001469   DAIYA V, EBENEZER J, JEHADEESAN R (Indira Gandhi Centre for Atomic Research Kalpakkam, Kalpakkam) : Mapping obfuscation-based phy security scheme for resource-constrained wireless sensor network. IETE Tech Rev 2021, 38(2), 221-30.

Wireless sensor network (WSN) physical layer (PHY) uses M-ary spread spectrum (MaSS). This paper explores MaSS and emphasizes that based on the implementation approach; the technology has the potential to provide security at the PHY of wireless devices. The MaSS parameters, namely, spreading sequences and symbol to sequence mapping logic, can be obfuscated for security implementation. In this paper, we have focused our analysis on obfuscating mapping logic, i.e. Mapping Obfuscation (MO). Mathematical analysis reveals that an eavesdropper with processing speed in the order of 1018 operations/sec can intercept and decode short length (maximum 8–10 bytes) packets in < 100 s. Simulation exposes that the eavesdropper can achieve a success rate of 50% for short-length packets if its signal-to-noise ratio exceeds −1 dB. An attacker has only one check metric for mapping sequence detection that is correct frame check sequence (FCS) detection. However, FCS detection may be misleading; if packet-embedded FCS and eavesdropper-generated FCS are the same for the wrong mapping sequence. For MO-based MaSS, false FCS detection probability is 30 times more than valid FCS detection probability. To reduce false FCS probability attacker need to analyse multiple radio frequency (RF) packets for detecting a valid mapping key; this increases the computation time. For MO-based PHY security, correct mapping sequence identification by exhaustive search demands cluster-based parallel processing.

6 illus, 4 tables, 21 ref

001413   LEE S, SIN C, KIM S (Navigation R&D Div, Korea Aerospace Research Institute, Daejeon, Korea) : A sequential approach to direct multi-target localization in mimo radar networks. IETE J Res 2021, 67(2), 180-5.

This paper presents a direct multi-target localization algorithm for multiple-input multiple-output radar networks employing code division multiple access signals. The proposed algorithm localizes targets one by one whose contributions remain dominant in the received signal after removing the contributions of the localized targets. The sequence of isolating the contributions improves the accuracy of multi-target localization and avoids the computational inefficiency of the maximum likelihood estimator (MLE). Simulation results demonstrate the superiority of the proposed algorithm in comparison with the MLE.

5 illus, 14 ref

003476   SRIVASTAVA S, DWIVEDI P N, KUMAR D M V (DRDO-Defence Research and Development Laboratory, Hyderabad - 500 058, Email: srikant.srivat@gmail.com) : 3-Loop structure based fuel flow controller design for robust operation of ducted ramjet rocket. Def Sci J 2021, 71 (4), 572 - 8.

This paper is about the designing of 3-loop structure based fuel flow controller (FFC) for efficient operation of supersonic ramjet based propulsion system. The main objective of the control design is to vary appropriately the engine controllable parameters (throttle value area) such that commanded thrust is achieved by ramjet engine without endangering the engine stability and performance. Various factors such as combustion-intake interaction, atmospheric disturbance and other flight conditions have a significant impact on the air intake operation which lead to effect on engine performance. Due to above effect, intake un-start and buzzing phenomena can occur due to back pressure fluctuation and it disturb the intake pressure recovery and air mass flow rate. So, back pressure based extra loop introduce in 2-loop FFC design to have tight control on back pressure margin for smooth and efficient operation of air intake without need of extra hardware. 

11 illus, 16 ref

003475   PRABHU G, KUMAR R A, NANDY T K (DRDO-Defence Metallurgical Research Laboratory, Hyderabad - 500 058, Email: gprabhu@dmrl.drdo.in) : Tungsten heavy alloys with two-phase matrix. Def Sci J 2021, 71 (4), 564 - 71.

WNiCo alloys subjected to a two-stage or cyclic heat treatment develop a unique microstructure wherein apart from tungsten grains and matrix phase, fine tungsten precipitates are distributed in the matrix. This is unlike conventional heavy alloys such as WNiFe and WNiFeCo where the matrix is single phase without any secondary microstructural features. The purpose of developing a two-phase matrix is to realise superior mechanical properties compared to conventional alloys, especially strength with comparable or superior elongation and impact toughness. This advantage has rendered WNiCo alloys (with two-phase matrix) suitable candidates for advanced kinetic energy penetrators. The present study focusses on processing 92W-5Ni-3Co alloy using cyclic heat treatment and optimisation of parameters involved in cyclic heat treatment as well as subsequent vacuum heat treatment. Any refinement in processing parameters will help in improving the mechanical properties given the fact that processing parameters, microstructural features and mechanical properties are strongly interdependent in the case of tungsten heavy alloys.

6 illus, 5 tables, 9 ref

003474   DIVYA G N, RAO S K (Koneru Lakshmaiah Education Foundation, Guntur - 522 502, Email: nagadivya.guduru@gmail.com) : Application of sigma point particle filter method for passive state estimation in underwater. Def Sci J 2021, 71 (4), 556 - 63.

Bearings-only tracking (BOT) plays a vital role in underwater surveillance. In BOT, measurement is tangentially related to state of the system. This measurement is also corrupted with noise due to turbulent underwater environment. Hence state estimation process using BOT becomes nonlinear. This necessitates the use of nonlinear filtering algorithms in place of traditional linear filters like Kalman filter. In general, these nonlinear filters utilize the assumption of measurements being corrupted with Gaussian noise for state estimation. The measurements cannot be always corrupted with Gaussian noise because of the highly unstable sea environment. These problems indicate the necessity for development of nonlinear non-Gaussian filters like particle filter (PF) for underwater tracking. However, PF suffers from severe problems like sample degeneracy and impoverishment and also it is tedious to select an appropriate technique for resampling. To overcome these difficulties in PF implementation, the strategy of combining PF with another filter like unscented Kalman filter is proposed for target’s state estimation. The detailed analysis of the same is presented in comparison with other particle filter combinations using the simulation results obtained in Matlab.

5 illus, 2 tables, 17 ref

003472   FERDJALI A, LECHEKHAB T, MANOJLOVI? S, STANKOVI? M, MADONSKI R, BUJAKOVIC B (Jinan Univ, Guangzhou, China, Email: momir_stankovic@yahoo.com) : Nonlinear extended state observer-based active disturbance rejection control of a laser seeker system. Def Sci J 2021, 71 (4), 535 - 44.

In this paper, the laser seeker control problem is solved in the framework of active disturbance rejection control (ADRC). The considered problem, which consists of laser seeker stabilisation and target tracking, is expressed here as a regulation problem. A nonlinear extended state observer (NESO) with varying gains is used to improve the performance of linear ESO (LESO), and thus enable better control performance in both transient period and steady-state, with lower control effort. Based on a detailed analysis of system disturbances, a special ADRC tuning method is proposed. The stability of the overall control structure is analysed with a description function method. Through comparative simulations LESO-based and the introduced NESO-based ADRC for the laser seeker system, the advantages of the proposed scheme are shown. 

6 illus, 29 ref

003468   MISHRA G, GUPTA I, MURTHY S V S S N V G K, PAL S K (DRDO-Scientific Analysis Group, Delhi - 110 054, Email: gmishratech28@gmail.com) : Deep learning based cryptanalysis of stream ciphers. Def Sci J 2021, 71 (4), 499 - 506.

Conventional cryptanalysis techniques necessitate an extensive analysis of non-linear functions defining the relationship of plain data, key, and corresponding cipher data. These functions have very high degree terms and make cryptanalysis work extremely difficult. The advent of deep learning algorithms along with the better and efficient computing resources has brought new opportunities to analyze cipher data in its raw form. The basic principle of designing a cipher is to introduce randomness into it, which means the absence of any patterns in cipher data. Due to this fact, the analysis of cipher data in its raw form becomes essential. Deep learning algorithms are different from conventional machine learning algorithms as the former directly work on raw data without any formal requirement of feature selection or feature extraction steps. With these facts and the assumption of the suitability of employing deep learning algorithms for cipher data, authors introduced a deep learning based method for finding biases in stream ciphers in the black-box analysis model. The proposed method has the objective to predict the occurrence of an output bit/byte at a specific location in the stream cipher generated keystream. The authors validate their method on stream cipher RC4 and its improved variant RC4A and discuss the results in detail. Further, the authors apply the method on two more stream ciphers namely Trivium and TRIAD. The proposed method can find bias in RC4 and shows the absence of this bias in its improved variant and other two ciphers. Focusing on RC4, the authors present a comparative analysis with some existing methods in terms of approach and observations and showed that their process is more straightforward and less complicated than the existing ones.

