• The Transactions of the Korean Institute of Power Electronics
• /
• v.9 no.6
• /
• pp.635-642
• /
• 2004

In electric motor coaches. the rolling stocks move by the adhesive effort between rail and driving wheel. Generally, the adhesive effort is defined by the function of both the weight of electric motor coach and the adhesive effort between rails and driving wheel. The characteristics of adhesive effort is strongly affected by the conditions between rails and driving wheel. When the adhesive effort decreases suddenly, the electric motor coach has slip phenomena. This paper proposes a re-adhesion control based on disturbance observer and sensor-less vector control. The numerical simulation and experimental results point out that the proposed readhesion control system has the desired driving wheel torque response for the tested bogie system of electric coach. Based on this estimated adhesive effort, the re-adhesion control is performed to obtain the maximum transfer of the tractive effort.

• Geophysics and Geophysical Exploration
• /
• v.9 no.3
• /
• pp.185-192
• /
• 2006

Cares should be taken when performing the P and S wave velocity loggings in engineering and environmental fields. Some of them are the effect of casing, which is installed to prevent the borehole collapsing when the drilling is done on the loose ground such as soil and/or soft rock, and the discrepancy of the velocities of the same media according to the difference of the source wave frequency spectrum. The elastic moduli obtained from the P and S wave velocity logging have the dynamic characteristics. To overcome these difficulties, the following suggestions are recommended; (1) develop and apply a careful drilling technique that can keep the borehole wall without a casing, and (2) apply the logging methods with the suitable frequency bandwidth for the object of the velocity logging. It is important to make the aseismological engineers understand the difference between the dynamic elastic moduli and the static ones obtained from mechanical test, and to advise them to use the information properly.

• Journal of the Korean Vacuum Society
• /
• v.14 no.4
• /
• pp.171-179
• /
• 2005

The influence of the surface roughness and the porosity on the apparent sticking coefficient of the getter was determined quantitatively by Monte Carlo simulation. The sorption characteristics of the getter was investigated by solving numerically the particle balance equation depending on the sticking probability and diffusivity.

• Journal of the Korean Geotechnical Society
• /
• v.36 no.4
• /
• pp.31-39
• /
• 2020

Shear wave velocity (or shear modulus) is very important in the evaluation of seismic performance of a fill dam under an earthquake. A shear wave velocity profile can be determined by surface wave method such as HWAW and SASW methods but this profile has uncertainty caused by spatial variation of material property in a fill dam. This uncertainty in shear wave velocity profile could be considered using a coefficient of variation of material property in the reliability based analysis. In this paper, the possible 600 shear wave velocity profiles in the core and rockfill zone of fill dam were generated by the random shear wave velocity profile generation method, proposed by Hwang and Park, based on the field shear wave velocity profiles determined by the HWAW and SASW methods. And, through the statistical analysis of generated shear wave velocity profiles in the fill dam, the coefficient of variation (COV) of shear wave velocity with depth were evaluated for the core and rock filled zone of fill dam in Korea.

• Journal of Korea Water Resources Association
• /
• v.31 no.1
• /
• pp.115-120
• /
• 1998

In this paper, a depth-averaged two-dimensional transport model is introduced, and its error bound is presented as the results of sensitivity analysis. The results show that the calculated SS concentration is highly dependant on Manning roughness coefficient, mixing coefficient. fall velocity. and critical shear stress. On the other hand, water level and dispersion coefficient are proved to be less significant in the variation of SS concentration.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.7 no.6
• /
• pp.1064-1071
• /
• 2006

In electric motor coaches, the rolling stocks move by the adhesive effort between rail and driving wheel. Generally, the adhesive effort is defined by the function of both the weight of electric motor coach and the adhesive effort between rails and driving wheel. The characteristics of adhesive effort is strongly affected by the conditions between rails and driving wheel. When the adhesive effort decreases suddenly, the electric motor coach has slip phenomena. This paper proposes a re-adhesion control based on disturbance observer and sensor-less vector control. The numerical simulation and experimental results point out that the proposed readhesion control system has the desired driving wheel torque response for the tested bogie system of electric coach. Based on this estimated adhesive effort, the re-adhesion control is performed to obtain the maximum transfer of the tractive effort.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2011.04a
• /
• pp.743-746
• /
• 2011

