• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.54-54
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• 2008

$Eu^{2+}$, $Nd^{3+}$ co-doped $BaAl_2O_4$ are known as a long afterglow phosphor. We found that $Eu^{2+}$-doped $BaAl_2O_4$ showed ptotoconductivity in the range of UV and visual light. In this study, $BaAl_2O_4$:Eu thin film has been prepared by RF sputtering method and a sensing characteristics to UV and visual light was performed. Only $Eu^{2+}$ and $Nd^{3+}$ co-doped $BaAl_2O_4$ powders and targets for deposition were prepared by a convention solid state method, and the deposition was performed in a reducing $H_2$-Ar mixture gas on Si substrates. The observation of crystalline phase and morphology of the sputtered film were performed using XRD, EDX. The photoluminescence and photocurrent to UV and visual light were measured simultaneously using 300W-Xe solar simulator as a light source. It was confirmed that the photocurrent induced by irradiation of light showed a linear relationship to the light intensity.

• KSBB Journal
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• v.9 no.3
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• pp.319-324
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• 1994

A biosensor for the measurement of malate has been constructed by the sodium-alginate immobilized bundle sheath cell tissue of corn leaf containing malate dehydrogenase (decarboxylating) (EC 1. 1. 1. 40) on the CO2 gas-sensing electrode. The proposed tissue sensor had the linear in the range of malate concentration $5.5{\times}10^{-5}M∼2.5{\times}10^{-2}M$ with a slope of 53.5 mV/decade in 0.02M Tris-HCl buffer solution at optimum pH 8.0, and $25^{\circ}C$. A response time was 16∼18min. The present L-malate sensing tissue sensor is stable for more than one week. At pH 7.4, Km value was $0.6{\times}10^{-5}M$. The various kinds of salt did not effect the signal of malate tissue biosensor as the inhibitor. We can measure the malate by the CO2 electrode at the pH=8.0. Thus, the proposed tissue sensor will be useful for the measurement of malate.

• Journal of Sensor Science and Technology
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• v.29 no.3
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• pp.156-161
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• 2020

In this study, hierarchical mesoporous CuO spheres, ZnO flowers, and heterojunction CuO/ZnO nanostructures were fabricated via a facile hydrothermal method. The as-prepared materials were characterized in detail using various analytical methods such as powder X-ray diffraction, micro Raman spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, and transmission electron microscopy. The obtained results are consistent with each other. The H₂S-sensing characteristics of the sensors fabricated based on the CuO spheres, ZnO flowers, and CuO/ZnO heterojunction were investigated at different temperatures and gas concentrations. The sensor based on ZnO flowers showed a maximum response of ~141 at 225 ℃. The sensor based on CuO spheres exhibited a maximum response of 218 at 175 ℃, whereas the sensor based on the CuO/ZnO nano-heterostructure composite showed a maximum response of 344 at 150 ℃. The detection limit (DL) of the sensor based on the CuO/ZnO heterojunction was ~120 ppb at 150 ℃. The CuO/ZnO sensor showed the maximum response to H₂S compared with other interfering gases such as ethanol, methanol, and CO, indicating its high selectivity.

• Journal of Microbiology and Biotechnology
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• v.25 no.8
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• pp.1299-1306
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• 2015

This study aims to investigate the mechanism of action of the cinnamon bark essential oil (CB), when used singly and also in combination with piperacillin, for its antimicrobial and synergistic activity against beta-lactamase TEM-1 plasmid-conferred Escherichia coli J53 R1. Viable count of bacteria for this combination of essential oil and antibiotic showed a complete killing profile at 20 h and further confirmed its synergistic effect by reducing the bacteria cell numbers. Analysis on the stability of treated cultures for cell membrane permeability by CB when tested against sodium dodecyl sulfate revealed that the bacterial cell membrane was disrupted by the essential oil. Scanning electron microscopy observation and bacterial surface charge measurement also revealed that CB causes irreversible membrane damage and reduces the bacterial surface charge. In addition, bioluminescence expression of Escherichia coli [pSB1075] and E. coli [pSB401] by CB showed reduction, indicating the possibility of the presence of quorum sensing (QS) inhibitors. Gas-chromatography and mass spectrometry of the essential oil of Cinnamomum verum showed that trans-cinnamaldehyde (72.81%), benzyl alcohol (12.5%), and eugenol (6.57%) were the major components in the essential oil. From this study, CB has the potential to reverse E. coli J53 R1 resistance to piperacillin through two pathways; modification in the permeability of the outer membrane or bacterial QS inhibition.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.8
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• pp.591-595
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• 2009

