Defence Science Journal
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SWaP Optimised Parameter Extraction of Radar Signals for Space Electronic Intelligence Application
Get PDFSpace-based electronic intelligence system provides wide coverage and unrestricted access to adversary radar signals. These systems play a vital role in strategic intelligence gathering for assessing electronic order of battle. These systems need to be SWaP optimized with highly efficient algorithms to extract accurate radar parameters. The realization of such a system is a persistent challenge due to the limited availability of space graded components and associated tools. Towards this, the paper deliberates upon various signal processing algorithms to achieve highly accurate direction-of-arrival (DOA), high-frequency resolution and precise timing information for pulse width and pulse repetition frequency extraction. All the proposed algorithms have been implemented, ported and tested on Xilinx Kintex Ultra Scale FPGA KU060 and being evaluated in the radiation setups to establish the performance. High DOA accuracy and frequency accuracy of the order of 0.3 degree and 0.64 MHz respectively have been achieved
Study of Gain Switching in Vertical Cavity Surface Emitting Laser under Different Electrical Pulse Inputs
Get PDFVertical cavity surface emitting laser (VCSEL) is a strong candidate for short pulse generation among the other semiconductor lasers in the era of laser technology. A 1550 nm, low power VCSEL is excited under different current shapes and the chief laser parameters are found out. The concept of gain switching under various current profiles are utilized effectively to bring out maximum laser power with minimum pulse width, which are the essential factors for long haul high speed optical data transmission. For a haversine electrical current input with 3.7 Ith amplitude, a laser peak power of 2.2 mW at 57 ps pulse width is obtained. In the case of trapezoidal pulse, 67 ps pulse width is obtained for 2.6 Ith current amplitude. It is also observed that square pulse of amplitude 2 Ith produces short optical pulse of 0.887 mW peak power and 89 ps width which shows the best performance when compared to other forms of pulses discussed in this work at the same input condition
Study on Crush Tube Geometric Cross sections and Topology for Axial Crashworthiness
Get PDFCrush tubes are used as crash impact energy absorbing structure (EAS) and are located in the frontal compartment of road vehicles. Ideal crashworthiness of an EAS mandates that the equivalent decelerations due to impact forces should to be ≤ 20g; and crush force and stroke efficiencies should tend to unity. It is understood from the literature that no single geometric cross-section shape exhibits a near-ideal crashworthiness; and most EAS members exhibit a high initial peak crush force which is detrimental to the occupant safety, and moderate stroke and crush force efficiencies leading to a compromise in the total energy absorbed. In this paper, finite element analysis (FEA) methodology is formulated and experimentally validated for axial crush of a crush tube of SS304 material with circular cross section. Subsequently, plastic deformation phenomenon and folding patterns in relation to crush force behaviour of crush tubes with various basic cross-sections of polygonal geometric shapes from triangle to octagon and circle are extensively studied through FEA. Further, two new geometric cross-section profiles with combination of basic shapes are proposed to combine the merits of different basic shapes. The crashworthiness of all basic cross-sections including the two proposed cross-section profiles is assessed based on standard parameters. The proposed new geometries may form a basis for the development of new EAS configurations for enhanced crashworthiness
A Robust Cooperative Modulation Classification Scheme with Intra sensor Fusion for the Time correlated Flat Fading Channels
Get PDFNetworks with distributed sensors, e.g. cognitive radio networks or wireless sensor networks enable large-scale deployments of cooperative automatic modulation classification (AMC). Existing cooperative AMC schemes with centralised fusion offer considerable performance increase in comparison to single sensor reception. Previous studies were generally focused on AMC scenarios in which multipath channel is assumed to be static during a signal reception. However, in practical mobile environments, time-correlated multipath channels occur, which induce large negative influence on the existing cooperative AMC solutions. In this paper, we propose two novel cooperative AMC schemes with the additional intra-sensor fusion, and show that these offer significant performance improvements over the existing ones under given conditions
Effect of Coating and Polishing of Cutting Tool on Machined Surface Quality in Dry Machining of Aluminium Alloy
Get PDFSurface quality is one of the major concerns in any machining process. To achieve the higher surface finish, mostly concentrated on machining parameter optimisation. This study has been carried out to study the effect of coating and polishing of flute surface of the solid carbide (WC-Co) endmill cutters on machined surface quality obtained during dry machining of Aluminium alloy 24345WP. Experiments were conducted on Aluminum workpieces with Ø6 mm 2 flute end- mill cutter with and without coating/polishing and their effect on surface quality studied for linear as well as areal surface roughness parameters using white light interferometery. The study concludes that polished flute tool, despite their non-sharp cutting edges, gives considerably better surface finish due to its lowering of chip tool friction. This was also supported by the results obtained from scanning electron microscopy of the cutting tool edge as well as optical microscopy of the obtained machined surface
Optimal Falling Track Design for Twice detonating Fuze of Double event Fuel air Explosive with High Speed
