Unsteady free convective flow and mass transfer through a porous medium bounded by an infinite vertical limiting surface with constant suction and time-dependent temperature

In this work an analysis of the two-dimensional unsteady free convective flow and mass transfer is given, for an incompressible viscous fluid through a porous medium bounded by an infinite vertical limiting surface. The suction velocity perpendicular to the limiting surface is constant and the temperature of the limiting surface fluctuates with time about a non-zero constant mean. Expressions for the velocity, temperature and concentration fields are obtained and the effects of the various parameters of the problem, e.g. modified Grashoff number, permeability of the porous medium and the frequency on the velocity field are discussed.     

The boson peak in Raman spectra of As<Subscript>x</Subscript>S<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript> glasses

The Raman spectra of As_xS_1?x glasses with x < 40 at % (Z < 2.4) have been studied in a wide temperature range (20–300 K). A well resolved boson peak is observed in the low-frequency portion of the spectrum, not withstanding the appearance of floppy modes in the glasses under study. It is shown that the boson peak is characterized by two parameters: intensity and the peak position. A comparison of the intensity variation for the boson peaks indicates that the degree of disorder increases as x decreases. This effect is caused by floppy modes in the glass network and by sulfur phase separation. Studies of reduced boson peaks in the Raman spectra of As_xS_1?x glasses confirms the theoretical assumption that the shape of the peaks is independent of composition and temperature.     

Role of rotation and hall currents on free convection and mass transfer flow through a porous medium

Effects of Hall current and rotation on free convection and mass transfer flow through a porous medium bounded by a vertical surface have been analysed. The problem is solved analytically. The velocity profiles are shown on graphs. Effects of m (Hall parameter), K★ (permeability parameter), E (Ekman number) and Sc (Schmidt number) on velocity are discussed.     

Multiwavelength interferometry and competing optical methods for the thermal probing of thin polymeric films

Multiple‐wavelength interferometry (MWI), a new optical method for the thermal probing of thin polymer films, is introduced and explored. MWI is compared with two standard optical methods, single‐wavelength interferometry and spectroscopic ellipsometry, with regard to the detection of the glass transition temperature (T_g) of thin supported polymer films. Poly(methyl methacrylate) films are deposited by spin coating on Si and SiO₂ substrates. MWI is also applied to the study of the effect of film thickness (25–600 nm) and polymer molecular weight (1.5 × 10⁴ to 10⁶) on T_g, the effect of film thickness on the coefficients of thermal expansion both below and above T_g, and the effect of deep UV exposure time on the thermal properties (glass transition and degradation temperatures) of the films. This further exploration of the MWI method provides substantial insights about intricate issues pertinent to the thermal behavior of thin polymer films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4764–4774, 2006     

Polymer-BaTiO3 composites: Dielectric constant and vapor sensing properties in chemocapacitor applications

In this work, composite materials, prepared by inclusion of various amounts of BaTiO₃ nanoparticles in PBMA and PHEMA polymer matrices, were characterized in respect to their dielectric properties and then used as the sensing layer of capacitive-type sensors. BaTiO₃ was found to be less effective in enhancing the permittivity of PHEMA, as compared to PBMA, in the range of 1 kHz–1 MHz, possibly due to the observed lower quality of dispersion in the polymer matrix and the higher polarity of the polymer in the former case. The response of the composite-based chemocapacitors to four vapor analytes, covering a wide range of dielectric constants, was studied in relation to the BaTiO₃ load. In all cases, with increasing amount of BaTiO₃ load, the absolute value of capacitance response was increased, due to the corresponding increase of the initial capacitance of the sensing composite layer. However, the corresponding normalized (to the initial capacitance of the sensing composite layer) capacitance values were reduced, due to the decreased volume fraction of the sorbing polymer material in the composite matrix. An exception to this trend, observed upon exposure of the PBMA/BaTiO₃ chemocapacitors to low humidity levels, is also presented and discussed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The potential of kernel classification techniques for land use mapping in urban areas using 5m-spatial resolution IRS-1C imagery

Two techniques, integrating texture and spatial context properties for the classification of fine spatial resolution imagery from the city of Athens (Hellas) have been tested in terms of accuracy and class specificity. Both techniques were kernel based, using an artificial neural network and the kernel reclassification algorithm. The study demonstrated the high potential of the kernel classifiers to discriminate residential categories on 5 m-spatial resolution imagery. The overall accuracy percentages achieved were 73.44% and 74.22% respectively, considering a seven-class classification scheme. The adopted scheme was subset of the nomenclature referred to as 'Classification for Land Use Statistics Eurostat's Remote Sensing programme' (CLUSTERS) used by the Statistical Office of the European Communities (EUROSTAT) to map urban and rural environment.     

Diffusion model of radon exhalation rates

Radon migration through walls is considered using an effective diffusion model. One and two dimensional models as well as a spherical geometry are compared. It is concluded that either the 1-dimensional or spherical model, both having analytical solution, may be used for practical purposes. Application is made for typical cases in Athens, Greece.