Academic literature on the topic 'ELASTICITY; SURFACE PROPERTIES; SOUND WAVES'
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Journal articles on the topic "ELASTICITY; SURFACE PROPERTIES; SOUND WAVES"
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Carmichael, Stephen W. "Imaging Based on Elasticity." Microscopy Today 6, no. 7 (September 1998): 3–4. http://dx.doi.org/10.1017/s1551929500068565.
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There are scores of microscopes that detect different properties of a specimen. Typically we image ‘visible” properties, but, for example, even the commonly-used atomic force microscope detects physical interactions rather than “visible” characteristics, Mostafa Fatemi and James Greenleaf have introduced the principle of imaging the elastic features of a specimen. This is done with sound waves, but we are not talking about just another acoustic microscope.The method demonstrated by Fatemi and Greenleaf uses radiation force to image the acoustic response of a specimen to mechanical excitation. The mechanical excitation results from focusing two coaxial and confocal ultrasound beams of slightly different frequencies onto a selected region of the specimen.
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Inoue, Kazuko, and Tomio Ariyasu. "Sound waves and shock waves in high-density deuterium." Laser and Particle Beams 9, no. 4 (December 1991): 795–816. http://dx.doi.org/10.1017/s026303460000656x.
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The possibility of compressing the cryogenic hollow pellet of inertial confinement nuclear fusion with multiple adiabatic shock waves is discussed, on the basis of the estimation of the properties of a high-density deuterium plasma (1024−1027 cm−3, 10−1−104 eV), such as the velocity and the attenuation constant of the adiabatic sound wave, the width of the shock wave, and the surface tension.It is found that in the course of compression the wavelength of the adiabatic sound wave and the width of the weak shock wave sometimes become comparable to or exceed the fuel shell width of the pellet, and that the surface tension is negative. These results show that it is rather difficult to compress stably the hollow pellet with successive weak shock waves.
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Gräff, Dominik, Fabian Walter, and Bradley P. Lipovsky. "Crack wave resonances within the basal water layer." Annals of Glaciology 60, no. 79 (April 25, 2019): 158–66. http://dx.doi.org/10.1017/aog.2019.8.
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ABSTRACTHydraulic processes within and beneath glacial bodies exert a far-reaching control on ice flow through their influence on basal sliding. Within the subglacial system, rapid changes in these processes may excite resonances whose interpretation requires an understanding of the underlying wave mechanics. Here, we explore these mechanics using observations from a kHz-sampled pressure sensor installed in a borehole directly above the hard granite bedrock of a temperate mountain glacier in Switzerland. We apply a previously established theory of wave propagation along thin, water-filled structures such as water-filled voids, basal water layers, or hydraulic fractures. Within such structures, short-wavelength waves experience restoring forces due to compressibility and are composed of sound waves. Long-wavelength resonances, in contrast, experience restoring forces due to elasticity and are composed of anomalously dispersed crack waves or Krauklis waves. Our borehole observations confirm the occurrence of both sound and crack waves within the basal water layer. Using both the resonance frequencies and attenuation of recorded crack waves we estimate thickness, aperture and length of the resonating basal water layer patch into which we drilled. We demonstrate that high-frequency observations of subglacial hydraulic processes provide new insights into this evolving dynamic system.
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Li, Yueqiu, Peijun Wei, and Changda Wang. "Propagation of thermoelastic waves across an interface with consideration of couple stress and second sound." Mathematics and Mechanics of Solids 24, no. 1 (December 28, 2017): 235–57. http://dx.doi.org/10.1177/1081286517736999.
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The reflection and transmission of thermoelastic waves across an interface between two different couple stress solids are studied based on the thermoelastic Green–Naghdi theory with consideration of second sound. First, some thermodynamic equations of a couple stress elastic solid are formulated and the function of free energy density is postulated. Second, equations of thermal motion and heat conduction of the couple stress elasticity are derived and constitutive relations with thermoelastic coupled effects are obtained. From these equations, four kinds of dispersive waves, namely, thermal-mechanically coupled MT1 wave and MT2 wave, uncoupled SV wave, and an evanescent wave that becomes the surface waves at interface, are derived. Then, the interfacial conditions of couple stress elastic solids with consideration of force stress, couple stress, and thermal effects are used to determine the amplitude ratios of the reflection and transmission waves with respect to the incident wave. The numerical results are validated by consideration of energy conservation.
