Measurement Of Absorption Coefficient Research Articles

The Sound Absorption Characteristics of Bamboo Twigs Based on Surface Combination Patterns

Bamboo twigs are branches of the bamboo plant. This study intends to confirm the potential of bamboo twigs as an alternative sound absorbing material in acoustic applications. The pieces of bamboo twigs are arranged according to their edges: hollow edges (RR) and node edges (BB), creating five upper-bottom surface combination patterns. The acoustical characteristics were examined through absorption coefficient (α) and standard deviation measurements. The result shows the best surfaces combination is the RB-RR specimen. RB-RR specimen is a combination of hollow and node edges on the upper surface and hollow edges on the bottom surface. Although narrower in frequency ranges, the specimen performs approximately equivalent to the well-known Glass wool in terms of maximum absorption coefficients (α). Refers to the measurement results, the abundant bamboo twigs can be qualified as a potential alternative for sound absorption material in the future.

Measurement of Black Carbon Absorption Coefficients Using an Aethalometer and Their Association with Visibility

Black carbon (BC) is a pollutant aerosol affecting climate and human health. Light absorption coefficients of black carbon (Babs) were measured using an aethalometer model AE33 at wavelengths 370, 470,520,660,880, and 950 nm. Babs for the seven wavelengths at seven sites in Jordan fluctuated with time and peaked at rush hours. The daily average values for all sites were inversely proportional to the wavelength. The average daily visibility values in the seven Jordan sites varied between 72 km and 211km. In the Irbid site, the daily average visibility values for 7-13 Nov. 2021 varied between 43 km and 107 km. BC varied from hour to hour and from day to day. The daily average values of BC in Irbid for the period of 7 -13 Nov. 2021 varied between 2.24 μg.m-3 and 4.66 μg.m-3. BC peaked at the rush hour and had the lowest values on Friday. About 90% of the measured BC was from fossil fuel sources and 10% from biomass-burning sources.

Impact of breast density on classification of infrared spectroscopy for breath-based breast cancer screening.

e13558 Background: While mammography is currently the standard of care for breast cancer screening, dense breast tissue can significantly degrade results. Alternatively, infrared spectroscopy analysis of breath offers a highly sensitive method for identifying exhaled volatile organic compounds (VOCs), which may circumvent issues with breast density. Methods: Alveolar breath samples were collected onto Tenax TA sorbent tubes using a SohnoXB™ breath sampler. Using four desorb temperatures (75, 150, 225 and 300°C), absorption spectra were measured by infrared cavity ring-down spectroscopy (IR-CRDS), a technique for measuring absorption coefficients due to VOCs in exhaled breath. Missing values in the absorption spectra were backfilled using interpolation, and the spectrum was min-max normalized and quadratic detrended. First and second derivatives of the preprocessed absorption spectra were used as features for a support vector machine machine-learning model. Features were ranked based on minimum redundancy maximum relevance (mRMR). The top 20 ranked features were selected to limit the potential for overfitting and then optimized. Model performance was validated using non-nested leave-one-out cross-validation (LOOCV) and nested LOOCV to provide optimistic and pessimistic results, respectively. Results: Absorption spectra from 111 participants (71 positive, 40 control) were used. Of the positive subjects, 30 had low- and 31 had high-density breast tissue (measures missing for 10). Model performance is outlined. A subgroup analysis compared model performance for subjects with low- and high-density breast tissue for both non-nested and nested LOOCV models. Breast density data was not captured for control subjects thus they were not included in the subgroup analysis. Fisher’s exact test was performed to assess for significant difference between model performance for those with low- vs high-density breast tissue, resulting in a p-value of 1.00. Conclusions: Our results suggest that the classification of alveolar breath using IR-CRDS is a promising technique for the detection of breast cancer that is independent of breast density. Breath analysis may therefore become a new alternative or corroborative to mammography to support clinical decision-making. [Table: see text]

Numerical Simulation of a Light Field Structure in an Integrating Sphere via the Monte Carlo Method

The integrated cavity absorption meter is designed to measure the seawater absorption coefficient spectra which are necessary for studying ocean productivity and heat balance. The performed numerical simulations of a light field structure made it possible to improve the measurement technique. Its results showed that the use of the Lambertian model allows to reduce the calculation time by two orders of magnitude with an acceptable loss of accuracy for these calculations. It is shown that in the case of an integrating sphere made of fluorilon, the use of different volume scattering functions does not affect the calculation result, which is not true in the case of using a sphere with a mirror coating. The effect of an air layer between quartz and fluorilon is considered, and the applicability of the diffusion approximation is verified. Examples of field measurements of the seawater absorption coefficient and its components performed in different water areas of the World Ocean in 2020–2022 are presented.

