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Vorgestellt wird ein System basierend auf einem 3D-Scanner nach dem Licht- schnitt-Prinzip mit dem es möglich ist, einen Menschen innerhalb von 1,5 Sekun- den dreidimensional zu erfassen. Mit Hilfe von Evolutionären Algorithmen wird über eine modellbasierte Dateninterpretation die Auswertung der Meßdaten betrie- ben, so daß beliebige Körpermaße ermittelt werden können. Das Ergebnis ist ein individualisiertes CAD-Modells der Person im Rechner. Ein derartiges Modell kann als virtuelle Kleiderpuppe zur Produktion von Maßbekleidung dienen.
This paper presents a new approach to parallel path planning for industrial robot arms with six degrees of freedom in an on-line given 3D environment. The method is based a best-first search algorithm and needs no essential off-line computations. The algorithm works in an implicitly discrete configuration space. Collisions are detected in the Cartesian workspace by hierarchical distance computation based on polyhedral models of the robot and the obstacles. By decomposing the 6D configuration space into hypercubes and cyclically mapping them onto multiple processing units, a good load distribution can be achieved. We have implemented the parallel path planner on a workstation cluster with 9 PCs and tested the planner for several benchmark environments. With optimal discretisation, the new approach usually shows very good speedups. In on-line provided environments with static obstacles, the parallel planning times are only a few seconds.
The World Wide Web is a medium through which a manufacturer may allow Internet visitors to customize or compose his products. Due to missing or rapidly changing standards these applications are often restricted to relatively simple CGI or JAVA based scripts. Usually, results like images or movies are stored in a database and are transferred on demand to the web-user. Viper (Visualisierung parametrisch editierbarer Raumkomponenten) is a Toolkit [VIP96] written in C++ and JAVA which provides 3D-modeling and visualization methodsfor developing complex web-based applications. The Toolkit has been designed to built a prototype, which can be used to construct and visualize prefabricated homes on the Internet. Alternative applications are outlined in this paper. Within Viper, all objects are stored in a scene graph (VSSG ), which is the basic data structure of the Toolkit. To show the concept and structure of the Toolkit, functionality, and implementation of the prototype are described.
A practical distributed planning and control system for industrial robots is presented. The hierarchical concept consists of three independent levels. Each level is modularly implemented and supplies an application interface (API) to the next higher level. At the top level, we propose an automatic motion planner. The motion planner is based on a best-first search algorithm and needs no essential off-line computations. At the middle level, we propose a PC-based robot control architecture, which can easily be adapted to any industrial kinematics and application. Based on a client/server-principle, the control unit estab-lishes an open user interface for including application specific programs. At the bottom level, we propose a flexible and modular concept for the integration of the distributed motion control units based on the CAN bus. The concept allows an on-line adaptation of the control parameters according to the robot's configuration. This implies high accuracy for the path execution and improves the overall system performance.
We derive a new class of particle methods for conservation laws, which are based on numerical flux functions to model the interactions between moving particles. The derivation is similar to that of classical Finite-Volume methods; except that the fixed grid structure in the Finite-Volume method is substituted by so-called mass packets of particles. We give some numerical results on a shock wave solution for Burgers equation as well as the well-known one-dimensional shock tube problem.
In the present paper multilane models for vehicular traffic are considered. A microscopic multilane model based on reaction thresholds is developed. Based on this model an Enskog like kinetic model is developed. In particular, care is taken to incorporate the correlations between the vehicles. From the kinetic model a fluid dynamic model is derived. The macroscopic coefficients are deduced from the underlying kinetic model. Numerical simulations are presented for all three levels of description in [10]. Moreover, a comparison of the results is given there.
In this paper the work presented in [6] is continued. The present paper contains detailed numerical investigations of the models developed there. A numerical method to treat the kinetic equations obtained in [6] are presented and results of the simulations are shown. Moreover, the stochastic correlation model used in [6] is described and investigated in more detail.
In this paper the kinetic model for vehicular traffic developed in [3,4] is considered and theoretical results for the space homogeneous kinetic equation are presented. Existence and uniqueness results for the time dependent equation are stated. An investigation of the stationary equation leads to a boundary value problem for an ordinary differential equation. Existence of the solution and some properties are proved. A numerical investigation of the stationary equation is included.
Groups can be studied using methods from different fields such as combinatorial group theory or string rewriting. Recently techniques from Gröbner basis theory for free monoid rings (non-commutative polynomial rings) respectively free group rings have been added to the set of methods due to the fact that monoid and group presentations (in terms of string rewriting systems) can be linked to special polynomials called binomials. In the same mood, the aim of this paper is to discuss the relation between Nielsen reduced sets of generators and the Todd-Coxeter coset enumeration procedure on the one side and the Gröbner basis theory for free group rings on the other. While it is well-known that there is a strong relationship between Buchberger's algorithm and the Knuth-Bendix completion procedure, and there are interpretations of the Todd-Coxeter coset enumeration procedure using the Knuth-Bendix procedure for special cases, our aim is to show how a verbatim interpretation of the Todd-Coxeter procedure can be obtained by linking recent Gröbner techniques like prefix Gröbner bases and the FGLM algorithm as a tool to study the duality of ideals. As a side product our procedure computes Nielsen reduced generating sets for subgroups in finitely generated free groups.
We present a parallel control architecture for industrial robot cells. It is based on closed functional components arranged in a flat communication hierarchy. The components may be executed by different processing elements, and each component itself may run on multiple processing elements. The system is driven by the instructions of a central cell control component. We set up necessary requirements for industrial robot cells and possible parallelization levels. These are met by the suggested robot control architecture. As an example we present a robot work cell and a component for motion planning, which fits well in this concept.
The term enterprise modelling, synonymous with enterprise engineering, refers to methodologies developed for modelling activities, states, time, and cost within an enterprise architecture. They serve as a vehicle for evaluating and modelling activities resources etc. CIM - OSA (Computer Integrated Manufacturing Open Systems Architecture) is a methodology for modelling computer integrated environments, and its major objective is the appropriate integration of enterprise operations by means of efficient information exchange within the enterprise. PERA is another methodology for developing models of computer integrated manufacturing environments. The department of industrial engineering in Toronto proposed the development of ontologies as a vehicle for enterprise integration. The paper reviews the work carried out by various researchers and computing departments on the area of enterprise modelling and points out other modelling problems related to enterprise integration.
We present a particle method for the numerical simulation of boundary value problems for the steady-state Boltzmann equation. Referring to some recent results concerning steady-state schemes, the current approach may be used for multi-dimensional problems, where the collision scattering kernel is not restricted to Maxwellian molecules. The efficiency of the new approach is demonstrated by some numerical results obtained from simulations for the (two-dimensional) BEnard's instability in a rarefied gas flow.
In this paper we present a domain decomposition approach for the coupling of Boltzmann and Euler equations. Particle methods are used for both equations. This leads to a simple implementation of the coupling procedure and to natural interface conditions between the two domains. Adaptive time and space discretizations and a direct coupling procedure leads to considerable gains in CPU time compared to a solution of the full Boltzmann equation. Several test cases involving a large range of Knudsen numbers are numerically investigated.
For the determination of the earth" s gravity field many types of observations are available nowadays, e.g., terrestrial gravimetry, airborne gravimetry, satellite-to-satellite tracking, satellite gradiometry etc. The mathematical connection between these observables on the one hand and gravity field and shape of the earth on the other hand, is called the integrated concept of physical geodesy. In this paper harmonic wavelets are introduced by which the gravitational part of the gravity field can be approximated progressively better and better, reflecting an increasing flow of observations. An integrated concept of physical geodesy in terms of harmonic wavelets is presented. Essential tools for approximation are integration formulas relating an integral over an internal sphere to suitable linear combinations of observation functionals, i.e., linear functionals representing the geodetic observables. A scale discrete version of multiresolution is described for approximating the gravitational potential outside and on the earth" s surface. Furthermore, an exact fully discrete wavelet approximation is developed for the case of band-limited wavelets. A method for combined global outer harmonic and local harmonic wavelet modelling is proposed corresponding to realistic earth" s models. As examples, the role of wavelets is discussed for the classical Stokes problem, the oblique derivative problem, satellite-to-satellite tracking, satellite gravity gradiometry, and combined satellite-to-satellite tracking and gradiometry.
The paper presents a process-oriented view on knowledge management in software development. We describe requirements on knowledge management systems from a process-oriented perspective, introduce a process modeling language MILOS and its use for knowledge management. Then we explain how a process-oriented knowledge management system can be implemented using advanced but available information technologies.
