Temat: absorption coefficient

Skocz do pozycji: 1.

Tytuł:: Optical properties of maize seeds
Autorzy:: Hernandez, A.
Cruz, O.
Ivanov, R.
Dominguez, P.
Carballo, C.
Moreno, I.
Tematy:: maize
optical absorption coefficient
photoacoustic spectroscopy
absorption coefficient
seed
optical property
raw material; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Agrofizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/25661.pdf Link otwiera się w nowym oknie
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Dose uncertainty due to energy dependence in dual-energy computed tomography
Autorzy:: Yokomachi, Kazushi
Fujioka, Chikako
Kawahara, Daisuke
Nagata, Yasushi
Toyoda, Takatoshi
Opis:: Purpose: To evaluate the absolute dose uncertainty at 2 different energies and for the large and small bowtie filters in dual-energy computed tomography (DECT). Material and methods: Measurements were performed using DECT at 80 kV and 140 kilovoltage peak (kVp), and single-energy computed tomography (CT) at 120 kV. The absolute dose was calculated from the mass-energy absorption obtained from the half-value layer (HVL) of aluminium. Results: The difference in the water-to-air ratio of the mean mass energy-absorption coefficients at 80 kV and 140 kV was 2.0% for the small bow-tie filter and 3.0% for the large bow-tie filter. At lower tube voltages, the difference in the absorbed dose with the large and small bow-tie filters was larger. Conclusions: The absolute dose uncertainty due to energy dependence was 3.0%, which could be reduced with single-energy beams at 120 kV or by using the average effective energy measurement with dual-energy beams.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 3.

Tytuł:: Utilizing Hollow-Structured Bamboo as Natural Sound Absorber
Autorzy:: Putra, A.
Khair, F. A.
Nor, M. J. M.
Tematy:: bamboo
hollow structure
acoustic absorber
absorption coefficient; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/177960.pdf Link otwiera się w nowym oknie
Opis:: Studies to find alternative low environmental-impact materials for acoustic absorbers are still progressing, particularly those originated from natural materials. However, most of the established works are mainly focused on the fibrous-type absorbers. Discussion on the non-fibrous-type absorbers is still lacking and this therefore becomes the objective of this paper. Use of bamboo by utilizing its hollow structure to absorb sound energy is discussed here. The normal incidence absorption coefficient was measured based on the length and diameter of the bamboo, as well as different arrangement of the bamboo structure subjected to the incidence sound, namely, axial, transverse, and crossed-transverse arrangements. The trend of absorption coefficient appears in peaks and dips at equally spacing frequencies. For all arrangements the peak of absorption can reach above 0.8. Introducing an air gap behind the bamboo shifts the peak absorption to lower frequency. Covering the front surface of the absorber improves the sound absorption coefficient for axial arrangement by widening the frequency range of absorption also towards lower frequency range. The transverse arrangement is found to have average absorption coefficient peaks of 0.7 above 1.5 kHz. By arranging the bamboo structure with crossed-transverse arrangement, the suppressed absorption peaks in normal transverse arrangement can be recovered.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Estimating Surface Acoustic Impedance With the Inverse Method
