简立方格点自避行走所模拟的高分子链吸附和塌缩

采用复合Markov链法,针对简立方格点上的自避行走模型,研究了同时具有对壁的吸附作用ε1和最近邻相互作用ε2的高分子链的热力学性质.相互作用能量参数ε1和ε2分别联系于参数α和β.令链长N=100,由这种Monte Carlo方法可得出链的自由能FN (α ,β),热容2FN(α,β)/2α和2FN(α,β)/2β,吸附点平均数〈m〉/N,最近邻相互作用对平均数〈n〉/N和均方末端距对壁的垂直分量RZ2.除已有方法由热容数据可绘出α-β相图外,建议由结构参数〈m〉/N ,〈n〉/N和RZ2绘制相图,并发现二者基本一致.所得相图表明,存在4个相区,分别是解吸-膨胀相(DE),吸附-膨胀相(AE),解吸-紧密相(DC)和吸附 -紧密相(AC).在伸展区和塌缩区,随着吸附作用的增强,会出现吸附相转变.在解吸区和吸附区,随着自相互作用的增大,也将出现塌缩相转变.相图出现了两个三相点,即AE-AC-DC三相点和AE-DE-D C三相点.     

显微镜图像分析研究聚丙烯/尼龙1010共混物相结构及其性能

用扫描电子显微镜图像分析研究了聚丙烯/聚酰胺1010共混物及其部分相容体系的相形态结构,计算了表征相结构和尺寸的结构参数,如分散相的平均直径、平均弦长和分散相的质心相关距等.并分别讨论了聚丙烯/聚酰胺1010共混物及其部分相容体系的相形态以及其结构参数与共混物组成的关系.测定了聚合物及其共混物体系的力学性能,讨论了共混物组成与力学性能的关系.聚丙烯/聚酰胺1010共混物的拉伸模量与组成的关系较为复杂,但其部分相容体系的拉伸模量与组成呈线性关系.聚丙烯/聚酰胺1010及其共混物体系的屈服强度与共混物组成均呈线性关系.表征相结构的两相平均弦长比(l-1/-l2)与组成以及共混物体系力学性能与组成的关系,二者相似.同时讨论了体系力学性能随相尺寸等的变化规律.     

G-M制冷机阀门相位配置的仿真研究

文中主要根据G-M制冷机采用阀切换式回热器和框架活塞运动的特点,采用分步式建模和仿真的方法研究其阀相位配置特性。综合考虑系统中气体质量变化,并采用变步长Simulink模型对膨胀机部分的工作过程进行仿真研究,得出了G-M制冷机中配气相位的关键问题,并对相位优化提出了初步的解决方案。     

Gas Chromatographic Analyses of Nitroxylene Isomers on Various New Liquid Phases

Abstract

Luminol, violuric acid, thymine, alloxane, orotic acid, imidazole, phthalimide and nicotinic acid effectively resolved all the nitroxylene (dimethylnitrobenzene) isomers and they are nitrogen containing heteroaromatic compounds. Ninhydrin (indantrione) also separated all the isomers and it is the only triketo-hydrocarbon among these effective liquid phases. Furthermore, almost all of these compounds resolved the isomers at a temperature below the melting points of the stationary phases.     

Effect of boron on the crystallization of amorphous Si–(B–)C–N polymer-derived ceramics

Amorphous Si–(B–)C–N polymer-derived ceramics (PDCs) with a boron content ranging from 0 to 8.3 at.%, were synthesized by thermolysis of boron-modified poly(methylvinylsilazane). Correlation of the boron content and the thermal stability of these materials in the course of annealing were investigated using high temperature thermal gravimetric analysis (HT-TGA). Furthermore, the initial crystallization of the as-thermolyzed amorphous ceramics was studied by X-ray diffraction (XRD) measurements. The increase of boron content promotes the crystallization of SiC, and inhibits the crystallization of Si₃N₄. Moreover, the ratio of α-Si₃N₄/β-Si₃N₄ in crystalline ceramic decreases with increasing boron content. Thermodynamic modeling proves the influence of boron content on driving force for crystallization. The available thermodynamic model of amorphous Si–C–N domains, nano-crystalline silicon nitride, and nano-crystalline silicon carbide treated as the separated phases has been used to interpret these results.     

