Pairwise interaction of drops of magnetic emulsion under the action of rotating field

Consideration is given to the dynamics of a pair of drops of a magnetic liquid that are suspended in a normal liquid with relatively low viscosity under the action of a rotating field. Account is taken of hydrodynamic and dipole-dipole interactions as well as of the electrodynamic torque due to the finite relaxation time of magnetization of the magnetic liquid. It is shown that hydrodynamic interaction leads to the formation of a rigid pair in the rotating field and the electrodynamic moment of forces governs its dynamics at large frequencies, leading to a growth that is linear in the field frequency in the rotational velocity for the pair of drops, whereas a pair of solid particles loses sensitivity to the field. Academic Scientific Complex “A. V. Luikov Institute of Heat and Mass Transfer of the Academy of Sciences of Belarus,” Minsk, Belarus. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 1, pp. 98–102, January–February, 1996.     

横向稳态磁场作用下微束等离子电弧数值分析

为分析外加横向稳态磁场作用下电弧特性与电弧对工件热、力输入的变化规律,本文建立了微束等离子电弧三维模型,将外加磁场简化为背景场添加至模型,使用有限元分析软件COMSOL进行求解计算.结果表明:外加横向稳态磁场作用下,喷嘴内部各项特性均未发生较大变化,喷嘴下方电弧等离子体在洛伦兹力的作用下向x负方向移动,电弧温度、等离子...     

Biofluid flow in a channel under the action of a uniform localized magnetic field

In this work the fundamental problem of the biomagnetic (blood) fluid flow in a channel under the influence of a steady localized magnetic field is studied. For the mathematical formulation of the problem both magnetization and electrical conductivity of blood are taken into account and blood is considered as a homogeneous Newtonian fluid. For the numerical solution of the problem, which is described by a coupled, non linear system of PDEs, with appropriate boundary conditions, the stream function–vorticity formulation is adopted. The solution is obtained by the development of an efficient numerical technique based on finite differences. Results concerning the velocity and temperature field, skin friction and rate of heat transfer, indicate that the presence of the magnetic field influences considerably the flow field. It is also obtained that the electrical conductivity of blood should be taken into account at the area of the uniform magnetic field.     

Penetration of a weak magnetic field into superconducting indium

The penetration depth of a low frequency, weak magnetic field into superconducting indium has been studied as a function of temperature between 2 K andT _c . The data are analyzed in terms of the BCS theory. Values of _L (0) and (0) have been determined as 299 and 553 Å, respectively, with an accuracy of 10%.     

On the carrier contribution to the elastic constants in ultrathin films of bismuth under quantizing magnetic field

We present a simple analysis of the carrier contribution to the elastic constants in ultrathin films of Bi under magnetic quantization in accordance with McClure-Choi, Cohen, Abrikosov, Lax and parabolic ellipsoidal band models in the presence of spin, broadening and temperature respectively. It appears that the said contribution increases with increasing electron concentration and decreasing film thickness in various manners. The McClure and Choi model shows this more significantly than other models. We have also suggested an experimental method of determining the said contribution in degenerate materials having arbitrary dispersion laws.     

Vortices in 3He-A in a weak magnetic field

The structure and the energy of vortices in rotating ³He-A are considered in the presence of a weak magnetic field. It is shown, using the logarithmic approximation for the free energy, that there will be a sequence of textural transitions when the magnetic field is increased. The transition from a nonsingular texture to a singular texture is studied in detail. It is shown that the l vector is almost uniform outside the cores of vortices. To verify these results, measurements by NMR and by ultrasound are suggested.This work has been financially supported by the Academy of Science of the USSR, by the Academy of Finland, and by the Committee of Scientific and Technical Cooperation between Finland and the USSR.     

Attenuation of coupled waves in antiferromagnetic elastic conductors in weak magnetic fields

Following along the same line of approach as in a previous paper in which dissipative mechanisms were ignored, the present paper discusses the attenuation of coupled magnetoelastic oscillations in a simple deformable antiferromagnet of which the material symmetry has been broken by a relatively weak bias magnetic field. The linearized equations needed in the analysis are deduced from a fully dynamical nonlinear, rotationally invariant and thermodynamically admissible theory of deformable antiferromagnets. Three types of dissipative mechanisms are taken into account: viscosity, Spin-lattice relaxation and electrical conduction. While all these mechanisms affect to a greater or lesser degree the propagation of essentially transverse elastic modes outside resonance regions, electrical conduction modifies the absorption of spin waves due to spin-lattice relaxation and both viscosity and spin-lattice relaxation are shown to contribute, collaboratively and equally, to the damping of mixed elastic-spin modes in the two magnetoacoustic resonance regions which correspond to the interaction of left-circularly polarized transverse elastic waves and an upper spin-wave branch and right-circularly polarized transverse elastic waves and a lower spin-wave branch, respectively. The analytical discussion of the resulting dispersive and attenuated coupled modes is achieved in terms of characteristically small parameters in a quasi-magnetostatic approximation. The phenomenon of heat conduction, important as it may be, is left out of the analysis.     

Turbulent biomagnetic fluid flow in a rectangular channel under the action of a localized magnetic field

The fundamental problem of the turbulent flow of a biomagnetic fluid (blood) between two parallel plates under the action of a localized magnetic field is studied. The blood is considered to be an electrically conducting, incompressible and Newtonian fluid and its flow is steady, two-dimensional and turbulent. The turbulent flow is described by the Reynolds averaged Navier–Stokes (RANS) equations. For the numerical solution of the problem under consideration, which is described by a coupled and non-linear system of PDEs, with appropriate boundary conditions, the stream function–vorticity formulation is used. For the eddy-kinematic viscosity, the low Reynolds number k–ε turbulence model is adopted. The solution of the problem, for different values of the dimensionless parameter entering into it, is obtained by developing and applying an efficient numerical technique based on finite differences scheme. Results concerning the velocity and temperature field, skin friction and rate of heat transfer, indicate that the presence of the localized magnetic field, appreciable influences the turbulent flow field. A comparison is also made with the corresponding laminar flow, indicating that the influence of the magnetic field decreases in the presence of turbulence.     

