新型地锚张弦梁式泥石流格栅坝构件受力的简化计算方法

针对常见泥石流防治结构被冲击破坏的问题，基于“柔性消能”理念，结合张弦梁结构和竖向预应力锚杆技术，提出一种既能改善结构受力性能、增加结构整体抗冲击能力、保证结构安全可靠，又能减小结构构件截面尺寸、节约成本、便于现场施工组装和后期运营维护的新型地锚张弦梁式泥石流格栅坝，并阐述其技术原理。根据泥石流荷载分布和新型地锚张弦梁式泥石流格栅坝的受力特征，给出其简化的内力计算方法；并利用SAP2000建立新结构有限元模型，分析了结构的整体受力，验证了构件简化计算方法的合理性；结合Python语言和Qt De? signer软件开发了相应的设计计算软件，对新型地锚张弦梁式泥石流格栅坝的内力进行求解。结果表明：提出的新结构抗冲击性能好，构件受力均匀；以后设计中应关注竖杆的剪切脆性破坏和立柱偏心受力情况，保证结构安全；变形协调仅使底层张弦梁与竖杆内力偏大，实际工程应用时，应着重验算底层构件，防止其破坏；文中提出的简化计算方法能较准确的反映结构的受力特性，具有一定的合理性，研究可为新型地锚张弦梁式泥石流格栅坝的设计计算和推广应用提供理论依据和技术支持。     

Influence of accelerated curing on the compressive strength of polymer-modified concrete

In recent building practice, rapid construction is one of the principal requisites. Furthermore, in designing concrete structures, compressive strength is the most significant of all parameters. While 3-d and 7-d compressive strength reflects the strengths at early phases, the ultimate strength is paramount. An effort has been made in this study to develop mathematical models for predicting compressive strength of concrete incorporating ethylene vinyl acetate (EVA) at the later phases. Kolmogorov-Smirnov (KS) goodness-of-fit test was used to examine distribution of the data. The compressive strength of EVA-modified concrete was studied by incorporating various concentrations of EVA as an admixture and by testing at ages of 28, 56, 90, 120, 210, and 365 d. An accelerated compressive strength at 3.5 hours was considered as a reference strength on the basis of which all the specified strengths were predicted by means of linear regression fit. Based on the results of KS goodness-of-fit test, it was concluded that KS test statistics value (D) in each case was lower than the critical value 0.521 for a significance level of 0.05, which demonstrated that the data was normally distributed. Based on the results of compressive strength test, it was concluded that the strength of EVA-modified specimens increased at all ages and the optimum dosage of EVA was achieved at 16% concentration. Furthermore, it was concluded that predicted compressive strength values lies within a 6% difference from the actual strength values for all the mixes, which indicates the practicability of the regression equations. This research work may help in understanding the role of EVA as a viable material in polymer-based cement composites.     

45 t门座起重机顶升方案设计

针对国内45 t门座起重机大车行走机构平衡梁裂缝问题。分析平衡梁裂缝产生原因并提出相应的维修方案,并对维修关键技术中的顶升方案设计,采用Ansys软件对其强度进行了有限元分析,同时对维修前后的平衡梁进行分析并对比。将维修方案应用于实际工程,取得了较好效果。该顶升机构修复方案设计符合工程实际,对工程实践具有一定的指导意义。     

100 MeV质子回旋加速器二期辐照效应管道设计

针对中国原子能科学研究院100 MeV质子回旋加速器上的单粒子效应辐照装置进行了二期管道设计，采用八极磁铁校正法对束流进行了扩束及均匀化，最终在靶上得到了一个30 cm×30 cm、均匀性好于92%的均匀分布的束斑，满足了单粒子效应实验的需求。为降低靶站处的束流能散及中子本底，采用两级降能的方案，在偏转磁铁前放置1个降能片，将能量分为100 MeV和40 MeV两档，并分别针对这两个能量点进行方案设计，束流利用率均在42%以上。公差分析结果表明，四极磁铁对靶上束斑均匀性的影响大于八极磁铁，安装过程中应优先保证四极磁铁的安装公差。     

Performance evaluation of structural concrete using controlled quality coarse and fine recycled concrete aggregate

This paper presents the fresh, mechanical, and durability performance, of a structural concrete mix classified as C-1, by the Canadian Standards Association (CSA) made with controlled quality Recycled Concrete Aggregate (RCA). Five mixes with water-to-cementing material (w/cm) ratio of 0.40 were produced with various RCA contents and tested against two 0% RCA control mixes made with General Use (GU) cement, and General Use Limestone cement (GUL). The RCA contents in the mixes were 10%, 20%, and 30% by coarse aggregate volume replacement, as well as 10% and 20% fine and coarse (granular) aggregate volume replacement. All evaluated mixes met the specifications from the CSA for fresh, mechanical, and durability properties. The coarse RCA mixes performed better than the granular RCA mixes in terms of flexural and splitting tensile strengths, linear drying shrinkage, water sorptivity, and rapid chloride-ion permeability, where the test results were significantly affected by the ultra fines present in the granular RCA.     

