17,451 research outputs found

    Thermal activation energy of 3D vortex matter in NaFe1-xCoxAs (x=0.01, 0.03 and 0.07) single crystals

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    We report on the thermally activated flux flow dependency on the doping dependent mixed state in NaFe1-xCoxAs (x=0.01, 0.03, and 0.07) crystals using the magnetoresistivity in the case of B//c-axis and B//ab-plane. It was found clearly that irrespective of the doping ratio, magnetoresistivity showed a distinct tail just above the Tc, offset associated with the thermally activated flux flow (TAFF) in our crystals. Furthermore, in TAFF region the temperature dependence of the activation energy follows the relation U(T, B)=U_0 (B) (1-T/T_c )^q with q=1.5 in all studied crystals. The magnetic field dependence of the activation energy follows a power law of U_0 (B)~B^(-{\alpha}) where the exponent {\alpha} is changed from a low value to a high value at a crossover field of B=~2T, indicating the transition from collective to plastic pinning in the crystals. Finally, it is suggested that the 3D vortex phase is the dominant phase in the low-temperature region as compared to the TAFF region in our series samples

    The Dropping of In-Medium Hadron Mass in Holographic QCD

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    We study the baryon density dependence of the vector meson spectrum using the D4/D6 system together with the compact D4 baryon vertex. We find that the vector meson mass decreases almost linearly in density at low density for small quark mass, but saturates to a finite non-zero value for large density. We also compute the density dependence of the η\eta\prime mass and the η\eta\prime velocity. We find that in medium, our model is consistent with the GMOR relation up to a few times the normal nuclear density. We compare our hQCD predictions with predictions made based on hidden local gauge theory that is constructed to model QCD.Comment: 20 pages, 7 figure

    The Estimation of Minimum Efficient Scale of the Port Industry

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    publisher: Elsevier articletitle: The estimation of minimum efficient scale of the port industry journaltitle: Transport Policy articlelink: http://dx.doi.org/10.1016/j.tranpol.2016.04.012 content_type: article copyright: © 2016 Elsevier Ltd. All rights reserved

    Inverted polymer fullerene solar cells exceeding 10% efficiency with poly(2-ethyl-2-oxazoline) nanodots on electron-collecting buffer layers

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    Polymer solar cells have been spotlighted due to their potential for low-cost manufacturing but their efficiency is still less than required for commercial application as lightweight/flexible modules. Forming a dipole layer at the electron-collecting interface has been suggested as one of the more attractive approaches for efficiency enhancement. However, only a few dipole layer material types have been reported so far, including only one non-ionic (charge neutral) polymer. Here we show that a further neutral polymer, namely poly(2-ethyl-2-oxazoline) (PEOz) can be successfully used as a dipole layer. Inclusion of a PEOz layer, in particular with a nanodot morphology, increases the effective work function at the electron-collecting interface within inverted solar cells and thermal annealing of PEOz layer leads to a state-of-the-art 10.74% efficiency for single-stack bulk heterojunction blend structures comprising poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-alt-3-fluorothieno[3,4-b]thiophene-2-carboxylate] as donor and [6,6]-phenyl-C71-butyric acid methyl ester as acceptor

    The impact of innovativeness on supply chain performance: is supply chain integration a missing link?

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    © Emerald Group Publishing Limited. Purpose - This purpose of this paper is to study the impact of innovativeness on supply chain integration (SCI) and supply chain performance (SCP) and the role of SCI in mediating between innovativeness in the supply chain and SCP. Innovativeness is an accepted driver to leverage firm performance. SCI and SCP require innovativeness in the supply chain, but their interrelationships have rarely been researched empirically.P Design/methodology/approach - A questionnaire survey and structural equation modelling were used in this work. After a structural and measurement model was devised from existing supply chain literature, the main data were collected in a web-based questionnaire survey of South Korean manufacturers. Structural equation modelling was applied to test proposed hypotheses on the associations between variables, following a hierarchical analysis process.P Findings - Innovativeness in the supply chain had a positive impact on both SCI and SCP. However, the direct impact of innovativeness on SCP disappeared when the model included SCI as a mediator. In specific, internal and supplier integration fully mediated innovativeness-SCP relationships, whereas customer integration had no mediating role on those relationships. The findings suggest that innovativeness can influence SCP only when the manufacturer’s level of SCI is sufficiently effective in developing necessary supply chain practices.P Research limitations/implications - In this work, innovativeness in the supply chain effectively influenced SCP through the mediation of SCI. However, cross-sectional analysis in one nation using one response per organisation invites validation embracing other geographical areas and longitudinal studies.P Practical implications - Design of an innovative culture within a firm and along a supply chain can enhance SCI practices by stimulating innovativeness. A high level of SCI should be pursued to effectively transform innovativeness into performance.P Originality/value - This work seminally examines the effect of innovativeness in the supply chain on SCI and SCP as well as the mediating role of SCI in the relationships between innovativeness and SCP

