Search

In this paper, the global-in-time inviscid limit of the three-dimensional (3D) isentropic compressible Navier-Stokes equations is considered. First, when viscosity coefficients are given as a constant multiple of density's power ((ρ ϵ) δ with δ > 1), for regular solutions to the corresponding Cauchy problem, via introducing one "quasi-symmetric hyperbolic"–"degenerate elliptic" coupled structure to control the behavior of the velocity near the vacuum, we establish the uniform energy estimates for the local sound speed in H 3 and (ρ ϵ) δ − 1 2 in H 2 with respect to the viscosity coefficients for arbitrarily large time under some smallness assumption on the initial density. Second, by making full use of this structure's quasi-symmetric property and the weak smooth effect on solutions, we prove the strong convergence of the regular solutions of the degenerate viscous flow to that of the inviscid flow with vacuum in H 2 for arbitrarily large time. It is worth pointing out that the result obtained here seems to be the first one on the global-in-time inviscid limit of solutions with large velocities and vacuum for compressible flow in 3D space without any symmetric assumption. [ABSTRACT FROM AUTHOR]

Abstract A multi-phase porous media transport model is built using distributed sublimation front approach and fixed grid meshing in order to simulate the freeze drying process. The model is tested numerically in multi-dimensions using 1D, 2D and 3D models. Models are solved for different aspect ratios with different heating methods like surface radiation, surface conduction and volumetric (microwave) heating. The involved critical parameters are discussed comprehensively in the results such as the maximum operating temperature, the maximum sublimation pressure, the total drying time and the overall power consumption. The results show that at low aspect ratios in surface heating technique, the 3D model is mandatory due to the large deviation in the drying time, maximum temperature and maximum pressure with both 2D and 1D models. Comparison between the present model and previous experimental and numerical works has been executed and good agreement has been observed. Highlights • Freeze drying is simulated via multi-phase porous media transport model. • Models are solved for different aspect ratios. • Surface heating and volume heating approaches are investigated. • The 3D model is mandatory at high aspect ratios. [ABSTRACT FROM AUTHOR]

Highlights • The asymptotic solution to the elasticity system in the vicinity of an crack in a 3-D domain is provided with emphasis to the T-stress. • Having this expansion, and using the quasi-dual function method we extract the T-stress from FE solutions. • Numerical examples show the efficiency and accuracy of the methods for the extraction of the edge T-stress. Abstract The T-stress in a three dimensional elastic domain containing a straight crack is considered. First the complete asymptotic expansion in the vicinity of the crack front, including the T-stress, is presented explicitly. Having obtained the asymptotic expansion, we compute the dual solution associated with the T-stress, and prove it must contain logarithmic terms. This dual solution is used to extend the quasi dual function method (QDFM) for the extraction of the T-stress from finite element solutions and express it as a function along the crack front. Since the stress field tends to infinity at the crack front whereas the T-stress remains constant, its extraction from finite element solutions, containing numerical errors, is a non-trivial task. We herein develop accurate and efficient methods for extracting the T-stress function along the crack edge by the QDFM. Numerical examples are provided for the computation of the T-stresses from conventional and high order finite element methods. [ABSTRACT FROM AUTHOR]

The competitive growth of bicrystals during directional solidification in both thin samples and three-dimensions (3D) was investigated by phase-field simulations. Unlike previous studies, which assumed the <001> orientation of the two competing grains to be in the same plane or in two parallel planes which are normal to the contacting plane of two grains, simulations in the present study focused on the more common configurations in which the <001> orientation of the two grains is non-uniplanar. Simulations of competitive growth in thin samples showed that the deviation of the <001> orientation of an unfavorably orientated grain from the sample plane caused difficulty in the generation of new primary arms from the unfavorably orientated grain. Therefore, the grain boundary orientation in thin samples may deviate from that in two-dimensions (2D), even though the bicrystal configuration observed in the thin-sample plane appeared similar to that in the 2D. It was found that in 3D, the new primary arms could develop from the favorably oriented dendrites along two directions to occupy the gap left by the unfavorably orientated grains, which led to a faster overgrowth rate of the unfavorably orientated grains than that in the case of diverging growth in 2D. [ABSTRACT FROM AUTHOR]

