共查询到20条相似文献，搜索用时 31 毫秒
1.
The effect of water compressibility on the seismic responses of arch dams is not well understood. In this paper, a numerical model is developed with rigorous representation of the dynamic interaction between arch dam-water-rock foundation. The model is applied to the seismic response a nalysis of an arch dam with a height of 292m designed to aseismic intensity of IX. It is shown that consideration of the water compressibility clearly decreases the stress responses at key positions of the dam, while the added mass model gives a conservative estimate. 相似文献
2.
Thallium pollution associated with mining of thallium deposits 总被引：3，自引：0，他引：3
Thallium pollution and poisoning have been found in mining districts of thalliuni deposits as a result of introduction of
thallium into surface waters, soils, plants and human body owing to weathering and leaching of TI-rich ores and rocks left
in the open air. Waters in these mining districts are divided into four types according to their T1 contents and concentration
of less than 1×10-9 is proposed as thallium standard for drinking water.
Project supported jointly by the National Natural Science Foundation of China (Grant No.49571063) and Science and Technology Foundation of Guizhou Province (Grant No. 3035). 相似文献
3.
速度型拾振器低频特性的拓展技术研究 总被引：10，自引：6，他引：4
本文介绍了速度型拾振器低频特性的拓展技术研究．在小体积的往复式摆上利用无源伺服技术、有源伺服技术和闭环极点补偿技术,实现了速度型拾振器低频特性和测量量程的扩展,满足了(超)低频工程振动测量的需要。 相似文献
4.
Geochemical characteristics and genesis of Dachadaban ophiolite in North Qilian area 总被引：6，自引：0，他引：6
There are three groups of pillow volcanics in the Dachadaban ophiolite. Group 1 is typical boninite, enriched in Si, Mg and
depleted in Ti, HREE and HFSE; group 2 is the evolved boninite, slightly higher abundance of Ti, HREE, HFSE and large variation
of Mg’ due to fractional crystallization; and group 3 is tholeiite with MORB character. The existence of MORB and boninite
indicates that the Dachadaban ophiolite was probably formed in islandare and back-arc environments.
Project supported by both the Department of Foundation Research and High Technology, State Science and Technology Commission
of PRC, and the National Natural Science Foundation of China (Grant No. 49472101). 相似文献
5.
A new approach to reducing the seismic response of spatial structures with magneto-rheological (MR) dampers is presented in
this paper. The Genetic Algorithm with small populations (μGA) is used to optimize the control for the MR dampers to reduce
structural vibration, which is difficult to achieve using classical optimal control. The advantages of μGA are the use of
global properties and that fewer conditions are required to obtain the optimal function. Numerical results demonstrate the
effectiveness of the proposed method in reducing the seismic response of structures.
Supported by: the Outstanding Youth Science Foundation of the National Natural Science Foundation of China Under Grant No. 50025823 相似文献
6.
Conduit system and formation mechanism of heat fluids in diapiric belt of Yinggehai basin, China 总被引：3，自引：0，他引：3
The conduit system of heat fluids in diapiric belt of Yinggehai basin is dominantly vertical faults and fractures. Detailed
research on the formation mechanism and their occurrence features shows that the faults and fractures can be classified into
three types: intrastratal dispersive hydrofracture, puncturing fault and upwarping-extensional fault. The development of the
fault and fracture system not only resulted in the changes of the temperature and pressure fields in the basin, but also affected
the hydrocarbon migration in the overpressured system. These faults and fractures constituted the main pathways for vertical
hydrocarbon migration, and opening and closing intermittently led to episodic expulsion of overpressured fluid compartment.
Thus there formed the pool-forming model of multi-source mixing and ploy-stage migration and accumulation for hydrocarbons
in the Yinggehai basin.
Project jointly supported by the Ministry of Science and Technology of China (Grant No.95-Pre-39) and the National Natural
Science Foundation of China (Grant No. 49732005), and A Hundred Excellent Researchers Foundation from the Ministry of Land
and Resources. 相似文献
7.
Cyclostratigraphy of the Induan (Early Triassic) in West Pingdingshan Section, Chaohu, Anhui Province 总被引：1，自引：0，他引：1
The Induan sequence in the West Pingdingshan Section, Chaohu, Anhui Province, displays a series of superimposed mudstone/limestone cycles. The lithological character of the cycles, combined with power spectral and wavelet analysis of magnetic susceptibility readings, reveals 12 short eccentricity and 56 precession Milankovitch cycles - obliquity cycles are not apparent. The uniformity of cycle thicknesses indicates a stable depositional setting making this section ideal to perform various geo-logical studies. Accordingly, the Induan Stage is estimated to have lasted 1.1 Ma, and the depositional rate for this part of the section is about 3.7 cm/ka. This places the Induan-Olenekian boundary in the West Pingdingshan Section at about 251.5 Ma based on an age of 252.6 Ma for the Permian-Triassic boundary. 相似文献
8.