4 illus, 4 tables, 27 ref

003465   SILVA R W D, REIS A L Q, STENDERS R M, ANDRADE E R D (Military Institute of Engineering, Brazil, Email: edson@ccen.ufpb.br) : Radiological consequences modelling for a land-based operation environment. Def Sci J 2021, 71 (4), 470 - 5.

Radiological Dispersive Devices (RDD) are often portrayed as weapons used by radical (asymmetric) forces, however they can also be used in a regular war. In this study, a hypothetical scenario where an asymmetric force contaminates the battlefield, by detonating an RDD prior to the soldier’s arrival without being detected, is simulated. The software HotSpot was used due to its speed and conservative results which can help inform the decisions made by the commanding officers. HotSpot performs a Gaussian simulation of the radioactive dispersion in the environment. The plumes that arise from the explosion are considered to be affected by the atmospheric conditions. In this study, those conditions are represented by the Pasquill-Gifford stability classes. The results of the simulation show that remaining stationary, if the contaminated area size is not affected by the PG class variation, may increase the radiological risk. It is better to move the soldiers around in order to avoid additional exposure, however that may also be a challenge for various reasons including changes in the shape of the contaminated area. Nevertheless, the variations in local PG classes gain importance as the distance from the release point increases.

4 illus, 1 table, 17 ref

003465   SILVA R W D, REIS A L Q, STENDERS R M, ANDRADE E R D (Military Institute of Engineering, Brazil, Email: edson@ccen.ufpb.br) : Radiological consequences modelling for a land-based operation environment. Def Sci J 2021, 71 (4), 470 - 5.

Radiological Dispersive Devices (RDD) are often portrayed as weapons used by radical (asymmetric) forces, however they can also be used in a regular war. In this study, a hypothetical scenario where an asymmetric force contaminates the battlefield, by detonating an RDD prior to the soldier’s arrival without being detected, is simulated. The software HotSpot was used due to its speed and conservative results which can help inform the decisions made by the commanding officers. HotSpot performs a Gaussian simulation of the radioactive dispersion in the environment. The plumes that arise from the explosion are considered to be affected by the atmospheric conditions. In this study, those conditions are represented by the Pasquill-Gifford stability classes. The results of the simulation show that remaining stationary, if the contaminated area size is not affected by the PG class variation, may increase the radiological risk. It is better to move the soldiers around in order to avoid additional exposure, however that may also be a challenge for various reasons including changes in the shape of the contaminated area. Nevertheless, the variations in local PG classes gain importance as the distance from the release point increases.

4 illus, 1 table, 17 ref

003464   PARATE B A, DEODHAR K D, DIXIT V K (DRDO-Armament Research & Development Establishment, Pune - 411 021, Email: baparate@gmail.com) : Qualification testing, evaluation and test methods of gas generator for IEDs application. Def Sci J 2021, 71 (4), 462 - 9.

In this work, the design qualification testing, evaluation and test methods of the gas generator using double base (DB) propellant having square flake shape is explained for an improvised explosive devices (IEDs) applications. Various kinds of the gas generators are used to save life of an aeronaut in the fastest way from the disable fighter aircraft. Due to their ruggedised design, compactness, safe transportation, repeatability in performance and quick operation, the gas generator are used. The gas generator is designed and developed keeping the functional, mechanical and structural requirements in mind. The gas generators are subjected to the various qualification tests, electrical characterisation followed by closed vessel (CV) firings at hot and cold temperatures. The gas generators after the successful qualification tests are validated through the ground trials i.e. dynamic firing of disruptor during the development phase. The damage caused due to impact of the projectile is assessed in terms of crater as acceptance criteria at stand-off distance of 0.5 m and 1m. The gas generator discussed in this research article is used to disrupt the suspected IEDs by creating a high-speed jet using water-jet disruptor. In conclusion, after the successful qualification testing, the gas generator for IEDs application meets all the specifications as per user’s requirements. 

12 illus, 8 tables, 8 ref

003463   KUMAR R, WAGH P B, INGALE S V, JOSHI K D (Bhabha Atomic Research Centre, Mumbai - 400 085, Email: ratanesh@barc.gov.in) : Degradation of mononitrotoluene by electrochemical method. Def Sci J 2021, 71 (4), 456 - 61.

Present paper deals with studies on the degradation of Mononitrotoluene (MNT) by electrochemical method.  The Electro-Fenton and Electro-Peroxide methods are explored to degrade MNT upto its drain discharge limit of 1 ppm. Effects of some important parameters which ultimately decide the rate of degradation of MNT viz. oxidizer, pH, catalyst and voltage etc. have been critically studied. The detailed studies have been carried out which includes variation in  different parameters viz. pH from acidic range to basic range, catalyst concentration from 10 ppm to 50 ppm, Oxidizer concentration from 5 mM to 40 mM and potential across electrodes  from 4 V to 24 V for efficient degradation of MNT. It is observed that optimised values of precursors viz. catalyst (FeSO₄) concentration of 40 ppm, pH of 3, potential across electrodes of 12V and oxidizer (H₂O₂) concentration of 25 mM; Electro-Fenton reaction has been carried out to degrade 50 ppm MNT solution up to its drain discharge limit of 1 ppm and on other hand under Electro-Peroxide reaction results in degradation of MNT from 50 ppm to 12 ppm. The comparative studies of   Electro-Fenton and Electro-Peroxide reactions have been carried out for MNT solution and the treated solution has been characterised by using UV-Visible spectrophotometer and Total Organic Carbon (TOC) analyzer and the obtained data on MNT effluent studies may be applicable to explore the efficient mineralisation of 2-Methyl-1, 3, 5-trinitrobenzene effluent. The observed results have been interpreted and reported in the present study.

6 illus, 24 ref

003460   GAUR R, GANESAN S, PRASAD B V S S S (DRDO-Gas Turbine Research Establishment, Bengaluru - 560 093`, Email: riteshgaur@gtre.drdo.in) : Comparative performance of new surface roughness element and pin-fin in converging channel for gas turbine application. Def Sci J 2021, 71 (4), 429 - 35.

Thermal performance of a novel surface roughness element, named as Double 45 Dimple (D45D), is compared with pin-fin element in a converging channel with rectangular cross section and presented. The Surface Roughness Element (SRE) is derived by combining protrusion & dimple in a particular fashion such that area available for transfer of heat increases. The objective of this study is to demonstrate the applicability of D45D element channel for trailing edge channel of a typical nozzle guide vane where typically pin-fin element is used. New cooling configuration of Nozzle Guide Vane (NGV) with D45D element is also proposed. All thermal and flow related results are derived using validated CFD approach with EARSM turbulence model for a typical value of Reynolds number. From this investigation, it is found that D45D element provides remarkable improvement in the averaged as well as heat transfer in local region for the corresponding surface which makes it a candidate for trailing edge channel cooling application.

7 illus, 1 table, 23 ref

003459   SHANKAR M R, NIRANJANAPPA A C, DATTAGURU B (DRDO-Centre for Airborne Systems, Bengaluru - 560 037, Email: mrsankar@cabs.drdo.in) : Aerodynamic and structural optimisation of maritime patrol radar system radome using evolutionary algorithms. Def Sci J 2021, 71 (4), 421 - 8.

Airborne early warning systems are deployed for collecting surveillance information on airborne enemy targets in real-time. The Maritime Patrol Radar system is used for surveillance of sea surface for various types of ships and low flying aircraft. Radio Detection And Ranging system, or RADAR, in short, is an Electromagnetic sensor integrated on such airborne platforms. An antenna of this radar system is generally mounted under the belly of the aircraft and protected by a cover called a radome. This radome is installed to protect the radar antenna from environmental disturbances. Due to the installation of the radome, increased drag is experienced by aircraft during its flight due to resistance to the flow of the oncoming air. Radome design is a multidisciplinary effort involving structural, aerodynamics, and electromagnetic disciplines. In this study, the multi-disciplinary design of the maritime patrol aircraft radome for optimality in terms of structural strength and aerodynamic performance is carried out by integrating both disciplinary analyses on an optimisation software platform. The utopia point in terms of these two disciplines is found.