A natural extension of SLD-resolution is introduced as a goal directed proof procedure
for the full first order implicational fragment of intuitionistic logic. Its intuitionistic semantic fits a procedural interpretation of logic programming. By allowing arbitrary nested implications it can be used for implementing modularity in logic programs. With adequate negation axioms it gives an alternative to negation as failure and leads to a proof procedure for full first order predicate logic.
Annual Report 1997
(1998)
Anwendungen effizienter Verfahren in Automation - Universität Karlsruhe auf der SPS97 in Nürnberg -
(1998)
Application of Moment Realizability Criteria for Coupling of the Boltzmann and Euler Equations
(1998)
The moment realizability criteria have been used to test the domains of validity of the Boltzmann and Euler Equations. With the help of this criteria teh coupling of the Boltzmann and Euler equations have been performed in two dimensional spatial space. The time evolution of domain decompositions for such equations have been presented in different time steps. The numerical resulta obtained from the coupling code have been compared with those from the pure Boltzmann one.
This paper discusses the problem of automatic off-line programming and motion planning for industrial robots. At first, a new concept consisting of three steps is proposed. The first step, a new method for on-line motion planning is introduced. The motion planning method is based on the A*-search algorithm and works in the implicit configuration space. During searching, the collisions are detected in the explicitly represented Cartesian workspace by hierarchical distance computation. In the second step, the trajectory planner has to transform the path into a time and energy optimal robot program. The practical application of these two steps strongly depends on the method for robot calibration with high accuracy, thus, mapping the virtual world onto the real world, which is discussed in the third step.
On the one hand, in the world of Product Data Technology (PDT), the ISO standard STEP (STandard for the Exchange of Product model data) gains more and more importance. STEP includes the information model specification language EXPRESS and its graphical notation EXPRESS-G. On the other hand, in the Software Engineering world in general, mainly other modelling languages are in use - particularly the Unified Modeling Language (UML), recently adopted to become a standard by the Object Management Group, will probably achieve broad acceptance. Despite a strong interconnection of PDT with the Software Engineering area, there is a lack of bridging elements concerning the modelling language level. This paper introduces a mapping between EXPRESS-G and UML in order to define a linking bridge and bring the best of both worlds together. Hereby the feasibility of a mapping is shown with representative examples; several problematic cases are discussed as well as possible solutions presented.
In order to improve the distribution system for the Nordic countries the BASF AG considered 13 alternative scenarios to the existing system. These involved the construction of warehouses at various locations. For every scenario the transportation, storage, and handling cost incurred was to be as low as possible, where restrictions on the delivery time were given. The scenarios were evaluated according to (minimal) total cost and weighted average delivery time. The results led to a restriction to only three cases, involving only one new warehouse each. For these a more accurate model for the cost was developped and evaluated, yielding results similar to a simple linear model. Since there were no clear preferences between cost and delivery time, the final decision was chosen to represent a compromise between the two criteria.
Knowledge about the distribution of a statistical estimator is important for various purposes like, for example, the construction of confidence intervals for model parameters or the determiation of critical values of tests. A widely used method to estimate this distribution is the so-called bootstrap which is based on an imitation of the probabilistic structure of the data generating process on the basis of the information provided by a given set of random observations. In this paper we investigate this classical method in the context of artificial neural networks used for estimating a mapping from input to output space. We establish consistency results for bootstrap estimates of the distribution of parameter estimates.
In this paper domain decomposition methods for radiative transfer problems including conductive heat transfer are treated. The paper focuses on semi-transparent materials, like glass, and the associated conditions at the interface between the materials. Using asymptotic analysis we derive conditions for the coupling of the radiative transfer equations and a diffusion approximation. Several test cases are treated and a problem appearing in glass manufacturing processes is computed. The results clearly show the advantages of a domain decomposition approach. Accuracy equivalent to the solution of the global radiative transfer solution is achieved, whereas computation time is strongly reduced.
The paper discusses the metastable states of a quantum particle in a periodic potential under a constant force (the model of a crystal electron in a homogeneous electric ,eld), which are known as the Wannier-Stark ladder of resonances. An ecient procedure to ,nd the positions and widths of resonances is suggested and illustrated by numerical calculation for a cosine potential.
Contrary to symbolic learning approaches, that represent a learned concept explicitly, case-based approaches describe concepts implicitly by a pair (CB; sim), i.e. by a measure of similarity sim and a set CB of cases. This poses the question if there are any differences concerning the learning power of the two approaches. In this article we will study the relationship between the case base, the measure of similarity, and the target concept of the learning process. To do so, we transform a simple symbolic learning algorithm (the version space algorithm) into an equivalent case-based variant. The achieved results strengthen the hypothesis of the equivalence of the learning power of symbolic and casebased methods and show the interdependency between the measure used by a case-based algorithm and the target concept.
The Wannier-Bloch resonance states are metastable states of a quantum particle in a space-periodic potential plus a homogeneous field. Here we analyze the states of quantum particle in space- and time-periodic potential. In this case the dynamics of the classical counterpart of the quantum system is either quasiregular or chaotic depending on the driving frequency. It is shown that both the quasiregular and the chaotic motion can also support quantum resonances. The relevance of the obtained result to the problem a of crystal electron under simultaneous influence of d.c. and a.c. electric fields is briefly discussed. PACS: 73.20Dx, 73.40Gk, 05.45.+b
Abstract: We show that the physical mechanism of population transfer in a 3-level system with a closed loop of coherent couplings (loop-STIRAP) is not equivalent to an adiabatic rotation of the dark-state of the Hamiltonian but coresponds to a rotation of a higher-order trapping state in a generalized adiabatic basis. The concept of generalized adiabatic basis sets is used as a constructive toolto design pulse sequences for stimulated Raman adiabatic passage (STIRAP) which give maximum population transfer also under conditions when the usual condition of adiabaticty is only poorly fulfilled. Under certain conditions for the pulses (generalized matched pulses) there exists a higher-order trapping state, which is an exact constant of motion and analytic solutions for the atomic dynamics can be derived.
Convex Analysis
(1998)
Preface Convex analysis is one of the mathematical tools which is used both explicitly and indirectly in many mathematical disciplines. However, there are not so many courses which have convex analysis as the main topic. More often, parts of convex analysis are taught in courses like linear or nonlinear optimization, probability theory, geometry, location theory, etc.. This manuscript gives a systematic introduction to the concepts of convex analysis. A focus is set to the geometrical interpretation of convex analysis. This focus was one of the reasons why I have decided to restrict myself to the finite dimensional case. Another reason for this restriction is that in the infinite dimensional case many proofs become more difficult and more technical. Therefore, it would not have been possible (for me) to cover all the topics I wanted to discuss in this introductory text in the infinite dimensional case, too. Anyway, I am convinced that even for someone who is interested in the infinite dimensional case this manuscript will be a good starting point. When I offered a course in convex analysis in the Wintersemester 1997/1998 (upon which this manuscript is based) a lot of students asked me how this course fits in their own studies. Because this manuscript will (hopefully) be used by some students in the future, I will give here some of the possible statements to answer this very question. - Convex analysis can be seen as an extension of classical analysis, in which still we get many of the results, like a mean-value theorem, with less assumptions on the smoothness of the function. - Convex analysis can be seen as a foundation of linear and nonlinear optimization which provides many tools to handle concepts in optimization much easier (for example the Lemma of Farkas). - Finally, convex analysis can be seen as a link between abstract geometry and very algorithmic oriented computational geometry. As already explained before, this manuscript is based on a one semester course and therefore cannot cover all topics and discuss all aspects of convex analysis in detail. To guide the interested reader I have included a list of nice books about this subject at the end of the manuscript. It should be noted that the philosophy of this course follows [3], [4] and THE BOOK of modern convex analysis [6]. The geometrical emphasis however, is also related to intentions of [1].^L
The greybody factors in BTZ black holes are evaluated from 2D CFT in the spirit of AdS3/CFT correspondence. The initial state of black holes in the usual calculation of greybody factors by effective CFT is described as Poincar'e vacuum state in 2D CFT. The normalization factor which cannot be fixed in the effective CFT without appealing to string theory is shown to be determined by the normalized bulk-to-boundary Green function. The relation among the greybody factors in different dimensional black holes is exhibited. Two kinds of (h; _h) = (1; 1) operators which couple with the boundary value of massless scalar field are discussed.
In this paper, a combined approach to damage diagnosis of rotors is proposed. The intention is to employ signal-based as well as model-based procedures for an improved detection of size and location of the damage. In a first step, Hilbert transform signal processing techniques allow for a computation of the signal envelope and the instantaneous frequency, so that various types of non-linearities due to a damage may be identified and classified based on measured response data. In a second step, a multi-hypothesis bank of Kalman Filters is employed for the detection of the size and location of the damage based on the information of the type of damage provided by the results of the Hilbert transform.
