Internal structure examination of lightweight concrete produced with polymer-coated pumice aggregate

In the construction sector, pumice is observed to be used in both structural and non-structural building elements. In this study, to produce a new kind of concrete, the aggregates are coated with three different polymers (Sonomeric1: SNMC, KB Pur 214: KBP and Polipol3455: PLP) that have multiple uses. The mineralogical-petrographical features of both polymer-coated and uncoated aggregates were examined, and SEM (Scanning Electron Microscope) and XRD (X-ray Diffraction) analyses were performed. Moreover, in the study, lightweight concrete elements with different dosages (300, 400 and 500) were produced by using polymer-coated and uncoated aggregates; and their internal structure examinations were performed and compressive strength values of 3, 7 and 28 days samples were investigated. As a conclusion; among the aggregate samples, it was determined that PLP-coated aggregates have a more porous structure than the other polymer-coated aggregates and KBP-coated aggregates could be used in lightweight concrete (500 dosage) production. It was also concluded that the compressive strength values of lightweight concrete elements produced with coated samples increased even more.     

Experimental behaviour of existing precast prestressed reinforced concrete elements strengthened with cementitious composites

Strengthening of reinforced concrete (RC) members by means of fibre reinforced polymers (FRP) has gained increasing importance in the last few decades. On the other hand the necessity of skilled labour, high costs and particularly the weak response under high temperature conditions represent critical issues for the effective application of this technique. The use of fibre reinforced cementitious matrix (FRCM) composites applied to RC members seems to be a promising technique since it combines cost economy and high performance. Despite the fact that a number of experimental investigations on strengthening of RC elements by means of fibre reinforced polymers (FRP) composites are available in the literature, very little information is available about fibre reinforced cementitious matrix composite (FRCM). Hence, the use of cementitious composites in strengthening of RC structures is strongly limited by the lack of design models, guidelines, and recommendations and by the few available experimental investigations.This work aims to better understand the behaviour of FRCM strengthened RC full-scale elements through experimental tests on precast prestressed double-T beams. In addition to investigating the experimental behaviour of an innovative and promising strengthening system, a further element of novelty of the work is that the tested beams belong to an actual existing industrial building, since the few experimental tests available in the literature are mostly related to small-scale and cast-in-place RC elements.     

Durability simulation of FRP bridge decks subject to weathering

Fiber Reinforced Polymer (FRP) composite panels are particularly attractive as bridge decks due to their high strength, low density, and durability, which are of importance in the bridge industry. Although the short term performance of FRP decks is satisfactory, the long-term performance under weather conditions still awaits future testimony and remains a major concern in their use as primary load bearing members. Since the load capacity and structural stiffness of FRP decks deteriorate over time at different rates, it is necessary to develop robust mechanics models to simulate the long-term performance of FRP deck structures subject to the combined effects of mechanical and environmental loading. To this end, a comprehensive mechanics framework has been developed, taking into account the critical deterioration rates of the FRP constituents. Such deterioration relationships were obtained by calibrating the accelerated laboratory durability test data with the in-service field measurements. Simulation results agree well with the 4-year performance data of a FRP-deck road bridge. Long-term validation data is, however, still needed.     

Reinforcement and quantitative description of inorganic particulate-filled polymer composites

Understanding the reinforcing mechanisms should be meaningful for preparation of new polymer composites. The reinforcing mechanisms of the inorganic particulate-filled polymer composites were analyzed and discussed in the present paper, and concluded several reinforcing theories on the basis of the previous studies, such as interfacial adhesion reinforcing theory, filler inducing crystallization reinforcing theory, filler frame reinforcing theory, and synergistic reinforcing effect theory. The reinforcing effects should be related closely to the filler shape and size, in addition to the filler concentration and dispersion in the matrix. Consequently, to describe accurately the reinforcing mechanisms of the composites, two or more reinforcing theories should be used for the actual composite system, and one of among them should be usually as the major reinforcing mechanism. Finally, the quantitative characterization of the reinforcement was described.     

18CrNiWA大型材冲击韧性的研究

本文通过对18CrNiWA大型材热处理工艺及性能试验结果的分析,研究了冲击韧性的影响因素,提出改进了工艺措施。     

基于分簇传感网的RSSD/TDOA协同定位方法

针对基于能量有限的分簇传感网实现对非配合辐射源的高精确度无源定位问题,提出了一种适用于传感网的接收信号强度差fRSSD）定位方法,并在其相关性能分析基础上提出了以RSSD定位为辅、到达时间差（TDOA）定位为主的两轮协同定位方案,即以RSSD定位结果作为目标位置初估计,并根据各簇在该初估计位置处的TDOA定位CRB,选择部分预期定位精确度较高的簇参与进一步的TDOA定位,最后通过对这些簇定位结果的加权平均得到最终的目标位置估计。仿真结果表明,相比基于GDOP的簇选择标准和定位融合方法,提出的改进措施提高了定位精确度,而RSSD／TDOA协同定位方案在保证较高定位精确度的同时,有效地减轻了网络负载,延长了网络生命周期,具有较好的工程应用前景。     

基于多LED的高精度室内可见光定位方法

针对可见光室内定位问题,该文基于接收信号强度(RSS)定位技术,提出一种利用多个LED发射端实现室内定位的方法,即MLED-RSS定位算法。该方法在充分考虑LED拓扑结构对定位性能影响的基础上,利用部署在室内的多个LED,合理选择其中3个LED作为发射节点,采用改进的三边定位法获得定位目标位置信息。定位算法可以有效地解决可见光定位存在的遮挡效应。仿真实验表明,MLED-RSS算法可以实现高定位精度。     

边缘惩罚层次区域合并SAR图像分割算法

该文利用方向边缘强度信息,建立一种新的边缘惩罚SAR图像分割模型,提出一种最小化该模型的层次区域合并算法。利用多方向比例边缘检测算子(MDRED)提取边缘强度信息,并结合分水岭变换获得高质量的初始过分割结果。利用多边形近似区域边缘,提取边缘的方向,将方向边缘强度映射(OESM)融入边缘惩罚中,获得惩罚强度与边缘强度呈反比的惩罚项。逐渐增大边缘惩罚项的强度,获得由图像特征驱动的层次区域合并算法。利用区域邻接图(RAG)表示图像分割,提高区域合并的速度。实验表明：该文方法与其它方法相比在性能和效率上都有优势,获得更好的分割结果。     

无卤素型挠性印制电路板材料

在制造挠性印制电路板用的挠性覆铜箔层压板的工艺过程中，为了提高线路图形用铜箔与绝缘基材聚酰亚胺薄膜的粘接性，研究开发了专用的表面处理技术和压制成型技术，制成了无卤素、两层结构型粘接性良好的挠性覆铜板；在线路图形表面的保护涂敷材料方面，研发了无机填料的处理技术，用少量的阻燃性填料即可使环氧树脂得出必要的阻燃性，保证了涂层的柔韧性：这两方面的技术促成了完全无卤素型印制电路板的产生。     

单星多波束天线下基于压缩感知的多目标干扰定位

针对卫星干扰处理中的多目标定位问题,该文提出基于压缩感知的定位方法.该方法利用目标的空间稀疏性,以及多波束天线在不同信号源方向上的增益不同,仅需要测量接收信号强度便可实现多个干扰的位置识别.研究结果表明,定位性能与节点分布、目标个数、波束覆盖半径、判决门限有关.在给定参数及原对偶内点算法下,该方法可实现1～4个干扰源的...