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Acta polytechnica HungaricaVolume 15, Issue No. 6. (2018.)


  • Jana Moravčíková ,
    Peter Pokorný :

    Abstract: This article describes various strategies of measurement and their influence on the accuracy of measured parameters. Maintaining and, in particular, increasing the accuracy of production plays a key role in production companies. Coordinates-based measuring technology enables measuring parameters with a high degree of accuracy, depending on the measuring method used and specific conditions. The scanning system available to the CMM has a significant impact on the result of the measuring. The measuring experiment is executed on a calibration ring of a known size using the PRISMO Ultra coordinate-measuring machine. The goal of the experiment is an analysis of the effect of measuring strategies while measuring a machine-part on the values of roundness and diameter of the calibration ring. This includes a change of measuring method, scanning rate, diameter of the scanning stylus, as well as the evaluation filter. The RONDCOM 60A high-precision measuring device is designed to establish reference values of roundness for the proposed experiment measurement. This paper focuses on the analysis of the impact of conditions of measuring roundness and diameter of the calibration ring on the results of the measurements.

    Keywords: coordinate measuring; measurement strategy; accuracy; roundness; diameter

  • Tamás Réti :
    Graph Irregularity and a Problem Raised by Hong27-43en [569.87 kB - PDF]EPA-02461-00083-0020

    Abstract: Starting with the study of the Collatz-Sinogowitz and the Albertson graph irregularity indices the relationships between the irregularity of graphs and their spectral radius are investigated. We also use the graph irregularity index defined as Ir(G) = Δ - δ, where Δ and δ denote the maximum and minimum degrees of G. Our observations lead to the answer for a question posed by Hong in 1993. The problem concerning graphs with the smallest spectral radius can be formulated as follows: If G is a connected irregular graph with n vertices and m edges, and G has the smallest spectral radius, is it true that Ir(G) =1? It will be shown that the answer is negative; counterexamples are represented by several cyclic graphs. Based on the previous considerations the problem proposed by Hong can be reinterpreted (refined) in the form of the following conjecture: If G is a connected irregular graph with n vertices and m edges, and G has the smallest spectral radius, then Ir(G)=1 if such a graph exists, and if not, then Ir(G)=2. Considering the family of unicyclic graphs for which Ir(G) ≥ 2, we prove that among n-vertex irregular unicyclic graphs the minimal spectral radius belongs to the uniquely defined short lollipop graphs where a pendent vertex is attached to cycle Cn-1. Moreover, it is verified that among n-vertex graphs there exists exactly one irregular graph Jn having a maximal spectral radius and an irregularity index of Ir(Jn)=1. Finally, it is also shown that by using the irregularity index Ir(G) a classification of n-vertex trees into (n-2) disjoint subsets can be performed.

    Keywords: irregularity indices; spectral radius; unicyclic graphs; lollipop

  • MohammadReza Saadat ,
    Benedek Nagy :

    Abstract: Cellular automata are parallel computing devices working on a discrete time-scale. In the paper, each cell of the triangular grid has a state from the binary set (i.e., we have a binary pattern, an image, on the grid), and the state in the next time instant depends only on the actual state of the cell itself and the states of its side-neighbor cells. We illustrate their use in image synthesis, e.g., generating snowflakes, and in image analysis: some of our automata are connected to image processing operations, e.g., dilation and erosion. Computation of Hausdorff distance of two binary images on the triangular grid is also presented. In image processing, and especially in mathematical morphology, operations are local operations, and thus, cellular automata are apt to use. On the other side, the triangular grid is not a point lattice, thus the definition of translation based image operations is not always straightforward.

    Keywords: parallel computing; cellular automaton; non-traditional grids; binary image processing; game of life; dilation; erosion; closing; opening; Hausdorff distance

  • Endre Börcsök ,
    Ágnes Gerse ,
    János Fülöp :

    Abstract: Almost half of the greenhouse gas emission from the energy sector in the world is related to heat demand. The development of nuclear cogeneration offers a convenient option for emission reduction; however, the examination of economic constrains is essential. This study focuses on the heat demand of households in the vicinity of Paks NPP and compares the economic and environmental aspects of several domestic heating alternatives. In the first part of our work, we analyze the competitiveness of nuclear cogeneration in the district heating sector. While in the second part we consider, the optimal heaters for different building typological groups by taking into account some economic and environmental aspects, the distance from Paks NPP and the heat demand density. We have found that the development of nuclear cogeneration is economically viable for the existing district heating network,above a carbon price of 5 Euro/ton of CO2. In a region of high heat demand density, the nuclear cogeneration-based district heating can be competitive with stand-alone heaters, in particular when the environmental external costs are considered, as well.

