• Journal of the Korean Society of Radiology
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• v.15 no.2
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• pp.201-210
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• 2021

This study was conducted not only to find out the effect of straight body exercise on neck pain, necks disability and neck length change of turtle neck syndrome patients but also to provide fundamental data for this field in the future. Number of 60 persons were selected by pre-test and divided to 21 persons in straight body exercise group, 19 persons in exercise group and 20 persons in control group(non-exercise group). 5 kinds of straight body exercise were applied in straight body exercise group, 8 kinds of strengthening cervical vertebral exercise were applied in exercise group and no exercise was applied in control group. Neck pain, necks disability index and neck length were measured before and after exercise and 10 weeks later as well. The data were analyzed by SPSS(v18.0). In straight body exercise group and exercise group, neck length, neck pain and necks disability index were significantly decreased after eight weeks of exercise and there was no significant difference in control group. Neck length which was checked every week in straight body exercise group and exercise group was significantly decreased and there were significant differences after 3 weeks.. After 2 weeks of 8 weeks exercise, neck length, neck pain and necks disability were checked again in post test and those results were maintained just like 8 weeks exercise status. As above results, it was more efficient in the straight body exercise group than exercise group and control group to decrease neck pain, necks disability and neck length of turtle neck syndrome patients. Furthermore, after 2 weeks of 8 weeks exercise, the results were maintained just like 8 weeks exercise status. Therefore, the author consider that straight body exercise will be effective exercise for turtle neck syndrome patients, and this study would provide fundamental data for this field in the future.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.254-257
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• 2010

Acoustic design parameters of a Helmholtz resonator are studied experimentally and numerically for acoustic stability in a model acoustic tube. Acoustic damping is quantified by the amplitude of the fluid velocity in mass-spring-damper system. The length of an orifice, the volume of a cavity, and the diameters of an orifice and a cavity in the resonator are selected as design parameters for tuning of the resonator. It is found that acoustic damping capacity is increased by shorter orifice and longer cavity in the resonator. As the ratio of the orifice diameter to the cavity diameter increases in the resonator, the damping capacity decreases.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.570-573
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• 2012

Performance characteristics of subscale diffuser for high-altitude simulation have been numerically investigated. The length of diffuser entrance with respect to nozzle exit diameter was changed to 0, 50, 100%, respectively. In addition, flow characteristics have been studied for various length to diameter ratio of secondary throat diffuser. As a result, the shape of plume was contracted for insufficient length of diffuser entrance. Also, if the length to diameter ratio of secondary throat diffuser were less than 7 or 8, mach disk has been formed inside the diffuser.

• Journal of the Korean Wood Science and Technology
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• v.48 no.6
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• pp.807-819
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• 2020

The aim of this study was to investigate the anatomical characteristics of Quercus mongolica infested by oak wilt disease. To analysis the anatomical characteristics of the wood specimens infested by the oak wilt, the anatomical structures of an infected wood, a dead wood, and sound wood were observed at 10-year-old intervals from 10 to 50 annual rings using both an optical and a scanning electron microscope. The fiber length was measured in units of 5 annual rings from the pith, and the diameter of the vessel element and the ratio of the vessel including the tyloses were measured for each 10 annual ring. In the cross section, on the infected and dead wood specimens, mycelium was also observed with the tyloses in the vessel. There was no signification difference between the wood specimens in the fiber length and the vessel diameter of the vessel element. The fiber length was not difference after 20-30 annual rings which is a part of juvenile wood. The average of the vessel ratio including tyloses in the infected wood was the highest. Especially, the ratio of tyloses was the highest 40-50 annual rings in the infected wood and the dead wood. Therefore, the large difference between the infested wood by oak wilt and the sound wood was the ratio of tyloses. This result can be used as a basic data to utilize the infested wood.

• Journal of the Korean Society of Propulsion Engineers
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• v.26 no.5
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• pp.11-23
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• 2022

For the design of the shortened ED(Expansion Deflection) nozzle, a numerical study of ED nozzle was performed according to the length reduction methods. The first method is to reduce the extension length of the ED nozzle with 80% bell nozzle length by 10%, 20% and 30%. The second method is to shorten the extension length by increasing the nozzle throat angle. Due to the increase in the curvature of the contour as the length shortened, the decrease in the nozzle exit velocity between the ED nozzle with 80% bell nozzle length and the ED nozzle in the first method was reduced, and the thrust become similar. The ED nozzle of the second method increased the thrust by increasing the nozzle exit velocity compared to the ED nozzle with 80% bell nozzle length.

