A New Framework for Manufacturing Planning and Control Systems*

This paper presents a new framework for manufacturing planning and control systems which we call iterative manufacturing planning in continuous time (IMPICT) that appears to have several advantages over the well-known material requirements planning (MRP) framework. IMPICT explicitly considers capacity constraints and total system cost (including tardiness) to determine order sizes, order release/due dates, and operation schedules in a deterministic, multi-level, finite horizon, dynamic demand environment. Continuous time scheduling variables allow setups to be carried over from one period to the next. Three new heuristics built on the IMPICT framework are presented and tested in a simulation-based, full-factorial experiment with a wide variety of problem environments. The benchmark for the experiment was materials requirements planning with operations sequencing (MRP/OS) implemented with best-case, fixed planned lead times. The experiment showed that all three heuristics were statistically better than MRP/OS. The total cost for the order merging (OM) heuristic was 25 percent better than the total cost for MRP/OS. Computational times for OM were substantially larger than for MRP/OS; however, the computational times in the experiment suggest that OM is still computationally viable for large-scale batch manufacturing environments found in industry. IMPICT is superior to standard MRP systems because it explicitly considers capacity constraints and total system costs when it creates a materials plan. IMPICT is superior to linear programming-based approaches to finite loading and scheduling found in the literature because it allows setups to be carried over from one period to another and because it is computationally viable for realistic-sized problems.     

General Feelings Toward Unions and Employers as Predictors of Union Voting Intent

The union voting intention literature shows that many nonunion employees who indicate that they think unions are instrumental in increasing wages, benefits, and working conditions would vote against forming a union. Although American workers have often been characterized as pragmatic with regard to their support for unions, the “disconnect” between union beliefs and union voting intentions just described suggests that more subtle forces are at work. In this paper, it is shown empirically that union instrumentality is a limited predictor of union voting intentions for a recent national cross-section of workers. Rather, more general feelings toward unions and employers are primary. These accounted for a large portion of the variance in union voting intentions, with general feelings towards unions by far the most critical predictor. A concluding section discusses whether the results may reflect changes in union power and changes in employee views of unions. Areas for future research are discussed.     

The impacts of rapid demographic transition on family structure and income inequality in Brazil, 1981–2011

This study analysed the impact of changing family structure on income distribution. Specifically, it analysed how changes in the proportions of different categories of family in the population contributed to increases in the income of the richest and poorest social strata in Brazil, and the consequent impacts on income inequality. Rural and urban families were compared in order to understand how these dynamics had different impacts on more developed (urban) and less developed (rural) areas. The results emphasize how changes observed in family structure are more pronounced among the richest families, contributing to an increase in (i) the income of the richest families and (ii) income inequality between the richest and poorest families, as well as between urban and rural areas.     

Social Class Correlates of Stability and Change in Levels of Alienation: a Longitudinal Study

Identical allenation items were used on questionnaires administered to 334 subjects in 1963 and again in 1971. Drawing upon the variables of powerlessness, meaninglessness, normlessness, and social isolation, an analysis was made of stability and change in alienation scores. The direction of change was toward disproportionate increases over decreases, with the largest increase occurring for normlessness. Differential educational and occupational status, along with other social characteristics, were examined for sources of subsequent change in different measures of alienation. The results indicated significant differences in levels of alienation by socioeconomic variables at the two points in time. The amount of change, however, was not differentiated by changes in socioeconomic characteristics.