• Journal of Mechanical Science and Technology
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• v.19 no.2
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• pp.674-681
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• 2005

The unsteady evolution of trailing vortex sheets behind wings in close formation flight near the ground is simulated using a discrete vortex method. The ground effect is included by an image method. The method is validated by comparing computed results with other numerical results. For a lifting line with an elliptic loading, the ground has an effect of moving wingtip vortices laterally outward and suppressing the development of vortex evolution. The gap between wings in close formation flight has an effect of moving up wingtip vortices facing each other. For wings flying in parallel, the ground effect causes the wingtip vortices facing each other to move up, and it makes the opposite wing tip vortices to move laterally outward. When there is a relative height between the wings in ground effect, right-hand side wingtip vortices from a mothership move laterally inward.

• Korean Journal of Applied Biomechanics
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• v.14 no.2
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• pp.69-83
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• 2004

The purpose of this study is searching for technical merits and demerits of each weight lifting player through qualitative motion analysis system. Moreover, It is also analysis the repeating the establishment of exercise purpose and studying for the effect of the field adaptation. The subject of this study was five male weight lifting players who have been engaged in Korean Delegation Team. The institution of exercise target was made through two times qualitative analysis and the result of studying for the effect of the field adaptation was produced before offering feedback. Moreover, two time analysis added after offering feedback. All analysis was based on 2-D visual analysis. The results of this study are as follows: 1. Maximal barbell moving speed in starting phase was decreased after offering feedback. This result implies advancement of technical skills after offering feedback. 2. From starting posture to 앉아받기, forward and backward moving distance of hip joint was decreased after offering feedback in all subjects. This result represents advancement of technical skills after offering feedback. 3. In terms of pull phase, forward and backward moving distance of hip and shoulder joint was decreased after offering feedback in all subjects. This result represents advancement of technical skills after offering feedback. 4. In terms of pull phase, the difference of horizontal value of coordinates was decreased after offering feedback in all subjects. This result represents advancement of technical skills after offering feedback. 5. In terms of pull phase, the motion range of hip joint was decreased after offering feedback in three of five subjects and this represents advancement of technical skills after offering feedback. However, the rest of them were not variable or narrow decreasing. This result represents that feedback system could not brought tremendous effects. 6. From apex point of barbell to 앉아받기, the difference of barbell height was decreased after offering feedback in three of five subjects and this represents advancement of technical skills after offering feedback. However, the rest of them weren't variable or narrow increasing. This result represents that feedback system could not brought tremendous effects. 7. In terms of last-pull phase, the angular velocity of knee joint was increased after offering feedback in four of five subjects and this represents advancement of technical skills after offering feedback. However, the rest of them, only one subject, decreased. This result represents that feedback system could not brought tremendous effects. 8. In terms of last-pull, the conversional tendency of maximal extension to flextion came out all but simultaneously without offering feedback in four of five subjects. This is well-performed technique. Only one subject, however, could not use power effectively because the fact that his maximal extension came out in serial, from ankle to knee and waist means dispersion of power. In addition to, after offering feedback, only one subject made increasing the maximal extension of knee in last-pull and this result represents advancement of skills after offering feedback. However, the rest of them could not make meaningful development after offering feedback. 9. It might be assumed that searching for technical merits and demerits of each weight lifting player through qualitative motion analysis system could improve player's skill.

• International Commerce and Information Review
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• v.18 no.3
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• pp.73-100
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• 2016

This study focused on the Korean Stock Market so as to recognize the actual Korea-China FTA effect in the firm level. The result are as follows. First, lifting embargo even before the FTA actually took into effect influenced negatively to the firms listed in Korean Stock Market unlike the expectations that effectuation could influence positively to Korean economy. Secondly, the industries that China has attracted more foreign investors than Korea have shown declining returns as they positioned comparative disadvantages in Korea. In this regard, foreign shares delivered signaling effects to domestic investors in Korea. Thirdly, information for effectuation(embargo lifting) has reflected in the stock prices immediately as it leaked in the industries expecting the negative impact, while investors showed the tenancy to retain the action until the FTA actually took into effect in the industries expecting the positive impact.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.1
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• pp.123-128
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• 2016

The effect of propeller surface roughness condition on ship performance is very significant even the influence of fouling on propeller performance is not well established compared to biofouling on the hull surface. In present study, predictions of open water efficiency of propeller are made for three different fouling conditions, and its application is given for the 7m full-scale propeller of a medium-size tanker in open water condition. The numerical predictions of propeller efficiency loss due to fouling are based on the results from laboratory-scale drag measurements and boundary layer similarity law analysis presented in Schultz (2007) together with an in-house unsteady lifting surface code which is an appropriate tool to predict the effect of propeller surface roughness on propeller performance. The results of this study indicate that the subject propeller with the small calcareous fouling ($k_s=0.001$) can lead to as high as 15 % loss at the propeller operating condition (J=0.5) and the loss of propeller efficiency due to fouling should be evaluated while the ship is operating.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.7 no.1
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• pp.35-42
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• 2009

Purpose : The purpose of this study was to investigate the effects of Swiss ball lumbar stabilization exercise on the strength and flexibility, balance for the subjects. 30 university students who aged an average $23.21{\pm}4.41$ years. Methods : The exercise program lasted for 4 weeks with a frequency of 3 times per week within 12 to RPE. The result was analyzed by case study were measured by sit-up for strength, and back muscle strength, and trunk flexion test and trunk extension lifting for flexibility, and also measured by balance test before and during, and after the Swiss ball exercise program. Statistical analysis was performed using SPSS/Win(15.0) version and t-test. Results : By the result of this study, we found that the number of performing sit-up strength was increased, and back muscle strength was increase, and trunk flexion test and trunk extension lifting was increased after the 4 weeks Swiss ball exercise program. Conclusion : These finding indicate that Swiss ball lumbar stabilization exercise using Swiss ball could be beneficial to the subjects. The effect of increasing strength and flexibility, balance was flexibility.

