光电倍增管脉冲性能研究

采用外腔式电光开光,调制主动照相探测光源,使光电倍增管处于脉冲工作状态下,以提高光电倍增管的输出幅度和动态范围,改善信号的信噪比,同时避免样品和探测器受长时间强激光照射.对滨松H6780光电倍增管进行了调试,使其线性输出电流由静态的0.1mA提升到脉冲状态的4.4mA,信噪比提高4.5倍.该技术对其他光敏探测有借鉴意义.     

p+209Bi核反应微观数据的理论计算

利用光学模型、激光模型、蒸发模型及扭曲波玻恩近似理论,对入射能量从阈能到300MeV,p+²⁰⁹Bi的中子反应截面、剩余核截面、出射粒子的多重数进行了理论计算及分析,并将计算结果与实验数据进行了比较.同时得到一组能量到50?0MeV与实验数据符合很好的光学势参数.     

非晶硅薄膜的低温快速晶化及其结构分析

在镀铝的廉价玻璃衬底上高速沉积的非晶硅薄膜在不同的温度下退火10min.退火温度为500℃时,薄膜表面形成了硅铝的混合相,非晶硅薄膜开始呈现了晶化现象 退火温度为550℃时,大部分(约80%)的非晶硅晶化为多晶硅,平均晶粒尺寸为500nm 退火温度为600℃时,几乎所有的非晶硅都转化为多晶硅,其平均晶粒尺寸约为15μm.     

相位差与q变形广义相干叠加态的压缩特性

对于q变形的非简谐振子广义相干态的叠加态β〉+eiφβeiδ〉,其量子涨落的可能高阶压缩阶数可以表示为k≠2πn/δ,这里n是整数.当δ=π时,压缩阶数不能是偶数即只能是奇数,这正是q变形非简谐振子广义奇偶相干态的结果.由此表明参数相位差δ对决定q变形的非简谐振子广义相干态叠加态的高阶压缩阶数起决定性作用.     

两亲性嵌段聚合物的同步辐射小角x射线散射研究

应用同步辐射小角x射线散射(SAXS)方法研究了不同聚合条件下苯乙烯对乙烯基苯甲酸两亲性嵌段聚合物的聚集行为,结果发现该聚合物在选择性溶液中自组装形成胶束.胶束的形态和结构取决于嵌段聚合物的组成、浓度以及溶剂的性质等因素 关键词： 小角x射线散射 两亲性嵌段聚合物 分形维数 粒径     

新疆野生黑加仑与马林果实的营养成分分析

通过对新疆野生黑加仑和野生马林的脂肪油，8种微量元素，17种氨基酸以及维生素C的含量进行测定得出：黑加仑脂肪油含量为17．9％，马林的脂肪油含量为22．3％，其中，黑加仑脂肪油中，r－亚麻酸的含量为19．02％，而马林中，其含量为9．40％，黑加仑中K，Na,Ca,Cu,Zn,Fe的含量比马林中的含量高，而Mn,Mg元素的含量却比马林含量低；马林的维生素C含量为16．22mg/g，黑加仑的含量为108mg/g，黑加仑的氨基酸的总量为1．63％，马林为1．14％。     

Investigation of chemical decomposition of CCl4 on TiO2 near room temperature

Dissociative adsorption of CCl₄ on TiO₂ at 35 °C has been studied by Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and electron spin resonance. CCl₄ decompose to form CO, CO₂, and CO₃ on the surface, at such a low temperature, in which CO₂ formation is not from CO oxidation on TiO₂, but CO₃ can be produced by CO and CO₂ adsorption. The Cl generated from CCl₄ decomposition is left on the surface and bonded to titanium ions. Mineralization of CCl₄ on TiO₂ involves the lattice oxygens. Thermodynamical driving force and possible reaction routes for CO and CO₂ formation in the CCl₄ decomposition on TiO₂ are discussed.     

Magnetic behavior of core–shell particles

We have prepared composite magnetic core–shell particles using the process of soap-free emulsion polymerization and the co-precipitation method. The shell of the synthesized composite sphere is cobalt ferrite (CoFe₂O₄) nanoparticles and the core consists of poly(styrene-co-methacrylic acid) polymer. The mean crystallite sizes of the coated CoFe₂O₄ nanoparticles were controlled in the range of 2.4–6.7 nm by the concentration of [NH₄⁺] and heated temperature. The magnetic properties of the core–shell spherical particles can go from superparamagnetic to ferromagnetic behavior depending on the crystalline sizes of CoFe₂O₄.     

高固体分羟基丙烯酸树脂的合成

以过氧化二苯甲酰（BPO）／过氧化二异丙苯（DCP）（质量比为2：3）为复合引发剂，二甲苯为溶剂，选用适量含羟基单体和分子量调节剂，以减缓树脂合成聚合反应中的自动加速现象，合成了分子量为3000-4000，多分散性指数d〈2的高固体分羟基丙烯酸树脂．该树脂与缩二脲多异氰酸酯（HDI）的配漆实验证明，所得漆膜鲜映性好、丰满度高、色泽好、雾影值低、综合性能较好．     

Asymmetric responses of international stock markets to trading volume

The major goal of this paper is to examine the hypothesis that stock returns and return volatility are asymmetric, threshold nonlinear, functions of change in trading volume. A minor goal is to examine whether return spillover effects also display such asymmetry. Employing a double-threshold GARCH model with trading volume as a threshold variable, we find strong evidence supporting this hypothesis in five international market return series. Asymmetric causality tests lend further support to our trading volume threshold model and conclusions. Specifically, an increase in volume is positively associated, while decreasing volume is negatively associated, with the major price index in four of the five markets. The volatility of each series also displays an asymmetric reaction, four of the markets display higher volatility following increases in trading volume. Using posterior odds ratio, the proposed threshold model is strongly favored in three of the five markets, compared to a US news double threshold GARCH model and a symmetric GARCH model. We also find significant nonlinear asymmetric return spillover effects from the US market.