A family of well behaved charge analogues of?a?well behaved neutral solution in?general relativity     

Sunil Kumar Maurya  Y. K. Gupta 《Astrophysics and Space Science》2011,332(2):481-490

A family of charge analogues of a neutral solution with g ₄₄=(1+Cr ²)⁶ has been obtained by using a specific electric intensity, which involves a parameter K. Both neutral and charged solutions are analysed physically subject to the surface density 2×10¹⁴ gm/cm³ (neutron star). The neutral solution is well behaved for 0.0<Ca ²≤0.10477 while its charge analogues are well behaved for a wide range of a parameter K (0≤K≤72) i.e. pressure, density, pressure-density ratio, velocity of sound is monotonically decreasing and the electric intensity is monotonically increasing in nature for the given range of the parameter K. The maximum mass and radius occupied by the neutral solution are 3.4126M _Θ and 18.9227 km for Ca ²=0.10447 respectively. While the red shift at centre Z ₀=0.9686 and red shift at the surface Z _a =0.4612. For the charged solution, the maximum mass and radius are 5.6111M _Θ and 17.2992 km respectively for K=3.0130 and Ca ²=0.2500, with the red shift Z ₀=3.0113 and Z _a =1.0538.  相似文献   

A longitudinal study of malaria associated with deforestation in Sonitpur district of Assam,India     

Manash J. Nath  Ashok Bora  P.K. Talukdar  N.G. Das  Sunil Dhiman  I. Baruah 《国际地球制图》2013,28(1):79-88

Assam–Arunachal forest fringed foothill area is endemic for malaria incidence. The present study deals with the temporal analysis of malaria incidence and determines its association with deforestation in 24 villages along the Assam–Arunachal forest fringed foothill area of Sonitpur district of Assam. Malaria epidemiological survey has been carried out in the study area from the year 1994 to 2005. Remote sensing (RS) technique has been used to map the areas of forest changes from the year 2000 to 2005. Geographical information system (GIS) was used to map the malaria incidence and forest cover. The study villages are endemic to malaria infections and there was increasing trend of malaria incidence over the years. The slide positivity rate (SPR) ranged from 5.1% in 1997 to 44.4% in 2005. The percentage forest cover decreased significantly from 23.6% during 2000 to 15.4% during 2005, whereas SPR was increased during 2000–2005. The present study is the first attempt to understand the role of deforestation in malaria incidence using RS and GIS in the north-eastern region of India at a micro-geographic level. The study suggests that the area is endemic to malaria transmission. The decrease in forest cover is a serious ecological concern besides its role in elevating the malaria incidence in the study area.  相似文献   

GPS-based precise orbit determination of Low Earth Orbiters with limited resources     

Amandeep Mander  Sunil Bisnath 《GPS Solutions》2013,17(4):587-594

The combination of GPS measurements and high-fidelity dynamic models via a Kalman filter/smoother, known as the reduced dynamic technique, allows 3D positioning of Low Earth Orbiters to the sub-decimeter level. Such accuracies can only be achieved if the GPS data are nearly continuous, post-processed and a dual-frequency receiver is utilized. The focus of this study is to quantitatively analyze the degradations in position accuracy in the presence of various limitations or constraints, which can be brought on by mission hardware limitations, for example, on micro- or nanosatellites. The constraints explored in this study are as follows: the use of single-frequency data only; real-time processing; limited dynamic modeling due to computing capabilities; and non-continuous GPS receiver operation due to power limits. The experiments are conducted with 6-h data arcs for 7 separate days using data from the CHAllenging Mini-Satellite Payload. A 3D root mean square (rms) error of 15 cm is observed in the best-case solution, in which dual-frequency data are post-processed with all available data. Various levels of accuracy degradations are observed as constraints are placed on this best-case solution. The 3D rms error of the post-processed, single-frequency solution is 68 cm and 1.3 m for the real-time, dual-frequency solution. In very challenging environments, for example, with the receiver on for only 10 min of a 90-min orbit, the 3D rms increases to 350 m.  相似文献   

