1,908 research outputs found
Coastal Bluff Retreat at Big Lagoon, California
Big Lagoon, located 30 miles north of Eureka, California is formed behind a bay barrier built across the mouth of a drowned river valley. To the south of the bay the beach follows rising wave cut slightly cemented sand and gravel sea cliffs and terminates at the south end of Agate Beach. The retreat of these sea cliffs and its effect on property development along the top of the cliff is the focus of the paper. Measurements of bluff retreat in this area have been documented extensively from November 1941 to March 1986 through ground surveys and air photos. Review of the data indicates that the retreat rate is not constant along the cliff but has either been decreasing or remaining the same over the last 45 years. Using information on the rate of retreat, a method is developed to predict the cliff erosion in the future
Cargo/Logistics Airlift System Study (CLASS), Volume 2
Air containerization is discussed in terms of lower freight rates, size and pallet limitations, refrigeration, backhaul of empties, and ownership. It is concluded that there is a need for an advance air cargo system as indicated by the industry/transportation case studies, and a stimulation of the air cargo would result in freight rate reductions
Cargo/Logistics Airlift System Study (CLASS), Volume 1
Current and advanced air cargo systems are evaluated using industrial and consumer statistics. Market and commodity characteristics that influence the use of the air mode are discussed along with a comparison of air and surface mode on typical routes. Results of on-site surveys of cargo processing facilities at airports are presented, and institutional controls and influences on air cargo operations are considered
Cargo/Logistics Airlift System Study (CLASS), Executive Summary
The current air cargo system is analyzed along with advanced air cargo systems studies. A forecast of advanced air cargo system demand is presented with cost estimates. It is concluded that there is a need for a dedicated advance air cargo system, and with application of advanced technology, reductions of 45% in air freight rates may be achieved
The NASA Auralization Framework and Plugin Architecture
NASA has a long history of investigating human response to aircraft flyover noise and in recent years has developed a capability to fully auralize the noise of aircraft during their design. This capability is particularly useful for unconventional designs with noise signatures significantly different from the current fleet. To that end, a flexible software architecture has been developed to facilitate rapid integration of new simulation techniques for noise source synthesis and propagation, and to foster collaboration amongst researchers through a common releasable code base. The NASA Auralization Framework (NAF) is a skeletal framework written in C++ with basic functionalities and a plugin architecture that allows users to mix and match NAF capabilities with their own methods through the development and use of dynamically linked libraries. This paper presents the NAF software architecture and discusses several advanced auralization techniques that have been implemented as plugins to the framework
Laser-micromachined Millimeter-wave Photonic band gap cavity structures
Cataloged from PDF version of article.We have used laser-micromachined alumina substrates to build a three-dimensional photonic
band-gap crystal. The rod-based structure has a three-dimensional full photonic band gap between
90 and 100 GHz. The high resistivity of alumina results in a typical attenuation rate of 15 dB per
unit cell within the band gap. By removing material, we have built defects which can be used as
millimeter-wave cavity structures. The resulting quality ~Q! factors of the millimeter-wave cavity
structures were as high as 1000 with a peak transmission of 10 dB below the incident
signal. © 1995 American Institute of Physics
Laetoli's lost tracks: 3D generated mean shape and missing footprints.
The Laetoli site (Tanzania) contains the oldest known hominin footprints, and their interpretation remains open to debate, despite over 35 years of research. The two hominin trackways present are parallel to one another, one of which is a composite formed by at least two individuals walking in single file. Most researchers have focused on the single, clearly discernible G1 trackway while the G2/3 trackway has been largely dismissed due to its composite nature. Here we report the use of a new technique that allows us to decouple the G2 and G3 tracks for the first time. In so doing we are able to quantify the mean footprint topology of the G3 trackway and render it useable for subsequent data analyses. By restoring the effectively 'lost' G3 track, we have doubled the available data on some of the rarest traces directly associated with our Pliocene ancestors
Effect of hydrogen on ground state structures of small silicon clusters
We present results for ground state structures of small SiH (2 \leq
\emph{n} \leq 10) clusters using the Car-Parrinello molecular dynamics. In
particular, we focus on how the addition of a hydrogen atom affects the ground
state geometry, total energy and the first excited electronic level gap of an
Si cluster. We discuss the nature of bonding of hydrogen in these
clusters. We find that hydrogen bonds with two silicon atoms only in SiH,
SiH and SiH clusters, while in other clusters (i.e. SiH,
SiH, SiH, SiH, SiH and SiH) hydrogen is bonded
to only one silicon atom. Also in the case of a compact and closed silicon
cluster hydrogen bonds to the cluster from outside. We find that the first
excited electronic level gap of Si and SiH fluctuates as a function
of size and this may provide a first principles basis for the short-range
potential fluctuations in hydrogenated amorphous silicon. Our results show that
the addition of a single hydrogen can cause large changes in the electronic
structure of a silicon cluster, though the geometry is not much affected. Our
calculation of the lowest energy fragmentation products of SiH clusters
shows that hydrogen is easily removed from SiH clusters.Comment: one latex file named script.tex including table and figure caption.
Six postscript figure files. figure_1a.ps and figure_1b.ps are files
representing Fig. 1 in the main tex
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