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Acta polytechnica HungaricaVolume 9, Issue No. 5 (2012.)


  • Gusztáv Fekete ,
    Patrick De Baets ,
    Magd Abdel Wahab ,
    Béla Csizmadia ,
    Gábor Katona ,
    Libardo V. Vanegas-Useche ,
    José Alfredo Solanilla :

    Abstract: The sliding-rolling ratio between the femoral and tibial condyles throughout the active functional arc of the knee (20-120º of flexion angle) is currently unknown. Since wear is the most determining lifetime factor of the current total knee replacements, the presence of sliding-rolling cannot be neglected. The reason lies in the fact that this phenomenon causes different material abrasion compared to pure sliding or rolling alone. Only a limited amount of studies have dealt with this question related to the condyles of the knee prostheses, most of them by means of experimental tests and only in the segment where the motion begins (0 to 20-30º). The primary aim of this paper is to investigate how the sliding-rolling ratio changes between the condyles of five different knee prostheses in the functional arc of the knee (20-120º) as a function of flexion angle. For the analysis, five prosthesis models with identical boundary conditions have been constituted and numerical simulations were carried out using the MSC.ADAMS program system. Beside the sliding-rolling ratio, the normal and friction force between the connecting surfaces has also been calculated as a function of flexion angle.

    Keywords: sliding-rolling ratio; contact forces; deep squat; knee prostheses

  • Andrea Katic ,
    Ilija Cosic ,
    Goran Andelic ,
    Saąa Raletic :
    Review of Competitiveness Indices that Use Knowledge as a Criterion25-44en [421.63 kB - PDF]EPA-02461-00037-0020

    Abstract: Orientation towards a knowledge economy is visible in all development strategies of both the EU and Serbia. This article first shows the classification and systematization of the most relevant competitiveness indices, along with the participation assessment of components measuring the knowledge competitiveness within them. Secondly, the article examines and demonstrates the position of Serbia. The basic hypothesis confirmed in the article is that the position of Serbia, as a transition country, was not sufficiently analyzed, especially in terms of knowledge indicators. This developed a second hypothesis, also confirmed in this article, that the existing indicator models are not adequate for transition countries such as Serbia, and that there is a need for setting up a new revised model.

    Keywords: competitiveness indices; knowledge society; knowledge as a criterion for competitiveness; Serbia

  • Péter Várlaki ,
    Imre J. Rudas :

    Abstract: Part IV of our paper on the historical (archetypal) background of the ―fine structure constant‖ deals with the general physical and psychic world views, concealing the dynamic isomorphic meaning systems, related to Saint Stephen (Sephanus Rex) found in works of 1000 years old. Following the comparison of the representations (pre-figurations of the dynamic models) of the demonstrated background languages, we present that the author devoted himself to create a common background language of different religious courses. We intend to show that the background language (considered in general as a mapping of primordial images for ―system and control‖ problems), was centred on his assumed proto-Cabbala, the Book of Bahir and its concealed meaning system, in close relation with the numeric archetype of 137 and the 137-type of ―fine structures‖ within the decimal sephirotic world ―controlling system‖ of the pleroma (the hypothesised ―transcendent cyber space‖).

    Keywords: Number archetype137; Fine structure constant; King Stephanus

  • Tatiana Olejnikova :
    Double Layer Tensegrity Grids95-106en [1.10 MB - PDF]EPA-02461-00037-0040

    Abstract: This paper describes the geometry of a double layer tensegrity grids assembled of three or four strut prismatic cells. The elementary cells are self-equilibrated and so is their assembly. The paper shows the creation of a planar grids composed of elementary equilibrium and grids with single or double curvatures composed of modified equlibrium shapes.

    Keywords: tensegrity system; compression; tension; equilibrium; prismatic cell; grid structures

  • Masa Bukorov ,
    Sinisa Bikic ,
    Miljana Prica :
    The Efficiency Rate of a Steam-Water Injector107-126en [1.12 MB - PDF]EPA-02461-00037-0050

    Abstract: This paper analyses the influence of relevant parameters on the efficiency rate of a supersonic injector and its parts. Forced condensation in the injector is achieved by the mixing of cold water and steam with the goal of getting higher pressures of hot water (6-12 bar) with an outlet temperature of 70-80 C to enable distant transportation of hot water and heating. Although the energy potential of pressure is not significant compared to inlet energy of steam, it is of importance since it represents the potential to realize external work. The complex flow process through the mixing chamber, the most important part of the injector, is presented with a diagram of forced condensation energy change, flow and geometry changes of the mixing chamber and the distribution of the relevant forces on the borders of the mixing chamber. It is shown that higher efficiency rates are achieved if condensation is speeded up by the reduced mixing of cold water and steam. Analyses are done according to analytical laws and experimental investigations of a steam-water injector prototype, with the data enclosed. The efficiency rates of the mixing chamber ranges from 60 to 85%, depending upon the following: the injection coefficient, the inlet pressures and the temperatures of the cold water and steam (and the desired outlet hot water temperature and pressure). Investigations are mostly directed to the particular needs of energy and process devices and the significance of the Mach number was not especially emphasized in them.

