• Journal of the Korean Society of Combustion
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• v.11 no.3
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• pp.26-35
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• 2006

This work forcus on the development of gas sensor that measure the concentrations of exhaust gas using diode laser, Each diode laser for exhaust gas measurement is set to work at near-IR using both DA and WMS methods. Also use of fiber-coupled optical elements makes such a sensor rugged and easy to align. The results showed that gas concentrations of $O_2$, CO, $CO_2$, NO are accurately measured within ${\pm}2%$ error. The application of WMS method increased the beam intensity 2-3 times higher than DA method. It were experimentally compared WMS (Wavelength Modulation Spectroscopy) with DA (Direct Absorption) for the accuracy.

• Journal of Sensor Science and Technology
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• v.17 no.1
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• pp.9-14
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• 2008

In this paper, the gas responses of tungsten oxide films prepared by anodic reaction was discussed. Sensing electrodes and heating electrodes were patterned by photolithography method on quartz substrate. Porous tungsten oxide was fabricated in electrolyte solutions of 5 % HF (HF :$C_2H_6OH:H_2O$=3 : 2 : 20) by anodic reaction. The anodic reaction with metal (platinum wire) as a cathode and the sensing device as an anode was conducted under the various reaction times (1-10 min) at 10 mA/$cm^2$ The surface structure and morphology of the fabricated sensor have been analysed by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). All the peaks of XRD results were well indexed to the pure phase pattern. The average diameter of the porous tungsten oxide surface were ranged about 100 nm. The fabricaed sensor showed good sensitivity to 200 ppm toluene at operating temperature of $250^{\circ}C$.

• Journal of Sensor Science and Technology
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• v.5 no.2
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• pp.21-27
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• 1996

Thick film $TiO_{2}/WO_{3}$ butane gas sensors were fabricated by the screen printing method and their gas sensing characteristics were investigated. The sensitivity of $TiO_{2}/WO_{3}$ thick film was higher than that of pure $WO_{3}$ film to butane. The $WO_{3}$ film with 2wt.% $TiO_{2}$ showed the highest sensitivity to butane. And the optimum heat treatment temperature was $650^{\circ}C$. That film showed the highest sensitivity to butane at the operating temperature of $350^{\circ}C$. The sensitivity of the film to 20000ppm butane in air was 80% at the operating temperature of $350^{\circ}C$.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.93-94
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• 2006

In this research, the enhancement of electron-transfer activity of hemoglobin (Hb) in dodecanoic acid film was investigated for the first time. This type of composite film was made on glassy carbon electrode by casting method. Cyclic voltammetric result of the modified electrode displays a well defined redox peaks which was attributed to the direct electrochemical response of Rb. Our results illustrate that Rb exchange electrons directly with electrode and exhibits the characteristics of peroxidase. When we apply this modified electrode as a biosensor, it gives excellent performances in the electrocatalytic reduction of hydrogen peroxide ($H_{2}O_{2}$). Through the optimal conditions, the proposed biosensor shows the linear range for H2O2 determination was from $1{\times}10^{-5}$ to $1.25{\times}10^{-4}mol/L$ with a detection limit of $1{\times}10^{-7}mol/L$. The biosensor retained more than 90% of the initial response after 14 days.

• Journal of Sensor Science and Technology
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• v.5 no.6
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• pp.60-67
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• 1996

The interfacial electrical properties of InSb MIS structure with low temperature remote PECVD $SiO_{2}$ have been characterized. The interlace-state density at mid-bandgap of the MIS structure was about $1{\sim}2{\times}10^{11}\;cm^{-2}eV^{-1}$, when the $SiO_{2}$ film was deposited at $105^{\circ}C$. However, large amount of interlace states and trap states were observed in the MIS structure fabricated at temperatures above $105^{\circ}C$. The time constant of $10^{-4}{\sim}10^{-5}\;sec$ of interface states was extracted from G- V measurement. As the deposition temperature increased, the hysteresis of C- V curves were increased due to the high trap density.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05b
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• pp.55-61
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• 2002

Ultra-fine particles of $SnO_{2}$ was synthersized by the sol-gel powder processing using tin(II) chloride dihydrate$(SnCl_{2}{\cdot}2H_{2}O)$ and ethanol$(C_{2}H_{5}OH)$ as raw materials. Gel powders can be obtained by drying of sol at $120^{\circ}C$ after aging 72hrs and 168hrs. The amount of $SnO_{2}$ phase was increased with temperature because of the evaporation of volatile components, and the creation of $SnO_{2}$ phase was almost done by the heat treatment at $700^{\circ}C/30min$ The grain sizes after firing are about 20-30nm, and it showed the narrow distribution of grain size. The specimens to measure electrical properties were fabricated by the thick film screen printing technique on the alumina substrates. The conductance of $SnO_{2}$ was increased with temperature up to $380^{\circ}C$ by the typical conduction mechanism of semiconducting ceramics. There was a region of constant conductance between about $200^{\circ}C$ and $380^{\circ}C$ due to the increment of electron concentration with temperature and the annihilation of conduction carriers by the absorption and electron trapped-ionization of oxygen on the surface of $SnO_{2}$, It was finally showed the intrinsic behaviors above $450^{\circ}C$. The sensing properties of response time, recovery, and sensitivity of CO were improved with aging time.

