Host sensitized near-infrared emission in Nd3+-Yb3+ Co-doped Na2GdMg2V3O12 phosphor

Yb³⁺/Nd³⁺ singly and co-doped Na₂GdMg₂V₃O₁₂ phosphors with near-infrared (NIR) emission were synthesized via sol-gel method. The phase purity and structure of samples were characterized by X-ray diffraction (XRD), the photoluminescence emission (PL) and excitation (PLE) spectra along with decay curves were also measured. Near infrared (NIR) emissions (850–1150 nm) from acceptors Yb³⁺ or Nd³⁺ matching well with the response curve of the silicon solar cell were obtained, in which VO₄³⁻ groups acted as sensitizers by capturing near ultraviolet photons which are not absorbed efficiently by silicon solar cell and transferred them to Yb³⁺/Nd³⁺ by energy transfer processes. The NIR emission intensities of the Nd³⁺-Yb³⁺co-doped samples Na₂GdMg₂V₃O₁₂ were enhanced greatly in comparison with that of Nd³⁺/Yb³⁺ singly doped samples, and the possible energy transfer processes were also discussed in detail. Results indicate that the obtained samples are potential solar spectral down-conversion (DC) convertors to enhance the conversion efficiency of the silicon solar cells.     

A continuous valence band through NO orbital hybridization in NTiO2 and its induced full visible-light absorption for photocatalytic hydrogen production

Photocatalytic hydrogen production represents an effective approach for solar energy conversion, which can greatly ease the current energy crisis. Herein, we report a successful NO orbital hybridization in N-doped TiO₂ nanotube, the absorption wavelength is greatly red-shifted to visible light (from 400 to 800 nm) with large absorbance. The doping N element can partially replace the oxygen sites in TiO₂ lattice to form NTiN bonds. The hybridization effect of N 2p and O 2p makes a continuous valence band and the position up-shift from 1.99 to 1.67 eV, the band gap is subsequently narrowed from 3.21 to 2.77 eV for 1.85-NTiO₂ nanotube, which has been confirmed by ultraviolet–visible diffuse reflectance spectra and X-ray photoelectron spectroscopy valence band spectra. Benefiting from the enhanced visible light absorption ability and ultrathin shell feature, 1.85-NTiO₂ nanotube exhibits exciting photocatalytic hydrogen evolution performance with a rate of 10870 μmol h⁻¹ g⁻¹ under the selected visible light irradiation (λ > 400 nm). This work demonstrates an alternative strategy for tuning visible light absorption ability by doping for wide-band-gap semiconductors in photocatalysts design, and the philosophy can also be extended to other photocatalytic systems.     

基于URLLC技术在智慧电网控制的应用

针对智慧电网发展的现状,分析了智慧电网在建设中面临的困难,并提出URLLC技术的超可靠和低延迟特性可减少智慧电网时延,增加其可靠性,并为特高压电网的建设提供支持的观点.文中通过对Polar编码的信道极化进行分析,对比其他编码方法,总结出更适合智慧电网的Polar编码的译码方法,即分布式CRC-Polar码.该方案不仅可减少电网下行通道时延,还能增加URLLC技术的可靠性,有一定的参考价值.     

In-situ construction of plasma-pretreated CNT networks endow the LPDS dual-layer coating with advanced thermal management and anti-static properties

Carbon nanotubes (CNTs) for temperature regulation have been proven to be promising for passive radiative heat dissipation. However, it remains a considerable challenge to assemble a CNTs layer in situ while simultaneously achieving horizontal electrical conductivity, vertical electrical insulation, and radiative heat dissipation. Herein, plasma pretreatment was employed to functionalize CNTs in an aqueous solution, thus improving their dispersion capability. Subsequently, a liquid-plasma-assisted particle deposition and sintering (LPDS) technology was proposed to prepare a dual-layer coating with an Al₂O₃-P₂O₅-SiO₂-In₂O₃ glass system embedded with crystalline indium tin oxide (ITO) as the porous bottom layer and ITO-CNTs as the top layer on the aluminum alloy surface. The results show that plasma pretreatment significantly increases the deposition amount of ITO nanoparticles and functionalized CNTs on the coating surface, resulting in the transition from a single-layer composite coating to a dual-layer coating. The surface micro-/nano hierarchical structure favors strong absorptance/emittance, exhibiting a high infrared emittance of 0.94 (3-20 μm) and high solar absorptance of 0.92 (0.2-2.5 μm). Meanwhile, the surface balance temperature of the dual-layer coating is about 392 K, which is 146 K lower than that of aluminum alloy. Furthermore, the top conductive ITO-CNTs layer contributes to the low surface resistivity of 3.46×10² Ω, while the glass phase of the bottom layer ensures vertical electrical insulation with a volume resistance of 4.20×10⁷ Ω. The process provides a new path for preparing thermal control coatings with anti-static function.     

Fabrication method and mechanical properties of biomimetic Cf/ZrB2-SiC ceramic composites with bouligand structures

Herein, biomimetic C_f/ZrB₂-SiC ceramic composites with bouligand structures are fabricated by combining precursor impregnation, coating, helical assembly and hot-pressing sintering. First, C_f/ZrB₂-SiC ceramic films are achieved through a precursor impregnation method using polycarbosilane (PCS). Second, the PCS-C_f/ZrB₂-SiC ceramic films are coated with ZrB₂ and SiC ceramic layers. Finally, hot-pressing sintering is employed to densify helical assembly C_f/ceramic films with a fixed angle of 30°. The microstructures and carbon fiber content on the mechanical properties of biomimetic C_f/ZrB₂-SiC ceramic composites are analyzed in detail. The results show that the coated ceramic layer on PCS-C_f/ZrB₂-SiC films can heal the cracks formed by pyrolysis of PCS, and the mechanical properties are obviously improved. Meanwhile, the mechanical properties could be tuned by the contents of the carbon fiber. The toughening mechanisms of C_f/ZrB₂-SiC ceramic composites with bouligand structures are mainly zigzag cracks, crack deflection, multiple cracks, carbon fiber pulling out and bridging.     