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Rousseau, Martine, and Gérard A. Maugin. "Rayleigh surface waves and their canonically associated quasi-particles." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 467, no. 2126 (August 11, 2010): 495–507. http://dx.doi.org/10.1098/rspa.2010.0229.
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Inspired by soliton theory and exploiting the conservation law of wave momentum, it is shown that one can associate with the surface Rayleigh wave of macroscopic elasticity a quasi-particle, a ‘surface phonon’, which is in inertial motion for the standard boundary conditions. The ‘mass’ of this ‘particle’ is determined in terms of the wave properties. Different types of alteration in the boundary conditions are shown to result in perturbations of this inertial motion in various ways. The essential tool in the presented derivation is the exploitation of the canonical equations of conservation, which are consequences of the celebrated Noether theorem of field theory. The results obtained may be useful in the mechanics of surface waves at the nanoscale, in particular in treating perturbations of various kinds.
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Otani, Takahiko. "Modeling of Ultrasonic Wave Propagation Path through Cancellous Bone and Quantitative Estimation of Bone Density and Bone Quality." Key Engineering Materials 321-323 (October 2006): 857–61. http://dx.doi.org/10.4028/www.scientific.net/kem.321-323.857.
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Osteoporosis is a disease characterized by decreasing bone density, and is assessed by the bone mass density of cancellous bone. An X-ray method is widely used for noninvasive measurement of bone mass density [mg/cm3]. An ultrasonic method has the potential to evaluate the elastic properties, however measured ultrasonic parameters are the slope of frequency dependent attenuation (BUA [dB/MHz]) and the speed of sound (SOS [m/s]), not the bone mass density [mg/cm3]. In previous study, two longitudinal waves, the fast and slow waves, were observed in cancellous bone. In this study, the propagation path through cancellous bone is modeled to specify the causality between ultrasonic wave parameters and bone density. Then bone density and bone elasticity are quantitatively formulated. A novel ultrasonic bone densitometry, prototype LD-100, have been developed. The bone density [mg/cm3] and the bone elasticity [GPa] are evaluated by ultrasonic parameters based on the fast and slow waves in cancellous bone using a modeling of ultrasonic wave propagation path.
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OU, Z. Y., and D. W. LEE. "EFFECTS OF INTERFACE ENERGY ON MULTIPLE SCATTERING OF PLANE COMPRESSIONAL WAVES BY TWO CYLINDRICAL FIBERS." International Journal of Applied Mechanics 04, no. 04 (December 2012): 1250040. http://dx.doi.org/10.1142/s1758825112500408.
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The multiple scattering of plane compressional waves by two cylindrical fibers with interface effects is investigated. Based on surface elasticity theory, the wave fields in a nanoscale solid medium can be obtained by applying the eigenfunction expansion method and the Graf's addition theorem. Our results indicate that surface energy significantly affects the diffraction of elastic waves, as the radii of the fibers approach nanometers. The dynamic stress concentration factors at the interfaces between the fibers and the matrix under incident plane compressional waves at different frequencies are examined to determine the effects of surface energy, properties of inhomogeneous materials, and the interaction between fibers in multiple scattering phenomena. These results are helpful in understanding the dynamic mechanical properties of nanocomposites, and the proposed method for investigating the multiple scattering of plane compressional waves can be extended to the case of fiber-reinforced composites.
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Sharifineyestani, Elham, and Navid Tahvildari. "A NUMERICAL STUDY ON SURFACE WAVE EVOLUTION OVER VISCOELASTIC MUD." Coastal Engineering Proceedings, no. 36 (December 30, 2018): 64. http://dx.doi.org/10.9753/icce.v36.waves.64.
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A numerical modeling approach is applied to investigate the combined effect of wave-current-mud on the evolution of nonlinear waves. A frequency-domain phase-resolving wave-current model that solves nonlinear wave-wave interactions is used to solve wave evolution. A comparison between the results of numerical wave model and the laboratory experiments confirms the accuracy of the numerical model. The model is then applied to consider the effect of mud properties on nonlinear surface wave evolution. It is shown that resonance effect in viscoelastic mud creates a complex frequency-dependent dissipation pattern. In fact, due to the resonance effect, higher surface wave frequencies can experience higher damping rates over viscoelastic mud compared to viscous mud in both permanent form solution and random wave scenarios. Thus, neglecting mud elasticity can result in inaccuracies in estimating total wave energy and wave shape.
