Boundary elements analysis of adhesively bonded piezoelectric active repair

This paper presents the analysis of active piezoelectric patches for cracked structures by the boundary element method. A two-dimensional boundary integral formulation based on the multidomain technique is used to model cracks and to assemble the multi-layered piezoelectric patches to the host damaged structures. The fracture mechanics behavior of the repaired structures is analyzed for both perfect and imperfect interface between patches and host beams. The imperfect interface, representing the adhesive between two different layers, is modeled by using a “spring model” that involves linear relationships between the interface tractions, in normal and tangential directions, and the respective discontinuity in displacements. Numerical analyses performed on a cracked cantilever beam repaired by single and multi-layered patches are presented. It is pointed out that the adhesive deeply influences the performances of the repair as highlighted by an increasing of the repairing voltage values with respect to perfect bonding case.     

基于ARM和DSP空中运动目标实时跟踪系统研究

对空中目标物体实时跟踪目前主要采用雷达探测的方法,但时常会受到电磁场与电磁波的干扰,降低了探测的准确性,为解决此类问题,提出了一种基于空中视觉实时跟踪系统的解决方案.该方案适用于小范围空中动态物体的跟踪,包括动态目标的差值提取,二值图像的滤波和模板图像的实时更新,以及动态目标的特征提取、云台控制.为提高系统的准确检测性,提出了一种基于改进的动态模板匹配与帧间差分相结合的空中目标检测方法.该方法有效地解决了电磁场干扰、环境变化使动态目标无法捕捉的问题,根据实验表明,该系统能够很好地检测到空中动态物体,具有很好的鲁棒性、实时性和清晰度.     

一种优化的多视点视频编码预测结构

首先分析了JMVC的参考预测结构,利用1个Go P(Group of Picture)中不同时间层上的帧与其参考帧之间的相关度不同和不同时间层上的帧数目也不同的特点,提出了去除奇数视点最高和次高时间层的视点间预测,并增加偶数视点非关键帧的最低和次低时间层的视点间预测的预测结构。实验结果表明,提出的预测结构基本不影响视频质量,且表现出了更加出色的编码效率,编码的复杂度减少幅度高达15%,输出码率也有所减少,较好地改善了编码的实时性能。     

球型毫米波金属桁架天线罩研究

从球形毫米波天线罩的空间分块设计、金属桁架和连接节点设计、透波窗口设计以及安装架设方式等方面进行了详细论述,并通过一直径7 m、工作在20 GHz的金属空间桁架天线罩的设计实例和实验研究,证明文中所用方法行之有效,可推广应用于各种大型天线罩的电性能分析和选形设计。     

西宁曹家堡机场T2航站楼钢结构安装技术

西宁曹家堡机场T2航站楼钢结构工程具有气候环境恶劣、现场条件极为有限、桁架结构复杂、倾斜钢柱安装难度大、结构稳定性差等特点.根据工程总体施工计划和工程特点,屋盖钢结构采用分段拼装、原位安装的施工方案.重点介绍了起重机械配置方案、支撑格构架设计方案、钢柱和桁架的吊装方案、测量控制方案.实践证明,所采取方案保证了桁架安装满足要求.     

Seismic design and performance analysis of buckling‐restrained braced RC frame structures

Due to the stable hysteretic behavior, buckling‐restrained braces (BRBs) have been increasingly adopted in reinforced concrete (RC) frame structures to develop a dual structural system (BRB‐RCF). This study proposed an alternative strength‐based design approach that decomposes the dual BRB‐RCF system into two independent RC frame and BRB system using the BRB‐carrying story shear ratio. The design of RC frame is performed in an integrated manner by considering the BRB postyielding force demands. Three RC frames with five, 10, and 15 stories were employed as prototype structures, and seven story shear ratios ranging from 0.1 to 0.7 were used to generate a total of 21 structural modes. The material usage, maximum axial compression ratio of columns, and elastic interstory drift ratio were compared for different story shear ratios. Nonlinear dynamic analysis of the BRB‐RCFs subjected to 12 ground motions were carried out. The seismic response including the maximum interstory drift ratio, hysteretic energy dissipation ratio, and actual BRB‐carrying story shear ratio were systematically assessed for different design story shear ratios. Based on the considerations of material usage and seismic performance, it is suggested that the design BRB‐carrying story shear ratio should be in the range of 0.3 to 0.5.     

The Small Open Reading Frame-Encoded Peptides: Advances in Methodologies and Functional Studies

Small open reading frames (sORFs) are an important class of genes with less than 100 codons. They were historically annotated as noncoding or even junk sequences. In recent years, accumulating evidence suggests that sORFs could encode a considerable number of polypeptides, many of which play important roles in both physiology and disease pathology. However, it has been technically challenging to directly detect sORF-encoded peptides (SEPs). Here, we discuss the latest advances in methodologies for identifying SEPs with mass spectrometry, as well as the progress on functional studies of SEPs.     

半刚性端板连接多层钢框架地震反应的弹性时程分析

由于缺乏计算理论和方法,大多数半刚性节点按刚性节点进行设计,与实际情况相差很大.本文采用有限元分析的方法,将半刚性连接节点视为弹簧单元,通过通用有限元软件ANSYS建立有限元模型进行时程计算分析,研究了节点刚度对多层钢框架结构抗震性能的影响.计算结果表明,采用了半刚性连接的钢框架结构,相对于理想刚接的情况,结构的自振周期和振型都有很大变化,在地震作用下结构的底部剪力明显减小,动力响应变化很大.在钢框架分析和设计中,应考虑半刚性节点的影响.     

偏心支撑钢框架延性抗震设计探讨

偏心支撑钢框架结构体系是一种非常适合强震地区的抗震结构体系.国内外许多高层建筑采用了该结构体系,尤其在美国与日本的高地震烈度地区.国内外现行规范对该体系的设计均未能充分体现其良好的延性与耗能能力,但只有通过结构的延性设计才能使结构真正具有耗能能力.本文从不同支撑类型的刚度、高跨比、延性和双重体系探讨了支撑类型的选择与布置形式,分析了耗能梁长度与截面设计以及耗能梁与支撑、柱的连接形式对偏心支撑钢框架结构体系延性和耗能能力的影响,提出了偏心支撑钢框架结构体系延性抗震设计的建议与思路,为规范修订和工程应用提供一些参考.     

减小门式刚架中柱平面外计算长度的方法

门式刚架的中柱设计中,常因为平面外计算长度较大,所选实腹式截面无法满足平面外稳定验算,从而导致用钢量增加.文中针对设有吊车梁的门式刚架中柱,对3种设计方案进行比较,证明利用吊车梁设置隅撑,为中柱提供可靠侧向支承点,从而减小其平面外计算长度,该方法最经济实用.