Comparisons: colonial or cosmopolitan?     

Jennifer Robinson 《Singapore journal of tropical geography》2011,32(2):125-140

Editors' Note: The following is the ninth in the Singapore Journal of Tropical Geography Lecture Series. It is based on the plenary presentation of 3 September at the Annual Conference of the Royal Geography Society (with the Institute of British Geographers) held in London in 2010. In the search for a more international approach to theorizing cities, comparative methods hold considerable promise, although one concern might be that in their theoretical ambitions they foster a universalising approach rather than one appreciative of diverse and sometimes divergent urban experiences. The potentially universalizing ambitions of comparative methods lead some postcolonial theorists to question the extent to which comparativism carries the marks of colonial histories. Critics argue that some aspects of formal comparative methods can be traced to ambitious and geographically encompassing intellectual projects from the colonial era, when the interest and capacity to bring different parts of the world together within the same intellectual frame advanced significantly. This paper explores the complexities of these colonial lineages of comparative research with a view to assessing their implications for postcolonial comparative urbanism. It concludes by assessing the potential for more modest comparative experiments in a postcolonial vein through attending to the diverse vernacular cosmopolitanisms of cities. Following the spatialities of cities themselves has the potential to offer non‐universalizing but variously internationalizing theoretical engagements with different places.  相似文献   

Interhemispheric comparison of mesospheric ice layers from the LIMA model     

F.-J. Lübken  U. Berger 《Journal of Atmospheric and Solar》2007,69(17-18):2292

The new LIMA/ice model is used to study interhemispheric temperature differences at the summer upper mesosphere and their impact on the morphology of ice particle related phenomena such as noctilucent clouds (NLC), polar mesosphere clouds (PMC), and polar mesosphere summer echoes (PMSE). LIMA/ice nicely reproduces the mean characteristics of observed ice layers, for example their variation with season, altitude, and latitude. The southern hemisphere (SH) is slightly warmer compared to the NH but the difference is less than 3 K at NLC/PMC/PMSE altitudes and poleward of 70N/S. This is consistent with in situ temperature measurements by falling spheres performed at 69N and 68S. Earth's eccentricity leads to a SH mesosphere being warmer compared to the NH by up to approximately 85 km and fairly independent of latitude. In general, NH/SH temperature differences in LIMA increase with decreasing latitude and reach at 50. The latitudinal variation of NH/SH temperature differences is presumably caused by dynamical forcing and explains why PMSE are basically absent at midlatitudes in the SH whereas they are still rather common at similar colatitudes in the NH. The occurrence frequency and brightness of NLC and PMC are larger in the NH but the differences decrease with increasing latitude. Summer conditions in the SH terminate earlier compared to NH, leading to an earlier weakening and end of the ice layer season. The NLC altitude in the SH is slightly higher by 0.6–1 km, whereas the NLC altitudes itself depend on season in both hemispheres. Compared to other models LIMA/ice shows smaller interhemispheric temperature differences but still generates the observed NH/SH differences in ice layer characteristics. This emphasizes the importance of temperature controlling the existence and morphology of ice particles. Interhemispheric differences in NLC/PMC/PMSE characteristics deduced from LIMA/ice basically agree with observations from lidars, satellites, and radars.  相似文献   

太平洋副热带高压及南亚高压在NCEP/NCAR和ECMWF再分析资料中的对比研究   总被引：3，自引：0，他引：3  

陈雯  智协飞 《热带气象学报》2008,24(2):189-194

利用NCEP/NCAR和ECMWF 1961～2000年北半球逐月平均的500 hPa和100 hPa高度场再分析资料对影响我国天气、气候的重要系统--北半球西太平洋副热带高压以及南亚高压做了对比研究,发现两者在不同的再分析资料中虽然具有一定的相似性,但也存在着明显的区别.在1980年以前两者存在较大差异.NCEP/NCAR再分析资料分析出的副高明显偏弱,而其所反映的副高的变化在幅度和强度上均大于ECMWF再分析资料的结果.进一步分析发现,NCEP/NCAR再分析资料所得出的副高的年代际变化可能是不真实的.在1969年、1979～1991年间,NCEP/NCAR再分析资料中的南亚高压中心强度明显比ECMWF的强,特别是1992～1995年间,NCEP/NCAR再分析资料中的南亚高压中心强度更强且中心范围更大.此外,NCEP/NCAR再分析资料所反映的南亚高压的变化在幅度和强度上也都大于ECMWF再分析资料的结果.  相似文献   

