• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.2170-2174
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• 2008

기후상승으로 해수면의 상승으로 인해 삼면이 바다로 둘러싸인 지형적 특성을 가진 우리나라 연안에 파도로부터 시설물의 보호가 중요한 요인으로 꼽히고 있다. 파의 에너지를 저감하여 연안에 위치한 시설물 보호에 많은 연구가 진행되고 있다. 여기서 다루게 될 수중방파제와 다공성 소파장치는 반사와 수심의 변화에 따른 분산효과로 입사파의 에너지 감소를 통해 연안에 위치한 구조물과 배후시설에 대한 피해를 줄이는데 주목적이 있다. 사다리꼴 수중방파제의 전 후면의 기울기를 변화시키며 장주기파의 입사파와 투과파에 대한 연구가 Chang과 Liou(2004)에 의해 연구되었고, 수직 다공성 소파장치의 두께를 변화하며 반사계수와의 상관 관계에 대한 연구가 Madsen(1983)에 의해 진행되었다. 본 연구에서는 해석해를 통해 수중방파제와 다공성 소파장치가 있는 경우에 투과파와 소파장치 전 후면에서의 처오름 높이의 변화에 대해 알아보고, 그에 따른 관계를 알아보고자 한다. 구간은 각각 수심이 일정한 지역과 변화하는 지역, 다공성 소파제가 있는 지역으로 설정하여 각 구간마다 해석해를 적용하여 파고를 측정하였다. 측정된 파고를 이용하여 투과율은 수중방파제를 통과한 입사파와 투과파의 관계를 통해 측정할 수 있다. 수중방파제를 투과한 파는 다공성 소파장치를 통과하면서 파고가 급감하는 현상을 다공성 소파장치 전 후면에서 측정되는 파고를 통해 알 수 있다.

• Journal of the Korean Society for Marine Environment & Energy
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• v.7 no.2
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• pp.82-88
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• 2004

To evaluate the tidal flow around the transmission type harbour structures, the numerical models considering hydraulic resistance are used. The traditional governing equations of depth-integratef hydrodynamics are modified by using of the drag force term. As a numerical model to evaluate the rate of tidal exchange, the Random-walk method is used. The models are applied in a design of the pile-supported pier structures in Busan harbour site, Korea, where the flow speed and the tidal exchange are more promotive than the case of non-transmission structure. The developed model will be applied usefully to design the transmission type structure in the ocean space.

• Solar Energy
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• v.14 no.2
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• pp.29-37
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• 1994

Radiative charaacteristics of glass windows and porous absorbing media which can be used for a solar air heater are determined through the measurements of spectral transmittances. Those in the visible range are measured by the UV-IR spectrometer. Refractive index of glass are obtained by the comparison of the measured transmittances and the correlations derived from the electromagnetic theory and are compared to the theoretical ones calculated from the classical dispersion theory. Absorption and back-scattering coefficients of 15-mesh stainless wire screens are calcuated by the comparison of the measured transmittances and the correlations derived from the two flux model.

• Membrane Journal
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• v.32 no.1
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• pp.50-56
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• 2022

In this work, the solvent permeation and separation performance of organic solvent nanofiltration (OSN) membranes were evaluated. Particularly, the PuraMem (PM) series developed for nonpolar solvents were analyzed and tested in dead-end filtration system. PM membranes exhibited higher permeance for nonpolar solvents compared to polar solvents, and their rejection data did not follow conventional trends with respect to solute size. The data showed that simple solution-diffusion model is not suitable to describe the OSN membrane behavior, and a better solvent-solute-membrane interaction parameter must be developed.

• Journal of the Korean Society for Railway
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• v.11 no.1
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• pp.1-6
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• 2008

Sound transmission characteristics are investigated on the test specimen for the railway vehicle's floor section. Transmission loss on the honeycomb structure has been examined experimentally with the reverberation chamber. Predicted transmission loss values using NASTRAN, AUTOSEA2, are compared with measured Haloes and the effect of resonance on the transmission loss is identified. Transmission loss of different shapes of honeycomb structure are predicted.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.15 no.4
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• pp.207-213
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• 2003

This study is to numerically investigate the characteristics of wave energy variations propagating over impermeable submerged breakwaters with irregular waves. Two-dimensional numerical wave flume based on the VOF method was used. VOF method is the most efficient capable of simulating free surfaces including wave breaking. From the computed frequency spectrum results, wave breaking play important role in ability of the submerged breakwaters to dissipate incident wave energy. In case of occurring wave breaking, our analysis shows that wave energy moves to short wave period on one-row impermeable submerged breakwater's lee side and is widely distributed not having peak period on two- row impermeable submerged breakwater's lee side.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.233-236
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• 2006

