8,190 research outputs found
Space education: Deriving benefits from industrial consortia
As the number of spacefaring nations of the world increases, so does the difficulty of competing in a global economy. The development of high technology products and services for space programs, and the economic exploitation of these technologies for national economic growth, requires professionals versed in both technical and commercial aspects of space. Meeting this requirement academically presents two challenges. On the technical side, enrollment in science and engineering is decreasing in some of the spacefaring nations. From the commerce perspective, very few colleges and universities offer specific courses in space business
Launch system development in the Pacific Rim
Several Western Pacific Rim nations are beginning to challenge the domination of the United States, Europe, and the former Soviet Union in the international market for commercial launch sevices. This paper examines the current development of launch systems in China, Japan, and Australia. China began commercial launch services with their Long March-3 in April 1990, and is making enhancements to vehicles in this family. Japan is developing the H-2 rocket which will be marketed on a commercial basis. In Australia, British Aerospace Ltd. is leading a team conducting a project definition study for an Australian Launch Vehicle, aimed at launching the new generation of satellites into low Earth orbit
Coalescence of Liquid Drops
When two drops of radius touch, surface tension drives an initially
singular motion which joins them into a bigger drop with smaller surface area.
This motion is always viscously dominated at early times. We focus on the
early-time behavior of the radius \rmn of the small bridge between the two
drops. The flow is driven by a highly curved meniscus of length 2\pi \rmn and
width \Delta\ll\rmn around the bridge, from which we conclude that the
leading-order problem is asymptotically equivalent to its two-dimensional
counterpart. An exact two-dimensional solution for the case of inviscid
surroundings [Hopper, J. Fluid Mech. , 349 (1990)] shows that
\Delta \propto \rmn^3 and \rmn \sim (t\gamma/\pi\eta)\ln [t\gamma/(\eta
R)]; and thus the same is true in three dimensions. The case of coalescence
with an external viscous fluid is also studied in detail both analytically and
numerically. A significantly different structure is found in which the outer
fluid forms a toroidal bubble of radius \Delta \propto \rmn^{3/2} at the
meniscus and \rmn \sim (t\gamma/4\pi\eta) \ln [t\gamma/(\eta R)]. This basic
difference is due to the presence of the outer fluid viscosity, however small.
With lengths scaled by a full description of the asymptotic flow for
\rmn(t)\ll1 involves matching of lengthscales of order \rmn^2, \rmn^{3/2},
\rmn\rmn^{7/4}$.Comment: 36 pages, including 9 figure
Changes in banking concentration in selected Fifth district SMSAs, 1970-1976
An abstract for this article is not availableBanks and banking ; Federal Reserve District, 5th
Paper Session II-A - Launch System Development in the Pacific Rim
Several Western Pacific Rim nations are beginning to challenge the domination of the United States, Europe, and the former Soviet Union in the international market for commercial launch services. This paper examines the current development of launch systems in China, Japan, and Australia.
China began commercial launch services with their Long March-3 in April 1990, and is making enhancements to vehicles in this family. Japan is developing the H-2 rocket which will be marketed on a commercial basis. In Australia, British Aerospace Ltd. is leading a team conducting a project definition study for an Australian Launch Vehicle, aimed at launching the new generation of satellites into low Earth orbit
Paper Session III-B - Space Education- Deriving Benefits from Industrial Consortia
As the number of spacefaring nations of the world increases, so does the difficulty of competing in a global economy. The development of high technology products and services for space programs, and the economic exploitation of these technologies for national economic growth, requires professionals versed in both technical and commercial aspects of space. Meeting this requirement academically presents two challenges. On the technical side, enrollment in science and engineering is decreasing in some of the spacefaring nations. From the commerce perspective, very few colleges and universities offer specific courses in space business.
The United States and Australia have each established programs targeted towards developing strong linkages between their universities, businesses, and space programs. The U.S. Centers for the Commercial Development of Space and the Australian Space Industry Development Centres are consortia composed primarily of universities and companies seeking to identify and exploit potentially commercially significant space-based technologies. Australia\u27s Cooperative Research Centres, which are not limited to space research, include Centre\u27s with a space interest. This paper describes each country\u27s industry consortia program and discusses the resulting benefits to space education
Optical/UV-to-X-Ray Echoes from the Tidal Disruption Flare ASASSN-14li
We carried out the first multi-wavelength (optical/UV and X-ray) photometric
reverberation mapping of a tidal disruption flare (TDF) ASASSN-14li. We find
that its X-ray variations are correlated with and lag the optical/UV
fluctuations by 324 days. Based on the direction and the magnitude of the
X-ray time lag, we rule out X-ray reprocessing and direct emission from a
standard circular thin disk as the dominant source of its optical/UV emission.
