A Note on Sufficient Conditions for Valid Unmodified t Testing in Correlation Analysis with Autocorrelated and Heteroscedastic Sample Data

Traditionally, sphericity (i.e., independence and homoscedasticity for raw data) is put forward as the condition to be satisfied by the variance–covariance matrix of at least one of the two observation vectors analyzed for correlation, for the unmodified t test of significance to be valid under the Gaussian and constant population mean assumptions. In this article, the author proves that the sphericity condition is too strong and a weaker (i.e., more general) sufficient condition for valid unmodified t testing in correlation analysis is circularity (i.e., independence and homoscedasticity after linear transformation by orthonormal contrasts), to be satisfied by the variance–covariance matrix of one of the two observation vectors. Two other conditions (i.e., compound symmetry for one of the two observation vectors; absence of correlation between the components of one observation vector, combined with a particular pattern of joint heteroscedasticity in the two observation vectors) are also considered and discussed. When both observation vectors possess the same variance–covariance matrix up to a positive multiplicative constant, the circularity condition is shown to be necessary and sufficient. “Observation vectors” may designate partial realizations of temporal or spatial stochastic processes as well as profile vectors of repeated measures. From the proof, it follows that an effective sample size appropriately defined can measure the discrepancy from the more general sufficient condition for valid unmodified t testing in correlation analysis with autocorrelated and heteroscedastic sample data. The proof is complemented by a simulation study. Finally, the differences between the role of the circularity condition in the correlation analysis and its role in the repeated measures ANOVA (i.e., where it was first introduced) are scrutinized, and the link between the circular variance–covariance structure and the centering of observations with respect to the sample mean is emphasized.     

苏区的反“围剿”战争与人民战争思想的形成

南昌、秋收、广州三大起义失败后,中国共产党开始将革命的重心逐渐由城市转向广大的农村。这一转移,也是共产党选择以＂面＂打＂点＂战略的开始。为了贯彻以＂面＂打＂点＂这一战略,共产党在各苏区进行了广泛的动员与组织,并围绕着反＂围剿＂战争的需要开展其他战争准备工作,从而使人民战争的思想在反＂围剿＂战争中得到不断的发展。     

The aesthetic life of artificial flavors

Abstract

Artificiality is usually understood as that which is man-made and is in contraposition to the natural. The term itself is increasingly recognized as a negative pole, while the label of “natural” is exploited as guarantee of healthiness in marketing food campaigns. This article takes issue with the natural/artificial debate by emphasizing the aesthetic side of artificial flavorings – chemical substances designed to alter or enhance the taste of processed foods. Here, I reconsider the conception of artificiality as a poor imitation of nature and instead underline the link between technology and aesthetics, by examining the practice of flavorists. Through ethnographic detail I call for moving the synthetic out of the “inauthentic” and argue that the attempt to mimic natural flavors through synthesis is not only an act of imitation and resemblance (as critics exclusively contend) but can also be thought as an act of representation and interpretation (as my fieldwork illuminates).     

A comparison of micro versus macro point estimators for markov-process models

We compare, by means of factorially designed Monte Carlo simulation experiments, the performance of (macro-data) restricted least-squares point estimators with that of (micro-data) maximum likelihood estimators for Markov-process models. We find, by various measures of estimator accuracy, that micro data are approximately ten times more valuable than macro data. We also find evidence that a small state space, a long time series, and a large number of entities observed enhance performance.     

Individualism and Collectivism in Israeli Society: Comparing Religious and Secular High-School Students

Triandis' theoretical framework, concerningcultural patterns labeled individualism andcollectivism, is probed with regard to the religiousmarker in the Israeli Jewish society. Three methods areused to examine collectivism-individualismconstructs in 185 religious and 956 secular high schoolstudents: value items, interest in different domains ofhistory, and attitudes toward political issues. A common collective basis of mutual value consensus wasfound in the two groups; however, as predicted, therewere differences between secular and religious studentson the three kinds of items, since the religious scored higher than the secular students onitems emphasizing collectivist orientation. Thedifferences, however, do not fit the common theoreticalframework of collectivism-individualism, but rather tend to reflect the distinction between in-group anduniversal collectivism.     

基于混合智能算法模型的无功优化的应用

电力系统无功优化是保证电网安全可靠运行的重要指标之一。从经济效益和运行约束条件出发,建立了符合实际数学模型。考虑到遗传算法的早熟收敛及蚁群算法需要较长的搜索时间,采用混合算法对IEEE-14进行仿真,结果和常规的算法作比较,结果证明时间效率和求解效率都优于传统的算法。     

基于消费者隐性需求的营销模式研究策略

消费者隐性需求的相关理论和实践研究逐渐受到国内外学者的重视,这对于营销理论的再造和营销学的演进具有一定的理论价值。本文从营销范式的演进规律归纳得出,营销范式的转换归根结底源于隐性需求的开发。在此基础上,对传统营销模式及营销组合对隐性需求研究的普适性进行了检验,并探讨了基于隐性需求的4Vs营销模式及其现实意义。     

Joint supplier selection and scheduling of customer orders under disruption risks: Single vs. dual sourcing

This paper presents a stochastic mixed integer programming approach to integrated supplier selection and customer order scheduling in the presence of supply chain disruption risks, for a single or dual sourcing strategy. The suppliers are assumed to be located in two different geographical regions: in the producer's region (domestic suppliers) and outside the producer's region (foreign suppliers). The supplies are subject to independent random local disruptions that are uniquely associated with a particular supplier and to random semi-global (regional) disruptions that may result in disruption of all suppliers in the same geographical region simultaneously. The domestic suppliers are relatively reliable but more expensive, while the foreign suppliers offer competitive prices, however material flows from these suppliers are more exposed to unexpected disruptions. Given a set of customer orders for products, the decision maker needs to decide which single supplier or which two different suppliers, one from each region, to select for purchasing parts required to complete the customer orders and how to schedule the orders over the planning horizon, to mitigate the impact of disruption risks. The problem objective is either to minimize total cost or to maximize customer service level. The obtained combinatorial stochastic optimization problem will be formulated as a mixed integer program with conditional value-at-risk as a risk measure. The risk-neutral and risk-averse solutions that optimize, respectively average and worst-case performance of a supply chain are compared for a single and dual sourcing strategy and for the two different objective functions. Numerical examples and computational results are presented and some managerial insights on the choice between the two sourcing strategies are reported.     

合成邻氨基苯甲醚反应条件的研究

用定量的试验方法,在合成邻氨基苯甲醚中,对甲氧基化反应和硝基还原反应的较佳反应条件做了探讨。结果是邻氨基苯甲醚的收率比现行工业各合成路线提高5％以上,为工业生产邻氨基苯甲醚提供了新的依据。     

论房屋承租人的优先购买权--以《合同法》第230条存在的必要性为视角

现行合同法对房屋承租人的保护主要体现在两方面:一是赋予房屋承租人优先购买权;二是“买卖不破租赁”。但房屋承租人的优先购买权虽是一项法定权利,承租人行使优先购买权的具体条件和方式,在实践中往往缺乏操作性,并且现实中鲜有发生;《合同法》第229条规定的“买卖不破租赁”已经能够有效保障承租人的权利。况且,随着我国住房制度的深入改革与房地产交易活动的频繁,这样的偏向性法律保护势必妨碍和限制私权,有悖于现代民法的精神。故笔者认为,在将来修改、完善法律时应当删除230条,从立法上取缔对房屋承租人优先购买权的保护。