bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a novel uniaxial force sensor with two-stage force resolutions
Authors: Jun Jiang , Jingmeng Liu , Weihai Chen , Wenjie Chen
Published: December 2018

This paper presents the concept design of a novel uniaxial force sensor with two stage force resolutions. Unlike conventional stain-gauge-based force sensing devices, the developed force sensor measures an external force through measuring the displacement of a movable member suspended by a compliant mechanism. The compliant mechanism is specially designed to have two stiffness values within its workspace. The low stiffness is used for small range and fine resolution force measurement, while the high stiffness is used for large range and coarse resolution force measurement. In order to get the required performance, the static stiffness as well as the dynamics of the sensing system is analyzed both analytically and numerically. After a prototype sensor is fabricated, preliminary characterization tests are carried out to verify the accuracy of the theoretical model and validate the effectiveness of the proposed design. The experimental results indicate that the structure of the force sensor is compact, and it has the ability to measure both micro range and macro range forces within one setup, meanwhile keeps very fine resolutions.
Optimizing of mathematical modeling of induced current for electronic anti-fouling system and estimate of system performance under different excitation signal
Authors: Han Yong , Zhao Yongping , Ding Mingli
Published: December 2018

A new optimizing method of mathematical analytical modeling of induced current for electronic anti-fouling technology is used in the present study to solve the problem of large calculated amount and complex deducing process caused by traditional segmented function method under different excitation signal, and an exact 2D finite element method is used to calculate induced current in a real electronic anti-fouling system, and the finite element calculation results can fit well with the results calculated by the optimizing analytical model of induced current under the excitation signal with different waveform. Furthermore, the average power density of induced current and the efficiency of energy transformation for EAF system are calculated to estimate the system performance under different excitation signal. The calculation result shows that: 1 the positive – negative square wave excitation signal can make the largest average power density of induced current and the sine wave excitation signal makes the smallest; 2 the sawtooth wave excitation signal can make the highest efficiency of energy transformation and the positive – negative square wave excitation signal makes the lowest.
Semi-permeable crack in a soft ferromagnetic solid
Authors: Shi Yan , Gao Cun-Fa , Chang Chao
Published: December 2018

On the crack problem of ferromagnetic solids, almost all studies in previous literatures used two simple crack models, e.g., permeable and impermeable crack models. This means that a crack is always assumed to be a slit without thickness (mathematical crack). In fact, when a ferromagnetic solid with a crack is placed in magnetic fields, the mechanical/or magnetic loadings will make the crack opening and the high magnetic fields will be induced inside the deformed crack. Thus, the crack should be modeled as a semi-permeable cavity. In the present work, the semi-permeable crack model is adopted to study the fracture problems of a soft ferromagnetic solid. The general solutions are derived for complex potential functions and the intensity factors of fields. For some special cases, more explicit solutions are given and compared with those in literature. Numerical results are also presented to discuss the effects of magnetic fields inside the crack on fracture behavior of the ferromagnetic solid, and it is found that the model of semi-permeable crack is more reasonable than that of permeable crack or impermeable crack.
Characteristic analysis of a flux-reversal motor driven by a four-switch converter with a compensated current regulation
Authors: Kim Tae Heoung
Published: December 2018

A 3-phase flux-reversal motor (FRM) driven by a 6-switch converter has been studied for its various merits such as a low inertia, a high efficiency and fault tolerance. However, it is needed to develop the FRM with a 4-switch converter to reduce motor and converter construction costs. Among the many different 4-switch converter topologies, the one with a compensated current regulation base on a novel pulse width modulation (PWM) control technique has been proposed as a good solution. In this paper, we introduce a two dimensional time-stepped voltage source finite-element method (2D-FEM) to analyze the FRM driven by the proposed 4-switch converter. We also compare the characteristics of the FRM when the compensated current regulation is adopted or not. To verify the analysis method and simulated results, the 4-switch converter and the prototype FRM are built and experiments are performed.
An improved design of MEMS switch for radio frequency applications
Authors: Sharma Ashish Kumar , Gupta Navneet
Published: December 2018

An improved design of microelectromechanical system (MEMS) switch for radio frequency (RF) applications has been proposed using non-uniform serpentine flexure structure. An analytical modeling of non-uniform serpentine flexure is obtained using small displacement theory and is compared with finite element method (FEM). It is observed that in comparison to the uniform serpentine flexure reported so far, the proposed design shows a considerable reduced spring constant of 0.65 to 0.04 N/m and pull-in voltage of 15 to 3 V with better RF power handling capabilities of 4.29 to 0.2 W for span beam length varying from 100 to 280 μm. The proposed switch design shows with better RF response in terms of return loss of−20 dB and isolation of −40 dB at 26 GHz.
Magneto-natural convection in square cavities with a source-sink pair on different walls
Authors: Mahmoodi Mostafa , Esfe Mohammad Hemmat , Akbari Mohammad , Karimipour Arash , Afrand Masoud
Published: December 2018

