• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.475-480
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• 2017

In this paper, the conductivity of the fine pattern is improved in the insulating substrate by laser-induced forward transfer (LIFT) process. The high laser beam energy generated in conventional laser induced deposition processes induces problems such as low deposition density and oxidation of micro-patterns. These problems were improved by using a polymer coating layer for improved deposition accuracy and conductivity. Chromium and copper were used to deposit micro-patterns on silicon wafers. A multi-pulse laser beam was irradiated on a metal thin film to form a seed layer on an insulating substrate(SiO2) and electroless plating was applied on the seed layer to form a micro-pattern and structure. Irradiating the laser beam with multiple scanning method revealed that the energy of the laser beam improved the deposition density and the surface quality of the deposition layer and that the electric conductivity can be used as the microelectrode pattern. Measuring the resistivity after depositing the microelectrode by using the laser direct drawing method and electroless plating indicated that the resistivity of the microelectrode pattern was $6.4{\Omega}$, the resistance after plating was $2.6{\Omega}$, and the surface texture of the microelectrode pattern was uniformly deposited. Because the surface texture was uniform and densely deposited, the electrical conductivity was improved about three fold.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.29 no.2
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• pp.123-127
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• 2003

Chemical burns onto oral mucosa which are infrequent, may result from contact with a wide variety of chemical agents. The degree of injury depends on the chemical, its concentration, duration of contact, and the natural penetrability and resistance of the tissues involved. Chemicals do not usually "burn" in that they do not cause destruction by hyperthermic activity. Rather, they damage tissue by causing coagulation of protein by one of several processes, reduction, oxidation, desiccation, corrosion, or vesication. Paraquat(Gramoxon) is the most frequently agricultural chemicals that induce the severe toxic reactions onto the organs of human body in Korea. The toxic reaction are composed of pulmonary edema and fibrosis, formation of hyaline membrane, inflammatory reaction and bleeding tendency, owing to the cell damage by the production of superoxide radicals. The contents of essential treatment in paraquat intoxication are commonly airway and breathing maintenance, gastric lavage, much hydration and diuresis, hemoperfusion and medications for the removal of the chemicals and the prevention of various complications. The sedative oral dressings, such as, orabase ointment application, warm saline gargling, lidocaine viscous gargling and oral gargling by the mixed solutions(tetracycline, prednisolone and 10% dextrose water) are important for the improvement of chemical oral mucositis and the comfortable feeding of diet. The authors managed properly two cases of oral chemical mucositis that were occurred by the incorrect use of agricultural chemicals(paraquat) and report the cases with the review of literatures about care of the chemical intoxication and oral mucositis.

• Clinical and Experimental Pediatrics
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• v.45 no.9
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• pp.1083-1089
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• 2002

Purpose : The prevalence of obese children has recently increased. Obesity is known to be associated with complications such as hypertension, fatty liver, hyperlipidemia, and insulin resistance. L-carnitine is an essential cofactor for the transport of long chain fatty acids into mitochondria for ${\beta}$-oxidation. The purpose of this study is to measure serum free fatty acid and carnitine levels, and evaluate the role of L-carnitine as a therapeutic drug in obese children with fatty liver. Methods : Nine obese children, ranging from seven to 18 years of age, and 10 normal children were examined. Serum lipid(total cholesterol, triglyceride, HDL-cholesterol, and LDL-cholesterol) and fatty acid levels were analyzed. Serum total, free, and acyl carnitine levels were performed also by a new enzymatic cycling technique. Results : Long chain fatty acids(myristic acid, palmitoleic acid, palmitic acid, linoleic acid, oleic acid, and stearic acid)were significantly increased in obese children compared to the control group. Total, and acyl carnitine levels were significantly increased in obese children compared to the control group. Conclusion : Serum free fatty acid and carnitine levels were significantly increased in obese children with fatty liver compared to the normal control. This may suggest that L-carnitine can be used as antilipidemic agent to decrease fatty acid and lipid levels for obese children. Prospective studies will investigate serum fatty acid and carnitine levels after treatment of L-carnitine in obese children in the future.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.4
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• pp.393-400
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• 2012