8 illus, 3 tables, 12 ref

003458   CARDOSO F A, ABRAHÃO F T M, SABA W B (Aeronautics Institute of Technology, Brazil, Email: cardosoaf@yahoo.com.br) : Resources package modelling supporting border surveillance operations. Def Sci J 2021, 71 (3), 410 - 7.

The  purpose  of  this  work  is  to  propose  a  military  planning  tool  capable  of  providing  logistical  bases  and patrol packages to most effectively support border surveillance. Presently, military patrols are employed along geographical borders to combat transnational crimes; acts such as drug trafficking, smuggling of goods and illegal natural resources exploitation. The patrols make temporary stops within specific time windows at specific places characterised by a high incidence of crime (hotspots). These hotspots have different criticalities within given time windows. To optimise the results, the proposed model allows additional stops in more critical hotspots. It achieves this using a mathematical optimisation model. Considering that there are not adequate logistical-military capacities (logistical bases and patrols) at all needed locations, developing a border surveillance plan that optimises resource use  is  imperative. The  model  was  run  using  black  hole-based  optimisation  and  a  real  patrol  mission’s  database  to ensure timely solutions. The solutions were then evaluated in terms of quality (number of bases and patrols, coverage efforts, and travel time) and computational processing time. Next, they were compared with solutions using the traditional  method,  thereby  demonstrating  the  model’s  robustness  in  providingtimely  surveillance  schemes  that ensure  high  coverage with  minimum resources.

5 illus, 4 tables, 15 ref

003453   AGARWAL S (Motilal Nehru National Institute of Technology Allahabad, Prayagraj - 211 004, Email: smritiagarwal@mnnit.ac.in) : Non-contact multiple ring csrr based planar microwave sensor for accurate quality estimation of water samples with varying TDS. Def Sci J 2021, 71 (3), 378 - 82.

Water pollution and scarcity of pure drinking water is a current challenging problem. In this situation, quality monitoring of water is of vital importance in order to avoid any health issues caused due to intake of contaminated water.  Hence,  in  this  paper,  a  non-destructive  technique  using  multiple  ring  CSRR  based  microwave  sensor  has been  proposed  for  accurate  estimation  of  relative  permittivity  of  unknown  water  of  varying  TDS  values.  Further, a closed form numerical expression using the curve fitting technique has been developed in order to accurately estimate  the  quality  of  any  unknown  water  sample.  Less  than  1%  of  error  has  been  achieved  in  the  prediction  of relative permittivity and hence, TDS of unknown water sample. The proposed planar microwave sensor will be of great importance towards  the  real-time water  quality monitoring systems  development.

5 illus, 2 tables, 16 ref

003450   ROY A, KUMAR A (Applied Mechanics Dep, Motilal Nehru National Institute of Technology Allahabad, Prayagraj - 211 004, Email: abhishek@mnnit.ac.in) : Corrosion behaviour of multiaxial compressed AlMgSi alloy. Def Sci J 2021, 71 (3), 359 - 64.

In the present study, AlMgSi alloy was processed through multi-axial compression (MAC) to produce ultrafine-grained microstructure at room temperature. The AlMgSi alloys are widely used in automobile industries for making cylinder heads and brake disks etc. MAC was performed up to three cycles and showed improvement in mechanical properties. The impact of different strain levels upon microstructure changes is investigated using electron backscatter diffraction (EBSD). The average grain size reduced from an initial average grain size of ~ 124 to ~ 3 μm after completion of three cycles of MAC processing. Samples were tested for mechanical properties using uniaxial tensile test, hardness measurements, and corrosion. Tensile test results show a considerable increase in yield strength from ~90 MPa to ~249 MPa after 3 cycles of MAC. The average hardness value increased from 52 VHN to 90 VHN after 3 cycles of MAC. The corrosion resistance of MAC processed samples was found to decrease in comparison to solution-treated samples.

6 illus, 3 tables, 29 ref

003446   CHANAKYA T, MANKER N K, NAIDU V B, DATTA S K (DRDO-Microwave Tube Research & Development Centre, Bengaluru - 560 013, Email: chanakyaiith@gmail.com) : Multipaction susceptibility margins in space travelling-wave tubes. Def Sci J 2021, 71 (3), 337 - 40.

Study of multipaction breakdown margins in the output connector of a travelling-wave tube (TWT) is essential for application in satellite-borne systems. A TWT uses a coaxial ceramic window, a coaxial output coupler and / or a waveguide output coupler that are prone to multipaction breakdown boosted by high RF power due to the ion accumulation in critical regions during the transition of the satellite through plasma pockets in space. A detailed procedure for estimating the multipaction susceptibility margins in a TWT using CST studio and analytical equations is presented in this paper, and output couplers of two typical TWTs are analysed and the results are presented.

5 illus, 3 table, 13 ref

003444   KUMAR M, GEETHA M K, KUMAR M V (DRDO-Microwave Tube Research & Development Centre, Bangalore - 600 013, Email: mvijay@mtrdc.drdo.in) : Design of magnetic focusing system for a compact ka-band helix TWT. Def Sci J 2021, 71 (3), 329 - 31.

In this paper we discuss the design of Magnetic focusing system (MFS) for a compact helix travelling wave tube (TWT) operating in Ka-band. Issues related to the design of the magnetic focusing system have been discussed in detail along with practical measurement results. The key design parameters considered for this TWT are: the cathode voltage is around 9.3 kV, beam current is 200 mA and total length of the tube not more than 6 inch with minimal weight.

8 illus, 7 ref

003443   JHA A, AJESH P, ANAND R, VASAVA P K, TRIVEDI R, MUKHERJEE A (ITER-India, Institute for Plasma Research, Gandhinagar - 382 428, Email: akhil.jha@iter-india.org) : Design of double barrier ceramic radio frequency vacuum window. Def Sci J 2021, 71 (3), 324 - 8.

Vacuum windows are an essential part of any radio frequency (RF) system which launches/couples RF power from an atmospheric to a vacuum environment. This paper describes the RF design of a double barrier ceramic coaxial vacuum  window. Alumina  99.5%  pure  is  considered  as  ceramic  barrier  material  while  inner  and  outer  conductors are  oxygen-free  copper. As  the  initial  design  approach  the  thickness,  slope,  depth  of  ceramic  in  the  conductor  is varied  and  the  performance  of  the  window  is  studied.  The  design  is  optimised  to  achieve  the  best  insertion  loss, return  loss  response  for  operating frequency  range  up  to  65MHz.

7 illus, 1 table, 10 ref

003442   MAITY S, KUMAR M S, KOLEY C, PAL D, BANDYOPADHYAY A K (National Institute of Technology Mizoram, Aizawl - 796 012, Email: chaitali.ece@nitmz.ac.in) : Design and simulation of extended interaction cavities for a ka-band multi-beam klystron. Def Sci J 2021, 71 (3), 320 - 3.

This article reports about the design approach, electromagnetic simulation and analysis results of high-frequency ladder-type input, output, and intermediate RF cavaties for Ka-band multi-beam extended interaction klystron. Several parameters of the cavity, such as quality factor, shunt impedance, etc., have been investigated by the assistance of electromagnetic software  CST  microwave  studio.  

3 illus, 1 table, 12 ref

003441   NAYEK N, NAIK A, PHATANGARE M, TIWARI T (Indian Institute of Technology, Guwahati - 781 039, Email: nnayek@sameer.gov.in) : Design and development of high power broad band Dry RF load. Def Sci J 2021, 71 (3), 315 - 9.

High  power  S-Band  ferrite  based  RF  load  is  designed  and  developed  which  is  capable  of  handling  3  kW average power at operating frequency 2998±20 MHz. Electrical and thermal design is carried out using CST Studio Suite. Mechanical parts are fabricated according to the design. Water cooling is provided to the absorbing ferrites to support high power operation. Various RF load parts are fabricated, chemically cleaned and brazed. The experimental return loss better than 30 dB for a bandwidth of 250 MHz is achieved. The numerical and experimental results are discussed  and  presented in  this  paper.

14 illus, 1 table, 9 ref

003439   THAKUR R, KUMAR K V (Applied Mechanics Dep, Indian Institute of Technology Delhi, New Delhi - 110 016, Email: shirgul33@gmail.com) : Investigation of the effect of ski jump on the flow dynamics around generic aircraft carrier. Def Sci J 2021, 71 (2), 296 - 303.