A high-resolution computer-generated stereogram for forming full-parallax three-dimensional (3-D) images is proposed. A full-parallax 3-D image is formed from 825 two-dimensional (2-D) projections and can be observed in a wide angular range. The stereogram is a reflective diffractive optical element (DOE) that consists of 50 x 50 μm² hogels, where each hogel corresponds to one pixel of the 2-D frames. A phase-type kinoform is computed in every hogel by solving a nonlinear inverse problem. The DOE relief is fabricated using electron-beam technology with pixel size of 0.2 x 0.2 μm². The effectiveness of the technology developed is illustrated by photographs and a video of a real DOE under monochromatic light and under white light. The new high-resolution full-parallax stereograms can be used for protecting bank notes, documents, and ID cards against counterfeit. [ABSTRACT FROM AUTHOR]

This paper presents a new set of three-dimensional rotation invariant texture descriptors based on the well-known local binary patterns (LBPs). In the approach proposed here, we extend an existing three-dimensional LBP based on the region growing algorithm using existing features developed exquisitely for two-dimensional LBPs (pixel intensities and differences). We have conducted experiments on a synthetic dataset of three-dimensional randomly rotated texture images in order to evaluate the discriminatory power and the rotation invariant properties of our descriptors as well as those of other two-dimensional and three-dimensional texture descriptors. Our results demonstrate the effectiveness of the extended LBPs and improvements against other state-of-the-art hand-crafted three-dimensional texture descriptors on this dataset. Furthermore, we prove that the extended LBPs can be used in medical datasets to discriminate between MR images of oxygenated and non-oxygenated brain tissues of newborn babies. [ABSTRACT FROM AUTHOR]

point light source (PLS) display with enhanced viewing angle (VA) is proposed. The maximum VA of a conventional PLS display is equal to the propagation angle of the PLS, so a light-source array (3 × 3) was used to enlarge the propagation angle of the PLS in the horizontal and vertical directions. The number of converging elemental image points increases due to the large propagation angle of the PLS; thus, the VA of the integrated point was enhanced. From the experimental results, the VA of the proposed method was 2.6 times larger than the maximum VA of a conventional PLS display [ABSTRACT FROM AUTHOR]

Three-dimensional mini-permeametry ofDiplocraterionburrows from the Middle Jurassic Scarborough Formation of North Yorkshire, UK, reveals some of the relationships between ichnofossils and reservoir quality in conventional siliciclastic petroleum reservoir facies. This work focuses on the effect that the variousDiplocraterionburrowing behaviours have on the permeability characteristics of the near-burrow environment. Samples were studied using serial grinding and mini-permeametry. This is the first documented attempt at combining these techniques to create an integrated understanding of the inter relationship of trace fossil morphology and reservoir quality in three dimensions. Palaeobiological insights arising from the three-dimensional modelling include evidence for resuspension feeding, deposit feeding, sediment cleaning and “collapse-cone feeding.” Higher than expected permeability values (>150 mD) were measured from the sandy shafts ofDiplocraterion and adjacent areas. Zones of enhanced permeability associated with the inter-shaft area are inferred to result from sediment cleaning, and grain-size selective deposit feeding. Bioturbation byDiplocraterionis found to improve reservoir quality by sediment cleaning and creation of highly permeable vertical conduits in a reservoir facies with otherwise low permeability. [ABSTRACT FROM PUBLISHER]

The reflection performance of periodic acoustic metasurfaces (AMs) subjected to a grazing flow, consisting of a uniform region and a finite sheared layer, is studied. A convective generalized Snell's law (CGSL) is derived to account for the effect of uniform mean flows on the reflection of AMs. Then, an AMs design method considering the mean flow profile is proposed based on the impedance transformation method. The strategy is to form a reflected phase gradient at the interface plane between the uniform and the sheared flow regions. The reflection characteristics of two acoustic porous metasurfaces (APMs), i.e., APM1 and APM2 designed for the uniform and the sheared flows, respectively, are numerically investigated. Results show that APM1 achieves efficient anomalous reflections in uniform flows, and the diffracted orders and directions of the reflected waves are well predicted by the proposed CGSL. However, the performance of APM1 deteriorates under oblique incidences if applied to a typical sheared flow. In contrast, APM2 realizes desired wavefront manipulations under the same conditions. Finally, the CGSL is extended into a three-dimensional (3D) space and is validated numerically. This study provides a means for AMs design in flow conditions, which holds good potential in aeroacoustic noise problems. [Display omitted] • A CGSL is derived to predict the reflection of AMs in a uniform flow. • An AMs design method is proposed to account for the effect of sheared flows. • The designed APM realizes reflected wavefront manipulation in a sheared flow. • The 3D reflection performance of AMs subjected to the external flows is studied. [ABSTRACT FROM AUTHOR]

