F and G Taylor series solutions to the Stark and Kepler problems with Sundman transformations     

Etienne Pellegrini  Ryan P. Russell  Vivek Vittaldev 《Celestial Mechanics and Dynamical Astronomy》2014,118(4):355-378

The classic $F$ and $G$ Taylor series of Keplerian motion are extended to solve the Stark problem and to use the generalized Sundman transformation. Exact recursion formulas for the series coefficients are derived, and the method is implemented to high order via a symbolic manipulator. The results lead to fast and accurate propagation models with efficient discretizations. The new $F$ and $G$ Stark series solutions are compared to the Modern Taylor Series (MTS) and 8th order Runge–Kutta–Fehlberg (RKF8) solutions. In terms of runtime, the $F$ and $G$ approach is shown to compare favorably to the MTS method up to order 20, and both Taylor series methods enjoy approximate order of magnitude speedups compared to RKF8 implementations. Actual runtime is shown to vary with eccentricity, perturbation size, prescribed accuracy, and the Sundman power law. The method and results are valid for both the Stark and the Kepler problems. The effects of the generalized Sundman transformation on the accuracy of the propagation are analyzed. The Taylor series solutions are shown to be exceptionally efficient when the unity power law from the classic Sundman transformation is applied. An example low-thrust trajectory propagation demonstrates the utility of the $F$ and $G$ Stark series solutions.  相似文献   

Scaling aspects of river flow routing     

Vivek Arora  Frank Seglenieks  Nick Kouwen  Eric Soulis 《水文研究》2001,15(3):461-477

Scaling aspects of river flow routing are studied by comparing two flow routing schemes, one designed for use in coupled general circulation models (GCMs) and operated at large spatial scales (～350 km), and the other designed for use in typical hydrological applications at small spatial scales (～25 km). The same runoff data are used as input into the two routing schemes, and comparisons are made between mean annual, mean monthly and daily streamflow simulated at four locations within the Mackenzie River Basin. The results suggest that for the purpose of realistically modelling monthly streamflow at the mouth of the rivers in GCMs, flow routing at large spatial scales gives similar results. However, the amplitude of the annual streamflow cycle is slightly but characteristically larger, when routing is performed at large spatial scales. Flow routing at large spatial scales also results in overestimation of high flows, while low flows are underestimated. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Mass Balance Estimation of Dokriani Glacier in Central Indian Himalaya Using Remote Sensing Data     

Har Amrit Singh Sandhu  Hemendra Singh Gusain  Manoj Kumar Arora  Arun Bawa 《Journal of the Indian Society of Remote Sensing》2018,46(11):1835-1840

Dokriani Glacier is regarded as one of the important glaciers of Bhagirathi River basin, which fed river Ganges. The length of the glacier is about 4.6 km, and snout elevation is about 4028 m m.s.l. The mass balance of this glacier was calculated using field-based measurements for few years during 1994 to 2000. However, due to remote and poor accessibility, the field-based measurements could not continue; thus, remote sensing-based methods become useful tool to estimate the long-term mass balance of the glacier. In this study, glacier mass balance has been determined using accumulation area ratio (AAR) method. Remote sensing data sets, e.g. Landsat TM, ETM?+?and OLI, have been used to estimate AAR for different years from 1994 to 2014. An attempt has also been made to develop a mathematical relationship between remote sensing-derived AAR and field-observed mass balance data of the glacier. Further, this relationship has been used to estimate mass balance of the glacier for different years using remote sensing-derived AAR. Estimated mass balance was validated from ground-observed mass balance for few years. The field-observed and remote sensing-derived mass balance data are compared and showed high correlation. It has been observed that AAR for the Dokriani Glacier varies from 0.64 to 0.71. Mass balance of the glacier was observed between ??15.54 cm and ??50.95 cm during the study period. The study highlights the application of remote sensing in mass balance study of the glaciers and impact of climate change in glaciers of Central Indian Himalaya.  相似文献   

Implications of new $$^{40}\hbox {Ar}/^{39}\hbox {Ar}$$ age of Mallapur Intrusives on the chronology and evolution of the Kaladgi Basin,Dharwar Craton,India     

Shilpa Patil Pillai  Kanchan Pande  Vivek S Kale 《Journal of Earth System Science》2018,127(3):32

The Kaladgi Basin on the northern edge of the Dharwar craton has characters diverse from the other epicratonic Purana basins of Peninsular India. Sedimentological studies in the basin have established the presence of three cycles of flooding separated by an event of intra-basinal deformation accompanied by low grade incipient metamorphism. The overall structural configuration of the basin indicates its development by supracrustal extension accompanied by shearing in a trans-tensional regime during the Mesoproterozoic. This was followed by sagging that yielded Neoproterozoic sedimentation in a successor nested basin. \(^{40}\)Ar/\(^{39}\)Ar dating of an intrusive mafic dyke along the axial plane of a fold has yielded a plateau age of \(1154{\pm }4\,\hbox {Ma}\). This helps constraint the age of the various events during the evolution of this basin.  相似文献   

Effect of pore connectivity on reflection amplitudes of an inhomogeneous wave in a composite porous solid saturated by two immiscible fluids     

