共查询到20条相似文献，搜索用时 93 毫秒
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11月2日至5日,2013中国国际矿业大会在天津市举行。大会经国务院批准,由国土资源部和天津市人民政府共同主办,发展改革委、科技部、工业和信息化部、财政部、环境保护部、商务部、国家开发银行、中国进出口银行、中国银行以及世界银行、澳大利亚驻华大使馆、加拿大驻华大使馆、南非驻华大使馆、智利驻华大使馆等单位协办。 相似文献
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《CT理论与应用研究》2012,(4):646
《临床放射学杂志》是一份面向国内外公开发行的医学影像学学术性刊物。以"保证质量、具有特色、重视临床、普及提高"为办刊宗旨。辟有:读片窗、中枢神经放射学、头颈部放射学、胸部放射学、腹部放射学、骨骼肌肉放射学、介入放射学、小儿放射学、实验研究、医学 相似文献
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1985年金秋时节,中国地质博物馆迎来了新中国第一个宝石(学)陈列室的诞生。新宝石馆就坐落在北京西四中国地质博物馆三楼北大厅。新馆建成至今已有27年。回首往事,思绪万千,特记一二,以资纪念。新馆陈列面积220余平方米。展出中外百余种高中档珠宝玉石标本,有钻石、红宝石、蓝宝石、祖母绿、猫眼、珍珠、翡翠、欧泊、碧玺、橄榄石、方柱石、石榴石、绿松石、青 相似文献
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利用地质学、天文学、地球物理学、古生物学资料进行约束,对地球的去气作用进行研究发现：太阳系的部分冷物质,通过吸积作用形成早期地球.在碰撞动能转变的热能作用下,造成了早期地球的表面熔融.在熔融状态的高温高压作用下,构成地球表面物质的结晶水排出地表进入原始大气;在高温高压下分解的碳酸盐、硫酸盐、卤化物等产生的二氧化碳、硫化氢、二氧化硫、氯化氢、氟化氢等气体进入原始大气,和水蒸汽一道共同组成原始大气.当地球内部在重力势能和放射能的作用下继续熔融时,地球表面固化为原始岩石圈.后来,地球除表面岩石圈外,整个地球完全熔融.地球内部物质熔融形成的水和二氧化碳等气体,被岩石圈圈闭.只有当冰川形成和消融,引起造海和造陆作用,导致火山喷发和地震时,这些气体才可能排出地表.这些气体的排出,受地球内部的熔融状态、冰川形成的位置（是在海洋或是在陆地）、生物的演化、太阳光的强度等因素的综合影响. 相似文献
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The chronologies are shown of sediment load on the banks of a river of the Ruhr district (Lippe) with radionuclides of radium, lead and cesium and preliminary chemical measurements for lead, zinc, arsenic, mercury, cadmium, barium, PAHs, PCDDs, PCDFs, PCBs, TOC, AOX and EOX. A new method of dating is developed and proved, which is especially suitable for rivers with radioactivity from coal mines. The method improves the well-known excess-210Pb-dating for the use with rivers in industrial regions and allows the preparation of load histories (chronologies). Conclusions are made on the historical trend of emissions in the region from the trend of the sediment load of known age and regular sedimentation without perturbation. 相似文献
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In order to recognize lateral and seasonal variations in composition of suspended particulate matter (SPM) in the Odra Estuary, samples were taken at four sites in the period July 1996 - July 1997 monthly if possible. The contents of the elements Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K, P, C, S as well as Ba, Cr, Sr, V, Zn, Cu, Zr, and of the minerals illite, chlorite, smectite, kaolinite and others have been determined. The decreasing influence of the river Odra towards the open sea could be realized with the help of the contents of the minerals quartz, smectite, and of the elements Ba, Cr, K, P, Si and other. 60% of the seasonal and lateral variations can be explained by changing contents of total carbon (TC), total organic carbon (TOC), Al, Fe, Si, Ti, P, Mn, and Ba. They are mainly caused by differences in the production of organic matter, resuspension, riverine input, and redox-sensitive processes. 相似文献
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地面磁共振方法探测地下水趋于成熟.随着研究的深入,磁共振技术在隧道超前探测方面也开展了应用.然而,由于隧道空间特殊环境限制,获取的磁共振信号信噪比极低,解释结果中各参数的确定性值得深思.基于这一问题,本文提出隧道磁共振测深超前探测模型参数不确定度分析方案,实际工作前,根据不同探测目标要求及环境噪声水平,优化仪器装置参数设计,提高解释结果准确性.本文首先在地面磁共振探测理论基础上,推导了考虑天线铺设角度影响的隧道矩形线圈激发场计算表达式,模拟了隧道准全空间磁共振测深正演响应.其次,基于后验模型协方差矩阵,计算模型参数标准偏差因子,划分参数不确定度等级.最后,构建三层含水模型,将第二层含水体作为观测目标.在仿真合成数据的基础上,分别探讨了电阻率、含水量、水体厚度、线圈边长、匝数、线圈旋转角度以及噪声水平等参数对目标含水体测定的影响.通过对比分析,得到如下结论：当探测目标前方地层的电阻率小于10 Ωm时,目标含水体的不确定度随着该电阻率的增大而降低;当该电阻率大于10 Ωm时,其不影响目标含水体的不确定度;目标体前方地层含水量的增大能够明显增加目标含水体的不确定度;目标层电阻率以及含水量对该层含水体的不确定度几乎不造成影响;目标层厚度越大其含水体的确定度越高;线圈边长和匝数的增大都能在很大程度上降低含水体的不确定度;线圈的偏转角度不影响目标体的不确定度;磁共振信号中噪声的幅度越大,含水体参数的不确定度越大.本文的研究结论有助于提高隧道磁共振探测数据反演参数的准确性,同时能够为实际探测提供预先优化参数的分析方案. 相似文献
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BELLIE SIVAKUMAR 《水文科学杂志》2013,58(2):203-219
Abstract The problem of transformation of rainfall data from one scale to another has been gaining considerable importance in recent years. Though the application of the concept of fractal theory, in the studies conducted thus far, nearly unanimously points at the possibility of such a transformation, the suitability of the theory to the highly variable rainfall in time and space has very often been questioned. A preliminary attempt is made herein to address this issue by investigating the existence of temporal scaling behaviour in rainfall data observed in two different climatic regions: (a) a subtropical climatic region (Leaf River basin, Mississippi, USA) and (b) an equatorial climatic region (Singapore). Rainfall data of three different resolutions, six-hourly, daily, and weekly, observed over a period of 25 years, are investigated. A mono- or simple-scaling method (box dimension method) is employed. The results achieved for the