Pleistocene radiolarian biostratigraphy in the South China Sea* 总被引：4，自引：0，他引：4
Based on a quantitative radiolarian analysis, 5 radiolarian zones (NR1-NR5) have been defined at Core. 17957-2 from the South
China Sea, considering radiolarian zonations from low latitudes. The absolute age assignment of the radiolarian zones and
the ranges of the six marker species is based on the direct correlation with the paleomagnetic and isotopic record, respectively.
A comparison of the radiolarian stratigraphic data obtained from Core 17957-2 from the South China Sea with those from the
equatorial Pacific and the tropical Indian Ocean shows a close similarity to the ages defined in the equatorial Pacific. The
obtained biostratigraphic data provide an excellent tool for further dating of Pleistocene sediments in the China Sea.
Project supported by the National Natural Science Foundation of China (Grant No. 49291100) and by the German Federal Ministry
for Education, Science, Research and Technology (BMBF) as part of a GermadChinese scientific cooperation program. This is
Alfred Wegener Contribution No. 1473. 相似文献
9.
ShanChi Peng Loren E. Babcock JingXun Zuo HuanLing Lin XueJian Zhu XianFeng Yang YuPing Qi Gabriella Bagnoli LongWu Wang 《中国科学D辑(英文版)》2009,52(4):434-451
Exposed in natural outcrops near the Duibian Village, Jiangshan County, Zhejiang Province, China, the Duibian B section is
proposed as the boundary stratotype for the base of an unnamed stage termed provisionally Cambrian Stage 9. The proposed position
of the GSSP is 108.12 m above the base of the Huayansi Formation, at a horizon coinciding with the first appearance of the
cosmopolitan agnostoid trilobite Agnostotes orientalis. This horizon coincides also with the first appearance of the cosmopolitan polymerid trilobite Irvingella angustilimbata. The section fulfills all the requirements for a GSSP, and the horizon can be constrained not only by the primary stratigraphic
marker (A. orientalis) but also with secondary biostratigraphic, chemostratigraphic, and sequence-stratigraphic correlation tools. The first appearance
of A. orientalis is one of the most readily recognizable levels in Cambrian, and can be correlated with precision to all paleocontinents.
Supported by Chinese Academy of Sciences (Grant No. KZCX2-YW-122), the Ministry of Science and Technology of China (Grant
Nos. 2006FY120300, 2006CB806400), National Natural Science Foundation of China (Grant Nos. 40072003, 40023002, 40332018, 40672023,
40602002), and the U.S. National Science Foundation (Grant No. EAR-0106883) 相似文献
10.
The stalagmite chronological table is established based on the definition of annual character of microlayers of a stalagmite
by comparing the laminated rhythm to natural cyclic processes. Climatic anomalies lasting over ten years and rapid climatic
changes such as abrupt changes of mean value, of variability, of trend and of cycles are discovered from the stalagmite chronological
table. Stalagmites which record interannual to century scale climatic changes are excellent
This work is a part of PANASH/PEP-II Project, and supported by the National Natural Science Foundation of China (Grant Nos.49672134,
49894170), Chinese Academy of Sciences (Grant No.KZ951-A1-402-06-02), and State Science & Technology Commission of China. 相似文献
11.
Constraining the stepwise migration of the eastern Tibetan Plateau margin by apatite fission track thermochronology 总被引：8，自引：1，他引：8
LAI QingZhou ? DING Lin WANG HongWei YUE YaHui & CAI FuLong Institute of Geology Geophysics Chinese Academy of Sciences Beijing China Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing China 《中国科学D辑(英文版)》2007,50(2):172-183
Granites sampled from Garzê-Litang thrust, Longmen Shan thrust, Garzê and Litang strike-slip faults in the eastern Tibetan Plateau have been analyzed with apatite fission track thermochronological method in this study. The measured fission track apparent ages, combined with the simulated annealing mod- eling of the thermal history, have been used to reconstruct the thermal evolutionary histories of the samples and interpret the active history of the thrusts and faults in these areas. Thermal history mod- eling shows that earlier tectonic cooling occurred in the Garzê-Litang thrust in Miocene (~20―16 Ma) whereas the later cooling occurred mainly in the Longmen Shan thrust since ~5 Ma. Our study sug- gests that the margin of eastern Tibetan Plateau was extended by stages: through strike-slip faults deformations and related thrusts, the upper crust formed the Garzê-Litang margin in the Miocene epoch and then moved to the Longmen Shan margin since ~5 Ma. During this process, the deformations of different phases in the eastern Tibetan Plateau were absorbed by the thrusts within them and conse- quently the tectonic events of long-distance slip and extrusion up to hundreds of kilometers have not been found. 相似文献
12.
