The origin of the Big-Bang     

R. K. Thakur 《Astrophysics and Space Science》1992,190(2):281-292

Within the framework of FLRW cosmology withk=+1 a singularity free model of the Universe is proposed which readily accounts for the origin of the Big-Bang and for the preponderance of matter over anti-matter. It is also free from the problems of accounting for the observed large-scale homogeneity and isotropy of the Universe as well as from the problems of horizon and flatness. It is pointed out that the collapsing universe might have acted as an ultra-high energy particle accelerator. In the collapsing phase of the Universe, when the interparticle distances10^–16 cm, the electromagnetic and weak interactions might have unified into electroweak interaction and as the collapse proceeded further the entire matter in the Universe might have been converted into quark-gluon plasma permeated by leptons. The gravitational energy released during the collapse might have been locked in this plasma. Ass approached 10^–28 cm, grand unification of electroweak and strong interactions might have occurred. It is also suggested that, with further collapse, whens<10^–33 cm super-symmetry (SUSY)—i.e., the unification of all the four interactions (viz., electromagnetic, weak, strong, and gravitational) might have occurred. During this process gravitinos, the supersymmetric partners of graviton might have been produced. As a result of the exchange of a pair of virtual gravitinos between two particles an ultra-strong repulsive force between them might have been generated. Due to this ultra-strong repulsive interaction between particles the motion of the Universe might have been reversed, i.e., the Universe might have started expanding. During expansion, whens10^–28 cm, SUSY might have broken down spontaneously toSU ₅ and gravity. Ass increased from 10^–28 to 10^–16 cm, the gravitational energy locked in the quark-gluon plasma might have been released with a gigantic explosion, the so-called Big-Bang. It is estimated here that during this Big-Bang more than 10⁸² GeV of energy might have been released. Whens10^–16 cm,SU ₅ might have broken down spontaneously toSU ₃ andU ₁. Expansion beyond this stage might have occurred in the manner described by the standard cosmology. It is further suggested that in due course of time expansion will be followed by contraction and the cycle of contraction-expansion-contraction will be repeated ad infinitum.  相似文献   

A mathematical interpretation of diffusion processes with concentration-dependent diffusion coefficient     

K. N. Rai  L. Thakur 《Astrophysics and Space Science》1991,180(1):133-142

The integral balance method has been used to obtain an approximate analytical solution of a nonlinear boundary value problem which arises in the theory of diffusion with a concentration-dependent coefficient. It is the purpose of this paper to give an interpretation of the supposition of interface reactions which obey the law of kinetic mass action.Nomenclature C(Z,t) concentration - C ₀ concentration at initial time - D diffusivity - D ₀ diffusivity at initial time - F(t) a function of time - K ₀ half-order reaction rate constant - k ₁ first-order reaction rate constant - k ₂ second-order reaction rate constante - L characteristic length - n parameter - t time - Z space variable Dimensionless variables and similarity criteria nondimensional half-order reaction rate constant - nondimensional first-order reaction rate constant - nondimensional second-order reaction rate constant - x=Z/L dimensionless space variable - F ₀=D ₀ t/L ² Fourier number - g(F ₀)=[F(t)–C ₀]/C ₀ a function of generalized time - (x, F ₀)=[C(x,t)–C ₀]/C ₀ dimensionless concentration - <(F ₀)> dimensionless average concentration  相似文献   

Tomographic approach for gas hydrate investigation in Kerala-Konkan region,India     

Naresh Kumar Thakur  Pasupuleti Prasada Rao  N. Vishwanath  Sanjeev Rajput  Bhaskarabhatla Ashalatha 《Marine Geophysical Researches》2007,28(4):373-378

Seismic tomography is an effective means of estimating velocity and structure from multichannel seismic (MCS) reflection data. In this study we have followed a 2D approach to arrive at the probable velocity field configuration from multichannel seismic data and infer the presence of gas hydrates/free-gas in the offshore Kerala-Konkan region, along the eastern part of a seismic line on which a bottom simulating reflector (BSR) has previously been identified. Tomographic modeling consists of the identification of reflection phases and picking of respective travel times for various source-receiver positions. These picks were then utilized to arrive at a 2D velocity field following a forward and inversion approach using a ray tracing technique. The modeling for the first time brought out the finer scale velocity structure under the region of investigation. Modeling through the 2D approach shows lateral variation in velocity field along the studied segment of the seismic line. The results indicate a thin (∼50–60 m) sedimentary cover with velocity ranging from 1,770 to 1,850 m/s. A sedimentary layer with high P-wave velocity 1,980–2,100 m/s below the sea floor was interpreted as the hydrate layer. The thickness of this layer varies between 110 and 140 m. The hydrate layer is underlain by a low-velocity layer having velocities in the range 1,660–1,720 m/s. This low velocity may represent a free gas layer, whose thickness varies between 50 and 100 m located below the hydrated layer. The investigation suggests the occurrence of gas hydrate underlain by free gas in some parts of the Kerala-Konkan offshore region.  相似文献   

Two-dimensional elastic anisotropic/AVO modelling for the identification of BSRs in marine sediments using multicomponent receivers     