• Journal of the Korean Society of Clothing and Textiles
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• v.18 no.2
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• pp.252-262
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• 1994

As a means to get a better understanding of the kind of form changes to which is subject the neck of the men, in its aging process, several measurement recordings on a vertical and horizontal sections were carried. Subjects were young, middle aged and elder men (15 in their twenties, 11 in their forties and again 11 in their sixties) 1) The analysis of the meansurement results led us to distinguish 3 types of subjects according to the position of the their Adam's apple with regard to the horizontal plane containing their 7th cervical vertebrae point : clearly above (Type I), next to(Type II), clearly below(Type III). We found that young men correspond to the Type I and II, middle aged men to the Type ll and 111 and elder men only to the Type III. 2) The comparison of the horizontal sectional surface contained in the planes corresponding to the 4 points, shows a larger sectional surface for elder men in the Adam's apple plane, accompanied by a change of position of the Adam's apple forwards. As for the front neck point plane, the body sectiolial surface is larger in depth in elder men, without much change in breadth. And for the acromion point plane, we observed also an increase in depth, but with a decrease in breadth corresponding partially to the atrophy of the thoraric cage in eldermen.

• Journal of Korean Society of Forest Science
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• v.109 no.2
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• pp.179-188
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• 2020

Weeding refers to the process of removing weeds around crop trees, which cause competition in nutrients, moisture, and light, and has a great effect on the early growth and survival of crop trees for establishing forest resources. This study was conducted to find out the timing and method of weeding that is the most suitable for the major afforestation species in national forests. We investigated (1) weeding time and frequency for each afforestation species and (2) the height of crop trees and the length of weeds. Up to 99% weeding operation was carried out until 5 years following afforestation. Pinus densiflora, Larix kaempferi, Chamaecyparis obtusa, Prunus sargentii, and Betula platyphylla plantations accounted for more than 70% of the total weeding sites. Once-a-year weeding process was conducted from late June to late July (67%), and twice-a-year weeding process was the highest in June-August by 31%. Most species were shorter than the weeds until the first and second year of planting, but the height of the crop trees was higher than that of the weeds by 48% in average from the third year. Therefore, from the third year of afforestation, except for some species, it is possible to reduce the cost of weeding operations while reducing nutrient competition by the weeds through the removal of weed sprouts, mainly woody weeds, rather than clear cutting. This study contributes to efficiently develop forest resource establishment while reducing operational costs through a detailed weeding schedule and species-specific method.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.764-766
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• 2002

본 연구에서는 가스 차단기의 소전류 차단성능을 개선하기 위한 최적화 과정에 대해서 나타낸다. 목적함수는 절연내력과 극간 인가전압의 차이의 최소값으로 선정하였으며, 목적함수가 최대가 되도록 최적화를 수행한다. 설계 변수로는 개극 전의 전극 이동길이, 노즐목 길이 및 노즐목 발산각과 노즐 하류장 형상을 채택하였다. 최적화 알고리즘으로는 (1+1) 진화알고리즘을, 유동해석을 위해서는 FVFLIC법을 사용하였다. 최적화 결과로 얻어진 모델은 초기 모델에 비해 소전류 차단성능이 상당히 개선되었음을 확인할 수 있었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.4
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• pp.281-286
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• 2007

The Navier-Stokes equations are numerically solved for a two-dimensional small nozzle with the area ratio of 1.8 between the throat and the exit. The shock structures are verified inside the nozzle and near the exit varying with the pressure ratio and the length of the diverging part, respectively. Especially the irregular patterns in the pressure distribution near the throat are analyzed based on the geometric characteristics. It is found that there are similar phenomena in the shock wave structure between the pressure ratio and the length changes. Also there exists a normal shock just between two different oblique shocks crossing each other in special cases.

• Proceeding of EDISON Challenge
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• 2013.04a
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• pp.210-213
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• 2013

실리콘 나노선 전계 효과 트랜지스터(Field Effect Transisor: FET)의 특성을 시뮬레이션을 통해 연구하였다. 일반적인 트랜스컨덕턴스(transconductance) 값을 이용하여 소자의 전계 효과 이동도(field effect mobility)를 추출했고, Y-function 방법을 이용하여 저전계 이동도(low field mobility)와 문턱전압(threshold voltage)를 구했다. 채널길이가 10nm로 매우 짧을 때와 100nm의 일반적인 길이 일 때의 전하 이동도 특성을 비교하여 Si 나노선 FET의 쇼트 채널 효과(short channel effect)를 보았다.