针对两个正态随机变量比率(Ratio of Two Normal Random Variables,RZ)监控的研究是近年来统计过程控制的重要方向之一。为了进一步提高传统休哈特型RZ控制图对过程中较小或中等参数偏移的灵敏度,本文以指数加权移动平均(Exponentially ...针对两个正态随机变量比率(Ratio of Two Normal Random Variables,RZ)监控的研究是近年来统计过程控制的重要方向之一。为了进一步提高传统休哈特型RZ控制图对过程中较小或中等参数偏移的灵敏度,本文以指数加权移动平均(Exponentially Weighted Moving Average,EWMA) RZ控制图为基础,提出了一种新的RZ控制图。首先,对EWMA-RZ控制图的平滑系数进行两次加权,提出了二次指数加权移动平均(Double EWMA,DEWMA) RZ控制图,并进一步引入了变采样间隔(Variable Sampling Interval,VSI)特性,提出了VSI-DEWMA-RZ控制图;其次,采用蒙特卡罗(Monte-Carlo,MC)仿真模拟所提出控制图的运行链长分布特征,并详细分析了控制图的性能;再次,针对不同的控制图参数,比较了VSI-DEWMA-RZ控制图与DEWMA-RZ和VSI-EWMA-RZ控制图的性能。仿真结果表明,本文提出的VSI-DEWMA-RZ控制图优于DEWMA-RZ控制图,且其对过程中较小和中等偏移的监控效果优于现有的VSI-EWMA-RZ控制图。最后,通过监控食品加工过程中“南瓜籽”和“亚麻籽”的重量,进一步说明了所提出控制图的优越性。展开更多
The objective of the study is to examine the conditions under which transition metal ion,Cu 2+ could catalyze potassium persulfate to oxidize gaseous mercury.The effects of the concentrations of potassium persulfate a...The objective of the study is to examine the conditions under which transition metal ion,Cu 2+ could catalyze potassium persulfate to oxidize gaseous mercury.The effects of the concentrations of potassium persulfate and copper sulfate,and addition of sodium thiosulfate and tertiary butanol（TBA）,a free radical scavenger on the efficiency of Hg removal were studied.The results showed that the efficiency of Hg removal increased with increasing concentrations of potassium persulfate,copper sulfate and the addition of sodium thiosulfate,while decreased with the addition of TBA.The oxidation reaction between Hg and K2S2O8 catalyzed by Cu 2+ followed pseudo-first-order kinetics.Direct rate constant and catalyzed rate constant were 3.52×10 -5 s -1 and 0.0927 L·mol -1 ·s -1 ,respectively.Furthermore,the possible reaction mechanism of gaseous mercury oxidation was also discussed.Cu 2+ was considered as an effective complex anion activator in persulfate-thiosulfate redox system and Hg removal can be achieved by both indirect oxidation of free radicals and direct oxidation by persulfate.展开更多
文摘针对两个正态随机变量比率(Ratio of Two Normal Random Variables,RZ)监控的研究是近年来统计过程控制的重要方向之一。为了进一步提高传统休哈特型RZ控制图对过程中较小或中等参数偏移的灵敏度,本文以指数加权移动平均(Exponentially Weighted Moving Average,EWMA) RZ控制图为基础,提出了一种新的RZ控制图。首先,对EWMA-RZ控制图的平滑系数进行两次加权,提出了二次指数加权移动平均(Double EWMA,DEWMA) RZ控制图,并进一步引入了变采样间隔(Variable Sampling Interval,VSI)特性,提出了VSI-DEWMA-RZ控制图;其次,采用蒙特卡罗(Monte-Carlo,MC)仿真模拟所提出控制图的运行链长分布特征,并详细分析了控制图的性能;再次,针对不同的控制图参数,比较了VSI-DEWMA-RZ控制图与DEWMA-RZ和VSI-EWMA-RZ控制图的性能。仿真结果表明,本文提出的VSI-DEWMA-RZ控制图优于DEWMA-RZ控制图,且其对过程中较小和中等偏移的监控效果优于现有的VSI-EWMA-RZ控制图。最后,通过监控食品加工过程中“南瓜籽”和“亚麻籽”的重量,进一步说明了所提出控制图的优越性。
文摘The objective of the study is to examine the conditions under which transition metal ion,Cu 2+ could catalyze potassium persulfate to oxidize gaseous mercury.The effects of the concentrations of potassium persulfate and copper sulfate,and addition of sodium thiosulfate and tertiary butanol（TBA）,a free radical scavenger on the efficiency of Hg removal were studied.The results showed that the efficiency of Hg removal increased with increasing concentrations of potassium persulfate,copper sulfate and the addition of sodium thiosulfate,while decreased with the addition of TBA.The oxidation reaction between Hg and K2S2O8 catalyzed by Cu 2+ followed pseudo-first-order kinetics.Direct rate constant and catalyzed rate constant were 3.52×10 -5 s -1 and 0.0927 L·mol -1 ·s -1 ,respectively.Furthermore,the possible reaction mechanism of gaseous mercury oxidation was also discussed.Cu 2+ was considered as an effective complex anion activator in persulfate-thiosulfate redox system and Hg removal can be achieved by both indirect oxidation of free radicals and direct oxidation by persulfate.
