Search results for "Layer thickness"
showing 10 items of 19 documents
Existence and Singularities for the Prandtl Boundary Layer Equations
2000
Prandtl's boundary layer equations, first formulated in 1904, resolve the differences between the viscous and inviscid description of fluid flows. This paper presents a review of mathematical results, both analytic and computational, on the unsteady boundary layer equations. This includes a review of the derivation and basic properties of the equations, singularity formation, well-posedness results, and infinite Reynolds number limits.
A Simple Apparatus for the Determination of the Optical Constants and the Thickness of Absorbing Thin Films
2001
We report on a simple and inexpensive apparatus useful for measuring the optical constants n, k and the thickness of weakly absorbing thin films. The measurement is based on an accurate determination of the reflectance and transmittance of a specimen illuminated by a laser beam. The laser beam is incident on a transparent substrate coated with the film to be evaluated, with an angle of incidence equal to the Brewster angle for the substrate, and its polarization can be switched between the p and s states. If the thickness is known to be within a presumptive range, measurements of the p and s reflectance and transmittance allow a calculation of the optical constants n, k and the thickness of…
Über die Verwendung von homogenen azeotropen Gemischen in der Dünnschichtchromatographie 8. Mitt.: Gaschromatographische Untersuchung einiger Fließmi…
1970
Homogene azeotrope Gemische wurden vor und nach ihrer Benutzung als Fliesmittel in der DC gaschromatographisch untersucht. Hierbei zeigte sich, das bei hohem Anteil an polaren Komponenten (> 15%) keine veranderung in der Zusammensetzung der Fliesmittel eintrat. Eine gewisse Abreicherung der polaren Komponenten war jedoch festzustellen, wenn deren Anteil klein sowie der Polaritatsunterschied der Einzelkomponenten gros war und die DC-Platten eine grosere Schichtdicke als 0,1 mm besasen. Homogeneous Azeotropic Mixtures in Thin-layer Chromatography Homogeneous azeotropic mixtures have been analyzed by gas chromatography before and after they were used as solvents in TLC. If polar components wer…
A study of hydrothermal convection in saturated porous media
1993
Abstract Because of its relevance to many geological and technical problems, hydrothermal convection is investigated here mainly with the aid of numerical models by a systematic analysis of the properties of this type of convection for a range of super-critical Rayleigh numbers. Calculations were performed for two-dimensional models with constant properties in a region of aspect ratio 2. The principal results in the case of temperature fixed at the impermeable top and bottom are the following for the Nusselt number Nu, the cell aspect ratio a, and the boundary layer thickness δ: Nu ≈ 1.7 R0.5, a ≈ 1.3 R−0.4, δc ≈ 0.4 R−0.4 for 2.5 R = R f /R f ∗ and Rf and R f ∗ are the ambient and critical…
Breakdown of Burton-Prime-Slichter approach and lateral solute segregation in radially converging flows
2005
A theoretical study is presented of the effect of a radially converging melt flow, which is directed away from the solidification front, on the radial solute segregation in simple solidification models. We show that the classical Burton-Prim-Slichter (BPS) solution describing the effect of a diverging flow on the solute incorporation into the solidifying material breaks down for the flows converging along the solidification front. The breakdown is caused by a divergence of the integral defining the effective boundary layer thickness which is the basic concept of the BPS theory. Although such a divergence can formally be avoided by restricting the axial extension of the melt to a layer of fi…
Tripotential data processing for HES interpretation
1994
In this paper some methods are proposed and compared to correct the experimental measurements for preliminary processing of tripotential data which are acquired for HES prospecting. However, the use of those methods should be based upon an accurate analysis of all experimental data. Such an analysis ought to involve: 1) an estimate of the averaged measurement errors with their variance and distribution in both the space and the three apparent-resistivities domains; 2) the choice of a resistivity model capable of describing the actual volume under study. The differences among the three values of apparent resistivity measured on a point are generally influenced both by the resistivity distrib…
Experimental characterisation of the CIRA plasma wind tunnel SCIROCCO test section
2008
Abstract During the Validation Phase of the CIRA-PWT SCIROCCO Facility located at Capua (Italy), a test campaign has been carried out to verify the performances of the facility with the use of the two conical nozzle configurations “D” and “F” with exit diameters are, respectively of, 1150 and 1950 mm. For the first time the data results of the tests have been used to characterize the plasma flow in the test section of the facility. In particular, analytical relationships between the main thermo-fluid-dynamic parameters in the test section and the reservoir conditions of the facility have been found, and compared to the CFD prediction developed during the Design Phase of the facility. Very i…
Polarization-sensitive hyperspectral imaging of human skin: From system design to clinical validation (Conference Presentation)
2020
We present the development and validation of a new approach for quantitative functional imaging of human skin based on the machine learning technique for the analysis of the hyperspectral skin images. The considered skin parameters include blood volume fraction, blood oxygenation, melanin content, and the epidermal layer thickness. Additionally, the degree of residual polarization of the reflected light has been analyzed. The validity of the approach has been confirmed by the initial preclinical tests with the tissue-mimicking phantoms, functional in-vivo skin tests, and pilot clinical study of type II diabetic patients. The proposed technique has great potential to be implemented in clinic…
Group analysis and similarity solutions of the compressible boundary layer equations
1989
In this paper the application of Lie's methods to the equations of the laminar boundary layer is discussed. The momentum and energy equations in Prandtl's form are considered for a steady, viscous, compressible laminar flow with non zero pressure gradient, variable viscosity and thermal conductivity. Group analysis yields similarity solutions for given pressure distributions and particular values of the invariance group parameters (group classification). Crocco's transformation is obtained for the infinite-dimensional group of the Lie's algebra admitted by the equations.
Materials, Techniques, and Conservation of Historic Stained Glass “Grisailles”
2015
A grisaille is a brown-blackish paint applied onto the inner surface of stained glass to draw the contours and details of the figures and to produce the effect of shades and volumes. Grisailles were traditionally made of finely ground oxides of iron but also of copper, zinc, lead, or manganese mixed with a flux such as lead ground glass and a binder and fixed onto the flat glass by firing. The grisailles have typical layer thickness varying between 10 and 100 µm and are formed by a complex mixture of pigment particles, crystalline, and amorphous reaction compounds, aging, and weathering compounds. The high brilliance, collimation, energy selection, and monochromacity of the SR beam are idea…