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Acta polytechnica HungaricaVolume 9, Issue No. 6 (2012.)


  • Gyula Sallai :
    Defining Infocommunications and Related Terms5-15en [470.13 kB - PDF]EPA-02461-00038-0010

    Abstract: The convergence of telecommunications, informatics (IT) and media based on the common digital technology affected these sectors in different ways and at different times, resulting in different approaches and terms. The paper presents infocommunications as an evolving expansion of telecommunications with information processing and content management functions. Information and communication(s) technology (ICT) is considered an extended synonym for IT to emphasis the integration of the unified (tele)communications. Contents involved in the convergence process are expanded by cognitive features; and the term cognitive infocommunications was established. Subtle distinctions between these and other terms that have emerged are clarified and compared, as well as a consistent terminology is proposed.

    Keywords: infocommunications; information and communication technologies; ICT; information society technologies; electronic communications; media informatics; cognitive infocommunications; digital convergence; TIM sector; Digital Ecosystem

  • Yi-Jen Mon ,
    Chih-Min Lin ,
    Imre J. Rudas :

    Abstract: In this paper, a wireless sensor network (WSN) is constructed to carry out certain applications. This WSN is composed of a sensor, monitor, controller, etc. It has the benefits of low cost and low power consumption. A WSN can be used in many applications in a range of different control technologies, such as temperature monitoring. ZigBee is used to test the performance of the WSN. The experimental results reveal that the design requirement can be achieved; they also demonstrate that the WSN control methodology allows good performance of data transfer using a liquid crystal display (LCD) and motor control.

    Keywords: wireless sensor network; WSN; ZigBee; temperature monitoring

  • Károly Nagy ,
    Szabolcs Divéki ,
    Péter Odry ,
    Matija Sokola ,
    Vladimir Vujicic :
    A Stochastic Approach to Fuzzy Control29-48en [841.42 kB - PDF]EPA-02461-00038-0030

    Abstract: The paper presents the utilization of low-resolution data for control purposes. The control is based on fuzzy logic, with the deployment of stochastic digital low-resolution time arrays. Every control decision contains a degree of imprecision, being derived from measured low-resolution data. The imprecision is eliminated by stochastic noise superimposed during the data gathering, while the negative effects of noise are suppressed both by the fuzzy nature of the decision-making process and by the energy inertia in the controlled object. The proposed stochastic fuzzy control is extremely fast, robust and so simple that it practically does not need a microprocessor. This approach is validated by a simulation of holding upright an inverse pendulum.

    Keywords: fuzzy control; fuzzy inference systems; approximate reasoning; fuzzification; alpha-cuts; stochastic

  • Fatima Tahri ,
    Ali Tahri ,
    Ahmed Allali ,
    Samir Flazi :
    The Digital Self-Tuning Control of Step a Down DC-DC Converter49-64en [185.81 kB - PDF]EPA-02461-00038-0040

    Abstract: A digital self-tuning control technique of DC-DC Buck converter is considered and thoroughly analyzed in this paper. The development of the small-signal model of the converter, which is the key of the control design presented in this work, is based on the state-space averaged (SSA) technique. Adaptive control has become a widely-used term in DC-DC conversion in recent years.

    A digital self-tuning Dahlin PID and a /Keviczky PID controller based on recursive leastsquares estimation are developed and designed to be applied to the voltage mode control (VMC) approach operating in a continuous conduction mode (CCM).

    A comparative study of these two digital self-tuning controllers for step change in input voltage magnitude or output load is also carried out.

    The simulation results obtained using a Matlab SimPowerSystems toolbox to validate the effectiveness of the proposed strategies are also given and discussed extensively.

    Keywords: Continuous Conduction Mode (CCM); Digital Self-tuning Controller; Dahlin PID; Bányász/Keviczky PID; State-Space Averaged (SSA); Voltage Mode Control (VMC)

  • Attila Meggyes ,
    Valéria Nagy :

    Abstract: Sustainable agricultural development and increasing the rate of renewable energy sources have become an economic issue after Hungary joined the EU. Under the present economic conditions the private sector cannot solve in its complexity the problems of environment protection and energy from its own sources. The paper introduces biogas production and utilization methods that are suitable for providing continuous operation of existing biogas plants and also for determining the parameters of establishing biogas plants. Experimental variants (mixtures of liquid pig manure and plant additives) were developed to produce biogas and intensify biogas yield, and then gas engine tests were done for the energy utilization. The eco-energy system can be built up by taking into consideration the specific local conditions. It does not require any change or transformation of agricultural structure. The system can be expanded by the utilization of other organic materials, so it supports efficient operation. Furthermore, it can be the pillar of energy independence of rural life, because during the establishing of the eco-energy system, ecological aspects are taken into consideration, which makes this system sustainable. Waste disposal requirements can be integrated, too. We created a complex biogas production and utilization system by developing variants, so that both the energy and the waste disposal goals can be achieved together. This system was presented as an alternative agricultural system for an animal farm.

