We study the process e+e−→π+π−ψ(3686) using 5.1 fb−1 of data collected at 16 center-of-mass energy (s) points from 4.008 to 4.600 GeV by the BESIII detector operating at the BEPCII collider. The ...measured Born cross sections for e+e−→π+π−ψ(3686) are consistent with previous results, but with much improved precision. A fit to the cross section shows contributions from two structures: the first has M=4209.5±7.4±1.4 MeV/c2 and Γ=80.1±24.6±2.9 MeV, and the second has M=4383.8±4.2±0.8 MeV/c2 and Γ=84.2±12.5±2.1 MeV, where the first errors are statistical and the second systematic. The lower-mass resonance is observed in the process e+e−→π+π−ψ(3686) for the first time with a statistical significance of 5.8σ. A charged charmoniumlike structure is observed in the π±ψ(3686) invariant mass spectrum for data at s=4.416 GeV. A fit with an S-wave Breit-Wigner function yields a mass M=4032.1±2.4 MeV/c2, where the errors are statistical only. However, there are still unresolved discrepancies between the fit model and data. The width of the intermediate state varies in a wide range for different kinematic regions within the data set. Therefore, no simple interpretation of the data has been found, and a future data sample with larger statistics and more theoretical input will be required to better understand this issue.
A shrouded oscillating-foil turbine is proposed to augment the energy extraction performance. The oscillating foil undergoes combined plunging and pitching motion to convert the flow energy. A ...diffuser is introduced into the oscillating-foil-based turbine as the shroud. The speed-up and energy extraction performance of the turbine were assessed numerically. The effects of three cost-independent geometrical factors, namely shroud entrance width, shroud angle and streamwise distance between shroud and foil, and shroud sectional shape on energy extraction performance were investigated in detail. The optimal motion parameters for the shrouded oscillating-foil turbine were re-explored due to the altered flow field in the shroud. The results demonstrated that the maximum energy extraction efficiency of bare oscillating foil (0.336) can be augmented by 35.8% to 0.456 by appropriate arrangement of the shroud with a relative chord length of 0.8. The optimal motion parameters for the shrouded foil are slightly different from those of bare foil. The re-tuned motion parameters can further improve the efficiency to 0.47. Considering both the manufacturing cost of the shaped sections and their performance, it is more advantageous and attractive to use a flat plate as the shroud in engineering practices.
•A shrouded oscillating-foil based turbine is proposed.•The effects of cost-independent geometric factors and sectional shape are investigated.•The mechanisms of speed-up and performance improvement are analyzed.•The optimal motion parameters are readjusted for the new turbine.•Side walls of flat plate shows good performance and low-cost.
We present here a detailed study of the oxidation resistance of chemical vapor deposition (CVD) graphene. The results reveal that CVD graphene shows an excellent performance as a passivation layer ...below 200°C, but the protection ability degenerates rapidly with increasing the air temperature. Our work demonstrates for the first time that the most adverse effect on the degeneration of oxidation resistance in high temperature air comes from wrinkles but not others, such as Cu grain boundaries, periodic surface depressions due to Cu surface reconstruction induced by the graphene overlay, graphene domain boundaries, which are always believed the primary factor for inferior quality of the CVD graphene at present. In addition, we found that the distribution of the wrinkles in CVD graphene depended on the Cu crystal structure, and the results of the Electron-backscatter diffraction indicate that the folded wrinkles always appear on Cu (001) facets, while the standing collapsed wrinkles appear more easily on the Cu (111) facets.
ABSTRACT
The follow-up timing observations were carried out for 24 pulsars discovered with the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in Commensal Radio Astronomy FAST Survey. ...We report their phase-connected timing ephemeris, polarization pulse profiles, and Faraday rotation measurements. With their spin periods spanning from 2.995 ms to 4.34 s, their period derivatives were determined to spread between 7.996(8) × 10−21 and 9.83(3) × 10−15 s s−1, which imply that they have characteristic ages from 1.97 × 106 to 5.93 × 109 yr. It is inferred that PSRs J0211+4235 and J0518+2431 are beyond the ‘traditional death line’. PSR J0211+4235 is beyond the ‘death valley’. The death line model of Zhang et al. also cannot explain the radio presence of PSR J0211+4235. This suggests that radiation theory needs to be improved. Besides, ten of the 22 canonical pulsars show nulling phenomena. Moreover, PSR J1617+1123 exhibits variation of emission and J0540+4542 shows subpulse drifting. The DM of five pulsars is larger than the estimated by the YMW16 electron density model, which could suggest that electron density models need updates for higher Galactic latitude regions. PSRs J0447+2447 and J1928−0548 are isolated millisecond pulsars. With their flux densities spanning from 5(1)–553(106) μJy, some of these new pulsars found by FAST are distant, dim, and low-$\dot{E}$ ones and are suitable for testing pulsar emission theories.
We present a new determination of the smallest neutrino mixing angle θ_{13} and the mass-squared difference Δm_{32}^{2} using a final sample of 5.55×10^{6} inverse beta-decay (IBD) candidates with ...the final-state neutron captured on gadolinium. This sample is selected from the complete dataset obtained by the Daya Bay reactor neutrino experiment in 3158 days of operation. Compared to the previous Daya Bay results, selection of IBD candidates has been optimized, energy calibration refined, and treatment of backgrounds further improved. The resulting oscillation parameters are sin^{2}2θ_{13}=0.0851±0.0024, Δm_{32}^{2}=(2.466±0.060)×10^{-3} eV^{2} for the normal mass ordering or Δm_{32}^{2}=-(2.571±0.060)×10^{-3} eV^{2} for the inverted mass ordering.
An ideal semiconducting material should simultaneously hold a considerable direct band gap and a high carrier mobility. A 2D planar compound consisting of zigzag chains of C–C and B–N atoms, denoted ...as BC2N, would be a good candidate. It has a direct band gap of 2 eV, which can be further tuned by changing the layer number. At the same time, our first-principles calculations show that few-layer BC2N possesses a high carrier mobility. The carrier mobility of around one million sqaure centimeters per volt-second is obtained at its three-layer. As our study demonstrated, few-layer BC2N has potential applications in nanoelectronics and optoelectronics.
Based on an e+e− collision data sample corresponding to an integrated luminosity of 567 pb−1 taken at the center-of-mass energy of s=4.6 GeV with the BESIII detector, we measure the absolute ...branching fraction of the inclusive decay Λc+→Λ+X to be B(Λc+→Λ+X)=(38.2−2.2+2.8±0.9)% using the double-tag method, where X refers to any possible final state particles. In addition, we search for direct CP violation in the charge asymmetry of this inclusive decay for the first time, and obtain ACP≡B(Λc+→Λ+X)−B(Λ¯c−→Λ¯+X)/B(Λc+→Λ+X)+B(Λ¯c−→Λ¯+X)=(2.1−6.6+7.0±1.6)%, a statistically limited result with no evidence of CP violation.
In the tensor-network framework, the expectation values of two-dimensional quantum states are evaluated by contracting a double-layer tensor network constructed from initial and final tensor-network ...states. The computational cost of carrying out this contraction is generally very high, which limits the largest bond dimension of tensor-network states that can be accurately studied to a relatively small value. We propose an optimized contraction scheme to solve this problem by mapping the double-layer tensor network onto an intersected single-layer tensor network. This reduces greatly the bond dimensions of local tensors to be contracted and improves dramatically the efficiency and accuracy of the evaluation of expectation values of tensor-network states. It almost doubles the largest bond dimension of tensor-network states whose physical properties can be efficiently and reliably calculated, and it extends significantly the application scope of tensor-network methods.
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