Vojnotehnicki glasnik / Military Technical Courier

7-22

Authors: Mrdak Mihailo R.

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.

37-54

Authors: Gretchihin Ivanovich Leonid

The paper discusses the general principle of energy conversion in open energy systems and presents the heat pump operating principle based on the molecular-kinetic theory. Various mechanisms of aircraft cooling during flight in the fixed atmosphere have been explained as well as the conditions in which electromagnetic systems can operate as heat pumps. It is stated that the aircraft in flight represents a heat pump.

84-104

Authors: Andrejić Milan M.

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 propose 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.

123-139

Authors: Đenadić Dalibor M., Tanikić Dejan I., Manić Miodrag T., Ranđelović Saša S., Đekić Petar S.

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.

159-181

Authors: Petrović Veljko P., Mrdak Veselin L., Luković Branka R.

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.

200-217

Authors: Stefanović Radiša R., Pavlović Boban Z.

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.

242-271

Authors: Tepšić Dejan M., Veinović Mladen Đ.

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 exchange 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.

291-308

Authors: Cice Jelena S., Andrejić Marko D., Dragović Nebojša K.

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.