SPECT were excellent for wall motion (r=0.95) and systolic thickening (r=0.88). On Bland-Altman analysis, two standard deviation was 2 mm for repeated measurement of segmental wall motion, and 20% for that of systolic thickening. The weighted kappa values of repeated measurements were 0.807 for wall motion and 0.708 for systolic thickening. Sex, perfusion, or segmental location had no influence on reproducibility. Segmental wall motion and systolic thickening quantified using AutoQUANT TM software on gated myocardial SPECT offers good reproducibility and is significantly different when the change is more than 2 mm for wall motion and more than 20% for systolic thickening

Extension of thickened and hot lithospheres: Inferences from laboratory modeling

NARCIS (Netherlands)

Tirel, C.; Brun, J.P.; Sokoutis, D.

2006-01-01

The extension of a previously thickened lithosphere is studied through a series of analogue experiments. The models deformed in free and boundary-controlled gravity spreading conditions that simulate the development of wide rift-type and core complex-type structures. In models, the development of

Observation of Droplet Size Oscillations in a Two Phase Fluid under Shear Flow

Science.gov (United States)

Courbin, Laurent; Panizza, Pascal

2004-11-01

It is well known that complex fluids exhibit strong couplings between their microstructure and the flow field. Such couplings may lead to unusual non linear rheological behavior. Because energy is constantly brought to the system, richer dynamic behavior such as non linear oscillatory or chaotic response is expected. We report on the observation of droplet size oscillations at fixed shear rate. At low shear rates, we observe two steady states for which the droplet size results from a balance between capillary and viscous stress. For intermediate shear rates, the droplet size becomes a periodic function of time. We propose a phenomenological model to account for the observed phenomenon and compare numerical results to experimental data.

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-02-15

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

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

Directory of Open Access Journals (Sweden)

JeeYeon N. Plohr

2016-02-01

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

Descemet Membrane Thickening as a Sign for the Diagnosis of Corneal Graft Rejection: An Ex Vivo Study.

Science.gov (United States)

VanDenBerg, Ryan; Diakonis, Vasilios F; Bozung, Alison; Gameiro, Gustavo Rosa; Fischer, Oliver; El Dakkak, Ahmed; Ulloa-Padilla, Jan Paul; Anagnostopoulos, Apostolos; Dubovy, Sander; Abou Shousha, Mohamed

2017-12-01

To disclose, using an ex vivo study, the histopathological mechanism behind in vivo thickening of the endothelium/Descemet membrane complex (En/DM) observed in rejected corneal grafts (RCGs). Descemet membrane (DM), endothelium, and retrocorneal membranes make up the total En/DM thickness. These layers are not differentiable by high-definition optical coherence tomography; therefore, the source of thickening is unclear from an in vivo perspective. A retrospective ex vivo study (from September 2015 to December 2015) was conducted to measure the thicknesses of DM, endothelium, and retrocorneal membrane in 54 corneal specimens (31 RCGs and 23 controls) using light microscopy. Controls were globes with posterior melanoma without corneal involvement. There were 54 corneas examined ex vivo with mean age 58.1 ± 12.2 in controls and 51.7 ± 27.9 years in RCGs. The ex vivo study uncovered the histopathological mechanism of En/DM thickening to be secondary to significant thickening (P < 0.001) of DM (6.5 ± 2.4 μm) in RCGs compared with controls (3.9 ± 1.5 μm). Our ex vivo study shows that DM is responsible for thickening of the En/DM in RCGs observed in vivo by high-definition optical coherence tomography and not the endothelium or retrocorneal membrane.

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

Science.gov (United States)

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

2018-01-12

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

Relating rheology to geometry in large-scale natural shear zones

Science.gov (United States)

Platt, John

2016-04-01

diffusion, or metamorphic reactions? (3) In two-phase / polyphase mixtures, does the strong phase generally form a load-bearing framework, favoring constant strain-rate (Voigt) bound behavior, or does the weak phase form through-going strain pathways, favoring constant stress (Reuss) bound behavior, or do the phases remain well mixed, favoring an intermediate behavior (e.g., Tullis et al model)? (4) How do we deal with the rheological effect of water? Is it simply an unconstrained variable in nature? Is the water fugacity model in flow laws adequate? (5) How can we better relate experimental results (often carried out at constant strain-rate, and not reaching microstructural steady state) to deformation in natural shear zones? Rheological observations on well-constrained natural shear zones are helping us answer some of these questions.

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

International Nuclear Information System (INIS)

Wan Liang; Wang Shaoqing

2010-01-01

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

Measurement of viscosity of slush at high shear rates

OpenAIRE

小林, 俊一; 川村, 公之; 津川, 圭一; 和泉, 薫; Kobayashi, Shun'ichi; Kawamura, Kimiyuki; Tugawa, Keiichi; Izumi, Kaoru

1988-01-01

Measurements of viscosity of slush were carried out using a method of flow along an inclined smooth surface in a 0℃cold room. The method was used to get the values of viscosity under high shear rates (25 and 75s^). From our experiments two important results were obtained: 1) the viscosity of slush decreases with increasing shear rates; 2) The fluid behavior is pseudoplastic that the values of non-Newtonian index of viscosity were less than unity.

Physical gelation of a microfiber suspension.

Science.gov (United States)

Perazzo, Antonio; Nunes, Janine K.; Guido, Stefano; Stone, Howard A.

2015-11-01

Hydrogels are among the most exploited materials in tissue engineering and there is growing interest in injectable hydrogels, especially as applied to surgical adhesives and bioprinting materials. Here we report a method to produce a hydrogel in a desired location by simply extruding a suspension of high aspect ratio and flexible microfibers from a syringe. The mechanism of gel formation is purely physical and based on irreversible entanglements formed by the microfibers under the action of flow. The single microfibers have been produced and finely tailored by microfluidic methods. Shear rheology has been performed in order to get insights on the entanglements, and results show that the formation of entanglements is related to a shear thickening behavior of the suspension, which in turn depends on shear rate and concentration of fibers. When shearing the suspension, highly non-linear viscoelastic behavior is observed and probed by a highly positive first normal stress difference. We also report the hydrogel swelling behavior and its linear viscoelastic properties as obtained by imposing small oscillatory stress to the material.

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

KAUST Repository

Sullivan, J. M.

2012-01-01

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

Measurement of the temperature-dependent threshold shear-stress of red blood cell aggregation.

Science.gov (United States)

Lim, Hyun-Jung; Nam, Jeong-Hun; Lee, Yong-Jin; Shin, Sehyun

2009-09-01

Red blood cell (RBC) aggregation is becoming an important hemorheological parameter, which typically exhibits temperature dependence. Quite recently, a critical shear-stress was proposed as a new dimensional index to represent the aggregative and disaggregative behaviors of RBCs. The present study investigated the effect of the temperature on the critical shear-stress that is required to keep RBC aggregates dispersed. The critical shear-stress was measured at various temperatures (4, 10, 20, 30, and 37 degrees C) through the use of a transient microfluidic aggregometry. The critical shear-stress significantly increased as the blood temperature lowered, which accorded with the increase in the low-shear blood viscosity with the lowering of the temperature. Furthermore, the critical shear-stress also showed good agreement with the threshold shear-stress, as measured in a rotational Couette flow. These findings assist in rheologically validating the critical shear-stress, as defined in the microfluidic aggregometry.

An evaluation of the lap-shear test for Sn-rich solder/Cu couples: Experiments and simulation

Science.gov (United States)

Chawla, N.; Shen, Y.-L.; Deng, X.; Ege, E. S.

2004-12-01

The lap-shear technique is commonly used to evaluate the shear, creep, and thermal fatigue behavior of solder joints. We have conducted a parametric experimental and modeling study, on the effect of testing and geometrical parameters on solder/copper joint response in lap-shear. It was shown that the farfield applied strain is quite different from the actual solder strain (measured optically). Subtraction of the deformation of the Cu substrate provides a reasonable approximation of the solder strain in the elastic regime, but not in the plastic regime. Solder joint thickness has a profound effect on joint response. The solder response moves progressively closer to “true” shear response with increasing joint thickness. Numerical modeling using finite-element analyses were performed to rationalize the experimental findings. The same lap-shear configuration was used in the simulation. The input response for solder was based on the experimental tensile test result on bulk specimens. The calculated shear response, using both the commonly adopted far-field measure and the actual shear strain in solder, was found to be consistent with the trends observed in the lap-shear experiments. The geometric features were further explored to provide physical insight into the problem. Deformation of the substrate was found to greatly influence the shear behavior of the solder.

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

Science.gov (United States)

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

2017-05-13

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

Complex rheological properties of a water-soluble extract from the fronds of the black tree fern, Cyathea medullaris.

Science.gov (United States)

Goh, Kelvin K T; Matia-Merino, Lara; Hall, Christopher E; Moughan, Paul J; Singh, Harjinder

2007-11-01

A water-soluble extract was obtained from the fronds of a New Zealand native black tree fern (Cyathea medullaris or Mamaku in Māori). The extract exhibited complex rheological behavior. Newtonian, shear-thinning, shear-thickening, thixotropic, antithixotropic, and viscoelastic behaviors were observed depending on polymer concentration, shear rate, and shear history. The extract also displayed rod-climbing and self-siphoning properties typical of viscoelastic fluids. Such complex rheological properties have been reported in synthetic or chemically modified polymers but are less frequent in unmodified biopolymers. Although Mamaku extract obtained from the pith of the fern has been traditionally used by the Māori in New Zealand for treating wounds and diarrhea among other ailments, this material has never been characterized before. This study reports on the chemical composition of the extract and on its viscoelastic properties through rotational and oscillatory rheological measurements. Explanations of the mechanism behind the rheological properties were based on transient network models for associating polymers.

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

Science.gov (United States)

Ji, Wendong; Zhang, Yuting; Jin, Yafei

2018-05-01

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

Shear strength of non-shear reinforced concrete elements

DEFF Research Database (Denmark)

Hoang, Cao linh

1997-01-01

The paper deals with the plastic shear strength of non shear reinforced T-beams.The influence of an un-reinforced flange on the shear capacity is investigated by considering a failure mechanism involving crack sliding in the web and a kind of membrane action over an effective width of the flange...

Nonlinear shear wave in a non Newtonian visco-elastic medium

Energy Technology Data Exchange (ETDEWEB)

Banerjee, D.; Janaki, M. S.; Chakrabarti, N. [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Calcutta 700 064 (India); Chaudhuri, M. [Max-Planck-Institut fuer extraterrestrische Physik, 85741 Garching (Germany)

2012-06-15

An analysis of nonlinear transverse shear wave has been carried out on non-Newtonian viscoelastic liquid using generalized hydrodynamic model. The nonlinear viscoelastic behavior is introduced through velocity shear dependence of viscosity coefficient by well known Carreau-Bird model. The dynamical feature of this shear wave leads to the celebrated Fermi-Pasta-Ulam problem. Numerical solution has been obtained which shows that initial periodic solutions reoccur after passing through several patterns of periodic waves. A possible explanation for this periodic solution is given by constructing modified Korteweg de Vries equation. This model has application from laboratory to astrophysical plasmas as well as in biological systems.

Journal Article: Localized Pleural Thickening: Smoking and Exposure to Libby Vermiculite

Science.gov (United States)

There is limited research on the combined effects of smoking and asbestos exposure on risk of localized pleural thickening (LPT). This analysis uses data from the Marysville cohort of workers occupationally exposed to Libby amphibole asbestos (LAA). Workers were interviewed to ...

INEXPENSIVE CO{sub 2} THICKENING AGENTS FOR IMPROVED MOBILITY CONTROL OF CO{sub 2} FLOODS

Energy Technology Data Exchange (ETDEWEB)

Robert M. Enick; Eric J. Beckman; Andrew Hamilton

2004-10-01

The objective of this research was the design, synthesis and evaluation of inexpensive, nonfluorous carbon dioxide thickening agents. We followed the same strategy employed in the design of fluorinated CO{sub 2} polymeric thickeners. First, a highly CO{sub 2}-philic, hydrocarbon-based monomer was to be identified. Polymers or oligomers of this monomer were then synthesized. The second step was to be completed only when a CO{sub 2}-soluble polymer that was soluble in CO{sub 2} at pressures comparable to the MMP was identified. In the second step, viscosity-enhancing associating groups were to be incorporated into the polymer to make it a viable thickener that exhibited high CO{sub 2} solubility at EOR MMP conditions. This final report documents the CO{sub 2} solubility of a series of commercial and novel polymers composed of carbon, hydrogen, oxygen and, in some cases, nitrogen.

Magnetic resonance imaging of thickened pituitary stalk proceeding to langerhans cell histiocytosis in a child

International Nuclear Information System (INIS)

Halefoglu, A.M.

2006-01-01

Magnetic resonance imaging has shown isolated pituitary stalk thickening in certain cases of idiopathic or secondary central diabetes insipidus (Dl) due to infiltrative processes. We present a 4-year-old boy who was initially diagnosed as having central Dl. The MRI showed isolated pituitary stalk thickening with prominent homogeneous contrast enhancement. The remaining findings on MRI were within normal limits. The patient's personal and family history and laboratory and clinical findings were unremarkable; therefore, he was initially diagnosed as having idiopathic Dl. Since central Dl and isolated pituitary stalk thickening may be considered to be the first manifestations of Langerhans cell histiocytosis, we decided to follow up the patient. After 5 months, following the initial diagnosis, on skeletal X-ray survey, the patient did indeed develop multiple lytic skull lesions which, on biopsy, were histologically typical bone lesions of Langerhans cell histiocytosis. Copyright (2006) Blackwell Science Pty Ltd

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

Science.gov (United States)

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

2011-12-01

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

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

Directory of Open Access Journals (Sweden)

Pedro Castro

2017-06-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2014-07-01

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

Shearing single crystal magnesium in the close-packed basal plane at different temperatures

Science.gov (United States)

Han, Ming; Li, Lili; Zhao, Guangming

2018-05-01

Shear behaviors of single crystal magnesium (Mg) in close-packed (0001) basal plane along the [ 1 bar 2 1 bar 0 ], [ 1 2 bar 10 ], [ 10 1 bar 0 ] and [ 1 bar 010 ] directions were studied using molecular dynamics simulations via EAM potential. The results show that both shear stress-strain curves along the four directions and the motion path of free atoms during shearing behave periodic characteristics. It reveals that the periodic shear displacement is inherently related to the crystallographic orientation in single crystal Mg. Moreover, different temperatures in a range from 10 to 750 K were considered, demonstrating that shear modulus decreases with increasing temperatures. The results agree well with the MTS model. It is manifested that the modulus is independent with the shear direction and the size of the atomic model. This work also demonstrates that the classical description of shear modulus is still effective at the nanoscale.

