2,484 research outputs found

    Interactive Inverse Design Optimization of Fuselage Shape for Low-Boom Supersonic Concepts

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    This paper introduces a tool called BOSS (Boom Optimization using Smoothest Shape modifications). BOSS utilizes interactive inverse design optimization to develop a fuselage shape that yields a low-boom aircraft configuration. A fundamental reason for developing BOSS is the need to generate feasible low-boom conceptual designs that are appropriate for further refinement using computational fluid dynamics (CFD) based preliminary design methods. BOSS was not developed to provide a numerical solution to the inverse design problem. Instead, BOSS was intended to help designers find the right configuration among an infinite number of possible configurations that are equally good using any numerical figure of merit. BOSS uses the smoothest shape modification strategy for modifying the fuselage radius distribution at 100 or more longitudinal locations to find a smooth fuselage shape that reduces the discrepancies between the design and target equivalent area distributions over any specified range of effective distance. For any given supersonic concept (with wing, fuselage, nacelles, tails, and/or canards), a designer can examine the differences between the design and target equivalent areas, decide which part of the design equivalent area curve needs to be modified, choose a desirable rate for the reduction of the discrepancies over the specified range, and select a parameter for smoothness control of the fuselage shape. BOSS will then generate a fuselage shape based on the designer's inputs in a matter of seconds. Using BOSS, within a few hours, a designer can either generate a realistic fuselage shape that yields a supersonic configuration with a low-boom ground signature or quickly eliminate any configuration that cannot achieve low-boom characteristics with fuselage shaping alone. A conceptual design case study is documented to demonstrate how BOSS can be used to develop a low-boom supersonic concept from a low-drag supersonic concept. The paper also contains a study on how perturbations in the equivalent area distribution affect the ground signature shape and how new target area distributions for low-boom signatures can be constructed using superposition of equivalent area distributions derived from the Seebass-George-Darden (SGD) theory

    Facet recovery and light emission from GaN/InGaN/GaN core-shell structures grown by metal organic vapour phase epitaxy on etched GaN nanorod arrays

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    The use of etched nanorods from a planar template as a growth scaffold for a highly regular GaN/InGaN/GaN core-shell structure is demonstrated. The recovery of m-plane non-polar facets from etched high-aspect-ratio GaN nanorods is studied with and without the introduction of a hydrogen silsesquioxane passivation layer at the bottom of the etched nanorod arrays. This layer successfully prevented c-plane growth between the nanorods, resulting in vertical nanorod sidewalls (∼89.8°) and a more regular height distribution than re-growth on unpassivated nanorods. The height variation on passivated nanorods is solely determined by the uniformity of nanorod diameter, which degrades with increased growth duration. Facet-dependent indium incorporation of GaN/InGaN/GaN core-shell layers regrown onto the etched nanorods is observed by high-resolution cathodoluminescence imaging. Sharp features corresponding to diffracted wave-guide modes in angle-resolved photoluminescence measurements are evidence of the uniformity of the full core-shell structure grown on ordered etched nanorods

    Dynamics of pedestrians in regions with no visibility - a lattice model without exclusion

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    We investigate the motion of pedestrians through obscure corridors where the lack of visibility (due to smoke, fog, darkness, etc.) hides the precise position of the exits. We focus our attention on a set of basic mechanisms, which we assume to be governing the dynamics at the individual level. Using a lattice model, we explore the effects of non-exclusion on the overall exit flux (evacuation rate). More precisely, we study the effect of the buddying threshold (of no-exclusion per site) on the dynamics of the crowd and investigate to which extent our model confirms the following pattern revealed by investigations on real emergencies: If the evacuees tend to cooperate and act altruistically, then their collective action tends to favor the occurrence of disasters.Comment: 20 page

    Finite type approximations of Gibbs measures on sofic subshifts

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    Consider a H\"older continuous potential ϕ\phi defined on the full shift A^\nn, where AA is a finite alphabet. Let X\subset A^\nn be a specified sofic subshift. It is well-known that there is a unique Gibbs measure μϕ\mu_\phi on XX associated to ϕ\phi. Besides, there is a natural nested sequence of subshifts of finite type (Xm)(X_m) converging to the sofic subshift XX. To this sequence we can associate a sequence of Gibbs measures (μϕm)(\mu_{\phi}^m). In this paper, we prove that these measures weakly converge at exponential speed to μϕ\mu_\phi (in the classical distance metrizing weak topology). We also establish a strong mixing property (ensuring weak Bernoullicity) of μϕ\mu_\phi. Finally, we prove that the measure-theoretic entropy of μϕm\mu_\phi^m converges to the one of μϕ\mu_\phi exponentially fast. We indicate how to extend our results to more general subshifts and potentials. We stress that we use basic algebraic tools (contractive properties of iterated matrices) and symbolic dynamics.Comment: 18 pages, no figure

    Electoral Performance and Policy Choices in the Front National

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    This article proposes a two-level analysis of the Front National (FN) in the 2017 French presidential and parliamentary elections. The first level focuses on the electoral performances of Marine Le Pen and the FN and analyses both elections in terms of gains and losses at the polls. The second level considers FN policy and argues that the party went into these elections with a programme targeting both left- and right-leaning voters, attempting a policy synthesis that partly fitted and partly subverted Kirchheimer’s paradigm of the ‘catch-all’ party. Both levels of analysis link to a number of strategic considerations prompting debate within the party over the direction to take in order to improve its future electoral prospects

