用光刻、软刻和氧化硅球晶体模板制备表面微结构

表面微结构的制备对获得超疏水性表面和改善生物医学材料性能具有重要意义. 为了制备微米、亚微米和纳米级表面微结构, 本文采用光刻(photo-lithography)和软刻技术(soft lithography) 制备了微米尺寸长方体或圆柱体的阵列, 压印出变形长方体(塔状)或圆柱体(圆盘状)阵列的微结构表面; 采用单分散氧化硅球自集聚紧密堆积而成的胶体晶体为模板, 制备了亚微米/纳米 尺寸网状微结构的表面. 用光学和扫描电子显微镜表征了所获得的表面微结构.     

非平衡光纤Mach-Zehder干涉仪偏振衰落及相位噪声分析

研究了非平衡光纤Mach-Zehnder干涉仪因两束干涉光偏振态变化引起的偏振衰落和相位噪声问题.运用波导耦合理论和光纤偏振光传输理论,通过详细的推导,得到非平衡光纤Mach-Zehnder干涉仪输出光强、可见度以及相位噪声的表达式,分析了干涉仪可见度、相位噪声与干涉仪输入光偏振态之间的关系,提出抑制偏振衰落和相移噪声的方法.     

胶体晶体模板法制备三维有序排列的大孔SiO2材料

将粒径为480 nm的聚苯乙烯微球离心组装为胶体晶体模板,以正硅酸乙酯为硅源配制SiO₂溶胶并填充到模板间隙,原位形成凝胶,最后通过焙烧去除模板,得到三维有序大孔（3DOM）SiO₂。通过SEM检测,大孔以六方有序的方式排列,其孔径及孔径收缩率分别为360 nm和25％。大孔之间由小窗口连通,构成内部三维交联的大孔网络。低温N₂吸附测试表明,大孔孔壁上存在中孔孔隙,其中在3～4 nm有一集中的孔分布。XRD显示,制备的3DOM材料由无定形SiO₂组成。     

The velocity of movement of isotherms near the thermal center of a cooled body

The behavior of isotherms near the thermal center of a cooled body has been considered. It is shown that closer to the thermal center the velocity of movement of isotherms increases sharply. An expression is obtained that describes the behavior of the velocity of movement of isotherms near the center of bodies of simple shapes (plate, infinite cylinder, rod of square cross section, sphere, and cube). Quantitatively the behavior of the velocity depends on the thermal diffusivity of the medium and the geometric form of the body but is independent of the absolute magnitude of the isotherms, body dimensions, and of the cooling inetnsity. The property indicated is typical of the processes described by parabolic-type equations. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 2, pp. 391–397, March–April, 2009.     

Magnetic Interaction Force and a Couple on a Superconducting Sphere in an Arbitrary Dipole Field

The calculation of the magnetostatic potential and levitation force due to a point magnetic dipole placed in front of a superconducting sphere in the Meissner state is readdressed. Closed-form analytical expression for the scalar potential function that yields the image system for an arbitrarily oriented magnetic dipole located in the vicinity of a superconducting sphere is given. Analytic expression for the lifting or levitation force acting on the sphere is extracted from the solution for a general dipole. A special case of our expression where the initial magnetic dipole makes an angle with the z-axis is derived. Our expression for the force in this particular case shows that a recently obtained result (J. Supercond. Nov. Magn. 21:93–96, 2008) for an arbitrary dipole is incorrect. A brief discussion of another erroneous result (J. Supercond. Nov. Magn. 15:257–262, 2002) for a transverse/tangential dipole–sphere configuration, corrected elsewhere recently, is reproduced. Correct expressions for the interaction energy with some limiting cases are also provided. The result derived here demonstrates that the value of the levitation force for a dipole that makes an angle with z-axis lies between the values for a radial dipole–sphere and transverse dipole–sphere configurations providing upper and lower bounds. It is found that for a magnetic dipole making an angle with z-axis, there exits a second force component along the negative y-direction, which influences a couple acting on the superconducting sphere. It is also shown that the couple is proportional to the second force component and that both the couple and second force components vanish for a radial dipole–sphere and transverse dipole–sphere configurations, respectively. These results appear to be new and have not had received due attention in the context of superconductivity.     

