Characteristics of a rectangular waveguide containing a magnetized cylindrical ferrite post

A rigorous formulation of the scattering by a magnetized ferrite in a rectangular waveguide is presented. The EM field depends on the dimension, the frequency and the internal static magnetic field of the ferrite post. For some special values of the above quantitites the reflection or the transmission coefficient becomes equal to zero. These values give a family of filters and the results which follow explain their characteristics.     

长叶柄轴对称植物叶片长度的图像测量方法

植物叶片的长度是重要的叶片形态参数之一。给出了一种基于图像的长叶柄轴对称叶片中轴长度测量方法。通过扫描仪获取叶片图像;利用阈值分割和数学形态学操作提取叶片区域;利用骨架化方法提取叶片区域骨架;利用数学形态学开操作去除叶柄部分,并确定叶柄根部的骨架点作为中轴的起点;对叶面区域的骨架进行分支和交叉块的标记,并对未落在叶面区域边缘的骨架端点进行延拓;穷举式地获取所有从中轴起点到其余骨架端点的路径,并根据等面积准则和最大曲率准则确定中轴;对中轴进行折线拟合,并根据拟合折线的长度和图像的物理分辨率计算得到叶片长度。在实际叶片图像上的实验结果表明所提出的方法有效,且测量精度优于已有的、基于最小外接矩形检测的方法。     

Exact solutions of cyclically symmetric oscillator equations with non-linear coupling

Kaplan and Yardeni have found very simple exact limit cycle solutions in cyclically symmetric systems of N oscillator equations with linear coupling in zero order of a perturbation parameter and non-linear coupling in first order. In contrast with such solutions in other non-linear systems, each of these limit cycles is a normal mode of the unperturbed equations, with no change in frequency. the sources of this simple behaviour are studied here with the equations expressed in terms of the normal mode co-ordinates of the unperturbed system rather than in the original co-ordinates. It is found that the simplicity of the Kaplan-Yardeni solutions arises partly from an additional symmetry of the perturbation terms beyond the cyclic symmetry and partly from the specific choices of the perturbations. Extension of their systems to arbitrary N leads to the result that all such sets of equations have similar simple limit cycles. More general cyclically symmetric sets of equations are also discussed, with limit cycle solutions whose frequencies are shifted from the zero-order values by easily calculated amounts or with solutions which are linear combinations of zero-order normal modes.     

Reactive flow analysis of nonthermal plasma in a cylindrical reactor

In the study reported herein, chemical reactive flow fields of nonthermal plasma were clarified by using both experimental and numerical methods. The plasma was generated by using needle-plate electrodes. The operating gas was air injected at a rate of 1-10 NL/min through a cylindrical reactor with a diameter of 6 mm. Applied voltage of 12 kV was positive or negative with a square wave of 20 Hz. Distributions of gas velocity, gas temperature, and NO and NO/sub 2/ concentrations were analyzed by experimental and numerical methods. Conservation equations of mass, chemical species, momentum and energy, and 22 chemical species and 89 chemical reactions are taken into consideration in the model herein proposed. Distributions of axial velocity and gas temperature, their concentrations of NO and NO/sub 2/, and the effects of gas flow rate were clarified. For these characteristics of the parameter, the same tendency was obtained by both experimental and numerical methods. Furthermore, distributions of radical species such as N and O were predicted by numerical analysis using experimental results.     

Distribution of the residual magnetic induction along a hollow cylindrical core magnetized by a longitudinal homogeneous static magnetic field

Experimental and numerical data on the distribution of the cross-section-averaged relative residual magnetic induction along the longitudinal axis of a hollow cylindrical core magnetized by a homogeneous static field obtained by the authors were analyzed. A new calculation formula was proposed. A distinguishing feature of this formula is that it takes into consideration the thickness of the core’s wall and the dependence of the magnetic properties of the material on the magnetizing field. A comparison between the numerical results and the experimental data for cores of different geometries manufactured of materials with different magnetic properties was made. The application area of the proposed formula was shown.     

Exact solutions of cyclically symmetric oscillator equations with non-linear coupling. Part II: Coupling with phase shift

Several authors have found very simple exact limit cycle solutions in cyclically symmetric systems of N oscillator equations with linear coupling in zero order of a perturbation parameter and non-linear coupling in first order. In contrast with such solutions in most other non-linear systems, each of these limit cycles is an exact normal mode of the unperturbed equations with no change in frequency or addition of higher harmonics. In Part I of this paper it was shown that the construction and analysis of such systems of equations are substantially simplified if the equations are expressed in terms of the normal mode co-ordinates of the unperturbed system. the effects of the cyclic symmetry, as well as those of a higher symmetry shared by previous authors' models, were studied. It is shown here that similar results can be obtained in systems if the coupling involves a phase shift. the phase shift places added conditions on the systems, so that some sets of equations, shown to have the simple limit cycle solutions, no longer have them after shift is introduced. the methods of the earlier paper, however, can be used to find families of systems with phase shifts which have such solutions. A result in Part I, that frequencies in a system with the higher symmetry mentioned above are unchanged from those of the unperturbed system, is not valid if phase shifts are introduced.     