The lag magnitude also rules out an AGN disk-driven instability as the origin
of ASASSN-14li and thus strongly supports the tidal disruption picture for this
event and similar objects. We suggest that the majority of the optical/UV
emission likely originates from debris stream self-interactions. Perturbations
at the self-interaction sites produce optical/UV variability and travel down to
the black hole where they modulate the X-rays. The time lag between the
optical/UV and the X-rays variations thus correspond to the time taken by these
fluctuations to travel from the self-interaction site to close to the black
hole. We further discuss these time lags within the context of the three
variants of the self-interaction model. High-cadence monitoring observations of
future TDFs will be sensitive enough to detect these echoes and would allow us
to establish the origin of optical/UV emission in TDFs in general.Comment: Publish in ApJ Letter
Calibrating Type Ia Supernovae using the Planetary Nebula Luminosity Function I. Initial Results
We report the results of an [O III] lambda 5007 survey for planetary nebulae
(PN) in five galaxies that were hosts of well-observed Type Ia supernovae: NGC
524, NGC 1316, NGC 1380, NGC 1448 and NGC 4526. The goals of this survey are to
better quantify the zero-point of the maximum magnitude versus decline rate
relation for supernovae Type Ia and to validate the insensitivity of Type Ia
luminosity to parent stellar population using the host galaxy Hubble type as a
surrogate. We detected a total of 45 planetary nebulae candidates in NGC 1316,
44 candidates in NGC 1380, and 94 candidates in NGC 4526. From these data, and
the empirical planetary nebula luminosity function (PNLF), we derive distances
of 17.9 +0.8/-0.9 Mpc, 16.1 +0.8/-1.1 Mpc, and 13.6 +1.3/-1.2 Mpc respectively.
Our derived distance to NGC 4526 has a lower precision due to the likely
presence of Virgo intracluster planetary nebulae in the foreground of this
galaxy. In NGC 524 and NGC 1448 we detected no planetary nebulae candidates
down to the limiting magnitudes of our observations. We present a formalism for
setting realistic distance limits in these two cases, and derive robust lower
limits of 20.9 Mpc and 15.8 Mpc, respectively.
After combining these results with other distances from the PNLF, Cepheid,
and Surface Brightness Fluctuations distance indicators, we calibrate the
optical and near-infrared relations for supernovae Type Ia and we find that the
Hubble constants derived from each of the three methods are broadly consistent,
implying that the properties of supernovae Type Ia do not vary drastically as a
function of stellar population. We determine a preliminary Hubble constant of
H_0 = 77 +/- 3 (random) +/- 5 (systematic) km/s/Mpc for the PNLF, though more
nearby galaxies with high-quality observations are clearly needed.Comment: 25 pages, 12 figures. Accepted for publication by the Astrophysical
Journal. Figures degraded to comply with limit. Full paper is available at:
http://www.as.ysu.edu/~jjfeldme/pnlf_Ia.pd
Breaking Ground: Planning and Building in Priority Growth Districts
The need to control sprawl, encourage Smart Growth, and create more livable neighborhoods that instill a sense of community through traditional neighborhood design, are topics in the forefront of national discussions about community planning and development. There is an innovative land use technique that can be used by communities to manage and define future growth in a way that creates more livable places, places that are environmentally, socially, and fiscally sound. Specifically, a community may designate mixed-use Priority Growth Districts, or PGDs, which direct development to selected locations and also specify a design that is attractive to the community’s current and future residents. This report provides the necessary tools and describes the steps that a community may take to designate Priority Growth Districts and reap their many benefits.
The PGD concept discussed here is particularly suited for outlying suburban and exurban counties, where the rate of growth is significant but there is still a rural character that can be preserved. Growth in these areas may result from the actions of transportation agencies, which make outlying communities more accessible, from housing shortages in areas near job centers, or from the changing housing needs of current residents. The pressure to provide new homes can best be addressed through the identification of PGDs where roadways and other infrastructure either exist or can be accommodated.
This report draws examples primarily from Dutchess and Orange counties in New York State, but the principles and techniques discussed here are applicable in various locations
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