松辽盆地三肇凹陷北部姚二+三段滩坝砂体沉积模式

利用岩心、测井和地震等资料,对松辽盆地三肇凹陷北部姚二+三段滩坝砂体的地层格架、沉积特征和沉积模式进行了研究。结果表明:采用顶部岩性突变面和底部稳定薄层滩砂下的泥岩为层序界面,将滩坝砂体垂向上划分为两个小层,其中上部1号小层主要发育坝砂,下部2号小层主要发育滩砂;坝砂具有反粒序、砂泥稳定互层、单砂层厚、水动力强等特征,而滩砂具有尖峰状、砂泥频繁互层、单砂层薄、水动力弱等特征;物源供给强度、水动力条件的强弱和古地貌的坡度是影响滩坝砂体形成和分布的主要控制因素,最终建立了三肇凹陷北部姚二+三段湖侵早期的滩坝沉积模式,指出坝砂主体发育区为有利勘探目标。     

Alternative U.S. biofuel mandates and global GHG emissions: The role of land use change,crop management and yield growth

We investigate the impacts of the U.S. renewable fuel standard (RFS2) and several alternative biofuel policy designs on global GHG emissions from land use change and agriculture over the 2010–2030 horizon. Analysis of the scenarios relies on GLOBIOM, a global, multi-sectoral economic model based on a detailed representation of land use. Our results reveal that RFS2 would substantially increase the portion of agricultural land needed for biofuel feedstock production. U.S. exports of most agricultural products would decrease as long as the biofuel target would increase leading to higher land conversion and nitrogen use globally. In fact, higher levels of the mandate mean lower net emissions within the U.S. but when the emissions from the rest of the world are considered, the US biofuel policy results in almost no change on GHG emissions for the RFS2 level and higher global GHG emissions for higher levels of the mandate or higher share of conventional corn-ethanol in the mandate. Finally, we show that if the projected crop productivity would be lower globally, the imbalance between domestic U.S. GHG savings and additional GHG emissions in the rest of the world would increase, thus deteriorating the net global impact of U.S. biofuel policies.     

Alkylphosphonic acid- and small amine-templated synthesis of hierarchical silicoaluminophosphate molecular sieves with high isomerization selectivity to di-branched paraffins

This article proposes a one-step strategy to hydrothermally synthesize SAPO-11 with hierarchical micro- and meso-porous structure. The structure and acidity properties and the isomerization performance of the resulting hierarchical SAPO-11 were extensively characterized and assessed, respectively, and compared with those of a microporous SAPO-11. The results showed that the SAPO-11 with mutually interpenetrating micropores and mesopores had been obtained by introducing tetradecylphosphoric acid into the synthesis system of microporous SAPO-11. Compared with microporous SAPO-11, the hierarchical SAPO-11 had much higher external surface and mesoporous volume, and more active sites with suitable Brönsted acid strength. These advantages endowed the hierarchical SAPO-11-based catalyst with superior isomerization activity, enhanced selectivity to di-branched products, and decreased cracking selectivity. The strategy proposed opens a new route to synthesizing a variety of hierarchical mesoporous SAPO molecular sieves for size-selective catalytic conversions of relatively large hydrocarbon molecules.     

Evaluation of (Ba0.5Sr0.5)0.85Gd0.15Co0.8Fe0.2O3−δ cathode for intermediate temperature solid oxide fuel cell

A perovskite-type (Ba_0.5Sr_0.5)_0.85Gd_0.15Co_0.8Fe_0.2O_3?δ (BSGCF) oxide has been investigated as the cathode of intermediate temperature solid oxide fuel cells (IT-SOFCs). Coulometric titration, thermogravimetry analysis, thermal expansion and four-probe DC resistance measurements indicate that the introduction of Gd³⁺ ions into the A-site of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3?δ (BSCF) leads to the increase in both oxygen nonstoichiometry at room temperature and electrical conductivity. For example, the conductivity of BSGCF is 148 S cm^?1 at 507 °C, over 4 times as large as that of BSCF. Furthermore, the electrochemical activity toward the oxygen reduction reaction is also enhanced by the Gd doping. Impedance spectra conducted on symmetrical half cells show that the interfacial polarization resistance of the BSGCF cathode is 0.171 Ω cm² at 600 °C, smaller than 0.297 Ω cm² of the BSCF cathode. A Ni/Sm_0.2Ce_0.8O_1.9 anode-supported single cell based on the BSGCF cathode exhibits a peak power density of 551 mW cm^?2 at 600 °C.     

Genetic algorithms for optimisation of chemical kinetics reaction mechanisms

The aim of this paper is to review the techniques that exist in the literature for finding the optimal values of the reaction rates coefficients for a given reaction mechanism. Although traditional gradient based methods are reviewed as well, the paper focuses on recently developed self-adaptive evolutionary algorithms that outperform classical methods. Unlike the traditional, gradient-based methods one of the most important characteristics of computational intelligence techniques, such as genetic algorithms (GA), is the effectiveness and robustness in coping with uncertainty, insufficient information and noise. In this approach minimum human effort and little insight into the details of the chemical mechanism is required to generate the optimal values for the reaction rate coefficients. The use of the GA inversion procedure is illustrated on chemical systems of various complexities which govern the combustion of hydrogen, methane and kerosene.