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Acta polytechnica HungaricaVolume 10, Issue No. 3 (2013.)


  • Yi-Jen Mon ,
    Chih-Min Lin ,
    Imre J. Rudas :

    DOI: 10.12700/APH.10.03.2013.3.2

    Abstract: The adaptive network fuzzy inference system (ANFIS)-based wireless sensor network (WSN) is designed to serve as a monitor of controller of an indoor air-conditioning system. The WSN comprises sensors to monitor the temperature of the indoor space and the ANFIS controller is used to control the fans in order to obtain energy-saving benefits. By using the application programming interface (API) of WSNs, many applications have been developed. The experimental results demonstrate that good data transference and control performance have been achieved.

    Keywords: wireless sensor network; ANFIS; air conditioner control

  • Lajos Tóth ,
    Tibor Tóth :
    On Finding Better Wavelet Basis for Bearing Fault Detection17-35en [639.95 kB - PDF]EPA-02461-00041-0020

    DOI: 10.12700/APH.10.03.2013.3.3

    Abstract: This paper considers the comparision of the Meyer and Morlet wavelet for bearing fault diagnosis. We created a wavelet based upon a transient vibration signal model established for signals generated in deep-groove ball bearings with pitting (spalling) formulation on their inner race. The wavelet creation used the sub-optimal algorithm devised by Chapa and Rao that matches a Meyer wavelet to a band limited signal in two steps. We tested the applicability of the matched wavelet for identifying this kind of bearing failure. The Morlet wavelet was used as a benchmark for evaluating the performance of the matched wavelet since many publications show its successful application. It was shown that for analysing exponentially or near-exponentially damped vibration responses like the vibration produced by spalling on the inner race of a deep-groove ball bearing, the Morlet wavelet is a reasonable choice and gives better results than the Meyer wavelet.

    Keywords: Wavelet analysis; bearing vibration analysis; wavelet matching; condition monitoring

  • Liberios Vokorokos ,
    Adrián Pekár ,
    Norbert Ádám ,
    Péter Darányi :
    Yet Another Attempt in User Authentication37-50en [570.65 kB - PDF]EPA-02461-00041-0030

    DOI: 10.12700/APH.10.03.2013.3.4

    Abstract: This paper deals with the Encrypted Key Exchange (EKE) authentication method, which offers an opportunity to log on to a server and to authenticate the user itself without using a certificate or any direct transmission of the password. This makes the method an interesting alternative solution, where at the end of the authentication process generated is a key that can be further used for the needs of symmetric encryption. In the paper, an implementation of a client-server application that uses EKE authentication method is described. This application after a successful login process enables the user to transfer files in encrypted form, while the encryption key is generated at the end of the authentication process.

    Keywords: authentication; Encrypted Key Exchange; Secure Password Exponential Key Exchange; shared key (secret); password; symmetric key

  • László Kovács ,
    Joel Ratsaby :

    DOI: 10.12700/APH.10.03.2013.3.5

    Abstract: An interpolation of fuzzy sets is an important method in development of efficient fuzzy rule systems. An important property of the interpolated set is the distance minimum property. As can be seen, the validity of this property depends on the applied distance metric. The authors analyse the distance relationship among the base and generated fuzzy sets in the case of KH linear interpolation. The paper presents new properties among the entropy-based distances and proposes an appropriate method for distance optimum interpolation.

    Keywords: fuzzy interpolation; descriptive complexity; entropy; distance metric

  • Darina Matisková ,
    ©tefan Gaąpar ,
    Ladislav Mura :

    DOI: 10.12700/APH.10.03.2013.3.6

    Abstract: This article deals with the analysis of the temperature factors of die casting and the conditions of the service life of moulds. It also describes a mechanism of the origin of internal structures and development of crystallisation grains of aluminium castings depending on the degree of undercooling. The monitored factors are very important in terms of production efficiency and the quality of the casting, which is positively reflected in the most important economic indicators of the production. In die casting, the melted metal is pressed under high temperature into a mould cavity of significantly lower temperature. The mould is then exposed to thermal strain of individual surface layers of the mould material. The speed of cooling of the castings in the metal mould increases, causing an increase of thermal gradients in the casting. Intensive heat exchange between the casting and the metal mould has a negative effect on fluidity, which increases the danger of incomplete replenishment and the occurrence of cold joints.

