Loop Quantum Cosmology and Probability of Inflation     

G. Vereshchagin  S. Bedić 《Astronomy Reports》2018,62(12):959-964

We study the measure on the set of initial conditions in remote past for Loop Quantum Cosmology with massive scalar field motivated by various choices of the measure present in the literature. The main finding of the paper is existence of an attractor at contracting phase of the universe, which, in addition to the well known attractor at expanding phase, predicts a very specific duration of inflationary stage with the number of e-foldings about 140.  相似文献   

Thermodynamical Structure of Atmosphere during Pre-monsoon Thunderstorm Season over Kharagpur as Revealed by STORM Data     

Bhishma Tyagi  A. N. V. Satyanarayana  Naresh Krishna Vissa 《Pure and Applied Geophysics》2013,170(4):675-687

Variation of atmospheric thermodynamical structure parameters between days of thunderstorm occurrence and non-occurrence is presented based on data sets obtained during Severe Thunderstorm-Observations and Regional Modeling (STORM) experiments conducted over Kharagpur (22.3°N, 87.2°E) in pre-monsoon season of 2009 and 2010. Potential instability (stable to neutral) is noticed in the lower layers and enhanced (suppressed) convection in the middle troposphere during thunderstorm (non-thunderstorm) days. Low-level jets are observed during all days of the experimental period but with higher intensity on thunderstorm days. Convective available potential energy (CAPE) builds up until thunderstorm occurrence and becomes dissipated soon after, whereas convective inhibition (CIN) is greatly decreased prior to the event on thunderstorm days. In contrast, higher CAPE and CIN are noticed on non-thunderstorm days. Analysis of thermodynamic indices showed that indices including moisture [humidity index (HI) and dew point temperature at 850 hPa (DPT850)] are useful in differentiating thunderstorm from non-thunderstorm days. The present study reveals that significant moisture availability in the lower troposphere in the presence of convective instability conditions results in thunderstorm occurrence at Kharagpur.  相似文献   

Effect of Different Growing Environments on Population Dynamics of Sucking Pests in Relation to Various Spectral Indices in Cotton     

Naresh Kumar  Ram Niwas  M. L. Khichar  R. K. Saini  Barun Biswas 《Journal of the Indian Society of Remote Sensing》2013,41(2):309-317

Present study was designed to determine the effect of various growing environments on sucking pest population dynamics in cotton and to work out their relation with spectral indices. Crop spectral reflectance in four IRS bands was measured with ground truth radiometer during 1000–1200 h in all the treatment combinations. Incidence of sucking pest in cotton was found out to be highly influenced by growing environments. The leafhopper and whitefly population was highest in 15 May sown cotton crop and was lowest in 15 April sown crop. Cultivar HS-6 was highly affected by both the sucking pest than the other cultivar H-1226. The spectral indices (SR, NDVI and TVI) were highest in 15 April sown crop at all the phenophases and were lowest in 15 May sown crop. The cultivar H-1226 showed higher values of spectral indices as compared to HS-6. The relationship of pests’ population with various spectral indices was established. Multiple regression models based on spectral indices can be used for prediction of sucking pest population more than 69 and 74 % accuracy in leafhopper and whitefly, respectively in cotton crop.  相似文献   

Stress drop and its relation to tectonic and structural elements for the meizoseismal region of great 1905 Kangra earthquake of the NW Himalaya     

Kumar  Naresh  Yadav  Dilip K.  Mondal  S. K.  Roy  P. N. S. 《Natural Hazards》2013,69(3):2021-2038

Natural Hazards - Investigations of micro- and low-magnitude earthquakes in the Kangra-Chamba region of the NW Himalaya were performed to evaluate the relationship between earthquake source,...  相似文献   

Petrology and geochemistry of A-type granites from Khanak and Devsar areas of Bhiwani district,southwestern Haryana     

Radhika Sharma  Naresh Kumar 《Journal of the Geological Society of India》2017,90(2):138-146

