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Acta polytechnica HungaricaVolume 9, Issue No. 4 (2012.)


  • Gükhan Gökmen ,
    Yelda Karatepe ,
    Tahir Çetin Akinci ,
    Memduh Kurtulmus :
    Spectrum Analysis of GMA Welter in Various Working Modes5-16en [324.68 kB - PDF]EPA-02461-00036-0010

    Abstract: In this study, a current drawn by a welter at initial, stable-state and finish modes is examined using spectral analysis. The current shunt measurement method is utilized in order to measure the current drawn by the welter. The study involves the examination of welding stages of a material with the electrode of a welter. First, the current drawn by the welter is measured in the initial mode of the welding process. Then the current value during the stable-state mode of the welding process is measured. Finally, the current drawn at the finishing mode of the welding process is measured. Fast Fourier Transform (FFT) of all these measured current values are calculated and spectral analysis is performed using these transforms. During the study, it is observed that current drawn by the welter during these three modes of welding are different from each other. For each mode, frequency domain analysis of the measured current is performed.

    Keywords: Welters; high frequency inverter; working modes; current shunt measurement; spectral analysis

  • Tomislav Doąlic ,
    Tamás Réti :

    Abstract: In the present study we investigate some general problems concerning the degeneracy of widely used topological indices (graph invariants), and we propose a novel family of molecular descriptors characterized by a decreased degeneracy level. A special feature of topological indices of novel type is that they take into account the degrees of vertices on increasing distances from a single vertex. According to the comparative tests performed on samples of isospectral graphs and of graphs of small diameter, the new descriptors are judged to be more efficient for discriminating between topological structures of molecular graphs than several traditional molecular indices.

    Keywords: Zagreb indices; pseudo-regular graphs; QSAR/QSPR studies

  • Peetr Girovský ,
    Jaroslav Timk ,
    Jaroslava ®ilková :

    Abstract: The paper deals with a shaft sensor-less field oriented control structure for an induction motor based on neural network estimators. The first part presents the theoretical knowledge. The second part presents the simulation and results of designing neural estimators for observing the magnetic flux and the motor angular speed for induction motor field oriented control in MATLAB-Simulink. Controllers for simulation of shaft sensor-less field oriented control have been designed by state space method. An achieved simulation result of the neural angular speed estimator has been verified by system of AC converter – induction motor by Real-Time system.

    Keywords: induction motor; neural network; sensor-less control; vector control

  • Ahmed Arab ,
    Mostefa Belkhatir :

    Abstract: This paper presents a laboratory study of the influence of low plastic fines and preloading on the cyclic behaviour of silty sand. The study is based on undrained triaxial cyclic tests which were carried out for fines content ranging from 0 to 40%. The paper is composed of three parts. The first one presents the characteristics of soils used in this study; the second provides an analysis of the effect of low plastic fines on the cyclic behaviour of the sand-silt mixtures. The third part presents the effect of the preloading on the soil liquefaction. The test results indicate that the liquefaction potential of the mixtures decreases with increasing the fines content until Fc=20%, after which the potential of liquefaction increases moderately with the fines content Fc=40%. The over-consolidation and the cyclic drained preloading of low stress amplitude improved the liquefaction resistance of the sand-silt mixtures.

    Keywords: fines; sand; undrained; potential; liquefaction; over-consolidation; cyclic preloading

  • Miklós F. Hatwágner ,
    András Horváth :

    Abstract: The Bacterial Evolutionary Algorithm (BEA) is an evolutionary method, originally meant to optimize the parameters of fuzzy systems. The authors have already proposed three modified versions of the original algorithm in a previous paper to make it usable in engineering applications with time-consuming object functions as well. Section 1 summarizes the earlier results. It presents the operators of the original BEA and the suggested parallel version. In Section 2, the optimal parameter settings and the analytical estimation of wall clock time in parallel computations are investigated. In Section 3, the paper deals with genetic diversity in different BEA versions. The effect of the modified gene transfer operators on genetic diversity is measured. The conclusion is that the proposed methods have quite good efficiency in all cases, and we can reach the ideal case if we have full control over the parameters.

