• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.105-105
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• 2011

ZnO is a promising material since it could be applied to many fields such as solar cells, laser diodes, thin films transistors and gas sensors. ZnO has a wide and direct band gap for about 3.37 eV at room temperature and a high exciton binding energy of 60 meV. In particular, ZnO features high sensitivity to toxic and combustible gas such as CO, NOX, so on. The development of gas sensors to monitor the toxic and combustible gases is imperative due to the concerns for enviromental pollution and the safety requirements for the industry. In this study, we investigated the effect of substrate temperature and post-annealing on structural and electrical properties of ZnO thin films. ZnO thin films were deposited by pulsed laser deposition (PLD) at various temperatures at from room temperature to $600^{\circ}C$. After that, post-annealing were performed at $600^{\circ}C$. To inspect the structural properties of the deposited ZnO thin films, X-ray diffraction (XRD) was carried out. For gas sensors, the morphology of the films is dominant factor since it is deeply related with the film surface area. Therefore, the atomic force microscopy (AFM) and field emission scanning electron microscopy (FE-SEM) were used to observe the surface of the ZnO thin films. Furthermore, we analyzed the electrical properties by using a Hall measurement system.

• Journal of the Korean Ceramic Society
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• v.38 no.12
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• pp.1180-1186
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• 2001

W $O_3$-Sn $O_2$thin film sensors with approximately 1${\mu}{\textrm}{m}$ in thickness were fabricated by using a high-vacuum resistance-heating evaporator, were annealed at 50$0^{\circ}C$ for 4 hours in air, and then their crystallinities and surface microstructures were analyzed. As results of gas-sensing characteristics to oxidizing gas, N $O_2$, and reducing gas, CO, of 100 ppm, the highest gas sensitivities (S= $R_{gas}$/ $R_{air}$) were the W $O_3$thin-film sensor measured at 25$0^{\circ}C$ for N $O_2$(S≒1000) and the Sn $O_2$thin-film sensor measured at 15$0^{\circ}C$ to 25$0^{\circ}C$ range for CO (S≒0.25), respectively.ely.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.160-161
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• 2008

$SnO_2$는 n형 반도체로써 3.6 eV의 큰 밴드갭을 가지는 물질로 CO와 NOx 가스에 좋은 감도를 나타내는 것으로 보고되고 있다. 문헌에 따른 일반적인 $SnO_2$ 가스센서는 후막이나 벌크형태로 제작되었다. 근래에는 가스감응체가 $SnO_2$ 나노선 형태인 가스센서가 활발한 연구 중에 있다. 본 논문에서는 기판 위에 서로 분리된 전극 패턴에 Au를 촉매로 하여 네트워크 구조로 된 $SnO_2$ 나노선이 합성되었다. 제작된 가스센서에 Pd 도핑에 따른 영향을 알아보기 위하여 1.8 mM의 Pd 용액 ($PdCl_2{\cdot}xH_2O$ 3 mg + $H_2O$ 10 ml)을 이용하여 센서에 도핑하였다. 측정 시스템에서 $NO_2$ 가스에 대한 센서의 특성을 분석한 결과 도핑하지 않은 $SnO_2$ 센서보다 20%정도의 감도가 개선되었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.3
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• pp.280-285
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• 1999

$\alpha$-$Fe_2O_3$ thin film gas sensors were deposited at various temperature by CVD method. Polycrystalline $\alpha$-$Fe_2O_3$ thin films were deposited at $175^{\circ}C$ and $200^{\circ}C$. $\gamma$-$\alpha$-$Fe_2O_3$ phase was obtained when the deposition temperature was higher than $250^{\circ}C$. The crystallite size of $\alpha$-$Fe_2O_3$ was affected by the deposition and annealing temperature. The specimen deposited at $175^{\circ}C$ showed maximum sensitivity. In this condition, the sensitivity of $\alpha$-$Fe_2O_3$ thin film for NO gas (at 250 ppm) was 3.2 and response time (at 100ppm) was 12 second.

• Journal of Digital Convergence
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• v.15 no.12
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• pp.313-321
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• 2017

Traffic accidents in the country have steadily increased. Although IOT technologies have been applied so as to prevent the primary accident, practical solutions to prevent the secondary accident have not been suggested. A general guideline is simply recommended. In this paper, utilizing existing communication technology, we implement a proposed model and its simulation to prevent the secondary accident. When it is possible for a driver to secure visibility, the secondary accident can be prevented; In areas like tunnel, mountain terrain, and curve road with heavy traffic, where the driver has difficulty in securing the visibility, the secondary accident rates after the primary accident have been increasing. Therefore, we implement an accident prevention system that determines the primary accident utilizing sensor technology and prevents the secondary accident communicating through V2V or V2I. After the simulation, we found that the proposed model and the existing model made no difference with regard to the secondary accident rates when the visibility of the driver is secured; With the application of the proposed model, however, the accident rates decreased for 3-7 percent even though the visibility and communication were not secured.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.1
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• pp.37-43
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• 2010

