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 | Effect of Feed Location on Rectangular Microstrip Antenna at TM/sub 11/ Mode
Author : Chowdhury, S.K. ;Roy., J.S.;Paul, P.
Source : Defence Science Journal ; Vol:46(3) ; 1996 ; pp 127-134
Subject : 623.61 Military Communications
Keywords : Conical radiation patterns ;Gain microstrip antennas;Patch antenna
Abstract : The variation of 2:1 VSWR impedance band width with the change of feed location, at TM/sub 11/ mode excitation is studied experimentally. Experimental investigations revealed that the 2:1 VSWR impedance band width of a rectangular microstrip patch antenna at TM/sub 11/ mode could be improved by properly choosing the location of the feed point along one of the radiating edges; and this is verified theoretically. This investigation may be useful for low gain microstrip antennas with conical radiation patterns. |
| | Cardiorespiratory and Neuromuscular Effects of Freshwater Cyanophyte Anabena flosaquae in Rats
Author : Bhaskar, A.S.B. ;Rao, P.V.L.;Kumar, Deo;Mazumder, P.K.;Dube, S.N.
Source : Defence Science Journal ; Vol:46(3) ; 1996 ; pp 135-141
Subject : 57 Biological Sciences
Keywords : Neostigmine ;Pulmonary vagal afferents;Bronchoconstriction;Hemicholinium-3;Prazosin;Hexamethonium;Anatoxin
Abstract : Anatoxin-a, recognised as a potent toxin warfare agent, is considered as a weapon of mass destruction due to its lethal anticholinesterase activity. The intravenous administration of cell-free extract of Anabena flosaquae UTEX-2383(anatoxin-a) produced a transient vasodepressor response followed by a sustained rise in blood pressure. The vasodepressor effect was potentiated by physostigmine and antagonised by atropine and bilateral vagotomy, suggesting the involvement of cholinergic system. On the contrary, the vasopressor response was antagonised by hexamethonium prazosin and hemicholinium-3, indicating that the toxin stimulates the sympathetic system through the release of catecholamines from nerve endings. Prolonged apnoea with attendant bronchoconstriction was observed corresponding to bradycardia and vasppressor response which remained unaltered by atropine while antagonised by bilateral vagotomy. The extract when administered intra-arterially did not modify the apnoea induced by veratridine; but phenyldiguanide potentiated the bronchoconstriction, indicating the involvement of pulmonary vagal afferents. The extract produced a dose- and time-dependent blockade of indirect muscle twitch recorded from gastrocnemius muscle. The neuromuscular blockade was potentiated by neostigmine but unaltered by DTC. |
| | Effect of Topically Applied Sulphur Mustard on Haematological Biochemical and Histological Parameters in Mice
Author : Pant, S.C. ;Bhaskar, A.S.B.;Jeevaratham, K.;Sugendran, K.
Source : Defence Science Journal ; Vol:46(3) ; 1996 ; pp 149-154
Subject : 620.261 Explosives ;66 Chemical Technology;623.459 War Gases
Keywords : Creatine phosophokinase ;Blood haemoglobin concentration;Chemical weapons;Blistering agent;Sulphur mustard
Abstract : "Sulphur mustard (SM) a potent blistering agent, has been frequently used as a chemical weapon. In the present study the effect of topically applied SM on haematological biochemical and histological parameters in mice were investigated over a period of seven days. The application of SM resulted in significant increase of blood haemoglobin concentration packed cell volume and erythrocyte count as well as plasma urea uric acid and cholesterol levels. There was a significant decrease in blood leukocyte count Plasma total protein and albumin. There was significant increase in bleeding clotting and prothrombin time. Elevated levels of alkaline phosphatase lactate dehydrogenase aspartate and alaine aminotransaminases and creatine phosophokinase activities were also observed revealing SM-induced liver damage and general state of illness. Histopathological observations revealed a mild to moderate degree of congestion and haemorrhage in the viscera examined. Also there were mild degeneration and ovliteration of chromatin material in liver and Kidneys. " |
| | Underwater Breathing Apparatus
Author : Mathew, Lazar ;Thammaiah, K.;Murthy, G.S.N.;Setty, B.V.S
Source : Defence Science Journal ; Vol:46(3) ; 1996 ; pp 155-160
Subject : 57.089 Biomedical Sciences ;629.5 Marine Sciences;623 Military Science and Engineering
Keywords : Life saving equipment ;Oxygen poisoning;Breathing appartus
Abstract : An independent closed circuit regenerative type of breathing apparatus has been developed for isolating the respiratory tract from the ambient medium for use during breathing by personnel working in underwater or polluted atmosphere. An oxygen reducer is used in the design of this apparatus for catering to the required flows of oxygen for breathing during use of the apparatus and thus avoiding oxygen poisoning. The paper describes some of the salient aspects of the breathing apparatus to be deployed for submariners and other diving personnel of the Indian Navy and its potential usefulness as a life saving equipment. |
| | Computer Aided Design and Heat Transfer Analysis of Handguard of a Gun
Author : Dhande, Sanjay G. ;Datar, A.M.;Singh, R.K.;Kishor, Shyam;Choudhary, Ashok K.
