• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.4
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• pp.299-304
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• 2013

The HAN which is an ionic liquid is a non-toxic monopropellant with high storability, and its specific impulse can be increased by blending methanol, thereby it can substitute the hydrazine. The HAN was synthesized by acid-base reaction of hydroxylamine and nitric acid, and the blending ratio of HAN and methanol is 8.2:1. The iridium catalyst was used to decompose the HAN, and 1 N class thruster with shower head type injector having one orifice was used to evaluate the HAN/Methanol propellant. The thermal stability of distributor was increased by using ceramic material to endure the high temperature of product gas. The preheating temperature of catalyst should be $400^{\circ}C$ at least for the complete decomposition. The feeding pressure should be increased to increase the $C^*$ efficiency, thereby the decomposition performance was decreased upstream catalyst, and the performance of thruster was decreased. The fine metal mesh was inserted after the injector to improve the atomization of propellant, thereby it can settle the performance decrease problem. The phenomenon of performance decrease was remarkably improved owing to the insertion of fine metal mesh.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.3
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• pp.218-229
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• 2003

A new biotelemetry method that the installation and the treatment of equipment is convenient and the instantaneously detailed location of the fish attached the pinger is able to track comparatively easily was developed. The receiving system in this biotelemetry method was advanced for track the detailed behavior of the fish by the miniature tracking pinger, because it was a burden to fish to add the pinger with the water temperature and the pressure sensor. By combining of the super short base line (SSBL) method to detect the direction of pinger and the pinger synchronizing method to measure the range from receiving transducer to pinger, the three dimensional locations of fish to the receiving transducer is gotten instantaneously. The receiving system is devised to realize the high precision or wide detection range by application of the basic design method for receiving system of biotelemetry developed by the present authors and the hydrophone array configuration. The measurement distance error in the pinger synchronizing method is minimized through the correction of which the deviation of transmission pluse period of pinger is caused by changing water temperature. A prototype system which is able to track the instantaneously detailed location of the fish by the SSBL and pinger synchronizing biotelemetry (SPB) method was produced.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.5
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• pp.517-532
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• 2010

After establishment of Banwol industrial complex in 1987, Ansan city becomes the largest industrial sector development in Gyeonggi-do, Korea. As the population and industrial activity grow over this region, toxic air pollutants, particularly POPs (Persistent Organic Pollutants) from various emission sources have been major public concerns. Air samples for POPs monitoring were collected at the industrial sites ($A_2$), residential sites ($B_1$, $B_2$), commercial site (C), and rural/remote site (D) of the area of Ansan during 2008 with a prolonged industrial sampling site $A_1$ from 2001 to 2008. All samples were analysed for 2,3,7,8 substituted-polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/Fs) and dioxin like polychlorinatd diphenyls (dl-PCBs). In site $A_1$, a steady decline of their concentrations from 2003 to 2008 was observed due to the reinforced emission guideline from waste incinerators. The average concentration of the PCDD/Fs and dl-PCBs ranged between 0.118 pg-TEQ/$m^3$ (rural/remote site D) and 0.532 pg-TEQ/$m^3$ (industrial area $A_2$). These level were generally consistent with previous studies in Gyeonggi-do, while higher than other places. Most of PCDD/Fs congener were partitioned into particle phase, whereas dl-PCBs were partitioned into gas phase. The logarithm of gas-particle partition coefficient $K_P$ of dl-PCBs and PCDD/Fs were well correlated with sub-cooled liquid vapor pressure $P_L$. The slope $m_T$ of log $K_P$ versus log $P_L$ for PCDD/Fs (-1.22) and dl-PCBs (-1.02) in industrial area ($A_2$) were high compared to other residential/commercial area. It suggests that this area was likely influenced by the direct emission source of PCDD/Fs and dl-PCBs. To simulate the partition of PCDD/Fs and dl-PCBs between gas and particle phase, Junge-Pankow model ($P_L$-base) and $K_{oa}$ model were applied. It was found that J-P model was more suitable than the $K_{oa}$ model in this study.

• Journal of radiological science and technology
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• v.37 no.1
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• pp.15-20
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• 2014

This study was to evaluate clinical feasibility of biodegradable polymeric membrane for interventional procedure in preliminary study. Bio-degradable polymetric membrane was produced into a solution by mixing hyaluronic acid powder with NaOH solution in a heating mantle. Three different concentrations of contrast media (10, 20, and 30 vol%) were added to the produced soluble powder, and vertical agitation was performed for 12 hours at a speed of 100 to 200 rpm at a room temperature. It was freeze dried for 24 hours at a temperature $80^{\circ}C$. Pressure on the freeze dried sample was exerted by a hydraulic press in order to form the freeze dried sample into a membrane. The membrane produced with varying contrast medium concentration was visually examined by a scanning electron microscope and radiographically inspected. Under the visual examination, the higher the concentration of contrast medium, the rougher the surface. Radiographic transparency was similar under all conditions of fluoroscopic radiography, simple radiography, and serial radiography. In conclusion, this preliminary study verified that bio-degradable membrane produced with hyaluronic acid was a material with clinical usability.