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Tang, Zihan, Yue Chen, and Wei Ye. "Calculation of Surface Properties of Cubic and Hexagonal Crystals through Molecular Statics Simulations." Crystals 10, no. 4 (April 22, 2020): 329. http://dx.doi.org/10.3390/cryst10040329.
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Surface property is an important factor that is widely considered in crystal growth and design. It is also found to play a critical role in changing the constitutive law seen in the classical elasticity theory for nanomaterials. Through molecular static simulations, this work presents the calculation of surface properties (surface energy density, surface stress and surface stiffness) of some typical cubic and hexagonal crystals: face-centered-cubic (FCC) pure metals (Cu, Ni, Pd and Ag), body-centered-cubic (BCC) pure metals (Mo and W), diamond Si, zincblende GaAs and GaN, hexagonal-close-packed (HCP) pure metals (Mg, Zr and Ti), and wurzite GaN. Sound agreements of the bulk and surface properties between this work and the literature are found. New results are first reported for the surface stiffness of BCC pure metals, surface stress and surface stiffness of HCP pure metals, Si, GaAs and GaN. Comparative studies of the surface properties are carried out to uncover trends in their behaviors. The results in this work could be helpful to the investigation of material properties and structure performances of crystals.
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Mei, Chiang C., and Usama Kadri. "Sound signals of tsunamis from a slender fault." Journal of Fluid Mechanics 836 (December 11, 2017): 352–73. http://dx.doi.org/10.1017/jfm.2017.811.
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Since the speed of sound in water is much greater than that of the surface gravity waves, acoustic signals can be used for early warning of tsunamis. We simplify existing works by treating the sound wave alone without the much slower gravity wave, and derive a two-dimensional theory for signals emanating from a fault of finite length. Under the assumptions of a slender fault and constant sea depth, the asymptotic technique of multiple scales is applied to obtain analytical results. The modal envelopes of the two-dimensional sound waves are found to be governed by the Schrödinger equation and are solved explicitly. An approximate method is described for the inverse estimation of fault properties from the pressure record at a distant hydrophone.
Dissertations / Theses on the topic "ELASTICITY; SURFACE PROPERTIES; SOUND WAVES"
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Puentes, Heras M. "The use of SAW methods in probing near-surface elastic properties." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299101.
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Bozhko, Andrii. "Physical Boundary as a Source of Anomalies in Transport Processes in Acoustics and Electrodynamics." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1404590/.
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Various anomalous effects that emerge when the interfaces between media are involved in sound-matter or light-matter interactions are studied. The three specific systems examined are a fluid channel between elastic metal plates, a linear chain of metallic perforated cylindrical shells in air, and a metal-dielectric slab with the interfaces treated as finite regions of smoothly changing material properties. The scattering of acoustic signals on the first two is predicted to be accompanied by the effects of redirection and splitting of sound. In the third system, which supports the propagation of surface plasmons, it is discovered that the transition region introduces a nonradiative decay mechanism which adds to the plasmon dissipation. The analytical results are supported with numerical simulations. The outlined phenomena provide the ideas and implications for applications involving manipulation of sound or excitation of surface plasmons.
Books on the topic "ELASTICITY; SURFACE PROPERTIES; SOUND WAVES"
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Veksler, Naum Davidovich. Resonance acoustic spectroscopy. Berlin: Springer-Verlag, 1993.
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Veksler, Naum Davidovich. Akusticheskai͡a︡ spektroskopii͡a︡. Tallinn: Valgus, 1989.
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V, Pak T., ed. Difrakt͡sii͡a ploskoĭ zvukovoĭ volny na zhestkom vyti͡anutom sferoide. Moskva: Vychislitelʹnyĭ t͡sentr AN SSSR, 1985.
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A, Auld B. Acoustic fields and waves in solids. 2nd ed. Malabar, Fla: R.E. Krieger, 1990.
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A, Auld B. Acoustic fields and waves in solids. 2nd ed. Malabar, Fla: R.E. Krieger, 1990.
