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Erscheinungsjahr
- 1997 (165) (entfernen)
A multicriterial statement of the above mentioned problem is presented. It differes from the classical statement of Spanning Tree problem. The quality of solution is estimated by vector objective function which contains weight criteria as well as topological criteria (degree and diameter of tree). Many real processes are not determined yet. And that is why the investigation of the stability is very important. Many errors are connected with calculations. The stability analysis of vector combinatorial problems allows to discover the value of changes in the initial data for which the optimal solution is not changed. Furthermore, the investigation of the stability allows to construct the class of the problems on base of the one problem by means of the parameter variations. Analysis of the problems with belong to this class allows to obtaine axact and adecuate discription of model
Renovation's peculiarities of industrial enterprises in conditions of economic selfsufficiency
(1997)
Probleme of recrienfation of building complex, to the sharp increase of share of reconstruction works, capital repair and modernisation of in-dustrial plants are concidered in this work. The conception of develop-ment and creation of unitified system of expluatation and renovation of industrial plants are worded out. This system is based on date-computer technology and taking into conciderations of real economic relations.
Ideally, multiple computational building evaluation routines (particularly simulation tools) should be coupled in real-time to the representational design model to provide timely performance feed-back to the system user. In this paper we demonstrate how this can be achieved effectively and conveniently via homology-based mapping. We consider two models as homologous if they entail isomorphic topological information. If the general design representation (i.e., a shared object model) is generated in a manner so as to include both the topological building information and pointers to the semantic information base, it can be used to directly derive the domain representations (>enriched< object models with detailed configurational information and filtered semantic data) needed for evaluation purposes. As a proof of concept, we demonstrate a computational design environment that dynamically links an object-oriented space-based design model, with structurally homologous object models of various simulation routines.
The theory of random matrices, or random matrix theory, RMT in what follows, has been developed at the beginning of the fties to describe the sta- tistical properties of energy levels of complex quantum systems, [1], [2], [3]. In the early eighties it has enjoyed renewed interest since it has been recognized as a very useful tool in the study of numerous physical systems. Specically, it is very useful in the analysis of chaotic quantum systems. In fact, in the last years many papers appeared about the problem of quantum chaos which implies the quantization of systems whose underlying classical dynamics is irregular (i.e. chaotic). The simplest models considered in this eld are billi- ards of various shapes. From the the classical point of view, a point particle in a 2-dimensional billiard displays regular or irregular motion depending on the shape of the billiard; for instance motion in a rectangular or circular billi- ard is regular thanks to the symmetries of the boundary. On the other hand, billiards of arbitrary shapes imply chaotic motion, i.e. exponential diver- gence of initially nearby trajectories. In order to study quantum billiards we have to consider the Schroedinger equation in various 2-dimensional domains. The eigenvalues of the Schroedinger equation represent the allowed energy levels of our quantum particle in the billiard under consideration, while the eigenfunction norms represent the probability density of nding the particle in a certain position. The question of quantum chaos is whether the charac- ter of the classical motion (regular or chaotic) can in uence some properties
Pseudorigidity method for solving the problem of limit equilibrium of rigid-plastic constructions
(1997)
1.Design calculations , based upon the theory elasticity , cannot completely satisfy engineers and designers , because cannot answer to basic question about overload capability . Only design calculations of limit equilibrium of rigid-plastic constructions can answer to this question completely enough. As a rule , such design calculations are made issue from hypothesis, that material of construction has rigid-plastic diagram Prandtl .This scheme of calculation gives qualitatively more correct results, then usual calculation, based upon law Hooke’s , and allows more really estimate ultimate strength of construction due to different loads. Universal algorithms for solving the problem of limit equilibrium have been created since the middle of the 60’s.These algorithms are based upon two basic theorems about limit analysis - static and kinetics. It was found , that with the help of above-mentioned theorems the problem of limit equilibrium can be formulated as a problem of linear programming (for linear yield) or nonlinear programming (for yield Guber-Mizes). The method of linear programming conformably to calculation of rod systems got the most development in the reports Prager W. [1] and Chiras A. [ 2 ]. The method of linear programming conformably to plates and shells was widely used by Rganizin A.[3]. [3[ contains more full bibliography about this problem. Calculation of limit equilibrium with the help of linear and nonlinear programming has a few significant lacks: - complexity and laboriousness preliminary preparation of problem for PC; - necessity to use special program means , which are not in usual program packet for strength analysis. Author worked out a new method about design calculation of limit equilibrium without above-mentioned lacks . The method is based upon analogy of relations between internal generalized efforts and generalized deformations in elastic system and between generalized efforts and velocities of change generalized deformations in rigid-plastic system. Because later rigid-plastic deformation would be treated as an elastic deformation in the system with special constructed rigidities , this method could be called >pseudorigidity method<.