Autorzy:: Piechowicz, J.
Tematy:: room acoustics
sound absorption coefficient
acoustic impedance; Pokaż więcej
Wydawca:: Centralny Instytut Ochrony Pracy
Powiązania:: https://bibliotekanauki.pl/articles/90473.pdf Link otwiera się w nowym oknie
Opis:: Sound field parameters are predicted with numerical methods in sound control systems, in acoustic designs of building and in sound field simulations. Those methods define the acoustic properties of surfaces, such as sound absorption coefficients or acoustic impedance, to determine boundary conditions. Several in situ measurement techniques were developed; one of them uses 2 microphones to measure direct and reflected sound over a planar test surface. Another approach is used in the inverse boundary elements method, in which estimating acoustic impedance of a surface is expressed as an inverse boundary problem. The boundary values can be found from multipoint sound pressure measurements in the interior of a room. This method can be applied to arbitrarily-shaped surfaces. This investigation is part of a research programme on using inverse methods in industrial room acoustics.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: Quantitative IR studies of the concentration of $Co^{2+}$ and $Co^{3+}$ sites in zeolites CoZSM-5 and CoFER
Autorzy:: Datka, Jerzy
Gil, Barbara
Góra-Marek, Kinga
Opis:: Quantitative IR experiments were realized to determine the concentration of cobalt in a form of trivalent cations being in the oxide form as well as divalent ions in exchange positions, oxide-like clusters and cobalt oxide, present in a series of cobalt-exchanged zeolites. The first step of such quantitative studies was to elaborate the experimental conditions in which probe molecules NO and CO should react selectively with either of these sites. Subsequently, the values of absorption coefficients of the 1940$cm^{-1}$ band of $Co^{3+}$–NO and the 2204$cm^{-1}$ band of $Co^{2+}$–CO for $Co^{2+}$ in exchange positions, together with the 2194$cm^{-1}$ band of $Co^{2+}$–CO for $Co^{2+}$ in oxide-like clusters were determined. The linear plots of the band intensities versus the concentration of NO and CO interacting with cationic sites showed the correlation coefficients higher than 0.99. Three zeolites were investigated: CoZSM-5 (Si/Al = 15) in which most of $Co^{2+}$ occupied the exchange positions, CoZSM-5 (Si/Al = 40) in which most of $Co^{2+}$ was in the form of oxide-like clusters and CoO, and CoFER prepared by the contact-induced ion exchange with nearly equal amount of $Co^{2+}$ in either type of the sites. The sum of the concentration of Co sites ($Co^{3+}$ and $Co^{2+}$) determined by IR spectroscopy was very close to the values obtained from the chemical analysis (AAS). The concentration ill-defined oxide form of $Co^{3+}$ was surprisingly high as in CoZSM-5 of Si/Al = 15 it constituted about half of the overall cobalt content, and in CoFER the contribution of $Co^{3+}$ reached almost 30%.
Dostawca treści:: Repozytorium Uniwersytetu Jagiellońskiego

