Performance of the Impedance Boundary Conditions for Eddy-Current Problems
Impedance boundary conditions are used to derive approximate expressions for the magnetic vector potential, field quantities, Joule losses and forces for conducting spheroids in the presence of circular turns carrying sinusoidal with time currents. Numerical results are generated to determine, by comparison with the results obtained applying the exact boundary conditions, the improvement achieved with the surface impedance model with respect to the simpler perfect conductor model and the range of validity of these models. The study performed is useful for evaluating various approximate numerical solutions for real world conductors
Benchmark computations of the fields, losses, and forces for conducting spheroids in the proximity of current-carrying turns
We derive exact analytical expressions for the quasi-stationary field quantities due to circular turns carrying current in the presence of conducting prolate and oblate spheroids. We use these expressions to generate numerical results of specified accuracy for the field quantities inside and outside the spheroids, as well as for the Joule losses inside them and the forces acting upon them. We present selected results in a normalized form for determined, extended ranges of the spheroid axial ratio, the ratio of the depth of penetration to the semi-minor axis, and the position of the inducing turns relative to the spheroids. The results constitute reference data for comprehensive comparisons of results from approximate volume methods or from boundary impedance models used for real-world conductors in the presence of nonuniform external magnetic fields.
Pedagogy of the “Not”: Negation, Exodus, and Postdigital Temporal Regimes
Postdigital capitalist time is an incessant acceleration that acts to homogenize time and wed us to the present, to which we have to constantly catch up. While the impulse of this is no doubt economic (the realization of value), it is crucially undergirded by a pedagogical logic wherein we have to perpetually learn and re-learn the latest apps, social media configurations, operating systems, and so on. Political strategies of resistance thus need to be bolstered by an alternative mode of educational life, and I propose a pedagogy of the “not” as one possibility. Such a pedagogy is an act of suspension that sustains a detachment from the present, clearing out oppositions and thereby exposing us to a radical indeterminacy and potentiality that is always untimely. Suspension is the praxis of negation, which means that negation operates by keeping sense indeterminate to meaning and signification. Rather than suppressing, disavowing, or annihilating the stated content, negation retains even that which is negated. While this would appear as a form of exopedagogy, which withdraws from the dialectic of the private/public, I instead argue that it redefines the terms of any dialectic, redefining the very categories exopedagogy withdraws from. Before concluding, I spend some time with Sandy Grande’s important critiques of Eurocentrism and progress in Western critical education, demonstrating how negation as suspension circumvents these errors through its accommodation of—or, better, insistence on—variegated temporalities and forms of life.