A novel multi−wavelength photoacoustic spectrometer for the measurement of the UV–vis-NIR spectral absorption coefficient of atmospheric aerosols

Purpose The aim of this paper is to present advanced experimental–numerical methods for identification of spectral absorption and scattering properties of highly porous ceria ceramics in the range of semi-transparency at room and elevated temperatures. Design/methodology/approach At room temperature, a period of quasi-steady oscillations of the sample surface temperature generated in response to recurrent laser heating at fixed values of the maximum and minimum temperature of the irradiated surface is measured along with the normal-hemispherical reflectance. Radiative properties are then identified using a combined heat transfer model. At elevated temperatures, an analytical solution proposed in an earlier study for zirconia ceramics is used to retrieve spectral absorption coefficient of ceria ceramics from the measured normal emittance. Findings and Originality/value This method can be used to obtain small absorption coefficient of ceria ceramics at room temperature. The required measurements of both the normal-hemispherical reflectance and the period of quasi-steady oscillations of the irradiated surface temperature of the ceramics sample between fixed values of the maximum and minimum temperatures can be readily conducted using thermal laboratory equipment. Another method has been suggested for identification of the spectral absorption coefficient of ceria ceramics at elevated temperatures. This method is based on a relation between the measured normal emittance of an isothermal sample and the absorption coefficient.

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The spectral absorption coefficient at 254 nm as a real-time early warning proxy for detecting faecal pollution events at alpine karst water resources

Water Science & Technology ◽

10.2166/wst.2010.500 ◽

2010 ◽

Vol 62 (8) ◽

pp. 1898-1906 ◽

Cited By ~ 20

Author(s):

H. Stadler ◽

E. Klock ◽

P. Skritek ◽

R. L. Mach ◽

W. Zerobin ◽

...

Keyword(s):

Absorption Coefficient ◽

Real Time ◽

Early Warning ◽

Data Communication ◽

Spring Water ◽

Karst Water ◽

Spectral Absorption ◽

Sampling Device ◽

Spectral Absorption Coefficient ◽

Faecal Pollution

Because spring water quality from alpine karst aquifers can change very rapidly during event situations, water abstraction management has to be performed in near real-time. Four summer events (2005–2008) at alpine karst springs were investigated in detail in order to evaluate the spectral absorption coefficient at 254 nm (SAC254) as a real-time early warning proxy for faecal pollution. For the investigation Low-Earth-Orbit (LEO) Satellite-based data communication between portable hydrometeorological measuring stations and an automated microbiological sampling device was used. The method for event triggered microbial sampling and analyzing was already established and described in a previous paper. Data analysis including on-line event characterisation (i.e. precipitation, discharge, turbidity, SAC254) and comprehensive E. coli determination (n>800) indicated that SAC254 is a useful early warning proxy. Irrespective of the studied event situations SAC254 always increased 3 to 6 hours earlier than the onset of faecal pollution, featuring different correlation phases. Furthermore, it seems also possible to use SAC254 as a real-time proxy parameter for estimating the extent of faecal pollution after establishing specific spring and event-type calibrations that take into consideration the variability of the occurrence and the transferability of faecal material It should be highlighted that diffuse faecal pollution from wildlife and live stock sources was responsible for spring water contamination at the investigated catchments. In this respect, the SAC254 can also provide useful information to support microbial source tracking efforts where different situations of infiltration have to be investigated.

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Spectral Absorption Coefficient of Additive Manufacturing Materials

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4048836 ◽

2021 ◽

Vol 13 (4) ◽

Author(s):

Nicholas J. Wallace ◽

Matthew R. Jones ◽

Nathan B. Crane

Keyword(s):

Additive Manufacturing ◽

Absorption Coefficient ◽

Radiative Heat ◽

Manufacturing Processes ◽

Spectral Absorption ◽

Spectral Absorption Coefficient ◽

Polyamide 12 ◽

Active Thermography ◽

Uncertainty Estimates ◽

Properties Of Materials

Abstract Active thermography techniques are of interest for quality assurance of additive manufacturing processes. However, accurate measurements of thermophysical properties of materials are required to successfully implement active thermography. In particular, the spectral absorption coefficient of materials commonly used in additive manufacturing must be known to accurately predict the spatial distribution of thermal energy generated from absorption of power emitted by a laser or pulsed flash lamp. Accurate measurements of these optical properties are also needed to develop greater understanding of additive manufacturing processes that rely on radiative heat transfer to fuse powders. This paper presents spectral absorption coefficient measurements and uncertainty estimates of fully and partially dense ABS, PLA, and Polyamide 12 samples.

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