Showing papers by "Bauhaus University, Weimar published in 2002"

Perspective shadow maps

Abstract: Shadow maps are probably the most widely used means for the generation of shadows, despite their well known aliasing problems. In this paper we introduce perspective shadow maps, which are generated in normalized device coordinate space, i.e., after perspective transformation. This results in important reduction of shadow map aliasing with almost no overhead. We correctly treat light source transformations and show how to include all objects which cast shadows in the transformed space. Perspective shadow maps can directly replace standard shadow maps for interactive hardware accelerated rendering as well as in high-quality, offline renderers.

Interactive visualization of complex plant ecosystems

Abstract: We present a method for interactive rendering of large outdoor scenes. Complex polygonal plant models and whole plant populations are represented by relatively small sets of point and line primitives. This enables us to show landscapes faithfully using only a limited percentage of primitives. In addition, a hierarchical data structure allows us to smoothly reduce the geometrical representation to any desired number of primitives. The scene is hierarchically divided into local portions of geometry to achieve large reduction factors for distant regions. Additionally, the data reduction is adapted to the visual importance of geometric objects. This allows us to maintain the visual fidelity of the representation while reducing most of the geometry drastically. With our system, we are able to interactively render very complex landscapes with good visual quality.

Occlusion shadows: using projected light to generate realistic occlusion effects for view-dependent optical see-through displays

Abstract: This paper presents projector-based illumination techniques for creating correct occlusion effects for optical see-through setups. We project view-dependent occlusion shadows onto the real surfaces that are located behind virtual objects. This results in a perfect occlusion of real objects by virtual ones. We have implemented and tested our approach in the context of the Virtual Showcase display. We describe a hardware extension for projecting light into the showcase and present our rendering techniques for displaying occlusion shadows for single and multi-user environments as well as for single and multi-light-projector configurations. We also report on the limitations of our system for multi-user situations and describe our experiences with a first experimental prototype.

Merging fossil specimens with computer-generated information

Abstract: While dinosaur fossils reveal much, they keep us guessing about the original organisms' color, sound, and behavior. For several years, modern paleontologists have used 3D computer graphics to help reconstruct these pieces of the past. Augmented reality (AR) leverages this technology to provide an interface that enhances the real world with synthetic supplements. Paleontologists can use AR to present virtual data directly within a real, 3D environment rather than on a flat monitor. This technology's immersiveness can give paleontologists new insights into their research and communicate the results to museum visitors in an exciting and effective way.

Octreemizer: a hierarchical approach for interactive roaming through very large volumes

Abstract: We have developed a hierarchical paging scheme for handling very large volumetric data sets at interactive frame rates. Our system trades texture resolution for speed and uses effective prediction strategies. We have tested our approach for datasets with up to 16GB in size and show that it works well with less than 500MB of main memory cache for 64MB of 3D-texture memory. Our approach makes it feasible to deal with these volumes on desktop machines.

Ultrasonic NDE of concrete

Abstract: In this contribution an overview of ultrasonic non-destructive evaluation (NDE) of concrete is given. The intention is to provide insight into the specific features of concrete testing, and to build a picture of this rapidly developing field by presenting examples of research results and applications. After introducing concrete as a construction material and inhomogeneous propagation medium, common inspection tasks at civil structures are identified. Characteristics of ultrasonic wave propagation in concrete are explained together with measurement and modeling methods. A short presentation of measurement systems precedes the description of research and applications examples. This subjective selection comprises measurement and signal processing techniques including imaging. The list encompasses well-tried methods as well as topics of current research. Finally, the current state of development is discussed in view of demanded testing objectives.

Is "entanglement" always entangled?

Abstract: Entanglement, including `quantum entanglement', is a consequence of correlation between objects. When the objects are subunits of pairs which in turn are members of an ensemble described by a wavefunction, a correlation among the subunits induces the mysterious properties of `cat-states'. However, correlation between subsystems can be present in purely non-quantum sources, thereby entailing no unfathomable behaviour. Such entanglement arises whenever the so-called `qubit space' is not afflicted with Heisenberg uncertainty. It turns out that all optical experimental realizations of the Einstein, Podolsky and Rosen (EPR) Gedanken experiment in fact do not suffer Heisenberg uncertainty. Examples will be analysed and non-quantum models for some of these described. The consequences for experiments that were to test EPRs contention in the form of Bell's theorem are drawn: valid tests of EPR's hypothesis have yet to be done.

