• 산업경영시스템학회지
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• 제42권4호
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• pp.145-152
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• 2019

All machines deteriorate in performance over time. The phenomenon that causes such performance degradation is called deterioration. Due to the deterioration, the process mean of the machine shifts, process variance increases due to the expansion of separate interval, and the failure rate of the machine increases. The maintenance model is a matter of determining the timing of preventive maintenance that minimizes the total cost per wear between the relation to the increasing production cost and the decreasing maintenance cost. The essential requirement of this model is that the preventive maintenance cost is less than the failure maintenance cost. In the process mean shift model, determining the resetting timing due to increasing production costs is the same as the maintenance model. In determining the timing of machine adjustments, there are two differences between the models. First, the process mean shift model excludes failure from the model. This model is limited to the period during the operation of the machine. Second, in the maintenance model, the production cost is set as a general function of the operating time. But in the process mean shift model, the production cost is set as a probability functions associated with the product. In the production system, the maintenance cost of the equipment and the production cost due to the non-confirming items and the quality loss cost are always occurring simultaneously. So it is reasonable that the failure and process mean shift should be dealt with at the same time in determining the maintenance time. This study proposes a model that integrates both of them. In order to reflect the actual production system more accurately, this integrated model includes the items of process variance function and the loss function according to wear level.

• 상하수도학회지
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• 제11권3호
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• pp.87-95
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• 1997

A river water quality management model was made by Dynamic programming. This model optimizes the wastewater treatment cost of the application area, and computed water quality with it must meet the water quality standard. And this model takes into consideration tributary input, wastewater treatment plant effluent, withdrawls for several purposes. Modified Streeter-Phelps equation was used to calculate BOD and DO. Optimization problem was solved with particular exceedance probability flow, and the water quality of each point was calculated with the decided treatment efficiencies. At that time, the probability satisfying the water quality standard of constraints to the exceedance probability of the flow. The developed model was applied to the lower part of the Han-River. The reliability to meet the water quality standard is 70 % when 4 wastewater treatment plants of Seoul City are operated by activated sludge system at autumn of the year 2001. Treatment cost of this case is 121.288 billion won per year.

• 품질경영학회지
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• 제17권2호
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• pp.47-54
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• 1989

This study is concerned with the reduction of fraction defective for quality improvement model in manufacturing system. For the methodology, a heuristic method for the selection of alternatives of process improvement is introduced for quality improvement and cost problem subject to cost constraints. This study suggests a model for selecting fraction defective reduction alternatives in multi-stage manufacturing system and a numerical example is presented.

• Asia pacific journal of information systems
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• 제20권2호
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• pp.87-101
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• 2010

Software as a service (SaaS) is one of the most-talked about trends in IT. Unlike traditional perpetual licensing model, software applications are sold on subscription bases and services are provided over web by the vendors. It is said that SaaS can make vendors to invest more on R&D than on marketing while offering its customers better quality software applications at lower costs. By empirically comparing vendors providing their software applications either by SaaS or by traditional perpetual licensing model, we examine whether or not SaaS really increases overall customer benefits in terms of cost efficiency, software quality, and customization. We show that SaaS may not provide better quality or cost efficient software applications than perpetual licensing does. Then we provide two practical tools which are useful for customers to evaluate whether SaaS is better than perpetual licensing for the purposes of software applications they want to adopt.

• 한국품질경영학회:학술대회논문집
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• 한국품질경영학회 1998년도 The 12th Asia Quality Management Symposium* Total Quality Management for Restoring Competitiveness
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• pp.217-224
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• 1998

A cost model, controlling multiple dependent subprocesses with minimum cost, is derived by renewal theory approach. The optimal multiple cause-selecting control chart and individual Y control chart are thus constructed to monitor the specific product quality and overall product quality contributed by the multiple dependent subprocesses. They may be used to maintain the process with minimum cost and effectively distinguish which component of the subprocesses is out of control. The optimal design parameters of the proposed control charts can be determined by minimizing the cost model using simple grid search method, An example is given to illustrate the application of the optimal multiple cause-selecting control chart and individual Y control chart.

