• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.8
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• pp.107-115
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• 1999

Hydrocarbon emission from spark ignition engines deeply relates with fuel evaporation mechanism. Therefore, fuel evaporation on the back of the intake valve is very important to understand fuel evaporation mechanism during engine warm up period. Intake valve heat transfer model was build up to estimate the amount of fuel evaporation on the intake valve back . Intake valve temperature was measured intake valve temperature is increased rapidly during few seconds right after engine start up and it takes an important role on fuel evaporation. The liquid fuel evaporation rate on the intake valve back proportionally increases as valve temperature increases, however its contribution slightly decreases as intake port wall temperature increases. The fuel evaporation rate on the valve back is about 40∼60% during engine warm-up period and it becomes about 20∼30% as intake port wall temperature increases. The estimation model also makes possible model also makes possible to review the effect of valve design parameters such as the valve mass and seat area on fuel evaporation rate through intake valve heat transfer.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.6
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• pp.621-626
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• 2002

The amplitude of a back-wall echo depends on the reflection coefficient of the interface between a transducer and a test material when using contact pulse-echo ultrasonic testing. A couplant is used to transmit ultrasonic energy across the interface, but has an influence on the amplitude of the pulse-echo signal. To investigate the couplant effect on pulse-echo ultrasonic testing, back-wall echoes are measured by using various couplants made of water and glycerine in a carbon and austenitic stainless steel specimens. The amplitude of the first back-wall echo and the apparent attenuation coefficient increases with the acoustic impedance of the couplant. The couplant having a higher value of the transmission coefficient is more effective for flaw detection. The reflection coefficient should be known in order to measure the attenuation coefficient of the test material.

• Journal of the Korean GEO-environmental Society
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• v.23 no.1
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• pp.25-30
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• 2022

It is very important to investigate the ground properties of a construction site for the stability during the construction of the retaining wall. In the retaining wall construction stage, ground properties are checked through ground investigation, but the actual ground properties may be different from the ground investigation result. In order to analyze the stability of the retaining wall in real time, it is important to reflect the properties of the actual ground. Also, when it is judged that the wall is unstable, an appropriate solution must be provided for the stability of the wall. This study aims to present a technique for predicting the actual ground properties through a differential evolution algorithm and judging the stability of the earth wall in real time through the digital twin of the retaining wall.

• Journal of the Korean GEO-environmental Society
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• v.14 no.9
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• pp.39-47
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• 2013

Local deformations in back filling materials of two sands and one glass bead with different particle shapes behind a rigid retaining wall were studied. Two kinds of boundary conditions were compared: active wall translation and active rotation of the wall about its toe. Effect of the speed of active wall translation was also investigated. The digital image correlation method was used to analyze local deformation developments inside the materials. Test results showed that particle shape and density mainly influence the inclination angle and width of the shear band. The general shear band pattern is strongly dependent on the wall movement mode, while it was little influenced by particle shape. Within a limited range of wall speed in this study, shear band became wider and local deformation became larger with increase of wall speed.

• Proceedings of the Optical Society of Korea Conference
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• 2004.07a
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• pp.176-177
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• 2004

• Journal of Biomedical Engineering Research
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• v.15 no.2
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• pp.209-216
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• 1994

The objective of the research reported in this paper is to design locomotion system of the motorized wheelchair, to develope the wall following algorithm. The indoor navigation of a motorized wheelchair can be based on the wall following techniques. In this paper, it is proposed to enhance stability and efficiency using the 3 ultrasonic sensors arranged at a same perpendicular pivot. Using this method, the angle between the motorized wheelchair and the wall is detected and the range of control commands has been increased. For the better stability, the calculated slope of a wall using LSLF algorithm was fed back to the control part. By adapting the suggested algorithm and method, the motorized wheelchair could follow a wall in 4 seconds, for a change of distance between the wheelchair and wall from 30 to 100cm.

