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The expressions describing the low frequency noise caused by defects in semiconductors and metals have been obtained in the framework of a general unified approach for both fluctuations in the number of carriers and their mobility. When fluctuations in the number of carriers are responsible for noise, the spectral noise density is inversely proportional to the carrier concentration squared and to the volume of the sample. The spectral density of the noise caused by mobility fluctuations is inversely proportional to the sample volume, and does not depend either on carrier concentration or on the total number of carriers. In the case when both mechanisms contribute to noise and they are correlated, the dependence of the noise on the number of carriers depends on the relative contribution of these two noise mechanisms. The expressions obtained can be associated with corresponding cases of the 1/f noise. The physical basis and limitations of the Hooge formula are discussed. [ABSTRACT FROM AUTHOR]

The texture of pavements influences the tyre/road noise. This refers especially to cement concrete pavements. This article presents the results of studies on sound level on concrete pavements in Poland, which were textured using burlap drag, broom drag and exposed aggregate methods. It was established that on exposed aggregate cement concrete, the maximum aggregate size, which is a key factor in the surface’s macrotexture, has a significant influence on tyre/road noise. It should not exceed 8 mm in the upper layer. When using aggregate size 11 mm, the maximum sound level of a passing-by car increases by approximately 2 dB. Pavements textured using the broom drag and burlap drag methods turned out to be not a beneficial solution due to the sound levels emitted by heavy vehicles moving at a speed above 80 kph. Pavement texturing using the transverse broom drag emits sound levels from heavy vehicles which are approximately 3 dB higher in comparison to values noted on SMA11. The methods of pavement texturing using diamond grinding, used in some countries, point towards the possibility of obtaining beneficial acoustic properties. [ABSTRACT FROM AUTHOR]

Today the use of recycled and second-hand materials can be considered as a suitable solution for the construction or the rehabilitation of road pavements. The increasing interest in this process lead to the study and the evaluation of different waste materials, not directly connected to the construction field, among these Crumb Rubber from end-of-life tires. To date, this recycled material has been added into bituminous mixes for road pavements according to several technologies, for the production of different mixtures. In the present paper, the crumb rubber was used for the production of Stone Mastic Asphalt (SMA) according to a new dry-hybrid technology. A full laboratory investigation and a trial field study are here presented. A complete physical and mechanical characterization was carried out to define a specific mix design. Once defined these properties, a full-scale test section was constructed: specific in situ tests and collection of samples were planned. In both the laboratory and trial field phases, tests results were always compared to those obtained with a traditional SMA mixture. In an environmental prospective, fumes and emissions during laying were also analyzed. The goal of this research project was to analyze and evaluate the different physical, mechanical and functional characteristics induced by the use of Crumb Rubber for the production of SMA mixtures according to the proposed new dry-hybrid technology. As overall result, the presence of Crumb Rubber does not seem to negatively affect the volumetric properties of the mixture. SMA1.20 shows mechanical properties comparable to the reference mixture and higher if compared to SMA0.75. As for the acoustic properties, both the rubberized surfaces reduce the emission of noise if compared to the traditional SMA layer. The monitoring of pollutants during paving operations confirms the effective environmental benefits deriving from the use of the new dry-hybrid technology here proposed. [ABSTRACT FROM AUTHOR]

The acoustic and anharmonic properties of ferromagnetic Cu2MnZ (Z = Al and In) Heusler alloys have been investigated by first-principles calculations method. The obtained lattice parameters, magnetic moments, elastic properties are found to be in good agreement with the available experimental values. From the elastic properties, the sound velocities and the related Debye temperatures and minimum thermal conductivities have been obtained for the two alloys. The sound velocities and thermal conductivities of both alloys are found to show significant anisotropy, and the Cu2MnAl with small density and large elastic constants has large sound velocities, high Debye temperature, and large thermal conductivities. Also, the effective second-order elastic constants, generalized Grüneisen constants, and nonlinear ultrasonic parameters to characterize anharmonic properties have been studied for the two alloys. These predictions on the acoustic and anharmonic properties can provide a valuable guidance or reference for further related investigations. [ABSTRACT FROM AUTHOR]

