Studies on high density polyethylene (HDPE) functionalized by ultraviolet irradiation and its application

The structure and properties of high density polyethylene (HDPE) functionalized by ultraviolet irradiation at different light intensities in air were studied by electron analysis, FTIR spectroscopy, contact angle with water, differential scanning calorimetry and mechanical properties measurement. The results show that oxygen‐containing groups such as C?O, C—O and C(?O)O were introduced onto the molecular chain of HDPE following irradiation, and the rate and efficiency of HDPE functionalization increased with enhancement of irradiation intensity. After irradiation, the melting temperature, contact angle with water and notched impact strength of HDPE decreased, the degree of crystallinity increased, and their variation amplitude increased with irradiation intensity. Compared with HDPE, the yield strength of HDPE irradiated at lower light intensity (32 W m^?2 and 45 W m^?2) increases monotonically with irradiation time, and the yield strength of HDPE irradiated at higher light intensity (78 W m^?2) increases up to 48 h and then decreased with further increase in irradiation time. The irradiated HDPE behaved as a compatibilizer in HDPE/polycarbonate (PC) blends, and the interface bonding between HDPE and PC was ameliorated. After adding 20 wt% HDPE irradiated at 78 W m^?2 irradiation intensity for 24 h to HDPE/PC blends, the tensile yield strength and notched Izod impact strength of the blend were increased from 26.3 MPa and 51 J m^?1 to 30.2 MPa and 158 J m^?1, respectively. Copyright © 2003 Society of Chemical Industry     

微机械热对流倾角仪温度补偿技术研究

介绍了微机械热对流倾角仪的工作原理和结构设计,利用有限元分析软件,计算了在不同倾斜状态下二维密闭腔中点热源引起的对流场和温度场,提出了环境温度对热对流倾角仪影响的模型。根据仿真结果,在电路中增加了加热丝恒定温度控制电路,建立了基于软件的环境温度补偿算法,实现了对温度影响的补偿。经测试,环境温度从-40℃变化到60℃时,倾角仪0°输入的温度稳定性为0.07°,10°输入的温度稳定性为0.02°。     

不锈钢管道坡口加工的新方法

对于不锈钢管及合金钢管坡口的加工,采用以往的加工方法切割出来的坡口一般参差不平、比较粗糙,难于打磨平整。使用LGK空气等离子切割机和磁力管道切割机的组合加上一定的辅助手段,改善了不锈钢管及合金钢管的坡口加工效果,使加工出来的坡口像碳钢管一样平整,更加容易打磨组焊。文章介绍了这一新方法所用的设备、材料、切割原理以及操作过程。     

摩擦换向抽油机悬点运动分析计算

摩擦换向抽油机采用开关磁阻电动机或变频调速电动机,其特点是可以频繁双向旋转,带动摩擦轮正反转,实现光杆的上行下行。该抽油机运动特点与游梁式抽油机运动特点有较大区别,文章分析了摩擦换向抽油机的运动特点,给出了该机悬点位移、速度、加速度的计算方法。     

基于USB总线的虚拟频谱分析仪设计

文章详细介绍了基于USB总线的虚拟频谱分析仪的设计过程。该仪器使用嵌入式混合处理器MC56F8323来实现动态信号的实时采集、频谱分析和数字滤波等功能。处理结果由USB2．0接口芯片CY7C68013上传至PC机．以完成数据显示、存储、绘制图形等功能。其中，CY7C68013工作于Slave FIFO模式，以实现与MC56F8323间的数据传输。该系统可同时对两路动态信号进行实时谱分析，每路采样频率高选500kHz。     

动力环境网络监控精细管理

叙述动力环境运行质量分析管理，包括故障管理，性能管理和专题分析管理，以动力环境网络监控细致八微、言之有据的月度分析管理实例展现了其精细管理的效果。     

农村通信如何"突围"

农村通信作为农村地区信息化的基础，对于全面建设小康具有特殊的重要地位。介绍了我国农村通信的发展现状，分析了农村通信发展的困难压其原因，最后对农村压边远、欠发达地区通信的均衡震展提出了一些建议。     

Alumina-supported catalysts for propane oxidative dehydrogenation from mixed VXM(6−X)O19 (M=W, Mo) hexametalate precursors

γ-Al₂O₃ supported vanadium oxides were modified by tungsten and molybdenum oxides in order to improve dispersion and selectivity towards olefins in propane oxidative dehydrogenation (ODH). Both vanadium–tungsten and vanadium–molybdenum catalysts were obtained by adsorption of mixed isopolyanions (VW₅O₁₉⁵⁻, V₂W₄O₁₉⁴⁻, VMo₅O₁₉⁵⁻ and V₂Mo₄O₁₉⁴⁻) from aqueous solutions. The isopolyanion solutions were characterized by UV-Vis and ⁵¹V NMR spectroscopy. Vanadium, vanadium–tungsten and vanadium–molybdenum precursors and catalysts were also characterized by UV-Vis (diffuse reflectance) and solid state ⁵¹V NMR spectroscopy. An improved selectivity to propene in the presence of tungsten and molybdenum in VO_x/γ-Al₂O₃ was observed and attributed to dilution of vanadium by tungsten or molybdenum oxides on the γ-Al₂O₃ surface.     

Scale-effects on mean and standard deviation of the mechanical properties of condensed matter: an energy-based unified approach

The size effects on the mean values of the mechanical properties of condensed matter and on the related variances are analysed by means of a unified approach based on the multiscale character of energy dissipation. In particular, the scaling law for fragmentation energy density is obtained taking into account the self-similarity of fragments. It is based on a generalization of the three classical comminution laws that has been performed to evaluate the energy dissipation, computing volume and surface area of the particles for one- two- and three-dimensional fragmented objects. The result is general and can be applied to different fractal energy dissipation mechanisms, e.g., plasticity. Based on this approach, the scaling laws for mean and standard deviation values of the main mechanical properties of materials can be derived, like Young's and shear elastic moduli, ultimate normal and shear stresses and strains, fracture energy and toughness.     

WC/Cu复合材料制备及其高温性能

用机械合金化法结合冷变形，制备了WC／Cu复合材料，研究了冷变形后复合材料的组织特征和高温退火时韵性能变化。结果表明：烧结后的材料经冷变形，组织呈显著纤维状，WC颗粒弥散分布，密度明显提高，达到理论密度的99．2％；复合材料经600～900℃高温退火，强度和硬度略有下降，塑性则有大幅提高；900℃退火时未发生明显的再结晶，界面结合良好；所制备的WC／Cu复合材料有优良的综合性能。