A novel cell-centred control-volume distributed multi-point flux approximation (CVD-MPFA) finite-volume formulation is presented for discrete fracture–matrix simulations on unstructured grids in three-dimensions (3D). The grid is aligned with fractures and barriers which are then modelled as lower-dimensional surface interfaces located between the matrix cells in the physical domain. The three-dimensional pressure equation is solved in the matrix domain coupled with a two-dimensional (2D) surface pressure equation solved over fracture networks via a novel surface CVD-MPFA formulation. The CVD-MPFA formulation naturally handles fractures with anisotropic permeabilities on unstructured grids. Matrix–fracture fluxes are expressed in terms of matrix and fracture pressures and define the transfer function, which is added to the lower-dimensional flow equation and couples the three-dimensional and surface systems. An additional transmission condition is used between matrix cells adjacent to low permeable fractures to couple the velocity and pressure jump across the fractures. Convergence and accuracy of the lower-dimensional fracture model is assessed for highly anisotropic fractures having a range of apertures and permeability tensors. A transport equation for tracer flow is coupled via the Darcy flux for single and intersecting fractures. The lower-dimensional approximation for intersecting fractures avoids the more restrictive CFL condition corresponding to the equi-dimensional approximation with explicit time discretisation. Lower-dimensional fracture model results are compared with equi-dimensional model results. Fractures and barriers are efficiently modelled by lower-dimensional interfaces which yield comparable results to those of the equi-dimensional model. Pressure continuity is built into the model across highly conductive fractures, leading to reduced local degrees of freedom in the CVD-MPFA approximation. The formulation is applied to geologically complex fracture networks in three-dimensions. The effects of the fracture permeability, aperture and grid resolution are also assessed with respect to convergence and computational cost. [ABSTRACT FROM AUTHOR]

Our ability to process information about an object’s location in depth varies along the horizontal and vertical axes. These variations reflect functional specialisation of the cerebral hemispheres as well as the ventral/dorsal visual streams for processing stimuli located in near and far space. Prior research has demonstrated visual field superiorities for processing near space in the lower and right hemispaces and for far space in the upper and left hemispaces. No research, however, has directly tested whether the functional specialisation of the visual fields actually makes objects look closer when presented in the lower or right visual fields. To measure biases in the perception of depth, we employed anaglyph stimuli where participants made closer/further judgments about the relative location of two spheres in a three-dimensional virtual space. We observed clear processing differences in this task where participants perceived the right and lower spheres to be closer and the left and upper spheres to be further away. Furthermore, no relationship between the horizontal and vertical dimensions was observed suggesting separate cognitive/neural mechanisms. Not only does this methodology clearly demonstrate differences in perceived depth across the visual field, it also opens up many possibilities for studying functional asymmetries in three-dimensional space. [ABSTRACT FROM AUTHOR]

While color video endoscopy has enabled wide-field examination of the gastrointestinal tract, it often misses or incorrectly classifies lesions.Many of thesemissed lesions exhibit characteristic three-dimensional surface topographies. An endoscopic system that adds topographical measurements to conventional color imagery could therefore increase lesion detection and improve classification accuracy. We introduce photometric stereo endoscopy (PSE), a technique which allows high spatial frequency components of surface topography to be acquired simultaneously with conventional two-dimensional color imagery.We implement this technique in an endoscopic form factor and demonstrate that it can acquire the topography of small features with complex geometries and heterogeneous optical properties. PSE imaging of ex vivo human gastrointestinal tissue shows that surface topography measurements enable differentiation of abnormal shapes from surrounding normal tissue. Together, these results confirm that the topographical measurements can be obtained with relatively simple hardware in an endoscopic form factor, and suggest the potential of PSE to improve lesion detection and classification in gastrointestinal imaging. [ABSTRACT FROM AUTHOR]

