Quantifying jet transport properties via large pTp_T hadron production

Nuclear modification factor $R_{AA}$ for large $p_T$ single hadron is studied in a next-to-leading order (NLO) perturbative QCD (pQCD) parton model with medium-modified fragmentation functions (mFFs) due to jet quenching in high-energy heavy-ion collisions. The energy loss of the hard partons in the QGP is incorporated in the mFFs which utilize two most important parameters to characterize the transport properties of the hard parton jets: the jet transport parameter $\hat q_{0}$ and the mean free path $\lambda_{0}$, both at the initial time $\tau_0$. A phenomenological study of the experimental data for $R_{AA}(p_{T})$ is performed to constrain the two parameters with simultaneous $\chi^2/{\rm d.o.f}$ fits to RHIC as well as LHC data. We obtain for energetic quarks $\hat q_{0}\approx 1.1 \pm 0.2$ GeV$^2$/fm and $\lambda_{0}\approx 0.4 \pm 0.03$ fm in central $Au+Au$ collisions at $\sqrt{s_{NN}}=200$ GeV, while $\hat q_{0}\approx 1.7 \pm 0.3$ GeV$^2$/fm, and $\lambda_{0}\approx 0.5 \pm 0.05$ fm in central $Pb+Pb$ collisions at $\sqrt{s_{NN}}=2.76$ TeV. Numerical analysis shows that the best fit favors a multiple scattering picture for the energetic jets propagating through the bulk medium, with a moderate averaged number of gluon emissions. Based on the best constraints for $\lambda_{0}$ and $\tau_0$, the estimated value for the mean-squared transverse momentum broadening is moderate which implies that the hard jets go through the medium with small reflection.Comment: 8 pages, 6 figures, revised versio

Valve Plate Structural Optimal Design and Flow Field Analysis for the Aviation Bidirectional Three-Port Piston Pump

This paper designed and optimized a bidirectional three-port valve plate structure for solving the matching problem of flow rate and pressure in the aerospace pump-controlled differential hydraulic cylinder. This design aims to make the valve plate work well under the bidirectional high-speed condition. The model was set up using dynamic mesh and sliding mesh, and the simulation is conducted by FLUENT. In addition, the flow field of inlet and outlet flow rate pulsations, pressure pulsation in cylinder, and non-dead-point transition zone of four cases are analyzed to optimize the valve plate in this work. The numerical results show that different angles of non-dead-point transition zones of the valve plate have a big impact on the performance of the piston pump. For example, the flow rate pulsation reaches the minimum when the angle of non-dead point transition zone is greater than or equal to the angle of a cylinder port. However, at this time, the closed compression would occur and the pressure inside the cylinder would rise rapidly as the piston moves to the non-dead point zone, thus resulting in serious pressure overshoot. In addition, if the angle of non-dead point transition zone is reduced within a certain range, the pressure overshoot will be reduced drastically, and the flow pulsation rate will rise a bit. The study suggests that it is necessary to adjust the angle of non-dead point transition zone to balance the pressure overshoot and flow pulsation of the pump to obtain the optimal kidney structure of the valve plate

Research on Hypothesizing and Sorting the Eg Candidates in Chinese Semantic Parsing

PACLIC 20 / Wuhan, China / 1-3 November, 200