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oe1(光电查) - 科学论文

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出版时间
  • 2018
研究主题
  • interdigital resonator
  • microwave gas sensor
  • PSE-coated
应用领域
  • Optoelectronic Information Science and Engineering
机构单位
  • King Mongkut’s University of Technology North Bangkok
  • Rajamangala University of Technology Suvarnabhumi
571 条数据
?? 中文（中国） ▾

  • Pulse dilation gas Cherenkov detector for ultra-fast gamma reaction history at the NIF (invited)

    摘要： The Cherenkov mechanism used in Gas Cherenkov Detectors (GCDs) is exceptionally fast. However, the temporal resolution of GCDs, such as the Gamma Reaction History diagnostic at the National Ignition Facility (NIF), has been limited by the current state-of-the-art photomultiplier tube technology to ～100 ps. The soon-to-be deployed Pulse Dilation Photomultiplier Tube (PD-PMT) at NIF will allow for temporal resolution comparable to that of the gas cell or ～10 ps. Enhanced resolution will contribute to the quest for ignition in a crucial way through precision measurements of reaction history and ablator areal density (ρR) history, leading to better constrained models. Features such as onset of alpha heating, shock reverberations, and burn truncation due to dynamically evolving failure modes may become visible for the ?rst time. Test measurements of the PD-PMT at Atomic Weapons Establishment con?rmed that design goals have been met. The PD-PMT provides dilation factors of 2 to 40× in 6 increments. The GCD-3 recently deployed at the NIF has been modi?ed for coupling to a PD-PMT and will soon be making ultrafast measurements.

    关键词： Gas Cherenkov Detectors,Pulse Dilation Photomultiplier Tube,National Ignition Facility,temporal resolution,Cherenkov mechanism

    更新于2025-09-09 09:28:46

  • Effects of a cathode output aperture on the hollow cathode glow discharge

    摘要： Glow discharge with a cylindrical hollow cathode mounted on a process vacuum chamber has been studied in a wide range of gas pressures from 0.01 to 10 Pa. The chamber serves as the discharge anode. A diaphragm is fastened on the cathode end to protect the discharge plasma inside the chamber from contamination with the sputtered cathode material. The discharge characteristics depend on area So of the diaphragm ori?ce. A double layer appears at the ori?ce when So < S* ≈ (2 m/M)1/2S, where m is the electron mass, M is the ion mass, and S is the cathode surface area. Electrons accelerated in the double layer effectively ionize the gas and can produce, inside the chamber, a plasma with the same density as inside the cathode. At the gas pressure less than ～0.3 Pa, the low-voltage double layer can be replaced with a high-voltage accelerating gap between the plasma inside the cathode and the plasma produced inside the chamber by a beam-plasma discharge.

    关键词： double layer,hollow cathode,glow discharge,gas pressure,plasma

    更新于2025-09-09 09:28:46

  • Precise gas discrimination with cross-reactive graphene and metal oxide sensor arrays

    摘要： Discriminating similar molecules remains a very challenging problem for semiconductor gas sensors. Here, we report a method to achieve precise gas discrimination of similar chemical vapors (mesitylene, o-xylene, and toluene) by using cross-reactive arrays consisting of metal oxide semiconductor and graphene sensors. It is dif?cult to identify these three chemicals as they have very similar responses to these sensors. Through cross-reactive Principal Component Analysis of the sensor response features, however, the discrimination accuracy improved from about 70% with a single gas sensor to almost 100% with the cross-reactive sensor array. Such a precise discrimination and the low-cost planar process make this approach a very attractive candidate for smart gas sensing and for future Internet of Things applications.

