Subjects

-N 0-9

Defence Science Journal

	Computational Fluid Dynamics in Hypersonic Aerothermodynamics Author : Krishnendu,Sinha. Source : Defence Science Journal ; Vol:60(6) ; 2010 ; pp 663-671 Subject : 532.542 Fluid Dynamics;Defence Science Journal Keywords : Computational fluid dynamics ;Hypersonic aerothermadynamics;scramjet engine;hypersonic flows;re-entry capsules Abstract : Hypersonic flows are characterised by high Mach number and high total enthalpy. An elevated temperature often results in thermo-chemical reactions in the gas, which play a major role in aerothermodynamic characterisation of high-speed aerospace vehicles. Hypersonic flows in propulsion components are usually turbulent, resulting in additional effects. Computational simulation of such flows, therefore, need to account for a range of physical phenomena. Further, the numerical challenges involved in resolving strong gradients and discontinuities add to the complexity of computational fluid dynamics (CFD) simulation. In this article, physical modelling and numerical methodology-related issues involved in hypersonic flow simulation are highlighted. State-of-the-art CFD challenges are discussed in the context of two prominent applicationsthe flow in a scramjet inlet and the flow field around a re-entry capsule.
	Contents Author : Source : Defence Science Journal ; Vol:60(4) ; 2010 ; pp 2-3 Subject : Defence Science Journal Keywords : Abstract :
	Target Recognition Based on Fuzzy Dempster Data Fusion Method Author : Deng, Yong;Su, Xiaoyan;Wang, Dong;Li, Qi Source : Defence Science Journal ; Vol:60(5) ; 2010 ; pp 525-530 Subject : 62 Engineering;Defence Science Journal Keywords : Evidence theory;fuzzy set theory;multisensor fusion;target recognition;data fusion technology;automatic target recognition system;Bayesian theorem;Dempster shafter evidence theory Abstract : Data fusion technology is widely used in automatic target recognition system. Problems in data fusion system are complex by nature and can often be characterised by not only randomness but also by fuzziness. To accommodate complex natural problems with both types of uncertainties, it is profitable to construct a data fusion structure based on fuzzy set theory and Dempster Shafer evidence theory. In this paper, after representing both, the individual attribute of target in the model database and the sensor observation or report as fuzzy membership function, a likelihood function was constructed to deal with fuzzy data collected by each sensor. The method to determine basic probability assignments of each sensor report is proposed. Sensor reports are fused through classical Dempster combination rule. A numerical example is illustrated to show the target recognition application of the fuzzy-Dempster approach.
	Contents Author : Source : Defence Science Journal ; Vol:60(2) ; 2010 ; pp 119-124 Subject : Defence Science Journal Keywords : Abstract :
	Advances in High Energy Materials Author : Nair, U.R.;Asthana, S.N.;Rao, A. Subhananda;Gandhe, B.R. Source : Defence Science Journal ; Vol:60(2) ; 2010 ; pp 137-151 Subject : 536 Thermodynamics;53 Applied Physics;Defence Science Journal Keywords : HEMs;performance;insensitive;explosives;propellants;high energy materials;green energetic materials;trinitrotoluene;cyclotrimethylenetrinitramine Abstract : Research and development efforts for realizing higher performance levels of high energy materials (HEMs) are continued unabated all over the globe. Of late, it is becoming increasingly necessary to ensure that such materials are also eco-friendly. This has provided thrust to research in the area of force multiplying HEMs and compounds free from pollution causing components. Enhancement of the performance necessitates introduction of strained structure or increase in oxygen balance to achieve near stoichiometry. The search for environment friendly molecules is focused on chlorine free propellant compositions and lead free primary explosives. Energetic polymers offer added advantage of partitioning of energy and thus not necessitating the concentration of only solid components (HEMs and metal fuels) in the formulations, to achieve higher performance, thereby leading to improvement in energetics without adversely affecting the processability and mechanical properties. During recent times, research in the area of insensitive explosives has received impetus particularly with the signature of STANAG. This paper gives a review of the all-round advances in the areas of HEMs encompassing oxidizers, high-energy dense materials, insensitive high-energy materials, polymers and plasticizers. Selected formulations based on these materials are also included.
	Design, Development, and Validation of a Vehicle-mounted Hydraulically-leveled Platform Author : Senthilkumar, K.;Chidanand, M.;Nijalingappa, P.;Shivhare, Manish M. Source : Defence Science Journal ; Vol:60(2) ; 2010 ; pp 169-177 Subject : 621 Mechanical Engineering;Defence Science Journal Keywords : Hydraulically-leveled platform;ISO shelter;ISO corner;deflection;stress;strain gauge;accelerometer;data acquisition system Abstract : Hydraulically-leveled platforms are required, to provide a leveled base for accurate leveling of high-rise masts and other vehicle-mounted communication devices. Design, development, and validation of one such platform on an 8x8, high mobility, wheeled vehicle is presented. The platform is a welded structure, designed to accommodate two ISO type shelters, and the shelters are secured to the platform at their four ISO corners using special twist locks. The leveling of the platform is enabled by actuation of four hydraulic cylinders bolted to the vehicle chassis. The concentrated type loading, resulting due to clearance maintained between the skids of shelters and the platform, and the loading pattern are the major design considerations. The other factors that have bearing on the design of platform include accommodation of variants of shelters, ease of operation of equipment mounted on the original chassis, and load distribution on axles, over-all height, ground clearance and departure angle of the integrated entity. Deflection and stress analysis of the platform structure using finite element analysis has been carried out for two types of shelter loadings. Limited track trials have been conducted at Vehicles Research & Development Establishment (VRDE) for assessment of structural integrity of the platform, and constructional and mobility aspects of platform-mounted-vehicle. Measurements of strain at critical locations, under-shelter loading, and while driving the vehicle at two different vehicle speeds on pave and cross-country tracks, have also been carried out for validation of design of platform. Details on problems faced during track trials, and the subsequent modifications carried out to the platform are also discussed.
	Wishbone Structure for Front Independent Suspension of a Military Truck Author : Jagirdar, V.V.;Dadar, M.S.;Sulakhe, V.P. Source : Defence Science Journal ; Vol:60(2) ; 2010 ; pp 178-183 Subject : 623 Military Science and Engineering;Defence Science Journal Keywords : Independent suspension;live axle;double wishbone configuration;MBD analysis Abstract : Wishbone structure for double wishbone front-independent Suspension for a military truck application is presented. At present, the vehicle is equipped with rigid axle with leaf springs. There are two aspects that dictate the design of wishbone structure, viz. the path of relative motion between the constituents of the suspension system and the forces transmitted between them. Also, enhancement of mobility was made possible by maintaining the live axle in the system. A double wishbone, double coil spring with twin damper configuration was employed for this application. MBD Analysis was carried out using MSC ADAMS. A double wishboneindependent suspension has been designed for the front axle and has been successfully integrated with the vehicle.
	Developments in Pyrotechnics Author : Danali, S.M.;Palaiah, R.S.;Raha, K.C. Source : Defence Science Journal ; Vol:60(2) ; 2010 ; pp 152-158 Subject : 620.261 Explosives;Defence Science Journal Keywords : Pyrotechnics;smokes;illuminants;flares;electro-explosive devices;delays;laser initiation;green pyrotechnics Abstract : The application of smoke and various types of smoke bombs/devices developed are narrated. The light output of 51 mm, 81 mm, 120 mm and 120 mm LRM illuminating bombs developed is 2.6, 9.0, 10.8 and 15 lakhs candela, respectively. The IR flares developed for first and second generation anti-tank missile are in regular production. An IR decoy flare is developed for CMDS. Feasibility study on multi-spectral smoke and IR flare compositions is completed. 1W-1A No fire capability EED is developed. Gas generators 1200 cc, 2400 cc, 6000 cc are developed. Accuracy of pyro delay is improved. Laser initiated pyrocartridge is developed. Nanoscale Fe2O3 is synthesised and studied. A few toxic ingredients are replaced to march towards green pyrotechnics. Objectives for improved pyrotechnics are included.
	Front Cover Author : Source : Defence Science Journal ; Vol:60(4) ; 2010 ; pp 1 Subject : Defence Science Journal Keywords : Abstract :
	Optimum Location and System Engineering of High Power, High Frequency Transmitter-Receiver in Combat Vehicles Author : Sathyamurthy, S.;Sheerlarani, B.;Sundaresh, S. Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 302-306 Subject : 623 Military Science and Engineering;623.4 Armaments and Ballistics;Defence Science Journal Keywords : Spectral congestion;electromagnetic interference;EMI;VSWR;vehicle penetration loss;voltage standing wave ratio;VPL Abstract : This paper discusses the procedure adapted after carrying out several iterations for selecting an ideal location to introduce a high power high frequency (HF) transmitter-receiver in a tactical combat vehicle from electromagnetic compatibility view. This radio set contributes for very high field strength to neighbouring electronic devices and other very high frequency (VHF) Tx-Rx situated in the same vehicular platform. An integrated approach was followed in deciding the optimum solution to locate the HF radio set. Leakage from HF radio set is to be minimised within the vehicle to reduce the field coupling level to neighbouring equipment. Radiation from HF antenna was maximised by careful installation of antenna, outside the vehicle environment to ensure optimum radiation of intended signal. Voltage standing wave ratio (VSWR) measurement was carried out to verify this. Four different locations experimented have been reported in this paper. The vehicle penetration loss (VPL) can reveal the amount of leakage from external field generated by antennas to field inside the turret. The HF, being a congested operating spectrum, due care was taken in electromagnetic interference control of HF-VHF radios and other tank electronic subsystems. High RF power of HF transmitter and very high sensitivity of HF receiver could affect systems either way. Hence, electromagnetic compatibility (EMC) measures and optimum location of HF radio set are important from MIL-STD461 C, MIL6051-D/MIL-STD464A point of view.
	Back Cover Author : Source : Defence Science Journal ; Vol:60(5) ; 2010 ; pp 564 Subject : Defence Science Journal Keywords : Abstract :
	Electrochemical Analysis of Natural Chemopreventive Agent (Curcumin) in Extracted Sample and Pharmaceutical Formulation Author : Modi, Garima;Pitre, K.S. Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 255-258 Subject : 57.089 Biomedical Sciences ;Defence Science Journal Keywords : Curcumin;DPP;anticarcinogenic;pharmaceutical formulation;differential pulse polarography Abstract : Curcumin has anti-oxidative and anticarcinogenic activities. This study shows the electrochemical behaviour of curcumin using polarography, i.e., DC polarography and differential pulse polarography (DPP) methods. In ammonium tartrate as supporting electrolyte, the differential pulse polarogram of curcumin shows two conjugated peaks with peak potential (Ep) 1125 mV and 1275 mV vs SCE. However, the direct current polarogram shows only one polarographic wave with E1/2 which was 1275 mV. The developed electrochemical methods have been standardised for the determination of curcumin in extracted sample of natural origin and its pharmaceutical formulation. The electrochemical analysis has been supplemented by ultraviolet and infrared spectral analyses of the samples.
	2-D Shape Fitting for Locating Exploding Projectile from Explosion Patch Author : Ray, Kunal Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 238-243 Subject : 53 Applied Physics;Defence Science Journal Keywords : Proximity fuze;variable-time fuze;explosion patch Abstract : For test and evaluation of a proximity fuze, it is necessary to know the distance offset of the exploding ammunition round, fitted with the fuze, from a specific target. If the event is recorded using in-line high-speed photography the event of explosion can be resolved in time, and it becomes necessary to ascertain the position of the round, wrt the target, as it is exploding. An estimation of intensity centroid position fails as the flash is non-uniform in nature and is partially occluded by the exploding round. This paper is about an approach to find the location of the round using 2-D shapes fitting of the explosion patch.
