Vojnotehnicki glasnik / Military Technical Courier

15-39

Authors: Evseev Sergej Petrovič, Dorohov Aleksandr Vasiljevič, Korolj Olga Grigorevna

Protocols of information protection in computer networks and systems are investigated. The basic types of threats of infringement of the protection arising from the use of computer networks are classified. The basic mechanisms, services and variants of realization of cryptosystems for maintaining authentication, integrity and confidentiality of transmitted information are examined. Their advantages and drawbacks are described. Perspective directions of development of cryptographic transformations for the maintenance of information protection in computer networks and systems are defined and analyzed.

62-78

Authors: Vladisavljević Goran T.

Membrane emulsification is a process of injecting a pure dispersed phase or pre-emulsion through a microporous membrane into the continuous phase. As a result of the immiscibility of the two phases, droplets of the dispersed phase are formed at the outlets of membrane pores. The droplets formed in the process are removed from the membrane surface by applying cross-flow or stirring of the continuous phase or using a dynamic (rotating or vibrating) membrane. The most commonly used membrane for emulsification is the Shirasu Porous Glass (SPG) membrane, fabricated through spinodal decomposition in a melt consisting of Japanese volcanic ash (Shirasu), boric acid and calcium carbonate. Microsieve membranes are increasingly popular as an alternative to highly tortuous glass and ceramic membranes. Microsieves are usually fabricated from nickel by photolithography and electroplating or they can be manufactured from silicon nitride via Reactive Ion Etching (RIE). An advantage of microsieves compared to the SPG membrane is in much higher transmembrane fluxes and higher tolerance to fouling by the emulsion ingredients due to the existence of short, straight through pores. Unlike conventional emulsification devices such as high-pressure valve homogenisers and rotor-stator devices, membrane emulsification devices permit a precise control over the mean pore size over a wide range and during the process insignificant amount of energy is dissipated as heat. The drop size is primarily determined by the pore size, but it depends also on other parameters, such as membrane wettability, emulsion formulation, shear stress on the membrane surface, transmembrane pressure, etc.

93-115

Authors: Ilić Slaviša M., Andrejić Marko D.

This paper analyzes the effectiveness of possible models for queuing at gas stations, using a mathematical model of the large-scale queuing theory. Based on actual data collected and the statistical analysis of the expected intensity of vehicle arrivals and queuing at gas stations, the mathematical modeling of the real process of queuing was carried out and certain parameters quantified, in terms of perception of the weaknesses of the existing models and the possible benefits of an automated queuing model.

134-157

Authors: Perić Sreten R.

Nowadays, a special attention is focused on the development of modern devices and methods for monitoring condition changes of tribomehanical characteristics in systems. There are different physical and chemical methods and tribology methods for tribomehanical system diagnosis. Experience in technical systems exploitation showed that the most effective failure prognosis is based on particles created as a result of wear. The analysis of oil samples containing particles-products of wear, enables the evaluation of system tribology conditions in different phases of system exploitation. The paper presents the tribological tests in the analysis of oils used for the assessment of its condition. The paper also deals with the results of the experimental research of tribological characteristics of motor and power transmitter oils sampled from engines and power transmitters of the Mercedes O 345, PUCH 300GD and PINZGAUER 710M vehicles in exploitation. The investigations showed that there is a change of tribological characteristics of lubrication oils in the vehicle engine and power transmitters. These changes are in a direct dependence of the state of all elements of the tribomechanical engine and power transmitters system, and they depend on their functional characteristics. The conclusion is based on the realized testing.

174-193

Authors: Viličić Aleksandar B., Jezdimirović Mirko M.

This paper describes a simulation of a real electrical servo drive with a digital equalizer. The whole system is simulated in the simulation toolkit of the LabView package. Real transfer functions are simulated (the transfer functions of the motor and the current and angular velocity gauges), as well as the nonlinearities of the motor and the gears. Clasical mathematical methods for modeling servosistems are used. The method for determining transfer function parameters is also used. The influence of neglecting the electrical time constant is analyzed.

208-247

Authors: Paligorić Anastas L

The development of the NORA family started as far as back to 1976 at the Military Technical Institute of the Yugoslav's People's Army. The programme covered development of several types of the main artillery weapon: the 152 mm NORA-A towed gun-howitzer, the 152 mm NORA-B self-propelled gun-howitzer and the 152 mm gun-howitzer with APU. Under the same programme, the conversion of the Russian 130 mm towed gun M46 into the 155 mm M46/84 gun (for export needs) and the 152 mm M46/86 gun respectively (for the needs of the YPA) was completed. Only the 152 mm M84 (NORA-A) towed howitzer was introduced in service, while the development of the NORA-B and NORA-C weapons was carried on until 1992. After it had been suspended for many years, the development of the NORAB weapon was continued in 2003, followed by serial production of the 155 mm NORA-B52 self-propelled system for the export needs.

261-271

Authors: Borisov Mirko A., Branković Radoje D.

The article deals with some possibilities of presenting and visualising geospatial data. The Internet is especially useful for analyzing and detection of geospatial reality and its features. In the field of geodesy and cartography the use of the Internet is very impressive. Virtual atlases have become very attractive.

282-293

Authors: Stopić Srećko R.

