Functional Outlier Detection by Means of h-Mode Depth and Dynamic Time Warping

Finding outliers in functional infinite-dimensional vector spaces is widely present in the industry for data that may originate from physical measurements or numerical simulations. An automatic and unsupervised process of outlier identification can help ensure the quality of a dataset (trimming), validate the results of industrial simulation codes, or detect specific phenomena or anomalies. This paper focuses on data originating from expensive simulation codes to take into account the realistic case where only a limited quantity of information about the studied process is available. A detection methodology based on different features, such as h-mode depth or the dynamic time warping, is proposed to evaluate the outlyingness both in the magnitude and shape senses. Theoretical examples are used to identify pertinent feature combinations and showcase the quality of the detection method with respect to state-of-the-art methodologies of detection. Finally, we show the practical interest of the method in an industrial context thanks to a nuclear thermal-hydraulic use case and how it can serve as a tool to perform sensitivity analysis on functional data.

A Numerically Efficient Technique for the Analysis of Metamaterial- and Metasurface-based Antennas

Metasurface-based antennas have received considerable recent attention in recent years because they are not only useful for designing new antennas, but for improving the performance of legacy designs as well. However, systematically designing these antennas is challenging because the antennas are usually multiscale in nature and they typically require a long time when simulated by using commercial solvers. In this work, we present a new approach for analyzing antennas that utilize Metasurfaces (MTSs) and Metamaterial (MTMs). The proposed method departs from the widely used technique based on an anisotropic impedance representation of the surface and relies on an equivalent medium approach instead. The principal advantage of the proposed approach is that such an equivalent medium representation can be conveniently inserted directly in commercial EM solvers, circumventing the need to develop special numerical EM simulation codes to handle metasurfaces. Several illustrative examples are presented in the paper to demonstrate the efficacy of the present approach when simulating MTS- and MTMbased antennas.

CTF and FLOCAL Thermal Hydraulics Validations and Verifications within a Multiscale and Multiphysics Software Development

Simulation codes allow one to reduce the high conservativism in nuclear reactor design improving the reliability and sustainability associated with nuclear power. Full-core coupled reactor physics at the rod level are not provided by most simulation codes. This has led in the UK to the development of a multiscale and multiphysics software development focused on LWRS. In terms of the thermal hydraulics, simulation codes suitable for this multiscale and multiphysics software development include the subchannel code CTF and the thermal hydraulics module FLOCAL of the nodal code DYN3D. In this journal article, CTF and FLOCAL thermal hydraulics validations and verifications within the multiscale and multiphysics software development have been performed to evaluate the accuracy and methodology available to obtain thermal hydraulics at the rod level in both simulation codes. These validations and verifications have proved that CTF is a highly accurate subchannel code for thermal hydraulics. In addition, these verifications have proved that CTF provides a wide range of crossflow and turbulent mixing methods, while FLOCAL in general provides the simplified no-crossflow method as the rest of the methods were only tested during its implementation into DYN3D.