Thin-shell approach for modeling superconducting tapes in the H-Φ finite-element formulation

This paper presents a novel finite-element approach for the electromagnetic modeling of superconducting coated conductors with transport currents. We combine a thin-shell (TS) method to the H-Φ formulation to avoid the meshing difficulties related to the high aspect ratio of these conductors and reduce the computational burden in simulations. The interface boundary conditions in the TS method are defined using an auxiliary 1-D finite-element (FE) discretization of N elements along the thinnest dimension of the conductor. This procedure permits the approximation of the superconductor's nonlinearities inside the TS in a time-transient analysis. Four application examples of increasing complexity are discussed: (i) single coated conductor, (ii) two closely packed conductors carrying anti-parallel currents, (iii) a stack of twenty superconducting tapes and a (iv) full representation of a HTS tape comprising a stack of thin films. In all these examples, the profiles of both the tangential and normal components of the magnetic field show good agreement with a reference solution obtained with standard black2-D H-Φ formulation. Results are also compared with the widely used T-A formulation. This formulation is shown to be dual to the TS model with a single FE (N=1) in the auxiliary 1-D systems. The increase of N in the TS model is shown to be advantageous at small inter-tape separation and low transport current since it allows the tangential components of the magnetic field to penetrate the thin region. The reduction in computational cost without compromising accuracy makes the proposed model promising for the simulation of large-scale superconducting applications.

Sensing Local Field Potentials with a Directional and Scalable Depth Array: DISC

A variety of electrophysiology tools are available to the neurosurgeon for diagnosis, functional therapy, and neural prosthetics. However, no tool can currently address these three critical recording needs: (i) a surgical method that can reach any cortical region in a minimally invasive manner; (ii) record microscale, mesoscale, and macroscale resolutions simultaneously; and (iii) enable recording from multiple brain regions. This work presents a novel device for recording local field potentials (LFPs) whose form is based on state-of-the-art stereo-electroencephalogram (sEEG). Using quasi-static electromagnetic modeling, the lead body is shown to shield LFP sources and this enables directional sensitivity and scalability when microelectrodes are positioned radially, which we refer to as a DISC array. As predicted, DISC demonstrated significantly improved signal-to-noise, directional sensitivity, and decoding accuracy in the rat barrel cortex during whisker stimulation. Critically, DISC also demonstrated equivalent fidelity at the macroscale and, uniquely, performs current source density in stereo. Directional sensitivity of LFPs may significantly improve brain-computer interfaces and many diagnostic procedures, including epilepsy foci detection and deep brain targeting.

Electromagnetic-Based Wireless Sensor Networks for Natural Gas Pipeline and Reservoir Monitoring

In this paper, we electromagnetically analyzed the wireless sensor nodes for natural gas transport system from the recovery process to our apartments. In light of the problems of poor localization accuracy, low recognition efficiency and high false rates in traditional pipeline security and detection technology, this paper suggests a type of new electromagnetic modeling for the natural gas pipeline and tank system. This paper describes the effect of natural gas at different temperature and pressure levels on the propagation characteristics of electromagnetic waves at Terahertz Band frequencies. Based on the calculated absorption and path losses, the channel capacity and SNR are studied to give an insight of future Terahertz communication networks. Results show that characteristics of electromagnetic waves propagation affected by both the temperature and pressure. As a result, in the paper we come to the conclusion that frequency bands for optimum performance should be determined by reviewing the absorption coefficient.