The GDMB Society for Mining, Metallurgy, Resource and Environmental Technology organized the 6th European Metallurgical Conference (2011) in Duesseldorf from June 26 to 29, 2011. The same venue hosted the most important international metallurgical trade fairs for metallurgy of iron and steel, new casting and thermochemical processes METEC, GIFA, THERMOPROCESS and NEWCAST. The previous European metallurgical conferences were organized by GDMB in Friedrichshafen (2001), Hanover (2003), Leipzig (2005), Duesseldorf (2007), Innsbruck (2009). The GDMB is a non-profit organization situated in Clausthal in Germany, which is related to combining science with the practical experience in metallurgy, mining, materials engineering, mineral processing, recycling and refining of metals, and manufacturing of semi- and finishing products. The European Metallurgical conference EMC is one of the most known conferences worldwide in the field of non-ferrous metallurgy and is attended regularly by the decision makers from the industry and universities. The scientific program contained 6 plenary lectures and more than 160 presentations from 40 countries in 5 parallel series. 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 best poster from the Montan-University in Leoben, Austria, was awarded the € 500 'Poster Award EMC 2011'. Not only were the most important European countries represented here, more than one third of the lecturers were from the non-European countries (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. More than 400 participants from all over the world participated at this conference. The scientific presentations of the conference are presented in five Proceedings: Vol. 1: Copper, General Pyrometallurgy, Vessel Integrity, Process Gas Treatment; Vol. 2: Lead and Zinc, Process Control, Process Modeling, Vol. 3: Light metals, General Hydrometallurgy, Precious Metals; Vol. 4: Process Metallurgy, Recycling, Waste Treatment and Prevention, Vol 5: Sustainable technologies, Sustainable of non-ferrous metals production, waste effluents Treatment and Biohydrometallurgical application. The plenary lectures will be published in the scientific journal 'World of Metallurgy - ERZMETALL', which is published by the GDMB.

29-44

Authors: Stopić Srećko R., Friedrich Bernd G.

A wide spectrum of hydrometallurgical processes offers many promising approaches for industrial application in order to improve the environmental impact of conventional metals productions, or for replacing hydrometallurgical processes whose gas emissions and a high content of formed metals (As, Cr, Pb) are becoming increasingly unacceptable. The main advantages of pressure hydrometallurgy are fast kinetics, enhanced selectivity over iron and other dissolved species. The pioneer work on hydrometallurgical operation (dissolution, precipitation, metal winning) was performed in Russia at the beginning of the previous century, mainly by Ipatieff and Bayer, each working independently in Saint Petersburg. Gradually, industrial application took place firstly in aluminium and later in nickel production. Today, in addition to nickel and aluminium, the pressure hydrometallurgy is well established in a wide spectrum of industrial applications for production of different metals (gold, zinc, molybdenium, titanium, germanium) from ore deposits and secondary materials. High pressure leaching in combination with other metallurgical operations (cementation, precipitation, solvent extraction, and electrowinning) provides an adequate technology to reintroduce lost metals into the industrial cycle, thereby saving resources and energy, while keeping the environment cleaner. It seems that pressure hydrometallurgy might be a very important key to better and nonpolluting processes in production of metals.

71-90

Authors: Kokelj Tugomir R., Milinović Momčilo P., Jeremić Olivera M.

A problem of selecting an artillery target while firing from a multiple launch rocket system (MLRS) is not considered frequently in literature. A solution to that problem involves a good agreement among many elements such as shooting dispersion law of distribution, destruction target laws, dimensions of target, and the rate of fire. In this paper, the problem is discussed only for a 128 mm multiple launch rocket system (MLRS) M77, known as 'OGANJ', with an unguided wrap around low-spin stabilized rockets with deflectors - aerodynamic brakes for ballistic trajectory control. The paper considered the advantages and disadvantages of the brakes in live fire using the proximity artillery service methodology.

106-130

Authors: Biočanin Stojko Lj., Pavlović Milan R.

The application of preventive maintenance contributes significantly to providing the required level of readiness of complex technical systems used in organizations of special purpose. The basic requirement in applying this model of maintenance is to determine the optimal periodicity that should satisfy some mutually conflicting criteria. This paper presents a methodology for determining the periodicity of the preventive maintenance of V46-6 engines on the basis of collecting and processing statistical data about their malfunctions. This problem can be solved if all important requests and limitations are determined. The basis of the presented methodology is the reliability parameters of the analyzed engine, obtained by observing the engine behavior, from the aspect of occurrence of failure in real service conditions, and also its maintenance costs.

146-160

Authors: Samčović Andreja B.

This paper gives an overview of the Digital Video Broadcasting - Handheld standard DVB-H, as a part of the DVB Project. This standard is based on the previous standard DVB-T, which was developed for the terrestrial digital television. The ways of DVB-H signal transmission are also described. Development of advanced technology enabled the digital video broadcasting over wireless portable terminals. This paper discusses the key technological features of the DVB-H standard, such as: time slicing, forward error correction, 4K mode and in-depth interleavers.

177-185

Authors: Bakrač Saša T.

In accordance with the requirements for the protection and development of environment, the usage of spatial data represents a specific need for different kinds of geographical and cartographical information. Theoretical and practical understanding of these requirements, with existing experiences and the use of appropriate standards, help in the process of solving particular ecological problems. In this paper, the analysis (theoretical understanding of the problem) and the comparison of models will try to point out the importance, requirements and possibilities of using existing data from different geo-topographical materials such as charts at different scales in analog as well as digital forms. Sources of information about an area: Cartographic-analytic collecting of spatial information for environmental purposes is carried out mainly from the following sources: satellite images, geographic information systems / Environmental Information Systems (GIS / EIS), Geo-topographic materials in analogue and digital (especially maps) forms and physical measurements of ambient environment. Types of maps which can be used for environmental protection: Base maps are widely used mostly for military purposes. Being highly detailed, these maps can be largely used for the purposes of environmental protection, especially topographic maps of a scale of 1:25 000 to 1:200 000 and 1:250 000. Thematic maps primarily give information on specific locations and specific content. For the purposes of environmental protection and improvement, thematic maps with specific topics are constructed most frequently. Combined maps are specific and they are a combination of base and thematic maps. These are, for example, political, travel, touristic, hydrological, and synoptic maps. Synthetic maps show the results and analysis of data collected. They cannot display all the characteristics or information related to the environment, especially data about complex ecosystems. Conclusion: For the purposes of environmental protection and improvement, the existing geo-topographic materials can be used, especially maps in the analogue and digital form. Based on the content and topics depicted, there are many different types of maps. All maps, especially those with the specific content important for environment, have highly variable characteristics. The geo-topographic materials of different scales and shapes, both in analogue and digital forms, in the Military Geographic Institute (MGI) are a good basis for environmental protection and improvement purposes.

