1,721,113 research outputs found
Numerical insights of an improved SPH method
Full text linkIn this paper we discuss on the enhancements in accuracy and computational demanding in approximating a function and its derivatives via Smoothed Particle Hydrodynamics. The standard method is widely used nowadays in various physics and engineering applications [1],[2],[3]. However it suffers of low approximation accuracy at boundaries or when scattered data distributions is considered. Here we reformulate the original method by means of the Taylor series expansion and by employing the kernel function and its derivatives as projection functions and integrating over the problem domain [3]. In this way, accurate estimates of the function and its derivatives are simultaneously provided and no lower order derivatives are inherent in approximating the higher order derivatives. Moreover, high order of accuracy can be obtained without changes on the kernel function avoiding to lead unphysical results such as negative density or negative energy that can lead to breakdown of the entire computation in simulating some problems [1]. The modified scheme obtains the required accuracy, but the high computational effort makes the procedure rather expensive and not easily approachable in the applications. To this aim we make use of fast summations to generate a more efficient procedure, allowing to tune the desired accuracy. Working with the Gaussian function we proceed by applying the improved fast Gaussian transform as valid alternative to efficiently com- pute the summations of the kernel and its derivatives [4]. We discuss about the accuracy and the computational demanding of the improved method dealing with different sets of data and bivariate functions
Metodo per calcolare il campo elettrico all’interno di uno strato di materiale dielettrico di un cavo elettrico in alta tensione per corrente elettrica continua, e relativo sistema
No full textDetection of the human brain activity with fundamental solution method
No full textHuman brain activity mapping is a fundamental task for the neurophysiological research and for the diagnostic purposes too. Non-invasive techniques such as Electroencephalography (EEG) and magnetoencephalography (MEG) allow the reconstruction of the cerebral electrical currents providing useful information on the neuronal activity in the human brain. Based on a typical inverse problem the M/EEG imaging techniques require to solve more times a forward one. In this paper we discuss on a numerical tool based on the Method of the Fundamental Solutions(MFS) to efficiently solve the M/EEG forward problem going over the BEM state-of-the-art procedure. Inspired by the Leave-One-Out Cross Validation (LOOCV) strategy we improve the accuracy of the numerical solver gaining promising results
Method for calculating the electric field inside a dielectric material layer of a high voltage electric cable for direct electric current, and system thereof
No full textANALISI DEL POSSIBILE IMPIEGO DI CAVI HVDC PER LO SMART STORAGE
Full text linkL’idea alla base dell’attività di ricerca è quella di investigarela possibilità di utilizzare l’energia che,durante il normale servizio,è immagazzinata nei cavi dei sistemi di trasmissione ad alta tensione in corrente continua (HVDC), quando si verifichino scenari tecnico-economici favorevoli tali da giustificare,o per necessità o per scelta, la messa fuori servizio dei cavi stessi
Partial Discharge Detection Using a Spherical Electromagnetic Sensor
Full text linkThe presence of a partial discharge phenomenon in an electrical apparatus is a warning signal that could determine the failure of the insulation system, terminating the service of the apparatus and/or the network. In this paper, an innovative partial discharge (PD) measurement instrument based on an antenna sensor is presented and analyzed. Being non-intrusive is one of the most relevant features of the sensor. The frequency response of the antenna sensor and the features to recognize different PD sources and automatically synchronize them with the supply voltage are described and discussed in details. The results show the performance of the instrument can make a fast and correct diagnosis of the health state of insulation systems
Computational Issues of an Electromagnetics Transient Meshless Method
No full textIn this paper we refer to the computational issues in solving Maxwell’ s curl equations without using any connectivity among the points in which the problem domain is discretized. The adopted procedure is able to approximate the electric and magnetic vector fields making use of the derivatives of a kernel function at points arranged in the computational domain. In order to improve the numerical accuracy, dealing with irregular data distribution or data located near the boundary, a suitable strategy is considered. The computational core of the overall process requires elementary linear algebra operations. In the paper the method is presented and the discussion is revolved to the computational issues. Moreover, some numerical simulations are presented to validate the numerical process
Review of the PEA Method for Space Charge Measurements on HVDC Cables and Mini-Cables
Full text linkThis review takes into account articles and standards published in recent years concerning the application of the Pulsed Electro Acoustic (PEA) method for space charge measurement on High Voltage Direct Current (HVDC) cables and mini-cables. Since the 80s, the PEA method has been implemented for space charge measurements on flat specimens in order to investigate space charge phenomena and to evaluate the ageing of dielectrics. In recent years, this technique has been adapted to cylindrical geometry. Several studies and experiments have been carried out on the use of the PEA method for full size cables and HVDC cable models. The experiments have been conducted using different arrangements of the measurement setup and focusing attention on different aspects of space charge phenomena. In this work, the importance of space charge measurement is highlighted and the state-of-the-art PEA method application to full size cables and mini-cables is described. The main aim of this paper is to offer a complete and current review of this technique. In addition, limits on the use of PEA method are examined and main possible directions of research are proposed in order to improve the applicability, reliability, and replicability of this method
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
- …
