650 research outputs found
Novel interface-selected waves and their influences on wave competitions
The topic of interface effects in wave propagation has attracted great
attention due to their theoretical significance and practical importance. In
this paper we study nonlinear oscillatory systems consisting of two media
separated by an interface, and find a novel phenomenon: interface can select a
type of waves (ISWs). Under certain well defined parameter condition, these
waves propagate in two different media with same frequency and same wave
number; the interface of two media is transparent to these waves. The frequency
and wave number of these interface-selected waves (ISWs) are predicted
explicitly. Varying parameters from this parameter set, the wave numbers of two
domains become different, and the difference increases from zero continuously
as the distance between the given parameters and this parameter set increases
from zero. It is found that ISWs can play crucial roles in practical problems
of wave competitions, e.g., ISWs can suppress spirals and antispirals
Stability results for a hierarchical size-structured population model with distributed delay
In this paper we investigate a structured population model with distributed delay. Our model incorporates two different types of nonlinearities. Specifically we assume that individual growth and mortality are affected by scramble competition, while fertility is affected by contest competition. In particular, we assume that there is a hierarchical structure in the population, which affects mating success. The dynamical behavior of the model is analysed via linearisation by means of semigroup and spectral methods. In particular, we introduce a reproduction function and use it to derive linear stability criteria for our model. Further we present numerical simulations to underpin the stability results we obtained
Parallel momentum distribution of the Si fragments from P
Distribution of the parallel momentum of Si fragments from the breakup
of 30.7 MeV/nucleon P has been measured on C targets. The distribution
has the FWHM with the value of 110.5 23.5 MeV/c which is consistent
quantitatively with Galuber model calculation assuming by a valence proton in
P. The density distribution is also predicted by Skyrme-Hartree-Fock
calculation. Results show that there might exist the proton-skin structure in
P.Comment: 4 pages, 4 figure
Dilute magnetism and spin-orbital percolation effects in Sr\u3csub\u3e2\u3c/sub\u3eIr\u3csub\u3e1−\u3cem\u3ex\u3c/em\u3e\u3c/sub\u3eRh\u3csub\u3e\u3cem\u3ex\u3c/em\u3e\u3c/sub\u3eO\u3csub\u3e4\u3c/sub\u3e
We have used a combination of resonant magnetic x-ray scattering and x-ray absorption spectroscopy to investigate the properties of the doped spin-orbital Mott insulator Sr2Ir1−xRhxO4 (0.07 ≤ x ≤ 0.70). We show that Sr2Ir1−xRhxO4 represents a unique model system for the study of dilute magnetism in the presence of strong spin-orbit coupling, and provide evidence of a doping-induced change in magnetic structure and a suppression of magnetic order at xc ∼ 0.17. We demonstrate that Rh-doping introduces Rh3+/Ir5+ ions which effectively hole-dope this material. We propose that the magnetic phase diagram for this material can be understood in terms of a novel spin-orbital percolation picture
Superconductivity in Fluorine-Arsenide Sr_{1-x}La_xFeAsF
Since the discovery of superconductivity\cite{1} at 26 K in oxy-pnictide
, enormous interests have been stimulated in the fields of
condensed matter physics and material sciences. Among the five different
structures in this broad type of superconductors\cite{2,3,4,5,6}, the ZrCuSiAs
structure has received special attention since the has been quickly
promoted to 55-56 K\cite{7,8,9,10,11} in fluorine doped oxy-pnictides REFeAsO
(RE = rare earth elements). The superconductivity can also be induced by
applying a high pressure to the undoped samples\cite{12,13}. The mechanism of
superconductivity in the FeAs-based system remains unclear yet, but it turns
out to be clear that any change to the structure or the building blocks will
lead to a change of the superconducting transition temperatures. In this
Letter, we report the fabrication of the new family of compounds, namely
fluorine-arsenides DvFeAsF (Dv = divalent metals) with the ZrCuSiAs structure
and with the new building block DvF instead of the REO (both the layers DvF and
REO have the combined cation state of "+1"). The undoped parent phase has a
Spin-Density-Wave like transition at about 173 K for SrFeAsF, 118 K for CaFeAsF
and 153 K for EuFeAsF. By doping electrons into the system the resistivity
anomaly associated with this SDW transition is suppressed and superconductivity
appears at 32 K in the fluorine-arsenide SrLaFeAsF (x = 0.4). Our
discovery here initiates a new method to obtain superconductors in the
FeAs-based system.Comment: 11 pages, 4 figures, typos added, references added, and one figure
adde
Total Reaction Cross Section in an Isospin-Dependent Quantum Molecular Dynamics (IDQMD) Model
The isospin-dependent quantum molecular dynamics (IDQMD) model is used to
study the total reaction cross section . The energy-dependent Pauli
volumes of neutrons and protons have been discussed and introduced into the
IDQMD calculation to replace the widely used energy-independent Pauli volumes.