Magnetohydrodynamic natural convection fluid flow and heat transfer in a square enclosure with a pair of source and sink on its walls, filled with liquid Gallium fluid with Prandtl number of 0.02 has been investigated numerically. The heat source and heat sink are maintained at a constant temperature T_{h} and T_{c} , respectively with T_{h} > T_{c} . By variation of relative location of the heat source and sink on the walls of the enclosure, five different cases are generated. The governing equations written in terms of the primitive variables are solved numerically using the finite volume method and the SIMPLER algorithm. Using the developed code, a parametric study is performed, and the effects of the Rayleigh number, the Hartman number, and the locations of the source and sink on the fluid flow and heat transfer inside the enclosure are investigated. The results show that the flow and temperature distributions inside the enclosure are affected by the strength of the magnetic field, the Rayleigh number, and the relative location of the heat source and sink. The magnetic field decreases the rate of heat transfer, suppresses the convection heat transfer, and tends to slows down the flow velocity in the cavity. Moreover in some cases the magnetic field changes the flow pattern inside the enclosure.
Computation and analysis of RCS for a kinetic energy type anti armour missile at Ka band
Authors: Muthu Ganesh Madhan , Kumar Jagadeesh Velan , Jayaraman Roopchand
Published: December 2018

Radar Cross Section (RCS) computation and analysis are carried out for a high speed, kinetic energy missile at 35 GHz. The radar cross section simulations were performed under bistatic conditions, using a 3D Electromagnetic field solver. RCS values for standard geometries such as cylinder, cone – cylinder combination are calculated under different excitation conditions and the results are verified with literature, so as to fix the settings in the solver. A maximum RCS value for the missile is obtained as −4.9 dBsm under broad side excitation. RCS values of−22.25 dBsm and 4.94 dBsm are obtained for 0° (Nose cone) and 180° direction, when excited in the frontal region, i.e., 0° azimuth and 0° elevation. Further, monostatic simulation under 0° to 180° excitation shows a large RCS value of−4 dBsm at 90°, corresponding to large surface area of the missile. The effect of frequency on the RCS of the missile is also determined in 30 to 40 GHz band. A comparison of integral equation solver and asymptotic solver for RCS computation indicates almost similar values, with a deviation less than 5 dB in most of the ranges. However, with compromise on accuracy, the asymptotic solver is found to consume only 5% of the total time required by integral equation solver.
Discussion of modified Jiles-Atherton model including dislocations and plastic strain
Authors: Xu Ming-Xiu , Chen Zhang-Hua , Xu Min-Qiang , You Tian-Qing
Published: December 2018

In metal magnetic memory (MMM) detection, the Jiles-Atherton model describes material magnetization caused by the geomagnetic field and cyclic stress. However, characterization of the effects of fatigue damage on magnetization remains an issue. In this paper, an expression for magnetization intensity M_{0} related to dislocation and plastic strain amplitude ε _{p} was incorporated into a modified Jiles-Atherton model. To validate the M_{0} expression, standard tensile fatigue tests were performed. Results indicate that the domain wall pinning parameter k_{1} in M_{0} is linear in both dislocation density ρ and average dislocations slippage distance �λ, as is also the shear plastic strain amplitude in the stress control fatigue. The stress amplitude in strain control fatigue however is linear with respect to ρ ^{1/2} . Therefore, M_{0} can be expressed as a function of stress andε _{p} (or �λ and stress amplitude). Experiments showed that calculated M_{0} variations in fatigue development processes can reflect a variation law in the MMM signal, with certain differences. There is a numerical difference between H_{px} and M_{0} because the surface magnetic field is much weaker than that within the ferromagnetic material. H_{px} increases after macro crack initiation caused by an additional material demagnetization field and a leakage field near the crack during cracking.
Electromagnetic reflection and transmission from a planar isotropic chiral-uniaxial chiral interface with optical axis normal to interface
Authors: Ghaffar A. , Alkanhal Majeed A.S.
Published: December 2018

In this paper, analysis and theoretical formulations are developed for the reflected and the transmitted waves from a planar interface of isotropic chiral-uniaxally anisotropic chiral media with optical axis normal to interface. General expressions for the reflection and transmission coefficients for right circularly polarized (RCP) and left circularly polarized (LCP) incident waves are derived. The results of the reflected and transmitted powers for materials with different isotropic chirality and uniaxial chirality values for both RCP and LCP incident waves are presented. The effects of the uniaxial chirality on three other cases of dielectric constant combinations are also studied. The numerical results computed by the developed transfer matrix technique expressions are found to coincide with published results obtained by computational techniques for special material cases.
On the investigation of scattered field from coated PEC cylinder buried beneath slightly rough surface
Authors: Fiaz M.A. , Ashraf M.A.
Published: December 2018

