• Korean Journal of Veterinary Service
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• v.30 no.1
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• pp.23-32
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• 2007

A total of 60 samples (38 domestic honeys and 22 foreign honeys) were collected from October in 2003 to May in 2004 in Incheon metropolitan area, and contents of important quality-related components in honeys were analyzed using methods of Korea Food Code. Most of the honeys were satisfied with Korean limit (21%) in moisture content even though 4 samples brought by Korean travellers and 1 sample in domestic honey (wild flower) were higher than the limit. The lowest mean level of moisture in the honeys was imported foreign honeys (16.95%). All of the samples were below of 0.6% in the analysis of ash contents. The highest content was imported foreign honey (0.19%) while the lowest content was in domestic acacia honey (0.05%). Acidity of domestic honeys (9.49-9.94meq/kg) was approximately half of that in foreign honeys. All samples were satisfied with Korean limit (40.0meq/kg). In the analysis of fructose and glucose, only three samples of foreign honeys were lower than Korean limit (sum of both ; 65%). The content of sucrose in all samples was less than 7%. Mean of Hydroxymethylfurfural (HMF) contents were 12.83-24.3mg/kg in domestic honey, and 31.34-45.58mg/kg in foreign honey. However, three samples brought by Korean travellers were not satisfied with Korean limit (${\leq}80mg/kg$). In conclusion, quality of domestic honey was better than that of foreign honey. Also, it may be needed that the honeys purchased by Korean travellers in foreign countries should be continuously monitored.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.43 no.3
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• pp.95-100
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• 2020

Machines and facilities are physically or chemically degenerated by continuous usage. One of the results of this degeneration is the process mean shift. The representative type of the degeneration is wear of tool or machine. According to the increasing wear level, non-conforming products cost and quality loss cost are increasing simultaneously. Therefore a periodic preventive resetting the process is necessary. The total cost consists of three items: adjustment cost (or replacement cost), non-conforming cost due to product out of upper or lower limit specification, and quality loss cost due to difference from the process target value and the product characteristic value among the conforming products. In this case, the problem of determining the adjustment period or wear limit that minimizes the total cost is called the 'process mean shift' problem. It is assumed that both specifications are set and the wear level can be observed directly. In this study, we propose a new model integrating the quality loss cost, process variance, and production volume, which has been conducted in different fields in previous studies. In particular, for the change in production volume according to the increasing in wear level, we propose a generalized production quantity function g(w). This function can be applied to most processes and we fitted the g(w) to the model. The objective equation of this model is the total cost per unit wear, and the determining variables are the wear limit and initial process setting position that minimize the objective equation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.4
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• pp.405-416
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• 2021

The safety speed 5030 policy, which is currently being implemented nationwide, tends to increase citizens' dissatisfaction due to reduced mobility and inconvenience. In order to successfully promote the Safety Speed 5030 policy, it is important to collect various opinions of citizens who use roads by deviating from quantitative policy evaluation criteria such as traffic accidents and traffic speed. Therefore, in this study, citizens who use roads were classified into a driver group and a non-driver group, and civic consciousness analysis such as adequacy evaluation of speed limit, satisfaction evaluation of road service quality (MDS), and importance-satisfaction analysis (IPA) was conducted. As a result of the analysis of civic consciousness, in particular, satisfaction with mobility, economy, and environment was low. Accordingly, it was intended to promote the successful implementation of the Safety Speed 5030 policy by presenting measures to improve the speed limit and quality of road service for roads with low satisfaction.

• Journal of Korean Society for Quality Management
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• v.31 no.2
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• pp.165-182
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• 2003

The fatigue has been considered to the most important failure mode where optimal design or reliability prediction of the machinery in aircraft, atomic reactors, and structure systems, etc., is required. When the statistical analysis of fatigue life data is performed, some difficulties are present because of the following facts : nonlinear relationship, heteroscedastic data, large scatter in the data, censored data (runouts), and existence of fatigue limit. To find the S-N curve models that characterize fatigue strength better, this research compares existing fatigue curve models developed recently in terms of the residual mean square and the estimate of fatigue limit, etc. for various fatigue data sets.

• Journal of Korean Institute of Industrial Engineers
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• v.30 no.2
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• pp.84-92
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• 2004

A process control procedure is proposed when 100% inspection is performed in a process with excellent capability. Only the incomplete measurement data is assumed to be available, i.e. the specific measurement value of the quality characteristic is not available for each item but it can be determined to be smaller or larger than any prescribed value. In the suggested model, a signal limit is introduced to determine whether the process under study is in control or not. If the quality characteristic of an incoming item exceeds the upper signal or the lower signal limit, the process is determined to be stopped or not by comparing the number of consecutively accepted items with a predetermined threshold number. The procedure is designed based on the type I and II errors. The performance of the model is evaluated by the expected number of items produced under the in-control and out-of-control states until the process is stopped.

