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采用均匀正交试验对水泥掺量、乳液用量、拌合用水量三个因素进行优选,得到阳离子乳化沥青混凝土的基础配合比参数。通过测定每组沥青混凝土试件的稳定度和流值,并采用投影寻踪回归分析法(PPR)研究了水泥掺量、乳液用量和拌合用水量对稳定度和流值的影响规律,研究发现,对于稳定度和流值影响最大的因素是水泥掺量,其次是乳液用量的影响,而拌合用水量对稳定度和流值影响较小。 相似文献
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建筑常用给水管道地震易损性试验研究 总被引:1,自引:0,他引:1
现行建筑设计规范对结构的抗震设计有着严格的要求,对非结构构件的抗震性能却缺乏足够的重视。地震后即使建筑物的结构损伤较小,也可能因为非结构构件的破坏而丧失使用功能。管道系统作为一种典型的非结构构件,是建筑实现给水、排水、消防、燃气等功能的重要保障。针对国内新老建筑中常用的PPR、镀锌钢管等建筑给水管材,以直径、水压、壁厚、加载方式为变量设计并完成24组共计72个往复加载试验。根据试验结果总结各类型管道的破坏特征和地震易损性,并通过算例介绍了试验易损性数据在管线抗震设计和分析中的应用。 相似文献
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Glaucio H. Paulino Kyoungsoo Park Waldemar Celes Rodrigo Espinha 《International journal for numerical methods in engineering》2010,84(11):1303-1343
Dependence on mesh orientation impacts adversely the quality of computational solutions generated by cohesive zone models. For instance, when considering crack propagation along interfaces between finite elements of 4k structured meshes, both extension of crack length and crack angle are biased according to the mesh configuration. To address mesh orientation dependence in 4k structured meshes and to avoid undesirable crack patterns, we propose the use of nodal perturbation (NP) and edge‐swap (ES) topological operation. To this effect, the topological data structure TopS (Int. J. Numer. Meth. Engng 2005; 64 : 1529–1556), based on topological entities (node, element, vertex, edge and facet), is utilized so that it is possible to access adjacency information and to manage a consistent data structure in time proportional to the number of retrieved entities. In particular, the data structure allows the ES operation to be done in constant time. Three representative dynamic fracture examples using ES and NP operators are provided: crack propagation in the compact compression specimen, local branching instability, and fragmentation. These examples illustrate the features of the present computational framework in simulating a range of physical phenomena associated with cracking. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Tricopeptide repeats are common in natural proteins, and are exemplified by 34- and 35-residue repeats, known respectively as tetratricopeptide repeats (TPRs) and pentatricopeptide repeats (PPRs). In both classes, each repeat unit forms an antiparallel bihelical structure, so that multiple such units in a polypeptide are arranged in a parallel fashion. The primary structures of the motifs are nonidentical, but amino acids of similar properties occur in strategic positions. The focus of the present work was on PPR, but TPR, its better-studied cousin, is often included for comparison. The analyses revealed that critical amino acids, namely Gly, Pro, Ala and Trp, were placed at distinct locations in the higher order structure of PPR domains. While most TPRs occur in repeats of three, the PPRs exhibited a much greater diversity in repeat numbers, from 1 to 30 or more, separated by spacers of various sequences and lengths. Studies of PPR strings in proteins showed that the majority of PPR units are single, and that the longer tandems (i.e., without space in between) occurred in decreasing order. The multi-PPR domains also formed superhelical vortices, likely governed by interhelical angles rather than the spacers. These findings should be useful in designing and understanding the PPR domains. 相似文献
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本文首先指出传统方法在研究悬移质扩散系数时存在的问题及困难,根据两相流理论确定出影响悬移质扩散系数的3个主要因子,并沿着“审视数据-模拟-预测”的途径,建立了固液两相流中悬移质扩散系数的投影寻踪回归(PPR)的数学模型,模拟结果表明本文所建立的模型稳健性和抗干扰性好,预测精度较高。 相似文献
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Three-layer pipe has many advantages over single layer one, especially for the pipe of glass fiber (GF) reinforced materials. But the hoop strength of the pipe produced via convention extrusion is poor because GFs orient along axial direction. In this work, a self-designed rotation extrusion system was adopted to extrude GF reinforced three-layer polypropylene random copolymer (PPR) pipe, in which a hoop shear field was applied to the polymer matrix and fibers in the middle layer. The structure and performance of pipes were investigated via scanning electronic microscope (SEM) and synchrotron two-dimensional wide-angel X-ray diffraction (2D-WAXD). Due to the hoop shear field, the orientation of GFs in middle layer deviated from axial direction. As a result, PPR pipes with enhanced hoop tensile strength were obtained. Because of the three-layer structure and the production process, the molecular chains of middle layer did not emerge distinct orientation after rotation shear, as shown in 2D-WAXD and SEM experimental results. This three-layer pipe rotation extrusion system offers a novel method for the modification of pipes in manufacture industry. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46985. 相似文献
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通过3个不同预应力度的预应力混凝土扁梁框架内节点试件的低周反复荷载加载试验,初步研究了节点的破坏形态、滞回曲线、延性、耗能能力等抗震性能。结果表明,对框架节点影响的本质原因是通过施加预应力在框架结构上,预应力度增大,框架节点的水平承载力随之增大。 相似文献
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