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851.
Effects of LiAl-layered double hydroxides on early hydration of calcium sulphoaluminate cement paste
As a 3D micro-nano material, layered double hydroxides have been widely used in many fields, especially for reinforced composite materials. In this paper, LiAl-LDHs was obtained by a hydrothermal method. In order to investigate the effects of LiAl-LDHs on the early hydration of calcium sulphoaluminate (CSA) cement paste, compressive strength, setting time and hydration heat were tested while X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scaning electron microscopy (SEM) and differential scanning calorimetry (DSC) analysis were employed. The results indicated that LiAl-LDHs could significantly improve the early compressive strength and shorten the setting time of calcium sulphoaluminate cement paste with 3wt% concentration. Besides, the hydration exothermic rate within 5 h was accelerated with increasing LiAl-LDHs content. Moreover, the addition of LiAl-LDHs did not result in the formation of a new phase, but increased the quantity of hydration products providing higher compressive strength, shorter setting time and denser microstructure. 相似文献
852.
鱼道是一种重要的生态补偿工程,以往研究的重点主要集中在水力学要素对鱼类通过效果及鱼类适应度的影响方面。针对泥沙在池室中可能造成的水流含沙量增高及淤积面积扩大进而影响过鱼效率和鱼道运行寿命这一关键问题,通过数值模拟方法,对不同泥沙粒径和来流流量组合情况下的池室水流含沙量变化及池底泥沙淤积分布进行了模拟计算,并在此基础上给出了解决上述问题的途径。可为在具有一定含沙特征的河流上建设更为长效的鱼道设施提供数据支撑。 相似文献
853.
郭飞 《重庆建筑大学学报》2017,39(1):13-19
为解决城市总规尺度气候评估工具缺乏的问题,分析了不同气候评估方法的特点和应用范围,研究了气象学工具WRF在城市热岛效应评估中的应用方法及有效性。建立了针对城市总规尺度的高精度城市规划信息数据库、气象数据库生成WRF模拟边界的方法;明确了高精度城市热岛效应模拟所需的WRF物理方案。以沿海城市大连夏季典型晴朗高温天气为例,利用WRF模型进行了300 m的高分辨率模拟。结果表明,WRF可以较好地模拟出城市热岛效应的强度和时空变化;将模拟结果与气象站和现场观测值进行了对比,两者变化趋势一致,偏差在可接受的范围之内。 相似文献
854.
黄河流域三门峡水文测区地处黄河中下游,测区所辖水文站分布在晋、陕、甘、豫区间,是黄河流域多沙、粗沙区,也是治理黄河泥沙的重点区域。多年来,测区各水文站大多采用置换法推求泥沙水样的沙重,泥沙密度值均取经验值2.70 g/cm~3。为了验证这一数值的准确性,在1990~1995年试验的基础上,于2007年和2013年,在本测区黄河干流和重要支流的12个水文站和库区取样,进行密度试验。通过统计分析,求出本测区黄河干流各站的泥沙密度值为2.71g/cm~3、支流各站的泥沙密度为2.73g/cm~3。 相似文献
855.
In this paper, the platoon control problem of autonomous vehicles in highway is studied. Since the autonomous vehicles have the characteristics of nonlinearities, external disturbances and strong coupling, a novel adaptive fuzzy sliding coordinated control system is constructed to supervise the longitudinal and lateral motions of autonomous vehicles, in which the fuzzy system is employed to approximate the unknown nonlinear functions. Due to the low sensitivity to disturbances and plant parameter variations, the proposed control approach is an efficient way to handle with the complex dynamic plants operating under un-certainty conditions. The asymptotic stability of adaptive coordinated platoon close-loop control system is verified based on the Lyapunov stability theory. The results indicate that the presented adaptive coordinated platoon control approach can accurately achieve the tracking performance and ensures the stability and riding comfort of autonomous vehicles in a platoon. Finally, simulation test is exploited to demonstrate the effectiveness of the proposed control approach. 相似文献
856.
LinJiang Chai ShuYan Wang Hao Wu ZhiNan Yang HuCheng Pan Bo Song Ning Guo 《中国科学:技术科学(英文版)》2017,60(4):587-592
A duplex-phase Zr-2.5Nb alloy was treated by pulsed laser, followed by careful microstructural characterization using field emission gun scanning electron microscope and attached electron backscatter diffraction. Beneath the modification zones with common uniform α-plate structures(UPS), a layer of unreported bimodal α-plate structures(BPS) featured by coarse(submicron)plates forming multiple cores surrounded by dense fine(nanoscale) plates was found. Presence of such BPS is attributed to non-equilibrium thermodynamic conditions induced by the pulsed laser treatments. Limited diffusion of Nb due to the short pulse during laser heating allows β phases with distinctly different Nb contents to be presented: Nb-enriched prior β films and Nb-depleted β phases, transforming into the fine and the coarse plates during cooling, respectively. Orientation analyses show that both types of plates in the BPS are aroused essentially from a single β orientation, suggesting epitaxial growth of the Nb-depletedβ phases from the preexisting β films. 相似文献
857.
