974 resultados para resonant push-pull


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We introduce a model of a nonlinear double-barrier structure to describe in a simple way the effects of electron-electron scattering while remaining analytically tractable. The model is based on a generalized effective-mass equation where a nonlinear local field interaction is introduced to account for those inelastic scattering phenomena. Resonance peaks seen in the transmission coefficient spectra for the linear case appear shifted to higher energies depending on the magnitude of the nonlinear coupling. Our results are in good agreement with self-consistent solutions of the Schrodinger and Poisson equations. The calculation procedure is seen to be very fast, which makes our technique a good candidate for a rapid approximate analysis of these structures.

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Seebeck nanoantennas, which are based on the thermoelectric effect, have been proposed for electromagnetic energy harvesting and infrared detection. The responsivity and frequency dependence of three types of Seebeck nanoantennas is obtained by electromagnetic simulation for different materials. Results show that the square spiral antenna has the widest bandwidth and the highest induced current of the three analyzed geometries. However, the geometry that presented the highest temperature gradient was the bowtie antenna, which favors the thermoelectric effect in a Seebeck nanoantenna. The results also show that these types of devices can present a voltage responsivity as high as 36  μV/W36  μV/W for titanium–nickel dipoles resonant at far-infrared wavelengths.

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Following a period when EU-Turkish relations have not been particularly close, the readmission agreement signed in December 2013 by the Home Affairs Commissioner Cecilia Malmstrom and the Turkish Minister of Foreign Affairs Ahmet Davutoglu could help inject some sorely needed goodwill and trust into the relationship. Yet, as pointed out in this commentary, there is always the risk that the challenges faced in the actual implementation of the agreement will aggravate the relationship.

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The institutionalisation of early retirement has become a universal feature of postwar industrial economies, though there are significant cross-national variations. This paper studies the impact of different types of welfare regimes, production systems and labour relations on early exit from work. After an analysis of the main trends, the paper discusses the costs and benefits of early retirement for the various actors — labour, capital and the state — at different levels. The paper outlines both the "pull” and "push” factors of early exit. It first compares the distinct welfare state regimes and private occupational pensions in their impact on early retirement. Then it looks at the labour-shedding strategies inherent to particular employment regimes, production systems and financial governance structures. Finally, the impact of particular industrial relations systems, and especially the role of unions is discussed. The paper finds intricate "institutional complementarities” between particular welfare states, production regimes and industrial relations systems, and these structure the incentives under which actors make decisions on work and retirement. The paper argues that the "collusion” between capital, labour and the state in pursuing early retirement is not merely following a labour-shedding strategy to ease mass unemployment, but also caused by the need for economic restructuration, the downsizing pressures from financial markets, the maintenance of peaceful labour relations, and the consequences of a seniority employment system.

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A thorough literature review has shown that although there are many theories to explain international trade, researchers are unanimous in affirming that hotel chains' internationalisation is influenced by pull factors, related to specific characteristics of the host country (contextual and transactional environment), and by push factors, related to specific characteristics of the companies and of their home country. This chapter aims to identify which factors influence hotel chains choosing a destination to invest over another. With this purpose, a theoretical model, that included six pull factors related to the contextual environment and five factors linked to the tourism industry, was developed. This model was validated through questionnaire surveys applied to foreign investors running accommodation units in mainland Portugal. Fifty three questionnaires were considered valid, representing 64% of the universe of foreign investors in Portugal (accommodation sector).

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Resonant fluorescence line narrowing of the R1 line of the [Cr(ox)3]3− chromophore in [Rh(bpy)3][NaCr(ox)3]ClO4 at 1.6 K neither gives rise to the usual three-line pattern nor to spectral diffusion. Instead multi-line spectra with spacings equal to the zero-field splitting of the ground state are observed. This phenomenon is attributed to efficient non-radiative resonant energy transfer within the R1 line.

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In the last years masses of ice, about 5 km long, have been protruding from the lowest part of an advancing glacier margin of the Kötlujökull in Southern Iceland. In the summer of 1983, they appeared as sediment-covered lobes, 10-60 m long, bordering the glacier rnargin like agarland. 1 to 3 push-rnoraines without ice core, rnostly sickle-shaped, occured first in the frontal parts of the lobes: behind thern came several ice-cored moraines with heights of up to several metres. The active ice in front of the precipice of the glacier is called the "glacier-foot" in this paper. The digging out of 9 lobes and the measuring of the advance of 19 lobes showed that in most cases this glacierfoot had split up at its distal end into several plate- or stem-shaped pieces of ice which were situated one upon the other, separated by moraine deposits and proceeding irregularly into the foreland at the rate of several mm/h, The sometimes different rate of advance in the same lobe and different rates of advanee in adjoining lobes (some being entirely inactive) point to a type of rnovement which is independent of the general advance of the glacier. Research in the winter of 1983/84 showed less activity in 3 examined lobes, but the activity had not ceased. The advancement of the lower parts of the glacier-foot into and across the sands of the foreland implies the following genesis of pushmoraines: Shoving off a plate of sand, folding it and pushing it over the foreland at average rates of up to 7,2 mm/h, according to the investigations in thc summer of 1983. At a certain stage of the folding process, new folds begin to develop in front of the old, and the old folds are shifted onto the backslope of thc folds in front of them until they are completely unired. In this way, "püe-moraines" arise, which become higher and higher. They include two or more folds declining towards the glacier. Systems of small moraines presumably of the same genesis occur on old moraine areas in front of the Kötlujökull. The possible cause of formation of a glacier-foot is discussed, and the moraines of the Kötlujökull are compared with certain pleistocene push-moraines.

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"Materials Laboratory Contract no. AF 33(038)-20840; Project no. 7360; Task no. 73604."

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"Contract AF33(616)-6079 Project No. 9-(13-6278) Task 40572. Sponsored by: Wright Air Development Center"