Strategies for balancing exploration and exploitation in electromagnetic optimisation

The paper focuses on the advantages and drawbacks of different strategies which may be used to assist kriging surrogate modelling with the purpose of selecting multiple design vectors for evaluation when stepping forward in optimisation routines. The combined criteria include the efficiency of finding the global optimum but also the quality of the approximation of the shape of the objective function; the latter may be used to make judgements about the robustness of the optimised design

Adaptive Weighted Expected Improvement With Rewards Approach in Kriging Assisted Electromagnetic Design

The paper explores kriging surrogate modelling combined with expected improvement approach for the design of electromagnetic devices. A novel algorithm based on the concept of rewards is proposed, tested and demonstrated in the context of TEAM Workshop Problem 22. Balancing exploration and exploitation is emphasized and robustness of the design considered

Defining and Computing Equivalent Inductances of Gapped Iron Core Reactors

The paper revisits the fundamental definitions and explores computational alternatives of equivalent inductances of gapped iron core reactors. Unlike in a transformer, the physical meaning of component inductances of a reactor is subject to uncertainty and open to different interpretations, leading to various equivalent circuits. It is argued that a definition based on flux distribution may not be reliable and calculations based on energy or co-energy are thus preferable

Numerical investigation of Fano resonances in metamaterials with electric asymmetry

The excitation of high-quality factor asymmetric Fano-type resonances on a double-layer metafilm structure is investigated through numerical simulation. The study demonstrates that it is possible to design simple structures capable to sustain a very high-quality factor resonance by reducing their radiation losses. An equivalent circuit formed by two linearly coupled resonant RLC circuits is extracted in an attempt to explain the observed Fano resonance through classical circuit theory

Implementation of packaged integrated antenna with embedded front end for Bluetooth applications

The design, integration and realization of system in enhanced package approach towards fully functional system level integration by using a compact Bluetooth USB dongle as the demonstrator is presented here. The integration was done on FR4 substrates, which is totally compatible with today’s printed circuit board manufacturing capability. A commercially available Bluetooth integrated chip was chosen as the chipset of our demonstrator, and a package integrated antenna together with an embedded front end completes the system in package integration. The front end developed here is based on an embedded meander line combline filter and an embedded transformer balun. The filter has a 35% area reduction when compared with the classical combline filter and similar performance. The balun has the coils distributed on three layers that minimized the board area needed it and optimizes the performances. The proposed packaged integrated antenna approach is successfully demonstrated here and the new module shows excellent performance when compared with a commercial solution, surpassing the normal Bluetooth class II dongle range which is up to 10 m and increasing the module range up to 120 m without an extra power amplifier

Numerical Modelling of Needle-Grid Electrodes Negative Surface Corona Charge System

Surface potential decay measurement is a simple and low cost tool to examine electrical properties of insulation materials. During corona charging stage, needle-grid electrodes system is often used to achieve uniform charge distribution on the surface of the sample. However, there is little report on the effects of geometrical parameters and voltage values of the charging system on the surface potential and its characteristics. In the present report simulations based on gas discharging physics similar to [1] have been carried out to investigate dynamic surface charge formation. The geometry of in the model includes a 174?m radius of curvature needle setting perpendicular to a 0.5mm thickness grid electrode and a 27.5mm diameter with 50?m thickness polyethylene. The bottom surface of the polyethylene is grounded and it is 3cm and 1.5cm away from the needle electrode and grid electrode respectively. The simulations were initially performed under the following conditions: the needle electrode was set as -8000V and the grid electrode -2000V. It has been found that an impulse current appeared after 0.3?s charging which represented the corona effect. The effect of adding a grid electrode can be clearly seen from the logarithmic plot of electrons. Finally, surface charge density on the sample has been obtained

Robust Global Optimization of Electromagnetic Designs Utilizing Gradient Indices and Kriging

Since uncertainties in design variables are inevitable an optimal solution must consider the robustness of the design. A methodology based on the use of first-order and second-order gradient indices is proposed introducing the notion of gradient sensitivity. A kriging method assisted by algorithms exploring the concept of rewards is utilized to facilitate function predictions for the robust optimization process. The performance of the proposed algorithms is assessed through a series of numerical experiments and the TEAM Workshop Problem 22

Evolution of the neutron quasi-elastic scattering through the ferroelectric phase transition in 93%PbZn1/3_{1/3}Nb2/3_{2/3}O3_3 - 7% PbTiO3_3

We show that the neutron diffuse scattering in relaxor ferroelectric (1-x)PbZn$_{1/3}$Nb$_{2/3}$O$_{3}$ - x PbTiO$_{3}$ (x=0.07) consists of two components. The first component is strictly elastic but extended in q-space and grows below 600 K. The second component, that was not reported before for the (1-x)PbZn$_{1/3}$Nb$_{2/3}$O$_{3}$ - x PbTiO$_{3}$ (x=0.07) relaxor ferroelectrics, is quasi-elastic with a line-width that has a similar temperature dependence as the width of the central peak observed by Brillouin spectroscopy. The temperature dependence of the susceptibility of the quasi-elastic scattering has a maximum at the ferroelectric transition