Mass fall-back and accretion in the central engine of gamma-ray bursts     

Pawan Kumar  Ramesh Narayan  Jarrett L. Johnson 《Monthly notices of the Royal Astronomical Society》2008,388(4):1729-1742

  相似文献   

A Low-Frequency (30 – 110 MHz) Antenna System for Observations of Polarized Radio Emission from the Solar Corona     

R. Ramesh  C. Kathiravan  M. S. SundaraRajan  Indrajit V. Barve  C. V. Sastry 《Solar physics》2008,253(1-2):319-327

An interferometer antenna system to observe polarized radio emission from the solar corona at different frequencies in the range 30?–?110 MHz has been commissioned recently by the Indian Institute of Astrophysics at the Gauribidanur Radio Observatory (latitude 13°36^′12^′′N and longitude 77°27^′07^′′E), about 100 km north of Bangalore (http://www.iiap.res.in/centres_radio.htm). This paper describes the antenna system, associated analog/digital receiver setup, calibration scheme, and preliminary results.  相似文献   

Autonomous underwater vehicles - challenging developments and technological maturity towards strategic swarm robotics systems     

N. Vedachalam  R. Ramesh  V. Bala Naga Jyothi  V. Doss Prakash  G. A. Ramadass 《Marine Georesources & Geotechnology》2013,31(5):525-538

ABSTRACT

Reliable power supply, precise position determination and effective communication are the key requirements for strategic autonomous underwater vehicles (AUV) involved in long duration scientific missions, search operations and when operated as a swarm. The paper presents the challenging range of AUV developed for deep water, Polar and intervention applications; demanding technical requirements for strategic AUV; reliability modeling done on the lithium-ion batteries to identify the redundancy requirements for achieving near-zero failures; navigation model to estimate the achievable level of position accuracies using the state-of-the-art navigation system; limitations in underwater communication; and their importance in realizing vehicle autonomy and swarm intelligence. It is identified that a strategic grade Doppler velocity- aided inertial navigation system could provide position accuracies of about 0.5% of the distance travelled when navigated using sea bottom or ice reference, and a 38?kWh lithium-ion battery pack requires about 7% redundant battery capacity to achieve a failure probability of <?1% in a period of 1 year.  相似文献   

Fine Particles (PM2.5) in Residential Areas of Lucknow City and Factors Influencing the Concentration     

S. C. Barman  Ramesh Singh  M. P. S. Negi  S. K. Bhargava 《洁净——土壤、空气、水》2008,36(1):111-117

Urban populations are exposed to a high level of fine and ultrafine particles from motor vehicle emissions which affect human health. To assess the hourly variation of fine particle (PM_2.5) concentration and the influence of temperature and relative humidity (RH) on the ambient air of Lucknow city, monitoring of PM_2.5 along with temperature and RH was carried out at two residential locations, namely Vikas Nagar and Alambagh, during November 2005. The 24 h mean PM_2.5 concentration at Alambagh was 131.74 μg/m³ and showed an increase of 13.74%, which was significantly higher (p < 0.05) than the Vikas Nagar level. The 24 h mean PM_2.5 on weekdays for both locations was found to be 142.74 μg/m³ (an increase of 66.23%) which was significantly higher (p < 0.01) than the weekend value, indicating that vehicular pollution is one of the important sources of PM_2.5. The mean PM_2.5 at night for all the monitoring days was 157.69 μg/m³ and was significantly higher (p < 0.01) than the daytime concentration (89.87 μg/m³). Correlation and multiple regressions showed that the independent variables, i. e., time, temperature, and RH together accounted for 54%, whereas RH alone accounted for 53% of total variations of PM_2.5, suggesting that RH is the best influencing variable to predict the PM_2.5 concentration in the urban area of Lucknow city. The 24 h mean PM_2.5 for all the monitoring days was found to be higher than the NAAQS recommended by the US‐EPA (65 μg/m³) and can be considered to be an alarming indicator of adverse health effects for city dwellers.  相似文献   

Medium Range Prediction of Summer Monsoon Activities over India vis-a-vis Their Correspondence with the Observational Features     

Swati Basu  K. J. Ramesh  Z. N. Begum 《大气科学进展》1999,16(1):133-146

１．ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｉｎｉｔｉａｔｉｏｎｏｆｔｈｅｃｒｏｓｅｑｕａｔｏｒｉａｌｆｌｏｗｏｆｔｈｅＳｏｍａｌｉａｃｏａｓｔｄｕｒｉｎｇＭａｙｉｎｒｅｓｐｏｎｓｅｔｏｔｈｅｈｅａｔｉｎｇｏｖｅｒｔｈｅＳｏｕｔｈＡｓｉａｎｃｏｎｔｉｎｅｎｔｍ...  相似文献   

Design and Development of Onsite Biofilter Unit for Effective Remediation of Contaminants from Wastewater     

Simranjeet Singh  Praveen C Ramamurthy  Daljeet Singh Dhanjal  Sikander Rana  Deepika Bhatia  Ramesh Kanwar  Neeta Raj Sharma  Joginder Singh 《洁净——土壤、空气、水》2023,51(3):2100396

