Absorption Coefficient Of Material Research Articles

Application of Gaba-Gaba Egg Rack Bio-Composite as Material Wall Meeting Room Acoustics

Bio composite materials are a combination of two or more natural polymer materials or biofiber (natural fibers) which can be degraded as reinforcement and polymer or matrix. Natural fibers generally have the ability to absorb sound well and have basic properties as composite reinforcements. If a wave hits a material, the wave can be straightened, reflected and absorbed. The ability of composite structures to absorb sound can be used to reduce noise levels. This research models a combination of egg rack waste mixed with sago leaf stem (gaba-gaba) waste as a bio-composite material for room acoustic panels. This research uses a material modeling engineering method which is a pure experiment, with the stages of making test samples based on fixed variables and measurable variables and then testing to obtain the material absorption coefficient, then the test results are based on the specified variables, then applying the material to the meeting room. After that tested the acoustic level of the room, especially the meeting room.

Design of an improved impedance tube to measure sound absorption coefficients of flexible textile materials

Textile materials have demonstrated significant potential in sound noise reduction due to their porous, lightweight, and easily processed nature. However, the current experimental setup for measuring the sound absorption of small-sized samples is expensive. Additionally, there is a lack of suitable equipment for measuring the sound absorption of flexible textiles as it is challenging to mount flexible samples into an impedance tube. This paper presents the design, fabrication, and testing of impedance tubes specifically designed for measuring the sound absorption coefficients of textile materials. The impedance tubes were designed based on the transfer function and two-microphone methods, with diameters of 100 mm and 30 mm. These tubes covered frequency ranges from 200–1600 Hz and 500–6400 Hz, respectively. Furthermore, improved sample holders were developed to mount flexible textile materials without altering the acoustic impedance characteristics of the front surface of the test sample. Validation experiments were conducted on melamine foams, and the results were compared with those obtained from the commercial B&K 4206 setup. The results obtained from the designed setup showed good agreement with those from the B&K 4206 system. The maximum error observed was 8% at 2800 Hz for the 30 mm diameter tube and 8.3% at 1600 Hz for the 100 mm diameter tube. Finally, the designed system was used to measure the sound absorption coefficients of textile materials with varying densities. The results obtained were consistent with the material properties, demonstrating the effectiveness of the designed setup.

On the area-averaged effective sound absorption coefficient of porous materials excited by a monopole

The area-averaged effective sound absorption coefficient (SAC) of a rigid-backed homogeneous porous material subjected to a monopole excitation is calculated as the absorbed-to-incident sound power ratio. Using Allard's model to describe the sound propagation above the porous material, an analytical model for this power-based SAC is proposed and proves to give a good approximation of the sound absorption performance under monopole excitation of sufficiently large areas of material. The impact of factors on the power-based SAC, such as monopole height, material radial dimension used to calculate the sound powers, and material properties is discussed. The power-based SAC frequency-dependent behavior is analyzed through sound intensity field assessments at the material surface and is compared to normal incident plane wave and diffuse field SACs. The sound absorption behavior of sound absorbers under monopole excitation exhibits notable distinctions and peculiar results compared to those observed under plane wave and diffuse fields, particularly at low frequencies and for sources close to the material.

Nondestructive measurement of the capillary water absorption coefficient and water transport behaviors of porous building materials by using single-sided NMR

Capillarity has an important effect on the durability of buildings, and the capillary absorption coefficient is a key parameter to describe the strength of material capillarity. Most of the methods currently used to measure the capillary absorption coefficient of materials can damage the sample or are not accurate enough and need to be improved. This paper proposes a method to measure the capillary absorption coefficient of brick, sandstone, mortar and concrete by using a single-sided nuclear magnetic resonance (NMR) technique, which has the advantages of accuracy, nondestructiveness, continuity and rapidity. The relative error of the capillary absorption coefficient obtained from three repetitions of the experiment ranges from 0 to 5.11%, which is in the range of 0.64%∼1.30% compared with that obtained by the partial impregnation method. This method has great potential for application in in situ testing. This paper also analyzed the water transport behaviors in porous building materials based on the variation in NMR signal intensity in the measured materials and established a water transport model. The model is divided into two stages: the first stage is mainly the one-dimensional rise in moisture in the vertical direction. The second stage is mainly the diffusion of moisture in the horizontal direction, which continuously fills each pore space to saturation. Difficulty in removing air leads to a reduced rate of water absorption in the second stage.

