Impact of Topography on Accuracy of Land Cover Spectral Change Vector Analysis Using AWiFS in Western Himalaya

The present paper discusses the impact of topography on accuracy for land cover classification and “from-to class change using improved spectral change vector analysis suggested by Chen et al. (2003). Two AWiFS sensor images of different dates are used. Double Window Flexible Pace Search (DFPS) is used to estimate threshold of change magnitude for change/no change classes. The topographic corrections show accuracy of 90% (Kappa coefficient 0.7811) for change/no change area as compared to 82% (Kappa coefficient 0.6512) in uncorrected satellite data. Direction cosines of change vector for determining change direction in n-dimensional spectral space is used for image classification with a minimum distance categorizing technique. The results of change detection are compared (i) Improved CVA with conventional two bands CVA and (ii) Improved CVA before and after topographic corrections. The improved CVA with topographic correction consideration using slope match show maximum accuracy of 90% (Kappa coefficient 0.83) as compared to conventional CVA which show maximum accuracy of 82% (Kappa coefficient 0.6624). The overall accuracy of ”from- to class using improved CVA increases from 86% (Kappa coefficient 0.7817) to 90% (Kappa coefficient 0.83) after topographic corrections. The improved CVA with proper topographic corrections is found to be effective for change detection analysis in the rugged Western Himalayan terrain.     

Heavy metal distribution and environmental status of Doon Valley soils, Outer Himalaya, India

 Doon Valley is surrounded by two major river systems (Ganga and Yamuna) on either side, with a water divide passing nearly across the centre of the valley, and is sandwiched between two mountain ranges in the fragile ecological systems of the Himalayan foothills. In total 398 soil samples were collected from the valley in a grid pattern (∼1 sample per 2 km²) and investigated for their heavy metal (Cr, Cu, Ni, Pb and Zn) abundances that are environmentally sensitive. Comparison of the heavy metal abundances with the contamination threshold values (CTV) revealed that most of these elemental abundances in Doon Valley soils fall well within the range of the uncontaminated to slightly contaminated category. In the case of Cr and Ni, a sizeable number of samples exceeded the CTV (250 and 100 mg kg^–1 respectively) with an overall background value of 109 and 52 mg kg^–1 respectively. Sites of high Cr and Ni mostly occur in the Ganga Catchment (GC) sector that includes even relatively undisturbed forestland. The source of this contamination is attributed to geological factors which indicate contribution from the mafic volcanics of the Lesser Himalaya. This is also consistent with the distribution pattern of Mn and Fe, though their abundance levels are not alarming. The background concentration of Pb is low (22 mg kg^–1) in Doon Valley soils; however, signs of gradual Pb contamination are palpable in and around the centre of the Dehra Dun city and along the highways. Aluminium normalized heavy metal ratios were found to exhibit narrow variability in the case of Cu, Ni and Cr and had good correlation with Al, indicating their affinity and association with the clay minerals. On the other hand, Pb and Zn seem to be associated with non-silicate sources. Received: 7 January 2000 · Accepted: 30 July 2000     

Design of a High Efficiency Acoustic Phased Array Antenna for an Acoustic Wind Profiler

Summary Improvements to the performance of acoustic wind profilers necessitate designing efficient acoustic antennas for the profilers, so that weak echoes can be received to enhance data availability. An efficient acoustic antenna needs to optimize electrical to acoustic and acoustic to electrical conversion efficiency as measured at the antenna axis. It also needs to provide a good directional response, and be able to handle increased electrical power. Phased array antennas, designed using piezo-electric transducers, should provide better characteristics in this regard. In the present study several different transducer elements were characterized with respect to their relative efficiencies. On the basis of this characterization, measurement of acoustic background noise at the expected site of antenna location and comparative study of atmospheric molecular absorption at the element peak efficiency frequencies, it is concluded that Motorola KSN 1025 A transducer is the best speaker element for the array antennas for profilers up to around 500 meters. The present array antenna has been designed using 104 KSN 1025 A piezo-electric transducer elements. The corner elements were removed from a 16 × 8 element speaker matrix, yielding an irregular octagonal pattern. Before installing the elements in the array, each element was individually characterized for its transmit and receive conversion efficiency, and variations in the product of these efficiencies (conversion gain) amongst the different elements, has been usefully employed to taper the array gain from centre to periphery. The antenna was systematically characterized, in an acoustic anechoic chamber, with respect to its axial transmit and receive conversion efficiencies and directional response. Received October 14, 1998 Revised March 1, 1999     

The two mooring dolphin concept for exposed tanker terminals

The conventional design for a tanker terminal provides for two or more mooring dolphins on each side of the breasting dolphins. Head and stern lines are attached to the outer mooring dolphins and breast lines to the inner mooring dolphins. In exposed locations, the expense of construction may be significantly reduced if a way can be found to reduce the number of mooring dolphins required for the safe mooring of ships at a fixed berth.This paper, based on studies for a proposed terminal for tankers from 25,000 to 100,000 DWT in the Bay of Fundy in Eastern Canada, discusses the possibility of reducing the total number of mooring dolphins from four to two. Results of a static analysis of mooring loads due to wind and current and a hydraulic model test for mooring loads due to waves are presented.Operational aspects of the two mooring dolphin layout are discussed. It is concluded that the two mooring dolphin concept is an efficient mooring arrangement which will reduce the cost of fixed berth terminals. It is noted, however, that many of the smaller, older tankers in the world fleet do not have adequate mooring equipment to use such a berth and it is recommended that the necessary change in deck equipment be made to allow for such an arrangement. It is also recommended that ship personnel acquaint themselves with mooring procedures using breast and spring lines alone.     

