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1.
A recently introduced model for an autonomous swimmer at low Reynolds number that is comprised of three spheres connected by two arms is considered when one of the spheres has a large radius. The Stokes hydrodynamic flow associated with the swimming strokes and net motion of this system can be studied analytically using the Stokes Green's function of a point force in front of a sphere of arbitrary radius R provided by Oseen. The swimming velocity is calculated, and shown to scale as 1/R 3 with the radius of the sphere.  相似文献   

2.
Flame interaction during the burning of two porous spheres in tandem arrangement fed with methanol and subjected to a mixed convective environment, has been studied experimentally and numerically. Porous sphere technique is employed for experimentally simulating the burning characteristics of methanol transpired spheres of different sizes, separated by fixed distances. The mass burning rates from both the spheres and visible flame stand-off distances from the sphere surfaces have been measured in the experiments. In the numerical simulations, transient, axisymmetric, mass, momentum, species and energy conservation equations are solved using a finite volume technique based on non-orthogonal semi-collocated grids. Features of the numerical model include finite rate chemistry and temperature and mixture composition dependent thermo-physical properties. Burning of tandem porous spheres in an air stream flowing vertically upwards, at atmospheric pressure has been simulated for different sphere sizes, separation distances and free stream velocities. The numerical predictions have been compared with experimental results. Results reveal that when two spheres burn one over the other, the transition from envelope to wake flame is delayed when compared with that of an isolated sphere. For two spheres of same diameter burning one over the other, depending on the separation distance, flame blows-off after the occurrence of transition from envelope to wake flame in the bottom sphere. For the case of larger sphere at the top, either the flame stabilises in the recirculation zone formed in between the spheres or the flame from the smaller sphere lifts off and stabilises near the front portion of the larger sphere, depending on the separation distance. At higher separation distances, around four times the diameter of the sphere, both the spheres burn independently. The burning rate undergoes complex variations with air stream velocity depending on the sphere sizes and separation distances.  相似文献   

3.
本文运用广义相对论讨论了满足负指数多方状态方程的流体多层球。经典引力理论与相对论性理论的差别由σ标志。σ是球体中心处的压力与密度之比。通过数值积分得到了n<0的相对论性Emden函数。在-1ed*也增大。 关键词:  相似文献   

4.
In [1] the image force was shown to impose additional conditions for the electrostatic suspension of a sphere without dynamic control of the electrode potential, and the dependence of the critical voltage between the electrodes on the sphere radius was derived experimentally. In this work, this dependence is found analytically by calculating electrical forces in the third-order approximation in shift of the sphere from equilibrium.  相似文献   

5.
王中林  郑丹  孙冬丽 《应用光学》2007,28(6):707-711
光学球面曲率半径是决定光学球面光学特性的重要参量,通过测量光学球面的曲率半径,可以审核光学元件设计制造质量。在基于白光干涉理论基础上,将莫尔光栅位移测量系统及CCD数字图像采集处理系统集成到迈克尔逊干涉仪上,利用CCD数字图像处理技术,构建了光学球面曲率半径自动测量系统。该测量系统对于大曲率半径的光学球面测量精度较高;对于半径R=71.2037mm的光学球面,其测量标准误差σR=0.4723mm。实验结果表明:设计的光学球面自动测量系统可以对大曲率半径光学球面实现高精度测量。  相似文献   

6.
This work addresses the relationship between grain properties and the permeability and permittivity spectra of non-crystalline materials or aerosols.

The scattered multipolar fields about a single sphere are related to the polarizability of a random collection of such spheres. Using the Clausius-Mossotti relation the effective permeability and permittivity spectra of an amorphous material is determined for arbitrary permittivity and permeability of the individual spheres, packing density, and sphere size. Although the author considers the spectra over a range where the product of the external wavevector and sphere radius is kept small, typically less than one-tenth, the product of the internal wavevector and sphere radius is unconstrained and seen to have a large effect on predicted spectra.

The result is a variety of possible spectral types which include resonances, relaxations and certain complex. conglomerate spectra that have been measured and far which no direct explanation is otherwise available.  相似文献   

7.
利用T-matrix方法对太赫兹波段亚波长半导体球形阵列进行了数值模拟并在数值模拟结果的基础上讨论了其光学特性。在太赫兹波段可以通过掺杂等手段调节半导体的表面等离子体特性。以半导体InSb为例并采用Drude模型,对单个亚波长球及两个或多个亚波长球组成的阵列进行了数值模拟,主要以归一化消光截面为参数,讨论了不同阵元半径、不同球形单元间距、不同单元数目及入射波不同极化方向对阵列特性的影响。  相似文献   

8.
Masafumi Fujii 《Optics Communications》2012,285(21-22):4553-4557
The force exerted on metal nano-particles is investigated numerically when the particles are in contact to form a cluster and are illuminated by a light of their fundamental plasmonic resonance frequency. For touching spheres, the mode of resonance changes drastically from those of separate spheres, and the resonance typically appears in the infrared wavelength range. For silver and gold two-sphere clusters, i.e. homo-dimers, of various radii, the magnitudes and the directions of the exerted forces are analyzed. It is found that the field enhancement in the gap region between the spheres depends largely on the sphere radius, and the force on the fundamental resonance exhibits binding only for small spheres; the greatest binding force is observed for radii of 40–60 nm; and the force turns to repelling when the radius becomes greater than approximately 100–150 nm as the field in the gap region becomes weaker.  相似文献   

9.
Absolute stability limit for relativistic charged spheres   总被引:1,自引:0,他引:1  
We find an exact solution for the stability limit of relativistic charged spheres for the case of constant gravitational mass density and constant charge density. We argue that this provides an absolute stability limit for any relativistic charged sphere in which the gravitational mass density decreases with radius and the charge density increases with radius. We then provide a cruder absolute stability limit that applies to any charged sphere with a spherically symmetric mass and charge distribution. We give numerical results for all cases. In addition, we discuss the example of a neutral sphere surrounded by a thin, charged shell.  相似文献   

10.
Abstract

This work addresses the relationship between grain properties and the permeability and permittivity spectra of non-crystalline materials or aerosols.

The scattered multipolar fields about a single sphere are related to the polarizability of a random collection of such spheres. Using the Clausius–Mossotti relation the effective permeability and permittivity spectra of an amorphous material is determined for arbitrary permittivity and permeability of the individual spheres, packing density, and sphere size. Although the author considers the spectra over a range where the product of the external wavevector and sphere radius is kept small, typically less than one-tenth, the product of the internal wavevector and sphere radius is unconstrained and seen to have a large effect on predicted spectra.

The result is a variety of possible spectral types which include resonances, relaxations and certain complex. conglomerate spectra that have been measured and far which no direct explanation is otherwise available.  相似文献   

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