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Skocz do pozycji: 6.

Tytuł:: Method of Determining the Sound Absorbing Coefficient of Materials within the Frequency Range of 5 000–50 000 Hz in a Test Chamber of a Volume of about 2 m3
Autorzy:: Mikulski, W.
Tematy:: ultrasonic noise
sound absorption coefficient of materials; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:: https://bibliotekanauki.pl/articles/177184.pdf Link otwiera się w nowym oknie
Opis:: Sound absorption coefficient is a commonly used parameter to characterize the acoustic properties of sound absorbing materials. It is defined within the frequency range of 100-5 000 Hz. In the industrial conditions, many appliances radiating acoustic energy of the frequency range of above 5000 Hz are used and at the same time it is known that a noise within the frequency range of 5 000-50 000 Hz can have a harmful effect on people,hence there is a need to define the coefficient in this frequency range. The article presents a proposal for a method of measurement of the sound absorption coefficient of materials in the frequency range from 5 000 Hz to 50 000 Hz. This method is a modification of the reverberation method with the use of interrupted noise.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Light absorption spectra for lubricate oil quality tracking in the combustion engine
Autorzy:: Baszanowska, E.
Otremba, Z.
Tematy:: lubricate oil
dissolved oil
absorption spectroscopy
absorption coefficient
engine system; Pokaż więcej
Wydawca:: Instytut Techniczny Wojsk Lotniczych
Powiązania:: https://bibliotekanauki.pl/articles/243648.pdf Link otwiera się w nowym oknie
Opis:: The important role in the proper functioning of combustion engines plays the quality of lubricates oil. However, the quality of oil changes with the time of exploitation. Therefore, several parameters for examination of oil quality were determined; however, the indicator for quick and efficient tracking of evolution of oil with exploitation time is still searched. Taking into account the complex composition of oils, the ability of oils components to absorb light in various wavelengths is considered. In the article absorption properties of oils is discussed in relation to the time of circulation of oil in the engine lubricate system. For this study, two lubricate oils designated to lubricate the cylinder of vessel engines with different brightness and transparency were used. Oil samples were dissolved in organic solvent –n-hexane and several oil concentration were prepared based on dilution method. Absorbance spectra for eachsamples of oil were registered in the range of wavelength 240-600 nm. Obtained results indicate the changes of value of absorbance in relation to the kind of oil; however, the shape of absorbance spectra is independent from the kind of oil. For studied kinds of oil, characteristic peak independent from the kind of oil located at 260 nm was determined. Based on Lambert-Beer law absorption coefficient was identified as a potential indicator to oil quality evaluation with the time of exploitation in the engine system. Preliminary test for two fresh lubricate oils allow to conclude that absorption coefficient for selected wavelength located at 260 nm could be a sensitive parameter for quick estimating the degree of deterioration of the oil in engine system.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: The use of Vacuum Packed Particles with adaptable properties in acoustic applications
Autorzy:: Zalewski, R.
Rutkowski, M.
Tematy:: Vacuum Packed Particles
absorption coefficient
experiments
Voronina model; Pokaż więcej
Wydawca:: Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Powiązania:: https://bibliotekanauki.pl/articles/280992.pdf Link otwiera się w nowym oknie
Opis:: The aim of this paper is to present possibilities of using a new type of granular media in acoustics as innovative sound absorbers. Most materials of this type have a porous or fibrous structure. It is constant, and once manufactured, does not easily change its configuration. The examined material – Vacuum Packed Particles (VPP) is of a changeable structure. It can be assumed that the acoustical absorption of such structures can be modified and partially adjusted by an external factor. First steps in an experimental approach have been made – the acquired results are optimistic. Additional tests are being planned to confirm the observed phenomenon and to apply VPP as novel materials in acoustics. Basing on the preliminary experimental tests, it can be concluded that the considered structures could become a significant part of a multilayered structure which would have controllable sound absorption properties.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Method for Calculating the Sound Absorption Coefficient for a Variable Range of Incidence Angles
Autorzy:: Yori, Alfio
Tematy:: sound absorbing material
sound absorption coefficient
circular wave incidence; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Czasopisma i Monografie PAN
Powiązania:: https://bibliotekanauki.pl/articles/177245.pdf Link otwiera się w nowym oknie
Opis:: The theoretical estimation of sound absorption coefficient of a surface may give very different results. This will depend on the type of sound field assumed in the theoretical model used for the estimation of its sound absorption coefficient. Absorption coefficients for normal and diffuse sound fields are widely known, although they may be far from the absorption values given by an absorbing material when it is finally installed inside a room or enclosed space, where a sound field closer to a spherical wavefront is more likely to be found. This work presents a theoretical study, which is addressed at obtaining a mathematical expression to calculate the sound absorption coefficient for a variable range of incidence angles, called α_s. The presented method uses a circular sound field incidence as an approximation to a spherical incidence. The estimation of this coefficient α_s is based on obtaining the incident and reflected sound fields for a surface located facing a lineal source. The advantage of this calculation method over others lies on its capability to give results for circular, normal and random wave incidence depending on the range of incidence angles considered in the calculation.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: GEANT4 simulation of implantation profiles for positrons injected in solids from radioactive sources 22Na and 68Ge/68Ga
Autorzy:: Horodek, P.
Dryzek, J.
Tematy:: positron annihilation
implantation profile
absorption coefficient
GEANT4 tool kit; Pokaż więcej
Wydawca:: Instytut Chemii i Techniki Jądrowej
Powiązania:: https://bibliotekanauki.pl/articles/146334.pdf Link otwiera się w nowym oknie
Opis:: We calculated theoretically the mass absorption coefficients for positrons emitted from the commonly used sources 22Na and 68Ge/68Ga in numerous materials. For this purpose, we used the tool kit GEANT4 which allows to generate the implantation profile. An excellent agreement between the experimental profile and the calculated one was achieved. The calculated values of the mass absorption coefficients coincide well with the experimental values determined by the DSIP method.
Dostawca treści:: Biblioteka Nauki

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