The nighttime winter anomaly (NWA) effect in the american sector as a consequence of interhemispheric ionospheric coupling     

M. Förster  N. Jakowski 《Pure and Applied Geophysics》1988,127(2-3):447-471

The nighttime winter anomaly (NWA) effect was observed during solar minimum conditions at the American sector by means of ionospheric electron content and vertical sounding measurements in Havana (Cuba). An effective interhemispheric transport of plasma is suggested to explain enhanced northern nighttime ionization during winter solstice. To elucidate this effect, an adequate physicalnumerical model of the coupled system ionosphere-plasmasphere is presented and applied to a corotating tube of plasma at L=1.5 in the American sector. The NWA can be explained by theoretically derived higher tube content during the December solstice and accordingly by more intense nighttime fluxes from the plasmasphere, compared to the June solstice.  相似文献   

中国大陆及邻近海域航磁——大地构造解释及分区   总被引：1，自引：0，他引：1       下载免费PDF全文

曲国胜  王绳祖 《地质科学》1997,32(4):455-464

地表地质研究及中国航磁异常表明中国航磁大地构造具以下3种类型:沉积盖层区(深浅层结果反映正常构造层序)、构造盖层区(地表及浅层为外来推覆山系,与深部构成异常构造层序)和航磁异常地质历史时期各期沉积-构造事件叠加的记录。按郯庐断裂两侧华北、扬子地台区航磁-构造异常带的可比性,郯庐断裂总位移可达500km.中国大陆及邻近海域航磁-大地构造分区为:Ⅰ光蒙区、Ⅱ华北区、Ⅲ哈萨克斯坦区、Ⅳ塔里木区、Ⅴ青藏高原区、Ⅵ扬子区、Ⅶ华夏——台湾区。  相似文献   

A comparison of multiscale methods for elliptic problems in porous media flow     

Vegard Kippe  Jørg E. Aarnes  Knut-Andreas Lie 《Computational Geosciences》2008,12(3):377-398

We review and perform comparison studies for three recent multiscale methods for solving elliptic problems in porous media flow; the multiscale mixed finite-element method, the numerical subgrid upscaling method, and the multiscale finite-volume method. These methods are based on a hierarchical strategy, where the global flow equations are solved on a coarsened mesh only. However, for each method, the discrete formulation of the partial differential equations on the coarse mesh is designed in a particular fashion to account for the impact of heterogeneous subgrid structures of the porous medium. The three multiscale methods produce solutions that are mass conservative on the underlying fine mesh. The methods may therefore be viewed as efficient, approximate fine-scale solvers, i.e., as an inexpensive alternative to solving the elliptic problem on the fine mesh. In addition, the methods may be utilized as an alternative to upscaling, as they generate mass-conservative solutions on the coarse mesh. We therefore choose to also compare the multiscale methods with a state-of-the-art upscaling method – the adaptive local–global upscaling method, which may be viewed as a multiscale method when coupled with a mass-conservative downscaling procedure. We investigate the properties of all four methods through a series of numerical experiments designed to reveal differences with regard to accuracy and robustness. The numerical experiments reveal particular problems with some of the methods, and these will be discussed in detail along with possible solutions. Next, we comment on implementational aspects and perform a simple analysis and comparison of the computational costs associated with each of the methods. Finally, we apply the three multiscale methods to a dynamic two-phase flow case and demonstrate that high efficiency and accurate results can be obtained when the subgrid computations are made part of a preprocessing step and not updated, or updated infrequently, throughout the simulation. The research is funded by the Research Council of Norway under grant nos. 152732 and 158908.  相似文献   

Homo erectus pekinensis''''s age and environment——with discussion on the relationship among Homo erectus from Beijing,Nanjing and Chenjiawo     

LIU Jinling & WANG WeimingNanjing Institute of Geology  Palaeontology  Chinese Academy of Sciences  Nanjing  China Correspondence should be addressed to Liu Jinling  Wang Weiming 《中国科学D辑(英文版)》2004,47(1)

