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991.
Two heuristics based on branch and bound (B&B) are developed to solve closed-loop material requirements planning (MRP) lot-sizing problems that have general product structures and variable costs. A “look ahead method'’(LAM) heuristic allows for variable production/purchasing costs and uses a single-level B&B procedure to rapidly improve lower bound values; thus, LAM efficiently uses computer-storage capacity and allows solution of larger problems. The “total average modification'’(TAM) heuristic uses B&B, applied level by level, and modified setup and carrying costs to solve the variable production/purchasing costs MRP lot-sizing problem. LAM and TAM are tested on problems and compared to heuristics in the literature. TAM may be used to solve large MRP lot-sizing problems encountered in practice. 相似文献
992.
Scientific techniques for inventory management typically are applied to systems containing many items. Such techniques require an estimation of the demand variance (and mean) of each item from historical data. This research demonstrates a significant potential for improvement in system cost performance from using least-squares regression fits of a variance-to-mean functional relation instead of the standard statistical variance estimate. Even when there is a moderate degree of heterogeneity among items and when the form of the variance-to-mean relation is misspecified, substantial cost savings may be realized. The cost of statistical uncertainty may be reduced by half. The research also provides evidence that system cost is fairly insensitive to the number of items used to fit the regression. This paper provides the underlying reason why a regression-derived variance estimator yields lower cost: it is less variable than the usual individual item variance estimator. 相似文献
993.
This paper develops a warning zone approach to make variance investigation decisions for a multiperiod process. The assumed cost generation process varies between an in-control and out-of-control state. These states cannot be directly observed, but must be inferred from the reported cost variances. Using the warning zone method of inference, the manager investigates the process whenever an upper threshold is exceeded or a lower threshold is exceeded for two consecutive periods. A four-state Markov chain models the resulting decision process. Steady state probabilities are derived for this chain and are used to obtain explicit formulas for the effectiveness and efficiency of the decision process. These formulas permit computation of the cost savings attainable by the warning zone method. Compared to other decision rules, the warning zone method is much simpler than the theoretically optimal Bayesian revision method, but uses more information than the Markovian control limit method. Numerical comparison of results shows that the warning zone method usually captures most of the available cost savings, even in cases where the Markovian control limit method does not perform well. 相似文献
994.
David J. Hess 《Sociological inquiry》2009,79(3):306-327
The term "undone science" refers to absences of scientific research that social movement and other civil society organizations find when attempting to make epistemic claims in the political field. The existing literature has identified various pathways for addressing the knowledge needs of civil society organizations, including asking elected and appointed political leaders to shift funding priorities and directly seeking support and partnerships with scientists. Here, a third pathway is identified and explored: civil society organizations that have the resources to fund their own research. A sample of such "civil society research" from large, mainstream, U.S. environmental organizations demonstrates that although the large organizations do engage in such research, most of it is not published in peer-reviewed journals. The peer-reviewed research is found almost exclusively in large preservation and conservation organizations that have staffs of scientists. Most of the other research reports are oriented toward documenting environmental problems and providing policy and management solutions. The research is highly applied and does not represent fundamental contributions to large mainstream scientific fields. Comparisons with civil society research in the author's previous research projects on religion, health, and economic development are discussed to assess applicability of the concept for other sociological subfields. 相似文献
995.
We explored the influences of women's social learning, marital resources and constraints, and exposure to norms about women's family roles on their views about wife hitting or beating among 5,450 participants in the 2005 Egypt Demographic and Health Survey. One half justified wife hitting or beating for some reason. Women from rural areas who were exposed to domestic violence more often justified such acts. Dependent wives whose husbands had more schooling, were blood relatives, and were coresident more often justified such acts. In settings where women tended to marry at older ages, women less often justified such acts. Women's resources and constraints in marriage accounted for the largest share of the variability in their attitudes about domestic violence against women. 相似文献
996.