The modified IDQMD calculation can reproduce the experimental well
for both stable and exotic nuclei induced reactions. Comparisons of the
calculated induced by with different initial density
distributions have been performed. It is shown that the calculation by using
the experimentally deduced density distribution with a long tail can fit the
experimental excitation function better than that by using the
Skyrme-Hartree-Fock calculated density without long tails. It is also found
that at high energy is sensitive to the long tail of density
distribution.Comment: 4 page, 4 fig
High-T_c superconductivity induced by doping rare earth elements into CaFeAsF
We have successfully synthesized the fluoride-arsenide compounds
CaREFeAsF (RE=Nd, Pr; x=0, 0.6). The x-ray powder diffraction
confirmed that the main phases of our samples are CaREFeAsF with
the ZrCuSiAs structure. By measuring resistivity, superconductivity was
observed at 57.4 K in Nd-doped and 52.8 K in Pr-doped samples with x=0.6. Bulk
superconductivity was also proved by the DC magnetization measurements in both
samples. Hall effect measurements revealed hole-like charge carriers in the
parent compound CaFeAsF with a clear resistivity anomaly below 118 K, while the
Hall coefficient in the normal state is negative for the superconducting
samples CaNdFeAsF and CaPrFeAsF. This indicates
that the rare earth element doping introduces electrons into CaFeAsF which
induces the high temperature superconductivity.Comment: 4 pages, 4 figure
Synthesis of Mesoporous Silica@Co–Al Layered Double Hydroxide Spheres: Layer-by-Layer Method and Their Effects on the Flame Retardancy of Epoxy Resins
Hierarchical mesoporous silica@Co–Al layered double hydroxide (m-SiO2@Co–Al LDH) spheres were prepared through a layer-by-layer assembly process, in order to integrate their excellent physical and chemical functionalities. TEM results depicted that, due to the electrostatic potential difference between m-SiO2 and Co–Al LDH, the synthetic m-SiO2@Co–Al LDH hybrids exhibited that m-SiO2 spheres were packaged by the Co–Al LDH nanosheets. Subsequently, the m-SiO2@Co–Al LDH spheres were incorporated into epoxy resin (EP) to prepare specimens for investigation of their flame-retardant performance. Cone results indicated that m-SiO2@Co–Al LDH incorporated obviously improved fire retardant of EP. A plausible mechanism of fire retardant was hypothesized based on the analyses of thermal conductivity, char residues, and pyrolysis fragments. Labyrinth effect of m-SiO2 and formation of graphitized carbon char catalyzed by Co–Al LDH play pivotal roles in the flame retardance enhancement
-scaling and Information Entropy in Ultra-Relativistic Nucleus-Nucleus Collisions
The -scaling method has been applied to ultra-relativistic p+p, C+C
and Pb+Pb collision data simulated using a high energy Monte Carlo package,
LUCIAE 3.0. The -scaling is found to be valid for some physical
variables, such as charged particle multiplicity, strange particle multiplicity
and number of binary nucleon-nucleon collisions from these simulated
nucleus-nucleus collisions over an extended energy ranging from = 20
to 200 A GeV. In addition we derived information entropy from the multiplicity
distribution as a function of beam energy for these collisions.Comment: 4 pages, 4 figures, 1 table; to appear in the July Issue of Chin.
Phys. Lett.. Web Page: http://www.iop.org/EJ/journal/CP
Pairing symmetry and properties of iron-based high temperature superconductors
Pairing symmetry is important to indentify the pairing mechanism. The
analysis becomes particularly timely and important for the newly discovered
iron-based multi-orbital superconductors. From group theory point of view we
classified all pairing matrices (in the orbital space) that carry irreducible
representations of the system. The quasiparticle gap falls into three
categories: full, nodal and gapless. The nodal-gap states show conventional
Volovik effect even for on-site pairing. The gapless states are odd in orbital
space, have a negative superfluid density and are therefore unstable. In
connection to experiments we proposed possible pairing states and implications
for the pairing mechanism.Comment: 4 pages, 1 table, 2 figures, polished versio
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