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

International Nuclear Information System (INIS)

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

2014-01-01

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

Stress-induced thickening of Ω phase in Al–Cu–Mg alloys containing various Ag additions

Energy Technology Data Exchange (ETDEWEB)

Bai, Song [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China); Liu, Zhiyi, E-mail: liuzhiyi@mail.csu.edu.cn [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China); Zhou, Xuanwei; Xia, Peng; Liu, Meng [Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083 (China); School of Material Science and Engineering, Central South University, Changsha 410083 (China)

2014-01-01

The thickening of Ω phase in Al–Cu–Mg alloys containing various bulk Ag contents during stress aging at 200 °C with a tensile stress of 240 MPa was investigated by a combination of transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and atom probe tomography (APT). TEM characterization confirmed preferred orientation of Ω phase in all stress-aged samples. Corresponding quantitative TEM calculations revealed the thickening kinetics of Ω phase was significantly accelerated during stress aging as compared to that during stress-free aging at 200 °C. HRTEM analysis on the α/Ω interfacial structure confirmed that the applied tensile stress facilitated the rapid nucleation of the growth ledge on the broad face of Ω phase, thereby resulting in the accelerated plate thickening during stress aging at 200 °C. Meanwhile, quantitative TEM analysis highlighted the stress-induced thickening of Ω phase at 200 °C was affected by the bulk Ag content. This was consistent with the HRTEM observation as the ledge nucleation was found to be suppressed with increasing Ag addition. Our APT analysis on different stress-aged samples further suggested the progressive enrichment of Ag atoms in the segregation layer helped to stabilize the interfacial structure and was responsible for the lowest nucleation rate of the ledge in 1.77Ag alloy as compared to that in 0.46Ag alloy.

Stress-induced thickening of Ω phase in Al–Cu–Mg alloys containing various Ag additions

International Nuclear Information System (INIS)

Bai, Song; Liu, Zhiyi; Zhou, Xuanwei; Xia, Peng; Liu, Meng

2014-01-01

The thickening of Ω phase in Al–Cu–Mg alloys containing various bulk Ag contents during stress aging at 200 °C with a tensile stress of 240 MPa was investigated by a combination of transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and atom probe tomography (APT). TEM characterization confirmed preferred orientation of Ω phase in all stress-aged samples. Corresponding quantitative TEM calculations revealed the thickening kinetics of Ω phase was significantly accelerated during stress aging as compared to that during stress-free aging at 200 °C. HRTEM analysis on the α/Ω interfacial structure confirmed that the applied tensile stress facilitated the rapid nucleation of the growth ledge on the broad face of Ω phase, thereby resulting in the accelerated plate thickening during stress aging at 200 °C. Meanwhile, quantitative TEM analysis highlighted the stress-induced thickening of Ω phase at 200 °C was affected by the bulk Ag content. This was consistent with the HRTEM observation as the ledge nucleation was found to be suppressed with increasing Ag addition. Our APT analysis on different stress-aged samples further suggested the progressive enrichment of Ag atoms in the segregation layer helped to stabilize the interfacial structure and was responsible for the lowest nucleation rate of the ledge in 1.77Ag alloy as compared to that in 0.46Ag alloy

Comparative Laboratory and Numerical Simulations of Shearing Granular Fault Gouge: Micromechanical Processes

Science.gov (United States)

Morgan, J. K.; Marone, C. J.; Guo, Y.; Anthony, J. L.; Knuth, M. W.

2004-12-01

Laboratory studies of granular shear zones have provided significant insight into fault zone processes and the mechanics of earthquakes. The micromechanisms of granular deformation are more difficult to ascertain, but have been hypothesized based on known variations in boundary conditions, particle properties and geometries, and mechanical behavior. Numerical simulations using particle dynamics methods (PDM) can offer unique views into deforming granular shear zones, revealing the precise details of granular microstructures, particle interactions, and packings, which can be correlated with macroscopic mechanical behavior. Here, we describe a collaborative program of comparative laboratory and numerical experiments of granular shear using idealized materials, i.e., glass beads, glass rods or pasta, and angular sand. Both sets of experiments are carried out under similar initial and boundary conditions in a non-fracturing stress regime. Phenomenologically, the results of the two sets of experiments are very similar. Peak friction values vary as a function of particle dimensionality (1-D vs. 2-D vs. 3-D), particle angularity, particle size and size distributions, boundary roughness, and shear zone thickness. Fluctuations in shear strength during an experiment, i.e., stick-slip events, can be correlated with distinct changes in the nature, geometries, and durability of grain bridges that support the shear zone walls. Inclined grain bridges are observed to form, and to support increasing loads, during gradual increases in assemblage strength. Collapse of an individual grain bridge leads to distinct localization of strain, generating a rapidly propagating shear surface that cuts across multiple grain bridges, accounting for the sudden drop in strength. The distribution of particle sizes within an assemblage, along with boundary roughness and its periodicity, influence the rate of formation and dissipation of grain bridges, thereby controlling friction variations during

Shear crack propagation in MBC strengthened concrete beams”

DEFF Research Database (Denmark)

Täljsten, Björn; Blanksvärd, Thomas; Carolin, Anders

2008-01-01

thermal compatibility to the base concrete and are often sensitive to the surface nature and surrounding temperature. By using mineral based composites (MBC) some of these challenges can be overcome. MBC refers here to a cementitious bonding agent and a carbon FRP grid. This paper is a part of an ongoing......Repair and upgrading existing concrete structures using FRPs and an epoxy adhesive as the bonding agent has some disadvantages when it comes to compatibility to the base concrete. Epoxies are often restricted by regulations of use, have low permeability which may create freeze/thaw problems, poor...... study of MBC systems. Emphasis is placed on the cracking behavior of the MBC system used for shear strengthening of RC beams. Traditional foil strain gauges and photometric measurements have been used for monitoring of the cracking behavior. In this study it is shown that the use of mineral based shear...

Multiaxial behavior of foams - Experiments and modeling

Science.gov (United States)

Maheo, Laurent; Guérard, Sandra; Rio, Gérard; Donnard, Adrien; Viot, Philippe

2015-09-01

Cellular materials are strongly related to pressure level inside the material. It is therefore important to use experiments which can highlight (i) the pressure-volume behavior, (ii) the shear-shape behavior for different pressure level. Authors propose to use hydrostatic compressive, shear and combined pressure-shear tests to determine cellular materials behavior. Finite Element Modeling must take into account these behavior specificities. Authors chose to use a behavior law with a Hyperelastic, a Viscous and a Hysteretic contributions. Specific developments has been performed on the Hyperelastic one by separating the spherical and the deviatoric part to take into account volume change and shape change characteristics of cellular materials.

The Influence of Thickener Content on the Properties of Acryl Emulsion Resin

Energy Technology Data Exchange (ETDEWEB)

Park, Young Sam; Choi, Sang Goo [Department of Chemical Technology, Ho-Won University, Kunsan (Korea)

2001-04-01

HW-100 (acryl oligomer), Aerosil 200 (fine silica), HEMC (hydroxyethyl methylcellulose) and HPMC (hydroxypropyl methylcellulose) were each mixed with acryl emulsion resin. For each mixture, various physical properties were tested experimentally. HW-100 mixtures showed higher viscosity and thixotropy than the other mixtures. The viscosity increased rapidly with adding of thickener. Fabrication workability decreased substantially with increased thixotropy. Aerosil mixture represented good properties in workability, adhesive strength and water-resistance, however, it had large shrinkage. The shrinkage was typically influenced by content of water and void. HEMC mixture showed higher pH and adhesion than others, while HPMC mixture had long drying-time and excellent alkali-resistance characteristics. Water-resistance and alkali-resistance were mainly influenced by the molecular structure of thickener and the content of void. 26 refs., 12 figs.

Cone-Beam Computed Tomography Analysis of Mucosal Thickening in Unilateral Cleft Lip and Palate Maxillary Sinuses.

Science.gov (United States)

Kula, Katherine; Hale, Lindsay N; Ghoneima, Ahmed; Tholpady, Sunil; Starbuck, John M

2016-11-01

  To compare maxillary mucosal thickening and sinus volumes of unilateral cleft lip and palate subjects (UCLP) with noncleft (nonCLP) controls.   Randomized, retrospective study of cone-beam computed tomographs (CBCT).   University.   Fifteen UCLP subjects and 15 sex- and age-matched non-CLP controls, aged 8 to 14 years.   Following institutional review board approval and reliability tests, Dolphin three-dimensional imaging software was used to segment and slice maxillary sinuses on randomly selected CBCTs. The surface area (SA) of bony sinus and airspace on all sinus slices was determined using Dolphin and multiplied by slice thickness (0.4 mm) to calculate volume. Mucosal thickening was the difference between bony sinus and airspace volumes. The number of slices with bony sinus and airspace outlines was totaled. Right and left sinus values for each group were pooled (t tests, P > .05; n = 30 each group). All measures were compared (principal components analysis, multivariate analysis of variance, analysis of variance) by group and age (P ≤ .016 was considered significant).   Principal components analysis axis 1 and 2 explained 89.6% of sample variance. Principal components analysis showed complete separation based on the sample on axis 1 only. Age groups showed some separation on axis 2. Unilateral cleft lip and palate subjects had significantly smaller bony sinus and airspace volumes, fewer bony and airspace slices, and greater mucosal thickening and percentage mucosal thickening when compared with controls. Older subjects had significantly greater bony sinus and airspace volumes than younger subjects.   Children with UCLP have significantly more maxillary sinus mucosal thickening and smaller sinuses than controls.

Shear Adhesion of Tapered Nanopillar Arrays.

Science.gov (United States)

Cho, Younghyun; Minsky, Helen K; Jiang, Yijie; Yin, Kaiyang; Turner, Kevin T; Yang, Shu

2018-04-04

Tapered nanopillars with various cross sections, including cone-shaped, stepwise, and pencil-like structures (300 nm in diameter at the base of the pillars and 1.1 μm in height), are prepared from epoxy resin templated by nanoporous anodic aluminum oxide (AAO) membranes. The effect of pillar geometry on the shear adhesion behavior of these nanopillar arrays is investigated via sliding experiments in a nanoindentation system. In a previous study of arrays with the same geometry, it was shown that cone-shaped nanopillars exhibit the highest adhesion under normal loading while stepwise and pencil-like nanopillars exhibit lower normal adhesion strength due to significant deformation of the pillars that occurs with increasing indentation depth. Contrary to the previous studies, here, we show that pencil-like nanopillars exhibit the highest shear adhesion strength at all indentation depths among three types of nanopillar arrays and that the shear adhesion increases with greater indentation depth due to the higher bending stiffness and closer packing of the pencil-like nanopillar array. Finite element simulations are used to elucidate the deformation of the pillars during the sliding experiments and agree with the nanoindentation-based sliding measurements. The experiments and finite element simulations together demonstrate that the shape of the nanopillars plays a key role in shear adhesion and that the mechanism is quite different from that of adhesion under normal loading.

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

Science.gov (United States)

Ingebrigtsen, Trond S; Tanaka, Hajime

2018-01-02

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

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

Science.gov (United States)

Ingebrigtsen, Trond S.; Tanaka, Hajime

2018-01-01

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

Atomistic origin of size effects in fatigue behavior of metallic glasses

Science.gov (United States)

Sha, Zhendong; Wong, Wei Hin; Pei, Qingxiang; Branicio, Paulo Sergio; Liu, Zishun; Wang, Tiejun; Guo, Tianfu; Gao, Huajian

2017-07-01

While many experiments and simulations on metallic glasses (MGs) have focused on their tensile ductility under monotonic loading, the fatigue mechanisms of MGs under cyclic loading still remain largely elusive. Here we perform molecular dynamics (MD) and finite element simulations of tension-compression fatigue tests in MGs to elucidate their fatigue mechanisms with focus on the sample size effect. Shear band (SB) thickening is found to be the inherent fatigue mechanism for nanoscale MGs. The difference in fatigue mechanisms between macroscopic and nanoscale MGs originates from whether the SB forms partially or fully through the cross-section of the specimen. Furthermore, a qualitative investigation of the sample size effect suggests that small sample size increases the fatigue life while large sample size promotes cyclic softening and necking. Our observations on the size-dependent fatigue behavior can be rationalized by the Gurson model and the concept of surface tension of the nanovoids. The present study sheds light on the fatigue mechanisms of MGs and can be useful in interpreting previous experimental results.

Generating Bulk-Scale Ordered Optical Materials Using Shear-Assembly in Viscoelastic Media

Directory of Open Access Journals (Sweden)

Chris E. Finlayson

2017-06-01

Full Text Available We review recent advances in the generation of photonics materials over large areas and volumes, using the paradigm of shear-induced ordering of composite polymer nanoparticles. The hard-core/soft-shell design of these particles produces quasi-solid “gum-like” media, with a viscoelastic ensemble response to applied shear, in marked contrast to the behavior seen in colloidal and granular systems. Applying an oscillatory shearing method to sub-micron spherical nanoparticles gives elastomeric photonic crystals (or “polymer opals” with intense tunable structural color. The further engineering of this shear-ordering using a controllable “roll-to-roll” process known as Bending Induced Oscillatory Shear (BIOS, together with the interchangeable nature of the base composite particles, opens potentially transformative possibilities for mass manufacture of nano-ordered materials, including advances in optical materials, photonics, and metamaterials/plasmonics.

A New Hyperbolic Shear Deformation Theory for Bending Analysis of Functionally Graded Plates

Directory of Open Access Journals (Sweden)

Tahar Hassaine Daouadji

2012-01-01

Full Text Available Theoretical formulation, Navier’s solutions of rectangular plates based on a new higher order shear deformation model are presented for the static response of functionally graded plates. This theory enforces traction-free boundary conditions at plate surfaces. Shear correction factors are not required because a correct representation of transverse shearing strain is given. Unlike any other theory, the number of unknown functions involved is only four, as against five in case of other shear deformation theories. The mechanical properties of the plate are assumed to vary continuously in the thickness direction by a simple power-law distribution in terms of the volume fractions of the constituents. Numerical illustrations concern flexural behavior of FG plates with metal-ceramic composition. Parametric studies are performed for varying ceramic volume fraction, volume fractions profiles, aspect ratios, and length to thickness ratios. Results are verified with available results in the literature. It can be concluded that the proposed theory is accurate and simple in solving the static bending behavior of functionally graded plates.

Tibetan garnet records early Eocene initiation of thickening in the Himalaya

DEFF Research Database (Denmark)

Smit, Matthijs Arjen; Hacker, Bradley; Lee, Jeffrey

2014-01-01

Tectonic reconstructions of the Himalayan orogeny depend on the age at which crustal thickening commenced. To investigate this age, we analyzed garnet from middle crustal rocks exposed in the north Himalayan Mabja and Kangmar gneiss domes of Tibet using Lu-Hf geochronology. Garnet yielded Lu-Hf a...

Comparison of the rheological properties of ready-to-serve and powdered instant food-thickened beverages at different temperatures for dysphagic patients.

