• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.246-250
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• 2000

Reactive radio frequency (RF)magnetron sputter has been used to deposit AlN thin film on a Si substrate. (002)Preferred orientation of AlN thin film has been obtained at low sputtering pressure and high $\textrm{N}_2$ concentration. Also it has been shown that properties of AlN thin film are affected by presputtering time. As presputtering time increased aluminum and nitride concentration of AlN thin film decreased. But oxygen concentration and grain size increased. The good preferred orientation was shown with the short presputtering time.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.224-227
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• 1999

Ferroelectric Pb(Zr$\sub$0.52/Ti$\sub$0.48/)O$_3$ thin films were fabricated by pulsed laser deposition, mainly varying process conditions such as substrate temperature, oxygen pressure, and laser energy, PZT films annealed at more than 600$^{\circ}C$ were crystallized into pure perovskite phases regardless of deposition temperatures. Lower deposition temperature of 400$^{\circ}C$ accompanied with post-annealing at 650$^{\circ}C$ resulted in denser microstructures with extremely small grains compated to those of thin films annealed at higher deposition temperatures. Hysteresis curves of thin film with small grains exhibitied good squareness and low leakage characteristics.

• Advances in materials Research
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• v.6 no.4
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• pp.343-348
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• 2017

High-pressure gas atomization was employed to prepare the Fe-based $Fe_{50}Cr_{24}Mo_{21}Si_2B_3$ alloy powder. The effect of flow rate of atomizing gas on the median powder diameter was studied. The results show that the powder size decreased with increasing the flow rate of atomizing gas. Fe-based alloy coatings with amorphous phase fraction was then prepared by high velocity oxygen fuel spraying (HVOF) of gas atomized $Fe_{50}Cr_{24}Mo_{21}Si_2B_3$ powder. Microstructural studies show that the coatings present dense layered structure and low porosity of 0.17% in about $200{\mu}m$ thickness. The Fe-based alloy coating exhibits an average hardness of about 1230 HV. Our results show that the HVOF process results in dense and well-bonded coatings, making it attractive for protective coatings applications.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.6
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• pp.95-99
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• 2013

Furnace is currently the most important doping process using POCl3 in solar cell. However furnace need an expensive equipment cost and it has to purge a poisonous gas. Moreover, furnace typically difficult appling for selective emitters. In this study, we developed a new atmospheric pressure plasma source, in this procedure, we research the atmospheric pressure plasma doping that dopant is phosphoric acid($H_3PO_4$). Metal tube injected Ar gas was inputted 5 kV of a low frequency(scores of kHz) induced inverter, so plasma discharged at metal tube. We used the P type silicon wafer of solar cell. We regulated phosphoric acid($H_3PO_4$) concentration on 10% and plasma treatment time is 90 s, 150 s, we experiment that plasma current is 70 mA. We check the doping depth that 287 nm at 90 s and 621 nm at 150 s. We analysis and measurement the doping profile by using SIMS(Secondary Ion Mass Spectroscopy). We calculate and grasp the sheet resistance using conventional sheet resistance formula, so there are 240 Ohm/sq at 90 s and 212 Ohm/sq at 150 s. We analysis oxygen and nitrogen profile of concentration compared with furnace to check the doped defect of atmosphere.

• The Korean Journal of Pharmacology
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• v.19 no.1
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• pp.61-69
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• 1983

Hypothermia is an essential preparatory procedure for cardiac surgery, which lows the metabolic rate and myocardial oxygen demand. However, hypothermia itself is a stress enough to change the tonus of sympathoadrenal system, especially the cardiovascular responses to the catecholamines. It is reported that the positive chronotropic and inotropic response of catecholamines is exaggerated during hypothermia because of decreased norepinephrine uptake at the junctional cleft or decreased catecholamine metabolism. On the other hand, there are evidences of diminished catecholamines responses in low temperature ana further, interconversion of adrenergic receptors is also suggested. Present investigation was planned to observe the cardiovascular changes and its responses to catecholamines during surface hypothermia in cat. Healthy mongrel cats, weighing $2{\sim}3\;kg$, anesthetized with secobarbital(30 mg/kg), were permitted to hypothermia by external cooling technic. Esophageal temperature, ECG (lead II), heart rate, left ventricular pressure with dP/dt, carotid artery pressure and left ventricular contractile force were monitored with Polygragh (Model 7, Grass), and the respiration was maintained with artificial respirator (V 5 KG, Narco). Followings are summarized results. 1) Surface cooling caused progressive decrease of body temperature and reached $l8.8{\pm}0.8^{\circ}C$ and $16.9{\pm}0.6^{\circ}C$ in 120 and 150 min respectively, after immersion into ice water, and ventricular fibrillation was developed at $20.4{\pm}0.65^{\circ}C$. 2) Heart rate, blood pressure and myocardial contractility were decreased after initial increase as the body temperature falls. 3) Systolic and diastolicdd P/dt of left ventricular pressure were decreased and that the decrement of diastolic dP/dt was more marked. 4) On ECG, ST depression, Twave inversion and prolongation of PR interval were prominent in hypothermia, and moreover, the prolongation of PR interval was marked just prior to the development of ventricular fibrillation. 5) The cardiovascular responses to catecholamines, especially to isoproterenol, were suppressed under hypothermia.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.451-454
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• 2006

