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

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.

Maximum Stresses in Beams and Plates Vibrating at Resonance

1962 ◽  
Vol 84 (1) ◽  
pp. 149-155 ◽  
Author(s):  
Eric E. Ungar
Keyword(s):  
Simple Formula ◽  
Maximum Stress ◽  
Rectangular Plates ◽  
Circular Plates ◽  
Simply Supported ◽  
At Resonance ◽  
Design Calculations ◽  
Maximum Stresses

Expressions are derived which relate the maximum stresses encountered in simply supported beams and rectangular plates and in clamped circular plates vibrating at resonance to modal displacements and modal loadings. Computation of modal loadings from time-wise harmonic or random pressures is discussed. It is shown that the resonant maximum stress may be reasonably approximated by a simple formula suitable for conservative design calculations for all types of beams and plates.

On the resonance frequencies of water-loaded circular plates

1984 ◽  
Vol 94 (2) ◽  
pp. 217-222 ◽  
Author(s):  
F. Montero de Espinosa ◽  
J.A. Gallego-Juárez
Keyword(s):  
Circular Plates ◽  
Resonance Frequencies

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.

Novel dual band patch antenna With Gap coupled composite right/left-handed transmission line

2018 ◽  
Vol 11 (1) ◽  
pp. 87-93
Author(s):  
Z. Ahmed ◽  
M. M. Ahmed ◽  
M. B. Ihsan ◽  
A. A. Chaudhary ◽  
J. K. Arif
Keyword(s):  
Transmission Line ◽  
Patch Antenna ◽  
Frequency Ratio ◽  
Unit Cell ◽  
Dual Band ◽  
Rectangular Patch ◽  
Left Handed ◽  
At Resonance ◽  
Low Profile ◽  
Resonance Frequencies

AbstractA novel low profile dual band patch antenna is presented. It consists of a composite right/left-handed transmission line (CRLH TL) unit cell gap coupled with the radiating edge of a rectangular patch antenna. The dual band behavior is achieved by coupling the zeroth order resonance mode of CRLH TL and TM10mode of the patch antenna. It is shown that frequency ratio can be changed by varying the gap between the patch and CRLH TL unit cell. The proposed configuration enables frequency reconfigurability by changing the CRLH TL unit cell using a switch. A prototype of the antenna having frequency ratiof2/f1= 1.08 is designed and fabricated. The proposed antenna shows measuredS11≤ −10 dB bandwidth of 100 and 50 MHz at resonance frequencies off1= 4.84 andf2= 5.22 GHz, respectively. A 2 × 2 dual band CRLH TL coupled patch array is also presented, showing more than 12.7 dBi gain at both resonance frequencies.

Sign in / Sign up

Export Citation Format

Share Document