3,781 research outputs found
Microstructural Characterization of Shrouded Plasma-Sprayed Titanium Coatings
Titanium and its alloys are often used for corrosion protection because they are able to
offer high chemical resistance against various corrosive media. In this paper, shrouded plasma spray
technology was applied to produce titanium coatings. A solid shroud with an external shrouding
gas was used to plasma spray titanium powder feedstock with aim of reducing the oxide content
in the as-sprayed coatings. The titanium coatings were assessed by optical microscope, scanning
electron microscopy, X-ray diffraction, LECO combustion method and Vickers microhardness testing.
The results showed that the presence of the shroud and the external shrouding gas led to a dense
microstructure with a low porosity in the plasma-sprayed titanium coatings. The oxygen and nitrogen
contents in the titanium coating were kept at a low level due to the shielding effect of the shroud
attachment and the external shrouding gas. The dominant phase in the shrouded titanium coatings
was mainly composed of α-Ti phase, which was very similar to the titanium feedstock powders.
The shrouded plasma-sprayed titanium coatings had a Vickers microhardness of 404.2 ± 103.2 HV
Star Formation Properties in Barred Galaxies(SFB). III. Statistical Study of Bar-driven Secular Evolution using a sample of nearby barred spirals
Stellar bars are important internal drivers of secular evolution in disk
galaxies. Using a sample of nearby spiral galaxies with weak and strong bars,
we explore the relationships between the star formation feature and stellar
bars in galaxies. We find that galaxies with weak bars tend to be coincide with
low concentrical star formation activity, while those with strong bars show a
large scatter in the distribution of star formation activity. We find enhanced
star formation activity in bulges towards stronger bars, although not
predominantly, consistent with previous studies. Our results suggest that
different stages of the secular process and many other factors may contribute
to the complexity of the secular evolution. In addition, barred galaxies with
intense star formation in bars tend to have active star formation in their
bulges and disks, and bulges have higher star formation densities than bars and
disks, indicating the evolutionary effects of bars. We then derived a possible
criterion to quantify the different stages of bar-driven physical process,
while future work is needed because of the uncertainties.Comment: 30 single-column pages, 9 figures, accepted for publication in A
Data transfer of non-matching meshes in a common dimensionality reduction space for turbine blade
A data transfer method in dimensionality reduction space is proposed for the fluil-structure-interaction problems, which commonly have non-matching meshes at interface. The method provided in the article can reduce the dimensionality of the data transfer by means of projecting interface surface meshes into a dimensionality reduction space. The dimensionality reduction projection can be realized by defining local coordinates system for interface surface. Furthermore, the size of interface surface meshes has little influence on the data transfer. At last, the method is validated using a temperature transfer problem of turbine blade
Robust Average Formation Tracking for Multi-Agent Systems With Multiple Leaders
In this paper, the formation tracking problem of the multi-agent system under disturbances and unmodeled uncertainties has been studied. An identifier-based robust control algorithm using the neighboring relative information has been proposed to ensure the followers to maintain a given, and time-varying formation and track the average state of the leaders at the same time. Some sufficient conditions for the second-order multi-agent system with multiple leaders in the presence of disturbances and unmodeled uncertainties have been proposed based on the graph theory and the Lyapunov method. Numerical simulations are provided to testify the validity of the algorithm
Effects of relative orientation of the molecules on electron transport in molecular devices
Effects of relative orientation of the molecules on electron transport in
molecular devices are studied by non-equilibrium Green's function method based
on density functional theory. In particular, two molecular devices, with the
planer Au and Ag clusters sandwiched between the Al(100) electrodes
are studied. In each device, two typical configurations with the clusters
parallel and vertical to the electrodes are considered. It is found that the
relative orientation affects the transport properties of these two devices
completely differently. In the Al(100)-Au-Al(100) device, the conductance
and the current of the parallel configuration are much larger than those in the
vertical configuration, while in the Al(100)-Ag-Al(100) device, an
opposite conclusion is obtained
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