Leipzig University of Applied Sciences

www.htwk-leipzig.de
Leipzig, Germany

The Leipzig University of Applied science is a Fachhochschule in Leipzig, Germany. With about 6,200 students, it is the biggest University of Applied science in Saxony.This article incorporates information from the equivalent article on the Deutsch Wikipedia. Wikipedia.

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Lenzen A.,Leipzig University of Applied Sciences | Vollmering M.,Leipzig University of Applied Sciences
Structural Control and Health Monitoring | Year: 2017

In this article, a new advantageous approach for damage identification of mechanical structures based on state projection estimation error (SP2E) is proposed. The theoretical foundation relies on output-only identification, H∞ theory, estimation error, and state projections. Finally, the proposed damage identification approach is verified by discussing results of laboratory experiments. Therein, structural changes have been applied at a mechanical structure, and the capability to localize them by SP2E has been studied subsequently. By analyzing several different structural alteration positions and extents, an experimental sensitivity study has been conducted, which confirmed the applicability of SP2E for damage localization. © 2017 John Wiley & Sons, Ltd.


Waldmann J.,Leipzig University of Applied Sciences
Electronic Proceedings in Theoretical Computer Science, EPTCS | Year: 2016

We consider directed graphs with edge labels from a semiring. We present an algorithm that allows efficient execution of queries for existence and weights of paths, and allows updates of the graph: Adding nodes and edges, and changing weights of existing edges. We apply this method in the construction of matchbound certificates for automatically proving termination of string rewriting. We re-implement the decomposition/completion algorithm of Endrullis et al. (2006) in our framework, and achieve comparable performance. © J. Waldmann.


Richter H.,Leipzig University of Applied Sciences
BioSystems | Year: 2017

Players of coevolutionary games may update not only their strategies but also their networks of interaction. Based on interpreting the payoff of players as fitness, dynamic landscape models are proposed. The modeling procedure is carried out for Prisoner's Dilemma (PD) and Snowdrift (SD) games that both use either birth-death (BD) or death-birth (DB) strategy updating. The main focus is on using dynamic fitness landscapes as a mathematical model of coevolutionary game dynamics. Hence, an alternative tool for analyzing coevolutionary games becomes available, and landscape measures such as modality, ruggedness and information content can be computed and analyzed. In addition, fixation properties of the games and quantifiers characterizing the interaction networks are calculated numerically. Relations are established between landscape properties expressed by landscape measures and quantifiers of coevolutionary game dynamics such as fixation probabilities, fixation times and network properties. © 2017 Elsevier B.V.


According to the principle of the static equilibrium, a definition of an equilibrium in production processes in civil engineering on the basis of the Game Theory is proposed. This creates an approach to solutions of dimensioning of construction processes, which has not been available through other methods. Furthermore, suggestions of fields of applications are given.


News Article | November 26, 2015
Site: phys.org

Image showing tightly packed tree crowns in a natural tropical forest, for investigating the forest's structure. Tree crowns of different sizes are shown as spheres. Credit: André Künzelmann, UFZ Explaining the complex structure of tropical forests is one of the great challenges in ecology. An issue of special interest is the distribution of different sizes of trees, something which is of particular relevance for biomass estimates. A team of modellers from the Helmholtz Centre for Environmental Research (UFZ), working together with research partners, has now developed a new method which can be used to explain the tree size distribution in natural forests. To do so, the scientists use principles from stochastic geometry, as they have reported in a contribution to the Proceedings of the National Academy of Sciences (PNAS, Early Edition). Using this approach, it is possible to assess the structure of natural forests across the world more quickly, and produce more accurate biomass estimates. For over one hundred years, the distribution of different sizes of trees in forests has been one of the core attributes recorded by foresters and ecologists world-wide, as it can be used to derive many other structural features, such as biomass and productivity. "We wanted to explain this important pattern", said Dr. Franziska Taubert. Working with her UFZ colleagues Dr. Thorsten Wiegand and Prof. Andreas Huth, and other research partners in the Leipzig University of Applied Sciences (HTWK) and the Karlsruhe Institute of Technology (KIT), they have applied the theory of stochastic sphere packing, which is usually used in physics or chemistry. This theory describes how spheres can be placed in an available space. To apply the theory, the scientists randomly distributed tree crowns of different sizes in forest areas. These tree crowns were not permitted to overlap, - just like packing apples into a box. The distribution of the trees that have been successfully placed in the packing process was then used to determine the tree size distribution. "Many forest models are based on a dynamic approach: they take into account processes such as growth, mortality, regeneration and competition between trees for light, water and soil nutrients", said Taubert. "These models are complex and data-hungry", added Thorsten Wiegand," so we decided to take a radically different approach, which is fundamentally simpler and only based on spatial structures". This model approach proved its effectiveness by enabling observed forest structures, especially the tree size distribution, to be reproduced accurately. The rules of stochastic geometry are thereby enriched by tree geometry relationships, and the resulting tree packing system is compared to inventory data from tropical forests in Panama and Sri Lanka. Although one might imagine that a tropical forest is very tightly packed, the scientists came to a surprising conclusion: the packing density of the tree crowns, which averages 15 to 20%, is astonishingly low. "In particular, the upper and lower canopy levels are less tightly packed with tree crowns", said Taubert. High packing densities of around 60%, which are also possible according to stochastic geometry, only occur at tree heights between 25 and 40 meters. The findings concerning the distribution of tree crowns are important, because they can be used to draw conclusions about, for example, the carbon content or productivity of a forest. Using this modelling approach, the researchers were also able to show that the decisive factor in shaping the tree size distribution is competition for space. "In classical forest models", said Andreas Huth, "the trees instead compete for light, or water and nutrients". The theory opens up several new perspectives. The team plans to assess how the model can be applied to natural forests in the temperate and boreal zone. They believe that the model can be used to identify disturbed forests. "That is of special interest  because it will enable us to develop a disturbance index", said Taubert, "and to better interpret remote sensing observations by using the structure of natural forests as a reference". Another benefit of the new theory is that this simple forest packing model takes much less effort than classical forest models. The new approach is an important step toward identifying a minimal set of processes responsible for generating the spatial structure of natural forests. Explore further: Mixed-conifer forests at risk for high-severity wildfire More information: Franziska Taubert et al. The structure of tropical forests and sphere packings, Proceedings of the National Academy of Sciences (2015). DOI: 10.1073/pnas.1513417112


