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In the present work, the study of variation of relaxation time (τ) with viscosity of the medium (η) is carried out on four polar samples: 2-Nitroaniline, 4-Bromoaniline, 4-Chloroaniline, 4-Chlorophenol, and also on the binary mixture of 2-Nitroaniline + 4-Bromoaniline at room temperature by using microwave bench operating at a frequency of 9.59 GHz. In this regard, the different parameters like dielectric constant (--> ε ′ -->), dielectric loss (--> ε ″ -->), relaxation time (τs), macroscopic steady state viscosity (ηs), dynamic viscosity (ηd), and viscoelastic relaxation time (τve) were determined for all the systems. It is observed that the relaxation time (τs) increases with the increase in the viscosity of the medium for all the systems. Plots of log(τs) versus log(ηs) for all the systems show that variation of relaxation time is found to be nonlinear in the higher viscosity regions. This suggests the failure of Debye's theory at these regions. Further, the nonlinear behaviour of relaxation time with the viscosity is explained by using the viscoelastic model suggested by Barlow et al. (Proc. R. Soc. A 309, 473 (1969). doi:10.1098/rspa.1969.0053). It is also observed that macroscopic steady state viscosity (ηs) values are greater than the dynamic viscosity (ηd), and viscoelastic relaxation time (τve) values were found to be lower compared to the relaxation time (τs). These results suggest that the effective frictional resistance experienced by the molecules during reorientation is lower and the measured values of macroscopic steady state viscosity (ηs) are frequency dependent. [ABSTRACT FROM AUTHOR]

In this paper, to study the viscoelastic effect on isotropic turbulence without wall effects, a two oscillating grid turbulence is built to investigate this phenomenon using particle image velocimetry. In the experiments, the classical drag-reducing additives are chosen: polyacrylamide (PAM) and cetyltrimethyl ammonium chloride (CTAC), which have shown remarkable drag-reducing effect in wall-bounded turbulent flows. The results show that the existence of drag-reducing additives makes velocity field more anisotropic and reduces turbulent kinetic energy. We propose an intuitive and natural definition for a reduction rate of turbulent kinetic energy to show viscoelastic effect. It suggests that there exists a critical concentration for the reduction rate of turbulent kinetic energy in the CTAC solution case. Also, the small-scale vortex structures are inhibited, which suggests the drag-reducing mechanism in grid turbulence without wall effect. [ABSTRACT FROM AUTHOR]

This work investigates the transient slip flow of viscoelastic fluids in a slit micro-channel under the combined influences of electro-osmotic and pressure gradient forcings. We adopt the generalized second-grade fluid model with fractional derivative as the constitutive equation and the Navier linear slip model as the boundary conditions. The analytical solution for velocity distribution of the electro-osmotic flow is determined by employing the Debye-Hückel approximation and the integral transform methods. The corresponding expressions of classical Newtonian and second-grade fluids are obtained as the limiting cases of our general results. These solutions are presented as a sum of steady-state and transient parts. The combined effects of slip boundary conditions, fluid rheology, electro-osmotic, and pressure gradient forcings on the fluid velocity distribution are also discussed graphically in terms of the pertinent dimensionless parameters. By comparison with the two cases corresponding to the Newtonian fluid and the classical second-grade fluid, it is found that the fractional derivative parameter β has a significant effect on the fluid velocity distribution and the time when the fluid flow reaches the steady state. Additionally, the slip velocity at the wall increases in a noticeable manner the flow rate in an electro-osmotic flow. [ABSTRACT FROM AUTHOR]

An analysis was carried out to study the effect of thermal radiation on magnetohydrodynamic boundary layer flow and heat transfer characteristics of a non-Newtonian viscoelastic fluid near the stagnation point of a vertical stretching sheet in a porous medium with internal heat generation-absorption. The flow is generated because of linear stretching of the sheet and influenced by the uniform magnetic field that is applied horizontally in the flow region. Using a similarity variable, the governing nonlinear partial differential equations have been transformed into a set of coupled nonlinear ordinary differential equations, which are solved numerically using an accurate implicit finite difference scheme. A comparison of the obtained results with previously published numerical results is done and the results are found to be in good agreement. The effects of the viscoelastic fluid parameter, magnetic field parameter, nonuniform heat source-sink, and the thermal radiation parameter on the heat transfer characteristics are presented graphically and discussed. The values of the skin friction coefficient and the local Nusselt number are tabulated for both cases of assisting and opposing flows. [ABSTRACT FROM AUTHOR]

