The network dynamics of co-offending careers

Despite the long-standing acknowledgement that crime is a group phenomenon, little research treats co-offending as a dynamic network process. This study analyses the individual and network processes responsible for long-lasting criminal relationships using co-offending dyads from eight years of arrest records in Chicago. Results from proportional hazard models suggest that homophily with respect to age, race, gender, geographic proximity, and gang identity lead to sustained partnerships. Victimization increases the probability of continued co-offending, while the victimization of one’s associates dissuade continued collaboration. Supra-dyadic processes (centrality, transitivity) influence the likelihood of continued co-offending. Results are discussed regarding opportunities and turning points.     

An LM-type test for idiosyncratic unit roots in the exact factor model with integrated factors

We consider an exact factor model with integrated factors and propose an LM-type test for unit roots in the idiosyncratic component. We show that, for a fixed number of panel individuals (N) and when the number of time points (T) tends to infinity, the limiting distribution of the LM-type statistic is a weighted sum of independent Chi-square variables with one degree of freedom, and when T tends to infinity followed by N tending to infinity, the limiting distribution is standard normal. The results should contribute to the challenging task of deriving likelihood-based unit-root tests in dynamic factor models.     

Replenishment Analysis in Distribution Requirements Planning*

Most research on lot sizing has been for the case of a manufacturing system. In this paper, analogous issues are studied for a distribution network. Specifically, we consider the choice of shipment quantities within distribution requirements planning (DRP). A simulation model of DRP in a multi-echelon, rolling-schedule environment is used to examine, in conditions of both certain and uncertain demand, the performance of five lot-sizing rules. We conducted a full-factorial experiment in which four additional parameters were varied: distribution network structure (two options), demand distribution (three options), forecast error distribution (three options), and ordering cost (three values), as suggested by the consulting study which motivated our research. We found that for DRP, contrary to the “shop floor” wisdom on MRP, the choice of lot-sizing method can be important. Generally the Silver-Meal and Bookbinder-Tan heuristics were significantly better than the other methods.     

An Empirical Study of Inbound Consolidation Opportunities

The current deregulated transportation environment has fostered wider freight rate differentials based on shipping weight. As a result, grouping inventory items for the purpose of consolidating inbound replenishment orders can be cost-effective. The pressure in some industries for just-in-time delivery of small lots has also created new opportunities for consolidation of orders. The objective of this research is to identify inventory-transport conditions where a consolidation strategy has cost-reduction potential. Logistics cost generated by ordering an ensemble of items consolidated into groups is compared to those generated by two independent, item reorder strategies. Using data from 150 ensembles, the cost-reduction potential of consolidating was correlated with characteristics of the individual inventory items in an ensemble, a dominant group of items in the ensemble, and the ensemble itself. Finally, response functions were derived and used to test the external validity of the results. For this purpose we used 25 randomly selected inventory ensembles obtained from a retail merchandising firm.     

PLANNING FOR TRUCK FLEET SIZE IN THE PRESENCE OF A COMMON-CARRIER OPTION

This paper considers a class of network optimization problems in which certain directed arcs must be covered by a set of cycles. Our study was motivated by a distribution planning problem of a commercial firm that had to make deliveries over several origin-destination pairs (directed arcs) and that could service any demand arc by using a vehicle in its own fleet or by paying a common carrier. The problem is to determine an optimal fleet size and the resulting vehicle routes while satisfying maximum route-time restrictions. We formulate the problem, describe some approximate solution strategies, and discuss important implementation issues.     

“中国碗要装中国粮”可行性与实践路径研究

构建系统动力学模型和灰色GM(1,1)预测模型,动态测度了“中国碗要装中国粮”的可行性。研究结果表明：未来我国口粮数量总体安全,粮食结构性供给风险较大,饲料粮短缺较为严重;我国水产品、蛋类和奶类等间接用粮消费潜力较大,猪肉供需关系紧张,国产植物油供能不足;我国居民的脂肪摄入量严重超标,仍需大量进口。据此,应严格守好耕地保护红线,提高耕地质量;充分发挥政策引导作用,调动农民种粮的积极性;推动农业科技进步,提升粮食稳产保供能力;改善我国居民膳食结构,改进牲畜饲料配比,以降低过旺的饲料粮和植物油需求。     

长三角区域创新系统模式及其构建研究

本文在长三角区域经济一体化的背景下,在分析苏浙沪各具特色的区域创新系统模式的基础上,通过与新古典区域、Perroux区域的比较,着重探索长三角区域创新系统＂多元均衡极化＂模式的形成过程,并从多样性、互动性、对偶性和双重性等四个层面揭示了其内在机理,提出了其市场导向的原发性和政府导向的后发性等两条基本构建途径。     

浙江城乡基本公共服务均等化问题探讨

城乡基本公共服务均等化是确保城乡居民生存和发展的起点平等、机会均等的基本要求.浙江的基本公共服务在城乡之间呈现出制度保障不均衡、公共服务资源配置不均等、基本公共服务受益程度不均等的非均衡态势.推动浙江城乡基本公共服务均等化必须建立健全推进城乡基本公共服务均等化的动力机制、以城乡基本公共服务均等化为导向的财政资金投入结构、基本公共服务管理体制以及推进城乡基本公共服务均等化的工作机制.     

略论儒家伦理普及教化的历史经验及当代启示——兼论社会主义核心价值体系的大众化

儒家伦理之所以至今仍广有影响,不仅是其作为封建社会主导价值观的逻辑结果,而且与其普及教化的形式要素密切相关.探讨儒家伦理与社会主义核心价值观的有机联系,总结、梳理儒家伦理合理内核及其普及教化的历史经验,对社会主义核心价值体系大众化无疑具有借鉴启示意义.