Refine
Has Fulltext
- yes (105) (remove)
Document Type
- Conference Proceeding (76)
- Doctoral Thesis (17)
- Article (3)
- Master's Thesis (3)
- Periodical (2)
- Study Thesis (2)
- Diploma Thesis (1)
- Report (1)
Institute
- In Zusammenarbeit mit der Bauhaus-Universität Weimar (50)
- Graduiertenkolleg 1462 (12)
- Institut für Strukturmechanik (ISM) (8)
- Professur Angewandte Mathematik (4)
- Junior-Professur Augmented Reality (3)
- Professur Informatik im Bauwesen (3)
- An-Institute (2)
- Institut für Europäische Urbanistik (2)
- Institut für Konstruktiven Ingenieurbau (IKI) (2)
- Professur Betriebswirtschaftslehre im Bauwesen (2)
Keywords
- Angewandte Informatik (74)
- Angewandte Mathematik (74)
- Architektur <Informatik> (74)
- Computer Science Models in Engineering; Multiscale and Multiphysical Models; Scientific Computing (74)
- Computerunterstütztes Verfahren (74)
- Computersimulation (3)
- CAD (2)
- IFC (2)
- Kulturwissenschaft (2)
- Maschinelles Sehen (2)
Year of publication
- 2010 (105) (remove)
THE FOURIER-BESSEL TRANSFORM
(2010)
In this paper we devise a new multi-dimensional integral transform within the Clifford analysis setting, the so-called Fourier-Bessel transform. It appears that in the two-dimensional case, it coincides with the Clifford-Fourier and cylindrical Fourier transforms introduced earlier. We show that this new integral transform satisfies operational formulae which are similar to those of the classical tensorial Fourier transform. Moreover the L2-basis elements consisting of generalized Clifford-Hermite functions appear to be eigenfunctions of the Fourier-Bessel transform.
This paper describes the application of interval calculus to calculation of plate deflection, taking in account inevitable and acceptable tolerance of input data (input parameters). The simply supported reinforced concrete plate was taken as an example. The plate was loaded by uniformly distributed loads. Several parameters that influence the plate deflection are given as certain closed intervals. Accordingly, the results are obtained as intervals so it was possible to follow the direct influence of a change of one or more input parameters on output (in our example, deflection) values by using one model and one computing procedure. The described procedure could be applied to any FEM calculation in order to keep calculation tolerances, ISO-tolerances, and production tolerances in close limits (admissible limits). The Wolfram Mathematica has been used as tool for interval calculation.
In this dissertation, a new, unique and original biaxial device for testing unsaturated soil was designed and developed. A study on the mechanical behaviour of unsaturated sand in plane-strain conditions using the new device is presented. The tests were mainly conducted on Hostun sand specimens. A series of experiments including basic characterisation, soil water characteristic curves, and compression biaxial tests on dry, saturated, and unsaturated sand were conducted. A set of bearing capacity tests of strip model footing on unsaturated sand were performed. Additionally, since the presence of fine content (i.e., clay) influences the behavior of soils, soil water characteristic tests were also performed for sand-kaolin mixtures specimens.
Im vorliegenden Beitrag wird ein Framework für ein verteiltes dynamisches Produktmodell (FREAC) vorgestellt, welches der experimentellen Softwareentwicklung dient. Bei der Entwicklung von FREAC wurde versucht, folgende Eigenschaften umzusetzen, die bei herkömmlichen Systemen weitgehend fehlen: Erstens eine hohe Flexibilität, also eine möglichst hohe Anpassbarkeit für unterschiedliche Fachdisziplinen; Zweitens die Möglichkeit, verschiedene Tools nahtlos miteinander zu verknüpfen; Drittens die verteilte Modellbearbeitung in Echtzeit; Viertens das Abspeichern des gesamten Modell-Bearbeitungsprozesses; Fünftens eine dynamische Erweiterbarkeit sowohl für Softwareentwickler, als auch für die Nutzer der Tools. Die Bezeichnung FREAC umfasst sowohl das Framework zur Entwicklung und Pflege eines Produktmodells (FREAC-Development) als auch die entwickelten Tools selbst (FREAC-Tools).
