Defence Science Journal
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Failure behavior of concrete subjected to high dynamic loading of new spiral projectile
Get PDFA new spiral warhead structure which makes concrete failure by self-rotation is proposed in this paper. Concrete dynamic response when subjected to the oval and new proposed spiral projectile vertical and oblique-angle (from 60° to 70°) impacts of different velocities is studied numerically. This investigation obtains the specific law between different residual velocity and rotation angle when concrete target subjected to the impact loading of spiral projectile ranging from 700 m/s ~ 1000 m/s. It also shows the law between different residual velocity and the groove depth. The rotational angular velocity vs time curves for different working condition are given
An Evidential Fractal Analytic Hierarchy Process Target Recognition Method
Get PDFTarget recognition in uncertain environments is a hot issue, especially in extremely uncertain situation where both the target attribution and the sensor report are not clearly represented. To address this issue, a model which combines fractal theory, Dempster-Shafer evidence theory and analytic hierarchy process (AHP) to classify objects with incomplete information is proposed. The basic probability assignment (BPA), or belief function, can be modelled by conductivity function. The weight of each BPA is determined by AHP. Finally, the collected data are discounted with the weights. The feasibility and validness of proposed model is verified by an evidential classifier case in which sensory data are incomplete and collected from multiple level of granularity. The proposed fusion algorithm takes the advantage of not only efficient modelling of uncertain information, but also efficient combination of uncertain information
Design and Development of Compact Conformal Microstrip Antenna at S-Band
Get PDFA compact microstrip antenna at S-Band is described in this work. This paper presents the theoretical and experimental investigations on conformal 90° Sectoral circular microstrip antenna using shorting wall. The performance of antenna characteristics is obtained using FEM based HFSS software and the computed results are verified by measurement. Here, microstrip antenna is loaded with shorting wall to achieve frequency reduction of about 75 per cent. The antenna characteristics were studied with radome surrounded by metallic ring. The radiation characteristics of antenna mounted on vehicle body is carried out. The antenna has moderate gain and wider coverage in roll plane as well as azimuth plane and may be used as small, compact antenna for onboard telemetry applications
Prediction of Shot Start Pressure for Rifled Gun System
Get PDFDetermination of short start pressure (SSP) for gun system has always been of paramount interest for gun designers. In this paper, a generalised model has been developed for theoretical prediction of SSP for rifled gun system using dimensional analysis approach. For this, parameters affecting the SSP of the gun like rifling dimensions, driving band dimensions, material properties of driving band, projectile mass and diameter are taken into consideration. For a particular case of large caliber rifled gun system, the model is established using linear relations among dimensionless groups of parameters. The model has been validated by data available from the open literature
A Survey of Adversarial Machine Learning in Cyber Warfare
Get PDFThe changing nature of warfare has seen a paradigm shift from the conventional to asymmetric, contactless warfare such as information and cyber warfare. Excessive dependence on information and communication technologies, cloud infrastructures, big data analytics, data-mining and automation in decision making poses grave threats to business and economy in adversarial environments. Adversarial machine learning is a fast growing area of research which studies the design of Machine Learning algorithms that are robust in adversarial environments. This paper presents a comprehensive survey of this emerging area and the various techniques of adversary modelling. We explore the threat models for Machine Learning systems and describe the various techniques to attack and defend them. We present privacy issues in these models and describe a cyber-warfare test-bed to test the effectiveness of the various attack-defence strategies and conclude with some open problems in this area of research.
Data Analysis and Validation of Acquired Temperature Data on Underwater Platform
Get PDFUnderwater missiles are launched from canister by hot gasses produced by a gas generator. Hot gasses eject the missile out of canister, positioned on an underwater platform in high seas at a depth of 50 m to 70 m. During development phase of submarine launched missile, maximum number of physical parameters related to platform and launching mechanism are acquired on a data acquisition system on-board platform and selected critical parameters are transmitted to control station in real time through an optical data communication link. Missile parameters are recorded on-board and transmitted to the control station by delayed transmission technique once the missile is out of water. Exit velocity of missile is very important parameter for the missile trajectory and range, which depends upon the heat loss in canister and annular gap pressure between missile and canister during the ejection process. Prediction of exit velocity is validated by heat loss calculation by measured temperature at different stations during the test. Temperature measurement is carried out by sensors mounted on the inner wall of canister and also by jumping type of temperature sensor, which measures canister gas temperature. In spite of all efforts, few sensors do not work as expected. It is important to measure various parameters according to instrumentation measurement plan. In case of temperature measurement, sometimes, it is required to predict temperature at location, where sensor was originally not mounted. To validate the recorded test data, another set of data is needed for which one has to wait till next test is conducted that may take years and practically impossible to ensure identical test setup and environmental condition. A mathematical approach to predict temperature at required location and to validate the recorded test data is presented.