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Iutam Symposium On Recent Advances Of Acoustic Waves In Solids Proceedings Of The Iutam Symposium On Recent Advances Of Acoustic Waves In Solid Taipe Taiwan May 2528 2009. Springer, 2010.
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Escudier, Marcel. Fluids and fluid properties. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198719878.003.0002.
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In this chapter it is shown that the differences between solids, liquids, and gases have to be explained at the level of the molecular structure. The continuum hypothesis makes it possible to characterise any fluid and ultimately analyse its response to pressure difference Δp and shear stress τ through macroscopic physical properties, dependent only upon absolute temperature T and pressure p, which can be defined at any point in a fluid. The most important of these physical properties are density ρ and viscosity μ, while some problems are also influenced by compressibility, vapour pressure pV, and surface tension σ. It is also shown that the bulk modulus of elasticity Ks is a measure of fluid compressibility which determines the speed at which sound propagates through a fluid. The perfect-gas law is introduced and an equation derived for the soundspeed c.
Book chapters on the topic "ELASTICITY; SURFACE PROPERTIES; SOUND WAVES"
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Garrett, Steven L. "Reflection, Transmission, and Refraction." In Understanding Acoustics, 513–42. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-44787-8_11.
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Abstract The behavior of one-dimensional waves propagating through media that are not homogeneous will be the focus of this chapter. We start with an examination of the behavior of planewaves impinging on a planar interface between two fluid media with different properties and then extend that analysis to multiple interfaces and to waves that impinge on such an interface from an angle that is not perpendicular to that surface. The extent of those boundaries separating regions with different acoustical properties will be much larger than the wavelength of the sound. Many cases to be examined here will assume that the extent of the boundary is infinite and the wave incident on such an interface will be both reflected back into the medium from which it originated and be transmitted into the second medium on the other side of the interface. This exploration concludes with consideration of wave propagation through a medium whose properties change slowly and continuously through space resulting in curved ray paths. If the variation of sound speed is linear with height or depth, then the ray paths are arcs of circles. Complicated sound speed profiles will be approximated by piecewise-linear segments that have constant sound speed gradients.
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Newnham, Robert E. "Acoustic waves II." In Properties of Materials. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780198520757.003.0026.
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Acoustic impedance, acoustic losses, acoustic waves in piezoelectric solids, and surface waves are discussed in this chapter, along with a number of nonlinear acoustic phenomena. The reflection and transmission of acoustic waves across a boundary is governed by acoustic impedance. One of the most important boundary value problems in acoustics concerns a plane wave incident upon a planar surface, dividing one medium from another. In the general case of an anisotropic medium, the incident beam consists of three waves (one quasilongitudinal, two quasitransverse), each traveling at a different velocity. Each of the three incident waves will be refracted and reflected at the boundary. If the second medium is also anisotropic, each incident wave will generate three reflected waves and three refracted waves, a total of 27 waves in all. Wave propagation in a polycrystalline solid where there are many grain boundaries becomes very complicated. The simpler case of a pure longitudinally-polarized wave at normal incidence to the boundary provides insight into the more general problem. In this case the reflection and transmission coefficients are governed by the relatively simple acoustic impedance parameter (ρc)1/2 = ρv, where ρ is the density, c the stiffness coefficient, and v the phase velocity. The reflection coefficient R at the interface between medium I and medium II is The MKS unit for acoustic impedance is the Rayl (=kg/m2 s). Atypical value for a solid is about 107 rayls. In many acoustic applications it is desirable to reduce reflection by matching the acoustic impedance of the two media. Lithium tantalate transducers are well-matched to iron, for example. Sound transmission from the transducer to the medium can be enhanced with composite materials or with graded coupling layers. Backing materials are often selected to promote reflection. In this case acoustic impedances are mismatched. Tungsten and air are two commonly used backing materials. In an isotropic material the acoustic impedance is (ρc11)1/2 for longitudinal waves and (ρc44)1/2 for shear waves. For anisotropic materials the wave velocities and acoustic impedance change with direction as indicated earlier.
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Blow, David. "Waves." In Outline of Crystallography for Biologists. Oxford University Press, 2002. http://dx.doi.org/10.1093/oso/9780198510512.003.0007.
