氯化钠盐土壤介电虚部特性的初步研究

含水含盐土壤的介电虚部模型是土壤含水量含盐量的函数。通过一系列关系研究：介电常数虚部ε＂，土壤导电率σa，土壤溶液导电率σw，土壤溶液离子浓度SMv，含盐量S，最终得到介电常数虚部ε＂和土壤含水量Mv。含盐量S的关系，即土壤介电模型。通过微波网络仪，对150组具有不同含水含盐量的土壤，在频率范围0．2-20GHz（频率取样间隔为0．05GHz）进行介电常数测量。在不同频率下，利用这些实测数据通过最佳拟合的方法确定土壤介电模型中的待定参数，从而得到不同频率时土壤介电虚部经验模型。另外，利用吉兰泰地区41个含盐土壤样品进行模型验证，结果表明，模型计算值与测量值高度相关。最后得出：（1）含盐量对介电常数虚部的影响随频率增大而降低；（2）土壤类型和介电常数虚部几乎没有相关性。     

Can Damage Mechanics Explain Temporal Scaling Laws in Brittle Fracture and Seismicity?

Time delays associated with processes leading to a failure or stress relaxation in materials and earthquakes are studied in terms of continuum damage mechanics. Damage mechanics is a quasi-empirical approach that describes inelastic irreversible phenomena in the deformation of solids. When a rock sample is loaded, there is generally a time delay before the rock fails. This period is characterized by the occurrence and coalescence of microcracks which radiate acoustic signals of broad amplitudes. These acoustic emission events have been shown to exhibit power-law scaling as they increase in intensity prior to a rupture. In case of seismogenic processes in the Earth's brittle crust, all earthquakes are followed by an aftershock sequence. A universal feature of aftershocks is that their rate decays in time according to the modified Omori's law, a power-law decay. In this paper a model of continuum damage mechanics in which damage (microcracking) starts to develop when the applied stress exceeds a prescribed yield stress (a material parameter) is introduced to explain both laboratory experiments and systematic temporal variations in seismicity.     

Differences Between Mode I and Mode II Crack Propagation

Although mode I and mode II crack propagation show many similarities, in particular when analysed by linear elastic fracture mechanics, they differ significantly in the micro-structural behaviour. These differences, which are clearly noticeable in the fracture surface morphology, lead to fundamental differences in the macroscopic behaviour. Thus, mode II crack expansion under remote loading, appears to obey micro-structural scaling laws, implying that the dimensions of the process region stay essentially constant during crack expansion, rather than increasing with crack length. Therefore, expanding mode II cracks can almost reach the Rayleigh velocity, and actually also intersonic velocities. An expanding mode I crack, on the other hand, seems to obey continuum scaling laws, implying that the dimensions of the process region increase in proportion to crack length, leading to self-similar crack expansion at a velocity significantly below the Rayleigh speed and dependent on the remote load.     

Spectral scaling in Mars topography: effect of craters

Extensive computer simulations aimed at testing a hypothesis that impact craters may explain the scaling behaviour of surface spectra are presented. The simulations show that indeed crater effects alone may explain the spectral scaling of Mars’ topography revealed from MOLA data. The range of the scaling exponents obtained for a wide range of simulation parameters does not exceed the limits observed for Mars. The simulations suggest that the shape of large craters is the key factor leading to the two scaling ranges in the surface spectra. Particular values of the scaling exponents may additionally depend on the depth-diameter relationship and the crater size distribution.     

A new solution for a partially penetrating constant‐rate pumping well with a finite‐thickness skin

A mathematical model describing the constant pumping is developed for a partially penetrating well in a heterogeneous aquifer system. The Laplace‐domain solution for the model is derived by applying the Laplace transforms with respect to time and the finite Fourier cosine transforms with respect to vertical co‐ordinates. This solution is used to produce the curves of dimensionless drawdown versus dimensionless time to investigate the influences of the patch zone and well partial penetration on the drawdown distributions. The results show that the dimensionless drawdown depends on the hydraulic properties of the patch and formation zones. The effect of a partially penetrating well on the drawdown with a negative patch zone is larger than that with a positive patch zone. For a single‐zone aquifer case, neglecting the effect of a well radius will give significant error in estimating dimensionless drawdown, especially when dimensionless distance is small. The dimensionless drawdown curves for cases with and without considering the well radius approach the Hantush equation (Advances in Hydroscience. Academic Press: New York, 1964) at large time and/or large distance away from a test well. Copyright © 2007 John Wiley & Sons, Ltd.     

Five dimensional universe model with variable cosmological term Λ and a big bounce

We assume the four dimensional induced matter of the 5D Ricci flat bouncing cosmological solution contains a perfect fluid. The big bounce singularity of simple 5D cosmological model is studied with the cosmological term Λ=α ρ and Λ=β H ² where α and β are constants and ρ and H are respectively energy density and Hubble parameter. This big bounce singularity is found to be an event horizon at which the scale factor and mass density of the universe are finite, while the pressure is infinite.      

太阳辐照的观测研究进展

太阳总辐照是指在地球大气层顶接收到的太阳总辐射照度,也叫"太阳常数",但它实际上并非常数。太阳总辐照随波长的分布即为太阳分光辐照。太阳辐照变化的研究,对理解太阳表面及内部活动的物理过程、机制,研究地球大气、日地关系,解决人类面临的全球气候变暖的挑战等,都具有重要意义。首先简单介绍了太阳辐照,回顾了太阳辐照的空间观测;接着介绍了观测数据的并合,以及对合成数据的一些研究;然后讨论了太阳辐照变化的原因,简述了太阳总辐照的重构及其在气候研究上的一些应用,并进行必要的评论;最后对未来的研究方向提出了一些看法。     

A Numerical Verification of Self-Similar Multiplicative Theory for Small-Scale Atmospheric Turbulent Convection

The self-similar multiplicative theory（SSM theory）, aims to interpret the scaling behavior of the temperature structure function. In the present paper, the author report results from a numerical simulation of atmospheric turbulent convection in order to verify this theory. The simulation was based on a shell model which was deduced from simplified atmospheric convection equations. The numerical results agreed well with the theory prediction of scaling law from the first order to the eighth order. They also showed that the prediction of this theory was better than that given by the Kolmogorov＇s theory in 1941, log-normal, and β model theories.     

构造地理要素趋势面的尺度转换普适性方法探讨

当前的遥感科学面临着遥感数据获取能力与数据应用能力之间突出的供需矛盾。尺度问题作为遥感科学中的关键问题,既限制了遥感作为一门科学向系统性、普适性的发展,又限制了遥感应用能力的发展。本文对定量遥感中的尺度问题进行了梳理,包括:遥感与传统站点观测之间的不一致、不同尺度遥感产品之间的不一致、机理模型的尺度适用问题,以及遥感产品与用户需求时空尺度间的不一致。对遥感中的尺度转换方法展开了讨论,总结了尺度转换的关键问题在于原数据信息量不足时引入额外信息和保留关键信息两方面。提出了构造地理要素趋势面的基本构想,搭建了一个具有普适性的尺度转换方法框架。核心内容是充分利用地表环境要素时间、空间上的信息作为先验知识,通过关联遥感观测新信息和先验趋势面生成指定时空尺度的地表要素产品。