Am 25. März 2010 veranstaltete die Professur Baubetrieb und Bauverfahren im Rahmen der jährlich stattfindenden baubetrieblichen Tagungsreihe gemeinsam mit der Arbeitsgruppe „Unikatprozesse“ in der Fachgruppe „Simulation in Produktion und Logistik“ (SPL) im Rahmen der Arbeitsgemeinschaft Simulation – ASIM einen ganztägigen Workshop mit dem Titel: „Modellierung von Prozessen zur Fertigung von Unikaten“. Viele Bauprozesse sind dadurch gekennzeichnet, dass sie Unikatcharakter besitzen. Unikate sind durch prototypische Einmaligkeit, Individualität, vielfältige Randbedingungen, einen geringen Grad an Standardisierung und Wiederholungen gekennzeichnet. Das erschwert die realitätsnahe Modellierung zur Simulation sogenannter Unikatprozesse. Dieser Besonderheit widmet sich die überwiegende Zahl der Tagungsbeiträge, die in diesem Band widergegeben sind.
Besides home entertainment and business presentations, video projectors are powerful tools for modulating images spatially as well as temporally. The re-evolving need for stereoscopic displays increases the demand for low-latency projectors and recent advances in LED technology also offer high modulation frequencies. Combining such high-frequency illumination modules with synchronized, fast cameras, makes it possible to develop specialized high-speed illumination systems for visual effects production. In this thesis we present different systems for using spatially as well as temporally modulated illumination in combination with a synchronized camera to simplify the requirements of standard digital video composition techniques for film and television productions and to offer new possibilities for visual effects generation. After an overview of the basic terminology and a summary of related methods, we discuss and give examples of how modulated light can be applied to a scene recording context to enable a variety of effects which cannot be realized using standard methods, such as virtual studio technology or chroma keying. We propose using high-frequency, synchronized illumination which, in addition to providing illumination, is modulated in terms of intensity and wavelength to encode technical information for visual effects generation. This is carried out in such a way that the technical components do not influence the final composite and are also not visible to observers on the film set. Using this approach we present a real-time flash keying system for the generation of perspectively correct augmented composites by projecting imperceptible markers for optical camera tracking. Furthermore, we present a system which enables the generation of various digital video compositing effects outside of completely controlled studio environments, such as virtual studios. A third temporal keying system is presented that aims to overcome the constraints of traditional chroma keying in terms of color spill and color dependency. ...
This paper deals with the modelling and the analysis of masonry vaults. Numerical FEM analyses are performed using LUSAS code. Two vault typologies are analysed (barrel and cross-ribbed vaults) parametrically varying geometrical proportions and constraints. The proposed model and the developed numerical procedure are implemented in a computer analysis. Numerical applications are developed to assess the model effectiveness and the efficiency of the numerical procedure. The main object of the present paper is the development of a computational procedure which allows to define 3D structural behaviour of masonry vaults. For each investigated example, the homogenized limit analysis approach has been employed to predict ultimate load and failure mechanisms. Finally, both a mesh dependence study and a sensitivity analysis are reported. Sensitivity analysis is conducted varying in a wide range mortar tensile strength and mortar friction angle with the aim of investigating the influence of the mechanical properties of joints on collapse load and failure mechanisms. The proposed computer model is validated by a comparison with experimental results available in the literature.
In recent years special hypercomplex Appell polynomials have been introduced by several authors and their main properties have been studied by different methods and with different objectives. Like in the classical theory of Appell polynomials, their generating function is a hypercomplex exponential function. The observation that this generalized exponential function has, for example, a close relationship with Bessel functions confirmed the practical significance of such an approach to special classes of hypercomplex differentiable functions. Its usefulness for combinatorial studies has also been investigated. Moreover, an extension of those ideas led to the construction of complete sets of hypercomplex Appell polynomial sequences. Here we show how this opens the way for a more systematic study of the relation between some classes of Special Functions and Elementary Functions in Hypercomplex Function Theory.
