• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.39 no.9
• /
• pp.727-734
• /
• 2015

Recently, because of the increased oil prices globally, there have been studies investigating the improvement of fuel-conversion efficiency in internal combustion engines. The improvements realized in thermal efficiency using lean combustion are essential because they enable us to realize higher thermal efficiency in gasoline engines because lean combustion leads to an increase in the heat-capacity ratio and a reduction of the combustion temperature. Gasoline direct injection (GDI) engines enable lean combustion by injecting fuel directly into the cylinder and controlling the combustion parameters precisely. However, the extension of the flammability limit and the stabilization of lean combustion are required for the commercialization of GDI engines. The reduction characteristics of three-way catalysts (TWC) for lean combustion engines are somewhat limited owing to the high excess air ratio and low exhaust gas temperature. Therefore, in the present study, we assess the reaction of exhaust gases and their production in terms of the development of efficient TWCs for lean-burn GDI engines at 2000 rpm / BMEP 2 bar operating conditions, which are frequently used when evaluating the fuel consumption in passenger vehicles. At the lean-combustion operating point, $NO_2$ was produced during combustion and the ratio of $NO_2$ increased, while that of $N_2O$ decreased as the excess air ratio increased.

• Tuberculosis and Respiratory Diseases
• /
• v.48 no.6
• /
• pp.944-955
• /
• 2000

Background : In patients with chronic obstructive pulmonary disease(COPD), several factors have been associated with a poor prognosis. These include old age, low $FEV_1$ low diffusing capacity, high alveolar-arterial oxygen pressure difference, and finally cor pulmonale. This study was done to investigate if the ECG signs suggesting cor pulmonale were independent prognostic factors in patients with COPD. Method : We analyzed ECG, pulmonary function data and arterial blood gas values in 61 patients who were admitted through the emergency department with an acute exacerbation of COPD. The ECG signs reflecting cor pulmonale were right strial overloading(RAO), right bundle branch block, right ventricular hypertrophy and low-voltage QRS. The 61 patients were divided into 2 groups ; group I with no ECG signs(n=36) and group II with one or more ECG signs(n=25) suggesting cor, pulmonale. Results : Poor, prognostic factors by univariate analysis were low $FEV_1$, $FEV_1$ % pred., VC % pred., DLco, DLco % pred., $PaO_2$ and $SaO_2$ high $PaCO_2$ presence of ECG signs reflecting cor pulmonale, presence of mental status change, use of mechanical ventilator, and long term use of glucocorticoid. A multivariate analysis indicated that age(risk ratio=1.13, 95% confidence interval 1.05-1.23), DLco % pred. (risk ratio=0,97. 95% confidence interval 0.94-0.99), $PaO_2$ (risk ratio=0.95, 95% confidence interval 0.90-0.99) and RAO(risk ratio=5.27, 95% confidence interval 1.40-19.85) were independent prognostic factors of survival. There was a significant difference in survival between the patients with and without RAO(p=0.038). The survival rates at 1, 2, and 5 years were 94.5%. 81.4%, and 50.0% in patients without RAO and 82.4%, 70.6%, and 27.5% in patients with RAO, respectively. Conclusion : These results suggest that the presence of ECG signs reflecting cor pulmonale is a predictor of survival and that RAO of these ECG signs is a significant independent predictor of survival in patients with COPD.

• Korean Journal of Materials Research
• /
• v.17 no.4
• /
• pp.203-206
• /
• 2007

Effects of doping rare earth elements on Ln site of $Ln_{0.7}Ca_{0.3}MnO_3$ (Ln = N d, Sm and La) were examined from structure, magnetic and electrical properties. Size of a-axis increased as following order of La < Nd < Sm, whereas c-axis was not much changed. Curie temperatures of 170 K for $Nd_{0.7}Ca_{0.3}MnO_3$, 110 K for $Sm_{0.7}Ca_{0.3}MnO_3$ and 250 K for $La_{0.7}Ca_{0.3}MnO_3$ were obtained. This result coincides with change of Mn-O bond length causing by a-axis lattice constant. The highest magnetroresistance ratios were 22% at 77 K for $Sm_{0.7}Ca_{0.3}MnO_3$, 32% at 110 K for $Nd_{0.7}Ca_{0.3}MnO_3$, and 33% at 180 K for $La_{0.7}Ca_{0.3}MnO_3$.

• The Korean Journal of Mycology
• /
• v.23 no.3 s.74
• /
• pp.275-283
• /
• 1995

The nutritional requirements of mycelial growth for Pleurotus spp. were studied. As the carbon sources, soluble starch and dextrin, nitrogen sources, arginine and ammonium tartrate, and calcium sources, $CaCO_3$ enhanced mycelial growth. Optimum C/N ratio was 100 : 1. On the base of results from the experiment on nutritional requirements, the following receipe is suggested for growth of Pleurotus spp.; starch 15 g, arginine 3.484 g, ammonium tartrate 3.06 g, $CaCO_3$ 0.314 g, $KH_2PO_4$ 8.138 g, $K_2HPO_4$ 1.584 g, $MgSO_4{\cdot}7H_2O$ 1.5 g for P. sajor-caju and 2.5 g for P. ostreatus. $FeSO_4{\cdot}7H_2O$ 0.02 g, $ZnSO_4{\cdot}7H_2O$ 0.03 g, $MnSO_4{\cdot}7H_2O$ 0.02 g, optimum pH 6.0. This new synthetic medium is tentatively designated as Park's medium.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.26 no.4
• /
• pp.289-293
• /
• 2013

We have studied structural, optical, and electrical properties of the Ga-doped ZnO (GZO) thin films being usable in transparent conducting oxides. The GZO thin films were deposited on the corning 1737 glass plate by the RF magnetron sputtering system. To find optimal properties of GZO for transparent conducting oxides, the Ar gas in sputtering process was varied as 40, 60, 80 and 100 sccm, respectively. As reaction gas decreased, the crystallinity of GZO thin film was increased, the optical bandgap of GZO thin film increased. The transmittance of the film was over 80% in the visible light range regardless of the changes in reaction gas. The measurement of Hall effect characterizes the whole thin film as n-type, and the electrical property was improved with decreasing reaction gas. The structural, optical, and electrical properties of the GZO thin films were affected by Ga dopant content in GZO thin film.