The purpose of this study was to examine the influence of a bout of repeated and prolonged passive static stretching on the innervation zone (IZ) location of the human biceps brachii muscle. Eleven men performed 12 sets of 100-s passive stretches on their biceps brachii. Before (Pre) and immediately after (Post) the stretching intervention, isometric strength was tested during the maximal voluntary contractions (MVCs) of the forearm flexors. The subjects also performed several separate isometric forearm flexion muscle actions at 30%, 50%, and 70% of their predetermined MVCs for examining the locations of the IZ at different contraction intensities. The IZ was identified through multi-channel surface electromyographic (EMG) recordings from a linear electrode array. The stretching intervention induced an average of 10% isometric strength loss for the forearm flexors (mean ± SD: Pre-MVC vs. Post-MVC = 332.12 ± 59.40 N vs. 299.53 ± 70.51 N; p < 0.001). In addition, the average IZ shift was nearly 4.5 mm in average in the proximal direction. However, this shift was not specific to the contraction intensity. We believe that the IZ shift was caused by the elongation of the entire muscle-tendon unit in the proximal direction. Therefore, caution should be taken when using surface EMG technique to examine possible changes in the EMG variables after a stretching protocol, as these variables can be contaminated by the shift of the IZ. [ABSTRACT FROM AUTHOR]

In this article, the boundary layer two-dimensional Hiemenz flow and heat transfer for a micropolar, viscoelastic electrically conducting fluid over a shrinking/stretching sheet with heat generation is investigated. The governing system of flow equations is first reduced to coupled nonlinear ordinary differential equations by means of similarity transformations. A purely analytical series solutions of these equations is obtained in which domain (0 ≤ η ≤ ∞) using an analytic technique, namely, the homotopy analysis method. The convergence of the series solutions is discussed explicitly. The influences of an emerging parameters on the fluid velocity, microrotation velocity and temperature field are shown graphically and discussed in detail. The comparison of present results with the existing results is also given and found in excellent agreement. [ABSTRACT FROM AUTHOR]

We tested the hypotheses that smoking-induced changes in vascular mechanics would be detected earlier in the lumped properties of peripheral vascular beds, which include the properties of microvasculature, than in the local properties of central conduits, and that such changes are reversible with lifestyle changes that include smoking cessation and exercise. Vascular measures were made in 53 young (18-40 years) female smokers and 25 age-matched non-smokers. Twenty-two of the smokers were tested before and after a 14-week smoking cessation program and, of these, 13 were tested again after 52 weeks of smoking cessation. Compared with non-smokers, lumped forearm vascular bed compliance ( C: mL/mm Hg) was lower, while lumped viscoelasticity ( K: mm Hg/(mL·min)) and resistance ( R: mm Hg/(mL·min)) were higher in the smoker group. Neither the carotid-to-toe pulse wave velocity nor local carotid artery elasticity indices were different between groups. Compared with non-smokers, brachial artery distensibility was less, and other markers of stiffness higher, in the smoker group. At 14 and 52 weeks of smoking cessation, forearm vascular R was reduced and C was increased while K was unchanged. The changes in C and R occurred while maintaining a constant R× C value, which represents a dynamic time constant. Thus, early changes in K were observed in the forearm vascular bed of smokers, which were not reflected in the local properties of central conduit vessels. Forearm C, but not K, was reversed following smoking cessation, a finding that may represent a persistent effect of smoking on the intercellular matrix of the vessel wall. [ABSTRACT FROM AUTHOR]

The steady mixed convection boundary layer flow over an inclined stretching surface immersed in an incompressible viscoelastic fluid is considered in this paper. Employing suitable similarity transformations, the governing partial differential equations are transformed into ordinary differential equations, and the transformed equations are solved numerically using Runge-Kutta-Fehlberg method. Herein, two different types of heating processes are considered, namely, ( i) prescribed surface temperature and ( ii) prescribed wall heat flux. The effects of the governing parameters on the flow field and heat transfer characteristics are obtained and discussed. It is found that velocity decreases and temperature increases with an increase in the value of angle of inclination. [ABSTRACT FROM AUTHOR]

