5,297 research outputs found
Electronic Mach-Zehnder interferometer as a tool to probe fractional statistics
We study transport through an electronic Mach-Zehnder interferometer recently
devised at the Weizmann Institute. We show that this device can be used to
probe statistics of quasiparticles in the fractional quantum Hall regime. We
calculate the tunneling current through the interferometer as the function of
the Aharonov-Bohm flux, temperature and voltage bias, and demonstrate that its
flux-dependent component is strongly sensitive to the statistics of tunneling
quasiparticles. More specifically, the flux-dependent and flux-independent
contributions to the current are related by a power law, the exponent being a
function of the quasiparticle statistics.Comment: 22 pages; 8 figure
Drive-By Blind Modal Identification with Singular Spectrum Analysis
© 2019 American Society of Civil Engineers. Drive-by bridge parameter identification has been an active research area in recent years. An instrumented vehicle passing over a bridge deck captures dynamic information of the bridge structure without bridge closure and on-site instrumentation. The vehicle dynamic response includes components associated with the bridge surface roughness and the vehicle and bridge vibration. It is a challenge to separate these components and extract the bridge modal parameters from the vehicle response. A novel drive-by blind modal identification with singular spectrum analysis is proposed to extract the bridge modal frequencies from the vehicle dynamic response. The single-channel measured vehicular response is decomposed into a multichannel data set using singular spectrum analysis, and the bridge frequencies are then extracted via the blind modal identification. Numerical results showed that the proposed method is effective and robust to extract the bridge frequencies from the vehicle response measurement even with Class B road surface roughness. The effects of the moving speed and the vehicle parameters on the identification were studied. A vehicle-bridge interaction model in the laboratory was studied to further verify the proposed method using one- and two-axle vehicles
The LuckyCam Survey for Very Low Mass Binaries II: 13 new M4.5-M6.0 Binaries
We present results from a high-angular-resolution survey of 78 very low mass
(VLM) binary systems with 6.0 = 0.15
arcsec/yr. 21 VLM binaries were detected, 13 of them new discoveries. The new
binary systems range in separation between 0.18 arcsec and 1.3 arcsec. The
distance-corrected binary fraction is 13.5% (+6.5%/-4%), in agreement with
previous results. 9 of the new binary systems have orbital radii > 10 AU,
including a new wide VLM binary with 27 AU projected orbital separation. One of
the new systems forms two components of a 2300 AU separation triple system. We
find that the orbital radius distribution of the binaries with V-K < 6.5 in
this survey appears to be different from that of redder (lower-mass) objects,
suggesting a possible rapid change in the orbital radius distribution at around
the M5 spectral type. The target sample was also selected to investigate X-ray
activity among VLM binaries. There is no detectable correlation between excess
X-Ray emission and the frequency and binary properties of the VLM systems.Comment: 11 pages, 8 figures. Submitted to MNRA
Fermi resonance-algebraic model for molecular vibrational spectra
A Fermi resonance-algebraic model is proposed for molecular vibrations, where
a U(2) algebra is used for describing the vibrations of each bond, and Fermi
resonances between stretching and bending modes are taken into account. The
model for a bent molecule XY_2 and a molecule XY_3 is successfully applied to
fit the recently observed vibrational spectrum of the water molecule and arsine
(AsH_3), respectively, and results are compared with those of other models.
