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981.
运城市冬小麦晚霜冻预报服务系统   总被引:2,自引:0,他引:2  
春季霜冻在运城市出现的范围比较广泛,危害机遇为2a-3a一遇,重灾区多在汾河、涑水河两岸及平川地区的低凹地带,峨嵋岭南部及中条山的沿山坡岭地区较轻。运城市的晚霜冻主要影响小麦、苹果、蔬菜等,晚霜冻严重的年份可能造成小麦、苹果大幅减产,本文主要就运城市的春季霜冻对小麦的影响做一些探讨。  相似文献   
982.
热带气旋的螺旋度特性   总被引:18,自引:1,他引:18  
将螺旋度的概念引入热带气旋,对热带气旋螺旋度的结构特征及其在热带气旋发展过程中的演变过程进行了研究。结果表明,热带气旋这种具有较强螺旋性的天气系统,其发展过程也就是螺旋度增强的过程。螺旋度对热带气旋稳定过程的维持及其长久的生命期具有重要的作用。  相似文献   
983.
山东各区夏季降水的多步预测试验   总被引:8,自引:0,他引:8  
在对山东夏季降水进行分区的基础上,用相当分析的方法分析了各区降水与前期、同期大气环流特征量及海温的遥相关关系,结果表明:山东夏季降水与大气环流特征量及海温相关性显著。在此基础上筛选因子,利用多维均生函数建模方案,对2000年前各区及全省夏季降水趋势进行预测。  相似文献   
984.
Shear wave velocity (V s) and the fundamental site period of the subsurface condition are the primary parameters that affect seismic soil amplification in particular sites. Within the topmost layer of the soil, which measures 30 m, the average shear wave velocity V s30 is commonly used to build codes for site classification for the design of earthquake-resistant structures and to conduct microzonation studies. In this study, the development of a microzonation map for V s30 distribution, National Earthquake Hazard Reduction Program V s30 site classification, and a fundamental site period for Penang are presented. The multichannel analysis of surface wave (MASW) test was conducted for more than 50 sites with available borehole data to develop the microzonation maps. The ten selected V s profiles measured by MASW show a good correlation with the data obtained using empirical correlations in a previous study. The highest V s values were identified at the northeastern and southeastern parts of Penang Island, corresponding to the shallow bedrock and the outcrop zone. Conversely, the lowest V s values were found in the northwestern and southwestern parts of the Penang mainland owing to the thick layer of soft clay and silt deposits. The site period map shows the variation in site periods, with the highest value of 1.03 s at the western part of the Penang mainland and the lowest value of 0.02 s at the eastern part of the Penang Island. The microzonation maps developed in this study are vital to studies on seismic hazard and earthquake mitigation programs in Malaysia.  相似文献   
985.
Iron-based nanotechnologies are increasingly used for environmental remediation; however, toxicologic impacts of iron nanoparticles on the aquatic ecosystem remain poorly understood. We treated larvae of medaka fish (Oryzias latipes) with thoroughly characterized solutions containing carboxymethyl cellulose (CMC)-stabilized nanoscale zerovalent iron (nZVI), aged nanoscale iron oxides (nFe-oxides) or ferrous ion (Fe[II]) for 12-14 days' aqueous exposure to assess the causal toxic effect(s) of iron NPs on the fish. With the CMC-nZVI solution, the dissolved oxygen level decreased, and a burst of reactive oxygen species (ROS) was generated as Fe(II) oxidized to ferric ion (Fe[III]); with the other two iron solutions, these parameters did not significantly change. CMC-nZVI and Fe(II) solutions caused acute lethally and sublethally toxic effects in medaka larvae, with nFe-oxide-containing solutions causing the least toxic effects. We discuss modes of toxic action of iron NPs and chronic toxic effects in terms of hypoxia, Fe(II) toxicity and ROS-mediated oxidative damage.  相似文献   
986.
