• Bulletin of the Korean Chemical Society
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• v.18 no.9
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• pp.985-994
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• 1997

The reaction of gas-phase atomic hydrogen with hydrogen atoms chemisorbed on Fe(110) surface is studied by use of classical trajectory procedures. Flow of energy between the reaction zone and bulk solid phase has been treated in the generalized Langevin equation approach. A London-Eyring-Polanyi-Sato energy surface is used for the reaction zone interaction. Most reactive events are found to occur in strong single-impact collisions on a subpicosecond scale via the Eley-Rideal mechanism. The extent of reaction is large and a major fraction of the available energy goes into the vibrational excitation of H2, exhibiting a vibrational population inversion. Dissipation of reaction energy to the heat bath can be adequately described using a seven-atom chain with the chain end bound to the rest of solid. The extent of reaction is not sensitive to the variation of surface temperature in the range of Ts=0-300 K in the fixed gas temperature, but it shows a minimum near 1000 K over the Tg=300-2500 K.

• Journal of computational fluids engineering
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• v.16 no.2
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• pp.94-101
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• 2011

The fast pyrolysis characteristics of lignocellulosic biomass are investigated for a bubbling fluidized bed reactor by means of computational fluid dynamics (CFD). To simulate multiphase reacting flows for gases and solids, an Eulerian-Eulerian approach is applied. Attention is paid for the primary and secondary reactions affected by gas-solid flow field. From the result, it is scrutinized that fast pyrolysis reaction is promoted by chaotic bubbling motion of the multiphase flow enhancing the mixing of solid particles. In particular, vortical flow motions around gas bubbles play an important role for solid mixing and consequent fast pyrolysis reaction. Discussion is made for the time-averaged pyrolysis reaction rates together with time-averaged flow quantities which show peculiar characteristics according to local transverse location in a bubbling fluidized bed reactor.

• Journal of the Korean Society of Safety
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• v.8 no.4
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• pp.107-113
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• 1993

Small rectangular explosion chamber of its size 25cmX25cmX32cm with a circular bursting diaphram at the top was used to study the mechanism of gas explosion to fire transition phenomena, the process of ignition of solid combustibles during a gas explosion. To visulize the explosion to fire transition phenomena, transparent acryl window and high speed camera system were used. The test piece of solid combustible in this experiments was a 5cm$\times$5cm square sheet of newspaper which was placed in the explosion chamber filled with a LPG-air mixture. The mixture was ignited by an electric spark at the center of the chamber. Explosion to fire transition phenomena and the behavior of out flow and in flow of gas through the opening yielded by bursting the diaphram was visualized with shlieren system and without shlieren system. Diameter of a bursting dlaphram at the top of the explosion chamber was varied 5cm, 10cm, and 15cm, and the position of test piece were varied with 6 point. Explosion pressure was measured with strain type pressure transducer, and the weight difference of the test piece before and after each experimental run was measured. By comparing the weight difference of solid combustibles before and after the experiment and the behavior of out flow and inflow of gas after explosion, it was found that the possibility of ignition was depends on the LPG-air mixture concentration and the exposure period of test piece to the burnt gas. Test result of this experiments it was found that the main factor of this phenomena are that heat transfer to the test piece, and the pyrolysis reaction of test piece. Based on the results, the mechanism of the explosion to fire transition phenomena were inferred ; gas explosion- heat transfer to solid combustibiles ; pyrolysis reaction of solid combutibles : air inflow ; mixing of the pyroly gas with air ignition.

• Bulletin of the Korean Chemical Society
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• v.28 no.10
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• pp.1656-1660
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• 2007

Using solid inorganic peroxides (including Li2O2, Na2O2, SrO2 and BaO2) as starting materials, three reaction paths for singlet oxygen (1O2) production were developed and studied. Their 1O2 emission spectra in the near- IR region and visible region from these reaction paths were simultaneously recorded by a near-IR sensitive Optical Multichannel Analyzer and a visible sensitive Optical Spectrum Analyzer, respectively. The comparison of their 1O2 emission spectra indicated that: (1) in term of the efficiency for 1O2 production, the gasliquid- solid reaction path (in which Cl2 or HCl and H2O reacted with the solid inorganic peroxides suspension in CCl4) was prior to the gas-solid reaction path (in which Cl2 or HCl reacted with the solid inorganic peroxides suspension in CCl4), but was inferior to the gas-liquid reaction path (in which Cl2 or HCl reacted with the solid inorganic peroxides solution in H2O or D2O); (2) the alkali metal peroxides (such as Li2O2 and Na2O2) was prior to the alkaline earth metal peroxides (such as SrO2 and BaO2) as the solid reactants, and Cl2 was favorable than HCl as the gas reactant in efficiency for 1O2 production in these reaction paths.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.9
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• pp.2353-2364
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• 1995

The ignition phenomena of a solid fuel plate of polymethyl-methacrylate(PMMA), which is vertically positioned and exposed to a thermal radiation source, is numerically studied here. A two-dimensional transient model includes such various aspects as thermal decomposition of PMMA, gas phase radiation absorption, gas phase chemical reaction and air entrainment by natural convection. Whereas the previous studies considers the problem approximately in a one-dimensional form by neglecting the natural convection, the present model takes account of the two-dimensional effect of radiation and air entrainment. The inert heating of the solid fuel is also taken into consideration. Radiative heat transfer is incorporated by th Discrete Ordinates Method(DOM) with the absorption coefficient evaluated using gas species concentration. The thermal history of the solid fuel plate shows a good agreement compared with experimental results. Despite of induced natural convective flow that induces heat loss from the fuel surface, the locally absorbed radiant energy, which is converted to the internal energy, is found to play an important role in the onset of gas phase ignition. The ignition is considered to occur when the rate of variation of gas phase reaction rate reaches its maximum value. Once the ignition takes place, the flame propagates downward.