    Keywords: optimization; Bacterial Evolutionary Algorithm; genetic diversity; parallel computing; parallel efficiency

  • Seref Aykut ,
    Aykut Kentli ,
    Servet Gülmez ,
    Osman Yazicioglu :

    Abstract: In this paper, a new multiobjective optimization approach is proposed for the selection of the optimal values for cutting conditions in the face milling of cobalt-based alloys. This approach aims to handle the possible manufacturing errors in the design stage. These errors are taken into consideration as a change in design parameter, and the design most robust to change is selected as the optimum design. Experiments on a cobalt-based superalloy were performed to investigate the effect of cutting speed, feed rate and cutting depth on the cutting forces under dry conditions. Material removal rate values were also obtained. Minimizing cutting forces and maximizing the material removal were considered as objectives. It is believed that the used method provides a robust way of looking at the optimum parameter selection problems.

    Keywords: face milling; robust optimization; cobalt-based superalloy; sensitivity; multiobjective optimization; optimum cutting parameters

  • Pál Michelberger Jr. ,
    Csaba Lábodi :

    Abstract: Security management for business enterprises is currently undergoing major changes. Instead of the separate regulation of distinct areas (guarding infrastructure, work safety, security technology, information security, etc.) there is an emerging holistic approach based on new management methods and company culture. Partly as a result of existing traditions, the professional business background to the implementation of these changes is rather fragmented and may not yet exist at all. Our survey calls attention to a new opportunity. In our opinion the expected level of company security and business continuity may be reached departing from information security-related international standards and recommendations, by business risk analysis and compliance with a wide range of security expectations.

    Keywords: information security; risk analysis; business continuity; process security; enterprise security model

  • Slavomír ©imonák :

    Abstract: Communication protocols define the set of rules needed to exchange messages between communicating entities. Networked and distributed systems, built around communicating protocols, are widely used nowadays. Since such systems are often deployed in safety-critical applications, confidence in protocol correctness is highly required. We propose an approach based on formal method integration to support the modeling and analysis of communication protocols. Process algebra and Petri nets are used together to combine the best properties from both methods – the exceptional properties for system description offered by process algebra, and the powerful analytical properties of Petri nets. The ideas described within the paper are demonstrated by an example – the Trivial FTP (TFTP) protocol.

    Keywords: protocol correctness; formal methods integration; Petri nets; process algebra

  • Igor Fürstner ,
    Zoran Aniąic ,
    Márta Takács :

    Abstract: When selling a customized product with the support of a product configurator, there is a risk that customers will abort the configuration process if the configuration dialogue does not suit the customer well. To reduce this risk, a product configurator that self-adapts to different levels of customer knowledge instead of vice versa is needed. In this paper, a self-adapting approach for product configurators is proposed, one which relies on a fuzzy logic-based algorithm. The approach is implemented for the configuration of the thermal insulation of buildings. The product configurator is tested by users with different capabilities and a comparison of results with professionally performed calculations is performed. It is shown that the proposed approach allows inexperienced customers, too, to make appropriate decisions about thermal insulation. This is an advancement that can considerably expand the scope of the application of product configurators.

    Keywords: mass customization; customer profiling; decision support systems; thermal insulation; fuzzy logic

  • Pál L. Pályi ,
    Attila Kőrösi ,
    Balázs Székely ,
    József Bíró ,
    Sándor Rácz :

    Abstract: In this paper we characterize the state space of the discriminatory processor sharing service discipline with peak-rate limitations of the flows. We analyze a bandwidthefficient rate sharing model, in which the unused capacity of the server by peak-rate limited flows is re-distributed among the non-limited flows. An efficient algorithmic approach is presented to determine which classes are subject to peak-rate limitations and based on this the bandwidth shares of flows of classes in a given state of this system.

    Keywords: Discriminatory Processor Sharing; bandwidth-efficient; Peak rate

  • Balázs Horváth :
    A Simple Method to Forecast Travel Demand in Urban Public Transport 165-176en [234.90 kB - PDF]EPA-02461-00036-0110

    Abstract: The key to the planning of public transport systems is the accurate prediction of the traffic load, or the correct execution of the planning stage assignment. This requires not only a well-functioning assignment method, but also reliable passenger data. Reliable passenger data means a time-dependent origin-destination matrix.

    To solve the problem of the lack of time-dependent passenger data, we have developed a forecasting method. It consists of three stages.

