Defence Research and Development Organisation
Defence Research and Development Organisation
Kumar A.S.,Naval Science and Technological Laboratory |
Rao K.V.,Naval Science and Technological Laboratory |
Prasad V.S.R.K.,Anil Neerukonda Institute of Technology and Science |
Rao V.B.,Defence Research and Development Organisation
Propellants, Explosives, Pyrotechnics | Year: 2014
The blast wave propagation in underwater explosion was studied. The shock propagation in water medium was different from that in air. The blast effect in water lasted longer and offered resistance to the expansion of hot gases and release of energy. A theoretical analysis of the expansion of blast wave in water was carried out and numerical results for pressures and temperatures were obtained as functions of distance and time by analytically solving the governing equations. The initial peak pressures of blast waves, which were required for theoretical analysis were calculated using the blast wave theory. Underwater blasts with different weights (0.045, 0.5, and 1.0 kg) of the aluminized high explosive HBX-3 were conducted to record pressure as a function of distance and time from the blast point. Theoretical results were compared with experimental data and empirical data for HBX-3 from literature. Since the measurement of pressure and temperature at close proximity of point of detonation is difficult, theoretical modeling of underwater blast is of significant importance. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Rao D.V.S.,Defence Metallurgical Research Laboratory |
Sankarasubramanian R.,Defence Metallurgical Research Laboratory |
Muraleedharan K.,Defence Research and Development Organisation |
Mehrtens T.,University of Bremen |
And 2 more authors.
Microscopy and Microanalysis | Year: 2014
In GaAs-based pseudomorphic high-electron mobility transistor device structures, strain and composition of the InxGa1-xAs channel layer are very important as they influence the electronic properties of these devices. In this context, transmission electron microscopy techniques such as (002) dark-field imaging, high-resolution transmission electron microscopy (HRTEM) imaging, scanning transmission electron microscopy-high angle annular dark field (STEM-HAADF) imaging and selected area diffraction, are useful. A quantitative comparative study using these techniques is relevant for assessing the merits and limitations of the respective techniques. In this article, we have investigated strain and composition of the InxGa1-xAs layer with the mentioned techniques and compared the results. The HRTEM images were investigated with strain state analysis. The indium content in this layer was quantified by HAADF imaging and correlated with STEM simulations. The studies showed that the InxGa1-xAs channel layer was pseudomorphically grown leading to tetragonal strain along the  growth direction and that the average indium content (x) in the epilayer is ~0.12. We found consistency in the results obtained using various methods of analysis. © Microscopy Society of America 2014.
Sadhukhan K.,Defence Research and Development Organisation |
Mallari R.A.,Defence Research and Development Organisation |
Yadav T.,Scientific Analysis Group
2015 International Conference on Computing and Network Communications, CoCoNet 2015 | Year: 2015
Attacks in cyberspace have got attention due to risk at privacy, breach of trust and financial losses for individuals as well as organizations. In recent years, these attacks have become more complex to analyze technically, as well as to detect and prevent from accessing confidential data. Although there are many methodologies and mechanisms which have been suggested for cyber-attack detection and prevention, but not from the perspective of an attacker. This paper presents the cyber-defence as hindrances, faced by the attacker, by understanding attack thread and defence possibilities with existing security mechanisms. Seven phases of Cyber Attack Thread are introduced and technical aspects are discussed with reference to APT attacks. The paper aims for security practitioner and administrators as well as for the general audience to understand the attack scenario and defensive security measures. © 2015 IEEE.
Mansukhani J.,Defence Research and Development Organisation |
Chakrabarti S.,Indian Institute of Technology Kharagpur
2013 International Conference on Computer Communication and Informatics, ICCCI 2013 | Year: 2013
Orthogonal frequency division multiplexing (OFDM) modulation using orthogonal subcarriers reduces the delay spread by increasing robustness to multipath fading and can use overlapped bandwidth due to orthogonality on frequency domain. The main drawback of Orthogonal Frequency Division Multiplexing (OFDM) systems is the high peak-to average power ratio (PAPR), which significantly reduces the efficiency of the transmit high power amplifier (HPA). Several methods have been proposed in the literature to reduce the peak power of OFDM signals and substantial gains were reported. In SLM technique of PAPR reduction, side information needs to be transmitted for demodulation while degrading transmission efficiency. Though many studies have been carried out to analyze the performance of various PAPR reduction methods for land, the studies for sea environment is hardly addressed in literature. In this paper, we have analyzed the effectiveness of SLM technique utilizing cyclic shifting of pilots for Marine Channel. © 2013 IEEE.
