The global flow of the parabolic restricted three-body problem

We have two mass points of equal masses m ₁=m ₂ > 0 moving under Newton’s law of attraction in a non-collision parabolic orbit while their center of mass is at rest. We consider a third mass point, of mass m ₃=0, moving on the straight line L perpendicular to the plane of motion of the first two mass points and passing through their center of mass. Since m ₃=0, the motion of m ₁ and m ₂ is not affected by the third and from the symmetry of the motion it is clear that m ₃ will remain on the line L. The parabolic restricted three-body problem describes the motion of m ₃. Our main result is the characterization of the global flow of this problem.     

Estimating the dispersion of biostratigraphic events in the subsurface by graphic correlation: an example from the Late Jurassic of the Wessex Basin, UK

The strikingly cyclic character of digitally filtered gamma ray logs from the Oxfordian to Portlandian interval of the Wessex Basin, onshore United Kingdom, facilitates high resolution log correlation over considerable distances, allowing the systematic calibration of biostratigraphic with lithostratigraphic data through graphic correlation. This involves the systematic cross-plotting of biostratigraphic events, based on samples taken from cuttings and sidewall cores, from a set of wells to produce a composite standard. Initially the standard is a single well, chosen for maximum thickness and completeness. Biostratigraphic events are added to by drawing lines of correlation and projecting the data points onto the composite standard. The scatter of biostratigraphic events is generally such that a line of correlation cannot be drawn with confidence from the biostratigraphic data alone. Independent lines of correlation are established between wells by first matching cycles (? parasequences) on digitally filtered gamma ray traces and using these as a framework for adding biostratigraphic events to the composite standard. This has advantages over the conventional approach in that the effects of outliers in the data are minimized and hiatuses and subtle changes in rock accumulation rates become apparent. By adding all the biostratigraphic events from all wells to the composite standard a range chart is produced depicting the scatter or dispersion of all biostratigraphic events relative to the log based cycles. The end result is an integrated stratigraphy in which biostratigraphic events are calibrated against rock events giving a measure of dispersion, and hence confidence, for each biostratigraphic event.     

Climate change and multi-dimensional sustainable urbanization

Global large-scale urbanization and climate change have become indisputable scientific facts yet are unresolved issues, and are a common concern for mankind. The relationship between these two topics is unclear and it is not known how to deal appropriately at the scientific level with climate change in the process of urbanization. Further exploration of the science, management and practice, are needed to achieve global and regional sustainadevelopment. This paper first considers the basic facts concerning mass urbanization and climate change and summarizes the interactions and possible mechanisms of urbanization and climate change. Urbanization leads to the heat island effect, an uneven distribution of precipitation and extreme weather, together with a local-regional-global multi-scale superposition effect, which aggravates the consequences of global climate change. The impact of climate change on urbanization is mainly manifested in aspects such as changes of energy consumption, mortality, and the spread of infectious diseases, sea level rise, extreme weather damage to infrastructure, and water shortages. This paper also briefly reviews relevant international research programs and action coalitions and puts forward an analysis framework multi-dimensional sustainable urbanization which can adapt to and mitigate climate change, from the perspective of the four key dimensions—population, land use, economy, and society. It is imperative that we strengthen the interdisciplinary activities involving the natural and social sciences, take urbanization and other human activities into consideration of the land-atmosphere system, and explore the human-land-atmosphere coupling process. The adaptation and mitigation from the perspective of human activities, as represented by urbanization, might be the most critical and realistic way to deal with climate change.     

