CPE-g-HEA/TDI热塑性弹性体的制备和性能研究

采用氯化原位接枝法合成主链为氯化聚乙烯(CPE)、支链为丙烯酸-2-羟基乙酯（HEA）的官能化接枝聚合 物(CPE-g-HEA),制备CPE-g-HEA/2,4-二异氰酸甲苯酯（TDI）热塑性弹性体,并对其性能进行研究。结果表明, CPE-g-HEA/TDI热塑性弹性体的物理性能较好;与溶液法产物相比,共混法CPE-g-HEA/TDI热塑性弹性体的强度 较大、相对分子质量较小、相对分子质量分布较宽,热行为基本无变化;共混法CPE-g-HEA/TDI热塑性弹性体的反 应温度应控制在60～70℃,共混次数(即打三角包次数) 为150次时拉伸强度较高、80次时拉断伸长率较高,HEA/TDI摩尔比为1/0.5时拉伸强度较高。

氯化原位接枝反应制备羟基官能化CPE—结构表征

以高密度聚乙烯(HDPE)为基体,采用气-固氯化原位接枝反应合成了以氯化聚乙烯(CPE)为骨架聚合物、丙烯酸-2羟基乙酯(HEA)为支链的接枝共聚物.反应中不需要加入任何引发剂,以氯自由基引发接枝及氯代反应,得到羟基官能化CPE接枝聚合物.并用1H-NMR,FT-IR,GPC及X-射线衍射等对接枝共聚物的结构进行了表征.

氯化原位接枝反应合成酐化CPE及结构表征

本硕士论文主要工作是利用氯化原位接枝反应对高密度聚乙烯（HDPE）进行氯化及醉基化。对上述反应体系的反应机理，产物的化学结构、链结构、反应条件对MAH接枝率（GD％）的影响以及物理机械性能等进行了详细的讨论。采用FT-IR和~1HNMR方法对氯化原位接枝反应的配化产物CPE-g-MAH进行了表征。二者均证明了MAH单体接枝到氯化聚乙烯主链上，证实了氯化原位接枝反应的可行性。并用~1HNMR，结合EI-Ms电喷雾质谱表征了氯化原位接枝共聚物CPE-g-MAH的链结构。反应过程中，主链及支链均被氯化。氯化原位接枝共聚物CPE-g-MAH凝胶含量的测定结果表明，在氯化原位接枝过程中没有交联反应的发生。论文中还研究了醉化CPE的合成过程。主要针对反应条件对MAH接枝率（GD％）的影响进行了详细的讨论，包括氯化原位接枝的温度模式、MAH单体量、氯气流量、氯含量等对MAH接枝率（GD％）的影响。同时探讨了氯化原位接枝反应历程。考查了氯化原位接枝MAH体系和氯化HDPE林系自由基浓度随时间变化的情况。接枝产物的硫化特性曲线表明：由于MAH的引入，聚合物主链上连接有酸配基团，使得氯化原位接枝共聚物CPE-g-MAH可以通过官能团之间相互反应而交联成为可能。随着MAH接枝量的升高，接枝率上升使得HDPE大分子链上带有更多MAH接枝点，CPE-g-MAH可硫化的程度相应提高。接枝产物的力学性能测试结果表明：随着MAH接枝率的增加，材料的拉伸强度上升，而材料的扯断伸长率、硬度等力学性能下降。

Direct numerical test of the B-G-K model equation by the DSMC method

In the present paper the rarefied gas how caused by the sudden change of the wall temperature and the Rayleigh problem are simulated by the DSMC method which has been validated by experiments both in global flour field and velocity distribution function level. The comparison of the simulated results with the accurate numerical solutions of the B-G-K model equation shows that near equilibrium the BG-K equation with corrected collision frequency can give accurate result but as farther away from equilibrium the B-G-K equation is not accurate. This is for the first time that the error caused by the B-G-K model equation has been revealed.

