623 research outputs found
Three body radiative decay in the PQCD approach
We study the three body radiative decay by
introducing the pair distribution amplitudes (DAs) in the perturbative
QCD approach. This nonperturbative inputs, the two meson DAs, is very important
to simplify the calculations. Besides the dominant electromagnetic penguin
operator , the subleading contributions from chromomagnetic
penguin operator , quark-loop corrections and annihilation type
amplitudes are also considered. We find that the branching ratio for the decay
is about
, which is much
smaller compared with that for the decay . It is mainly
because that the former decay induces by with small CKM matrix
element being proportional to . The prediction for the direct CP
asymmetry is , which is well consistent with
the result from the U-spin symmetry approach. we also predict the decay spectrum, which exhibits a maximu at the
invariant masss around 1.95 GeV.Comment: 17 pages,6 figures, Accepted for publication in EPJ
Study of the mixing in the decays
We studied the B meson decays in the pQCD
approach beyond the leading order. With the vertex corrections and the NLO
Wilson coefficients included, the branching ratios of the considered decays are
, and with the mixing angle
, which can agree well with the data or the present
experimental upper limit within errors. So we support the opinion that
is much more favored than . Furthermore,
we also give the predictions for the polarization fractions, direct CP
violations from the different polarization components, the relative phase
angles for the considered decays with the mixing angle
and , respectively. The direct CP violations of the two charged
decays are very small ,
because there is no weak phase until up to with the
Wolfenstein parameter . These results can be tested at the
running LHCb and forthcoming Super-B experiments.Comment: 14 pages,3 figures,to appear in EPJ
Tractor and Semitrailer Routing Problem of Highway Port Networks under Unbalanced Demand
In China, highway port networks are essential in carrying out tractor and semitrailer transportation operations. To analyze the characteristics of tractor and semitrailer routing in highway port networks, this study examined the situation in which the demands at both ends of the operation might be unbalanced and multiple requirements might be raised in the operation of tractor and semitrailer transportation. An optimal tractor and semitrailer routing model for an entire network was established to reduce the total transportation costs and the number of towing vehicles in the network. Moreover, a heuristic algorithm was designed to solve the model. The comparisons of Strategy 1 and Strategy 2 for a two-stage network swap trailer show that the number of pure network swaps trailer tractors decreases by 21.6% and 18.6%, respectively; and that the cost drops by 7.8% and 7.9%, respectively. In other words, swap trailer transport enterprises can abandon the original swap trailer transportation mode for a two-stage network and adopt a routing optimization strategy for an entire network to achieve superior operation performance, reduce costs, and enhance profits. The study provides a reference for optimizing tractor and semitrailer routing in highway port networks with balanced and multiple demands
On converse bounds for classical communication over quantum channels
We explore several new converse bounds for classical communication over
quantum channels in both the one-shot and asymptotic regimes. First, we show
that the Matthews-Wehner meta-converse bound for entanglement-assisted
classical communication can be achieved by activated, no-signalling assisted
codes, suitably generalizing a result for classical channels. Second, we derive
a new efficiently computable meta-converse on the amount of classical
information unassisted codes can transmit over a single use of a quantum
channel. As applications, we provide a finite resource analysis of classical
communication over quantum erasure channels, including the second-order and
moderate deviation asymptotics. Third, we explore the asymptotic analogue of
our new meta-converse, the -information of the channel. We show that
its regularization is an upper bound on the classical capacity, which is
generally tighter than the entanglement-assisted capacity and other known
efficiently computable strong converse bounds. For covariant channels we show
that the -information is a strong converse bound.Comment: v3: published version; v2: 18 pages, presentation and results
improve
Direct sampling method to inverse wave-number-dependent source problems (part I): determination of the support of a stationary source
This paper is concerned with a direct sampling method for imaging the support
of a frequency-dependent source term embedded in a homogeneous and isotropic
medium. The source term is given by the Fourier transform of a time-dependent
source whose radiating period in the time domain is known.
The time-dependent source is supposed to be stationary in the sense that its
compact support does not vary along the time variable.
