2,889 research outputs found
Theory of electron transport in normal metal/superconductor junctions
On the basis of the Keldysh method of non-equilibrium systems, we develop a
theory of electron tunneling in normal-metal/superconductor junctions. By using
the tunneling Hamiltonian model (being appropriate for the tight-binding
systems), the tunneling current can be exactly obtained in terms of the
equilibrium Green functions of the normal metal and the superconductor. We
calculate the conductance of various junctions. The discrepancy between the
present treatment and the well-known scheme by Blonder, Tinkham, and Klapwijk
is found for some junctions of low interfacial potential barrier.Comment: 5 pages, 4 figure
Structural Stability of Lexical Semantic Spaces: Nouns in Chinese and French
Many studies in the neurosciences have dealt with the semantic processing of
words or categories, but few have looked into the semantic organization of the
lexicon thought as a system. The present study was designed to try to move
towards this goal, using both electrophysiological and corpus-based data, and
to compare two languages from different families: French and Mandarin Chinese.
We conducted an EEG-based semantic-decision experiment using 240 words from
eight categories (clothing, parts of a house, tools, vehicles,
fruits/vegetables, animals, body parts, and people) as the material. A
data-analysis method (correspondence analysis) commonly used in computational
linguistics was applied to the electrophysiological signals.
The present cross-language comparison indicated stability for the following
aspects of the languages' lexical semantic organizations: (1) the
living/nonliving distinction, which showed up as a main factor for both
languages; (2) greater dispersion of the living categories as compared to the
nonliving ones; (3) prototypicality of the \emph{animals} category within the
living categories, and with respect to the living/nonliving distinction; and
(4) the existence of a person-centered reference gradient. Our
electrophysiological analysis indicated stability of the networks at play in
each of these processes. Stability was also observed in the data taken from
word usage in the languages (synonyms and associated words obtained from
textual corpora).Comment: 17 pages, 4 figure
Learning One-Class Hyperspectral Classifier from Positive and Unlabeled Data for Low Proportion Target
Hyperspectral imagery (HSI) one-class classification is aimed at identifying
a single target class from the HSI by using only positive labels, which can
significantly reduce the requirements for annotation. However, HSI one-class
classification is far more challenging than HSI multi-class classification, due
the lack of negative labels and the low target proportion, which are issues
that have rarely been considered in the previous HSI classification studies. In
this paper, a weakly supervised HSI one-class classifier, namely HOneCls is
proposed to solve the problem of under-fitting of the positive class occurs in
the HSI data with low target proportion, where a risk estimator -- the
One-Class Risk Estimator -- is particularly introduced to make the full
convolutional neural network (FCN) with the ability of one class
classification. The experimental results obtained on challenging hyperspectral
classification datasets, which includes 20 kinds of ground objects with very
similar spectra, demonstrate the efficiency and feasibility of the proposed
One-Class Risk Estimator. Compared with the state-of-the-art one-class
classifiers, the F1-score is improved significantly in the HSI data with low
target proportion
Prediction of fully metallic {\sigma}-bonded boron framework induced high superconductivity above 100 K in thermodynamically stable Sr2B5 at 40 GPa
Metal borides have been considered as potential high-temperature
superconductors since the discovery of record-holding 39 K superconductivity in
bulk MgB2. In this work, we identified a superconducting yet thermodynamically
stable F43m Sr2B5 at 40 GPa with a unique covalent sp3-hybridized boron
framework through extensive first-principles structure searches. Remarkably,
solving the anisotropic Migdal-Eliashberg equations resulted in a high
superconducting critical temperature (Tc) around 100 K, exceeding the boiling
point (77 K) of liquid nitrogen. Our in-depth analysis revealed that the
high-temperature superconductivity mainly originates from the strong coupling
between the metalized {\sigma}-bonded electronic bands and E phonon modes of
boron atoms. Moreover, anharmonic phonon simulations suggest that F43m Sr2B5
might be recovered to ambient pressure. Our current findings provide a
prototype structure with a full {\sigma}-bonded boron framework for the design
of high-Tc superconducting borides that may expand to a broader variety of
lightweight compounds.Comment: 5 page
Editorial: Episodic plate destruction and construction in Southeast Asia: observations, modeling, and case studies
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