Guo Jingxue Sun Bo Tian Gang 《应用地球物理》2007,4(3):214-220
As an important component of the cryosphere, sea ice is very sensitive to climate change. The study of sea ice physics needs accurate sea ice thickness. This paper presents an electromagnetic induction （EM） technique which can be used to measure the sea ice thickness distribution efficiently and its successful application in the Antarctic Neila Fjord. Based on the electrical properties of sea ice and seawater and the application of electromagnetic field theory, this technique can accurately detect the distance between the EM instrument and the ice/water interface to measure the sea ice thickness. Analyzing the apparent conductivity data obtained by the electromagnetic induction technique and drill-hole measurements at same location allows the construction of a transform equation for the apparent conductivity and sea ice thickness. The verification of the calculated sea ice thickness using this equation indicates that the electromagnetic induction technique is able to determine reliable sea ice thickness with an average relative error of only 5.5%. The ice thickness profiles show the sea ice distribution in Neila Fjord is basically level with a thickness of 0.8 - 1.4 m. 相似文献
13.
Wang ChuanYuan Du JianGuo Duan Yi Xie HongSen Chen GuoJun Wang WanChun 《中国科学D辑(英文版)》2007,50(10):1488-1493
Pyrolysis of lignite in closed systems was conducted at temperatures from 400 to 700℃ and pressure from 1 to 3 GPa in order to investigate the evolutive characteristics of aromatics and the effects of pressure and temperature on the maturation of organic matter under the extreme conditions. The total yield of liquid hydrocarbons decreased with increasing pressure and the aromatics shows more mature with increasing temperature at a given pressure. The data indicate that high pressure significantly suppresses the thermal evolution of geological organic matter especially at lower temperature, but favors the cyclization, polymerization and aromatization of pyrolysate. The pressure effect on maturation of organic matter is nonlinear. Therefore, it can be inferred that sediment organic-matters in the subducted slab could be retained in the deep lithosphere, and the results are also significant for understanding the accumulation and preservation of petroleum in deep reservoirs. 相似文献
14.
Fanbing Xue 《中国科学D辑(英文版)》1998,41(6):586-591
In consideration of the characteristics of spectral average of the Rossby wave trains and the adoption of a climatic mean
stream field as the basic stream field, an approximate analytical formula for the period of atmospheric low-frequency oscillation
(LFO) and the group velocity is deduced from a barotropic and non-divergent linearized vorticity equation. All the action
centers of atmosphere are found to be the oscillators of low frequency. The LFO propagates southward across the streamlines
in the wind field with a southward component or propagates northward across the streamlines in the wind field with northward
component instead of along a great circle. The switch of the propagation direction takes place near the top of ridge or the
bottom of trough. The angle between the wave rays and the zonal direction can be determined.
Project supported by the National Natural Science Foundation of China (Grant No. 49175241). 相似文献
15.
SNR changes of VLF radio signals detected onboard the DEMETER satellite and their possible relationship to the Wenchuan earthquake 总被引：3，自引：0，他引：3
M. Parrot 《中国科学D辑(英文版)》2009,52(6):754-763
Here we used the VLF signal data received by the DEMETER satellite, transmitted from various ground VLF transmitters which
are located around China, to study the changes in the signal to noise ratio (SNR) before and after the Wenchuan earthquake,
which had a magnitude of 8.0. We also found that the SNRs of different frequency signals decreased significantly over the
epicenter region before the earthquake, and reverted to their original levels after the earthquake. This phenomenon may be
related to the earthquake.
Special Foundation of Basic Research from Institute of Geophysics, China Earthquake Administration (Grant No. DQJB08Z08),
National Key Technology R & D Program (Grant No. 2008BAC35B01) 相似文献
16.
Experimental observation of the nano-scale particles in geogas matters and its geological significance 总被引：2，自引：0，他引：2
The geogas collectors showing a geogas anomaly in field geogas prospecting and in simulation tests were selected for the observation
under high resolution microscopy. The result demonstrates that the geogas matter is transported in the form of nano-scale
particles with a size of aboutN nm to N-10 nm, and accumulated into aggregations of 1-2 μm to N.10 μm, with globular and film shape, and the component of
Cu, Zn, Cr, Au, Al, V, Si, Br, C1, S, Ca, etc. Based on the knowledge of nano science and technique, the mechanism of the
geogas prospecting and its significance in geology and mineral prospecting are discussed.