The numerical simulation of microstructure models in 3D requires, due to enormous d.o.f., significant resources of memory as well as parallel computational power. Compared to homogeneous materials, the material hetrogeneity on microscale induced by different material phases demand for adequate computational methods for discretization and solution process of the resulting highly nonlinear problem. To enable an efficient/scalable solution process of the linearized equation systems the heterogeneous FE problem will be described by a FETI-DP (Finite Element Tearing and Interconnecting - Dual Primal) discretization. The fundamental FETI-DP equation can be solved by a number of different approaches. In our approach the FETI-DP problem will be reformulated as Saddle Point system, by eliminating the primal and Lagrangian variables. For the reduced Saddle Point system, only defined by interior and dual variables, special Uzawa algorithms can be adapted for iteratively solving the FETI-DP saddle-point equation system (FETI-DP SPE). A conjugate gradient version of the Uzawa algorithm will be shown as well as some numerical tests regarding to FETI-DP discretization of small examples using the presented solution technique. Furthermore the inversion of the interior-dual Schur complement operator can be approximated using different techniques building an adequate preconditioning matrix and therewith leading to substantial gains in computing time efficiency.
Within the scheduling of construction projects, different, partly conflicting objectives have to be considered. The specification of an efficient construction schedule is a challenging task, which leads to a NP-hard multi-criteria optimization problem. In the past decades, so-called metaheuristics have been developed for scheduling problems to find near-optimal solutions in reasonable time. This paper presents a Simulated Annealing concept to determine near-optimal construction schedules. Simulated Annealing is a well-known metaheuristic optimization approach for solving complex combinatorial problems. To enable dealing with several optimization objectives the Pareto optimization concept is applied. Thus, the optimization result is a set of Pareto-optimal schedules, which can be analyzed for selecting exactly one practicable and reasonable schedule. A flexible constraint-based simulation approach is used to generate possible neighboring solutions very quickly during the optimization process. The essential aspects of the developed Pareto Simulated Annealing concept are presented in detail.
A practical framework for generating cross correlated fields with a specified marginal distribution function, an autocorrelation function and cross correlation coefficients is presented in the paper. The contribution promotes a recent journal paper [1]. The approach relies on well known series expansion methods for simulation of a Gaussian random field. The proposed method requires all cross correlated fields over the domain to share an identical autocorrelation function and the cross correlation structure between each pair of simulated fields to be simply defined by a cross correlation coefficient. Such relations result in specific properties of eigenvectors of covariance matrices of discretized field over the domain. These properties are used to decompose the eigenproblem which must normally be solved in computing the series expansion into two smaller eigenproblems. Such decomposition represents a significant reduction of computational effort. Non-Gaussian components of a multivariate random field are proposed to be simulated via memoryless transformation of underlying Gaussian random fields for which the Nataf model is employed to modify the correlation structure. In this method, the autocorrelation structure of each field is fulfilled exactly while the cross correlation is only approximated. The associated errors can be computed before performing simulations and it is shown that the errors happen especially in the cross correlation between distant points and that they are negligibly small in practical situations.
From passenger’s perspective, punctuality is one of the most important features of tram route operation. We present a stochastic simulation model with special focus on determining important factors of influence. The statistical analysis bases on large samples (sample size is nearly 2000) accumulated from comprehensive measurements on eight tram routes in Cracow. For the simulation, we are not only interested in average values but also in stochastic characteristics like the variance and other properties of the distribution. A realization of trams operations is assumed to be a sequence of running times between successive stops and times spent by tram at the stops divided in passengers alighting and boarding times and times waiting for possibility of departure . The running time depends on the kind of track separation including the priorities in traffic lights, the length of the section and the number of intersections. For every type of section, a linear mixed regression model describes the average running time and its variance as functions of the length of the section and the number of intersections. The regression coefficients are estimated by the iterative re-weighted least square method. Alighting and boarding time mainly depends on type of vehicle, number of passengers alighting and boarding and occupancy of vehicle. For the distribution of the time waiting for possibility of departure suitable distributions like Gamma distribution and Lognormal distribution are fitted.