    Keywords: biogas production; biogas utilization; energy; complex system; environment; waste disposal

  • Mirica Karlovits ,
    Diana Gregor-Svetec :

    Abstract: The paper presents a study of the stability of cellulose and synthetic papers exposed to various methods of accelerated ageing. Particular consideration was given to the optical and mechanical stability of six paper samples (one film synthetic paper, two fibre synthetic papers, one lignin-free paper of higher quality and two security cellulose papers), which have undergone changes during accelerated ageing. The papers were artificially aged using standard techniques of accelerated ageing, e.g. moist-heat (80 °C and 65% RH), dry-heat (105 °C) and treatment with a xenon arc lamp (35 °C CT, 50 °C BST, 35% RH). The ageing was performed for the periods of 1, 2, 3, 6 and 12 days. The changes in the optical (ISO brightness, Yellowness Index), surface (roughness, paper topography) and mechanical stability (zero-span tensile strength, elongation at break, folding endurance) of papers were measured during the periods of accelerated ageing. The results show that the differences between synthetic and cellulose papers exist. On average, the dry-heat ageing had the highest influence on ISO brightness and Yellowness Index on synthetic papers, while the treatment with a xenon lamp had the strongest influence on cellulose papers. A comparison of mechanical properties showed that synthetic papers are more durable than cellulose paper; they had higher zero-span tensile strength and folding endurance, and showed substantially better ageing resistance to dry-heat and moist-heat accelerated ageing than cellulose papers. It was also noticed that the surface roughness increased after all three accelerated ageing processes.

    Keywords: synthetic paper; cellulose paper; accelerated ageing; optical properties; mechanical properties; paper topography

  • Balázs Mikó ,
    Jozef Beno ,
    Ildikó Manková :

    Abstract: The paper deals with the experimental verification of cusp height when finishing an elementary surface by end ball milling. The relationship expressing the effect of the direction of milling cutter motion on cusp heights has been derived from the geometrical interpretation of inclined elementary surface. Experimental verification has been carried out as 3D milling of surface with definite roundness while surface roughness was measured considering normal vectors of tool-workpiece contact. An approach based on process window has been used to evaluate the measured data.

    Keywords: ball end milling; cusp height; roughness data; process window

  • Mehdi Ghannad ,
    Mohammad Zamani Nejad :

    Abstract: An analytical formulation based on the first-order shear deformation theory (FSDT) is presented for axisymmetric thick-walled heterogeneous cylinders under internal and external uniform pressure. It is assumed that the material is isotropic heterogeneous with constant Poisson's ratio and radially varying elastic modulus. First, general governing equations of the heterogeneous thick cylinders are derived by virtual work principle, and using FSDT. Then the obtained equations are solved under the generalized plane strain assumptions. The results are compared with the findings of both plane elasticity theory (PET) and finite element method (FEM).

    Keywords: thick cylinder; shear deformation theory (SDT); heterogeneous; functionally graded material (FGM); finite element method (FEM)

  • Goran Martinovic ,
    Zdravko Krpic :
    Advanced Character Collage CAPTCHA137-151en [325.42 kB - PDF]EPA-02461-00038-0090

    Abstract: Text based CAPTCHA systems are widely used as a security mechanism for web access control. Considering their broad use, many attacks are challenging them every day. Most of the attacks aimed at CAPTCHAs are based on the latest computer vision techniques, AI methods and OCRs, so it is imperative to enhance these methods even more. There are number of proposals for CAPTCHA security, but it is hard to achieve a good balance between CAPTCHA practicality and its security. Advanced Character Collage CAPTCHA is a highly random novel method which uses the strengths of unbroken CAPTCHAs along with the weaknesses of present ones, and relies on imperfection of computer vision techniques. The proposed CAPTCHA is generated through a series of unique creation steps, each of them implementing carefully analyzed features in order to increase human recognition rate, and at the same time, to reduce computer recognition rate. The degree of recognition within the proposed method is evaluated using several tests, while its readability by humans is tested through two surveys.