Future trends in oil and gas visualization

Abstract: The question that this panel wishes to explore is: What are the future visualization trends and requirements for the oil and gas industry to efficiently handle and explore the ever-increasing volume and variety of available data?It has been proven many times that 3D visualization helps to reduce the risk in the search for, and development of, oil and gas resources and has been generally acknowledged to be an indispensable technology for the oil and gas industry. The role of the geoscientist is to combine his/her geological and geophysical expertise with the wide variety of data to find these natural resources and minimize the risk in the search for nature resources at the same time. The variety and size of the data makes the requirements unique in the visualization field: The data volumes that must be visualized range from a few megabytes to over 100 gigabytes. Multiple kinds of data and interpretation must be overlaid on the visualization. Multiple models of the subsurface are possible. Multiple specialized visualization software tools are available for the geoscientist to use.Combining the right visualization tools with the right data can reduce exploration risk and make the geoscientist a productive explorationist. This panel will explore the trends that are anticipated to meet the future needs of the Oil and Gas industry.

Representation theory for classes of initial value problems with quaternionic analysis

Abstract: We consider time-dependent Stokes problems for the case of low Reynolds number in smoothly bounded domains. By using a finite difference time discretization, the problem is reduced to a sequence of steady-state Stokes problems. These boundary value problems are solved by means of hypercomplex analysis. In the second part, we consider initial boundary value problems of the so-called Galpern–Sobolev type. An implicit time discretization method is deduced. Making use of a modified Teodorescu transform and suitable quaternionic Hilbert space projections, we obtain a representation of the solution. Copyright © 2002 John Wiley & Sons, Ltd.

The Improbability of Nonlocality

Abstract: (Dated: 5 Dec 2000) Abstract: Both philosophical and mathematical considerations argue against the existence of 'non-locality,' or faster than light interaction. Nevertheless, it is widely accepted that non-locality has been established by Bell's Theorems as an intrinsic feature of the natural world. Herein it is shown, to the contrary, that the analysis supporting Bell's Theorems contains implicit hypotheses that are fully disputable and unacceptable on the basis logic, probability theory and basic physics. Finally, the consequences of the rejection of non-locality for the interpretation of Quantum Mechanics are discussed. Resume: Les considerations philosophiques aussi bien que mathematiques semblent contredire l'existence de la non-localite, l'interaction plus rapide que la vitesse lumiere. Neanmoins, il est generallement reconnue que la non-localite est demontree par le Theoreme de Bell comme une qualite intrinsique du monde naturel. Nous essaierons de montrer ici, au contraire, que l'analyse sur laquelle sappuie le Theoreme de Bell comporte des hypotheses implicites qui sont entierement contestables est inacceptables en termes de logique, de theorie de la prbabilite et de physique elementaire. Enfin nous parlerons des consequences du rejet de la non-localite sur l'interpretation de Mechanique Quantique.

Microstructural SANS – studies of hydrating tricalcium silicate (C3S)

Abstract: According to the typical composition of cement powder, the cement clinker phase tricalcium silicate (C3S) is of high importance for the formation of the hydration products in cement paste. This presentation exemplarily discusses results of small angle neutron scattering (SANS) investigations to study the effect of different parameters on the microstructure of hydrating C3S. Here the samples were stored for a given time under various climatic conditions (CO2 content of the ambient air). On simulating a very high degree of carbonation (3.00 vol % in air), microstructural changes are most evident.

Verformungsverhalten und rechnerische Abschätzung der Ermüdungslebensdauer metallischer Werkstoffe unter mehrachsig nichtproportionaler Beanspruchung

Abstract: Ziel des Forschungsvorhabens ist die Erstellung und Uberprufung eines Modells zur rechnerischen Lebensdauerabschatzung fur mehrachsig nichtproportionale Beanspruchung auf mechanismenorientierter Basis. Hierfur wird davon ausgegangen, dass die technische Anrisslebensdauer im Wesentlichen aus der Phase des Kurzrissfortschritts besteht. Das Wachstum des kurzen Risses wird unter Verwendung bruchmechanischer Ansatze berechnet. Als Beanspruchungsparameter dient das zyklische effektive J-Integral. Es wird ebenso wie das Rissschliesen mit Hilfe von Naherungsgleichungen berechnet. Zur Abbildung des Deformationsverhaltens wird ein Plastizitatsmodell verwendet, das auf dem Modell von Jiang [1993] basiert und zur Beschreibung der nichtproportionalen Zusatzverfestigung erweitert wurde. Auf experimenteller Seite werden Versuche an Rohr- und Kerbproben mit einem breiten Spektrum an verschiedenartigen Beanspruchungen durchgefuhrt. Die Ergebnisse der Versuche dienen der Verifikation des Modells und der Identifizierung von Schadigungsmechanismen. Deformation behaviour and numerical fatigue lifetime prediction of metallic materials under multiaxial nonproportional loading The development and evaluation of a model for lifetime prediction under multiaxial nonproportional loading is the aim of the current research project. It is assumed that the technical crack initiation life is consumed by short crack growth. This phenomenon is described using a fracture mechanics based approach. Herein, the effective cyclic J-integral is used as crack tip parameter. Crack opening levels and J-integral values are calculated applying approximation formulas. A plasticity model that is based on the Jiang model [Jia93] and extended to describe nonproportional hardening is used to predict the deformation behaviour. Experimental investigations on tubular and notched specimens with a wide range of different loading spectra serve for the verification of the model and for the identification of damage mechanisms.

