7,370 research outputs found
Towards Understanding Astrophysical Effects of Nuclear Symmetry Energy
Determining the Equation of State (EOS) of dense neutron-rich nuclear matter
is a shared goal of both nuclear physics and astrophysics. Except possible
phase transitions, the density dependence of nuclear symmetry \esym is the most
uncertain part of the EOS of neutron-rich nucleonic matter especially at
supra-saturation densities. Much progresses have been made in recent years in
predicting the symmetry energy and understanding why it is still very uncertain
using various microscopic nuclear many-body theories and phenomenological
models. Simultaneously, significant progresses have also been made in probing
the symmetry energy in both terrestrial nuclear laboratories and astrophysical
observatories. In light of the GW170817 event as well as ongoing or planned
nuclear experiments and astrophysical observations probing the EOS of dense
neutron-rich matter, we review recent progresses and identify new challenges to
the best knowledge we have on several selected topics critical for
understanding astrophysical effects of the nuclear symmetry energy.Comment: 77 pages. Invited Review Article, EPJA (2019) in pres
RESEARCH ON EFFICIENCY OF PRIMARY HEALTHCARE SERVICE OF SHANGHAI IN CHINA
Object: The article researches on efficiency of Shanghai Community Health Service (SCHS) and establishes production function of SCHS.Method: Establishing the production function of SCHS by Weighted Least Squares Estimation .Result: 1. Formulating the reasonable production function of SCHs based on Cobb: Douglas (C-D) function. 2. The article reveals SCHS production function with constant returns to scale.Conclusion: 1. Increasing human resource investment is a key factor for raising SCHS.2.Strenghten management and explore an efficient service model will improve SCHS level
Constraining the Skyrme effective interactions and the neutron skin thickness of nuclei using isospin diffusion data from heavy ion collisions
Recent analysis of the isospin diffusion data from heavy-ion collisions based
on an isospin- and momentum-dependent transport model with in-medium
nucleon-nucleon cross sections has led to the extraction of a value of MeV for the slope of the nuclear symmetry energy at saturation density.
This imposes stringent constraints on both the parameters in the Skyrme
effective interactions and the neutron skin thickness of heavy nuclei. Among
the 21 sets of Skyrme interactions commonly used in nuclear structure studies,
the 4 sets SIV, SV, G, and R are found to give values
that are consistent with the extracted one. Further study on the correlations
between the thickness of the neutron skin in finite nuclei and the nuclear
matter symmetry energy in the Skyrme Hartree-Fock approach leads to predicted
thickness of the neutron skin of fm for Pb, fm for Sn, and fm for Sn.Comment: 10 pages, 4 figures, 1 Table, Talk given at 1) International
Conference on Nuclear Structure Physics, Shanghai, 12-17 June, 2006; 2) 11th
China National Nuclear Structure Physics Conference, Changchun, Jilin, 13-18
July, 200
Poisson quadrature method of moments for 2D kinetic equations with velocity of constant magnitude
This work is concerned with kinetic equations with velocity of constant
magnitude. We propose a quadrature method of moments based on the Poisson
kernel, called Poisson-EQMOM. The derived moment closure systems are well
defined for all physically relevant moments and the resultant approximations of
the distribution function converge as the number of moments goes to infinity.
The convergence makes our method stand out from most existing moment methods.
Moreover, we devise a delicate moment inversion algorithm. As an application,
the Vicsek model is studied for overdamped active particles. Then the
Poisson-EQMOM is validated with a series of numerical tests including spatially
homogeneous, one-dimensional and two-dimensional problems.Comment: 26 pages, 9 figure
Experimental realization of universal high-dimensional quantum gates with ultra-high fidelity and efficiency
Qudit, a high-dimensional quantum system, provides a larger Hilbert space to
process the quantum information and has shown remarkable advantages over the
qubit counterparts. It is a great challenge to realize the high fidelity
universal quantum gates with qudits. Here we theoretically propose and
experimentally demonstrate a set of universal quantum gates for a single
optical qudit with four dimensions (including the generalized Pauli gate,
Pauli gate, and all of their integer powers), which are encoded in the
polarization-spatial degree of freedom without multiple unstable cascaded
interferometers. Furthermore, we also realize the controlled- gate and all
of its integer powers. We have achieved both the ultra-high average gate
fidelity and efficiency , which are above the the error
threshold for fault-tolerant quantum computation. Our work paves a way for the
large-scale high-dimensional fault-tolerant quantum computation with a
polynomial resource cost
Probing nuclear symmetry energy at high densities using pion, kaon, eta and photon productions in heavy-ion collisions
The high-density behavior of nuclear symmetry energy is among the most
uncertain properties of dense neutron-rich matter. Its accurate determination
has significant ramifications in understanding not only the reaction dynamics
of heavy-ion reactions especially those induced by radioactive beams but also
many interesting phenomena in astrophysics, such as the explosion mechanism of
supernova and the properties of neutron stars. The heavy-ion physics community
has devoted much effort during the last few years to constrain the high-density
symmetry using various probes. In particular, the pion-/pion+ ratio has been
most extensively studied both theoretically and experimentally. All models have
consistently predicted qualitatively that the pion-/pion+ ratio is a sensitive
probe of the high-density symmetry energy especially with beam energies near
the pion production threshold. However, the predicted values of the pion-/pion+
ratio are still quite model dependent mostly because of the complexity of
modeling pion production and reabsorption dynamics in heavy-ion collisions,
leading to currently still controversial conclusions regarding the high-density
behavior of nuclear symmetry energy from comparing various model calculations
with available experimental data. As more pion-/pion+ data become available and
a deeper understanding about the pion dynamics in heavy-ion reactions is
obtained, more penetrating probes, such as the kaon+/kaon0 ratio, eta meson and
high energy photons are also being investigated or planned at several
facilities. Here, we review some of our recent contributions to the community
effort of constraining the high-density behavior of nuclear symmetry energy in
heavy-ion collisions. In addition, the status of some worldwide experiments for
studying the high-density symmetry energy, including the HIRFL-CSR external
target experiment (CEE) are briefly introduced.Comment: 10 pages, 10 figures, Contribution to the Topical Issue on Nuclear
Symmetry Energy in EPJA Special Volum
- …