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排序方式: 共有271条查询结果,搜索用时 15 毫秒
61.
Simon Portegies Zwart Steve McMillan Stefan Harfst Derek Groen Michiko Fujii Breanndán Ó Nualláin Evert Glebbeek Douglas Heggie James Lombardi Piet Hut Vangelis Angelou Sambaran Banerjee Houria Belkus Tassos Fragos John Fregeau Evghenii Gaburov Rob Izzard Mario Jurić Stephen Justham Andrea Sottoriva Marcel Zemp 《New Astronomy》2009,14(4):369-378
We present MUSE, a software framework for combining existing computational tools for different astrophysical domains into a single multiphysics, multiscale application. MUSE facilitates the coupling of existing codes written in different languages by providing inter-language tools and by specifying an interface between each module and the framework that represents a balance between generality and computational efficiency. This approach allows scientists to use combinations of codes to solve highly coupled problems without the need to write new codes for other domains or significantly alter their existing codes. MUSE currently incorporates the domains of stellar dynamics, stellar evolution and stellar hydrodynamics for studying generalized stellar systems. We have now reached a “Noah’s Ark” milestone, with (at least) two available numerical solvers for each domain. MUSE can treat multiscale and multiphysics systems in which the time- and size-scales are well separated, like simulating the evolution of planetary systems, small stellar associations, dense stellar clusters, galaxies and galactic nuclei. In this paper we describe three examples calculated using MUSE: the merger of two galaxies, the merger of two evolving stars, and a hybrid N-body simulation. In addition, we demonstrate an implementation of MUSE on a distributed computer which may also include special-purpose hardware, such as GRAPEs or GPUs, to accelerate computations. The current MUSE code base is publicly available as open source at http://muse.li. 相似文献
62.
A number of archeological features, including in‐filled irrigation canals of uncertain prehistoric age, occur within the Holocene floodplain of the Salt River at Phoenix, Arizona. In the first attempt to date irrigation‐canal sediments using luminescence methods, we obtained age estimates of 1640 ± 190 yr B.P. (1σ) (multi‐aliquot or MA) and 1621 ± 95 yr B.P. (post‐IR single‐aliquot‐regenerative‐dose or SAR) for a single sample from the base of the oldest canal‐infilling deposits (all IR‐PSL ages reported in this article are in calendar years before A.D. 2001). For the remaining canal samples, weighted mean luminescence ages of 819 ± 45 yr (MA) and 826 ± 32 yr (post‐IR SAR) were obtained. Thus from photonic dating we can resolve the first and last phases of canal use at this Phoenix site: initiation at ca. 1600 years ago and final use at ca. 800 years ago. These results demonstrate the power of SAR luminescence sediment dating to enhance our understanding of prehistoric irrigation‐canal development and usage here and elsewhere in the world. © 2004 Wiley Periodicals, Inc. 相似文献
63.
Archaeological investigations into the processes and factors controlling the magnetic enhancement of soils were initiated in the 1960s in conjunction with the application of magnetic prospection surveys. After a highly productive period of research, archaeological interest in soil magnetism experienced a downswing, which has just recently been reversed. Continuing research within the fields of rock magnetism and environmental magnetism has refined our understanding of the processes and products of magnetic enhancement and demonstrated the broad applicability of soil magnetic analyses. Using this information, together with recent archaeological studies, we update archaeologists on the variety of soil magnetic techniques and how they can be utilized to define, detail, and understand archaeological sites, features, and environments. A case study at the Cahokia Mounds Site in southwestern Illinois illustrates how soil magnetic techniques can be interfaced with other methods to understand archaeological landscapes and landscape change. © 1998 John Wiley & Sons, Inc. 相似文献
64.
Forecasting of groundwater level in hard rock region using artificial neural network 总被引:2,自引:0,他引:2
In hardrock terrain where seasonal streams are not perennial source of freshwater, increase in ground water exploitation has
already resulted here in declining ground water levels and deteriorating its’ quality. The aquifer system has shown signs
of depletion and quality contamination. Thus, to secure water for the future, water resource estimation and management has
urgently become the need of the hour. In order to manage groundwater resources, it is vital to have a tool to predict the
aquifer response for a given stress (abstraction and recharge). Artificial neural network (ANN) has surfaced as a proven and
potential methodology to forecast the groundwater levels. In this paper, Feed-Forward Network based ANN model is used as a
method to predict the groundwater levels. The models are trained with the inputs collected from field and then used as prediction
tool for various scenarios of stress on aquifer. Such predictions help in developing better strategies for sustainable development
of groundwater resources. 相似文献
65.