The landing operation on an aircraft carrier is a complicated and risky process. Unlike land-based operations, the landing area available on carriers is in continuous motion in all the six degrees of freedom. The ski jump, flight deck, hull, and superstructure of the carrier interact with the oncoming wind’s flow-field which creates a turbulent airflow behind the carrier. This ‘burble effect’ is very dangerous and has caused various mishaps in the past. To complement the work being undertaken at IIT Delhi to study the flow dynamics in the carrier environment, the present study investigates the effect of ski jump and superstructure on the flow around the generic aircraft carrier (GAC). Computational fluid dynamics (CFD) studies are undertaken to simulate the airwake and establish a baseline with the ski jump. Subsequently, further studies are carried out to analyse the sensitivity of the wake to changes in carrier  geometry. The  introduction  of  the  ski  generates  a  major  proportion  of  turbulence  encountered  in  the  aft  by the approaching pilot. This is reduced significantly by optimising ski jump geometry in various ways. 

10 illus, 4 tables, 30 ref

003438   MISHRA J K, RAO C S P, BOSE P S C, NATH N K, RAO G R (DRDO-Advanced Systems Laboratory, Hyderabad - 500 058, Email: jkmishra06@gmail.com) : Experimental studies of resin systems for ablative thermal protection system. Def Sci J 2021, 71 (2), 289 - 95.

The present work was initiated to finalise resin for the development of thermal protection system (TPS) for the external surface of a polymeric composite rocket motor case made up of Carbon roving and Epoxy resin. The temperature on the outer surface of the composite case increases due to kinetic heating caused by aerodynamic drag and vehicle velocity. These rocket motor casings are functionally required only in the ascent phase of missile trajectory till motor action time and stage separation. Due to which the experienced heat flux is relatively less, and the temperature on the external composite case is in order of 250 °C - 300 °C depending on missile configuration and trajectory, unlike extreme thermal conditions on ablative nozzle liners exposed to rocket motor exhaust. The maximum allowable temperature in the present study for the Carbon-Epoxy case is 100 °C due to degradation in mechanical properties. The thermal protection system on the external surface will function as a heat-insulating layer based on the working mechanism of ablation. The resin of the thermal protection layer has a substantial impact on the manufacturing process and curing aspects, especially compatibility with the pre-cured carbon epoxy case layer. The generation of test results for thermal stability, cure characteristics and Tg for Epoxy resin has also been included in present studies as an additional objective that provides significant inputs for process development. The test results for Epoxy resin is also used as a basis for the finalisation of resin for the thermal protection layer for processing aspects apart from its basic thermal stability characteristics. The ablative thermal protection working mechanism is based on the ablation phenomenon. In the case of ablation, resin plays a vital role due to pyrolysis and other thermal characteristics. In the present experimental studies, the Phenolic resin and Silicone resin are considered as candidate resin materials for ablative thermal protection system based on available literature and in house experience. The main objective of the present studies is to evaluate thermal stability, char yield after final decomposition through DSC and TGA techniques for both resins as these are fundamental characteristics needed for the present specific application. The test results for specific grades (formulation) of phenolic and Silicone resins are generated and compared. In the present work, the experimental studies to evaluate glass transition temperature (Tg), thermal stability, and cure characteristics for Epoxy resin is also carried through DSC. The test results of specific grade Epoxy resin provides a basis to assess thermal margins for resins selected for ablative thermal protection system and inputs for process development and design requirements. The scope of the present studies is aimed to finalise the resin system for external thermal protection of composite rocket motor case based on thermal characteristics test results and other compatibility aspects with the structural layer.

7 illus, 4 tables, 14 ref

003435   SRIVASTAVA S, DWIVEDI P N, KUMAR D M V (DRDO-Defence Research and Development Laboratory, Hyderabad - 500 058, Email: srikant.srivat@gmail.com) : 2-Loop nonlinear dynamic inversion fuel flow controller design for air-to-air ducted ramjet rocket. Def Sci J 2021, 71 (2), 265 - 70.

Fuel Flow controller based ramjet propulsion system have a flexibility to change rocket velocity depending on guidance requirement by controlling the fuel flow rate as a function of atmospheric conditions like altitude, Mach no. and angle of attack. In this paper, Design objectives & requirements of fuel flow controller have been brought out from guidance loop for air-to-air target engagement. 2-loop non-linear dynamic inversion (DI) based controller design has been proposed to track the commanded thrust and to meet the time constant requirement as a function of altitude, Mach no. and angle of attack. The outer thrust loop is to control commanded thrust and to generate the demand for gas generator pressure loop and inner pressure loop is to meet outer loop demand by controlling throttle valve area. The engine state space plant model has been adapted with improvement of existing model. Throttle valve actuator specifications requirement are also brought out.

9 illus, 12 ref

003432   LAVANYA D L, RAMAPRABHA R, GUNASEELAN K (DRDO-Defence Research and Development Laboratory, Hyderabad - 500 058, Email: lavanya@drdl.drdo.in) : Privacy preserving physical layer authentication scheme for LBS based wireless networks. Def Sci J 2021, 71 (2), 241 - 7.

With the fast development in services related to localisation, location-based service (LBS) gains more importance amongst  all  the  mobile  wireless  services.  To  avail  the  service  in  the  LBS  system,  information  about  the  location and identity of the user has to be provided to the service provider. The service provider authenticates the user based on their identity and location before providing services. In general, sharing location information and preserving the user’s privacy is a highly challenging task in conventional authentication techniques. To resolve these challenges in authenticating the users, retaining users’ privacy, a new SVD (singular value decomposition) based Privacy Preserved Location Authentication Scheme (SPPLAS) has been proposed. In this proposed method, physical layer signatures such as channel state information (CSI) and carrier frequency offset (CFO) are used for generating secret key required for encrypting the user’s location and identity information, and thus encrypted user’s information is sent to service provider for authentication. Secret key is generated by applying SVD on CSI vector. The proposed scheme aids  in  authenticating  the  user  through  location  information  while  protecting  the  user’s  privacy.  The  performance of  the  proposed  method  is  evaluated  in  terms  of  bit  mismatch,  leakage  and  bit  error  rate  performance  of  receiver and  adversary. The  simulation  results  show  that  the  proposed  scheme  achieves  better  robustness  and  security  than the  existing  location-based authentication techniques.

7 illus, 19 ref

003431   MANOJ K, NARAYANAMURTHY V, KORLA S (DRDO-Research Centre Imarat, Hyderabad - 500 069, Email: v.narayanamurthy@rcilab.in) : Performance of a cantilever energy harvester under harmonic and random excitations. Def Sci J 2021, 71 (2), 231 - 40.

The technique of harvesting the energy from base structural vibration through a piezoelectric transducer attached at  an  appropriate  location  on  the  vibrating  structure  is  gaining  popularity  in  recent  years. Although  the  amount  of energy harvested depends on the type and magnitude of base excitation, the energy harvest under random excitation as compared to equivalent harmonic excitations is not yet well understood and is investigated in this paper through a  cantilever  energy  harvester.  Initially,  the  energy  harvested  under  harmonic  excitations  is  numerically  simulated and experimentally validated under increasing base accelerations with different load resistances. Subsequently, the performance  of  this  energy  harvester  is  experimentally  studied  under  random  excitations. The  results  demonstrate that  the  harvested  energy  (a)  reaches  maximum  value  when  the  base  excitation  matches  the  natural  frequency  of the  harvester,  (b)  increases  with  the  increase  in  base  accelerations  irrespective  of  the  type  of  excitation,  and  (c) increases  by  2-14  times  under  random  excitations as  compared  to  equivalent  harmonic  excitations i.e.  under  same energy input. It is recommended that the energy harvester be used in aerospace structures where random vibration amplitude is  higher,  to  harvest  more  energy.

11 illus, 4 tables, 44 ref

003430   AGRAWAL L, BHARDWAJ A, GANOTRA D, SRIVASTAVA H B (DRDO-Laser Science and Technology Centre, Delhi - 110 054, Email: lalitaagrawal@lastec.drdo.in) : Estimation and management of performance limiting factors in the development of 1 kW peak power pulsed fiber MOPA at 1550 nm. Def Sci J 2021, 71 (2), 222 - 30.

