HTWK Leipzig

Leipzig, Germany

HTWK Leipzig

Leipzig, Germany
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Biedert R.,German Research Center for Artificial Intelligence | Dengel A.,German Research Center for Artificial Intelligence | Kading C.,HTWK Leipzig
Eye Tracking Research and Applications Symposium (ETRA) | Year: 2012

In this paper we present an approach to build an eye-tracking based text cursor placement system. When triggered, the system employs a computer vision based analysis of the screen's content around the current gaze position to find the most likely designated gaze target. Eventually it synthesizes a mouse event at that position, allowing for a rapid text cursor repositioning even in applications which do not support eye tracking explicitly. For our system we compared three different computer vision methods in a simulation run and evaluated the best candidate in two double blinded user studies. We used a total of 19 participants to assess the system's objective and perceived end user speed up. We can demonstrate that in terms of reposition time the OCR based method is superior to the other tested methods, it also beats common keyboard-mouse interaction for some users. We conclude that while the tool was almost universally preferred subjectively over keyboard-mouse interaction, the highest speed can be achieved by using the right amount of eye tracking. © 2012 ACM.

Gorke U.-J.,Helmholtz Center for Environmental Research | Kaiser S.,TU Chemnitz | Bucher A.,HTWK Leipzig | Kreissig R.,TU Chemnitz
European Journal of Mechanics, A/Solids | Year: 2012

This paper presents the theoretical background of a phenomenological biphasic model at large strains based on a generalized material description of the theory of porous media, and its numerical realization within the context of a mixed finite element formulation. The study is aimed at the simulation of coupled hydro-mechanical (HM) problems with special focus on geo- and biomechanics. If, in the sense of an initial approximation, the materials of interest can be considered as a mixture of two immiscible components (solid and fluid phases), they can be modeled as saturated porous media. For the numerical treatment of according problems within a finite element approach, the weak formulation of the balance equations of mass and linear momentum of the overall continuum are developed. Within this context, a generalized material approach is preferred assuming the initial configuration of the solid phase as reference configuration of the overall continuum. The transient problem results in a weak formulation with respect to the displacement and pore pressure fields as well as their time derivatives. Following, time discretization is performed using a generalized single step approach, and a linearization technique based on Taylor series representation is applied. After the usual spatial discretization, a global system for the incremental solution of the initial-boundary value problem within the framework of a stable mixed u/p-c finite element approach is defined. This algorithmic proceeding comprises some different conceptual aspects compared to the known literature, and is characterized by a consistent and comprehensive representation. The presented numerical model was implemented into a scientific in-house finite element code based on hierarchical structures, which support the straightforward use of an iterative solver with hierarchical preconditioning, local adaptive remeshing techniques, and parallelized programming features. The accuracy and the efficiency of the numerical algorithms are demonstrated on typical examples. Therewith, the importance of the consideration of large strains in a consistent and proper way is demonstrated as well as the differences compared to models based on small strains. © 2011 Elsevier Masson SAS. All rights reserved.

Bau A.,HTWK Leipzig | Waldmann J.,HTWK Leipzig
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2014

We present a functional programming language for specifying constraints over tree-shaped data. The language allows for Haskell-like algebraic data types and pattern matching. Our constraint compiler CO4 translates these programs into satisfiability problems in propositional logic. We present an application from the area of automated analysis of termination of rewrite systems, and also relate CO4 to Curry. © 2014 Springer International Publishing Switzerland.

Guttke S.,HTWK Leipzig | Laukner M.,HTWK Leipzig | Weber P.,HTWK Leipzig
Journal of Physics: Conference Series | Year: 2013

The non-invasive measurement of biological signals is prone to failure when the proband is in motion. In clinical practice disposable wet adhesive Ag/AgCl electrodes are used for ECG measurements to minimize failure caused by motion. For sportive action a chest strap with conductive rubber electrodes is widespread for continuous monitoring of the heart rate. Complaints about poor comfort and friction at the skin caused by the chest strap leaded to new developments with textile electrodes. The dynamic properties of electrodes and the coupling to the skin are important to optimize signal quality. We compare new textile with standard ECG electrodes and tested their suitability to the heart-rate measurement with impedance plethysmography under motion conditions.

