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Acta polytechnica HungaricaVolume 12, Issue No. 1. (2015.)


  • Vesna D. Jovanović ,
    Dragoslav B. Janošević ,
    Dragan Z. Marinković :

    Abstract: The paper presents a general selection procedure for an axial bearing of a slewing platform drive in hydraulic excavators based on the spectrum of equivalent bearing loads. A mathematical model of an excavator, with a backhoe and a shovel attachment, is defined to determine the spectrum of bearing loads on the basis of possible digging resistances specified in the entire working range of the excavator. As an example, by using the developed software, the size of an axial bearing was selected for a slewing platform drive in a hydraulic excavator with the mass of 100,000 kg, according to the spectrums of equivalent bearing loads obtained from the analysis of an excavator with a backhoe and shovel attachment.

    Keywords: axial bearing; hydraulic excavators; slewing platform

  • Alexander Hošovský :

    Abstract: Water temperature control of biomass-fired boilers represents a process with extreme delay which makes it quite difficult to stabilize it using conventional PID controller tuned according to commonly used PID tuning rules. It is proposed here to use a controller based on Varela-Countinho second generation immune network which was shown to have very good anti-delay capabilities. Since there are currently no tuning rules for this type of controller, simulated annealing algorithm is used for optimizing the set of controller parameters to achieve good performance according to IAE criterion. The resulting controller is shown to offer stable performance even for such a long time-delay which is also robust for up to 30% variations in system time constant compared to a nominal case.

    Keywords: B-cells; antibody; temperature; optimization; controller

  • Kalman Ziha :
    Stress-Strain Interaction Model of Plasticity41-54en [928.95 kB - PDF]EPA-02461-00055-0030

    Abstract: The article firstly investigates a discrete numerical model of finite interaction between successive microstructural bond failures and remaining intact internal bonds in materials. Secondly, it reveals the general linear finite continuous cause and effect interaction concept. The interaction model is examined numerically, experimentally and analytically on an illustrative case of a parallel system of bonds. The general concept is applied to the macroscopic stress-strain interaction model of material plasticity. Examples of metallic materials are elaborated on reported theoretical and experimental strain data.

    Keywords: yielding; necking; plasticity; tensile test; metals; interaction

  • Péter Tállai ,
    Sándor Csuka ,
    Sándor Sipos :
    Thread Forming Tools with Optimised Coatings55-66en [604.34 kB - PDF]EPA-02461-00055-0040

    Abstract: Different tool geometries have been developed by leading companies in the tool industry to different aims of application. The fastest progress can be observed in the development of coatings, in spite of this it can be noticed that there are only few coating types, but they can be used in a wide range. For users it offers the great advantage to select appropriate tool easier. Coating types, developed specially to individual aim of application, offer much better solution, compared to the generally used coating types. Platit AG, dealing with the development of optimised coating types, has requested our specialised group to carry out tests on specialised coating types. Our present study is going to summarise the results of the tests, carried out with thread forming tools.

    Keywords: thread forming; minimal quantity of lubrication; coating types; CrTiN; AlCrN; AlTiN

  • J. A. Tenreiro Machado ,
    Maria Eugénia Mata :

    Abstract: The last 40 years of the world economy are analyzed by means of computer visualization methods. Multidimensional scaling and the hierarchical clustering tree techniques are used. The current Western downturn in favor of Asian partners may still be reversed in the coming decades

    Keywords: Economic development; Multi-dimensional scaling; global hegemony

  • Liberios Vokorokos ,
    Anton Baláž ,
    Branislav Madoš :
    Application Security through Sandbox Virtualization83-101en [470.24 kB - PDF]EPA-02461-00055-0060

    Abstract: This article is aimed at the creation of a secure, virtualized system sandbox environment at the level of the respective applications. The proposed sandbox model allows us to generate a secure environment for various untrusted applications and resolve potential security incidents, such as zero day vulnerabilities. The resulting work is a functional sandbox within the MS Windows operating system, which protects the system against potentially hazardous applications. The sandbox has a minimal impact on the semantics and the time of the executed program and provides an efficient sandbox configuration interface.

