Molecular dynamics study of anisotropic growth of silicon

Based on the Tersoff potential, molecular dynamics simulations have been performed to investigate the kinetic coefficients and growth velocities of Si(100),(110),(111), and(112) planes. The sequences of the kinetic coefficients and growth velocities are μ_((100)) μ_((110)) μ_((112)) μ_((111))and v_((100)) v_((110)) v_((112)) v_((111)), respectively, which are not consistent with the sequences of the interface energies, interplanar spacings, and melting points of the four planes. However,they agree well with the sequences of the distributions and diffusion coefficients of the melting atoms near the solid–liquid interfaces. It indicates that the atomic distributions and diffusion coefficients affected by the crystal orientations determine the anisotropic growth of silicon. The formation of stacking fault structure will further decrease the growth velocity of the Si(111) plane.     

溶剂热结晶FeS2及其光吸收特性

以硝酸铁和硫脲为原料、乙醇为溶剂,采用溶剂热法生长了二硫化铁(FeS2、黄铁矿型)微纳米结晶体.通过调节反应温度和原料浓度,有效地控制了FeS2微纳米晶体的微观生长形态.采用XRD 和SEM等手段表征了FeS2结晶样品,结果表明溶剂热结晶的FeS2具有良好的立方晶型,随着反应温度、原料浓度的改变,溶剂热法生长的FeS2分别呈现光滑表面球晶、六方片状结晶和堆积状球晶等特殊的微观形态.对于溶剂热法生长FeS2,本文也从化学反应的角度给出了可能的形成机理,同时利用UV-vis光谱测定了FeS2结晶的光吸收性能.     

Teleportation of a two-atom entangled state using a single EPR pair in cavity QED

We propose a scheme for teleporting a two-atom entangled state in cavity quantum electrodynamics (QED). In the scheme, we choose a single Einstein--Podolsky--Rosen (EPR) pair as the quantum channel which is shared by the sender and the receiver. By using the atom--cavity-field interaction and introducing an additional atom, we can teleport the two-atom entangled state successfully with a probability of 1.0. Moreover, we show that the scheme is insensitive to cavity decay and thermal field.     

高效液相色谱法同时测定双酚伪麻干混悬剂中的盐酸伪麻黄碱和氢溴酸右美沙芬

建立了可同时测定双酚伪麻干混悬剂中盐酸伪麻黄碱和氢溴酸右美沙芬含量的反相高效液相色谱方法。样品先经甲醇溶解,过滤,然后以Lichrospher C6H6化学键合硅胶为固定相、乙腈-水-H3PO4（体积比为50∶50∶0.1,pH 2.5,内含1 g/L十二烷基硫酸钠)为流动相进行色谱分离,在220 nm处定量测定。结果表明,氢溴酸右美沙芬、盐酸伪麻黄碱的质量浓度分别为1.03~206 mg/L和5~200 mg/L时,其峰面积与质量浓度的线性关系良好;批内(n=7)测定的平均相对标准偏差（RSD）分别为1.8%和1.0%,批间(n=5)测定的RSD分别为2.2%和1.5%;对双酚伪麻干混悬剂中氢溴酸右美沙芬、盐酸伪麻黄碱测定回收率分别为100.0%~101.8%和95.7%~98.7%。该法适用于双酚伪麻干混悬剂中氢溴酸右美沙芬和盐酸伪麻黄碱的质量控制及含量测定,方法准确,操作简便。     

高效液相色谱法测定精浆中过氧化脂质水平及其在男性不育症研究中的应用

采用高效液相色谱法测定精浆中过氧化脂质(lipid peroxidation,LPO)含量,研究了有正常生育能力的男子和不育症患者精浆中LPO含量水平差异及其对男子不育症的影响。精浆样品经酸化后,分解生成的丙二醛(malondialdehyde,MDA)与硫代巴比妥酸(thiobarbituric acid,TBA)缩合反应形成紫红色产物,以Lichrospher C18化学键合硅胶为固定相,0.025 mol/L KH2PO4 (pH 6.2)-甲醇(体积比为58∶42)为流动相进行色谱等度分离     