An analytic technique based on spectral plane wave representation of fields (SPRF) for the scattering of a plane wave from a perfectly electric conductor (PEC) cylinder coated with double positive (DPS) or double negative(DNG) materials buried beneath a slightly rough surface is formulated. Small Perturbation Method is used to consider scattering from rough surface. Spectral integrals are evaluated using saddle point method. A comparison with the previously available results has been done for validity. Both TM and TE polarizations are considered to obtain results varying different geometrical and physical parameters.
FEA of electromagnetic forming using a new coupling algorithm
Authors: Abdelhafeez Ali M. , Nemat-Alla M.M. , El-Sebaie M.G.
Published: December 2018

Finite element modeling of electromagnetic forming includes modeling of mechanical aspects, modeling of electromagnetic aspects, and a coupling method between the two models. The electromagnetic problem is to determine the magnetic pressure and its temporal and spatial distribution. Whereas the mechanical problem is to find out workpiece deformation resulting from the magnetic pressure applied on this workpiece. Nonetheless complications in the simulation exist due to pressure variation with workpiece deformation. These difficulties can be resolved by using one of the known coupling algorithms; loose coupling, or strong coupling. But these coupling strategies either have low accuracy of results or take long simulation time. The current research introduces an enhanced loose coupling algorithm for simulation of electromagnetic sheet metals bulging. The proposed coupling strategy takes into account deformation effects on pressure without the need for solving the updated electromagnetic model every new time step. Comparison between present simulation results and experimental results of other researchers showed good agreement. Effective plastic strain, and effective plastic strain rate distribution and evolution were presented in addition to thickness and deflection evolution of the workpiece.
Piezoelectric device wirelessly driven by electric field
Authors: Bhuyan Satyanarayan , Panda Sanjib K. , Hu Junhui
Published: December 2018

Wireless drive of piezoelectric component by electric field has been proposed and experimentally investigated. The electric field is generated by a spiral coil antenna-like electric field generator. Wireless electric energy transmission to the piezoelectric component can be enhanced when the spiral coil antenna is in electric resonance with a capacitor. It has been found that the output power achieved wirelessly by the piezoelectric component depends on the operating frequency, electrical load, distance and electric field. At resonant frequency of 772 kHz and optimum electrical load resistance of 350Ω, a maximum power of 0.362 mW has been received wirelessly by the piezoelectric plate operating in the thickness vibration mode, placed 4 mm away from antenna plane with input source power of 1.294 W. The excitation of the piezoelectric component is done remotely, so as the component does not require any wiring to the source and can be used in various sensors and actuators applications.
Application of hybrid boundary element method to 2D microstrip lines analysis
Authors: Perić Mirjana T. , Ilić Saša S. , Aleksić Slavoljub R. , Raičević Nebojša B.
Published: December 2018

The hybrid boundary element method is applied for the calculation of the characteristic impedance of 2D microstrip lines with a finite width dielectric layer and with finite width or infinite ground planes. Even though these forms of microstrips are very typical in practice, they have not been investigated very often. The basic idea of this method is that an arbitrary shaped electrode can be replaced by equivalent electrodes, and an arbitrary shaped boundary surface between any two dielectric layers can be replaced by discrete equivalent total line charges placed in the air. The discretization technique is similar to the method of moments and is well known. As a contribution to the boundary element method, we combine it with the equivalent electrodes method, creating in that way a new hybrid boundary element method. This method could be applied to a large variety of very complex 2D problems, regarding microstrip lines with or without symmetry. The quasi TEM analysis is applied. We compare values of characteristic impedance obtained applying our method with the corresponding ones obtained by the finite element method and values already reported in the literature. Relative error less than 0.5%, fast convergence of the results and several times shorter computation time comparing to the time required by finite element method make our method very efficient in the calculation of parameters of 2D microstrip lines.
Broadband CPW-fed circularly polarized antenna with machine-gun-shaped feeding line and symmetric-aperture
Authors: Xi Li , Lin Yang , Shang Jun-Ping , Xi Chen , Feng Xue-Yong , Yi Wang
Published: December 2018

This paper presents a new design for wide slot circularly polarized(CP) antenna (WSCPA). Compared with existing WSCPA, the proposed design possesses much wider return loss S _{11} bandwidths and CP bandwidths. The main features of the antenna structure include a machine-gun-shaped CPW feeding line and a wide symmetric-aperture along the diagonal axis. Wideband return loss and CP radiations have been achieved by properly tuning circular-shaped aperture and feeding line. The measured bandwidths of 10 dB return loss and 3 dB axial ratio (AR) are around 110.2%(2.2–7.6 GHz) and 105.9% (2–6.5 GHz), respectively. Throughout this letter, the improvement process of the AR and S _{11} properties is completely presented and discussed.
Design of truncated microstrip based radiating structure loaded by split ring resonator
Authors: Patel Shobhit K. , Kosta Y.P.
Published: December 2018