	Controlling a Mobile Robot with a Biological Brain Author : Warwick, Kevin;Xydas, Dimitris;Nasuto, Slawomir J.;Becerra, Victor M.;Hammond, Mark W.;Downes, Julia H.;Marshall, Simon;Whalley, Benjamin J. Source : Defence Science Journal ; Vol:60(1) ; 2010 ; pp 005-014 Subject : Computer Science;Computer Networks;Defence Science Journal Keywords : Mobile Robot;Machine Learning;Neural Network;Biological Neuronal Networks;Intelligent Controlling Mechanism;Biological Neurons Abstract : The intelligent controlling mechanism of a typical mobile robot is usually a computer system. Some recent research is ongoing in which biological neurons are being cultured and trained to act as the brain of an interactive real world robotthereby either completely replacing, or operating in a cooperative fashion with, a computer system. Studying such hybrid systems can provide distinct insights into the operation of biological neural structures, and therefore, such research has immediate medical implications as well as enormous potential in robotics. The main aim of the research is to assess the computational and learning capacity of dissociated cultured neuronal networks. A hybrid system incorporating closed-loop control of a mobile robot by a dissociated culture of neurons has been created. The system is flexible and allows for closed-loop operation, either with hardware robot or its software simulation. The paper provides an overview of the problem area, gives an idea of the breadth of present ongoing research, establises a new system architecture and, as an example, reports on the results of conducted experiments with real-life robots.
	Method for Thermo-optic Analysis in a Star Sensor Author : Liu, Hai-bo;Tan, Ji-chun;Yang, Jian-kun;Li, Xiu-jian;Fan, Qing-chun Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 276-281 Subject : 681.586 Sensors;Defence Science Journal Keywords : Star sensor;optical system;thermo-optic analysis;finite element analysis;FEA;ray tracing Abstract : An autonomous star sensor is a highly accurate attitude-measuring instrument used in spacecraft, and its performance is restricted by ambient temperature of the outer space. This paper puts forward an effective scheme to the thermooptic analysis using finite element analysis (FEA) and ray tracing in star sensor. Specific difficulties: (a) how to evaluate thermo-optic effect in star sensor, and (b) how to make FEA results useful in optical design mode have been resolved using the scheme. Based on this scheme, the errors of star sensor, which are caused by thermo-optic effects, can be investigated in any complicated temperature condition, and the required temperature scope for the thermal design can be achieved. For example, the errors of the star sensor were 0.0863 and 2.2933, when the temperature differences of the experimental optical system were 10 °C and 5 °C in axial and lateral, respectively.
	Guest Editorial Author : Shri Kant Source : Defence Science Journal ; Vol:60(4) ; 2010 ; pp 345-347 Subject : Defence Science Journal Keywords : Abstract :
	Robotic Architectures Author : Mtshali, Mbali;Engelbrecht, Andries Source : Defence Science Journal ; Vol:60(1) ; 2010 ; pp 015-022 Subject : 681.3 Computer Science;Defence Science Journal Keywords : Mobile robotic systems;autonomous robots;robotic architectures;robotics;mobile robots Abstract : In the development of mobile robotic systems, a robotic architecture plays a crucial role in interconnecting all the sub-systems and controlling the system. The design of robotic architectures for mobile autonomous robots is a challenging and complex task. With a number of existing architectures and tools to choose from, a review of the existing robotic architecture is essential. This paper surveys the different paradigms in robotic architectures. A classification of the existing robotic architectures and comparison of different proposals attributes and properties have been carried out. The paper also provides a view on the current state of designing robot architectures. It also proposes a conceptual model of a generalised robotic architecture for mobile autonomous robots.
	Inconsistent Performance of a Tandem-shaped Charge Warhead Author : Harikrishnan, S.;Murthy, K.P.S. Source : Defence Science Journal ; Vol:60(2) ; 2010 ; pp 164-168 Subject : 623.4 Armaments and Ballistics;620.261 Explosives;Defence Science Journal Keywords : Tandem warhead;precursor blast;blast isolator;explosive reactive armour Abstract : Tandem shaped charge warhead is one of the efficient methods to defeat the explosive reactive armour (ERA) protected main battle tanks (MBT). In this concept, two shaped charges mounted in the same missile are initiated one after the other with certain time delay. First shaped charge jet would remove the ERA and the second jet would penetrate the bare armour. Both these explosive charges are mounted close to each other most of the time due to severe space constraints in the system. It is necessary to protect the second charge from the blast effects of first charge, during the time delay between the initiations of two charges. Blast effect of precursor charge on main charge is understood to have detrimental effects on the performance of warhead system.This paper presents a case study of an investigation into the inconsistent performance of a tandem warhead for a third generation antitank missile. The warhead generated a crooked jet resulting in inconsistent penetration performance. Typical crater profiles were observed when the penetration performance deteriorated. Systematic analysis was carried out and simulations were performed using Autodyn-3D to reproduce the phenomenon. Experiments were conducted using Flash X-ray which substantiated the assumptions made for simulation studies.
	Radar Cross-section Measurement Techniques Author : Borkar, V.G.;Ghosh, A.;Singh, R.K.;Chourasia, N. Source : Defence Science Journal ; Vol:60(2) ; 2010 ; pp 204-212 Subject : 621.396.9 Radars;Defence Science Journal Keywords : Radar cross-section;inverse synthetic aperture radar;stealth;RCS control;anechoic chamber Abstract : Radar cross-section (RCS) is an important study parameter for defence applications specially dealing with airborne weapon system. The RCS parameter guides the detection range for a target and is therefore studied to understand the effectiveness of a weapon system. It is not only important to understand the RCS characteristics of a target but also to look into the diagnostic mode of study where factors contributing to a particular RCS values are studied. This further opens up subject like RCS suppression and stealth. The paper discusses the RCS principle, control, and need of measurements. Classification of RCS in terms of popular usage is explained with detailed theory of RF imaging and inverse synthetic aperture radar (ISAR). The various types of RCS measurement ranges are explained with brief discussion on outdoor RCS measurement range. The RCS calibration plays a critical role in referencing the measurement to absolute values and has been described.The RCS facility at Reseach Centre Imarat, Hyderabad, is explained with some details of different activities that are carried out including RAM evaluation, scale model testing, and diagnostic imaging.
	Computational Fluid Dynamics in Combustion Author : Paul, P. J. Source : Defence Science Journal ; Vol:60(6) ; 2010 ; pp 577-582 Subject : 532.542 Fluid Dynamics;Defence Science Journal Keywords : Computational fluid dynamics;Combustion;Composite Solid Propellant Abstract : Computational fluid dynamics has reached a stage where flow field in practical situation can be predicted to aid the design and to probe into the fundamental flow physics to understand and resolve the issues in fundamental fluid mechanics. The study examines the computation of reacting flows. After exploring the conservation equations for species and energy, the methods of closing the reaction rate terms in turbulent flow have been examined briefly. Two cases of computation, where combustion-flow interaction plays important role, have been discussed to illustrate the computational aspects and the physical insight that can be gained by the reacting flow computation.
	Effect of Temperature on Aging of Ferroelectric Lead-Strontium- Zirconate-Titanate Ceramics Author : Wathore, N.N.;Lonkar, C.M.;Kharat, D.K. Source : Defence Science Journal ; Vol:60(6) ; 2010 ; pp 683-686 Subject : 532.542 Fluid Dynamics;Defence Science Journal Keywords : Computational fluid dynamics ;dielectric constant;ferroelectric ceramics;PSZT ceramics Abstract : The effect of aging on Sr2+ modified lead-zirconate-titanate (PSZT) ceramics has been studied. Aging was assessed by the measurement of dielectric constant and dielectric loss tangent as a function of time and temperature. Dielectric constant and dielectric loss tangent were measured at different temperature ranges. Absolute rate of aging and relative rate of aging were determined. The PSZT ceramic showed sharp dielectric peak at 300 °C. The results shows that with increase temperature, both the dielectric constant and rate of aging increase.
	Handling Out-of-Sequence Data: Kalman Filter Methods or Statistical Imputation? Author : Twala, Bhekisipho Source : Defence Science Journal ; Vol:60(1) ; 2010 ; pp 087-099 Subject : 681.3 Computer Science;Defence Science Journal Keywords : Multi-Sensor Data;Time Delayed Measurements;Out-of-Sequence Measurements;Kalman Filter;Fusion;Imputation;Multi-Sensor Tracking Abstract : The issue of handling sensor measurements data over single and multiple lag delays also known as outof- sequence measurement (OOSM) has been considered. It is argued that this problem can also be addressed using model-based imputation strategies and their application in comparison to Kalman filter (KF)-based approaches for a multi-sensor tracking prediction problem has also been demonstrated. The effectiveness of two model-based imputation procedures against five OOSM methods was investigated in Monte Carlo simulation experiments. The delayed measurements were either incorporated (or fused) at the time these were finally available (using OOSM methods) or imputed in a random way with higher probability of delays for multiple lags and lower probability of delays for a single lag (using single or multiple imputation). For single lag, estimates of target tracking computed from the observed data and those based on a data set in which the delayed measurements were imputed were equally unbiased; however, the KF estimates obtained using the Bayesian framework (BF-KF) were more precise. When the measurements were delayed in a multiple lag fashion, there were significant differences in bias or precision between multiple imputation (MI) and OOSM methods, with the former exhibiting a superior performance at nearly all levels of probability of measurement delay and range of manoeuvring indices. Researchers working on sensor data are encouraged to take advantage of software to implement delayed measurements using MI, as estimates of tracking are more precise and less biased in the presence of delayed multi-sensor data than those derived from an observed data analysis approach.
	Novel Redundant Sensor Fault Detection and Accommodation Algorithm for an Air-breathing Combustion System and its Real-time Implementation Author : Walambe, Rahee;Gupta, Nitin K;Bhange, Niteen Source : Defence Science Journal ; Vol:60(1) ; 2010 ; pp 061-075 Subject : 681.586 Sensors;Defence Science Journal Keywords : Extended Kalman filter;analytical redundancy;air-breathing combustion systems;ACS;fault detection and accommodation;FDA Abstract : Failure of sensors used to provide a feedback signal in control system can cause serious deterioration in performance of system, and even instability may be observed. Based on knowledge of aircraft engine systems, the main cause of fault in such air-breathing combustion systems (ACS) with no rotating parts is due to the pressure sensors. Fast online detection of faults before the error grows very large and accommodation is critical to the success of the mission. However, at the same time, it is necessary to avoid false alarms. Hence, early detection of small magnitude faults with acceptable reliability is very challenging, especially in the presence of sensor noise, unknown engine-to-engine variation and deterioration and modeling uncertainty. This paper discusses the novel fault detection and accommodation (FDA) algorithm based on analytical redundancy based technique for ACS.
	Focal Adjustment for Star Tracker Author : Liu, Hai-bo.;Yang, Jian-kun;Tan, Ji-chun.;Su, De-zhi.;Wang, Wen-liang.;jian Li, Xiu.;Jia, hui Source : Defence Science Journal ; Vol:60(6) ; 2010 ; pp 678-682 Subject : 532.542 Fluid Dynamics;Defence Science Journal Keywords : Computational fluid dynamics ;Star tracker;focal adjustment;star spot image Abstract : Technique of measuring intensity distribution and size of spot image developed has been discussed, which is especially suitable for defocus adjustment in ground test of star tracker. A novel approach for choosing a proper defocusing position has been proposed based on collimator, Gaussian surface fitting method, and other ordinary instruments. It proves to be practical and adequate in the development of distant object tracking such as star tracker.
	Expert Knowledge Base to Support Maintenance of a Radar System Author : Duer, Stanislaw Source : Defence Science Journal ; Vol:60(5) ; 2010 ; pp 531-540 Subject : 621.38 Electronics;Defence Science Journal Keywords : Maintenance process;expert system;knowledge base;diagnostic information Abstract : This paper presents the method for the creation of an expert knowledge base of a military object, for example a radar system. Such a knowldge base can be widely used to support the process of the maintenance of a complex technical object. The first step is a maintenance evaluation of the object. During this kind of analysis, it is necessary to perform the grouping and classification of the functional elements of the object. It is realised using the functional scheme of the object presented. Further, diagnostic information is combined with specialised experts knowledge and transformed it into a set of servicing information. The participation of experts in the process of expert knowledge base preparation is significant. The purpose is to capture information that will be a fundamental for the design of a maintenance system dedicated to the particular technical object. The methods proposed were verified with appropriate examples, in which the set of specialised diagnostic information of the object was determined.
