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Based on Spectrum Modeling and Optimization
摘要： Bistatic synthetic aperture radar (SAR) is able to break through the limitation of monostatic SAR on forward-looking area imaging with appropriate geometry configurations. Thanks to such an ability, bistatic forward-looking SAR (BFSAR) has extensive potential practical applications. For the focusing problem of conventional side-looking SAR, ω–k algorithm is accepted as the ideal solution. In this paper, the ω–k algorithm will be discussed in BFSAR geometry. As for the bistatic configuration, spatial domain linearization procedure should be carried out to extract a range variable from the point target reference spectrum (PTRS) in the existing ω–k algorithms. With respect to the BFSAR geometry, nevertheless, the linearization procedure reduces the accuracy of PTRS seriously. To cope with such a problem, a novel ω–k algorithm for BFSAR is proposed. In the proposed method, the range variable is modeled as a parameterized polynomial, and the corresponding PTRS with respect to two-dimensional frequencies is established. Then, the parameters are estimated by differential evolution to minimize the PTRS errors for each range coordinate and frequency point. Based on the estimated PTRS, the BFSAR data can be focused well by the proposed ω–k algorithm. Simulation results verify the effectiveness of the proposed method.
关键词： Bistatic forward-looking synthetic aperture radar (BFSAR),differential evolution (DE),ω–k,point target reference spectrum (PTRS)
更新于2025-09-23 15:23:52
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2D MOFs enriched g-C3N4 nanosheets for highly efficient charge separation and photocatalytic hydrogen evolution from water
摘要： Here we report a D-2D heterostructure of g-C3N4/UMOFNs photocatalysts via mechanical grinding two kinds of two-dimensional nanosheets of g-C3N4 nanosheets and UMOFNs, which exhibits enhanced H2 evolution from water with simulated solar irradiation. g-C3N4 nanosheets are in close contact with UMOFNs, and there is a certain interaction between them, showing the effect of superimposition on the two-dimensional layer. The 2D-2D heterostructure offers a maximal photocatalytic hydrogen production activity of 1909.02 mmol g-1 h-1 with 3 wt% of UMOFNs, which is 3-fold higher than that of g-C3N4 nanosheets (628.76 mmol g-1 h-1) and 15-fold higher than that of bulk g-C3N4 (124.30 mmol g-1 h-1). The significant increasement of photocatalysis is due to 2D-2D heterostructure possessing a short charge transfer distance and large contact area between g-C3N4 and UMOFNs. The highly dispersed Ni-O, Co-O and p-p bonds in UMOFNs of 2D-2D structure also promote charge transfer and enhance the photocatalytic activity.
关键词： H2 evolution,Photocatalyst,g-C3N4,2D-2D heterostructure,UMOFNs
更新于2025-09-23 15:23:52
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Excellent thermal-stability and low dielectric loss of BaTiO3-Bi(Sr2/3Nb1/3)O3 solid solution ceramics in a broad temperature range applied in X8R
摘要： (1?x)BaTiO3-xBi(Sr2/3Nb1/3)O3 [(1?x)BT-xBSN, 0.02 ≤ x ≤ 0.1] ceramics were synthesized by a traditional solid state reaction technique. The transition from tetragonal phase to pseudo cubic phase at 0.02 ≤ x ≤ 0.04 was observed in Raman spectra and X-ray di?raction patterns. As the BSN contents increased, the grain size increased. With adding Bi(Sr2/3Nb1/3)O3, the thermal stability of permittivity and dielectric loss of ceramics got a good optimization. Especially, 0.9BT-0.1BSN ceramics have small Δε/ε25°C values (≤ ± 15%) in a wide temperature range of ?75 °C to 153 °C, high relative permittivity (～1505 to 1700) and low dielectric loss (tan δ ≤ 0.02) from ?88 °C to 200 °C, showing that BT-BSN ceramics are suitable for using in MLCCs of X8R. Impedance spectroscopy was analyzed the conduction and relaxation processes. The results showed that the relaxation and the conduction process in the high temperature region are thermally activated, and the oxygen vacancies are charge carriers.
