@misc{IlgenfritzKerlerMuellerPreusskeretal.2000, author = {Ilgenfritz, Ernst-Michael and Kerler, Werner and M{\"u}ller-Preussker, Michael and St{\"u}ben, Hinnerk}, title = {Parallel tempering and decorrelation of topological charge in full QCD}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5930}, number = {00-25}, year = {2000}, abstract = {The improvement of simulations of QCD with dynamical Wilson fermions by combining the Hybrid Monte Carlo algorithm with parallel tempering is studied on \$10^4\$ and \$12^4\$ lattices. As an indicator for decorrelation the topological charge is used.}, language = {en} } @misc{SperberDalitz2000, author = {Sperber, Wolfram and Dalitz, Wolfgang}, title = {Portale, Search Engines und Math-Net}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5923}, number = {00-24}, year = {2000}, abstract = {Wie sucht ein Wissenschaftler im Internet die ben"otigten Informationen f{\"u}r seine Arbeit? Welche relevanten Informationen gibt es {\"u}berhaupt im Web? Sind daf{\"u}r solche Suchmaschinen wie AltaVista, Google oder HotBot die richtigen Werkzeuge? Die Antwort der Mathematiker heisst Math-Net, ein Informations- und Kommunikationssystem f{\"u}r die Mathematik. Math-Net besteht zun{\"a}chst aus den Informationen von Personen und Institutionen, die ihre f{\"u}r die Mathematik relevanten Informationen dort bereitstellen wollen. Das soll i.a. auf den Web-Servern der Personen oder Institutionen geschehen. Hierin unterscheidet sich die Situation im Math-Net nicht von der im WWW insgesamt. Im Math-Net sollen aber die Informationen in einheitlicher Weise erschlossen werden. Dazu gibt es sowohl f{\"u}r Server als auch f{\"u}r die Dokumente Empfehlungen f{\"u}r deren Strukturierung. Die lokalen Informationen werden dann im Math-Net durch automatische Verfahren gesammelt, ausgewertet und indexiert. Diese Indexe sind die Basis f{\"u}r die Math-Net Dienste. Das sind Search Engines und Portale, die einen qualifizierten und effizienten Zugang zu den Informationen im Math-Net bieten. Die Math-Net Dienste sind auf die Mathematik spezialisiert. Im Gegensatz zu den oben erw{\"a}hnten universellen Suchmaschinen decken sie nur einen winzigen Bruchteil des Web ab, aber daf{\"u}r den f{\"u}r die Mathematik relevanten Teil. Math-Net ist mehr als nur Search Engine oder Portal zu Informationen in der Mathematik. Es ist auch ein Informations- und Kommunikationssystem sowie ein Publikationsmedium f{\"u}r die Mathematik. Die mathematische Community hat sich in der Math-Net Initiative organisiert. Diese Initiative wird von der International Mathematical Union (IMU), der weltweiten Dachorganisation der mathematischen Gesellschaften, koordiniert. Die Entwicklung des Math-Net wird von dem breiten Konsens der Mathematiker getragen, den Zugang zu der f{\"u}r die Mathematik relevanten Information zu erleichtern und zu verbessern.}, language = {de} } @misc{Luegger2000, author = {L{\"u}gger, Joachim}, title = {{\"U}ber Suchmaschinen, Verb{\"u}nde und die Integration von Informationsangeboten}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5919}, number = {00-23}, year = {2000}, abstract = {Die Entwicklung einer bibliothekarischen Suchmaschine ist das technisch-organisatorische Herzt{\"u}ck des Kooperativen Bibliotheksverbundes Berlin-Brandenburg (KOBV). Auf dem Wege {\"u}ber diese Innovation verfolgen die L{\"a}nder Berlin und Brandenburg und ihre Bibliotheken das Ziel, ihr Bibliothekswesen zu erneuern und zu reorganisieren. Die Entwicklung der Suchmaschine ist f{\"u}r die Partner im KOBV-Projekt kein Selbstzweck, sondern nur Mittel zum Zweck - insbesondere, um die heterogene Welt der in Berlin und in Brandenburg eingesetzten integrierten Bibliotheksinformationssysteme harmonisch miteinender zu verbinden. Mit der KOBV-Suchmaschine sind informationstechnische Sichtweisen und Methoden entstanden, die sich potentiell auch auf die {\"u}berregionale Arbeit des KOBV auswirken k{\"o}nnen und in Kooperation mit den Bibliotheksverb{\"a}nden auf die Zusammenarbeit der Verb{\"u}nde insgesamt. Der Artikel konzentriert sich am Beispiel der KOBV-Such!'ma!'schine auch auf diesen Aspekt. Auf die Bibliotheken kommen mit dem Internet und dem World Wide Web f{\"u}r sie neuartige Medien, Mittel und Aufgaben zu, in erster Linie aus dem Bereich der Wissenschaften und der wissenschaftlichen Fachgesellschaften. Die Herausforderung besteht darin, die neuen elektronischen Informationen und Angebote zu integrieren. Das Stichwort hierzu lautet digitale Bibliothek bzw. virtuelle Fachbibliothek. Auch zu der Diskussion um diese aktuelle Entwicklung will der Artikel einen Beitrag leisten.}, language = {de} } @misc{HoeselKosterLeenseletal.2000, author = {Hoesel, Stan P.M. van and Koster, Arie M.C.A. and Leensel, Robert L.M.J. van de and Savelsbergh, Martin W.P.}, title = {Polyhedral Results for the Edge Capacity Polytope}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5907}, number = {00-22}, year = {2000}, abstract = {Network loading problems occur in the design of telecommunication networks, in many different settings. The polyhedral structure of this problem is important in developing solution methods for the problem. In this paper we investigate the polytope of the problem restricted to one edge of the network (the edge capacity problem). We describe classes of strong valid inequalities for the edge capacity polytope, and we derive conditions under which these constraints define facets. As the edge capacity problem is a relaxation of the network loading problem, their polytopes are intimately related. We, therefore, also give conditions under which the inequalities of the edge capacity polytope define facets of the network loading polytope. Furthermore, some structural properties are derived, such as the relation of the edge capacity polytope to the knapsack polytope. We conclude the theoretical part of this paper with some lifting theorems, where we show that this problem is polynomially solvable for most of our classes of valid inequalities. In a computational study the quality of the constraints is investigated. Here, we show that the valid inequalities of the edge capacity polytope are not only important for solving the edge capacity problem, but also for the network loading problem, showing that the edge capacity problem is an important subproblem.}, language = {en} } @misc{LangErdmann2000, author = {Lang, Jens and Erdmann, Bodo}, title = {Adaptive Linearly Implicit Methods for Heat and Mass Transfer Problems}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5892}, number = {00-21}, year = {2000}, abstract = {Dynamical process simulation of complex real-life problems often requires the use of modern algorithms, which automatically adapt both the time and space discretization in order to get error-controlled approximations of the solution. In this paper, a combination of linearly implicit time integrators of Rosenbrock type and adaptive multilevel finite elements based on a posteriori error estimates is presented. This approach has proven to work quite satisfactorily for a wide range of challenging practical problems. We show the performance of our adaptive method for two applications that arise in the study of flame balls and brine transport in porous media.