Transparent Boundaries Research Articles

Crystal Plasticity Analyses Around Grain Boundaries Using a Dislocation Dynamics Finite Element Model

We setup a dislocation dynamics finite element framework by bridging a dislocation dynamics program and an open source finite element program. As part of initial verification, deformation of single crystal micro-pillar having single and double glide activation is demonstrated. A case study of a twin boundary is presented wherein the dislocation pile-up at the grain boundary and formation of a residual dislocation are shown. For studying the dislocation interactions with other grain boundaries, model grain boundaries are considered. We consider three synthetic grain boundaries namely transparent, semi-transparent, and impenetrable. The model’s transparent and semi-transparent grain boundaries contain no dislocations and very low density of dislocations in them, respectively, and thus low number of interactions with other dislocations. More junctions and cross-slip occurrences are recorded near the semi-transparent grain boundary. The most dislocation–dislocation interactions near grain boundaries result into glissile junctions. The current results are compared against literature data and it is observed that other than junction formation, cross-slip is very frequency observed near grain boundaries.

Transparent boundaries as scenographies of trust: the COVID-19 pandemic from the view of material cultural studies and artistic works

From the start, the profound transformations that accompanied the COVID-19 pandemic found expression in a plethora of objects and facilities that dominated our daily lives far beyond the clinical sphere....

THE EFFECT OF VARIED ENRICHMENT TYPES ON SNAKE BEHAVIOR.

Environmental enrichment is a strategy used to improve the welfare of animals under human care. While enrichment techniques for mammals and birds have been studied extensively, reptilian enrichment has received less attention. There has been an increase in enrichment programs for reptiles in zoological institutions, however many are not accompanied by behavioral studies. Detailed recording of behavioral responses to enrichment is necessary to assess the efficacy of the enrichment type and to determine its utility in various settings. In this study, 18 snakes of multiple species, from two Families (Colubridae, Pythonidae), were exposed to four enrichment types (Humid Hide, Olfactory, Climbing, Suspended Hide). Baseline recordings were conducted prior to the introduction of enrichment. Snakes were recorded for two hours after introduction of each item. Five behavior types were identified based on baseline videos: tongue flicking, climbing, hiding, interacting with transparent boundaries, and utilizing non-enrichment items. Interacting with transparent boundaries was classified as an undesirable behavior, while the other four behaviors were classified as desirable. Changes in climbing and tongue flicking behaviors were noted with introduction of each item- these changes were not statistically significant. The increase in these behaviors may indicate clinical importance, and shows that snakes under human care respond to environmental enrichment. As some snakes showed a reduction in undesirable behaviors when compared to baseline conditions, this may suggest increased welfare during times when enrichment is offered. The extent to which these results can be applied to other species merits further study.

Infinite perimeter selective segmentation model

Accurate boundary determination and segmentation of an object of interest in an image is a difficult image segmentation task. In this paper, we propose a new model which improves the old selective segmentation of Rada et al. [23] by combining two penalization and two fitting terms. To better deal with oscillatory boundaries, a H^1 weighted length term and L^2 Lebesgue measure have been employed as penalization terms, whereas the fitting terms consist of a region-based and area fitting term. The model has the same speed as the previous one-level set interactive segmentation model by Rada et al. [23] and much faster compared to previously dual-level set models by Rada et al. [25, 24] by having the same segmentation accuracy and reliability. On the other hand, the model shows a better performance while dealing with irregular and oscillatory object boundaries compared to Rada et al. [25] model. Further comparison with segmentation algorithms of the same nature, such as the Nguyen et al. [21] method, shows that the proposed model shows the same or improved performance for object segmentation with transparent boundaries or inhomogeneous intensity of the aimed object. Through experiments, it is shown that the proposed model finds the aimed object boundaries successfully for smooth or challenging oscillatory topological structures.