The search for a precise method of measurement in psychical experiments

Abstract: In a series of three brief case studies, it is reconstructed how cognition and psychic activity were explored as energetic and economic transformations in a variety of experimental settings. 1. In the 1870s, the German psychiatrist Emil Kraepelin started his search for an objective measurement of cognitive performance in which he engaged over several decades. His investigations resulted in a graphic representation of cognitive efficiency, the "arbeitscurve", delineating the numbers of additions per time interval in close resemblance to representations of machine efficiency. 2. At the turn of the century, the American nutrition scientist and agronomist Wilbur Olin Atwater convinced himself in a series of precision measurements that the human motor was a so perfectly closed input-output system that he rejected any mental surplus in the form of cognitive energy transformations as contradictions to the principle of the conservation of energy. 3. At the beginning of the twentieth century and on the basis of Atwater's results, the German psychiatrist Hans Berger stipulated a special form of psychic energy for mediating between the principle of the conservation of energy and mental causality. Berger attempted to quantify psychic energy as one factor of brain metabolism. In the three cases of precision investigations into psychic life presented here, the experimental space of psychophysiology turned mental activity into a form of machine-like behavior.

One year experiences in bridge testing using the loading truck BELFA

Abstract: In Germany, a group of researchers from four universities has developed an advanced experimental supported objective condition assessment method for concrete bridges, called 'EXTRA'. This method is useable preferably in cases where conventional assessment methods cannot be applied successfully. In the past more than 250 bridges and buildings were evaluated regarding their real actual load bearing capacity using this objective assessment method. In Germany, an authorized guideline for the practical application of concrete structures is available. Because in the past the process of mounting and dismantling the loading equipment did require the most time of the test duration and also the traffic interruption, the same researchers developed the loading truck BELFA, suitable for bridges with single spans 1

Fast normal map generation for simplified meshes

Abstract: Approximating detailed models with coarse, normal mapped meshes is a very efficient method for real-time rendering of complex objects with fine surface detail. In this paper, we present a new and fast normal map construction algorithm. We scan-convert each triangle of the simplified model, which results in a regularly spaced point set on the surface of each triangle. The original model and all these point samples of the simplified model are rendered from uniformly distributed camera positions. The actual normal map is created by computing the corresponding normals for the point sets. For each point, the normal of the closest point from the high resolution mesh over the set of all camera positions is chosen. Our approach works for general triangle meshes and exploits fully common graphics rendering hardware. Normal map construction times are generally in the range of only a few seconds even for large models. We render our normal-mapped meshes in real-time with a slightly modified version of the standard bump-mapping algorithm. In order to evaluate the approximation error, we investigate the distance and normal errors for normal-mapped meshes. Our investigation of the approximation errors shows that using more than 12 viewpoints does not result in a further improvement in the normal maps for our test cases.

The virtual showcase: a projection-based multi-user augmented reality display

Abstract: The Virtual Showcase is a new projection-based and application-specific Augmented Reality display that offers an innovative way of accessing, presenting, and interacting with scientific and cultural content. Conceptually, the Virtual Showcase is compatible with the conventional showcases used, for instance, by museums. However, it allows the display of computer generated 3D graphics and animations together with real artifacts within the same space. From the technological point of view, the Virtual Showcase provides perspective correct stereoscopic viewing for multiple users, high resolution, low parallax (reflected projection plane inside the showcase), and support for mutual occlusion between real and virtual objects.

One less quantum mystery

Abstract: A classical model for 'Franson'-type Einstein, Podolsky and Rosen (EPR) experiments is described and compared with alternative, local, realistic models to be found in the literature. A brief analysis is presented which shows that such a model is possible because of unrecognized assumptions in Bohm's reformulation of the EPR gedanken experiment which preclude its use for addressing EPR's challenge.

