铝合金活塞CO2激光焊接中功率密度的影响

使用3 kW横流CO2气体激光器焊接某型汽车空调压缩机用铝合金活塞,研究了激光功率密度对铝合金活塞焊接质量包括焊缝形状、焊缝中气孔数量、气孔尺寸大小、焊缝抗拉强度、焊缝成分及焊缝显微硬度的影响。研究结果表明,由于铝合金对CO2激光的反射非常强烈,低功率的CO2激光只能对铝合金进行热传导焊接,焊接深度不能满足铝合金活塞的要求,应当尽量提高激光器的输出功率,才能实现铝合金的深熔焊。在用现有3 kW横流CO2激光器对铝合金活塞的激光焊接中,高功率焊接改善了铝合金活塞的焊接质量。     

DAMAGE MECHANISM ANALYSIS OF 2D 1× 1 BRAIDED COMPOSITES UNDER UNIDIRECTIONAL TENSION

Coupling with the periodical displacement boundary condition, a representative volume element （RVE） model is established to simulate the progressive damage behavior of 2D 1×1 braided composites under unidirection- al tension by using the nonlinear finite element method. Tsai-Wu failure criterion with various damage modes and Mises criterion are considered for predicting damage initiation and progression of yarns and matrix. The anisotropic damage model for yarns and the isotropic damage model for matrix are used to simulate the microscopic damage propagation of 2D 1×1 braided composites. Murakami＇s damage tensor is adopted to characterize each damage mode. In the simulation process, the damage mechanisms are revealed and the tensile strength of 2D 1 × 1 braided composites is predicted from the calculated average stress-average strain curve. Numerical results show good agreement with experimental data, thus the proposed simulation method is verified for damage mechanism analysis of 2D braided composites.     

衬底温度对共溅射法制备的Cu2ZnSnS4薄膜晶粒生长的影响

研究了衬底温度对采用Cu2ZnSnS4靶和Cu靶共溅射制备的Cu2ZnSnS4薄膜晶粒生长的影响。采用拉曼光谱、X射线能量色散谱仪、扫描电子显微镜和紫外 可见 近红外分光光度计对在不同衬底温度条件下制备的Cu2ZnSnS4薄膜 的元素比例、形貌以及光学带隙进行了表征与分析。结果表明制备的Cu2ZnSnS4薄膜晶粒生长遵循不同规律。室温衬底条件下制备的Cu2ZnSnS4薄膜晶粒生长遵循两步法,导致颗粒尺寸和元素分布不均;而在120~200 ℃衬底温度条件下制备的Cu-Zn-Sn-S预置层在溅射过程中已有Cu2ZnSnS4晶粒形成,这些晶粒在后续硫化生长过程中起到形核点的作用, 促进了Cu2ZnSnS4晶粒的长大与元素的均匀分布。随着衬底温度的升高,Cu-Zn-Sn-S预置层及由此制备出的Cu2ZnSnS4薄膜的结晶性变好,Cu2ZnSnS4薄膜的带隙先升高后减小至1.55 eV。     

基于灰色关联分析的中国二氧化碳排放量影响因素分析(英文)

如何实现中国碳减排目标已经成为当前的研究热点,为完成减排目标首先要研究中国CO2排放量的影响因素。首先利用灰色关联分析方法选择与中国CO2排放量灰色关联度最高的3个变量:能源消费量、第三产业比重、外贸依存度。协整检验表明中国CO2排放量和3个影响因素之间存在长期协整关系,本文同时建立中国CO2排放量的长期协整方程和短期误差修正模型。运用误差修正模型得到的中国CO2排放量预测值与真实值的比较和得到的统计值均表明本文建立的模型有较好的解释能力和信度。     

基于FPGA的实时视频图像采集与存储系统(英文)

针对传统视频采集存储系统存在的问题,设计了一种以FPGA为核心的实时视频图像采集与存储系统。采用模块化设计方法,通过Verilog编程实现了视频解码A/D配置,视频图像采集逻辑控制和图像存储逻辑控制等功能模块;采用IDE接口硬盘作为存储介质,FAT32文件系统作为图像存储形式来记录实时图像。实验结果表明,系统具有实时性强、集成度高、存储能力强及易于扩展等优点。     

微波烧结ZrO_2/LaNbO_4-MoSi_2复合陶瓷耐磨性研究

文章测定了无润滑条件下ZrO2/LaNbO4-MoSi2纳米复合陶瓷的磨损特性曲线,并对其磨损特征进行了分析.结果表明,ZrO2/LaNbO4-MoSi2纳米复合陶瓷的磨损特征以粘着磨损为主.第二相纳米ZrO2颗粒和LaNbO4颗粒的加入能明显改善MoSi2陶瓷的耐磨性.     

9Cr13Mo3Co3Nb2V马氏体不锈钢微观组织研究

对不同热处理状态下的微观组织结构进行了研究.采用物理化学相分析技术研究了9Cr13Mo3Co3Nb2V退火、淬火以及最终热处理制度下析出相的类型、含量及组成结构式.并用X射线小角散射(SAXS)(small angle x-ray scatter)分析了不同热处理制度下析出相在不同粒度间隔中的质量分布.结果表明:①9Cr13Mo3Co3Nb2V钢退火状态的组织为珠光体 碳化物(M23C6,MC和M6C),淬火状态组织为马氏体 碳化物(M23C6和MC),最终热处理状态的组织为回火马氏体 碳化物(M23 C6,MC和M3C);②小颗粒(≤300nm)碳化物析出相粒度分析表明,9Cr13Mo3Co3Nb2V钢退火、淬火状态析出相平均粒度相差不大,粗大颗粒较多,而最终热处理状态的析出相平均粒度明显减小,且细小颗粒比例较大.     

纳米孔ZrO_2气凝胶的制备研究

以硝酸氧锆(ZrO(NO3)2.5H2O)为原料,采用水热法和超临界干燥技术制备了ZrO2气凝胶.利用SEM和BET等测试手段对所得气凝胶的结构和孔特征进行表征,分析了孔隙分布情况和孔结构.结果表明:气凝胶具有典型的纳米孔隙结构,孔径5＜Dp＜60nm,比表面积达916.5m2/g,孔分布均匀.对ZrO2凝胶过程进行了探讨.     

Preparation and Mechanical Properties of Glass Coats with High Temperature Radar Absorber

BaO-La2O3-B2O3 (BLB) glass, suitable to be used as a sealing between metals, was chosen to be the binder in preparing glass coats on the Ti-alloy substrate. The SiCN nano-powder was introduced as the filler for the absorbing coat because it is considered to be a good high temperature absorber. The effect of the coating temperature and coating time on the tensile strength of the glass coat was investigated and the proper coating parameters to get good mechanical properties were determined. In addition, the effects of the SiCN content on the tensile strength of the absorbing coat were also discussed. Results show that it is possible to prepare the glass coat using the BLB glass as a binder. That the coat formed at 730 ℃ for 30 min has the best tensile strength witnesses 730 ℃, 30 min to be the proper parameter to prepare the glass coat. The BLB glass coat without SiCN powder possesses good tensile strength and the introduc-tion of the SiCN absorber into the glass coat will lower the tensile strength. As the SiCN content increases, the tensile strength of the absorbing coat decreases, which could be attributed to the aggregation of SiCN in the coats.     

一种基于二维傅里叶变换的数字水印算法

数字水印技术是信息隐藏的重要应用，广泛应用于数字媒体的版权保护，有很大的发展前景。介绍了一种基于二维离散傅里叶变换的数字水印算法，并得到了较好的鲁棒性和不可见性。