Laser manipulation of micro untransmissive particles in water

The laser trapping of untransmissive particles are discussed in this paper. Photon can generate the momentum to the untransmissive particle by diffraction and reflection on the surface of the particles. We tried laser trapping of untransmissive particles using an attractive force caused by the diffraction and radiation force caused by reflection. The laser trapping system includes CW YAG laser, which has 1.064 μm in wave length and an optical microscope. The motions of particles were monitored by a CCD camera on the top of the microscope and recorded by PC connected to the CCD camera.     

矿井直流电法超前预报球体构造的初步理论及沙槽实验研究

针对矿井直流电法掘进超前探测技术理论发展不够完善的现状,建立了独头巷道掘进面前方存在球体溶洞时的超前探测数学模型,发展了预报球体溶洞的超前探测理论,探讨了溶洞至掘进面距离、溶洞半径、埋深等参数与视电阻率异常的联系,给出了相应理论曲线或经验公式,并采用沙槽模拟实验对理论进行验证,对完善超前探测的资料解释技术,提高预报准确度具有指导意义.     

Diffusion cloud around and downstream of active sphere immersed in granular bed through which fluid flows

The concentration distribution in the wake of (and around) a soluble or fast reacting sphere, immersed in a granular bed of inert particles through which liquid or gas flows, with “uniform velocity”, has been obtained numerically, for solute transport by both advection and diffusion.Fluid flow in the granular bed around the sphere was assumed to follow Darcy's law and the elliptic PDE equation, resulting from a differential material balance on the solute in an elementary control volume, was solved numerically over the “whole range” of values of the Peclet number. The solution gives the steady state concentration contour plots around the sphere and, for each concentration level, the downstream extent and approximate maximum width of the corresponding contour surface were determined. General expressions are presented (as Eqs. (20) and (21)) to relate those variables with the Peclet number and this provides simple formulae to compute the approximate size of the diffusion wake downstream of the active sphere.     

Fabrication of egg-shell-roofed macroporous nickel films by a template-mediated electrodeposition process

Through an electrostatics-induced adsorption effect, nickel ions were found to be preferentially adsorbed onto the surface of colloidal particles at template top during the template-mediated electrodeposition process for preparing macroporous structures. This phenomenon results in the preferential reduction and growth of nickel on colloid surface on the template top, instead of filling into the channels among the colloids. After removing the template, an egg-shell-roofed macroporous nickel, consisting of macroporous film covered with monolayer of hollow spheres, can be created.     

Measurement of the Fluorescence Quantum Yield Using a Spectrometer With an Integrating Sphere Detector

A method is proposed for measuring the fluorescence quantum yield (QY) using a commercial spectrophotometer with a 150 mm integrating sphere (IS) detector. The IS detector is equipped with an internal cuvette holder so that absorbance measurements can be performed with the cuvette inside the IS. In addition, the spectrophotometer has a cuvette holder outside the IS for performing conventional absorbance measurements. It is shown that the fluorescence quantum yield can be obtained from a combination of absorbance measurements of the buffer and the analyte solution inside and outside the IS detector. Due to the simultaneous detection of incident and fluorescent photons, the absorbance measurements inside the IS need to be adjusted for the wavelength dependence of the photomultiplier detector and the wavelength dependence of the IS magnification factor. An estimate of the fluorescence emission spectrum is needed for proper application of the wavelength-dependent adjustments. Results are presented for fluorescein, quinine sulfate, myoglobin, rhodamine B and erythrosin B. The QY of fluorescein in 0.1 mol/L NaOH was determined as 0.90±0.02 where the uncertainty is equal to the standard deviation of three independent measurements. The method provides a convenient and rapid estimate of the fluorescence quantum yield. Refinements of the measurement model and the characteristics of the IS detector can in principle yield an accurate value of the absolute fluorescence quantum yield.