Excitation equilibrium for low lying levels in Cii,Niii, Oiv,Nevi, Mgviii,Six, and Siii     

Suresh Chandra 《Solar physics》1978,58(2):291-297

The populations of the excited state ² P _3/2 relative to the ground state ² P _1/2 have been investigated in C ii, N iii, O iv, Ne vi, Mg viii, Si x, and Si ii by considering all the radiative and collisional processes including the collisional transitions to the higher states which cascade to the upper level. The relative populations are used for the calculation of the line emissivities. The intensities of 76 320, 30 258 and 14 302 lines of Nevi, Mgviii, and Six ions respectively in the chromosphere-corona transition region are also calculated.  相似文献   

Cometary impacts and ice-ages     

Fred Hoyle  Chandra Wickramasinghe 《Astrophysics and Space Science》2001,275(4):367-376

Cycles of glaciation with an average period of 100 kyr are mediatedby impacts of cometary bolides. Ice-age conditions are dry and dusty withlow rates of precipitation. Comets in the mass range 10¹⁵ -10¹⁶ gimpacting the oceans could release enough water vapour into the atmosphereto enhance a depleted greenhouse effect. The energy deposited in the oceanswould also warm the surface layers, thus starting up anevaporation-precipitation cycle which ushers in warmer interglacialinterludes. The latter have neutral stability and are necessarilyshort-lived, eventually drifting back to glacial conditions on timescalesof 10 kyr.  相似文献   

GEOLOGICAL STUDIES OF METAMORPHIC ROCKS IN THE VICINITY OF M.C.T./LESSER HIMALAYAN SHEAR ZONE, PARTS OF SIKKIM HIMALAYAS     

Chandra Shekhar Dubey 《地学前缘》2000,(Z1)

GEOLOGICAL STUDIES OF METAMORPHIC ROCKS IN THE VICINITY OF M.C.T./LESSER HIMALAYAN SHEAR ZONE, PARTS OF SIKKIM HIMALAYAS  相似文献   

Geological Studies of Metamorphic Rocks in the Vicinity of M. C. T./Lesser Himslayan Shear zone, Parts of Sikkim Himalayas     

Chandra Shekhar Dubey 《地学前缘》2000,(Z1)

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Performance evaluation of soil mixtures treated with graphite and used as barrier fill material for high-level radioactive waste repository     

Liu  Xiaoyan  Congress  Surya Sarat Chandra  Cai  Guojun  Liu  Songyu 《Acta Geotechnica》2021,16(5):1487-1507

Buffer/backfill material is an important engineering barrier in a deep geological repository of high-level radioactive waste (HLW). Its thermo-hydro-mechanical (THM) performance is very important for the safe and stable operation of the HLW repository system. Natural graphite powder mixed with sodium bentonite forms a buffer/backfill material that can dissipate heat quickly and provide strong isolation. In this paper, the THM characteristics of bentonite–sand–graphite–polypropylene fiber (BSGF) mixtures, used as a buffer/backfill material, were studied through a series of laboratory tests. The influence of graphite and polypropylene fiber contents on thermal conductivity, swelling pressure, hydraulic conductivity, and strength properties of BSGF mixtures with different sand contents was analyzed. Experimental results indicated that the graphite content, the maximum graphite mesh number, and the initial dry density of bentonite–graphite mixtures influenced the thermal conductivity of bentonite–graphite mixtures. The addition of polypropylene fiber was found to enhance the shear strength and inhibit cracking without significantly affecting the expansivity, permeability, and thermal conductivity of the BSGF mixtures. This study provides a new buffer/backfill material that can improve the stability, functionality, and thermal efficiency of the HLW repository.

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Analysis of Families of Triple Close Approaches Occurring inStellar Systems in Three Dimensions (II)     

Navin Chandra  K.B. Bhatnagar 《Astrophysics and Space Science》2000,271(4):395-422

This is the second paper of a trilogy dealing with the role of triple encounters with low initial velocities and equal masses in the evolution of stellar systems in three dimensional space. It shows how a condition of complete collapse may be perturbed to obtain well-established families of asymmetric triple close approaches with systematic regularity of escape with the formation of a binary. The main result is that when perturbation is introduced two close approaches called the first close approach and the second close approach occur in the same plane but the binary formed and the escaper are not in that plane. Further it is observed that the conjecture of Szebehely (1977) viz. `The measure of escaping orbits is significantly higher than the measure of stable orbits' is likely to be true. The third and last paper offers applications in stellar systems. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Spectral analysis of wind and temperature components during lightning in pre-monsoon season over Ranchi     

Arun K. Dwivedi  Sagarika Chandra  Manoj Kumar  Sanjay Kumar  N. V. P. Kiran Kumar 《Meteorology and Atmospheric Physics》2015,127(1):95-105

