Defence Science Journal
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Multiple Region Coverage Path Planning for Autonomous Underwater Vehicle.
Get PDFCoverage path planning methodology for an autonomous underwater vehicle to search multiple non-overlapping regions has been proposed in the paper. The proposed methodology is based on the genetic algorithm (GA). The GA used in the proposed methodology has been tuned for the specific problem, using design of experiment on an equivalent travelling salesman problem benchmark instance. Optimality of the generated paths was analysed through simulation studies. Results indicated that the proposed methodology generated shorter paths in comparison to conventional methods
Stress Redistribution Near a Crack in Maraging Steel using Composite Patch
Get PDFThe presence of a crack significantly reduces the load bearing capacity of a structure made of fracture prone material. The conventional process of repairing a defect is gouging and filling the gouged location by rewelding. It is not only time consuming but also constrained by the number of repairs that can be done as material properties degrade with each round of rewelding. In an attempt to overcome the limitation of the conventional repair process, repairing a defect using composite patch is proposed. The study is carried out on Maraging steel (M250) and the defect considered is a crack. Stress intensity factor (SIF), being an important parameter in fracture-based design, it is evaluated in Abaqus. Extended finite element method is used to model the crack. SIF is used to predict the failure load of a surface cracked tension specimen and the same is compared with the values reported in literature. Composite patch is modelled using woven ply properties. A separate layer of adhesive is also modelled to predict the properties adhesive properties. Failure analysis of each component namely, the Maraging steel plate, the composite patch and the adhesive is carried. It was observed that the addition of a composite patch completely nullifies the presence of a crack. The patch with thickness 1mm and woven ply properties is having minimal damage initiation and likely to survive. The adhesive properties required is also obtained from the finite element analysis. Thus, it was observed that a composite patch with woven ply properties and thickness 1mm is able to completely nullify the effect of a crack when bonded with a suitable adhesive as predicted by the analysis
A Non Contact Multiple Ring CSRR Based Planar Microwave Sensor for Accurate Quality Estimation of Water Samples with Varying TDS
No full textWater 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
A Novel Pseudonym Assignment and Encryption Scheme for Preserving the Privacy of Military Vehicles
Get PDFIn this digital era, security has become one of the important topics of concern, and things become more critical for military vehicles where safety plays a vital role. In this paper, we have discussed a pseudonym-based approach that preserves the real identity of military vehicles. This paper also focuses on military vehicles’ location privacy by deploying a novel pseudonym assignment and encryption schemes. The proposed security scheme is based on a hybrid approach of matrix array symmetric key and the intelligent water drop scheme. After implementing the proposed security scheme, each military vehicle will obtain its pseudonym for hiding their original identities. The proposed algorithm effectively manages pseudonym generation and change requests for the local region and inter-region environment. The proposed security scheme not only provides secure communication and preservation of location privacy of military vehicles but also ensures their security against various attacks. Finally, the time efficiency of proposed algorithms is obtained for both local and inter-region requests. Comparative analysis shows that the proposed scheme is more efficient than other existing techniques
Investigate the Structural Response of Ultra High Performance Concrete Column under the High Explosion
Get PDFMost of the structures that are damaged by an explosion are not initially designed to resist this kind of load. In the overall structure of any building, columns play an important role to prevent the collapse of frame structure under blast impact. Hence, the main concept in the blast resistance design of the structure is to improve the blast load capacity of the column. In this study, dynamic analysis and numerical model of Ultra High Performance Concrete (UHPC) column under high explosive load, is presented. Based on the Johnson Holmquist 2 damage model and the subroutine in the ABAQUS platform, a total of twenty UHPC model of the column were calculated. The objective of the article is to investigate the structural response of the UHPC column and locate the most vulnerable scenarios to propose necessary recommendations for the UHPC column in the blast loading resistance design. The input parameters, including the effect of various shapes of cross-section, scaled distance, steel reinforcement ratio, and cross-section area, are analyzed to clarify the dynamic behavior of the UHPC column subjected to blast loading. Details of the numerical data, and the discussion on the important obtained results, are also provided in this paper
Software in Loop Simulation based Waypoint Navigation for Fixed Wing UAV
