• Journal of Ocean Engineering and Technology
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• v.27 no.4
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• pp.76-82
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• 2013

Motion reduction of an offshore structure at resonant frequency is essential for avoiding critical damage to the topside and mooring system. A damping plate has a distinct advantage in reducing the motion of a floating structure by increasing the added mass and the damping coefficient. In this study, the heave motion responses of a circular cylinder with an impermeable and a permeable damping plate attached at the bottom of the cylinder were investigated thru a model test. The viscous damping coefficients for various combinations of porosity were obtained from a free-decay test by determining the ratio between any pair of successive amplitudes. Maximum energy dissipation occurred at a porous plate with a porosity P = 0.1008. Experimental results for regular and irregular waves were compared with an analytical solution by Cho (2011). The measured heave RAO and spectrum reasonably followed the trends of the predicted values. A significant motion reduction at resonant frequency was pronounced and the heaving-motion energy calculated by the integration of the area under the heave motion spectrum was reduced by more than 75% by the damping plate. However, additional energy dissipation by eddies of strong vorticity and flow separation inside a porous damping plate was not found in the present experiments.

• Journal of Ocean Engineering and Technology
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• v.31 no.2
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• pp.81-90
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• 2017

The 1MW OTEC (Ocean Thermal Energy Conversion) platform was designed for application in equatorial seas. In this study, the OTEC platform was investigated using numerical and experimental methods. An octagon-shaped OTEC platform was investigated using the Ocean Engineering Basin of KRISO. These experiments included various tests of regular waves, irregular waves and irregular waves with current (wave+current). The responses of the platform in regular waves showed good agreement between the numerical and experimental results, including the motion RAO, wave run up, and mean drift force. The peak period of heave and pitch motions were observed around 0.5 rad/s, and the effect of the total reflection was found under short wave conditions. The standard deviation (STD) of the platform motion was checked in irregular waves of equatorial and Hawaiian seas. The STD of the pitch was less than $4^{\circ}$ different from the operability requirement under equatorial conditions and the surge STD of the wave frequency showed good agreement between the numerical and experimental results. The STD values of the surge and pitch were increased 66.6% and 92.8% by the current effects in irregular waves, but the pitch STD was less than $4^{\circ}$ under equatorial conditions. This study showed that the STD of the surge was affected by spring effects. Thus, the watch circle of the platform and tension of the mooring lines must be evaluated for a specific design in the future.

• Child Health Nursing Research
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• v.23 no.2
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• pp.249-257
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• 2017

Purpose: The aim of this study was to assess the body weight perception of adolescents and to investigate the difference between mental health and weight control behavior according to body weight perception. Methods: Study data on 12-18 years old adolescents with normal BMI was obtained from the 6th Korea National Health and Nutrition Examination Survey (2013-2015). Rao-Scott Chi-square test and ANOVA were used for the analysis. Results: The percentage of adolescents with a misperception of body weight was 43.3%, and their subjective health status (p=.013), stress perception (p=.001), and depression (p=.001) were worse than for adolescents who had the correct perception of their body weight. The percentage of adolescents who were trying to lose weight while perceiving their body weight as normal was 36.9%. Body weight control behavior had significant differences according to dietary intake (frequency of eating dinner (p=.015)), energy intake (p=.004), and carbohydrate intake (p<.001), but there was no significant difference according to exercise. Conclusion: Parents, school teachers, and nurses should make efforts to ensure that Korean adolescents perceive their body weight correctly, and prevent unhealthy weight control behaviors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.169-180
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• 2021

This study was undertaken to determine the degree of quality of life, and factors influencing osteoarthritis in hypertensive elderly 65 years or older patients, using data from the 7th National Health and Nutrition Survey 2018. Totally, 843 subjects were included from a national sample. The SPSS WIN 26.0 program was used to analyze complex samples by applying the Rao-Scott chi-square test, t-test, and multiple regression analysis. Results indicate that quality of life of the hypertensive group with osteoarthritis is significantly lower than the group with only hypertension (t=5.07, p<0.001). Factors affecting the decrease in quality of life of the hypertensive group were age, subjective health status, and activity restrictions, and the explanatory power was 46.1% (F=12.33, p<0.001). In the hypertensive group with osteoarthritis, the effective factors included gender, cohabitation status, economic activity, subjective health status, activity restriction, body mass index, sleep time, stress perception, and depression, and the explanatory power was 44.6% (F=99.82, p<0.001). Subsequent studies showed that in order to improve the quality of life of hypertensive seniors, intervention programs are required to actively accommodate health conditions and minimize activity restrictions. In addition, for the elderly with osteoarthritis and hypertension, it is necessary to include exercise and nutrition education for body mass index management, and the development and intervention of multidisciplinary participation programs to strengthen mental health.

