From brain drain to brain gain: reverse migration to Bangalore and Hyderabad, India’s globalizing high tech cities   总被引：1，自引：0，他引：1  

Elizabeth Chacko 《GeoJournal》2007,68(2-3):131-140

This paper assesses the mutual impact of returning Indian-origin skilled workers on the cities of Bangalore (Bengaluru) and Hyderabad, which have emerged as India’s leading “tech cities”. During the 1970s and 1980s, there was concern that India was losing its educated workforce to the West, particularly to the United States through a phenomenon known as “brain drain”. More recently, there is evidence that reverse brain drain is occurring, as U.S.-trained Indian professionals are returning to their home country in increasing numbers to take advantage of new growth and employment opportunities. The effects of this skilled, transnationally active labor force on various sectors of the economy, on the social and physical infrastructure of Bangalore and Hyderabad and in forging and solidifying transnational linkages between India and the United States are explored in this paper. This study also investigates the reasons why successful US professionals of Asian-Indian origin are returning to their home country via a series of personal interviews. The paper offers Bangalore and Hyderabad as “worldwide leading cities” with a niche status in the global Information Technology (IT) sector.  相似文献   

Alternatives to tap water: a case study of the Gaza Strip, Palestine     

H. A. El-Nakhal 《Environmental Geology》2004,46(6-7):851-856

Gaza Strip is a highly populated, small area in which the groundwater is the main water source. During the last few decades, groundwater quality has deteriorated to a limit that the municipal tap water became brackish and unsuitable for human consumption in most parts of the strip. To overcome this serious situation, several attempts were made to replace the tap water or to improve its quality by water desalination applying the reverse osmosis (RO) technology, bottled water, importing water, and storm water harvesting. Water desalination, which is widely applied in the strip, has environmental and health risks. Brine water resulting from the RO systems has adverse environmental effects, whereas the produced fresh water with very low chemical concentrations may have harmful effects on human health. Therefore, introducing international water quality standards to delineate the harmless minimum limits is necessary. Storm water harvesting can provide a partial solution for the water problems in the strip.  相似文献   

清水气举反循环钻探工艺在深水井施工中的应用     

刘清晓  陈金荣等 《城市地质》2001,13(3):37-39

清水气举反循环钻探工艺是解决含水层裂隙在钻探过程中被堵塞问题的一种有效方法，尤其是对层压较低、裂隙稀少的含少层段，含水裂隙一旦发生堵塞则不易清洗干净，严重影响水井出水量，甚至造成水井报废。该方法的引入，对提高北京地热井水量有积极作用。  相似文献   

近百年来南京降水变化的趋势和特征     

范金松  陈开喜 《气象科学》1997,17(3):237-245

本文对近百年来（１９０５－１９９４年）南京实测降水量资料序列和降水的其他统计特征作了详尽的诊断分析，得到如下十分有益的气候变化信息。  相似文献   

P-f图反演电离层参数和散射源距离的一种方法   总被引：1，自引：0，他引：1       下载免费PDF全文

李乐伟  焦培南 《地球物理学报》1991,34(1):115-119

高频返回散射探测一般可得最小时延与频率关系的P-f电离图。而使用高增益大型天线阵列的高频天波雷达系统可以获得高分辨率的返回散射P-f图,它能显示离散散射源（独立的海岛、城市、山峰）的斜投射回波描迹,如图1a所示;对一般返回散射仪与同步应答机联测所得P-f图有同样的描迹,如图2所示。高频返回散射电离图反演问题至  相似文献   

新疆吉木萨尔大龙口背斜核部露头构造样式研究     

路成  李晓剑  路顺行 《江苏地质》2015,39(2):211-217

通过对新疆吉木萨尔大龙口背斜核部露头剖面的野外观察、实地测量和特征描述,分析研究了其构造发育特征和演化模式。认为大龙口背斜核部露头的构造属于"褶皱相关断层"范畴,岩层能干性对构造变形具有重要影响,最为典型的是发育了"褶翼楔入组"、"类冲起"和"分离反向褶曲"3种特殊的构造样式。  相似文献   

