17 research outputs found
An Anomalous Extinction Law in the Cep OB3b Young Cluster: Evidence for dust processing during gas dispersal
We determine the extinction law through Cep OB3b, a young cluster of 3000
stars undergoing gas dispersal. The extinction is measured toward 76 background
K giants identified with MMT/Hectospec spectra. Color excess ratios were
determined toward each of the giants using and photometry from the
literature, ,, and photometry from SDSS and , , and
photometry from 2MASS. These color excess ratios were the used to construct the
extinction law through the dusty material associated with Cep OB3b. The
extinction law through Cep OB3b is intermediate between the and
laws commonly used for the diffuse atomic ISM and dense molecular
clouds, respectively. The dependence of the extinction law on line-of-sight
is investigated and we find the extinction law becomes shallower for
regions with magnitudes. We speculate that the intermediate dust
law results from dust processing during the dispersal of the molecular cloud by
the cluster.Comment: 31 pages, 10 Figures, 3 Tables, accepted for publication in Ap
Non-Linear Mechanical Behavior of Plasma Sprayed Alumina Under Mechanical and Thermal Loading
Correlation of Microstructures and Tribological Properties of Ferrous Coatings Deposited by Atmospheric Plasma Spraying on Al-Si Cast Alloy Substrate
The microstructure and tribological properties of ferrous coatings applicable to cylinder bores were investigated in this study. Two kinds of ferrous powders were sprayed on Al-Si cast alloy (EN AlSi10Mg) substrate by atmospheric plasma spraying. Microstructural analysis showed that various Fe oxides were formed in the coatings. The presence of pores, unmelted particles, and Fe precipitates was also noticed. The pin-on-ring tribometer was used to carry out tribological tests under lubricated sliding conditions: sliding speed of 0.5 m/s, sliding distance of 5000 m, and normal load of 450 N. High porosity and the presence of larger and irregularly shaped pores as well as the amount of oxides were the controlling factors for the crack initiations and, consequently, the wear rate. Tribological properties of the coatings were compared with gray cast iron as a standard material for cylinder blocks and showed that, for the investigated conditions, both coatings could be an adequate substitution