29-40

Authors: Donevski Dragan V.

Nowadays, a number of light terrain wheeled vehicles are used for various purposes. Their basic performances are related to achieving high average speed off roads and to overcoming various obstacles. This type of vehicles is mainly used for commercial purposes. Models of these vehicles have been modernized and upgraded during the time but their basic purpose remains the same. However, nowadays there is a need to use these vehicles for other purposes. This is carried out through the process of conversion. The conversion means that a vehicle changes its purpose by the application of various technical solutions. One of conversions is related to the application of weapons on the vehicle chassis. The weapon mounting is connected with various problems such as vehicle stiffness, weapon precision, presence of various oscillations, overall vehicle layout and crew deployment. In order to mount weapons efficiently, the methodology of its selection is proposed. It consists of several phases and the most important of them are the following ones: the consideration of performances of modern light terrain wheeled vehicles, analysis of weapons convenient for application, creation of the vehicle-platform-weapon system mathematical model, analysis of the dynamic characteristics of the created model and the selection of the best solution, experimental research and analysis of theoretical and experimental results. The realization of the proposed methodology will considerably improve the quality of the design of vehicle- platform-weapon systems.

60-77

Authors: Ilić Slaviša M., Radosavljević Vladan R.

The paper has solved the problem of optimizing the existing inefficient and irrational system of the quantitative monitoring of the situation in peacetime fuel supplies at the pumping stations in the Army of Serbia. A study of existing organizational forms, military pumping stations as well as civilian ones, was carried out. Based on the completion of the survey by competent persons in the military, the methods of expert evaluation and the obtained quantitative indicator of the tested models, a multicriteria optimization was performed in order to select the optimal model. The optimization of the existing models, in terms of efficiency and economy, would be the rationalization and modernization - automation of military capacity and greater reliance on automated civilian pumping stations. Introduction Within the framework of the undergoing reform of the Serbian Army and in order to reduce the total costs, it is necessary to optimize the existing supply system that is technologically outdated, inefficient and uneconomic. The problem of research in this paper is reduced to the selection of an optimal model of the quantitative monitoring of the state of peacetime stocks of fuel at the pumping stations in the Serbian Army, in order to ensure economical operation and efficient monitoring of available and issued quantities, aiming at better decision making and management in the supply system as well as at achieving faster system response, with greater reliance on government logistics. Organization of work and monitoring the fuel quantitative status at pumping stations The existing system of monitoring the quantitative state of fuel pumping stations in the Army of Serbia has the following disadvantages: getting unreliable data, due to outdated equipment for fuel handling and measuring equipment, and manual collection of data; creation of unauthorized shortages (due to subjective human error or deception); inadequate engagement of respective material and human resources. Optimization of quantitative monitoring of peacetime supplies of fuel at gas stations should aim at reducing the impact of the human factor, introducing automated quantitative monitoring of fuel condition with modern equipment for handling as well as applying technology for fast reading and dissemination of information and reports. Civilian pumping stations have been modernized gradually with new digital pump machines, systems for automated production and automated systems for measuring the fuel level in buried tanks. The objectives and criteria of the optimization of model monitoring In order to solve the problem of multi-criteria nature, the methods of operational research have been applied and the formalization of problem solving has been carried out. Models have been identified, criteria and subcriteria have been defined as well as respective criteria values, sub-criteria and weight coefficients for chosen variants in order to rank the alternatives - models. On the basis of the defined objectives and optimization approaches, the task of optimization to be solved is to choose one optimal model of monitoring the quantitative condition of peacetime stocks of fuels at gas stations, out of three variations or alternative models. Application of expert assessment and methods of analytical hierarchy process The problem was solved first 'manually', by using MS Excell, and after that by using the Expert Choice software package. The Expert Choice software package is based on the application of the method of analytical hierarchy process and combines the benefits that this method offers with the speed and visibility of computerized calculations and their result display. The purpose of the AHP method is to rank alternative decisions by their importance and to select the most acceptable alternative on the basis of a defined set of criteria and alternatives. The problem of determining the weight of criteria has been determined by applying the method of expert evaluation, along with interviewing and taking into account the competence of the interviewees. Conclusion The existing solutions in the system of logistics support, focused on the monitoring of the quantitative status of peacetime fuel supplies at the pumping stations in the Serbian Army, are not the product of system analysis and optimization. Therefore, it is not rational for them to get an IT support. The continuous task should thus be to monitor the phenomena and problems and their formalized description in order to create a foundation for their automation and successful problem solving.

94-110

Authors: Sokolović Vlada S., Oklopdžija Milan N., Marković Goran B.

