• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.6 s.336
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• pp.23-30
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• 2005

In this paper, OPPS(oxidized porous poly-silicon) field emitters were fabricated by using various emitter-electrode metal and these electron emission characteristics were investigated for different thermal annealing effects. The addressed OPPS field emitter with Pt/Ti emitter electrode annealed at $300^{\circ}C$-1hr showed the efficiency of $2.98\%$ at $V_{ps}$=12 V and one annealed at $350^{\circ}C$-1hr showed the highest efficiency of $3.37\%$at $V_{ps}$=16V. They are resulted from the improvement of interfacial contact characteristics of thin emitter metal to an oxidized porous poly-silicon and the decrease of electrical resistance of emitter metal. The brightness of the OPPS field emitter increases linearly in $V_{ps}$ and after oxidation process for $900^{\circ}C$-50min, the brightness of the OPPS field emitter with the as-deposited Pt/Ti emitter electrode was 3600 cd/$m^2$ at the $V_{ps}$=15 V, 6260 cd/$m^2$ at the $V_{ps}$=20 V. Thermal treatment improved the adhesion between the Ti buffer layer and the oxidized porous poly-silicon and also played an important role in the uniform distribution of electric field to the emitter electrode.

• Journal of the Korean Ceramic Society
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• v.39 no.12
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• pp.1153-1157
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• 2002

The fabrication of a three-layered asymmetric ceramic membrane was performed by slip casting of the porous alumina support and dip coating of the alumina intermediate layer using high purity ${\alpha}-Al_2O_3$ powders that have different particle size, followed by screen printing-pyrolysis of the $Tio_2$ layer as an ultrafilteration membrane using Ti-naphthenate solution. The bending strength, porosity and mean pore size of the alumina support were 231 kg/$cm^2$s, 30.26% and 0.19 ${mu}m$, respectively. The thickness of the intermediate layer was 30 ${mu}m$ and the mean pore size of that was 0.063 ${mu}m$. Also, the top layer was 0.5 ${mu}m$ thick and micropores with about 20 nm size were formed uniformly.

• Explosives and Blasting
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• v.29 no.2
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• pp.89-99
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• 2011

Recently on Jeju island there has been a lot of development and construction. However random distribution of porous basalt and clinker seam generated from volcanic activities often interrupt and greatly reduce efficiency of blasting necessary for construction. Three test blasts were operated to solve the inefficiency problem and results indicated that a powder factor of 0.40~0.45 $kg/cm^3$ is necessary to increase the efficiency of blasting. Also the blasting scheme should be concerned whether clinker seams exists in excavation levels or not.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.792-796
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• 2002

In this work, porous silicon(PS) layer is used as a sensing material to detect organic gases. To do this, PS sensors with membrane structure are fabricated. The sensors were made by applying the technologies of membrane formation by anisotropic etching of silicon, and PS layer formation by anodization in HF solution. From fabricated sensors, current-voltage (I-V) curves were measured against ethanol (called alcohol), methanol and acetone gases evaporated from 0.1 to 0.5% solution concentrations at $36^{\circ}C$. As the result, all curves showed rectifying behavior due to a diode structure between Si and PS, and the conductance of sensor devices increased largely with the organic solution concentration at high voltage of 5V.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.1014-1016
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• 1998

A capacitance-type humidity sensor using porous silicon layer is developed. The unique property of this sensor is a structure which has electrodes on the surface of the wafer like a general IC device. To do this. the sensor was fabricated using process such as localized formation of porous silicon, oxidation of porous silicon layer, and etching of oxidized porous silicon layer. The measurement of humidity-sensing ability was done for two type of sensors using porous silicon layer formed in 25 and 35% HF solutions, respectively. As the result, the former sensors showed larger value and variation of capacitance for the relative humidity.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.04a
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• pp.132-135
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• 2001

To understand and compare tracer transport in fractured and porous media. multiple tracer tests were conducted in Wonju and Uiwang sites. The target media were fractured in Wonju site and porous in Uiwang site. It was known that groundwater flow for the two hydrogeologic systems could be represented using a EPM approach. However, the tracer transport in the two aquifer systems was greatly different. In this study, we analyzed the different tracer transport behavior in the two systems, from which our understanding of the tracer dispersion was greatly enhanced. we used bromide and chloride as tracers.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.157-160
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• 2000