Richter H.,Leipzig University of Applied Sciences
Studies in Computational Intelligence | Year: 2013

Solving optimization problems with time varying objective functions by methods of evolutionary computation can be grounded on the theoretical framework of dynamic fitness landscapes. In this chapter, we define such dynamic fitness landscapes and discuss their properties. To this end, analyzing tools for measuring topological and dynamical landscape properties are studied. Based on these landscape measures we obtain an approach for drawing conclusion regarding characteristic features of a given optimization problem. This may allow to address the question of how difficult the problem is for an evolutionary search, and what type of algorithm is most likely to solve it successfully. The methodology is illustrated using a well-known example, the moving peaks. © 2013 Springer-Verlag Berlin Heidelberg.


Richter H.,Leipzig University of Applied Sciences
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2015

Intransitivity is supposed to be a main reason for deficits in coevolutionary progress and inheritable superiority. Besides, coevolutionary dynamics is characterized by interactions yielding subjective fitness, but aiming at solutions that are superior with respect to an objective measurement. Such an approximation of objective fitness may be, for instance, generalization performance. In the paper a link between rating– and ranking–based measures of intransitivity and fitness landscapes that can address the dichotomy between subjective and objective fitness is explored. The approach is illustrated by numerical experiments involving a simple random game with continuously tunable degree of randomness. © Springer International Publishing Switzerland 2015.


Kudrass T.,Leipzig University of Applied Sciences
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2010

This paper gives a survey of the deployment of ideas from the area of real-time, active and heterogeneous database systems in the years from 1991 to 2010 as they have been embraced by IT industry. During that time the Database and Distributed Systems group (DVS) led by Alejandro Buchmann has made lots of contributions to the development of those ideas by many research projects. After 20 years it is time to conclude insights how far the ideas of the first project REACH are still valid for the development of commercial products and standards. In some cases, industry has taken another direction as it has been expected. In other cases, the DVS research prototypes were forerunners for commercial products that are now well-established. © 2010 Springer-Verlag Berlin Heidelberg.


Waldmann J.,Leipzig University of Applied Sciences
Leibniz International Proceedings in Informatics, LIPIcs | Year: 2010

Matrix interpretations can be used to bound the derivational complexity of rewrite systems. We present a criterion that completely characterizes matrix interpretations that are polynomially bounded. It includes the method of upper triangular interpretations as a special case, and we prove that the inclusion is strict. The criterion can be expressed as a finite domain constraint system. It translates to a Boolean constraint system with a size that is polynomial in the dimension of the interpretation. We report on performance of an implementation. © Johannes Waldmann.


Richter H.,Leipzig University of Applied Sciences
Proceedings of the 2014 IEEE Congress on Evolutionary Computation, CEC 2014 | Year: 2014

Coevolutionary minimal substrates are simple and abstract models that allow studying the relationships and codynamics between objective and subjective fitness. Using these models an approach is presented for defining and analyzing fitness landscapes of coevolutionary problems. We devise similarity measures of codynamic fitness landscapes and experimentally study minimal substrates of test-based and compositional problems for both cooperative and competitive interaction. © 2014 IEEE.

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