a borítólapra  Súgó epa Copyright 
Acta polytechnica HungaricaVolume 15, Issue No. 8. (2018.)


  • Mazuriah Said ,
    Shabudin Mat ,
    Shuhaimi Mansor ,
    Airi Ali :

    Abstract: This paper presents the results obtained from wind tunnel experiments on VFE-2 wing profile model which are differentiated by their leading edge profiles; medium- and large-edged. VFE-2 was established to investigate the effects of Reynolds number, angle of attack, Mach number and leading edge bluntness on vortex properties above-blunt-edged delta wing. The original VFE-2 wing has 4 sets of interchangeable leading edge profile namely sharp, small, medium and large-edge ratio. There were lot of experiments and simulations data in VFE that compares sharp-edged with the medium-edged wings within the VFE campaign. This paper presents the current data on a blunter wing or large-edged wing. These experiments were conducted at UTM - Low Speed Wind Tunnel, Aerolab. The experiments were carried out at speed of 18, 36 and 54 m/s representing Reynolds numbers of 1×106, 2×106 & 3×106. Two measurement techniques were employed on the wing, i.e. steady balance and surface pressure measurements. The results obtained from the large-edged wing were compared with the results from medium-edge wing. The results showed that the primary vortex depends on the leading edge bluntness, angle of attack and Reynolds number. The results obtained from steady balance data showed that lift coefficient is sensitive to leading edge bluntness at higher Reynolds numbers. Several important observations were noted on the large-edged wing; i.e. the development of primary vortex has been delayed and the vortex breakdown occurred further aft of the wing. The data obtained provide a better insight into the leading edge effect on the delta-shaped wing and also for the development of Unmanned Combat Air Vehicle (UCAV) which most of them are integrated with delta wing technology.

    Keywords: Delta wing; VFE-2 profile; Vortex; blunt leading edge; Reynolds number

  • Artúr István Károly ,
    Róbert Fullér ,
    Péter Galambos :
    Unsupervised Clustering for Deep Learning: A tutorial survey29-53en [282.55 kB - PDF]EPA-02461-00085-0020

    Abstract: Unsupervised learning methods play an essential role in many deep learning approaches because the training of complex models with several parameters is an extremely datahungry process. The execution of such a training process in a fully supervised manner requires numerous labeled examples. Since the labeling of the training samples is very time-consuming, learning approaches that require less or no labeled examples are sought. Unsupervised learning can be used to extract meaningful information on the structure and hierarchies in the data, relying only on the data samples without any ground truth provided. The extracted knowledge representation can be used as a basis for a deep model that requires less labeled examples, as it already has a good understanding of the hidden nature of the data and should be only fine-tuned for the specific task. The trend for deep learning applications most likely leads to substituting as much portion of supervised learning methods with unsupervised learning as possible. Regarding this consideration, our survey aims to give a brief description of the unsupervised clustering methods that can be leveraged in case of deep learning applications.

    Keywords: Unsupervised learning; Clustering; Deep learning

  • Umar Farooq ,
    Muhammad Usman Asad ,
    Jason Gu ,
    Ghulam Abbas ,
    Valentina E. Balas ,
    Marius M. Balas :

    Abstract: This paper presents the design of a nonlinear teleoperation system which is comprised of a single master and multiple slave (SM/MS) units. The interaction between these units follows the extended state convergence architecture which allows multiple linear master units to influence multiple linear slave units. However, in this study, the nonlinear dynamics of the master and slave units is considered and the resulting nonlinear teleoperation system is analyzed in the presence of time delays. To be specific, the following objectives are defined: (i) the nonlinear teleoperation remains stable in the presence of time varying delays, (ii) the slave units follow the position commands of the master unit and (iii) the operator receives a force feedback proportional to the interaction forces of the slaves with their environments. Towards this end, Lyapunov-Krasovskii theory is utilized which provides guidelines to select the control gains of the extended state convergence architecture such that the aforementioned objectives are achieved. The efficacy of the proposed scheme is finally verified through simulations in MATLAB/Simulink environment by considering a two degrees-of-freedom (DoF) single-master/tri-slave nonlinear teleoperation system.