Science.gov (United States)

Adeleye, Bernice; Rachal, Corryn

2007-07-01

Dysphagia, or difficulty swallowing, affects an estimated 15 million Americans. Its management may include use of instant food thickener (IFT) to modify beverage consistency to minimize the risk of aspiration and prevent dehydration. However, inconsistencies with the desired viscosity of these thickened liquids occur both within and across product lines for both ready-to-serve commercially packaged prethickened (CPPT) and IFT-thickened beverages. To examine the rheological property differences between CPPT and similar IFT-thickened beverages, and to assess the stability of these products at two temperature ranges using three viscosity measurement techniques. The rheological properties of five CPPT and IFT-thickened beverages at both nectar- and honey-like consistencies were evaluated at 10 degrees C (50 degrees F) and 20 degrees C (68 degrees F) using the line spread, funnel, and viscometry methods. One-way analysis of variance was used for data analysis. When a significant difference was observed, Tukey's test was used to separate the means. Each viscosity measurement technique showed the CPPT nectar- and honey-like consistency beverages were significantly more viscous (Pbeverages at nectar and honey consistencies were almost always more viscous than the National Dysphagia Diet Task Force-defined standards, whereas the IFT-thickened beverages were more frequently within those standards. A reevaluation of the viscosity of CPPT beverages with reference to the National Dysphagia Diet Task Force set standard ranges needs to be considered. A strong need also exists for development of a standard protocol on product labels that includes the expected rheological properties of CPPT and IFT-thickened beverages. To the clinicians, especially registered dietitians, it is an important clinical consideration to recognize that CPPT products may be thicker than IFT-thickened products and also may be more viscous than the National Dysphagia Diet Task Force-defined standards.

The experimental study of sinal wall thickening on CT

International Nuclear Information System (INIS)

Kase, Yasuhiro; Iinuma, Tositaka; Oyama, Kazuyuki.

1988-01-01

In our previous report, we investigated several factors which cause apparent thickening of the walls of maxillary sinus. We confirmed, however, that the major factor for the sinal wall thickening is the artifact of CT. In present study, we report the results obtained by phantom models of isolated maxillary bone and egg shell. As the substance corresponding to the soft tissue density, solutions of CaCl 2 in various concentrations were used. In the maxillary bone studies, the thickness of the anterior sinus wall by CT was larger than the actual value even though only the air was contained. When solutions of CaCl 2 were contained and in touch with the anterior wall, the thickness by CT was larger than that of containing air. In the egg shell studies, the increase in thickness by CT correlated to the increase in percentage of solutions. The above results indicate that the apparent increased thickness of the sinal walls by CT is largely the artifact by CT and is dependent upon the soft tissue density or CT value (X-ray attenuation coefficient) of substances in touch with the sinal walls. In CT images obtained by clinical cases, the increased thickness of the sinal walls, in sinuses filled with soft tissue density, is more apparent than real. (author)

Shear failure of granular materials

Science.gov (United States)

Degiuli, Eric; Balmforth, Neil; McElwaine, Jim; Schoof, Christian; Hewitt, Ian

2012-02-01

Connecting the macroscopic behavior of granular materials with the microstructure remains a great challenge. Recent work connects these scales with a discrete calculus [1]. In this work we generalize this formalism from monodisperse packings of disks to 2D assemblies of arbitrarily shaped grains. In particular, we derive Airy's expression for a symmetric, divergence-free stress tensor. Using these tools, we derive, from first-principles and in a mean-field approximation, the entropy of frictional force configurations in the Force Network Ensemble. As a macroscopic consequence of the Coulomb friction condition at contacts, we predict shear failure at a critical shear stress, in accordance with the Mohr-Coulomb failure condition well known in engineering. Results are compared with numerical simulations, and the dependence on the microscopic geometric configuration is discussed. [4pt] [1] E. DeGiuli & J. McElwaine, PRE 2011. doi: 10.1103/PhysRevE.84.041310

Experimental study of shear rate dependence in perpetually sheared granular matter

Science.gov (United States)

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

2017-06-01

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

Investigation of Rheological Properties of Blended Cement Pastes Using Rotational Viscometer and Dynamic Shear Rheometer

Directory of Open Access Journals (Sweden)

Yoo Jae Kim

2018-01-01

Full Text Available To successfully process concrete, it is necessary to predict and control its flow behavior. However, the workability of concrete is not completely measured or specified by current standard tests. Furthermore, it is only with a clear picture of cement hydration and setting that full prediction and control of concrete performance can be generalized. In order to investigate the rheological properties of blended cement pastes, a rotational viscometer (RV was used to determine the flow characteristics of ordinary and blended pastes to provide assurance that it can be pumped and handled. Additionally, a dynamic shear rheometer (DSR was used to characterize both the viscous and elastic components of pastes. Ordinary Portland cement paste and blended pastes (slag, fly ash, and silica fume were investigated in this study. The stress and strain of the blended specimens were measured by the DSR, which characterizes both viscous and elastic behaviors by measuring the complex shear modulus (the ratio of total shear stress to total shear strain and phase angle (an indicator of the relative amounts of recoverable and nonrecoverable deformation of materials. Cement pastes generally exhibit different rheological behaviors with respect to age, mineral admixture type, and cement replacement level.

Crushed tablets: does the administration of food vehicles and thickened fluids to aid medication swallowing alter drug release?

Science.gov (United States)

Manrique, Yady J; Lee, Danielle J; Islam, Faiza; Nissen, Lisa M; Cichero, Julie A Y; Stokes, Jason R; Steadman, Kathryn J

2014-01-01

To evaluate the influence of co-administered vehicles on in vitro dissolution in simulated gastric fluid of crushed immediate release tablets as an indicator for potential drug bioavailability compromise. Release and dissolution of crushed amlodipine, atenolol, carbamazepine and warfarin tablets were tested with six foods and drinks that are frequently used in the clinical setting as mixers for crushed medications (water, orange juice, honey, yoghurt, strawberry jam and water thickened with Easythick powder) in comparison to whole tablets. Five commercial thickening agents (Easythick Advanced, Janbak F, Karicare, Nutilis, Viscaid) at three thickness levels were tested for their effect on the dissolution of crushed atenolol tablets. Atenolol dissolution was unaffected by mixing crushed tablets with thin fluids or food mixers in comparison to whole tablets or crushed tablets in water, but amlodipine was delayed by mixing with jam. Mixing crushed warfarin and carbamazepine tablets with honey, jam or yoghurt caused them to resemble the slow dissolution of whole tablets rather than the faster dissolution of crushed tablets in water or orange juice. Crushing and mixing any of the four medications with thickened water caused a significant delay in dissolution. When tested with atenolol, all types of thickening agents at the greatest thickness significantly restricted dissolution, and products that are primarily based on xanthan gum also delayed dissolution at the intermediate thickness level. Dissolution testing, while simplistic, is a widely used and accepted method for comparing drug release from different formulations as an indicator for in vivo bioavailability. Thickened fluids have the potential to retard drug dissolution when used at the thickest levels. These findings highlight potential clinical implications of the addition of these agents to medications for the purpose of dose delivery and indicate that further investigation of thickened fluids and their

Thickened water-based hydraulic fluid with reduced dependence of viscosity on temperature

Energy Technology Data Exchange (ETDEWEB)

Deck, C. F.

1985-01-01

Improved hydraulic fluids or metalworking lubricants, utilizing mixtures of water, metal lubricants, metal corrosion inhibitors, and an associative polyether thickener, have reduced dependence of the viscosity on temperature achieved by the incorporation therein of an ethoxylated polyether surfactant.

Experimental study of shear rate dependence in perpetually sheared granular matter

Directory of Open Access Journals (Sweden)

Liu Sophie Yang

2017-01-01

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

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

KAUST Repository

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

2016-01-01

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

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

KAUST Repository

Snijkers, F.

2016-03-31

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

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

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Pedro Henrique Santos

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

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

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Wada Kentaro

2018-01-01

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

Nonlinear oscillatory rheology and structure of wormlike micellar solutions and colloidal suspensions

Science.gov (United States)

Gurnon, Amanda Kate

The complex, nonlinear flow behavior of soft materials transcends industrial applications, smart material design and non-equilibrium thermodynamics. A long-standing, fundamental challenge in soft-matter science is establishing a quantitative connection between the deformation field, local microstructure and macroscopic dynamic flow properties i.e., the rheology. Soft materials are widely used in consumer products and industrial processes including energy recovery, surfactants for personal healthcare (e.g. soap and shampoo), coatings, plastics, drug delivery, medical devices and therapeutics. Oftentimes, these materials are processed by, used during, or exposed to non-equilibrium conditions for which the transient response of the complex fluid is critical. As such, designing new dynamic experiments is imperative to testing these materials and further developing micromechanical models to predict their transient response. Two of the most common classes of these soft materials stand as the focus of the present research; they are: solutions of polymer-like micelles (PLM or also known as wormlike micelles, WLM) and concentrated colloidal suspensions. In addition to their varied applications these two different classes of soft materials are also governed by different physics. In contrast, to the shear thinning behavior of the WLMs at high shear rates, the near hard-sphere colloidal suspensions are known to display increases, sometimes quite substantial, in viscosity (known as shear thickening). The stress response of these complex fluids derive from the shear-induced microstructure, thus measurements of the microstructure under flow are critical for understanding the mechanisms underlying the complex, nonlinear rheology of these complex fluids. A popular micromechanical model is reframed from its original derivation for predicting steady shear rheology of polymers and WLMs to be applicable to weakly nonlinear oscillatory shear flow. The validity, utility and limits of

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

CERN Document Server

Krüger, Timm

2012-01-01

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

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

International Nuclear Information System (INIS)

Rigos, A.A.; Wilemski, G.

1992-01-01

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

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

Science.gov (United States)

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

2018-02-01

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

Integration of thickener underflow into thermal dryer circuit. Final report

Energy Technology Data Exchange (ETDEWEB)

McClaine, A.W.; Breault, R.W.

1998-12-31

A large number of coal preparation plants in the United States are troubled with coal fines and associated plant operation problems. As part of their process, these plants use thermal dryers for producing product coal, cyclones for first-stage recovery of coal fines, and wet scrubbers for the second-stage removal of coal fines carry-over from the dryer exhaust gas. The first challenge for these plants is to recover the clean ultra-fine coal captured in the scrubbers rather than to dispose of it in settling ponds. The second challenge is to mitigate the over-dry fine coal dusting problems in the dryer product. Prior to the completion of this program, the difficulties of the first challenge involving the recovery and use of fine clean coal from the thermal dryer scrubber effluent had not been solved. The second challenge, controlling fine coal dusting, was previously met by applying a solution of surfactants and process water to the over-dry coal fraction. As a result of the demonstration provided by the performance of this program, the implementation of a simple process improvement, involving the use of a thickener in combination with a belt press, simultaneously solved both challenges: the de-dusting and the dryer scrubber effluent recovery issues. The objective of this project was to: (1) Use a clean coal thickener with a squeeze belt press to recover the ultra-fine coal in dryer scrubber effluent; (2) Demonstrate that the coal-water mixture (CWM) produced from scrubber sludge of a thermal dryer can be used as a dust suppressant. The thickener/belt press system has increased the production of JWRI Mine Number 4 by approximately 0.7%. This production increase was accomplished by recovering and re-using 3 metric tons/hr (3.3 tons/hr) of coal fines that were previously sent to holding ponds, returning this as a 50% CWM to de-dust the 430 metric tons/hr (470 tons/hr) of existing dryer production.

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

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Sergio Carmona Malatesta

2009-01-01

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

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

Science.gov (United States)

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

2017-10-01

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

Thickened boundary layer theory for air film drag reduction on a van body surface

Science.gov (United States)

Xie, Xiaopeng; Cao, Lifeng; Huang, Heng

2018-05-01

To elucidate drag reduction mechanism on a van body surface under air film condition, a thickened boundary layer theory was proposed and a frictional resistance calculation model of the van body surface was established. The frictional resistance on the van body surface was calculated with different parameters of air film thickness. In addition, the frictional resistance of the van body surface under the air film condition was analyzed by computational fluid dynamics (CFD) simulation and different air film states that influenced the friction resistance on the van body surface were discussed. As supported by the CFD simulation results, the thickened boundary layer theory may provide reference for practical application of air film drag reduction on a van body surface.

Research Status on Reinforcement Connection Form of Precast Concrete Shear Wall Structure

Science.gov (United States)

Zhang, Zhuangnan; Zhang, Yan

2018-03-01

With the rapid development of Chinese economy and the speeding up the process of urbanization, housing industrialization has been paid more and more attention. And the fabricated structure has been widely used in China. The key of precast concrete shear wall structure is the connection of precast components. The reinforcement connection can directly affect the entirety performance and seismic behavior of the structure. Different reinforcement connections have a great impact on the overall behavior of the structure. By studying the characteristics of the reinforcement connection forms used in the vertical connection and horizontal connection of precast concrete shear wall, it can provide reference for the research and development of the reinforcement connection forms in the future.

Diffuse interlobular septal thickening in a coal miner

Energy Technology Data Exchange (ETDEWEB)

Thrumurthy, S.G.; Kearney, S.; Sissons, M.; Haider, Y. [Lancashire Teaching Hospital for NHS Funding Trust, Chorley (United Kingdom)

2010-01-15

Diffuse interlobular septal thickening (DIST) is an abnormality seen on high-resolution CT (HRCT) scanning of the thorax. While DIST may be present to variable extents in a number of lung conditions, it is uncommon as a predominant finding except in a few entities. This report features an ex-coal miner, thought to have coal workers' pneumoconiosis (CWP), in whom the HRCT scan showed no evidence of CWP and instead showed DIST. The patient's condition progressed incessantly towards death from severe secondary pulmonary hypertension. The case links fatal pulmonary hypertension to DIST, a pattern not previously described in coal workers.

The unexpected stability of multiwall nanotubes under high pressure and shear deformation

International Nuclear Information System (INIS)

Pashkin, E. Y.; Pankov, A. M.; Kulnitskiy, B. A.; Mordkovich, V. Z.; Perezhogin, I. A.; Karaeva, A. R.; Popov, M. Y.; Sorokin, P. B.; Blank, V. D.

2016-01-01

The behavior of multiwall carbon nanotubes under a high pressure (up to 55 GPa) combined with shear deformation was studied by experimental and theoretical methods. The unexpectedly high stability of the nanotubes' structure under high stresses was observed. After the pressure was released, we observed that the nanotubes had restored their shapes. Atomistic simulations show that the hydrostatic and shear stresses affect the nanotubes' structure in a different way. It was found that the shear stress load in the multiwall nanotubes' outer walls can induce their connection and formation of an amorphized sp"3-hybridized region but internal core keeps the tubular structure.