Interoperability between different CAx systems involved in the development process of cars is presently one of the most critical issues in the automotive industry. None of the existing CAx systems meets all requirements of the very complex process network of the lifecycle of a car. With this background, industrial engineers have to use various CAx systems to get an optimal support for their daily work. Today, the communication between different CAx systems is done via data files using special direct converters or neutral system independent standards like IGES, VDAFS, and recently STEP, the international standard for product data description. To reduce the dependency on individual CAx s ystem vendors, the German automotive industry developed an open CAx system architecture based on STEP as guiding principle for CAx system development. The central component of this architecture is a common, system-independent access interface to CAx functions and data of all involved CAx systems, which is under development in the project ANICA. Within this project, a CAx object bus has been developed based on a STEP data description using CORBA as an integration platform. This new approach allows a transparent access to data and functions of the integrated CAx systems without file-based data exchange. The product development process with various CAx systems concerns objects from different CAx systems. Thus, mechanisms are needed to handle the persistent storage of the CAx objects distributed over the CAx object bus to give the developing engineers a consistent view of the data model of their product. The following paper discusses several possibilities to guarantee consistent data management and storage of distributed CAx models. One of the most promising approaches is the enhancement of the CAx object bus by a STEP-based object-oriented data server to realise a central data management.
Das Problem der Integration heterogener Softwaresysteme stellt sich auch auf dem Gebiet der CAx-Systeme, wie sie in vielfältigen Ausprägungen etwa in der Automobilbranche für die Fahrzeugentwicklung eingesetzt werden. Zunächst werden die heute in diesem Bereich
praktizierten Lösungen und die dabei auftretenden Probleme kurz dargestellt. Danach werden der neue Standard für Produktdaten, STEP, und der Standard für die Interoperabilität heterogener Softwaresysteme, CORBA, sowie einige CORBA-Entwurfsmuster erläutert. Als nächstes wird eine auf diesen beiden Standards basierende CAx-Integrationsarchitektur, die im Projekt ANICA entwickelt wurde, vorgestellt und die prinzipielle Vorgehensweise bei
ihrer Realisierung beschrieben. Daran anschließend wird über eine erste Umsetzung dieser Architektur in die Praxis berichtet. Zum Abschluß wird kurz auf die gewonnenen Erfahrungen eingegangen und ein Ausblick auf zukünftige Entwicklungen gegeben.
The paper studies differential and related properties of functions of a real variable with values in the space of signed measures. In particular the connections between different definitions of differentiability are described corresponding to different topologies on the measures. Some conditions are given for the equivalence of the measures in the range of such a function. These conditions are in terms of socalled logarithmic derivatives and yield a generalization of the Cameron-Martin-Maruyama-Girsanov formula. Questions of this kind appear both in the theory of differentiable measures on infinite-dimensional spaces and in the theory of statistical experiments.
Bekanntlich gibt es keinen befriedigenden unendlich dimensionalen Ersatz für das Lebesgue-Mass. Andererseits lassen sich viele Techniken klassischer Analysis auch auf unendlich dimensionale Situationen übertragen. Eine Möglichkeit hierzu gibt die Theorie differenzierbarer Masse. Man definiert Richtungsableitungen für Masse ähnlich wie für Funktionen. Eines der zentralen Beispiele ist das Wiener-Mass. Stochastische Integration bezüglich der Brownschen Bewegung, insbesondere das Skorokhod-Integral ergeben sich in natürlicher Weise durch diesen Ansatz und auch die Grundideen des MalliavinKalküls lassen sich in diesem Rahmen einfach erläutern. Die Vorträge geben die meisten Beweise.
The pure-Skyrme limit of a scale-breaking Skyrmed O(3) sigma model in 1+1 dimensions is employed to study the effect of the Skyrme term on the semiclassical analysis of a field theory with instantons. The instantons of this model are self-dual and can be evaluated explicitly. They are also localised to an absolute scale, and their fluctuation action can be reduced to a scalar subsystem. This permits the explicit calculation of the fluctuation determinant and the shift in vacuum energy due to instantons. The model also illustrates the semiclassical quantisation of a Skyrmed field theory.
Der vorliegende Artikel setzt die Beitragsreihe zur Vorstellung der Ergebnisse der FEMEX fort, die mit der Präsentation einer allgemeinen Feature-Definition in [BWE-96] begonnen wurde. FEMEX (Feature Modelling Experts) ist eine internationale und interdisziplinäre Gruppe von Forschern, Entwicklern und Anwendern aus Universitäten, Forschungsinstituten und Industrie, die sich zum Ziel gesetzt haben, Grundlagen für eine Feature-basierte Produktentwicklung zu erarbeiten. Der Anwender steht dabei im Mittelpunkt der Bemühungen: die Feature-Technologie hat die Aufgabe, ihm Methoden und Werkzeuge an die Hand zu geben, mit denen er in den unterschiedlichen Phasen einer komplexen Prozeßkette effizient arbeiten kann. Vier Arbeitsgruppen wurden gebildet, die sich mit unterschiedlichen Aspekten der Feature-Technologie beschäftigen. In diesem Beitrag werden die Ergebnisse der Arbeitsgruppe II Feature Modelling Methods and Application Areas" vorgestellt. Ihre Aufgabe ist es, die Modellierungsmethoden und Anwendungsgebiete der Feature-Technologie im Kontext des Produktentwicklungs- prozesses zu untersuchen. Ausgangspunkt für die Arbeiten ist neben den benutzerspezifischen Anforderungen die Feature-Definition der Arbeitsgruppe I [BWE-96]. An dieser Definition ist hervorzuheben, daß Features keine physikalischen Elemente sind und auch keine physikalischen Entsprechungen haben müssen, sondern nur in der Welt der informationstechnischen Modelle existieren. Desweiteren sind die für den Anwender relevanten Eigenschaften der bearbeiteten Objekte, welcher Art sie auch sein mögen (beispielsweise die Funktion des Bauteils), die eigentliche Grundlage der Definition. Keiner Eigenschaft wird von vorneherein eine höhere Priorität gegeben, wodurch die Bauteilgeometrie ihre tragende Rolle bei der Modellierung verliert (bei den meisten der heute angebotenen CAD/CAM-Systemen wird dagegen üblicherweise davon ausgegangen, daß die in einem System verarbeitete Produktgeometrie die Basis für das gesamte Produktmodell darstellt).
A new method of determining some characteristics of binary images is proposed based on a special linear filtering. This technique enables the estimation of the area fraction, the specific line length, and the specific integral of curvature. Furthermore, the specific length of the total projection is obtained, which gives detailed information about the texture of the image. The influence of lateral and directional resolution depending on the size of the applied filter mask is discussed in detail. The technique includes a method of increasing directional resolution for texture analysis while keeping lateral resolution as high as possible.
Diese Arbeit beschäftigt sich mit einer Möglichkeit zur Effizienzverbesserung, wobei das SNLP-basierte Planungssystem CAPlan verwendet wird. Dabei werden neue, zu lösende Probleme einer Vorverarbeitung unterzogen. Dort werden bestimmte Eigenschaften ermittelt, ohne jedoch das Problem zu lösen. Anschliessend wird dem Planungssystem das neue Problem mit dem Zusatzwissen in Form der analysierten Eigenschaften übergeben. Das Planungssystem verwendet das Wissen, um effizienter eine Lösung zu finden.
Ein verhaltensorientierter Ansatz zum flächendeckenden Fahren in a priori unbekannter Umgebung
(1998)
In diesem Aufsatz wird ein Verfahren zum flächendeckenden Fahren in zu- nächst unbekannter Umgebung beschrieben, wie es z.B. für Reinigungsanwen- dungen im Heimbereich benötigt wird. Parallel zur Durchführung der Reini- gungsaufgabe wird dabei die Umgebung exploriert und kartiert. Der verhaltensorientierte Ansatz ermöglicht eine robuste, zielgerichtete und dennoch ressourcenschonende Implementierung und gestattet es, einzelne Ver- haltensweisen leicht durch verbesserte oder auch speziell erlernte Versionen auszutauschen. Das vorgestellte Verfahren wurde simulativ getestet und wird in Kürze auf einem realen Roboter erprobt.