Via a multi-frequency direct sampling method, we show that the smallest strip
containing the source support and perpendicular to the observation direction
can be recovered from far-field patterns at a fixed observation angle. With
multiple but sparse observation directions, the shape of the convex hull of the
source support can be recovered. The frequency-domain analysis performed here
can be used to handle inverse time-dependent source problems.
Our algorithm has low computational overhead and is robust against noise.
Numerical experiments in both two and three dimensions have proved our
theoretical findings
Attitude, Knowledge, and Practice on Evidence-Based Nursing among Registered Nurses in Traditional Chinese Medicine Hospitals: A Multiple Center Cross-Sectional Survey in China
Objective. This study was to describe RNs’ attitude, knowledge, and practice on evidence-based practice (EBP) in traditional Chinese nursing field and to estimate the related sociodemographic and professional factors. Methods. A multiple institutional cross-sectional survey design with self-reported EBP Questionnaire (EBPQ) and self-designed questionnaires were used. Results. The average scores of the total EBPQ were with a mean of 4.24 (SD = 0.79). The score of attitude was the highest one, followed by the knowledge score, and the lowest one is practice. RNs with longer experience reported stronger EBP knowledge (H=6.64, P<0.05). And RNs under higher working pressure reported less positive attitudes (ρ=0.17, P<0.001), whereas RNs holding negative professional attitude reported lower scores (Spearman’s ρ: 0.12 to 0.15, P<0.001). Significant statistics were found between RNs with research experience and without in attitude (t=-2.40, P<0.05) and knowledge (t=-2.43, P<0.05). Conclusions. Respondents generally viewed EBP positively and their attitudes towards EBP tended to be more positive than knowledge and practice of EBP. Data also showed that longer working experience, having administrative position, research experience, lighter working load, and better professional attitude might facilitate EBP
Optimization Method Based On Optimal Control
In this paper, we focus on a method based on optimal control to address the
optimization problem. The objective is to find the optimal solution that
minimizes the objective function. We transform the optimization problem into
optimal control by designing an appropriate cost function. Using Pontryagin's
Maximum Principle and the associated forward-backward difference equations
(FBDEs), we derive the iterative update gain for the optimization. The steady
system state can be considered as the solution to the optimization problem.
Finally, we discuss the compelling characteristics of our method and further
demonstrate its high precision, low oscillation, and applicability for finding
different local minima of non-convex functions through several simulation
examples
Interlayer Interactions in Anisotropic Atomically-thin Rhenium Diselenide
Recently, two-dimensional (2D) materials with strong in-plane anisotropic
properties such as black phosphorus have demonstrated great potential for
developing new devices that can take advantage of its reduced lattice symmetry
with potential applications in electronics, optoelectronics and
thermoelectrics. However, the selection of 2D material with strong in-plane
anisotropy has so far been very limited and only sporadic studies have been
devoted to transition metal dichalcogenides (TMDC) materials with reduced
lattice symmetry, which is yet to convey the full picture of their optical and
phonon properties, and the anisotropy in their interlayer interactions. Here,
we study the anisotropic interlayer interactions in an important TMDC 2D
material with reduced in-plane symmetry - atomically thin rhenium diselenide
(ReSe2) - by investigating its ultralow frequency interlayer phonon vibration
modes, the layer dependent optical bandgap, and the anisotropic
photoluminescence (PL) spectra for the first time. The ultralow frequency
interlayer Raman spectra combined with the first study of polarization-resolved
high frequency Raman spectra in mono- and bi-layer ReSe2 allows deterministic
identification of its layer number and crystal orientation. PL measurements
show anisotropic optical emission intensity with bandgap increasing from 1.26
eV in the bulk to 1.32 eV in monolayer, consistent with the theoretical results
based on first-principle calculations. The study of the layer-number dependence
of the Raman modes and the PL spectra reveals the relatively weak van der Waals
interaction and 2D quantum confinement in atomically-thin ReSe2.Comment: 17 pages, 5 figures, supplementary informatio
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