Validation of qualitative microbiological test methods

This paper considers a statistical model for the detection mechanism of qualitative microbiological test methods with a parameter for the detection proportion (the probability to detect a single organism) and a parameter for the false positive rate. It is demonstrated that the detection proportion and the bacterial density cannot be estimated separately, not even in a multiple dilution experiment. Only the product can be estimated, changing the interpretation of the most probable number estimator. The asymptotic power of the likelihood ratio statistic for comparing an alternative method with the compendial method, is optimal for a single dilution experiment. The bacterial density should either be close to two CFUs per test unit or equal to zero, depending on differences in the model parameters between the two test methods. The proposed strategy for method validation is to use these two dilutions and test for differences in the two model parameters, addressing the validation parameters specificity and accuracy. Robustness of these two parameters might still be required, but all other validation parameters can be omitted. A confidence interval‐based approach for the ratio of the detection proportions for the two methods is recommended, since it is most informative and close to the power of the likelihood ratio test. Copyright © 2014 John Wiley & Sons, Ltd.     

基于步进电机控制的伺服钻孔机设计

采用高性能的STC89C516RD+单片机,控制步进电机完成点动、快进、工进以及精确定位的任务。定位系统是通过设定原点和精确控制脉冲数来实现的。解决了钻头在刚性材料表面上不能精确定位以及金属屑不易排出去的难题。与传统的手动钻孔机相比,该伺服钻孔机控制方便、精度高、生产效率高。     

利用AD574A设计基于FPGA的高速数据采集系统

在分析FPGA数据采集控制系统结构与工作原理的基础上,利用AD574A作为控制器,构建了一种基于FPGA的数据采集系统。该系统的核心电路,包含控制器、内嵌双口RAM、地址计数器3个模块,结合模数转换器件AD574A构成高精度、快速采集、存储控制系统。可以通过单片机或DSP进行数据的后续处理。并在Quartus II平台下实现FPGA内部3个功能模块,给出了时序仿真波形图。     

关于土地补偿款村级留存问题的法律思考

土地补偿款依法归农村集体经济组织所有，其村级留存比例反映了集体经济组织与村民之间土地补偿款分配的利益博弈，这场利益博弈的本质是村民的个人利益与集体利益、眼前利益与长远利益之间的矛盾问题。实践中，许多地方的村民利用“一事一议”的优势制度安排，以村民（代表）大会决议的法律形式否定村集体对土地补偿款的留存权，将土地补偿款“分光花净”，导致集体经济实力不断弱化，服务村民的职能日益衰弱，以至于在严重的旱灾面前，丧失了组织乡村抗旱的基本功能。文章针对问题的成因分析，提出了解决土地补偿款村级留存问题的法律对策。     

An efficient two-stage randomized response model under stratified random sampling

A two-stage randomized response model is extended to stratified random sampling in order to find out more efficient estimators of proportions built from sensitive questions, which respondents may not answer truthfully, in a population divided into homogeneous subgroups. In each subgroup, the respondents who have not answered the sensitive question in the first stage are requested in the second stage to either answer the sensitive question (second attempt then) or to draw a card indicating “yes” or “no”. In the latter case, they are required to report the outcome. Such extension provides a more efficient estimator of the proportion of the population having a given sensitive attribute than its counterpart in simple random sampling. The extended two-stage randomized response model is more efficient than the stratified randomized response model, where respondents must answer the sensitive question either in the first or in the second stage. Moreover, it increases the respondents’ cooperation. When strata weights are unknown, they are estimated by the double sampling method.     

人为因素与空中交通管制员素质优化

人的因素是影响空中交通管理安全和运行品质的关键因素。人在空中交通安全管理中居于中心位置,需要人与人,人与硬件、人与软件,人与环境等要素之间的契合。优化与完善空中交通管制服务人员的知识与专业技术、心理素质、职业道德与责任心、生理与身体素质等,是消除人为因素对空中交通管制安全与运行品质影响的有效策略。     

Sample size requirements for rare or abundant attribute sampling

Two approximation procedures to determine required sample size for a Fixed width binomial confidence interval are given and compared to exact calculations as well as the normal and Poisson approximations. The approximation procedures are found to be quite simple but very accurate for estimating sample sizes for either rare or abundant attributes.     

对广义夏普准则应用问题的进一步研究

广义夏普准则考虑了待选资产和现有投资组合之间的相关性,因而是一种更有效的投资决策准则。本文对广义夏普准则的具体应用进行了研究,讨论了一种待选资产是否值得投资的比例范围以及最佳投资水平的确定问题,得出了一些重要结论。本研究对基金管理人的投资决策具有指导意义。     

阶段性投资最优比例问题的实物期权方法

以研发成功的初创企业为例,针对两阶段投资决策问题,描述了柔性决策所具有的实物 期权思想,根据相应的投资准则得到项目决策的执行概率,再结合项目收益过程的分析,建立 起包括决策柔性价值在内的项目总价值的数学模型. 在此基础上可以分析投资比例对项目价 值的影响,并得到最优值. 文章结合案例进行了数值计算,并对结果做了分析.     

车辆悬架系统LQG控制器的仿真研究

根据已建立的1/2车体动力学模型和单轨路面输入模型,设计车辆主动悬架的线性二次型高斯(LQG)最优控制器,利用MATLAB/SIMULINK软件构建路面输入仿真模型和1/2车体仿真模型.结果分析证实,具有LQG控制器的主动悬架可以改善车辆的运行性能.