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131.
D. Pellion K. Jradi A. Le Padellec A. Rennane F. Moutier V. Borrel D. Esteve C. Magenc A. R. Bazer-Bachi 《Experimental Astronomy》2010,27(3):187-195
Due to its sensitivity and speed, the detector still widely used in Cerenkov astrophysics experiments remains the PhotoMultiplier
Tube (PMT). For instance, recent pathbreaking experiments in Very High Energy astrophysics (VHE), such as MAGIC and HESS,
have used mainstream PMT technology [Aharonian, F. et al Astron. Astrophys. 492(1):L25–L28 (2008)]. Moreover the Cerenkov Telescope Array (CTA) which is now in its design phase, is also planed to be based on PMT’s. However,
there are some disadvantages to the PMT technology: the rather poor quantum efficiency, the use of high voltages, the high
cost when used in large number in a matrix arrangement and the large weight. Hence, we have investigated the possibility to
design future Cerenkov telescopes based on solid state technology, specifically Geiger avalanche photodiodes. In a preliminary
development test, we placed HAMAMATSU avalanche photodiodes at the focal plane of a 60 cm diameter telescope at the Pic du
Midi in the French Pyrénées, in order to record incident cosmic rays. In this paper, we describe not only the experimental
setup but we also put special emphasis to the reduction of the semi-conductor noise. We also show first data that were recorded
during two runs in the fall of 2006, and conclude by the presentation of the design of an “integrated, low-cost solid state
photodiode arrangement” which might be an alternative to PMT’s for future VHE telescopes. 相似文献
132.
Hydrated minerals on Mars are most commonly found in ancient terrains dating to the first billion years of the planet’s evolution. Here we discuss the identification of a hydrated light-toned rock unit present in one Chasma of the Noctis Labyrinthus region. Stratigraphy and topography show that this alteration layer is part of a thin unit that drapes pre-existing bedrock. CRISM spectral data show that the unit contains hydrated minerals indicative of aqueous alteration. Potential minerals include sulfates such as bassanite (CaSO4·1/2H2O) or possibly hydrated chloride salts. The proximity of a smooth volcanic plain and the similar crater model age (Late Amazonian, <100 Myr) of this plain and the draping deposits suggest that the alteration layer may be formed by the interaction of water with ash layers deposited during this geologically recent volcanic activity. The alteration phases may have formed due to the presence of snow in contact with hot ash, or eventually solid-gas interactions due to the volcanic activity. The relatively young age of the volcanic plain implies that recent alteration processes have occurred on Mars in relation with volcanic activity, but such local processes do not require conditions different than the current climate. 相似文献
133.
The evolution of the 27-day recurrence in the series of two solar indices (Wolf number WN and 10.7 cm radio flux F) and two geomagnetic indices (Dst and ζ, variance of the geomagnetic field recorded at a magnetic observatory) have been studied over the 1957 – 2007 time
span. Spectral energies contained in two period domains (25 – 27.3 and 27.3 – 31 days), designated as E
1 and E
2, have been computed. Whereas the evolution of E
1 is the same for the four indices, that of E
2 is essentially different for WN and F on the one hand, Dst and ζ on the other hand. Some general conclusions on the dynamics of the solar outer layers are inferred from these results.
First the solar activity, as measured by WN, and when averaged over a few years, evolves in the same way whatever the latitude.
Second, two families of coronal holes (CHs) are identified; the rapidly and the slowly rotating CHs evolve quite differently. 相似文献
134.
沈阳长白乡-观音阁断裂、抚顺浑河断裂的定位和活动性研究 总被引:3,自引:0,他引:3
本文基于对沈阳长白乡-观音阁断裂,以及抚顺浑河断裂开展的1:10000地质地貌填图工作,获得了这两条断裂在最老第四纪地层热释光的测年结果,它们分别为(112±6.7)ka和(150±9.0)ka。长白乡-观音阁断裂为一沿丘陵山地前缘分布的断裂,由2—3条分支断裂组成,最新的断面活动显示为压扭性正断层性质。断裂在晚更新世坡洪积扇堆积形成以来没有活动显示。3条浅层人工地震测线探测结果表明,其上断点均未错断第四系上更新统底界。断裂为中更新世活动断裂,晚更新世以来没有活动。浑河断裂为一沿丘陵山地前缘分布的断裂,由3—4条分支断裂组成,最新的断面活动显示为压扭性正断层性质。断裂在晚更新世坡洪积扇堆积形成以来没有活动显示。5条浅层人工地震测线探测结果表明,其上断点均在第四系上更新统底界以下。断裂为中更新世活动断裂,晚更新世以来没有活动。 相似文献
135.
<正>Sequence stratigraphical analysis was applied to the Upper Carboniferous-Lower Permian sedimentary succession of the northeastern Ordos Basin,north China based on data acquired from ten entire logging curves and eight outcrops.The facies framework of the lithostratigraphical unit,the Taiyuan Formation comprises seven facies in two facies associations,varying from fluvio-delta to shelf-barrier islands.The facies are presented within a chronostratigraphical framework,linked by systems tract,which in turn are limited by flooding surfaces and sequence boundaries.Six third-order depositional sequences are recognised,bounded by six type 2 unconformities.An upwards-shallowing epicontinental sea sedimentary model is created,which consists of a sandstone,coal seam and carbonate succession. 相似文献
136.