This paper inspects the relationship between Homo erectus from Beijing, Nanjing and Chenjiawo on the viewpoint of environmental variations. Pieces of evidence show that Nanjing and Chenjiawo Homo erectus lived in glacial age at the Marine Oxygen Isotope Stage (MIS) 16, while Homo erectus pekinensis in major interglacial age at MISs 15-13. It is also recovered that the cave deposits in Tangshan, Nanjing, and Zhoukoudian, Beijing, as well as the deposits at the Homo erectus site in Chenjiawo, have undergone some similar development process. All of them originated from early-middle Middle Pleistocene, and have gone through the test of the major glacial age at MIS 16 and the major interglacial period at the paleosol stage S5. At the same time, they were also closely connected with some environment events, such as the uplift of the Qinghai-Xizang Plateau, the formation of glaciations and the loess accumulations.  相似文献   

Diet studies of seabirds: a review and recommendations   总被引：8，自引：0，他引：8  

Barrett  Robert T.; Camphuysen  Kees ; Anker-Nilssen  Tycho; Chardine  John W.; Furness  Robert W.; Garthe  Stefan; Huppop  Ommo; Leopold  Mardik F.; Montevecchi  William A.; Veit  Richard R. 《ICES Journal of Marine Science》2007,64(9):1675-1691

  相似文献   

不同地磁活动水平下电离层H⁺上行的半球对比研究   总被引：3，自引：1，他引：2       下载免费PDF全文

赵凯  蒋勇  门可佩  黄林峰  傅帅 《地球物理学报》2014,57(11):3715-3728

使用FAST/TEAMS仪器在第23太阳活动周下降相的数据,从地磁活动水平的角度,分别分析在磁静日(Kp≤2⁺)和磁扰日(Kp≥3⁺)时南(SH)、北半球(NH)高纬(>50°)电离层H⁺的上行强度,计算其上行率和净上行积分能通量,以期得到H⁺上行的长期水平并分析地磁扰动期间南、北半球离子上行强度的异同.研究结果表明,磁扰期间上行强度显著加强,平静期南、北半球的平均上行率分别是~15%和~20%,而磁扰期的平均上行率分别增强了1.45倍和1.04倍,磁扰期间南半球上行强度的增长更显著;平静期南半球的上行强度小于北半球,但磁扰期两个半球的上行强度相当;磁午夜和黎明区间受地磁扰动的影响最显著,其磁扰期与平静期上行率的比值(S/Q)最大,同时南半球在各个地方时区间的S/Q值均大于北半球;另外,我们发现磁扰期间的上行率在极光椭圆带下边界附近增幅最明显,而积分通量在上边界附近增加显著.上行源区以平静期的源区为中心从日侧极尖区扩展到磁午夜、且向低磁纬延伸,同时,极尖区上行源区在磁扰期有向晨侧偏移的趋势.  相似文献   

考虑试验阻尼效应的一种土体动力双型抛物线本构模型   总被引：3，自引：3，他引：0  

陈学良  金星  陶夏新  韦永祥 《岩土力学》2008,29(8):2102-2110

针对土动力试验中土体反向卸载（或加载）曲线形状有时表现为先变化平缓后变化剧烈这一特征,基于土体实验结果的 和 曲线,建立了不规则荷载作用下可调的双型抛物线形式的本构曲线规则,阐述了A型和B型抛物线的函数表达式及实现过程。采用9种方法对试验阻尼比的模拟对比,表明所建立的加卸载准则尤其能准确拟合试验阻尼值,是对广义Masing准则的一种简化及实用化。由于调制因子 的可变性,它具有更强地模拟试验本构曲线形状的能力。针对台湾Lotung DHB钻井台阵试验场地,以等效线性化方法SHAKE91、LSSRLI-1,时域非线性方法DESRA-2、Pyke方法、非Masing准则模型1、“隐式应力阻尼等效”模型、“阻尼比退化系数”模型和非Masing准则模型2以及双型抛物线本构模型等9种方法（或模型）分别进行了非线性地震反应分析,并将结果与强震观测记录进行比较,结果表明,双型抛物线本构模型计算的复合加速度地震动的峰值大小、波形大小相对关系及后续波形,与实际地震记录较相一致,说明了模型的合理性以及实际工程应用的可行性。  相似文献