793 research outputs found
X-ray photoemission characterization of La_{0.67}(Ca_{x}Sr_{1-x})_{0.33}MnO_{3} films
The Curie temperature and x-ray photoemission spectra of thin films of
La_{0.67}(Ca_{x}Sr_{1-x})_{0.33}MnO_{3} (LCSMO) have been studied as a function
of the Ca/Sr ratio. The films were grown by off-axis cosputtering from
individual targets of La_{0.67}Ca_{0.33}MnO_{3} (LCMO) and
La_{0.67}Sr_{0.33}MnO_{3} (LSMO) onto (100) oriented NdGaO_{3} substrates. The
films grow with a (100) orientation, with no other orientations observed by
x-ray diffraction. For the alloy mixtures, the Curie temperature, T_C, varies
slowly as the Ca/Sr is decreased, remaining 300 K, while for the LCMO
and LSMO films T_C is 260 and 330 K, respectively. The Mn-O valence structure
is composed of two dominant peaks, whose positions undergo a change as the Ca
fraction is decreased. The core lines behave as linear combinations of lines
from pure LCMO and LSMO.Comment: 3 pages, 5 eps figures. To be published in Journal of Applied Physics
(Proceedings of MMM'98
Characterization of transport and magnetic properties in thin film La(0.67)(Ca(x)Sr(1-x))(0.33)MnO(3) mixtures
We have grown thin films of (100) oriented
La_{0.67}(Ca_{x}Sr_{1-x})_{0.33}MnO_{3} on (100) NdGaO_{3} substrates by
off-axis sputtering. We have looked at the changes in the resistivity and
magnetoresistance of the samples as the Ca/Sr ratio was varied. We find that as
the calcium fraction is decreased, the lattice match to the substrate
decreases, and the films become more disordered, as observed in transport
measurements and the variation in Curie and peak resistance temperatures. We
find a correlation between the temperature independent and T^2 terms to the low
temperature resistivity. The room temperature magnetoresistance exhibits a
maximum as the peak temperature is increased by the substitution of Sr for Ca,
and a change in the field dependence to the resistivity at room temperature is
observed.Comment: 5 pages, 6 eps figures, to be published in Journal of Applied Physic
Weak Localization Thickness Measurements of Si:P Delta-Layers
We report on our results for the characterization of Si:P delta-layers grown
by low temperature molecular beam epitaxy. Our data shows that the effective
thickness of a delta-layer can be obtained through a weak localization analysis
of electrical transport measurements performed in perpendicular and parallel
magnetic fields. An estimate of the diffusivity of phosphorous in silicon is
obtained by applying this method to several samples annealed at 850 Celsius for
intervals of zero to 15 minutes. With further refinements, this may prove to be
the most precise method of measuring delta-layer widths developed to date,
including that of Secondary Ion Mass Spectrometry analysis
Extraordinary Magnetoresistance in Hybrid Semiconductor-Metal Systems
We show that extraordinary magnetoresistance (EMR) arises in systems
consisting of two components; a semiconducting ring with a metallic inclusion
embedded. The im- portant aspect of this discovery is that the system must have
a quasi-two-dimensional character. Using the same materials and geometries for
the samples as in experiments by Solin et al.[1;2], we show that such systems
indeed exhibit a huge magnetoresistance. The magnetoresistance arises due to
the switching of electrical current paths passing through the metallic
inclusion. Diagrams illustrating the flow of the current density within the
samples are utilised in discussion of the mechanism responsible for the
magnetoresistance effect. Extensions are then suggested which may be applicable
to the silver chalcogenides. Our theory offers an excellent description and
explanation of experiments where a huge magnetoresistance has been
discovered[2;3].Comment: 12 Pages, 5 Figure
Fast and low cost analysis of dioxin and dioxin-like compounds in marine matrices: final report
0info:eu-repo/semantics/publishe
Nonlocal transport near the charge neutrality point in a two-dimensional electron-hole system
Nonlocal resistance is studied in a two-dimensional system with a
simultaneous presence of electrons and holes in a 20 nm HgTe quantum well. A
large nonlocal electric response is found near the charge neutrality point
(CNP) in the presence of a perpendicular magnetic field. We attribute the
observed nonlocality to the edge state transport via counter propagating chiral
modes similar to the quantum spin Hall effect at zero magnetic field and
graphene near Landau filling factor Comment: 5 pages, 4 figure
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Tight bounds on the size of neural networks for classification problems
This paper relies on the entropy of a data-set (i.e., number-of-bits) to prove tight bounds on the size of neural networks solving a classification problem. First, based on a sequence of geometrical steps, the authors constructively compute an upper bound of O(mn) on the number-of-bits for a given data-set - here m is the number of examples and n is the number of dimensions (i.e., R{sup n}). This result is used further in a nonconstructive way to bound the size of neural networks which correctly classify that data-set
Batch Adsorber based PSA Model for Rapid and Efficient Screening of Adsorbents in Post-Combustion CO2 Capture
The adsorption-based CO capture has shown promising potential overcoming the limitations posed by commercialised solvent amine-based systems. The choice of an adsorbent is critical to the design of pressure swing adsorption (PSA) processes. Since adsorption processes are cyclic, their design and optimization are computationally challenging. Hence, simple models that capture the essential process characteristics are required for rapid screening of adsorbents. The objective of this work is to come up with a simplified process design model for PSA process which could reliably screen the adsorbents at a faster rate. The model considers only a batch adsorber thereby significantly reducing the complexity, allowing for rapid computation. The model is used to estimate CO purity, recovery and energy consumption. The model results are compared with detailed process optimizations to develop a classification metric to identify adsorbents that satisfy U. S. Department of Energy’s requirement for CO capture processes. The model is then used to screen favourable adsorbents from a set of 100+ real and hypothetical adsorbents. The results indicate that the batch adsorber model can be used for screening a large database of adsorbents in a fast and efficient manner.Fil: Subramanian Balashankar, V.. University of Alberta; CanadáFil: De Pauw, R.. University of Alberta; CanadáFil: Rajagopalan, A. K.. University of Alberta; CanadáFil: Avila, Adolfo MarÃa. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - Tucumán. Instituto de QuÃmica del Noroeste. Universidad Nacional de Tucumán. Facultad de BioquÃmica, QuÃmica y Farmacia. Instituto de QuÃmica del Noroeste; ArgentinaFil: Rajendran, A.. University of Alberta; CanadáXXIX Interamerican Congress of Chemical EngineeringTorontoCanadáCanadian Society for Chemical Engineerin
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