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31.
Anish K. Warrier K. Sandeep B.G. Harshavardhana R. Shankar Shanti Pappu Kumar Akhilesh C.N. Prabhu Y. Gunnell 《Journal of archaeological science》2011,38(12):3681-3693
Attirampakkam, an open-air stratified Palaeolithic site in southeastern India is the focus of ongoing studies to investigate the nature of Lower and Middle Palaeolithic occupation in relation to changing Pleistocene environments. The paucity of faunal or palaeobotanical remains at the site required the use of rock magnetic properties (χlf, χfd, χfd %, χARM, SIRM, χARM/SIRM, SIRM/χlf, χARM/χlf, χARM/χfd, S-ratio, HIRM and HIRM/IRM300mT) as proxies for deciphering the palaeoenvironments and palaeoclimates of the region. Rock magnetic data from stratified deposits within excavated trenches show that the bulk of the sedimentation was intermittent with no subaerial exposure of sediments for long periods, and points to fluctuating wetter and drier climates associated with the Acheulian to Late Middle Palaeolithic levels. There is a general trend towards a wetter climate from Layer 5 upwards. Layer 7 offers evidence of bacterial magnetite (χARM/χlf > 40 and χARM/χfd > 1000), suggesting the onset of micro-anaerobic environments as a result of floods. Greigite is indicated in Layer 5 (SIRM/χlf > 30 × 103 A m?1), which indicates a reducing environment. Layer 2 represents an arid climate (higher proportion of haematite and a coarser magnetic grain size). Layer 1a again is indicative of an arid climate (presence of calcrete, magnetically “hard” minerals and coarser magnetic grain size). Results indicate that the southeast coast of India experienced a mostly dry tropical climate during the Pleistocene. The detected occurrence of a few notably more arid intervals did not disrupt occupation of the site by successive groups of hominins. 相似文献
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There is an increasing policy focus on India’s demographic potential and associated growth benefits. This paper provides empirical evidence regarding the net growth benefits derived from an increased share of working-age population in India. The analysis adopts decomposition and econometric methods, using data at the state and national level in India, to robustly test the nature and magnitude of the demographic dividend in India. We find that the Indian economy is drawing significant benefits from the ongoing process of demographic transition, with dividend effects estimated to be over one percentage point per annum during 1980–2010. However, to derive high growth from the demographic potential would require tackling some of the growth constraints. The paper discusses ways in which these constraints can be addressed to fully tap the potential of demographic dividend. 相似文献
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Patrick D. Nunn Roselyn Kumar Sepeti Matararaba Tomo Ishimura Johnson Seeto Sela Rayawa Salote Kuruyawa Alifereti Nasila Bronwyn Oloni Anupama Rati Ram Petero Saunivalu Preetika Singh Esther Tegu 《Archaeology in Oceania》2004,39(3):139-143
A newly‐discovered Lapita settlement at Bourewa on southwest Viti Levu Island, Fiji, was established originally on an offshore island perhaps as much as 1220 BCE by people whose main concern was optimal access to the broad fringing reef. Satellite settlements were established at nearby Rove and Waikereira later in Lapita times. The three oldest radiocarbon dates obtained from the base of the tightly‐packed shell midden layer excavated at Bourewa and charcoal in the beach sand below are calibrated/corrected to 1220‐970 BCE, 1210‐940 BCE, and 1130‐910 BCE. The Bourewa Lapita site appears to be the oldest‐known in Fiji. 相似文献
34.
Frank R. Thomas Patrick D. Nunn Tamara Osborne Roselyn Kumar Francis Areki Sepeti Matararaba David Steadman Geoff Hope 《Archaeology in Oceania》2004,39(1):42-49
A large sea cave on the southeastern tip of Vanuabalavu Island, northeast Fiji was excavated and shown to have been used by humans from about 1100 cal BP with rapid accumulation of material. The cave may have been uninhabitable until sufficient sand had built up to make flooding by the sea a rare event, and a possible fall in sea‐level could have contributed. With rapid cooling and sea‐level fall after about 700 BP, more intensive use followed. The cave probably gained prominence in serving as a location where marine resources were cooked prior to being carried to nearby mountain‐top settlements, established as a consequence of environmental change affecting coastal settlements. It fell into disuse with the re‐establishment of coastal villages about 150 years ago. 相似文献
35.
