We present results of a sensitive 76 ksec Chandra observation of the young stellar cluster in NGC 2024, lying at a distance of ∼415 pc in the Orion B giant molecular cloud. Previous infrared observations have shown that this remarkable cluster contains several hundred embedded young stars, most of which are still surrounded by circumstellar disks. Thus, it presents a rare opportunity to study X...

In this study, the transitions of land use that occurred in the urban and peripheral areas of Chihuahua City, Mexico, were determined for the period 1989–2014. Landsat TM and OLI scenes, as well as the method of Markov Chains (MC) were used. Grasslands and Shrublands were the land uses that experienced the highest pressures for land use. Grasslands occupied 23.5% of the area in 1989, decreasing...

Aluminum 2024 and 7075 alloys which are widely used in aerospace and marine applications were chosen to investigate their strengthening mechanisms. Using differential thermal analysis (DIA), metallography and tension tests, the best solutionizing conditions were determined to be 500±5°C and 2 hours for 2024 and 480?±5°C and 1 hour for 7075 alloy. Aging was performed in the range of 100 to 200°C...

The material flow and microstructural evolution in the friction stir welds of a 6061-Al alloy to itself and of a 6061-Al alloy to 2024-Al alloy plates of 12.7 mm in thickness were studied under different welding conditions. The results showed that plastic deformation, flow, and mechanical mixing of the material exhibit distinct asymmetry characteristics at both sides of the same and dissimilar ...

In this paper we study the class of square matrices A such that AA − AA is nonsingular, where A stands for the Moore–Penrose inverse of A. Among several characterizations we prove that for a matrix A of order n, the difference AA−AA is nonsingular if and only if R(A) ⊕ R(A) = Cn,1, where R(·) denotes the range space. Also we study matrices A such that R(A) = R(A).

We conducted wide-field JHKs imaging polarimetry toward NGC 2024, which is a massive star-forming region in the Orion B cloud. We found a prominent and extended polarized nebula over NGC 2024, and constrained the location of illuminating source of the nebula through the analysis of polarization vectors. A massive star, IRS 2b with a spectral type of O8 − B2, is located in the center of the symm...

We determine the distribution of circumstellar disk masses in the young (∼ 0.3 Myr) cluster NGC 2024 by imaging a 2. 5×2. 5 region in λ3mm continuum emission to an RMS noise level of ∼ 0.75 mJy beam with the Owens Valley Millimeter Array. The mosaic encompasses 147 K-band sources as well as the molecular ridge seen previously in dust continuum emission. We detect 10 point-like sources in λ3mm c...