Petrological and geochemical characteristics of the granites from the Khanak and Devsar areas have been discussed in this paper. Based on field, petrographical and geochemical observations, three types of granites (grey, green and pink granite) have been identified in these areas. Grey granites consist of quartz, plagioclase, biotite, hornblende as essential minerals and hematite, zircon, annite, monazite & rutile as accessory minerals. Petrographically, green granites are same as grey granites including perthite and zircon as accessory minerals. Pink granites consist of quartz, k-feldspar and biotite in Khanak whereas in Devsar granites alike as Khanak granites, but plagioclase is replaced by perthite and occurs as dominantly. Microscopically, granites of both areas show porphyritic, hypidiomorphic, granophyric, perthitic and micro granophyric textures. Geochemically, major oxide elements (except alkalies) and trace elements (Ba, Sr, Cr, Ni, V, Cu, Zn, Ga, Pb, Th and Zr) are more in green and grey granites of Khanak and Devsar areas than pink granites. Generally, they show enrichments in SiO₂, Na₂O+K₂O, Fe/Mg, Rb, Zr, Y and and AI (Agpaitic Index) (ranges from 0.10 to 1.18) and depletion in MgO, CaO, P, Ti, Ni, Cr and V indicate their A-type affinity which is very similar to the A-type granites of MIS (Malani igneous suite) in northwestern peninsular India. Green and grey granites of Devsar area show high concentrations of Heat production (HP) 9.68 & 11.70 μWm^-3 and total Heat Generation Unit (HGU) i.e 23.04 & 27.86 respectively. On the other hand, pink granites of Khanak area display a higher enrichment of HP (16.53 μWm^-3) and HGU (39.37) than those granites of Devsar area. Overall, they have much a higher values of HP and HGU than the average value of continental crust (3.8 HGU), which imply a possible linear relationship with the surface heat flow and crustal heat generation in the rocks of MIS. From the petrography as well as the chemistry of Khanak and Devsar granites, it is suggested that they might have derived from the different degree of partial melting from the similar source of magma.  相似文献   

The Himalayan cryosphere: A critical assessment and evaluation of glacial melt fraction in the Bhagirathi basin     

Abul Amir Khan  Naresh Chandra Pant  Anindaya Sarkar  S.K. Tandon  Meloth Thamban  Mahalinganathan K. 《地学前缘(英文版)》2017,8(1):107-115

The cryosphere constitutes an important subset of the hydrosphere.The Himalayan cryosphere is a significant contributor to the hydrological budget of a large river system such as the Ganges.Basic data on the cryosphere in the Himalaya is inadequate and also has large uncertainties.The data on glacial melt component in the Himalayan rivers of India also shows high variability.The Gangotri glacier which constitutes nearly a fifth of the glacierized area of the Bhagirathi basin represents one of the fastest receding,large valley glaciers in the region which has been surveyed and monitored for over sixty years.The availability of measurement over a long period and relatively small glacier-fed basin for the Bhagirathi river provides suitable constraints for the measurement of the glacial melt fraction in a Himalayan river.Pre- and post-monsoon samples reveal a decreasing trend Of depletion of δ~(18)O in the river water from glacier snout(Gaumukh) to the confluence of the Bhagirathi river with the Alaknanda river near Devprayag.Calculations of existing glacial melt fraction(~ 30%at Rishikesh) are not consistent with the reported glacial thinning rates.It is contended that the choice of unsuitable end-members in the three component mixing model causes the overestimation of glacial melt component in the river discharge.Careful selection of end members provides results(~11%at Devprayag) that are consistent with the expected thinning rates.  相似文献   

Geological and mineralogical study of eclogite and glaucophane schists in the Naga Hills Ophiolite,Northeast India     

Naresh C. Ghose  Om Prakash Agrawal  Nilanjan Chatterjee 《Island Arc》2010,19(2):336-356