Natural and mixed convection in a vertical water-flow chamber in the presence of solar radiation

Natural and mixed convection in a vertical plane channel in the presence of solar radiation are analytically studied. The physical problem under consideration simulates water flow and heat transfer in a chamber with transparent rigid boundaries exposed to solar radiation. The intensity of the volumetric heat source across the channel declines exponentially as described by the Beer–Lambert law for light absorption in near-infrared and visible spectra. The flows are assumed laminar and fully-developed. The properties of the liquid are considered constant except for the variation of density defining the Boussinesq term in the momentum equation. For both natural and mixed convection it is possible to observe one, two or no reverse flows and the conditions for the existence of reverse flows are derived. Heat fluxes across the chamber as well as the power outlet and the bulk liquid temperature are calculated for values of the Reynolds number between zero and 500 and the Prandtl number for water. It is shown that the solar heat source in combination with the liquid heating from the chamber walls has a pronounced effect on the flow behavior and the heat transfer.

On the effect of slip transfer at grain boundaries on the strength of FCC polycrystals

The effect of slip transfer on the flow strength of various FCC polycrystals was analyzed by means of computational homogenization of a representative volume element of the microstructure. The crystal behavior was governed by a physically-based crystal plasticity model in the framework of finite strains where slip transfer at grain boundaries was allowed between slip systems suitably oriented according to geometrical criteria. Conversely, slip transfer was blocked if the conditions for slip transfer were not fulfilled, leading to the formation of dislocation pile-ups. All the model parameters for each material were identified from either dislocation dynamics simulations or experimental data from the literature. Slip transfer led to a reduction in the flow stress of the polycrystals (as compared with the simulations with opaque grain boundaries) which was dependent on the fraction of translucent and transparent grain boundaries in the microstructure. Moreover, dislocation densities and Von Mises stresses were much higher around opaque grain boundaries, which become suitable places for damage nucleation. Finally, predictions of the Hall–Petch effect in Al, Ni, Cu and Ag polycrystals including slip transfer were in better agreement with the literature results, as compared with predictions assuming that all grain boundaries are opaque, particularly for small grain sizes (<20μm).

Emerging ASL Distinctions in Sign-Speech Bilinguals' Signs and Co-speech Gestures in Placement Descriptions.

Previous work on placement expressions (e.g., “she put the cup on the table”) has demonstrated cross-linguistic differences in the specificity of placement expressions in the native language (L1), with some languages preferring more general, widely applicable expressions and others preferring more specific expressions based on more fine-grained distinctions. Research on second language (L2) acquisition of an additional spoken language has shown that learning the appropriate L2 placement distinctions poses a challenge for adult learners whose L2 semantic representations can be non-target like and have fuzzy boundaries. Unknown is whether similar effects apply to learners acquiring a L2 in a different sensory-motor modality, e.g., hearing learners of a sign language. Placement verbs in signed languages tend to be highly iconic and to exhibit transparent semantic boundaries. This may facilitate acquisition of signed placement verbs. In addition, little is known about how exposure to different semantic boundaries in placement events in a typologically different language affects lexical semantic meaning in the L1. In this study, we examined placement event descriptions (in American Sign Language (ASL) and English) in hearing L2 learners of ASL who were native speakers of English. L2 signers' ASL placement descriptions looked similar to those of two Deaf, native ASL signer controls, suggesting that the iconicity and transparency of placement distinctions in the visual modality may facilitate L2 acquisition. Nevertheless, L2 signers used a wider range of handshapes in ASL and used them less appropriately, indicating that fuzzy semantic boundaries occur in cross-modal L2 acquisition as well. In addition, while the L2 signers' English verbal expressions were not different from those of a non-signing control group, placement distinctions expressed in co-speech gesture were marginally more ASL-like for L2 signers, suggesting that exposure to different semantic boundaries can cause changes to how placement is conceptualized in the L1 as well.

Modeling a “pile-soil array” system under the seismic load action taking into account shock-absorbing properties of the soil

In this article, in a spatial setting, the modeling technique for a reinforced concrete pile immersed in the soil array under the seismic load action has been considered. Modeling of the “pile-soil mass” system elements is performed by the volumetric finite elements. The calculation includes the shock-absorbing properties of the soil mass model (“transparent boundaries”). A comparison of the proposed methodology with the known solutions has been performed. The prospects of further development and practical application of the pile operation proposed model together with the soil under the seismic load action has been given.

