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We use lattice-Boltzmann simulations to examine late stage spinodal decomposition in binary fluids, showing that the scaling hypothesis for phase ordering does not hold in all cases. We also examine the effects of an applied shear on the coarsening of the spinodal pattern.

Using the proper time description and the usual cosmological observer field, it is possible to construct general space–time metrics representing a class of shearfree cosmological models.

In this paper, Split Hopkinson Bar technique was used to investigate the shear behaviour of adhesively bonded assemblies at high rates of loading. New sample geometry was adopted so that the compressive wave is transformed in a shear loading in the sample. Samples are conditioned at 20°C and 50% of hygrometry to eliminate any interference with temperature and humidity effects. The new technique is applied to an assembly built with a cyanoacrylate based adhesive and a metallic (Steel) adherent. They are found to be highly rate sensitive.

Molecular dynamic (MD) method is used to study the coalescence and fusing process of Au and Cu nanoclusters. The results show that shear deformation, surface and interface diffusion play important role in different stages of all simulation procedure. In most cases, shear deformation produces the twin boundary or/and stacking fault in particles by particle rotation and slide. The angle between the {111} of Au and Cu particles decrease with increasing temperature, which promotes the formation of the stable interface. Furthermore, the coalescence point and melting temperature increase as cluster diameter increases. For the other cases, there are no particle rotation and slide phenomenon in the elevating temperature process because the stable interface can be formed by forming twin boundaries once two particles contact.

A model is proposed for a collapsing radiating star consisting of a fluid with shear motion undergoing radial heat flow with outgoing radiation. The pressure of the star, at the beginning of the collapse, is isotropic but due to the presence of the shear motion of the fluid the pressure becomes more and more anisotropic. The radial and temporal behaviors of the density, the pressure, the total mass, the luminosity, the effective adiabatic index and the Kretschmann scalar are analyzed for a star with 6 M_⊙. The final evolution is a star that radiates all its mass during the collapse, and thus, neither forming a black hole, as in the previous model, nor a naked singularity.

A recent study of dissipative collapse considered a contracting sphere in which the areal and proper radii are equal throughout its evolution. The interior space–time was matched to the exterior Vaidya space–time which generated a temporal evolution equation at the boundary of the collapsing sphere. We present a solution of the boundary condition which allows the study of the gravitational and thermodynamical behavior of this particular radiating model.

A new model is proposed to collapsing stars consisting of an anisotropic fluid with bulk viscosity, radial heat flow and outgoing radiation. In a previous paper one of us has introduced a time-dependent function into the g_rr, besides the time-dependent metric functions g_θθ and g_ϕϕ. The aim of this work is to generalize this previous model by introducing bulk viscosity and comparing it to the non-viscous collapse. The behavior of the density, pressure, mass, luminosity and the effective adiabatic index is analyzed. Our work is also compared to the case of a collapsing fluid with bulk viscosity of another previous model, for a star with 6 M_⊙. The pressure of the star, at the beginning of the collapse, is isotropic, but due to the presence of the bulk viscosity the pressure becomes more and more anisotropic. The black hole is never formed because the apparent horizon formation condition is never satisfied, in contrast to the previous model where a black hole is formed. An observer at infinity sees a radial point source radiating exponentially until it reaches the time of maximum luminosity, and suddenly the star turns off. This is in contrast to the former model where the luminosity also increases exponentially, reaching a maximum and decreases thereafter until the formation of the black hole. The effective adiabatic index diminishes due to the bulk viscosity, thus increasing the instability of the system, in both models, in the former paper as well as in this work.

In this paper, we investigate the effect of charge on the collapse of a radiating, shearing sphere. The junction conditions required for the smooth matching of a general spherically symmetric spacetime (in the absence of rotation) to the exterior Vaidya–Reissner–Nordström leads to a temporal evolution equation at the boundary of the collapsing star. We are in a position to integrate these equations in the presence of charge and shear. The solutions obtained here are new and generalize recent treatments of dissipative, shearing collapse to the charged case.

In this paper, we investigate the physics of a radiating star undergoing dissipative collapse in the form of a radial heat flux. Our treatment clearly demonstrates how the presence of shear affects the collapse process; we are in a position to contrast the physical features of the collapsing sphere in the presence of shear with the shear-free case. By employing a causal heat transport equation of the Maxwell–Cattaneo form we show that the shear leads to an enhancement of the core temperature thus emphasizing that relaxational effects cannot be ignored when the star leaves hydrostatic equilibrium.

