A hybrid approach to sequencing jobs using heuristic rules and neural networks

A hybrid approach to solve job sequencing problems using heuristic rules and artificial neural networks is proposed. The problem is to find a job sequence for a single machine that minimizes the total weighted tardiness of the jobs. Two different cases are considered: (1) when there are no setups, and (2) when there are sequence-dependent setup times. So far, successful heuristic rules for these cases are: apparent tardiness cost (ATC) rule proposed by Vepsalainen and Morton for the former case, and an extended version of the ATC rule (ATCS) proposed by Lee, Bhaskaran, and Pinedo for the latter. Both approaches utilize some look-ahead parameters for calculating the priority index of each job. As reported by Bhaskaran and Pinedo, the proper value of the look-ahead parameter depends upon certain problem characteristics, such as due-date tightness and due-date range. Thus, an obvious extension of the ATC or the ATCS rule is to adjust the parameter values depending upon the problem characteristics: this is known to be a difficult task. In this paper, we propose an application of a neural network as a tool to ‘predict’ proper values of the look-ahead parameters. Our computational tests show that the proposed hybrid approach outperforms both the ATC rule with a fixed parameter value and the ATCS using the heuristic curve-fitting method.     

QUANTIFYING THE IMPACT OF INVENTORY HOLDING COST AND REACTIVE CAPACITY ON AN APPAREL MANUFACTURER'S PROFITABILITY

This paper was motivated by the operational problems faced by Northco, a school uniform manufacturer in the Northeastern United States. Northco was facing high working capital costs while also incurring high stockout and markdown costs. This paper models the impact of inventory holding cost and reactive capacity on Northco's targeted understocking and overstocking cost and offers a solution methodology for such problems. We quantify the impact of varying inventory carrying costs (and hence, high working capital costs) on stockout costs and the value of additional capacity. Our results illustrate that apparel manufacturers with high working capital costs, and hence high inventory carrying costs, should target higher stockout costs and achieve lower capacity utilization. The results presented have application beyond Northco because high working capital cost is endemic to many supply chains.     

EFFECTS OF INTEGRATING ORDER/BACKORDER QUANTITY AND PRICING DECISIONS

We consider a monopolistic situation where the retailer aims to find the profit-maximizing selling price, and the order and backorder quantity of an item. The price and demand are assumed to be inversely related. We develop a simple optimal approach, the proportion-balancing algorithm (PBA), which utilizes the proportions of cost components to sales revenue. We demonstrate that the PBA can handle three commonly used demand functions. However, applicability of the PBA depends on how the price-demand relationship is specified. A sensitivity analysis shows that the effects of changes in cost parameters on the order and backorder quantities can be very different from those of the classical economic order quantity model with backorders.     

Indians, the State and Law: Public Works and the Struggle to Control Labor in Liberal Ecuador

Abstract This article explores the functioning of the state-system and the emergence of a particular state-idea in early twentieth century Ecuador by analysing relations between Indians and the state in labor recruitment for municipal public works construction in the Andean region of Alausí. The idea of the state as a dispenser of equal justice was successfully called on by indigenous peons in their resistance to forced labor recruitment by local officials of the state. The enhancement of this idea of the state simultaneously undermined the functioning of the state-system at the local level, and legitimized central state authority.     

茶山的性命与心:实践道德论

茶山试图建立一种与生活和行动不可分割的儒学世界观,在他关于人的本性的理论中,他对上帝的自然神论者的解释为人事中的道德和善提供了本体论的基础。他以天命赋予每个人的人性作为道德倾向,认为这种人性是人自我实现的必要动力。他用一种他认为可以指导行动,在实践和人伦中完成儒家理想的理论来取代理学,其目的在于理解和发展来自于宇宙和人的理。     

Minimizing the mean squared deviation from a common due date: unconstrained and constrained cases

The problem of minimizing the mean squared deviation (MSD) of completion times from a common due date in both unconstrained and constrained cases is addressed. It is shown that the unconstrained MDS function is unimodal for n ≤ 6, where n is the number of jobs. The constrained case is shown to be unimodular for n ≤ 3, The unconstrained case is shown, by counterexample, not to be unimodular for n = 8. The constrained case is shown not to be unimodular for n = 5. For the unimodular cases, a proposed search routine can find the optimum solution in less than three CPU seconds for n = 100. It provides an excellent heuristic solution otherwise. Computational results are shown in both cases.     

STOCK RETURNS, ASYMMETRIC VOLATILITY, RISK AVERSION, AND BUSINESS CYCLE: SOME NEW EVIDENCE

We study how three interrelated phenomena—excess stock returns and risk relation, risk aversion, and asymmetric volatility movement—change over business cycles. Using an asymmetric generalized autoregressive conditional heteroskedasticity in mean model and a Markov switching model, we find that excess stock return increases and asymmetric volatility movement is weakened during boom periods. This suggests that investors become more risk-averse during boom periods (i.e., procyclical risk aversion), which we confirm using a calibration of a simple equilibrium model . ( JEL C32, E32, G12)     

A Simple Estimator of Error Correlation in Non-parametric Regression Models

Abstract.  It is well known that major strength of non-parametric regression function estimation breaks down when correlated errors exist in the data. Positively (negatively) correlated errors tend to produce undersmoothing (oversmoothing). Several remedies have been proposed in the context of bandwidth selection problem, but they are hard to implement without prior knowledge of error correlations. In this paper we propose a simple estimator of error correlation which is ready to implement and reports a reasonably good performance.     

A robust logistic discrimination model

Logistic discrimination is a well documented method for classifying observations to two or more groups. However, estimation of the discriminant rule can be seriously affected by outliers. To overcome this, Cox and Ferry produced a robust logistic discrimination technique. Although their method worked in practice, parameter estimation was sometimes prone to convergence problems. This paper proposes a simplified robust logistic model which does not have any such problems and which takes a generalized linear model form. Misclassification rates calculated in a simulation exercise are used to compare the new method with ordinary logistic discrimination. Model diagnostics are also presented. The newly proposed model is then used on data collected from pregnant women at two district general hospitals. A robust logistic discriminant is calculated which can be used to predict accurately which method of feeding a woman will eventually use: breast feeding or bottle feeding.     

论国家治理的若干基本问题

行动者、制度、秩序以及此三者间关系,是考察国家治理问题的基本出发点,因为通过前两者才能说明人类社会不可或缺的秩序,而国家治理是属于秩序范畴的问题,但直接决定某种秩序状态的是相关领域的机制。在讨论国家治理问题时,有必要分开国家能力和国家治理能力,而国家治理能力是由政府、市场、社会等在制度平台上通过竞争与合作,以和平的方式解决公共问题的综合能力。正是由于这一点,治理又与信任密切相关,而国家治理所需要的信任应该建立在制度和共识的基础上。必须强调,国家治理并不只是富强的手段,富强只是现代化的一个结果,而现代化与国家治理在根本上是同一个过程,这个过程伴随着社会领域的自治,这就要求必须推动社会的组织化,从而可以提升整个国家的理性化程度。