• Title/Summary/Keyword: Gas Resistance

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Analysis of dew point and corrosion resistance for power plant economizer tube with exhaust gas temperature and sulfuric acid concentration (발전소 절탄기 튜브의 배기가스 온도와 황산 농도에 따른 노점 및 내식성 분석)

  • Choi, Jae-Hoon;Lee, Seung-Jun
    • Journal of the Korean institute of surface engineering
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    • v.55 no.6
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    • pp.433-440
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    • 2022
  • Environmental pollution caused by power plant exhaust gas is highlighted and eco-friendly regulations are being strengthened. However, due to the abundant reserves and low prices of coal, still the most used for power generation in the world. Therefore, flexible operation of coal-fired power plants to reduce emissions has become an inevitable option. However, lowering the output increases the possibility of acid dew point corrosion as the exhaust gas temperature decreases. The dew point corrosion occurs when condensable gases such as SO3, HCl, NO2 and H2O cools below the saturation temperature. SO3 is already well known to cause severe low- temperature corrosion in coal-fired power plants. Therefore, this study aims to prevent damage that may occur during operation by analyzing the dew point and corrosion resistance with exhaust gas temperature and sulfuric acid concentration of the power plant economizer tube.

Pattern recognition using AC treatment for semiconductor gas sensor array

  • Nguyen, Viet-Dung;Joo, Byung-Su;Huh, Jeung-Su;Lee, Duk-Dong
    • Proceedings of the IEEK Conference
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    • 2003.07d
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    • pp.1549-1552
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    • 2003
  • Semiconductor gas sensor using tin oxide as sensing material has been used to detect gases based on the fact that impedance of the sensing material varies when the gas sensor is exposed to the gases. This variation comprises of two parts. The first one is variation in resistance of the sensing material and the other is expressed in terms of the sensor capacitance variation. Normally, only variation of the sensor resistance is considered. In this paper, using AC measurement with a capacitor-coupled inverting amplifier circuit, both changes in the sensor resistance and variations in the sensor capacitance were investigated. These characteristics were represented as magnitude gain and phase shift of AC signal at a specific frequency after passing it through the sensor and the designed circuit. A two-stage artificial neural network, which utilized the information above, was employed to identify and quantify three combustible gases: methane, propane and butane. The network outputs were approximately proportional to concentrations of test gases with reasonable level of error.

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Electrical Conductivity Properties of the Vacuum Forming Packing Materials by Ion Implantation (이온주입에 의한 진공성형 포장재의 전기전도 특성)

  • 이재형;이찬영;길재근
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.16 no.11
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    • pp.1055-1061
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    • 2003
  • A study has been made of surface modification of various organic materials by ion implantation to increase the surface electrical properties. The substrate used were PP(polypropylene), PET(polyethylene teraphthalate), ECOP(ethylene copolyester), PS(polystyrene). N$_2$, Ar ion implantation was performed at energies of 40 and 50keV with fluences from 5${\times}$ 10$\^$15/ to 7${\times}$10$\^$16/ ions/$\textrm{cm}^2$ with and without H$_2$O gas environment. Surface resistance decrease of implanted polymers was affected by ion implantation energy, ion species, atmosphere of chamber and kind of polymer. In result, surface conductivity of polymers irradiated with atmosphere gas H$_2$O was 10 times more higher than normal vacuum atmosphere, but after 90 hours, surface conductivity returned to the without H$_2$O gas atmosphere condition caused by aging effect. After vacuum forming, surface resistance value was changed to over 10$\^$16/$\Omega$/$\square$, because creation of surface cracks.

The Effects of Etch Process Parameters on the Ohmic Contact Formation in the Plasma Etching of GaN using Planar Inductively Coupled $CH_4/H_2/Ar$ Plasma (평판 유도 결합형 $CH_4/H_2/Ar$ 플라즈마를 이용한 GaN 건식 식각에서 공정변수가 저항성 접촉 형성에 미치는 영향)