Introduction This paper presents a critical analysis of the signal processing flow carried out in a software GPS receiver and a critical comparison of different architectures for signal processing within the GPS receiver. A model of software receivers is shown. Based on the displayed model, a receiver has been realized in the MATLAB software package, in which the simulations of signal processing were carried out. The aim of this paper is to demonstrate the advantages and disadvantages of different methods of the synchronization of signals in the receiver, and to propose a solution acceptable for possible implementation. The signal processing flow was observed from the input circuit to the extraction of the bits of the navigation message. The entire signal processing was performed on the L1 signal and the data collected by the input circuit SE4110. A radio signal from the satellite was accepted with the input circuit, filtered and translated into a digital form. The input circuit ends with the hardware of the receiver. A digital signal from the input circuit is brought into the PC Pentium 4 (AMD 3000 +) where the receiver is realized in Matlab. Model of software GPS receiver The first level of processing is signal acquisition. Signal acquisition was realized using the cyclic convolution. The acquisition process was carried out by measuring signals from satellites, and these parameters are passed to the next level of processing. The next level was done by monitoring the synchronization signal and extracting the navigation message bits. On the basis of the detection of the navigation message the receiver calculates the position of a satellite and then, based on the position of the satellite, its own position. Tracking of GPS signal synchronization In order to select the most acceptable method of signal synchronization in the receiver, different methods of signal synchronization are compared. The early-late-DLL (Delay Lock Loop), TDL (Tau Dither Loop) and Costas's PLL (Phase Lock Loop) models of loop tracking of signal synchronization are presented. The analysis is performed by processing the signals from the same satellite and under the same conditions of the initial signal synchronization. The multiple signal processing showed the advantages and disadvantages of the particular methods and the most acceptable solution proved to be the implementation of the DLL tracking loop phase synchronization and the code tracking loop PLL carrier frequency synchronization. The influence of the parameters of the loop itself is shown as well. After the extraction of navigation bits, all bit extracts do not come with an equal phase. This may lead to a wrong decision in rejecting the Decider and bits. Therefore, the paper proposes an additional synchronization of the extracted bits selected by the navigation messages NDA (Non-Data-Aided) algorithm in order to perform their correct detection and to position the receiver much faster. Comparison of methods of signal synchronization Based on the analysis of the methods, the simulation results are compared. The results showed that the TDL loop is not resistant to dynamic disturbances of signals, since the synchronization tracking breaks up. In addition, this loop shows susceptibility to the noise from free space. These are sufficient reasons to propose the implementation of the DLL signal tracking loop as an acceptable solution. In addition to the proposal of the tracking loop, tracking loop coefficient values are determined. Conclusion The performed analysis showed that the TDL loop is not resistant to noise and dynamic disorders of the input signal. Therefore, an appropriate solution for the implementation is the DLL loop with six correlates. The DLL tracking loop coefficients are determined as a compromise solution and they are B = 2Hz and γ = 0.7. Also, the coefficients of the PLL tracking loop of frequency synchronization are B = 20Hz and γ = 0.7. The application of the NDA algorithm results in an additional synchronization of the navigation bit message, thus making the receiver operate faster and more precisely.

120-141

Authors: Majkić Zoran Đ., Vukčević Novak S.

The paper presents the basic requirements for transport vehicles. A special request regarding the adaptation of transport vehicles for the transport of various types of cargo was taken into consideration. Superstructures and the situation arising after mounting superstructures on wheeled transport vehicles were analyzed and the following was described: console coupling, stirrups, simplex elastic coupling, two-way elastic and rigid connection elements. Vehicle torsional elasticity is provided by a proper choice of the type of connection between the superstructure and the vehicle chassis. Applying the instructions of vehicle manufacturers for using appropriate connections between the truck superstructure and the vehicle chassis provides positive torsional elasticity of the vehicle. The paper gives the general recommendations of the Volvo, Mercedes and Renault transport vehicle producers for the use of particular connection types of locations as well as structural requirements for the mounting of concrete mixers, tippers and truck tanks on their vehicles. Introduction Achieving a high level of transport effectiveness depends on a number of factors. One of the most important ones is the possibility to increase the payload share in the gross vehicle weight. This share depends on the net vehicle weight, a method of coupling the truck superstructure with the chassis frame as well as on the truck superstructure construction. Realization of this requirement is of significant importance, particularly for large business systems since it results in the reduction of number of necessary vehicles, more economic fleet maintenance and the fleet capacity increase. It is also relatively easy to adapt the vehicle for the transportation of other loads, depending on user's current needs. The adaptation is correctly performed if manufacturer's recommendations are followed during the mounting of the superstructure on the chassis. This paper gives the analysis of the types of coupling used for particular truck superstructures. Types of truck superstructure A truck superstructure is generally a torsionally stiffer structure of the vehicle chassis and by its mounting on the vehicle main frame the torsion stiffness of the whole vehicle increases. In order to retain the vehicle torsional elasticity because of its positive reaction to strain, it is necessary to apply a particular type of coupling for a particular type of truck superstructure. Regarding the torsional stiffness, truck superstructures can be divided into three groups: 1. Torsionally elastic 2. Torsionally semielastic 3. Torsionally rigid Connection of the chassis and the truck superstructure In order to retain the vehicle torsional elasticity because of its positive reaction to strain, it is necessary to apply a particular type of coupling for a particular type of truck superstructure: Panel connection Panel connection allows longitudinal motion and prevents lateral or vertical motion of the chassis runner in relation to the main vehicle frame. Stirrup (U bolt) connection Stirrup connections enable longitudinal motion of the chassis runner in relation to the main frame but they cannot accept lateral forces, so additional leading plates are mounted for that purpose. Simplex elastic connection Simplex elastic connections enable vertical motions of the automotive frames due to the effect of longitudinal torsion moments as well as longitudinal motion of the chassis runner due to the effect of longitudinal forces and frame flexion moments. Two - way elastic connection This kind of connections is used to connect the truck tank with the vehicle automotive frame. The connection supports lateral and longitudinal forces and enables vertical motion of the automotive frame in relation to the truck tank, during the torsion and lifting of the vehicle. Stiff connection (connection plates, sheets) This type of connections enables rigid connection of the automotive frame and the chassis runner thus making them behave as a whole. Connection plates transfer longitudinal, lateral and vertical forces. They are mounted from the front of the anterior support of the rear suspension to the end of the automotive (chassis runner) frame. The upper part of the plate is welded for the chassis runner, while the lower part of the plate is bolted for the automotive frame. Guidelines for the application of particular truck superstructures A truck superstructure must not prevent the chassis movement; therefore, it is important to choose a proper type of connection between the chassis and the truck superstructure. Chassis twisting is most expressed in the area behind the driver's cabin and it should decline towards the rear of the vehicle. If a rigid superstructure is mounted on the basic frame and the coupling is also rigid, the twisting of the main frame is not gradual but sudden and restricted to a limited area where high levels of torsion stress occur. The principal rule regarding the rigidity of superstructures is: the stiffer superstructure is, the more elastic connection must be. Manufacturer's recommendations for particular types of truck superstructures Manufacturer's recommendations for concrete mixer superstructures The truck superstructure of a concrete mixer is an example of torsionally flexible mounting. Figs. 7, 8, and 9 show types and cites of connections as well as some structural requirements of Volvo, Mercedes and Renault transport vehicles [2, 3, 4, 5]. In a 6x2 Volvo (Fig. 7), the first three couplings are cantilevered and five other connections are achieved with midfielder plates. The mixer is mounted on 6x2 vehicles with suspension or on 4x2 or 6x2 vehicles with air damping. All twin - shaft trucks could be loaded with 13t on the rear axle. Mercedes does not give much information related to the concrete mixer superstructure. To ensure stability and reduce strain of truck frames, the chassis runner is stiffened in the rear. Fig. 6 shows that the Mercedes chassis runner bends outwards, because of the possibility of embedding a larger drum or because of lowering the existing one in order to lower the focus down and thus increase the stability of the entire vehicle. Recommendations of the body tipper manufacturer A body tipper is an example of a torsionally flexible superstructure. Fig. 10 shows some types of sites and links, as well as some structural requirements of Volvo and Mercedes tippers [2, 3, 4]. Linking the main frame with the mounting one is performed using the console connection in the front part while near the axles connecting plates are used. To ensure the stability of the vehicle when unloading and to reduce stress, the frames are stiffened in the rear (Fig. 8). Recommendations of the manufacturer for mounting tanks Tank compartments are usually of circular or elliptical cross section, and as such they have large shaft, polar or torsion inertional moments. If the theories of material resistance and construction resistance are applied, it can be easily shown that the bending and torsion rigidity directly depend on the size of the moment inertia; x x c ~ I ; ϕ ϕ c ~ I , from which it can be concluded that the tank is a very rigid structure regarding bending and twisting. To connect the superstructure to the vehicle base, two-way elastic connections are used. Fig. 9 shows a twin-shaft Volvo tank with the number and types of connections used in connecting the main frame with the tank compartment. Three-axle tanks and four-axle tanks with the type and number of links of the main vehicle frame with the tank compartment are also shown. Similarly to the case of the tipper MB [3], there is no much information about linking the basic frame with the tank. Fig. 9 shows only a simplified method of coupling, without defining the number of connections and a more detailed description of connections. However, an important difference observed in relation to the solution of the Volvo manufacturer is that a chassis runner is used. Conclusion The analysis of the guidelines of leading manufacturers for upgrades, transport vehicle chassis and their connections leads to the following conclusions: The connection with the basic superstructure frame is an extremely complex issue. It is necessary to consider many factors (type of connection, the connection location, size and shape of the assembly - extra frames, the types of upgrades, etc.) since its characteristics directly affect both the reliability and the payload mass. As shown in the guidelines for the implementation of certain kinds of connection upgrades, a type of interactions on the basic frame depends on the torsional stiffness of the superstructure. Truck superstructures must not move to limit the chassis and is thus important to properly choose the types of connections and chassis upgrades. The connection of the upgrade to the basic frame is taken as already given by the manufacturer, having in mind extensive research of the manufacturer in this field. Regardless the simplifications in the application of general recommendations, the comparative analysis shows that there is a proper connection of the base and mounting frame which eliminates the possibility of breakdown.

