Vojnotehnicki glasnik / Military Technical Courier / Военно-технический вестник

Plasma spray coatings play an important role in the design of surface properties of engineering components in order to increase their durability and performance under different operating conditions. Coatings are the most often used for wear resistance. This paper presents the microstructure and mechanical properties Al2O3 40wt.%TiO2 coating resistant to dry friction slide, grain abrasion and erosion of particles at operating temperatures up to 540°C. In order to obtain the optimal characteristics of coating was performed optimization of deposition parameters. The powder Al2O340wt.%TiO2 is deposited atmospheric plasma spraying (APS) process with a plasma current of 700, 800 and 900A. Evaluate the quality of the coating Al2O340wt.%TiO2 were made on the basis of their hardness, tensile bond strength and microstructure. The best performance showed the deposited layers with 900A. The morphology of the powder particles Al2O340wt.%TiO2 was examined with SEM (Scanning Electron Microscope). Microstructure of the coatings was examined by light microscopy. Analysis of the deposited layers was performed in accordance with standard Pratt & Whitney. Evaluation of mechanical properties of the layers was done by examining HV0.3 microhardness and tensile strength of the tensile testing. Studies have shown that plasma currents significantly affects the mechanical properties and microstructure of coatings which are of crucial importance for the protection for components subjected to wear.

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Chemical accidents are inevitable in modern technological development and they cause a number of effects on people, property and the environment. The nuclear-biological-chemical (NBC) services as well as specialized units of the Army of Serbia perform particular tasks in the elimination of the consequences of chemical accidents. This paper presents a modeling of the effects of chemical accidents and one possible method for the selection of NBC services engaged in the elimination of the consequences of chemical accidents, using the method of analytic hierarchy processes.

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An application of differential geometry in hiding text-data is presented in this paper. This application is a generalization of similar previously presented methods. Matrix valued functions of more than one variable are used in text hiding. This method is covered by the corresponding programs in the MATHEMATICA software package and compared with the previously presented method.

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The sol-gel method was successfully utilized for the synthesis of the highly concentrated α-Fe2O3/SiO2 nanocomposite containing 45 wt% of hematite. TEM micrograph showed that spherical particles of 10 nm average size were evenly dissolved in glassy silica matrix. Both DC magnetization and AC susceptibility measurements indicated su perparamagnetic behaviour of the system with the blocking tempera ture TB ≈ 65 K. Magnetization vs. field data at 300 K was successfully fitted to a weighted Langevin’s curve for superparamagnetic system and the particle size obtained from this fit was in excellent agreement with the TEM results. Several features evinced in the magnetic data pointed to the presence of non-negligible magnetic interaction between hematite nanoparticles: the weak field dependence of the magnetization as a function of temperature, narrowing of the hysteresis loop at low applied field below TB, and high value of TB for hematite nanoparti cles of 10 nm in size. On the other hand, features like continuous in crease of the ZFC magnetization with decreasing temperature and the absence of a plateau or a peak in the FC branch showed that no strong magnetic interactions were present in the system.The AC susceptibility study showed that the Vogel-Fulcher model for single-domain inter-acting particles was applicable, while the empirical parameters C1 = 0,055 and C2 = 0,57 that lie between values for strongly interacting systems and non-interacting systems obtained have pointed to the presence of the interactions of intermediate strength. On the ba sis of the above listed results, we can conclude that the system under consideration consists of interacting single- domain hematite nanoparticles with magnetic properties that are located between weakly and strongly interacting systems.

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In accordance with SORS 1029/89 and SORS 1762/89 military standards, electromagnetic compatibility tests of equipment and weapon systems and military equipment of the Serbian Army are carried out in a Faraday cage. A Faraday cage has many parasitic resonances due to the reflective walls, floor, and ceiling. In order to improve electromagnetic compatibility tests, a complete Faraday cage was modeled. Various imperfections of the cage were detected by comparing the results of simulations and experiments, and they were included into the model.

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We propose a novel method to fuse true colour images with monochromatic non-visible range images that seeks to encode important structural information from monochromatic images efficiently but also preserve the natural appearance of the available true chromacity information. We utilise the β colour opponency channel of the lαβ colour as the domain to fuse information from the monochromatic input into the colour input by the way of robust gray scale fusion. This is followed by an effective gradient structure visualisation step that enhances the visibility of monochromatic information in the final colour fused image. Images fused using this met hod preserve their natural appearance and chromacity better than conventional methods while at the same time clearly encode structural information from the monochormatic input. This is demonstrated on a number of well-known true colour fusion examples and confirmed by the results of subjective trials on the data from several colour fusion scenarios.

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Hydraulic systems of mobile machines are often contaminated by solid particles. Solid particles increase the abrasive wear intensity of hydraulic components and present one of the main causes of system failure. The paper presents a representative example of the solid particle influence on the wear intensity of hydraulic hammer parts, in the cement industry environment.

