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Acta polytechnica HungaricaVolume 12, Issue No. 8. (2015.)


  • Csaba Hegedűs J. :
    Reorthogonalization Methods Revisiteden [255.87 kB - PDF]EPA-02461-00062-0010

    Abstract: New theoretical background of Parlett-Kahan’s ”twice is enough” algorithm for computing accurate vectors in Gram-Schmidt orthogonalization is given. An unorthodox type of error analysis is applied by considering lost digits in cancellation. The resulting proof is simple and that makes it possible to calculate the number of accurate digits after all reorthogonalization steps. Self improving nature of projection matrices is found giving a possible explanation for the stability of some ABS methods. The numerical tests demonstrate the validity and applicability of the theoretical results for the CGS, MGS and rank revealing QR algorithms.

    Keywords: twice is enough, Gram-Schmidt with reorthogonalization, self-improving nature of projections, ABS methods, rank-revealing QR.

  • Ondrej Kassak ,
    Michal Kompan ,
    Maria Bielikova :

    Abstract: In this paper we propose a novel user model for personalized recommendation in domains, where items are described by multiple characteristics (e.g., metadata attributes) and users’ preferences are expressed on the level of items by some kind of explicit feedback (e.g., rating) or derived from implicit user feedback (e.g., time spent on items). The proposed user model is composed of two parts. The first one represents user preferences by items descriptive metadata (e.g., genres, keywords, actors and directors in movie domain used as an example in this paper) expressed as preference vectors. The second part is represented by a vector describing user’s preferences on previously rated items. Our main contribution is the addition of individual user preference measures to the vectors of both user model parts. User preferences expressed as the vector weights are calculated based on the global preference of large amount of users and also on individual variations in preferences of particular users to the average of the whole set of users. The weights reflect how much the different types of information are important to the user. We evaluated the proposed user model in movie domain through collaborative recommendation by comparing its performance to two reference user models using Movielens 10 M dataset.

    Keywords: user model; weighted vector; user similarity; personalized recommendation; multimedia domain; movie recommendation

  • Nemanja Maček ,
    Borislav Đorđević ,
    Jelena Gavrilović ,
    Komlen Lalović :
    An Approach to Robust Biometric Key Generation System Design43-60en [335.73 kB - PDF]EPA-02461-00062-0030

    Abstract: This paper presents a novel approach to the design of robust multimodal biometric cryptosystems. The design objectives behind the system are robustness, privacy of user’s biometric templates and stable cryptographic key generation. The framework presented in this paper employs two modalities and a look-up table. The hashes of cryptographic keys generated from a biometric template during the enrollment phase are stored in the look-up table with cancelable templates generated from the sample belonging to different modality of the same subject. During the operation phase, the system releases the key, only if the hash of the key generated from the provided biometric sample is found in the look-up table, and the similarity score between corresponding cancelable templates is less than a predefined threshold. The implementation of the proposed framework with iris and fingerprint biometrics is evaluated with the CASIA biometric template database.

    Keywords: biometry; multimodal; cryptography; key generation; robustness

  • Xin Chen ,
    Nao-Aki Noda ,
    Magd Abdel Wahab ,
    Yu-Ichiro Akaishi ,
    Yoshikazu Sano ,
    Yasushi Takase ,
    Gusztáv Fekete :

    Abstract: In this paper, fatigue failure is considered, for bolt-nut connections, when a slight pitch difference is introduced between the bolt and the nut. To improve the fatigue life, three types of pitch difference are produced on the specimens and the experimental results are compared and discussed in terms of FEM analysis. Considering the standard bolt-nut connection of α=0 μm, the bolt fracture does not happen at the No. 1 thread by introducing a slight pitch difference of α=5 μm and α=15 μm, as observed from the experiments. Furthermore, it is found that the fatigue life can be extended by introducing suitable pitch differences. The effect of bolt-nut fitted clearance, on the fatigue failure is also investigated.

    Keywords: Bolt-Nut Connection; Fatigue Fracture; Pitch Difference; Finite Element Method; Fitting Clearance

  • Zsolt Szántó ,
    Richárd Farkas :
    Constituency Parse Reranking for Morphologically Rich Languages81-94en [279.34 kB - PDF]EPA-02461-00062-0050

    Abstract: In this article we introduce a constituent parsing system which can achieve stateof-the-art results on morphologically rich languages. Our system consists of a Probabilistic Context Free Grammars (PCFG) and n best reranking steps. We compare two methods to handle lexical sparsity in a PCFG parser. The n best reranking step, the discriminative reranker extracts large amount of features from n best parses of the PCFG parser and selects the best tree from these parses. We introduce three feature templates which extend the standard feature set of rerankers. We propose to extract features from Brown clustering – which is a context-based clustering over the words – and analyze the effect of dependency-based and morphology-based feature templates. The effects of these techniques are evaluated on datasets of eight morphologically rich languages.