Dwivedi P.,Canadian Department of National Defence |
Alam S.I.,Canadian Department of National Defence |
Kumar O.,Defence Research and Development Organisation |
Kumar R.B.,Canadian Department of National Defence
Infection, Genetics and Evolution | Year: 2015
Clostridium perfringens is an obligately anaerobic rod-shaped bacterium and etiological agent for several diseases in humans and animals. The pathogen has been listed as Validated Biological Agent and warrants development of medical countermeasures. The homologs of some of the lipoproteins identified from various fractions of C. perfringens in our previous studies were observed to be virulence determinants in other pathogenic bacteria. Three putative virulence associated lipoproteins; polysaccharide deacetylase family protein, probable ion-uptake ABC transporter, and a putative lipoprotein of no known function are reported here with respect to their immuno-protective potentials. The three proteins were over expressed and purified to near homogeneity. The lipoproteins were shown to be exposed on the C. perfringens surface and, hence, accessible to antibodies and potentially visible to the host immune system. Immunization of mice with purified recombinant proteins elicited protective immunity against challenge with C. perfringens in mouse gas gangrene model. Distribution and relationship of orthologous proteins across other bacterial select agents especially among the members of Firmicutes, was carried out to look for conserved antigenic determinants. © 2015 Elsevier B.V.
Sankar H.R.,Gandhi Institute of Technology and Management |
Srikant R.R.,Gandhi Institute of Technology and Management |
Krishna P.V.,Gandhi Institute of Technology and Management |
Rao V.B.,Defence Research and Development Organisation |
Babu P.B.,National Institute of Technology Warangal
International Journal of Automotive and Mechanical Engineering | Year: 2013
Conventional materials are being replaced in the field of engineering by composite materials, due to their tailorable properties and high specific properties. These materials are extensively used in structural applications. Damping is one of the important properties of the materials used in structures, and needs to be enhanced in order to reduce structural vibrations. In the present work, the improvement of the material damping of glass fabric epoxy composites with particle rubber inclusions is studied. The effect of particle size on the damping and stiffness parameters at different frequencies and temperatures is studied experimentally. Considerable enhancement in damping without significant reduction in stiffness is observed at lower particle sizes. The damping property in both bending and shear modes is more with 0.254 mm rubber particle inclusions among the selected sizes. A lower reduction in stiffness is observed with the inclusion of lower particle sizes (0.254 mm and 0.09 mm) when compared with higher particle sizes. An ANN-based prediction model is developed to predict these properties for a given frequency/temperature and particle size. The predicted values are very close to the experimental values with an maximum error of 5%. © Universiti Malaysia Pahang.
Bhardwaj A.,TERI University |
Joshi P.K.,TERI University |
Snehmani,Snow and Avalanche Study Establishment Research and Development Center |
Singh M.K.,Snow and Avalanche Study Establishment Research and Development Center |
And 3 more authors.