Effects of Particle of BA, CMA and FA on Water Absorption of Concrete

The porosity of concrete is the root cause of durability problems in concrete. Water absorption rate and water absorption speed can be used to detect the pore structure distribution of concrete. Based on the principle of permeability coefficient method, the water absorption method was improved in this study. This paper conducted an experimental study on how BA (biomass ash), CMA (cattle manure ash), and FA (fly ash) with different particle sizes affect the water absorption speed and coefficient of concrete. The results showed that among BA, FA, and CMA, the water absorption speed and coefficient of FA are the smallest among all admixtures in concrete, and the water absorption speed and coefficient of BA are the smaller. The water absorption coefficient is greater than that of FA, and the water absorption speed and coefficient of CMA are greater than those of BA. With the same dosage (15% in this test), the smaller the water cement ratio, the smaller the water absorption rate of CMA concrete; The water absorption rate of CMA concrete decreases with the increase of age. When the dosage is the same, the influence of particle size on the water absorption coefficient of concrete is the same as the influence of particle size on the water absorption speed of concrete. Factors affecting the water absorption coefficient of CMA materials include particle size distribution, shape, specific surface area, and so on. The results provide a reference for studying the durability of CMA concrete.

Evaluation of Optical and Radiation Protection Parameters of High Refractive Index Polymers

The optical properties of the prescription and non-prescription (plano) samples of the MR-8 high index lens were examined by UV/VIS spectrometry. The results showed that the light transmittance of the two MR-8 lens samples examined was over 90%, and the transmittance at the wavelength (~550nm) to which the human eye is most sensitive was 83.437% and 84.602% for the prescription and non-prescription samples, respectively. In terms of quality of vision, it is expected that the visible light transmittance will be high and the ultraviolet light transmittance will be minimal. It is very important that both the prescription and non-prescription organic MR-8 lenses tested have no transmittance below approximately 398nm. This means that this lens material protects against UVA and UVB rays, even though it is uncoated. It is also important to reduce the dose to the lens, which is a radiosensitive tissue. In the study, the mass absorption coefficients of MR-8 and Ormix lens materials in the 0.15-2.00 MeV energy range were calculated using the web-based XCOM programme. LAC, HVL, TVL, MFP, RPE and TF values were calculated from the MAC values obtained. At energies below 0.05 MeV, the maximum MAC value was 0.974 and 4.416 for the MR-8 and Ormix lenses, respectively. The RPE and TF values were 0.807-16.235%, 0.996-0.992% for the MR-8 lens and 0.862-55.233%, 0.448-0.991% for the Ormix lens. The results showed that the photon absorption ability of the Ormix lens is relatively better in the region where the photoelectric interaction is dominant. This research is also important in terms of determining the optical and nuclear radiation parameters of the material used in the manufacture of high index lenses and investigating its effectiveness in reducing the dose to the eyepiece.

Determination of the refractive-index change in the excited state based on transient absorption microscopy

Photoinduced excited-state carriers can affect both the absorption coefficient and refractive index of materials and influence the performance of photoelectric devices. Femtosecond time-resolved pump–probe transient absorption (TA) spectroscopy is usually used to detect carrier dynamics and excited-state absorption coefficients; however, measurements of transient refractive-index change are still difficult. We propose a method for determining the excited-state refractive-index change using TA microscopy. In TA measurements, a Fabry–Pérot cavity formed by the front and back surfaces of the sample could lead to interference of the probe light. As the wavelength of standing waves in the Fabry–Pérot cavity is closely related to the refractive index, the carrier-induced excited-state refractive-index change was obtained by comparing the transmission probe spectra between the ground and excited states. The proposed method was used to study the dynamics of excited-state refractive-index change in a perovskite film.

Predicting the effect of microstructural variations in porous sound absorbers on their sound absorption performance using the perturbation method

Noise reduction is one of the most important issues in various industries. Quantifying the variation in acoustic properties is an essential task to improve the quality of products. Porous sound-absorbing materials are commonly applied to reduce noise. Variations in the microstructure of porous materials have a significant impact on variations of sound absorption coefficient. Experimental methods have been used to predict manufacturing variability of sound-absorbing porous materials. However, they take a lot of time and cost. In this study, a perturbation method is applied to predict variations of sound absorption coefficient of sound-absorbing porous materials combined with the homogenization method based on an asymptotic expansion. Properties of microstructure of a sound-absorbing porous material, such as fiber diameter and cell size, are assumed to follow normal distribution and identify the expectation and variance from the observation of microscopic images obtained by scanning electron microscope. Calculated variability of sound absorption coefficient is compared with measured variability and they agree well in the frequency range of interest.