关键词： Thermal stability,Dielectric properties,Impedance,Phase evolution
更新于2025-09-23 15:23:52
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Synthesis of a MoS <i> <sub/>x</sub></i> -O-PtO <i> <sub/>x</sub></i> Electrocatalyst with High Hydrogen Evolution Activity Using a Sacrificial Counter-Electrode
摘要： Water splitting is considered to be a very promising alternative to greenly produce hydrogen, and the key to optimizing this process is the development of suitable electrocatalysts. Here, a sacrificial-counter-electrode method to synthesize a MoSx/carbon nanotubes/Pt catalyst (0.55 wt% Pt loading) is developed, which exhibits a low overpotential of 25 mV at a current density of 10 mA cm?2, a low Tafel slope of 27 mV dec?1, and excellent stability under acidic conditions. The theory calculations and experimental results confirm the high hydrogen evolution activity that is likely due to the fact that the S atoms in MoSx can be substituted with O atoms during a potential cycling process when using Pt as a counter-electrode, where the O atoms act as bridges between the catalytic PtOx particles and the MoSx support to generate a MoSx–O–PtOx structure, allowing the Pt atoms to donate more electrons thus facilitating the hydrogen evolution reaction process.
关键词： sacrificial-counter-electrodes,O substitution,MoSx,hydrogen evolution reaction,PtOx
更新于2025-09-23 15:23:52
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Conjugated donor-acceptor polymer photocatalysts with electron-output “tentacles” for efficient hydrogen evolution
摘要： The tunable structures and versatile properties for conjugated polymers (CPs) make them viable as a molecular platform for photocatalytic water splitting. Normally, structure design of polymer photocatalyst is focus on tuning its optical band structure or charge-separation ability, the importance of electron-output ability in photocatalytic process is always ignored. This study demonstrates a molecular engineering strategy by introducing an electron-output “tentacle” site, i.e. dibenzothiophene-S,S-dioxide (FSO) unit, into the polymer backbone to construct a series of donor-acceptor type conjugated polymer photocatalysts for efficient hydrogen evolution, which not only results in optimized light absorption ability and excellent exciton-separation, but also leads to the efficient electron-output ability. Detailed DFT calculations further theoretically confirm the vital role of FSO unit as an electron-output “tentacle” site.
关键词： Conjugated polymer,Electron-output “tentacles”,Artificial photosynthesis,Hydrogen evolution,Photocatalysis
更新于2025-09-23 15:23:52
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Perovskite photocatalyst CsPbBr3-xIx with a bandgap funnel structure for H2 evolution under visible light
摘要： A simple and efficient light-assisted method is employed to prepare powder samples of all-inorganic mixed-perovskite CsPbBr3-xIx from CsPbBr3 by ion exchange in aqueous HBr/KI solution such that the concentration of I in a sample particle decreases on going from the surface to the interior. CsPbBr3-xIx/Pt, namely, CsPbBr3-xIx samples loaded with Pt nanoparticles, shows a high performance for the hydrogen evolution under visible-light irradiation in aqueous HBr solution saturated with CsPbBr3. The H2 evolution rate of the CsPbBr3-xIx/Pt powders (200 mg) is determined to be 224 μmol h-1, under 120 mW cm-2 visible-light (λ ≥ 420 nm) illumination. The CsPbBr3-xIx samples have a high stability, with no apparent decrease in the catalytic activity after 50 h of repeated H2 evolution experiments. The apparent quantum efficiency of CsPbBr3-xIx/Pt is determined to be 2.15% under the irradiation of 450 nm light.
关键词： photocatalysis,hydrogen evolution,bandgap funnel,all-inorganic perovskite,halide gradient
更新于2025-09-23 15:23:52
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MgO/g-C3N4 nanocomposites as efficient water splitting photocatalysts under visible light irradiation
摘要： A series of MgO/g-C3N4 nanocomposites was prepared by calcination of the mixture of magnesium nitrate hexahydrate and g-C3N4, and applied as photocatalysts for hydrogen evolution from water splitting. The results demonstrate that the MgO/g-C3N4 nanocomposites can effectively harvest sunlight to produce hydrogen from water with higher photocatalytic efficiency than the bare g-C3N4. A high hydrogen evolution rate (HER) of 30.1 μmol h-1 was achieved under visible light for the MgO/g-C3N4 composite loaded with 1 wt% MgO, which is much higher than that of the bare g-C3N4 (5.76 μmol h-1). The enhanced photocatalytic activity of the MgO/g-C3N4 composite could be attributed to the formation of heterojunction between g-C3N4 and MgO that promotes the photo-induced charge carriers' transmission and separation.