  • Kim, Mun-Yeong;Tae, Heung-Sik;Lee, Ho-Jun;Lee, Yong-Hyeon;Lee, Jeong-Hui;Baek, Yeong-Sik
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.49 no.8
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    • pp.438-444
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    • 2000
  • We report the effects of etch process parameters on the ohmic contact formation in the plasma etching of GaN. Planar inductively coupled plasma system with $CH_4/H_2/Ar$gas chemistry has been used as etch reactor. The contact resistance and the specific contact resistance have been investigated using transfer length method as a function of RF bias power and %Ar gas concentration in total flow rate. AES(Auger electron spectroscopy) analysis revealed that the etched GaN has nonstoichiometric Ga rich surface and was contaminated by carbon and oxygen. Especially large amount of carbon was detected at the sample etched for high bias power (or voltage) condition, where severe degradation of contact resistance was occurred. We achieved the low ohmic contact of $2.4{\times}10^{-3} {\Omega}cm^2$ specific contact resistance at the input power 400 W, RF bias power 150 W, and working pressure 10mTorr with 10 sccm $CH_4$, 15 sccm H2, 5 sccm Ar gas composition.

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Investigations of the Boron Diffusion Process for n-type Mono-Crystalline Silicon Substrates and Ni/Cu Plated Solar Cell Fabrication

  • Lee, Sunyong;Rehman, Atteq ur;Shin, Eun Gu;Lee, Soo Hong
    • Current Photovoltaic Research
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    • v.2 no.4
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    • pp.147-151
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    • 2014
  • A boron doping process using a boron tri-bromide ($BBr_3$) as a boron source was applied to form a $p^+$ emitter layer on an n-type mono-crystalline CZ substrate. Nitrogen ($N_2$) gas as an additive of the diffusion process was varied in order to study the variations in sheet resistance and the uniformity of doped layer. The flow rate of $N_2$ gas flow was changed in the range 3 slm~10 slm. The sheet resistance uniformity however was found to be variable with the variation of the $N_2$ flow rate. The optimal flow rate for $N_2$ gas was found to be 4 slm, resulting in a sheet resistance value of $50{\Omega}/sq$ and having a uniformity of less than 10%. The process temperature was also varied in order to study its influence on the sheet resistance and minority carrier lifetimes. A higher lifetime value of $1727.72{\mu}s$ was achieved for the emitter having $51.74{\Omega}/sq$ sheet resistances. The thickness of the boron rich layer (BRL) was found to increase with the increase in the process temperature and a decrease in the sheet resistance was observed with the increase in the process temperature. Furthermore, a passivated emitter solar cell (PESC) type solar cell structure comprised of a boron doped emitter and phosphorus doped back surface field (BSF) having Ni/Cu contacts yielding 15.32% efficiency is fabricated.

An Experimental Study on GHG Emissions Reduction and Fuel Economy Improvement of Heavy-Duty Trucks by Using Aerodynamics Device Package (공기저항 저감장치 패키지를 이용한 대형화물차량의 연비개선 및 온실가스 저감효과에 관한 실험적 연구)

  • Park, Seungwon;Dong, Lang;Her, Chulhaeng;Yun, Byoeunggyu;Kim, Daewook
    • Transactions of the Korean Society of Automotive Engineers
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    • v.25 no.2
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    • pp.207-218
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    • 2017
  • Improving fuel consumption, particularly that of commercial vehicles, has become a global concern. The reduction in logistics cost has been a key issue in efforts to improve fuel economy and efficiency of transportation equipment. Typical technologies for reducing reduce fuel usage include air resistance reduction technologies, tire rolling resistance technologies, and idle technologies among others. Air resistance technology is a highly effective method that can be easily applied in a short period. As with air resistance technology, several devices involving side skirt, boat tail and gap fairing have been developed based on an analytical 3-D modeling technique for reducing air resistance attributed to the vehicle configuration. The devices were on a 45 feet tractor-trailer and the emission test was done using PEMS equipment. Fuel economy was evaluated by introducing several devices to reduce outer air resistance. The test was conducted by changing the experimental method of SAE J1321 Joint TMC/SAE Fuel Consumption Test Procedure - Type II test. As a result, air resistance decreased by at least 15 % and fuel economy improved by at least 13 %. This study sought to reduce greenhouse gas and improve fuel economy by applying several devices to a test vehicle to lower air resistance.