Numerical simulation and experimental validation of ultrafast laser ablation on aluminum

In this paper, a numerical study of the ultrashort single pulse ablation process in aluminum has been conducted using the two-temperature model, taking into consideration the several dependencies of the parameters on temperature. The evolution of temperatures for each point within the material over time is obtained, allowing to comprehend the distribution of energy in the laser-metal interaction and its subsequent diffusion within the material. This study allows to gain a more precise understanding of the thermophysical and optical properties throughout the material heating and ablation process. The ablation process has been experimentally validated using a femtosecond laser on a polished aluminum film for a wide range of fluences. The developed theoretical model and the experimental values are in good agreement for both ablation depth and diameter across the entire range of powers studied, enabling reliable determination of the threshold fluence, laser spot size and material absorption coefficient. These parameters are crucial for achieving optimal micromachining processes.

Assessment of acoustical materials sound absorption coefficient under oblique incidence plane wave and diffuse field using a virtual source antenna

The measurement of the absorption coefficient of acoustic materials is usually performed in an impedance tube under normal incidence on a small sample, or in a reverberant room under diffuse field incidence on a large sample of material. Both methods are prone to well-documented experimental limitations and errors. The approach proposed here uses a virtual source antenna (a point source moved at successive positions) over a material sample typically 1 to 4 m2 in size, and a fixed microphone pair directly above the material surface. Several methods have been tested to reconstruct the absorption coefficient under oblique plane wave or diffuse field incidence. Among these, the inversion of the Allard propagation model over an absorbing plane, in order to extract the material properties (complex wavenumber and density) from measured microphone transfer functions, is presented here. Absorption coefficients are shown for various acoustic materials.

Estimation of the random incidence sound absorption coefficients of different size rectangular samples.

The sound absorption coefficient (SAC) of materials measured in a reverberation room is affected by both the intrinsic properties of the material and geometrical dimensions of the sample. A different size of the same material may produce a different SAC primarily due to the edge effect phenomenon. In this research, the experimental data from multiple laboratories was analyzed to evaluate the influence of the edge effect. An empirical function was established based on these measurement data and the linear relationship between the SAC and the relative edge length. Thomasson's method, the two geometric methods, and the analytical method were used to estimate the SAC of an absorber from measurements on a different size sample and compared with results obtained using the empirical function. The results show that the proposed empirical method is a reliable way to predict the SAC of a sample from measurements on a different size sample of the same material, which only requires the thickness, density, and size of the material.

Sound effect of transmitting specific emotions in music performance based on the acoustic properties of conjugated materials.

In music performances, instruments made of traditional materials often cannot accurately express specific emotions through means such as tone, pitch, and timbre, and it is difficult to adjust the sound effects according to specific emotions. This article studies the impact of conjugated materials on the timbre, frequency response, etc. of musical instruments, hoping to achieve sound effects that better convey specific emotions. This article analyzes the acoustic properties of conjugated materials and applies them to musical performances. It is found that conjugated materials can provide a wider selection of tones, pitches and timbres, performers can choose appropriate tone, pitch, and timbre from conjugated materials to express emotions according to specific emotional needs, or adjust and transform the tone, pitch, and timbre for specific emotions, thereby arousing emotional resonance from the audience, so that specific emotions can be conveyed to the audience more accurately and powerfully. At the same time, this research also found that compared with an environment with poor sound insulation, the average sound absorption coefficient of metal materials in a room with good sound insulation increased by 6.5%, and the average sound absorption coefficient of conjugate materials increased by 25.4%, which shows that the increase in the average sound absorption coefficient of conjugate materials is much greater than that of metallic materials. The research shows that studying the sound effects of musical performances based on the acoustic properties of conjugated materials will help explore and develop more immersive and emotionally rich musical experiences.