SIMULATION AND MATHEMATICAL OPTIMIZATION OF THE HYDRATION OF CONCRETE FOR AVOIDING THERMAL CRACKS
(2010)
After mixing of concrete, the hardening starts by an exothermic chemical reaction known as hydration. As the reaction rate depends on the temperature the time in the description of the hydration is replaced by the maturity which is defined as an integral over a certain function depending on the temperature. The temperature distribution is governed by the heat equation with a right hand side depending on the maturity and the temperature itself. We compare of the performance of different time integration schemes of higher order with an automatic time step control. The simulation of the heat distribution is of importance as the development of mechanical properties is driven by the hydration. During this process it is possible that the tensile stresses exceed the tensile strength and cracks occur. The goal is to produce cheap concrete without cracks. Simple crack-criterions use only temperature differences, more involved ones are based on thermal stresses. If the criterion predicts cracks some changes in the input data are needed. This can be interpreted as optimization. The final goal will be to adopt model based optimization (in contrast to simulation based optimization) to the problem of the hydration of young concrete and the avoidance of cracks. The first step is the simulation of the hydration, which we focus in this paper.
In this paper three different formulations of a Bernoulli type free boundary problem are discussed. By analyzing the shape Hessian in case of matching data it is distinguished between well-posed and ill-posed formulations. A nonlinear Ritz-Galerkin method is applied for discretizing the shape optimization problem. In case of well-posedness existence and convergence of the approximate shapes is proven. In combination with a fast boundary element method efficient first and second order shape optimization algorithms are obtained.
In spite of the extensive research in dynamic soil-structure interaction (SSI), there still exist miscon-ceptions concerning the role of SSI in the seismic performance of structures, especially the ones founded on soft soil. This is due to the fact that current analytical SSI models that are used to evaluate the influence of soil on the overall structural behavior are approximate models and may involve creeds and practices that are not always precise. This is especially true in the codified approaches which in-clude substantial approximations to provide simple frameworks for the design. As the direct numerical analysis requires a high computational effort, performing an analysis considering SSI is computationally uneconomical for regular design applications. This paper outlines the set up some milestones for evaluating SSI models. This will be achieved by investigating the different assumptions and involved factors, as well as varying the configurations of R/C moment-resisting frame structures supported by single footings which are subject to seismic excita-tions. It is noted that the scope of this paper is to highlight, rather than fully resolve, the above subject. A rough draft of the proposed approach is presented in this paper, whereas a thorough illustration will be carried out throughout the presentation in the course of the conference.
Schwerpunkt Mediephilosophie
(2010)
Die prominent und polemisch geäusserte Ansicht, bei der Medienphilosophie handele es sich um eine vorübergehende Angelegenheit, ist vermutlich sehr zutreff end. Medienphilosophie selbst hat nie etwas anderes behauptet. Und genau aus diesem Grund, also eben wegen ihrer Vorläufigkeit, ist Medienphilosophie so wichtig. Sie tritt vielleicht tatsächlich als neue, modische Unterdisziplin der Philosophie auf. Aber sie tut dies, weil sie eine sehr ernsthafte Herausforderung an die Philosophie darstellt. Wie und wann sie wieder vergeht, das hängt davon ab, was sie ausrichtet. Medienphilosophie ist nämlich in ihrem Selbstverständnis ein grundlegend operatives und operationales Unternehmen. Daher rührt ihre große Nähe zu und ihr vitales Interesse an den Kulturtechniken und ihrer Erforschung.
Sie interessiert sich für Eingriff e aller Art – und ist selbst einer. Sie hat – und zwar keineswegs nur metaphorisch – Anteil am materiellen Körper der Philosophie, für den Philosophie selbst, immer hart am Begriff , sich gar nicht interessiert und dies auch nicht tun muss. Zum materiellen Körper der Philosophie zählten bereits die schreibende Hand, vielleicht das vorrangige Medium des philosophischen Eingriffs, und ihr Werkzeug, das Schreibzeug, das sie führt. Als Medienphilosophie widmet sich die Philosophie den Gesten, die sie in der Welt ausführt, und den Operationen, die sie an den Dingen und mit ihrer Hilfe vornimmt.
