• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.391-398
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• 2000

To evaluate the seismic performance of a base isolated building accurate analytical model should be selected. The analytical results such as reduced accelerations member forces and relative displacements of the superstructure of the base isolated building are only meaningful when the analytical model is close enough to the real structure. Real size one bay-two story steel frame and two kinds of seismic isolators(laminated elastomeric bearing and lead-rubber bearing) are designed. manufactured and constructed in the laboratory. Free vibration tests using fuse bars were conducted to evaluate the change of dynamic characteristics(period and damping) before and after base isolation of the steel frame. The experimental results of free vibration tests were also used as a bench mark for adjusting the selected analytical modeling to real base isolated steel frame.

• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.59-66
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• 2004

This study compared the reinforcing effect of sand by Geocell to those of newly devised Tirecell$^{\circledR}$ made by waste tires, tire mat by sidewalls of tires. Plate loading tests in a large chamber were conducted for different reinforcing materials at the same conditions of relative density, embedded depth of sand. The combination of Tirecell and sidewall gives the highest increase of bearing capacity and reduction of settlement. The Geocell with the same height of Tirecell gives similar reinforcement effect to the tire mat made by sidewalls.

• Journal of Ocean Engineering and Technology
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• v.20 no.5 s.72
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• pp.63-69
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• 2006

An isolated bridge using a laminated rubber bearing provides an elastic support of continuous span and prevents the transmission of excessive seismic force from the substructure of the bridge, which uses a metal bearing, as this permits a relative displacement between the super-and substructure. Hawever, this kind of bridge is caused long periodic, as a result of enlargingtotal thickness of the rubber, since it corresponds to temperature change and increases the horizontal displacement of the superstructure. This paper uses a numerical study to describe the pounding problem between adjacent decks when subjected to a strong earthquake. Furthermore, numerical results are clarified for the buffer rubber used to mitigate the pounding force between adjacent decks.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1996.10a
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• pp.202-206
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• 1996

An experimental study of the characteristics of the repulsiveytype magnetic bearing using high Tc superconductor is presented. In field cooling superconductor has the position-stability due to a flux pinning effect and the strong damping due to hysterisis, while in zero field cooling it has the only strong repulsive force due to Meissner effect. Lift force in superconducting levitation has a hysterisis characteristics, and it is the dissipation of energy, the mechanism of damping. As the relative linear velocity between a magnet and a superconductor increases, the area of the hysterisis loop becomes smaller. It means the decrease of damping. In field cooling, the static stiffness is very nonlinear in smaller than initial gap, but almost linear in larger than initial gap.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.6
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• pp.139-146
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• 2000

The development of high performance materials is very important subject in order to enhance the properties of bearings whose role is to transfer energy harmoniously by reducing the problem of friction and wear down, etc. between the interacting solid surfaces in relative motion under high loads in comply with mechanical operating mechanism of engines. In this study, several (100-x)Al-xSn coating films (where x=85, 75, 65 atomic % at Al) on substrates which are abt. 2mm thickenss of Kelmet layer sintered back steel were prepared by using RF sputtering system. These coating films were observed the morphology by SEM(Scanning Electron Microscope) and investigated the crystal structure by XRD(X-ray Diffractor) for their properties. And friction coefficient of these films was measured by ball-on-disc tester for their tribological properties. From the experimental results, it was shown that high performance properties of bearing can be improved greatly by controlling the composition and morphology of material surface with effective use of the plasma-assisted sputtering process.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.6
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• pp.52-63
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• 1995

This paper presents a detailed derivation of the equations of motion for the stable member of a four-axis platform. Gimbal bearing friction is considered for motion analysis. First, dynamic characteristics of platform, gimbal and gyro with Coulomb friction are studied due to vehicle's angular motion. Second, Vehicle's motion is assumed the sinusoidal function and dynamic characteristics of platform, gimbal and gyro are studied. Conclusively, considering effects of Coulomb friction, they could not follow the vehicle's angular motion and have constant errors. In case of sinusoidal motion, relative angles for each gimbal are amplified, but they are sinusoidal function with almost the same phases.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.6
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• pp.803-809
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• 2018

Generally, the gap-and-sag method is used in the shipbuilding stage before coupling the shafts to check whether they are installed at the same position as designed and derived from shaft alignment calculation. The primary installed propeller shaft becomes a reference point, the position of the remaining shafts are sequentially determined through the gap-and-sag value derived from the deflection and deflection angle at each shaft flange by own weight. If the reference point varies against the design value, it would have a series of effects on the installation of the remaining shafts. Moreover, after coupling the shafts, even if the bearing reaction forces derived from measurement are satisfied by the allowable limit range, consequently it might have an adverse effect on the stability of the shafting system by not being able to estimate the relative slope angle between the propeller shaft and the after-stern tube bearing. In this paper, to deal with above-mentioned phenomenon, the theoretical calculations related to designing an effective support point of the aft stern tube bearing and analysis by measurement is conducted through a case of open-up inspections. Based on this, a shaft installation guideline is proposed to minimize the misalignment related to preventing wiping damage of the after-stern tube bearing.

• Journal of the Korean Geotechnical Society
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• v.24 no.12
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• pp.13-22
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• 2008

Fourteen calibration ehamber tests were performed using one cylindrical and two tapered piles with different taper angles to investigate the changes of the bearing capacity of tapered piles with soil state and taper angle of piles. The results of calibration chamber tests show that the ultimate base resistance of tapered piles increases with increasing mean stress and relative density of soil. It also increases with increasing taper angle for medium sand, but with decreasing taper angle for dense sand. The ultimate shaft resistance of tapered piles increases as vertical and horizontal stresses, relative density and taper angle increase. Based on the results of model pile load tests, a new design method with shape factors for estimation of the bearing capacity of tapered piles is proposed considering the effect of soil state and taper angle on bearing capacity of tapered piles. In order to check the accuracy of predictions calculated using the new method, middle-scale field pile load tests were also conducted on cylindrical and tapered drilled shafts in clayey sand. Comparison of calculated values with measured ones shows that the new design method produces satisfactory predictions tor tapered piles.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.3
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• pp.191-197
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• 2016

The shaft system of a vessel becomes stiffer because of larger engine power, whereas the hull structure becomes more flexible because of scantling optimization conducted by using high-tensile thick steel plates. The draught-dependent deformation of the hull affects each bearing offset and reaction force comprising the subsequent shaft system. This is the reason that more sophisticated shaft alignments are required. In this study, an FE analysis performed under the expected operating conditions of two (2) vessels, as maximum draught change and to analyze the shaft alignment using the relative bearing offset change, which was derived from an FE analysis of the 50,000 DWT oil/chemical tanker, which has become an eco-friendly vessel in recent years. Based on this, the influence of the hull deflection on the bearing offset was reviewed against results for shaft alignment conditions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.4
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• pp.915-922
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• 1994

This paper presents a new method of soil improvement by using semi-flexible vertical reinforcing elements which shows promise for future work. Load tests were conducted on two model footings in a sand box using unreinforced sand and also by reinforcing the sand with vertical reinforcing elements. The ultimate bearing capacity for the unreinforced and reinforced sand has been compared. The effect of length, spacing, lateral extent of the reinforcement, and the initial relative density of sand in increasing the ultimate bearing capacity have been evaluated. The effect of roughness of the reinforcing elements has also been investigated. Based on the results of these model footing tests, it appears that significant improvement in the ultimate bearing capacity of loose and medium sands can be achieved by reinforcing with vertical elements.