Numerical simulation of ballistic surface transport in cylindrical nanosystems

We study, by numerical simulations, the effect of topology on coherent electron transport through cylindrical junctions and bent cylindrical surfaces. The dynamics of a particle bound to a curved surface is described by a modified Schrödinger equation depending on two curvilinear coordinates. The modeling approach based on a finite-difference discretization of the latter equation is described, and a comparison with the standard solution of Schrödinger equation for flat surfaces is given. The effect of the geometrical parameters of the structures is reported.     

变接触面圆柱形锂电池组液冷散热的热特性

设计了一种液冷散热的新方法,考虑到沿液冷管道,经过热量的累积,末端的温度高于前端,因此在沿流道方向设定接触面积阶梯变化的散热铝块,电池热量通过铝块传递到液冷管道,显著改善温度的均匀性.采用STAR-CCM+软件模拟的方法,对比接触面变化与等接触面的热性能,结果显示,相对于接触面积恒定的模组,变接触面积的模组冷却效率提高4.82％,温度一致性程度降低1.1℃.     

Design and field-weakening performance of a synchronous reluctancemotor with axially laminated rotor

Axially laminated reluctance motors can be designed to have high saliency and so offer very good performance in terms of torque capacity, power factor and efficiency. This paper presents the design and performance of a 7.5 kW four-pole machine, using thin rotor laminations, which achieved an unsaturated saliency ratio of 12.5. Finite-element analysis is used to predict machine parameters, paying special attention to modeling of the thin rotor elements and to saturation effect on the d axis. Computed parameters are compared with test measurements, showing good agreement. Load tests with 50Hz supply confirm the expected performance characteristics, but also show the occurrence of additional losses associated with the axially laminated rotor construction. A design modification to reduce the extra losses is demonstrated. A detailed investigation of field-weakening performance is reported, showing constant-power characteristics and good agreement between predicted and measured performance over a speed range of 2.25:1 above base speed     

Two-dimensional cylindrical model of the sector motor with a solid rotor

Contents In the paper, the Bubnov-Galerkin method coupled with the separation of variables was used to determine the electromagnetic field distribution. The field was assumed to be two-dimensional. On the basis of the calculations obtained the torque-slip characteristics of the sector motor were determined. The results were compared with the data presented in the literature of the subject.

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Das zweidimensionale zylindrische Modell eines Sektormotors mit einem massiven Rotor

Übersicht Zur Ermittlung der Verteilung vom elektromagnetischen Feld im betrachteten Modell hat man die Bubnov-Galerkin-Methode in Verbindung mit der Methode der Variablentrennung angewandt. Man hat dabei angenommen, daß dieses Feld zweidimensional ist. Unter Verwendung der berechneten Feldverteilung hat man auch die mechanischen Kennlinien des Sektormotors ermittelt, sowie die erhaltenen Ergebnisse mit den in der Literatur zutrittlichen Daten verglichen.

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List of symbols A vector potential, actual value - A vector potential (complex r.m.s. value) - A vector potential component with respect to thez-axis (complex r.m.s. value) - B _r ,B components of the magnetic induction vector in the cylindrical coordinates (complex r.m.s. values) - F force vector, actual value - F _a mean value of the vectorF - I r.m.s. value of the phase current per phase, layer and a pair of poles - imaginary unit - J current density vector (complex r.m.s. value) - J exciting specific electric loading (complex r.m.s. value) - J _n (u) Bessel function,n-th order, 1 st kind - k _c Carter coefficient taking into account the stator grooves - M _n mean torque for then-th harmonic - p number of the pairs of poles in the stator winding - |u| module of the complex number - z number of turns per phase, layer and a pair of poles - Re(u), Im(u) real and imaginary part of the complex numberu - derivative in the normal external direction - included angle taken by the specific electric loading of the stator - _Fe total included angle of the stator - ₀ magnetic permeability of vacuum - _Fe magnetic permeability of the rotor - conductivity - pulsation - _r angular velocity of the rotor - n _s synchronous rotational speed     

FDTD analysis of switching characteristics in magnetooptic functional devices using magnetostatic surface waves

