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Roos, A
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Publications (10 of 67) Show all publications
Björn, L. O., Bengtson, S.-A., Shaoshan, L., Hecker, C., Ullah, S., Roos, A. & Nilsson, A. M. (2016). Thermal emissivity of avian eggshells. Journal of Thermal Biology, 57, 1-5
Open this publication in new window or tab >>Thermal emissivity of avian eggshells
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2016 (English)In: Journal of Thermal Biology, ISSN 0306-4565, E-ISSN 1879-0992, Vol. 57, p. 1-5Article in journal (Refereed) Published
Abstract [en]

The hypothesis has been tested that evolution has resulted in lower thermal emissivity of eggs of birds breeding openly in cold climates than of eggs of birds that nest under protective covering or in warmer climates. Directional thermal emissivity has been estimated from directional-hemispherical reflectance spectra. Due to several methodological difficulties the absolute emissivity is not accurately determined, but differences between species are obvious. Most notably, small waders of the genus Calidris, breeding in cold climates on the tundra, and in most cases with uniparental nest attendance, have low directional emissivity of their eggshells, about 0.92 when integration is carried out for wavelengths up to 16 mu m. Species belonging to Galloanserinae have the highest directional emissivity, about 0.96, of their eggs. No differences due to climate or breeding conditions were found within this group. Eggs of most other birds tested possess intermediate emissivity, but the values for Pica pica and Corvus corone cornix are as low as for Calidris. Large species-dependent differences in spectral reflectance were found at specific wavelengths. For instance, at 4.259 mu m the directional-hemispherical reflectance for galliforms range from 0.05 to 0.09, while for Fratercula arctica and Fulmarus glacialis it is about 0.3. The reflection peaks at 6.5 and 11.3 mu m due to calcite are differentially attenuated in different species. In conclusion, the hypothesis that evolution has resulted in lower thermal emissivity of bird eggs being exposed in cold climates is not supported by our results. The emissivity is not clearly related to nesting habits or climate, and it is unlikely that the small differences observed are ecologically important. The spectral differences between eggs that nevertheless exist should be taken into account when using infrared thermometers for estimating the surface temperature of avian eggs.

Keywords
Avian eggs; Birds; Heat dissipation; Egg cooling; Thermal emissivity; Incubation; Seabirds; Thermal radiation; Waders
National Category
Other Biological Topics Bio Materials
Identifiers
urn:nbn:se:uu:diva-284493 (URN)10.1016/j.jtherbio.2015.11.008 (DOI)000374359800001 ()27033033 (PubMedID)
Available from: 2016-04-18 Created: 2016-04-18 Last updated: 2017-11-30Bibliographically approved
Nilsson, A. M., Roos, A. & Wilson, H. R. (2014). Homogenisation or scattered transmitted light in an integrating sphere using a highly diffusing film on the entry port. In: : . Paper presented at Colloquium optische Spektrometrie (COSP 2014), Berlin, Germany, 17-18 March, 2014.
Open this publication in new window or tab >>Homogenisation or scattered transmitted light in an integrating sphere using a highly diffusing film on the entry port
2014 (English)Conference paper, Poster (with or without abstract) (Refereed)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-285896 (URN)
Conference
Colloquium optische Spektrometrie (COSP 2014), Berlin, Germany, 17-18 March, 2014
Available from: 2016-04-20 Created: 2016-04-20 Last updated: 2016-04-22
Försth, M., Zhao, S. & Roos, A. (2014). Spectrally selective and adaptive surfaces for protection against radiative heating: ITO and VO2. Fire and Materials, 38(1), 111-124
Open this publication in new window or tab >>Spectrally selective and adaptive surfaces for protection against radiative heating: ITO and VO2
2014 (English)In: Fire and Materials, ISSN 0308-0501, E-ISSN 1099-1018, Vol. 38, no 1, p. 111-124Article in journal (Refereed) Published
Abstract [en]

