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Acta polytechnica HungaricaVolume 9, Issue No. 2 (2012.)


  • Endre Pap ,
    Vivona Doretta :
    Basic Equations of Fluid Dynamics Treated by Pseudo-Analysis5-23en [151.46 kB - PDF]EPA-02461-00034-0010

    Abstract: There is given an application of pseudo-analysis in the the- ory of uid mechanics. First, the monotonicity of the components of the velocity for the solutions of Euler equations is proven, which allows to obtain the pseudo-linear superposition principle for Euler equations. This principle is proven also for the Navier-Stokes equations but with respect to two dif- ferent pairs of pseudo-operations. It is shown that Stokes equations satisfy the pseudo-linear superposition principle with respect to a pair of pseudo- operations which are generated with the same function of one variable.

    Keywords: Fluid mechanics, Euler equations, Navier-Stokes equations, Stokes equations, pseudo-linear superposition principle, semiring.

  • Kun Ma ,
    Bo Yang ,
    Ajith Abraham :

    Abstract: Software-as-a-Service (SaaS) and Model-Driven Engineering (MDE) are two of the most dominant software engineering paradigms nowadays. Multi-tenancy is the key to successful SaaS. In this paper, we introduce a data middleware to customize the multi-tenant database first. In addition, with the help of model transformation, it is possible to generate SaaS applications from the models. However, most of the current model transformation approaches do not fully support the requirements for model synchronization, and they do not cater for the specific problems faced in the multi-tenancy. Therefore, an effective and simple template-based model transformation and model synchronization approach based on model evolution of MDE paradigms is fully integrated for the development of SaaS multi-tenant applications. The proposed framework uses a novel extensible business component model (xBC) to sufficiently describe both the structural and behavioral properties of SaaS applications. The distribution and uninterrupted running of the generated SaaS applications proves that our approach is feasible and correct in practice.

    Keywords: Software-as-a-Service; multi-tenancy; textual template evolution; model transformation; model synchronization

  • Imre Norbert Orbulov ,
    János Ginsztler :
    Compressive Behaviour of Metal Matrix Syntactic Foams43-56en [669.74 kB - PDF]EPA-02461-00034-0030

    Abstract: The compressive behaviour of three different metal matrix syntactic foams (MMSFs) was investigated. The results showed that the engineering factors such as the size of the used hollow spheres, the aspect ratio (height / diameter ratio) of the specimens and the temperature of the tests have significant effects on the compressive strength and properties. The smaller microballoons with thinner wall ensured higher compressive strength due to their more flawless microstructure and better mechanical stability. The higher aspect ratio of the specimens resulted in worse compressive characteristics (lower strength, lower specific energy consuming capacity). The elevated temperature tests revealed ~30% drop in the compressive strength. However, the strength remained high enough for structural applications; therefore MMSFs are good choices for light structural parts working at elevated or room temperature. The proper size selection of the reinforcing hollow spheres ensures potential for tailoring the compressive characteristics of MMSFs.

    Keywords: metal matrix composite; syntactic foams; metallic foams; compressive properties

  • Radu-Emil Precup ,
    Marius-Lucian Tomescu ,
    Emil M. Petriu ,
    Stefan Preitl ,
    Claudia-Adina Dragoş :

    Abstract: This paper presents a new stability analysis approach dedicated to a class of nonlinear discrete-time multi input-multi output (MIMO) Takagi-Sugeno fuzzy control systems (FCSs). The theorem presented in this paper offers sufficient conditions for the global stability of the FCSs. The applicability of the theoretical results is illustrated by the stable design of Takagi-Sugeno fuzzy controllers for the level control of spherical three tank systems as nonlinear MIMO processes. Digital simulation results are included.

    Keywords: eigenvalues; MIMO fuzzy control systems; stability analysis; Takagi-Sugeno fuzzy controllers; three tank systems

  • János Fülöp ,
    Rita Markovits-Somogyi :

    Abstract: Ever since the birth of data envelopment analysis (DEA) the question of ranking the decision making units (DMUs) has been one of the focal points of research in the area. Among several other approaches, promising attempts have been made to marry DEA with the analytic hierarchy process (AHP) method. Keeping the idea of using DEA-based pairwise comparisons between the DMUs, as proposed in some DEA-AHP variants published in the literature, a new method is presented for combining DEA with techniques for eliciting weights from pairwise comparison matrices. The basic idea is to apply a variant of the CCR problem instead of the classic one. The ensuing scores are then utilized to build a nonreciprocal pairwise comparison matrix which serves as the basis for eliciting the ranking values of the DMUs. The main advantage of this new method is the wider range of the resulting ranking values which subsequently leads to better distinction between the DMUs. Besides the eigenvector method, optimization based methods are also considered for eliciting the ranking values from the nonreciprocal pairwise comparison matrix. Numerical examples are supplied for comparing the proposed techniques.