    In the first stage, we collect full scope cross-section data. This can be done either with personnel or with an automatic counting system. If personnel are used it costs a lot, and there is the chance for many possible errors. However, the results in most cases are good enough. Automatic counting system can be either a counter machine or even a simple "Check in" E-ticketing system.

    In the second stage, we link boarding and alighting. As result, we get the origin-destination matrix for each run. This method is based on the likelihood of alighting at a given stop. In the third stage, we combine origin-destination matrices of the runs through transfers. At this stage we assume that the probability of a transfer between two runs in a given stop is proportional to the travel possibilities in this relation.

    To view the entire method in practice we proved it in a Hungarian city (Dunaújváros). The results were reliable, so they could be used in the planning process.

    Keywords: public transport; transport planning; demand; OD matrix

  • Radhwane Sadouni ,
    Abdelkader Meroufel :

    Abstract: We present in this paper, a comparative study between a PI regulator and fuzzy regulator for a control speed of a Dual Star Induction Machine (DSIM) supplied with a two PWM voltage source inverter (VSI) and decoupled by field-oriented control (FOC).The simulation results illustrate the robustness and efficiency of the fuzzy regulator to the parametric variations.

    Keywords: dual star induction machine (DSIM); field-oriented control (FOC); fuzzy logic

  • Cagatay Catal :
    Performance Evaluation Metrics for Software Fault Prediction Studies193-206en [135.43 kB - PDF]EPA-02461-00036-0130

    Abstract: Experimental studies confirmed that only a small portion of software modules cause faults in software systems. Therefore, the majority of software modules are represented with non-faulty labels and the rest are marked with faulty labels during the modeling phase. These kinds of datasets are called imbalanced, and different performance metrics exist to evaluate the performance of proposed fault prediction techniques. In this study, we investigate 85 fault prediction papers based on their performance evaluation metrics and categorize these metrics into two main groups. Evaluation methods such as cross validation and stratified sampling are not in the scope of this paper, and therefore only evaluation metrics are examined. This study shows that researchers have used different evaluation parameters for software fault prediction until now and more studies on performance evaluation metrics for imbalanced datasets should be conducted.

    Keywords: performance evaluation; software fault prediction; machine learning

  • Tamás Tettamanti ,
    Hunor Demeter ,
    István Varga :
    Route Choice Estimation Based on Cellular Signaling Data207-220en [594.99 kB - PDF]EPA-02461-00036-0140

    Abstract: The rapid growth of mobile phone communications has induced novel and emerging technologies in the past decades. Signaling data of cellular phones can be used as valuable information for state-of-the-art traffic applications especially in urban areas. The paper focuses on the applicability for estimating the traces of traveling mobiles in the transportation system. By observing anonym mobile phones, typical route choices can be determined and thus other traffic characteristics can be obtained. These information may serve as efficacious basis for transportation forecasting and planning, traffic control measures or even for real-time route guidance.

    Keywords: cellular network; Voronoi tessellation; handover; location update; mobile phone; estimation; route choice; traffic assignment

  • Anna Jadlovská ,
    ©tefan Jajciąin :

    Abstract: The main goal of this paper is to present the suitability of predictive control application on a mechatronic system. A theoretical approach to predictive control and verification on a laboratory Helicopter model is considered. Firstly, the optimization of predictive control algorithms based on a state space, linear regression ARX and CARIMA model of dynamic systems are theoretically derived. A basic principle of predictive control, predictor deducing and computing the optimal control action sequence are briefly presented for the particular algorithm. A method with or without complying with required constraints is introduced within the frame of computing the optimal control action sequence. An algorithmic design manner of the chosen control algorithms as well as the particular control structures appertaining to the algorithms, which are based on the state space or the input-output description of dynamic systems, are presented in this paper. Also, the multivariable description of the educational laboratory model of the helicopter and a control scheme, in which it was used as a system to be controlled, is mentioned. In the end of the paper, the results of the real laboratory helicopter model control with the chosen predictive control algorithms are shown in the form of time responses of particular control closed loop’s quantities.

    Keywords: ARX; CARIMA model; generalized predictive control; state model-based predictive control; optimization; quadratic programming; educational Helicopter model