• 한국운동역학회지
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• 제15권2호
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• pp.119-127
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• 2005

The purpose of this research helps to make full use for perfect performance by grasping the defects of Ropez motion performed by athlete CSM who was under the training for the 28th 2004 Athene Olympic Garnes, and by presenting complementary methods. For the better Ropez motion which had been performed by CSM for the 1st dispatch selection test and the final for the 28th Athene Olympic Game was analyzed with 3-dimensional cinematographic method. Here are the conclusions: 1. During the board contact phase, powerful kicking and rapid forward flexion motion of upper body make increasing vertical velocity of C. O. G and enlarging body angle. 2. It was indicated that rapid forward flexion motion of upper body during the board contact phase get a large body angle in horse take-off. 3. rapid forward flexion motion of upper body during the board contact phase makes a longer time at horse contacting phase. It showed that this result increased velocity of horse take-off causing by powerful blocking motion. 4. Increasing of air-borne height during pre- flight phase, makes a higher C. O. G; and larger angle of hip, angle of knee and body angle in the landing phase. And it revealed that these results have a stable landing.

• 한국운동역학회지
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• 제16권3호
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• pp.165-172
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• 2006

The purpose of this study was to determine effects of 12-week wearing of unstable shoe on the standing posture and gait mechanics. Nine healthy men were asked to wear the unstable shoes for 12-week and walk for 30 minute everyday. Their standing posture and gait mechanics were measured before and after treatment. Standing posture was measured for each side(anterior, posterior, lateral) for standing position. And gait analysis was measured joint angle of a right lower limb between first right heel contact and second right heel contact. Kinematic data were collected using video camera at 30 frame per seconds. Statistical analysis was paired t-test(p<.05) to compare before training with after that. A head tilt angle was significantly decreased for posterior side(p<.05). The angle of between center of line and surface was significantly decreased at midstance and take off during walking(p<.05). Ankle dorsiflexion significantly increased at heel contact2(p<.05) and ankle plantarflexion significantly increased at midstance and midswing(p<.05). The increase of ankle dorsiflexion showed that our results consisted with previous study. In conclusion, there was not large significant difference in static standing posture but joint angle of lower limb represented many changes with increasing of ankle motion during walking. These were of benefit to body by increasing leg muscle activity but it was necessary for man having a ankle problem to consider. Further studies concerning optimum outsole angle of unstable shoes are necessary.

• 한국세라믹학회지
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• 제19권1호
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• pp.24-34
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• 1982

The effect of the several variables on wetting of AISIB1113 steel by molten glass was studied by Sessible-drop method. Experimental variables were temperature, firing atmospheres, Fe2O3 addition to the sealing glass and steel surface conditions. The degree of wetting in terms of contact angles between molten glass and metal tested at different test conditions was analyzed by using Young's equation. The results showed that contact angles in H2 atmosphere in the glass metal systems were high but in N2 atmosphere, were small for studied glass metal systems. Especially, when the glass drop was in contact with oxidized steel in N2 atmosphere, The best adherence with contact angle of approximately 9°was obtained. In the case of Fe2O3 addition in glass contact angles subtantially increased due to the increase of surface tension of glass. Wetting phenomena were also discussed under the basis of these experimental results.

• 한국지반신소재학회논문집
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• 제22권4호
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• pp.43-49
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• 2023

본 연구에서는 흙 입자 표면이 소수성으로 구현된 사질토에 대하여 세립분 함유율이 사질토의 습윤성에 미치는 영향을 평가하기 위한 시험을 수행하였다. 습윤성은 주문진 표준사와 세립토가 함유된 사질토에 대하여 물방울 시험 결과로부터 얻은 접촉각으로 평가하였다. 시험 결과, 모래와 세립토로 구성된 사질토의 습윤성은 소수성 수준과 세립토 함유율 조건에 따라 변화하였다. 세립토 함유율이 사질토의 습윤성에 미치는 영향을 평가한 결과, 5% 세립토 함유율 조건에 있어서 소수성 수준이 1%와 3%인 사질토의 접촉각은 표준사의 접촉각에 비하여 각각 94.4%, 32.4%가 감소하였다. 그리고, 소수성 수준이 5%인 경우, 5%와 10%의 세립토 함유율 조건에 대한 접촉각 감소율은 각각 24.4%와 37.3%였다. 즉, 세립토 함유율은 사질토 접촉각의 크기 및 증감율에 큰 영향을 미치기 때문에, 오염물 거동 예측에 있어서 지반의 세립토 함유율에 따른 습윤성 평가가 수반되어야 한다.