• The Journal of Korean Physical Therapy
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• v.24 no.5
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• pp.319-324
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• 2012

Purpose: This study examined the muscle activities of the erector spinae (ES) and gluteus maximus (GM) during bridging exercises with and without abdominal-hollowing. Methods: Nineteen healthy subjects with no medical history of low back pain or hip flexion contracture were enrolled in this study. The subjects performed bridging exercises with and without abdominal hollowing or with and without a one-leg lift. The muscle activities of the ES and GM were measured by surface electromyography during bridging exercises under each condition. A 2 (abdominal hollowing)X2 (one-leg lift) repeated ANOVA was used to compare the normalized muscle activities of the ES and GM. Results: The muscle activity of the ES during bridging exercise with abdominal-hollowing was significantly smaller than that without abdominal-hollowing (p=0.00). The muscle activities of the GM during bridging exercise with abdominal-hollowing were significantly greater than those without abdominal-hollowing (p=0.00). In addition, the muscle activities of the GM during bridging exercise with one-leg lifting was significantly greater than that without one-leg lifting (p=0.00). Conclusion: Bridging exercise with abdominal-hollowing appears to be more effective on activating the GM muscle than that without abdominal-hollowing minimizing the activation of the ES muscle.

• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.248-255
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• 1998

The objective of this study is to conduct the prevention method using electromyography that is to resist the strain on L5/S1 disc and to measure the heart rate for the prevention of low back pain during lifting. EMG signals and heart rate were analyzed under the condition of fixed vertical factor (20∼80cm), two horizontal factors (35cm, 55cm), and two weight factors (10kg, 25kg) 2 times per minute for each lifting task. Eight healthy male workers performed nine-step stretching exercises which were intensified back power at the L5/S1 disc for six months. After completion of the two trials, the results were compared. The results of this analysis show that EMG signals have more an effect on the weight than the horizontal factors similar to those analyzed previous study, and are decreased. Therefore, those exercises presented very efficient. Also, there are not statistically significant differences on the analysis result of heart rate between weight factors.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.4
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• pp.533-542
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• 2010

For a long times it has been believed that the Magnus effect of the rotating cylinder could be utilized for the lifting devices applicable to marine practices. It has been reported that the rotating cylinder installed on upper deck of commercial vessel could play a energy saving role however the idea might be applicable in a very rare case in ship building practices. In this study special high lift rudder system equipped with the trailing edge rotor has been suggested in correspondence with the increasing requirement of greater rudder force. Through the numerical simulation it is cleared that the trailing edge rotor could play a role in enhancement of circulation and refinement of boundary layer of the rudder system. At the same time it is found out that the lift force of the rudder system without rotation of trailing edge rotor could be doubled when the circumferential velocity of the trailing edge rotor is equal to twice of the inflow velocity.

• Journal of the Korean Institute of Rural Architecture
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• v.22 no.1
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• pp.13-20
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• 2020

As the number of plastic greenhouses has increased in Korea, the damage from typhoons and snow has also increased. Structural design codes for a disaster-resistant plastic greenhouse have been revised over the last few decades. In particular, the revised code draft in 2017 have changed in many ways compared to the 1995 code. Nevertheless, There is no study of the effect of new design code on plastic greenhouse. Therefore, this study evaluated the safety of plastic greenhouse against wind load according to 1995 and 2017 codes for type 1 houses, which is most commonly built in Jeju, through comparing the analytical results of plastic greenhouses designed by 1995 code and 2017 code draft. The results are as follows. (1) The uplift load due to the negative pressure on the roof of the plastic greenhouse increased significantly in 2017 code draft. (2) Since the existing members could not meet the design requirements, the rafters had to be replaced with members of the same cross-section as the columns. (3) Due to excessive lifting, measures were also needed to prevent lifting at the foundation of the plastic greenhouse.

• Journal of Korean Physical Therapy Science
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• v.17 no.3_4
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• pp.29-39
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• 2010

Purpose: The purpose of this study was to examine the effect of foot position and lifting an object on muscle activity and foot pressure during sit to stand(STS) in hemiparetic patients. Methods: Fourteen patients participated in this study. Surface electromyography was used to collect muscle activity and foot pressure measurement system was used to analyze foot pressure in hemiparetic side. Three different foot position was assumed(anterior, neutral, posterior) in hemiparetic side. The repeated two-way analysis of variance and multiple comparisons were conducted to determine statistical significance with a significance level of 0.05. Results: The results were as follows. 1) Lower extremity muscle activity was significantly higher(p<0.05) in biceps femoris and tibialis anterior muscle during STS without holding an object. With changing positions of the affected foot, muscle activity was significantly increased (p<0.05) in vastus medialis and lateral gastrocnemius when the foot was positioned in posterior. 2) There was no significant difference(p>0.05) in foot pressure during STS with object holding and foot positioning. Conclusion: Muscle activity showed a significant increase when the foot was positioned in posterior in comparison to the muscle activity when the foot was in neutral or anterior position.