scispace - formally typeset
Search or ask a question
Institution

Defence Research and Development Laboratory

FacilityHyderabad, India
About: Defence Research and Development Laboratory is a facility organization based out in Hyderabad, India. It is known for research contribution in the topics: Mach number & Turbulence. The organization has 404 authors who have published 420 publications receiving 4183 citations. The organization is also known as: DRDL.


Papers
More filters
Journal ArticleDOI
TL;DR: This paper proposes a censored spectrum sharing strategy which considers both the detection and estimation performances simultaneously and is capable of improving the throughput of MIMO cognitive radio network.
Abstract: Multi-antenna technologies have been widely used in modern wireless communication systems to achieve diversity gain, spatial multiplexing gain, and better interference suppression. Beamforming has been considered as a potential candidate for throughput maximization in MIMO cognitive radio networks. However, the efficient implementation of beamforming demands for accurate knowledge of channel estimate. Conventional spectrum sharing strategies treat the detection and estimation problems in uncoupled manner, which may not result in the overall optimum performance. In this paper, we propose a censored spectrum sharing strategy which considers both the detection and estimation performances simultaneously and is capable of improving the throughput of MIMO cognitive radio network. We derive analytical expressions for the critical parameters and provide simulation results to validate our derivations.

3 citations

Journal ArticleDOI
01 Jul 2014
TL;DR: In this paper, a multi-objective optimization is carried out for the first time to optimize abrasive water jet machining (AWJM) process parameters for graphite, where the input process parameters considered are pressure (P), traverse rate (TR), and mesh size (MS).
Abstract: Multi-objective optimization is carried out for the first time to optimize abrasive water jet machining (AWJM) process parameters for graphite. Experiments are carried out by Response Surface Methodology (RSM) using Box-Behnken method. The input process parameters considered are pressure (P), traverse rate (TR) and mesh size (MS). Results are analyzed using Analysis of Variance (ANOVA) and response surface considering individually output parameters such as depth of cut (DOC) and surface roughness (Ra). ANOVA and response surface analyses indicated that similar combinations of AWJM process parameters such as high pressure (176 MPa), medium mesh size (# 100) and low traverse rate (1000 mm/min) resulted in higher depth of cut as well as lower Ra. Therefore, in order to verify the above combinations and to improve productivity, multi-objective optimization is carried out using Particle Swarm Optimization (PSO) to achieve higher depth of cut and low Ra together. From the PSO analysis, it is observed that pressure of 154 MPa, traverse rate of 1877 mm/min and mesh size of # 100 result in high depth of cut and low Ra together. The result obtained from the PSO is compared with that of ANOVA. The outcome of this study will be useful to the manufacturing engineers for selecting appropriate input AWJM process parameters for machining graphite, which has various applications such as aerospace, defence, etc. Multi-Objective Optimization of Abrasive Waterjet Machining Process Parameters Using Particle Swarm Technique

3 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of temperature dependency of material properties on thermal buckling and free vibration of functionally graded material (FGM) beams is studied, and an exhaustive set of numerical results, in terms of buckling temperatures and frequencies, are presented, considering the temperature independent and temperature dependent material properties.
Abstract: The effect of temperature dependency of material properties on thermal buckling and free vibration of functionally graded material (FGM) beams is studied. The FGM beam is assumed to be at a uniform through thickness temperature, above the ambient temperature. Finite element system of equations based on the first order shear deformation theory is developed. FGM beam with axially immovable ends having the classical boundary conditions is analysed. An exhaustive set of numerical results, in terms of buckling temperatures and frequencies, is presented, considering the temperature independent and temperature dependent material properties. The buckling temperature and fundamental frequency obtained using the temperature independent material properties is higher than that obtained by using the temperature dependent material properties, for all the material distributions, geometrical parameters in terms of length to thickness ratios and the boundary conditions considered. It is also observed that the frequencies of the FGM beam will reduce with the increase in temperature. This observation is applicable for the higher modes of vibration also. The necessity of considering the temperature dependency of material properties in determining thermal buckling and vibration characteristics of FGM beams is clearly demonstrated.Defence Science Journal, 2013, 63(3), pp.315-322, DOI:http://dx.doi.org/10.14429/dsj.63.2370

3 citations

Journal ArticleDOI
01 Oct 2014
TL;DR: In this paper, the authors explored the growth rate of high-speed mixing layer between two dissimilar gases through the model free simulation results and found that the correlation between temperature and density fluctuations no longer remain correlated completely for the mixing layer formed between two different gases at different temperatures in contrast to the complete pressure density correlation for similar gases.
Abstract: The growth rate of high-speed mixing layer between two dissimilar gases is explored through the model free simulation results. To analyse the cause for the higher mixing layer growth rate in comparison to the existing values reported in literature, the results were compared with the model free simulations of mixing of two high-speed streams of nitrogen (similar gas) at matched temperature and density. The analysis indicates that pressure and density fluctuations no longer remain correlated completely for the mixing layer formed between two dissimilar gases at different temperatures in contrast to the complete pressure density correlation for similar gases. It has been observed that the correlation between temperature and density fluctuations is near -1.0 for dissimilar gases in the mixing layer region and is much higher than for similar gases. It is concluded that mixing layer of similar gases shows a decrease in growth rate due to compressibility effect, while that of dissimilar gases shows a decrease due to dominant temperature effect on density.

3 citations

Journal ArticleDOI
TL;DR: In this paper, a robust, largedeflection, and large-force MEMS-based microballoon actuator for aerodynamic control of flight vehicles such as projectiles, micro air vehicles, aircrafts, etc.
Abstract: The development of microelectromechanical systems (MEMS) technology and the suitability and compatibility of sizes of microactuators with the boundary layer thickness fueled the active flow separation control to gain the air flow momentum for the last few years. The present paper deals with the development of a robust, largedeflection, and large-force MEMS-based microballoon actuator for aerodynamic control of flight vehicles such as projectiles, micro air vehicles, aircrafts, etc. Experiments were carried out on the scaled-up models for different input pressure conditions to study the response of microballoon actuator. To evaluate the performance of the microballoon actuators, simulation studies on MEMS scale models were conducted in the CoventorWare environment. Simulation studies involving static and dynamic analyses have been carried-out on the microballoon actuator models. Various geometric and input parameters influencing the behaviour of the microballoon actuator were investigated. It has been observed that a maximum deflection of 1.2 mm to 1.5 mm can be achieved using microballoon actuators and the maximum operational frequency of 60 Hz to 80 Hz can be used for the operation of microballoon actuators. Also, the sizes of the microballoon actuators designed are compatible and suitable to be used in turbulent boundary layer of aerodynamic flight vehicles. Defence Science Journal, 2009, 59(6), pp.642-649 , DOI:http://dx.doi.org/10.14429/dsj.59.1570

2 citations


Authors

Showing all 406 results

Network Information
Related Institutions (5)
Defence Metallurgical Research Laboratory
2.6K papers, 51.6K citations

78% related

Indian Space Research Organisation
5.7K papers, 62.3K citations

70% related

National Institute of Technology, Karnataka
7K papers, 70.3K citations

69% related

Indian Institute of Technology Bhubaneswar
3.1K papers, 48.8K citations

69% related

Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
20224
202117
202017
201923
201840
201735