• Journal of Sensor Science and Technology
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• v.5 no.6
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• pp.68-73
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• 1996

ZnO thin films were prepared on glass and (012) sapphire substrates by rf magnetron sputtering. Polycrysralline ZnO films with a (002) orientation were obtained on glass substrates. (110) ZnO films were epitaxially grown on the (012) sapphire substrates. Surface acoustic wave properties were also measured for propagating along the c axis of ZnO film on the glass and sapphire substrates. The phase velocities ($V_{p}$) on glass and sapphire substrate at center frequency were 2680 m/sec and 5980 m/sec and the effective coupling coefficient ($k^{2}$) on the 0th mode were 0.98 % and 1.43 %, respectively.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2765-2770
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• 2011

Organic dye-doped glasses, viz., ruthenium (II) tris(4,7'-diphenyl-1,10'-phenanthroline) $[Ru(dpp)_3]^{2+}$ incorporated into thin silica xerogel films produced by the sol-gel method, were prepared and their $O_2$ quenching properties investigated as a function of the $[Ru(dpp)_3]^{2+}$ concentration (3-400 ${\mu}M$) within the xerogel. The ratio of the luminescence from the $[Ru(dpp)_3]^{2+}$-doped films in the presence of $N_2$ and $O_2$ ($I_{N2}/I_{O2}$) was used to describe the film sensitivity to $O_2$ quenching. ($I_{N2}/I_{O2}$ changed three-fold over the $[Ru(dpp)_3]^{2+}$ concentration range. Time-resolved intensity decay studies showed that there are two discrete $[Ru(dpp)_3]^{2+}$ populations within the xerogels (${\tau}_1$ ~ 300 ns; ${\tau}_2$ ~ 3000 ns) whose relative fraction changes as the $[Ru(dpp)_3]^{2+}$ concentration changes. The increased $O_2$ sensitivity that is observed at the higher $[Ru(dpp)_3]^{2+}$ concentrations is a manifestation of a greater fraction of the 3000 ns $[Ru(dpp)_3]^{2+}$ species (more susceptible to $O_2$ quenching). A model is presented to describe the observed response characteristics resulting from $[Ru(dpp)_3]^{2+}$ distribution within the xerogel.

• Journal of Microbiology and Biotechnology
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• v.14 no.5
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• pp.991-995
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• 2004

Immobilized sensor spots were applied for online measurement of dissolved $O_2$, in test tubes. Oxygen transport was quantified at varied shaking frequency and filling volumes. The k$_{L}$ a increased with increasing shaking frequency and decreasing filling volume. In non-baffled tubes the maximum $k_{L}a$ value was $70h^{-1}$, equivalent to a maximum $O_2$ transfer capacity of 15mMh^{-1}$. Monitoring of the hydrodynamic profile revealed that the liquid bulk rotated inside the tube with an inclined liquid surface, whereby the angle between the surface and tube wall increased with increasing shaking frequency. The $k_{L}a$ clearly correlated to the surface area. Placement of four baffles into the tubes improved the oxygen transfer up to 3-fold. The highest increase in $k_{L}a$ was observed at high filling volume and high shaking frequency. The maximum $k_{L}a$ in baffled tubes was $100 h^{-1}$.

• Journal of Chest Surgery
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• v.19 no.4
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• pp.563-568
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• 1986

Tissue 02 tension is an important guide in detection of the general condition in critical patients. The tissue 0, is more difficult to measure with 0, sensor in skeletal muscle and subcutaneous tissues to present. But it is much easier to measure 0, tension in bladder urine with Censini catheter in Foley catheter than in tissue. We have measured 0, tension in bladder urine, main pulmonary artery and radial artery in 16 patients in chest surgical department of Yonsei University. College of Medicine from September 26 to December 22, 1981. Six patients were male and ten patients were female. Their ages ranged from 8 to 43 years. The correlation equation between the simultaneously measured PuO2 and PvO2 was found to be Ypvo2=4.04 + 0.88 Xpuo2 [r=0.88, p<0.0001] in regression curve with computer [HP/3,000, Program: SPSS] in the Yonsei University. Measurement of 0, tension in bladder urine and MPA will be rather simple, rapid and reproducible method than that of the 0, tension in tissues. But the speed of 0, consumption in urine is fast and so the 0, tensions in bladder urine were measured as soon as possible after they were collected. They were no complications or morbidity during measurement of 0, tension in these procedures except spontaneous removal of radial arterial cannulas in 2 patients.