    Keywords: thermal factors of die casting; service life of a mould; quality of a casting

  • László Mihály Vas ,
    Fatma Göktepe ,
    Péter Tamás ,
    Marianna Halász ,
    Dicle Özdemir ,
    Lívia Palicska-Kokas ,
    Norbert Szakály :
    Modeling and Analysing the Tensile Behavior of Fabric Samples79-95en [398.13 kB - PDF]EPA-02461-00041-0060

    DOI: 10.12700/APH.10.03.2013.3.7

    Abstract: This paper presents a structural-mechanical model for describing the tensile behavior of textile fabrics in main directions based on the fiber-bundle-cells modeling theory and method. The applicability of this model, created by a variable transformed E-bundle shifted along the deformation axis, was demonstrated by analyzing the tensile load-deformation behavior and the breaking process including some size effects of a plain woven fabric made of OE rotor cotton yarns.

    Keywords: tensile behavior of textile; modeling of textile; structural mechanical model; fiber-bundle-cells modeling; size effect of fabric samples

  • Zvezditza Nenova ,
    Georgi Dimchev :

    DOI: 10.12700/APH.10.03.2013.3.8

    Abstract: Methods for gas control have been extensively developed for the monitoring of air quality, for gas leak control, for the development of ‘electronic nose’ systems, etc. Metal oxide gas sensors have been widely used in particular. However, apart from changes in the controlled gas concentration, changes in their parameters also depend on ambient conditions. The main impact comes from temperature and humidity. Therefore, the compensation of these disturbances is important for increasing the accuracy of concentration measurements of the controlled gases and the reliability of control. The present paper proposes a method for compensating the impact of temperature and humidity on gas sensor characteristics using artificial neural networks. This compensation method is applied to the control of methane concentration by gas sensors TGS813 and TGS2611. The results obtained confirm the applicability of this method.

    Keywords: compensation; gas sensors; disturbing factors; artificial neural networks

  • Aleksandar Rodic ,
    Gyula Mester :

    DOI: 10.12700/APH.10.03.2013.3.9

    Abstract: This paper regards the synthesis of intelligent non-visual sensor-based navigation, motion planning and the integrated control of indoor ambient adaptive wheel-based mobile robots in unknown environments with tire-ground interaction uncertainties. The problem relates to searching appropriate techniques how to navigate towards a target position in an unknown environment when the obstacles to avoid are discovered in real time, and how to maintain collision free motion of a high dynamic performance. Environments characterized by variable ground surface conditions with immobile obstacles of different shapes and sizes will be considered in the paper as unexpected disturbances, i.e. system uncertainties. The tools developed to address this issue thus consist of the combination of cognitive motion planning and control theory techniques, including a non-linear model-based approach. Two characteristic approaches to integrated control are evaluated in the paper: a kinematical as well as dynamic one, in the sense of control efficiency and robustness to the environmental and model uncertainties. Characteristic simulation tests are performed to verify the proposed algorithms.

    Keywords: mobile robots; sensor-based navigation; integrated control; tire-ground interaction

  • Silvo Dajčman :

    DOI: 10.12700/APH.10.03.2013.3.10

    Abstract: The paper examines contagion between the sovereign bond markets of six Eurozone countries (France, Germany, Ireland, Italy, Spain, and Portugal) in the period from January 2000 to August 2011. A multinomial logistic model is applied to analyze contagion based on measuring joint occurrences of large yield changes (i.e., co-exceedances), while controlling for developments in common and regional factors that affect all sovereign bond markets simultaneously. I found that the Eurozone’s stock markets (EUROSTOXX50) returns, United States’ Treasury note yields, and the Euro-U.S. dollar (EUR-USD) exchange rate significantly impact the probability of extreme positive yield moves in the Eurozone’s sovereign bond markets. Positive EUROSTOXX50 returns and upside moves in U.S. Treasury note yields increased the probability of extreme positive sovereign bond yield moves in the Eurozone, whereas an increase in the EUR-USD exchange rate significantly reduced the probability. Conditional volatility in the Eurozone stock markets and the money market interest rate do not significantly impact the probability of extreme yield increases in the Eurozone’s sovereign bond markets. Furthermore, the probability of observing exceedance across Eurozone sovereign bond markets increased dramatically during the Eurozone debt crisis compared to the pre-crisis period. This study’s results also indicate less synchronous extreme yield dynamics across the Eurozone sovereign bond markets during the global financial crisis, especially during the Eurozone debt crisis compared to the pre-crisis period.

    Keywords: Sovereign bond markets; Eurozone debt crisis; Contagion

  • Andrew Rusinko :

    DOI: 10.12700/APH.10.03.2013.3.11

    Abstract: Kinetics of the loading surface of a material gives precious information on the level of the hardening of the material. This paper is concerned with the evolution of the loading surface during successive actions, such as: (i) plastic deformation, (ii) annealing of the pre-strained specimen, and (iii) secondary creep of the treated material. The analysis of the loading surface is carried out in terms of the synthetic theory of irrecoverable deformation.