Effect of Drying on the Index Properties of Lateritic Soils     

B. M. Sunil  H. Krishnappa 《Geotechnical and Geological Engineering》2012,30(4):869-879

Due to significant variation in geological and climatic conditions the characteristics of lateritic soils vary from place to place. Because of the prevailing climatic conditions, the laterites and lateritic soils of a particular region may be different from those found in other parts of the world. Some investigators report that the pretest drying has significant effect on the properties of soils. In such studies the authors associate the effect of drying on the properties of soils due to the mineralogy of soil. From this context there is a need to investigate the effect of sample preparation on lateritic soils prior to testing. In the present study lateritic soils from different sources in west coast region of India were studied to investigate the effect of drying on their index properties. Due to pretest drying it is observed from the results that there is a significant change in Atterberg limits and other properties of soils tested. These changes are attributed due to aggregation of particles. The observed changes are found to be permanent.  相似文献   

Source parameters of earthquakes in the reservoir-triggered seismic (RTS) zone of Koyna–Warna, Western India     

Amrita Yadav  D. Shashidhar  K. Mallika  N. Purnachandra Rao  Sunil Rohilla  H. V. S. Satyanarayana  D. Srinagesh  Harsh Gupta 《Natural Hazards》2013,69(1):965-979

New empirical relations are derived for source parameters of the Koyna–Warna reservoir-triggered seismic zone in Western India using spectral analysis of 38 local earthquakes in the magnitude range M _L 3.5–5.2. The data come from a seismic network operated by the CSIR-National Geophysical Research Institute, India, during March 2005 to April 2012 in this region. The source parameters viz. seismic moment, source radius, corner frequency and stress drop for the various events lie in the range of 10¹³–10¹⁶ Nm, 0.1–0.4 km, 2.9–9.4 Hz and 3–26 MPa, respectively. Linear relationships are obtained among the seismic moment (M ₀), local magnitude (M _L), moment magnitude (M _w), corner frequency (fc) and stress drop (?σ). The stress drops in the Koyna–Warna region are found to increase with magnitude as well as focal depths of earthquakes. Interestingly, accurate depths derived from moment tensor inversion of earthquake waveforms show a strong correlation with the stress drops, seemingly characteristic of the Koyna–Warna region.  相似文献   

Effect of Shock Loads on the Process Stability and Behavior of an Anammox Hybrid Reactor          下载免费PDF全文

Swati Tomar  Sunil Kumar Gupta 《洁净——土壤、空气、水》2016,44(9):1131-1139

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Assessment of Land use/land cover Change in the North-West District of Delhi Using Remote Sensing and GIS Techniques   总被引：1，自引：0，他引：1  

Atiqur Rahman  Sunil Kumar  Shahab Fazal  Masood A Siddiqui 《Journal of the Indian Society of Remote Sensing》2012,40(4):689-697

Land is one of the prime natural resources. A city grows not only by population but also by changes in spatial dimensions. Urban population growth and urban sprawl induced land use changes and land transformation. The land transformation is a natural process and cannot be stopped but it can be regulated. Many geographical changes at the urban periphery are associated with the transfer of land from rural to urban purpose. There is an urgent need for fast growing areas like Delhi, which can be easily done by high-resolution remote sensing data. Land use/land cover of North West of Delhi has been analyzed for the time period of 1972?C2003. The remote sensing data used in study is Aster image of 2003 with a spatial resolution of 15?m and other data of 1972 Survey of India (SOI) toposheet at the scale of 1:50,000. Supervised digital classification using maximum likelihood classifier was applied for preparing land use/land cover. A change detection model was applied in ERDAS Imagine to find out the land use/land cover during 1972 to 2003. Eight land use classes was identified but main dominated classes were built up and agricultural land. A drastic change has been recorded during 30 years of time i. e. (1972-2003). In 1972, 92.06% of the land was under agricultural practice, which reduced to 64.71% in 2003. This shows 27.35% decrease in agricultural land in three decades. On the other hand built up area was 6.31% in 1972, which increased to 34% in 2003. One of the main cause of this land use change is the population growth due to the migration in the district from small cities and rural areas of Delhi.  相似文献   