Immunosensor Interface Based on Physical and Chemical Immunogylobulin G Adsorption onto Mixed Self-Assembled Monolayers

An immunosensor interface based on mixed hydrophobic self-assembled monolayers (SAMs) of methyl and carboxylic acid terminated thiols with covalently attached human Immunoglobulin G (hIgG), is investigated. The densely packed and organised SAMs were characterised by contact angle measurements and cyclic voltammetry. The effect of the non-ionic surfactant, Tween 20, in preventing nonspecific adsorption is addressed by ellipsometry during physical and covalent hIgG immobilization on pure and mixed SAMs, respectively. It is clearly demonstrated that nonspecific adsorption due to hydrophobic interactions of hIgG on methyl ended groups is totally inhibited, whereas electrostatic/hydrogen bonding interactions with the exposed carboxylic groups prevail in the presence of surfactant. Results of ellipsometry and Atomic Force Microscopy, reveal that the surface concentration of covalently immobilized hIgG is determined by the ratio of COOH/CH3-terminated thiols in SAM forming solution. Moreover, the ellipsometric data demonstrates that the ratio of bound anti-hIgG/hIgG depends on the density of hIgG on the surface and that the highest ratio is close to three. We also report the selectivity and high sensitivity achieved by chronoamperometry in the detection of adsorbed hIgG and the reaction with its antibody.

Numerical simulation of g-jitter effects on half floating zone convection under microgravity environment

The g-jitter effects on the thermocapillary convection in liquid bridge of floating half zone were studied by numerical simulation for unsteady and axi-symmetric model in the cylindrical coordinate system. The g-jitter field was given by a steady microgravity field in addition to an oscillatory low-gravity field, and the effects on the flow field, temperature distribution and free surface deformation were analyzed numerically.

G-jitter effects on half floating-zone convection in intermediate-frequency range

The g-jitter influence on thermocapillary convection and critical Marangoni number in a liquid bridge of half-floating rone was discussed in the low frequency range of 0.4 to 1.5 Hz in a previous paper. This paper extended the experiments to the intermediate frequency range of 2 to 18 Hz, which htrs often been recorded as vibration environment of spacecrafts. The experiment was completed on the deck of a vibration machine, which gave a periodical applied acceleration to simulate the effects of g-jitter. The experimental results in the intermediate frequency range are different from that in the low frequency range. The velocity field and the shape of the free surface have periodical fluctuations in response to g-jitter. The amplitude of the periodical varying part of the temperature response decreases obviously with increasing frequency of g-jitter and vanishes almost when the frequency of g-jitter is high enough. The critical Marangoni number is defined to describe the transition from a periodical convection in response to g-jitter to an oscillatory convection due to internal instability, and will increase with increasing g-jitter frequency. According to the spectral analysis, it can be found that the oscillatory part of temperature is a superposition of two harmonic waves if the Marangoni number is larger than a critical value.

Effects of g-jitter on the critical marangoni number

A half floating zone is fixed on a vibrational deck, which supports a periodical applied acceleration to simulate the effect of g-jitter. This paper deals with the effects of g-jitter on the fluid fields and the critical Marangoni number, which describes the transition from a forced oscillation of thermocapillary convection into an instability oscillatory convection in a liquid bridge of half floating zone with top rod heated. The responses of g-jitter field on the temperature profiles and flow pattern in the liquid bridge were obtained experimentally. The results indicated that the critical Marangoni number decreases with the increasing of g-jitter effect and is slightly smaller for higher frequency of g-jitter with fixed strength of applied gravity.

Quantum and variational monte-carlo interaction potentials for li2 (x1-sigma-g+)

Optimized trial functions are used in quantum Monte Carlo and variational Monte Carlo calculations of the Li₂(X ¹Σ⁺_g) potential curve. The trial functions used are a product of a Slater determinant of molecular orbitals multiplied by correlation functions of electron—nuclear and electron—electron separation. The parameters of the determinant and correlation functions are optimized simultaneously by reducing the deviations of the local energy E_L (E_L  Ψ⁻¹_THΨ_T, where Ψ_T denotes a trial function) over a fixed sample. At the equilibrium separation, the variational Monte Carlo and quantum Monte Carlo methods recover 68% and 98% of the correlation energy, respectively. At other points on the curves, these methods yield similar accuracies.