School Buildings for the 21st Century: Some Features of New School Buildings in Iceland

The aim of this study is to identify features of change in the recent design of school buildings in Iceland, and how they might affect teaching practices. Environmental and architectonic features characterising school buildings designed and built at the beginning of the 21st century are examined in light of challenges involving architecture, educational ideology, school policy and digital technology. The sample for the study consists of 20 schools located in four municipalities. Four of the school buildings were developed and built in this century, while the other 16 were designed in the 20th century. The design of all of the buildings wasexplored and reviewed by a multidisciplinary team. Data was collected by observations and photography at each school site, as well as by reviewing technical documents. The relationship between school design and school practices was studied through a questionnaire survey among all teachers, in order to find out whether teachers working in new environmentsdiffer from teachers in more traditional classroom settings. The results indicate a clear shift in the design of educational buildings. Flexibility, flow, openness and teamwork seem to guide recent school design. Clusters of classrooms or open spaces, transparent or movable boundaries, as well as shared spaces allowing for manifold interactions in flexible groupsseem to be replacing traditional classrooms along confining corridors. Teachers working in open classroom environments collaborate more often than their counterparts. Teaching practices are also characterised by more opportunities for pupils to choose between tasks and enjoy more variation regarding group division and workspace arrangements.

IMPLEMENTATION OF A NON-SPLITTING FORMULATION OF PERFECTLY MATCHED LAYER IN A 3D – 4TH ORDER STAGGERED-GRID VELOCITY-STRESS FINITE-DIFFERENCE SCHEME

One of the major problems in numerical simulations of wave propagation in elastodynamics using grid-point methods is the truncation of the computational space by artificial boundaries. These boundaries produce spurious reflections, polluting the results with artificial noise, therefore several efforts have been realized in order to achieve transparent or non-reflecting boundaries for truncating the computational space. Perfectly Matched Layer (PML) has been one of the most efficient methods for implementing artificial boundaries at the edges of the computational models. However the application of PML requires the “tuning” of several variables, for which very limited work has been presented. In the present study we employ the Non-Splitting formulation of PML (NPML) technique presented by Wang &amp; Tang (2003), based on the introduction of small perturbations in the wavefield. The NPML formulation shows the same accuracy with the originally introduced PML but is easier to be implemented because it does not require the field splitting. The main scope of this paper is to perform a full analysis of the efficiency of NMPL based on numerical tests using a 3D–4th order staggered-grid velocity-stress finite-difference scheme. The analysis consists of direct, quantified comparisons with reference solution waveforms from a semi-analytical method (Discrete Wavenumber Method) with synthetic waveforms produced using the most popular Absorbing Boundary Conditions (ABCs) and PML, in various canonical models (homogeneous and layer over half-space).

Immersed Boundary Method for Radiative Heat Transfer Problems in Nongray Media With Complex Internal and External Boundaries

The immersed boundary method (IBM) is gaining attention in the computational fluid dynamics but its applications in the field of a conjugated radiative–conductive or radiative–convective heat transfer seem limited. Therefore, the paper presents extension of this method to heat transfer problems dominated by thermal radiation in a nongray medium. The present model enables simulation of heat and fluid flows in a domain with complex stationary or moving internal and external boundaries on a fixed Cartesian grid (FCG) by applying the finite volume method. The special attention is paid to modeling thermal radiation and optical phenomena at highly curved, opaque, or transparent boundaries which confine the computational domain or separate zones of different thermophysical and optical properties, e.g., different values of a refractive index. The model is limited to a 2D planar or axisymmetric spaces. Detailed verification procedure proves accuracy and correctness of the developed model and shows its potential application field. The model may be used for simulations of a conjugated radiative–conductive or radiative–convective heat transfer in a nongray medium in a complex domain with opaque or transparent curved internal or external boundaries without unstructured or body fitted mesh generation.

