Implantation of Poly(ethyl acrylate) in Mesoporus Poly(styrene-co-divinylbenzene) Microspheres as a Particulate Sound Absorbent

2004 ◽  
Vol 856 ◽  
Author(s):  
Yeap Hung Ng ◽  
Liang Hong
Keyword(s):  
Acoustic Waves ◽  
Pore Radius ◽  
Suspension Polymerization ◽  
Ethyl Acrylate ◽  
Sound Waves ◽  
Frequency Range ◽  
Attenuation Level ◽  
Polymerization Reactor ◽  
The Individual ◽  
Individual Particles

ABSTRACTPorous microspheres of poly(styrene-co-divinylbenzene) (SD) have been synthesized by suspension polymerization. They present a narrow porosity gap (21–24%) and a mean pore-radius range (106–117 Å). The mesoporous voids are then made use as the polymerization reactor for ethyl acrylate (EA), and as a result of the embedded polymerization, linear EA formed is trapped inside the individual particles (SD-EA), and its Tg is brought up to as high as the ambient temperature. Two specific loadings of EA were attained: 11% and 28% by weight. The acoustic absorption behaviors of SD-EA and SD microspheres are assessed by the attenuation coefficient (a = IAttenuated/IIncidence), in which the incident acoustic waves are two arbitrary audio frequency bands, 100–1000 Hz and 4000–5000Hz. In contrast to porous SD microspheres, SD-EA microspheres apparently relax the incident frequencies and attenuate more effectively the higher frequency sound waves. The maximum attenuation level (a) of SD-EA absorbent is about 80% (dB). It was found that the higher EA loading could improve rather slightly the attenuation level in the higher frequency range.

Concealed Weapon Detection Using Acoustic Spectral Characterisation

2009 ◽  
Author(s):  
George A. Vadakkel ◽  
S. Olutunde Oyadiji
Keyword(s):  
Acoustic Signal ◽  
Acoustic Waves ◽  
Natural Frequencies ◽  
Sound Waves ◽  
Frequency Range ◽  
Ultrasonic Sound ◽  
Audible Frequency ◽  
Spectral Characterisation ◽  
Concealed Weapon Detection ◽  
Experimental Trials

This paper focuses on showing how one could identify a component by using acoustic waves within the audible frequency range. The purpose of this study is to incorporate the findings from this paper in concealed weapon detection (CWD) where objects hidden behind a person’s clothing could be detected using acoustic or ultrasonic sound waves. Experimental trials are carried out using a directional speaker which generates a highly directional acoustic beam. This can then be pointed at any target and the sound reflected from it analyzed. Initially, a sound source is selected based on the maximum frequency range. The characteristic of the acoustic signal produced by the source is then recorded to be used as reference. Different objects are selected to be used as targets. The sound reflected from these objects is recorded. The spectrograms from these targets reveal that the incident sound waves have been modulated. By taking the ratio of the reflected and the incident sound signals one could obtain the natural frequencies of the object and the spectrogram of the reflected acoustic signal could give indication of the object’s shape.

Flexibly guiding of acoustic waves by one-dimensional sonic crystal with omnidirectional bandgap

2015 ◽  
Vol 29 (28) ◽  
pp. 1550193 ◽  
Author(s):  
Hai-Long He ◽  
Shi-Liang Ou-Yang ◽  
Zhaojian He ◽  
Ke Deng ◽  
Heping Zhao
Keyword(s):  
Numerical Simulations ◽  
Crystal Structures ◽  
Acoustic Waves ◽  
High Efficiency ◽  
Wide Frequency Range ◽  
Sound Waves ◽  
Frequency Range ◽  
Bending Angle ◽  
One Dimensional ◽  
Sonic Crystal

An acoustic waveguide based on the omnidirectional reflection of one-dimensional (1D) sonic crystal (sc) is designed to realize the flexible guiding of sound waves. Numerical simulations indicate that high-efficiency transmission can be achieved at arbitrary bending angle and over a wide frequency range. Moreover, flexible waveguide branches can also be easily constructed by introducing more crystal structures into the waveguides. Owing to its designing flexibility, this waveguide would be very useful in various integrated applications based on SCs.