生物土壤结皮中微生物群落特征综述北大核心CSCD

生物土壤结皮(也称生物结皮)是联结荒漠区地表生物成分与非生物成分的纽带,它不仅是荒漠区生物多样性的“热点”,也是退化生态系统修复的“工程师”。生物结皮的拓殖不仅能稳定地表,影响土壤水文过程,对土壤形成起着重要作用,还对荒漠区土壤碳氮循环等产生重要影响。蓝藻、细菌、真菌和古菌等微生物在生物结皮形成和发挥生态功能过程中发挥重要作用。本文系统总结了全球寒漠、冷漠和热漠生物结皮中微生物的组成和群落特征,厘清了主要生物气候区不同演替阶段的生物结皮中主要微生物物种,对相关微生物的研究进展和存在问题进行了分析,最后从微生物相互作用角度为明确关键枢纽微生物种提出了建议,以期对筛选潜在高效固沙菌种、培育人工结皮促进受损生态系统恢复提供参考。     

区域要素市场分割与要素配置效率的时空演变及关系

在修正的全局参比价格法基础上,结合非参数DEA-Hybrid模型评测了中国29个省份的要素市场分割水平及要素配置效率,进而构建考虑地理距离与经济规模的综合权重矩阵,利用空间Durbin模型实证分析区域要素市场分割对要素配置效率的影响。研究发现:东部地区的要素市场分割水平相对较低,中部次之,西部最高;要素市场分割将引致要素配置效率扭曲且存在显著的空间溢出效应,适度财政分权能有效抑制要素市场分割引致的要素配置效率扭曲;较高的国有经济占比、产业结构高级化、交通基础设施和外商直接投资能有效改善区域要素配置效率,对外开放的效率改进作用尚不明显。清除地区间要素市场壁垒并充分发挥市场配置资源的决定性作用是提升要素配置效率的着力点。     

从跨国广告业看全球化和全球城市——以中国广告业为例

本文从广告业的视角出发 ,分析了伴随全球生产者服务业空间布局的扩张而来的区域市场和空间结构的重塑。研究的主要发现为 :(1)在跨国公司的支配下 ,中国广告业在生产组织上逐渐向专业代理演化 ,在行业规范上也逐渐向 4A的主流靠拢 ;(2 )中国广告业在上海、北京、广州三大城市的集中 ,体现了在全球化过程中形成的“区域性服务业市场” ;(3)由于市场规模大 ,中国广告业有可能向“前端” (产品定位和沟通策略 )发展 ;(4 )由于中国幅员广大 ,进入区域市场需要不同的媒体计划 ,也使得广告的全球标准化产品产出更多的地方版本。在理论争论方面 ,本文认为全球城市是都市区域全球化制度和空间的中介。     

Groundwater Depletion and Agricultural Land Use Change in the High Plains: A Case Study from Wichita County,Kansas*

Shifts in resource availability and resulting land use changes are important research themes for coupled human and natural systems and human dimensions of global environmental change. This study examines the relationship between groundwater depletion and agricultural land use change within a single county in the High Plains, where agro-economic systems and populations are dependent on access to reliable groundwater supplies. Results indicate a significant relationship between high proportionate decreases in groundwater and land being removed from irrigation. This case study strengthens the links among local, regional, and global environmental change, and contributes to a greater understanding of the High Plains in the context of regional sustainability and vulnerability concerns.     

全球化与全球变化关系研究

全球化是本世纪人类社会发展的最重要特征之一,它不仅促进了产品和服务的流动,而且促进了劳动力、金融、资源及环境生产要素等的流动,技术的发展提高了生产效率和物质要素的可利用性.全球化扩大了人类活动的范围和影响程度,对人类社会、政治、文化、经济等各个方面都产生了影响,从而加深了全球环境变化.全球环境变化已经成为伞球化进程的重要方面,人类对全球环境变化的应对方式直接关系到人类的生存及可持续发展.全球化深化了国际分工,发达国家制造业大量向发展中国家转移,从而导致发展中国家承担了更多的环境污染,造成发展中国家碳排放增长较快.在全球化进程中,中国在享受初级产品大量出口并产生顺差的同时,也把环境污染输入进来,并把大量资源输出去,从而造成中国资源紧张和环境污染.随着中国经济实力的增强,中国的政治、文化等都会在全球产生更大影响,研究全球化进程对中国现代化进程的影响及中国现代化进程对全球化的影响、全球化进程与全球环境变化的关系具有重要的理论和实践意义.