Source : Defence Science Journal ; Vol:46(3) ; 1996 ; pp 161-169
Subject : 536.2 Heat Transfer;536 Thermodynamics;681.3 Computer Science
Keywords : Finite element predictions;Finite defferences;Finite elements;Thermal analysis;Handguard temperatures
Abstract : "The study presents thermal analysis of the handguard of a gun using finite elements as well as finite differences. The thermal loading corresponds to continuous firing of 300 rounds for 600s follwed by an inactive period of 300s. The maximum barrel temperature recorded was around 300 degree celsius. Three different handguard materials namely Ryton-4 PEEK-450G and PEI were tested. The effectiveness of a reflector shield located between the barrel and the handguard was studied. Two major results that emerged from the study are:(1)Ryton-4 gives the lowest temperature rise among the three materials studied and (ii)The reflector shield is crucial for maintaining the handguard temperature within limits. Spatial and temporal variation of temperature are qualitatively similar in the two numerical models. Owing to certain factors the finite element predictions for the handguard are on the higher side compared to finite differences. The maximum handguard temperatures as determined in the present model including the reflector are summarized in the Table 1. It is clear that the Ryton-4 as the handguard material can be considered as most desirable. " |
| | FTIR Spectral Evaluation of Polyurethane Adhesive Bonds in Perspex Canopies of Aircraft
Author : Sadafule, D.S. ;Panda, S.P.
Source : Defence Science Journal ; Vol:46(3) ; 1996 ; pp 171-174
Subject : 66 Chemical Technology;629.7 Aeronautics
Keywords : Infrared spectral analysis ;Fourier transform;Capron glue
Abstract : Failure of capron glue (polyurethane) adhesive joint between nylon strips and perspex canopy of aircraft has been studied by (Fourier transform infrared spectral analysis. It is concluded that the brittle failure of the joint is due to time-dependent crosslinking of residual isocyanate group with residual hydroxyl or the amino groups produced as a results of reaction of absorbed moisture with the isocyanate moiety: A service life of eight years has been estimated for the glue joint. |
| | Advanced Fibre Reinforced Methyl Nadicimide Resins
Author : Varma, I.K. ;Kandpal, L.D.;Alam, Sarfaraz
Source : Defence Science Journal ; Vol:46(3) ; 1996 ; pp 175-180
Subject : 665 Resins;66 Chemical Technology
Keywords : Kevlar fabrics ;Methyl nadicimide resins
Abstract : Glass/carbon/kevlar-reinforced composites were fabricated using two structurally different methl nadicimide resins. The resin content of the laminates was in the range of 32-39 per cent. Interlaminar shear strength (ILSS)and flexual strength (FS) depended on the structure of the methyl nadicimide resins. A significant decrease in the ILSS was observed on treatment with boiling water for 500 h and on isothermal ageing at 300 degree celsius for 100,250 and 500 h. The limiting oxygen index (LOI) was the lowest for laminates based on Kevlar fabrics (i.e.54) whereas the laminates based on glass/carbon showed very high LOI(>90). |
| | Technology Management in our Liberalised Environment
Author : Shenoy, R.P.
Source : Defence Science Journal ; Vol:46(3) ; 1996 ; pp 181-193
Subject : 658 Management Sciences
Keywords : Technology management ;Technology fusion
Abstract : The article reviews the present state of technology management in our liberalised environment. For our industries, technology management is mainly technology import and for our scientists it is management of Research and Development. The changes introduced in technology management by the intense competitive environment are discussed and the effects of the broadened scope for technology management for sustained competitiveness are brought out. Technology fusion and core competence as part of the strategic framework follow as a response to the environment. The Indian scenario is now discussed in the light of these developments. The paper concludes that all parties involved in technology management namely government industries and the scientists/technologists have to recognise these changes and act in a concerted manner for the nation to gain and sustain the competitive edge. |
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