Application and validation of a statistically derived risk-based sampling plan to improve efficiency of inspection and enforcement

The statistically derived risk-based sampling plan for surveillance sample assignments of chemical and biological hazards was designed using binomial probability distribution. The binomial statistics was applied to the past 3-year data to estimate a confidence interval and a sample size aiming to improve efficiency and effectiveness of the agency's sampling and inspectional activities. The accuracy of the statistical models and computed estimates were validated in the following years. The ranges of confidence interval and sample size appeared to be significantly influenced by a level of the violation rate of feed product samples, an acceptable error, a number of the analyzed samples, and a statistical significance level. The violation rates of feed products for target analytes (aflatoxins, fumonisins, Salmonella, and dioxin) in the validation data were lower than those of the average 3-year data in most feed products. Besides, the actual violation rates of the validation samples did not exactly fall within the anticipated range of the confidence interval estimates. Such a discrepancy is considered introduced by several factors such as sample size adequacy, skewed distribution of a target analyte in feed products, and unique analyte/product combination. The overall study results indicate that the risk-based plan of work would provide a more effective and efficient risk management tool to help improve the oversight of the feed industry and the compliance to feed safety standards.     

设计洪水估计值的抽样误差分析与应用

在设计洪水估计值的抽样误差分析中,采用B值诺模图方法估计均方误差简单易用。文章对在水电工程中经常采用的P-Ⅲ型经验适线法估计的设计洪水成果如何借助优化适线法参数来估算设计洪水值的抽样误差进行了分析说明。不同的优化适线法会得到不同的诺模系数B,估算设计洪水估计值的抽样误差时,选用某一准则的优化适线要使用相应的诺模系数B值。并分别对实测洪水的连序系列及含历史洪水的不连序系列资料进行了应用分析。     

粗纱退绕张力的电测及导纱杆水平位置的选择

将微机数据采集系统引入粗纱退绕张力的电测与分析，探索了导纱杆水平方向的最佳位置，以减少粗纱退绕张力的波动。     

小信号幅度测量中的差分同步解调技术

本文介绍一种用于测量小信号幅度的电路，被测信号范围为微伏级到几毫伏。电路设计方法适用于将数模混合型正弦波发生器作为信号源的测量仪器。文中主要讨论两方面问题，对两个正弦波信号之差的正确解调和测量中的共模信号校正。     

The food safety impact of the Codex sampling plans for Listeria monocytogenes in ready-to-eat foods: An empirical case study applying the FAO/WHO sampling plan tool

Sampling plans are specified by the Codex Alimentarius Commission microbiological criteria for Listeria monocytogenes in ready-to-eat foods. This case study evaluates the direct food safety impact of the Codex sampling plans as estimated by the FAO/WHO web-based microbiological sampling plan analysis tool under different assumptions about the pathogen distribution, test procedures, and the fraction of lots tested. The case study uses L. monocytogenes concentration data available for deli-type salads to empirically illustrate application of the sampling tool. The results indicate that the estimated impact of the sampling plans is dependent on the partitioning of total observed variance into its within- and between-lot components. The presence-absence based sampling plan is relatively insensitive to the substantial uncertainty and variability of the sensitivity of the reference method for detection of L. monocytogenes. The analytical sample size for enumeration impacts the ability of the concentration-based sampling plan to discriminate between compliant and non-compliant lots. Reducing the frequency of lot testing dramatically changes the statistical properties of the sampling schemes. Skip-lot sampling places greater importance on compliance assurance than on the direct, curative impact of lot acceptance sampling.     

Optimizing discrete point sample patterns and measurement data analysis on internal cylindrical surfaces with systematic form deviations

Selection of an appropriate sampling strategy and of the correct fitting algorithm are two of the key issues in the practice of modern coordinate metrology. A recent report described the development of new techniques for modeling the form errors of machined part features and illustrated their use in identifying and understanding the relation of form errors to machining process variables. In this report, these mathematical tools are further developed and applied for the determination of optimum, reasonably-sized probing patterns for measurement under time and economic constraints. The focus of the work reported here is on full internal cylindrical surfaces. The technique is, however, of general utility and can be employed with any nominal feature geometry. Its application does, in many cases, produce significant improvements in the uncertainty of derived geometric dimensioning and tolerancing parameters with modest or no increase in measurement time. In contrast to most work on these problems, extensive use is made of process-dependent information in selection of sampling protocol and data analysis method. Since the method begins with an understanding of the form errors introduced into the part by the particular manufacturing regime, at least partial benefit can be seen even when the sample pattern optimization is employed in conjunction with commercial, off-the-shelf CMM control and data analysis software.     

采样设计数据处理与直方图的自动实现

为在采样设计时,做好矿石不同类型、不同品位区间样品的统计工作,笔者用采样设计数据处理系统实现了若干区间品位统计表、统计直方图的自动生成。本文对此进行了分析和说明。     

基于LHS抽样RSM数据表的边坡可靠度研究

为有效求解边坡可靠度,采用拉丁超立方(LHS)抽样提出了基于响应面法(RSM)数据表的边坡可靠度计算模型。考虑影响边坡稳定性的主要强度参数c,φ的不确定性,采用LHS抽样构建RSM随机样本点,借助岩土工程极限平衡的Slide程序获取样本响应值;通过将数据表法与RSM结合求解边坡可靠指标及失效概率。以Monte Carlo法计算结果作为可靠性分析的基准解,并与基本2层土坡模型和托巴110 kV施工变电站边坡计算结果进行对比分析,结果表明此方法不仅精度满足要求,且计算量较小、效率高,对实际工程边坡可靠度分析具有一定指导意义。     

The bacterial quality of red meat and offal in Casablanca (Morocco)

The present study aimed to evaluate the bacteriological quality of beef (n = 52), lamb (n = 52) and beef offal (n = 52) marketed in Casablanca, Morocco. Meat and offal samples (n = 156), were collected randomly from butcheries, supermarkets, and slaughterhouses. Two sampling periods were considered, one during the hot season and the second one during the cold season. The samples were analyzed for the presence of the following bacteria: Escherichia coli, coagulase-positive Staphylococcus, Clostridium perfringens, Salmonella, and Listeria monocytogenes. Results indicated that counts of the aerobic plate count, and fecal coliforms were particularly high in all the samples analyzed. E. coli, coagulase-positive Staphylococcus and C. perfringens were detected in 37.8, 16, and 4.5% of the meat samples, respectively. Neither Salmonella nor L. monocytogenes were isolated from meat samples. Approximately 26.9% of beef, 34.6% of lamb and 28.8% of beef offal samples contained bacteria above the maximum limits established by the Moroccan regulatory standards for meat and meat products. Seasonality and the distribution location significantly (p < 0.05) affected bacterial populations: the hot season and butcheries appeared to be cases where the highest populations of bacteria in meat were observed. These high levels of microbiological contamination attest the poor hygienic quality of meat and offal, possibly due to uncontrolled processing, storage, and handling of these products.     

化工装置样品采集系统的设计

介绍化工装置样品采集系统设计的重要意义,并提出了几个问题以供参考。