• Title/Summary/Keyword: Temperature Sensitivity

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A Study on the factors of Quality variation for High Flowing Concrete in Site (고유동 콘크리트의 품질변동 요인에 관한 연구)

  • Kwon Yeong-Ho;Lee Hyun-Ho;Lee Hwa-Jin;Ha Jae-Dam
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.11a
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    • pp.743-746
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    • 2004
  • This research investigates experimentally an effect on the properties of the high flowing concrete according to variations of concrete materials and site conditions. Variations of sensitivity test are selected items as followings; (1)Concrete temperature, (2)Unit water(Surface moisture of fine aggregate), (3)Fineness modulus of fine aggregate, (4)Addition ratio of high-range water reducing agent. And fresh conditions of the high flowing concrete should be satisfied with required range including slump flow$(65{\pm}5cm)$, 50cm reaching time of slump flow$(4\~10sec)$, V-box flowing time$(10\~20sec)$, U-box height(min.300mm) and air content$(4{\pm}1\%)$. As results of sensitivity test, material variations and site conditions should be satisfied with the range as followings; (1)Concrete temperature is $10\~20^{\circ}C$ (below $30^{\circ}C$), (2)Surface moisture of fine aggregate is within ${\pm}0.6\%$, (3)Fineness modulus of fine aggregate is $2.6{\pm}0.2$ and (4)addition ratio of high range water reducing agent is within $1\%$ considered flow-ability, self-compaction and segregation resistance of the high flowing concrete.

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Development of alcohol gas sensors measurable at room temperature (상온에서 측정 가능한 음주 측정용 알코올 가스 센서)

  • Jeon, Byung-Hyun;Lee, Ju-Hyuk;Kim, Seong-Jean;Lee, Cheol-Jin;Choi, Bok-Gil
    • Proceedings of the KIEE Conference
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    • 1999.07g
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    • pp.3265-3267
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    • 1999
  • Capacitance-type alcohol gas sensors using porous silicon (PS) layer as sensitive film were fabricated to measure low alcohol gas concentration. Though sensors using porous silicon layer have show high sensitivity by large internal surface area, there is still much room for improvement to measure low breath alcohol concentration especially at room temperature. In this work, to discuss the response properties against exposure to organic vapor for breath alcohol measurements on the basis of experimental results. we measured the variation of the capacitance for the range of 0 to 0.5% alcohol concentration, and observed the improvement of sensitivity by illumination of UV light. In addition, the effect of CO2 and N2 gases involved commonly in exhaling breath was estimated, and the same procedure against methanol vapor was executed to compare qualitatively with the capacitance characteristics by alcohol vapor.

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Annealing Effect on $SnO_2$ Thin Films Properties ($SnO_2$ 박막 특성에 미치는 annealing 효과)

  • Park, Kyung-Hee;Seo, Yong-Jin;Lee, Woo-Sun;Park, Jin-Seong
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.05c
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    • pp.99-102
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    • 2003
  • Tin dioxide thin films were deposited at $375^{\circ}C$ on alumina substrate by metal-organic chemical vapor deposition process to find the relationship between physicochemical properties and the annealing treatments. The small grains with heat treatments grew to the bunch of grains and then showed the hillocks on the film surface. The thickness decreased with annealing treatment. The measured binding energy (BE) and branching ratio of the Sn 3d spin-orbital doublet were typical of oxidized states of Sn and the BE of the O1s core level of about 530~530.65eV also confirmed the presence of O-Sn bonds. The BE of oxygen and tin with annealing treatment shifted to higher position. O/Sn atomic ratios of films deposited at $375^{\circ}C$ for 2min and 4min were 1.99 and 2.01, respectively. The value of the atomic ratio O/Sn of films deposited at $375^{\circ}C$ for 2min changed from 1.99 to 2.45 with annealing treatment. Gas sensitivity depended on annealing temperature, the sensitivity increased with increasing annealing temperature.