This paper presents the performance evaluation of unmodified and lime-modified hot mix asphalt (HMA) mixtures at varying asphalt content using asphalt mixture performance test developed from National Cooperative Highway Research Program project 9-19 and 9-29 and the viscoelastic continuum damage finite element analysis. Test methods adopted in this study are the dynamic modulus test for stiffness, the triaxial repeated load permanent deformation test for rutting, and the direct tension test for fatigue cracking. The findings from this study support conventional understanding of the effects of asphalt content and lime modification on the fatigue cracking and rutting performance. Finally, the optimum asphalt content for both lime-modified and unmodified mixtures are proposed based on the knowledge gleaned from the performance-based mix design methodology. With additional validation and calibration, the comprehensive methodology described in this paper may serve as the foundation for a performance-based HMA mix design and performance-related HMA specifications. [ABSTRACT FROM AUTHOR]

The benefits of using hydrated lime as an additive in asphalt concrete are well known. When added to asphalt concrete mixtures hydrated lime shows the beneficial effects of filler, while also improving resistance to moisture damage. Even with the great deal of literature and experience extolling the benefits of hydrated lime, little research exists regarding the impact of hydrated lime on the fundamental behavior and performance of asphalt concrete mixtures. This paper presents findings of the impact of lime introduction method on the volumetric optimums and the fundamental behavior and performance of asphalt concrete mixtures. The behavior of various mixtures is assessed with the dynamic modulus tests and through characterization tests for the viscoelastic continuum damage model, a mechanistically based material model. Permanent deformation performance assessment is made with triaxial repeated load permanent deformation tests. From the experimental investigation it is found that the method of lime introduction can have an important effect on the optimum volumetric asphalt content. Regarding mixture performance it is found that hydrated lime has a minimal impact on the dynamic modulus of the mixtures in this study. Conversely, it is found that hydrated lime has a positive effect on both the permanent deformation and fatigue cracking performance of asphalt concrete mixtures. The magnitude of this positive impact is shown to be affected by the method used to introduce hydrated lime into the mixture. [ABSTRACT FROM AUTHOR]

For the past few decades, the stiffness of asphalt material has been commonly characterized by means of resilient modulus. However, the resilient modulus is not a fundamental material property, and hence, the concept of resilient modulus has been subsequently diminished in the latest Mechanistic-Empirical Pavement Design Guide (MEPDG). Although the MEPDG could not endorse the resilient modulus as the primary means for asphalt concrete characterization, it has been a primary mixture test, and a considerable amount of laboratory testing has been conducted to date. In this paper, an analysis methodology for backcalculating the dynamic modulus from the resilient modulus test data is introduced. The strong advantage of such a methodology is that the existing resilient modulus data can be reused for estimating the dynamic modulus. The approach would significantly save time and effort in reevaluating the dynamic modulus of asphalt mixture for which the resilient modulus test data are available. [ABSTRACT FROM AUTHOR]

Passive energy dissipation devices, such as, viscous, viscoelastic, and friction devices are generally installed in buildings using diagonal or chevron braces. To increase the effective damping force and to reduce the damper volume, various magnifying system of the damper displacement, such as, toggle brace system and scissor-jack-damper configuration have been developed with increase in installation cost. In this study, new installation scheme for passive dampers was proposed using cables installed in such a way that relative displacement equal to storey displacement occurs between the cable and the structure when the structure is subjected to lateral load. The cables can be installed continuously or discretely between base and top storey of the structure. To verify the validity of the proposed method nonlinear dynamic analysis of model structures with viscoelastic dampers installed using the proposed configuration scheme was carried out using three earthquake records and two sinusoidal forces. According to the analysis, the proposed method resulted in significant reduction in the size of dampers compared with the conventional installation methods. Les dispositifs passifs de dissipation d'énergie, tels que les amortisseurs visqueux, viscoélastiques et à friction, sont généralement installés dans les bâtiments en utilisant des entretoises diagonales ou en chevron. Afin d'accroître la force efficace d'amortissement et de réduire le volume de l'amortisseur, divers systèmes d'amplification du déplacement de l'amortisseur, tels qu'un système d'amortisseurs pour contreventements à fixations grenouillères et des amortisseurs à vérin hydraulique ont été développés avec l'augmentation du coût d'installation. Dans cette étude, un nouveau plan d'installation des amortisseurs passifs est proposé qui utilise des câbles installés de manière à ce qu'un déplacement relatif égal au déplacement des étages survienne entre le câble et la structure lorsque cette structure est soumise à une charge latérale. Les câbles peuvent être installés en continu ou en discontinu entre la fondation et l'étage supérieur de la structure. Pour vérifier la validité de la méthode proposée, une analyse dynamique non linéaire des structures de modèles avec amortisseurs viscoélastiques installés en utilisant la configuration proposée a été réalisée en utilisant les registres de trois séismes et de deux forces sinusoïdales. Selon les résultats de l'analyse, la méthode proposée permet de réduire significativement la dimension des amortisseurs par rapport aux méthodes conventionnelles d'installation. [ABSTRACT FROM AUTHOR]

