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A Production-Accessible Method: Spectrophotometric Iron Speciation in Wine Using Ferrozine and Ethylenediaminetetraacetic Acid
摘要： Wine oxidation is reported to be linked to the iron species present in the wine, but spectrophotometric speciation is plagued by unstable measurements due to alterations to the reduction potential of iron by complexing agents. Ferrozine raises the reduction potential of iron by complexing preferentially to iron(II), inducing the reduction of iron(III) during analysis; here, EDTA is added to chelate iron(III) and to stabilize the forms of iron. Bisulfite addition allows the use of ferrozine for red wine analysis by mitigating color interference. Measurements agree with values from a previous method for iron(II) and from FAAS for total iron. Spike recoveries were in the range of 103.5?110.1%. The method is linear for iron concentrations in the range of 0.10?6.00 mg L?1 and offers good precision (CV 0.4?10.1%) and low limits of detection (0.02 mg L?1) and quantification (0.06 mg L?1). The method demonstrated changes to iron speciation during the oxygenation of red wines.
关键词： reduction potential,oxidation,wine,spectrophotometry,ferrozine,iron speciation
更新于2025-09-23 15:23:52
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AIP Conference Proceedings [Author(s) THE 3RD INTERNATIONAL SEMINAR ON CHEMISTRY: Green Chemistry and its Role for Sustainability - Surabaya, Indonesia (18–19 July 2018)] - Green synthesis of silver nanoparticles using photo-induced reduction method
摘要： Silver Nanoparticles (AgNPs) has been successfully synthetized in this study using photoinduced reduction method with monochromatic light. In this method we use sodium citrate as capping agent without additional reducing agent. Silver nanoparticles characterized using Ultraviolet-Visible Spectroscopy (UV-Vis) and X-ray Diffraction (XRD). The synthetized AgNPs show that wavelength of light can affect the properties of AgNPs based on absorption spectra of UV-Vis. XRD measurement showed the characteristic peak of silver at 2θ of 38.060, 44.140, 64.470, and 77.400.
关键词： Photochemistry,Reduction,Sodium Citrate,AgNPs,Monochromatic light
更新于2025-09-23 15:23:52
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Drag reduction effect of ultraviolet laser-fabricated superhydrophobic surface
摘要： Superhydrophobic (SH) surface has been found effective for drag reduction in wall-bounded turbulence for decades, especially the metallic durable SH surfaces are believed very promising for improving the velocity and voyage of marine vehicles. We present stainless steel SH surfaces with U-groove patterns that fabricated by ultraviolet laser texturing and coating modifier treatment. The drag-reducing effects of the SH surfaces are tested by a self-built gravity sliding speed improving evaluation device. The results show that the different drag-reduction performance of the SH surfaces can be achieved by adjusting the line spacing of the crossing U-groove patterns. With the line spacing equalling to 80 μm, the ultraviolet laser textured stainless steel SH surface acquires the static contact angle of 161.5° and the dynamic sliding angle of only 2°, which leads to the maximum speed improving rate of 29.7%.
关键词： drag reduction,Superhydrophobic surface,stainless steel,laser texturing
更新于2025-09-23 15:23:52
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Effect of nitrogen gas pressure during heat treatment on the morphology of silicon nitride fibers synthesized by carbothermal nitridation
摘要： The effects of N2 gas pressure on the diameter and morphology of Si3N4 fibers obtained via carbothermal nitridation were investigated. Sol–gel-derived precursors containing a silica and carbon mixture were placed in an Al2O3 crucible and heat-treated under various N2 pressures from 0.1 to 0.5 MPa at 1500oC. The heat-treated samples were characterized by X-ray diffraction (XRD), a scanning electron microscope (SEM) coupled with an energy dispersion X-ray (EDX) spectrometer, and transmission electron microscopy (TEM). Various nitride fibers with α- and β-phase Si3N4 were formed. The fiber diameter decreased with increases in N2 pressure, and nanometer-scale fibers of around 200 nm in diameter were obtained at a N2 pressure of 0.5 MPa. It was found that silicon oxynitride Si2N2O or its Al-doped form, O′-SiAlON, was produced due to high N2 pressure and doping with Al originating from the Al2O3 crucible. This oxynitride was considered to act as a template for Si3N4 fiber growth by the direct phase transformation mechanism. It was shown that the diameter of the Si3N4 fibers decreased for two reasons: decreased partial pressure of SiO gas due to high N2 pressure and increased formation of the silicon oxynitride templates.
