14,599 research outputs found
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Mineralogy and Geochemistry of Shergottite RBT 04262
This abstract presents mineralogical and geochemical data on newly discovered shergottite RBT 04262 and compares it with other known shergottites
Development of a mechatronic sorting system for removing contaminants from wool
Automated visual inspection (AVI) systems have been
extended to many fields, such as agriculture and the food, plastic
and textile industries. Generally, most visual systems only inspect
product defects, and then analyze and grade them due to the lack
of any sorting function. This main reason rests with the difficulty of
using the image data in real time. However, it is increasingly important
to either sort good products from bad or grade products into
separate groups usingAVI systems. This article describes the development
of a mechatronic sorting system and its integration with a
vision system for automatically removing contaminants from wool
in real time. The integration is implemented by a personal computer,
which continuously processes live images under the Windows
2000 operating system. The developed real-time sorting approach
is also applicable to many other AVI systems
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Origin of the ungrouped achondrite NWA 4518: mineralogy and geochemistry of FeNi-metal
Ungrouped achondrite NWA 4518 is an ultramafic breccia with abundant siderophile rich IIA-like metal. Its silicate chemistry is similar to that of WINs, HEDs, and silicate inclusions of IIE irons. Oxygen isotopic composition is nearby IAB-IIICD-WIN
Generation of internal stress and its effects
Internal stresses may be generated continually in many polycrystalline materials. Their existence is manifested by changes in crystal defect concentration and arrangement, by surface observations, by macroscopic shape changes and particularly by alteration of mechanical properties when external stresses are simultaneously imposed
Crowding at the Front of the Marathon Packs
We study the crowding of near-extreme events in the time gaps between
successive finishers in major international marathons. Naively, one might
expect these gaps to become progressively larger for better-placing finishers.
While such an increase does indeed occur from the middle of the finishing pack
down to approximately 20th place, the gaps saturate for the first 10-20
finishers. We give a probabilistic account of this feature. However, the data
suggests that the gaps have a weak maximum around the 10th place, a feature
that seems to have a sociological origin.Comment: 5 pages, 2 figures; version 2: published manuscript with various
changes in response to referee comments and some additional improvement
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Tafassasset: The Saga Continues
In this study, we compare data for two separate Tafassasset stones and supply new oxygen isotope data for our sample. We include a discussion of the debate surrounding the classification of Tafassasset and offer a hypothesis for its origin based upon new information
The effect of combustor outlet temperature profiles on ramjet thrust
The desirability of obtaining an even distribution of
temperature at the outlet of a ramjet combustor is indicated
theoretically. Results of experiments on a particular
combustion system over a limited range of conditions using
a series of mixers are presented. The results suggest that
mixers are desirable for high Mach Number ramjets operating
at low overall fuel-air ratios.
The material presented in this report is based on the
work carried out by M. R. Williams in partial fulfilment of the requirements for the Diploma of the College of
Aeronautics, and is essentially a summary of his thesis.
The work was part of M.O.S. Research Contract 7/Exptl./72
Irreversibility in response to forces acting on graphene sheets
The amount of rippling in graphene sheets is related to the interactions with
the substrate or with the suspending structure. Here, we report on an
irreversibility in the response to forces that act on suspended graphene
sheets. This may explain why one always observes a ripple structure on
suspended graphene. We show that a compression-relaxation mechanism produces
static ripples on graphene sheets and determine a peculiar temperature ,
such that for the free-energy of the rippled graphene is smaller than
that of roughened graphene. We also show that depends on the structural
parameters and increases with increasing sample size.Comment: 4 pages, 4 Figure
Influence of copper on the electronic properties of amorphous chalcogenides
We have studied the influence of alloying copper with amorphous arsenic
sulfide on the electronic properties of this material. In our
computer-generated models, copper is found in two-fold near-linear and
four-fold square-planar configurations, which apparently correspond to Cu(I)
and Cu(II) oxidation states. The number of overcoordinated atoms, both arsenic
and sulfur, grows with increasing concentration of copper. Overcoordinated
sulfur is found in trigonal planar configuration, and overcoordinated
(four-fold) arsenic is in tetrahedral configuration. Addition of copper
suppresses the localization of lone-pair electrons on chalcogen atoms, and
localized states at the top of the valence band are due to Cu 3d orbitals.
Evidently, these additional Cu states, which are positioned at the same
energies as the states due to ([As4]-)-([S_3]+) pairs, are responsible for
masking photodarkening in Cu chalcogenides
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