Defence Science Journal
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Determination of Nonlinear Refractive Index of Zinc Phthalocyanine by Pump Induced Fizeau Interferometry
Get PDFExperimental measurement of intense light induced refractive index is demonstrated using Fizeau interferometer. Refractive index is induced in a specific region of the sample with intense light pulse of a linearly polarized, Q- switched Nd:YAG laser at 1064nm wavelength. The respective change in optical path difference (OPD) is measured using Fizeau interferometer. The OPD so obtained is mapped in terms of change in refractive index in the area of interaction of pump beam and sample. The measured induced refractive index is then used to calculate thermo-optic coefficient of the ZnPc embedded polymeric sample
Recent Trends in Computational Electromagnetics for Defence Applications
Get PDFInnovations in material science, (nano) fabrication techniques, and availability of fast computers are rapidly changing the way we design and develop modern defence applications. When we want to reduce R&D and the related trial-and-error costs, virtual modelling and prototyping tools are valuable assets for design engineers. Some of the recent trends in computational electromagnetics are presented highlight the challenges and opportunities . Why researchers should equip themselves with the state-of-the-art tools with multiphysics and multiscale capabilities to design and develop modern defence applications are discussed
Failure Behaviours of Steel Projectiles with Localised Melting Against Armour Plates
Get PDFThe surface remelting technology of high energy beam can locally weaken the case for controlled fragmentation, which may affect the survivability of the impacting projectiles. Failure behaviours of steel projectiles with melted layers grid normally perforating armour plates was investigated. The results reveal that shear fracture mainly occurs in the nose region of projectiles due to high loading, and the melting zone of projectiles can keep integrity with no damage, which means the survivability of projectile can be assured. Furthermore, an analytical model was proposed to the structural analysis of projectile, which is in accordance with the test results
Blind Identification of Block Interleaved Convolution Code Parameters
Get PDFMost of the digital communication system uses forward error correction (FEC) in addition with interleaver to achieve reliable communication over a noisy channel. To get useful information from intercepted data, in non-cooperative context, it is necessary to have algoritihms for blind identification of FEC code and interleaver parameters. In this paper, a matrix rank-based algebraic algorithm for the joint and blind identification of block interleaved convolution code parameters for cases, where interleaving length is not necessarily an integer multiple of codeword length is presented. From simulations, it is observed that the code rate and block interleaver length are identified correctly with probability of detection equal to 1 for bit error rate values of less than or equal to 10-4
Synthesis of Polycarbosilane, Polymer Impregnation Pyrolysis based C SiC Composites and Prototype Development
Get PDFDue to some extraordinary thermo-mechanical properties, silicon carbide is considered one of the best materials used for high temperature applications in defence and aerospace. Polycarbosilane (PCS) has been widely used as SiC precursor. This paper describes the research and development work undertaken to establish the technologies for synthesis and characterisation of PCS, fabrication process and characterisation of Carbon fibre reinforced SiC matrix (C/SiC) composite laminates and shaped articles. The molecular weight and softening point of the PCS was found to be 1400-1800 Mn and 140-150 °C respectively. Flexural stress of the unidirectional (UD) C/SiC composites and bidirectional (2D) C/SiC composites was found to be 400-450 MPa and 300-350 MPa respectively. Tensile stress of the 2D C/SiC composite was found to be around 200 MPa. Coefficient of thermal expansion and thermal diffusivity of the 2D C/SiC composites at RT- 1000 °C were found to be in range of 0.3-2.2×10-6/ °C and 32-6 mm2/s respectively. The fabrication process developed for the UD and 2D C/SiC composites using the indigenous PCS has been also demonstrated to fabricate typical size divergent rocket nozzle and hot structure. Fabrication process of the SiC fibre has also been described in brief
Formulation of an Empirical Relation between Chlorophyll and Sea Surface Temperature in the Southeastern Arabian Sea
Get PDFPresent study formulates an empirical relation between sea surface temperature (SST) and chlorophyll (Chl) in the Southeastern Arabian Sea using data collected during 2017. SST was found to decrease due to upwelling of cold nutrient rich waters, thus causing enhancement of Chl in the coastal and nearshore waters. Based on this, an empirical relationship exists which is inversely correlated during peak upwelling and intense biological production. The linear regression generated a significant correlation coefficient (0.52 ≤ R2 ≥ 0.64) in the month of July, August and October. Although other factors influence Chl, SST can be considered as a significant indicator of biological production with respect to seasonal upwelling. Among the empirical relations, a definite single equation requires the assessment of subsurface Chl to reveal the underlying relationship
Effect of Azimuthal Asymmetry Caused by Upwelling on 3D Ocean Acoustic Propagation
Get PDF3-D underwater parabolic equation model based on implicit finite difference method has been implemented for South Eastern Arabian Sea (SEAS). The bathymetric and geo-acoustic features have been integrated in the model for a 50 km circular region in SEAS. The model can simulate the effects of azimuthal variation in oceanographic features and compute azimuthally coupled pressure due to an omni-directional source. The azimuthal variation in oceanographic conditions can be observed during an upwelling event. In the first case study, the effect of upwelling event on three-dimensional acoustic propagation has been studied by using sound speed profile data derived from INS Sagardhwani observations. The difference in Transmission loss mosaic for upslope and downslope propagation is due to bathymetry as well as upwelling. In the second case study, the effect of upwelling only, is studied by running a model corresponding to range independent sound speed profile field and range dependent bathymetry. It was observed that during this upwelling event, the transmission loss is higher at longer ranges during upslope propagation than downslope propagation. This is due to the increase in the thickness of sonic layer duct as acoustic wave propagates from shallow to deep water. The effect of azimuthal variation
Efficient Digital System Management using IEEE 1451.0 Enabled Control Architecture
Get PDFThe IEEE and National Institute of Standards and Technology have formulated an open universal standard called IEEE 1451 for ‘Smart Transducer Interface’ with digital systems. The objectives of this paper is to propose IEEE 21450 enabled control architectures for efficient management of power system with embedded system parameters as electronic documentation. The control architecture accommodates appropriate number of transducer interface module along with transducer electronic data sheet, which enables active calibration, adaptive tuning and failure proof operation of system management
A Rapid Flow through Membrane Enzyme Linked Immunosorbent Assay for Bacillus anthracis using Surface Array Protein as a Biomarker
Get PDFAnthrax, caused by Bacillus anthracis is an important disease of biowarfare and public health importance. It is imperative to develop a simple system which can detect and differentiate B. anthracis from other closely related species. The surface array protein (Sap), which is secreted during the early growth phase of bacteria can be an important biomarker for detection of B. anthracis. In the present study, we have developed a rapid flow through membrane ELISA for detection of B. anthracis. Polyclonal antibodies were used to develop a sandwich plate ELISA, which could detect 3.9 ng/ml of recombinant Sap. B. anthracis bacteria grown in culture broth could be detected after 5 h of growth. Finally, a rapid flow through membrane ELISA was developed which can be accomplished just within 2 minutes, instead of 3-4 h as required in sandwich plate ELISA. The results established that the developed flow through membrane ELISA may be used for detection of B. anthracis. The proposed method is rapid, safe and user friendly for detection of B. anthracis culture