Inflationary solution in higher dimensions     

Ashok KR. Chakraborty 《Astrophysics and Space Science》1992,192(2):321-324

In this Letter the five-dimensional Kaluza-Klein cosmological model is studied in the presence of a massless scalar field, whose potential has a flat part. By use of the polynomial relation between the two scale factors, inflationary solutions are obtained. The results show that the scale factor corresponding to the extra dimension is either constant or varies inversely as some power of the usual scale factor.  相似文献   

Stability analysis of a jointed beam     

Ashok K. Chugh 《国际地质力学数值与分析法杂志》1977,1(4):323-341

A numerical step-by-step procedure, analogous to the ‘Initial Stress Method,’ is presented for the analysis of a single-layer jointed rock beam subjected to gravity loads and in-plane in situ formation pressure. The joints are permitted to open at locations where the flexural stresses exceed flexural strength. The material properties may be different for each rock block and joint. A detailed algorithm is given for the solution of the problem. The results of several analyses indicating the relative effects of initial formation pressure, transverse load, stiffness of the joint material, and joint spacing on the response of a jointed beam are presented. The convergence characteristics of the numerical procedure are included. The joint material is assumed to be ‘no-tension’ type. Both the geometric and material non-linear effects are considered.  相似文献   

Do Stable Isotope Data from Calcrete Record Late Pleistocene Monsoonal Climate Variation in the Thar Desert of India?     

Julian E. Andrews  Ashok K. Singhvi  Ansu J. Kailath  Ralph Kuhn  Paul F. Dennis  Sampat K. Tandon  Ram P. Dhir 《Quaternary Research》1998,50(3):240-251

Late Pleistocene terrestrial climate records in India may be preserved in oxygen and carbon stable isotopes in pedogenic calcrete. Petrography shows that calcrete nodules in Quaternary sediments of the Thar Desert in Rajasthan are pedogenic, with little evidence for postpedogenic alteration. The calcrete occurs in four laterally persistent and one nonpersistent eolian units, separated by colluvial gravel. Thermoluminescence and infrared- and green-light-stimulated luminescence of host quartz and feldspar grains gave age brackets for persistent eolian units I–IV of ca. 70,000–60,000, ca. 60,000–55,000, ca. 55,000–43,000, and ca. 43,000–25,000 yr, respectively. The youngest eolian unit (V) is <10,000 yr old and contains no calcrete. Stable oxygen isotope compositions of calcretes in most of eolian unit I, in the upper part of eolian unit IV, and in the nonpersistent eolian unit, range between −4.6 and −2.1‰ PDB. These values, up to 4.4‰ greater than values from eolian units II and III, are interpreted as representing nonmonsoonal¹⁸O-enriched “normal continental” waters during climatic phases when the monsoon weakened or failed. Conversely, 25,000–60,000-yr-old calcretes (eolian units II and III) probably formed under monsoonal conditions. The two periods of weakened monsoon are consistent with other paleoclimatic data from India and may represent widespread aridity on the Indian subcontinent during isotope stages 2 and 4. The total variation in δ¹³C is 1.7‰ (0.0–1.7‰), and δ¹³C covaries positively and linearly with δ¹⁸O. δ¹³C values are highest when δ¹⁸O values indicate the most arid climatic conditions. This is best explained by expansion of C₄grasses at the expense of C₃plants at low latitudes during glacial periods when atmosphericpCO₂was lowered. C₄dominance was overridingly influenced by global change in atmosphericpCO₂despite the lowered summer rainfall.  相似文献   

Regional investment effectiveness and development levels in China     

Xie Yichun  Ashok K. Dutt 《GeoJournal》1990,20(4):393-407

For centuries, it has been taken for granted that social and economic development in China has an east-west spread, or from the coast to the interior. Even though a tremendous effort was made by the socialist government for thirty years (1949-1978) on rectifying this unhealthy imbalance, most people hold the belief that the spatial patterns of China's development remain the same as they were forty years ago. This deep-rooted concept plays an important role in shaping China's present economic development strategies. Thus, an evaluation of the impact of the goverment's regional balance effort remains critical. Understanding the changes and patterns of China's regional development is central to formulating appropriate policies for future planning. In this paper an overview of regional development is presented from the perspective of history. Regression between the total fixed capital investment and the combined industrial and agricultural output is analyzed, and an effort is made to find out the spatial distribution of regional investment effectiveness. A factor analysis based on twenty socio-economic variables revealed that apart from the traditional E-W regional disparity, the modern socialist dispersal policy has also affected the regional development in China. Though the historical economic factors unbalanced the development from E to W, the economic pratice advocated by Socialist China has reversed the tendency to some extent. A cluster analysis of 21 provinces, five autonomous administrative regions, and three municipalities identified new spatial patterns, and the result strengthened the finding that the effort of regional balance in the period of 1949–1978 is still at work.  相似文献   

Indian Participation in XVIII International Union for Quaternary Research (INQUA) Congress, 2011     

