• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.3
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• pp.345-351
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• 2016

This study was carried out to determine an optimal lean $NO_x$ trap (LNT) regeneration condition based on a $NO_x$ storage fraction. The LNT regeneration was performed by an in-cylinder post fuel injection method. A $NO_x$ storage fraction is defined by the ratio of current cumulated $NO_x$ amount in the LNT to the $NO_x$ storage capacity: 0 means empty and 1 fully loaded. In this study five engine operating conditions were chosen to represent the New European Driving Cycle. With various $NO_x$ storage fractions each engine operating condition, the LNT regeneration was executed and then $NO_x$ conversion efficiency, additional fuel consumption, CO and THC slip, peak catalyst temperature were measured. The results showed that there exist an optimal condition to regenerate the LNT, eg. 1500 rpm 6 bar BMEP with below 0.7 $NO_x$ storage fraction in this experimental constraint.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.2
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• pp.60-66
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• 2014

A control oriented model of the Lean $NO_x$ trap (LNT) was developed to determine the timing of $NO_x$ regeneration. The LNT model consists of $NO_x$ storage and reduction model. Once $NO_x$ is stored ($NO_x$ storage model), at the right timing $NO_x$ should be released and then reduced ($NO_x$ reduction model) with reductants on the catalyst active sites, called regeneration. The $NO_x$ storage model simulates the degree of stored $NO_x$ in the LNT. It is structured by an instantaneous $NO_x$ storage efficiency and the $NO_x$ storage capacity model. The $NO_x$ storge capacity model was modeled to have a Gaussian distribution with a function of exhaust gas temperature. $NO_x$ release and reduction reactions for the $NO_x$ reduction model were modeled as Arrhenius equations. The parameter identification was optimally performed by the data of the bench flow reactor test results at space velocity 50,000/hr, 80,000/hr, and temperature of $250-500^{\circ}C$. The LNT model state, storage fraction indicates the degree of stored $NO_x$ in the LNT and thus, the timing of the regeneration can be determined based on it. For practical purpose, this model will be verified more completely by engine test data which simulate the NEDC transient mode.

• Korean Journal of Plant Resources
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• v.12 no.3
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• pp.198-203
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• 1999

7S and 11S globulins are two major storage proteins in soybean seed. For improving the quality of soybean seed protein, an increase of 11S/7S ratio would be a desirable objective because 11S globulin contains much more sulfur-containing amino acids than 7S globulin. In this study, six soybean varieties grown at three locations were used for genetic variation analysis of 7S and 11S globulins. It was possible to screen the soybean genotypes having aberrant subunit compositions of the two globulins by a sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). So, heritabilities, genotypic and phenotypic correlations among eight globulin fraction contents of soybean seeds were estimated. The mean value of 7S and 11S globulin fraction contents were 38.9% and 61.1%, respectively, and the ratio of 7S to 11S globulin ranged from 0.58 to 0.74. The high heritability value was found in $\beta$ subunits but the values of acidic and basic subunits were relatively low. Genotypic correlations were higher than the corresponding phenotypic correlations in most of globulin subunit contents. $\beta$ subunits was negatively correlated with $\alpha$ and $\alpha$' subunits among 7S fractions, while no significant correlation between $\alpha$ and $\alpha$' subunits could be found In case of 11S fractions, acidic and basic subunits exhibited no genotypic but negative phenotypic correlation.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.5
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• pp.13-19
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• 2014

Urea-SCR system is the selective catalytic reduction to reduce nitrogen oxides ($NO_x$) emitted from diesel vehicles. The objective of this study is numerical analysis of 3-dimensional unsteady melting problems of frozen urea by using an electric heater. It can be applied to determine capacity of power with respect to time and the location of the urea suction pipe in urea storage tank. The study includes the change of liquid volume fraction, temperature profiles and a influence of natural convection by using the commercial software STAR-CCM+(v7.06). The accuracy of the numerical analysis is estimated by comparisons with experimental data. After validation, a numerical analysis for freezing urea is conducted with four different heating power. From the results, it was found that relation of velocity of phase interface and amount of melting urea by increasing heating power in a container. There is also a difference in trend between velocity of phase interface and amounts of melting urea because of effect of natural convection.