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Tokic A.,University of Tuzla | Jukan A.,University of Tuzla | Smajic J.,University of Applied Sciences of Eastern Switzerland
IEEE Transactions on Power Delivery | Year: 2016

The recent rapid concentration increase of single-phase rectifier-based loads has led to the increasingly significant problem of current and voltage distortion in low-power electrical networks. To successfully perform a prediction of the current and voltage distortion in power systems due to such nonlinear loads, it is necessary to know the structure and model parameters of those power-electronics circuits. Generally speaking, since the structure of a typical single-phase rectifier-based load is rather known, the parameters of those loads remain to be determined. Concerning this matter, an algorithm for estimating the unknown parameters of a typical single-phase rectifier based load is presented in this paper. The algorithm is based on a general approach for determining analytically the waveform of the ac load current and the dc capacitor voltage within an arbitrary number of time periods. The described nonlinear load model along with the model parameters obtained by using the suggested estimation algorithm were verified by comparison against a laboratory-designed typical rectifier-based load. Excellent agreement between the estimated and measured load parameters, as well as between the measured and simulated current and voltage waveforms was found. © 1986-2012 IEEE. Source

Smajic J.,University of Applied Sciences of Eastern Switzerland | Hafner C.,ETH Zurich | Leuthold J.,ETH Zurich
IEEE Transactions on Magnetics | Year: 2016

The multiple multipole program (MMP) is a boundary method for computing electromagnetic fields, which is well established in high-frequency electromagnetics and computational optics due to its flexibility in terms of accuracy control, field excitation, and fast convergence. As any other boundary method, MMP cannot efficiently solve nonlinear problems. The purpose of this paper is to show a novel numerical method for treating local nonlinear regions within a large linear MMP model. The main idea of this approach is to apply the well-known discretization scheme of the domain finite-element method (FEM) within the nonlinear region and to couple it over a special numerical interface with the linear MMP model surrounding it. The theoretical details of this FEM-MMP coupling and practical examples are presented in this paper. © 1965-2012 IEEE. Source

Anvaari M.,Norwegian University of Science and Technology | Zimmermann O.,University of Applied Sciences of Eastern Switzerland
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2014

Architectural decision making is a non-trivial task for architects in the software development projects. Researchers have developed several concepts, methods and tools to assist practitioners in their decision making and decision capturing activities. One of these approaches is a decision identification technique that creates architectural guidance models from decisions made in previous projects and from knowledge about a domain found in the literature. To apply this technique, significant manual knowledge engineering effort has to be invested initially. In this paper, we introduce a framework that automatically extracts architectural knowledge entities from architectural related documents by applying natural language processing. A knowledge engineer then manually post processes and fine-tunes the extracted knowledge entities. We applied evaluation techniques from the information retrieval community to measure the sensitivity and accuracy of the framework. Our results show that the automatic approach has the highest recall and shortest processing time while the semi-automatic approach has the highest precision. © 2014 Springer International Publishing Switzerland. Source

Zimmermann O.,University of Applied Sciences of Eastern Switzerland
Proceedings - 2nd International Workshop on Software Architecture and Metrics, SAM 2015 | Year: 2015

During architectural analysis and synthesis, architectural metrics are established tacitly or explicitly. In architectural evaluation, these metrics then can be consulted to assess whether architectures are fit for purpose and in line with recommended practices and published architectural knowledge. This experience report presents a personal retrospective of the author's use of architectural metrics during 20 years in IT architect roles in professional services as well as research and development. This reflection drives the identification of use cases, critical success factors and elements of risk for architectural metrics management. An initial catalog of architectural metrics is then compiled, which is organized by viewpoints and domains. The report concludes with a discussion of practical impact of architectural metrics and potential research topics in this area. © 2015 IEEE. Source

Zimmermann O.,University of Applied Sciences of Eastern Switzerland
IEEE Software | Year: 2015

A refactoring aims to improve a certain quality while preserving others. For example, code refactoring restructures code to make it more maintainable without changing its observable behavior. Given the success of code refactoring, it's surprising that architectural refactoring (AR) hasn't taken off yet. This article examines AR from a new angle: as an evolution technique that revisits architectural decisions and identifies related design, implementation, and documentation tasks. © 2015 IEEE. Source

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