MASS LOAD ESTIMATION ERRORS UTILIZING GRAB SAMPLING STRATEGIES IN A KARST WATERSHED1

ABSTRACT: Developing a mass load estimation method appropriate for a given stream and constituent is difficult due to inconsistencies in hydrologic and constituent characteristics. The difficulty may be increased in flashy flow conditions such as karst. Many projects undertaken are constrained by budget and manpower and do not have the luxury of sophisticated sampling strategies. The objectives of this study were to: (1) examine two grab sampling strategies with varying sampling intervals and determine the error in mass load estimates, and (2) determine the error that can be expected when a grab sample is collected at a time of day when the diurnal variation is most divergent from the daily mean. Results show grab sampling with continuous flow to be a viable data collection method for estimating mass load in the study watershed. Comparing weekly, biweekly, and monthly grab sampling, monthly sampling produces the best results with this method. However, the time of day the sample is collected is important. Failure to account for diurnal variability when collecting a grab sample may produce unacceptable error in mass load estimates. The best time to collect a sample is when the diurnal cycle is nearest the daily mean.     

大空间火灾实验中温度测量的误差分析

在大空间火灾实验中，由于测温系统的庞大和复杂，导致影响温度测量的误差因素增多。该文主要从热电偶测温误差理论分析入手，讨论全尺寸火灾实验温度测量误差的因素和大小，阐述了大空间烟气温度测量的误差引入方式和减少误差的措施，并对一组大空间内火灾机械排烟实验的温度数据进行了误差分析。     

一种人因可靠性分析(HRA)方法

从控制论角度说明人因可靠性分析方法，在分析现有两代人因可靠性分析方法不足的基础上，结合控制论，提出了一种新的人因可靠性分析方法的构想。     

建筑物火灾疏散中人的失误研究

火灾是人类所面临的最为严重的灾害之一。通过建筑物火灾现场勘察表明 ,造成火灾中人员伤害的重要原因之一是火灾现场疏散人员行为的失误。而火灾现场疏散人员行为的失误是一个极为复杂的问题 ,它既与影响疏散中人的行为因素有关 ,又与火灾疏散中人的认知模式有关。因此 ,笔者基于行为学的基本原理和建筑物火灾的特点 ,定义了建筑物火灾中人失误的内涵 ,对建筑物火灾中疏散人员失误的机理和分类进行了分析 ,建立了相应的模型 ,讨论了减少建筑物火灾中疏散人员失误的措施 ,并着重讨论了火灾疏散教育和培训的内容和形式。     

人的可靠性分析:历史、需求和进展

人的可靠性分析 (HRA)是人机工程、安全科学极为关注的问题。近年来 ,该领域的理论研究和应用技术发展很快 ,尤其将认知科学与人的失误的研究相结合 ,从失误模型到计算方法都更加与现实情景相吻合。笔者介绍了HRA的发展历史和相关的第一代HRA计算方法及其特点 ,并且就HRA在我国核电领域中的应用状况和前景进行了探讨 ,重点介绍了国际原子能机构赞助的中国核电厂操纵员可靠性研究项目 ,其成果对于进一步完善安全管理和提高我国核电厂人员可靠性提供了科学的依据和借鉴经验。     

The contribution of computer‐based information systems to partnership between public agencies and voluntary environmental groups

This paper considers the contribution of computing to the implementation of a policy of partnership between public environmental agencies and local voluntary groups. The present policy commitment to partnerships of this kind is reviewed. Particular information needs arise when public agencies seek to give co‐ordinated support to the environmental action undertaken by local groups. These stem from the disaggregated nature of the structure and functions of the voluntary sector. Computer‐based information systems are identified as a bridge between the regional organisation of public agencies and the local activities of voluntary groups. A computer system devised to aid the forward planning of public support for voluntary action is described. It is considered that this technique has value as part of a wider strategy of interaction between the public and voluntary sectors.     

SOURCES OF VARIABILITY IN PHOSPHORUS AND CHLOROPHYLL AND THEIR EFFECTS ON USE OF LAKE SURVEY DATA1

Summer lake survey measurements of total phosphorus (TP) and chlorophyll a (CHLa) from 188 reserviors and natural lakes in the midwest were analyzed to determine the magnitude of major sources of variability. Median variance among replicate samples collected at the same location and time was about 7-8 percent of the mean for both TP and CHLa. Median observed temporal variability within summers was 27 percent of the mean for TP and 45 percent of the mean for CHLa. Median values of year-to-year variance in average TP and CHLa were 22 percent and 31 percent of the mean, respectively. A range of approximately two orders of magnitude was observed among individual estimates of variance in each of these categories. The magnitude of observed temporal variability was affected only slightly by variance among replicate samples on individual days and was weakly correlated with the length of time during which samples were collected from individual lakes. Observed temporal variation was similar between reservoirs and natural lakes when variances were calculated with logtransformed data. The magnitude of temporal and year-to-year variance can severely limit the power of statistical comparisons of TP and CHLa means, but has less effect on establishing relative rankings of lake means, Sources and relative magnitude of variability are important in the use of TP and CHLa data in regression models and in the planning of lake surveys and subsequent data analysis.     

EVALUATION OF NEXRAD STAGE III PRECIPITATION DATA OVER A SEMIARID REGION1

This study examines NEXRAD Stage III product (hourly, cell size 4 km by 4 km) for its ability in estimating precipitation in central New Mexico, a semiarid area. A comparison between Stage III and a network of gauge precipitation estimates during 1995 to 2001 indicates that Stage III (1) overestimates the hourly conditional mean (CM) precipitation by 33 percent in the monsoon season and 55 percent in the nonmonsoon season; (2) overestimates the hourly CM precipitation for concurrent radar‐gauge pairs (nonzero value) by 13 percent in the monsoon season and 6 percent in the nonmonsoon season; (3) overestimates the seasonal precipitation accumulation by 11 to 88 percent in monsoon season and underestimates by 18 to 89 percent in the nonmonsoon season; and (4) either overestimates annual precipitation accumulation up to 28.2 percent or underestimates it up to 11.9 percent. A truncation of 57 to 72 percent of the total rainfall hours is observed in the Stage III data in the nonmonsoon season, which may be the main cause for both the underestimation of the radar rainfall accumulation and the lower conditional probability of radar rainfall detection in the nonmonsoon season. The study results indicate that the truncation caused loss of small rainfall amounts (events) is not effectively corrected by the real‐time rain gauge calibration that can adjust the rainfall rates but cannot recover the truncated small rainfall events. However, the truncation error in the monsoon season may be suppressed due to the larger rainfall rate and/or combined effect of overestimates by bright band and hail contaminations, virga, advection, etc. In general, improvement in NEXRAD performance since the monsoon season in 1998 is observed, which is consistent with the systematic improvement in the NEXRAD network.     

综放工作面微气候对工人操作失误影响研究

阐述综放工作面微气候的特点,即综采工作面的温度、湿度、煤尘等普遍偏高的情况。指出微气候的各个指标对于工人操作可靠性的影响;利用人因学原理分析了综放工作面温度、湿度、风速和煤尘对于工作操作可靠性影响的机理;强调要将综放工作面微气候中的温度、湿度、煤尘控制在一个合理的范围内;针对不同的因素提出有效的应对措施。研究取得的成果为改善井下综采工作面微气候,提高工人操作可靠性提出了理论依据。     

几种降低有机样品分析系统误差的方法

有机痕量分析的样品处理包括从样品采集直到最终分离测定的全过程,在有机痕量分析中,必须严格防止所用器皿、化学试剂、溶剂等污染,减少系统误差。