The purpose of this paper is to investigate the effect of air-fuel ratio on the combustion and emissions characteristics of spark ignition (SI) gasoline engine fueled with bio-ethanol. A 1.6L SI engine with 4 cylinders was tested on EC dynamometer. In addition, lambda sensor and lambda meter were connected with universal ECU to control the lambda value which is varied from 0.7 to 1.3. The engine performance and combustion characteristics of bio-ethanol fuel were compared to those obtained by pure gasoline. Furthermore, the exhaust emissions such as carbon monoxide (CO), unburned hydrocarbon (HC), oxides of nitrogen ($NO_X$) and carbon dioxide ($CO_2$) were measured by emission analyzers. The results showed that the brake torque and cylinder pressure of bio-ethanol fuel were slightly higher than those of gasoline fuel. Brake specific fuel consumption (BSFC) of bio-ethanol was increased while brake specific energy consumption (BSEC) was decreased. The exhaust emissions of bio-ethanol fuel were lower than those of gasoline fuel under overall experimental conditions. However, the specific emission characteristics of the engine with bio-ethanol fuel were influenced by air-fuel ratio.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.11
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• pp.1630-1636
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• 2003

Automobile companies and research institutions in leading automobile-manufacturing nations have recently been very active with research regarding the HCCI engine for use in future vehicles. Because HCCI engines take advantage of high compression ratio and heat release rate, they exhibit high efficiency found in compression ignition engines. HCCI engines also utilize a lean air/fuel ratio resulting in low emissions of NO$_{x}$ and PM (particulate matter). The objective of this research is to determine the effects of EGR rate on the combustion processes of HCCI. for this purpose, a 4-cylinder, compression ignition engine was converted into a HCCI engine, and a heating device was installed to raise the temperature of the intake air and also to make it more consistent. In addition, a pressure sensor was inserted into each of the cylinders to investigate the differences in characteristics among the cylinders. The experimental study of the effects of EGR rate on various gas emissions, engine performance, etc. should prove to be a valuable source of information for the development of the HCCI engine.e.

• Journal of the Korean Society of Clothing and Textiles
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• v.21 no.4
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• pp.750-756
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• 1997

The purpose of the study was to investigate a transmittance rate of UVB (Ultraviolet B) through summer fabrics and a protection rate of summer fabric from UVB. The subjects were randomly selected 159 fabrics from Korean common summer fabrics. The protection rates of 159 fabrics from UVB were measured by UVB lamp and UVB sensor, and 14 fabrics among these fabrics were selected for an assay of MTT(3-(4, 5-dimethylthiazol-2-yl) -2, 5 -diphenyltetrazolium). The protection rate of fabrics from cell toxicity of UVB was measured by investigating the difference of the amount of cell toxic substance on between fabrics covered with and without HeLa cell The average protection rate of 159 fabrics from UVB was 95.08%. As result findings, three negative correlations were found between: 1) the transmittance rate of UVB and the amount of MTT on fabrics (y=0.0373+0.O0518 x, r=-0.9323, p<0.001); 2) the air permeability of fabrics and the amount of MTT (r: -0.79, p< 0.01); 3) the air permeability of fabrics and the protection rate of fabrics from UVB (r=0.89, p<0.01). However, there was no effect of thickness of fabrics on the protection rate from UVB and the amount of MTT.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.678-681
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• 2009

A single-pixel photon counter is designed using a folded cascode CMOS operational amplifier which is self-biased. Since there is no need for a voltage bias circuit, the layout area and power consumption of the designed counter are reduced. The signal voltage of the designed charge sensitive amplifier (CSA) with the MagnaChip $0.18{\mu}m$ CMOS process is simulated to be 138mv, near the theoretical voltage of 151mV. And the layout area of the designed counter is $100{\mu}m{\times}100{\mu}m$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.19-25
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• 2019

The CleanSYS(Clean SYStem) is operated to monitor air pollutants emitted from specific industrial complexes in Korea. So the industrial complexes without the system are directly monitored by the control officers. For efficient monitoring, studies using various sensors have been conducted to monitor air pollutants emitted from industrial complex. In this study, hyperspectral sensors were used to model and verify the equations for estimating the concentration of $NO_2$(nitrogen dioxide) in air pollutants emitted. For development of the equations, spectral radiance were observed for $NO_2$ at various concentrations with different SZA(Solar Zenith Angle), VZA(Viewing Zenith Angle), and RAA(Relative Azimuth Angle). From the observed spectral radiance, the calculated value of the difference between the values of the specific wavelengths was taken as an absorption depth, and the equations were developed using the relationship between the depth and the $NO_2$ concentration. The spectral radiance mixed gas of $NO_2$ and $SO_2$(sulfur dioxide) was used to verify the equations. As a result, the $R^2$(coefficient of determination) and RMSE(Root Mean Square Error) were different from 0.71~0.88 and 72~23 ppm according to the form of the equation, and $R^2$ of the exponential form was the highest among the equations. Depending on the type of the equations, the accuracy of the estimated concentration with varying concentrations is not constant. However, if the equations are advanced in the future, hyperspectral sensors can be used to monitor the $NO_2$ emitted from the industrial complex.