Browsing by Author "Wu, CW"

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A Bayesian approach for assessing process precision based on multiple samples
(2005-09-16)
Pearn, WL
;
Wu, CW
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工業工程與管理學系
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Department of Industrial Engineering and Management
Using process capability indices to quantify manufacturing process precision (consistency) and performance, is an essential part of implementing any quality improvement program. Most research works for testing the capability indices have focused on using the traditional distribution frequency approaches. Cheng and Spiring [IIE Trans. 21 (1) 97) proposed a Bayesian procedure for assessing process capability index C-P based on one single sample. In practice, manufacturing information regarding product quality characteristic is often derived from multiple samples, particularly, when a routine-based quality control plan is implemented for monitoring process stability. In this paper, we consider estimating and testing C-P with multiple samples using Bayesian approach, and propose accordingly a Bayesian procedure for capability testing. The posterior probability, p, for which the process under investigation is capable, is derived. The credible interval, a Bayesian analogue of the classical lower confidence interval, is obtained. The results obtained in this paper, are generalizations of those obtained in Cheng and Spiring [IIE Trans. 21 (1), 97]. Practitioners can use the proposed procedure to Cheng and Spiring determine whether their manufacturing processes are capable of reproducing products satisfying the preset precision requirement. (c) 2004 Elsevier B.V. All rights reserved.
A Sigma-Delta modulation based analog BIST system with a wide bandwidth fifth-order analog response extractor for diagnosis purpose
(2004)
Hong, HC
;
Wu, CW
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Cheng, KT
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電控工程研究所
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Institute of Electrical and Control Engineering
A wide bandwidth Sigma-Delta modulation based analog built-in self-test (BIST) system that can diagnose the prototype is presented. It consists of a low-cost design-for-testability (DfT) switched-capacitor filter as the circuit under test (CUT) and a wide bandwidth analog response extractor (ARE) to digitize the analog responses for final DSP analysis. The first stage of the DfT CUT is reconfigured to accept a repetitive Sigma-Delta modulated bit-steam as its stimulus. This DfT technique reuses every original component and thus provides the advantages of lowering the testing cost, increasing the fault coverage as well as the accuracy, and being able to perform the at-speed tests. The ARE is a cascaded 2-1-1-1 fifth-order Sigma-Delta modulator equipped with single-bit quantizers to extend the testing bandwidth while retaining moderate tolerance of circuit imperfections. Our measurement results show that this ARE is able to provide a -95 dB spurious free dynamic range over 1 MHz bandwidth when operates at 30 MHz. A multi-tone test is performed to manifest the wide bandwidth and high accuracy of our BIST system. Based on the BIST results, a novel method of diagnosing the prototype to speed up the time-to-market is also proposed and demonstrated by our BIST system.
A universal velocity field for the extrusion of non-axisymmetric rods with non-uniform velocity distribution in the extrusion direction
(2000-01-01)
Wu, CW
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Hsu, RQ
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機械工程學系
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Department of Mechanical Engineering
This study formulates a universal velocity field that is kinematically admissible for application in the extrusion of non-axisymmetric rods. Then upper bound theorem dictates that a better upper bound solution heavily depends on the precise conformity of the velocity field postulated. However, a compromise must frequently be made, since the formulation is in general rather complicated. The kinematically admissible velocity field proposed herein has the following features: (a) it is three-dimensional, (b) it is non-uniformally distributed in the axial direction, and (c) the formulation is straight-forward once the boundary of the deformation zone is specified. In addition, the velocity field is applied to the extrusion of rectangular, hexagonal, and octagonal rods from round billets. Moreover, the extrusion loads are calculated against process variables such as the semi-die angle, the percentage reduction of area, and the friction factor. Furthermore, the velocity field is compared with results from the Literature, indicating that the present results render a better upper bound solution for application in extrusion than do previous results. (C) 2000 Published by Elsevier Science S.A. All rights reserved.