Neeru Bala  Ashish Arora 《Journal of Earth System Science》2018,127(4):59

Present paper aims to study the phenomenon of reflection and transmission when an inhomogeneous wave strikes some discontinuity in a composite porous medium saturated by two immiscible viscous fluids. The incident wave splits into six reflected and six transmitted waves at the interface. All reflected and transmitted waves are inhomogeneous in nature with different directions of propagation vector and attenuation vector. A dimensionless parameter \(\varsigma \in [0, 1]\) is introduced to represent the extent of connection among the pores at the interface. Expression of Umov–Poynting vector is derived to obtain energy flux vector. Continuity of energy flux vector at the interface gives the required boundary conditions for the system. Connecting parameter \(\varsigma \) is also employed in boundary conditions to model the partial connection of pores at the interstices of two media. For numerical discussion we consider a porous medium composed of sandstone and ice, saturated with oil and water. The effect of parameter \(\varsigma \) and angle of incidence is determined numerically on the amplitude and the energy ratios of reflected and transmitted waves.  相似文献   

Use of site amplification and anelastic attenuation for the determination of source parameters of the Sikkim earthquake of September 18, 2011, using far-field strong-motion data     

A. Joshi  Parveen Kumar  Sandeep Arora 《Natural Hazards》2014,70(1):217-235

An earthquake of magnitude 6.9 (M _w) occurred in the Sikkim region of India on September 18, 2011. This earthquake is recorded on strong-motion network in Uttarakhand Himalaya located about 900 km away from the epicenter of this earthquake. In this paper acceleration record from six far-field stations has been used to compute the source parameters of this earthquake. The acceleration spectra of ground motion at these far-field stations are strongly affected by both local site effects and near-site anelastic attenuation. In the present work the spectrum of S-phase recorded at these far-field stations has been corrected for anelastic attenuation at both source and site and the site amplification terms. Site amplifications at different stations and near-site shear wave attenuation factor have been computed by the technique of inversion of acceleration spectra given by Joshi et al. (Pure Appl Geophys 169:1821–1845, 2012a). For estimation of site amplification and shear wave quality factor [Q _β (f)] at the recording sites, ten local events recorded at various stations between July 2011 and December 2011 have been used. The obtained source spectrum from acceleration records is compared with the theoretical source spectrum defined by Brune (J Geophys Res 76:5002, 1970) at each station for both horizontal components of the records. Iterative forward modeling of theoretical source spectrum gives the average estimate of seismic moment (M _o), source radius (r _o) and stress drop (Δσ) as (3.2 ± 0.8) × 10²⁶ dyne cm, 13.3 ± 0.8 km and 59.2 ± 8.8 bars, respectively, for the Sikkim earthquake of September 18, 2011.  相似文献   

The effect of the variability of wind forcing on ENSO simulation in an OGCM: case of canonical and protracted event     

Arora  Anika 《Theoretical and Applied Climatology》2022,147(1-2):265-281

Theoretical and Applied Climatology - This study is an attempt to understand the onset and the evolution of canonical (typical length ~ 18–24 months; CE) and protracted...  相似文献   

Bottom Boundary Layer Characteristics in the Hooghly Estuary Under Combined Wave-Current Action     

Chitra Arora  B. Prasad Kumar  Indu Jain  Ashoke Bhar  A. C. Narayana 《Marine Geodesy》2013,36(2-3):261-281

The development of a theoretical model for estimating bottom boundary layer characteristics in the Hooghly estuary, located in the east coast of India, under combined effects of waves and currents is reported. Three numerical models, viz a depth averaged hydrodynamic model, SWAN wave model, and bottom boundary layer model, were integrated. In the bottom boundary layer parameters, maximum bottom stress, effective friction factor, and near-bed velocity both during ebb and flood phases of the tidal forcing are investigated and validated for the Haldia channel. The close match seen from results signifies applicability of this model for entire Hooghly basin.  相似文献   

Polyfluoroalkyl substances requiring a renewed focus on groundwater-surface water interactions     

Craig Divine  Amar Wadhawan  Vivek Pulikkal  Prashanth Khambhammettu  Jay Erickson 《Ground Water Monitoring & Remediation》2023,43(1):14-31

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The Cadmium Zinc Telluride Imager on AstroSat     

V. Bhalerao  D. Bhattacharya  A. Vibhute  P. Pawar  A. R. Rao  M. K. Hingar  Rakesh Khanna  A. P. K. Kutty  J. P. Malkar  M. H. Patil  Y. K. Arora  S. Sinha  P. Priya  Essy Samuel  S. Sreekumar  P. Vinod  N. P. S. Mithun  S. V. Vadawale  N. Vagshette  K. H. Navalgund  K. S. Sarma  R. Pandiyan  S. Seetha  K. Subbarao 《Journal of Astrophysics and Astronomy》2017,38(2):31

The Cadmium Zinc Telluride Imager (CZTI) is a high energy, wide-field imaging instrument on AstroSat. CZTI’s namesake Cadmium Zinc Telluride detectors cover an energy range from 20 keV to \(>200\) keV, with 11% energy resolution at 60 keV. The coded aperture mask attains an angular resolution of 17\(^\prime \) over a 4.6\(^\circ \) \(\times \) 4.6\(^\circ \)  (FWHM) field-of-view. CZTI functions as an open detector above 100 keV, continuously sensitive to GRBs and other transients in about 30% of the sky. The pixellated detectors are sensitive to polarization above \(\sim \)100 keV, with exciting possibilities for polarization studies of transients and bright persistent sources. In this paper, we provide details of the complete CZTI instrument, detectors, coded aperture mask, mechanical and electronic configuration, as well as data and products.  相似文献