• Journal of Nutrition and Health
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• v.26 no.6
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• pp.680-691
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• 1993

Rats were fed for an 8-week period a low riboflavin diet(5ug riboflavin/day) or a control diet(30ug/day) supplied either ad libitum or by pair feeding in order to study the effect of riboflavin on the metabolism of lipids and neurotransmitters. Erythrocyte glutathione reductase (EGR) and monomine oxidase(MAO) activity in the liver and brain were assayed. EGR activity coefficient in riboflavin deficient rats was significantly higher than in ad libitum controls whereas MAO activity was decreased in the deficient rats. Fatty acid composition showed a different trend in the serum, liver and brain. In the serum, the concentrations of essential fatty acids and $\omega$-3 fatty acids(eicosapentaenoic acid, docosahexaenoic acid)were decreased about 20-40% in the deficient and pair-fed than in the ad libitum controls. Brain serotonin and 5-HIAA(5-hydroxyindole acetic acid) concentrations were decreased in the riboflavin deficient rats. Learning ability measured by a water maze and exploratory activity using the open field test were not impaired in the deficient rats. These results indicate that brain lipid metabolism was protected in subclinical riboflavin deficiency, however, riboflavin deficiency affected brain serotonin content.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.3
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• pp.335-342
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• 2012

Nowadays, automobile manufacturers are focusing on the reduction of exhaust-gas emissions because of the harmful effects on humans and the environment, such as global warming by greenhouse gases. Gasoline direct injection (GDI) combustion is a promising technology that can improve fuel economy significantly compared to conventional port fuel injection (PFI) gasoline engines. In the present study, ultra-lean combustion with an excess air ratio of over 2.0 is realized with a spray-guided-type GDI combustion system, so that the fuel consumption is improved by about 13%. The level of exhaust-gas emissions and the operation performance with the multiple injection strategy and exhaust-gas recirculation (EGR) are examined in comparison with the emission regulations and from the point of view of commercialization.

• Journal of ILASS-Korea
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• v.16 no.3
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• pp.119-125
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• 2011

Due to the oxygen contents in biodiesel, application of the fuel to compression ignition engines has significant advantages in terms of lowering PM formation in the combustion chamber. In recent days, considerable studies have been performed to extend the low temperature combustion regime in diesel engines by applying biodiesel fuel. In this work, low temperature combustion characteristics of biodiesel blends in dilution controlled regime were investigated at a fixed engine operating condition in a single cylinder diesel engine, and the comparisons of engine performances and emission characteristics between biodiesel and conventional diesel fuel were carried out. Results show that low temperature combustion can be achieved at $O_2$ concentration of around 7~8% for both biodiesel and diesel fuels. Especially, by use of biodiesel, noticeable reduction (maximum 50% of smoke was observed at low and middle loads compared to conventional diesel fuel. In addition, THC(total hydrocarbon) and CO(Carbon monoxide) emissions decreased by substantial amounts for biodiesel fuel. Results also indicate that even though about 10% loss of engine power as well as 14% increase of fuel consumption rate was observed due to lower LHV(lower heating value) of biodiesel, thermal efficiencies for biodiesel fuel were slightly elevated because of power recovery phenomenon.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.3
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• pp.85-91
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• 2003

In this study, the potential possibility of oxygenated fuel such as Methyl tertiary butyl ether (MTBE) was investigated for the sake of exhausted smoke reduction from diesel engine. MTBE has been used as a fuel additive blended into unleaded gasoline to improve octane number, but the study of application for diesel engine was incomplete. Because MTBE includes oxygen content approximately 18%, it is a kind of oxygenated fuel that the smoke emission of MTBE is reduced remarkably compared with commercial diesel fuel. But, the NOx emission of MTBE blended fuel is increased compared with commercial diesel fuel. And, it was tried to analyze not only total hydrocarbon but individual hydrocarbon components from $C_1$ to $C_6$ in exhaust gas using gas chromatography to seek the reason for remarkable reduction of smoke emission. Individual hydrocarbons($C_1$~$C_6$) as well as total hydrocarbon of oxygenated fuel are reduced remarkably compared with diesel fuel. And, the effects of exhaust gas recirculation(EGR) on the characteristics of NOx emission has been investigated, too. It was found that simultaneous reduction of smoke and NOx was achieved with oxygenated fuel and cooled EGR method.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.3
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• pp.35-40
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• 2007

Our environment is faced with serious problems related to the air pollution from automobiles in these days. In particular, the exhaust emissions of diesel engine are recognized main cause which influenced environment strong, In this study, the potential possibility of biodiesel fuel was investigated as an alternative fuel for a naturally aspirated common rail diesel engine. The smoke emission of biodiesel fuel 5vol-%(min. content) was reduced in comparison with diesel fuel, that is, it was reduced approximately 60% at 4000rpm, full load. But, power, torque and brake specific energy consumption didn't have no large differences. But, NOx emission of biodiesel fuel was increased compared with a commercial diesel fuel. Also, the effects of exhaust gas recirculation(EGR) on the characteristics of NOx emission has been investigated. It was found that simultaneous reduction of smoke and NOx was achieved with biodiesel fuel(5vol-%) and cooled EGR method($5{\sim}10%$) in a common rail diesel engine.

