99,201 research outputs found
Experience in the use of engineering product design principles to extend novice engineer capability
Thermopower Oscillation Symmetries in a Double-Loop Andreev Interferrometer
Andreev interferometers, normal metal wires coupled to superconducting loops,
display phase coherent changes as the magnetic flux through the superconducting
loops is altered. Properties such as the electronic and thermal conductance of
these devices have been shown to oscillate symmetrically about zero with a
period equal to one superconducting flux quantum, . However, the
thermopower of these devices can oscillate symmetrically or antisymmetrically
depending on the geometry of the sample, a phenomenon not well understood
theoretically. Here we report on thermopower measurements of a double-loop
Andreev interferometer where two Josephson currents in the normal metal wire
may be controlled independently. The amplitude and symmetries of the observed
thermopower oscillations may help to illuminate the unexplained dependence of
oscillation symmetry on sample geometry.Comment: 6 Pages, 5 figures, to appear in Physica
Medical imaging analysis with artificial neural networks
Given that neural networks have been widely reported in the research community of medical imaging, we provide a focused literature survey on recent neural network developments in computer-aided diagnosis, medical image segmentation and edge detection towards visual content analysis, and medical image registration for its pre-processing and post-processing, with the aims of increasing awareness of how neural networks can be applied to these areas and to provide a foundation for further research and practical development. Representative techniques and algorithms are explained in detail to provide inspiring examples illustrating: (i) how a known neural network with fixed structure and training procedure could be applied to resolve a medical imaging problem; (ii) how medical images could be analysed, processed, and characterised by neural networks; and (iii) how neural networks could be expanded further to resolve problems relevant to medical imaging. In the concluding section, a highlight of comparisons among many neural network applications is included to provide a global view on computational intelligence with neural networks in medical imaging
Laser-catalyzed spin-exchange process in a Bose-Einstein condensate
We show theoretically that it is possible to optically control collective
spin-exchange processes in spinor Bose condensates through virtual
photoassociation. The interplay between optically induced spin exchange and
spin-dependent collisions provides a flexible tool for the control of atomic
spin dynamics, including enhanced or inhibited quantum spin oscillations, the
optically-induced ferromagnetic-to-antiferromagnetic transition, and coherent
matter-wave spin conversion.Comment: 4 pages, 4 figure
Querying Geometric Figures Using a Controlled Language, Ontological Graphs and Dependency Lattices
Dynamic geometry systems (DGS) have become basic tools in many areas of
geometry as, for example, in education. Geometry Automated Theorem Provers
(GATP) are an active area of research and are considered as being basic tools
in future enhanced educational software as well as in a next generation of
mechanized mathematics assistants. Recently emerged Web repositories of
geometric knowledge, like TGTP and Intergeo, are an attempt to make the already
vast data set of geometric knowledge widely available. Considering the large
amount of geometric information already available, we face the need of a query
mechanism for descriptions of geometric constructions.
In this paper we discuss two approaches for describing geometric figures
(declarative and procedural), and present algorithms for querying geometric
figures in declaratively and procedurally described corpora, by using a DGS or
a dedicated controlled natural language for queries.Comment: 14 pages, 5 figures, accepted at CICM 201
Hartree-Fock calculations of a finite inhomogeneous quantum wire
We use the Hartree-Fock method to study an interacting one-dimensional
electron system on a finite wire, partially depleted at the center by a smooth
potential barrier. A uniform one-Tesla Zeeman field is applied throughout the
system. We find that with the increase in the potential barrier, the low
density electrons under it go from a non-magnetic state to an antiferromagnetic
state, and then to a state with a well-localized spin-aligned region isolated
by two antiferromagnetic regions from the high density leads. At this final
stage, in response to a continuously increasing barrier potential, the system
undergoes a series of abrupt density changes, corresponding to the successive
expulsion of a single electron from the spin-aligned region under the barrier.
Motivated by the recent momentum-resolved tunneling experiments in a parallel
wire geometry, we also compute the momentum resolved tunneling matrix elements.
Our calculations suggest that the eigenstates being expelled are spatially
localized, consistent with the experimental observations. However, additional
mechanisms are needed to account for the experimentally observed large spectral
weight at near in the tunneling matrix elements.Comment: 10 pages, 14 figure
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