scholarly journals Demultiplexing Infrasound Phonons With Tunable Magnetic Lattices

2020 ◽  
Vol 7 ◽  
Author(s):  
Audrey A. Watkins ◽  
Osama R. Bilal
Keyword(s):  
Self Assembly ◽  
Small Volume ◽  
Low Frequency ◽  
Acoustic Metamaterials ◽  
Propagation Characteristics ◽  
Low Frequencies ◽  
Experimental Realization ◽  
Nonlinear Properties ◽  
Potential Applications ◽  
Low Frequency Waves

Controlling infrasound signals is crucial to many processes ranging from predicting atmospheric events and seismic activities to sensing nuclear detonations. These waves can be manipulated through phononic crystals and acoustic metamaterials. However, at such ultra-low frequencies, the size (usually on the order of meters) and the mass (usually on the order of many kilograms) of these materials can hinder its potential applications in the infrasonic domain. Here, we utilize tunable lattices of repelling magnets to guide and sort infrasound waves into different channels based on their frequencies. We construct our lattices by confining meta-atoms (free-floating macroscopic disks with embedded magnets) within a magnetic boundary. By changing the confining boundary, we control the meta-atoms’ spacing and therefore the intensity of their coupling potentials and wave propagation characteristics. As a demonstration of principle, we present the first experimental realization of an infrasound phonon demultiplexer (i.e., guiding ultra-low frequency waves into different channels based on their frequencies). The realized platform can be utilized to manipulate ultra-low frequency waves, within a relatively small volume, while utilizing negligible mass. In addition, the self-assembly nature of the meta-atoms can be key in creating re-programmable materials with exceptional nonlinear properties.

scholarly journals Inverse Measurement of the Thickness and Flow Resistivity of Porous Materials via Reflected Low Frequency Waves-Frequency Approach

2021 ◽  
Author(s):  
Mustapha Sadouki
Keyword(s):  
Reflection Coefficient ◽  
Direct Problem ◽  
Fluid Model ◽  
Low Frequency ◽  
Low Frequencies ◽  
Reflected Waves ◽  
Two Samples ◽  
Flow Resistivity ◽  
Theoretical Reflection ◽  
Low Frequency Waves

A direct and inverse method is proposed for measuring the thickness and flow resistivity of a rigid air-saturated porous material using acoustic reflected waves at low frequency. The equivalent fluid model is considered. The interactions between the structure and the fluid are taken by the dynamic tortuosity of the medium introduced by Johnson et al. and the dynamic compressibility of the air introduced by Allard. A simplified expression of the reflection coefficient is obtained at very low frequencies domain (Darcy’s regime). This expression depends only on the thickness and flow resistivity of the porous medium. The simulated reflected signal of the direct problem is obtained by the product of the experimental incident signal and the theoretical reflection coefficient. The inverse problem is solved numerically by minimizing between simulated and experimental reflected signals. The tests are carried out using two samples of polyurethane plastic foam with different thicknesses and resistivity. The inverted values of thickness and flow resistivity are compared with those obtained by conventional methods giving good results.

scholarly journals Finite Element Analysis on Acoustic and Mechanical Performance of Flexible Perforated Honeycomb-Corrugation Hybrid Sandwich Panel

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Jiaming Hu ◽  
Junyi Wang ◽  
Yu Xie ◽  
Chenzhi Shi ◽  
Yun Chen
Keyword(s):  
Finite Element ◽  
Sandwich Panel ◽  
Mechanical Performance ◽  
Mechanical Energy ◽  
Low Frequency ◽  
Rigid Wall ◽  
Acoustic Metamaterials ◽  
Mechanical Stiffness ◽  
Element Analysis ◽  
Low Frequencies

Since proposed, the perforated honeycomb-corrugation sandwich panel has attracted a lot of attention due to its superior broadband sound absorption at low frequencies and excellent mechanical stiffness/strength. However, most existing studies have assumed a structure made of high-strength materials and studied its performance based on the ideal rigid-wall model with little consideration for acoustic-structure interaction, thereby neglecting the structural vibrations caused by the material’s elasticity. In this paper, we developed a more realistic model considering the solid structural dynamics using the finite element method (FEM) and by applying aluminum and rubber as the structural material. The enhancement of the low-frequency performance and inhibition of broadband absorption coexisted in low-strength rubbers, implying a compromise in the selection of Young's modulus to balance these two influences. Further analysis on thermal-viscous dissipation, mechanical energy, and average structural stress indicated that the structure should work right below the resonant frequency for optimization. Based on these findings, we designed a novel aluminum-rubber composite structure possessing enhanced low-frequency absorption, high resistance to shear load, normal compression, and thermal expansion. Our research is expected to shed some light on noise control and the design of multifunctional acoustic metamaterials.

