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Acta polytechnica HungaricaVolume 12, Issue No. 3. (2015.)


  • Vladimír Gazda ,
    Denis Horváth ,
    Marcel Rešovský :

    Abstract: In our paper, the class of graph tractable problems of mutual debt compensation (MDC) among firms is introduced. We demonstrate that the debt compensation is related to the optimization problems maximizing the circulation of the consecutive compensation in the digraph of debts. Each optimization problem is firstly formulated by linear programming methods. It is subsequently redeveloped in order to apply the more efficient Klein’s cycle-cancelling algorithm. The class of the formulated compensation problems consists of the following models: (i) the model maximizing the returns of the MDC organizer; (ii) the model of profitable subsidies and (iii) the model minimizing the claims exposition of the MDC organizer.

    Keywords: mutual debt compensation; digraph of debts; Klein’s cycle cancelling

  • András Szűts ,
    István Krómer :

    Abstract: Reducing the energy consumption of households and making them more energy efficient are indispensable for fulfilling the European Union's energy strategy since more than one-third of total EU energy use is consumed by households. Our research here focuses on the development of building design methods since, decisions made during the early design phase significantly affect the energy consumption and energy efficiency of the building. In Hungary, current simulation methods are not sufficiently effective in evaluating potential alternatives in the early design process; therefore, in our research, we look for new solutions based on decision support systems. In our view, either a classic AHP or a Hybrid Fuzzy AHP based system could fulfil this task. In this article, we will demonstrate the structure and use of the developed systems, and we will compare them to the simulation methods commonly used nowadays. Further, we will test and evaluate the performance of the decision support system based models developed by us, applying them to four typical buildings in Hungary. Lastly, we will propose opportunities for further development.

    Keywords: fuzzy logic controllers; analytic hierarchy process; energy; households

  • Marina Dobrota ,
    Veljko Jeremić ,
    Milica Bulajić ,
    Zoran Radojičić :

    Abstract: The evaluation of education systems and the measurement of their quality, have become increasingly important research subjects for all stakeholders. This paper measures the efficiency of countries’ educational performance and ranks countries according to the obtained results. The research is complemented by an examination of how uncertainty and sensitivity analyses affect the changes in rankings. Efficiency of countries’ educational performance is presented through a single composite indicator that consists of PISA indicators and is measured using the Distance Based Analysis (DBA) methodology. Uncertainty and sensitivity of a composite indicator are results of different normalization methods. One of the contributions of this paper is the analysis of uncertainty and sensitivity impact on the efficiency measurement.

    Keywords: uncertainty analysis; sensitivity analysis; composite indicators; normalization; educational performance; efficiency; PISA; Distance Based Analysis (DBA)

  • Sándor Szilágyi M. :
    Spatio-Temporal Shape Parameterization of the Human Ventricles59-72en [409.93 kB - PDF]EPA-02461-00057-0040

    Abstract: This paper gives a solution for improving the geometric estimation of the human ventricles, by reducing their shape estimation error. The parametric description of the studied organ can be performed at arbitrary resolution during the whole visualization process. After the problem description, the paper presents each main step of the proposed shape estimation algorithm. The presented method determines not only the general shape of the ventricles, but the internal tissue direction, too. The estimation error decreases more than 10 times if the resolution is increased by 3 times. The biological parameters like gender or age also affect the estimation performance. The obtained accuracy of the method was slightly higher in the case of female hearts and for the left ventricle. Finally, concluding remarks emphasize some important features of the given approach and the future research directions.

    Keywords: ventricle modeling; heart geometry; shape estimation; interpolation techniques

  • Zoran Nesic ,
    Leon Ljubic ,
    Miroslav Radojicic ,
    Jasmina Vesic Vasovic :

    Abstract: In this paper, the major elements of the information flow in car parks information system has been presented. A detailed analysis of information flow in one of the key elements for a parking service company, thus, providing the basis for developing the information system in this area. The analysis of decomposition diagrams and charts, in the context of the information flow, has also been presented here, as well as, the formation of a logical and relational database model. The focus is on the performance of a detailed analysis of the information flow, with the aim of improving the overall functioning of a parking service company. The development of the information system of car parks is the most important step in both the development of the overall information system of this company and its improvement. The results presented in this paper might be a starting point in the development of information systems for parking service companies, in general. The obtained results help in the formation of a clear and consistent information system in this area.

