• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.810-818
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• 2021

A leakage current of ESS is classified mainly by the occurrence from a PCS(Power Conditioning System) section and an unbalanced grid current. The reason for the leakage current from the PCS section is a voltage change by IGBT (Insulated Gate Bipolar Transistor) switching and stray capacitance between the IGBT and heatsink. The leakage current caused by the grid unbalanced current flows to the ESS through the neutral line of grid-connected transformer for the ESS with a three limb iron type of Yg-wire connection. This paper proposes a mechanism for the occurrence of leakage current caused by stray capacitance, which is calculated using the heatsink formula, from the aspect of the PCS section and grid unbalance current. Based on the proposed mechanisms, this study presents the modeling of the leakage current occurrence using PSCAD/EMTDC S/W and evaluates the characteristics of leakage currents from the PCS section and grid unbalanced current. From the simulation result, the leakage current has a large influence on the battery side by confirming that the leakage current from the PCS is increased from 7[mA] to 34[mA], and the leakage current from an unbalanced load to battery housing is increased from 3.96[mA] to 10.76[mA] according to the resistance of the housings and the magnitude of the ground resistance.

• Journal of Industrial Convergence
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• v.20 no.1
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• pp.13-21
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• 2022

Globally, the baby boomer generation is economically retired, and the MZ generation is emerging as a new economic force. This study demonstrated the effect of service quality on user satisfaction and customer loyalty for IT services, and checked whether it had a moderating effect on the MZ generation's perception of service quality and its effect on user satisfaction. In addition, we tried to find implications for service satisfaction of the MZ generation. For this purpose, valid responses were obtained from 496 members of companies receiving IT services from Company A. then, a hierarchical regression analysis were performed to verify the hypothesis. As a result of the analysis, the influence relationship between service quality, user satisfaction, and customer loyalty was confirmed, similar to the results of previous studies, and it was confirmed that the negative moderating effect of lower perception of user satisfaction through interaction. Therefore, it can be suggested that there is a need to develop a new digital-based service that can share and sympathize with special experiences, consumption values and beliefs. In the future, if research is conducted on a variety of consumers, it will be possible to more accurately explore the service perception of the MZ generation.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.36 no.3
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• pp.280-285
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• 1991

The rice culture techniques of the ancient China which have played a key role directly and indirectly, in development of ancient farming and its techniques of Korea, were established before Christ in terms of dry-farming and the spirit of the farming-first principle. Especially techniques of rice culture were developed by cultivation methods for deep plowing, storage of water and preservation use of soil fertility. Therefore, the techniques of transplanting methods, seeding in rows, use of iron-made farming tools and dam construction for irrigation were advanced. And rice varieties were differentiated to avoid disasters or to supply of rice for various uses in many areas. Also, because north China was the origin of Chinese agriculture in which population density was low and flat land was wide that were the cradle of Chinese agriculture, ‘Hwayungsunubeob’(firing and drawning weed control method) and fallowing were quickened as intensive techniques of rice culture. In connection with the view of agricuture with 'the theory of the cosmic dual forces and the five primary substances' of Han Mooje and Chamwye scholars, the techniques of seeding and selection of crops were gradually developed. From ‘Jeminyosul’ of the 6th century to ‘Wangjongnongseo’ of the 14th century, the techniques of rice culture have been developed continuously and additively, but were not improved thereafter Won dynasty. From this point of time, the time of agriculture in the end of Koryo age and by ‘Nongsajiksul’ were initiated.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5A
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• pp.901-908
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• 2006

The structural integrity of containment building in Nuclear Power Plants has to be verified by the ISI(In Service Inspection) because there are some variations on the structural behavior of it due to the change of the physical properties of concrete and tendon with the lapse of time. In this study, the program 'SAPONC-CANDU' which can monitor and analyze the structural behavior of the containment building with grouted tendon (CANDU-type, 'Wolsong unit-2, 3, and 4' in Korea) was developed. This program is based on the algorithm which can calculate the prediction values of the quantities of strain variation for the vibrating-wire strain gauges embedded into the concrete of the containment building under temperature and time dependent factors which are creep, shrinkage, and prestressing force. The readings of the strain gauges are used as input data for the operation of the program. And it finally provides graphically a prediction value, line and band of the quantity of strain variation for the respective strain gauges, therefore, it is thought that the site engineers are able to assess the structural integrity of the domestic containment building with grouted tendon with easy using this program.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.4
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• pp.395-406
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• 2023

