Magnetic activity inside the auroral zones and field-aligned currents

Big perturbations of the magnetic field (amplitudes larger than 250 nT) are simply detected by subtracting the values of a model from the measurements of CHAMP satellite. Taking a full year of CHAMP data and organizing them in four subsets of three months length (spring, summer, autumn, winter), it is found that: (a) the two domains where such big perturbations mainly exist are limited, in both hemispheres, by a parallel of high latitude of the corrected geomagnetic coordinates system; (b) a conspicuous seasonal (annual) variation affects the density of the perturbations and is opposite in the two hemispheres. We hold that these perturbations are linked to the midday magnetic activity within the auroral zone, long ago described by one of us (Mayaud, 1956). The source of the perturbations observed at the satellite altitude would be field-aligned currents resulting from the penetration of the solar wind into the magnetospheric cusps. To cite this article: J.-L. Le Mouël et al., C. R. Geoscience 335 (2003).     

Jurassic Dextral and Cretaceous Sinistral Movements Along the Hida Marginal Belt

The Hida marginal belt (HMB), which consists of various kinds of fault-bound blocks, is located between the continental massif of the Hida belt and the Mesozoic accretionary complex of the Mino belt in Central Japan. Detailed field investigation reveals that the HMB had grown through the two different movements, i.e., Jurassic dextral and Cretaceous sinistral movements. The Jurassic dextral ductile shear zones run in the southern marginal part of the Hida belt and the northern part of the HMB, whereas the Cretaceous sinistral cataclastic shear zones occur in the southern part of the HMB and the northern marginal part of the Mino belt. Geologic map and field evidence seem to suggest that the Jurassic dextral movement form the fault-bound blocks of the HMB to form the basic structure of the Hida marginal belt, i.e., formation of the ‘proto-HMB.’ Following the dextral movement, the sinistral one restructured the ‘proto-HMB’ to complete the present feature of the Hida marginal belt. The Cretaceous sinistral movement might result in the sinistral collision between the proto-HMB and the Mino belt.     

Preliminary Rock-Slope-Susceptibility Assessment Using GIS and the SMR Classification

This paper aims to examine the impact of large-scale structuraladjustments (like the Greater Dhaka Flood Protection Project, GDFPP) on local living environment.It focuses the importance of environmental factors in flood hazard mitigation, and examines theenvironmental attitudes of the floodplain residents arising from the large-scale structural adjustments.Based on `perceived natural hazard research perspectives', this paper examines: (i) the reasons for persistentfloodplain occupation, and (ii) the importance of environmental factors in the choice, motivations and decision-makingof floodplain residents.This research used data collected from 300 households situated inthe eastern part of Dhaka. The face-to-face household survey data provided individuals' responses to a structuredquestionnaire on hazards and environment. Survey concerned urban floodplains, and looked fordata on housing, household characteristics, and residents' attitudes. Results of interview surveys wereused to: (i) explore the reasons of floodplain occupation, and (ii) residents' attitudes to tolerable levelof flood risk and willingness to accept environmental change resulting from the proposed structural embankments inthe eastern perimeter of Dhaka City, Bangladesh.Findings revealed that floodplain occupation (by theindividuals' decision-making) was a result of overall reaction to the Government's structuraladjustment policies that resulted from institutional, locational and socio-economic factors. The attitude survey results provided residents' perception to hazards and environment to be dependenton the socio-economic factors – but in a complex manner, many factors are interrelated.In addition to support for structural embankments, the study sample displayed a common concernand widespread environmental awareness. In terms of any `trade-off' between thebenefits (resources) from the embankments and costs (hazards) due to the detrimental impact on environment, the residents of Dhaka, despite some concern forsacrificing embankments for environment, tended to show a generalconsensus for embankments.     

