934 resultados para string breaking


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As an important physical process at the air-sea interface, wave movement and breaking have a significant effect on the ocean surface mixed layer (OSML). When breaking waves occur at the ocean surface, turbulent kinetic energy (TKE) is input downwards, and a sublayer is formed near the surface and turbulence vertical mixing is intensively enhanced. A one-dimensional ocean model including the Mellor-Yamada level 2.5 turbulence closure equations was employed in our research on variations in turbulent energy budget within OSML. The influence of wave breaking could be introduced into the model by modifying an existing surface boundary condition of the TKE equation and specifying its input. The vertical diffusion and dissipation of TKE were effectively enhanced in the sublayer when wave breaking was considered. Turbulent energy dissipated in the sublayer was about 92.0% of the total depth-integrated dissipated TKE, which is twice higher than that of non-wave breaking. The shear production of TKE decreased by 3.5% because the mean flow fields tended to be uniform due to wave-enhanced turbulent mixing. As a result, a new local equilibrium between diffusion and dissipation of TKE was reached in the wave-enhanced layer. Below the sublayer, the local equilibrium between shear production and dissipation of TKE agreed with the conclusion drawn from the classical law-of-the-wall (Craig and Banner, 1994).

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Based on the effective medium approximation theory of composites, the empirical model proposed by Pandey and Kakar is remedied to investigate the microwave emissivity of sea surface under wave breaking driven by strong wind. In the improved model, the effects of seawater bubbles, droplets and difference in temperature of air and sea interface (DTAS) on the emissivity of sea surface covered by whitecaps are discussed. The model results indicate that the effective emissivity of sea surface increases with DTAS increasing, and the impacts of bubble structures and thickness of whitecaps layer on the emissivity are included in the model by introducing the effective dielectric constant of whitecaps layer. Moreover, a good agreement is obtained by comparing the model results with the Rose's experimental data.

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The rules which epitomise good writing may on occasions be broken, deliberately and with what the writers judge to be good purpose. This can well occur when students or staff set out to engage effectively with their personal and professional development, through personal reflection on and in experiences. They may do this in what has been called “stream of consciousness” writing, which is deliberately compiled in a manner at variance with the general rules for best practice. The rationale for such an unusual decision, namely to engage in what is frankly disorderly writing, is set out briefly in this chapter. Its characteristics are summarised, in implicit contrast with more conventional styles of writing. Examples are included of claims for the effectiveness of this style when used for developmental purposes by students and staff; and reference is made to the publications of some of those who have endorsed this approach.

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http://www.archive.org/details/clearsunshineofg00sheprich

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University of California Libraries

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We study the motion of electrons in a single miniband of a semiconductor superlattice driven by THz electric field polarized along the growth direction. We work in the semiclassical balance-equation model, including different elastic and inelastic scattering rates, and incorporating the self-consistent electric field generated by electron motion. We explore regions of complex dynamics, which can include chaotic behaviour and symmetry-breaking. We estimate the magnitudes of dc current and dc voltage that spontaneously appear in regions of broken-symmetry for parameters characteristic of modern semiconductor superlattices. This work complements PRL 80(1998)2669 [ cond-mat/9709026 ].

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This study contexualises the relationship between the armed forces and the civil authority in Ireland using and revising the theoretical framework advanced by Huntington. It tracks the evolution of the idea of a representive body for soldiers in the late 1980s, to the setting up of statutory associations under the Defence Amendment Act 1990. The study considers Irish soldiers political agitation and their use of peaceful democratic activities to achieve their aims. It highlights the fundamental policy arguments that were made against the idea of representation for the army and positions those arguments in the study of civil-military relations. Utilising unique access to secret Department of Defence files, it reveals in-depth ideological arguments advanced by the military authories in Ireland against independent representation. This thesis provides an academic study of the establishment of PDFORRA. It answers key questions regarding the change in the position of Irish government who were categorically opposed to the idea of representation in the army. It illustrates the involvement of other agencies such as the European Organisation of Military Associations (Euromil) reveals reciprocal support by the Irish associations to other emerging groups in Spain. Accessing as yet unpublished Department of Defence files, study analyses tension between the military authorities and the government. It highlights for the first time the role of enlisted personnel in the shaping of new state structures and successfully dismmisses Huntingtons theoretical contention that enlisted personnel are of no consequence in the study of civil-military relations. It fills a gap in our understanding, identified by Finer, as to how politicisation of soldiers takes place. This thesis brings a new dimension to the discipline of civil-military relations and creates new knowledge that will enhance our understanding of an area not covered previously.

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We consider a wide class of cascading gauge theories which usually lead to runaway behaviour in the IR, and discuss possible deformations of the superpotential at the bottom of the cascade which stabilize the runaway direction and provide stable non-supersymmetric vacua. The models we find may allow for a weakly coupled supergravity analysis of dynamical supersymmetric breaking in the context of the gauge/string correspondence. © SISSA 2006.