The first technological advance to improve the output and efficiency of the latest steam turbines operating in co-generation plants in Korea can be said to be progress in the field of materials that can use high-temperature, high-pressures steam. As a result of design efforts to improve the internal efficiency of steam turbines along with the development of materials, only a few manufacturers of steam turbine have produced high efficiency steam turbines. The internal efficiency of a steam turbine on the steam path operating for a long period of time is gradually lost owing to the limit of mechanical life, and efficiency and output decrease. Therefore, this study aims to develop a model that can analyze the steam flow path performance of HP (High Pressure) and IP (Intermediate Pressure) steam turbine for a co-generation plant using a commercial program and propose a performance calculation method. Owing to the complex performance calculation method of steam turbines, major variables are presented to serve as practically useful references for steam turbine practitioners. In addition, the thermal dynamic analysis(such as heat balance diagram calculation) and the the thermal dynamic calculation required for steam turbine performance calculation and the suitability of the steam turbine performance calculation results were compared with the performance test results.

• Korean Chemical Engineering Research
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• v.53 no.5
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• pp.590-596
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• 2015

Estimating potential of $CO_2$ emission reduction of non-capture $CO_2$ utilization (NCCU) technology was evaluated. NCCU is sodium bicarbonate production technology through the carbonation reaction of $CO_2$ contained in the flue gas. For the estimating the $CO_2$ emission reduction, process simulation using process simulator (PRO/II) based on a chemical plant which could handle $CO_2$ of 100 tons per day was performed, Also for the estimation of the indirect $CO_2$ reduction, the solvay process which is a conventional technology for the production of sodium carbonate/sodium bicarbonate, was studied. The results of the analysis showed that in case of the solvay process, overall $CO_2$ emission was estimated as 48,862 ton per year based on the energy consumption for the production of $NaHCO_3$ ($7.4GJ/tNaHCO_3$). While for the NCCU technology, the direct $CO_2$ reduction through the $CO_2$ carbonation was estimated as 36,500 ton per year and the indirect $CO_2$ reduction through the lower energy consumption was 46,885 ton per year which lead to 83,385 ton per year in total. From these results, it could be concluded that sodium bicarbonate production technology through the carbonation reaction of $CO_2$ contained in the flue was energy efficient and could be one of the promising technology for the low $CO_2$ emission technology.

• Journal of Hospice and Palliative Care
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• v.17 no.3
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• pp.179-184
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• 2014

Purpose: We investigated the safety and efficacy of peripherally inserted central catheters (PICCs) in terminally ill cancer patients. Methods: A retrospective review was conducted on patients who underwent PICC at the hospice-palliative division of KEPCO (Korea Electric Power Corporation) Medical Center between January 2013 and December 2013. All PICCs were inserted by an interventional radiologist. Results: A total of 30 terminally ill cancer patients received the PICC procedure during the study period. Including one patient who had had two PICC insertions during the period, we analyzed a total of 31 episodes of catheterization and 571 PICC days. The median catheter life span was 14.0 days (range, 1~90 days). In 25 cases, catheters were maintained until the intended time (discharge, transfer, or death), while they were removed prematurely in six other cases (19%; 10.5/1000 PICC days). Thus, the catheter maintenance success rate was 81%. Of those six premature PICC removal cases, self-removal due to delirium occurred in four cases (13%; 7.0/1000 PICC days), and catheter-related blood stream infection and thrombosis were reported in one case, each (3%; 1.8/1000 PICC days). Complication cases totaled eight (26%; 14.1/1000 PICC days). The time to complication development ranged from two to 14 days and the median was seven days. There was no PICC complication-related death. Conclusion: Considering characteristics of terminally ill cancer patients, such as a poor general condition, vulnerability to trivial damage, and a limited period of survival, PICC could be a safe intravenous procedure.