158-174

Authors: Borisov Mirko A., Banković Radoje D.

Application of computer technology in the Earth science has led to the creation and development of new scientific disciplines, particularly digital cartography and GIS. This paper describes the application of GIS from several points of view such as: multi-scale, multi-thematic, multi-viewing, accommodation to standard software platforms and multi-user data accesses. Introduction The premise of a successful usage of topographic data nowadays implies their disposal in a digital form and organisation in a modern way, suitable for further computer processing. It is a unanimous opinion that it can be successfully completed only through creating data basis of space developing GIS. The theme of the written work is the development and application of GIS, and management of topographic data in accordance with international standards and users' needs. Moving to digital technology of creating and using topographic data should not be literal translation of the analogue map into a digital picture or just the automation of the map making using digital technology. The new method implies the formation of the central topographic data base which would generate displays of arbitrary scales, desired volumes of content, changeable sheet dimensions, various thematic displays, altogether in accordance with users' demands and needs. Digital cartography and GIS The development and application of computers in the area of earth sciences caused the creation of new definitions and disciplines among which are noticeable computer supported cartography and GIS. The computer-supported cartography was in its later phase called digital cartography and it can be used in two ways: like modern technology of date processing about space and like a new discipline. The main principle on which digital cartography as a discipline is based represents the processing and visualization of data about space but with computer supported technology. Application of GIS from various aspects Topographic maps have existed for many years in more or less similar or the same traditional form. By creating the basic data base about space through the application of GIS technology, a wide range of possibilities for dynamic selection of content appears. This content will further be shown on the screen or as a drawing on a piece of paper. The aspects of multidisciplinarity promote topographic data base as a significant part of general spatial data infrastructure. Application from the multiscale aspect There are different information levels which differ among themselves in quantity and content of data necessary for various levels of observation management and decision making. One of the principal tasks which emerges is a choice of the basic scale and resolution of the display for which the data are gathered. In cartography, that is a scale of 1:25,000, based on which the topographic map (TM) is created. Mutual complement of GIS and WWW will completely change the classic delivery of spatial data. Various topographic and thematic maps will be created and obtained from the unique data base. Application from the multithematic aspect The main objective of the formation of spatial data infrastructure is the creation of the standard GIS platform but also the possibility of multi purpose application of GIS for environment (farming, forestry, waterpower engineering) land development (commercial and business), itinerary analysis, tracing of retail and wholesale routes distributional nets (shops and warehouse locations) media and marketing planning (locations, sales territory, sales prospects, market analysis according to users), finances - insurance (from the users aspect, investors and areas of low/high risk), healthcare (general healthcare, appearance of epidemic and its spreading) and non-productive activities (tourism, archaeology, environment protection). Application from the aspect of multidisplay Once formed, the spatial data base, or GIS, should offer to the user a lot of graphic, descriptive and other important information which is, in fact, a digital or traditional display in a form of a determined output. One of the ways of using GIS implies cartographic publishing (getting the reproductive originals and printing geographic map sheets) in a traditional form. Application from the aspect of adjustment to standard software platforms In the groundbreaking period of civilization with radical changes in a scientific - technological sphere, it was necessary to select a new, most suitable software platform with attaching hardware components. After thorough analyses (analyses of foreign and national literature and the usage of demo versions of various GIS software), the American company ESRI software platform was selected. Application from the aspect of multiusers data access Internet and Intranet are deeply rooted technologies and have been increasingly used as technologies to accomplish the growing number of distributed informational systems. Therefore, the above-mentioned technologies are needed for distributed work with spatial data. Maintenance of GIS data The maintenance of the topographic data denotes a process of updating old-fashioned content and entering new geospatial data as well as the elimination and the correction of details which are not in accordance with the real state on the field. In connection with the volume and the method of work, difference should be made between the spatial data maintenance aspects for the basic scale, which refer to the entire content and specific elements of the content. Regarding periods in which the present space data maintenance is done, there are continuous and periodical ones. Conclusion When establishing the unique GIS, we ought to apply a principle according to which all the data once gathered in one State institution can be used variedly as well as in many other institutions (military, administrative, economic, scientific, cultural, etc.). This principle does not apply only to the rationalization but also to uniqueness and quality of the research of common geospace. In the present state of the development, it is hard to predict the trends of cartographic and generally speaking GIS processes, but the most important is that topographic data have digital form the meaning of which is universal, regardless of the current development of technique and technology.

