The aim of this study is to obtain, by optimizing the deposit parameters, optimal structural and mechanical properties of Ni20Al layers to be applied on a radar station part. The powder was deposited by the process of atmospheric plasma spraying (APS), with a plasma spray (PS) distance of 80, 90 and 100 mm. The coating with the best characteristics was deposited on the hardener of the GTD 2PV8 turbo gas engine for a radar station, in order to reduce the effect of oxidation and vibration on the wear at 450 500°C. The quality of Ni20Al coating layers was assessed on the basis of their microstructure, microhardness and tensile strength. The best structure and mechanical properties were found in the layers deposited with a distance of plasma spray of 80 mm. The surfaces morphology of the deposited coatings and the fracture morphology of the best layers were examined with the SEM (scanning electron microscope). The microstructure of the deposited layers of coatings was examined by light microscopy. The microstructural analysis of the deposited layers was performed according to the Pratt-Whitney standard. The evaluation of the mechanical properties of the layers was done by examining microhardness with the HV0.,3 method and tensile testing was used for the bond strength. Studies have shown that the plasma spray distance significantly affects the mechanical properties and the microstructure of coatings. The effect of Ni20Al coating application has been tested on a hardener of the GTD 2PV8 turbo gas engine on a radar station.
Vojnotehnicki glasnik / Military Technical Courier / Военно-технический вестник
2013. — Выпуск 2
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A method for the identification of the DC state space model para meters based on the minimization of the error function using the least squares method is described in this paper. The algorithm is practically applied in the laboratory environment on an industrial DC motor. The verification of the results was performed by comparing the characteristic signals of real and modeled systems. The results show that the quality of the identification is satisfactory.
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Рассмотрен общий принцип преобразования энергий в открытых энергосистемах. Дано обоснование работы теплового насоса на основе молекулярно-кинетической теории. Выяснены разные механизмы охлаждения самолета при его полете в неподвижной атмосфере. Показано, в каких условиях электромагнитные системы могут работать как тепловой насос. Установлено, что самолет в полете представляет собой тепловой насос .
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Mobile station localization in mobile networks started with simple methods (e.g. Cell-ID method) which required only slight modifications of network infrastructures. Principally, it was about network localization by which a localization service became available to all types of mobile phones. Due to low precision, the initiated development of more sophisticated methods has not been finished yet. Among the advanced location-based methods are those based on the measurement of location parameters in the time domain. In this paper the general consideration of radio location methods in 3G (UMTS) radio networks is presented. The use of time based measurement methods was analysed in detail. Due to the limited article length, the use of other locating methods in 3G networks (based on power measurements, on radio direction measurement, and on cells identification - Cell ID and global positioning system - GPS) are not described.
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Dynamic market and environmental changes greatly affect operating of logistics systems. Logistics systems have to realize their activities and processes in an efficient way. The main objective of this paper is to analyze different aspects of efficiency measurement in logistics and to pr opose appropriate models of measurement. Measuring efficiency in logistics is a complex process that requires consideration of all subsystems, processes and activities as well as the impact of various financial, operational, environmental, quality and other factors. The proposed models have a basis in the Data Envelopment Analysis method. They could help managers in decision making and corrective actions processes. The tests and results of the model show the importance of input and output variables selection.
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The fixed orthodontic appliance consists of brackets that are bonded to the teeth. When the wire is engaged in the slot of the brackets, it generates forces for orthodontic tooth movement. The change in periodontal blood supply provides a biological response which leads to remodelling of the alveolar bone and the orthodontic tooth movement. Many variables influencing orthodontic treatment cannot be controlled fully, such as growth and tissue response to appliances. However, the force placed on the tooth should be a controllable variable, and a care ful study of the physics underlying clinical applications can help in reducing undesirable side effects. The properties of orthodontic wires such as: strength, stiffness, elasticity and spring-back define their clinical usefulness. The ideal orthodontic wire should exhibit the following properties: large spring-back, low stiffness, good formability, high stored energy, biocompatibility and environmental stability, low surface friction, and the capability of being welded or soldered to auxiliaries. The ideal arch wire has not been introduced yet. Once the wire is activated or bent, it is the unloading or deactivating forces that produce the orthodontic tooth movement. For these reasons, it is necessary to know the force level caused by each individual wire used in orthodontic treatment. Finally, the purpose of this paper is a presentation of force measurements which are generated by different super-elasticity NiTi wires.
