Investigating the effect of hydrophobic structural parameters on the thickening properties of HEUR associative copolymers

Hydrophobically modified ethoxylated urethanes (HEUR) associative copolymers are prepared through the hydrophobic modification of polyethylene glycol based polyurethanes. These types of thickeners are categorized as anionic associative thickeners. To investigate the effect of structure of the hydrophobic groups on the thickening properties, three different hydrophobic groups were selected. These groups were comprised of cetyl alcohol (16 carbons), dodecyl alcohol (12 carbons) and a cyclic group such as cyclo hexanol. These functional groups were substituted on the identical prepolymers made from H₁₂MDI and polyethylene glycol. Here, three different urethane associative polymers containing hydrophobic segments and different hydrophobic groups were synthesized. The viscoelastic characteristics of all the samples were determined using a cone and plate rheometer. The viscosities of the examined HEUR samples showed both Newtonian and non-Newtonian behaviours (shear thinning and thickening) for the explored shear rates window. The steady shear viscosity results were interpreted using the theories by Raspaud [Macromolecules 27 (1994) 2956] and Semenov [Macromolecules 28 (1995) 1066]. The Cox-Merz rule happened to be applicable to these systems for the various hydrophobic ends and concentrations at lower shear rates indicating typical associative polymer behaviour. The cyclic end groups did not show viscoelasticity for the frequencies window explored. The zero shear viscosity increased by almost two orders of magnitude from HEUR-cyc to HEUR-dod and by four orders of magnitude from HEUR-cyc to HEUR-cet. The intermediate shear thickening was only observed for the concentrated HEUR-cet samples.     

Fraction of H-bonded segments of N-ethylpyrrolidone,oligomeric and polymeric vinylpyrrolidone adsorbed from CHCl3 on silica measured by IR spectrometry

The adsorption of N-ethylpyrrolidone (NEP), oligomeric and polymeric vinylpyrrolidone (OVP, PVP) on silica (Aerosil 200) from CHCl₃ solution is investigated by IR spectrometry. The influence of the annealing temperature of the silica on the adsorbed amount and on the fraction of adhered segments was studied. The dependences of the amount adsorbed on solution concentration result for NEP in a Langmuir isotherm for OVP and PVP in high affinity isotherms. The fraction of adhered H-bridged carbonyl groups determined by compensation procedures, the fraction of surface SiOH groups occupied and the multiple interaction quotientQ show different dependences on the amount adsorbed for the measured adsorptives, indicating different interactions of the monomeric segments with the surface groups. This behaviour is explained by comparing the amount adsorbed in saturation with monolayer capacities, surface concentration of SiOH groups and frequency shifts. A splitting of the band of the bound carbonyl groups in a double peak was observed with OVP and PVP, referring to an additional interaction of polymer segments neighboured to specifically bound segments.Herrn Professor Dr. Robert Kerber zum 60. Geburtstag gewidmet.     

Material differences of auditory source retrieval: Evidence from event-related potential studies

Two event-related potential experiments were conducted to investigate the temporal and the spatial distributions of the old/new effects for the item recognition task and the auditory source retrieval task using picture and Chinese character as stimuli respectively. Stimuli were presented on the center of the screen with their names read out either by female or by male voice simultaneously during the study phase and then two testa were performed separately. One test task was to differentiate the old items from the new ones, and the other task was to judge the items read out by a certain voice during the study phase as targets and other ones as non-targets. The results showed that the old/new effect of the auditory source retrieval task was more sustained over time than that of the item recognition task in both experiments, and the spatial distribution of the former effect was wider than that of the latter one. Both experiments recorded reliable old/new effect over the prefrontal cortex during the source retrieval task. However, there existed some differences of the old/new effect for the auditory source retrieval task between picture and Chinese character, and LORETA source analysis indicated that the differences might be rooted in the temporal lobe. These findings demonstrate that the relevancy of the old/new effects between the item recognition task and the auditory source retrieval task supports the dual-process model; the spatial and the temporal distributions of the old/new effect elicited by the auditory source retrieval task are regulated by both the feature of the experimental material and the perceptual attribute of the voice.     