In der vorliegenden Arbeit wurde die chirale Induktion cholesterischer Phasen von unverbrückten 1,1'- Binaphthylen und über die 2,2'-Position verbrückten 1,1'-Binaphthylen untersucht, um eine Struktur/Wirkungsbeziehung zu entwickeln. Dazu wurden enantiomerenreine 1,1'-Binaphthyle (2 - 7) sowie ihre deuterierten Analoga (1, 3 - 7) für die 2H-NMR-Spektroskopie und die Racemate für die UV-Spektroskopie (3 - 7) synthetisiert. Die Verbindungen 6 und 7 sind bisher in der Literatur nicht beschrieben. Alle untersuchten Verbindungen bestehen aus Molekülen mit der Symmetriegruppe C2, sind inhärent dissymmetrisch (Klasse C) und als hinreichend starr anzusehen, so daß nur der intermolekulare Chiralitätstransfer zu diskutieren ist. Es zeigt sich, daß die chirale Induktion, ausgedrückt durch die helical twisting power (HTP), dann zum einen durch die chiralen Strukturelemente der Verbindungen und zum zweiten durch die Orientierung der Verbindungen in der Phase bestimmt wird. Verbrückte und unverbrückte 1,1'-Binaphthyle verhalten sich so unterschiedlich, daß sie in ihren Mechanismen getrennt diskutiert werden müssen. Über die 2H-NMR-Spektroskopie und z.T. über die polarisierte UV-Spektroskopie ergab sich für die verbrückten 1,1'-Binaphthyle (4, 5 und 6) daß die Orientierungsachse x3* etwa in Richtung der Naphthyl-Naphthyl- Bindungsrichtung liegt. Nimmt man Verbindung 4 als Basis und führt am Brückenatom einen spiro-verknüpften Cyclohexylring (Verbindung 5) oder als Brücke eine Di-tert.-butyl-Silizium-Gruppe ein (Verbindung 6), so wird die Ordnung bezüglich S* erniedrigt und die molekulare Biaxialität D* vergrößert. Ein spiro-verknüpfter Acetal- Fünfring zusätzlich zum Cyclohexylring von 5 (Verbindung 7), führt bei 7 zu einem Kippen der Orientierungsachse in Richtung der C2-Symmetrieachse. Das Ordnungsverhalten von 3 ließ sich nach I. Kiesewalter [Dissertation, Universität Kaiserslautern, 1999] und E. Dorr [Dissertation, Universität Kaiserslautern, 1999] nicht eindeutig bestimmen. Die Ergebnisse aus dem 2H-NMR sprechen bei 3 für eine Drehung der Orientierungsachse, die dann senkrecht zur C2-Symmetrieachse und der Naphthyl-Naphthyl-Bindungsrichtung steht. Mit den so erhaltenen Ordnungsparametern führt bei 3 der Versuch, die Lage des Hauptachsensystems aus dem 2H-NMR mit den Ergebnissen aus der anisotropen UV-Spektroskopie zu verifizieren, was für alle anderen untersuchten Verbindungen gelingt, zu Widersprüchen, die bisher nicht aufgelöst werden konnten. Das Chiralitätselement, das die HTP der verbrückten 1,1'-Binaphthyle bestimmt, wird durch die Verdrehung der beiden Naphthyl-Ebenen gegeneinander um einen Winkel theta gebildet, wobei zwischen theta = 0 Grad und theta = 180 Grad entgegen der Literaturbeschreibung keine achirale Nullstelle exisitiert. Die Substitution am Brückenatom erhöht die HTP woraus geschlossen werden kann, daß durch den Cyclohexyl-Substituenten eine dritte Ebene eingeführt wird, die mit den Ebenen der Naphthyle ein bzw. zwei neue Chiralitätselemente bildet, die zur HTP einen Beitrag leisten. Bei Verbindung 7 führt die veränderte Ordnung zu einem stärkeren Induktionseffekt, d.h. einem verstärkten intermolekularen Chiralitätstransfer. Bei unverbrückten 1,1'-Binaphthylen (1 bis 3), die weit niedrigere HTP-Werte als 4 bis 7 besitzen, findet man bei einer Verbindung (3) mit sterisch aufwendigen Substituenten in 2,2'-Position eine Vorzeichenumkehr der HTP. Dieser Effekt wurde von Gottarelli et al. als eine Umkehr der Helizität der 1,1'-Binaphthyle interpretiert. Diese Interpretation erweist sich als unzulässig, weil sie keine reale physikalische Basis hat. Bei unverbrückten 1,1'- Binaphthylen kann sich durch Aufdrehen des Diederwinkels theta das Orientierungsverhalten verändern und die Orientierungsachse drehen, was durch das Modell von Nordio bestätigt wird. Da dem Modell von Nordio ein spurloser Helizitätstensor zugrunde liegt, kann eine Veränderung der Tensorkoordinaten des Ordnungstensors unter bestimmten Voraussetzungen zu einer Vorzeichenumkehr der HTP führen. Wegen der Befunde aus der CD- Spektroskopie, die eine im Mittel transoide Konformation für die unverbrückten 1,1'-Binaphthyle ausschließen, kommt die Nordio'sche Interpretation für die hier untersuchten unverbrückten 1,1'-Binaphthyle nur unter der Annahme in Frage, daß bei den unverbrückten 1,1'-Binaphthyle eine breite Verteilung über den Diederwinkel theta vorliegt (LAM-Verhalten). Die theoretische Beschreibung der HTP, die von Nordio eingeführt wurde, erlaubt es nicht, die HTP eines Dotierstoffes in seiner Temperaturabhängigkeit zu beschreiben. Berechnet man mit Hilfe experimentell bestimmter Ordnungsparameter auf Basis der Gleichung von Nordio und Ferrarini aus den temperaturabhängigen HTP- Kurven die Tensorkoordinaten des Helizitätstensors, so zeigen sich systematische Abweichungen in den "rückgerechneten" HTP-Kurven. Im Rahmen der vorliegenden Arbeit wurde deshalb ein neuer Ansatz zur quantitativen Beschreibung der HTP eingeführt, der auf Annahmen einer Theorie basiert, die die ACD- Spektroskopie (CD anisotroper Proben) beschreibt. Es wurde ein Chiralitätswechselwirkungstensor eingeführt, dessen Koordinaten durch multiple Regression aus den temperaturabhängigen HTP-Kurven mit den Ordnungsparametern aus dem 2H-NMR erhalten wurden. Mit dem neuen Ansatz ergibt sich eine sehr gute Beschreibung der Größe und Temperaturabhängigkeit der experimentellen HTP-Werte. Die Analyse dieser Daten zeigt, daß die mittlere Lage der HTP-Kurven von der Spur des Chiralitätswechselwirkungstensors (bzw. von dem Term W/3 mit W = Summe(Wii*)) bestimmt wird, also dem Anteil an der HTP, der durch ein Dotierstoff-Molekül induziert werden würde, das in der anisotropen Phase isotrop verteilt ist. Die Krümmung der HTP-Kurven wird durch den D*-Anteil des Effekts verursacht. Der S*- Anteil führt bei niedriger Ordnung nur zu einer geringen Verschiebung der HTP-Kurve. Bei hoher Ordnung kann durch den S*-Anteil bei den Verbindungen 1, 3, 4 und 5 eine Helixinversion in der (theoretischen) HTP-Kurve vorausgesagt werden. Analysiert man den Gesamteffekt hinsichtlich seiner Anteile aus den Richtungen der Hauptachsen des Ordnungstensors, d.h. die Produkte gii33*Wii*, so findet man bei verbrückten 1,1'-Binaphthylen 4 bis 7, daß entlang der C2-Symmetrieachse der 1,1'-Binaphthyle der bei weitem größte Anteil am Gesamteffekt gefunden wird. Dieser Befund erklärt auch warum die Beschreibung von Nordio zu einer guten Übereinstimmung mit den experimentellen HTP-Werten führt, obwohl nach Nordio ein isotrop verteilter Dotierstoff keine HTP hat. Auch im Modell von Nordio wird der Effekt von dem Produkt einer Tensorkoordinate des Helizitätstensors und einer Tensorkoordinate des Ordnungstensors bestimmt, das der Richtung der C2-Symmetrieachse zuzuordnen ist. Allerdings ist das Modell von Nordio nur für eine "mittlere Ordnung" des Dotierstoffs anwendbar, da für sehr kleine Ordnung des Dotierstoffes die HTP gegen Null geht. Die Interpretation der Tensorkoordinaten des Chiralitätswechselwirkungstensors der unverbrückten 1,1'- Binaphthyle ist problematischer als bei den verbrückten 1,1'-Binaphthylen weil für die unverbrückte Verbindung 3 der Widerspruch zwischen den Resultaten aus der anisotropen UV-Spektroskopie und dem 2H-NMR besteht. Nach den vorliegenden Daten dominiert wie auch bei 4 bis 6 der Term g2233*W22* den Effekt, dieser ist aber nicht der Richtung der C2-Symmetrieachse zugeordnet. Die Tensorkoordinaten Wii* sind signifikant kleiner als bei den verbrückten 1,1'-Binaphthylen. Möglicherweise führt das LAM-Verhalten zu einer Verteilung über den Winkel theta und damit zu einer Orientierungsverteilung, die zu kleinen Werten im Chiralitätswechselwirkungstensor und der HTP führt.