Most existing routing protocols for object detection and tracking in wireless sensor networks concentrate on finding ways to detect and track one and more individual objects, e.g. people, animals, and vehicles, but they do not be interested in detecting and tracking of continuous objects, e.g., poison gas and biochemical. Such continuous objects have quite different properties from the individual objects since the continuous objects are continuously distributed across a region and usually occupy a large area, Thus, the continuous objects could be detected by a number of sensor nodes so that sensing data are redundant and highly correlated. Therefore, an efficient data collection and report scheme for collecting and locally aggregating sensing data is needed, In this paper, we propose the Continuous Object Tracking Mechanism based on Dynamic Rectangle Zone for detecting, tracking, and monitoring the continuous objects taking into account their properties.

• Korean Journal of Remote Sensing
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• v.19 no.3
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• pp.217-221
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• 2003

The Measurement of Pollution in the Troposphere (MOPITT) instrument is an eight-channel gas correlation radiometer that launched on the Earth Observing System (EOS) Terra spacecraft in 1999. Its main objectives are to measure carbon monoxide (CO) and methane (CH4) concentrations in the troposphere. This study analyzes tropospheric carbon monoxide distributions using MOPITT data and compare with ozone distributions in Northeast Asia. In general, seasonal CO variations are characterized by a peak in spring and decrease in summer. Also, this study revealed that the seasonal cycles of CO are maximum in spring and minimum in summer with average concentrations ranging from 118ppbv to 170ppbv. The monthly average of CO shows a similar profile to those of O3. This fact clearly indicates that the high concentration of CO in spring is caused by two possible causes: the photochemical CO production in the troposphere, or the transport of the CO in the northeast Asia. The CO and $O_3$ seasonal cycles in the Northeast Asia are influenced extensively by the seasonal exchange of the different types of air mass due to the Asian monsoon. The continental air masses contain high concentrations of $O_3$ and CO due to higher continental background concentrations and sometimes due to the contribution of regional pollution. In summer the transport pattern is reversed. The Pacific marine air masses prevail over Korea, so that the marine air masses bring low concentrations of CO and $O_3$, which tend to give the apparent minimum in summer.

• Journal of Adhesion and Interface
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• v.17 no.4
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• pp.141-148
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• 2016

In this work, mesoporous silica (SBA-15) was synthesized via self-assembly process using triblock copolymer ($PEO_{20}PPO_{70}PEO_{20}$, P123) as template and tetraethyl orthosilicate (TEOS) as silica source under acidic condition. SBA-15 have high surface area ($704m^2g^{-1}$) and uniform pore size (8.4 nm) with well-ordered hexagonal mesostructure. Spiropyran-functionalized SBA-15 (Spiropyran-SBA-15) was synthesized via post-synthesis process using 3-(triethoxysilyl)propyl isocyanate (TESPI) and 1-(2-Hydroxyethyl)-3,3-dimethy-lindolino-6'-nitrobenzopyrylo-spiran (HDINS). Spiropyran-SBA-15 was produced with hexagonal array of mesopores without damage of mesostructre. Surface area and pore size of Spiropyran-SBA-15 were $651m^2g^{-1}$ and 8.0 nm, respectively. Optochemical properties of Spiropyran-SBA-15 was studied with chemical vapors such as EtOH, THF, $CHCl_3$, Acetone and HCl. Main peaks of photofluorescence of Spiropyran-SBA-15 exhibited blue shift in the range of 603.4~592.1 nm after exposure under EtOH, THF, $CHCl_3$, and Acetone vapors. Normalized peak intensities decreased in the range of 0.8~0.3. The main peak of photofluorescence of Spiropyran-SBA-15 showed significant blue shift of 592.1 nm after exposure under HCl vapor, while normalized peak intensity decreased to 0.1.

