• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.19 no.3
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• pp.119-123
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• 2013

Simplified control logic was devised to fabricate and operate the modified atmosphere (MA) container of fresh produce equipped with gas-diffusion tube whose opening/closing was controlled in response to real time $O_2$ concentration. This is a simplified ramification of the previously developed control logic using both $O_2$ and $CO_2$ concentrations ([$O_2$] & [$CO_2$]). The developed logic was applied to and tested by a container system filled with spinach at $10^{\circ}C$ having optimum MA window of [$O_2$] of 7~10% and [$CO_2$] of 5~10%. It was shown that setting the proper on-off limit (11%) for $O_2$ control based on the assumed relationship $[O_2]+[CO_2]$=21% could attain the desired $CO_2$ concentration just below the upper tolerance limit ($[CO_2]_H$, 10%). The $O_2$ control point can be the lower tolerance limit or adjusted one (21-$[CO_2]_H$) depending on the commodity's MA requirement. The developed logic using single $O_2$ sensor could attain the equilibrated [$O_2$] of 11% with [$CO_2$] of 8~9% which was desired and similar to that of its predecessor ([$O_2$] of 9~10% with [$CO_2$] of 10%) using both $O_2$ and $CO_2$ sensors. Both MA containers (one only with single $O_2$ sensor control and one with $O_2$ and $CO_2$ sensors) could also keep the spinach quality without significant difference between them, but significantly better than perforated control package of air.

• Journal of Sensor Science and Technology
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• v.11 no.2
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• pp.118-123
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• 2002

$ZnGa_2O_4$ thin film phosphors have been deposited using a pulsed laser deposition technique on $Al_2O_3$(0001) substrates at a substrate temperature of $550^{\circ}C$ with various oxygen pressures 100, 200 and 300 mTorr. The films grown under different growth oxygen pressures have been characterized using microstructural and luminescent measurements. The different photoluminescence (PL) characteristics with the increase in oxygen pressures may result from the change of the crystallinity and the composition ratio of Zn and Ga in the films. The luminescent spectra show a broad band extending from 300 to 600 nm peaking at 460 nm. The PL brightness data obtained from the $ZnGa_2O_4$ films grown under optimized conditions have indicated that the sapphire is a promising substrate for the growth of high quality $ZnGa_2O_4$ thin film phosphor.

• Journal of Sensor Science and Technology
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• v.30 no.6
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• pp.376-380
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• 2021

The accurate detection of hydrogen gas molecules is considered to be important for industrial safety. However, the selective detection of the gas using semiconductive metal oxides (SMOs)-based sensors is challenging. Here, we describe the fabrication of H₂ sensors in which a nanocellulose/graphene oxide (GO) hybrid membrane is attached to SnO₂ nanosheets (NSs). One-dimensional (1D) nanocellulose fibrils are attached to the surface of GO NSs (GONC membrane) by mixing GO and nanocellulose in a solution. The as-prepared GONC membrane is employed as a sacrificial template for SnO₂ NSs as well as a molecular sieving membrane for selective H₂ filtration. The combination of GONC membrane and SnO₂ NSs showed substantial selectivity to hydrogen gas (R_air / R_gas > 10 @ 0.8 % H₂, 100 ℃) with noise level responses to interfering gases (H₂S, CO, CH₃COCH₃, C₂H₅OH, and NO₂). These remarkable sensing results are attributed mainly to the molecular sieving effect of the GONC membrane. These results can facilitate the development of a highly selective H₂ detector using SMO sensors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.169-170
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• 2005

본 연구에서는 초음파 센서에 응용 가능한 $0.4Pb(Ni_{1/3}Nb_{2/3})O_3-0.6Pb(Zr_xTi_{1-x})O_3+0.5Wt%$ $MnO_2$ 세라믹스에 Zr/(Ti+Zr)비를 0.37에서 0.41로 변화시킨 조성을 1175 $\sim$ 1200$^{\circ}C$ 온도에서 소결하여 이의 결정구조 및 미세조직을 분석하였고, 압전, 유전 특성을 고찰하였다. 본조성에서 x=0.385 조성에서 최대 유전상수 값 3490 이 나타났으며, 그 이상의 첨가에서는 감소하였다. 상경계 영역인 x=0.385 조성에서 $\varepsilon$r, $K_p$, $d_{33}$ 값이 최대값을 나타내었다. $0.4Pb(Ni_{1/3}Nb_{2/3})O_3-0.6Pb(Zr_xTi_{1-x})O_3+0.5Wt%$ $MnO_2$, 세라믹스에서는 kp 와 $d_{33}$ 는 Zr/(Ti+Zr)비 0.385조성까지 증가하였다가 그 이상 조성에서 감소하였다. $1175^{\circ}C$에서 2시간 소결한 x=0.385조성에서 $\varepsilon$r=3490, kp=0.71, Qm=476의 우수한 압전 특성을 나타내었다.

