A VARIANCE-REDUCTION STRATEGY FOR RSM SIMULATION STUDIES

The application of optimization techniques in digital simulation experiments is frequently complicated by the presence of large experimental error variances. Two of the more widely accepted design strategies for the resolution of this problem include the assignment of common pseudorandom number streams and the assignment of antithetic pseudorandom number streams to the experimental points. When considered separately, however, each of these variance-reduction procedures has rather restrictive limitations. This paper examines the simultaneous use of these two techniques as a variance-reduction strategy in response surface methodology (RSM) analysis of simulation models. A simulation of an inventory system is used to illustrate the application and benefits of this assignment procedure, as well as the basic components of an RSM analysis.     

COST-VOLUME-PROFIT ANALYSIS IN STOCHASTIC PROGRAMMING MODELS

This paper applies mathematical programming to cost-volume-profit (CVP) analysis under contribution margin uncertainty. Three CVP probabilistic chance-constraint models based on various safety-first criteria for decisions under uncertainty are presented and compared. It is shown that a break-even segment of the mean-standard deviation frontier is a set of optimal solutions for the proposed models. An operational parametric quadratic programming (QP) model is constructed, and the efficiency frontier is generated. The procedures for locating an optimal solution on the efficiency frontier are then presented. The recommended QP procedure offers both technical relief from the computational difficulties posed by the probabilistic constraints and a desired flexibility in generating and presenting the relevant information for decisions under uncertainty.     

Parental characteristics and the schooling progress of the children of immigrant and U.S.-born blacks

In this study, I examine disparities in schooling progress among children born to immigrant and U.S.-born blacks. I find that in one- and two-parent families, children born to black immigrants are less likely to fall behind in school than those born to U.S.-born blacks. In two-parent immigrant families, children born to two immigrant parents have a significant schooling advantage over children born to one immigrant parent. While children born to two immigrant parents in the wealthiest black immigrant families do better in the second generation than in the first, the reverse is observed among children in less wealthy families. These findings contribute in two ways to our understanding of the assimilation processes of children born to black immigrant parents. First, they show that there is a positive association between the number of immigrant parents in a family and children’s schooling performance. Second, they suggest that disparities in the assimilation patterns of the children of black immigrants are a likely product of the interaction between their parental characteristics and the socioeconomic circumstances of their families.     

From Mothers of the “People's Home” to Biologically Rational Consumers

The aim of the present article is to study how women's alcohol consumption has been defined and contested in the Swedish press from 1955 to 2010 in relation to the development of Swedish society from a social democratic welfare state to a neoliberal competition state. Our material consists of articles published in the largest Swedish national and regional newspapers in 1955, 1965, 1977, 1982, 1995, 2004, and 2010. In the study, we apply Fraser's concepts of recognition and redistribution to analyse how the press contributed to the formation of cultural injustices and counter-claims through its recognition of women's drinking, and how these cultural injustices and counter-claims have conditioned the redistribution of societal resources. Our analysis shows that, during the study period, women were recognized in the Swedish press in limited and stigmatizing subject positions. These dominating representations of drinking women changed over time in an unpredictable way. As collectively shared, widely accepted cultural images, they tended to downplay the possibility of women achieving equal and just participation in cultural interaction, social activities, and healthcare services. In counter-discourses, the possibilities for women to formulate public claims in order to make surrounding structures more “enabling” of their independency, weakened during the study period.     

Effects of child support and welfare policies on nonmarital teenage childbearing and motherhood

This paper is an assessment of the impact of child support enforcement and welfare policies on nonmarital teenage childbearing and motherhood. We derive four hypotheses about the effects of policies on nonmarital teenage childbearing and motherhood. We propose that teenage motherhood and school enrollment are joint decisions for teenage girls. Based on individual trajectories during ages 12–19, our analysis uses an event history model for nonmarital teenage childbearing and a dynamic model of motherhood that is jointly determined with school enrollment. We find some evidence that child support policies indirectly reduce teen motherhood by increasing the probability of school enrollment, which, in turn, reduces the probability of teen motherhood. This finding suggests that welfare offices may wish to place greater weight on outreach programs that inform more teenagers of the existence of strong child support enforcement measures. Such programs might reduce nonmarital teen motherhood further and thus reduce the need for welfare support and child support enforcement in the long run.

