相变界面流动技术的计算精度

对用于固液相变问题数值模拟的界面流动技术的精度进行了讨论，分析表明对移动界面项使用一阶有限差分不能精确地描述界面的运动，特别是在解决如爆融情况下的高热流问题，建议使用二阶方法，其在所有情况下均可保证足够的精度。     

Improving Cancer Dose–Response Characterization by Using Physiologically Based Pharmacokinetic Modeling: An Analysis of Pooled Data for Acrylonitrile-Induced Brain Tumors to Assess Cancer Potency in the Rat

Historically, U.S. regulators have derived cancer slope factors by using applied dose and tumor response data from a single key bioassay or by averaging the cancer slope factors of several key bioassays. Recent changes in U.S. Environmental Protection Agency (EPA) guidelines for cancer risk assessment have acknowledged the value of better use of mechanistic data and better dose–response characterization. However, agency guidelines may benefit from additional considerations presented in this paper. An exploratory study was conducted by using rat brain tumor data for acrylonitrile (AN) to investigate the use of physiologically based pharmacokinetic (PBPK) modeling along with pooling of dose–response data across routes of exposure as a means for improving carcinogen risk assessment methods. In this study, two contrasting assessments were conducted for AN-induced brain tumors in the rat on the basis of (1) the EPA's approach, the dose–response relationship was characterized by using administered dose/concentration for each of the key studies assessed individually; and (2) an analysis of the pooled data, the dose–response relationship was characterized by using PBPK-derived internal dose measures for a combined database of ten bioassays. The cancer potencies predicted for AN by the contrasting assessments are remarkably different (i.e., risk-specific doses differ by as much as two to four orders of magnitude), with the pooled data assessments yielding lower values. This result suggests that current carcinogen risk assessment practices overestimate AN cancer potency. This methodology should be equally applicable to other data-rich chemicals in identifying (1) a useful dose measure, (2) an appropriate dose–response model, (3) an acceptable point of departure, and (4) an appropriate method of extrapolation from the range of observation to the range of prediction when a chemical's mode of action remains uncertain.     

The relationship between employer‐provided training and the retention of older workers: Evidence from Germany

A substantial portion of Germany's workforce will soon retire, making it difficult for businesses to meet their human capital needs; training older workers may help to manage this demographic transition. The authors therefore examine the relationships between employer‐provided training programmes, wages and retirement among older workers. They find that when establishments offer special training programmes targeted at these workers, women – especially low‐paid women – are less likely to retire, possibly because of consequent wage growth. Their results suggest that such targeted training can indeed play an important role in retaining low‐wage older women and advancing their careers.     

Grading with norm-referenced or criterion-referenced measurements: To curve or not to curve,that is the question

Assigning grades is an integral and everyday part of social work education. However, social work educators, especially those teaching the academically-based as opposed to practice-based courses, must decide whether to use norm-referenced or criterion-referenced measurements to grade exams and other assignments. Norm-referenced measurement is commonly called grading on a curve in higher education. While grading on the curve is not obsolete in academia, I have eliminated it in my courses. New and perhaps experienced social work educators may benefit from a review of both grading methods. This article examines both sides of a grading issue relevant to the wider context of higher education and, therefore, relevant to social work education. Grading with norm-referenced or criterion-referenced measurements is reviewed along with issues related to both types of grading. I will describe why I grade with criterion-referenced measurement and why I believe it is a better choice for social work education.     

Pseudo maximum likelihood estimation for the dirichlet-multinomial distribution

Pseudo maximum likelihood estimation (PML) for the Dirich-let-multinomial distribution is proposed and examined in this pa-per. The procedure is compared to that based on moments (MM) for its asymptotic relative efficiency (ARE) relative to the maximum likelihood estimate (ML). It is found that PML, requiring much less computational effort than ML and possessing considerably higher ARE than MM, constitutes a good compromise between ML and MM. PML is also found to have very high ARE when an estimate for the scale parameter in the Dirichlet-multinomial distribution is all that is needed.     

Bayesian credible intervals for response surface optima

In response surface methodology, one is usually interested in estimating the optimal conditions based on a small number of experimental runs which are designed to optimally sample the experimental space. Typically, regression models are constructed from the experimental data and interrogated in order to provide a point estimate of the independent variable settings predicted to optimize the response. Unfortunately, these point estimates are rarely accompanied with uncertainty intervals. Though classical frequentist confidence intervals can be constructed for unconstrained quadratic models, higher order, constrained or nonlinear models are often encountered in practice. Existing techniques for constructing uncertainty estimates in such situations have not been implemented widely, due in part to the need to set adjustable parameters or because of limited or difficult applicability to constrained or nonlinear problems. To address these limitations a Bayesian method of determining credible intervals for response surface optima was developed. The approach shows good coverage probabilities on two test problems, is straightforward to implement and is readily applicable to the kind of constrained and/or nonlinear problems that frequently appear in practice.     

Endogenous socio-economic development in the European union — issues of evaluation

The public sector, in its policy statements and in the design of programmes of intervention, appears to be subscribing to a rhetoric of “grassroots participation”. At the same time, however, pressures are increasing for bureaucracies to adopt a managerialist modus operandi. This article considers the tensions that arise when participative service provision and programmes are subjected to evaluation scrutiny by managerialist bodies. The discussion takes place in the context of an EU-sponsored endogenous socio-economic development initiative. This prepares the ground for an exploration of participative evaluation.     

Manufacturing ghost fathers: the paradox of father presence and absence in child welfare

Fathers exist in the lives of women and children involved with child welfare authorities, and yet, they are rarely seen by child welfare. This invisibility exists whether or not fathers are deemed as risks or as assets to their families. Using an analysis of fundamental child welfare policies and practices and relevant literature, the paper examines how 'ghost' fathers are manufactured, and how this phenomenon affects families and professionals in child welfare. An analysis of gender, class, race and culture of child welfare discourses shows how these fathers are seen as deviant, dangerous, irresponsible and irrelevant, and even further, how absence in child welfare is inextricably linked to blaming mothers. In failing to work with fathers, child welfare ignores potential risks and assets for both mothers and children.