Browsing by Author "Yang, Dong-Yuh"

Now showing 1 - 19 of 19

An Improved Approach for Estimating Product Performance Based on the Capability Index C(pmk)
(2009-01-01)
Pearn, W. L.
;
Yang, Dong-Yuh
;
Cheng, Ya-Ching
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
In this article, we construct an improved procedure for estimating the process capability index C(pmk). We propose a new Cpmk lower-bound approach based on the GCI concept, and compare it with other existing methods. Based on the comparison results, we conclude with a recommendation, and construct a step-by-step procedure for the recommended approach to estimate the actual process capability Cpmk for various sample sizes. The lower bound attended by our recommended approach, indeed, improves other existing lower bound methods. We also investigate a real-world application to illustrate how we could apply the recommended approach to the actual manufacturing processes.
An Improved Approach for Estimating Product Performance Based on the Capability Index C-pmk
(2009-01-01)
Pearn, W. L.
;
Yang, Dong-Yuh
;
Cheng, Ya-Ching
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
In this article, we construct an improved procedure for estimating the process capability index C-pmk. We propose a new Cpmk lower-bound approach based on the GCI concept, and compare it with other existing methods. Based on the comparison results, we conclude with a recommendation, and construct a step-by-step procedure for the recommended approach to estimate the actual process capability Cpmk for various sample sizes. The lower bound attended by our recommended approach, indeed, improves other existing lower bound methods. We also investigate a real-world application to illustrate how we could apply the recommended approach to the actual manufacturing processes.
ANALYTICAL METHOD FOR ACCURACY ANALYSIS OF THE RANDOMIZED T-POLICY QUEUE
(2012-03-01)
Wang, Kuo-Hsiung
;
Yang, Dong-Yuh
;
Pearn, W. L.
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
We consider a randomized policy to control the M/G/1 queueing system with an unreliable server, second optional service and general startup times. The server is subject to breaking down according to a Poisson process, and the repair time obeys a general distribution. All arrived customers demand the first required service, and only some of the arrived customers demand the second optional service. After all the customers are served in the system, the server immediately takes a vacation and operates the (T, p)-policy. For this queueing system, we employ maximum entropy approach with several constraints to develop the probability distributions of the system size and the expected waiting time in the queue. Based on the accuracy comparison between the exact and approximate methods, we show that the maximum entropy approach is quite accurate for practical purpose, which is a useful method for solving complex queueing systems.
Assessing Profitability of a Newsboy-Type Product with Normally Distributed Demand Based on Multiple Samples
(2013-09-17)
Su, Rung-Hung
;
Yang, Dong-Yuh
;
Pearn, W. L.
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
This article develops a new index Achievable Capacity Index, I-A, which can accurately measure the profitability of newsboy-type product with normally distributed demand. An unbiased and effective estimator of I-A is derived to estimate actual I-A as the parameters of distribution are unknown. Practically, the market information regarding demand is obtained from multiple samples rather than single sample. Therefore, we estimate and test I-A based on multiple samples. A hypothesis testing for examining whether the profitability meets designated requirement is presented. Critical values of the test are calculated to determine the evaluation results. Finally, a real case on the sales of donuts is presented to illustrate the applicability of our approach.
Comparative analysis of a randomized N-policy queue: An improved maximum entropy method
(2011-08-01)
Wang, Kuo-Hsiung
;
Yang, Dong-Yuh
;
Pearn, W. L.
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
We analyze a single removable and unreliable server in an M/G/1 queueing system operating under the < p,N >-policy. As soon as the system size is greater than N, turn the server on with probability p and leave the server off with probability (1 p). All arriving customers demand the first essential service, where only some of them demand the second optional service. He needs a startup time before providing first essential service until there are no customers in the system. The server is subject to break down according to a Poisson process and his repair time obeys a general distribution. In this queueing system, the steady-state probabilities cannot be derived explicitly. Thus, we employ an improved maximum entropy method with several well-known constraints to estimate the probability distributions of system size and the expected waiting time in the system. By a comparative analysis between the exact and approximate results, we may demonstrate that the improved maximum entropy method is accurate enough for practical purpose, and it is a useful method for solving complex queueing systems. (C) 2011 Elsevier Ltd. All rights reserved.
Comparison of two randomized policy M/G/1 queues with second optional service, server breakdown and startup
(2010-06-01)
Wang, Kuo-Hsiung
;
Yang, Dong-Yuh
;
Pearn, W. L.