    Keywords: heat sector; district heating; cost-benefit analysis; optimization

  • Nenad Katic :

    Abstract: Smart grid solutions are considered as a set of automation and telecommunication equipment connected to an intelligent master system, with aim to provide higher energy efficiency, optimized grid control and data processing. If applied in a power distribution network, it would include a wide set of smart applications for efficient operation, analysis, fault management, planning and optimization of grid operation. Together with field automation, as substation automation, feeder automation, remote terminal units and communication links, they constitute distribution automation management systems to provide higher efficiency and reduce cost of grid operation. In this paper, benefits and costs of a distribution automation management system is investigated and evaluated. The performance analysis is conducted considering the lifetime of the system, to manifest the profitability of the solution.

    Keywords: Power Distribution; Smart Grid; Energy efficiency; Power system economics

  • Antal Ürmös ,
    Zoltán Farkas ,
    László Dobos ,
    Szilvia Nagy ,
    Ákos Nemcsics :
    Contact Problems in GaAs-based Solar Cells99-124en [1.41 MB - PDF]EPA-02461-00083-0060

    Abstract: The present work deals with contact problems of GaAs-based solar cells. In the introduction the most basic GaAs-based solar cell structures are introduced. Then, the energy and electronic properties are investigated. In the third part of this publication, the technological aspects of the metallization are discussed. Here the surface patterns are investigated, that are formed at the surface of the Au/GaAs and Au/TiN/GaAs material systems, as the effect of the annealing process. The further aim of these investigations to investigate, how the properties of ohmic contact depends on the properties of the material system. If these relations are known, the relationships between different morphologies and their electric qualities will be also known.

    Keywords: solar cell; ohmic contacts; surface pattern; fractal dimension; structural entropy

  • ®olt Namestovski ,
    Lenke Major ,
    György Molnár ,
    Zoltán Szűts ,
    Péter Esztelecki ,
    Gábor Kőrösi :
    External Motivation, the Key to Success in the MOOCs Framework125-142en [652.37 kB - PDF]EPA-02461-00083-0070

    Abstract: This paper aims at presenting the findings and sharing the experiences of a case study whose data were gathered from an experimental MOOC (massive open online course) platform. The content was designed with an end view of favoring media-based education, students' activities, and their interactive communication. The main advantage of the devised system is that students were able to learn using their mother tongue, Hungarian. This research involved 208 students, enabling the authors to test the following variables by applying statistical methods: residence (country), sex, occupation, age, external (offline) motivation, amount of time spent in front of the computer, length of time in the LMS (learning management system) and achievements during a specific course. Statistical analysis revealed correlations between numerous factors, which may later serve as a solid ground for further studies in this field.

    Keywords: student achievements; e-learning; external motivation; LMS; MOOC; K-MOOC

  • Gusztáv Fekete ,
    Dong Sun ,
    Gongju Liu ,
    Yao Dong Gu ,
    Gábor P. Balassa ,
    István Bíró ,
    Patric D. Neis ,
    Endre Jánosi :

    Abstract: This paper deals with two fundamental questions with regard to total knee replacement kinematics. First, it provides quantitative information about the effect of knee prosthesis size on restored knee rotation by the so-called performance function. Second, the paper introduces a hypothesis which considers the effect of slide-roll on the performance function. By means of statistical methods, a strong linear correlation between slide-roll and performance-function of the examined total knee replacements was deduced. This result can be interpreted as follows: alteration of slide-roll ratio may enhance the overall performance of total knee replacements with regard to the restored kinematics, or in this specific case, the rotation.

    Keywords: qualification method; total knee replacement; rotation; slide-roll; size-effect

  • Juraj Mihaµov ,
    Emília Pietriková ,
    Anton Baláľ ,
    Branislav Madoą ,
    Norbert Ádám :

    Abstract: The article investigates systems, which represent a modern and popular approach to Virtual Reality and controlling systems. We would like to focus on low-cost motion sensors used in applications which are oriented on object tracking and gesture recognition. There are various types of sensors. Some of them measure the infrared light reflected from the opposing surface, previously emitted by the device in to gather information about any movement in the observed environment. Another way how to recognize not only a moving object present in the environment, but also its gestures and further characteristics of the movement is to use the Kinect. Therefore, we included Kinect also in our research. There is also a sensoric device called Leap Motion, which is specially developed to analyze gestures of human hands and track their motion with very high accuracy. We will provide pros and cons of every mentioned type of sensors or sensoric devices. Our aim is to summarize specific characteristics of mentioned devices to evaluate their ability to be beneficial in the recently very intensively expanding IoT sector. Considering new trends, we decided to focus on low cost sensors in to make our research more relevant also for small businesses and start-ups whose initiative leads to further development of sensoric soloutions and involving them in IoT. We decided to include also Myo Armband. It uses eight electromyography sensors, combined with a gyroscope and an accelerometer to sense electrical activity produced by the muscles of the forearm. Of the multiple programming environments available, we decided to compare and evaluate three programming engines most frequently used for programming applications processing sensoric data. For gaming purposes, the Unreal and Unity 3D engines are the most frequent. For robotics, medicine or for industrial purposes usually LabVIEW is the best choice. In this, we compare the aforementioned three programming environments using different algorithms, utilizing the three motion controllers, and we discuss their (dis)advantages and programming perspectives.

