17,058 research outputs found
Artificial meteor ablation studies: Olivine
Artificial meteor ablation was performed on a Mg-rich olivine sample using an arc-heated plasma of ionized air. Experimental conditions simulated a meteor traveling about 12 km/sec at an altitude of 70 km. The mineral content of the original olivine sample was 98% olivine (including traces of olivine alteration products) and 2% chromite. Forsterite content of the original olivine was Fo-89. After ablation, the forsterite content had increased to Fo-94 in the recrystallized olivine. In addition, lamella-like intergrowths of magnetite were prevalent constituents. Wherever magnetite occurred, there was an increase in Mg and a corresponding decrease in Fe for the recrystallized olivine. The Allende fusion crust consisted of a recrystallized olivine, which was more Mg-rich and Fe-deficient than the original meteorite's olivine, and abundant magnetite grains. Although troilite and pentlandite were the common opaque mineral constituents in this meteorite, magnetite was the principal opaque mineral found in the fusion crust
The structure of 110 tilt boundaries in large area solar silicon
The models of Hornstra and their connection to the repeating group description of grain boundaries (7-10) are discussed. A model for the Sigma = 27 boundary containing a zig-zag arrangement of dislocations is constructed and it is shown that zig-zag models can account for the contrast features observed in high resolution transmission electron micrographs of second and third order twin boundaries in silicon. The boundaries discussed are symmetric with a 110 tilt axis and a (110) boundary plane in the median lattice (the median plane). The median lattice is identical in structure and halfway in orientation between the crystal lattices either side of the boundary
Observation of HCN hyperfine line anomalies towards low- and high-mass star-forming cores
HCN is becoming a popular choice of molecule for studying star formation in
both low- and high-mass regions and for other astrophysical sources from comets
to high-redshift galaxies. However, a major and often overlooked difficulty
with HCN is that it can exhibit non-local thermodynamic equilibrium (non-LTE)
behaviour in its hyperfine line structure. Individual hyperfine lines can be
strongly boosted or suppressed. In low-mass star-forming cloud observations,
this could possibly lead to large errors in the calculation of opacity and
excitation temperature, while in massive star-forming clouds, where the
hyperfine lines are blended due to turbulent broadening, errors will arise in
infall measurements that are based on the separation of the peaks in a
self-absorbed profile. The underlying line shape cannot be known for certain if
hyperfine anomalies are present. We present a first observational investigation
of these anomalies across a range of conditions and transitions by carrying out
a survey of low-mass starless cores (in Taurus & Ophiuchus) and high-mass
protostellar objects (in the G333 giant molecular cloud) using hydrogen cyanide
(HCN) J=1-0 and J=3-2 emission lines. We quantify the degree of anomaly in
these two rotational levels by considering ratios of individual hyperfine lines
compared to LTE values. We find that all the cores observed show some degree of
anomaly while many of the lines are severely anomalous. We conclude that HCN
hyperfine anomalies are common in both lines in both low-mass and high-mass
protostellar objects, and we discuss the differing hypotheses for the
generation of the anomalies. In light of the results, we favour a line overlap
effect for the origins of the anomalies. We discuss the implications for the
use of HCN as a dynamical tracer and suggest in particular that the J=1-0,
F=0-1 hyperfine line should be avoided in quantitative calculations.Comment: 17 pages, 8 figure
An investigation of wing buffeting response at subsonic and transonic speeds: Phase 1: F-111A flight data analysis. Volume 1: Summary of technical approach, results and conclusions
The structural response to aerodynamic buffet during moderate to high-g maneuvers at subsonic and transonic speeds was investigated. The investigation is reported in three volumes. This volume presents a summary of the investigation with a complete description of the technical approach, description of the aircraft, its instrumentation, the data reduction procedures, results and conclusion
An investigation of wing buffeting response at subsonic and transonic speeds. Phase 1: F-111A flight data analysis. Volume 2: Plotted power spectra
Volume 2 of this three volume report is presented. This volume presents plotted variations of power spectral density data with frequency for each structural response item for each data sampled and analyzed during the course of the investigation. Some of the information contained in Volume 1 are repeated to allow the reader to identify the specific conditions appropriate to each plot presented and to interpret the data
Using qualitative research methods to inform user centred design of an innovative assistive technology device
The SPECS project aims to develop a speech-driven device that will allow the home environment to be controlled (for example turning on or off the lights or television). The device developed will be targeted at older people and people with disabilities and will be sensitive to disordered speech. Current environmental control systems (ECS) work using either a switch interface or speech recognition software that does not comprehend disordered speech well. Switch-interface systems are often slow and complicated to use and the uptake of the available speech recognition system has been poor. A significant proportion of people requiring electronic assistive technology (EAT) have dysarthria, a motor speech disorder, associated with their physical disability. Speech control of EAT is seen as desirable for such people but machine recognition of dysarthric speech is a difficult problem due to the variability of their articulatory output. Other work on large vocabulary adaptive speech recognition systems and speaker dependent recognisers has not provided a solution for severely dysarthric speech. Building on the work of the STARDUST project our goal is to develop and implement speech recognition as a viable control interface for people with severe physical disability and severe dysarthria. The SPECS project is funded by the Health Technology Devices Programme of the Department of Health
NLC-2 graph recognition and isomorphism
NLC-width is a variant of clique-width with many application in graph
algorithmic. This paper is devoted to graphs of NLC-width two. After giving new
structural properties of the class, we propose a -time algorithm,
improving Johansson's algorithm \cite{Johansson00}. Moreover, our alogrithm is
simple to understand. The above properties and algorithm allow us to propose a
robust -time isomorphism algorithm for NLC-2 graphs. As far as we
know, it is the first polynomial-time algorithm.Comment: soumis \`{a} WG 2007; 12
System remotely inspects, measures, and records internal irregularities in piping
Video electromechanical probe visually inspects and measures internal offset and peaking of welds in relatively large piping. Irregularity dimensions are recorded on peripheral equipment consisting of video tape and X-Y plotter. The probe is used for inspection of vacuum-jacketed liquid lines that cannot be inspected externally
A method for predicting full scale buffet response with rigid wind tunnel model fluctuating pressure data. Volume 1: Prediction method development and assessment
The method requires unsteady aerodynamic forces, natural airplane modes, and the measured pressure data as input. A gust response computer program is used to calculate buffet response due to the forcing function posed by the measured pressure data. By calculating both symmetric and antisymmetric solutions, upper and lower bounds on full-scale buffet response are formed. Comparisons of predictions with flight test results are made and the effects of horizontal tail loads and static aeroelasticity are shown. Discussions are also presented on the effects of primary wing torsion modes, chordwise and spanwise phase angles, and altitude
Between Treewidth and Clique-width
Many hard graph problems can be solved efficiently when restricted to graphs
of bounded treewidth, and more generally to graphs of bounded clique-width. But
there is a price to be paid for this generality, exemplified by the four
problems MaxCut, Graph Coloring, Hamiltonian Cycle and Edge Dominating Set that
are all FPT parameterized by treewidth but none of which can be FPT
parameterized by clique-width unless FPT = W[1], as shown by Fomin et al [7,
8]. We therefore seek a structural graph parameter that shares some of the
generality of clique-width without paying this price. Based on splits, branch
decompositions and the work of Vatshelle [18] on Maximum Matching-width, we
consider the graph parameter sm-width which lies between treewidth and
clique-width. Some graph classes of unbounded treewidth, like
distance-hereditary graphs, have bounded sm-width. We show that MaxCut, Graph
Coloring, Hamiltonian Cycle and Edge Dominating Set are all FPT parameterized
by sm-width
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