AN ANALYSIS OF CAPACITY PLANNING PROCEDURES FOR A MATERIAL REQUIREMENTS PLANNING SYSTEM*

This paper is concerned with planning work-center capacity levels in manufacturing firms that employ a material requirements planning (MRP) system. It presents four procedures for developing work-center capacity plans designed to insure the production of components and assemblies as specified by the MRP plan and the master production schedule (MPS). These procedures (capacity planning using overall factors, capacity bills, resource profiles, and capacity requirements planning) are compared using simulation analysis. The results indicate that the performance of a procedure when measured against the MPS depends on the operating conditions of the manufacturing system. The results also indicate that the choice of a particular procedure often represents a compromise among the benefits of improved MPS performance, the costs of preparing and processing data, and the premium expenses required for more frequent adjustments in work-center capacity levels.     

THE HARMS SHOE COMPANY: DEVELOPMENT OF A COMPUTER MODEL FOR THE CLASSROOM

This paper describes a case that examines five key topics in production and operations management [1]—forecasting, inventory control, transportation planning, aggregate planning, and the disaggregation of the aggregate plan—in an integrated, realistic manner for upper-level undergraduate business majors [3]. The case structure stresses the linkage of these interrelated subjects and supplements the regular classroom presentations dealing with them. The case relies on computer calculations at each stage to provide the information input for calculations at the next stage. It is a static model with a twelve-month planning horizon. Students complete several exercises and assume several roles as the case unfolds. They act on their own in filling some roles and as members of teams in performing others. They do not compete with each other, as the purpose of the case is to help them develop an appreciation of the factors that persons performing the role must consider.     

Social Sources of Failure in Education: The Case in East and Southeast Turkey

The efficiency of education in East and Southeast Turkey (E&SE) has long been a subject of debate. Both regions are similar to each other and different from the other regions in terms of economy, culture, ethnic origin, and languages spoken. Sahin (1997) studied the efficiency of education in the E&SE and proposed that illiteracy is significantly the highest in both regions, the female student population is significantly lower, and students are significantly less successful in nationwide general proficiency examinations (OSS and OYS) compared to all the other regions. Social sources of failure were studied in terms of the distinguishing characteristics of both regions, from both practical and theoretical standpoints. The findings indicated inequality of educational opportunity rooted in geographical, economical, social (cultural, linguistic), and political factors.     

The Quality of Urban Environments in the Brazilian Amazon

In the Brazilian Amazon during the 1980s,urban population growth outstripped rural growth, andby 1991, most of the region's population resided inurban areas. Much of this urban growth involvedestablishment of unplanned housing with inadequateinfrastructure, which resulted in rising pollution. This paper compares indicators of environmentalquality in urban populations of the Amazon in 1980 and1991, and among different kinds of urban populationsin 1991. The results show that environmental qualityin the region deteriorated during the 1980s as theproduction of and exposure to environmental hazardsrose while resources to ward off hazards eroded. Thefindings also show that environmental quality wasparticularly poor in more rapidly growing urbancenters. The urban Amazon may not afford an adequatestandard of living and this may generate out-migrationfrom the region.     

Using age and spatial flow structures in the indirect estimation of migration streams

This article outlines a formal model-based approach for inferring interregional age-specific migration streams in settings where such data are incomplete, inadequate, or unavailable. The estimation approach relies heavily on log-linear models, using them to impose some of the regularities exhibited by past age and spatial structures or to combine and borrow information drawn from other sources. The approach is illustrated using data from the 1990 and 2000 U.S. and Mexico censuses.     

Was there compression of disability for older Americans from 1992 to 2003?

Medical advances and the growth of the elderly population have focused interest on trends in the health of the elderly. Three theories have been advanced to describe these trends: compression of morbidity, expansion of morbidity, and dynamic equilibrium. We applied multistate life table methods to the Medicare Current Beneficiary Survey to estimate active and disabled life expectancy from 1992 to 2003, defining disability as having difficulty with instrumental activities of daily living or activities of daily living. We found increases in active life expectancy past age 65 and decreases in life expectancy with severe disability. These trends are consistent with elements of both the theory of compression of morbidity and the theory of dynamic equilibrium.     

The construction and validation of the homopositivity scale: an instrument measuring endorsement of positive stereotypes about gay men

Social scientists appear to focus on negative beliefs about, and attitudes toward, gay men and lesbian women. This emphasis, though understandable in view of the widespread oppression of gay and lesbian individuals, is somewhat myopic because it ignores what might be referred to as the positive dimension of stereotypes. Although such a concept may appear oxymoronic, it is widely recognized that individuals may endorse a mixture of positive and negative stereotypes toward stigmatized groups such as African Americans and women. The purpose of the current series of studies (Study 1, N = 212; Study 2, N = 105) was to devise an instrument measuring endorsement of positive stereotypes about gay men (Homopositivity Scale; HPS). Two versions of the HPS (of varying length) were evaluated, with scale scores on both appearing to be internally consistent and factorially distinct from scales measuring negative stereotypes and prejudices about gay men. These studies also suggest that females are more likely than males to endorse positive stereotypes about gay men, and that such endorsement is negatively associated with need for uniqueness and need for cognition, and positively associated with media contact and benevolent sexism. The limitations of the two studies are outlined and the importance of assessing positive stereotypes about gay men in conjunction with oft-examined homonegativity is discussed.     

Suicide and mental health problems among Swedish youth in the wake of the 1990s recession

The purpose of this explorative study is to bring together a variety of Swedish data sources with indicators of youth mental health and living conditions in order to illuminate trends during the last decades, elucidate possible determinants of mental ill health and develop hypotheses to explain the observed trend patterns. The analyses in the study reveal some surprising inconsistencies with respect to the mental health trends among young people during the 1990s. Most striking is the pattern of increasing youth unemployment coinciding with almost inverse trends in the rates of suicide. The secular trends in fatal suicides during this period do not show any increase but some actual decrease in sub‐populations despite high sustained levels of unemployment. In contrast, survey data indicate that the general mental health of youth during this period appears to have deteriorated.     

Differential equation models for statistical functions

Differential equations have been used in statistics to define functions such as probability densities. But the idea of using differential equation formulations of stochastic models has a much wider scope. The author gives several examples, including simultaneous estimation of a regression model and residual density, monotone smoothing, specification of a link function, differential equation models of data, and smoothing over complicated multidimensional domains. This paper aims to stimulate interest in this approach to functional estimation problems, rather than provide carefully worked out methods.