RF oscillator circuit for absorption coefficient measurement of piezoelectric materials.

We have introduced an approach for low optical absorption coefficient measurement of piezoelectric materials based on the piezoelectric resonance laser calorimetry (PRLC) method. An RF oscillator circuit provides a convenient way to track the piezoelectric resonance frequency during laser irradiation. In this work, the optical absorption coefficient of lithium triborate crystal under high-power IR laser irradiation was measured using the oscillator circuit and the conventional PRLC technique.

Measurements of Nonlinear Absorption and Refraction Coefficients of Pure and Nd Doped Calcium Lanthanum Borate Glasses

Measurements of Nonlinear Absorption and Refraction Coefficients of Pure and Nd Doped Calcium Lanthanum Borate Glasses

Phonon-assisted optical absorption of SiC polytypes from first principles

Silicon carbide (SiC) is an indirect-gap semiconductor material widely used in electronic and optoelectronic applications. While experimental measurements of the phonon-assisted absorption coefficient of SiC across its indirect gap have existed for more than 50 years, theoretical investigations of phonon-assisted absorption have been hampered by their excessive computational cost. In this work, we calculate the phonon-assisted temperature-dependent optical absorption spectra of the commonly occurring SiC polytypes (3C, 2H, 4H, 6H, and 15R), using first-principles approaches based on density functional theory and related techniques. We show that our results agree with experimentally determined absorption coefficients in the spectral region between the direct and indirect band gaps. The temperature dependence of the spectra can be well predicted with taking the temperature dependence of the band gaps into account. Lastly, we compare the spectra obtained with second-order perturbation theory to those determined by the special displacement method and we show that the full consideration of the electronic energy renormalization due to temperature is important to further improve the prediction of the phonon-assisted absorption in SiC. Our insights can be applied to predict the optical spectra of the less common SiC polytypes and other indirect-gap semiconductors in general.

A pptv Level Incoherent Broadband Cavity-Enhanced Absorption Spectrometer for the Measurement of Atmospheric NO3

NO3 radicals are one of the very important trace gases in the atmosphere. Accurate measurements of NO3 can provide data support for atmospheric chemistry research. Due to the extremely low content of NO3 radicals in the atmosphere, it is a challenge to accurately detect it. In this paper, an incoherent broadband cavity-enhanced absorption spectrometer (IBBCEAS) with high sensitivity is developed for measuring atmospheric NO3. The IBBCEAS absorption spectra of NO3 in the range of 648–674 nm are measured. The concentration of NO3 is retrieved by fitting the absorption cross-section of NO3 to the measured absorption coefficient using the least square method. The interference absorption of water vapor is effectively removed by an iterative calculation of its absorption cross-section. The detect limit of the spectrometer is analyzed using the Allan variance and the standard variance. The NO3 detection limit (1σ) of the spectrometer is 1.99 pptv for 1 s integration time, and improves to be 0.69 pptv and 0.21 pptv for 10 s and 162 s integration time, respectively. The developed spectrometer with pptv level sensitivity is applied to the measurements of the real atmospheric NO3 for verifying the effectiveness.

Interrogation on Optical Properties of Electrolyte Minerals, TSS and Turbidity in Water - Spectrophotometer and IOP Profiler Based Hyperspectral Analysis Approach

The optical properties of total suspended solids, turbidity, and electrolyte minerals in water such as sodium, potassium, and calcium were studied under laboratory and field-oriented conditions. Spectrophotometer and Wet Lab Instrument Inherent Optical Properties profiler have been used to measure the optical properties. The polynomial fit between the field measured absorption spectra and laboratory measured absorption spectra of each mineral explains in detail the chemical water quality parameters and optical properties. The spectrophotometrically derived absorption coefficient of electrolyte minerals such as sodium (1,000 ppm), potassium (100 ppm), and calcium (1,000 ppm), TSS (500 ppm) and Turbidity (100 NTU) makes virtuous correlation with the IOP profiler measured absorption coefficient donates the best polynomial fit R2 values of 0.9076, 0.9019, 0.9645, 0.9823 and 0.9354 respectively. Results in this study exhibits that, the absorption coefficient of electrolyte minerals, TSS, and Turbidity in water increases with increasing their concentrations at the wavelengths range from 200 to 300 nm. HIGHLIGHTS The absorption coefficient values are increasing with the increasing concentration of sodium as well as for calcium and Total suspended solids The absorption spectra of potassium are exponentially increasing with decreasing wavelength The absorption curves show an evolution from a solitary, well defined absorption trough at 550 nm at lower turbidity values to a broader, more flat-topped absorption encompassing from 550 to 650 nm at higher turbidity levels GRAPHICAL ABSTRACT

