• Journal of Welding and Joining
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• 제32권5호
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• pp.13-20
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• 2014

A brief overview is given of the corrosion and hydrogen diffusion behaviors of high strength pipe steel in sour environment. Firstly, hydrogen adsorption and diffusion mechanism of the pipe steel is introduced. Secondly, the effect of iron sulfide film precipitated as a result of the corrosion reaction on the steel surface on hydrogen reduction reaction and subsequent hydrogen permeation through the steel is discussed. Moreover, the hydrogen diffusion behavior of the pipe steel under tensile stress in both elastic and plastic ranges is reviewed based on a number of experimental permeation data and theoretical models describing the hydrogen diffusion and trapping phenomena in the steel. It is hoped that this paper will result in significant academic contributions in the field of corrosion and hydrogen related problems of the pipe steel used in sour environment.

• Tribology and Lubricants
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• 제17권6호
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• pp.426-434
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• 2001

The hermetic reciprocating compressor driven by the BLDC motor rotating with variable speeds, is modelled and analyzed for dynamic characteristics. The governing equations of piston, connecting rod and crank-shaft of the reciprocating compression mechanism and characteristics of driving torque of the motor are obtained. Dynamic behavior of the crankshaft supported on 2 journal bearings is analyzed considering compression load and eccentric unbalance for the 4 rotating speeds of crankshaft. And. reaction forces generated from oil film in the journal bearings are analyzed under transient condition using Reynolds' equation. To take into account the dynamic characteristics depending on the variable rotating speeds, comparison on the dynamic behavior of crank-shaft is made for the 4 operating modes of the compressor. Results show that the magnitude of crankshaft locioperating on the lower rotating speeds is more larger than the higher ones due to reduction of inertia force of the reciprocating piston.

• Journal of Photoscience
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• 제1권2호
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• pp.107-111
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• 1994

Photocatalytic ($\lambda$$_{ex}$ > 300 nm) reaction at room temperature by platinized titanium (IV) oxide particles produced 1-methyl-1, 2, 3, 4-tetrahydroisoquinolines (MIQ's) from phenethylamines in aqueous ethanol suspension under deaerated atmosphere. Among the phenethylamines, dopamine (2-(3, 4-dihydroxyphenyl) ethylamine) showed the highest reactivity to give MIQ almost selectively under the neutralized conditions. The other phenethylamines gave predominantly N-alkylated and N, N-dialkylated products in the methanol or ethanol solutions. The reaction mechanism includes a Schiff base intermediate to undergo either nucleophilic attack leading to MIQ or reduction to N-alkylated products.

• 한국자동차공학회논문집
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• 제20권1호
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• pp.95-105
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• 2012

The selective catalytic reduction (SCR) system is a highly-effective aftertreatment device for NOx reduction of diesel engines. Generally, the ammonia ($NH_3$) was generated from reaction mechanism of SCR in the SCR system using the liquid urea as the reluctant. Therefore, the precise urea dosing control is a very important key for NOx and $NH_3$ slip reduction in the SCR system. This paper investigated NOx and $NH_3$ emission characteristics of urea-SCR dosing system based on model-based control algorithm in order to reduce NOx. In the map-based control algorithm, target amount of urea solution was determined by mass flow rate of exhaust gas obtained from engine rpm, torque and $O_2$ for feed-back control NOx concentration should be measured by NOx sensor. Moreover, this algorithm can not estimate $NH_3$ absorbed on the catalyst. Hence, the urea injection can be too rich or too lean. In this study, the model-based control algorithm was developed and evaluated on the numerical model describing physical and chemical phenomena in SCR system. One channel thermo-fluid model coupled with finely tuned chemical reaction model was applied to this control algorithm. The vehicle test was carried out by using map-based and model-based control algorithms in the NEDC mode in order to evaluate the performance of the model based control algorithm.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2918-2922
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• 2007

This is a report of a feasibility study on the reduction of harmful substances such as particulate matters and nitric oxides emitted from diesel engines by using a plasma reforming system that can generate hydrogen-rich gas. In this paper, an exhaust reduction mechanism of the non-thermal plasma reaction was investigated to perform its efficiency and characteristics on producing hydrogen-rich gas. Firstly, we explain briefly the chemistry of hydrocarbon reforming. The experimental system is showed in the second part. Finally, we demonstrate the feasibility of producing hydrogen using non-thermal plasma. The experimental results are focused on the influence of the different operating parameters (air ratio, inlet flow rates, voltage) on the reformer efficiency and the composition of the produced gas.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2000년도 창립총회 및 춘계학술발표회
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• pp.108-111
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• 2000

FeS/FeS$_2$ minerals have been known to be potentially useful reductant to the removal of common organic contaminants in groundwater and soil. This research is aimed at improving our understanding of factors affecting the pathways and rates of reductive transformation of Hexachloroethane by catalytical iron minerals in natural system. Hexachloroethane is reduced by FeS/FeS$_2$ minerals under anaerobic condition to tetrachloroethylene and trichloroethylene with pentachloroethyl radical as the intermediate products. The kinetics of reductive transformations of the Hexachloroethane have been investigated in aqueous solution containing FeS, FeS$_2$. The proposed reduction mechanism for the adsorbed nitrobenzene involves the electron donor-acceptor complex as a precursor to electron transfer. The adsorbed Hexachloroethane undergo a series of electron transfer, proton transfer and dehydration to achieve complete reduction. It can be concluded that the reductive transformation reaction takes place at surface of iron-bearing minerals and is dependent on surface area and pH. Nitrobenzene reduction kinetics is affected by reductant type, surface area, pH, the surface site density, and the surface charge. FeS/FeS$_2$-mediated reductive dechlorination may be an important transformation pathway in natural systems.