基于保辛算法的声波叠前逆时偏移          下载免费PDF全文

冯兰兰  杨顶辉  周艳杰 《地球物理学报》2014,57(12):4157-4170

叠前逆时偏移是目前成像精度最高的地震偏移方法之一,其实现过程中的一个重要步骤是数值求解全波方程,所以快速有效求解全波方程的数值算法对逆时偏移至关重要. 四阶近似解析辛可分Runge-Kutta (NSPRK) 方法是近年发展的一种具有高效率、高精度的数值求解波动方程的保辛差分方法, 能在粗网格条件下有效压制数值频散, 从而提高计算效率, 节省计算机内存需求量. 本文利用四阶NSPRK方法构造的基本思想,发展了具有六阶空间精度的NSPRK方法,并对新的六阶NSPRK方法进行了详细的稳定性和数值频散分析,以及计算效率比较和波场模拟. 同时将该方法用于声波叠前逆时偏移中, 得到一种时间上保辛、空间具有六阶精度、低数值频散、可应用大步长进行波场延拓并能长时计算的叠前逆时偏移方法,对Sigsbee2B模型进行了偏移成像, 并和四阶NSPRK方法、传统的六阶差分方法、四阶Lax-Wendroff correction (LWC) 方法进行了对比. 数值结果表明, 基于六阶NSPRK方法的叠前逆时偏移能得到更好的成像结果, 是一种优于四阶NSPRK方法、传统的六阶差分方法、四阶LWC叠前逆时偏移的方法, 尤其是在粗网格情况下具有更明显的优越性.  相似文献   

Implementation aspects of attenuation compensation in reverse‐time migration          下载免费PDF全文

Tieyuan Zhu 《Geophysical Prospecting》2016,64(3):657-670

Attenuation compensation in reverse‐time migration has been shown to improve the resolution of the seismic image. In this paper, three essential aspects of implementing attenuation compensation in reverse‐time migration are studied: the physical justification of attenuation compensation, the choice of imaging condition, and the choice of a low‐pass filter. The physical illustration of attenuation compensation supports the mathematical implementation by reversing the sign of the absorption operator and leaving the sign of the dispersion operator unchanged in the decoupled viscoacoustic wave equation. Further theoretical analysis shows that attenuation compensation in reverse‐time migration using the two imaging conditions (cross‐correlation and source‐normalized cross‐correlation) is able to effectively mitigate attenuation effects. In numerical experiments using a simple‐layered model, the source‐normalized cross‐correlation imaging condition may be preferable based on the criteria of amplitude corrections. The amplitude and phase recovery to some degree depend on the choice of a low‐pass filter. In an application to a realistic Marmousi model with added Q, high‐resolution seismic images with correct amplitude and kinematic phase are obtained by compensating for both absorption and dispersion effects. Compensating for absorption only can amplify the image amplitude but with a shifted phase.  相似文献   

基于解析时间波场外推与波场分解的逆时偏移方法研究   总被引：1，自引：0，他引：1       下载免费PDF全文

胡江涛  王华忠 《地球物理学报》2015,58(8):2886-2895

双程波方程逆时深度偏移是复杂介质高精度成像的有效技术,但其结果中通常包含成像方法引起的噪音和假象,一般的滤波方法会破坏成像剖面上的振幅,其中的假象也会给后续地质解释带来困扰.将波场进行方向分解然后实现入射波与反射波的相关成像能够有效地消除这类成像噪音,并提高逆时偏移成像质量.波传播方向的分解通常在频率波数域实现,它会占用大量的存储和计算资源,不便于在沿时间外推的逆时深度偏移中应用.本文提出解析时间波场外推方法,可以在时间外推的每个时间片上实现波传播方向的显式分解,逆时深度偏移中利用分解后的炮检波场进行对应的相关运算,实现成像噪音和成像信号的分离.在模型和实际数据上的测试表明,相比于常规互相关逆时偏移成像结果,本文方法能够有效地消除低频成像噪音和特殊地质构造导致的成像假象.  相似文献   

CT在航空深弹结构分析和拆卸中的应用研究     

孙明太  梁跃旋  胡柱喜  徐建华 《CT理论与应用研究》2008,17(1):50-55

通过对逆向工程研究方法的分析,提出了利用工业CT断层扫描对航空深弹进行结构分析,精确测量其零部件位置、尺寸变化的方法。并据此绘制图纸、制定拆卸方案,从而保证了深弹拆卸和研究的安全性和可靠性。  相似文献