• Journal of the Korean Society of Combustion
• /
• v.13 no.4
• /
• pp.47-53
• /
• 2008

The reaction mechanism of methane dry reforming has been investigated using an arc-jet reactor. The effects of input power, $CO_2/CH_4$ and added $O_2$ were investigated by product analysis, including CO, $H_2$, $C_{2}H_{Y}$ and $C_{3}H_{Y}$ as well as $CH_4$ and $CO_2$. In the process, input electrical power activated the reactions between $CH_4$ and $CO_2$ significantly. The increased feed ratio of the $CO_2$ to $CH_4$ in the dry reforming does not affect to the $CH_4$ conversion. but we could observe increase in CO selectivity together with decreasing $H_2$ generation. Added oxygen can also increase not only CO selectivity but also $CH_4$ conversion. However, hydrogen selectivity was decreased significantly due to a increased $H_{2}O$ formation.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2011.05a
• /
• pp.50.1-50.1
• /
• 2011

Lead-free ceramics with a composition of 0.55 mol%$K_4CuNb_8O_23-(K_{1-x}Na_x)NbO_3$ (KCN-KNNx) where $0.45{\leq}x{\leq}0.60$ were synthesized by conventional ceramic processing. Results revealed that the addition of Na was effective in changing the microstructure and relative density of KCN-KNNx. Further, the addition of Na resulted in a slight shift of the phase transition temperatures (To-t and Tc) toward low values. A high mechanical quality factor (Qm) of 1850 was found atx=0.54, which might be due to the build-up of an internal bias field (Ei) within KCN. Thermal hysteresis in KNNx was confirmed with an increase in the Na content during the heating and cooling cycles, resulting from structural changes. Thus, KCN-KNNx with x=0.54 exhibits excellent piezoelectric properties with d33 (97 pC/N), kp (36%), and Qm (1850), being promising candidates for application in high-power piezoelectric devices.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.51 no.11
• /
• pp.526-530
• /
• 2002

The $(Sr_{0.9}Ca_{0.1})TiO_3(SCT)$ thin films were deposited on Pt-coated electrode (Pt/TiN/$SiO_2$/Si) using RF sputtering method. The composition of SCT thin film deposited on Si substrate at room temperature is close to stoichiometry(1.081 in A/B ratio). The maximum dielectric constant of SCT thin film was obtained by ammealing at $600^{\cric}C$. The temperature dependence of dielectric loss showed a value within 0.02 in temperature ranges of -80 ${\sim}$ +90$^{\circ}C$. The capacitance characteristics showed a stable value within ${\pm}$4%. The drastic decrease of dielectric constant and increase of dielectric loss in SCT thin films was observed at the frequency above 200kHz.

• The Bulletin of The Korean Astronomical Society
• /
• v.42 no.1
• /
• pp.58.4-59
• /
• 2017

Sanduleak's star is a suspected symbiotic binary located in the Large Magellanic Cloud. It is known that it has a giant jet with physical size ~ 14pc. Its spectrum shows two strong emission bands at $6825{\AA}$ and $7082{\AA}$, which are originated from Raman-scattering of O VI by neutral hydrogen atoms. We present the high-resolution spectrum of Sanudleak's star obtained with MIKE at the Magellan-Caly telescope to investigate the O VI emission region based on the profiles of the two Raman features. In this spectrum, it is noted that the Raman $6825{\AA}$ feature exhibits a single broad peak profile, which is in high contrast with a clear triple peak profile of the Raman $7082{\AA}$ feature. In our analysis we suggest that the O VI emission region consist of three main emission parts: an accretion disk, a bipolar outflow and an optically thick, compact component surrounding the white dwarf. By performing Monte Carlo simulation we constrain the representative column density of the H I scattering region N_HI ~1${\times}$10^23 cm^-2, which is in accordance with the observed flux ratio in the two Raman features F(6825)/F(7082) ~ 4.5.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.14 no.3
• /
• pp.223-229
• /
• 1994

To find out the effects of phosphatic fertilizer application levels on the botanical composition, mineral contents and mineral nutrient deprivation of grasses and the chemical properties of soil, this expriment was arranged as a randomized complete block design with six treatments(0, 50, 100, 150, 200 and 250kg $P_2O_5$/ha) and conducted at hilly land in Gwangju, Gyeonggi Province from September, 1989 to October, 1992. The results obtained are summarized as follows: The botanical composition of grasses without posphatic fertilizer application was poor but with 150kg $P_2O_5$/ha application, remarkably increased in legume of grasses and decreaed in weed. As the phophatic fertilizer levels increase, P, Ca and Mg content of grasses were increased but N and K content tended not to be regular, and Ca/p and K/Ca+ Mg equivalent ratio were lowered. Up to 150kg $P_2O_5$/ha application level, the mineral nutrient content deprived by dry matter yield was increased but with that over application, tend not to be increased. Most of applied mineral elements were accumulated at a subsurface of grassland and as the phosphatic fertilizer application levels increase, the available $P_2O_5$ and exchangeable Mg contents of the soil tended to be remarkably increased and exchangeable K content tended to be decreased, but pH, OM and exchangeable Ca content tended not to be regular.