Implementation of a Lattice Boltzmann kernel using the Compute Unified Device Architecture developed by nVIDIA

In this article a very efficient implementation of a 2D-Lattice Boltzmann kernel using the Compute Unified Device Architecture (CUDA?) interface developed by nVIDIA^® is presented. By exploiting the explicit parallelism exposed in the graphics hardware we obtain more than one order in performance gain compared to standard CPUs. A non-trivial example, the flow through a generic porous medium, shows the performance of the implementation.     

Numerical simulation of segmented penetrator impact

The performance of segmented and continuous penetrators impacting semi-infinite and spaced armor is studied using both the EPIC-2 and HULL hydrocodes. First the performance of a segmented rod is studied, striking semi-infinite armor, for various parameters such as striking velocity, segment spacing and number of segments. Then an actual penetrator configuration proposed by A. Charters is analyzed and the use of normalized penetration is discussed. Finally three-dimensional simulations are presented for segmented and continuous penetrators impacting oblique spaced armor varying such parameters as striking velocity, segment spacing, number of segments, and target thickness.     

Contrasting the use of tools for presentation and critique: Some cases from architectural education

This study investigates video recordings of design reviews in architectural education, focusing on how presentations and discussions of designs are contingent on the specific tools employed. In the analyzed recordings, three different setups are utilized: traditional posters, digital slide-show technologies, and combinations of the two. This range of different setups provides a set of contrasts that make visible the role of technologies in shaping the ways in which the reviews are conducted. The analysis is structured in three themes. First, we examine the sequential organization of digital presentations in relation to the spatial structure of poster-based presentations. Second, the different ways in which shared attention is established in digital, paper-based, and hybrid presentation practices are analyzed. Third, we address part-whole relations—how details in presented materials are put in relation to the overarching project or the presentation as a whole. Taken together, the analyses suggest that the detailed organization of the design review is transformed in subtle yet consequential ways through the introduction of digital slide-show technologies. These transformations are consequential not only locally, for the design review itself, but also for the instructive work that is accomplished through this practice. We conclude by discussing some implications for design, arguing that an increased awareness of how the practice is influenced by the different setups might be key for the proper adaptation of presentation technologies to particular purposes.     

A generalized Ufnarovski graph

An important tool for studying standard finitely presented algebras is the Ufnarovski graph. In this paper we extend the use of the Ufnarovski graph to automaton algebras, introducing the generalized Ufnarovski graph. As an application, we show how this construction can be used to test Noetherianity of automaton algebras.     

A non-Newtonian model based on limiting shear stress and slip planes—parametric studies

Parametric studies and corresponding results are presented using a rheological model based on the limiting shear stress and possible occurrence of slip planes. The model is applied to elastohydrodynamically lubricated line contacts with smooth surfaces and isothermal conditions. A few investigations are carried out where different parameters are varied. The first study investigates the influence on the film thickness distribution due to a variation of the maximum Hertzian pressure when the slide-to-roll ratio is constant. The second study investigates how far the non-Newtonian region propagates at low slide-to-roll ratios for a few different values of the Hertzian pressure. The results show that it is a remarkably small slide-to-roll ratio necessary to cause slip planes in a large part of the Hertzian contact zone. A third study regards the influence of the entrainment velocity on the film thickness generation at different slide-to-roll ratios. Finally some rheological parameters are varied. First, only the limiting shear stress at atmospheric pressure (τ₀) is varied, and second, a few different lubricants are studied, each with their own set of rheological parameters.     

Fast, accurate, and stable algorithm for the stress field around a zig-zag-shaped crack

A new scheme decreases memory usage and execution time for the evaluation of certain weighted Cauchy type singular integrals. The scheme is incorporated into an algorithm based on an integral equation of Fredholm second kind. The algorithm computes mode I and II stress intensity factors of cracks in infinite elastic domains. Problems with analytical solutions are solved with relative errors less than 10⁻¹⁵. Earlier investigators' results for kinked cracks with one to four corners are improved. Cracks with a large number of corners can also be studied. In an example the stress intensity factors of a crack with 100 corners are calculated with a relative error of less than 10⁻⁶.     

Creep and rupture behaviour in fibre bundles

The time dependent rupture of a fibre bundle under constant tensile load and with scatter in fibre stiffness and fibre strength is analysed using a general formulation of the creep law. The total rupture time is divided into an incubation time, with all fibres intact, and a failure propagation time where fibres fail progressively. Governing equations are given for both time intervals. It is shown that the failure propagation time interval is independent of the load if no spatial stress redistribution occurs and all fibres remain intact upon loading. For a bundle consisting of originally uniform fibres where a fraction is afflicted with a certain defect, the time intervals are calculated assuming Norton's non linear creep law.