• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.10
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• pp.117-124
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• 2019

Military Vehicles of the Korean army had been developed before 2004 and used manual transmissions. Manual transmissions contain a clutch system regulating the force from engine to transmission. In this study, a 2.5-ton military vehicle's clutch system was investigated. The existing clutch system had the characteristics that need to adjust the clearance between the clutch cover and release bearing. Improper clearance led to early wear of the clutch disk and failure of the clutch cover. To solve these problems, an improved clutch system was suggested and tested. The improved clutch system contains auto adjustment of the clearance and an enhanced clutch disk. To verify the improved clutch systems, 2 stage tests were conducted: an accelerated life test of the clutch system, and a driving test by trainee of driving more than 3,000km. As a result, the problems caused by the improper clearance adjustment were solved and this design was verified.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.703-709
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• 2017

Korea Utility Helicopter(KUH) is a project to replace the aging helicopter presently being operated by the military with a domestic helicopter. The auxiliary power unit is a device that supplies emergency power to the system by an alternator installed when the main generator fails and the start motor converts the electrical energy of the battery into mechanical rotational energy to rotate the auxiliary power unit engine. With continuing power and operation, defects of the starting motor were found and improvements were carried out to solve it. In the failure mode analysis, the causes of possible defects were classified into 5 categories. Analysis of the 5 factors revealed that the main cause of defects is mechanical wear, which was found to be related to spring pressure. 250 tests were conducted through the theoretically determined pressure and regression analysis was performed with 4 sampling.The results showed that pressure was related to wear rate. In conclusion, early wear and breakage due to wear can be controlled through spring force and test showed the prediction of wear and the validity of the result were confirmed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.344-347
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• 2011

This paper presents qualification process of the T700/701K turbo-shaft engine for Korean Utility Helicopter(KUH). The T700/701K is the rear-drive variant of the GE's T700-701C/D engine which was qualified for military applications in the world. The main scope of the development is the modification from a front-drive engine to a rear-drive one, the performance enhancement of the power turbine and the incorporation of two channel FADEC(Full Authority Digital Engine Control) system for more reliable operation. Therefore, T700/701K engine must be qualified by Korean government in order to perform a flight in the country. Reflecting the influence of developing scope, the main requirements including performance and control are verified by test and analysis, while the requirement for module or component that is same to that of T700-701C/D are verified by similarity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.383-388
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• 2020

This study aimed to identify the influence of the power components of the ammunition vehicle on the maximum speed. The maximum speeds of the engine and transmission changes were 3% and 1.7%, respectively. In the case of strong tension based on the track tension, the decrease was 4.6%. A 1.5% increase was obtained when the tension was weak. An examination of the maximum speed by dividing the track tension into six sections revealed the maximum speed to be highest when it was maintained below the middle. Experiments were performed by varying the orbital tension on both sides of the equipment. The maximum speed of the machine was affected by a large part of the tension. The maximum speed test was conducted by adjusting the tension at the driving test site. The results showed that when the tension was strong, the speed was 16.7% higher than the standard requirement. The speed was 28.3% at low tension. The influence of the maximum speed on the track tension was confirmed; the effect was greater than replacing the large parts.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1599-1603
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• 2008

발전소 냉각수 배수로에는 유속 2 m/s 이상의 빠른 흐름의 수로가 존재하여 수력발전을 꾀할 수 있어, 하동화력의 경우 조류발전 수차인 헬리컬 수차를 이용한 수력 개발이 진행 중이다. 하동화력 배수로는 약 630 m의 암거와 약 250 m의 개수로로 이루어져 있는데, 현재 상업용 발전설비 개발을 위해 시험용 수차발전 설비를 개수로로 이어지는 암거 출구부에 설치하여 성능 시험을 추진하고 있다. 이에 본 연구에서는 발전 설비의 설치로 인한 수위 증가가 냉각수 순환 계통에 미치는 영향을 파악하기 위하여 배수로 구간의 수위변화 또는 압력변화를 수치해석을 통해 분석하였다. 배수로 암거 출구부에 가로 3.6 m ${\times}$ 세로 1.5 m 헬리컬 수차 1 set를 설치하는 경우 저조시에는 seal well 후단(하류측)의 수위가 seal well의 위어 정부표고를 넘지 않아 수차구조물에 의한 압력변화가 상류로 미치는 영향이 없었다. 그러나 고조시에는 seal well 전 후단이 만관 관수로 흐름이 되어 하류의 압력변화가 상류로 전파되었다. 단, 수차구조물을 설치한 경우 순환수 펌프를 처음 기동할 때 압력파의 전파로 인해 초기 약 10 분간 불안정한 압력변화가 발생하나 수차구조물 설치 전인 현상태에서 발생하는 압력변화 범위를 벗어나지는 않고 이내 안정되며, 수차구조물 설치로 인한 수위 증가분만큼의 펌프 양정고 증가로 소요 동력이 증가할 수 있으나 0.2 m 내외의 미약한 증가이므로 정상 운전에는 문제가 없을 것으로 판단되었다. 따라서 수차구조물 설치 시, 저조시에는 순환수계통에 영향을 주지 않으며, 고조시에도 일부 시간 동안 미약한 수두변화만 있을 뿐 순환수 계통의 안전에는 지장을 주지 않을 것으로 확인되었다.