• Journal of Chest Surgery
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• v.9 no.2
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• pp.220-238
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• 1976

Six cases of congenital heart disease were operated on by means of cardiopulmonary bypass between December, 1975 and April, 1976. Two cases of ventricular septal defects (VSD), two cases of VSD, associated with ruptured aneurysm of sinus Valsalva, two cases of atrial septal defects (ASD) and one case of pulmonic stenosis with patent ductus arteriosus were operated. Sarns roller pumps and Bentley Temptrol oxygenators were used for extracorporeal circulation. Pump oxygenator was primed with Ringer's lactate solution, 5% dextrose in water, mannitol, and ACD blood. Flow rate ranged from 2.0 to $2.4L/M^2/min$. Bicarbonate was added to the oxygenator with estimated amount as 15 mEq/L/hr. Venous catheters were introduced into superior and inferior vena cava, and oxygenated blood was returned to the body through aortic cannula inserted into ascending aorta. Moderate hypothermia ($30^{\circ}C$) was induced by core cooling. Aorta was cross clamped for 15 minutes and released for 3 minutes, and repeated clamping when necessary. Atrial and ventricular septal efects were closed by direct sutures. Aneurysms of sinus Valsalva ruptured into the right ventricle were repaired through right ventriculotomy by d:rect closure with Dacron patch reinforcement. Cardiopulmonary bypass time varied from 66 to 209 minutes, and aorta cross clamping time ranged from 13 to 56 minutes. Postoperative bleeding was minimal except one case who needed for evacuation of substernal hematoma. Intra- and postoperative urinary output was satisfactory. Acid-base balance, partial pressure of $O_2$, electrolytes, and hematological changes during intra- and post-perfusion period remained at the acceptable ranges. No mortality was experienced.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.7
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• pp.563-567
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• 2011

The most widely used piezoelectric ceramics are lead oxide based ferroelectrics (PZT). However, the toxicity of lead oxide and its high vapor pressure during processing have led to a demand for alternative lead-free piezoelectric materials. We synthesized Lead-free piezoelectric ceramics of $0.96(K_{0.5}Na_{0.5})NbO_3-0.04SrZrO_3+x$ mol% $ZrO_2$ [KNN-SZ+$xZrO_2$; x= 0~0.10] doped with 0.1 wt% $MnO_2$ by a conventional solid state method. We investigated the piezoelectric properties and microstructures of these disk samples sintered in reduced atmosphere in order to evaluate the possibility of the multilayered piezoelectric ceramics having the base metal such as Ni as a internal electrode. All of these KNN-SZ samples sintered in 3%$H_2-97%N_2$ atmosphere at $1,140^{\circ}C$ exhibit pure perovskite structure irrespective of the content of $ZrO_2$. Meanwhile, the sintering denisty and piezoelectric properties such as $K_p$, $Q_m$ and $d_{33}$ of KNN-SZ samples as a function of $ZrO_2$ content show the maxima ($k_p$=28.07%, $Q_m$= 101.34, $d_{33}$= 156 pC/N) at x= 0.04 and it is likely that there is some morphotropic phase boundary(MPB) in this KNN-SZ+$xZrO_2$ composition system. These results indicate that the ceramic composition is a promising candidate material for applications in lead free multilayer piezoelectric ceramics.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.1
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• pp.97-106
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• 2011

Purpose: This review article was written to theoretically compare the depressing force (pressure, adhesion) to the cornea between when the spherical lenses were being tightly and flat fitted. Methods: Mathematical equations and their numerical solution programs (model) were formulated to calculate the depressing (adhesion) force to the cornea by both the tightly and flat fitted contact lenses. Based on this proposed model the effects of parameters characterizing a contact lens such as BCs, diameters, edge shape and corneal shape (ratio of long and short corneal axis, p) on the depressing force to the cornea were predicted/analyzed in both tightly and flat fitting regimes. Results: Corneal adhesion increased as the corneal p-value increased. Adhesion increase caused by the increased p-value was much larger in flat fitted case than in tight fitted one. Corneal adhesion reduced abruptly as the BC increased in flat fitting regimes while the adhesion rise was insignificant in tight fitting ones. Reduction in corneal adhesion due to lens-size increase was predicted to be insignificant in both tight and flat fitting regimes. Both the lens edge shape (edge angle) and thickness were relevant only in tight fitting regime. Corneal adhesion increased as the increased with tight-fitted lenses. As the thickness of tight fitted lenses increased, corneal adhesion inversely decreased. Conclusions: The two most significantly affecting the depressing force to cornea were found to be the degree of corneal bending toward the periphery and the BCs of lenses.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.420-424
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• 2016

