Effects of Product Structure Complexity on Multi-level Lot Sizing*

As an input to the materials requirement planning (MRP) process, the product structure interacts with the lot-sizing rules to affect inventories, materials flow, and production costs. Despite engineering constraints, considerable latitude is still available to construct alternate product structures for the same product. An important concern of MRP managers and designers is the impact of product structure complexity on the cost performance of the lot-sizing rules. To date, there exists no detailed research that provides managers with guidelines that relate the lot-sizing rules to individual product structure parameters. We report on an extensive experiment to test the effects of individual product structure parameters on the relative cost performance of 11 lot-sizing rules. Three parameters—the number of items, number of levels, and commonality index—are proposed to characterise product structure complexity and used as factors in an experiment involving a large variety of product structures. The results indicate that all three parameters affect the relative cost differences but not the ranking of the rules. The overall best lot-sizing rule is Bookbinder and Koch's [11] rule.     

Determining Uses and Gratifications for the Internet

Uses and gratifications (U&G) is a media use paradigm from mass communications research that guides the assessment of consumer motivations for media usage and access. It has been used previously in research and decision making related to the promotion of emerging radio and television media. Recent adaptations of U&G research to the Internet are incomplete and have not identified important new Internet‐specific gratifications. This paper empirically derives dimensions of consumer Internet use and usage gratifications among customers of a prominent Internet Service Provider (ISP). Results describe three key dimensions related to consumer use of the Internet, including process and content gratifications as previously found in studies of television, as well as an entirely new social gratification that is unique to Internet use. All three dimensions of gratification are relevant to managing the Internet as a commercial medium, and measures developed from the gratification profiles identified here can serve as trait‐valid scales in future Internet and e‐commerce research.     

A Bayesian piecewise exponential phase II design for monitoring a time-to-event endpoint

A robust Bayesian design is presented for a single-arm phase II trial with an early stopping rule to monitor a time to event endpoint. The assumed model is a piecewise exponential distribution with non-informative gamma priors on the hazard parameters in subintervals of a fixed follow up interval. As an additional comparator, we also define and evaluate a version of the design based on an assumed Weibull distribution. Except for the assumed models, the piecewise exponential and Weibull model based designs are identical to an established design that assumes an exponential event time distribution with an inverse gamma prior on the mean event time. The three designs are compared by simulation under several log-logistic and Weibull distributions having different shape parameters, and for different monitoring schedules. The simulations show that, compared to the exponential inverse gamma model based design, the piecewise exponential design has substantially better performance, with much higher probabilities of correctly stopping the trial early, and shorter and less variable trial duration, when the assumed median event time is unacceptably low. Compared to the Weibull model based design, the piecewise exponential design does a much better job of maintaining small incorrect stopping probabilities in cases where the true median survival time is desirably large.     

Design of a collaborative monitoring and evaluation system for a community-based nutrition project in rural Bangladesh

Poor diet and undernutrition are common among children living in Bangladesh. To promote appropriate complementary feeding of young children, an economic development (ED) program involving income-generating asset transfer was implemented alongside a social and behavior change (SBC) program. This paper introduces a collaborative monitoring and evaluation (M&E) system in which diverse collaborators (“research group”, “implementation team”, and “coordinators”) facilitate M&E data acquisition by leveraging their comparative advantages. The implementation team built a monitoring system to track the ED (n = 2960) and SBC participants (n=∼10,000) over 12 months. Based on the baseline design and the monitoring records, the collaborators planned an impact evaluation introducing a quasi-experimental design using two cross-sectional surveys and a prospective cohort survey of child feeding and nutritional status. Using various data sources generated from the M&E system, the collaborators will also reveal the program impact pathway through which each intervention component is delivered, received, and utilized alongside the context-specific facilitators and barriers, including the programs’ uptake. The collaborative M&E system enables the sharing of program goals, strengthens collaborators' commitment to the program, and extends the understanding of the program's progress and evaluation activities.     

Examining the Impact of Interorganizational Systems on Process Efficiency and Sourcing Leverage in Buyer–Supplier Dyads

Manufacturing firms are increasingly seeking cost and other competitive advantages by tightly coupling and managing their relationship with suppliers. Among other mechanisms, interorganizational systems (IOS) that facilitate boundary‐spanning activities of a firm enable them to effectively manage different types of buyer–supplier relationships. This study integrates literature from the operations and information systems fields to create a joint perspective in understanding the linkages between the nature of the IOS, buyer–supplier relationships, and manufacturing performance at the dyadic level. External integration, breadth, and initiation are used to capture IOS functionality, and their effect on process efficiency and sourcing leverage is examined. The study also explores the differences in how manufacturing firms use IOS when operating under varying levels of competitive intensity and product standardization. In order to test the research models and related hypothesis, empirical data on buyer–supplier dyads is collected from manufacturing firms. The results show that only higher levels of external integration that go beyond simple procurement systems, as well as who initiates the IOS, allow manufacturing firms to enhance process efficiency. In contrast, IOS breadth and IOS initiation enable manufacturing firms to enhance sourcing leverage over their suppliers. In addition, firms making standardized products in highly competitive environments tend to achieve higher process efficiencies and have higher levels of external integration. The study shows how specific IOS decisions allow manufacturing firms to better manage their dependence on the supplier for resources and thereby select system functionalities that are consistent with their own operating environments and the desired supply chain design.     