关键词： carbothermal reduction,nanofibers,alumina,Silicon nitride
更新于2025-09-23 15:23:52
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Segmented and non-segmented stacked denoising autoencoder for hyperspectral band reduction
摘要： Hyperspectral image (HSI) analysis often requires selecting the most informative bands instead of processing the whole data without losing the key information. Existing band reduction (BR) methods have the capability to reveal the nonlinear properties exhibited in the data but at the expense of losing its original representation. To cope with the said issue, an unsupervised non-linear segmented and non-segmented stacked denoising autoencoder (UDAE)-based BR method is proposed. Our aim is to find an optimal mapping and construct a lower-dimensional space that has a similar structure to the original data with least reconstruction error. The proposed method first confronts the original HS data into smaller regions in the spatial domain and then each region is processed by UDAE individually. This results in reduced complexity and improved efficiency of BR for classification. Our experiments on publicly available HS datasets with various types of classifiers demonstrate the effectiveness of UDAE method which equates favorably with other state-of-the-art dimensionality reduction and BR methods.
关键词： Autoencoder (AE),Hyperspectral imaging (HSI),Classification,Clustering,Band reduction (BR)
更新于2025-09-23 15:23:52
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Photoluminescence of partially reduced Eu2+/Eu3+ active centers in a NaF–Al2O3–P2O5 glassy matrix with tunable smooth spectra
摘要： In this work, a series of photoluminescent materials have been synthesized based on optically transparent and chemically stable glasses of the nominal composition Na3Al2(PO4)2F3 (NaF–Al2O3–P2O5 system) doped with 1 wt % of europium. It has been shown that the synthesis conditions (mainly the temperature and duration of the melting stage under reducing conditions) strongly affected the photoluminescence spectra of the material. This effect has been ascribed to varying proportions between Eu3+ and Eu2+ ions concentrations, imposed by the synthesis conditions, which was confirmed by XPS, absorption and decay times measurements. As both Eu3+ and Eu2+ centers exhibit photoluminescence in different ranges of the visible spectra (Eu3+ – red, and Eu2+ – mainly blue) the possibility, shown by us, to control relative proportions of the oxidation states of europium and consequently to control the photoluminescence spectra, may be advantageous from the viewpoint of potential applications of such materials as novel phosphors for white LEDs with the emission spectra resembling natural light.
关键词： glassy matrix,europium facile reduction,scalable synthesis,tunable luminescence
更新于2025-09-23 15:23:52
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Enhanced visible light photocatalytic activity of BiFeO3-ZnO p-n heterojunction for CO2 reduction
摘要： The visible light photocatalytic ability of bismuth ferrite-zinc oxide composites with different molar ratios was investigated for conversion of CO2 in the gas phase. The catalysts were successfully synthesized by hydrothermal method, and characterized by XRD, EDS, FESEM, UV–vis, and PL analyses. Also, the gaseous products were identified by FTIR technique. The FESEM illustrated the well crystalline particles of ZnO and BiFeO3. The UV–vis and PL analyses revealed that by increasing BiFeO3 content, the composites showed higher optical response in visible region and higher efficiency of charge separation, respectively. Compared with the pure ZnO and BiFeO3, which had poor performances under visible light irradiation, the as-synthesized photocatalysts showed the enhanced visible light photocatalytic activity for CO2 reduction. The highest photocatalytic conversion of CO2, 21%, was achieved by the as-synthesized photocatalyst with molar ratio of 1:1 under visible light. The enhanced visible light photocatalytic activity of BiFeO3-ZnO was assigned to the synergistic effect of p-n heterojunction and visible light sensitive property of perovskite structure of BiFeO3.
