北祁连造山带两种构造基底岩块及成矿系统

北祁连造山带中存在“南方型”和“北方型”构造基底岩块。“南方型”构造基底岩块和柴达木古陆相似 ,“北方型”构造基底岩块则和华北古陆相似。两种不同的构造基底岩块随着祁连洋的消失而相遇于北祁连造山带 (缝合带 )中。在祁连洋的俯冲过程中 ,形成了不同的成矿系统 ,与“北方型”构造基底岩块有关的成矿系统为加里东期活动大陆边缘成矿系统———白银、清水沟铜及多金属成矿组合 ;与“南方型”构造基底岩块有关的成矿系统为中、新元古代活动大陆边缘弧后裂解成矿系统———镜铁山—柳沟峡铁成矿组合 ,加里东期活动大陆边缘与俯冲作用有关的成矿系统———岩浆热液钨成矿组合及铅锌成矿组合。两种构造基底岩块的确认 ,可为北祁连缝合带的成矿系统的建立及找矿工作 ,提供新的思路 ,也为北祁连造山带性质的认定 ,提供成矿作用信息方面的限制。     

High order symplectic integrators for perturbed Hamiltonian systems

A family of symplectic integrators adapted for the integration of perturbed Hamiltonian systems of the form H=A+B was given in (McLachlan, 1995). We give here a constructive proof that for all integer p, such integrator exists, with only positive steps, and with a remainder of order O(^p + ²²), where is the stepsize of the integrator. Moreover, we compute the analytical expressions of the leading terms of the remainders at all orders. We show also that for a large class of systems, a corrector step can be performed such that the remainder becomes O(^p +⁴²). The performances of these integrators are compared for the simple pendulum and the planetary three-body problem of Sun–Jupiter–Saturn.     

成矿动力系统在混沌边缘分形生长——一种新的成矿理论与方法论(上)

“成矿动力系统在混沌边缘分形生长”理论是笔者将复杂性理论及非线性科学与矿床地质学相结合 ,对中国扬子古陆周缘六个矿集区的基本范式进行长期系统研究所取得的总结性成果。研究指出 ,成矿系统总体上是开放、远离平衡、时空延展的动力学系统。它们具有复杂性和自组织临界性的内禀基本属性 ,并且在混沌边缘分形生长。该理论以“地质作用与时 空结构是一切地质现象的本质与核心”的自然哲学理念作为根本立足点 ,建立起一种具有普适性的理论框架。然后进一步将其具体化为三大组成部分 ,即 ( 1)矿床的动力学属性 ,( 2 )矿床地质学场 ,( 3 )成矿系统的演化。体现了成矿作用 (其核心为成矿作用动力学 )、空间结构 (矿床地质学场 )和时间结构 (成矿系统的演化 )三位一体的整体耦合与交织 ,从而又使该理论具有包容性。在此基础上进而归纳出“成矿动力系统在混沌边缘分形生长”的 5项判定准则以及表征这些准则的 10项相应的动力学行为特征。最后笔者提出“矿质局部活化导致成矿的发生”的命题 ,拟定了“成矿的发生”的重要科学问题 ,以“元胞非线性网络”(CNN)作为复杂性的范式 ,定量揭示成矿的发生 ,并对矿床在混沌边缘作精确定位 ,对“成矿动力系统在混沌边缘”理论作进一步的延伸、深化与发展。该理论在矿?     

Experimental study of the formation of inverted-V structures and their stratification using AUREOL-3 observations

Multiple inverted-V structures are commonly observed on the same auroral zone crossing by a lowaltitude orbiting satellite. Such structures appear grouped and apparently result from an ionospheric and/or magnetospheric mechanism of stratification. More than two years of AUREOL-3 satellite observations were analyzed to study their properties and their formation in the framework of the ionosphere-magnetosphere coupling model proposed by Tverskoy. This model predicts some natural periodicity in the electrostatic potential profile (and subsequently in the field-aligned current profiles) that could account for oscillations experimentally observed in the auroral zone, such as successive inverted-Vs. Experimental results obtained during quiet or moderately active periods demonstrate that the number of structures observed within a given event is well described by a scaling parameter provided by the hot plasma stratification theory and expressed in terms of the field-aligned current density, the total width of the current band, the plasma sheet ion temperature, and the height-integrated Pedersen conductivity of the ionosphere. The latitudinal width, in the order of 100/200 km at ionospheric altitudes, is relatively independent of the current density, and is determined not only by the existence of a potential difference above the inverted-Vs, but also by basic oscillations of the ionosphere-magnetosphere coupling system predicted by Tverskoy. The large number of cases studied by the AUREOL-3 satellite provides reliable statistical trends which permits the validation of the model and the inference that the multiple structures currently observed can be related directly to oscillations of the magnetospheric potential (or the pressure gradients) on a scale of 1000/2000 km in the near-Earth plasma sheet. These oscillations arise in the Tverskoy model and may naturally result when the initial pressure gradients needed to generate a large-scale field-aligned current have a sufficiently wide equatorial scale, of about 1 R_E or more.     

