International Journal of Applied Electromagnetics and Mechanics - Volume 41, issue 4

Authors: Wang, Shuyun | Kan, Junwu | Wang, Bin | Yang, Zhenyu | Ling, Ronghua | Xu, Hailong | Cheng, Guangming

Article Type: Research Article

Abstract: To enhance the energy-generating capability and obtain the optimal structural/material parameters, the deflection function of piezodisc and analytical model of energy generation is established based on the summation method in the theory of plates and shells. The influence of radius/thickness/Young's-modulus ratios of the piezodisc on energy generation was investigated. The research results show that there are different optimal thickness/radius/Young's-modulus ratios for a piezodisc generator under given central force and displacement to obtain …maximal electrical energy. To enhance generated energy of a piezodisc under given central force, low Young's modulus ratio is helpful. While, high Young's modulus ratio should be utilized for a piezodisc generator under given central displacement. The Young's modulus radios of the piezodiscs with beryllium-bronze/brass/aluminum substrates are 1.5/1.1/0.94 respectively, and the optimal thickness-ratios/radius-ratios/maximal-energy under central force of 25 N are 0.55/0.43/0.35, 0.64/0.67/0.69, and 2.24/2.63/2.96 × 10^{-4} J. Whereas, those under given central displacement of 0.25 mm are 0.4/0.35/0.3, 0.85/0.86/0.87, and 2.7/2.19/1.96 × 10^{-4} J, respectively. Show more

Keywords: Circular piezodisc, energy harvesting, modeling, simulation, summation method

DOI: 10.3233/JAE-121617

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 41, no. 4, pp. 349-360, 2013

Authors: Zhang, Chunli | Chen, Weiqiu | Yang, Jiashi

Article Type: Research Article

Abstract: We derive two-dimensional equations for high-frequency vibrations of piezoelectric plates from a semi-mixed variational principle with the mechanical displacement vector, the electric potential, and the electric displacement vector as independent fields. This variational formulation allows independent expansions of the three fields into power series of the plate thickness coordinate. Similar to the shear correction factors used in Mindlin's equations for piezoelectric plates to adjust the thickness-shear frequencies predicted by the plate equations …slightly so that they become the same as the exact frequencies from the three-dimensional equations, a charge correction factor is conveniently introduced in the plate equations in the present paper so that the inaccuracy of the plate equations in the literature in predicting the charge or current on the electrodes of an electroded plate is corrected. The final equations obtained are convenient and accurate to use for both electroded and unelectroded plates, and for calculating both the voltage and the charge on the electrodes at the plate surfaces in the case of an electroded plate. Show more

Keywords: Piezoelectric, plate, resonator

DOI: 10.3233/JAE-121618

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 41, no. 4, pp. 361-373, 2013

Authors: El-Kharashi, Eyhab

Article Type: Research Article

Abstract: Simply to improve the energy conversion process in the switched reluctance motor the magnetic circuit topology must be modified and the losses must be minimized. The magnetic geometry of switched reluctance machines has been effectively fixed for many years. The paper introduces different new magnetic circuit topologies to improve the energy conversion process in the switched reluctance motor. The switched reluctance motors always operate in the transient mode because of the switching process between the phases …consequently the iron losses have a high value in comparison with the rest of the electrical machines due to the switching frequency. From this point of view the magnetic circuit of the switched reluctance motor must be re-shaped by a particular way to minimize the losses. There are many advantages of the presented new designs such as they are quite easy to be built and possess an efficient energy conversion process. Show more

Keywords: Energy conversion process, new designs, magnetic circuit topology, minimizing losses, new rotors, cascade rotors

DOI: 10.3233/JAE-121619

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 41, no. 4, pp. 375-387, 2013

Authors: Liu, Haili | Xu, Tianzhu | Huang, Zhenyu | Chen, Dayue

Article Type: Research Article

Abstract: Vibration-based piezoelectric energy harvesters usually work at their resonant frequencies. The resonant frequencies can match, at most, one or two ambient exciting frequencies. In order to freely design multiple operating frequencies to match the given exciting frequencies, several oscillators were attached on a piezoelectric cantilever in this paper, which is named as a multi-mode piezoelectric energy harvester (MPEHer). A distributed-parameter model of the MPEHer was established to predict its output power, and then a …lumped-parameter model was derived to determine its operating frequencies. With the lumped-parameter model, the oscillator parameters can be searched for given exciting frequencies. Considering the volume and weight limitation in engineering application, optimizing procedures for the MPEHer were further proposed. Following these procedures, an MPEHer limited by the oscillator-to-cantilever mass ratio of 2.7 was designed for two given exciting frequencies. Experiments show that, under the same input excitation, the average output power of the designed MPEHer is increased by 82% compared with that of a classical configuration, i.e. a piezoelectric cantilever with a tip mass. Show more

Keywords: Piezoelectric energy harvesting, multi-mode, cantilever, oscillator, resonance

DOI: 10.3233/JAE-121620

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 41, no. 4, pp. 389-405, 2013

Authors: Awasthi, Mukesh Kumar

Article Type: Research Article

Abstract: The electrohydrodynamic Kelvin-Helmholtz instability of the interface between two uniform superposed viscous and electrically conducting fluids in the presence of a free surface charge has been studied, when there is heat and mass transfer across the interface. Viscous potential flow theory has been used for the investigation. A dispersion relation has been derived for the linear stability analysis and the stability of the system is analyzed theoretically and numerically. Various graphs with respect to physical …parameters, such as electric field, heat transfer coefficients, viscosity of the fluids and permittivity ratio have been drawn and effect of various parameters have been described. It has been observed that free surface charge and electric field both have stabilizing effect while heat transfer destabilizes the system. Show more

