8,412 research outputs found
The development of a solar powered residential heating and cooling system
A solar energy collector design is disclosed that would be efficient for both energy transfer and fluid flow, based upon extensive parametric analyses. Thermal design requirements are generated for the energy storage systems which utilizes sensible heat storage in water. Properly size system components (including the collector and storage) and a practical, efficient total system configuration are determined by means of computer simulation of system performance
Wind turbine generator interaction with conventional diesel generators on Block Island, Rhode Island. Volume 2: Data analysis
Assessing the performance of a MOD-OA horizontal axis wind turbine connected to an isolated diesel utility, a comprehensive data measurement program was conducted on the Block Island Power Company installation on Block Island, Rhode Island. The detailed results of that program focusing on three principal areas of (1) fuel displacement (savings), (2) dynamic interaction between the diesel utility and the wind turbine, (3) effects of three models of wind turbine reactive power control are presented. The approximate two month duration of the data acquisition program conducted in the winter months (February into April 1982) revealed performance during periods of highest wind energy penetration and hence severity of operation. Even under such conditions fuel savings were significant resulting in a fuel reduction of 6.7% while the MOD-OA was generating 10.7% of the total electrical energy. Also, electrical disturbance and interactive effects were of an acceptable level
Wind turbine generator interaction with conventional diesel generators on Block Island, Rhode Island. Volume 1: Executive summary
Primary results are summarized for a three-part study involving the effects of connecting a MOD-OA wind turbine generator to an isolated diesel power system. The MOD-OA installation considered was the third of four experimental nominal 200 kW wind turbines connected to various utilities under the Federal Wind Energy Program and was characterized by the highest wind energy penetration levels of four sites. The study analyses address: fuel displacement, dynamic interaction, and three modes of reactive power control. These analyses all have as their basis the results of the data acquisition program conducted on Block Island, Rhode Island
Organizing information on the next generation web - Design and implementation of a new bookmark structure
The next-generation Web will increase the need for a highly organized and ever evolving method to store references to Web objects. These requirements could be realized by the development of a new bookmark structure. This paper endeavors to identify the key requirements of such a bookmark, specifically in relation to Web documents, and sets out a suggested design through which these needs may be accomplished. A prototype developed offers such features as the sharing of bookmarks between users and groups of users. Bookmarks for Web documents in this prototype allow more specific information to be stored such as: URL, the document type, the document title, keywords, a summary, user annotations, date added, date last visited and date last modified. Individuals may access the service from anywhere on the Internet, as long as they have a Java-enabled Web browser
The non-Gaussian tail of cosmic-shear statistics
Due to gravitational instability, an initially Gaussian density field
develops non-Gaussian features as the Universe evolves. The most prominent
non-Gaussian features are massive haloes, visible as clusters of galaxies. The
distortion of high-redshift galaxy images due to the tidal gravitational field
of the large-scale matter distribution, called cosmic shear, can be used to
investigate the statistical properties of the LSS. In particular, non-Gaussian
properties of the LSS will lead to a non-Gaussian distribution of cosmic-shear
statistics. The aperture mass () statistics, recently introduced as
a measure for cosmic shear, is particularly well suited for measuring these
non-Gaussian properties. In this paper we calculate the highly non-Gaussian
tail of the aperture mass probability distribution, assuming Press-Schechter
theory for the halo abundance and the `universal' density profile of haloes as
obtained from numerical simulations. We find that for values of
much larger than its dispersion, this probability distribution is closely
approximated by an exponential, rather than a Gaussian. We determine the
amplitude and shape of this exponential for various cosmological models and
aperture sizes, and show that wide-field imaging surveys can be used to
distinguish between some of the currently most popular cosmogonies. Our study
here is complementary to earlier cosmic-shear investigations which focussed
more on two-point statistical properties.Comment: 9 pages, 5 figures, submitted to MNRA
GaBoDS: The Garching-Bonn Deep Survey -- I. Anatomy of galaxy clusters in the background of NGC 300
The Garching-Bonn Deep Survey (GaBoDS) is a virtual 12 square degree cosmic
shear and cluster lensing survey, conducted with the [email protected] MPG/ESO telescope
at La Silla. It consists of shallow, medium and deep random fields taken in
R-band in subarcsecond seeing conditions at high galactic latitude. A
substantial amount of the data was taken from the ESO archive, by means of a
dedicated ASTROVIRTEL program.
In the present work we describe the main characteristics and scientific goals
of GaBoDS. Our strategy for mining the ESO data archive is introduced, and we
comment on the Wide Field Imager data reduction as well. In the second half of
the paper we report on clusters of galaxies found in the background of NGC 300,
a random archival field. We use weak gravitational lensing and the red cluster
sequence method for the selection of these objects. Two of the clusters found
were previously known and already confirmed by spectroscopy. Based on the
available data we show that there is significant evidence for substructure in
one of the clusters, and an increasing fraction of blue galaxies towards larger
cluster radii. Two other mass peaks detected by our weak lensing technique
coincide with red clumps of galaxies. We estimate their redshifts and masses.Comment: 20 pages, 16 figures, gzipped. An online postscript version with
higher quality figures (3.3 MBytes) can be downloaded from
http://www.mpa-garching.mpg.de/~mischa/ngc300/ngc300.ps.gz . Submitted to A&
Cavity Assisted Nondestructive Laser Cooling of Atomic Qubits
We analyze two configurations for laser cooling of neutral atoms whose
internal states store qubits. The atoms are trapped in an optical lattice which
is placed inside a cavity. We show that the coupling of the atoms to the damped
cavity mode can provide a mechanism which leads to cooling of the motion
without destroying the quantum information.Comment: 12 page
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