The unexpected stability of multiwall nanotubes under high pressure and shear deformation

Energy Technology Data Exchange (ETDEWEB)

Pashkin, E. Y.; Pankov, A. M.; Kulnitskiy, B. A.; Mordkovich, V. Z. [Technological Institute for Superhard and Novel Carbon Materials, 7a Centralnaya Street, Troitsk, Moscow 142190 (Russian Federation); Moscow Institute of Physics and Technology, 9 Institutsky Lane, Dolgoprudny 141700 (Russian Federation); Perezhogin, I. A. [Technological Institute for Superhard and Novel Carbon Materials, 7a Centralnaya Street, Troitsk, Moscow 142190 (Russian Federation); Lomonosov Moscow State University, Leninskie Gory, Moscow 119991 (Russian Federation); Karaeva, A. R. [Technological Institute for Superhard and Novel Carbon Materials, 7a Centralnaya Street, Troitsk, Moscow 142190 (Russian Federation); Popov, M. Y.; Sorokin, P. B.; Blank, V. D. [Technological Institute for Superhard and Novel Carbon Materials, 7a Centralnaya Street, Troitsk, Moscow 142190 (Russian Federation); Moscow Institute of Physics and Technology, 9 Institutsky Lane, Dolgoprudny 141700 (Russian Federation); National University of Science and Technology MISiS, 4 Leninskiy Prospekt, Moscow 119049 (Russian Federation)

2016-08-22

The behavior of multiwall carbon nanotubes under a high pressure (up to 55 GPa) combined with shear deformation was studied by experimental and theoretical methods. The unexpectedly high stability of the nanotubes' structure under high stresses was observed. After the pressure was released, we observed that the nanotubes had restored their shapes. Atomistic simulations show that the hydrostatic and shear stresses affect the nanotubes' structure in a different way. It was found that the shear stress load in the multiwall nanotubes' outer walls can induce their connection and formation of an amorphized sp{sup 3}-hybridized region but internal core keeps the tubular structure.

Simulation of reinforced concrete short shear wall subjected to cyclic loading

International Nuclear Information System (INIS)

Parulekar, Y.M.; Reddy, G.R.; Vaze, K.K.; Pegon, P.; Wenzel, H.

2014-01-01

Highlights: • Prediction of the capacity of squat shear wall using tests and analysis. • Modification of model of concrete in the softening part. • Pushover analysis using softened truss theory and FE analysis is performed. • Modified concrete model gives reasonable accurate peak load and displacement. • The ductility, ultimate load and also crack pattern can be accurately predicted. - Abstract: This paper addresses the strength and deformation capacity of stiff squat shear wall subjected to monotonic and pseudo-static cyclic loading using experiments and analysis. Reinforced concrete squat shear walls offer great potential for lateral load resistance and the failure mode of these shear walls is brittle shear mode. Shear strength of these shear walls depend strongly on softening of concrete struts in principal compression direction due to principal tension in other direction. In this work simulation of the behavior of a squat shear wall is accurately predicted by finite element modeling by incorporating the appropriate softening model in the program. Modification of model of concrete in the softening part is suggested and reduction factor given by Vecchio et al. (1994) is used in the model. The accuracy of modeling is confirmed by comparing the simulated response with experimental one. The crack pattern generated from the 3D model is compared with that obtained from experiments. The load deflection for monotonic loads is also obtained using softened truss theory and compared with experimental one

Regional wall thickening in gated myocardial perfusion SPECT in a Japanese population: effect of sex, radiotracer, rotation angles and frame rates

Energy Technology Data Exchange (ETDEWEB)

Akhter, Nasima; Nakajima, Kenichi; Okuda, Koichi; Matsuo, Shinro; Yoneyama, Tatsuya; Taki, Junichi; Kinuya, Seigo [Kanazawa University Hospital, Department of Nuclear Medicine, Kanazawa, Ishikawa (Japan)

2008-09-15

Gated single-photon emission computed tomography (SPECT) imaging of myocardium by {sup 99m}Tc and {sup 201}Tl is used extensively to measure quantitative cardiac functional parameters. However, factors affecting normal values for myocardial functional parameters and population-specific standards have not yet been established. The aim of the study was to determine the effect of sex, radiotracer, rotation angles and frame rates on resting myocardial wall thickening (WT) and to develop a Japanese standard of normal values for WT. Data from a total of 202 patients with low possibility of having cardiac problems were collected from nine hospitals throughout Japan. Patients were divided into five groups according to study protocol, and WT was evaluated according to the 17-segment and four-region (basal, mid and apical regions and the apex) polar map distribution. WT was generally higher in women than in men irrespective of the use of radiotracers, rotation angles or frame rates, and the difference was highly significant in the mid and apical regions. In any protocol used, resting myocardial thickening in the apex was higher than in the mid and apical regions, and thickening was lowest in the basal region, suggesting heterogeneous regional myocardial thickening (%) in normal subjects. Different rotation angles showed no significant change on WT, but different frame rates and tracers showed significant WT change in both sexes. Percent thickening of the myocardium was significantly higher in imaging by {sup 99m}Tc-labelled tracers than in {sup 201}Tl. Sex, radiotracers and frame rates had a significant effect on myocardial thickening, and the importance of population-specific standards should be emphasized. A normal database can serve as a standard for gated SPECT evaluation of myocardial thickening in a Japanese population and might be applicable to Asian populations having a similar physique. (orig.)

Stiffness of individual quadriceps muscle assessed using ultrasound shear wave elastography during passive stretching

Directory of Open Access Journals (Sweden)

Jingfei Xu

2018-04-01

Full Text Available Background: Until recently it has not been possible to isolate the mechanical behavior of individual muscles during passive stretching. Muscle shear modulus (an index of muscle stiffness measured using ultrasound shear wave elastography can be used to estimate changes in stiffness of an individual muscle. The aims of the present study were (1 to determine the shear modulus–knee angle relationship and the slack angle of the vastus medialis oblique (VMO, rectus femoris (RF, and vastus lateralis (VL muscles; (2 to determine whether this differs between the muscles. Methods: Nine male rowers took part in the study. The shear modulus of VMO, RF, and VL muscles was measured while the quadriceps was passively stretched at 3°/s. The relationship between the muscle shear modulus and knee angle was plotted as shear modulus–knee angle curve through which the slack angle of each muscle was determined. Results: The shear modulus of RF was higher than that of VMO and VL when the muscles were stretched over 54° (all p  0.05. The slack angle was similar among the muscles: 41.3° ± 10.6°, 44.3° ± 9.1°, and 44.3° ± 5.6° of knee flexion for VMO, RF, and VL, respectively (p = 0.626. Conclusion: This is the first study to experimentally determine the muscle mechanical behavior of individual heads of the quadriceps during passive stretching. Different pattern of passive tension was observed between mono- and bi-articular muscles. Further research is needed to determine whether changes in muscle stiffness are muscle-specific in pathological conditions or after interventions such as stretching protocols. Keywords: Muscle tension, Optimal length, Shear modulus, Slack angle, Stretch, Ultrasonography, Vastus lateralis, Vastus medialis

Hagfish slime and mucin flow properties and their implications for defense

Science.gov (United States)

Böni, Lukas; Fischer, Peter; Böcker, Lukas; Kuster, Simon; Rühs, Patrick A.

2016-07-01

When hagfish (Myxinidae) are attacked by predators, they form a dilute, elastic, and cohesive defensive slime made of mucins and protein threads. In this study we propose a link between flow behavior and defense mechanism of hagfish slime. Oscillatory rheological measurements reveal that hagfish slime forms viscoelastic networks at low concentrations. Mucins alone did not contribute viscoelasticity, however in shear flow, viscosity was observed. The unidirectional flow, experienced by hagfish slime during suction feeding by predators, was mimicked with extensional rheology. Elongational stresses were found to increase mucin viscosity. The resulting higher resistance to flow could support clogging of the attacker’s gills. Shear flow in contrast decreases the slime viscosity by mucin aggregation and leads to a collapse of the slime network. Hagfish may benefit from this collapse when trapped in their own slime and facing suffocation by tying a sliding knot with their body to shear off the slime. This removal could be facilitated by the apparent shear thinning behavior of the slime. Therefore hagfish slime, thickening in elongation and thinning in shear, presents a sophisticated natural high water content gel with flow properties that may be beneficial for both, defense and escape.

Effects of opening in shear walls of 30- storey building

Directory of Open Access Journals (Sweden)

Ruchi Sharma

2015-03-01

Full Text Available Tall towers and multi-storey buildings have fascinated mankind from the beginning of civilization, their construction being initially for defense and subsequently for ecclesiastical purposes. These tall buildings because of its height, is affected by lateral forces due to wind or earthquake actions tends to snap the building in shear and push it over in bending. In general, the rigidity (i.e. Resistance to lateral deflection and stability (i.e. Resistance to overturning moments requirement become more important. Shear walls (Structural walls contribute significant lateral stiffness, strength, and overall ductility and energy dissipation capacity. In many structural walls a regular pattern of openings has to be provided due to various functional requirements such as to accommodate doors, windows and service ducts. Such type of openings reduces the stiffness of the shear wall to some extent depending on the shape and size of the opening. In the present parametric study, efforts are made to investigate and critically assess the effects of various size of openings in shear walls on the responses and behaviors of multi-storey buildings. The 30 storey Prototype buildings with different types of openings in shear wall with and without incorporating the volume of shear wall reduced in the boundary elements are analyzed using software E-TABS using Response spectrum method (1893(Part-1-2002 and Time history method.

Analytical Study on the Beyond Design Seismic Capacity of Reinforced Concrete Shear Walls

Energy Technology Data Exchange (ETDEWEB)

Nugroho, Tino Sawaldi Adi [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Chi, Ho-Seok [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

2015-10-15

The OECD-NEA has organized an international benchmarking program to better understand this critical issue. The benchmark program provides test specimen geometry, test setup, material properties, loading conditions, recorded measures, and observations of the test specimens. The main objective of this research is to assess the beyond design seismic capacity of the reinforced concrete shear walls tested at the European Laboratory for Structural Assessment between 1997 and 1998 through participation in the OECD-NEA benchmark program. In this study, assessing the beyond design seismic capacity of reinforced concrete shear walls is performed analytically by comparing numerical results with experimental results. The seismic shear capacity of the reinforced concrete shear wall was predicted reasonably well using ABAQUS program. However, the proper calibration of the concrete material model was necessary for better prediction of the behavior of the reinforced concrete shear walls since the response was influenced significantly by the material constitutive model.

Dependence of Shear and Concentration on Fouling in a Membrane Bioreactor with Rotating Membrane Discs

DEFF Research Database (Denmark)

Jørgensen, Mads Koustrup; Pedersen, Malene Thostrup; Christensen, Morten Lykkegaard

2014-01-01

Rotating ceramic membrane discs were fouled with lab-scale membrane bioreactors (MBR) sludge. Sludge filtrations were performed at varying rotation speeds and in different concentric rings of the membranes on different sludge concentrations. Data showed that the back transport expressed by limiting...... flux increased with rotation speed and distance from membrane center as an effect of shear. Further, the limiting flux decreased with increasing sludge concentration. A model was developed to link the sludge concentration and shear stress to the limiting flux. The model was able to simulate the effect...... of shear stress and sludge concentration on the limiting flux. The model was developed by calculating the shear rate at laminar flow regime at different rotation speeds and radii on the membrane. Furthermore, through the shear rate and shear stress, the non-Newtonian behavior of MBR sludge was addressed...

A Novel Geometry for Shear Test Using Axial Tensile Setup

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Sibo Yuan

2018-05-01

Full Text Available This paper studies a novel geometry for the in-plane shear test performed with an axial electromechanical testing machine. In order to investigate the influence of the triaxiality rate on the mechanical behavior, different tests will be performed on the studied material: simple tensile tests, large tensile tests and shear tests. For the whole campaign, a common equipment should be employed to minimize the impact of the testing device. As a consequence, for the shear tests, the geometry of the specimen must be carefully designed in order to adapt the force value and make it comparable to the one obtained for the tensile tests. Like most of the existing shear-included tensile test specimens, the axial loading is converted to shear loading at a particular region through the effect of geometry. A symmetric shape is generally preferred, since it can restrict the in-plane rotation of the shear section, keep shear increasing in a more monotonic path and double the force level thanks to the two shear zones. Due to the specific experimental conditions, such as dimensions of the furnace and the clamping system, the position of the extensometer or the restriction of sheet thickness (related to the further studies of size effect at mesoscale and hot temperature, several geometries were brought up and evaluated in an iterative procedure via finite element simulations. Both the numerical and experimental results reveal that the final geometry ensures some advantages. For instance, a relatively low triaxiality in the shear zone, limited in-plane rotation and no necking are observed. Moreover, it also prevents any out-of-plane displacement of the specimen which seems to be highly sensitive to the geometry, and presents a very limited influence of the material and the thickness.

Comparação entre uma fórmula infantil pré-espessada e fórmula de espessamento caseiro no tratamento do refluxo gastroesofágico Comparison between pre-thickened and home-thickened formulas in gastroesophageal reflux treatment

Directory of Open Access Journals (Sweden)

Francisco J. Penna

2003-02-01

Full Text Available Objetivo: o presente estudo foi realizado com o objetivo de comparar a eficácia de uma fórmula infantil pré-espessada (Nan AR com fórmula convencional, de espessamento caseiro, com amido de milho, na redução de episódios de regurgitações e vômitos de lactentes com refluxo gastroesofágico (RGE. Métodos: foram estudadas 100 crianças, menores de 12 meses de idade, que não faziam uso de leite materno exclusivo. Por sorteio, 48 receberam fórmula convencional, e 52 receberam fórmula infantil pré-espessada (Nan AR, com comparação dos resultados clínicos após 3 meses. Resultados: não houve diferença estatisticamente significativa na melhora ou cura dos sintomas entre os dois grupos, tendo sido ambos os tratamentos eficazes. Conclusões: o espessamento dietético, seja com fórmulas infantis especiais, seja com medidas caseiras, tem eficácia semelhante no tratamento do refluxo gastroesofágico do lactente.Objective: the purpose of this study was to compare the effectiveness of a pre-thickened infant formula (Nan AR with a conventional homemade formula in the reduction of regurgitation and vomiting in infants with gastroesophageal reflux. Methods: a hundred children, under 12 months, not exclusively breast feeding, were select for the study. Forty-eight were treated with conventional formula with starch and 52 with pre-thickened infant formula. Results: there was no statistically significant difference between the two groups in the improvement or cure of symptoms, each treatment having been effective. Conclusions: thickened formulas, pre-thickened or home-thickened, have shown the same efficacy in the management of gastroesophageal reflux in children.

