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Acta polytechnica HungaricaVolume 12, Issue No. 6. (2015.)


  • Changjian Yan ,
    Chaojian Shi ,
    Hamido Fujita ,
    Nan Ma :

    Abstract: Case-based Reasoning (CBR), an approach for analogical reasoning, has recently emerged as a major reasoning methodology in the field of artificial intelligence. The knowledge contained in a case base is crucial to solve problem for a CBR system and thus, there is always a tradeoff between the number of cases and the retrieval performance. Although many people attempt to deal with this issue these years, constructing a well compact competent case base needs much effort. In this paper, a new approach is proposed to maintain the size of case base. The maintenance process is divided into two separate stages. The former focuses on overcoming the competence of sparse cases and the latter emphasizes the dense cases. Using this strategy, we could appropriately maintain the size of the case base by extending the competence without losing significant information. We illustrate our approach by applying it to a range of standard UCI data sets. Experimental results show that the proposed technique outperforms current traditional approaches.

    Keywords: Case Base; competence; hybridization ;density; sparse

  • József Abaffy ,
    Szabina Fodor :
    Reorthogonalization Methods in ABS Classes23-41en [1.14 MB - PDF]EPA-02461-00060-0020

    Abstract: In this paper we analyze two subclasses of ABS class of methods which produce orthogonal projection vectors. We theoretically prove that the “twice is enough” selective reorthogonalization criterion of Parlett-Kahan [14] and of Hegedüs [8] can be used in the various ABS classes. Here we also provide a detailed numerical analysis of these ABSbased algorithms. We revealed that the ABS-based algorithm combined with the modified Parlett-Kahan criterion by Hegedüs provided more accurate results in the three considered cases (the rank of the coefficient matrix, the determination of the orthogonal bases, and the QR factorization) than the built-in rank and qr MATLAB functions.

    Keywords: ABS methods; orthogonalization; reorthogonalization; Gram-Schmidt; ParlettKahan

  • Manuel J. Cobo ,
    A. G. López-Herrera ,
    Enrique Herrera-Viedma :
    A Relational Database Model for Science Mapping Analysisen [477.06 kB - PDF]EPA-02461-00060-0030

    Abstract: This paper presents a relational database model for science mapping analysis. It has been specially conceived for use in almost all of the stages of a science mapping workflow (excluding the data acquisition and pre-processing stages). The database model is developed as an entity-relations diagram using information that is typically presented in science mapping studies. Finally, several SQL queries are presented for validation purposes.

    Keywords: Science Mapping Analysis; Bibliometric mapping; Bibliometric Studies; Bibliometric networks; Co-word; Co-citation; Database model

  • Balázs Villányi ,
    Péter Martinek :
    Improved Accuracy Evaluation of Schema Matching Algorithms63-76en [636.18 kB - PDF]EPA-02461-00060-0040

    Abstract: Application integration is one of the most relevant topics in enterprise computing today. To support Enterprise Application Integration, various algorithms, methods and complex systems are applied. Automated schema matchers support application integration by identifying the semantically related entities of the input schemas. In this article, we present the notion of the cutting threshold problem in schema matching and propose a solution. Our approach incorporates the definition of a threshold function, which is conceptually similar to a fuzzy membership function. We have also redefined the accuracy measures most commonly used for accuracy evaluation of schema matchers. Employing the threshold function, we managed to obtain a 9.85% average accuracy improvement. The introduction of the threshold function also enables the redefinition of the schema matching accuracy maximization problem.

    Keywords: Enterprise Application Integration; Schema Matching; Algorithm Optimization; Fuzzy Logic; Threshold Function; Accuracy Measure Improvement

  • Aleksandra Melińska ,
    Andrzej Czamara ,
    Lukasz Szuba ,
    Romuald Będziński ,
    Ryszard Klempous :

    Abstract: The aim of the study was to evaluate balance during the landing phase in a control group and patients after anterior cruciate ligament reconstruction (ACLR). ACL tear is a frequent injury, particularly in athletes. It often requires proper rehabilitation, during which time the patients should be re-evaluated. We performed a jump-down assessment using a motion capture and force platform system. The tests comprised a series of time-space and dynamic parameters measurements using a motion capture system and a force plate. We tested 28 men (22 controls and 6 patients who had undergone ACLR). The tests are conducted under jump-down conditions (0.1-, 0.2-, and 0.3-m step heights). We compared horizontal components of force during the landing phase. The division of registered three-dimensional (3D) motion was demonstrated, and the fluctuations of the estimated center of gravity (eCOG) during this motion were analyzed. Compared with the controls, patients showed statistically significant differences in fluctuations in the eCOG repositioning and horizontal components of force ratios (t-test, p0.05). We propose a comparative assessment of balance attainment during the landing phase of a jump. We indicate the possibility of efficient detection of ACL injuries. In summary, horizontal ground reaction forces and eCOG positioning can be used to evaluate the performance of the human biomechanical system during the jump-down phase.

