Library
July 2011
The thesis presents an initial concept of modification and calculation of a light armoured vehicle’s hull structure. It aims at enhancing the protection of the crew through the modification of the base-plate armour. The results of numerical calculations for the elements of an armoured vehicle structure exposed to the impact generated by the explosion of an underbelly blast mine are presented.
Bioaerosol weapons pose a severe threat to the safety and security of military forces and civilians. During an attack, these weapons release into the atmosphere biological warfare agents, which form stratified cloud layers over a small area. Detection of such bioaerosol clouds at safe standoff distances from the location of a sensor is very important for timely deployment of countermeasures. LIDAR is the only standoff technique that can detect and identify the composition of the clouds in near real time. In this paper, we present the parametric studies of a fluorescence LIDAR system for detection of bioaerosol clouds for given conditions. The elastic backscattered and induced fluorescence signals as a function of range, concentration and optical background levels have been simulated for given system parameters. We considered a Nd:YAG laser at the quadrupled wavelength of 266 nm as a transmitter and a Cassegrain telescope as a receiver with two detection channels namely: a Mie channel (elastic signal), and a fluorescence channel. The performance of various combinations of system design parameters comprising laser pulse energies and receiver telescopes have been determined to detect a bioaerosol cloud located at 1–2 km during day and night time. Our analysis revealed that fluorescence LIDAR with a pulse energy of 100 mJ and receiver telescope diameter of 300 mm can detect the presence of tryptophan containing bioaerosols clouds of 200m thickness and concentration of 8107 particles/litre (ppl) up to a distance of 1.5 km during daytime. We also estimated the sensitivity of the system in terms of minimum detectable concentration with respect to number of transmitted laser pulses. The averaging of 1,000 pulses (equal to the detection time of 50 seconds) resulted in the fluorescence detection range of 520m for a lethal infective dose of ~10,000 ppl.
Modern warfare includes extensive use of laser-based devices and laser-guided weapons. This large-scale use of laser-based systems means that all weapon platforms are vulnerable to attack by laser-guided munitions (LGM). Such a situation emphasises the importance of timely detection and recognition of laser threats. This necessitates that friendly platforms are equipped with a suitable laser-warning sensor that will provide timely information about the incoming laser threat with a high level of angle-of-arrival accuracy so that a suitable countermeasure action can be initiated against it. This paper (Part II of a two-part series of papers) discusses the design of the electronic processing module of a laser-warning system (LWS) having an opto-electronic front end designed using an array of discrete photo-diodes (the design aspects of, and test results for, the opto-electronic front end has been discussed in the first part). This is followed by a brief discussion on its simulated evaluation process and the test results for the determination of the angle of arrival and PRF of a laser threat.
A Mie LIDAR system has been designed and developed at the Laser Science and Technology Centre (LASTEC), Delhi by using a minimal number of commercially available off-the-shelf components. A Nd:YAG laser operating at 1064 nm with variable pulse energies between 25–400 mJ, 10 Hz repetition rate and 7 ns pulse duration is used as a transmitter and a Cassegrain telescope with a 200 mm diameter mirror as a receiver. A silicon avalanche photodiode module with built-in preamplifier is used as a detector. A data acquisition system has been designed using a data acquisition card (National Instruments) and a BNC connector terminal block. Graphical user-friendly LabVIEW-based software has been developed to configure the hardware and acquire the backscattered signal. This software also controls the transmitter to fire the laser pulses with the given sequences. The experimental setup is installed on a movable tripod platform for conducting field experiments. Experiments have been conducted using this set up and preliminary results on measurements of aerosols, clouds, visibility and depolarization are discussed in this paper.
This paper considers the task of object recognition for the possible introduction of target discrimination capabilities in unmanned aircraft. We are concerned with a naval scenario, and attempt to identify automatically four different ships in simulated infrared imagery, using a popular feature extractor and object recognition method: the Scale Invariant Feature Transform (SIFT). Features generated in test images are matched to features in a model database of labelled images using a modified minimum Euclidean distance metric. Pose clustering via the Generalised Hough Transform is also used to reduce outlying feature matches. Particular attention is paid to the robustness of the identification process to variations in scene illumination and the inclusion of Gaussian noise.