Optical properties of Nd-doped Ca3(VO4)2 single crystal fiber

Optical absorption and photoluminescence of Ca₃(VO₄)₂ single crystal grown by a floating-zone technique and containing Nd³⁺ ions were investigated. High absorption coefficients and broadening of most absorption bands are present at 300 K, while substructures in some of the same bands can be evidenced at 12 K. Most features of measured spectra are characteristic of random occupation of more than a single Ca²⁺ site by the Nd³⁺ ion and of distortions provoked by different charge compensation mechanisms involving oxygen vacancies promotion in the crystal lattice. Nd³⁺ optical properties were studied by using the Judd-Ofelt theory to calculate the spectral parameters relevant for laser applications.     

镨掺杂分布对1.3μm光纤放大器特性影响

对掺氟化镨玻璃光纤放大器的小信号增益，用广义的高斯近似公式可获得精确的分析表达。文中研究了限制光纤芯层中央部分的镨掺杂对光纤放大器特性的影响，结果发现限制镨掺杂分布能改进光纤放大器的工作效率，且截止波长比芯层全部均匀掺镨的光纤更长。     

Fluorine analysis of nuclear waste glasses

A method for analyzing the fluorine content of glass using a microwave oven to digest the glass is presented. Analysis time and secondary waste generation are reduced using this method, without sacrificing accuracy.     

厚壳玻璃钢艇体选材、铺层设计及工艺

本文涉及玻璃钢猎扫雷艇艇体材料的优选、铺层设计和工艺等内容。试验确定了以１６２９间苯聚酯树脂为基体、以９００ｇ／ｍ２无碱无捻粗纱短切毡（Ｍ）和８１０ｇ／ｍ２无碱无捻粗纱方格布（Ｒ）为增强体以及（Ｍ＋Ｒ）为基本铺层设计单元的方案。试验表明，按上述材料和铺层制作的层板，性能达到Ｌｅｒｉｃｉ和ＭＨＣ－５１艇壳层板的指标要求。     

Photo-reversible Reaction in Polymer Langmuir-Blodgett Films

Preparation of photoreactive Langmuir-Blodgett (LB) films was carried out using polymers/oligomers prepared from long-chain dialkyl esters of di-and tetra-olefins and having cyclobutane rings in the main chain. These polymers/oligomers formed stable monolayers on a water surface when mixed with arachidic acid. These monolayers could be deposited onto a substrate successfully forming Y-type films. The oligomer LB films were polymerized on irradiation. The polymer LB films showed a photo-reversible process between polymers and oligomers, depending on wavelength of the irradiating light. On the basis of spectral data and molecular weight change, this behaviour was found to be caused by cleavage and formation of cyclobutane rings.     

Dynamics of hydrated iron(II) cations in nafion polymer membranes

Mössbauer studies of Fe²⁺ in water-soaked nafion polymer membranes in the temperature range between 90 K and 250 K have been performed. Above a critical temperature (～ 180 K) the spectra exhibit both elastic narrow absorption lines and quasielastic broad lines. These spectra are typical of bounded diffusion phenomena observed by Mössbauer spectroscopy in macromolecular systems like haemoglobin, myoglobin and ferritin. Similar spectral shapes have been observed by quasielastic neutron scattering from water in nafion membranes. Within 50 K above the critical temperature the total Mössbauer absorption area decreases by an order of magnitude whereas the narrow absorption line decreases by two orders of magnitude. The results are interpreted in terms of bounded diffusive motion of the iron. Using a model based on overdamped harmonically bound Brownian motion, the essential parameters of the iron motion can be derived as a function of temperature. The iron motion most probably reflects the motion of a large Fe²⁺ complex, e.g. Fe(H₂O)²⁺₆, which is attached to the polymer side chains via the sulphonic group.     

Calorimetric determination of the enthalpy change for the binding of methyl orange to poly(vinylpyrrolidone) in aqueous solution

Thermodynamic parameters have been determined for the interaction of methyl orange and poly(vinylpyrrolidone) in aqueous solutions containing tris, tris and hydrochloric acid, or water only. Enthalpy changes were determined by use of a flow microcalorimeter. Free energy changes were calculated from the results of equilbrium dialysis studies. The results are interpreted in terms of the behaviour of poly(vinylpyrrolidone) in these systems. Analysis of data shows that the hydrophobic interactions in the systems are in the order: tris > wateronly > tris-HC1.     

Linear viscoelastic properties of mixtures of 3- and 4-arm polybutadiene stars

The viscoelastic properties of a three-arm and a four-arm star polybutadiene with the same arm molecular weight (M_a) were studied. The zero-shear recoverable compliance (J⁰_e) and plateau modulus (G⁰_N) for these stars are the same. The zero-shear viscosity (η₀) of the three-arm star is 20% lower than that of the four-arm star. Mixtures of the stars had J⁰_e and G⁰_N unchanged. A $\text{50}\text{50}$ mixture of the three- and four-arm star was diluted with a low molecular weight linear polybutadiene. G⁰_N∝ø²; J⁰_e∝ø^?1 and M_e∝ø^?1, as expected for dilution with a θ-solvent.     

光纤的淬冷增强原理

本文从拉丝工艺技术的角度出发，讨论了高速、高温拉丝工艺方法对光纤的淬冷增强原理。