16,423 research outputs found
Earth's gravity field mapping requirements and concept
A future sensor is considered for mapping the Earth's gravity field to meet future scientific and practical requirements for earth and oceanic dynamics. These are approximately + or - 0.1 to 10 mgal over a block size of about 50 km and over land and an ocean geoid to 1 to 2 cm over a distance of about 50 km. To achieve these values requires a gravity gradiometer with a sensitivity of approximately 10 to the -4 power EU in a circular polar orbiting spacecraft with an orbital altitude ranging 160 km to 180 km
New considerations on scale extrapolation of wing pressure distributions affected by transonic shock-induced separations
Use of this analytical parameter, it is shown, highlights the distinction between cases which are dominated by trailing-edge separation, and those for which separation at the shock foot is dominant. Use of the analytical parameter and the distinction noted above greatly improves the correlation of separation data and the extrapolation of wind tunnel data to flight conditions
How Protostellar Outflows Help Massive Stars Form
We consider the effects of an outflow on radiation escaping from the
infalling envelope around a massive protostar. Using numerical radiative
transfer calculations, we show that outflows with properties comparable to
those observed around massive stars lead to significant anisotropy in the
stellar radiation field, which greatly reduces the radiation pressure
experienced by gas in the infalling envelope. This means that radiation
pressure is a much less significant barrier to massive star formation than has
previously been thought.Comment: 4 pages, 2 figures, emulateapj, accepted for publication in ApJ
Letter
Secondary Star Formation in a Population III Object
We explore the possibility of subsequent star formation after a first star
forms in a Pop III object, by focusing on the radiation hydrodynamic (RHD)
feedback brought by ionizing photons as well as H2 dissociating photons. For
the purpose, we perform three-dimensional RHD simulations, where the radiative
transfer of ionizing photons and H2 dissociating photons from a first star is
self-consistently coupled with hydrodynamics based on a smoothed particle
hydrodynamics method. As a result, it is shown that density peaks above a
threshold density can keep collapsing owing to the shielding of H2 dissociating
radiation by an H2 shell formed ahead of a D-type ionization front. But, below
the threshold density, an M-type ionization front accompanied by a shock
propagates, and density peaks are radiation hydrodynamically evaporated by the
shock. The threshold density is dependent on the distance from a source star,
which is for the source distance of 30pc. Taking into
consideration that the extent of a Pop III object is pc and
density peaks within it have the density of cm, it is
concluded that the secondary star formation is allowed in the broad regions in
a Pop III object.Comment: 4pages, 2 figures, submitted to Ap
Strengthening of reinforced concrete columns for earthquake resistance
Issued as Annual report, and Final report, Project E-20-61
Diversity and conservation status of Peruvian palms
Indigenous palm species of Peru are listed with data on their distribution patterns, ecology, frequency. density in the ecosystems, and conservation status. Peruvian palm flora includes 140 native species in 34 genera with the following distribution patterns: strictly Andean (17), Andean and Subandean (3), strictly Subandean (19), Subandean and Amazonian (20), strictly Amazonian (7&), Amazonian and South peripheral (2) , South peripheral (1). About 43 % of the species occur at very low or low frequency in the country and about 9 % are insufficiently known in situ for their conservation status to be defined. There are no Extinct species. Sixteen of the 17 strictly Andean palms are threatened species; 3 of them are Endangered, while only 5 strictly Subandean, 3 Subandean-Amazonian, and 4 strictly Amazonian palms are in these categories
Cross-modal cue effects in motion processing
The everyday environment brings to our sensory systems competing inputs from different modalities. The ability to filter these multisensory inputs in order to identify and efficiently utilize useful spatial cues is necessary to detect and process the relevant information. In the present study, we investigate how feature-based attention affects the detection of motion across sensory modalities. We were interested to determine how subjects use intramodal, cross-modal auditory, and combined audiovisual motion cues to attend to specific visual motion signals. The results showed that in most cases, both the visual and the auditory cues enhance feature-based orienting to a transparent visual motion pattern presented among distractor motion patterns. Whereas previous studies have shown cross-modal effects of spatial attention, our results demonstrate a spread of cross-modal feature-based attention cues, which have been matched for the detection threshold of the visual target. These effects were very robust in comparisons of the effects of valid vs. invalid cues, as well as in comparisons between cued and uncued valid trials. The effect of intramodal visual, cross-modal auditory, and bimodal cues also increased as a function of motion-cue salience. Our results suggest that orienting to visual motion patterns among distracters can be facilitated not only by intramodal priors, but also by feature-based cross-modal information from the auditory system.First author draf
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