• Pediatric Infection and Vaccine
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• v.21 no.3
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• pp.181-190
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• 2014

Purpose: This study was performed to investigate the epidemiological trend of rotavirus acute gastroenteritis (RV-AGE) in children. Methods: A retrospective review was performed in patients (1 month to 18 years of age) with acute gastroenteritis at KEPCO Medical Center from September 2004 to August 2013. Comparative analyses were performed based on periods: pre-vaccine (2004-2006) and post-vaccine (2008-2012) in all patients; 2004-2006 (period A), 2007-2009 (period B) and 2010-2012 (period C) in patients under 5 years of age. Results: Proportion of RV-AGE decreased from 25.0% (337/1,346) in pre-vaccine period to 20.8% (459/2,210) in post-vaccine period (rate ratio (RR), 0.83 [95% CI, 0.73-0.93]; P=0.0029). The median age of patients with RV-AGE in post-vaccine period (2.6 years) was significantly (P<0.0001) higher than that in pre-vaccine period (1.6 years). In patients hospitalized with AGE, proportion of RV-AGE was significantly reduced in patients 6 to 23 months old (RR, 0.62 [95% CI, 0.51-0.75]; P<0.0001). Significant decline in proportion of RV-AGE was observed in patients under 5 years of age: period A, 26.9% (308/1,144); period B, 22.7% (295/1,299); period C, 20.6% (186/902) (P =0.0007). After the introduction of rotavirus vaccine, a significant decreasing trend of RV-AGE proportion was observed in patients 6 to 11 months old (P =0.0018) and 12 to 23 months old (P =0.0152). Conclusion: Decrease in RV-AGE proportion and increase in age of patients with RV-AGE were observed after the introduction of rotavirus vaccine in this single center study. Continued and systematic surveillance is needed to assess the impact of rotavirus vaccine.

• The Korean Journal of Pesticide Science
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• v.14 no.4
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• pp.427-432
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• 2010

Rice bakanae disease caused by Fusarium fujikuroi is one of the most serious rice diseases in Korea. From 2006 to 2009, 118 F. fujikuroi isolates were collected from various regions of rice fields in Korea. Resistance assay of 118 F. fujikuroi isolates to prochloraz, tebuconazole, and benomyl, were performed using agar dilution method. To investigate inhibitory effects of the fungicides, minimum inhibitory concentration of mycelial growth (MIC) and effective concentration inhibiting mycelial growth by 50% ($EC_{50}$) for 118 isolates were calculated using Sigmaplot 8.02 (Antro, SPSS UK, Ltd). Based on the means of $EC_{50}$ values, baseline resistance values were determined as $0.5{\mu}g{\cdot}mL^{-1}$ for prochloraz, $5.0{\mu}g{\cdot}mL^{-1}$ for tebuconazole and $2.5{\mu}g{\cdot}mL^{-1}$ for benomyl. Number of resistant isolates to each fungicide was 17, 19 and 43 for prochloraz, tebuconazole and benomyl, respectively. Furthermore, 4 isolates showed the double resistance to both prochloraz and tebuconazole, 6 isolates to prochloraz and benomyl, and 11 isolates to tebuconazole and benomyl. Isolates CF366 and LF335 isolated from Gyeongbuk province were resistant to the three fungicides tested, prochloraz, tebuconazole and benomyl.

• Environmental and Resource Economics Review
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• v.14 no.2
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• pp.519-547
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• 2005

The aim of this study is to analysis how economic welfare lost happens within the present korea seasonal and time period electricity pricing system and find out reasonable electricity price system acceptable during the transitional period of korea electricity industry restructuring To analyze economic welfare lost in the electricity industry, in advance seasonal and time periodic 9 demand curves(summer, spring ＆fall, winter/peak-load time, middle-load time, low-load time) and one market supply curve are made and then using these demand and supply curve, seasonal and time periodic market equilibrium prices is calculated. Finally, comparing these market equilibrium prices with present regulated classified seasonal and time periodic prices, the whole economic welfare lost in the electricity industry is calculated. The result of this study shows that in 2002, the total economic welfare lost in electricity industry is 137,770 million Won and under present price system, the worst welfare lost is happening seasonally in spring ＆ fall, time periodically in the middle-load time. Specifically analyzing the characteristics of welfare lost, especially on the industry customers and service customers which are applied in seasonal and time periodic pricing, for the industry customers, the welfare lost calculated in this class occupies 51% of the total welfare lost in the whole electricity industry and the worst welfare lost is happening seasonally in spring ＆ fall, time periodically in the middle-load time. For service customers, the welfare lost calculated in this class occupies 13% of the total welfare lost in the whole electricity industry and the worst welfare lost is happening seasonally in summer, time periodically in the peak time Finally, this study was made based on the year of 2002 and KEPCO has practiced two times of rate change until now. The result of rate change was positively analyzed in the direction of economic welfare improvement(welfare improvement achieved by 16.3% compared to 2002 result).