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
The problem addressed in this paper is to compare the minimum cost of the two randomized control policies in the M/G/1 queueing system with an unreliable server, a second optional service, and general startup times. All arrived customers demand the first required service, and only some of the arrived customers demand a second optional service. The server needs a startup time before providing the first required service until the system becomes empty. After all customers are served in the queue, the server immediately takes a vacation and the system operates the (T, p)-policy or (p, N)-policy. For those two policies, the expected cost functions are established to determine the joint optimal threshold values of (T, p) and (p, N), respectively. In addition, we obtain the explicit closed form of the joint optimal solutions for those two policies. Based on the minimal cost, we show that the optimal (p, N)-policy indeed outperforms the optimal (T, p)-policy. Numerical examples are also presented for illustrative purposes. (C) 2010 Elsevier B.V. All rights reserved.
Controlling arrivals for a queueing system with an unreliable server: Newton-Quasi method
(2009-07-01)
Wang, Kuo-Hsiung
;
Yang, Dong-Yuh
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
This paper deals with the control policy of a removable and unreliable server for an M/M/1/K queueing system, where the removable server operates an F-policy. The so-called F-policy means that when the number of customers in the system reaches its capacity K (i.e. the system becomes full), the system will not accept any incoming customers until the queue length decreases to a certain threshold value F. At that time, the server initiates an exponential startup time with parameter c and starts allowing customers entering the system. It is assumed that the server breaks down according to a Poisson process and the repair time has an exponential distribution. A matrix analytical method is applied to derive the steady-state probabilities through which various system performance measures can be obtained. A cost model is constructed to determine the optimal values, say (F*, mu*, gamma*), that yield the minimum cost. Finally, we use the two methods, namely, the direct search method and the Newton-Quasi method to find the global minimum (F*, mu*, gamma*). Numerical results are also provided under optimal operating conditions. (C) 2009 Elsevier Inc. All rights reserved.
Cost-minimization analysis of a working vacation queue with N-policy and server breakdowns
(2015-04-01)
Yang, Dong-Yuh
;
Wu, Chia-Huang
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
This paper investigates the N-policy M/M/1 queueing system with working vacation and server breakdowns. As soon as the system becomes empty, the server begins a working vacation. The server works at a lower service rate rather than completely stopping service during a vacation period. The server may break down with different breakdown rates during the idle, working vacation, and normal busy periods. It is assumed that service times, vacation times, and repair times are all exponentially distributed. We analyze this queueing model as a quasi-birth-death process. Furthermore, the equilibrium condition of the system is derived for the steady state. Using the matrix-geometric method, we find the matrix-form expressions for the stationary probability distribution of the number of customers in the system and system performance measures. The expected cost function per unit time is constructed to determine the optimal values of the system decision variables, including the threshold N and mean service rates. We employ the particle swarm optimization algorithm to solve the optimization problem. Finally, numerical results are provided, and an application example is given to demonstrate the applicability of the queueing model. (C) 2015 Elsevier Ltd. All rights reserved.
Decision-making in a single-period inventory environment with fuzzy demand
(2011-03-01)
Su, Rung-Hung
;
Yang, Dong-Yuh
;
Pearn, W. L.
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
This paper first defines the profitability to be the probability of achieving a target profit under the optimal ordering policy, and introduces a new index (achievable capacity index; I(A)) which can briefly analyze the profitability for newsboy-type product with normally distributed demand. Note that since the level of profitability depends on the demand mean mu and the demand standard deviation sigma if the related casts, selling price, and target profit are given, the index I(A) is a function of mu and sigma. Then, we assess level performance which examines if the profitability meets designated requirement. The results can determine whether the product is still desirable to order/manufacture. However, mu and sigma are always unknown, and the demand quantity is common to be imprecise, especially for new product. To tackle these problems, a constructive approach combining the vector of fuzzy numbers is introduced to establish the membership function of the fuzzy estimator of I(A). Furthermore, a three-decision testing rule and step-by-step procedure are developed to assess level performance based on fuzzy critical values and fuzzy p-values. (C) 2010 Elsevier Ltd. All rights reserved.
Dynamic Control of a Machine Repair Problem with Switching Failure and Unreliable Repairmen
(1970-01-01)
Wu, Chia-Huang
;
Yang, Dong-Yuh
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
This study examines the dynamic control of an M/M/2 machine repair system with R operating machines, S standbys, and two unreliable repairmen, wherein standbys are subject to switching failures. We apply the matrix analytic method to derive explicit expressions of the stationary probability distributions as well as matrix expressions of the system performance measures. We construct a cost model and determine the optimal dynamic operating policy to minimize the expected cost function per unit time. Sensitivity analysis is conducted using numerical examples. The results of sensitivity analysis indicate that the optimal thresholds and corresponding minimum expected cost increase as the number of operating machines or standbys increases. Moreover, the minimum expected cost is sensitive to the mean arrival and repair rates. The results provide managers with decision reference for productivity improvement and cost reduction.