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In this very short chapter, some basic facts about waves are presented. Attached to this short chapter are several boxes which give the fundamental mathematical basis for understanding waves in a more quantitative fashion. There are many physical examples of waves. Waves in water are perhaps the most familiar example. A water wave is created by a disturbance in the height of the water surface. The amount by which the height of the water is disturbed by the wave is called its amplitude. Another important form of wave is sound, which is a variation of pressure in a gas or liquid (or of stress in a solid). But for our purposes the most important waves are electromagnetic waves, specifically X-rays, with wavelengths of an Ångström or so. Electromagnetic waves create a disturbance in both the electric field and the magnetic field: usually the wave is represented by its electric component. All these waves carry energy. The rate of energy transfer is called the intensity, and at a given wavelength the intensity is proportional to the square of the amplitude. Detectors of X-rays, discussed in Chapter 1, respond to the quantity of energy delivered by the beam, which is also proportional to the number of photons. The amplitude of any wave is thus proportional to the square root of its intensity. The most simple form of wave is a sinusoidal disturbance which moves forward at a fixed velocity. ‘Sinusoidal’ means shaped like a sine wave (Fig. 3.1). For reasons that will emerge, we will work more often with a cosine function, which is just the same shape as a sine wave, but which has its origin at a maximum point of the wave. A sinusoidal wave can be described by several properties: • the wavelength, which is the distance from one peak to the next; • the amplitude, which is the height of the wave peak above its mean level; • the phase, which specifies where the peak of the wave is, relative to an origin of measurement at the position x=0, and the time t =0; • the wave velocity, which is the velocity at which the wave advances along the propagation direction.
Conference papers on the topic "ELASTICITY; SURFACE PROPERTIES; SOUND WAVES"
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Sharotri, Nidhi, and Dhiraj Sud. "One pot synthesis of nanosized anion doped TiO2: Effect of irradiation of sound waves on surface morphology and optical properties." In ADVANCED MATERIALS AND RADIATION PHYSICS (AMRP-2015): 4th National Conference on Advanced Materials and Radiation Physics. AIP Publishing LLC, 2015. http://dx.doi.org/10.1063/1.4929292.
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Torrent, Daniel, and Jose´ Sa´nchez-Dehesa. "Acoustic Properties of Fluidlike Metamaterials Based on Sonic Crystals." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-41844.
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A homogenization method is used to get the effective parameters of two-dimensional clusters of solid cylinders embedded in a non viscous fluid or gas. The full elasticity is employed to describe the properties of cylinders. Asymptotic relations are derived and employed to formulate a method of homogenization based on the scattering properties of the cluster. Exact formulas for the effective parameters (i.e., effective sound velocity and effective density) are obtained as a function of the location of each cylinder, its physical parameters, and the embedded medium. Results of several solid-fluid composites will be reported. Also, phase-diagrams of fluid-like metamaterials based on sonic crystal will be analyzed. It is concluded that the method provides a tool to design acoustic metamaterials with prefixed refractive properties. The long wavelength behavior (homogenization) of two dimensional sonic crystals (periodic arrangements of two dimensional sound scatters) has been widely studied in the last years [1–9] due to its possible use as refractive acoustic devices. In a previous paper [2] the authors develop a theory to obtain the effective acoustic parameters of a cluster of fluid cylinder embedded in a non viscous fluid or gas, both for ordered and disordered case. The application of this theory to solid cylinder-fluid medium is only possible when the cylinder is rigid, that is, the sound does not propagates inside the cylinder. When it happens, elasticity must be taken into account, and a solid cylinder, in principle, cannot be considered a fluid cylinder with similar parameters. Here, the theory will be completed for the case of an elastic cylinder, and it will be discussed under what conditions an elastic cylinder can be considered a fluid cylinder, and which ones are the acoustic parameters of this fluid cylinder. It will be shown also that the effective parameters of clusters of elastic cylinders can lead to an effective medium with an effective speed of sound both higher and lower than that of the surrounding medium, and a phase diagram to analyze and predict this behavior will be given. Finally, a method to obtain a relative acoustic impedance equal to one (zero surface reflectance) will be discussed, and also a phase diagram to obtain it will be given.
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Asmatulu, R., W. Khan, and M. B. Yildirim. "Acoustical Properties of Electrospun Nanofibers for Aircraft Interior Noise Reduction." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-12339.
