• Journal of Sensor Science and Technology
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• v.5 no.3
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• pp.87-92
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• 1996

The PLT thin films on (100) cleaved MgO single crystal substrate have been fabricated by rf magnetron sputtering using a PbO-rich target. The dependence of physical and electrical properties on the degree of c-axis orientation has been studied. The degree of c-axis orientation of PLT thin films depends on fabrication conditions. Fabrication conditions of the PLT thin films were such that substrate temperature, working pressure, gas ratio of $Ar/O_{2}$, and rf power density were $640^{\circ}C$, 10 mTorr, 10 seem, and $1.7\;W/cm^{2}$, respectively. In these conditions, the PLT thin film showed the Pb/Ti ratio of 1/2 at the surface, the resistivity of $8{\times}10^{11}{\Omega}{\cdot}cm$, and dielectric constant of 110. The pyroelectric infrared sensors with these PLT thin films showed the peak to peak voltage of 450 m V and signal to noise ratio of 7.2.

• 한국가스학회:학술대회논문집
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• 2000.09a
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• pp.124-129
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• 2000

• Korean Journal of Food Science and Technology
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• v.29 no.6
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• pp.1075-1081
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• 1997

The objective of this research was to develop a glutamate enzyme sensor for rapid determinations of glutamate in samples. Glutamate oxidase was immobilized onto activated nylon, chitosan and other membranes. The enzymic and nonactin membranes were attached to an ammonia electrode to detect ammonia generated by the reaction between glutamate oxidase and glutamate. The enzyme immobilized on activated nylon membrane was stable for 2 months, and was able to perform about 250 glutamate determinations without losing activities. The enzyme immobilized on chitosan membrane had higher enzyme activity, but was not as much stable as that immobilized on nylon. The glutamate biosensor was able to accurately determine $0.1{\sim}5\;mM$ of glutamate in samples.

• Korean Journal of Materials Research
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• v.26 no.9
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• pp.468-471
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• 2016

$SnO_2:CNT$ thick films for gas sensors were fabricated by screen printing method on alumina substrates and were annealed at $300^{\circ}C$ in air. The nano $SnO_2$ powders were prepared by solution reduction method using tin chloride ($SnCl_2.2H_2O$), hydrazine ($N_2H_4$) and NaOH. Nano $SnO_2:CNT$ sensing materials were prepared by ball-milling for 24h. The weight range of CNT addition on the $SnO_2$ surface was from 0 to 10 %. The structural and morphological properties of these sensing material were investigated using X-ray diffraction and scanning electron microscopy and transmission electron microscope. The structural properties of the $SnO_2:CNT$ sensing materials showed a tetragonal phase with (110), (101), and (211) dominant orientations. No XRD peaks corresponding to CNT were observed in the $SnO_2:CNT$ powders. The particle size of the $SnO_2:CNT$ sensing materials was about 5~10 nm. The sensing characteristics of the $SnO_2:CNT$ thick films for 5 ppm $H_2S$ gas were investigated by comparing the electrical resistance in air with that in the target gases of each sensor in a test box. The results showed that the maximum sensitivity of the $SnO_2:CNT$ gas sensors at room temperature was observed when the CNT concentration was 8wt%.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.9
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• pp.444-449
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• 2001

In this paper, a novel ultraviolet sensor is presented based on a photoluminescent porous silicon. Porous silicon layer was formed by chemical etching of surface of pn junction in a $HF(48%)-HNO_3(60%)-H_20$ solution. Incident ultraviolet(UV) light is converted to visible light by photoluminescent porous silicon layer, and then this visible light generates electron-hole pairs in the pn junction, which produces a photocurrent flow through the device. In order to maximize detection efficiency, the peak sensitivity wavelength of the pn junction diode was matched with the peak wavelength of Photoluminescence from porous silicon layer. The porous silicon ultraviolet sensor showed a large output current as UV intensity increases and but very low sensitivity to visible light. The detection sensitivity of porous silicon sensor was calculated as 2.91mA/mW. These results are expected to open up a possibility that the present porous silicon sensor can be used for detecting UV light in a visible background, compared to silicon UV detectors which have an undesirable response to visible light.

