• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2004.11a
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• pp.207-212
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• 2004

• Journal of Korea Society of Industrial Information Systems
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• v.15 no.2
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• pp.83-90
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• 2010

Sensor is a key element in various fields of applications such as sensor networks. However, they could not be easily developed because of several factors such as temperature dependence of output characteristics and/or nonlinearity. Calibration of sensor is also needed to solve these problems. Conventional calibration process required a lot of time and expenses. Therefore, it is important to develop sensor systems which can shorten development time and minimize expense. In this paper, we develop CO and $CO_2$ Sensor modules and propose a multiple sensor calibration system to resolve problems of conventional calibration process. A proposed system is composed of sensor module, system board and monitor program. Regression analysis method based on the least mean squares is used for calibration. We introduced the structure of calibration systems and experimental results. Calibration results can be used to confirm the effectiveness of the proposed system.

• Applied Chemistry for Engineering
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• v.9 no.1
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• pp.6-12
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• 1998

A FET(Field Effect Transistor) type dissolved $CO_2$ sensor based on Severinghaus type $CO_2$ sensor was fabricated by the photolithographic process. The sensor consists of Ag/AgCl reference electrode and membranes (hydrogel membrane and $CO_2$ gas permeable membrane) on the pH-ISFET base chip. Ag/AgCl reference electrode was fabricated as follows. Ag layer was thermally evaporated and then its upper surface was chemically chloridized into the AgCl. The hydrogel used as an internal electrolyte solution was fabricated by a photolithographic method using 2-hydroxyethyl methacrylate(HEMA) and acrylamide. $CO_2$ permeable membrane on the top of the hydrogel layer was formed by photolithographic process with UV-oligomer. The FET type $pCO_2$ sensor fabricated by photolithographic method showed good linearity within the concentration range of $10^{-3}{\sim}10^0mole/{\ell}$ of dissolved $CO_2$ in aqueous solution with high sensitivity.

• Journal of the Korea Safety Management & Science
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• v.17 no.2
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• pp.129-137
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• 2015

This study is in regard to the gas detection system and gas detection method utilizing smart phone. This study includes; 1) the sensor module attached to the smart phone to detect and measure flammable gas or toxic gas; and 2) gas detection APP which is installed inside the smart phone and recognizes the user information and location information automatically by reading RFID tag indicating the user or the location to detect gas through the contact area where RFID and blue tooth reader is installed inside of the above mentioned smart phone, and then measures the combustible gas or toxic gas by operating above mentioned sensor module and obtains the data thus measured, and above mentioned smart phone is characterized by its transmission of the above mentioned user information, location information and measured data which are obtained by above mentioned gas detecting APP to operation server via communication network. With this, reliability for the location detecting gas by the user, the result of the measurement, etc. can be secured. Furthermore, this provides the effect of preventing artificial manipulation at the time of input which is associated with the identification of the user to be measured by utilizing removable sensor module and application or the mistake resulted from wrong input by the user. In addition, by transmitting the measured data from the sensor module carrying out gas detection to operation server, this provides the effect of making it possible to process the data thus collected to a specialized data for combustible gas or toxic gas.

• Journal of ILASS-Korea
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• v.7 no.2
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• pp.1-6
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• 2002

It is necessary to develope a high frequency diode laser sensor system based on the absorption spectroscopy for the measurement of temperature of the spray flame. DFB diode laser operating near $2.0{\mu}m$ was used to scan over selected $H_2O$ transitions near $1.9{\mu}m\;and\;2.2{\mu}m$, respectively. The measurement sensitivity at wide range of sweep frequency was evaluated using multi-pass cell containing $CO_2$ gas. This diode laser absorption sensor with high temporal resolution up to 10kHz was applied to measure the gas temperature in the spray flame region of liquid-gas 2-phase counter flow flame. The successful demonstration of time series temperature measurement in the spray flame gives us motivation of trying to establish non-intrusive temperature measurement method in the practical spray flame.

• Journal of Sensor Science and Technology
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• v.19 no.5
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• pp.356-360
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• 2010

Due to the high surface-to-volume ratio, the 3-dimensional(3D) nanostructures of metal oxides are regarded as the best candidate materials for the chemical gas sensors. Here we have synthesised flower-like 3D zinc oxide nanostructures through a simple hydrothermal route. Specific surface area of the 3D zinc oxide nanostructures synthesised in different pH values from 9.0 to 12.0 were evaluated by using a BET analyzer and the results were compared with that of a zinc oxide thin film fabricated by rf sputtering. Using interdigitated electrodes, superior CO gas sensing properties of the 3D zinc oxide nanostructures on the ZnO thin film to those of the ZnO thin film were demonstrated.

