What Cruising Infants Understand about Support for Locomotion

“Cruising” infants can only walk using external support to augment their balance. We examined cruisers' understanding of support for upright locomotion under four conditions: cruising over a wooden handrail at chest height, a large gap in the handrail, a wobbly unstable handrail, and an ill‐positioned low handrail. Infants distinguished among the support properties of the handrails with differential attempts to cruise and handrail‐specific forms of haptic exploration and gait modifications. They consistently attempted the wood handrail, rarely attempted the gap, and occasionally attempted the low and wobbly handrails. On the wood and gap handrails, attempt rates matched the probability of cruising successfully, but on the low and wobbly handrails, attempt rates under‐ and overestimated the probability of success, respectively. Haptic exploration was most frequent and varied on the wobbly handrail, and gait modifications—including previously undocumented “knee cruising”—were most frequent and effective on the low handrail. Results are discussed in terms of developmental changes in the meaning of support.     

Improved cross-entropy method for estimation

The cross-entropy (CE) method is an adaptive importance sampling procedure that has been successfully applied to a diverse range of complicated simulation problems. However, recent research has shown that in some high-dimensional settings, the likelihood ratio degeneracy problem becomes severe and the importance sampling estimator obtained from the CE algorithm becomes unreliable. We consider a variation of the CE method whose performance does not deteriorate as the dimension of the problem increases. We then illustrate the algorithm via a high-dimensional estimation problem in risk management.     

Social networks and the organisation of big business groups in post New Economic Policy (NEP) era in the 1990s in Malaysia

Personal ties are generally regarded as important to big business growth in Malaysia, particularly after the New Economic Policy (NEP) in the 1990s. Common types are informal ones established between multi-ethnic big business people and Malay key state and political leaders. Other types of ties, company directorship links and informal ties, are seldom studied especially those between the business people and former state bureaucrats and corporate professionals. Thus, by conceptualising the directorship links and informal personal ties as social networks, the author conducted a sociological analysis of some intra- and inter-ethnic directorship links and ties established by four prominent big businessmen after the NEP in the 1990s. This article reports the main finding on the links and ties becoming a common organisational mechanism of business groups owned and controlled by the businessmen, besides providing access to the state. Therefore, another understanding of inter- and intra-ethnic personal ties in big business growth, especially after the NEP is achieved.     

Improving Weight of Evidence Approaches to Chemical Evaluations

Federal and other regulatory agencies often use or claim to use a weight of evidence (WoE) approach in chemical evaluation. Their approaches to the use of WoE, however, differ significantly, rely heavily on subjective professional judgment, and merit improvement. We review uses of WoE approaches in key articles in the peer‐reviewed scientific literature, and find significant variations. We find that a hypothesis‐based WoE approach, developed by Lorenz Rhomberg et al., can provide a stronger scientific basis for chemical assessment while improving transparency and preserving the appropriate scope of professional judgment. Their approach, while still evolving, relies on the explicit specification of the hypothesized basis for using the information at hand to infer the ability of an agent to cause human health impacts or, more broadly, affect other endpoints of concern. We describe and endorse such a hypothesis‐based WoE approach to chemical evaluation.     

Impact of Parenting Behaviors on Recent Alcohol Use Among African American Students

Parenting is a critical factor in substance abuse prevention. Positive parenting behaviors are identified as a protective factor for substance abuse among youth. Limited research exists that investigates the role of parenting practices on minority youth substance use. The present study seeks to examine correlates between parenting and recent alcohol use among African American youth. Specifically, to what extent do African American students report experiencing specific parenting behaviors that are measured by the National Household Survey on Drug Use and Health?, do specific parenting behaviors increase the risk of recent alcohol use among African American youth?, does the impact of parenting behaviors on recent alcohol use among African American youth differ based on sex (males and females) and age category (12–13, 14–15, and 16–17 years old) were examined in this study? Logistic regression analysis of the National Household Survey on Drug Use and Health was conducted to examine the research questions. Findings indicated that parenting behaviors was associated with recent alcohol among youth. Significant differences were found for males, females, 12–13, 14–15, and 16–17 years olds. Study findings demonstrate the importance of positive parenting behaviors in youth alcohol prevention. Program specialists may target parenting as a means of preventing and reducing youth alcohol use among African American youth.     

New recursive estimators of the time-average variance constant

Estimation of the time-average variance constant (TAVC) of a stationary process plays a fundamental role in statistical inference for the mean of a stochastic process. Wu (2009) proposed an efficient algorithm to recursively compute the TAVC with \(O(1)\) memory and computational complexity. In this paper, we propose two new recursive TAVC estimators that can compute TAVC estimate with \(O(1)\) computational complexity. One of them is uniformly better than Wu’s estimator in terms of asymptotic mean squared error (MSE) at a cost of slightly higher memory complexity. The other preserves the \(O(1)\) memory complexity and is better then Wu’s estimator in most situations. Moreover, the first estimator is nearly optimal in the sense that its asymptotic MSE is \(2^{10/3}3^{-2} \fallingdotseq 1.12\) times that of the optimal off-line TAVC estimator.     

“镇改市”过程中的制约因素与改革进路

“镇改市”是我国基层行政体制改革的试验,也是在新型城镇化过程中对基层行政区划改革做出的有益尝试。以构建大中小城市和小城镇协调发展的城镇化空间格局为目标指向,通过激活中小城市的发展“命脉”,改变单纯依靠经济推动乡镇发展的路径依赖,实现“农民城”向新型城镇的跨越,是中国经济发展的新探索。然而,随着改革的推进,缺位的行政规划设计、有限的乡镇管理能力、被异化的政绩观念、社会组织发育不成熟以及市民文化普及不到位等,对“镇改市”的推进造成一定程度的制约,成为“镇改市”过程中难以回避的现实问题。问题的化解离不开政策的引导、技术的支持和法治的保障,这三个维度相互联系、缺一不可,共同为“镇改市”改革的顺利实施“保驾护航”。     

THE IMPACT OF EXTREME OBSERVATIONS ON SIMPLE FORECASTING METHODS*

In general linear modeling, an alternative to the method of least squares (LS) is the least absolute deviations (LAD) procedure. Although LS is more widely used, the LAD approach yields better estimates in the presence of outliers. In this paper, we examine the performance of LAD estimators for the parameters of the first-order autoregressive model in the presence of outliers. A simulation study compared these estimates with those given by LS. The general conclusion is that LAD does not deal successfully with additive outliers. A simple procedure is proposed which allows exception reporting when outliers occur.     

A DISCRETE DYNAMIC OPTIMIZATION MODEL FOR MADE-TO-ORDER COST ANALYSIS

A model is presented that yields optimal production rates for a firm producing a contracted order. The model is unique in that it considers the influence of production rate and learning on total program cost. An application to the specific characteristics of two military production programs is presented. As demonstrated by the application, models of this type may be used as decision-making tools when negotiating the cost impact of contract modifications.