• Solar Energy
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• v.15 no.2
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• pp.77-90
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• 1995

An effective heat transfer during freezing process was proposed in the vertical cylinder to improve the effectiveness of the heat storage. Vertical cylinder was filled with pure water in order to investigate ice-shape, temperature distribution of the liquid, temperature distribution of the cylinder tube wall, total heat storage per unit mass in the test section under the two experimental conditions; inlet temperature of working fluid is constant($-10^{\circ}C$) and inlet direction of working fluid is either upward flow or downward. Both the mean temperature of the liquid and temperature difference of cylinder tube wall in the upward were lower than those in the downward. In case that the initial temperature of water was $7^{\circ}C$ and $4^{\circ}C$, the shape of ice layer in the upward was more uniform than that in the downward. In case of $1^{\circ}C$, the shape of ice layer is formed by inlet direction of working fluid. Finally, time-varying total heat energy stored in the water in the upward was higher than that in the downward.

• Research in Community and Public Health Nursing
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• v.29 no.3
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• pp.371-381
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• 2018

Purpose: The purpose of this study is to identify the mediating effects of self-esteem between social comparison orientation and social network service (SNS) addiction in university students. Methods: Descriptive cross-sectional survey design was employed. The data were statistically analyzed by using the descriptive and inferential statistics. Sobel test and Bootstrap method, and Kappa squared mediation effect size measure were used to identify the mediator's significance. A convenience sample of 195 subjects was recruited from two universities in Korea. Results: The mean age of the subjects was $22.58{\pm}1.81$. The subjects showed relatively high levels of SNS addiction with a mean score of $14.33{\pm}4.80$. The overall model significantly explained 37.0% of variances in the subjects' SNS addiction after controlling gender, age, grade, major, period of SNS using, time spent on SNS per day, and times accessed SNS per day. Of the predictors, time spent on SNS per day, social comparison orientation, and self-esteem were significantly associated with SNS addiction. Self-esteem was the mediator between social comparison orientation and SNS addiction. Conclusion: When developing strategies for preventing SNS addiction, interventions for reducing time spent on SNS per day, not having upward social comparison orientation, and improving the self-esteem should be considered. These findings might provide a theoretical basis for developing effective strategies for preventing SNS addiction in university students.

• Journal of the Korean Society for Marine Environment & Energy
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• v.20 no.2
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• pp.100-106
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• 2017

Artificial upwelling structure has been set up in sea mount. Bottom water can upwelling euphotic zone. Plentiful nutrient included in bottom water could not only enhance primary production but also expect food chain reaction and gathering fish. This study explain flowing features subject to porosity changes according to the material and shape of artificial upwelling structure. As a result, the upward flux is getting decreased while the porosity is increasing. And it figured out when the upward flux was decreased, the downward flux was also decreased. Futhermore, it was confirmed that the best efficiency of upwelling flux was shown up when the porosity was 10% according to the volume of artificial upwelling structure in case of 20% of porosity, it also has a good efficiency in comparison with impermeable artificial upwelling structure. Therefore, to build the artificial upwelling structure, It is encouraged to design it less than 20% of porosity for the best performance.

• The korean journal of orthodontics
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• v.46 no.5
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• pp.301-309
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• 2016

Objective: The aim of this study was to evaluate the skeletal and dental changes after intraoral vertical ramus osteotomy (IVRO) with and without presurgical orthodontics by using cone-beam computed tomography (CBCT). Methods: This retrospective cohort study included 24 patients (mean age, 22.1 years) with skeletal Class III malocclusion who underwent bimaxillary surgery with IVRO. The patients were divided into the preorthodontic orthognathic surgery (POGS) group (n = 12) and conventional surgery (CS) group (n = 12). CBCT images acquired preoperatively, 1 month after surgery, and 1 year after surgery were analyzed to compare the intergroup differences in postoperative three-dimensional movements of the maxillary and mandibular landmarks and the changes in lateral cephalometric variables. Results: Baseline demographics (sex and age) were similar between the two groups (6 men and 6 women in each group). During the postsurgical period, the POGS group showed more significant upward movement of the mandible (p < 0.05) than did the CS group. Neither group showed significant transverse movement of any of the skeletal landmarks. Moreover, none of the dental and skeletal variables showed significant intergroup differences 1 year after surgery. Conclusions: Compared with CS, POGS with IVRO resulted in significantly different postsurgical skeletal movement in the mandible. Although both groups showed similar skeletal and dental outcomes at 1 year after surgery, upward movement of the mandible during the postsurgical period should be considered to ensure a more reliable outcome after POGS.

