Characteristic lengths and the structure of salt free polyelectrolyte solutions. A small angle neutron scattering study

We have studied salt free semi dilute polyelectrolyte solutions by small angle neutron scattering. Specific labelling associated with an extrapolation method has allowed the separation of the form factor of a single polyelectrolyte chainS ₁(q) and the structure factorS ₂(q). Two lengths are deduced from these two factors: the persistence lengthb _t which characterizes the electrostatic interactions along the chain by a fitting ofS ₁(q) with calculation of the scattering function for a wormlike chain, and fromS ₂(q),q _m ^–1 which characterizes the interactions between chains. These two lengths vary in the same way with the concentration of polyions (b _t C _p ^–1/2 ,q _m ^–1 C _p ^–1/2 ) and a constant relation exists between them: only one length is then necessary to describe the structure of polyelectrolyte soltuion on this semidilute concentration range.Laboratoire Commun CEA-CNRS.     

Kinetic simulation of living carbocationic polymerizations. II. Simulation of living isobutylene polymerization using a mechanistic model

This paper discusses the kinetic simulation of TiCl₄--coinitiated living carbocationic isobutylene (IB) polymerizations governed by dormant-active equilibria, using a mechanistic model. Two kinetic models were constructed from the same underlying mechanism: one using a commercial simulation software package (Predici^®), and the other using the method of moments. Parameter estimation from experimental batch reactor data with Predici yielded a rate constant of propagation k_p = 4.64 × 10⁸ ± 2.75 × 10⁸ L/mol s, with no constraints imposed. This agrees with k_p data measured with diffusion clock and competition methods, but disagrees with kinetically obtained k_p values. Estimation of rate constants with Predici^® and the GREG parameter estimation software packages revealed that it was difficult to estimate the complete set of kinetic parameters, due to correlated effects of the parameters on model predictions. Estimability analysis confirmed that some of the strongly correlating parameters could not be estimated simultaneously using the available experimental data. Using k_p = 6 × 10⁸ ± 2.75  × 10⁸ L/mol s measured by Mayr, and using starting estimates of other rate constants defined by experimentally observed correlations, yielded the set of rate constants required for the simulations. Both kinetic models yielded good agreement with experimental data, with the exception of M_w values that slightly diverged from the theoretically predicted ‘M_w−M_n = constant’ relationship. This may indicate the occurrence of a minor side reaction. However, the k_p/k₋₁ = 17.5 L/mol average run length calculated from measured and simulated MWD data agrees well with earlier literature values.     

杨树无性系木材纤维长度和宽度的株内变异

对7个杨树无性系纤维形态的测定研究表明，前6、8、11年内7个无性系纤维长度在胸径处的变异不显，最大的I-69杨比最小的95杨纤维长度增加了6．6％。纤维长度和宽度在7个无性系中从髓心到树皮的径向变异均表现为显增加，但宽度增加没有长度增加显。纤维形态在株内纵向变异规律为：纤维长度在同一年轮内不同高度间的变异均是树干基部较小，随树高的增加纤维长度逐渐增加，树高增加到5．6m后纤维长度达到最大，随后波动较小，至17．6m又开始下降；纤维宽度在树干基部到3．6m的范围内较大，而超过3．6m后开始减小。回归分析表明，纤维长度与年轮及树干高度的关系可用多项式描述。树木生理年龄是影响纤维形态的一个主要因子。     

面向自主机器人的实时彩色视觉系统

设计开发了一种新型的机器人实时彩色视觉系统，以及基于颜色的实时分割和识别软件系统，采用即插即用型的USB接口数字摄像头，简化了系统的使用和维护，首先把输入的彩色图像从RGB空间转换到YIQ颜色空间，提取出和颜色有关的IQ平面的信息；然后根据目标颜色在IQ平面里分割图像，再对图像进行游程编码，并从游程编码中提取出有效的图像信息；最后通过TCP／IP接口将视觉信息发送给机器人控制系统，为了抑制光强变化的影响，采用了一种阈值学习方法，实验结果表明，整套系统具有很高的实时性和较好的识别效果。     

焊接孔长度对钢框架梁-柱刚性节点性能的影响

对焊接孔长度扩大的钢框架梁－柱刚性节点进行了空间非线性有限分析。分析结果表明，焊接孔长工的扩大显著地降低了梁－柱连接面处的对接焊缝和焊接孔切角端开裂以及翼缘脆性破坏的可能性，但过长的焊接孔也会导致梁侧向稳定的丧失。     

柔性桩荷载传递机理研究

运用弹性半空间无限体的明德林解签和浅基础中的分层总和法，桩土间滑动采用刚塑性模型，分析了柔性桩的荷载传递规律，提出了柔性桩有效长度的概念，计算了结果经与实测资料对比，证明是正确的。     

炮孔中堵塞材料运动规律及堵塞长度研究

本文分析了炮孔堵塞材料的作用机理,受力情况及在炮孔中运动速度规律.根据爆破理论.得到了炮孔堵塞材料的最大长度和最佳长度.     

投影带变换对长度变形的影响

文章对晋城矿区由矿区独立坐标系改用部定3°带平面坐标系后引起的边长影响进行了分析和计算,提出了应采取的对策及相关注意事项。     

跳频扩频系统的两种混沌扩频序列

介绍了跳频扩频通信系统的原理，给出了两种利用Chebyshev混沌映射产生数字混沌序列的方法，验证比较了其特性，结果均可满足扩频码的要求，同时搭建混沌跳频扩频系统进行了仿真，仿真结果证明了方法的正确性．     

微分变换在压杆稳定问题中的应用

通过一个例子说明微分变换法在压杆稳定问题中的应用方法。