흡음원리의 측면에서 저음의 흡음은 재료 자체에서의 효과보다는 그 재료의 배열에서 발생하는 공명등의 역할이 크다. 따라서 단일흡음재료 보다는 공명체나 판상재와 다공질 흡음재, 그리고 그 배후의 공기층에 의해 구성되는 복합적 흡음구조가 더욱 효과적인 저음흡음재가 될 수 있다. 본 연구에서는 여러 가지 목재나 철제의 슬릿, 그리고 철제나 MDF 재질의 유공판을 표면재료로 하는 저음흡음구조를 설계하기 위한 준비단계로서 저음흡음구조에서 표면재료의 번화가 가져올 수 있는 흡음특성의 차이를 알아보고자 한다.

• Geophysics and Geophysical Exploration
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• v.18 no.4
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• pp.223-231
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• 2015

Self-potential (SP) is sensitive to groundwater flow and there are many causes to generate SP. Among many mechanisms of SP, pore-fluid flow in porous media can generate potential without any external current source, which is referred to as electrokinetic potential or streaming potential. When calculating SP responses on the surface due to geothermal fluid within an engineered geothermal system (EGS) reservoir, SP anomaly is usually considered to be generated by fluid injection or production within the reservoir. However, SP anomaly can also result from geothermal water fluid within EGS reservoirs experiencing temperature changes between injection and production wells. For more precise simulation of SP responses, we developed an algorithm being able to take account of SP anomalies produced by not only water injection and production but also the fluid of geothermal water, based on three-dimensional finite-element-method employing tetrahedron elements; the developed algorithm can simulate electrical potential responses by both point source and volume source. After verifying the developed algorithm, we assumed a simple geothermal reservoir model and analyzed SP responses caused by geothermal water injection and production. We are going to further analyze SP responses for geothermal water in the presence of water production and injection, considering temperature distribution and geothermal water flow in the following research.

• Journal of the Korean earth science society
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• v.21 no.5
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• pp.553-562
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• 2000

Daejeonsa basalt in the Mt. Juwang area is composed of 12 lava flows alternate with 9 peperites, and each lava and peperite has variable thickness. Globular peperites yielded in Daejeonsa basalt are mixed basalt clasts with reddish shale. Based on field description, when lava flows over unconsolidated wet shale or injectes into unconsolidated wet shale, peperites were formed at the contacts between lava and shale. Daejeonsa basalt are massive lava flows with rare vesicules: some vesicules are found in upper part of a flow unit. The basalt has mainly pseudomorphs of olivine as phenocryst, and also plagioclase and clinopyroxene phenocrysts in rocks with higher Mg-number. Matrix is mainly subophitic texture, sometimes showing ophitic and intergranular textures due to different cooling rate. Clinopyroxene is augite(Wo$_{41.6}$En$_{45.1}$Fs$_{13.3}$), and plagioclase is mostly labradorite(An$_{55.0}{\sim}_{67.7}$), but some is andesine(An$_{44.3}$) and bytownite(An$_{74.5}$). Oxide minerals are composed of titanomagnetite and ilmenite.

• Journal of Korea Water Resources Association
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• v.42 no.11
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• pp.1005-1015
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• 2009

Saltwater intrusion in coastal aquifer was investigated using a laboratory model. Salt-wedge profiles were reproduced in a porous media tank 140 cm long, 70 cm high, and 10 cm wide. The experiments were performed with various conditions of porous media hydraulic conductivity, salinity, and ground surface slope to assess relationships on salt wedge location and inclination. Salt-wedge profiles induced by saltwater intrusion were observed in porous media equilibrium state, and compared with previously derived formulas of the Glover (1959), Henry (1959) and Strack (1976). It was found that salt-wedge shape and formations were affected by the water level ratio ($H_F/H_S$) due to high hydraulic conductivity, saltwater salinity and ground surface slope. High $H_F/H_S$ of porous media having high hydraulic conductivity shifted the saltwater interface toward the saltwater reservoir. Increasing surface slope of the porous media caused the salt-wedge profile inclination to decrease. Saltwater salinity also contributed to the location of saltwater interface, yet the impact was not more significant than hydraulic conductivity.