• Journal of Sensor Science and Technology
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• v.13 no.4
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• pp.282-286
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• 2004

${\alpha}-Fe_{2}O_{3}$ films were prepared by ultrasonic spray pyrolysis (USP) on $SiO_{2}$ coated Si wafers using iron acetylacetonate as an iron precursor. The crystallographic properties and surface morphologies of the films were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. X-ray photoelectron spectroscopy (XPS) was carried out to determine the Fe oxidation states. In order to observe stability of the films to temperature, the resistance variation of the films with an ambient temperature was measured. The effects of substrate temperature on the structural and electrical properties of the ${\alpha}-Fe_{2}O_{3}$ films were studied. The films were densified from the substrate temperature of $350^{\circ}C$. The grain size of the films grown at $400^{\circ}C$ was shown to be increased abruptly comparing with that of $350^{\circ}C$. The films showed a low resistance variation between the ambient temperature of $300^{\circ}C$ and $350^{\circ}C$.

• Journal of the Korean Society for Heat Treatment
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• v.25 no.5
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• pp.239-243
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• 2012

$SnO_2$ thin films were prepared on the Si substrate by radio frequency (RF) magnetron sputtering and then post deposition vacuum annealed to investigate the effect of annealing temperature on the structural properties and hydrogen gas sensitivity of the films. The films that annealed at $300^{\circ}C$ show the higher sensitivity than the other films annealed at $150^{\circ}C$. From atomic force microscope observation, it is supposed that post deposition annealing promotes the rough surface and also, increase gas sensitivity of $SnO_2$ films for hydrogen gas. These results suggest that the vacuum annealed $SnO_2$ thin films at optimized temperatures are promising for practical high-performance hydrogen gas sensors.

• Journal of Sensor Science and Technology
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• v.13 no.6
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• pp.424-429
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• 2004

$Cr_{2}O_{3}$ thick films were fabricated by screen printing method on alumina substrates and annealed at $700^{\circ}C$, $800^{\circ}C$, and $900^{\circ}C$ in air, respectively. Structural properties examined by XRD and SEM showed (116) dominant $Cr_{2}O_{3}$ peak and increased grain sizes with the annealing. The resistance of the films decreased with increasing the annealing temperature. Gas sensing characteristics to $NH_{3}$, CO, $C_{4}H_{10}$, and NO gases showed sensitivity only to $NH_{3}$ gas. $Cr_{2}O_{3}$ thick films annealed at $700^{\circ}C$ had the sensitivity of about 15 % for 100 ppm $NH_{3}$ gas at the working temperature of $300^{\circ}C$. The thick films had good selectivity to the $NH_{3}$ gas. The response time to $NH_{3}$ gas was about 10 seconds.

• Journal of Sensor Science and Technology
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• v.3 no.2
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• pp.74-80
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• 1994

Silicon direct bonding technology is very attractive for both silicon-on-insulator devices and sensor fabrication because of its thermal stress free structure and stability. The process of SDB includes hydration of silicon wafer and heat treatment in a wet oxidation furnace. After hydration process, hydroxyl groups of silicon wafer were analyzed by using Fourier transformation-infrared spectroscopy. In case of hydrophilic treatment using a ($H_{2}O_{2}\;:\;H_{2}SO_{4}$) solution, hydroxyl groups are observed in a broad band around the 3474 $cm^{-1}$ region. However, hydroxyl groups do not appear in case of diluted HF solution. The bonded wafer was etched by using tetramethylammonium hydroxide etchant. The surface of the self etch-stopped silicon dioxide is completely flat, so that it can be used as sensor applications such as pressure, flow and acceleration, etc..

• Journal of IKEEE
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• v.24 no.4
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• pp.1117-1121
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• 2020

In this work, it was confirmed that a SnO2 catalyst deposited by an atomic layer deposition(ALD) process can be employed in AlGaN/GaN heterostructure FET to detect NO2 gas. The fabricated HFET sensors on AlGaN/GaN-on-Si platform demonstrated that the devices with or without n-situ SiN have sensitivity of 5.5 % and 38 % at 200 ℃, respectively with response to 100 ppm-NO2.

• Journal of Sensor Science and Technology
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• v.8 no.3
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• pp.232-238
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• 1999

Single mode fiber optic interferometers using the Fabry-Perot configuration were embedded in a reinforced concrete structure. These interferometers investigated the character of phase shift and strain for internal loads. The 10 mm length of FFPI in the continuous length of single mode fiber (SMF) were produced with two pieces of SMF coated were $TiO_2$ dielectric film utilizing the fusion splicing technique. The fabricated fiber optic Fabry-Perot interferometer(FFPI) and the 6 mm length of steel bar were buried with specimen ($100{\times}100{\times}50\;mm^3$) which was made of concrete structure. The resin protects FFPI and fiber leads from squeezed concrete. Sensors at different point in the structure were multiplexed by TDM (Time Division Multiplexing) method and the deformation to the external loads at each point could be monitored simultaneously. The output signals were proportional to the external loads applied to the structure and the sensitivity of the sensors were $1.03^{\circ}/kg$ and $0.76^{\circ}/kg$ respectively.