Improvement of Vertical Diffusion Analytic Schemes Under Stable Atmospheric Conditions

Based on gradient transport theory or K-theory, turbulent transport in the atmosphere has long been parameterized using the eddy diffusivity. Due to its simplicity, this approach has often been applied in many numerical models but rarely tested with observations. Here, the widely used O’Brien cubic polynomial approach has been validated together with an exponential approach against eddy diffusivity profiles determined from measurements and from large-eddy simulation data in stable conditions. Verification is completed by analyzing the variability effects on pollutant concentrations of two different vertical diffusion (K(z)) schemes incorporated in an atmospheric chemical model. It is shown that the analytical, exponential solution agrees better with observations than the O’Brien profile and should be used henceforth in practical applications.     

AMT法勘查贵州铝土矿

贵州铝土矿资源储量丰厚,分布面广,但多为隐伏型沉积型矿,仅有的易辨别、易发现的地表或浅层铝土矿已经开发殆尽,在此开展隐伏铝土矿的物探方法试验研究对今后勘查工作具有重要的指导意义。本文简要介绍了AMT基本工作方法以及贵州金沙长沟工区的地质和地球物理特征,重点讨论了AMT在长沟工区铝土矿勘查中的应用效果,通过对电阻率断面图的综合推断解释,划分出了二叠系、石炭系、寒武系之间地层界面,圈出了含矿有利部位。经钻孔验证,取得了较好的找矿效果。     

Magnetic field measurements in India during the last two centuries

Summary The direction of the geomagnetic field has changed substantially less in India than in Europe since the end of the 18th century.Whereas the European geomagnetic time series indicate a tendency of secular variation from which a remarkable westward drift of the non-axial field can be deduced, in India the field direction seems to have remained more or less fixed over the last two centuries. The drift of the non-axial field seems to be very small, or even eastward.     

A contribution to the measurement of frequency dependence of electrical conductivity of rocks

Summary Some errors of method occurring in A. C. measurements of the electrical conductivity of rocks are discussed. It is demonstrated that the difference between A.C. and D.C. conductivities, at given frequency, depends mostly on the magnitude of the D.C. conductivity and magnitude of the dielectric constant.     

Effect of viscous,viscoplastic and friction damping on the response of seismic isolated structures

In this paper the efficiency of various dissipative mechanisms to protect structures from pulse‐type and near‐source ground motions is examined. Physically realizable cycloidal pulses are introduced, and their resemblance to recorded near‐source ground motions is illustrated. The study uncovers the coherent component of some near‐source acceleration records, and the shaking potential of these records is examined. It is found that the response of structures with relatively low isolation periods is substantially affected by the high‐frequency fluctuations that override the long duration pulse. Therefore, the concept of seismic isolation is beneficial even for motions that contain a long duration pulse which generates most of the unusually large recorded displacements and velocities. Dissipation forces of the plastic (friction) type are very efficient in reducing displacement demands although occasionally they are responsible for substantial permanent displacements. It is found that the benefits by hysteretic dissipation are nearly indifferent to the level of the yield displacement of the hysteretic mechanism and that they depend primarily on the level of the plastic (friction) force. The study concludes that a combination of relatively low friction and viscous forces is attractive since base displacements are substantially reduced without appreciably increasing base shears and superstructure accelerations. Copyright © 2000 John Wiley & Sons, Ltd.     

几类叠前深度偏移方法的研究现状

叠前深度偏移是解决复杂地质构造成像的有力手段,关于叠前深度偏移方法的研究一直是勘探地球物理研究的热点和难点。本文在收集、整理国内外有关研究资料的基础上,有选择地对若干类型方法研究背景及现状、基本原理及方法特点等进行分析,目的在于作为研究工作的起点,把握叠前深度偏移方法的发展趋势,以期生成适合我国复杂油气储集特点的地震成像方法及技术手段。     

Diurnal asymmetry of radio wave absorption on anomalous winter days

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Monitoring ionospheric scintillations and TEC at the Polish Polar Station on Spitsbergen: instrumentation and preliminary results

As a partial contribution to the International Polar Year, the Space Research Centre of the Polish Academy of Sciences has installed on the Polish Polar Station, located in the region of the Hornsund Bay in southern Spitsbergen, the equipment intended to monitor ionospheric scintillation and total electron content. We describe the equipment setup and the aims of the experiment. As an illustration of data analysis, we present the reconstruction of irregular structure of the ionosphere from the complex amplitude data, and the estimate of the form and drift of diffraction pattern based on the spaced receiver measurements.