Rice-fish culture: status and potential for increased production in the southwestern states of India

The scope of increasing production through rice-fish integration, suitable for coastal districts of Kerala, Karnataka, Goa and Maharashtra, is reviewed. The method of adopting the lowlying freshwater rice fields to raise 2 rice crops along with 4-species fish culture, followed by a third non-cereal summer crop in a year, is discussed. A calendar of operation and economics of the system are presented.

Fishery potential of the Gulf of Kachchh

Fishery potential of the interior Gulf of Kachchh and adjacent creek regions was reported for the first time as baseline data for future ecological assessment. The experimental trawling and gill netting indicated that the inner Gulf (av. 7.8 kg/h) was three times more productive than the creek (av. 2.3 kg/h). The number of species found in the Gulf and creek were respectively 34 and 20 suggesting good biodiversity of the living resources of the area.

Fishery potential along the Indian coastal waters between Porbandar and Ratnagiri

As part of the ongoing marine pollution monitoring programme the coastal stretch between Porbandar and Ratnagiri was considered to assess the fishery potential. Regular experimental trawling was done off Porbandar, Veraval, Diu, Hazira, Daman, Bassein, Bombay, Murud and Ratnagiri at a depth range of 5-25 m during 1988 to 1992. The catch rate varied from 1.2 to 225 kg/h (av.20.3 kg/h). Zonewise maximum catch (av.56.8 kg/h) was observed off Ratnagiri followed by off Porbandar (av.30.1 kg/h), off Bombay (av.23.9 kg/h) and off Murud (av.19.8 kg/h). The area between Hazira and Daman was poor in fish catch. In general, the catch rate showed a fluctuating trend during the period of observation. Among the hundred species identified from the collections the most common species were Coilia dussumieri, Johnius glaucus, Scoliodon laticaudus, Lepturacanthus savala, Harpadon nehereus, Sardinella longiceps, Pampus sp. and Congresox sp. The community structure and species assemblage at different zones are discussed in detail.

Potential tuning of porous silicon luminescence

Electrochemical investigations were conducted of the effect of potential on the luminescence of porous silico (PS). The use of liquid contacts allows the potential to be controlled during studies of the photoluminescence (PL) and electroluminescence (EI). The PL and EL of PS samples prepared from n-type substrates is considered. To obtain luminescence from such PS it is necessary to generate holes in the valence band. This is achieved by either photoexcitation or an electrochemical process involving the reduction of persulfate. This paper describes the investigations of the effect of potential on the PL and EL of PS. A mechanism of 'potential tuning' based on electron occupancy and Auger quenching is then proposed.

A Preliminary survey of 21 Ceylon lakes. 2. Limnology and fish production potential

Some morphometric, physical and chemical conditions of 21 lakes in Ceylon are described. The values for the organic matter in the plankton and for the dry weight of bottom fauna in the lakes have been calculated. These values have been utilised to evaluate the potential fish production figures for the lakes. Fishing trials were made in each lake. Suggestions regarding mesh sizes and time of fishing are put forward.

Wake, shock and potential field interactions in a 1.5 stage turbine: Part I: Vane-rotor and rotor-vane interaction

The composition of the time-resolved surface pressure field around a high-pressure rotor blade caused by the presence of neighboring blade rows was studied, with the individual effects of wake, shock and potential field interaction being determined. Two test geometries were considered: first, a high-pressure turbine stage coupled with a swan-necked diffuser exit duct; secondly, the same high-pressure stage but with a vane located in the downstream duct. Both tests were carried out at engine-representative Mach and Reynolds numbers. By comparing the results to time-resolved computational predictions of the flowfield, the accuracy with which the computation predicts blade interaction was determined. It was found that in addition to upstream vane-rotor and rotor-downstream vane interactions, a new interaction mechanism was found resulting from the interaction between the downstream vane's potential field and the upstream vane's trailing edge potential field and shock.

Wake, shock and potential field interactions in a 1.5 stage turbine: Part II: Vane-vane interaction and discussion of results

The composition of the time-resolved surface pressure field around a high-pressure rotor blade caused by the presence of neighboring blade rows was studied, with the individual effects of wake, shock and potential field interaction being determined. Two test geometries were considered: first, a high-pressure turbine stage coupled with a swan-necked diffuser exit duct; secondly, the same high-pressure stage but with a vane located in the downstream duct. Both tests were carried out at engine-representative Mach and Reynolds numbers. By comparing the results to time-resolved computational predictions of the flowfield, the accuracy with which the computation predicts blade interaction was determined. Evidence was obtained that for a large downstream vane, the flow conditions in the rotor passage, at any instant in time, are close to being steady state.