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Effect of Er3+-doping on 65GeS2-25Ga2S3-10CsCl glass probed by annihilating positrons
摘要： Effect of Er3+-doping resulting in pronounced mid-IR fluorescence functionality was examined first in chalcohalide 65GeS2-25Ga2S3-10CsCl glass using positron annihilation lifetime (PAL) spectroscopy. The detected PAL spectra were reconstructed from unconstrained x2-term analysis employing two-state simple trapping model for one kind of positron trapping free-volume defects, the parameterization being performed at the example of 65GeS2-25Ga2S3-10CsCl glass doped with 0.6 at. % of Er3+. The observed decrease in positron trapping rate was proved to be primary void-evolution process in this Er-activated glass, like in many other chalcogenide glasses affected by rare earth doping. The nature of this effect was explained in terms of positron trapping reduction model as competitive contribution of changed occupancy sites in Ga-modified glassy matrix available for rare earth ions and annihilating positrons.
关键词： Chalcohalide glass,Positron trapping reduction,Rare earth doping,Photoluminescence
更新于2025-09-23 15:23:52
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Learning compact q-space representations for multi-shell diffusion-weighted MRI
摘要： Diffusion-weighted MRI measures the direction and scale of the local diffusion process in every voxel through its spectrum in q-space, typically acquired in one or more shells. Recent developments in microstructure imaging and multi-tissue decomposition have sparked renewed attention in the radial b-value dependence of the signal. Applications in motion correction and outlier rejection therefore require a compact linear signal representation that extends over the radial as well as angular domain. Here, we introduce SHARD, a data-driven representation of the q-space signal based on spherical harmonics and a radial decomposition into orthonormal components. This representation provides a complete, orthogonal signal basis, tailored to the spherical geometry of q-space and calibrated to the data at hand. We demonstrate that the rank-reduced decomposition outperforms model-based alternatives in human brain data, whilst faithfully capturing the micro- and meso-structural information in the signal. Furthermore, we validate the potential of joint radial-spherical as compared to single-shell representations. As such, SHARD is optimally suited for applications that require low-rank signal predictions, such as motion correction and outlier rejection. Finally, we illustrate its application for the latter using outlier robust regression.
关键词： Diffusion-weighted imaging,Blind source separation,Multi-shell HARDI,Dimensionality reduction
更新于2025-09-23 15:23:52
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Compact Dual-Channel Balanced Filter and Balun Filter Based on Quad-Mode Dielectric Resonator
摘要： In this paper, we propose a method for designing a dual-channel balanced filter and a dual-channel balun filter based on the quad-mode dielectric resonator (DR) for the first time. By sharing one common quad-mode DR, two balanced filters or two balun filters are integrated as one single-cavity configuration, featuring compact size and high integration. A cylindrical DR with two short ends is investigated to construct the quad-mode DR. By properly arranging input and output feeding probes, two modes of the DR are only excited by the feeding probes of one channel and the other two modes are excited by that of the other channel. Accordingly, signals cannot be transmitted between the two channels, resulting in high isolation. Moreover, the required out-of-phase characteristics of the balanced and balun filters can be obtained by the inherent electromagnetic field properties of the DR without adding additional circuits, featuring a simple structure. For demonstration, a dual-channel balanced filter and a dual-channel balun filter are designed and fabricated, showing excellent balanced or balun filter performance of each channel as well as high isolation between the two channels. As compared to the other reported DR balanced and balun filters, the proposed designs exhibit a significant size reduction, which are attractive in wireless systems.
关键词： Balanced filter,high Q factor,dielectric resonator (DR),balun filter,MIMO,size reduction,dual-channel
更新于2025-09-23 15:23:52
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Adaptive Fuzzy Switching Noise Reduction Filter for Iris Pattern Recognition
摘要： Noise reduction is a necessary procedure for the iris recognition systems. This paper proposes an adaptive fuzzy switching noise reduction (AFSNR) filter to reduce noise for iris pattern recognition. The proposed low complexity AFSNR filter removes noise pixels by fuzzy switching between an adaptive median filter and the filling method. The threshold values of AFSNR filter are calculated on the basis of the histogram statistics of eyelashes, pupils, eyelids, and light illumination. The experimental results on the CASIA V3.0 iris database, with genuine acceptance rate equals 99.72%, show the success of the proposed method.
