A counterexample to Beder's conjectures about Hadamard matrices

In this note we provide a counterexample which resolves conjectures about Hadamard matrices made in this journal. Beder [1998. Conjectures about Hadamard matrices. Journal of Statistical Planning and Inference 72, 7–14] conjectured that if H$\mathit{H}$ is a maximal m×n$m\times n$ row-Hadamard matrix then m is a multiple of 4; and that if n   is a power of 2 then every row-Hadamard matrix can be extended to a Hadamard matrix. Using binary integer programming we obtain a maximal 13×32$13\times 32$ row-Hadamard matrix, which disproves both conjectures. Additionally for n being a multiple of 4 up to 64, we tabulate values of m   for which we have found a maximal row-Hadamard matrix. Based on the tabulated results we conjecture that a m×n$m\times n$ row-Hadamard matrix with m?n-7$m?n-7$ can be extended to a Hadamard matrix.     

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.     

A re-evaluation of random-effects meta-analysis

Summary.  Meta-analysis in the presence of unexplained heterogeneity is frequently undertaken by using a random-effects model, in which the effects underlying different studies are assumed to be drawn from a normal distribution. Here we discuss the justification and interpretation of such models, by addressing in turn the aims of estimation, prediction and hypothesis testing. A particular issue that we consider is the distinction between inference on the mean of the random-effects distribution and inference on the whole distribution. We suggest that random-effects meta-analyses as currently conducted often fail to provide the key results, and we investigate the extent to which distribution-free, classical and Bayesian approaches can provide satisfactory methods. We conclude that the Bayesian approach has the advantage of naturally allowing for full uncertainty, especially for prediction. However, it is not without problems, including computational intensity and sensitivity to a priori judgements. We propose a simple prediction interval for classical meta-analysis and offer extensions to standard practice of Bayesian meta-analysis, making use of an example of studies of 'set shifting' ability in people with eating disorders.     

Nonparametric density deconvolution by weighted kernel estimators

Nonparametric density estimation in the presence of measurement error is considered. The usual kernel deconvolution estimator seeks to account for the contamination in the data by employing a modified kernel. In this paper a new approach based on a weighted kernel density estimator is proposed. Theoretical motivation is provided by the existence of a weight vector that perfectly counteracts the bias in density estimation without generating an excessive increase in variance. In practice a data driven method of weight selection is required. Our strategy is to minimize the discrepancy between a standard kernel estimate from the contaminated data on the one hand, and the convolution of the weighted deconvolution estimate with the measurement error density on the other hand. We consider a direct implementation of this approach, in which the weights are optimized subject to sum and non-negativity constraints, and a regularized version in which the objective function includes a ridge-type penalty. Numerical tests suggest that the weighted kernel estimation can lead to tangible improvements in performance over the usual kernel deconvolution estimator. Furthermore, weighted kernel estimates are free from the problem of negative estimation in the tails that can occur when using modified kernels. The weighted kernel approach generalizes to the case of multivariate deconvolution density estimation in a very straightforward manner.     

质量建设是辅导员队伍建设的根本

辅导员工作在高校思想政治工作中居于重要地位。在新的历史时期,辅导员工作内容发生了根本性的改变,要求其从业人员具有更高的综合素质。加强辅导员队伍质量建设已成为高校思想政治工作中亟待解决的问题。     

英国农村发展模式对中国新农村建设的启示

农村发展模式是指农村发展的样式及所呈现的特点。在这个意义上,英国的农村发展道路走的是典型的内发变迁模式,即结合本国实际情况主要依靠本国自身力量来实现农业现代化和城乡一体化的一种方式。在中国建设社会主义新农村的关键时期,针对中国新农村建设在资金、组织方式等方面的实际情况和问题,英国农村发展模式的特征及经验,具有有益的借鉴启示。     

Race and opportunity in a public alternative school

This qualitative case-study explores questions about the stratifying role of public alternative schools created for ‘at-risk’ youth by analyzing the school experience of students who attend a single continuation high school and the process of student enrollment and referral to that school. Drawing on the concept of whiteness as property, this article demonstrates how the continuation high school maintained and protected the property functions of whiteness through acts of symbolic violence and the systematic removal of non-white students from the school district’s mainstream high school. Instead, students were placed in a substandard alternative school lacking in material and intellectual resources. Furthermore, teachers, counselors, and administrative staff at the mainstream and continuation high schools alike drew upon the racial ideology of merit to rationalize the overrepresentation of non-white youths at the study school and to ‘deracialize’ the student referral process.     

