• Title/Summary/Keyword: Chemical Gas Sensor

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Determination of Glutamine Utilizing New Plant Tissue Bio-Sensor (새로운 식물조직 바이오센서에 의한 글루타민의 정량)

  • Ihn, Gwon Shik;Kim, Bong Won;Jeon, Yeong Guk
    • Journal of the Korean Chemical Society
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    • v.34 no.6
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    • pp.622-628
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    • 1990
  • The bio-sensor for glutamine has been constructed by immobilizing petal of the rose structural elements on an ammonia gas sensor. This sensor was investigated for the effects of pH, temperature, buffer solution, tissular amounts, interferences and lifetime. As a result, the tissue sensor showed linear range of $8.0 {\times} 10^{-4}$$5.0 {\times} 10^{-2}$ M glutamine with a slope of 52 mV/decade in pH 7.8, 0.2M phosphate beffer solution at 37$^{\circ}C$. The tissular amounts used for this sensor was 50 mg. This sensorr showed excellent selectivity. This sensor was compared with other structural elements of rose. Actually, this tissue sensor appeared to be very useful for the determination of glutamine.

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A Study on the Methyl Salicylate Dispersion in the Vicinity of Obstacles by Wind Tunnel Test (아음속 풍동을 이용한 구조물 형상 변화에 따른 살리실산메틸 확산 유동 연구)

  • Hong, Chang-Ki;Uhm, Han-Sup;Choi, Seung-Ki;Kim, Youn-Jea
    • The KSFM Journal of Fluid Machinery
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    • v.17 no.6
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    • pp.69-73
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    • 2014
  • To predict flow fields and chemical agent dispersion in urban area, wind tunnel experiments was performed. The agent was adopted MS (methyl salicylate) because the real chemical agent is unsafe. The exact concentration of methyl salicylate was generated by the commercial gas generator (STI-2500) and three different obstacle shapes were applied (i.e., rectangular, cylinder and pyramid). The concentration was measured with the qualified ion mobility sensor and gas chromatography. The data necessary for virtual test method of the real chemical agent were obtained.

[ $NO_2$ ] Gas Sensing Characteristics of Carbon Nanotubes (탄소 나노튜브를 이용한 이산화질소 감지 센서의 특성)

  • Lee R. Y.
    • Journal of the Microelectronics and Packaging Society
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    • v.12 no.3 s.36
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    • pp.227-233
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    • 2005
  • Carbon nanotubes (CNT) which were grown, on the alumina substrate with a pair of comb-type Au electrodes, by plasma enhanced chemical vapor deposition have been investigated for $NO_2$ gas sensor. The electrical resistance of CNT film decreased with temperature, indicating a semiconductor type of CNT, and also the resistance of CNT sensor decreased with increasing $NO_2$ concentration. Upon exposure to $NO_2$ gas, the electrical resistance of CNT film sensor rapidly decreased within 3 minutes, and then showed a constant value after $20\~30$ minutes. It is found that the sensitivity of CNT sensor has been improved by air oxidation. The CNT sensor oxidized at $450^{\circ}C$ for 30 minutes showed higher sensitivity value than that without oxidation by $27\%$, even for a low 250 ppb $NO_2$ concentration at operating temperature of $200^{\circ}C$. But it needs a recovery time more than 20 minutes for reuse after detection of $NO_2$ gas.

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Fabrication of oxide semiconductor thin film gas sensor array (산화물 반도체 박막 가스센서 어레이의 제조)

  • 이규정;김석환;허창우
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.4 no.3
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    • pp.705-711
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    • 2000
  • A thin film oxide semiconductor micro gas sensor array which shows only 60 mW of power consumption at an operating temperature of $300^{\circ}C$ has been fabricated using microfabrication and micromachining techniques. Excellent thermal insulation of the membrane is achieved by the use of a double-layer structure of $0.1\mum\; thick\; Si_3N_4 \;and\; 1 \mum$ thick phosphosilicate glass (PSG) prepared by low-pressure chemical-vapor deposition (LPCVD) and atmospheric-pressure chemical-vapor deposition (APCVD), respectively. The sensor array consists of such thin film oxide semiconductor sensing materials as 1 wt.% Pd-doped $SnO_2,\; 6 wt.% A1_2O_3-doped\; ZnO,\; WO_3$/ and ZnO. Baseline resistances of the four sensing materials were found to be stable after the aging for three days at $300^{\circ}C$. The thin film oxide semiconductor micro gas sensor array exhibited resistance changes usable for subsequent data processing upon exposure to various gases and the sensitivity strongly depended on the sensing layer materials.