Superselection rules induced by the interaction with the environment are investigated with the help of exactly soluble Hamiltonian models. Starting from the examples of Araki and of Zurek more general models with scattering are presented for which the projection operators onto the induced superselection sectors do no longer commute with the Hamiltonian. The example of an environment given by a free quantum field indicates that infrared divergence plays an essential role for the emergence of induced superselection sectors. For all models the induced superselection sectors are uniquely determined by the Hamiltonian, whereas the time scale of the decoherence depends crucially on the initial state of the total system.
In this paper we study a particular class of \(n\)-node recurrent neural networks (RNNs).In the \(3\)-node case we use monotone dynamical systems theory to show,for a well-defined set of parameters, that,generically, every orbit of the RNN is asymptotic to a periodic orbit.Then, within the usual 'learning' context of NeuralNetworks, we investigate whether RNNs of this class can adapt their internal parameters soas to 'learn' and then replicate autonomously certain external periodic signals.Our learning algorithm is similar to identification algorithms in adaptivecontrol theory. The main feature of the adaptation algorithm is that global exponential convergenceof parameters is guaranteed. We also obtain partial convergence results in the \(n\)-node case.
Aesthetic Design bzw. Styling ist mehr und mehr ein zentrales Merkmal für den Erfolg von Automobilen auf dem Weltmarkt. Entsprechend den firmenspezifischen Vorstellungen werden diese Eigenschaften der Karosserien in komplexen Abläufen herausgearbeitet. Computer Aided Styling (CAS), Computer Aided Aesthetic Design (CAAD) sind die Werkzeuge zur Schaffung optimaler Karosserieformen. Die Abläufe sind von Unternehmen zu Unternehmen unterschiedlich, haben aber ähnliche Strukturen: es wird die Form der Karosserie erstellt, anschließend wird mit Hilfe geeigneter Werkzeuge die Qualität der Flächen beurteilt. In einem nächsten Schritt werden die Flächen entsprechend dieser Beurteilung wieder verändert. Diese Schleifen werden wiederholt, bis das Ergebnis die Verantwortlichen zufriedenstellt. Im Brite-EuRam-Projekt FIORES von 12 Partnern aus 6 Ländern, mit Automobilunternehmen (BMW, Saab), Design-Firmen (Eiger, Formtech, Pininfarina, Taurus), Systemherstelllern und Forschungsinstituten wird jetzt versucht, Methoden zu entwickeln, die den Design-Ablauf verbessern könnten: Die Bewertungskriterien für ästhetische Flächen sollen formalisiert werden und dann direkt zur Modifikation der Freiformflächen benutzt werden im Sinne einer zielgesteuerten Modellierung (Engineering in Reverse, EiR). Dieser Artikel stellt die Ergebnisse des Projekts innerhalb des ersten Jahres dar: der Design-Prozeß in verschiedenen Unternehmen wird analysiert, die sich daraus ergebenden Beurteilungskriterien für ästhetische Formen werden formalisiert und der zielgesteuerten Modellierung zugeführt. Ausblicke auf weitere Ziele des Projekts werden gegeben. Die vorgestellten Arbeiten sind das gemeinsame Ergebnis des Projekt-Konsortiums.
Beim Greifen deformierbarer oder zerbrechlicher Werkstücke kommen der Greifgeschwindigkeit sowie der Greifkraft besondere Bedeutung zu. In dieser Arbeit wird eine universelle Steuerung für pneumatische Greifer beschrieben, die eine einfache Einstellung dieser Größen über zwei spannungsgesteuerte Proportionalventile gestattet. Diese Anordnung wird für eine Einflußanalyse von Greifkraft und Greifgeschwindigkeit beim Greifen von Kabeln und Kabelbäumen genutzt, welche sich als robust und unproblematisch erwiesen haben.
Es wird die Aufgabe der vollständigen räumlichen Abdeckung von Regionen in durch mobile Roboter betrachtet. Da-bei können die Regionen in vollständig, teilweise oder nicht bekannten Umgebungen liegen. Zur Lösung wird ein Verfahren aus der Computer-grafik zum Füllen von Bildregionen zugrunde gelegt. Das Verfahren hat eine lokale Sichtweise und läßt somit den Einsatz von Sensordaten und das Auftreten von unvorhergesehenen Hindernissen zu. Die Regionen können durch Karten off-line vorgegeben sein oder durch Sensordaten on-line aufgebaut werden. Dennoch ist eine vollständige und genau einma-lige Flächenbearbeitung garantiert. Dies wird an Beispielen in einer graphischen Visualisierung der Realzeit-Steuerung des Roboters validiert.
Functional Analysis
(1998)
The aim of this course is to give a very modest introduction to the extremely rich and well-developed theory of Hilbert spaces, an introduction that hopefully will provide the students with a knowledge of some of the fundamental results of the theory and will make them familiar with everything needed in order to understand, believe and apply the spectral theorem for selfadjoint operators in Hilbert space. This implies that the course will have to give answers to such questions as - What is a Hilbert space? - What is a bounded operator in Hilbert space? - What is a selfadjoint operator in Hilbert space? - What is the spectrum of such an operator? - What is meant by a spectral decomposition of such an operator?
Wavelet transform originated in 1980's for the analysis of seismic signals has seen an explosion of applications in geophysics. However, almost all of the material is based on wavelets over Euclidean spaces. This paper deals with the generalization of the theory and algorithmic aspects of wavelets to a spherical earth's model and geophysically relevant vector fields such as the gravitational, magnetic, elastic field of the earth.A scale discrete wavelet approach is considered on the sphere thereby avoiding any type of tensor-valued 'basis (kernel) function'. The generators of the vector wavelets used for the fast evaluation are assumed to have compact supports. Thus the scale and detail spaces are finite-dimensional. As an important consequence, detail information of the vector field under consideration can be obtained only by a finite number of wavelet coefficients for each scale. Using integration formulas that are exact up to a prescribed polynomial degree, wavelet decomposition and reconstruction are investigated for bandlimited vector fields. A pyramid scheme for the recursive computation of the wavelet coefficients from level to level is described in detail. Finally, data compression is discussed for the EGM96 model of the earth's gravitational field.
A formalism is developed for calculating the quasienergy states and spectrum for time-periodic quantum systems when a time-periodic dynamical invariant operator with a nondegenerate spectrum is known. The method, which circumvents the integration of the Schr-odinger equation, is applied to an integrable class of systems, where the global invariant operator is constructed. Furthermore, a local integrable approximation for more general non-integrable systems is developed. Numerical results are presented for the doubleresonance model.
The lowest resonant frequency of a cavity resonator is usually approximated by the classical Helmholtz formula. However, if the opening is rather large and the front wall is narrow this formula is no longer valid. Here we present a correction which is of third order in the ratio of the diameters of aperture and cavity. In addition to the high accuracy it allows to estimate the damping due to radiation. The result is found by applying the method of matched asymptotic expansions. The correction contains form factors describing the shapes of opening and cavity. They are com- puted for a number of standard geometries. Results are compared with numerical computations.
A new approach is proposed to model and simulate numerically heterogeneous catalysis in rarefied gas flows. It is developed to satisfy all together the following points: i) describe the gas phase at the microscopic scale, as required in rarefied flows, ii) describe the wall at the macroscopic scale, to avoid prohibitive computational costs and consider not only crystalline but also amorphous surfaces, iii) reproduce on average macroscopic laws correlated with experimental results and iv) derive ana- lytic models in a systematic and exact way. The problem is stated in the general framework of a non static flow in the vicinity of a catalytic and non porous surface (without ageing). It is shown that the exact and systematic resolution method based on the Laplace transform, introduced previously by the author to model collisions in the gas phase, can be extended to the present problem. The proposed approach is applied to the modelling of the Eley-Rideal and Langmuir-Hinshelwood recombinations, assuming that the coverage is locally at equilibrium. The models are developed considering one atomic species and extended to the gen eral case of several atomic species. Numerical calculations show that the models derived in this way reproduce with accuracy behaviours observed experimentally.
This paper describes a tableau-based higher-order theorem prover HOT and an application to natural language semantics. In this application, HOT is used to prove equivalences using world knowledge during higher-order unification (HOU). This extended form of HOU is used to compute the licensing conditions for corrections.