    Keywords: Leap Motion; LabVIEW; Myo Armband; Unity 3D; Unreal Engine

  • Andrea Bencsik ,
    Renáta Machová ,
    Lilla Csókás ,
    Tímea Juhász ,
    Kornélia Lazányi :

    Abstract: The research presented in this study is focusing on upright managerial skills, considering the expectations towards the manager and ethical leadership behavior. The research, including quantitative and qualitative elements have addressed 3 countries (Hungary, Slovakia, Czech Republic). The questions of the survey focused on differences between upright managerial and leadership qualities, as well as the questions of ethical managerial behavior. In addition to employee opinion and considering the managerial aspects, the authors conducted a questionnaire survey to complement the research results. The results of the descritive and complex statistical analysis have shown that there is significant difference in the opinion of respondents of the mentioned countries regarding the leadership qualities and expectations, as well as the ethical behavior.

    Keywords: leader; leadership; ethics; code of ethics

  • Anna Dunay ,
    József Lehota ,
    Éva Mácsai ,
    Csaba Bálint Illés :
    Short Supply Chain: Goals, Objectives and Attitudes of Producers199-217en [540.54 kB - PDF]EPA-02461-00083-0110

    Abstract: The research discusses the objectives, goals and attitudes of Hungarian fruit and vegetable producers using the method of Theory of Planned Behaviour. The objective of the paper is to explore the factors which may influence the decision-making process of agricultural producers in choosing the appropriate marketing channel. Research results showed that main goals of producers using direct sales are focused on economic issues, but non-economic goals (tradition, consumer relations, local values, environmental aspects) were highly preferred in their business processes. Producers, who prefer direct sales activities, generally have a wider product supply and undertake to build closer relations with their consumers. They consider stability and traditional products produced by conventional technologies as the key business success factor.

    Keywords: short food supply chain; Theory of Planned Behaviour; marketing channel; fruit and vegetable producer; agricultural enterprises

  • István Vajda ,
    Alexander Glazyrin ,
    Irina Ustinova ,
    Evgeniy Bolovin :

    Abstract: The authors have developed the methods of preparing the difference schemes re-quired for dynamic identification of the parameters of a DC motor as an object of the electric drives with control system during idling start-up. A system of differential equations describing the separately excited DC motor is reduced to the system of difference equations for constructing the discrete model. The authors have used three methods: direct difference, bilinear transformation method and multipoint approximation for writing the difference equations system. The estimations of the parameters of the discrete model based on the linear algebraic equations system applied this way were obtained by the matrix method. Comparing the estimates obtained the authors detected the influence of the methods of constructing the object discrete model on the error in the parameters’ estimations obtained.

    Keywords: discrete model; difference equations; bilinear transformation method; multipoint approximation; direct difference; linear algebraic equations system; dynamic identification; parameters estimations

  • Adrienn Dobai ,
    Zsolt Markella ,
    Miklós Mezei ,
    Tamás Vizkelety :

    Abstract: Although some articles have already assessed the reliability of three dimensional (3D) cephalometric landmarks, but the results were questionable because most of them analized the landmarks using linear or angular measurements instead of the coordinates. Therefore, the aim of this study was to eliminate the mistakes of the 3D landmark selection by the means of statistics based landmark selection model and a practically useable decision tree. In our study three medical doctors - the ”examiners” - identified 55 particular landmarks on 30 non-orthodontic Cone Beam Computed Tomography (CBCT) scans using the Cranioviewer software. The identification process has been done three times in order to increase the accuracy. Intraclass correlation coefficient and analysis of variance were applied to decrease the intra- and inter- examiner variability, while standard deviation (SD) and mean absolute difference (MAD) were used for characterization of landmark locations. Inaccurate coordinates were grouped according to both the intra- and the inter-examiner deviation of ≥ 1mm and the difference between the two statistical methods (SD vs. MAD). The intra-examiner identification errors were ≤ 1mm. The inter-examiner SD and MAD were ≥ 1mm except in cases of four landmarks with MAD and in cases of two with SD. Inter-examiner deviations were always higher than intra-examiner deviations. Standard deviation distorted more than mean absolute difference. Based on these result we have created a decision tree for landmark selection. Most of the coordinates belong to the landmarks can be reliably adapted to 3D cephalometric, but the statistics based decision model could be useful to eliminate mistakes in landmark selection as well. Since, the statistical rules are summarized like a decision tree it can be easily used in practice.

    Keywords: Cephalometry, Planning Techniques, Computer-Generated 3D Imaging, Cone-Beam Computerized Tomography, Dimensional Measurement Accuracy