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Long-term historic changes in climatic variables of Betwa Basin,India   总被引：2，自引：1，他引：1  

Shakti Suryavanshi  Ashish Pandey  Umesh Chandra Chaube  Nitin Joshi 《Theoretical and Applied Climatology》2014,117(3-4):403-418

In this study, trend analyses of historic past climatic variables were investigated for the Betwa basin located in Central India. In the serially independent climatic variables, Mann–Kendall test (MK test) was applied to the original sample data. However, in the serially correlated series, pre-whitening is used before employing the MK test. The long-term trend analysis showed several of the meteorological stations to exhibit a decreasing trend in annual and seasonal precipitation in the study area. Seasonal and yearly numbers of rainy days are decreased. However, onset of effective monsoon (except for Shivpuri and Tikamgarh stations) did not show any trend during the study period. For maximum temperature, five out of 12 stations showed a decreasing trend in monsoon season whereas almost all other stations showed an increasing trend in winter and no trend in summer season. For minimum temperature, only two stations of the basin showed a decreasing trend in monsoon and all other stations exhibited a significant increase in winter and summer season. The increase of winter temperature may adversely affect the growth of Rabi crop (wheat and mustard) in the study area. Potential evopotranspiration (PET) did not show any trend in monsoon, except for Jalaun and Jhansi stations, showing decreasing trends. Raisen and Vidisha stations showed an increasing trend in winter only, and the trend for other stations were random in nature. In summer, five out of 12 stations showed an increasing trend in PET. Results of this study can be employed in preparation of water resources development and management plan in the Betwa Basin.  相似文献   

Structural analyses of the crystalline rocks between Dirang and Tawang,West Kameng district,Arunachal Himalaya     

Hari B. Srivastava  Vaibhava Srivastava  Rajesh K. Srivastava  Chandra Kant Singh 《Journal of the Geological Society of India》2011,78(1):45-56

In Kameng Valley of Arunachal Pradesh, the crystalline rocks of Se La Group of Higher Himalaya are thrust over the Lesser Himalayan rocks of Dirang Formation, Bomdila Group along the Main Central Thrust and exhibit well preserved structures on macro- to microscopic scales. Detailed analysis of structures reveals that the rocks of the area have suffered four phases of deformation D₁, D₂, D₃ and D₄. These structures have been grouped into (i) early structures (ii) structures related to progressive ductile thrusting and (iii) late structures. The early structures which developed before thrusting formed during D₁ and D₂ phases of deformation, synchronous to F₁ and F₂ phases of folding respectively. The structures related to progressive ductile shearing developed during D₃ phase of deformation, when the emplacement of the crystalline rocks took place over the rocks of Dirang Formation along the Main Central Thrust. Different asymmetric structures/kinematic indicators developed during this ductile/brittle-ductile regime suggest top-to-SSW sense of movement of the crystalline rocks of the area. D₄ is attributed to brittle deformation. Based on satellite data two new thrusts, i.e. Tawang and Se La thrusts have been identified parallel to Main Central Thrust, which are suggestive of imbricate thrusting. Strain analysis from the quartz grains of the gneissic rocks reveals constriction type of strain ellipsoid where k value is higher near the MCT, gradually decreases towards the north. Further, the dynamic analysis carried out on the mesoscopic ductile and brittle-ductile shear zones suggest a NNE-SSW horizontal compression corresponding to the direction of northward movement of Indian Plate.  相似文献   

Post-Cyclone Sidr illness patterns in coastal Bangladesh: an empirical study     

Bimal Kanti Paul  Munshi Khaledur Rahman  Bankim Chandra Rakshit 《Natural Hazards》2011,56(3):841-852

After the landfall of Cyclone Sidr along the southwestern coast of Bangladesh on November 15, 2007, emergency and public health personnel within and beyond Bangladesh anticipated a massive outbreak of water-borne and other diseases in most affected areas. Fortunately, such an outbreak did not occur. The objectives of this paper are to examine the extent and pattern of illnesses experienced by Cyclone Sidr survivors in the aftermath of its landfall and to investigate household and individual-level factors associated with such illnesses. Based on face-to-face interviews conducted among 277 randomly selected Sidr survivors living in the four most severely impacted coastal districts, this study found that the post-cyclone incidence of water-borne, respiratory, and other diseases was not unusually high. Only 52 persons suffered Sidr-related illnesses, and their illnesses were significantly associated with household income, and gender and age of the Sidr survivors. A major outbreak of such diseases was largely avoided because of the proper distribution of food and safe drinking water, as well as the timely implementation of health care intervention measures. This important finding will aid relevant authorities in successfully responding to outbreaks of diseases following a future extreme event in Bangladesh and perhaps elsewhere.  相似文献