Sandy Taut Flavio Cortés Christian Sebastian David Preiss 《Evaluation and program planning》2009,32(2):129-137
This evaluation examined school and parent reports of the national student achievement testing system (SIMCE) in Chile regarding three dimensions: access, comprehension, and use. We conducted phone surveys with a representative sample of directors (N = 375), teachers (N = 1145) and parents (N = 625), and we collected more in-depth data through interviews and focus groups in 16 of these schools. The results indicate that access to the reports is not an obstacle to use for school actors, but it is for parents. While summative ratings of the reports in terms of their clarity and utility were generally very positive, the actual recall and interpretation of even basic information (assessed through case scenarios) was incorrect for a majority of teachers and parents, and reported uses of the information were both intended and unintended in nature. We also found some statistically significant differences regarding comprehension and use among subgroups of our sample. Our findings are especially relevant given the expectations attached to the use of the reports for school improvement on the one hand, and parents’ behavior as critical consumers of education on the other hand. 相似文献
997.
The present research examined whether the emotions of others (i.e., disappointment versus happiness with respect to a received outcome) influence own self-esteem when being overpaid. Results from two experiments demonstrated that participants reported higher performance self-esteem when the other expressed happiness rather than disappointment. This effect was only found in the condition where one was overpaid relative to the condition where one did not yet know one’s own outcome. In the second experimental study we further found that this interaction between the emotion of the other and the distribution situation only emerged among participants low (relative to high) in personal need for structure. Implications with respect to the relationship between overpayment and self-esteem and the interpersonal effects of emotions in this process are discussed. 相似文献
998.
Vertex betweenness centrality is a metric that seeks to quantify a sense of the importance of a vertex in a network in terms of its ‘control’ on the flow of information along geodesic paths throughout the network. Two natural ways to extend vertex betweenness centrality to sets of vertices are (i) in terms of geodesic paths that pass through at least one of the vertices in the set, and (ii) in terms of geodesic paths that pass through all vertices in the set. The former was introduced by Everett and Borgatti [Everett, M., Borgatti, S., 1999. The centrality of groups and classes. Journal of Mathematical Sociology 23 (3), 181–201], and called group betweenness centrality. The latter, which we call co-betweenness centrality here, has not been considered formally in the literature until now, to the best of our knowledge. In this paper, we show that these two notions of centrality are in fact intimately related and, furthermore, that this relationship may be exploited to obtain deeper insight into both. In particular, we provide an expansion for group betweenness in terms of increasingly higher orders of co-betweenness, in a manner analogous to the Taylor series expansion of a mathematical function in calculus. We then demonstrate the utility of this expansion by using it to construct analytic lower and upper bounds for group betweenness that involve only simple combinations of (i) the betweenness of individual vertices in the group, and (ii) the co-betweenness of pairs of these vertices. Accordingly, we argue that the latter quantity, i.e., pairwise co-betweenness, is itself a fundamental quantity of some independent interest, and we present a computationally efficient algorithm for its calculation, which extends the algorithm of Brandes [Brandes, U., 2001. A faster algorithm for betweenness centrality. Journal of Mathematical Sociology 25, 163] in a natural manner. Applications are provided throughout, using a handful of different communication networks, which serve to illustrate the way in which our mathematical contributions allow for insight to be gained into the interaction of network structure, coalitions, and information flow in social networks. 相似文献
999.
Drawing on interviews with parents of children with complex disabilities in several school systems in a US state, this paper examines how temporal units such as the school day and school year and practices organized around artifacts like clocks and calendars work as ‘devices of temporal distanciation’ to separate children with disabilities from other children and exclude their families from critical relations with schools. The paper focuses on two kinds of effects: the ways differentiated timetables separate children and the ways constructing school time in bounded, discrete units limits the ability of parents and children to make key elements of their lives visible to the school. 相似文献
1000.
David G. Phillips 《Clinical Social Work Journal》2009,37(1):1-6
As clinical social work developed in America it was highly influenced by the concepts and techniques of psychoanalysis and
many of its practitioners became interested in seeking psychoanalytic training. More and more psychoanalysts are now coming
from a background in clinical social work due to the development of a network of interdisciplinary training institutes and
the opening of the Institutes of the American Psychoanalytic Association to non-medical candidates. This special issue considers
how psychoanalysis may be affected as more of its practitioners and contributors come from a background in clinical social
work. This introduction reviews the history of the development of clinical social work and outlines the issues related to
“lay analysis” in this country.
相似文献
David G. PhillipsEmail: |