Synthesis,characterization, and curing kinetics of novel ladder‐like polysilsesquioxanes containing side‐chain maleimide groups

Two ladder‐like polysilsesquioxanes (LPS) containing side‐chain maleimide groups have been synthesized successfully by reacting N‐(4‐hydroxyphenyl)maleimide (HPM) with LPS containing 100 mol % of chloropropyl groups (Ladder A ) and 50 mol % of each methyl and chloropropyl group (Ladder B ). HPM was synthesized by reacting maleic anhydride with 4‐aminophenol, and the resulting amic acid was imidized using p‐toluenesulfonic acid as a catalyst (Scheme 1 ). The LPSs were characterized by Fourier transform infrared (FTIR), ¹H nuclear magnetic resonance (NMR), proton‐decoupled ¹³C NMR, ²⁹Si NMR, wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Characterization indicated that these polymers had ordered ladder‐like structures with possible defects. These polymers were soluble in common solvents at ambient temperature, which suggested that they were not crosslinked. Both the polymers and the HPM were cured, and their kinetics were followed by dynamic DSC. The Ozawa and Kissinger methods were used to calculate activation energies for curing. Curing increased the temperature at which both 5% weight loss and maximum rate of weight loss were observed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4036–4046, 2004     

Mutual influence of the morphology and capillary rheological properties in nylon/glass‐fiber/liquid‐crystalline‐polymer blends

Nylon‐6/glass‐fiber (GF)/liquid‐crystalline‐polymer (LCP) ternary blends with different viscosity ratios were prepared with three kinds of nylon‐6 with different viscosities as matrices. The rheological behaviors of these blends were characterized with capillary rheometry. The morphology was observed with scanning electron microscopy and polarizing optical microscopy. This study showed that although LCP did not fibrillate in binary nylon‐6/LCP blends, LCP fibrillated to a large aspect ratio in some ternary blends after GF was added. The addition of 5 wt % LCP significantly reduced the melt viscosity of nylon‐6/GF blends to such an extent that some nylon‐6/GF/LCP blends had quite low viscosities, not only lower than those of neat resins and nylon‐6/GF blends but also lower than those of corresponding nylon‐6/LCP blends. The mutual influence of the morphology and rheological properties was examined. The great reduction of the melt viscosity was considered the result of LCP fibrillation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1619–1627, 2004     

Effect of α‐cyclodextrin on the crystallization of poly (3‐hydroxybutyrate)

The effect of α‐cyclodextrin (α‐CD) on the crystallization behavior of poly(3‐hydroxybutyrate) (PHB) was investigated with polarized optical microscopy, differential scanning calorimetry, and wide‐angle X‐ray diffraction. We found that the addition of α‐CD can greatly accelerate the crystallization of PHB and that α‐CD has a potential not only to enhance the nucleation but also to accelerate the crystallization of PHB. Compared to a conventional nucleation agent, such as talc, α‐CD is a natural product and has many advantages because it is environmentally friendly and safe to humans. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3461–3469, 2004     

0.8W/80K直线驱动斯特林制冷机的研制

介绍了一种 0 .8W/ 80 K分置式斯特林制冷机。该制冷机采用当前国外先进的直线电机驱动 ,双活塞对称布置结构。该制冷机已通过军品所要求的环境试验 ,输入功率小于 4 0 W(DC)情况下 ,其 +6 0℃高温环境下制冷量≥ 0 .5 W/ 80 K ,带载 0 .5 W工况下 MTTF已突破 2 0 0 0小时。文中主要论述了其工作原理、结构特点、试验情况。     

二氟甲烷分子3a1和2b2轨道的电子动量谱

借助电子动量谱学结合量子化学理论和其他方法可以给出轨道电子在整个空间的分布信息,由此给出电子运动的完备描述[1,2 ] .清华大学电子动量谱学实验室近几年已成功地对甲烷[3] 、异丁烷[4 ] 、环戊烷[5] 、二乙酰等[6 ] 分子的轨道电子动量分布进行了测量.我们利用第二代电子动量谱仪首次对CH2 F2 分子3a1和2b2 轨道的电子动量谱进行测量,并与理论计算结果作了比较.同时还计算了坐标空间和动量空间中电子在x - y平面的密度分布.电子动量谱学最基本的过程是(e ,2e)反应,即电子与靶粒子碰撞而发生的电离过程.而对于(e ,2e)反应,含有大量信…     

薄膜外延生长的计算机模拟

以Cu膜为例，用Monte-Carlo算法模拟了薄膜生长的随机过程，并提出了更加完善的模型.在合理选择原子间相互作用计算方法的基础上，考虑了原子的吸附、在生长表面的迁移及迁移所引起的近邻原子连带效应、从生长表面的脱附等过程.模拟计算了薄膜的早期成核情况以及表面粗糙度和相对密度.结果表明，随着衬底温度的升高或入射率的降低，沉积在衬底上的原子逐步由离散型分布向聚集状态过渡形成一些岛核，并且逐步由二维岛核向三维岛核过渡.在一定的原子入射率下，存在三个优化温度，成核率最高时的最大成核温度Tn、薄膜的表面粗糙度最低 关键词： Monte-Carlo算法 计算机模拟 薄膜生长     

多目标优化发射层析算法在等离子体场光谱诊断中的应用

提出一种基于多目标优化原理的发射光谱层析(EST)图像重建新算法MCIRT.通过计算机数值 模拟，考察了该算法对非对称发射系数场分布的重建效果.结果表明，与传统层析算法相比 ，MCIRT算法具有收敛快，重建精度高的优势，适合于非完全数据情况下的等离子体发射系 数场重建，并且实时性更好.作为一个应用实例, 运用谱线相对强度法重建了自由电弧等离 子体的三维温度及粒子数密度分布. 关键词： 等离子体诊断 图像重建     

p型导电掺In的SnO2薄膜的制备及表征

采用溶胶-凝胶提拉法成功地制备了p型导电掺In的SnO2薄膜.x射线衍射测试结果表明，掺In的SnO2薄膜保持SnO2的金红石结构.吸收谱测试结果表明，掺In的SnO2禁带宽度为3.8eV.霍尔测量结果表明，空穴浓度与热处理温度有很大的关系，525℃为最佳热处 理的温度.铟锡原子比在0.05—0.20范围内，空穴的浓度与In的含量有直接的关系，并随In含量的增加而增加. 关键词： SnO2 溶胶-凝胶法 p型导电     

喷气Z箍缩内爆等离子体的雪铲模型

 在喷气Z pinch内爆等离子体研究中，雪铲模型是一种常用的、比较简单的物理模型。根据实验中提供的电流波形，负载线质量和初始半径，可以通过雪铲模型来估算内爆到心的时刻。根据一维运动方程和不同构形下的解析解以及部分实验结果相结合，讨论了雪铲模型的适用范围。数值计算的内爆时间和实验（Gamble II, Double EAGLE, BLACKJACK 5）测量值符合得较好。结果表明，雪铲模型在喷气Z pinch实验的负载优化设计研究中是很有参考价值的方法。     

能动反射镜低频像差补偿能力分析

 采用Algor软件包并利用有限元法对37单元能动反射镜低频误差补偿能力进行了分析计算，确定了镜面厚度8mm，驱动器间距46mm，极头直径12mm等能动反射镜制造的关键参数。通过计算机仿真分析证明，基于这些参数所设计的能动反射镜可以对低频误差进行有效校正，校正精度的均方根值小于等于λ／８，从而可以为能动反射镜的制造提供理论依据。