磁场作用下轴向运动功能梯度Timoshenko梁的振动特性

轴向运动结构的工程振动问题一直是动力学领域中的重要课题之一。为了更全面地分析工程中的振动,针对磁场作用下轴向运动功能梯度Timoshenko 梁的振动特性展开论述。基于梁的动力学方程组和相应的简支边界条件,应用复模态方法,得到不同参数时固有频率和衰减系数与轴向运动速度的对应关系。采用微分求积法分析磁场作用下前四阶固有频率和衰减系数随轴向运动速度的变化,并与复模态方法的结果进行对比验证。数据结果表明复模态方法得到的结果是精确解析解。衰减系数呈现不对称性,耦合固有频率呈现分离性。随着轴速、磁场强度和功能梯度指数的增大,梁的固有频率减小;随着支撑刚度参数的增大,梁的固有频率增大。     

Voltage-current characteristics of an arc in an annulus moving under a magnetic field

Voltage-current relationships are presented in dimensionless terms for the high-current arc rotating in an annular gap under the influence of a magnetic field; air passes through the gap. It is found that one can neglect the effects of the air flow if the speed of the air is small.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 20, No. 4, pp. 683–689, April, 1971.     

弱酸性固化剂对UF树脂固化性能的影响分析

为研究不同种类固化剂对弱酸性起始合成脲醛树脂(UF)固化性能的影响,选用6种固化剂研究固化剂对弱酸性起始合成UF树脂的固化速度、适用期、胶接材料的胶接强度和材料甲醛释放量的影响.研究结果表明:单组份固化剂中,双氧水作为固化剂时UF树脂适用期最长,氯化铵固化速度最快;双氧水加入量是UF树脂质量的5%时,树脂胶接材料的甲醛释放量最低,胶合强度最高;聚醋酸乙烯酯、磷酸二氢铵、氯化铝、柠檬酸和尿素组成的多组分固化剂适用期最长.氯化铵、硫酸铝和尿素组成复合固化剂的UF树脂固化物的甲醛释放量和固化温度最低.     

Dynamic response of an elastic fence under wind action

Abstract

The along‐wind response of a surface‐mounted elastic fence under the action of wind was investigated numerically. In the computations, two sets of equations, one for the simulation of the unsteady turbulent flow and the other for the calculation of the dynamic motion of the fence, were solved alternatively. The resulting time‐series tip response of the fence as well as the flow fields were analyzed to examine the dynamic behaviors of the two.

Results show that the flow is unsteady and is dominated by two frequencies: one relates to the shear layer vortices and the other one is subject to vortex shedding. The resulting unsteady wind load causes the fence to vibrate. The tip deflection of the fence is periodic and is symmetric to an equilibrium position, corresponding to the average load. Although the along‐wind aerodynamic effect is not significant, the fluctuating quantities of the tip deflection, velocity and acceleration are enhanced as the fundamental frequency of the fence is near the vortex or shedding frequency of the flow due to the occurrence of resonance. In addition, when the fence is rather soft, a higher mode response can be excited, leading to significant increases in the variations of the tip velocity and acceleration.     

Mechanico-electromagnetic waves in elastic dielectric crystals in a magnetic field

The mechanico-electromagnetic coupled waves under an external magnetic field are theoretically investigated, where elastic dielectric crystals with higher symmetry are taken into consideration. There are three types of the coupled waves: the predominantly electromagnetic waves, the predominantly mechanical transverse and longitudinal waves. Their propagation velocities, and the amplitude ratios of the polarization, the mechanical vibration, and the electromagnetic fields are obtained, which depend not only on the material constants but also on the suppressed magnetic intensity and its direction relative to the propagation direction.     

Influence of interelectrode gap and magnetic induction on the voltage of an electric arc moving in air under the action of a magnetic field

For arcs that are initiated in an air medium in rotation in a ventilated annular gap and move along parallel electrodes under the action of an external magnetic field, the influence of the magnitude of the interelectrode gap and magnetic induction on the discharge voltage is considered. The accuracy of the volt-ampere characteristics of the arc in approximating by means of simple empirical power formulas and with the use of criterial relations between generalized variables is estimated. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 3, pp. 469–475, May–June, 1997.     

Electrodynamics of superconductors. Response to a weak,low-frequency magnetic field

The phenomenon of the penetration of a low-frequency weak magnetic field into a superconductor has stimulated extensive theoretical and experimental studies. These have led to important clarifications regarding the nature of the superconducting phase by, for example, making concrete the idea of the long-range order in terms of the coherence length, which in turn has provided an understanding of the details of the penetration phenomenon under various conditions realized for different relative values of the penetration depth and the coherence length. This work is a review of the theoretical and experimental studies of the penetration phenomenon. The theory of the penetration phenomenon is discussed phenomenologically and microscopically. Different experimental techniques employed to study the phenomenon are discussed. Many of the experimental studies are concerned with the temperature dependence of the penetration depth. These results are reviewed for different elemental superconductors. Practical difficulties in a quantitative analysis of such data are pointed out. A new strategy adopted recently by Egloffet al. for analyzing the penetration depth data of pure lead is discussed. Effects of impurities, anisotropy of the Fermi surface, and the magnetic field on the penetration phenomenon are also discussed.