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31.
Fine round gravel soil is widely employed in the subgrade of high speed railways in cold regions to prevent frost heaving and thawing. The lower the fines content in fine round gravel soil, the smaller the quantities of frost heaving and thawing, but compaction difficulty increases. This study is to obtain the optimum fines content and limited frost heaving and thawing. The fine round gravel soil filling (FRGSF) used in the Harbin-Qiqihaer Passenger Dedicated Line is taken as the study object. Influence of fines content on optimum water content, maximum dry density and frost heaving properties of FRGSF were studied by means of compaction and frost heaving tests. Results show that the maximum dry density of the FRGSF increases first and then decreases with an increase of fines content, namely there is an optimum fines content for easy compaction. The method of surface-vibratory instrument is fit for coarse-grained soils, and wet state of coarse-grained soil is in favor of compaction. Considering the relationship of fines content with maximum dry density and the frost heaving ratio of FRGSF, the fines content should be limited to within the range of 9%-10%, so that the frost heaving ratio is less than 1%, and the FRGSF is easily compacted. Water supply is proved to be an important factor influencing the amount of frost heaving of FRGSF. We also conclude that in the field, it is imperative to control waterproofing and drainage measures.  相似文献   
32.
Lake area information in the Badain Jaran Desert in 1973, 1990, 2000, and 2010 was obtained by visual interpretation and water index analysis of remote sensing images, based on the spatial and temporal characteristics of lake area changes during 37 years. Results indicated that the number of lakes declined from 94 to 82 and the total surface area was reduced by 3.69 km2 during 1973–2010. The desert lake area reduced by different degrees in different periods, but this occurred most rapidly during 1973–1990. According to the statistics of lake area changes, lake area decreases mainly occurred in the lakes with areas less than 0.2 km2, while the areas of lakes greater than 0.9 km2 only fluctuated. The changes of lake areas were probably due to changes in the quantity of underground water supplies rather than the effects of local climate change or human factors.  相似文献   
33.
本文以岩性地层、气候地层(CaCO3含量、古温度和Rb/Sr比值等)、年代地层、沉积化学地层和生物组合地层等资料为基础,根据地层规范以及建组要求将渤海湾西岸全新世地层划分为3个组:独流镇组( Qh3 dl)、大黄洼组(Qh2dh)和西翟庄组(Qh1xz).其地层埋深界线及测年界线分别为:晚全新世独流镇组(Qh3dl)与...  相似文献   
34.
Peroxisome proliferators-activated receptor gamma(PPARγ) plays important regulatory roles in adipocyte differentiation. In this study, we cloned the full-length sequence of the PPARγ gene and analyzed its expression profile in different developmental stages and tissues of Strongylocentrotus intermedius. The full-length cDNA of PPARγ contains 2286 base pairs(bp) with a putative open reading frame of 1755 bp, and the gene encodes encoding a polypeptide of 584 amino acid residues. The predicted molecular mass of the protein is 67.27 kDa, and its theoretical isoelectric point(pI) is 10.07. The protein contains conserved motifs, including an RRM(RNA recognition motif) domain. PPARγ expression with the highest level was observed in the gonad, and the lowest was observed in the tube feet of S. intermedius. Time-course expression measurements at different developmental stages showed that the highest expression level of PPARγ is in the eggs and its weakest expression level is in the 32-cells stage. Knock-down of PPARγ by specific siRNA revealed that UCP2 expression is significantly decreased in the gonads and intestines 48 h post-transfection, indicating that the UCP2 is a downstream target gene of PPARγ.This finding suggests that PPARγ and UCP2 have positive regulatory effects in regulating adipocyte differentiation. Changes in fatty acid levels in the gonads before and after PPARγ interference were assessed, and decreased C18:2(trans, n-6) and C20:3(n-6) levels were observed 48 h after siRNA transfection. The results showed the function of PPARγ in fatty acid anabolism, The data are helpful to improve the current understanding of the fatty acid synthesis pathways and regulatory mechanisms in S. intermedius. They also provide an experimental basis for improving fatty acid synthesis in sea urchins, which is important for cultivating sea urchins with high nutritional value.  相似文献   
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36.
In the first half of winter 2020/21,China has experienced an extremely cold period across both northern and southern regions,with record-breaking low temperatures set in many stations of China.Meanwhile,a moderate La Ni?a event which exceeded both oceanic and atmospheric thresholds began in August 2020 and in a few months developed into its mature phase,just prior to the 2020/21 winter.In this report,the mid?high-latitude large-scale atmospheric circulation anomalies in the Northern Hemisphere,which were forced by the negative phase of Arctic Oscillation,a strengthened Siberian High,an intensified Ural High and a deepened East Asian Trough,are considered to be the direct reason for the frequent cold surges in winter 2020/21.At the same time,the synergistic effect of the warm Arctic and the cold tropical Pacific(La Ni?a)provided an indispensable background,at a hemispheric scale,to intensify the atmospheric circulation anomalies in middle-to-high latitudes.In the end,a most recent La Ni?a prediction is provided and the on-coming evolution of climate is discussed for the remaining part of the 2020/21 winter for the purpose of future decision-making and early warning.  相似文献   
37.
以往坡、沟侵蚀关系研究主要限于水沙关系的探讨 ,有关原型尺度小流域坡、沟地貌侵蚀演化关系的定量研究甚少 ,尤其是坡、沟地貌特征对流域切割程度的综合影响与交互作用的定量研究尚属空白。本文在 3S技术支持下 ,根据晋西王家沟小流域 196 7年 1∶5 0 0 0正摄影像图 (DOM )、高程数字化模型 (DEM )和同期、同比例尺地形图 ,利用正交多项式回归分析方法 ,定量分析了坡、沟地貌特征对流域切割程度的影响与交互作用。研究表明 ,沟谷地在流域地貌演化及地表切割程度中起主导作用 ,在沟间地面积相同时 ,沟谷地面积约为0 1km2 是影响流域切割裂度侵蚀演化强度最大的区域 ,流域面积愈小影响流域地表破碎的程度最大。其沟道流域坡、沟地貌演化机制可用坡、沟水流动能的地貌指标的综合影响与交互作用来解释  相似文献   
38.
The Solar Upper Transition Region Imager(SUTRI) focuses on the solar transition region to achieve dynamic imaging observation of the upper transition region. In this paper, we report the optical system design, mechanical design, ultrasmooth mirror manufacture and measurement, EUV multilayer film coating, prelaunch installation and calibration for the SUTRI payload at IPOE, Tongji University. Finally, the SUTRI carried by the SATech-01satellite was successfully set to launch. All functions of thi...  相似文献   
39.
Rare earth elements (REEs) can be used to trace source materials and identify their provenances,because of significant conservation and immobility during chemical alteration processes after erosion of materials from the provenance.This study focused on the temporal variation of REEs for columnar sediments from the mouth of Jiaozhou Bay in North China to understand the potential controls for the geochemical variations of sediments.Through extraction experiments,we identified that the residual fra...  相似文献   
40.
耿良玉  王Yue 《地层学杂志》1997,21(4):241-246
iklaensis-emmastensis胞石带可以与sedgwicki笔石带对比。根据iklaensis-emmasten-sis胞石带的存在,表明英国兰多维列区CefnCerig公路剖面的腕足类Eocoeliaintermedia和Stricklandialens最高层位之上的地层,并不相当于turiculatus笔石带的底,按照定义,不是特列奇阶的底界。  相似文献   
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