• Nuclear Engineering and Technology
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• v.54 no.8
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• pp.2883-2897
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• 2022

According to the Renewable Energy 3020 Implementation Plan announced in 2017 by the South Korean government, the electricity share of renewable energy will be expanded to 20% of the total electricity generation by 2030. Given the intermittency of electricity generation from renewable energy, realization of such a plan presents challenges to managing South Korea's isolated national electric grid and implies potentially large excess electricity generation in certain situations. The purpose of this study is: 1) to develop a model to accurately simulate the effects of excess electricity generation from renewables which would arise during the transition, and 2) to propose strategies to manage excess electricity generation through effective utilization of domestic electricity generating capabilities. Our results show that in periods of greater PV and wind power, namely the spring and fall seasons, the frequency of excess electricity generation increases, while electricity demand decreases. This being the case, flexible operation of coal and nuclear power plants along with LNG and pumped-storage hydroelectricity can be used to counterbalance the excess electricity generation from renewables. In addition, nuclear energy plays an important role in reducing CO₂ emissions and electricity costs unlike the fossil fuel-based generation sources outlined in the 8th Basic Plan.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3878-3887
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• 2022

For the future energy-mix policy for carbon neutrality, demand for the capability of load-follow operation has emerged in nuclear power plants in order to accommodate the intermittency of renewable energy. The short-term decay heat analysis is also required to evaluate the decay heat level varied by the power level change during the load-follow operation, which is a very important parameter in terms of short-term decay heat removal during a grace time. In this study, the short-term decay heat level for 10 days after the shutdown was evaluated for both seasonal and daily load-follow cases. Additionally, the nuclide-wise contribution to the accumulated decay heat for 10 days was analyzed for further understanding of the short-term decay heat behavior. The result showed that in the seasonal case, the decay heat level was mainly determined by the power level right before the shutdown and the amount of each nuclide was varied with the power variation due to the long variation interval of 90 days. Whereas, in the daily case, the decay heat level was strongly impacted by the average power level during operation and meaningful mass variations for those nuclides were not observed due to the short variation interval of 0.5 days.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.7
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• pp.809-815
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• 2018

Distributed generations (DGs) using renewable energy resources in power systems have been widely integrated, and many of these DGs have intermittency. DGs can significantly affect the overall voltage profile of the system through the reactive power control for a voltage support. Therefore, in the planning stage of the optimal operation and dispatch of voltage regulation devices, DGs' hosting capacity with the reactive power control scheme should be considered. In this paper, we model the IEEE 34-bus test feeder, including all essential equipment. An optimization method is utilized to determine the optimal siting and operation of the voltage regulation devices in the presence of DGs with reactive power control scheme. Finally, we compare the optimal results of the each case to analyze the relationship among the hosting capacity of the DGs and voltage regulation devices operation.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.4
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• pp.19-29
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• 2007

This study compares various ground-truth designs of radar rainfall using rain-gauge data sets from Korea Meteorological Administration (KMA), AWS and Ministry of Construction and Transportation (MOCT). These Rain-gauge data sets and the Mt. Gwanak radar rainfall data for the same period were compared, and then the differences between two observed rainfall were evaluated with respect to the amount of bias. Additionally this study investigated possible differences in bias due to different storm characteristics. The application results showed no distinct differences between biases from three rain-gauge data sets, but some differences in their statistical characteristics. In overall, the design bias from MOCT was estimated to be the smallest among the three rain-gauge data sets. Among three storm events considered, the jangma with the highest spatial intermittency showed the smallest bias.

• Korean Journal of Adult Nursing
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• v.21 no.1
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• pp.43-52
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• 2009

Purpose: The purpose of this study was to investigate the relationships between LLFDI and quality of sleep in older men with prostatic hypertrophic symptoms. Methods: The secondary analysis of data collected for the 2nd stage BK(Brain Korea)21 project was performed. The original data were collected using a cross-sectional, face-to-face, and private interview method. The questionnaires consisted of prostatic hypertrophic symptoms, late-life function and disability, quality of sleep, and demographic profiles. Results: A total of 112 older men included in this study. The major findings of this study were as follow; 1) 29.5% of participants had more than moderate symptoms of prostatic hypertrophy. 2) There were a significant positive correlation of prostatic hypertrophic symptoms with subjective sleep quality, sleep latency, sleep disturbances, use of sleeping medication, and daytime dysfunction found, whereas there was a negative relationship with frequency dimension. 3) The LLFDI is significantly associated with urgency, weak stream, and intermittency. The quality of sleep is significantly associated with weak stream which explained 11.2% of variance. Conclusion: These results may contribute to a better understanding late-life function and disability, quality of sleep in older men with prostatic hypertrophic symptoms. Therefore, health programs for prompting older men's health should be planned based on results of the study.