This paper presents the results of an exploratory analysis of falling weight deflectometer (FWD) data collected on a large project about the spring thaw behaviour of pavements. The test site includes four test sections, two of which are conventional flexible pavement structures, whereas the other two are built with a cement-treated base. The aim of this study is to verify the applicability of using FWD time history data to evaluate damage to a road during the thawing period. The applicability of the analysis techniques is verified through the phase angle and dissipated energy. The data analyzed were obtained from tests conducted with an FWD on one flexible pavement test section. The results obtained showed a clear difference between the winter, thawing, and summer periods. It was found that the phase angle and dissipated energy can be used to evaluate the road damage during the thawing period through quantification of the phase angle and dissipated energy. These factors can also be used to describe the pavement behaviour in terms of elasticity and viscoelasticity. Cet article présente les résultats d'une analyse exploratoire de données de déflectomètre à masse tombante (FWD) colligées lors d'un grand projet sur le comportement des chaussées lors du dégel du printemps. Le site d'essai comprend quatre sections : deux ont des structures conventionnelles de chaussée flexible et les deux autres sont construites sur une fondation traitée au ciment. L'objectif de l'étude est de vérifier l'applicabilité des données historiques FWD pour évaluer le dommage à la route durant la période de dégel. L'applicabilité des techniques d'analyse est vérifiée par l'angle de phase et l'énergie dissipée. Les données analysées ont été obtenues lors d'essais réalisés avec le déflectomètre à masse tombante sur une section d'essai de chaussé flexible. Les résultats montrent une différence évidente entre les périodes d'hiver, de dégel et d'été. Il s'est avéré que l'angle de phase et l'énergie dissipée peuvent être utilisés pour évaluer les dommages à la route durant la période de dégel en quantifiant l'angle de phase et l'énergie dissipée et en décrivant le comportement de la chaussée en termes d'élasticité et de viscoélasticité. [ABSTRACT FROM AUTHOR]

The relaxation modulus E(t), creep compliance D(t), and complex modulus E*(ω) are functions often used to characterize the linear viscoelastic (LVE) behavior of hot mix asphalt (HMA). Interconversions among these LVE functions are often required. To perform an interconversion, one of the key steps is to express both the source and target LVE functions in Prony series representations. To obtain the corresponding Prony series coefficients, the collocation method and linear least squares method were often used in the past. However, the problem encountered with these two methods is in manually assigning part of the Prony series coefficients; resulting in unrealistic or negative Prony coefficients and big discrepancies between the fitting data and the original data. To address this problem, this paper developed a new algorithm by incorporating the Levenberg-Marquardt method. This new algorithm has four unique features, it (1) allows all the Prony series coefficients to be freely adjustable, (2) guarantees all positive Prony series coefficients, (3) determines all Prony series coefficients automatically and simultaneously, and (4) ensures very accurate interconversion through the fact that the fitting curve almost completely coincides with the original curve. Furthermore, to facilitate the implementation of practical applications of this new algorithm, it was incorporated into a stand-alone, windows-based software named “LVEmaster”. The simplicity and accuracy of this new interconversion software was demonstrated through a series of interconversions among HMA LVE functions. [ABSTRACT FROM AUTHOR]