    Keywords: Ground reaction forces; Body mass center repositioning; ACLR; Motion analysis

  • Peter Kucsera ,
    Zsolt Béres :

    Abstract: In this article the AGC (Automated Gauge Control) system, of a hot rolling mill is analyzed and different methods are described to improve its performance. The mill stretch compensation and other disturbances during the rolling process are compensated and a rolling speed dependent, adaptive PI controller is developed to accomplish fine thickness control. The improved system has been validated by measurements. Future improvement options are also analyzed, like eccentricity compensation, and predictive control of thickness.

    Keywords: Hot rolling mill; AGC; Automatic Gauge Control; HGC; Hydraulic Gap Control; Mill stretch compensation; Roll eccentricity compensation; Thickness control; Adaptive; Predictive control

  • Miroslav Milovanović ,
    Dragan Antić ,
    Miodrag Spasić ,
    Saša S. Nikolić ,
    Staniša Perić ,
    Marko Milojković :

    Abstract: This paper proposes a method for improving the DC motor velocity estimations and the estimations obtained from the state observer, when the system operates with large moments of inertia. First, the state observer for estimating velocity and DC motor position, is designed. Then, the variable structure controller is formed using estimated position and velocity values. State observer and designed controller are implemented in default system control logic. Dependences between estimated velocities and moments of inertia are established and presented by experimental results. It is noted that velocity time responses of the designed controller are not as expected when the system operates with large moments of inertia on the motor shaft. The feedforward neural network is empirically designed and implemented in control logic with purpose to solve poor velocity estimations and to improve overall system performances. It is experimentally shown that an artificial network improves estimation quality of the observer and overall control of the system for different input signals.

    Keywords: variable structure controller; neural network; state observer; servo system; DC motor; moment of inertia

  • Read Basbous ,
    Benedek Nagy :
    Strategies to Fast Evaluation of Tree Networksen [951.59 kB - PDF]EPA-02461-00060-0080

    Abstract: Special tree graphs could model Cognitive Infocommunication Networks. The various modalities of the network are represented by various types of vertices, e.g., additions, multiplications. Tree graphs/networks are widely used in several other theoretical and practical fields. Expression trees are well-known tools to visualize the syntactic structure of the expressions. They are helpful also in evaluations, e.g., decision trees are widely used. Games and game theory form an important field in Artificial Intelligence and it has several connections to Optimization, Business and Economy. Game trees are used to represent games. In this paper, certain types of tree networks are considered using various operations at their inner vertices, e.g., multiplication, (constrained) addition and the usual minimum and maximum (related to conjunction and disjunction of Boolean algebra). Evaluation techniques are presented, as well as, various pruning algorithms (related to short circuit evaluation in the Boolean case) that can quicken the evaluation in most cases. Based on the commutativity of the used operations, the evaluations can be more effective (faster) by reordering the branches of the tree. The presented techniques are useful to optimize (minimize) the size of the tree networks in various cases without affecting the final result/decision of the network.

    Keywords: expression trees; game trees; short circuit evaluation; pruning of trees; decision making; reordered trees

  • Dalibor Fiala ,
    Gabriel Tutoky ,
    Peter Koncz ,
    Ján Paralič :

    Abstract: In this paper we show that assigning weights to the edges in a collaboration network of authors, according to a decreasing exponential function depending on the time elapsed since the publication of a common paper, may add valuable information to the process of ranking authors based on importance. The main idea is that a recent collaboration represents a stronger tie between the co-authors than an older one and, therefore, reduces the weight of potential citations between the co-authors. We test this approach, on a well-known data set and with an established methodology of using PageRank-based ranking techniques and reference sets of awarded authors and demonstrate that edge ageing may improve the ranking of authors.

    Keywords: collaborations; citations; PageRank; scholars; rankings

  • Mustafa Tuncay Saritaş :

    Abstract: With the rapid development and increase in Internet speed in network technology, communication and interaction with others, even with objects, as well as sharing and creation of knowledge is supported and facilitated more effectively than ever before. The characteristics of society are in an incessant change towards a more social, networked, and connected one. The education sector is also in a constant state of evolution, naturally as a result of emerging technologies and theories. Based on this fact, educational institutions, inevitably, have to transform their existing frameworks to promote learning and teaching in the 21st Century. This paper introduces background and fundamentals about emerging technology paradigms – Cloud Computing (CC) and Internet of Things (IoT), and an emerging learning theory – Connectivism. The relationships between these three are investigated to provide insights and raise awareness on their rich potentials for and impacts on learning experiences.