Two surface materials for reducing absorptivity of heat radiation from fires have been investigated. The first is VO2, which is a thermochromic material. When the temperature of a VO2 surface increases over a certain temperature, it switches, ideally, from infrared (IR)-absorbing to IR-reflecting. VO2 window coatings are still on a research level, yet to be commercialized. In this study, VO2 powder available on the market was investigated. The thermochromic effect could be identified but was not large enough to significantly improve the fire properties of treated surfaces. Some thoughts concerning how to improve the performance of VO2 are discussed. The second investigated material is indium tin oxide (ITO), which is a so called low-e coating, which means that it has low emissivity and absorptivity in the IR part of the spectrum. ITO is spectrally selective in the sense that it transmits visible light while reflecting a large fraction of the IR radiation, which is a rare property for surfaces in general but a typical property of thin electrically conducting non-metallic films. It is shown that the application of ITO to poly(methyl methacrylate) (PMMA) significantly improves its fire properties. ITO coating is a mature technology already in widespread use today in the electronics industry.

Keywords
spectral absorptivity, radiative heat transfer, low-e coating, indium tin oxide, thermochromicity, VO2
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-218960 (URN)10.1002/fam.2167 (DOI)000329855700009 ()
Available from: 2014-02-20 Created: 2014-02-20 Last updated: 2017-12-06Bibliographically approved
Nilsson, A. M., Jonsson, J. C. & Roos, A. (2014). Spectrophotometric measurements and ray tracing simulations of mirror light pipes to evaluate the color of the transmitted light. Solar Energy Materials and Solar Cells, 124, 172-179
Open this publication in new window or tab >>Spectrophotometric measurements and ray tracing simulations of mirror light pipes to evaluate the color of the transmitted light
2014 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 124, p. 172-179Article in journal (Refereed) Published
Abstract [en]

Tubular daylighting systems are designed to guide light to the building's core using a highly reflective pipe. The intensity of the transmitted light is essential for the performance of the system. For the qualitative perception of the provided illumination, the color of the delivered light is also an important aspect. For highly reflective mirror light pipes, spectral variations are generally assumed not to affect the color of the transmitted light. Here, spectrophotometric measurements and ray tracing simulations of mirror light pipes are used to verify this commonly made assumption. The characterization methods employ spectral evaluations for both direct and diffuse incident light. The color properties are evaluated for mirror light pipes with a length to diameter aspect ratio of up to 16, using the CIE chromaticity diagram and CIELAB coordinates. For the xy chromaticity diagram, a larger color shift was noted for different illuminants than as a result of the optical properties of the reflective material. Using the CIELAB coordinates, a small color shift was noted for light incident at low solar altitudes. Overall, highly reflective films with spectral variations of a few percent do not markedly affect the color of the transmitted light.

National Category
Energy Engineering
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-183305 (URN)10.1016/j.solmat.2014.01.049 (DOI)000335111000024 ()
Available from: 2012-10-24 Created: 2012-10-24 Last updated: 2017-12-07Bibliographically approved
Magnus, F., Moubah, R., Roos, A. H., Kruk, A., Kapaklis, V., Hase, T., . . . Andersson, G. (2013). Tunable giant magnetic anisotropy in amorphous SmCo thin films. Applied Physics Letters, 102(16), 162402
Open this publication in new window or tab >>Tunable giant magnetic anisotropy in amorphous SmCo thin films
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2013 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 102, no 16, p. 162402-Article in journal (Refereed) Published
Abstract [en]

SmCo thin films have been grown by magnetron sputtering at room temperature with a composition of 2-35 at.% Sm. Films with 5 at.% or higher Sm are amorphous and smooth. A giant tunable uniaxial in-plane magnetic anisotropy is induced in the films which peaks in the composition range 11-22 at.% Sm. This cross-over behavior is not due to changes in the atomic moments but rather the local configuration changes. The excellent layer perfection combined with highly tunable magnetic properties make these films important for spintronics applications. 

