Technical University Monchen


Technical University Monchen

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Alkadhi R.,Technical University Monchen | Lata T.,Technical University Monchen | Guzmany E.,Technical University Monchen | Bruegge B.,University of Zürich
IEEE International Working Conference on Mining Software Repositories | Year: 2017

Chat messages of development teams play an increasinglysignificant role in software development, having replacedemails in some cases. Chat messages contain informationabout discussed issues, considered alternatives and argumentationleading to the decisions made during software development. These elements, defined as rationale, are invaluable duringsoftware evolution for documenting and reusing developmentknowledge. Rationale is also essential for coping with changesand for effective maintenance of the software system. However, exploiting the rationale hidden in the chat messages is challengingdue to the high volume of unstructured messages covering a widerange of topics. This work presents the results of an exploratorystudy examining the frequency of rationale in chat messages, the completeness of the available rationale and the potential ofautomatic techniques for rationale extraction. For this purpose, we apply content analysis and machine learning techniques onmore than 8,700 chat messages from three software developmentprojects. Our results show that chat messages are a rich source ofrationale and that machine learning is a promising technique fordetecting rationale and identifying different rationale elements. © 2017 IEEE.

Liebl C.,Technical University Monchen | Zah M.F.,Technical University Monchen
WT Werkstattstechnik | Year: 2014

Due to the energy transition and the extension of the use of re-newable energy sources, German industries will be confronted with a volatile energy supply. One opportunity to react to this is to adapt the own energy consumption to the supply. On the basis of numerous measurings of energy requirements of production facilities it is planned to model and simulate the energy requirements of a produc-tion system as a valuation basis for energy flexibility. © Springer-VDI-Verlag GmbH & Co. KG, Düsseldorf.

Kolling C.,Bayerische Landesanstalt for Wald und Forstwirtschaft | Mette T.,Bayerische Landesanstalt for Wald und Forstwirtschaft | Knoke T.,Technical University Monchen
Schweizerische Zeitschrift fur Forstwesen | Year: 2016

Changes in climate conditions will lead to strong yet uncertain changes concerning forest growth and cultivation risk. Economic success as an important criterion for management decisions depends on both aspects, natural yield and risk. This study presents a new concept how (potential) yield and risk can be estimated from large-scale inventory data. As a result, any stand can be plotted in a yield-risk coordinate system and its future yield expectancy can be described by a trajectory in the yield-risk space. This strictly analytical approach cannot take over silvicultural decisions, but facilitates them from an objective basis. The implementation of approved economic guidelines such as the caution principle or the principle of flexibility builds upon the yield-risk approach and demonstrates benefits of climate-Adapted stable mixed forest silviculture.

Roehm H.,Robert Bosch GmbH | Oehlerking J.,Robert Bosch GmbH | Woehrle M.,Robert Bosch GmbH | Althoff M.,Technical University Monchen
HSCC 2016 - Proceedings of the 19th International Conference on Hybrid Systems: Computation and Control | Year: 2016

Industrial-sized hybrid systems are typically not amenable to formal veri-cation techniques. For this reason, a common approach is to formally verify abstractions of (parts of) the original system. However, we need to show that this abstrac-tion conforms to the actual system implementation including its physical dynamics. In particular, veri-ed properties of the abstract system need to transfer to the implementation. To this end, we introduce a formal conformance relation, called reachset conformance, which guarantees transference of safety properties, while being a weaker relation than the existing trace inclusion conformance. Based on this formal relation, we present a conformance testing method which allows us to tune the trade-off between accuracy and com-putational load. Additionally, we present a test selection algorithm that uses a coverage measure to reduce the num-ber of test cases for conformance testing. We experimentally show the benefits of our novel techniques based on an exam-ple from autonomous driving. © 2016 ACM.

Pham M.-D.,VU University Amsterdam | Passing L.,Technical University Monchen | Erling O.,OpenLink Software | Boncz P.,CWI
WWW 2015 - Proceedings of the 24th International Conference on World Wide Web | Year: 2015

We motivate and describe techniques that allow to detect an "emergent" relational schema from RDF data. We show that on a wide variety of datasets, the found structure explains well over 90% of the RDF triples. Further, we also describe technical solutions to the semantic challenge to give short names that humans find logical to these emergent tables, columns and relationships between tables. Our techniques can be exploited in many ways, e.g., to improve the efficiency of SPARQL systems, or to use existing SQL-based applications on top of any RDF dataset using a RDBMS.

