RADIATION GRAFT COPOLYMER OF ACRYLIC-ACID ONTO EVA

The structure of the radiation graft copolymer of acrylic acid onto EVA has been studied by infrared spectroscopy and XPS. It was found that along with the main peak C there is a photoelectron peak at 288.5 eV attributed to [GRAPHICS] group in XPS spectra and the content of its area in XPS increases with increasing of grafting degree of EVA. It was also found that hydrophilicity of EVA increases with the increase of grafting degree.

BETA-RELAXATION IN POLYIMIDES

A series of polyimides with different structures have been synthesized and studied by dynamic mechanical analysis. The results obtained indicate that the beta relaxation in polyimides is related to the rotation of rigid segment(s) of p-phenylene and imide groups around 'hinges' such as -O-, -CH2- and so on in diamines. It is noticed that two kinds of polyimides both with [GRAPHICS] imide groups have verv weak beta relaxation below the glass transition temperature. This phenomenon is due to the fact that the configuration of chains with the above imide groups hinders the rotation of the rigid segments in the chains.

CRITERION OF POLYMER POLYMER MISCIBILITY DETERMINED BY VISCOMETRY

The criteria of polymer-polymer miscibility determined by viscometry are reviewed, and a new criterion is proposed based on the classical Huggins equation and the Huggins coefficient K(m) in the blends. It was found that, in a ternary (polymer-A)-(polymer-B)-solvent system, [GRAPHICS] In the absence of strong specific interaction forces between molecules that would encourage aggregation and at sufficiently low concentration, the above equation can be written thus: [GRAPHICS] This equation can be used to determine the miscibility of polymer blends, when: alpha greater-than-or-equal-to 0 miscible, alpha < 0 immiscible. It is found that the new criterion is reasonable and suitable to predict polymer-polymer miscibility by the viscometry method.

A parametric method of retrieving ocean wave spectra from synthetic aperture radar images

A parametric method that extracts the ocean wave directional spectra from synthetic aperture radar (SAR) image is presented. The 180 degrees ambiguity of SAR image and the loss of information beyond the azimuthal cutoff can be overcome with this method. The ocean wave spectra can be obtained from SAR image directly by using iteration inversion mapping method with forward nonlinear mapping. Some numerical experiments have been made by using ERS-1 satellite SAR imagette data. The ocean wave direction retrieved from SAR imagette data is in agreement with the wind direction from the scatterometer data.

Asymptotic periodicity of the Volterra equation with infinite delay

For some species, hereditary factors have great effects on their population evolution, which can be described by the well-known Volterra model. A model developed is investigated in this article, considering the seasonal variation of the environment, where the diffusive effect of the population is also considered. The main approaches employed here are the upper-lower solution method and the monotone iteration technique. The results show that whether the species dies out or not depends on the relations among the birth rate, the death rate, the competition rate, the diffusivity and the hereditary effects. The evolution of the population may show asymptotic periodicity, provided a certain condition is satisfied for the above factors. (c) 2006 Elsevier Ltd. All rights reserved.

Asymptotic weighted-periodicity of the impulsive parabolic equation with time delay

The main aim of this paper is to investigate the effects of the impulse and time delay on a type of parabolic equations. In view of the characteristics of the equation, a particular iteration scheme is adopted. The results show that Under certain conditions on the coefficients of the equation and the impulse, the solution oscillates in a particular manner-called "asymptotic weighted-periodicity".

Structural studies on a novel fucogalactan sulfate extracted from the brown seaweed Laminaria japonica

A low molecular weight fucogalactan, obtained from the brown seaweed Laminaria japonica, was separated into three fractions (LF1, LF2 and LF3) by DEAE-Sepharose FF column chromatography. All three fractions contained predominantly fucose, sulfate group and galactose. The results showed that the main fraction LF2 consisted of L-fucose, D-galactose and sulfate at a molar ratio 6:1:9. Structural study on the LF2 was carried out by NMR spectroscopy. The backbone of LF2 was primarily (1 -> 3)-linked alpha-L-fucopyranose residues (75%) and a few (1 -> 4)-alpha-L-fucopyranose linkages (25%). The branch points were at C-4 of 3-linked alpha-L-fucopyranose residues by beta-D-galactopyranose unites (35%, molar ratio) or at C-2 of 3-linked alpha-L-fucopyranose residues by non-reducing terminal fucose unites (65%, molar ratio). Sulfate groups occupied at position C-4 or C-2, sometimes C-2, 4 to fucose residues, and C-3 and/or C-4 to galactose residues. The structure of LF2 was supposed as following: [GRAPHICS] (C) 2010 Elsevier B.V. All rights reserved.

