1,721,002 research outputs found
Fixec Scale Trasformation Approach to Linear and Branched Polymers
No full textThe radius exponent of two- and three-dimensional self-avoiding walks and branched polymers are computed in the fixed-scale transformation framework. The method requires the knowledge of the critical fugacity kc, but from this non-universal parameter it is possible to compute the universal critical exponent. The results obtained are within 1% of exact or numerical values. This confirms the versatility and quantitative power of this new theoretical approach and gives the opportunity to provide a discussion of the analogies and differences between the real space renormalization group and the fixed-scale transformation method
"Non-Homogeneous Charge Distribution in Layered High Tc Superconductors"
No full textWe consider the problem of the charge distribution of holes among the various CuO2 layers in the unit cell for compounds of the type Tl2Ba2Can−1CunO2n+4. In analogy with graphite intercalation compounds, the charge distribution is strongly nonhomogeneous (for n≥3) with a depletion in the central layers. This result points to a special importance of the bounding layers and it provides a way to understand the observed maximum Tc as a function of n
MARKET ANALYSIS, TLARS SELECTION AND PRELIMINARY DESIGN INVESTIGATIONS FOR A REGIONAL HYBRID-ELECTRIC AIRCRAFT
Full text linkThis paper is framed in the context of the GENESIS Project (Gauging the ENvironmEntal Sustainability of electrIc and hybrid aircraft Systems), which complies with the European Union topic JTI-CS2-2020-CFP11-THT13 (Sustainability of Hybrid-Electric Aircraft System Architectures) as part of the Clean Sky 2 programme for Horizon 2020. The research work is focused on gauging the environmental sustainability of electric aircraft in a life-cycle-based, foresight perspective to support the development of a technology roadmap for transitioning towards sustainable and competitive electric aircraft systems. The analyzed aircraft segment is regional aircraft, to identify, design and assess prospectively the best energy storage and transmission topology. Different alternatives including batteries, fuel cells, hybrid and conventional powertrain technologies are evaluated and compared over different time horizons. In particular, the paper is focused on the description of the workflow implemented to define the Top-Level Aircraft Requirements for a non-conventional regional class hybrid-electric aircraft with 50 passengers, and on the identification of key specifications in terms of on-board energy storage, shaft power level and weight
Automatic modeling of aircraft external geometries for preliminary design workflows
No full textThis article introduces a high-fidelity geometry definition methodology enabling Multidisciplinary Design, Analysis and Optimization (MDAO) of aircraft configurations. All definitions and functional features have been implemented within the JPAD software, a Java-based computing library for aircraft designers, which provides a dedicated geometric modeling module called JPADCAD. The geometric module, that comes as an application programming interface (API) built on top of the OpenCASCADE Technology solid modeling kernel, is conceived for the automatic production of parametric aircraft CAD geometries. The tool allows the definition of input geometries for low-fidelity as well as high-fidelity aerodynamic analyses, hence proves to be a key factor in the entire MDAO process, particularly in conceptual or preliminary design analysis workflows. The main goal of such a geometric library remains ease of use and support for automation to minimize unnecessary or repetitive human effort. The backbone of the presented methodology is the parametric definition of a generic commercial transport aircraft configuration that translates into software data structures and functionalities of CAD surface modelers. These aspects are discussed in the first part of the article. The second part presents a use case example of the geometric modeling API, where an automated aerodynamic analysis workflow is used to construct a prediction model for canard-wing configurations
GENESIS - Gauging the ENvironmEntal Sustainability of electrIc aircraft Systems
No full textGENESIS project will gauge the environmental sustainability of electric aircraft (A/C) in a life-cycle-based, foresight perspective to support the development of a technology roadmap for transitioning towards sustainable and competitive electric A/C systems. The focus is on regional class, 50 pax aircraft to identify, design and assess prospectively the best energy storage and transmission topology. Different alternatives within battery, fuel cell, hybrid and conventional powertrain technologies are evaluated and compared over different time horizons. To meet these objectives and scoping, GENESIS relies on a strong consortium of 10 partners, 4 R&D-active SMEs and 1 large company – gathering excellence and complementary competences that cover all key aspects of the project. GENESIS will design electric (all-electric and hybrid) aircraft and elicit specific requirements, which will feed into technology foresight analyses. These will allow highlighting technological limits and potential solutions within each component of the aircraft system life cycle, which includes the life cycle of the aircraft itself as well as the life cycle of the fuels and that of the on-ground infrastructures. The analyses will enable the development of time- and technology-specific life cycle inventories, used as basis for a full-fledged prospective life cycle assessment. Combining the resulting environmental performances with those from an economic analysis and a technical analysis, comprehensive scenario comparisons between the different powertrain alternatives will be made, enabling a sustainability-based Technology Roadmap. GENESIS is anticipated to have large impact on all aeronautics stakeholders as its outputs will help moving towards environmentally sustainable aviation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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