Hydrogeology of a buried channel,village Shenoli,District Satara,Maharashtra

A buried channel has been located, in the basaltic terrain, near village Shenoli, District Satara, Maharashtra. It is composed of a gritty mass formed of a semi-consolidated material. The resistivity value of the semi-consolidated formation is 6.30 Ohm — m whereas the resistivity values of the vesicular basalts range between 18 and 32 Ohm-m. The specific capacity, unit area specific capacity, specific capacity index, transmissivity and hydraulic conductivity, with respect of the buried channel, are 609.07 LPM/m of drawdown, 12.12 LPM/m³, 95.47 LPM/m², 353.26 m²/day and 55.37 m/day, respectively whereas the values of these parameters for basalt aquifers range from 67 to 117 LPM/m of drawdown, 0.7 to 4.27 LPM/m³, 14.08 to 31.04 LPM/m², 33.5 to 73.71 m²/day and 9.44 to 18.32 m/day, respectively. A comparison of the well characteristics and aquifer parameters reveal that the buried channel with semi-consolidated formation has distinctly better groundwater yielding properties.     

Geochemistry,petrogenesis and tectonic significance of the basic volcanic units of the Zildat ophiolitic mélange,Indus suture zone,eastern Ladakh (India)

Abstract

Basic volcanic rocks within the Zildat ophiolitic mélange of Indus suture zone in eastern Ladakh are medium to fine grained with partially preserved primary texture and mineralogy. These rocks are predominantly alkaline basalt with high Nb/Y and enriched incompatible trace element characteristics, similar to those of the oceanic island basalt (OIB). The minor sub-alkaline basaltic rocks resemble N-type mid ocean ridge basalt (N-MORB) but with much lower abundances of incompatible trace element including REE. The alkaline rocks probably generated through variable, but low degrees of partial melting of enriched mantle source and evolved through high pressure olivine and clinopyroxene fractionation. Low pressure plagioclase and Fe- Ti oxide do not appear to be major fractionating phases. Limited data on the sub-alkaline rocks suggest that their parental melts were derived from mantle sources some what similar to that of N- MORB. Significant role of added cumulates of olivine, clinopyroxene and Fe- Ti oxides is also indicated in their genesis. Ophiolitic mélanges all along the Indus suture zone appear to have formed due to the accumulation of mélange material in the upper part of the subduction zone where they suffered glaucophanitic (blueschist) metamorphism and retrograded partially to greenschist grade as these were subsequently obducted to its present position probably during the Cenozoic Himalayan orogeny due to collision of Indian and Eurasian plates.     

Studies of proton-irradiated cometary-type ice mixtures

Radiation synthesis has been proposed as a mechanism for changing the nature of the outer few meters of ice in a comet stored 4.6 billion years in the Oort cloud and may explain some of the differences observed between new and more evolved comets. Cometary-type ice mixtures were studied in a laboratory experiment designed to approximately simulate the expected temperature, pressure, and radiation environment of the interstellar Oort cloud region. The 2.5- to 15-μm infrared absorption features of thin ice films were analyzed near 20°K before and after 1 MeV proton irradiation. Various ice mixtures included the molecules H₂O, NH₃, CH₄, N₂, C₃H₈, CO, and CO₂. All experiments confirm the synthesis of new molecular species in solid phase mixtures at 20°K. The synthesized molecules, identified by their infrared signatures, are C₂H₆, CO₂, CO, N₂O, NO, and CH₄ (weak). Synthesized molecules, identified by gas chromatographic (GC) analysis of the volatile fraction of the warmed irradiated ice mixture, are C₂H₄ or C₂H₆, and C₃H₈. When CH₄ is present in the irradiated ice mixture, long-chained volatile hydrocarbons and CO₂ are synthesized along with high-molecular-weight carbon compounds present in the room temperature residue. Irradiated mixtures containing CO and H₂O synthesize CO₂ and those CO₂ and H₂O synthesize CO. Due to radiation synthesis, ～1% of the ice was converted into a nonvolatile residue containing complicated carbon compounds not present in blank samples. These results suggest that irrespective of the composition of newly accreted comets, initial molecular abundances can be altered and new species created as a result of radiation synthesis. Irradiated mixtures exhibited thermoluminescence and pressure enhancements during warming; these phenomena suggest irradiation synthesis of reactive species. Ourbursts in new comets resulting from similar radiation induced exothermic activity would be expected to occur beginning at distances of the order of 100 AU.