Debunking the Buzz Words OR Can hermeneutic analysis be used to evaluate pedagogically based learning objects designed from constructivist epistemological ontologies defined in XML Metadata

Abstract: Arguably the biggest "buzz word" of the current year has been "learning or knowledge object". To understand the learning object and why it should be such a highly desirable commodity, it is necessary to unpack not only this concept but more importantly revisit some contributing concepts and constructs (more buzz words) that support the building of truly pedagogically informed reusable objects (Boyle & Cook 2001). The words and relationships explored in this paper are: learning or knowledge objects--the desirable construct in today's E-learning environment; ontologies and ways of expressing them through topic maps as they allow users to define and describe the components of an entity; metadata and XML used to create categorize, label and communicate the value of these objects; and hermeneutics and phenomenology as they refer to the interpretation of experience and events and evaluation of learning events. (Contains 23 references.) (Author) Reproductions supplied by EDRS are the best that can be made from the original document.

The Schrödinger equation and a multidimensional inverse scattering transform

Abstract: The Schrodinger equation is one of the most important equations in mathematics, physics and also engineering. We outline some connections between transformations of non-linear equations, the Schrodinger equation and the inverse scattering transform. After some remarks on generalizations into higher dimensions we present a multidimensional ∂¯ method based on Clifford analysis. To explain the method we consider the formal solution of the inverse scattering problem for the n-dimensional time-dependent Schrodinger equations given by A.I. Nachman and M.J. Ablowitz. Copyright © 2002 John Wiley & Sons, Ltd.

Ambiguous Digitizations by Dilation.

Abstract: This article deals with ambiguous surface digitizations by dilation in n-dimensional space. The digitization of a sufficiently regular surface is separating but not necessarily minimal. We will determine conditions under which the supercover and the grid intersection digitizations are discrete surfaces. It will also be proven that non-overlapping domains do not solve the problem of simple points in digitizations. No matter how the digitization domain is chosen there will occur ambiguous cases which have to be treated differently.

Architectural Content System - ACS Internet Based Support for Architectural Planning Proceses

Abstract: As building projects become increasingly more complex, the number of project participants increases as does their spatial distribution. An effective decentralised work process and co-operation is of increasing importance. The global computer network, the internet, has great potential and recent times have seen the development of a variety of techniques in this field. The project proposal described here is based upon this approach and also takes it a step further. A specific analysis of the subject and the subsequent identification of potential approaches formed the basis for an architectural application that brings the architect in contact with other project participants using the internet as a powerful yet simple and easy to use medium.

Untersuchungen zur Schwermetallfreisetzung bei der thermischen Abfallbehandlung auf einem Vorschubrost mit Hilfe von Radiotracern

Abstract: Der vorliegende Beitrag berichtet uber den Einsatz von kurzlebigen radioaktiven Isotopen ausgewahlter Schwermetalle zum Zweck der mestechnischen Erfassung von Ort, Zeit und Menge ihrer Freisetzung bei der Verbrennung von Hausmull in einer kleintechnischen Vorschubrostfeuerungsanlage. Dabei kamen Zn (13,8 Stunden Halbwertszeit) und Cu (12,7 Stunden Halbwertszeit) als Vertreter relativ gut bzw. kaum fluchtiger Schwermetalle zum Einsatz. Alle Meswerte wurden beruhrungslos und probenahmefrei erfast, da es sich bei allen genannten Isotopen um Gamma-Strahler handelt. Die Bestimmung des Freisetzungsortes erfolgte durch entlang des Vorschubrostes angeordneter NaI(Tl)-SzintillationsStrahlungsdetektoren; die Erfassung der Freisetzungsrate mit Hilfe eines Detektors, der innerhalb eines Absorbers zur Wasche eines Rauchgasteilstroms positioniert war.

Curves in ℤn

Abstract: A new definition of closed curves in n-dimensional discrete space is proposed. This definition can be viewed as a generalization of closed quasi curves and is intended to overcome the limitations of known definitions for practical purposes. Following the proposed definition, a set of points forms a closed curve in discrete space if the set admits a parameterization, i.e. there exists a Hamiltonian cycle in the set. Adjacencies that do not indicate the parameterization are allowed only between points that are “close to each other” along the parameterization. Additionally, it is proven that discrete curves satisfying the new definition in two-dimensional discrete space have the Jordan property.