Analyzing the stochastic behavior of ferroresonance initiation regarding initial conditions and system parameters

Power quality and power disturbances are the most important increasing factors throughout electrical networks. Ferroresonance as one of these disturbances can cause quality and security problems. This paper analyzes the stochastic behavior of ferroresonance as a nonlinear resonance phenomenon of the erratic nature and difficult prediction. Furthermore, the impact of different parameters on the initiation of ferroresonance is investigated. It is illustrated that a small change in the initial conditions leads to a large difference in the long-term behavior of the system, and this makes the future of the system unpredictable. Based on the stochastic behavior of ferroresonance some papers took different parameters into account and attempted to identify the basins of attraction for different ferroresonance regions. Here, according to real condition it is illustrated that these basins are highly depending on the initial conditions and there are no transparent boundaries for them. Also, by changing different parameters and initial conditions, the probability degree of ferroresonance initiation is calculated and depicted. Moreover, the impact of source angle on the ferroresonance initiation is investigated.

Convergence of Hardy Space Infinite Elements for Helmholtz Scattering and Resonance Problems

We perform a convergence analysis for discretizations of Helmholtz scattering and resonance problems obtained by Hardy space infinite elements. Superalgebraic convergence rates with respect to the number of Hardy space degrees of freedom are achieved. We consider spheres and piecewise polytopes as transparent boundaries. The analysis is based on a G\aa rding-type inequality and standard operator theoretical results. While the obtained results are related to those for the radial perfectly matched layer method, different techniques are used in the analysis.

Solid state synthesis and characterization of bulk FeTe0.5Se0.5 superconductors

FeTe0.5Se0.5 polycrystalline superconductor samples were synthesized by solid- state reaction method at different heating temperatures. The morphological and structural characterization of FeTe0 5Se0.5 samples were carried out by X-rays Diffraction, Scanning Electron Microscope and Energy Dispersive X-ray Spectroscopy. The electrical, magnetic and thermal transport properties were investigated up to 8 T by using physical property measurement system. The results reveal that the sensitivity of electrical and magnetic properties strongly depends on the heat treatment cycles. The upper critical field, Hc2(0), was determined with the magnetic field parallel to the sample surface. It gives a maximum value of 36.3 T. The lower critical field, Hc1(T), was obtained as 210, 140 and 70 Oe at 5, 8 and 12 K, respectively. The coherence length, ξ, at the zero field, was calculated to be 1.94 nm and suggested a transparent intergrain boundaries peculiarity. The μ0Hc2(0)/kBTc rate shows higher value (3.36 T/K) than the Pauli limit (1.84 T/K) which suggests unconventional nature of superconductivity for the polycrystalline FeTe0.5Se0.5 superconducting samples.

Video chroma keying via global sampling and trimap propagation

Chroma keying is a widely used video editing technique, which finely separates the foreground objects from the background. Two major concerns are involved in chroma keying problems: alpha estimation and foreground color restoration. The alpha values reveal the opacity property of the foreground objects. The foreground color restoration removes the background color influence to the foreground appearance especially at transparent regions and objects' boundaries. In this paper, the color range of the solid background is well analyzed to automatically separate foreground from background. Global sampling is utilized to robustly and reliably estimate the foreground color at boundaries and transparent regions. Furthermore, we propose to propagate the geometric shape of foreground boundaries between adjacent frames by using optical flow and thin plate splines interpolation. The trimap, which is an initial foreground/background/unknown segmentation of each frame can be automatically updated for each video frame by using our proposed propagation method. Compared to previous methods, our proposed matting method estimates high-quality alpha matte and reliable foreground color with least user interference.

In no-man's land: citizens and kin in transnational commercial surrogacy in India

Every year, large numbers of aspiring parents from all over the world come to India to fulfil their dreams of parenthood. They hire an Indian surrogate and with the help of state-of-the-art medical technology, they are able to conceive children they can call their ‘own’. Since 2005, commercial gestational surrogacy in India has become a lucrative industry thanks to the cheap gestational labour, and cheaper medical services. However, this largely unregulated industry is facing roadblocks in international bureaucratic processes. The child born from the arrangement is often caught between conflicting international laws and deemed ‘stateless’. I wish to look at how the state and international laws tend to define persons and relationships by regulating entry and exit, especially through verification and authentication of kin. The world of transparent and visible boundaries – and their policing – is seen through the transnational processes of identifying the stateless children born through the arrangement.