A multi-phase composite with periodic distributed inclusions with a smooth boundary is considered in this contribution. The composite component materials are supposed to be linear viscoelastic and aging (of the non-convolution integral type, for which the Laplace transform with respect to time is not effectively applicable) and are subjected to isotropic shrinkage. The free shrinkage deformation can be considered as a fictitious temperature deformation in the behavior law. The procedure presented in this paper proposes a way to determine average (effective homogenized) viscoelastic and shrinkage (temperature) composite properties and the homogenized stress-field from known properties of the components. This is done by the extension of the asymptotic homogenization technique known for pure elastic non-homogeneous bodies to the non-homogeneous thermo-viscoelasticity of the integral non-convolution type. Up to now, the homogenization theory has not covered viscoelasticity of the integral type. Sanchez-Palencia (1980), Francfort & Suquet (1987) (see [2], [9]) have consid- ered homogenization for viscoelasticity of the differential form and only up to the first derivative order. The integral-modeled viscoelasticity is more general then the differential one and includes almost all known differential models. The homogenization procedure is based on the construction of an asymptotic solution with respect to a period of the composite structure. This reduces the original problem to some auxiliary boundary value problems of elasticity and viscoelasticity on the unit periodic cell, of the same type as the original non-homogeneous problem. The existence and uniqueness results for such problems were obtained for kernels satisfying some constrain conditions. This is done by the extension of the Volterra integral operator theory to the Volterra operators with respect to the time, whose 1 kernels are space linear operators for any fixed time variables. Some ideas of such approach were proposed in [11] and [12], where the Volterra operators with kernels depending additionally on parameter were considered. This manuscript delivers results of the same nature for the case of the space-operator kernels.
We report on the exchange bias effect as a function of the in-plane direction of the applied field in twofold symmetric, epitaxial Ni 80 Fe 20 /Fe 50 Mn 50 bilayers grown on Cu~110! single-crystal substrates. An enhancement of the exchange bias field, H eb , up to a factor of 2 is observed if the external field is nearly, but not fully aligned perpendicular to the symmetry direction of the exchange bias field. From the measurement of the exchange bias field as a function of the in-plane angle of the applied field, the unidirectional, uniaxial and fourfold anisotropy contributions are determined with high precision. The symmetry direction of the unidirectional anisotropy switches with increasing NiFe thickness from [110] to [001].
Abstract: We predict the possibility of sharp, high-contrast resonances in the optical response of a broad class of systems, wherein interference effects are generated by coherent perturbation or interaction of dark states. The properties of these resonances can be manipulated to design a desired atomic response.
Abstract: The effect of intracavity Electromagnetically Induced Transparency on the properties of optical resonators and active laser devices is discussed theoretically. A pronounced frequency pulling and cavity linewidth narrowing are predicted. The effect can be used to substantially reduce classical and quantum phase noise of the beat-note of optical oscillators. Fundamental limits of this stabilization mechanism are discussed as well as its potential application to high-resolution spectroscopy.
Abstract: We develop a constructive method to derive exactly solvable quantum mechanical models of rational (Calogero) and trigonometric (Sutherland) type. This method starts from a linear algebra problem: finding eigenvectors of triangular finite matrices. These eigenvectors are transcribed into eigenfunctions of a selfadjoint Schrödinger operator. We prove the feasibility of our method by constructing an " AG_3 model" of trigonometric type (the rational case was known before from Wolfes 1975). Applying a Coxeter group analysis we prove its equivalence with the B_3 model. In order to better understand features of our construction we exhibit the F_4 rational model with our method.
We develop a constructive method to derive exactly solvable quantum mechanical models of rational (Calogero) and trigonometric (Sutherland) type. This method starts from a linear algebra problem: finding eigenvectors of triangular finite matrices. These eigenvectors are transcribed into eigenfunctions of a selfadjoint Schrödinger operator. We prove the feasibility of our method by constructing a new "\(AG_3\) model" of trigonometric type (the rational case was known before from Wolfes 1975). Applying a Coxeter group analysis we prove its equivalence with the \(B_3\) model. In order to better understand features of our construction we exhibit the \(F_4\) rational model with our method.
On a family F of probability measures on a measure space we consider the Hellinger and Kullback-Leibler distances. We show that under suitable regulari ty conditions Jeffreys' prior is proportional to the k-dimensional Hausdorff measure w.r.t. Hellinger dis tance respectively to the k2 -dimensional Hausdorff measure w.r.t. Kullback-Leibler distance. The proof i s based on an area-formula for the Hausdorff measure w.r.t. to generalized distances.
In der vorliegenden Arbeit wird die Methode der Molekulardynamik benutzt, um das Transmissionsverhalten von niederenergetischen Sauerstoffionen durch dünne Edelgasfilme mit Hilfe von klassischen Wechselwirkungs-Potentialen zu untersuchen. In einer quantenmechanischen Form, der sogenannten Tight-Binding Näherung, wird die Molekulardynamik verwendet, um die Dynamik des Phasenübergangs von der Flüssigkeit, oder vom Gas, zur amorphen Phase von Silizium, oder von hydrogenisiertem Silizium, zu untersuchen. Ich simuliere ein Experiment von N. J. Sack et. al., in dem Sauerstoffionen durch Elektronenbeschuß von einer WOx-Oberfläche desorbiert wurden und deren Transmissionsverhalten durch dünne Edelgasfilme gemessen wurde. Wenn in der Simulation nur elastische Streuung durch Paarpotentiale zugelassen wird, finde ich gute Übereinstimmung für die Transmissionsausbeuten zwischen Experiment und Simulation für Xe- und Kr-Filme. Die große Anzahl der gefundenen Transmissionen kann auf den kleinen Wechselwirkungsradius der Sauerstoffionen zurückgeführt werden. Die Diskrepanz zwischen Experiment und Simulation, die für Ar-Filme zu verzeichnen ist, wird auf elektronisch inelastische Wechselwirkungen oder strukturelle Effekte im Experiment zurückgeführt. In einem einfachen geometrischen Modell kann ich die Transmissions-Daten der Simulation für Xe- und Kr- Filme interpretieren, nicht jedoch die Daten für Ar-Filme. Dieses geometrische Modell wird dann zur Interpretation eines weiteren, ähnlichen Experiments von N. J. Sack et. al. herangezogen. Neue dynamische Gleichungen für klassische und quantenmechanische Molekulardynamik im kanonischen - , Enthalpie - und freien Enthalpie Ensemble werden vorgeschlagen. Ich zeige, daß Atome, die in den neuen dynamischen Gleichungen in der Zeit propagiert werden, die Phasenraum-Verteilungsfunktionen der entsprechenden Ensembles korrekt abtasten. Basierend auf einem verallgemeinerten Liouville Theorem werden numerische Integrations-Algorithmen entwickelt, die die fundamentalen Symmetrieen der dynamischen Gleichungen respektieren. Silizium gehört zu den am besten studierten Materialien überhaupt. In theoretischen Untersuchungen wird flüssiges und amorphes Silizium üblicherweise ohne Kontrolle des Drucks untersucht. In dieser Arbeit wird gezeigt, daß Druckkontrolle in der Beschreibung sowohl einer thermodynamischen Phase als auch in Phasenübergängen in der Simulation wichtig ist. Der Übergang von der flüssigen zur amorphen Phase von Silizium in einer Tight-Binding Beschreibung mit und ohne Druckkontrolle führt zu Strukturen, die halbleitend mit Druckkontrolle und nicht halbleitend ohne Druckkontrolle sind. Weiterhin werden Evidenzen gefunden, die die Erweiterung der üblichen minimalen Valenzbasis des Siliziums durch d-Orbitale nahelegen, um korrekte Resultate speziell für flüssiges Silizium zu erhalten. Amorphes hydrogenisiertes Silizium ist technisch wichtig, da die Bandlücke durch Wasserstoffgehalt und Herstellung beeinflußt werden kann. In dieser Arbeit wird ein mikroskopisches Modell für amorphes Silizium, erhalten durch Abkühlung eines Silizium-Wasserstoff Gases, mit Hilfe der Molekulardynamik in einer Tight-Binding Beschreibung simuliert. Die Rolle des Wasserstoffs im amorphen Netzwerk wird mit Hilfe einer Vielzahl von Korrelationsfunktionen aufgezeigt. Diese Korrelationsfunktionen demonstrieren die hohe Flexibilität des Wasserstoffs. In Übereinstimmung mit neueren NMR-Daten von Y. Wu et. al finde ich im amorphen Netzwerk eine Klusterung der Wasserstoffatome, die die Tendenz zweier Wasserstoffatome reflektiert unabgesättigte Silizium Bindung, die sich ohne Wasserstoff zu ungünstigen Bindungsgeometrien vereinigen würden, zu passivieren.
We study the statistics of the Wigner delay time and resonance width for a Bloch particle in ac and dc fields in the regime of quantum chaos. It is shown that after appropriate rescaling the distributions of these quantities have universal character predicted by the random matrix theory of chaotic scattering.
