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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.


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Journal ArticleDOI
TL;DR: This letter considers simultaneous primary user (PU) detection and channel estimation for censoring-based spectrum sensing in cognitive radio networks over fading channels and optimize the censoring parameter and the power allocation for throughput maximization under transmit and interference power constraints.
Abstract: This letter considers simultaneous primary user (PU) detection and channel estimation for censoring-based spectrum sensing in cognitive radio networks over fading channels. We formulate the problem mathematically for Rician and Rayleigh fading channels. Closed-form expressions are derived for the critical performance metrics in low SNR regime. Further, we optimize the censoring parameter and the power allocation for throughput maximization under transmit and interference power constraints. Our results demonstrate that simultaneous PU detection and channel estimation substantially improve the throughput of cognitive radio networks over an approach where PU detection and channel estimation are treated independently.

8 citations

Journal ArticleDOI
TL;DR: In this paper, a 3D modified proportional navigation (PN)-based guidance law based on the total demand vector concept is presented, which can maintain the navigation constant to the designer-selected value for any 3D engagement scenario with associated lead angles and any velocity profile with missile longitudinal accelerations/decelerations.
Abstract: Different proportional navigation (PN)-based guidance laws-pure proportional navigation (PPN), true proportional navigation (TPN), and proportional navigation with boost acceleration compensation generally used cannot maintain fundamental parameter of proportional navigation, viz, Navigation constant to the desired value in the presence of significantly high lead angles and missile longitudinal accelerations/decelerations In a real-life situation with sensor noises and hardware constraints, this navigation constant should be maintained tightly at the selected value, which is generally between 3 and 4, for optimum performance In this paper; a new 3-D modified PN guidance law based on a total demand vector concept is presented, which can maintain the navigation constant to the designer-selected value for any 3-D engagement scenario with associated lead angles and any velocity profile with missile longitudinal accelerations1 decelerations Generality of this guidance law is brought out and superiority of this guidance law over the commonly used proportional navigation-based laws like PPN, TPN and PN with boost acceleration compensation has been demonstrated by applying it to the real-life 3-D engagement scenarios of different hypothetical missiles

8 citations

Journal ArticleDOI
TL;DR: In this article, three-dimensional Navier Stokes equations along with two-equation turbulence models and Eddy dissipation concept (EDC)-based combustion models are solved using commercial CFD software.
Abstract: Thermochemical exploration of mixing and combustion of parallel hydrogen injection into supersonic vitiated air stream in a divergent duct is presented. Three-dimensional Navier Stokes equations along with twoequation turbulence models and Eddy dissipation concept (EDC)-based combustion models are solved using commercial CFD software. Chemical reaction for H2-air system is modelled by two different simple chemical kinetic schemes namely; infinitely fast rate kinetics as well as the single-step finite rate kinetics. Grid convergence of the solution is demonstrated and a grid convergence index-based error estimate has been provided. Insight into the mixing and combustion of high-speed turbulent reacting flow is obtained through the analysis of various thermochemical variables. Very good comparisons are obtained for the exit profiles for various fluid dynamical and chemical variables for the mixing case. For reacting case, the comparison between the experimental and the numerical values are reasonable. Parametric studies were carried out to study the effect of different turbulence models and turbulent Schmidt numbers. It is seen that Wilcox k-w turbulence model performed better than the other two-equation turbulence models in its class. Strong dependence of flow behaviour on turbulent Schmidt number was observed. The results indicate that simple chemical kinetics is adequate to describe the H2-air reaction in the scramjet combustor. Defence Science Journal, 2010, 60(5), pp.465-475 , DOI:http://dx.doi.org/10.14429/dsj.60.57

8 citations


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