Prozessuale Gestaltung
(1997)
Processing technical and environmental data on building materials, components, and systems has become more important during the last few years. Increased sensitivity towards environmental and energy problems has lead to the demand for simulation and evaluation of the long term behavior of buildings. The results of such simulations are expected to enable architects and engineers to develop a broader, interdisciplinary understanding of the impact of their products (buildings) on the environment. However, conducting such evaluations is currently hampered by the lack of comprehensive, up-to-date, and ecologically relevant data on building materials, components, and systems. To address this problem, this paper proposes an approach to deal with the absent or uncertain attributes of building materials, components, and systems. In the past, various information systems have been developed to provide data on a limited set of building materials, including precise values pertaining to some of their characteristics, such as availability, manufacturers, costs, etc. These traditional information systems have difficulty in dealing with uncertain, incomplete and sparse data. However, uncertainty and incompleteness characterize the nature of most of the available and environmentally related characteristics of materials, components, and systems. In this paper, a fuzzy-logic-based augmentation of traditional information systems is proposed towards providing management, utilization and manipulation of incomplete and uncertain data.
The paper analyses the influence of the effect of inertia on the reliability of production systems. Systems inertia represents the phenomenon of continuing work for some time after the breakdown of one of the former phases. In our considerations, inertia is treated as the time elapsed from the onset of breakdown till the system's inability to work. A special method had to be devised to investigate the effect of inertia in order to evaluate the reliability of production systems and to attempt algorithmization to control the reliability of production system by means of inertia or reserving. The method of reliability analysis is presented only in an inform aspect. The possibilities of increasing reliability of production systems are listed. A comparison of the redundancy method and inertia method is presented. The results of this comparison and simulated investigations of influence of inertia on reliability of system are essential scope of the paper. Selected conclusions are as follows: when inertia approaches the last phase in the system, its influence on the shape of the distribution of the system's ability increases; an increase in inertia causes an increase in the availability of the system which approaches a certain border value; dependence of the average of a system's disability on inertia has a saddle-like character whereas dependence of the number of breakdowns (stoppages) in the system has the nature of an S-curve.
Der englische Physiker und Mathematiker Roger Penrose hat eine mathematische Pflasterung entdeckt, deren Formenreichtum neue Impulse in der Architektur setzen kann. In der Gemeinde Bütgenbach im Hohen Venn, Belgien, wurde das Verwaltungszentrum durch den Essener Architekten Ernst Burghartz mit mehrereren Penrose-Pflasterungen versehen. Diese beruhen auf einem Computer-Programm, welches der Vortragende zusammen mit Dr. Frank Martini entwickelt hat. Herr Burghartz hat jedoch diesen Vorentwurf nach seinen künstlerischen Vorstellungen abgewandelt.
