• Korean Journal of Remote Sensing
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• v.37 no.6_2
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• pp.1793-1801
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• 2021

From 2015 to June 2020, the backscattering coefficients of 532 and 1064 nm measured using LIDAR and the depolarization ratio at 532 nm were used to separate the backscattering coefficient at 532 nm as three types as PM₁₀, PM_2.5-10, PM_2.5 according to particle size. The mass extinction efficiency (MEE) of three types was calculated using the mass concentration measured on the ground. The overall mean values of the calculated MEE were 5.1 ± 2.5, 1.7 ± 3.7, and 9.3 ± 6.3 m²/g in PM₁₀, PM_2.5-10, and PM_2.5, respectively. When the mass concentration of PM₁₀ and PM_2.5 was low, higher than average MEE was calculated, and it was confirmed that the MEE decreased as the mass concentration increased. When the MEE was calculated for each type according to the mixing degree of Asian dust, PM_2.5-10 was twice at pollution aerosol as high as 2.1 ± 2.8 m²/g, compare to pollution-dominated mixture, dust-dominated mixture, and pure dust of 1.1 ± 1.8, 1.4 ± 3.3, 1.1 ± 1.5 m²/g, respectively. However, PM_2.5 MEE showed similar values irrespective of type: 9.4 ± 6.5, 9.0 ± 5.8, 10.3 ± 7.5, and 9.1 ± 9.0 m²/g. The MEE of PM₁₀ was 5.6 ± 2.9, 4.4 ± 2.0, 3.6 ± 2.9, and 2.8 ± 2.4 m²/g in pollution aerosol (PA), pollution-dominated mixture (PDM), dust-dominated mixture (DDM), and pure dust (PD), respectively, and increased as the dust ratio value decreased. Even if the same type according to the same mass concentration or Asian dust mixture was shown, as the PM_2.5/PM₁₀ ratio decreased, the MEE of PM_2.5-10 decreased and the MEE of PM_2.5 showed a tendency to increase.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.4
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• pp.287-295
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• 2012

Hydrodynamic performance of a movable submerged breakwater was analyzed using energy dissipation model. Based on two-dimensional boundary element method the equation of motion including a viscous dissipation term proportional to velocity squared was solved by Newton-Raphson method. Energy dissipation coefficients as well as reflection and transmission coefficients of a submerged flat plate were calculated with various plate lengths and thickness. Both real and imaginary components of body displacement and forces were used to solve the motion of breakwater accurately. The effect of the magnitude of dissipation coefficient on the body displacement was evaluated. The results from the potential theory with no dissipation term were found to be an overestimate in resonance frequency.

• 한국해양학회지
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• v.9 no.2
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• pp.59-64
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• 1974

Relative light intensity was observed with underwater illuminometer (Cs Photoelectric cell, glass window) at the mouth of Yeong-il Bay, and relative vertical clearness and extinction coefficient were calculated from the relative light intensity data. Relationship between extinction coefficient and transparency in this region is also shown.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.44-48
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• 2011

본 연구에서는 구조물 상치에 에어챔버를 설치하여 챔버 내부의 공기주입량에 따라 흘수심을 조절 할 수 있는 유공 및 투수성부유식방파제를 사용하였으며, 부유식방파제의 흘수심구간에 유공을 두어 내부의 흐름에 따른 에너지소산 효과를 수리모형실험을 통하여 분석하였다. 기존 연구에 의하여 선행되어진 부유식방파제의 형상은 구조물 제체의 입사면과 투과면이 막힌 형태의 연구가 대다수였으나, 계류라인의 장력에 따른 부체의 안정성을 고려하여 본 수리모형실험에서는 입사면 흘수심구간과 투과면 흘수심구간에 유공 및 투수층을 두어 진행하는 입사파랑을 일부 흡수하도록 하였다. 또한, 부유식방파제 흘수심단면의 내부에서 흐름변화에 의한 에너지소산 효과와 입사면과 투과면의 유공률 변화에 따른 방파성능을 무공 부유식방파제와 비교하며 효율성을 분석하였다.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.22-28
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• 2000

The fiber reinforced composite materials is widely used in aircraft, space structures and robot arms because of high specific strength and high specific modulus. The on-line cure monitoring during the cure process of the composite materials has become an important research area for the better quality and productivity. In this paper, the dielectric circuit of the wheatstone bridge type for measuring the dissipation factor was designed and manufactured. Also, the dielectric sensor for the cure monitoring of the high temperature composites was developed. The residual thermal stresses of the dielectric sensor were analyzed by the finite element method and its dielectric characteristics under high temperature were evaluated. The on-line cure monitoring of the BMI resin was performed using the wheatstone bridge type circuit and developed high-temperature dielectric sensor.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1995.06b
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• pp.7-13
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• 1995

