3种人工草地不同植被覆盖度实地测量方法比较

植被覆盖度是植被垂直投影面积占统计区域面积百分比;理想覆盖度实地测量方法耗时短,工具简单,结果准确,受人为因素影响小.以结缕草(Zoysia japonica)、白三叶(Trifolium repens)和雀稗(Paspalum thunbergii)人工草地为研究对象,以照相法测量值为参考,比较样线法、目估法、样针法...     

What is a static head measurement? Evaluating structural error and implications for regional groundwater modeling

Most groundwater modelers avoid using static heads measured from active production wells because they can introduce a bias into model calibration. However, in the deep confined Cambrian-Ordovician Sandstone Aquifer System in the Central Midcontinent of North America, dedicated observation wells are sparse and remote from areas of most concentrated pumping. As a result, in areas where drawdown is the greatest and modeling is most needed, only static heads from production wells are available for calibration. This paper evaluates two leading sources of discrepancies in using production well data, spatial and temporal structural error (S.E.). A simple Theis solution is used to evaluate the potential magnitude of spatial S.E. when calibrating a regional MODFLOW model with coarse cell resolution. Despite theoretical analyses indicating that spatial S.E. could be significant, statistical analysis of the model results suggests that temporal S.E. is dominant. Long (ranging over decades) or frequent (monthly) head datasets are key in understanding temporal S.E., to better capture water-level variability. In this study, the range in static head observations impacted estimates of the remaining time a well could extract water from the aquifer by 0.1 to 16.0 years. This uncertainty in future water supply is highly relevant to stakeholders and must be assessed in hydrographs depicting risk.     

人-机-环境系统工程在井下运输安全中的应用

运用人-机-环境系统工程理论,对煤矿井下运输系统中的人、机、环境三大要素及其对运输事故的影响进行分析,尤其是对人为失误的原因及其控制,人的模糊可靠性,运输事故与人的因素的关系,事件树分析,事故树分析,灰色关联分析,模糊聚类分析以及灰色综合评判等进行了深入的研究,提出了相应的控制措施。     

复杂系统中人误原因因素的层次分析法

介绍和评析了人误分析历史上有重要影响的几种人误原因因素分类方法:传统人因分类法、信息处理分类法和认知系统工程分类法.基于认知可靠性及失误分析方法(CREAM)的人误原因因素分类,运用层次分析法(AHP)基本原理,建立了大规模复杂人-机系统人误原因因素层次结构模型及相应的AHP程序,并以JCO公司超临界事故为实例进行了分析.分析和应用结果表明,本文所建立的人误原因因素层次结构模型及AHP程序能够辨识出大规模复杂人-机系统中人误的主要原因因素,进而寻找出最优预防方案,对预防和减少此类人误事故的发生有积极意义.     

Why did the pilots shut down the wrong engine? Explaining errors in context using Schema Theory and the Perceptual Cycle Model

Although human error remains a dominant issue in aviation research, methods that predict human error have been criticised for not providing adequate causal explanations, rather they have focused on classification. The concept of Schemata has prevailed in the literature and has been shown to describe the contextual causes of human error. The purpose of this paper is to review the recent error literature and demonstrate that Schema Theory (as incorporated in the Perceptual Cycle framework) offers a compelling causal account of human error. Schema Theory offers a system perspective with a focus on human activity in context to explain why apparently erroneous actions occurred, even though they may have appeared to be appropriate at the time. This is exemplified in a case study of the pilots’ actions preceding the 1989 Kegworth accident. Schema Theory is presented as a promising avenue for further exploration into the context of human error in aviation.     

Fisher法在土壤污染综合评价优化布点中的应用

根据Fisher最优分割的理论,研究其应用于土壤环境监测优化布点的可行性。以福建省闽江河口湿地土壤重金属污染综合评价为实例,用Fisher法计算不同分类方式下的最小误差函数,确定最优的分割方法,确定优化布点方案。结果表明,原布设的8个监测点用Fisher法优化为3个典型点位,可客观反映闽江河口湿地土壤重金属污染的综合评价结果。     

Determining Decision Thresholds and Evaluating Indicators when Conservation Status is Measured as a Continuum

Categorization of the status of populations, species, and ecosystems underpins most conservation activities. Status is often based on how a system's current indicator value (e.g., change in abundance) relates to some threshold of conservation concern. Receiver operating characteristic (ROC) curves can be used to quantify the statistical reliability of indicators of conservation status and evaluate trade‐offs between correct (true positive) and incorrect (false positive) classifications across a range of decision thresholds. However, ROC curves assume a discrete, binary relationship between an indicator and the conservation status it is meant to track, which is a simplification of the more realistic continuum of conservation status, and may limit the applicability of ROC curves in conservation science. We describe a modified ROC curve that treats conservation status as a continuum rather than a discrete state. We explored the influence of this continuum and typical sources of variation in abundance that can lead to classification errors (i.e., random variation and measurement error) on the true and false positive rates corresponding to varying decision thresholds and the reliability of change in abundance as an indicator of conservation status, respectively. We applied our modified ROC approach to an indicator of endangerment in Pacific salmon (Oncorhynchus nerka) (i.e., percent decline in geometric mean abundance) and an indicator of marine ecosystem structure and function (i.e., detritivore biomass). Failure to treat conservation status as a continuum when choosing thresholds for indicators resulted in the misidentification of trade‐offs between true and false positive rates and the overestimation of an indicator's reliability. We argue for treating conservation status as a continuum when ROC curves are used to evaluate decision thresholds in indicators for the assessment of conservation status. Determinación de Umbrales de Decisiones y Evaluación delos Indicadores cuando se Mide el Estado de de Conservación como un Continuo     

城市路面径流污染负荷及采样次数对其估算准确性的影响

在西安市城市主干道南二环路建立路面径流原位采样站,利用自制流量等比例采样装置,采集2009年3月-2010年2月的36场降雨径流,测试各场次径流SS、COD、溶解性COD、NH4-N、Pb、Zn和溶解态Pb、Zn的事件平均浓度(EMC),计算径流年污染负荷,并采用随机抽样方法研究采样次数对污染负荷估算准确性的影响.结果...     

CREAM-based communication error analysis method (CEAM) for nuclear power plant operators’ communication

Communication error has been considered a primary cause of many incidents and accidents in the nuclear industry. In order to prevent these accidents, a method for the analysis of such communication errors is proposed here. This paper presents a qualitative and a quantitative method to analyze communication errors. The qualitative method focuses on finding a root cause of the communication error and predicting the type of communication error which could happen in nuclear power plants. We develop context conditions and antecedent-consequent links of influential factors related to communication errors. The quantitative analysis method focuses on estimating the probability of communication errors. To accomplish the quantification of communication errors, the Cognitive Speaking Process (CSP) is defined and a method to estimate the weighting factors and the probability is suggested. Finally, case studies conducted to validate the applicability of the proposed methods are detailed. From the results, we can foresee the effects of given plant conditions on communication errors and reduce the error occurrences.