Petrochemical studies on trap rocks around tandur,Andhra Pradesh,India

The basalts of Tandur and adjoining areas in Andhra Pradesh are olivinefree tholeiites. Major element abundances in thirty samples indicate that these basalts are poorer in silica and richer in iron, magnesium, phosphorous and titanium relative to the normal basalts. The high Fe₂O₃/FeO ratio (1.07) could mean either that the traps were extruded under oxidising conditions or that the magma held excess amount of water. The relative enrichment of iron and depletion of silica in the Tandur basalts may have been controlled by the partial pressure of oxygen, presence of significant amounts of water, depth of generation of source magma etc.     

Determination of moisture changes prior to the onset of south-west monsoon over Kerala using NOAA/TOVS satellite data

Summary The temperature and moisture data from TIROS operational vertical sounder (TOVS) are examined to obtain humidity parameters like, mid and upper tropospheric water vapour, and scale height of water vapour. Their usefulness in characterizing the onset of south-west (SW) monsoon over India is studied. The NOAA satellite data (finished product) with a resolution of 2.5° lat/lon are used to obtain these parameters during and prior to the SW monsoon season over selected regions during 1979 to 1985. The pentad averaged values in the western Indian Ocean showed an increase in scale height of water vapour and mid-tropospheric moisture (700–500 mb) over about 8 to 10 days prior to the onset over Kerala coast. The association of the moisture flux across the Indian Ocean and the rainfall over Kerala coast has also been examined. Results showed that the gradient of middle level moisture is stronger in the case of rainfall deficit years.With 13 Figures     

Terrestrial heat flow in the North Island of New Zealand

Large variations in terrestrial heat flow from 21 to 209 mW/m² have been observed over the North Island, New Zealand. This is generally in good agreement with the pattern of existing geological and geophysical observations. A high heat flow zone with a value of 92 ±3 mW/m², which corresponds to melting temperatures near the base of the crust, is delineated in the northern part of the Taranaki Basin. In the rest of the island, heat flow appears to be low to normal, but some isolated high values are also found. Observed results are interpreted in terms of crust and mantle structure in a region of plate subduction.     

Correlation analysis of geothermal data for the sedimentary basins of India

Correlation coefficients are calculated from the available geothermic data for the sedimentary basins of India to reveal some significant association between: (1) heat flow and thermal conductivity, (2) heat flow and geothermal gradient, (3) geothermal gradient and thermal conductivity, and (4) heat flow and related crustal thickness. The observed negative correlationship between heat flow and thermal conductivity for all Indian sedimentary basins suggests corresponding changes in crustal thickness.     

Estimation of fundamental period for structures supported on pile foundations

One of the significant effects of considering soil-structure interaction in the analysis of structures is the increase in the fundamental natural period compared to the fundamental natural period of a similar structure, fixed at the base. Applied Technology Council (ATC) originally set forth some provisions to calculate the fundamental natural period of flexible based structures using the period of a similar structure, fixed at the base, and lateral and rocking stiffness coefficients of the foundation. These provisions became the basis of current soil-structure interaction recommendations in several building codes. The fundamental natural periods of structures founded on different types of foundations computed using recommendations of the ATC are compared with those computed using a simplified model to perform soil-structure interaction of shear-type structures. Results show that the provisions given in ATC may be used for structures supported on shallow footings but may not be applicable for structures supported on pile foundations or foundations having the ratio of lateral to rotational stiffness coefficients different from those of shallow foundations. An equation, similar to the equation recommended by ATC, is presented to estimate the fundamental natural period of structures supported on pile foundations. This revised version was published online in July 2006 with corrections to the Cover Date.     

Remote Sensing of suspended sediments along the Tamil Nadu coastal waters

Indian Remote Sensing satellite (IRS) 1A & 1B digital data in combination with field measurement were used to map distribution and concentration of suspended sediments along the Tamil Nadu coastal waters for monsoon and non-monsoon periods. Qualitative suspended sediment mapping was done for entire Tamil Nadu coast while quantitative studies were taken at two selected sites (eg. Tuticorin and Ennore). For qualitative mapping both monsoon (17-12-90) and non-monsoon (18-4-90) season data were analysed by level slicing technique and a qualitative scale was assigned to different sediment classes based on tonal variations. The suspended sediment concentration (SSC) samples were collected on April 15, 1992 and March 10, 1992 around Ennore and Tuticorin coastal waters respectively, synchronous to IRS-1A satellite overpass. This data was used for quantitative estimation of SSC using digital chromaticity technique. The study shows that the plumes of high suspended sediment concentration are contributed from the nearshore wetlands and river mouths and were finally dispersing towards Jaffna coast. Different classes of high to low SSC values ranging from less than 5 mg/L in offshore areas to 21 mg/L in nearshore of Tuticorin were also delineated. The dispersal pattern of the sediments on different is discussed.     

Buckling and vibration analysis of flexible beams resting on an elastic half-space

The present paper deals with the buckling and vibration of prismatic beams resting on an elastic half-space. The computational procedure developed herein utilizes the advantages of both an analytical approach and a finite element scheme. This is accomplished by deriving exact frequency and axial force dependent stiffness matrices using the analytical solutions of the governing differential equation as ‘shape functions’. The major advantages of the proposed approach over previous ones are pointed out and discussed in detail. Numerical results demonstrating the performance of the proposed method are presented in the final part of the paper.     

A Study on Soil Erosion in Pasighat Town (Arunachal Pradesh) India

Pasighat which lies on the foothills of the Himalayas is one of the important townsof Arunachal Pradesh. A very turbulent river named Siang flows through the townand causes frequent flash floods, inundating the low-lying areas. This river and townis also under threat due to continuous soil erosion. This soil erosion affects theneighbouring state of Assam as well. Due to the soil erosion this river known asBrahmaputra in Assam is constantly changing its course making a large numberof water channels with sand bars thus inundating vast cultivable land every year.The study analyses the cause of the problem at Pasighat in the backdrop of theexisting river system, morphology and the geographical evolution of the TransHimalayas.     

Experimental evidence of ion plasma oscillations in the apogee region of the Nike-Apache rocket

Several Nike-Apache rockets with Lang muir probe payloads were launched from Thumba (India) to study the disturbances produced by a moving rocket. The rockets were launched during different times of the day and night. It was found that low frequency ion plasma oscillations of the order of 1 KHz frequency were observed in the altitude region 145 to 200 km. This altitude region corresponds to the rocket apogee region where the rocket velocity is subsonic. The amplitude of the fluctuations was about 1 to 2% and was found to be dependant on rocket velocity electron density in the ambient medium, rocket spin and probe voltage. It was noticed that in the case of Centaure and Petrel rockets such types of oscillations were not observed. The Nike-Apache rockets are made of aluminium while Centaure and Petrel rockets are made of stainless steel.