• Journal of Sensor Science and Technology
• /
• v.32 no.4
• /
• pp.219-222
• /
• 2023

Partial discharges (PD) have long been recognized as a major contributing factor to catastrophic failures in high-power equipment. As the demand for high voltage direct current (HVDC) facilities continues to rise, the significance of on-line and real-time monitoring of PD becomes increasingly prominent. In this study, we have designed, fabricated, and characterized a highly sensitive and cost-effective PD sensor comprising a pair of copper electrodes with different arc lengths. The key advantage of our sensor is its non-invasive nature, as it can be installed at any location along the entire power cable without requiring structural modifications. In contrast, conventional PD sensors are typically limited to installation at cable terminals or insulation joint boxes, often necessitating invasive alterations. Our PD sensor demonstrates exceptional accuracy in estimating PD location, with a success rate exceeding 95% in the straight sections of the power cable and surpassing 89% in curved sections. These remarkable characteristics indicate its high potential for realtime and on-line detection of PD.

• International conference on construction engineering and project management
• /
• 2013.01a
• /
• pp.375-385
• /
• 2013

As climate change and environmental pollution become one of the biggest global issues today, new renewable energy, especially solar photovoltaic (PV) system, is getting great attention as a sustainable energy source. However, initial investment cost of PV system is considerable, and thus, it is crucial to predict electricity generation accurately before installation of the system. This study analyzes the loss ratio of solar photovoltaic electricity generation from the actual PV system monitoring data to predict electricity generation more accurately in advance. This study is carried out with the following five steps: (i) Data collection of actual electricity generation from PV system and the related information; (ii) Calculation of simulation-based electricity generation; (iii) Comparative analysis between actual electricity generation and simulation-based electricity generation based on the seasonality; (iv) Stochastic approach by defining probability distribution of loss ratio between actual electricity generation and simulation-based electricity generation ; and (v) Case study by conducting Monte-Carlo Simulation (MCS) based on the probability distribution function of loss ratio. The results of this study could be used (i) to estimate electricity generation from PV system more accurately before installation of the system, (ii) to establish the optimal maintenance strategy for the different application fields and the different season, and (iii) to conduct feasibility study on investment at the level of life cycle.

• The Journal of Economics, Marketing and Management
• /
• v.12 no.3
• /
• pp.23-33
• /
• 2024

This study aims to enhance the accuracy of effective demand analysis for publicly supported private rental housing by integrating the RIR into the traditional Mankiw-Weil (MW) model. Traditional models like the M-W model, which account for household income, housing costs, and household size, often fall short in estimating demand driven by large-scale development projects. By integrating the RIR factor, this study introduces a more accurate and practical approach to analyzing effective housing demand. Findings show that the modified M-W model incorporating RIR predicts effective demand with greater precision than traditional methods. This advancement allows developers to plan projects more efficiently and aids governments and local authorities in implementing more effective housing policies. Furthermore, the study assesses the real housing cost burden on households, elucidating their capacity to pay housing costs based on household size and income quintile. This information enables policymakers to design targeted housing support policies for specific demographic groups. Additionally, the research provides comprehensive policy recommendations tailored to various regions and housing types. Overall, this study lays a vital groundwork for the long-term analysis of the effects of economic changes and housing market trends on effective demand.

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

• Korean Journal of Construction Engineering and Management
• /
• v.15 no.5
• /
• pp.94-102
• /
• 2014

This study analyzes necessity of expanding construction insurance and estimates required budget. Construction insurance is obliged by National Contract Law and Local Contract Law to protect projet owners and contractors from any unexpected construction risk such as financial losses in construction process. Currently the contracts of design-build and alternate-bid projects as well as PQ project, which are greater than 20 billion won, require the contractors to provide construction insurances in Korea. Insurance premiums are borne by the public project owner. Those contractors whose contract volume is less than 20 billion won burden all risks of projects at their cost. This causes equity problem. Because small-and-medium contractors are discriminated against large contractors since insurance-obliged projects are performed by large contractors and insurance premiums are borne by the public project owner. On the other hands, in all engineering projects, regardless of volume, insurance premiums are borne by the project owner. Therefore current regulation has to be improved, by expanding to all public projects. The average ratio of unobliged projects is 46%, in recent 3 years, prime cost of insurance companies is estimated 0.2%. Moreover considering risks of each construction type, prime cost of unobliged works is estimated as 0.13%. Hence additional necessary budget is estimated to be 2.09 billion won if total volume of public work is 3.5 trillion won. And 2.39 billion won is derived if total volume of public projects is 4 trillion won.

