高能超声作用下数种金属基复合材料的制备及机制

利用高能超声振动制备了A l/陶瓷, ZA 22/陶瓷(粒子平均直径2L) ,A l/P b (Pb 粒子直径< 25L) 和A l/F eA l₃等金属基复合材料, 弥散相在基体中有良好的分布均匀性。依据超声波对熔体作用时的空化和声流效应, 讨论了上述数种复合材料的制备机制。试验结果显示, 该项技术在制备数类金属基复合材料方面具有广泛的适用性。     

退火对Cu50Zr42Al8非晶合金电阻的影响

采用惠更斯电桥法和X射线衍射技术测试了Cu50Zr42Al8块状非晶合金在不同温度(500~600℃)保温20min和550℃保温不同时间(10~60min)条件下的电阻值与结构变化。研究发现,Cu50Zr42Al8块状非晶合金的电阻值在接近晶化温度Tx的515~520℃温度区间附近增加得较快,呈现出电阻极大现象,且随着退火温度的升高和保温时间的延长,电阻值均呈现出先增大后减小的变化趋势。     

Effect of heat treatment on the mechanical properties of FeCoZrWB bulk metallic glass

A Fe61Co10Zr5W4B20 bulk metallic glass (BMG) with a diameter of 2 mm was prepared by using copper mould suction casting. The X-ray diffraction (XRD), differential scanning calorimetry (DSC), micro-hardness and compression tests were adopted to investigate the structure, thermal stability, especially, the effect of heat treatment on the micro-hardness and compression strength of this BMG. The BMG exhibits micro-hardness of about 1 207 Hv and compression fracture strength of about 1 707.6 MPa. After being annealed below the onset of crystallization temperature, the micro-hardness almost keeps constant. But after being annealed above the peak of crystallization temperature, the micro-hardness increases firstly and then declines gradually with the elongation of annealing time. However, annealed for the same period of time, the micro-hardness will increase with the rise of annealing temperature, while the compression fracture strength will apparently decrease.     

移动电话资费管制的研究

伴随着中国电信行业,特别是移动电话用户数量的高速发展和有效市场竞争格局的初步建立,移动电话资费的调整、改革与管制等问题成为近几年社会各界关注的焦点.本文从电信管制理论出发,分析和介绍了电信资费管制理论的演进过程,进而对中国电信市场特别是移动电话资费的管制实践进行了系统研究,深入地分析了中国建立的新的移动电话资费管制体系,并对未来移动电话资费管制的发展趋势作了展望.     

Effect of High-energy Ball Milling on Synthetic Reaction in Al-TiO2-C System

High-energy ball milling has a great influence on the temperature characters of synthetic reaction in Al-TiO2-C system by changing the size,distribution state and wet ability of reactants.Reaction temperature characters（reaction ignition time,ignition temperature time.the maximum temperature and temperature rising rate）were changed by different milling time.The longer the milling time.the earlier the reaction.the quicker the temperature rise and the higher the maximum temperature.When the milling time exceeded 10 hours,the reactivity of reactants was so high that the synthetic reaction could take place at 850℃ directly without a long time pretreatment at 670℃.The microstructure of synthetic composites became uniform and the reinforced particles（TiC and α-Al2O3）became fine with milling time increasing.     

拓宽摩托车汽油机排气系调谐转速范围的研究

本文采用加装排气调谐腔的方法，拓宽了摩托车用二冲程汽油机排气系统的调谐转速范围，有效地改善了发动机在中低速区的性能。     

我国涉外企业避税与反避税问题探讨—兼议由于外汇调剂导致的外商避税

本文从产生国际避税的一般原因出发,结合我国涉外企业税法及会计制度的现状,具体分析了我国涉外企业避税的若干形式,最后提出了反避税的若干对策,以规范我国涉外企业的纳税行为,维护我国的主权和经济利益。     

预退火温度对Cu基块状非晶玻璃转变及晶化的影响

采用差示扫描量热（Dsc）分析方法测定了Cu50Zr42Al8块状非晶合金在不同温度（350～450℃）预退火4h后的玻璃转变温度Tg、起始晶化温度Tx、晶化峰值温度Tp和玻璃转变过程中的比热容变化。结果表明：预退火处理试样的玻璃转变温度Tg、玻璃转变比热变化ΔCp，g随退火温度的升高呈现逐渐增加的趋势，而其起始晶化温度Tx和晶化峰值温度Tp随退火温度的变化不明显。并利用结构弛豫理论分析了预退火温度对玻璃转变和晶化的     

Properties of well aligned SWNT modified poly (methyl methacrylate) nanocomposites

The PMMA/SWNT composites with good uniformity, dispersion and alignment of SWNT were fabricated in a stretching process. The semidried mixture was stretched along one direction at a draw ratio of 50 before it was dried, and then folded along the same direction stretching repeatedly for 100 times. The TEM and SEM observation demonstrated that SWNT in the PMMA/SWNT composite tend to align in the stretching direction. The electrical conductivity and the mechanical properties of composite rise with the increase of SWNT concentration, composite films showed higher conductivity and higher mechanical draw ratios along the stretched direction than perpendicular to it. The TGA revealed that embedding the SWNTs into the PMMA matrix also improves the thermal stability of the composite.     

一种改进的Montgomery阶梯算法及其实现

提出了利用Montgomery阶梯算法实现快速模幂运的两种方案.第一种是将每个时钟周期内乘法和平方并行执行,且使用2×2正交变换器选择输出,使Montgomery阶梯算法简单、高效;第二种是使用循环展开技术将循环数减少一半,且只需要一半的时钟,运算效率得到更大的提高.