Dual-finite distributed H∞ filtering in sensor networks

2021 ◽  
pp. 095965182199758
Author(s):  
Changshuo Wang ◽  
Jiwei Wen ◽  
Xiaoli Luan
Keyword(s):  
Sensor Networks ◽  
Disturbance Attenuation ◽  
Time Interval ◽  
Frequency Range ◽  
Frequency Scale ◽  
Attenuation Level ◽  
Exogenous Noise ◽  
Disturbance Attenuation Level ◽  
Reference Input ◽  
Filtering Approach

Generally, distributed H∞ filtering approach achieves a certain disturbance attenuation level in the full frequency range. However, the energy of system noise or reference input usually limits in a specified frequency range. To reduce such a design conservatism, this article develops a distributed filtering approach based on dual scale, that is, filtering over a finite-time interval from time scale and also on a specified finite-frequency region from the frequency scale. Our target is to make the filtering error under sensor networks monitoring be relaxed into an ellipsoid bound rather than asymptotically converging to zero for exogenous noise in a specified frequency range. Finally, two illustrative examples demonstrate the strength of the developed filtering approach.

Photoacoustic Nanotracers for Subsurface Applications: Opportunities and Challenges

2021 ◽  
Author(s):  
Jesus Manuel Felix Servin ◽  
Hala A. Al-Sadeg ◽  
Amr Abdel-Fattah
Keyword(s):  
Acoustic Waves ◽  
Oil And Gas ◽  
Continuous Wave ◽  
Tracer Tests ◽  
Oil And Gas Industry ◽  
Oil Reservoirs ◽  
Medical Community ◽  
Sound Waves ◽  
Time Data ◽  
Gas Industry

Abstract Tracers are practical tools to gather information about the subsurface fluid flow in hydrocarbon reservoirs. Typical interwell tracer tests involve injecting and producing tracers from multiple wells to evaluate important parameters such as connectivity, flow paths, fluid-fluid and fluid-rock interactions, and reservoir heterogeneity, among others. The upcoming of nanotechnology enables the development of novel nanoparticle-based tracers to overcome many of the challenges faced by conventional tracers. Among the advantages of nanoparticle-based tracers is the capability to functionalize their surface to yield stability and transportability through the subsurface. In addition, nanoparticles can be engineered to respond to a wide variety of stimuli, including light. The photoacoustic effect is the formation of sound waves following light absorption in a material sample. The medical community has successfully employed photoacoustic nanotracers as contrast agents for photoacoustic tomography imaging. We propose that properly engineered photoacoustic nanoparticles can be used as tracers in oil reservoirs. Our analysis begins by investigating the parameters controlling the conversion of light to acoustic waves, and strategies to optimize such parameters. Next, we analyze different kind of nanoparticles that we deem potential candidates for our subsurface operations. Then, we briefly discuss the excitation sources and make a comparison between continuous wave and pulsed sources. We finish by discussing the research gaps and challenges that must be addressed to incorporate these agents into our operations. At the time of this writing, no other study investigating the feasibility of using photoacoustic nanoparticles for tracer applications was found. Our work paves the way for a new class of passive tracers for oil reservoirs. Photoacoustic nanotracers are easy to detect and quantify and are therefore suitable for continuous in-line monitoring, contributing to the ongoing real-time data efforts in the oil and gas industry.

Hypersonic Velocity, Absorption and Relaxation in Molten CSNO3

1977 ◽  
Vol 32 (1) ◽  
pp. 57-60 ◽  
Author(s):  
H. E. Gunilla Knape ◽  
Lena M. Torell
Keyword(s):  
Relaxation Time ◽  
High Frequency ◽  
Viscosity Coefficient ◽  
Sound Waves ◽  
Frequency Range ◽  
Ultrasonic Velocities ◽  
Hypersonic Velocity ◽  
Frequency Shifts ◽  
Bulk Viscosity Coefficient ◽  
Good Agreement