• Korean Journal of Adult Nursing
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• v.13 no.2
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• pp.305-316
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• 2001

The purpose of this study was to identify the frequency of Urinary Incontinence and lower urinary tract symptoms, to identify life style problems for UI of Women in anIsland. The sample consisted of 88 women in an island, a urinary symptom questionnaire developed by Jackson, et. al. and a demographic questionnaire were used to collect the data. The results of study were as following. 1. It was reported that the subjects have experienced UI and various lower urinary symptoms such as stress incontinence, nocturia, intermittency, abnormal stream, feeling of incomplete emptying and also they have experienced some degree of 'bother' 2. It was reported that the subjects have experienced various life style problems for UI 3. There was significant relationship between age and urgency (p=0.0262), bladder pain (p=0.0268), abnormal strength of stream (p=0.0074), inability to stop midstream (p=0.0026), and ability to perform daily tasks (p=0.0488), 4. There was a significant relationship between the number of discharges and urgency (p=0.0273), abnormal strength of stream (p=0.0307), and inability to stop midstream (p=0.0122). 5. There was a significant relationship between menopause and bladder pain (p=0.0020), abnormal strength of stream (p=0.0245), and inability to stop midstream (p=0.0002). 6. There was a significant relationship between the degree of experiences for lower urinary tract symptoms and life style behavior. Therefore, based on the results, a developing and carrying out of adequate UI care program is needed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.5
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• pp.323-334
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• 2020

Since boundary layer transition has a significant impact on the aero-thermodynamic performance of hypersonic flight vehicles, capability of accurate prediction of transition location is essential for design and performance analysis. In this study, γ-Re_θt model is improved to predict transition of hypersonic boundary layers and validated. A coefficient in the production term of the intermittency transport equation that affects the transition onset location is constructed and applied as a function of Mach number, wall temperature, and freestream stagnation temperature based on the similarity numerical solution of compressible boundary layer. To take into account a Mach number dependency of transition onset momentum thickness Reynolds number and transition length, additional correlation equations are determined as function of Mach number and applied to Re_θc and F_length correlations of the baseline model. The suggested model is implemented to a commercial CFD code in consideration of practical use. Analysis of hypersonic flat plate and circular cone boundary layers is carried out by using the model for validation purpose. An improvement of prediction capability with respect to variation of Mach number and unit Reynolds number is identified from the comparison with experimental data.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.1
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• pp.65-76
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• 2024

With the recent activation of the offshore wind power industry, there has been a development of power plants with a scale exceeding 400MW, comparable to traditional thermal power plants. Renewable energy, characterized by intermittency depending on the energy source, is a prominent feature of modern renewable power generation facilities, which are structured based on controllable inverter technology. As the integration of renewable energy sources into the grid expands, the grid codes for power system connection are progressively becoming more defined, leading to active discussions and evaluations in this area. In this paper, we propose a method for selecting optimal reactive power compensation capacity when multiple offshore wind farms are integrated and connected through a shared interconnection facility to comply with grid codes. Based on the requirements of the grid code, we analyze the reactive power compensation and excessive stability of the 400MW wind power generation site under development in the southwest sea of Jeonbuk. This analysis involves constructing a generation site database using PSS/E (Power System Simulation for Engineering), incorporating turbine layouts and cable data. The study calculates reactive power due to charging current in internal and external network cables and determines the reactive power compensation capacity at the interconnection point. Additionally, static and dynamic stability assessments are conducted by integrating with the power system database.

• Childhood Kidney Diseases
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• v.18 no.2
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• pp.71-76
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• 2014

Purpose: Attention deficit hyperactivity disorder (ADHD) has been associated with impairments in frontal inhibitory function and the catecholaminergic system. ADHD is diagnosed in 3-5% of children. Children with ADHD seem develop various forms of urinary problems such as nocturnal enuresis, dysfunctional voiding, and diurnal incontinence. However, no data exist to confirm the presence of these problems in Korean children with ADHD. We investigated the clinical findings of voiding dysfunction in children with ADHD. Methods: Between October 2009 and March 2011, a total of 63 children (33 with ADHD, 30 with an upper respiratory infection, as a control group) were enrolled. ADHD was diagnosed using the diagnostic and statistical manual of mental disorders (DSM)-IV criteria. A comprehensive survey of voiding and defecation was administered. Results: The patient group included 28 boys and 5 girls; the control group comprised 20 boys and 10 girls. The mean age was $9.09{\pm}2.8$ years in the ADHD group and $8.58{\pm}3.1$ years in the control group. Children with ADHD had a statistically significantly higher incidence of urgency (P =0.017), urge incontinence (P =0.033), and constipation (P =0.045). There was no significant difference in the incidence of straining, intermittency, holding maneuvers, or nocturnal enuresis. Conclusion: Children with ADHD in Korea have significantly higher rates of urgency, urge incontinence, and constipation than those without ADHD.