Estimating Achievable Capacity Index based on Multiple Samples
(2011-01-01)
Wang, Tsung-Yin
;
Liou, Cheng-Hwai
;
Su, Rung-Hung
;
Yang, Dong-Yuh
;
工業工程與管理學系
This paper investigates the profitability which measures for the newsboy-type product and develops a new index "Achievable Capacity Index", denoted by I-A. It can accurately measure the profitability of newsboy-type product with normally distributed demand. Furthermore, the interrelationship between profitability and I-A is also performed. An unbiased and effective estimator is derived to estimate I-A. Practically, market information regarding demand is obtained from multiple samples rather than single sample. Then we estimate I-A based on multiple samples. Finally, a numerical result is presented to show the probability density function of the unbiased estimator of (I) over cap (A) under different groups and sample sizes. (C) 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the Asia Pacific Business Innovation and Technology Management Society
Estimating and Testing Achievable Capacity Index with Exponentially Distributed Demand
(2015-06-01)
Su, Rung-Hung
;
Yang, Dong-Yuh
;
Pearn, W. L.
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Achievable Capacity Index proposed by Su and Pearn [12-13] is a new evaluation tool, which can accurately measure the profitability of newsboy-type product with normally distributed demand. However, in practical situations, the demand variable is non-normal distributed. In this paper, we attempt to investigate a probable case that the demand is exponentially distributed. The corresponding index denoted by is developed and the statistical properties of its estimator are derived. Based on this index, we implement a hypothesis testing for examining whether the profitability reaches a specified level. The critical values of the test are tabulated for some commonly used profitability requirements. We also carry out the sample size determination by means of designated Type I error and Type II error. Finally, a real example taken from a retail store in Taiwan is presented to illustrate the applicability of our approach.
Modelling and optimisation of a two-server queue with multiple vacations and working breakdowns
(1970-01-01)
Yang, Dong-Yuh
;
Chen, Yi-Hsuan
;
Wu, Chia-Huang
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
This paper presents a steady-state analysis of an M/M/2 queue with heterogeneous servers (Server 1 and Server 2). Server 1 is reliable and may leave for a vacation when the system becomes empty. Sever 2 is unreliable and may break down while serving customers. When a breakdown occurs, Server 2 reduces the service rate rather than halting service. We formulate this queueing model as a quasi birth-and-death (QBD) process, using the matrix geometric method to compute the stationary distribution of system size. We also develop several measures to evaluate the performance of the system. A cost model based on system performance measures is formulated as a heuristic cost optimisation problem subject to stability conditions. A canonical particle swarm optimisation algorithm is used to obtain numerical solutions for the approximate optimal service rates of Server 1 and Server 2. Moreover, we present numerical results showing the effects of various parameters on the approximate optimal service rates as well as a practical example illustrating the application of the proposed model.
Optimal management of the machine repair problem with working vacation: Newton's method
(2009-11-15)
Wang, Kuo-Hsiung
;
Chen, Wei-Lun
;
Yang, Dong-Yuh
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
This paper studies the M/M/1 machine repair problem with working vacation in which the server works with different repair rates rather than completely terminating the repair during a vacation period. We assume that the server begins the working vacation when the system is empty. The failure times, repair times, and vacation times are all assumed to be exponentially distributed. We use the MAPLE software to compute steady-state probabilities and several system performance measures. A cost model is derived to determine the optimal values of the number of operating machines and two different repair rates simultaneously, and maintain the system availability at a certain level. We use the direct search method and Newton's method for unconstrained optimization to repeatedly find the global minimum value until the system availability constraint is satisfied. Some numerical examples are provided to illustrate Newton's method. (C) 2009 Published by Elsevier B.V.
