Environmental changes in the north‐east Sunda region over the last 40 000 years     

Chuanxiu Luo  Simon Haberle  Zhuo Zheng  Rong Xiang  Chixin Chen  Gang Lin  Kumar Sazal 《第四纪科学杂志》2019,34(3):245-257

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Future growth patterns of world regions – A GDP scenario approach     

《Global Environmental Change》2017

Global GDP projections for the 21st century are needed for the exploration of long-term global environmental problems, in particular climate change. Greenhouse gas emissions as well as climate change mitigation and adaption capacities strongly depend on growth of per capita income. However, long-term economic projections are highly uncertain. This paper provides five new long-term economic scenarios as part of the newly developed shared socio-economic pathways (SSPs) which represent a set of widely diverging narratives. A method of GDP scenario building is presented that is based on assumptions about technological progress, and human and physical capital formation as major drivers of long-term GDP per capita growth. The impact of these drivers differs significantly between different shared socio-economic pathways and is traced back to the underlying narratives and the associated population and education scenarios. In a highly fragmented world, technological and knowledge spillovers are low. Hence, the growth impact of technological progress and human capital is comparatively low, and per capita income diverges between world regions. These factors play a much larger role in globalization scenarios, leading to higher economic growth and stronger convergence between world regions. At the global average, per capita GDP is projected to grow annually in a range between 1.0% (SSP3) and 2.8% (SSP5) from 2010 to 2100. While this covers a large portion of variety in future global economic growth projections, plausible lower and higher growth projections may still be conceivable. The GDP projections are put into the context of historic patterns of economic growth (stylized facts), and their sensitivity to key assumptions is explored.  相似文献   

澳门回归与粤澳经济和空间一体化   总被引：2，自引：0，他引：2  

李燕  司徒尚纪 《热带地理》1999,19(4):318-323

在澳门回归、广东与澳门之间政治关系转变的基础上, 结合改革开放后两地在经济与空间互补和紧密结合的历史事实, 指出澳门回归后, 在历史、经济、政治、文化等因素作用和影响下, 粤澳经济和空间一体化是一种必然趋势, 应充分利用两地资源和空间优势互补关系, 推动两个地区的发展。  相似文献   

Analysis of thick, non-planar boundaries using the discontinuity analyser     

M. W. Dunlop  T. I. Woodward 《Annales Geophysicae》1999,17(8):984-995

The advent of missions comprised of phased arrays of spacecraft, with separation distances ranging down to at least mesoscales, provides the scientific community with an opportunity to accurately analyse the spatial and temporal dependencies of structures in space plasmas. Exploitation of the multi-point data sets, giving vastly more information than in previous missions, thereby allows unique study of their small-scale physics. It remains an outstanding problem, however, to understand in what way comparative information across spacecraft is best built into any analysis of the combined data. Different investigations appear to demand different methods of data co-ordination. Of the various multi-spacecraft data analysis techniques developed to affect this exploitation, the discontinuity analyser has been designed to investigate the macroscopic properties (topology and motion) of boundaries, revealed by multi-spacecraft magnetometer data, where the possibility of at least mesoscale structure is considered. It has been found that the analysis of planar structures is more straightforward than the analysis of non-planar boundaries, where the effects of topology and motion become interwoven in the data, and we argue here that it becomes necessary to customise the analysis for non-planar events to the type of structure at hand. One issue central to the discontinuity analyser, for instance, is the calculation of normal vectors to the structure. In the case of planar and ‘thin’ non-planar structures, the method of normal determination is well-defined, although subject to uncertainties arising from unwanted signatures. In the case of ‘thick’, non-planar structures, however, the method of determination becomes particularly sensitive to the type of physical sampling that is present. It is the purpose of this article to firstly review the discontinuity analyser technique and secondly, to discuss the analysis of the normals to thick non-planar structures detected in magnetometer data.  相似文献   

The application of a shift theorem analysis technique to multipoint measurements     

M. E. Dieckmann  S. C. Chapman 《Annales Geophysicae》1999,17(3):321-327

A Fourier domain technique has been proposed previously which, in principle, quantifies the extent to which multipoint in-situ measurements can identify whether or not an observed structure is time stationary in its rest frame. Once a structure, sampled for example by four spacecraft, is shown to be quasi-stationary in its rest frame, the structure’s velocity vector can be determined with respect to the sampling spacecraft. We investigate the properties of this technique, which we will refer to as a stationarity test, by applying it to two point measurements of a simulated boundary layer. The boundary layer was evolved using a PIC (particle in cell) electromagnetic code. Initial and boundary conditions were chosen such, that two cases could be considered, i.e. a spacecraft pair moving through (1) a time stationary boundary structure and (2) a boundary structure which is evolving (expanding) in time. The code also introduces noise in the simulated data time series which is uncorrelated between the two spacecraft. We demonstrate that, provided that the time series is Hanning windowed, the test is effective in determining the relative velocity between the boundary layer and spacecraft and in determining the range of frequencies over which the data can be treated as time stationary or time evolving. This work presents a first step towards understanding the effectiveness of this technique, as required in order for it to be applied to multispacecraft data.  相似文献   