关键词： Perovskite,P-n heterojunction,Gaseous phase,Photocatalyst,CO2 reduction
更新于2025-09-23 15:23:52
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Ratio-Based Multitemporal SAR Images Denoising: RABASAR
摘要： In this paper, we propose a fast and efficient multitemporal despeckling method. The key idea of the proposed approach is the use of the ratio image, provided by the ratio between an image and the temporal mean of the stack. This ratio image is easier to denoise than a single image thanks to its improved stationarity. Besides, temporally stable thin structures are well preserved thanks to the multitemporal mean. The proposed approach can be divided into three steps: 1) estimation of a 'superimage' by temporal averaging and possibly spatial denoising; 2) denoising of the ratio between the noisy image of interest and the 'superimage'; and 3) computation of the denoised image by remultiplying the denoised ratio by the 'superimage.' Because of the improved spatial stationarity of the ratio images, denoising these ratio images with a speckle-reduction method is more effective than denoising images from the original multitemporal stack. The amount of data that is jointly processed is also reduced compared to other methods through the use of the 'superimage' that sums up the temporal stack. The comparison with several state-of-the-art reference methods shows better results numerically (peak signal-noise-ratio and structure similarity index) as well as visually on simulated and synthetic aperture radar (SAR) time series. The proposed ratio-based denoising framework successfully extends single-image SAR denoising methods to time series by exploiting the persistence of many geometrical structures.
关键词： ratio image,speckle reduction,Multitemporal synthetic aperture radar (SAR) series,superimage
更新于2025-09-23 15:22:29
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Fe-N3/C active catalytic sites for the oxygen reduction reaction prepared with molecular level geometry control via covalent immobilization of iron-terpyridine motif onto carbon
摘要： A model for a non-precious metal catalyst for the oxygen reduction reaction (ORR) in aqueous media has been prepared by functionalizing a commercial Vulcan XC-72 carbon support with a terpyridine-based nitrogenous ligand. The terpyridine ligand geometry allows the formation of active catalytic sites by selectively embedding an N3/C structural motif into the carbon support confirmed by thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) measurements. Room temperature metal-ligand coordination results in desired Fe-N3/C moieties on the surface. This model system was used to demonstrate catalytic activity of the surfaces containing mainly Fe-N3 sites for ORR in acidic and basic media. Importantly, we demonstrate that the system could be prepared at mild reaction conditions, does not require high-temperature treatments, and shows catalytic activity for ORR. Interestingly, when the system was pyrolyzed in an N2 atmosphere at 700?C, the resulting activity declined. The non-heat-treated Fe-N3/C surface demonstrates comparable activity in acidic electrolyte medium when compared to most literature catalysts that are typically heat treated to produce four nitrogen’s coordinated to one iron center (Fe-N2+2/C). Interestingly, despite the fact that many systems reported so far in the literature exhibit enhanced activity after heat treatment, our system showed an increase in activity when the material was not pyrolyzed.
关键词： catalyst,oxygen reduction reaction,nitrogen,iron,non-precious metal
更新于2025-09-23 15:22:29
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[IEEE 2018 OCEANS - MTS/IEEE Kobe Techno-Ocean (OTO) - Kobe, Japan (2018.5.28-2018.5.31)] 2018 OCEANS - MTS/IEEE Kobe Techno-Oceans (OTO) - A Speed Measurement Method Using AUV Radiated Noise Spectrum
摘要： The noise produced by a motor can be easily controlled because its speed is from 0 to 1000 rpm. The noise of a motor is mainly caused by the interaction between the stator and rotor, and the noise can be reduced by controlling the speed of the motor. In this paper, we use a motor to produce noise and control it by a computer. The motor is driven by a computer and the noise is measured by a microphone. The computer controls the speed of the motor and the noise is reduced.
关键词： noise reduction,motor noise,speed control,computer control
更新于2025-09-23 15:22:29