烃基五甲氧羰基环戊二烯的合成

五甲氧羰基环戊二烯(简称PMCPH)(1)以富烯形式(2)和各种金属生成M-O结合的络合物,但早年及Bruce近期工作表明,当PMCP^θ的银衍生物烷基化时,得到的是一个和环上碳连结的取代产物。     

聚氯乙烯接近玻璃化转变温度时的蠕变行为研究

利用动态力学分析仪,详细研究了小应力作用下聚氯乙烯（PVC）接近玻璃化转变温度（63℃）时的短期蠕变性能．根据Struik-Kohlrausch (SK)方程及Struik移位方法,分析了物理老化对PVC瞬时蠕变柔量的影响,并提出了基于多松弛机制的新模型定量描述初始蠕变柔量、松弛时间和形状因子．结果表明:SK方程虽可表征不同老化时间下PVC的蠕变性能,但通过Struik移位方法却无法获得理想的主曲线,且初始蠕变柔量、松弛时间、形状因子和蠕变率均受物理老化显著影响,并在双对数坐标下随老化时间呈明显的非线性变化;新模型不仅揭示了物理老化控制参量的演化规律,而且极好地预测了PVC在物理老化进程中的高温蠕变行为．     

用阻尼最小二乘法解梯形薄板的大挠度弯曲问题

本文以双重三角级数为试函数，用配点法建立残值方程，并用阻尼最小二乘法求解，研究了分析周边简支可动梯形薄板的几何非线性弯曲问题，并给出两个算例，由计算结果显示，效果良好且工作量较少，本文的计算结果可直接用于工程。     

Creep performance of PVC aged at temperature relatively close to glass transition temperature

In order to predict the mechanical performance of the polyvinyl chloride(PVC) at a high operating temperature,a series of short-term tensile creep tests(onetenth of the physical aging time) of the PVC are carried out at 63 C with a small constant stress by a dynamic mechanical analyzer(DMA).The Struik-Kohlrausch(SK) formula and Struik shifting methods are used to describe these creep data for various physical aging time.A new phenomenological model based on the multiple relaxation mechanisms of an amorphous polymer is developed to quantitatively characterize the SK parameters(the initial creep compliance,the characteristic retardation time,and the shape factor) determined by the aging time.It is shown that the momentary creep compliance curve of the PVC at 63 C can be very well fitted by the SK formula for each aging time.However,the SK parameters for the creep curves are not constant during the aging process at the elevated temperatures,and the evolution of these parameters and the creep rate versus aging time curves at the double logarithmic coordinates have shown a nonlinear phenomenon.Moreover,the creep master curves obtained by the superposition with the Struik shifting methods are unsatisfactory in such a case.Finally,the predicted results calculated from the present model incorporating with the SK formula are in excellent agreement with the creep experimental data for the PVC isothermally aged at the temperature relatively close to the glass transition temperature.     

稀土五甲氧羰基环戊二烯基配合物的合成和性质

取代环戊二烯和未取代环戊二烯均能和金属生成相应的η~5-型茂金属物.例如五甲基环戊二烯基的过渡金属、镧系和锕系金属、五苯基环戊二烯基镥等均已合成.但是Bruce报道,五甲氧羰基环戊二烯,HC_5(CO_2Me)_5(简作Hpmcp),却不生成相应的η~5型茂金属物.已报道许多M(pmcp)_x(M=IA,IB,IIA,IIB,过渡金属)都是水溶性的在空气中极为稳定的物质.Bruce对这些化合物的物性,光谱性质和X衍射结构分析的结果,认为由于五个强吸电     

Experimental study on injection-locked Ti:sapphire lasers

An injection-locked Ti:sapphire laser is developed,with injection locking achieved using the Pound-DreverHall technique.By measuring the dependence of output power on the pump power with various Ti:sapphire laser parameters,we experimentally studied the influences of the ring cavity length,the focal length of the pump-laser mode-matching lens,and the output-coupler transmission on the threshold and slope efficiency.The dependence of the output power on the master laser power is also investigated.The present study provides a guideline for developing a Ti:sapphire laser with high slope efficiency and low threshold.