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781.
The first attempt is made to evaluate quantitatively the changes of accumulation rates in the South China Sea during the last
glaciation and Holocene, based on the data of 72 sediment cores taken from six areas deeper than 100 m. As shown from the
calculations, the accumulation rate during the last glaciation is much higher than that during the Holocene. The southern
and northern continental slopes are distinguished from other areas by the highest accumulation rates, with different features
of sedimentation for aifferent stages: The Glacial-Holocene contrast in accumulation rate of terrigenous material is more
distinct in the southern slope, while the contrast in biogenic sedimentation rate is more remarkable in the northern slope.
Project supported by the National Natural Science Foundation of China (Grant No. 49576268). 相似文献
782.
新疆克孜尔水库形变前兆异常的初步研究 总被引:8,自引:4,他引:4
对克孜尔水库蓄水前18 年的水准、基线测量资料进行研究认为:水准高差正常年变形态的消失是趋势性前兆异常的表现;震前半年左右测值曲线出现较大幅度的上下跳动,或呈台阶状大幅度下降,或出现直线状的“静止不变”异常,则是短临异常的主要特点。研究中发现:(1)异常的形态可能与断层运动的方式和状态有关;(2)异常幅度、异常持续时间与之后发生的中强震的强度及频度有一定关系;(3)近距离强震发生前,断层垂直位移有明显异常,而较远处强震发生前则地表倾斜异常较明显。基线测量没有观测到与水准相呼应的前兆异常 相似文献
783.
The neural network system has been developing very fast recently. It has been widely used in many industries such as automation, nuclear power plant, chemical industry, etc. Neural network systems have a great advantage in dealing with problems in which many factors influence the process and result, and the understanding of this process is poor, and there are experimental data or field data. In rock engineering, many problems are of this nature. In this paper, a brief introduction to neural network systems is given. Problems such as what is a neural network, how it works and what kind of advantages it has are discussed. After this, several applications in rock engineering, made by us, are presented. Case 1 is ore boundary delineation. In this case, the rock are divided into three classes, i.e.: (1) waste rock; (2) semi-ore; and (3) ore for mining purposes. The neural network system built can judge whether it is ore, semi-ore or waste rock along the borehole according its corresponding geophysical logging data, such as gamma-ray, gamma-gamma, neutron and resistivity. Case 2 is aggregate quality prediction. In this case, the quality parameters: (1) impact value; (2) abrasion value I; and (3) abrasion value II are predicted by using a neural network system based on density, point load, content of quarts and content of brittle minerals. Case 3 is rock indentation depth prediction. In this case, the rock indentation depth under indentation load is predicted by the established neural network system based on the indentation load on rock, indenter type and rock mechanical properties, such as uniaxial compressive strength, Young's modulus. Poisson's ratio, critical energy release rate and density. In all these cases, the neural network systems have been applied successfully. The testing results are satisfactory and better than the existing techniques. 相似文献
784.
某些测震学指标与地震相关性研究 总被引:3,自引:0,他引:3
通过对10项测震学指示宾10a的大范围时空扫描得出的有震和无震“预报”进行了与5.0级以上的地震的相关性研究,结果证明这10项指标当显性水平较低时,均可通过统计检验,表明是有效的提取异常指标。作还依统计检验结果对10项测震学指标与地震相关性好坏进行了排序,并通过分析得到各指标今后优化方向. 相似文献
785.
786.
787.
本文以对营前特大桥桥位区的砂土液化的综合评判为例子,提出砂土液化必须运用定值准则的概念与方法并结合各种宏观液化势判定手段进行综合评判,文中还针对水下孔的水位取值进行了讨论。 相似文献
788.
用研制的全自动辐射计在97.8GHz上测量南京市内大气的不透明度以及这种不透明度随时间的变化.辐射计记录大气在不同天顶高度的辐射温度,由此测出天顶方向的大气不透明度。在56小时的测量时间内,取得了1400多组数据,拟合得到了在观测时段内天顶方向的大气不透明度在0.2至0.7之间,典型值为0.4,表明测试地点的大气条件允许进行3mm波段的射电天文观测.由于在工作频段内大气不透明度的主要来源是对流层水汽的吸收,测量的不透明度可用来直接反映大气内水汽的含量,并实时校准大气吸收. 相似文献
789.
In this paper, we report our preliminary results on enhanced star formation activity in Seyfert 2 galaxies. By re-analysing
the Tully-Fisher relation for Whittle's (1992) sample and for a Seyfert 2s' sample selecting from Veron-Cetty and Veron (1996),
we find that (1) almost all Seyfert 2 galaxies with circumnuclear star formation have a ratio of far infrared (FIR) to blue
luminosities (LFIR/LB) to be larger than 1/3; (2) for Seyfert 2 galaxies with LFIR/LB > 1/3, the Tuly-Fisher relation is similar to that of the normal spiral galaxies; while for those with LFIR/LB ≥ 1/3, they are significantly different from the normal ones, which confirms Whittle's suggestion of enhanced star formation
activities in the circumnuclear regions of these Seyfert 2 galaxies.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
790.
纹泥反映了湖相沉积物中特有的沉积韵律,是气候的季节变化和年际变化的产物。山西榆社张村地区上新世晚期的湖心相沉积中发育了极为完好的纹泥剖面。纹泥深浅相间形成清晰的纹理,分别代表夏秋和冬春。一深一浅组成一对,代表一年。纹泥层的单层厚度平均为0.12~0.25mm/条,薄者<0.1mm/条,厚者可达0.3mm/条。暗色纹泥层的厚度大于浅色纹泥层。暗色纹泥的有机质含量丰富,木本植物孢粉占优势,同时CaO的含量低;浅色纹泥恰好相反。湖相纹泥具有建立高分辨率时间标尺和环境演化序列的特殊优越条件。 相似文献