Behavior of hollow clay brick masonry walls during fire. Part 2: 3D finite element modeling and spalling assessment

In the first part of this work [1], the fire behavior of masonry walls made with hollow fired-clay bricks was investigated experimentally. Several complex mechanisms occurred during firing are analyzed and identified. In particular, in cases of load-bearing walls, the local spalling of bricks is considered as an important factor governing the fire performance of masonry walls.In this second part, fired-clay masonry is investigated by theoretical approach with the finite element method in order to predict its behavior and its performance under fire exposure. For this purpose, a 3D numerical simulation is conducted with paying a particular attention to the spalling risks of alveolus bricks.     

Influence of dynamic strain aging pre-treatment on the low-cycle fatigue behavior of modified 9Cr–1Mo steel

The influence of dynamic strain aging (DSA) pre-treatment on the low-cycle-fatigue (LCF) behavior of modified 9Cr–1Mo steel was investigated at 550 °C. The DSA pre-treatment reduces the fatigue life, which is reflected on the fracture surface as multiple crack initiation. The samples pre-treated by DSA have higher peak tensile stress and positive mean stress effects, which is responsible for the lifetime reduction. The DSA pre-treatment does not change cross-slip mechanisms during mechanical cycling, compared without DSA process, but results in accelerating the microstructure transformation from lath to cells with low dislocation densities, which reduces the number of cycles to failure.     

不同花生油对月饼饼皮面团特性及月饼品质的影响

旨在通过改变油脂来提升广式月饼的品质，以市售压榨一级花生油（PO，高温压榨）、市售压榨精制高油酸花生油 (HO，高温压榨)、低温压榨高油酸花生油（RO，经脱胶处理）、低温压榨高油酸花生油（CO，未脱胶处理）为油脂原料来制作月饼，探究了4种花生油的品质差异，及其对月饼饼皮面团动态流变学特性、水分分布、质构特性的影响，以及对广式月饼理化特性和感官评分的影响。同时，对月饼饼皮面团特性与月饼品质进行了Pearson相关性分析。结果表明：低温压榨花生油在酸值、过氧化值和氧化稳定性方面均优于高温压榨花生油；相比于普通花生油，高油酸花生油的油酸含量较高，而亚油酸含量大幅减少；RO制作的面团与PO制作的面团相比弹性模量和黏性模量均显著降低，损耗因子显著增加，且PO制作的面团最大曲率时间最长，CO制作的面团最大曲率时间最短，不同花生油制作的面团质构特性不存在显著差异；RO制作的月饼感官得分最高，品质最好；面团黏性模量、最大曲率时间与月饼硬度呈显著正相关，面团最大曲率时间与月饼感官得分呈显著负相关。综上，低温压榨高油酸花生油可以改变月饼饼皮面团的流变学特性和水分分布，并对最终产品的感官品质具有一定的改善作用。     

Influence of the compaction process on the air void homogeneity of asphalt mixtures samples

The effectiveness of laboratory compaction methods, for reproducing asphalt mixtures specimens with the same characteristics as on the actual building site, remains relatively unknown. The present paper is aimed at investigating the variability in air void content, therefore in compaction level, of three asphalt mixture types: a continuously-graded mix, an open-graded sandy mix, and a gap-graded asphalt. Several types of compactors are tested and the influence of sample dimensions and compaction axis vs. the main sample axis regarding air void homogeneity are studied using gamma-ray measurement. This study shows that for the studied materials, the samples cored in the plate are the most homogeneous, the ones produced by gyratory compaction yield scattered results but rather homogeneous samples can be obtained by respecting geometry criteria for the samples to be produced, and by sawing the edges where the compaction is the least efficient.     

A lateral flow immunoassay for measuring ochratoxin A: Development of a single system for maize,wheat and durum wheat

A quantitative lateral flow immunoassay for the detection of ochratoxin A (OTA) in cereals has been developed. The ready-to-use device includes a nitrocellulose membrane on which capturing reagents are immobilized in spatially confined zones and a conjugate pad on which the antibody labelled with gold nanoparticles is pre-adsorbed. Stabilization of gold labelled antibodies and blocking of non-specific interactions of the nitrocellulose membrane were obtained by using 1% ovalbumin. This, combined with the use of PEG in the extraction of OTA from cereal samples, allows us to level the matrix effects caused by various cereals (maize, wheat and durum wheat). The immunochromatographic assay developed includes a rapid and very simple treatment of samples, which, in addition, does not involve the use of organic solvents and allows the quantitative determination of OTA with limits of detection as low as 1.5 μg kg^?1. The coefficients of inter–assay variations are below 20%, with recoveries which ranged from 87 to 119%. Fifteen maize samples, four wheat and six durum wheat samples were extracted with the aqueous medium and analysed by the developed assay. A good correlation was observed (y = 0.99 x + 0.18, r² = 0.982, n = 25) when data was compared with that obtained through a reference method.     

Effect of nano-metal particles on the fracture toughness of metal–ceramic composite

A theoretical model is proposed to study the influence of nano-metal particles (NMPs) on the fracture toughness of metal–ceramic composites (MCC). In the framework of the model, the crack tip intersects the grain boundary of the NMPs. Stress concentration at crack tip initiates edge dislocations which makes a shielding effect on the crack and leads to fracture toughness of the MCC. The dependence of critical crack intensity factors on grain size of the NMPs was calculated. The calculation suggested that the existence of the NMPs lead to an increase of critical crack intensity factors by 14%.     

基于GPRS的车辆监控系统技术研究

为了对危险品运输,客运、货运、工程车辆等特殊行业的车辆定位跟踪,采用了GPS定位系统和GPRS通信技术实现了车辆实时监控系统;实现了以GPRS通信技术作为信息传输载体在车载终端,监控中心进行数据通信,GPS定位和WebGIS技术实时展示车辆信息;该系统具有通信速度快、通信格式扩展性强、通信可靠性高,客户端对车辆的控制性强,前端使用Web页面展示车辆状态和位置,系统无需安装,用户使用便捷等特点。     

水下传感器网络路由协议研究

现有水下传感器网络路由协议都属于地理路由协议,需要知道各个节点的水下三维位置信息,从而导致大量水下通信,难以有效延长网络生存时间。本文深入分析了现有研究的不足,提出一种基于深度信息与能量均衡的水下路由协议,只需要节点深度信息,节点间通信量极少;设计了协议的算法,并提出了空洞处理对策。     

基于VST的电力系统电压稳定分岔分析

概述了非线性动力系统分岔理论,介绍了基于MATLAB的电压稳定分析工具箱(Voltage Stability Tool-box,VST)。运用VST对IEEE-5节点系统在几种不同控制参数变化模式下进行了静态和动态分岔点的搜索,获得了比较满意的结果,验证了非线性的分岔理论在电压稳定分析中的相关结论。