The light-cone Hamiltonian approach is applied to the super D2- brane, and the equivalent area-preserving and U(1) gauge-invariant effective Lagrangian, which is quadratic in the U(1) gauge field, is derived. The latter is recognised to be that of the three- dimensional U(1) gauge theory, interacting with matter supermultiplets, in a special external induced supergravity metric and the gravitino field, depending on matter fields. The duality between this theory and 11d supermembrane theory is demonstrated in the light-cone gauge.
Abstract: We analyze the long-time quantum dynamics of degenerate parametric down-conversion from an initial sub-harmonic vacuum (spontaenous down-conversion). Standard linearization of the Heisenberg equations of motions fails in this case, since it is based on an expansion around an unstable classical solution and neglects pump depletion. Introducing a mean-field approximation we find a periodic exchange of energy between the pump and subharmonic mode goverened by an anharmonic pendulum equation. From this equation the optimum interaction time or crystal length for maximum conversion can be determined. A numerical integration of the 2-mode Schrödinger equation using a dynamically optimized basis of displaced and squeezed number states verifies the characteristic times predicted by the mean-field approximation. In contrast to semiclassical and mean-field predictions it is found that quantum uctuations of the pump mode lead to a substantial limitation of the efficiency of parametric down-conversion.
In der vorliegenden Arbeit wurden Wirkstoffe aus unterschiedlichen Substanzklassen auf ihre antineoplastische Aktivität an humanen Tumorzellinien untersucht. Einige der getesteten Substanzen zeigten gute Ansätze für einen möglichen späteren Einsatz in der Tumortherapie. Die Alkaloide Lycorin und Lycobetain zeigten im Sulforhodamin B-Assay eine sehr gute Wachstumshemmung. Der IC50-Wert der Substanzen lag bei allen getesteten humanen Tumorzellinien unter 3 microM. Trotz der hervorragenden Wachstumshemmung konnte für Lycorin kein Wirkmechanismus gefunden werden. Ein Arrest der Zellen in der G2/M-Phase des Zellzyklus konnte jedoch gezeigt werden. Für Lycobetain kristallisierte sich eine duale Hemmung von Topoisomerase I und II als möglicher Wirkmechanismus heraus. Die Aktivität von Topoisomerase II konnte durch 100 microM Lycobetain vollständig inhibiert werden. Bereits bei 10 microM Lycobetain war keine Topoisomerase I Aktivität mehr detektierbar, was nachweislich auf der Stabilisierung des DNA-Topoisomerase-Komplexes beruhte. Diese resultierte in einer Induktion von DNA-Strangbrüchen, Arrest der Zellen in der G2/M-Phase des Zellzyklus und schließlich der Induktion von Apoptose. Alle diese Eigenschaften deuteten auf eine Topoisomerase-Hemmung als Wirkmechanismus von Lycobetain hin. Untersuchungen von fünf Flavonoiden aus der chinesischen Heilpflanze Scutellaria baicalensis zeigten, daß Baicalin, Baicalein, Skullcapflavon II und Wogonin das Wachstum verschiedener humaner Tumorzellinien hemmten, während Wogonosid bis zu Konzentrationen von 100 microM keine Wirkung zeigte. Baicalein und Baicalin wiesen trotz großer Strukturübereinstimmung keinen einheitlichen Wirkmechanismus auf. Baicalein hemmt, wie Lycobetain, die Aktivität der Topoisomerasen I und II, wobei für Topoisomerase I eine Stabilisierung des binären Intermediates von Topo-isomerase und DNA nachgewiesen werden konnte. Im Gegensatz zu Lycobetain interkaliert Baicalein nicht in doppelsträngige DNA, kompetiert jedoch mit dem Hoechst-Farbstoff H33258 um die Bindung an die kleine Furche der DNA. Die Induktion von DNA-Strangbrüchen, sowie der Arrest der Zellen in der G2/M-Phase des Zellzyklus und die Induktion von Apoptose konnten auch für Baicalein gezeigt werden. Messungen mit Baicalin ergaben keinen Hinweis auf Hemmung von humanen Topoisomerasen. Zellzyklusanalysen zeigten einen Arrest in der G0/G1-Phase, was im Gegensatz zu Baicalein auf einen völlig unterschiedlichen, bisher nicht geklärten, Mechanismus hindeutet. Skullcapflavon II hemmte Topoisomerase I und II ab Konzentrationen von 100 microM. Die Stabilisierung des DNA-Topoisomerase-Komplexes konnte jedoch für diese Substanz nicht nachgewiesen werden. Aufgrund der Struktur könnte jedoch auf einen anderen Mechanismus der Topoisomerase-Inhibierung, möglicherweise die Bindung an die freie Topoisomerase I und die damit verbundene Hemmung der Komplexbildung, geschlossen werden. Für Wogonin konnte in dieser Arbeit kein Wirkmechanismus gefunden werden. In unserer Arbeitsgruppe wurden verschiedene indigoide Bisindole synthetisiert [Hössel, 1996; Hössel, nicht veröffentlicht], die ebenfalls auf ihre antineoplastische Wirkung untersucht wurden. Ein großes Problem stellte dabei die schlechte Löslichkeit dieser Substanzklasse dar. Der Vergleich der Substanzen im Sulforhodamin B-Assay an der Zellinie LXFL529L ergab sehr unterschiedliche Ergebnisse. Indirubin und 5-Jod-Indirubin waren die besten Wachstumshemmstoffe mit IC50-Werten unter 10 microM. Die indigoiden Bisindole besaßen die Fähigkeit in Doppelstrang-DNA zu interkalieren und an die kleine Furche der DNA zu binden, während dies für Deoxytopsentin nicht nachzuweisen war. Im Tubulinpolymerisationsassay hemmten Indirubin, 5-Jod-Indirubin und Bisindolylindol die Polymerisation von Tubulinmonomeren. Im Vergleich zur Referenzsubstanz Colchicin war diese Hemmung jedoch für die Wirkung der Substanzen nicht von Bedeutung. Messungen zur Hemmung der cyclinabhängigen Kinase 1 (cdk1) weisen darauf hin, daß die indigoiden Substanzen ein inhibitorisches Potential für Zellzykluskinasen besitzen. Neben cdk1 hemmen Indirubin und 5-Jod-Indirubin unter anderem cdk5, eine Kinase, die an Mikrotubuliproteinen assoziiert vorliegen kann. Mittels Western-Blotting konnte gezeigt werden, daß die eingesetzte Tubulinpräperation cdk5 enthält. Die geringfügige Hemmung der Tubulinpolymerisation läßt sich möglicherweise durch die Hemmung von mit Tubulin assoziierter cdk5 erklären. Aus dem Labor von Stalina Melnik, Moskau, Rußland wurden unserer Arbeitsgruppe 13 Wirkstoffe zur Untersuchung zur Verfügung gestellt. Bei den Substanzen handelte es sich um Indolocarbazole und Bisindolylmaleimide, die sich durch verschiedene Zuckersubstitutionen an R1 sowie verschiedene Reste an X und R2 unterschieden. Im Sulforhodamin B-Assay konnte mit Ausnahme der Substanzen 1 und 11 für alle Substanzen ein IC50-Wert unter 10 microM ermittelt werden, was auf eine hohe wachstumshemmende Potenz hinweist. Wegen der Strukturähnlichkeit mit Staurosporin wurde zunächst die Inhibierung der Proteinkinase C überprüft. Am isolierten zytosolischen Extrakt konnte, ebenfalls mit Ausnahme der Substanzen 1 und 11, eine Hemmung der PKC nachgewiesen werden, wobei sich die IC50-Werte zwischen 0,4 und 34 microM bewegten. Im Gegensatz dazu waren nur zwei Substanzen (4 und 10) in der Lage in der Zellkultur die PKC-Aktivität im niedrigen Konzentrationsbereich zu hemmen. Bei den Substanzen 2 und 5 war ein IC50-Wert ermittelbar, der aber mindestens zehnfach höher lag als bei der Messung am isolierten Enzym. Eine mögliche Erklärung für dieses Phänomen ist, daß die Substanz das Zielprotein in der Zelle nicht erreichen kann. Die Strukturverwandschaft mit den Topoisomerase-Inhibitoren NB 506 und Rebeccamycin, deutete auf humane Topoisomerasen als potentiellen Angriffspunkt der Wirkstoffe hin. Tatsächlich erwiesen sich mehrere Substanzen als mögliche Hemmstoffe von Topoisomerase I und/oder II (siehe Tabelle 13). Ein weiteres Phänomen war die Fähigkeit aller Substanzen, sich an die kleine Furche der DNA anzulagern, während keine Interkalationsfähigkeit nachweisbar war. Die Induktion von Strangbrüchen war lediglich für die Substanzen 4 und 8 im unteren mikromolaren Bereich nachweisbar, während die meisten erst ab 50 microM DNA-Schäden induzierten. Die beste Wirkung zeigten aber auch diese Substanzen bei Untersuchungen zur Hemmung von cyclinabhängigen Kinasen. Dabei muß berücksichtigt werden, daß es sich bei der cdk1 um ein isoliertes Enzym handelt und die Hemmung im zellulären System möglicherweise nicht meßbar ist. Aufgrund der in dieser Arbeit erhaltenen Daten konnte für drei Indolocarbazole ein potentieller Wirkmechanismus gefunden werden. Für Substanz 8 ist die Hemmung von Topoisomerasen ein möglicher Wirkmechanismus, während Substanz 10 sich als möglicher Proteinkinase C-Hemmstoff herausstellte. Substanz 4 scheint einen potentiellen cdk1 Hemmstoff darzustellen.
