17,648 research outputs found
Calculated Momentum Dependence of Zhang-Rice States in Transition Metal Oxides
Using a combination of local density functional theory and cluster exact
diagonalization based dynamical mean field theory, we calculate many body
electronic structures of several Mott insulating oxides including undoped high
T_{c} materials. The dispersions of the lowest occupied electronic states are
associated with the Zhang-Rice singlets in cuprates and with doublets,
triplets, quadruplets and quintets in more general cases. Our results agree
with angle resolved photoemission experiments including the decrease of the
spectral weight of the Zhang--Rice band as it approaches k=0
Retrieval of phase memory in two independent atomic ensembles by Raman process
In spontaneous Raman process in atomic cell at high gain, both the Stokes
field and the accompanying collective atomic excitation (atomic spin wave) are
coherent. We find that, due to the spontaneous nature of the process, the
phases of the Stokes field and the atomic spin wave change randomly from one
realization to another but are anti-correlated. The phases of the atomic
ensembles are read out via another Raman process at a later time, thus
realizing phase memory in atoms. The observation of phase correlation between
the Stokes field and the collective atomic excitations is an important step
towards macroscopic EPR-type entanglement of continuous variables between light
and atoms
Online optimization of visual stimuli for reducing fatigue in SSVEP-based BCIs
INTRODUCTION: Visual fatigue induced by flickering stimuli has always been a problem to steady state visual evoked potential (SSVEP)-based brain-computer interfaces (BCIs). Some previous studies revealed that different stimulation properties such as frequencies, duty cycles and colors have impact on user’s fatigue and performance. Importantly, the stimulation inducing less fatigue usually causes a reduction of system performance [1], and thus to design an optimal visual stimulator for SSVEP-based BCIs, there is a tradeoff between the user’s fatigue and performance. Unfortunately, so far most of the visual fatigue evaluation methods relied on subjective ...published_or_final_versio
Fatigue evaluation through EEG analysis using multi-scale entropy in SSVEP-based BCIs
INTRODUCTION: Fatigue is a big challenge when moving a steady state visual evoked potential (SSVEP) based brain-computer interfaces (BCIs) from laboratory into real-life applications [1], as it not only harms the system performance, but also causes users’ discomfort. Towards eventually fatigue reduction, an accurate and objective evaluation of fatigue level is the first and also a crucial step. On the other hand, multi-scale entropy (MSE) can ...published_or_final_versio
Fluctuation of Conductance Peak Spacings in Large Semiconductor Quantum Dots
Fluctuation of Coulomb blockade peak spacings in large two-dimensional
semiconductor quantum dots are studied within a model based on the
electrostatics of several electron islands among which there are random
inductive and capacitive couplings. Each island can accommodate electrons on
quantum orbitals whose energies depend also on an external magnetic field. In
contrast with a single island quantum dot, where the spacing distribution is
close to Gaussian, here the distribution has a peak at small spacing value. The
fluctuations are mainly due to charging effects. The model can explain the
occasional occurrence of couples or even triples of closely spaced Coulomb
blockade peaks, as well as the qualitative behavior of peak positions with the
applied magnetic field.Comment: 13 pages, 4 figures, accepted for publication in PR
Damage-free single-mode transmission of deep-UV light in hollow-core PCF
Transmission of UV light with high beam quality and pointing stability is
desirable for many experiments in atomic, molecular and optical physics. In
particular, laser cooling and coherent manipulation of trapped ions with
transitions in the UV require stable, single-mode light delivery. Transmitting
even ~2 mW CW light at 280 nm through silica solid-core fibers has previously
been found to cause transmission degradation after just a few hours due to
optical damage. We show that photonic crystal fiber of the kagom\'e type can be
used for effectively single-mode transmission with acceptable loss and bending
sensitivity. No transmission degradation was observed even after >100 hours of
operation with 15 mW CW input power. In addition it is shown that
implementation of the fiber in a trapped ion experiment significantly increases
the coherence times of the internal state transfer due to an increase in beam
pointing stability
Classification of Overlapped Audio Events Based on AT, PLSA, and the Combination of Them
Audio event classification, as an important part of Computational Auditory Scene Analysis, has attracted much attention. Currently, the classification technology is mature enough to classify isolated audio events accurately, but for overlapped audio events, it performs much worse. While in real life, most audio documents would have certain percentage of overlaps, and so the overlap classification problem is an important part of audio classification. Nowadays, the work on overlapped audio event classification is still scarce, and most existing overlap classification systems can only recognize one audio event for an overlap. In this paper, in order to deal with overlaps, we innovatively introduce the author-topic (AT) model which was first proposed for text analysis into audio classification, and innovatively combine it with PLSA (Probabilistic Latent Semantic Analysis). We propose 4 systems, i.e. AT, PLSA, AT-PLSA and PLSA-AT, to classify overlaps. The 4 proposed systems have the ability to recognize two or more audio events for an overlap. The experimental results show that the 4 systems perform well in classifying overlapped audio events, whether it is the overlap in training set or the overlap out of training set. Also they perform well in classifying isolated audio events
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