Calculations show that algebraic approaches can be used as an effective method
for describing molecular vibrations with small standard deviations
Characterizing the Growth Trajectories of Language-Impaired Children Between 7 and 11 Years of Age
A number of different systems have been suggested for classifying language impairment in children but, to date, no one system has been widely accepted. Method: This paper outlines an alternative system looking for distinct patterns of change in receptive language skills across time, involving a secondary analysis of children identified as having specific language impairment. Participants: The participants were 184 children age-assessed at 3 time points-7, 8, and 11 years of age. Results: The pattern of receptive language development is highly predictable. The dominant pattern of growth is consistent with declining rates of growth over time for all children. The primary way in which the children differ is with respect to their initial severity. The testing of the 2 classification systems revealed some statistically significant differences among the subtypes with regard to the shape of the growth rates, but the effect sizes associated with these differences were very small. Thus, it is possible to conclude that beyond the dominant pattern of growth, some subtypes of language impairment at 7 years of age showed only subtle differences in receptive language change across time. The results are discussed in terms of the sample selection and the age of the children who were studied. American Speech-Language-Hearing Association.CIHR51pub75
Searching (the) FIRST radio arcs near ACO clusters
Gravitational lensing (GL) of distant radio sources by galaxy clusters should
produce radio arc(let)s. We extracted radio sources from the FIRST survey near
Abell cluster cores and found their radio position angles to be uniformly
distributed with respect to the cluster centres. This result holds even when we
restrict the sample to the richest or most centrally condensed clusters, and to
sources with high S/N and large axial ratio. Our failure to detect GL with
statistical methods may be due to poor cluster centre positions. We did not
find convincing candidates for arcs either. Our result agrees with theoretical
estimates predicting that surveys much deeper than FIRST are required to detect
the effect. This is in apparent conflict with the detection of such an effect
claimed by Bagchi & Kapahi (1995).Comment: 6 pages; 8 figures and 1 style file are included; to appear in Proc.
"Observational Cosmology with the New Radio Surveys", eds. M. Bremer, N.
Jackson & I. Perez-Fournon, Kluwer Acad. Pres
A Two-Step Drive-By Bridge Damage Detection Using Dual Kalman Filter
© 2020 World Scientific Publishing Company. Drive-by bridge inspection using acceleration responses of a passing vehicle has great potential for bridge structural health monitoring. It is, however, known that the road surface roughness is a big challenge for the practical application of this indirect approach. This paper presents a new two-step method for the bridge damage identification from only the dynamic responses of a passing vehicle without the road surface roughness information. A state-space equation of the vehicle model is derived based on the Newmark-β method. In the first step, the road surface roughness is estimated from the dynamic responses of a passing vehicle using the dual Kalman filter (DKF). In the second step, the bridge damage is identified based on the interaction force sensitivity analysis with Tikhonov regularization. A vehicle-bridge interaction model with a wireless monitoring system has been built in the laboratory. Experimental investigation has been carried out for the interaction force and bridge surface roughness identification. Results show that the proposed method is effective and reliable to identify the interaction force and bridge surface roughness. Numerical simulations have also been conducted to study the effectiveness of the proposed method for bridge damage detection. The vehicle is modeled as a 4-degrees-of-freedom half-car and the bridge is modeled as a simply-supported beam. The local bridge damage is simulated as an elemental flexural stiffness reduction. Effects of measurement noise, surface roughness and vehicle speed on the identification are discussed.The results show that the proposed drive-by inspection strategy is efficient and accurate for a quick review on the bridge conditions
Continuous quantum nondemolition feedback and unconditional atomic spin squeezing
We discuss the theory and experimental considerations of a quantum feedback
scheme for producing deterministically reproducible spin squeezing. Continuous
nondemolition atom number measurement from monitoring a probe field
conditionally squeezes the sample. Simultaneous feedback of the measurement
results controls the quantum state such that the squeezing becomes
unconditional. We find that for very strong cavity coupling and a limited
number of atoms, the theoretical squeezing approaches the Heisenberg limit.
Strong squeezing will still be produced at weaker coupling and even in free
space (thus presenting a simple experimental test for quantum feedback). The
measurement and feedback can be stopped at any time, thereby freezing the
sample with a desired amount of squeezing.Comment: 17 pages, 5 figures, submitted to JP
Generating entangled atom-photon pairs from Bose-Einstein condensates
We propose using spontaneous Raman scattering from an optically driven
Bose-Einstein condensate as a source of atom-photon pairs whose internal states
are maximally entangled. Generating entanglement between a particle which is
easily transmitted (the photon) and one which is easily trapped and coherently
manipulated (an ultracold atom) will prove useful for a variety of
quantum-information related applications. We analyze the type of entangled
states generated by spontaneous Raman scattering and construct a geometry which
results in maximum entanglement
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