• Journal of Power System Engineering
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• v.9 no.3
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• pp.15-20
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• 2005

In this paper, the effect of oxygen component in fuel on the exhaust emissions has been investigated for an indirect injection diesel engine. It was tested to estimate change of engine performance and exhaust emission characteristics for the commercial diesel fuel and oxygenated blended fuel which has four kinds of mixed ratio. And, the effects of exhaust gas recirculation(EGR) on the characteristics of NOx emission have been investigated. Ethylene glycol mono-n-butyl ether(EGBE) contains oxygen component 27% in itself, and it is a kind of effective oxygenated fuel of mono-ether group that the smoke emission of EGBE is reduced remarkably compared with commercial diesel fuel, that is, it can supply oxygen component sufficiently at higher loads and speeds in diesel engine. It was found that simultaneous reduction of smoke and NOx was achieved with oxygenated fuel(10vol-%) and cooled EGR method(10%).

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.4
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• pp.447-453
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• 2016

The reduction technologies of exhaust gas from both the off-road engine and on-road vehicles are important. It is possible to apply various combustion technologies with engines after the application of a treatment technology to this field. In this study, main injection timing, pilot injection timing, and exhaust gas recirculation (EGR) rate were selected as the experimental parameters whose effects on the emission of exhaust gases and on the fuel consumption characteristics were to be determined. In the experiment, the emission of nitrogen oxide (NOx) and Smoke, and the Torque at the same fuel consumption level, were measured. The experimental data were analyzed using the Taguchi method with an L9 orthogonal array. Additionally, analysis of variation (ANOVA) was used to confirm the influence of each parameter. Consequently, the level of each parameter was selected based on the signal-to-noise ratio data (main injection timing, 3; pilot injection timing, 3; EGR rate, 2), and the results of the Taguchi prediction were verified experimentally (error: NOx, 10.3 %; Smoke, 6.6 %; brake-specific fuel consumption (BSFC), 0.6 %).

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.6
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• pp.128-136
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• 2007

It is well known that two representative methods satisfy EURO-IV regulation from EURO-III. The first method is to achieve the regulation through the reduction of NOx in an engine by utilizing relatively high EGR rate and the elimination of subsequently increased PM by DPF. However, it results in the deterioration of fuel economy due to relatively high EGR rate. The second is to use the high combustion strategy to reduce PM emission by high oxidation rate and trap the high NOx emissions with DeNOx catalysts such as Urea-SCR. While it has good fuel economy relative to the first method mentioned above, its infrastructure is demanded. In this paper, the number distribution of nano PM has been evaluated by Electrical Low Pressure Impactor(ELPI) and CPC in case of Urea-SCR system in second method. From the results, the particle number was increased slightly in proportion to the amount of urea injection on Fine Particle Region, whether AOC is used or not. Especially, in case of different urea injection pressure, the trends of increasing was distinguished from low and high injection pressure. As low injection pressure, the particle number was increased largely in accordance with the amount of injected urea solution on Fine Particle Region. But Nano Particle Region was not. The other side, in case of high pressure, increasing rate of particle number was larger than low pressure injection on Nano Particle Region. From the results, the reason of particle number increase due to urea injection is supposed that new products are composited from HCNO, sulfate, NH3 on urea decomposition process.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.3
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• pp.390-401
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• 2000

In this study, numerical calculation is carried out to investigate the influence of injection timing, fuel amount, intake $O_2$ concentration, and EGR on Nitric Oxide(NO) formation using a two-zone model in a diesel engine. Results can be summarized as follows. The NO formation is very sensitive to the burned gas temperature, so multi-zone model must be applied to combustion process to predict the burned gas temperature exactly. Since the burned gas temperature increases rapidly during the premixed combustion, most NO is formed within 20 crank angle degrees after ignition. As the injection timing is retarded, the combustion occurs later in the expansion process which causes the decrease of burned gas temperature and, as a result, NO formation decrease. The increase of fuel amount results in the increase of earlier formation of NO in the engine. As the intake $O_2$ concentration increases, the maximum pressure and burned gas temperature increase due to activate combustion. And, [O] mole fraction of equilibrium combustion products also increase. Therefore NO exponentially increases. If exhaust gas is recirculated, the burned gas temperature decreases which results in NO decrease. If exhaust gas is cooled, more NO can be decreased.

• Experimental and Molecular Medicine
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• v.51 no.2
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• pp.9.1-9.10
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• 2019

Mesangial cell proliferation has been identified as a major factor contributing to glomerulosclerosis, which is a typical symptom of diabetic nephropathy (DN). Lysophosphatidic acid (LPA) levels are increased in the glomerulus of the kidney in diabetic mice. LPA is a critical regulator that induces mesangial cell proliferation; however, its effect and molecular mechanisms remain unknown. The proportion of ${\alpha}-SMA^+/PCNA^+$ cells was increased in the kidney cortex of db/db mice compared with control mice. Treatment with LPA concomitantly increased the proliferation of mouse mesangial cells (SV40 MES13) and the expression of cyclin D1 and CDK4. On the other hand, the expression of $p27^{Kip1}$ was decreased. The expression of $Kr{\ddot{u}}ppel$-like factor 5 (KLF5) was upregulated in the kidney cortex of db/db mice and LPA-treated SV40 MES13 cells. RNAi-mediated silencing of KLF5 reversed these effects and inhibited the proliferation of LPA-treated cells. Mitogen-activated protein kinases (MAPKs) were activated, and the expression of early growth response 1 (Egr1) was subsequently increased in LPA-treated SV40 MES13 cells and the kidney cortex of db/db mice. Moreover, LPA significantly increased the activity of the Ras-related C3 botulinum toxin substrate (Rac1) GTPase in SV40 MES13 cells, and the dominant-negative form of Rac1 partially inhibited the phosphorylation of p38 and upregulation of Egr1 and KLF5 induced by LPA. LPA-induced hyperproliferation was attenuated by the inhibition of Rac1 activity. Based on these results, the Rac1/MAPK/KLF5 signaling pathway was one of the mechanisms by which LPA induced mesangial cell proliferation in DN models.