As the previous chapters of this book have shown, case-based reasoning is a technology that has been successfully applied to a large range of different tasks. Through all the different CBR projects, both basic research projects as well as industrial development projects, lots of knowledge and experience about how to build a CBR application has been collected. Today, there is already an increasing number of successful companies developing industrial CBR applications. In former days, these companies could develop their early pioneering CBR applications in an ad-hoc manner. The highly-skilled CBR expert of the company was able to manage these projects and to provide the developers with the required expertise.
The term enterprise modeling, synonymous with enterprise engineering, often refers to methodologies, developed for modeling activities, states, time, and cost within an enterprise architecture. They serve as a vehicle for evaluating and modeling activities resources and so on. CIM - OSA (Computer Integrated Manufacturing Open Systems Architecture) is a methodology for modeling computer integrated environments, and its major objective is the appropriate integration of enterprise operations by means of efficient information exchange within the enterprise. Although there are other methodo- logies in the industry that serve the same purpose, most of them concentrate on the internal aspect of an enterprise. The paper is concerned with the modeling of the links between enterprises. The aim is to examine these relationships or links in detail and suggest a method for modeling enterprise networks drawing on the methodologies currently used in the industry and extending with the method proposed here.
Monomial representations and operations for Gröbner bases computations are investigated from an implementation point of view. The technique ofvectorized monomial operations is introduced and it is shown how it expedites computations of Gröbner bases. Furthermore, a rank-based monomialrepresentation and comparison technique is examined and it is concluded that this technique does not yield an additional speedup over vectorizedcomparisons. Extensive benchmark tests with the Computer Algebra System SINGULAR are used to evaluate these concepts.
The Monte Carlo complexity of computing integrals depending on a parameter is analyzed for smooth integrands. An optimal algorithm is developed on the basis of a multigrid variance reduction technique. The complexity analysis implies that our algorithm attains a higher convergence rate than any deterministic algorithm. Moreover, because of savings due to computation on multiple grids, this rate is also higher than that of previously developed Monte Carlo algorithms for parametric integration.
This paper presents a new approach to parallel motion planning for industrial robot arms with six degrees of freedom in an on-line given 3D environment. The method is based on the A-search algorithm and needs no essential off-line computations. The algorithm works in an implicitly descrete configuration space. Collisions are detected in the Cartesian workspace by hierarchical distance computation based on the given CAD model. By decomposing the 6D configuration space into hypercubes and cyclically mapping them onto multiple processing units, a good load distribution can be achieved. We have implemented the parallel motion planner on a workstation cluster with 9 PCs and tested the planner for several benchmark environments. With optimal discretisation, the new approach usually shows linear speedups. In on-line provided environments with static obstacles, the parallel planning times are only a few seconds.
We present a parallel path planning method that is able to automatically handle multiple goal configurations as input. There are two basic approaches, goal switching and bi-directional search, which are combined in the end. Goal switching dynamically selects a fa-vourite goal depending on some distance function. The bi-directional search supports the backward search direction from the goal to the start configuration, which is probably faster. The multi-directional search with goal switching combines the advantages of goal switching and bi-directional search. Altogether, the planning system is enabled to select one of the pref-erable goal configuration by itself. All concepts are experimentally validated for a set of benchmark problems consisting of an industrial robot arm with six degrees of freedom in a 3D environment.
This paper motivates the necessity for support for negotiation during Sales Support on the Internet within Case-Based Reasoning solutions. Different negotiation approaches are discussed and a general model of the sales process is presented. Further, the tradition al CBR-cycle is modified in such a way that iterative retrieval during a CBR consulting session is covered by the new model. Several gen eral characteristics of negotiation are described and a case study is shown where preliminary approaches are used to negotiate with a cu stomer about his demands and available products in a 'CBR-based' Electronic Commerce solution.
In this paper we derive nonparametric stochastic volatility models in discrete time. These models generalize parametric autoregressive random variance models, which have been applied quite successfully to nancial time series. For the proposed models we investigate nonparametric kernel smoothers. It is seen that so-called nonparametric deconvolution estimators could be applied in this situation and that consistency results known for nonparametric errors- in-variables models carry over to the situation considered herein.
The flow of a liquid into an empty channel is simulated. The simulation is based on a recently published model for general fluid/liquid/solid systems which eliminates the shear stress singularity at the moving contact line between the liquid/fluid interface and the solid. This model is carefully analyzed for low Reynolds and Capillary numbers, adapted to the channel inflow problem, and implemented. Very convincing numerical results are presented.
The first observation of spatiotemporal self-focusing of spin waves is reported. The experimental results are obtained for dipolar spin waves in yttrium-iron-garnet films by means of a newly developed space- and time-resolved Brillouin light scattering technique. They demonstrate self-focusing of a moving wave pulse in two spatial dimensions, and formation of localized two-dimensional wave packets, the collapse of which is stopped by dissipation. The experimental results are in good qualitative agreement with numerical simulations.
Todd and Coxeter's method for enumerating cosets of finitely generated subgroups in finitely presented groups (abbreviated by Tc here) is one famous method from combinatorial group theory for studying the subgroup problem. Since prefix string rewriting is also an appropriate method to study this problem, prefix string rewriting methods have been compared to Tc. We recall and compare two of them briefly, one by Kuhn and Madlener [4] and one by Sims [15]. A new approach using prefix string rewriting in free groups is derived from the algebraic method presented by Reinert, Mora and Madlener in [14] which directly emulates Tc. It is extended to free monoids and an algebraic characterization for the "cosets" enumerated in this setting is provided.
Finding "good" cycles in graphs is a problem of great interest in graph theory as well as in locational analysis. We show that the center and median problems are NP hard in general graphs. This result holds both for the variable cardinality case (i.e. all cycles of the graph are considered) and the fixed cardinality case (i.e. only cycles with a given cardinality p are feasible). Hence it is of interest to investigate special cases where the problem is solvable in polynomial time. In grid graphs, the variable cardinality case is, for instance, trivially solvable if the shape of the cycle can be chosen freely. If the shape is fixed to be a rectangle one can analyse rectangles in grid graphs with, in sequence, fixed dimension, fixed cardinality, and variable cardinality. In all cases a com plete characterization of the optimal cycles and closed form expressions of the optimal objective values are given, yielding polynomial time algorithms for all cases of center rectangle problems. Finally, it is shown that center cycles can be chosen as rectangles for small cardinalities such that the center cycle problem in grid graphs is in these cases completely solved.
We propose a new discretization scheme for solving ill-posed integral equations of the third kind. Combining this scheme with Morozov's discrepancy principle for Landweber iteration we show that for some classes of equations in such method a number of arithmetic operations of smaller order than in collocation method is required to appoximately solve an equation with the same accuracy.
For defining attribute types to be used in the case representation, taxonomies occur quite often. The symbolic values at any node of the taxonomy tree are used as attribute values in a case or a query. A taxonomy type represents a relationship between the symbols through their position within the taxonomy-tree which expresses knowledge about the similarity between the symbols. This paper analyzes several situations in which taxonomies are used in different ways and proposes a systematic way of specifying local similarity measures for taxonomy types. The proposed similarity measures have a clear semantics and are easy to compute at runtime.
Enhancing the quality of surgical interventions is one of the main goals of surgical robotics. Thus we have devised a surgical robotic system for maxillofacial surgery which can be used as an intelligent intraoperative surgical tool. Up to now a surgeon preoperatively plans an intervention by studying twodimensional X-rays, thus neglecting the third dimension. In course of the special research programme "Computer and Sensor Aided Surgery" a planning system has been developed at our institute, which allows the surgeon to plan an operation on a threedimensional computer model of the patient . Transposing the preoperatively planned bone cuts, bore holes, cavities, and milled surfaces during surgery still proves to be a problem, as no adequate means are at hand: the actual performance of the surgical intervention and the surgical outcome solely depend on the experience and the skill of the operating surgeon. In this paper we present our approach of a surgical robotic system to be used in maxillofacial surgery. Special stress is being laid upon the modelling of the environment in the operating theatre and the motion planning of our surgical robot .