}, language = {en} } @misc{MeyerSchnurreReissbrodtetal.2000, author = {Meyer, Michael and Schnurre, R{\"u}diger and Reissbrodt, Rolf and Trowitzsch-Kienast, Wolfram}, title = {Computer-aided design of novel siderophores: Pyridinochelin}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5887}, number = {00-20}, year = {2000}, abstract = {Pyridinochelin, a novel catecholate type siderophore, has been designed on the basis of the active analog enterobactin. Growth promotion tests indicate that this synthetic siderophore feeds various pathogenic bacteria effectively with iron even though it lacks one catecholate group compared to enterobactin. The superposition of the siderophore structures suggests that the structure of the skeleton connecting the catecholate groups might be an important factor for the iron transport.}, language = {en} } @misc{KrumkeNoltemeierWirth2000, author = {Krumke, Sven and Noltemeier, Hartmut and Wirth, Hans-Christoph}, title = {Graphentheoretische Konzepte und Algorithmen}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5873}, number = {00-19}, year = {2000}, abstract = {Das vorliegende Skript bietet eine Einf{{\"u}}hrung in die Graphentheorie und graphentheoretische Algorithmen. Im zweiten Kapitel werden Grundbegriffe der Graphentheorie vorgestellt. Das dritte Kapitel besch{{\"a}}ftigt sich mit der Existenz von Wegen in Graphen. Hier wird auch die L{{\"o}}suung des ber{{\"u}}hmten K{{\"o}}nigsberger Br{{\"u}}ckenproblems aufgezeigt und der Satz von Euler bewiesen. Im vierten Kapitel wird gezeigt, wie man auf einfache Weise die Zusammenhangskomponenten eines Graphen bestimmen kann. Im Kapitel sechs wird dann sp{{\"a}}ter mit der Tiefensuche ein Verfahren vorgestellt, das schneller arbeitet und mit dessen Hilfe man noch mehr Informationen {{\"u}}ber die Struktur eines Graphen gewinnen kann. In den folgenden Kapiteln werden Algorithmen vorgestellt, um minimale aufspannenden B{{\"a}}ume, k{{\"u}}rzeste Wege und maximale Fl{{\"u}}sse in Graphen zu bestimmen. Am Ende des Skripts wird ein kurzer Einblick in die planaren Graphen und Graphhomomorphismen geboten.}, language = {de} } @misc{Koster2000, author = {Koster, Arie M.C.A.}, title = {Re-Optimization of Signaling Transfer Points}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5863}, number = {00-18}, year = {2000}, abstract = {In this paper we describe the results of a computational study towards the (re)optimization of signaling transfer points (STPs) in telecommunication networks. The best performance of an STP is achieved whenever the traffic load is evenly distributed among the internal components. Due to the continuously changing traffic pattern, the load of the components has to be re-optimized on a regular basis. Besides the balancing objective also the number of rearrangements have to be taken into account. In this paper we present two alternative formulations to deal with both requirements. Computational results show that for both formulations (near) optimal solutions can be obtained within reasonable time limits.}, language = {en} } @misc{OPUS4-974, title = {Jahresbericht 1999}, issn = {0934-5892}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-9749}, number = {1999}, year = {2000}, language = {de} } @misc{Steinbach2000, author = {Steinbach, Marc}, title = {Hierarchical Sparsity in Multistage Convex Stochastic Programs}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5837}, number = {00-15}, year = {2000}, abstract = {Interior point methods for multistage stochastic programs involve KKT systems with a characteristic global block structure induced by dynamic equations on the scenario tree. We generalize the recursive solution algorithm proposed in an earlier paper so that its linear complexity extends to a refined tree-sparse KKT structure. Then we analyze how the block operations can be specialized to take advantage of problem-specific sparse substructures. Savings of memory and operations for a financial engineering application are discussed in detail.}, language = {en} } @misc{MeyerSteinkeBrandletal.2000, author = {Meyer, Michael and Steinke, Thomas and Brandl, Maria and S{\"u}hnel, J{\"u}rgen}, title = {Density functional study of guanine and uracil quartets and of guanine quartet metal/ion complexes}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5842}, number = {00-16}, year = {2000}, abstract = {The structures and interaction energies of guanine and uracil quartets have been determined by B3LYP hybrid density functional calculations. The total interaction energy \$\Delta\$E\$^{T}\$ of the \$\it{C}\$\$_{4h}\$-symmetric guanine quartet consisting of Hoogsteen type base pairs with two hydrogen bonds between two neighbour bases is -66.07 kcal/mol at the highest level. The uracil quartet with C6-H6...O4 interactions between the individual bases has only a small interaction energy of -20.92 kcal/mol and the interaction energy of -24.63 kcal/mol for the alternative structure with N3-H3...O4 hydrogen bonds is only slightly more negative. Cooperative effects contribute between 10 and 25 \\% to all interaction energies. Complexes of metal ions with G-quartets can be classified into different structure types. The one with Ca\$^{2+}\$ in the central cavity adopts a \$\it{C}\$\$_{4h}\$-symmetric structure with coplanar bases, whereas the energies of the planar and non-planar Na\$^{+}\$ complexes are almost identical. The small ions Li\$^{+}\$, Be\$^{2+}\$, Cu\$^{+}\$ and Zn\$^{2+}\$ prefer a non-planar \$\it{S}\$\$_{4}\$-symmetric structure. The lack of co-planarity prevents probably a stacking of these base quartets. The central cavity is too small for K\$^{+}\$ ions and therefore this ion favours in contrast to all other investigated ions a \$\it{C}\$\$_{4}\$-symmetric complex, which is 4.73 kcal/mol more stable than the \$\it{C}\$\$_{4h}\$-symmetric one. The distance 1.665 {\AA} between K\$^{+}\$ and the root mean squares plane of the guanine bases is approximately half of the distance between two stacked G-quartets. The total interaction energy of alkaline earth ion complexes exceeds the ones with alkali ions. Within both groups of ions the interaction energy decreases with an increasing row position in the periodic table. The B3LYP and BLYP methods lead to similar structures and energies. Both methods are suitable for hydrogen-bonded biological systems. Compared with the before mentioned methods the HCTH functional leads to longer hydrogen bonds and different relative energies for two U-quartets. Finally we calculated also structures and relative energies with the MMFF94 forcefield. Contrary to all DFT methods, MMFF94 predicts bifurcated C-H...O contacts in the uracil quartet. In the G-quartet the MMFF94 hydrogen bond distances N2-H22...N7 are shorter than the DFT distances, whereas the N1-H1...O6 distances are longer.