Antarctic expeditions in search of living resources

This paper deals in general terms with the historical expeditions to the Antarctica by various explorers leading to the exploration and identification of various living resources of the Antarctica and also a cautionary note not to pollute or disturb the existing ecosystem either for economic or political reasons

Length frequency and growth studies on Cynoglossus macrolepidotus (Bleeker) off Bombay coast

Specimens randomly collected from Sassoon Docks, Bombay, India, at monthly intervals during 1979 to 1981 were considered for age/growth studies. Cynoglossus macrolepidotus, the fish, attained a length of 202 mm at 1 year, 250 mm at 1 1/2 year and 272 mm at 21 months respectively; the maximum length of the fish could be 353 mm and the life span could be 7 years. The scale ring studies showed presence of only 0 to 3+ rings. Majority of the fishes were of 1 and 1+ year class

Application of Computer Graphics to Performance Studies of Missile Warheads

Intercept geometry of target aircraft and missiles play an important role in determining the effectiveness of the warhead. Factors such as fragment spatial distribution profile, damage capabilities, target and missile characteristics have been considered and visualised through computer graphics and optimum intercept intercept angles have been arrived. Computer graphics has proved to be an important tool to enhance perception and conceptual design capabilities in the design environment

Design Philosophy of variable Mass Preformed Fragmented Missile Warhead

Fragment hit density and hit probability of the warhead are the critical parameters in the selection of a preformed fragment-type missile warhead against ground targets. Hence these factors are to be maximised. The parametric studies of these factors have lead to a new concept of variable mass preformed fragmented (VMPF) warhead. A philosophy was evolved for the VMPF-type missile warheads. A computer software for generating the external configuration of the VMPF-type missile warhead was developed and basic algorithm is discussed in this paper. With this new design approach, the fragment hit density and hit probability were improved considerably in the shorter ranges, when compared to that of a uniform mass preformed fragmented warhead of conventional design

A magnetic resonance imaging surface coil transceiver employing a metasurface for 1.5T applications

A capacitive impedance metasurface combined with a transceiver coil to improve the radio frequency magnetic field for 1.5T magnetic resonance imaging applications is presented. The novel transceiver provides localized enhancement in magnetic flux density when compared to a transceiver coil alone by incorporating an electrically small metasurface using an interdigital capacitance approach. Full field simulations employing the metasurface show a significant improvement in magnetic flux density inside a homogeneous dielectric phantom, which is also shown to perform well for a range of depths into the phantom. The concept was experimentally demonstrated through vector network analyzer measurements and images have been taken using a 1.5T MRI scanner. The results show there is a 216% improvement in transmission efficiency, a 133% improvement in receiver signal-to-noise-ratio (SNR), and a 415% improvement in transceiver SNR for a particular transmission power when compared against a surface coil positioned at the same distance from the phantom, where these improvements are the maximum observed during experiments

An experimental investigation of the use of air jet vortex generators to control shock induced boundary layer separation

Air jet vortex generators were originally investigated by R.A. Wallis. Results showed that their effectiveness in delaying shock induced boundary layer separation was not as good as conventional vane type generators. Recent low speed wind tunnel tests carried out at City University indicated that the strength of the vortex could be increased considerably by using rectangular jet exits rather than round ones as used by Wallis. On this basis an investigation into air jet vortex generators was undertaken to find out whether similar improvements in vortex strength may be gained at transonic speeds and hence achieve a more effective method of controlling shock induced boundary layer separation. It was felt that in order to design air jet vortex generators it would be necessary to understand the mechanism by which an air jet forms a vortex, and to evaluate the effects of various jet parameters on vortex size, strength and position. The parameters investigated in this thesis were: (i) exit shape (ii) exit size (iii) jet direction (iv) jet inclination and (v) blowing pressure. The tests were conducted using a combination of high speed wind tunnel tests and flow visualisation in a water tunnel. The wind tunnel tests used the half aerofoil or 'bump technique' as used by Wallis. Bumps with thickness to chord ratios of 8%, 10% and 14% were tested. Increasing the thickness of the bumps resulted in higher local Mach numbers ahead of the shock and hence an increase in the severity of the shock induced separation. Vane vortex generators designed using the criteria laid down by H.H. Pearcey were used to establish a datum of control effectiveness. As a result of this investigation a method by which an air jet forms a vortex has been proposed together with a hypothesis on the influence of the various jet parameters. The results have shown that air jet vortex generators can be designed to be more effective than conventional vane type generators. Based on the work reported in this thesis a set of design guidelines has been proposed together with suggestions for further work

Effect of sailkite in improving trawl gear performance

Effectiveness of sailkite has been evaluated in two trawl designs, namely, a 25m high opening trawl and a 32m large mesh demersal trawl, rigged with sailkite through full scale comparative field trials. A 25m high opening trawl showed significant increase in total catch by 54.4% ribbon fish (Trichiurus spp.) alone by 138.3% with a reduction in miscellaneous catch, comprising mostly small sciaenids and juvenile fish, by 13.2% while 32m large mesh demersal trawl showed an improvement in total catch by 9%, ribbon fish by 17.2% and miscellaneous catch by 7.7%. The difference in fishing performance between the two gear arrangements has been attributed to changed net mouth configuration because of higher head line lift and also the possible herding effect on the fish in the vicinity of trawl mouth, due to addition of sailkite