Enhanced adaptive CUSUM charts for process mean

A statistical quality control chart is an important tool of the statistical process control, which is widely used to control and monitor a production process. The CUSUM chart is designed to detect a specific shift, provided that the shift size is known in advance. In practice, however, shift sizes are rarely known. It is then customary to use an adaptive CUSUM chart, which can effectively detect a range of shift sizes. In this paper, we enhance the sensitivities of the improved adaptive CUSUM mean charts using an auxiliary-information-based (AIB) mean estimator. The run length performances of the proposed charts are compared with those of the AIB adaptive and non-adaptive CUSUM charts in terms of the average run length (ARL), extra quadratic loss, and integral relative ARL. These run length comparisons reveal that the proposed charts are more sensitive than the existing charts when detecting different kinds of shift in the process mean. An example is given to demonstrate the implementation of existing and proposed charts.     

The effect of Phase I sample size on the run length performance of control charts for autocorrelated data

Traditional control charts assume independence of observations obtained from the monitored process. However, if the observations are autocorrelated, these charts often do not perform as intended by the design requirements. Recently, several control charts have been proposed to deal with autocorrelated observations. The residual chart, modified Shewhart chart, EWMAST chart, and ARMA chart are such charts widely used for monitoring the occurrence of assignable causes in a process when the process exhibits inherent autocorrelation. Besides autocorrelation, one other issue is the unknown values of true process parameters to be used in the control chart design, which are often estimated from a reference sample of in-control observations. Performances of the above-mentioned control charts for autocorrelated processes are significantly affected by the sample size used in a Phase I study to estimate the control chart parameters. In this study, we investigate the effect of Phase I sample size on the run length performance of these four charts for monitoring the changes in the mean of an autocorrelated process, namely an AR(1) process. A discussion of the practical implications of the results and suggestions on the sample size requirements for effective process monitoring are provided.     

基于DirectX软件包进行三维图形的开发应用

介绍了3D图形技术应用的概况和Windows平台上DirectX编程的框架结构，及利用DirectX8.1软件包进行3D图形开发应用的一些基本概念。用Visual Basic进行了实践，建立了一个3D数据图表控件（DX Chart)，叙述了此控件的设计规划与具体实现。     

铁氧体全极化器信号流图分析

应用信号流图分析了 3种不同组合全极化器 ,同时考虑 2个铁氧体杆之间的反射 .尽管反射系数和损耗都是小量 ,但精确圆极化仍无法得到 .     

AutoCAD中化工工艺流程图图幅设置的实现研究

本文利用AutoCAD的二次开发功能，开发了化工工艺流程图图样幅面设置功能。该功能根据用户选择的标准图样幅面，可实现工艺流程图所需图样幅面的任意加长，并可使图样自动左移任意个1／4标准幅面长和绘制标题栏。     

可编程控制器PLC在电厂气力除灰装置中的应用

介绍了电厂气力除灰装置控制系统中,用PLC控制的总体功能图,并给出了控制程序.     

Mental Health Concerns of Gay and Bisexual Men Seeking Mental Health Services

ABSTRACT

Little data exist about the mental health needs of gay and bisexual men. This is due to limitations of existing studies such as small and nonrepresentative samples, failure to assess sexual orientation, and concerns about stigmatization, possibly causing sexual minority individuals to be reluctant to disclose their sexual orientation to researchers. Fenway Community Health is a large urban health center that serves the LGBT community. The large number of gay and bisexual men who present for mental health treatment allows for a unique opportunity to gain insight into mental health, prevention, and intervention needs for this group. The current study is a review of the mental health information from all of the gay and bisexual men who reported that they were HIV-negative during their mental health intake over a six-month period at Fenway Community Health (January to June 2000; N = 92). The most frequent presenting problems were depression, anxiety, and relationship issues. Additionally, presenting problems included current or past abuse, substance abuse, finance and employment, recent loss, and family issues. The most frequent diagnoses were depression, anxiety disorders, and adjustment disorders. These findings support the notion that presenting problems and mental health concerns among gay and bisexual men are similar to those frequently reported by individuals in other mental health facilities, however, specific psychosocial stressors are unique to this population.     

Two parameter cuscore qualty control procedures

This paper is concerned with the problem of simultaneously monitoring the process mean and process variability of continuous production processes using combined Shewhart-cumulative score (cuscore) quality control procedures developed by Ncube and Woodall (1984). Two methods of approach are developed and their properties are investigated. One method uses two separate Shewhart-cuscore control charts, one for determining shifts in the process mean and the other for detecting shifts in process variability. The other method uses a single combined statistic which is sensitive to shifts in both the mean and the variance. Each procedure is compared to the corresponding Shewhart schemes. It will be shown by average run length calculations that the proposed Shewhart- cuscore schemes are considerably more efficient than the comparative Shewhart procedures for certain shifts in the process mean and process variability for the case when the underlying process control variable is assumed to be normally distributed.     

ON THE ECONOMIC DESIGN OF MULTIVARIATE CONTROL CHARTS

ABSTRACT

It is an increasingly common practice to monitor several related quality characteristics of a product or process using a multivariate control chart procedure. Several types of multivariate control charts, including Hotelling's χ ² and T ² control charts, have been developed in attempts to improve monitoring by using the correlation structure that exists between quality characteristics. The purpose of this paper is to summarize the assumptions made regarding the out-of-control process shift in the economic design of multivariate control charts and to address their consequences. We study the average run length (ARL) properties of the χ ² control chart using a numerical example and show that this chart can perform ineffectively under the assumed out-of-control conditions when designed using the economic approach. Following Healy,[1] Healy, J.D. 1987. A Note on the Multivariate CUSUM Procedures. Technometrics, 29: 409–412. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar] we offer an alternative procedure that has improved ARL properties and overall performance. These results can be important to researchers and practitioners who are interested in using the economic design of multivariate control procedures.     

Parallel discretization of the Markov chain approximation for the autoregressive moving average chart

Abstract

In the Markov chain model of an autoregressive moving average chart, the post-transition states of nonzero transition probabilities are distributed along one-dimensional lines of a constant gradient over the state space. By considering this characteristic, we propose discretizing the state space parallel to the gradient of these one-dimensional lines. We demonstrate that our method substantially reduces the computational cost of the Markov chain approximation for the average run length in two- and three-dimensional state spaces. Also, we investigate the effect of these one-dimensional lines on the computational cost. Lastly, we generalize our method to state spaces larger than three dimensions.