}, language = {en} } @misc{OevermannKleinBergeretal.2000, author = {Oevermann, Michael and Klein, Rupert and Berger, Marsha and Goodman, Jonathan}, title = {A Projection Method for Two-Phase Incompressible Flow with Surface Tension and Sharp Interface Resolution}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5851}, number = {00-17}, year = {2000}, abstract = {We present a fully second order projection method for the simulation of two-phase incompressible flow with surface tension. The Navier-Stokes equations are solved with a projection method on a fixed Cartesian grid. The free interface between the two fluids is tracked with a level set approach. The conditions at the interface for the pressure, the pressure gradient, and the velocity are explicitly incorporated into the scheme leading to a sharp representation of the pressure discontinuity and the interfacial force. The scheme in the presented form does not introduce additional points in the standard finite difference stencils. Computational results are compared with analytic solutions for a static round bubble, damped surface waves, and Rayleigh-Taylor instabilities.}, language = {en} } @misc{BienstockBley2000, author = {Bienstock, Daniel and Bley, Andreas}, title = {Capacitated Network Design with Multicast Commodities}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5823}, number = {00-14}, year = {2000}, abstract = {This paper addresses the problem of designing a minimum cost network whose capacities are sufficiently large to allow a feasible routing of a given set of multicast commodities. A multicast commodity consists of a set of two or mo re terminals that need to be connected by a so called broadcast tree, which consumes on all of its edges a capacity as large as the demand value associated with that commodity. We model the network design problem with multicast commodities as the problem of packing capacitated Steiner trees in a graph. In the first part of the paper we present three mixed-integer programming formulations for this problem. The first natural formulation uses only one integer capacity variable for each edge and and one binary tree variable for each commodity-edge pair. Applying well-known techniques from the Steiner tree problem, we then develop a stronger directed and a multicommodity flow based mixed-integer programming formulation. In the second part of the paper we study the associated polyhedra and derive valid and even facet defining inequalities for the natural formulation. Finally, we describe separation algorithms for these inequalities and present computational results that demonstrate the strength of our extended formulations.}, language = {en} } @misc{GalliatDeuflhard2000, author = {Galliat, Tobias and Deuflhard, Peter}, title = {Adaptive hierarchical cluster analysis by Self-Organizing Box Maps}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5815}, number = {00-13}, year = {2000}, abstract = {The present paper aims at an extension of {\sc Kohonen's} Self-Organizing Map (SOM) algorithm to be called Self-Organizing Box Map (SOBM) algorithm; it generates box codebooks in lieu of point codebooks. Box codebooks just like point codebooks indirectly define a Voronoi tessellation of the input space, so that each codebook vector represents a unique set of points. Each box codebook vector comprises a multi-dimensional interval that approximates the related partition of the Voronoi tessellation. Upon using the automated cluster identification method that has recently been developed by the authors, the codebook vectors can be grouped in such a way that each group represents a point cluster in the input space. Since the clustering usually depends on the size of the SOM, one cannot be sure, whether the clustering comes out to be optimal. Refinement of part of the identified clusters would often improve the results. This paper presents the concept of an adaptive multilevel cluster algorithm that performs such refinements automatically. Moreover the paper introduces a concept of essential dimensions and suggests a method for their identification based on our herein suggested box codebooks. Applications of the algorithm to molecular dynamics will be described in a forthcoming paper.}, language = {en} } @misc{Rusch2000, author = {Rusch, Beate}, title = {Kooperativer Bibliotheksverbund Berlin-Brandenburg: Erste Erfahrungen im Produkionsbetrieb}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5793}, number = {00-11}, year = {2000}, abstract = {In diesem Artikel wird der Status des Projekts Kooperativer Bibliotheksverbund Berlin-Brandenburg beschrieben, der im November 1999 mit der KOBV-Suchmaschine seinen produktiven Betrieb aufgenommen hat. Die Recherchem{\"o}glichkeiten im WWW werden erl{\"a}utert, Zugriffszahlen genannt und Entwicklungsperspektiven skizziert. Dieser Bericht entspricht der schriftlichen Fassung eines gleichnamigen Vortrages, der auf dem 1. Gemeinsamen Kongreß der Bundesvereinigung Deutscher Bibliotheksverb{\"a}nde e.V. und der Deutschen Gesellschaft f{\"u}r Informationswissenschaft und Informationspraxis e.V. Information und {\"O}ffentlichkeit gehalten wurde, der vom 20. bis 23. M{\"a}rz 2000 in Leipzig stattfand.}, language = {de} } @misc{BrandtBrandt2000, author = {Brandt, Andreas and Brandt, Manfred}, title = {Asymptotic Results and a Markovian Approximation for the M(n)/M(n)/s+GI System}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5801}, number = {00-12}, year = {2000}, abstract = {In this paper for the \$M(n)/M(n)/s+GI\$ system, i.e.\ for a \$s\$-server queueing system where the calls in the queue may leave the system due to impatience, we present new asymptotic results for the intensities of calls leaving the system due to impatience and a Markovian system approximation where these results are applied. Furthermore, we present a new proof for the formulae of the conditional density of the virtual waiting time distributions, recently given by Movaghar for the less general \$M(n)/M/s+GI\$ system. Also we obtain new explicit expressions for refined virtual waiting time characteristics as a byproduct.}, language = {en} } @misc{KonjevodKrumkeMarathe2000, author = {Konjevod, Goran and Krumke, Sven and Marathe, Madhav}, title = {Budget Constrained Minimum Cost Connected Medians}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5783}, number = {00-10}, year = {2000}, abstract = {Several practical instances of network design problems require the network to satisfy multiple constraints. In this paper, we address the \emph{Budget Constrained Connected Median Problem}: We are given an undirected graph \$G = (V,E)\$ with two different edge-weight functions \$c\$ (modeling the construction or communication cost) and \$d\$ (modeling the service distance), and a bound~\$B\$ on the total service distance. The goal is to find a subtree~\$T\$ of \$G\$ with minimum \$c\$-cost \$c(T)\$ subject to the constraint that the sum of the service distances of all the remaining nodes \$v \in V\setminus T\$ to their closest neighbor in~\$T\$ does not exceed the specified budget~\$B\$. This problem has applications in optical network design and the efficient maintenance of distributed databases. We