音乐厅音质设计

音乐厅音质设计除了和其他有音质要求的建筑一样满足一些共同要求外,本文就其音质设计在体型设计、声扩散处理和演奏台设计等方面进行了探讨．体型设计将影响直达声、早期友射声和混响声在时间和空间上的分布．较宽频率范围的声扩散程度是音质优美的关键．演奏台则主要是为乐队各声部提供良好的平衡     

Polymer science applied to biological problems: Prediction of cytotoxic drug interactions with DNA

It is taken for granted in the polymer world that the fundamental thermodynamic insights of Hansen solubility parameters (HSP) can be used to predict solvent/chemical interactions with polymers. The same principles should apply equally to bio-molecules interacting with that key polymer, DNA. A necessary (but not sufficient) condition for a drug to be cytotoxic is that it penetrates cell walls and be (thermodynamically) compatible with the core of the DNA polymer. The HSP of 9 cytotoxic drugs conform well to the basic HSP principle that “like (cell walls, DNA) attracts like (all 9 drugs)”. A correlation is not proof. But at the very least, HSP offer a fecund methodology for making predictions not only of how single molecules might interact with biological polymers, but how mixtures of chemicals could be more potent than the individual components. It is predicted, for example, that alcohols would provide synergism with many chemicals with their mixtures having higher affinity for the DNA bases than the individual components.     

基于SVM图像分割方法的自动导盲系统

传统的自动导盲系统直接将图像映射为声音模式,使得声音模式中包含很多背景信息,干扰了盲人对图像的理解.针对这一问题,提出了一种基于SVM图像分割方法的自动导盲系统.首先使用SVM算法将摄像头采集到的环境图像分割为目标和背景两部分,并用灰度变换增强目标消除背景.然后将目标映射为声音模式.实验表明,经过训练,盲人能够理解系统合成的声音模式,从而形成对目标形状、尺寸以及位置的感知.     

极限论在中学数学中的应用

数学分析中最基本的理论是极限理论,本文用极限论证明了中学数学中一些重要的公式.     

大跨度卸载对下卧盾构隧道影响的数值分析

结合哈大客专沈阳站房改造工程研究了大跨度卸载对下卧既有盾构隧道管片及接头的影响.为准确反映管片环向接头在附加荷载作用下的张开、错位等情况,基于Flac3D建立三维模型,运用嵌入式梁单元模拟了螺栓接头,并针对实际工程中坑底堆载保护措施进行了数值计算.结果表明,既有隧道在2倍卸载宽度范围内发生隆起变形,最大隆起量为1593mm,最小纵向曲率半径为28248m,并且管片环向接头在附加荷载作用下产生的错位量及张开量分别为067,137mm,各项控制指标均满足工程要求.表明坑底堆载措施能保证盾构管片及接头在上部基坑施工期间的安全性.     

基于优化听觉模型的机床工况识别方法研究

准确识别机械制造设备工况,对判断设备的当前健康状态、设备平稳性,以及科学评价设备操作人员的工作效率具有重要意义.运用遗传算法优化后的ZCPA(zero crossings with peak amplitudes)听觉模型对设备的振动信号进行特征提取,通过与各种工况标准听觉谱计算相关性,以识别设备当前工况.优化后的ZCPA听觉模型计算简洁,能够模仿人耳听觉系统对输入信号进行提取,弥补传统听觉模型适应性差、识别率低的缺陷,同时使不同工况特征差异性增大,提高设备工况识别率.以某种普通车床为例,车床振动信号经过优化后的ZCPA模型处理后,工况识别率达到95%以上.     

少数民族民歌研究的艺术人类学意义

研究少数民族民歌具有重要的艺术人类学意义。它有利于新兴的艺术人类学摆脱传统美学对精英艺术的过度关注和对民间艺术、群众性艺术漠视的狭窄思想束缚,拓宽美学研究的视野和领域,使美学得到民间审美经验和大众审美经验的启发、汲取边缘文化的活力和来自听觉艺术的审美经验,从而弥合美学与草根文化之间的裂痕,激活中国美学对本土艺术与现实文化的理性思考。