• Journal of Convergence for Information Technology
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• v.11 no.3
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• pp.54-67
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• 2021

This study is a secondary data study that analyzes the factors affecting the quality of life of the elderly with metabolic syndrome and the elderly with metabolic syndrome with osteoporosis using data from the 7th year of the National Health and Nutrition Survey (2018). The subjects of this study were 639 patients with metabolic syndrome and 161 patients with metabolic syndrome with osteoporosis. For data analysis, the composite sample Rao-Scott χ2 test, general linear model t-test, and regression model were used. As a result of the study, the factors that lowered the quality of life of metabolic syndrome were age, cohabitation, strength training, subjective health status, activity restriction, body mass index and depression, and the explanatory power was 50.4% (F=515.96, p<.001). In metabolic syndrome with osteoporosis, age, subjective health status, activity restriction, and stress were the factors that lowered the quality of life, and the explanatory power was 48.6% (F=10.42, p<.001). Based on these results, it is necessary to develop and provide an intensive multidisciplinary program for the elderly with metabolic syndrome accompanied by osteoporosis to solve the problem of activity restrictions and manage stress reduction through positive acceptance of health status, instrumental and social support, and caring support.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.7
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• pp.904-914
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• 2020

Through the Ministry of Trade, Industry, and Energy, South Korea is trying to support the "Building Project for Liquified Natural Gas (LNG) Bunkering Ship," centered on the Korea Gas Corporation, while the Ministry of Maritime Af airs and Fisheries is pushing to construct an LNG bunkering terminal at Busan New Port. LNG bunkering ships are essential for supplying LNG fuel from the terminal to the ships, resulting in the need for safety operation procedures. Therefore, in this study, the stability of a coastal LNG bunkering ship operating from Busan New Port to the anchorage in Busan Port was assessed to investigate the need for operational procedures for coastal LNG bunkering ships. Seakeeping analysis of the LNG bunkering ship was performed for each significant wave height by combining the response amplitude operator from the ship motion analysis under the potential flow theory with the actual observed sea data for five years and Texel, Marsen, and Arsloe (TMA) spectrum suitable for the Busan coast. The results showed that the roll and horizontal acceleration were the main risks that affected the navigation seakeeping performance above a significance wave height of 2 m. The operational periods of the LNG bunkering ship ranged from 83.3% to 99.9% of the total observation period.

• The Journal of Korean Society for School & Community Health Education
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• v.19 no.1
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• pp.27-45
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• 2018

목적: 본 연구는 한국 청소년의 가정환경, 건강행태, 심리적 요인 및 식습관 요인에 따른 주관적 건강상태의 차이를 분석하고, 주요 관련요인을 파악하고자 수행되었다. 방법: 분석자료로서 2015~2016년도 한국 청소년 건강행태 온라인조사 자료를 이용하였으며, 분석대상자 수는 중학생 53,791명, 고등학생 50,959명, 총 104,750명이었다. 학생들의 건강수준은 주관적 건강상태를 기준으로 건강집단과 비건강집단으로 구분하였다. 건강수준에 영향을 미치는 요인으로서 성별, 가정환경, 건강행태, 심리적 요인 및 식습관이 검토되었다. 이들 요인 간 건강집단과 비건강집단의 비율차이 검증을 위해 표본설계 정보를 반영한 Rao-scott 카이제곱검정을 실시하였다. 또한 주관적 건강수준에 영향을 주는 요인을 알아보고자 로지스틱회귀분석을 실시하였다. 결과 및 결론: 주관적 건강수준은 양친부모와 살지 않은 경우, 모의 교육수준이 낮을 때, 주관적 가정경제수준이 낮을수록 낮았다. 음주군, 고강도운동이나 근력운동을 실천하지 않는 군, 과체중이나 비만인군에서 주관적 건강수준이 낮았다. 또한 스트레스나 우울감 등 부정적인 감정이나 행복감을 느끼지 못할 때도 주관적 건강수준은 낮았다. 아침을 결식하거나 탄산음료, 고카페인음료, 패스트푸드 등의 비건강식품을 자주 섭취하는 군에서도 주관적 건강수준은 낮은 것으로 관찰되었다. 한국 청소년들에게서 건강 불평등(health inequalities)은 가정환경, 건강행태, 심리적 요인, 식습관 등 여러 요인들로부터 제기되는 것을 알 수 있었다. 이러한 요인들을 충분히 반영하여 청소년들이 건강해 질 수 있는 다각적 접근 방안이 모색되어야 할 것이다.