This paper investigates the sound absorbing property of porous metal materials quantitatively using turbulence analogy model. Firstly, the improved Kolmogorov’s turbulence theory is obtained by catastrophe theory for the first time, to our knowledge. Secondly, a quantitative turbulence analogy model is proposed though the improved Kolmogorov’s turbulence theory. Finally, this model is adopted to analyze the wave propagation inside the porous metal materials. The quantitative relationship of energy spectrum density is fully obtained, which is also related to the average pore diameter and porosity. With the increase of excitation frequency, the energy spectrum density decreases with certain power law. And the energy increases with the increase of the average pore diameter. Our theoretical results are consistent with the experimental results. Our study can provide a feasible theoretical guidance for controlling the vibration and noise of porous metal materials. [ABSTRACT FROM AUTHOR]

Different sound atmosphere effects were investigated on SnO2:Sb thin films, which were deposited with dip coating technique. Two sound atmospheres were used in this study; one of them was nay sound atmosphere for soft sound, another was metallic sound for hard sound. X-ray diffraction (XRD) graphs have indicated that the films have different orientations and structural parameters in quiet room, metallic and soft sound atmospheres. It could be seen from UV-Vis spectrometer measurements that films have different band gaps and optical transmittances with changing sound atmospheres. Scanning electron microscope (SEM) and AFM images of the films have been pointed out that surfaces of films have been affected with changing sound atmospheres. The electrical measurements have shown that films have different I- V plots and different sheet resistances with changing sound atmospheres. These sound effects may be used to manage atoms in nano dimensions. [ABSTRACT FROM AUTHOR]

The corrosion behavior of steel in concrete is an engineering issue that needs to be monitored to ensure structural safety. Novel cement/polymer-based piezoelectric composites were used to fabricate embedded ultrasonic transducers. This study investigated the corrosion development of reinforcement bar in concrete by employing ultrasonic transmission technique. The transmitted ultrasonic wave and acoustic parameters were extracted to reveal the corrosion process of steel. Results show that ultrasonic time- and frequency-domain spectra have weak amplitude attenuation when the corrosion rate of steel is less than 1%. Corrosion then weakens further when the corrosion rate is higher than 5%. A similar variation is observed on the frequency-domain spectrum. Variations in the corrosion rates of steel bars in concrete can be categorized into three periods based on the acoustic parameters, namely, the initial corrosion period when the corrosion rate is less than 1%, rapid corrosion period at a corrosion rate of 1%–6%, and corrosion development period when the corrosion rate is higher than 6%. [ABSTRACT FROM AUTHOR]

Drawing processes apply to obtain the bimetallic tubes from the different metals and alloys, combined in the solid state, which significantly affects the specificity of this process. The manufacturing of bimetallic tubes by drawing process depends on many factors which include: preparation of the surface of materials joined in the solid state, the geometric parameters of the working tool, technological parameters of the drawing process (drawing speed, type of lubricant, the use of back pull etc.). Generally, the cold drawing process of producing the bimetallic tubes refers to metals which have high ductility (copper, aluminum, etc.). The tube sinking (tube drawing without a mandrel) of bimetallic tubes together with joining them at the interface of the two metal in the solid-state is applied for tubes of the diameter range between 6 to 20 mm and based on of the reducing the diameter of the tube. However, a slight increase of wall thickness ca. 0.05 ÷ 0.10 mm can appear, which is not dangerous phenomenon in case of producing the bimetallic tubes by joining in the solid-state. The aim of the research was to investigate the technology of tubes drawing process from non-ferrous metal, drawing process of bimetallic tubes and the production of bimetallic tubes in layers composition: cooper Cu-ETP - brass CuZn37 and CuZn37 brass - copper Cu-ETP in the tube sinking process. The research program included: production of bimetallic tubes with a different composition (Cu- ETP-CuZn37 and CuZn37-Cu-ETP) and a different percentage of the cross-section components; analysis of changes of tube wall thickness and the layer composition of the bimetallic tube, based on measurements on the workshop microscope; analysis of the material flow in the process of the bimetallic tubes production based on the measurements results of a profilograph CP-200. [ABSTRACT FROM AUTHOR]

Studies are made of the acoustic properties of metals obtained from steels 08kp, 25, and 50 and aluminum alloy AL2. New metals characterized by reduced sound radiation have been developed, and the effect of heat treatment on this property is evaluated. [ABSTRACT FROM AUTHOR]

