板块俯冲对岩浆作用影响的同位素地球化学示踪研究

同位素已成为俯冲带岩浆作用研究中灵敏的地球化学示踪剂,是约束岩浆运移过程和时间尺度的有力工具。综述了近几十年来利用Sr-Nd-Pb-Hf同位素、Li和B同位素以及Be和短周期铀系同位素等方法,在俯冲带岩浆作用过程、时间尺度、岩浆源区物质特征、岩浆形成演化及控制机制等方面取得的进展和成果。最后指出将不同同位素研究应用于弧后盆地岩浆作用的研究中,必将为全球俯冲带岩浆作用研究带来突破性的进展和成果。     

Status of two <Emphasis Type="Italic">Coreius</Emphasis> species in the Three Gorges Reservoir,China

Dam construction alters natural flow regimes which, in turn, cause significant changes in fish communities during and after impoundment. The construction of the Three Gorges Reservoir, from impoundment of the Changjiang (Yangtze) River, China, may have affected native fish species. Thus, the status of two lotic freshwater fish species, Coreius heterodon and C. guichenoti, were monitored in the Three Gorges Reservoir, including fish abundance, individual composition, growth, condition, and mortality. Data on both species were gathered from upstream, midstream and downstream areas of the reservoir and, where available, from studies published before and after dam construction. Lower abundance, slower growth, a less diversified age structure, poorer fish condition (indicated by hepatosomatic index) and higher mortalities were recorded in sites nearest the dam compared with upstream areas. Furthermore, after final impoundment, individual Coreius species inhabiting the area changed, with young individuals becoming more abundant, while upstream of the reservoir the two Coreius species became smaller at a given age. The results show that the status of the two Coreius species was subject to dramatic changes after impoundment.     

Solutions for Displacement and Stress in Strain-Softening Surrounding Rock Incorporating the Effects of Hydraulic–Mechanical Coupling and Rockbolts Effectiveness

This study focuses on the stress and displacement of a circular opening that is excavated in a strain-softening rock mass incorporating the effects of hydraulic–mechanical coupling and rockbolts effectiveness. It follows the generalized Hoek–Brown failure criterion. Moreover, an improved numerical approach and stepwise procedure are proposed. This approach considers the deterioration of the strength, deformation, and dilation angle and the variation of elastic strain in the plastic region considering the effect of the hydraulic–mechanical coupling and the rockbolts effectiveness. The presented solutions were validated by FLAC results. Several examples are conducted to demonstrate the validity and accuracy of the proposed solution through MATLAB programming. Parametric studies are also conducted to highlight the influences of hydraulic–mechanical coupling and rockbolts effectiveness on stress and displacement. Results show that stress and displacement, incorporating the effects of hydraulic–mechanical coupling and rockbolts effectiveness, are between those when hydraulic–mechanical coupling or rockbolts effectiveness is considered separately. However, this theory needs more verification from practical engineering.     

省界断面水资源监测站网建设实施与探讨

省界断面水资源监测是实行最严格水资源管理制度的重要基础工作,介绍了省界断面水资源监测站网建设的建设目标、主要任务、建设内容和投资,阐述了项目的实施和安排,并针对当前项目实施情况和特点,探讨了项目实施和运行管理需要注意的问题。     

Developed and developing world contributions to climate system change based on carbon dioxide,methane and nitrous oxide emissions

One of the key issues in international climate negotiations is the formulation of targets for emissions reduction for all countries based on the principle of "common but differentiated responsibilities". This formulation depends primarily on the quantitative attribution of the responsibilities of developed and developing countries for historical climate change. Using the Commuity Earth System Model(CESM), we estimate the responsibilities of developed countries and developing countries for climatic change from 1850 to 2005 using their carbon dioxide, methane and nitrous oxide emissions. The results indicate that developed countries contribute approximately 53%–61%, and developing countries approximately 39%–47%, to the increase in global air temperature, upper oceanic warming, sea-ice reduction in the NH, and permafrost degradation. In addition, the spatial heterogeneity of these changes from 1850 to 2005 is primarily attributed to the emissions of greenhouse gases(GHGs)in developed countries. Although uncertainties remain in the climate model and the external forcings used, GHG emissions in developed countries are the major contributor to the observed climate system changes in the 20 th century.     

Remote sensing of human beings – a perspective from nighttime light

City lights, fishing boats, and oil fields are the major sources of nighttime lights, therefore the nighttime light images provide a unique source to map human beings and their activities from outer space. While most of the scholars focused on application of nighttime light remote sensing in urbanization and regional development, the actual fields are much wider. This paper summarized the applications of nighttime light remote sensing into fields such as the estimation of socioeconomic parameters, monitoring urbanization, evaluation of important events, analyzing light pollution, fishery, etc. For estimation of socioeconomic parameters, the most promising progress is that Gross Domestic Product and its growth rate have been estimated with statistical data and nighttime light data using econometric models. For monitoring urbanization, urban area and its dynamics can be extracted using different classification methods, and spatial analysis has been employed to map urban agglomeration. As sharp changes of nighttime light are associated with important socioeconomic events, the images have been used to evaluate humanitarian disasters, especially in the current Syrian and Iraqi wars. Light pollution is another hotspot of nighttime light application, as the night light is related to some diseases and abnormal behavior of animals, and the nighttime light images can provide light pollution information on large scales so that it is much easier to analyze the effects of light pollutions. In each field, we listed typical cases of the applications. At last, future studies of nighttime light remote sensing have been predicted.     

社交媒体地理大数据的旅游景点热度分析

针对大数据时代,蕴含地理位置信息的社交媒体(Social Media)数据规模正呈爆炸性增长,通过对这类时空数据的挖掘可以整合用户的群体智慧,发现热门景点或线路,为用户提供更加精细的旅行服务。该文基于2005—2016年Flickr图片分享网站中用户分享的带地理标签的图片信息,通过空间聚类以及文本语义挖掘的方法对北京市的热门景点进行了提取。此外,本文还利用北京市的历史天气信息与用户图片信息进行融合,分析在不同时间、不同天气情景下,不同景点的热度分布规律,可以为旅行爱好者提供热门景点在多种视角下的游览规律。