Abstract Brillouin spectra of molten CSNO3 were investigated for scattering angles between 40 and 140° and in a temperature interval of 420-520 °C. An Ar+ singlemode laser was used for excitation and the total instrumental width was ~265 MHz. The measured frequency shifts and linewidths of the Brillouin components were used to determine velocities and attenuations of thermal sound waves in the frequency range 2.3-7.0 GHz. A dispersion of 4-5% was found between the present hyper­ sonic velocities and reported ultrasonic velocities. A considerable decrease in attenuation with frequency was observed in the investigated frequency range, with the value at high frequency ap­ proaching the classical attenuation. The results are in good agreement with Mountain's theory of a single relaxation time. The relaxation time of the bulk viscosity coefficient was calculated to 1.2×10-10S.

scholarly journals An Experimental Observation Related To The Pore Space Between Particles Of Cement In Pastes At Early Ages

1988 ◽  
Vol 137 ◽  
Author(s):  
Hamlin M. Jennings
Keyword(s):  
Surface Charge ◽  
Experimental Observation ◽  
Cement Paste ◽  
Pore Space ◽  
The Individual ◽  
Individual Particles

Cement paste of water:cement ratios less than about 0.3 usually are not workable, but workability can be maintained at these lower water:cement ratios by using superplasticizers. A typical explanation [1] of the mechanism behind the effectiveness of superplasticizers is that they adsorb on the surface of cement particles and adjust the surface charge so that the particles become deflocculated. The individual particles flow more easily than larger flocs.

scholarly journals Non-Wovens as Sound Reducers

2018 ◽  
Vol 55 (2) ◽  
pp. 64-76
Author(s):  
D. Belakova ◽  
A. Seile ◽  
S. Kukle ◽  
T. Plamus
Keyword(s):  
Absorption Coefficient ◽  
Surface Density ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Sound Transmission ◽  
Sound Insulation ◽  
Material Structure ◽  
Sound Transmission Loss ◽  
Sound Waves ◽  
Frequency Range

Abstract Within the present study, the effect of hemp (40 wt%) and polyactide (60 wt%), non-woven surface density, thickness and number of fibre web layers on the sound absorption coefficient and the sound transmission loss in the frequency range from 50 to 5000 Hz is analysed. The sound insulation properties of the experimental samples have been determined, compared to the ones in practical use, and the possible use of material has been defined. Non-woven materials are ideally suited for use in acoustic insulation products because the arrangement of fibres produces a porous material structure, which leads to a greater interaction between sound waves and fibre structure. Of all the tested samples (A, B and D), the non-woven variant B exceeded the surface density of sample A by 1.22 times and 1.15 times that of sample D. By placing non-wovens one above the other in 2 layers, it is possible to increase the absorption coefficient of the material, which depending on the frequency corresponds to C, D, and E sound absorption classes. Sample A demonstrates the best sound absorption of all the three samples in the frequency range from 250 to 2000 Hz. In the test frequency range from 50 to 5000 Hz, the sound transmission loss varies from 0.76 (Sample D at 63 Hz) to 3.90 (Sample B at 5000 Hz).

Proof of the no-interaction theorem without hamiltonian and lagrangian formalism

1994 ◽  
Vol 445 (1923) ◽  
pp. 221-229 ◽  
Keyword(s):  
Angular Momentum ◽  
Conservation Laws ◽  
Lagrangian Formalism ◽  
The Individual ◽  
Individual Particles

The proofs of the no-interaction theorem have been given by many authors in the framework of hamiltonian and lagrangian formalism. They are based on the assumption that there is hamiltonian or lagrangian describing the interaction between particles. This paper presents the proof without such an assumption for one, two, three and four particles. We assume the conservation laws for the linear and angular momentum that are the sums of the respective quantities of individual particles. Then there is no interaction, i. e. the worldlines of the individual particles are straight.

scholarly journals The straggling of β-particles

1929 ◽  
Vol 125 (798) ◽  
pp. 420-445 ◽  
Keyword(s):  
Classical Theory ◽  
Experimental Investigations ◽  
Theoretical Treatment ◽  
A Value ◽  
Thin Foils ◽  
New Ideas ◽  
The Subject ◽  
The Individual ◽  
Individual Particles ◽  
Α Particles

