Beyond improved quality: the motivational effects of statistical process control

The deployment of statistical process control (SPC) in manufacturing environments is a prominent global phenomenon. Managers have frequently justified investments in SPC by citing and/or demonstrating the improvements in quality and costs from the effective implementation and practice of SPC. This paper complements this rationalization by presenting conceptual arguments and empirical evidence to further our understanding of the motivational effects that result from the deployment of SPC within production environments. Several hypotheses derived from relating the deployment of SPC to process operators’ jobs and their affective reactions to work are tested using data provided by 100 process operators. The empirical results, generated from applying path analysis, suggest that the effective implementation and practice of SPC, in fact, would create more enriched jobs for process operators that lead to higher levels of work motivation and job satisfaction.     

On random fuzzy variables of second order and their application to linear statistical inference with fuzzy data

This paper summarizes some results on random fuzzy variables with existing expectation and variance, called random fuzzy variables of second order. Using the Frechét-principle and – via support functions – the embedding of convex fuzzy sets into a Banach space of functions it especially presents a unified view on expectation and variance of random fuzzy variables. These notions are applied in developing linear statistical inference with fuzzy data. Detailed investigations are presented concerning best linear unbiased estimation in linear regression models with fuzzy observations. Received: November 1999     

Estimating the returns to education for Australian youth via rank-order instrumental variables

This paper employs the rank-order instrumental variable (IV) procedure of Vella and Verbeek [Vella, F., Verbeek, M., 1997. Using rank order as an instrumental variable: an application to the return to schooling, CES Discussion Paper 97.10, K.U. Leuven.] to estimate the returns to education for Australian youth. The attraction of this approach is that it can account for the endogeneity of schooling in the wage equation via the use of instrumental variables without the use of exclusion restrictions. We find, after accounting for the endogeneity of schooling, that an additional year of schooling is associated with an increase in wages of approximately 8%. Furthermore, we find that the rank-order IV approach is able to identify the presence of endogeneity in this particular empirical example. However, despite this, the adjusted estimate of how schooling affects wage is close to the ordinary least squares (OLS) estimate.     

Estimation in Shewhart control charts: effects and corrections

The influence of the estimation of parameters in Shewhart control charts is investigated. It is shown by simulation and asymptotics that (very) large sample sizes are needed to accurately determine control charts if estimators are plugged in. Correction terms are developed to get accurate control limits for common sample sizes in the in-control situation. Simulation and theory show that the new corrections work very well. The performance of the corrected control charts in the out-of-control situation is studied as well. It turns out that the correction terms do not disturb the behavior of the control charts in the out-of-control situation. On the contrary, for moderate sample sizes the corrected control charts remain powerful and therefore, the recommendation to take at least 300 observations can be reduced to 40 observations when corrected control charts are applied.Acknowledgements. The authors would like to thank Sri Nurdiati for doing the Monte Carlo studies.     

Performance assessment and improvement of control charts for statistical batch process monitoring

This paper describes the concepts of statistical batch process monitoring and the associated problems. It starts with an introduction to process monitoring in general which is then extended to batch process monitoring. The performance of control charts for batch process monitoring is discussed by means of two performance indices: the overall type I error and the action signal time. Problems associated with the existing approach are discussed and highlighted. Improvements are suggested and checked with the performance indices. To evaluate the effect of the proposed improvements as well as to assess the performance of the existing approach, an industrial batch production process is used.     

隧道衬砌台车在衬砌施工中的质量控制对策

文章通过多年从事衬砌台车的设计、生产与使用的工作实践,并以昆河线玉蒙铁路特长隧道--通海隧道衬砌施工为例,阐述了衬砌台车在隧道衬砌施工过程中如何进行质量控制、确保衬砌质量良好的对策。     

Using On-Line Process Data to Improve Quality: Challenges for Statisticians*

In the process industries measurements on a large number of process variables are routinely collected at regular intervals by on-line computers. This paper makes a case for incorporating these process variables into Statistical Process Control (SPC) schemes. Multivariate statistical methods such as Principal Component Analysis (PCA) and Partial Least Squares (PLS) can be used to project these data down into low dimensional spaces where analysis, monitoring and diagnosis are easily performed. Strong justifications for taking this approach are presented and examples are given. The statistical process control community has been slow in adapting to the data explosion brought about by the computer era. It has continued to stick with traditional control charts on the quality variables and ignored this rich source of additional information on the process. This paper explores some of the reasons for this and argues that the SPC community must adapt rapidly or lose control of the field to scientists and engineers. The paper also tries to induce statisticians into looking more seriously at the many unsolved problems in this area of reduced rank multivariate statistics.     