Project supported by the National Natural Science Foundation of China (Grant No. 49673202) and the Department of Science and
Technology of MGMR, PRC (Grant No. 9505201-1) 相似文献
17.
P wave velocity structure of upper and middle crust beneath the Three Gorges reservoir dam and adjacent regions 总被引：3，自引：0，他引：3
The three-dimensional P wave velocity structures of upper and middle crust beneath the Three Gorges reservoir dam and adjacent
regions were reconstructed by means of the seismic tomography, using the absolute P-arrivals from the events observed by the
Three Gorges seismic network. Our preliminary study of the deep structure shows: (1) the lithology of the Huangling anticline,
integral and highly solidified, exhibits a uniformity. Down to a depth of 20 km, the Huangling anticline still shows high-velocity
anomalies. Note that the characteristics of the velocity images with the different depths are not the same; (2) the depth
of the sedimentary rocks beneath the entire Zigui basin is not constant, which is less than 6 km; (3) the top boundary of
the crystalline basement varies from 0 to 7 km, whereas the bottom one between 14 and 16 km; (4) the partially molten substances
of the upper mantle are located in the Badong-Zigui and its adjacent regions as well as nearby Peishi area. The development
and evolution of the current tectonics are associated with the cooling and solidifying process of the molten substances within
the upper mantle; (5) the different velocity structures of the deep crust in both east and west side of the Jiuwanxi fault
are to be investigated in order to understand the origin of gravitational gradient zone in the Three Gorge areas; and (6)
the velocities within the upper crust would be affected by reservoir water permeability.
Supported by National Natural Science Foundation of China (Grant No. 40574039), National Key Technology R& D Program (Grant
No. 2008BAC38B02) 相似文献
18.
Zheng Wenzhong Ji Jing 《地震工程与工程振动(英文版)》2008,7(2):137-146
Tests of nine angle-steel concrete column （ASCC） specimens under low cyclic loading are described in a companion paper （Zheng and Ji, 2008）. In this paper, the skeleton curves from the numerical simulation are presented, and show good agreement with the test results. Furthermore, parametric studies are conducted to explore the influence of factors such as the axial compression ratio, shear steel plate ratio, steel ratio, prismatic concrete compression strength, yield strength of angle steel and shear span ratio, etc., on the monotonic load-displacement curves of the ASCCs. Based on a statistical analysis of the calculated results, hysteretic models for load-displacement and moment-curvature are proposed, which agree well with the test results. Finally, some suggestions concerning the conformation of ASCCs are proposed, which could be useful in engineering practice. 相似文献
19.
In recent years, Structural Health Monitoring (SHM) has emerged as a new research area in civil engineering. Most existing
health monitoring methodologies require direct measurement of input excitation for implementation. However, in many cases,
there is no easy way to measure these inputs - or alternatively to externally excite the structure. Therefore, SHM methods
based on ambient vibration have become important in civil engineering. In this paper, an approach is proposed based on the
Damage Location Vector (DLV) method to handle the ambient vibration case. Here, this flexibility-matrix-based damage localization
method is combined with a modal expansion technique to eliminate the need to measure the input excitation. As a by-product
of this approach, in addition to determining the location of the damage, an estimate of the damage extent also can be determined.
Finally, a numerical example analyzing a truss structure with limited sensors and noisy measurement is provided to verify
the efficacy of the proposed approach.
Sponsored by: Notional Science Foundation Grant CMS 99-00234 相似文献
20.
A primitive confuciusornithid bird from China and its implications for early avian flight 总被引：1，自引：0，他引：1
Confuciusornithids, lived from 120―125 million years ago, form a basal bird group and include the oldest birds with horny beaks. Here we describe Eoconfuciusornis zhengi, gen. et sp. nov. from the Early Cretaceous Dabeigou Formation (131 Ma) in Fengning, Hebei Province, northern China. It repre- sents a new and, more primitive than other known, member of this group and extends the lifespan of this family to 11 Ma, the longest of any known Early Cretaceous avian lineages. Furthermore, Eoconfuciusornis and its relatives present many osteological transformations, such as the size increase of the deltopectoral crest of the humerus and the keel of the sternum, apparently an adaptation toward improved flight in the evolution of the Confuciusornithidae. 相似文献