When a beam of electric particles is passed through a sheet of matter the energy of the individual particles is reduced. The loss of energy is not the same for all the particles so that particles incident on the foil with the same energy emerge with different energies. This dispersion of the energy caused by the foil is known as the "straggling" of the particles. The straggling of α-particles has been the subject of several experimental investigations, and the theory in this case was adequately developed by Bohr in 1915. In the case of β-particles, however, the straggling was not experimentally investigated until quite recently and no theoretical treatment of the phenomenon has been given, the calculations of Bohr being, as he showed, applicable only to α-particles. The purpose of the work described in this paper is to develop a theory of the straggling of β-particles by thin foils and by means of it to interpret the results of experiment. The paper is arranged as follows. In 2 an account is given of the state of the experimental work on the subject, and in particular the effect of the complications introduced by "scattering" are considered. The formula derived by Bohr for the straggling of electric particles is given in 3 and its inapplicability to β-particles demonstrated. The present calculations of the straggling of β-particles are given in 4. The theory of the straggling of electric particles resolves itself into two parts. The first deals with the dynamics of collisions between electric particles and atoms, and is the same whether we are concerned with the straggling or some other phenomena such as ionisation of "stopping power." This may be called the fundamental theory and its requirements may be summarised in the function ϕ (Q) which express the frequency of collisions in which the electric particle loses energy of amount Q. The second part of the theory is the process of calculating the straggling by means of probability theory from the function ϕ . This may be regarded as the straggling theory proper and it is the main subject of 4. When the present calculations were started it was intended to calculate the straggling on the basis of classical theory only, the value of the function ϕ on this theory being definitely known. However, after some practice with the type of calculation involved it was decided to calculate the straggling for other forms of ϕ . From the results obtained it is possible to deduce the straggling corresponding to any form which ϕ may reasonably have, and if a new theory leads to a value of ϕ different from the classical value, the straggling on the new theory may readily be determined. Alternatively this fuller treatment may be used for the reverse process of calculating from the observed straggling the value of ϕ to which it corresponds. This is considered to be the most convenient procedure and in 5 the form of ϕ which explains the experimental results is deduced. this is compared in 6 with the value of ϕ on classical theory. A brief outline is given in 7 of certain new ideas concerning the nature of collisions of electric particles with electrons and atoms.

A physically motivated approach for filtering acoustic waves from the equations governing compressible stratified flow

2008 ◽  
Vol 601 ◽  
pp. 365-379 ◽  
Author(s):  
DALE R. DURRAN
Keyword(s):  
Acoustic Waves ◽  
Large Scale ◽  
Mass Conservation ◽  
Simple Expression ◽  
Reference State ◽  
Small Scale ◽  
Sound Waves ◽  
State Equations ◽  
Planetary Scale ◽  
Atmospheric Motions

An incompressibility approximation is formulated for isentropic motions in a compressible stratified fluid by defining a pseudo-density ρ* and enforcing mass conservation with respect to ρ* instead of the true density. Using this approach, sound waves will be eliminated from the governing equations provided ρ* is an explicit function of the space and time coordinates and of entropy. By construction, isentropic pressure perturbations have no influence on the pseudo-density.A simple expression for ρ* is available for perfect gases that allows the approximate mass conservation relation to be combined with the unapproximated momentum and thermodynamic equations to yield a closed system with attractive energy conservation properties. The influence of pressure on the pseudo-density, along with the explicit (x,t) dependence of ρ* is determined entirely by the hydrostatically balanced reference state.Scale analysis shows that the pseudo-incompressible approximation is applicable to motions for which ${\cal M})$2 ≪ min(1,${\cal R})$2, where ${\cal M})$ is the Mach number and ${\cal R}$ the Rossby number. This assumption is easy to satisfy for small-scale atmospheric motions in which the Earth's rotation may be neglected and is also satisfied for quasi-geostrophic synoptic-scale motions, but not planetary-scale waves. This scaling assumption can, however, be relaxed to allow the accurate representation of planetary-scale motions if the pressure in the time-evolving reference state is computed with sufficient accuracy that the large-scale components of the pseudo-incompressible pressure represent small corrections to the total pressure, in which case the full solution to both the pseudo-incompressible and reference-state equations has the potential to accurately model all non-acoustic atmospheric motions.

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