采样过程和模数转换对记录的影响及“真实地面运动”获取——地震学上用的数字信号处理的基本原理和实例(讲座3)

通过采样过程和模数转换对记录影响的分析,讨论了数字地震仪记录的动态范围,以及如何使用谱分析方法去除仪器对最终记录的影响,以便获取“真实地面运动”的近似。     

中国农情采样网络的组织与实施

首先分析了农情采样网络建设所面临的问题 ,确定了中国农情采样网络的采样目的主要是农作物分类成数调查 ,并将全国划分为 9个采样片分别组织采样队伍进行农情采样的方案。从采样片划分及调整、农情采样队伍建设、农情采样内容、采样频次和采样时间 ,以及质量控制等角度讨论了农情采样网络的组织建设工作。从技术培训、督促、野外采样、室内汇总、质量检查和年终总结等方面介绍了中国农情采样网络的实施情况。实践证明 ,文中介绍的农情采样方案效率高 ,成本低 ,仅用 9个专业小组就完成了全国的农情采样工作 ,是一种符合中国国情的农情采样方案 ,有一定的推广价值。     

Importance sampling based algorithm for efficient reliability analysis of axially loaded piles

In reliability analysis, the crude Monte Carlo method is known to be computationally demanding. To improve computational efficiency, this paper presents an importance sampling based algorithm that can be applied to conduct efficient reliability evaluation for axially loaded piles. The spatial variability of soil properties along the pile length is considered by random field modeling, in which a mean, a variance, and a correlation length are used to statistically characterize a random field. The local averaging subdivision technique is employed to generate random fields. In each realization, the random fields are used as inputs to the well-established load transfer method to evaluate the load–displacement behavior of an axially loaded pile. Failure is defined as the event where the vertical movement at the pile top exceeds the allowable displacement. By sampling more heavily from the region of interest and then scaling the indicator function back by a ratio of probability densities, a faster rate of convergence can be achieved in the proposed importance sampling algorithm while maintaining the same accuracy as in the crude Monte Carlo method. Two examples are given to demonstrate the accuracy and the efficiency of the proposed method. It is shown that the estimate based on the proposed importance sampling method is unbiased. Furthermore, the size of samples can be greatly reduced in the developed method.     

Improved reliability in the interpretation of geochemical measurements by the quantification of uncertainty from sampling

All geochemical measurements require the taking of field samples, but the uncertainty that this process causes is often ignored when assessing the reliability of the interpretation, of the geochemistry or the health implications. Recently devised methods for the estimation, optimisation and reduction of this uncertainty have been evaluated by their application to the investigation of contaminated land. Uncertainty of measurement caused by primary sampling has been estimated for a range of six different contaminated land site investigations, using an increasingly recognized procedure. These site investigations were selected to reflect a wide range of different sizes, contaminants （organic and metals）, previous land uses （e.g. tin mining, railway sidings and gas works）, intended future use （housing to nature reserves） and routinely applied sampling methods. The results showed that the uncertainty on measurements was substantial, ranging from 25% to 186% of the concentration values at the different sites. Sampling was identified as the dominant source of the uncertainty （〉70% of measurement uncertainty） in most cases. The fitness-for-purpose of the measurements was judged using the optimized contaminated land investigation （OCLI） method. This identifies the optimal level of uncertainty that reduces to overall financial loss caused by the measurement procedures and the misclassification of the contamination, caused by the uncertainty. Generally the uncertainty of the actual measurements made in these different site investigations was found to be sub-optimal, and too large by a factor of approximately two. The uncertainty is usually limited by the sampling, but this can be reduced by increasing the sample mass by a factor of 4 （predicted by sampling theory）. It is concluded that knowing the value of the uncertainty enables the interpretation to be made more reliable, and that sampling is the main factor limiting most investigations. This new approach quantifies this problem for the first time, and allows sampling procedures to be critically evaluated, and modified, to improve the reliability of the geochemical assessment.     

基于OLHS随机模拟的地下水源地保护区划分

为解决确定性模型可能为地下水源地划分带来的保护不足或过保护问题,探索采用基于正交拉丁超立方抽样法的地下水模型研究,并结合粒子反向追踪技术,进行地下水流随机模拟和对应保护区的概率统计分析,最终得到具有分布概率的保护区范围。为验证该方法的实用性与可靠性,选取北京市平谷区王都庄应急水源地进行实例应用研究。在考虑渗透系数和降雨补给量随机抽样组合基础上进行地下水流动随机模拟,并完成对应保护区划分和加权统计。与确定性模拟划分结果相对比:一级保护区中,确定性模拟划分结果仅相当于随机模拟结果中统计概率70%以上的范围;对于二级保护区,确定法对应保护面积相当于随机模拟结果中50%概率以上的范围。实例研究表明,基于正交拉丁超立方抽样的随机模拟法可完成多个不确定性输入变量条件下的随机模拟,且在小样本数的基础上获得理想结果,适用于复杂水文地质条件下的地下水源地保护区划分研究。     

