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Parametric study of hexagonal castellated beams in post-tensioned self-centering steel connections

Hassan ABEDI SARVESTANI

《结构与土木工程前沿（英文）》 2019年第13卷第5期页码 1020-1035 doi: 10.1007/s11709-019-0534-6

摘要： The effects of important parameters (beam reinforcing plates, initial post-tensioning, and material properties of steel angles) on the behavior of hexagonal castellated beams in post-tensioned self-centering (PTSC) connections undergone cyclic loading up to 4% lateral drift have been investigated by finite element (FE) analysis using ABAQUS. The PTSC connection is comprised of bolted top and bottom angles as energy dissipaters and steel strands to provide self-centering capacity. The FE analysis has also been validated against the experimental test. The new formulations derived from analytical method has been proposed to predict bending moment of PTSC connections. The web-post buckling in hexagonal castellated beams has been identified as the dominant failure mode when excessive initial post-tensioning force is applied to reach greater bending moment resistance, so it is required to limit the highest initial post-tensioning force to prevent this failure. Furthermore, properties of steel material has been simulated using bilinear elastoplastic modeling with 1.5% strain-hardening which has perfectly matched with the real material of steel angles. It is recommended to avoid using steel angles with high yielding strength since they lead to the yielding of bolt shank. The necessity of reinforcing plates to prevent beam flange from local buckling has been reaffirmed.

关键词： finite element analysis hexagonal castellated beam parametric study post-tensioned self-centering steel connection steel moment-resisting frame

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Mechanical responses of pristine and defective hexagonal boron-nitride nanosheets: A molecular dynamics

Mohammad SALAVATI, Arvin MOJAHEDIN, Ali Hossein Nezhad SHIRAZI

《结构与土木工程前沿（英文）》 2020年第14卷第3期页码 623-631 doi: 10.1007/s11709-020-0616-5

摘要： In this work we conducted classical molecular dynamics (MD) simulation to investigate the mechanical characteristics and failure mechanism of hexagonal boron-nitride (h-BN) nanosheets. Pristine and defective structure of h-BN nanosheets were considered under the uniaxial tensile loadings at various temperatures. The defective structure contains three types of the most common initial defects in engineering materials that are known as cracks, notches (with various length/size), and point vacancy defects (with a wide range of concentration). MD simulation results demonstrate a high load-bearing capacity of extremely defective (amorphized) h-BN nanosheets. Our results also reveal that the tensile strength decline by increasing the defect content and temperature as well. Our MD results provide a comprehensive and useful vision concerning the mechanical properties of h-BN nanosheets with/without defects, which is very critical for the designing of nanodevices exploiting the exceptional physics of h-BN.

关键词： hexagonal boron-nitride mechanical properties crack notch point defects molecular dynamics

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Rh₂O₃/hexagonal CePO₄ nanocatalysts for N₂O decomposition

Huan Liu, Zhen Ma

《化学科学与工程前沿（英文）》 2017年第11卷第4期页码 586-593 doi: 10.1007/s11705-017-1659-6

摘要： Hexagonal CePO nanorods were prepared by a precipitation method and hexagonal CePO nanowires were prepared by hydrothermal synthesis at 150 °C. Rh(NO ) was then used as a precursor for the impregnation of Rh O onto these CePO materials. The Rh O supported on the CePO nanowires was much more active for the catalytic decomposition of N O than the Rh O supported on CePO nanorods. The stability of both catalysts as a function of time on stream was studied and the influence of the co-feed (CO , O , H O or O /H O) on the N O decomposition was also investigated. The samples were characterized by N adsorption-desorption, inductively coupled plasma optical emission spectroscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron microscopy, hydrogen temperature-programmed reduction, oxygen temperature-programmed desorption, and CO temperature-programmed desorption in order to correlate the physicochemical and catalytic properties.

