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Vummadisetty P.N.,Symbiosis International University | Kumar R.,Armament Research and Development Establishment
Turkish Journal of Electrical Engineering and Computer Sciences | Year: 2016

Two CPW-fed compact printed slot antennas for UWB applications are proposed in this paper. In both antennas, the slot in the ground plane is of octagonal shape, while the patch is rectangular in one of the antennas and hexagonal in the other. Thin metallic stubs of different lengths are added to the ground plane and protrude into the slot. These stubs help to improve the impedance matching over a broader bandwidth. The antennas are very compact in size and designed on low-cost FR4 substrate. The measured impedance bandwidths (S11 < -10 dB) achieved by the rectangular and hexagonal patch antennas are from 3.1 GHz to 5.6 GHz and 3.14 GHz to 5.34 GHz, respectively. The slot antenna with hexagonal patch is further modified to have dual-band characteristics. An L-shaped stub is attached to the ground plane to achieve an additional band from 2.45 GHz to 2.52 GHz for WLAN applications. The radiation patterns of the antennas are dumb-bell shape in the E-plane and omnidirectional in the H-plane. Detailed parametric studies of the antennas have been carried out. The simulated results are found to be in good agreement with the measured results. © 2016 Tübitak. Source

Rajan K.M.,Armament Research and Development Establishment
Proceedings of the 10th International Conference on Technology of Plasticity, ICTP 2011 | Year: 2011

Electro Slag Refined (ESR) AISI 4130 steel performs with fully tempered martensite microstructure having fine grain size of ASTM 7-8 have been used as the input material for a 3-pass reverse flow forming process for manufacturing high strength thin wall pressure vessel for a critical application. The forming machine parameters such as roller feed, spindle speed and roller stagger were experimentally fine tuned to achieve desired level of out of roundness and straightness of the finished flow formed tube for practical application. Heavily cold-formed thin wall tubes are likely to develop considerable residual stresses due to non-uniform deformation. Residual stresses can lead to failure of a component by buildup of stresses or by enhancing susceptibility to failure by mechanisms such as fatigue. Hence it is considered essential to measure the residual stress on the flow formed tube by x-ray diffraction technique. The measured residual stresses are quantified. A suitable sub-critical annealing process has been evolved and the flow formed tubes were subjected to the same. Residual stresses were measured again at the same locations and its magnitude was found to be negligible. The geometrical tolerances were found to be unaffected after the stress relief operation and hence a 3 pass forming followed by subcritical annealing has been followed for manufacture of large number of tubes. © 2011 IBF (RWTH Aachen) & IUL (TU Dortmund). Source

Arlulkar P.V.,Indian Defence Institute of Advanced Technology | Naik S.D.,Armament Research and Development Establishment | Naik S.D.,Applied Mathematics Group
Journal of Guidance, Control, and Dynamics | Year: 2014

An algorithm is developed to find the optimal two impulse solutions for a rendezvous problem between two noncoplanar elliptical orbits. The algorithm is based on the solution obtained using the dynamical approach for a MRLP (multiple-revolution Lambert problem). The algorithm requires a calculation of at most two solutions for any time of flight. The difference between velocity change for a stationary/fixed and a moving target is obtained. Sharp variation in velocity change is observed for the moving target. Coasting substantially reduces velocity change for rendezvous. Source

Nene M.J.,Defense Institute of Advanced Technology | Deodhar R.S.,Armament Research and Development Establishment | Patnaik L.M.,Indian Institute of Science
IEEE Sensors Journal | Year: 2015

In this paper, sensing coverage by wireless camera-embedded sensor networks (WCSNs), a class of directional sensors is studied. The proposed work facilitates the autonomous tuning of orientation parameters and displacement of camera-sensor nodes in the bounded field of interest (FoI), where the network coverage in terms of every point in the FoI is important. The proposed work is first of its kind to study the problem of maximizing coverage of randomly deployed mobile WCSNs which exploits their mobility. We propose an algorithm uncovered region exploration algorithm (UREA-CS) that can be executed in centralized and distributed modes. Further, the work is extended for two special scenarios: 1) to suit autonomous combing operations after initial random WCSN deployments and 2) to improve the network coverage with occlusions in the FoI. The extensive simulation results show that the performance of UREA-CS is consistent, robust, and versatile to achieve maximum coverage, both in centralized and distributed modes. The centralized and distributed modes are further analyzed with respect to the computational and communicational overheads. © 2001-2012 IEEE. Source

Murali V.,University of Pune | Naik S.D.,Armament Research and Development Establishment
Journal of Defense Modeling and Simulation | Year: 2014

This paper reports important parameters that affect water ricochet studies for artillery projectiles. The factors affecting ricochet are critical angle and critical velocity of impact. This study has developed mathematical models for ricochet studies and derived expressions for critical angle and critical velocity. Simulations have been carried out for standard bullets, the data for which are available in open literature. The effects of mass, diameter, and length of the projectile on critical velocity and angle are studied through two non-dimensional parameters, µ and θ. The results suggest how ricochet conditions can be avoided by defining initial data at launch. © 2014 The Society for Modeling. Source

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