• Journal of Internet Computing and Services
• /
• v.16 no.4
• /
• pp.1-11
• /
• 2015

This study uses the contingent valuation method to estimate the switching cost for adopting the MVNO service. The findings are as follows.: First, Willingness To Switch(WTS) increases as users' using pattern and perceived degree of MVNO service, but satisfaction with current service provider does not play a significant role in predicting Switching Cost. This means that as amount of money users can save exceeds a certain level, users decide to willingly change their service provider to MVNO regardless of their level of satisfaction with current service provider. Second, there are differences in WTS among service subscribers in SKT, KT and LGU+. It means that there will be a difference in the tendency to switch to MVNO among subscribers of service providers. This study suggest the following mangerial perspective to effectively promote the MVNO and boost the MVNO market for activation of mobile data services.: First, MVNOs are better off applying differentiated pricing scheme at attractive rates than using a differentiation of service product and quality. Second, regulators should consider how to implement an MVNO regulatory policy when there is an asymmetric customer loyalty among MNOs. This research will be used to set the MVNO's pricing strategy and to build up a successful regulatory policies.

• Quality Improvement in Health Care
• /
• v.11 no.1
• /
• pp.46-60
• /
• 2004

Background : Recently, we have experienced various changes in the healthcare environment. Healthcare organizations are facing a financial crisis due to more competitive relationships among themselves as well with low health insurance fees. The purposes of the current study were: (1) to develop a data warehouse-based system for evaluating and monitoring the case management activities, and (2) to measure and analyze its effects. Methods : In order to collect the data for the study, the database on discharged patients was utilized at a university hospital located in Seoul from June 1, 2002 through December 31, 2002. Initially, a data warehouse was built for the case management system. The case management activities were analyzed using structured methodology to establish the case management system. Results : The findings of this study were as follows: (1) A case management system was developed to make it possible to monitor of healthcare quality and resource utilization. The Case management System included monitoring functions regarding utilization reviews, critical pathways, and clinical indicators. (2) Utilizing the case management system, unplanned readmissions were documented among total discharged patients during two months from November 1, 2002 through December 31, 2002. The unplanned readmission rate was 2.3%(276 patients) in total of 11,960 discharged patients. Among them 81 patients(0.7% of total discharges, 29.3% of unplanned readmission) were readmitted to the same physician in charge under the same diagnosis. No significant differences were found in the demographic variables such as gender and age among the patients. (3) After implementing the case management system, 2.9% of average length of stay reduced. Applying cost-benefit analysis, the 2.9% reduction of length of stay represents net profit of ${\backslash}$ 279,592,000 in the year of 2004. In addition, applying value acceleration analysis, cumulative net benefit of ${\backslash}$ 1,481,000,000 was expected by the year of 2007. Also we were able to expect ${\backslash}$ 247,800,000 of cumulative benefit for the prospective 5 years in value linkage analysis. It represents average ${\backslash}$ 787,700,000 of pure net benefit a year. Conclusion : The value of present study would be not only implementing the knowledge management system into the existing case management activities, but also evaluating its effects and estimating its financial benefits. This study suggested that the case management system would be a supportive tool for monitoring and improving the quality of healthcare, and a cost-effective tool for increment of healthcare organization's financial benefit.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.8 no.3
• /
• pp.96-106
• /
• 2005

The ability of remote sensing and GIS technique, which used to provide valuable informations in the time and space domain, has been known to be very useful in providing permanent records by mapping and monitoring flooded area. In 2000, floods were at the worst stage of devastation in Tonle Sap Lake, Mekong River Basin, for the second time in records during July and October. In this study, Landsat ETM+ and RADARSAT imagery were used to obtain the basic information on computation of the inundation area and volume using ISODATA classifier and segmentation technique. However, the extracted inundatton area showed only a small fraction than the actually inundated area because of clouds in the imagery and complex ground conditions. To overcome these limitations, the cost-distance method of GIS was used to estimate the inundated area at the peak level by integrating the inundated area from satellite imagery in corporation with digital elevation model (DEM). The estimated inundation area was simply converted with the inundation volume using GIS. The inundation volume was compared with the volume based on hydraulic modeling with MIKE 11. which is the most poppular among the dynamic river modeling system. The method is suitable for estimating inundation volume even when Landsat ETM+ has many clouds in the imagery.

