• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.9
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• pp.2313-2321
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• 2014

A concentration meter is widely used at purification plants, sewage treatment plants and waste water treatment plants to sort and transfer high concentration sludge and to control the amount of chemical input. This study has been prepared for improving efficiency of operation on sludge processes and to establish a basic for factory automation by accuracy improvement and problem solution of sludge concentration meter. The concentration meter's accuracy and stability is improved by applying multi-beam sensors and minimum deviation linear average filtering. Furthermore maintenance without cut-off of water in sludge operation is possible by detachable sensors. The performance of multi-beam concentration meter has been variously verified by the pilot plant experiment.

• Journal of Sensor Science and Technology
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• v.5 no.5
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• pp.31-37
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• 1996

This paper presents characteristics of pressure sensor using shear-type piezoresistor of LPCVD(low pressure chemical vapour deposition) grown polycrystalline silicon films. The sensor has 3.1mV/V of pressure sensitivity in the pressure range of $1kgf/cm^{2}$, ${\pm}0.012%FS/^{\circ}C$ of TCO, and ${\pm}0.08%FS/^{\circ}C$ of TCS in the temperature range of $-20{\sim}+125^{\circ}C$. It showed ${\pm}0.2%FS$ of hysteresis and ${\pm}1.5%FS$ of non-linearity. Shear-type polycrystalline silicon pressure sensor can eliminate temperature dependence of offset caused by resistors mismatch and be used in relatively wide temperature range, compared to the conventional full-bridge silicon pressure sensors.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.174-174
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• 2010

Gallium Nitride(GaN) attracts great attention due to their wide band gap energy (3.4eV), high thermal stability to the solid state lighting devices like LED, Laser diode, UV photo detector, spintronic devices, solar cells, sensors etc. Recently, researchers are interested in synthesis of polycrystalline and amorphous GaN which has also attracted towards optoelectronic device applications significantly. One of the alternatives to deposit GaN at low temperature is to use Single Source Molecular Percursor (SSP) which provides preformed Ga-N bonding. Moreover, our group succeeds in hybridization of SSP synthesized GaN with Single wall carbon nanotube which could be applicable in field emitting devices, hybrid LEDs and sensors. In this work, the GaN thin films were deposited on c-axis oriented sapphire substrate by MBE (Molecular Beam Epitaxy) using novel single source precursor of dimethyl gallium azido-tert-butylamine($Me_2Ga(N_3)NH_2C(CH_3)_3$) with additional source of ammonia. The surface morphology, structural and optical properties of GaN thin films were analyzed for the deposition in the temperature range of $600^{\circ}C$ to $750^{\circ}C$. Electrical properties of deposited thin films were carried out by four point probe technique and home made Hall effect measurement. The effect of ammonia on the crystallinity, microstructure and optical properties of as-deposited thin films are discussed briefly. The crystalline quality of GaN thin film was improved with substrate temperature as indicated by XRD rocking curve measurement. Photoluminescence measurement shows broad emission around 350nm-650nm which could be related to impurities or defects.

• Journal of Sensor Science and Technology
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• v.30 no.5
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• pp.320-325
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• 2021

Biochemical oxygen demand (BOD) and chemical oxygen demand (COD) methods are conventional analytical methods to analyze water quality. Both of these methods are technically indirect measurement methods, require complicated preconditions, and are time-consuming. On the other hand, the total organic carbon (TOC) method is a direct and fast measurement method which is more intuitive and accurate than the BOD and COD methods. However, general TOC analysis methods involve complicated processes and high power consumption owing to the process of phase transition from liquid to gas by a high-temperature heater. Furthermore, periodic consumables are also required for the removal of inorganic carbon (IC). Titanium dioxide (TiO₂) is one of the most suitable photocatalysts for simple processes. Its usage involves low power consumption because it only reacts with the organic carbon (OC) without the requirement of any other reagents and extra processes. We investigated a TiO₂ photocatalyst-based TOC analysis for simple and affordable products. TiO₂-coated fiber substrate maintained under carbon included water was exposed to ultraviolet (UV) radiation of wavelength 365 nm. This method is suitable for the real-time monitoring of water pollution because of its fast reaction time. Its linear property is also sufficient to match the real value.

• Smart Media Journal
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• v.13 no.4
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• pp.23-32
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• 2024

Large-scale fires and their consequential damages are becoming increasingly common, but confidence in fire detection systems is waning. Recently, widely-used chemical fire detectors frequently generate lots of false alarms, while video-based deep learning fire detection is hampered by its time-consuming and expensive nature. To tackle these issues, this study proposes a fire detection model utilizing an autoencoder approach. The objective is to minimize false alarms while achieving swift and precise fire detection. The proposed model, employing an autoencoder methodology, can exclusively learn from normal data without the need for fire-related data, thus enhancing its adaptability to diverse environments. By amalgamating data from five distinct sensors, it facilitates rapid and accurate fire detection. Through experiments with various hyperparameter combinations, the proposed model demonstrated that out of 14 scenarios, only one encountered false alarm issues. Experimental results underscore its potential to curtail fire-related losses and bolster the reliability of fire detection systems.