反相高效液相色谱法测定雷公藤提取物中雷公藤甲素含量

应用反相高效液相色谱法检测了雷公藤提取物中雷公藤甲素的含量。样品经洗脱提取后,以Ｃ１８化学键合硅胶为固定相,乙腈－水（４０∶６０,Ｖ／Ｖ）为流动相,用２１０ｎｍ波长定量检测。测定结果表明,雷公藤甲素浓度在０．２５～４．００ｍｇ／Ｌ范围内线性良好,最低进样检测浓度为０．１ｍｇ／Ｌ。批内（ｎ＝５）及批间（ｎ＝５）测定相对标准偏差分别为１．９％～６．５％和２．７％～７．８％,回收率为８９．８％～９２．０％。     

用于递模塑料的有机硅树脂

本文指出提高水解温度,或使用丙酮和甲苯混合溶剂,有利于甲基三氟硅烷与苯基三氯硅烷和二甲基二氯硅烷的共水解缩聚反应,而不易产生凝胶现象。并以此合成了适于递模塑料的R/Si较小、C_6H_5/R较低、羟基含量较高的羟基缩合型无溶剂树脂,简化了步骤,大大缩短了操作时间,树脂质量稳定。此外还讨论了树脂的结构与递模塑料性能的关系,选择了较好的固化剂以及通用的补强剂,使塑料具有优异的性能。     

香云多糖的分子表征和稀溶液性质研究

The polysaccharide of lentinus edodes and polytictus versicolor has been fractionated by repeated precipitation method.All fractions and the unfractionated samples have been characterized by rapid dynamic membrane osmometry. For its aqueous solution, the second virial coefficient A₂ decreases as the molecular weight increases. The relationship is A₂= 2 slope (MnRT)-1/2.Determination of the distribution curve by means of fractional precipitation. Separation of a polysaccharide into six fractiona by a fractional precipitation carried out. The distribu-tion-curve of integral and differential is obtained. After according to the modified Elias'cloud-point titration method and using an Abbe's refractometer to define the clou-point,^[6-]8it was found that water/acetone (89:11 by vo-lume) is a θ solvent for the polymer at 25±0.05 C. For θ conditions,the intrinsic viscosities were determined by capillary viscometry. Thus a monodispersed [n]-M relationship has been obtained: [n]_θ=2.59×10^-2M^0.509 From the result above the unperturbed dimensi on(r²_θ)^1/2 was found to be 4.7×10^-9M^1/2.     

紫外分光光度法测定双酚A聚砜分子量的研究

前文已报道了用电位滴定和电导滴定的方法,测定了酚瑞基双酚A聚砜的数均分子量至20000。本文用紫外吸收光谱来分析聚合物中酚端基浓度,进而求其数均分子量。 Shchori和Mcgratb曾研究,直接测定在稀溶液中酚端基的聚碳酸酮的电子吸收光谱,可以用来迅速、灵敏的测定其到100000。这个方法主要基于     

基于FPGA自主控制浮点加减控制器设计

为实现一种能够自主完成浮点数加/减运算功能的浮点数加/减运算执行控制器,提出了一种基于采用FPGA并行操作电路硬连接的浮点数加/减运算控制电路及其时序控制方法;该控制器在接收到操作数类型与参与运算的操作数后,在内部时序脉冲作用下,可以自主完成操作数的配置以及浮点数加/减法运算的功能,运算结果传输到系统数据总线;论述了该控制器的电路构成和基本原理,分析操作数类型与操作数在内部时序脉冲作用下的执行过程,应用Verilog HDL语言实现相关硬件的构建和连接;设计完成后通过仿真测试可知,该控制器运行的最高频率可达178.317 M,从输入端口到输出端口的延时数据为:最小延时是3.185 ns,最大延时是15.336 ns,耗用的IO输入输出端口占总资源的27.92%,数据表明该控制器提高了运算器的运算速度,且能够自主完成浮点数加/减运算。