• Journal of Ocean Engineering and Technology
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• v.26 no.6
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• pp.53-58
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• 2012

An experimental study on the hydrodynamic performance of a backward bent duct buoy (BBDB) was performed in a 2D wave tank. The BBDB is one of the promising oscillating water column (OWC) types of floating wave energy converters. Two different corner-shaped BBDBs (sharp-corner and round-corner) were used to measure the maximum chamber surface elevations and body motions for various incident wave conditions, and their hydrodynamic characteristics were compared. In order to investigate the effect of the pneumatic pressure inside the chamber, the heave and pitch angle interacted with elevations were compared for both open chamber and partially open chamber BBDBs. From the comparison study, the deviation in the chamber surface elevations between the two shapes of BBDBs was found to be significant near the resonance period, which may be explained by viscous energy loss. It was also found that the pneumatic pressure noticeably affected the chamber surface elevation and body motions.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.1031-1037
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• 2021

The frequency of marine accidents of vessels in Korea is steadily increasing and it is concentrated on small vessels with less than 10 tons of gross tonnage. Therefore, preventing capsizing accidents in small vessels is important to reduce the cost in terms of human and property damage due to such accidents. However, research on the seakeeping performance of small vessels has been insufficient, and there are no domestic and international regulations on seakeeping performance. Therefore, in this study, capsizing accidents caused by poor loading conditions were investigated by examining the adjudications of the small vessels in which the capsizing accidents occurred. Hydrostatic calculations and seakeeping performance analysis were performed for a representative vessel. A vessel generally performs a six-degree-of-freedom motion during operation. In this study, the response amplitude operator and response spectrum of a representative vessel were calculated to determine the roll motion. Moreover, a short-term statistical analysis of the vessel according to the loading conditions was performed for the wave stationary status for 3 h. From the results, it was estimated that, when the loading condition of a small vessel is poor, its roll motion increases, greatly reducing its stability.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.3
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• pp.479-488
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• 2018

This study was conducted to investigate factors affecting low body weight of solitary elderly people by grasping the illness and health behavior of elderly living alone. Using the raw data of the community health survey from 2014, the data of 922 elderly living alone who are 65 years or older were used for the final analysis. Data were analyzed by technical analysis statistics, The Rao Scott $x^2$ test, and logistic regression analysis using the composite analysis module of the SPSS/WIN 22.0 program. The results of this study showed that elderly living alone had a high percentage of chronic diseases as well as poor health behaviors such as smoking, drinking, lack of exercise, poor eating habits, difficulties in dentistry due to dentures, and poor subjective health status. Result of logistic regression analysis the risk probability of low-weight due to gender of the elderly living alone is as follows. Risk of low body weight because of smoking was 3.004 times among occasional smokers in women and the elderly, while risk of low body weight due to walking amount is less than 3 days the possibility that the person walking is low is 1.420 times significantly higher. When feeling subjective stress, the possibility of low body weight was 2.220 times greater for male elderly and 1.282 times for female elderly. The probability of low body weight for a person with a poor subjective health level was 3.633 times for male elderly and 1.590 times for female elderly. Based on the results of this study, it is necessary to establish appropriate nursing intervention and management strategies to improve health behavior of low body weight elderly living alone. It is also necessary to conduct additional studies considering various variables such as physical, psychological, and social characteristics of low-weight elderly individuals.