A Structural Analysis of Field/Circuit Coupled Problems Based on a Generalised Circuit Element

In some applications there arises the need of a spatially distributed description of a physical quantity inside a device coupled to a circuit. Then, the in-space discretised system of partial differential equations is coupled to the system of equations describing the circuit (Modified Nodal Analysis) which yields a system of Differential Algebraic Equations (DAEs). This paper deals with the differential index analysis of such coupled systems. For that, a new generalised inductance-like element is defined. The index of the DAEs obtained from a circuit containing such an element is then related to the topological characteristics of the circuit's underlying graph. Field/circuit coupling is performed when circuits are simulated containing elements described by Maxwell's equations. The index of such systems with two different types of magnetoquasistatic formulations (A* and T-$\Omega$) is then deduced by showing that the spatial discretisations in both cases lead to an inductance-like element

Reduced Order Modelling for the Simulation of Quenches in Superconducting Magnets

This contributions discusses the simulation of magnetothermal effects in superconducting magnets as used in particle accelerators. An iterative coupling scheme using reduced order models between a magnetothermal partial differential model and an electrical lumped-element circuit is demonstrated. The multiphysics, multirate and multiscale problem requires a consistent formulation and framework to tackle the challenging transient effects occurring at both system and device level

Long living carriers in a strong electron-phonon interacting two-dimensional doped semiconductor

Carrier doping by the electric field effect has emerged recently as an ideal route for monitoring many-body physics in two-dimensional (2D) materials where the Fermi level is tuned in a way that -- indirectly -- the strength of the interactions can also be scanned. The possibility of systematic doping in combination with high resolution photoemission has allowed to uncover a genuinely many-body electron spectrum in single-layer MoS2 transition metal dichalcogenide, resolving three clear quasi-particle states, where only one state should be expected if the electron-phonon interaction vanished. Our analysis combines first-principles and consistent complex plane analytic approaches and brings into light the presence and the physical origin of two gaps and the three quasi-particle bands which are unambiguously present in the photoemission spectrum. One of these states, though being strongly interacting with the accompanying virtual phonon cloud, presents a notably long lifetime which is an appealing property when trying to understand and take advantage of many-body interactions to modulate the transport properties.Comment: Editorially accepted for publication in "Communications Physics" (14 pages, 3 figures

Application of the Waveform Relaxation Technique to the Co-Simulation of Power Converter Controller and Electrical Circuit Models

In this paper we present the co-simulation of a PID class power converter controller and an electrical circuit by means of the waveform relaxation technique. The simulation of the controller model is characterized by a fixed-time stepping scheme reflecting its digital implementation, whereas a circuit simulation usually employs an adaptive time stepping scheme in order to account for a wide range of time constants within the circuit model. In order to maintain the characteristic of both models as well as to facilitate model replacement, we treat them separately by means of input/output relations and propose an application of a waveform relaxation algorithm. Furthermore, the maximum and minimum number of iterations of the proposed algorithm are mathematically analyzed. The concept of controller/circuit coupling is illustrated by an example of the co-simulation of a PI power converter controller and a model of the main dipole circuit of the Large Hadron Collider

Programes 3D en l'aprenentatge de Cicles Formatius de la família de Tèxtil, confecció i pell. Estudi d'implementació i viabilitat

Les noves tecnologies cada cop estan més presents i treballar amb programes 3D de moda resultaria interessant i útil per l'alumnat dels cicles formatius de la família de Tèxtil, confecció i pell. L'objectiu d'aquest estudi és investigar l'ús de programes 3D de moda en aquests cicles formatius en centres catalans, i valorar l'interès i la viabilitat que podria tenir la incorporació d'aquest tipus de programes per a complementar l'aprenentatge en aquests cicles en els centres d'estudi. Es tracta d'un estudi quantitatiu transversal. Es va entrevistar a professorat i alumnat de dos centres catalans amb aquest tipus d'estudis, seleccionats per conveniència, mitjançant uns qüestionaris estructurats autoemplenats enviats per correu electrònic a través d'un enllaç. Els participants van manifestar tenir un interès i una necessitat en la implementació d'aquest tipus de programes, a més de considerar-la viable. A partir dels resultats obtinguts, es considera necessària i viable la implementació de programes 3D de tèxtil i moda en l'aprenentatge dels cicles formatius de la família de Tèxtil, confecció i pell. Altrament, es podria dur a terme en qualsevol dels grups d'aquests cicles, preferentment als graus superiors, assenyalant CLO 3D com a programa més adient

Parareal for index two differential algebraic equations

This article proposes modifications of the Parareal algorithm for its application to higher index differential algebraic equations (DAEs). It is based on the idea of applying the algorithm to only the differential components of the equation and the computation of corresponding consistent initial conditions later on. For differential algebraic equations with a special structure as, e.g. given in flux-charge modified nodal analysis, it is shown that the usage of the implicit Euler method as a time integrator suffices for the Parareal algorithm to converge. Both versions of the Parareal method are applied to numerical examples of nonlinear index 2 differential algebraic equations

Index-aware learning of circuits

Electrical circuits are present in a variety of technologies, making their design an important part of computer aided engineering. The growing number of tunable parameters that affect the final design leads to a need for new approaches of quantifying their impact. Machine learning may play a key role in this regard, however current approaches often make suboptimal use of existing knowledge about the system at hand. In terms of circuits, their description via modified nodal analysis is well-understood. This particular formulation leads to systems of differential-algebraic equations (DAEs) which bring with them a number of peculiarities, e.g. hidden constraints that the solution needs to fulfill. We aim to use the recently introduced dissection concept for DAEs that can decouple a given system into ordinary differential equations, only depending on differential variables, and purely algebraic equations that describe the relations between differential and algebraic variables. The idea then is to only learn the differential variables and reconstruct the algebraic ones using the relations from the decoupling. This approach guarantees that the algebraic constraints are fulfilled up to the accuracy of the nonlinear system solver, which represents the main benefit highlighted in this article.Comment: 15 pages, 15 figure

A Stabilized Circuit-Consistent Foil Conductor Model

The magnetoquasistatic simulation of large power converters, in particular transformers, requires efficient models for their foils windings by means of homogenization techniques. Using the standard solid and stranded conductor models is not computationally feasible for a foil winding. In this article, the classical foil conductor model is derived and, for the first time, an inconsistency in terms of circuit theory is reported, which may lead to time-stepping instability. The inconsistency can be related to the differential-algebraic nature of the resulting system of equations. A new modified definition of the turn-by-turn conductance matrix of the foil conductor model is shown to mitigate this problem. The different structure of the systems using the alternative turn-by-turn conductance matrix definitions is examined in detail. Numerical results are presented to demonstrate the instability of the original foil conductor model and to verify the effectiveness of the new proposed model