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Tudose V.,Polytechnic University of Bucharest | Cirmaci M.,Military Technical Academy of Bucharest | Gheorghiu H.,Polytechnic University of Bucharest
UPB Scientific Bulletin, Series D: Mechanical Engineering | Year: 2012

The paper presents a study of the influence of the temperature difference ensued as a result of automatic fire on the accuracy of sight of an optical device mounted on an automatic weapon. Thermal analysis was carried out by numerical calculation for a model of the mechanical structure of the device, which led to the values of displacements produced by expansion, for two different materials analyzed: duralumin and steel. It made findings concerning the possible use of the material most suitable. Source

Takacs A.,CNRS Laboratory for Analysis and Architecture of Systems | Takacs A.,National Polytechnic Institute of Toulouse | Takacs A.,Military Technical Academy of Bucharest | Fonseca N.J.G.,CNRS Laboratory for Analysis and Architecture of Systems | And 4 more authors.
IEEE Antennas and Wireless Propagation Letters | Year: 2010

This letter addresses the miniaturization of the open-ended quadrifilar helical antenna for satellite VHF frequency band telemetry links systems. The miniaturization is achieved using combinations of sinusoidal profiles, and several designs are obtained using an optimization process based on intensive electromagnetic simulations. The design and experimental validation are reported in this letter, and a significant height reduction from 48% to 72% is obtained using various combinations of sinusoidal profiles (i.e., wires mathematically described by sinusoidal functions) without a significant degradation of the radiation pattern, directivity, and polarization purity. Moreover, the input matching is slightly improved for the compact antennas. It was observed that the efficiency and gain do not decrease linearly with the reduction of the antenna height. © 2010 IEEE. Source

Sebesan I.,Polytechnic University of Bucharest | Badea C.-N.,Polytechnic University of Bucharest | Stefan V.,Polytechnic University of Bucharest | Sebesan M.R.,METROREX SA | And 2 more authors.
Journal of the Balkan Tribological Association | Year: 2015

The railway vehicle running is accompanied by forced vibration of the sprung mass, the springs may have large amplitudes vibrations that are hazardous to produce the phenomenon of resonance. Oppose this danger damping properties of the material elements of suspension and friction between oscillating masses liaison bodies which in most cases are insufficient. Therefore, in modern vehicles, in which suspension was used without friction spring elements (helical spring, torsion spring) should be introduced shock. They produce strong forces that dissipate vibration energy and thus limit their amplitudes. The freight wagon ride quality is determined by the appropriate choice of the damping characteristics to satisfy both structural and functional parameters of freight wagons as well as its operating system. Using buffers that were designed for a specific type of freight car wagons, the other cars driving leads to compromise their quality. The silencer (shock absorber) must have stable damping characteristics as changing the thermal and operating conditions, susceptibility to damage reduced weight and size and allow easy access for intervention. The vibration dampers are mounted directly between vehicle parts connected by springs (between axle box and the bogie frame and / or between the bogie and vehicle box) or the insertion of a resilient damper shock absorber to protect against excessive dynamic applications. To achieve the desired damping, the dampers directions are mounted vertically, horizontally or obliquely. After the acting principle on freight wagons, in generally it is used the hydraulic dampers (viscous) and friction dampers (for Coulomb friction). Source

Mazare P.,Military Equipment and Technologies Research Agency | Szilagyi A.,Military Equipment and Technologies Research Agency | Stoica D.-S.,Military Equipment and Technologies Research Agency | Cazanaru D.,Military Equipment and Technologies Research Agency | And 3 more authors.
2010 8th International Conference on Communications, COMM 2010 | Year: 2010

The paper presents a method to generate the symmetrical plan curve for a Cosec2 radiation pattern double curved antenna reflector, for the case when the primary radiation source has a Cos4 radiation pattern. There is also shown the diffraction calculus for the antenna having the reflector generated by using the calculated vertical profile. ©2010 IEEE. Source

Sebesan I.,Polytechnic University of Bucharest | Popa G.,Polytechnic University of Bucharest | Badea C.-N.,Polytechnic University of Bucharest | Spiroiu M.A.,Polytechnic University of Bucharest | Badea A.,Military Technical Academy of Bucharest
Journal of the Balkan Tribological Association | Year: 2015

The general conditions which must comply the railway vehicle suspension, with special reference to freight cargo wagons are directly related to the fact that when driving the vehicle is subjected to the action of vibrating pulses, with adverse effects on the quality of gait. The vehicle responds to impulses generated during runtime through suspension, which aims to reduce the acceptable values. Ensuring the integrity and the integrity of the transported goods vehicle depends crucially on the quality of the vehicle suspension. The suspension of the vehicle must ensure stable dynamic behaviour going straight and stable dynamics behaviour with little guiding force when passing through curves. The suspension should contribute to reducing mutual forces between the vehicle and the path, keeping them within the limits determined by the traffic safety and the need to ensure the protection of both the rolling and track. At walking circulation in curved, under the centrifugal forces unmatched vehicle moving box and bowed transverse spring suspension, there is a danger of overall output. For vehicles that do not have special devices to compensate for insufficient super-elevation path, this function is performed by the vehicle suspension. With increasing speed, the forces of inertia of the masses involved in hunting movement grow and come to dominate the movement and the speed to a certain value, called the critical speed, they break pseudo-sliding balance of forces between wheels and rails. It produces cross slip axle fitted within the guide track and appointed by the lips of the wheel rims, which in normal walking in line, is only a supplement safety. With the loss of hunting motion stability, transverse efforts exerted itself become excessive, can endanger road safety. Source

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