formulate this problem as bicriteria network design problem, and present bicriteria approximation algorithms. We also prove lower bounds on the approximability of the problem that demonstrate that our performance ratios are close to best possible}, language = {en} } @misc{Krumke2000, author = {Krumke, Sven}, title = {News from the Online Traveling Repairman}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5767}, number = {00-08}, year = {2000}, abstract = {The traveling repairman problem (TRP) is a variant of the famous traveling salesman problem (TSP). The objective for the TRP is to minimize the latency, that is the the weighted sum of completion times of the cities, where the completion time of a city is defined to be the time in the tour before the city is reached. In the online traveling repairman problem (OLTRP) requests for visits to cities (points in a metric space) arrive online while the repairman is traveling. We analyze the performance of algorithms using competitive analysis, where the cost of an online algorithm is compared to that of an optimal offline algorithm. An optimal offline algorithm knows the entire request sequence in advance and can serve it with minimum cost. Recently, Feuerstein and Stougie presented a \$9\$-competitive algorithm for the OLTRP on the real line. In this paper we show how to use techniques from online-scheduling to obtain an \$8\$-competitive deterministic algorithm which works for any metric space. We also present a randomized algorithm which has a competitive ratio of \$\frac{4}{\ln 2}\approx 5.7708\$ against an oblivious adversary. All of our results also hold for the ``dial-a-ride'' generalization of the OLTRP, where objects have to be picked up and delivered by a server.}, language = {en} } @misc{BlomKrumkePaepeetal.2000, author = {Blom, Michiel and Krumke, Sven and Paepe, Willem de and Stougie, Leen}, title = {The Online-TSP Against Fair Adversaries}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5779}, number = {00-09}, year = {2000}, abstract = {In the online traveling salesman problem requests for visits to cities (points in a metric space) arrive online while the salesman is traveling. The salesman moves at no more than unit speed and starts and ends his work at a designated origin. The objective is to find a routing for the salesman which finishes as early as possible. Performance of algorithms is measured through their competitive ratio, comparing the outcome of the algorithms with that of an adversary who provides the problem instance and therefore is able to achieve the optimal offline solution. Objections against such omnipotent adversaries have lead us to devise an adversary that is in a natural way, in the context of routing problems, more restricted in power. For the exposition we consider the online traveling salesman problem on the metric space given by the non-negative part of the real line. We show that a very natural strategy is~\$3/2\$-competitive against the conventional adversary, which matches the lower bound on competitive ratios achievable for algorithms for this problem. Against the more ``\emph{fair adversary}'', that we propose, we show that there exists an algorithm with competitive ratio \$\frac{1+\sqrt{17}}{4}\approx 1.28\$ and provide a matching lower bound. We also show competitiveness results for a special class of algorithms (called zealous algorithms) that do not allow waiting time for the server as long as there are requests unserved.}, language = {en} } @misc{DeuflhardHegeSeebass2000, author = {Deuflhard, Peter and Hege, Hans-Christian and Seebass, Martin}, title = {Progress Towards a Combined MRI/Hyperthermia System}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5755}, number = {00-07}, year = {2000}, abstract = {Regional hyperthermia, a clinical cancer therapy, is the main topic of the Sonderforschungsbereich Hyperthermia: Scientific Methods and Clinical Applications'' at Berlin. In recent years, technological improvements towards a better concentration of heat to the desired target region have been achieved. These include a rather sophisticated integrated software environment for therapy planning and a new hyperthermia applicator. In a next step, a detailed closed loop monitoring of the actual treatment is to be developed. For this purpose the hyperthermia applicator is combined with an MRI system, which will allow to check the positioning of the patients and to measure individual blood perfusion as well as the 3D temperature distribution. The measurements will then be employed for an on-line control of the whole treatment. In this intended setting, new fast feedback control algorithms will come into play.}, language = {en} } @misc{YevickFrieseSchmidt2000, author = {Yevick, David and Friese, Tilmann and Schmidt, Frank}, title = {A Comparison of Transparent Boundary Conditions for the Fresnel Equation}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5738}, number = {00-05}, year = {2000}, abstract = {We establish the relationship between the transparent boundary condition (BPP) of Baskakov and Popov [Wave Motion 14 (1991) 121-128] and Pakpadakis et. al. [J. Acoust. Soc. Am. 92 (1992) 2030-2038] and a second boundary condition (SDY) introduced by Schmidt and Deuflhard [Comp. Math. Appl. 29 (1995) 53-76] and Schmidt and Yevick [J. Compu. Phys. 134 (1997) 96-107], that is explicitly tailored to the form of the underlying numerical propagation scheme. Our analysis demonstrates that if the domain is first discretized in the propagation direction, the SDY expression can be obtained by applying the exact sequence of steps used to derive the BPP procedure. The BPP method is thus an approximate realization of the computationally far simpler and unconditionally stable SDY boundary condition.}, language = {en} } @misc{Schmidt2000, author = {Schmidt, Frank}, title = {Discrete Nonreflecting Boundary Conditions for the Helmholtz Equation}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5744}, number = {00-06}, year = {2000}, abstract = {We derive exact discrete nonreflecting boundary conditions for time-harmonic scattering problems modeled by the Helmholtz equation. The main idea is to consider the exterior problem as an initial value problem with initial data given on the boundary of the computational domain. The solution of the exterior problem is obtained via Laplace transformation techniques which supply the boundary conditions in terms of discrete Dirichlet-to-Neumann operators.