• 산업경영시스템학회지
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• 제41권3호
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• pp.145-153
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• 2018

Taguchi regarded the concept of quality as 'total loss to society due to fluctuations in quality characteristics from the time of supplied to the customer.' The loss function is a representative tool that can quantitatively convert the loss that occurs due to the deviation of the quality characteristic value from the target value. This has been utilized in various studies with the advantage that it can change the social loss caused by fluctuation of quality characteristics to economic cost. The loss function has also been used extensively in the study of producer specification limits. However, in previous studies, only the second order loss function of Taguchi is used. Therefore, various types of losses that can occur in the process can't be considered. In this study, we divide the types of losses that can occur in the process considering the first and second loss functions and the Spiring's reflected normal loss function, and perform total inspection before delivering the customer to determine the optimal producer specification limit that minimizes the total cost. Also, we will divide the quality policy for the products beyond the specification limits into two. In addition, we will show the illustration of expected loss cost change of each model according to the change of major condition such as customer specifications and maximum loss cost.

• 산업공학
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• 제24권2호
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• pp.128-138
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• 2011

This research proposes a resource allocation model of Data QC (Quality Control) activities using COQ (Cost of Quality). The model has been developed based on a series of research efforts such as COQ classifications, weight determination of Data QC activities, and an aggregation approach between COQ and Data QC activities. In the first stage of this research, COQ was divided into the four typical classifications (prevention costs, appraisal costs, internal failure costs and external failure costs) through the opinions from five professionals in Data QC. In the second stage, the weights of Data QC activities were elicited from the field professionals. An aggregation model between COQ and Data QC activities has been then proposed to help the practitioners make a resource allocation strategy. DEA (Data Envelopment Analysis) was utilized for locating efficient decision points. The proposed resource allocation model has been validated using the case of Korea national defense information system. This research is unique in that it applies the concept of COQ to the data management for the first time and that it demonstrates a possible contribution to a real world case for budget allocation of national defense information.

• Journal of Preventive Medicine and Public Health
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• 제43권4호
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• pp.352-361
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• 2010

Objectives: This study estimated the annual socioeconomic costs of food-borne disease in 2008 from a societal perspective and using a cost-of-illness method. Methods: Our model employed a comprehensive set of diagnostic disease codes to define food-borne diseases with using the Korea National Health Insurance (KNHI) reimbursement data. This study classified the food borne illness as three types of symptoms according to the severity of the illness: mild, moderate, severe. In addition to the traditional method of assessing the cost-of-illness, the study included measures to account for the lost quality of life. We estimated the cost of the lost quality of life using quality-adjusted life years and a visual analog scale. The direct cost included medical and medication costs, and the non-medical costs included transportation costs, caregiver's cost and administration costs. The lost productivity costs included lost workdays due to illness and lost earnings due to premature death. Results: The study found the estimated annual socioeconomic costs of food-borne disease in 2008 were 954.9 billion won (735.3 billion won-996.9 billion won). The medical cost was 73.4 -76.8% of the cost, the lost productivity cost was 22.6% and the cost of the lost quality of life was 26.0%. Conclusions: Most of the cost-of-illness studies are known to have underestimated the actual socioeconomic costs of the subjects, and these studies excluded many important social costs, such as the value of pain, suffering and functional disability. The study addressed the uncertainty related to estimating the socioeconomic costs of food-borne disease as well as the updated cost estimates. Our estimates could contribute to develop and evaluate policies for food-borne disease.

• 산업경영시스템학회지
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• 제43권3호
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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.

• Journal of Construction Engineering and Project Management
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• 제4권3호
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• pp.53-59
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• 2014

Project managers are responsible to conduct project on time with least amount of costs and the most possible quality with respect to shortage of resources and environmental certainties. They have to make the best decision to reach such conflicting objects. In this study the project scheduling with multi goals-multi modes was planned in fuzzy conditions under resource constraints and expanded by fuzzy goal programing (FGP). The project cost was calculated by the price of renewable resources and the quality criteria were evaluated by the quality function deployment method (QFD). Finally the model was verified by a construction case study with 22 activities along with solving by GAMS. The results showed that this model could provide a systematic framework to facilitate the decision making process and made the project managers to be able to schedule the project closer to reality.