    关键词： gas discrimination,metal oxide,sensor arrays,cross-reactive,graphene

    更新于2025-09-09 09:28:46

  • Characterization of Evanescent Field Gas Sensor Structures Based on Silicon Photonics

    摘要： Photonic sensors that operate in the mid-infrared spectral range are an emerging field for photonic microsystems. In this paper, we present a photonic gas sensor concept based on silicon waveguides using infrared evanescent field absorption. The waveguides were specifically designed for CO2 sensing at a wavelength of λ = 4.26 μm as possible application for the proposed sensor platform. The waveguide cross section as well as the substructure were investigated using finite-element simulations and the devised structures were fabricated using mass fabrication processes exclusively. In order to evaluate the potential for long interaction path lengths using polysilicon strip waveguides, a study on the intrinsic losses of polysilicon waveguides was conducted. The lowest intrinsic damping that was obtained for polysilicon strip waveguides was 3.98 dB/cm. Furthermore, the sensing capability of the devised waveguides was tested with quantitative CO2 measurements down to a concentration of 500 ppm CO2. From the quantitative measurements, the evanescent field ratio was estimated and was in the range between η = 14%–16%.

    关键词： integrated silicon photonics,intrinsic losses,evanescent field absorption,silicon waveguide,Optical gas sensing

    更新于2025-09-09 09:28:46

  • Vertical Current Transport in AlGaN/GaN HEMTs on Silicon: Experimental Investigation and Analytical Model

    摘要： We investigate the vertical leakage mechanism in metal–organic chemical vapor deposition-grown carbon (C)-doped AlGaN/GaN High Electron Mobility Transistors (HEMTs) on 6-in silicon wafer. Substrate bias polarity-dependentI–Vs, temperature-dependent ?tting, and band diagram analysis pointed to the Poole–Frenkel (P–F) type of conduction mechanism for vertical transport in the devices with breakdown as high as 580 V for a buffer of 4 μm. Trap activation energy of 0.61 eV was estimated from the P–F ?tting which matches well with values reported in the literature. We propose that higher dislocation density leads to shallower traps in the buffer and build an analytical model of dislocation-mediated vertical leakage around this. The variation in leakage as a function of dislocation density at a given ?eld is predicted and is found to be the most abrupt in the range from ～107 to ～109 cm?2 of dislocation density. This can be attributed to a sharp decrease in trap activation energy in the above range of dislocation density, possibly due to complex formation between point defects and dislocations.

    关键词： high-electron mobility transistor (HEMT),vertical leakage,Poole–Frenkel (P–F),2-D electron gas,hopping conduction,AlGaN

    更新于2025-09-09 09:28:46

  • Polymer Foam-Supported Chemically Reduced Graphene Oxide Conductive Networks for Gas Sensing

    摘要： In this work, gas sensors based on chemically reduced graphene oxide (rGO) foams were reported for NH3 detection. Polymer foams were used as scaffolds to support rGO, and the resultant soft sensing devices exhibited a high sensitivity, high selectivity, and rapid recovery for NH3 detection at room temperature. The sensor showed more than 0.90% and 3.67% resistance changes respectively, when it’s exposed to 1 ppm and 50 ppm NH3. The graphene foam gas sensors (FGS) also showed excellent repeatability. Furthermore, the response of rGO foam gas sensor to NH3 was more than two times higher than that to methanol vapors diluted to 1% of the saturated vapor concentration. Above all, the unique features, such as simple preparation, low cost and energy consumption, as well as excellent sensing performance, endow the sensor a great potential for NH3 detection.

    关键词： Ammonia,Three-Dimensional,Graphene,Gas Sensor,Foam

    更新于2025-09-09 09:28:46

  • Synthesis, Characterization and Photocatalytic Efficiency of ZnO/MWCNT Nanocomposites Prepared Under Different Solvent Conditions

