Engineering topics
Guo, Y.
Publications and source records attributed to Guo, Y..
Luminosity measurements for the R scan experiment at BESIII
By analyzing the large-angle Bhabha scattering events e + e - → (γ)e + e - and diphoton events e + e - → (γ)γγ for the data sets collected at center-of-mass (c.m.) energies between 2.2324 and 4.5900 GeV (131 energy points in total) with the upgraded Beijing Spectrometer (BESIII) at the Beijing Electron-Positron Collider (BEPCII), the integrated luminosities have been measured at the different c.m. energies, individually. Finally, the results are important inputs for the R value and J/ψ resonance parameter measurements.
Amplitude Analysis of the Decays η ' → π + π - π 0 and η ' → π 0 π 0 π 0
Based on a sample of 1.31 × 10 9 J / ψ events collected with the BESIII detector, an amplitude analysis of the isospin-violating decays η'→ π + π - π 0 and η' → π 0 π 0 π 0 is performed. A significant P-wave contribution from η'→ ρ ± π ∓ is observed for the first time in η' → π + π - π 0 . The branching fraction is determined to be B ( η'→ ρ ± π ∓ ) = ( 7.44 ± 0.60 ± 1.26 ± 1.84 ) × 10 -4 , where the first uncertainty is statistical, the second systematic, and the third model dependent. In addition to the nonresonant S -wave component, there is a significant σ meson component. The branching fractions of the combined S -wave components are determined to be B ( η' → π + π - π 0 ) S = ( 37.63 ± 0.77 ± 2.22 ± 4.48 ) × 10 -4 and B ( η' → π 0 π 0 π 0 ) = ( 35.22 ± 0.82 ± 2.54 ) × 10 -4 , respectively. Finally, the latter one is consistent with previous BESIII measurements.
Charge-Dependent Directed Flow in Cu + Au Collisions at s N N = 200 GeV
Here we present the first measurement of charge-dependent directed flow in Cu + Au collisions at $\sqrt{s}$$_ {NN}$ = 200 GeV . The results are presented as a function of the particle transverse momentum and pseudorapidity for different centralities. A finite difference between the directed flow of positive and negative charged particles is observed that qualitatively agrees with the expectations from the effects of the initial strong electric field between two colliding ions with different nuclear charges. The measured difference in directed flow is much smaller than that obtained from the parton-hadron-string-dynamics model, which suggests that most of the electric charges, i.e., quarks and antiquarks, have not yet been created during the lifetime of the strong electric field, which is of the order of, or less than, 1fm / c .
Measurements of the branching fractions for D + → K S 0 K S 0 K + , K S 0 K S 0 π + and D 0 → K S 0 K S 0 , K S 0 K S 0 K S 0
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Measurements of the absolute branching fractions for D s + → η e + ν e and D s + → η ′ e + ν e
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Measurement of Singly Cabibbo Suppressed Decays Λ c + → p π + π − and Λ c + → p K + K −
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Experimental Investigation of Bearing Slip in a Wind Turbine Gearbox During a Transient Grid Loss Event
This work investigates the behaviour of the high speed stage of a wind turbine gearbox during a transient grid loss event. Dynamometer testing on a full scale wind turbine nacelle is used. A combination of external and internal gearbox measurements is analysed. Particular focus is on the characterization of the high speed shaft tapered roller bearing slip behaviour. This slipping behaviour is linked to dynamic events by many researchers and described as potential bearing failure initiator. However only limited full scale dynamic testing is documented. Strain gauge bridges in grooves along the circumference of the outer ring are used to characterize the bearing behaviour in detail. It is shown that during the transient event the high speed shaft experiences a combined torsional and bending deformation. These unfavourable loading conditions induce roller slip in the bearings during the torque reversals indicating the potential of the applied load case to go beyond the preload of the tapered roller bearing.
Measurement of the absolute branching fraction of D + → $\bar{K}$ 0 e + ν e via $\bar{K}$ 0 → π 0 π 0
By analyzing 2.93 fb–1 data collected at the center-of-mass energy with the BESIII detector, we measure the absolute branching fraction of the semileptonic decay D+ → $\bar{K}$0 e+νe to be Β(D + → $\bar{K}$ 0 e + ν e ) = (8.59 ± 0.14 ± 0.21)% using $\bar{K}$ 0 → K 0 s → π 0 π 0 , where the first uncertainty is statistical and the second systematic. Finally, our result is consistent with previous measurements within uncertainties..
