• 산업경영시스템학회지
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• 제40권1호
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• pp.165-172
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• 2017

Machines are physically or chemically degenerated by continuous usage. One of the results of this degeneration is the process mean shift. Under the process mean shift, production cost, failure cost and quality loss function cost are increasing continuously. Therefore a periodic preventive resetting the process is necessary. We suppose that the wear level is observable. In this case, process mean shift problem has similar characteristics to the maintenance policy model. In the previous studies, process mean shift problem has been studied in several fields such as 'Tool wear limit', 'Canning Process' and 'Quality Loss Function' separately or partially integrated form. This paper proposes an integrated cost model which involves production cost by the material, failure cost by the nonconforming items, quality loss function cost by the deviation between the quality characteristics from the target value and resetting the process cost. We expand this process mean shift problem a little more by dealing the process variance as a function, not a constant value. We suggested a multiplier function model to the process variance according to the analysis result with practical data. We adopted two-side specification to our model. The initial process mean is generally set somewhat above the lower specification. The objective function is total integrated costs per unit wear and independent variables are wear limit and initial setting process mean. The optimum is derived from numerical analysis because the integral form of the objective function is not possible. A numerical example is presented.

• 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.

• 산업공학
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• 제16권spc호
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• pp.39-44
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• 2003

As one of many design variables, the role of dimension tolerances is to restrict the amount of size variation in a manufactured feature while ensuring functionality. In this study, a nonlinear integer model has been modeled to allocate the optimal tolerance to each individual feature at a minimum manufacturing cost. While a normal distribution determines statistically worst tolerances with its symmetrical property in many previous tolerance allocation studies, a asymmetrical distribution is more realistic because its mean is not always coincident with a process center. A nonlinear integer model is modeled to allocate the optimal tolerance to a feature based on a beta distribution at a minimum total cost. The total cost as a function of tolerances is defined by machining cost and quality loss. After the convexity of manufacturing cost is checked by the Hessian matrix, the model is solved by the Complex Method. Finally, a numerical example is presented demonstrating successful model implementation for a nonlinear design case.

• Journal of applied mathematics & informatics
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• 제31권5_6호
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• pp.907-912
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• 2013

This paper focuses on the situation of optimizing the total cost with m given messages and n network nodes. Associated with each network node, a fixed cost is incurred to the receiver if at least one message is received. The mean and variance of the total costs are obtained. Normal approximation is used. Empirical results showed that the derived method reduces research work substantially.

• Journal of Korean Neurosurgical Society
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• 제57권6호
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• pp.455-459
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• 2015

Objective : A cost comparison of the surgical clipping and endovascular coiling of unruptured intracranial aneurysms (UIAs), and the identification of the principal cost determinants of these treatments. Methods : This study conducted a retrospective review of data from a series of patients who underwent surgical clipping or endovascular coiling of UIAs between January 2011 and May 2014. The medical records, radiological data, and hospital cost data were all examined. Results : When comparing the total hospital costs for surgical clipping of a single UIA (n=188) and endovascular coiling of a single UIA (n=188), surgical treatment [$mean{\pm}$standard deviation (SD) : \$8,280,000{\pm}1,490,000$] resulted in significantly lower total hospital costs than endovascular treatment ($mean{\pm}SD$ : \$11,700,000{\pm}3,050,000$, p<0.001). In a multi regression analysis, the factors significantly associated with the total hospital costs for endovascular treatment were the aneurysm diameter (p<0.001) and patient age (p=0.014). For the endovascular group, a Pearson correlation analysis revealed a strong positive correlation (r=0.77) between the aneurysm diameter and the total hospital costs, while a simple linear regression provided the equation, y (\)=6,658,630+855,250x (mm), where y represents the total hospital costs and x is the aneurysm diameter. Conclusion : In South Korea, the total hospital costs for the surgical clipping of UIAs were found to be lower than those for endovascular coiling when the surgical results were favorable without significant complications. Plus, a strong positive correlation was noted between an increase in the aneurysm diameter and a dramatic increase in the costs of endovascular coiling.

• 자원ㆍ환경경제연구
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• 제11권4호
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• pp.659-687
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• 2002

This study used a discrete choice model to investigate an association between air pollution and hospital visits for acute respiratory symptoms with the national health interview survey conducted in 1998 in South Korea. The results showed that $NO_2$ and TSP were significantly related to hospital visits in a single-pollutant model, but when they were simultaneously considered, only $NO_2$ remained significant. It was estimated as $NO_2$ level increased by 10%(0.0027ppm) from 0.027ppm (the mean $NO_2$ level), hospital visits increase by 0.176%. This study also measured respondent's out-of-pocket expense and the time cost for commuting and waiting for the visit. We found that on the average, out-of-pocket expense is 5,600 won per hospital visit, but the total cost per hospital visit is measured at 33,440 won with time cost of commuting and waiting at 27,840 won. Time cost was over 63.6~83.3% of the total cost per hospital visit.

