String fluid cosmological models in general relativity     

S. K. Tripathy  S. K. Nayak  S. K. Sahu  T. R. Routray 《Astrophysics and Space Science》2008,318(1-2):125-131

LRS Bianchi type-I string cosmological models are studied in the frame work of general relativity when the source for the energy momentum tensor is a bulk viscous fluid containing one dimensional strings embedded in electromagnetic field. A barotropic equation of state for the pressure and density is assumed to get determinate solutions of the field equations. The bulk viscosity is assumed to be inversely proportional to the scalar expansion. The physical and kinematical properties of the models are discussed. The effect of viscosity and electromagnetic field on the physical and kinematical properties is also investigated.  相似文献   

String cloud cosmologies for Bianchi type-III models with electromagnetic field     

S. K. Tripathy  S. K. Sahu  T. R. Routray 《Astrophysics and Space Science》2008,315(1-4):105-110

The Saez-Ballester field equations for spatially homogeneous and anisotropic Bianchi type-III cosmological models have been solved for pure geometric cosmic string cloud pervading the universe either in the absence or in presence of electromagnetic field. It has been established here that the model does not survive for geometric cosmic string cloud pervading the universe when there is no electromagnetic field. But in presence of electromagnetic field the model can have plausible solutions fostering the idea that strings forming the surface of the world sheet have to co-exist with electromagnetic field.  相似文献   

Chemical heterogeneity in an enderbite-hosted pseudotachylite,eastern India: evidence for syn-deformation multi-reaction melting in pseudotachylite     

Radhika?Patro  S.?N.?Mahapatro  A.?BhattacharyaEmail author  N.?C.?Pant  J.?K.?Nanda  A.?Dey  A.?K.?Tripathy 《Contributions to Mineralogy and Petrology》2011,161(4):547-563

The origin of chemical and mineralogical heterogeneity in tens-of-microns wide layers and domains in enderbite-hosted couple-of-centimeters wide pseudotachylite vein is examined based on the results of BSE and X-ray element imaging, and electron probe microanalyses of major elements of host-rock minerals, clasts, microphenocrysts, and pseudotachylite matrix. The pseudotachylite layers and domains containing variable proportions of orthopyroxene and magnetite microphenocrysts continue as mantles around quartz, K-feldspar, plagioclase and garnet clasts. The clasts are chemically modified along margins and intra-clast pseudotachylite injections. The chemical modifications are extensive in smaller clasts <5 μm diameter. At least three chemically distinct layers and domains in the pseudotachylite, and their fine-grained matrices, plot in sharply defined, well-segregated and non-overlapping fields in FeO + MgO−Al₂O₃–SiO₂, FeO–CaO–MgO and CaO–Na₂O–K₂O and FeO vs. FeO/FeO + MgO diagrams. The compositions of the layers and domains—smeared between a feldspar + quartz component and a ferromagnesian component of garnet + Fe–Ti oxides (±orthopyroxene)—possibly correspond to fractionated quenched melts, or admixtures of microphenocrysts that cannot be resolved by the microbeam techniques employed. The compositional variations are incompatible with deformation-driven crystal fractionation in melt. Instead the layers and domains possibly are crystal-melt mushes produced by syn-deformation ultra-high temperature (1,250–1,375°C) melting reactions involving variable proportions of host-rock minerals determined by time-transient local phase aggregates experiencing strain. The similar element variation trends in pseudotachylite examined here and those reported from anorthosite, metapelite and charnockite elsewhere suggests local phase aggregate controlled multi-reaction melting is a phenomenon commoner than hitherto realized in pseudotachylites.  相似文献   

On the Use of Skempton’s Compression Index Equation     

Snehasis Tripathy  Anil Kumar Mishra 《Geotechnical and Geological Engineering》2011,29(1):129-135

In this study, an alternate approach to establish the e-log p relationships for clayey soils within a vertical pressure range of 10–1,000 kPa is discussed. Skempton’s compression index equation correlating the liquid limit, w _L, and the compression index, C _c, and the reported equation correlating the void ratio at liquid limit, e _L, and the void ratio at a vertical pressure of 100 kPa, e ₁₀₀, by Burland (1990), were used to establish the e-log p relationships for several reconstituted normally consolidated clayey soils. Consolidation test results of 13 clayey soils covering a sufficiently wide range of liquid limit were selected from the literature. Also, consolidation tests were carried out on two highly expansive soils in this study. A comparison of the experimental consolidation test results with the calculated e-log p relationships in the current study indicated that in general, the agreements between the calculated relationships and the experimental results are good. The agreements were found to be slightly better for soils with liquid limits less than about 70%. A comparison of the calculated e-log p relationships in the current study with that determined following methods suggested by Nagaraj and Srinivasa Murthy (1983) and Burland (1990) showed that all the three methods yielded very similar results for soils with liquid limit less than 70%. For soils with liquid limits greater than 70%, the difference between the e-log p relationships calculated in this study and that following Burland (1990)’s method was insignificant, whereas Nagaraj and Srinivasa Murthy (1983)’s method slightly over-predicted the void ratios at larger vertical stresses.  相似文献   

Effects of Post-compaction Residual Lateral Stress and Electrolyte Concentration on Swelling Pressures of a Compacted Bentonite     

Snehasis Tripathy  Ramakrishna Bag  Hywel Rhys Thomas 《Geotechnical and Geological Engineering》2014,32(4):749-763

