A Combined Component-Based Approach for the Design of Distributed Software Systems

Component-based software development enables the construction of software artefacts by assembling binary units of production, distribution and deployment, the so-called components. Several approaches to component-based development have been proposed recently. Most of these approaches are based on the Unified Modeling Language (UML). UML has been increasingly used in component-based development, despite some shortcomings of this language. This paper presents a methodology for the design of component-based applications that combines a model-based approach with a UML-based approach. This combined approach tackles some of the limitations of UML, allowing a better control of the design proces

Unpacking the ‘developing’ country classification: origins and hierarchies

The division of the world into ‘developing’ and ‘developed’ countries has grown increasingly problematic in the past decades. Nonetheless, it remains embedded in legal documents, foreign policy discourse, and colloquial use. This paper explores this complexity by unpacking the different ways in which the ‘developing’ label is used in the international system. It argues that understanding the complexity around its use requires a rigorous analysis of the label’s diverse meanings and consequences. This is done by introducing a taxonomy that intersects two elements: (1) the source of the classification (External or Internal) and (2) the kind of hierarchy implied in the classification (Narrow or Broad). This two-by-two matrix generates four approaches in which the ‘developing’ vs ‘developed’ dichotomy is used: Technocratic, Elective, Northern Gaze, and Southern Solidarity. Each approach is explored empirically, illustrated by cases connected to international organizations and multilateral treaties. In doing so, the paper teases out the underlying reasons why the use of the dichotomy is so challenging, based on what kinds of contestation it generates, and which actors are pushing for demise or longevity (and where)

Tunable diffusion of magnetic particles in a quasi-one-dimensional channel

The diffusion of a system of ferromagnetic dipoles confined in a quasi-one-dimensional parabolic trap is studied using Brownian dynamics simulations. We show that the dynamics of the system is tunable by an in-plane external homogeneous magnetic field. For a strong applied magnetic field, we find that the mobility of the system, the exponent of diffusion and the crossover time among different diffusion regimes can be tuned by the orientation of the magnetic field. For weak magnetic fields, the exponent of diffusion in the subdiffusive regime is independent of the orientation of the external field.Comment: 9 pages, 13 figures, to appear in Phys. Rev. E (2013

Wavepacket scattering on graphene edges in the presence of a (pseudo) magnetic field

The scattering of a Gaussian wavepacket in armchair and zigzag graphene edges is theoretically investigated by numerically solving the time dependent Schr\"odinger equation for the tight-binding model Hamiltonian. Our theory allows to investigate scattering in reciprocal space, and depending on the type of graphene edge we observe scattering within the same valley, or between different valleys. In the presence of an external magnetic field, the well know skipping orbits are observed. However, our results demonstrate that in the case of a pseudo-magnetic field, induced by non-uniform strain, the scattering by an armchair edge results in a non-propagating edge state.Comment: 8 pages, 7 figure

All-strain based valley filter in graphene nanoribbons using snake states

A pseudo-magnetic field kink can be realized along a graphene nanoribbon using strain engineering. Electron transport along this kink is governed by snake states that are characterized by a single propagation direction. Those pseudo-magnetic fields point towards opposite directions in the K and K' valleys, leading to valley polarized snake states. In a graphene nanoribbon with armchair edges this effect results in a valley filter that is based only on strain engineering. We discuss how to maximize this valley filtering by adjusting the parameters that define the stress distribution along the graphene ribbon.Comment: 8 pages, 6 figure

Transition from single-file to two-dimensional diffusion of interacting particles in a quasi-one-dimensional channel

Diffusive properties of a monodisperse system of interacting particles confined to a \textit{quasi}-one-dimensional (Q1D) channel are studied using molecular dynamics (MD) simulations. We calculate numerically the mean-squared displacement (MSD) and investigate the influence of the width of the channel (or the strength of the confinement potential) on diffusion in finite-size channels of different shapes (i.e., straight and circular). The transition from single-file diffusion (SFD) to the two-dimensional diffusion regime is investigated. This transition (regarding the calculation of the scaling exponent ($\alpha$) of the MSD $$ $\propto t^{\alpha}$) as a function of the width of the channel, is shown to change depending on the channel's confinement profile. In particular the transition can be either smooth (i.e., for a parabolic confinement potential) or rather sharp/stepwise (i.e., for a hard-wall potential), as distinct from infinite channels where this transition is abrupt. This result can be explained by qualitatively different distributions of the particle density for the different confinement potentials.Comment: 13 pages, 11 figure

Optimization of the transmission of observable expectation values and observable statistics in Continuous Variable Teleportation

We analyze the statistics of observables in continuous variable quantum teleportation in the formalism of the characteristic function. We derive expressions for average values of output state observables in particular cumulants which are additive in terms of the input state and the resource of teleportation. Working with Squeezed Bell-like states, which may be optimized in a free parameter for better teleportation performance we discuss the relation between resources optimal for fidelity and for different observable averages. We obtain the values of the free parameter which optimize the central momenta and cumulants up to fourth order. For the cumulants the distortion between in and out states due to teleportation depends only on the resource. We obtain optimal parameters for the second and fourth order cumulants which do not depend on the squeezing of the resource. The second order central momenta which is equal to the second order cumulants and the photon number average are optimized by the same resource. We show that the optimal fidelity resource, found in reference (Phys. Rev. A {\bf 76}, 022301 (2007)) to depend also on the characteristics of input, tends for high squeezing to the resource which optimizes the second order momenta. A similar behavior is obtained for the resource which optimizes the photon statistics which is treated here using the sum of the squared differences in photon probabilities of input and output states as the distortion measure. This is interpreted to mean that the distortions associated to second order momenta dominates the behavior of the output state for large squeezing of the resource. Optimal fidelity and optimal photon statistics resources are compared and is shown that for mixtures of Fock states they are equivalent.Comment: 25 pages, 11 figure