共查询到19条相似文献,搜索用时 703 毫秒
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塔源二支线矿床位于兴蒙造山带的东段,德尔布干构造-岩浆带的东北段,是近年来发现的一个中型矽卡岩型PbZn-Cu-Mo多金属矿床。矿体呈透镜状赋存于上石炭统新伊根河组的接触交代成因矽卡岩中。该矿床中金属硫化物主要有方铅矿、闪锌矿、黄铁矿、黄铜矿。根据塔源二支线多金属矿床的金属硫化物生成顺序,由黄铁矿→黄铜矿→闪锌矿→方铅矿,结合电子探针数据分析,通过计算所得的各金属硫化物平均化学式与其对应金属硫化物的标准化学式对比表明,其平均化学式的S元素比例逐渐减弱,表明对应矿物生成的还原环境在逐渐减弱。显微镜下,闪锌矿多呈灰褐色,常见闪锌矿被方铅矿交代,形成交代结构,也可见方铅矿与闪锌矿形成共边结构,电子探针数据显示闪锌矿Zn/Fe的变化范围为31.10-103.20,分布在低温(150℃)和中温(150-250℃)区间。Zn/Cd的变化范围为172-204,说明本矿床闪锌矿属于中偏低温闪锌矿。 相似文献
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使用5-D-谷氨酰-D-半胱氨酰甘氨酸(D-谷胱甘肽)及其同分异构体1-L-谷氨酰-D-半胱氨酰甘氨酸作为稳定剂,在水溶液中合成了碲化镉(CdTe)量子点.通过控制反应回流时间,研究了在不同的反应时间内由2种同分异构体稳定的CdTe量子点的紫外光谱,发现分子结构的细微差别能够引起量子点的表面状态不同,进而导致制备的量子点荧光性质不同.通过荧光光谱研究了2种分子稳定CdTe纳米粒子荧光性质的差异,并结合紫外-可见光谱,讨论了引起2种CdTe量子点荧光性质不同的原因. 相似文献
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一个计算平均土壤呼吸速率和土壤碳密度的简单模型 总被引:7,自引:0,他引:7
根据大量实测的土壤碳密度资料并结合生产力模型,得到一组直接利用气候资料来计算平均土壤呼吸速率和土壤碳密度的公式,并同实测资料进行了对比.根据此模型的模拟结果,对最近基于观测资料而得出的平均土壤呼吸速率对温度变化的响应并不显著的结论提出了质疑.利用此模型还对全球潜在的土壤碳密度分布做了模拟,计算出全球土壤碳库为1152Pg.该模型成功地模拟了土壤碳密度随降水(或湿度)状况而变化的特征. 相似文献
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为了便于精密水准测量的数据处理,基于Excel强大的数据处理和丰富的函数计算功能,研究了Excel在水准测量的数据处理与平差过程中的计算和应用方法.以中国矿业大学精密水准测量为例,对计算结果进行验证.结果表明:将EXCEL应用于精密水准测量平差计算中是可行的,结果正确可靠,可以节省大量的人力和时间. 相似文献
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光子单缝衍射过程的动态模拟 总被引:1,自引:0,他引:1
随机游走的理论是蒙特卡罗中的重要组成部分,应用十分广泛,根据光子在观测屏上出现的几率密度分布函数进行随机抽样,便得到按此几率密度函数分布的随机数序列.再依据光子单缝衍射的几率密度函数,运用蒙特卡罗随机模拟方法,然后用费曼的路径积分理论对光子单缝衍射态和几率分布进行定量分析得出光子单缝衍射的几率密度函数.最后,借助Mat... 相似文献
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复杂晶体的化学键和非线性光学效应 总被引:1,自引:0,他引:1
系统地提出了复杂晶体化学键的介电理论方法 ,计算了一些非线性晶体的二阶极化系数dij.计算结果和实验值符合很好 ,同时表明这种方法不仅可应用于复杂晶体 ,还提供了材料设计的某些依据 . 相似文献
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Sangjo Shim Katherine Stemke-Hale Jamileh Noshari Frederick F. Becker Peter R. C. Gascoyne 《Biomicrofluidics》2013,7(1)
The number of circulating tumor cells (CTCs) found in blood is known to be a prognostic marker for recurrence of primary tumors, however, most current methods for isolating CTCs rely on cell surface markers that are not universally expressed by CTCs. Dielectrophoresis (DEP) can discriminate and manipulate cancer cells in microfluidic systems and has been proposed as a molecular marker-independent approach for isolating CTCs from blood. To investigate the potential applicability of DEP to different cancer types, the dielectric and density properties of the NCI-60 panel of tumor cell types have been measured by dielectrophoretic field-flow fractionation (DEP-FFF) and compared with like properties of the subpopulations of normal peripheral blood cells. We show that all of the NCI-60 cell types, regardless of tissue of origin, exhibit dielectric properties that facilitate their isolation from blood by DEP. Cell types derived from solid tumors that grew in adherent cultures exhibited dielectric properties that were strikingly different from those of peripheral blood cell subpopulations while leukemia-derived lines that grew in non-adherent cultures exhibited dielectric properties that were closer to those of peripheral blood cell types. Our results suggest that DEP methods have wide applicability for the surface-marker independent isolation of viable CTCs from blood as well as for the concentration of leukemia cells from blood. 相似文献
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利用1960-2011年石羊河流域及周边12个气象站的逐日气象资料,采用FAO Penman-Monteith公式计算研究区各气象站的潜在蒸散发,并由此计算出各站的相对湿润度指数.在ArcGIS 9.3平台下得到区域相对湿润度指数的时空变化特征,并对影响其变化的气象要素进行了探讨.结果表明: 石羊河流域52年来有微弱变干趋势;该区相对湿润度指数自南向北逐渐增加,与降水量和海拔的空间分布比较一致,与潜在蒸散发的空间分布呈相反关系;流域大部分地区的地表相对湿润度指数倾向率呈增加趋势,增加较明显的区域位于祁连山脉附近,呈下降趋势的区域位于上游古浪县附近;流域地表相对湿润度指数在年内呈单峰型变化,1月、11月和12月最低,8月和9月最高,且随气温变暖,自流域南部向北部逐渐推移增大,当气温开始降低时,该指数又从北到南逐渐减少;石羊河流域地表干湿事件的变化与降水量、风速和相对湿度呈正相关,与潜在蒸散发、平均温度和日照时数呈负相关. 相似文献
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Peng Zhang Haoqi Tang Chuanchuan Gu Hong Wang Guangfu Luo Yalin Lu X-D Xiang 《国家科学评论(英文版)》2021,8(4):86-94