Methods for spatial and temporal land use and land cover assessment for urban ecosystems and application in the greater Baltimore-Chesapeake region

Understanding contemporary urban landscapes requires multiple sets of spatially and temporally compatible data that can integrate historical land use patterns and disturbances to land cover. This paper presents three principal methods: (1) core analysis; (2) historic mapping; and (3) gradient analysis, to link spatial and temporal data for urban ecosystems and applies their use in the Baltimore-Chesapeake region. Paleoecological evidence derived from the geochronology of sediment cores provides data on long-term as well as recent changes in vegetative land cover. This information, combined with contemporary vegetation maps, provides a baseline for conducting trend analyses to evaluate urbanization of the landscape. A 200-year historical land use database created from historical maps, census data, and remotely sensed data provides a spatial framework for investigating human impacts on the region. A geographic information system (GIS) integrates core analyses with historic data on land use change to yield a comprehensive land use and land cover framework and rates of change. These data resources establish the regional foundation for investigating the ecological components of an urban ecosystem. Urban-rural gradient analyses and patch analyses are proposed as the most appropriate methods for studying the urban ecosystem as they link ecological and social patterns and processes for varying degrees of urbanization.     

人口流动对基督教全球传播的影响

基督教流动人口是基督教在全球传播过程中的关键因素。在基督教存在的前五个世纪,广泛的人口流动将基督教变成了全球化的信仰。广泛的人口流动在其它主要的世界宗教在世界各地的传播过程中也发挥了重要作用,但是,就基督教来说,流动可能是这种信仰固有的因素。基督教超越罗马帝国成为全球性信仰是个非常复杂的过程,包含许多不同类型的人口流动。跨国界的领袖们、俘虏、难民和流浪者、商人是人口流动的四种主要类型。虽然,东部教会传教的成功是短暂的,但是东部教会在第一个千年形成的移民传教模式无疑为21世纪的基督教提供了典范。基督教在过去的两三个世纪里再次全球化,基督信仰作为新的中心在非洲、拉丁美洲和亚洲的某些地区出现,表明"人口流动"在基督教全球传播过程中的作用比以前更加明显。当代基督教的全球化与早期基督教的全球化在发展道路上有很大不同,但有一点是不变的,即基督教的全球化仍将主要依靠流动者的行动和决策。     

Crossing the border: immigrant student identities in Swaziland schools

This paper sets out to explore how the resettlement of immigrant students in a host country and schooling context influenced the constitution, negotiation and representation of their identities. Data capture included a mix of semi-structured interviews, focus group interviews, observations and a researcher journal. Data were analyzed by means of the content analysis method. Findings were fivefold. First, the sociocultural context influenced the way immigrant students constructed their identities. Second, categorization was based on phenotypical features, accent, negative attitudes and stereotypical perceptions of immigrants by Swaziland society. Third negotiated identities were multiple in nature and rooted in their culture of origin. Fourth, self-determination was a strong trait of immigrants; reflected in their work ethic, in the resolution of culture conflicts, and in their drive to achieve linguistic competency. And fifth, psychosocial passing was consistent with second generation immigrants. New knowledge generated from this study revealed that African immigrants preferred to be clustered with Mozambican immigrants, as it provided solid ground from which they negotiated identities in Swaziland schools. Mozambican immigrants recruited other African immigrants into their cluster, which they referred to as the ‘Chico nation’. And, the culture of non-Christian immigrants was suppressed to promote Christian religious beliefs and values.