Production and changeover control policies of a class of failure prone buffered flow-shops

This article deals with a stochastic optimal control problem for a class of buffered multi-parts flow-shops manufacturing system. The involved machines are subject to random breakdowns and repairs. The flow-shop under consideration is not completely flexible and hence requires setup time and cost in order to switch the production from a part type to another, this changeover is carried on the whole line. Our objective is to find the production plan and the sequence of setups that minimise the cost function, which penalises inventories/backlogs and setups. A continuous dynamic programming formulation of the problem is presented. Then, a numerical scheme is adopted to solve the obtained optimality conditions equations for a two buffered serial machines two parts case. A complete heuristic policy, based on the numerical observations which describe the optimal policies in system states, is developed. It will be shown that the obtained policy is a combination of a KANBAN/CONWIP and a modified hedging corridor policy. Moreover, based on our observations and existent research studies extension to cover more complex flow-shops is henceforth possible. The robustness of such a policy is illustrated through sensitivity analysis.     

‘Business under new management’ — lessons from Canada on regulation of the social work profession

Abstract

In December 1998 the Social Work and Social Service Work Act (hereafter the Ontario Act) was passed in Ontario, Canada marking the effective completion of social work regulatory legislation across provincial Canada. This article outlines the principal features of the Ontario regulations, and summarises the strengths and limitations of the various arrangements which have been implemented across Canada. As moves toward control of the Australian social work profession are contemplated, the implications for such a move are discussed in the light of the Canadian experience.     

On the α-risks for shewhart control charts

The performance of the usual Shewhart control charts for monitoring process means and variation can be greatly affected by nonnormal data or subgroups that are correlated. Define the α_k-risk for a Shewhart chart to be the probability that at least one “out-of-control” subgroup occurs in k subgroups when the control limits are calculated from the k subgroups. Simulation results show that the α_k-risks can be quite large even for a process with normally distributed, independent subgroups. When the data are nonnormal, it is shown that the α_k-risk increases dramatically. A method is also developed for simulating an “in-control” process with correlated subgroups from an autoregressive model. Simulations with this model indicate marked changes in the α_k-risks for the Shewhart charts utilizing this type of correlated process data. Therefore, in practice a process should be investigated thoroughly regarding whether or not it is generating normal, independent data before out-of-control points on the control charts are interpreted to be due to some real assignable cause.     

Stop the Beat: Quiet Regulation and Cultural Conflict1

This article explores a recent conflict over the youth phenomenon known as “raving” in the City of Chicago. By interviewing participants involved in the conflict, I set out to understand the extent to which the crackdown on raves in Chicago was similar to earlier social reactions to jazz, comic books, rock and roll, and Dead Head culture, as well as to more recent conflicts over punk, rap music, and raves in other cities. While most previous research on cultural conflict has focused on moral crusades, campaigns, and panics, the Chicago conflict represents an example of “quiet regulation.” Opponents refrained from highly visible, morally charged attacks; instead, in the absence of media hype and visible public discourse, public officials justified the crackdown in highly bureaucratic terms—avoiding risk, collecting taxes, enforcing codes. Nonetheless, they also drew on cultural schemas that linked raves and raving with drugs, sex, and deviance. As a result, officials selected a course of regulation that criminalized DJs and discredited the artform. In the absence of a highly visible moral campaign, the rave participants were unable to mobilize and resist the regulation and defend their lifestyle. Sociologists must move beyond highly visible campaigns and crusades and pay greater attention to quiet regulation, both because such regulation is likely to increase in the future and because it has significant consequences for power, cultural expression, and identity.     

Sequential estimation problems for negative exponential populations

The literature on sequential estimation problems for negative exponential populations has been reviewed here, We attempt to bring in all the published and unpublished materials known to us in a fairly coherent fashion. Both the concepts and theoretical findings are discussed.     

Estimation of a process capability index for inverse gaussian distribution

In this article, interval estimates of Clements' process capability index are studied through bootstrapping when the underlying distribution is Inverse Gaussian. The standard bootstrap, the percentile bootstrap, and the bias-corrected percentile bootstrap confidence intervals are compared.     

On second-order improved estimation of a gamma scale parameter

This paper concludes our comprehensive study on point estimation of model parameters of a gamma distribution from a second-order decision theoretic point of view. It should be noted that efficient estimation of gamma model parameters for samples ‘not large’ is a challenging task since the exact sampling distributions of the maximum likelihood estimators and its variants are not known. Estimation of a gamma scale parameter has received less attention from the earlier researchers compared to shape parameter estimation. What we have observed here is that improved estimation of the shape parameter does not necessarily lead to improved scale estimation if a natural moment condition (which is also the maximum likelihood restriction) is satisfied. Therefore, this work deals with the gamma scale parameter estimation as a separate new problem, not as a by-product of the shape parameter estimation, and studies several estimators in terms of second-order risk.     

Some tests for the power series distibutions in one parameter using the kullback-leibler information measure

The purpose of the article is, in case of one sample, to obtain tests concerning the parameter in the power series distribution in one parameter using Ku11back-Leibier information measure. The class of power series distibutions contains a host of discrete distributions. Ve illustrate the general results obtained in case of the geometric distibution.     

谈建设工程造价的全过程控制

建设项目工程造价管理的基本内容就是合理确定和有效地控制工程造价．本文对如何做到“事前把关、过程与动态管理为特征”的全过程控制进行了论述．     

乙二醇机组的温度模糊控制器设计与仿真

针对我国通信行业和计算机行业大型机房耗电量大的现状，提出了一种乙二醇机组控制系统。介绍了它的工作原理，阐述了它的总体控制方案，并重点阐述了采用温度模糊PID控制器对室内温度进行调节。仿真和实验结果表明：采用温度模糊控制器的系统运行稳定、可靠性高、节能效果明显，具有广阔的应用前景。