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91.
以史料为依据,叙述了1925年3月16日云南大理7级地震后,民众自发组织的筹集赈灾款项、物资,救助赈济灾民的情况。  相似文献   
92.
据艾肯达坂风雪流形成条件,提出了贴地气层分离是公路吹雪堆积的机理,通过对密闭式下导风能量转换和流场结构的剖析,创造了透风式下导风防雪工程。其实施后,改变了公路因冬半年严重雪阻而不能通车的状况,经济效益和社会效益俱佳;  相似文献   
93.
Field measurements were carried out to calculate the threshold friction velocity for snow saltation, and mass fluxes during snow drift. The wind was measured in three components by an ultrasonic anemometer, and the mass fluxes were determined using an optical sensor (snow particle counter), acoustic sensors (Flowcapt) and mechanical traps. The threshold friction velocity was found to be correlated to the grain size (R2=0.75). The mass flux measurements were compared with numerical simulations of snow drift, and it was demonstrated that the maximum snow transport takes place at shear stress values of roughly two times the average shear stress over 20 min. By implementing a probability distribution for the shear stress the mass flux was simulated with only the mean measured value of the shear stress as input. This procedure enables the future use of the numerical model for operational applications.  相似文献   
94.
Review of behaviour of oil in freezing environments   总被引:2,自引:0,他引:2  
The current knowledge of the physical fate and behaviour of crude oil and petroleum products spilled in Arctic situations is reviewed. The fate and final deposition of oil in marine conditions is presented as based on the extant literature.

Spreading models were evaluated for oil on ice, under ice, in snow, in brash ice, and between blocks of ice. Models of oil transport under sheet and broken ice were considered, both for sea and river conditions. The ability of ice sheets to trap oil is discussed in relation to oil storage capacity. The effects of oil on a growing ice sheet were examined, both in terms of ice formation and the thermal effects of oil inclusions in ice. The migration of oil through ice was reviewed, focussing primarily on the movement through brine channels. The effects of oil on the surface of ice were considered, with emphasis on the effects of surface pools on ice melt. Similar consideration was given to the effects of oil on snow on the surface of ice.

The few quantitative studies of oil in open and dynamic ice conditions are reviewed. Observations of intentional small-scale spills in leads and ice fields are reviewed and compared with observations from real spills. The conditions under which “oil pumping” from leads occurs were quantified. The most common ultimate fate of oil in an ice field is to be released onto the water surface.  相似文献   

95.
This article describes a methodology to localise areas with high potential towards natural snowpack instability under particular meteorological conditions, at the scale of an Alpine valley. Localisation is based on statistically relating known release areas of past avalanche events to maps of: (1) slope inclination, (2) slope orientation (aspect), (3) elevation, (4) distance from crest lines, (5) terrain roughness and (6) concavities/convexities. The maps have been built using two different GIS softwares while the statistical analyses have been performed with a specific software handling also Fuzzy Set theory algorithms. The results of the statistical analyses have been verified on test release—areas which have not been used as input data for the statistical analyses. Verification allowed to quantify how reliably the susceptibility values were calculated, to compare the values obtained using different combinations of terrain features and to finally decide on the most efficient combination. The susceptibility maps were calculated and verified for three different meteorological scenarios (given by three classes of snow depth). Verification has shown that the accuracy of the susceptibility maps was between 67% and 82%. The three susceptibility maps show a remarkable difference in the spatial pattern of the highest susceptibility pixels suggesting that for different meteorological scenarios different classes of terrain features need to be considered.The possibility to make combinations of terrain features and to assess and verify their statistical relationship with release areas of past avalanche events is the major original step made by STARTER. Linking those release areas to meteorological scenarios is an attempt to include in the analysis the combined influence of terrain features and meteorological conditions towards snowpack instability.  相似文献   
96.
居住在山区的人们主要活动空间是斜坡。人们对斜坡利用的有效与否是由人们对斜坡认识充分与否决定的。倘若人们对斜坡认识不足,就可能遭受因斜坡失稳所带来的损失。因此,对这类斜坡的稳定状况的正确认识很有必要。以清江流域典型滑坡——瓦屋场滑坡的复活为例,通过介绍清江流域瓦屋场滑坡人类活动与该滑坡产生的变形情况,根据滑坡体工程地质条件,针对变形原因用萨尔玛法及不平衡推力法进行了稳定分析,同时对复活机制进行分析。在此基础上按照顺应性准则和协调性原则,提出相应的工程治理措施。鉴于该滑坡为该地区的典型滑坡,从灾害学角度说明人类在利用坡体前,对坡体稳定状况认识的重要性并给出人们合理利用该地区自然边坡的建议。  相似文献   
97.
Are human able to foresee the future? For thou-sands of years close attention has been paid to this issue. At the present day, in order to survive from competition and to predominate over the nature, hu-man抯 desire of forecasting things has become more and more intense. Compared to conquering space, more people yearn for being able to control the time. From ancient to the present, mankind always dream of contacting the past, governing the present and tran-scending the future. Recent years in…  相似文献   
98.
用EOS/MODIS资料反演积雪深度参量   总被引:4,自引:1,他引:4  
利用EOS/MODIS可见光、近红外及短红外多通道资料以及新疆地区积雪深度气象台站实测资料等,在考虑积雪性质包括积雪粒子相态、积雪年龄等的差异以及积雪区的下垫面条件包括地表粗糙度、土地覆盖类型等的不同的情况下进行积雪分类,在此基础上,建立EOS/MODIS积雪深度反演模型,实现深度在30 cm以内的积雪深度反演的主要原理、思路及方法,并对模型的反演结果进行了验证。结果表明,利用该模型对30 cm以内的积雪进行深度反演计算,其精度能达到80%以上。  相似文献   
99.
本文利用MM5模式,采用数值模拟方法,诊断分析了北京“12.7”强降雪的发生机理,发现500hPa湿位涡与降雪区有较好的相关性  相似文献   
100.
灾害损失率计算是农作物保险费率确定的基础。确定为农作物保险费率服务的灾害损失率需要较强的稳定性,为此我们采用多年平均损失率指标,并利用多年平均损失率进行分区。它既能反映出灾害损失率宏观分布规律,又能刻划出灾害损失率较微观的空间分布差异,使区域费率确定更加准确、合理。由于研究区域灾情信息的不完全性,依据大系统理论的递阶控制原理,我们设计了多年平均损失率的双层控制体系,使区域费率的厘定实现了稳定性和灵活性的统一。  相似文献   
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