Dreams of urbanization: Quantitative case studies on the local impacts of nuclear power facilities using the synthetic control method

This paper uses the synthetic control (SC) method to examine how the establishment of nuclear power facilities (NPFs) in Japan in the 1970s and 1980s has affected local per capita income levels in the municipalities in which they were localted (NPF municipalities). Eight quantitative case studies using the SC method clarify that the effects of NPF establishment on per capita taxable income levels are highly heterogeneous. The estimated effects are often economically meaningful and in some cases huge: the income level was 11% higher on average and 62% higher in one municipality in 2002 when compared with counterfactual units. On the other hand a few of the NPF municipalities have received only weak or negligible effects from NPF establishment. The post-estimation comparisons of employment between the NPF municipalities and the SC units suggest that the size of the direct labor demand shocks and subsequent indirect employment effects on nontradable service sectors have contributed to the increase in per capita income levels.     

Comparisons of control schemes for monitoring the means of processes subject to drifts

Although statistical process control (SPC) techniques have been focused mostly on detecting step (constant) mean shift, drift which is a time-varying change frequently occurs in industrial applications. In this research, for monitoring drift change, the following five control schemes are compared: the exponentially weighted moving average (EWMA) chart and the cumulative sum (CUSUM) charts which are recommended detecting drift change in the literature; the generalized EWMA (GEWMA) chart proposed by Han and Tsung (2004) and two generalized likelihood ratio based schemes, GLR-S and GLR-L charts which are respectively under the assumption of step and linear trend shifts. Both the asymptotic estimation and the numerical simulation of the average run length (ARL) are presented. We show that when the in-control (IC) ARL is large (goes to infinity), the GLR-L chart has the best overall performance among the considered charts in detecting linear trend shift. From the viewpoint of practical IC ARL, based on the simulation results, we show that besides the GLR-L chart, the GEWMA chart offers a good balanced protection against drifts of different size. Some computational issues are also addressed.     

浅论如何加强企业内部会计控制

文章认为单位内部会计控制制度是我国会计监督体系的重要组成部分,强化企业内部会计控制,在建立现代企业制度,强化内部自我约束机制,提高会计信息质量等多方面发挥着十分重要的作用。     

A control function approach for testing the usefulness of trending variables in forecast models and linear regression

Many predictors employed in forecasting macroeconomic and finance variables display a great deal of persistence. Tests for determining the usefulness of these predictors are typically oversized, overstating their importance. Similarly, hypothesis tests on cointegrating vectors will typically be oversized if there is not an exact unit root. This paper uses a control variable approach where adding stationary covariates with certain properties to the model can result in asymptotic normal inference for prediction regressions and cointegration vector estimates in the presence of possibly non-unit root trending covariates. The properties required for this result are derived and discussed.     

Performance effects of using an ERP system for manufacturing planning and control under dynamic market requirements

Enterprise resource planning (ERP) systems have a controversial reputation. Critics say that even if ERP systems may be beneficial for organizations operating in stable conditions, they are surely detrimental to organizations that face dynamic market requirements. This is because ERP systems are said to impose such procedures and constraints on organizations that make business processes inflexible to change. In contrast, proponents argue that the information-processing capabilities of ERP systems are crucial for organizations that face dynamic market requirements and also that the criticized procedures and constraints actually support process reengineering. These two contradictory arguments are often found in practitioner literature, but both of them can also be supported by management theory. The central tenets of the Organic Theory of organization design imply that ERP systems should be detrimental when market requirements change frequently, whereas the principles of Rigid Flexibility Theory suggest that they should be advantageous. In this study, we use cross-sectional data from 151 manufacturing plants to determine which argument is more applicable in the context of manufacturing planning and control. The results strongly favor the use of ERP systems under dynamic market requirements. To facilitate the reconciliation of the two contradictory arguments, we discuss how the results may have been influenced by two contextual factors: the predominantly technical nature of the studied organizational system and the tight interdependence of the studied activities.     

A new approach to capital control for emerging market economies

The present paper proposes a new approach to capital control for emerging market economies, which restricts capital inflows to a fraction of the gap between foreign currency denominated loans and deposits in the economy. We show that the foreign-currency-gap capital control proposed here outperforms tax-based capital control in attenuating the negative effects of external shocks on business cycle fluctuations. This attenuation effect works via the interest rate channel and the capital control constraint itself. Compared to tax-based capital control, the foreign-currency-gap capital control is welfare enhancing, effectively mitigating financial instability with little cost in terms of macroeconomic stability. Countries with a high level of foreign currency denominated loans and deposits need to implement a stricter foreign-currency-gap capital control.     

