Browsing by Author "Wang, KH"

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A multiprocess performance analysis chart based on the incapability index C-pp: an application to the chip resistors
(2002-07-01)
Pearn, WL
;
Ko, CH
;
Wang, KH
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Statistical process control charts, such as the (X) over bar, R, S-2, S, and MR charts, have been widely used in the manufacturing industry for controlling/monitoring process performance, which are essential tools for any quality improvement activities. Those charts are easy to understand, which effectively communicate critical process information without using words and formula. In this paper, we introduce a new control chart, called the C-pp multiple process performance analysis chart (MPPAC), using the incapability index C-pp. The C-pp MPPAC displays multiple processes with the departure, and process variability relative to the specification tolerances, on one single chart. We demonstrate the use of the C-pp MPPAC by presenting a case study on some resistor component manufacturing processes, to evaluate the factory performance. (C) 2002 Elsevier Science Ltd. All rights reserved.
Capability measure for asymmetric tolerance non-normal processes applied to speaker driver manufacturing
(2005)
Pearn, WL
;
Wu, CW
;
Wang, KH
;
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.
Cost benefit analysis of series systems with warm standby components
(2003-11-01)
Wang, KH
;
Pearn, WL
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
This paper deals with the cost benefit analysis of series systems with warm standby components. The time-to-repair and the time-to-failure for each of the primary and warm standby components is assumed to have the negative exponential distribution. We develop the explicit expressions for the mean time-to-failure, MTTF, and the steady-state availability, A(T)(infinity) for three configurations and perform a comparative analysis. Under the cost/benefit (C/B) criterion, comparisons are made based on assumed numerical values given to the distribution parameters, and to the cost of the components. The configurations are ranked based on: MTTF, A(T)(infinity), and C/B where B is either MTTF or A(T)(infinity).
Cost benefit analysis of series systems with warm standby components and general repair time
(2005-06-01)
Wang, KH
;
Liu, YC
;
Pearn, WL
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
We study the availability analysis of three different series system configurations with warm standby components and general repair times. The time-to-failure for each of the primary and warm standby components is assumed to be exponentially distributed with respective parameter λ and α. This paper presents a recursive method, using the supplementary variable technique and treating the supplementary variable as the remaining repair time, to develop the steady-state probability distribution of the number of working components in the system. We develop the explicit expressions for the steady-state availability, Aν, for three configurations and perform comparisons. For all three configurations, comparisons are made for specific values of distribution parameters and of the cost of the components. The configurations are ranked based on Aν and cost/benefit, for three various repair time distributions: exponential, 3-stage Erlang, and deterministic, where benefit is Aν.
Exploiting communication complexity for Boolean matching
(1996-10-01)
Wang, KH
;
Hwang, TT
;
Chen, C
;
資訊工程學系
;
Department of Computer Science
Boolean matching is to check the equivalence of two functions under input permutation and input/output phase assignment, A straightforward implementation takes time complexity O(n!(n)2), where n is the number of variables, Various signatures of variables were used to prune impossible permutations by many researchers. In this paper, based on communication complexity, we also propose two signatures, cofactor and equivalence signatures, which are general forms of many existing signatures, These signatures are used to develop an efficient Boolean matching algorithm which is based on checking structural equivalence of OBDD's. Experimental results on a set of benchmarks show that our algorithm is indeed very effective in solving Boolean matching problem.
Exploiting communication complexity for Boolean matching
(1996-10-01)
Wang, KH
;
Hwang, TT
;
Chen, C
;
資訊工程學系
;
Department of Computer Science
Boolean matching is to check the equivalence of two functions under input permutation and input/output phase assignment, A straightforward implementation takes time complexity O(n!(n)2), where n is the number of variables, Various signatures of variables were used to prune impossible permutations by many researchers. In this paper, based on communication complexity, we also propose two signatures, cofactor and equivalence signatures, which are general forms of many existing signatures, These signatures are used to develop an efficient Boolean matching algorithm which is based on checking structural equivalence of OBDD's. Experimental results on a set of benchmarks show that our algorithm is indeed very effective in solving Boolean matching problem.
