C80高强混凝土的研发与试应用

该文介绍了C80预拌混凝土的研发与试应用过程,包括原材料选择、配合比设计、配合比验证,以及混凝土搅拌、运输、泵送、振捣和养护。为重庆预拌混凝土企业提供参考。     

Synthesis of phenyl silicone resin with epoxy and acrylate group and its adhesion enhancement for addition-cure silicone encapsulant with high refractive index

A novel phenyl silicone resin with epoxy and acrylate group (PSREA) was successfully synthesized via the non-hydrolytic sol-gel condensation reaction of 3-glycidoxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, and diphenylsilanediol, and was employed as the adhesion promoter for addition-cure silicone encapsulant (ASE) with high refractive index. The structure of PSREA was confirmed by Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance spectroscopy, and ²⁹Si nuclear magnetic resonance spectroscopy. The influence of PSREA on the properties of ASE was studied. It was found that PSREA could markedly enhance the adhesion strength of ASE to aluminum (Al) and poly(p-phenylene terephthamide) (PPA) substrate. When the content of PSREA was 1.5 phr, the shear strength of ASE was 4.43 and 2.27 MPa for Al and PPA substrate, which was about 71 and 266% higher than that of ASE without the adhesion promoter, respectively. In addition, PSREA had little effect on the mechanical properties, refractive index, and viscosity of ASE.     

重量法测定脲甲醛缓释肥料活性指数的研究

研究重量法测定脲甲醛缓释肥料的活性指数,对重量法和行业标准HG/T 4137—2010指定测定方法测定结果进行相关性研究。结果表明,两种方法的测定结果存在极显著正相关性,相关系数为0.996 6,两种方法测定值的绝对差值范围为-0.85%~0.56%。重量法具有简便、高效和准确的特点,可替代HG/T 4137—2010中脲甲醛缓释肥料活性指数测定方法。     

基于统一控制策略的光伏微网控制器参数敏感性分析

针对低压光伏微网中逆变器的控制,设计了一种基于统一控制策略的控制器,能够避免微网在并网和孤岛两种运行方式间切换时控制策略的转换,实现不同运行模式间的平滑切换及光伏微源功率均分。对传统的下垂控制进行改进,在传统下垂控制的基础上引入一个功率PI补偿器。根据阶跃响应动态指标和稳定性要求,利用根轨迹法优化设计控制器参数。最后,在Matlab/Simulink环境下进行了仿真,结果验证了所设计的控制器的可行性和有效性。     

转子速率正弦变化对流体混合的影响

建立了圆形转子混合设备的二维流动有限元模型,采用网格重叠技术,利用粒子跟踪法对瞬态混炼流场进行了数值模拟,对不同相位差下的的分散混合性能、分布混合性能、线拉伸以及混合效率进行了统计和比较;分析了相位角对流体混沌混合对效率的影响,为密炼机驱动系统的新的优化方向提供了一定的理论参考。     

封闭玻璃管道内液体折射率的非接触测量

为了实时、原位和非接触测量工业生产过程中封闭管道系统内透明、半透明液体折射率,提出了一种简单的基于玻璃管壁光学特性的液体折射率测量方法。该方法通过涂覆在玻璃管壁外表面上的透射散射层,将入射激光束转换为进入玻璃管壁的大角度分布的透射散射光;透射散射光到达玻璃管壁与液体的界面上后,符合全反射条件的散射光反射到透射散射层上,自动形成与玻璃管内液体折射率值相关的椭圆形暗斑图像。根据椭圆形暗斑长轴长度与液体折射率之间的解析关系,即可实现玻璃管内液体折射率的原位、非接触测量。对几种常见的透明、半透明液体的折射率进行了实验测量,结果表明:该测量方法的准确性与目前商用数字阿贝折射仪相当(±2×10-4 RIU)。该测量方法具有成本低、稳定性好、抗干扰且光源稳定等优点,而且在处理与液体折射率相关的光学图像时无需调试,光照即显,有望用于封闭管道在非常温、非常压状态下液体折射率的实时、自动和非接触在线监测。     

主余震序列作用下钢筋混凝土框架结构损伤分析

一次强震过后通常伴有多次余震发生。由于主震和其后续余震之间的间隔时间较短,使得主震损伤结构未能得到及时修复而进一步遭受余震作用,产生“二次损伤”。为此,以一栋5层按我国相关设计规范设计的钢筋混凝土框架结构为研究对象,对主余震序列对结构造成累积损伤及余震对结构造成的增量损伤进行了研究。选取75条真实主震及其余震记录构成序列型地震动输入。同时,采用真实主余震序列中的主震记录,分别采用重复法和随机法两种人工余震构造方法,构造两组人工主余震序列作为地震输入。采用改进的Park-Ang损伤指数作为结构损伤指标,对结构在主震及其在真实和人工主余震序列作用的损伤进行计算,并对余震产生的结构增量损伤进行评估。进一步以峰值加速度、谱加速度、Arias强度作为主震和余震强度参数,研究了余震与主震强度比与余震增量损伤之间的相互关系。分析结果表明：基于随机法的人工主余震序列会对结构造成最显著的增量损伤;采用余震和主震强度比可以较好地预测余震增量损伤的显著性。     

Probabilistic analysis of site-specific load-displacement behaviour of cement-fly ash-gravel piles

Cement-fly ash-gravel (CFG) piles comprise one of the novel ground-improvement methods. They are attracting considerable attention, as their beneficial role in accessible soft foundations is being increasingly exploited by the surging urban industrial development in China. Despite their recognised significance, however, the load-settlement behaviour of CFG piles is poorly understood, particularly in the context of probabilistic assessments. This study focuses on six full-scale CFG pile load test datasets, consisting of 245 samples collected at six sites in the Beijing region, under static axial compression loading. As a part of this investigation, a regression curve is applied to the load-settlement data for each load test in the database using a two-parametric hyperbolic or power law curve-fitting equation. Moreover, an assessment of the multiple load-displacement curves, based on the full set of pile load measurements conducted at a particular test site, reveals that the scatter observed in the regression parameter values is mainly caused by the inherent soil variability.Thus, a bivariate copula-based mixed distribution is chosen to represent the dependence between these regression parameters. A simple copula-based simulation model is used to estimate the reliability index at any specific allowable settlement for the serviceability limit state (SLS) design. The correlation coefficients in the copula-based distributions of the regression parameters are proven to have an impact on the reliability index of this pile foundation. A scatter analysis of the load-displacement behaviour provides insight into the probabilistic design of site-specific CFG pile foundations.