Sangerlaub S.,Fraunhofer Institute for Process Engineering and Packaging | Sangerlaub S.,TU Munich | Bohmer M.,HTWK Leipzig | Stramm C.,Fraunhofer Institute for Process Engineering and Packaging
Journal of Applied Polymer Science | Year: 2013

The incorporation of salt in a polymer matrix could potentially achieve a humidity-regulating film system of high porosity for packaging applications. In this study, sodium chloride (NaCl) powder was used as a model substance for humidity-regulating fillers in polypropylene films. A polypropylene homopolymer was extrusion-blended with NaCl at concentrations of 0.03, 0.06, 0.12, and 0.24 g NaCl·g film-1. Films were produced and were subsequently oriented mono and biaxially. At stretching ratios (SRs) of between 2 and 25 a porosity of 20% v/v to 50% v/v was achieved. The porosity positively correlated with the SR. An empirical model based on ellipsoids that approximated the correlation between the SR and the porosity was developed. This correlation offers a basis for further studies on other salt-polymer systems that have undergone differing orientation processes. Copyright © 2012 Wiley Periodicals, Inc.

Kaseberg S.,HTWK Leipzig
Proceedings of the 6th European Workshop - Structural Health Monitoring 2012, EWSHM 2012 | Year: 2012

The fields of activity in civil engineering are subjected to a constant change. Thereby maintenance, strengthening and monitoring of existing buildings have become more and more important. During the last ten years an increasing amount of Carbon Fiber Reinforced Polymer (CFRP) applications to rehabilitate damaged concrete or steel elements was observed. Thereby some important disadvantages of the brittle materials must be considered, for example the low ductility of the bond between CFRP and concrete and brittle failure of FRP. With embedded sensor systems it is possible to measure crack propagation and strains. In this paper a sensor based CFRP system will be presented, that can be used for strengthening and measuring. The used optical fibers with Fiber Bragg Gratings (FBG) have a large number of advantages in opposite to electrical measuring methods. Examples are small dimensions, low weight as well as high static and dynamic resolution of measured values. A Bragg Grating consists of a periodic sequence of artificial and equidistant refraction switches in the core of an optical fiber. It can be produced over emblazing of an interference pattern of ultraviolet light. The core is surrounded by cladding. The main problem during the investigations was the fixing of the glass fiber and the small FBG at the designated position. In this paper the possibility of setting the glass fiber with embroidery at the reinforcing fiber material will be presented. The direct embroider of the optical fiber (and the FBGS) clearly simplifies the fixing. An embroidery machine, using computerized support, is able to fix the fiber optical system accurately fitting at the carbon fiber material. By using computer-controlled machines it is possible to achieve a very high degree of préfabrication as well as a high productiveness. The economic industrial fabrication of smart structures can be realized. Another possibility is the direct converting at the building site by hand made lamination with an epoxy resign.

Wassmann M.,HTWK Leipzig | Weicker K.,HTWK Leipzig
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

To determine the stability of LEGO® structures is an interesting problem because the special binding mechanism prohibits the usage of methods of structural frame design or dynamic physics engines. We propose a new two-phase approach where instances of maximum-flow networks are constructed. In a first phase, the distribution of compressive and tensile forces is computed which is used in a second phase to model the moments within the structure. By solving the maximum-flow networks we can use the resulting flow as a sufficient criterion for the stability of the structure. The approach is demonstrated for two exemplary structures which outperform previous results using a multi-commodity flow network. © 2012 Springer-Verlag.

Finsterbusch M.,HTWK Leipzig | Muller J.-A.,HfT Leipzig
Proceedings - International Conference on Network Protocols, ICNP | Year: 2013

Internet traffic identification and validation has been the subject of intensive study for many years. It is used to provide Quality of Service, to provide security and to implement many other tasks. The reliability of these methods, however, is not proved by formal verification. Therefore, the results of these methods can vary from the lab where these methods were developed and their deployment in real world application. In this paper, we present an idea to overcome this problem in order to guarantee reliability and provide more optimised solutions. © 2013 IEEE.

Bau A.,HTWK Leipzig | Waldmann J.,HTWK Leipzig
CEUR Workshop Proceedings | Year: 2014

The CO4 language is a Haskell-like language for specifying constraint systems over structured finite domains. A CO4 constraint system is solved by an automatic transformation into a satisfiability problem in propositional logic that is handed to an external SAT solver. We investigate the problem of predicting the size of formulas produced by the CO4 compiler. The goal is to help the programmer in understanding the resource consumption of CO4 on his program.We present a basic cost model, with some experimental data, and discuss ongoing work towards static analysis. It turns out that analysis steps will use constraint systems as well.

Waldmann J.,HTWK Leipzig
CEUR Workshop Proceedings | Year: 2014

We describe the design, implementation, and empirical evaluation of some automated exercises that we are using in a lecture on Constraint Programming. Topics are propositional satisfiability, resolution, the DPLL algorithm, with extension to DPLL(T), and FD solving with arc consistency. The automation consists of a program for grading student answers, and in most cases also a program for generating random problem instances. The exercises are part of the autotool Eassessment framework. The implementation language is Haskell. You can try them at cgi?lecture=199.

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