Shear-induced particle migration in suspensions of rods

Energy Technology Data Exchange (ETDEWEB)

Mondy, L.A. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)); Brenner, H. (Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)); Altobelli, S.A. (The Lovelace Institutes, 2425 Ridgecrest Drive, S. E., Albuquerque, New Mexico 87108 (United States)); Abbott, J.R.; Graham, A.L. (Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States))

1994-03-01

Shear-induced migration of particles occurs in suspensions of neutrally buoyant spheres in Newtonian fluids undergoing shear in the annular space between two rotating, coaxial cylinders (a wide-gap Couette), even when the suspension is in creeping flow. Previous studies have shown that the rate of migration of spherical particles from the high-shear-rate region near the inner (rotating) cylinder to the low-shear-rate region near the outer (stationary) cylinder increases rapidly with increasing sphere size. To determine the effect of particle shape, the migration of rods suspended in Newtonian fluids was recently measured. The behavior of several suspensions was studied. Each suspension contained well-characterized, uniform rods with aspect ratios ranging from 2 to 18 at either 0.30 or 0.40 volume fraction. At the same volume fraction of solids, the steady-state, radial concentration profiles for rods were independent of aspect ratio and were indistinguishable from those obtained from suspended spheres. Only minor differences near the walls (attributable to the finite size of the rods relative to the curvature of the walls) appeared to differentiate the profiles. Data taken during the transition from a well-mixed suspension to the final steady state show that the rate of migration increased as the volume of the individual rods increased.

Shear transfer in concrete reinforced with carbon fibers

Science.gov (United States)

El-Mokadem, Khaled Mounir

2001-10-01

Scope and method of study. The research started with preliminary tests and studies on the behavior and effect of carbon fibers in different water solutions and mortar/concrete mixes. The research work investigated the use of CF in the production of concrete pipes and prestressed concrete double-tee sections. The research then focused on studying the effect of using carbon fibers on the direct shear transfer of sand-lightweight reinforced concrete push-off specimens. Findings and conclusions. In general, adding carbon fibers to concrete improved its tensile characteristics but decreased its compressive strength. The decrease in compressive strength was due to the decrease in concrete density as fibers act as three-dimensional mesh that entrapped air. The decrease in compressive strength was also due to the increase in the total surface area of non-cementitious material in the concrete. Sand-lightweight reinforced concrete push-off specimens with carbon fibers had lower shear carrying capacity than those without carbon fibers for the same cement content in the concrete. Current building codes and specifications estimate the shear strength of concrete as a ratio of the compressive strength. If applying the same principals then the ratio of shear strength to compressive strength for concrete reinforced with carbon fibers is higher than that for concrete without carbon fibers.

Characteristic thickened cell walls of the bracts of the 'eternal flower' Helichrysum bracteatum.

Science.gov (United States)

Nishikawa, Kuniko; Ito, Hiroaki; Awano, Tatsuya; Hosokawa, Munetaka; Yazawa, Susumu

2008-07-01

Helichrysum bracteatum is called an 'eternal flower' and has large, coloured, scarious bracts. These maintain their aesthetic value without wilting or discoloration for many years. There have been no research studies of cell death or cell morphology of the scarious bract, and hence the aim of this work was to elucidate these characteristics for the bract of H. bracteatum. DAPI (4'6-diamidino-2-phenylindol dihydrochloride) staining and fluorescence microscopy were used for observation of cell nuclei. Light microscopy (LM), transmission electron microscopy (TEM) and polarized light microscopy were used for observation of cells, including cell wall morphology. Cell death occurred at the bract tip during the early stage of flower development. The cell wall was the most prominent characteristic of H. bracteatum bract cells. Characteristic thickened secondary cell walls on the inside of the primary cell walls were observed in both epidermal and inner cells. In addition, the walls of all cells exhibited birefringence. Characteristic thickened secondary cell walls have orientated cellulose microfibrils as well as general secondary cell walls of the tracheary elements. For comparison, these characters were not observed in the petal and bract tissues of Chrysanthemum morifolium. Bracts at anthesis are composed of dead cells. Helichrysum bracteatum bracts have characteristic thickened secondary cell walls that have not been observed in the parenchyma of any other flowers or leaves. The cells of the H. bracteatum bract differ from other tissues with secondary cell walls, suggesting that they may be a new cell type.

Laboratory investigation of nonlinear flow characteristics in rough fractures during shear process

Science.gov (United States)

Rong, Guan; Yang, Jie; Cheng, Long; Zhou, Chuangbing

2016-10-01

To understand the influence of shear behavior on the transporting properties of fluid through a single fracture, splitting fractures were made in the laboratory and shear flow tests were carried out under constant normal load conditions. The applied normal stress is in the range of 0.5-3.0 MPa. Before the physical test, the fracture's morphology is measured for identification of the roughness. At each shear step, we performed 5-8 high precise hydraulic tests with different hydraulic gradient. The relationship between pressure gradient and volume flow rate demonstrates to be nonlinear and fits very well with Forchheimer's and Izbash's laws. The linear and nonlinear coefficients in Forchheimer's law are quite sensitive to shear deformation (closure or dilation), experienced 1-2 and 1-3 orders of magnitude reduction during shear, respectively. An empirical equation is proposed to quantify the relationship between linear coefficient and nonlinear coefficient based on the experimental observations. The two coefficients in Izbash's law are quantified. The m value is in the range between 1.06 and 1.41 and the λ value experiences a reduction of 1-2 orders of magnitude during shear. In addition, the studied critical Reynolds number exhibits a decreasing and increasing variation corresponding to shear contraction and shear dilation of rock fracture. For all the cases in this study, the critical Reynolds number ranges between 1.5 and 13.0.

Structures and shear response of lipid monolayers

International Nuclear Information System (INIS)

Dutta, P.; Ketterson, J.B.

1993-02-01

This report discusses our work during the last 3 years using x-ray diffraction and shear measurements to study lipid monolayers (membranes). The report is divided into: (1) structure: phase diagram of saturated fatty acid Langmuir monolayers, effect of head group interactions, studies of transferred monolayers (LB films); (2) mechanical properties: fiber=optic capillary wave probe and centrosymmetric trough, mechanical behavior of heneicosanoic acid monolayer phases

2D micromechanical analysis of SiC/Al metal matrix composites under tensile, shear and combined tensile/shear loads

DEFF Research Database (Denmark)

Qing, Hai

2013-01-01

The influence of interface strength and loading conditions on the mechanical behavior of the metal-matrix composites is investigated in this paper. A program is developed to generate automatically 2D micromechanical Finite element (FE) models including interface, in which both the locations...... and dimensions of Silicon-Carbide (SiC) particles are randomly distributed. Finite element simulations of the deformation and damage evolution of SiC particle reinforced Aluminum (Al) alloy composite are carried out for different microstructures and interphase strengths under tensile, shear and combined tensile....../shear loads. 2D cohesive element is applied to describe the fracture and failure process of interphase, while the damage models based on maximum principal stress criterion and the stress triaxial indicator are developed within Abaqus/Standard Subroutine USDFLD to simulate the failure process of SiC particles...

Optimal Water Recovery with Emphasis on Flocculant Consumption Rate in the Thickener

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Marzieh Hosseininasab

2017-11-01

Full Text Available Water plays a vital role in mineral processing as evidenced by the approximately 2 to 3 tons of water used for the treatment of one ton of ore. A major portion of this water may be recovered in thickeners. This study aimed to control the wet tailings output of the Hematite Gol-e-Gohar plant by changing  flocculant dosage and type and solid percentage in the feed in order to enhance effluent clarity and reduce water consumption. Materials and A series of settling experiments were performed using different combinations of the flocculants (A25, A26 Yazd, A26 Esfahan, A27, and A28, flocculant doses (20, 25, 30, 35, and 40 gr/ton, and solid loads in the feed (5, 7, 9, 10, and 11% to the thickener. The L25 Taguchi design method was chosen to handle the five different levels of the three factors. Adopting a 95% confidence interval, the results of analysis of variance (ANOVA revealed that flocculant consumption rate had a high effect on settling velocity (p = 0.006 while flocculant type and solid percentage in the feed had no significant effects. Moreover, it was found that A26 (Akhtar-chemistry Company, Yazd used at a rate of 40 g/ton improved the settling performance to yield an optimal water clarity. Using the findings of this study in process planning at the plant led to a considerable reduction (from the original 0.86 to 0.49 m3 in average water consumption per ton of input material so that the solid content of the thickener underflow rose from 7 to 45%.

Hemolysis in a laminar flow-through Couette shearing device: an experimental study.

Science.gov (United States)

Boehning, Fiete; Mejia, Tzahiry; Schmitz-Rode, Thomas; Steinseifer, Ulrich

2014-09-01

Reducing hemolysis has been one of the major goals of rotary blood pump development and in the investigational phase, the capability of hemolysis estimation for areas of elevated shear stresses is valuable. The degree of hemolysis is determined by the amplitude of shear stress and the exposure time, but to date, the exact hemolytic behavior at elevated shear stresses and potential thresholds for subcritical shear exposure remain vague. This study provides experimental hemolysis data for a set of shear stresses and exposure times to allow better estimations of hemolysis for blood exposed to elevated shearing. Heparinized porcine blood with a hematocrit of 40% was mechanically damaged in a flow-through laminar Couette shear flow at a temperature of 23°C. Four levels of shear stress, 24, 592, 702, and 842 Pa, were replicated at two exposure times, 54 and 873 ms. For the calculation of the shear stresses, an apparent viscosity of 5 mPas was used, which was verified in an additional measurement of the blood viscosity. The hemolysis measurements were repeated four times, whereby all conditions were measured once within the same day and with blood from the same source. Samples were taken at the inlet and outlet of the shear region and an increase in plasma-free hemoglobin was measured. An index of hemolysis (IH) was thereby calculated giving the ratio of free to total hemoglobin. The results are compared with data from previously published studies using a similar shearing device. Hemolysis was found to increase exponentially with shear stress, but high standard deviations existed at measurements with elevated IH. At short exposure times, the IH remained low at under 0.5% for all shear stress levels. For high exposure times, the IH increased from 0.84% at 592 Pa up to 3.57% at the highest shear stress level. Hemolysis was significant for shear stresses above ∼600 Pa at the high exposure time of 873 ms. Copyright © 2014 International Center for Artificial

Bulk and shear viscosities of hot and dense hadron gas

International Nuclear Information System (INIS)

Kadam, Guru Prakash; Mishra, Hiranmaya

2015-01-01

We estimate the bulk and the shear viscosity at finite temperature and baryon densities of hadronic matter within a hadron resonance gas model which includes a Hagedorn spectrum. The parameters of the Hagedorn spectrum are adjusted to fit recent lattice QCD simulations at finite chemical potential. For the estimation of the bulk viscosity we use low energy theorems of QCD for the energy momentum tensor correlators. For the shear viscosity coefficient, we estimate the same using molecular kinetic theory to relate the shear viscosity coefficient to average momentum of the hadrons in the hot and dense hadron gas. The bulk viscosity to entropy ratio increases with chemical potential and is related to the reduction of velocity of sound at nonzero chemical potential. The shear viscosity to entropy ratio on the other hand, shows a nontrivial behavior with the ratio decreasing with chemical potential for small temperatures but increasing with chemical potential at high temperatures and is related to decrease of entropy density with chemical potential at high temperature due to finite volume of the hadrons

Effects of different aging statuses and strain rate on the adiabatic shear susceptibility of 2195 aluminum–lithium alloy

International Nuclear Information System (INIS)

Yang, Y.; Tan, G.Y.; Chen, P.X.; Zhang, Q.M.

2012-01-01

The adiabatic shear susceptibility of 2195 aluminum–lithium alloy was investigated by means of split Hopkinson pressure bar. The stress collapse in true stress–true strain curves and true stress–time curves was observed. The adiabatic shear susceptibility of different aging statuses and strain rate were discussed by means of metallography observation. The critical strain, stress collapse time and formation energy of adiabatic shear bands were compared. The results show that different aging statuses and strain rate have significant influences on adiabatic shear behaviors of 2195 aluminum–lithium alloy. The peak-aged specimen has the highest adiabatic shearing susceptibility, while the under-aged specimen has the least adiabatic shear susceptibility. The susceptibility of adiabatic shearing increases with the increases of strain rate.

Effects of different aging statuses and strain rate on the adiabatic shear susceptibility of 2195 aluminum-lithium alloy

Energy Technology Data Exchange (ETDEWEB)

Yang, Y. [School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan (China); State Key Laboratory of Explosion Science and Technology, Beijing 100081 (China); Tan, G.Y., E-mail: yangyanggroup@163.com [School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan (China); Chen, P.X. [School of Materials Science and Engineering, Central South University, Changsha 410083, Hunan (China); Zhang, Q.M. [State Key Laboratory of Explosion Science and Technology, Beijing 100081 (China)

2012-06-01

The adiabatic shear susceptibility of 2195 aluminum-lithium alloy was investigated by means of split Hopkinson pressure bar. The stress collapse in true stress-true strain curves and true stress-time curves was observed. The adiabatic shear susceptibility of different aging statuses and strain rate were discussed by means of metallography observation. The critical strain, stress collapse time and formation energy of adiabatic shear bands were compared. The results show that different aging statuses and strain rate have significant influences on adiabatic shear behaviors of 2195 aluminum-lithium alloy. The peak-aged specimen has the highest adiabatic shearing susceptibility, while the under-aged specimen has the least adiabatic shear susceptibility. The susceptibility of adiabatic shearing increases with the increases of strain rate.

Irradiated Effect on Shear-Moment Interaction of Reinforced Concrete Slab

Energy Technology Data Exchange (ETDEWEB)

Kwon, Tae-Hyun; Kim, Jun Yeon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Kim, HyungTae; Park, Kyoungsoo [Yonsei University, Seoul (Korea, Republic of); Kim, Sang-Ho [Hyundai Engineering, Seoul (Korea, Republic of)

2015-10-15

Several deleterious mechanisms include chronic high-temperature exposure, freeze-thaw, and chemical attack and have been reviewed extensively in the literature. On the other hand, the effect of irradiation on RC needs further investigations for the long-term operation of existing NPPs. In this regard, the RC biological shield structure is located in closest proximity to a reactor core and expected to see the highest levels of irradiation over the lifetime. The biological shield structure may undergo a large lateral load from earthquake and become thicker for a suitable shielding. Although the bending strength is easily predictable with the altering steel properties, the more complete behaviors should be studied to see if the promised performance is achievable. Given this, in this study, the shear-moment (VM) interaction of a typical one-way slab representing the biological shield structure is investigated with incremental neutron irradiation. The effect of radiation on the behavior of one-way slab is presented by the shear and moment capacity interaction diagram. The results suggest that the yield strength increase of the longitudinal reinforcement barely affects the shear strength but it increases the bending strength significantly. This may be misleading, however, as the structural capacity to observe the energy from environmental loadings such as earthquake would be actually reducing.

A hidden variable in shear transformation zone volume versus Poisson's ratio relation in metallic glasses

Science.gov (United States)

Kim, S. Y.; Oh, H. S.; Park, E. S.

