AN APPROACH TO REASONING ABOUT HYBRID SYSTEMS

A formal approach is presented for proving temporal properties of dynamic systems. Its main advantage is that it can be used to prove properties of hybrid systems, i.e. those whose state contains both discrete and continuous parameters. In contrast, most current temporal reasoning techniques are restricted either to purely discrete systems or to purely continuous systems. Our approach is based upon a new modeling technique called DMOD. A DMOD model of a system defines the causality relation between events in the system, using definite clauses, i.e. logic programs. Thereby, the problem of reasoning about hybrid systems is reduced to one of reasoning about the behavior of definite clauses. As these possess a simple proof theory, reasoning is substantially simplified.     

Geometric correction and radiometric normalisation of NOAA AVHRR data for fisheries applications

Sea surface temperature (SST) has been found useful for locating potential fishing grounds (PFGs). Thermal data of the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) was acquired using a microcomputer (PC/AT 486) based Direct Reception and Processing Terminal (DRPT) developed in-house to map surface thermal fronts. Geometric correction using orbital ephemeris and ground control points (GCPs) resulted in locational accuracy of 1·73 km by 2·1 km. Besides, the corrections for artificially lowering SST in case of passes with large satellite zenith angles (LSZA) through a radiance normalization based on the mean vectors and dispersion matrices to make it comparable with small satellite zenith angle (SSZA) pass is presented in this letter.     

Remote sensing of phytoplankton An attempt from the Landsat Thematic Mapper

Abstract

An atmospheric correction scheme using Landsat Thematic Mapper (TM) bands 1, 2 and 4 was developed and the data corrected for atmospheric effects due to Rayleigh scattering and aerosols. Secondly phytoplankton pigment mapping was achieved through substitution of corrected radiances in TM bands 1 and 2 into a bio-optical algorithm developed for the study area off Azhikal in the Arabian Sea. A C map showing near-surface concentrations of phytoplankton pigments (mgm_?3)and a K map showing the pigment distribution (m?1) in one attenuation length were generated.     

LINEAR CODES HAVING A SUB-BLOCK STRUCTURE

Linear codes having a sub-block structure are discussed. A substitute method of constructing codes capable of detecting and correcting combinations of error patterns in various sub-blocks is given. Codes where error-correction capabilities are determined in terms of various sub-blocks of the word length are introduced.     

Joint experiments programme in remote sensing of marine fish resources

A joint experiments programme was undertaken between three government agencies to pool their resources and expertise to develop techniques for ocean-colour sensing. During October, November and December 1981 a remote-sensing experiment was carried out using vessel-based observations and aircraft underflights synchronous to NIMBUS-7 overpasses in coastal waters off Cochin. The area is well known for the abundance of surface schools of oil sardine (Sardinella hngiceps Val) and mackerel (Rastrelliger kanagurta). An aircraft sensor (Ocean Colour Radiometer) with spectral channels similar to that of the Coastal Zone Colour Scanner (CZCS) on board the NIMBUS-7 satellite was flown to collect data at different altitudes to examine the aspects of atmospheric correction and developing a pigment algorithm. From the analysis of the data it was found that (i) vessel-based measurement of upwelling/downwelling irradiance and the derivation of the spectral diffuse attenuation coefficient and reflectance factor is useful in understanding the optical properties of ocean water, (ii) upwelled radiance data derived from the aircraft sensor could be suitably used in the understanding of atmospheric effects and in developing a pigment algorithm and (iii) a non-linear relationship is observed between fish catch and pigment concentration.     

Dynamic Headspace Concentration and Gas Chromatography of Volatile Flavor Components in Peach

Dynamic headspace concentration was used to trap peach flavor volatiles from a promising cultivar under development. Separation and identification of components were by high resolution gas chromatography and mass spectrometry. One hundred ten compounds including alcohols, aldehydes, alkanes, esters, ketones, aromatic hydrocarbons, sulfur-containing compounds and some miscellaneous compounds were positively or tentatively identified. Forty-six compounds were positively identified in peach for the first time.     

Location of tuna resources in Indian waters using NOAA AVHRR data

Abstract

The world demand for tuna resources is ever increasing and there is scope for better economic returns in terms of foreign exchange earnings. It is one of the least exploited resources of the Indian seas. Remote sensing based studies on the tuna environment began in the seventies in the Gulf of Guinea. This study helped to establish a fishing strategy during the eighties. But so far this has not been attempted in Indian waters. With the basic understanding that most of the species of tuna respond directly to temperature, a study using NOAA AVHRR data was carried out to locate tuna resources. Thermal data of NOAA AVHRR for eight dates in the 1989-90 season were analysed to generate sea surface temperature (SST) images. Catch per unit effort (CPUE) of tuna longline data acquired from the Fishery Survey of India pertaining to fishing conducted by chartered vessels, was plotted on the SST images. Yellowfin tuna (YFT) comprises the maximum catch plus small quantities of marlins. It was observed that almost all the data points were located near the edge of warm water (27°-29°C). A relation between average CPUE of YFT and multi-channel sea surface temperature (MCSST) charts generated by OPC (the Ocean Products Centre) of NOAA was established. It shows on an average an increasing trend in the CPUE of YFT from 26° C (hooking rate ～ 1 per cent) to 29°C (hooking rate ～3 65 per cent) and then shows a drop with further rise in temperature. Since YFT is known to be present in a wide range of temperatures, it can be concluded that the location of warm water edges having a gradient of about 1°C and the above mentioned range of temperature will be desirable in locating tuna potential areas.