27-39

Authors: Đorđević Miroslav Lj.

For telecommunication purposes, a monopole antenna is usually positioned on the tank turret. At low frequencies the whole tank has to be treated as a part of the antenna system. In this paper a method for electromagnetic modeling of metallic structures is presented and applied to the analysis of radiation of a tank monopole antenna. Radiation simulations are performed at the frequency range from 1MHz to 30MHz. A special attention is given to the analysis of the effects of increased elevation of the tank main gun to the radiation pattern of the antenna. The analysis of the radiation of the tank monopole is performed with and without the presence of conducting ground. It is shown that the increase in the main gun elevation at certain frequencies can lead to degradation of uniformity of radiation in the horizontal plane. Introduction Informational technologies and reliable and secure communications are an important part of a modern military doctrine. Regarding telecommunications, armored vehicles and tanks in particular present a specific problem. In this paper, a theoretical basis of the electromagnetic analysis of metallic structures and a modeling technique will be presented. The effect of the tank on the radiation pattern will be investigated both for a tank in free space and above the conducting ground. Method of moments The method of moments (MoM) is a method for an approximate solution of integral equations. This section presents the fundamentals of the MoM and the higher-order quadrilaterals as the basic elements used for geometry modeling. The currents in our method are approximated using high-order two-dimensional polynomials. Modeling of the tank geometry The tank is modeled using only 28 elements, out of which 10 bilinear quadrilaterals and 18 second-order surfaces. The monopole antenna is modeled using one straight wire segment. Results The use of the polynomial current approximation yields a reduction in the number of unknowns required for the analysis, compared to classical methods that use linear current distribution defined on small triangles. The analysis of the tank from 1MHz to 30MHz, with a 1MHz step, requires from 130 to 337 unknowns and about one minute of the CPU time on a Dell Vostro 1015 laptop computer. Tank in free space At low frequencies, the monopole-tank system acts as a dipole antenna and the computed directivity is 1.76dBi, almost equal to that of a short dipole. The elevation of the tank main gun does not influence the radiation pattern much at low frequencies. In the resonant range, the effect of the main gun elevation is much more pronounced. At 17MHz, the difference between the minimum and the maximum of radiation in the horizontal plane is 1.22dB, 1.90dB, and 2.33dB for the main gun elevation of 0°, 13°, and 20°, respectively. The effect of conducting ground The effect of the conducting ground (in this paper we assume the ground is perfectly conducting) is taken into account using the image theory. Since the original currents and their images are electrically close at low frequencies (their distance is small compared to the wavelength), their mutual coupling cannot be neglected. Once again, at low frequencies the whole structure acts as a short dipole antenna and the computed directivity is 4.76dBi; at the same time, the radiation pattern in the horizontal plane is almost uniform. At the frequency of 13MHz, however, the difference between the minimum and the maximum of the radiation in the horizontal plane is almost 8dB for the main gun elevation of 20°. Conclusion This paper presented an electromagnetic modeling and an analysis of the monopole antenna positioned on the tank turret. The antenna was analyzed at frequencies from 1MHz to 30MHz, and the effect of the main gun elevation on the antenna radiation pattern was studied. It was determined that at low frequencies the elevation of the gun does not influence the radiation pattern much, but at higher frequencies, where the tank can be considered as a resonant structure, the detrimental effect on the radiation pattern can be quite substantial. At the frequency of 13MHz, the range of communication in the horizontal plane can be almost cut in half for certain directions if the elevation of the main gun is 20°.

62-80

Authors: Borisov Mirko A., Banković Radoje D., Drobnjak Siniša M.

