Extension of a Classic Low Frequency Dielectric Dispersion Theory of Colloidal Suspensions to Include Different Counterion and Co-Ion Valences, a Broad Frequency Range, and the Stagnant Layer Conductivity

2012 ◽  
Vol 116 (45) ◽  
pp. 13538-13553 ◽  
Author(s):  
Constantino Grosse
Keyword(s):  
Low Frequency ◽  
Colloidal Suspensions ◽  
Dielectric Dispersion ◽  
Dispersion Theory ◽  
Frequency Range ◽  
Broad Frequency Range

scholarly journals Pre-selection of the candidate fields for deep imaging of the epoch of reionization with SKA1-low

2020 ◽  
Vol 499 (3) ◽  
pp. 3434-3444
Author(s):  
Qian Zheng ◽  
Xiang-Ping Wu ◽  
Quan Guo ◽  
Melanie Johnston-Hollitt ◽  
Huanyuan Shan ◽  
...  
Keyword(s):  
Surface Brightness ◽  
Low Frequency ◽  
Far Field ◽  
Frequency Range ◽  
High Quality ◽  
Average Surface ◽  
Square Kilometre Array ◽  
Broad Frequency Range ◽  
Deep Imaging ◽  
Selection Of

ABSTRACT The Square Kilometre Array (SKA) will be the first low-frequency instrument with the capability to directly image the structures of the epoch of reionization (EoR). Indeed, deep imaging of the EoR over five targeted fields of 20 sq deg each has been selected as the highest priority science objective for SKA1. Aiming at preparing for this highly challenging observation, we perform an extensive pre-selection of the ‘quietest’ and ‘cleanest’ candidate fields in the southern sky to be suited for deep imaging of the EoR using existing catalogues and observations over a broad frequency range. The candidate fields should meet a number of strict criteria to avoid contaminations from foreground structures and sources. The candidate fields should also exhibit both the lowest average surface brightness and smallest variance to ensure uniformity and high-quality deep imaging over the fields. Our selection eventually yields a sample of 7 ‘ideal’ fields of 20 sq deg in the southern sky that could be targeted for deep imaging of the EoR. Finally, these selected fields are convolved with the synthesized beam of SKA1-low stations to ensure that the effect of sidelobes from the far-field bright sources is also weak.

Dielectric dispersion of BiFeO3 thin film over a broad frequency range (100 Hz–10 GHz)

2009 ◽  
Vol 94 (2) ◽  
pp. 022907 ◽  
Author(s):  
Xiao-Yu Zhang ◽  
Qing Song ◽  
Feng Xu ◽  
C. K. Ong
Keyword(s):  
Thin Film ◽  
Dielectric Dispersion ◽  
Bifeo3 Thin Film ◽  
Frequency Range ◽  
Broad Frequency Range

Active attenuation of sound transmission through a soft-core sandwich panel into an acoustic enclosure using volume velocity cancellation

2015 ◽  
Vol 229 (17) ◽  
pp. 3096-3112 ◽  
Author(s):  
Kiran Chandra Sahu ◽  
Jukka Tuhkuri ◽  
JN Reddy
Keyword(s):  
Active Control ◽  
Sandwich Panel ◽  
Control Method ◽  
Low Frequency ◽  
Sound Transmission ◽  
Soft Core ◽  
Frequency Range ◽  
Broad Frequency Range ◽  
Volume Velocity ◽  
Numerical Studies

In this paper, active control of harmonic sound transmitted through a soft-core sandwich panel into a rectangular enclosure is studied. As it has already been shown for the low frequency region, the noise transmission through a soft-core sandwich panel mainly occurs due to the flexural and the dilatational modes. Therefore, in this study, volume velocity cancellation control strategy is used to control these modes, and achieve sound attenuation in a broad frequency range. Point force and uniformly distributed force actuators are used as the secondary actuator to cancel the volume velocity of the bottom faceplate, which opens to the cavity, of the sandwich panel. Cancelling the net volume velocity of the bottom faceplate is compared not only in terms of the reduction in sound transmission through the sandwich panel into cavity but also in terms of the faceplate velocities. Also, the effectiveness of the volume velocity cancellation strategy has been studied for different values of isotropic loss factor of the core. Sound transmission into the cavity has also been calculated by considering the effect of cavity pressure on the sandwich panel. Numerical studies indicate that the active control method controls both the flexural and the dilatational modes of the sandwich panel and therefore, attenuates significant amount of sound pressure inside the cavity irrespective of the isotropic loss factors of the viscoelastic core in a broad frequency range. Also a finite element study has been done in the commercially available COMSOL Multiphysics software to compare with the analytical results.

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