关键词： fuzzy switching median,iris normalization,eyelash detection,fuzzy weighted median,noise reduction,Iris pattern recognition
更新于2025-09-23 15:23:52
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A Green and Facile Synthesis for rGO/Ag Nanocomposites Using One-step Chemical Co-reduction Route at Ambient Temperature and Combined First Principles Theoretical Analyze
摘要： Recently, graphene decorated with various inorganic nanoparticles, such as Pt, Au, Ag, TiO2 and Fe3O4, among which Ag nanocomposites are good candidates for electronics, optics, electrochemistry and catalysis. However, preparation techniques for Ag nanoparticles/carbon matrix hybrids require tedious multi-step processes often involving toxic reducing agents / high temperatures which is not viable for scalable production. Here, a facile, one step and eco-friendly chemical co-reduction route was utilized to synthesis of a new nanocomposites by Ag nanoparticle anchored on reduced graphene oxide (rGO) at ambient temperature and combined first principles theoretical analyze their interfacial adsorption behavior, is reported. In this way, graphene oxide (GO) and Ag+ simultaneously reduced by thiourea dioxide (TD) without using any additional reduced reactants. Results indicated that GO was successfully reduced to rGO and well-dispersed Ag nanoparticles with sizes of 6~7 nm, anchored on the surface of rGO sheets. Reduction mechanism was attributed to the synergistic effect of its hydrolysis products in aqueous media. The experiment and theoretical calculation results obtained demonstrate this method to be applicable to the synthesis of other metals on rGO sheets in order to improve wettability and interfacial bonding between rGO and metal and may possibly find various forthcoming medicinal, industrial and technological applications.
关键词： In-stiu co-reduction,Green reduce graphene/Ag nanocomposites,Interfacial behavior,First principles,Thiourea dioxide
更新于2025-09-23 15:23:52
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Artificial Photosynthesis for Carbon Dioxide Reduction and Conversion
摘要： In recent years, solar fuel or chemical production based on the photoreduction or fixation of CO2, the so-called “artificial photosynthesis” has received considerable attention. Thus, the development of an effective catalyst for the conversion of CO2 to useful organic molecules is desirable. Biocatalysts for CO2 reduction and conversion are useful catalyst for the artificial photosynthesis system. In this review, two types of artificial photosynthesis systems for CO2 reduction and conversion consisting of the visible-light sensitizer and biocatalyst are introduced. One is the artificial photosynthesis with visible-light sensitizer and biocatalyst for CO2 photoreduction to formic acid or methanol. The other one is the artificial photosynthesis with visible-light sensitizer, and novel electron carrier molecule and biocatalyst for the carbon-carbon bond formation from CO2 as a feedstock.
关键词： carbon-carbon bond formation,artificial photosynthesis,biocatalyst,CO2 reduction and conversion
更新于2025-09-23 15:23:52
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Device noise reduction for silicon nanowire field-effect-transistor based sensors by using a Schottky junction gate
摘要： The sensitivity of metal-oxide-semiconductor field-effect transistor (MOSFET) based nanoscale sensors is ultimately limited by noise induced by carrier trapping/detrapping processes at the gate oxide/semiconductor interfaces. We have designed a Schottky junction gated silicon nanowire field-effect transistor (SiNW-SJGFET) sensor, where the Schottky junction replaces the noisy oxide/semiconductor interface. Our sensor exhibits significantly reduced device noise, 2.1×10-9 V2μm2/Hz at 1 Hz, compared to reference devices with the oxide/semiconductor interface operated at both inversion and depletion modes. Further improvement can be anticipated by wrapping the nanowire by such a Schottky junction thereby eliminating all oxide/semiconductor interfaces. Hence, a combination of the low-noise SiNW-SJGFET device with a sensing surface of the Nernstian response limit holds promises for future high signal-to-noise ratio sensor applications.