scholarly journals Experimental measurement of the porosity and the viscous tortuosity of rigid porous material in low frequency

2018 ◽  
Vol 37 (2) ◽  
pp. 385-393 ◽  
Author(s):  
M Sadouki
Keyword(s):  
Porous Material ◽  
Acoustic Pulse ◽  
Low Frequency ◽  
Acoustic Method ◽  
Simple Relation ◽  
Low Frequencies ◽  
Reflected Waves ◽  
Rigid Frame ◽  
Temporal Model ◽  
Low Frequency Waves

In this paper, an acoustic method is presented for measuring the porosity and the viscous tortuosity of air-saturated-porous materials at low frequencies. The proposed method is based on a temporal model of the direct and inverse problem for the reflection of low-frequency waves by homogeneous isotropic slab of porous material having a rigid frame. Reflected coefficient for a slab of porous material is derived from the responses of the medium to an incident acoustic pulse where a simple relation between flow resistivity, porosity, viscous tortuosity and the reflected waves is obtained. A numerical method and efficient tool for the estimation of the porosity and the viscous tortuosity are presented and discussed.

A Design Method for Sound Absorbing Structure at Low Frequency

2020 ◽  
Vol 982 ◽  
pp. 39-50
Author(s):  
Ying Jie Fu ◽  
Xiao Ming Wang ◽  
Yu Lin Mei
Keyword(s):  
Design Method ◽  
Low Frequency ◽  
Acoustic Energy ◽  
Channel Structure ◽  
Response Analysis ◽  
Acoustic Metamaterials ◽  
Element Analysis ◽  
Low Frequencies ◽  
Mass Unit ◽  
The Masses

Traditional acoustic absorbing materials are not effective for low-frequency engineering applications, but on the basis of the locally resonant principle, acoustic metamaterials can utilize the resonance of vibrators to dissipate acoustic energy and realize the subwavelength design of acoustic absorbers, therefore the acoustic metamaterials have great potential applications for noise reduction at low frequencies. This paper firstly employs the Bloch theory to investigate the effects of the parameters of the unit cell of the embedded membrane-and-mass metamaterials on the dispersion characteristics of the metamaterials, and the band gap is verified by the full wave finite element analysis. And then, a model of acoustic metamaterials is constructed by embeding an array of membrane-and-masses into a channel structure filled with acoustic materials. Next the transient frequency response analysis is performed to simulate the wave propagation in the model, the results show that the acoustic metamaterials can absorb the sound through the local resonance of the membrane-and-mass vibrators. Finally, an acoustic metamaterial maze structure is designed and analyzed, in the structure the membrane-and-mass array is embedded and the masses varies periodically. The research illustrates that the acoustic metamaterials with membrane-and-mass unit cells have excellent performances on the sound absorption at low frequency.

Experimental Study of the Transmission Spectrum of a Sonic/Ultrasonic Acoustic Metamaterial

2016 ◽  
Author(s):  
Yanbo He ◽  
Jeffrey S. Vipperman
Keyword(s):  
Band Gap ◽  
Frequency Band ◽  
Transmission Spectrum ◽  
Physical Phenomenon ◽  
Experimental Studies ◽  
Low Frequency ◽  
Acoustic Metamaterials ◽  
Acoustic Metamaterial ◽  
Potential Applications ◽  
Lower Frequency Band

Acoustic metamaterials have received much attention recently. In the past decades, countless structures have been studied for their novel physical phenomenon or potential applications. The goals of many of the works were to explore ways to enlarge the band gap, lower the band gap frequency, and/or generate greater attenuation of vibration. However, most of the work was limited to simulation, with experimental studies rarer. In this work, we would like to experimentally present the transmission spectrum of an acoustic metamaterial with a proposed structure called the coated double hybrid lattice (CDHL) [1]. The CDHL has both crystalline structure and local resonators, which provide high-frequency and low-frequency band gaps, respectively. A structure was fabricated and tested to experimentally determine the transmission spectrum. Both, a higher frequency band gap and a lower frequency band gap, were obtained. Vibration is clearly attenuated in the frequency range of 70–90 kHz. This is due to the Bragg scattering effect. At the same time, around the frequency of 4.8kHz, another band gap is observed which is attributed to local resonance. It turns out that our experimental results coincide with our previous simulation quite well.

