• 한국결정성장학회지
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• 제15권4호
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• pp.152-156
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• 2005

아코야 진주의 양식은 수산화아파타이트로 제조한 바이오 진주핵을 사용하여 행하였다. 양식된 아코야 진주는 대부분 크림색을 나타내었으며, 다양한 진주층에서 빛의 활동으로 인한 광택과 오리엔트효과는 매우 뛰어났다. 진주층은 아라고나이트형 탄산칼슘임을 XRD 분석 결과로부터 알았다. 그리고 SEM 관찰 결과, 아라고나이트형 탄산칼슘과 콘키올 린은 규칙적인 층상구조를 이루고 있었다. 이상의 결과로부터: 바이오 진주핵을 이용하여 양식한 아코야 진주의 특성은 섭 조개로 만든 진주핵으로 양식한 아코야 진주와 동일함을 알았다. 본 연구에서 개발한 바이오 진주핵은 진주의 크기, 형상 등을 자유롭게 할 수 있기 때문에 아코야 진주의 양식에 매우 유리하다.

• 한국군사과학기술학회지
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• 제12권3호
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• pp.266-271
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• 2009

Electronic equipments and a missile carried by heavy trucks are often subjected to vibration and shock excitation during their transportation. Electronic equipments are so vulnerable to vibration and shock input that it is necessary to know in advance the vibration level of the truck which cause the damage of equipments. Road tests of a heavy truck carrying a canister on different road conditions such as paved road, unpaved road, and washboard are performed and the effect of road conditions on the vibration characteristics are analyzed. Vibration levels were measured at various locations of the truck along the path through which vibration was transmitted. This study reveals that the velocity of the truck as well as the road surface conditions are main factors which affect the vibration levels of the truck. The power spectrum density of the measured vibration signal and the factors affecting the PSD are also analyzed in this paper.

• 한국도로학회논문집
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• 제20권1호
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• pp.9-18
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• 2018

PURPOSES : In this research, the initiation and development of corrugation on a gravel road with certain wheel and boundary conditions were evaluated using a coupled discrete-element method (DEM) with multibody dynamics (MBD). METHODS : In this study, 665,534 particles with a 4-mm diameter were generated and compacted to build a circular roadbed track, with a depth and width of 42 mm and 50 mm, respectively. A single wheel with a 100-mm diameter, 40-mm width, and 0.157-kg mass was considered for the track. The single wheel was set to run slowly on the track with a speed of 2.5 rad/s so that the corrugation was gradually initiated and developed without losing contact between the wheel and the roadbed. Then, the shape of the track surface was monitored, and the movement of the particles in the roadbed was tracked at certain wheel-pass numbers to evaluate the overall corrugation initiation and development mechanism. RESULTS : Two types of corrugation, long wave-length and short wave-length, were observed in the circular track. It seems that the long wave-length corrugation was developed by the longitudinal movement of surface particles in the entire track, while the short wave-length corrugation was developed by shear deformation in a local section. Properties such as particle coefficients, track bulk density, and wheel mass, have significant effects on the initiation and development of long-wave corrugation. CONCLUSIONS : It was concluded that the coupled numerical method applied in this research could be effectively used to simulate the corrugation of a gravel road and to understand the mechanism that initiates and develops corrugation. To derive a comprehensive conclusion for the corrugation development under various conditions, the driver's acceleration and deceleration with various particle gradations and wheel-configuration models should be considered in the simulation.