33,952 research outputs found
Assessment of risk to Boeing commerical transport aircraft from carbon fibers
The possible effects of free carbon fibers on aircraft avionic equipment operation, removal costs, and safety were investigated. Possible carbon fiber flow paths, flow rates, and transfer functions into the Boeing 707, 727, 737, 747 aircraft and potentially vulnerable equipment were identified. Probabilities of equipment removal and probabilities of aircraft exposure to carbon fiber were derived
Comparative VET European Research since the 1980s: Accommodating Changes in VET Systems and Labour Markets
The article assesses the role comparative research plays from the 1980s in understanding vocational education and training (VET) systems in Europe, driven by political, economic, social and labour market changes. This research has been transformed, moving from national comparisons of VET systems, grounded in institutional theory and engaging with convergence versus divergence debates or human capital theory, to the varieties of capitalism approach considering groups of countries as representative of particular capitalist economies, to transcending national boundaries and emphasising capitalist diversity, governance and labour agency. Drawing on examples of research in which the authors and others have been involved, particularly on the construction industry, the article traces this development and shows how, despite governance weaknesses, comparative research has been enriched by the addition of a European Union level through the introduction of tools, such as the European Qualifications Framework. Four dimensions are proposed - labour market, governance, education and competence - capable of identifying VET 'families' and intra-national variations and capturing the dynamics of VET systems. Through a multi-dimensional and multi-level framework, comparative VET research can provide a deeper understanding of how and why VET systems respond to the challenges of technological, economic and environmental change
Molecular Dynamics Simulations of a Pressure-induced Glass Transition
We simulate the compression of a two-component Lennard-Jones liquid at a
variety of constant temperatures using a molecular dynamics algorithm in an
isobaric-isothermal ensemble. The viscosity of the liquid increases with
pressure, undergoing a broadened transition into a structurally arrested,
amorphous state. This transition, like the more familiar one induced by
cooling, is correlated with a significant increase in icosahedral ordering. In
fact, the structure of the final state, as measured by an analysis of the
bonding, is essentially the same in the glassy, frozen state whether produced
by squeezing or by cooling under pressure. We have computed an effective
hard-sphere packing fraction at the transition, defining the transition
pressure or temperature by a cutoff in the diffusion constant, analogous to the
traditional laboratory definition of the glass transition by an arbitrary, low
cutoff in viscosity. The packing fraction at this transition point is not
constant, but is consistently higher for runs compressed at higher temperature.
We show that this is because the transition point defined by a constant cutoff
in the diffusion constant is not the same as the point of structural arrest, at
which further changes in pressure induce no further structural changes, but
that the two alternate descriptions may be reconciled by using a thermally
activated cutoff for the diffusion constant. This enables estimation of the
characteristic activation energy for diffusion at the point of structural
arrest.Comment: Latex using Revtex macro
Clonal analysis of meningococci during a 26 year period prior to the introduction of meningococcal serogroup C vaccines
Meningococcal disease remains a public health burden in the UK and elsewhere. Invasive Neisseria meningitidis, isolated in Scotland between 1972 and 1998, were characterised retrospectively to examine the serogroup and clonal structure of the circulating population. 2607 isolates causing invasive disease were available for serogroup and MLST analysis whilst 2517 were available for multilocus sequence typing (MLST) analysis only. Serogroup distribution changed from year to year but serogroups B and C were dominant throughout. Serogroup B was dominant throughout the 1970s and early 1980s until serogroup C became dominant during the mid-1980s. The increase in serogroup C was not associated with one particular sequence type (ST) but was associated with a number of STs, including ST-8, ST-11, ST-206 and ST-334. This is in contrast to the increase in serogroup C disease seen in the 1990s that was due to expansion of the ST-11 clonal complex. While there was considerable diversity among the isolates (309 different STs among the 2607 isolates), a large proportion of isolates (59.9%) were associated with only 10 STs. These data highlight meningococcal diversity over time and the need for ongoing surveillance during the introduction of new meningococcal vaccines
Energetic Impact of Jet Inflated Cocoons in Relaxed Galaxy Clusters