• Korean Chemical Engineering Research
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• v.48 no.4
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• pp.499-505
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• 2010

In this study, hydrodynamics and reaction characteristic of K-based solid sorbents for $CO_2$ capture were investigated using a continuous system composed of two bubbling fluidized-bed reactors(1.2 m tall bed with 0.11 m i.d.). Potassium-based dry sorbents manufactured by the Korea Electric Power Research Institute were used, which were composed of $K_2CO_3$ of 35% for $CO_2$ absorption and supporters of 65% for mechanical strength. The continuous system consists of two bubbling fluidized-bed reactors, solid injection nozzle, riser, chiller, analyzer and heater for regeneration reaction. The minimum fluidizing velocity of the continuous system was 0.0088 m/s and the solid circulation rate measured was $10.3kg/m^2{\cdot}s$ at 1.05 m/s velocity of the solid injection nozzle. The $CO_2$ concentration of the simulated gas was about 10 vol% in dry basis. Reaction temperature in carbonator and regenerator were maintained about $70^{\circ}C$ and $200^{\circ}C$, respectively. Differential pressures, which were maintained in carbonator and regenerator, were about $415mmH_2O$ and $350mmH_2O$, respectively. In order to find out reaction characteristics of dry sorbents, several experiments were performed according to various experimental conditions such as $H_2O$ content(7.28~19.66%) in feed gas, velocity (0.053~0.103 m/s) of simulated gas, temperature($60{\sim}80^{\circ}C$) of a carbonator, temperature($150{\sim}200^{\circ}C$) of a regenerator and solid circulation rate($7.0{\sim}10.3kg/m^2{\cdot}s$). The respective data of operating variables were saved and analyzed after maintaining one hour in a stable manner. As a result of continuous operation, $CO_2$ removal tended to increase by increasing $H_2O$ content in feed gas, temperature of a regenerator and solid circulation rate and to decrease by increasing temperature of a carbonator and gas velocity in a carbonator.

• Archives of Pharmacal Research
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• v.27 no.1
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• pp.25-30
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• 2004

Combinatorial homoserine lactone mixtures and individual products were obtained from the methionine-functionalized resin in solid-phase synthesis. The four-step process consisting of a coupling step of an N-Fmoc-L-methionine, deprotection of N-Fmoc group, N-coupling with a carboxylic acid, and cleavage reaction through a polymer supported strategy is described. Gas chromatography-mass selective detector (GC-MSD) techniques provide the most powerful methods for identifying both the combinatorial mixtures and individual products.

• Journal of the Korean Society of Combustion
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• v.22 no.2
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• pp.27-35
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• 2017

This paper reviews the previous industrial solid bed process simulations to provide a better understanding of the modeling approaches to the particle reactions in the bed. Previous modeling studies on waste incinerator, iron ore sintering bed, blast furnace, iron ore pellet indurator, and biomass combustor can be seen on the common ground of unsteady 1-D modeling scheme. Approaches to the particle reaction modeling have been discussed in terms of the status of solid particles in the bed, types of reaction progression in a particle, and the consideration of the intra-particle temperature gradient.

• Journal of the Korean Electrochemical Society
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• v.8 no.2
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• pp.106-114
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• 2005

This article covers the theoretical ac-impedance models for the analysis of oxygen reduction on the porous cathode electrode f3r solid oxide fuel cell (SOFC). Firstly, ac-impedance models were explained on the basis of the mechanism of oxygen reduction, which were classified into the rate-determining steps; (i) adsorption of oxygen atom on the electrode surface, (ii) diffusion of adsorbed oxygen atom along the electrode surface towards the three-phase (electrode/electrolyte/gas) boundaries, (iii) surface diffusion of adsorbed oxygen atom m ixed with the adsorption reaction of oxygen atom on the electrode surface and (iv) diffusion of oxygen vacancy through the electrode coupled with the charge transfer reaction at the electrode/gas interface. In each section for ac-impedance model, the representative impedance plots and the interpretation of important parameters attributed to the oxygen reduction reaction were explained. Finally, we discussed in detail the applications of the proposed theoretical ac-impedance models to the real electrode of SOFC system.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.04a
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• pp.173-179
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• 1998

The processing conditions for the synthesis of platelet WS$_2$ lubricant powder through the solid-gas reaction were optimized. The tungsten and sulfur powders were sealed in a vacuum of 10$^{-6}$ torr, prior to heat-treating at 850$\circ$C for 8 days. The react~on product showed the well-developed platelet WS$_2$ powder with an average size of 3.8 $\mu$m. The synthesized WS$_2$ powder was coated on the commercial deep grooved ball bearing (No. 6203) to examine the effects of WS$_2$ coating layer on the noise and endurance of the ball bearing. The level of noise obtained from WS$_2$ coated-ball bearing was higher (56 dB) than the value occurred in the case of greece (37 dB). The life-time of the ball-bearing assembled after coating WS$_2$ powder increased 50 times compared to the non-coated bali-bearing.