• Journal of Korean Society for Quality Management
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• v.25 no.1
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• pp.182-192
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• 1997

The well-known standard normal distribution has been used within the limit of standard variable value of u=3.59. However, the probability values above the limit are not given in the literature. In this study, a probability computation program for standard normal distribution to u=5.99 with the proportional normal distribution a, pp.oximation suggested by Abramowitz and Stegun, Hastings is developed. The new standard normal distribution table developed by the program is presented and will be of help to estimate of probability values for testing and estimation of process mean value, lot acceptable probability, defective percentage of PPM unit of an out-of specification limit, process capability, test power of control charts, probability and statistics.

• Journal of Korean Society for Quality Management
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• v.34 no.4
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• pp.125-132
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• 2006

An adjusted control limit of the $\overline{X}$ chart is proposed for monitoring the continually improving processes. The continual improvement of the process implies the decrease of the process variance, which is represented by a logistic curve. The process standard deviation is estimated by the exponentially weighted moving average of the sample standard deviations from the past to the current times. The control limits are adjusted by the estimated standard deviation at every sampling time. The performance of the adjusted control limit is compared with that of the standard control limits for various cases of the decreasing speed and size of the variance. The results show that the $\overline{X}$ chart with the adjusted control limits provides better performances for monitoring the small and moderate shifts in continually improving processes.

• Korean Management Science Review
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• v.24 no.1
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• pp.77-90
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• 2007

Taguchi assumed that a product characteristic has the uniform distribution in its preventive maintenance limit when deriving the expected loss generated by the quality deviation. But it is reasonable to assume that a product characteristic has the normal distribution than the uniform distribution. On this paper, we first find the optimum inspection interval and the optimum preventive maintenance limit under the truncated triangular distribution. Secondly we use the beta-general distribution and compare with the truncated triangular distribution. By using the numerical examples, we find the optimum inspection interval and the optimum preventive maintenance limit under their distributions. As a result, we find that the beta-general distribution gives the best solution and easy calculation.

• Industrial Engineering and Management Systems
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• v.8 no.3
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• pp.131-138
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• 2009

The variable sampling inspection scheme with screening for the purpose of assuring the upper limit of maximum expected surplus loss after inspection has been proposed. In this inspection scheme, it has been assumed that a product lot consists of products manufactured through a single production line and lot quality characteristics follow a normal distribution. In the previous literature with respect to inspection schemes, it has been commonly assumed that lot quality characteristics obey a single normal distribution under the condition that all products are manufactured in the same condition. On the other hand, the production line is designed in order that the workload of respective processes becomes uniform from the viewpoint of line balancing. One of the solutions for the bottleneck process is to arrange the workshops in parallel. The lot quality characteristics from such a production line with the process consisting of some parallel workshops might not follow strictly the single normal distribution. Therefore, we expand an applicable scope of the above mentioned variable sampling inspection scheme with screening in this article. Concretely, we consider the variable sampling inspection with screening for the purpose of assuring the upper limit of average outgoing surplus quality loss in the production lots when the lot quality follows the mixed normal distribution.

• Journal of Food Hygiene and Safety
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• v.38 no.4
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• pp.236-245
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• 2023

In this study, the quality safety limit period of seven types of bakery bread was analyzed, and their use-by date was calculated. For evaluating product quality, storage conditions were set as 5, 15, 25, and 35℃ for 50 days, and moisture, microorganisms, sensory characteristics, and dominant bacteria were examined. The quality and safety standards followed the Korea Food Code and Korean industrial standards (KS). The results showed that all products stored at 5℃ satisfied the standard for bacterial count for day 50, but the sensory quality was below the standard level. Samples stored at 15℃ showed high variability from 3-39 days. At 25℃, a quality safety limit period of 2-20 days was set, and one sample was found to have the same shelf life. Bread stored at 35 ℃ had the shortest quality safety limit period. Considering a safety factor of 0.87, a use-by date period of 1.7-13.1 days was calculated. Therefore, setting the use-by date according to the product type is necessary, even for the same product category. Among the bread products sold in bakeries, those managed as room temperature products (1-35℃) can be distributed and stored in a temperature range of up to 35℃. Overall, this study demonstrates the importance of setting a quality retention period based on the product characteristics and carefully considering the safety factor.