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The purpose of this paper is the derivation and efficient implementation of surface impedance boundary conditions (SIBCs) for nonlinear magnetic conductors.

An approach based on perturbation theory is proposed, which expands to nonlinear problems the methods already developed by the authors for linear problems. Differently from the linear case, for which the analytical solution of the diffusion equation in the semi-infinite space for the magnetic field is available, in the nonlinear case the corresponding nonlinear diffusion equation must be solved numerically. To this aim, a suitable smooth map is defined to reduce the semi-infinite computational domain to a finite one; then the diffusion equation is solved by a Galerkin method relying on basis functions constructed via the push-forward of a Lagrangian polynomial basis whose degrees of freedom are collocated at Gauss–Lobatto nodes. The use of such basis in connection with a suitable under-integration naturally leads to mass-lumping without impacting the order of the method. The solution of the diffusion equation is coupled with a boundary element method formulation for the case of parallel magnetic conductors in terms of E and B fields.

The results are validated by comparison with full nonlinear finite element method simulations showing very good accordance at a much lower computational cost.

Limitations of the method are those arising from perturbation theory: the introduced small parameter must be much less than one. This implies that the penetration depth of the magnetic field into the magnetic and conductive media must be much smaller than the characteristic size of the conductor.

The efficient implementation of a nonlinear SIBC based on a perturbation approach is proposed for an electric and magnetic field formulation of the two-dimensional problem of current driven parallel solid conductors.

This paper aims to design metaguide- or metasurface-based compact inexpensive beam-steering devices, which play an important role in modern cellular networks, radar imaging and satellite communication.

This paper uses finite element analysis to study, design and optimize arrays of resonating elements as beam steering devices. The first set of such devices involves metamaterial-based apertures fed by a waveguide, tunable via the permittivity of the host material. In the second approach, dynamic beam steering is effected by alternating between two or more waveguide feeds.

Particular examples show how the direction of the main lobe of the radiated beam can be reliably switched by approximately 30° in one of the quadrants by changing a single global control parameter within a very reasonable range.

The findings pave the way for the design and fabrication of inexpensive compact beam steering devices. This study anticipates that the proposed designs can be further improved and fine-tuned using “heavy duty” optimization packages.

In many published designs of similar beam-steering devices, the radiation pattern of an array of resonating elements is controlled by complex circuitry, so that each radiating element is tuned separately. In contrast with these existing approaches, the designs rely just on a simple global control parameter.

Ground Penetrating Radar is a multidisciplinary Nondestructive Evaluation technique that requires knowledge of electromagnetic wave propagation, material properties and antenna theory. Under some circumstances this tool may require auxiliary algorithms to improve the interpretation of the collected data. Detection, location and definition of target’s geometrical and physical properties with a low false alarm rate are the objectives of these signal post-processing methods. Basic approaches are focused in the first two objectives while more robust and complex techniques deal with all objectives at once. This work reviews the use of Artificial Neural Networks and Machine Learning for data interpretation of Ground Penetrating Radar surveys. We show that these computational techniques have progressed GPR forward from locating and testing to imaging and diagnosis approaches.

Problem 2 of the International Workshop for Eddy Current Code Comparison is a hollow cylinder with its axis perpendicular to a uniform sinuosoidal field. A total of 10 solutions, employing 9 different computer codes, are described and compared with analytic results. Most codes were 2‐D finite element and were found to give satisfactory solutions.

Two different ‘a posteriori’ error estimation techniques are proposed in this paper. The effectiveness of the error estimates in adaptive mesh refinement for 2D and 3D electrostatic problems are also analyzed with numerical test results. The post‐processing method employs an improved solution to estimate the error, whereas the gradient of field method utilizes the gradient of the field solution for estimating the ‘a posterior’ error. The gradient of field method is computationally inexpensive, since it solves a local problem on a patch of elements. The error estimates are tested by solving a set of self‐adjoint boundary value problems in 2D and 3D using a hierarchical minimal tree based mesh refinement algorithm. The numerical test results and the performance evaluation establish the effectiveness of the proposed error estimates for adaptive mesh refinement.

This work discusses the use of exponentially and reciprocally decaying infinite elements and assesses their respective value for magnetostatic and eddy current problems. In particular, the need for different decaying parameters for different materials is shown to be detrimental to their application in many practical situations. A simple method, whereby a 2‐D solution is used to find the approximate boundary conditions for a closely truncated 3‐D mesh is presented and shown to give good results without the complications of infinite elements. This method is applied to a large eddy current problem.

A summary of results for Problem 9 of the TEAM workshop is presented in the form of a documentation of the available results. Due to unforseen complications in the problem no comparisons have been made and the problem, with modification, will be retained for future workshops.

To provide a time domain formulation for reconstruction of transient currents flowing in massive parallel conductors from magnetic data collected in the dielectric space surrounding the conductors.

A boundary integral equation (BIE) formulation involving Mitzner's and Rytov's high order surface impedance boundary conditions (SIBCs) is used. Input data of the inverse problem are the magnetic fields at given locations near the conductors. In order to validate the inversion algorithm, the magnetic field data are computed solving the direct problem with FEM for given current waveforms.

The improvement in reconstruction accuracy of the new time domain BIE formulation employing high order SIBCs has been demonstrated numerically in a simple test case. The range of validity of the technique has been extended to current pulses of longer duration and the computational burden has shown to increase only by a factor of 4.

The proposed formulation can be compared with other possible formulations, both in the time and in the frequency domain.

Based on this formulation a new current sensing technique is proposed for realization of low cost current sensors based on magnetic sensor arrays.

The inverse problem addressed in the paper has been solved for the first time.

Development of a method of balancing an AC bridge with minimum computation time. The applications envisioned are in power system monitoring and sensing

The method is based on a recursive algorithm, first matching the phase followed by that of amplitude. Each phase step requires three samples per steps.Voltage matching is based on halving the range of measured amplitudes in each step, resulting in an n-step recursive algorithm.

Computation is minimal - only requires 4 phase matching steps for an error of 1º. Further steps improve on this error. Matching of amplitude is equally fast. The resolution in amplitude is directly proportional to the number of steps. An example and experimental results demonstrate the efficiency of the method.

Balancing of AC bridges in conjunction with automated measurement systems is a fairly complex process requiring either extensive computation or dedicated hardware (tunable devices, microprocessors, etc.). The current method is recursive and very light on computation. This means the method can be used in sensing systems where neither extensive hardware nor computational resources are readily available.

The method has been developed for power line AC impedance sensing as part of a power line monitoring system. It is however a general method that can be used in any AC bridge application.

The methods used as well as the implementation are entirely original. These have been developed as part of a research in instrumentation of power line monitoring.

Global mobility remains one of the most pressing challenges of our times. Countries in the north are turning to major ‘sending’ countries in the south to secure their cooperation in controlling their borders and in repatriation processes. By explicitly linking migration to global security threats and weak governance, these migration control initiatives are justified by development goals and sometimes financed by official development assistance (ODA). By connecting criminology with international development scholarship, this chapter seeks to advance our understanding of the novel intersections between criminal justice, security and development to govern mass migration. Focusing on UK policies and the analysis of specific programmes, it interrogates what does the sustainable development goal (10.7) of facilitating ‘orderly, safe, regular and responsible migration’ concretely entail? And to what extent does the language of ‘managed migration’ legitimise restrictive border controls policies and even conflict with other global development goals?