Cold Regions Science and Technology | Year: 2014
Supraglacial debris significantly hampers the mapping of glaciers using remote sensing data. A semi-automated approach for the mapping of debris-covered glacier was applied, which combined the inputs from thermal and optical remote sensing data and the Digital Elevation Model (DEM) derived morphometric parameters. A thermal mask that delineates the supraglacial debris extent was generated by the thresholding of surface temperature layer obtained from Landsat TM/ETM. + thermal band satellite data. The extent of clean glacier ice was identified by band ratioing and thresholding of TM/ETM. + 4 and TM/ETM. + 5 bands. Morphometric parameters like slope, plan curvature and profile curvature were rearranged in similar surface groups using the technique of cluster analysis. All these masks were vectorized and final classification maps were generated using geographic information system (GIS) overlay operations. The areal extent of semi-automated outlines of Hamtah and Patsio Glaciers derived from cluster analysis varied from manually derived outline using pan-sharpened Landsat ETM. + September 2000 image by -. 1.3% and -. 1.6%, respectively. Year 2011 classification map for Patsio Glacier was compared with the field observations and a high correlation and overall accuracy (~. 91%) were observed. The same classification methodology was adopted for images of years 2000 and 1989 for Patsio Glacier to observe the effects of varying snow cover patterns on adopted methodology. Also the methodology was adopted and verified for Hamtah Glacier, with different geometry and terrain conditions as compared to Patsio Glacier. Although the spatial resolution limitation of ASTER GDEM and Landsat TM/ETM. + thermal band limits the automated mapping of small debris-covered glaciers, the outcomes are still favorable enough to apply such methodologies for mapping different types of debris-covered glaciers in the future. © 2014 Elsevier B.V.
Dash A.P.,Indian Institute of Technology Madras |
Velmurugan R.,Indian Institute of Technology Madras |
Prasad M.S.R.,Defence Research and Development Organisation |
Sikarwar R.S.,Defence Research and Development Organisation
Thin-Walled Structures | Year: 2016
Improvement of stability of thin isotropic shell in the presence of soft elastic filler has been investigated. Critical buckling loads for empty and filled cylinder have been studied both experimentally and theoretically using FE analysis. Various percentage of cross sectional filling are examined as a parametric variation. Nonlinear analysis with proper geometric imperfection modeling is carried out to represent correct behavior of soft elastic filler. The experimental results and FE analysis corroborate well to establish this improvement in buckling strength. It is observed that critical buckling load of the cylinder subjected to external pressure improves upto an extent of five times depending upon percentage of filling. It is concluded that improved strength can be utilized for more efficient design of thin tubular shells. © 2015 Elsevier Ltd.
Yadav T.,Defence Research and Development Organisation |
Rao A.M.,Defence Research and Development Organisation
Communications in Computer and Information Science | Year: 2015
Recent trends in targeted cyber-attacks has increased the interest of research in the field of cyber security. Such attacks have massive disruptive effects on organizations, enterprises and governments. Cyber kill chain is a model to describe cyber-attacks so as to develop incident response and analysis capabilities. Cyber kill chain in simple terms is an attack chain, the path that an intruder takes to penetrate information systems over time to execute an attack on the target. This paper broadly categories the methodologies, techniques and tools involved in cyber-attacks. This paper intends to help a cyber security researcher to realize the options available to an attacker at every stage of a cyberattack. © Springer International Publishing Switzerland 2015.
Ghosh S.,Defence Research and Development Organisation |
Mukhopadhyay S.,Indian Institute of Technology Kharagpur
IEEE Transactions on Aerospace and Electronic Systems | Year: 2011
In this paper an acceleration model and a jerk model are proposed for estimation of the kinematic state of reentry ballistic targets (RBTs) using extended Kalman filters (EKF). The models proposed here use the equations of target kinematics only and do not assume any model parameterization for variation of the ballistic coefficient and air density a priori, as found in the literature. The novelty lies in estimation of the ratio (γ) of air density and ballistic coefficient and its time derivatives using a separate Kalman filter (KF) (γ-filter) which utilizes pseudo measurements of γ computed from the velocity and acceleration estimated by the EKF at each time step. The parameter γ and its derivatives estimated by the γ-filter are, in turn, used for the estimation of position, velocity, acceleration, and jerk in the EKF. The use of the pseudo measurements of γ makes the algorithms inherently adaptive to variations of the ballistic coefficient and air density during reentry. A comparative assessment of several dynamic models for reentry of ballistic targets reported in the literature and those proposed here demonstrates that the estimation errors in velocity and acceleration are significantly less for the proposed models compared with the existing ones. © 2011 IEEE.