• Journal of the Korean Vacuum Society
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• v.10 no.3
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• pp.289-297
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• 2001

Highly-porous $SnO_2$thin films were prepared for recognizing and detecting of the inflammable gases, like butane, propane, LPG, carbon monoxide. To obtain sensing films, Sn, Pt/Sn, Au/Sn, and Pt,Au/Sn films were deposited employing a thermal evaporator for Sn film and a sputter for novel metals of Pt or/and Au. These films were annealed for 2 h at $700^{\circ}C$ to form $SnO_2$-based thin films. The films showed the tetragonal structure and also exhibited many defects and porosity, which could give high sensitivity to thin films. The thin films showed high sensitivity and reproductivity to the tested gases(butane, propane, LPG, and carbon monoxide) to even to low gas concentrations in range of workplace environmental standards. Especially, Pt/$SnO_2$film showed the highest sensitivity to butane, LPG, and carbon monoxide. And pure $SnO_2$ film manifested the highest sensitivity to propane. By using the sensing patterns from the films, we could reliably recognize the kinds and the quantities of the tested inflammable gases within the range of the threshold limit values(TLV) and the lower explosion limit(LEL) through the principal component analysis(PCA).

• Journal of the Korean Institute of Gas
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• v.21 no.2
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• pp.41-49
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• 2017

Recently, as the number of facilities using chemicals is increasing, the amount of handling is rapidly increasing. However, chemical spills are occurring steadily, and if large quantities of chemicals are leaked in time, they are likely to cause major damage. These industrial complexes use information obtained from a number of sensors to detect and monitor leaking areas, and are used in industrial fields by applying existing fixed sensors to robots and drones. Therefore, it is necessary to propose a sensor placement method at the interface for rapid detection and response based on various leaking scenarios reflecting leaking conditions and environmental conditions of the chemical handling process. In this study, COMSOL was used to analyze the actual accident scenarios by applying the medium parameter to the case of chemical leaks. Based on the accident scenarios, the objective function is selected so that the velocity of each robot is calculated by attaching importance to each item of sensor detection probability, sensing time and sensing scenario number. We also confirmed the feasibility of this method of reliability analysis for unexpected leak accidents. Based on the above results, it is expected that it will be helpful to trace back the leakage source based on the concentration data of the portable sensor to be applied later.

• Journal of Sensor Science and Technology
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• v.7 no.4
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• pp.254-262
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• 1998

Multilayer Langmuir-Blodgett (LB) films coated on quartz crystal microbalance (QCM) of octa-substituted metallophhtalocyanines ($MPc(OEH)_8$, M = Cu, Co, and Sn) and dihydrogen phthalocyanines ($H_2Pc(OEH)_8$) were used to quantify $NO_2$ concentrations. They were exposed to various concentrations of $NO_2$ in dry $N_2$. Among the four phthalocyanines we tested, the metal-free $H_2Pc(OEH)_8$ was observed to be most sensitive to $NO_2$. However, its LB film showed a partially irreversible behavior, that is part of the frequency change due to $NO_2$ adsorption could not be recovered even after purging with pure $N_2$ gas for an extended period. Examining the spectra of NMR and FTIR revealed fact that the irreversible portion of frequency change was due to ether groups in the linkage between side chains and the Pc unit. In order to remove the effect of such initial deactivation, on $NO_2$ quantification experiment, a freshly fabricated LB film was treated at a high concentration of $NO_2$ so that the ether sites were saturated. A pretreated LB film showed a reproducible performance for repeated uses. The $CuPc(OEH)_8$ LB film showed a satisfactory sensing performance down to as low as 4 ppm. For the $H_2Pc(OEH)_8$ LB film, the lower detection limit was found to be 35ppb of $NO_2$. In order to make the experimental condition more realistic, the carrier gas, dry nitrogen, was replaced by air. It was observed that the presence of oxygen, a weak electron acceptor, reduced the sensitivity and thus increased the sensing limit to hundreds of ppb. Results of experiments with moisture added showed that the interference of moisture was quite severe.