Generalized teleparallel gravity via some scalar field dark energy models     

M. Sharif  Shamaila Rani 《Astrophysics and Space Science》2013,345(1):217-223

We consider generalized teleparallel gravity in the flat FRW universe with a viable power-law f(T) model. We construct its equation of state and deceleration parameters which give accelerated expansion of the universe in quintessence era for the obtained scale factor. Further, we develop correspondence of f(T) model with scalar field models such as, quintessence, tachyon, K-essence and dilaton. The dynamics of scalar field as well as scalar potential of these models indicate the expansion of the universe with acceleration in the f(T) gravity scenario.  相似文献   

Atmospheric Dry Deposition to Marble and Red Stone     

Ranjit?Kumar  Abha?Rani  K.?Maharaj?Kumari  S.?S.?SrivastavaEmail author 《Journal of Atmospheric Chemistry》2005,50(3):243-261

This paper presents dry deposition flux and deposition velocity of atmospheric particles on white marble and red stone at Dayalbagh, a suburban site of semi arid region, which is 10 km away from the industrial sector of the Agra city where due to agricultural practices vegetation predominates. The wind speed at Agra is mostly in the range of 1–2 m s^–1. The atmospheric calm conditions at Agra in summer, monsoon, and winter seasons are 47%, 35%, and 76%, respectively. Industrial areas of the city are away from Dayalbagh and are located in the NE, E, SE, and SW sectors. The main industrial activities, which are in operation in Agra city and its outskirts, are foundry and forging industry. The other industrial activities in Agra are rubber processing, lime oxidation and pulverization, chemicals, engineering and brick refractory kilns. Dry deposition samples were collected on dry days on white marble and red stone (0.224 m × 0.224 m × 0.02 m) using surface washing method. Both slabs were fixed to an iron stand (1.5 m height) at an angle of about 80 from the horizontal and exposed for 24 h on the roof of the faculty building. The order of deposition flux on white marble is NH₄⁺ > Mg²⁺ > Ca²⁺ > Na⁺ > Cl^– > K⁺ > NO₃^– > SO₄^2– > F^– and that on red stone is NH₄⁺ > Mg²⁺ > Ca²⁺ > SO₄^2– > Na⁺ > NO₃^– > K⁺ > F^– > Cl^–. Average dry deposition flux of major ions varies from 3.4 to 128.5 M m^–2 d^–1. The sum of major cations on white marble and red stone are 516.4 and 450.4 eq m^–2 d^–1, respectively while sum of major anions are 425.3 and 400.4 eq m^–2 d^–1 on white marble and red stone, respectively. Higher deposition of all ions was observed when wind blows from NE as most of the Agra Iron foundries and Ferozabad glass industries lie in this direction. The mean values of dry deposition velocity of ions vary between 0.22 cm s^–1 to 1.49 cm s^–1. Deposition velocity for all ions is higher on white marble than red stone inspite of rougher surface of red stone as compared to white marble. This could be due to the chemical nature of white marble, which is made of dolomite and hence adds significant amount of ions by dissolution during washing. Seasonally the deposition velocity was highest in winter.  相似文献   

Photogrammetry and 3D laser scanning as spatial data capture techniques for a national craniofacial database     

Zulkepli  Majid  Albert K.  Chong  Anuar  Ahmad  Halim  Setan  Abdul Rani  Samsudin 《The Photogrammetric Record》2005,20(109):48-68

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A note on 2-D lithospheric deformation due to a blind strike-slip fault     

Sunita Rani  Sarva Jit Singh 《Journal of Earth System Science》2005,114(1):105-110

Analytical solution for the problem of a surface-breaking long strike-slip fault in an elastic layer overlying an elastic half-space is well known. The purpose of this note is to obtain the corresponding solution for a blind fault. Since the solution is valid for arbitrary values of the fault-depth and the dip angle, the effects of these two important fault parameters can be studied numerically. The variation of the parallel displacement and shear stress with the distance from the fault is studied numerically for different values of the fault-depth and dip angle.  相似文献   

A Long Term Study on Chemical Composition of Rainwater at Dayalbagh, a Suburban Site of Semiarid Region     