In this paper, for the very first time, four corners truncated triple band square patch antenna loaded with Split ring resonator (SRR) structure has been reported. Based on truncated square patch antenna, it has a double split square ring resonant structure embedded in the center of the substrate of the square patch antenna. The resonant structure has a strong electric response in a certain frequency of interest, and can be used to construct metamaterial. The antenna is designed to function in triple bands in the frequency range of 0.5–2.0 GHz. The comparison of the metamaterial design with the conventional dielectric material design is also shown in the paper. Design results are obtained by a High Frequency Structure Simulator which is used for simulating microwave passive components.
Free vibration for an electromechanical integrated harmonic piezodrive system
Authors: Xu Lizhong , Li Huaiyong
Published: December 2018

The Authors propose an electromechanical integrated harmonic piezodrive system in which the piezodrive principle is combined with the harmonic drive and the movable tooth drive principles. The free vibration behavior of the flexible ring has important effects on operating performance of the drive system. Here, the dynamic equations for the harmonic piezodrive system are deduced. The natural frequencies and dynamic displacements of the drive system are investigated. Results show that a large length of the flexible ring, a small thickness of the flexible ring should be selected, and the flexible ring should be made with Cu in order to obtain better operating behavior of the drive system. These results are useful in design and manufacture of the drive system.
Viscous corrections for the viscous potential flow analysis of electrohydrodynamic Kelvin-Helmholtz instability with heat and mass transfer
Authors: Awasthi Mukesh Kumar , Asthana Rishi , Agrawal G.S.
Published: December 2018

The linear analysis of Kelvin-Helmholtz instability of the interface between two viscous fluids in the presence of horizontal electric field has been carried out when there is heat and mass transfer across the interface. The viscous correction for the viscous potential flow theory has been used for the investigation. Both fluids are taken as incompressible, viscous and dielectric with different kinematic viscosities and different permittivities. In the viscous potential flow theory, viscosity enters through normal stress balance and effect of shearing stresses is completely neglected. We include the viscous pressure in the normal stress balance along with irrotational pressure and it is assumed that this viscous pressure will resolve the discontinuity of the tangential stresses at the interface of two fluids. A dispersion relation has been derived and stability is discussed theoretically as well as numerically. Stability criterion is given in terms of a critical value of relative velocity of two fluids as well as critical value of the applied electric field. It has been observed that tangential electric field and vapor fraction both have stabilizing effect on the stability of the system while heat and mass transfer destabilizes the interface. Also, it has been found that the effect of irrotational shearing stresses stabilizes the system.
Magnetic effect on direct numerical simulations of fluid flow through a rotating rectangular straight duct
Authors: Wahiduzzaman Mohammad , Kamruzzaman Md. , Alam Md. Mahmud , Ferdows M.
Published: December 2018

This work has been numerically studied the fluid flow structure in the presence of magnetic field through a rotating rectangular straight duct under various flow conditions. Spectral method is applied as a main tool for the numerical calculation technique, where the Chebyshev polynomial, the Collocation method and the Newton-Raphson method are also used as secondary tools. The Magnetohydrodynamics incompressible viscous steady fluid flows in a straight duct of rectangular cross-section rotating at a constant angular velocity about the center of the duct of the cross-section is numerically investigated to examine the combined effects of Magnetic parameter( M_g ), Rotational Parameter ( T_r ), Pressure driven parameter (D_n ) and aspect ratio(γ)=b/a whereas a is the half width and b is the half height of the duct cross-section, Ω is the angular velocity, μ is the viscosity, ν is the kinematic viscosity. One of the interesting phenomena of the flow is the solution curve and the flow structure. The flow structures in case of small rotation of the duct axis and the pressure gradient with small Magnetic parameter as well as large Rotational Parameter and Large Magnetic Parameter have been considered while other parameters are remain constant. The calculations are carried out for 0.1⩽ M _g ⩽ 32000, 5⩽ T _r ⩽ 32000, D_n = 500, 1000, 1500, 2000,9000,10000,11000,12000 and 12500 where the aspect ratio γ=1.0.
Investigation of a vacuum packaged MEMS gyroscope architecture's temperature robustness
Authors: Cao Huiliang , Li Hongsheng
Published: December 2018

A novel method is investigated in this paper to estimate the temperature's influence upon the resonant frequency (RESF) and quality factor(Q) of a vacuum packaged Micro-Electro-Mechanical-System (MEMS) gyroscope, which can give suggestions to improve the architecture's temperature robustness. The dual-mass decoupled gyroscope's architecture is introduced, and the drive and sense modes' mechanical character are analyzed. The models of RESF and damping are established, and the influence factors are investigated. Four samples are tested and the results indicate that the models can estimate and evaluate the tendency of the RESF and Q in different temperature. The investigation also considers the Young Modulus is the dominate element influencing RESF and increasing the thickness and width of the U-shaped spring can decrease this influence; Q is impacted mainly by the air viscosity coefficient and ambient pressure. The errors of the models are caused by manufacture error and the air getter's influence.
Angular-diversity target recognition by kernel scatter-difference based discriminant analysis on RCS
Authors: Chan Sheng-Chih , Lee Kun-Chou
Published: December 2018

