Nonparametric Ranked-set Sampling Confidence Intervals for Quantiles of a Finite Population

Ranked-set sampling from a finite population is considered in this paper. Three sampling protocols are described, and procedures for constructing nonparametric confidence intervals for a population quantile are developed. Algorithms for computing coverage probabilities for these confidence intervals are presented, and the use of interpolated confidence intervals is recommended as a means to approximately achieve coverage probabilities that cannot be achieved exactly. A simulation study based on finite populations of sizes 20, 30, 40, and 50 shows that the three sampling protocols follow a strict ordering in terms of the average lengths of the confidence intervals they produce. This study also shows that all three ranked-set sampling protocols tend to produce confidence intervals shorter than those produced by simple random sampling, with the difference being substantial for two of the protocols. The interpolated confidence intervals are shown to achieve coverage probabilities quite close to their nominal levels. Rankings done according to a highly correlated concomitant variable are shown to reduce the level of the confidence intervals only minimally. An example to illustrate the construction of confidence intervals according to this methodology is provided.     

空气中挥发性有机物监测技术的研究进展

讨论了空气中挥发性有机化合物（VOCs）的监测分析方法研究进展。重点介绍了空气中VOCs的采集、分析和测定；简要叙述了样品前处理的新方法--固相微萃取法（SPME）与其它前处理方法的研究概况。     

Sampling and physico-chemical analysis of precipitation: a review

Wet deposition is one of two processes governing the transfer of beneficial and toxic chemicals from the atmosphere on to surfaces. Since the early 1970s, numerous investigators have sampled and analyzed precipitation for their chemical constituents, in the context of "acidic rain" and related atmospheric processes. Since then, significant advances have been made in our understanding of how to sample rain, cloud and fog water to preserve their physico-chemical integrity prior to analyses. Since the 1970s large-scale precipitation sampling networks have been in operation to broadly address regional and multi-regional issues. However, in examining the results from such efforts at a site-specific level, concerns have been raised about the accuracy and precision of the information gathered. There is mounting evidence to demonstrate the instability of precipitation samples (e.g. with N species) that have been subjected to prolonged ambient or field conditions. At the present time precipitation sampling procedures allow unrefrigerated or refrigerated collection of wet deposition from individual events, sequential fractions within events, in situ continuous chemical analyses in the field and even sampling of single or individual rain, cloud and fog droplets. Similarly analytical procedures of precipitation composition have advanced from time-consuming methods to rapid and simultaneous analyses of major anions and cations, from bulk samples to single droplets. For example, analytical techniques have evolved from colorimetry to ion chromatography to capillary electrophoresis. Overall, these advances allow a better understanding of heterogeneous reactions and atmospheric pollutant scavenging processes by precipitation. In addition, from an environmental perspective, these advances allow better quantification of semi-labile (e.g. NH4+, frequently its deposition values are underestimated) or labile species [e.g. S (IV)] in precipitation and measurements of toxic chemicals such as Hg and PCBs (polychlorinated biphenyls). Similarly, methods now exist for source-receptor studies, using for example, the characterization of reduced elemental states and/or the use of stable isotopes in precipitation as tracers. Future studies on the relationship between atmospheric deposition and environmental impacts must exploit these advances. This review provides a comprehensive and comparative treatment of the state of the art sampling methods of precipitation and its physico-chemical analysis.     

A closer look at detectability

Environmental and Ecological Statistics - The theory underlying line transect and variable circular plot surveys—distance sampling—begins with an assumed detectability function, giving...     

Quantifying the efficiency of soil sampling designs: A multivariate approach

The objective of this paper is to quantify and compare the loss functions of the standard two-stage design and its composite sample alternative in the context of multivariate soil sampling. The loss function is defined (conceptually) as the ratio of cost over information and measures design inefficiency. The efficiency of the design is the reciprocal of the loss function. The focus of this paper is twofold: (a) we define a measure of multivariate information using the Kullback–Leibler distance, and (b) we derive the variance-covariance structure for two soil sampling designs: a standard two-stage design and its composite sample counterpart. Randomness in the mass of soil samples is taken into account in both designs. A pilot study in Slovenia is used to demonstrate the calculations of the loss function and to compare the efficiency of the two designs. The results show that the composite sample design is more efficient than the two-stage design. The efficiency ratio is 1.3 for pH, 2.0 for C, 2.1 for N, and 2.5 for CEC. The multivariate efficiency ratio is 2.3. These ratios primarily reflect cost ratios; influence of the information is small.     

外来有害生物风险评估技术

概述了有害生物风险分析的概念、必要性、生物学基础和一般程序 ;论述了生态气候图、农业气候相似距库、生态气候评价的分析模型、地理信息系统、专家系统、基于定性分析与定量估算相结合的数学模型等有害生物风险分析技术的原理和特点 ;认为应用网络技术 ,建立基于分布式计算的全球入侵物种风险评价数据体系 ,可有效提高风险评价的速度和准确性。     

土壤环境背景值图件的绘制方法

土壤环境背景值图件是一种综合信息载体。本文通过对环境背景值影响因素的综合分析、主要影响因素聚类分析、聚类一判别分级等步骤,选择和确定了制图单元。按多元统计单元进行编图,其表达更为清晰、科学、准确。     

沂河流域土地利用时空变化图谱特征分析

基于沂河流域1995年、2005年和2015年土地利用空间数据,运用地学信息图谱方法构建1995-2005年和2005-2015年两个时序单元的土地利用转移图谱和涨落势图谱,分析了沂河流域近20年来的土地利用时空变化规律及发展过程。结果表明：（1）1995-2015年,沂河流域土地利用结构以耕地和林地为主,其中耕地和草地减少,林地和建设用地增加是主要变化趋势。（2）土地利用转移图谱以耕地与林地、草地之间的相互转换以及建设用地占用耕地为主,林地、草地转变为耕地主要发生在费县和平邑县中部地势平缓的山前平原,耕地转变为林地、草地则主要分布于研究区北部和西南部土壤侵蚀较为严重的山区,耕地转变为建设用地主要集中在各县市城区周边经济相对发达的区域。两个时序单元中,发生变化的主要图谱单元类型及面积存在显著差异,2005-2015年土地利用发生转换的空间进一步扩张。（3）土地利用涨势图谱中新增耕地面积最大,占新增面积的比例为33.87%;落势图谱中耕地萎缩面积最大,占萎缩面积的比例为51.38%。两个时序单元中,各县市涨落势图谱变化存在明显差异。该研究可为沂河流域土地资源的可持续利用及生态建设提供科学依据。     

高氯离子废水COD的吸收测定方法探讨

本法基于可定量测定K2Cr2O7和Cl-的反应产物Cl2这一原理,在用吸收装置吸收Cl2后,用碘量法测定余氯,从而消除氯离子的干扰.本法具有较高的准确度和精密度.