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.     

Bemerkungen zu der Arbeit von Lauersen und Orth: Die Verteilung der Ascorbins?ure in der Kartoffelknolle

Ohne ZusammenfassungDiese Z.83, 193 (1942).     

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.     

Creation of arteriovenous fistulae for hemodialysis in octogenarians

Elderly patients, defined as octogenarians and nonagenarians, are an increasing population entering renal replacement therapy. Advanced age appears as an exclusive factor negatively influencing dialysis practice. Elderly patients are referred late for the initiation of hemodialysis and more likely are offered catheters rather than arteriovenous fistulae (AVF), which increase mortality and negatively affect quality of life. We present our approach to the creation of vascular access for hemodialysis in this demanding population. In 2006–2012, 39 patients aged 85.9 ± 2.05 with end‐stage renal disease, mainly resulting from ischemic nephropathy, were admitted to the Department of Nephrology to establish permanent vascular access for hemodialysis: preferably AVF. Temporary dialysis catheters were implanted in uremic emergency to bridge the time to fistula creation/maturation. AVF was attempted in 87.2% of the patients. Primary AVF function was achieved in 54% of the patients. Cumulative proportional survival of AVF at months 12 and 24 was 81.5%. Ninety‐four percent of AVF were localized on the forearm: 74% in the distal and 20% in the proximal part. Mean duration of hemodialysis therapy was 20.80 ± 19.45 months. The mean time of AVF use was 15.9 ± 20.2 months. Until present, 38% have been dialyzed using AVF for 31.0 ± 18.8 months. Five patients died with functioning fistula. Eight patients initiated hemodialysis therapy with fistula. During further observation, the use of AVF increased to 62%. Elderly patients should not be denied creation of AVF as a rule. The outcome of AVF benefits more from acknowledging individual vascular conditions rather than age of the patient.     

Sensitivity Analysis as a Tool for Estimating Numerical Modeling Results

Modeling of real physical processes by numerical methods is highly time-consuming and requires significant computational capacity. In some cases, tens or even hundreds of hours of high-power computing are needed to virtually model a real process that lasts one second. Processes that take many hours, such as drying, pose an even greater challenge. This problem can be solved in two ways: by using faster computers (such as computing clusters) or by significantly simplifying the modeled process (its geometry, physical phenomena, or the impact of individual factors). For this reason, all methods which speed up or minimize the number of simulations required to achieve the research objective should be analyzed. This article focuses on the latter approach, and it proposes a simple method for predicting the responses of a numerical model (values of any output parameter) to changes in input values (values of any input parameter). This method requires a base model, such as a numerical model which is qualitatively and quantitatively consistent with experimental observations, and a sensitivity analysis. This article discusses the mathematical and logical premises for the discussed model, and it proposes two methods for predicting numerical simulation results. Those methods are illustrated with examples which analyze the behavior of the Eulerian Multiphase Model and describe phase interactions based on Gidaspow's approach. The discussed example relies on data from a series of articles published by the authors in Drying Technology. This article was inspired by the observations made during a time-consuming process of modeling a spouted bed grain dryer, which was described in the above publications. The objective of this study was to discuss the advantages and possibilities created by sensitivity analyses of numerical models and to encourage their practical application.     

Evaluation of Antioxidative Constituents from Thyme

The non-polar fraction of thyme was examined for the occurrence of phenolic components and their antioxidative activity. In addition to carvacrol ( II ) and thymol ( III ), p -cymene-2,3-diol (I ; 2,3-dihydroxy-4-isopropyl-1-methylbenzene) was isolated for the first time from thyme. The structure of I was elucidated using ¹H nuclear magnetic resonance (NMR), ¹³C NMR, and mass spectrometry. Antioxidative activity was investigated with the Rancimat method (100°C) and the Schaal test (60°C). Compound I exhibited the strongest antioxidative activity which was greater than that of α-tocopherol and butylated hydroxyanisole. Five thyme species were analysed by means of HPLC with electrochemical detection for the concentration of compounds I – III . The highest amounts of I – III were found in Thymus vulgaris L.