현재 교통인구 비중에 큰 비중을 차지하고 있는 철도 차량은 기술의 발전으로 인한 고속화에 성공하여 300km/h대의 속도를 달성하기에 이르렀다. 열차가 고속화됨으로 인하여 열차 주행시 운동에너지가 더욱 커졌고 이를 소산하기 위한 제동 역시 더욱 중요하게 되었다. 열차의 제동시 중요한 점은 wheel의 skidding을 방지함으로 wheel의 편마멸을 줄이는 것이며 이를 위해선 제동장치의 설계시 wheel과 rail간의 점착현상의 이해가 필수적이다. 제동력이 점착력보다 클 경우는 skidding이 발생하며 제동력이 점착력보다 작은 경우는 충분한 제덩을 하지 못한다는 것을 의미한다. 그러므로 열차의 제동장치를 설계함에 있어서 점착계수는 필수적인 요소가 되었으며 미국, 일본, 독일 등의 선진 각국에서는 점착계수를 측정하여 그 특성을 파악하려는 실험이 실험실 및 실차 차원에서 많이 행하여졌다. 각각 다른 접척조건, 속도 등에 따른 실험이 진행되어 왔으나 각 연구의 결과는 조금씩 다른 결향을 나타내었고, 점착현상에 관한 물리적인 설명은 못하고 있는 실정이다. 본 연구에서는 wheel과 rail의 접촉인 경우에 있어 점착현상의 변화를 속도, 하중, 접촉조건에 따른다고 보고 점착현상의 특성을 각각 sliding, pure rolling실험을 통해 파악하고 기타 참고문헌에서 발표된 점착계수와 비교하여 물리적으로 이해하고자 하였다.

• Korean Journal of Remote Sensing
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• v.29 no.4
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• pp.415-421
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• 2013

A new approach to retrieve the single-scattering albedo (SSA) of Asian dust plume, mixed with pollution particles, using multi-wavelength Raman lidar system was suggested in this study. Asian dust plume was separated as dust and non-dust particle (i.e. spherical particle) by the particle depolarization ratio at 532 nm. The vertical profiles of optical properties (the particle extinction coefficient at 355 and 532 nm and backscatter coefficient at 355, 532 and 1064 nm) for non-dust particle were used as input parameter for the inversion algorithm. The inversion algorithm provides the vertical distribution of microphysical properties of non-dust particle only so that the estimation of the SSA for the Asian dust in mixing state was suggested in this study. In order to estimate the SSA for the mixed Asian dust, we combined the SSA of non-dust particles retrieved by the inversion algorithms with assumed the SSA of 0.96 at 532 nm for dust. The retrieved SSA of Asian dust plume by lidar data was compared with the Aerosol Robotics Network (AERONET) retrieved values and showed good agreement.

• Journal of the Korean Geotechnical Society
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• v.22 no.1
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• pp.53-61
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• 2006

Soil liquefaction occurs by complex dynamic interaction between soil particles and pore fluid. Therefore, experimental researches have been widely performed to analyze liquefaction phenomena. In this research, centrifuge tests were performed to analyze the liquefaction behavior of horizontal sand ground. Centrifugal acceleration was 40g and the thickness of model ground was 25cm, which simulates 10m thickness in prototype scale. Viscous fluid was used as pore fluid to remove the time scaling difference between dissipation and dynamic shaking. Test results showed that the dissipation of excess pore pressure is the combined behavior of solidification and consolidation. In addition, the solidification rate, the ground acceleration amplitude, and the dynamic permeability during solidification were influenced by the confining pressure.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.4
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• pp.390-399
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• 2007

In order to investigate the mixing of sea waters on the continental shelf in the northern East China Sea, Korea Ocean Research and Development Institute conducted hydrographic surveys including turbulence measurements using the R/V Eardo in August 2005 and August 2006. The turbulent kinetic energy dissipation rates based on velocity shear measurements are estimated to be $10^{-7}{\sim}10^{4}$, $10^{-7}{\sim}10^{-6}$, and $10^{-7}$ W/kg in the surface layer, bottom layer, and lower thermocline, respectively. The data sets suggest that surface layer water is being constantly mixed by winds. High dissipation rate in the lower thermocline seems to be caused by internal waves. The bottom layer with high dissipation rate also shows high turbidity, indicating the effect of tidal stirring turbulence. The vertical eddy diffusivities are $10^{-3}{\sim}10^{-2}m^2/s$ near the bottom, and these high values appear to arise from both the low stability and high turbulent mixing.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.4192-4200
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• 2015

In this paper, dispersibility of steel fiber is improved mixing with form for material development of protection and blast resistant structure sprayed concrete. And it is developed a high toughness cellular sprayed concrete material using steel fiber. Oversupply form for dispersibility improvement of steel fiber is mostly fade away through sprayed, finally it is satisfied with the proper mixing ratio under 3 % ~ 6 %. This is considered for compressive strength and flexural toughness. Test results of compressive strength showed superior strength capability in 28, 56 days, also flexural strength and flexural toughness is great. Then oversupply form is enhanced for dispersibility of steel fiber and I think that it did not cause decreasing of strength. But analysis results of pore structure through image analysis failed for a great spacing factor and specific surface area. This is largely measured in spacing factor because air content have a grate evaporation effect for sprayed.