In this study, we developed photocatalytic technology to address the emerging serious problem of air pollution through indoor air cleaning. A single layer of $WO_3$ was prepared by using the dry process of general RF magnetron sputtering. At a base vacuum of $1.8{\times}10^{-6}$[Torr], the optical and electrical properties of the resulting thin films were examined for use as a transparent electrode as well as a photocatalyst. The single layer of $WO_3$ prepared at an RF power of 100 [W], a pressure of 7 [mTorr] and Ar and $O_2$ gas flow rates of 70 and 2 sccm, respectively, showed uniform and good optical transmittance of over 80% in the visible wavelength range from 380 [nm] to 780 [nm]. The optical catalyst characteristics of the $WO_3$ thin film were examined by investigating the optical absorbance and concentration variance in methylene blue, where the $WO_3$ thin film was immersed in the methylene blue. The catalytic characteristics improved with time. The concentration of methylene blue decreased to 80% after 5 hours, which confirms that the $WO_3$ thin film shows the characteristics of an optical catalyst. Using the reflector of a CCFL (cold cathode fluorescent lamp) and the lens of an LED (lighting emitting diode), it is possible to enhance the air cleaning effect of next-generation light sources.

• Journal of Welding and Joining
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• v.15 no.1
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• pp.92-100
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• 1997

Weld repair of ASTM A-470 class 8 high pressure (HP) steam turbine rotor steel has been performed to extend the service life of older fossil units. Microhardness measurements were conducted across the weldment from unaffected base metal (BM) to weld metal (WM). The hardness of the BM was VHN 253, however it dropped up to VHN 227 at the heat affected zone (HAZ) close to unaffected BM for multipass SAW. This area of hardness drop is called "siftening zone" and has a width of 0.5-0.6mm. During creep rupture test, failure occurred around the softening zone and rupture time was 772.4hr at 19Ksi (132 Mpa) and 593.deg. C. Multipass MIG and TIG welding have been employed to reduce the softening zone width. The softening zone width for MIG was 0.3-0.4mm and for TIG was zero-0.4mm depending on heat inputs. However creep rupture time was decreased as softening zone width reduced. Creep rupture time also showed a close relationship with heat inputs in TIG process. The higher heat input, the longer rupture time. Most failure occurred at intercritical HAZ (ICHAZ), however rupture location was shifted to coarse grained HAZ (CGHAZ) as heat input decreased. The rupture surface showed tearing and dimple which indicated transgranular fracture. fracture.

• Economic and Environmental Geology
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• v.32 no.5
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• pp.445-454
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• 1999

The Sanjeon Au-Ag deposit consists of three subparallel hydrothermal quartz-calcite veins which filled fault-related fractures (generally $N20^{\circ}$ to 35"W-trending and $70^{\circ}$ to $80^{\circ}$ SW-dipping) within quartz porphyry. The vein mineralization shows an apparent variation of mineral assemblages with paragenetic time: (1) early, white quartz + pyrite + arsenopyrite + brown sphalerite, (2) middle, white (vein) to clear quartz (vug) + base-metal sulfides + electrum + argentite, (3) late, calcite + pyrite + native silver. Mineralogic and fluid inclusion data indicate that gold-silver minerals were deposited at temperatures from 2l $0^{\circ}$ to $250^{\circ}$ with salinities of 4 to 5 wt. % equiv. NaCl and log fS2 values from -14.0 to -12.2 atm. The linear relationship between homogenization temperature and salinity data indicates that gold-silver deposition was a result of meteoric water mixing. Ore mineralization occurred at pressure conditions of about 70 bars, which corresponds to the mineralization depths of about 260 m to 700 m. There is a remarkable decrease of the calculated 1)180 values of water from 1.3 to -9.7%0 in hydrothermal fluid with increasing paragenetic time. This indicates a progressive increase of meteoric water influx in the hydrothermal system at the Sanjeon deposit. Oxygen-hydrogen, sulfur, and carbon isotope values of hydrothermal fluids indicate that the ore mineralization was formed largely from meteoric waters with the contribution of sulfur and carbon from a deep igneous source.