    Keywords: syntactic parsing; constituent parsing; morphologically rich languages; lexical sparsity; Brown clustering

  • Árpád Takács ,
    Levente Kovács ,
    Imre Rudas J. ,
    Radu-Emil Precup ,
    Tamás Haidegger :
    Models for Force Control in Telesurgical Robot Systems95-114en [221.74 kB - PDF]EPA-02461-00062-0060

    Abstract: Surgical robotics is one of the most rapidly developing fields within robotics. Besides general motion control issues, control engineers often find it challenging to design robotic telesurgery systems, as these have to deal with complex environmental constrains. The unique behavior of soft tissues requires special approaches in both robot control and system modeling in the case of robotic tissue manipulation. Precise control depends on the appropriate modeling of the interaction between the manipulated tissues and the instruments held by the robotic arm, frequently referred to as the tool–tissue interaction. Due to the nature of the physiological environment, the mechatronics of the systems and the time delays, it is difficult to introduce a universal model or a general modeling approach. This paper gives an overview of the emerging problems in the design and modeling of telesurgical systems, analyzing each component, and introducing the most widely employed models. The arising control problems are reviewed in the frames of master–slave type teleoperation, proposing a novel soft tissue model and providing an overview of the possible control approaches.

    Keywords: surgical robotics; force control; tissue modeling; teleoperation; time delay control

  • Aleksandar M. Dejanović ,
    Slavka T. Nikolić ,
    Jelena Stanković :

    Abstract: The main goal of this study is the construction of an integral model of strategic management, based on the comparative analysis among many well-established management concepts. It was found that new product development, total quality management (TQM), brand management and customer relationship management (CRM) share common characteristics such as strategic dimension, corporate culture dimension, customer focus, etc. Thus, the object of this paper refers to the potential of connection of these managerial concepts into a single Integral model of strategic management together with a measuring system based on Balanced Scorecard (BSC). After the relevant literature review and theoretical constructs on a conceptual level, the model has been tested in practice. The experiment has proved that the Integral model of strategic management is applicable and it positively impacts on a company's performance.

    Keywords: Integral Model of Strategic Management; New Product Development; Total Quality Management; Brand Management; Customer Relationship Management

  • Henrietta Finna ,
    János Erdei :

    Abstract: Due to the increasing expansion in higher education and the boom in the number of students, new challenges of employment have emerged. In the labor-market, different tendencies of fresh graduates can be highlighted, so it is essential to identify which success factors of the labor-market are relevant to the different training fields. A certain group of former BME students was chosen as a sample group and special variables, which can appear as important attributes of entering the labor-market, gender and field of studies were applied. We based our analysis on the BME career tracking survey that had been taken for 10 years among the graduates, with the purpose of examining main influencing factors of entering the labor-market and the correlation between these factors and further variances of qualification. We can declare that there are significant differences between the different fields of studies. Thus, in the center of our research is the detailed examination of the relationship between the factors of course duration and employment in the acquired professions in relation to the faculties. Despite the results of our correspondence maps painting a rosy picture of the situation for the recent graduates, due to the differences between the faculties, several tasks related to the qualitative aspects of the labor-market demand emerge for the higher education institutions and the students.

    Keywords: engineering; recent graduates; qualification; labor-market indicators; correspondence map

  • Essia Ben Alaia ,
    Imen Harbaoui Dridi ,
    Hanen Bouchriha ,
    Pierre Borne :

    Abstract: In this paper, multi-vehicles, multi-depots pick-up and delivery problems with time windows (m-MDPDPTW) is presented as a multi-criteria optimization problem. The m-MDPDPTW is a variant of pick-up and delivery problem (PDP) and a challenging problem in the field of vehicle routing problem (VRP). The aim is to discover a set of satisfying solutions (routes) minimizing total travel distance, total tardiness time and the total number of vehicles. These routes satisfy transportation requests without contravening any of the instance specific constraints (precedence, capacity and time window constraints). In our problem each request is transported by one of the vehicles between paired pick-up and delivery locations. Such that, the depot does not retain the goods. In this paper, we assume that all vehicles have the same capacity and depart from and return to the same depot. The new encoding and structure algorithm on which this contribution is based uses a genetic algorithm, a selection process using ranking with several Pareto fronts and an elitist selection strategy for replacement. An improved encoding chromosome path representation is given to simulate the process of evolution using several types of populations in different sizes. The performance of the new algorithm is tested on data sets instances of Li & Lim's PDPTW benchmark problems. The results indicate that the proposed algorithm gives good results.