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Synthesis of Mesoporous Tin Oxide and Its Application as a Gas Sensor (메조세공을 갖는 이산화 주석의 합성 및 가스센서로서의 응용)

  • Kim, Nam-Hyon;Kim, Geon-Joong
    • Applied Chemistry for Engineering
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    • v.18 no.2
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    • pp.142-147
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    • 2007
  • In this study, mesoporous tin oxide was synthesized by sol-gel method using $C_{16}TMABr$ surfactant as a template in a basic condition. The optimum conditions for the synthesis of mesoporous $SnO_2$ were investigated and the obtained samples were characterized by XRD, nitrogen adsorption and TEM analysis. A mesoporous and nanostructured $SnO_2$ gas sensor with Au electrode and Pt heater has been fabricated on alumina substrate as one unit via a screen printing process. Sensing abilities of fabricated sensors were examined for CO and $CH_4$ gases, respectively, at $350^{\circ}C$ in the concentration range of 1~10,000 ppm. Influence of loading amount of palladium impregnated on $SnO_2$ was also tested in detection of those gases. High sensitivity to detecting gases and the fast response speed with stability were obtained with the mesoporous tin oxide sensor as compared to a non-porous one under the same detection conditions.

RF Gas Sensor Using 4-Port Hybrid Coupler with Conducting Polymer (전도성 고분자 물질이 결합된 하이브리드 커플러를 적용한 RF 가스 센서)

  • Lee, Yong-Joo;Kim, Byung-Hyun;Lee, Hee-Jo;Hong, Yunseog;Lee, Seung Hwan;Choi, Hyang Hee;Yook, Jong-Gwan
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.26 no.1
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    • pp.39-46
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    • 2015
  • In this paper, a gas sensor using a modified $90^{\circ}$ hybrid coupler structure with conducting polymer which operates at 2.4 GHz is represented. Conducting polymers are used to the gas sensing material in proposed sensors. The conducting polymer varies its electrical property, such as work function and conductivity corresponding to the certain gas. To verify this variation of electrical property of conducting polymer at microwave frequencies, the conducting polymer is incorporated with the $90^{\circ}$ hybrid coupler structure, and this proposed sensor operates as reflection type variable attenuator and variable phase shifter. The conducting polymer is employed as impedence-variable transmission lines that cause a impedance mismatching between the general transmission line and conducting polymer. The experiment was conducted with 100 ppm ethanol gas at temperature of $28^{\circ}C$ and relative humidity of 85 %. As a result, the amplitude deviation of $S_{21}$ is 0.13 dB and the frequency satisfying ${\angle}S_{21}=360^{\circ}$ is shifted about 2.875 MHz.

Sensor array optimization techniques for exhaled breath analysis to discriminate diabetics using an electronic nose

  • Jeon, Jin-Young;Choi, Jang-Sik;Yu, Joon-Boo;Lee, Hae-Ryong;Jang, Byoung Kuk;Byun, Hyung-Gi
    • ETRI Journal
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    • v.40 no.6
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    • pp.802-812
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    • 2018
  • Disease discrimination using an electronic nose is achieved by measuring the presence of a specific gas contained in the exhaled breath of patients. Many studies have reported the presence of acetone in the breath of diabetic patients. These studies suggest that acetone can be used as a biomarker of diabetes, enabling diagnoses to be made by measuring acetone levels in exhaled breath. In this study, we perform a chemical sensor array optimization to improve the performance of an electronic nose system using Wilks' lambda, sensor selection based on a principal component (B4), and a stepwise elimination (SE) technique to detect the presence of acetone gas in human breath. By applying five different temperatures to four sensors fabricated from different synthetic materials, a total of 20 sensing combinations are created, and three sensing combinations are selected for the sensor array using optimization techniques. The measurements and analyses of the exhaled breath using the electronic nose system together with the optimized sensor array show that diabetic patients and control groups can be easily differentiated. The results are confirmed using principal component analysis (PCA).