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The CO sensing properties of thick film gas sensor using Co3O4 powders prepared by hydrothermal reaction method (수열합성법으로 제조된 Co3O4 분말을 사용한후막 가스센서의 CO 감지 특성)

  • Kim, Kwang-Hee;Kim, Jeong-Gyoo;Park, Ki-Cheol
    • Journal of Sensor Science and Technology
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    • v.19 no.5
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    • pp.385-390
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    • 2010
  • CO sensing thick film gas sensors using $Co_3O_4$ powders prepared by hydrothermal reaction method, were fabricated, and their structural, electrical and CO gas sensing properties were investigated. The specific surface area of the $Co_3O_4$ powders obtained from BET analysis was about 79.0 $m^2/g$. XRD and SEM results show that the thick films heat-treated at $500^{\circ}C$ for 30 min after screen printing had the preferred orientation of (311) direction and the crystalline size was calculated to 221 $\AA$. The maximum activation energy obtained from the temperature-resistance characteristics was 3.11 eV in the temperature range of $290^{\circ}C$ to $310^{\circ}C$. The sensitivity to 1,000 ppm CO was about 150 %. The specific surface area, crystalline size, and maximum activation energy were increased significantly and the sensitivity for CO gas was improved largely.

Growth and optoelectrical properties for $Cd_{1-x}Zn_xS$ thin films byg Hot Wall Epitaxy method (HWE에 의한 $Cd_{1-x}Zn_xS$ 박막의 성장과 광전기적 특성)

  • Lee, Sang-Youl;Hong, Kwang-Joon
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2004.07a
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    • pp.304-308
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    • 2004
  • The $Cd_{1-x}Zn_xS$ thin films were grown on the Si(100) wafers by a hot wall epitaxy method(HWE). The source and substrate temperature are $600^{\circ}C\;and\;440^{\circ}C$ respectively. The crystalline structure of epilayers was investigated by double crystal X-ray diffraction(DCXD). Hall effect on the sample was measured by the van der Pauw method and studied on the carrier density and mobility dependence on temperature. In order to explore the applicability as a photoconductive cell, we measured the sensitivity($\gamma$), the ratio of photocurrent to darkcurrent(pc/dc), maximum allowable power dissipation(MAPD), spectral response and response time. The results indicated that the photoconductive characteristic were the best for the $Cd_{0.53}Zn_{0.47}S$ samples annealed in Cu vapor compare with in Cd, Se, air and vacuum vapour. Then we obtained the sensitivity of 0.99, the value of pc/dc of $1.65{\times}10^7$, the MAPD of 338mW, and the rise and decay time of 9.7ms and 9.3ms, respectively

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New Soluble and Intrinsically Photosensitive Polyimide: Synthesis and Properties of Poly(amide-co-imide) Containing p-Phenylenediacryloyl Moiety

  • Lee, Myong-Hoon;Cheong, Yun-Sang;Gong, Myoung-Seon
    • Macromolecular Research
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    • v.9 no.6
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    • pp.327-331
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    • 2001
  • A new soluble photosensitive poly(amide-co-imide) containing p-phenylenediacryloyl moiety was synthesized and its photoreactivity was characterized. The copolymer was synthesized fromp-phenylenediacryloyl chloride, 4,4-(hexafluoroisopropylidene)diphthalic anhydride and two equivalents of bis(4-aminophenyl) ether in NMP with a subsequent chemical imidization of the resulting poly[amide$\xi$ο-(amic acid)] by acetic anhydride and pyridine. The structure and thermal properties of the polymer were characterized by spectroscopic methods and thermal analyses. The polymer was stable up to 350$\^{C}$, showed good solubility in polar aprotic solvents, and became insoluble after UV irradiation due to the[2+2] cycloaddition of phenylenediacryloyl moiety. Photoreactivity of the polymer was investigated in solution or as a film with respect to the various exposure conditions by UV/Vis spectroscopy. The photosensitivity was noticeably increased with the irradiation temperature, especially in the presense of photosensitizer. The reason for the increased sensitivity was speculated based on the flexibilization of main chain at elevated temperature. Exposure characteristic curves were obtained from the gel fraction experiments after UV irradiation. The sensitivity and contrast at 160$\^{C}$ were measured to be 293 mJ/㎠ and 1.64, respectively.

