二次电流场多次叠加概率成像

基于地下电流场的积分公式,离散化的二次电流场被分解为电性不连续界面上的一系列点电荷电场的代数和.单位正点电荷电场被引入作为空间扫描函数（SDS）,积累电荷出现的概率（COP）函数定义为二次电流场与SDS的互相关.为对概率成像结果进行定量分析解释,提出了规范的积累电荷出现的概率（NCOP）函数.通过应用有限元算法对2D地电模型进行二次电流场合成,实现了二次电流场的多次叠加概率成像.结果表明对均匀半空间中赋存地质异常体的电性结构,概率成像方法对地下异常体的空间位置有较好的指示作用.     

Observation and study on the whole process of cloud-to-ground lightning using narrowband radio interferometer

A narrowband radio interferometer has been developed and used to locate the entire sources of VHF radiations from a negative cloud-to-ground (CG) lightning discharge which contains 19 strokes. This system uses five antennas to form an array consisting of short- and long-baselines along two or- thogonal directions. The system error which comes from frequency conversion is reduced by phase detection through direct high frequency amplifying. An interactive graphic analysis procedure is used to remove the fringe ambiguities which exist inherently in interferometry and to determine the direction of lightning radiation sources in two dimensions (azimuth and elevation) as a function of time at a time resolution of microsecond orders. With the developed system, the whole progression process in time and space of a lightning flash can be reconstructed. In this paper, combining the synchronous data of electric filed change and VHF radiation, the whole processes of an example negative CG flash have been studied in detail. It is found that the preliminary breakdown event of the CG flash started from negative charge region and exhibited firstly a downward pregression and then an upward propagation. There were very intense and continuous radiations during stepped leaders which became much stronger when the first return stroke began. In contrast, there were less and only discrete radiations during dart leaders. Stepped leader and dart leader may transform to each other depending on the state of the ionization of the path. The progression speed of initial stepped leaders was about 105 ms?1, while that was about 4.1×106 and 6.0×106 ms?1 for dart leaders and dart-stepped leaders, respectively. M events produced hook-shaped field changes accompanied by active burst of radiations at their begin- nings. Followed these active radiation processes, M events appeared to contact finally into conducting main discharge channels. The mean progression speed of M events was about 7×107 ms?1, greater than that of the dart leaders and dart-step leaders. K events and attempted leaders were essentially the same as dart leaders except that they could not reach the ground and initiate return strokes.     

On the importance of auroral processes in the Universe

Acceleration of charged particles in magnetic field-aligned electric potential differences at Earth and at the outer planets in the solar system is summarized and its general importance in the Universe is briefly discussed.The role of field-aligned currents, driven by parallel electric fields, in causing filamentary structure in stellar atmospheres is briefly reviewed.The differences between auroral optical emissions at various planets are summarized.The important role of field-aligned potential differences in the generation of AKR and corresponding emissions from other objects is discussed.Finally, aurora-associated processes for ejection of planetary plasma into space are briefly reviewed.     

Time and space nonlocalities underlying fractional-derivative models: Distinction and literature review of field applications

We investigate the spatiotemporal nonlocality underlying fractional-derivative models as a possible explanation for regional-scale anomalous dispersion with heavy tails. Properties of four fractional-order advection–dispersion equation (fADE) models were analyzed and compared systematically, including the space fADEs with either maximally positive or negative skewness, the time fADE with a temporal fractional-derivative 0<γ<1$0<\gamma <1$, and the extension of the time fADE with 1<γ<2$1<\gamma <2$. Space fADEs describe the dependence of local concentration change on a wide range of spatial zones (i.e., the space nonlocality), while time fADEs describe dynamic mass exchange between mobile and multiple immobile phases and therefore record the temporal history of concentration “loading” (i.e., the time-nonlocality). We then applied the fADEs as models of anomalous dispersion to four extensively-studied, regional-scale, natural systems, including a hillslope composed of fractured soils, a river with simultaneous active flow zones and various dead-zones, a relatively homogeneous glaciofluvial aquifer dominated by stratified sand and gravel, and a highly heterogeneous alluvial aquifer containing both preferential flowpaths and abundant aquitards. We find that the anomalous dispersion observed at each site might not be characterized reasonably or sufficiently by previous studies. In particular, the use of the space fADE with less than maximally positive skewness implies a spatial dependence on downstream concentrations that may not be physically realistic for solute transport in watershed catchments and rivers (where the influence of dead-zones on solute transport can be described by a temporal, not spatial, fractional model). Field-scale transport studies show that large ranges of solute displacement can be described by a space nonlocal, fractional-derivative model, and long waiting times can be described efficiently by a time-nonlocal, fractional model. The unknown quantitative relationship between the nonlocal parameters and the heterogeneity, and the similarity in concentration profiles that are solutions to the different nonlocal transport models, all demonstrate the importance of distinguishing the representative nonlocality (time and/or space) for any given regional-scale anomalous dispersion process.     

On the spectrum of mid-latitude sporadic-E irregularities

We discuss the creation of mid-latitude sporadic-E plasma irregularities (with length-scales smaller than sporadic layer thickness) by the neutral atmosphere turbulence. Using fluid equations, the relation between plasma density fluctuations and the velocity field of neutrals is derived. After a brief discussion of the relevant neutral turbulence, the analytical expression for the power spectrum of plasma irregularities is obtained. This expression allows a power-law type of experimental irregularity spectra (the spectral index depends on sporadic-E characteristics) and possible departures in detail of the irregularity spectra from the power-law form to be explained. In addition, it allows us to make estimates of length-scales at which such departures must occur.     

`Our resistance will be as transnational as capital': Convergence space and strategy in globalising resistance

This paper analyses the emerging globalising networks of communication, solidarity, and information-sharing between social movements and other resistance formations in opposition to neoliberal globalisation. In particular, the paper focuses upon People's Global Action – a network of various social movemnets and grassroots intitiatives from around the world. The paper argues that such a network represents not an organisation, but rather a convergence space – a heterogenous affinity of common ground between resistance formations wherein certain interests, goals, tactics and strategies converge. The paper analyses how space and strategy are negotiated in these globalising terrains of resistance, and argues that place-specific struggles are engaging with alliances and collaborations across diverse boundaries of gender, generation, class, and ethnicity – globalising the common ground between different struggles. Explaining how the internet has been crucial to the development of these networks, the paper argues that the strategies of such networks can be interpreted, in part, through the Taoist text, The Art of War, especially the Taoist notions of terrain, knowing others, and form/lessness. In addition, the paper argues that convergence spaces are fragmented by important issues of language, power, and mobility.     

Introduction to the solar space telescope

The design of the space solar telescope (SST) (phase B) has been completed. The manufacturing is under development. At the end of 2000, it will be assembled. The basic aspect will be introduced in this paper.     

加入WTO与中国出口发展空间分析

本文首先分析了中国出口面临的主要问题和地理格局,接着探讨了中国加入ＷＴＯ后给出口发展带来的机会,最后提出了拓宽中国未来出口发展空的对策。     

新亚欧大陆桥新疆段水害时空分维特征研究

基于区域自然灾害发生的复杂性和不确定性,运用分形、混沌理论,对新亚欧大陆桥新疆段近３８年的洪水灾害资料进行了时空分维特研究。结果表明：陆桥新疆段洪水灾害不仅在时间序列上具有自相似性,其容量维Ｄｆ在０．０４９７～０．０６８７间,而且在空间序列上也具有自似性,存在明显分维结构,其信息Ｄ１在０．０５３７～０．０７９７之间。洪水灾严重区段的信息分维值较低,并且信息分维与洪水灾害发生频率呈反相关。这一特征将