对碎裂结构岩体似连续介质特征的一点研究

通常情况下认为碎裂结构的岩体具有非连续介质的特征。但是随着西部大量水电工程的勘查和建设,遇到了一类比较特殊的岩体,这类岩体中裂隙发育,结构面间距很小,按照国标划分为碎裂结构岩体,但是其本身又具有较高的力学性质,表现为具有较高的变形模量、抗剪强度参数和完整性系数,并且具有似连续介质的特征,这与通常的碎裂结构岩体有本质的区别。本文将利用两个实例工程对这一现象进行初步的分析,得到了水电工程可利用岩体的一种新的评价方法。     

Overview of Direct Measurements of Cosmic Rays

The history of cosmic ray studies can be traced back to the 1910s when Hess and other scientists first discovered them. Cosmic rays are very important laboratories of particle physics, and have led to many important discoveries of fundamental particles, such as the positrons, muons, pions, and a series of strange particles. Cosmic rays are nowadays the key probes of the extremely high-energy physics and dark matter particles. A brief review about the history and recent progresses of direct observations of cosmic rays is presented. In recent years, the new space-borne experiments such as PAMELA and AMS-02, as well as a few of balloon-borne experiments, have measured the energy spectra of cosmic rays very precisely, and revealed several new features/anomalies. Remarkable excesses of positron fraction in the total electron plus positron fluxes have been observed, which may be caused by the annihilation/decay of dark matter particles or by astrophysical pulsars. The cosmic ray antiprotons, which are expected to have the same secondary origin as that of positrons, do not show significant excesses compared with the background prediction. This result also constrains the modeling of the positron excesses. In addition, the spectral hardening above several hundred GeV of cosmic ray nuclei has been revealed. These results have important and interesting implications on our understandings of the origin, acceleration, and propagation of cosmic rays. In particular, China has launched the Dark Matter Particle Explorer (DAMPE) to indirectly search for the dark matter and explore the high-energy universe in the TeV window. Most recently, the DAMPE collaborators reported the new measurements of the cosmic ray electron plus positron fluxes up to about 5 TeV with a very high precision. The DAMPE data revealed clearly a deflection around 0.9 TeV in the electron energy spectrum. Possible fine structures of the electron plus positron spectra can be critically addressed with the accumulation of data in the coming years.     

福建地区前兆资料的信息熵空间扫描特征

在较大地震的孕育过程中, 随着弹性应变能的不断积累, 孕震区有可能从原来的无序状态转变为一种在时间、 空间上的有序状态, 与之相联系的各种信息量的有序程度都有可能增加。 本文引入信息熵来描述前兆观测资料的空间扫描特征: 结果表明: 在4次福建地区中等地震前半个月至2个月, 在未来震中附近围成异常区域, 但异常表现各不相同, 异常区和异常量的大小与震级无明显关系, 震后异常区域均消失; 在4次地震中, 有1次地震发生在信息熵空间扫描围出的异常区内, 另外3次地震虽然不发生在异常区域内, 但震中都处于异常区域边缘, 最大距离不超过50 km以内, 这为判定震中位置提供了一定的依据。     

Fast meridional transport in the lower thermosphere by planetary-scale waves

Observations showed that the main engine water exhaust plumes from space shuttles released at ～110 km altitude from Florida could be transported over thousands of kilometers northward or southward, reaching the Arctic after a day or so, and in one case Antarctica after three days (Stevens et al., 2003, Stevens et al., 2005). In this work, we study the meridional transport associated with the quasi-two-day wave (QTDW) and migrating tides. Diagnostic calculations are performed to trace the particle trajectories using winds from the Thermosphere–Ionosphere–Mesosphere-Electrodynamics General Circulation Model (TIME-GCM) simulations for January, when the amplitude of the QTDW usually peaks. The calculations demonstrate that the mean meridional circulation, a QTDW or a migrating tide cannot individually sustain planetary-scale meridional transport for one to three days, but the combined effects of a QTDW and a tide can. In particular, when the QTDW and the tides are scaled according to the observed amplitudes, particles released at ～110 km and appropriate longitudes/local times can undergo transport fast enough to reach Antarctica within three days as observed. The magnitude and direction of the transport depend on the amplitudes and phases of the tides and the QTDW. These simulations thus suggest that the observed rapid planetary-scale meridional transport of the shuttle main engine plume can be driven by planetary waves and tides.     