In order to study the type of collapse mentioned in the title, we introduce a physically meaningful object, called the horizon function. It directly enters the expressions for many of the stellar characteristics. The main junction equation, which governs the collapse, transforms into a Riccati equation with simple coefficients for the horizon function. We integrate this equation in the geodesic case. The same is done in the general case when one or another of the coefficients vanish. It is shown how to build classes of star models in this formulation of the problem and simple solutions are given.

This study investigates the roles of fracture roughness, normal stress and shear displacement on the fluid flow characteristics through three-dimensional (3D) self-affine fractal rock fractures, whose surfaces are generated using the modified successive random additions (SRA) algorithm. A series of numerical shear-flow tests under different normal stresses were conducted on rough rock fractures to calculate the evolutions of fracture aperture and permeability. The results show that the rough surfaces of fractal-based fractures can be described using the scaling parameter Hurst exponent $(H)$, in which $H=3-D_f$, where $D_f$ is the fractal dimension of 3D single fractures. The joint roughness coefficient (JRC) distribution of fracture profiles follows a Gauss function with a negative linear relationship between $H$ and average JRC. The frequency curves of aperture distributions change from sharp to flat with increasing shear displacement, indicating a more anisotropic and heterogeneous flow pattern. Both the mean aperture and permeability of fracture increase with the increment of surface roughness and decrement of normal stress. At the beginning of shear, the permeability increases remarkably and then gradually becomes steady. A predictive model of permeability using the mean mechanical aperture is proposed and the validity is verified by comparisons with the experimental results reported in literature. The proposed model provides a simple method to approximate permeability of fractal-based rough rock fractures during shear using fracture aperture distribution that can be easily obtained from digitized fracture surface information.

In the technology of optical surface measurement, the phase-shifting shear interferometer had been widely used. In measurement, the phase-shifting was introduced in time domain, and the measurement system adopted double optical path for change phase-shifting and shear, so the measurement accuracy was limited. To decrease error, a commonpath phase-shifting shear system based on birefringent optical devices was introduced. In this system, the lateral shear and phase-shifting 0, π/2, π, 3π/2 was introduced in the commonpath optical system. Because the birefringent optical devices can introduce shear in the collinear optical system, a new Jones matrix was established. Based on the Jones matrix theory, the principle theory was analyzed in detail. In the experiment, an optical surface was measured with this system. The theoretical analysis and experiment results demonstrate the feasibility of this approach.

Use of thin-walled steel sections in structures represents a tread further in the exploitation of structural form from its early ponderousness to the present day's trend towards tenuity. In the past seventy years, extensive experimental and analytical research has been carried out to examine the behavior of thin-walled structures containing openings. The experimental results have not been fully utilized by other researchers. As part of this review, an endeavor is made to cluster the experimental and analytical results with particular importance on plates, beams and plate girders and compression members and cellular structures containing perforations as an elucidative database using a handy spreadsheet program written in Visual Basic.

In the Great Hanshin–Awaji earthquake of 1995, the phenomena of repetitive inelastic buckling were observed in many steel girders including horizontal girders of portal steel piers on elevated highways. The authors have been interested in the ability of steel girders to dissipate the hysteretic plastic strain energy due to such repetitive buckling of steel girders for earthquake-resistance design. This paper is focused on the repetitive buckling behavior of eight steel plate girders under inelastic shear or the combined shear and bending due to a concentrated point load adopting two independent cyclic loading patterns. The model girders were selected considering the combined variations of flange thickness, flange width and depth-to-thickness ratio of the web. Good correlations were found between the results of tests and finite element analyses using shell elements considering the material and geometrical nonlinearities in the repetitive inelastic buckling behavior of plate girders.

In the framework of the Reissner–Simo rod theory and following Haringx’ approach for studying axial buckling in shear deformable rods, we give a mechanical interpretation of tensile instability, together with its mathematical justification, and we perform a linearized eigenvalue buckling analysis for tense planar rods. Buckled shapes and critical loads are calculated for most usual boundary conditions.

