• Korean Journal of Food Science and Technology
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• v.29 no.5
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• pp.827-838
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• 1997

Optimal substrates and reaction conditions were studied to develop boiled or roasted meat flavor by Maillard reaction under a model system. Sugars for the reactions were xylose, ribose, glucose, lactose, maltose, and sucrose. Amino acids were cystine, cysteine, methionine, lysine, and glycine as the reaction substrates. The reacted solutions were measured their absorbances at 278 nm and 420 nm and were evaluated their sensory properties. Except cysteine, the pentose mixtures with all of the four amino acids showed a faster reaction rate than those mixtures with hexose or disaccharides. pH was decreased rapidly until 8 hours and then changed a little thereafter. Sensory evaluation showed that cystine-lactose or cystine-xylose from single substrate and cystine-lactose-maltose, and cystine-lactose-xylose from mixed substrates reacted at $100^{\circ}C$ for 16 or 20 hours were found to be close to boiled or roasted meat flavor. The volatile compounds from the four selected sugar-amino acid solutions by GC/MS were 8 hydrocarbons, 10 aldehydes, 6 ketones, 7 alcohols, 2 aromatics (benzene), 1 ester, 4 furans, 1 base and 5 sulfur compounds.

• Korean Chemical Engineering Research
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• v.50 no.1
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• pp.76-82
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• 2012

Biomass and coal are great potential energy sources for gasification process. These solids can be gasified to produce syngas and bio-oil which can be upgraded further to transportation fuel. Two biomass and three coals have been gasified with steam in a thermobalance reactor under atmospheric pressure in order to evaluate their kinetic rate information The effects of gasification temperature ($600{\sim}850^{\circ}C$) and partial pressure of steam (30~90 kPa) on the gasification rate have been investigated. The three different types of gas-solids reaction models have been applied to the experimental data to compare their predictions of reaction behavior. The modified volumetric reaction model predicts the conversion data well, thus that model was used to evaluate kinetic parameters in this study. The gasification reactivity of five solids has been compared. The obtained activation energy of coal and biomass gasification were well in the reasonable range. The expression of apparent reaction rates for steam gasification of five solids have been proposed as basic information for the design of coal gasification processes.

• Journal of Ginseng Research
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• v.28 no.3
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• pp.143-148
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• 2004

Brown color intensity has been a major factor to estimate the quality of red ginseng and its products. This study deals with the relationship between the browning reaction of ginseng root and two compounds, arginyl-fructosyl-glucose(Arg-fru-glc) and arginyl-fructose (Arg-fru), in the model system of steaming and heat-drying processes for the preparation of red ginseng. During the steaming process, a marked decrease of starch and a considerable formation of maltose occurred in main roots of raw ginseng, but the formation of glucose was scarcely observed. After the heat-drying process, the brown color intensity of the powdered preparation of steamed main roots was 3 to 4 times higher than that of the powdered preparation of raw main roots. Also, when the heat- drying process was done with the addition of L-arginine, brown color intensity of the powdered preparation of steamed main roots was 12 to 13 times higher than that of the powdered preparation of raw main roots. The amount ratios of browning reaction products formed from sugar compounds and amino acids in the model system of steaming and heat-drying treatments in vitro were in order of xylose > glucose > fructose > maltose > dextrin (DE 9) > sucrose > dextrin (DE 8) and soluble starch. Each solution of Arg-fru-glc and Arg-fru that were synthesized chemically from maltose plus L-arginine and glucose plus L-arginine, respectively, changed from colorless to brown color during the heat-drying treatment. Amino acids or sugars were effective on the acceleration of each browning reaction of Arg-fru-gIc and Arg-fru during the heat-drying treatment.

• Computers and Concrete
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• v.31 no.5
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• pp.405-417
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• 2023

The submerged floating tunnel (SFT) is tethered by mooring lines anchored to the seabed, therefore, the structural integrity of the anchor should be sensitively managed. Despite their importance, reaction forces cannot be simply measured by attaching sensors or load cells because of the structural and environmental characteristics of the submerged structure. Therefore, we propose an effective method for estimating the reaction forces at the seabed anchor of a submerged floating tunnel using a structural pattern model. First, a structural pattern model is established to use the correlation between tunnel motion and anchor reactions via a deep learning algorithm. Once the pattern model is established, it is directly used to estimate the reaction forces by inputting the tunnel motion data, which can be directly measured inside the tunnel. Because the sequential characteristics of responses in the time domain should be considered, the long short-term memory (LSTM) algorithm is mainly used to recognize structural behavioral patterns. Using hydrodynamics-based simulations, big data on the structural behavior of the SFT under various waves were generated, and the prepared datasets were used to validate the proposed method. The simulation-based validation results clearly show that the proposed method can precisely estimate time-series reactions using only acceleration data. In addition to real-time structural health monitoring, the proposed method can be useful for forensics when an unexpected accident or failure is related to the seabed anchors of the SFT.

