触针式轮廓仪弹性测量杆的设计

针对传统的触针式轮廓仪杠杆式测量杆的转动支点由于滚动体跳动容易引入随机误差的问题,提出并设计了一种基于弹性变形理论的轮廓仪测量杆。利用高精度电容传感器测量测量杆的弹性变形量,然后利用悬臂梁的挠曲线公式求出触针针尖的位移量从而得到待测面的微观不平度信息,消除了杠杆式测量杆引入的随机误差,进一步提高了粗糙度测量精度。     

NEW TUNING METHOD FOR PID CONTROL OF A PLANT WITH UNDER‐DAMPED RESPONSE

In this paper, a tuning formula is derived for PID control of plants with under‐damped step responses. The under‐damped systems are modeled by second‐order plus dead time transfer functions. To derive the tuning rule, the dominant pole assignment method was applied to design the PID controllers for a variety of plant models. Then, the correlation between the controller parameters and the parameters of the models was found and the tuning formula derived. Several simulation examples are given to demonstrate the effectiveness and robustness of this formula.     

Pre-tensioning of fabrics in cement-based composites

This paper studies the effects induced by applying a pre-tension load during the production of fabric-cement composites. The flexural behavior as well as the bonding between the different fabrics and the cement matrix was examined, as a means for characterizing the processing parameters. Microstructure characteristics of the fabric-matrix interface as well as the viscous elasticity properties of the fabrics were also explored and correlated with the mechanical properties of the composite. It was found that pre-tensioning of fabrics and the time at which the tension is removed can significantly influence the performance of the composite depending on yarn properties, mainly the viscous-elastic properties, and fabric geometry.     

Autogenous shrinkage in high-performance cement paste: An evaluation of basic mechanisms

In this paper, various mechanisms suggested to cause autogenous shrinkage are presented. The mechanisms are evaluated from the point of view of their soundness and applicability to quantitative modeling of autogenous shrinkage. The capillary tension approach is advantageous, because it has a sound mechanical and thermodynamical basis. Furthermore, this mechanism is easily applicable in a numerical model when dealing with a continuously changing microstructure. In order to test the numerical model, autogenous deformation and internal relative humidity (RH) of a Portland cement paste were measured during the first week of hardening. The isothermal heat evolution was also recorded to monitor the progress of hydration and the elastic modulus in compression was measured. RH change, degree of hydration and elastic modulus were used as input data for the calculation of autogenous deformation based on the capillary tension approach. Because a part of the RH drop in the cement paste is due to dissolved salts in the pore solution, a method is suggested to separate this effect from self-desiccation and to calculate the actual stress in the pore fluid associated with menisci formation.     

特种粘土固化浆液在军山水库除险加固中的应用

本文介绍江西省于都县军山水库大坝坝体防渗所采用的特种粘土固化浆液灌浆技术的施工工艺和技术要求.     

龚嘴水电站水轮发电机转子 绝缘处理

龚嘴水电站1号水轮发电机转子绝缘为B级绝缘,运行至今已三十多年。由于运行环境湿度大等因数,转子绝缘性能降低,严重影响机组正常的安全运行。2003年11月该厂改造了1号发电机组的定子线圈、铁心和水涡轮,通过采用新型通风系统改善了转子绝缘性能,实现了定子、转子温升分布均匀,温升较低,提高了发电机转子绝缘性能,达到了机组增容10 MW的目的。     

淮安市建设苏北重要中心城市动力机制研究

在深入分析与探索可以促使淮安市中心城市建设持续推进和发展的主要动力因素基础上,运用系统动力学的理论和原理,构建由相关决策变量、增长极、动力变量和城市中心化水平等因素构成的概念模型,从而在理论和逻辑上理清淮安市中心城市建设的动力机制问题,并可作为政府部门决策参考及后续研究基础。     

继电保护算法中数字滤波器设计暂态响应问题

在电力系统发生故障后,数字式继电保护中的数字滤波器的暂态响应速度将影响到故障的切除时间。文章分析了超高压电力线发生单相接地故障时电流中的指数分量,估算出与实际录波电流相近的衰减系数。将该指数分量和基波分量的叠加信号作为研究对象,讨论了设计零、极点数字滤波器时的极点位置对于数字滤波器的暂态响应速度的影响。在设计数字滤波器时要根据输入信号的特点,兼顾滤波性能和响应速度选择适当的极点位置。     

Numerical simulation of 3D sulfate ion diffusion and liquid push out of the material capillaries in cement composites

This study treats 3D diffusion of sulfate ions into cement composite and simultaneous effects, such as microcapillary filling and subsequent liquid push out of them. A numerical algorithm provides account for various conditions specified at the interface, as well as possibility to model separate volume sections as inert fillers. Cases discussed illustrate the capabilities of the proposed model and those of the algorithm designed to study diffusion and liquid push out for specimen complex configuration. Results found allow for the assessment of the effects of convective and diffusion ion transfer. Comparison with experimental observations of corrosion processes that have more or less one-dimensional character prove the necessity to use a 3D mathematical model for a fuller clarification of sulfate corrosion.     

水泥预分解窑用碱性耐火材料的技术进展

介绍了水泥预分解窑的工作条件及其对窑衬耐火材料的影响 ,论述了目前世界水泥预分解窑的技术进展及其对窑用碱性耐火材料的要求 ,以及窑用碱性耐火材料的技术进展 ,分析了我国预分解窑生产技术的发展及预分解窑用耐火材料的发展 ,指出了中国预分解窑用耐火材料近期的发展趋势