This paper describes the results of cold flow test and hot firing tests of an uni-element coaxial swirl injector and hot firing tests of a subscale combustor, as to the development effort of coaxial swirl injector for high performance liquid rocket engine combustor. A major design parameter for coaxial swirl injector is the recess number of a bi-swirl injector. The results of hot firing tests of the uni-element injector combustor and the sub-scale combustor are analyzed to investigate the effect of the recess number influencing on the combustion performance and pressure fluctuation. The test results of a cold flow test of the unielement combustor shows that it was shown that the change in recess number has significant effect on mixing characteristics and efficiency, while the effect of recess number on atomization characteristic is not The results of a series of firing tests using unielement and subscale combustor show that the recess length significantly affects the hydraulic characteristics, the combustion efficiency, and the dynamics of the liquid oxygen/kerosene bi-swirl injector. As a point of combustion performance, combustion efficiencies are 90% for unielement combustor and 95% for subscale combustor. The difference in the characteristic velocities between the unielement combustor and the subscale combustor may be caused by the difference in thermal loss to the combustor wall and the relative lengths of the combustion chamber. For a mixed type coaxial swirl combustor, the pressure drop across the injector increases as recess number becomes larger. The low frequency pressure fluctuation observed in unielement combustor can be related to the propellant mixing characteristics of the coaxial bi-swirl injector. The effect of the recess number on the pressure fluctuation inside the combustion chamber is more significant in un i-element combustor than the subscale combustor, of which the phenomena are also observed in time domain and frequency domain.

• Journal of Chest Surgery
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• v.22 no.6
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• pp.894-900
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• 1989

It has been suggested that mixed venous $O_{2}$ tension is a predicor of cardiac output especially in a critically ill patient after an open heart surgery. From April 1988 through September 1989, we monitored mixed venous $O_{2}$ tension and pulmonary arterial pressure in 48 patients with acyanotic congenital heart disease at postoperative 1 hour, 6 hour, 12 hour, 24 hour, and 48 hour respectively. They were divided into Group I, with severe pulmoary hypertension, and Group II, without severe pulmonary hypertension. In Group I, mixed venous $O_{2}$ tension and cardiac index showed significant increase with time (p<0.05), but the ratio of pulmonary-aortic systolic pressure didn't show significant change. The increase was significant only 24 hour after operation, and so this low cardiac performance in early postoperative period should be considered when postoperative management is being planned in the risky patient. In Group II, all of the three variables didn't show any significant change with time. The correlation coefficient between mixed venous $O_{2}$ tension and cardiac index was significantly different from zero in both Group I (p<0.001) and group II (p<0.05) at each imeperiod, but the ratio of pulmonary-aortic systolic pressure didn't correlated well with the other 2 variables. Our study showed that serial determination of mixed venous $O_{2}$ tension in acyanotic congenital heart disease could be used as a guide in estimating the cardiac index postoperatively.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.4
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• pp.381-386
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• 2015

Environmental pollution and alternative energy has attracted increasing interest. The use of diesel engines is expected to increase in the world owing to their fuel economy. The problem of air pollution emissions from marine engines is causing a major concern in many areas. An alternative fuel was introduced as an environmentally friendly fuel to reduce the toxic emissions from conventional fossil fuels. Biodiesel fuel, which is a renewable energy is highlighted as environmentally friendly energy. This energy can be operated in regular diesel engines when it is blended with invariable ratios without making changes. In this study, a bio-diesel fuel was produced from waste cooking oil and applied to a marine diesel engine to examine the effects on the characteristics of combustion. Waste cooking oil contains a high cetane number and viscosity component, a low carbon and oxygen content. As a result, the brake specific fuel consumption was increased, and the cylinder pressure, rate pressure rise and rate of heat release were decreased.

• Journal of the Korean Electrochemical Society
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• v.11 no.4
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• pp.289-296
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• 2008

Electrochemical studies were performed by a half-cell test for the nickel hydroxide (cathode) and hydrogen storage alloy(anode) electrodes for the sealed Ni-MH batteries applicable to industrial use. The electrodes were fabricated and checked a charge efficiency and an internal pressure of the battery during charge-discharge cycling. In order to reduce the internal pressure of the sealed Ni-MH battery, cyclic voltammetry (CV) were performed on the electrodes of nickel hydroxide(cathode) and hydrogen storage alloy(anode), respectively. The results of the test showed clearly the oxidation/reduction and oxygen evolution reaction in a nickel hydroxide electrode and the hydrogenation behavior of a hydrogen storage electrode. The sealed Ni-MH battery of 130Ah was fabricated by using nickel hydroxide of a high over-voltage for an oxygen gas evolution and hydrogen storage alloy of a good performance for activation The battery showed a good characteristics such as a high charge efficiency of 98% at 1 C charge current, a low level internal pressure of 4 atm on a continuous over-charging and a large preservation capacity of 95% at 400 cycle.

• Journal of the Korean Ceramic Society
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• v.28 no.6
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• pp.457-464
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• 1991

Aluminum nitride (AlN) has excellent properties such as high thermal conductivity and electrical resistivity, whereas it has some disadvantages such as low sinterability and tendency to be hydrolyzed by moisture at room temperature. In the present work, the relative density, modulus of rupture and microhardness were examined for pressure-less-sintered AlN (synthetic and commercial) bodies which were prepared under the conditions of various sintering temperatures, holding times and additions of CaCO3 which showed the best effect on sinterability among the various sintering aids. As a result, the AlN bodies with 1.0 wt% CaCO3 (0.56wt% CaO) which were sintered at 1800$^{\circ}C$ for 20 min showed good densification. In this case, the relative densities were 95.9% and 95.2%, and microhardnesses were 10.3 GPa and 9.8 GPa for synthetic and commercial AlN respectively. And as the holding time at 1800$^{\circ}C$ was increased from 10 min to 60 min, the relative density was increased from 91.9% to 96.5%. It was considered that impurities of metals and oxygen promoted the densification of AlN at low temperature (1600$^{\circ}C$).