A potassium dihydrogen phosphate (KDP) optical crystal was machined to an ultra-precision surface with water-in-oil (W/O) micro emulsion polishing fluid. The micro water dissolution principle utilized in the machining process is discussed, its planarization mechanism is illustrated, and an ultra-precision polished surface with 2.205 nm RMS roughness is obtained. However, a substantial quantity of residual contamination remained on the polished surface after machining. This can seriously impact the optical performance of the crystal, and so it must be removed. Fourier transform infrared (FTIR) spectroscopy was used to conduct an investigation into the composition of the surface residue, and the results showed that the residue was comprised of organic chemicals with hydrocarbon chains and aromatic ether, i.e., mostly the polishing fluid. The cleaning method and the principle on which the KDP ultra precision surface investigation is based are discussed in detail, and the cleaning experiments with selected KDP-compatible organic solvents were then performed. FTIR transmittance spectra measurement and microscopic observations were employed to assess the effects of the cleaning process on the surface of the KDP crystal. The results showed that toluene cleaning achieved the most desirable results. This cleaning method produced a surface roughness of 1.826 nm RMS, which allows the KDP crystal to be applied to subsequent engineering applications. 相似文献
858.
Dynamic responses of K-type and inverted-K-type jacket support structures for offshore wind-turbines
Journal of Central South University - The jacket structure has become more popular as the offshore wind-turbine support structure. K-type and inverted-K-type jacket support structures have superior... 相似文献
859.
以丙烯酰胺(AM)与甲基丙烯酰胺丙基三甲基氯化铵(MAPTAC)为共聚单体,通过紫外光引发聚合法制备阳离子聚丙烯酰胺絮凝剂P(AM-MAPTAC)。通过红外光谱(IR)与差热热重分析(TG/DSC)分别对P(AM-MAPTAC)进行结构表征与热稳定性分析,并采用响应曲面法得到优化制备条件:反应体系pH为4.75,引发剂v-044质量分数为0.07%,EDTA-2Na质量分数为0.20%,n(MATPAC)/n(AM)为0.33,光照时间为60 min。在优化条件下制备P(AM-MAPTAC)絮凝剂,特性粘度可达14.72 dL/g,通过污泥脱水实验可验证该特性粘度下的污泥脱水效果最好,滤饼含水率(FCMC)达70%,污泥比阻(SRF)达6.94×1012m/kg,上清液剩余浊度达9.70 NTU,污泥脱水效果优于市售常用絮凝剂。 相似文献
860.
Spinel LiMn2O4 microspheres and hollow microspheres with adjustable wall thickness have been prepared using controllable oxidation of MnCO3 microspheres precursors and following solid reactions with lithium salts. Scanning electron microscopy (SEM) investigations demonstrate that the microsphere morphology and hollow structure of precursors are inherited. The effect of hollow structure properties of as-prepared LiMn2O4 on their performance as cathode materials for lithium-ion batteries has been studied. Electrochemical performance tests show that LiMn2O4 hollow microspheres with small wall thickness exhibit both superior rate capability and better cycle performance than LiMn2O4 solid microspheres and LiMn2O4 hollow microspheres with thick wall. The LiMn2O4 hollow microspheres with thin wall have discharge capacity of 132.7 mA·h·g-1 at C/10 (14.8 mA·g-1) in the first cycle, 94.1% capacity retention at C/10 after 40 cycles and discharge capacity of 116.5 mAh·g-1 at a high rate of 5C. The apparent lithium-ion diffusion coefficient (D app) of as-prepared LiMn2O4 determined by capacity intermittent titration technique (CITT) varies from 10-11 to 10-8.5 cm2·s-1 showing a regular “W” shape curve plotted with test voltages. The Dapp of LiMn2O4 hollow microspheres with thin wall has the largest value among all the prepared samples. Both the superior rate capability and cycle stability of LiMn2O4 hollow microspheres with thin wall can be ascribed to the facile ion diffusion in the hollow structures and the robust of hollow structures during repeated cycling. 相似文献