Analysis of the crystallization kinetics in poly(ethylene oxide) by calorimetric measurements

Summary Differential scanning calorimetric measurements in the early stage of isothermal crystal growth of polyethylene oxide are analysed in the light of irreversible thermodynamics. An accurate evaluation of the equilibrium melting temperature is done by fitting the thermograms obtained at different undercoolings and referring to the activation energy values already known from the literature. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.     

Chemically controlled pattern formation in phase-separating materials

Summary The role of chemical reactions in the selection of patterns in phase-separating mixtures is presented. Linearized theory and computer simulation show that the initial long-wavelength instability characteristic of spinodal decomposition is suppressed by chemical reactions, which restrict domain growth to intermediate length scales even in the late stages of phase separation. Our findings suggest that chemical reactions may provide a novel way to stabilize and tune the steady-state morphology of phase-separating materials. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.     

Yb原子高激发态的斯塔克光谱

采用ππ偏振激光，通过两步激发和光电离方法，在０－１５４Ｖ／ｃｍ电场范围内，测定了Ｙｂ原子ｎ－１８附近ｍ＝０的斯塔克光谱，首次把包含斯塔克效应的能量矩阵对角化方法推广到Ｙｂ原子，所获得的理论斯塔克图与实验结果基本符合，观察到低场中斯塔克簇随电场增加呈现线性结构以及＾１Ｐ１态与斯塔克簇在抗交叉过程中振子强度发生转移的现象，讨论了结构与量子亏损的关系。     

示差半微分循环伏安法研究琥珀酰胆碱在水/硝基苯界面的传递行为

研究了油/水界面电解的示差半微分循环伏安行为。在0.01mol/L LiCl(w)-0.01mol/L TBATCIPB(nb)体系“电位窗”比TBATPB(nb)向正方向扩展约50mV,残余电流基本消除,使“电位窗”内的平台向左右拓宽约50mV。算得界面电容约为16μF/cm~2。考察了琥珀酰胆碱离子在w/nb界面的传递伏安特性,结果与一般半微分循环伏安法相似。但峰形改善,检测限降低一个数量级(1×10~(-6)mol/L),相对标准偏差在5％以内,可用于定量测定琥珀酰胆碱。     

降雨衰减对移动卫星系统通信的影响及补偿

针对移动卫星系统的特点，分析了降雨引起的信号衰减的原因，给出了雨衰的计算方法。Ka波段一般用于移动通信业务，从分析结果上看该波段信号受降雨影响较大。提出几种补偿雨衰的方法，给出了上行功率控制法的系统原理图。     

Normal Vietoris Implies Compactness: A Short Proof

One of the most celebrated results in the theory of hyperspaces says that if the Vietoris topology on the family of all nonempty closed subsets of a given space is normal, then the space is compact (Ivanova-Keesling-Velichko). The known proofs use cardinality arguments and are long. In this paper we present a short proof using known results concerning Hausdorff uniformities.     

Inorganic Sol-Gel Preparation of Medium Sized Microparticles of Li2TiO3 from TiCl4 as Tritium Breeding Material for Fusion Reactors

Microspheres of Li₂TiO₃ were fabricated by a classical, inorganic sol-gel process from commercially available TiCl₄. Elaborated process consists of the following main steps: (1) dissolving of TiCl₄ in concentrated aqueous HCl and addition of LiOH; (2) formation of sol emulsion in 2-ethylhexanol-1 containing the surfactant SPAN-80 (EH); (3) gelation of emulsion drops by extraction of water with partially dehydrated EH; (4) impregnation of gel to Li:Ti molar ratio MR = 2; (5) thermal treatment at 1200°C in order to receive chloride free product. This temperature can be significantly lowered (to 750°C) by dechlorination starting solution TiCl₄ by chemical treatment of the with nitric acid to form of nitrate-stabilized titania sols. Tritium release from sol-gel made Li₂TiO₃ microspheres were found very close to that observed for other traditional materials, however for the first sample process starts slightly earlier.     

A purely algebraic characterization of the hyperreal numbers

The hyperreal numbers of nonstandard analysis are characterized in purely algebraic terms as homomorphic images of a suitable class of rings of functions.