    Keywords: Teleoperation; nonlinear dynamics; state convergence; MATLAB

  • Zoltán Fazekas ,
    Gábor Balázs ,
    Péter Gáspár :

    Abstract: A method that distinguishes between urban road environment types, based on traffic sign (TS) and crossroad (CR) data is presented in this paper. The types and the along-the-route locations of the TSs and the CRs - encountered during car trips - are recorded either by a human data entry assistant, or by an advanced driver assistance subsystem that has been enhanced for the purpose. A feed-forward artificial neural network (ANN) - trained in a supervised manner - carries out the classification tasks. ANNs with different topologies and training regimes are considered and tested for the purpose. These ANNs are characterized by different degrees of modularity ranging from fully modular to non-modular networks. The fully modular ANN consists of three functional modules. Two of these three were trained initially as standalone ANNs, to infer the actual road environment type solely from the TS and the CR data, respectively. The outputs of these two modules are combined via the third module. Further synapses supplement the module-level connections in the less modular ANNs. During the training of the full ANN, the TS and the CR modules are kept relatively intact, while the weights and the biases within the merger module can evolve. Test results for the considered ANNs are provided and compared.

    Keywords: detection of the road environment; artificial neural networks; traffic sign recognition systems

  • Rita Remeikiene ,
    Ligita Gaspareniene ,
    Romualdas Ginevicius :

    Abstract: The main purpose herein, is to assess the popularity of the innovative funding mechanisms when acquiring land at the national level. The results of the research suggest that the innovative funding mechanisms are neither popular nor available when making the investment in land in Lithuania. The unavailability of the innovative real estate funding mechanisms was determined by the lessons of the financial crisis of 2008. Now land plots are mainly acquired with personal funds as loans issued by credit unions. The future prospects are not very favorable, since a very small part of the transactions in the land market in Lithuania are funded with bank loans due to the Scandinavian banking policy which is currently responding to the crisis in the Scandinavian asset market. Issuance of corporate bonds serves as another source of funding. Although, theoretically, the mechanism of “crowd funding” could also be employed, the cases of its employment, thus far, have not been registered at the national level. The novelty of this article lies in the provision of a comprehensive approach to the innovative land funding mechanisms since scientific literature, thus far, has lacked the research on innovative real estate funding mechanisms.

    Keywords: real estate; funding mechanisms; investment; land; innovative funding

  • Vasile Alexa ,
    Imre Kiss :

    Abstract: Many of the hydraulic and pneumatic devices are made from high quality stainless steels, through complex and elaborated manufacturing technologies. Thus, not infrequently the semi–finished product used for obtaining the pneumatic and hydraulic equipment is subjected to different kinds of strains in the manufacturing process. Obviously, the units that are currently producing pneumatic and hydraulic equipment should focus on the manufacturing of products mostly requested in a market economy. This requires the modernization of existing production capacities in line with the EU requirements, followed by the update of technologies to the standards applied in the EU economy. The knowledge about the characteristics of deformability has for the technologist, as well as for the designer and researcher, a great practical significance, because they are important elements in establishing a correct technological process. The change of deformation conditions existing in the industrial process, such as the temperature and rate of deformation, are difficult to consider for correcting the deformability determined by testing. In this paper, through ”deformability” we understand all the properties characterizing the deformation behavior of the metals and alloys, and the „deformation resistance” of the metals is expressed through the unit strain required to produce a certain degree of plastic deformation, under the conditions of a particular diagram of tensions, deformations and deformation rates, in the absence of external friction forces. Thisstudy includes the results of the experimental tests conducted to find the plasticity and deformability characteristics of several stainless steel grades: one martensitic stainless steel (grade X46Cr13), one ferritic stainless steel (grade X6Cr17) and one austensitic stainless steel (grade X5CrNi18-10).

    Keywords: plasticity; deformability; stainless steel grades; temperature; heating; tests

  • Csongor Márk Horváth ,
    Péter Korondi :

    Abstract: Heavy welding is a demanding task with high robotization potential. This applies especially for the runners of Francis hydropower turbines, due to the high working costs and EHS requirements in Europe. However, heavy welding is often related to small-series production with long processing time. This sets high demands on the planning and monitor-ing functionality of the robot system. The research in this field is gaining momentum, yet very few articles suggest suitable solutions. This paper presents a robotic welding control system design and application that facilitates the planning, control, and monitoring of the welding process of non-uniform grooves of large-dimension joints. Its primary and unique characteristic is the simplified operator assisted programming method, where the three-dimensional path modification problem is translated into consecutive two-dimensional modifications. Therefore, reference cross-sections are created along the welding groove, where the sequence planning task of multi-pass weld bead placement is performed, and to the online modifications together with the adjustments are referred. The planning, changes and process supervision are supported by the robot system to handle uncertainties along the welding groove and adaptively utilize the robot operator experience. The activities are tracked and organized to supply information for later performance enhancement and reus-ability between similar processes. The supportive system design is particularly suitable for advanced, large-dimension, heavy robotic welding applications. A use case is presented on a welding a runner of Francis hydropower turbine.