Optimal randomized control policy of an unreliable server system with second optional service and startup
(2008)
Yang, Dong-Yuh
;
Wang, Kuo-Hsiung
;
Ke, Jau-Chuan
;
Pearn, Wen Lea
;
工業工程與管理學系
Purpose - To study the optimization of a randomized control problem in an M/G/1 queue in which a removable and unreliable server may provide two phases of heterogeneous service to arriving customers. Design/methodology/approach - Arriving customers follow a Poisson process and require the first essential service (FES). As soon as FES of a customer is completed, the customer may leave the system or opt for the second optional service (SOS). The service times of FES channel and SOS channel are assumed to be general distribution functions. The server requires a startup time with random length before starting service. When the server is working, he may meet unpredictable breakdowns but is immediately repaired. The inter-breakdown time and repair time of the removable server are exponentially random variable and generally random variable, respectively. By the convex combination property and the renewal reward theorem, several system performances are obtained. A cost model is developed to search the optimal two-threshold policy at a minimum cost. Sensitivity analysis is performed. Findings - Expressions for various system performances are derived. Sensitivity analysis of optimal randomized control policy (based on the developed expected cost function) with respect to system parameters is investigated. Originality/value - It is the first time that analytic results of sensitivity analysis of optimal randomized control policy for the complex system have been obtained which is quite useful and significant for engineers.
Optimization and sensitivity analysis of controlling arrivals in the queueing system with single working vacation
(2010-05-15)
Yang, Dong-Yuh
;
Wang, Kuo-Hsiung
;
Wu, Chia-Huang
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
This paper analyzes the F-policy M/M/1/K queueing system with working vacation and an exponential startup time. The F-policy deals with the issue of controlling arrivals to a queueing system, and the server requires a startup time before allowing customers to enter the system. For the queueing systems with working vacation, the server can still provide service to customers rather than completely stop the service during a vacation period. The matrix-analytic method is applied to develop the steady-state probabilities, and then obtain several system characteristics. We construct the expected cost function and formulate an optimization problem to find the minimum cost. The direct search method and Quasi-Newton method are implemented to determine the optimal system capacity K, the optimal threshold F and the optimal service rates (mu(B), mu(V)) at the minimum cost. A sensitivity analysis is conducted to investigate the effect of changes in the system parameters on the expected cost function. Finally, numerical examples are provided for illustration purpose. (C) 2010 Elsevier B.V. All rights reserved.
Performance analysis and optimization of a retrial queue with working vacations and starting failures
(1970-01-01)
Yang, Dong-Yuh
;
Wu, Chia-Huang
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
This paper presents a steady-state analysis of an M/M/1 retrial queue with working vacations, in which the server is subject to starting failures. The proposed queueing model is described in terms of the quasi-birth-death (QBD) process. We first derive the system stability condition. We then use the matrix-geometric method to compute the stationary probability distribution of the orbit size. Some performance measures for the system are developed. We construct a cost model, and our objective is to determine the optimal service rates during normal and vacation periods that minimize the expected cost per unit time. The canonical particle swarm optimization (CPSO) algorithm is employed to deal with the cost optimization problem. Numerical results are provided to illustrate the effects of system parameters on the performance measures and the optimal service rates. These results depict the system behaviour and show how the CPSO algorithm can be used to find numerical solutions for optimal service rates.
Production yield measure for multiple characteristics processes based on S-pk(T) under multiple samples
(2012-03-01)
Pearn, W. L.
;
Yen, Ching-Ho
;
Yang, Dong-Yuh
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Process yield is an important criterion used in the manufacturing industry for measuring process performance. Methods for measuring yield for processes with single characteristic have been investigated extensively. However, methods for measuring yield for processes with multiple characteristics have been comparatively neglected. Chen et al. (Qual Reliab Eng Int 19:101-110, 2003) proposed a measurement formula called S-pk(T) which provides an exact measure of the overall process yield, for processes with multiple characteristics. In this paper, we considered the natural estimator of S-pk(T) under multiple samples, and derived the asymptotic distribution for the estimator. In addition, a comparison between the SB (standard bootstrap) and the proposed method based on the lower confidence bound is executed. Generally, the result indicates that the proposed approach is more reliable than the standard bootstrap method.
The multi-server retrial system with Bernoulli feedback and starting failures
(2015-05-04)
Yang, Dong-Yuh
;
Ke, Jau-Chuan
;
Wu, Chia-Huang
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
In this paper, we present a detailed analysis of a multi-server retrial queue with Bernoulli feedback, where the servers are subject to starting failures. Upon completion of a service, a customer would decide either to leave the system with probability p or to join the retrial orbit again for another service with complementary probability 1-p. We analyse this queueing system as a quasi-birth-death process. Specifically, the equilibrium condition of the system is given for the existence of the steady-state analysis. Applying the matrix-geometric method, the formulae for computing the rate matrix and stationary probabilities are obtained. We further develop the matrix-form expressions for various system performance measures. A cost model is constructed to determine the optimal number of servers, the optimal mean service rate and the optimal mean repair rate subject to the stability condition. Finally, we give a practical example to illustrate the potential applicability of this model.