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Showing papers by "Bauhaus University, Weimar published in 1999"


Book ChapterDOI
01 Jan 1999
TL;DR: It is proposed that VEs are mentally represented as meshed sets of patterns of actions and that presence is experienced when these actions include the perceived possibility to navigate and move the own body in the VE.
Abstract: Presence, the sense of being in a virtual environment (VE), is analysed in an embodied cognition framework. We propose that VEs are mentally represented as meshed sets of patterns of actions and that presence is experienced when these actions include the perceived possibility to navigate and move the own body in the VE. A factor analyses of survey data shows 3 different presence components: spatial presence, involvement, and judgement of realness. A path analysis shows that spatial presence is mostly determined by sources of meshed patterns of actions: interaction with the VE, understanding of dynamics, and perception of dramatic meaning.

210 citations


Journal ArticleDOI
TL;DR: It is shown that both the projection onto the Wiener chaos and the Hermite-transform lead to the same fully discrete equations.

99 citations


Journal ArticleDOI
TL;DR: In this paper, an importance sampling concept is proposed, which automatically adapts the simulation densities in two subsequent simulation runs in order to reduce the sample size, and the probability of failure is formulated as first passage probability of a given threshold within the observation period.

40 citations


Journal ArticleDOI
TL;DR: In this paper, a definition of Qp-spaces for quaternion-valued functions of three real variables is proposed and some basic properties of its basic properties are studied.
Abstract: We consider a definition of Qp-spaces for quaternion-valued functions of three real variables and study some of its basic properties.

37 citations


Book ChapterDOI
01 Jan 1999
TL;DR: This paper corrects the early taxonomy of interaction devices and actions introduced by Foley for screen based interactive systems by adapting it to real world and to virtual reality systems.
Abstract: The growing power of computing devices allows the representation of three-dimensional interactive virtual worlds. Interfaces with such a world must profit from our experience in the interaction with the real world. This paper corrects the early taxonomy of interaction devices and actions introduced by Foley for screen based interactive systems by adapting it to real world and to virtual reality systems. Basing on the taxonomy derived, the paper presents a model for a Virtual Reality system based on Systems Theory. The model is capable of including both traditional event-based interaction input devices, as well as continuous input devices. It is strongly device oriented, and allows to model mathematically all currently possible input devices for Virtual Reality. The model has been used for the implementation of a general input device library serving as an abstraction layer to a Virtual Reality system.

29 citations


Journal ArticleDOI
TL;DR: In this paper, a class of generalizations of the complex one-dimensional II-operator in spaces of quaternion-valued functions depending on four real variables is considered and its basic properties are studied.
Abstract: We consider a class of generalizations of the complex one-dimensional II-operator in spaces of quaternion-valued functions depending on four real variables and study some of its basic properties.

18 citations


Journal ArticleDOI
TL;DR: In this article, a spatial modified Miura transform is used to map solutions of the modified Korteweg-de Vries equation into solutions of a non-linear first-order system of partial differential equations.
Abstract: We investigate a spatial modified Miura transform. To describe this transform we have to solve a non-linear first-order system of partial differential equations. This investigation will be done by the help of quaternionic analysis. The main goal is to find a hypercomplex factorization of the Schrodinger equation. In one dimension Miura's transformation is needed to map solutions of the modified Korteweg-de Vries equation into solutions of Korteweg-de Vries equation.

15 citations



Proceedings ArticleDOI
15 Oct 1999
TL;DR: In this article, the authors describe the use of microwave moisture measurement instrumentation for a variety of possible applications in different areas of industry and agriculture, in order to control the dosage of water, the quality of products and the reduction of applied energy.
Abstract: The quality of products depends on the moisture content. By means of the introduction of ISO 9000 the market of microwave moisture measurement instrumentation has been grown up to a great variety of possible applications in different areas of industry and agriculture. Moisture measurement systems have to determine the exact moisture content (MC) of a certain material, in order to allow the control of the dosage of water, the quality of products and the reduction of applied energy. The methods show the advantage of being non- destructive with high accuracy under severe environmental industrial conditions. The effect of disturbances, such as bulk density variations, material grain size or salt content, can be reduced by both suitable data processing and choice of measuring frequency.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

4 citations


Book ChapterDOI
01 Jan 1999
TL;DR: In this article, the stiffness matrices of a beam element are determined based on the assumption of linear elastic material behavior and small deformations within the element, where the beam element is defined by the cross-section at the left and right element end, by its material constants, and by the number of integration segments along the beam axis.
Abstract: Publisher Summary The determination of the element stiffness matrices is based on the assumption of linear elastic material behavior and small deformations within the element The beam element is defined by the cross-section at the left and right element end, by its material constants, and by the number of integration segments along the beam axis The stiffness within the element is computed in the integration points of the actual cross-section The Monte-Carlo-Methods are characterized by a very simple structure of the optimization algorithm For each beam element a subroutine is called to choose the geometrical data at random The quality of these random variables is then assessed and valued on the total structure This sample is repeated N-times, with every sample being independent of all previous ones The results of all samples are compared with each other For a weight optimization, the quality of a solution is assessed by the total weight of the structure and the violation of the constraints The Monte-Carlo-Methods are especially effective for the solution of tasks, which require no greater accuracy than 5%–10%

2 citations


Journal ArticleDOI
01 Jan 1999
TL;DR: In this paper, an implicit integration algorithm for arbitrary multi-surface plasticity is presented, which uses isotrop and anisotropic Mohr-Coulomb criteria with tension-cutoff and associated or non-associated flow rules.
Abstract: Summary An implicit integration algorithm for arbitrary multi- surface plasticity is presented. This perfectly-plastic model uses isotrop and anisotrop Mohr-Coulomb criteria with tension-cutoff and associated or non-associated flow rules. So materials with anisotropic deformation and strength behaviour like intact rock with sets of joints can be described. With an extended Drucker-Prager-criterion for the isotrop material matrix this model can be used as well for modelling other materials such as masonry or concrete. Problems resulting from arbitrary multisurface yield criteria are discussed. Consistent numerical algorithms for robust numerical solutions are presented. The Multisurface plasticity model was implemented in a finite-element-program. The example of calculation of a dam on jointed rock mass shows the applicability and new possibilities for the description of anisotropic materials.

Book ChapterDOI
01 Jan 1999
TL;DR: This work considers the following problem: A given pile — consisting of elementsv i of a set V — should be moved step by step to a final pile with a possibly different structure, and Calculating the number of necessary auxiliary piles is known to be NP-complete.
Abstract: Pileproblems are difficult discrete optimization problems. They deal with practical tasks like loading and unloading trains trucks or ships. We find problems of this kind also in civil engineering and in logistics of course. Even simpler definitions remain such problems hard to solve. We consider the following problem: A given pile — consisting of elementsv i of a set V — should be moved step by step to a final pile with a possibly different structure. To reach the required final situation there are auxiliary places available. Calculating the number of necessary auxiliary piles is known to be NP-complete. We report on experiences with a branch-and-bound algorithm and a heuristic method.