Jets from active galactic nuclei (AGN) in the cores of galaxy clusters have
the potential to be a major contributor to the energy budget of the
intracluster medium (ICM). To study the dependence of the interaction between
the AGN jets and the ICM on the parameters of the jets themselves, we present a
parameter survey of two-dimensional (axisymmetric) ideal hydrodynamic models of
back-to-back jets injected into a cluster atmosphere (with varying Mach numbers
and kinetic luminosities). We follow the passive evolution of the resulting
structures for several times longer than the active lifetime of the jet. The
simulations fall into roughly two classes, cocoon-bounded and non-cocoon
bounded sources. We suggest a correspondence between these two classes and the
Faranoff-Riley types. We find that the cocoon-bounded sources inject
significantly more entropy into the core regions of the ICM atmosphere, even
though the efficiency with which energy is thermalized is independent of the
morphological class. In all cases, a large fraction (50--80%) of the energy
injected by the jet ends up as gravitational potential energy due to the
expansion of the atmosphere.Comment: 12 pages, Accepted for publication in Ap
Processing Spatial Keyword Query as a Top-k Aggregation Query
We examine the spatial keyword search problem to retrieve objects of interest that are ranked based on both their spatial proximity to the query location as well as the textual relevance of the object’s keywords. Existing solutions for the problem are based on either using a combination of textual and spatial indexes or using specialized hybrid indexes that integrate the indexing of both textual and spatial attribute values. In this paper, we propose a new approach that is based on modeling the problem as a top-k aggregation problem which enables the design of a scalable and efficient solution that is based on the ubiquitous inverted list index. Our performance study demonstrates that our approach outperforms the state-of-theart hybrid methods by a wide margin
XMM-Newton Observation of the Northwest Radio Relic Region in Abell 3667
Abell 3667 is the archetype of a merging cluster with radio relics. The NW
radio relic is the brightest cluster relic or halo known, and is believed to be
due to a strong merger shock. We have observed the NW relic for 40 ksec of net
XMM time. We observe a global decline of temperature across the relic from 6 to
1 keV, similar to the Suzaku results. Our new observations reveal a sharp
change of both temperature and surface brightness near the position of the
relic. The increased X-ray emission on the relic can be equivalently well
described by either a thermal or nonthermal spectral model. The parameters of
the thermal model are consistent with a Mach number M~2 shock and a shock speed
of ~1200 km s^-1. The energy content of the relativistic particles in the radio
relic can be explained if they are (re)-accelerated by the shock with an
efficiency of ~0.2%. Comparing the limit on the inverse Compton X-ray emission
with the measured radio synchrotron emission, we set a lower limit to the
magnetic field in the relic of 3 muG. If the emission from the relic is
non-thermal, this lower limit is in fact the required magnetic field.Comment: 11 pages, ApJ in pres
Physical profiling of international cricket players: an investigation between bowlers and batters
Objective: This study aims to develop a physical profile of international cricketers, and investigate if positional differences exist between bowlers and batters.
Methods: Nineteen, international male cricketers, eleven bowlers (age 24.1 ± 5.2 years; height 179.73 ± 5.27 cm; weight 73.64 ± 6.65 kg), and eight batters (age 22.9 ± 3.8 years; height 180.25 ± 5.57 cm; weight 77.01 ± 8.99 kg) participated in this study. The physical test battery included; power, speed, strength and aerobic fitness tests.
Results: Batters demonstrated significantly higher scores for the countermovement jump (p < 0.03; ES = -1.55) and squat jump (p < 0.03; ES = -0.98). Batters showed non-significant but small ES for faster 0-5 m (ES = 0.40) and 0-10 m (ES = 0.35) sprint times, superior hand grip strength (ES = -0.20), and higher Yo-Yo intermittent recovery test scores (ES = -0.46). Bowlers showed non-significant but small ES for faster 5 km time trials (ES = -0.51), lower bodyweight (ES = -0.42) and body fat percentage (ES = -0.30). Intra-positional (i.e., seam and spin bowlers) and individual differences amongst players were observed.
Conclusion: This study provides a physical profile of international cricketers. Batters demonstrated superior lower-body power compared to bowlers and other physical test results were similar across positions. However, individual scores for each physical test demonstrated that differences exist amongst players. This should be accounted for by strength and conditioning coaches when using physical profiling data to inform the design and evaluation of their programs
The Refill Wizard: Improving Efficiency At Daresbury Laboratory's Synchrotron Radiation Source
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