Role of 26Al and impact-generated atmosphere in the early thermal evolution, differentiation, and volatile-rich core of Mars

The InSight mission's high-quality seismic data and cosmochemical models have demonstrated that Mars has a volatile-rich core. It is proposed that Mars formed early, before the solar nebular gas dispersed, and/or it accreted volatile-rich material to account for its volatile-rich interior. The early accreted Mars must have gravitationally attracted proto-atmosphere from the surrounding solar nebula. If its building blocks were rich in volatiles, it might have acquired impact-generated atmosphere during accretion. By considering the decay energy of the short-lived radionuclide (SLR) 26Al and the blanketing effect of the primordial and impact-generated atmosphere during the initial 10 Ma of the formation of the solar system, we present the results of numerical simulations carried out for the early thermal evolution and core formation of Mars. To explain the formation of a large iron core of Mars as suggested by the seismometer of InSight mission, we considered the 60% EH- and 40% CI-chondrite composition for the building blocks of Mars. The blanketing effect of impact generated H2O + CO2+CO + H2 atmosphere caused the melting of surface silicates to form magma ocean at surface. We thoroughly examined the effects of several variables on the timing of complete core formation, including the initial water content in the accreted material, timescale of onset of accretion after the formation of CAIs, duration of accretion, absorption coefficient of CO2, efficiency of degassing of volatiles, and melting temperature. The results of present study show that the decay energy of SLR 26Al caused the widespread heating and melting of interior of Mars. For complete core formation, Mars must accrete within the first ∼2 Ma in order to explain the volatile-rich core. Further, the timescales of core formation were found to be strongly dependent on the assumed melting curve. For longer timescales of accretion, the interior of Mars experienced incomplete differentiation even by assuming high water content in the accreted material and larger absorption coefficient for CO2. However, Mars does not have to accrete within 2 Ma for the core to fully develop if the Rayleigh- Taylor (RT) instability is present in the dense metallic layer on top of the undifferentiated interior. A short accretion time is only valid if RT-instability is neglected. Hence, we expect that the volatiles in the magma ocean could also be transferred to core by Rayleigh-Taylor instability. We also parameterized the thermal influence of gravitational heat produced during the differentiation of Mars to study its influence on the thermal evolution of the planet. The outcomes of the present work have implications to explain the timing of partition of volatiles in the Martian interior and formation of an early atmosphere on Mars.

Practical applications at field environments of sound absorption measurement method using the ensemble averaging technique

To construct appropriate boundary conditions for wave-based room acoustics simulations, the authors have proposed a measurement method for sound absorption characteristics, surface impedance, and sound absorption coefficient of materials using the ensemble averaging technique. We have also shown the robustness as well as the reproducibility of the results obtained by the method at various environments. The method consists of two kinds according to sensor types employed so far: i.e., two-microphone and PU-sensor. Generally speaking, the method using a PU-sensor is more advantageous than one using a two-microphone because of its geometrical straightforwardness. However, at various field environments where environmental noise and/or wind blowing exist, the method using a two-microphone is expected to give more favorable results. In this paper, several applicational measurements of the method conducted at field environments using the two sensor types are summarized to show the plausibility of the method.

Inverse Model for Simultaneously Estimating Material Parameters and Absorption Coefficient in a Laser-Irradiated Sheet

Inverse Model for Simultaneously Estimating Material Parameters and Absorption Coefficient in a Laser-Irradiated Sheet

Luminescent solar concentrator efficiency versus edge solar cell coverage.

This Letter introduces an analytical approach to estimate the waveguiding efficiency of large-area luminescent solar concentrators (LSCs), where the edges are covered by a varied number of mirrors and solar cells. The model provides physically relevant description in the whole range of optical (absorption, scattering) and geometrical (size) parameters of rectangular LSCs. A 19 × 19cm2 silicon quantum dot-based LSC has been fabricated to verify the theory. Within an experimental error, the predicted waveguiding efficiency matched well the measured one. A critical LSC size, beyond which a part of the device turns inactive, has been determined as N/α for N attached solar cells (one or two) and LSC material absorption coefficient α. This model provides a straightforward waveguiding analysis tool for large-area LSCs with different structural parameters relevant for both high concentration ratio and glazing applications.

