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Numerically quantifying the relative importance of topography and buoyancy in driving groundwater flow

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science china {2. sciences 2010年第1期53卷 64-71页

作者： YANG JianWen 1,2.FENG ZuoHai 1,LUO XianRong 1 & CHEN YuanRong 1 1 Faculty of earth sciences,Guilin University of {2.,Guilin 541004,china 2.department of earth and Environmental sciences,University of Windsor,Windsor,Ontario,N9B 3P4,Canada Faculty of earth sciences Guilin University of Technology Guilin China department of earth and Environmental {2. University of Windsor Windsor Canada

Both topography and buoyancy can drive groundwater flow;however,the interactions between them are still poorly *** this paper,the authors conduct numerical simulations of variable-density fluid flow and heat transport to quantify their relative *** finite element modeling experiments on a 2.D conceptual model reveal that the pattern of groundwater flow depends largely upon the relative magnitude of the flow rate due to topography alone and the flow rate due to buoyancy *** fluid velocity due to topography is greater than that due to buoyancy at large water table gradients,topography-driven 'forced convection' overwhelms buoyancy-driven 'free convection'.When flow velocity due to buoyancy is greater than that due to topography at small water table gradients,mixed free and forced convection takes *** this case,free convection becomes dominant,but topography-driven flow still plays an important role since it pushes the free convection cells to migrate laterally in the downhill ***,hydrothermal fluid flow remains changing periodically with time and no steady state can be *** presence of a low-permeability layer near the surface helps eliminate the topography effect on the underlying free convection.

关键词： hydrothermal flow free convection forced convection topography buoyancy finite element modeling

On the Isometric Minimal Immersion into a Euclidean space

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Acta Mathematica Sinica,English Series 1999年第4期15卷 555-560页

作者： Qing Chen department of Mathematics,The University of science and {2. of china,hefei 2.002.,P.R.china E-mail:qchen@*** department of Mathematics The University of Science and Technology of China Hefei P. R. China

We study the volume growth of the geodesic balls of a minimal submanifold in a Euclidean space.A necessary condition for the isometric minimal immersion into a Euclidean space is obtained. A classification of non-posi... 详细信息

关键词： Minimal immersion Geodesic ball Volume growth Ruled submanifolds

SULFUR ISOTOPIC EVIDENCE FOR MAGMA DEGASSING

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Scientia Geologica Sinica 1994年第1期 41-49页

作者： Zheng Yongfei(department of earth and {2. sciences, University of science and technology Of china, hefei,Anhui 2.002.)

ＳＵＬＦＵＲＩＳＯＴＯＰＩＣＥＶＩＤＥＮＣＥＦＯＲＭＡＧＭＡＤＥＧＡＳＳＩＮＧ￥ＺｈｅｎｇＹｏｎｇｆｅｉ（ＤｅｐａｒｔｍｅｎｔｏｆＥａｒｔｈａｎｄＳｐａｃｅＳｃｉｅｎｃｅｓ，ＵｎｉｖｅｒｓｉｔｙｏｆＳｃｉｅｎｃｅａｎ... 详细信息

ＳＵＬＦＵＲＩＳＯＴＯＰＩＣＥＶＩＤＥＮＣＥＦＯＲＭＡＧＭＡＤＥＧＡＳＳＩＮＧ￥ＺｈｅｎｇＹｏｎｇｆｅｉ（ＤｅｐａｒｔｍｅｎｔｏｆＥａｒｔｈａｎｄＳｐａｃｅＳｃｉｅｎｃｅｓ，ＵｎｉｖｅｒｓｉｔｙｏｆＳｃｉｅｎｃｅａｎｄＴｅｃｈｎｏｌｏｇｙＯｆＣｈｉｎ...

关键词： MAGMA SULFUR ISOTOPIC EVIDENCE FOR MAGMA DEGASSING

CONSTRUCTION OF EQUILIBRIUM P-T BUNDLES OF COMBINATION OF n+2.PHASES ON PETROGENETIC GRIDS

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science china Chemistry 1989年第2期32卷 193-204页

作者：程伟基王基镕郭其悌 department of earth and {2. sciences the University of Science and Technology of China Hefei department of Mathematics the University of Science and Technology of China Hefei Institute of Geochemistry Academia Sinica Guiyang

This paper first discusses the algorithm for balancing reactions of the combination of n + 2.phases around an invariant point on a P-Tdiagram, and then emphatically develops a new algorithm for the arrangement of univariant reaction lines, using a signum matrix V·F or S·F, where V and S are diagonal matrixes of signum of △V and △S in n+2.univariant reactions respectively, and F is a signum matrix of stoichiometric coefficients of phases in reactions. Using this new algorithm greatly simplifies relative computer programs, brings out the automatic construction of equilibrium P-T curves of combination of n +2.phases, and further makes it possible to construct a whole petrogenetic grid automatically

关键词： P-T bandles of combination of n + 2 phases.