The interpretation of the results of acoustic-emission (AE) testing of the states of objects under complex loading, which possess a branched structure that changes in time and space, is based on the statistical approach to the search for correlation links between diagnostic parameters and parameters of the state, which is not always efficient. The methodology, the results of laboratory and test-bench testing of welded joints, the technique of nondestructive testing of the strength and the diagnostics of the state of metal structures of hoisting and transport machines under complex loading, which are based on the application of the developed physical approach, are considered. [ABSTRACT FROM AUTHOR]

In this study, bismuth sodium titanate (BNT)–Portland cement (PC) composites with 1–3 connectivity pattern were fabricated by the dice-and-fill technique with different BNT ceramic content ranging from 30 to 70 vol%. The acoustic impedance ( Z c ) and electrical properties of the composites were studied. When the BNT content varies from 30 to 70 vol%, Z c value increases from 8.95 to 14.79 × 10 6 kg/m 2 s. At BNT ceramic content of 70 vol%, dielectric constant ( ϵ r ), electromechanical coupling coefficients ( K t ) and piezoelectric coefficient ( d 33 ) are 346, 21.28% and 70 pC/N, respectively. Interestingly, the piezoelectric voltage coefficient ( g 33 ) values exhibited an opposite trend, that is, the g 33 value decreases as the BNT content increases. Therefore, 1–3 connectivity of bismuth sodium titanate–Portland cement composites can be tailored by adjusting the piezoelectric ceramic content in composite; the developed composites have potential to be used as sensors for structural health monitoring applications in smart structures. [ABSTRACT FROM AUTHOR]

Full evaluation of the elasticity tensor of a bulk metallic glass (Pd40Cu30Ni10P20) shows anisotropy induced by creep under uniaxial compression changing sign with increasing strain. Anisotropy due to anelastic strain is erased by zero stress annealing. At higher strain anisotropy of opposite sign suggests structural alignment by plastic flow. Induced anisotropy is most evident in the Poisson ratio, may relate to other properties, including the strength and toughness of metallic glasses, and may lead to misinterpretation of annealing effects. [Copyright &y& Elsevier]

The temperature dependences of the logarithmic decrement and dynamic Young's modulus of polycrystalline coarse-grained and nanostructured Zr are studied at temperatures of 2.5-340 K. A nanostructured state of samples with grain sizes on the order of 100 nm was produced by intensive plastic deformation (IPD). The measurements were made using a two-component vibrator technique at frequencies of 73-350 kHz. A relaxation peak in the internal friction near 250 K was discovered in the coarse-grained, annealed Zr which is retained after IPD, but its height increases by roughly a factor of 10 and the localization temperature shifts to lower values. In addition, after IPD a new internal friction peak shows up at moderately low temperatures near 80 K. The activation parameters for the observed peaks are estimated and it is shown that they arise from different thermally activated dislocation processes: interactions of dislocations with impurities and kink pair formation in dislocations. It was found that IPD is accompanied by a significant (1-8%) reduction in the Young's modulus because of quasistatic and dynamic dislocation effects. A glass-like anomaly appears in the temperature dependence of the Young's modulus of nanostructured Zr at T<20 K which may be determined by tunnelling and thermally activated relaxation of quasilocal excitations. [ABSTRACT FROM AUTHOR]

Abstract: The density and elastic moduli of green compacts can be determined by ultrasonic method with the help of pre-prepared diagrams. In this way, pressing conditions can be taken under control easily. In this study, fly ash particles were used as fillers in an aluminum alloy matrix material. The weight fractions of fly ash in the composites were in the range of 5–30%. The resulting composites were compacted at pressures ranging from 63MPa to 316MPa. It was observed that the green density increased with increasing compacting pressure and decreased with increasing weight percent of fly ash particles resulting in lightweight composites. The green compact composites were also tested using an ultrasonic non-destructive evaluation method. Results showed that ultrasonic velocities are a strong function of the density and the fly ash fraction in this material and could be potentially used to predict the density and the fly ash fraction as well as the elastic moduli of the metal matrix composite. [Copyright &y& Elsevier]

Abstract: PbMoO4 and SrMoO4 particles were successfully prepared via a simple solvothermal process. The obtained samples were characterized by X-ray diffraction, Brunauer–Emmett–Teller (BET) surface area analysis, UV–vis diffuse reflectance spectroscopy, scanning electron microscopy and a photoluminescence technique with terephthalic acid. The as-prepared PbMoO4 samples show different photocatalytic activities for salicylic acid under UV light irradiation. PbMoO4 exhibits relatively high photocatalytic activity for salicylic acid, Rhodamine B and benzene. While, SrMoO4 possessing a similar structure to PbMoO4 shows negligible photocatalytic activity though they exhibit similar BET surface areas and morphologies. Theoretical calculations reveal that PbMoO4 contains higher dispersive valence and conduction bands than SrMoO4. The highly dispersive valence and conduction bands can lead to higher mobility of the photo-generated carries and therefore a better photocatalytic activity. [Copyright &y& Elsevier]

