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.     

QT600—3材料的拉伸模表面强化处理研究

目前用球墨铸铁材质经表面强化处理后制造的各种工模具，在生产上得到了越来越多的应用。长期的生产实践表明，用QT600-3制做的拉伸模，经正火后氮碳共渗处理，不仅具有良好的力学性能和使用寿命，而且经济上合理,技术上可靠。因此必将得到日益广泛的应用，为我们以铁代钢，在模具材料的选择上拓宽了道路。     

增强泡沫铝复合材料制备工艺的研究

在泡沫铝材中复合硬度很高的ZrO2陶瓷球可以起到增强泡沫铝的作用。本文采用盐粒与陶瓷球复合预制体及渗流成型工艺,通过改进模具和优化工艺参数,成功制备了ZrO2陶瓷球增强泡沫铝复合材料试样。试验结果表明,在实验室条件下,当浇注温度为805℃～815℃（纯铝）、760℃～770℃（铝硅）,模具和填料预热温度为600℃～610℃（纯铝）、560℃～570℃（铝硅）时,可以获得外形尺寸为φ30×50（mm）、孔隙率为56%～75%、陶瓷球尺寸为φ1mm,陶瓷球与盐粒体积比例为1：5、2：3的试样。为泡沫复合材料的进一步开发和研究奠定了基础。     

Principle and application of ball SAW devices

A thin beam of waves usually diverges due to diffraction, which is a limitation of any device using such waves. However, a surface acoustic wave (SAW) on a sphere with an appropriate aperture does not diverge but is collimated, realizing ultra‐multiple roundtrips along an equator of the sphere. This effect is caused by the balance between diffraction and focusing on a spherical surface, and it enables realization of high‐performance ball SAW sensors. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(1): 41–51, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20817     

THE DISSOLUTION OR GROWTH OF A SPHERE

The problem of the dissolution or growth of an isolated, stationary, sphere in a large fluid body is analyzed. The motion of the boundary as well as the resulting motion in the liquid are properly taken into account. The governing equations are solved using a recently developed technique (Subramanian and Weinberg, 1981) which employs an asymptotic expansion in time. Results for the radius of the sphere as a function of time are calculated. The range of utility of the present solution is established by comparison with a numerical solution of the governing equations obtained by the method of finite differences.     

Microsphere tensiometry to measure advancing and receding contact angles on individual particles

In this paper, a method to measure the advancing and receding contact angles on individual colloidal spheres is described. For this purpose, the microspheres were attached to atomic force microscope cantilevers. Then the distance to which the microsphere jumps into its equilibrium position at the air-liquid interface of a drop or an air bubble was measured. From these distances the contact angles were calculated. To test the method, experiments were done with silanized silica spheres (4.1 μm in diameter). From the experiments with drops, an advancing contact angle of 101 ± 4° was determined. A receding contact angle of 101 ± 2° was calculated from the jump-in distance into a bubble. Both experimental techniques gave the same contact angle. In contrast, on similarly prepared planar silica surfaces, a clear hysteresis was measured with the sessile drop method; contact angles of 104.5 ± 1° and 93.8 ± 1° were determined for the advancing and receding contact angles, respectively.     

表面修饰二氧化硅微球的制备、表征及分散性能

采用一步法制备了亚微米纯二氧化硅微球及8种有机硅表面修饰的二氧化硅微球,用扫描电镜、氮吸附、零电荷点测定等方法对微球进行了表征,对比研究了微球在不同介质中的分散性能。所有微球都呈球形,形貌较好,依表面修饰基团的不同,粒子直径在0.42~0.54nm之间。所有微球均为实心,比表面积均小于21m2/g。微球的零电荷点在8.25~8.93之间变化。粒子经过表面修饰后,在不同介质中表现出了不同的分散行为,微球的分散行为可以由微球的亲水及疏水性,以及DLVO理论得到基本解释。     

探讨高温均匀化对Ly_(12)硬铝合金板锭塑性的影响

通过高温均匀化试验， 用金相法探讨不同的均热温度对 Ｌｙ１２ 板锭塑性的影响；不同的冷却方式改善 Ｌｙ１２ 板锭的微组织和工艺塑性。     

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.