Geomorphometric exploration applied in the military terrain analysis is based on the GIS methodology of spatial analyses and is related primarily to military terrain analyses. It includes relief assessment aiming at producing ground clearance charts for the analysis of terrain maneuverability and its deployment, cover and concealment possibilities. An evaluation analysis of geomorphological parameters was performed for the Avala test area using a few terrain parameters (visibility, terrain aspect and slope) as well as some terrain qualitative categories (e.g. vegetation density). Terrain slope Slope and aspect are morphometric terrain parameters that can be derived directly from the DTM using some GIS operations. Slope is the first derivative of a surface and has both magnitude and direction. Slope is perhaps the most important aspect of the surface form, since surfaces are formed completely of slopes, and slope angles control the gravitational force available for geomorphic work. Mathematically, the tangent of the slope angle is the first derivative of altitude, and it is a tangent or percent slope as this surface parameter is generally referred to. Slope is defined at each point as the slope of a plane tangent to the surface at that point. In practice, however, slope is generally measured over a finite distance, especially when data are obtained from a contour map. Terrain aspect Aspect is also the first derivative of a surface and has both magnitude and direction. The term aspect is defined as the direction of the biggest slope vector on the tangent plane projected onto the horizontal plane. Aspect is the bearing (or azimuth) of the slope direction, and its angle ranges from 0 to 360°. Analyses of terrain slope and ground clearance for military forces The analysis of land assessment of the Avala test area included the definition of relief categories in relation to cover and concealment purposes with the aim to include the geomorphological basis into the standard military procedure OCOKA (Observation and fields of fires; Cover and concealment; Obstacles and movement; Key terrain; Avenues of approach). A few parameters of relief significantly influencing the possibilities for cover and concealment (visibility, slope and aspect) were included into the definition of the model of terrain spatial analysis The morphometric data included in partial assessment categories were determined on the basis of the digital model relief analysis and by using GIS tools and given morphometric relief exploration methods. Analysis of vegetation effects on ground clearance for military forces Vegetation, in addition to terrain slope, presents one of the main factors in cross-country analyses and ground clearance assessments. In classification and extraction of vegetation from satellite images, numerous algorithms of two basic classification types, supervised and unsupervised classification, are applied. Supervised classification requires the identification of cover types of interest by user. Samples of pixels are then selected, based on available ground real information to represent each cover type. These samples are called training areas. The selection of appropriate training areas is based on the analyst's familiarity with the geographical area and his knowledge of the actual surface cover types presented in the image. Thus, the analyst 'supervises' the categorization of a set of specific classes. Unsupervised classification basically reverses the supervised classification process. Spectral classes are grouped first, based solely on the numerical information in the data, and then they are matched by the analyst to information classes (if possible). Programs, called clustering algorithms, are used to determine the natural (statistical) groupings or structures in the data. The analyst usually specifies how many groups or clusters are to be looked for in the data. In addition to specifying the desired number of classes, the analyst may also specify parameters related to the separation distance among the clusters and the variation within each cluster. The result of this iterative clustering process may result in some clusters that the analyst will want to combine subsequently, or clusters that should be broken down further on - each of these requiring a further application of the clustering algorithm. Thus, unsupervised classification is not completely without human intervention. Study area and THE used data The Avala hill test area, located in the central part of the Republic of Serbia, has been mapped extensively over the years and several GIS layers are available at various scales. The study area corresponds with one sheet topographic map at a scale of 1:25 000 (TM25 430-3-1) produced in the Military Geographical Institute (MGI). The main geomorphometric features of the test area include hill summits and shoulders, eroded slopes of small valleys, valley bottoms, a large abandoned river channel, and the river terrace. The elevation of the area ranges from 70 m to 500 m with an average of 195.05 m and a standard deviation of 56.7 m. The basic sources of information were the SPOT 5 image and the digital elevation model generated from the contour lines.

96-110

Authors: Jevtović Milojko V., Pavlović Boban Z.

A topological analysis of the structure of telecommunications networks is a very interesting topic in the network research, but also a key issue in their design and planning. Satisfying multiple criteria in terms of locations of switching nodes as well as their connectivity with respect to the requests for capacity, transmission speed, reliability, availability and cost are the main research objectives. There are three ways of presenting the topology of telecommunications networks: table, matrix or graph method. The table method is suitable for a network of a relatively small number of nodes in relation to the number of links. The matrix method involves the formation of a connection matrix in which its columns present source traffic nodes and its rows are the switching systems that belong to the destination. The method of the topology graph means that the network nodes are connected via directional or unidirectional links. We can thus easily analyze the structural parameters of telecommunications networks. This paper presents the mathematical analysis of the star-, ring-, fully connected loop- and grid (matrix)-shaped topology as well as the topology based on the shortest path tree. For each of these topologies, the expressions for determining the number of branches, the middle level of reliability, the medium length and the average length of the link are given in tables. For the fully connected loop network with five nodes the values of all topological parameters are calculated. Based on the topological parameters, the relationships that represent integral and distributed indicators of reliability are given in this work as well as the values of the particular network. The main objectives of the topology optimization of telecommunications networks are: achieving the minimum complexity, maximum capacity, the shortest path message transfer, the maximum speed of communication and maximum economy. The performance of telecommunications networks is analyzed in particular. Efficiency as an integral feature of reliability represents a measure of satisfying specific requirements of the mission (adequacy) over time (reliability) in a certain moment of time (availability). Today, modern telecommunications networks face another condition: the operation in extreme conditions (major floods, catastrophic earthquakes, forest fires, electromagnetic jamming and bombing from aircraft or remote control posts). In order to realize communication in such circumstances, it is necessary to introduce a new parameter - network survivability. The network survivability is defined as the ability of a network to maintain communication features while establishing, maintaining and terminating connections in extremely difficult conditions. This paper proposes a comprehensive definition of telecommunications networks including the network survivability as a very important factor. The best results in terms of network survivability are obtained by the network with full connection, but the drawback is its high implementation cost. The grid network is more favorable since it results in reducing the number of links between network nodes. With the number of branches increasing, the delay in the network also increases. The previous analysis shows that the average path length and the average length of links are critical values when selecting a configuration of functionally resistant telecommunications networks.

121-148

Authors: Pejanović Miloš J.