• Korean Journal of Applied Biomechanics
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• v.34 no.1
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• pp.25-33
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• 2024

Objective: The purpose of this study was to compare the lower extremity muscle activity and knee joint load according to movement speed conditions during the barbell back squat. Method: Nine males with resistance training experience participated in this study. Participants performed the barbell back squat in three conditions (Standard, Fast, and Slow) differing movement speed. During the barbell back squat, muscle activity of the rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), biceps femoris long head (BFL), semitendinosus (ST), gluteus maximus (GM), gastrocnemius (GCN), and tibialis anterior (TA) was collected using an 8 channel wireless EMG system. The peak flexion angle of the lower extremity joints and the peak resultant joint force in each direction of the knee joint were calculated using eight motion capture cameras and ground reaction force plates. This study was to used the Friedman test and the Wilcoxon signed rank test, to compare lower extremity muscle activity and peak resultant joint force at knee joint according to movement speed conditions during the barbell back squat, and the statistical significance level was set at .01. Results: In the downward phase of the barbell back squat, the RF and TA showed the higher muscle activity in the fast condition, and in the upward phase, RF, VL, VM, BFL, ST, GM, and TA showed the higher muscle activity in the fast condition. As a results, analyzing of the load on the knee joint, in the downward phase, and in the upward phase, the higher peak compressive force of the knee joint was showed in the fast condition. Conclusion: The barbell back squat with fast movement speed was more effective due to increased muscle activity of lower extremity, but one must be careful of knee joint injuries because the load on the knee joint may increase during the barbell back squat with fast movement speed.

• The Journal of Information Systems
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• v.26 no.4
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• pp.39-62
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• 2017

Purpose The purpose of this study is to investigate the factors which affect users' fatigue and reluctant intention of using a SNS. In particular, this study focused on the fatigue of SNS users, as the recent excessive use of SNS has led to negative effects such as invasion of privacy, addition and social overload. fatigue This research will explain how producing adverse effects by using SNS caused psychological and mental depression. Previous researches explained that mental fatigue associated with SNS is not simple one and it is complicated with various psychological factors. Considering this fact, this study introduced a behavioral economics concept and a social comparison theory in the research model. Design/methodology/approach For research purposes, this study developed research hypotheses in order to empirically examine the factors that affect SNS users' fatigue and reluctant intention. The empirical research was based on a poll done through 800 research candidates in the SNS fields and the final 451 responses were collected and used in statistical data analysis. The adaptability, trust, and validity to measurement model were verified and the structural relationship in the research model was analyzed through these 451 responses. Findings First of all, maintenance fatigue of SNS had a positive significant effect on coupling and fatigue of SNS and information privacy had a non-significant effect on fatigue. Second, coupling had a negative significant effect on rational inattention, however, perceived cost had a non-significant effect on rational inattention. Third, lateral/upward comparison had a positive significant on user's negative emotions. Meanwhile, user's negative emotions did not have a significant effect on rational inattention.

• Nuclear Engineering and Technology
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• v.29 no.3
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• pp.251-259
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• 1997

This paper describes experimental investigations of helium-air exchange flows through partitioned opening and too-opening. Such exchange flows may occur following rupture accident of stand pipe in high temperature engineering test reactor. A test vessel with the too types of small opening on top of test cylinder is used for experiments. An estimation method of mass increment is developed to measure the exchange now rate. Upward flow of the helium and downward flow of the air in partitioned opening system interact out of entrance and exit of the opening. Therefore, an experiment with too-opening system is made to investigate effect of the fluids interaction of partitioned opening system. As a result of comparison of the exchange flow rates between too types of the opening system, it is demonstrated that the exchange flow rate of the two-opening system is larger than that of the partitioned opening system because of absence of the effect of fluids interaction.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.28 no.4
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• pp.130-141
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• 2015

Objectives : The aim of this study is to report the effect of Korean medicine treatment on ocular motility disorders (ptosis, bilateral upward gaze palsy, adduction impairment, and strabismus) caused by thalamus, midbrain and pontine infarctions.Methods : The patient was treated by using acupuncture, hominis placenta pharmacoacupuncture, and electroacupuncture treatment. The change of ptosis was evaluated by measurement of palpebral fissure width. The change of gaze palsy and strabismus were evaluated by comparison the photographs of the extraocular movements of patient. Strabismus also was evaluated by corneal reflex test.Results : Gaze palsy and strabismus were improved. Ptosis disappeared after Korean medicine treatment.Conclusions : Korean medicine treatment should be effective for the ocular motility disorders caused by thalamus, midbrain and pontine infarctions.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.4
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• pp.59-67
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• 2004

Direct numerical simulations of turbulent flows over riblet-mounted surfaces are performed to educe the mechanism of drag reduction by riblets. Numerical simulations are performed for flow fields with R $e_$\tau$/=180. For riblet ridge angle $\alpha$=60$^{\circ}$, two different riblet spacings of $s^+/=20 and 40 are used in this study. The computed drag on the riblet surfaces is in good agreement with existing computational and experimental data. The mean velocity profiles show upward and downward shifts in the log-law for drag-decreasing and drag-increasing cases, respectively Turbulence statistics above the riblets are computed and compared with those above a flat plate. The purpose of this study is in two categories: first, to understand the drag reduction mechanism on riblet surface, second, to verify our own code by comparison of the present results with those from previous studies.udies.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.12
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• pp.15-21
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• 2015

We proposed 50W-LED modules of using Heat-pipe and Stack-fin and produced LED modules was evaluated heat dissipation characteristics with comparison of the conventional die-casting type. It verified the application of products by applying it to 150W-LED road luminaires through simulation. The LED module was measures aimed design temperature of the Stack-fin and showed 26% upward heat dissipation effect than a conventional die-casting type. The luminous efficacy of 150W-LED road luminaires using this LED module reached over 112lm/W, and the simulation results showed average of horizontal luminance, overall luminance uniformity($U_O$) and lane luminance uniformity($U_I$) that is suitable for five-lane road with the KS standards.