Docking and molecular dynamics studies toward the binding of new natural phenolic marine inhibitors and aldose reductase

Phenolic marine natural product is a kind of new potential aldose reductase inhibitors (ARIs). In order to investigate the binding mode and inhibition mechanism, molecular docking and dynamics studies were performed to explore the interactions of six phenolic inhibitors with human aldose reductase (hALR2). Considering physiological environment, all the neutral and other two ionized states of each phenolic inhibitor were adopted in the simulation. The calculations indicate that all the inhibitors are able to form stable hydrogen bonds with the hALR2 active pocket which is mainly constructed by residues TYR48, HIS110 and TRP111, and they impose the inhibition effect by occupying the active space. In all inhibitors, only La and its two ionized derivatives La_ion1 and La_ion2, in which neither of the ortho-hydrogens of 3-hydroxyl is substituted by Br, bind with hALR2 active residues using the terminal 3-hydroxyl. While, all the other inhibitors, at least one of whose ortho-sites of 3- and 6-hydroxyls are substituted by Br substituent which take much electron-withdrawing effect and steric hindrance, bind with hALR2 through the lactone group. This means that the Br substituent can effectively regulate the binding modes of phenolic inhibitors. Although the lactone bound inhibitors have relatively high RMSD values, our dynamics study shows that both binding modes are of high stability. For each inhibitor molecule, the ionization does not change its original binding mode, but it does gradually increase the binding free energy, which reveals that besides hydrogen bonds, the electrostatic effect is also important to the inhibitor–hALR2 interaction.

基于逆向参数化的B样条曲面重建算法

目的解决B样条曲面重建问题中矩形拓扑网自动生成和参数化两大难点问题,提出一种基于逆向参数化的B样条曲面重建算法.方法首先构建基曲面,在基曲面上根据参数(u,v)进行采样,沿其法线方向进行数据的滤波和精简,求得参数(u,v)对应的精简点,然后对采样求取的精简点集进行B样条曲面拟合,该方法提供了B样条曲面重建的一个新思路.结果新算法突破了传统密集散乱点云数据的B样条曲面重建基本过程,采用与正向参数化相反的过程进行参数化,解决了B样条曲面重建问题中矩形拓扑网自动生成和参数化的难题;具体试验分析表明新算法不仅在参数化的同时完成了数据滤波和精简,而且在时间和迭代效率方面都具有优势.结论新算法避免了求取法线的迭代过程,并且可以较容易的实现矩形拓扑网的自动生成,新算法在自主开发的智能测量建模加工一体化装备中得到了应用验证.

外科手术计算机辅助导航技术

外科手术计算机辅助导航即利用计算机图形图像技术对放射影像学资料进行处理 ,重建二维或三维的医学图像模型 ,同时结合各种空间定位技术 ,在医师的双眼、手术工具及患者的头部之间建立一个实时的环路 ,实现手术过程中器械位置的实时或准实时显示。我们综述了外科手术计算机辅助导航系统的发展历史和研究现状 (重点阐述了其系统结构和关键技术 ,包括空间定位技术、图像处理与显示技术、系统配准技术、头部定位技术等 (最后给出了手术导航系统的发展趋势

非完整自主车基于圆轨迹的道路避障

本文就四轮非完整自主车提出了一种基于圆轨迹的道路避障策略。先将道路上的障碍按照障碍距离自主车的远近划分层次,使一个层次的障碍能在自主车视场中全部出现。然后给出基于圆轨迹的避障算法,即自主车沿由自主车出发位姿和子目标点确定的圆弧轨迹走行。在此之前推导四轮非完整车的运动模型为提出避障策略的基础准备。尽量减小自主车在走行过程中运动状态的改变,基于圆轨迹避障策略能够很好地满足这一要求。最后引入代价函数,给出对于此方法的评价,体现了本方法的优越性。

虚拟现实辅助机器人遥操作技术研究

本文以水下机器人的遥操作作业为应用背景 ,提出并实现了虚拟现实技术和视觉感知信息辅助机器人遥操作实验系统 .该系统使用了 CAD模型和立体视觉信息完成遥操作机器人及其作业环境的几何建模和运动学建模 ,实现了虚拟作业环境的生成和实时动态图形显示 .采用了基于立体视觉的虚拟环境与真实环境的一致性校正、图形图像叠加、作业体与环境位姿关系建立、基于网络的监控通讯等关键技术 .在这个实验系统中 ,操作人员可利用所生成的虚拟环境 ,在多视点、多窗口作业状态图形和图像显示帮助下 ,实时动态地进行作业观测与机器人遥操作与运动规划 ,为先进遥操作机器人系统的实现提供了经验和关键技术 .

并联机器人机床运动学正、逆解

基于一般ＳＴＥＷＡＲＴ机构研制的并联机器人机床是新一代智能化金属切削加工机床．然而，机床的运动学位置正、逆解呈强非线性，求解困难．出于机床精度的需要，本研究的模型样机在结构上采用了滚珠丝杠传动，因此又带来了关节运动耦合，导致机床运动学位置正、逆解求解更加复杂．利用运动学等效的原则，引入整机等效串联机构及分支等效串联机构，以等效广义坐标为中间变量建立机床运动学正、逆解求解迭代算法．仿真与控制实验表明，该算法具有收索速度快便于实际应用等特点。

非线性未建模不确定系统的自适应控制

讨论了非线性未建模不确定系统的自适应镇定问题。通过边界层次分析的方法，提出一和种简单的间接自适应控制方法。该方法克服了现有非线性自适应控制方法容易产生过渡控制的缺点。

基于运动耦合结构的并联机器人的运动学正逆解

根据运动学等效的原则，在并联机器人中引入等效串联机器人及分支等效串联机器人，以等效广义坐标为中间变量建立并联机器人运动学正道解求解算法。该算法能有效处理结构带来的运动耦合，并且规划的软件具有自动生成迭代初始点、避免多解性以及便于实际应用等特点，从而为并联机器人的结构设计与创新提供了理论支持。