	Index of Garbledness for Automatic Recognition of Plain English Texts Author : Saxena, P.K.;Yadav, Pratibha;Mishra, Girish Source : Defence Science Journal ; Vol:60(4) ; 2010 ; pp 415-419 Subject : 681.3 Computer Science;Defence Science Journal Keywords : Index of garbledness;automatic recognition;fuzzy sets;fuzzy similarity relation;fuzzy dissimilarity measure;fuzzy pattern recognition;cryptanalysis Abstract : In this paper, an Index of Garbledness (IG) has been defined for automatic recognition of plain English texts based on linguistic characteristics of English language without using a dictionary. It also works for continuous text without word break-up (text without blank spaces between words). These characteristics, being vague in nature, are suitably represented through fuzzy sets. A fuzzy similarity relation and a fuzzy dissimilarity measure have been used to define this Index. Based on a threshold value of the Index, one can test whether the given text (continuous without word break-up) is a plain English text or not. In case the text under consideration is not a plain text, it also gives an indication to what extent it is garbled.
	Discrete Cosine Transform-based Image Fusion Author : Naidu, V.P.S. Source : Defence Science Journal ; Vol:60(1) ; 2010 ; pp 048-054 Subject : 62 Engineering;681.3 Computer Science;Defence Science Journal Keywords : Multi-sensor image fusion;multi-resolution DCT;image fusion performance evaluation metrics;discrete cosine transform Abstract : Image fusion by multi-resolution discrete cosine transform (MDCT) algorithm has been implemented and evaluated. The performance of this algorithm is compared with that of well known image fusion technique using wavelets. It is observed that image fusion by MDCT perform almost similar to that of wavelets. It is computationally very simple and it could be well suited for real time applications.
	INFORMATION FOR CONTRIBUTORS Author : Source : Defence Science Journal ; Vol:60(2) ; 2010 ; pp 231-232 Subject : Defence Science Journal Keywords : Abstract :
	Future Armoured Troop Carrying Vehicles Author : Balos, Sebastian;Grabulov, Vencislav;Sidjanin, Leposava Source : Defence Science Journal ; Vol:60(5) ; 2010 ; pp 483-490 Subject : 623 Military Science and Engineering;Defence Science Journal Keywords : Heavy armoured vehicles;protection;mobility;cost;logistics Abstract : Present-day reliance on wheeled and tracked armour personnel carriers (APCs) and infantry fighting vehicles (IFVs), may be changed in the future. Shaped charge grenades and impovised explosive devices (IEDs) represent a considerable threat, even to well protected main battle tanks (MBTs). Paradoxically, the crew of wheeled and tracked troop-carrying vehicles is numerically three to four times larger than that of MBTs, however, their protection in all aspects is significantly lower. Therefore, heavier vehicles may get more attention in the future, where sharing the chassis and a number of components with MBTs could provide significant reductions in procurement costs and maintenance, as well as a simplified logistics in relation to the latest tracked. Obviously, the IFVs mobility of heavy vehicles would be lower than that of lighter vehicles. However, by applying various degrees of modular armour protection, a significant rise in strategic, operational, and tactical mobility could be achieved. Such heavy tracked vehicles, built on a common chassis as MBTs, may equip the future heavy brigades, which will be in contrast to the lighter wheeled vehicles included in rapid deployment brigades. As a result, tracked personnel carrying vehicles may extinct in the future.
	Viscoelastic Modelling of Solid Rocket Propellants using Maxwell Fluid Model Author : Shekhar, Himanshu;Sahasrabudhe, A.D. Source : Defence Science Journal ; Vol:60(4) ; 2010 ; pp 423-427 Subject : 532.5 Hydrodynamics;629.76 Rockets and Missiles ;Defence Science Journal Keywords : Solid rocket propellants;mechanical properties;viscoelasticity;Maxwell fluid;spring constant;damping coefficient Abstract : Maxwell fluid model consisting of a spring and a dashpot in series is applied for viscoelastic characterisation of solid rocket propellants. Suitable values of spring constant and damping coefficient were employed by least square variation of errors for generation of complete stress-strain curve in uniaxial tensile mode for case-bonded solid propellant formulations. Propellants from the same lot were tested at different strain rates. It was observed that change in spring constant, representing elastic part was very small with strain rate but damping constant varies significantly with variation in strain rate. For a typical propellant formulation, when strain rate was raised from 0.00037/s to 0.185/s, spring constant K changed from 5.5 MPa to 7.9 MPa, but damping coefficient D was reduced from 1400 MPa-s to 4 MPa-s. For all strain rates, stressstrain curve was generated using Maxwell model and close matching with actual test curve was observed. This indicates validity of Maxwell fluid model for uniaxial tensile testing curves of case-bonded solid propellant formulations. It was established that at higher strain rate, damping coefficient becomes negligible as compared to spring constant. It was also observed that variation of spring constant is logarithmic with strain rate and that of damping coefficient follows power law. The correlation coefficients were introduced to ascertain spring constants and damping coefficients at any strain rate from that at a reference strain rate. Correlation for spring constant needs a coefficient H, which is function of propellant formulation alone and not of test conditions and the equation developeds K2 = K1 + H ´ ln{(de2/dt)/(de1/dt)}. Similarly for damping coefficient D also another constant S is introduced and prediction formula is given by D2 = D1 ´ {(de2/dt)/(de1/dt)}S. Evaluating constants H and S at different strain rates validate this mathematical formulation for different propellant formulations. Stress-strain curves for solid propellants can be generated at those strain rates at which actual testing is not possible. Close matching of test and predicted stress-strain curve indicates propellant behavior as visco-elastic Maxwell fluid.
	Modelling and Simulation of Pseudolite-based Navigation: A GPS-independent Radio Navigation System Author : Tiwary, K.;Behera, S.K.;Sharada, G.;Singh, Amarjit Source : Defence Science Journal ; Vol:60(5) ; 2010 ; pp 541-550 Subject : 621.38 Electronics;Defence Science Journal Keywords : Pseudolite;global navigation satellite system;indian regional navigation satellite system;inverted positioning;carrier phase navigation Abstract : The use of global positioning system (GPS) for precision guidance of weapons is being questioned due to its vulnerability of jamming and spoofing for non-military code users. In this paper a novel approach is proposed for guidance of weapons where use of GPS or other civilian Satellite-based navigation system is threatened. The proposed approach is modelled and simulated using SIMULINK for realistic trajectories and scenario. The results of simulation are validated with the actual GPS data.
	Large Eddy Simulation Author : Joseph, Mathew Source : Defence Science Journal ; Vol:60(6) ; 2010 ; pp 598-605 Subject : 532.542 Fluid Dynamics;Defence Science Journal Keywords : Computational fluid dynamics ;Large Eddy Simulation;Turbulent Flow;Subgrid Modelling Abstract : Large eddy simulation (LES) is an emerging technique for obtaining an approximation to turbulent flow fields. It is an improvement over the widely prevalent practice of obtaining means of turbulent flows when the flow has large scale, low frequency, unsteadiness. An introduction to the method, its general formulation, and the more common modelling for flows without reaction, is discussed. Some attempts at extension to flows with combustion have been made. Examples from present work for flows with and without combustion are given. The final example of the LES of the combustor of a helicopter engine illustrates the state-of-the-art in application of the technique.
	Thermal Stability of Zirconia-coated Multiwalled Carbon Nanotubes Author : Manivannan, R.;Daniel, Alex;Srikanth, I.;Kumar, Anil;Sarkar, Rajdeep;Ghoshal, P.;Devi, Rohini Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 337-342 Subject : 62 Engineering;Defence Science Journal Keywords : Carbon nanotubes;MWCNTs;multiwalled carbon nanotubes;sol-gel;zirconia coating;thermal stability Abstract : Sol-gel method has been used to coat multiwalled carbon nanotubes (MWCNTs) with zirconia at room temperature and the coated tubes were sintered at high temperature. The samples were characterised by Raman spectroscopy, x-ray diffraction, environmental scanning electron microscope, transmission electron microscopy, and energy-dispersive x-ray analyses. The performance of the coated-MWCNTs was investigated as a function of temperature. The TGA studies indicated that sintering of coated-MWCNTs has improved its oxidation resistance and this improvement is related to the proper selection of sintering temperature.
	INDEX TO DEFENCE SCIENCE JOURNAL, Author : Source : Defence Science Journal ; Vol:60(6) ; 2010 ; pp 687-692 Subject : Defence Science Journal Keywords : Abstract :
	Temporal Logic Motion Planning Author : Seotsanyana, Motlatsi Source : Defence Science Journal ; Vol:60(1) ; 2010 ; pp 023-038 Subject : 53 Applied Physics;Defence Science Journal Keywords : Motion Planning;Temporal Logic;Real-Time;Formal Languages;Automata;Mobile Agents Abstract : In this paper, a critical review on temporal logic motion planning is presented. The review paper aims to address the following problems: (a) In a realistic situation, the motion planning problem is carried out in real-time, in a dynamic, uncertain and ever-changing environment, and (b) The accomplishment of high-level specification tasks which are more than just the traditional planning problem (i.e., start at initial state A and go to the goal state B) are considered. The use of theory of computation and formal methods, tools and techniques present a promising direction of research in solving motion planning problems that are influenced by high-level specification of complex tasks. The review, therefore, focuses only on those papers that use the aforementioned tools and techniques to solve a motion planning problem. A proposed robust platform that deals with the complexity of more expressive temporal logics is also presented.
	Impact Analysis of Concrete Structural Components Author : Murthy, A. Rama Chandra;Palani, G.S.;Iyer, Nagesh R. Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 307-319 Subject : 62 Engineering;Defence Science Journal Keywords : Concrete structures;reinforced concrete;concrete material models;finite element analysis;impact loading;numerical simulations;impact analysis;compact behaviour Abstract : This paper presents an overview on the concrete structural components subjected to impact loading. The review includes empirical formulae, analytical models, and numerical simulations. Various empirical formulae on penetration depth, perforation, and scabbing limits as well as their ranges of application have been provided. It has been observed that the information available on the validation of these models is limited. There is wider scope to study the performance of well known empirical formulae. Penetration resistance function play an important role in any analytical model. It has been observed that the major limitation is rigid projectile assumption. There is scope to develop new/improved analytical models to represent projectile characteristics. The numerical simulation of concrete structural components subjected to impact loads is a complex phenomenon. From the review, it is observed that employing appropriate material model for concrete, equation-of-state, contact algorithm and definition of yield surface plays significant role in the accurate simulation of concrete structural components. There is ample scope to develop improved methodologies in terms of development of material models and contact algorithms, which can be employed in nonlinear explicit finite element analysis of concrete structural components subjected to impact loading.
	Computational Elements for High-fidelity Aerodynamic Analysis and Design Optimisation Author : Kim, Chongam Source : Defence Science Journal ; Vol:60(6) ; 2010 ; pp 628-638 Subject : 532.542 Fluid Dynamics;Defence Science Journal Keywords : Computational fluid dynamics ;Aerodynamic Analysis;Aerodynamic shape optimisation;High-fidelity numerical methods;Genetic algorithm Abstract : The study reviews the role of computational fluid dynamics (CFD) in aerodynamic shape optimisation, and discusses some of the efficient design methodologies. The article in the first part, numerical schemes required for high-fidelity aerodynamic flow analysis are discussed. To accurately resolve high-speed flow physics, high-fidelity shock-stable schemes as well as intelligent limiting strategy mimicking multi-dimensional flow physics are essential. Exploiting these numerical schemes, some applications for 3-D internal/external flow analyses were carried out with various grid systems which enable the treatment of complex geometries. In the second part, depending on the number of design variables and the way to obtain sensitivities or design points, several global and local optimisation methods for aerodynamic shape optimisation are discussed. To avoid the problem that solutions of gradient-based optimisation method, (GBOM) are often trapped in local optimum, remedy by combining GBOM with global optimum strategy, such as surrogate models and genetic algorithm (GA) has been examined. As an efficient grid deformation tool, grid deformation technique using NURBS function is discussed. Lastly, some 3-D examples for aerodynamic shape optimisation works based on the proposed design methodology are presented.