Abstract: The transmission of sound through a rectangular double-leaf metallic panel partition clamp mounted on a rigid acoustic baffle has been investigated analytically. It is found that, at a specific frequency, sound transmission through the structure is significantly enhanced for incident sound with a certain incidence angle. This physical phenomenon, namely, transparent effect, is analyzed in terms of both dynamical panel modal responses and radiating acoustic pressure. The enhanced transmission is attributed to the unique mass-air-mass effect of the double-panel partition system. Numerical results clearly demonstrate that this effect does not completely stem from the point-to-point out-of-plane motion of the two panels, due to the additional constraining effect of the clamped supports. [Copyright &y& Elsevier]

This paper is a study about sound absorption properties of porous metals at high sound pressure levels. A method of deriving the nonlinear static flow resistance for highly porous fibrous metals is proposed by solving Oseen's equation to take account of the inertia effect, validated by experiments of airflow measurement. In order to predict nonlinear sound absorbing performance of a finite thickness porous metal layer, a numerical method is employed, verified by sound absorption measurement in an impedance tube. Accordingly, the effects of the nonlinear coefficient on the porous metal sound absorption are investigated. [ABSTRACT FROM AUTHOR]

Rubber has traditionally been used for underwater sound absorption. Porous metal is a relatively lightweight material and also has higher strength than rubber. However, exactly how porous metals can be used as effective underwater sound absorbers remains unclear. This paper shows how to use porous metal absorbers so that they work well under water, even under fairly constrained conditions. A method of nondimensional analysis is proposed that allows identification of vital characteristics. This means that such characteristics can be varied and the absorbers themselves filled with different types of viscous fluids. Such analysis suggests that the sound absorption coefficient of porous metals does not always increase when there are either increases in porosity or decreases in average pore size. The same method of analysis can show how, by choice of the right characteristics to choose a suitable viscous fluid, a porous metal absorber can be built that takes up little space but still effectively absorbs underwater sounds at low frequencies. [ABSTRACT FROM AUTHOR]

Pulse-echo-overlap measurements of ultrasonic wave velocity have been used to determine the elastic stiffness moduli and related elastic properties of aluminum nitride (AlN) ceramic samples as functions of temperature in the range 100–295 K and hydrostatic pressure up to 0.2 GPa at room temperature. Aluminum nitride is an elastically stiff but light ceramic: at 295 K, the longitudinal stiffness ( CL), shear stiffness (μ), adiabatic bulk modulus ( BS), Young's modulus ( E) and Poisson's ratio (σ) are 373 GPa, 130 GPa, 200 GPa, 320 GPa and 0.234, respectively. The temperature dependences of CL and BS show normal behaviour and can be approximated by the conventional model for vibrational anharmonicity. The results of measurements of the effects of hydrostatic pressure on the ultrasonic wave velocity have been used to determine the hydrostatic-pressure derivatives of elastic stiffnesses and the acoustic-mode Grüneisen parameters. The values determined at 295 K for the hydrostatic-pressure derivatives (∂ CL/∂ P) P=0, (∂μ/∂ P) P=0 and (∂ BS/∂ P) P=0 are 4.7 ± 0.1, 0.22 ± 0.03 and 4.4 ± 0.15, respectively. The adiabatic bulk modulus BS and its hydrostatic-pressure derivative (∂ BS/∂ P) P=0 are in good agreement with the results of recent high pressure X-ray diffraction measurements and theoretical calculations. The longitudinal (γL), shear (γS), and mean (γel) acoustic-mode Grüneisen parameters of AlN are positive: the zone-centre acoustic phonons stiffen under pressure. The shear γS (=0.006) is much smaller than the longitudinal γL (=1.09) accounting for the low thermal Gr¨neisen parameter γth (=0.65) obtained for this ceramic: since the acoustic Debye temperature ΘD (=980 ± 5 K) is so high, the shear modes play an important role in acoustic phonon population at room temperature. Hence knowledge of the elastic and nonlinear acoustic properties sheds light on the thermal properties of ceramic AlN. [ABSTRACT FROM AUTHOR]