In recent years, nano-structured thin film systems are often applied in industries such as MEMS/NEMS device, optical coating, semiconductor or like this. Thin films are used for many and varied purpose to provide resistance to abrasion, erosion, corrosion, or high temperature oxidation and also to provide special magnetic or dielectric properties. Quite a number of articles to evaluate the characterization of thin film structure such as film density, film grain size, film elastic properties, and film/substrate interface condition were reported. Among them, the evaluation of film adhesive to substrate has been of great interest. In this study, we fabricated the polymeric thin film system with different adhesive conditions to evaluate the adhesive condition of the thin film. The nano-structured thin film system was fabricated by spin coating method. And then V(z) curve technique was applied to evaluate adhesive condition of the interface by measuring the surface acoustic wave(SAW) velocity by scanning acoustic microscope(SAM). Furthermore, a nano-scratch technique was applied to the systems to obtain correlations between the velocity of the SAW propagating within the system including the interface and the shear adhesive force. The results show a good correlation between the SAW velocities measured by acoustic spectroscope and the critical load measured by the nano-scratch test. Consequently, V(z) curve method showed potentials for characterizing the adhesive conditions at the interface by acoustic microscope.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.6 s.336
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• pp.23-30
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• 2005

In this paper, OPPS(oxidized porous poly-silicon) field emitters were fabricated by using various emitter-electrode metal and these electron emission characteristics were investigated for different thermal annealing effects. The addressed OPPS field emitter with Pt/Ti emitter electrode annealed at $300^{\circ}C$-1hr showed the efficiency of $2.98\%$ at $V_{ps}$=12 V and one annealed at $350^{\circ}C$-1hr showed the highest efficiency of $3.37\%$at $V_{ps}$=16V. They are resulted from the improvement of interfacial contact characteristics of thin emitter metal to an oxidized porous poly-silicon and the decrease of electrical resistance of emitter metal. The brightness of the OPPS field emitter increases linearly in $V_{ps}$ and after oxidation process for $900^{\circ}C$-50min, the brightness of the OPPS field emitter with the as-deposited Pt/Ti emitter electrode was 3600 cd/$m^2$ at the $V_{ps}$=15 V, 6260 cd/$m^2$ at the $V_{ps}$=20 V. Thermal treatment improved the adhesion between the Ti buffer layer and the oxidized porous poly-silicon and also played an important role in the uniform distribution of electric field to the emitter electrode.

• Korean Chemical Engineering Research
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• v.49 no.1
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• pp.15-20
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• 2011

The contamination effect of toluene in the airstream on PEM fuel cell performance was studied with various toluene concentration under different operation conditions. And the recovery of the cell performance by applying clean air and the removal of toluene in the air by adsorption of active carbon were investigated. The toluene concentration range used in the experiments was from 0.1 ppm to 5.0 ppm. The performance degradation and recovery were measured by constant-current discharging and electrochemical impedance spectroscopy(EIS). Toluene adsorption capacity of KOH impregnated active carbon was obtained from the adsorption isotherm curve. The severity of the contamination increased with increasing toluene concentration, current density and air stoichiometry, but decrease with increasing relative humidity. The cell performance was recovered by toluene oxidation with oxygen and water in humidified neat air. EIS showed that the increase of charge transfer resistance due to toluene adsorption on Pt surface mainly reduced the performance of PEMFC. Toluene adsorption capacity of active carbon decreased as KOH weight increased in KOH impregnated active carbon.

• Journal of the Korean institute of surface engineering
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• v.42 no.1
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• pp.26-33
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• 2009

Recently ultra-supercritical steam power plants operate at $1000^{\circ}F$ ($538^{\circ}C$) and 3500 psi (24.1 MPa). Thermal efficiency of power plant will be increased about 2% if steam temperature increases from $1000^{\circ}F$ to $1150^{\circ}F$ ($621^{\circ}C$). In this study valve materials Incoloy901 (IC901) and Inconel718 (IN718) were nitrided to improve the surface hardness and solid lubrication function of the valve materials. The hardness of both IC901 and IN718 increased about two times by ion nitriding. IC901, IN718 and their nitrided specimens were corroded under ultra super-critical condition (USC) of $621^{\circ}C$. and 3600 psi (24.8 MPa) for 2000 hours. Oxidations of both IC901 and IN718 were very small due to the formation of protective oxide layer on the surface. But the corrosion resistance of both nitrided specimens decreased because of the formation of non-protective nitride layer of $Fe_{4}N$, $Fe_{2}N$ and CrN on the surface layer. The hardness of both nitrided IC901 and IN718 at $20{\mu}m$ depth from the surface decreased about 30% and 20% respectively by USC 2000 hours.

