• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 34
  • 21
  • 13
  • Tagged with
  • 34
  • 34
  • 34
  • 20
  • 15
  • 13
  • 11
  • 11
  • 11
  • 11
  • 10
  • 10
  • 9
  • 9
  • 9
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

應用資料包絡法降低電源轉換器溫升之研究

廖 合, Liao,Ho Unknown Date (has links)
由績效觀點,品質(適質)與成本(適量),在概念上是完全一致的。因此,績效的管理,應以品質與成本作為其目標達成與否的衡量標準。本研究以績效觀點來解決公司面臨到品質與成本的兩難的問題。隨著電子產品的功能多樣化,發熱問題卻接踵而來,發熱密度的不斷提昇,對於散熱設計的需求也越來越受到重視。本研究以電源轉換器為對象,其目前已設計完成且已通過美國UL安規認證,但因為其溫升及其變異很大,因此降低電源轉換器的溫升及其變異是一急需解決的問題,以期能找出穩健於不可控因子,使產品變異小且各零件溫升與損失均能降至最低的最適外部零件組合。透過了田口與實驗設計的方法規劃及進行實驗並收集數據。引用加權SN比(multi-response S/N ratio)的方法,分別透過(1)管制圖法及(2)資料包絡法的CCR保證領域法(指CCR-AR模型)來決定加權SN比的權數,以決定可控因子及其水準值。對矩陣實驗的數據利用MTS ( M a h a l o n o b I s - Taguchi System)來篩選研究問題中較重要的特性變數,再針對篩選結果中較重要的特性變數的數據分別利用(1)倒傳遞類神經網路結合資料包絡法及(2)資料包絡法結合主成份分析法兩種分析方法,得到外殼鑽孔形狀與矽膠片大小的最佳因子組合。由改善後的確認實驗結果得知,雖然平均溫升下降的程度不大,然而大部份量測點的溫升標準差都顯著變小了,因此本研究在降低該電源轉換器溫升變異的效果顯著。
32

新的加權平均損失管制圖 / A new weighted average loss control chart

歐家玲, Ou, Chia Ling Unknown Date (has links)
近幾年來,有一些研究提出了只用單一一個管制圖即可同時偵測平均數和變異數。根據此目的,我們提出了加權平均損失管制圖,此管制圖是利用加權平均損失所建立的,在一個製成的目標值和平均數不一定相等時,它可同時監控一個製成的平均數和變異數。此加權平均損失統計量是應用一個加權因子,去調整製程平均和目標值的平方差和變異數的損失比重,所以此管制圖的效能比未經由加權因子調整過的管制圖還好。我們不只建立了固定管制參數(FP)加權平均損失管制圖,也建立了適應性加權平均損失管制圖,包括變動抽樣間隔(VSI)、變動樣本數與抽樣間隔(VSI)、變動管制參數(VP);我們利用平均連串長度(ARL)來衡量固定管制參數管制圖的偵測績效,利用馬可夫鏈的方法計算偵測出異常訊息所需的平均時間(ATS)來衡量適應性管制圖的績效,並且做比較,我們發現適應性管制圖比固定管制參數管制圖的效能還要好。我們也利用最佳化技術建立最加適應性管制圖,當製成失控時,此最佳化管制圖能使ATS1最小。此外,當平均數和變異數的偏移幅度很小時,我們利用指數加權移動平均法(EWMA)建立EWMA加權平均損失管制圖,使其有較好的偵測力。這些我們所提出的管制圖,是只根據單一一個統計量所建立的,和X bar-S管制圖相比,有較好的效能,且和使用兩個管制圖同時偵測平均數和變異數相比,比較輕易理解且容易執行。 / In recent years, a few researchers had proposed different types of single charts that jointly monitor the process mean and the variation. In this project, we use the weighted average loss (WL) to construct WL control charts for monitoring the process mean and variance simultaneously while the target value may be different from the in-control mean. This statistic WL applied a weighted factor to adjust the weights of the loss due to the square of the deviation of the process mean from the target and the variance change. So the WL charts are more effective than unadjusted loss function charts. We not only construct the fixed parameters (FP) WL chart but also the adaptive WL charts which included variable sampling interval (VSI) WL chart, variable sample size and sampling interval (VSSI) WL chart and variable parameters (VP) WL chart. We calculate the average run length (ARL) for FP WL chart and using Markov chain approach to calculate the average time to signal (ATS) for adaptive WL charts to measure the performance and compare each other. From the comparison, we find the adaptive WL charts are more effective than the FP WL chart. We also proposed the optimal adaptive WL charts using an optimization technique to minimize ATS1 (ARL1) when the process was out-of-control. In addition, in order to detect the small shifts of the process mean and variance effectively, we construct the WL charts using the EWMA scheme. The proposed charts are based on only one statistic and are more effective than the X bar-S chart. And the WL charts are easy to understand and apply than using two charts for detecting the mean and variance shifts simultaneously.
33