The deformation pattern and fault rate in the Tianshan Mountains inferred from GPS observations

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science china {2. sciences 2008年第8期51卷 1064-1080页

作者： YANG ShaoMin1,2. LI Jie1,3 & WANG Qi2.1 1 Research Center of space science and {2., china University of Geosciences, Wuhan 430074, china 2.Institute of Seismology, china earthquake Administration, Wuhan 430071, china 3 earthquake Administration of Xinjiang Uygur Autonomous Region, Urumqi 830011, china Research Center of space science and {2. China University of Geosciences Wuhan China Institute of Seismology China Earthquake Administration Wuhan China earthquake Administration of Xinjiang Uygur Autonomous Region Urumqi China

Based on GPS measurements conducted from 1992.to 2.06, we present the current crustal movement velocity field for approximately 400 sites in the Tianshan Mountains and their adjacent areas, and estimate slip rates on the major faults using a 2.D elastic dislocation model. Our studies show slip rates within the range of 1―4 mm/a on the NW-SE trending strike-slip faults (such as Talas-Fergana fault) in the Tianshan Mountains. We also found the slip rates on the approximately WE-SN trending gently-dipping detachment fault vary from 10―13 mm/a for the southwest Tianshan Mountains to 2.5 mm/a for the eastern Tianshan Mountains, and to 6―12.mm/a for the Kyrgrz Tianshan. The GPS velocity field reveals that the total convergence is not uniformly distributed across the Tianshan Mountains, with 80%―90% of the N-S shortening absorbed along the southern and northern edges, and relatively little deformation accommodated within the interior. This first-order feature of strain pattern is explained best by underthrusting of adjacent blocks beneath the Tianshan Mountains along a basal detachment fault. We found the occurrence of historical M7―8 earthquakes somewhere in the locked ramp that connects the creeping and locking segments of the detachment, thereby resulting in elastic strain concentration and accumulation around it. The elastic strain confined in the upper crustal layer above the detachment ultimately releases through infrequent great earthquakes in the Tianshan Mountains, resulting in considerable folding and faulting at their margins. The Tianshan Mountains propagated outward and rose progressively as a wedge-shaped block.

关键词： Tianshan Mountains GPS slip rates tectonic deformation

Coronal Magnetic Flux Rope Equilibria and Magnetic Helicity

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Chinese Journal of Astronomy and Astrophysics 2001年第1期1卷 77-84页

作者： You－QinHu Yan－WeiJiang 等 departmentofearthand{2.science UniversityofScienceandTechnologyofChinaHefei230026 departmentofEart

Using a 2.5-dimensional (2.5-D) ideal MHD model, this paper analyzes the equilibrium properties of coronal magnetic flux ropes in a bipolar ambient magnetic field. It is found that the geometrical features of the magnetic flux rope, including the height of the rope axis, the half-width of the ropes and the length of the vertical current sheet below the ropes are determined by a single magnetic parameter, the magnetic helicity, which is the sum of the self-helicity of the rope and the mutual helicity between the rope field and the ambient magnetic field. All the geometrical parameters increase monotonically with increasing magnetic helicity. The implication of this result in solar active phenomena is briefly discussed.

关键词： Sun: magnetic fields - Sun: magnetic flux rope - Sun: magnetic helicity

Energy distributions of the large-scale horizontal currents caused by wind in the baroclinic ocean

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science china {2. sciences 2005年第12期48卷 2267-2275页

作者： ZHOU Lei1, TIAN Jiwei1 & WANG Dongxiao2.1. Physical Oceanography Laboratory, Ocean University of china, Qingdao 2.6003, china 2. Key Laboratory of Tropical Marine Environmental Dynamics, South china Sea Institute of Oceanology, Chinese Academy of sciences, Guangdong 510301, china Physical Oceanography Laboratory Ocean University of China Qingdao China Key Laboratory of Tropical Marine Environmental Dynamics South China Sea Institute of Oceanology Chinese Academy of Sciences Guangdong China