Parallele Netzgenerierung
(1997)
Bei der Berechnung von statischen oder dynamischen Problemen mit Hilfe der Methode der Finiten Elemente ist eine Diskretisierung des zu berechnenden Gebietes notwendig. Bei einer sinnvollen Modellierung des Gebietes ist die Elementgröße meist nicht konstant, sondern ist an kritischen Stellen kleiner. Die Vorgaben hierfür können einerseits aus Erfahrungen des Anwenders, andererseits aus einer Fehlerabschätzung einer vorangegangenen FE-Berechnung resultieren [5]. Soll die FE-Berechnung auf einem Parallelrechner geschehen, ist eine Partitionierung des Gebietes, d.h. eine Zuordnung der Elemente zu den Prozessoren, notwendig. Bei dem hier beschriebenen Ansatz werden nun im Gegensatz zu den üblichen Verfahren erst die Eingangsdaten für den Netzgenerator umgewandelt und dann das Elementnetz direkt auf dem Parallelrecher gleichzeitig auf allen Prozessoren erzeugt. Eine Aufteilung der Elemente auf die Prozessoren entsteht als Nebenprodukt der Netzaufteilung. Die entstehenden Teilgebietsgrenzen werden geometrisch minimiert. Die Lastbalance der Netzaufteilung sowie der FE-Rechnung wird durch ein annähernd gleiche Anzahl der Elemente je Partition gewährleistet. Als Eingabedaten wird eine Beschreibung des Gebietes durch Polygonzüge, sowie einer Netzdichtefunktion, z.B. durch Punkte mit Angaben über die angestrebte Elementgröße, benötigt.
The effectiveness of working processes accomplished by various technological machines to a large extend depends on working quality of supply, transporting and orientating mechanisms which are very often produced as positional hydro-mechanical systems. The choice of their best type and regimes of work requires construction and analysis of models of their optimum steering which are complicated by nonlinearness, multy-criterialness of problem and also by occasional outbreaks of parameters and moments of steering regime changing. It was developed the common structure of such systems allowing within common scheme to vary the complexity degree of PHMS and the methods of inhibitory efforts supplement. For some systems which are complicated in series (from two-measured linear system to nine-measured non-linear) puzzles of the most fast zero-ambit getting are solved and two-criterial problems are analyzed. (T-min-speed, Z(T)- accuracy). There are suggested the computing procedures of optimum PHMS synthesis. The effectiveness of accepted methods of solving is asserted by the analogy of the results of gradually complicated models investigation and by their good analogy with the natural experiment. It was exposed the sense of heuristic methods of improving of approximately optimum steering, their elaboration on the base of theoretical models. The basic methods of optimum PGMS construction were also nominated.
Anwendungen der Methoden des Operations Research in der Praxis des Projektmanagements sind so gut wie kaum zu finden. Diese Anwendungslücke ist umso erstaunlicher, als es eine große Zahl von theoretischen Veröffentlichungen zum Themenkreis >Operations Research und Projektmanagement< gibt . Der Beitrag arbeitet die verschiedenen Ursachen für die bislang geringe praktische Relevanz der Disziplin >Operations Research< heraus und macht Vorschläge, wie in Zukunft anwendungsfreundlichere Modelle entwickelt werden können.
With the help of functional analytical methods complex analysis is a powerful tool in treating non-linear first-order partial differential equations in the plane. Some of the most important of these equations are the Beltrami equations. This is due to the fact that the theory of Beltrami systems is related to many problems of geometry and analysis, like non-linear subsonic two-dimensional hydrodynamics, problems of conformal and quasiconformal mappings of two-dimensional Riemannian manifolds, or complex analytic dynamics. The theory of Beltrami equations is strongly connected with the -operator. This singular integral operator is immediately recognized as two-dimensional Hilbert-transform, known also under the name of integral operator with Beurling kernel, acting as an isometry of L2(C) onto L2(C). In hypercomplex function theory the Beltrami equations have not yet this importance, but nevertheless, they are a basic condition for the transfer of complex methods and efforts for solving partial differential equations, especially of non-linear type, to the spatial case. Here we deal with hypercomplex Beltrami systems. For this we restrict ourselves to the quaternionic case, but without any loss of generality. We will show how a spatial generalization of the complex -operator can be used to solve systems of non-linear partial differential equations, in particular different types of spatial Beltrami systems. Also, the for practical purposes so important norm estimates will be derived. Some of our results are stronger as known results in the complex case, but they are applicable in the complex situation, too.