	Commemorative Issue of Defence Science Journal on Golden Jubilee of DRDO Author : Source : ; Vol: ; 2010 ; pp 121-123 Subject : Defence Science Journal Keywords : Golden Jubilee;DRDO Abstract : Defence Research and Development Organisation (DRDO), Ministry of Defence, is dedicatedly working towards enhancing self-reliance in Defence systems. DRDO undertakes design and development leading to production of world class weapon systems and equipment in accordance with the expressed needs and the qualitative requirements laid down by the three Services. The vision of DRDO is to make India prosperous by establishing world class science and technology base and provide the Defence Services a decisive edge by equipping them with internationally competitive systems and solutions.
	Sensor/Control Surface Fault Detection and Reconfiguration using Fuzzy Logic Author : Savanur, Shobha R.;Patel, Ambalal V. Source : Defence Science Journal ; Vol:60(1) ; 2010 ; pp 076-086 Subject : 681.586 Sensors;Defence Science Journal Keywords : Fuzzy logic;SFDIR;sensor fault detection isolation and reconfiguration;fault reconfiguration;sensor fault detection;control surface fault detection;Kalman filter Abstract : In the aircraft flight control systems, a quick detection of the faults, that occur in actuators, control surfaces or sensors, is necessary. In this paper, sensor fault detection and reconfiguration is performed using Kalman filter by estimating the states of the plant and comparing them with respective measured values from the sensors. Sensor fault detection and reconfiguration is carried out using non-model-based fuzzy logic technique. Control surface fault detection and reconfiguration is carried out by identifying the elements of control distribution matrix using extended Kalman filter and fuzzy logic. In estimating the factor of effectiveness of the control surface using fuzzy logic, different implication methods such as Mamadanis minimum, Larsens product, bounded product and drastic product have been used and a comparison is made.
	Aerial Delivery Systems and Technologies Author : Gupta, Balraj Source : Defence Science Journal ; Vol:60(2) ; 2010 ; pp 124-136 Subject : 533.6 Aerodynamics;53 Applied Physics;Defence Science Journal Keywords : Parachute systems;emergency floating systems;controlled aerial delivery systems;heavy drop system;supply drop system;flexible aerodynamic decelator;aerostat Abstract : Aerial Delivery Research & Development Establishment (ADRDE) was started at Kanpur during latter part of 1950s consisting of two Aerial Delivery Sections primarily for the indigenisation of Parachutes and related equipment for Para-dropping of men and materials. Today, the charter of ADRDE includes design & development of parachutes, Aerostat Systems, Aircraft Arrester Barrier Systems and Heavy-Drop Systems for both military and civilian applications. The technological competence built in Aeronautical, Textile, Mechanical and Electronics engineering has imparted ADRDE, a unique combination of know-how and capabilities to evolve new solutions in these fields, with emphasis on quality assurance. This paper highlights the design and development of technologies developed by ADRDE to stengthen the Indias aerial delivery system and its future plans.
	Smart Munitions Author : Mahajan, C.P.;Motghare, Vaishnavi C. Source : Defence Science Journal ; Vol:60(2) ; 2010 ; pp 159-163 Subject : 355 Defence Sciences;623.4 Armaments and Ballistics;Defence Science Journal Keywords : Smart munitions;sensored munitions;influence land munition Abstract : In modern land warfare, munitions are considered as highly effective means of the defence against an invading force, especially armoured fighting vehicles. In recent decades, new technologies have transformed the dumb land munitions, into sophisticated smart munitions that can be used for offensive purposes. The evolution in the munitions technology was marked by the introduction of sensored smart munitions. Armament Research and Development Establishment (ARDE) has achieved a technological breakthrough by developing world class sensor-based influence land munitions Adrushy MK-I and subsequently Adrushy MK-II. Successful development of these smart influence munitions has made India proud and at par with the world market.
	Military Malaria in Northeast Region of India Author : Dhiman, Sunil;Baruah, Indra;Singh, Lokendra Source : Defence Science Journal ; Vol:60(2) ; 2010 ; pp 213-218 Subject : 57.089 Biomedical Sciences ;Defence Science Journal Keywords : Malaria;armed forces;paramilitary forces;Plasmodium;Anopheles Abstract : Malaria has always been a pernicious problem of serious health hazard in the northeast region of India. The problem is worst for military and paramilitary forces deputed in all the states of this part of country. The forces are deployed for a short time generally from non malarious regions and thus become highly vulnerable to acquire the malaria infection. Several potential malaria vectors with very high vectorial capacity and high slide positivity rate in civil population manifold the chances of infection. In the present review, the incidence of malaria in the armed forces and paramilitary forces are discussed in detail and minimal measures for the control of malaria in northeastern region have been suggested.
	Path Planning in the Presence of Dynamically Moving Obstacles with Uncertainty Author : Singh, G.K.;Gopal, Ajith Source : Defence Science Journal ; Vol:60(1) ; 2010 ; pp 055-060 Subject : 53 Applied Physics;Defence Science Journal Keywords : Path-planning;genetic algorithm;elliptical obstacles Abstract : In this paper, the problem of path-planning with dynamically moving elliptical obstacles is addressed. A new analytical result for computing the axes aligned bounding box for the ellipses with bounded uncertainty in the position of the centre and the orientation is presented. Genetic algorithm is utilised for finding the shortest path from the initial to goal position avoiding the moving obstacles.
	Adhesively-bonded Patch Repair with Composites Author : Pandey, P.C.;Kumar, S. Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 320-329 Subject : 62 Engineering;Defence Science Journal Keywords : Three-dimensional finite elements;adhesively-bonded composite-patch repair;structure life extension;geometric and material nonlinearity Abstract : Adhesively-bonded composite patch repairs over cracked or corrosion-damaged metallic aircraft structures have shown great promise for extending life of ageing structures. This study presents the numerical investigation into the interface behaviour of adhesively-bonded cracked aluminum alloy substrate patched with fibre-reinforced composite material. The adhesive is modelled as an elasto-plastic bilinear material to characterise the debond behaviour, while the defective substrate is regarded as linear elastic continuum. Two typical patch shapes were selected based on information available in the literature. Geometric and material nonlinear analyses for square and octagonal patches were performed to capture peel and shear stresses developed between the substrate and the patch to examine the possibility of interface delamination/debonding. Parametric studies on adhesive thickness and patch thickness were carried out to predict their infuence on damage tolerance of repaired structures.
	Emulsification and Hydrolysis of Oil by Syncephalastrum racemosum Author : Mathur, Chandni;Prakash, Ranjana;Ali, Amjad;Kaur, Jasminder;Cameotra, Swaranjit Singh;Prakash, N. Tejo Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 251-254 Subject : 57 Biological Sciences;Defence Science Journal Keywords : Fungus;Syncephalastrum racemosum;emulsification;esterification;vegetable oil;biotransformation;lipolysis Abstract : A fungal strain, Syncephalastrum racemosum, was isolated from oil-leak contaminated soils from Kanpur, India. The strain was examined for potential to emulsify soybean oil using a 18 per cent oil supplement as carbon source in minimal salt medium. On 72 h growth of the fungus in oil and salt medium, the cellfree supernatant (CFS) showed presence of mono- and di-glycerides indicating degradation of oils to free fatty acids (FFAs). Increasing concentration of oil resulted in enhanced formation of FFAs. The degradation process was observed to be related to the emulsification activity in CFS which was observed to increase with time. The study reports the emulsification and hydrolytic activity of S. racemosum, an activity that can be exploited for increasing the accessibility and treatment of hazardous substance including hydrophobic explosives.
	Temporal Pattern Classification using Kernel Methods for Speech Recognition and Speech Emotion Recognition Author : Chandra Sekhar, C.;Chandrakala, S. Source : Defence Science Journal ; Vol:60(4) ; 2010 ; pp 348-363 Subject : 681.3 Computer Science;681.3:355 Computer Applications in Defence;Defence Science Journal Keywords : Hidden Markov model;support vector machine;string kernel;Gaussian mixture model;score vector;parametric vector;speech recognition and speech emotion recognition Abstract : There are two paradigms for modelling the varying length temporal data namely, modelling the sequences of feature vectors as in the hidden Markov model-based approaches for speech recognition and modelling the sets of feature vectors as in the Gaussian mixture model (GMM)-based approaches for speech emotion recognition. In this paper, the methods using discrete hidden Markov models (DHMMs) in the kernel feature space and string kernel-based SVM classifier for classification of discretised representation of sequence of feature vectors obtained by clustering and vector quantisation in the kernel feature space are presented. The authors then present continuous density hidden Markov models (CDHMMs) in the explicit kernel feature space that use the continuous valued representation of features extracted from the temporal data. The methods for temporal pattern classification by mapping a varying length sequential pattern to a fixed-length sequential pattern and then using an SVM-based classifier for classification are also presented. The task of recognition of spoken letters in E-set, it is possible to build models that use a discretised representation and string kernel SVM based classification and obtain a classification performance better than that of models using the continuous valued representation is demonstrated. For modelling sets of vectors-based representation of temporal data, two approaches in a hybrid framework namely, the score vector-based approach and the segment modeling based approach are presented. In both approaches, a generative model-based method is used to obtain a fixed length pattern representation for a varying length temporal data and then a discriminative model is used for classification. These two approaches are studied for speech emotion recognition task. The segment modeling based approach gives a better performance than the score vector-based approach and the GMM-based classifiers for speech emotion recognition.
	Prioritising Emergency Bridgeworks Assessment under Military Consideration using an Enhanced Fuzzy Weighted Average Approach Author : Hung, Kuo-Chen;Tuan, Han-Wen Source : Defence Science Journal ; Vol:60(4) ; 2010 ; pp 451-461 Subject : 622 Civil Engineering;Defence Science Journal Keywords : Fuzzy weighted average;fuzzy multi-criteria decision making (FMCDM);bridgeworks assessment;military circumstance Abstract : Prioritising emergency bridgeworks assessment has been a key to winning battles in combat circumstances because of soldier safety, attack or defence tactics, and logistic supply ability. However, an imprecise or vague satisfaction level of importance of criteria may also affect the prioritising evaluation of bridgeworks under military consideration. In this paper, the fuzzy set theory is employed to treat this aspect. With linguistic variables, fuzzy numbers and an enhanced fuzzy weighted average approach will be used. The proposed approach is used to investigate an example to illustrate its applications in emergency bridgeworks assessment. The approach is shown to be useful and effective. In order to make computing and ranking results easier and to increase recruiting productivity, a computer-based decision support system has been developed, which may help the commander make decisions more efficiently.
	Attributes of Seabuckthorn (Hippophae rhamnoides L.) to Meet Nutritional Requirements in High Altitude Author : Stobdan, Tsering;Chaurasia, O.P.;Korekar, Girish;Mundra, Sunil;Ali, Zulfikar;Yadav, Ashish;Singh, Shashi Bala Source : Defence Science Journal ; Vol:60(2) ; 2010 ; pp 226-230 Subject : 631 Agriculture;Defence Science Journal Keywords : Hippophae rhamnoides L.;high altitude;nutrition;Seabuckthorn Abstract : The diet of humans living in different geographical and climatic regions of the earth varies greatly in both quantity and composition of foods. Evidence is accumulating that indicates that there is a high risk of malnutrition at high altitude because of the usual lack of fresh food and environmental factors. Lack of nutritious diet in the difficult terrain is a potential stressor that elicits oxidative stress. The excretion of minerals from the body is higher in high altitude condition. The altered nutritional requirement can be met to a large extend by regular consumption of locally grown fruits and vegetables. Results of analysis of Seabuckthorn growing in Leh valley of Trans-Himalaya showed the presence of high content of multivitamins including vitamin C (275 mg/100g), vitamin A (432.4 IU/100g), vitamin E (3.54 mg/100g), Riboflavin (1.45 mg/100g), Niacin (68.4 mg/100g), Pantothenic acid (0.85 mcg/100g), vitamin B-6 (1.12 mg/100g), and vitamin B-2 (5.4 mcg/100g). Similarly, mineral elements composition revealed high amount of minerals including potassium (647.2 mg/l), calcium (176.6 mg/l), iron (30.9 mg/l), magnesium (22.5 mg/l), phosphorous (84.2 mg/l), sodium (414.2 mg/l), zinc (1.4 mg/l), copper (0.7 mg/l), manganese (1.06 mg/l) and selenium (0.53 mg/l).