Ba11KX7O2 (X  P,As): Two Novel Zintl Phases with infinite chains of oxygen centered Ba6 octahedra,isolated X3− and dimeric X24− anions

Reactions of “BaX” (X ? P, As) with Ba, K and BaO in tantalum tubes at 900–1000°C yielded black, very air- and moisture-sensitive crystals of Ba₁₁KP₇O₂ and isotypic Ba₁₁KAs₇O₂ which were characterized by EDX and X-ray diffraction (orthorhombic, Fddd, Z = 8; a = 1069.9(1), b = 1514.3(2), c = 3164.6(4) pm and a = 1087.8(2), b = 1542.3(2), c = 3232.4(4) pm, respectively). The structure contains infinite zigzag chains, [Ba₄Ba_2/2O], of oxygen-centered, corner-sharing Ba₆ octahedra along [100]. They are connected by linear strings built of alternating isolated X atoms and X₂ dimers to form layers parallel to (001). While the isolated X atoms are surrounded by eight Ba forming a distorted cube, the X₂ dimers center a Ba₁₂ polyhedron which is comprised of a pair of face-sharing Ba square antiprisms. This results in a cube–antiprism-antiprism-cube sequence of face-sharing Ba polyhedra. Additional X atoms function as spacers between the layers and connect them along [001]. Two atom positions are statistically occupied by Ba and K, and the formula may be written as Ba²⁺₁₁K⁺X^3?₅(X₂)^4?O^2?₂ according to the Zintl-Klemm concept.     

Variable-temperature,solid-state NMR studies of bonded liquid crystal stationary phases for HPLC

Summary The spin-spin relaxation time measured from the line width (T ₂*) is used to study bonded phase dynamics of two liquid crystal materials in the solid state as a function of temperature. The motion of these two bonded phases is much more restricted than either C-18 or butyl phenyl bonded to the same substrate. Plots ofT ₂* vs. 1/T indicate a structural transition of the bonded phase moiety for the two liquid crystal materials but no such change is seen for either C-18 or butyl phenyl over the same temperature range (243–353 K), suggesting a higher degree of association between adjacent bonded moieties for the two liquid crystal materials in comparison to the other two phases. The conclusions from solid-state NMR data coincide with results obtained in earlier chromatographic studies.     

简立方格点自避行走所模拟的高分子链吸附和塌缩

采用复合Markov链法 ,针对简立方格点上的自避行走模型 ,研究了同时具有对壁的吸附作用ε1 和最近邻相互作用ε2 的高分子链的热力学性质 .相互作用能量参数ε1 和ε2 分别联系于参数α和 β .令链长N=10 0 ,由这种MonteCarlo方法可得出链的自由能FN(α ,β) ,热容2 FN(α ,β) /2 α和2 FN(α ,β) /2 β ,吸附点平均数〈m〉/N ,最近邻相互作用对平均数〈n〉/N和均方末端距对壁的垂直分量RZ2 .除已有方法由热容数据可绘出α β相图外 ,建议由结构参数〈m〉/N ,〈n〉/N和RZ2 绘制相图 ,并发现二者基本一致 .所得相图表明 ,存在 4个相区 ,分别是解吸 膨胀相 (DE) ,吸附 膨胀相 (AE) ,解吸 紧密相 (DC)和吸附 紧密相 (AC) .在伸展区和塌缩区 ,随着吸附作用的增强 ,会出现吸附相转变 .在解吸区和吸附区 ,随着自相互作用的增大 ,也将出现塌缩相转变 .相图出现了两个三相点 ,即AE AC DC三相点和AE DE DC三相点