2017-10-01

Herein, we elucidate a hidden variable in a shear transformation zone (STZ) volume (Ω) versus Poisson's ratio (ν) relation and clarify the correlation between STZ characteristics and the plasticity of metallic glasses (MGs). On the basis of cooperative shear model and atomic stress theories, we carefully formulate Ω as a function of molar volume (Vm) and ν. The twofold trend in Ω and ν is attributed to a relatively large variation of Vm as compared to that of ν as well as an inverse relation between Vm and ν. Indeed, the derived equation reveals that the number of atoms in an STZ instead of Ω is a microstructural characteristic which has a close relationship with plasticity since it reflects the preference of atomistic behaviors between cooperative shearing and the generation of volume strain fluctuation under stress. The results would deepen our understanding of the correlation between microscopic behaviors (STZ activation) and macroscopic properties (plasticity) in MGs and enable a quantitative approach in associating various STZ-related macroscopic behaviors with intrinsic properties of MGs.

Shear strength of non-shear reinforced concrete elements

DEFF Research Database (Denmark)

Hoang, Cao linh

1997-01-01

The paper deals with the shear strength of prestressed hollow-core slabs determined by the theory of plasticity. Two failure mechanisms are considered in order to derive the solutions.In the case of sliding failure in a diagonal crack, the shear strength is determined by means of the crack sliding...

Mesoscale modeling of amorphous metals by shear transformation zone dynamics

International Nuclear Information System (INIS)

Homer, Eric R.; Schuh, Christopher A.

2009-01-01

A new mesoscale modeling technique for the thermo-mechanical behavior of metallic glasses is proposed. The modeling framework considers the shear transformation zone (STZ) as the fundamental unit of deformation, and coarse-grains an amorphous collection of atoms into an ensemble of STZs on a mesh. By employing finite element analysis and a kinetic Monte Carlo algorithm, the modeling technique is capable of simulating glass processing and deformation on time and length scales greater than those usually attainable by atomistic modeling. A thorough explanation of the framework is presented, along with a specific two-dimensional implementation for a model metallic glass. The model is shown to capture the basic behaviors of metallic glasses, including high-temperature homogeneous flow following the expected constitutive law, and low-temperature strain localization into shear bands. Details of the effects of processing and thermal history on the glass structure and properties are also discussed.

An in vitro Evaluation of Shear Bond Strength of Adhesive Precoated Brackets

Directory of Open Access Journals (Sweden)

A S Sibi

2014-01-01

Full Text Available Newer materials have been introduced in the field of orthodontics to improve clinical efficacy as well as to simplify the technique. In an effort to reduce the time and steps to bond orthodontic attachments, adhesive precoated (APC brackets were introduced. In this study, an attempt is made to evaluate the shear bond strength (SBS and debonding behavior of APC brackets compared with uncoated ceramic brackets. A total of 60 human premolar teeth were divided into two groups of 30 each, bonded with APC ceramic brackets and uncoated ceramic brackets. Group I bonded with APC brackets as prescribed by the manufacturers and group II was bonded with conventional bonding using Turbobond. After bonding, sthe samples were kept in distilled water at 37°C for 24 hours and a universal testing mechine was used to apply an occlusal shear force at a speed of 0.5 mm/min. The shear bond strength of the groups was compared using Student t-test and the debonding behavior were compared using Mann-Whitney′s U test. Mean shear bond strength and standard deviation of the groups were group I - 9.09 ± 2.5 MPa and group II - 12.95 ± 2.81 MPa. There were significant differences in bond strength observed between the two groups. The debonding behavior showed an adhesive remnant index score of 0.90 ± 0.08 for group I and 1.10 ± 0.04 for group II, which indicates there is significant difference between each other. When considering the values required for optimum bond strength, APC brackets in this study showed adequate bond strength and could be used for routine clinical use.

Deformation and failure response of 304L stainless steel SMAW joint under dynamic shear loading

International Nuclear Information System (INIS)

Lee, Woei-Shyan; Cheng, J.-I.; Lin, C.-F.

2004-01-01

The dynamic shear deformation behavior and fracture characteristics of 304L stainless steel shielded metal arc welding (SMAW) joint are studied experimentally with regard to the relations between mechanical properties and strain rate. Thin-wall tubular specimens are deformed at room temperature under strain rates in the range of 8 x 10 2 to 2.8 x 10 3 s -1 using a torsional split-Hopkinson bar. The results indicate that the strain rate has a significant influence on the mechanical properties and fracture response of the tested SMAW joints. It is found that the flow stress, total shear strain to failure, work hardening rate and strain rate sensitivity all increase with increasing strain rate, but that the activation volume decreases. The observed dynamic shear deformation behavior is modeled using the Kobayashi-Dodd constitutive law, and it is shown that the predicted results are in good agreement with the experimental data. Fractographic analysis using scanning electron microscopy reveals that the tested specimens all fracture within their fusion zones, and that the primary failure mechanism is one of the extensive localized shearing. The fracture surfaces are characterized by the presence of many dimples. A higher strain rate tends to reduce the size of the dimples and to increase their density. The observed fracture features are closely related to the preceding flow behavior

Direct displacement-based design of special composite RC shear walls with steel boundary elements

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H. Kazemi

2016-06-01

Full Text Available Special composite RC shear wall (CRCSW with steel boundary elements is a kind of lateral force resisting structural system which is used in earthquake-prone regions. Due to their high ductility and energy dissipation, CRCSWs have been widely used in recent years by structural engineers. However, there are few studies in the literature on the seismic design of such walls. Although there are many studies in the literature on the Direct Displacement-Based Design (DDBD of RC structures, however, no study can be found on DDBD of CRCSWs. Therefore, the aim of present study is to evaluate the ability of DDBD method for designing CRCSWs. In this study, four special composite reinforced concrete shear walls with steel boundary elements of 4, 8, 12 and 16 story numbers were designed using the DDBD method for target drift of 2%. The seismic behavior of the four CRCSWs was studied using nonlinear time-history dynamic analyses. Dynamic analyses were performed for the mentioned walls using 7 selected earthquake records. The seismic design parameters considered in this study includes: lateral displacement profile, inelastic dynamic inter-story drift demand, failure pattern and the composite RC shear walls overstrength factor. For each shear wall, the overall overstrength factor was calculated by dividing the ultimate dynamic base shear demand (Vu by the base shear demand (Vd as per the Direct Displacement Based-Design (DDBD method. The results show that the DDBD method can be used to design CRCSWs safely in seismic regions with predicted behavior.

Rheology and characteristics of sulfated polysaccharides from chlorophytan seaweeds Ulva fasciata.

Science.gov (United States)

Shao, Ping; Qin, Minpu; Han, Longfei; Sun, Peilong

2014-11-26

The rheological characteristics of polysaccharides which were extracted and separated from Ulva fasciata (UFP) were investigated in aqueous solutions under conditions of concentration, temperature, solution pH and salt concentrations. It was described by the power-law model with a consistency index (k) and a flow behavior index (n). The rheology results showed UFP exhibited as a shear-thickening fluid and a possible mechanism was proposed to explain this phenomenon that might be the collapse of UFP necklace-type structures. UFP characteristics were evaluated by determining the chemical analysis and zeta potential. The findings indicated UFP may consist of partially ulvan, as the results were in accordance with the ulvan structure. Additionally, a rod-climbing effect and cold-set gelation were observed in the UFP semidilute solution. Therefore, the cold-set gelling properties and unique shear-thickening fluid properties in this work could be valuable for the exploration of U. fasciata as a new source of water-soluble gelling polysaccharides. Copyright © 2014 Elsevier Ltd. All rights reserved.

Continuous shear - a method for studying material elements passing a stationary shear plane

DEFF Research Database (Denmark)

Lindegren, Maria; Wiwe, Birgitte; Wanheim, Tarras

2003-01-01

circumferential groove. Normally shear in metal forming processes is of another nature, namely where the material elements move through a stationary shear zone, often of small width. In this paper a method enabling the simulation of this situation is presented. A tool for continuous shear has beeen manufactured...... and tested with AlMgSil and copper. The sheared material has thereafter been tested n plane strain compression with different orientation concerning the angle between the shear plane and the compression direction....

Intron-mediated alternative splicing of WOOD-ASSOCIATED NAC TRANSCRIPTION FACTOR1B regulates cell wall thickening during fiber development in Populus species.

Science.gov (United States)

Zhao, Yunjun; Sun, Jiayan; Xu, Peng; Zhang, Rui; Li, Laigeng

2014-02-01

Alternative splicing is an important mechanism involved in regulating the development of multicellular organisms. Although many genes in plants undergo alternative splicing, little is understood of its significance in regulating plant growth and development. In this study, alternative splicing of black cottonwood (Populus trichocarpa) wood-associated NAC domain transcription factor (PtrWNDs), PtrWND1B, is shown to occur exclusively in secondary xylem fiber cells. PtrWND1B is expressed with a normal short-transcript PtrWND1B-s as well as its alternative long-transcript PtrWND1B-l. The intron 2 structure of the PtrWND1B gene was identified as a critical sequence that causes PtrWND1B alternative splicing. Suppression of PtrWND1B expression specifically inhibited fiber cell wall thickening. The two PtrWND1B isoforms play antagonistic roles in regulating cell wall thickening during fiber cell differentiation in Populus spp. PtrWND1B-s overexpression enhanced fiber cell wall thickening, while overexpression of PtrWND1B-l repressed fiber cell wall thickening. Alternative splicing may enable more specific regulation of processes such as fiber cell wall thickening during wood formation.

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

Science.gov (United States)

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

2014-09-01

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

Closed compact Taylor's droplets in a phase-separated lamellar-sponge mixture under shear flow

Science.gov (United States)

Courbin, L.; Cristobal, G.; Rouch, J.; Panizza, P.

2001-09-01

We have studied by optical microscopy, small-angle light scattering, and rheology, the behavior under shear flow of a phase-separated lamellar-sponge (Lα - L3) ternary mixture. We observe in the Lα-rich region (ΦLα > 80%) the existence of a Newtonian assembly made of closed compact monodisperse lamellar droplets immersed in the sponge phase. Contrary to the classical onion glassy texture obtained upon shearing Lα phases, the droplet size scales herein as dot gamma-1, the inverse of the shear rate. This result is in good agreement with Taylor's picture. Above a critical shear rate, dot gammac, the droplets organize to form a single colloidal crystal whose lattice size varies as dot gamma-1/3. To the memory of Tess Melissa P.

A new local thickening reverse spiral origami thin-wall construction for improving of energy absorption

Science.gov (United States)

Kong, C. H.; Zhao, X. L.; Hagiwara, I. R.

2018-02-01

As an effective and representative origami structure, reverse spiral origami structure can be capable to effectively take up energy in a crash test. The origami structure has origami creases thus this can guide the deformation of structure and avoid of Euler buckling. Even so the origami creases also weaken the support force and this may cut the absorption of crash energy. In order to increase the supporting capacity of the reverse spiral origami structure, we projected a new local thickening reverse spiral origami thin-wall construction. The reverse spiral origami thin-wall structure with thickening areas distributed along the longitudinal origami crease has a higher energy absorption capacity than the ordinary reverse spiral origami thin-wall structure.

Orthophragminids with new axial thickening structures from the Bartonian of the Indian subcontinent

Energy Technology Data Exchange (ETDEWEB)

Ozcan, E.; Kumar Saraswati, P.; Hanif, M.; Ali, N.

2016-07-01

The ‘axial thickening’, a morphological character of certain Eocene orthophragminids refers to the thickening of the equatorial and/or lateral layers in axial directions forming radial external structures, namely the ribs. The occurrence of ribs is considered to be a diagnostic specific character of the orthophragminids in the periMediterranean region and Europe (western Tethys). In the Bartonian orthophragminids of the Indian subcontinent we observe a new type of axial thickening that we name ‘bulges’. The bulges are semi-rounded to rounded, localized structures on the test surface formed solely by the greater development of lateral chamberlets. These specimens, with trybliolepidine to umbilicolepidine type embryon configuration, co-occur with ribbed discocyclinids having completely different internal features. We also record another type of axial thickening of the lateral layers in notably small omphaloid tests that are characterized by a thick umbo, deeply depressed at the center such that the periphery of it forms a thick circular structure. The reported omphaloid specimens possess a small, semiisolepidine to nephrolepidine type embryon configuration and characteristic early chambers, not comparable to any known species in the Tethys. These specimens occasionally may have incomplete and/or irregular septula, reminiscent of certain Caribbean orthophragminids. The specimens with bulges, identified in two geographically distant regions of the Indian subcontinent, possibly represent endemic foraminiferal fauna confined to the IndoPakistan region. We introduce two new species, Discocyclina kutchensis sp. nov. (characterized by bulges) and ‘D’. sulaimanensis sp. nov. (characterized by circular structures in omphaloid tests). The status of both taxa in the Tethys is discussed. (Author)

Offshore vertical wind shear: Final report on NORSEWInD’s work task 3.1

DEFF Research Database (Denmark)

Pena Diaz, Alfredo; Mikkelsen, Torben; Gryning, Sven-Erik

of power outputs. Background related to the parametrization of the vertical wind speed profile and the behavior of the vertical wind shear in and beyond the atmospheric surface layer is presented together with the application of the long-term atmospheric stability parameters for the analysis of the long......This document reports on the analysis performed by the work task 3.1 of the EU NORSEWInD project and includes the following deliverables: 3.2 Calculated vertical wind shears 3.3 Multi-variational correlation analysis 3.4 NWP data for wind shear model 3.5 Vertical extrapolation methodology 3.......6 Results input into satellite maps The nature of the offshore vertical wind shear is investigated using acquired data from the NORSEWInD network of mast and wind lidar stations. The importance of the knowledge of the vertical wind speed profile and wind shear is first illustrated for the evaluation...

Evaluate the capability and accuracy of response-2000 program in prediction of the shear capacities of reinforced and prestressed concrete members

Directory of Open Access Journals (Sweden)

Ibrahim M. Metwally

2012-08-01

Member response analysis and sectional analysis were both used in Response-2000 to predict the behavior of the beams. Member response calculates the full member behavior including the deflection and curvature along the member length, as well as predicted failure modes. The analysis was performed by specifying the length subjected to shear and any constant moment region. Response-2000 provided a very good prediction of experimental behavior when compared to a database of 534 beams tested in shear. These include prestressed and reinforced sections, very large footing-like sections, sections made with very high strength concrete and elements with unusual geometry. All are predicted well. The results include that Response-2000 can predict the failure shear with an average experimental over predicted shear ratio of 1.05 with a coefficient of variation of 12%. This compares favorably to the ACI 318-08 [2] Code prediction ratios that have an average of 1.20 and a coefficient of variation of 32%.

Separate structure of two branches of sheared slab ηi mode and effects of plasma rotation shear in weak magnetic shear region

International Nuclear Information System (INIS)

Jiquan Li; Kishimoto, Y.; Tuda, T.