Dynamics of cosmic current layers with localized lower-hybrid-drift turbulence

A two-dimensional magnetohydrodynamic model of the dynamics of tail-like current layers caused by anomalous electrical resistivity in a plasma with lower-hybrid-drift (LHD) turbulence is considered. Additionally to the LHD-resistivity, a resistivity pulse in the magnetic neutral sheet is given initiating a magnetic reconnection process. Then the temporal and spatial evolution of the magnetic and electric fields, the plasma convection and the anomalous resistivity are obtained numerically. Taking into account more exact expressions for the LHD-resistivity in the current layer as done in former works, the LHD-turbulence is found to be excited farther from the neutral sheet, and thus, with the time, secondary current sheets are obtained in the plasma-magnetic field system. It is shown that the inductive electric field moving from the magnetic neutral sheet to the current layer periphery during the reconnection process may be considered as indicator of the plasma disturbances.     

Small satellites for global coverage: Potential and limits

There is an increasing need for Earth Observation (EO) missions to meet the information requirements in connection with Global Change Studies. Small and cost-effective missions are powerful tools to flexibly react to information requirements with space-borne solutions. Small satellite missions can be conducted relatively quickly and inexpensively by using commercial off-the-shelf-technologies, or they can be enhanced by using advanced technologies. A new class of advanced small satellites, including autonomously operating “intelligent” satellites may be created, opening new fields of application. The increasing number of small satellites and their applications drive developments in the fields of small launchers, small ground station networks, cost-effective data distribution methods, and cost-effective management and quality assurance procedures. There are many advantages of small satellite missions, like more frequent mission opportunities, a faster return of data, larger variety of missions, more rapid expansion of the technical and/or scientific knowledge base, greater involvement of small industry, feasibility by universities and others.This paper deals with general trends in the field of small satellite missions for Earth observation. Special attention is given to the potential of spatial, spectral, and temporal resolution of small satellite based systems. Examples show small satellites offer also the unique possibility to install affordable constellations to provide good daily coverage of the globe and/or allow us to observe dynamic phenomena.The facts and examples given in this paper lead to the conclusion: Small satellites are already powerful tools for monitoring global, regional and local phenomena. In the future, their application spectrum will even broaden based on the ongoing development in many areas of technology and observation techniques.     

国际地震预警研究现状与研究热点的可视化分析

检索Web of Science数据库中有关地震预警的文献数据,使用Web of Science的数据分析功能和Cite Space可视化分析工具,对地震预警领域的文献数据进行统计分析,探究地震预警领域的研究现状和研究热点,以期为相关机构和研究人员提供参考。     

Space–time forecasting of groundwater level using a hybrid soft computing model

Forecasting of space–time groundwater level is important for sparsely monitored regions. Time series analysis using soft computing tools is powerful in temporal data analysis. Classical geostatistical methods provide the best estimates of spatial data. In the present work a hybrid framework for space–time groundwater level forecasting is proposed by combining a soft computing tool and a geostatistical model. Three time series forecasting models: artificial neural network, least square support vector machine and genetic programming (GP), are individually combined with the geostatistical ordinary kriging model. The experimental variogram thus obtained fits a linear combination of a nugget effect model and a power model. The efficacy of the space–time models was decided on both visual interpretation (spatial maps) and calculated error statistics. It was found that the GP–kriging space–time model gave the most satisfactory results in terms of average absolute relative error, root mean square error, normalized mean bias error and normalized root mean square error.     

湖南香花岭矿田一号锡多金属矿化带空间几何学的研究

香花岭矿田一号锡多金属矿化带中矿体与花岗岩体空间关系的统计研究发现：最有利于锡多金属矿体定位的空间条件是控矿断层与岩体交线上方１６０米左右范围的构造空间；相对较大和稳定的成矿温度场和较开放的环境是锡多金属矿体富集的重要物理化学条件。