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41.
西藏地区旱涝等级划分及时空分布特征 总被引:7,自引:3,他引:7
利用西藏22个站点1969-1998年逐日降水资料,采用d指数旱涝等级方法。按夏季(5-9月),初夏(5-6月),盛夏(7-8月)时段进行了旱涝等级划分。采用EOF分析方法对全区22个站点旱涝等级展开分解,得出西藏地区的旱涝时空分布特征,主要类型和周期,而且对西藏地区夏季(5-9月)的旱涝做了预测。 相似文献
42.
Mass size distribution of the crustal elements (Al, Ca, Fe, Mg, Si, Ti), anthropogenic elements (Zn, Mn, Cr, Cu, K, P, Pb) and sea elements (Na, Cl) were obtained from measurements carried out with an inertial cascade impactor in Sfax. A fitting procedure by data inversion was applied to those data. This procedure yields accurate size distributions of aerosols in the diameter range 0.1–25 μm in two different sites. In a coastal industrial site, the mass distribution of the aerosol showed a bimodal structure; and in urban area, the lower particle mode cannot be observed. The elemental dry deposition flux was calculated as a function of particle size. The element flux size distribution increased rapidly with particle size. The modelling results indicate that the majority of the crustal and anthropogenic elements flux (>90%) was due to particles larger than 3 μm in diameter. 相似文献
43.
The political turning point in the former GDR and the transformation processes that have been observed since then have significantly
affected economic and social structures in the new Federal States. Gender roles, however, were subjected to even more dramatic
changes. Whilst many women experienced the employment policies of the GDR era as beneficial, social researchers often designate
them as the losers of unification nowadays. This is largely because the abundance of State support measures for employed women
and mothers has been drastically reduced and women as a group have been hit hardest by the crisis on the East German labour
market. Using two cases (Mecklenburg-Westpommerania and Thuringia), this paper aims to illustrate the impact of the transformation
process on the everyday (working) lives of women. We are particularly concerned with a comparative analysis of how women experience
and deal with regional disparities in East Germany.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
44.
This paper presents an improved generalisation of cation distribution determination based on an accurate fit of all crystal-chemical
parameters. Cations are assigned to the tetrahedral and octahedral sites of the structure according to their scattering power
and a set of bond distances optimised for spinel structure. A database of 295 spinels was prepared from the literature and
unpublished data. Selected compositions include the following cations: Mg2+, Al3+, Si4+, Ti4+, V3+, Cr3+, Mn2+, Mn3+, Fe2+, Fe3+, Co2+, Ni2+, Zn2+ and vacancies. Bond distance optimisation reveals a definite lengthening in tetrahedral distance when large amounts of Fe3+ or Ni2+ are present in the octahedral site. This means that these cations modify the octahedral angle and hence the shared octahedral
edge, causing an increase in the tetrahedral distance with respect to the size of the cations entering it. Some applications
to published data are discussed, showing the capacity and limitations of the method for calculating cation distribution, and
for identifying inconsistencies and inaccuracies in experimental data.
Received: 19 February 2001 / Accepted: 1 June 2001 相似文献
45.
新疆宏观生态的空间分异与变化 总被引:11,自引:12,他引:11
根据新疆环境和生态特点,将新疆划分为14个二级生态区进行了研究。结果表明,新疆荒漠与非荒漠生态景观面积大致相当,但空间分异较大。新疆北部荒漠景观占全区域的约1/3,非荒漠景观占2/3,宏观生态相对稳定;新疆东部荒漠景观占全区域的2/3以上,宏观生态十分严峻;新疆南部荒漠景观占全区域的1/2,宏观生态稳定性差。沙漠、绿洲、水体三种主要景观类型中,北疆阿尔泰山南坡、伊犁盆地及南疆叶尔羌-喀什河三角洲地区沙漠化呈降低趋势;天山北坡各段及准噶尔盆地西部,20世纪90年代以来沙漠化明显减缓;新疆东部及南部其余各地区沙漠化均呈现增强趋势。新疆水体景观的变化表现为天然和人工水体面积的消长。近50年来,新疆修建的水库和坑塘等人工水体总面积与同期天然水体缩小的面积基本相当,表明新疆水体景观再近50年来的变化主要体现为水体的空间位移。绿洲景观的变化表明,北疆地区天然绿洲与人工绿洲面积的比例已经从50年代的5:1以上下降到约1:1,南疆由6:1以上下降到3:1左右。天然绿洲的减少是绿洲生态局部劣变的标志。研究还表明,新疆宏观生态的空间分异主要受自然因素的影响,其中,区域降水量的影响最为重要。 相似文献
46.