The quantum relaxation time of electrons in condensed matters is an important physical property, but its direct measurement has been elusive for a century. Here, we report a breakthrough that allows direct determination of quantum relaxation time at zero and non-zero frequencies using optical measurement. Through dielectric loss function, we connect bound electron effects to the physical parameters of plasma resonance and find an extra term of quantum relaxation time from inelastic scattering between bound electrons and conduction electrons at non-zero frequencies. We demonstrate here that the frequency-dependent inelastic polarization effect of bound electrons is the dominant contribution to quantum relaxation time of conduction electrons at optical frequencies, and the elastic polarization effect of bound electrons also dramatically changes the plasma resonance frequency through effective screening to charge carriers. 相似文献
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《Journal of The Franklin Institute》1987,323(2):209-233
The dispersion characteristics of inhomogeneous dielectric waveguides are studied using a transverse transmission line representation. With the techniques of distributed circuit analysis the behavior of graded index optical fiber is explained using network theoretic ideas. Specifically, network models are developed through which insight as to the mechanisms underlying the dispersion characteristics of such structures is gained from a transmission line filter analogy. For the case of circular geometries, new approximations for the radial Bessel functions are presented which again results in a simple transmission line filter. 相似文献
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北京地区战略性新兴产业选择研究 总被引:1,自引:1,他引:0
基于北京的区域资源特点,构建北京地区战略性新兴产业选择的指标体系与模型,运用AHP方法确定指标权重,从北京地区的高技术产业以及信息传输、软件和服务业共六大产业中选择战略性新兴产业,进行实证研究,发现信息传输、软件和服务业综合得分最高为0.666,其次为航空航天产业(0.476),进而为北京地区发展战略性新兴产业提出选择建议。 相似文献
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Herbert J. Carlin Pier Paolo Civalleri Jeffrey C. Hantgan 《Journal of The Franklin Institute》1981,311(4):209-230
A general procedure is outlined for obtaining single or coupled transmission line models to represent the propagation of surface wave modes in conductively unshielded dielectric waveguides. The procedure uses a homogeneous electrically or magnetically walled waveguide having the same dimensions as the dielectric of the surface waveguide, to produce a set of orthogonal eigenfunctions. These eigenfunctions are projected upon Maxwell's equations resulting in a system of transmission lines coupled together through a wave immittance, which represents the ratio of a longitudinal and a transverse field component at the dielectric-air interface. Examples are given for various modes of the dielectric slab and the dielectric rod, in particular the HE1n modes for the latter. The transmission line models derived for these examples consist of a single trasmission line found directly by projection or reduced from a coupled transmission line model by port elimination, or of two transmission lines coupled together. All circuit models derived preserve the basic properties of surface waves (e.g. no solution below cut-off), and any of the single line models can be solved to give explicit approximate algebraic formulae for the propagation constant as a function of frequency. Numerical results show that the dispersion curves calculated from the models versus exact values are generally excellent over the entire frequency spectrum. 相似文献
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北京地区大气气溶胶光学特性及其直接辐射强迫的研究 总被引:6,自引:0,他引:6
利用2003年9月-2004年12月天空辐射计观测数据初步反演得到了北京地区大气气溶胶光学特性的参数,包括:500 nm大气气溶胶光学厚度,Angstrom波长指数,单次散射反照率和粒子谱分布的季节变化特征。将反演得到的结果代入辐射传输模式,计算北京地区大气层顶和地面在晴空条件下大气气溶胶的辐射强迫,并分析了其季节变化特征。 相似文献
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人口密度是研究人口分布格局所使用的一个指标。然而以往的研究对人口密度的尺度效应没有给予应有的关注。本文以沈阳市为例,在对人口统计数据进行空间化处理的基础上,从统计特征、空间自相关性和空间格局三个方面分析人口密度在十种粒度下的异同,充分证明了人口密度尺度效应的存在,并基于景观指数确定了沈阳市人口分布研究的适宜尺度。本研究认为在使用人口密度这一指标来研究城市人口分布格局时,学者们必须面对尺度效应、选择适宜尺度,并充分考虑数据来源的尺度、分析的尺度、结果表达的尺度以及他们之间的关系和转换。 相似文献