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절리면의 방향, 절리선 길이 및 광주 형상비가 광주 강도에 미치는 영향 분석
최지원(Ji-won Choi),이용기(Yong-Ki Lee),송재준(Jae-Joon Song) 한국암반공학회 2020 터널과지하공간 Vol.30 No.3
지하 광산 공동의 안전성은 광주의 강도와 밀접한 관계가 있다. 광주의 강도를 알고 있다면 광주의 위험성을 판단할 수 있고 그에 따른 적절한 조치를 취할 수 있다. 광주의 강도는 광주 내에 존재하는 불연속면의 특성과 광주의 형상에 영향을 받는다. 본 연구에서는 광주를 관통하는 불연속면과 광주의 종횡비, 광주 내부에 존재하는 소규모의 내포 절리에 따른 강도 변화를 PFC 3D를 이용하여 분석하였다. 그 결과, 광주의 강도는 불연속면의 경사각에 영향을 받으며, 광주의 폭이 넓어질수록 강도가 증가하고 내포 절리의 수가 증가할수록 강도가 감소함을 확인하였다. 내포 절리로 인해 광주 표면에 나타나는 절리선 길이의 총합과 광주 강도와의 관계를 지수 함수로 회귀한 결과, 두 인자 사이의 높은 상관계수를 얻었다. 따라서 하나의 절리군이 존재할 때, 지수 함수식을 통해 절리선 길이의 총합으로부터 광주의 강도를 예측할 수 있다. 마지막으로 경사각이 60°, 30°인 두 절리군이 존재할 때 절리선 길이의 총합으로부터 광주 강도를 추정할 수 있는 식을 제시하였다. The stability of underground mine cavity is closely related with pillar strength. The vulnerability of pillars can be judged and reinforced if the pillar strength is known. The pillar strength is affected by characteristics of discontinuities and shape of a pillar. The change of pillar strength due to a discontinuity passing through the center of a pillar, width-to-height ratio of a pillar and small joints existing within a pillar was analyzed using PFC 3D. The result showed that the pillar strength is influenced by dip angle of a discontinuity and it increases as width-to-height ratio of a pillar increases. The pillar strength decreases as the number of contained joints increases. The relationship between total trace length observable from the pillar surface and the pillar strength was regressed with exponential function. The correlation coefficient of the regression was high enough so that pillar strength can be predicted using total trace length if a joint set exists in a pillar. Lastly, the method to estimate the strength of a pillar that includes two joint sets was proposed if the joint dip angles are 60°, 30°. The method also need total trace lengths of two joint sets.
Jeong, Myunggeun,Kim, Youngjin,Zhou, Wenjing,Tao, Wen Quan,Ha, Man Yeong Elsevier 2017 Computers & fluids Vol.147 No.-
<P><B>Abstract</B></P> <P>The present study investigated the Couette flow in a nano-channel using the hybrid method that combines the numerical solutions from the continuum region and the particle region. The governing equations in the continuum region were numerically solved using the finite volume method, while those in the particle region were numerically solved using a molecular dynamics simulation. An overlap region was defined to couple the continuum region with the particle region and to transfer the computational results obtained in one region to another region as boundary conditions. This study considered the effects of the wettability between the liquid and solid, the height of the pillar on the bottom wall, the velocity of the moving wall, and the channel height on the Couette flow in a nano-channel. The slip velocity on the wall decreases with increasing wettability because of the increasing attractive force between the fluid and solid wall. The slip velocity decreases with increasing pillar height as a result of increasing resistance to the fluid motion in the presence of pillar. The no-slip and locking conditions are independent of the moving wall velocity when the attractive force is large enough to satisfy these conditions. The slip velocity decreases as the channel height increases. When the channel height is large enough, the no-slip condition assumption at macroscale is available. The relative slip velocity and slip length are presented as a function of wettability for different velocity of moving wall and pillar heights.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The slip velocity on the wall decreases with increasing wettability. </LI> <LI> The slip velocity decreases with increasing pillar height. </LI> <LI> The no-slip and locking conditions are independent of the moving wall velocity. </LI> </UL> </P>
차량 조건 변화에 따른 승차 만족도 및 동작분석에 관한 연구
박세진,임윤경,이현자,김철중,Park, Se-Jin,Yim, Yun-Kyung,Lee, Hyun-Ja,Kim, Cheol-Jung 대한인간공학회 2006 大韓人間工學會誌 Vol.25 No.3
As national income increases, consumers began to place a great deal of weight on products or quality of their life. They would like to have products which are more convenient to use and could meet their emotional desire in addition to its basic functional requirements. An automobile is one of the transportation system for human beings and the factor such as safety or environmentaly-friendly is regarded as important things resulting from it's popularization. In fact, domestic design technology leaves much to be desired compared with excellent manufacturing techniques. For this reason, some problems, like lowering of usage, could be caused by introducing technological data as it is from overseas. A survey of domestic car users has found that the most preferred condition (step height) is 460~495cm when they get in and out of their car. Men use their visual information and then get in the car, taking motion fit for each condition when automobile condition is changed. In other words, men get in cars actively within the range of conditions used for this study. These results were found from a motion study, when getting in a car, and checking the possibility of getting injury in accordance with the change of condition as well.