Imagining mobility: the prospective cognition question in migration research

Most migration research is focused on migrant experiences after mobility and settlement. We argue that empirical researchers would benefit from studying how cognitive migration, the narrative imagining of oneself inhabiting a foreign destination prior to the actual physical move, influences migration behaviour. This article notes a gap in our current understanding of the process by which individuals decide to cross international borders and offers an agenda for remedying this. The interdisciplinarity of migration research has not fully extended to social psychology or cognitive social sciences, where a dynamic research agenda has examined human decision-making processes, including prospection and the connections between culture and cognition. The study of socio-cognitive processes in migration decision-making has been largely overlooked because of the after-the-fact nature of data collection and analysis rather than an aversion to these approaches per se. We highlight a number of strategic findings from this diverse field, provide examples of migration scholarship that has benefited from these insights, and raise questions about the sides of migration process that have received insufficient attention. A more nuanced understanding of prospective thinking—imagining potential futures—can shed light on the classic puzzle of why some people move while others in comparable situations do not.     

Emotions and cosmopolitan sociability: Barriers and opportunities for intercultural encounters amongst new Chinese migrants in New Zealand

Emotions matter, particularly in experiences of migration. This article explores how emotions are involved in everyday intercultural encounters and the role of emotions in generating cosmopolitan sociability in the context of migration. The article is based upon qualitative research with 80 Chinese 1st and 1.5 generation migrants in New Zealand. We focus on ‘contact zones’ as social spaces where migrants have uneven opportunities to encounter cultural others and where ‘emotional dissonance’ can emerge through unsuccessful intercultural exchanges. In order to generate a sense of comfort and familiarity in such conflicted spaces, migrants need to invest in ‘emotional labour’ to engage in more cosmopolitan sociability as an attempt to transform ‘contact zone’ to ‘comfort zone’. Through this article we argue that emotions can both promote and encourage, but also undermine and limit the capacity to perform cosmopolitan sociability and build intercultural relations.     

Bullying and Victimization Among Young Elementary School Children: The Role of Child Ethnicity and Ethnic School Composition

School-aged children with an ethnic minority background are relatively often involved in bullying and victimization, but the role of ethnic composition of schools in this context remains unclear. This study examined the relation between ethnic minority background, ethnic school composition, and bullying behaviour around primary school entry in the Netherlands. The study was based on a 2008/2009 school survey in Rotterdam, a Dutch city where about 50 % of children have a non-Dutch background. For 8523 children, teacher reports of bullying behaviour at age 5–6 years were available. Children with a non-Dutch background had higher odds of being a victim (adjusted OR 1.41, 95 % CI 1.11, 1.80), bully (OR 1.38, 95 % CI 1.20, 1.58) or bully-victim (OR 1.38, 95 % CI 1.19, 1.62) than children of Dutch national origin. Ethnic diversity in schools increased children’s risk of bullying behaviour (e.g. OR_victim per 0.1 increase in 0–1 diversity range = 1.06, 95 % CI 1.00, 1.13), with children of both Dutch and non-Dutch national origin relatively more often involved in bullying in ethnically diverse schools. The proportion of same-ethnic peers in school reduced the risk of bullying among children of Dutch national origin (e.g. OR_victim per 10 % more same-ethnic children = 0.90, 95 % CI 0.83, 0.98), but not among non-Dutch children. In conclusion, ethnic minority background and ethnic diversity within schools are risk factors for bullying among 5–6 year olds. Plausibly, reductions in absolute numbers of bullying events may be obtained with tailor-made interventions in ethnically diverse schools. Such interventions should preferably be offered early in the school curriculum.