適應性計數值損失函數管制圖之設計 / Design of the Adaptive Loss Function Control Chart for Binomial Data

李宜臻, Lee,I Chen Unknown Date (has links)
This article proposes the algorithm of a new control chart (loss function control chart) based on the Taguchi loss function with an adaptive scheme for binomial data. The loss function control chart is able to monitor cost variation from the process by applying loss function in the design. This new angle economically explores production cost. This research provides designs of the loss function control chart with specified VSI, optimal VSI, VSS and VP, respectively. Numerical analyses show that the specified VSI loss function chart, the optimal VSI loss function chart, the optimal VSS loss function chart and the optimal VP loss function chart outperform the Fp loss function chart significantly and show costs can be controlled systematically.
34

變動樣本大小的無母數平均值管制圖之研究 / Study of nonparametric mean control chart with variable sample sizes

周遊宇, Zhou, Youyu Unknown Date (has links)
自舒華特發明以管制圖監測製程以來,管制圖在工程的應用日趨重要。在特殊工程中,一個高效的管制圖方法尤為重要。基於此項事實,在文獻中各式各樣的管制圖層出不窮且技術日益完善。但傳統管制圖往往受制于常態分佈,因此在無母數管制圖研究方向仍有大量工作值得探討。於是本文在母體分佈未知情況下,推廣Yang (2015)的無母數平均值管制圖方法建立變動樣本指数加权移动平均管制圖,VSS EWMA-np control chart。新的管制圖將變動樣本大小(VSS)和指數加權移動平均(EWMA)方法結合建立一種新的管制圖方法,並用這種新型管制圖監測未知分佈母體的平均值是否發生變動。而為了監測平均數是否發生變化,也為了減少抽樣損失,本文評估管制圖監測效力的指標為管制圖偵測出異常訊息所需抽樣的樣本數期望值(EN)、平均連串長度(ARL)和平均觀測值總數(ANOS)。從本文的比較結果看出新的變動樣本指數加權移動平均管制圖擁有更好的失控偵測力。 / Since Shewhart invention control chart monitor the process, control charts are increasingly important in engineering applications. In special projects, an efficient control chart is especially important. Based on this fact, the various kinds of control charts in the literature are not poor and the technology is improving. However, traditional control charts are often subject to normal distribution, so there is still a lot of work to be discussed in the direction of the study of non-parametric control charts. So in this paper under unknown distribution in the matrix, Yang (2015) established on the basis of the theory of a non-parametric method of control chart - Exponentially Weighted Moving Average Control Chart with Variable Sampling Sizes (VSS EWMA - np control chart). New control chart will change the sample size (VSS) and exponential weighted moving average (EWMA) method to establish a new control chart, and use new control chart for monitoring the mean of unknown distribution matrix is changed. And whether to monitor the average changes in order to reduce the loss of sampling, this paper mainly evaluate control chart for monitoring the effectiveness of the statistics for the expected value of the sample size (EN), the average run length (ARL) and the average number of observations to signal (ANOS). From the comparison shown in this paper, the new control chart has better detection.

Page generated in 0.0235 seconds