• Analytical Science and Technology
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• v.6 no.2
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• pp.167-180
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• 1993

The effects of coating variables on the formation of aluminide coating layer with good oxidation resistance on the strongest hot-forged superalloy in the world, KM 1557 developed at KIST by pack cementation process were studied. Pack aluminizing were performed by high-activity process with pure aluminium powders and by low-activity process with codep powders. For high-activity process, Al deposition rate, growth rate of coating layer, and cross-sectional microstructures were influenced by the species and additive amounts of activators and the additive amounts of pure aluminium powders. For low-activity process, Al deposition rate, growth rate of coating layer, and the cross-sectional microstructures were not influenced by the species but additive amounts of activators. Surface structures of coating layer were influenced by the species of activators. Regardless of aluminium activity, Al deposition rate was proportional to the square root of time and parabolic rate constants were different with the species of activators. The activation energy for deposition of aluminium was different with the species of activators for high-activity process. Regardless of the species of activators, the activation energy for deposition of aluminium was 12~14 Kcal/mole for low-activity process.

• Applied Chemistry for Engineering
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• v.18 no.5
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• pp.522-526
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• 2007

Structural features and electrochemical performances of cokes pyrolized from oxidized cokes were examined, and compared with KOH-activated coke. Needle cokes ($d_{002}=3.5{\AA} $), having a graphene layer structure, were changed to a single phase of graphite oxide after oxidation treatment with an acidic solution having an $NaCLO_3$/needle coke composition ratio of above 7.5, and the inter-layer distance of the oxidized coke was expanded to $6.9{\AA} $ with increasing oxygen content. After heating at $200^{\circ}C$, the oxidized coke was pyrolized to the graphene layer structure with inter-layer distance of $3.6{\AA} $. However, the change of the inter-layer distance of the needle coke was not observed in the KOH activation process. On the other hand, an intercalation of electrolyte ions into the pyrolized coke, observed at first charge, occurred at 1.0 V, in which the value was lower than that of KOH-activation coke. The cell capacitor using pyrolized coke exhibited a lower internal resistance of $0.57{\Omega}$ in 1 kHz, and a larger capacitance per weight and volume of 30.3 F/g and 26.9 F/ml at the two-electrode system in the potential range 0~2.5 V than those of the cell capacitor using KOH-activation of coke. This better electrochemical performance may be associated with structure defects in the graphene layer derived from the process of the inter-layer expansion and shrinkage.

• Journal of Sensor Science and Technology
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• v.8 no.2
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• pp.115-123
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• 1999

A micro-gas sensor with heater and sensing electrode on the same plane was fabricated on phosphosilicate glass(PSG, 800nm)/$Si_3N_4$ (150nm) dielectric membrane. PSG film was provided by atmospheric pressure chemical vapor deposition(APCVD), and $Si_3N_4$ film by low pressure chemical vapor deposition (LPCVD). Total area of the fabricated device was $3.78{\times}3.78mm^2$. The area of diaphragm was $1.5{\times}1.5mm^2$, and that of the sensing layer was $0.24{\times}0.24mm^2$. Finite-element simulation was employed to estimate temperature distribution for a square-shaped diaphragm. The power consumption of Pt heater was about 85mW at $350^{\circ}C$. Tin thin films were deposited on the silicon substrate by thermal evaporation at room temperature and $232^{\circ}C$, and tin oxide films($SnO_2$) were prepared by thermal oxidation of the metallic tin films at $650^{\circ}C$ for 3 hours in oxygen ambient. The film analyses were carried out by SEM and XRD techniques. Effects of humidity and ambient temperature on the resistance of the sensing layer were found to be negligible. The fabricated micro-gas sensor exhibited high sensitivity to butane gas.