Design, construction and commissioning of a reverberation room

In this paper we discuss the design, construction and commissioning of a reverberation room that meets the requirements of ISO 354:2003. The new room was built using lightweight double walls rather than the more usual monolithic construction. We present an analysis of measurements made during the commissioning of the room and discuss these results; these measurements include the effect of adding various diffusing elements, lighting and heating. We made measurements of the sound absorption coefficient of different materials in the commissioned room and these are compared with measurements of the same materials in two other reverberation rooms that also comply with the requirements of ISO 354:2003.

A method for determining the density fluctuations of supercritical fluids absolutely based on small-angle scattering experiments and application to supercritical methanol

Density fluctuation is a vital concept for understanding disordered systems. A supercritical fluid is a typical disordered system having extremely large inhomogeneity. To determine the density fluctuations using a scattering method, the key physical quantities are the fluid density and the normalized scattering intensity, as well as the small-angle scattering signals. Here, we propose a methodology to obtain all of these quantities absolutely from a scattering experiment. Normalization of scattering intensity relating to the number of molecules per unit volume was performed using fluid density evaluated directly from in situ measurements of the X-ray absorption coefficients. Conversion of scattering intensity to absolute value concerning scattering volume was achieved utilizing the value of the density fluctuation in the ideal state. An analysis of supercritical carbon dioxide confirmed the validity of the present method. By applying this method, the density fluctuations of supercritical methanol were quantitatively determined for the first time.

Comprehensive, Continuous, and Vertical Measurements of Seawater Constituents with Triple-Field-of-View High-Spectral-Resolution Lidar.

Measuring the characteristics of seawater constituent is in great demand for studies of marine ecosystems and biogeochemistry. However, existing techniques based on remote sensing or insitu samplings present various tradeoffs with regard to the diversity, synchronism, temporal-spatial resolution, and depth-resolved capacity of their data products. Here, we demonstrate a novel oceanic triple-field-of-view (FOV) high-spectral-resolution lidar (HSRL) with an iterative retrieval approach. This technique provides, for the first time, comprehensive, continuous, and vertical measurements of seawater absorption coefficient, scattering coefficient, and slope of particle size distribution, which are validated by simulations and field experiments. Furthermore, it depicts valuable application potentials in the accuracy improvement of seawater classification and the continuous estimation of depth-resolved particulate organic carbon export. The triple-FOV HSRL with high performance could greatly increase the knowledge of seawater constituents and promote the understanding of marine ecosystems and biogeochemistry.

Precise measurements of the low optical absorption coefficients of massive lithium triborate crystal boules with untreated facets formed during the growth process.

A spatial diagnostic of optical quality of the massive lithium triborate crystal boule with untreated facets was performed by measuring optical absorption coefficients at 1070 and 1908nm wavelengths using the piezoelectric resonance laser calorimetry technique.

Intercomparison of airborne and surface-based measurements during the CLARIFY, ORACLES and LASIC field experiments