Nonwoven fabrics developed from agriculture and industrial waste for acoustic and thermal applications

Numerous researchers in the field of noise control and acoustics have found success in using biomaterials to create a porous sound absorber that is both effective and environmentally friendly. This paper discusses the utilization of fibers extracted from the waste from coffee husk (CH) and waste from the cotton (CO) spinning industry to be an alternative to synthetic-based acoustic materials. The study was conducted within the range of 50–6300 (Hz) frequency. Five well-known mathematical prediction models, namely Delany–Bazley (D–B), Garai–Pompoli (G–P), Miki, Allard Champoux (AC), and Johnson–Champoux–Allard (JCA) models are theoretically used to predict the sound absorption coefficient of nonwoven fibrous materials. When compared with the experimental data, it was discovered that the JCA and AC model is the most acceptable model for predicting the absorption behavior of CH/CO nonwoven fibrous materials. Additionally, the thermal insulation of nonwoven fibrous materials has been experimentally and numerically studied. It is noteworthy that, when compared to the Herman model, the Bhattacharyya model’s results showed slightly greater thermal conductivities. Overall, this work used an environmentally friendly way to turn waste into a valuable product.

Acoustic modelling of 3D-printed hybrid materials: a preliminary study

Analytical and finite element (FE) models are developed to predict the sound absorption coefficient of hybrid materials obtained through assembly of folded quarter-length resonators and periodic porous material. The analytical model uses the sum of the acoustic admittances. The acoustic admittance of resonators is simulated with Stinson's model. Johnson-Champoux-Allard-Lafarge (JCAL) model and transfer matrix method (TMM) are used to calculate the acoustic admittance of 1, 2 and 4-layers of porous materials with different geometric parameters. The FE model is implemented using the COMSOL Multiphysics. The helical tubes are simulated using the visco-thermal acoustic module while the porous layers are simulated with JCAL poro-acoustic module. 30-mm thick samples of hybrid materials are produced via additive manufacturing (AM). Normal incident sound absorption coefficient of the hybrid materials is measured using an impedance tube. The experimental and simulated sound absorption coefficients are compared. The impact of the structure parameters (resonator diameter and length as well as number of porous layers) on the sound absorption is assessed. The hybrid materials present low frequency and broadband sound absorption. Higher broadband sound absorption is obtained with 4-layers of porous material. Low frequency absorption ( 1000 Hz) is achieved with long folded resonators (L 100 mm).

Experimental study on the effect of salt on the water absorption characteristic of cement mortar

Coastal buildings are exposed to salt spray environments for prolonged periods of time, and salt accumulates in the building walls. The effect of salt on the water absorption characteristics of the material is unclear and requires further investigation of the coupled heat and moisture transfer processes in coastal building walls. To address this issue and quantify this effect, cement mortar specimens were pretreated, and a capillary water absorption experiment was conducted on a salt-containing cement mortar to obtain the laws of the water absorption coefficient and capillary saturation moisture content with salt content. In addition, equations for fitting the water absorption coefficient and capillary saturation moisture content of salt-containing materials were established by integrating the salt impact factors proposed in this study. The obtained results showed that as the salt content increased, the water absorption coefficient first increased and then decreased, with a peak increase of 7.5% compared to that of the control group. The capillary saturation moisture content gradually decreased with increasing salt content, decreasing by 15.8% at the maximum salt content. Combined with scanning electron microscopy (SEM) observations of microstructural changes in specimens containing different amounts of salt, it was inferred that the dominant factors affecting the water absorption characteristics would be different when the salt content of the material was varied. In addition, the optimal formulae for the water absorption coefficient and capillary saturation moisture content of salt-containing materials were obtained.

On the Piezophototronic Effect in Heterojunction Photodiode with Type‐II Energy Band: Theoretical Model for Anisotype Heterojunction

The piezophototronic effect has been widely explored to improve the performance of optoelectronic devices. However, modulation of piezoelectric charges varies with different energy band structures. Thus, it is important to investigate the specific role of the piezophototronic effect from a theoretical perspective. Herein, the piezophototronic effect in anisotype p‐Si/n‐ZnO heterojunction photodiodes with type‐II energy band diagrams through analytical derivation and numerical simulation is thoroughly studied. It is found that both the depletion region and quasineutral region have a decisive effect on photocurrent in their respective regions. Specifically, modulations of piezoelectric charges on depletion region current and quasineutral region current are opposite and compensate each other, resulting in reduced piezophototronic effect. Heterojunctions under short diode conditions are preferred for better piezophototronic effect as modulation on quasineutral region current is weakened while that on depletion region current remains unchanged. The effects of doping concentration, absorption coefficient, and minority carrier lifetime of semiconductor materials on device characteristics are also studied. This work provides deeper insight into the underlying device physics of the piezophototronic effect.