1,721,111 research outputs found
Global formulation of 3D magnetostatics using flux and gauged potentials
No full textThe use of algebraic formulation for the solution of electromagnetic fields is becoming more and more widespread. This paper presents the theoretical development of two algebraic formulations of the magneto-static problem and their implementation in a three dimensional computational procedure based on an unstructured tetrahedral mesh. A complete description of the variables used and of the solution algorithm is provided together with a discussion about the performances of the method. The performances of the two procedures are tested and assessed versus cases with known solutions
Optimal prize allocations in group contests
Full text linkWe characterize the optimal prize allocation, namely the allocation that maximizes a group’s effectiveness, in a model of contests. The model has the following features: (i) it allows for heterogeneity between and within groups; (ii) it classifies contests as “easy” and “hard” depending on whether the marginal costs are concave or convex. Thus, we show that in an “easy” contest the optimal prize allocation assigns the entire prize to one group member, the most skilled one. Conversely, all group members receive a positive share of the prize when the contest is “hard” and players have unbounded above marginal productivities. If the contest is “hard” and the marginal productivities are bounded above, then only the most skilled group members are certain of receiving a positive share of the prize for any distribution of abilities. Finally, we study the effects of a change in the distribution of abilities within a group. Our analysis shows that if the contest is either “easy” or a particular subset of “hard”, then the more the heterogeneity within a group, the higher its probability of winning the prize
Electrostatic Analysis for Plane Problems with Finite Formulation
No full textThe Finite Formulation is an alternative to the widely used Finite Elements or Edge Elements methods and adopts the global variables as a starting point. The Finite Formulation allows one to straightforwardly deduce the set of algebraic equations. This method has been applied to the solution of plane electrostatic problems on the basis of two different topologies of the primal mesh elements: triangular and quadrilateral. The obtained results in the two cases have been compared each other and also with those from the Finite Elements
An Approach to the Plasma Magnetic Contour Identification in Presence of Eddy Currents
No full textThe research in the thermonuclear fusion area has entered the design phase of ITER, the first experimental Tokamak reactor. In the ITER device, the plasma shape and position are controlled by an active system on the basis of a real-time estimate of the plasma magnetic boundary. This identification process must be prompt and accurate enough to satisfy the tight control requirements. In this paper, a brief discussion about the reconstruction of the plasma boundary by means of the "equivalent currents" (EC) method, in presence of conducting structures, will be presented. Some hints about a possible way to include the differential equations describing the vessel eddy currents will be illustrated
Design, Construction and Commissioning of SGPR, the Fast Protection System of RFX
No full textRFX, the largest machine for magnetic confinement of plasmas in the RFP line, is provided with a system named SGPR specifically designed for the machine global protection against fast faults which can develop in the plasma, in the windings, in the power supply circuits and in the control system. SGPR is a cabled logic HLL machine, able to organise in few tens of microseconds coordinated machine protection, dealing with more than forty fault signals and activating almost thirty protection commands. SGPR design, manufacture and test program conform the quality control criteria necessary to assure the required high reliability. After a careful and cumbersome commissioning work the system has assumed its protection role. Up to now it has been called to a number of interventions which, even if never due to major faults, have shown its capability of proper operation
Real-Time Design and Characterization of Inductive Position Sensors Through AI-Driven DesSS
No full textWe propose a fast method to characterize inductive position sensors with zero physical prototypes. The technique is based on an in-house developed electromagnetic simulation tool which shows three orders of magnitude improvement with respect to the most widely used commercial software. This simulation software is used for producing synthetic data for training a machine learning surrogate model based on a neural network. In this way, the characterization of a sensor takes just milliseconds. This opens the possibility of devising a Design Support System (DesSS), a software that guide the user in sensor design for the best possible outcome, thereby saving development time
An adaptive method to identify the plasma magnetic contour from magnetic and polarimetric measurements
No full textThe identification of a plasma magnetic contour can be cast as an inverse problem in which a set of equivalent currents, representing (the effect of) the actual plasma current distribution, have to be determined in order to best fit a set of external measurements. The diagnostic systems are typically provided with arrays of magnetic measurements, including both flux and field probes, positioned outside the plasma chamber, and some non magnetic measurements, such as motion Stark effect or multichord FIR polarimetry. In the framework of the method discussed, the basic external (magnetic) measurements have been integrated with internal (polarimetric) measurements to improve the identification process and gain information about the internal plasma current profile. The inverse problem can be formulated as the pseudo-inversion of the transfer matrix linking the unknown equivalent currents to the magnetic and polarimetric measurements. In this paper, the equivalent currents method is improved by means of a procedure that adaptively tries to allocate the EC to obtain the best estimate of the plasma contour. The adaptive strategy is presented in detail and its performance evaluated against two ITER equilibrium plasma configurations
Dynamic identification of plasma magnetic contour in fusion machines
No full textThe paper presents a method to identify the plasma magnetic contour in fusion machines, when eddy currents are present in the conducting structures surrounding the plasma. The approach presented is based on the integration of an electromagnetic model of the plasma with a lumped parameters model of the conducting structures around the plasma. This approach has been validated against experimental data from RFX, a reversed field pinch machine
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