氡气异常解释方法的初步探讨

在铀矿勘探中,根据氡气异常计算矿体埋深的工作是十分重要的。本文从运用测氡及其子体的方法寻找深部铀矿的事实出发,探讨了氡气运移的方式及其可能分布的模式,并对M.M.索科洛夫的实验结果进行了初步的理论讨论。同时,对根据氡气异常计算矿体埋深的解释问题进行了探索性的研究。本文所提出的方法,在一定的地质条件下,原则上适用于各种放射性测量异常的解释方法。实践表明,本法在矿床勘探工作中能提供关于矿体的某些参数(埋深和产状),有一定的实用价值。     

Climate-Induced migration and unemployment in middle-income Africa

One of the major unresolved questions in the study of vulnerability to climate change is how human migration will respond in low and middle-income countries. The present study directly addresses this lacuna by using census data on migration from 4 million individuals from three middle-income African countries over a 22-year period. We link these individuals to climate exposures in their origins and estimate climatic effects on migration using a fixed-effects regression model. We show that climate anomalies affect mobility in all three countries. Specifically, mobility declines by 19% with a 1-standard deviation increase in temperature in Botswana. Equivalent changes in precipitation cause declines in migration in Botswana (11%) and Kenya (10%), and increases in migration in Zambia (24%). The mechanisms underlying these effects appear to differ by country. Negative associations between precipitation anomalies, unemployment, and inactivity suggest migration declines may be due to an increased local demand for workers to offset production risk, while migration increases may be indicative of new opportunities in destinations. These country-specific findings highlight the contextually-specific nature of climate-migration relationships, and do not support claims that climate change is widely contributing to urbanization across Africa.     

Forecasting the impact of transport improvements on commuting and residential choice

This paper develops a probabilistic, competing-destinations, assignment model that predicts changes in the spatial pattern of the working population as a result of transport improvements. The choice of residence is explained by a new non-parametric model, which represents an alternative to the popular multinominal logit model. Travel times between zones are approximated by a normal distribution function with different mean and variance for each pair of zones, whereas previous models only use average travel times. The model’s forecast error of the spatial distribution of the Dutch working population is 7% when tested on 1998 base-year data. To incorporate endogenous changes in its causal variables, an almost ideal demand system is estimated to explain the choice of transport mode, and a new economic geography inter-industry model (RAEM) is estimated to explain the spatial distribution of employment. In the application, the model is used to forecast the impact of six mutually exclusive Dutch core-periphery railway proposals in the projection year 2020.

探地雷达小波域三维波动方程偏移

阐述了矩阵多分辨分析理论中的标准形式与非标准形式,并以Hilbert算子为例,说明了算子多分辨表示的压缩效果,为小波域偏移算法奠定了理论基础.从三维雷达波动方程出发,利用爆炸反射原理和浮动坐标变换,推导出三维探地雷达波动方程差分格式,并通过方程分裂算法及小波多分辨算法,在小波域求解波场外推矩阵,进而得到探地雷达小波域三维波动方程偏移算法,在此基础上,开发了探地雷达小波域偏移处理程序,并把该程序应用于三个球体空洞的3-D正演结果及实际的雷达数据中,通过对比偏移处理前后的雷达资料,得知该三维偏移算法能使3-D正演剖面中的反射波归位、绕射波收敛,极大地提高了雷达剖面的分辨率,有利于探地雷达资料的地质解释.     

塔里木盆地轮南低凸起断裂系统与复式油气聚集

塔里木盆地轮南低凸起复式油气聚集区的提出对高效指导轮南地区的油气勘探起了促进作用。基于区域石油地质研究成果,充分利用成像测井、高分辨三维地震断裂精细描述和有机地球化学等新技术新方法,本文系统研究了轮南低凸起复式油气聚集成藏的关键地质条件,全面刻画了轮南断裂系统的复杂特征,明确了轮南多含油层系具有相同的寒武系海相烃源,证实了在多期次成藏过程中,断裂系统既是早期成藏的油气充注通道,又是晚期调整气侵的输导体系。对轮南海相碳酸盐岩大型油气田的成藏,断裂系统既是有效的储集空间,又是储集性能改善和连通性增强的重要条件,提出复杂断裂系统多期活动下油气渐进幕式成藏和跨越动态成藏模式。从前提(古隆起)、基础(多套储盖组合)和关键(断裂系统)3方面探讨了复式油气聚集成藏的机理,并指出轮古东走滑断裂带是近期扩大轮南复式油气聚集区规模、实施天然气勘探的现实领域。     

气候变化对我国历史时期人口迁移的影响

我国历史时期曾发生过多次大规模的人口迁移。影响其迁移发生的因素是复杂的、多方面的,而气候变化的作用过去一直被大多数研究者所忽视。本文的讨论表明历史上的一些人口迁移时期,尤其是中亚和蒙古高原游牧民族大规模南下时期,往往也是我国北方气候偏干,旱灾、尘暴和冬季雷暴出现频繁,湖泊退缩,土地沙漠化强烈和黄河决溢频率减小的时期。湖泊面积变化的能量平衡计算表明,干旱、半干旱地区这时的降水量较先前的湿润期减少了35～40％以上。这种强烈的变化导致了畜牧业的严重减产,使其产量不能维持湿润期已增长起来的人口的需求而发生了人口的向外流动,并多次导致了全国性人口大迁移。与此同时,气候变化和气候灾害也直接影响了汉族内部的人口迁移。     

胜利油田部分岸段岸滩演化和防护问题

本文在综合我所多年实地观测资料的基础上,讨论了黄河三角洲胜利油田所辖部分岸段岸滩演化和防护问题。认为岸滩演化主要受制于黄河尾闾变化和海动力的相互作用,预测了１９９６年汛期到来前黄河入海口由北汊１南侧人工改道后,岸滩发育的基本趋势和需要重视的问题。文章也讨论了防潮堤和有关海上设施的防护问题。     

苏北东海水晶矿床的形成机理初探

通过对硅的迁移形式和条件、苏北东海水晶矿床中石英流体包裹体的化学成分、部分飘动气体自然、晶洞与水晶的密切相关性以及水晶的共生伴生矿物等的研究,提出该矿床的形成机制为：在地球深部高温高压强还原富氢环境下,硅呈气态硅氢络合物活化并纯化、迁移至地壳浅部低温低压氧化环境,硅氢化物较快氧化形成石英脉,并在有利部位形成石英外壳（晶洞壳）,晶洞内的硅氢化物在温和稳定环境中缓慢氧化,并自由结晶分异纯化形成水晶矿床。