    Keywords: information flow; information systems; databases

  • Orestes Appel ,
    Francisco Chiclana ,
    Jenny Carter :

    Abstract: This article has multiple objectives. First of all, the fundamental concepts and challenges of the research field known as Sentiment Analysis (SA) are presented. Secondly, a summary of a chronological account of the research performed in SA is provided as well as some bibliometric indicators that shed some light on the most frequently used techniques for addressing the central aspects of SA. The geographical locations of where the research took place are also given. In closing, it is argued that there is no hard evidence that fuzzy sets or hybrid approaches encompassing unsupervised learning, fuzzy sets and a solid psychological background of emotions could not be at least as effective as supervised learning techniques.

    Keywords: sentiment analysis; opinion mining; social media; fuzzy sets; supervised learning; unsupervised learning

  • Valentin Kónya ,
    Leposava Grubić-Nešić ,
    Dejan Matić :

    Abstract: It is clear that accomplishing the goals of leadership can be easier and the process is far more successful, if both leaders and their coworkers are fully committed to their organizations, especially in stressful, demanding working environments with high levels of responsibility, such as in the health care sector. The subject of this paper is to investigate the influence of social exchange between leaders and their followers on the organizational commitment of employees. The main research question, to which this paper should give an answer, is whether social exchange between leaders and coworkers have significant influence on the organizational commitment of employees in a large hospital? The research was conducted in a Central European hospital with over 1000 employees. A total number of 359 valid questionnaires were returned. Two questionnaires were used for the research: the quality of leader-member exchange was measured with LMX-7 questionnaire for members and organizational commitment was measured with the Organizational Commitment Questionnaire – OCQ. Identical questionnaires were given to every employee included in the research, so no leader-member distinction was made among them, as the focus was on how employees as members evaluate their exchange with their leaders generally and what impact it has on their commitment. The area of interest of this research was not on specific leader-member relationships. Employees were asked to assess the quality of the exchange relationship with all of their leaders generally. The findings revealed that leader-member communication and organizational commitment have positive connectivity in a non-western environment. It was also revealed that leader-member communication and value commitment have much stronger relationship than the relationship between leader-member communication and commitment to stay.

    Keywords: leader-member communication; LMX; organizational commitment; hospital; large organization; Central Europe

  • Laslo Tot ,
    Gojko Grubor ,
    Márta Takács :

    Abstract: This paper looks into the background of the internal leakage effect on the dynamic behavior of an electrohydraulic servo positioning system. The electrohydraulic servo systems are widely used in precise control at high forces, but the overall quality of this servo control could be impaired by faults in the system. There could be several defects which have effect on the system response, but this work points to the effect of internal leakage of the hydraulic cylinder because this error cannot be easily detected. To show the effect of internal leakage on electrohydraulic servo system a complex nonlinear mathematical model considering the leakage of the hydraulic cylinder is used. The work herin demonstrates the relationship between internal leakage and the dynamic behaviour of the servo positioning system. Laboratory test results are used to verify the conclusions drawn from the mathematical model of the complete servo positioning system.

    Keywords: servo system; mechatronics; position control; hydraulic servo; leakage

  • Abderrahmen Mechter ,
    Karim Kemih ,
    Malek Ghames :
    Sliding Mode Control of a Wind Turbine with Exponential Reaching Law167-183en [428.22 kB - PDF]EPA-02461-00057-0100

    Abstract: Numerous organizations coordinate and certify their information security systems according to the Information Security Management System (ISMS) standard. Available Cloud Computing Services (CCSs) include new types of vulnerability (management, virtualization, sprawl, etc.) and differ in management requirements from other computational systems. Establishing a consistent security management framework (SMF) and information security management system (ISMS) in CC environment is a complicated, demanding and time-consuming process. Every experience from applying ISMS standard solutions is certainly useful, but not enough to entirely cover all security requirements of the customers and Cloud Service Provider (CSP). Attempts of establishing an integrated and consistent SMF and ISMS in CC environment have not been researched in-depth in recent available literature. In this paper, authors suggested a framework for an establishing quality management system (QMS) of CCSs, including CC SMF and CC ISMS, proactive digital forensic (DF), proactive and predictive security controls and corporate DF investigation process up to the level specified in Service Level Agreement (SLA).