高效非损伤性扇贝DN A提取方法的建立及效果评价

本研究建立了一种高效、经济的非损伤性扇贝DNA提取方法,在不影响扇贝个体生存状态的前提下,采用擦拭法和室温裂解相结合的方式在20 min内即可获得个体基因组DNA。以虾夷扇贝(Patinopecten yessoensis)、栉孔扇贝(Chlamys farreri)和海湾扇贝(Argopecten irradians)为实验对象,研究了不同擦拭材料(棉签、滤纸)和不同擦拭部位(外套膜、鳃丝、内脏团)的核酸提取效果,评估了本方法在贝类基因分型领域应用的可行性。研究表明,用棉签、滤纸2种材料擦拭扇贝的鳃丝、内脏团或外套膜组织均能获得主带清晰完整的基因组DNA,且不影响扇贝的存活状态。在3种扇贝中采用棉签擦拭法的DNA得率均高于滤纸法,以这2种方式获得的DNA为模板进行SSR和SNP标记分析,能获得均一稳定的扩增条带,SSR标记分型结果准确可靠。本研究建立了简便、快速进行扇贝基因型分析的非损伤性DNA提取方法,为贝类全基因组选育和珍稀贝类资源的种质保护开发提供了新的技术手段。     

国内外钼资源供需形势分析

全面、系统地建立钼矿石、钼矿粉分析方法,对钼元素研究开发和保障钼矿工业发展具有重要意义。目前多采用酸溶或碱熔样品后进行分析,其不足是测定钼含量的范围窄,消耗样品量大,还需使用大量酸碱,且受仪器限制,分析高含量钼时多需对样品溶液进行数次稀释,使分析步骤更加繁琐。发射光谱法则可避免上述问题,但用之准确分析高含量钼矿石钼矿粉尚有测试方法的瓶颈需要突破。本文研究通过内标元素、分析线对、缓冲剂配比、电流程序等环节的实验分析,建立了固体进样-交流电弧发射光谱法测定钼矿石中高含量钼的分析方法：优化样品与光谱缓冲剂质量比至1∶2,优化分析线对,截取曝光时间35s,采用以国家一级合成硅酸盐光谱分析标准物质和国家一级矿石标准物质组成的自研标准系列制作标准曲线,由全谱交直流电弧发射光谱仪自动扣除分析线和内标线背景后以对数坐标二次曲线拟合计算,使测定范围扩展为500～500800μg/g,检出限为27.38μg/g,相对标准偏差（RSD）为3.28%～8.30%,相对误差为-0.43%～0.73%。结果表明,本文方法在实现绿色分析的同时,在检出限相当、精密度合格的条件下,一次性分析高含量钼的上限从5%提高至50%。

     

GVG采样线代表性检验

通过在实验区内设置不同类型的采样线,对GVG采样线的代表性进行检验.结果表明,高速公路和乡村道路类型的采样线对区域代表性的精度在95%以上;国道为86.726%;省道为65.447%.对于不同的缓冲区,高速公路、省道和乡村道路类型采样线,以200m缓冲区的代表性最好.而国道则以800m缓冲区的代表性最好.对于不同的作物而言,无论何种类型的采样线或者缓冲区,种植面积最大的棉花的精度是最好的.最低的是省道采样线1000m缓冲区,精度是78.146%,最好的是国道采样线800m缓冲区,精度是99.974%.除省道外,其他精度都在94.8%以上.这说明GVG采样线所获得的成数对于区域主要作物的代表性是很好的.     

常见稀有气体采样容器研究进展及意义

稀有气体是地学研究的重要手段之一,在研究成矿流体来源、壳幔相互作用过程中具有重要的研究意义,其组成及同位素比值是研究天体和地质体来源、成岩机理及各种地质和物理化学过程的关键,可作为地球化学示踪剂。如何有效地在大气圈、水圈和岩石圈进行稀有气体同位素样品的提取,是气体同位素研究急需解决的基础科学问题,所以气体采样容器和取样技术显得尤为重要。本文在文献调研的基础上,对常见的采样容器的优缺点进行对比,并总结了不同采样容器对稀有气体取样的优劣性。常见的气体采集容器包括不锈钢瓶、铜管、玻璃瓶、气体采样袋、注射器等,而稀有气体的采集容器常为不锈钢瓶和铜管等;通过对比表明不锈钢瓶具有耐高温、耐高压、抗强腐蚀、不易燃、不易爆等特点和优越性,在气体样品采集和运输过程中稳定性最好,实验效果也最好;铜管采样效果和密封性好,但操作较为复杂;玻璃采样容器效果次之;石英玻璃瓶虽然操作简便,但是运输保存不便;气体采样袋和注射器的采集和运输储存效果较差。因此建议稀有气体样品采集使用不锈钢瓶和铜管以及钠钙材质的玻璃瓶,不建议将石英材质玻璃容器以及注射器和气袋作为稀有气体的采样工具。该工作可为气体地球化学的研究提供新的参考。     

Monitoring polycyclic aromatic hydrocarbons in the Northeast Aegean Sea using Posidonia oceanica seagrass and synthetic passive samplers

The concentrations of 22 polyaromatic hydrocarbons (PAH) in Posidonia oceanica seagrass, sediments, and seawater from the Alexandroupolis Gulf in the Aegean Sea, were investigated from 2007 to 2011. Temporal trends of total PAH contents in P. oceanica and sediments were similar. PAH levels in seawater, sediments, and seagrasses generally decreased with increasing distance from Alexandroupolis Port. Leaves and sheaths of P. oceanica had higher PAH levels than roots and rhizomes. P. oceanica accumulates PAHs and has good potential as a bioindicator of spatiotemporal pollution trends. PAH concentrations were also examined using in situ passive seawater sampling and were compared to results of passive sampling in the laboratory using local sediments and seawater. Levels of high molecular weight PAHs assessed using passive samplers confirmed the decreasing gradient of pollution away from Alexandroupolis Port. Passive sampling also proved useful for investigating sources of PAHs in P. oceanica meadows.