551 research outputs found

    Measuring CRM Aptitude: Is NOTECHS a Suitable Tool for Pilot Selection?

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    Airline pilot’s primary job requirements have shifted from stick-and-rudder to CRM skills. At the same time, eliminating airline pilots from the job due to a lack of CRM skills is highly inefficient. Hence, an efficient and usable selection tool that helps to evaluate airline pilot candidates’ CRM skills prior their advanced training is needed. This paper examines the usability of the NOTECHS CRM assessment tool for already trained airline pilots for the purpose of pilot selection. CRM skills were evaluated during a scripted simple flying scenario in a Flight Navigation Procedure Trainer 2 (FNPT 2). Results indicate that the standard JAR TEL NOTECHS score form, which is subdivided into two social (cooperation; leadership & managerial skills) and two cognitive (situation awareness; decision making) categories, is efficiently usable by examiners who do not have to be psychologists, such as Human Resource personnel and airline pilots. Based on the experiment, some modifications to the NOTECHS score form were suggested

    Frequency dependent polarisation switching in h-ErMnO3_3

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    We report an electric-field poling study of the geometric-driven improper ferroelectric h-ErMnO3_3. From a detailed dielectric analysis we deduce the temperature and frequency dependent range for which single-crystalline h-ErMnO3_3 exhibits purely intrinsic dielectric behaviour, i.e., free from extrinsic so-called Maxwell-Wagner polarisations that arise, for example, from surface barrier layers. In this regime ferroelectric hysteresis loops as function of frequency, temperature and applied electric fields are measured revealing the theoretically predicted saturation polarisation in the order of 5 - 6 Ό\muC/cm2^2. Special emphasis is put on frequency-dependent polarisation switching, which is explained in terms of domain-wall movement similar to proper ferroelectrics. Controlling the domain walls via electric fields brings us an important step closer to their utilization in domain-wall-based electronics.Comment: 5 pages, 3 figure

    Multiferroic spin-superfluid and spin-supersolid phases in MnCr2S4

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    Spin supersolids and spin superfluids reveal complex canted spin structures with independent order of longitudinal and transverse spin components. This work addresses the question whether these exotic phases can exhibit spin-driven ferroelectricity. Here we report the results of dielectric and pyrocurrent measurements of MnCr2S4 as function of temperature and magnetic field up to 60 T. This sulfide chromium spinel exhibits a Yafet-Kittel type canted spin structure at low temperatures. As function of external magnetic field, the manganese spins undergo a sequence of ordering patterns of the transverse and longitudinal spin components, which can be mapped onto phases as predicted by lattice-gas models including solid, liquid, super-fluid, and supersolid phases. By detailed dielectric and pyrocurrent measurements, we document a zoo of multiferroic phases with sizable ferroelectric polarization strongly varying from phase to phase. Using lattice-gas terminology, the title compound reveals multiferroic spin-superfluid and spin-supersolid phases, while the antiferromagnetic solid is paraelectric.Comment: 14 pages including 5 figure

    The dual nature of magnetism in a uranium heavy fermion system

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    The duality between localized and itinerant nature of magnetism in 5f5\textit{f} electron systems has been a longstanding puzzle. Here, we report inelastic neutron scattering measurements, which reveal both local and itinerant aspects of magnetism in a single crystalline system of UPt2_{2}Si2_{2}. In the antiferromagnetic state, we observe broad continuum of diffuse magnetic scattering with a resonance-like gap of ≈\approx 7 meV, and surprising absence of coherent spin-waves, suggestive of itinerant magnetism. While the gap closes above the Neel temperature, strong dynamic spin correlations persist to high temperature. Nevertheless, the size and temperature dependence of the total magnetic spectral weight can be well described by local moment with J=4J=4. Furthermore, polarized neutron measurements reveal that the magnetic fluctuations are mostly transverse, with little or none of the longitudinal component expected for itinerant moments. These results suggest that a dual description of local and itinerant magnetism is required to understand UPt2_{2}Si2_{2}, and by extension, other 5ff systems in general.Comment: see supplementary material for more detail