Applications of the Web-based collaborative visualization in distributed product development
(2006-04-01)
Chu, CH
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Cheng, CY
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Wu, CW
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資訊工程學系
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Department of Computer Science
This paper illustrates applications of the Web-based collaborative visualization (WCV) in distributed product development. Three software prototypes were developed using the WCV technologies. The first one enables the end users to configure individual parts of 3D assembly in a regular browser, and thus provides an effective tool to collect the customer's voices in e-commerce. The second system realizes mass customization for car interior design. Online ergonomic evaluation is conducted based on the interactions between a digital human mimicking the user and the design model. Finally, an Internet-based design review system is implemented. It enables synchronous communications between a designer and people involved in the change process with no access to CAD. These prototypes demonstrate the practicality, flexibility, and versatility of the WCV in integration with other proprietary software tools using a variety of platforms like ASP framework, Java-based technology, and Windows C/C++ applications. This work shows that the WCV is an interfacing technology, which facilitates 3D information sharing for most product-centric activities in a simple and cost-effective manner. (c) 2006 Elsevier B.V. All rights reserved.
Bootstrap approach for estimating process quality yield with application to light emitting diodes
(2005)
Pearn, WL
;
Chang, YC
;
Wu, CW
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Process capability indices have been widely used by quality professionals for measuring process performance. Although process yield is the most common criterion used in the manufacturing industry for measuring process performance, a more advanced measurement formula Y-q, called quality yield index, has been proposed as an alternative measure of process performance. Quality yield can be viewed as the classical process yield minus the truncated expected relative process loss, within the specifications, which focuses on customer satisfaction. By taking customer loss into consideration, the advantage of using the quality-yield measure as process performance is that the formula can be applied to processes with arbitrary distributions. Unfortunately, statistical properties of the estimated Y-q are mathematically intractable. Therefore, capability testing cannot be performed. In this paper, a nonparametric but computer intensive method called bootstrap is used to obtain a lower confidence bound on quality yield for capability testing purposes. Simulation studies are conducted to examine the sampling distribution of the estimated Y-q. An application using the index Y-q for the light emitting diode manufacturing process is presented for illustration purposes.
Capability measure for asymmetric tolerance non-normal processes applied to speaker driver manufacturing
(2005)
Pearn, WL
;
Wu, CW
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Wang, KH
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工業工程與管理學系
;
Department of Industrial Engineering and Management
Process capability indices, C-p(u, v), including Cp, C-pk, C-pm, and C-pmk, have been proposed in the manufacturing industry to provide numerical measures on process potential and performance for normal processes. Earlier studies considered a class of flexible capability indices, called C-Np(u, v), for processes with non-normal distributions where the tolerances are symmetric. In this paper we consider an extension of C-Np(u, v), called C-Np''(u, v), to handle non-normal processes with asymmetric tolerances. The extension takes into account the important property of the asymmetric loss function, which is shown to be more sensitive to process shift and more accurate than C-Np(u, v) in measuring process capability, hence provides better manufacturing quality assurance. Comparisons between C-Np(u, v) and the extension C-NP''(u, v) are provided. We propose a sample percentile estimator, and apply the bootstrap method to find the lower confidence bound for testing manufacturing capability. We also develop an integrated S-PLUS program to calculate the percentile estimator and the corresponding lower confidence bound. As an illustration, the proposed approach is applied to capability testing of home-theater speaker systems.
Capability testing based on CPM with multiple samples
(2005-02-01)
Wu, CW
;
Pearn, WL
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Numerous process capability indices have been proposed in the manufacturing industry to provide unitless measures on process performance, which are effective tools for quality improvement and assurance. Most existing methods for capability testing are based on the distribution frequency approaches. Recently, Bayesian approaches have been proposed for testing capability indices C-p and C-p. but restricted to cases with one single sample. In this paper, we consider estimating and testing capability index C-pm based on multiple samples. We propose accordingly a Bayesian procedure for testing C-pm. Based on the Bayesian procedure, we develop a simple but practical procedure for practitioners to use in determining whether their manufacturing processes are capable of reproducing products satisfying the preset capability requirement. A process is capable if all the points in the credible interval are greater than the pre-specified capability level. To make the proposed Bayesian approach practical for in-plant applications, we tabulate the minimum values of C* (p) for which the posterior probability p reaches various desirable confidence levels. Copyright (C) 2004 John Wiley Sons, Ltd.
Critical acceptance values and sample sizes of a variables sampling plan for very low fraction of detectives
(2006-01-01)
Pearn, WL
;
Wu, CW
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工業工程與管理學系
;
Department of Industrial Engineering and Management
Acceptance sampling plans are practical tools for quality control applications, which involve quality contracting on product orders between the vendor and the buyer. Those sampling plans provide the vendor and the buyer rules for lot sentencing while meeting their preset requirements on product quality. In this paper, we introduce a variables sampling plan for unilateral processes based on the one-sided process capability indices C-PU (or C-PL), to deal with lot sentencing problem with very low fraction of defectives. The proposed new sampling plan is developed based on the exact sampling distribution rather than approximation. Practitioners can use the proposed sampling plan to determine accurate number of product items to be inspected and the corresponding critical acceptance value, to make reliable decisions. We also tabulate the required sample size n and the corresponding critical acceptance value C-0 for various alpha-risks, beta-risks, and the levels of lot or process fraction of defectives that correspond to acceptable and rejecting quality levels. (c) 2004 Elsevier Ltd. All rights reserved.