• Journal of Sensor Science and Technology
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• v.10 no.5
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• pp.279-285
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• 2001

The capnograph system for determining the partial pressure of carbon dioxide in the blood of a patient was developed based on the NDIR(non-dispersive infrared) absorption technology. NDIR gas analyzing method requires an optical absorption chamber and signal processing hardware. In this paper, we have designed and implemented NDIR type $CO_2$ gas chamber in consideration of the time response characteristics and lamp chopping frequency. And we have implemented signal processing hardware using two infrared sources to reduce the thermal background effect. The implemented gas chamber and signal processing hardware were tested in the temperature variation experiment and human expiratory experiment. The results showed that the system could produce a stable output signal and a good $CO_2$ gas concentration curve like a typical capnogram.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.8
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• pp.705-710
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• 2003

MoO$_3$thin films were deposited on electrode of alumina substrates in $O_2$atmosphere by RF reactive sputtering using molybdenum metal target. The deposition was performed at 30$0^{\circ}C$ with 350 W of a forward power in an Ar-O$_2$atmosphere. The working pressure was maintained at 3$\times$10$^{-2}$ torr and all deposited films were annealed at 50$0^{\circ}C$ for 5 hours. The surface morphology of films was observed by using a SEM and crystalline phases were analyzed by using a XRD. To investigate gas sensing characteristics of the doped MoO$_3$thin film, Co, Ni and Pt were used as dopants. The sensing properties were investigated in term of gas concentration under exposure of reducing gases such as H$_2$, NH$_3$and CO at optimum working temperature. Co-doped MoO3 thin film shows the maximum 46.8 % of sensitivity in NH$_3$ and Ni-doped MoO$_3$thin film exhibits 49.7 % of sensitivity in H$_2$.

• Journal of the Korean Ceramic Society
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• v.37 no.12
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• pp.1135-1139
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• 2000

본 연구에서는 Pt/Sn $O_2$박막의 CO 감지특성을 향상시키기 위하여 표면 형상을 제어하였다. Pt/Sn $O_2$계 박막센서의 최적 동작온도는 175$^{\circ}C$이었다. Pt가 12초 동안 증착된 Sn $O_2$가 200ppm의 CO 가스에 대하여 1.23의 최대감도를 나타내었고, 그 이상의 Pt 증착시간 증가에 따라 Sn $O_2$위의 Pt의 coverage가 증가하여 센서의 감도를 감소시켰다. 다층박막(multi-layer thin film)의 단층의 Pt/Sn $O_2$복합체 위에 다시 Sn $O_2$및 Pt의 cluster 층들을 연속적으로 증착함으로서 제작되었다. 단지 하나의 Pt 층만을 증착한 Sn $O_2$막보다 다층의 Pt/Sn $O_2$막이 더욱 우수한 감도( $R_{air}$/ $R_{co}$=1.72, CO: 200 ppm)를 나타내었다. Pt/Sn $O_2$다층박막의 우수한 감도의 원인은 Pt와 Sn $O_2$사이의 계면적 증대 때문인 것으로 생각되어 진다.다.

• Journal of Sensor Science and Technology
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• v.30 no.2
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• pp.94-98
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• 2021

In this study, pure and Co3O4/CoFe2O4-loaded Indium oxide (In2O3) nanofibers were synthesized by the electrospinning of an Indium/Polyvinylpyrrolidone precursor solution containing cobalt and iron bimetallic zeolitic imidazolate frameworks and subsequent heat treatment. The ethanol, toluene, p-xylene, benzene, carbon monodxide, and hydrogen gas sensing characteristics of the solution were measured at 250-400 ℃. 0.5 at%-Co3O4/CoFe2O4-loaded In2O3 nanofibers exhibited extreme response (resistance ratio - 1) to 5 ppm of ethanol (210.5) at 250 ℃ and excellent selectivity over the interfering gases. In contrast, pure In2O3 nanofibers exhibited relatively low responses to all the analyte gases and low selectivity above 250-400 ℃. The superior response and selectivity toward ethanol is explained by the catalytic roles of Co3O4 and CoFe2O4 in gas sensing reaction and the electronic sensitization induced by the formation of p (Co3O4/CoFe2O4)-n (In2O3) junctions.