• 근관절건강학회지
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• 제3권2호
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• pp.166-176
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• 1996

This is a study through survey with the purpose of analysing of treatment cost for arthritis. Treatment cost can be devided Into two characteristics, one is the direct cost and the other is the indirect cost. Direct cost contains fees of medical treatment Including cost of self treatment & purchsing price of herb durg. On the other hand indirect cost means the using money of tansportation, lodging charge & labor-losing-time cost. For the succession of medical treatment of chronic diseases patients have to control themselves to go shopping around for the cure remeadies. And also it is important that the cost for unefficient or probably hamful folk remeadies should be reduced in order to distribute appropriatively the limited financial resources. As the result of this study, the fees for self treatment & herb drug are two times as much as those of regural medical treatment. Within the direct cost, there are the mean cost of regural medical treatment 59,630 won/mon., self-treatment 42,790 won/mon., and herb drug 78,380won/mon. therefore total mean direct cost is 180,800won per month. Moreover patients intermittently pay the cost of prostheses If folk remedies, these are added to the direct cost as above mentioned. Attributes of folk remedies are various from cure & analgesics to nutrients and their virtues as medicine are not clear in view of scientific knowledge. But 56% of arthritis patients have ever been experienced folk remedies. the cost for these remedies has wide ranges from 40,000 won to 1,000,000won. Total mean indirect cost including the transfortation fee, lodging charge & labor-losing-time cost has the range from 82,825won/month to 106,150won/month. Among these cost, labor-losing-time cost has a mojority because the waiting times are too long for seeing a doctor. In conclusion those patients having arthritis have a large burden against the treatment cost for continuous care. Therefore health professional should make effort to guide the patient to determine themselves informed choice about the treatment process.

• 대한간호학회지
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• 제32권4호
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• pp.435-446
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• 2002

Purpose : The purpose of the study were to describe outcomes of CHP activities, and to evaluate the economic validity of CHP through a cost-benefit analysis. Method : The sample size was 272. Data were collected using a researcher developed questionnaire from November 1999 to March, 2000. Result : The mean age of CHPs was 39.6 (SD-36). In regard to marital status, 90.8% of the respondents were married. 72% of the CHPs had associate degree. Among CHP activities, providing medical services was 50%, followed by home care visits 20% and health promotion services 20%, preventive services 10%. Total costs per month incurred to CHP activities was \3,053,437($2,442.7). Total benefits per month was \6,711,525($5,369.2). Hence, net benefit was calculated as \3,658,089($2,926). Conclusion : Cost-benefit ratio was 2.20, which provides the evidence of the economic viability of CHP program. The result of cost-benefit analysis, however, would more strongly support the economic value of CHP if intangible benefits of CHP activities such as decreases in pain and suffering and increased quality of life, could be counted.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회/대한산업공학회 1999년도 춘계공동학술대회:정보화시대의 지식경영
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• pp.426-426
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• 1999

;There are many sources of uncertainty in a typical production and inventory system. There is uncertainty as to how many items customers will demand during the next day, week, month, or year. There is uncertainty about delivery times of the product. Uncertainty exacts a toll from management in a variety of ways. A spurt in a demand or a delay in production may lead to stockouts, with the potential for lost revenue and customer dissatisfaction. Firms typically hold inventory to provide protection against uncertainty. A cushion of inventory on hand allows management to face unexpected demands or delays in delivery with a reduced chance of incurring a stockout. The proposed strategies are used for the design of a probabilistic inventory system. In the traditional approach to the design of an inventory system, the goal is to find the best setting of various inventory control policy parameters such as the re-order level, review period, order quantity, etc. which would minimize the total inventory cost. The goals of the analysis need to be defined, so that robustness becomes an important design criterion. Moreover, one has to conceptualize and identify appropriate noise variables. There are two main goals for the inventory policy design. One is to minimize the average inventory cost and the stockouts. The other is to the variability for the average inventory cost and the stockouts The total average inventory cost is the sum of three components: the ordering cost, the holding cost, and the shortage costs. The shortage costs include the cost of the lost sales, cost of loss of goodwill, cost of customer dissatisfaction, etc. The noise factors for this design problem are identified to be: the mean demand rate and the mean lead time. Both the demand and the lead time are assumed to be normal random variables. Thus robustness for this inventory system is interpreted as insensitivity of the average inventory cost and the stockout to uncontrollable fluctuations in the mean demand rate and mean lead time. To make this inventory system for robustness, the concept of utility theory will be used. Utility theory is an analytical method for making a decision concerning an action to take, given a set of multiple criteria upon which the decision is to be based. Utility theory is appropriate for design having different scale such as demand rate and lead time since utility theory represents different scale across decision making attributes with zero to one ranks, higher preference modeled with a higher rank. Using utility theory, three design strategies, such as distance strategy, response strategy, and priority-based strategy. for the robust inventory system will be developed.loped.

• Journal of Chest Surgery
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• 제47권1호
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• pp.20-25
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• 2014

Background: Symptomatic or asymptomatic patients with significant carotid artery stenosis (range, 70% to 99%) generally undergo either carotid artery endarterectomy (CEA) or carotid artery stenting (CAS) to prevent stroke. In this study, we evaluated the cost effectiveness of these two treatment modalities. Methods: A total of 47 patients (mean age, $67.1{\pm}9.1$ years; male, 87.2%) undergoing either CEA (n=28) or CAS (n=19) for the treatment of significant carotid artery stenosis were enrolled in this study. Hospitalization costs were subdivided into three parts, namely pre-procedure, procedure and resource, and post-procedure costs. Results: Total hospitalization costs were similar in both groups of CEA and CAS (6,377 thousand won [TW] vs. 6,703 TW, p=0.255); however, the total cost minus the pre-procedure cost was higher in the CAS group than in the CEA group (4,948 TW vs. 5,941 TW, p<0.0001). The pre-procedure cost of the CEA group was higher than that of the CAS group (1,429 TW vs. 762 TW, p<0.0001). However, the procedure and resource cost was higher in the CAS group because the resource cost was approximately three times higher in the CAS group than in the CEA group. The post-procedure cost was higher in the CEA group because hospital stays were approximately two times longer. Conclusion: The total hospitalization cost was not different between the CEA and the CAS groups. The pre-procedure cost was high in the CEA group, but the cost from procedure onset to discharge, including the resource cost, was significantly lower in this group.