SOME COMMENTS ON “A SYSTEMS PERSPECTIVE ON MATERIALS REQUIREMENTS PLANNING”*

We believe there are some serious deficiencies in the Morecroft article on MRP problems which appeared in a recent issue of this journal. The article, at the most, shows that MRP, inappropriately imposed on an existing production system, can result in undesirable system performance. This does not represent a new or startling conclusion. Four problem areas in the article are discussed, and suggested alternative approaches are offered.     

Empirical Prediction Intervals for County Population Forecasts

Population forecasts entail a significant amount of uncertainty, especially for long-range horizons and for places with small or rapidly changing populations. This uncertainty can be dealt with by presenting a range of projections or by developing statistical prediction intervals. The latter can be based on models that incorporate the stochastic nature of the forecasting process, on empirical analyses of past forecast errors, or on a combination of the two. In this article, we develop and test prediction intervals based on empirical analyses of past forecast errors for counties in the United States. Using decennial census data from 1900 to 2000, we apply trend extrapolation techniques to develop a set of county population forecasts; calculate forecast errors by comparing forecasts to subsequent census counts; and use the distribution of errors to construct empirical prediction intervals. We find that empirically-based prediction intervals provide reasonably accurate predictions of the precision of population forecasts, but provide little guidance regarding their tendency to be too high or too low. We believe the construction of empirically-based prediction intervals will help users of small-area population forecasts measure and evaluate the uncertainty inherent in population forecasts and plan more effectively for the future.     

预期寿命增长、年龄结构改变与我国国民储蓄率

人口年龄结构趋于老龄化和人均预期寿命逐步增长是目前我国人口发展的两个典型特征,而年龄阶段不同,个人的收入、消费与储蓄行为也不同。基于生命周期理论,在选定相关分析指标的基础上,文章使用我国省际平衡面板数据,实证分析了我国人口预期寿命增长和年龄结构改变对国民储蓄率的影响。分析结论表明,人口预期寿命增长提高了我国国民储蓄率;不考虑时间效应时,幼年人口负担比提高会减少国民储蓄率,而老年人口负担比提高会增加国民储蓄率;在考虑时间效应时,幼年人口负担比提高会增加国民储蓄率,而老年人口负担比提高会减少国民储蓄率。对此,文章给出了合理的解释。通过使用多种估计方法,我们发现所得到的结论是基本稳健的。     

Modeling Synergy and Learning under Multiple Advanced Manufacturing Technologies

The advent of the wide variety of new, highly integrated, advanced manufacturing technologies available for acquisition by a firm's managers has brought to light an accompanying set of unexpected issues. These issues include expectations for the benefits and costs of these technologies, determining the appropriate order of implementation and finding a way to justify acquisition when many of the benefits are a function of the technology's learning and synergistic effects on other operations and technologies. We present here a model that captures the interaction effects of these highly integrated technologies and discuss the data requirements for application of the construct. We then illustrate the model's workings with a number of multitechnology examples and show the danger of ignoring the synergistic and learning effects of these technologies when considering their acquisition.     

Postmigration Living Difficulties,Help-Seeking and Community Resilience in the Initial Stages of Migration: Coproducing Community Practice with Recent Irish Migrants to London

This article describes a community-based participatory action research (CBPAR) project that examined the postmigration living difficulties (PMLD), help-seeking and community resilience of recent Irish migrants to London (n = 176). The majority of respondents were young adults, in managerial or professional occupations and in good or very good health. Mixed methods indicate inadequate planning for relocation and poor social support as the main difficulties in the initial stages of migration. Community factors promoting resilience included employment opportunities, local and transnational supports, and cultural familiarity and acceptance. Community participation in the action orientated phase of this CBPAR is discussed.     

Developmental Change in Action Perception: Is Motor Experience the Cause?

Human actions are complex stimuli containing several perceptual dimensions an observer could attend to. Research indicates that attention to the perceptual dimensions of action undergoes a process of perceptual narrowing between 4 and 10 months, during which infants’ attention to configural and temporal information in action decreases over time, while attention to hand information is maintained. This research explored whether infants’ active experience with grasping is related to perceptual narrowing in action. Across two studies, we tested 6‐month‐old infants’ attention to changes in these action dimensions and also assessed their grasping ability. Infants who were more proficient at grasping showed a pattern more consistent with perceptual narrowing (decreasing attention to configural and temporal information) relative to those less proficient at grasping, especially for attention to configural information. In addition, attention to hand information appears to undergo U‐shaped development between 4 and 10 months, as 6‐month‐olds did not recover attention to the hand change. These findings add to a growing body of research showing that infants’ motor experience broadly influences their perception of others’ action and may follow a complex developmental pathway that diverges from perceptual narrowing over the first year.     

Mortality among elder abuse victims in rural Malaysia: A two-year population-based descriptive study

Our study aims at describing mortality among reported elder abuse experiences in rural Malaysia. This is a population-based cohort study with a multistage cluster sampling method. Older adults in Kuala Pilah (n = 1,927) were interviewed from November 2013 to May 2014. Mortality was traced after 2 years using the National Registration Department database. Overall, 139 (7.2%) respondents died. Fifteen (9.6%) abuse victims died compared to 124 (7.0%) not abused. Mortality was highest with financial abuse (13%), followed by psychological abuse (10.8%). There was a dose-response relationship between mortality and clustering of abuse: 7%, 7.7%, and 14.0% for no abuse, one type, and two types or more, respectively. Among abuse victims, 40% of deaths had ill-defined causes, 33% were respiratory-related, and 27% had cardiovascular and metabolic origin. Results suggest a link between abuse and mortality. Death proportions varied according to abuse subtypes and gender.