Abstract. Data are presented from intercomparisons between two research aircraft, the FAAM BAe-146 and the NASA Lockheed P3, and between the BAe-146 and the surface-based DOE (Department of Energy) ARM (Atmospheric Radiation Measurement) Mobile Facility at Ascension Island (8∘ S, 14.5∘ W; a remote island in the mid-Atlantic). These took place from 17 August to 5 September 2017, during the African biomass burning (BB) season. The primary motivation was to give confidence in the use of data from multiple platforms with which to evaluate numerical climate models. The three platforms were involved in the CLouds–Aerosol–Radiation Interaction and Forcing for Year 2017 (CLARIFY-2017), ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES), and Layered Atlantic Smoke and Interactions with Clouds (LASIC) field experiments. Comparisons from flight segments on 6 d where the BAe-146 flew alongside the ARM facility on Ascension Island are presented, along with comparisons from the wing-tip-to-wing-tip flight of the P3 and BAe-146 on 18 August 2017. The intercomparison flight sampled a relatively clean atmosphere overlying a moderately polluted boundary layer, while the six fly-bys of the ARM site sampled both clean and polluted conditions 2–4 km upwind. We compare and validate characterisations of aerosol physical, chemical and optical properties as well as atmospheric radiation and cloud microphysics between platforms. We assess the performance of measurement instrumentation in the field, under conditions where sampling conditions are not as tightly controlled as in laboratory measurements where calibrations are performed. Solar radiation measurements compared well enough to permit radiative closure studies. Optical absorption coefficient measurements from all three platforms were within uncertainty limits, although absolute magnitudes were too low (<10 Mm−1) to fully support a comparison of the absorption Ångström exponents. Aerosol optical absorption measurements from airborne platforms were more comparable than aircraft-to-ground observations. Scattering coefficient observations compared adequately between airborne platforms, but agreement with ground-based measurements was worse, potentially caused by small differences in sampling conditions or actual aerosol population differences over land. Chemical composition measurements followed a similar pattern, with better comparisons between the airborne platforms. Thermodynamics, aerosol and cloud microphysical properties generally agreed given uncertainties.

Measurement of the sound absorption coefficient of palm frond fiber composites with synthetic adhesives

Natural fiber composite materials have been widely applied for various purposes, one of which is reducing noise. Many efforts have been tried to reduce noise by using sound absorbing materials such as glasswool, rockwool, and gypsum as sound absorbers, but because of the high price and bad impact on health, many studies have been conducted to find materials that are practical, cheap, and abundant availability in nature, one of which is natural fiber as an alternative to commercial sound absorbing materials. In this study, we want to know the effect of the composition of palm fronds with polyester resin can affect the sound absorption of a material and the effect of composition on sound absorption. The composition of palm frond fiber and polyester resin was varied 60%:40%, 65%:35%, 70%:30%, 75%:25%, 80%:20%, 85%:15%, 90%:10%, arranged randomly with a length of 5 mm. The specimen synthesis process starts with cutting the palm fronds, decomposing the palm frond fibers so that the fibers are separated from the flesh. Acoustic testing was conducted using a single microphone impedance tube. The test results showed that the largest absorption coefficient value is 0.984 at a frequency of 1500 Hz and is obtained in materials with a composition of 70%: 30%, and for the largest acoustic impendance value is 1.714 which is found at a frequency of 500 Hz and is obtained in the composition of 85%: 15%.

Enhancement of the sound absorption coefficient experimental reproducibility for different size samples

Sound absorption coefficient (SAC) measurements in a reverberation room may produce different values for different sample sizes of the same material because of the edge effect which depends on the geometrical properties of the sample. In this paper, the theory of the maximum SAC for a given size and shape of sample is extended to non-locally reacting sound absorbers to expand its application. A two-dimensional analytic strip theory is developed to calculate the value of the maximum SAC. The numerical integration method is presented and compared with the proposed analytical method and Thomasson’s tabulated results. Four different approaches are implemented to estimate the SAC of a sample using measurement on a different size sample of the same material. Results in the frequency range of 100 Hz to 10000 Hz are compared, and recommendations are given. It is shown that the proposed approach, which is a modification of a linear interpolation method, is an improved method for estimating the random SAC of a full/large size sample from measurements on a small size sample.

Optical Measurement of Molar Absorption Coefficient of HbA1c: Comparison of Theoretical and Experimental Results.

Diabetes can cause dangerous complications if not diagnosed in a timely manner. The World Health Organization accepts glycated hemoglobin (HbA1c) as a measure of diagnosing diabetes as it provides significantly more information on the glycemic behavior from a single blood sample than the fasting blood sugar reading. The molar absorption coefficient of HbA1c is needed to quantify the amount of HbA1c present in a blood sample. In this study, we measured the molar absorption coefficient of HbA1c in the range of 450 nm to 700 nm using optical methods experimentally. We observed that the characteristic peaks of the molar absorption coefficient of HbA1c (at 545 nm and 579 nm for level 1, at 544 nm and 577 nm for level 2) are in close agreement with those reported in previous studies. The molar absorption coefficient values were also found to be close to those of earlier reports. The average molar absorption coefficient values of HbA1c were found to be 804,403.5 M-1cm-1 at 545 nm and 703,704.5 M-1cm-1 at 579 nm for level 1 as well as 503,352.4 M-1cm-1 at 544 nm and 476,344.6 M-1cm-1 at 577 nm for level 2. Our experiments focused on calculating the molar absorption coefficients of HbA1c in the visible wavelength region, and the proposed experimental method has an advantage of being able to easily obtain the molar absorption coefficient at any wavelength in the visible wavelength region. The results of this study are expected to help future investigations on noninvasive methods of estimating HbA1c levels.

