Nonlinear free thermal convection in a spherical shell:A variable viscosity model

Introduction The velocity field of surface plate motion can be split into a poloidal and a toroidal parts.At the Earth′s surface,the toroidal component is manifested by the existence of transform faults,and the poloidal component by the presence of convergence and divergence,i.e.spreading and subduc-tion zones.They have coupled each other and completely depicted the characteristics of plate tec-tonic motions.The mechanism of poloidal field has been studied fairly clearly which is related to …     

The dependence of response spectrum on the tectonic ambient shear stress field

Introduction The acceleration response spectrum and peak ground acceleration are the necessary and im-portant parameters in earthquake-resistant design at present. They are still active research field. With the increase of digital high accurate strong motion observation data, especially the earth-quakes of Loma Prieta (M=7.0) in 1989; Landers (M=7.3) in 1992; Big Bear (M=6.4) in 1994 and Northridge (M=6.7) in 1994 in USA; Kozani (M=6.6) earthquake and afteshocks in 1995 in Greece; Dinar…     

Thermodynamic conditions of framework grain dissolution of clastic rocks and its application in Kela 2 gas field

Feldspar and clastic debris are the most important constituent framework grains of sedimentary clastic rocks and their chemical dissolution plays an essential role in the formation and evolution of the secondary pore in the reservoir rocks. On the basis of thermodynamic phase equilibrium, this study investigates the chemical equilibrium relationships between fluid and various plagioclase and K-feldspar in diagenesis of the sediments, particularly, the impact of temperature and fluid compositions (pH, activity of K+, Na+, Ca2+ and so on) on precipitation and dissolution equilibria of feldspars. Feldspar is extremely easily dissolved in the acid pore water with a low salinity when temperature decreases. The dissolution of anorthite end-member of plagioclase is related to the Ca content of the mineral and the fluid, higher Ca either in the mineral or in the fluid, easier dissolution of the feldspar. Moreover, the dissolution of albite end-member of plagioclase is related to Na of both the mineral and fluid,     

Distribution of chlorophyll-a off the Changjiang River and its dynamic cause interpretation

Red tide,also called harmful algal bloom interna-tionally,is a disaster abnormal phenomenon of oceanecology with an explosive breed or dense assemble ofone or several phytoplanktons in a specific ocean en-vironment condition,colors the seawater,influencesand harms ocean living things.The formation of redtide is controlled mainly by a complex interplay ofbiological,physical and chemical processes,but themost main cause influencing the occurrence of red tideis the seawater eutrophication,i.e.,the…     

Geochemistry of ore-forming fluids and geological significance of the Kuoerzhenkuola gold field in Xinjiang, China

The Kuoerzhenkuola gold field (including the Kuo- erzhenkuola and the Buerkesidai gold deposits), lo- cated 68 km east of Jimunai County in northern Xing- jiang, China, is an important component of the Sawuer gold belt which is the eastward extending part of the Zarma-Sawur gold-copper belt in Kazakhstan. Some studies are concerned with the geology of the gold ores[1―3], the associated volcanic rocks[4], radiogenic isotope[5―8], and the ore-forming environment[8]. Most researchers inferr…     

Strain accumulation in sand due to cyclic loading: drained triaxial tests

Our aim is the prediction of the accumulation of strain and/or stress under cyclic loading with many (thousands to millions) cycles and relatively small amplitudes. A high-cycle constitutive model is used for this purpose. Its formulas are based on numerous cyclic tests. This paper describes drained tests with triaxial compression and uniaxial stress cycles. The influence of the strain amplitude, the average stress, the density, the cyclic preloading history and the grain size distribution on the direction and the intensity of strain accumulation is discussed.     

Model identification for hydrological forecasting under uncertainty

Methods for the identification of models for hydrological forecasting have to consider the specific nature of these models and the uncertainties present in the modeling process. Current approaches fail to fully incorporate these two aspects. In this paper we review the nature of hydrological models and the consequences of this nature for the task of model identification. We then continue to discuss the history (“The need for more POWER‘’), the current state (“Learning from other fields”) and the future (“Towards a general framework”) of model identification. The discussion closes with a list of desirable features for an identification framework under uncertainty and open research questions in need of answers before such a framework can be implemented.     

Determining the maximum degree of harmonic coefficients in geopotential models by Monte Carlo methods

Random errors for the harmonic coefficients of a geopotential model are generated from the matrix of normal equations by a parallel computer applying the Gibbs sampler. This leads to random values for the harmonic coefficients. They are transformed by nonlinear, quadratic transformations to random values for the square roots of degree variances, of mean squares of geoid undulations and gravity anomalies. The expected values of these quantities are not equal to the values of these quantities computed by the estimated harmonic coefficients, due to correlations and errors in the estimation. By hypothesis tests estimated harmonic coefficients distorted by correlations and errors are detected. Applying the tests to the geopotential model ITG-CHAMP01 of the Institute of Theoretical Geodesy in Bonn it is concluded that above the degree 62 the harmonic coefficients cannot add any information to the geopotential model.     

南半球对流层气候年代际变化及其与太阳活动的联系

通过南半球对流层温度场谱分析和逐次滤波分析发现，南半球对流层大气温度场半个多世纪以来呈现明显的持续升温趋势，升温幅度由低层到高层逐步增加，其中地面层1 000 hPa年升温率为0.013℃/a，对流层中部500 hPa年升温率为0.019℃/ a，对流层上部300 hPa年升温率为0.036℃/ a；滤除南半球大气温度场的趋势变化，发现南半球大气温度场从地面层直至对流层顶广泛盛行着十分显著的与太阳磁场磁性22年周期变化相一致的变化周期。太阳磁场磁性周期变化趋势略有超前，分析认为，这是南半球对流层大气气候系统对太阳磁场周期性变化的响应。进一步分析还发现，南半球从地面层1 000 hPa到对流层顶，再到平流层中部10 hPa各层次大气温度变化22年周期分量振荡位相基本一致，周期振幅由低层到高层迅速增大，说明太阳磁场变化对对流层高层比低层影响大，对平流层影响更大。其中地面层1 000 hPa温度场的22年变化周期是在滤除趋势变化和11年周期之后才显现出来的，所以太阳磁场磁性周期变化对地面层气候的影响较小并且经常处于被掩盖状态；南半球地面层1 000 hPa温度场滤除趋势变化之后显示出十分显著的与太阳活动11年周期相一致的变化周期，分析认为，这是南半球对流层大气气候系统对太阳活动11周期性变化的响应。对流层上层300 hPa温度场滤除趋势变化和22年周期之后也显示出11年变化周期，而对流层中部500 hPa则无此周期反应，说明太阳活动11年周期对地面层1 000 hPa大气气候影响最明显，对流层中上层影响较弱。     

当前国际水文学科技术领域的研究方向

根据联合国有关机构发布的公报和世界各国近年来的学术研究情况，整理出了近期水文学科在地表水、地下水、水质、水资源系统、大气～土壤～植被、大陆侵蚀、冰雪、遥感技术和示踪技术等领域的热门研究课题，在一定程度上反映了当前国际上水文学科的研究和发展方向，对国内同行有一定的参考价值。