Get PDFTo prevent the initiation failure caused by the uncontrolled fuze and improve the weapon reliability in the high-speed double-event fuel-air explosive (DEFAE) application, it is necessary to study the TDF motion trajectory and set up a twice-detonating fuze (TDF) design system. Hence, a novel approach of realising the fixed single-point center initiation by TDF within the fuel air cloud is proposed. Accordingly, a computational model for the TDF motion state with the nonlinear mechanics analysis is built due to the expensive and difficult full-scale experiment. Moreover, the TDF guidance design system is programmed using MATLAB with the equations of mechanical equilibrium. In addition, by this system, influences of various input parameters on the TDF motion trajectory are studied in detail singly. Conclusively, the result of a certain TDF example indicates that this paper provides an economical idea for the TDF design, and the developed graphical user interface of high-efficiency for the weapon designers to facilitate the high-speed DEFAE missile development
Modelling the Constraint Effect on Reference Temperature with Finite Element Parameters for Reactor Pressure Vessel Material 20MnMoNi55 Steel
Get PDFA series of experiments were performed in the ductile to brittle transition region on three-point bending specimens of different thicknesses and a/W ratio of 20MnMoNi55 steel. master curve and reference temperature (T0) are obtained as per ASTM E1921-02 with different thickness and a/W ratio of the specimen and a variation of T0 is obtained, which indicates constant dependent on T0. Mathematic models are formulated to correlate T0 with Q-stress, T-stress and Triaxiality ratio to count for the constraint loss. Both the average value and also the maximum value of the finite element parameters are considered to predict T0 at different constraint label and compared with the experimental results
Dual Frequency Electronically Controlled Radiation Beam Reconfigurable slotted Antenna for Detection of a Stationary or Nonstationary Target
Get PDFA dual-frequency and radiation pattern reconfigurable microstrip patch antenna for detecting a stationary as well as a non-stationary target is described. Six angular patches, that collectively form a circular shape, are used. All the six patches radiate one by one after a fixed interval of time and their feed controlling is done by six PIN diodes. The switching of PIN diodes is controlled by an embedded biasing network. This antenna provides radiation beam scanning characteristics. It gives the main lobe scanning at every 60o clockwise (or anticlockwise) continuously by applying a signal to patches one by one. The purpose of introducing the slot is to get the radiation pattern in the desired direction since by changing the length, width, and position of the slot, the direction of the radiation pattern can be controlled. The slotted antenna operates in a C band with two frequencies 4.21 GHz and 4.82 GHz and provides a radiation pattern, 90o apart from each other. The scanning rate of 0.6 deg/ms is obtained; however, the scanning rate can be changed with the help of ATMEGA 2560 microcontroller. This compact Microstrip patch antenna can be widely used for short-range applications i.e. ground surveillance radar, missile control, mobile battlefield surveillance for military and many other applications in a modern wireless communication system. The designed antenna along with the switching application will be able to track the stationary as well as a non-stationary target
Two Dimensional Materials for Military Applications
Get PDFThis paper particularly focuses on 2D materials and their utilization in military applications. 2D and heterostructured 2D materials have great potential for military applications in developing energy storage devices, sensors, electronic devices, and weapon systems. Advanced 2D material-based sensors and detectors provide high awareness and significant opportunities to attain correct data required for planning, optimization, and decision-making, which are the main factors in the command and control processes in the military operations. High capacity sensors and detectors or energy storage can be developed not only by using 2D materials such as graphene, hexagonal boron nitride (hBN), MoS2, MoSe2, MXenes; but also by combining 2D materials to obtain heterostructures. Phototransistors, flexible thin-film transistors, IR detectors, electrodes for batteries, organic photovoltaic cells, and organic light-emitting diodes have been being developed from the 2D materials for devices that are used in weapon systems, chemical-biological warfare sensors, and detection systems. Therefore, the utilization of 2D materials is the key factor and the future of advanced sensors, weapon systems, and energy storage devices for military applications
A Comparison of Circular and Slotted Synthetic Jets for Flow Control in a Twin Air Intake
Get PDFThe performance of an aircraft engine depends on air flow quality at the engine face / the exit of the air-intake also known as aerodynamic inlet plane (AIP). A single-engine aircraft has complex Y-shaped twin air-intake which causes severe flow separation, distortion and flow non-uniformity at the AIP. The present study compares the efficacy of slotted synthetic jet and a row of four circular synthetic jets attached to inner faces of a twin air-intake to improve aerodynamic performance at the AIP. The results are obtained using computational fluid dynamics. The velocity and vorticity plots show that lateral spread of the circular jets is limited as compared to the slotted jet. The circular jets are found to be weak as compared to slotted jet to prevent separation of main flow occurring in the twin air-intake. The various aerodynamic performance parameters, such as static pressure recovery coefficient, total pressure loss coefficient, distortion coefficient and secondary flow uniformity are compared for both the cases, exhibiting marked improvement in all these parameters. The study demonstrates that the slotted synthetic jets is a better option for controlling flow in twin air-intake as compared to a row of circular synthetic jets