Véronique Lavastre Corinne Le Gal La Salle Jean-Luc Michelot Sophie Giannesini Lucilla Benedetti Joël Lancelot Bernard Lavielle Marc Massault Bertrand Thomas Eric Gilabert Didier Bourlès Norbert Clauer Pierre Agrinier 《Applied Geochemistry》2010
Groundwaters from the Tithonian/Kimmeridgian, Oxfordian and Upper Dogger aquifers, within the eastern part of the Paris basin (France), were characterised using 3H, 14C and 36Cl, and noble gases tracers, to evaluate their residence times and determine their recharge period. This information is an important prerequisite to evaluating the confinement properties of the Callovo-Oxfordian clay formation sandwiched between the Oxfordian aquifer and the Dogger aquifer, currently being investigated by the French nuclear waste management agency (Andra) for radioactive waste disposal. Data presented in this paper are used to test 4 hypotheses. 相似文献
137.
138.
广东省1960~2007年降雨侵蚀力变化趋势分析 总被引:3,自引:0,他引:3
降雨侵蚀力反映由降雨引起的土壤侵蚀的潜在能力.本文利用广东省25个站点48年(1960~2007)的日雨量资料计算了各站的降雨侵蚀力,并用Mann-Kendall(M-K)非参数检验和克里格空间插值法分析了降雨侵蚀力的时空变化规律.结果表明:广东省降雨侵蚀力的空间分布呈沿海向内陆逐渐递减的趋势.全省大部分地区的年降雨侵蚀力呈现不明显上升趋势,且存在较明显的年代际和年际变化.降雨侵蚀力的年内分布特征和降雨量分布类似,呈"双峰型",主要集中在4~9月的雨季.对于季节序列,冬季、春季和夏季大部分地区的降雨侵蚀力有不同程度的上升,秋季全省几乎所有地区呈下降趋势.汛期的降雨侵蚀力变化特征与年降雨侵蚀力相似. 相似文献
139.
P.A. Balykin G.V. Polyakov A.E. Izokh Tran Trong Hoa Ngo Thi Phuong Tran Quoc Hung T.E. Petrova 《Russian Geology and Geophysics》2010,51(6):611-624
The Jinping–Song Da rift structure in the Emeishan Large Igneous Province is composed of Permian high- and low-Ti volcanic and volcanoplutonic ultramafic-mafic associations of different compositions and genesis. High-Ti picrites, picrobasalts, basalts, and dolerites are enriched in LREE and depleted in HREE and show low Al2O3/TiO2 ratios (~4), commensurate εNd(T) values (+0.5 to +1.1), and low (Th/Nb)PM ratios similar to those of OIB-enriched mantle source. The established geochemical characteristics evidence that the parental melts of these rocks were generated from garnet lherzolite at the depths of garnet stability (~200 to 400 km). Later, high-Mg low-Ti volcanics (komatiites, komatiitic basalts, and basalts) and associating small peridotite-gabbro massifs and komatiite-basalt dikes were produced as a result of ~20% partial melting of depleted water-poor (≤0.03 wt.% H2O) peridotite substratum from the hottest upper part of mantle plume at relatively shallow depths (100–120 km). The LREE-depleted komatiites and komatiitic basalts are characterized by low (Ce/Yb)CH values, 187Re/188Os = 0.05–1.2, 87Sr/86Sr = 0.704–0.706, positive εNd(T) values (+3 to +8), γOs = –0.5 to +0.9, and strong negative anomalies of Ba, K, and Sr on the spidergrams. The scarcer LREE-enriched komatiites, komatiitic basalts, and basalts vary greatly in chemical composition and values of εNd(t) (+6.4 to –10.2), 87Sr/86Sr (0.706–0.712), and γOs (+14.8 to +56), which is due to the different degrees of crustal contamination of parental magmas. The Rb-Sr isotopic age of basaltic komatiite is 257 ± 24 Ma. The Re-Os age determined by analysis of 12 komatiite samples is 270 ± 21 Ma. These data agree with the age of flood basalts of the Emeishan Large Igneous Province. The komatiite-basalt complex of the Song Da rift is still the only Phanerozoic PGE-Cu-Ni-complex of this composition. The geochemistry of accompanying Cu-Ni-PGE-ores confirms their relationship with komatiite-basaltic magmatism. 相似文献
140.
Pilot Block Method Methodology to Calibrate Stochastic Permeability Fields to Dynamic Data 总被引:1,自引:1,他引:0
Mickaele Le Ravalec-Dupin 《Mathematical Geosciences》2010,42(2):165-185
In the present paper, a new geostatistical parameterization technique is introduced for solving inverse problems, either in
groundwater hydrology or petroleum engineering. The purpose of this is to characterize permeability at the field scale from
the available dynamic data, that is, data depending on fluid displacements. Thus, a permeability model is built, which yields
numerical flow answers similar to the data collected. This problem is often defined as an objective function to be minimized.
We are especially focused on the possibility to locally change the permeability model, so as to further reduce the objective
function. This concern is of interest when dealing with 4D-seismic data. The calibration phase consists of selecting sub-domains
or pilot blocks and of varying their log-permeability averages. The permeability model is then constrained to these fictitious
block-data through simple cokriging. In addition, we estimate the prior probability density function relative to the pilot
block values and incorporate this prior information into the objective function. Therefore, variations in block values are
governed by the optimizer while accounting for nearby point and block-data. Pilot block based optimizations provide permeability
models respecting point-data at their locations, spatial variability models inferred from point-data and dynamic data in a
least squares sense. A synthetic example is presented to demonstrate the applicability of the proposed matching methodology. 相似文献