A general topology-based framework for adaptive insertion of cohesive elements in finite element meshes

Large-scale simulation of separation phenomena in solids such as fracture, branching, and fragmentation requires a scalable data structure representation of the evolving model. Modeling of such phenomena can be successfully accomplished by means of cohesive models of fracture, which are versatile and effective tools for computational analysis. A common approach to insert cohesive elements in finite element meshes consists of adding discrete special interfaces (cohesive elements) between bulk elements. The insertion of cohesive elements along bulk element interfaces for fragmentation simulation imposes changes in the topology of the mesh. This paper presents a unified topology-based framework for supporting adaptive fragmentation simulations, being able to handle two- and three-dimensional models, with finite elements of any order. We represent the finite element model using a compact and “complete” topological data structure, which is capable of retrieving all adjacency relationships needed for the simulation. Moreover, we introduce a new topology-based algorithm that systematically classifies fractured facets (i.e., facets along which fracture has occurred). The algorithm follows a set of procedures that consistently perform all the topological changes needed to update the model. The proposed topology-based framework is general and ensures that the model representation remains always valid during fragmentation, even when very complex crack patterns are involved. The framework correctness and efficiency are illustrated by arbitrary insertion of cohesive elements in various finite element meshes of self-similar geometries, including both two- and three-dimensional models. These computational tests clearly show linear scaling in time, which is a key feature of the present data-structure representation. The effectiveness of the proposed approach is also demonstrated by dynamic fracture analysis through finite element simulations of actual engineering problems.

Fast and versatile texture-based wireframe rendering

This paper revisits the problem of wireframe rendering, which, at first, appears to be an easily solved problem. However, the conventional solution is inefficient and does not result in high-quality images. Recently, graphics hardware programming has been employed to achieve high-quality solid line rendering. In this paper, we present a simpler and faster technique for wireframe rendering based on texture mapping. Our technique does not require (but can benefit from) graphics hardware programming and thus can be easily integrated into existing rendering engines, while resulting in fast, accurate, high-quality, anti-aliased, and still versatile, wireframe drawing. For topologically structured meshes, our approach allows the rendering of wireframe decoupled from the underlying mesh, making possible the rendering of original wireframes on top of decimated meshes.     

A roadmap for a methodology to assess,improve and sustain intra‐ and inter‐enterprise system performance with respect to technology‐product life cycle in small and medium manufacturers

Increased manufacturing costs are forcing U.S. manufacturing firms to send their operations off shore. Such business practices are greatly impacting the vitality of small and medium manufacturers (SMMs) in the U.S. economy. This article intends to advance the notion of the need for a methodology for assessment, improvement, and sustainability of intra‐ and inter‐enterprise system performance along the technology–product development life cycle. The aims of this article are to: (1) provide an overview of the technology–product development process; (2) document the different states of manufacturing technology readiness levels; (3) present an overview of prior methodologies reported on the subject in the published literature; and (4) establish a road map for assessment, improvement, and sustainability of intra‐ and inter‐enterprise system performance along the path of the technology–product development life cycle. A notion is advanced about the readiness of SMMs with respect to assessment, improvement, and sustainability of intra‐ and inter‐enterprise system performance. A road map is outlined for the deployment of a methodology to address the issues across the supply chain. © 2007 Wiley Periodicals, Inc.     

The emergence of distributed component platforms

Several vendors and consortia have independently developed standards that define the basic mechanics for building and interconnecting software components. Sun's JavaBeans has emerged as the leading rival to Microsoft's DCOM, supplanting the OpenDoc standard from the now defunct Component Integration Laboratories. Component software is moving from its original focus on desktop-bound compound documents to enterprise applications that include distributed server components. The backers of competing standards are racing to capture market leadership by delivering the tangible benefits of component standards via distributed component platforms-integrated development and runtime environments that isolate much of the conceptual and technical complexity involved in building component-based applications. With DCPs, businesses can assign their few highly skilled programmers to component construction and use less sophisticated developers to carry out the simpler assembly tasks. By making component standards available to the broadest possible spectrum of developers, DCPs essentially drive those standards to market. This article reviews the state of component software as embodied in DCPs. The two DCP market leaders are Microsoft's DCOM (or ActiveX/DCOM) and Sun's JavaBeans. However, Internet and OMG component standards are emerging that will likely impact both the content and status of these two DCPs. The article also discusses component frameworks, which extend DCPs to provide more complete application development solutions     

Applications of fuzzy‐based linguistic patterns for the assessment of computer screen design quality

The main objective of this study was to develop a modeling framework which would unify different aspects of computer screen design and result in a quantitative criterion for an optimized computer screen format. The fuzzy set‐based linguistic design patterns were utilized as a tool to build this model. The linguistic patterns are based on categories of expressions related closely to natural language and truth values, which are close to a human designer's intuition. The proposed framework is capable of assessing the quality of computer screen design based on existing knowledge in human‐computer interface domain using the fuzzy‐based linguistic pattern approach. Exemplary patterns for an optimal screen density, information grouping, and some aspects of screen layout are presented, along with a sequence of calculations based on the exemplary screen format. This study showed that it is possible to achieve a rational and relatively easy to interpret assessment of different screen designs in the form of the degrees of truth. Such an evaluation criterion reflects the compatibility of a given screen design with the optimal one based on the current knowledge in the field. It is believed that the proposed methodological framework for computer screen design should significantly augment the efforts of human designers.     

Influence of hydrodynamic instability on the heat transfer coefficient during condensation of R134a and R404A refrigerants in pipe mini-channels

This paper presents the results of an investigation of the influence of hydrodynamic instabilities on heat transfer intensity during the condensation of R134a and R404A refrigerants in pipe mini-channels. The heat transfer coefficient h is a measure of the effectiveness of the condensation process. It is particularly important to determine the value of the coefficient in the two-phase condensation area in a compact condenser. In other condenser areas (i.e., precooling of superheated vapor and subcooling of condensate), the heat efficiency is substantially smaller. Hydrodynamic instabilities of a periodic nature have an influence on size changes in these areas. A decrease in the heat transfer coefficient h in the two-phase area results in decreased intensity of the heat removal process in the whole condenser.The experimental investigations were based on the condensation of R134a and R404A refrigerants in horizontal pipe mini-channels with internal diameters of d = 0.64; 0.90; 1.40; 1.44; 1.92; 2.30 and 3.30 mm. Disturbances of the condensation process were induced with a periodic stop and a repetition of the flow of the refrigerant.In the range of frequencies, f = 0.25–5 Hz, of the periodically generated disturbances, an unfavorable influence on the intensity of the heat transfer during the condensation process in pipe mini-channels was identified. The reduction in the intensity of the heat transfer during the condensation process, which was induced with hydrodynamic instabilities, was presented in the form of the dependence of the heat transfer coefficient h on the vapor quality x and the frequencies f of the disturbances.The influence of the refrigerant, the diameter of the mini-channels and the frequency f on the damping phenomenon of the periodical disturbances in the pipe mini-channels was identified.