The corrected induced surface current for arbitrary conducting objects at resonance frequencies

1995 ◽  
Vol 43 (5) ◽  
pp. 448-452 ◽  
Author(s):  
A.A. Mohsen ◽  
A.-R.A. Helaly ◽  
H.M. Fahmy
Keyword(s):  
Surface Current ◽  
At Resonance ◽  
Resonance Frequencies

scholarly journals VIBRATION OF CRACKED CIRCULAR PLATES AT RESONANCE FREQUENCIES

2000 ◽  
Vol 236 (4) ◽  
pp. 637-656 ◽  
Author(s):  
CHI-HUNG HUANG ◽  
CHIEN-CHING MA
Keyword(s):  
Circular Plates ◽  
At Resonance ◽  
Resonance Frequencies

Schwingung eines Plasmazylinders in einem axialen Magnetfeld II

1960 ◽  
Vol 15 (3) ◽  
pp. 220-226 ◽  
Author(s):  
Klaus Körper
Keyword(s):  
Magnetic Field ◽  
Refractive Index ◽  
External Magnetic Field ◽  
Field Strength ◽  
Axial Magnetic Field ◽  
Surface Current ◽  
The Other ◽  
Plasma Cylinder ◽  
Resonance Frequencies ◽  
The Magnetic Field

Radial oscillations are excited in a homogeneous infinite plasma cylinder in a homogeneous axial magnetic field by a surface current which is homogeneous in the axial and azimuthal directions. The modes of oscillations corresponding to the axial and azimuthal components of current are not coupled, and so they may be analysed separately. The magnetic field in the plasma and vacuum is obtained, and the indices of refraction for both types of oscillations are discussed thoroughly. When the currents are parallel to the external magnetic field, the oscillations are characterized by the refractive index of Eccles. On the other hand, when the current is perpendicular to the magnetic field two resonance frequencies exist, which depend on the density of the plasma and the magnetic field strength. — In the latter case the radial characteristic oscillations of the plasma cylinder in an external magnetic field are considered.

scholarly journals Analysis of the Scattering from a Two Stacked Thin Resistive Disks Resonator by Means of the Helmholtz–Galerkin Regularizing Technique

2021 ◽  
Vol 11 (17) ◽  
pp. 8173
Author(s):  
Mario Lucido
Keyword(s):  
Cross Section ◽  
Near Field ◽  
Surface Current ◽  
Coefficient Matrix ◽  
Hankel Transform ◽  
General Purpose ◽  
Analytical Technique ◽  
Planar Surfaces ◽  
Natural Modes ◽  
Resonance Frequencies

In this paper, the scattering of a plane wave from a lossy Fabry–Perót resonator, realized with two equiaxial thin resistive disks with the same radius, is analyzed by means of the generalization of the Helmholtz–Galerkin regularizing technique recently developed by the author. The disks are modelled as 2-D planar surfaces described in terms of generalized boundary conditions. Taking advantage of the revolution symmetry, the problem is equivalently formulated as a set of independent systems of 1-D equations in the vector Hankel transform domain for the cylindrical harmonics of the effective surface current densities. The Helmholtz decomposition of the unknowns, combined with a suitable choice of the expansion functions in a Galerkin scheme, lead to a fast-converging Fredholm second-kind matrix operator equation. Moreover, an analytical technique specifically devised to efficiently evaluate the integrals of the coefficient matrix is adopted. As shown in the numerical results section, near-field and far-field parameters are accurately and efficiently reconstructed even at the resonance frequencies of the natural modes, which are searched for the peaks of the total scattering cross-section and the absorption cross-section. Moreover, the proposed method drastically outperforms the general-purpose commercial software CST Microwave Studio in terms of both CPU time and memory occupation.

scholarly journals Symmetric resonator based tunable epsilon negative near zero index metamaterial with high effective medium ratio for multiband wireless applications

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Md. Moniruzzaman ◽  
Mohammad Tariqul Islam ◽  
Ismail Hossain ◽  
Mohamed S. Soliman ◽  
Md Samsuzzaman ◽  
...  
Keyword(s):  
Refractive Index ◽  
Frequency Tuning ◽  
Surface Current ◽  
Split Ring Resonator ◽  
Effective Medium ◽  
Negative Permittivity ◽  
Wireless Applications ◽  
Compact Size ◽  
Resonance Frequencies ◽  
Electric And Magnetic Fields

AbstractIn this paper, a tuned metamaterial (MTM) consisting of a symmetric split ring resonator is presented that exhibits epsilon negative (ENG), near zero permeability and refractive index properties for multiband microwave applications. The proposed metamaterial is constituted on a Rogers (RT-5880) substrate with 1.57 mm thickness and the electrical dimension of 0.14λ × 0.14λ, where wavelength, λ is calculated at 4.2 GHz. The symmetric resonating patch is subdivided into four equal and similar quartiles with two interconnecting split rings in each quartile. The quartiles are connected at the center of the substrate with a square metal strip with which four tuning metal strips are attached. These tuning metal strips are acted as spacers between four quartiles of the resonator patch. Numerical simulation of the proposed design is executed in CST microwave studio. The proposed MTM provides four resonances of transmission coefficient (S21) at 4.20 GHz, 10.14 GHz, 13.15 GHz, and 17.1 GHz covering C, X and Ku bands with negative permittivity, near zero permeability and refractive index. The calculated effective medium ratio (EMR) is 7.14 at 4.2 GHz indicates its compactness. The resonance frequencies are selective in nature which can be easily tuned by varying the length of the tuning metal stubs. The equivalent circuit of the proposed MTM is modelled in Advanced Design Software (ADS) that exhibits a similar S21 compared with CST simulation. Surface current, electric and magnetic fields are analyzed to explain the frequency tuning property and other performances of the MTM. Compact size, ENG with near zero permeability and refractive index along with frequency selectivity through tuning provides flexibility for frequency selective applications of this MTM in wireless communications.

