波令-阿勒罗德间冰期时期西南印度夏季季风降雨的变化性     

Ashish Sinha  徐明芝 《海洋地质前沿》2006,22(5):15-17

北方春季时期印度次大陆和西藏高原的差异性增热吸引了印度洋的潮湿空气穿越印度大陆,产生了世界上最显著的西南印度夏季季风(ISM)体系(Webster,1987)。世界上大约25%的人口受到这种季节降雨的影响。20世纪60年代末期,印度约150万人死于连续3年的季风失常(重大灾害数据库,2005)  相似文献   

Linking hydrology and sediment dynamics of large alluvial rivers to landscape diversity in the Ganga dispersal system,India          下载免费PDF全文

Nonigopal G. Roy  Rajiv Sinha 《地球表面变化过程与地形》2017,42(7):1078-1091

Discharge and sediment load data for several stations along the Ganga River and its major tributaries in the western Ganga plains (WGP) for a period of ~30 years have been analysed to understand the hydrological characteristics and sediment dynamics. In terms of hydrology, the rivers are less flood‐prone than believed, exceeding bankfull discharges less frequently than the expected 1.5 year return interval. This has been attributed to the rivers of this region occupying incised valleys formed in the Late Quaternary period. Rivers draining the WGP are supply‐limited systems compared to those draining the eastern Ganga plains (EGP) which have been characterized as transport‐limited systems. We suggest that such geomorphic diversity as a function of spatial variability in precipitation regime and hinterland geology has existed for at least the Late Quaternary period and they in turn influence the modern day hydrology of the river systems in a significant way. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Seismic time‐lapse imaging using interferometric least‐squares migration: Case study          下载免费PDF全文

Mrinal Sinha  Gerard T. Schuster 《Geophysical Prospecting》2018,66(8):1457-1474

Seismic time‐lapse surveys are susceptible to repeatability errors due to varying environmental conditions. To mitigate this problem, we propose the use of interferometric least‐squares migration to estimate the migration images for the baseline and monitor surveys. Here, a known reflector is used as the reference reflector for interferometric least‐squares migration, and the data are approximately redatumed to this reference reflector before imaging. This virtual redatuming mitigates the repeatability errors in the time‐lapse migration image. Results with synthetic and field data show that interferometric least‐squares migration can sometimes reduce or eliminate artifacts caused by non‐repeatability in time‐lapse surveys and provide a high‐resolution estimate of the time‐lapse change in the reservoir.  相似文献   

Target-oriented imaging using extended image volumes: a low-rank factorization approach     

Rajiv Kumar  Marie Graff  Ivan Vasconcelos  Felix J. Herrmann 《Geophysical Prospecting》2019,67(5):1312-1328

Imaging in geological challenging environments has led to new developments, including the idea of generating reflection responses by means of interferometric redatuming at a given target datum in the subsurface, when the target datum lies beneath a complex overburden. One way to perform this redatuming is via conventional model-based wave-equation techniques. But those techniques can be computationally expensive for large-scale seismic problems since the number of wave-equation solves is equal to two times the number of sources involved during seismic data acquisition. Also conventional shot-profile techniques require lots of memory to save full subsurface extended image volumes. Therefore, we can only form subsurface image volumes in either horizontal or vertical directions. To exploit the information hidden in full subsurface extended image volumes, we now present a randomized singular value decomposition-based approach built upon the matrix probing scheme, which takes advantage of the algebraic structure of the extended imaging system. This low-rank representation enables us to overcome both the computational cost associated with the number of wave-equation solutions and memory usage due to explicit storage of full subsurface extended image volumes employed by conventional migration methods. Experimental results on complex geological models demonstrate the efficacy of the proposed methodology and allow practical reflection-based extended imaging for large-scale five-dimensional seismic data.  相似文献   

