Defence Science Journal
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Template free Micro Doppler Signature Classification for Wheeled and Tracked Vehicles
Get PDFThe micro-Doppler signature is a time-varying frequency modulation imparted on radar echo caused by target’s micro-motion. To save the trouble of constructing template in the target classification, this paper investigates the micro-Doppler signature of wheeled and tracked vehicles and proposes a template-free classification method. Firstly, the echo signature is established and the micro-Doppler difference of these two kinds of targets is analysed. Secondly, some new micro-Doppler features are defined according to their difference. The new defined features are micro-Doppler bandwidth, micro-Doppler expansion rate and micro-Doppler peak number. According to the characteristic of the micro-Doppler in the time-frequency domain, we proposed to realise the feature extraction by Hough transformation. Lastly, template-free subjection functions are proposed to define the relationship between the features and the vehicles. By fuzzy comprehensive evaluation, the final classification result is obtained by combining the subjection probabilities together. Experimental results based on the simulated data and measured data are presented, which prove that the algorithm has good performance
On the Possible Mechanisms for Saltening of the Bay of Bengal
Get PDFThe Bay of Bengal (BoB) is a low saline basin owing to large influx of freshwater from precipitation and river runoff. To maintain the salt balance of the BoB, the incessant lowering of salinity is to be balanced by the inflow of saltier water into the basin. In the present work, various processes that contribute to the saltening of the BoB, viz. coastal upwelling, eddies and their interaction, lateral advection from Arabian Sea and tropical cyclones are discussed. In the near-shore regions, the coastal upwelling due to wind induced Ekman transport plays a dominant role in increasing the surface salinity. On the other hand, in the open ocean, the divergence induced by eddies and their mutual interaction contributes significantly to the salt water pumping. In the southern BoB, the advection from the Arabian Sea increases the salinity. The formation of cyclones in the BoB also leads to an increase in the surface salinity. However, the magnitude of saltening of the Bay due to these processes varies from north to south. The uplift of saltier water from subsurface levels increases the salinity in the surface layers thereby creating a salinity gradient and a salinity front
Methodology for Integrating Computational Tree Logic Model Checking in Unified Modelling Language Artefacts A Case Study of an Embedded Controller
Get PDFA unified modelling language (UML) based formal verification methodology that can be easily integrated into an embedded system software development life cycle is suggested. The approach augments UML diagrams with formal models through an interfacing domain and adds semantics to these diagrams. The suggested methodology; commences from functional specification and use case modelling, selects the most critical behaviour where formal verification can add value to the development cycle, analyses the selected behaviour using UML state transition diagram, derives a state chart matrix from the same, and a high level language software translates the state chart matrix to a labelled transition system. Safety properties are derived from system specifications and are expressed as computation tree logic (CTL) formulae. CTL model-checking algorithm from the literature is used for model- checking. The applicability of the suggested approach is established using a safety critical embedded controller used for deployment and recovery of sensor structures from an airborne platform
Approximate Solution and its Convergence Analysis for Hypersingular Integral Equations
Get PDFThis paper propose a residual based Galerkin method with Legendre polynomial as a basis functions to find the approximate solution of hypersingular integral equations. These equations occur quite naturally in the field of aeronautics such as problem of aerodynamics of flight vehicles and during mathematical modeling of vortex wakes behind aircraft. The analytic solution of these kind of equations is known only for a particular case ( m(x,t) =0 in Eqn (1)). Also, in these singular integral equations which occur during the formulation of many boundary value problems, the known function m(x,t) in (Eqn (1)) is not always zero. Our proposed method find the approximate solution by converting the integral equations into a linear system of algebraic equations which is easy to solve. The convergence of sequence of approximate solutions is proved and error bound is obtained theoretically. The validation of derived theoretical results and implementation of method is also shown with the aid of numerical illustrations.  