云南省滑坡泥石流灾害评估方法研究

通过对云南省滑坡泥石流灾害资料的收集和调研,提出了滑坡泥石灾害分类与等级划分标准,根据滑坡泥石流灾害评估的综合性、客观性、科学性和实用性原则,建立了人员伤亡、房屋破坏、基础设施破坏和农业损失的评价指标体系。提出了调查、统计、评估和核灾等滑坡泥石流灾害结合评估办法,以期实现抗灾救灾管理工作的规范化和制度化。     

龙羊峡库区环境动态监测信息系统的建立与应用

以黄河上游最大的水利工程－－龙羊峡水库为实验区,围绕库区存在的主要环境问题的研究,应用遥感与ＧＩＳ一体化的方法,研究设计了系统结构、功能及数据库的组成,并建立了可运行的龙羊峡库区环境动态监测信息系统,在系统支持下有效的实现了库区环境动态监测与应用,由于该系统较强的可操作性和适应性,其成果在高寒干旱与半干旱地区环境研究中具有推广和应用价值。     

木卫三的动力学参数

木卫三是太阳系中最大的一颗天然卫星。当伽利略飞船于1996年6月和9月两次飞经木卫三时,定出了二阶带谐和扇谐Stokes系数J2和C22。本文利用最新的木卫三的物理参数,首先建立了一组内部结构模型,然后估算出木卫三的若干动力学参数,并与月球的相应值进行比较,结果表明这两个天然卫星最显著的不同是,木卫三满足静力学平衡条件,而月球偏离了静力学平衡条件。     

Equation of a Barotropic Fluid on a Rotating Spherical Surface and its Inertial Manifold

The inertial manifold is a positive invariant set which exponentially attracts all the trajectories of a dissipative dynamic system. It was introduced for the purpose of studying the asymptotic behaviour of such systems. The initial infinitely dimensional dynamic system, generated by a partial differential evolution equation, can be projected on to it, in order to obtain the final system of ordinary differential equations (inertial equations). These equations then simulate the initial object. Although the inertial manifold is an object relatively simpler than the attractor (a very complicated set of non-integer dimension may be an attractor) it is more difficult to prove its existence than that of the attractor. The equation of a barotropic fluid on a rotating spherical surface is one of the examples of dissipative dynamic systems with an inertial manifold. This kindles the hope that also the equations of the dynamics of the real atmosphere will have an inertial manifold. The reduction of the sample system to this Lipschitz manifold of finite dimension thus justifies us in analysing the behaviour of the atmosphere on non-linear models of finite dimensions and few parameters, in a finite system of ordinary differential equations.     

Contrasting hydrothermal activity at Sierra Negra and Alcedo volcanoes, Galapagos Archipelago, Ecuador

2 and approximately 85% SO₂ of the total sulfur gas. Relative amounts of He, Ar, and N₂ show a distinct hot-spot signature ( ). The δ¹³C–CO₂ is approximately −3.6‰ and δ³⁴S_T is approximately +3.3‰. The δD/δ¹⁸O of fumarole H₂O indicates steam separation from local meteoric waters whose estimated minimum mean residence time from ³H analyses is ≤40 years. Fumarolic activity at Alcedo is controlled by a caldera-margin fault containing at least seven hydrothermal explosion craters, and by an intracaldera rhyolite vent. Two explosion craters which formed in 1993–1994 produce approximately 15 m³/s of steam, yet discharge temperatures are ≤97°C. Water content of the total gas is 95–97 mol.%, noncondensible gas is 92–98 mol.% CO₂, and sulfur gas is dominated by H₂S. Relative amounts of He, Ar, and N₂ show extensive mixing between hot spot and air or air-saturated meteoric water components but the average . The δ¹³C–CO₂ is approximately −3.5‰ and δ³⁴S_T is approximately −0.8‰. The δD/δ¹⁸O of fumarole steam indicates separation from a homogeneous reservoir that is enriched 3–5‰ in ¹⁸O compared with local meteoric water. ³H indicates that this reservoir water has a maximum mean residence time of approximately 400 years and empirical gas geothermometry indicates a reservoir temperature of 260–320°C. The intracaldera hydrothermal reservoir in Alcedo is probably capable of producing up to 150 MW; however, environmental concerns as well as lack of infrastructure and power users will limit the development of this resource. Received: 19 April 1999 / Accepted: 23 October 1999     

Population geography with GIS in Japan

Japanese geography studies are now being greatly affected by the rapid development of geographical information systems (GIS). Unfortunately, there has been little response from Japanese population geographers to this movement. Is GIS a welcome or an unwelcome guest? After discussing the significance of employing GIS, this article introduces some recent papers that used GIS in the field of population geography on such issues as mortality mapping, migration analysis, and household studies. Then, the two promising population-related topics of married one-person households and fertility are discussed. The ability of GIS to greatly facilitate analysis, which previously needed much time and energy, can be an encouraging stimulus of innovation in studies of current population geography. Therefore, GIS is clearly a welcome guest, although it is too wishful to think that its use would lead directly to a revitalization of contemporary population geography studies.