• Ocean Systems Engineering
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• v.11 no.4
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• pp.313-330
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• 2021

In this study, the dynamic interaction between an Arctic Spar and drifting level ice is examined in time domain using the newly developed ice-hull-mooring coupled dynamics program. The in-house program, CHARM3D, which is the hull-riser-mooring coupled dynamic simulator is extended by coupling with the open-source discrete element method (DEM) simulator, LIGGGHTS. In the LIGGGHTS module, the parallel-bonding method is implemented to model the level ice using an assembly of multiple bonded spherical particles. As a case study, a spread-moored Artic Spar platform, whose hull surface near waterline is the inverted conical shape, is chosen. To determine the breaking-related DEM parameter (the critical bonding strength), the four-point numerical bending test is used. A series of numerical simulations is systematically performed under the various ice conditions including ice drift velocity, flexural strength, and thickness. Then, the effects of these parameters on the ice force, platform motions, and mooring tensions are discussed. The simulations reveal various features of dynamic interactions between the drifting ice and moored platform for various ice conditions including the novel synchronous resonance at low ice speed. The newly developed simulator is promising and can repeatedly be used for the future design and analysis including ice-floater-mooring coupled dynamics.

• Women's Health Nursing
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• v.15 no.1
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• pp.64-72
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• 2009

Purpose: The purposes of this study were to identify Korean primary school students' knowledge of menstruation, their emotional reaction to menarche, the attitude toward menstruation and coping behaviors. Method: A cross-sectional survey design was employed in this study. The subjects were 200 female students who were recruited from 5th and 6th grade in five primary schools in J city, Korea. Data was collected by a structured questionnaire. Result: About forty-four percent of the subjects had experiences with menarche. The mean age of menarche was 12.4. The mean score of the students' knowledge of menstruation was 2.26 on a seven point scale. The mean scores of the emotional reaction to menarche and the attitude toward menstruation were 3.20 and 3.74 on a five point scale, respectively. Knowledge of menstruation was significantly related with a positive emotional reaction to menarche and a positive attitude toward menstruation. Also, there were significant differences in the knowledge of menstruation, the emotional reaction to menarche and attitude of menstruation among female students with positive coping behaviors and those without positive coping behaviors. Conclusion: Beyond the simple transference of knowledge, girls need to also be given mental and emotional support in order to minimize emotional and socio-psychological problems caused by early menarche.

• Journal of the Korean Magnetics Society
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• v.19 no.5
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• pp.161-164
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• 2009

The effect of periodic vacancies to the magnetism of the Fe monolayer was investigated by calculating the electronic structures using the full-potential linearized augmented plane wave method within the GGA approximation. We considered four types of vacancies, point defect, I type, + type, and H type which are consisted of one, three, five and seven vacant sites, respectively. We found that the Fe atoms nearest to the vacancy have the largest magnetic moment in each system, and the value of magnetic moment of the atom was increased as the number of vacancy site is increased. The value of the largest magnetic moment in the systems of point defect, I type, + type, and H type are 3.08, 3.09, 3.15, and 3.30 bohr magnetons, respectively.

• Korean Journal of Adult Nursing
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• v.18 no.1
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• pp.136-145
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• 2006

Purpose: This study was performed to identify relationships among stress, hardiness, and the level of self-care in kidney transplant patients and use the results of this study as baseline data for developing self-care promotion programs. Method: Subjects were 41 patients who undergone a kidney transplantation surgery at least one month before and were receiving regular follow-up care via OPD. Four researchers interviewed each subjects by filling out questionnaires. Results: The mean score of the level of stress was 2.32(SD=0.54) on a 4 point scale and the mean score of hardiness was 4.68(SD=0.62) on a 6 point scale. The mean score of self-care among the subjects was 3.83(SD=0.55). There was statistically a significant positive relationship between selfcare and hardiness(r=0.42). Especially, relationships between self-care and commitment (r=.51) and control(r=.36) as the subdimensions of hardiness were significant. The item suggested as most stressful was economic burden and the item suggested as least stressful was sexual activity. Conclusion: Although transplant patients have various stressors, the positive self-care activities of the patients could be increased if the commitment and control were enhanced by proper intervention programs.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.9
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• pp.25-31
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• 2007

In this paper, a novel MPPT(Maximum Power Point Tracking) algorithm for power of PV(Photovoltaic) systems is presented using a boost converter for a connected single phase inverter. On the basic principle of power generation for the PV(photovoltaic) module, the model of a PV system is presented. On the basis of this model, simulation of this PV system and algorithms for maximum power point tracking are described by utilizing a boost converter to adjust the output voltage of the PV module. Based on output power of a boost converter, single phase inverter uses predicted current control to control four IGBT#s switch in full bridge. Furthermore, a low cost control system for solar energy conversion using the DSP is developed, based on the boost converter to adjust the output voltage of the PV module. The effectiveness of the proposed inverter system is confirmed experimentally and by means of simulation. Finally, experimental results confirm the superior performance of the proposed method.