青藏高原土壤水热分布特征及冻融过程在季节转换中的作用 总被引:21,自引:0,他引:21
利用GAME-Tibet期间所取得的高分辩率土壤温度和含水量资料,对青藏高原(主要是藏北高原)土壤水热分布特征及冻融过程在季节转换中的作用进行了分析。指出藏北高原4cm学深处土壤在10月份开始冻结,次年4-5月份开始消融,冻结持续时间长达5-7个月。冻结过程有利于土壤维持其水分,因此,在刚刚开始消融时土壤含水量仍然很高。从而为夏季风爆发前土壤通过蒸发向大气提供水分打下了基础。指出土壤冻融过程可能在高原季节转换中起着重要作用。 相似文献
47.
On the spatial relationship between landslides and causative factors on Lantau Island, Hong Kong 总被引:8,自引:0,他引:8
This paper presents a statistical approach to study the spatial relationship between landslides and their causative factors at the regional level. The approach is based on digital databases, and incorporates such methods as statistics, spatial pattern analysis, and interactive mapping. Firstly, the authors propose an object-oriented conceptual model for describing a landslide event, and a combined database of landslides and environmental factors is constructed by integrating the various databases within such a conceptual framework. The statistical histogram, spatial overlay, and dynamic mapping methods are linked together to interactively evaluate the spatial pattern of the relationship between landslides and their causative factors. A case study of an extreme event in 1993 on Lantau Island indicates that rainfall intensity and the migration of the center of the rainstorm greatly influence the occurrence of landslides on Lantau Island. A regional difference in the relationship between landslides and topography is identified. Most of the landslides in the middle and western parts of the island occurred on slopes with slope angles of 25–35°, while in the eastern part, the corresponding range is 30–35°. Overlaying landslide data with land cover reveals that a large number of landslides occurred in the bareland and shrub-covered area, and in the transition zones between different vegetation types. The proposed approach can be used not only to analyze the general characteristics of such a relationship, but also to depict its spatial distribution and variation, thereby providing a sound basis for regional landslide prediction. 相似文献
48.
49.
基于网格的空间信息模型与服务技术研究 总被引:12,自引:0,他引:12
空间信息基础设施是实现数字城市的核心与基础,现有的万维网已经不能满足空间信息访问与处理的需要。该文对以空间信息为核心和基础的数据网格——空间信息网格的基础理论及网格中的空间信息模型与服务技术:进行研究。提出了空间信息网格的若干关键技术及网格中的空间信息模型的特点与要求,并对空间信息网格服务进行了初步的探讨。 相似文献
50.
京、津、冀区域群发性强沙尘暴分析 总被引:1,自引:2,他引:1
利用1954—2002年82个站的气象观测资料,探讨京、津、冀区域群发性强沙尘暴的认定标准,构建较完整的群发性强沙尘暴序列,并分析该地区群发性强沙尘暴的时空分布特征和气候变化趋势。近50a京、津、冀区域共出现了39例群发性强沙尘暴,河北省的冀西北高原区和石家庄、保定、衡水、沧州四市交接处饶阳一带是京、津、冀区域强沙尘暴天气的多发区。多发季节为3—5月,占全年总数的76.9%,其中4月份最多,占全年总数的51.3%。群发性强沙尘暴年代际变化呈现总体减少趋势,其发生次数、覆盖面积均是以20世纪90年代为最低值. 相似文献