Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences最新文献

Plasmons in two-dimensional electron channels have potential applications in the terahertz frequency range. Equivalent circuit models provide a convenient framework for analysing the plasmons. This article introduces a circuit model for plasmons in the presence of a dc current that flows in a gated channel. It is shown that drifting plasmons can be described by an LC-transmission line with distributed dependent sources. A circuit analogue of the Dyakonov-Shur instability is demonstrated. Then, a lumped-element transmission line with dependent sources is analysed, and non-reciprocity is demonstrated for examples of a right- and a left-handed transmission line. Effects of ohmic loss are discussed. The results could be used for the design of non-reciprocal transmission line devices. This article is part of the theme issue 'Celebrating the 15th anniversary of the Royal Society Newton International Fellowship'.

Concepts and evolution of multi-scale modelling from the perspective of wave-structure interaction have been discussed. In this regard, both domain and functional decomposition approaches have come into being. In domain decomposition, the computational domain is spatially segregated to handle the far-field using potential flow models and the near field using Navier-Stokes equations. In functional decomposition, the velocity field is separated into irrotational and rotational parts to facilitate identification of the free surface. These two approaches have been implemented alongside partitioned or monolithic schemes for modelling the structure. The applicability of multi-scale modelling approaches has been established using both mesh-based and meshless schemes. Owing to said diversity in numerical techniques, massively collaborative research has emerged, wherein comparative numerical studies are being carried out to identify shortcomings of developed codes and establish best-practices in numerical modelling. Machine learning is also being applied to handle large-scale ocean engineering problems. This paper reports on the past, present and future research consolidating the contributions made over the past 20 years. Some of these past as well as future research contributions have and shall be actualized through funding from the Newton International Fellowship as the next generation of researchers inherits the present-day expertise in multi-scale modelling. This article is part of the theme issue 'Celebrating the 15th anniversary of the Royal Society Newton International Fellowship'.

Solid-state ionic conductors find application across various domains in materials science, particularly showcasing their significance in energy storage and conversion technologies. To effectively utilize these materials in high-performance electrochemical devices, a comprehensive understanding and precise control of charge carriers' distribution and ionic mobility at interfaces are paramount. A major challenge lies in unravelling the atomic-level processes governing ion dynamics within intricate solid and interfacial structures, such as grain boundaries and heterophases. From a theoretical viewpoint, in this Perspective article, my focus is to offer an overview of the current comprehension of key aspects related to solid-state ionic interfaces, with a particular emphasis on solid electrolytes for batteries, while providing a personal critical assessment of recent research advancements. I begin by introducing fundamental concepts for understanding solid-state conductors, such as the classical diffusion model and chemical potential. Subsequently, I delve into the modelling of space-charge regions, which are pivotal for understanding the physicochemical origins of charge redistribution at electrified interfaces. Finally, I discuss modern computational methods, such as density functional theory and machine-learned potentials, which offer invaluable tools for gaining insights into the atomic-scale behaviour of solid-state ionic interfaces, including both ionic mobility and interfacial reactivity aspects. This article is part of the theme issue 'Celebrating the 15th anniversary of the Royal Society Newton International Fellowship'.

Unmanned aerial vehicles (UAVs) equipped with a miniaturized sensor package were developed for aerial observations, which realizes aerial observations affordable to scientists in atmospheric science and achieves aerial measurements in high spatial resolution. UAVs are deployed to a variety of aerial detecting tasks in different scientific scenarios including chemical industry parks (CIPs) with hazardous gases emissions, and some places difficult for humans to reach. In this study, UAV sensing technology was deployed to detect air pollutants in a suburb, a CIP and a natural gas plant, respectively. The effects of atmospheric conditions such as the atmospheric boundary layer height, long-distance transport and atmospheric stability on the spatiotemporal variations of the air pollutants vertical profiles were investigated by the UAV. The UAV with the sensor package was deployed to capture the methane (CH₄) leakages in a natural gas plant. The spatiotemporal variations of CH₄ in both vertical and horizontal directions studied by UAV were employed to calculate accurate CH₄ emissions, which is crucial to reducing the emissions of greenhouse gases. The low-cost UAV sensing technology for air pollutants was developed by Dr. Xiaobing Pang, who was funded by the Newton Fellowship in 2009 and worked in the University of York. This article is part of the theme issue 'Celebrating the 15th anniversary of the Royal Society Newton International Fellowship'.

Four-dimensional (4D) constellations with up to 131 072 points (17 bit/4D-sym) are designed for the first time using geometric shaping. The constellations are optimized in terms of mutual information (MI) and generalized MI (GMI) for the additive white Gaussian noise (AWGN) channel, targeting a forward error correction (FEC) rate of 0.8 at finite signal-to-noise ratios. The presented 15-17 bit constellations are currently the highest-performing constellations in the literature, having a gap to the AWGN capacity as low as 0.17 dB (MI) and 0.45 dB (GMI) at 17 bit/4D-sym. For lower cardinalities, our constellations match or closely approach the performance of previously published optimized constellations. We also show that (GMI-)optimized constellations with a symmetry constraint, optimized for a FEC rate of 0.8, perform nearly identical to their unconstrained counterparts for cardinalities above 8 bit/4D-sym. A symmetry constraint for MI-optimized constellations is shown to have a negative impact in general. The proposed procedure relies on a Monte-Carlo-based approach for evaluating performance and is extendable to other (nonlinear) channels. Stochastic gradient descent is used for the optimization algorithm for which the gradients are computed using automatic differentiation. This article is part of the theme issue 'Celebrating the 15th anniversary of the Royal Society Newton International Fellowship'.