Distributional and inferential properties of the process loss indices
(2004-11-01)
Pearn, WL
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Chang, YC
;
Wu, CW
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工業工程與管理學系
;
Department of Industrial Engineering and Management
Johnson (1992) developed the process loss index L,, which is defined as the ratio of the expected quadratic loss to the square of half specification width. Tsui (1997) expressed the index L-e as L-e = L-pe + L-ot, which provides an uncontaminated separation between information concerning the potential relative expected loss (L-pe) and the relative off-target squared (L-ot), as the ratio of the process variance and the square of the half specification width, and the square of the ratio of the deviation of mean from the tat-get and the half specification width, respectively. In this paper, we consider these three loss function indices, and investigate the statistical properties of their natural estimators. For the three indices, we obtain their UMVUEs and MLEs, and compare the reliability of the two estimators based on the relative mean squared errors. In addition, we construct 90%, 95%, and 99%) upper confidence limits, and the maximum values of (L) over cap (c) for which the process is capable, 90%, 95%, and 99% of the time. The results obtained in this paper are useful to the practitioners in choosing good estimators and making reliable decisions on judging process capability.
Effects of a new combination of additives in electroplating solution on the properties of Cu films in ULSI applications
(2000-07-01)
Hu, JC
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Chang, TC
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Wu, CW
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Chen, LJ
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Hsiung, CS
Effects of a new combination of additives in acid electroplating solution on the properties of Cu thin films have been investigated, The electroplated Cu films exhibit an excellent superfilling behavior. 0.18 mu m vias with an aspect ratio exceeding 5 were filled completely without any void or seam. Strong (111) texture was found for the electroplated Cu films. The resistivity of a 450-nm-thick Cu film was measured to be 1.84 mu Omega cm. (C) 2000 American Vacuum Society. [S0734-2101(00)08004-0].
Extrusion analysis and workability prediction of three-layer composite hexagonal clad rods
(2006-05-25)
Wu, CW
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Hsu, RQ
;
機械工程學系
;
Department of Mechanical Engineering
This study uses upper bound method to predict the workability for the extrusion of three-layer composite hexagonal clad rods. A velocity field is generated with the assistance of a product's cross-section profile functions. The velocity component in the extrusion axis is expressed as a convex distribution. The simultaneous deformation of each constituent material with quite different mechanical properties may lead to fracture. A criterion for fracture based on the velocity deviation existing on the layer interface was proposed. Material fractures under extrusion are affected by a set of independent process parameters, including the initial area percentage of each layer, friction condition of die, mechanical characteristics of three constituent materials and reduction of area of billet. Finally, figures of extrusion limits containing safety and fracture zones for each process parameter are obtained for extrusion of three-layer composite hexagonal clad rods. (c) 2006 Elsevier B.V. All rights reserved.
Extrusion of three-layer composite hexagonal clad rods
(2002-04-10)
Wu, CW
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Hsu, RQ
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機械工程學系
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Department of Mechanical Engineering
Composite clad rods consisting of three different materials are applied extensively as conductors, electrodes and chemical devices. Commercial applications involving low temperature niobium-tin alloy (Nb3Sn) superconductor rods, which have a pure niobium (Nb) core, a copper-tin (Cu-Sn) alloy outer sleeve and a Nb3Sn diffusion layer in between, stipulate these conductors as, electrodes that are intended for processing as rods of various shapes. During the extrusion process, non-homogeneous deformation tends to occur because the billet consists of materials with different mechanical properties. In this study, the authors present a numerical simulation model based on the upper-bound theorem to analyze three-layer composite clad rods with a hexagonal cross-section under extrusion. A velocity field is also generated with the assistance of a product's cross-section profile functions. The velocity component in the extrusion axis is expressed as a convex distribution. Analytical results indicate that various process variables such as the semi-die angle, reduction of area, friction condition of the die and combinations of the three constituent materials, prominently influence the extrusion process. Moreover, the extrusion pressure, product dimension-change and the probability of sound extrusion are related closely to the process variables. (C) 2002 Elsevier Science B.V. All rights reserved.