    Keywords: loading surface; mechanical-thermal treatment; creep and plastic strain; synthetic theory of irrecoverable deformation

  • Jana Rovnáková ,
    Duąan Kocur :

    DOI: 10.12700/APH.10.03.2013.3.12

    Abstract: In many applications of ultra-wideband (UWB) radar a character of target motion is a priori not known and naturally can differ within a group of multiple targets. Usually a signal processing aimed at the positioning of only moving persons or only static persons leads to a loss of information. To solve this task, the utilization of combined processing based on detection of non-stationary signal components in the time domain and human respiratory motions in the frequency domain is proposed in this paper. The results of such processing are more reliable and robust with respect to motion activity of all monitored persons, which is demonstrated by processing of measured UWB radar signals.

    Keywords: Moving targets; positioning; signal processing; static targets; UWB radar

  • József Kabók ,
    Tibor Kis ,
    Mária Csüllög ,
    Imre Lendák :

    DOI: 10.12700/APH.10.03.2013.3.13

    Abstract: In this paper, the data envelopment analysis method is used to examine the competitiveness of higher education in selected countries / regions in Europe. The competitiveness of higher education is analyzed on the basis of available information on the chosen indicators, interacting with a model of investment which is applied in the field of higher education. The purpose of the research is to determine the level of competitiveness of higher education of the Republic of Serbia and its Autonomous Province of Vojvodina, as a European region, compared to selected European countries. The research results indicate that the application of the new investment model would improve the unsatisfactory competitiveness of the higher education of the Republic of Serbia and AP Vojvodina. Because of the large differences in the competitiveness of higher education among the analysed countries / regions, the research results point to the need for a unified approach in creating a development strategy and improving the competitiveness of higher education in Europe.

    Keywords: competitiveness index; investment model; higher education

  • Sanjay Misra ,
    Ferid Cafer ,
    Ibahim Akman ,
    Luis Fernandez-Sanz :
    Multi-Paradigm Metric and its Applicability on JAVA Projects203-220en [230.10 kB - PDF]EPA-02461-00041-0130

    DOI: 10.12700/APH.10.03.2013.3.14

    Abstract: JAVA is one of the favorite languages amongst software developers. However, the numbers of specific software metrics to evaluate the JAVA code are limited. In this paper, we evaluate the applicability of a recently developed multi paradigm metric to JAVA projects. The experimentations show that the Multi paradigm metric is an effective measure for estimating the complexity of the JAVA code/projects, and therefore it can be used for controlling the quality of the projects. We have also evaluated the multi-paradigm metric against the principles of measurement theory.

    Keywords: Multi-paradigm metric; Software complexity; JAVA; software development

  • Ramin Taheri ,
    Karim Mazaheri :

    DOI: 10.12700/APH.10.03.2013.3.15

    Abstract: Here a propeller design method based on a vortex lattice algorithm is developed, and two gradient-based and non-gradient-based optimization algorithms are implemented to optimize the shape and efficiency of two propellers. For the analysis of the hydrodynamic performance parameters, a vortex lattice method was used by implementing a computer code. In the first problem, one of the Sequential Unconstraint Minimization Techniques (SUMT) is employed to minimize the torque coefficient as an objective function, while keeping the thrust coefficient constant as a constraint. Also, chord distribution is considered as a design variable, namely 11 design variables. In the second problem, a modified Genetic algorithm is used. The objective function is to maximize efficiency by considering the design variables as non-dimensional blade's chord and thickness distribution along the blade, namely 22 design variables. The hydrodynamic performance analyzer code is modified by a higher order Quasi-Newton scheme. Also, a hybrid function is used to improve the accuracy of the convergence. The solution of the optimization problems showed that a nearly 13% improvement in efficiency and a nearly 15% decrease in torque coefficient for the first propeller, as well as nearly 10% improvement for efficiency of the later propeller, is possible.

    Keywords: Marine propeller; gradient-based optimization algorithm; Genetic algorithm; Vortex lattice

  • István Lakatos :
    Diagnostic Measurement for the Effective Performance of Motor Vehicles239-249en [725.70 kB - PDF]EPA-02461-00041-0150

    DOI: 10.12700/APH.10.03.2013.3.16

    Abstract: Diagnostics means instrumental measurement without dismantling. So measuring the engines on rolling roads is not incorporated in this concept, as this measurement is accomplished on engines taken out from vehicles. During service, it is often necessary to measure the performance of the engines, or to judge the performance projection of some corrections. The new method discussed in this article provides a solution to this problem.

    Keywords: drive train; wheel performance; effective performance; free acceleration