Dissertation com dez 2004 (3 résultats)

Taschenbuch. Etat : Neu. Neuware - The high degree of heterogeneity of textile composites was found to be the primary problem in analysis and testing. A concept was developed based on a description of the local variation of the material stiffness matrix using a spline interpolation. The role of this stiffness function is to facilitate the calculation of the material stiffness matrix at any given position or for arbitrary domains in the form of finite elements.Based on this approach, two different methods were developed. In the first method the average material stiffness matrix is calculated for a finite element and subsequently the elemental stiffness matrix of this element is assembled. In the second approach the elemental stiffness matrix is calculated directly using the local material stiffness at the integration points of the finite element.This concept was then applied to the plate twist test. The numerical analysis of this test was done in order to determine the influence of heterogeneity on the test results. It was shown that this test measures the in-plane shear modulus largely independent of the representative volume element (RVE) size. Both finite element approaches were then applied to the V-notched beam shear test, to investigate the applicability of this test to the measurement of the shear properties. The test set-up as well as numerical parameters of the finite element analysis of the test were studied. It was possible to derive limits for the applicability of the V-notched beam shear test in terms of RVE size, as well as set up guidelines for the finite element analysis of textile composites.With electronic speckle pattern interferometry, which enables full-field displacement and strain measurements, tensile tests were carried out on 3D-woven textile composite specimens. With the agreement of the experimental results and the theoretical predictions the validity of the developed approach was again shown.…

Taschenbuch. Etat : Neu. Neuware - There has been a lot of interest among marketing practitioners and researchers in the concept of marketing communications as related to computer-mediated marketing environments as a result of the commercialization of the World Wide Web (WWW) as a marketing and communication medium. Despite growing interest, there is a dearth of research on the processual nature of communication between marketers and consumers. The overall aim of this study, therefore, is to expand our understanding of marketing communication within the computer-mediated marketing environments. This understanding is achieved in the thesis by incorporating ideas from traditional marketing communication models those based on a one-way, general outbound, linear model in which marketers deliver communication to customers and prospects and contemporary marketing communications theory within a contextualist framework, to examine the evolving marketing communication medium. Given the growing empowerment of customers through information technology that has created the interactive marketplace, the study aims to illuminate concretely that Internet exerts a mediating influence on the relationship between marketers and consumers.Following this articulation, the study considers computer-mediated marketing environments as a technological development that increases the options for marketing communications. Placing marketing communication and computer-mediated marketing environments within a historical context of technology as consistent with social constructivist framework rather than thinking about the medium as an isolated phenomenon, builds the base for understanding the opportunities and difficulties associated with marketing communications and the Internet in contrast to capabilities for marketing prior to the Internet. The current study indicates that marketing communication in the computer-mediated marketing environments possess some fundamental uniqueness, which are ancillary and augment the consumption processes. The study proposed a conceptual framework for understanding marketing communication trajectory in the evolving interactive marketplace. The framework proposed provides a new base for developing a wide range of marketing communication programmes for practitioners and academic researchers.…

Taschenbuch. Etat : Neu. Neuware - This research is dedicated to two main problems in finding shortest paths in the graphs. The first problem is to find shortest paths from an origin to all other vertices in non-negatively weighted graph. The second problem is the same, except it is allowed that some edges are negative. This is a more difficult problem that can be solved by relatively complicated algorithms. We attack the first problem by introducing a new data structure - Relaxed Heaps that implements efficiently two main operations critical for the improvement of Dijkstra's shortest path algorithm. R2-heaps with suspended relaxation proposed in this research gives the best known worst-case time bounds of O(1) for a decrease_key operation and O(logn) for a delete_min operation. That results in the best worst-case running time for Dijkstra's algorithm O(m+nlogn), and represents an improvement over Fibonacci Heaps, which give the same, but amortized time bounds. The new data structure is simple and efficient in practical implementation. The empirical study with R2-heaps demonstrated strong advantage of its use for Dijkstra's algorithm over the 'raw' Dijkstra's without heaps. This advantage is especially dramatic for sparse graphs. R2-heaps can be used in a large number of applications in which set manipulations should be implemented efficiently. For the problem of finding shortest paths in graphs with some negative edges, we present a new approach of reweighting graphs by first reducing the graph to its canonical form, which allows to apply an effective algorithm to reweight the graph to one with non-negative edges only and simultaneously to find shortest paths from an origin to all other vertices in the graph. This approach allows to give new algebraic and geometric interpretations of the problem. The experiment with the Sweeping Algorithm demonstrated O(n logn) expected time complexity. These results open new prospects to improve algorithms for a wide variety of problems including different network optimization problems that use Dijkstra's algorithm as a subroutine, as well as multiple Operations Research and Modeling problems that can be reduced to finding shortest paths on graphs.…