Porphyrin-functionalized coordination star polymers and their potential applications in photodynamic therapy

2019 ◽  
Vol 10 (45) ◽  
pp. 6116-6121 ◽  
Author(s):  
Tan Ji ◽  
Lei Xia ◽  
Wei Zheng ◽  
Guang-Qiang Yin ◽  
Tao Yue ◽  
...  
Keyword(s):  
Photodynamic Therapy ◽  
Self Assembly ◽  
Star Polymers ◽  
New Family ◽  
Potential Applications

We present a new family of porphyrin-functionalized coordination star polymers prepared through combination of coordination-driven self-assembly and post-assembly polymerization. Their self-assembly behaviour in water and potential for photodynamic therapy were demonstrated.

PEMANFAATAN RADIASI ENERGI TEGANGAN 150 KV UNTUK LAMPU LED PENERANGAN JALAN

Jurnal Teknik ◽  
2018 ◽  
Vol 7 (1) ◽  
Author(s):  
Mauludi Manfaluthy
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
High Voltage ◽  
Low Frequency ◽  
Energy Utilization ◽  
World Health ◽  
Electromagnetic Signals ◽  
Health Organization ◽  
The Magnetic Field ◽  
Low Frequency Waves

WHO (World Health Organization) concludes that not much effect is caused by electric field up to 20 kV / m in humans. WHO standard also mentions that humans will not be affected by the magnetic field under  100 micro tesla and that the electric field will affect the human body with a maximum standard of 5,000 volts per meter. In this study did not discuss about the effect of high voltage radiation SUTT (High Voltage Air Channel) with human health. The research will focus on energy utilization of SUTT radiation. The combination of electric field and magnetic field on SUTT (70-150KV) can generate electromagnetic (EM) and radiation waves, which are expected to be converted to turn on street lights around the location of high voltage areas or into other forms. The design of this prototype works like an antenna in general that captures electromagnetic signals and converts them into AC waves. With a capacitor that can store the potential energy of AC and Schottky diode waves created specifically for low frequency waves, make the current into one direction (DC). From the research results obtained the current generated from the radiation is very small even though the voltage is big enough.Keywords : Radiance Energy, Joule Thief, and  LED Module.

Computational and Experimental Binding Mechanism of DNA-drug Interactions

2019 ◽  
Vol 24 (32) ◽  
pp. 3739-3757 ◽  
Author(s):  
Chandrabose Selvaraj ◽  
Sanjeev K. Singh
Keyword(s):  
Small Molecules ◽  
Self Assembly ◽  
Genetic Material ◽  
Dna Interaction ◽  
Significant Feature ◽  
Drug Molecules ◽  
Potential Applications ◽  
Novel Drug ◽  
Groove Binders ◽  
Molecular Docking And Dynamics

Nucleic acid is the key unit and a predominant genetic material for interpreting the fundamental basis of genetic information in an organism and now it is used for the evolution of a novel group of therapeutics. To identify the potential impact on the biological science, it receives high recognition in therapeutic applications. Due to its selective recognition of molecular targets and pathways, DNA significantly imparts tremendous specificity of action. Examining the properties of DNA holds numerous advantages in assembly, interconnects, computational elements, along with potential applications of DNA self-assembly and scaffolding include nanoelectronics, biosensors, and programmable/autonomous molecular machines. The interaction of low molecular weight, small molecules with DNA is a significant feature in pharmacology. Based on the mode of binding mechanisms, small molecules are categorized as intercalators and groove binders having a significant role in target-based drug development. The understanding mechanism of drug-DNA interaction plays an important role in the development of novel drug molecules with more effective and lesser side effects. This article attempts to outline those interactions of drug-DNA with both experimental and computational advances, including ultraviolet (UV) -visible spectroscopy, fluorescent spectroscopy, circular dichroism, nuclear magnetic resonance (NMR), molecular docking and dynamics, and quantum mechanical applications.

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