中国的空间环境研究与空间环境预报   总被引：1，自引：0，他引：1  

叶宗海  都亨  龚建村 《地球物理学进展》1999,(Z1)

本文主要介绍我国在空间环境研究与空间环境预报方面的进展, 包括空间环境资料和模式的收集、研究与应用; 空间环境与航天器的相互作用及其对航天器的影响; 以及空间环境预报方法和预报技术等的进展  相似文献   

一种基于天基的瞬变电磁高分辨探测小尺度太空碎片的方法          下载免费PDF全文

李文翰  李贺  鲁凯亮  崔洪亮 《地球物理学报》2018,61(12):5066-5076

目前,太空碎片的天基探测方法一般是激光雷达法.由于激光雷达的辐射频率一般为可见光或红外波段,在分辨厘米量级的太空碎片时具有一定的优势.但激光雷达在探测时也面临一些客观问题：即（1）难以捕捉快速移动的太空碎片;（2）对目标体穿透能力低;（3）外层空间的强干扰环境对激光雷达的不良影响等.这些问题在一定程度上限制了激光雷达在太空碎片探测方面的应用.本文针对太空碎片体积小、预警距离远和强干扰环境等特点,提出使用高性能瞬变电磁辐射源对远距离、小尺度的太空碎片进行探测.通过三维矢量有限元方法,分析了利用高性能瞬变电磁辐射源的优点,对比不同瞬变电磁辐射源的幅频特性,从发射机理上证明高性能瞬变电磁辐射源在辐射能力与频率带宽方面都优于传统瞬变电磁辐射源.并通过调整脉冲宽度,得到最适合探测本文太空碎片模型的辐射脉冲.最后通过电场分布图和多测道图对太空碎片的明显电场分异结果,证实了高性能瞬变电磁辐射源在探测远距离、小尺度太空碎片方面的有效性.  相似文献   

Characteristics of eigen-system for flexural gravity wave problems     

S. Mandal  A. Chakrabarti 《地球物理与天体物理流体动力学》2017,111(4):249-281

For a class of boundary value problems associated with flexural gravity waves, characteristics of the eigen-system are analysed which are used to study the convergence of the expansion formulae in both cases of single and two layer fluids in water of finite and infinite depths. Using Green’s function technique, the spectral representations of the vertical eigenfunctions are obtained which are used along with the orthogonal mode-coupling relations to prove the convergence of the expansion formulae. Using the expansion formulae flexural gravity wave scattering due to multiple articulations in the presence of compression are investigated. The problem is studied in both the cases of single-layer and two-layer fluids in finite water depth. Effects of compressive force, stiffness of the connectors, length of the elastic plates and water depth, position of interface on wave scattering by articulated plates are studied by analysing the reflection and transmission coefficients. This procedure of proving the convergence of expansion formulae is independent of water depth. The concept and methodology for dealing with wave-structure interaction problems discussed here can be generalised to deal with problems of similar nature arising in the broad area of mathematical physics and engineering.  相似文献   

地磁活动对气候要素影响的研究进展   总被引：2，自引：0，他引：2       下载免费PDF全文

金巍  张效信  宋燕  何飞  李丽光  于超  吕景天  肖子牛 《地球物理学报》2017,60(4):1276-1283

地磁活动是太阳爆发现象引起地球近地空间磁场扰动的重要空间天气过程之一.地球磁场的变化具有多种时间尺度,其中从数十年到数世纪的长时间地磁场变化主要是由地核磁场引起的,而从数秒到数年的短时间地磁变化与太阳活动有关.近年来,越来越多的统计研究表明,地磁活动与太阳活动和地球气候变化之间存在着显著的相关性.地球磁场和地球大气系统的耦合现象驱动着人们探索地磁活动对地球天气和气候系统影响的研究.本文的目的就是综述国内外地磁变化对气候影响的研究进展,介绍我们最新的研究成果,探索地磁活动对气候要素的影响特征和可能机理过程,为深入研究地磁活动对地球天气和气候的影响提供基础和依据,以期对地磁活动和气候要素关系有进一步的认识.  相似文献   

基于改进型BP网络的空间电场分类研究     

张伟  李忠  刘海军  安建琴  宋奕瑶 《地震》2017,37(4):173-180

空间电场信号异常识别是研究地震引起电离层扰动的重要内容。 将空间超低频电场电位数据看作随机数字信号, 以均值、 均方差、 偏度和峰度等四个指标进行描述, 采用“5·12”汶川大地震前空间超低频电场电位数据作为原始数据, 训练改进型BP神经网络, 建立了空间电场信号异常分类识别模型, 并以SOM神经网络进行验证。 计算结果显示, 空间超低频电场电位异常信号主要集中在5°~25°N, 88°~120°E之间的区域, 汶川大地震影响范围内的电离层扰动, 可能是汶川地震发生前引起的, 这与前人研究一致, 说明采用改进型BP神经网络异常分类识别模型研究地震引起的电离层扰动是可行的。  相似文献