• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.1124-1128
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• 2021

As regulations of emissions from ships become more stringent, electric propulsion systems have been increasingly used to solve this problem in vessels ranging from large merchant ships to small and medium-sized ships. Methods for improving the efficiency of the electric propulsion system include the improvement of power sources; the use of a system linked to environmentally friendly power sources, such as batteries, fuel cells, and solar power; and the development of hardware and control methodology for rectifiers, power conversion devices, and propulsion motors. The method using a phase-shifting transformer with diodes has been widely used for rectification. Power semiconductor devices with grid connection to an environmentally friendly power source using DC distribution, a variable speed power source, and the application of small and medium-sized electric propulsion systems have been developed. Accordingly, the demand for active front-end (AFE) rectifiers is increasing. In this study, a method using a neural network rather than a conventional proportional-integral controller was proposed to control the AFE rectifier. Tested controller data were used to design a neural network controller trained through MATLAB/Simulink. The neural network controller was applied to a rectification system designed using PSIM software. The results indicated the effectiveness of improving the waveform and power factor DC output stage according to the load variation. The proposed system can be applied as a rectification system for small and medium-sized environmentally friendly ships.

• The Journal of Pediatrics of Korean Medicine
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• v.16 no.2
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• pp.171-185
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• 2002

Objectives : The purpose of this study was to investigate the spine distortion and self-conscious pain in high school students. Method : Using the phase-shifting moire developed by KAIST(Korea Advanced Institute of Science and Technology) we measured the back surface distortion, and using questionnaire investigation, we investigated the self-conscious pain in 30 high school students(17 boy students and 13 girl students). Results : This study show that low back pain was most cases, and next headache, upper back pain, abdominal pain, neck pain, shoulder pain, leg pain, chest pain and gluteal pain. The ratio of each self-conscious pain was 90.0%, 86.7%, 83.3%, 83.3%, 80.0%, 76.7%, 66.7%, 33.3%, 33.3%, 30.0%. In remainder value of left and right shoulder, above of 3.0 were three students., above 2.0 to bellow 3.0 were 10 students, bellow 2.0 were 17 students. In remainder value of left and right gluteal, above of 2.0 was one students, above 1.0 to bellow 2.0 were 18 students, bellow 1.0 were 10 students. In remainder value of cervical vertical line to left and right axillae, above 4.0 was 1 student, above 3.0 to bellow 2.0 were 2 students, above 2.0 to bellow 3.0 were 3 students, above 1.0 to bellow 2.0 were 16 students, bellow 1.0 were 7 students. In remainder value of gluteal vertical line to left and right axillae, above 6.0 was 1 student, above 5.0 to bellow 6.0 were 7 students, above 4.0 to bellow 5.0 were 3 students, above 3.0 to bellow 4.0 were 2 students, above 2.0 to bellow 3.0 were 5 students, above 1.0 to bellow 2.0 were 7 students, bellow 1.0 were 5 students. In remainder value of cervical vertical line to gluteal vertical line, above 40 was 1 student, above 3.0 to bellow 4.0 were 4 students, above 3.0 to bellow 3.0 were 6 students, above 1.0 to bellow 2.0 were 8 students, bellow 1.0 were 11 students. Conclusion : It is suggested that the significant correlation exist between the spinal distortion and self-conscious pain. And we can find many cases as spinal distortion in high school students also. We have to study further more about juvenile postural distortion and it's prevention.