An all-fiber three-stage master oscillator power amplifier (MOPA), based on Erbium and Erbium-Ytterbium co-doped fibers, has been designed and developed. The performance of such a laser is primarily limited by amplified spontaneous emission (ASE), Yb bottlenecking, and non-linear effects. Other important factors, that need to be considered towards performance improvement, are fiber bend diameter and heat generated in the fiber. This paper describes the methodology for the estimation and management of these limiting factors for each amplifier stage. The work presented here is limited to the fibers which are commercially easily available, unlike customised Yb-free large mode area (LMA) Erbium-doped fibers, where very high peak and average powers are being reported due to the absence of Yb ASE. Presented experimental results and discussion shall be beneficial for the fiber laser amplifier designers. With suitable management, 1 kW peak power pulses of 30 ns duration at 200 kHz repetition rate have been achieved with 30 % optical efficiency.  The collimated output of 6 W average power (limited by Yb ASE) with high beam quality (M2≈1.6) at 1550 nm can be employed for a variety of applications. By adding additional amplifier stages, power can be scaled further.

15 illus, 1 table, 29 ref

003429   RATAN R, YADAV A (DRDO-Scientific Analysis Group, Delhi - 110 054, Email: ramratan_sag@hotmail.com) : Security analysis of bit-plane level image encryption schemes. Def Sci J 2021, 71 (2), 209 - 21.

A selective bit-plane encryption scheme was proposed for securing the transmission of image data in mobile environments with a claim that it provides a high security viz. the encryption of the four most significant bit-planes is sufficient for a high image data security. This paper presents the security analysis of the said encryption scheme and  reports  new  important  results. We  perform  the  security  analysis  of  the  bit-level  encryption  by  considering  the normal images and their histogram equalised enhanced images. We consider different bit-plane aspects to analyse the security of the image encryption, and show that the encryption of the four most significant bit-planes is not adequate. The contents of the images can be obtained even when all the bit-planes except one least significant bit-plane are encrypted in the histogram equalised images as shown in the results. The bit-plane level security analysis seems  very  useful  for  the  analysis  of  the  bit-plane level image encryption  schemes

9 illus, 5 tables, 49 ref

003425   ELBEIH A, ABDELHAFIZ M, HUSSEIN A K (Military Technical Coll, Cairo, Egypt, Email: elbeih.czech@gmail.com) : Influence of different polymeric matrices on the properties of pentaerythritol tetranitrate. Def Sci J 2021, 71 (2), 177 - 84.

Six different polymeric matrices were fabricated to reduce the sensitivity of PETN (Pentaerythritol tetranitrate). The polymeric matrices used were individually based on Acrylonitrile butadiene rubber (NBR) softened by plasticizer, styrene-butadiene rubber (SBR) softened by oil, polymethyl methacrylate (PMMA) plasticised by dioctyl adipate (DOA), polydimethylsiloxane (PDMS), polyurethane matrix, and Fluorel binder. A computerised plastograph mixer was utilised for producing three polymer-bonded explosives (PETN-NBR, PETN-SBR, and PETN-PDMS) based on the non-aqueous method. A cast-cured method was used to prepare PBX based on polyurethane (PETN-HTPB), while the slurry technique was used to prepare beads of PETN coated by either fluorel binder (PETN-FL) or based on PMMA forming (PETN-PMMA). The heat of combustion and sensitivities were investigated. The velocity of detonation was measured, while the characteristics of the detonation wave were deduced theoretically by the EXPLO 5 (thermodynamic code). The ballistic mortar experiment was performed to determine the explosive strength. By comparing the results, it was found that PDMS has the highest influence on decreasing the impact sensitivity of PETN, while the cast cured PETN-HTPB has the lowest friction sensitivity. On the other side, PETN-FL has the highest detonation parameters with high impact sensitivity. Several relationships were verified and the matching between the measured results with the calculated ones was confirmed.

10 illus, 2 tables, 45 ref

003424   BUI X N, KOMENDA J, VÍTEK R (Munition Dep, Le Quy Don Technical Univ, Hanoi, Vietnam, Email: buixuanson.mta@gmail.com) : Frangibility quantification of frangible bullet upon impact on a hard target. Def Sci J 2021, 71 (2), 171 - 6.

The article presents a new method of quantitative evaluation of the degree of disintegration, called frangibility of  frangible  bullets,  based  on  shooting  experiments.  On  the  basis  of  the  dependence  of  the  Frangibility  Factor  of the bullet on its impact velocity, the frangibility index is determined as a quantifier of the projectile’s ability to disintegrate  into  fragments  applied  for  a  certain  range  of  interest. The  method  can  be  used  to  assess  the  ability  to disintegrate into fragments of various types of bullets, preferably frangible bullets produced by powder metallurgy technologies. The proposed method was used to quantify the frangibility of five experimental frangible bullets.

6 illus, 4 tables, 17 ref

003422   JAYALAKSHMI M, PATEL V V, SINGH G K (eronautical Development Agency, Bengaluru - 560 017, Email: jayalakshmim@nal.res.in) : Relook at aileron to rudder interconnect. Def Sci J 2021, 71 (2), 153 - 61.

The  implementation  of  interconnect  gain  from  aileron  to  rudder  surface  on  the  majority  of  the  aircraftis  to decrease sideslip which is generated because of adverse yaw with the movement of control stick in lateral axis and also enhances the turning rate performance.The Aileron to Rudder Interconnect (ARI)involves significant part to decouple the Dutch roll oscillations from roll rate response to aileron command. ARI is feed-forward gain whichis susceptible to aircraft system uncertainty. Incorrect ARI gain can lead to side slip buildup which can cause aircraft to depart in case of fault scenarios. Four systematic ARI design methods are proposed. One of the proposed methods which use the norm of ARI transfer function at roll damping frequency is suitable for online reconfiguration of control law. The reconfiguration of ARI gain is illustratedwith the simulation responses of fault scenario case of aileron surface    damage. 

6 illus, 2 tables, 18 ref

003421   MONDAL P (Space Engineering and Rocketry Dep, Birla Institute of Technology Mesra, Ranchi - 835 215, Email: pmondal@gmail.com) : Prediction of moment using a modified discrete vortex method in ground effect. Def Sci J 2021, 71 (2), 146 - 52.

The aerodynamics around a wing is modified when it comes near the ground. This is generally referred to as ground effect. In this work, a discrete vortex method based model which can predict two-dimensional (2D) ground effect from its free flight data is proposed. The required data in free flight could be generated either from high fidelity CFD solver or experiments. In this method, strength of the vortex distribution as obtained from discrete vortex based method is modified using a constrained optimisation procedure to match the free flight aerodynamic data. This vortex distribution is further modified due the presence of the ground. The efficacy of present model is demonstrated for predicting the moment of multi element airfoils in ground effect. The predicted aerodynamic coefficient in ground effect compares well with high fidelity CFD data.

5 illus, 30 ref

003420   MALIK L, TEVATIA A (Netaji Subhas Univ of Technology, New Delhi - 110 078, Email: abhishek.tevatia@nsut.ac.in) : Comparative analysis of aerodynamic characteristics of f16 and f22 combat aircraft using computational fluid dynamics. Def Sci J 2021, 71 (2), 137 - 45.

This paper presents the computational investigation of air flow over an aircraft at realistic speeds while demonstrating the importance of extending the existing analysis to the complete airplane and how pivotal it is in improving its in-flight performance. The study is done for F16 and F22 aircraft using ANSYS Fluent (19.2) to  obtain  pressure  distribution,  shear  stress  distribution  and  temperature  variation  on  the  complete  surface  of  the aircraft. Since the front section of the aircraft is prone to direct initial impact of surrounding environment, this portion is also examined. Here, as the speed is doubled from Mach 1 to Mach 2, a rise in the value of all the three variables is noticed for the F16 aircraft, whereas the pressure distribution for F22 aircraft shows strange behaviour for the highest speed (Mach 2). On comparing the results over the whole surface, it is seen that F16 experiences smaller pressure (29% lower for Mach 1 and 30% for Mach 2), temperature (9.5% lower for Mach 1 and 30% for Mach 2) and shear stress relative to F22 and the stress shows a huge change (90% lower for Mach 1 and 83% for Mach 2). Results of the present study imply that the design of the aircraft highly influences its performance as the parameters discussed touch their limits.

10 illus, 1 table, 33 ref

003417   SANKAR R B, TIWARI P K, BANDYOPADHYAY B, ARYA H (DRDO-Defence Research and Development Laboratory,, Hyderabad - 500 058, Email: rambsankar@gmail.com) : Choice of interceptor aerodynamic lifting surface location based on autopilot design considerations. Def Sci J 2021, 71 (1), 108 - 16.

