5,664 research outputs found
Improving driver behaviour by design : a cognitive work analysis methodology
Within the European Community both the environmental and safety costs of road
transport are unacceptably high. ‘Foot-LITE’ is a UK project which aims to encourage
drivers to adopt ‘greener’ and safer driving practices, with real-time and retrospective
feedback being given both in-vehicle and off-line. This paper describes the early
concept development of Foot-LITE, for which a Cognitive Work Analysis (CWA) was
conducted. In this paper, we present the results of the first phase of CWA – the Work
Domain Analysis, as well as some concept interface designs based on the WDA to
illustrate its application. In summary, the CWA establishes a common framework for
the project, and will ultimately contribute to the design of the in-vehicle interface
Modeling Differently Oriented Loblolly Pine Strands Incorporating Variation of Intraring Properties Using a Stochastic Finite Element Method
Wood strands are a biological material with variations in material properties because of the presence of earlywood and latewood, juvenile wood and mature wood as well as the sectional cut used to generate strands. This variation should be accounted for to produce reliable modeling results. This study used both a deterministic finite element method (FEM) and a stochastic finite element method (SFEM) to model the stiffness of wood strands from three different orientations (radial, tangential, and angled) incorporating intraring property variation from two growth ring positions. In addition, a homogeneous model was used as a control to compare the results from both deterministic FEM and SFEM. The homogeneous model predicted the stiffness well for radial and tangential orientation strands but provided unrealistic physical strain distributions. Assumptions of strand homogeneity oversimplified the strain distribution present in the strand, eliminating local maximum and minimum values. Cumulative probability curves comparing previous experimental results and SFEM results showed general agreement. Average differences in the effective tensile modulus of elasticity ranged 0.96-22.31%. Based on the modeling results, the earlywood tensile modulus of elasticity was the input parameter that had the greatest influence on the strand stiffness. The order of correlation of the earlywood and latewood Poisson ratios changed based on strand orientation. SFEM techniques provided accurate results and material property distributions as compared with the experimental results
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The identification of Late Holocene bog bursts at Littleton bog, Ireland: ecohydrological changes display complex climatic and non-climatic drivers
In order to clearly understand the response of raised mires to past climate change, it is important to consider the full range of drivers and responses of these ecohydrological archives. To this end, a high resolution ecohydrological record from Littleton bog, Co. Tipperary, Ireland, was generated utilizing a combination of plant macrofossils, testate amoebae, and humification analysis. Chronological control for this record was provided by a Bayesian age-depth model based on AMS radiocarbon dates. Testate amoebae-derived reconstructed peatland water tables indicate a series of sudden shifts to dry bog surface conditions at c.3140, c.2510, and c.1540 cal BP. These events display a distinctive palaeoecological signal and chronological tempo that is best explained as a result of a series of bog burst events, and which seem inconsistent with other explanations. The chronological correspondence between the bog bursts at Littleton and a set of similar events at Derryville bog, c.5km to the north, is noted, as is the broad correspondence of these events with wet-shifts indicated in regional peatland water table compilations from Britain and Ireland. A range of possible driving mechanisms for these events is proposed, including anthropogenic disturbance of the bog surface, non-linear response to climate forcing, internal bog dynamics, vegetation succession, or a combination of factors. We illustrate the need for further multi-proxy investigations to fully understand these phenomena
Distributions of gaps and end-to-end correlations in random transverse-field Ising spin chains
A previously introduced real space renormalization-group treatment of the
random transverse-field Ising spin chain is extended to provide detailed
information on the distribution of the energy gap and the end-to-end
correlation function for long chains with free boundary conditions. Numerical
data, using the mapping of the problem to free fermions, are found to be in
good agreement with the analytic finite size scaling predictions.Comment: 12 pages revtex, 10 figures, submitted to Phys. Rev.
Evidence of two lineages of metriorhynchid crocodylomorphs in the Lower Cretaceous of the Czech Republic
Metriorhynchid crocodylomorphs were an important component in shallow marine ecosystems during the Middle Jurassic to Early Cretaceous in the European archipelago. While metriorhynchids are well known from western European countries, their central and eastern European record is poor and usually limited to isolated or fragmentary specimens which often hinders a precise taxonomic assignment. However, isolated elements such as tooth crowns, have been found to provide informative taxonomic identifications. Here we describe two isolated metriorhynchid tooth crowns from the upper Valanginian (Lower Cretaceous) of the Stramberk area, Czech Republic. Our assessment of the specimens, including multivariate analysis of dental measurements and surface enamel structures, indicates that the crowns belong to two distinct geosaurin taxa (Plesiosuchina? indet. and Torvoneustes? sp.) with different feeding adaptations. The specimens represent the first evidence of Metriorhynchidae from the Czech Republic and some of the youngest metriorhynchid specimens worldwide.Web of Science66236735
Phase relations in K_xFe_{2-y}Se_2 and the structure of superconducting K_xFe_2Se_2 via high-resolution synchrotron diffraction
Superconductivity in iron selenides has experienced a rapid growth, but not
without major inconsistencies in the reported properties. For
alkali-intercalated iron selenides, even the structure of the superconducting
phase is a subject of debate, in part because the onset of superconductivity is
affected much more delicately by stoichiometry and preparation than in cuprate
or pnictide superconductors. If high-quality, pure, superconducting
intercalated iron selenides are ever to be made, the intertwined physics and
chemistry must be explained by systematic studies of how these materials form
and by and identifying the many coexisting phases. To that end, we prepared
pure K_2Fe_4Se_5 powder and superconductors in the K_xFe_{2-y}Se_2 system, and
examined differences in their structures by high-resolution synchrotron and
single-crystal x-ray diffraction. We found four distinct phases: semiconducting
K_2Fe_4Se_5, a metallic superconducting phase K_xFe_2Se_2 with x ranging from
0.38 to 0.58, an insulator KFe_{1.6}Se_2 with no vacancy ordering, and an
oxidized phase K_{0.51(5)}Fe_{0.70(2)}Se that forms the PbClF structure upon
exposure to moisture. We find that the vacancy-ordered phase K_2Fe_4Se_5 does
not become superconducting by doping, but the distinct iron-rich minority phase
K_xFe_2Se_2 precipitates from single crystals upon cooling from above the
vacancy ordering temperature. This coexistence of metallic and semiconducting
phases explains a broad maximum in resistivity around 100 K. Further studies to
understand the solubility of excess Fe in the K_xFe_{2-y}Se_2 structure will
shed light on the maximum fraction of superconducting K_xFe_2Se_2 that can be
obtained by solid state synthesis.Comment: 12 pages, 16 figures, supplemental materia
Where do we go from here? An assessment of navigation performance using a compass versus a GPS unit
The Global Positioning System (GPS) looks set to replace the traditional map and
compass for navigation tasks in military and civil domains. However, we may ask
whether GPS has a real performance advantage over traditional methods. We present
an exploratory study using a waypoint plotting task to compare the standard magnetic
compass against a military GPS unit, for both expert and non-expert navigators.
Whilst performance times were generally longer in setting up the GPS unit, once
navigation was underway the GPS was more efficient than the compass. For mediumto
long-term missions, this means that GPS could offer significant performance
benefits, although the compass remains superior for shorter missions.
Notwithstanding the performance times, significantly more errors, and more serious
errors, occurred when using the compass. Overall, then, the GPS offers some clear
advantages, especially for non-expert users. Nonetheless, concerns over the
development of cognitive maps remain when using GPS technologies
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