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Разработана аэродинамика замкнутого овального крыла эл липсоидальной формы с применением молекулярно-кинетической теории. Выяснены положительные и отрицательные качества летательного аппарата с овальным крылом. Осуществлена эк спериментальная проверка теоретических расчетов.

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This paper presents possible ways for determining criteria weights based on the criteria ranks.The linear weights with a variable slope, reciprocal weights, rank order centroid weights, rank sum weights, geometric weights and rank order distribution weights are shown in this paper. When the ranking process involves several experts, there is a possibility for aggregating criteria ranks (weights) using selected mat hematical methods, social choice theory methods and the Kemeni me dian. The application of the selected methods is illustrated with one numerical example and the obtained results are analysed. The main aim of this paper is a systematic review of possible ways for determining the criteria weights based on criteria ranks given by one or more experts.

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The differential conversion curves of the non-isothermal NiO reduction process by hydrogen are fitted by the Weibull (non-isothermal)probability density function (Wpdf), in a wide range of the degree of conversion (α = 0.06 - 0.96). It was established that the Weibull distribution parameters (β and η) show the different dependences on the heating rate of the system (vh) (shape parameter (β) - linear form and scale parameter (η) - exponential form). Model independent values of the apparent activation energy were calculated using the Friedman’s isoconversional method. It was found that the calculated apparent activation energy depends on the degree of conversion, α, and it shows a constant value in the range of the degree of conversion 0.20 ≤α≤ 0.60 (Ea = 90.8 kJ mol 1 ). Knowing the Weibull distribution function of reaction times, it is possible to determine the density distribution function of apparent activation energies at different heating rates. It was established that the changes of the symmetry of density distribution functions may be an indication for deviations from the simple crystallization kinetics as expressed by the Johnson-Mehl-Avrami (JMA) model, and this behaviour is probably dueto a more complex transformation process such as a process described by the two-parameter autocatalytic Šesták-Berggren model.

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В этой статье реферат о новейшем взрывном устройстве. Тема не секретная. Патенты общедоступны. Известны гидриды разных металлов и сплавов. Они способны накапливать и отдава ть водород. При определенных условиях процесс выделения идет лавинообразно, в форме «физического» взрыва. Методы получе ния условий лавинообразного выделения. Метод получения нужных параметров гидридов. Перспективы взрывных устройств.

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This paper describes the modernization by installing frequency converters, their features and benefits as well as the disadvantages of the existing solutions and the advantages of the upgraded status. The existing state was such that the motors were switched on through the contactor and were always working at full capacity. In the new solution, one motor will be switched on through frequency converters, thus working with a particular intensity, depending on the need. This will bring savings in power consumption as well as in the maintenance.

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From June 23 - 26, 2013, the GDMB Society for Mining, Metal lurgy, Resource and Environmental Technology organized 7th European Metallurgical Conference (EMC 2013) in Weimar, Germany. The previous European metallurgical conferences were organized by the GDMB in Friedrichshafen (2001), Hanover (2003), Leipzig (2005), Duesseldorf (2007), Innsbruck (2009), and Duesseldorf (2011). The GDMB is a non-profit organization from Clausthal, Germany, focused on combining science with practical experience in metallurgy, mining, materials engineering, mineral processing, recycling and refining of metals, and manufacturing of semi and finishing products. The Euro pean Metallurgical conference EMC is one of the most well-known con ferences worldwide in the field of non-ferrous metallurgy and is at tended regularly by decision makers from industry and universities. The scientific program contained 6 plenary lectures and more than 130 presentations. An extensive poster exhibition was held, during which the authors had an opportunity to introduce their posters to the entire plenum as a part of a brief presentation., The € 500 worth “Poster Award EMC 2011 was awarded to Christoph Pichler from the Montan-University in Leoben, Austria. Not only the most important European countries were represented here, but also more than one third of the lecturers were from countries outside Europe (Canada, Japan, China, USA, South Africa, Australia). The origin of the participants reflects the aim of the organizers: to make this conference a worldwide platform for the scientific exchange of experience and information. The scientific presentations of the conference are presented in Proceedings: Vol. 1: Copper, Precious Metals, Waste effluents Treatment/ Bio hydrometallurgical applications; Process Metallurgy, Bridging Non-Ferrous and Ferrous Metallurgy; Vol. 2: Lead and Zinc, Light metals, Sustainable technologies, Sustainable of non-ferrous metals production, Process Control/Process Modelling, Waste heat recovery by ORC Power Generation Vol. 3: General Hydrometallurgy, General Pyrometallurgy, Vessel Integrity, Process Gas Treatment; Recycling The plenary lectures will be published in the scientific journal “World of Metallurgy - ERZMETALL”, published by GDMB. The next 8 th European Metallurgical Conference will be held between June 14 and June 17, 2015 in Duesseldorf.

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