National Category
Natural Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-201256 (URN)10.1063/1.4802908 (DOI)000318269300046 ()
Available from: 2013-06-10 Created: 2013-06-10 Last updated: 2017-12-06Bibliographically approved
Yamada, Y., Tajima, K., Okada, M., Tazawa, M., Roos, A. & Yoshimura, K. (2012). Dehydrogenation process of Mg-Ni based switchable mirrors analyzed by in situ spectroscopic ellipsometry. Solar Energy Materials and Solar Cells, 99(SI), 84-87
Open this publication in new window or tab >>Dehydrogenation process of Mg-Ni based switchable mirrors analyzed by in situ spectroscopic ellipsometry
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2012 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 99, no SI, p. 84-87Article in journal (Refereed) Published
Abstract [en]

The dehydrogenation process of hydrogenated switchable mirrors using magnesium-nickel alloy thin film was studied in situ using spectroscopic ellipsometry. Ellipsometric angles Psi and Delta of the switchable mirrors varied drastically as a result of dehydrogenation, which is a transformation from transparent to reflective states. The process was analyzed by dividing into the following three phases. The first phase was the dehydrogenation process of a thin Mg4Ni layer with several nanometers at a hydrogenated Pcl/Mg4Ni interface. The second phase was the dehydrogenation processes of the hydrogenated Mg4Ni layer, which proceeded from the Pd/Mg4Ni interface to the substrate. The final phase was the desorption process of hydrogen, which was absorbed in Mg4Ni as solid solution and the dehydrogenation process was terminated.

Keywords
Switchable mirrors, Mg-Ni alloy, in situ ellipsometry, Dehydrogenation processes, Black state
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-253286 (URN)10.1016/j.solmat.2011.03.035 (DOI)000301167200012 ()
Available from: 2015-05-25 Created: 2015-05-25 Last updated: 2017-12-04Bibliographically approved
Su, R., Kirillin, M., Ekberg, P., Roos, A., Sergeeva, E. & Mattsson, L. (2012). Optical coherence tomography for quality assessment of embedded microchannels in alumina ceramic. Optics Express, 20(4), 4603-4618
Open this publication in new window or tab >>Optical coherence tomography for quality assessment of embedded microchannels in alumina ceramic
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2012 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, no 4, p. 4603-4618Article in journal (Refereed) Published
Abstract [en]

Large-scale and cost-effective manufacturing of ceramic micro devices based on tape stacking requires the development of inspection systems to perform high-resolution in-process quality control of embedded manufactured cavities, metal structures and defects. With an optical coherence tomography (OCT) system operating at 1.3 mu m and a dedicated automated line segmentation algorithm, layer thicknesses can be measured and laser-machined channels can be verified in alumina ceramics embedded at around 100 mu m depth. Monte Carlo simulations are employed to analyze the abilities of OCT in imaging of the embedded channels. The light scattering parameters required as input data for simulations are evaluated from the integrating sphere measurements of collimated and diffuse transmittance spectra using a reconstruction algorithm based on refined diffusion approximation approach.