In this paper, radar target recognition is given by KSDA (kernel scatter-difference discriminant analysis) pattern recognition on RCS (radar cross section). The kernel method converts the traditional FLDA (Fisher linear discriminant analysis) to a nonlinear high-dimensional space and such a kernel technique is called KFDA (kernel Fisher discriminant analysis). The basic concept of KFDA is to map training samples in the original space to a high-dimensional feature space via a nonlinear mapping function. Pattern recognition is then implemented in the feature space through extracted nonlinear discriminant features. However, as the kernel within-class scatter matrix is singular, the optimal discriminant features can not be achieved directly. To improve this drawback of KFDA, this study utilizes the scatter difference as the discriminant function, i.e., KSDA, to implement radar target recognition. The KSDA can modify the Fisher discrimination function and then serves as an efficient tool of radar target recognition. As a result, the computational complexity is reduced and then the computational speed is increased. Of great importance, the proposed target recognition scheme (based on KSDA) can still work well even though the kernel within-class scatter matrix is singular. Our KDSA based target recognition scheme is accurate, efficient and has good ability to tolerate random noises.
Preliminary studies on the design principles of capacitive imaging probes for non-destructive evaluation
Authors: Yin Xiaokang , Hutchins David A , Chen Guoming , Li Wei
Published: December 2018

As a novel electromagnetic non-destructive evaluation (NDE) technique, capacitive imaging (CI) has been successfully used on a various types of materials, including concrete, glass/carbon fibre composite, steel, etc. In this work, studies on the design principles for the CI probes were presented. Firstly, measures for the evaluation of the CI probe performance are presented. The concept of volume of influence is then raised, to evaluate the imaging ability of a given CI probe. Examples of CI probe designs are then provided, namely symmetric and concentric geometries. Design factors, such as separation between electrodes, guard electrodes, and electrode shapes are also discussed and examined experimentally. CI scans were performed on two typical specimens, namely Perspex and aluminium, to evaluation the imaging performance of CI probes with different geometries.
Interfacial penny-shaped crack between magnetoelectroelastic thin film and elastic substrate
Authors: Li Y.S. , Liu L.B. , Meng W.Q. , Cai Z.Y.
Published: December 2018

In this paper, an interfacial penny-shaped crack between magnetoelectroelastic thin film and elastic substrate subjected to mechanical and electric loads is investigated. Four kinds of crack-face magnetoelectrically boundary conditions are adopted. Using Hankel transform technique, the mixed boundary value problem is reduced to a system of singular integral equations. The integral equations are further reduced to a system of algebraic equations with the aid of Jacobi polynomials. The stress intensity factor and energy release rate are determined. Numerical results reveal the effects of electric and magnetic loadings, magnetoelectroelastic boundary conditions and material parameters of composite on crack propagation and growth. The results seem useful for design of the magnetoelectroelastic composite structures and devices of high performance.
Modeling the environmental effects on the radiated fields of a passive RFID system
Authors: Shirvani Moghaddam Shahriar
Published: December 2018

The main objective of this paper is to model environmental effects on the read range of radio frequency identification (RFID) system. In order to evaluate the performance of an RFID system in real applications, electric and magnetic radiated fields (E or H) of a circular loop antenna should be derived. In this investigation, three cases are considered, free space model, the case that there is a perfect parallel or non-parallel surface, and finally the general model considering non-parallel non-perfect conductive/dielectric surface. In general model, besides the method of images, a new approach is proposed which model non-parallel main and image CLAs as two equivalent vertical and horizontal loops. According to this model, the radiated fields and also induced voltage are functions of the current intensity, wavenumber, reflection coefficient of the surface, both angle and the distance between antenna and surface, and the distance between the RFID tag and reader. To compare the analytical values extracted from E and B formulas of proposed model and associated results derived from computational methods, MATLAB and FEKO outputs are compared in the same conditions.

Using this new proposed model, the performance of an RFID system operating in metal environment and also effective read range can be evaluated. It is also able to show the environmental effects on radiated fields of reader as well as tag's antenna. In addition, the interference effect of different RFIDs can be easily modeled by these new formulas.
Fields in fractional dual DB', D'B and D'B' waveguides containing chiral nihility medium
Authors: Gulistan Samina , Syed A.A.
Published: December 2018

In electromagnetics, a set of boundary conditions requiring vanishing of the normal components of the flux densities D and B (DB boundary) or their normal derivatives (D'B' boundary) have assumed great importance, recently. In the present study, we employ D'B', DB' and D'B boundary conditions to investigate the fields in a three layered fractional dual planar waveguide. Middle layer of the waveguide is filled with air and other two layers are filled with chiral nihility metamaterial. Fractional dual solutions for the waveguide are obtained using a fractional curl operator with a parameter'α' defining the fractional order of the operator. For limiting values of the parameter, i.e., α =0 and α =1, the solutions to the Maxwell's equations correspond to the original and dual to the original solutions, respectively. Whereas, in general ( 0<α<1), so called intermediate solutions are obtained. It has been noted that fields do exist in chiral nihility material backed by D'B', DB' or D'B boundary, and a circular wave behaviour of the fields is observed in the core of the waveguide. In this sense DB', D'B and D'B' chiral nihility waveguides behave identical to their DB counterpart.
Nanofluid implementation for heat transfer augmentation of magneto hydrodynamic flows in a lid-driven cavity using experimental-based correlations
Authors: Ghadi Ariyan Zare , Noroozi Mohammad Javad , Esfe Mohammad Hemmat
Published: December 2018

