聚羧酸系高性能减水剂的研究现状与发展方向

聚羧酸系高性能减水剂是减水剂的新品种,具有很多良好的使用性能。介绍了聚羧酸系高性能效减水剂国内外研究现状、目前3种不同合成方法的研究现状及优缺点、作用机理的研究,提出一些亟待深入研究的问题及聚羧酸系高性能减水剂今后的研究方向。     

高效减水剂在高性能混凝土中的应用

简要叙述了高效减水剂的作用机理及其品种。通过工程实例说明高效减水剂在高性能混凝土中所起的作用和经济效果,提出了进一步研究开发用于高性能混凝土的新一代减水剂的建议。     

高性能减水剂的研究现状与发展方向

概述了国内高性能减水剂的研究进程和现状,从化学结构的角度对高性能减水剂进行了分类并介绍其特征,从分子设计的观点出发,提出减水剂高性能化的途径和理论基础,指出单环芳烃型和聚羧酸系是高性能减水剂的研究方向,并介绍其研究内容。     

聚羧酸系高效减水剂的研究现状与展望

聚羧酸系高性能减水剂是一种新型的高效减水剂,具有很多良好的性能.文章结合国内外资料综述了聚羧酸系高性能减水剂的作用机理、国内外研究及合成方法,总结了当前研究与应用中存在的问题,并对未来发展方向进行了展望.     

JY-PCA型聚羧酸系高性能减水剂合成与性能研究

介绍了JY-PCA型聚羧酸系高性能减水剂的合成,重点研究了该减水剂的性能。研究表明,JY-PCA型聚羧酸系高性能减水剂具有良好的减水效果与保坍性能,与传统萘系减水剂相比,聚羧酸系高性能减水剂可以明显改善混凝土的收缩性能。     

聚羧酸系减水剂在C60高性能混凝土中应用的对比试验研究

通过对比试验,探讨了萘系减水剂和聚羧酸系高效减水剂配制的C60高性能混凝土性能。试验结果表明,聚羧酸系减水剂能够很好地满足C60高性能混凝土工作性和强度要求,而萘系减水剂很难达到C60高性能混凝土的要求,聚羧酸系高效减水剂用于C60及以上高强、高性能混凝土,是其应用发展的重要方向。     

高性能聚醚类减水剂的制备及其性能研究

以甲代烯丙基聚乙二醇、马来酸酐、链转移剂为主要原料制备了一种高性能聚醚类减水剂,对该种减水剂的分子结构与性能的关系进行了深入的研究。另外,对制备的高性能聚醚类减水剂与聚酯类减水剂、普通聚醚类减水剂进行了性能对比,试验结果显示:相比普通聚醚类减水剂,高性能聚醚类减水剂具有较好的保坍性、较高的减水率以及较好水泥适应性,其在某些方面的性能甚至优于聚酯类减水剂。     

对国内外聚羧酸减水剂研究进展的探讨

聚羧酸高性能减水剂是一种新型的高效的减水剂,亦是目前国内外研究的热点。本文结合国内外资料综述了聚羧酸高性能减水剂的组成,讨论了反应单体、聚氧烷基链和聚合物相对分子质量及其分布、减水剂掺量等影响减水剂性能的因素。     

高效减水剂在高性能混凝土中的掺加技术

针对高效减水剂在高性能混凝土中不同的掺加技术 ,对高性能混凝土性能的影响进行了研究。研究证实 ,高效减水剂不同的掺加技术 ,对高性能混凝土的性能有显著影响。     

PC-HB减水剂对高性能混凝土力学性能的影响

文中主要研究了PC-HB减水剂对高性能混凝土力学性能的影响,结果表明,PC-HB减水剂能够显著提升高性能混凝土抗压强度与抗折强度,并且对高性能混凝土的早期强度影响较大。     

复合桩基工作性状的非线性分析

运用有限元与无限元相结合的手段,分别以非线性模型和线性模型描述桩间土体和桩周土体的变形特征,通过计算结果的分析,揭示了复合桩基的工作原理,总结了复合桩基的基本特征,研究了一些主要因素对复合桩基工作性状的影响,指出了复合桩基应用中需要注意的问题.     