J. P. Singh Pankaj Agarwal Ashok Kumar S. K. Thakkar 《Journal of Earthquake Engineering》2014,18(3):444-457
Modal parameters of an instrumented multi-storied reinforced concrete building (G +9) have been studied using strong motion records of Bhuj Earthquake, 2001. The Ambient Vibration Testing (AVT) is also conducted to measure the modal parameters of the same building under ambient environmental forces. Frequency Domain Decomposition (FDD) or Peak Picking (PP) in frequency domain and Stochastic Subspace Identification (SSI) technique in time domain is used for extracting the modal parameters. The observed natural frequencies during strong motion are smaller than the ambient vibration testing. The difference in the frequencies may be caused by interaction between structure and soil due to high level of strain during strong motion earthquake. The modal pattern of first five modes obtained from strong motion records and ambient vibration records are identical. 相似文献
36.
Hemant Kumar Vinayak Ashok Kumar Pankaj Agarwal Shashi Kant Thakkar 《Journal of Earthquake Engineering》2013,17(5):771-787
This article puts forth the work on a neural network-based approach to determine the degree of damaged floors of the building considering changes in the transfer function. The transfer function is considered for that part of forced vibration in which system vibrates linearly after the structure has been damaged considering the building is instrumented during the earthquake. The results showed that accuracy of degree of damage detected increased with the increase in the number of combination of damages. The instrumentation of the first floor is expected to give best results for damage detection based on the transfer function-based approach. 相似文献
37.
Prabha Kalia Prabhas Kumar Pande Trilochan Singh 《Alcheringa: An Australasian Journal of Paleontology》2013,37(3):207-227
Foraminiferal assemblage from Permian rocks of Eastern Himalaya, India are recorded for the first time. Twenty-two genera and twenty-eight species are documented from the Garu Formation, Eastern Himalaya. The foraminiferal assemblage supports previous age determinations based on megafauna. The distinctive foraminiferal assemblage from India supports the recognition of Australian and Afghanistan-Indian provinces in the Early Permian Austral realm. An appreciable number of common species in these provinces is indicative of close geographic links. 相似文献
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Shale gas reservoirs like coalbed methane (CBM) reservoirs are promising targets for geological sequestration of carbon dioxide (CO2). However, the evolution of permeability in shale reservoirs on injection of CO2 is poorly understood unlike CBM reservoirs. In this study, we report measurements of permeability evolution in shales infiltrated separately by nonsorbing (He) and sorbing (CO2) gases under varying gas pressures and confining stresses. Experiments are completed on Pennsylvanian shales containing both natural and artificial fractures under nonpropped and propped conditions. We use the models for permeability evolution in coal (Journal of Petroleum Science and Engineering, Under Revision) to codify the permeability evolution observed in the shale samples. It is observed that for a naturally fractured shale, the He permeability increases by approximately 15% as effective stress is reduced by increasing the gas pressure from 1 MPa to 6 MPa at constant confining stress of 10 MPa. Conversely, the CO2 permeability reduces by a factor of two under similar conditions. A second core is split with a fine saw to create a smooth artificial fracture and the permeabilities are measured for both nonpropped and propped fractures. The He permeability of a propped artificial fracture is approximately 2‐ to 3fold that of the nonpropped fracture. The He permeability increases with gas pressure under constant confining stress for both nonpropped and propped cases. However, the CO2 permeability of the propped fracture decreases by between one‐half to one‐third as the gas pressure increases from 1 to 4 MPa at constant confining stress. Interestingly, the CO2 permeability of nonpropped fracture increases with gas pressure at constant confining stress. The permeability evolution of nonpropped and propped artificial fractures in shale is found to be similar to those observed in coals but the extent of permeability reduction by swelling is much lower in shale due to its lower organic content. Optical profilometry is used to quantify the surface roughness. The changes in surface roughness indicate significant influence of proppant indentation on fracture surface in the shale sample. The trends of permeability evolution on injection of CO2 in coals and shales are found analogous; therefore, the permeability evolution models previously developed for coals are adopted to explain the permeability evolution in shales. 相似文献
40.
Chronology of red dune aggradations of South India and its Palaeo-environmental significance 总被引：1，自引：0，他引：1
Linto Alappat Palaniandy Seralathan Anil D. Shukla Kyth Pillai Thrivikramji Ashok Kumar Singhvi 《Geochronometria》2013,40(4):274-282
Red sand dunes occur in the coastal plains of south east and west of Tamil Nadu, India between the coordinates of 8°00′ to 9°30′ N; 77°18′ to 79° 00′ E. OSL dating of these sands indicated aggradations between ～16-9 ka and ～9-3 ka in the west and east coasts respectively. Dating results from inland red dunes at the foothills of Western Ghats show a break in deposition at ～6 ka and aggradation since ～2 ka. The sand aggradations in the west coast occurred during the transition period when SW monsoon in the area was reestablishing. The dunes attained their stability by 9 ka. In the coastal region, the aggradations were controlled by sea level changes and a local recycling of earlier dunes (in the east coast). In the inland areas, the dune building was controlled by sand supply from fluvial sources. 相似文献