• International conference on construction engineering and project management
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• 2022.06a
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• pp.188-195
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• 2022

Although issuing change orders is a common practice in the construction phase of any project, non-structural utility subcontractors are struggling and seek to find a way to reduce change orders. Therefore, this paper presents the analysis results on change orders to cultivate possible suggestions and solutions on how to reduce or minimize change orders in mechanical, electrical, and plumbing (MEP) works. Change orders in non-structural utility works are analyzed based on six categories such as rerouting and change of location, changes in weight, rejected design by Office of Statewide Health Planning and Development, District Structural Engineer, or the Structural Engineer of Record, unforeseen conditions, changed equipment, and owner-initiated change. The analysis findings showed that rerouting and changing location is the most significant cause, followed by unforeseen conditions. The results not only contribute to the existing body of knowledge on change order research area, but also help MEP contractors reduce the time and cost of change orders.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.161-162
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• 2023

The construction inspection is conducted by the contractor or construction supervisor after a certain stage of work has been completed. As the consturction inspection task is dependant on construction schedule, however, it is difficult to plan inspection task systematically, resulting in increased supervision costs, delays in construction, and disputes. Therefore, this study aims to integrate inspection work with schedule management to systematize inspection procedures. Firstly, the inspection work is defined based on the construction supervision checklist. Then its relationship with the construction process, required time, and resources for inspection tasks are defined in construction schedule. Lastly, a process management program is used to assess the effects of applying the inspection work and examine changes in the overall construction period and process management. The proposed method in this study can support to plan construction inspection more systematically and to improve the effectiveness of construction quality management.

• Journal of Distribution Science
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• v.14 no.2
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• pp.41-45
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• 2016

Purpose - Finding an optimal path is an essential component for the design and operation of smart transportation or logistics network. Many applications in navigation system assume that travel time of each link is fixed and same. However, in practice, the travel time of each link changes over time. In this paper, we introduce a new transportation problem to find a latest departing time and delivery path between the two nodes, while not violating the appointed time at the destination node. Research design, data, and methodology - To solve the problem, we suggest a mathematical model based on network optimization theory and a backward search method to find an optimal solution. Results - First, we introduce a dynamic transportation problem which is different with traditional shortest path or minimum cost path. Second, we propose an algorithm solution based on backward search to solve the problem in a large-sized network. Conclusions - We proposed a new transportation problem which is different with traditional shortest path or minimum cost path. We analyzed the problem under the conditions that travel time is changing, and proposed an algorithm to solve them. Extending our models for visiting two or more destinations is one of the further research topics.

• Journal of Korean society of Dental Hygiene
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• v.19 no.3
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• pp.375-385
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• 2019

Objectives: The purpose of this study was to provide basic data for gingivitis management programs by dental hygienists by evaluating the effect of oral health education, oil pulling, and professional toothbrushing on gingivitis. Methods: A total of 38 subjects were divided into three groups: control group (12 subjects), experimental group 1 (13 subjects), and experimental group 2 (13 subjects). The control and experimental groups were instructed to brush using the rotating method. Distilled water was provided to the control group after training. Coconut oil was provided every morning for about 10 minutes. In the experimental group 2, a professional brushing method was used at each visit. Results: There were no significant differences in oral health among the three groups, and there was homology between patient hygiene performance (PHP) index (p=0.144) and bleeding rate (p=0.213). The PHP index showed a significant interaction between the group and measurement time. The control and experimental groups showed changes in the PHP index with time (F=3.711; p=0.013). The bleeding rate showed a significant interaction between the group and measurement period. The control and experimental groups showed changes in the bleeding rate with time (F=6.707; p<0.001). Conclusions: Oral health education, professional toothbrushing, and oil pulling specialists in oral care of gingivitis were effective in managing gingivitis. It is necessary to educate people on self-management methods for oral health promotion using gingivitis management programs by dental hygienists.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.11a
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• pp.165-168
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• 2006

Exponential smoothing methods do not adapt well to unexpected changes in underlying process. Over the past few decades a number of adaptive smoothing models have been proposed which allow for the continuous adjustment of the smoothing constant value in order to provide a much earlier detection of unexpected changes. However, most of previous studies presented ad hoc procedure of adaptive forecasting without any theoretical background. In this paper, we propose a detection-adaptation procedure applied to simple and Holt's linear method. We derive level and slope change detection statistics based on Bayesian statistical theory and present distribution of the statistics by simulation method. The proposed procedure is compared with previous adaptive forecasting models using simulated data and economic time series data.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.111-113
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• 2015