Thermodynamic analysis of designed and fabricated shell- and tube-type heat exchanger by DSTHE software: Kern method

In this research work, shell- and tube-type heat exchanger has been designed by Kern method. To eliminate design problems, computer software (DSTHE software) has been developed. All design parameters have been calculated by this method with the help of DSTHE software such as number of tubes, shell diameter, pipe pitch and pitch ratio. And then velocity of the tube side fluid, convective heat transfer coefficients for tube and shell side fluids and overall heat transfer coefficient have been calculated. By developed DSTHE software, tube side and shell side fluids pressure drops, entropy generation and entransy dissipation have also been found. Shell- and tube-type heat exchanger has been fabricated with calculated parameters. At various operating conditions, a number of experiments have been performed. For each condition, entropy generation analysis, entransy dissipation analysis and entransy-based thermal resistance analysis have been done. Maximum value of effectiveness, minimum values of entropy generation, entransy dissipation and entransy-based thermal resistance have been found and that actual operating conditions have been identified.     

An experimental study on delamination of FRP plates bonded to concrete

Results of an experimental campaign on FRP–concrete delamination are presented. Specimens with different bonded lengths and plate widths have been tested. Strain gauges along the FRP plate have been used to measure longitudinal strains. For long bonded lengths, progressive debonding along the specimens has been followed. Starting from experimental data, average shear stress–slips data have been computed. By post-processing these data, non-linear interface laws for two different plate widths have been calibrated. Increase of maximum shear stress with decreasing plate width has been observed, whereas no significant plate width effect on fracture energy and delamination force has been found. Experimental tests have been simulated by adopting a numerical bond-slip model and the above mentioned non-linear law for the FRP–concrete interface. Numerical results in good agreement with experimental results have been obtained, both at low and very high loading levels.     

Modelling anaerobic biomass growth kinetics with a substrate threshold concentration

Many bacteria have been observed to stop growing below a certain substrate threshold concentration. In this study, a modification of the Monod kinetics expression has been proposed to take into account this substrate threshold concentration observed in bacterial growth. Besides the threshold concentration no additional parameters have been added to the kinetic expression and so, only the substrate threshold concentration and the half-saturation constant have to be estimated for model calibration purposes. Furthermore, for parameter estimation purposes, practical identifiability of this new function has been studied and the results have been satisfactory. The new model has been applied, as an example, to a simple anaerobic model to simulate the competition for hydrogen between sulphate reducers and methanogens in a thermophilic methanol-fed bioreactor. Oscillatory behaviour and mathematical instabilities have been avoided by using the proposed model. Parameter sensitivities have also been calculated along the simulation period in order to investigate the importance of hydrogen threshold concentration parameters.     

Short- and long-term analytical solutions for composite beams with partial interaction and shear-lag effects

This paper presents an analytical model for the short- and long-term analysis of composite steel-concrete beams with partial shear interaction and accounting for shear-lag effects. The material properties of the concrete have been assumed to be time-dependent and have been modelled by means of the algebraic methods while the remaining materials forming the cross-section have been supposed to behave in a linear-elastic manner. The global balance condition of the problem has been obtained by means of the principle of virtual work and, integrating this by parts, the governing system of differential equations and corresponding boundary conditions have been determined. Analytical expressions for both short- and long-term solutions have been derived and, to outline their ease of use, a number of case studies relevant for bridge applications have been proposed.     

我国建筑抗震技术的发展水平与成就

邢台地震以来，我国在抗震技术的各个领域都得了长足的进步。抗震基础理论的研究和应用已处于世界前沿的位置，并制定了相应的标准规范。多层和高层建筑的抗震设计有了很大发展，还进行了２亿ｍ＾２建筑的抗震加固工作。     

洁净室流场数值模拟的研究进展

对洁净室的应用和发展进行了回顾，分析了洁净室的流场，介绍了数值模拟方面常用的几种模型及国内外在洁净室模拟方面取得的成果，列举了常用的CFD软件，分析了国内研究所存在的问题。     

装配式混凝土框架结构节点构造方法简介

对装配预制式混凝土框架结构承重构件的连接进行分类,介绍了连接在设计和施工阶段中应注意的事项,同时介绍了几种梁柱连接的构造形式及特点。     

水工混凝土抗软水接触性溶蚀试验研究

本文通过试验研究了水工混凝土的接触溶蚀性能。论述了混凝土外加剂、环境水化学成分对混凝土接触溶蚀性能的影响，通过试验结果估算了混凝土的溶蚀耐久性，分析了软水对混凝土的溶蚀机理，提出了防止和减缓混凝土溶蚀破坏的有效措施。     

桩基静载试验的几种反力装置与应用

本文简要介绍了桩基静载试验中常用的几种反力装置 ,并讨论了这几种反力装置的优缺点及应用情况。