Vojnotehnicki glasnik / Military Technical Courier / Военно-технический вестник

The cermet coatings of WC-12wt.%Co are extensively used to improve the wear resistance of a wide range of technical components. This paper analyses the influence of the plasma gas flow of helium on the microstructure and mechanical properties of WC-12wt.%Co coatings deposited by plasma spraying at atmospheric pressure (APS). In order to obtain homogeneous and denser coatings, three different flows of He (8 l/min., 16 l/min. and 32 l/min.) were used in the research. With the application ofHe, coatings achieved higher values of hardness due to less degradation of the primary WC carbides. The main goal was to deposit dense and homogeneous layers of WC-12wt.%Co coatings with improved wear resistance for different applications. The test results of the microstructure oft he layers were evaluated under a light microscope. The analysis of the microstructure and the mechanical properties of the deposited layers was made in accordance with the standard of Pratt-Whitney. The morphology of the powder particles and the microstructure of the best coating was examined on the SEM (scanning electron microscope). The evaluation of the mechanical properties of the layers was done by applying the HV0. 3 method for microhardness testing and by applying tensile testing to test the bond strength. The research has shown that the flow of He plasma gas significantly affects the microstructure, the mechanical properties and the structure of WC-12 wt.%Co coatings.

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Разработана молекулярно-кинетическая модель газодинамиче ского обтекания шара. Установлены три области разных механи змов взаимодействия движущегося шара с неподвижной газовой сре дой. Показано, что срывное течение является решающим при ма лых скоростях движения шара, а при скоростях движения близких к скорости звука решающую роль выполняет ударное взаимодей ствие шара на молекулы окружающей среды в передней полусфере. Срывное течение за шаром создает конус с неподвижной газовой средой. Установлен закон, определяющий размер срывного конуса.

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Chaotic spreading sequences can increase secrecy and resistance to interception in signal transmission. Chaos-based CDMA systems have been well investigated in the case of flat fading and noise presence in the channel. However, these systems operating in wideband channels, characterized by the frequency selective fading and white Gaussian noise, have not been investigated to the level of understanding their practical applications. This paper presents a detailed mathematical model of a CDMA system based on chaotic spreading sequences. In a theoretical analysis, all signals are represented in the discrete time domain. Using the theory of discrete time stochastic processes, the probability of error expressions are derived in a closed form for a multi-user chaos based CDMA system. For the sake of comparison, the expressions for the probability of error are derived separately for narrowband and wideband channels. The application of the system interleaving technique is investigated in particular, which showed that this technique can substantially improve probability of error in the system. The system is simulated and the findings of the simulation confirmed theoretically expected results. Possible improvements in the probability of bit error due to multipath channel nature, with and without interleavers, are quantified depending on the random delay and the number of users in the system. In the analyzed system, a simplified version of the wideband channel model, proposed for modern wideband wireless networks, is used.

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This paper presents the results of applying the optimal model of the concept of maintenance of modern radio-relay equipment (RRE). The model, is based on condition based preventive maintenance with the control of the level of reliability, and uses a number of positive structural and technological capabilities of the machine in order to decrease overall maintenance costs while maintaning the achieved level of the required device reliability.

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In the field of transmission and power transformation from the power engine to the working machine, gear pairs, are mostly used in mechanical engineering due to their compactness of the structure, high reliability and capacity. One way of improving the performance characteristics of gear pairs, and thus the gear transmitters, is to increase the number of simultaneously meshed pairs of teeth, or increasing the transverse contact ratio. To this end, this paper analyzes in detail the partial and simultaneous influence of the number of teeth and tooth profile shapes, moving through shifting coefficient and pressure angle, to the number of simultaneously meshed pairs of teeth. The obtained results allow us to define the optimum parameters of cylindrical gear pairs, in terms of the size of the transverse contact ratio.

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There has always been a need to directly perceive and study the events whose extent is beyond people's possibilities. In order to get new data and to make observations and studying much more objective in comparison with past syntheses - a new method of examination called remote sensing has been adopted. The paper deals with the principles and elements of remote sensing, as well as with the basic aspects of using remote research in examining meteorological (weather) parameters and the conditions of the atmosphere. The usage of satellite images is possible in all phases of the global and systematic research of different natural phenomena when airplane and satellite images of different characteristics are used and their analysis and interpretation is carried out by viewing and computer added procedures.

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В статье показывается новый способ борьбы с генерато рами пульсирующих инфракрасных помех, новый вид борьбы с инфракрасными головками самонаведения, и анализ средств бо рьбы с ВВС и средств противодействия. Описание модернизации инфракрасных головок самонаведения, для преодоления генераторов пульсирующих инфракрасных помех. Также описывается оригинальный способ постановки ло жных тепловых целей с применением медно-алюминиевого тер мита и сплава «электрон».

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This paper deals with the control of presses for sheet metal stamping. The analysis will be based on the experimental setup of the ram height. The experiment will be done for five different positions, i.e.metal sheet thicknesses. The previous state of the press was such that for every change of a position, i.e. metal sheet thickness it was necessary to adjust the ram height The new solution shown in this pa per, makes the process much easier and more efficient. In order to use another position, it will be enough to select a particular position and the ram will be automatically adjusted to a required height. This will speed up production and reduce scrap that would be otherwise created due to adjustment. The state diagram for the new solution is shown as well as the control program for the new solution.

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This paper presents problem solving using heuristics and operational research in order to make appropriate decisions in emergency situations with a particular emphasis on the application of a heuristic model of team training for emergency situations. It is intended for military command and teaching personnel as well as for civil defense personnel (Department of Emergency Management) and local government authorities (administrative district chiefs and mayors commanders). The heuristic approach to problem solving should enable adequate decision making for command staff from the local to the national level after the proclamation of emergency and a state of emergency in some regions or the whole territory of Serbia.

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In the Serbian Armed Forces, oil and petroleum products are tran sported primarily for military units and institutions. The route for the movement of vehicles is selected during the transportation planning process. This paper describes a methodology for the selection of a route for the transport of dangerous goods and its application on one particular case in the Serbian Armed Forces.

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