• Korea-Australia Rheology Journal
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• v.20 no.2
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• pp.59-63
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• 2008

A theoretical model was developed to describe the flow behavior of a filled polymer in the packing stage of reaction injection molding and predict the residual stress distribution of thin injection-molded parts. The model predictions were compared with experiments performed for phenol-formaldehyde resin filled with wood dust and cured by urotropine. The packing stage of reaction injection molding process presents a typical example of complex non-isothermal flow combined with chemical reaction. It is shown that the time evolution of pressure distribution along the mold cavity that determines the residual stress in the final product can be described by a single 1D partial differential equation (PDE) if the rheological behavior of reacting liquid is simplistically described by the power-law approach with some approximations made for describing cure reaction and non-isothermality. In the formulation, the dimensionless time variable is defined in such a way that it includes all necessary information on the cure reaction history. Employing the routine separation of variables made possible to obtain the analytical solution for the nonlinear PDE under specific initial condition. It is shown that direct numerical solution of the PDE exactly coincides with the analytical solution. With the use of the power-law approximation that describes highly shear thinning behavior, the theoretical calculations significantly deviate from the experimental data. Bearing in mind that in the packing stage the flow is extremely slow, we employed in our theory the Newtonian law for flow of reacting liquid and described well enough the experimental data on evolution of pressure.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.1
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• pp.75-82
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• 2011

The numerical analysis of the reduction of reaction mechanism for the ignition of dimethyl ether (DME) was performed. On the basis of a detailed reaction mechanism involving 79 species and 351 reactions, the peak molar concentration and sensitivity analysis were conducted in a homogeneous reactor model. The reduced reaction mechanism involving 44 species and 166 reactions at the threshold value $7.5{\times}10^{-5}$ of the molar peak concentration was established by comparing the ignition delays the reduced mechanism with those the detailed mechanism. The predicted results of the reduced mechanism applied to the single-zone homogeneous charge compression ignition (HCCI) engine model were in agreement with those of the detailed mechanism. Therefore, this reduced mechanism can be used to accurately simulate the ignition and combustion process of compression ignition engine using DME fuel.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.9
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• pp.709-717
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• 2009

Heat transfer rate is a very important factor for the performance of a steam reformer because a steam reforming reaction is an endothermic reaction. Coaxial cylindrical reactor is the reactor design which can improve the heat transfer rate. Temperature, fuel conversion and heat flux in the coaxial cylindrical steam reformer are studied in this paper using numerical method under various operating conditions. Langmuir-Hinshelwood model and pseudo-homogeneous model are incorporated for the catalytic surface reaction. Dominant chemical reactions are assumed as a Steam Reforming (SR) reaction, a Water-Gas Shift (WGS) reaction, and a Direct Steam Reforming (DSR) reaction. Although coaxial cylindrical steam reformer uses 33% less amount of catalyst than cylindrical steam reformer, its fuel conversion is increased 10 % more and its temperature is also high as about 30 degree. There is no heat transfer limitation near the inlet area at coaxial-type reactor. However, pressure drop of the coaxial cylindrical reactor is 10 times higher than that of cylindrical reactor. Operating parameters of coaxial cylindrical steam reformer are the wall temperature, the inlet temperature, and the Gas Hourly Space Velocity (GHSV). When the wall temperature is high, the temperature and the fuel conversion are increased due to the high heat transfer rate. The fuel conversion rate is increased with the high inlet temperature. However, temperature drop clearly occurs near the inlet area since an endothermic reaction is active due to the high inlet temperature. When GHSV is increased, the fuel conversion is decreased because of the heat transfer limitation and short residence time.

• Bulletin of the Korean Chemical Society
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• v.28 no.7
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• pp.1135-1140
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• 2007

Pseudo-first-order rate constants (kobs) for the reaction of N-benzylphthalimide (NBPT) with HO- have been determined at 2.0 × 10?4 M NBPT, 1.0 × 10?3 and 2.0 × 10?3 M NaOH as well as varying concentrations of cetyltrimethylammonium bromide ([CTABr]T = 0.0-1.7 × 10?1 M). The effects of [CTABr]T ? CMC (with CMC representing the critical micelle concentration of CTABr) on kobs have been analyzed in terms of Berezin's pseudophase (BPP) model and pseudophase ion-exchange (PIE) model. Although both models give the best observed data fit with least-squares values not significantly different from each other, the calculated values of KS from BPP model appear to be more reliable compared to those from PIE model because the values of KS from BPP model are similar to the corresponding KS values determined spectrophotometrically.

• Journal of Environmental Health Sciences
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• v.30 no.5 s.81
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• pp.395-401
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• 2004

In this study, lots of methods have been studing to utilize energy and decrease contaminated effluents. There has been great progress on IGCC (Integrated gasification combined cycle) to reduce thermal energy losses. The following results have been conducted from desulfurization experiments using waste shell to remove $H_{2}S$. Unreacted core model ior desulfuriration rate prediction of sorbent was indicated. These were linear relationship between time and conversion. So co-current diffusion resistance was conducted reaction rate controlling step. The sulfidation rate is likely to be controlled primarily by countercurrent diffusion through the product layer of calcium sulfide(CaS) formed. Maximum desulfurization capacity was observed at 0.631 mm for lime, oyster and hard-shelled mussel. The kinetics of the sorption of $H_{2}S$ by CaO is sensitive to the reaction temperature and particle size at $800^{\circ}C$, and the reaction rate of oyster was faster than the calcined limestone at $700^{\circ}C$.

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.79-82
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• 2012

The gas-solid reactor, such as rotary kiln, sintering bed, incinerator and CFB boiler, is the one of most widely used industrial reactors for contacting gases and solids. the gas-solid reactor are mainly used for drying, calcining and reducing solid materials. In the gas-solid reactor, heat is supplied to the outside of the wall or inside of the reactor. The heat transfer in gas-solid reactor encompasses all the modes of transport mechanisms, that is, conduction, convection and radiation. The chemical reactions occurring in the bed are driven by energy supplied by the heat transfer. This paper deal with the effect of heat transfer and chemical reaction in the gas-solid reactor.