Merting S.,Technical University Monchen | Karaenke P.,Technical University Monchen | Bichler M.,Technical University Monchen
Multikonferenz Wirtschaftsinformatik, MKWI 2016 | Year: 2016

Long waiting times at loading docks of retailers are a substantial problem in retail logistics. Congestion results from a lack of coordination among carriers. One possibility for reducing the waiting time of carriers at warehouses is to coordinate the carriers and retailers by a central timeslot management. Since carriers have to visit several warehouses in a special order, they have preferences over subsets of timeslots describing the retailers on a route, which we call bundles. Carriers need to get all relevant timeslots on a route. We are interested in coordination mechanisms that do not require monetary transfers. Matching with complementarities is an extension of the Capacitated House Allocation problem, where agents have preferences over bundles of objects. We present a generalisation of the Random Serial Dictatorship that is strategy-proof, symmetric, and computes Pareto optimal matchings.

Kosiol M.,Technical University Monchen | Bohmer A.I.,Technical University Monchen | Lindemann U.,Technical University Monchen
Proceedings of the International Conference on Engineering Design, ICED | Year: 2015

People aspire to individuality and look for products that correspond to their needs as much as possible. In the InnoCyFer project the complete process of individualization-starting with the personalization by the customer and ending with the individual manufacturing-is implemented on the basis of a fully automatic coffee machine. This paper focused on the individualization of an existing product based on the given product architecture and developed a system of criteria to evaluate the existing product with reference to possibilities for individualizations. Approaches to develop customized products are shown. Both modular and customized product development, as well as the product creation process of customized products, are discussed. An analysis of the fully automatic coffee machine is outlined and a possibility to evaluate standardized and customized components. Further options for individualization, like add-on modules or the restructuring of the product architecture of the fully automatic coffee machine are discussed.

Moller K.W.,Technical University Monchen | Birzle A.M.,Technical University Monchen | Wall W.A.,Technical University Monchen
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2016

Molecular motors are proteins that excessively increase the efficiency of subcellular transport processes. They allow for cell division, nutrient transport and even macroscopic muscle movement. In order to understand the effect of motors in large biopolymer networks, e.g.The cytoskeleton, we require a suitable model of a molecular motor. In this contribution, we present such a model based on a geometrically exact beam finite-element formulation. We discuss the numerical model of a non-processive motor such as myosin II, which interacts with actin filaments. Based on experimental data and inspired by the theoretical understanding offered by the powerstroke model and the swinging-cross-bridge model, we parametrize our numerical model in order to achieve the effect that a physiological motor has on its cargo. To this end, we introduce the mechanical and mathematical foundations of the model, then discuss its calibration, prove its usefulness by conducting finite-element simulations of actin-myosin motility assays and assess the influence of motors on the rheology of semi-flexible biopolymer networks. ©2016 The Author(s) Published by the Royal Society. All rights reserved.

Kahlert S.,Technical University Monchen | Spliethoff H.,Technical University Monchen
Proceedings of the ASME Turbo Expo | Year: 2016

Intermittency of renewable electricity generation poses a challenge to thermal power plants. While power plants in the public sector see a decrease in operating hours, the utilization of industrial power plants is mostly unaffected because process steam has to be provided. This study investigates to what extent the load of a CHP plant can be reduced while maintaining a reliable process steam supply. A dynamic process model of an industrial combined CHP plant is developed and validated with operational data. The model contains a gas turbine, a single pressure HRSG with supplementary firing and an extraction condensing steam turbine. Technical limitations of the gas turbine, the supplementary firing and the steam turbine constrain the load range of the plant. In consideration of these constraints, different operation strategies are performed at variable loads using dynamic simulation. A simulation study shows feasible load changes in 5 min for provision of secondary control reserve. The load change capability of the combined cycle plant under consideration is mainly restricted by the water-steam cycle. It is shown that both the low pressure control valve of the extraction steam turbine and the high pressure bypass control valve are suitable to ensure the process steam supply during the load change. The controllability of the steam turbine load and the process stability are sufficient as long as the supplementary is not reaching the limits of the operating range. Copyright © 2016 by ASME.

Herrmann S.,Technical University Monchen | Kahlert S.,Technical University Monchen | Wuerth M.,Technical University Monchen | Spliethoff H.,Technical University Monchen
Proceedings of the ASME Turbo Expo | Year: 2016

This paper presents the results of a thermodynamic and economic evaluation of a novel hybrid combination of a compressed air energy storage and a combined cycle power plant. The new cycle is modeled on basis of a GE LM6000 gas turbine model, an adiabatic compressor model, an air expander and a conventional dual pressure HRSG configuration. Furthermore, a detailed design of the recuperator is presented. With the simulated components, a storage efficiency of 60% is reached. In CHP configuration the total efficiency of the plant reaches up to 86.2%. The thermodynamic and economic performance is compared to a conventional LM6000 combined cycle. For the economic evaluation the German electricity dayahead prices and average gas price of the year 2014 are used. Overall it is found that the CAES/CCPP concept exhibits far more operation hours per year and a higher profit margin than the compared CCPP. Taking into account the investment and operational costs, especially with steam extraction the net present value of the novel cycle is higher than that of the combined cycle, despite the challenging market environment for storage technologies in Germany. Copyright © 2016 by ASME.

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