35,708 research outputs found
k-dependent SU(4) model of high-temperature superconductivity and its coherent-state solutions
We extend the SU(4) model [1-5] for high-Tc superconductivity to an SU(4)k
model that permits explicit momentum (k) dependence in predicted observables.
We derive and solve gap equations that depend on k, temperature, and doping
from the SU(4)k coherent states, and show that the new SU(4)k model reduces to
the original SU(4) model for observables that do not depend explicitly on
momentum. The results of the SU(4)k model are relevant for experiments such as
ARPES that detect explicitly k-dependent properties. The present SU(4)k model
describes quantitatively the pseudogap temperature scale and may explain why
the ARPES-measured T* along the anti-nodal direction is larger than other
measurements that do not resolve momentum. It also provides an immediate
microscopic explanation for Fermi arcs observed in the pseudogap region. In
addition, the model leads to a prediction that even in the underdoped regime,
there exist doping-dependent windows around nodal points in the k-space, where
antiferromagnetism may be completely suppressed for all doping fractions,
permitting pure superconducting states to exist.Comment: 10 pages, 7 figure
A Learning-Based Steganalytic Method against LSB Matching Steganography
This paper considers the detection of spatial domain least significant bit (LSB) matching steganography in gray images. Natural images hold some inherent properties, such as histogram, dependence between neighboring pixels, and dependence among pixels that are not adjacent to each other. These properties are likely to be disturbed by LSB matching. Firstly, histogram will become smoother after LSB matching. Secondly, the two kinds of dependence will be weakened by the message embedding. Accordingly, three features, which are respectively based on image histogram, neighborhood degree histogram and run-length histogram, are extracted at first. Then, support vector machine is utilized to learn and discriminate the difference of features between cover and stego images. Experimental results prove that the proposed method possesses reliable detection ability and outperforms the two previous state-of-the-art methods. Further more, the conclusions are drawn by analyzing the individual performance of three features and their fused feature
Vector control for a bearingless induction motor based on nonsingular terminal sliding mode structure
© 2017 IEEE. To improve the performance of the bearingless induction motor (BIM) under disturbances, a nonsingular fast terminal sliding mode control (NFTSMC) strategy is proposed. The sliding mode surface is designed as a combination of linear sliding mode and nonsingular terminal sliding mode. Besides, considering the power function of the state variables, which make the approaching speed correlate with the state variables, so as to improve convergence performance of the linear sliding mode and solve the singularity of terminal sliding mode. Meanwhile, current signal and radial force are extracted by the electromagnetic torque and the equation of levitation force. Therefore, the convergence speed of system can be accelerated during the whole process, which contributes to chattering-free operating. The simulation and experiment results indicate that the proposed method can not only track the given value of the speed and radial displacement quickly, but also improve the operation quality and enhance the system robustness
Temperature-dependent gap equations and their solutions in the SU(4) model of high-temperature superconductivity
Temperature-dependent gap equations in the SU(4) model of high-Tc
superconductivity are derived and analytical solutions are obtained. Based on
these solutions, a generic gap diagram describing the features of energy gaps
as functions of doping P is presented and a phase diagram illustrating the
phase structure as a function of temperature T and doping P is sketched. A
special doping point P_q occurs naturally in the solutions that separates two
phases at temperature T = 0: a pure superconducting phase on one side (P > P_q)
and a phase with superconductivity strongly suppressed by antiferromagnetism on
the other (P < P_q). We interpret P_q as a quantum phase transition point.
Moreover, the pairing gap is found to have two solutions for P < P_q: a small
gap that is associated with competition between superconductivity and
antiferromagnetism and is responsible for the ground state superconductivity,
and a large gap without antiferromagnetic suppression that corresponds to a
collective excited state. A pseudogap appears in the solutions that terminates
at P_q and originates from the competition between d-wave superconductivity and
antiferromagnetism. Nevertheless, this conclusion does not contradict the
preformed pair picture conceptually if the preformed pairs are generally
defined as any pairs formed before pairing condensation.Comment: 23 pages, 5 color figure
Space Charge Effect and Mirror Charge Effect in Photoemission Spectroscopy
We report the observation and systematic investigation of the space charge
effect and mirror charge effect in photoemission spectroscopy. When pulsed
light is incident on a sample, the photoemitted electrons experience energy
redistribution after escaping from the surface because of the Coulomb
interaction between them (space charge effect) and between photoemitted
electrons and the distribution of mirror charges in the sample (mirror charge
effect). These combined Coulomb interaction effects give rise to an energy
shift and a broadening which can be on the order of 10 meV for a typical
third-generation synchrotron light source. This value is comparable to many
fundamental physical parameters actively studied by photoemission spectroscopy
and should be taken seriously in interpreting photoemission data and in
designing next generation experiments.Comment: Journal of Electron Spectroscopy and Related Phenomena 142(2004)27-3
Analysis of Pina and Pinb alleles in the micro-core collections of Chinese wheat germplasm by Ecotilling and identification of a novel Pinb allele
Molecular cloning and characterization of two genes - PHKG2 and IRAK4 from black-boned sheep (Ovis aries)
The complete coding sequences of two sheep genes-PHKG2 and IRAK4 were amplified using the rapid amplification of cDNA ends (RACE) method based on three sheep expressed sequence tags whose translated amino acids contain the mitochondrial carrier domain. The sequence analyses of these two genes revealed that the sheep PHKG2 gene encodes a protein of 406 amino acids which has high homology with the phosphorylase kinase, gamma 2 protein of five species: Cattle (99%), human (96%), mouse (92%), rat (91%) and chicken (63%). The sheep IRAK4 gene encodes a protein of 456 amino acids which has high homology with the interleukin-1 receptor-associated kinase 4 protein of six species: Cattle (94%), pig (88%), human (87%), mouse (79%), rat (79%) and chicken (54%). The tissue transcription profile analyses indicated that the Black-boned sheep PHKG2 and IRAK4 genes are generally but differentially expressed in the detected tissues including spleen, muscle, skin, kidney, lung, liver, heart, fat and small intestine. These data serve as a foundation for further insight into these two genes.Key words: Black-boned sheep, PHKG2 and IRAK4, tissue transcription profile
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