Synthesis and characterization of soluble polyimides containing trifluoromethyl groups in their backbone

A series of polyimides were synthesized from 2,2‐Bis(3,4‐dicarboxyphenyl)hexafluoropropane, 2,2‐bis(3‐amino‐4‐hydroxyphenyl)‐hexafluoropropane, and 4,4′‐oxydianiline by chemical imidization. The effects of the diamine ratios on the properties of the films were evaluated through the study of their thermal, electrical, and morphological properties. All the polymers exhibited better solubility in most of the organic solvents and hence were easily processable. Polyimides with more 2,2‐bis(3‐amino‐4‐hydroxyphenyl)‐hexafluoropropane exhibited better solubility and a low refractive index, which is highly desired for microelectronic applications. The dielectric constant and birefringence were strongly dependent on the fluorine content. With an increase in the fluorine substitution, both the dielectric constant and birefringence decreased. All the polymers exhibited high thermal stability (>400 °C). The absence of crystalline melting in differential scanning calorimetry and broad wide‐angle X‐ray diffraction patterns revealed the amorphous nature of the polymers, which was due to the presence of bulky CF₃ groups and hinged ether linkages of the diamine component. The residual stress values decreased with an increase in the 4,4′‐oxydianiline content, and the results were in agreement with the dielectric constant. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4303–4312, 2004     

超短脉冲超强激光与固体靶相互作用中高能离子的产生

 用2D3V PIC粒子模拟方法得到了超短脉冲超强激光与固体靶相互作用中高能离子产生的图像，并对其机理进行了研究。在靶前后表面都观察到了高能离子的产生，并诊断了离子能谱。模拟结果表明，在靶前表面所产生的高能离子，角分布较大，在向靶内输运过程中会损失能量；在靶后表面产生的高能离子，定向性很好，能获得很高的能量。模拟得到的离子能量和实验观测结果在量级上相符。     

The First and Facile Synthesis of (±) Syringaresinol

The first and facile synthesis of (±)syringaresinol was described.     

THE RELATIONSHIP BETWEEN PROJECTIVE GEOMETRIC AND RATIONAL QUADRATIC B-SPLINE CURVES

For two rational quadratic B-spline curves with same control vertexes, the cross ratio of four eollinear points are represented; which are any one of the vertexes, and the two points that the ray initialing from the vertex intersects with the corresponding segments of the twocurves, and the point the ray intersecting with the connecting line between the two neighboring vertexes. Different from rational quadratic Beeier curves, the value is generally related with the loeation of the ray, and the necessary and sufficient condition o5 the ratio being independent of the ray‘s loeation is showed. Alsn another cross ratio o5 the following four collinear points are suggested, i.e. one vertex, the points that the ray from the initlal vertex intersects respectivdy with the curve segmentt the line connecting the segments end points, and the line connecting the two neighboring vertexes. This cross ratio is concerned only whh the ray‘s location, butnot with the weights of the curve. Furthermore, the cross ratio is projective invariant under the projective transformation between the two segments.     

时滞种群模型的正周期解对所有正解的吸引性

建立了对数种群模型Ｎ′（ｔ）＝Ｎ（ｔ）｛ｒ（ｔ）－ａ１（ｔ）ｌｎ［Ｎ（ｔ）］－ａ２（ｔ）ｌｎ［Ｎ（ｔ－τ（ｔ））］｝的周期正解的存在性，并得到了正周期解对所有正解的吸引性．     

不可压缩流的集中消失现象

分别对二维和三维不可压缩流体给出了一个较为直观的集中消失现象的充分条件,即若与近似解序列相应的弱*亏损测度所集中的集合在位置空间上的投影的Hausdorff维数小于1,则近似解序列在L²中的弱极限是Euler方程的经典弱解.利用这个充分条件,验证了一个集中的例子.     

Vibrational spectrum of uridine obtained by means of nonresonant-background-free CARS spectroscopy

Received: 18 June 1996/Revised version: 3 January 1997     

处理原子-辐射场相互作用系统的变分方法

用Heisenberg-Weyl(简H-W)群直积SU(2)群上的相干态表述了原子-辐射场相互作用系统的非平衡态统计力学.引入一个新定义的含时分布函数,将非平衡态下密度矩阵所满足的von Neumann方程转化成可分离变量的偏微分方程,给出了方程的形式解,算符的平均值表示.本文还就便于作微扰展开的相互作用绘景作了讨论.     

采用MSDI严格角动量投影46Ti、48Cr形变HF谱

采用修正的表面δ相互作用(MSDI),以球形壳模型单粒子态作基矢,对fp壳层区偶偶核⁴⁶Ti、⁴⁸Cr进行形变Hartree–Fock(HF)计算,并用形变HF单粒子态构造Slater行列式波函数,即形变HF内禀态,然后对其实施严格角动量投影程序,得到比较合理的结果.