High-resolution FIB-TEM-STEM structural characterization of grain boundaries in the high dielectric constant perovskite CaCu3Ti4O12

In this work, the grain boundaries composition of the polycrystalline CaCu₃Ti₄O₁₂ (CCTO) was investigated. A Focused Ion Beam (FIB)/lift-out technique was used to prepare site-specific thin samples of the grain boundaries interface of CCTO ceramics. Scanning transmission electron microscopy (STEM) coupled with energy dispersive X-ray spectrometry (EDXS) and Electron Energy Loss Spectroscopy (EELS) systems were used to characterize the composition and nanostructure of the grain and grain boundaries region. It is known that during conventional sintering, discontinuous grain growth occurs and a Cu-rich phase appears at grain boundaries. This Cu-rich phase may affect the final dielectric properties of CCTO but its structure and chemical composition remained unknown. For the first time, this high-resolution FIB-TEM-STEM study of CCTO interfacial region highlights the composition of the phases segregated at grain boundaries namely CuO, Cu₂O and the metastable phase Cu₃TiO_4.     

大宗粉煤灰的综合利用及提质方案

对于大宗粉煤灰原灰进行分选加球磨机粉磨，同时添加合适的激发剂进行提质，可以生产出不同细度和活性的粉煤灰产品，提升粉煤灰在水泥及商品砼中的用量。介绍了某发电公司的粉煤灰处置现状，在此基础上，对商品砼的粉煤灰性能要求进行了大量市场调研，针对性地给出了该公司粉煤灰的提质方案，最后进行了提质粉煤灰的应用市场和产品竞争力分析。     

Stress distribution in thick-walled cylinder due to non-uniform radial pressure on the example of reinforcement corrosion in concrete

This paper presents an analytical solution to the non-uniform pressure on thick-walled cylinder. The formulation is based on the linear elasticity theory (plain strain) and stress function method. As an example, the proposed solution is used to model the stress distribution due to non-uniform steel reinforcement corrosion in concrete. The model is formulated considering different scenarios of corrosion pressure distribution. It is validated against the finite element model for different cases of non-uniform pressure distributions. The results show that the corrosion-induced cracks are likely to start just beyond the anodic zone. This is confirmed by the experimental tests on concrete cylinder exposed to non-uniform accelerated corrosion of steel reinforcement. The model can be effectively used to calculate the distribution of corrosion-induced stresses in concrete.     

靶面激光光斑尺寸原位测量的研究

提供了一种简便易行的靶面激光光斑尺寸原位测量的方法。从高斯光束的横向光强分布特性出发,建立了激光烧蚀斑半径与辐照激光能量、光斑尺寸、烧蚀阈值间的关系式,模拟分析发现辐照激光光斑尺寸对烧蚀斑半径随辐照能量变化曲线有较大影响。对于脉宽为2 ms,波长为1064 nm的激光,实验测量了不同能量激光辐照下相纸烧蚀斑半径,并用推导出的关系式拟合测量数据,获得了靶面处光斑尺寸和样品烧蚀阈值。同时,也测量了不同位置处的光斑尺寸和样品烧蚀阈值,对高斯光束束腰位置和样品烧蚀阈值的光斑尺寸效应进行了验证。研究结果表明该技术结果可靠,简单高效。该技术可以为高能激光与固体物质相互作用的基础研究和激光加工等应用领域中实现简单方便地测量靶面光斑尺寸提供帮助。     

Effect of steel slag on 3D concrete printing of geopolymer with quaternary binders

A new type of 3D-printable ‘one-part’ geopolymer was synthesized with fly ash (FA), granulated blast furnace slag (GBFS), steel slag (SS) and flue gas desulfurization gypsum (FGD). The effects of SS content (0–40%) on the rheological properties, 3D-printability, mechanical anisotropy and reaction kinetics of geopolymer were investigated. The yield stress and plastic viscosity monotonically decreased with the increasing SS content. Contrarily, the geopolymer with 10% of SS presented better extrudability, buildability and mechanical strength than those with 0, 20%, 30% and 40% of SS. This was mainly attributed to the conflicting influence of SS on geopolymerization, of which the OH^? produced by hydration of SS raised the alkalinity of the reaction system and accelerated the dissolution of SiO₄^4? and AlO₄^5?, while the low reactivity prohibited the following polymerization process. Furthermore, the 3D-printed geopolymer presented more compact microstructure and less mechanical anisotropy thanks to the crosslinking of morphologically complementary products, including N(C)-A-S-H, C–S–H, AFt and CH, formed via synergistic reaction of FA-GBFS-SS-FGD system.