• Magazine of the Korean Society of Agricultural Engineers
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• v.33 no.4
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• pp.52-60
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• 1991

This study was conducted to investigate the appropriate operation method minimizing the deviation between irrigation water demand and release from the reservoirs, and the simulation technique was used in the operation model. This model was applied to the grouped reservoirs system consisted of Dongsang, Daia and Keungchun reservoirs and Eowoo-weir in Chonbuk FLIA district. The results obtained in this study are summarized as follows; 1.The area above the Eowoo weir point was divided into 6 small watersheds, and daily inflows from each watershed were calculated by Tank model. It showed that the average annual runoff ratio was 40-60% respectively. 2.Based on the Blaney-Criddle formula daily water requirement of Chonbuk FLIA irrigation area was estimated, mean water requirement for paddy field during the irrigation period was 818.lmm. 3.Using the basic data such as inflow and water demand, four different release types were selected. Through the simulated operation the difference between intake water required at Eowoo-weir point and release from the 3 reservoirs was estimated. The best result was obtained when Daia and Keungchun reservoirs are operated parallelly at fixed release ratio and the release of Dongsang reservoir was determined according to the storage of Daia reservoir.

• Korean Journal of Health Education and Promotion
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• v.33 no.5
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• pp.107-119
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• 2016

Objectives: This study aims at examining the association of sense of community with community participation for health promotion in urban areas of Korea. Methods: We analyzed data from 'Community Capacity for Healthy Gangdong Communites' Survey' in 2007. The survey was based on self-reported questionnaires, which were distributed to 1,800 community residents over the age of nineteen in five administrative communities of Gangdong-gu, Seoul, in Korea by using proportionate probability sampling method. We measured 'Sense of community' with four indicators including 'Good neighborhoods', 'Perceived possibility of cooperation', 'Pride of community' and 'Possibility of development' by using 5-point Likert scales. Community participation was measured with the experience rate or the extent of participation by 5-point Likert scales in seven community actions or activities including voting, community program planning, social actions, etc. We examined the association of sense of community with community participation by using regression analyses. Results: This study has shown that sense of community was associated with and made positive impacts on community participation in diverse community actions or activities in urban communities. Conclusions: For promoting community health in urban areas, we can increase community participation more effectively with the efforts of enhancing sense of community.

• Journal of Korean Society of Forest Science
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• v.98 no.2
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• pp.189-196
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• 2009

This study was conducted to evaluate spatial distribution pattern and spatial association of crowns (${\geq}10m$ of height) and saplings (<10 m of height and ${\geq}2cm$ of DBH) for four major tree species (Pinus koraiensis, Abies nephrolepis, Acer mono, and Tilia amurensis) in the mixed broadleaved-Korean pine forest of Xiaoxing'an Mts. Vegetation data were collected in the 9 ha permanent sample plot, and the analysis adopted the point pattern analysis method. Main results are as follows; 1) crowns and saplings of major species showed clumped distribution pattern in small scale, became random distribution as the scale was increased. 2) Saplings of Pinus koraiensis performed poor regeneration under the crowns of Pinus koraiensis and Abies nephrolepis; Saplings of Abies nephrolepis did good regeneration under the crowns of Pinus koraiensis and Abies nephrolepis; and crowns of Acer mono and Tilia amurensis had little effect on the distribution of saplings of Pinus koraiensis and Abies nephrolepis. Saplings of Acer mono and Tilia amurensis made good regeneration under the crowns of Pinus koraiensis and Tilia amurensis; and the crowns of Acer mono and Abies nephrolepis had little effect on the distribution of saplings of Acer mono.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.488-491
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• 2006

In this paper proposed method of maximum power point tracking using boost converter for a connected single phase inverter with photovoltaic system. The maximum power point tracking control is based on generated circuit control MOSFET switch of boost converter and single phase inverter uses predicted current control to control four IGBT's switch in full bridge. The predicted current control provide current with sinusoidal wave shape and inphase with voltage. The generation control circuit allows each photovoltaic module to operate independently at peak capacity, simply by detecting of the output power of the system. Furthermore, the generation control circuit attenuates low-frequency ripple voltage, which is caused by the full-bridge inverter, across the photovoltaic modules. Consequently, the output power of system is increased due to the increase in average power generated by the photovoltaic modules. The effectiveness of the proposed inverter system is confirmed experimentally and by means of simulation.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.242-246
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• 2004

Effects of circumferentially local wall thinning on the fracture behavior of pipes were investigated by monotonic four-point bending. Local wall thinning was machined on the pipes in order to simulate erosion/corrosion metal loss. The configurations of the eroded area included an eroded ratio of d/t= 0.2, 0.5, 0.6, and 0.8, and an eroded length of I = 10 mm, 25 mm, and 120 mm. Fracture type could be classified into ovalization, local buckling, and crack initiation depending on the eroded length and eroded ratio. Three-dimensional elasto-plastic analyses were also carried out using the finite element method, which is able to accurately simulate fracture behaviors excepting failure due to cracking. It was possible to predict the crack initiation point by estimating true fracture ductility under multi-axial stress conditions at the center of the eroded area.