The Fabrication of Flow Sensors Using Pt Micro Heater (백금 미세발열체를 이용한 유량센서의 제작)

  • Noh, Sang-Soo;Chung, Gwiy-Sang
    • Proceedings of the KIEE Conference
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    • 1997.11a
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    • pp.609-611
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    • 1997
  • Pt thin films flow sensors were fabricated by using aluminum oxide films as medium layer and their characteristics were investigated after annealing at $600^{\circ}C$ for 60min. Aluminum oxide improved adhesion of Pt thin films to $SiO_2$ layer without any chemical reactions to Pt thin films under high annealing temperatures. Output voltages increased as gas flow rate and gas conductivity increased because heat loss of heater, which was integrated with a sensing resistor in the flow sensor, increased. Output voltage of flow sensor fabricated on membrane structure was 101mV at $O_2$ flow rate of 2000sccm, heating power of 0.8W while flow sensor fabricated on Si substrate without membrane had output voltage of 78mV under the same conditions.

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Development of Wireless Real-Time Gas Detector System for Chemical Protection Performance Test of Personal Protective Equipment (화생방 보호의 성능평가를 위한 무선 실시간 가스 검출기 개발)

  • Kah, Dong-Ha
    • Journal of the Korea Institute of Military Science and Technology
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    • v.23 no.3
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    • pp.294-301
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    • 2020
  • Man-In-Simulant Test(MIST) provides a test method to evaluate chemical protective equipments such as protective garments, gloves, footwear and gas mask. The MIST chamber is built to control concentration of chemical vapor that has a activity space for two persons. Non-toxic methyl-salicylate(MeS) is used to simulate chemical agent vapor. We carried out to measure inward leakage MeS vapors by using passive adsorbent dosimeter(PAD) which are placed on the skin at specific locations of the body while man is activity according to the standard procedure in MIST chamber. But more time is required for PADs and there is concern of contamination in PADs by recovering after experiment. Therefore detector for measuring in real time is necessary. In order to analyze in real time the contamination of the personal protective equipment inside the chemical environment, we have developed a wireless real-time gas detector. The detector consists of 8 gas-sensors and 1 control-board. The control-board includes a CPU for processing a signal, a power supply unit for biasing the sensor and Bluetooth-chipset for transmission of signals to external PC. All signals from gas-sensors are converted into digital signals simultaneously in the control-board. These digital signals are stored in external PC via Bluetooth wireless communication. The experiment is performed by using protective equipment worn on manikin. The detector is mounted inside protective equipment which is capable of providing a real-time monitoring inward leakage MeS vapor. Developed detector is demonstrated the feasibility as real-time detector for MIST.

Fabrication of Optical Fiber Gas Sensor with Polyaniline Clad

  • Lee, Yun-Su;Song, Kap-Duk;Joo, Byung-Su;Lee, Sang-Mun;Choi, Nak-Jin;Lee, Duk-Dong;Huh, Jeung-Soo
    • Journal of Sensor Science and Technology
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    • v.13 no.2
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    • pp.96-100
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    • 2004
  • Optical fiber sensors have been used to detect small amounts of chemical species. In this work, a new thin polymer-clad fiber sensor is developed. Polyaniline is chemically synthesized and thin clad layers of the polymer are easily deposited on optical fiber by dip-coating technique. The optical property of polyaniline as a sensing material is analyzed by UV-Vis-NIR. The light source is stabilized He-Ne laser at 635 nm wavelength with 1 mW power. The light power transmitted through the optical fiber is measured with a spectrophotometer. By selecting a fixed incident angle, variation of transmitted light intensity through the optical fiber can be detected as gas molecules absorbed in the polyaniline clad layer. Among the various gases, the fabricated optical fiber sensor shows good sensitivity to $NH_{3}$ gas. The optical fiber sensors was shown more improved properties than polymer based sensors which measure conductivity changes.