13,929 research outputs found
Multi-frequency fine resolution imaging radar instrumentation and data acquisition
Development of a dual polarized L-band radar imaging system to be used in conjunction with the present dual polarized X-band radar is described. The technique used called for heterodyning the transmitted frequency from X-band to L-band and again heterodyning the received L-band signals back to X-band for amplification, detection, and recording
Operations planning simulation model extension study. Volume 2: Life sciences shuttle laboratory LS-09-S Sortie payload
For abstract, see N75-20432
Operations planning simulation model extension study. Volume 3: Dedicated solar sortie mission SO-01-S sortie payload
For abstract, see N75-20432
Computer Communications: Government Regulation
As the sole suppliers of telephone or telegraph services, certain carriers have the market power to tie or compel the purchase of their data processing services; they can subsidize the cost of their data processing services with the revenue derived from their monopoly; and they are able to divert resources needed to provide basic telecommunications services to promote their competitive data processing business. The issues raised by such competition will ultimately affect the services and facilities available to all users of computers and communications components needed to link the computer to the user. In this Article, Herbert E. Marks and Stephen R. Bell maintain that the present federal regulatory scheme is unsatisfactory because the areas within which the computer and communications industries may permissibly operate are not clearly defined. As a result, there is considerable overlap and competition. Congress and the FCC in its Second Computer Inquiry are presently considering new methods of regulation
LANDSAT-D investigations in snow hydrology
Work undertaken during the contract and its results are described. Many of the results from this investigation are available in journal or conference proceedings literature - published, accepted for publication, or submitted for publication. For these the reference and the abstract are given. Those results that have not yet been submitted separately for publication are described in detail. Accomplishments during the contract period are summarized as follows: (1) analysis of the snow reflectance characteristics of the LANDSAT Thematic Mapper, including spectral suitability, dynamic range, and spectral resolution; (2) development of a variety of atmospheric models for use with LANDSAT Thematic Mapper data. These include a simple but fast two-stream approximation for inhomogeneous atmospheres over irregular surfaces, and a doubling model for calculation of the angular distribution of spectral radiance at any level in an plane-parallel atmosphere; (3) incorporation of digital elevation data into the atmospheric models and into the analysis of the satellite data; and (4) textural analysis of the spatial distribution of snow cover
Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes
Whether BDs form as stars through gravitational collapse ("star-like") or BDs
and some very low-mass stars constitute a separate population which form
alongside stars comparable to the population of planets, e.g. through
circumstellar disk ("peripheral") fragmentation, is one of the key questions of
the star-formation problem. For young stars in Taurus-Auriga the binary
fraction is large with little dependence on primary mass above ~0.2Msun, while
for BDs it is <10%. We investigate a case in which BDs in Taurus formed
dominantly through peripheral fragmentation. The decline of the binary
frequency in the transition region between star-like and peripheral formation
is modelled. A dynamical population synthesis model is employed in which
stellar binary formation is universal. Peripheral objects form separately in
circumstellar disks with a distinctive initial mass function (IMF), own orbital
parameter distributions for binaries and a low binary fraction. A small amount
of dynamical processing of the stellar component is accounted for as
appropriate for the low-density Taurus-Auriga embedded clusters. The binary
fraction declines strongly between the mass-limits for star-like and peripheral
formation. The location of characteristic features and the steepness depend on
these mass-limits. Such a trend might be unique to low density regions hosting
dynamically unprocessed binary populations. The existence of a strong decline
in the binary fraction -- primary mass diagram will become verifiable in future
surveys on BD and VLMS binarity in the Taurus-Auriga star forming region. It is
a test of the (non-)continuity of star formation along the mass-scale, the
separateness of the stellar and BD populations and the dominant formation
channel for BDs and BD binaries in regions of low stellar density hosting
dynamically unprocessed populations.Comment: accepted for publication in A&A, 11 pages, 4 figures, 1 tabl
Remote sensing applications to hydrologic modeling
An energy balance snowmelt model for rugged terrain was devised and coupled to a flow model. A literature review of remote sensing applications to hydrologic modeling was included along with a software development outline
Geobase Information System Impacts on Space Image Formats
As Geobase Information Systems increase in number, size and complexity, the format compatability of satellite remote sensing data becomes increasingly more important. Because of the vast and continually increasing quantity of data available from remote sensing systems the utility of these data is increasingly dependent on the degree to which their formats facilitate, or hinder, their incorporation into Geobase Information Systems. To merge satellite data into a geobase system requires that they both have a compatible geographic referencing system. Greater acceptance of satellite data by the user community will be facilitated if the data are in a form which most readily corresponds to existing geobase data structures. The conference addressed a number of specific topics and made recommendations
Traps of multi-level governance. Lessons from the implementation of the Water Framework Directive in Italy
During recent decades, different patterns of multi-level governance (MLG) have spread across Europe as a consequence of Europeanisation of public policies, which have increasingly adopted decentralized and participatory procedures conceived as a tool of more effective and accountable policy-making. It appears, however, that the implementation of operational designs based on MLG may be rather problematic and it does not necessarily bring to the expected performance improvements. Referring to the case of the EU Water Framework Directive (2000/60/EC), which conceives the creation of new multi-level institutional settings as a key tool for enacting a new holistic approach to water management and protection, this article explores the difficulties that the implementation of such settings has brought in Italy, despite some favorable pre-conditions existing in the country. Evidence is provided that along with institutional and agency variables, the implementation effectiveness of MLG arrangements promoted by the EU can be challenged by their inherent characteristics
The influence of gas expulsion and initial mass-segregation on the stellar mass-function of globular star clusters
Recently de Marchi, Paresce & Pulone (2007) studied a sample of twenty
globular clusters and found that all clusters with high concentrations have
steep stellar mass-functions while clusters with low concentration have
comparatively shallow mass-functions. No globular clusters were found with a
flat mass-function and high concentration. This seems curious since more
concentrated star clusters are believed to be dynamically more evolved and
should have lost more low-mass stars via evaporation, which would result in a
shallower mass-function in the low-mass part.
We show that this effect can be explained by residual-gas expulsion from
initially mass-segregated star clusters, and is enhanced further through
unresolved binaries. If gas expulsion is the correct mechanism to produce the
observed trend, then observation of these parameters would allow to constrain
cluster starting conditions such as star formation efficiency and the
time-scale of gas expulsion.Comment: accepted for publication in MNRAS, 10 pages, 6 figure
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