In this research, effects of adding nano-sized particles to base fluid on heat transfer and fluid flow in a lid-driven cavity in presence of magnetic field has been numerically analyzed. In the present work, nano-sized additives are alumina nanoparticles which play controlling role in the adjustment of heat transfer performance and fluid motion behavior for an application which is under a variable strength magnetic field. Since a fairly low value of volume fraction is assumed in this research, nanoparticles together with the base fluid behave like a new fluid. Top moving lid and bottom walls of cavity are insulated, whereas left and right walls are defined as hot and cold sources, respectively. Relevant parameters in the present article are Reynolds number, considered to be 100, Prandtl number, assumed to be 6.2, Rayleigh number (10 ^{2} < Gr < 10 ^{5} ), volume fraction number (0 < φ 0.05) and Hartmann number (0 < Ha < 50). Results are presented in form of streamlines, isotherms, local and average Nusselt numbers.
A novel antenna design with DGS for emergency management
Authors: Kakkar Sushil , Rani Shweta
Published: December 2018

This paper presents an analysis and design of a novel planar antenna in corporation with fractal shaped defected ground structure (DGS) for wireless communication devoted to emergency management. The conventional ground plane can be replaced by a Fractal DGS ground plane to get size reduction, better efficiency and suppress surface-waves. The synthesis of proposed antenna is carried out by means of particle swarm optimization (PSO) to identify the geometrical descriptors of the structure. The representative results reveals that the proposed geometry exhibit better impedance matching and multiband characteristics in comparison to conventional planar antenna (without any defects). The analyses from simulations, numerical and experimental validations are reported in order to illustrate the effectiveness of varying scale factor that contributes 69.08% size reduction of ground plane.
Reflection and transmission of electromagnetic waves from a uniaxial chiral slab placed in an isotropic chiral medium
Authors: Shoukat Sobia , Syed Aqeel A. , Naqvi Q.A.
Published: December 2018

In this article, we investigate the reflection and transmission properties of a uniaxial chiral slab of infinite extent and placed in an isotropic chiral medium. The effect of polarization of the incident field and material parametric dependence of the reflected and transmitted power has been analyzed. The formulas for the reflected and transmitted power are derived and numerical results for various slab parameters are presented. It has been shown that the transmission or rejection of the fields can be controlled by varying the material parameters of the slab.
Design of magnetic coupler for EVs' wireless charging
Authors: Hu Chao , Sun Yue , Wang Zhihui , Tang Chunsen , Xiong Qingyu
Published: December 2018

Remote and high power Inductive Power Transfer (IPT) system has proved its capability as a power source for Electric Vehicles' (Evs') wireless charging. The performance of magnetic coupler is the major factor which limits the transmission distance, power levels and the feasibility of IPT system. Maximum output power ( P_m ) is one of the most important parameters for these systems. By analyzing the correlative factors which affect P_m , the result reveals that P_m is inversely proportional with magnetic flux or uncompensated power of power receiving coils. New ferrite core matrices array has been designed as the basic component for magnetic coupler, which allows for a variety of winding ways according to the actual application. The result of a 3D finite element model shows that P_m produced by the proposed winding ways is much higher than that of air core, and this could be a solution to satisfy the requirements from power transmission in wireless charging.
Propagation of high-power microwave pulses in air-SF_6 mixtures at high pressure
Authors: Zhao Pengcheng , Liao Cheng , Lin Wenbin
Published: December 2018

Simulations of the interaction of high-power microwave (HPM) pulses with air-SF _6 mixtures at high pressure in the fluid model are presented, where various reaction sets of air and SF _6 are taken into account. Introducing a small amount of SF _6 in air can drastically increase the breakdown threshold. At a higher pressure or for a larger pulse width, the breakdown threshold increases more significantly as the percentage of SF _6 in the mixture increases. The amplitude of the transmitted pulse in the air breakdown decreases with time and its width is shortened. Due to the higher attachment frequencies in the air-SF _6 mixture and SF _6 , the amplitude of the transmitted pulse keeps almost unchanged after it experiences a short-time attenuation, and the pulse width is not strongly influenced. Most of the energy loss of the transmitted pulse in the gas breakdown propagates in the opposite direction, and the rest of energy loss is due to electron heating. The accuracy of the fluid model is verified by experimental results.
Testing device and experimental investigation to influencing factors of Magnetorheological fluid
Authors: Sun Tiger , Peng Xianghe , Li Jingzhi , Feng Chao
Published: December 2018

