悬浮液进样-火焰原子吸收光谱法测定怀地黄中的铜

介绍了一种悬浮液进样火焰原子吸收光谱法（FAAS）测定怀地黄中铜的方法。以琼脂为悬浮剂将粉碎、过筛的怀地黄样品均匀、稳定地悬浮于琼脂溶胶中,直接喷入空气-乙炔火焰中,采用标准加入法测定,省去了以往繁琐的样品化学前处理过程,解决了因操作环节多,被测元素丢失或污染所引起的分析误差。用该法测定怀地黄样品,并与湿法消化法对照,获得满意结果。该方法简便、快速,准确,可以代替湿法消化法。     

Sample Selection in Randomized Experiments: A New Method Using Propensity Score Stratified Sampling

Abstract

Randomized experiments are often seen as the “gold standard” for causal research. Despite the fact that experiments use random assignment to treatment conditions, units are seldom selected into the experiment using probability sampling. Very little research on experimental design has focused on how to make generalizations to well-defined populations or on how units should be selected into an experiment to facilitate generalization. This article addresses the problem of sample selection in experiments by providing a method for selecting the sample so that the population and sample are similar in composition. The method begins by requiring that the inference population and eligibility criteria for the study are well defined before study recruitment begins. When the inference population and population of eligible units differs, the article provides a method for sample recruitment based on stratified selection on a propensity score. The article situates the problem within the example of how to select districts for two scale-up experiments currently in recruitment.     

多变量模型参数的贝叶斯估计及其在农业研究中的应用

对于农业研究中多变量线性模型参数的估计,以往常采用经典统计方法。随着计算机技术的进步,贝叶斯统计方法在科学研究的各个领域迅速发展。文章利用贝叶斯统计方法对农业研究中的多变量模型进行参数估计,并与经典统计方法进行比较,验证了贝叶斯方法的有效性。该方法可为农业研究中多变量模型参数的估计提供新的途径和手段。     

关于随机抽样教学的探讨

结合教学实践,对在随机抽样教学中如何充实内容,合理地处理教材,以激发学生的求知欲望,培养其创新能力等问题进行了探讨。     

我国民众心理和谐状况研究

心理和谐是国家构建和谐社会的重要组成部分。项目组采用质化和量化研究相结合的方法,理清了心理和谐的内涵和结构,自主开发出满足心理测量学要求的测量工具。在全国进行了较大规模的抽样调查,初步揭示了我国民众当前的心理和谐状况,并基于研究结果,提出了心理和谐建设的政策建议。     

General space-efficient sampling algorithm for suboptimal alignment

Suboptimal alignments always reveal additional interesting biological features and have been successfully used to informally estimate the significance of an optimal alignment. Besides, traditional dynamic programming algorithms for sequence comparison require quadratic space, and hence are infeasible for long protein or DNA sequences. In this paper, a space-efficient sampling algorithm for computing suboptimal alignments is described. The algorithm uses a general gap model, where the cost associated with gaps is given by an affine score, and randomly selects an alignment according to the distribution of weights of all potential alignments. If x and y are two sequences with lengths n and m, respectively, then the space requirement of this algorithm is linear to the sum of n and m. Finally, an example illustrates the utility of the algorithm.     

微分作用在仪表控制算法中的仿真和应用

讨论数字PID控制中采样周期、饱和限幅对微分量的影响。在增量型PID公式的基础上,提出一种变采样周期的算法。在带时滞惯性的工业过程控制中,可以更精确地实现微分控制。经过仿真验证,证明该思路适合工业现场使用的嵌入式PID控制器。     

一种基于遗传算法的采样网页更新策略

研究一种基于采样的网页更新策略,并在此基础上提出一种基于遗传算法的求网页改变率及影响其值的相关参数的方法。     

输出快采样的ARMA模型最小二乘盲辨识方法

利用输出比输入快速采样方法研究ARMA模型的盲辨识问题,提出了最小二乘盲辨识方法。通过选择适当的快采样率及归一化系统模型参数之后,仅利用快采样得到的输出信号实现了系统模型参数的估计。仿真例子表明所提盲辨识方法的有效性。     

菜用大豆核心种质构建策略研究

核心种质是种质资源研究的新领域,构建核心种质是研究和利用植物遗传资源的便捷途径。本研究采用基于田间实际数据的计算机模拟方法构建两个菜用大豆种质资源群体,应用最小距离逐步取样法研究菜用大豆核心种质的构建策略,采用极差符合率和变异系数变化率两个参数对构建策略进行评价,利用主成分分析确认核心种质的代表性。研究表明,采用最小距离逐步取样法构建菜用大豆核心种质的最佳遗传距离为欧式距离,最佳取样比例为95%。