• Journal of the Microelectronics and Packaging Society
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• v.15 no.3
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• pp.35-40
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• 2008

Investigation on immersion gold layers was carried out using TEM analysis for the purpose of understanding the defect of immersion gold layer. The immersion gold layers prepared with three different types of baths were observed. The results showed that the defect structure of immersion gold layer is strongly dependent on the types of gold baths. Spherical defects of average 10 nm size were located along the grain boundaries for the specimen formed at KAu$(CN)_2$ bath containing no reducing agent. In the case of the specimen processed at KAu$(CN)_2$ bath containing a reducing agent, the spherical defects of 5-10 nm size were distributed randomly in grains as well as at grain boundaries. However, such defects disappeared almost completely when $Na_{3}Au(SO_3)_2$ bath was used to fabricate an immersion gold.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2001.11a
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• pp.45-45
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• 2001

종이 표변에 전분 사이징을 하는 목적은 종이가 액체에 대하여 침투저항성을 부여하 여 종이의 인쇄적성을 향상시키며 아울랴 종이의 표면적성과 종이강도 등의 물리적 특 성을 향상시키기 위해서 사용된다. 표면 사이징은 기본적으로 종이 표면에 전분을 이용 한 필름을 형성하여 종이 표면의 공극크기를 줄여 인쇄잉크 등과 같은 액체의 침투속 도를 늦여준다. 현재 국내에서 널리 사용되는 표면 사이징용 전분으로는 산화전분과 자 가변성용 일반전분이 있다. 자가변성용 전분은 효소나 APS로 전분의 chain 길이를 적 당한 점도로 잘라주는 것으로 전분 호액의 노화가 쉽게 일어나는 경향이 있다. 산화전 분은 전분회사에서 산화제를 이용하여 전분의 점도를 사용자의 요구에 따라 조절한 것 으로 water holdout이 개선되고 자가변성용 전분보다는 노화 안정성이 개선되지만 종 이 내부로의 칩투가 많이 일어나 전분 필름 강도가 약해지며 표면 강도 향상 효과가 적고 종이의 광학적 특성을 저하시키는 단점을 지니고 있다. 또한 약 10 ~ 20% 정도 사 용되는 파지의 재활용시 펄프 섬유에 흡착되지 않는 전분으로 인해 백수 내의 COD 및 B BOD를 증가시키는 원인이 된다.따라서 본 연구에서는 펄프 섬유와 친화력이 높아 지료 내첨용 지력증강제로 널리 사용되고 있는 양성 전분의 양이온 치환도 및 점도를 사이즈 프레스에 적합하게 조절 하여 백상지 제조업체의 라언에 적용하였다. 결과분석 항목으로는 파지 재활용에 따른 백수내 COD, 칼숨 이온함량 등의 백수 시스템의 변화와 종이의 물리적, 광학적 특성 및 ink jet 용지의 인쇄적성 등을 측정하여 산화전분과 비교하였다. 그 결과 약 20%의 C COD 감소 효과와 10%정도의 OPR 향상 효과를 얻을 수 있었다. 종이 물성의 경우 인 장강도와 뺏뺏이(stiffness) 및 지분 등을 측정한 결과 산화전분 보다 향상되었다. 특히 지분의 경우, 참여한 회사의 지분관련 complain이 약 80% 정도 감소하는 결과를 나타 내었다. 또한 백상지의 경우 ink jet 프린터에 많이 사용됨으로 ink jet 프린터의 인쇄 적성을 image analyzer로 측정한 결과 산화전분 보다 향상된 결과를 나타내었다.