    Keywords: CAPTCHA; recognition rate; security; web access control

  • Zsolt Csaba Johanyák ,
    Olga Papp :
    A Hybrid Algorithm for Parameter Tuning in Fuzzy Model Identification153-165en [168.90 kB - PDF]EPA-02461-00038-0100

    Abstract: Parameter tuning is an important step in automatic fuzzy model identification from sample data. It aims at the determination of quasi-optimal parameter values for fuzzy inference systems using an adequate search technique. In this paper, we introduce a new hybrid search algorithm that uses a variant of the cross-entropy (CE) method for global search purposes and a hill climbing type approach to improve the intermediate results obtained by CE in each iteration stage. The new algorithm was tested against four data sets for benchmark purposes and ensured promising results.

    Keywords: cross-entropy; hill climbing; fuzzy rule interpolation; fuzzy model identification

  • Róbert Sánta :

    Abstract: The article aims to present, analyze and select two-phase condensation heat transfer coefficients for the refrigerant-side in the condenser of the heating and cooling system of a heat pump. The heat transfer models are analyzed for condensation in horizontal smooth tubes. The mathematical models published by various authors refer to the range of heterogeneous condensation. The final aim of the analysis is to select the optimal model from the examined two-phase condensation heat transfer models. The selection of the condensing refrigerant two-phase heat transfer model is based on the boundary condition. The applied method of analysis is numerical-graphical.

    Keywords: heat pump; condenser; R134a; heat transfer; boundary condition

  • ®ivko Pavlovic ,
    Tadeja Muck ,
    Aleą Hladnik ,
    Igor Karlovic :

    Abstract: Printing plate performance is one of the crucial factors affecting the printed product quality. In particular, when producing printing plates for larger print runs, a rigorous quality control has to be performed, since any bulk and surface imperfection can have a large detrimental effect on print sharpness, contrast, non-uniformity, colour gamut, and other print properties. In our research two characteristics of an aluminium-based offset printing plate after 0, 123,000, 177,000 and 300,000 runs were studied: surface topography and contact angle. Each was determined using two assessment methods. For the surface roughness determination, the conventional mechanical profilometry and scanning electron microscope (SEM) imaging followed by an implementation of a texture analysis method Gray level co-occurrence matrix (GLCM) were applied. The contact angle of a printing plate with water was acquired by the sessile drop method using a DataPhysics OCA30 instrument and, alternatively, by implementing image analysis routines on a sequence of images captured by a simple image acquisition system. Image analysis for both surface topography and contact angle assessment was accomplished using ImageJ, a public domain Java image processing program. Both image analysis-based evaluation methods proved to be a viable alternative to the two established ones, providing a reliable tool for the monitoring of the wearing and other surface changes of a printing plate during the print run.

    Keywords: surface roughness; contact angle; scanning electron microscopy; gray level cooccurrence matrix

  • Gábor Kiss :

    Abstract: An analysis of Information Technology knowledge of Hungarian and Slovakian students was made using a web based Informatics Test. After the evaluation of the test results, there were found some significant differences in IT skills and programming knowledge of the students from different countries, but these differences do not depend on a different way of teaching. In the following statistical analysis Levene’s test, T-test and Ztest was used. The monitoring was held on the p=5% significance level throughout the analysis. The underlying causes are discussed. Survey results are traced back to differences in the educational systems of the two countries.

    Keywords: comparative analysis; measuring; knowledge level; IT skills; programming; Hungary; Slovakia

  • Gustavo Aragon ,
    M. J. Escalona ,
    Jose R. Hilera ,
    Luis Fernandez-Sanz ,
    Sanjay Misra :

    Abstract: This paper proposes an approach for Web requirements validation by applying the model-driven paradigm in classical requirements validation techniques. In particular, we present how the Navigational Development Techniques (NDT) approach exploits the model-driven paradigm to improve its requirements validation task by exploring tool cases that systematize or even automate the application of requirements validation techniques. Our solution is validated by applying it in a real industrial environment. The results and the learned lessons are presented accordingly.

    Keywords: Requirement; validation techniques; Web-application; NDT; Model-driven paradigm

  • Balázs Magyar ,
    Bernd Sauer ,
    Péter Horák :
    Tribological Investigation of K Type Worm Gear Drives233-252en [1.44 MB - PDF]EPA-02461-00038-0150

    Abstract: This paper presents a calculation method to determine the locally changing tooth friction coefficient along each contact line based on the TEHD lubrication theory for worm gear drives operating in mixed lubrication conditions. This also involves a detailed presentation of a procedure to specify the proportions of boundary lubrication and hydrodynamic lubrication as well as temperature states in contact. By comparing the calculated tooth friction coefficients with experimental test results, it can be stated that the calculated results properly approximate the measurement results.

    Keywords: worm gear drive; TEHD lubrication theory; mixed lubrication; numerical and experimental investigation; tooth friction coefficient