M. C. Manoj  Ashok Singhvi  Alpa Sridhar 《Journal of the Geological Society of India》2012,79(2):223-223

  相似文献   

Application of geogrids in waste dump stability: a numerical modeling approach   总被引：1，自引：0，他引：1  

Rajesh Rai  Manoj Khandelwal  Ashok Jaiswal 《Environmental Earth Sciences》2012,66(5):1459-1465

Geosynthetic is widely used to reinforce the weak rock mass, mine waste dump, soil slopes road cut slopes, etc. The present paper discusses the effect of geogrids on the stability of mine waste dump. The stability of mine waste dump has been done by Fast Langrage Analysis of Continua (FLAC) slope software, which is based on finite difference method. Reinforcement by geogrids mainly depends on the tensile strength, aperture size of geogrids, and particle size distribution of dump rock mass. Different permutations and combinations of spacing between two geogrid sheets have been taken into consideration to study the stability of mine waste dump. The factor of safety is calculated to quantify the effect of geogrids on waste dump slope. It has been observed from numerical modeling that the maximum slope angle is 45° at a height of 10 m. The scope of increasing slope angle from 45 to 60° is evaluated using geogrids. It has been found from the study that the factor of safety increases as the spacing between geogrids decreases. Maximum strain is also plotted of each case to identify the slip circle. The positions of geogrids modify the probable slip circle or failure plane of mine waste dump. Using ten geogrids at a spacing of 1 m, the slope angle can be increased up to 60° with factor of safety of 1.4.  相似文献   

Toward physical aspects affecting a possible leakage of geologically stored CO2 into the shallow subsurface     

Ashok Singh  Jens Olaf Delfs  Uwe Jens Görke  Olaf. Kolditz 《Acta Geotechnica》2014,9(1):81-86

In geological formations, migration of CO₂ plume is very complex and irregular. To make CO₂ capture and storage technology feasible, it is important to quantify CO₂ amount associated with possible leakage through natural occurring faults and fractures in geologic medium. Present work examines the fracture aperture effect on CO₂ migration due to free convection. Numerical results reveal that fracture with larger-aperture intensify CO₂ leakage. Mathematical formulation and equations of state for the mixture are implemented within the object-oriented finite element code OpenGeoSys developed by the authors. The volume translated Peng–Robinson equation of state is used for material properties of CO₂ and water.  相似文献   

Oxygen isotope analysis of bone and tooth enamel phosphate from paleogene sediments: Experimental techniques and initial results     

M. K. Bera  Kasturi Bhattacharya  A. Sarkar  A. Samanta  Kishor Kumar  Ashok Sahni 《Journal of the Geological Society of India》2010,76(3):275-282

Oxygen isotope composition (δ¹⁸O) of fossil bone and tooth enamel phosphate (bioapatite) is an important tool for estimating the isotopic composition of past environmental water. Lack of analytical facility was a hindrance for studying such bioapatites in spite of large number of fossil materials reported from various geological ages in India. We have established in our laboratory, based on available methods, the chemical procedure for extraction of very small amount (<1000 μg) PO₄ ⁻³ from bioapatite and on-line mass spectrometric measurement of its δ¹⁸O composition by high temperature (∼1450°C) pyrolysis. The achieved precision is ∼± 0.3 ‰ similar to obtained elsewhere, with interlaboratory calibration showing excellent agreement of standard phosphates. Inferred δ¹⁸O values of environmental water, based on the analysis of teeth and bones of sharks, fish and terrestrial mammals from the Paleogene successions of the northwest sub-Himalayan and the Peninsular India show strong correspondence with animal habitats. The freshwater δ¹⁸O values are much depleted having range similar to modern monsoon precipitation. However, owing to our small dataset it is not possible at this stage to infer about the existence of monsoon over the Indian sub-continent during the Eocene-Oligocene time.  相似文献   

Helioseismic effects of energetic transients     

Ashok Ambastha 《Journal of Astrophysics and Astronomy》2008,29(1-2):93-101

Photospheric and chromospheric signatures related to large, energetic transients such as flares and CMEs, have been extensively reported during the last several years. In addition, energetic solar transients are expected to cause helioseismic effects. Some of the recent results are reviewed here; in particular, the helioseismic effects of the powerful flares in superactive region, NOAA 10486, including the 4B/X17 superflare of October 28, 2003. We also examine the temporal variations of power in low-l modes during the period May 1995–October 2005, and compare with daily, disk-integrated flare-and CME-indices to infer the effect of transients on the scale of whole solar disk.  相似文献   

On the boundary conditions in slope stability analysis     

Ashok K. Chugh 《国际地质力学数值与分析法杂志》2003,27(11):905-926

Boundary conditions can affect computed factor of safety results in two‐ and three‐dimensional stability analyses of slopes. Commonly used boundary conditions in two‐ and three‐dimensional slope stability analyses via limit‐equilibrium and continuum‐mechanics based solution procedures are described. A sample problem is included to illustrate the importance of boundary conditions in slope stability analyses. The sample problem is solved using two‐ and three‐dimensional numerical models commonly used in engineering practice. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献