    Keywords: robotic welding; multi-pass welding; non-uniform groove; small series produc-tion

  • Péter Gárdonyi ,
    István Szabó ,
    László Székely ,
    László Kátai :

    Abstract: The V-belt drive heats up during power transmission, i.e. a significant part of power loss turns into heat and is transferred to the environment. In this paper, the temperature rise in the V-belt was studied as loss intensity as a function of the drives parameters. It was justified in the scope of the major characteristics affecting power loss that by ideally selecting the parameters of the V-belt drive power loss can be measurably reduced. Based on earlier results as well, a regression model was used to examine the temperature rise in the V-belt. With the help of analysis of variance (ANOVA), the magnitude of the effect of each drive parameter was determined on the warming of the V-belt. According to our results, the most relevant drive parameter is the pulley diameter.

    Keywords: ANOVA; Efficiency; Power loss; Temperature; V -belt

  • Tamás Csiszér :

    Abstract: This article introduces a set of indicators and their interpretation called DQNET for the assessment of information structures in documents of quality regulatory systems. This complex system is considered a network with a piece of information in documents nodes; and links between them arcs. Like in citation network of scientific publications there are several network indicators in such information networks, which can reflect the ‘positions’ and ‘roles’ of elements in this system. By in- and out-degrees and other matrices documentations can be identified with, e.g. ‘high importance’ or with ‘high sensitivity’, requiring different ways of handling. By the indicators of structure functional suitability of regulation can be analyzed and predicted too.

    Keywords: Documentation analyses; importance and sensitivity; networkscience

  • Tamás Berek ,
    Judit Kovács :

    Abstract: In order to establish the concept of building and infrastructure defense, a complex security system must be created by making, analyzing and interpreting an appropriate plan. This task is especially difficult and complex for defending buildings of unknown functions. Industrial projects usually differ from what was planned both in space and in time. The authors of the article introduce the general aspects of security personnel and the characteristics of risk assessment. The basic points of configuring the labor force components of building and infrastructure defense are also introduced.

    Keywords: complex security; defense concepts; risk assessment; human factor

  • Andrea Bencsik ,
    Gabriella Horváth-Csikos :
    The Role of Knowledge Management in Developing Quality Culture209-226en [536.21 kB - PDF]EPA-02461-00085-0110

    Abstract: The study reveals the connecting points, where the elements of knowledge management system as part of the corporate processes (studiously the quality systems) play an important role in the successful operation of the company. The characteristic features of quality culture are in focus, of which support is put in parallel with the characteristic features of the learning organisation’s culture phrased as a precondition of knowledge management system. With this comparison, the author guarantees the understanding that by solving quality problems and developing quality culture with supporting the elements of knowledge management system will contribute to reaching corporate success and strategic goals.

    Keywords: knowledge management; organizational culture; learning organization; quality culture; TQM

  • Jarmila Lazíková ,
    Anna Bandlerová ,
    Oµga Roháčiková ,
    Pavol Schwarcz ,
    Ąubica Rumanovská :
    Regional Disparities of Small and Medium Enterprises in Slovakia227-246en [433.62 kB - PDF]EPA-02461-00085-0120

    Abstract: Small and medium enterprises are mostly considered as key elements of a market economy. Their share is 99% of a total number of all enterprises in Slovakia on average. The aim of the paper is to identify regional disparities of the SMEs development in Slovakia. As methods, we used chain indexes to compare the changes among numbers of small, medium and large enterprises, time series analysis, non-parametric method for investigation of the statistically significant differences and correlation analysis. According to the results we expect increasing numbers of SMEs in Slovakia in the next four years, mainly an increasing of small enterprises. The development of SMEs is very different in particular regions of Slovakia. The number of enterprises in remote rural areas grow less rapidly then the number of those in more accessible rural areas of Slovakia. The strong correlation between SMEs and large enterprises indicates suitable conditions for doing business in rural areas for SMEs as well as for large enterprises. The support policy of SMEs should be more intensive, especially in the rural areas that are not suitable for a large scale business.

    Keywords: small and medium enterprises; regional disparities; forecasting; rural areas