Effects of Gas Composition on the Characteristics of Surface Layers Produced on AISI316L Stainless Steel during Low Temperature Plasma Nitriding after Low Temperature Plasma Carburizing (AISI 316L stainless steel에 저온 플라즈마 침탄 및 질화처리 시가스조성이 표면특성에 미치는 영향)

  • Lee, In-Sup;Ahn, Yong-Sik
    • Journal of the Korean institute of surface engineering
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    • v.42 no.3
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    • pp.116-121
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    • 2009
  • The 2-step low temperature plasma processes (the combined carburizing and post-nitriding) offer the increase of both surface hardness and thickness of hardened layer and corrosion resistance than the individually processed low temperature nitriding and low temperature carburizing techniques. The 2-step low temperature plasma processes were carried out for improving both the surface hardness and corrosion resistance of AISI 316L stainless steel. The influence of gas compositions on the surface properties during nitriding step were investigated. The expanded austenite (${\gamma}_N$) was formed on all of the treated surface. The thickness of ${\gamma}_N$ and concentration of N on the surface increased with increasing both nitrogen gas and Ar gas levels in the atmosphere. The thickness of ${\gamma}_N$ increased up to about $20{\mu}m$ and the thickness of entire hardened layer was determined to be about $40{\mu}m$. The surface hardness was independent of nitrogen and Ar gas contents and reached up to about 1200 $HV_{0.1}$ which is about 5 times higher than that of untreated sample (250 $HV_{0.1}$). The corrosion resistance in 2-step low temperature plasma processed austenitic stainless steels was also much enhanced than that in the untreated austenitic stainless steels due to a high concentration of N on the surface.

Characteristics of Contact resistivity on RTP annealing temperature and time after Plasma ion implant (플라즈마 이온주입 후 RTP 열처리 온도와 시간에 따른 접촉저항 특성)

  • Choi, Jang-Hun;Do, Seung-Woo;Lee, Yong-Hyun
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.06a
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    • pp.5-6
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    • 2009
  • In this paper, plasma ion implant is performed with $PH_3$ gas diluted by helium gas on P-type Si wafer (100). Spike Rapid Thermal Processing(RTP) annealing performed for 30~60 sec from $800\;^{\circ}C$ to $1000\;^{\circ}C$ in $N_2+O_2$ ambient. Crystalline defect is analyzed by Transmission Electron Microscope(TEM) and Double crystal X-ray Diffraction(DXRD). Contact resistivity($\rho c$), contact resistance(Rc) and sheet resistance(Rs) are analyzed by measuring Transfer Length Method(TLM) using 4155C analysis. As annealing temperature increase, Rs decrease and ${\rho}c$ and Rc increase at temperature higher than $850\;^{\circ}C$. We achieve low Rs, ${\rho}c$ and Rc with Plasma ion implant and spike RTP.

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The Effect of Oil-Starvation on the Lubrication Characteristics of High-Speed Bearing: Part II-Roller Bearing (가스터어빈용 고속 베어링의 Oil-Starvation 윤활특성: Part II-Roller Bearing)

  • Kim, Ki-Tae
    • Tribology and Lubricants
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    • v.13 no.1
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    • pp.76-81
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    • 1997
  • The lubrication characteristics of high-speed roller bearings at oil-starvation have been investigated empirically using the bearings employed in small industrial gas turbine engines. Testing was done by simulating the oil-starvation conditions in engines, such as stopping the oil-supply to the bearing during normal operating, starting without oil-supply at atmospheric temperature, and accelerating with oil-supply at atmospheric temperature. During testing, the temperature of bearing, the power consumption, and the rotating resistance of the bearing were measured. From this study, on the contrary to the ball bearing, it was found that the resistance of the bearing was higher at the regime of without oil-supply than that at the regime of with oil-supply, despite less power consumption.

Electrical Characteristic Change of Al/Pd Film by Hydrogen Gas (수소 기체에 의한 Al/Pd 박막의 전기 특성 변화)

  • Cho, Young-Sin
    • Journal of Hydrogen and New Energy
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    • v.16 no.4
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    • pp.386-390
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    • 2005
  • Al film(135.5 nm thick) with Pd film(39.6 nm thick) on the top of it was made by thermal evaporation method. Electrical resistance change due to hydrogen absorption and desorption was measured by four point measurement method. The sample was activated by hydrogen absorption and desorption cycling at room temp. Hydrogen was introduced into the film by increasing hydrogen gas pressure step by step up to 640 torr at room temp. The resistance change ratio was decreased to 12 % with increasing hydrogen pressure in contrast to normal metal behavior. This strange tendency was not understood yet. Further study is needed to find out the mechanism of hydrogen absorption in Al in Al/Pd film.