Interceptors  operate  at  wide  range  of  operating  conditions  in  terms  of  Mach  number,  altitude  and  angle  of attack. The aerodynamic design caters for such wide operating envelope by appropriate sizing of lifting and control surfaces for meeting the normal acceleration capability requirements. The wide range of operating conditions leads to an inevitable spread in center of pressure location and hence spread in static stability. The performance of control design  is  a  strong  function  of  the  aerodynamic  static  stability. The  total  operating  envelope  can  be  bifurcated  into statically stable and unstable zones and the aerodynamic lifting surface location can be used as a control parameter to identify the neutral stability point. During the homing phase lesser static stability is desirable for good speed of response, hence the lifting surface location needs to be chosen based on the capability of control to handle instability. This  paper  analyses  the  limitations  of  autopilot  design  for  the  control  of  an  unstable  interceptor  and  brings  out  a method to identify the optimum aerodynamic lifting surface location for efficiently managing static margin while satisfying  the  control  limitations  and  homing  phase  performance.  This  provides  an  input  on  the  most  appropriate lifting surface location to the aerodynamic designer during the initial CFD based aerodynamic characterisation stage itself, before  commencing the  rigorous  wind  tunnel based  characterisation.

10 illus, 14 ref

003416   PRASAD M V K S, RAO P S, NAYAK J (DRDO-Research Centre Imarat, Hyderabad - 500 069, Email: malapakaprasad@gmail.com) : Aeroload simulation of interceptor missile using fin load simulator. Def Sci J 2021, 71 (1), 102 - 7.

Interceptor missiles are designed to destroy enemy targets in air. Targets can be destroyed either in atmosphere or  out  of  atmosphere.  So  for Air  Defence  scenario,  a  two  layer  protection  system  is  required  with  one  taking  care of    exo  atmosphere  and  another  endo  atmosphere.  In  this Air  Defence  scenario,  irrespective  of    target  trajectory interceptor should neutralise it. So the control, guidance are to be designed and  validated thoroughly  with various scenarios of interceptor and target. These interceptors sense the rates from rate gyroscopes and accelerations from accelerometers which are fitted on board the interceptor. The navigation algorithm calculates the interceptor’s position and velocity from these rates and accelerations from time to time. Using these interceptor data and target information  received  from  ground  RADAR  or  on  board  seeker,  guidance  calculates  accelerations  demand  and subsequently  rate  demand.  The  control  algorithm  runs  in  on  board  mission  computer  along  with  guidance.  The control algorithm calculates the commanded rate and eventually commanded deflections to the control fins to move towards the target. The fins have to move as per commanded deflections to meet the mission objective of hitting the target. But  the load known as aeroload which comes on the control fins during mission, causes control fins not to move as per command. Due to the difference between control command and physical movement of fin, the expected path towards target deviates. This increases the miss distance and also misses the target hit. This aeroload scenario is to be simulated on ground and some feature is to be designed to take care of it during mission. By studying the control system behaviour due to load, the control autopilot is to be automatically tuned to compensate for the loss in commanded deflections. This scenario can be carried out in Hardware-in-Loop simulation (HILS) setup. Mission load conditions can be applied on hardware actuation system in HILS setup and mission performance can be seen and also with different loads and different autopilot tunings.

11 illus, 9 ref

003414   ?AHINER B, ÖZBEK S, BAYKARA T, DEMIRURAL A (Dogus Unive, Turkey, Email: brssahiner@gmail.com) : Advanced layered composite structures for underwater acoustic applications. Def Sci J 2021, Vol 71 (1), 87 - 93.

The detection of underwater objects is one of the most critical technologies, and there have been constant efforts for developing sophisticated sonar systems in naval warfare. Against such efforts, the countermeasure of hiding underwater vehicles, equipment and weapons is another technological challenge. One of the effective countermeasures against sonic detection for the submarines and other underwater objects, such as naval mines, is to employ composite/hybrid materials to prevent ease of detection. Geometrical forms, shapes and layers, along with the tuning of the acoustical impedance, lead to a considerable decrease of the sonar signals via absorption of the sonic waves. In this study, an original and novel design of multi-layered composite/hybrid structure was developed and underwater acoustic testing procedures of reflection, transmission and scattering were applied in 80 kHz-100 kHz frequency range. The findings obtained in this study showed that the multi-layered composite/hybrid materials with porous structure possess much lower values in millivolt than steel plates and might be potential candidates as covering and/or casing materials for underwater mines to reduce the acoustical signature against detection and identification. 

9 illus, 4 tables, 22 ref

003412   SHUKLA S, BISHNU A, BHATIA V (Indian Institute of Technology, Indore - 453 552, Email: shukla.sidharth@gmail.com) : Channel sounding and measurements for pico cells for LTE and future wireless networks. Def Sci J 2021, Vol 71 (1), 71 - 8.

Wireless networks are the preferred future access networks for both defense and civilian deployments as part of telecommunication networks. The successful implementation of long term evolution (LTE) networks and applications such as the Internet of Things (IoT) in the telecommunication infrastructure has guaranteed rates of up to 100 Mbps while supporting ultra-dense wireless access network. With the incorporation of LTE-Advanced and fifth-generation wireless protocols, the data rates are expected to reach upto 1 Gbps. Hence, there is a pertinent requirement to carry out channel measurements at sub 1 GHz, 2 GHz, and 3 GHz bands to enable the design and implementation of optimum transceivers for pico-cells of LTE and future wireless networks. For the first time measurements and comparison with standard models of channel impulse response models have also been carried out in five different terrains namely Urban, Semi-Urban, Forest, Rural, and Desert terrains in the Indian sub-continent to effectively cover a variety of deployments of future wireless access networks for defense wireless networks.

10 illus, 5 tables, 30 ref

003411   RAJ KUMAR, VERMA P K, KARTIKEYAN M V (DRDO-Defence Electronics Applications Laboratory, Dehradun - 248 001, Email: raj.kumar@deal.drdo.in ) : A wide beam printed quadrifilar helix based circularly polarised radiating element for electronically steered antenna. Def Sci J 2021, Vol 71 (1), 66 - 70.

Wide beam and low axial ratio performance of printed quadrifilar antennas result in very attractive circularly polarised radiating element for wide scanned Electronically Steered Antenna. A compact printed quadrifilar Helix antenna (PQHA) has been designed and realised at S-Band frequency. Simulation and optimisation of designed antenna has been performed using ANSYS’s high frequency structure simulation (HFSS) software for its impedance, axial ratio (AR) performance and radiation characteristics. The developed circularly polarised antenna has 3-dB beam width of 130° and peak gain of 3.4dBic at 2.6 GHz. The developed antenna shows excellent AR performance over the frequency band as well as over the radiated beam. Half power axial ratio bandwidth of developed antenna is 27.4 % (2.2 GHz - 2.9 GHz) while the impedance bandwidth is 32 % (2.1 GHz - 2.9 GHz). Design has been validated through measured results. Designed wide band PQHA can be used as radiating element for electronically steered antenna for large beam steering application.

8 illus, 1 table, 21 ref

003409   SAINI T K, SHARMA S C (DRDO-Defence Electronics Applications Laboratory, Dehradun - 248 001, Email: trilok.saini@deal.drdo.in) : Context-aware routing to assist routing decisions for quality improvement in multi-hop Ad hoc networks. Def Sci J 2021, Vol 71 (1), 46 - 54.

The context information is an intriguing aspect of decision making. The context-awareness can be useful in the ad hoc networks in which nodes are mobile, and the conditions are dynamic. In ad hoc networks, routing protocols are intended to discover the route over multi-hop wireless links under varying conditions. The context-awareness can assist the routing protocols in determining the appropriate path. This paper investigates into choosing the appropriate route by applying the context information and presents the approach to improve the decision making and the quality of the route. We consider nodes, connecting links, and different layers as the context. The paper introduces the scalability and flexibility in the set of parameters that govern the eminence of the node inter-connection that, in turn, influences the overall quality of the route. We propose the context-aware dynamic routing protocol (CADR) and present the approach, algorithm, and analysis. We simulate the protocol by taking the flexible combination of the context attributes and the values, also compares the performance with AODV. The simulation results show that the protocol chooses the appropriate route as per the considered attributes and weight, and provide the enhanced performance. 

5 illus, 4 tables, 29 ref

003408   HRISTOV N, PAMUCAR D, AMINE M S M E (Univ of Defence in Belgrade, Belgrade – 11000, Serbia, Email: dragan.pamucar@va.mod.gov.rs) : Application of a D number based LBWA model and an interval MABAC model in selection of an automatic cannon for integration into combat vehicles. Def Sci J 2021, Vol 71 (1), 34 - 45.