    Keywords: multi-depots pick-up and delivery problem with time window; genetic algorithm; Pareto dominance; multi-objective optimization

  • Andrea Bencsik ,
    Timea Juhasz ,
    Renata Machova ,
    Zsuzsanna Toth :

    Abstract: Hungarian organizations have to solve a lot of problems when their female employees take maternity leave and mothers may stay at home, with their child, for up to three years. During this long period of time, organizations have to organize her substitute, and, more importantly, they also have to insure that her knowledge stays relevant to the organization. Empirical research was conducted last year, concerning the knowledge management processes applied, when a member of the organization goes on maternity leave. Research questions: What can the employer and the employee do in this situation to make the knowledge transfer processes optimal? Also, do both sides feel this knowledge transfer is in their best interest? It is important because preserving knowledge is vital for a company in this special situation. The current article examines these critical questions from the point of view of employers and employees alike. The authors studied whether the career opportunities and the position of employees influence the success of knowledge transfer and whether employers expect special knowledge from their employees. The research was conducted in 2013-2014 in the form of a qualitative and quantitative survey. The results showed that, regarding women on maternity leave, the knowledge transfer conducted, during their materity leave, was not affected by their position and career prospects at the organization; similarly, the process was not significantly influenced by whether the organizations expected specialized knowledge from their employees or not.

    Keywords: knowledge management; maternity leave; motherhood; knowledge transfer; Hungarian practice; labor market

  • Éva Orbán-Mihálykó ,
    László Koltay ,
    Ferenc Szabó ,
    Péter Csuti ,
    Renáta Kéri ,
    János Schanda :

    Abstract: A new method of ranking different light stimuli based on subjective points of view is presented. The objects are pairwise compared and ranked on the basis of the judgments of the observers. More than two options for judgment are allowed. Observers’ perceptions are considered as random variables. The differences between the sensations are supposed to be independent, identically distributed random variables with Gauss distribution and equal standard deviations. On the basis of the judgments of the observers the expectations of the random variables are estimated by maximum likelihood method and the maximizations are carried out numerically. Computations were performed by the statistical program package R. The rank of the expectations is considered to be the rank of the observers’ perception under the test light stimuli. Equalities of the expectations are tested by likelihood ratio tests. The results are compared to the results derived by the AHP method. Finally, some results in connection with the investigated questions are presented.

    Keywords: color quality; LED; lights; ranking; pairwise comparison; statistical evaluation; Thurstone method; AHP

  • Regina Reicher ,
    Nándor Komáromi ,
    Ágnes Szeghegyi :

    Abstract: The information technology projects within companies often end with failure. It may be due to various reasons, but the human factor almost always can be blamed. The organizations, as groups or staff communities, frequently resist change and the introduction of CRM systems can lead to significant corporate changes. A smaller team should participate in the selection and implementation of a CRM IT system. Our research focuses on the competencies required in the course of an implementation and the impact they may have on the decisions, within the process. We tried to explore the possible correlation, with the “index of success”, if the stakeholders in the implementation can be arranged in well-defined segments, on the basis of specific factors. According to our results, the pairing specific factors can lead to a more successful project implementation and it is worth priority consideration, as the main factors when setting up the team.

    Keywords: CRM implementation; CRM selection; factors affecting successful implementation; SME

  • Zoltán Juvancz ,
    Edina Garai ,
    Lóránt Szabó ,
    Rita Boda-Kendrovics ,
    Gabriella Köteles-Suszter :

    Abstract: The problem of the persistent organic pollutants (POP) is an important part of the education program of Environmental Studies. The literature data refer several unwanted side effects of the intensive use of DDT. On the other hand the widely spread malaria epidemic infection makes the use of DDT necessary even today. The occurrence of DDT and its metabolites is a good representative of the persistency of such pollutants in the human breast milk. The samples were donated by university students and young teachers. This way the students could get personal involvement of the topic and measurements. The conventional and QuEChERS sample treatments were applied and their effectiveness were compared. GC-ECD instrumental analyses were used with parallel columns to demonstrate the selectivity and sensitivity of the required analysis. The results demonstrate the presence of DDE traces in breast milk of the majority of Hungarian mothers, even after the agricultural use of DDT was banned in 1968. No fresh DDT pollution was recognized in the tested samples. Correlations were established among the DDE contents of the breast milk samples and the ages and weights of the tested mothers. The measurements also show the persistency and biomagnificational feature of DDT. The educational aspects of each step of the applied procedures are emphasized in this paper. The analytical processes allow a deep insight for the environmental analysis for environmental engineering students. These offer a manual and theoretical practice with real samples, for improving the environmental attitudes

    Keywords: DDT and its metabolites; human breast milk; education of features of POPs