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Acta polytechnica HungaricaVolume 3, Issue No. 2 (2006.)


  • Jozef Vojtko ,
    Irena Kovácová ,
    Ladislav Madarász ,
    Dobroslav Kovác :

    Abstract: The paper deals with an elastomagnetic sensor of pressure force and neural network design in order to achieve linear sensor output. There are described basic properties of such sensor and its equivalent electrical scheme. The feeding and evaluating circuits were designed in order to obtain the optimal working conditions.

    Keywords: measurement, elastomagnetic sensor, neural network, non-linearity, hysteresis

  • Pavel Záskalický ,
    Mária Záskalická :

    Abstract: A synchronous motor with ferrite permanent magnet rotor is a good solution for small pump applications. It also has some drawbacks. The most important of them seems to be its inability to start directly on the mains, Permanent magnet motor has to by equipped with an electronic circuit for direct starting, which increases motor price. Another drawback is the torque ripple for the non-harmonic supply. This paper shows analytical calculation of the torque ripple of the small permanent magnet motor, which does a triac converter supply. The converter forms two-phase supply voltage of 25 Hz frequency, from one-phase 50Hz mains.

    Keywords: torque ripple, synchronous motor, permanent magnet, triac converter

  • Ján Kollár ,
    Jaroslav Porubän ,
    Peter Václavík :
    Time and Memory Profile of a Process Functional Program 27-40en [255.66 kB - PDF]EPA-02461-00006-0030

    Abstract: An execution profiling attempts to provide feedback by reporting to the programmer information about inefficiencies within the program Instead of writing whole code highly optimized, the programmer can initially write simple maintainable code without much concern for efficiency. Profiling is an effective tool for finding hot spots in a program or sections of code that consumes most of the computing time and space. The paper presents already implemented execution profiler for process functional program. From the viewpoint of implementation, process functional language is between an impure eager functional language and a monadic lazy pure functional language. The key problem of execution profiling is to relate gathered information about an execution of the program back to the source code in well defined manner. The paper defines language constructs for monitoring resource utilization during the program execution. In our solution programmer can associate label with each expression in a program. All resources used during the evaluation of a labeled expression are mapped to the specified label. The paper is concerned with formal profiling model. Research results are presented on sample program illustrating different types of time and space profiles generated by already implemented profiler for process functional programs.

    Keywords: Functional programming, program profiling, process functional language, formal profiling model

  • Ferenc Farkas ,
    Sándor Halász :
    Embedded Fuzzy Controller for Industrial Applications41-63en [469.27 kB - PDF]EPA-02461-00006-0040

    Abstract: The concept of the fuzzy logic makes feasible the creation of fuzzy controllers with low cost 16 bit microcontroller having the same performance as of controllers realized with more expensive Digital Signal Processor (DSP). In this article the implementation of such a fuzzy controller is proposed for 16 bit microcontroller with fast fuzzyficationinference- defuzzyfication algorithm. Because the microcontroller receives information from the process via Analog-Digital Converter(s) and controls the process with the help of Digital-Analog Converter(s) the implemented algorithm does not use floating-point operations, only integer ones. However, for some type of fuzzy controllers, the error made by this algorithm is not greater than the error of a DSP based floating point algorithm.

    Keywords: fuzzy logic, microcontroller, embedded systems

  • Frank Schindler :
    Coping with Security in Programming65-72en [103.61 kB - PDF]EPA-02461-00006-0050

    Abstract: This article deals with importance of security issues in computer programming. Secure software can only be designed with security as a primary goal. To achieve that we would have to redesign our computer systems with security in our mind including entire computer environment, e.g. hardware, programming languages and, of course, operating systems. In software development process the quality of resulting computer code should be the most important aspect during the whole program development process. Simplicity of the code in computer programs always pays off. Extra options and features can result in unmanageable complexity. For computer security purposes, program modularisation is of a paramount importance and seems to be the only way how to properly cope with complexity. Internal consistency of the whole program should be frequently checked via assertions. They are the best way to check parameter validity coming from other program units e.g. modules. Especially each module must distrust everything else coming from other modules and/or from the user. Frequently used code optimisations are classically leading to some sort of redundant code options and features and thus indirectly causing a useless code complexity. Extensive testing of programs is necessary for finding possible bugs in programs. However it does not locate security holes in the system. Standard software implementation techniques are completely inadequate in the production of a secure code. Consequently an introductory programming course as a college course should be taught in parallel with introductory security of computer systems, since it is too late to teach it as an elective at the end of computer science curriculum. In general, security of computer systems and programming should not be separated as two different and separate disciplines instead of it they should be integrated together.

