1,573 research outputs found

    Effective medium theory of left-handed materials

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    We analyze the transmission and reflection data obtained through transfer matrix calculations on metamaterials of finite lengths, to determine their effective permittivity and permeability. Our study concerns metamaterial structures composed of periodic arrangements of wires, cut-wires, split ring resonators (SRRs), closed-SRRs, and both wires and SRRs. We find that the SRRs have a strong electric response, equivalent to that of cut-wires, which dominates the behavior of left-handed materials (LHM). Analytical expressions for the effective parameters of the different structures are given, which can be used to explain the transmission characteristics of LHMs. Of particular relevance is the criterion introduced by our studies to identify if an experimental transmission peak is left- or right-handed.Comment: to be published in Phys. Rev. Let

    Immersive Learning Research Network

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    Computer games have now been around for over three decades and the term serious games has been attributed to the use of computer games that are thought to have educational value. Game-based learning (GBL) has been applied in a number of different fields such as medicine, languages and software engineering. Furthermore, serious games can be a very effective as an instructional tool and can assist learning by providing an alternative way of presenting instructions and content on a supplementary level, and can promote student motivation and interest in subject matter resulting in enhanced learning effectiveness. REVLAW (Real and Virtual Reality Law) is a research project that the departments of Law and Computer Science of Westminster University have proposed as a new framework in which law students can explore a real case scenario using Virtual Reality (VR) technology to discover important pieces of evidence from a real-given scenario and make up their mind over the crime case if this is a murder or not. REVLAW integrates the immersion into VR as the perception of being physically present in a non-physical world. The paper presents the prototype framework and the mechanics used to make students focus on the crime case and make the best use of this immersive learning approach

    Electron transport in strongly disordered structures

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    Using the transfer matrix technique, we investigate the propagation of electron through a two dimensional disordered sample. We find that the spatial distribution of electrons is homogeneous only in the limit of weak disorder (diffusive transport regime). In the limit of very strong disorder, we identify a narrow channel through which the electron propagates from one side of the sample to the opposite side. Even in this limit, we prove the wave character of the electron propagation.Comment: Presented at ETOPIM

    AI EDAM special issue: advances in implemented shape grammars: solutions and applications

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    This paper introduces the special issue “Advances in Implemented Shape Grammars: Solutions and Applications” and frames the topic of computer implementations of shape grammars, both with a theoretical and an applied focus. This special issue focuses on the current state of the art regarding computer implementations of shape grammars and brings a discussion about how those systems can evolve in the coming years so that they can be used in real life design scenarios. This paper presents a brief state of the art of shape grammars implementation and an overview of the papers included in the current special issue categorized under technical design, interpreters and interface design, and uses cases. The paper ends with a comprehensive outlook into the future of shape grammars implementations.info:eu-repo/semantics/acceptedVersio

    Time-dependent local Green's operator and its applications to manganites

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    An algorithm is presented to calculate the electronic local time-dependent Green's operator for manganites-related hamiltonians. This algorithm is proved to scale with the number of states NN in the Hilbert-space to the 1.55 power, is able of parallel implementation, and outperforms computationally the Exact Diagonalization (ED) method for clusters larger than 64 sites (using parallelization). This method together with the Monte Carlo (MC) technique is used to derive new results for the manganites phase diagram for the spatial dimension D=3 and half-filling on a 12x12x12 cluster (3456 orbitals). We obtain as a function of an insulating parameter, the sequence of ground states given by: ferromagnetic (FM), antiferromagnetic AF-type A, AF-type CE, dimer and AF-type G, which are in remarkable agreement with experimental results.Comment: 9 pages, 11 figure

    Kinetic energy storage using a dual braking system for unmanned parallel hybrid electric vehicle

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    In this paper a novel regenerative dual braking strategy is proposed for utility/goods delivery unmanned vehicles in public roads, which improves the regenerative energy capturing ability and consequently improves the fuel use of parallel hybrid power train configurations for land unmanned vehicles where the priority is not comfort but extending the range. Furthermore, the analysis takes into account the power handling ability of the electric motor and the power converters. In previous research a plethora of regenerative braking strategies is shown, for this paper the key contribution is that the vehicle electric regeneration is related to a fixed braking distance in relation to the energy storage capabilities specifically for unmanned utility type land vehicles where passenger comfort is not a concern but pedestrian safety is of critical importance. Furthermore, the vehicle’s power converter capabilities facilitate the process of extending the braking time via introducing a variable deceleration profile. The proposed approach has therefore resulted in a regenerative algorithm which improves the vehicle’s energy storage capability without considering comfort since this analysis is applicable to unmanned vehicles. The algorithm considers the distance as the key parameter, which is associated to safety, therefore it allows the braking time period to be extended thus favouring the electric motor generation process while sustaining safety. This method allows the vehicle to brake for longer periods rather than short bursts hence resulting in a more effective regeneration with reduced use of the dual (i.e. caliper/stepper motor brake system). The regeneration method and analysis is addressed in the following paper sections. The simulation results show that the proposed regenerative braking strategy has improved significantly the energy recapturing ability of the hybrid power train configuration. The paper is also supported with experimental data that verify the theoretical development and the simulation results. The two strategies developed and implemented are Constant Braking Torque (CBT) and Constant Braking Power (CBP). Both methods were limited to a fixed safety-based distance. Overall the results demonstrate that the CBT method results in better energy-based savings

    Propagation of the surface plasmon polaritons through gradient index and periodic structures

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    We study the propagation of surface electromagnetic waves along the metallic surface covered by various layered dielectric structures. We show that strong radiative losses typical for the scattering of the surface wave can be considerably suppressed when single dielectric step is substituted by gradient index or periodic layered structure

    Finite-temperature hole dynamics in the t-J model: Exact results for high dimensions

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    We discuss the dynamics of a single hole in the t-J model at finite temperature, in the limit of large spatial dimensions. The problem is shown to yield a simple and physically transparent solution, that exemplifies the continuous thermal evolution of the underlying string picture from the T=0 string-pinned limit through to the paramagnetic phase.Comment: 6 pages, including 2 figure

    Small-q electron-phonon scattering and linear dc resistivity in high-T_c oxides

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    We examine the effect on the DC resistivity of small-q electron-phonon scattering, in a system with the electronic topology of the high-T_c oxides. Despite the fact that the scattering is dominantly forward, its contribution to the transport can be significant due to ``ondulations'' of the bands in the flat region and to the umpklapp process. When the extended van-Hove singularities are sufficiently close to EFE_F the acoustic branch of the phonons contribute significantly to the transport. In that case one can obtain linear TT dependent resistivity down to temperatures as low as 10 K, even if electrons are scattered also by optical phonons of about 500 K as reported by Raman measurements.Comment: LATEX file and 4 Postscript figure
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