Design Optimisation of Muzzle Brake for Sniper Rifle
Get PDFMuzzle brakes (MBs) have a great effect on reducing the recoil force of weapons during firing. In this paper, optimum MB efficiency, MB force and recoil force for (12,7 x 99 mm) sniper rifle have been studied. The objective is to obtain the optimum area of side openings, inclination angle and number of chambers for the MB in order to increase the MB efficiency and MB force and thereby to decrease their coil force of the weapon. An analytical model for calculating MB efficiency, MB force and weapon recoil force for MBs of two, three and four chambers has been established. This Model is then utilised in combination with design of experiment (DOE) and Response Surface Method (RSM) statistical techniques to develop a smooth response function which can be efficiently used in optimisation formulation. Finally, multi objectives generic algorithm (MOGA) optimisation method has been employed to find the optimum MB design parameters. The optimisation results show that the three or four chambers MBs have no significant effect on reducing the weapon recoil force compared with the two chamber MB for this sniper rifle
Design, Development and Performance Evaluation of Eddy Current Displacement Sensor Based Pressure Sensor with Target Temperature Compensation
Get PDFIn Aerospace applications, pressure measurement plays a vital role as it serves as one of the input to onboard controller to aid decision- making on initiating or terminating some of the critical events. In this paper, the design aspects of pressure sensor using linear eddy current displacement sensor (ECDS) are presented along with its performance evaluation. The static calibration is carried out to select the best position of ECDS in the proposed pressure sensor. The effect of target temperature on sensor output is presented with test results to aid compensation. A compensation algorithm is developed to minimise the error due to target temperature. The developed compensation algorithm is validated using thermal calibration. The designed pressure sensor is calibrated using Arson dynamic pressure calibrator to evaluate its bandwidth. The calibration results are analysed to aid future sensor design towards improvement of accuracy, bandwidth and miniaturisation
Energy-Efficient Multiple Relay Selection in Cognitive Radio Networks
Get PDFCognitive Radios play very important role in military applications due to their capability to adapt intelligently according to the prevailing environmental conditions. Relays form the main communication enablers in infrastructure-less networks. In this paper, relay selection for increasing the energy efficiency of a cognitive radio network is considered. The proposed approach considers the multiple - relay selection scheme with strict outage probability constraints. Energy maximisation is posed as an optimisation problem, the solution to which shows that relay selection under outage constraints is different from the one without such a constraint. It can be observed from the simulations that energy efficiency and outage behaviour follows trade-off relations. Moreover, the original Branch and Bound algorithm has been re-designed for faster convergence. It has also been demonstrated that when strict outage constraints are imposed, the optimal number of relays selected will be more in comparison to the case where there is no outage consideration
Design and Validation of Blast Non-propagation Wall for Multi-Compartmented Explosive Storage Structure of Capacity 5T NEC per Compartment
Get PDFConventional magazines for hazard division 1.1 are constructed using bricks and reinforced cement concrete (RCC) for which storage inside quantity distance (SIQD) is 2.4 W1/3 m, where W is Net Explosive Content in kg. New composite called laced reinforced concrete (LRC) has been developed recently, for which SIQD has been reduced up to 0.5 W1/3 m. Due to substantial reduction in separation distances, the requirement of land area has been reduced significantly. Although SIQD has been reduced drastically due to development of new composite, the other quantity distances like process inside quantity distance (PIQD) and outside quantity distance (OQD) decreased marginally. To reduce these quantity distances, the solution is multi-compartmented structures based on Unit Risk Principle. The application of unit risk principle enables the separation of explosives into compartments in such a manner that initiation of explosives in one compartment does not result in initiation of the explosives in adjacent compartments. This is achieved by special design of explosive storage buildings incorporating blast non-propagation walls between adjacent compartments storing explosives. Quantity distances are reduced for such magazines, as maximum credible limit corresponds to the quantity of explosive in one compartment. Present paper describes design and full scale testing of blast non-propagation wall between two compartments of a multi-compartmented explosive storage structure with storage capacity of 5 T Net Explosive Content (NEC) of HD 1.1 per compartment. The blast non-propagation wall comprising of sand filling and air gap between LRC walls has been designed for desired attenuation of blast parameters as well as for arresting high velocity fragments/debris. The design has been validated by fully instrumented design validation field trial. The conduct of the trial as well as the results are discussed in this paper