}, language = {en} } @misc{Fischer2000, author = {Fischer, Alexander}, title = {An Uncoupling-Coupling Technique for Markov Chain Monte Carlo Methods}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5720}, number = {00-04}, year = {2000}, abstract = {Uncoupling-coupling Monte Carlo (UCMC) combines uncoupling techniques for finite Markov chains with Markov chain Monte Carlo methodology. By determining almost invariant sets of the associated Markov operator, the Monte Carlo sampling splits by a hierarchical annealing process into the essential regions of the state space; therefore UCMC aims at avoiding the typical metastable behavior of Monte Carlo techniques. From the viewpoint of Monte Carlo, a slowly converging long-time Markov chain is replaced by a limited number of rapidly mixing short-time ones. The correct weighting factors for the various Markov chains are obtained via a coupling matrix, that connects the samplings from the different almost invariant sets. The underlying mathematical structure of this approach is given by a general examination of the uncoupling-coupling procedure. Furthermore, the overall algorithmic scheme of UCMC is applied to the \$n\$-pentane molecule, a well-known example from molecular dynamics.}, language = {en} } @misc{Groetschel2000, author = {Gr{\"o}tschel, Martin}, title = {Verkehrsplanung: Bessere L{\"o}sungen mit Mathematik}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4439}, number = {SC-99-54}, year = {2000}, abstract = {Anwendungen der Mathematik in der Verkehrs- und Transporttechnologie haben eine große und bedeutende Tradition. Nat{\"u}rlich wurden die ersten Fahrzeuge mit der ingenieurm{\"a}ßigen Methode von Versuch, Irrtum und Verbesserung entworfen. Aber schon sehr bald kamen mathematische Berechnungen hinzu, mit denen mechanische Eigenschaften von Fahrzeugteilen ermittelt und zum Teil optimiert wurden. Die hierzu erforderliche Mathematik wurde in diesem Jahrhundert zu einem m{\"a}chtigen Werkzeugkasten ausgebaut. Mit diesem kann man heute z.B. hocheffiziente Motoren mit geringem Schadstoffausstoß entwerfen, aerodynamisch g{\"u}nstige Fahrzeugprofile ermitteln und Flugzeugfl{\"u}gel berechnen, die die gew{\"u}nschte Last sicher und mit geringem Treibstoffaufwand tragen. Die Mathematik unterst{\"u}tzt die Technologie des Verkehrs beginnend bei globalen Designfragen bis hin zur Spezifizierung von Materialeigenschaften kleinster Bauteile; sie berechnet mit hoher Pr{\"a}zision energieoptimale Bahnen von Raumflugk{\"o}rpern oder zeitoptimale Trajektorien f{\"u}r Flugzeuge, steuert automatische Roboteranlagen oder innerbetriebliche Transportsysteme.}, language = {de} } @misc{LangMerz2000, author = {Lang, Jens and Merz, Wilhelm}, title = {Two-Dimensional Adaptive Simulation of Dopant Diffusion in Silicon}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5716}, number = {00-03}, year = {2000}, abstract = {One important step in the fabrication of silicon-based integrated circuits is the creation of semiconducting areas by diffusion of dopant impurities into silicon. Complex models have been developed to investigate the redistribution of dopants and point defects. In general, numerical analysis of the resulting PDEs is the central tool to assess the modelling process. We present an adaptive approach which is able to judge the quality of the numerical approximation and which provides an automatic mesh improvement. Using linearly implicit methods in time and multilevel finite elements in space, we are able to integrate efficiently the arising reaction-drift-diffusion equations with high accuracy. Two different diffusion processes of practical interest are simulated.}, language = {en} } @misc{Wolf2000, author = {Wolf, Thomas}, title = {The Symbolic Integration of Exact PDEs}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5702}, number = {00-02}, year = {2000}, abstract = {An algorithm is described to decide if a given polynomial differential expression \$\Delta\$ of multivariate functions is exact, i.e. whether there exists a first integral \$P\$ such that \$D_xP = \Delta\$ for any one of a set of variables \$x\$ and to provide the integral \$P\$. A generalization is given to allow integration in the case that the exactness is prohibited by terms which contain only functions of not all the independent variables.}, language = {en} } @misc{EhrigNowak2000, author = {Ehrig, Rainald and Nowak, Ulrich}, title = {Algorithmen- und Softwareoptimierung f{\"u}r die Satellitenbahn- und Schwerefeldmodellierung}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-5694}, number = {00-01}, year = {2000}, abstract = {Dieser Report enth{\"a}lt die Ergebnisse der Untersuchungen, die gem{\"a}ss dem Forschungs-- und Entwicklungsvertrag Gravity zwischen dem GeoForschungsZentrum Potsdam und dem Konrad--Zuse--Zentrum Berlin vorgenommen wurden. Die damit vereinbarte wissenschaftliche Kooperation hat die folgenden Ziele: \item{die am GFZ vorhandenen Algorithmen und Softwaremodule auf ihre Effizienz hisichtlich Nutzung der Rechnerresourcen zu untersuchen und L{\"o}sungen f{\"u}r einen schnelleren Datendurchsatz zu entwickeln und zu implementieren,} \item{Methoden zur Regularisierung und L{\"o}sung schlecht konditionierter Normalgleichungssysteme (f{\"u}r Schwerefeldkoeffizienten) kritisch zu untersuchen und eine mathematisch objektive Strategie der Regularisierung zu entwickeln, und} \item{insbesondere im Hinblick auf die Anforderungen bei GRACE, verschiedene Bahnintegrationsverfahren hinsichtlich ihrer numerischen Genauigkeit und Einsatzm{\"o}glichkeiten zu untersuchen.}}, language = {de} } @misc{BengerHegeHeusler2000, author = {Benger, Werner and Hege, Hans-Christian and Heusler, Stefan}, title = {Visions of Numerical Relativity 1999}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4429}, number = {SC-99-53}, year = {2000}, abstract = {We present visualizations of recent supercomputer simulations from numerical relativity, exploiting the progress in visualization techniques and numerical methods also from an artistic point of view. The sequences have been compiled into a video tape, showing colliding black holes, orbiting and merging neutron stars as well as collapsing gravitational waves. In this paper we give some background information and provide a glance at the presented sequences.}, language = {en} } @misc{GroetschelKuberekLohrumetal.1999, author = {Gr{\"o}tschel, Martin and Kuberek, Monika and Lohrum, Stefan and L{\"u}gger, Joachim and Rusch, Beate}, title = {Der Kooperative Bibliotheksverbund Berlin-Brandenburg}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4418}, number = {SC-99-52}, year = {1999}, abstract = {Im Herbst 1999 ging der Kooperative Bibliotheksverbund Berlin-Brandenburg (KOBV) in Routinebetrieb. In technischer Hinsicht setzt der KOBV auf ein neuartiges, zukunftsweisendes Verbundkonzept, in dem die zentrale Datenbank mit dem Verbundkatalog ersetzt wird durch verteilte Datenbanken und lokale Kataloge, die durch das Netz (Internet) miteinander verbunden sind. Die zentrale Recherchefunktion wird ersetzt durch die KOBV-Suchmaschine. Beschrieben werden die Hintergr{\"u}nde, die zu diesem Konzept gef{\"u}hrt haben, die Kriterien, die die Architekturentscheidungen der Software bestimmt haben, sowie die einzelnen realisierten Komponenten.