Efficient score tests for heteroskedasticity in micro-economics

Kruskal's theorem is used to provide simple and elegant alternative derivations of the efficiency of some two step estimators (2SE) for models containing anticipated and unanticipated variables. Several new results are established: 2SE is not efficient for a structural equation with current and lagged values of both anticipated and unanticipated variables; 2SE is always efficient for the parameter associated with the current unanticipated variable, and for the parameter associated with the lagged unanticipated variable if there is no lagged dependent variable in the expectations equation; the inclusion of additional regressors in the structural equation and contemporaneous correlation of the structural and expectations errors can both be analysed in a straightforward manner; the single-equation generalized least squares estimator can be as efficient as the systems maximum likelihood estimator.     

Trainees' Views of the Step Up to Social Work Programme

There are long-standing concerns about the quantity and quality of social workers in England. Several initiatives have sought to change application and training processes, among which are employment-based routes whereby students are placed with social work employers and receive substantial funding compared to other students, and employers are more closely engaged with higher education elements of their training. This article presents and analyses the views of the first cohort of students, termed trainees, in one such initiative, the Step Up to Social Work programme that commenced in 2010. Data were collected by online survey, administered at four time points with response rates ranging from 78% at Time 1 to 71% at Time 2, 64% at Time 3 and 71% at Time 4. Findings revealed that the respondents were largely satisfied with their training and the Step Up initiative, although reservations were expressed by some about academic teaching, programme organisation and apparent lack of account of trainees' previous experiences. Findings also reveal the type and extent of the trainees' academic achievements and professional experiences. The findings from this first cohort of trainees may usefully inform other employment-based routes and social work education more generally.     

Covariance changes detection in multivariate time series

This paper studies the detection of step changes in the variances and in the correlation structure of the components of a vector of time series. Two procedures based on the likelihood ratio test (LRT) statistic and on a cumulative sums (cusum) statistic are considered and compared in a simulation study. We conclude that for a single covariance change the cusum procedure is more powerful in small and medium samples, whereas the likelihood ratio test is more powerful in large samples. However, for several covariance changes the cusum procedure works clearly better. The procedures are illustrated in two real data examples.     

二项分布的一种新的计算方法——逐步逼近法

本文指出了二项分布的Poisson分布逼近误差,并提出了改进的办法,即在Poisson分布的基础上乘上一系列的修正因子,使逼近精度逐次提高。从而将庞大的阶乘循环运算(容易产生溢出)转化为简单的函数运算,并能达到任意给定的精度要求。     

A Bayesian restoration of an ion channel signal

We present a Bayesian method of ion channel analysis and apply it to a simulated data set. An alternating renewal process prior is assigned to the signal, and an autoregressive process is fitted to the noise. After choosing model hyperconstants to yield 'uninformative' priors on the parameters, the joint posterior distribution is computed by using the reversible jump Markov chain Monte Carlo method. A novel form of simulated tempering is used to improve the mixing of the original sampler.     

功率步进电机的细分驱动

随着数字控制技术、微电子技术的发展和微型计算机的普及与应用,作为步进电机驱动技术重要分支之一的细分驱动技术的研究与应用显得日益重要了。本文对功率步进电机细分驱动技术作了较全面的理论分析,并给出了步进电机步距角均匀细分获得较高的细分精度的运行条件。     

When are two step estimators efficient?

Kruskal's theorem is used to provide simple and elegant alternative derivations of the efficiency of some two step estimators (2SE) for models containing anticipated and unanticipated variables. Several new results are established: 2SE is not efficient for a structural equation with current and lagged values of both anticipated and unanticipated variables; 2SE is always efficient for the parameter associated with the current unanticipated variable, and for the parameter associated with the lagged unanticipated variable if there is no lagged dependent variable in the expectations equation; the inclusion of additional regressors in the structural equation and contemporaneous correlation of the structural and expectations errors can both be analysed in a straightforward manner; the single-equation generalized least squares estimator can be as efficient as the systems maximum likelihood estimator.     

《尚书·牧誓》誓师解

《牧誓》是一篇誓师词,然而"步伐止齐"旧解难圆。根据文意,"伐"当解为"口伐"(声讨)而不是"击刺",而"步伐止齐"是部队向敌军进逼过程中的动作与要求,避免了旧解"击剌"所带来的打打停停的矛盾。根据周武王伐商部队的多方国联合特点,其整齐阵容虽然是从部队整体着眼,而在较大程度上是针对其余的八个方国在进军中可能发生的首鼠两端和惧死不前现象。     

Stepping Down and Stepping In: Youth's Perspectives on Making the Transition from Residential Treatment to Treatment Foster Care

Older youth preparing to emancipate from the foster care system are often served in residential treatment settings where they have limited opportunities to practice skills for independent living in a community setting. Stepping these youth down to less restrictive environments such as treatment foster care is a growing trend, especially for youth with mental health issues. Yet, few studies have explored the youth's perspective on making this transition. This study utilized qualitative interviews with youths who were participating in a treatment foster care intervention study (n = 8) to gain their perspectives on the process of transitioning from residential care. Youths were interviewed right before they exited residential care and two months after placement in the new foster home. Youths reported hopes for gaining family in the new home as well as fears of placement disruption. Findings point to the need to enlist youths in discussion and problem solving about difficulties they anticipate in the new home and expectations for their relationship with the new foster parents. In addition, the struggles described after two months in the home point to the need for youths to build specific skills to better manage ongoing relationships with foster parents and for foster parent training on how to help build these skills.     

PLC实现的模糊PID控制器研究

设计了模糊PID控制器,在MTLAB环境下离线计算出了查询表,采用西门子S7—300在Step7软件中利用查表法实现了程序的设计。结合一阶模型进行实验,结果表明,这种方法能在线调整PID参数,取得了不错的效果。