压电陶瓷表面硅钙复合膜的制备与表征

采用溶胶-凝胶法制备了硅钙复合溶胶，并在压电陶瓷表面制备硅钙复合膜，以改善水泥基压电陶瓷复合材料界面。确定了溶胶配比，研究了陈化、低温热处理和硅烷偶联剂对覆硅钙复合膜压电陶瓷接触角、压电和介电性能的影响。结果表明，硅钙复合溶胶中Ca与Si摩尔比>0.2时不利于成膜；提高陈化温度和延长陈化时间可明显减小硅钙复合膜的接触角；硅钙复合膜层数最佳为3层，烧结温度不大于160℃；加入微量硅烷偶联剂可有效改善膜层开裂。制备的硅钙复合膜接触角最小为27°，亲水性好。      

A novel fast distance relay for series compensated transmission lines

This paper presents a fast distance relay for series compensated transmission lines based on the R–L differential-equation algorithm using the theory of equal transfer process of transmission lines. The measuring distances based on the proposed algorithm can fast approach the actual value of fault distance when a fault occurs in front of the series capacitor. When a fault occurs behind of the series capacitor, the fault loop, including the series capacitor, does not match the R–L transmission line model, so the measuring distances fluctuate severely. Based on this, the relative position of the fault with respect to the series capacitor can be judged effectively according to the fluctuation range of the measuring distances, and the accurate fault location can be obtained fast. A variety of PSCAD/EMTDC simulation tests show that the new relay has fast operating speed and high accuracy when applied to the long series compensated transmission lines.     

浅谈混凝土防冻泵送剂行业标准以及工程应用

《混凝土防冻泵送剂》行业标准已于2012年8月1日起实施。本文根据多年对防冻泵送剂的研究与应用,结合对该标准的学习和试用,从对《混凝土防冻泵送剂》标准的认识以及防冻泵送剂产品的工程应用两个方面提出了几个观点。     

海外施工中应关注的测量坐标系问题(待续)

目前世界各国采用的测量坐标系各不相同且同一国家内也常并存几种测量坐标系统,给相关的土木工程施工活动(比如土建及交通施工等)带来了很多不便,分析整理目前国际现行的各测量坐标系的基本情况及特点,给出了不同测量坐标系间坐标转换的基本原则和相关方法,为海外各种土木工程施工提供技术支持。     

寒冷地区混合钢结构住宅节能检测与分析

为了评价寒冷地区混合钢结构住宅的节能性能,通过对该地区典型钢结构住宅的调研,选取一幢具有代表性的混合钢结构住宅进行现场节能检测,根据实测数据计算围护结构传热系数和实际能耗,分析能耗影响因素、评价主要耗能部位的节能效果,检测结果表明:典型建筑仅达到节能50%,不满足现阶段节能65%的要求;混合结构中钢框架部分形成的热桥对整体热工性能产生较大影响;混合钢结构建筑常用的蒸压轻质混凝土墙板存在明显的热工缺陷。针对存在问题,提出相关热工设计建议。     

浅析涂装颗粒的防治

通过对涂装现场颗粒来源的分析,采取了一系列针对性的防治措施,取得了较为明显的实际改善,为实现涂装生产的无颗粒化作业提供了过程控制思路。     

A multi-factor comprehensive risk assessment method of karst tunnels and its engineering application

Bulletin of Engineering Geology and the Environment - The tunnel collapse, a large deformation of surrounding rock, water and mud inrush are the main geological disasters in the process of tunnel...     

On Dimensions of Linear Discrete Dimension-unbounded Systems

This letter investigates the variance of state dimensions of linear discrete dimension-unbounded systems, which are a class of cross-dimensional systems. First, the dimensional relationship of states, initial values and system matrices of some special cases is discussed. Then, for the general case, to directly calculate the transition time and state dimensions after the transition time, an algorithm is established on the basis of the iterative time, dimensions of initial values and system matrices. Finally, there is an illustrative example to show the effectiveness of these obtained results.

     

F−-Eu3+ charge transfer energy and local crystal environment in Eu3+ doped calcium fluoride

A series of CaF₂:xEu³⁺ (x = 0.01–0.05) phosphors were synthesized by coprecipitation and high temperature solid-state method. Three different F^--Eu³⁺ charge transfer (CT) bands in CaF₂:xEu³⁺ (x = 0.01–0.05) were detected through the PL spectra. Three local crystal environments (deformed O_h octahedron, C_3V, C_4V) were proposed in Eu³⁺ doped CaF₂. The broad peak at 277 nm is F^- → Eu³⁺ CT peak, in which Eu³⁺ ions located deformed O_h octahedron sites, the broad peak at 312 nm is due to Eu³⁺ ions situating at C_4v sites, also, Eu³⁺ ions with C_3v sites can make the F^- → Eu³⁺ CT produce a 38-nm redshift to 315 nm. Density functional theory (DFT) was performed to calculate the energy band gap(Eg) according to the three models. The calculation results consist with the experiment. The excitation peaks can be tuned in the same host through changing the local structure of Eu³⁺.     

扬州瘦西湖隧道湖东段基坑工程设计与实测分析

扬州瘦西湖隧道湖东段基坑全长580 m,宽度10.2～22.6 m,深度1.24～25.9 m,是典型的狭长且深度差异大的基坑工程。本工程作为扬州市重点城市规划项目,工期紧张,工程造价控制严格。针对基坑特点及周边环境特点,随着基坑深度的增加,依次采用地下连续墙、钻孔灌注桩+止水帷幕、SMW工法桩、水泥土搅拌桩挡墙、放坡作为围护结构形式,结合水平内支撑体系,达到了较好的支护效果。基坑工程支护系统设计方案的顺利实施为保证基坑安全、节省工程造价及实现预定的工期目标创造了有利条件。