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We develop a model for stochastic processes with random marginal distributions. Our model relies on a stick-breaking construction for the marginal distribution of the process, and introduces dependence across locations by using a latent Gaussian copula model as the mechanism for selecting the atoms. The resulting latent stick-breaking process (LaSBP) induces a random partition of the index space, with points closer in space having a higher probability of being in the same cluster. We develop an efficient and straightforward Markov chain Monte Carlo (MCMC) algorithm for computation and discuss applications in financial econometrics and ecology. This article has supplementary material online.

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This piece explores the changing nature of emotion focusing especially on the feeling of sorrow. The opening and ending parts of the first movement represent the overall motive of sorrow. The first movement opens with an augmented chord G-C#-F-B and from this chord the first violin expands upwards while the cello moves downwards towards the C chord (p.2). As the melody alternates between each part, there is a subtle change in harmony which creates tension and release and changes the sound color. In addition, ornamentation in each part reinforces the movement towards the C chord. This progression represents the inner emotion of lament. Sostenuto e largamente section (p.2) uses heterophony in order to express a feeling of chaos. Section Scherzando (p.4) uses the interval relationship M7 and m2, and is a respite from the overwhelming feeling of sorrow. The ending of the first movement (p.12) returns to create a second tension by every instrument ascending slowly, and the viola produces a distinctive melody derived from the previous chaotic section that ends on an Ab. The second movement contrasts with the first movement in order to express a concealed, not explicit, sorrow, and differs in both tempo and texture. The tempo is a waltz that is faster than the first movement. This produces a light, playful figure and a simple melody without much ornamentation. Imitation and canonic structure emphasize the individuality of the strings. The third movement merges material from the first movement rhythmic figure and the second movement pizzicato (p.17). It shows timbral change through con sordino, pizzicato arpeggio, and sul ponticello to display string techniques. An Allegro section (p.19) especially contrasts with Misterioso in rhythm and dynamics. In the Grazioso (p.22), random beats are accentuated by pizzicato arpeggio to de-emphasize the meter. Finally, there is a return to the ending figure of the first movement with con sordino (p.23) and sul ponticello in viola that articulates the internal tension and the timbral change to return to a voice of sorrow.

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In the later decades of the nineteenth century and the early decades of the twentieth, large numbers of Canadian women were stepping out of the shadows of private life and into the public world of work and political action. Among them, both a cause and an effect of these sweeping social changes, was the first generation of Canadian women to work as professional authors. Although these women were not unified by ideology, genre, or date of birth, they are studied here as a generation defined by their time and place in history, by their material circumstances, and by their collective accomplishment. Chapters which focus on E. Pauline Johnson (Tekahionwake), the Eaton sisters (Sui Sin Far and Onoto Watanna), Joanna E. Wood, and Sara Jeannette Duncan explore some of the many commonalities and interrelationships among the members of this generation as a whole. This project combines archival research with analytical bibliography in order to clarify and extend our knowledge of Johnson’s and Duncan’s professional lives and publishing histories, and to recover some of Wood’s “lost” stories. This research offers a preliminary sketch of the long tradition of the platform performance (both Native and non-Native) with which Johnson and others engaged. It explores the uniquely innovative ethnographic writings of Johnson, Duncan, and the Eaton sisters, among others, and it explores thematic concerns which relate directly to the experiences of working women. Whether or not I convince other scholars to treat these authors as a generation, with more in common than has previously been supposed, the strong parallels revealed in these pages will help to clarify and contextualize some of their most interesting work.

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To predict where a catalytic reaction should occur is a fundamental issue scientifically. Technologically, it is also important because it can facilitate the catalyst's design. However, to date, the understanding of this issue is rather limited. In this work, two types of reactions, CH4 CH3 + H and CO C + 0 on two transition metal surfaces, were chosen as model systems aiming to address in general where a catalytic reaction should occur. The dissociations of CH4 - CH3 + H and CO --> C + O and their reverse reactions on flat, stepped, and kinked Rh and Pd surfaces were studied in detail. We find the following: First, for the CH4 Ch(3) + H reaction, the dissociation barrier is reduced by similar to0.3 eV on steps and kinks as compared to that on flat surfaces. On the other hand, there is essentially no difference in barrier for the association reaction of CH3 + H on the flat surfaces and the defects. Second, for the CO C + 0 reaction, the dissociation barrier decreases dramatically (more than 0.8 eV on Rh and Pd) on steps and kinks as compared to that on flat surfaces. In contrast to the CH3 + H reaction, the C + 0 association reaction also preferentially occurs on steps and kinks. We also present a detailed analysis of the reaction barriers in which each barrier is decomposed quantitatively into a local electronic effect and a geometrical effect. Our DFT calculations show that surface defects such as steps and kinks can largely facilitate bond breaking, while whether the surface defects could promote bond formation depends on the individual reaction as well as the particular metal. The physical origin of these trends is identified and discussed. On the basis of our results, we arrive at some simple rules with respect to where a reaction should occur: (i) defects such as steps are always favored for dissociation reactions as compared to flat surfaces; and (ii) the reaction site of the association reactions is largely related to the magnitude of the bonding competition effect, which is determined by the reactant and metal valency. Reactions with high valency reactants are more likely to occur on defects (more structure-sensitive), as compared to reactions with low valency reactants. Moreover, the reactions on late transition metals are more likely to proceed on defects than those on the early transition metals.