A LOWER BOUND FOR THE SINGLE-LEVEL DYNAMIC HORIZON LOT-SIZING PROBLEM

Conventional production planning methods assume the existence of a medium- or longrange demand horizon. However, demand usually is known over a much shorter range; scheduling decisions must be made within this “decision window,” which rolls forward in time. This paper presents a new lower bound for lot-sizing heuristics in a rolling-horizon framework and compares it to the well-known Wagner-Whitin bound. The new bound indicates heuristic schedules that have costs close to the optimum. Rolling-horizon schedule costs are compared to corresponding static-horizon schedule costs (assuming the whole horizon is known in advance), using the ratio of decision-window size to the natural order cycle as a parameter. For values below unity, the rolling-horizon policy is significantly more costly. For values above one, the two policies have similar costs and actually converge as the parameter value increases.     

On nonlinear multi-covering problems

In this paper we define the exact k-coverage problem, and study it for the special cases of intervals and circular-arcs. Given a set system consisting of a ground set of n points with integer demands \(\{d_0,\dots ,d_{n-1}\}\) and integer rewards, subsets of points, and an integer k, select up to k subsets such that the sum of rewards of the covered points is maximized, where point i is covered if exactly \(d_i\) subsets containing it are selected. Here we study this problem and some related optimization problems. We prove that the exact k-coverage problem with unbounded demands is NP-hard even for intervals on the real line and unit rewards. Our NP-hardness proof uses instances where some of the natural parameters of the problem are unbounded (each of these parameters is linear in the number of points). We show that this property is essential, as if we restrict (at least) one of these parameters to be a constant, then the problem is polynomial time solvable. Our polynomial time algorithms are given for various generalizations of the problem (in the setting where one of the parameters is a constant).     

Gambling: The shaping of an opinion

Examining historical and contemporary writings, the authors show that many of the negative arguments about gambling spring from selfish interests in the business and political sectors. The stigma associated with gambling turns out to be a method of preventing competition from gambling, and leads to misguided social policies.The authors are, respectively, associate professor of economics at the Business School of the University of Montreal (HEC), and professor of economics in the department of economics of the University of Montreal. The paper draws on our recently published bookGambling and Speculation (Cambridge University Press, 1990), as well as on events that took place since we finished writing it. We thank Loto-Québec for its financial support.     

Technological knowledge,curriculum and occupational role potential*

This paper examines technological curricula in terms of their potential to be realized in occupational roles. The more the curriculum is oriented towards roles (as opposed to skills or pure knowledge), the greater the probability that it will be articulated in the labour market and the greater its efficacy and legitimacy. The concept of role has been analytically divided into six components: value commitment, normative, communicative, interactive, role intelligence and proficiency components. Theoretically, the more components are present in a given curriculum, the higher the probability that a given occupational role will be effectively articulated. However, their presence is a necessary but insufficient condition for effective role performance; their integration is of equal, if not greater importance, and the latter is meaningful only when the social context of the articulation is taken into account. It was found that the role components do not appear in a balanced manner in technological curricula investigated in Israel, and some hardly receive any attention. Those that are present are weakly linked to actual economic contexts. Thus, it appears that students in technological education, are socialized to minimal role articulation; ie, they are more likely to implement decontextualized tasks than to assume integral occupational roles.     

Data bases for large energy-economic models

The collection, collation and transformation of data into the form required by a large energy-economic model constitutes a significant part of the overall modelling activity. The correct basis for setting up a model data base rests on the separation of the model specification into the four areas of external data transformation, internal data representation, internal data transformation and the mathematical relationships. From this specification, the model may be generated. The internal data base is comprised of a series of tables, covering intersectoral transactions, capital stock transactions, energy sector operating characteristics, consumption patterns and other data. These tables may be compiled direct from source material, or via some research requiring prior data processing. In both cases the process should be fully documented, so that data accuracy is ensured and the data may be updated reliably when new material becomes available. It is recommended that a data coordinating function be established within the modelling group, in order to plan and control data-related activities.     

Communal Decline: The Vanishing of High-Moral Servant Leaders and the Decay of Democratic, High-Trust Kibbutz Cultures

What is the connection between leaders’morality and the output performance of organizations? Can their morality explain, through trust, continuity, and change of organizational cultures? Is periodic rotation of managers the right solution for the distrust caused by self‐serving conservatism due to Michels's “Iron Law of Oligarchy”? An anthropological study of kibbutzim, whose innovative and adaptive cultures declined recently, found that past success was dependent on high‐moral servant leaders who backed democracy and promoted high‐trust cultures that engendered innovation by creative officers in some kibbutzim, which others imitated. However, conservatism of continuous leaders as heads of low‐trust kibbutz federative organizations, which were ignored by customary kibbutz research, engendered oligarchization which rotation enhanced rather than prevented. However, creativity deteriorated only after decades of growing oligarchy, with the vanishing of the high‐moral old guard. Thus, the crux of democratic communal culture sustainability is pinpointed in the superiority of trusted, high‐moral leaders. A preliminary idea for achieving that aim, predicated on officers’continuation in office being conditional on periodic tests of trust, is herein presented.     

An analytic hierarchy process based simulation model for entry mode decision regarding foreign direct investment

A methodology is developed for ranking entry mode alternatives encountered by individual firms considering foreign direct investment (FDI). The methodology deals with the risks and uncertainties related to FDI. The analytic hierarchy process (AHP) is used to solve the multiple criteria decision-making problem using input from a firm's management. A simulation approach is incorporated into the AHP to handle the uncertainty considerations encountered in an FDI environment. The uncertainties include: (1) uncertainty regarding the future characteristics of the FDI decision making environment, (2) uncertainty associated with the decision maker's judgment regarding pairwise comparisons necessitated by the AHP.     

Linking leader inclusiveness to work unit performance: The importance of psychological safety and learning from failures

Despite burgeoning interest in how groups and organizations learn from failures, little is known about how leader behavior influences these learning processes. We analyzed longitudinal data collected at a large hospital and found that leader inclusiveness was positively associated with members' perceptions of psychological safety at Time 1, and that this relationship was stronger for members in low-performing units. Unit psychological safety climate appeared to facilitate learning from failures within the work unit (Time 2), which was positively associated with subsequent unit performance (Time 3).     

A comparative study of multiattribute decision making methodologies

Three real life cases are considered in this paper to apply and compare the rankings obtained by the Analytic Hierarchy Process (AHP) and other Multicriteria Decision Making (MCDM) techniques such as Simple Additive Weighting (SAW), ELECTRE and Weighted Linear Assignment Method (WLAM). The results indicated that the AHP, SAW, and ELECTRE rankings do not differ significantly, however, the WLAM tends to exhibit more disagreement. However, because of the limited nature of this study, we do not suggest this as a general conclusion.     

Informal Youth Organizations: A General Model*

An attempt is made to construct an ideal type of informal youth organization having the following components: an active, expressive pattern of action, multi-dimensional patterns of performances, symmetric relationships among participants, a dual structure, and the principle of moratorium; all these are based on a high degree of voluntary participation. These components are related (in an organizational framework) to such outcomes as the generation of value commitment, the integration of various strata, and mediation between childhood and adulthood. The paper exposes a dilemma: how to semi-institutionalize these organizations in an attempt to diminish the risk of developing antisocial commitment and at the same time to preserve their unique properties.