关键词： Rh₂O₃ CePO₄ N₂O decomposition

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Preparation and characterization of ZnO/ZnS hybrid photocatalysts via microwave-hydrothermal method

ZHAO Jinglian, WANG Xinping, ZHAO Liang

《环境科学与工程前沿（英文）》 2008年第2卷第4期页码 415-420 doi: 10.1007/s11783-008-0056-2

摘要： The photocatalytic performance of ZnO/ZnS hybrid nanocomposite was largely higher than that of the mere ZnO or ZnS nanoparticles, but the complicated procedure and misdistribution of final products limited its large-scale productions. The exploration of a novel synthesis route of ZnO/ZnS hybrid photocatalysts with high catalytic performance is becoming a crucial step for the large-scale application of ZnO/ZnS hybrid photocatalytic technique. Preparation and characterization of nanosized ZnO/ZnS hybrid photocatalysts were studied in this paper. The photocatalysts were obtained via microwave-hydrothermal crystallization with the help of sodium citrate. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), particle size distribution (PSD), and Fourier transformed infrared spectroscopy (FT-IR). The results indicated that so-synthesized ZnO/ZnS samples consisted of the high pure cubic (sphalerite) ZnS and hexagonal ZnO nanocrystallines with a narrow particle size distribution. The possible formation mechanisms of ZnO/ZnS nanocrystallines were mainly attributed to the superficially protective effect of citrate. The photocatalytic experiments demonstrated that the ZnO/ZnS photocatalysts exhibited a higher catalytic activity for the degradation of acid fuchsine than other monocomponents.

关键词： large-scale hexagonal misdistribution characterization nanocomposite

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Preparation and photocatalytic kinetics of nano-ZnO powders by precipitation stripping process

ZHANG Dongxiang, XUE Min, XU Hang, XU Wenguo, TARASOV V

《化学科学与工程前沿（英文）》 2008年第2卷第3期页码 319-324 doi: 10.1007/s11705-008-0051-y

摘要： Ultra-fine zinc oxalate powders were prepared through a precipitation stripping method with bis(2-ethylhexyl) phosphate (HDEHP) diluted by tetrachloride carbon as the extractant, and oxalic acid ethanol aqueous solution as the re-extractant and precipitator. Zinc oxide powders were obtained by decomposing zinc oxalate powders at 450°C. The prepared zinc oxide powders were characterized by transmission electron microscope (TEM), Scanning electron microscope (SEM), Thermogravimetric analysis (TG), X-ray diffraction (XRD) and Fourier transmission infrared (FT-IR) spectrum. The photocatalytic performance of methylene blue by zinc oxide was studied based on the Langmuir model and Photo-Layer model. The results show that some zinc oxide powders were micro-multipore materials with hexagonal crystal. The particle size was around 32 nm. The photocatalytic process was the control step in the chemical reaction. The photo catalytic process followed pseudo-first order kinetics and •OH concentration inside the photo-layer in different reaction condition were calculated according to the Photo-Layer model.

关键词： 2-ethylhexyl micro-multipore Photo-Layer hexagonal methylene

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以NH₃OH⁺/NH₂NH₃⁺作为B位阳离子的无金属六方钙钛矿含能材料 Article

尚宇, 余志鸿, 黄瑞康, 陈劭力, 刘德轩, 陈晓娴, 张伟雄, 陈小明

《工程（英文）》 2020年第6卷第9期页码 1013-1018 doi: 10.1016/j.eng.2020.05.018

摘要：

寻找可经由简单路线合成的高性能含能材料是发展先进实用含能材料的重要问题。文中通过合理地选择分子组分，经由易于规模放大的简单合成路线，以NH₃OH⁺和NH₂NH₃⁺分别作为B位点阳离子构筑了两例无金属六方钙钛矿含能材料(H₂dabco)B(ClO₄)₃（分别命名为DAP-6和DAP-7，其中H₂dabco²⁺是1,4-二氮杂双环[2.2.2]辛烷-1,4-二鎓离子）。与基于NH₄⁺阳离子构筑的立方钙钛矿类似物(H₂dabco)(NH₄)(ClO₄)₃相比，DAP-6和DAP-7有较高的晶体堆积密度和生成焓，从而具有更高的爆轰性能。特别地，DAP-7具有超高热稳定性（起始分解温度T_d = 375.3 °C）、高爆速（D = 8.883 km·s^‒1）和高爆压（P = 35.8 GPa），因此具有作为耐热炸药的应用潜力。计算表明，DAP-6不仅具有较高的热稳定性（T_d = 245.9 °C）以及优异的爆轰性能（D = 9.123 km·s^‒1，P = 38.1 GPa），而且其爆热值（Q = 6.35 kJ·g^‒1）和理论比冲值（I_sp= 265.3 s）均稍优于六硝基六氮杂异伍兹烷（CL-20：Q = 6.23 kJ·g^‒1，I_sp = 264.8 s），在炸药和推进剂领域中具有很好的应用前景。