Monitoring of TDS and conductivity in groundwater in the seismically active region in NW Himalayas, India     

Arvind Kumar  Surinder Singh  Bikramjit Singh Bajwa  Sandeep Mahajan  Rajeev Kalia  Sunil Dhar 《地震学报(英文版)》2010,(3):295-299

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187Re-187Os in Lesser Himalayan sediments: Measurement techniques and preliminary results     

J. R. Trivedi  Sunil K. Singh  S. Krishnaswami 《Journal of Earth System Science》1999,108(3):179-187

The applications of the¹⁸⁷Re-¹⁸⁷Os isotope pair as a petrogenetic and geologic tracer are increasing in recent years due to several advances in the chemical extraction and purification of Re and Os, occurring at ppb levels in environmental samples, and in the precise determination of the Os isotope composition. We have established in our laboratory; based on available methods, chemical procedures and Negative Thermal Ionisation Mass Spectrometric techniques for the measurement of Re-Os concentrations in environmental samples and the Os isotope composition in them. Using these techniques, we are able to determine¹⁸⁷Os/¹⁸⁶Os ratios with a precision of ∼ 1% (±2σ_μ; twice the standard error of the mean) in several tens of picogram of Os. Preliminary analysis of black shales from the Lower Tal section of the Maldeota phosphorite mine yields a mean¹⁸⁷Re-¹⁸⁷Os model age of 597 ± 30 Ma. The¹⁸⁷Os/¹⁸⁶Os and Os concentration in black shales of the Lesser Himalaya range from 8 to 96 and 0.02 to 13 ng g^-1 respectively. The mean¹⁸⁷Os/¹⁸⁶Os in these samples is ∼ 25, significantly higher than the crustal value of ∼ 10.5, suggesting that these black shales could be an important source of radiogenic Os to the rivers draining the Himalaya and to the steady increase in¹⁸⁷Os/¹⁸⁶Os of the oceans through the Cenozoic.  相似文献   

What triggers Koyna region earthquakes? Preliminary results from seismic tomography digital array   总被引：1，自引：0，他引：1  

S. S. Rai  Sunil K. Singh  P. V. S. S. Rajagopal Sarma  D. Srinagesh  K. N. S. Reddy  K. S. Prakasam  Y. Satyanarayana 《Journal of Earth System Science》1999,108(1):1-14

The cause for prolific seismicity in the Koyna region is a geological enigma. Attempts have been made to link occurrence of these earthquakes with tectonic strain as well as the nearby reservoirs. With a view to providing reliable seismological database for studying the earth structure and the earthquake process in the Koyna region, a state of the art digital seismic network was deployed for twenty months during 1996–97. We present preliminary results from this experiment covering an area of 60 × 80 km² with twenty seismic stations. Hypocentral locations of more than 400 earthquakes confined to 11×25 km² reveal fragmentation in the seismicity pattern — a NE — SW segment has a dip towards NW at approximately 45°, whilst the other two segments show a near vertical trend. These seismic segments have a close linkage with the Western Ghat escarpment and the Warna fault. Ninety per cent of the seismicity is confined within the depth range of 3–10 km. The depth distribution of earthquakes delimits the seismogenic zone with its base at 10 km indicating a transition from an unstable to stable frictional sliding regime. The lack of shallow seismicity between 0 and 3 km indicates a mature fault system with well-developed gouge zones, which inhibit shallow earthquake nucleation. Local earthquake travel time inversion for P- and S-waves show ≈ 2% higher velocity in the seismogenic crust (0–10 km) beneath the epicentral tract relative to a lower velocity (2–3%) in the adjoining region. The high P- and S-wave velocity in the seismogenic crust argues against the presence of high pressure fluid zones and suggests its possible linkage with denser lithology. The zone of high velocity has been traced to deeper depths (≈ 70 km) through teleseismic tomography. The results reveal segmented and matured seismogenic fault systems in the Koyna region where seismicity is possibly controlled by strain build up due to competent lithology in the seismic zone with a deep crustal root.  相似文献