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Chip-scale Temperature-compensated Superstructured Waveguide Bragg Grating Based Multiparametric Sensor

  • Vishwaraj, Naik Parrikar;Nataraj, Chandrika Thondagere;Jagannath, Ravi Prasad Kogravalli;Gurusiddappa, Prashanth;Talabattula, Srinivas
    • Current Optics and Photonics
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    • v.4 no.4
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    • pp.293-301
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    • 2020
  • In this paper we propose and theoretically analyze a monolithic multiparametric sensor consisting of a superstructure of surface-relief waveguide Bragg gratings (WBGs), a micro-machined diaphragm, and a cantilever beam. Diaphragms of two different configurations, namely circular and square, are designed and analyzed separately for pressure measurement. The square diaphragm is then selected for further study, since it shows relatively higher sensitivity compared to the circular one, as it incurs more induced stress when any pressure is applied. The cantilever beam with a proof mass is designed to enhance the sensitivity for acceleration measurement. A unique mathematical method using coupled-mode theory and the transfer-matrix method is developed to design and analyze the shift in the Bragg wavelength of the superstructure configuration of the gratings, due to simultaneously applied pressure and acceleration. The effect of temperature on the wavelength shift is compensated by introducing another Bragg grating in the superstructure configuration. The measured sensitivities for pressure and acceleration are found to be 0.21 pm/Pa and 6.49 nm/g respectively.

The latest trend in magnetocardiogram measurement system technology

  • Lee, Y.H.;Kwon, H.;Kim, J.M.;Yu, K.K.
    • Progress in Superconductivity and Cryogenics
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    • v.22 no.4
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    • pp.1-5
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    • 2020
  • Heart consists of myocardium cells and the electrophysiological activity of the cells generate magnetic fields. By measuring this magnetic field, magnetocardiogram (MCG), functional diagnosis of the heart diseases is possible. Since the strength of the MCG signals is weak, typically in the range of 1-10 pT, we need sensitive magnetic sensors. Conventionally, superconducting quantum interference devices (SQUID)s were used for the detection of MCG signals due to its superior sensitivity to other magnetic sensors. However, drawback of the SQUID is the need for regular refill of a cryogenic liquid, typically liquid helium for cooling low-temperature SQUIDs. Efforts to eliminate the need for the refill in the SQUID system have been done by using cryocooler-based conduction cooling or use of non-cryogenic sensors, or room-temperature sensors. Each sensor has advantage and disadvantage, in terms of magnetic field sensitivity and complexity of the system, and we review the recent trend of MCG technology.

Ammonia Gas-sensing Characteristics of $Cr_{2}O_{3}$ Thick Films ($Cr_{2}O_{3}$ 후막의 암모니아 가스 감지 특성)

  • Cho, Chul-Hyung;Park, Ki-Cheol;Ma, Tae-Young;Kim, Jeong-Gyoo
    • 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.

Analyses of International Standard Problem ISP-47 TOSQAN experiment with containmentFOAM

  • Myeong-Seon Chae;Stephan Kelm;Domenico Paladino
    • Nuclear Engineering and Technology
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    • v.56 no.2
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    • pp.611-623
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    • 2024
  • The ISP-47 TOSQAN experiment was analyzed with containmentFOAM which is an open-source CFD code based on OpenFOAM. The containment phenomena taking place during the experiment are gas mixing, stratification and wall condensation in a mixture composed of steam and non-condensable gas. The k-ω SST turbulence model was adopted with buoyancy turbulence models. The wall condensation model used is based on the diffusion layer approach. We have simulated the full TOSQAN experiment which had a duration 20000 s. Sensitivity studies were conducted for the buoyancy turbulence models with SGDH and GGDH and there were not significant differences. All the main features of the experiments namely pressure history, temperature, velocity and gas species evolution were well predicted by containemntFOAM. The simulation results confirmed the formation of two large flow stream circulations and a mixing zone resulting by the combined effects of the condensation flow and natural convection flow. It was found that the natural convection in lower region of the vessel devotes to maintain two large circulations and to be varied the height of the mixing zone as result of sensitivity analysis of non-condensing wall temperature. The computational results obtained with the 2D mesh grid approach were comparable to the experimental results.