A variety of low‐ to high‐pressure metamorphic assemblages occur in the metabasic rocks and metachert in the Upper Cretaceous–Eocene ophiolite belt of the central part of the Naga Hills, an area in the northern sector of the Indo–Myanmar Ranges in the Indo–Eurasian collision zone. The ophiolite suite includes peridotite tectonite containing garnet lherzolite xenoliths, layered ultramafic–mafic cumulates, metabasic rocks, basaltic lava, volcaniclastics, plagiogranite, and pelagic sediments emplaced as dismembered and imbricated bodies at thrust contacts between moderately metamorphosed accretionary rocks/basement (Nimi Formation/Naga Metamorphics) and marine sediments (Disang Flysch). It is overlain by coarse clastic Paleogene sediments of ophiolite‐derived rocks (Jopi/Phokphur Formation). The metabasic rocks, including high‐grade barroisite/glaucophane‐bearing epidote eclogite and glaucophane schist, and low‐grade greenschist and prehnite–clinochlore schist, are associated with lava flows and ultramafic cumulates at the western thrust contact. Chemically, the metabasites show a low‐K tholeiitic affinity that favors derivation from a depleted mantle source as in the case of mid‐ocean ridge basalt. Thermobarometry indicates peak P–T conditions of about 20 kb and 525°C. Retrogression related to uplift is marked by replacement of barroisite and omphacite by glaucophane followed by secondary actinolite, albite, and chlorite formation. A metabasic lens with an eclogite core surrounded by successive layers of glaucophane schist and greenschist provides field evidence of retrogression and uplift. Presence of S‐C mylonite in garnet lherzolite and ‘mica fish’ in glaucophane schist indicates ductile deformation in the shear zone along which the ophiolite was emplaced.  相似文献   

The effects of chemical reactions on the dispersion of air pollutants over area sources     

Ram Naresh  R. Nath 《Earth, Moon, and Planets》1990,48(2):99-111

An analytical study has been performed to examine the characteristics of two-dimensional steady-state advective-diffusive transport of air pollutants emitted from ground-based area sources. The solutions for the concentration of air pollutants are obtained by Integral and Variational Imbedding methods taking chemical reaction process into account. A comparative study of concentration is displayed graphically, followed by a quantitative discussion.  相似文献   

Seasonal monsoon forecast for the years 1987 and 1988     

T. N. Krishnamurti  H. S. Bedi  G. Rohaly  M. Fulakeza  D. Oosterhof  K. Ingles 《Global and Planetary Change》1995,10(1-4)

The results of several seasonal integrations with an atmospheric global circulation model with prescribed “perfect” sea surface temperatures are presented. These experiments illustrate the results of seasonal simulations for the years 1987 and 1988. These were a dry and a wet monsson year, respectively, when compared to the average. The integrations cover the period from June 1 through August 31 for both years and were carried out at two horizontal resolutions, T42 and T106, of a global model containing two different parameterizations of surface hydrology. The seasonal differences of the motion fields, divergent circulations and rainfall distributions for these respective experiments are compared with the corresponding observed fields.The sensitivity of seasonal simulations to the initial state is explored with integrations starting on two successive dates. In these experiments we diagnose differences of the simulated time mean states from residue free budgets of the complete vorticity equation.  相似文献   

The effects of pre-season high flows,climate, and the Three Gorges Dam on low flow at the Three Gorges Region,China     

Zhenkuan Su  Xun Sun  Naresh Devineni  Upmanu Lall  Zhenchun Hao  Xi Chen 《水文研究》2020,34(9):2088-2100

The efficient operation of a multipurpose reservoir requires information on high and low flows. However, analyses of inflows for high flows and for low flows are typically done independently. In this paper, we considered the joint dependence of the low flow on the preceding high flow volume and duration for the wet season in the Three Gorges region of the Yangtze River Basin in China. High flow volume and duration were found to have a strong association with the annual minimum 7-day flow in Cuntan, Wanxian, and Yichang stations. Furthermore, we identified the Arctic Oscillation, Pacific Decadal Oscillation, and snow cover in the Tibetan Plateau to have statistically significant teleconnections with the annual minimum 7-day flow. Bayesian models that consider a different level of pooling of the site by site regressions were then developed for the annual minimum 7-day flow conditional on the climate indices and high flow volume (or duration). The full pooling model performed best, suggesting that a homogeneous regional response is best identified given the global climate predictors. Statistics such as the deviance information criterion and reduction of error, coefficient of efficiency, and coverage rate under cross validation indicate the good performance of the model. Snow cover in the western Tibetan Plateau and high flow volume were identified as the most influential factors of the annual minimum 7-day flow through their impact on water storage in the basin. Recent simulations since June 2003, when the Three Gorges Dam operation started, were used to analyse the effect of dam operation on the annual minimum 7-day flow. A comparison of observations and predictions during the post-dam period demonstrated that the dam operation effectively modifies the annual minimum 7-day flow period to have higher flows.  相似文献