• Journal of Sensor Science and Technology
• /
• v.6 no.6
• /
• pp.476-482
• /
• 1997

A portable electronic nose system has been fabricated and characterized using an oxide semiconductor gas sensor array and pattern recognition techniques such as principal component analysis and back-propagation artificial neural network. The sensor array consists of six thick-film gas sensors whose sensing layers are Pd-doped $WO_{3}$, Pt-doped $SnO_{2}$, $TiO_{2}-Sb_{2}O_{5}-Pd$-doped $SnO_{2}$, $TiO_{2}-Sb_{2}O_{5}-Pd$-doped $SnO_{2}$ + Pd coated layer, $Al_{2}O_{3}$-doped ZnO and $PdCl_{2}$-doped $SnO_{2}$. The portable electronic nose system consists of an 16bit Intel 80c196kc as CPU, an EPROM for storing system main program, an EEPROM for containing optimized connection weights of artificial neural network, an LCD for displaying gas concentrations. As an application the system has been used to identify 26 carbon monoxide/hydrocarbon (CO/HC) car exhausting gases in the concentration range of CO 0%/HC 0 ppm to CO 7.6%/HC 400 ppm and the identification has been successfully demonstrated.

• KSBB Journal
• /
• v.24 no.2
• /
• pp.207-211
• /
• 2009

In this study, the sensing membranes for detection of pH and dissolved oxygen(DO) were prepared by immobilizing 6-aminofluorescein or ruthenium complex onto the sol-gel matrixes of GPTMS, MTMS, and TEOS and then recoated with the mixture of hydrophobic sol-gel and graphite for light insulation. The pH and DO sensing membranes recoated with the light insulation layer showed a higher sensitivity than those without light insulation layer. The sensing membranes were immobilized on the wells of 24-well microplate and used to monitor the fluorescence intensity for pH and DO in E.coli JM109 and P.pastoris X-33 fermentation processes. The change of the fluorescence intensity in the DO sensing membrane agreed with the growth patterns of microorganisms, that the membranes are valuable to monitor the DO in fermentation processes. In the case of pH monitoring, the fluorescence intensity has showed good correlation to the off-line pH data, that the pH membranes are valuable to monitor pH values in fermentations.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.13 no.5
• /
• pp.254-259
• /
• 2003

In the fabrication process of transparent conducting thin films of the ATO (antimony-doped tin oxide) on a soda lime glass substrate by a sol-gel dip coating method, the effects of the $SiO_2$ buffer layer formed on the substrate and $N_2$ annealing treatment were investigated by XPS (X-ray photoelectron spectroscopy) analysis. Optical transmittance and electrical resistivity of the 400 nm-thick ATO thin films which were deposited on $SiO_2$ buffer layer/soda lime glass and then annealed under nitrogen atmosphere were 84 % and $5.0\times 10^{-3}\Omega \textrm{cm}$ respectively. The XPS analysis confirmed that a $SiO_2$ buffer layer inhibited Na ion diffusion from the substrate, resulting in prohibiting the formation of a secondary phase such as $Na_2SnO_3$ and SnO and increasing Sb ion concentration and ratio of $Sb^{5+}/Sb^{3+}$ in the film. And it was also found that $N_2$ annealing treatment leads to the reduction of $Sn^{4+}$as well as $Sb^{5+}$ however the reduction of $Sn^{4+}$ is more effective and therefore consequently results in decrease in the electrical resistivity to produce an excellent electrical properties of the film.

• Journal of Advanced Marine Engineering and Technology
• /
• v.39 no.7
• /
• pp.779-785
• /
• 2015

Cathodic protection is recognized as the most cost-effective and technically appropriate corrosion prevention method for the submerged zone of offshore structures, ships, and deep-sea facilities. When cathodic protection is applied, the cathodic currents cause dissolved oxygen reduction, generating hydroxyl ions near the polarized surface that increase the interfacial pH and result in enhanced carbonate ion concentration and precipitation of an inorganic layer whose principal component is calcium carbonate. Depending on the potential, magnesium hydroxide can also precipitate. This mixed deposit is generally called "calcareous deposit." This layer functions as a barrier against the corrosive environment, leading to a decrease in current demand. Hence, the importance of calcareous deposits for the effective, efficient operation of marine cathodic protection systems is recognized by engineers and scientists concerned with cathodic protection in submerged marine environments. Calcareous deposit formation on a marine structure depends on the potential, current, pH, temperature, pressure, sea-water chemistry, flow, and time; deposit quality is significantly influenced by these factors. This study determines how calcareous deposits form in sea water, and assesses the interrelationship of formation conditions (such as the sea water temperature and surface condition of steel), deposited structure, and properties and the effectiveness of the cathodic protection.