    Keywords: Cloud computing; connectivism; Internet of Things; education; learning

  • Tamás Vinkó ,
    David Hales :
    Towards the Coevolution of Incentives in BitTorrent181-199en [1.59 MB - PDF]EPA-02461-00060-0110

    Abstract: BitTorrent is a peer-to-peer file sharing system that is open to variant behavior at the peer level through modification of the client software. A number of different variants have been released and proposed. Some are successful and become widely used whereas others remain in a small minority or are not used at all. In previous work we explored the performance of a large set of client variants over a number of dimensions by applying Axelrod’s round-robin pairwise tournament approach. However, this approach does not capture the dynamics of client change over time within pairwise tournaments. In this work we extend the tournament approach to include a limited evolutionary step, within the pairwise tournaments, in which peers copy their opponents strategy (client variant) if it outperforms their own and also spontaneously change to the opponents strategy with a low mutation probability. We apply a number of different evolutionary algorithms and compare them with the previous non-evolutionary tournament results. We find that in most cases cooperative (sharing) strategies outperformed free riding strategies. These results are comparable to those previously obtained using the round-robin approach without evolution. We selected this limited form of evolution as a step towards understanding the full coevolutionary dynamics that would result from evolution between a large space of client variants in a shared population rather than just pairs of variants. We conclude with a discussion on how such future work might proceed.

    Keywords: peer-to-peer; BitTorrent; selection rules; design space analysis

  • Corina Daniela Cunţan ,
    Ioan Baciu ,
    Mihaela Osaci :

    Abstract: The paper analyses the operation of a single phase – three phase frequency converter, built with insulated-gate bipolar transistors (IGBT). The bridge inverter control is made via the Basys 2 development board which generates voltages, at the output terminals, compatible with the logic levels of complementary metal–oxide–semiconductor (CMOS) circuits. The diagram for obtaining the control pulses is realized with Xilinx software that allows changing the output frequency to a value of 1 KHz. The analysis of converter operation shall be made using either a resistive load or an inductive load. The installation model presented in the paper highlights the operation modality and the study possibility, by experiments at various frequencies and load circuits. By analyzing the waveforms obtained in various points of the circuit diagram, it results the possibility to improve certain operating parameters over others, according to the user requirements and the regulations in force for a harmonic regime.

    Keywords: frequency converter; galvanic separation circuit; pulse sequence; development board; circuit switching; DC/AC power convertors

  • S. Bharathi ,
    R. Sudhakar ,
    Valentina E. Balas :
    Hand Vein based Multimodal Biometric Recognition213-229en [709.86 kB - PDF]EPA-02461-00060-0130

    Abstract: Multi-modal biometric recognition utilizes more than one modality for recognition of a person, when compared to the single modality with the help of enhanced security. The vascular patterns are one of the physiological biometrics and internal feature of the body, hence, it cannot be easily cracked, falsified or spoofed. This paper proposes a novel approach for biometric recognition, using finger vein, palm vein and dorsal vein of the hand. Our proposed method utilizes both the Shearlet transform and Scale-invariant feature transform to extract features from the hand vein images. The extracted features in the form of coefficients are stored in the data base. Then the matching is done between the coefficients of the input test images and the features stored in the data base using distance measure and finally the fusion is carried out using the maximum likelihood ratio technique. This approach was tested on standard data bases of finger vein, palm vein and dorsal vein images of hands. The proposed method provides a maximum accuracy of 94%, with a reduction in false acceptance and false rejection rates, illustrating the efficiency of the technique compared to other current methods.

    Keywords: hand vein; shearlet transform; scale-invariant feature transform; multi-modal biometric recognition; maximum likelihood-based fusion

  • András Szűts :

    Abstract: Currently, energy efficiency and energy security are among the most important energy issues that face Hungary and the European Union. Since households are responsible for one third of the primary energy consumption, we believe that significant results can be achieved in this area. According to our research, the typical design methods currently utilized are not entirely suitable to achieve the stated energy goals, since the goal of these methods is not to search and design an energetically optimal solution, but rather to comply with target values stipulated by law. Therefore, in order to increase the energy efficiency of the design of the buildings, we have developed a complex decision support model that enables in the conceptual design phase to effectively evaluate the emerging alternatives, taking into consideration both convenience and economy, as well as various subjective elements. This article presents a methodology developed through examples of four typical family homes in Hungary.

    Keywords: analytic hierarchy process; energy; households; property investments; net present value