}, language = {de} } @misc{GroetschelKuberekLohrumetal.1999, author = {Gr{\"o}tschel, Martin and Kuberek, Monika and Lohrum, Stefan and L{\"u}gger, Joachim and Rusch, Beate}, title = {Die KOBV-Suchmaschine geht in Routinebetrieb}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4407}, number = {SC-99-51}, year = {1999}, abstract = {Im Herbst 1999 nimmt die KOBV-Suchmaschine, das technische "Herzst{\"u}ck" des KOBV, den Routinebetrieb auf. Nach einer kurzen Einf{\"u}hrung in die politischen und rechtlichen Grundlagen des KOBV-Projektes werden in diesem Aufsatz die Funktionalit{\"a}ten der KOBV-Suchmaschine, ihre Leistungen f{\"u}r Bibliotheksbenutzer und Bibliothekare, vorgestellt. Der Aufsatz schließt mit einem {\"U}berblick {\"u}ber den bisherigen Projektverlauf und der Erl{\"a}uterung der wichtigsten Prinzipien des KOBV - Offenheit, Dezentralit{\"a}t und Heterogenit{\"a}t.}, language = {de} } @misc{Kuberek1999, author = {Kuberek, Monika}, title = {Der Kooperative Bibliotheksverbund Berlin-Brandenburg (KOBV) - Ein innovatives Verbundkonzept f{\"u}r die Region}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4399}, number = {SC-99-50}, year = {1999}, abstract = {Auf dem 89. Deutschen Bibliothekartag, der vom 25. bis 29. Mai 1999 in Freiburg (Breisgau) stattgefunden hat, wurde der Kooperative Bibliotheksverbund Berlin-Brandenburg (KOBV) zum ersten Mal der großen bibliothekarischen {\"O}ffentlichkeit vorgestellt. Am KOBV-Stand, der im Rahmen des gemeinsamen Standes der Arbeitsgemeinschaft der Verbundsysteme organisiert wurde, f{\"u}hrte die KOBV-Projektgruppe Funktionalit{\"a}ten der KOBV-Suchmaschine vor. In der Vortragsreihe zum Themenkreis XI "Neue Entwicklungen in den Verbund- und Lokalsystemen", die unter Mitwirkung der Arbeitsgemeinschaft der Verbundsysteme veranstaltet wurde, war der KOBV mit einem eigenen Vortrag vertreten: "Der Kooperative Bibliotheksverbund Berlin-Brandenburg (KOBV) - Ein innovatives Verbundkonzept f{\"u}r die Region". In dem Vortrag hat die Verfasserin einen umfassenden {\"U}berblick {\"u}ber das KOBV-Projekt und den bisherigen Projektverlauf gegeben, die Projektziele und den politischen Rahmen er{\"o}rtert sowie die KOBV-Suchmaschine, das technische Kernst{\"u}ck des neuen Verbundes, vorgestellt. Der hier vorliegende Text ist die schriftlich ausgearbeitete Fassung dieses Vortrages.}, language = {de} } @misc{Helmberg1999, author = {Helmberg, Christoph}, title = {The m-Cost ATSP}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4374}, number = {SC-99-48}, year = {1999}, abstract = {Although the m-ATSP (or multi traveling salesman problem) is well known for its importance in scheduling and vehicle routing, it has, to the best of our knowledge, never been studied polyhedraly, i.e., it has always been transformed to the standard ATSP. This transformation is valid only if the cost of an arc from node \$i\$ to node \$j\$ is the same for all machines. In many practical applications this is not the case, machines produce with different speeds and require different (usually sequence dependent) setup times. We present first results of a polyhedral analysis of the m-ATSP in full generality. For this we exploit the tight relation between the subproblem for one machine and the prize collecting traveling salesman problem. We show that, for \$m\ge 3\$ machines, all facets of the one machine subproblem also define facets of the m-ATSP polytope. In particular the inequalities corresponding to the subtour elimination constraints in the one machine subproblems are facet defining for m-ATSP for \$m\ge 2\$ and can be separated in polynomial time. Furthermore, they imply the subtour elimination constraints for the ATSP-problem obtained via the standard transformation for identical machines. In addition, we identify a new class of facet defining inequalities of the one machine subproblem, that are also facet defining for m-ATSP for \$m\ge 2\$. To illustrate the efficacy of the approach we present numerical results for a scheduling problem with non-identical machines, arising in the production of gift wrap at Herlitz PBS AG.}, language = {en} } @misc{Helmberg1999, author = {Helmberg, Christoph}, title = {Semidefinite Programming}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4382}, number = {SC-99-49}, year = {1999}, abstract = {Due to its many applications in control theory, robust optimization, combinatorial optimization and eigenvalue optimization, semidefinite programming had been in wide spread use even before the development of efficient algorithms brought it into the realm of tractability. Today it is one of the basic modeling and optimization tools along with linear and quadratic programming. Our survey is an introduction to semidefinite programming, its duality and complexity theory, its applications and algorithms.}, language = {en} } @misc{Stueben1999, author = {St{\"u}ben, Hinnerk}, title = {Decorrelation of the Topological Charge in Tempered Simulations of Full QCD}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4369}, number = {SC-99-47}, year = {1999}, abstract = {The improvement of simulations of QCD with dynamical Wilson fermions by combining the Hybrid Monte Carlo algorithm with parallel tempering is studied. As an indicator for decorrelation the topological charge is used.}, language = {en} } @misc{MarchandMartinWeismanteletal.1999, author = {Marchand, Hugues and Martin, Alexander and Weismantel, Robert and Wolsey, Laurence}, title = {Cutting Planes in Integer and Mixed Integer Programming}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4339}, number = {SC-99-44}, year = {1999}, abstract = {This survey presents cutting planes that are useful or potentially useful in solving mixed integer programs. Valid inequalities for i) general integer programs, ii) problems with local structure such as knapsack constraints, and iii) problems with 0-1 coefficient matrices, such as set packing, are examined in turn. Finally the use of valid inequalities for classes of problems with structure, such as network design, is explored.}, language = {en} } @misc{FrieseSchmidtYevick1999, author = {Friese, Tilman and Schmidt, Frank and Yevick, David}, title = {Transparent Boundary Conditions for a Wide-Angle Approximation of the One-Way Helmholtz Equation}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4345}, number = {SC-99-45}, year = {1999}, abstract = {We present nonlocal discrete transparent boundary conditions for a fourth-order wide-angle approximation of the two-dimensional Helmholtz equation. The boundary conditions are exact in the sense that they supply the same discrete solution on a bounded interior domain as would be obtained by considering the problem on the entire unbounded domain with zero boundary conditions at infinity. The proposed algorithm results in an unconditionally stable propagation method. Numerical examples from optics illustrate the efficiency of our approach.}, language = {en} } @misc{SchmidtFrieseYevick1999, author = {Schmidt, Frank and Friese, Tilmann and Yevick, David}, title = {Transparent Boundary Conditions for Split-Step Pade Approximations of the One-Way Helmholtz Equation}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4353}, number = {SC-99-46}, year = {1999}, abstract = {In this paper, we generalize the nonlocal discrete transparent boundary condition introduced by Schmidt and Deuflhard {[}Comp. Math. Appl. 29 (1995) 53-76{]} and Schmidt and Yevick {[}J. Comput. Phys. 134 (1997) 96-107{]} to propagation methods based on arbitrary Pad\'e approximations to the two-dimensional one-way Helmholtz equation. Our approach leads to a recursive formula for the coefficients appearing in the nonlocal condition which then yields an unconditionally stable propagation method.