The effects of post-compaction residual lateral stress and salt concentration in the hydrating fluid on swelling pressures of compacted MX80 bentonite is brought out in this paper. In order to release the residual lateral stresses, following the static compaction process during preparation of specimens, compacted bentonite specimens were extruded from the specimen rings and then inserted back prior to testing them for swelling pressures in isochoric condition. The swelling pressure tests were carried out at several dry densities of the bentonite with distilled water and solutions of NaCl (0.1 and 1.0 M) as the hydrating fluids. With water, the test results showed that specimens that underwent extrusion and insertion processes exhibited about 10–15 % greater swelling pressures as compared to the specimens those that were compacted and tested. The influence of saline solutions was found to reduce the swelling pressure of the bentonite, but their impact was less significant at high compaction dry densities.  相似文献   

Solar Oscillation Frequency Changes on Time Scales of Nine Days     

S. C. Tripathy  F. Hill  K. Jain  J. W. Leibacher 《Solar physics》2007,243(2):105-120

We establish that global solar p-mode frequencies can be measured with sufficient precision on time scales as short as nine days to detect activity-related shifts. Using ten years of GONG data, we report that mode-mass and error-weighted frequency shifts derived from nine days are significantly correlated with the strength of solar activity and are consistent with long-duration measurements from GONG and the SOHO/MDI instrument. The analysis of the year-wise distribution of the frequency shifts with change in activity indices shows that both the linear-regression slopes and the magnitude of the correlation varies from year to year and they are well correlated with each other. The study also indicates that the magnetic indices behave differently in the rising and falling phases of the activity cycle. For the short-duration nine-day observations, we report a higher sensitivity to activity.  相似文献   

Anisotropic cosmological model with variable G and Λ     

S. K. Tripathy  D. Behera  T. R. Routray 《Astrophysics and Space Science》2012,340(2):211-215

Anisotropic Bianchi-III cosmological model is investigated with variable gravitational and cosmological constants in the framework of Einstein’s general relativity. The shear scalar is considered to be proportional to the expansion scalar. The dynamics of the anisotropic universe with variable G and Λ are discussed. Without assuming any specific forms for Λ and the metric potentials, we have tried to extract the time variation of G and Λ from the anisotropic model. The extracted G and Λ are in conformity with the present day observations. Basing upon the observational limits, the behavior and range of the effective equation of state parameter are discussed.  相似文献   

Geometrical analysis of mesoscopic shear zones in the crystalline rocks of MCT zone of Garhwal Higher Himalaya   总被引：1，自引：0，他引：1  

Hari B. Srivastava  Nihar R. Tripathy 《Journal of Asian Earth Sciences》2007,30(5-6):599-612

The crystalline rocks of the MCT Zone of Garhwal Higher Himalaya exhibit well-preserved mesoscopic shear zones. Majority of these shear zones are of ductile and brittle ductile type with both sinistral and dextral sense of movement. Detailed analysis of mesoscopic shear zones reveals that sinistral shear zones exhibit a strike variation from NNE to ENE and dextral shear zones exhibit variation from NNW to WNW directions thus forming a conjugate pair. The bisectors of statistically preferred orientations of the two sets of the shears indicate that they generated due to NNE–SSW horizontal compression. These dextral and sinistral shear zones exhibit strike–slip geometry developed during progressive ductile shearing.  相似文献   

Optimum tracking of ship routes in 3g-WAM simulated rough weather using IRS-P4 (MSMR) analysed wind fields     

J. K. Panigrahi  J. K. Tripathy  P. A. Umesh 《Journal of the Indian Society of Remote Sensing》2008,36(2):149-158

Rough weather ship routing is studied using model hindcast wave climate. With the launch of IRS-P4 (OCEANSAT-I), it became possible to carry out routine wave forecasting over the Indian Ocean. The MSMR channel of the satellite gives scalar wind, which is analysed at National center for Medium Range Weather Forecasting (NCMRWF), India for converting to vector winds. The same is used as input to third generation wave model for the rough weather month of July 2000. Simulations are carried out using Cycle-4 of third generation spectral wave model WAM for regional grid system. This simulated wave climate formed the basis for computing effective ship velocity in the irregular seaway. This study gives a quantitative estimation of change in ship velocity in the open Indian Ocean for a Liberty type ship. The optimal route is charted using Dijkstra’s algorithm for minimal time path between Calcutta and Sumatra. The optimum track information has broad scope for obtaining a safer route, least time route by avoiding delay in schedule with minimum fuel consumption.  相似文献   

Nayagarh氟化物污染区土壤的地球化学性质：因素分析评价     

S.Tripathy  M.K.Panigrahi  N.Kundu  葛秀珍 《水文地质工程地质技术方法动态》2006,(3):1-9

本文旨在研究奥里萨邦[印度邦名]Nayagarh区温泉地带土壤受氟化物污染的情况。文中分析两种土壤（大部分是在0-30cm深度采集的土壤以及0-90cm深度采集的剖面土壤）的总氟化物浓度（Ft）和0．01MCaCl2可萃取的氟化物浓度（Fca）主要的元素、pH、EC以及有机碳。通过对Singhpur村周围区域和温泉的观察，结果表明Ft和Fca浓度都高。大部分土壤参数的主要因素分析（PFA）表明，两种主要的化学过程是由于三个因素控制区域土壤的地球化学性质。第一个因素占总变化的37．11％，对Al、Si、Fe、F。和F。有很强的载荷能力，而且说明了土壤富集氟化物的原因；而第二和第三个因素分别占16．6％和12．2％，说明碳酸盐沉淀的控制过程和土壤的碱度。对因素做多元回归分析是为了取得土壤的氟化物污染指数。因素影响范围的大小（因素-1〉因素-2〉因素-3）影响污染指数。污染指数的空间分布可以用来划分污染区域的污染等级，即：高度污染区、中度污染区和未污染区。  相似文献