关键词： photocatalysis,MgO/g-C3N4 nanocomposite,heterojunction,hydrogen evolution
更新于2025-09-23 15:23:52
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Carbon Nanotube-Supported Cu <sub/>3</sub> P as High-Efficiency and Low-Cost Cocatalysts for Exceptional Semiconductor-Free Photocatalytic H <sub/>2</sub> Evolution
摘要： Developing an inexpensive and high-efficiency hydrogen-production cocatalyst to replace the noble metal Pt remains a big challenge in the fields of sustainable photocatalytic hydrogen evolution. Herein, we report the exploration of a high-efficient binary noble metal free Cu3P-CNT H2-evolution cocatalyst by direct high-temperature phosphatizing of Cu(OH)2-CNT. Impressively, combining the advantages of noble metal free Cu3P and carbon nanotube (CNT), the binary Cu3P-CNT cocatalysts show high-efficient photocatalytic H2 evolution in Eosin Y(EY)-contained semiconductor-free photocatalytic systems. The maximum visible-light H2-generation rate for promising EY-Cu3P-CNT systems was 17.22 mmolg-1h-1. The highest apparent quantum efficiency (AQE) could reach 10.23% at 500 nm. More importantly, we found that the separation of photogenerated electrons and holes in the Eosin Y, the efficiency of electron transfer from EY to the active edge sites of Cu3P, and the electrocatalytic H2-evolution activity of Cu3P, could be simultaneously boosted via readily adding the conductive CNT, thus achieving the significantly improved photocatalytic H2 evolution. This work provides a simple and facile strategy to design highly efficient semiconductor-free photocatalytic proton-reduction systems using high-activity transition metal phosphides (TMPs) and inexpensive carbon nanomaterials.
关键词： Photocatalytic Hydrogen Evolution,noble metal-free Cu3P Co-catalysts,Solar Fuel,Carbon nanotube (CNT),Dye sensitization
更新于2025-09-23 15:23:52
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Highly efficient H2 production over NiCo2O4 decorated g-C3N4 by photocatalytic water reduction
摘要： Herein, ternary nickel cobalt oxide (NiCo2O4) was firstly employed to increase the photocatalytic water reduction ability of g-C3N4. 17.5wt%-NiCo2O4/g-C3N4 shows excellent water splitting performance with a H2 production rate of 5480 μmol·h-1·g-1, which is extremely better than that of Co3O4, NiO, Pt modified g-C3N4. The quantum efficiency of 17.5wt%-NiCo2O4/g-C3N4 can reach 4.5% under 400 (±7.5) nm light irradiation. The greatly increased activity of 17.5wt%-NiCo2O4/g-C3N4 can be attributed to the richer active sites and the superior electrical performance provided by co-existing nickel and cobalt ions with multivalent state. Moreover, the activity of composite almost shows no significant weaken even after 20 h irradiation. A Z-scheme route was put forwarded for H2 production over NiCo2O4/g-C3N4 instead of the traditional p-n junction based on our study.
关键词： NiCo2O4,bimetallic complex,photocatalysis,hydrogen evolution
更新于2025-09-23 15:23:52
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<i>Spitzer Planck Herschel</i> Infrared Cluster (SPHerIC) survey: Candidate galaxy clusters at 1.3 < <i>z</i> < 3 selected by high star-formation rate
摘要： There is a lack of large samples of spectroscopically confirmed clusters and protoclusters at high redshifts, z > 1.5. Discovering and characterizing distant (proto-)clusters is important for yielding insights into the formation of large-scale structure and on the physical processes responsible for regulating star-formation in galaxies in dense environments. The Spitzer Planck Herschel Infrared Cluster (SPHerIC) survey was initiated to identify these characteristically faint and dust-reddened sources during the epoch of their early assembly. We present Spitzer/IRAC observations of 82 galaxy (proto-)cluster candidates at 1.3 < zp < 3.0 that were vetted in a two step process: (1) using Planck to select by color those sources with the highest star-formation rates, and (2) using Herschel at higher resolution to separate out the individual red sources. The addition of the Spitzer data enables efficient detection of the central and massive brightest red cluster galaxies (BRCGs). We find that BRCGs are associated with highly significant, extended and crowded regions of IRAC sources which are more overdense than the field. This result corroborates our hypothesis that BRCGs within the Planck–Herschel sources trace some of the densest and actively star-forming proto-clusters in the early Universe. On the basis of a richness-mass proxy relation, we obtain an estimate of their mean masses which suggests our sample consists of some of the most massive clusters at z ≈ 2 and are the likely progenitors of the most massive clusters observed today.
关键词： galaxies: star formation,submillimeter: galaxies,infrared: galaxies,galaxies: evolution,galaxies: clusters: general,galaxies: high-redshift
更新于2025-09-23 15:23:52