	Table of Contents Author : Source : Defence Science Journal ; Vol:60(1) ; 2010 ; pp 002 Subject : Defence Science Journal Keywords : Abstract :
	Aircraft Height Estimation using 2-D Radar Author : Hakl, H.;Davies, E.;Roux, W.H. le Source : Defence Science Journal ; Vol:60(1) ; 2010 ; pp 100-105 Subject : 621.396.9 Radars;Defence Science Journal Keywords : Radar Tracking;Aircraft Height Estimation;2-D Search Radar;Target Tracking;Aircraft Altitude Estimation;2-D Radar Abstract : A method to infer height information from an aircraft tracked with a single 2-D search radar is presented. The method assumes level flight in the target aircraft and a good estimate of the speed of the aircraft. The method yields good results for medium to high altitudes, though performs weaker at low altitudes. The method can distinguish between high and low targets on a normal 2-D radar, and can reach a height resolution of 100 m provided the 2-D radar is optimised to the task.
	Guest Editorial Author : Chakraborty, Debasis Source : Defence Science Journal ; Vol:60(6) ; 2010 ; pp 567-576 Subject : 532.542 Fluid Dynamics;Defence Science Journal Keywords : Computational fluid dynamics;CFD codes;Propulsion;Combustion Abstract : A review of the emergence and maturing of computational fluid dynamics (CFD) research in India over the last four decades is presented. The status of in-house developed CFD codes in various aerospace laboratories and academic institutions in the country is described along with their strengths and weaknesses. Although, some level of maturity is achieved in CFD to address the external flow problems of an aerospace vehicle, the slow growth of indigenous reacting CFD codes forced Indian aerospace industry to depend solely on the commercial software for addressing the internal flow problems related to propulsion and combustion. A brief account of various technical and managerial issues in CFD development is presented. A roadmap is proposed for the graduation of CFD codes, from analysis tool to design tool.
	Bayes Reliability Measures of Lognormal and Inverse Gaussian Distributions under ML-II e-contaminated Class of Prior Distributions Author : Sinha, Pankaj;Prabha, J. Source : Defence Science Journal ; Vol:60(4) ; 2010 ; pp 442-450 Subject : 681.5.017 Simulation;Defence Science Journal Keywords : Bayes reliability;lognormal distribution;inverse Gaussian distribution;Bayesian methodology Abstract : ML-II e-contaminated class of priors are employed to study the sensitivity of Bayes reliability measures for a lognormal (LN) distribution and inverse Gaussian (IG) distribution to mis-specification in the prior is employed. The numerical illustrations suggest that reliability measures of both the distributions are not sensitive to moderate amount of mis-specification in prior distributions belonging to the class of ML-II e-contaminated.
	Numerical Simulation of Incompressible Turbulent Flow using Linear Eddy Viscosity-based Turbulence Models Author : Majumdar, Sekhar;Rajani, B.N.;Kulkarni, D.S.;Subrahmanya, M.B. Source : Defence Science Journal ; Vol:60(6) ; 2010 ; pp 614-627 Subject : 532.542 Fluid Dynamics;Defence Science Journal Keywords : Computational Fluid Dynamics;Eddy viscosity-based turbulence models;Multi-block boundary-conforming grid Abstract : The present study focuses on the recent development of an implicit pressure-based finite volume algorithm for numerical solution of Reynolds averaged Navier-Stokes equations (RANS) in an inertial frame of reference for the prediction of unsteady incompressible flow problems. The algorithm uses boundary-conforming, multiblock structured grid with moving boundaries, collocated variable arrangement with momentum equations resolved along cartesian directions, second-order accurate spatial and temporal discretisation schemes for the convective fluxes and a pressure-velocity solution strategy. Effect of turbulence was simulated using appropriate linear eddy viscosity-based turbulence models. The capabilities and limitations of the cost-effective unsteady Reynolds averaged Navier-Stokes (URANS) approach has been demonstrated for few application problems of engineering interest.
	Front Cover Author : Source : Defence Science Journal ; Vol:60(5) ; 2010 ; pp 01 Subject : Defence Science Journal Keywords : Abstract :
	Flexural Vibration Characteristics of Initially Stressed Composite Plates Author : Daripa, Rupesh;Singha, M.K. Source : Defence Science Journal ; Vol:60(1) ; 2010 ; pp 106-111 Subject : 620.1 Material Science and Technology;Defence Science Journal Keywords : Composite Plate;Partial in-Plane Load;Flexural Vibration;Nonlinear Frequency;Loads;Stress Abstract : The influence of localised in-plane load on the flexural vibration characteristics of isotropic and composite plates have been studied using a four-noded shear flexible high precision plate bending finite element. First, the critical buckling loads of such plates subjected to partial or concentrated compressive loads were calculated, then the linear and nonlinear flexural vibration frequencies were obtained. Limited parametric study was carried out to study the influences of location and distribution of tensile or compressive in-plane load on the vibration frequencies of such plates.
	State-of-the-Art in Active Electronically-Steered Array Surveillance Radar: Indian Value Addition Author : Christopher, S. Source : Defence Science Journal ; Vol:60(2) ; 2010 ; pp 184-188 Subject : 621.396.9 Radars;623 Military Science and Engineering;Defence Science Journal Keywords : Air-to-air surveillance;air-to-surface surveillance;radar;EW;mechanically steered array;active electronically steered array;AEW;airborne early warning and control;AWACS;AEW&C Abstract : The advent of active electronically steered arrays (AESA) marked the most important development in radar technology. With exceptional reliability, superior performance, and unprecedented beam-steering agility, this technology has drastically changed many aspects of airborne surveillance, and thereby the tactics of air warfare. The optimal configuration for the AESA antenna is still evolving towards exploitation of the radar's total potential in the airborne surveillance application. The paper briefly enumerates the efforts being made in this direction globally and elaborates the Indian line of approach for its current and future AEW&C systems.
	Development of Three-dimensional Grid-free Solver and its Applications to Multi-body Aerospace Vehicles Author : Anandhanarayanan, K. Source : Defence Science Journal ; Vol:60(6) ; 2010 ; pp 653-662 Subject : 532.542 Fluid Dynamics;Defence Science Journal Keywords : Computational fluid dynamics ;Grid-free method;chimera clouds;Moving multi-body Abstract : Grid-free solver has the ability to solve complex multi-body industrial problems with minimal effort. Grid-free Euler solver has been applied to number of multi-body aerospace vehicles using Chimera clouds of points including flight vehicle with fin deflection, nose fairing separation of hypersonic launch vehicle. A preprocessor has been developed to generate connectivity for multi-bodies using overlapped grids. Surface transpiration boundary condition has been implemented to model aerodynamic damping and to impose the relative velocity of moving components. Dynamic derivatives are estimated with reasonable accuracy and less effort using the grid-free Euler solver with the transpiration boundary condition. Further, the grid-free Euler solver has been integrated with six-degrees of freedom (6-DOF) equations of motion to form store separation dynamics suite which has been applied to obtain the trajectory of a rail launch air-to-air-missile from a complex fighter aircraft.
	Statistical Measures to Determine Optimal Structure of Decision Tree: One versus One Support Vector Machine Author : Bala, Manju;Agrawal, R.K. Source : Defence Science Journal ; Vol:60(4) ; 2010 ; pp 399-404 Subject : 681.3:355 Computer Applications in Defence;Defence Science Journal Keywords : Support vector machine;decision tree;information gain;gini index;chi-square;SVM-BDT;binary decision tree Abstract : In this paper, one versus one optimal decision tree support vector machine (OvO-ODT SVM) framework is proposed to solve multi-class problems where the optimal structure of decision tree is determined using statistical measures, i.e., information gain, gini index, and chi-square. The performance of proposed OvO-ODT SVM is evaluated in terms of classification accuracy and computation time. It is also shown that proposed OvO-ODT SVM using all the three measures is more efficient in terms of time complexity for both training and testing phases in comparison to conventional OvO and support vector machine binary decision tree (SVMBDT). Experiments on University of California, Irvine (UCI) repository dataset illustrates that ten crossvalidation accuracy of our proposed framework is comparable or better in comparison to conventional OvO and SVM-BDT for most of the datasets. However, the proposed framework outperforms the conventional OvO and SVM-BDT for all the datasets in terms of both training and testing time.
	Maximum Likelihood Estimator for Bearings-only Passive Target Tracking in Electronic Surveillance Measure and Electronic Warfare Systems Author : Rao, S. Koteswara Source : Defence Science Journal ; Vol:60(2) ; 2010 ; pp 197-203 Subject : 623 Military Science and Engineering;Defence Science Journal Keywords : Maximum likelihood estimator;pasive target tracking;target tracking;ESM system;EW system Abstract : Maximum likelihood estimator is a suitable algorithm for passive target tracking applications. Nardone, Lindgren and Gong introduced this approach using batch processing. In this paper, the batch processing is converted into sequential processing for real-time applications like passive target tracking using bearings-only measurements. Adaptively, the variance of each measurement is computed and is used along with the measurement in such a way that the effect of false bearings can be reduced. The transmissions made by radar on a target ship are assumed to be intercepted by an electronic warfare (EW) system of own ship. The generated bearings in intercept mode are processed through maximum likelihood estimator (MLE) to find out target motion parameters. Instead of assuming some arbitrary values, pseudo linear estimator outputs are used for the initialisation of MLE. The algorithm is tested in Monte-Carlo simulation and its results are presented for two typical scenarios.
	Influence of Terrain on Modern Tactical Combat: Trust-based Recommender System Author : Bedi, Punam;Sinha, A.K.;Agarwal, Sumit Source : Defence Science Journal ; Vol:60(4) ; 2010 ; pp 405-411 Subject : 623 Military Science and Engineering;Defence Science Journal Keywords : Recommender systems;trust;clustering;intuitionistic fuzzy set;agent;tactical combat Abstract : In Army Services, there are a number of valuable decisions that have to be taken for mission accomplishment. These decisions are very important and the choice of a weapon may be able to alter the outcome of a battle decisively. Among several such decisions one is to decide which weapons to deploy/assign over a given terrain. Recommender systems are intelligent applications to assist users in a decision-making process where they want to choose one item amongst a potentially overwhelming set of alternative products or services. This paper proposes the design of recommender system that automates the process of finding the appropriate type of weapon(s) that can be deployed over a terrain having certain characteristics. The user agent seeks recommendations, which are in the form of intuitionistic fuzzy set (IFS), from trustworthy peers and produces aggregated order of recommendations taking degree of trust on recommenders into consideration. Trust on recommender is also updated based on importance of recommendation given to the user. A prototype of the trust-based recommender system for modern tactical combat system has been designed and developed through which the user can get the recommendation to use a specific kind of weapon or a set of weapons that would be best-suited in a given type of terrain.
	Front Cover Author : Source : Defence Science Journal ; Vol:60(2) ; 2010 ; pp 1 Subject : Defence Science Journal Keywords : Abstract :
	Damage Effects of Explosion of Shelled Explosive in Concrete Author : Yan, Liu.;Zhuoping, Duan.;Fenglei, Huang.;Xinsheng, Wang. Source : Defence Science Journal ; Vol:60(6) ; 2010 ; pp 672-677 Subject : 532.542 Fluid Dynamics;Defence Science Journal Keywords : Computational fluid dynamics ;Shelled explosive;explosive leading;protective engineering blast loading Abstract : The damage of concrete subjected to explosion loading is an important issue in defence engineering. The degree of damage to concrete is related to many factors, such as type of explosive charge, depth of burial, and parameters of concrete. In this study, three factors have been considered for experiments of shelled explosives in concrete targets, which are filling coefficient, length-to-diameter ratio, and depth of burial. The filling coefficient is from 0.1 to 1.0 by changing thickness of shell, and the length-to-diameter ratio is from 2.5. The unconfined compressive strength of concrete targets for test is 35 MPa. The experimental results showed that sizes of craters of concretes were varied depending upon the filling coefficient, the length-todiameter ratio, and the depth of burial. The optimal values of filling coefficient, length-to-diameter ratio, and depth of burial of shelled charges have been obtained to get maximal damage regions of concrete targets. This study has provided a base for evaluating damage of concrete and designing penetrating warhead.