This paper describes the development and application of a computational modeling approach incorporated with pertinent laboratory testing that can be used to predict fracture damage performance of bituminous paving mixtures. In the model, material viscoelasticity, mixture microstructure, and cohesive zone fracture properties are implemented within a finite element method, which is intended to simulate nonlinear-inelastic microscale fracture and its propagation to complete failure in bituminous mixtures. The model is applied to different materials, and the resulting model simulations are compared to experimental results for model validation. With some limitations and technical issues to be overcome in the future, the model presented herein clearly demonstrates several advancements based on its features accounting for material viscoelasticity, heterogeneity, and cohesive zone fracture. Potentially, the model can provide significant savings in time and costs and can also be used to improve currently available design analysis tools. [ABSTRACT FROM AUTHOR]

An analysis is performed to study the effect of variable viscosity and variable thermal conductivity on the flow and heat transfer of a thin viscoelastic liquid (obeying Walters' liquid B model) film on a horizontal unsteady stretching sheet taking into account the effect of viscous dissipation. The fluid viscosity is assumed to decrease exponentially with temperature but the thermal conductivity is assumed to vary as a linear function of temperature. Numerical solutions are obtained for some representative values of the viscosity and thermal conductivity variation parameters, unsteadiness parameter, and Eckert number. Typical temperature and velocity profiles, dimensionless film thickness, free-surface velocity and temperature, local skin-friction coefficient, and the local surface heat flux are obtained for a wide range of governing parameters. In general, it is found that a viscoelastic fluid is more sensitive to the variable fluid properties effect than a Newtonian fluid. Also, for constant and (or) variable fluid properties, the film thickness and the local surface heat flux of a viscoelastic fluid is small compared to that of a Newtonian fluid. For all values of the variable viscosity parameter and for both viscoelastic and Newtonian fluid films, the viscous dissipation effect increases the free-surface temperature significantly whereas it reduces the heat transfer rate markedly. However, viscous dissipation does not influence the velocity profiles of both Newtonian and viscoelastic liquid films impressively although the film thickness changes noticeably. [ABSTRACT FROM AUTHOR]

The impact of temperature on the linear viscoelastic region, which is characterized by critical strain, of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) was investigated at various temperatures between –100 and 220 °C for specimens with a moisture content of approximately 0.6%. The effect of oscillation frequency on the linear viscoelastic region under various constant temperatures was also examined. The results indicated that critical strain generally decreased with increasing temperature except at –80, –20, 40, 120, and 220 °C. These five exceptions were attributed to the occurrence of relaxation processes. With an increase in testing frequency from 1 to 20 Hz, the critical strain decreased slightly at all temperatures. It is suggested that the stored elastic energy and yield stress, which were obtained at critical strain, could be indicators to predict wood mechanical performance. [ABSTRACT FROM AUTHOR]

A dynamic analysis based on the spectral element method is described for the interpretation of falling weight deflectometer (FWD) tests on flexible pavements. This dynamic approach was implemented in the computer code Dynamic Analysis of Pavement - Université Laval (DYNAPAV-UL) that includes both frequency-independent hysteretic damping and frequency-dependent viscous damping material models. A parametric study was conducted on a four-layer flexible pavement to evaluate the influence of different layer moduli on deflection basins and deflection histories. The viscous behaviour of the asphalt concrete layer was also investigated. While the deflection basin currently used in static methods gives some details of the pavement response under transient loading, the simulations of FWD tests using the dynamic model suggest that the time histories should be included as well for the interpretation of FWD deflection measurements. In fact, important dynamic phenomena due to inertial effects and viscous effects are only revealed by deflection histories. [ABSTRACT FROM AUTHOR]

A one-dimensional model of the two-temperature generalized magneto-viscoelasticity with two relaxation times in a perfect conducting medium is established. The state space approach is adopted for the solution of one-dimensional problems for any set of boundary conditions. The resulting formulation together with the Laplace transform techniques are applied to a specific problem of a half-space subjected to thermal shock and traction-free surface. The inversion of the Laplace transforms is carried out using a numerical approach. Numerical results are given and illustrated graphically for the problem. Some comparisons have been shown in figures to estimate the effects of the temperature discrepancy and the applied magnetic field. [ABSTRACT FROM AUTHOR]