More attentions have been paid to Magnetorheological fluid, which is a kind of new functional materials. An elegant device is designed for the test of the mechanical properties of Magnetorheological fluid, and the mechanical properties of ten samples of Magnetorheological fluid are tested with the device. In the experimental investigation, we choose ten samples of Magnetorheological fluid to analyze and obtain the material parameters with the testing device. The effects of the typical influencing factors, such as magnetic induction intensity, ferromagnetic particle volume fraction, base solutions, temperature, shear strain rate, response time, sedimentation stability, yield shear stress, viscosity and zero-field viscosity, etc., are investigated. This work proves that Magnetorheological fluid is reliable and practical through experimental results. We welcome warmly the relevant experts and scholars to exchange and guide further.
Exponent model for stress distributions in a superconducting cylinder with a concentric elliptic hole
Authors: Feng W.J. , Li Q.H.
Published: December 2018

In this paper, the distributions of the stresses induced by flux pinning in a superconducting cylinder with a concentric elliptic hole are investigated. First, the distribution function of the flux density during field descent after field cooling process is given by adopting the exponent model for the critical current state. Then, the flux pinning forces are further derived. Finally, numerous numerical results are plotted by using finite element method and are analyzed in detail. Numerical results show that for the superconducting cylinder with an elliptic hole, along the direction of the long axis, the phenomenon of stress concentration for hoop stress occurs at the hole edge, and that in general, the radial stress changes rapidly near the hole edge. In addition, both the shape of the hole and the model parameter of the present critical state model have important and different effects on the stress distributions. Results presented in this paper should have potential applications to the design of superconducting materials.
Global optimization of a parallel hybrid vehicle using optimal energy management
Authors: Reinbold Vincent , Vinot Emmanuel , Gerbaud Laurent
Published: December 2018

Fuel consumption of a hybrid electrical vehicle (HEV) depends on the driving cycle (i.e. the use of the vehicle), on the powertrain components and on the energy management. The paper proposes an optimal component sizing process taking into account the entire system. An optimal energy management is used in order to minimize the fuel consumption on a driving cycle. This optimization approach of the HEV uses Radial Basis Function models which allow a fast constrained optimization.
Structure and coupling analysis of a novel 3-DOF conical magnetic bearing
Authors: Wang Chun'e , Fang Jiancheng , Tang Jiqiang , Sun Jinji
Published: December 2018

This paper deals with the novel structure and coupling analysis of a 3-degrees of freedom (3-DOF) conical magnetic bearing. The conical stators of the bearing are designed symmetrical to provide the axial control exclusively, and the radial stators are separated by nonmagnetic material between X and Y channels, so the magnetic flux path can be separated among different channels. The configuration and working principle of the bearing are provided, and the mathematical model is derived based on the bias and control magnetic circuits. In order to evaluate the degree of force coupling between different channels, the concept of coupling factor is proposed, which is defined as the ratio of force variation caused by coupling to the original force when there is no coupling. The coupling factors are analyzed not only among the translational movement of X, Y and Z channels but also between the translational and rotational degrees of freedom. The calculation results show that although the component coupling factors of each magnetic poles are a little larger, the resultant ones in X, Y and Z directions of the designed bearing are all less than 4%. Therefore, the magnetic forces and torques of different channels are weakly coupled, and it is convenient for the control of the magnetic bearing.
Antenna design using variable-fidelity electromagnetic simulations
Authors: Koziel Slawomir , Ogurtsov Stanislav
Published: December 2018

Design optimization of antennas is challenging, in most cases it involves electromagnetic (EM) simulations. High-fidelity simulation is computationally expensive and, therefore, employing EM solver in an optimization loop may be prohibitive. In this paper, we discuss optimization approaches that exploit coarse-discretization EM simulations as a low-fidelity model, and allow us to locate the optimum design of the antenna at a low computational cost. Some practical issues, including the importance and selection of the model fidelity are also discussed.
Design and optimization of new hybrid fractal tree antenna
Authors: Rani Shweta , Singh A.P.
Published: December 2018

An optimized design of printed hybrid fractal tree (PHFT) antenna based on binary fractal tree geometry is presented and discussed. In this paper miniaturization has been achieved by inserting a modified Koch curve in the conventional fractal binary tree. A comparative study shows that the new antenna provides 6.87% increase in radiation efficiency and 2.57% increase in antenna efficiency than conventional fractal tree antenna designed with similar dimensions. The geometrical descriptors of the proposed antenna have been synthesized using Bacterial Foraging Optimization (BFO) and Particle Swarm Optimization (PSO) for optimizing the values of electrical parameters within specifications. A performance comparison have also been done for both of these computational techniques which reveals that BFO gives better results in terms of accuracy than PSO for required working frequencies (5.2 GHz and 10.6 GHz). Representative results of optimized PHFT antenna for both simulations and experimental validations are reported in order to access the effectiveness of the developed approach for reliable implementation in wireless telemedicine applications.
Investigation on the numerical relationship between the power frequency electric field and air parameters
Authors: Yang Fan , Zhong Jie , Zhao Gen , Liu Xinghua , Ran Wei , He Wei
Published: December 2018