S. Rajput  P. P. Rao  N. K. Thakur 《Geo-Marine Letters》2005,25(4):241-247

In seismic sections, the presence of a gas hydrate stability zone (GHSZ) is often marked by a bottom-simulating reflector, which has a negative polarity with respect to the seafloor. The present study reveals the response of seismic wave characteristics and amplitude versus offset (AVO) effects of large offset compressional (P) and converted (PS) waves for a GHSZ/free-gas configuration, using a two-dimensional elastic anisotropic modelling technique. The modelling results would provide a priori information, which allows unique determination of parameters of seismic models for the design of ocean bottom seismometer experiments over continental margins for the purpose of gas hydrate exploration. The AVO analyses on long offset P and PS waves based on synthetic data yield a typical gas hydrate/free-gas response, as the reflectivity increases with incidence angle.  相似文献   

Seasonal Variation of Temperature,Alkalinity and Dissolved Oxygen in the Sagar Lake     

S. S. Thakur  V. S. Bais 《洁净——土壤、空气、水》1987,15(2):143-147

The present study deals with the seasonal variation of temperature, alkalinity and dissolved oxygen in the Sagar lake. Different abiotic and biotic factors were investigated and a diurnal study was made, too. The investigation shows that the surface water values were always higher than the bottom water values. The water temperature ranged from 16.0 to 31.0 °C, carbonate alkalinity ranged from 0.0 to 46.0 mg/1, bicarbonate alkalinity ranged from 62.0 to 138.0 mg/1, dissolved oxygen ranged between 1.6 and 13.2 ppm. The water temperature was found to be positively correlated with carbonate alkalinity while an inverse correlation existed with bicarbonate alkalinity. Dissolved oxygen had a significant positive correlation with carbonate alkalinity, while a negative correlation was observed with bicarbonate alkalinity during all the seasons.  相似文献   

Geology of the area around Dharmsala,Kangra District,H. P., India     

Dr. Vishwajit J. Gupta  Dr. Vikram C. Thakur 《International Journal of Earth Sciences》1974,63(2):548-558

In the present paper an attempt has been made to describe the geology of the area around Dharmsala, Kangra District, Himachal Pradesh. The stratigraphic position of the problematic horizons, i. e., Dharmkot Limestone and Dharmsala Traps is discussed in detail.  相似文献   

Redshift distribution in extragalactic objects and evolution of galaxies     

R. K. Thakur  A. K. Sapre 《Astrophysics and Space Science》1980,70(2):281-293

In order to see whether the study of redshift distribution in different classes of extragalactic objects, suspected of belonging to different phases in the evolutionary sequence of galaxies, helps in arriving at a possible picture of the evolutionary sequence of galaxies, histograms have been plotted between the number and the redshift for each of the five classes of extragalactic objects, namely, the QSOs, N-galaxies, Seyfert galaxies, radio galaxies and normal galaxies. It is found that: (i) the highest peaks in the five histograms occur at distinctly different redshifts in the order (Z _peak)_QSOs>(Z _peak)_N-galaxies>(Z _peak)_{Seyfert galaxies}>(Z _peak)_{radio galaxies}> (Z _peak)_{normal galaxies} and (ii) sufficient overlap occurs in the redshift ranges of (a) QSOs and N-galaxies, (b) N-galaxies and Seyfert galaxies, (c) Seyfert galaxies and radio galaxies and (d) radio galaxies and normal galaxies. These facts suggest that the extragalactic objects might be evolving in the sequence: QSOsN-galaxiesSeyfert galaxiesradio galaxiesnormal galaxies. Other independent evidences in support of such an evolutionary sequence have been given. Finally, various aspects of the problem associated with the picture of the evolutionary sequence of galaxies have been critically examined.  相似文献   

Assessment of chemical and microbial contamination in groundwater through leaching of sewage waste in Delhi,India     

Ashwani Kumar  Anuj Ranjan  Khushbu Gulati  Shalini Thakur  Tanu Jindal 《Environmental Earth Sciences》2016,75(3):275

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Phenomenological issues related to strain localization in sensitive clays     

Vikas Thakur  Steinar Nordal  Gustav Grimstad 《Geotechnical and Geological Engineering》2006,24(6):1729-1747

A negative second order work, strain softening, is often noticed in contractant material like sensitive clays. Failure in such clays will lead to the formation of localized deformation zone of intense inelastic strain, known as shear band. Conditions, emergence and inclination of shear band has been very well demonstrated in past decades in different manners, however a definite thickness of shear band is still an open question due to several reasons. Mesh dependency, loss of ellipticity is another challenge associated with finite element analyses for strain softening clays. This paper covers a comprehensive review of classical theories of strain localization and associated limitation. Mesh dependency, ill-possed boundary value problem is addressed using finite element simulation examples and experimental results.  相似文献   

Crossover analysis of geophysical data in Bay of Bengal     

N. K. Thakur  T. Gangadhara Rao  C. Subrahmanyam  Ramesh Khanna 《Geo-Marine Letters》1999,19(4):262-269

Geophysical data (magnetic, gravity, and bathymetric) collected by international and national agencies along intersecting track lines in the Bay of Bengal show discrepancies that are analyzed and adjusted by crossover techniques. The original magnetic anomaly map over this region exhibits high gradients over the entire region, which do not fit with the known geological framework. The corrected map is devoid of artifacts, and the contours became smooth, which can be utilized for meaningful geological interpretation. The corrected free-air gravity map indicates improvements from the original in resolution with clear isolated anomalies in high track density areas. Corrected bathymetry does not show much improvement. Received: 29 May 1998 / Revision received: 23 February 1999  相似文献