• Composites Research
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• 제25권3호
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• pp.76-81
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• 2012

대기압 플라즈마 처리를 통해 탄소나노튜브(CNT) 표면은 개질 되며 개질된 입자의 표면과 탄소섬유 강화 CNT 페놀 복합재료간에 계면접착력에 변화를 확인하였다. CNT 표면에 플라즈마 처리에 따라 표면 변화가 발생되고 표면 개질의 결과를 확인하기 위해 FT-IR을 사용하였다. 또한, 정적 접촉각 실험법을 통해 플라즈마 처리에 따른 CNT의 젖음성을 비교 평가하였다. 순수 CNT 입자의 접촉각은 $118^{\circ}$ 였으나, 플라즈마 처리를 할 경우 $60^{\circ}$도로 표면 개질을 통해 젖음성이 향상됨을 확인하였다. 탄소섬유와 CNT-페놀복합재료 간 계면접착력은 플라즈마 처리에 따라 겉보기 강성도가 증가되는 결과를 확인하였으며, 음향방출 실험법과 전기저항 측정법을 병행한 이중기지평가법을 통해 계면전단강도 (IFSS)를 계산하여 계면접착력 향상을 확인하였다.

• 한국정밀공학회지
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• 제23권2호
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• pp.104-112
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• 2006

The influence of tire belt angle on the Plysteer Residual Aligning Torque(PRAT) and the cornering stiffness by the FEM has been studied. The PRAT is a performance factor of the tire about vehicle pull, and the cornering stiffness has relation to vehicle steering response of outdoor test. To validate FE model for analysis, simulation data for both the static stiffness(vertical, lateral) and the PRAT have been compared with the experimental data. In addition to the characteristics of the PRAT and the cornering stiffness due to the tire belt angle, rolling and cornering contact characteristics have been studied. The tendency of the PRAT and the cornering stiffness due to the belt angle can be used as a guide line for the tire design in relation to vehicle pull and vehicle steering response.

• 한국정밀공학회지
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• 제24권1호
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• pp.79-84
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• 2007

Some surface pattern of tribological application is an attractive technology of engineered surface. Therefore, friction reduction is considered to be necessary for improved efficiency of machine. This study investigated the effect of friction property for angles of micro-crosshatch groove surface pattern on bearing steel using pin-on-disk test. We obtain sample which can be fabricated by photolithography process. We discuss the friction property depend on an angle of crosshatch groove surface pattern. We can verify the lubrication mechanism as Stribeck curve, which has a relationship between the friction coefficient and a dimensionless parameter under the lubrication condition. It was found that the friction coefficient was related to angle of crosshatch groove pattern on contact surface.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 C
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• pp.1465-1468
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• 1997

In this study we investigated the aging characteristic such as leakage current, dielectric loss, contact angle, of EPDM for outdoor use by thermal treatment. And also observed the color change of surface, changing of chemical ingredient of the marterials by optical microscope. SEMI, FTIR and EDX at the section and surface. The test result show that leakage current is increased with thermal aging time. contact angle and dielectric loss is slightly decreased. Moreover, micro-void or crack in bulk is severely increased with aging time. However, the result affect to the tan $\delta$ at bulk of EPDM. It seems that carrier sources are removed by degassing with heat treatment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1572-1574
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• 2000

In this paper, study on the properties of the thermal degradated epoxy resin which is used in cast resin transformer is performed to investigate the problems of the decreasing insulation characteristics and crack in the cast resin transformer. In the test, contact angle, weight loss, surface resistivity and relative dielectric constant are measured. As the results of the above measurements, the epoxy resin has increased to 150$^{\circ}C$ in the contact angle and surface resistivity but at the above 150$^{\circ}C$ the values have decreased. The relative dielectric constants have increased in the thermal treated samples with the degradation temperature. Consequently, the insulation properties of the epoxy resin which is used in cast resin transformer have increased by the 150$^{\circ}C$ but decreased in the above 150$^{\circ}C$.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.81-84
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• 2006

To investigate the characteristics of water droplet on the gas diffusion layer from both upper-view and side-view of flow channel, a rig test apparatus was designed and fabricated with L-shape acryl plate in a $1mm{\times}1mm$ micro-channel. This experimental device is used to simulate the single droplet growth and its transport process under fuel cell operating condition. As a first step, we investigated the growth and transport of single water droplet with working temperature and air flow velocity. The contact angle and its hysteresis of water droplet at departing moment are measured and analyzed. It is expected that this study can provide the basic understanding of liquid water droplet behavior in gas flow channel and GDL interface during the PEM fuel cell operation.