Maximum entropy analysis to the N policy M/G/1 queueing system with a removable server
(2002-12-01)
Wang, KH
;
Chuang, SL
;
Pearn, WL
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
We study a single removable server in an M/G/1 queueing system operating under the N policy in steady-state. The server may be turned on at arrival epochs or off at departure epochs. Using the maximum entropy principle with several well-known constraint, we develop the approximate formulae for the probability distributions of the number of customers and the expected waiting time in the queue. We perform a comparative analysis between the approximate results with exact analytic results for three different service time distributions, exponential, 2-stage Erlang, and 2-stage hyper-exponential, The maximum entropy approximation approach is accurate enough for practical purposes. We demonstrate, through the maximum entropy principle results, that the N policy M/G/1 queueing system is sufficiently robust to the variations of service time distribution functions. (C) 2002 Elsevier Science Inc. All rights reserved.
Maximum entropy analysis to the N policy M/G/1 queueing system with server breakdowns and general startup times
(2005-06-06)
Wang, KH
;
Wang, TY
;
Pearn, WL
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
We study a single removable and unreliable server in the N policy M/G/1 queueing system with general startup times where arrivals form a Poisson process and service times are generally distributed. When N customers are accumulated in the system, the server is immediately turned on but is temporarily unavailable to the waiting customers. He needs a startup time before providing service until the system becomes empty. The server is subject to breakdowns according to a Poisson process and his repair time obeys an arbitrary distribution. We use maximum entropy principle to derive the approximate formulas for the steady-state probability distributions of the queue length. We perform a comparative analysis between the approximate results with established exact results for various distributions, such as exponential (M), fc-stage Erlang (E-k), and deterministic (D). We demonstrate that the maximum entropy approach is accurate enough for practical purposes and is a useful method for solving complex queueing systems. (c) 2004 Published by Elsevier Inc.
Maximum likelihood estimates and confidence intervals of an M/M/R queue with heterogeneous servers
(2006-05-01)
Wang, TY
;
Ke, JC
;
Wang, KH
;
Ho, SC
;
工業工程與管理學系
This paper studies maximum likelihood estimates as well as confidence intervals of an M/M/R queue with heterogeneous servers under steady-state conditions. We derive the maximum likelihood estimates of the mean arrival rate and the three unequal mean service rates for an M/M/3 queue with heterogeneous servers, and then extend the results to an M/M/R queue with heterogeneous servers. We also develop the confidence interval formula for the parameter rho, the probability of empty system P-0, and the expected number of customers in the system E[N], of an M/M/R queue with heterogeneous servers.
Normal approximation to the distribution of the estimated yield index S-pk
(2004-02-01)
Pearn, WL
;
Lin, GH
;
Wang, KH
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Process yield is the most common criterion used in the manufacturing industry for measuring process performance. A measurement index, called S-pk, has been proposed to calculate the yield for normal processes. The measurement index S-pk establishes the relationship between the manufacturing specifications and the actual process performance, which provides an exact measure on process yield. Unfortunately, the sampling distribution of the estimated S-pk is mathematically intractable. Therefore, process performance testing cannot be performed. In this paper; we consider a normal approximation to the distribution of the estimated S-pk, and investigate its accuracy computationally. We compare the critical values calculated from the approximate distribution with those obtained using the standard simulation technique, for various commonly used quality requirements. Extensive computational results are provided and analyzed. The investigation is useful to the practitioners for making decisions in testing process performance based on the yield.
On the Maximum Benefit Chinese Postman Problem
(2003-08-01)
Pearn, WL
;
Wang, KH
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
The Maximum Benefit Chinese Postman Problem (MBCPP) is a practical generalization of the classical Chinese Postman Problem (CPP), which has many real-world applications. In this paper, we consider the MBCPP on undirected networks, and show that the MBCPP is more complex than the Rural Postman Problem (RPP). We present a sufficient condition for the MBCPP solution to cover the whole network, and provide an upper bound. Based on the upper bound, we propose an efficient solution procedure to solve the MBCPP approximately. The proposed algorithm applies the minimal spanning tree and the minimal-cost matching algorithms, which performs well on problems satisfying the sufficient condition. (C) 2003 Elsevier Science Ltd. All rights reserved.