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Electrospun micro and nanofibers produced via electrospinning method were used for the sound absorption purposes. Polymers were initially dissolved in dimethyleformamide (DMF) or ethanol with a ratio of 80:20 and electrospun at 20 kV, 20 cm separation distance and 3 ml/hrs pump speed. The two-microphone transfer function method of the B&K impedance tube was used to determine the acoustical properties of the manufactured nanofibers at various frequencies. The test results showed that the absorption coefficients of nanofibers (∼500 nm) drastically increased. The reason behind this phenomenon may be attributed to the higher surface area of nanofibers and their interactions with more sound waves/air molecules. This result may open up new possibilities for the sound absorption problems in many fields, such as aircrafts, other transportation vehicles and infrastructures.
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Ishihama, Masao, Akane Shimizu, Yu Kakumoto, and Masato Hayashi. "Tire Sound Quality Evaluation Tool Using Sound Synthesis With Physical Modeling." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-41142.
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A computer aided tool for tire sound quality evaluation was developed. Automotive engineers can evaluate a tire structure by listening to synthesized sound that the tire would radiate when it rolls on a specific type of road surface. Among three kinds of tire sound, this study dealt with only the tire sound that radiates through its structural vibration caused by road surface texture excitation. The tool can be used on personal computers. To make it happen, tire sound radiation process is modeled into two parts. One is excitation. Tire deformation at the contact patch was calculated from road surface texture database by rolling contact analyses using multi-body dynamics simulation software. The model includes rolling tire structure model with contact compliance and simple suspension system for the wheel axle. Observation of the calculation results gives such an insight that excitation waveforms from road surface have prominent peaks that occur only at high peaks isolated from others, and do not have dips. This transformation process from road surface waveform to excitation is more accurate than tire envelope model and also not prohibitive considering today’s low-price computing power. The other process is tire structure vibration response. By limiting the usage of tire structure models just in representing over all vibration modal responses to road surface excitations in relatively low frequency range, a simple structural finite element model (FEM) was created. In this FEM, tire wall composite structures are modeled as assembly of solid elements with uniform material properties. The trick in using this FEM model lies in its boundary condition setting. By measuring vibration transfer functions from many points on a contact patch to tire tread and sidewalls, excitation in the middle of the contact patch was found to be blocked to travel to the sidewalls in higher frequency range due to the contact restriction on the periphery of the patch. This finding is essential in giving suitable boundary conditions to the FEM model and choosing the excitation points. To make the computing time minimum for synthesis, the vibration responses of the tire are represented by infinite impulse response (IIR) digital filter banks. The waveform obtained by applying the measured road texture waveforms to the IIR filter, was transferred to sound waves by the sound command of Matlab. By modifying the IIR filter, automotive engineers can judge the effect of tire structural design changes.
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Meinhold, Waiman, Efe Ozkaya, Jun Ueda, and Mehmet Kurt. "Tuneable Resonance Actuators for Magnetic Resonance Elastography." In 2019 Design of Medical Devices Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/dmd2019-3313.
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Palpation, or physical manipulation of tissue to assess mechanical properties is one of the most prevalent and valuable clinical evaluations. Because physical interaction is needed, historically palpation has been limited to easily accessible surface level tissues. Magnetic resonance elastography (MRE) combines non-invasive Magnetic Resonance Imaging (MRI) with mechanically induced shear waves, producing the ability to map elasticity of soft tissues in vivo. Actuator design has been a limiting factor in MRE advancements. In this study, a mechanical resonator with adjustable resonant frequency was designed to be used in MRE applications. The designed piezoelectric actuator was fully MRI compatible, and capable of dynamically adjusting its resonant frequency. The purpose was to keep the displacement amplitude sufficiently large over a wide actuation frequency range. The outer stage of the amplifier contained movable side masses for tuning resonance frequency.
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Ley, Jens, and Ould el Moctar. "An Enhanced 1-Way Coupling Method to Predict Elastic Global Hull Girder Loads." In ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-24199.