Santanu Banerjee Shovan Lal ChattorajP.K. Saraswati Somnath DasguptaUrbashi Sarkar 《Marine and Petroleum Geology》2012,30(1):144-160
Formation and maturation of glauconites within the early Middle Eocene Harudi Formation, built up in a lagoon to shelf transition in western Kutch, India is addressed taking recourse to a combined sedimentological, micropalaeontological and mineralogical investigation. The glauconite is authigenic and its occurrence coincides with maximum flooding. The glauconite is more matured within the fecal pellets and is less matured within the intra-particle pores of bioclasts namely, foraminifera, ostracoda, gastropoda and bryozoa. SEM-EDS, XRD and geochemical studies clearly document that the infilling within the intra-particle pores of bioclasts belong to nascent to slightly evolved glauconite (<5 wt% K2O), while the pellet belongs to slightly evolved to evolved glauconite (5-7 wt% K2O). Based on chemical characteristics and SEM investigations the glauconitization process can be best explained by the ‘verdissement theory’. The glauconite possibly formed as initial authigenic glauconitic smectite precipitates; while the pellet matured subsequently by addition of K, the process was hindered in case of infillings. The maturation process also involved addition of Si and release of Al, with or without release of Mg. The glauconite maturation was facilitated in case of fecal pellets because of higher porosity, inter-granular nature of pores and availability of necessary elements in semi-confined micro-environments. In contrast, the maturation was aborted at an early stage in case of infillings because of the minute, closed nature of the pores and prevalent alkaline conditions not allowing dissolution of calcitic tests. A low negative cerium anomaly suggests glauconite formation in sub-oxic micro-environments, created by decay of organic matters within the fecal pellets and bioclasts. A clear case of substratum control on glauconitization becomes apparent. 相似文献
66.
67.
Geochemistry of the Sub-Himalayan foreland basin Siwalik sediments has been used for interpreting the nature of the source rocks. This study has shown that the compositional changes are a function of stratigraphic height, demonstrated by the upward increase of P2O5, Na2O, CaO, MgO and SiO2 content from Lower to the Upper Siwalik rocks. On the other hand, K2O, Fe2O3, TiO2 and Al2O3 show decrease with the increasing stratigraphic height. These trends are a clear reflection of time-controlled changes in the source lithology. Ratios such as Eu/Eu*, (La/Lu)cn, La/Sc, Th/Sc, La/Co, and Cr/Th suggest a prominent felsic source area for the Siwalik sediments. Chondrite-normalized REE pattern with LREE enrichment and moderately flat HREE pattern with sharp negative Eu anomaly are attributed to a felsic source. Contrary to the existing belief, this study has ruled out any contribution from the mafic sources and highlighted the compositional similarities of Siwalik sediments with the crustal proxies like PAAS, NASC and UCC. The geochemical data point to a significant role played by the Precambrian and early Paleozoic granitic rocks of the Himalayan tectogene in shaping the composition of the foreland sediments. The variable CIA values and marked depletion in Na, Mg and Ca exhibited by the Lower, Middle and Upper Siwalik sediments reflect variable climatic zones and variations in the rate of tectonic uplift of the source area. Our results demonstrate that in the Lower Siwalik and part of the Middle Siwalik, Higher Himalayan Crystalline sequence (HHCS) was the primary source area with minor contributions by the meta-sedimentary succession of the Lesser Himalaya. Later, during the deposition of the upper part of the Middle Siwalik and Upper Siwalik, the source terrain switched positions. These two prominent source terrains supplied sediments in steadily changing proportion through time. 相似文献
68.
Santanu Banerjee 《Gondwana Research》2000,3(4):521-528
The 1.2 Ga-old Koldaha shale, central India reveals three orders of depositional cyclicities in its basal storm-dominated shelf succession. Visual appraisal as well as Fourier and MEM analyses concurs in this respect. Only the major storm events at intervals of a few thousands of years have left recognizable imprints. Interbedding of storm sandstones and fairweather shales is apparently climate-controlled. Packaging of about seven such climatic cycles results the second-order cyclicity befitting eccentricity cycles of contemporary scale. Nonetheless, for the erratic storm bed-thickness trends within the cycles some other factor/s might have played a role. The third order cycles are, more dominantly, correlatable with basinal tectonics. 相似文献
69.
70.
Rupsha Banerjee Josey Kamanda Cynthia Bantilan Naveen P. Singh 《Natural Hazards》2013,65(3):1443-1464
This paper examines the relationship between local institutions and adaptation to climate variability in four semi-arid villages in India. Based on a qualitative survey, it draws attention to the constraints that farming households face, the role of institutions, and the implications for their capacities to adapt. Using an institutional framework, the study examines the role of local institutions in facilitating community adaptation to perceived climate variability. It was found that at the institutional and community level farmers rely on government schemes that provide social safety nets and the private sector such as moneylenders as sources of adaptation options regarding access to credit. Serious constraints emerged, however, in terms of adaptation to what may be a more challenging future. These constraints were further explored by means of grounded theory. The lack of collective feeling and action has hindered bargaining for better market prices and the development of alternate livelihood options. The need for better financial inclusion and access to more formal systems of finance is necessary to increase the overall adaptive capacity of households. During crisis situations or climatic shocks, the absence of these systems means the sale of household assets and resources especially among small and landless groups of farmers. Overall, rural households perceive that public, civic, and private institutions play a significant role in shielding them against the adverse effects of climate variability. The perceived importance of different institutions is, however, different across different categories of farmers, women, and labourers. 相似文献