Collinear magnetooptic interaction with magnetostatic surface waves (MSSW) can be used for wavelength‐selective switches, wavelength filters, and frequency shifters in wavelength‐division‐multiplexed (WDM) photonic networks and optical processing systems. The switching efficiency can be improved with a multilayer waveguide structure. To investigate the dynamic switching characteristics, the FDTD method was employed. The mode conversion between TE and TM mode was successfully demonstrated with FDTD simulation. The filtering characteristics were also evaluated. The FDTD results were compared with the result from the coupled mode theory, and good agreement was obtained. Switching of an optical pulse was also demonstrated by the FDTD method. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(1): 40–47, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20501     

Effect of plasma surface modification on electrical conduction in polyethylene

High-density polyethylene films 50 μm thick were exposed to the downstream plasma flow of RF glow discharges in argon, hydrogen, or oxygen. It was found that many transvinylene and unreacted radicals remain after the argon or hydrogen plasma treatment, and that carbonyl groups are formed in the oxygen plasma treatment. The conduction current was smaller in the hydrogen-plasma treated samples and the samples exposed to oxygen or ozone after hydrogen-plasma treatment than in the untreated samples. Thermal pulse current measurements indicate that the treated surface layer traps electrons or holes and reduces the field strength at the electrode surface, thus suppressing further injection of electrons or holes.     

Earthing impedance of cylindrical conductor in a two-layer soil

Contents The paper deals with the determination of the earthing impedance of a cylindrical electrode modelling an earthing system of a transmission tower. Assuming a soil of two layers, the effect of the eddy currents in the soil is investigated with the conductivity and the thickness of the layers varied. The solution of the Helmholtz equation given for the magnetic field intensity is obtained by a global variation method. The satisfaction of Dirichlet boundary conditions on the surface of earth and along thez-axis as well as of the continuity conditions on the interface of the layers is ensured with the aid ofR-functions.

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Bestimmung der Erdausbreitungsimpedanz von zylindrischen Elektroden

Übersicht Die Arbeit beschäftigt sich mit der Bestimmung Erdausbreitungsimpedanz von zylindrischen Elektroden. Im Fall von aus zwei Schichten bestehendem Erdboden wird die Abhängigkeit der Wirkung der Wirbelströme von der spezifischen Leitfähigkeit bzw. von der Schichtdicke untersucht. Die Lösung der Helmholtz'schen Differentialgleichung, die die magnetische Feldstärke beschreibt, erfolgt durch die Globalelementmethode der Variationsrechnung. Die Erfüllung der Dirichlet'schen Randbedingungen an der Oberfläche der Erde und entlang derz-Achse, sowie die Erfüllung der Kontinuitätsbedingungen an den Schichtgrenzen ist durch die Anwendung derR-Funktionen gesichert.

     

Analysis of grounding systems in soils with cylindrical soilvolumes

A theoretical model for the analysis of grounding systems located in soils with cylindrical soil volumes is presented for the first time. Exact closed-form analytical expressions for earth potentials due to current sources in different regions of such soil structures have been obtained. More precisely, the soil models considered contain horizontal semi-cylindrical soil volumes and vertical cylindrical soil volumes. Numerical results are presented for different grounding systems and for different types of cylindrical soil volumes. The results clearly show that these soil structures have a significant influence on the performance of grounding systems. The results obtained are in agreement with well-known simple case results and converge asymptotically to the uniform soil case     

Numerical investigations of electromagnetic processes in a solid cylindrical shield

A mathematical model is suggested to describe the processes in a solid cylindrical shield in protection against an alternating magnetic field. The model is constructed with respect to the complex amplitude of magnetic vector potential. Since magnetic field lines are in a plane perpendicular to the axis of a cylindrical shield, the problem becomes two-dimensional. The electromagnetic parameters of the considered media are constant and isotropic. The plates at which the magnetic potential is set are the source of the magnetic field. A distribution of real and imaginary components of the complex amplitude of magnetic potential is described by four differential equations in the conducting medium and by two equations in the dielectric one. An equality of magnetic potential at both sides of the interface is predetermined at the interfaces. The Robin boundary condition provides equality of the magnetic vector potential to zero at an infinite distance from the shield. The obtained differential equation system supplemented with the boundary conditions can be numerically solved by the finite elements method using the Galerkin method. As a result, distributions of magnetic potential and magnetic field intensity in the absence and presence of a shield are determined; shielding attenuation is then calculated. It is found that, with increasing shield thickness and noise frequency, the efficiency of electromagnetic shielding is increased. The adequacy of the suggested model and technique of determination of the shielding efficiency is corroborated by comparison with the results of an analytical model for a copper cylindrical shield.