Specification and site control of the permeability of the cover concrete: The Swiss approach

It is recognized that most damage to reinforced concrete structures is caused by insufficient durability rather than by low strength. In most cases, the quality and thickness of the cover concrete (“covercrete”) determine the service life of the structure. Since the quality of the covercrete is influenced, not only by the mix composition, but also by the placing and curing conditions, it is appropriate to measure the achieved properties on the structure rather than just on separately cast specimens. Swiss Standard SIA 262 on “Concrete Construction” recommends checking the “impermeability” of the cover concrete on site. With that aim, a non‐destructive method to measure the air‐permeability on site has been standardized (SIA 262/1 Annex E). A team of Swiss experts was appointed by the Swiss Federal Highway Administration (ASTRA) to prepare recommendations for specifying, measuring, and assessing the conformity of the air‐permeability kT. This paper describes these recommendations covering: (a) specification of limiting values of kT as function of the exposure class; (b) sampling of the measurement points; (c) testing (including suitable temperature and moisture conditions); (d) evaluation of conformity with specified values; (e) expected impact on service life.     

Molecularly imprinted polymers by phase inversion technique for the selective recognition of saccharides of biomedical interest in aqueous solutions

The purpose of this work was the preparation and characterization of polymeric membranes for the selective recognition of saccharides using molecular imprinting technology associated with phase inversion. A system able to bind saccharides with high selectivity is particularly important in the pharmaceutical sector, since some of these compounds are constituents of molecules which can exert serious toxic effects even at very low concentrations. Two polymeric matrices were prepared using poly(ethylene‐co‐vinyl alcohol) copolymers, with an ethylene molar content of 32% and 44%, and were imprinted with two different saccharide molecules: maltose and 2‐keto‐3‐deoxy‐d ‐manno‐octulosonate (KDO). Matrices imprinted against maltose and KDO showed an easy template extraction, high binding capability and satisfactory selectivity, particularly for the matrix with an ethylene molar content of 44%. © 2017 Society of Chemical Industry     

网络入侵检测系统中的漂移检测

目前基于机器学习的入侵检测系统大都建立在入侵数据始终保持统计平稳的假设之上,无法应对攻击者有意改变数据特性或新型攻击方式的出现,而导致的检测率下降的状况.对于上述问题,即攻击漂移,提出了加权Rényi距离的检测方法.在KDD Cup99数据集上的实验证明,Rényi距离可以有效地增强检测效果;在检测到漂移后,通过重新训练模型可以使得对攻击的识别率显著提高.     

有理二次Bézier形式共轭双曲线段的几何计算

考虑有理二次Bézier形式的相互共轭的双曲线的控制顶点之间的关系,给定表示一段双曲线的标准型有理二次Bézier曲线,目标是求出它的共轭双曲线上相应段的控制顶点。首先给出共轭双曲线段的自然定义;接着通过参数变换,将有理二次Bézier形式和一般参数形式进行转换,并把这种转换对应到矩阵,以给出所求控制顶点的显式表达;最后,给出表达式的几何意义,即共轭双曲线段的控制顶点可由原双曲线的控制顶点通过两次线性插值得到。     

一类双参数三次Bézier曲线的形状分析

为了分析清楚形状参数对一类双参数三次Bézier曲线形态的影响及实现其对该曲线形状的调控,利用包络理论与拓扑映射的方法对一类双参数三次Bézier曲线进行了形状分析,明确了形状参数对曲线的影响,画出了曲线的形状特征分布图,得出了曲线上有奇点、拐点和曲线为局部凸或全局凸的充分必要条件,这些条件完全由控制多边形的相对位置表示,并进一步讨论了形状参数对曲线形状的影响。     

基于Bézier曲线的两平行线间缓和曲线构造

利用五次 Bézier 曲线,构造了一条含形状参数的两平行线间满足 G2连续的缓和曲线。这条曲线在 t=1/2含有唯一的曲率极值点。利用形状参数可以方便地控制曲率极值的大小和调节曲线的形状。     

我国成品油管道相关技术进展及展望

近年来,我国成品油管道技术发展迅速,成品油管网已初具雏形。着重介绍了成品油管道技术在混油处理、调度、运行和完整性管理等方面的工程以及理论进展情况,并结合国内外管道发展现状及趋势,给未来我国成品油管道技术的进一步发展、管网系统成熟化提供参考。     

10 000 t/d回转窑液压挡轮装置的优化设计

结合中国中材国际工程股份有限公司设计的某10000t/d熟料生产线的回转窑挡轮装置,介绍了挡轮装置的优化设计,其中创新设计了不同与以往1个挡轮的3个挡轮的设置;对其挡轮装置的结构也作了优化,采用了3组轴承,使挡轮受力更加合理,寿命延长。2012年该10000t/d回转窑装备被评为科技进步二等奖,至今已应用于国内外多条生产线,均取得了良好的业绩和效果。