    Keywords: security of computer systems, principle of least privileges, lack of functionality, module, module's specification, module's implementation

  • Sándor Horváth ,
    Géza Körtvélyesi ,
    László Legeza :
    The Statics of the Traditional Hungarian Composite Reflex Bow73-89en [700.46 kB - PDF]EPA-02461-00006-0060

    Abstract: The operation of the Hungarian bow raises several fascinating mechanical questions. To answer these questions a good number of experiments and calculations need to be made, moreover the mechanical model of the bow is needed to be prepared which appropriately confirm the results of experiments. Teachers in the Bánki Donát Mechanical Engineering College of Budapest Polytechnic set up a small laboratory in 1997 in order to study and measure the physical characteristics of traditional bows. The mechanical analysis of bows is based on the experiments gained in the laboratory and the results of measurements. The knowledge acquired about the mechanical model of bows facilitates not only the analysis of the traditional Hungarian bow, but also provides a good foundation for the comparison from the technical point of view of various composite reflex bows belonging to different historic ethnic groups.

  • Juraj Ritók ,
    Marek Hicár :
    Robust Crane Control 91-101en [454.34 kB - PDF]EPA-02461-00006-0070

    Abstract: The paper presents robust crane design by asynchronnous motor with frequency convertor at ensuring system robustness against load weight and rope length variation. Exact position control and elimination of swinging in the final position are required too. Firstly were assemblied mathematical models of main crane components: crab, bridge and uplift by real model of double beamed bridge experimental crane. Was designed robust control for defined interval variation of weight and rope length for real crane. Load weight and swinging are determined by estimators. Finally measured results gained on a laboratory crane are introduced.

    Keywords: robust control, crane crab and bridge, uplift, poles region assignment method, observer, estimator, swinging model

  • Kristína Machová ,
    Frantisek Barcák ,
    Peter Bednár :
    A Bagging Method using Decision Trees in the Role of Base Classifiers121-132en [197.64 kB - PDF]EPA-02461-00006-0090

    Abstract: This paper describes a set of experiments with bagging – a method, which can improve results of classification algorithms. Our use of this method aims at classification algorithms generating decision trees. Results of performance tests focused on the use of the bagging method on binary decision trees are presented. The minimum number of decision trees, which enables an improvement of the classification performed by the bagging method was found. The tests were carried out using the Reuters 21578 collection of documents as well as documents from an internet portal of TV broadcasting company Markíza.

    Keywords: classification algorithms, bagging, binary decision trees, text categorisation, recall and precision

  • Tibor Kovács :
    Developed Physical Detection-Possibilities of Chemical Agents133-141en [251.15 kB - PDF]EPA-02461-00006-0100

    Abstract: We can’t preclude the possibility of the use of chemical agents by terrorists - I can recall the attempt committed with Sarin in the Tokyo-subway in 1995. For that reason it is necessary to know the chemical situation in the battlefield and in our urban environment as well, for example in the subway. Actually the possible detection principles of toxic-agent-detection-devices are chemical (simple detection devices: e. g. paper detector, detection tubes), biochemical, physical (ion mobility spectroscopy, flame photometry, photoacoustic spectroscopy, infrared or laser remote sensing detectionsystems). To control the real time chemical situation it is essential to establish, set up an accurate and rapid reconnaissance. The solution is a monitoring system, which includes developed toxic-agent-detection-devices.

    Keywords: Monitoring, real time chemical situation, toxic-agent-detection, principle of physical detection, CAM, AP2C, PAS, remote sensing detection