Rhizobium trifolii capsular polysaccharide: a novel biopolymer with striking physical properties

The physical properties of the capsular polysaccharide of Rhizobium Trifolii (CPS) were investigated. Viscosity measurements provided information about the hydrodynamic volume of single coils, the perturbation of solvent flow and the shear-thinning behaviour of concentrated solutions. Changes in chain geometry and the development of an intermolecular network as a function of temperature were monitored using the techniques of optical rotation and dynamic oscillation. Finally, analysis of calorimetric thermograms elucidated the type of interactions between CPS and the bacterial levan. Overall, the Rhizobium polysaccharide was found to form thermally-reversible gels at an extremely low 'minimum critical gelling concentration' (c_o∼ 0.35gl^-1). At temperatures above the gel melting point (∼ 48°C), however, the compact polymer coils entangled at comparatively high concentrations (about 60 times higher than c_o). In the presence of a highly branched levan, the thermal stability of ordered CPS structures increased as a consequence of thermodynamic incompatibility between the two polymers.     

凝土温度特性参数反分析及其应用

建立混凝土温度场材料特性参数反演分析模型,并用有限单元法仿真计算和可变容差法编制了优化反演程序。数值算例表明该算法是稳定的,收敛速度较快,并给出具体的在建工程实例的应用情况。通过现场温度观测值,进行优化反演计算得到混凝土温度的有关特性参数,这将成为部分或全部替代仅靠实验室选取参数的行之有效的途径之一。     

二维地震过障碍观测系统模式及其参数设计

在二维地震勘探中,为了避免因地表障碍物使地震反射剖面出现间断现象,需要改变观测系统设计,跨越障碍物(江河、城镇等),以保证反射同相轴能连续追踪对比。在以往地震勘探中,有时因过障碍观测系统设计不合理,不但增加勘探费用,而且影响采集质量。因此只有科学合理地设计过障碍观测系统模式和参数,才能保证地震测线顺利通过障碍物,得到较好的障碍物下方的地震资料并降低勘探成本。为此本文在调查和研究大量野外实际的过障碍观测系统的基础上,总结归纳成三大类过障碍观测系统模式,并分析其特点和应用范围。采用图解法,推导出主要模式的跨越宽度、最小炮检距及最大炮检距等参数公式。采用这套过障碍观测模式不仅可以得到和障碍区两侧等质量的地震资料,而且可以有效地降低勘探成本。     

固定化酵母粒子中生产乙醇的定态分岔行为研究

运用变分原理和打靶法将分布参数系统的非线性边值问题转化为集总参数系统的初值问题，基于延拓算法，研究了固定床中球形固定化酵母粒子表面乙醇和葡萄糖浓度随参数的变化关系，得出了单颗粒固定化酵母生产乙醇的多定态特性。结果表明：随系统尺度三的变化，方程出现分岔点；方程的解与液相主体浓度有关。在某些条件下酵母粒子表面浓度有三个定态：在多定态区域，随三的增加，方程一个解支的乙醇浓度迅速增加，从而可以在固定床中通过控制粒径而使反应器达到较高的产率。研究结果为固定床反应器的开工及控制提供了重要的理论依据。     

Phase equilibria of quasi-binary systems consisting of multicomponent polymers 1 and 2. IV: Poly(ethylene oxide)/poly(propylene oxide) systems

To confirm the reliability of the theory of phase equibria of multicomponent polymer 1/multicomponent polymer 2 systems (i.e. quasi-binary systems) and the method of computer experiment based on this theory (Brit. Polym. J., 23 (1990)285; 23 (1990)299; Polym. Int., 29 (1992)219), could point curves (CPC), two-phase volume ratios ( R ) and critical solution points (CSP) have been determined experimentally for the quasi-binary mixtures of poly(ethylene oxide) (M¯_w = 647, M¯_w/M¯_n = 1.15; M¯_w and M¯_n, the weight-average and numberaverage molecular weights, respectively) and poly(propylene oxide) (M¯_w = 2028, M¯_w/M¯_n = 1.08; and M_w = 2987, M_w/M_n = 1.13). The hydroxyl end groups of both polymers were methoxylated in advance by the Cooper & Booth method (Polymer, 18 (1977)164). The thermodynamic interaction parameter between both polymers, χ₁₂, and the concentration dependence parameters for the above quasi-binary systems were determined by the method proposed in a previous paper (Brit. Polym. J., 23 (1990)299). CPC, R and CSP values calculated on the basis of the theory are in good agreement with the values determined experimentally.     

用有限元确定起重机裂纹补强板的参数

采用ANSYS有限元分析软件，对因出现裂纹的起重机主梁而添加的补强板进行系列计算，得出修补后主梁裂纹的应力及应力强度因子的变化规律。结果表明，采用参数适当的补强板，可降低起重机主梁裂纹尖端的应力，从而保证起重机的安全。     

剂量率对聚四氟乙烯辐射裂解的影响

本文研究了在以电子加速器的电子射线为辐射源时,剂量率对PTFE辐射裂解的影响。在剂量相同的条件下,剂量率从1.44×10~4 rad/s增至5.75×10~4 rad/s,裂解效率提高3.3倍。剂量率和各断裂参数(单位剂量裂解度a_0,G(s)值等)均成线性关系。当裂解度一定时,剂量率与剂量成反变关系。     

广西某矿区托帕石的宝石学特征

广西某矿区的脉石矿物——黄玉分三个世代,其中第三世代的黄玉晶体无色透明,重量大于0.9克拉,瑕疵不明显,密度(3.50)、硬度(7.8430)和折射率(1.6330)等特征均达宝石级,经系统研究测试,可以命名为托帕石(Topaz)。     

STM tunneling spectroscopy on high Tc superconductors

STM tunneling spectroscopy has been performed on the bulk single crystals of BiSrCaCuO (BSCCO) and the epitaxial thin films of YBaCuO (YBCO) at cryogenic temperatures. The STM images and tunneling spectra observed on the (001) surfaces can be classified into three cases; 1) Atomic image is visible. However, the tunneling spectrum shows semiconducting or smeared superconducting gap structures, depending on the tip-sample distance. 2) Clear atomic image can not be obtained. But, the tunneling spectrum shows flat bottom region with quite low zero bias conductance. 3) Tunneling spectra demonstrate gapless behavior, independent of the tip-sample separation. These observations support the quasi-2D electronic picture in whichs-wave like 2D superconducting layers are coupled with each other through the Josephson effect.     

水泥基压电复合材料的制备及极化工艺研究

采用压制成型法，首次以快硬早强的硫铝酸盐水泥为基体制备了水泥基压电复合材料。详细阐述了水泥基压电复合材料的制备过程；通过实验确定了适宜的极化条件，分析讨论了极化过程中出现漏电流的原因，并提出了一些初步的解决途径。结果表明，对硫铝酸盐水泥基压电复合材料来说，适宜的极化工艺参数：极化电场强度为4kV／mm，极化时间为45min，极化温度应低于130℃。