Zero Spillover Active Structural Acoustic Control

2004 ◽  
Author(s):  
Moustafa Al-Bassyiouni ◽  
B. Balachandran
Keyword(s):  
Experimental Study ◽  
Three Dimensional ◽  
Frequency Range ◽  
Sound Fields ◽  
Rectangular Enclosure ◽  
Acoustic Control ◽  
Structural Acoustic Control

In this article, a combined analytical and experimental study conducted on the feasibility of implementing a relaxed zero spillover control (RZSC) scheme for active structural acoustic control (ASAC) is presented. The aim of this effort is to actively control sound fields inside a three-dimensional rectangular enclosure into which noise is transmitted through a flexible boundary. Piezoceramic patches, which are mounted on the flexible boundary, are used as actuators, and microphones, which are placed inside and outside the enclosure, are used as sensors. In the experiments, an attenuation of 5.56 dB is obtained for broadband excitation in the frequency range of 20 Hz ≤ f ≤ 220 Hz.

Density-based discrimination of protein and RNA in the ribosome

1992 ◽  
Vol 50 (1) ◽  
pp. 464-465
Author(s):  
Joachim Frank
Keyword(s):  
Transfer Function ◽  
Spatial Frequency ◽  
Three Dimensional ◽  
Wiener Filter ◽  
Dark Field Image ◽  
Dark Field ◽  
Frequency Range ◽  
Bright Field ◽  
Contrast Transfer Function ◽  
Pass Filter

Cryo-electron microscopy combined with single-particle reconstruction techniques has allowed us to form a three-dimensional image of the Escherichia coli ribosome.In the interior, we observe strong density variations which may be attributed to the difference in scattering density between ribosomal RNA (rRNA) and protein. This identification can only be tentative, and lacks quantitation at this stage, because of the nature of image formation by bright field phase contrast. Apart from limiting the resolution, the contrast transfer function acts as a high-pass filter which produces edge enhancement effects that can explain at least part of the observed variations. As a step toward a more quantitative analysis, it is necessary to correct the transfer function in the low-spatial-frequency range. Unfortunately, it is in that range where Fourier components unrelated to elastic bright-field imaging are found, and a Wiener-filter type restoration would lead to incorrect results. Depending upon the thickness of the ice layer, a varying contribution to the Fourier components in the low-spatial-frequency range originates from an “inelastic dark field” image. The only prospect to obtain quantitatively interpretable images (i.e., which would allow discrimination between rRNA and protein by application of a density threshold set to the average RNA scattering density may therefore lie in the use of energy-filtering microscopes.

scholarly journals Advanced Micro-Actuator/Robot Fabrication Using Ultrafast Laser Direct Writing and Its Remote Control

2020 ◽  
Vol 10 (23) ◽  
pp. 8563
Author(s):  
Sangmo Koo
Keyword(s):  
Three Dimensional ◽  
Processing Technique ◽  
Direct Writing ◽  
Laser Direct Writing ◽  
Precise Control ◽  
Two Photon ◽  
Non Invasive ◽  
Acoustic Control ◽  
Fs Laser ◽  
Invasive Control

Two-photon polymerization (TPP) based on the femtosecond laser (fs laser) direct writing technique in the realization of high-resolution three-dimensional (3D) shapes is spotlighted as a unique and promising processing technique. It is also interesting that TPP can be applied to various applications in not only optics, chemistry, physics, biomedical engineering, and microfluidics but also micro-robotics systems. Effort has been made to design innovative microscale actuators, and research on how to remotely manipulate actuators is also constantly being conducted. Various manipulation methods have been devised including the magnetic, optical, and acoustic control of microscale actuators, demonstrating the great potential for non-contact and non-invasive control. However, research related to the precise control of microscale actuators is still in the early stages, and in-depth research is needed for the efficient control and diversification of a range of applications. In the future, the combination of the fs laser-based fabrication technique for the precise fabrication of microscale actuators/robots and their manipulation can be established as a next-generation processing method by presenting the possibility of applications to various areas.

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