Concerning dispersion relations for the magnetotelluric impedance tensor   总被引：1，自引：0，他引：1  

E. Yee  K. V. Paulson 《Geophysical Journal International》1988,95(3):549-559

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建鲤与黄河鲤的RAPD分子标记及其杂交优势的遗传分析   总被引：3，自引：0，他引：3  

佟雪红  董在杰  缪为民  袁新华  王建新  岳春梅  林连升 《广东海洋大学学报》2007,27(1):1-6

利用RAPD技术对建鲤、黄河鲤及其杂交子代进行了遗传分析,筛选的33个引物共扩增出155条带,其中多态性片段为105条,片段S18-1600、S472-300具有种的特异性,可作为鉴别建鲤与黄河鲤的分子遗传标记。建鲤、黄河鲤及其正、反交子代群体内的遗传相似系数分别为0.8240、0.7921、0.7920、0.8569,黄河鲤与正交F1具有较高的遗传变异水平,反交F1变异最小。正交F1、反交F1与亲本(建鲤、黄河鲤)的遗传距离分别为0.2233、0.2436、0.1749、0.2026,说明子代均继承了较多的建鲤的遗传物质。分析了子代与亲本的RAPD标记类型以及各类型的条带数。应用PIT标记系统测定了子代的杂种优势并探讨了优势产生的遗传机理。  相似文献   

Variational Principles For Surface Wave Propagation On A Laterally Heterogeneous Earth-Iii. Potential Representation     

Jeroen Tromp  F. A. Dahlen 《Geophysical Journal International》1993,112(2):195-209

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地理案例推理及其应   总被引：17，自引：0，他引：17  

杜云艳  周成虎  邵全琴  苏奋振  史忠植  叶施仁 《地理学报》2002,57(2):151-158

由于案例推理接近于人类认识、解决问题最原始的思维方式，具有在无法获取机理模型、确定规则或统计模型时，采用简单的历史相似性实现问题的定量求解和预测的特点，成为当前人工智能中备受关注的领域。在讨论案例推理方法发展的基础上，探讨应用案例推理进行地学问题求解的具体方法。从地学数据分析的角度提出了地理案例推理，并结合地理案例的特点，具体讨论了地理案例的表达模式和推理模型，最后结合东海中心渔场预报的实际工作，给出这种方法的具体应用实例。  相似文献   

Multiple ruptures for Long Valley microearthquakes: a link to volcanic tremor?     

A. Stroujkova  P. Malin 《Journal of Volcanology and Geothermal Research》2001,106(1-2)

Despite several episodes of ground deformation and intense seismic activity starting in 1978, the Long Valley, California, volcanic area has not produced clearly recognized volcanic tremor. Instead, a variety of atypical microearthquakes have been recorded during these episodes, including events dominated by low-frequency (long-period) or mixed high and low-frequency (hybrid) signals. During a 1997 episode, a number of unusual microearthquakes occurred within a temporary 40-station seismic network surrounding the Casa Diablo area, allowing the events to be precisely located and analyzed as a function of azimuth, offset, and source characteristics. Eight prime examples lie within two, 7 km-deep clusters of seismicity separated by about 1 km, with four events in each cluster. Empirical Green's function deconvolution shows that these events are composed of two to three sub-events, the sub-events consisting of ordinary (single rupture, double-couple) microearthquakes. The delay times between the sub-events are constant within each cluster, equaling 0.092 s in one and 0.06 s in the other. Events from other clusters show similar delays. The signal interference produced by the closely spaced sub-events gives rise to modulated, delay-dependent source spectra. The regularity of the delays suggests that the sub-events are being triggered by a fixed length and/or time scale process, an example being the length/inflation rate of a magmatic or hydrothermal flow structure. With continued action of the triggering process, the sub-events could proliferate and evolve into observable volcanic tremors at Mammoth.  相似文献   

Rethinking the dumping grounds: questioning assumptions about movement into the relocation settlement of Bilanyoni     

Paula Meth 《Area》2001,33(3):228-241

Historical accounts of relocation settlements in South Africa have emphasized processes of dispossession in the creation of these settlements. This paper considers other related histories of movement into relocation settlements as evidence of seldom considered contradictory and ambiguous experiences around movement and attachment to place — hence encouraging a rethink of the laden term 'the dumping grounds'.  相似文献   

我国陆地均匀重力测量补点问题的研究   总被引：5，自引：3，他引：5  

孙凤华  孔维兵  李慧智  霍伯承 《武汉大学学报(信息科学版)》2001,26(4):349-353,373

推导了重力布点公式，应用全国重力点检验了原有代表误差系数的可靠性，估计了我国目前和将来5′×5′平均高的精度，阐述了陆地重力测量布点系统的建立方法和应用方法，给出了我国陆地重力点补测方案，应用它即可确定我国陆地每个5′×5′内应补测的重力点数及其分布。  相似文献   

Introductory Human Geography Textbook Representations of Africa     

Garth Andrew Myers 《The Professional geographer》2001,53(4):522-532

This article analyzes representations of Africa found in ten introductory human geography textbooks. Recent research in communications studies cites the common tendencies of the U.S. media to represent Africa in rhetorical tropes of disaster that are ahistorical and rife with geographical abstraction and misrepresentation. The main textbooks in geography tend to avoid ahistorical and geographical simplification, yet they often repeat stereotypes and misleading media imagery concerning Africa. A broad body of works by geographers in the last decade that offers critical scholarly analysis of both African crises and African everyday life is generally underrepresented in the discipline's introductory textbooks, although some encouraging exceptions do exist to that generalization. It is suggested that geographers need to critically re‐examine the ways in which African examples are utilized to teach fundamentals of human geography.  相似文献   

The discursive nature of environmental conflicts: the case of the Öresund link     

Hannah Dekker Linnros  & Per Olof Hallin 《Area》2002,33(4):391-403

This paper analyzes the environmental conflict concerning the construction of a permanent link between Malmo, Sweden and the Danish capital, Copenhagen. The conflict is approached as both a discursive and institutional struggle, in which representations of nature and the environment are used not only to legitimize, but also to question institutional policies and development plans. The analysis focuses primarily on three of the counter-discourses that have emerged in conflict with the hegemonic, institutional discourse, and also indicates how spatial representations have become important constituents of the discourses.  相似文献   

对应各类重力场边值的调和性扰动场源解     

李斐 《测绘学报》1996,25(1):73-78

从实际应用的需要出发，本文对现代物理大地测量学及地球物理学研究中日益关注的高和性扰动场源问题的求解模式进行了推演和分析。建立起在边界条件分别为扰动位、扰动重力、重力异常以及其中两类以上同时作为边界输入的情况下，对应的调和性扰动场源的球谐函数表达式及封闭解式。进而对调和性扰动场源在物理大地测量及地球物理中应用的有关问题进行了评注。  相似文献