大地电磁全信息资料三维共轭梯度反演研究(英文)   总被引:7,自引:2,他引:5  
在对张量阻抗数据、倾子数据和共轭梯度算法深入分析的基础上,我们实现了大地电磁全信息资料三维共轭梯度反演算法。基于全信息资料的三维共轭梯度反演研究,探讨了同时利用五个电磁场分量整理得到的大地电磁资料进行三维反演定量解释的方法以及全信息数据在三维反演中的作用。理论模型合成数据的反演结果表明,在三维反演中使用张量阻抗和倾子数据结合的全信息数据的反演结果优于只使用张量阻抗数据(或只使用倾子数据)的反演结果,提高了反演结果的分辨率和可信度。合成数据的反演算例也验证了所实现的大地电磁全信息资料三维共轭梯度反演算法的正确性和稳定性。  相似文献   
987.
在考虑环境气压的影响下,引进环境半径参量对藤田公式改进并将其应用到9711号台风研究预报中.结果表明:①改进的藤田公式能够基本解决藤田公式计算的外围气压和气压梯度偏小这一问题,合理地给出整个台风域内气压和气压梯度力的分布.②改进的藤田公式由于引入了环境半径的影响,使得计算的风向内偏角减小而风速增大;特别是它能使台风外围...  相似文献   
988.
高空业务新规范和新质量考核办法意义的延伸   总被引:1,自引:1,他引:0  
通过新、旧规范和质量考核办法的比较,发现新规范和新质量考核办法的变更重点.联系高空业务现状.通过分析,探讨其意义的延伸。  相似文献   
989.
The Shengli River-Changshe Mountain oil shale zone, located in the North Qiangtang depression, northern Tibet plateau, represents a potentially large marine oil shale resource in China. Twenty-eight samples including oil shale, micritic limestone and marl were collected from the Shengli River area to determine the contents and distribution patterns of rare earth elements (REEs) in marine oil shale. Oil shale samples from the Shengli River area have high ash yield (61.86–67.48%) and TOC content (8.02–13.67%) with low total sulfur (St,d) content (0.76–1.39%) and intermediate shale oil content (3.60–16.30%). The total rare earth element (ΣREE) content in oil shale samples is notably depleted (46.79–67.90 μg/g), approximately one third of the mean value of the North American Shale Composite (NASC), and lower than that of world-wide black shales and Chinese coals, but higher than that of world-wide coals and micritic limestone samples (29.21 μg/g) from the Shengli River area. The oil shale samples from the Shengli River area exhibit shale-like Chondrite or NASC-normalized REE patterns similar to those of micritic limestone and marl samples from this area, indicating that REEs of these different lithological samples may have been derived from a similar terrigenous source.REE contents of oil shale samples are highly positive correlated with ash yield and show a positive correlation with Fe and a weakly positive correlation with organic sulfur, and the vertical variations of REEs mainly follow those of Si, Al, K and Ti. All these facts indicate that the REE contents in oil shale seams are mainly controlled by clay minerals and, to a lesser extent, by pyrite, as well as partly associated with oil shale organic constituents. Rare earth elements in the Shengli River oil shale have originated from two sources: a felsic volcanic rock source and a clastic or/and limestone source.  相似文献   
990.
Fundamental knowledge of the isotopic fractionation between the hydration water and the mother solution and whether the primary information recorded in hydration water can be preserved or not in deposits or mines have long been unclear. In order to calculate the accurate hydrogen and oxygen isotopic fractionation factors between gypsum hydration water and its mother solution with new methods, to understand the mechanism of fractionation and synthetically assess the record-keeping abilities of the isotopic composition of hydration water during the process of diagenesis after deposition, experiments on the hydrogen and oxygen isotopic compositions of gypsum hydration water and its mother solution at different isothermal temperatures from 5 to 50°C were systematically conducted. In addition, samples from two typical gypsum deposits formed in different environmental conditions were also determined. Results show that during gypsum crystallisation, both hydrogen and oxygen isotopes show significant fractionation between the hydration water and the mother solution. The calculated hydrogen isotopic fractionation factors are <1, while the oxygen isotopic fractionation factors are >1 at temperatures from 5 to 50°C. The fractionation factors show no functional relationships with temperature. Isotopic compositions of gypsum hydration water in arid lake sediments can be used to trace the source of water and primary deposit environmental information. However, the isotopic composition of the gypsum hydration water can easily be altered by dissolution and secondary precipitation of gypsum during later diagenesis, particularly in areas with humid climate and abundant groundwater. A very careful assessment on record-keeping abilities of the primary isotopic composition of hydration water in gypsum during later diagenesis must be considered before application.  相似文献   
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