• Journal of Navigation and Port Research
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• v.39 no.3
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• pp.209-215
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• 2015

Miraculous victory of Myeongnyang sea battle turned the tide of the Joseon's entire war against Japan and it is regarded as one of the most remarkable sea victories in the world history. In the sea battle of Myeongnyang, on September 16, 1597(lunar calender), the Joseon navy with 13 battle ships, led by Admiral Yi Sun-sin, won the Japanese navy with their fleet of 133 warships. There were several reasons why Admiral Yi decided on this location for battle. Myeongnyang strait is so narrow and had currents so powerful that many ships could not pass strait simultaneously. Therefore, despite being vastly outnumbered, Admiral Yi used terrain and tidal current advantage to defeat Japanese navy's numerical advantage. In order to find out the tidal state of Myeongnyang strait on September 16, 1597, topological phase of sun and moon was studied by orbital period of earth and moon. The tidal state of Myeongnyang strait on September 16, 1597 is estimated based on the theories of tide and tide tables. As a result of this study, time of slack water were found to be 0636, 1248, 1906 and time/speed of maximum tidal current were found to be 0930/8.3kts(NW), 1612/9.9kts(SE).

• Journal of Korean Orthopaedic Sports Medicine
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• v.2 no.1
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• pp.62-70
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• 2003

Purpose: We examined the kinematics and kinetics of the shoulder in youth baseball pitchers in light of the mechanisms of development of little league shoulder and humeral retrotorsion. Materials and Methods: The joint kinematics and the net force and torque acting on the humerus were calculated in fourteen youth pitchers throwing in a simulated game. Results: The major force component acting on the humerus was a tensile force of 378$\pm$81 N that peaked just after ball release. The predominant torque on the humerus was an external rotation torque about the long axis of the humerus. This torque reached a peak value of 35.3$\pm$6.7 Nm about 73$\%$through the pitching motion. This torque is approximately 66$\%$ of the torque required to fracture of the adult humerus. Conclusions: The direction of the humeral torque was consistent with the development of increased humeral retrotorsion in the throwing arm. Shear stress arising from the high torque during the late cocking phase likely leads to deformation the relatively weak proximal humeral epiphysis. The external rotation torque applied to the humerus during the pitch also agrees with the proposed mechanism for development little league shoulder, which has been hypothesized to be due to rotational stresses acting on the epiphysis during the throwing motion.

• Journal of Digital Convergence
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• v.20 no.1
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• pp.191-202
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• 2022

The purpose of this study is to examine the effect of a 10-week body stability exercise program, which was conducted on 24 male football players. The result of the Visual Response Speed Test using BlazePod, showed a significant increase of the upper arms, left foot and right foot for 15 second in number of reactions and reaction time (p<0.001). As a result of evaluating whether or not 7 functional movements were improved in order to evaluate the functional movement screen, Hurdle Step (p=0.001) and Active Straight Leg Rise (p=0.022) movements were significantly improved. significantly improved. As a result of measuring the y-balance Test in order to evaluate the balance ability, composite score(p<0.001) of both sides was significantly improved. The result of evaluating vital capacity, which was conducted to evaluate mobility and muscle endurance, showed a significant improvement in Forced vital capacity(p<0.001) and Forced expiratory volume in 1.0(p=0.003). In conclusion, a 10-week BSE program intervention in high school period, which can most improve the technical fitness necessary for the game in power, agility, leg strength, leg stability, mobility, and muscle endurance, will improve overall technical fitness, prevent football players from being injured and enhance their performance.

• Journal of Practical Agriculture & Fisheries Research
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• v.10 no.1
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• pp.43-58
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• 2008

This research was conducted to determine the alternative tool of chemical spray for rice cultivation using the unmanned helicopter(Yamaha, R-Max Type 2G-remote controlled system) at farmer's field in Korea. The unmanned helicopter tested was introduced form Japan. In Korea the application of chemicals by machine sprayer for pest management in rice cultivation has been ordinarily used at the farmer's level. However, it involved a relatively high cost and laborious for the small scale of cultivation per farm household. Farm population has been highly decreased to 7.5% in 2002 and the population is expected to rapidly reduce by 3.5% in 2012. In Japan, pest control depending on unmanned helicopter has been increased by leaps and bounds. This was due in part to the materialization of the low-cost production technology under agricultural policy and demand environmentally friendly farm products. The practicability of the unmanned helicopter in terms of super efficiency and effectiveness has been proven, and the farmers have understood that the unmanned helicopter is indispensable in the future farming system that they visualized. Also, the unmanned helicopter has been applied to rice, wheat, soybean, vegetables, fruit trees, pine trees for spraying chemicals and/or fertilizers in Japan Effect of disease control by unmanned helicopter was partially approved against rice blast and sheath blight. However, the result was not satisfactory due to the weather conditions and cultural practices. The spray density was also determined in this experiment at 0, 15, 30, and 60cm height from the paddy soil surface and there was 968 spots at 0cm, 1,560 spots at 15cm, 1,923 spots at 30cm, and 2,999 spots at 60cm height. However, no significant difference was found among the treatments. At the same time, there was no phytotoxicity observed under the chemical stray using this unmanned helicopter, nor the rice plant itself was damaged by the wind during the operation.