参数未知的房地产投资系统混沌同步

针对经济增长系统参数未知时,房地产投资驱动系统与经济增长响应系统的同步问题,基于Lya-punov稳定性理论和自适应控制方法,给出了两系统渐近同步的一个充分条件和自适应控制律。数值模拟验证了控制策略的有效性。     

Cointegration in Fractional Systems with Unknown Integration Orders

Cointegrated bivariate nonstationary time series are considered in a fractional context, without allowance for deterministic trends. Both the observable series and the cointegrating error can be fractional processes. The familiar situation in which the respective integration orders are 1 and 0 is nested, but these values have typically been assumed known. We allow one or more of them to be unknown real values, in which case Robinson and Marinucci (2001, 2003) have justified least squares estimates of the cointegrating vector, as well as narrow‐band frequency‐domain estimates, which may be less biased. While consistent, these estimates do not always have optimal convergence rates, and they have nonstandard limit distributional behavior. We consider estimates formulated in the frequency domain, that consequently allow for a wide variety of (parametric) autocorrelation in the short memory input series, as well as time‐domain estimates based on autoregressive transformation. Both can be interpreted as approximating generalized least squares and Gaussian maximum likelihood estimates. The estimates share the same limiting distribution, having mixed normal asymptotics (yielding Wald test statistics with χ² null limit distributions), irrespective of whether the integration orders are known or unknown, subject in the latter case to their estimation with adequate rates of convergence. The parameters describing the short memory stationary input series are √n‐consistently estimable, but the assumptions imposed on these series are much more general than ones of autoregressive moving average type. A Monte Carlo study of finite‐sample performance is included.     

Youth interaction with online strangers: experiences and reactions to unknown people on the Internet

Previous research on youths’ experiences with online strangers has mostly utilized quantitative designs which may result in the omission of important parts of the youths’ experiences and perceptions. In this qualitative study, we adopt a child-centred approach and focus on the children’s and adolescents’ experiences with unknown people from the Internet. This is one of the most pronounced parental concerns, despite the fact that an online presence is now normative for most children. We use the data from focus-groups and individual interviews in nine European countries (N?=?368) conducted with youths between the ages of 9 and 16 years. Participants were asked about their perceptions of potentially negative or problematic situations while using the Internet and digital technology. Using thematic analysis, we classified youths’ experiences and reactions related to interacting with online strangers in four themes: (1) non-verbal interaction; (2) initiation of contact; (3) communication; and (4) face-to-face meeting. In all four levels of interactions, children and adolescents reported a variety of positive and negative experiences and reactions. We interpret our findings with a co-construction model which perceives children and adolescents as active participants in the online world. We conclude that children are successfully making active decisions to initiate, continue, and stop interactions with unknown people from the Internet. These findings broaden the current perspectives of youths’ meetings with unknown people online.     

老子“知不知”的养生观

老子是中国养生学的开创者,其养生智慧集中体现在＂知不知＂的要求上。在他看来,人的疾病主要是由于心智不明所导致的。因此,他在＂病病不病＂的独特疾病观基础上,强调养生要诀在于知常复命,关键是抱道不失。如此说来,在生活中坚持＂惟道是从＂与＂唯施是畏＂,就是养生健康的不二法门,亦即,要知＂道＂、行＂道＂。     

Some comments on two-stage selection procedures

In this paper we study the procedures of Dudewicz and Dalal ( 1975 ), and the modifications suggested by Rinott ( 1978 ), for selecting the largest mean from k normal populations with unknown variances. We look at the case k = 2 in detail, because there is an optimal allocation scheme here. We do not really allocate the total number of samples into two groups, but we estimate this optimal sample size, as well, so as to guarantee the probability of correct selection (written as P(CS)) at least P^?, 1/2 < P^? < 1 . We prove that the procedure of Rinott is “asymptotically in-efficient” (to be defined below) in the sense of Chow and Robbins ( 1965 ) for any k  2. Next, we propose two-stage procedures having all the properties of Rinott's procedure, together with the property of “asymptotic efficiency” - which is highly desirable.     

基于免疫的Windows未知病毒检测方法

Windows未知病毒令传统反病毒技术疲于应付、防不胜防,且查杀效果不佳。该文借鉴人工免疫思想,在深入剖析Windows PE病毒逻辑结构基础上,提出利用病毒重定位模块作为病毒基因来生成抗体以检测病毒的方法,且建立了自体与非自体、抗原提呈以及抗体生成的动态演化数学模型。实验表明,该方法对于未知WindowsPE病毒的检测率较高,且具有自适应、自学习能力。     

Comparison of estimators for heteroskedastic models

Ordinary least squares (OLS) yield inefficient parameter estimates and inconsistent estimates of the covariance matrix in case of heteroskedastic errors. Robinson's adaptive estimator and the Cragg estimator avoid any explicit parameterization of heteroskedasticity, and reduce the danger of misspecification. A small Monte Carlo experiment is performed to compare the behavior of the adaptive estimator with the performance of the Cragg estimator. The Monte Carlo experiment includes simulations of the Generalized Least Squares (GLS) estimator. Indeed, an interesting question is how more sophisticated techniques, like the adaptive estimator, compare with GLS when the latter relies on an incorrect specification of the heteroskedastic process. It turns out that the regression parameters, when estimated adaptively, display small mean squared errors and great efficiency in case of medium or high heteroskedasticity. The covariance matrix, instead, is better estimated by the Cragg estimator or by GLS based on a misspecified error term, since the adaptive estimator overpredicts the standard errors of the regression parameters.     

Adaptive sequential procedures for comparing new treatments with a standard

In this paper we propose and study two sequential elimination procedures for selecting all new treatments better than a standard or control treatment. These procedures differ from those previously proposed in that we assume variances are unequal and unknown. Expressions for asymptotic expected sample sizes are given. Confidence intervals associated with the procedures are also discussed.     

Critical values and powers for tests of uniformity of directions under multivariate normality

The Rayleigh, Ajne, Giné and two new tests of uniformity of directions are investigated as tests for multivariate normality when the population mean vector and covariance matrix are assumed to be unknown. The new tests include one which is designed especially to detect for bimodal alternatives and one which is designed to perform well under a wide variety of alternatives. Simulated percentile points are obtained under the assumption that the variates constitute a random sample from a multivariate normal distribution. Powers of the five tests are compared under alternatives in the bivariate as well as higher dimensional settings.     

读者体验与创造中的《未选之路》

美国读者反应批评打开了通向讨论文学解释中个人体验的大门.其主要理念是:文学是通过读者的阅读体验,促进读者对文本意义进行创造性的创作和现实化.这是把文学范式的批评中心从文学的本义转向读者的体验的一个决定性的转折.笔者以此为基点,选取罗伯特·弗罗斯特的<未选之路>为典型,深刻观察读者对诗歌的体验和创作经历,揭示了文学实体向生活回归中的价值意义和哲学启示.