• The Journal of Fisheries Business Administration
• /
• v.46 no.2
• /
• pp.59-74
• /
• 2015

This study aims to estimate optimal harvesting production, fishing efforts, and stock levels of yellow croaker caught by the offshore Stow Net and the offshore Gill Net fisheries using the current value Hamiltonian method and the surplus production model. As analyzing processes, firstly, this study uses the Gavaris general linear model to estimate standardized fishing efforts of yellow croaker caught by the above multiple fisheries. Secondly, this study applies the Clarke Yoshimoto Pooley(CY&P) model among the various exponential growth models to estimate intrinsic growth rate(r), environmental carrying capacity(K), and catchability coefficient(q) of yellow croaker which inhabits in offshore area of Korea. Thirdly, the study determines optimal harvesting production, fishing efforts, and stock levels of yellow croaker using the current value Hamiltonian method which is including average landing price of yellow croaker, average unit cost of fishing efforts, and social discount rate based on standard of the Korean Development Institute. Finally, this study tries sensitivity analysis to understand changes in optimal harvesting production, fishing efforts, and stock levels of yellow croaker caused by changes in economic and biological parameters. As results drawn by the current value Hamiltonian model, the optimal harvesting production, fishing efforts, and stock levels of yellow croaker caught by the multiple fisheries were estimated as 19,173 ton, 101,644 horse power, and 146,144 ton respectively. In addition, as results of sensitivity analysis, firstly, if the social discount rate and the average landing price of yellow croaker continuously increase, the optimal harvesting production of yellow croaker increases at decreasing rate and then finally slightly decreases due to decreases in stock levels of yellow croaker. Secondly, if the average unit cost of fishing efforts continuously increases, the optimal fishing efforts of the multiple fisheries decreases, but the optimal stock level of yellow croaker increases. The optimal harvest starts climbing and then continuously decreases due to increases in the average unit cost. Thirdly, when the intrinsic growth rate of yellow croaker increases, the optimal harvest, fishing efforts, and stock level all continuously increase. In conclusion, this study suggests that the optimal harvesting production and fishing efforts were much less than actual harvesting production(35,279 ton) and estimated standardized fishing efforts(175,512 horse power) in 2013. This result implies that yellow croaker has been overfished due to excessive fishing efforts. Efficient management and conservative policy on stock of yellow croaker need to be urgently implemented.

• Journal of Preventive Medicine and Public Health
• /
• v.41 no.5
• /
• pp.287-294
• /
• 2008

Objectives : To estimate the economic burden of osteoporotic vertebral fracture (VF) from a societal perspective. Methods : From 2002 to 2004, we identified all National Health Insurance claims records for women ${\geq}50$ years old with a diagnosis of VF. The first 6-months was defined as a "clearance period," such that patients were considered as incident cases if their first claim of fracture was recorded after June 30, 2002. We only included patients with ${\geq}$ one claim of a diagnosis of, or prescription for, osteoporosis over 3 years. For each patient, we cumulated the claims amount for the first visit and for the follow-up treatments for 1 year. The hospital charge data from 4 hospitals were investigated to measure the proportion of the non-covered services. Face-to-face interviews were conducted with 106 patients from the 4 study sites to measure the out-of-pocket spending outside of hospitals. Results : During 2.5 years, 131,453 VF patients were identified. The patients had an average of 3.38 visits, 0.40 admissions and 6.36 inpatient days. The per capita cost was 1,909,690 Won: 71.5% for direct medical costs, 20.6% for direct non-medical costs and 7.9% for indirect costs. The per capita cost increased with increasing age: 1,848,078 Won for those aged 50-64, 2,084,846 Won for 65-74, 2,129,530 Won for 75-84and 2,121,492 Won for those above 84. Conclusions : Exploring the economic burden of osteoporotic VF is expected to motivate to adopt effective treatment options for osteoporosis in order to prevent the incidence of fracture and the consequent costs.