Dynamical Processes in Open Quantum Systems from a TDDFT Perspective: Resonances and Electron Photoemission.

We present a review of different computational methods to describe time-dependent phenomena in open quantum systems and their extension to a density-functional framework. We focus the discussion on electron emission processes in atoms and molecules addressing excited-state lifetimes and dissipative processes. Initially we analyze the concept of an electronic resonance, a central concept in spectroscopy associated with a metastable state from which an electron eventually escapes (electronic lifetime). Resonances play a fundamental role in many time-dependent molecular phenomena but can be rationalized from a time-independent context in terms of scattering states. We introduce the method of complex scaling, which is used to capture resonant states as localized states in the spirit of usual bound-state methods, and work on its extension to static and time-dependent density-functional theory. In a time-dependent setting, complex scaling can be used to describe excitations in the continuum as well as wave packet dynamics leading to electron emission. This process can also be treated by using open boundary conditions which allow time-dependent simulations of emission processes without artificial reflections at the boundaries (i.e., borders of the simulation box). We compare in detail different schemes to implement open boundaries, namely transparent boundaries using Green functions, and absorbing boundaries in the form of complex absorbing potentials and mask functions. The last two are regularly used together with time-dependent density-functional theory to describe the electron emission dynamics of atoms and molecules. Finally, we discuss approaches to the calculation of energy and angle-resolved time-dependent pump-probe photoelectron spectroscopy of molecular systems.

Plasmastatic models of galathea traps with magnetically transparent boundaries

Mathematical models and results of calculation of plasma equilibrium in a circular cylinder with three helical or straight imbedded current-carrying conductors (i.e., in a straightened analog of a toroidal Galathea trap) are presented. The equilibrium is described in the framework of two-dimensional boundary value problems with plane and helical analogs of the Grad-Shafranov equation for the scalar magnetic flux function. Problems with first-kind boundary conditions corresponding to a magnetically transparent boundary of the cylinder and problems with second-kind boundary conditions and a given value of the electric current flowing in plasma (in addition to those flowing in the conductors) are considered. Deformations of magnetoplasma configurations in the cylinder for different formulations of the above-specified problems are investigated numerically.

MODA: a new algorithm to compute optical depths in multidimensional hydrodynamic simulations

We introduce a new algorithm for the calculation of multidimensional optical depths in approximate radiative transport schemes, equally applicable to neutrinos and photons. Motivated by (but not limited to) neutrino transport in three-dimensional simulations of core-collapse supernovae and neutron star mergers, our method makes no assumptions about the geometry of the matter distribution, apart from expecting optically transparent boundaries. Based on local information about opacities, the algorithm figures out an escape route that tends to minimize the optical depth without assuming any pre-defined paths for radiation. Its adaptivity makes it suitable for a variety of astrophysical settings with complicated geometry (e.g., core-collapse supernovae, compact binary mergers, tidal disruptions, star formation, etc.). We implement the MODA algorithm into both a Eulerian hydrodynamics code with a fixed, uniform grid and into an SPH code where we make use a tree structure that is otherwise used for searching neighbours and calculating gravity. In a series of numerical experiments, we compare the MODA results with analytically known solutions. We also use snapshots from actual 3D simulations and compare the results of MODA with those obtained with other methods such as the global and local ray-by-ray method. It turns out that MODA achieves excellent accuracy at a moderate computational cost. In an appendix we also discuss implementation details and parallelization strategies.

Principled Moral Outrage

Moral distress is the pain or anguish affecting the mind, body or relationships in response to a situation in which the person is aware of a moral problem, acknowl-edges moral responsibility, and makes a moral judgment about the correct action; yet, as a result of real or perceived constraints, participates in perceived moral wrongdoing. 1 (p421)