Measurement of the D s + → ℓ + ν ℓ branching fractions and the decay constant f D s +
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Measurement of the leptonic decay width of J/ψ using initial state radiation
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Measurement of elliptic flow of light nuclei at s N N = 200 , 62.4, 39, 27, 19.6, 11.5, and 7.7 GeV at the BNL Relativistic Heavy Ion Collider
Here we present measurements of second-order azimuthal anisotropy ( v 2 ) at midrapidity ( |y| < 1.0 ) for light nuclei d , t , 3 He (for $\sqrt{s}$$_{NN}$ = 200 , 62.4, 39, 27, 19.6, 11.5, and 7.7 GeV) and antinuclei$\bar{d}$ ( $\sqrt{s}$$_{NN}$ = 200 , 62.4, 39, 27, and 19.6 GeV) and 3 ¯¯¯¯¯ He ( $\sqrt{s}$$_{NN}$ = 200 GeV) in the STAR (Solenoidal Tracker at RHIC) experiment. The v 2 for these light nuclei produced in heavy-ion collisions is compared with those for p and $\bar{p}$. We observe mass ordering in nuclei v 2 ( p T ) at low transverse momenta ( p T < 2.0 GeV/c). We also find a centrality dependence of v 2 for d and $\bar{d}$ . The magnitude of v 2 for t and 3 He agree within statistical errors. Light-nuclei v 2 are compared with predictions from a blast-wave model. Atomic mass number ( A ) scaling of light-nuclei v 2 (p T ) seems to hold for p T / A < 1.5 GeV/c . Results on light-nuclei v 2 from a transport-plus-coalescence model are consistent with the experimental measurements.
MAGNETO-FRICTIONAL MODELING OF CORONAL NONLINEAR FORCE-FREE FIELDS. I. TESTING WITH ANALYTIC SOLUTIONS
We report our implementation of the magneto-frictional method in the Message Passing Interface Adaptive Mesh Refinement Versatile Advection Code (MPI-AMRVAC). The method aims at applications where local adaptive mesh refinement (AMR) is essential to make follow-up dynamical modeling affordable. We quantify its performance in both domain-decomposed uniform grids and block-adaptive AMR computations, using all frequently employed force-free, divergence-free, and other vector comparison metrics. As test cases, we revisit the semi-analytic solution of Low and Lou in both Cartesian and spherical geometries, along with the topologically challenging Titov–Démoulin model. We compare different combinations of spatial and temporal discretizations, and find that the fourth-order central difference with a local Lax–Friedrichs dissipation term in a single-step marching scheme is an optimal combination. The initial condition is provided by the potential field, which is the potential field source surface model in spherical geometry. Various boundary conditions are adopted, ranging from fully prescribed cases where all boundaries are assigned with the semi-analytic models, to solar-like cases where only the magnetic field at the bottom is known. Our results demonstrate that all the metrics compare favorably to previous works in both Cartesian and spherical coordinates. Cases with several AMR levels perform in accordance with their effective resolutions. The magneto-frictional method in MPI-AMRVAC allows us to model a region of interest with high spatial resolution and large field of view simultaneously, as required by observation-constrained extrapolations using vector data provided with modern instruments. The applications of the magneto-frictional method to observations are shown in an accompanying paper.
Jet-like correlations with direct-photon and neutral-pion triggers at s N N = 200 GeV
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Determination of the number of J/ψ events with inclusive J/ψ decays
A measurement of the number of J/ψ events collected with the BESIII detector in 2009 and 2012 is performed using inclusive decays of the J/ψ. The number of J/ψ events taken in 2009 is recalculated to be (223.7 ± 1.4) × 10 6 , which is in good agreement with the previous measurement, but with significantly improved precision due to improvements in the BESIII software. The number of J/ψ events taken in 2012 is determined to be (1086.9 ± 6.0) × 10 6 . In total, the number of J/ψ events collected with the BESIII detector is measured to be (1310.6 ± 7.0) × 10 6 , where the uncertainty is dominated by systematic effects and the statistical uncertainty is negligible.
Observation of e + e − → η ′ J / ψ at center-of-mass energies between 4.189 and 4.600 GeV
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