Schwerpunkt Kulturtechnik
(2010)
Medientheorie und historische Medienwissenschaft sind seit geraumer Zeit dabei, einen Schritt zu tun, der sie hierzulande zumindest teilweise in historische und systematische Kulturtechnikforschung überführt. Die Möglichkeit existiert, dass die Medien als Referenz eines Wissenschaftsparadigmas, das gerade dabei ist, die Forschungs- und Lehrstrukturen dieses Landes zu erobern, sich bereits im Zustand bloßen Nachlebens befinden. Damit kommen mindestens jene Teile der Medienforschung zu sich, die seit der Institutionalisierung von Medienwissenschaft realisieren mussten, dass jene Medien, mit denen sie es seit den 1980er Jahren zu tun hatten, sich nur schwer in den Rahmen der Medien der Medienwissenschaft fügen wollen. Es scheint daher so, als ließe sich mit dem Begriff der Kulturtechniken etwas fassen, das schon seit den 80er Jahren eine Spezifik der entstehenden deutschen Medienwissenschaft gewesen ist, eine Spezifik, die sie den angloamerikanischen media studies ebenso entfremdete wie der Kommunikationswissenschaft oder gar der Soziologie, die, im Banne der Aufklärung und des Gesellschaftsbegriff s stehend, über Medien grundsätzlich nur unter dem Aspekt der Öff entlichkeit nachdenken wollte. Was sich in den 80er Jahren des letzten Jahrhunderts etwa unter dem Titel einer Diskurs- und Medienanalyse formierte, zielte nicht primär auf eine Medientheorie oder die Geschichte von Einzelmedien ab, die längst identitätsstiftend für je eigene Forschungsdisziplinen geworden waren (Fotografie, Film, Fernsehen, Rundfunk), sondern auf eine Geschichte der Literatur, des Geistes, der Seele und der Sinne, die man der Literaturwissenschaft, der Philosophie, der Psychologie und der Ästhetik wegzunehmen gedachte, um sie auf einem anderen Schauplatz aufzuführen: dem der Medien – und gegenwärtig der Kulturtechniken. Weil aber gar nicht die Medien im Fokus der Entdeckung standen, sondern eine Rekontextualisierung der traditionellen Gegenstände der Geisteswissenschaften, genauer eine »Austreibung des Geistes aus den Geisteswissenschaften« (Friedrich Kittler), kam von vornherein anderes in den Blick als diejenigen Medien, die die Publizistik- und Kommunikationswissenschaft, die Massenmedienforschung oder die Einzelmedienwissenschaften als ihre primären Untersuchungsfelder auswiesen.
We investigate aspects of tram-network section reliability, which operates as a part of the model of whole city tram-network reliability. Here, one of the main points of interest is the character of the chronological development of the disturbances (namely the differences between time of departure provided in schedule and real time of departure) on subsequent sections during tram line operation. These developments were observed in comprehensive measurements done in Krakow, during one of the main transportation nodes (Rondo Mogilskie) rebuilding. All taken building activities cause big disturbances in tram lines operation with effects extended to neighboring sections. In a second part, the stochastic character of section running time will be analyzed more detailed. There will be taken into consideration sections with only one beginning stop and also with two or three beginning stops located at different streets at an intersection. Possibility of adding results from sections with two beginning stops to one set will be checked with suitable statistical tests which are used to compare the means of the two samples. Section running time may depend on the value of gap between two following trams and from the value of deviation from schedule. This dependence will be described by a multi regression formula. The main measurements were done in the city center of Krakow in two stages: before and after big changes in tramway infrastructure.
Due to increasing numbers of wind energy converters, the accurate assessment of the lifespan of their structural parts and the entire converter system is becoming more and more paramount. Lifespan-oriented design, inspections and remedial maintenance are challenging because of their complex dynamic behavior. Wind energy converters are subjected to stochastic turbulent wind loading causing corresponding stochastic structural response and vibrations associated with an extreme number of stress cycles (up to 109 according to the rotation of the blades). Currently, wind energy converters are constructed for a service life of about 20 years. However, this estimation is more or less made by rule of thumb and not backed by profound scientific analyses or accurate simulations. By contrast, modern structural health monitoring systems allow an improved identification of deteriorations and, thereupon, to drastically advance the lifespan assessment of wind energy converters. In particular, monitoring systems based on artificial intelligence techniques represent a promising approach towards cost-efficient and reliable real-time monitoring. Therefore, an innovative real-time structural health monitoring concept based on software agents is introduced in this contribution. For a short time, this concept is also turned into a real-world monitoring system developed in a DFG joint research project in the authors’ institute at the Ruhr-University Bochum. In this paper, primarily the agent-based development, implementation and application of the monitoring system is addressed, focusing on the real-time monitoring tasks in the deserved detail.