More and more ultra-high voltage (UHV) transmission line will be built in China, and the design of external insulation is critical for the safe operation of UHV transmission line. Air relative humidity (RH) and temperature can affect its permittivity and electric field around the transmission line, hence in the paper the numerical relationship between the electric field, air permittivity and air temperature, RH is investigated by field measurement test and numerical analysis. Firstly the measurement tests are setup to measure electric field strength and atmospheric parameters, in which the electric field, air temperature and RH at same measuring point are measured repeatedly on different days. Then scatter plots are used to reflect the relationship between field strength and temperature along with relative humidity intuitively, and correlation analysis is conducted on the measurement data. Finally the numerical model for the electric field and air RH & temperature, numerical model for the air permittivity and air RH & temperature are obtained. The results provide reference for UHV external insulation design to improve their operation stability and performance.
Novel design of dual-band unequal Wilkinson power divider
Authors: Li Xi , Yang Lin , Hou Jia , Guo Yan-Ping , Gong Chen
Published: December 2018

The analysis and design of a dual-band unequal Wilkinson power divider are presented in this paper. A structure including isolation stubs is proposed in order to reduce the parasitic effects between the two stubs that are connected by the isolation resistor. The design parameters of the dual-band unequal power divider are presented in explicit closed form. The validity of this analysis is confirmed through the design, simulation, and experimental results with a power divider for 1 and 2 GHz.
Eddy current loss analysis in the rotor of surface-mounted permanent magnet brushless machine with retainer
Authors: Lee Sang-Yub , Ro Jong-Suk , Jung Hyun-Kyo
Published: December 2018

For a permanent magnet machine, temperature rise due to the losses in the rotor can affect the performance of the permanent magnet. This is a critical problem for the designers of electric machine. These losses, especially eddy current losses in the conductive part of the rotor, cause heat which cannot easily be mitigate due to the mechanical structure. Therefore, it is very important to consider the losses in the designing step to ensure that the machine operates stably.

The most common technique of reducing the eddy current losses is to divide them into smaller parts. The analysis for this segmentation structure is only possible in 3D-FEM (Finite Element Method) and though this requires a considerable amount of time during design step. Therefore, it is necessary to calculate the eddy current losses rapidly and accurately.

In this paper, an eddy current loss analysis method in the retainer of the permanent magnet machine which has a high power density is proposed. First, the concept of effective conductivity is introduced to solve the segmentation problems not to use 3D-FEM. Also, in order to improve the accuracy of the proposed method, the skin effect which occurs in high speed driving region is considered and a FFT analysis is also performed on the harmonic components of air gap flux density. Finally the thermal analysis result which is based on the loss analysis result is also demonstrated and it is verified to compare with the thermal experimental results.
Investigation on the electromagnetic transient characteristics of an AC-DC interconnected system under different faults
Authors: Yang Fan , Guo Xingye , Liu Xinghua , Dai Feng , Fan Lingqiang , He Wei
Published: December 2018

The electromagnetic transient can be used to analyze the stability of power systems. In the paper, the electromagnetic transient of an AC-DC interconnected system under different faults is investigated, and interaction between the AC system and DC system is analyzed. Firstly electromagnetic transient models for the components in a high voltage direct current (HVDC) transmission system are presented, including model for converter transformer, harmonic filters, transmission line and control system. Then simulation based on electromagnetic transient model for a ± 800 kV bipolar HVDC-AC interconnected system is carried out, and both the steady state and step response performance are checked to verify the accuracy of the model. Finally electromagnetic transient of the system under different faults is investigated, including different grounding faults on AC side, fault on DC side and fault of filters. Transient responses are analyzed, including the recovering time from oscillation caused by faults and possibility of commutation failure (CF).
A simple and efficient local Petrov-Galerkin meshless method and its application
Authors: Liu Zehui , He Wei , Yang Fan , Zhai Jinqian , Zhang Ruiqiang
Published: December 2018

In the MLPG method of this paper, only the boundary integrations over local subdomains is involved, which make the MLPG method is very easy to carry out because the local sub-domains are chosen in MLPG method as simple circular or rectangular ranges. In order to simplify the MLPG method, the radius of local sub-domains has been adjusted for the nodes close to the global boundary but not exactly on the boundary. In addition, the boundary conditions including the essential and natural boundary are imposed directly by the nodes which are exactly on the global boundary. Two electromagnetic models have been studied in this paper to investigate the accuracy and computational efficiency of the MLPG method. The results, which are compared with the solutions obtained from the MLPG in the reference and the FEM, show that the MLPG method in this paper can obtain more accurate results by using fewer nodes.