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This paper introduces a numerical method to predict global hull girder loads of sea-going vessels, taking into account the structural elasticity. A field method based on a Finite Volume discretisation is applied to simulate the nonlinear rigid ship motions and provides the external loads at the hull surface. The structural response is computed in a full transient 3D-Finite-Element Analysis. The lowest global structural mode shapes and eigenfrequencies are covered by the 3D-FE model. The mapping between the Finite Volume mesh and Finite Element grid, is performed by the Mesh-Based Code Coupling Interface (MpCCI). As long as only global vertical bending modes are considered, simplified beam models may sufficiently cover the structural response. However, the use of the 3D-FE model is motivated by the prediction of the global torsional and local loads that are influenced by hydroelastic effects. A 1-way coupling method is applied. To account for hydromass effects, the Finite-Element model is enhanced by acoustic elements. Acoustic wave equations are solved to simulate the sound wave propagation in water and to obtain realistic eigenfrequencies of the wetted hull. Structural and hydrodynamic damping is controlled by the Rayleigh-Damping method. Simulations are performed for an ultra large container vessel sailing in regular head waves. The computed time histories of the vertical bending moment are compared with experimental data and with numerical simulations using a strong 2-way coupling simulation that employs a Finite-Element Timoshenko-Beam.
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Meral, Faik Can, Thomas J. Royston, and Richard L. Magin. "Fractional Order Models for Viscoelasticity of Soft Biological Tissues." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-68137.
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Dynamic mechanical properties of soft tissues provide information that may be used in medical diagnosis. Developing a better fundamental understanding of the governing constitutive relations could improve diagnostic techniques. The mechanical behavior of soft tissues and tissue mimicking phantoms, such as gels, can be represented by viscoelastic material models. Static loading of viscoelastic materials yields information related to elasticity, creep and stress relaxation. However, a broader measure of rate-dependent properties that affect mechanical wave propagation and wave attenuation in such materials can only be extracted from measured response to dynamic excitation. The well known linear viscoelastic material models of Voigt, Maxwell and Kelvin cannot represent the more complicated frequency dependency of these materials over a broad spectral range. Therefore, fractional calculus methods have been considered to model the viscoelastic behavior of soft tissue-like materials. Fractional order models capture the viscoelastic material behavior using fractional orders of differential equations that may yield a more accurate representation of viscoelastic material behavior. This paper focuses on experimental measurements on the tissue mimicking phantom, CF11. Surface waves on the phantom material are studied experimentally and theoretically. Theoretical calculations using linear and fractional order methods are compared with experimental measurements.
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Burby, M., G. G. Nasr, and T. Cox. "Painting and Coating of Acoustic Materials." In ASME 2006 Pressure Vessels and Piping/ICPVT-11 Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/pvp2006-icpvt-11-93861.
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Acoustic materials are used to treat indoor and outdoor spaces to make speech intelligible, and places less noisy and more pleasant to be in. Whilst most treatments are old and well established, in recent years there has been a growth in innovative products, which overcome difficulties with the old technologies, especially when making the treatments more visually acceptable to architects. Modern construction depends a great deal on acoustic materials to act as sound containment or sound control, either in residential or commercial applications. Sound-absorbing materials are highly porous to increase their sound absorption qualities. The amount of absorption depends on the thickness of the porous material, the size and number of pores, and the frequency of the noise. When painting acoustic materials, the painter should be very careful that the paint does not close up the acoustic surfaces; perforations or fissures. It is through these openings in the surface that sound waves enter the body of the acoustic material and are absorbed. It is the control of the paint droplet size upon the surface that affects the acoustic properties and the aesthetic appearance of the coated surface. An investigation into the coating performance with regard to acoustic absorption and aesthetic appearance was performed in a true-scale automotive spray booth using five different types of paint: three aerosol paints, domestic emulsion and acoustic paint. The sprays produced by the aerosols, emulsion and acoustic paints, applied using an air assist spray-gun, were characterised using a Mastersizer-X laser instrument. The flow rate of the paint through the spray gun was varied during the experiments between 50 ml/min and 500 ml/min. The work has highlighted the operating parameters for the air-assist spray gun in order to produce the smallest drop sizes. The measuring of the acoustic coefficient of the coated materials has shown that the aerosol and air-assist gun produced too large a droplet to produce a good acoustic coating. The use of the acoustic paint did create a good absorption coefficient but the work has highlighted the requirement for the atomizing process to be optimised for this highly viscous acoustic paint.