精确建模的双圆弧齿轮有限元分析

圆弧齿轮是凹形齿廓与凸形齿廓之间的啮合，具 有承载能力强、润滑性能好、加工方便等优点，广泛应 用于石油、煤炭、钢铁等行业.但在使用中，也暴露了其 噪音较高、动力性能较差的缺点，并阻碍了进一步的推 广应用.所以对其进行受力变形分析显得极为重要，而 精确建模却是进行     

CdTe/CdS核/壳结构纳米晶量子点的结构及荧光性能

采用水相合成法,制备出核/壳结构CdTe/CdS纳米晶量子点,用红外光谱和X射线衍射对其结构进行了表征,并对CdTe纳米晶量子点光稳定性以及CdTe/CdS纳米晶量子点荧光特性影响因素进行了研究.结果表明:随着放置时间的增加,CdTe量子点的光学稳定性下降;随着反应时间的增加和壳/核比例的增加,CdTe/CdS纳米晶量子点的荧光发射波长均发生红移;且反应时间增加,荧光强度增强;当CdS与CdTe壳/核比例为2∶1时,荧光强度最强.     

植物根系对重金属在土壤中运移影响的数值模拟研究

土壤重金属污染是全球面临的一个重要环境问题。本文通过数值模拟,探讨了低吸收植物、普通植物和超富集植物3种植物根系对重金属在土壤中运移的影响。污染初期,有植物土柱的污染程度均高于无植物土柱。随着污染的持续,超富集植物土柱污染程度最先低于无植物土柱,然后普通植物土柱污染程度也开始低于无植物土柱。超富集植物土柱重金属浓度分布很快达到稳定,而普通植物土柱重金属浓度分布范围和峰值仍随时间而增大。低吸收植物土柱污染程度最为严重,重金属浓度峰值会超过污染源输入浓度,且峰值下移。     

Numerical simulation of single bubble motion in ionic liquids

In this work a numerical simulation is studied to investigate the motion of single bubble in ionic liquids using an improved volume-of-fluid (VOF) method. In the improved method, besides the gravity and surface tension, a new drag force is added to the momentum equation in order to describe the gas–liquid interaction in the ionic liquids, which possess some special properties compared with the traditional solvents. The deformation, velocity and equivalent diameter of single bubble rising in three ionic liquids, i.e., bmimBF₄, bmimPF₆ and omimBF₄, are simulated and the calculation results agree well with the experimental data. Furthermore, the detailed velocity fields and pressure fields around the bubbles are predicted with the proposed numerical simulation model. This work is important for understanding the fluid dynamic performance of bubbles in ionic liquids, and could provide a useful tool for designing a bubble column with ionic liquids as its solvents.     

麦秸秆防腐评价及加筋滨海盐渍土的补强机制

为开发加筋新材料,提出了以防腐处理后的麦秸秆作加筋固化滨海盐渍土的构想。利用扫描电镜观察被SH胶浸泡后的麦秸秆,发现麦秸秆孔隙中渗入了胶体物质且在麦秸秆内外表皮附着了胶膜,浸泡SH胶能增强麦秸秆的防腐能力。拉伸试验结果证实,浸胶后再浸水的麦秸秆较天然麦秸秆的极限拉力和极限延伸率均有较大提高,浸泡SH胶增强了麦秸秆的抗拉能力和延展性能。若利用浸胶后的麦秸秆加筋固化滨海盐渍土,可将麦秸秆与滨海盐渍土均匀拌和在一起,以增强土体的强度和整体性。麦秸秆加筋滨海盐渍土的补强机制可用“弯曲机理”和“交织机理”予以解释。     

An Adaptive Gaussian Mixture Model for Non-rigid Image Registration

This paper presents a new model based on statistical and variational methods for non-rigid image registration. It can be viewed as an improvement of the intensity-based model whose dissimilarity term is based on minimization of the so-called sum of squared difference(SSD). In the proposed model, it is assumed that the residue of two images can be described as a mixture of Gaussian distributions. Then we incorporate the features of variational regularization methods and expectation-maximization(EM) algorithm, and propose the new model. The novelty is the introduction of two weighting functions and some control parameters in dissimilarity term. The weighting functions could identify low and high contrast objects of the residue automatically and effectively, and the control parameters help to improve the robustness of the model to the choice of regularization parameters. By the introduced parameters and weighting functions, the algorithm could locally adjust the behavior of deformation in different contrast regions. Numerical experimental results of 2D synthetic and 3D MR brain images demonstrate the efficiency and accuracy of the proposed approach compared with other methods.     