• Journal of the Microelectronics and Packaging Society
• /
• v.13 no.4
• /
• pp.51-56
• /
• 2006

Polymer light emitting diodes (PLEDs) with ITO/EDOT:PSS/PVK/PFO-poss/LiF/Al structures were prepared by the spin coating method on ITO(indium tin oxide)/glass substrates. PFO-poss[Poly(9,9-dioctylfluorenyl-2,7-diyl) end capped with poss] was used as light emitting polymer. PVK[poly(N-vinyl carbazole)] and PEDOT:PSS [poly(3,4-ethylenedioxythiophene):poly(styrene sulfolnate)] polymers were used as the hole injection and transport materials. The effect of PFO-poss concentration and the heating temperatures on the electrical and optical properties of the devices were investigated. At the same concentration of PFO-poss solution, the current density and luminance of PLED device tend to increase as the annealing temperature increase from $100^{\circ}C$ to $200^{\circ}C$. The maximum luminance was found to be about 958 cd/m2 at 13V for the PLED device with 1.0 wt% PFO-poss at the annealing temperature of $200^{\circ}C$. In addition, the PLED device showed bluish white emission through the strong greenish peak with 523 nm in wavelength. As the concentration of PFO-poss increase from 0.5 wt% to 1.0 wt% and temperature of PLEDs increase from $100^{\circ}C$ to $200^{\circ}C$, the emission color tend to be shifted from blue with (x, y) = (0.17,0.14) to bluish white with (x, y) : (0.29,0.41) in CIE color coordinate.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.338-338
• /
• 2012

사파이어 ($Al_2O_3$)는 높은 밴드갭 에너지 (~19.5 eV)를 가진 물질로서 우수한 내마모성, 강도, 전기 절연성 및 안정한 화학적 특성을 갖고 발광다이오드 기판, 보석재료 등 각종 산업 및 기술적 분야에서 널리 사용되고 있다. 특히, 플립칩 발광다이오드 구조의 경우 광추출효율을 향상시키기 위해 높은 투과도를 갖는 사파이어 기판이 요구되어 왔으며, 지금까지 건식/습식식각방법을 이용한 사파이어 표면에 마이크로 크기의 심한 거칠기 또는 요철이 형성된 나노크기의 격자구조를 형성시키는 연구가 진행되어 오고 있다. 그 중, 나노 크기의 격자구조는 공기에서 반도체 기판까지 선형적인 유효굴절률 분포를 갖기 때문에 표면에서 생기는 Fresnel 반사 손실을 줄일 수 있다. 이러한 구조를 형성하기 위해서는 식각 마스크가 필요한데, 형성 방법으로 레이저 간섭 리소그래피, 전자빔 리소그래피, 나노임프린트 리소그래피 등이 있으나, 비싼 가격과 복잡한 공정 절차 등의 단점을 지니고 있다. 따라서 본 연구에서는 식각 마스크 패턴을 위해, 보다 저렴하고 간단한 실리카 나노구 및 열적응집 금 나노 입자를 이용하였다. 양면 폴리싱 c-plane 사파이어 기판을 사용하였고, 단일 층의 주기적인 실리카 나노구를 기판 표면에 스핀코팅에 의해 도포한 후 유도결합플라즈마 식각 장비를 이용하여 식각하여 주기적인 패턴을 갖는 렌즈모양의 격자구조를 형성하였다. 그리고 주기적으로 형성된 격자 위에 열 증착기를 이용하여 금 박막을 증착한 후 급속열적어닐닝(rapid thermal annealing)을 이용하여 열처리함으로써 비주기적인 금 나노입자를 형성시켰다. 형성된 금 나노패턴을 이용하여 동일한 조건으로 식각함으로써 광대역 및 전방향성 높은 투과도를 갖는 원뿔 모양의 사파이어 나노구조를 제작하였다. 제작된 샘플의 패턴 및 식각 형상은 전자현미경을 사용하여 관찰하였으며, UV-vis-NIR 분광광도계 (spectrophotometer)를 사용하여 투과율을 측정하였다. 렌즈 모양 표면 위에 원뿔모양의 나노구조를 갖는 사파이어 기판은 일반적인 사파이어 기판보다 향상된 투과율 특성을 보였다.