    摘要： Here we report the application of zinc oxide (ZnO) coated multi-walled carbon nanotube (MWCNT) composites in the photocatalytic decomposition of acetaldehyde (AA). Zinc oxide nanoparticles were successfully coated on the multi-walled carbon nanotube via impregnation process using zinc acetate (Zn(CH3COO)2 × 2H2O) as precursor and sodium dodecyl sulfate (SDS) treated multi-walled carbon nanotube as raw material under different solvent conditions. The applied solvents during preparation were ethanol (EtOH) and water (H2O). As-prepared materials were characterized by thermal analysis (TG), X-ray diffraction (XRD), specific surface area measurement (BET) and transmission electron microscopy (TEM) techniques. Photocatalytic efficiencies of as-prepared composites were investigated in a stationary reactor equipped with UV lamp. Decomposition of acetaldehyde was followed by using gas chromatography (GC). Observations revealed that using impregnation method and different solvents the preparation of ZnO/MWCNT nanocomposites can be controlled easily. The highest degradation rate was achieved with the nanocomposite was synthetized using ethanol as solvent. The photocatalytic experiments revealed that the composite has higher photocatalytic activity than that of both the zinc oxide nanoparticles and the mechanical mixture of multi-walled carbon nanotube and zinc oxide.

    关键词： Transmission Electron Microscopy,Zinc Oxide,Photocatalysis,Gas Chromatography,Nanocomposite

    更新于2025-09-09 09:28:46

  • On-Line Analysis of Oil-Dissolved Gas in Power Transformers Using Fourier Transform Infrared Spectrometry

    摘要： To address the problem of on-line dissolved gas analysis (DGA) of a power transformer, a Fourier transform infrared (FT-IR) spectrometer was used to develop an analysis instrument. Carbon monoxide (CO), carbon dioxide (CO2), methane (CH4), ethane (C2H6), ethylene (C2H4) and acetylene (C2H2) were the analytes for the FT-IR spectrometer while propane (C3H8), propylene (C3H6), propyne (C3H4), n-butane (n-C4H10) and iso-butane (iso-C4H10) were the interferents, which might exist in the dissolved gas but are not currently used as analytes for detecting an internal fault. The instrument parameters and analysis approach are first introduced. Specifically, an absorption spectra reading approach by switching two cone-type gas cells into separate light-paths was presented for reducing the effects of gas in the gaps between gas cells and spectrometers, scanning the background spectrum without clearing the sample cell, and increasing the dynamics. Then, the instrument was tested with a standard gas mixture that was extracted from insulation oil in a power transformer. The testing results show that the detection limit of every analyte component is lower than 0.1 μL/L, and the detection limits of all analytes meet the detection requirements of oil-dissolved gas analysis, which means that the FT-IR spectrometer may be an ideal instrument due to its benefits, such as being maintenance-free and having a high stability.

    关键词： power transformer,oil-dissolved gas,gas chromatograph,spectral analysis,Fourier transform infrared spectrometer

    更新于2025-09-04 15:30:14

  • Synthesis, Characterization and Gas-Sensing Properties of Pristine and SnS2 Functionalized TeO2 Nanowires

    摘要： We report the gas-sensing properties of pristine and SnS2 functionalized TeO2 nanowires (NWs). TeO2 NWs were synthesized by a vapor–liquid–solid growth method, and SnS2 functionalization was performed using an atomic layer deposition technique followed by thermal treatment. Structural and morphological analyses verified the formation of pristine and SnS2 functionalized TeO2 NWs with desired composition, phase, and morphology. Interestingly, sensing results showed that the pristine TeO2 NW gas sensor had better sensing properties relative to the SnS2 functionalized TeO2 NW gas sensor. An underlying sensing mechanism is explained in detail, and reasons for the decrease of sensing performance with the SnS2 functionalized TeO2 NW sensor was attributed to the coverage of TeO2 surface by the SnS2 nanoparticles.

    关键词： Gas sensor,SnS2,NO2 gas,TeO2,Sensing mechanism

    更新于2025-09-04 15:30:14

  • Technology Update: Characterizing a Coal-Seam Gas Reservoir by Interpreting Permanent DTS Data

    摘要： In Australia’s Surat Basin, gas is contained in hundreds of coal seams, which have highly variable properties and are grouped into four distinct reservoir zones of similar qualities. Economically producing these wells from multiple reservoir units is generally favored and as a result, understanding the relative contribution to production by different zones at different times in the well’s life—and whether production is dominated by a single zone—adds value to planning future wells.

    关键词： FloQuest,zonal allocation,DTS data,production logging tools,coal-seam gas

    更新于2025-09-04 15:30:14