• Journal of the Korean Geotechnical Society
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• v.32 no.11
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• pp.83-96
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• 2016

The surface settlement of the back ground of a braced wall due to the ground excavation has the great influence on the safety of the surrounding area. But it is not easy to predict the settlement of the surrounding area due to proud excavation. Estimation of the settlement of the surface ground induced by the deformation of the braced wall is performed by FEM and empirical method (Peck, Clough etc). In this research, surface settlement of the back ground braced wall depending on the joint dips in rocks during excavating the composit ground was measured at the large scale model test (standard: $0.3m{\times}0.3m{\times}0.5m$). The scale of model test was 1/14.5 and the ground was excavated in ten steps. Earth pressure on the braced wall and ground surface settlement on the back ground of a braced wall were investigated. The surface settlement during the excavation depended on the joint dips in rocks on of the ratio of rock layer. Maximum earth pressure and maximum surface settlement were masured at the same excavation step. In accordance with the increase of the rock layer dips and rock layer ratio, the ground surface settlement increased. The maximum ground surface settlement was 17 times larger at 60 degree joint dips in rocks than that of the horizontal ground conditions. And the position of the maximum surface settlement by empirical method was calculated at the point, which was 17%~33% of excavation depth. In accordance with the increase of the rock layer dips and rock layer ratio, the ground maximum surface settlement increased. The ground surface settlement of composite ground is smaller than that of the empirical.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.506-509
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• 2008

Mathematical models have been developed to calculate hydrodynamic characteristics of perforated-wall structures. Most of the models separate the fluid regions into front and back of the wall, assume the solution in each region, and calculate the solution by using the matching condition at the wall. The matching condition involves the permeability parameter, which can be calculated by the methods proposed by Mei et al. or Sollitt and Cross. In this study, we compare these two methods. The former is advantageous because all the related variables are known, but it gives wrong result in the limit of long waves, i.e. zero transmission and perfect reflection of very long waves. In deep water, the latter predicts smaller transmission and larger reflection than the former, and vice versa in shallow water. In the latter method, the friction coefficient decreases as the wall thickness or the porosity of the wall increases.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1206-1215
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• 2008

In this study, the equivalent pressure acting on the face of drilled hole was determined by back analysis. This analysis was continued until the difference between the displacement directly measured during field test construction of CGS and the displacement evaluated by numerical analysis was below 10 percent, and the affect of diaphragm wall adjacent to grout bulb was evaluated by numerical analysis using the equivalent pressure. From the analysis results, it was observed that the increase of the pressure acting on the diaphragm wall was greater at reclaimed sandfill layer than silty clay layer during the installation of CGS. Two methods were adopted to reduce the pressure acting on the diaphragm wall. One is installing of trench between diaphragm wall and grout bulb, the other is pre-installing of CGS before construction of diaphragm wall. From the numerical analysis results, above two methods can be considered as an effective method to reduce the pressure. It was analyzed that the amount of reduction of the pressure and the displacement are 689.8% and 564.6%, respectively, in the case of adopting the trench method, and 463.7% and 214.0%, respectively, in the case of adopting pre-installing of 3 columns CGS.

• Journal of the Korean Geotechnical Society
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• v.25 no.5
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• pp.39-46
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• 2009

In this study, behavior of a rigid continuous wall, earth pressure distribution with construction stage, and axial force of earth anchors were evaluated based on field monitoring data and numerical analysis results. For this purpose, a construction site excavated using the diaphragm wall was selected and full instrumentation system was introduced. From monitoring results, it was found that the values of horizontal displacement of the wall measured from the inclinometers, which were installed within the diaphragm wall were similar to analytical value. The earth pressure increased with excavation progress due to jacking force of the ground anchors installed in previous excavation stages. When the excavation depth reached 60% of the final depth, observed earth pressure distribution was similar to that estimated from Peck's apparent earth pressure distribution. When the excavation depth was around 90% of the final depth, values of observed earth pressure showed middle values between those of Peck's and Tschebotarioffs apparent earth pressures. It was also observed that, when excavation depth is deep, values of the earth pressures from the rigid wall were similar to those estimated from conventional earth pressure distribution shape proposed for flexible walls.