    Blocks of cyclotomic Hecke algebras and Khovanov-Lauda algebras

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    We construct an explicit isomorphism between blocks of cyclotomic Hecke algebras and (sign-modified) Khovanov-Lauda algebras in type A. These isomorphisms connect the categorification conjecture of Khovanov and Lauda to Ariki's categorification theorem. The Khovanov-Lauda algebras are naturally graded, which allows us to exhibit a non-trivial Z-grading on blocks of cyclotomic Hecke algebras, including symmetric groups in positive characteristic.Comment: 32 pages; minor changes to section

    Multimaterial Piezoelectric Fibres

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    Fibre materials span a broad range of applications ranging from simple textile yarns to complex modern fibre-optic communication systems. Throughout their history, a key premise has remained essentially unchanged: fibres are static devices, incapable of controllably changing their properties over a wide range of frequencies. A number of approaches to realizing time-dependent variations in fibres have emerged, including refractive index modulation1, 2, 3, 4, nonlinear optical mechanisms in silica glass fibres5, 6, 7, 8 and electroactively modulated polymer fibres9. These approaches have been limited primarily because of the inert nature of traditional glassy fibre materials. Here we report the composition of a phase internal to a composite fibre structure that is simultaneously crystalline and non-centrosymmetric. A ferroelectric polymer layer of 30 Όm thickness is spatially confined and electrically contacted by internal viscous electrodes and encapsulated in an insulating polymer cladding hundreds of micrometres in diameter. The structure is thermally drawn in its entirety from a macroscopic preform, yielding tens of metres of piezoelectric fibre. The fibres show a piezoelectric response and acoustic transduction from kilohertz to megahertz frequencies. A single-fibre electrically driven device containing a high-quality-factor Fabry–Perot optical resonator and a piezoelectric transducer is fabricated and measured.National Science Foundation (U.S.) (Materials Research Science and Engineering Centers Program, award number DMR-0819762)United States. Defense Advanced Research Projects Agency (Griggs)United States. Army Research Office (Institute for Soldier Nanotechnologies, contract no. W911NF-07-D-0004

    A volumetric technique for fossil body mass estimation applied to Australopithecus afarensis

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    Fossil body mass estimation is a well established practice within the field of physical anthropology. Previous studies have relied upon traditional allometric approaches, in which the relationship between one/several skeletal dimensions and body mass in a range of modern taxa is used in a predictive capacity. The lack of relatively complete skeletons has thus far limited the potential application of alternative mass estimation techniques, such as volumetric reconstruction, to fossil hominins. Yet across vertebrate paleontology more broadly, novel volumetric approaches are resulting in predicted values for fossil body mass very different to those estimated by traditional allometry. Here we present a new digital reconstruction of Australopithecus afarensis (A.L. 288-1; ‘Lucy’) and a convex hull-based volumetric estimate of body mass. The technique relies upon identifying a predictable relationship between the ‘shrink-wrapped’ volume of the skeleton and known body mass in a range of modern taxa, and subsequent application to an articulated model of the fossil taxa of interest. Our calibration dataset comprises whole body computed tomography (CT) scans of 15 species of modern primate. The resulting predictive model is characterized by a high correlation coefficient (r2 = 0.988) and a percentage standard error of 20%, and performs well when applied to modern individuals of known body mass. Application of the convex hull technique to A. afarensis results in a relatively low body mass estimate of 20.4 kg (95% prediction interval 13.5–30.9 kg). A sensitivity analysis on the articulation of the chest region highlights the sensitivity of our approach to the reconstruction of the trunk, and the incomplete nature of the preserved ribcage may explain the low values for predicted body mass here. We suggest that the heaviest of previous estimates would require the thorax to be expanded to an unlikely extent, yet this can only be properly tested when more complete fossils are available
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