Geomechanical Properties of Shear Zones in the Eastern Aar Massif,Switzerland and their Implication on Tunnelling

Summary ¶Rock zones containing a high fracture density and/or soft, low cohesion materials can be highly problematic when encountered during tunnel excavation. For example in the eastern Aar massif of central Switzerland, experiences during the construction of the Gotthard highway tunnel showed that heavily fractured areas within shear zones were responsible for overbreaks in the form of chimneys several metres in height. To understand and estimate the impact of the shear zones on rock mass behaviour, knowledge concerning the rock mass strength and deformation characteristics is fundamental. A series of laboratory triaxial tests, performed on samples from granite- and gneiss-hosted shear zones revealed that with increasing degree of tectonic overprint, sample strength decreases and rock behaviour shows a transition from brittle to ductile deformation. These trends may be explained by increasing fracture densities, increasing foliation intensity, increasing thickness of fine-grained, low cohesion fracture infill, and increasing mica content associated with the increasing degree of tectonic overprint. As fracture density increases and the influence of discrete, persistent discontinuities on rock mass strength decreases, behaviour of the test samples becomes more and more representative of rock mass behaviour, i.e. that of a densely fractured continuum. For the purpose of numerical modeling calculations, the shear zones may be subdivided with respect to an increasing fracture density, foliation intensity and mica content into a strongly foliated zone, a fractured zone and a cohesionless zone, which in turn exhibit brittle, brittle-ductile and ductile rock mass constitutive behaviour, respectively.Received December 17, 2001; accepted January 9, 2003 Published online April 29, 2003     

Kinematics of throughgoing fractures in jointed rocks

Throughgoing fractures play a major role in subsurface fluid flow yet the kinematics of their formation, which directly impact rock flow properties, are often difficult to establish. We investigate throughgoing fractures in the Monterey Formation of California that developed by the coalescence of pre-existing joints. At Lompoc Landing, throughgoing fractures fall into three main groups: linked, linked with aperture, and breccia zones. The segmented nature of their walls provides numerous piercing points to firmly establish the sense of displacement. Analysis of displacement vectors derived from piercing points demonstrates that the NW–SE trending throughgoing fractures, often interpreted as strike–slip faults, are in fact extensional structures in origin. We suggest that this method may be applied to throughgoing fractures that form by the same mechanism in other geologic settings. Establishing kinematics of throughgoing fractures will lead to a better understanding of their contribution to subsurface fluid flow.     

数字水印技术与算法实现

综述了数字水印技术的起源、概念、特点和应用；提出了数字水印处理技术的基本框架；列出了一些主要的基于图像的水印嵌入算法和水印检测算法；并展望了水印处理技术的未来发展趋势；最后给出了一种基于DCT变换的水印嵌入与检测算法。     

香港的土地利用与环境保护

香港地区地域狭小，地形崎岖，可利用地少，人口众多，用地紧张，但严谨的用地政策、规划用地和严格管地，使城镇有序，城乡结合协调，基础设施完善，做到合理用地，有效用地和高效用地，从而成为一座名副其实、整洁、美丽的现代化国际大都市。     

遥感技术在化工环境保护中的应用

遥感技术获取的可见光、红外及微波信息，可以对化工企业及化学矿山环境污染（水、粉尘、大气、废渣污染等）及环境地质灾害（滑坡、泥石流、地面塌陷等）进行实时动态监测，并可获得较高的社会经济效益，达到地面环保及常规环境地质工作难以达到的效果。特别是对重点大中型化工企业及化学矿山建立环境遥感信息动态监测系统，可以为国家决策部门及时准确地提供环境治理和改造的依据。     

西藏聂拉木高喜马拉雅结晶岩系的伸展变形

西藏聂拉木高喜马拉雅结晶岩系在区域上以单一的叶理和单一的拉伸线理占主要地位，其变形带的组构主要反映了透入性的伸展变形；根据显微构造分析表明早期由北往南推覆，晚期由南向北伸展，且晚期表现非常明显。     

一种简单方便的防拷贝程序设计方法——识别计算机的C语言程序设计

本文主要讨论一种特殊的Ｃ语言程序设计方法，这种程序能有效地对自身的关键模块加密，并能在运行时完成动态解密。该方法主要利用了“硬盘分区表”和最初安装在硬盘中程序自身的位置等信息，采用伪随机数加密法来实现。因所设计的程序具有识别计算机的能力，能有效地防止非法复制，从而保护软件制作者的知识产权和经济利益