Acoustic Properties of Rigid Polyurethane Foam Mixed with Pet Bottle Wastes

Rigid closed-cell polyurethane foam is renowned for its outstanding sound absorption properties and its application as sound insulation panels. Studies show that mixing of rigid polyurethane foam with non-reactive filler materials during fabrication improves the sound absorption properties of the composite material. In this composite, foam was fabricated from polyol and isocyanate monomers with shredded pet bottle waste as a filler component. The percentages of pet wastes mixed with the polyurethane foam composites were varied by 0%, 10%, 15%, 20% and 25% of total weight. The measurement of sound absorption coefficient has been done using impedance tube technique. The results showed that the rigid polyurethane foam with 0% pet waste has poor acoustic absorption. Also, sound absorption coefficient results showed that a sample with higher amount of upto 20%pet bottle waste had better sound absorption even at higher frequencies. From this research it is clear that mixing of pet waste as a filler material upto 20% is ideal for fabricating sound absorption panels with better sound absorption average.

Characteristics of wintertime carbonaceous aerosols in two typical cities in Beijing-Tianjin-Hebei region, China: Insights from multiyear measurements

In order to investigate the impact of “Blue Sky War” implemented during 2018–2020 on carbonaceous aerosols in Beijing-Tianjin-Hebei (BTH) region, China, fine particulate matter (PM2.5) samples were collected simultaneously in Tianjin and Handan in three consecutive winters from 2018 to 2020. Organic carbon (OC) and elemental carbon (EC) in PM2.5 were measured with the same thermal-optical methods and analysis protocols. Significant reductions in primary organic carbon (POC) and EC concentrations were observed both in Tianjin and Handan, with decreasing rates of 0.65 and 2.95 μg m−3 yr−1 for POC and 0.13 and 0.64 μg m−3 yr−1 for EC, respectively. The measured absorption coefficients of EC (babs, EC) also decreased year by year, with a decreasing rate of 1.82 and 6.16 Mm−1 yr−1 in Tianjin and Handan, respectively. The estimated secondary organic carbon (SOC) concentrations decreased first and then increased in both Tianjin and Handan, accounting for more than half of the total OC in winter of 2020–2021 and with increasing contributions especially in highly polluted days. SOC was recognized as one of key factors influencing EC light absorption. EC in the two cities was relatively more related to coal combustion and industrial sources. The reductions of primary carbonaceous components may be attributed to the air quality regulations targeting coal combustion and industrial sources emissions in BTH area. Potential source contribution function (PSCF) analysis results indicated that the major source areas of OC and EC in Tianjin were the southwest region of the sampling site, while the southeast areas for Handan. These findings demonstrated the effectiveness of air quality regulation in primary emissions in typical polluted cities in BTH region and highlighted the needs for further control and in-depth investigation of SOC formation along with implementation of air pollution control act in the future.

Finite-difference diffusion-equation modeling of reverberation chambers in time-domain

Conventional chamber-based methods of random incidence absorbing coefficients overlook the non-diffused sound field in the room acoustics, which decreases accuracy and may even lead to conflicting results. This work applies the diffusion equation model to room-acoustic simulations of standardized reverberation chambers. The simulations can more efficiently capture the chamber's non-diffuse sound field and energy flows than wave-based simulation models. The diffusion equation represents the governing equation of reverberant sound energy densities within the reverberation chamber which is solved using the finite-difference time-domain method. Its computational efficiency of diffusion equation-based modeling lies in a highly sparse domain meshing condition dictated by the mean-free path length rather than wavelengths and still derives a wideband simulation result. This work also dedicates the effort to reexamine the meshing condition, particularly for standardized finite sizes of sound absorbers for measurements of random incidence absorption coefficients. By comparing the outcomes of simulations with measurement data, an a posteriori absorption coefficient is inversely estimated involving Bayesian parameter estimation.