Earth–Ionosphere Cavity Resonances and Effective Ionospheric Parameters

1964 ◽  
pp. 413-420 ◽  
Author(s):  
F.W. CHAPMAN ◽  
D. LLANWYN JONES
Keyword(s):  
Cavity Resonances

ON THE THEORY OF SCHUMANN RESONANCES IN THE EARTH–IONOSPHERE CAVITY

1964 ◽  
Vol 42 (4) ◽  
pp. 575-582 ◽  
Author(s):  
James R. Wait
Keyword(s):  
Cavity Resonator ◽  
Current Work ◽  
Alternative Derivation ◽  
Schumann Resonances ◽  
The Earth ◽  
Cavity Resonances ◽  
Concentric Region ◽  
The Subject

The concept that the concentric region between the earth and the ionosphere acts as a cavity resonator was proposed by Schumann over a decade ago. It is the purpose of this paper to review the theory of these cavity resonances. Some of the assumptions used in current work on the subject are also discussed. An alternative derivation is presented which appears to be more general than any given heretofore.

scholarly journals Cavity resonances of metal-dielectric-metal nanoantennas

2008 ◽  
Vol 16 (14) ◽  
pp. 10315 ◽  
Author(s):  
Bhuwan P. Joshi ◽  
Qi-Huo Wei
Keyword(s):  
Cavity Resonances

Using noise control principles when evaluating the acoustic impacts of face coverings during the coronavirus pandemic

2021 ◽  
Vol 263 (3) ◽  
pp. 3554-3561
Author(s):  
Richard Ruhala ◽  
Laura Ruhala
Keyword(s):  
Classroom Environment ◽  
Noise Control ◽  
Experimental Tests ◽  
Analytical Models ◽  
Octave Band ◽  
Interference Level ◽  
Cavity Resonances ◽  
The Face ◽  
Clear Plastic ◽  
Stiffness And Damping

Several different combinations of face masks and shields are evaluated for their acoustic performance using a head and torso simulator (HATS). The HATS is used as a controlled and repeatable artificial sound source using white noise in a classroom environment. Sound pressure levels at octave band frequencies due to the face coverings are evaluated at a location of 2.0 meters from the HATS which is within the direct field to reduce the room acoustical effects. The problem is modeled as a barrier separating a source and receiver using fundamental noise control principles. Fabric material properties are used such as thickness, density, stiffness, and damping. The results are compared with experimental tests. The face shield with clear plastic barrier produces a resonance in the 1000 Hz octave band. Analytical models of cavity resonances, standing wave resonances, or plate resonances are calculated and compared with the experimental resonance. The speech interference level is used to determine the frequency content that is most likely to cause hearing difficulties and compared with A-weighted differences between the unmasked condition and masked.

Micromachined Ultrasonic Print-Head for Deposition of High-Viscosity Materials

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
J. Mark Meacham ◽  
Amanda O’Rourke ◽  
Yong Yang ◽  
Andrei G. Fedorov ◽  
F. Levent Degertekin ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Three Dimensional ◽  
High Viscosity ◽  
The Novel ◽  
Glycerol Water ◽  
Print Head ◽  
Cavity Resonances ◽  
Allowable Range ◽  
Novel Method ◽  
Manufacturing Techniques

The recent application of inkjet printing to fabrication of three-dimensional, multilayer and multimaterial parts has tested the limits of conventional printing-based additive manufacturing techniques. The novel method presented here, termed as additive manufacturing via microarray deposition (AMMD), expands the allowable range of physical properties of printed fluids to include important, high-viscosity production materials (e.g., polyurethane resins). AMMD relies on a piezoelectrically driven ultrasonic print-head that generates continuous streams of droplets from 45 μm orifices while operating in the 0.5–3.0 MHz frequency range. The device is composed of a bulk ceramic piezoelectric transducer for ultrasound generation, a reservoir for the material to be printed, and a silicon micromachined array of liquid horn structures, which make up the ejection nozzles. Unique to this new printing technique are the high frequency of operation, use of fluid cavity resonances to assist ejection, and acoustic wave focusing to generate the pressure gradient required to form and eject droplets. We present the initial characterization of a micromachined print-head for deposition of fluids that cannot be used with conventional printing-based rapid prototyping techniques. Glycerol-water mixtures with a range of properties (surface tensions of ∼58–73 mN/m and viscosities of 0.7–380 mN s/m2) were used as representative printing fluids for most investigations. Sustained ejection was observed in all cases. In addition, successful ejection of a urethane-based photopolymer resin (surface tension of ∼25–30 mN/m and viscosity of 900–3000 mN s/m2) was achieved in short duration bursts. Peaks in the ejection quality were found to correspond to predicted device resonances. Based on these results, we have demonstrated the printing of fluids that fall well outside of the accepted range for the previously introduced printing indicator. The micromachined ultrasonic print-head achieves sustained printing of fluids up to 380 mN s/m2, far above the typical printable range.

Large-area, flexible, full-color printings based on asymmetry Fabry–Perot cavity resonances

2020 ◽  
Vol 464 ◽  
pp. 125483
Author(s):  
Yanfeng Su ◽  
Xinyue Tang ◽  
Guanhua Huang ◽  
Peng Zhang
Keyword(s):  
Large Area ◽  
Full Color ◽  
Fabry Perot ◽  
Cavity Resonances
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