6,235 research outputs found
Anisotropic Electron Spin Lifetime in (In,Ga)As/GaAs (110) Quantum Wells
Anisotropic electron spin lifetimes in strained undoped (In,Ga)As/GaAs (110)
quantum wells of different width and height are investigated by time-resolved
Faraday rotation and time-resolved transmission and are compared to the
(001)-orientation. From the suppression of spin precession, the ratio of
in-plane to out-of-plane spin lifetimes is calculated. Whereas the ratio
increases with In concentration in agreement with theory, a surprisingly high
anisotropy of 480 is observed for the broadest quantum well, when expressed in
terms of spin relaxation times.Comment: 4 pages, 4 figures, revise
Fractal Descriptors in the Fourier Domain Applied to Color Texture Analysis
The present work proposes the development of a novel method to provide
descriptors for colored texture images. The method consists in two steps. In
the first, we apply a linear transform in the color space of the image aiming
at highlighting spatial structuring relations among the color of pixels. In a
second moment, we apply a multiscale approach to the calculus of fractal
dimension based on Fourier transform. From this multiscale operation, we
extract the descriptors used to discriminate the texture represented in digital
images. The accuracy of the method is verified in the classification of two
color texture datasets, by comparing the performance of the proposed technique
to other classical and state-of-the-art methods for color texture analysis. The
results showed an advantage of almost 3% of the proposed technique over the
second best approach.Comment: Chaos, Volume 21, Issue 4, 201
Dynamic quantum clustering: a method for visual exploration of structures in data
A given set of data-points in some feature space may be associated with a
Schrodinger equation whose potential is determined by the data. This is known
to lead to good clustering solutions. Here we extend this approach into a
full-fledged dynamical scheme using a time-dependent Schrodinger equation.
Moreover, we approximate this Hamiltonian formalism by a truncated calculation
within a set of Gaussian wave functions (coherent states) centered around the
original points. This allows for analytic evaluation of the time evolution of
all such states, opening up the possibility of exploration of relationships
among data-points through observation of varying dynamical-distances among
points and convergence of points into clusters. This formalism may be further
supplemented by preprocessing, such as dimensional reduction through singular
value decomposition or feature filtering.Comment: 15 pages, 9 figure
Positions of septal papillary muscles in human hearts
Septal papillary muscles, similarly to other papillary muscles, are essential elements
of the heart valvular system. Damage to their structure may lead to
a considerable life risk.
Of all the papillary muscles, the septal papillary muscles are characterized by
the greatest topographical and morphological variability. However, information
about these muscles is scarce and fragmentary. The objective of this study
was to ascertain their occurrence and the region in which they are placed in
the inter-ventricular septum.
One hundred and eleven human hearts were examined. The hearts belonged
to the Clinical Anatomy Department of the Medical University of Gdańsk. They
were fixed in formalin with ethanol and came from middle-aged and older
individuals of both sexes, devoid of pathological changes and birth defects.
During the tests, classic anatomical methods were applied.
The region where the papillary muscles are found covers a sizeable surface of
the septum, from the conus arteriosus up to the back angle of the right chamber.
Depending on their location the following septal papillary muscles (musculi
papillares septales, MPS) were singled out: 1) lying on the front wall of the
septum (anterior papillares septales), 2) in the central part of the septum (central
muscles), and 3) in the posterior section of the septum (posterior papillares
septales). A trial to determine the types of MPS was based on this diversity of
location. Consequently, five types of MPS were specified: type I: anterior-central
(44.1%); type II: anterior (15.3%); type III: anterior-posterior (13.5%); type IV:
anterior-central-posterior (24.3%); and type V: uniform (2.75%).
This study is an attempt to systematize and standardize the terminology of
these structures. (Folia Morphol 2010; 69, 2: 101-106
Research and applications: Artificial intelligence
The program is reported for developing techniques in artificial intelligence and their application to the control of mobile automatons for carrying out tasks autonomously. Visual scene analysis, short-term problem solving, and long-term problem solving are discussed along with the PDP-15 simulator, LISP-FORTRAN-MACRO interface, resolution strategies, and cost effectiveness
Population inversion of a NAHS mixture adsorbed into a cylindrical pore
A cylindrical nanopore immersed in a non-additive hard sphere binary fluid is
studied by means of integral equation theories and Monte Carlo simulations. It
is found that at low and intermediate values of the bulk total number density
the more concentrated bulk species is preferentially absorbed by the pore, as
expected. However, further increments of the bulk number density lead to an
abrupt population inversion in the confined fluid and an entropy driven
prewetting transition at the outside wall of the pore. These phenomena are a
function of the pore size, the non-additivity parameter, the bulk number
density, and particles relative number fraction. We discuss our results in
relation to the phase separation in the bulk.Comment: 7 pages, 8 Figure
Camera distortion self-calibration using the plumb-line constraint and minimal Hough entropy
In this paper we present a simple and robust method for self-correction of
camera distortion using single images of scenes which contain straight lines.
Since the most common distortion can be modelled as radial distortion, we
illustrate the method using the Harris radial distortion model, but the method
is applicable to any distortion model. The method is based on transforming the
edgels of the distorted image to a 1-D angular Hough space, and optimizing the
distortion correction parameters which minimize the entropy of the
corresponding normalized histogram. Properly corrected imagery will have fewer
curved lines, and therefore less spread in Hough space. Since the method does
not rely on any image structure beyond the existence of edgels sharing some
common orientations and does not use edge fitting, it is applicable to a wide
variety of image types. For instance, it can be applied equally well to images
of texture with weak but dominant orientations, or images with strong vanishing
points. Finally, the method is performed on both synthetic and real data
revealing that it is particularly robust to noise.Comment: 9 pages, 5 figures Corrected errors in equation 1
QL-CONST1: an expert system for quality level prediction in concrete structures
Current trends in the fields of artifical intelligence and expert systems are moving towards the exciting possibility of reproducing and simulating human expertise and expert behaviour into a knowledge base, coupled with an appropriate, partially ‘intelligent’, computer code. This paper deals with the quality level prediction in concrete structures using the helpful assistance of an expert system, QL-CONST1, which is able to reason about this specific field of structural engineering. Evidence, hypotheses and factors related to this human knowledge field have been codified into a knowledge base. This knowledge base has been prepared in terms of probabilities of the presence of either hypotheses or evidence and the conditional presence of both. Human experts in the fields of structural engineering and the safety of structures gave their invaluable knowledge and assistance to the construction of the knowledge base. Some illustrative examples for, the validation of the expert system behaviour are included
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