• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.4
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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.

• Journal of Korean Society of Steel Construction
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• v.21 no.1
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• pp.1-14
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• 2009

Estimating appropriate construction cost at the design phase is judged with one important issue to the efficient security and the execution of budget. Therefore, in this paper, to build fundamental data of appropriate construction cost for steel box bridges, the existing calculated document such as the quantity, unit price document and detail items etc.. was analyzed and the basic specification of the bridges was investigated. Also, by estimating the relationship between predetermined cost and construction items on the bridges, the paper is intended to produce basic data for the calculation of appropriate construction cost in planning phase. From the result, it was calculated ratio of construction item in the total construction cost and unit cost. And then it was deduced effect factor of construction cost in steel box bridge.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• autumn
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• pp.119-126
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• 2001

This paper analyzes problems related to total cost changes in private investment projects, and then proposes an improvement measure for the control of cost changes within the framework of the project management, contract, human resource, project communication, cost, and time management. From the viewpoint of contract management, the basis of cost change ought to be cleared up with standardization of related provisions in the concession agreement, and potentiality of change ought to be excluded with prescription of the private investor's leading role from the design phase. Regarding human resource management, this paper proposes a standard work flow granting much sovereign rights to private parts by putting restriction on work scopes of the entrusted authority of government, and transferring the rights of assignment, contract, and control about the responsible supervisor to the concessionaire. With regard to project communication management the notification of changes on drawings and technical documents ought to be automated and the realtime database ought to be established with DMIS (Drawings & Documents Management Information System). From the cost management point of view, this thesis integrates the control of cost-change-approved items and disapproved items to one cost breakdown system, and then harmonizes the actual progress with EVMS in time management.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.44 no.1
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• pp.45-50
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• 2021

Machines and facilities are physically or chemically degenerated by continuous usage. The representative type of the degeneration is the wearing of tools, which results in the process mean shift. According to the increasing wear level, non-conforming products cost and quality loss cost are increasing simultaneously. Therefore, a preventive maintenance is necessary at some point. The problem of determining the maintenance period (or wear limit) which minimizes the total cost is called the 'process mean shift problem'. The total cost includes three items: maintenance cost (or adjustment cost), non-conforming cost due to the non-conforming products, and quality loss cost due to the difference between the process target value and the product characteristic value among the conforming products. In this study, we set the production volume as a decreasing function rather than a constant. Also we treat the process variance as a function to the increasing wear rather than a constant. To the quality loss function, we adopted the Cpm+, which is the left and right asymmetric process capability index based on the process target value. These can more reflect the production site. In this study, we presented a more extensive maintenance model compared to previous studies, by integrating the items mentioned above. The objective equation of this model is the total cost per unit wear. The determining variables are the wear limit and the initial process setting position that minimize the objective equation.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.3
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• pp.35-41
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• 1998

Cost estimate system Will be changed from the prime. cost calculation to the historical cost data because the present system has some problems. In this situation, each owner should prepare his own cost estimate system based on the historical cost data. In this study, the standard work items were classified and the criteria of their work amount computation were established for rural improvement projects. And also the historical cost data were collected in all range of rural improvement projects, and the database system, "HICOMS" (HIstorical COst data Management System) was built. In order to test the applicability of the HICOMS, standard work cost and contractor cost were compared. The results by HICOMS showed high significance and it was concluded that the HICOMS could be applicable for the cost estimate of the rural improvement projects. projects.

• Journal of Home Health Care Nursing
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• v.10 no.2
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• pp.113-122
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• 2003

Purpose: This is a simple survey for discussion about cost analysis methodological issues in home care nursing service studies. Method: The subject of this study were articles published in Korea from 1961 to August, 2002, and searched by key word 'cost' and 'nursing' from various DB(National Assembly Library, The National Library of Korea, RICH etc). Finally, 13 articles were collected. Result: 1) The major type of cost analysis studies was a cost comparison or a simple cost study. 2) The important methodological weaknesses were as followers; (1) few studies were suggested cost analysis framework or analytic perspective, (2) it ,was not enough to describe for basis of selection of cost/effectiveness items, (3) few studies were done by sensitivity analysis. Conclusion: These above results will be used to develop a more proper cost analysis methodological framework in home care nursing services and also to contribute as a guideline for further studies.

• Journal of the Korean Institute of Landscape Architecture
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• v.50 no.4
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• pp.20-36
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• 2022

This study aims to provide basic data for high-quality street tree management by setting reasonable management items and appropriate unit prices by reviewing the adequacy of current street tree management. Currently, street tree management items, except for street tree pruning, use general landscape tree quantity per unit for the street tree management quantity per unit. KEPCO (Korea Electric Power Corporation) applied pruning items from standard electric production infrastructure and carried out the activities at an average unit price of 51% lower for heavy pruning and 39% lower for light pruning than the standard estimate. This was judged to be a level that could not maintain or increase the quality of street tree management. It was determined that an appropriate standard unit price for street tree management was necessary. To improve the quantity per unit for the proper management of street trees, it was necessary to review costs in the field. However, due to the absence of data on actual construction costs in the domestic landscape field, detailed items of the US RSMeans Building Construction Cost Data (RSMeans) were reviewed, and the actual construction costs were calculated by applying personal domestic expenses. As a result, the standard of the estimated unit showed a good ratio of 107% for heavy pruning of street tree pruning compared to the actual construction cost, but light pruning was underestimated with a 59% ratio. Shrub pruning was 82%, weeding was 92%, tree fertilization was 87%, and windbreak wall installation was 91% under-engineered. In addition, it was also confirmed that the watering by sprinkler trucks and chemical spraying were over-designed compared to the actual construction cost at the rates of 118% and 124%, respectively. Due to the specificity of the street trees, the increase in personal expenses and the input cost of equipment, such as road safety controls, were judged to be the main cause of the underestimation of items. Therefore, it is necessary to add items related to street trees and general landscape trees to the landscape maintenance items of the standard of the estimated unit.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1999.04a
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• pp.323-324
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• 1999

• Journal of Korean Institute of Industrial Engineers
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• v.38 no.2
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• pp.116-124
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• 2012

This paper concerns a joint replenishment problem for a single buyer who sells multiple types of items to end-customers. The buyer periodically replenishes the inventory of each item to a preset order-up-to-level to satisfy the end customers' demands, which may be non-stationary. A joint replenishment policy characterized by variable order-up-to-levels is proposed for the buyer who wishes to minimize the expected cost of operating the retail system. The proposed policy starts each period by calculating the expected cost of ordering and not ordering action based on the information of the current inventory position and forecasted demand for the upcoming period. It then takes advantage of an integer programming model to get a cost effective joint replenishment plan. Computer experiment was performed to test efficiency of the proposed policy. When compared with the most efficient policy currently available, our policy showed a considerable cost savings especially for the problems having non-stationary demands.

• Plant Journal
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• v.10 no.4
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• pp.29-34
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• 2014

In this consideration, this research investigated the piping design items and drew out key design items through interview with experts and surveys to apply them to actual project examples and look into piping design item-specific significance and cost variation ranges. Based on this investigation, the Monte-Carlo simulation was employed herein to analyze the cost variation range for the entire piping design costs with a view to presenting a way to calculate a reasonable bidding price for any similar project and verify the appropriateness of joining a bid.