1,720,989 research outputs found
Development of gas insulated high voltage components for Neutral Beam Injectors (NBI)
Full text linkLa tecnologia dei sistemi di trasmissione di corrente continua ad alto voltaggio (HVDC) isolati in gas (GIS) giocherà un ruolo fondamentale nella futura generazione di iniettori a fasci di neutri (NBI) operanti ad alti livelli energetici. I componenti HVDC-GIS saranno infatti utilizzati per trasferire la potenza elettrica prodotta dal sistema elettrico di alimentazione delle griglie (AGPS), alle griglie dell'iniettore a fasci di neutri adibite all'accelerazione degli ioni. Lo scopo principale della tesi di dottorato consiste nello sviluppo di strumenti numerici specializzati, in grado di risolvere il comportamento non lineare dipendente dal tempo dei sistemi HVDC-GIS, analizzare le correnti di perdita che fluiscono nel gas in diverse condizioni, la possibile insorgenza di scariche elettriche nel gas e la capacità di svolgere l'ottimizzazione delle forme dei componenti stessi. Gli strumenti proposti consentiranno di analizzare correttamente i fenomeni che avvengono nel gas dielettrico e potranno essere utilizzati per studiare il comportamento dielettrico dei nuovi materiali impiegati per gli isolatori solidi al fine di aumentare l'affidabilità e la tenuta dielettrica dei componenti.
Sebbene focalizzata principalmente sulla progettazione dei componenti ad alta tensione per l'NBI che equipaggerà l'esperimento Divertor Tokamak Test (DTT), la cui costruzione è in fase di avvio a Frascati in Italia, le metodologie descritte nella tesi di dottorato costituiscono un efficace strumento per l'analisi e l'ottimizzazione progettuale di generici apparati HVDC-GIS.The High Voltage Direct Current (HVDC) gas-insulated (GIS) technology will play a fundamental role for the future generation of Neutral Beam Injectors (NBI) operating at very high energy levels. As a matter of fact, the HVDC-GIS components will be used to transfer the electric power provided by the Acceleration Grid Power Supply (AGPS), to the ion acceleration grids of the NBI. The main focus of this Ph.D. thesis is to develop specialized numerical tools capable of resolving the nonlinear time-dependent behavior of the HVDC-GIS, analyze the leakage currents flowing in the gas under different conditions, the breakdown detection and the shape optimization of the components themselves. The proposed tools will allow to correctly analyze the phenomena occurring in the dielectric gas and can be used to study the dielectric behavior of the new materials used for solid insulators to increase the reliability and dielectric performances of the equipments. Although mainly focused on the design of the high voltage components for the NBI that will equip the Divertor Tokamak Test (DTT) facility, the construction of which is in the start phase in Frascati, Italy, the methodologies described in the Ph.D. thesis constitute an effective tool for analysis and design optimization of general HVDC-GIS equipments
Simple Extraction of the First Resonant Frequency via Integral Equation Method
No full textThe accurate determination of the first resonant frequency (FRF) is important for the design of electromagnetic (EM) devices and for establishing safety margins for their operation. However, the numerical extraction of the FRF typically involves a costly parametric sweep across operational frequencies. This article introduces a method for extracting the FRF based on energetic considerations and the PEEC scheme for the solution of EM problem. Despite its simplicity, the proposed approach significantly reduces the computational cost while maintaining a good accuracy compared to conventional methods. This advancement promises to enhance the efficiency and accuracy of FRF extraction in EM device characterization
Development of HVDC Gas-Insulated Components for the Power Supply of Neutral Beam Injectors
Full text linkThe development of High Voltage Direct Current Gas-Insulated components that will be employed for the power supply of Neutral Beam Injectors, requires specific numerical tools to analyze the electric field distribution, with the purpose of supporting the engineering and operational phases.The tools must comply with the nonlinearity of the material properties of solid insulators and the transport mechanisms in the dielectric gas. Despite its high Global Warming Potential, SF6 will be considered as the baseline dielectric gas for the development of HVDC gas-insulated components to be used for the Acceleration Grid Power Supply of Neutral Beam Injectors. Attention especially to the mechanisms driving to an increase of leakage current flowing in the gas, thus giving rise to possible discharge phenomena is here placed, mainly focusing on radiation and injection regimes. The described methodologies are adopted for the numerical modeling of the 500 kV DC gas-insulated components that will be used for the power supply of the Neutral Beam Injector of the Divertor Tokamak Test facility. In particular, a conceptual design of the SF6 Transmission Line and the SF6-air bushing is conceived
A Fast Integral Equation of J−φe Formulation for Superconducting Structures
No full textThis article presents an integral equation method based on the current–potential ( J−φe ) formulation, for the solution of the eddy currents problem in superconducting structures. Two efficient methods for storing and manipulating the fully populated matrices resulting from the discretization of the integral equation are proposed in this work. These approaches leverage hierarchical ( H ) matrices and the fast Fourier transform technique, tailored for voxelized structures. These techniques drastically reduce the computational cost of the numerical simulations. The proposed approach is compared to existing methods, as the H−φm formulation, and is efficiently applied to calculate the power losses for a realistic high-temperature superconductor coil
The proposed approach is compared to existing methods, as the formulation, and is efficiently applied to calculate the power losses for a realistic High-Temperature Superconductor (HTS) coil
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
Automatic Optimization of Gas Insulated Components Based on the Streamer Inception Criterion
Full text linkGas insulated transmission lines (GILs) are used in electrical systems mainly for power transmission and High Voltage substation interconnection. In this paper, we focus on the development of complex numerical tools for the optimization of gas insulated HVDC components by the estimation of realistic electric field distribution and the voltage holding of the designed geometry. In particular, the paper aims at describing the correct modelling approach suitable to study high voltage components in DC, considering the nonlinear behaviour characterizing the electrical conductivity of solid and gas insulators. The simulated field distribution is then adopted to estimate the voltage holding of the dielectric gas, with a convenient engineering technique, based on the streamer criterion. These two tools are integrated in an automatic optimization package developed in COMSOL® and MATLAB®, with the purpose of adjusting the critical geometry features, suffering from excessive electrical stress and possibly giving rise to electrical breakdown, in order to guide the designer towards a robust solution
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
TopIE: An Integral Equation Tool for Topology Optimization in Electromagnetics
Full text linkTopology optimization for the design of electromagnetic devices has recently garnered significant interest, thanks to advancements in additive manufacturing techniques that enable the fabrication of intricate geometries. This has opened up new possibilities for utilizing integral equation methods to solve electromagnetic (EM) problems, particularly in the analysis of Inductive Power Transfer (IPT) devices. In this context, we introduce a novel topology optimization tool called TopIE, which is built upon the Integral Equation method for EM problem solutions. TopIE adopts the logic of Topology Optimization of Binary Structures (TOBS), a sensitivity-based approach that leverages binary design variables to clearly differentiate the material properties within the design domain. The tool is specifically employed for optimizing IPT devices, and sample implementations of the method are made publicly available. By combining the power of topology optimization and integral equation methods, TopIE offers a promising avenue for enhancing the design and performance of EM devices
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