12,855 research outputs found
Impingement of Water Droplets on NACA 65A004 Airfoil at 8 deg Angle of Attack
The trajectories of droplets in the air flowing past an NACA 65AO04 airfoil at an angle of attack of 8 deg were determined.. The amount of water in droplet form impinging on the airfoil, the area of droplet impingement, and the rate of droplet impingement per unit area on the airfoil surface were calculated from the trajectories and presented to cover a large range of flight and atmospheric conditions. These impingement characteristics are compared briefly with those previously reported for the same airfoil at an angle of attack of 4 deg
Millimeter wave satellite concepts, volume 1
The identification of technologies necessary for development of millimeter spectrum communication satellites was examined from a system point of view. Development of methodology based on the technical requirements of potential services that might be assigned to millimeter wave bands for identifying the viable and appropriate technologies for future NASA millimeter research and development programs, and testing of this methodology with selected user applications and services were the goals of the program. The entire communications network, both ground and space subsystems was studied. Cost, weight, and performance models for the subsystems, conceptual design for point-to-point and broadcast communications satellites, and analytic relationships between subsystem parameters and an overall link performance are discussed along with baseline conceptual systems, sensitivity studies, model adjustment analyses, identification of critical technologies and their risks, and brief research and development program scenarios for the technologies judged to be moderate or extensive risks. Identification of technologies for millimeter satellite communication systems, and assessment of the relative risks of these technologies, was accomplished through subsystem modeling and link optimization for both point-to-point and broadcast applications
Cosmic Pathways for Compact Groups in the Milli-Millennium Simulation
We detected 10 compact galaxy groups (CGs) at in the semi-analytic
galaxy catalog of Guo et al. (2011) for the milli-Millennium Cosmological
Simulation (sCGs in mGuo2010a). We aimed to identify potential canonical
pathways for compact group evolution and thus illuminate the history of
observed nearby compact groups. By constructing merger trees for sCG
galaxies, we studied the cosmological evolution of key properties, and compared
them with Hickson CGs (HCGs). We found that, once sCG galaxies come
within 1 (0.5) Mpc of their most massive galaxy, they remain within that
distance until , suggesting sCG "birth redshifts". At stellar masses
of sCG most-massive galaxies are within . In several cases, especially in the two 4- and 5-member
systems, the amount of cold gas mass anti-correlates with stellar mass, which
in turn correlates with hot gas mass. We define the angular difference between
group members' 3D velocity vectors, , and note that
many of the groups are long-lived because their small values of
indicate a significant parallel component. For
triplets in particular, values range between
and so that galaxies are coming together along
roughly parallel paths, and pairwise separations do not show large pronounced
changes after close encounters. The best agreement between sCG and HCG physical
properties is for galaxy values, but HCG values are higher overall,
including for SFRs. Unlike HCGs, due to a tail at low SFR and , and a
lack of galaxies, only a few sCG galaxies
are on the star-forming main sequence.Comment: Style fixes to better match ApJ published version. Uses likeapj1.1
style files: 17 pages, 13 figures, 2 tables. LaTex style files available at
https://github.com/qtast/likeapj/releases/lates
An Unfinished Canvas: Allocating Funding and Instructional Time for Elementary Arts Education
An Unfinished Canvas found that California's elementary schools face unique challenges inproviding all students with sequential, standards-based arts education. In particular, elementary principals identified inadequate funding and insufficient instructional time as significant barriers to the provision of arts education. For this study, we sought to further understand the impact of funding and time on elementary arts education. To do so, we examined the allocation of funding and instructional time in 10 schools across five states (Kentucky, Massachusetts, Minnesota, New Jersey, and California)
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