• 한국표면공학회지
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• 제26권1호
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• pp.3-9
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• 1993

Chemical vapor deposited tungsten films were formed in a cold wall reactor at pressures higher (10~120torr) than those conventionally employed (<1torr). SiH4, in addition to H2, was used as the reduction gas. The effects of pressure and reaction temperature on the deposition rate and morphology of the films were ex-amined under the above conditions. No encroachment or silicon consumption was observed in the tungsten de-posited specimens. A high deposition rate of tungsten and a good step coverage of the deposited films were ob-tained at 40~80 torr and at a temperature range of $360~380^{\circ}C$. The surface roughness and the resistivity of the deposited film increased with pressure. The deposition rate of tungsten increased with the total pressure in the reaction chamber when the pressure was below 40 torr, whereas it decreased when the total pressure ex-ceedeed 40 torr. The deposition rate also showed a maximum value at $360^{\circ}C$ regardless of the gas pressure in the chamber. The results suggest that the deposition mechanism varies with pressure and temperature, the surface reac-tion determines the overall reaction rate and (2) at higher pressures(>40 torr) or temperatures(>36$0^{\circ}C$), the rate is controlled by the dtransportation rate of reactive gas molecules. It was shown from XRD analysis that WSi2 and metastable $\beta$-W were also formed in addition to W by reactions between WF6 and SiH4.

• Bulletin of the Korean Chemical Society
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• 제26권1호
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• pp.103-106
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• 2005

In order to investigate the catalytic mechanism for the growth of carbon nanotubes (CNTs), a comprehensive study was conducted using carbon materials synthesized at 680 ${^{\circ}C}$ with a gas mixture of CO-H$_2$ after reduction at 800 ${^{\circ}C}$ by H$_2$ gas from iron oxide, and metal Pt. The resulting material was observed by scanning electron microscopy (SEM) and X-ray diffraction patterns (XRD) after a variety of reaction times. The carbon materials synthesized by metal Pt were little affected by reaction time and the sintered particles did not form CNTs. Xray analysis revealed that metal Fe was completely converted to iron carbide (Fe$_3$C) without Fe peaks in the early stage. After 5 min, iron carbide (Fe$_3$C) and carbon (C) phases were observed at the beginning of CNTs growth. It was found that the intensity of the carbon(C) peak gradually increased with the continuous growth of CNTs as reaction time increases. It was also found that the catalyst of growth of CNTs was metal carbide.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.264-264
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• 2012

As an environment-friendly alternative energy resource, ethanol may be used to obtain hydrogen, a clean energy source. Thus, studies on catalytic reactions involving ethanol have been studied to understand the underlying principles in the reaction mechanism using various oxide-supported catalysts. Among them, Au-based catalysts have shown a superior activity in producing hydrogen gas. In the present study, Au/$TiO_2$ catalysts were prepared by deposition-precipitation method to understand their catalytic activities toward ethanol and acetaldehyde with increasing gold loading, especially at the very low Au loading regime. A commercially available $TiO_2$ (Degussa P-25) was employed and the Au loading was varied to 0, 0.1, 0.5, and 1.0 wt% respectively. The catalysts showed characteristic x-ray diffraction (XRD) features at $2{\theta}=78.5^{\circ}$ that could be assigned to the presence of gold nanoparticles. Its reactivity measurements were performed under a constant flow of ethanol and acetaldehyde at a flow rate of ${\sim}0.6{\mu}mol/sec$ and the substrate temperature was slowly raised at a rate of 0.2 K/sec. We observed that the overall reactivity of the catalysts increased with increasing Au loading along with selectivity favoring dehydrogenation to product hydrogen gas. In addition, we disclosed various reaction channels involving competitive reaction paths such as dehydrogenation, dehydration, and condensation. In addition, subsequent reactions of acetaldehyde obtained from dehydrogenation of ethanol, were found to occur and produce butene, crotonaldehyde, furan, and benzene. Based on the results, we proposed overall reaction pathways of such reaction channels.

• Journal of Microbiology and Biotechnology
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• 제19권1호
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• pp.37-41
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• 2009

Previous studies have demonstrated that Shewanella decolorationis S12 can grow on the azo compound amaranth as the sole electron acceptor. Thus, to explore the mechanism of energy generation in this metabolism, membranous vesicles (MVs) were prepared and the mechanism of energy generation was investigated. The membrane, which was fragmentized during preparation, automatically formed vesicles ranging from 37.5-112.5 nm in diameter under electron micrograph observation. Energy was conserved when coupling the azoreduction by the MVs of an azo compound or Fe(III) as the sole electron acceptor with $H_2$, formate, or lactate as the electron donor. The amaranth reduction by the vesicles was found to be inhibited by specific respiratory inhibitors, including $Cu^{2+}$ ions, dicumarol, stigmatellin, and metyrapone, indicating that the azoreduction was indeed a respiration reaction. This finding was further confirmed by the fact that the ATP synthesis was repressed by the ATPase inhibitor N,N'-dicyclohexylcarbodiimide (DCCD). Therefore, this study offers solid evidence of a mechanism of microbial dissimilatory azoreduction on a subcell level.