源于G.I.Taylor工作的现代经典物理学

一位科学家的工作提供了一门完整课程的素材，涉及从流体动力学稳定性、湍流到流体电动力学、微生物的运动．

Starting Nozzle Flow Simulation Using K-G Two-Equation Turbulence Model

The starting process of two-dimensional nozzle flows has been simulated with Euler, laminar and k - g two-equation turbulence Navier-Stokes equations. The flow solver is based on a combination of LUSGS subiteration implicit method and five spatial discretized schemes, which are Roe, HLLE, MHLLE upwind schemes and AUSM+, AUSMPW schemes. In the paper, special attention is for the flow differences of the nozzle starting process obtained from different governing equations and different schemes. Two nozzle flows, previously investigated experimentally and numerically by other researchers, are chosen as our examples. The calculated results indicate the carbuncle phenomenon and unphysical oscillations appear more or less near a wall or behind strong shock wave except using HLLE scheme, and these unphysical phenomena become more seriously with the increase of Mach number. Comparing the turbulence calculation, inviscid solution cannot simulate the wall flow separation and the laminar solution shows some different flow characteristics in the regions of flow separation and near wall.

液氮温区G-M制冷机的数值分析及新型结构制冷机的研制

G-M制冷机是回热式的小型低温制冷机，它利用绝热放气膨胀原理（又称为西蒙膨胀法）获得低温，具有振动小、运行稳定、寿命长、操作方便等特点，在对效率、重量、尺寸等没有太高要求的场合应用非常广泛。在八十年代末，G-M制冷机已经突破了液氦温度，非常适合在液氦温区为超导器件或电子元件提供冷量，在低温真空泵、MRI超导磁体冷却系统、SQUID再冷凝系统等方面有良好的应用前景，推广其应用已属当务之急。本文围绕着探索氦温区G-M制冷机工作机理、提高低温蓄冷器性能及新型结构G-M制冷机的研制等方面，进行了系统地理论分析和纳归纳，以及初步地实验研究：一. 首次比较完善地建立了液氦温区G-M型制冷机整机数值模拟方法，数值模拟方法给出了制冷机内工质参数瞬态分布及动态变化曲线，为分析制冷机独特的循环特性提供了直观的依据，为探讨运行及结构参数对制冷性能的影响机理提供了强有力的工具。模型中考虑了制冷机中的阻力、实际进排气角、物性变化及蓄冷器内空隙率的存在等多种实际因素：解决了一、二级耦合及部件交界处物性变化不连续对计算影响等问题；采取网格非均匀化、牛顿迭代法以及负反馈原理等措施，提高了计算精度和收敛性。在微机上成功地模拟了液氦温区G-M制冷机的工作过程，程序采用模块化编程，具有一定通用性。二. 运用液氦温区整套机数值模拟方法，计算了制冷机内工质参数（氦流温度、压力、流速等）周期性变化和空间分布，采用一级蓄冷器与低温蓄冷器工作特性对比法，从整机内工质参数动态变化规律分析的角度，验证了液氦温区G-M制冷机工质氦的循环主要分为两部分：常规循环、低温循环。并详细地讨论了运行参数（频率、工作压力）及一级制冷机结构参数对整机内工数动态变化的影响规律以及制冷机性能的影响机理。三. 首次建立了较完善的液氦温区多层混合填料型低温蓄冷器的数值模拟方法，运用数值模拟方法，首次详细地研究了常用填料的不同组合、一定组合下填料比例以及蓄冷器结构对制冷机性能的影响机理，提出了不同填料的最佳节组合及一定组合下填料最佳比例的确定和低温蓄冷器结构和填料优化的原则，为合理有效地设计高性能液氦温区低温蓄冷器提供了依据。四. 提出并设计、加工了一种新型结构的液氦温区双级G-M型制冷机，该机结构在国内外属于首创。其具有以下主要结构特点：一、二级分别独立驱动；一、二级之间通过热桥连接；二级蓄冷器外置于汽缸等。同时建立了新型结构液氦温区双级G-M型制冷机实验系统，为今后整机性能和内部动态过程的研究奠定了基础。五. 新型结构双级G-M型制冷机二级单机动转频率为0.6Hz时，制冷温度为13.6K，且在20K时有4.4W的制冷量；制冷机已达到液氦温区，f = 0.4Hz时，最低温度为4.6K；f = 1Hz，制冷温度为10K时，制冷量大于6W，上述结果目前均未见有文献报道。在新型G-M制冷机上，初步进行了低温蓄冷器性能测试实验及运行参数对制冷机性能影响的实验研究。