Get PDFSoftware in loop simulation (SILS) based waypoint navigation test platform being presented in this paper for fixed wing unmanned aerial vehicle. The proposed platform helps to test waypoint navigation algorithm before implementing into real time environment. Matlab/Simulink and X-plane flight simulator are chosen for the proposed platform. The interface between these two platforms are done by using user datagram protocol (UDP). The waypoint navigation which is to be tested is run in Matlab/Simulink environment where as fixed wing model runs in X-plane simulator. Inverted T tail fixed wing unmanned aerial vehicle configuration is chosen for this research work to verify both its inner loop (attitude control) and outer loop (navigation control). Navigation algorithm executed in Matlab/Simulink compares difference between current and desired latitude longitude position to command flight simulator to reach its desired waypoint. Navigation towards a desired waypoint will be achieved by varying inner loop attitude command of an unmanned aerial vehicle. Finally results are observed and performances are verified in X-plane simulator
Through Wall Imaging Radar Antenna with a Focus on Opening New Research Avenues
Get PDFThis review paper is an effort to develop insight into the development in antennas for through wall imaging radar application. Review on literature on antennas for use in through wall imaging radar, fulfilling one or more requirements/specifications such as ultrawide bandwidth, stable and high gain, stable unidirectional radiation pattern, wide scanning angle, compactness ensuring portability and facilitating real-time efficient and simple imaging is presented. The review covers variants of Vivaldi, Bow tie, Horn, Spiral, Patch and Magneto-electric dipole antennas demonstrated as suitable antennas for the through wall imaging radar application. With an aim to open new research avenues for making better through wall imaging radar antenna, review on relevant compressive reflector antennas, surface integrated waveguide antennas, plasma antennas, metamaterial antennas and single frequency dynamically configurable meta-surface antennas are incorporated. The review paper brings out possibilities of designing an optimum through wall imaging radar antenna and prospects of future research on the antenna to improve radiation pattern and facilitate overall simple and efficient imaging by the through wall imaging radar
Perturbation Propagation Models for Underwater Sensor Localisation using Semidefinite Programming
Get PDFReal time Underwater sensor networks (UWSNs) suffer from localisation issues due to a dearth of incorporation of different geometric scenarios in UWSN scenarios. To address these issues, this paper visualises three specific scenarios of perturbation. First, small sized and large numbered particles of perturbance moving in a tangential motion to the sensor nodes; second, a single numbered and large-sized particle moving in a rectilinear motion by displacing the sensor nodes into sideward and forward direction, and third, a radially outward propagating perturbance to observe the influenced sensor nodes as the perturbance moves outwards. A novel target localisation and tracking is facilitated by including marine vehicle navigation as a source of perturbation. Using semidefinite programming, the proposed perturbation models minimise localisation errors, thereby enhancing physical security of underwater sensor nodes. By leveraging the spin, cleaving motion and radial cast-away behaviour of underwater sensor nodes, the results confirm that the proposed propagation models can be conveniently applied to real time target detection and estimation of underwater target nodes
DRLDO A Novel DRL based De obfuscation System for Defence Against Metamorphic Malware
Get PDFIn this paper, we propose a novel mechanism to normalise metamorphic and obfuscated malware down at the opcode level and hence create an advanced metamorphic malware de-obfuscation and defence system. We name this system as DRLDO, for deep reinforcement learning based de-obfuscator. With the inclusion of the DRLDO as a sub-component, an existing Intrusion Detection System could be augmented with defensive capabilities against ‘zero-day’ attack from obfuscated and metamorphic variants of existing malware. This gains importance, not only because there exists no system till date that use advance DRL to intelligently and automatically normalise obfuscation down even to the opcode level, but also because the DRLDO system does not mandate any changes to the existing IDS. The DRLDO system does not even mandate the IDS’ classifier to be retrained with any new dataset containing obfuscated samples. Hence DRLDO could be easily retrofitted into any existing IDS deployment. We designed, developed, and conducted experiments on the system to evaluate the same against multiple-simultaneous attacks from obfuscations generated from malware samples from a standardised dataset that contain multiple generations of malware. Experimental results prove that DRLDO was able to successfully make the otherwise undetectable obfuscated variants of the malware detectable by an existing pre-trained malware classifier. The detection probability was raised well above the cut-off mark to 0.6 for the classifier to detect the obfuscated malware unambiguously. Further, the de-obfuscated variants generated by DRLDO achieved a very high correlation (of ≈ 0.99) with the base malware. This observation validates that the DRLDO system is actually learning to de-obfuscate and not exploiting a trivial trick
Channel Sounding and Measurements for Pico Cells for LTE and Future Wireless Networks
Get PDFWireless 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 network