Problem of discretic programming in conditions of manycriterial is considered. Set of work, being subject to fulfilment, is available. Are certain also: set of the executors; set, machines; set of resources (materials, semifinished items and etc.) and other set. As a functional complex name set, which will be formed, when on one representative of each of the specified sets is nominated to one working place. The allowable decision of a examined problem represents set of not crossed complexes provided that, for each working place one functional complex is certain in the accuracy. The elementary case of a formulated above problem is known under the name >a problem about purposes< [1], when the complex is defined as a pair >an executor - working place<. In case of three-element complexes we come to a problem about three-combinations. In a general case the complex consists from m of elements and the problem of formation of m-element complexes is formulated on the m-colour column.
A technique for using object-oriented technologies to write structural analysis software has been developed. The structural design information of an individual building is stored in an object-oriented database. A global database provides general design values as material data and safety factors. A class library for load elements has been evolved to model the transfer of loads in a building. This class library is the basis for the development of further classes for other structural elements such as beams, columns or slabs. A software has been developed to monitor the forces transferred from one structural member to another in a building for load cases and combinations according to Eurocode 1. The results of the analysis are stored in the projects database from which a structural design report may be generated. The software was developed under Microsoft Visual C++. The Microsoft Foundation Class Library (MFC) was used to program the Graphical User Interface (GUI). Object Linking and Embedding (OLE) technology is useful to include any type of OLE server objects for example texts written with a word processor or CAD drawings in the structural design report. The Object-Oriented Database Management System (OODBMS) ObjectStore provides services to store the large amount of objects.
Gegenstand der Betrachtung ist ein spezielles Tourenproblem der Schüttgutoptimierung. Man stelle sich als Realitätsbezug ein Transportunternehmen vor, das eine Anzahl von gleichartigen Fahrzeugen in einem Fuhrpark stationiert hat. Vorgegebene Mengen von Schüttgut müssen von einer Kiesgrube zu mehreren Baustellen transportiert werden. Dabei sind Be- und Entladezeiten, unterschiedliche mittlere Geschwindigkeiten für Leer- bzw. Lastfahrten und Schichtzeiten zu berücksichtigen. Gesucht ist eine optimale Anzahl von einzusetzenden Fahrzeugen und die zugehörigen Tourenpläne mit dem Ziel der Minimierung der Transportkosten unter Beachtung der Lieferverträge. Die Lösung des Problems erfolgt in zwei Phasen. Zuerst wird die Frage geklärt, wieviele Fahrzeuge bei minimalem Kostenniveau einzusetzen und welche zu den Leerfahrten gehörigen Teilstrecken wie oft zu befahren sind. Anschließend wird mit heuristischen Verfahren versucht, die Menge der zu fahrenden Teilstrecken so auf die Fahrzeuge aufzuteilen, daß für jedes Fahrzeug eine zulässige Tour entsteht. Zur komplexen Lösung einer denkbaren Aufgabe liegt ein Programm in der Programmiersprache PASCAL vor. Die erzielten numerischen Resultate belegen, daß auch für Probleme größerer Dimension eine Optimallösung oder sehr gute Näherungen in vernünftiger Zeit gefunden werden.
