简论语料库与教师角色之转变

现代电子语料库已有了近50年的发展,但语料库应用于课堂教学才刚刚起步。通过近年语料库辅助课堂教学诸多实践研究,教师们不仅可以获得教学中的例句,还可引导学生们学习更地道、更准确的表达方式。     

论魏晋南朝的忠孝实践——以阳翟褚氏为例

忠孝取舍孰先孰后在魏晋南朝时期有一个演变的过程,弃忠从孝是当时社会的趋势和需要。阳翟褚氏在这一时期屡屡背信弃义违背＂忠＂的道德却又信守家族＂孝＂的传统,是当时忠孝实践观的集中代表。     

A longitudinal study of depressiveness in children in public care

Rajhvajn Bulat L. A longitudinal study of depressiveness in children in public care Int J Soc Welfare 2010: 19: 412–423 © 2009 The Author, Journal compilation © 2009 Blackwell Publishing Ltd and the International Journal of Social Welfare. The aim of this article is to analyse the challenges involved when making longitudinal observations of depressiveness in children raised in public care. The first measurement comprised 375 children from children's homes and foster families; however, most of the results are based on an analysis of the 139 children who participated in both parts of the research. We used the Child Depression Inventory and the anxiety/depression subscales of Youth Self Report and Child Behaviour Checklist as measures of depressiveness. The comparison of results from the first and second measurements showed that depressiveness in children in public care decreased over time. Children who grew up in children homes were, in the first measurement, more depressed than those living in foster families, but after five years that difference had disappeared. Furthermore, decrease in depressiveness is predominantly associated with less frequent delinquent, aggressive or hyperactive behaviour, less withdrawal and better control over uncomfortable emotions.     

金融危机下中国创业投资“囚徒困境”演化研究

创业投资家和创业企业家的＂囚徒困境＂是制约中国创业投资进一步发展的主要障碍之一。对短期利益的追求和缺乏信任是造成中国创业投资＂囚徒困境＂的两个重要原因。在金融危机背景下,＂囚徒困境＂的演化将朝着有利于创业投资家的方向发展。金融危机虽然能改变博弈的结果,却未能改变＂囚徒困境＂的成因。     

New imperfect rankings models for ranked set sampling

Ranked set sampling is a sampling approach that leads to improved statistical inference in situations where the units to be sampled can be ranked relative to each other prior to formal measurement. This ranking may be done either by subjective judgment or according to an auxiliary variable, and it need not be completely accurate. In fact, results in the literature have shown that no matter how poor the quality of the ranking, procedures based on ranked set sampling tend to be at least as efficient as procedures based on simple random sampling. However, efforts to quantify the gains in efficiency for ranked set sampling procedures have been hampered by a shortage of available models for imperfect rankings. In this paper, we introduce a new class of models for imperfect rankings, and we provide a rigorous proof that essentially any reasonable model for imperfect rankings is a limit of models in this class. We then describe a specific, easily applied method for selecting an appropriate imperfect rankings model from the class.     

Inferences on correlation coefficients: One-sample,independent and correlated cases

This article concerns inference on the correlation coefficients of a multivariate normal distribution. Inferential procedures based on the concepts of generalized variables (GVs) and generalized p$p$-values are proposed for elements of a correlation matrix. For the simple correlation coefficient, the merits of the generalized confidence limits and other approximate methods are evaluated using a numerical study. The study indicates that the proposed generalized confidence limits are uniformly most accurate even for samples as small as three. The results are extended for comparing two independent correlations, overlapping and non-overlapping dependent correlations. For each problem, the properties of the GV approach and other asymptotic methods are evaluated using Monte Carlo simulation. The GV approach produces satisfactory results for all the problems considered. The methods are illustrated using a few practical examples.     

Wavelet goodness-of-fit test for dependent data

We introduce a new goodness-of-fit test which can be applied to hypothesis testing about the marginal distribution of dependent data. We derive a new test for the equivalent hypothesis in the space of wavelet coefficients. Such properties of the wavelet transform as orthogonality, localisation and sparsity make the hypothesis testing in wavelet domain easier than in the domain of distribution functions. We propose to test the null hypothesis separately at each wavelet decomposition level to overcome the problem of bi-dimensionality of wavelet indices and to be able to find the frequency where the empirical distribution function differs from the null in case the null hypothesis is rejected. We suggest a test statistic and state its asymptotic distribution under the null and under some of the alternative hypotheses.     

INSIGHTS ON SERVICE SYSTEM DESIGN FROM A NORMAL APPROXIMATION TO ERLANG'S DELAY FORMULA

We show how a simple normal approximation to Erlang's delay formula can be used to analyze capacity and staffing problems in service systems that can be modeled as M/M/s queues. The numbers of servers, s, needed in an M/M/s queueing system to assure a probability of delay of, at most, p can be well approximated by s ≅ p + z_***I-p+, where z_1-p, is the (1 - p)th percentile of the standard normal distribution and ρ, the presented load on the system, is the ratio of Λ, the customer arrival rate, to μ, the service rate. We examine the accuracy of this approximation over a set of parameters typical of service operations ranging from police patrol, through telemarketing to automatic teller machines, and we demonstrate that it tends to slightly underestimate the number of servers actually needed to hit the delay probability target—adding one server to the number suggested by the above formula typically gives the exact result. More importantly, the structure of the approximation promotes operational insight by explicitly linking the number of servers with server utilization and the customer service level. Using a scenario based on an actual teleservicing operation, we show how operations managers and designers can quickly obtain insights about the trade-offs between system size, system utilization and customer service. We argue that this little used approach deserves a prominent role in the operations analyst's and operations manager's toolbags.