A decision making procedure for selection of a weapon system involves different, often contradictory criteria  and reaching decisions under conditions of uncertainty. This paper proposes a novel multi-criteria methodology  based on D numbers which enables efficient analysis of the information used for decision making. The proposed  methodology has been developed in order to enable selection of an efficient weapon system under conditions when  a large number of hierarchically structured evaluation criteria has to be processed. A novel D number based Level  Based Weight Assessment – Multi Attributive Border Approximation area Comparison (D LBWA-MABAC) model  is used for selection of an automatic cannon for integration into combat vehicles. Criteria weights are determined  based on the improved LBWA-D model. The traditional MABAC method has been further developed by integration  of interval numbers. A hybrid D LBWA-MABAC framework is used for evaluation of an automatic cannon for  integration into combat vehicles. Nine weapon systems used worldwide have been ranked in this paper. This multi- criteria approach allows decision makers to assess options objectively and reach a rational decision regarding the  selection of an optimal weapon system. Validation of the proposed methodology is performed through sensitivity  analysis which studies how changes in the weights of the best criterion and the elasticity coefficient affect the  ranking results.  

6 illus, 9 tables, 55 ref

003407   ÖGÜNÇ G I (Gendarmerie and Coast Guard Academy, Turkey, Email: gokhan.ogunc@jsga.edu.tr) : The effectiveness of armoured vehicles in urban warfare conditions. Def Sci J 2021, Vol 71 (1), 25 - 33.

Since the Second World War, the major armed conflicts have been occurred in or in the vicinity of the urban areas rather than rural areas, amongst conventional armies and armed groups or terrorists/insurgents. The architectural and construction characteristics of the urban area increase the opportunities for armed groups to ambush, easily escape, conceal, relocate and attack. Additionally, the narrow streets, the blocked roads by the debris of buildings, and IED threats make the urban areas one of the most dangerous conditions for infantries and armoured vehicles. The majority of present armoured combat vehicle types due to the limited visibility, low manoeuvre capability, and limited firing power, they are insufficient for performing the standalone operation without infantry forces and combat engineer support in urban warfare conditions. In this study, 13.400 data belonging to 676 attacks towards armoured vehicles during the counter-terrorism operations against PKK/PYD and ISIS in the urban areas were analysed within the perspective of forensic science techniques such as forensic ballistics and shooting reconstruction. According to the examinations and analyses carried out within the scope of this study; the leading critical features that an armoured combat vehicle that will operate in the urban areas may be listed under five general headings: Structure, Ballistic Protection and Armour, Self Defence and Weapon Systems, Situational/peripheral Awareness and C4I2 Systems and Integrated Warfare Systems.

8 illus, 3 tables, 44 ref

003406   HOQUE E, PANT C S, DAS S (DRDO-Advanced Centre for Energetic Materials, Nasik - 422 207, Email: cspant79@gmail.com) : Statistical evaluation of burning rate data of composite propellants obtained from acoustic emission technique. Def Sci J 2021, Vol 71 (1), 18 - 24.

The acoustic emission technique has been considered to be one of the most reliable and robust methods for the measurement of the steady burning rate of composite propellants. In this work, attempts were made to quantify the measurement variability of the burning rate of composite solid propellants by acoustic emission method using statistical tools. A total of 1100 individual measurements were subjected to statistical treatment. The combination of confidence interval and repeatability limit delineated the extent of natural dispersion in the burning rate measurement data. The very high coefficient of variation values for the propellant compositions, having a burning rate of more than 25 mm s^–1 raised concerns about the suitability of the acoustic emission method for high burning rate compositions. The Reliability interval approach was employed to determine the statistically significant sample size for different composite propellants having a burning rate range of 5–31 mm s^–1. The entire set of data was screened for identification of outlying observation using the Dixon Q test, and the extent of contamination was quantified. Moreover, the application of statistical techniques could have far-reaching implications for quality control perspectives of burning rate measurement by acoustic emission and could be implemented as reference tolerance limits and preventive measures for ensuring the good health of the instrument as well as propellant processing.

3 illus, 5 tables, 27 ref

003405   HUERTA-TORRES J K, SILVA-RIVERA U S, VERDUZCO-CEDEÑO V F, FLORES-HERRERA L A, SANDOVAL-PINEDA J M (Army and Air Force Univ, Mexico, Email: jsandovalp@ipn.mx) : Numerical and experimental analysis of sound suppressor for a 5.56 mm caliber. Def Sci J 2021, Vol 71 (1), 12 - 7.

A sound suppressor is an internal or external device coupled to the barrel of a firearm. Its development has been historically related to the negative effects produced by the noise. This article presents the numerical and experimental analysis of a sound suppressor for a 5.56 mm caliber rifle. It was designed, manufactured, and tested inside a shooting tunnel for 911 m/s and 344 m/s velocities. Three geometric configurations with curved deflectors, conical deflectors, and finally with a reactive spiral capable of dissipating the acoustic wave were compared considering reactive and dissipative systems. The attenuation of the sound inside the silencer depends directly on the reduction of the projectile wave velocity and the deflagration of the gases at the instant of firing. Then the MIL-STD-1474E standard was used to carry out the experiments. The results in the computational numerical simulation show an average value of 143 dB for the considered three models, the Sound Pressure Level in the reactive core model decreased by 25 % with respect to other proposals, which have an average value of 141 dB. These results can be useful to improve in the design of sound suppressors based on the needs of the users and under the specific characteristics of each weapon ballistic.

7 illus, 2 tables, 33 ref

003404   BALAKRISHNAN N, SHAH M, ANUPAMA K R, SHARMA N (BITS Pilani, Goa - 403 726, Email: nbalki66@gmail.com) : Optimisation of flight and maintenance planning for defence aviation with modified artificial bee colony algorithm. Def Sci J 2021, Vol 71 (1), 3 - 11.

The planning of flight operations and maintenance is a crucial activity for both commercial and military aircraft. Military aircraft have to be always mission-ready. The task of ensuring this can become quite challenging when several operational requirements and maintenance constraints are to be fulfilled simultaneously. This paper, therefore, addresses the optimisation of flight and maintenance planning (FMP) when several diverse factors such as aircraft flying hours (AFH), flight cycles (FC), calendar life, annual flying requirement (AFR), etc. are to be factored in. Such a problem has not been considered previously. Because the problem can become unwieldy to solve by other methods, two schemes, that is, the genetic algorithm (GA) and modified artificial bee colony (ABC) algorithm for constrained optimisation have been utilised. The objective is to maximise the utilisation rate (UR) of aircraft, while also satisfying other operational and maintenance constraints. The algorithm is tested on a fleet of eight aircraft. In addition to a one-year planning period, a planning horizon of ten years has also been simulated. The results show that both the GA and modified ABC algorithm can be effectively used to solve the FMP problem.

9 illus, 5 tables, 21 ref

045635   GEETHA K, CHELLAPANDIAN M, ARULNATHAN N, RAMANATHAN A (Nanotechnology Div, Periyar Maniammai Institute of Science and Technology, Thanjavur, Tamil Nadu, Email: ramanathangri@gmail.com) : Nano zinc oxide – An alternate zinc supplement for livestock. Vet World 2020, 13(1), 121-6.

This study was aimed to investigate antimicrobial and cytotoxicity effect of nano ZnO in in vitro for the application of livestock feed supplement. Nano ZnO was synthesized by wet chemical precipitation method using zinc acetate as a precursor and sodium hydroxide was used for reducing the precursor salt. The properties of synthesized powder were characterized using ultraviolet (UV)–visible spectroscopy, Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD), respectively. In vitro antimicrobial activities were analyzed against the pathogenic bacteria in poultry Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Streptococcus aeruginosa. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was conducted to analyze the cytotoxicity effect of nano ZnO. SEM showed a spherical ZnO particle in the range of 70-100 nm. The size of the particle and purity of the sample were confirmed by XRD. The nano-sized ZnO particles exhibited the UV absorption peak at 335 nm. In FTIR spectroscopy, pure ZnO nanoparticles showed stretching vibrations at 4000-5000 cm−1. ZnO nanoparticles exhibited remarkable antibacterial activity against E. coli, S. aureus, K. pneumoniae, and S. aeruginosa bacterial strains. Cell viability was significantly reduced in a dose-dependent manner in the cytotoxicity study. From the broad-spectrum antibacterial activity and the lower cytotoxicity observed at the prescribed dose, it is concluded that nano ZnO powder is a potential alternate zinc supplement for livestock.