본 연구에서는 유한요소해석을 이용하여 차량속도 및 긴장재의 설계에 따른 CFTA 거더의 동적거동 및 동적증폭계수를 분석하였다. 긴장재의 해석변수로서는 긴장재의 양과 긴장력을 고려하였으며 차량하중은 도로교설계기준의 DB-24 하중을 선택하였다. 차량하중은 3축-2트랙에 작용하는 등가절점하중으로 변환하여 속도에 따라 시간함수로 모델링하였다. 긴장재의 양은 외측 �� 내측 덕트의 유무에 따라 변화시켰으며 긴장력은 설계긴장력의 0%에서 100%까지 25%씩 증가시켰다. 차량속도는 40km/hr에서 100km/hr까지 20km/hr씩 증가시켰으며, 해석결과 긴장재의 긴장력 변화는 거더의 동적거동에 영향을 주지 않았으며 초기처짐에만 영향을 주었다. 긴장재의 양에 따라서는 거더의 동적거동이 다르게 나타났으며 긴장재의 양이 적을 수록 동적처짐은 증가하였다. 이를 바탕으로 거더의 동적증폭계수(DAF)를 산출하였으며, 이 결과 긴장재가 없는 경우에도 도로교표준시방서에서 정한 기준 값보다 매우 작은 거동을 보였다.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.5 no.2
• /
• pp.77-81
• /
• 1981

1200.deg.C-1300.deg.C 의 열간 단조작업에서의 강철은 스트레인 속도에 민감하고 그 기계적인 특성방정식은 .delta.=.delta.$_{0}$ .epsilon.$^{m}$ 이다. 이 연구는 열간압출시 필요고 하는 작용력을, 상계이론을 사용하여 해석하고 쟤료의 기계적 특성상수들을 대입하여, 계산한다. 이 결과를 실험치와 비교하고 압출각, 마찰계수, 스트레인 속도와 점성계수등의 일반적인 영향에 대해서도 토의하였다.특히 변형역내의 평균스트레인 속도에 의한 일정 항복용력을 사용하였을 경우에 대해서도 비교 검토되었다.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1996.05c
• /
• pp.188-192
• /
• 1996

재결정 Zircaloy-2의 요드에 의한 응력부식균열의 전파속도를 직류전압강하측정법 (DCPD, Direct Current Potential Drop)을 이용하여 측정하고 임계응력집중계수( $K_{ISCC}$)를 구하였다. 임계요드농도 이상인 0.01 MPa의 요드농도에서, $K_{ISCC}$는 300 $^{\circ}C$의 경우 약 15 MPa√m, 350 $^{\circ}C$의 경우 약 12 MPa√m의 응력계수였으며, plateau 구역에서의 균열속도는 $10^{-4}$~ $10^{-3}$ mm/sec 영역이었다.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 1998.04a
• /
• pp.64-68
• /
• 1998

본 연구에서는 다양한 종류의 섬유를 일방향으로 배향시켜 제작한 복합재료의 트라이볼로지 연구를 수행하였으며 특히 섬유의 배향과 활주속도가 트라이볼로지 성질에 미치는 영향을 연구하였다. 실험에 쓰인 시편은 유리 섬유, 아라미드 섬유, 그리고 고탄성 탄소 섬유를 보강재료로 에폭시 수지를 모재로 사용한 일방향섬유 복합재료이며 각각의 시편을 스테인레스 강 상대 마찰면에 마찰시켜 마모량과 마찰 계수를 구하였다. 실험조건으로 사용한 여러 활주속도에서 탄소섬유복합재료가 모든 섬유배열방향에서 아라미드섬유복합재료와 유리섬유 복합재료보다 마모율과 마찰계수가 낮은 경향을 보였으며 특히 높은 속도에서는 탄소섬유복합재료의 특성이 뛰어남을 알 수 있었다.