• Transactions of the Korean hydrogen and new energy society
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• v.18 no.3
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• pp.223-229
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• 2007

여과막 생물반응기를 이용하여 $60^{\circ}C$에서 혐기 세균 복합체가 포도당으로부터 수소를 생산할 수 있는 최적조건을 연구하였다. 여과막 생물반응기는 연속교반 탱크반응기와 외부에 장착된 PVDF (polyvinylidene fluoride) 중공사막 여과장치로 구성되었다. 접종슬러지는 하수처리장 소화 슬러지조에서 얻었고, 포자형성 수소생산 미생물을 얻기 위해 $90^{\circ}C$에서 20분 간 열처리하였다. 16S rRNA PCR-DGGE(polymer chain reaction-denaturing gradient gel electrophoresis) 분석을 통해 열처리 전후의 미생물상 변화를 조사하였다. 열처리 후 DGGE 밴드의 수는 감소하였고, 주요 밴드는 Clostridium perfringens와 유사한 염기서열을 나타내었다. 운전 기간 동안 바이오가스 내 수소함량은 60%(v/v)를 유지하였고, 메탄은 검출되지 않았다. 연속교반 탱크반응기를 여과막 없이 수력학적 체류 4시간에서 운전하였을 때 공급된 포도당의 95.0%가 제거되었고, 이때 균체농도 및 수소생산속도는 각각 1.35 g cell/L 및 7.4 L $H_2$/L/day이었다. 동일한 체류시간에서 PVDF중공사막 여과장치를 장착하여 연속교반 탱크반응기를 운전하였을 때, 균체농도는 1.62 g cel/L로 증가하였고 높은 포도당 제거율(99.5%) 및 수소생산속도(8.8 L $H_2$/L/day)가 관찰되었다. 40 nm 및 100 nm의 공극크기를 가진 여과막은 균체농도 및 수소생산 측면에서 유사한 성능을 나타내었다. 여과막 생물반응기는 여과막의 반복적인 세척을 통해 30일 이상 안정적으로 운전될 수 있었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.2
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• pp.25-33
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• 1984

The effect of particle size on adsorption of trihalomethane have been studied. Using mean particle sizes ranging from 0.73 to 2.03 mm, physical properties of carbon and trihalomethane adsorption characteristics have been investigated experimentally. With increasing particle size specific surface area and pore volume decreased, and the mean pore radius increased significantly. Large pores were dominant in large particles, while small particles were composed of small pores. Isotherm studies were conducted using static bottle point technique and the results were well described by the Freundlich isotherm equations. The adsorption capacity increased significantly with decreased particle size. Additionally micro-column tests were carried out, and the results were compared with the model simulation. From the micro-column studies it was found out that the film transfer coefficient were almost constant, and the differences in the trihalomethane removal efficiency was mainly due to the differences in the adsorption capacity of the particles of different size.

• Journal of IKEEE
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• v.10 no.2 s.19
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• pp.161-167
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• 2006

The effect of aging on the optoelectronic properties of a single ZnO nanowire is investigated in this study. The photoluminescence (PL), photocurrent spectrum, current-voltage characteristics, and photoresponse were measured for the as-grown ZnO nanowire and for the same nanowire exposed to air for three months. For the aged nanowire, the broad PL band is weaker, the intensity of the photocurrent is strengthened, and the photoresponse is slower, compared with the as-grown nanowire. It Is suggested in this paper that the observed aging effect on the PL is due to the reduction in the number of oxygen vacancies within the nanowire and that the aging effect on the photocurrent and photoresponse originates from the formation of oxygen vacancies near the surface.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.10
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• pp.865-871
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• 2016

In recent years, traditional scaffold fabrication techniques such as gas foaming, salt leaching, sponge replica, and freeze casting in tissue engineering have significantly limited sufficient mechanical property and cell interaction effect due to only random pores. Fused deposition modeling is the most apposite technology for fabricating the 3D scaffolds using the polymeric materials in tissue engineering application. In this study, 3D slurry mould was fabricated with a blended biphasic calcium phosphate (BCP)/Silica/Alginic acid sodium salt slurry in PCL mould and heated for two hours at $100^{\circ}C$ to harden the blended slurry. 3D dual-pore BCP/Silica scaffold, composed of macro pores interconnected with micro pores, was successfully fabricated by sintering at furnace of $1100^{\circ}C$. Surface morphology and 3D shape of dual-pore BCP/Silica scaffold from scanning electron microscopy were observed. Also, the mechanical properties of 3D BCP/Silica scaffold, according to blending ratio of alginic acid sodium salt, were evaluated through compression test.

