Size Effects on the Mechanical Properties of Nanoporous Graphene Networks

It is essential to understand the size scaling effects on the mechanical properties of graphene networks to realize the potential mechanical applications of graphene assemblies. Here, a “highly dense‐yet‐nanoporous graphene monolith (HPGM)” is used as a model material of graphene networks to investigate the dependence of mechanical properties on the intrinsic interplanar interactions and the extrinsic specimen size effects. The interactions between graphene sheets could be enhanced by heat treatment and the plastic HPGM is transformed into a highly elastic network. A strong size effect is revealed by in situ compression of micro‐ and nanopillars inside electron microscopes. Both the modulus and strength are drastically increased as the specimen size reduces to ≈100 nm, because of the reduced weak links in a small volume. Molecular dynamics simulations reveal the deformation mechanism involving slip‐stick sliding, bending, buckling of graphene sheets, collapsing, and densification of graphene cells. In addition, a size‐dependent brittle‐to‐ductile transition of the HPGM nanopillars is discovered and understood by the competition between volumetric deformation energy and critical dilation energy.     

Matlab ActiveX技术在“数字信号处理”教学中的应用

针对"数字信号处理"教学中电子课件与Matlab之间的切换导致课堂衔接出现断点的问题,本文提出了利用Matlab ActiveX自动化服务器技术,使用户可以在PowerPoint电子课件中输入Matlab命令,现场显示计算结果或实时绘图。该方法实现了多媒体与Matlab计算软件的无缝链接,提高了课堂教学效果。     

Passive neighbor discovery with social recognition for mobile ad hoc social networking applications

Wireless Networks - Neighbor discovery is the cornerstone of the mobile social applications over mobile ad hoc networks. Most current neighbor discovery protocols adopt a carefully designed...     

一种基于背景减法和帧差的运动目标检测算法

针对帧差分法易产生空洞以及背景减法不能检测出与背景灰度接近的目标的问题,提出了一种将背景减和帧差法相结合的运动目标检测算法.首先利用连续两帧图像进行背景减法得到两种差分图像,并用最大类间与类内方差比法得到合适的阈值将这两种差分图像二值化,然后将得到的两种二值化图像进行或运算,最后利用图像形态学滤波得到准确的运动目标.实验结果表明,该算法简单、易实现、实时性强.     

LD泵浦Nd:YVO_4/KTP激光器晶体长度对输出的影响

利用四能级激光系统的速率方程 ,对激光二极管 (LD)纵向泵浦Nd :YVO4 /KTP腔内倍频绿光激光器激活介质和倍频晶体的长度对输出激光功率的影响进行了理论计算 ,给出了参数优化结果 ,分析了它的工作特性 ,得到与理论计算符合较好的实验结果。     

微电脑时控系统

介绍的微电脑时控系统主要是按学校、工厂、机关等单位的供电要求而设计的,以实现对电能及设备的合理应用,避免繁杂的工人操作,它以８０３１单片机为核心,通过键盘实现人机对话,可完成日在、电子表功能及实时控制功能。     

线性啁啾光纤光栅反射谱特性与啁啾量关系的模拟研究

从耦合模方程出发,利用传输矩阵法,模拟研究了线性啁啾光纤光栅的反射谱特性,给出了反射谱的３ｄＢ带宽、反射峰值、峰值波长处的色散和边带抑制率与啁啾量的关系曲线,并得到了啁啾量优化取值范围。     

啁啾光纤光栅的制备研究进展

对连续啁啾光纤光栅和阶跃啾光纤光栅的制备研究情况做了概述,并对各种制备方法的特点进行了简要分析。     

The experiment about a plane mirror cavity with dielectric tubes

This paper introduce the experiment about a new type of quasi-optic cavity Making a experimental model, measuring all parameters of the cavity, giving experiment results. It shows that theoritical research in reference[1] is correct Its results coincide with theory. At same time, it also indicates the cavity is hopeful device in MMW.     

暖气供热换热器开裂失效分析

某公司的CB300型暖气供热换热器于1994年开始使用,1999年11月发现发生锈蚀,多处起鼓包开裂,要求分析腐蚀及开裂原因。该换热器系瑞典进口,由不锈钢波纹薄板交叠铜钎焊而成。母材为Cr18Ni10奥氏体不锈钢,焊缝为纯铜。一次网为高温高压热水,水压力1.2MPa,水温12℃,Cl-为115～191mg/L,溶解氧4.2～8.7mg/L,pH6.65～8.32。二次网为用户取暖热水,水源为自来水或井水,其水质比一次网好。从一次网开裂面看,铜焊缝均已腐蚀开裂,残留在不锈钢板上的铜焊缝已失去紫铜光泽,变为黑灰色CuO,而且断口粗糙,而相对的不锈钢波纹板仍为银白色,但已发雾失光…