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Tulu M.E.,VESTEL Electronics | Yildirim D.,Technical University of Istanbul
12th International Conference on Environment and Electrical Engineering, EEEIC 2013 | Year: 2013

The principle of induction cooker is based on heating the metallic pan with circulating eddy currents induced by high frequency AC magnetic field. The coil within the induction cooker and the load (pan / pot) acts as a transformer if the load has an electrically conducting base. If the conducting base is ferromagnetic, then the power is transferred with high efficiency. In this document, the quasi resonant topology for induction heating is analyzed. Moreover, pan detection and the method to determine the amount of power delivered to the pan is covered. Jitter method and the three basic benefits of using jitter method during switching action is pointed out. An experimental prototype with a power rating of 2300W is constructed to test the validity of the proposed methods and control algorithms. It was observed that the quasi resonant topology is advantageous over half bridge topology when jitter method is used to drive the semiconductor switches. The test results of the prototype reveal that the current harmonics drawn from the utility is within the limits of the standard EN 61000-3-2. © 2013 IEEE.

Hilavin S.,Vestel Electronics | Kustepeli A.,Izmir Institute of Technology
IEEE Transactions on Electromagnetic Compatibility | Year: 2014

In this paper, a stripline for radiated field immunity testing of audio/video products is designed, constructed, calibrated, and verified. Since the canonical one is only suitable for testing equipments with height less than 70 cm, there is a need of a new device which is also in compliance with EN 55020 standard for testing new large sets, like 47″ thin-film transistor liquid crystal display (TFT LCD) television sets, in the frequency range of 150 kHz-150 MHz. Increasing the height and width of testing area causes important problems in terms of field uniformity regarding the higher order modes, characteristic impedance, and reflections in addition to the room resonances and field interference sources like corners at the edges of stripline. Comprehensive numerical study is performed to overcome these problems and obtain the optimum design before the construction. Measured data show that the new stripline is in very good agreement with the specifications determined by the standards and therefore it can be used for the electromagnetic compatibility (EMC) testing. © 2013 IEEE.

Karakuzu R.,Dokuz Eylül University | Demirgoren O.,Vestel Electronics | Icten B.M.,Dokuz Eylül University | Deniz M.E.,Dokuz Eylül University
Materials and Design | Year: 2010

This paper presents the effect of hole positions on the failure behavior of glass-epoxy laminated composite plates fabricated from stacking sequence [0/90/±45]S subjected to a traction force by three-pins. Three different hole distance parameters, namely the ratio of free edge distance to the outer holes/pin diameter (E/D = 1, 2, 3, 4, 5), the ratio of longitudinal distance between the holes/pin diameter (F/D = 2, 4, 6) and the ratio of transverse distance between the parallel holes/pin diameter (G/D = 3, 4, 5) were used to investigate the effects of hole positions on failure load and failure mode. Shear out failure mode which is not the desired mode for a structure occurs around the first and second pin holes very close to the free edge of the specimen (E/D = 1). The other specimens were damaged in bearing mode which is the most desired mode. © 2009 Elsevier Ltd. All rights reserved.

Gebizli C.S.,Vestel Electronics | Sozer H.,Ozyegin University
Proceedings - IEEE 38th Annual International Computers, Software and Applications Conference Workshops, COMPSACW 2014 | Year: 2014

Model-based testing facilitates automatic generation of test cases by means of models of the system under test. Correctness and completeness of these models determine the effectiveness of the generated test cases. Critical faults can be missed due to omissions in the models, which are primarily created manually. In practice, these faults are usually detected with exploratory testing performed manually by experienced test engineers. In this paper, we propose an approach for refining system models based on the experience and domain knowledge of these test engineers. Our toolset analyzes the execution traces that are recorded during exploratory testing activities and identifies the omissions in system models. The identified omissions guide the refinement of models to be able to generate more effective test cases. We applied our approach in the context of an industrial case study to improve the models for model-based testing of a Digital TV system. After applying our approach, three critical faults were detected. These faults were not detected by the initial set of test cases and they were also missed during the exploratory testing activities. © 2014 IEEE.

Gebizli C.S.,Vestel Electronics | Sozer H.,Ozyegin University
Proceedings - 2016 IEEE International Conference on Software Quality, Reliability and Security-Companion, QRS-C 2016 | Year: 2016

Model-based testing automates test case generation based on usage models of a system. In this paper, we introduce an approach for systematic reuse of these models for testing a large family of products. In our approach, we model system usage with hierarchical Markov chains. These models capture all possible usage scenarios for a family of systems. We document variability explicitly and separately with a feature model. We map optional and alternative features in the feature model to a set of transitions in the usage model. Transition probabilities are modified according to the selected features so that the generated test cases focus only on these features. We performed an industrial case study to evaluate the feasibility and efficiency of the approach. We observed that the cost of product line engineering adoption can be amortized with the testing of even a small number of products. © 2016 IEEE.

