510 research outputs found
The influence of rotating magnetic field on the welding arc motion status
A device generating rotating magnetic field is designed on the bas is of the mechanism of a rotating magnetic field. A rotating magnetic field and electric arc jointing together simulation is studied in this paper to elaborate arc characteristics and behavior under the action of a rotating magnetic field. The rotation radius of the arc are inversely proportional to the rotational frequency of the magnetic field. It is proportional to the field current. Due to constraint function of its own magnetic field of underwater wet welding arc. The influence on the underwater welding arc is smaller than the air welding arc while the magnetic field rotation frequency and magnetic field intensity is changed
Isospin fractionation in the nucleon emissions and fragment emissions in the intermediate energy heavy ion collisions
The degree of isospin fractionation is measured by /
, where and are the saturated
neutron-proton ratio of nucleon emissions (gas phase) and that of fragment
emissions (liquid phase) in heavy ion collision at intermediate energy . The
calculated results by using the isospin-dependent quantum molecular dynamics
model show that the degree of isospin fractionation is sensitive to the
neutron-proton ratio of colliding system but insensitive to the difference
between the neutron-proton ratio of target and that of projectile. In
particular, the degree of isospin fractionation sensitively depends on the
symmetry potential. However its dependences on the isospin dependent in-medium
nucleon-nucleon cross section and momentum dependent interaction are rather
weak.
The nucleon emission (gas phase) mainly determines the dynamical behavior of
the degree of isospin fractionation in the isospin fractionation process,
compared to the effect of fragment emission. In this case, we propose that
/ or can be directly compared with
the experimental data so that the information about symmetry potential can be
obtaine
Food Markets with Live Birds as Source of Avian Influenza
A patient may have been infected with highly pathogenic avian influenza virus H5N1 in Guangzhou, People's Republic of China, at a food market that had live birds. Virus genes were detected in 1 of 79 wire cages for birds at 9 markets. One of 110 persons in the poultry business at markets had neutralizing antibody against H5N1.link_to_subscribed_fulltex
A general model for collaboration networks
In this paper, we propose a general model for collaboration networks.
Depending on a single free parameter "{\bf preferential exponent}", this model
interpolates between networks with a scale-free and an exponential degree
distribution. The degree distribution in the present networks can be roughly
classified into four patterns, all of which are observed in empirical data. And
this model exhibits small-world effect, which means the corresponding networks
are of very short average distance and highly large clustering coefficient.
More interesting, we find a peak distribution of act-size from empirical data
which has not been emphasized before of some collaboration networks. Our model
can produce the peak act-size distribution naturally that agrees with the
empirical data well.Comment: 10 pages, 10 figure
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