	Numerical Simulation of Supersonic Combustion with Parallel Injection of Hydrogen Fuel Author : Murty, M.S.R. Chandra;Mishal, R.D.;Chakraborty, Debasis Source : Defence Science Journal ; Vol:60(5) ; 2010 ; pp 465-475 Subject : 681.5.017 Simulation;Defence Science Journal Keywords : Numerical simulation;supersonic combustion;hydrogen fuel;turbulent Schmidt number;scramjet combustor 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.
	The Evolution of AUSM Schemes Author : Liou, Meng-Sing Source : Defence Science Journal ; Vol:60(6) ; 2010 ; pp 606-613 Subject : 532.542 Fluid Dynamics;Defence Science Journal Keywords : Computational fluid dynamics;Hyperbolic Syatems;Upwinding;Conservatio Laws Abstract : This paper focuses on the evolution of advection upstream splitting method(AUSM) schemes. The main ingredients that have led to the development of modern computational fluid dynamics (CFD) methods have been reviewed, thus the ideas behind AUSM. First and foremost is the concept of upwinding. Second, the use of Riemann problem in constructing the numerical flux in the finite-volume setting. Third, the necessity of including all physical processes, as characterised by the linear (convection) and nonlinear (acoustic) fields. Fourth, the realisation of separating the flux into convection and pressure fluxes. The rest of this review briefly outlines the technical evolution of AUSM and more details can be found in the cited references.
	Back Cover Author : Source : Defence Science Journal ; Vol:60(1) ; 2010 ; pp 121-122 Subject : Defence Science Journal Keywords : Abstract :
	Guest Editorial: Mobile Intelligent Autonomous Systems Author : Rao, Jitendra R.;Gopal, Ajith Source : Defence Science Journal ; Vol:60(1) ; 2010 ; pp 003-004 Subject : Defence Science Journal Keywords : Abstract :
	Front Cover Author : Source : Defence Science Journal ; Vol:60(1) ; 2010 ; pp 001 Subject : Defence Science Journal Keywords : Abstract :
	Compression Process of Pore inside Explosive Charge in a Warhead under Launching Load Author : Li, W.;Yan, H.;Zhang, Q;Ji, Y.H. Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 244-250 Subject : 620.261 Explosives;623.41 Weapon Systems ;Defence Science Journal Keywords : Thermobaric warhead;numerical computing;dynamical response Abstract : In this paper, the compression process of the pore inside explosive charge in a warhead under launching load is simulated and its influence on premature explosion is discussed. The relationship between the pore compression, distortion, and the form of igniting hot spot has been established. The analysis of result indicates that the stress wave in the explosive charge developed due to launching load is a key factor in the pore compression process. The volume change of the pore, which is related to its original volume, is a major factor affecting the form of ignition hot spot. It appears that a specific size of the pore may not lead to the premature explosion of explosive charge in a warhead under launching load. The quantitative relationship between the dangerous size range of the pore and the launching load is a core research subject of warhead safety during launching. With this objective, numerical computing was undertaken to assess the pores distortion parameter inside the explosive charge of a warhead, and generate database for warhead safety under launching load.
	Least Squares Kinetic Upwind Mesh-free Method Author : Deshpande, S. M.;Ramesh, V.;Malagi, Keshav. Source : Defence Science Journal ; Vol:60(6) ; 2010 ; pp 583-597 Subject : 532.542 Fluid Dynamics;Defence Science Journal Keywords : Computational fluid dynamics ;Boltzman Equation;Kinetic Theory;Euler Equation;Gas Dynamics;Chimera Cloud Abstract : Least squares kinetic upwind mesh-free (LSKUM) method has been the subject of research over twenty years in our research group. LSKUM method requires a cloud (W) of points or nodes and connectivity N(P0) for every P0 ÎW . The connectivity of P0 is a set of neighbours i ( 0) PÎN P of P0. The cloud can be a simple cloud, Cartesian cloud or chimera cloud or can be obtained rapidly using advancing front method. The discrete approximation to spatial derivatives was obtained using of least squares and it can be made accurate using defect correction method. The LSKUM first operates on the Boltzmann level and then passes on to Euler or Navier-Stokes level by taking suitable moments (so called y moments) of the Boltzmann equation of kinetic theory of gases. The upwinding in LSKUM method is enforced by stencil or connectivity splitting based on the signs of v1, v2 in 2-D and v1, v2, v3 in 3-D. This leads to split fluxes encountered in Kinetic Flux Vector Splitting (KFVS) method. The higher-order accurate LSKUM method can be made more efficient using entropy variables, thus leading to q-LSKUM method. Lastly, boundary conditions are implemented using specular reflection model on the wall (KCBC method) and by using kinetic outer boundary condition (KOBC) method for a point on the outer boundary.
	Transmission Loss Variability Associated with Upwelling and Downwelling Off the Southwest Coast of India Author : Kumar, P.V. Hareesh;Radhakrishnan, K.G. Source : Defence Science Journal ; Vol:60(5) ; 2010 ; pp 476-482 Subject : 62 Engineering;53 Applied Physics;Defence Science Journal Keywords : Transmission loss;upwelling process;downwelling process;acoustic propagation model;upslope propagation;downslope propagation;bathymetry Abstract : Fine resolution spatial survey carried out off the west coast of India during June and December 2004 was utilised to study the transmission loss (TL) variability associated with the upwelling and downwelling processes in this region. During June, the upwelling was confined to the upper 80 m. Downsloping of isotherms below this depth towards the coast and the occurrence of low saline waters indicated the presence of undercurrent. Between the periods of upwelling and downwelling, temperature and salinity in the surface layers increased by 1-2 oC and 2 PSU, respectively, while at the sub-surface levels, the corresponding increase was ~8 oC and ~0.5 PSU. A range-dependent acoustic propagation model based on parabolic equation method was utilised to compute TL for these two periods. The model was run with a source frequency of 3 kHz kept at 5m depth for different environmental setup, viz. propagation along the constant-depth contour, range-independent and range-dependent environment, and upslope/downslope propagation. The computations revealed significant variability in the TL characteristics between the upwelling and downwelling scenario, though bathymetry and geo-acoustic properties were the same. The analysis also stressed the need of range-dependent acoustic propagation model for realistic prediction of transmission loss variability.
	Back Cover Author : Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 43 Subject : Defence Science Journal Keywords : Abstract :
	Development of Surface Acoustic Wave Electronic Nose using Pattern Recognition System Author : Jha, S.K.;Yadava, R.D.S. Source : Defence Science Journal ; Vol:60(4) ; 2010 ; pp 364-376 Subject : 53 Applied Physics;681.586 Sensors;Defence Science Journal Keywords : SAW sensor array;electronic nose;TNT vapour detection;SVD denoising;pattern recognition;pattern recognition system;singular valve decompostion based denoising Abstract : The paper proposes an effective method to design and develop surface acoustic wave (SAW) sensor array-based electronic nose systems for specific target applications. The paper suggests that before undertaking full hardware development empirically through hit and trial for sensor selection, it is prudent to develop accurate sensor array simulator for generating synthetic data and optimising sensor array design and pattern recognition system. The latter aspects are most time-consuming and cost-intensive parts in the development of an electronic nose system. This is because most of the electronic sensor platforms, circuit components, and electromechanical parts are available commercially-off-the-shelve (COTS), whereas knowledge about specific polymers and data analysis software are often guarded due to commercial or strategic interests. In this study, an 11-element SAW sensor array is modelled to detect and identify trinitrotoluene (TNT) and dinitrotoluene (DNT) explosive vapours in the presence of toluene, benzene, dimethylmethylphosphonate (DMMP) and humidity as interferents. Additive noise sources and outliers were included in the model for data generation. The pattern recognition system consists of: (i) a preprocessor based on logarithmic data scaling, dimensional autoscaling, and singular value decomposition-based denoising, (ii) principal component analysis (PCA)-based feature extractor, and (iii) an artificial neural network (ANN) classifier. The efficacy of this approach is illustrated by presenting detailed PCA analysis and classification results under varied conditions of noise and outlier, and by analysing comparative performance of four classifiers (neural network, k-nearest neighbour, naïve Bayes, and support vector machine).
	Boosting Principal Component Analysis by Genetic Algorithm Author : Somvanshi, Divya;Yadava, R.D.S. Source : Defence Science Journal ; Vol:60(4) ; 2010 ; pp 392-398 Subject : 681.3 Computer Science;681.3:355 Computer Applications in Defence;Defence Science Journal Keywords : Feature extraction;genetic algorithm;feature fusion;principal component analysis;pattern recognition Abstract : This paper presents a new method of feature extraction by combining principal component analysis and genetic algorithm. Use of multiple pre-processors in combination with principal component analysis generates alternate feature spaces for data representation. The present method works out the fusion of these multiple spaces to create higher dimensionality feature vectors. The fused feature vectors are given chromosome representation by taking feature components to be genes. Then these feature vectors are allowed to undergo genetic evolution individually. For genetic algorithm, initial population is created by calculating probability distance matrix, and by applying a probability distance metric such that all the genes which lie farther than a defined threshold are tripped to zero. The genetic evolution of fused feature vector brings out most significant feature components (genes) as survivours. A measure of significance is adapted on the basis of frequency of occurrence of the surviving genes in the current population. Finally, the feature vector is obtained by weighting the original feature components in proportion to their significance. The present algorithm is validated in combination with a neural network classifier based on error backpropagation algorithm, and by analysing a number of benchmark datasets available in the open sources.
	Contents Author : Source : Defence Science Journal ; Vol:60(5) ; 2010 ; pp 02-03 Subject : Defence Science Journal Keywords : Abstract :
	Computational Fluid Dynamics in Aerospace Industry in India Author : Singh, K.P. ;Mathur, J.S.;Ashok, V.;Chakraborty, Debasis Source : Defence Science Journal ; Vol:60(6) ; 2010 ; pp 639-652 Subject : 532.542 Fluid Dynamics;Defence Science Journal Keywords : Computational fluid dynamics ;Missile Aerodynamics;Aerospace vehicles design Abstract : The role of computational fluid dynamics (CFD) in the design of fighter aircraft, transport aircraft, launch vehicle and missiles in India is explained. Indigenous developments of grid generators, 3-D Euler and Navier- Stokes solvers using state-of-the-art numerical techniques and physical models have been described. Applications of these indigenous softwares for the prediction of various complex aerodynamic flows over a wide range of Mach number, angle of attacks, are presented. Emergence of CFD methods as an efficient tool for aerospace vehicle design is highlighted.
	Protected Cultivation for Food and Nutritional Security at Ladakh Author : Mishra, Gyan P.;Singh, Narendra;Kumar, Hitesh;Singh, Shashi Bala Source : Defence Science Journal ; Vol:60(2) ; 2010 ; pp 219-225 Subject : 631 Agriculture;Defence Science Journal Keywords : Protective cultivation;high altitude cultivation;greenhouse technology;nutritional security;high altitude agriculture;high altitude agro-animal technologies Abstract : Ladakh, being cold, arid, high altitude region of India has a very harsh climate and a short agriculture season. Due to extreme long winter, the agriculture season is short, which extends from May-September in general, and in case of particular location, it depends upon altitude. Although the greenhouse technology is more than 200 years old but with the advent of plastics during the World War-II, a new phase in the greenhouse technology has emerged. The Defence Institute of High Altitude Research (DIHAR), one of the DRDO laboratories, is providing adequate support and technological help to set various types of green houses, both for the Army Units deployed in the far-flung areas and for the local farmers in the Ladakh. Till date, there were 65 greenhouses being established by DIHAR in most of the Army Units deployed in the L sector with the average vegetable production of around 2000 kg/greenhouse/year. At present, the much needed vegetables are being grown throughout the year in these hostile climates under protective cultivation, which not only gives them the fresh food but also the nutritional security of the troops deployed.
