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Based on the theory of pH evolution of sea water and the balance between the seawater and the atmosphere the authors discussed the problems about (i) the method ofcalculating P_(CO_2) in the ancient atmosphere with the associations of sedimentary miner-als; (ii) the evolution of P_(CO_2) values in the geologic history; (iii) the relations of thepH evolution of sea water with carbonate precipitations; and (iv) calculation of the pHlimit for some associations of sedimentary minerals and its corresponding P_(CO_2) valuesin the atmosphere. The authors pointed out that though carbonates had deposited little in the Archaean,the content of CO_2 gas in the Archaean atmosphere was very high and was gradually go-ing up to form a thick CO_2 atmosphere. Up to 2600 Ma ago, the P_(CO_2) had reached a gradeof 10- 50 atm. There was a general trend of evolution that from the early Proterozoicera to the present the depositional horizon of carbonate layers was gradually risingand finally surpassed the horizons of clay min 相似文献
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Devonian carbonate strata—the most important ore-bearing strata are widespread in South China. Most strata-bound deposits occur in them. This paper discusses in detail the petrological features and sedimentary environments of two reef facies—the basin reef facies and the platform reef facies, the dependence of the sedimentary environment upon the reefdevelopment, the geochemical features of various facies, the relationship between strata-bound base metal deposits, and sedimentary environments and sedimentary facies. 相似文献
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采用近红外(NIR)光谱技术和最小二乘支持向量机(LSSVM)参数优化方法,建立定标预测模型测定鱼粉灰分的含量,采用去趋势校正和标准正交校正(DC-SNV)相结合的方式进行光谱预处理,基于网格搜索法建立LSSVM的参数优化模型,提高NIR光谱定量分析的预测精度。结果表明,LSSVM参数网格搜索方法能够有效地应用于鱼粉NIR光谱模型优化,获得的鱼粉灰分的光谱预测值与化学测定值能较准确的匹配,有利于NIR光谱技术快速检测在养殖饲料产品中的应用。 相似文献
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根据沉积矿物的共生组合恢复大气CO_2气分压值的演化 总被引:1,自引:0,他引:1
本文依据海水pH值演化和海气平衡理论,讨论了根据地层中沉积矿物共生组合恢复大气CO_2气分压值的理论和方法,研究了海水pH值的演化与碳酸岩层沉淀的关系,计算了地层中一系列与碳酸盐矿物伴生的沉积矿物组合生成的pH值范围及其所对应的大气CO_2气分压值。指出太古代沉积碳酸岩层虽然很少,但大气CO_2气含量却很高,且逐渐增多,直至形成稠密CO_2气圈。26×10~2Ma前后,CO_2气分压曾达10—50atm。从早元古代至现代表现为碳酸岩层沉积层位逐渐升高。最后超越硫化物层和硅酸盐粘土矿物层的总趋势,与此相应大气CO_2气分压值逐渐降低,由稠密CO_2气圈降为现在的0.03%,按CO_2气分压值的范围和波动特点可将其历史演变划分为三个历史阶段。 相似文献
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中国散裂中子源(China Spallation Neutron Source, CSNS)快循环同步加速器(Rapid Cycling Synchrotron, RCS)磁铁由24块二极磁铁、48块四极磁铁、16块六极磁铁和若干斜四极磁铁以及校正磁铁组成, 其中二极磁铁和四极磁铁是带直流偏置的25Hz正弦交流励磁, 铁芯和线圈导体将产生不可忽视的涡流效应. 为了积累批量生产磁铁的制造经验, 探索磁铁后期处理和磁场测量方法, 已完成了中空水冷铝绞线试样线圈的研制, 启动了二极磁铁和四极磁铁样机的研制. 本文将对相关进展进行介绍. 相似文献
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北京正负电子对撞机(BEPC)改造工程是将原来的单环升级为高亮度的双环对撞机(BEPCⅡ),即在现存的BEPC隧道里增加一个新的储存环.使得BEPC Ⅱ能够提供从1.0GeV到2.1GeV能量范围的高亮度对撞束流供高能物理实验用,同时外环还要兼容2.5GeV能量250mA流强的同步辐射专用模式运行,实际上相当于有3个储存环运行.由于受到BEPC储存环隧道空间的局限,物理上的高亮度要求,以及BEPCⅡ真空盒设计采用带前室(Antechamber)结构,因此给各种磁铁设计与制造增加了相当大的难度.着重介绍BEPCⅡ储存环和对撞区中几种主要常规磁铁的设计、制造概况,同时也给出了相应的磁场测量结果. 相似文献
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中国散裂中子源(china spallation Neutron source,CSNS)快循环同步加速器(Rapid cyclingSync,arotron,RCS)磁铁由24块二极磁铁、48块四极磁铁、16块六极磁铁和若干斜四极磁铁以及校正磁铁组成,其中二极磁铁和四极磁铁是带直流偏置的25Hz正弦交流励磁,铁芯和线圈导体将产生不可忽视的涡流效应.为了积累批量生产磁铁的制造经验,探索磁铁后期处理和磁场测量方法,已完成了中空水冷铝绞线试样线圈的研制,启动了二极磁铁和四极磁铁样机的研制.本文将对相关进展进行介绍. 相似文献