Agricultural biomass is proven ecofriendly and effective adsorbent for the remediation of contaminants from wastewater. Here, rice husk biochar (600 °C) prepared by a one-step pyrolysis method is used for the remediation of different contaminants in real samples. An onsite biofilter unit is fabricated with parallel trenches of different layers of coconut coir and biochar and is used as a biofiltration unit. The efficiency of the designed unit is assessed for the removal of different contaminants in pilot-scale experiments. Results show that removal efficiency varies from metal to metal and ranges from 5.52% to 90.76% using the biofilter unit. Fourier-transform infrared spectroscopy, scanning electron microscopy with energy dispersive X-ray analysis, carbon, hydrogen, nitrogen, and Brunauer–Emmett–Teller analysis before and after the adsorption represent the changes in the morphology and surface functionalization of the biochar. Results indicate that the designed biofilter unit could also be used as a promising agent for the remediation of pharmaceutical and other emerging contaminants from wastewater.  相似文献   

Assessment of quality and impact of full resolution TOVS temperature profile data on the operational global data assimilation-forecast system of India     

V. S. Prasad  K. J. Ramesh  A. K. Bohra  R. C. Bhatia 《Meteorology and Atmospheric Physics》1998,68(3-4):197-212

Summary TOVS temperature profile data (SATEM) at its full resolution (85 km) has now become available in India on experimental basis. An attempt is made in this study to examine the quality and impact of this on the medium range forecasts over India and neighbourhood. For this purpose, a seven day period starting from 15 March 1996 is chosen to study the impact of the data on the global analysis-forecasting system operational in India. Though one week data is utilized for the impact study, the complete data of march 1996 is used for examining quality, representativeness and consistency of the retrievals. In the operational system of the National Centre for Medium Range Weather Forecasting (NCMRWF), all types of data, including coarse resolution (500 km) global TOVS retrievals-coarse grid SATEM (CGS) data, received on GTS at hourly intervals are used in the assimilation cycle. For the present study the assimilation cycle is repeated for the above period by including high resolution data over the geographical regions covered by the New Delhi's high resolution picture transmission (HRPT) station and simultaneously removing coarse resolution SATEM data. The analysis and forecast fields thus generated are compared with the corresponding operational archives. The impact of the data is examined in terms of various objective scores and through circulation characteristics.The study reveals that the quality of high resolution SATEM (HRS) data is satisfactory and is such that it can be utilized in the global data assimilation system on real-time basis. A general improvement in the RMSE and ACC scores of the medium range forecasts is found over the data void equatorial sectors of the Indian Ocean after the incorporation of the HRS data fields in the assimilation cycle. With regard to a typical easterly wave activity of moderate intensity during the period of experimentation a marginal modulation in low level vorticity and divergence forecasts is found to be improving the precipitation magnitudes over the south peninsular India as well.With 11 Figures  相似文献   

Rupture histories of two stable continental region earthquakes of India     

D. S. Ramesh  C. H. Estabrook 《Journal of Earth System Science》1998,107(3):L225-L233

  相似文献   

TOPEX/Poseidon and Jason-1: Absolute Calibration in Bass Strait, Australia   总被引：2，自引：0，他引：2  

Christopher Watson  Neil White  Richard Coleman  John Church  Peter Morgan  Ramesh Govind 《Marine Geodesy》2004,27(1):107-131

Updated absolute calibration results from Bass Strait, Australia, are presented for the TOPEX/Poseidon (T/P) and Jason-1 altimeter missions. Data from an oceanographic mooring array and coastal tide gauge have been used in addition to the previously described episodic GPS buoy deployments. The results represent a significant improvement in absolute bias estimates for the Bass Strait site. The extended methodology has allowed comparison between the altimeter and in situ data on a cycle-by-cycle basis over the duration of the dedicated calibration phase (formation flight period) of the Jason-1 mission. In addition, it has allowed absolute bias results to be extended to include all cycles since the T/P launch, and all Jason-1 data up to cycle 60. Updated estimates and formal 1-sigma uncertainties of the absolute bias computed throughout the formation flight period are 0 ± 14 mm for T/P and +152 + 13 mm for Jason-1 (for the GDR POE orbits). When JPL GPS orbits are used for cycles 1 to 60, the Jason-1 bias estimate is 131 mm, virtually identical to the NASA estimate from the Harvest Platform off California calculated with the GPS orbits and not significantly different to the CNES estimate from Corsica. The inference of geographically correlated errors in the GDR POE orbits (estimated to be approximately 17 mm at Bass Strait) highlights the importance of maintaining globally distributed verification sites and makes it clear that further work is required to improve our understanding of the Jason-1 instrument and algorithm behavior.  相似文献   

June 19 2015 Rainfall Event Over Mumbai: Some Observational Analysis     

Sudipta Sarkar  Ramesh P. Singh 《Journal of the Indian Society of Remote Sensing》2017,45(1):185-192

Some of the major metropolitan centers in the world are highly susceptible to flash floods and major disruptions, owing to sudden and excessive rainfall events. The city of Mumbai, India’s financial capital, suffered one such event on 19 June, 2015. This was a second event of such nature, following the landmark event of 26 July, 2005. Such extreme rainfall events are often brought about by certain rapidly developing, local disturbances, which if actively monitored, may be provide important information that can be of great use for early warning to civic authorities and emergency planners. In this paper, we have analyzed a number of different meteorological and remotely sensed parameters, a few days before the actual event, to track the development and eventual culmination of a “perfect storm” that affected Mumbai and left the city tattered. We show how regional upper layer disturbance patterns are developed, induced by warming of sea-surface temperature (SST) and sustained by instability in the atmospheric boundary layers to quickly develop into massive cyclonic storms.  相似文献