• Korean Journal of Optics and Photonics
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• v.17 no.3
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• pp.290-295
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• 2006

The coupling between copper wire and a THz electromagnetic wave is one of the important factors to build up the magnitude and spectrum of a THz wave. We measured a I THz spectrum range THz pulse into a $480{\mu}m$ diameter and 23cm long copper wire waveguide. We measured THz pulses up to $275{\mu}m$ air gap between the end of the copper wire and transmitter or receiver chips. The coupling sensitivity of the transmitter is 3 times bigger than that of the receiver. The THz pulses propagated to air by the end of the receiver-side copper wire tip acting as a transmitter antenna. We confirmed that the THz field concentrates near the copper wire surface by opening the pin hole to the copper wire waveguide.

• Resources Recycling
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• v.21 no.1
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• pp.75-81
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• 2012

Porous pellets for immobilizing heavy metals were manufactured from coal tailings and iron oxide powder. Coal tailings was pulverized and mixed with iron oxide powder. The mixed powder was granulated into spherical pellets and roasted. Over $1100^{\circ}C$, residual coal in coal tailings reduced iron oxide to ZVI(Zero-Valent Iron). The pellets have 34.63% of porosity, 1.31 g/mL of bulk density, and 9.82.urn median pore diameter. The pellets were reacted with synthetic solutions containing each heavy metals: arsenic(V), copper(II), chrome(VI), and cadmium(II), respectively. On the test of immobilizing heavy metal, the pellets made at $1100^{\circ}C$ were superior to the other pellets made under $1000^{\circ}C$. Immobilizing over 99.9% of 10ppm heavy metal solutions required I hour for arsenic, 2 hours for chrome, and 4 hours for copper. However, immobilizing capacity of cadmium was inferior to that of the other metals and it was decreased in reversely proportion to initial concentration of the solutions.

• Journal of Korea Water Resources Association
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• v.54 no.11
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• pp.863-873
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• 2021

The mechanical dispersion which dominates solute transport in porous media is caused by the difference in flow velocity within pores. Longitudinal dispersion coefficient and longitudinal dispersivity that are hydro-dispersive parameters of advection-dispersion equation can only be obtained by experiment. Hydraulic mean radius that represents the amount and intensity of flowing water within pores can be obtained by the formula using the factors for physical properties. A slug injection test was conducted and a power type empirical formula for obtaining a longitudinal dispersivity using a hydraulic mean radius in rockfill porous media was derived. It is possible to obtain the longitudinal dispersivity depending on transport distance because it contains a formula for a scale constant, and expected to be applicable to waterways filled with homogeneous gravel and small flow rate.

• Korean Journal of Environmental Agriculture
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• v.22 no.1
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• pp.60-64
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• 2003

This study was conducted to examine the effects of plug tray cell size and growth media on good seedling production of Gerbera hybrida Hort. Seedlings were grown for 60 days in 50, 72, 128, 162 cell trays contanning perlite, cocopeat and perlite+cocopeat(1:1, v/v). Perlite showed higher bulk density than cocopeat and perlite+cocopeat. Total porosity was greater in perlite, cocopeat and perlite+cocopeat in order. Cocopeat showed the highest water holding capacity. Number of leaves were greatest in 128 cell tray containing cocopeat. Leaf area was greatest in 50 cell tray containing cocopeat. Seedling growth was also better in plug tray of bigger cell size. Seedling growth of fresh and dry weight of shoot and root was much better in the growth media of perlite+cocopeat.