Measuring manufacturing capability for couplers and wavelength division multiplexers
(2005)
Wu, CW
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Pearn, WL
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
The couplers and wavelength division multiplexers have been widely used in high-speed, high-volume image data transmission systems to provide sufficient bandwidth and smaller channel spacing for greater throughput. In this paper, we develop a method for measuring the manufacturing capability of a process making couplers and wavelength division multiplexers. The proposed method measures the process capability of reproducing product items meeting the manufacturing specifications where multiple product quality characteristics are involved, including the polarization dependent loss, and the insertion loss, which are critical in fiber-optic transmission quality.
Procedure for supplier selection based on C-pm applied to super twisted nematic liquid crystal display processes
(2004-07-01)
Pearn, WL
;
Wu, CW
;
Lin, HC
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工業工程與管理學系
;
Department of Industrial Engineering and Management
The loss-based process capability index C-pm, sometimes called the Taguchi index, has been proposed to the manufacturing industry as a method to measure process performance. The index C-pm takes into account the targeting degree of the process, which essentially measures process performance based on average process loss. Based on the C-pm index, a mathematically complicated approximation method was developed previously for selecting a subset of processes containing the best supplier from a given set of processes. The present paper implements this method and develops a practical step-by-step procedure to aid supplier selection decisions. The accuracy of the selection method is investigated using a simulation technique. The accuracy study provides useful information about the sample size required for a designated selection power. A two-phase selection procedure is developed to select a better supplier and to examine the magnitude of the difference between the two suppliers. Also investigated is a real-world case on the super twisted nematic liquid crystal display manufacturing process, and it is applied to the selection procedure using actual data collected from the factories to reach a decision in supplier selection.
Procedures for testing manufacturing precision C(p)based on ((X)over-bar, R) or ((X)over-bar, S) control chart samples
(2005)
Pearn, WL
;
Wu, CW
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Chuang, HC
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Process precision index C-p has been widely used in the manufacturing industry for measuring process potential and precision. Estimating and testing process precision based on one single sample have been investigated extensively. In this paper, we consider the problem of estimating and testing process precision based on multiple samples taken from ((X) over bar, R)or ((X) over bar, S)control chart. We first investigate the statistical properties of the natural estimator of C-p and implement the hypothesis testing procedure. We then develop efficient MAPLE programs to calculate the lower confidence bounds, critical values, and p-values based on m samples of size n. Based on the test, we develop a step-by-step procedure for practitioners to use in determining whether their manufacturing processes are capable of reproducing products satisfying the preset precision requirement.
Process capabitity assessment for index C-pk based on bayesian approach
(2005)
Pearn, WL
;
Wu, CW
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Process capability indices have been proposed in the manufacturing industry to provide numerical measures on process reproduction capability, which are effective tools for quality assurance and guidance for process improvement. In process capability analysis, the usual practice for testing capability indices from sample data are based on traditional distribution frequency approach. Bayesian statistical techniques are an alternative to the frequency approach. Shiau, Chiang and Hung (1999) applied Bayesian method to index C-pm and the index C-pk but under the restriction that the process mean μ equals to the midpoint of the two specification limits, m. We note that this restriction is a rather impractical assumption for most factory applications, since in this case C-pk will reduce to C-p. In this paper, we consider testing the most popular capability index C-pk for general situation - no restriction on the process mean based on Bayesian approach. The results obtained are more general and practical for real applications. We derive the posterior probability, p, for which the process under investigation is capable and propose accordingly a Bayesian procedure for capability testing. To make this Bayesian procedure practical for in-plant applications, we tabulate the minimum values of C-pk for which the posterior probability p reaches desirable confidence levels with various pre-specified capability levels.
