• Journal of Applied Reliability
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• v.13 no.4
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• pp.229-239
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• 2013

This paper reports a manner to use a Bayesian approach to derive the optimal replacement policy. In order to produce a system with minimal repair warranty, a replacement model with the extended warranty is considered. Within the warranty period, the failed system is minimally repaired by the manufacturer at no cost to the end-user. The failure time is assumed to follow a Weibull distribution with unknown parameters. The expected cost rate per unit time, from the end-user's viewpoints, is induced by the Bayesian approach, and the optimal replacement policy to minimize the cost rate is proposed. Finally, a numerical example illustrating to derive the optimal replacement policy based on the Bayesian approach is described.

• Communications for Statistical Applications and Methods
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• v.25 no.1
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• pp.91-97
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• 2018

In this paper, we show that there exists an optimal investment policy for the surplus in a risk model, in which the surplus is continuously invested to other business at a constant rate a > 0, whenever the level of the surplus exceeds a given threshold V > 0. We assign, to the risk model, two costs, the penalty per unit time while the level of the surplus being under V > 0 and the opportunity cost per unit time by keeping a unit amount of the surplus. After calculating the long-run average cost per unit time, we show that there exists an optimal investment rate $a^*$>0 which minimizes the long-run average cost per unit time, when the claim amount follows an exponential distribution.

• Journal of Korean Society for Quality Management
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• v.14 no.2
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• pp.21-27
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• 1986

This paper deals with a continuous review (s,S) spare part inventory system. The distributions of service life of each part and the replenishment lead time are assumed to be exponential. Assuming that there is never more than a single order outstanding, we obtain the average annual cost of operating the inventory system. If the length of stockout period is small enough to be neglected compared to the length of operating period, the optimal operating policy variables minimizing the cost rate can be calculated iteratively. For the case of one-for-one ordering (that is, s=S-1), an exact cost rate, and a closed form decision rule minimizing the cost rate are obtained for a more general situation in which more than one order is allowed to be outstanding and the distribution of the replenishment lead time is general.

• Korea Journal of Hospital Management
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• v.26 no.2
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• pp.17-26
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• 2021

Purposes: This study aims to identify factors affecting dental university hospitals' profitability and understand recent their business condition. Methodology: Data from 2016 to 2019 was collected from financial statement, public open data in 8 dental university hospitals. For the study, multiple regression test with stepwise selection was applied. Findings: First of all, 9 out of 19 independent variables were selected by stepwise selection. As a result of multiple regression test with selected independent variables and the dependent variable(operating profit margin ratio), the factors affecting hospitals' profitability were the number of dental unit chair, hospital location, debt ratio, total capital turnover ratio, employment cost rate, material cost rate, management expense rate, the number of patient per a dentist. Practical Implication: To improve dental university hospitals' profitability, hospitals specifically analysis and manage their cost such as employment, material and management cost and seek effectiveness by managing the proper number of patient per a dentist.

• Journal of Integrative Natural Science
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• v.14 no.4
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• pp.197-204
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• 2021

Under the two-phase warranty, the warranty period is divided into two intervals, one of which is for renewing replacement warranty, and the other is for minimal repair warranty. Jung^[13] discusses the two types of extended two-phase warranty models. In this paper, we suggest the replacement model after the extended two-phase warranty that has been proposed by Jung^[13]. To determine the optimal replacement policy, we adopt the expected cost rate per unit time. So, the expressions for the total expected cost, the expected length of the cycle and the expected cost rate per unit time from the user's point of view are derived. Also, we discuss the optimal replacement policy and the uniqueness of the solution for the optimization. Furthermore, the numerical examples are provided to illustrate the proposed the replacement model.

• The Journal of Sustainable Design and Educational Environment Research
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• v.14 no.1
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• pp.1-9
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• 2015

The accurate estimation of construction cost is critical for effective budgeting and financing of the project. Accurate estimates also allow for informed decisions when considering the responsiveness of bids or proposals and for a contractor to better monitor construction progress. However, current method for construction cost of the public educational facility uses a basic criteria in Korea, e.g, construction cost per unit floor area. Therefore, the purpose of this study is to examine present architectural work cost rate of elementary, middle, and high school delivered by BTL(Build-Transfer-Lease). We examined real construction cost of educational facility according to level of school, such as elementary, middle, and high school. The examination revealed that unit price of BTL educational construction cost are different to the level of school, but the composing rate of architectural work cost of the educational facility are very similar. As a result, it is recommended that future researches are initiated to create specific methods to support the accurate cost estimation of educational facility.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5D
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• pp.849-859
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• 2006

Earnings of domestic enterprises are expected a serious damage because the lowest cost bid system and the current cost estimate system. In 2005 average successful bid rate for the lowest cost bid project is below 60%, this is not reach at the operating budget of enterprise. Many problems such as illegal construction, low price subcontract, chain enterprise loss com in to practice because of low successful bid rate. In addition earnings of the enterprises expected to be the minimum, because of enlarge execution of the current cost estimate system. This study tries to lend assistance by giving alternative for the construction enterprise by presenting the bid system, investigate and compare foreign system with domestic and analyze correlation of the lowest cost bid and the current cost estimate system.

• Current Research on Agriculture and Life Sciences
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• v.32 no.3
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• pp.165-169
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• 2014

This study assessed the economic feasibility of an automatic egg washer. Based on various cost benefit analysis methods, including the net present value (NPV), internal rate of return (IRR) and benefit cost ratio (B/C Ratio), the automatic egg washer was confirmed to have economic feasibility. The NPVs were 38,565,991 won at 5% discount rate and 32,013,916 won at 10% discount rate, respectively. The IRRs were 1.325 at 5% discount rate and 1.299 at 10% discount rate, respectively. Finally, the B/C ratios were 1.726 at 5% discount rate and 1.699 at 10% discount rate.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.1
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• pp.64-69
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• 2011

A novel concept of the gridable desalination plant is to provide an operation management to enable an electricity plant operation cost reduction. Adjusting recovery rate responded to electricity price, an electricity plant operation cost can be saved. To show a suggested approach, the data of 10 [MIGD](Million Imperial Gallons per Day) SWRO testbed are used. The result shows that total cost reduction rate is calculated about 1.6[%] of annual total electric plant operation cost.

• IE interfaces
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• v.16 no.1
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• pp.27-33
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• 2003

The maintenance cost in K Steelworks has been continuously increased in proportion to the production cost. However, there seems to be a possibility of reducing cost through the optimization of maintenance actions. The failure types of the equipment in steelworks ate various with different failure cost. Thus the failure rate and cost of each type of failures should be considered simultaneously when the optimum maintenance period is to be determined. It is considered that the equipment undergoes periodic replacement and a specified number of incomplete preventive maintenance actions are performed during a replacement period. Assuming that the time to failure follows a Weibull distribution, the parameters of the failure rate are estimated using the maximum likelihood estimation. The optimal replacement period is determined to minimize the average cost per unit time. As the result of analysis it is suggested that the existing maintenance period for a hot-rolling equipment can be extended significantly.