• Journal of Biomedical Engineering Research
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• v.28 no.2
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• pp.310-315
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• 2007

The axial-flow type blood pump(XVAD) which has been developed in our group consists of mechanical parts (an impeller, a diffuser and a flow straightener) and electrical parts (a motor and a magnetic bearing). The magnetic bearing system fully levitates the impeller to remove mechanical coupling with other parts of the pump with constant gap, which needs non-contact type gap sensing. Conventional gap sensors are too large to be adopted to the implantable axial -flow type blood pump. Thus, in this paper, the compact eddy current type gap sensor system proper for the implantable axial-flow type blood pump was developed and its performance was evaluated in vitro. The developed eddy current type gap sensor system is a transformer type and has a differential probe. Sensor coil(probe) has small dimensions(6 mm diameter, 2 mm thickness) and its optimal inductance was determined as 0.068 mH for the measurement range of $0\sim3mm$. It could be manufactured with 130 turns of the 0.04 mm diameter copper coil. The characteristics of the developed eddy current type gap sensor system was evaluated by in vitro experiment. At experiment, it showed satis(actory performance to apply to the magnetic bearing system of the XVAD. It could measure the gap up to 3mm, but the linearity was decreased at the range of $1.8\sim3.0mm$. Moreover, it showed no difference in different media such as the water and the blood at the temperature range of $35\sim40^{\circ}C$.

• Korean Journal of Materials Research
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• v.13 no.12
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• pp.796-800
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• 2003

The polypyrrole prepared with pyrrole monomer, APS and DBSA was synthesized by chemical Polymerization at $V^{\circ}C$ under atmosphere conditions. After dissolving polypyrrole powder to the chloroform including DBSA, polypyrrole film was prepared on the alumina substrate with an interdigitated electrode by using the dip-coating method. This film was soaked in methanol solvent for 1 h at room temperature and heated to $70^{\circ}C$ for 4 h in $N_2$. Initial resistance was increased with the increasing humidity and decreasing temperature. The sensitivity was increased with lower humidity and decreasing temperature. The best linearity was achieved at $25^{\circ}C$ and low humidity of 0%.

• Journal of Korean Society of Forest Science
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• v.89 no.3
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• pp.405-413
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• 2000

This study was conducted to develop an on-line monitoring system for a forest hydrological environment and its meteorological condition, such as temperature, wind direction and speed, rainfall and water level on V-notch, electrical conductivity(EC), potential of hydrogen(PH) by the motor drive sensor unit and measurement with a single-chip microprocessor as controller. These results are summarized as follows ; 1. The monitoring system consists of a signal process unit, motor drive sensor unit, radio modem unit and power supply. 2. The motor drive sensor unit protects the sensor from swift current or freezing and can constantly maintain fixed water level during measurements. 3. This monitoring system can transfer the data by radio modem. Additionally, this system can monitor hydrological conditions in real time. 4. The hardware was made of several modules with an independent CPU. They can be mounted, removed, repaired and added to. Their function can be changed and expanded. 5. These are the result of an accuracy test, the values of temperature, EC and pH measured within an error range of ${\pm}0.2^{\circ}C$, ${\pm}1{\mu}S$ and ${\pm}0.1pH$ respectively. 6. This monitoring system proved to be able to measure various factors for a forest hydrological environment in various experimental stations.

• Korean Journal of Materials Research
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• v.25 no.7
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• pp.358-363
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• 2015

We present an excellent detection for nitrogen monoxide (NO) gas using polycrystalline ZnO wire-like films synthesized via a simple method combined with sputtering of Zn metallic films and subsequent thermal oxidation of the sputtered Zn nanowire films in dry air. Structural and morphological characterization revealed that it would be possible to synthesize polycrystalline hexagonal wurtzite ZnO films of a wire-like nanostructure with widths of 100-150 nm and lengths of several microns by controlling the sputtering conditions. It was found from the gas sensing measurements that the ZnO wire-like thin film gas sensor showed a significantly high response, with a maximum value of 29.2 for 2 ppm NO at $200^{\circ}C$, as well as a reversible fast response to NO with a very low detection limit of 50 ppb. In addition, the ZnO wire-like thin film gas sensor also displayed an NO-selective sensing response for NO, $O_2$, $H_2$, $NH_3$, and CO gases. Our results illustrate that polycrystalline ZnO wire-like thin films are potential sensing materials for the fabrication of NO-sensitive high-performance gas sensors.

• Journal of Sensor Science and Technology
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• v.5 no.1
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• pp.63-70
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• 1996

Silicon epitaxial films of submicron level were successfully grown by the RTCVD method. For the growth of silicon epitaxial layers, $SiH_{2}Cl_{2}\;/\;H_{2}$ gas mixtures and various process parameters including $H_{2}$ prebake process were used. The growth conditions were varied to investigate their effects on the interface abruptness of doping profile, the film growth rates and crystalline properties. The crystallinity of the undoped silicon was excellent at the growth temperature of $900^{\circ}C$. The doping profiles were measured by SIMS technique. The abruptness of doping profile would be controlled within about $200{\AA}/decade$ in the structure of undoped Si / $n^{+}-Si$ substrate.