Ranjit Kumar  Abha Rani  S. P. Singh  K. Maharaj Kumari  S. S. Srivastava 《Journal of Atmospheric Chemistry》2002,41(3):265-279

Rainwater samples were collected for the monsoon period of 1988 and 1991–1996 at Dayalbagh (Agra), a suburban site situated in semiaridregion. The mean pH was 7.01 ±1.03 well above 5.6, which is the reference pH. Concentration of Ca²⁺ was observed to be highest followed by Mg²⁺, NH₄ ⁺,SO₄ ^2–, Cl^–,NO₃ ^–, Na⁺, F^– and K⁺. The ratios of SO₄ ^2– + NO₃ ^– andCa²⁺ + Mg²⁺ (TA/TC) have been considered as indicatorfor acidity. In the Agra region ratio of TA/TC is quite below 1.0 indicating alkaline nature of rainwater. The lowest value of 0.24 was observed in 1991 likely due to the lowest rain depth of the decade. The highest value of 0.54 was observed in 1996, a year with a large rain depth and increase in line (vehicular traffic) and area sources (population growth). Good correlation between Ca²⁺ and NO₃ ^–,Ca²⁺ and SO₄ ^2– andSO₄ ^2– and NO₃ ^–,indicates that wind carried dust and soil play a significant role in neutralization of precipitation acidity.  相似文献   

Spatial distribution of altered minerals in the Gadag Schist Belt (GSB) of Karnataka,Southern India using hyperspectral remote sensing data     

Nisha Rani  Tejpal Singh 《国际地球制图》2017,32(3):225-237

Spatial distribution of altered minerals in rocks and soils in the Gadag Schist Belt (GSB) is carried out using Hyperion data of March 2013. The entire spectral range is processed with emphasis on VNIR (0.4–1.0 μm) and SWIR regions (2.0–2.4 μm). Processing methodology includes Fast Line-of-sight Atmospheric Analysis of Spectral Hypercubes correction, minimum noise fraction transformation, spectral feature fitting (SFF) and spectral angle mapper (SAM) in conjunction with spectra collected, using an analytical spectral device spectroradiometer. A total of 155 bands were analysed to identify and map the major altered minerals by studying the absorption bands between the 0.4–1.0-μm and 2.0–2.3-μm wavelength regions. The most important and diagnostic spectral absorption features occur at 0.6–0.7 μm, 0.86 and at 0.9 μm in the VNIR region due to charge transfer of crystal field effect in the transition elements, whereas absorption near 2.1, 2.2, 2.25 and 2.33 μm in the SWIR region is related to the bending and stretching of the bonds in hydrous minerals (Al-OH, Fe-OH and Mg-OH), particularly in clay minerals. SAM and SFF techniques are implemented to identify the minerals present. A score of 0.33–1 was assigned for both SAM and SFF, where a value of 1 indicates the exact mineral type. However, endmember spectra were compared with United States Geological Survey and John Hopkins University spectral libraries for minerals and soils. Five minerals, i.e. kaolinite-5, kaolinite-2, muscovite, haematite, kaosmec and one soil, i.e. greyish brown loam have been identified. Greyish brown loam and kaosmec have been mapped as the major weathering/altered products present in soils and rocks of the GSB. This was followed by haematite and kaolinite. The SAM classifier was then applied on a Hyperion image to produce a mineral map. The dominant lithology of the area included greywacke, argillite and granite gneiss.  相似文献   

Chemical characteristics and deposition fluxes of dust-carbon mixed coarse aerosols at three sites of Delhi,NCR     

Manisha Mishra  Umesh Kulshrestha 《Journal of Atmospheric Chemistry》2017,74(4):399-421