    Keywords: steam-water injector; efficiency rate; supersonic steam-water injector; forced condensation

  • Krisztián Kósi :
    Method of Data Center Classifications127-137en [467.87 kB - PDF]EPA-02461-00037-0060

    Abstract: This paper is about the Classification of big data centers, based on top500.org’s data. The classification begins with data weighting and Multidimensional Scaling. Multidimensional Scaling produces 3D data. The clustering method, K-means, helps to classify the data. Nine different groups of data centers have been identified with appropriate parameters.

    Keywords: Multidimensional Scaling; MDS; K-means; C-means; Clustering; Petri Net; Classical Multidimensional Scaling; CMDS

  • Ali Kies ,
    Zoulikha Mekkakia Maaza ,
    Redouane Belbachir :

    Abstract: A connected dominating set (CDS) has been proposed as a virtual backbone for routing in wireless ad hoc networks. Ad hoc networks offer new routing paradigms. Therefore, the routing operation needs a broadcast algorithm. Broadcasting in an ad hoc network is still an open issue. The main focus here will be on optimizing the energy and the bandwidth utilization for packet diffusion.

    In this paper, we describe the Connected Dominating Set-Energy Protocol (CDSEP) for mobile ad hoc networks to optimize broadcast in the network. The key concept used in this protocol is a new distributed algorithm which computes the connected dominating set (CDS) based on node energy and node connectivity. In the CDSEP protocol, the CDS nodes are selected to forward broadcast packets during the flooding process, and the information flooded in the network through these CDS is also about the CDS. Thus, a second optimization is achieved by minimizing the contents of the control packets flooded in the network. Hence, only a small subset of links with the nodes is declared instead of all the links and the nodes. Our simulation experiment results demonstrate that the CDSEP responds well to scaling in terms of broadcast control packet and energy consumption.

    Keywords: ad hoc; self-organization; CDS; energy; routing

  • Aleą Hladnik ,
    Tadeja Muck ,
    Maja Stanic ,
    Marjeta Cernic :

    Abstract: The Fast Fourier transform was applied to demonstrate how to solve two related technological problems in the fields of papermaking and printing using ImageJ, a public domain Java image processing program. By converting a digital image of a multifunctional office paper surface from the spatial- into the frequency domain followed by an appropriate filtering, it was possible to identify and separate two different types of patterns – non-periodic structures such as formation, and periodic structures such as fabric marks. In addition, the moiré pattern, a negative phenomenon often occurring in printing, was eliminated to a large extent. The method proved to be a valuable tool in investigating and quantifying various paper and print quality-related phenomena.

    Keywords: image processing; Fast Fourier transform; fabric marks; paper formation; print quality; moiré

  • Daniel Tischler ,
    Marie Válová ,
    Ivo ©tepánek :

    Abstract: Due to very little depth of indent, the cyclic nanoindentation test is used for nondestructive testing of thin films of amorphous hydrogenated silicon carbide (a-SiC: H). We prepared the films, containing various volumes of hexamethyldisiloxane (0.6 g/h and 1 g/h), onto stainless steel substrates by Plasma Enhanced Chemical Vapor Deposition technique. In this paper, the mechanical properties, especially nanohardness, are assessed by the cyclic nanoindentation test. We found out that higher volumes of vapors of Hexamethyldisiloxane cause increases in the nanohardness and thickness of the prepared film.

    Keywords: cyclic nanoindentation; a-SiC: H thin film; hexamethyldisiloxane; PECVD

  • Pavol Semanco ,
    Vladimír Modrák :

    Abstract: We propose a constructive heuristic approach for the solution of the permutation flow-shop problem. The objective function of all algorithms is the minimization of the makespan. Our approach employs Johnson’s rule to give a good initial solution for the improvement heuristic, also known as metaheuristics. The proposed heuristic algorithm, named MOD, is tested against four other heuristics that are well-known from the open literature, namely, NEH, Palmer’s Slope Index, CDS and Gupta’s algorithm. The computational experiment itself contains 120 benchmark problem data sets proposed by Taillard. We compare our results to the solutions represented by NEH outputs. The computational experiment shows that the proposed algorithm is a feasible alternative for practical application when solving n-job and m-machine in flow-shop scheduling problems to give relatively good solutions in a short-time interval.

    Keywords: heuristic algorithm; NEH; Palmer’s Slope Index; CDS; Gupta’s algorithm; benchmark problem; flow shop

  • Dragan Mitic ,
    Aleksandar Lebl ,
    ®arko Markov :

    Abstract: The bandwidth of signaling channel with bursty errors can be larger or smaller than the bandwidth of channels with random errors. In this paper, we give the answer to the question: Is it possible in an easy way to determine the relationship between the bandwidths of these two models? First, we define the method that determines the bandwidth of the signaling CCS No7 channel under the influence of random errors, and then the method that determines the bandwidth of the signaling CCS No7 channel under the influence of bursty errors. The paper also gives the procedure, which easily compares the channel bandwidth for these two types of errors.

    Keywords: bandwidth of signaling CCS No7 channel; random errors; bursty errors; Jensen’s inequality