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The fixator is a medical device that provides support to fractured biological structures. Metal biomaterials are mainly used for replacing broken or damaged hard tissues such as bones because of their high strenght, toughness and corrosion resistance. Materials such as stainless steel, titanium and aluminium alloys (Ti-6Al-4V), cobalt and chromium alloys, composite materials and other biocompatible materials are used in orthopedy for the stabilization of connective tissue injuries or as a substitute for the bone tissues. Fixators are classified according to the place of installation to external and internal fixators. Widely used medical fixators are pins, rods plates, screws, pipes, wires, nails and external fixators. Conventional and non-conventional methods of processing are used in the production process for all types of fixators.
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The cost-benefit analysis is a very useful tool for the evaluation and selection of public projects, especially those with a life expectancy of 30 or more years, such as: building hospitals, irrigation canals, bridges, tunnels, development and production of new funds and new weapons and military equipment (WME), etc. The analysis can also be applied in the private sector for the evaluation of projects which are in one part financed by state funds or through loans when entrepreneurs or companies doe not show interest or do not have sufficient funds for the realization of projects (for opening schools, theaters, etc). The cost-benefit analysis provides information for government agencies and commercial banks about the profitability of investments, without which they cannot make a decision of financial support for the project realization. The selection of the best investment alternatives is realized on the basis of financial and economic analyses as two integral parts of the cost-benefit analysis. The content of this paper is the financial analysis that examines the financial viability of the project only from the standpoint of the sponsor and financier. In one of the next issues of the journal, we will also process the economic analysis as well as a complete analysis of the effectiveness of the project.
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This paper describes models and conditions for the application of the Mass Serving Theory in order to analyze relations between clients demanding the service and channels which provide the service as well as to design technological elements in the optimal regime for the given maintenance system. Based on the actual data collected and the statistical analysis of the expected intensity of combat vehicle arrivals and queuing at service for technical maintenance, the mathematical modeling of a real process of queuing was carried out and certain parameters quantified, in terms of determining the weaknesses of the existing models and the corrective actions needed.
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Infrared (IR) thermography, as a diagnostic technique, is used to find anomalies in the thermal signature of the Military museum building in Belgrade, to identify irregularities or deficiencies, such as wet materials, voids, or missing insulation and to inspect energy efficiency of the museum building and microclimatic indoor conditions. It is very important to perform preventative maintenance and stop undesirable environment influences that induce structural damage, modification of materials and agglomeration of pollutants and microorganisms on the cultural heritage artifacts, stored in the museum depot or exhibited in the galleries. The main causes for corrosion in historical buildings and museum artifacts are moisture and changeable temperature conditions. This paper deals with the results obtained in the application of IR thermography in determination of these conditions in the Military museum building, where very important metal artifacts are exhibited and deposed. The results show poor thermal insulation, wet walls and, generally, low energy efficiency.
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This paper describes an ad hoc network, specific for its mobility, more abruptness and self-organization. Because of their properties, routing protocols in ad hoc networks must be adapted to applications and satisfy safety requirements - confidentiality, integrity and availability. These are the characteristics and challenges for the development of protocols to counter attacks, especially in military applications. Some of the known attacks are described and one of the methods for safety testing routing protocols is listed.