scholarly journals Evidence for frequency-dependent cortical plasticity in the human brain

2017 ◽  
Vol 114 (33) ◽  
pp. 8871-8876 ◽  
Author(s):  
Caroline A. Lea-Carnall ◽  
Nelson J. Trujillo-Barreto ◽  
Marcelo A. Montemurro ◽  
Wael El-Deredy ◽  
Laura M. Parkes
Keyword(s):  
Somatosensory Cortex ◽  
Hebbian Learning ◽  
Response Times ◽  
Functional Coupling ◽  
Frequency Dependent ◽  
Tactile Localization ◽  
Network Activation ◽  
At Resonance ◽  
Resonance Frequencies ◽  
The Impact

Frequency-dependent plasticity (FDP) describes adaptation at the synapse in response to stimulation at different frequencies. Its consequence on the structure and function of cortical networks is unknown. We tested whether cortical “resonance,” favorable stimulation frequencies at which the sensory cortices respond maximally, influenced the impact of FDP on perception, functional topography, and connectivity of the primary somatosensory cortex using psychophysics and functional imaging (fMRI). We costimulated two digits on the hand synchronously at, above, or below the resonance frequency of the somatosensory cortex, and tested subjects’ accuracy and speed on tactile localization before and after costimulation. More errors and slower response times followed costimulation at above- or below-resonance, respectively. Response times were faster after at-resonance costimulation. In the fMRI, the cortical representations of the two digits costimulated above-resonance shifted closer, potentially accounting for the poorer performance. Costimulation at-resonance did not shift the digit regions, but increased the functional coupling between them, potentially accounting for the improved response time. To relate these results to synaptic plasticity, we simulated a network of oscillators incorporating Hebbian learning. Two neighboring patches embedded in a cortical sheet, mimicking the two digit regions, were costimulated at different frequencies. Network activation outside the stimulated patches was greatest at above-resonance frequencies, reproducing the spread of digit representations seen with fMRI. Connection strengths within the patches increased following at-resonance costimulation, reproducing the increased fMRI connectivity. We show that FDP extends to the cortical level and is influenced by cortical resonance.

scholarly journals Dissimilar trend of nonlinearity in ultrasound transducers and systems at resonance and non-resonance frequencies

Ultrasonics ◽  
2017 ◽  
Vol 74 ◽  
pp. 21-29 ◽  
Author(s):  
Negareh Ghasemi ◽  
Firuz Zare ◽  
Pooya Davari ◽  
Mahinda Vilathgamuwa ◽  
Arindam Ghosh ◽  
...  
Keyword(s):  
Ultrasound Transducers ◽  
At Resonance ◽  
Resonance Frequencies

scholarly journals Effect of Electrical Damping Ratio on Maximum Average Power of an Electromagnetic Vibration Harvester at Resonance and off-Resonance Conditions

2019 ◽  
Vol 8 (2S7) ◽  
pp. 328-333
Keyword(s):  
Average Power ◽  
Experimental Studies ◽  
Vibration Source ◽  
Mass System ◽  
Vibrating System ◽  
At Resonance ◽  
Resonance Frequencies ◽  
Electrical Damping ◽  
Set Up ◽  
Copper Coil

Energy harvesting has opened up new ways to power low energy electronics without any need for batteries. The most advanced types of harvesters are piezoelectric, electrostatic and electromagnetic which use kinetic energy in form of vibrations. Electromagnetic harvesters (EHs) are efficient, less costly and offer huge design flexibility. As such, in this paper some analytical and experimental studies on maximum average harvestable power (Pave) from typical design of EH using the popular coupling architecture (a cylindrical magnet oscillating in a copper coil) have been carried out. The effect of frequency of excitation and electrical (ζe ) and mechanical damping ratios (ζm) on Pave obtained from an EH has been investigated. For this purpose, an EH using NdFeB (neodymium magnet) magnet oscillating in a copper coil has been designed and developed. An experimental test set up has developed which comprises of (i) a cam-follower type drive mechanism to simulate a vibration source with variable amplitude and frequency of base excitation, (ii) a spring-mass system with an EH system in parallel with the spring to provide the relative motion between the magnet and the copper coil, (iii) the attendant instrumentation comprising of ultrasonic sensor to sense the displacements of base and mass, motor drive speed measurement and an open source platform (ARDUINO) with programmable circuit board and software and data acquisition system. Using the developed experimental set up, (i)frequency response curve for vibrating system with EH has been obtained from which equivalent electrical damping ζe has been determined using half power point method, and (ii)the values of relative displacements of magnet and coil, at various excitation frequencies have been recorded. Using the analytical expression for the Pave of SDOF EH has been determined both at resonance and off resonance conditions, for three different values of ζe namely ζe = ζm, ζe = 5ζm, and ζe = 10ζm. It is observed that the maximum Pave is obtained for condition ζe = ζm. As the value of ζe increases, the Pave increases, at resonant frequency and considerable power is made available at off-resonance frequencies. It is concluded that ζe should be increased to enhance the maximum average harvestable power from EH and vibrating system should be so designed to have ζm, as small as possible.

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