36,942 research outputs found
Effect of quantum fluctuations on structural phase transitions in SrTiO_3 and BaTiO_3
Using path-integral Monte Carol simulations and an ab initio effective
Hamiltonian, we study the effects of quantum fluctuations on structural phase
transitions in the cubic perovskite compounds SrTiO3 and BaTiO3. We find
quantum fluctuations affect ferroelectric (FE) transitions more strongly than
antiferrodistortive (AFD) ones, even though the effective mass of a single FE
local mode is larger. For SrTiO3 we find that the quantum fluctuations suppress
the FE transition completely, and reduce the AFD transition temperature from
130K to 110K. For BaTiO3, quantum fluctuations do not affect the order of the
transition, but do reduce the transition temperature by 35-50 K. The
implications of the calculations are discussed.Comment: Revtex (preprint style, 14 pages) + 2 postscript figures. A version
in two-column article style with embedded figures is available at
http://electron.rutgers.edu/~dhv/preprints/index.html#wz_qs
A unified smith predictor approach for power system damping control design using remote signals
Published versio
Generalized Friedberg-Lee model for neutrino masses and leptonic CP violation from mu-tau symmetry breaking
Assuming the Majorana nature of massive neutrinos, we generalize the
Friedberg-Lee neutrino mass model to include CP violation in the neutrino mass
matrix M_\nu. The most general case with all the free parameters of M_\nu being
complex is discussed. We show that a favorable neutrino mixing pattern (with
\theta_12 \approx 35.3^\circ, \theta_23=45^\circ, \theta_13 \neq 0^\circ and
\delta=90^\circ) can naturally be derived from M_\nu, if it has an approximate
or softly-broken \mu-\tau symmetry. We also point out a different way to obtain
the nearly tri-bimaximal neutrino mixing pattern with \delta=0^\circ and
non-vanishing Majorana phases.Comment: 4 pages. Talk given by He Zhang at the 4th International Conference
on Flavor Physics, 24-28 September 2007, Beijing (to appear in the
proceedings
Deep Long Short-Term Memory Adaptive Beamforming Networks For Multichannel Robust Speech Recognition
Far-field speech recognition in noisy and reverberant conditions remains a
challenging problem despite recent deep learning breakthroughs. This problem is
commonly addressed by acquiring a speech signal from multiple microphones and
performing beamforming over them. In this paper, we propose to use a recurrent
neural network with long short-term memory (LSTM) architecture to adaptively
estimate real-time beamforming filter coefficients to cope with non-stationary
environmental noise and dynamic nature of source and microphones positions
which results in a set of timevarying room impulse responses. The LSTM adaptive
beamformer is jointly trained with a deep LSTM acoustic model to predict senone
labels. Further, we use hidden units in the deep LSTM acoustic model to assist
in predicting the beamforming filter coefficients. The proposed system achieves
7.97% absolute gain over baseline systems with no beamforming on CHiME-3 real
evaluation set.Comment: in 2017 IEEE International Conference on Acoustics, Speech and Signal
Processing (ICASSP
The Carriers of the "Unidentified" Infrared Emission Features: Clues from Polycyclic Aromatic Hydrocarbons with Aliphatic Sidegroups
The "unidentified" infrared emission (UIE) features at 3.3, 6.2, 7.7, 8.6,
and 11.3 m are ubiquitously seen in various astrophysical regions. The UIE
features are characteristic of the stretching and bending vibrations of
aromatic hydrocarbons. The 3.3 m feature resulting from aromatic C--H
stretches is often accompanied by a weaker feature at 3.4 m often
attributed to aliphatic C--H stretches. The ratio of the observed intensity of
the 3.3 m aromatic C--H feature () to that of the 3.4 m
aliphatic C--H feature () allows one to estimate the aliphatic
fraction (i.e. , the number of C atoms in
aliphatic units to that in aromatic rings) of the UIE carriers, provided the
intrinsic oscillator strengths of the 3.3 m aromatic C--H stretch
() and the 3.4 m aliphatic C--H stretch () are known.
In this article we summarize the computational results on and
and their implications for the aromaticity and aliphaticity of the
UIE carriers. We use density functional theory and second-order perturbation
theory to derive and from the infrared vibrational spectra
of seven PAHs with various aliphatic substituents (e.g., methyl-, dimethyl-,
ethyl-, propyl-, butyl-PAHs, and PAHs with unsaturated alkyl-chains). The mean
band strengths of the aromatic () and aliphatic () C--H
stretches are derived and then employed to estimate the aliphatic fraction of
the UIE carriers by comparing / with /. We
conclude that the UIE emitters are predominantly aromatic, as revealed by the
observationally-derived ratio ~ 0.12 and the
computationally-derived ratio ~ 1.76 which suggest an
upper limit of ~ 0.02 for the aliphatic
fraction of the UIE carriers.Comment: 67 pages, 18 figures, 8 tables; invited article accepted for
publication in "New Astronomy Review"; a considerable fraction of this
article is concerned with the computational techniques and results, readers
who are mainly interested in astrophysics may wish to only read
"Introduction", and "Astrophysical Implications
Can CPT Symmetry Be Tested With K^0 vs \bar{K}^0--> \pi^+\pi^-\pi^0 Decays?
We show that the CP-violating effect in K^0 vs \bar K^0-->\pi^+\pi^-\pi^0
decays differs from that in K_{\rm L}-->\pi^+\pi^-, K_{\rm L}-->\pi^0\pi^0 or
the semileptonic K_{\rm L} transitions, if there exists CPT violation in
K^0-\bar{K}^0 mixing. A delicate measurement of this difference in the KTeV
experiment and at the \phi factory will provide a new test of CPT symmetry in
the neutral kaon system.Comment: RevTex 6 pages. Phys. Rev. D (in printing
A New Solution of the Yang-Baxter Equation Related to the Adjoint Representation of
A new solution of the Yang-Baxter equation, that is related to the adjoint
representation of the quantum enveloping algebra , is obtained by
fusion formulas from a non-standard solution.Comment: 16 pages (Latex), Preprint BIHEP-TH-93-3
- …