	Front Cover Author : Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 1 Subject : Defence Science Journal Keywords : Abstract :
	Assessment of Poissons Ratio for Hydroxy-terminated Polybutadine-based Solid Rocket Propellants Author : Shekhar, Himanshu;Sahasrabudhe, Anil D. Source : Defence Science Journal ; Vol:60(5) ; 2010 ; pp 497-501 Subject : 623 Military Science and Engineering;Defence Science Journal Keywords : Composite propellants;Poissons ratio;tensile test;incompressible materials;filled polymers;solid rocket-propellants Abstract : Poissons ratio of hydroxy-terminated polybutadine (HTPB)-based composite propellant is estimated from uni-axial tensile testing. Double dumbbell specimens as per ASTM D638 type IV standard were used and Poissons ratio at break, obtained by change in volume of specimen, was calculated as approximately 0.25. It was also observed that Poissons ratio is different along different lateral directions of the propellant specimen. Poissons ratios in two orthogonal directions perpendicular to longitudinal axis were calculated as 0.17 and 0.30. As ASTM specimen has rectangular cross-section of approximate size 6 mm x 4 mm, the directional behaviour of Poissons ratio may be attributed to initial dimensions. Prismatic propellant specimen with square cross-section and of 115 mm x 6 mm x 6 mm dimension do not show any variation wrt Youngs modulus, tensile strength, and percentage elongation as compared to ASTM specimen. Directional behaviour of Poissons ratio with almost similar numerical value was again observed, thus ruling out dependence of this behaviour on different initial dimensions of propellant cross-section. Further, Poissons ratio varies linearly with strain even in linear portion of stress-strain curve in uni-axial tensile testing. The rate of reduction of Poissons ratio with increase in strain is slower in linear region and it accelerates after dewetting due to formation of vacuoles. Variation of Poissons ratio with strain has two different slopes in linear (slope = 0.3165) and nonlinear regions (slope = 0.61364). Numerical value of slope for variation of Poissons ratio with strain almost doubles after dewetting. It must be noted that no change in volume does not necessarily indicate constant Poissons ratio equal to 0.5. Composite propellants behave as compressible material in most of the regions and near-failure region or at higher strains; Poissons ratio is not anywhere near to 0.5, instead it is near 0.25.
	Performance Degradation in Pre-rake Frequency-division Duplex/ Direct Sequence-code Division Multiple Access Systems Author : Subhas, C.;Naidu, K. Rama;Reddy, Y. Venkatarami Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 282-289 Subject : 62 Engineering;Defence Science Journal Keywords : Direct sequence-code division multiple access;DS-CDMA;rake receiver;pre-rake;inter-symbol interference;frequency-division duplex;FDD;channel prediction Abstract : The transmitter-based pre-rake diversity combining technique reduces the complexity, size and cost of the mobile unit (MU), while achieving the same inter symbol interference (ISI) mitigation effects of rake receiver for direct sequence-code division multiple access (DS-CDMA) systems. The technique is based on preprocessing of transmitted signal relying on knowledge of the channel state information (CSI) before transmission. In most of the previous works, this a priori information is either assumed or estimated for the uplink and the same is applied to the downlink in time division duplex (TDD) systems due to channel reciprocity. In this paper, a method for channel prediction to evaluate the pre-rake system using binary phaseshift keying (BPSK) modulation in frequency-division duplex (FDD) through analytical and computer simulations for DS-CDMA downlink has been proposed. The performance of the system was also evaluated under ideal and predicted channel conditions using different spreading codes. The findings will have widespread applications in defence communication equipment.
	Split-and-merge Procedure for Image Segmentation using Bimodality Detection Approach Author : Chaudhuri, D.;Agrawal, A. Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 290-301 Subject : 62 Engineering;Defence Science Journal Keywords : Segmentation;clustering;bimodality;minimal spanning-tree;homogeneity factor;split-and-merge technique;image segmentation Abstract : Image segmentation, the division of a multi-dimensional image into groups of associated pixels, is an essential step for many advanced imaging applications. Image segmentation can be performed by recursively splitting the whole image or by merging together a large number of minute regions until a specified condition is satisfied. The split-and-merge procedure of image segmentation takes an intermediate level in an image description as the starting cutest, and thereby achieves a compromise between merging small primitive regions and recursively splitting the whole images to reach the desired final cutest. The proposed segmentation approach is a split-andmerge technique. The conventional split-and-merge algorithm is lacking in adaptability to the image semantics because of its stiff quadtree-based structure. In this paper, an automatic thresholding technique based on bimodality detection approach with non-homogeneity criterion is employed in the splitting phase of the split-and-merge segmentation scheme to directly reflect the image semantics to the image segmentation results. Since the proposed splitting technique depends upon homogeneity factor, some of the split regions may or may not split properly. There should be rechecking through merging technique between the two adjacent regions to overcome the drawback of the splitting technique. A sequential-arrange-based or a minimal spanning-tree based approach, that depends on data dimensionality of the weighted centroids of all split regions for finding the pair wise adjacent regions, is introduced. Finally, to overcome the problems caused by the splitting technique, a novel merging technique based on the density ratio of the adjacent pair regions is proposed. The algorithm has been tested on several synthetic as well as real life data and the results show the efficiency of the segmentation technique.
	Feature Extraction by Wavelet Decomposition of Surface Acoustic Wave Sensor Array Transients Author : Singh, Prashant;Yadava, R.D.S. Source : Defence Science Journal ; Vol:60(4) ; 2010 ; pp 377-386 Subject : 53 Applied Physics;681.586 Sensors;Defence Science Journal Keywords : SAW sensor transients;wavelet decomposition;feature extraction;VOC identification;machine olfaction;surface acoustic wave;discrete wavelet transformer Abstract : The paper presents a new approach to surface acoustic wave (SAW) chemical sensor array design and data processing for recognition of volatile organic compounds (VOCs) based on transient responses. The array is constructed of variable thickness single polymer-coated SAW oscillator sensors. The thickness of polymer coatings are selected such that during the sensing period, different sensors are loaded with varied levels of diffusive inflow of vapour species due to different stages of termination of equilibration process. Using a single polymer for coating the individual sensors with different thickness introduces vapour-specific kinetics variability in transient responses. The transient shapes are analysed by wavelet decomposition based on Daubechies mother wavelets. The set of discrete wavelet transform (DWT) approximation coefficients across the array transients is taken to represent the vapour sample in two alternate ways. In one, the sets generated by all the transients are combined into a single set to give a single representation to the vapour. In the other, the set of approximation coefficients at each data point generated by all transients is taken to represent the vapour. The latter results in as many alternate representations as there are approximation coefficients. The alternate representations of a vapour sample are treated as different instances or realisations for further processing. The wavelet analysis is then followed by the principal component analysis (PCA) to create new feature space. A comparative analysis of the feature spaces created by both the methods leads to the conclusion that both methods yield complimentary information: the one reveals intrinsic data variables, and the other enhances class separability. The present approach is validated by generating synthetic transient response data based on a prototype polyisobutylene (PIB) coated 3-element SAW sensor array exposed to 7 VOC vapours: chloroform, chlorobenzene o-dichlorobenzene, n-heptane, toluene, n-hexane and n-octane.
	Payload Estimation in Universal Steganalysis Author : P.P., Amritha;Madathil, Anoj Source : Defence Science Journal ; Vol:60(4) ; 2010 ; pp 412-414 Subject : 681.3 Computer Science;Defence Science Journal Keywords : Support vector machine;support vector regression;principal component analysis;steganalysis;payload estimation;image classification;universal steganalysis Abstract : Universal Steganalysis can classify images without the knowledge of steganographic algorithms. This steganalysis will blindly classify an image as cover or not, but finding how much payload embedded, is still an open problem. This paper focuses on the above problem. Firstly, they use features from universal steganlysers and apply principal component analysis to improve the false positive rate. The above features are then used to estimate the payload by using support vector regression. The support vector machine classifier capable of assigning stego images to six popular steganographic algorithm after applying Principal Component Analysis: JP Hide & Seek, PVD, LSB flipping, Outguess, S-Tool and F5 is trained. This provides significantly more reliable results compared to their previous work on universal steganalysis. The performance is also evaluated by quantitative steganalysis for six steganographic algorithms.
	Contents Author : Source : Defence Science Journal ; Vol:60(6) ; 2010 ; pp 003 Subject : Defence Science Journal Keywords : Abstract :
	Classification of Encrypted Text and Encrypted Speech Author : Asthana, Rajesh;Verma, Neelam Source : Defence Science Journal ; Vol:60(4) ; 2010 ; pp 420-422 Subject : 681.3 Computer Science;Defence Science Journal Keywords : Feature extraction;projection pursuit techniques;minimum distance classifier;maximum likelihood classifier;Sammon's algorithm;Chien's algorithm Abstract : The information to be exchanged between two parties can be text data or speech data. This data is encrypted for its security and communicated (to the other end). When an adversary intercepts these encrypted data then in order to recover the actual information, his first step is to identify whether intercepted data is encrypted text or encrypted speech are used. The next step is to get the actual information from encrypted text or encrypted speech. In this paper, pattern recognition techniques are applied for identification of encrypted text and encrypted speech. Some new and modified feature extraction techniques have been used to convert the text and speech data into three-dimensional, four-dimensional, and five-dimensional measurement vectors. These multi-dimensional measurement vectors are converted into two-dimensional vectors using projection pursuit technique based on Sammon.s algorithm and Chien.s algorithm. The quantified classification performances using minimum distance classifier and maximum likelihood classifier have also been given.
	Decontamination of Chemical Warfare Agents Author : Singh, Beer;Prasad, G.K.;Pandey, K.S. Source : Defence Science Journal ; Vol:60(4) ; 2010 ; pp 428-441 Subject : 54 Chemistry;Defence Science Journal Keywords : Chemical warfare agents;neutralisation;decontamination;decontamination media Abstract : Chemical warfare agents (CWA) pose inevitable threat, both to soldiers and civilians. Risk on contact with these deadly agents can be avoided by neutralisation of their toxic effects. A suitable media with essential physico-chemical properties is required for this purpose. Considerable efforts have been made to develop several decontamination media suitable for neutralisation of highly toxic CWAs. This paper reviews history and details of recent technological advancements in the development of versatile, broad spectrum decontamination formulations against CWAs, as also nanosized metal oxides as CWA decontaminants.
	Determination of Acetonitrile-hexane Partition Coefficient of O,O'-dialkyl Methylphosphonates by NMR Spectroscopy for the Verification Analysis of Chemical Weapon Convention Author : Mazumder, Avik;Gupta, Hemendra K.;Srivastava, Rajendra K.;Dubey, D.K. Source : Defence Science Journal ; Vol:60(5) ; 2010 ; pp 502-506 Subject : 54 Chemistry;Defence Science Journal Keywords : O,O'-dialkyl methylphosphonates;chemical warfare agents;partition-coefficient;official proficiency tests;NMR spectroscopy Abstract : The extractability of the O,O'-dialkyl methylphosphonates, (the important markers of nerve agents) included in the schedule 2B4 of the Chemical Weapons Convention (CWC) has been studied by NMR, the aim being the optimisation of extraction protocols routinely used for the identification of Convention-related Chemicals (CRCs) during Official Proficiency Tests (OPTs) conducted by the Organization for Prohibition of Chemical Weapons (OPCW) and for the off-site analysis of real field samples. The technique is easy to optimise, fast, nondestructive, and shows excellent reproducibility.
	Success Probability Assessment Based on Information Entropy Author : Chen, Xuan;Huang, Hanyan;Wang, Zhengming Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 271-275 Subject : 623 Military Science and Engineering;Defence Science Journal Keywords : Information entropy;equivalent surrogate test;equivalent source;Bayesian method;Bootstrap method Abstract : The Bayesian method is superior to the classical statistical method on condition of small sample test. However, its evaluation results are not so good if subjective prior information is intervened. The success probability assessment about the success or failure tests of weapon products focussed in this paper, and a fusing evaluation method based on information entropy is proposed. Firstly, data from equivalent surrogate tests is converted into the prior information of an equivalent source by the information entropy theory. Secondly, the prior distribution of the success probability is identified via the Bootstrap method, and the posterior distribution is provided by the Bayesian method with the information of prototype tests in succession. Lastly, an example is given, and the results show that the proposed method is effective and valuable.