In this paper, I try to measure characteristic transmission-reflection by environmental change or solar cell. I keep my eye on the characteristics variation of solar cell as environmental change. As a result, A variation caused by voltage by an effect on the efficiency of solar PV cell. Hence, it is an important variable when a designer plan to make a solar cell.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.3
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• pp.121-129
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• 2004

The different types of coastal souctures have been constructed for the protection of coastal region from the incident waves. Among them. the permeable submerged breakwater has been widely used as a wave dissipater and sediment transport controller because of its excellent advantages in scenery effects, construction efficiency and environment aspects. This study numerically investigated the characteristics of wave energy variations and transmission coefficient at the rear of the permeable submerged breakwater installed in the irregular wave field. To analyze it's performance numerically, a two-dimensional numerical wave flume based on VOF method was used. A frequency spectral analysis showed that the spectral peak moved to the short-period in the one-row submerged breakwater, and the wave energy was distributed evenly for the whole period in the two-row submerged breakwater in the case of breaking on the submerged breakwater. The spectral peak was shown to be converged within the significant wave period at the rear of the permeable submerged breakwater in the case of non-breaking conditions. From the result of transmission coefficients analysis. it was confirmed that a considerable quantity of wave energy was transmitted to the rear of the permeable submerged breakwater in the case of non-breaking rather than breaking.

• Tunnel and Underground Space
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• v.31 no.1
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• pp.41-51
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• 2021

The hydraulic fracturing developed to improve permeability of tight reservoir is one of key stimulation technologies for developing unconventional resources such as shale gas and deep geothermal energy. The experimental study was conducted to improve disadvantage of hydraulic fracturing which has simple fracture pattern and poor fracturing efficiency. The fracturing experiments was conducted for tight rock using various fracturing fluids, water, N2, and CO2 and the created fracture pattern and fracturing efficiency was analyzed depending on fracturing fluids. The borehole pressure increased rapidly and then made fractures for hydraulic fracturing with constant injection rate, however, gas fracturing shows slowly increased pressure and less fracture pressure. The 3D tomography technic was used to generate images of induced fracture using hydraulic and gas fracturing. The stimulated reservoir volume (SRV) was estimated increment of 5.71% (water), 12.72% (N2), and 43.82% (CO2) respectively compared to initial pore volume. In addition, permeability measurement was carried out before and after fracturing experiments and the enhanced permeability by gas fracturing showed higher than hydraulic fracturing. The fracture conductivity was measured by increasing confining stress to consider newly creating fracture and closing induced fracture right after fracturing. When the confining stress was increased from 2MPa to 10MPa, the initial permeability was decreased by 89% (N2) and 50% (CO2) respectively. This study shows that the gas fracturing makes more permeability enhancement and less reduction of induced fracture conductivity than hydraulic fracturing.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.334-334
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• 2012

태양전지 기술은 우주 항공에서부터 핸드폰과 같은 소규모 가전 시설에까지 폭 넓게 사용되고 있다. 현재 태양전지 기술은 기존의 화석 에너지에 비해 효율 측면에서의 열세함으로 인해 변환 효율을 높이는 연구가 진행되고 있다. 태양전지의 기본 구조에서 고반사막을 대신하여 선택적 투과막을 채용하면 적외선 영역은 광흡수층으로 재반사시키고 가시광선 영역은 선택적으로 투과시킬 수 있기 때문에 태양전지의 변환 효율을 높임과 동시에 채광에 유리한 투명 태양전지를 얻을 수 있다. 본 연구에서는 반응성 분위기에서 AlTi 단일 타겟을 스퍼터링하여 유리 기판 위에 AlTiO 선택적 투과막을 형성하고 광학적 특성을 평가하였다. 기존의 연구에서 스퍼터링으로 형성한 AlTiO 선택적 투과막은 가시광선 영역에서 약 30%의 비교적 높은 반사율을 나타내었다. 이번 연구에서는 광학 두께를 조절함으로써 가시광선 영역에서 반사율이 평균 20% 이상 감소하고 적외선 영역에서 약 30% 이상의 반사율을 나타내는 선택적 투과막을 형성한 결과를 보고한다.