    Keywords: system sandbox; operating system security; virtualization; security policy

  • Santhosh P. Mathew ,
    Valentina E. Balas ,
    Zachariah K. P. :
    A Content-based Image Retrieval System Based On Convex Hull Geometry103-116en [627.62 kB - PDF]EPA-02461-00055-0070

    Abstract: Developments in data storage technologies and image acquisition methods have led to the assemblage of large data banks. Management of these large chunks of data in an efficient manner is a challenge. Content-based Image Retrieval (CBIR) has emerged as a solution to tackle this problem. CBIR extracts images that match the query image from large image databases, based on the content. In this paper, a novel approach of comparing the convex hull geometry of the query image to that of the database image in terms of a relative metric which is denoted as the Convex Hull Area Ratio (CHAR) is used. The metric CHAR is the ratio of the area of the intersection of the two convex hulls to the area of their union. Convex hull shape polygon is extracted from the database images and the coordinate values are stored in the feature library. When a query image is given, the convex hull values are extracted in the same fashion. Ratio of the intersected area to union area of the two convex hulls (CHAR) are found and stored in an array. Subsequently, similarity measurement is performed and the maximum value of the CHAR indicates the closest match. Thus, the database images that are relevant to the given query image are retrieved. Scale and translational invariance have been preserved by a suitable co-ordinate transformation. The proposed CBIR technique is evaluated by querying different images and the retrieval efficiency is evaluated by determining precision-recall values for the retrieval results.

    Keywords: Image Retrieval; Shape Signature; Image Segmentation; Edge detection; Convex hull; Area ratio

  • Árpád Beszédes :
    Global Dynamic Slicing for the C Language117-136en [795.54 kB - PDF]EPA-02461-00055-0080

    Abstract: In dynamic program slicing, program subsets are computed that represent the set of dependences that occur for specific program executions and can be associated with a program point of interest called the slicing criterion. Traditionally, dynamic dependence graphs are used as a preprocessing step before the actual slices are computed, but this approach is not scalable. We follow the approach of processing the execution trace and, using local definition-use information, follow the dependence chains “on the fly” without actually building the dynamic dependence graph, but we retain specialized data structures. Here, we present in detail the practical modifications of our global dynamic slicing algorithm, which are needed to apply it to programs written in the C language.

    Keywords: program slicing; dynamic slicing; program analysis; program dependence; C

  • Mircea-Bogdan Radac ,
    Radu-Emil Precup ,
    Emil M. Petriu :

    Abstract: This paper proposes a data-driven Iterative Reference Input Tuning (IRIT) algorithm that solves a reference trajectory tracking problem viewed as an optimization problem subjected to control signal saturation constraints and to control signal rate constraints. The IRIT algorithm incorporates an experiment-based stochastic search algorithm formulated in an Iterative Learning Control (ILC) framework in order to combine the advantages of model-free data-driven control and of ILC. The reference input vector’s dimensionality is reduced by a linear parameterization. Two neural networks (NNs) trained in an ILC framework are employed to ensure a small number of experiments in the gradient estimation. The IRIT algorithm is validated by two case studies concerning the position control of a nonlinear aerodynamic system. The results prove that the IRIT algorithm offers the significant control system performance improvement by few iterations and experiments conducted on the real-world process. The paper successfully merges the use of ILC in both model-free reference input tuning and NN training.

    Keywords: constraints; Iterative Reference Input Tuning algorithm; linear parameterization; mechatronics; neural networks

  • Abstract: Accuracy of colour reproduction and colourfastness are the most significant parameters of the quality of printed fabrics in the textile industry. The aim of this paper is to gain deeper insights into the colour difference of textiles printed by ink jet method before and after light exposure. In order to accomplish this, 60 samples were printed, using four process colours (CMYK) on three textile materials with different characteristics (fabric weight and thread count). Additionally, number of ink layers varied (from 1 to 5 layers). Afterwards, printed samples were exposed to the light. The colour of the samples was measured using spectrophotometer before and after exposition to the light, colour difference was calculated and afterwards analysed. Colour difference analysis has shown the significant difference of colour fastness within samples that were printed with different number of ink layers and also between different textile materials.