Extended family households among children in the United States: Differences by race/ethnicity and socio-economic status

This study uses nationally representative longitudinal data from the Panel Study of Income Dynamics, to examine the prevalence and predictors of extended family households among children in the United States and to explore variation by race/ethnicity and socio-economic status (SES). Findings suggest that extended family households are a common living arrangement for children, with 35?per cent of youth experiencing this family structure before age 18. Racial/ethnic and SES differences are substantial: 57?per cent of Black and 35?per cent of Hispanic children ever live in an extended family, compared with 20?per cent of White children. Further, 47?per cent of children whose parents did not finish high school spend time in an extended family, relative to 17?per cent of children whose parents earned a bachelor's degree or higher. Models of predictors show that transitions into extended families are largely a response to social and economic needs.     

More Than a Feeling? An Empirical Analysis of the Dual-Continua Model on a National Sample of Lesbian,Gay, and Bisexual Identified Canadians

The goal of the study is to investigate whether positive mental health complements mental illness within a theoretically informed (the dual-continua model) and psychometrically tested (the Mental Health Continuum-Short Form) framework. National-level, population-based data from the 2012 Canadian Community Health Survey on Mental Health (CCHS-MH) was used, with comparisons between sexual minority and heterosexual adults. Results show that gay, lesbian, and bisexual Canadians have substantially lower rates of positive mental health and are more likely to have been diagnosed with a mental illness, with the disparities between health and illness being the most pronounced among lesbians and bisexual females. Results show considerable support for the dual-continua model, which posits that the absence of health does not automatically translate into the presence of illness, and vice versa. Suggestions are made for practitioners and researchers toward the use of the dual-continua model as a surveillance tool, especially among sexual minority individuals.     

A qualitative viewpoint on the Southern eurozone highly skilled labour mobility in the metropolitan area of Copenhagen in times of crisis and austerity

The paper explores patterns of skilled labour mobility from the Southern eurozone to the metropolitan area of Copenhagen by means of a qualitative micro-study. The key hypothesis is that in/outflows may not only be a consequence of the present economic crisis but may also rely on the deep-rooted, democratic-socio-cultural aspects or dissimilar policy choices of sending/hosting countries. These same aspects are expected to influence return/circular migration. In contrast to mainstream theories of international migration, this viewpoint is supported by findings which illustrate how non-economic factors can be also crucial and why enhancing beneficial return/circular migration in the Southern eurozone can be incompatible with the application of austerity.     

Using geographically weighted regression for environmental justice analysis: Cumulative cancer risks from air toxics in Florida

Previous quantitative research on environmental justice has been limited by simplistic assumptions used to measure health risks and traditional regression techniques that fail to discern spatial variations in statistical relationships. We address these gaps through a case study that examines: (a) whether potential health risks from exposure to hazardous air pollutants in Florida are related to race/ethnicity and socioeconomic status, and (b) how the significance of statistical associations between health risk and race/ethnicity or socioeconomic status vary across the state. This study integrates census tract level estimates of cumulative cancer risk compiled by the EPA with Census 2000 data and a spatial statistical technique known as geographically weighted regression that allows us to explore spatial variability in analytical results. Our findings indicate that while race and ethnicity are significantly related to cancer risks in Florida, conventional regression can hide important local variations in statistical relationships relevant to environmental justice analysis.     

Extended-family resources and racial inequality in the transition to homeownership

We use longitudinal data from the Panel Study of Income Dynamics to examine how access to financial resources in the extended family affects the accumulation of wealth among non-owners and how these resources subsequently affect transitioning into homeownership. Our findings show that economic conditions of the extended family have substantial effects on non-owners’ wealth accumulation and likelihood of becoming homeowners, even after adjusting for individual sociodemographic and economic characteristics. We find significant effects of extended-family wealth for both black and white households, but effects of extended-family income insufficiency for blacks only. Consequently, limited access to wealth and greater level of poverty in the extended family hamper blacks’ transition to homeownership. Our results show that the level of extended-family wealth necessary for black householders to equalize their likelihood of becoming homeowners with whites is very high. In fact, our findings indicate that white householders embedded in extended families with no net wealth are just as likely to make the transition to ownership as are black householders with affluent extended families. These findings support arguments related to the importance of extended-family resources in processes of residential attainment but also point to important racial differences in not only levels but also consequences of these family resources.