2000-01-01

The separate structure of two branches of the sheared slab η i mode near the minimum-q magnetic surface is analysed and the effects of plasma rotation shears are considered in the weak magnetic shear region. Results show that the separation condition depends on the non-monotonous q profile and the deviation of rational surface from the minimum-q surface. Furthermore, it is found that the diamagnetic rotation shear may suppress the perturbation of the sheared slab η i mode at one side of the minimum-q surface, the poloidal rotation shear from the sheared E-vector x B-vector flow has a similar role to the slab mode structure when it possesses a direction same as the diamagnetic shear. A plausible interrelation between the separate structures of the two branches of the sheared slab mode and the discontinuity or gap of the radially global structure of the drift wave near the minimum-q surface observed in the toroidal particle simulation (Kishimoto Y et al 1998 Plasma Phys. Control. Fusion 40 A663) is discussed. It seems to support such a viewpoint: the double or/and global branches of the sheared slab η i mode near the minimum-q surface may become a bridge to connect the radially global structures of the drift wave at two sides of the minimum-q surface and the discontinuity may originate from the separate structures of these slab modes for a flatter q profile. (author)

Influences of Shear History and Infilling on the Mechanical Characteristics and Acoustic Emissions of Joints

Science.gov (United States)

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

2017-08-01

Filled joints, which are characterized by high deformability and low shear strength, are among the most critical discontinuities in rock mass and may be sheared repeatedly when subject to cyclic loading. Shear tests were carried out on tension splitting joints, with soil and granular cement mortar particles used as infillings, and the effects of the shear history on the mechanical behavior and acoustic emission (AE) of clean and filled joints were studied. The maximum strength in the subsequent shears was approximately 60% of the peak strength of the first shear for a clean joint, and the friction angle degraded from 63° to 45° after the first shear. The maximum shear strength of the filled joints was lower than 35% of the peak strength of the clean joint under the same normal stress. The change in the shear strength of filled joints with the number of shearing cycles was closely related to the transformation of the shear medium. Rolling friction occurred and the shear strength was low for the granular particle-filled joint, but the strength was elevated when the particles were crushed and sliding friction occurred. The AEs were significantly reduced during the second shear for the clean joint, and the peak AEs were mainly obtained at or near the turning point of the shear stress curve for the filled joint. The AEs were the highest for the cement particle-filled joint and lowest for the dry soil-filled joint; when subjected to repeated shears, the AEs were more complex because of the continuous changes to the shear medium. The evolution of the AEs with the shear displacement can accurately reflect the shear failure mechanism during a single shear process.

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

Science.gov (United States)

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

2017-11-01

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

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

International Nuclear Information System (INIS)

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

2010-01-01

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

Flexural Strengthening of RC Slabs Using a Hybrid FRP-UHPC System Including Shear Connector

Directory of Open Access Journals (Sweden)

Jiho Moon

2017-01-01

Full Text Available A polymeric hybrid composite system made of UHPC and CFRP was proposed as a retrofit system to enhance flexural strength and ductility of RC slabs. While the effectiveness of the proposed system was confirmed previously through testing three full-scale one-way slabs having two continuous spans, the slabs retrofitted with the hybrid system failed in shear. This sudden shear failure would stem from the excessive enhancement of the flexural strength over the shear strength. In this study, shear connectors were installed between the hybrid system and a RC slab. Using simple beam, only positive moment section was examined. Two full-scale RC slabs were cast and tested to failure: the first as a control and the second using this new strengthening technique. The proposed strengthening system increased the ultimate load carrying capacity of the slab by 70%, the stiffness by 60%, and toughness by 128%. The efficiency of shear connectors on ductile behavior of the retrofitted slab was also confirmed. After the UHPC top is separated from the slab, the shear connector transfer shear load and the slab system were in force equilibrium by compression in UHPC and tension in CFRP.

Shear test on viscoelastic granular material using Contact Dynamics simulations

Science.gov (United States)

Quezada, Juan Carlos; Sagnol, Loba; Chazallon, Cyrille

2017-06-01

By means of 3D contact dynamic simulations, the behavior of a viscoelastic granular material under shear loading is investigated. A viscoelastic fluid phase surrounding the solid particles is simulated by a contact model acting between them. This contact law was implemented in the LMGC90 software, based on the Burgers model. This model is able to simulate also the effect of creep relaxation. To validate the proposed contact model, several direct shear tests were performed, experimentally and numerically using the Leutner device. The numerical samples were created using spheres with two particle size distribution, each one identified for two layers from a road structure. Our results show a reasonable agreement between experimental and numerical data regarding the strain-stress evolution curves and the stress levels measured at failure. The proposed model can be used to simulate the mechanical behavior of multi-layer road structure and to study the influence of traffic on road deformation, cracking and particles pull-out induced by traffic loading.

Constitutive Curve and Velocity Profile in Entangled Polymers during Start-Up of Steady Shear Flow

KAUST Repository

Hayes, Keesha A.

2010-05-11

Time-dependent shear stress versus shear rate, constitutive curve, and velocity profile measurements are reported in entangled polymer solutions during start-up of steady shear flow. By combining confocal microscopy and particle image velocimetry (PIV), we determine the time-dependent velocity profile in polybutadiene and polystyrene solutions seeded with fluorescent 150 nm silica and 7.5 μm melamine particles. By comparing these profiles with time-dependent constitutive curves obtained from experiment and theory, we explore the connection between transient nonmonotonic regions in the constitutive curve for an entangled polymer and its susceptibility to unstable flow by shear banding [Adams et al. Phys. Rev. Lett. 2009, 102, 067801-4]. Surprisingly, we find that even polymer systems which exhibit transient, nonmonotonic shear stress-shear rate relationships in bulk rheology experiments manifest time-dependent velocity profiles that are decidedly linear and show no evidence of unstable flow. We also report that interfacial slip plays an important role in the steady shear flow behavior of entangled polymers at shear rates above the reciprocal terminal relaxation time but has little, if any, effect on the shape of the velocity profile. © 2010 American Chemical Society.

Discrimination between pleural thickening and minimal pleural effusion using color Doppler chest ultrasonography

Directory of Open Access Journals (Sweden)

Ali A. Hasan

2013-07-01

Conclusions: Application of color Doppler examination increases the accuracy of real time chest ultrasound to discriminate pleural thickening from minimal pleural effusion and hence color Doppler examination proved to be a useful diagnostic tool to real-time gray-scale ultrasound for diagnosis of minimal pleural effusion.

Healing of shear strength and its time dependency in a single rock fracture

International Nuclear Information System (INIS)

Kawaguchi, Yuta; Nakashima, Shinichiro; Yasuhara, Hideaki; Kishida, Kiyoshi

2011-01-01

Evolution of the long-term mechanical, hydraulic, and transport characteristics of rock fractures should be, in advance, predicted in considering an issue on entombment of energy byproducts of high level radioactive wastes. Under stressed and temperature conditions, those behaviors of the rock fractures of interest may be evolved in time and space likely due to the change in topographical aperture distributions. This irreversible process may be induced by pure mechanical and/or chemo-mechanical creeps such as water-rock reactions like stress corrosion and pressure solution, and chemical effects including mineral dissolution and reprecipitation in the free-walls of fractures. Specifically, the chemo-mechanical processes active at the contacting asperities within rock fractures may exert a significant influence on the mechanical, hydraulic, and transport behaviors throughout a long period, and thus, should be vigorously examined theoretically and experimentally. This paper presents the slide-hold-slide shear test results for fully saturated, single-jointed mortar specimens so as to investigate the effects of load holding on mechanical properties of rock joints. From the test results, it was confirmed that shear strength increased for mortar specimens in both short and long time holding cases. However, the evolution of shear strength recovery in two cases is different. This is because a dominant factor of shear strength recovery during the short time holding may be attributed to a pure mechanical process like creep deformation at contacting asperities, while the one during long time holding is affected by both mechanical and chemical processes like pressure solution. Moreover, to reproduce the shear strength recovery during short time holding we develop a direct shear model by including temporal variation of dilation during holding. The model predictions are in relatively good agreement with the test measurements. (author)

Enhancement of shear strength and ductility for reinforced concrete wide beams due to web reinforcement

Directory of Open Access Journals (Sweden)

M. Said

2013-12-01

Full Text Available The shear behavior of reinforced concrete wide beams was investigated. The experimental program consisted of nine beams of 29 MPa concrete strength tested with a shear span-depth ratio equal to 3.0. One of the tested beams had no web reinforcement as a control specimen. The flexure mode of failure was secured for all of the specimens to allow for shear mode of failure. The key parameters covered in this investigation are the effect of the existence, spacing, amount and yield stress of the vertical stirrups on the shear capacity and ductility of the tested wide beams. The study shows that the contribution of web reinforcement to the shear capacity is significant and directly proportional to the amount and spacing of the shear reinforcement. The increase in the shear capacity ranged from 32% to 132% for the range of the tested beams compared with the control beam. High grade steel was more effective in the contribution of the shear strength of wide beams. Also, test results demonstrate that the shear reinforcement significantly enhances the ductility of the wide beams. In addition, shear resistances at failure recorded in this study are compared to the analytical strengths calculated according to the current Egyptian Code and the available international codes. The current study highlights the need to include the contribution of shear reinforcement in the Egyptian Code requirements for shear capacity of wide beams.

Novel CO{sub 2}-thickeners for improved mobility control

Energy Technology Data Exchange (ETDEWEB)

Enick, Dr. Robert M.; Beckman, Dr. Eric J.; Hamilton, Dr. Andrew

2000-02-02

The objective of this study was to design, synthesize, and characterize thickening agents for dense carbon dioxide and to evaluate their solubility and viscosity-enhancing potential in CO{sub 2}. Hydrocarbon-fluorocarbon random copolymers, sulfated hydrocarbon-fluorocarbon random copolymers, semifluorinated trialkyltin fluorides and small hydrogen-bonding compounds were evaluated. Random copolymers of styrene and heptadecafluorodecyl acrylate were characterized by high solubility ion dense carbon dioxide and the most substantial increases in solution viscosity. Falling cylinder viscometry results indicated that the 29%styrene--71%fluoroacylate bulk-polymerized copolymer induced 2--250 fold increases in viscosity at copolymer concentrations of 0.2--5.0wt%.

Shear Capacity of C-Shaped and L-Shaped Angle Shear Connectors.

Directory of Open Access Journals (Sweden)

Farzad Tahmasbi

Full Text Available This paper investigates the behaviour of C-shaped and L-shaped angle shear connectors embedded in solid concrete slabs. An effective finite element model is proposed to simulate the push out tests of these shear connectors that encompass nonlinear material behaviour, large displacement and damage plasticity. The finite element models are validated against test results. Parametric studies using this nonlinear model are performed to investigate the variations in concrete strength and connector dimensions. The finite element analyses also confirm the test results that increasing the length of shear connector increases their shear strength proportionately. It is observed that the maximum stress in L-shaped angle connectors takes place in the weld attachment to the beam, whereas in the C-shaped angle connectors, it is in the attached leg. The location of maximum concrete compressive damage is rendered in each case. Finally, a new equation for prediction of the shear capacity of C-shaped angle connectors is proposed.

Shear Capacity of C-Shaped and L-Shaped Angle Shear Connectors

Science.gov (United States)

Tahmasbi, Farzad; Maleki, Shervin; Shariati, Mahdi; Ramli Sulong, N. H.; Tahir, M. M.

2016-01-01

This paper investigates the behaviour of C-shaped and L-shaped angle shear connectors embedded in solid concrete slabs. An effective finite element model is proposed to simulate the push out tests of these shear connectors that encompass nonlinear material behaviour, large displacement and damage plasticity. The finite element models are validated against test results. Parametric studies using this nonlinear model are performed to investigate the variations in concrete strength and connector dimensions. The finite element analyses also confirm the test results that increasing the length of shear connector increases their shear strength proportionately. It is observed that the maximum stress in L-shaped angle connectors takes place in the weld attachment to the beam, whereas in the C-shaped angle connectors, it is in the attached leg. The location of maximum concrete compressive damage is rendered in each case. Finally, a new equation for prediction of the shear capacity of C-shaped angle connectors is proposed. PMID:27478894

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

Science.gov (United States)

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

2002-04-01

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

Identification of pleural effusion with low levels of adenosine deaminase but without signs of acute inflammation or pleural thickening to diagnose early malignant pleural mesothelioma

International Nuclear Information System (INIS)

Moriyama, Satoru; Tanahashi, Masayuki; Suzuki, Eriko

2012-01-01

We reviewed the clinical findings and diagnostic methods used in the diagnosis of malignant pleural mesothelioma (MPM) in patients with pleural effusion with low levels of adenosine deaminase (ADA), but without signs of acute inflammation or pleural thickening. The hospital records of 40 patients with pleural effusion of unknown origin or pleural thickening were retrospectively investigated. In all of those studies, pleural effusion was exudative, lymphocyte-dominant, no mycobacteria or other bacteria, and low levels of ADA. There were 30 men and 10 women with an average age of 62.8 years old. The diagnosis of MPM was obtained by cytology of the pleural effusion in 3 patients and by core-needle biopsy of the thickened pleura in 3. Thoracoscopic pleural biopsy under general anesthesia was performed for the other 34 patients. The pathologic diagnosis of pleural biopsy was MPM in 20 patients, inflammatory change in 12, and pleural dissemination of cancer in 2. All of the 7 patients with more than 100 μg/ml of hyaluronic acid in their pleural effusion received a diagnosis of MPM. A total of 20 of 23 patients with irregular or nodular pleural thickening on computed tomography findings were confirmed to have MPM. Moreover, 6 of 17 patients with smooth pleural thickening were confirmed to have MPM. In patients with nodular pleural thickening it was easy to make the diagnosis. However, in those with smooth thickening, careful observation was required to select the appropriate biopsy site and resection margins of full-thickness pleura. As the rate of MPM in the patients with pleural effusion with low levels of ADA, but without signs of acute inflammation or pleural thickening is high (65%), an early thoracoscopic pleural biopsy is strongly recommended. (author)

Plasticity Approach to Shear Design

DEFF Research Database (Denmark)

Hoang, Cao Linh; Nielsen, Mogens Peter

1998-01-01

The paper presents some plastic models for shear design of reinforced concrete beams. Distinction is made between two shear failure modes, namely web crushing and crack sliding. The first mentioned mode is met in beams with large shear reinforcement degrees. The mode of crack sliding is met in non......-shear reinforced beams as well as in lightly shear reinforced beams. For such beams the shear strength is determined by the recently developed crack sliding model. This model is based upon the hypothesis that cracks can be transformed into yield lines, which have lower sliding resistance than yield lines formed...... in uncracked concrete. Good agree between theory and tests has been found.Keywords: dsign, plasticity, reinforced concrete, reinforcement, shear, web crushing....