Yuksel U.,Vestel Electronics | Yuksel U.,Ozyegin University | Sozer H.,Ozyegin University
IEEE International Conference on Software Maintenance, ICSM | Year: 2013

Static code analysis tools automatically generate alerts for potential software faults that can lead to failures. However, developers are usually exposed to a large number of alerts. Moreover, some of these alerts are subject to false positives and there is a lack of resources to inspect all the alerts manually. To address this problem, numerous approaches have been proposed for automatically ranking or classifying the alerts based on their likelihood of reporting a critical fault. One of the promising approaches is the application of machine learning techniques to classify alerts based on a set of artifact characteristics. In this work, we evaluate this approach in the context of an industrial case study to classify the alerts generated for a digital TV software. First, we created a benchmark based on this code base by manually analyzing thousands of alerts. Then, we evaluated 34 machine learning algorithms using 10 different artifact characteristics and identified characteristics that have a significant impact. We obtained promising results with respect to the precision of classification. © 2013 IEEE.

Sozer H.,Ozyegin University | Gebizli C.S.,Vestel Electronics
Software Quality Journal | Year: 2016

Model-based testing is a promising approach for increasing the efficiency of the testing process and for improving software quality. It has been employed in the industry for more than a decade. Nevertheless, there are still challenges regarding its application in different domains. Some of these challenges are general, while some others are domain-specific. In this paper, we explain our experiences in enhancing model-based testing for its adoption in the consumer electronics domain, in particular for Digital TV systems. We applied the so-called industry-as-laboratory approach to define/refine research problems and evaluate our research results. We summarize these results and provide an evaluation of relevant research problems for our context. We observed that the industry-as-laboratory approach is highly effective for industry-academia collaboration and technology transfer in the scope of model-based software testing. © 2016 Springer Science+Business Media New York

Gulcu K.,Vestel Electronics | Sozer H.,Ozyegin University | Aktemur B.,Ozyegin University
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2012

In service-oriented architectures, composite services depend on a set of partner services to perform the required tasks. These partner services may become unavailable due to system and/or network faults, leading to an increased error rate for the composite service. In this paper, we propose an approach to prevent the occurrence of errors that result from the unavailability of partner services. We introduce an external Web service, FAS (Fault Avoidance Service), to which composite services can register at will. After registration, FAS periodically checks the partner links, detects unavailable partner services, and updates the composite service with available alternatives. Thus, in case of a partner service error, the composite service will have been updated before invoking the partner service. We provide mathematical analysis regarding the error rate and the ratio of false positives with respect to the monitoring frequency of FAS for different partner service availabilities. We also provide empirical results regarding these metrics based on several tests we performed using the Amazon Elastic Compute Cloud. © 2012 Springer-Verlag.

Gebizli C.S.,Vestel Electronics | Sozer H.,Ozyegin University
Software Quality Journal | Year: 2016

Model-based testing relies on models of the system under test to automatically generate test cases. Consequently, the effectiveness of the generated test cases depends on models. In general, these models are created manually, and as such, they are subject to errors like omission of certain system usage behavior. Such omitted behaviors are also omitted by the generated test cases. In practice, these faults are usually detected with exploratory testing. However, exploratory testing mainly relies on the knowledge and manual activities of experienced test engineers. In this paper, we introduce an approach and a toolset, ARME, for automatically refining system models based on recorded testing activities of these engineers. ARME compares the recorded execution traces with respect to the possible execution paths in test models. Then, these models are automatically refined to incorporate any omitted system behavior and update model parameters to focus on the mostly executed scenarios. The refined models can be used for generating more effective test cases. We applied our approach in the context of 3 industrial case studies to improve the models for model-based testing of a digital TV system. In all of these case studies, several critical faults were detected after generating test cases based on the refined models. These faults were not detected by the initial set of test cases. They were also missed during the exploratory testing activities. © 2016 Springer Science+Business Media New York

Gezer C.,Vestel Electronics
2014 22nd Signal Processing and Communications Applications Conference, SIU 2014 - Proceedings | Year: 2014

In this study we are exploiting the periodic nature of human activities in order to better utilize the channel between the on body sensors and a sink that collects the data coming from those sensors. We propose a health-care monitoring system where nodes having good quality links use the channel and the ones with poor quality links defer their packet transmissions until better link conditions. In such an adaptive way, the allocated bandwidth for the nodes with good quality links is also improved. We use the periodic beacons send by the IEEE 802.15.4 coordinator (sink) for the link quality estimation. Besides, we define a two-level prioritization scheme compatible with IEEE 802.15.4, for different application requirements. © 2014 IEEE.

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