• Title/Summary/Keyword: WO$_3$

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An Investigation of Information Usefulness of Google Scholar in Comparison with Web of Science (Google Scholar의 학술정보 검색을 위한 정보 유용성 비교연구)

  • Kim, Hyunjung
    • Journal of the Korean BIBLIA Society for library and Information Science
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    • v.25 no.3
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    • pp.215-234
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    • 2014
  • The purpose of this study is to investigate whether Google Scholar (GS) can substitute Web of Science (WoS) for those who don't have access to the subscription-based indexing service and if users feel GS is useful for scholarly information. To achieve the research purpose, the study evaluates both quantitative and qualitative aspects of the two databases. The major results through statistical analysis show that GS indexes much more records and citations for LIS journals than WoS(p < .01), but users' feedback about GS is not better than those about WoS.

$NO_{2}$ Sensing Properties of Oxide Semiconductor Thick Films (산화물 반도체형 후막 가스 센서의 이산화질소 감지 특성)

  • Kim, Seung-Ryeol;Yun, Dong Hyun;Hong, Hyung-Ki;Kwon, Chul-Han;Lee, Kyu-Chung
    • Journal of Sensor Science and Technology
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    • v.6 no.6
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    • pp.451-457
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    • 1997
  • The thick films of oxide semiconductors such as $WO_{3}$, $SnO_{2}$ and ZnO for the $NO_{2}$ detection of sub-ppm range have been prepared and their characteristics were investigated. It is showed that the optimum operating temperatures of the sensors are $300^{\circ}C$ and $220{\sim}260^{\circ}C$ for $WO_{3}$-based and $SnO_{2}$-based thick films, and ZnO-based thick films, respectively. Since the resistance of ZnO-based thick films are extremely high($>10^{6}{\Omega}$), the signal to noise ratio was comparatively low. In order to determine the selectivity, the films are exposed to the interfering gases such as ozone, ammonia, methane and the mixture of carbon monoxide and propane. $WO_{3}$-ZnO(3 wt.%) and $SnO_{2}-WO_{3}$(3 wt.%) thick film sensors show high sensitivity, good selectivity, excellent reproducibility and the linearity of $NO_{2}$ concentration versus sensor resistance. The preliminary results clearly demonstrated that the sensor can be successfully applied for the detection of $NO_{2}$ in sub-ppm range.

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Development of devices and methods for simulation of hurricane winds in a full-scale testing facility

  • Huang, Peng;Chowdhury, Arindam Gan;Bitsuamlak, Girma;Liu, Roy
    • Wind and Structures
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    • v.12 no.2
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    • pp.151-177
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    • 2009
  • The International Hurricane Research Center (IHRC) at Florida International University (FIU) is pursuing research to better understand hurricane-induced effects on residential buildings and other structures through full-scale aerodynamic and destructive testing. The full-scale 6-fan Wall of Wind (WoW) testing apparatus, measuring 4.9 m tall by 7.3 m wide, is capable of generating hurricane-force winds. To achieve windstorm simulation capabilities it is necessary to reproduce mean and turbulence characteristics of hurricane wind flows. Without devices and methods developed to achieve target wind flows, the full-scale WoW simulations were found to be unsatisfactory. To develop such devices and methods efficiently, a small-scale (1:8) model of the WoW was built, for which simulation devices were easier and faster to install and change, and running costs were greatly reduced. The application of such devices, and the use of quasiperiodic fluctuating waveforms to run the WoW fan engines, were found to greatly influence and improve the turbulence characteristics of the 1:8 scale WoW flow. Reasonable reproductions of wind flows with specified characteristics were then achieved by applying to the full-scale WoW the devices and methods found to be effective for the 1:8 scale WoW model.

Heterogeneous Porous WO3@SnO2 Nanofibers as Gas Sensing Layers for Chemiresistive Sensory Devices

  • Bulemo, Peresi Majura;Lee, Jiyoung;Kim, Il-Doo
    • Journal of Sensor Science and Technology
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    • v.27 no.5
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    • pp.345-351
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    • 2018
  • We employed an unprecedented technique to synthesize porous $WO_3@SnO_2$ nanofibers exhibiting core-shell and fiber-in-tube configurations. Firstly, 2-methylimidazole was uniformly incorporated in as-spun nanofibers containing ammonium metatungstate hydrate and the sacrificial polymer (polyacrylonitrile). Secondly, the 2-methylimidazole on the surfaces of nanofibers was complexed with tin(II) chloride ($SnCl_2$) via simple impregnation of the as-spun nanofibers in ethanol containing tin(II) chloride dihydrate ($SnCl_2{\cdot}2H_2O$). The presence of vacant p-orbitals in tin (Sn) and the nucleophilic nitrogen on the imidazole ring allowed for the reaction between $SnCl_2$ and 2-methylimidazole, forming adducts on the surfaces of the as-spun nanofibers. The calcination of these nanofibers resulted in porous $WO_3@SnO_2$ nanofibers with a higher surface area ($55.3m^2{\cdot}g^{-1}$) and a better response to 1-5 ppm of acetone than pristine $SnO_2$ NFs synthesized using a similar method. An improved response to acetone was achieved upon functionalization of the $WO_3@SnO_2$ nanofibers with catalytic palladium nanoparticles. This work demonstrates the potential application of $WO_3@SnO_2$ nanofibers as sensing layers for chemiresistive sensory devices for the detection of acetone in exhaled breath.

Synthesis of ZnWO4 Nanopowders by Polymerized complex Method (Polymerized complex법에 의한 ZnWO4 nanopower의 제조)

  • Ryu, Jeong-Ho;Lim, Chang-Sung;Auh, Keun-Ho
    • Journal of the Korean Ceramic Society
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    • v.39 no.3
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    • pp.321-326
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    • 2002
  • ZnWO$_4$ nano-powders were successfully prepared by polymerized complex method using zinc nitrate and tungstic acid as starting materials. In order to investigate the thermal decomposition and crystallization process, the polymeric precursors were heat-treated at temperatures from 300 to 600$^{\circ}$C for 3 h, and the heat-treated powders were characterized by XRD and FTIR. The surface morphology of the heat-treated powders were observed using SEM and TEM. The crystallite size was measured by X-ray analysis. Crystallization of the ZnWO$_4$ powders were detected at 400$^{\circ}$C and entirely completed at a temperature of 600$^{\circ}$C. The particles heat-treated 400 and 500$^{\circ}$C showed primarily co-mixed morphology with spherical and silkworm-like forms, while the particles heat-treated at 600$^{\circ}$C showed more homogeneous morphology. The average crystalline size were 19.9∼24.nm showing an ordinary tendency to increase with the temperatures from 400 to 600$^{\circ}$C.