    Keywords: data envelopment analysis; ranking decision making units; pairwise comparisons; techniques for eliciting weights

  • Zlatko Čović ,
    Miodrag Ivković ,
    Biljana Radulović :

    Abstract: This paper describes several approaches in the development of mobile web sites, including the concept of detection and adaptation for mobile content. A mobile site lacking optimization can lead to prolonged downloading of data as well as difficulties with browsing. For that reason, we need to optimize web content on such sites. Our research was conducted to determine the most adequate and most effective detection technique. This technique was then used in the development of the Mobile Detection Algorithm Based on Tera-Wurfl (MDABTW). The MDABTW algorithm is based on the Tera-Wurfl library and allows for the generation of web content in several markup languages. The basic principles of how this algorithm works are described in this paper. The MDABTW algorithm was further implemented in the regional mobile CMS, called Mobko, which is the main part of an integrated health IS providing counseling and education services for youth in the Subotica region.

    Keywords: mobile web sites; mobile device detection; content adaptation; mobile algorithm

  • Krisztián Balázs ,
    Zoltán Horváth ,
    László T. Kóczy :

    Abstract: This paper proposes approaches for adapting chromosome-based evolutionary methods to the Permutation Flow Shop Problem. Two types of individual representation (i.e. encoding methods) are proposed, which are applied on three different chromosome based evolutionary techniques, namely the Genetic Algorithm, the Bacterial Evolutionary Algorithm and the Particle Swarm Optimization method. Both representations are applied on the two former methods, whereas one of them is used for the latter optimization technique. Each mentioned algorithm is involved without and with local search steps as one of its evolutionary operators. Since the evolutionary operators of each technique are established according to the applied representation, this paper deals with a total number of ten different chromosome-based evolutionary methods. The obtained techniques are evaluated via simulation runs carried out on the well-known Taillard's benchmark problem set. Based on the experimental results the approaches for adapting chromosome based evolutionary methods are compared to each other.

    Keywords: Chromosome-based evolutionary methods; Memetic algorithms; Combinatorial optimization; Permutation Flow Shop Problem

  • M’hamed Beriache ,
    Hassan Naji ,
    Ahmed Bettahar ,
    Leila Mokhtar Saidia :

    Abstract: This research work presents a numerical simulation of the CPU (Central Processor Unit) heat sink with a parallel plate fin and impingement air cooling. The governing equations are discretized by using the finite difference technique. The objective of this article is to investigate the thermal and hydraulic performances of a heat sink with impinging air flow to evaluate the possibility of improving heat sink performances. The numerical simulations are done by a personal C++ developed code. The thermal and hydraulic characterization of a heat sink under air-forced convection cooling condition is studied. The hydraulic and thermal parameters, including velocity profiles, the distribution of static pressure, pressure drop and temperature distributions through the fins, the base heat sink and the heat sink body through the heat sink are analyzed and presented schematically. The results show that the heat transferred by the heat sink increases with impinging Reynolds number. The performance of the proposed model computed by the numerical calculation is high compared with literature results.

    Keywords: electronics cooling; heat sink; air flow; impingement jet; thermal resistance; pressure drop

  • András Urbán ,
    Mihály Ormos :
    Performance Analysis of Equally weighted Portfolios: USA and Hungary155-168en [665.27 kB - PDF]EPA-02461-00034-0090

    Abstract: Investigating U.S. equally weighted portfolios, one can measure positive abnormal returns (Jensen alphas) according to the classical equilibrium models. Applying the Carhart four-factor model, we show that excess returns generated by the equally weighted multi-period investment strategy are neither caused by the small-firm effect, nor by the book-to-market equity, nor even by persistence. We document that this phenomenon cannot be observed in the Hungarian stock market, where the equally weighted rebalancing strategy neither achieves significant abnormal return, nor outperforms the value weighted index in terms of mean return. This latter result suggests that, from this point of view, the Hungarian capital market exhibits a higher level of efficiency than its US counterpart.

    Keywords: equally weighted portfolio, performance measure, market efficiency

  • Ebrahim Zolgharnein ,
    Vagif M. Mirsalimov :
    Nucleation of a Crack under Inner Compression of Cylindrical Bodies169-183en [425.11 kB - PDF]EPA-02461-00034-0100

    Abstract: The problem of fracture mechanics of crack nucleation in plunger pair bushing is considered. It is assumed that under the repeated reciprocating motion of a plunger there happens crack nucleation and a failure of materials of pair elements. Crack nucleuses are simulated by a bridged prefracture zone that is considered as areas of weakened interparticle bonds of the material. It is assumed that the inner boundary of the bushing is close to the annular one and has rough surfaces.