Wall morphology, blood flow and wall shear stress: MR findings in patients with peripheral artery disease

Energy Technology Data Exchange (ETDEWEB)

Galizia, Mauricio S.; Barker, Alex; Collins, Jeremy; Carr, James [Northwestern University, Department of Radiology, Feinberg School of Medicine, Chicago, IL (United States); Liao, Yihua [Northwestern University' s Feinberg School of Medicine, Department of Preventive Medicine, Chicago, IL (United States); McDermott, Mary M. [Northwestern University' s Feinberg School of Medicine, Department of Preventive Medicine, Chicago, IL (United States); Northwestern University' s Feinberg School of Medicine, Department of Medicine, Chicago, IL (United States); Markl, Michael [Northwestern University, Department of Radiology, Feinberg School of Medicine, Chicago, IL (United States); Northwestern University, Department Biomedical Engineering, McCormick School of Engineering, Chicago, IL (United States)

2014-04-15

To investigate the influence of atherosclerotic plaques on femoral haemodynamics assessed by two-dimensional (2D) phase-contrast (PC) magnetic resonance imaging (MRI) with three-directional velocity encoding. During 1 year, patients with peripheral artery disease and an ankle brachial index <1.00 were enrolled. After institutional review board approval and written informed consent, 44 patients (age, 70 ± 12 years) underwent common femoral artery MRI. Patients with contra-indications for MRI were excluded. Sequences included 2D time-of-flight, proton-density, T1-weighted and T2-weighted MRI. Electrocardiogram (ECG)-gated 2D PC-MRI with 3D velocity encoding was acquired. A radiologist classified images in five categories. Blood flow, velocity and wall shear stress (WSS) along the vessel circumference were quantified from the PC-MRI data. The acquired images were of good quality for interpretation. There were no image quality problems related to poor ECG-gating or slice positioning. Velocities, oscillatory shear stress and total flow were similar between patients with normal arteries and wall thickening/plaque. Patients with plaques demonstrated regionally increased peak systolic WSS and enhanced WSS eccentricity. Combined multi-contrast morphological imaging of the peripheral arterial wall with PC-MRI with three-directional velocity encoding is a feasible technique. Further study is needed to determine whether flow is an appropriate marker for altered endothelial cell function, vascular remodelling and plaque progression. (orig.)

Turbulence suppression by E x B shear in JET optimized shear pulses

International Nuclear Information System (INIS)

Beer, M.A.; Budny, R.V.; Challis, C.D.; Conway, G.

2000-01-01

The authors calculate microinstability growth rates in JET optimized shear plasmas with a comprehensive gyrofluid model, including sheared E x B flows, trapped electrons, and all dominant ion species in realistic magnetic geometry. They find good correlation between E x B shear suppression of microinstabilities and both the formation and collapse of the internal transport barrier

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

Science.gov (United States)

1980-05-01

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

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

Directory of Open Access Journals (Sweden)

Kun Sang Lee

2011-08-01

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

Interfacial Shear Strength of Multilayer Graphene Oxide Films.

Science.gov (United States)

Daly, Matthew; Cao, Changhong; Sun, Hao; Sun, Yu; Filleter, Tobin; Singh, Chandra Veer

2016-02-23

Graphene oxide (GO) is considered as one of the most promising layered materials with tunable physical properties and applicability in many important engineering applications. In this work, the interfacial behavior of multilayer GO films was directly investigated via GO-to-GO friction force microscopy, and the interfacial shear strength (ISS) was measured to be 5.3 ± 3.2 MPa. Based on high resolution atomic force microscopy images and the available chemical data, targeted molecular dynamics simulations were performed to evaluate the influence of functional structure, topological defects, and interlayer registry on the shear response of the GO films. Theoretical values for shear strength ranging from 17 to 132 MPa were predicted for the different structures studied, providing upper bounds for the ISS. Computational results also revealed the atomic origins of the stochastic nature of friction measurements. Specifically, the wide scatter in experimental measurements was attributed to variations in functional structure and topological defects within the sliding volume. The findings of this study provide important insight for understanding the significant differences in strength between monolayer and bulk graphene oxide materials and can be useful for engineering topological structures with tunable mechanical properties.

Comparison of Shear Strength Properties for Undisturbed and Reconstituted Parit Nipah Peat, Johor

Science.gov (United States)

Azhar, A. T. S.; Norhaliza, W.; Ismail, B.; Abdullah, M. E.; Zakaria, M. N.

2016-11-01

Shear strength of soil is required to determine the soil stability and design the foundations. Peat is known as a soil with complex natural formations which also contributes problems to the researchers, developers, engineers and contractors in constructions and infrastructures. Most researchers conducted experiment and investigation of shear strength on peat using shear box test and simple shear test, but only a few had discovered the behavior of peat using triaxial consolidated undrained test. The aim of this paper is to determine the undrained shear strength properties of reconstituted peat and undisturbed peat of Parit Nipah, Johor for comparison purposes. All the reconstituted peat samples were formed with the size that passed opening sieve 3.35 mm and preconsolidation pressure at 100 kPa. The result of undrained shear strength of reconstituted peat was 21kPa for cohesion with the angle of friction, 41° compare to the undisturbed peat with cohesion 10 kPa and angle of friction, 16°. The undrained shear strength properties result obtained shows that the reconstituted peat has higher strength than undisturbed peat. For relationship deviator stress-strain, σd max and excess pore pressure, Δu, it shows that both of undisturbed and reconstituted gradually increased when σ’ increased, but at the end of the test, the values are slightly dropped. The physical properties of undisturbed and reconstituted peat were also investigated to correlate with the undrained shear strength results.

Model tests on dynamic performance of RC shear walls

International Nuclear Information System (INIS)

Nagashima, Toshio; Shibata, Akenori; Inoue, Norio; Muroi, Kazuo.

1991-01-01

For the inelastic dynamic response analysis of a reactor building subjected to earthquakes, it is essentially important to properly evaluate its restoring force characteristics under dynamic loading condition and its damping performance. Reinforced concrete shear walls are the main structural members of a reactor building, and dominate its seismic behavior. In order to obtain the basic information on the dynamic restoring force characteristics and damping performance of shear walls, the dynamic test using a large shaking table, static displacement control test and the pseudo-dynamic test on the models of a shear wall were conducted. In the dynamic test, four specimens were tested on a large shaking table. In the static test, four specimens were tested, and in the pseudo-dynamic test, three specimens were tested. These tests are outlined. The results of these tests were compared, placing emphasis on the restoring force characteristics and damping performance of the RC wall models. The strength was higher in the dynamic test models than in the static test models mainly due to the effect of loading rate. (K.I.)

Intramural hypoattenuated nodules in thickened wall of the gallbladder; CT features according to their primary causes

International Nuclear Information System (INIS)

Lee, Jun Hyung; Ha, Hyun Kwon; Lee, Jeong Hyun; Lee, Jean Hwa; Kim, Tae Kyoung; Kim, Pyo Nyun; Lee, Moon Gyu; Kim, Myung-Jin

2001-01-01

According to published reports, a common feature of xanthogranulomatous cholecystitis is the presence of intramural hypoattenuated nodules in thickened gallbladder wall. These nodules can, however, also be seen in pathological conditions such as acute cholecystitis, hyperplastic cholecystoses (cholesterolosis and adenomyomatosis), gallbladder cancer, and other inflammatory diseases such as tuberculosis. Retrospective review of the abdominal CT findings in 622 patients who for various reasons underwent cholecystectomy during a one-year period showed that intramural nodules were present in 60. In this pictorial essay we illustrate the imaging features of the many different pathological conditions which give rise to intramural hypoattenuated nodules in thickened wall of the gallbladder, correlating these features with the histopathological findings

Locating the origin of stick slip instabilities in sheared granular layers

Science.gov (United States)

Korkolis, Evangelos; Niemeijer, André

2017-04-01

Acoustic emission (AE) monitoring is a non-invasive technique widely used to evaluate the state of materials and structures. We have developed a system that can locate the source of AE events associated with unstable sliding (stick-slip) of sheared granular layers during laboratory friction experiments. Our aim is to map the spatial distribution of energy release due to permanent microstructural changes, using AE source locations as proxies. This will allow us to determine the distribution of applied work in a granular medium, which will be useful in developing constitutive laws that describe the frictional behavior of such materials. The AE monitoring system is installed on a rotary shear apparatus. This type of apparatus is used to investigate the micromechanical processes responsible for the macroscopic frictional behavior of granular materials at large shear displacements. Two arrays of 8 piezoelectric sensors each are installed into the ring-shaped steel pistons that confine our samples. The sensors are connected to a high-speed, multichannel oscilloscope that can record full waveforms. The apparatus is also equipped with a system that continuously records normal and lateral (shear) loads and displacements, as well as pore fluid pressure. Thus, we can calculate the frictional and volumetric response of our granular aggregates, as well as the location of AE sources. Here, we report on the results of room temperature experiments on granular aggregates consisting of glass beads or segregated mixtures of glass beads and calcite, at up to 5 MPa normal stress and sliding velocities between 1 and 100 μm/s. Under these conditions, glass beads exhibit unstable sliding behavior accompanied by significant AE activity, whereas calcite exhibits stable sliding and produces no AEs. We recorded a range of unstable sliding behaviors, from fast, regular stick slip at high normal stress (> 4 MPa) and sliding velocities below 20 μm/s, to irregular stick slip at low normal

Hydrodynamic of a deformed bubble in linear shear flow

International Nuclear Information System (INIS)

Adoua, S.R.

2007-07-01

This work is devoted to the study of an oblate spheroidal bubble of prescribed shape set fixed in a linear shear flow using direct numerical simulation. The three dimensional Navier-Stokes equations are solved in orthogonal curvilinear coordinates using a finite volume method. The bubble response is studied over a wide range of the aspect ratio (1-2.7), the bubble Reynolds number (50-2000) and the non-dimensional shear rate (0.-1.2). The numerical simulations shows that the shear flow imposes a plane symmetry of the wake whatever the parameters of the flow. The trailing vorticity is organized into two anti-symmetrical counter rotating tubes with a sign imposed by the competition of two mechanisms (the Lighthill mechanism and the instability of the wake). Whatever the Reynolds number, the lift coefficient reaches the analytical value obtained in an inviscid, weakly sheared flow corresponding to a lift force oriented in the same direction as that of a spherical bubble. For moderate Reynolds numbers, the direction of the lift force reverses when the bubble aspect ratio is large enough as observed in experiments. This reversal occurs for aspect ratios larger than 2.225 and is found to be directly linked to the sign of the trailing vorticity which is concentrated within two counter-rotating threads which propel the bubble in a direction depending of their sign of rotation. The behavior of the drag does not revel any significant effect induced by the wake structure and follows a quadratic increase with the shear rate. Finally, the torque experienced by the bubble also reverses for the same conditions inducing the reversal of the lift force. By varying the orientation of the bubble in the shear flow, a stable equilibrium position is found corresponding to a weak angle between the small axis of the bubble and the flow direction. (author)

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

KAUST Repository

Liu, Hongyi

2012-01-25

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

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

KAUST Repository

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

2012-01-01

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

Axillary bud and pericycle involved in the thickening process of the rhizophore nodes in Smilax species

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B Appezzato-da-Glória

Full Text Available AbstractThe species of the genus Smilax, popularly known as sarsaparilla, are widely used in folk medicine due to the antirheumatic properties of its underground structures. Smilax fluminensis and S. syphilitica occur in forested areas and form thickened stems called rhizophores from which adventitious roots grow. To provide information for more accurate identification of the commercialised product and for elucidating the process of stem thickening, a morphology and anatomy study of the underground organs of the two species was conducted. The adventitious roots differ in colour and diameter depending on the stage of development. They are white and have a larger diameter in the early stages of development, but as they grow, the adventitious roots become brown and have a smaller diameter due to the disintegration of the epidermis and virtually the entire cortex. In brown roots, the covering function is then performed by the lignified endodermis and the remaining walls of the cells from the last parenchyma cortical layer. These results are similar to those found in studies of other Smilax and suggest that the anatomy of the roots can be useful for identifying fraud in commercialised materials. The thickening process of the nodal regions of the rhizophores in both species involves the activity of axillary buds and pericyclic layers.

Effect of formulation variables on the physical properties and stability of Dead Sea mud masks.

Science.gov (United States)

Shahin, Sawsan; Hamed, Saja; Alkhatib, Hatim S

2015-01-01

The physical stability of Dead Sea mud mask formulations under different conditions and their rheological properties were evaluated as a function of the type and level of thickeners, level of the humectant, incorporation of ethanol, and mode of mud treatment. Formulations were evaluated in terms of visual appearance, pH, moisture content, spreadability, extrudability, separation, rate of drying at 32 degrees C, and rheological properties. Prepared mud formulations and over-the-shelf products showed viscoplastic shear thinning behavior; satisfactory rheological behavior was observed with formulations containing a total concentration of thickeners less than 10% (w/w). Casson and Herschel-Bulkley models were found the most suitable to describe the rheological data of the prepared formulations. Thickener incorporation decreased phase separation and improved formulation stability. Bentonite incorporation in the mud prevented color changes during stability studies while glycerin improved spreadability. Addition of 5% (w/w) ethanol improved mud extrudability, slightly increased percent separation, accelerated drying at 32 degrees C, and decreased viscosity and yield stress values. Different mud treatment techniques did not cause a clear behavioral change in the final mud preparation. B10G and K5B5G were labeled as "best formulas" based on having satisfactory physical and aesthetic criteria investigated in this study, while other formulations failed in one or more of the tests we have performed.

Characteristic Thickened Cell Walls of the Bracts of the ‘Eternal Flower’ Helichrysum bracteatum

Science.gov (United States)

Nishikawa, Kuniko; Ito, Hiroaki; Awano, Tatsuya; Hosokawa, Munetaka; Yazawa, Susumu

2008-01-01

Background and Aims Helichrysum bracteatum is called an ‘eternal flower’ and has large, coloured, scarious bracts. These maintain their aesthetic value without wilting or discoloration for many years. There have been no research studies of cell death or cell morphology of the scarious bract, and hence the aim of this work was to elucidate these characteristics for the bract of H. bracteatum. Methods DAPI (4'6-diamidino-2-phenylindol dihydrochloride) staining and fluorescence microscopy were used for observation of cell nuclei. Light microscopy (LM), transmission electron microscopy (TEM) and polarized light microscopy were used for observation of cells, including cell wall morphology. Key Results Cell death occurred at the bract tip during the early stage of flower development. The cell wall was the most prominent characteristic of H. bracteatum bract cells. Characteristic thickened secondary cell walls on the inside of the primary cell walls were observed in both epidermal and inner cells. In addition, the walls of all cells exhibited birefringence. Characteristic thickened secondary cell walls have orientated cellulose microfibrils as well as general secondary cell walls of the tracheary elements. For comparison, these characters were not observed in the petal and bract tissues of Chrysanthemum morifolium. Conclusions Bracts at anthesis are composed of dead cells. Helichrysum bracteatum bracts have characteristic thickened secondary cell walls that have not been observed in the parenchyma of any other flowers or leaves. The cells of the H. bracteatum bract differ from other tissues with secondary cell walls, suggesting that they may be a new cell type. PMID:18436550

Strip waves in vibrated shear-thickening wormlike micellar solutions