Search results for "method."
showing 10 items of 13043 documents
Generalised bisection method for optimum ultrasonic ray tracing and focusing in multi-layered structures
2021
Ultrasonic testing has been used for many decades, proving itself very efficient for detecting defects in many industrial sectors. The desire to apply ultrasonic testing to geometrically complex structures, and to anisotropic, inhomogeneous materials, together with the advent of more powerful electronics and software, is constantly pushing the applicability of ultrasonic waves to their limits. General ray tracing models, suitable for calculating the proper incident angle of single element probes and the proper time delay of phased array, are currently required. They can support the development of new imaging techniques, as Full Matrix Capture and Total Focusing Method, and the execution of …
First principles hybrid Hartree-Fock-DFT calculations of bulk and (001) surface F centers in oxide perovskites and alkaline-earth fluorides
2020
Valuable discussions with E. A. Kotomin are gratefully acknowledged. Research contribution of R. E. and A. I. P. has been performed within the framework of the EUROfusion Enabling Research project: ENR-MFE19.ISSP-UL-02 “Advanced experimental and theoretical analysis of defect evolution and structural disordering in optical and dielectric materials for fusion applications.” The views and opinions expressed herein do not necessarily reflect those of the European Commission.
Measurements on partial discharge in on‐site operating power transformer: a case study
2018
This study presents the case study of a substation in-service power transformer referred to the on-site partial discharge (PD) detection and evaluation methods. An original methodology for simultaneous application of three methods is proposed: electrical, acoustic and ultra-high frequency. Transformer is powered by the power grid and no external generator is required according to the proposed methodology. Furthermore, several possibilities of applying these concurrent measurements and benefits of such solution in terms of result interpretation, interference resistance and on-site measurement applicability are indicated. The proposed methodology allows for a fast, accurate and secure PD diag…
Modeling Stator Winding Inter-Turn Short Circuit Faults in PMSMs including Cross Effects
2020
Author's accepted manuscript. © 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. This paper presents a detailed analysis of stator winding inter-turn Short Circuit (ITSC) faults, taking the cross effects in the three phases of a permanent magnet synchronous motor (PMSM) into account by considering insulation degradation resistances. A PMSM with series coils in eac…
Pulsed Electro-Acoustic Method for specimens and cables employed in HVDC systems: Some feasibility considerations
2018
Recent experiments on the use of the PEA method for testing dielectric materials in specimens and comparison with a detailed model provide an insight of the phenomenon and suggest the need of adopting similar models also for cables. What is said is even more important considering the possible future adoption of the PEA methodology to test DC cables for Pre-Qualification and Type Tests. The use of an accurate model of the PEA cell used for testing specimens and related experiments prove that the thickness of the different parts composing the PEA setup is a basic element for providing accurate charge reading and interpretation of the phenomenon. Both simulation and experimental results, carri…
Determining the deformation and resulting coupling efficiency degradation of ultrastable fiber-coupled optical benches under load.
2020
Fiber-coupled optical benches are an integral part of many laser systems. The base of such an optical bench is usually a slab of solid material, onto which optical components are fixed. In many environments, the ability to retain high fiber coupling efficiency under mechanical loads is essential. In this article, we study the fiber-to-fiber coupling efficiency under the application of static mechanical loads experimentally and theoretically: We constructed a simple three-point bending setup to interferometrically measure the deformation of an optical bench under load. Using the same setup, we further recorded the resulting coupling efficiency variations. The examined optical benches are bas…
A New Approach to Partial Discharge Detection Under DC Voltage: Application to Different Materials
2021
Usability of a new Direct Current Periodic waveform for partial discharge qualification in HVDC systems is exemplified by tests performed on different materials.
Review of space charge measurement systems: acoustic, thermal and optical methods
2016
In the last decade, remarkable developments have concerned the methods of space charge measurement in the field of insulation systems diagnostic. In particular, methods based on acoustic and thermal phenomena have been largely used. The present review provides a broad overview on the different techniques used describing, for each of them, the working principle, the main features and the most relevant applications. Further details are provided for the Pulsed Electro-Acoustic (PEA) method, as it seems to be the most used. This article provides more details on its historical evolution, showing evidence for its technological limits and taking into consideration the advantages and drawn from the…
A Magnetohydrodynamic Auxiliary Propulsion system for docking assistance of autonomous vehicle
2016
In this article we present an approach to the description of Magnetohydrodynamic Auxiliary Propulsion system for docking assistance of autonomous vehicle. Preliminarily, an analytical model which includes an electromagnetic model and a thermal model is presented. Successively, in order to move beyond the analytical model, a 3-D MHD modeling tool and a Runge Kutta method based solver are presented and they are used to investigate an alternative MHD solutions. Some numerical analysis are given
Modeling self-sustaining waves of exothermic dissolution in nanometric Ni-Al multilayers
2016
Abstract The self-sustained propagating reaction occurring in nanometric metallic multilayers was studied by means of molecular dynamics (MD) and numerical modeling. We focused on the phenomenon of the exothermic dissolution of one metallic reactant into the less refractory one, such as Ni into liquid Al. The exothermic character is directly related to a negative enthalpy of mixing. An analytical model based on the diffusion-limited dissolution [1] coupled with heat transfer was derived to account for the main aspects of the process. Together, several microscopic simulations were carried out. The first series were set up to obtain all the parameters governing the process, including the heat…