Rapid solidification synthesis of novel (La,Y)2(Zr,Ti)2O7 pyrochlore-based glass-ceramics for the immobilization of high-level wastes

Pyrochlore-based glass-ceramics are attracting attention as a promising host material for immobilizing minor actinide in high-level wastes. However, the loading capacity of pyrochlore-based materials for actinide elements is to be improved, and only conventional synthetic approaches of powder sintering and glassy bulk crystallization were reported. Here, new (La,Y)₂(Zr,Ti)₂O₇ pyrochlore-based glass-ceramics were subtly designed and successfully prepared through a rapid melting and solidification process. The solidification behavior of samples with different cooling rates was investigated, the dense and crack-free (La,Y)₂(Zr,Ti)₂O₇ pyrochlore-based glass-ceramics were prepared at the cooling rate of 500 °C/s (within 1.5 s). The present amorphous La₂O₃-TiO₂-Al₂O₃ phase demonstrates the outstanding thermal stability compared with the currently used borosilicate glass for high-level waste immobilization due to the lack of conventional glass-forming components. The results show the great feasibility of this novel synthesis route for glass-ceramics by direct solidification and its good potential for immobilizing high-level wastes.     

一种双轴向列相液晶两体势模型的标准化形式

研究刘红等提出的液晶双轴向列相两体势模型,将该模型两体势转化成标准形式。据此,可以清楚地看出它的色散力近似本质,确定势参数的取值范围,并对双轴向列相的研究进行了展望。     

High capacity immobilization of U3O8 in Gd2Zr2O7 ceramics via appropriate occupation designs

An optimal occupation of U⁴⁺ and U⁶⁺ in Gd₂Zr₂O₇ is necessary for a really high immobilization capacity of U₃O₈ in Gd₂Zr₂O₇ based waste forms. Based on four kinds of occupation methods, a series of U₃O₈-doped Gd₂Zr₂O₇ compositions have been synthesized. The effects of U₃O₈ content on the phase and microstructure evolution of Gd₂Zr₂O₇ pyrochlore waste forms were investigated. Detailed XRD analysis show that the four sets of samples exhibit a single defect fluorite structure within the range of 0<x≤0.4, 0<x≤0.66, 0<x≤0.6 and 0<x≤1, respectively. The highest solubility of U₃O₈ is about 82.29 wt% when the occupation design (U⁴⁺ and U⁶⁺ substitute for Gd and Zr, respectively) was employed. It was found that the cell parameters of compounds in Set A (Gd_2–3x(U⁴⁺_xU⁶⁺_2x)Zr₂O_7+7x/2) decrease with increasing _x, while those of the other compositions increase. Moreover, the uranium are almost homogeneously distributed in all samples.     

基于接触理论的水垫塘底板数值模拟研究

平底板的稳定主要靠自重和锚固钢筋维持,因此合理的锚固钢筋模拟方法对解决底板的稳定计算问题至关重要。对锚固钢筋的工作原理进行了研究,用几种锚固钢筋的模型对实际工程底板稳定问题进行了计算。水垫塘止水破坏后,板块受脉动上举力的作用,与板块四周水体一起在座穴内不断的振动,是一种流固耦合振动,且底板与基岩相互碰撞、滑动,又表现为典型的接触问题,计算相当复杂。建立的底板-地基-水体-锚固钢筋联合作用有限元模型比较真实的模拟了底板的实际运动状态,并对平底板失稳的各个不同阶段进行了全过程的仿真模拟,计算结果更加真实可靠。