Keywords: Kelvin-Helmholtz stability, heat and mass transfer, electrohydrodynamics

DOI: 10.3233/JAE-121621

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 41, no. 4, pp. 407-418, 2013

Authors: Zhou, Hongliang | Bai, Minghua | He, Yunhua | Ren, Subo

Article Type: Research Article

Abstract: Magnetorheological fluid (MRF) exhibits drastic changes in rheological properties adjustable and controllable yield stress under external magnetic field. Based on its specialty, the MRF seal technique is proposed to deal with the air leakage of circular cooler to improve the energy efficiency for the steel industry. MRF is regarded as Bingham fluid with its magnetization vector and magnetic force expressed by mathematical functions. The FEM analysis results show that, under magnetic field, MRF which presents good …pressure resistance as a result of its yield stress is in a dynamic equilibrium state in non-magnetic seal groove even with pressure difference, and due to the volume force, it presents unsteady swirl flow obviously at the right-angle edges of the two permanent magnets nearby non-magnetic separator, whereas, due to pressure difference, it shows an obvious flow without magnetic field. In the meantime, according to the experiment, it indicates that the air leakage of circular cooler is solvable effectively with the MRF seal method, and it is also proved that MRF shows controllable yield stress under magnetic field. Show more

Keywords: FEM analysis, yield stress, magnetic field, MRF seal, experiment

DOI: 10.3233/JAE-121622

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 41, no. 4, pp. 419-431, 2013

Authors: He, Wei | Ran, Peng | Xu, Zheng | Li, Bing

Article Type: Research Article

Abstract: This paper addresses the augmentation of a conventional plane electrode arrays electrical impedance tomography (EIT) system to form a combined electrode arrays EIT system. This enhances the system performs of providing more accordant information of objects. The system is built up of 65 electrodes, composing of 4 horizontal and 8 axial intercrossing image planes. A phantom experiment has been taken and the measurements been processed by Tikhonov Regularization algorithm and reconstructed by the data obtained from …the corresponding model. From comparing the reconstructed volume of anomaly with the target, the results indicate that the described method augments the EIT 3-D rebuilding to a distinguishable level. The qualitative results illustrate the feasibility of this composite approach in exploiting sensitivity in 3-D space with expectable spatial resolution and positioning accuracy. Moreover, this method effectively reduces the amount of computation and demonstrates the practical potential of EIT for clinical inspection and monitoring. Show more

Keywords: Electrical impedance tomography, combined plane reconstruction, Tikhonov Regularization, volume estimate

DOI: 10.3233/JAE-121623

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 41, no. 4, pp. 433-446, 2013

Authors: Mukherjee, Biswajeet | Tiwari, Shashank | Samariya, Ajay Lal

Article Type: Research Article

Abstract: Filters have always remained a field of immense interest in the high frequency domain. Emerging applications such as wireless communications continue to challenge RF/microwave filters with ever more stringent requirements-high performance, smaller size, lightweight, and lower cost. In this paper we propose and investigate the application of Electromagnetic Bandgap (EBG) structures for improving the performance of a stub type 5 pole Low Pass Filter with spur line resonators. Whereas the spur line resonators, …improve the roll off factor significantly from −22.666 dB/GHz to −38.0893 dB/GHz, the effect of the EBG is evident in reducing the radiation losses of the spur line resonators and getting almost the same return loss and roll off factor. Show more

Keywords: Filters, Electromagnetic Band Structures (EBG), roll off factor, radiation, return loss

DOI: 10.3233/JAE-121635

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 41, no. 4, pp. 447-455, 2013

Authors: Mukherjee, Biswajeet | Raj, Ankit

Article Type: Research Article

Abstract: Due to small size, ease of fabrication; high radiation efficiency, increased bandwidth and low production cost Dielectric Resonator Antennas (DRAs) are very promising for application in wireless communications. Further, the ability to withstand high temperature variations gives it a very wide application range. In our research, a Hemispherical DRA has been investigated whose bandwidth has been enhanced from 11.4% to 16.44% under different structural geometries. It was also found that in some cases there was an …improvement of Gain and Bandwidth along with a lower return loss to mark a sharp resonance peak. The results were verified using the S-parameter analysis, Impedance Bandwidth calculation and VSWR at the source port with CST and HFSS solvers. Show more

Keywords: Dielectric Resonator Antenna, directivity, gain, bandwidth, resonant frequency

DOI: 10.3233/JAE-121636

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 41, no. 4, pp. 457-466, 2013

Authors: Ram, Paras | Bhandari, Anupam

Article Type: Research Article

Abstract: In this problem, negative viscosity effects are presented on the ferrofluid flow due to a rotating disk. An alternating magnetic field does not single out any direction of the flow but it changes the angular velocity of the particles relative to the vorticity of the flow. The frequency dependent relative magnetization and the angular velocity of the particles are studied here for various dimensionless parameters. Components of ferrofluid velocity and pressure profile are compared with the …ordinary case where the frequency of an alternating magnetic field matches with relaxation of magnetization resulting in no effect of negative viscosity on the shear viscosity. The nonlinear coupled differential equations involved here are solved numerically by Shooting Method and the results are graphically expressed. Show more

Keywords: Magnetic field, ferrofluid, negative viscosity, rotating disk

DOI: 10.3233/JAE-121637

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 41, no. 4, pp. 467-478, 2013