Microwave Absorption Performance of Graphene Nanoplatelets Dispersed SiC
Get PDFMicrowave absorption performance of graphene nanoplatelets based SiC composites have been studied in the present work. Graphene nanoplatelets were dispersed at varying weight fractions viz. 0.5, 1, 2, 2.5 and 3 wt.% in SiC using ultrasonication and ball milling methods. Microwave attenuation behaviour of the prepared composites have been observed in the 2-18 GHz range. The results reflect that dispersion of graphene in SiC proves to be very instrumental in attenuating the incident microwave signals translating into enhanced absorption. The enhancement in the microwave absorption performance is due to the presence of conductive graphene nanoplatelets which is very instrumental in promoting conduction and polarisation losses in the composite translating into enhanced absorption. For 3 wt.% graphene nanoplatelets dispersion in SiC, the value of reflection loss (RL) was obtained as -38.67 dB at 14.67 GHz frequency for 2.2 mm thickness with the corresponding bandwidth of 5 GHz
Development of Neural Network Based Adaptive Change Detection Technique for Land Terrain Monitoring with Satellite and Drone Images
Get PDFRole of satellite images is increasing in day-to-day life for both civil as well as defence applications. One of the major defence application while troop’s movement is to know about the behaviour of the terrain in advance by which smooth transportation of the troops can be made possible. Therefore, it is important to identify the terrain in advance which is quite possible with the use of satellite images. However, to achieve accurate results, it is essential that the data used should be precise and quite reliable. To achieve this with a satellite image alone is a challenging task. Therefore, in this paper an attempt has been made to fuse the images obtained from drone and satellite, to achieve precise terrain information like bare land, dense vegetation and sparse vegetation. For this purpose, a test area nearby Roorkee, Uttarakhand, India has been selected, and drone and Sentinel-2 data have been taken for the same dates. A neural network based technique has been proposed to obtain precise terrain information from the Sentinel-2 image. A quantitative analysis was carried out to know the terrain information by using change detection. It is observed that the proposed technique has a good potential to identify precisely bare land, dense vegetation, and sparse vegetation which may be quite useful for defence as well as civilian application
Design and Selection Criteria of Main Parachute for Re entry Space Payload
Get PDFParachutes are used as a decelerator in the re-entry, descent, and landing of space recovery payloads, providingstability and desired descent rate for a safe landing. The selection of the main parachute is the most critical andimportant part of the space module recovery system. Parachute size is restricted by the required landing speed,materials, and weight of the payload. Parachute materials are selected based on the various forces experienced bythe parachute. An investigation has been carried out to design a parachute system which gives less impact velocity, less angle of oscillation and less impact load for the landing of a crew module. Therefore, in this paper, selection criteria for the main parachute have been discussed considering recovery of re-entry space payload of 500 kg (unmanned) and 3500 kg (manned) class. Based on analysis carried out on the parachute size, canopy filling time, velocity reduction, peak deceleration, and opening shock, authors have proposed a unique type of solid canopy with slots (slots of the minimum area equivalent to geometry porosity) for the main parachute rather than a complex ringsail or disk-band type canopy. With this new concept, the parachute has been designed, developed and qualified through testing, trials and maiden flight of space capsule in LEO and is propose to use in the next manned space mission program
Effect of Formaldehyde to Phenol Ratio in Phenolic Beads on Pore Structure, Adsorption and Mechanical Properties of Activated Carbon Spheres
Get PDFPhenolic beads (PBs) prepared from different formaldehyde to phenol (F/P) molar ratios were used as polymeric precursor for activated carbon. Activated carbon spheres (ACSs) have been produced from PBs via the physical activation process using carbon dioxide (CO2) as activating agent at 950 °C for different burn-off. The prepared ACSs were investigated for nitrogen adsorption, surface morphology and compressive strength by means of BET surface area analyser, scanning electron microscopy (SEM) and carbon and sphere tester techniques. The results indicated that the effects of F/P ratio observed, especially variation in the adsorption and mechanical properties. It was found that ACSs obtained from F/P ratio one showed the superior adsorption properties, possessed a high BET surface area in a range of 836 m2 g-1 to 3694 m2 g-1 with high pore volume (0.47 cm3 g-1 - 2.47 cm3 g-1) and 73-97 per cent microporosity. The BET surface area and pore volume increased, while the microporosity gradually decreased, with increasing the extent of burn-off. Compressive strength decreased with increasing F/P ratio as well as the extent of burn-off. ACSs upheld improved compressive strength (from 160 N mm-2 to 9 N mm-2) than those obtained from F/P ratio 2 and 3 in PBs. SEM studies of ACSs demonstrated well developed pore structure
Efficient Embedded Hardware Architecture for Stabilised Tracking Sighting System of Armoured Fighting Vehicles
Get PDFA line-of-sight stabilised sighting system, capable of target tracking and video stabilisation is a prime requirement of any armoured fighting tank vehicle for military surveillance and weapon firing. Typically, such sighting systems have three prime electro-optical sensors i.e. day camera for viewing in day conditions, thermal camera for night viewing and eye-safe laser range finder for obtaining the target range. For laser guided missile firing, additional laser target designator may be a part of sighting system. This sighting system provides necessary parameters for the fire control computer to compute ballistic offsets to fire conventional ammunition or fire missile. System demands simultaneous interactions with electro-optical sensors, servo sensors, actuators, multi-function display for man-machine interface, fire control computer, logic controller and other sub-systems of tank. Therefore, a complex embedded electronics hardware is needed to respond in real time for such system. An efficient electronics embedded hardware architecture is presented here for the development of this type of sighting system. This hardware has been developed around SHARC 21369 processor and FPGA. A performance evaluation scheme is also presented for this sighting system based on the developed hardware
Implementation of Peltier Cooling in Hermetically Sealed Electronic Packaging Unit for Sub-sea Vessel
Get PDFThis paper presents the methodology adopted for implementation of Peltier cooling in hermetically sealed electronic packaging units used in sub-sea vessels. In sub-sea vessels, sonar front-end electronics is packaged in hermetically sealed electronic packaging units. The thermal design of the unit is a highly challenging task considering the heat dissipation of 300W from the electronics, non-availability of chilled air for cooling and IP68 sealing requirements. Cooling fans cannot be integrated, since these units are to be placed in acoustically sensitive pressure capsule area of the subsea vessel. The electronic cooling in this unit is achieved using conduction cooling with external fins. To enhance the cooling, suitable Peltier cooling (Thermo-electric cooling or TEC) module is selected and implemented with the system. Computational fluid dynamic analysis of the unit is carried-out to study the air-flow and thermal performances with Peltier cooler. The unit is realised and the estimated temperatures validated by experimental temperature measurements on the realised unit. The measured temperatures are within the safe operating limits of the electronic components and hence the cooling design of the unit is satisfactory. It is also observed that maximum temperature reduction has occurred at 1.5A current and card edge temperature of Printed circuit board lowered by 9.28 °C by implementing Peltier cooling