The present paper reports chemistry and fluxes of dust-carbon mixed coarse particles. For the purpose of this study, different carbonaceous fractions i.e. organic carbon ((OC), elemental carbon (EC) and carbonate carbon (CC) of atmospheric dust and their respective local soils were quantified at three sites of National Capital Region (NCR) of Delhi viz. Jawaharlal Nehru University campus (JNU), Connaught Place (CP) and Vishali area of Ghaziabad (GB). It has been observed that the OC and EC levels were approximately five to nine times higher in urban atmospheric dust than their corresponding soils, whereas CC levels were about three times higher than the corresponding soils. Average dustfall fluxes were significantly different at all the sites due to their different land-use patterns. At urban background site (JNU), the dust flux was lowest (172 mg/m²/day) followed by CP, a commercial site, (192 mg/m²/day) and GB, an industrial/residential area, (302 mg/m²/day). Similar to the dustfall pattern, the mean values of OC, EC and CC deposition fluxes were also observed to be lowest at JNU (9.2, 0.8 and 1.0 mg/m²/day, respectively) as compared to CP (12.2, 1.2 and 1.3 mg/m²/day, respectively) and GB sites (11.1, 1.1 and 1.4 mg/m²/day, respectively). Interestingly, unlike fine mode, different correlation pattern of OC and EC in coarse mode dust aerosols at three sites has suggested their independent deposition processes and source contribution. Fluxes of major water soluble inorganic ions (Na⁺, NH₄ ⁺, K⁺, Ca²⁺, Mg²⁺, F^?, Cl^?, NO₃ ^? and SO₄ ^2?) were also determined. Ca²⁺, Cl^? and SO₄ ^2? were found to be the major ionic species of water soluble fraction of the urban dust at all the sites. These interactions are corroborated by the morphology of the mixed aerosols. High levels of measured chemical species and their spatial distribution revealed close correspondence with the local emissions from transport, industries, biomass burning, road dust and construction activities etc.  相似文献   

Static deformation of two welded half-spaces due to dip-slip faulting     

Sunita Rani  Sarva Jit Singh 《Journal of Earth System Science》1992,101(3):269-282

Closed-form expressions for the displacements and stresses at any point of either of two elastic half-spaces in welded contact caused by a dip-slip line source obtained earlier are integrated analytically to derive the elastic residual field due to a long dip-slip fault of finite width. The results are valid for an arbitrary dip of the fault. The variation of the displacement field with the distance from the fault as well as with the distance from the interface is studied numerically. It is found that the displacement field is heavily dependent on the dip angle. Contour maps showing the residual elastic field in the two half-spaces caused by a vertical dip-slip fault located in one of the half-spaces are also obtained.  相似文献   

Crustal deformation due to non-uniform slip along a long fault     

Sarva Jit Singh  Mukesh Punia  Sunita Rani 《Geophysical Journal International》1994,118(2):411-427

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Topology of Rayleigh–Bénard convection and magnetoconvection in plane layer     

Hari Ponnamma Rani  Jozef Brestenský 《地球物理与天体物理流体动力学》2019,113(1-2):208-221

ABSTRACT

The present study aims to link the dynamics of geophysical fluid flows with their vortical structures in physical space and to study the transition of these structures due to the control parameters. The simulations are carried in a rectangular box filled with liquid gallium for three different cases, namely, Rayleigh–Bénard convection (RBC), magnetoconvection (MC) and rotating magnetoconvection (RMC). The physical setup and material properties are similar to those considered by Aurnou and Olson in their experimental work. The simulated results are validated with theoretical results of Chandrasekhar and experimental results of Aurnou and Olson. The results are also topologically verified with the help of Euler number given by Ma and Wang. For RBC, the onset is obtained at Ra greater than 1708 and at this Ra, the symmetric rolls are orientated in/along a horizontal axis. As the value of Ra increases further, the width of the horizontal rolls starts to amplify. It is observed that these two-dimensional rolls are nothing but the cross-sections of three-dimensional (3D) cylindrical rolls with wave structures. When the vertically imposed magnetic field is added to RBC, the onset of convection is delayed due to the effect of Lorentz force on the thermal buoyancy force. The presence of 3D rectangular structures is highlighted and analysed. When the magnetically influenced rectangular box rotates about vertical axis at low rotation rates in magnetoconvection model, the onset of convection gets further delayed by magnetic field, which is in general agreement with the theoretical predictions. The critical Ra increases linearly with magnetic field intensity. Coherent thermal oscillations are detected near the onset of convection, at moderate rotation rates.  相似文献