Numerical modelling of rheological properties of landslide debris     

Ray  Arunava  Verma  Harshal  Bharati  Ashutosh Kumar  Rai  Rajesh  Koner  Radhakanta  Singh  Trilok Nath 《Natural Hazards》2022,110(3):2303-2327

Debris flow has caused severe human casualties and economic losses in landslide-prone areas around the globe. A comprehensive understanding of the morphology and deposition mechanisms of debris flows is crucial to delineate the extent of a debris flow hazard. However, due to inherent complex field topography and varying compositions of the flowing debris, coupled with a lack of fundamental understanding about the factors controlling the geomaterial flow, interparticle interactions and its final settlement resulted in a limited understanding of the flow behaviour of the landslide debris. In this study, a physical model was set up in the laboratory to simulate and calibrate the debris flow using PFC, a distinct element modelling-based software. After calibration, a case study of the Varunavat landslide was taken to validate the developed numerical model. Following validation with an acceptable level of confidence, several models were generated to evaluate the effect of slope height, slope angle, slope profile, and grain size distribution of the dislodged geomaterial in the rheological properties of debris flow. Both qualitative and quantitative analysis of the landslide debris flow was performed. Finally, the utility of retaining wall and their effect on debris flow is also studied with different retaining wall positions along the slope surface.

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Acknowledgement     

Michael Grubb  Ray Purdy 《Climate Policy》2013,13(4)

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Charged compact objects in the linear regime     

P. Mafa Takisa  S. Ray  S. D. Maharaj 《Astrophysics and Space Science》2014,350(2):733-740

Astrophysical compact stars provide a natural laboratory for testing theoretical models which are otherwise difficult to prove from an experimental setup. In our present work we analyse an exact solution to the Einstein-Maxwell system for a charged anisotropic compact body in the linear regime. The charged parameter may be set to zero which gives us the case of neutral solutions. We have tuned the model parameters for the uncharged case so as to match with recent updated mass-radius estimates for five different compact objects. Then we make a systematic study of the effect of charge for the different parameter set that fits the observed stars. The effect of charge is clearly illustrated in the increase of mass. We show that the physical quantities for the objects PSR J1614-2230, PSR J1903+327, Vela X-1, SMC X-1, Cen X-3 are well behaved.  相似文献   

Probing outflow activity in very low mass stars and brown dwarfs     

E.T. Whelan  T.P. Ray  F. Bacciotti  R. Jayawardhana 《New Astronomy Reviews》2006,49(10-12):582

The discovery that newborn very low mass stars and brown dwarfs have optical forbidden line spectra similar to low mass young stars was a strong indication that these objects can also launch outflows. Forbidden lines are the traditional tracers of outflow activity in young stars and observations at these wavelengths have contributed much to the understanding of outflows. However in the case of brown dwarfs, the forbidden emission line regions observed are not well resolved spatially. Thus, their origin in an outflow could not be confirmed. Here, the technique of spectro-astrometry as a means of spatially probing the forbidden emission line regions of very low mass stars and brown dwarfs is introduced. Indeed spectro-astrometric data presented here demonstrates, for the first time, that young brown dwarfs that are actively accreting can drive outflows. Also discussed is the important role adaptive optics will play when it comes to spatially resolving the forbidden emission line regions of sub-stellar objects and the potential for developing spectro-astrometry to a 2D form through integral field spectroscopy.  相似文献   

GMOS spectroscopy of the S0 galaxy NGC 3115     

Mark A. Norris  Ray M. Sharples  Harald Kuntschner 《Monthly notices of the Royal Astronomical Society》2006,367(2):815-824

We present Gemini Multi-Object Spectrograph longslit spectroscopy of the isolated S0 galaxy NGC 3115. We have determined kinematical data and Lick/IDS absorption line-strength indices for the major axis out to around 9 kpc and for the minor axis out to around 5 kpc (around 2R _e ). Using stellar population models which include the effects of variable [α/Fe] ratios, we derive metallicities, abundance ratios and ages for the stellar population of NGC 3115. We find that [α/Fe] remains fairly constant with increasing radius at around  [α/Fe]= 0.17  for the major axis but increases rapidly for the minor axis to around  [α/Fe]= 0.3  . We also find that to first order, this behaviour can be explained by a simple spheroid + disc model, where the spheroid has  [α/Fe]= 0.3  and the disc shows close to solar abundance ratios. The disc also appears considerably younger than the spheroid, having an age of around 6 Gyr compared to 12 Gyr for the spheroid. We compare these results to those previously presented for the globular cluster system of NGC 3115.  相似文献   

Testing the Models for Jet Generation with Hubble Space Telescope Observations     

F. Bacciotti  T.P. Ray  D. Coffey  J. Eislöffel  J. Woitas 《Astrophysics and Space Science》2004,292(1-4):651-658

Many magneto-hydrodynamic (MHD) models have been developed to describe the acceleration and collimation of stellar jets, in the framework of an infall/outflow process. Thanks to high angular resolution instrumentation, such as the one on-board the Hubble Space Telescope (HST), we are finally able to test observationally the proposed ideas. We present the results obtained by us from the first 0”.1 resolution spectra of the initial portion (within 100–200 AU from the source) of the outflows from visible T Tauri stars, taken with the Space Telescope Imaging Spectrograph (STIS). We obtain the jet morphology, kinematics and excitation in different velocity intervals, and we derive the jet mass and momentum fluxes. These results confirm the predictions of magneto-centrifugal models for the jet launch. Recently we have also found indications for rotation in the peripheral regions of several flows. The derived rotational motions appear to be in agreement with the expected extraction of angular momentum from the star/disk system caused by the jet, which in turn allows the star to accrete up to its final mass. Improvements to resolution are expected from observations with STIS in the ultraviolet, and with the forthcoming AMBER spectrometer to be mounted at the VLTI.  相似文献   

Trace metal geochemistry of core sediments between Visakhaptanam and Kakinada,along the eastcoast of India     

Nalla  Purnachander Reddy  Neethipudi  Alien Sravanthi  Vangala  Sarma V.  Ray  Ajay Kumar 《中国地球化学学报》2006,25(1):19-19

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Critical properties and stability of stationary solutions in multitransonic pseudo-Schwarzschild accretion     

Soumini Chaudhury  Arnab K. Ray  Tapas K. Das 《Monthly notices of the Royal Astronomical Society》2006,373(1):146-156

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Gemini/GMOS imaging of globular clusters in the Virgo galaxy NGC 4649 (M60)     

Duncan A. Forbes  Favio Raul Faifer  Juan Carlos Forte  Terry Bridges  Michael A. Beasley  Karl Gebhardt  David A. Hanes  Ray Sharples  Stephen E. Zepf 《Monthly notices of the Royal Astronomical Society》2004,355(2):608-616

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On the thermal evolution of the terrestrial planets     

Peter E. Fricker  Ray T. Reynolds  Audrey L. Summers 《Earth, Moon, and Planets》1974,9(1-2):211-218

Physical and chemical constraints for such different planetary objects as the Earth, the Moon and meteorite parent bodies can best be satisfied by thermal history models having high initial temperatures. On the basis of thermal calculations it is suggested that the evolution of the other terrestrial planets (Mars, Venus and Mercury) was also characterized by high initial temperatures. Under these conditions, melting and, consequently, fractionation would set in at an early stage. Because of the resulting redistribution of the long-lived radioactive heat sources and the concentration of these elements in the surface layers, large-scale differentiation could be achieved by partial melting.Paper presented at the Lunar Science Institute Conference on Geophysical and Geochemical Exploration of the Moon and Planets, January 10–12, 1973.  相似文献