This paper presents a new analysis of the physics of closed head injury following brief, intense acceleration of the head. It focuses upon the buoyancy of the brain in cerebrospinal fluid, which protects against damage; the propagation of strain waves through the brain substance, which causes damage; and the concentration of strain in critical anatomic regions, which magnifies damage. Numerical methods are used to create animations or "movies" of brain motion and deformation. Initially, a 1 cm gap filled with cerebrospinal fluid (CSF) separates the brain from the skull. Whole head acceleration induces artificial gravity within the skull. The brain accelerates, because its density differs slightly from that of CSF, strikes the inner aspect of the skull, and then undergoes viscoelastic deformation. The computed pattern of brain motion correlates well with published high-speed photographic studies. The sites of greatest deformation correlate with sites of greatest pathological damage. This fresh biomechanical analysis allows one to visualize events within the skull during closed head injury and may inspire new approaches to prevention and treatment.

This paper presents a new analysis of the physics of closed head injury caused by intense acceleration of the head. At rest a 1 cm gap filled with cerebrospinal fluid (CSF) separates the adult human brain from the skull. During impact, whole head acceleration induces artificial gravity within the skull. Because its density differs slightly from that of CSF, the brain accelerates, strikes the inner aspect of the rigid skull, and undergoes viscoelastic deformation. Analytical methods for a lumped parameter model of the brain predict internal brain motions that correlate well with published high-speed photographic studies. The same methods predict a truncated hyperbolic strength-duration curve for impacts that produce a given critical compressive strain. A family of such curves exists for different critical strains. Each truncated hyperbolic curve defines a head injury criterion (HIC) or threshold for injury, which is little changed by small offsetting corrections for curvature of the brain and for viscous damping. Such curves predict results of experimental studies of closed head injury, known limits for safe versus dangerous falls, and the relative resistance of smaller versus larger animals to acceleration of the head. The underlying theory provides improved understanding of closed head injury and better guidance to designers of protective equipment and to those extrapolating research results from animals to man.

The aim of this study was to model the blood flow and predict related hemodynamics characteristics in healthy superior mesenteric artery (SMA) and saccular aneurysm cases. A fluid–structure interaction (FSI) method was performed, using an arbitrary Langrangian–Eulerian mesh. The computational mesh was generated using anatomical data from available human computed tomography (CT)-images. Combining constitution and momentum equations, projection method, the discretized resultant equation were numerically solved for velocity, pressure, shear stress and vortices for healthy/aneurysmal artery. The results including velocity contours, pressure contours, shear rate values, and vortices were obtained and analyzed for three main steps including peak systole, diastole, and end of cardiac cycle. Profiles show the varying velocity and pressure for a pulsatile flow input before and after aneurysms. They also show the formation of single or multiple vortices at aneurysmal area and decrease of wall shear stress with aneurysm enlargement. Furthermore, shear rate values at the neck of aneurysms exceed throughout the entire cardiac cycle. The outcome of the computational analysis is then compared to information available on pressure, vortices and wall shear stress from some clinical findings.

The homogeneous and anisotropic Bianchi type-V cosmological model with variable gravitational and cosmological “constants” with a general (nonstiff) perfect fluid is investigated. The Einstein field equations (EFEs) are numerically integrated with the fourth-order Runge–Kutta method for different values of $\alpha$ and $\beta$ parameters of quantum fields in a curved and expanding background. Three realistic models, namely matter, radiation and phantom dark energy models are also discussed. In all these models, it was found that the cosmological “constant” decreases with time, whereas the gravitational “constant” increases over time. It is shown that the universe in these models becomes isotropic at late times.

We investigate the role of bulk and shear viscosity in the spatially homogeneous anisotropic spacetime, in particular, the Kantowski–Sachs (KS) spacetime. General conditions for the bouncing evolution of universe in anisotropic background have been obtained by using the derived propagation equations of expansion scalar, shear scalar and spatial 3-curvature. We show that the presence of shear viscosity in the model prohibits the energy density to attain its extremum in the bouncing model. We explore the qualitative behavior of KS cosmologies by formulating the Einstein’s field equations into a plane-autonomous system of equations by taking dimensionless equation of state. The stability of the system has been investigated by evaluating and analyzing the eigenvalues at the critical points. The stable solutions exist for the system composed of bulk and shear viscosity. The present analysis through dynamical system method illustrates that the universe does not exhibit synchronous bounce with perfect fluid and/or viscous fluids in the KS spacetime.