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Introduction Accounting of telecommunication services is closely related to the functions of authentication and authorization. These functions are usu ally considered together and implemented within the same server using a common protocol. The most renowned protocols for authentication, authorization and accounting are the RADIUS and Diameter protocols. AAA functions and related protocols In this chapter, the accounting management architecture developed by IETF is presented. It includes the interaction between network elements, accounting servers and billing and charging servers. Ac counting data can be used for management, planning and charging users as well as other (specific) purposes. Authentication is the process of confirming a user's digital identity, usually through some type of identifiers and related data. Authorization determines whether a particular entity is authorized to perform an activity. Basic Functions of the RADIUS Protocol The RADIUS architecture is based on a client-server model. It uses UDP on the transport layer. Transactions between the client and the server are authenticated, which is achieved by using a common secret key that is never sent through the network. Given the limited resources available to network devices, RADIUS facilitates and centralizes charging end users, provides some protection against active attacks by unauthorized users and it has great support from different network equipment vendors. Although RADIUS is a widely accepted protocol for the mechanisms of authentication, authorization and accounting, it has certain shortcomings that may be caused by the protocol itself or by its poor implementation. Architecture and Operation of the Diameter Protocol Diameter is a scalable protocol designed by the IETF working group in order to eliminate shortcomings and functional limitations of the RADIUS protocol and eventually to replace it in the near future. Most of the basic Diameter mechanisms and its functionality are based on the fundamental functionality of the RADIUS protocol and the rest is a result of new solutions and improvements to the existing ideas. The Diameter protocol focuses on the expansion of flexible, advanced rou ting algorithms, dynamic troubleshooting and safety characteristics of the transport layer. This paper defines the basic packet formats, data transfer mechanisms and error management, methods of communication between individual elements of the architecture and basic security functions. The Diameter protocol architecture is based on the peer-to peer model. Besides clients and servers, network agents can be the elements of this architecture. The Diameter agent is an element that does not allow authentication / authorization locally, but the server per forms this operation, while one node can be both the client and the server simultaneously. The role of agents can be forwarding (Relay Agent), redirection (Redirect Agent), mediation (Proxy Agent) and translation (Translation Agent). Since the peer-to-peer model is applied, each Diameter element can establish more connections at the same time. Diameter enables the delivery of attribute value pairs, the possibility of negotiation, error notification, extensibility by adding new commands and attribute value pairs, the basic services necessary for applications such as managing user sessions or accounting. Comparison of the RADIUS and Diameter protocols Although at the protocol market for authentication, authorization and accounting, the RADIUS protocol remains the most popular, its popularity and dominance has a decreasing tendency. The main reasons for this are more prominent limitations which are particularly perceived due to new and increasingly popular technology. There fore, the main issue is about a protocol that will replace RADIUS. The peer-to-peer architecture used by Diameter is much more flexible than the client-server model because in the peer-to-peer architecture every element can be both the client and the server, depending on the current needs of the network. At the transport layer, Diameter uses the TCP or SCTP protocols. When compared to UDP, these protocols provide reliable transmission which is very important for applications exchanging data related to accounting. In addition, the Diameter protocol allows the transmission of accounting information in real time and it incorporates several methods for troubleshooting in order to minimize the loss of accounting data when a failure occurs, which is not the case with RADIUS. Given the present benefits, introduced improvements, flexibility, expandability, IETF and 3GPP's sup port and the support of big companies, there is a great chance that Diameter will replace RADIUS. Conclusion This paper presents a general overview of the RADIUS and Diameter protocols, including some of their basic operations with a special emphasis on accounting applications. The similarities of these protocols are reflected in the support of the same functions in a similar format of the packages. The differences are related to the protocol architectures and the methods of determining authentication, authorization and accounting mechanisms. Regarding accounting aspects, the most important advantages of the Diameter protocol are its possibility to transmit accounting information in real time and implemented mechanisms for troubleshooting in order to minimize the loss of ac counting data in case of failure. Owing to to these characteristics, the Diameter protocol achieves a significant advantage over RADIUS in next generation networks.
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Security of wireless computer networks was initially secured with the WEP security protocol, which relies on the RC4 encryption algorithm and the CRC algorithm to check the integrity. The basic problems of the WEP are a short initialization vector, unsafe data integrity checking, using a common key, the lack of mechanisms for management and ex change of keys, the lack of protection from the endless insertion of the same package into the network, the lack of authentication of access points and the like. The consequences of these failures are easy attacks against the WEP network, namely their complete insecurity. Therefore, the work began on the IEEE 802.11i protocol, which should radically improve the security of wireless networks. Since the development of a protocol lasted, the WPA standard was released to offset the security gap caused by the WEP. The WPA also relies on RC4 and CRC algorithms, but brings temporary keys and the MIC algorithm for data integrity. The 802.1X authentication was introduced and common keys are no longer needed, since it is possible to use an authentication server. The length of the initialization vector was increased and the vector is obtained based on the packet serial number, in order to prevent the insertion of the same packet into the network. The weakness of the WPA security mechanism is the use of a common key. WPA2 (802.11i) later appeared. Unlike the WPA mechanism that worked on old devices with the replacement of software, WPA2 requires new network devices that can perform AES encryption. AES replaces the RC4 algorithm and delivers much greater security. Data integrity is protected by encryption. Despite progress, there are still weaknesses in wireless networks. Attacks for denial of service are possible as well as spoofing package headers attacks. For now, it is not advisable to use wireless networks in environments where unreliability and unavailability are not tolerated.