In the boundless landscape of scientific exploration, there exists a hidden, yet easily accessible, dimension that has often not only intrigued and puzzled researchers but also provided the key. This dimension is chirality, the property that describes the handedness of objects. The influence of chirality extends across diverse fields of study from the parity violation in electroweak interactions to the extremely large macroscopic systems such as galaxies. In this opinion piece, we will delve into the power of chirality in scientific exploration by examining some examples that, at different scales, demonstrate its role as a key to a better understanding of our world. Our goal is to incite researchers from all fields to seek, implement and utilize chirality in their research. Going this extra mile might be more rewarding than it seems at first glance, in particular with regard to the increasing demand for new functional materials in response to the contemporary scientific and technological challenges we are facing. This article is part of the theme issue 'Celebrating the 15th anniversary of the Royal Society Newton International Fellowship'.

Polymers have distinctive optical properties and facile fabrication methods that have been well-established. Therefore, they have immense potential for nanophotonic devices. Here, we demonstrate the temperature-sensing potential of SU8-meta-phenylenediamine (SU8-mPD), produced by epoxy amination of the SU-8 polymer. Its properties were examined through a series of molecular structural techniques and optical methods. Thin layers have demonstrated optical emission and absorption in the visible range around 420 and 520 nm, respectively, alongside a strong thermal responsivity, characterized by the 18 ppm °C^-1 expansion coefficient. A photonic chip, comprising a thin 5-10 μm SU8-mPD layer, encased between parallel silver and/or gold thin film mirrors, has been fabricated. When pumped by an external light source, this assembly generates a pronounced fluorescent signal that is superimposed with the Fabry-Pérot (FP) resonant response. The chip undergoes mechanical deformation in response to temperature changes, thereby shifting the FP resonance and encoding temperature information into the fluorescence output spectrum. The time response of the device was estimated to be below 1 s for heating and a few seconds for cooling, opening a new avenue for optical sensing using SU8-based polymers. Thermoresponsive resonant structures, encompassing strong tunable fluorescent properties, can further enrich the functionalities of nanophotonic polymer-based platforms. This article is part of the theme issue 'Celebrating the 15th anniversary of the Royal Society Newton International Fellowship'.

The Spherical Tokamak for Energy Production (STEP) programme aims to deliver a first-of-a-kind fusion prototype powerplant (SPP). The SPP plasma places extreme heat, particle and structural loads onto the plasma-facing components (PFCs) of the divertor, limiters and inboard and outboard sections of the first wall. The PFCs must manage the heat and particle loads and wider powerplant requirements relating to safety, net power generation, tritium breeding and plant availability. To enable STEP PFC concepts to be identified that satisfy these wide-ranging requirements, an iterative design ('Decide & Iterate') methodology has been used to synchronize a prioritized set of decisions, within the fast-paced, iterative, whole plant concept design schedule. This paper details the 'Decide and Iterate' methodology and explains how it has enabled the identification of the SPP PFC concepts. These include innovative PFC solutions such as a helium-cooled discrete and panel limiter design to increase tritium breeding while providing sufficient coverage and enabling individual limiter replacement; the integration of the outboard first wall with the breeding zone to enhance fuel self-sufficiency and power generation; and the use of heavy water (D₂O) within the inboard first wall and divertor PFCs to increase tritium breeding within the outboard breeding zone. This article is part of the theme issue 'Delivering Fusion Energy - The Spherical Tokamak for Energy Production (STEP)'.

The UK's fusion energy approach has developed over the past 5 years to include government policy initiatives and a range of public sector investments designed to be delivered in partnership with the private sector. These have aimed to create an environment that stimulates innovation and investment to deliver economic as well as scientific and environmental benefits throughout the lifetime of the public sector fusion energy programme. The Spherical Tokamak for Energy Production acts as a focus and anchor for both public and private sector efforts to develop fusion energy, developing the supply chain and potential for Intellectual Property development and export opportunities well ahead of the anticipated STEP completion date of 2040. This is maximized by the UK's approach to a holistic research and innovation programme backed up by a regulatory and skills programme. This article is part of the theme issue 'Delivering Fusion Energy - The Spherical Tokamak for Energy Production (STEP)'.

Success of the UK's Spherical Tokamak for Energy Production (STEP) programme requires a robust plasma control system. This system has to guide the plasma from initiation to the burning phase, maintain it there, produce the desired fusion power for the desired duration and then terminate the plasma safely. This has to be done in a challenging environment with limited sensors and without overloading plasma-facing components. The plasma parameters and the operational regime in the STEP prototype will be very different from tokamaks, which are presently in operation. During fusion burn, the plasma regime in STEP will be self-organizing, adding further complications to the plasma control system design. This article describes the work to date on the design of individual controllers for plasma shape and position, magneto hydrodynamic instabilities, heat load and fusion power. Having studied 'normal' operation, the article discusses the philosophy of how the system will handle exceptions, when things do not go exactly as planned. This article is part of the theme issue 'Delivering Fusion Energy - The Spherical Tokamak for Energy Production (STEP)'.