3,770 research outputs found
On Relaxed Averaged Alternating Reflections (RAAR) Algorithm for Phase Retrieval from Structured Illuminations
In this paper, as opposed to the random phase masks, the structured
illuminations with a pixel-dependent deterministic phase shift are considered
to derandomize the model setup. The RAAR algorithm is modified to adapt to two
or more diffraction patterns, and the modified RAAR algorithm operates in
Fourier domain rather than space domain. The local convergence of the RAAR
algorithm is proved by some eigenvalue analysis. Numerical simulations is
presented to demonstrate the effectiveness and stability of the algorithm
compared to the HIO (Hybrid Input-Output) method. The numerical performances
show the global convergence of the RAAR in our tests.Comment: 17 pages, 26 figures, submitting to Inverse Problem
A study of dynamical processes in the Orion KL region using ALMA-- Probing molecular outflow and inflow
This work reports a high spatial resolution observations toward Orion KL
region with high critical density lines of CHCN (12-11) and
CHOH (8-7) as well as continuum at 1.3 mm band.
The observations were made using the Atacama Large Millimeter/Submillimeter
Array with a spatial resolution of 1.5 and sensitives
about 0.07 K and 0.18 K for continuum and line, respectively. The
observational results showed that the gas in the Orion KL region consists of
jet-propelled cores at the ridge and dense cores at east and south of the
region, shaped like a wedge ring. The outflow has multiple lobes, which may
originate from an explosive ejection and is not driven by young stellar
objects. Four infrared bubbles were found in the Spitzer/IRAC emissions. These
bubbles, the distributions of the previously found H jets, the young
stellar objects and molecular gas suggested that BN is the explosive center.
The burst time was estimated to be 1300 years. In the mean time,
signatures of gravitational collapse toward Source I and hot core were detected
with material infall velocities of 1.5 km~s and 0.6 km~s,
corresponding to mass accretion rates of 1.210M_{\sun}/Yr and
8.010M_{\sun}/Yr, respectively. These observations may support
that high-mass stars form via accretion model, like their low-mass
counterparts.Comment: Accepted to Ap
A CO observation of the galactic methanol masers
Context: We investigated the molecular gas associated with 6.7 GHz methanol
masers throughout the Galaxy using a J=1-0 transition of the CO isotopologues.
Methods:Using the 13.7-meter telescope at the Purple Mountain Observatory
(PMO), we have obtained ^{12}CO and ^{13}CO (1-0) lines for 160 methanol masers
sources from the first to the third Galactic quadrants. We made efforts to
resolve the distance ambiguity by careful comparison with the radio continuum
and HI 21 cm observations.
Results: First, the maser sources show increased ^{13}CO line widths toward
the Galactic center, suggesting that the molecular gas are more turbulent
toward the Galactic center. This trend can be noticeably traced by the ^{13}CO
line width. Second, the ^{12}CO excitation temperature shows a noticeable
correlation with the H_2 column density. A possible explanation consistent with
the collapse model is that the higher surface-density gas is more efficient to
the stellar heating and/or has a higher formation rate of high-mass stars.
Third, comparing the IRDCs, the maser sources on average have significantly
lower H_2 column densities, moderately higher temperatures, and similar line
widths. Fourth, in the mapped regions, 51 ^{13}CO cores have been revealed.
Only 17 coincide with the radio continuum emission (F_{cm}>6 mJy), while a
larger fraction (30 cores) coincide with the infrared emissions. The IR-bright
and radio-bright sources exhibit significantly higher CO excitation
temperatures than the IR-faint and radio-faint sources, respectively.
Conclusions: The 6.7 GHz masers show a moderately low ionization rate but
have a common-existing stellar heating that generates the IR emissions. The
relevant properties can be characterized by the ^{12}CO and ^{13}CO (1-0)
emissions in several aspects as described above.Comment: 38 pages, 13 figures, 4 tables, accepted to Astronomy and
Astrophysic
Collective quantum phase slips in multiple nanowire junctions
Realization of robust coherent quantum phase slips represents a significant
experimental challenge. Here we propose a new design consisting of multiple
nanowire junctions to realize a phase-slip flux qubit. It admits good
tunability provided by gate voltages applied on superconducting islands
separating nanowire junctions. In addition, the gates and junctions can be
identical or distinct to each other leading to symmetric and asymmetric setups.
We find that the asymmetry can improve the performance of the proposed device,
compared with the symmetric case. In particular, it can enhance the effective
rate of collective quantum phase slips. Furthermore, we demonstrate how to
couple two such devices via a mutual inductance. This is potentially useful for
quantum gate operations. Our investigation on how symmetry in multiple nanowire
junctions affects the device performance should be useful for the application
of phase-slip flux qubits in quantum information processing and quantum
metrology.Comment: 12 pages, 6 figure
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