    20 K superconductivity in heavily electron doped surface layer of FeSe bulk crystal

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    A superconducting transition temperature Tc as high as 100 K was recently discovered in 1 monolayer (1ML) FeSe grown on SrTiO3 (STO). The discovery immediately ignited efforts to identify the mechanism for the dramatically enhanced Tc from its bulk value of 7 K. Currently, there are two main views on the origin of the enhanced Tc; in the first view, the enhancement comes from an interfacial effect while in the other it is from excess electrons with strong correlation strength. The issue is controversial and there are evidences that support each view. Finding the origin of the Tc enhancement could be the key to achieving even higher Tc and to identifying the microscopic mechanism for the superconductivity in iron-based materials. Here, we report the observation of 20 K superconductivity in the electron doped surface layer of FeSe. The electronic state of the surface layer possesses all the key spectroscopic aspects of the 1ML FeSe on STO. Without any interface effect, the surface layer state is found to have a moderate Tc of 20 K with a smaller gap opening of 4 meV. Our results clearly show that excess electrons with strong correlation strength alone cannot induce the maximum Tc, which in turn strongly suggests need for an interfacial effect to reach the enhanced Tc found in 1ML FeSe/STO.Comment: 5 pages, 4 figure

    Extensive spatiotemporal analyses of surface ozone and related meteorological variables in South Korea for the period 1999–2010

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    Spatiotemporal characteristics of surface ozone (O<sub>3</sub>) variations over South Korea are investigated with consideration of meteorological factors and timescales based on the Kolmogorov–Zurbenko filter (KZ filter), using measurement data at 124 air quality monitoring sites and 72 weather stations for the 12 yr period of 1999–2010. In general, O<sub>3</sub> levels at coastal cities are high due to dynamic effects of the sea breeze while those at the inland and Seoul Metropolitan Area (SMA) cities are low due to the NO<sub>x</sub> titration by local precursor emissions. We examine the meteorological influences on O<sub>3</sub> using a combined analysis of the KZ filter and linear regressions between O<sub>3</sub> and meteorological variables. We decomposed O<sub>3</sub> time series at each site into short-term, seasonal, and long-term components by the KZ filter and regressed on meteorological variables. Impact of temperature on the O<sub>3</sub> levels is significantly high in the highly populated SMA and inland region, but low in the coastal region. In particular, the probability of high O<sub>3</sub> occurrence doubles with 4 °C of temperature increase in the SMA during high O<sub>3</sub> months (May–October). This implies that those regions will experience frequent high O<sub>3</sub> events in a future warming climate. In terms of short-term variation, the distribution of high O<sub>3</sub> probability classified by wind direction shows the effect of both local precursor emissions and long-range transport from China. In terms of long-term variation, the O<sub>3</sub> concentrations have increased by +0.26 ppbv yr<sup>−1</sup> (parts per billion by volume) on nationwide average, but their trends show large spatial variability. Singular value decomposition analyses further reveal that the long-term temporal evolution of O<sub>3</sub> is similar to that of nitrogen dioxide, although the spatial distribution of their trends is different. This study will be helpful as a reference for diagnostics and evaluation of regional- and local-scale O<sub>3</sub> and climate simulations, and as a guide to appropriate O<sub>3</sub> control policy in South Korea
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