The development of personal computers and Internet technology causes continuous changes in methodological approaches and concepts of development of information systems. Most existing information systems, due to their heterogeneity, have a problem of integration of subsystems. In order to overcome this problem, software vendors offer different solutions. In this work we explore different approaches and propose an optimal way, with a special emphasis on its application in the military organization. By applying modern approaches in the development of information systems on the concept of distributed component systems, we come to the set of proposed solutions from different manufacturers. The solutions are related to the mechanisms which should ensure that components written in different languages cooperate with each other in heterogeneous systems that are in different nodes in the computer network. This work describes the concept of component distributed information systems of Internet technology and their capabilities and offers a solution specifying the implementation environment in the military organization. Access to the development of information systems In the development of information systems, an important role is given to the choice of appropriate methods and tools. For large systems such as military organizations, standardized procedures and methodologies for the development of information systems are recommended. There are different methodological approaches in the development of information systems: a systematic integrated approach to development (from design, implementation to implementation and maintenance) and development of information systems as technical - technological structures (standard computer and network service). The combination of these two approaches leads to the concept of 'open systems' that allow different standards and IT services to operate on these systems. The UML system description of the process of software development has many different but interconnected models: use case model, analysis model, design model and implementation model. The previously mentioned methods of development of information systems can be systematized and described in a unique way called the Larmanova method, usually through several stages: 1.Specification request 2.Analysis, 3. Design, 4.Implementation and 5. Testing. Development of information systems in a military organization The problem of development of information systems in the Internet environment by using software components is reduced to finding ways of determining a set of methodological procedures, concepts and approaches from the repositories of methods that support distributed information systems in Internet technology. Therefore, it is necessary to design a methodological approach that will be adaptive in accordance with the specific characteristics of military organizations. While developing their information systems, most foreign armed forces use standardized procedures and methodologies applied in their environment. In cases where it is not specifically defined, there is a tendency to use modern methodological procedures in accordance with technical and technological development. Component distributed information systems with an object-oriented approach in the Internet environment The usage of distributed objects can create client/server applications with a three-layer or multi-layer architecture which enables the implementation of synchronous or asynchronous solutions for the Internet and intranet. An example of a direct execution of transactions is an approach that relies on the CORBA model (Common Object Request Broker Architecture) and the Object Request Broker (ORB). However, the applications that use them are difficult and expensive to maintain. It is one of the reasons why the development of component models has become popular and experienced great development in recent years. Components with the implemented mechanism for performing transactions can be thus used in developing new applications. The component model allows easier changes and maintenance, and also shortens the time required for implementation, because there are various ready-made components that can be used. This approach to the implementation of transactions is called the declarative approach. Developers are free of care for the realization of mechanisms for controlling the execution of transactions. Important component models are implemented in COM + technologies (Component Object Model), EJB (Enterprise Java Beans), CORBA (Common Object Request Broker Architecture) and SOA (Service Oriented Architecture). Technologies for the implementation of component distributed information systems with an object-oriented approach in the Internet environment The results of testing with different communication models for remote component calls resulted in the following technologies: COM + / DCOML, CORBA / IIOP, EJB / RMI / IIOP and SOAP. Web Services represent the basic building blocks of future information systems, and in fact are applications available on the network and suitable for executing what is necessary at that moment. The main communication protocol is SOAP, ie. XML over HTTP. They can be created from the already made applications or from the start, while programming languages, finished components and platforms can be used by the user's choice. SOAP represents the environment for message exchange based on XML in the network and it uses the HTTP protocol application used by Web servers. Implementation of component distributed information systems with an object-oriented approach in the Internet environment From the aspect of this study, it can be concluded that there are two approaches through the J2EE (Java 2 Platform Enterprise Edition) environment and the Microsoft. NET set of technologies. SOAP is a new approach to professional development of distributed applications. It solves major problems with the platform and language dependences. It is able to work over the Internet and represents an open standard maintained by the W3C (the World Wide Web Consortium). The drawback of SOAP is interoperability which is not always 100% practicable with CORBA, ie. the existing implementation does not always meet the required reliability. This may be one of the causes of an insufficient number of available Web services on the Internet. The implementation of SOAP is possible in almost any programming language, on all popular platforms, so it has the potential to create a transparent web of services and applications that can be accessed on demand by everyone from every point, which will lead to the explosive growth of new services and therefore profits. SOAP does not try to replace CORBA or any other distributed system. Compared to CORBA, SOAP is less powerful, but it is impressive in its simplicity and scalability, which is very useful from the aspect of need for a wider acceptance by companies and by developers. SOAP is still developing, and a number of new protocols will appear, simplifying and facilitating the implementation of Web services in all business areas, including military information systems. Conclusion The possibility to connect the existing solutions is of great importance in determining the development strategy of information systems in the Army as well as in other complex organizational systems that contain heterogeneous hardware and software platforms. The research and analysis of the application of these standardized concepts, technologies and development platforms, including the experience of foreign armed forces lead to the conclusion that the concept of development of information systems in the Internet environment by using software components is a recommendation for strategic determination to overcome incompatible and unrelated existing partial software solutions. The basic idea is based on Web services which can be created from finished applications or from the start, while programming languages, finished components and platforms can be used by the user's choice. The applications for mutual remote communication used to use Remote Procedure Calls - RPC such as DCOM and CORBA, or they used to be completely unrelated. The SOAP protocol allows communication between applications on different operating systems, on different platforms, written in different programming languages. The world organization W3C12 has already published the SOAP version 1.1 as re commendation. and it continues with the development of the recommendation of the SOAP version 1.2. The applications exchange messages of the agreed format. Since the messages are formatted as XML documents, their processing and testing is simple and can be realized by any program designed to work with XML documents. The SOAP client creates an XML document that contains the corresponding request. This document is formatted in accordance with the SOAP specification. The document comes to the SOAP protocol which processes incoming requests and based on the received requests launches the appropriate application. Upon completion of processing, the SOAP protocol returns a response message to the SOAP client. It is, therefore, concluded that the data transformation relates to the use of the XML format. Web Services represent the basic building blocks of future information systems, ie. in fact they may be available applications on the military network. When the decision on a type of service is concerned, it is not decisive whether the standard Web service will be implemented or a specific, particularly developed one, for example for military use. In other words, these are resources which are addressable using a URL and which return the information to the user. Analyses determine the SOAP communication protocol ie. XML over HTTP. It also concluded that the main initiator of these changes is XML which through its simplicity allows the practical independence of applications and systems because it is understandable both for a man and a machine.