Production quality and yield assurance for processes with multiple independent characteristics
(2006-09-01)
Pearn, WL
;
Wu, CW
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Process capability indices have been widely used in the manufacturing industry providing numerical measures on process potential and process performance. Capability measure for processes with single characteristic has been investigated extensively, but is comparatively neglected for processes with multiple characteristics. In real applications, a process often has multiple characteristics with each having different specifications. Singhal [Singhal, S.C., 1990. A new chart for analyzing multiprocess performance. Quality Engineering 2 (4), 397-390] proposed a multi-process performance analysis chart (MPPAC) for analyzing the performance of multi-process product. Using the same technique, several MPPACs have been developed for monitoring processes with multiple independent characteristics. Unfortunately, those MPPACs ignore sampling errors, and consequently the resulting capability measures and groupings are unreliable. In this paper, we propose a reliable approach to convert the estimated index values to the lower confidence bounds, then plot the corresponding lower confidence bounds on the MPPAC. The lower confidence bound not only gives us a clue minimum actual performance which is tightly related to the fraction of non-conforming units, but is also useful in making decisions for capability testing. A case study of a dual-fiber tip process is presented to demonstrate how the proposed approach can be applied to in-plant applications. (c) 2005 Elsevier B.V. All rights reserved.
Quality yield measure for processes with asymmetric tolerances
(2006-08-01)
Pearn, WL
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Lin, PC
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Chang, YC
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Wu, CW
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工業工程與管理學系
Process capability indices provide numerical measures on whether or not a process is able to produce products that meet prespecified quality targets and are often used by manufacturers to evaluate manufacturing performance. Although process yield is the primary focus of the performance criteria, a formula that combines the yield and the average process loss, called the quality yield index, has been developed. This index, the quality yield, can be viewed as the conventional process yield minus the truncated expected relative process loss within the specifications. Although cases with symmetric tolerances dominate in practical situations, cases with asymmetric tolerances can also occur. In this paper, we generalize the quality yield index for asymmetric tolerances. The generalization technique is justified, and some statistical properties of the estimated generalization are investigated. An application example on high-density light emitting diodes is also presented to illustrate the applicability of the generalization.
Quality-yield measure for production processes with very low fraction defective
(2004-12-01)
Pearn, WL
;
Chang, YC
;
Wu, CW
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Process yield is the most common criterion used in manufacturing industry for measuring process performance. A more advanced measurement formula, called the quality yield index, Y-q, is proposed to calculate the quality yield for arbitrary processes by taking customer loss into consideration. Y-q, penalizes yield for the variation of the product characteristics from its target, which presents a measure of the average product loss. Quality yield could be expressed as the traditional yield minus the truncated expected relative loss within the specifications to quantify how well a process can reproduce product items satisfactory to the customers. The paper proposes a reliable approach for measuring quality yield by converting the estimate into a lower confidence bound for processes with a very low fraction of defectives. The lower confidence bound not only provides information about actual process performance that is tightly related to both the fraction of defective units and customer quality loss, but also is useful in making decisions for capability testing.
The syntheses of pyrazino-containing sultines and their application in Diels-Alder reactions with electron-poor olefins and [60]fullerene
(2000-06-02)
Liu, JH
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Wu, AT
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Huang, MH
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Wu, CW
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Chung, WS
The Diels-Alder reactions of heterocyclic o-quinodimethanes, generated in situ from 6,7-disubstituted quinoxalino[2,3-d]-[1,2 lambda(4)]oxathiine 2-oxides (6a-c), 2,3-disubstituted-8,9-dihydro-6H-8 lambda(4)-[1,2]oxathiino[4,5-g]quinoxalin-8-one (7a-c) (sultines), and pyrazinosultine (22), with electron-poor olefins and [60]fullerene are described. The heterocyclic-fused sultines 7a-c and 22 are readily prepared from the corresponding dibromides 9a-c and 24 with the commercially available Rongalite (sodium formaldehyde sulfoxylate). When heated in the presence of electron-poor dienophiles and [60]fullerene, all of the sultines underwent extrusion of SO2, and the resulting heterocyclic o-quinodimethanes (3a-d, 4a-c, and 25) were intercepted as the 1:1 adducts in good to excellent yields. The temperature-dependent H-1 NMR spectra of fullerene derivatives 31-38 show a dynamic process for the methylene protons. The activation free energies (Delta G(e)double dagger) determined for the boat-to-boat inversion of these pyrazino-containing C-60 compounds (31-34 and 38) are found to be in the range of 14.1-14.8 kcal/mol, but they are in the range of 15.2 to >17.1 kcal/mol for adducts 35-87. The activation free energies (Delta G(c)double dagger) are significantly affected by (1) the orientations and (2) the substituents of the quinoxaline rings and (3) the extended benzannulation in the arenes of C-60 adducts (see Table 2), which implies that both electronic interactions and steric effects between the aromatic addends and C-60 are important. Tautomerization of methylquinoxaline to its enamine is invoked as a rationalization for the lowering of Delta G(c)double dagger in some of the fulleroadducts.