1,640 research outputs found
Ellipsometric measurements of epitaxial GaAs layers on a GaAs substrate
An extensive examination of ellipsometric equations for anisotropic surfaces and films is reported. It is shown that the reflection matrix can be calculated by writing Maxwell's equations in 6 x 6 matrix form and by applying appropriate boundary conditions at proper points in the development of the formalism, reducing the equation for the propagation of light to an eigenvalue problem using a 4 x 4 matrix
Development of Surfaces Optically Suitable for Flat Solar Panels
Three areas of research in the development of flat solar panels are described. (1) A reflectometer which can separately evaluate the spectral and diffuse reflectivities of surfaces was developed. The reflectometer has a phase locked detection system. (2) A coating composed of strongly bound copper oxide that is formed by an etching process performed on an aluminum alloy with high copper content was also developed. Because of this one step fabrication process, fabrication costs are expected to be small. (3) A literature search was conducted and conclusions on the required optical properties of flat plate solar collectors are presented
Development of Surfaces Optically Suitable for Flat Solar Panels
Innovations in reflectometry techniques are described; and the development of an absorbing selective coating is discussed along with details of surface properties. Conclusions as to the parameterization desired for practical applications of selective surfaces are provided
Comparison of numerical prediction techniques for sound propagation in complex outdoor environments
Extending the functionalities of shear-driven chromatography nano-channels using high aspect ratio etching
An new injection system is presented for shear-driven chromatography. The device has been fabricated by high aspect ratio etching of silicon. The performance of the injection slit is studied through the aid of computational fluid dynamics, and the first experimental results are presented
Alignment and algebraically special tensors in Lorentzian geometry
We develop a dimension-independent theory of alignment in Lorentzian
geometry, and apply it to the tensor classification problem for the Weyl and
Ricci tensors. First, we show that the alignment condition is equivalent to the
PND equation. In 4D, this recovers the usual Petrov types. For higher
dimensions, we prove that, in general, a Weyl tensor does not possess aligned
directions. We then go on to describe a number of additional algebraic types
for the various alignment configurations. For the case of second-order
symmetric (Ricci) tensors, we perform the classification by considering the
geometric properties of the corresponding alignment variety.Comment: 19 pages. Revised presentatio
Biodiversity and climate change: Risks to dwarf succulents in Southern Africa.
The aim of this study was to explore the effects of anthropogenic climate change on the dwarf succulent genus Conophytum (Aizoaceae) within areas recognised for their floral biodiversity, namely the Succulent Karoo, Fynbos, Desert and Nama Karoo biomes of South Africa and Namibia. Niche-based modelling was used to identify the key climatic and geological variables influencing the distribution of members of the genus Conophytum. The distribution of the genus is primarily controlled by a small number of environmental variables, notably winter and summer rainfall levels, together with geology. Assuming a zero-dispersal model, the predicted effect of both the A1B and A2 climatic emission scenarios was a severe contraction in the area satisfying the bioclimatic envelope for the genus coupled with significant range dislocation. Reductions of >90% in suitable habitat for 10 of the 16 taxonomic Sections that comprise the genus and represent >80% of taxa under the A2 scenario are predicted. Under A1B the projected effects are ameliorated, but reductions of >50% of habitat can be seen in a majority of Sections. Significant projected reductions in the habitable bioclimatic envelope are very likely to increase risk of extinction of ~80% of taxa even under a partly mitigated emissions scenario
The kinetic plot method applied to gradient chromatography: theoretical framework and experimental validation
VITO combineert sensorplatformen met aardobservatie voor een betere monitoring van water
De huidige systemen om de toestand van het water op te volgen, voldoen vaak niet aan de noden van waterbeheerders, baggeraars, waterbedrijven, havenbeheerders, enzovoort. De data schieten tekort in kwaliteit en kwantiteit. Daarom ontwikkelt VITO een monitoringssysteem dat geautomatiseerde sensoren op onbemande vaartuigen combineert met aardobservatie: SAVEWATER. Ook het beschikbaar stellen van de data maakt deel uit van dit systeem. Het project wordt samen met de Europese ruimtevaartorganisatie ESA uitgewerkt
- …