14,491 research outputs found

    Origin of the Mosaicity in Graphene Grown on Cu(111)

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    We use low-energy electron microscopy to investigate how graphene grows on Cu(111). Graphene islands first nucleate at substrate defects such as step bunches and impurities. A considerable fraction of these islands can be rotationally misaligned with the substrate, generating grain boundaries upon interisland impingement. New rotational boundaries are also generated as graphene grows across substrate step bunches. Thus, rougher substrates lead to higher degrees of mosaicity than do flatter substrates. Increasing the growth temperature improves crystallographic alignment. We demonstrate that graphene growth on Cu(111) is surface diffusion limited by comparing simulations of the time evolution of island shapes with experiments. Islands are dendritic with distinct lobes, but unlike the polycrystalline, four-lobed islands observed on (100)-textured Cu foils, each island can be a single crystal. Thus, epitaxial graphene on smooth, clean Cu(111) has fewer structural defects than it does on Cu(100).Comment: Article revised following reviewer comment

    Cargo/Logistics Airlift System Study (CLASS), Volume 2

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    Air containerization is discussed in terms of lower freight rates, size and pallet limitations, refrigeration, backhaul of empties, and ownership. It is concluded that there is a need for an advance air cargo system as indicated by the industry/transportation case studies, and a stimulation of the air cargo would result in freight rate reductions

    Cargo/Logistics Airlift System Study (CLASS), Volume 1

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    Current and advanced air cargo systems are evaluated using industrial and consumer statistics. Market and commodity characteristics that influence the use of the air mode are discussed along with a comparison of air and surface mode on typical routes. Results of on-site surveys of cargo processing facilities at airports are presented, and institutional controls and influences on air cargo operations are considered

    Cargo/Logistics Airlift System Study (CLASS), Executive Summary

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    The current air cargo system is analyzed along with advanced air cargo systems studies. A forecast of advanced air cargo system demand is presented with cost estimates. It is concluded that there is a need for a dedicated advance air cargo system, and with application of advanced technology, reductions of 45% in air freight rates may be achieved

    Real-time observation of epitaxial graphene domain reorientation.

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    Graphene films grown by vapour deposition tend to be polycrystalline due to the nucleation and growth of islands with different in-plane orientations. Here, using low-energy electron microscopy, we find that micron-sized graphene islands on Ir(111) rotate to a preferred orientation during thermal annealing. We observe three alignment mechanisms: the simultaneous growth of aligned domains and dissolution of rotated domains, that is, 'ripening'; domain boundary motion within islands; and continuous lattice rotation of entire domains. By measuring the relative growth velocity of domains during ripening, we estimate that the driving force for alignment is on the order of 0.1 meV per C atom and increases with rotation angle. A simple model of the orientation-dependent energy associated with the moiré corrugation of the graphene sheet due to local variations in the graphene-substrate interaction reproduces the results. This work suggests new strategies for improving the van der Waals epitaxy of 2D materials

    Exploring ethnic inequalities in health: Evidence from the Health Survey for England, 1998-2011

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    Issues of social justice and social and spatial inequalities in health have long been researched, yet there is a relative paucity of research on ethnic inequalities in health. Given the increasing ethnic diversity of England's population and the persistence of unjust differences in health this research is timely. We used annual data from the Health Survey for England between 1998 and 2011, combined into a time-series dataset, to examine the influence of socioeconomic and spatial factors on ethnic variations in health and to explore whether inequalities have changed over time. Our analysis reveals that ethnic differences in health are largely rooted in socioeconomic or spatial difference, although variations by health outcome are observed. This work builds on existing literature which looks to socioeconomic and spatial difference for explanations of ethnic inequalities in health, rather than any supposed inherent underlying risk of poor health for minority ethnic groups

    Magnetic resonance at 41 meV and charge dynamics in YBa_2Cu_3O_6.95

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    We report an Eliashberg analysis of the electron dynamics in YBa_2Cu_3O_6.95. The magnetic resonance at 41 meV couples to charge carriers and defines the characteristic shape in energy of the scattering rate \tau^{-1}(T,\omega) which allows us to construct the charge-spin spectral density I^2\chi(\omega,T) at temperature T. The T dependence of the weight under the resonance peak in I^2\chi(\omega,T) agrees with experiment as does that of the London penetration depth and of the microwave conductivity. Als, at T=0 condensation energy, the fractional oscillator strength in the condensate, and the ratio of gap to critical temperature agree well with the data.Comment: 7 Pages, 3 Figures, accepted for publication in Europhysics Letter

    Effect of Magnetic Impurities on Energy Exchange between Electrons

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    In order to probe quantitatively the effect of Kondo impurities on energy exchange between electrons in metals, we have compared measurements on two silver wires with dilute magnetic impurities (manganese) introduced in one of them. The measurement of the temperature dependence of the electron phase coherence time on the wires provides an independent determination of the impurity concentration. Quantitative agreement on the energy exchange rate is found with a theory by G\"{o}ppert et al. that accounts for Kondo scattering of electrons on spin-1/2 impurities.Comment: 4 page

    Design and implementation of smart farming system for fig using connected-argonomics

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    This paper proposes a design and implementation approach of smart farming system using connected-agronomics technique for fig farm application. Nowadays, fig plants having a rapid growth in the current market demand due to its rich in natural health benefiting nutrients, antioxidants and vitamins where some farming systems have been used  in maintaining fig plant’s environmental resources to grow without fail. Smart farming is a system applied to provide user with real time information and plan for desired plant such as time intervals for watering systems. There are two major problems on maintaining the fig fruit quality; watering system fail during emergency blackout and a contagious disease known as leaf rust due to external environments. The system implements two microcontrollers, the Arduino Uno & Raspberry Pi along with smartphone Android application. The system performance is evaluated based on the requirement specification, irrigation soil, surrounding temperature and moisture. It is found that all data collected by the sensors are within the optimal range of values, which are 1500 µS/cm to 1599 µS/cm for the EC reading of the fertilizer while 6.0 to 6.5 for the pH value of the soil. This prototype of smart farming was well developed and can be applied to the fig plantation environment
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