}, language = {en} } @misc{BengerHegeMerzkyetal.1999, author = {Benger, Werner and Hege, Hans-Christian and Merzky, Andre and Radke, Thomas and Seidel, Edward}, title = {Efficient Distributed File I/O for Visualization in Grid Environments}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4326}, number = {SC-99-43}, year = {1999}, abstract = {Large scale simulations running in metacomputing environments face the problem of efficient file I/O. For efficiency it is desirable to write data locally, distributed across the computing environment, and then to minimize data transfer, i.e.\ reduce remote file access. Both aspects require I/O approaches which differ from existing paradigms. For the data output of distributed simulations, one wants to use fast local parallel I/O for all participating nodes, producing a single distributed logical file, while keeping changes to the simulation code as small as possible. For reading the data file as in postprocessing and file based visualization, one wants to have efficient partial access to remote and distributed files, using a global naming scheme and efficient data caching, and again keeping the changes to the postprocessing code small. However, all available software solutions require the entire data to be staged locally (involving possible data recombination and conversion), or suffer from the performance problems of remote or distributed file systems. In this paper we show how to interface the HDF5 I/O library via its flexible Virtual File Driver layer to the Globus Data Grid. We show, that combining these two toolkits in a suitable way provides us with a new I/O framework, which allows efficient, secure, distributed and parallel file I/O in a metacomputing environment.}, language = {en} } @misc{PowellWeiser1999, author = {Powell, Gary and Weiser, Martin}, title = {Container Adaptors}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4308}, number = {SC-99-41}, year = {1999}, abstract = {The C++ standard template library has many useful containers for data. The standard library includes two adpators, queue, and stack. The authors have extended this model along the lines of relational database semantics. Sometimes the analogy is striking, and we will point it out occasionally. An adaptor allows the standard algorithms to be used on a subset or modification of the data without having to copy the data elements into a new container. The authors provide many useful adaptors which can be used together to produce interesting views of data in a container.}, language = {en} } @misc{Galliat1999, author = {Galliat, Tobias}, title = {Clustering Data of Different Information Levels}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4319}, number = {SC-99-42}, year = {1999}, abstract = {For using Data Mining, especially cluster analysis, one needs measures to determine the similarity or distance between data objects. In many application fields the data objects can have different information levels. In this case the widely used euclidean distance is an inappropriate measure. The present paper describes a concept how to use data of different information levels in cluster analysis and suggests an appropriate similarity measure. An example from practice is included, that shows the usefulness of the concept and the measure in combination with {\sc Kohonens} Self-Organizing Map algorithm, a well-known and powerful tool for cluster analysis.}, language = {en} } @misc{Beck1999, author = {Beck, Rudolf}, title = {Algebraic Multigrid by Component Splitting for Edge Elements on Simplicial Triangulations}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4290}, number = {SC-99-40}, year = {1999}, abstract = {Our focus is on Maxwell's equations in the low frequency range; two specific applications we aim at are time-stepping schemes for eddy current computations and the stationary double-curl equation for time-harmonic fields. We assume that the computational domain is discretized by triangles or tetrahedrons; for the finite element approximation we choose N\'{e}d\'{e}lec's \$H(curl)\$-conforming edge elements of the lowest order. For the solution of the arising linear equation systems we devise an algebraic multigrid preconditioner based on a spatial component splitting of the field. Mesh coarsening takes place in an auxiliary subspace, which is constructed with the aid of a nodal vector basis. Within this subspace coarse grids are created by exploiting the matrix graphs. Additionally, we have to cope with the kernel of the \$curl\$-operator, which comprises a considerable part of the spectral modes on the grid. Fortunately, the kernel modes are accessible via a discrete Helmholtz decomposition of the fields; they are smoothed by additional algebraic multigrid cycles. Numerical experiments are included in order to assess the efficacy of the proposed algorithms.}, language = {en} } @misc{SchmidtEhrenbergHege1999, author = {Schmidt-Ehrenberg, Johannes and Hege, Hans-Christian}, title = {Visualizing Quantum Mechanical Phenomena}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4287}, number = {SC-99-39}, year = {1999}, abstract = {In this paper we discuss several ways to visualize stationary and non-stationary quantum mechanical systems. We demonstrate an approach for the quantitative interpretation of probability density isovalues which yields a reasonable correlation between isosurfaces for different timesteps. As an intuitive quantity for visualizing the momentum of a quantum system we propose the probability flow density which can be treated by vector field visualization techniques. Finally, we discuss the visualization of non-stationary systems by a sequence of single timestep images.}, language = {en} } @misc{GalliatHuisingaDeuflhard1999, author = {Galliat, Tobias and Huisinga, Wilhelm and Deuflhard, Peter}, title = {Self-Organizing Maps Combined with Eigenmode Analysis for Automated Cluster Identification}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4279}, number = {SC-99-38}, year = {1999}, abstract = {One of the important tasks in Data Mining is automated cluster analysis. Self-Organizing Maps (SOMs) introduced by {\sc Kohonen} are, in principle, a powerful tool for this task. Up to now, however, its cluster identification part is still open to personal bias. The present paper suggests a new approach towards automated cluster identification based on a combination of SOMs with an eigenmode analysis that has recently been developed by {\sc Deuflhard et al.} in the context of molecular conformational dynamics. Details of the algorithm are worked out. Numerical examples from Data Mining and Molecular Dynamics are included.}, language = {en} } @misc{HelmbergKiwiel1999, author = {Helmberg, Christoph and Kiwiel, K.C.