• Journal of Sensor Science and Technology
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• v.6 no.1
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• pp.35-42
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• 1997

The optical biosensor using the electrically controlled release of reactive reagent is developed for the detection of peroxide. Rapid degradation of polymer complex of PEOx and PMAA occurs as the applied current increases and thus released amount of HPA increases. The degradation velocity of polymer and the amount of HPA released are linearly proportional to the applied current. Peroxide is reacted with the released reagent by peroxidase and then the product, a fluorescent dimer DBDA, is formed. The monochromic light from light source (150W Xe arc ramp) excites the DBDA and the excited light is transmitted through an optical fiber to be detected by a photodiode array. The change of fluorescence intensity is related to the change of peroxide concentration. The peroxidase is entrapped in Ca-alginate get on the inner surface. The biosensor has the linear signal range of 0.025mM-10.mM peroxide. By applying the step function of peroxide, reproducibility of biosensor has been investigated. The mathematical model is constructed by the combination of enzyme kinetics with reactor flow model. Good agreement is obtained between the experimental result and model prediction in the sensor signal.

• Applied Chemistry for Engineering
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• v.29 no.2
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• pp.191-195
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• 2018

In this study, the influence of microporous structures of activated carbon fibers (ACFs) on dimethyl methylphosphonate (DMMP) gas sensing properties as a nerve agent simulant was investigated. The pore structure was given to carbon fibers by chemical activation process, and an electrode was fabricated for gas sensors by using these fibers. The PAN based ACF electrode, which is an N-type semiconductor, received electrons from a reducing gas such as DMMP, and then electrical resistance of its electrode finally decreased because of the reduced density of electron holes. The sensitivity of the fabricated DMMP gas sensor increased from 1.7% to 5.1% as the micropore volume increased. It is attributed that as micropores were formed for adsorbing DMMP whose molecular size was 0.57 nm, electron transfer between DMMP and ACF was facilitated. In conclusion, it is considered that the appropriate pore structure control of ACFs plays an important role in fabricating the DMMP gas sensor with a high sensitivity.

• Applied Chemistry for Engineering
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• v.34 no.3
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• pp.207-212
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• 2023

Near-infrared (NIR) absorbing dyes have been applied to various applications such as optical filters, biotechnology, energy storage and conversion, coating additive, and traditionally information-storage materials. Because image sensors used in cellphones and digital cameras have sensitivity in the NIR region, the NIR cut-off filter is essential to achieving more clear images. As energy storage and conversion have been important, diverse NIR absorbing materials have been developed to extend the absorption region to the NIR region, and NIR absorbing materials-based research has proceeded to improve device performances. Adding NIR-absorbing dye with a photo-thermal effect to a self-healable coating system has been attractive for future mobility technology, and more effective self-healing properties have been reported. In this report, the chemical structures of representative NIR-absorbing dyes and state of the art research based on NIR-absorbing dyes are introduced.

• Journal of Sensor Science and Technology
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• v.8 no.2
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• pp.115-123
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• 1999

A micro-gas sensor with heater and sensing electrode on the same plane was fabricated on phosphosilicate glass(PSG, 800nm)/$Si_3N_4$ (150nm) dielectric membrane. PSG film was provided by atmospheric pressure chemical vapor deposition(APCVD), and $Si_3N_4$ film by low pressure chemical vapor deposition (LPCVD). Total area of the fabricated device was $3.78{\times}3.78mm^2$. The area of diaphragm was $1.5{\times}1.5mm^2$, and that of the sensing layer was $0.24{\times}0.24mm^2$. Finite-element simulation was employed to estimate temperature distribution for a square-shaped diaphragm. The power consumption of Pt heater was about 85mW at $350^{\circ}C$. Tin thin films were deposited on the silicon substrate by thermal evaporation at room temperature and $232^{\circ}C$, and tin oxide films($SnO_2$) were prepared by thermal oxidation of the metallic tin films at $650^{\circ}C$ for 3 hours in oxygen ambient. The film analyses were carried out by SEM and XRD techniques. Effects of humidity and ambient temperature on the resistance of the sensing layer were found to be negligible. The fabricated micro-gas sensor exhibited high sensitivity to butane gas.

• Journal of the Korean Electrochemical Society
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• v.23 no.3
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• pp.66-72
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• 2020

In this study, the development of biosensors capable of bi-enzyme reactions by including Horseradish peroxidase and glucose oxidase was carried out for detection of glucose. The sensors were manufactured using electro deposition method to reduce production time, and screen printed electrodes (SPE) were used to produce economical sensors. To check the bienzyme effect, the sensor was compared and analyzed with single enzyme biosensor. The characteristics of the sensor were evaluated using scanning electron microscopy(SEM), cyclic voltammetry(CV), electrochemical impedance spectroscopy(EIS), chronoamperometry(CA), and flow injection analysis(FIA). Analysis results from SEM, CV and EIS confirmed that the enzymes are well fixed to the electrode surface. In addition, it was confirmed that bi-enzyme biosensors manufactured from the CA method improved signal performance by 200% compared to single enzyme biosensors. From this results, we were able to explain that HRP and GOD react catalyzed to each other. And the results of FIA showed that the intensity of each current signal was constant when the same concentration of glucose was injected four times. In addition, by analyzing the intensity of current signals for glucose concentrations, the biosensors manufactured in this study showed excellent trends in signal sensitivity, reproducibility and stability.