Optical properties of solar absorbers : results on Round Robin and guidelines

ABSTRACT: The scope of the standard ISO 22975-3:2014 is the determination of the long term behavior and service life of selective solar absorbers for use in vented flat plate collectors used in typical solar domestic hot water systems or combisystems. With this scope, this standard can be the basis for the certification of solar absorbers in the framework of Solar Keymark European Certification Scheme. Measurements of optical properties are fundamental to support this certification. Six test laboratories participated in a Round Robin test for the measurement of solar absorptance and thermal emittance of different absorber coatings. The samples used were one PVD coating and two selective paint coatings all on aluminum substrates. The results were submitted anonymously and were analyzed according to standard ISO 13528:2015. The results obtained showed good agreement among the measurements made by the participants and allowed the preparation of guidelines to guarantee quality of the measurements of optical properties of solar absorbers. A proposal to include absorber coatings in the Solar Keymark certification scheme was prepared.info:eu-repo/semantics/acceptedVersio

Cochrane Effective Practice and Organisation of Care (EPOC) Qualitative Evidence Syntheses, Differences From Reviews of Intervention Effectiveness and Implications for Guidance

Systematic reviews of qualitative research (‘qualitative evidence syntheses’) are increasingly popular and represent a potentially important source of information about people’s views, needs and experiences. Since 2013, Cochrane has published qualitative evidence syntheses, and the Cochrane Effective Practice and Organisation of Care group has been involved in the majority of these reviews. But more guidance is needed on how to prepare these reviews in an environment that is more familiar with reviews of quantitative research. In this paper, we describe and reflect on how Cochrane qualitative evidence syntheses differ from reviews of intervention effectiveness and how these differences have influenced the guidance developed by the EPOC group. In particular, we discuss how it has been important to display to end users, firstly, that qualitative evidence syntheses are carried out with rigour and transparency, and secondly, that these quality standards need to reflect qualitative research traditions. We also discuss lessons that reviews of effectiveness might learn from qualitative research

Qualitative Evidence Syntheses Within Cochrane Effective Practice and Organisation of Care: Developing a Template and Guidance

A growing number of researchers are preparing systematic reviews of qualitative evidence, often referred to as ‘qualitative evidence syntheses’. Cochrane published its first qualitative evidence synthesis in 2013 and published 27 such syntheses and protocols by August 2020. Most of these syntheses have explored how people experience or value different health conditions, treatments and outcomes. Several have been used by guideline producers and others to identify the topics that matter to people, consider the acceptability and feasibility of different healthcare options and identify implementation considerations, thereby complementing systematic reviews of intervention effectiveness.Guidance on how to conduct and report qualitative evidence syntheses exists. However, methods are evolving, and we still have more to learn about how to translate and integrate existing methodological guidance into practice. Cochrane’s Effective Practice and Organisation of Care (EPOC) (www.epoc.org) has been involved in many of Cochrane’s qualitative evidence syntheses through the provision of editorial guidance and support and through co-authorship. In this article, we describe the development of a template and guidance for EPOC’s qualitative evidence syntheses and reflect on this process

A parametric model for the changes in the complex valued conductivity of a lung during tidal breathing

Classical homogenization theory based on the Hashin-Shtrikman coated ellipsoids is used to model the changes in the complex valued conductivity (or admittivity) of a lung during tidal breathing. Here, the lung is modeled as a two-phase composite material where the alveolar air-filling corresponds to the inclusion phase. The theory predicts a linear relationship between the real and the imaginary parts of the change in the complex valued conductivity of a lung during tidal breathing, and where the loss cotangent of the change is approximately the same as of the effective background conductivity and hence easy to estimate. The theory is illustrated with numerical examples, as well as by using reconstructed Electrical Impedance Tomography (EIT) images based on clinical data from an ongoing study within the EU-funded CRADL project. The theory may be potentially useful for improving the imaging algorithms and clinical evaluations in connection with lung EIT for respiratory management and monitoring in neonatal intensive care units

The Reno Aerosol Optics Study: An evaluation of aerosol absorption measurement methods

The Reno Aerosol Optics Study (RAOS) was designed and conducted to compare the performance of many existing and new instruments for the in situ measurement of aerosol optical properties with a focus on the determination of aerosol light absorption. For this study, simple test aerosols of black and white particles were generated and combined in external mixtures under low relative humidity conditions and delivered to each measurement system. The aerosol mixing and delivery system was constantly monitored using particle counters and nephelometers to ensure that the same aerosol number concentration and amount reached the different instruments. The aerosol light-scattering measurements of four different nephelometers were compared, while the measurements of seven light-absorption instruments (5 filter based, 2 photoacoustic) were evaluated. Four methods for determining the aerosol lightextinction coefficient (3 cavity ring-down instruments and 1 folded path optical extinction cell) were also included in the comparisons. An emphasis was placed on determining the representativeness of the filter-based light absorption methods, since these are used widely and because major corrections to the raw attenuation measurements are known to be required. The extinction measurement from the optical extinction cell was compared with the scattering measurement from a high-sensitivity integrating nephelometer on fine, nonabsorbing ammonium sulfate aerosols, and the two were found to agree closely (within 1% for blue and green wavelengths and 2% for red). The wavelength dependence of light absorption for small kerosene and diesel soot particles was found to be very near λ−1, the theoretical small-particle limit. Larger, irregularly shaped graphite particles showed widely variable wavelength dependencies over several graphite runs. The light-absorption efficiency at a wavelength of 530 nm for pure kerosene soot with a number size distribution peak near 0.3 μm diameter was found to be 7.5 +/- 1.2 m2 g−1. The two most fundamental independent absorption methods used in this study were photoacoustic absorption and the difference between suspended-state light extinction and scattering, and these showed excellent agreement (typically within a few percent) on mixed black/white aerosols, with the photoacoustic measurement generally slightly lower. Excellent agreement was also observed between some filter-based light-absorption measurements and the RAOS reference absorption method. For atmospherically relevant levels of the aerosol light-absorption coefficient (less than 25 Mm−1), the particle soot absorption photometer (PSAP) absorption measurement at mid-visible wavelengths agreed with the reference absorption measurement to within 11% for experiment tests on externally mixed kerosene soot and ammonium sulfate. At higher absorption levels (characterized by lower single-scattering albedo aerosol tests), this agreement worsened considerably, most likely due to an inadequate filter loading correction used for the PSAP. The PSAP manufacturer’s filter loading correction appears to do an adequate job of correcting the PSAP absorption measurement at aerosol single-scattering albedos above 0.80–0.85, which represents most atmospheric aerosols, but it does a progressively worse job at lower single-scattering albedos.Anew filter-based light-absorption photometer was also evaluated inRAOS, the multiangle absorption photometer (MAAP), which uses a two-stream radiative transfer model to determine the filter and aerosol scattering effects for a better calculation of the absorption coefficient. The MAAP absorption measurements agreed with the reference absorption measurements closely (linear regression slope of 0.99) for all experimental tests on externally mixed kerosene soot and ammonium sulfate