Browsing by Subject "Quality Control"

Now showing 1 - 3 of 3

Open Access
A hybrid model for designing attributes sampling plans
(1994) Sanin, M. Başar
In single sampling plans by attributes, statistical and economical considerations have traditionally been discussed separately. An approach taking into account both considerations simultaneously would be more useful in terms o f quality assurance. The suggested model involves minimization o f the expected total cost comprising the inspection cost, the annoyance cost o f rejecting a lot and the cost o f outgoing defective items, while the producer's risk and consumer's risk are not allowed to be greater than specified values. To find the optimal sample size and the optimal acceptance number, a two stage solution method is proposed. The accuracy and the efficiency o f the solution procedure are tested on randomly generated problems, by comparing the solutions obtained by the proposed method to those obtained by enumeration. Sensitivity o f the model is discussed by analyzing the effects o f parameters on the optimal sampling plans.
Open Access
Joint economic design of EWMA control charts for mean and variance
(Elsevier, 2008-01-01) Serel, D. A.; Moskowitz, H.
Control charts with exponentially weighted moving average (EWMA) statistics (mean and variance) are used to jointly monitor the mean and variance of a process. An EWMA cost minimization model is presented to design the joint control scheme based on pure economic or both economic and statistical performance criteria. The pure economic model is extended to the economic-statistical design by adding constraints associated with in-control and out-of-control average run lengths. The quality related production costs are calculated using Taguchi's quadratic loss function. The optimal values of smoothing constants, sampling interval, sample size, and control chart limits are determined by using a numerical search method. The average run length of the control scheme is computed by using the Markov chain approach. Computational study indicates that optimal sample sizes decrease as the magnitudes of shifts in mean and/or variance increase, and higher values of quality loss coefficient lead to shorter sampling intervals. The sensitivity analysis results regarding the effects of various inputs on the chart parameters provide useful guidelines for designing an EWMA-based process control scheme when there exists an assignable cause generating concurrent changes in process mean and variance. (C) 2006 Elsevier B.V. All rights reserved.
Open Access
Optimization of the gain-bandwidth product of capacitive micromachined ultrasonic transducers
(IEEE, 2005-12) Olcum, S.; Senlik, M. N.; Atalar, Abdullah
Capacitive micromachined ultrasonic transducers (cMUT) have large bandwidths, but they typically have low conversion efficiencies. This paper defines a performance measure in the form of a gain-bandwidth product and investigates the conditions in which this performance measure is maximized. A Mason model corrected with finite-element simulations is used for the purpose of optimizing parameters. There are different performance measures for transducers operating in transmit, receive, or pulse-echo modes. Basic parameters of the transducer are optimized for those operating modes. Optimized values for a cMUT with silicon nitride membrane and immersed in water are given. The effect of including an electrical matching network is considered. In particular, the effect of a shunt inductor in the gain-bandwidth product is investigated. Design tools are introduced, which are used to determine optimal dimensions of cMUTs with the specified frequency or gain response.