    Keywords: ink jet printing; light exposure; colour difference

  • Mónika Bakos-Diószegi ,
    Miklós Horváth :
    Experiments with a Newly Developed Biogas Reactor Block175-188en [600.70 kB - PDF]EPA-02461-00055-0110

    Abstract: Increasing energy security can be found in the principal objectives of all countries. There is a competition in the research of long-term available renewable energy sources and their high efficiency utilization, and also in time. From the renewable energy sources the biomass, as an inexhaustible commodity was used in the experiments. Digestion was chosen from the several methods to explore green energy from waste and then to produce valuable biogas. However, the experiments related to anaerobic fermentation of organic materials take a long time, up to several months, so the results gained from these carefully prepared and accurately conducted experiments are definitely valuable. By optimizing the fermentation equipment it was possible to increase the time-efficiency of the measurements. The results are given in this paper.

    Keywords: renewable energy; biogas; biogas reactor block

  • Application of AdaBoost Algorithm in Basketball Player Detection189-207en [1.03 MB - PDF]EPA-02461-00055-0120

    Abstract: Video materials contain huge amount of information. Their storage in databases and analysis by various algorithms is a constantly developing area. This paper presents the process of basketball game analysis by AdaBoost algorithm. This algorithm is mainly used for face and body parts recognition, and was not tested on player detection in basketball. It consists of a linear combination of weak classifiers. In this paper, we used stumps, i.e. decision trees with only one level as such classifiers. The aim of this research is to assess the accuracy of this algorithm when applied in player detection during basketball games. We examined the capabilities of AdaBoost algorithm on a video footage obtained from the single moving camera, without any previous processing. First training was performed using images of a basketball player’s entire body (head, legs, arms and torso), while the second training was performed using images of a head and torso. By applying the algorithm to the given set of images that include head and torso, the algorithm obtained an accuracy of 70.5%. Training on the set of entire body images was not successful due to the large amount of background that goes into the training, and which represents noise in training process. This research concluded that AdaBoost could not be applied to object detection in sports events. We also concluded that this algorithm gives much better results when applied on simpler objects (like face recognition) and that its application could be in detection of players’ body parts or as a first step in object detection in order to eliminate as much area as possible. Its application in detecting players' upper body or entire players gives large number of false positive, which makes algorithm inapplicable in real situations.

    Keywords: AdaBoost; Object detection; Basketball

  • Béla Takarics ,
    Péter Baranyi :

    Abstract: Active stabilisation of the 2 and 3 degrees-of-freedom (DoF) aeroelastic wind sections with structural nonlinearities led to various control solutions in the recent years. The paper proposes a control design strategy to stabilise the 3 Dof aeroelastic model. It is assumed that the aeroelastic model has uncertain parameters in the trailing edge dynamics and only one state variable, the pitch angle is measurable, therefore, robust output feedback control solution is derived based on the Tensor Product (TP) type convex representation of the aeroelastic model. The control performance requirements include robust asymptotic stability and constraint on the l2 norm of the control signal. The control performance requirements are formulated in terms of Linear Matrix Inequalities (LMIs). As the first step of the proposed strategy, the TP type model is obtained by executing TP transformation. As the second step, LMI based control design is performed resulting in controller and observer solution defined with the same polytopic structure as the TP type model. The validation and evaluation of the derived control solutions is based on numerical simulations.

    Keywords: aeroelastic wing, robust LMI-based multi-objetive control, TP model transformation, qLPV systems

  • Abstract: In the era of globalization of world markets, movement of the European Union toward the knowledge-based society, and Serbia's EU accession process, competition has become one of the most important characteristics of successful development and achievement of these objectives. The existing competitiveness indices are discussed in this study, and it has been found that they do not reflect the position of transition countries and Serbia appropriately. A great impact of the quality indicators on Serbian ranking was determined based on the analysis of the existing studies. A new, original index is therefore proposed – the Competitiveness Index of the Knowledge-Based Society. The index is applied to 18 territorial units, including the EU and the Western Balkan countries, Serbia, and Vojvodina as a European region. The new model set out in this article provides a more realistic and objective picture of the state of Serbia and the Western Balkans as regards the competitiveness of knowledge. In other words, the new competitiveness model of knowledge-based society provides a better monitoring of the development of the Republic of Serbia and the Western Balkans on their way towards development of knowledge society. The results are analyzed and discussed.

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