National Category
Physical Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-173362 (URN)10.1364/OE.20.004603 (DOI)000301041900124 ()
Available from: 2012-04-24 Created: 2012-04-23 Last updated: 2017-12-07Bibliographically approved
Wilson, H. R., Nilsson, A. M., Bretschneider, J., Hoffmann, T., Hutchins, M. G., Jonsson, J., . . . van Nijnatten, P. A. (2012). Transmittance of patterned solar glass panes results of a measurement roud-robin by ICG TC10.11th ESG Conference. In: : . Paper presented at Annical meeting of the EU Society of Glass, Maastricht, The Netherlands, 3-6 June, 2012.
Open this publication in new window or tab >>Transmittance of patterned solar glass panes results of a measurement roud-robin by ICG TC10.11th ESG Conference
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2012 (English)Conference paper, Poster (with or without abstract) (Refereed)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-285903 (URN)
Conference
Annical meeting of the EU Society of Glass, Maastricht, The Netherlands, 3-6 June, 2012
Available from: 2016-04-20 Created: 2016-04-20 Last updated: 2016-04-26
Forsth, M. & Roos, A. (2011). Absorptivity and its dependence on heat source temperature and degree of thermal breakdown. Fire and Materials, 35(5), 285-301
Open this publication in new window or tab >>Absorptivity and its dependence on heat source temperature and degree of thermal breakdown
2011 (English)In: Fire and Materials, ISSN 0308-0501, E-ISSN 1099-1018, Vol. 35, no 5, p. 285-301Article in journal (Refereed) Published
Abstract [en]

The spectral absorptivity of 62 products has been measured in the wavelength region of 0.3-20 mu m. Effective absorptivity for fire-induced heat radiation typically lies in the range of 0.75-0.95. It was found that the effective absorptivity varies significantly with the temperature of the heat source. This has implications on the heating of a surface. The effect is more important when the absorptivity is used as input for calculations of ignition temperature and thermal inertia. It was also found that the absorptivity of radiation from fires for products exposed to irradiation in many cases decreased with increased exposure time. This is surprising since, for example, wood that is darkened when exposed to heat obviously has a higher absorptivity in the visual part of the spectrum than fresh non-darkened wood. The reason that was identified for this is because the absorptivity in the IR drops, and measurement results are given which clearly illustrate this.

Keywords
spectral absorptivity, blackbody temperature, radiative heat transfer, cone calorimeter
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-158606 (URN)10.1002/fam.1053 (DOI)000294175800003 ()
Available from: 2011-09-12 Created: 2011-09-12 Last updated: 2017-12-08Bibliographically approved
Lansåker, P. C., Gunnarsson, K., Roos, A., Niklasson, G. & Granqvist, C.-G. (2011). Au thin films deposited on SnO2:In and glass: Substrate effects on the optical and electrical properties. Thin Solid Films, 519(6), 1930-1933
Open this publication in new window or tab >>Au thin films deposited on SnO2:In and glass: Substrate effects on the optical and electrical properties
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2011 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 519, no 6, p. 1930-1933Article in journal (Refereed) Published
Abstract [en]

We report on a detailed study on the optical and electrical properties of Au films made by sputter deposition onto glass substrates with and without transparent and electrically conducting layers of SnO2:In. The Au films had thicknesses up to 10.7 nm and hence spanned the range for thin film growth from discrete islands, via large scale coalescence and formation of a meandering conducting network, to the formation of a more or less "holey" film. Scanning electron microscopy and atomic force microscopy demonstrated that the SnO2:In films were considerably rougher than the glass itself, and this roughness influenced the Au film formation so that large scale coalescence set in at a somewhat larger thickness for films on SnO2:In than on glass. Measurements of spectral optical transmittance and reflectance and of electrical resistance gave a fully consistent picture that could be reconciled with impeded Au film formation on the SnO2:In layer; this led to pronounced "plateaus" in the near infrared optical spectra for Au films on SnO2:In and a concomitant change from such two-layer films having a lower resistance than the single gold film at thicknesses below large scale coalescence to the opposite behavior for larger film thicknesses. Our work highlights the importance of the substrate roughness for transparent conductors comprising coinage metal films backed by wide band gap transparent conducting oxides.

Keywords
Transparent conductors, Gold films, Indium doped tin oxide, Sputter deposition, Optical properties, Electrical resistance, Thin film growth, Large scale coalescence
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
urn:nbn:se:uu:diva-148464 (URN)10.1016/j.tsf.2010.09.048 (DOI)000287339000028 ()
Available from: 2011-03-08 Created: 2011-03-07 Last updated: 2018-08-30Bibliographically approved
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