This paper presents constitutive design considerations for a semi-rigid, resin-impregnated fiberglass grid that enhances the mechanical performance of an asphalt concrete overlay and provides a pattern to retard crack propagation. An acrylic polymer resin covers the grid-structured fiberglass strands, thus making their viscoelastic nature compatible with the asphalt materials. The remarkable temperature susceptibility of the resin is observed using time-temperature superposition. The grid tensile strength of 100 kN/m was qualified using standard measurements. Three-point bending and cyclic fatigue loading mechanical tests affirm the retardation performance of the grid-reinforced system in terms of crack propagation. The retardation mechanism is affected by synchronizing the cracking pattern with the flexural stress-strain profile through image analysis. A National Center for Asphalt Technology full-scale road testing program provides assessment of the grid-reinforced pavements. A visual inspection of the grid extracted from the traffick zone showed fair condition of the pavement. Cet article présente les facteurs constitutifs de conception d’une grille semi-rigide en fibres de verre imprégnées de résine qui augmente le rendement mécanique d’un revêtement en béton asphaltique et qui permet de réduire la propagation des fissures. Une résine de polymère acrylique recouvre les brins de fibres de verre formant une grille, rendant ainsi leur nature viscoélastique compatible avec les matériaux asphaltiques. La susceptibilité remarquable à la température de la résine est observée en utilisant une superposition temps-température. La résistance à la traction de 100 kN/m de la grille a été quantifiée en utilisant des mesures normalisées. Les essais mécaniques de flexion à trois points et de charges de fatigue cyclique confirment l’efficacité de ralentissement de la propagation des fissures offerte par le système renforcé par une grille. Le mécanisme de retardement est s’effectue en synchronisant le patron de fissuration avec le profile contrainte-déformation en flexion grâce à l’analyse d’images. Un programme d’essais à pleine échelle sur route du National Center for Asphalt Technology permet l’évaluation des chaussées renforcées par ces grilles. Une inspection visuelle de la grille extraite d’une zone soumis au trafic a montré un état acceptable de la chaussée. [ABSTRACT FROM AUTHOR]

A micromechanical-based finite element (FE) model was used to predict the dynamic complex modulus ( E*) of the hot-mix asphalt (HMA). The microstructure of HMA was captured with a high resolution scanner. Two material phases (aggregates and sand mastic) of HMA were modelled with finite elements. The sand mastic herein was composed of fines and asphalt binder with some fine aggregates. The dynamic complex modulus of the sand mastic under different temperatures and loading frequencies was measured in an experimental program. The corresponding principles were applied to bridge the elastic simulation and viscoelastic behavior with the input of the viscoelastic mastic properties. The input parameters in the FE model include the dynamic complex modulus of the sand mastic, the elastic modulus of the aggregates, and the microstructure of the HMA. The E* values of the HMA were measured and used to compare the E* predicted from the FE model. It is found that the FE approach used in this paper has the ability to predict HMA dynamic modulus across a range of temperatures and loading frequencies. The FE prediction of the E* was compared with a recently developed discrete element modelling approach and found the E* prediction from these two approaches to be very similar. [ABSTRACT FROM AUTHOR]

The steady flow of an incompressible Oldroyd 8-constant fluid in the annular region between two spheres, or so-called spherical Couette flow, is investigated. The inner sphere rotates with anangular velocity Ω about the z-axis, which passes through the center of the spheres, while the outer sphere is kept at rest. The viscoelasticity of the fluid is assumed to dominate the inertia such that the latter can be neglected in the momentum equation. An analytical solution is obtained through the expansion of the dynamical variables in a power series of the dimensionless retardation time. The leading velocity term denotes the Newtonian rotation about the z-axis. The first-order term results in a secondary flow represented by the stream function that divides the flow region into four symmetric parts. The second-order term is the viscoelastic contribution to the primary viscous flow. The first-order approximation depends on the viscosity and four of the material time-constants of the fluid. The second-order approximation depends on the eight viscometric parameters of the fluid. The torque acting on the outer sphere has an additional term due to viscoelasticity that depends on all the material parameters of the fluid under consideration. For an Oldroyd-B fluid this contributed term enhances the primary torque but in the case of fluids with higher elasticity the torque components may be enhanced or diminished depending on the values of the viscometric parameters.PACS Nos.: 47.15.Rq [ABSTRACT FROM AUTHOR]