关键词： Noise reduction,field-effect transistor,ion sensor,low frequency noise,schottky junction gate,silicon nanowire
更新于2025-09-23 15:23:52
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Theoretical and experimental insights into the effects of oxygen-containing species within CNTs towards triiodide reduction
摘要： Heteroatom-doped micro/nano-structured carbon materials feature unique superiorities for replacement of noble metal Pt counter electrode (CE) in dye-sensitized solar cells. Nevertheless, the effects of oxygen-containing species on/within carbon matrix on its electrocatalytic activity are seldomly considered and concerned, which will be hindered by a trade off between oxygen defects and conductivity. Herein, we present activated carbon nanotubes (P-CNTs) with abundant active edge sites and oxygen species for simultaneous achieving the activation of sidewalls and open ends. Also, the positive effects of oxygen species are decoupled by experimental data together with theoretical analysis. When capitalizing on the P-CNTs as the CE of DSSCs, the device delivers a high power conversion efficiency of 8.35% and an outstanding electrochemical stability, outperforming that of Pt reference (8.04%). The density functional theory calculation reveals that compared with the carboxylic groups, the hydroxyl groups and carbonyl groups on the surface of CNTs can greatly reduce the ionization energy of reaction, accelerate the electron transfer from external circuit to triiodide, thus being responsible for an enhanced electrocatalytic performance. This work demonstrates that a certain amount of oxygen atoms within carbon materials is also indispensable for the improvement in the reactivity of the triiodide.
关键词： Counter electrodes,Triiodide reduction,Defective carbon nanotubes,Ionization energy,Electrochemical stability,Oxygen species
更新于2025-09-23 15:23:52
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The superior photocatalytic activity of Nb doped TiO2/g-C3N4 direct Z-scheme system for efficient conversion of CO2 into valuable fuels
摘要： In this study, we firstly aimed to use Nb as dopant to dope into the TiO2 lattice in order to narrow band gap energy or enhance photocatalytic activity of the Nb-TiO2. Then, the prepared Nb-TiO2 was combined with g-C3N4 to establish Nb-TiO2/g-C3N4 direct Z-scheme system for superior reduction of CO2 into valuable fuels even under visible light. The obtained results indicated that the band gap energy of the Nb-TiO2 (2.91 eV) was lower than that of the TiO2 (3.2 eV). In the successfully established Nb-TiO2/g-C3N4 direct Z-scheme system, the photo-excited e- in the CB of the Nb-TiO2 combined with the photo-excited h+ in the VB of the g-C3N4 preserving the existence of e- in the CB of the g-C3N4 and h+ in the VB of Nb-TiO2, and thereby, the system produced numerous amount of available e-/h+ pairs for the reduction of CO2 into various valuable fuels. In addition, the produced e- of the Nb-TiO2/g-C3N4 existing in the CB of the g-C3N4, which the potential energy is approximately - 1.2 V, would be strong enough for the reduction of CO2 to generate not only CH4 and CO but also HCOOH. Among established Nb-TiO2/g-C3N4 materials, the 50Nb-TiO2/50g-C3N4 material was the best material for the CO2 reduction.
关键词： Nb dopant,CO2 reduction,Nb-TiO2,g-C3N4,direct Z-scheme
更新于2025-09-23 15:23:52
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Photoelectrochemical hydrogen production from water splitting using heterostructured nanowire arrays of Bi2O3/BiAl oxides as a photocathode
摘要： To date, most metal oxide-based photocathodes used in photoelectrochemical cells for water splitting contain copper cations in its composition, which can be reduced to metal Cu under cathodic bias leading to deactivation of the photoelectrode. Here, a Cu-free photocathode composed by a ternary heterostructure of Bi2O3/Al2Bi24O39/Al2Bi48O75 nanowires is reported with a narrow band gap energy (1.83 eV) and suitable conduction band edge potential (?0.98 VRHE) for water reduction to hydrogen. Photoelectrochemical measurements display that the highest photocurrent density of ?4.85 mA cm?2 at 0 VRHE under simulated sunlight is achieved by tuning the Bi:Al molar ratio of photocathode to 21:1. The photocurrent onset potential of the Bi2O3/BiAl oxides photoelectrode was estimated to be 0.57 VRHE at pH 7, which is comparable to that of silicon. Controlled potential photoelectrolysis at 0 VRHE showed a stable photocurrent of about ?2 mA cm?2 for 2 h of continuous operation. The H2 measured at this time was 696 μmol cm?2, which corresponds to a Faradaic efficiency of 93%. Finally, this work gives a new generation of Cu-free photocathodes and demonstrates a promising future of BiAl oxides in constructing photoelectrochemical devices for water splitting.
关键词： Oxides,Solar energy,PEC cells,Water reduction,Spray pyrolysis,Heterojunction
更新于2025-09-23 15:23:52