Abstract: This study investigated synergistic actions of hand–pen contact forces during circle drawing tasks in three-dimensional (3D) space. Twenty-four right-handed participants drew thirty concentric circles in the counterclockwise (CCW) and clockwise (CW) directions. Three-dimensional forces acting on an instrumented pen as well as 3D linear and angular positions of the pen were recorded. These contact forces were then transformed into the 3D radial, tangential, and normal force components specific to circle drawing. Uncontrolled manifold (UCM) analysis was employed to calculate the magnitude of the hand–pen contact force synergy. Three hypotheses were tested. First, hand–pen contact force synergies during circle drawing are dependent on the angular position of the pen tip. Second, hand–pen contact force synergies are dependent on force components in circle drawing. Third, hand–pen contact force synergies are greater in CCW direction than CW direction. The results showed that the strength of the hand–pen contact force synergy increased during the initial phase of circle drawing and decreased during the final phase. The synergy strength was greater for the radial and tangential components as compared to the normal component. Also, the circle drawing in CW direction was associated with greater hand–pen contact force synergy than the CCW direction. The results of this study suggest that the central nervous system (CNS) prioritizes hand–pen contact force synergies for the force components (i.e., radial and tangential) that are critical for circle drawing. The CNS modulates hand–pen contact force synergies for preparation and conclusion of circle drawing, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Multi-layer biodegradable polymer drug delivery microstructures with micro-chambers have many exceptional advantages in a long-term controlled drug delivery. In this paper, a mathematical model for the drug release from this type of three-dimensional (3D) drug delivery microstructures is presented by using 3D cellular automata and discrete iterations. The validity of the model is proved by comparing with the Gőpferich’s simulated profiles for the same composite polymer cylinder matrices. Based on this model, furthermore, the simulations are done to describe the dynamic behavior of drug release from this type of microstructures. The simulation results show that this 3D mathematical model can describe accurately the drug release behavior and therefore can provide a new optimal design tool for this kind of multi-layer biodegradable polymer drug delivery microstructure. [Copyright &y& Elsevier]

We consider a Dirichlet boundary-value problem for the three-dimensional convection-diffusion equations with constant coefficients in the unit cube. A high order compact finite difference scheme is constructed on a 19-point stencil using the Steklov averaging operators. We prove that the finite difference scheme converges in discrete W 2m (ω)-norm with the convergence rate O(hs-m), where the real parameter s satisfies the condition max(1.5, m) < s ≤ m + 4, m = 0, 1, 2, and the exact solution belongs to the Sobolev space W2s (Ω). [ABSTRACT FROM AUTHOR]

Abstract: The nearly singular integrals occur in the boundary integral equations when the source point is close to an integration element (as compared to its size) but not on the element. In this paper, the concept of a relative distance from a source point to the boundary element is introduced to describe possible influence of the singularity of the integrals. Then a semi-analytical algorithm is proposed for evaluating the nearly strongly singular and hypersingular integrals in the three-dimensional BEM. By using integration by parts, the nearly singular surface integrals on the elements are transformed to a series of line integrals along the contour of the element. The singular behavior, which appears as factor, is separated from remaining regular integrals. Consequently standard numerical quadrature can provide very accurate evaluation of the resulting line integrals. The semi-analytical algorithm is applied to analyzing the three-dimensional elasticity problems, such as very thin-walled structures. Meanwhile, the displacements and stresses at the interior points very close to its bounding surface are also determined efficiently. The results of the numerical investigation demonstrate the accuracy and effectiveness of the algorithm. [Copyright &y& Elsevier]

Analysis of the dermo-epidermal surface in three-dimensions has great value in evaluating cosmetics. One approach is based on the active contour model, which is used extensively in computer vision and image processing applications, particularly for local object boundaries with closed curve form. The dermo-epidermal surface, however, is a plane with open form. We have developed a method of automatically extracting the dermo-epidermal surface from volumetric confocal microscopic images, as well as constructing a 3D visual model of the surface by using the geometric information contained in the control points. Our method is a 3D extension of the active contour model, so we call it the active open surface model (AOSM). The initial surface for AOSM is an open curve plane, guided by a 3D internal force, a 3D external constraint force, and a 3D image force, which pull it towards the objective surface. The proposed tecnique has been applied to extract actual dermo-epidermal surface in the given volumetric confocal microscopic images. [ABSTRACT FROM AUTHOR]

In this paper, the Cauchy problem for the three-dimensional (3-D) isentropic compressible Navier-Stokes equations with degenerate viscosities is considered. By introducing some new variables and making use of the "quasi-symmetric hyperbolic"–"degenerate elliptic" coupled structure to control the behavior of the fluid velocity, we prove the global-in-time well-posedness of regular solutions with vacuum for a class of smooth initial data that are of small density but possibly large velocities. Here the initial mass density is required to decay to zero in the far field, and the spectrum of the Jacobi matrix of the initial velocity are all positive. The result here applies to a class of degenerate density-dependent viscosity coefficients, is independent of the BD-entropy, and seems to be the first on the global existence of smooth solutions which have large velocities and contain vacuum state for such degenerate system in three space dimensions. [ABSTRACT FROM AUTHOR]

Discusses the American Board of Forensic Odontology's measurement tool for photographic documentation and analysis of bitemarks and wound patterns. Capability to rectify distortion due to incorrect camera position and angulation; Ability to analyze and give accurate life-size reproduction in three-dimensional space and facilitate forensic analysis.