	Fuzzy Support Vector Machine-based Multi-agent Optimal Path Planning Approach to Robotics Environment Author : T., Gireesh Kumar;Poornaselvan, K.J.;Sethumadhavan, M. Source : Defence Science Journal ; Vol:60(4) ; 2010 ; pp 387-391 Subject : 681.3 Computer Science;681.3:355 Computer Applications in Defence;Defence Science Journal Keywords : Fuzzy logic;fuzzy support vector machine;FSVM;optimal path planning;multi-agent;mobile robot;robotic navigation Abstract : A mobile robot to navigate purposefully from a start location to a target location, needs three basic requirements: sensing, learning, and reasoning. In the existing system, the mobile robot navigates in a known environment on a predefined path. However, the pervasive presence of uncertainty in sensing and learning, makes the choice of a suitable tool of reasoning and decision-making that can deal with incomplete information, vital to ensure a robust control system. This problem can be overcome by the proposed navigation method using fuzzy support vector machine (FSVM). It proposes a fuzzy logic-based support vector machine (SVM) approach to secure a collision-free path avoiding multiple dynamic obstacles. The navigator consists of an FSVM-based collision avoidance. The decisions are taken at each step for the mobile robot to attain the goal position without collision. Fuzzy-SVM rule bases are built, which require simple evaluation data rather than thousands of input-output training data. The effectiveness of the proposed method is verified by a series of simulations and implemented with a microcontroller for navigation.
	Development of Cube Recrystallisation Texture and Microstructure of an Aluminium Alloy Suitable for Cartridge Case Manufacturing Author : Mukhopadhyay, Prantik;Verma, Arun Kumar Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 330-336 Subject : 53 Applied Physics;62 Engineering;Defence Science Journal Keywords : Recrystallisation;cube-orientation;cellular automaton Abstract : Electron backscattered diffraction investigations on just fully recrystallised orientation image microstructures, showed that the cube-oriented grains had the largest size in all microstructures of an aluminium alloy, which have potential use in the cartridge case manufacturing for defence purpose. The simulation of cube microstructure and texture of that aluminium alloy was tried. The recrystallisation texture and microstructure simulation by the 3-D cellular automaton model with the consideration of highest mobility of 40º<111> grainboundary, predicted the volume fraction of the cube texture orientation which was validated by experiment.
	Battlefield Lasers and Opto-electronics Systems Author : Laser;opto-electronic systems;laser devices;military usage;warfare;electro-optic countermeasures Source : Defence Science Journal ; Vol:60(2) ; 2010 ; pp 189-196 Subject : 623 Military Science and Engineering;621.375.826 Laser Science;Defence Science Journal Keywords : Laser;opto-electronic systems;laser devices;military usage;warfare;electro-optic countermeasures Abstract : During the last four decades or so, there has been an explosive growth in commercial, industrial, medical, scientific, technological, and above all, military usage of laser devices and systems. In fact, lasers have influenced every conceivable area of application during this period. While the expansion of non-military application spectrum of lasers is primarily driven by emergence of a large number of laser wavelengths followed by ever increasing power levels and reducing price tags at which those wavelengths could be generated, the military applications of lasers and related electro-optic devices have grown mainly because of technological maturity of the lasers that were born in the late 1960s and the early 1970s. Lasers have been used in various military applications since the early days of development that followed the invention of this magical device. There has been large scale proliferation of lasers and opto-electronic devices and systems for applications like range finding, target designation, target acquisition and tracking, precision guided munitions, etc. during 1970s and 1980s. These devices continue to improve in performance and find increased acceptance and usage in the contemporary battle-field scenario. Technological advances in optics, opto-electronics, and electronics, leading to more rugged, reliable, compact and efficient laser devices are largely responsible for making these indispensable in modern warfare. Past one decade or so has seen emergence of some new potential areas of usage. Some of these areas include rapid growth in the usage of lasers and opto-electronics devices and systems for electrooptic countermeasure (EOCM) applications, test and evaluation systems that can perform online functionality checks on military opto-electronics systems and also their interoperability. In this paper, an overview of the current and emerging military applications of lasers and opto-electronics systems has been given with an outline on the likely trends leading to performance enhancement of the existing systems and emergence of new application areas. Also, a brief on the developmental activity in the field of laser and opto-electronics devices and systems at Laser Science and Technology Centre (LASTEC), Delhi has been given.
	Identification of Military-related Science and Technology Author : Kostoff, Ronald N.;Bhattacharya, Sujit Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 259-270 Subject : 623 Military Science and Engineering;Defence Science Journal Keywords : India;text mining;military-relevant;pattern extraction;defence infrastructure Abstract : A proof-of-principle demonstration for extracting military-related technologies from a countrys total technology publications has been performed, and applied to the Indian science and technology literature#. The method is general and can be applied to the extraction of any meta-category (e.g., intelligence-relevant technologies, infrastructure-relevant technologies, etc) which is not easily obtained from document clustering or factor analysis. The methodology for identifying relevant literature on military science appears to provide credible results. The volume of literature retrieved will vary depending on how strongly relevant is the desired literature. For the same definitions of military relevant, the volume of Indias literature in the Ei Compendex database was an order of magnitude less than that of the USA or China.
	Back Cover Author : Source : Defence Science Journal ; Vol:60(6) ; 2010 ; pp 693-694 Subject : Defence Science Journal Keywords : Abstract :
	Strength Investigation of Thick Welded T-Joint using Finite Element Modelling Author : Ali, Aidy;Yung, Tun Chun;Zulkefli, Z.A.;Aziz, Nuraini Abdul;Sahari, B.B.;Zadeh, M. Source : Defence Science Journal ; Vol:60(1) ; 2010 ; pp 112-119 Subject : 620.1 Material Science and Technology;Defence Science Journal Keywords : T-Joints;Finite Element Modelling;FEM;MSC PATRAN;Welded T-Joints;MSC NASTRAN Abstract : The paper discusses the computation of finite element modelling (FEM) of a thick welded joint as a high load transfer joint. The FEM utilises MSC PATRAN/NASTRAN software programs to predict and simulate the critical area of a welded joint. The elasticity limit for the specimen was determined and stress distribution was achieved in the joint to indicate critical parts of a welded T-joint and predict the critical locations for crack initiation in this kind of joint. Simulation and experimental results show good in agreement and the sources of some differences in these results are discussed.
	Motion Segmentation Algorithm using Spectral Framework Author : Vrinthavani R;Kaimal, M.R. Source : Defence Science Journal ; Vol:60(1) ; 2010 ; pp 039-047 Subject : 681.3 Computer Science;Defence Science Journal Keywords : Spectral framework;motion segmentation;motion vectors;BMA;block matching algorithm Abstract : This paper presents a new motion segmentation method using iterative maximum likelihood framework. The method consists of two steps. In the first step, motion regions are detected and motion vectors are computed for these detected regions. In the second step, a similarity matrix is computed from the motion vectors and motion segmentation is done using maximum likelihood method. The method has been tested using real world motion sequences and is found to give very low error rate and it also detects the slow moving objects.
	Defence Applications of Polymer Nanocomposites Author : Kurahatti, R.V.;Surendranathan, A.O.;Kori, S. A. Source : Defence Science Journal ; Vol:60(5) ; 2010 ; pp 551-563 Subject : 54 Chemistry;355 Defence Sciences;Defence Science Journal Keywords : Nanocomposites;nanotechnologies;defence applications;smart materials;polymer-based nanocomposites;medical applications;fuel sources Abstract : The potential opportunities promised by nanotechnology for enabling advances in defence technologies are staggering. Although these opportunities are likely to be realised over a few decades, many advantages are currently being explored, particularly for defence applications. This review provides an insight into the capabilities offered by nanocomposites which include smart materials, harder/lighter platforms, new fuel sources and storage as well as novel medical applications. It discusses polymer-based nanocomposite materials, nanoscale fillers and provides examples of the actual and potential uses of nanocomposite materials in defence with practical examples.
	Parametric Analysis of Energy Absorption in Micro-particle Photophoresis in Absorbing Gaseous Media Author : Li, W.K.;Soong, C.Y.;Liu, C.H.;Tzeng, P.Y. Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 233-237 Subject : 53 Applied Physics;Defence Science Journal Keywords : Heat source function;size parameter;absorptivity;refractivity;particle photophoresis Abstract : The study deals with photophoresis of a spherical micro-particle suspended in absorbing gaseous media. Photophoretic motion of the particle stems from the asymmetric distribution of absorbed energy within the particle. By evaluating the so-called heat source function at various conditions, the study focuses on the effects of governing parameters on the energy distribution within the particle and their potential influences to the photophoresis. The results reveal that the increase in either particle size or absorptivity enhances the energy intensity on the illuminated (leading) side and tends to generate positive photophoresis. For a particle of low absorptivity, the energy distribution is dominated by particle refraction. Enhancing particle refractivity, the energy tends to be focused onto a certain spot area on the shaded (trailing) side and leads to a tendency of negative photophoresis. Increasing medium absorptivity significantly degrades the level of energy absorbed by the particle and in turn weakens the driving force of the particle photophoresis.
	Front Cover Author : Source : Defence Science Journal ; Vol:60(6) ; 2010 ; pp 001 Subject : Defence Science Journal Keywords : Abstract :
	Synthesis of Cobalt Oxide Nanoparticles/Fibres in Alcoholic Medium using gamma-ray Technique Author : Athawale, Anjali A.;Majumdar, Megha;Singh, Hema;Navinkiran, K. Source : Defence Science Journal ; Vol:60(5) ; 2010 ; pp 507-513 Subject : 53 Applied Physics;Defence Science Journal Keywords : Oxides;X-ray diffraction;X-ray photoelectron spectroscopy;XPS;optical properties;gamma irradiation technique;magnetic nanoparticles;UV-visible spectroscopy;spectroscopy;cobalt-oxide nanoparticles;nanoparticle synthesis Abstract : Nanoparticles of cobalt oxides were synthesised by steady state g irradiation technique using various alcoholic salt solutions of cobalt ions with aniline acting as a stabiliser. Preliminary results were investigated using UV-vis and Fourier transform infra red analysis. The X-ray diffractograms revealed major peaks at 2q values of ~ 36.4°, 39.1°, 44.2°, and 65.7° corresponding to the Co3O4 phase and one peak at ~30.7° (100 per cent intensity) for Co2O3 phase. Lower alcohols yielded particles while fibres were formed in higher alcohols as observed from transmission electron microscopic analysis. Iso-propanol was observed to yield cobalt oxide nanoparticles with highest stability, conversion yield and homogeneity in size. The average measured diameter and length of these fibres were ~29 nm and 130 nm respectively. Energy dispersive spectroscopy supports the formation of cobalt oxide. The X-ray photoelectron spectroscopic results for iso-propanol sample show a peak at 781.6 eV confirming the formation of Co3O4.
	Contents Author : Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 2-3 Subject : Defence Science Journal Keywords : Abstract :
	Assessing Expected Fractional Damage of Above-ground Buildings from Air-to-surface Weapons based on Indirect Fire Concept Author : Park, Jong Yil Source : Defence Science Journal ; Vol:60(5) ; 2010 ; pp 491-496 Subject : 623 Military Science and Engineering;Defence Science Journal Keywords : Weaponeering;air-to-surface;joint munitions effectiveness manuals;expected fractional damage;air-to air-tosurface weapons Abstract : For the expected fractional damage of building targets from air-to-surface weapons, the US has used the JMEM/AS method, which is based on the direct-fire concept. However, the damage redistribution assumption in the direct-fire concept could induce serious errors in damage estimation of building targets. In this paper, a method for the expected fractional damage of building targets is proposed based on the indirect-fire concept. From the proposed model, it is shown that the joint munitions effectiveness manuals/air-to-surface (JMEM/ AS) method is not appropriate for building targets, especially for attacks with multiple aiming points. It is recommended that the indirect-fire concept should be adopted for weaponeering even for air-to-surface weapons.
	Multi-echelon Repair Inventory Systems: Select Issues in Modular Electronic Equipment Author : Garg, Amik;Deshmukh, S.G. Source : Defence Science Journal ; Vol:60(5) ; 2010 ; pp 514-524 Subject : 62 Engineering;Defence Science Journal Keywords : Multi-echelon repair inventory;modular equipment;maintenance Abstract : Flow of modules/printed circuit boards (PCBs) in a multi-echelon repair inventory system pertaining to modular electronic equipment for large maintenance organisations having large inventory in range and depth, like defence has been critically examined using a case study. Desirable features of the proposed system are identified and a general framework suggested for examining its feasibility and implementation in an organisation. An analytical model with an objective to reduce number of echelons is also suggested and compared with the base model. It is suggested that various models can be compared through simulation and their performance measured using balanced scorecard approach.