• Applied Chemistry for Engineering
• /
• v.17 no.4
• /
• pp.391-396
• /
• 2006

When radioactive wastewater was solidified treatment by cement, the drying rate of cement and the volume reduction ratio was decreased because of boric acid component in the wastewater. In order to supplement the demerit, effects of paraffin wax investigated in this study. Paraffin wax has a hydrophobic properties and a low affinity with inorganic materials. When the radioactive wastewater was tested by a small of wax, the compressive strength of solidified waste are decreased Therefore boric acid in radioactive wastewater are first treated by alkali salt and coated by the stearic acid. During the solidification step, The amount of paraffin wax addition get the result that the compressive strength of solidification with cement was the same as that with paraffin wax. The leaching properties of radioactive waste solidified was the same CFL (cumulative fraction leached), PR (penetration rate), effective diffusivity if paraffin wax content in solidified waste was 20% or 25%.

• Membrane Journal
• /
• v.17 no.1
• /
• pp.44-53
• /
• 2007

The primary objective of this study is to increase the extent of water flux and fouling resistance of nano-filtration or reverse osmosis membranes. This study was performed to investigate the effect of surface characteristics of silane coated membranes on modified fouling index. Commercial polyamide composite RO membrane (RE1812-LP) and NF membrane (ESNA4040-LF) were treated with silane coupling agents in ethanol at five different concentrations. The silane coupling reagent, aminopropylmethoxydiethoxysilane, contains one aminoalkyl and three alkoxy groups. The hydrophilic effect of aminoalkyl group of APMDES on the permeability and fouling resistance of the modified membrane was examined. The surfaces of the modified membranes were characterized by FE-SEM, contact angle analyzer, and zeta potentiometer in order to confirm successful sol-gel methods. The modified NF membranes showed significantly enhanced water flux and fouling resistance without a decrease in salt rejection in divalent ionic feed solution.

• Membrane Journal
• /
• v.19 no.1
• /
• pp.25-33
• /
• 2009

PES (polyethersulfone) membranes with highly enhanced their asymmetry were prepared by phase inversion process. The membranes were prepared by using PES/DMF (N,N-dimethylformamide)/TSA (p-toluenesulfonic acid)/PVP (polyvinylpyrrolidone) casting solution and water coagulant. The pre-coagulation of membrane surface which was induced by an addition of TSA as a demixing agent and PVP as a swelling polymer in the PES solution and humid exposure time, played a crucial role in determining morphological properties and the PWP (pure water permeation) performance. The PES solution was coated on polyester film under condition of 80% humidity for a while ($72{\sim}144$ sec) before immersing in a coagulation bath. The characterization of membranes was carried out by a capillary flow porometer, a FE-SEM and a permeation test apparatus. As the thickness of the smallest pore size layer (SPL) decreased, the asymmetry of membrane increased under conditions of 20 wt% of TSA and 10 wt% of PVP in 11 wt% of PES solution during longer humid contact time. As a result, the membranes showed a remarkable increase of PWP.

• Journal of the Microelectronics and Packaging Society
• /
• v.14 no.4
• /
• pp.71-77
• /
• 2007

In this study, the mechanical and electrical properties of three different ball grid array (BGA) solder joints, consisting of Sn-37Pb, Sn-3.5Ag and Sn-3.5Ag-0.75Cu (all wt.%), with organic solderability preservative (OSP)-finished Cu pads were investigated as a function of reflow number. Based on scanning electron microscopy (SEM) analysis results, a continuous $Cu_6Sn5$, intermetallic compound (IMC) layer was formed at the solder/substrate interface, which grew with increasing reflow number. The ball shear testing results showed that the shear force peaked after 3 reflows (in case of Sn-Ag solder, 4 reflows), and then decreased with increasing reflow number. The electrical property of the joint gradually decreased with increasing reflow number.