Floats are used by the parties involved in a construction project. The owner may use float by changing order(s) or by executing risk avoidance plan; the contractor may use it for leveling resources or substituting activities' construction methods to reduce costs. Floats are accepted either just as by-product obtained by critical path method(CPM) scheduling or as asset having significant value. Succinctly, existing studies involved in float value does not consider its' changes on project time domain. It is important to identify float ownership and to quantify its' corresponding values. This paper presents a method that quantifies float value of money that changes over project execution. The method which accurately computes the monetary value of float may contributes to resolve conflicts relative to float ownership and/or delay issues among project participants. It compares the difference between the monetary value of total float - on non-critical path in each and every schedule update. It makes use of critical path method (CPM) and commercial software with which practitioners are already familiar.

• Journal of the Korean Operations Research and Management Science Society
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• v.29 no.1
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• pp.31-41
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• 2004

This study analyzes the structure of the variations In the domestic bank earnings and examines their dynamic features by estimating the short-run response and the long-run adjustment Process after the changes in financial market variables. A system of the equations for the bank stock price index and KOSPI is formulated to utilize the whole information in the market and simultaneously estimated to identify the relationships between the market variables and the bank earnings. Since the bank stock price is found to be responsive to changes in none of the market variables in the short run, while being relatively responsive to dollar exchange rate and business state, It implies that a good economic conditions and a stable foreign exchange rate should be maintained to Improve the level of the stock price In the long run. In addition, the dynamic structure of the responses of the bank stock price index and KOSPI to the initial changes in the market variable are compared and anlayzed. The response of the bank stock price appears to take much longer in adjusting to the long-run eouilibrium level than that of KOSPI. As a result, the cumulative response of the bank stock price index over time is found much bigger than that of HOSPI.

• Communications for Statistical Applications and Methods
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• v.30 no.4
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• pp.369-388
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• 2023

In this paper, we develop the two-step procedure that detects and estimates the position of structural changes for multivariate nonstationary time series, either on mean parameters or second-order structures. We first investigate the presence of mean structural change by monitoring data through the aggregated cumulative sum (CUSUM) type statistic, a sequential procedure identifying the likely position of the change point on its trend. If no mean change point is detected, the proposed method proceeds to scan the second-order structural change by modeling the multivariate nonstationary time series with a multivariate locally stationary Wavelet process, allowing the time-localized auto-correlation and cross-dependence. Under this framework, the estimated dynamic spectral matrices derived from the local wavelet periodogram capture the time-evolving scale-specific auto- and cross-dependence features of data. We then monitor the change point from the lower-dimensional approximated space of the spectral matrices over time by applying the dynamic principal component analysis. Different from existing methods requiring prior information on the type of changes between mean and covariance structures as an input for the implementation, the proposed algorithm provides the output indicating the type of change and the estimated location of its occurrence. The performance of the proposed method is demonstrated in simulations and the analysis of two real finance datasets.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.34 no.1
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• pp.63-70
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• 2016

From 1990, Seoul Metropolitan Government has established an urban master plan for the efficient city management by introducing the central place structure with a multi-tiered hierarchy. In the plan, Seoul City uses the strategy of developing the station influence area around the urban railway, in order to form the central place structure, effectively. . Therefore, reviewing impacts of urban railway is the most fundamental study for understanding changes in the spatial structures of Seoul. In the study, we have analyzed the changes in the central place structure of Seoul City with the public land price changes in station influence area around the urban railway at each year of 2000, 2005, and 2010. As a result, we could easily recognize the changes in the hierarchical central place structure by analyzing the time-series changes of public land price in station influence area.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 1993.09a
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• pp.33-37
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• 1993

This is a study on the Changes of the Apartment House Managerial Problems to grope for the way of more pratical management about increasing the apartment house in Korea. The documentary research method was used for this study and the Han-Kook newspaper(1954-1991) was used as an ananlysis data. On the basis of it, I examined the changes, such as the number of whole articles by time series and the column of head title. I also classified it into several subjects and analyzed it. Finally, I attemped to divide an chronological section on the Changes of the Apartment House Managerial Problems. On the basis of this study, I expect that various documents, related laws and regulations will be analyzed in no distant future. These is going to make the Apartment House Managerial Problems gave more systemic and efficiency.