    Keywords: CC ISMS; CC SMF; Proactive Digital Forensic; Digital forensics; CCS QMS

  • Zoran Ciric ,
    Dragan Stojic ,
    Otilija Sedlak :

    Abstract: This paper presents a novel control strategy of a wind turbine based on Doubly Fed Induction Generator (DFIG) to maximize the electrical power generated by the DFIG, for low wind speed. To achieve this objective, the nonlinear sliding mode control with exponential reaching law (ERL ), the Bees algorithm and the fuzzy maximum power point tracking MPPT are applied to the system. The ERL and the Bees algorithm are used to obtain a good reference tracking and to suppress the chatter phenomenon. The effectiveness of this control strategy is proven through the simulation results.

    Keywords: Wind Energy; Doubly fed induction generator; Sliding Mode Control; Exponential Reaching Law; Bees algorithm; fuzzy maximum power point tracking

  • Bedri Kekezoglu ,
    Mugdeşem Tanriöven ,
    Ali Erduman :
    A New Wind Turbine Concept: Design and Implementation199-211en [541.22 kB - PDF]EPA-02461-00057-0120

    Abstract: Electrical energy demand has been continuously increasing. Depleting fossil fuel reserves, environmental concerns, and insufficiency of conventional generation techniques in meeting growing demand, renewable energy use has been widely adopted in the world. When considering the application of renewable energy sources in the world, it can be seen that wind energy is mostly preferred over other renewable energy sources. In this study, a new prototype wind energy conversion system suitable for urban use is designed and manufactured. The proposed design is modular and has flexible structure. In the new design, an outer gear ring attached to turbine blades is used. In the design stage, both the number of blades and the number of outer gear rings are varied to analyze their effect on turbine performance. Performance analysis of the prototype wind turbine is completed under real life conditions and results are given. As a result of this study, it is shown that increasing the gearwheels and blade numbers caused turbine output power increases. The most efficient structure identified during the field analysis is a three gearwheel with six blade system.

    Keywords: renewable energy resources; wind energy; wind turbine prototype; urban use

  • Stipe Lovreta ,
    Jelena Končar ,
    Ljiljana Stanković :

    Abstract: Highly noticeable processes of retail market concentration have marked the end of the last and the beginning of this century. The intensive development of retail chains and high-level of increasing of their power caused the shifting of powers, changes of positions and the establishment of new relationships between the members of marketing channels. Retailing revolution which makes substantial changes to former marketing channels is under way. A lack of understanding these changes is especially noticeable on the developing markets where large retail chains assume key roles in creating and managing the channels. Strengthening of their position is more than evident. The position of wholesalers in these trends, i.e. need for their intermediating role between producers and retailers, becomes especially interesting. The situation is alarming, primarily, in the field of food and other fast moving consumer goods, where the changes manifest themselves to a high extent and with special content. Wholesalers are facing a less significant role with growing retailers, which are constantly making more numerous and more complex demands of them. In such conditions, many wholesalers disappear from the market. However, wholesalers still have significant possibilities and advantages of cooperation with large retail chains, which can strengthen their position and ensure survival in the marketing channels. This study confirms it, by proving that increasing the power of retailers brings a higher level of satisfaction for wholesalers and that they achieve a higher level of satisfaction in doing business with large rather than with small and medium-sized retailers.

    Keywords: marketing channels; retail chains; wholesalers; power

  • József Poór ,
    Allen D. Engle ,
    Éva Ildikó Kovács ,
    Agnes Slavic ,
    Geoffrey Wood ,
    Katalin Szabó ,
    Marzena Stor ,
    Kinga Kerekes ,
    Zsuzsa Karoliny ,
    Ruth Alas ,
    Krisztina Némethy :

    Abstract: There is only limited literature on Human Resource Management (HRM) activities in Multinational Companies (hereafter MNC) in the Central and Eastern European region. The research presented below is part of an ongoing research project developed by the Central and Eastern European International Research Team (CEEIRT), a consortium of researchers from universities across the Central and Eastern European (CEE) region with the aim of describing the ongoing patterns of HR practices, policies, practices and pursued by regional MNCs. Statisticians and descriptive results are present from surveys carried out in 2008-2009 and again in 2012-2013.

    Keywords: HR practices; multinational companies; Central-Eastern Europe