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This paper presents the assessment of the operational - geographic features of the Drina-Velika Morava strategic direction. Due to the scope of the article, a variant of the assessment of the strategic direction is presented through its socio-geographic factors, while the mathematical-geographical and physical-geographic factors, as well as the opera ting lines of action are not discussed. Within the socio-geographic factors, the characteristics of the population, economy and communication networks are considered. The geographic area of the direction is nationally compact and provides war mobilization of units with no particular strain. The transportation network is not fully developed which makes combat operations difficult to attackers and facilitates them for the def-fenders.. There are significant technical and technological potentials in the direction of the zone, but they are not evenly distributed. After the consideration of the complex socio-geographical factors, it is concluded that the shown strategic direction enables, without any special restrictions, a successful execution of combat operations in the long run.
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The design of physical security measures is a specialized technical area that does not fall in the normal skill record and resume of commanders, architects, engineers, and project managers. This document provides guidance to those parties tasked with implementing existing and emerging physical protection system requirements: - Creation of a single-source reference for the design and construction of physical security measures for high-risk personnel (HRP). - Promulgation of multi-service standard recommendations and considerations. - Potential increase of productivity of HRP and reduced temporary housing costs through clarification of considerations, guidance on planning, and provision of design solutions. - Reduction of facility project costs. - Better performance of modernized facilities, in terms of force protection, than original facilities. Throughout this process you must ensure: confidentiality, appropriate Public Relations, sustainability, compliance with all industrial guidelines and legal and regulatory requirement, constant review and revision to accommodate new circumstances or threats.
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В настоящей книге на современном уровне развития физи ческих представлений о взаимодействии движущегося тела с неподвижной атмосферой континуальная теория д-Аламбера Эйлера и ударная теория Ньютона объединены в единую тео рию, которая позволила правильно описать полет существую щих летательных аппаратов и установить, что полет лета тельных аппаратов в атмосфере Земли представляет собой тепловой насос. В результате предсказана возможность поле та летательных аппаратов с овальным крылом, а в бортовом энергетическом комплексе применить тепловые насосы.
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Poboljšаni EMTAS kompjuterski sistem za kontrolu minobаcаčke vаtre iz Mistrаl Inc, Otkazan nastavak projekta vojnog balona LEMV, Projekat MULE (LS3) - Četvoronožni roboti izvršavaju glasovne komande, Projekat Gladijus - nemački sistem vojnika budućnosti, Odeća za zaštitu od osmatračkih uređaja bespilotnih letelica, Ruske padobranske jedinice naoružavaju se jurišnim robotom MRK-27 BT, Očno sočivo umesto naglavnog displeja za proširenu stvarnost.
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Zašto se gasi program Global Hawk Block 40, Veoma brze letelice sa vertikalnim poletanjem i sletanjem, Iran otkriva nove protivvazduhoplovne sisteme, Kineski transportni avion Y-20 na svom prvom letu, Kompanija Rheinmetall izvršila je uspešnu probu visokoenergetskog lasera, Novi dizajn za indijski napredni srednji borbeni avion, Odobrena proizvodnja serije novog E-2D Hawkeye, Probni let kineskog mornaričkog lovca dvoseda J-15, Ruski koreni u kineskom Z-10, Satcom na izraelskim F 15.
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Pripreme za opitovanje opsežnih modifikacija strategijskih bombardera B-1B, Uspešna provera integracije avio-bombe GBU-53/B na jurišnik F-35.
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Инструкция для авторов о порядке подготовки статьи к опубликованию в журнале «Военно-технический вестник» разработана в соответствии с Актом о редактировании научных журналов Министерства науки и технологического развития Республики Сербия, № 110-00-17/2009-01 от 09.07.2009 г. Применением этого Акта, в первую очередь, обеспечивается совершенствование качества отечественных журналов и их более полного включения в международную систему обмена научной информацией. Инструкция соответствует международным стандартам ISO 4, ISO 8, ISO 18, ISO 215, ISO 214, ISO 18, ISO 690, ISO 690-2, ISO 999, ISO 5122 и соответствующим отечественным стандартам.