}, title = {A Spectral Bundle Method with Bounds}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4256}, number = {SC-99-37}, year = {1999}, abstract = {Semidefinite relaxations of quadratic 0-1 programming or graph partitioning problems are well known to be of high quality. However, solving them by primal-dual interior point methods can take much time even for problems of moderate size. The recent spectral bundle method of Helmberg and Rendl can solve quite efficiently large structured equality-constrained semidefinite programs if the trace of the primal matrix variable is fixed, as happens in many applications. We extend the method so that it can handle inequality constraints without seriously increasing computation time. Encouraging preliminary computational results are reported.}, language = {en} } @misc{SchuetteHuisingaDeuflhard1999, author = {Sch{\"u}tte, Christof and Huisinga, Wilhelm and Deuflhard, Peter}, title = {Transfer Operator Approach to Conformational Dynamics in Biomolecular Systems}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4247}, number = {SC-99-36}, year = {1999}, abstract = {The article surveys the development of novel mathematical concepts and algorithmic approaches based thereon in view of their possible applicability to biomolecular design. Both a first deterministic approach, based on the Frobenius-Perron operator corresponding to the flow of the Hamiltonian dynamics, and later stochastic approaches, based on a spatial Markov operator or on Langevin dynamics, can be subsumed under the unified mathematical roof of the transfer operator approach to effective dynamics of molecular systems. The key idea of constructing specific transfer operators especially taylored for the purpose of conformational dynamics appears as the red line throughout the paper. Different steps of the algorithm are exemplified by a trinucleotide molecular system as a small representative of possible RNA drug molecules.}, language = {en} } @misc{LinkeKrebsSchuenemann1999, author = {Linke, Matthias and Krebs, Carsten and Sch{\"u}nemann, Marion}, title = {Metacomputing zwischen Berlin und Rostock}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4239}, number = {SC-99-35}, year = {1999}, abstract = {Das Konrad-Zuse-Zentrum f{\"u}r Informationstechnik Berlin (ZIB) und das Rechenzentrum der Universit{\"a}t Rostock, beide Einrichtungen betreiben massiv-parallele Rechner vom Typ CRAY T3E, haben sich an Hand einer Anwendung aus dem Bereich der Botanik mit den M{\"o}glichkeiten der Verteilung auf zwei Parallelrechner, gekoppelt nur {\"u}ber das Breitband-Wissenschaftsnetz des Deutschen Forschungsnetzes, vertraut gemacht. Das Projekt besteht aus zwei Teilen. Im ersten Teil wird ausf{\"u}hrlich das zwischen den Rechnern liegende Netz und die Ergebnisse einer Performanceanalyse dieses Netzes dokumentiert. Der zweite Teil beschreibt die Anwendung "Simulation des Wachstums von Pflanzen"' sowie die Ergebnisse der Verteilung dieser Anwendung auf beide Rechner. \begin{center} \bf{Abstract} \end{center} The "'Konrad-Zuse-Zentrum f{\"u}r Informationstechnik Berlin"' (ZIB) and the Computing Centre of the University of Rostock operate high-performance computers of type CRAY T3E. In this project an application from the area of the botany is distributed on two parallel computers, only coupled through the Broadband Science Network of the German Research Network (DFN). This project consists of two parts. In the first part the network which is situated between the computers and the results of a performance analysis is documented in detail. The second part describes the application "'Simulation of the growth of plants"' as well as the results of the distribution of this application to both computers.}, language = {de} } @misc{Deuflhard1999, author = {Deuflhard, Peter}, title = {Differential Equations in Technology and Medicine. Computational Concepts, Adaptive Algorithms, and Virtual Labs}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4223}, number = {SC-99-34}, year = {1999}, abstract = {This series of lectures has been given to a class of mathematics postdocs at a European summer school on Computational Mathematics Driven by Industrial Applications in Martina Franca, Italy (organized by CIME). It deals with a variety of challenging real life problems selected from clinical cancer therapy, communication technology, polymer production, and pharmaceutical drug design. All of these problems from rather diverse application areas share two common features: (a) they have been modelled by various differential equations -- elliptic, parabolic, or Schr{\"o}dinger--type partial differential equations, countable ordinary diffential equations, or Hamiltonian systems, (b) their numerical solution has turned out to be real challenge to computational mathematics.}, language = {en} } @misc{ZoecklerStallingHege1999, author = {Z{\"o}ckler, Malte and Stalling, Detlev and Hege, Hans-Christian}, title = {Fast and Intuitive Generation of Geometric Shape Transitions}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4219}, number = {SC-99-33}, year = {1999}, abstract = {We describe a novel method for continuously transforming two triangulated models of arbitrary topology into each other. Equal global topology for both objects is assumed, extensions for genus changes during metamorphosis are provided. The proposed method addresses the major challenge in 3D metamorphosis, namely specifying the morphing process intuitively, with minimal user interaction and sufficient detail. Corresponding regions and point features are interactively identified. These regions are parametrized automatically and consistently, providing a basis for smooth interpolation. Utilizing suitable 3D interaction techniques a simple and intuitive control over the whole morphing process is offered.}, language = {en} } @misc{BorndoerferGroetschelLoebel1999, author = {Bornd{\"o}rfer, Ralf and Gr{\"o}tschel, Martin and L{\"o}bel, Andreas}, title = {Der Schnellste Weg zum Ziel}, doi = {10.1007/978-3-322-96366-6_5}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4209}, number = {SC-99-32}, year = {1999}, abstract = {Wir geben eine Einf{\"u}hrung in die Mathematik von und mit Wegen. Nicht auf dem k{\"u}rzesten, aber auf einem hoffentlich kurzweiligen Weg!}, language = {de} } @misc{Steinbach1999, author = {Steinbach, Marc}, title = {Markowitz Revisited: Single-Period and Multi-Period Mean-Variance Models}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-4183}, number = {SC-99-30}, year = {1999}, abstract = {Mean-variance portfolio analysis provided the first quantitative treatment of the tradeoff between profit and risk. We investigate in detail the interplay between objective and constraints in a number of single-period variants, including semi-variance models. Particular emphasis is laid on avoiding the penalization of overperformance. The results are then used as building blocks in the development and theoretical analysis of multi-period models based on scenario trees. A key property is the possibility to remove surplus money in future decisions, yielding approximate downside risk minimization.}, language = {en} }