    Displacement Talbot lithography: an alternative technique to fabricate nanostructured metamaterials

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    Nanostructured materials are essential for many recent electronic, magnetic and optical devices. Lithography is the most common step used to fabricate organized and well calibrated nanostructures. However, feature sizes less than 200 nm usually require access to deep ultraviolet photolithography, e-beam lithography or soft lithography (nanoimprinting), which are either expensive, have low-throughput or are sensitive to defects. Low-cost, high-throughput and low-defect-density techniques are therefore of interest for the fabrication of nanostructures. In this study, we investigate the potential of displacement Talbot lithography for the fabrication of specific structures of interest within plasmonic and metamaterial research fields. We demonstrate that nanodash arrays and ‘fishnet’-like structures can be fabricated by using a double exposure of two different linear grating phase masks. Feature sizes can be tuned by varying the exposure doses. Such lithography has been used to fabricate metallic ‘fishnet’-like structures using a lift-off technique. This proof of principle paves the way to a low-cost, high-throughput, defect-free and large-scale technique for the fabrication of structures that could be useful for metamaterial and plasmonic metasurfaces. With the development of deep ultraviolet displacement Talbot lithography, the feature dimensions could be pushed lower and used for the fabrication of optical metamaterials in the visible range

    Fabrication of high-aspect ratio GaN nanostructures for advanced photonic devices

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    This dataset is the result of an investigation into the impact of the temperature and pressure on the fabrication of Gallium Nitride nanostructures. The dataset contains data acquired from etched nanorods and nanopores.The data was acquired using a Hitachi S-4300 scanning electron microscope (SEM). The secondary electron (SE) images were produced using the manufacturer-supplied software. Figure numbers in the data file descriptions refer to the Microelectronic Engineering article by Le Boulbar et al. (2016) referenced in the related publications section.The height and diameter of the nanostructure were extracted from the SE image. Measurements were taken on more than five nanostructures to obtain representative and accurate dimensions.An Inductively Coupled Plasma (ICP) (Oxford Instrument 100 Cobra) were used for the dry-etching process

    Pleomorphic adenocarcinoma of the lacrimal gland with multiple intracranial and spinal metastases

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    BACKGROUND: Pleomorphic adenoma of the lacrimal gland is known to undergo malignant transformation when incompletely excised. Even if such a malignant change occurs, intracranial direct invasion and leptomeningeal seeding are seldom encountered. CASE PRESENTATION: A 50-year-old woman presented with malignant transformation associated with both intracranial invasion and multiple intracranial and spinal disseminations in the third recurrence of pleomorphic adenoma of the lacrimal gland, 6 years after initial treatment. MRI demonstrated increased extent of orbital mass, extending to the cavernous sinus. The patient underwent intensity-modulated radiation therapy (IMRT) and Gamma Knife radiosurgery. Follow-up MRI showed multiple leptomeningeal disseminations to the intracranium and spine. CONCLUSION: It is important to recognize that leptomeningeal intracranial and spinal disseminations of pleomorphic adenocarcinoma can occur, although it is extremely rare. To our knowledge, we report the first case of pleomorphic adenocarcinoma of the lacrimal gland presumably metastasizing to the intracranium and spine

    Non-resonant dot-cavity coupling and its applications in resonant quantum dot spectroscopy

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    We present experimental investigations on the non-resonant dot-cavity coupling of a single quantum dot inside a micro-pillar where the dot has been resonantly excited in the s-shell, thereby avoiding the generation of additional charges in the QD and its surrounding. As a direct proof of the pure single dot-cavity system, strong photon anti-bunching is consistently observed in the autocorrelation functions of the QD and the mode emission, as well as in the cross-correlation function between the dot and mode signals. Strong Stokes and anti-Stokes-like emission is observed for energetic QD-mode detunings of up to ~100 times the QD linewidth. Furthermore, we demonstrate that non-resonant dot-cavity coupling can be utilized to directly monitor and study relevant QD s-shell properties like fine-structure splittings, emission saturation and power broadening, as well as photon statistics with negligible background contributions. Our results open a new perspective on the understanding and implementation of dot-cavity systems for single-photon sources, single and multiple quantum dot lasers, semiconductor cavity quantum electrodynamics, and their implementation, e.g. in quantum information technology.Comment: 17 pages, 4 figure

    A meta-analysis of the relation between therapeutic alliance and treatment outcome in eating disorders.

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    The therapeutic alliance has demonstrated an association with favorable psychotherapeutic outcomes in the treatment of eating disorders (EDs). However, questions remain about the inter-relationships between early alliance, early symptom improvement, and treatment outcome. We conducted a meta-analysis on the relations among these constructs, and possible moderators of these relations, in psychosocial treatments for EDs. Twenty studies met inclusion criteria and supplied sufficient supplementary data. Results revealed small-to-moderate effect sizes, βs = 0.13 to 0.22 (p < .05), indicating that early symptom improvement was related to subsequent alliance quality and that alliance ratings also were related to subsequent symptom reduction. The relationship between early alliance and treatment outcome was partially accounted for by early symptom improvement. With regard to moderators, early alliance showed weaker associations with outcome in therapies with a strong behavioral component relative to nonbehavioral therapies. However, alliance showed stronger relations to outcome for younger (vs. older) patients, over and above the variance shared with early symptom improvement. In sum, early symptom reduction enhances therapeutic alliance and treatment outcome in EDs, but early alliance may require specific attention for younger patients and for those receiving nonbehaviorally oriented treatments
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