Temporal-frequency spectra for plane and spherical waves in a millimetric wave absorption band

1991 ◽  
Vol 39 (2) ◽  
pp. 229-235 ◽  
Author(s):  
G.L. Siqueira ◽  
R.S. Cole
Keyword(s):  
Absorption Band ◽  
Temporal Frequency ◽  
Millimetric Wave ◽  
Frequency Spectra ◽  
Wave Absorption ◽  
Spherical Waves

The Structure of Polyisoprenes. V. Ultraviolet Absorption Spectra of Certain Carbalkoxy-Substituted 1,5-Dienes, and the Charge-Resonance Spectra of Glutaconic Ester Enolate Ions

1946 ◽  
Vol 19 (1) ◽  
pp. 23-33
Author(s):  
L. Bateman ◽  
H. P. Koch
Keyword(s):  
Absorption Band ◽  
Absorption Spectra ◽  
Special Interest ◽  
Crystalline State ◽  
Marked Change ◽  
Cyanine Dyes ◽  
Structural Type ◽  
Wave Absorption ◽  
Long Wave ◽  
Ester Enolate

Abstract Spectral evidence supports the conclusion reached in Part IV that ring-chain mesomerism in methyl and ethyl Δ1,5-hexadiene-l,1,3,3,4,4,6,6-octacarboxylates is nonexistent in solution, just as in the crystalline state. The data are not inconsistent with chain hyperconjugation in these molecules. The marked change in structural type that follows the addition of one molecule of hydrogen or hydrolytic reagent has been verified spectrographically. The spectra of methyl and ethyl α,γ-dicarboxyglutaconic esters and their sodium and cupric derivatives have been measured in various solvents, and their tautomeric behavior compared with that of other keto-enols. Of special interest is the intense long-wave absorption band of the enolate ions, which are recognized as simple structural analogs of the cyanine dyes giving rise to similar charge-resonance spectra. A preliminary comment is made on the present accepted structure of ethyl 6-ethoxy-α-pyrone-3:5-dicarboxylate.

Turbulent boundary layers absent mean shear

2017 ◽  
Vol 835 ◽  
pp. 217-251 ◽  
Author(s):  
Blair A. Johnson ◽  
Edwin A. Cowen
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Turbulent Boundary Layer ◽  
Turbulent Kinetic Energy ◽  
Temporal Frequency ◽  
Synthetic Jet ◽  
Mean Flow ◽  
Frequency Spectra ◽  
Empirical Constant ◽  
The Mean

We perform an experimental study to investigate the turbulent boundary layer above a stationary solid glass bed in the absence of mean shear. High Reynolds number $(Re_{\unicode[STIX]{x1D706}}\sim 300)$ horizontally homogeneous isotropic turbulence is generated via randomly actuated synthetic jet arrays (RASJA – Variano & Cowen J. Fluid Mech. vol. 604, 2008, pp. 1–32). Each of the arrays is controlled by a spatio-temporally varying algorithm, which in turn minimizes the formation of secondary mean flows. One array consists of an $8\times 8$ grid of jets, while the other is a $16\times 16$ array. Particle image velocimetry measurements are used to study the isotropic turbulent region and the boundary layer formed beneath as the turbulence encounters a stationary wall. The flow is characterized with statistical metrics including the mean flow and turbulent velocities, turbulent kinetic energy, integral scales and the turbulent kinetic energy transport equation, which includes the energy dissipation rate, production and turbulent transport. The empirical constant in the Tennekes (J. Fluid Mech. vol. 67, 1975, pp. 561–567) model of Eulerian frequency spectra is calculated based on the dissipation results and temporal frequency spectra from acoustic Doppler velocimetry measurements. We compare our results to prior literature that addresses mean shear free turbulent boundary layer characterizations via grid-stirred tank experiments, moving-bed experiments, rapid-distortion theory and direct numerical simulations in a forced turbulent box. By varying the operational parameters of the randomly actuated synthetic jet array, we also find that we are able to control the turbulence levels, including integral length scales and dissipation rates, by changing the mean on-times in the jet algorithm.

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