VFPI: an isolation device for aseismic design     

M. Pranesh  Ravi Sinha 《地震工程与结构动力学》2000,29(5):603-627

Sliding isolators with curved surface are effective base isolation systems incorporating isolation, energy dissipation and restoring mechanism in one unit. However, practical utility of these systems, such as friction pendulum system (FPS) has limitations due to constant isolator period and restoring force characteristics. A new isolator called the variable frequency pendulum isolator (VFPI) that overcomes these limitations while retaining all the advantages has been described in this paper. VFPI has oscillation frequency decreasing with sliding displacement, and the restoring force has an upper bound so that the force transmitted to the structure is limited. The mathematical formulations for the response of a SDOF structure and energy balance are also described. Parametric studies have been carried out to critically examine the behaviour of structures isolated with VFPI, FPS and PF system. From these investigations, it is concluded that the VFPI combines the advantages of both FPS and PF system, without their undesirable properties. The VFPI performance is also found to be stable during low‐intensity excitations, and fail‐safe during high‐intensity excitations. VFPI is found to exhibit robust performance for a wide range of structure, isolator and ground motion characteristics clearly demonstrating its advantages. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Historical analogues of the recent extreme minima observed in the Atlantic meridional overturning circulation at 26°N     

Adam T. Blaker  Joël J.-M. Hirschi  Gerard McCarthy  Bablu Sinha  Sarah Taws  Robert Marsh  Andrew Coward  Beverly de Cuevas 《Climate Dynamics》2015,44(1-2):457-473

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Influence of binary fraction on the fragmentation of young massive clusters—a Monte Carlo simulation     

Tanuka Chattopadhyay  Abisa Sinha  Asis Kumar Chattopadhyay 《Astrophysics and Space Science》2016,361(4):120

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Quantification of Urban Landscape Dynamics Using Patch Parameters and Landscape Indices: An Analytical Study of Ranchi     

Pammi Nitin Sinha  Nilanchal Patel  Ayyemperumal T. Jeyaseelan  Vivek K. Singh 《Journal of the Indian Society of Remote Sensing》2011,39(2):225-233

Urbanization incepts serious challenges of growth and its management. The issues of urbanization manifest in the form of overcrowding, congestion, insufficient infrastructure, inadequate service provisioning, environmental degradation, pollution etc and affect the socioeconomic development of the city. Ranchi, the capital of newly formed state of Jharkhand (India) has been witnessing the same scenario; raising the question of its planning and management of growth to make it more efficient and sustainable. It hoists the necessity to study the pattern of urbanization and its impact on other landuse/landcover categories in Ranchi city. In order to assess the urbanization pattern and spatio-temporal dynamics in the study area, the changing pattern of the three significant patch parameters viz. patch frequency, largest patch size and average patch size of all affected landuse/landcover categories over a time gradient representing the pre-capital and post-capital formation phases of the Ranchi city have been analyzed. The two conventional landscape indices viz. Shannon’s diversity Index and Simpson’s diversity index and a newly developed index ‘Normalized Patch size Range Index’ have been employed in the analyses which not only ascertained the finding derived but also provided meaningful insights pertaining to the spatio-temporal urban landscape dynamics prevailing in the Ranchi city.  相似文献   

Robe’s problem: its extension to 2+2 bodies     

Bhavneet Kaur  Rajiv Aggarwal 《Astrophysics and Space Science》2012,339(2):283-294

In the problem of 2+2 bodies in the Robe’s setup, one of the primaries of mass m^*₁m^{*}_{1} is a rigid spherical shell filled with a homogeneous incompressible fluid of density ρ ₁. The second primary is a mass point m ₂ outside the shell. The third and the fourth bodies (of mass m ₃ and m ₄ respectively) are small solid spheres of density ρ ₃ and ρ ₄ respectively inside the shell, with the assumption that the mass and the radius of third and fourth body are infinitesimal. We assume m ₂ is describing a circle around m^*₁m^{*}_{1}. The masses m ₃ and m ₄ mutually attract each other, do not influence the motion of m^*₁m^{*}_{1} and m ₂ but are influenced by them. We also assume masses m ₃ and m ₄ are moving in the plane of motion of mass m ₂. In the paper, the equations of motion, equilibrium solutions, linear stability of m ₃ and m ₄ are analyzed. There are four collinear equilibrium solutions for the given system. The collinear equilibrium solutions are unstable for all values of the mass parameters μ,μ ₃,μ ₄. There exist an infinite number of non collinear equilibrium solutions each for m ₃ and m ₄, lying on circles of radii λ,λ′ respectively (if the densities of m ₃ and m ₄ are different) and the centre at the second primary. These solutions are also unstable for all values of the parameters μ,μ ₃,μ ₄, φ, φ′. Such a model may be useful to study the motion of submarines due to the attraction of earth and moon.  相似文献   

Maria Evgen’evna Raaben (1920–2012)     

Anshu Kumar Sinha  Mukund Sharma 《Journal of the Geological Society of India》2013,81(5):721-721

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