The finite-difference method is widely used in the formulation of a mathematical representation of the solidification process in metal/mold systems. When complex geometries have to be analyzed, precision of simulations will depend on a multigrid computational scheme covering the spatial domain, which can represent a significant increase in computational time. The present work proposes an approach that modifies the finite-difference network from thermal to electrical elements, permitting a flexible and versatile representation and connection between grid patterns, and consequently an easier transmittal of information at these boundaries. Results of simulations have shown that the proposed approach provides good numerical accuracy and substantial savings in computational time and computer storage requirements, due mainly to the significant reduction of number of elements within the computational domain. [ABSTRACT FROM AUTHOR]

Discusses the application of the method for investigating the electron properties of metals for studying acoustoelectronic effects in layered conductors with a strongly anisotropic conductivity of the metallic type. Weak attenuation of acoustic waves along layers in strong magnetic fields.

The article reports that quality of Thema's portfolio–composed of innovative technical products with comprehensive and competitive response to the new installations with Line glazed partition which has minimalist aesthetic of safety glass panels and high-quality extruded aluminum profiles. Topics include use of double glass increases the acoustic properties of metals in senior management offices; and inner chamber is composed of a combination of fireproof and thermal insulating materials.

To diversify the measurement techniques of Avogadro's number in physics teaching, I propose a simple acoustic method for the experimental determination of Avogadro's number based only on the measurement of the speed of sound in metals, provided that their Debye temperatures are known. [ABSTRACT FROM AUTHOR]

The mechanical and acoustic properties of Ti2NiZ (Z = Al, Ga and In) Heusler alloys under different pressures were studied based on the second- and third-order elastic constants obtained by the ab initio calculations combined with homogeneous deformation theory. The results showed that the mechanical stability is reduced while the ductility is improved with increasing pressure for all three alloys. As the pressure increases, the acoustic velocities of these alloys increase except for the transverse acoustic velocities in ⟨110⟩ direction of Ti2NiGa and Ti2NiIn. The Debye temperature and minimum thermal conductivity were also predicted in terms of the obtained acoustic velocities, which increase with increasing pressure for all three alloys. The calculated lattice constants, band gaps and second-order elastic constants were in agreement with the available theoretical values. [ABSTRACT FROM AUTHOR]

A simple setup was designed for a ‘time-of-flight’ measurement of the sound speed in a metal bar. The experiment requires low cost components and is very simple to understand by students. A good use of it is as a demonstration experiment. [ABSTRACT FROM AUTHOR]

The chemical states and band alignments of HfOxNy films on Si substrates as a function of post-thermal treatment were systematically investigated. Analysis of N1s spectra reveals that there are four components in N chemical states, which are assigned to the N–Hf, N ≡ Si, Si2 = N–O and N–O bonds. The N–O bond is very unstable upon annealing as compared with the N–Hf, N ≡ Si and Si2 = N–O bonds. The relationship between band alignments and chemical states in the HfOxNy/Si stack upon annealing is also studied. It is found that the conduction-band offset shows no obvious change upon annealing, while the band gap and the valence-band offset increase with the increase in the annealing temperature, which is mainly due to the reduction in the N–O bond during the annealing process. With the values of band gap and band offsets of the HfOxNy film, the energy-band alignments of the HfOxNy/Si stack as a function of post-deposition annealing were constructed. [ABSTRACT FROM AUTHOR]

Abstract: The mechanical response of bulk metallic glasses is ultimately controlled by interatomic forces between the randomly distributed atoms. The study of collective dynamics in amorphous systems, either liquid or glassy, opens a window to better understand this interaction. We present here results of recent IXS experiments performed at the ID16 beamline of the European Synchrotron Radiation Facility (ESRF) on a metallic glass. In particular, the high-frequency response of Pd77Si16.5Cu6.5 alloys, produced as a ribbon with an ultra-fast quenching rate (∼106 K/s) and as a bulk with a slow one (∼102 K/s), was determined. Previous experiments showed a discrepancy between the sound speed of metallic glasses measured by ultrasounds and by IXS. This was explained as a consequence of density fluctuations in the glass, although other explanations are possible. Here, the dispersion relation of the acoustic modes at room temperature and pressure are measured for both samples, allowing us to compute the sound speed and discuss the differences in the acoustic properties of both samples. [Copyright &y& Elsevier]