    Keywords: contact pair; nucleation of a crack; bonds between surfaces; prefracture zone; cohesive forces; rough surfaces

  • Klára Wenzel ,
    Krisztián Samu :
    Pseudo-Isochromatic Plates to Measure Colour Discrimination185-195en [644.16 kB - PDF]EPA-02461-00034-0110

    Abstract: We have developed 3 series of pseudoisochromatic plates for colour vision testing. The plates are arranged in order of increasing difficulty. In the first (red/green) series, a red Landolt C is shown in front of a green background. This series is used to determine the severity of colour vision deficiency. In the second series, colours are located on the protan confusion line, whereas in the third series, on the deutan confusion line. The plates were printed by a calibrated colour printer, then bound in a book. The plates were used to test 320 persons with colour vision deficiency and 20 ones with normal colour vision. Our results showed a 96.25% efficiency in separating colour anomals and colour normals as verified by an anomaloscope. The test book gives prompt results and it is fun to use. A test takes about 5 minutes so it is suitable for mass tests and moreover, it may also be used to test the colour vision of children.

    Keywords: colour vision deficiency; anomaloscope; ishihara test; D15 test

  • Ivan Michalec ,
    Milan Marônek :

    Abstract: Steel sheets treated by nitrooxidation in comparison to material without surface treatment are characterized by increased mechanical properties and enhanced corrosion resistance. The paper deals with the comparison of solid-state laser beam welding and plasma arc welding in order to reduce the high initial costs of laser beam equipment and to find an adequate counterpart from the arc welding sphere. Results prove solid-state laser beam welding is the most suitable welding method for welding of this type of treated steels, although plasma arc welding, especially after parameters optimizing, can be an adequate alternative to laser beam welding.

    Keywords: nitrooxidation; plasma arc welding; laser beam welding

  • Merouane Mekkakia Maaza ,
    Ahmed Arab ,
    Mostefa Belkhatir ,
    Saaed Hammoudi ,
    Minh Phong Luong ,
    Abdelatif Benaissa :
    Non-Linear Behavior of Sands under Longitudinal Resonance Testing209-220en [611.30 kB - PDF]EPA-02461-00034-0130

    Abstract: One of the fundamental features needed to evaluate soil response during earthquakes, is the study of controllable external variables that may affect the instability phenomena of granular materials under vibration, such as acceleration, frequency, the interaction of grains and their arrangements. Despite previous researches in this field, an understanding of these phenomena is still incomplete. A more accurate description of one of the phenomena that we will see, is how the resonance curve changies and how the jump occurs with the frequency change. For this purpose, a series of longitudinal resonance excitation laboratory tests were carried out on dry sandy soils with different grain size distributions (spread and tight) and different densities to identify the instability zone.This type of test may be assimilated to a system subjected to a forced excitation with damping. The test results confirm the existence of a non-linearity zone represented by a "jump" just after the resonance for tight-grained sand. Moreover, this study shows that the grains interact with the contact forces. Indeed, a slight local density increase induces more collisions and friction, and therefore more dissipation, creating a pressure drop that attracts the neighboring particles and finally a low damping.

    Keywords: sand; resonance; dynamic; vibration; non-linearity; frequency; velocity

  • Mihail Boiangiu ,
    Georgeta Boiangiu :
    On the Calculus of Centrifugal Moments for Plane Plates and Plane Bars221-230en [473.64 kB - PDF]EPA-02461-00034-0140

    Abstract: This paper is focused on the calculus of centrifugal moments for plane plates and bars, starting from the definition. General cases of plane plates and bars are studied. General formulae of calculus for centrifugal moments are established. These formulae are based on the positions of the mass centers of the rotation surfaces and rotation bodies generated by the bars and plates in rotation, respectively.

    Keywords: centrifugal moments; plane plate; plane bar

  • Kerem Par ,
    Oguz Tosun :

    Abstract: This paper presents a parallel implementation and performance analysis of a system for traffic sign recognition with digital map fusion on emerging multicore processors and graphics processing units (GPU). The system employs a particle filter based localization and map matching and template-based matching for sign recognition. In the proposed system, a GPS, odometer and camera are fused with digital map information. The system utilizes the depth sensor of a Kinect camera for the detection of signs and achieves high recognition rates for both day and night conditions. Tests were performed on real data captured in the vehicle environment comprising various road and lighting conditions. Test results show that speed increases of up to 75 times for localization and 35 times for sign recognition can be achieved on parallel GPU implementation over sequential counterparts. As those speedups comply with real-time performance requirements, high computational cost of using map topology information with large number of particles in localization implementation and template based matching for sign recognition is proven to be handled by emerging technologies. The system is unique since it is not limited to certain sign types; it can be used in both day and night conditions and utilizes a Kinect sensor to achieve a good price/performance.

    Keywords: traffic sign recognition; particle filter; Kinect; multicore; gpu computing