Bei der Berechnung von Stahlbeton- bzw. Spannbetonkonstruktionen müssen die Zusatzverformungen infolge Kriechen und Schwinden des Betons unter anderem dann berücksichtigt werden, wenn durch sie der Schnittgrößenzustand des Gesamttragwerks bzw. einzelner Tragwerksteile ungünstig verändert wird. Das trifft vor allem auf schlanke Druckglieder zu. Die Ermittlung der Kriechausmitte erfolgt im allgemeinen unter Zugrundelegung einer Kriechzahl, die vom Beanspruchungsniveau des Betons unabhängig ist. Diese Annahme ist unzulässig, wenn die Betonspannungen oberhalb des Gebrauchslastniveaus (>30..50% der Druckfestigkeit) liegen, da in diesem Bereich die Kriechdehnungen überproportional zu den kriecherzeugenden Spannungen anwachsen (nichtlineares Kriechen). Theoretische Untersuchungen zum Tragverhalten hochbeanspruchter Stahlbetonstützen unter Berücksichtigung des nichtlinearen Kriechens sind aufgrund der Komplexität des Problems und dem damit verbundenen Berechnungsaufwand gegenwärtig in nur geringem Umfang vorhanden. Im vorliegenden Beitrag wird ein Algorithmus vorgestellt, bei dem die Ermittlung der Schnittgrößen und Deformationen auf die sukzessive Lösung quadratischer Optimierungsaufgaben für im voraus festgelegte Betrachtungszeitpunkte zurückgeführt wird, wobei die Ergebnisse der vorangegangenen Zeitpunkte Eingangswerte für die Berechnung darstellen. Die Berücksichtigung der Nichtlinearität des Kriechens unter hoher Spannung sowie geometrisch nichtlinearer Effekte erfolgt iterativ innerhalb jedes Betrachtungszeitpunkts. Mit der Einführung von Spannungsbegrenzungen als zusätzliche Nebenbedingungen können in jeder Iteration Materialplastizierungen, Rißbildungen des Betons bzw. >tension stiffening<-Effekte ohne prinzipielle Veränderung des mathematischen Modells berücksichtigt werden. Durch Nachrechnung von Langzeitversuchen an Stahlbetonstützen erfolgt die Verifikation des Berechnungsmodells
The dynamic behaviour of shells, which are widely used in construction and mechanical engineering as critical components of machinery and 3-D structures, under static and dynamic loadings is described by system of deep nonlinear differential equations. Solution of these equations can be received with assistance of technique basing on a modern numerical algorithms and computer modeling.. The system of nonlinear differential equations of vibration of the shells is proposed taking into account the inertia forces in the tangential and normal directions. Its solution is based on combination of parameter prolongation method, finite-difference method and the Newton-Kantorovich iterative algorithm that allows plotting the loading trajectories and determination of bifurcation points on them. Package of Applied Programs >SEVSOR< is a computation means to be used in research of deformation, stability and vibration in thin axically-symmetric shells of complicated shape Input data include information on shell geometry, physical and mechanical properties, bearing conditions, types of loadings and load application. Frame output of motion forms in real time or either in decelerated or accelerated time scales for creating cartoons or video films is used for analysis of the compound dynamic processes in shell-type structures.
Multimodel Numerical Analysis of the Elasto-Visco-Plastic Deformation of Materials and Constructions
(1997)
At the present time there is no a generally accepted theory of visco-plasticity which is applicable for a wide class of materials and arbitrary paths of loading. The multimodel approach, based on the creation of hierarchical sequence of the models, is the most rational. The developed library of elasto-visco-plastic models includes both simplest and sophistic models demanding numerous experimental data. A unified general form of constitutive equations for all used elasto-visco-plastic models are presented based upon the concept of tensorial internal state variables. It permits to use unified algorithm of boundary tasks solution for different variants of material models. The developed selection criteria system generates the necessary conditions and provides the choice of the simplest variant of theory sufficient for correct problem solution. Formulation of the selection criteria system is based on peculiarities of viscoplastic materials behavior for the wide range thermomechanical loading and numerous computational experiments with structures different complexity levels. A set of effective schemes of integration stress-strain relations and non-linear finite element system solution are discussed for the considered class of material models. Application possibility of different material models is studied both for material element and for complicated structures. Application of the multimodel approach in numerical computations has demonstrated possibility of reliable prediction of stress-strain response under wide variety of combined loading.