5 illus, 1 table, 30 ref

045165   KRISHNAPRIYA M, NAYAK R K, ALLAHUDEEN S, BHUVANACHANDRA A, DADHWAL V K, JHA C S, SHESHASAI M V R, SASMAL S K, PRASAD K V S R (Indian Space Research Organization (ISRO), Balanagar- 500 037, Hyderabad) : Seasonal variability of tropospheric CO2 over India based on model simulation, satellite retrieval and in-situ observation. J Earth Syst Sci 2020, 129(1), 10.1007/s12040-020-01478-x.

In this study, investigation of the seasonal cycle of the tropospheric CO₂ concentration over India was carried out using the GEOS-Chem atmospheric transport model, Greenhouse gas Observation SATellite (GOSAT) retrievals, and in-situ measurements. The model simulation is highly coherent with the satellite and in-situ datasets, and it shows a distinct seasonal cycle of the tropospheric CO₂ tendency over India with a negative phase (decreasing concentration) during April–August and a positive phase (increasing concentration) during September–March. The model diagnostics were analyzed to estimate budgets of the surface layer CO₂, up to 650 hPa pressure level, for the two-phases of the seasonal cycle. A mean tendency, equivalent to −0.70 ppmv month⁻¹, observed during April–August, which results from the loss of CO₂ content in the surface layer through horizontal advection (−2.25 ppmv month⁻¹) and vertical diffusion (−0.20 ppmv month⁻¹), that dominates the gain from vertical advection (1.53 ppmv month⁻¹). The negative contribution of horizontal advection in this period comes from the transport of CO₂ depleted air-parcels over the oceanic region to India by the southwest monsoon winds and the positive contributions of vertical advection comes from upwelling of CO₂ enriched air-parcels. The mean tendency, equivalent to 1.01 ppmv month⁻¹, during September–March results from the gain through vertical advection (0.78 ppmv month⁻¹) and horizontal advection (0.37 ppmv month⁻¹) and a small contribution of vertical diffusion (−0.15 ppmv month⁻¹). In this period, positive contribution of horizontal advection is due to the transport of CO₂ enriched air-parcels from the southeast Asian region to India by north-east monsoon winds. At the annual scale, CO₂ content of the surface layer over India has a net gain of 0.75 GtC that comes from 14.31 GtC through vertical advection that exceeds the loss due to horizontal advection (−11.10 GtC) and vertical diffusion processes (−2.46 GtC). This net gain is almost 85% higher than the input of 0.4 GtC through surface fluxes, which composed of 0.61 GtC anthropogenic emission and −0.21 GtC net terrestrial ecosystem exchanges. Additional sensitivity experiment was carried out to elucidate the semi-annual features of the seasonal cycle of CO₂ for north India, in contrast to the annual characteristics of the seasonal cycle for south India in relation to the GOSAT observation.

68 ref

039286   HOODA E, VERMA U, HOODA B K (Mathematics & Statistics Dep, CCS Haryana Agricultural Univ, Hisar- 125 004, Email: ektahooda@gmail.com) : ARIMA and state-space models for sugarcane (Saccharum officinarum) yield forecasting in northern agro-climatic zone of Haryana. J Appl Nat Sci 2020, 12(1), 53-8.

Advance estimates of significant cereal and commercial crops are given by the Directorate of Economics and Statistics and the central Ministry of Agriculture, Cooperation & Farmers’ Welfare. However, the final estimates are released a few months after the actual harvest of the crops. In this study, ARIMA and State-Space models have been developed for sugarcane yield forecasting in Ambala and Karnal districts of Haryana. The above-mentioned models have been developed using yield data of sugarcane crop for the time period 1966-67 to 2009-10 of Ambala and Karnal districts. The validity of fitted models has been tested over the years 2010-11 to 2016-17. The forecasting performance of the developed models has been studied using percent deviations of sugarcane yield forecasts in relation to the actual yield, and root means squared errors. It has been observed that state-space models outperform the popular ARIMA models for forecasting of sugarcane yield in Northern Agro-climatic Zone of Haryana. 

3 illus, 8 tables, 15 ref

039187   ARVIND, HOODA R S, SHEORAN H S, KUMAR D, SATYAWAN , BHARDWAJ A, BHARDWAJ S (Haryana Space Applications Center, Hisar- 125 004, Email: arvinddhaloiya@gmail.com) : RS- based regional crop identification and mapping: A case study of Barwala sub - branch of western yamuna canal in Haryana (India). Indian J Tradit Know 2020, 19, 182-6.

Information on spatial land use is the main input in strategic and tactical plan-making by all agricultural participants in countries like india with agriculture at the mainstay of the econom. In addition, accurately evaluation of the management of crops in a spatio-temporal context, information on a regional scale are scarcely available. The spectrum of multiannual patterns of land use on cultivable land, however, remains unknown. The paper thus focuses on the mapping of the cropping systems that are actually practiced in Hisar District of Haryana (India). The objectives of this research was to use satellite data and Remote Sensing (RS) techniques to identify the cropping pattern of Barwala sub-branch of sirsa of the Western Yamuna canal in Haryana. To identify classes of interest, handled GPS was used to collect ground-truth information. Mask of mixed classes was developed to reclassify an image under the mask. Morever, appropriate classification of images and application of logical combinations helped in generating cropping pattern maps and statistics. Results revealed that major crops identified in the study area were cotton, rice and pearl- millet in Kharif season, which accounts for about 70 % of total cultivated area. In the case of Rabi season, wheat and mustard were observed as the major crops covering approximately 57 % of total area. RS technology is currently capable of providing cropping pattern with 90 % accuracy. The results of the current study could be useful in the land use and efficient water management in the canal command areas in the water-scarce southern haryana , India. some crops like guar, pearl-millet, horticultural crops, etc. were also identified during this period but the major crops that were identified during Kharif season were Rice and cotton.   

2 illus, 6 tables, 14 ref

039084   TYAGI S, RAI S C (Geography Dep, Delhi Univ, Delhi- 110 007, Email: raisc1958@rediffmail.com) : Monitoring shoreline changes along Andhra coast of India using remote sensing and geographic information system. Indian J Geo-Mar Sci 2020, 49(2), 218-24.

A shoreline is dynamic in nature which makes the interface of land and water that offers socio-economic and cultural protection to its adjacent population. The purpose of this study was to understand long-term (1973-2015 and 2015-2057) shoreline transformation as well as the patterns of soil loss/sedimentation owing to physical and anthropogenic activities along the Andhra coast. Satellite imageries of LANDSAT from 1973 to 2015 were utilized to delineate the shoreline. Shoreline fluctuations were analyzed by Net Shoreline Movement (NSM) and End Point Rate (EPR) statistics using the Digital Shoreline Analysis System (DSAS) computer software of USGS. The highest and lowest EPR of about 67.63 m/y and -43.14 m/y were recorded in the Andhra coast. The high rate of deposition was recorded in the Godavari delta, whereas Krishna delta experienced low erosion. This study establishes the use of remote sensing data and statistical techniques such as EPR and NSM for shoreline monitoring are helpful for soil loss/accretion evaluation and future shoreline prediction.

7 illus, 1 table, 24 ref

039083   VU M T, LACROIX Y, THAN V V, NGUYEN V T (Toulon Univ, France, Email: yves.lacroix@univ-tlf.fr) : Prediction of shoreline changes in Almanarre beach using geospatial techniques. Indian J Geo-Mar Sci 2020, 49(2), 207-17.

In this study, the remote sensing and Geographic Information System (GIS) techniques coupled with the Digital Shoreline Analysis System (DSAS) is applied to detect the historical shoreline changes as well as to predict the future shoreline position along Almanarre beach which is being threatened by severe erosion. The results show that Almanarre beach suffered erosion with an average annual change rate of about -0.24 m/year over the period of 1973- 2015. The most severe erosion was observed near Landmark B17 with the maximum erosion rate of -0.86 m/year. Moreover, the shoreline change in 2020 and 2050 are predicted at approximately -0.05 m/year and -0.22 m/year, respectively. The areas around Landmarks B06-08 and Landmarks B16-18 will be eroded with the maximum recession rates of -0.89 m/year and -0.94 m/year, respectively. This research proves that the combination of geospatial techniques and numerical model can be a reliable approach for investigating the shoreline change trend.

5 illus, 3 tables, 24 ref