A weakly nonlinear interfacial wave propagating between two dielectric fluids and influenced by an oblique electric field is studied. The analysis considers the surface tension and viscoelastic effects. Due to the presence of streaming and viscoelasticity, a mathematical simplification is considered. The viscoelastic contribution is demonstrated through the boundary conditions. Therefore, the equations of motion are solved in the absence of the viscoelastic effects. The solutions of the linearized equations of motion under the nonlinear boundary conditions lead to a nonlinear characteristic equation governing the surface evolution. This equation is accomplished by utilizing cubic nonlinearity. Taylor theory is adopted to expand the characteristic nonlinear equation in the light of the multiple-scales technique. The perturbation analysis produces two levels of the solvability conditions, which are used to construct the Ginzburg–Landau equation. Stability criteria are discussed both theoretically and computationally in which stability diagrams are obtained. Under appropriate data choices, we can recover some reported works as limiting cases. The effects of the orientation of the electric fields on the stability configuration in linear as well as nonlinear approaches are discussed. PACS Nos.: 47.65.+a, 47.20.–k, 47.50.+d [ABSTRACT FROM AUTHOR]

The unsteady Hartmann flow, with heat transfer, of an electrically conducting incompressible non-Newtonian viscoelastic fluid between two parallel horizontal nonconducting porous plates is studied taking into consideration the Hall effect. A sudden uniform and constant-pressure gradient, an external uniform magnetic field that is perpendicular to the plates, and uniform suction and injection through the surface of the plates are applied. The two plates are kept at different but constant temperatures while the Joule and viscous dissipations are taken into consideration. Numerical solutions for the governing momentum and energy equations are obtained using finite-difference approximations. The effect of the Hall term, the parameter describing the non-Newtonian behavior, and the velocity of suction and injection on both the velocity and temperature distributions is examined.PACS No.: 47.27.-i [ABSTRACT FROM AUTHOR]

Fatigue of bituminous asphalts is one of the main types of pavement destruction. This phenomenon was studied extensively in Europe (RILEM) and in the United States (SHRP). There are no standardized tests in Quebec to assess asphalt fatigue resistance. In France, a new approach based on the determination of damage rates due to fatigue has been developed for a tension–compression test on asphalt core samples to study their fatigue strength. This paper presents a summary of the knowledge on asphalt fatigue. Damage rate analyses, developed by the DGCB (Département de Génie Civil et du Bâtiment) of the ENTPE at Lyon, is detailed and applied to stone matrix asphalt (SMA). Results show the validity of the approach by damage and the good fatigue damage strength of the SMA. [ABSTRACT FROM AUTHOR]

The equations of generalized thermo-viscoelasticity for an isotropic medium are given. Using Laplace transforms, a uniqueness theorem for these equations is proved. Also, a reciprocity theorem is obtained and some applications are given. PACS No.: 46.35.+z [ABSTRACT FROM AUTHOR]

The problem of the onset of stability in a horizontal layer of a viscoelastic dielectric liquid with one relaxation time heated from below under the action of a vertical ac electric field is analyzed. Linear stability theory is used to derive an eigenvalue system of order eight and an exact eigenvalue equation for a neutral instability is obtained. Under somewhat artificial boundary conditions, this equation can be solved exactly to yield the required eigenvalue relationship from which various critical values are determined in detail. The critical Rayleigh number and wave number for the onset of instability are presented graphically as functions of the Grashof number for various values of the Prandtl number and one relaxation time. A comparison is made with the results obtained in the absence of an electric field. [ABSTRACT FROM AUTHOR]

The flow of a conducting, viscoelastic fluid between two horizontal porous plates in the presence of a transverse-magnetic field is studied. The plates are assumed to be nonconducting and maintained at two fixed but different temperatures. The fluid viscosity is assumed to be temperature dependent and the fluid is subjected to a uniform suction from above and injection from below. The motion of the fluid is produced by a uniform horizontal pressure gradient. The equation of motion and the energy equation are solved numerically to yield the velocity and temperature distributions. [ABSTRACT FROM AUTHOR]