Ocean current data for nearly 3 months in the South china Sea (SCS), combined with the NCEP/NCAR reanalysis wind data, are analyzed. The results indicate that the wind en-ergy enters the upper mixed layer in a wide continuous frequency band. In addition, the interac-tion between the low-frequency wind anomaly and the low-frequency current anomaly is the most ‘effective’ way for the energy input from the wind to the upper ocean. However, only the inertial and the near inertial energy propagate downwards through the upper mixed layer. The down-ward-propagating energy is distributed into the barotropic currents, the baroclinic currents and each mode of the baroclinic currents following the normal distributions. The energy change ratios between the barotropic motion to the baroclinic motion induced by the wind present a normal distribution of N (0.02.2. 0.3947). The energy change ratios of the first 4 baroclinic modes to the whole baroclinic currents also follow the normal distributions. The first baroclinic mode follows N (0.2.2., 0.1872., the second N (0.1979, 0.1504), the third N (0.1331, 0.1633), and the fourth N (0.0650, 0.1540), respectively.

关键词： wind anomaly, ocean current anomaly, energy transportation, wide frequency band, near-inertial fre-quency, energy distribution.

Research on the reconstruction method of porous media using multiple-point geostatistics

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science china(Physics,Mechanics & Astronomy) 2010年第9期53卷 122-134页

作者： ZHANG Ting 1,2.3, LI DaoLun 1,2., LU DeTang 1,2.& YANG JiaQing 1,2.1 department of Modern Mechanics, University of science and {2. of china, hefei 2.002., china 2.Research Center of Oil and Natural Gas, University of science and {2. of china, hefei 2.002., china 3 The 2.th Research Institute, china Electronics {2. Group Corporation, Nanjing, 2.0007, china department of Modern Mechanics University of Science and Technology of China Hefei China Research Center of Oil and Natural Gas University of Science and Technology of China Hefei China The 2.th Research Institute China Electronics Technology Group Corporation Nanjing China

The pore structural characteristics have been the key to the studies on the mechanisms of fluids flow in porous media. With the development of experimental technology, the modern high-resolution equipments are capable of capturing pore structure images with a resolution of microns. But so far only 3D volume data of millimeter-scale rock samples can be obtained losslessly. It is necessary to explore the way of virtually reconstructing larger volume digital samples of porous media with the representative structural characteristics of the pore space. This paper proposes a reconstruction method of porous media using the structural characteristics captured by the data templates of multiple-point geostatistics. In this method, the probability of each structural characteristic of a pore space is acquired first, and then these characteristics are reproduced according to the probabilities to present the real structural characteristics in the reconstructed images. Our experimental results have shown that: (i) the deviation of LBM computed permeability respectively on the virtually reconstructed sandstone and the original sample is less than 1.2.; (ii) the reconstructed sandstone and the original sample have similar structural characteristics demonstrated by the variogram curves.

关键词： porous media reconstruction multiple-point geostatistics pore space training image variogram data template

Numerical study of the auroral particle transport in the polar upper atmosphere

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science china(Technological {2.) 2008年第10期51卷 1759-1771页

作者： CAI HongTao1,2. MA ShuYing1,2.& PU ZuYin3 1 School of Electronic Information, Wuhan University, Wuhan 430079, china 2.Key Laboratory of Geospace Environment and Geodesy, Ministry of Education of PRC, Wuhan 430079, china 3 School of earth and space sciences, Peking University, Beijing 100871, china School of Electronic Information Wuhan University Wuhan China Key Laboratory of Geospace Environment and Geodesy Ministry of Education of PRC Wuhan China School of earth and space {2. Peking University Beijing China

Starting from the Boltzmann equation and with some reasonable assumptions, a one-dimensional transport equation of charged energetic particles is derived by taking account of major interactions with neutral species in the upper atmosphere, including the processes of elastic scattering, the excitation, the ionization and the secondary electron production. The transport equation is numerically solved, for a simplified atmosphere consisting only of nitrogen molecules (N2., to obtain the variations of incident electron fluxes as a function of altitude, energy and pitch angle. The model results can describe fairly the transport characteristics of pre-cipitating auroral electron spectra in the polar upper atmosphere; meanwhile the N2.ionization rates calculated from the modeled differential flux spectra also exhibit good agreements with existing empirical models in terms of several key parameters. Taking the energy flux spectra of precipitating electrons observed by FAST satellite flying over EISCAT site on May 15, 1997 as model inputs, the model-calculated ionization rate profile of neutral atmosphere consists reasonably with that recon-structed from electron density measurements by the radar.

关键词： aurora particle precipitation polar upper atmosphere electron transport equation numerical simulation