大体积混凝土裂缝控制及处理措施探讨

文章针对大体积混凝土裂缝的成因进行探讨,以大体积混凝土施工阶段的裂缝控制为研究对象,在对裂缝的种类及成因进行分析的基础上,阐述了大体积混凝土裂缝控制的理论及措施,并对工程实例进行分析比较。     

我国企业内部会计控制问题浅议

会计控制是企业管理的一部分。然而,我国企业内部会计控制方面存在着诸多的问题,导致了内部会计控制的弱化,笔者对此进行了分析,并提出了相应的对策建议。     

注重发挥标准在宏观调控中的积极作用

标准作为一项基础的技术制度，能够规范市场秩序，激励自主创新，推动产业升级，支持可持续发展，促进国际贸易，能够在宏观调控中发挥重要的积极作用。文章认为注重标准在宏观调控中的地位，充分发挥标准在宏观调控中的积极作用，对于做好宏观调控工作，建设资源节约型和环境友好型社会，实现“十一五”规划提出的战略目标，具有十分重要的现实意义。文章对宏观调控中标准的作用机制进行了分析，在此基础上提出了在宏观调控中发挥标准积极作用的路径和措施，为做好宏观调控工作提供了一种新的视角。     

Policy reconciliation for access control in dynamic cross-enterprise collaborations

In dynamic cross-enterprise collaborations, different enterprises form a – possibly temporary – business relationship. To integrate their business processes, enterprises may need to grant each other limited access to their information systems. Authentication and authorization are key to secure information handling. However, access control policies often rely on non-standardized attributes to describe the roles and permissions of their employees which convolutes cross-organizational authorization when business relationships evolve quickly. Our framework addresses the managerial overhead of continuous updates to access control policies for enterprise information systems to accommodate disparate attribute usage. By inferring attribute relationships, our framework facilitates attribute and policy reconciliation, and automatically aligns dynamic entitlements during the evaluation of authorization decisions. We validate our framework with a Industry 4.0 motivating scenario on networked production where such dynamic cross-enterprise collaborations are quintessential. The evaluation reveals the capabilities and performance of our framework, and illustrates the feasibility of liberating the security administrator from manually provisioning and aligning attributes, and verifying the consistency of access control policies for cross-enterprise collaborations.     

Estimating distributions of potential outcomes using local instrumental variables with an application to changes in college enrollment and wage inequality

This paper extends the method of local instrumental variables developed by Heckman and Vytlacil [Heckman, J., Vytlacil E., 2005. Structural equations, treatment, effects and econometric policy evaluation. Econometrica 73(3), 669–738] to the estimation of not only means, but also distributions of potential outcomes. The newly developed method is illustrated by applying it to changes in college enrollment and wage inequality using data from the National Longitudinal Survey of Youth of 1979. Increases in college enrollment cause changes in the distribution of ability among college and high school graduates. This paper estimates a semiparametric selection model of schooling and wages to show that, for fixed skill prices, a 14% increase in college participation (analogous to the increase observed in the 1980s), reduces the college premium by 12% and increases the 90–10 percentile ratio among college graduates by 2%.     

Conditions for policy implementation via co-production: the control of dengue fever in Brazil

In this paper, we identify the conditions that must be present for effective policy implementation using co-production. To this end, we investigated five cases in which co-production was used to combat the vector of dengue, the Aedes Aegypti mosquito, in Brazil. Data were analysed using content analysis and crisp-set QCA methods to identify the combination of conditions that explain successful outcomes. Five conditions were found to be necessary for effective implementation via co-production: technical, economic, normative, cognitive and structural. The contribution of this study is to provide empirical evidence with respect to the conditions that effectively lead to successful outcomes.     

Linking performance drivers in production planning and inventory control to process choice

This study investigates how process choice relates to production planning and inventory control decisions. We empirically examine the validity of deductively derived patterns about these types of decisions. More importantly, we look for normative insights by exploring how production planning and inventory control decisions affect operations performance. Our findings show that production line and continuous flow plants use more of a level production strategy, and carry less raw material and work-in-process inventory. The performance drivers for these plants, through which the operations function excels, are effective utilization of equipment, reduced finished goods inventory, and reduced setup down time. To gain forward demand visibility and batching economies, job and batch shops rely much more on backlogs in their planning process. These plants use more of a production chase strategy and position inventory lower in the bills of materials. Four performance drivers for top-performing job and batch shops are to find ways that better anticipate customers' orders, have a more responsive chase strategy, carry less raw material or purchased inventory, and shorten production planning horizon, partly through less reliance on backlogs. It is intriguing that top-performing plants not only do the expected things, given their choice of process, but also excel in selected dimensions—some of which fit the profile normally associated with a different process choice. To monitor and continuously improve operations, evaluation ‘scorecards’ should pay particular attention to performance drivers, which change depending on the plant's process choice.