different data sets clearly indicate the existence of temporal scaling in rainfall observed in the two regions, an encouraging news on the suitability of fractal theory in understanding and modelling the rainfall process. However, the insufficiency of a single dimension to characterize the rainfall behaviour is realized, as the dimension depends on the rainfall intensity level, which, in turn, may be related to the rainfall generating mechanisms. A comparison of the box-dimension results obtained for data of different resolutions, from each of the regions, seems to indicate a possible connection between them, a prospect of tremendous practical importance. Another interesting observation is the similarity between the box dimension results obtained for rainfall data from Leaf River basin and Singapore, but this is also clearly related to the intensity level. The dependence of the dimension on the intensity threshold suggests the use of a multi-dimensional fractal approach, where the process is characterized by more than one dimension (or a dimension function) instead of one single dimension. On the basis of the present results, some potential areas for further study are identified. 相似文献
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Twentyfive years of research on the effects of acid rain on rivers and lakes has, to a very small extent, documented changes in the nature and properties of natural organic matter (NOM). In Western Norway, a "whole-watershed-artificial-acidification-experiment" took place in the period 1988–1996. The goals of this long-term experiment were to study the role of NOM in acidification of surface water and the effects of acid precipitation on the quality and properties of NOM. In the HUMEX project (Humic Lake Acidification Experiment) one half of a lake and the corresponding catchment was artificially acidified with H2SO4 and NH4NO3 over a period of 5 years. The other half of the lake and catchment served as a control. In addition to monitoring of the general chemical composition of the water from the two lake halves, a number of other chemical and biological characteristics were studied. Here, we report the results related to changes in the nature and chemical properties of NOM. During the first few years of acidification, a significantly lower concentration of NOM was recorded in the acidified half of the catchment, compared with the control. However, statistical analyses of all data (covering a 2-years pre-treatment period and 5 years of treatment) related to the concentration of NOM (TOC, colour, and UV absorbance) did not suggest any significant effect on the quantity of NOM. This apparent discrepancy between the initial decrease in the concentration of NOM and no effect when the whole 5-years period is considered, may be due to the results of two different simultaneous processes. The results suggest that there first was a reduction of TOC and colour, as a consequence of the acidification, followed by an increase, perhaps owing to increased fertilisation (nitrogen) and in addition to a general temperature increase during the period. In addition, short-term studies of the aquatic surface microlayers, lipophilicity of the NOM, content of organic sulfur, and molecular size indicate differences in the quality of the NOM between the two lake halves, which could affect light absorption. 相似文献
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防灾避难场所应急标识在防灾避难场所中属于基础设施部分,在场所的建设中必不可少,一个完善的标识系统在疏散和安置灾民、减少伤亡等方面发挥着重要作用。首先分析了目前防灾避难场所应急标识系统存在的问题;其次,以标识牌系统的完整性、美观性、安全性和平灾结合为优化设计原则,通过问卷调查,确定影响应急标识设计的各项指标及重要度,进行防灾避难场所应急标识优化设计;最后,以泰州中学新校区中心避难场所为例,结合防灾避难场所的防灾类型、使用功能和要求以及地方的风俗文化与环境,从大小、类型、高度和颜色等方面对防灾避难场所应急标识系统进行规划方案整体优化设计。 相似文献
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Abstract An important and relatively complete fossil mysticete cetacean specimen was collected from the Oligocene age Ashiya Group in Kyushu, Japan. The specimen includes a complete skull, with the anterior part of the vertebral column, several ribs, and the left pectoral limb. It provides significant information about the early evolution of cetotheres and transitional steps from the Archaeoceti to Mysticeti. Several features of the specimen, such as the anterior position of the nasal opening and large mandibular foramen, are primitive, but others are derived, such as the wide maxilla, broad supraorbital process of the frontal, occipital shield overhanging the temporal fossae, and the flat articulation of the distal end of the humerus. This animal, therefore, has a mixture of primitive and derived characters. It represents a stage of evolution in mysticetes that has been previously unrecognized. 相似文献