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Conversion between longitudinal and shear waves at normal incidence using tailored meta-structures
Get PDFThe ability to manipulate elastic waves and achieve efficient mode conversion is important for many applications including energy harvesting, vibration mitigation and elastic wave control. In this paper, we present a novel metamaterial-based wave mode conversion device that enables the conversion of longitudinal-to-shear waves (and vice versa) at normal incidence. The devices achieve this by rotating the direction of polarisation (i.e. the motion vector) of the longitudinal waves to match the (normally orthogonal) polarisation of shear waves. Previously we have demonstrated mode conversion by adjusting the spatial–temporal distribution of the incident wave amplitude, but this approach cannot convert between modes with orthogonal motion vectors. Here we demonstrate conversion between orthogonal motion vectors without changing the spatial–temporal distribution of the field. The devices presented here reorient the direction of motion by coupling the waves into thin waveguides or “elastic wave pipes” such that a single mode is supported. The pipes are curved, and the motion vectors of the guide waves are thus rotated as the wave follows the pipe. Fabrication of these geometrically complex structures has recently been made practical through additive manufacturing allowing devices to be built that operate in the megahertz frequency range. We present the design methodology, finite element simulations and experimental demonstration of broadband mode conversion
Microwave-enhanced heap leaching of porphyry copper ores: Part 2 – Leaching studies and flowsheet development
Get PDFThe effect of ore mineralogy and texture on the extent of microwave-induced fractures and leaching performance has been investigated using porphyry copper sulphide ores with differing lithologies to identify potential ore candidates for microwave-assisted heap leaching. The extent of ore pre-damage due to microwave treatment was determined (qualitatively and quantitatively) using non-destructive tests (X-ray computed tomography (X-ray CT) and ultrasonic pulse velocity (UPV)). Pairs of sawn ore fragments (microwave treated versus untreated) from each ore type were leached in a strongly acidic solution, and results were compared to assess the influence of microwave treatment on leaching performance. Thereafter, several conceptual flowsheet possibilities incorporating microwave ore pre-treatment in heap leaching were proposed. Ore types with amenable mineralogy and texture for microwave treatment (e.g., coarse mineralization and high abundance of microwave-absorbent phases including pyrite) exhibited greater induced damage (up to 39% UPV reduction), faster leaching kinetics (by a factor of 2–8), and higher copper recovery enhancement (up to 28 % absolute). Moreover, the X-ray CT imaging clearly revealed that microwave ore pre-treatment generates new fractures or exacerbates the naturally occurring fractures (containing sulphide mineralisation), with many of these fractures occurring in the vicinity of sulphide mineralisation, which resulted in a mineral dissolution improvement by a factor of 4–10 % (absolute). Flowsheet development indicated the possibility of treating the whole ore or a portion of the feed with amenable texture. The authors conclude that the potential benefits of microwave ore pre-treatment in heap leaching flowsheets are twofold, namely simplification of comminution requirements (including energy reduction) and improving leaching performance (dissolution kinetics and ultimate metal recovery). On-going work is aimed at defining the details of the potential improvements and the economic impact
Assessing Mountain Soil Water Storage and Release in a Colombian Páramo With APSIS‐InSAR Data
Get PDFDirect observation of montane and upland water resources provides valuable data in support of national scale water management and policy, but direct observation is challenging on large spatial scales. To address the need for large spatial scale hydrological data we use InSAR surface motion signals, indicative of surface swelling due to increased soil water content, at approximately 90 m resolution over a tropical Colombian mountain range covered with Páramo, a biome widespread along the Northern Andes. Considering uncertainty of vegetation and mountainous terrain on the InSAR signal, we observe a regional, spatially consistent sequence of soil surface motion, which can be related to storage and movement of water through montane catchments. Swelling on the ridges and upper slopes occurs during the wet season and is consistent with infiltration and increased saturation of ridge and upper slope soils. This is followed by a marked swelling of the valley floors towards the end of the wet season and into the dry season. The InSAR signal also captures movement of water through the basin with swelling subsiding sequentially downslope and downstream. The results indicate that a shallow hillslope flow dominates during the wet season, but this alone is insufficient to explain shallow ground water storage in superficial valley deposits lasting into the late wet season and dry season. We conclude that InSAR signals can provide a qualitative insight in the storage and release mechanisms at a basin scale, thus complementing sparse point-scale measurements
A Dynamically Reconfigurable Multiactive Bridge Converter With Extended Topology-Level Decoupling
No full textThe cross-coupling effect and complicated control present significant challenges when implementing multiport dc-dc converters such as those enabled by multiactive bridge (MAB) converters. These challenges are typically addressed through additional control layers for implementing power flow decoupling functionality. Besides various control-level methods, the coupling effect can also be mitigated at the hardware level. Designing one of the ports with a small series inductance and feeding it with a rigid voltage source can enable decoupled power transfer without control complexities. However, a failure in the rigid voltage source of that port causes the cross-coupling to reappear. This article proposes a dynamically reconfigurable bridge that can maintain decoupled power flow when the main low-inductance port fails or is islanded. In this approach, a reconfigurable bridge requires two additional switches to bypass the external inductor during failure. The operating principles of the proposed approach are discussed, and its decoupling performance is compared with conventional control-level decoupling and a coupled MAB. The modulation technique is also adapted and implemented to achieve the desired performance. The effectiveness of the proposed solution is validated through testing on a 4kW SiC-MOSFET-based four-port experimental setup
Development and Experiment of Manta Ray-Inspired Robot Actuated by Dielectric Elastomer Actuator
No full textThe manta ray-inspired robots have attracted widespread attention. Although, current biomimetic pectoral fins actuated by soft actuators have realized simple oscillating motion, the biomimicry needs to be improved and the strategies for improving swimming performance also need to be further investigated. In this study, a manta ray-inspired robot actuated by dielectric elastomer actuator (DEA) is developed. To achieve the large flapping amplitude of biomimetic pectoral fin, an oscillating guide bar mechanism is used to amplify the output capability of DEA. The experimental research was conducted to investigate the influence of flexible deformation of pectoral fin on swimming performance. The locomotion of the biomimetic pectoral fin has been evaluated based on the motion capture and compared with the natural manta rays quantitatively. The results indicate that oscillating motion with biological traveling wave can achieve faster swimming velocity, greater thrust, and higher efficiency. The maximum swimming velocity of biomimetic manta ray robot is 36 mm/s, and the power efficiency is up to 20.1%. The turning test of robot fish is used to verify the maneuverability (8.5°/s). Our work highlights the development and experimental study of the DEA-driven robotic manta ray, which are potentially extendable to other underwater devices and robots
Clinical management of bispecific antibody therapy for lymphoma: A British Society for Haematology Good Practice Paper
Get PDFCasimir Force in Layered Materials and Control of the Stable Equilibrium
Get PDFQuantum interactions between nearly touching neutral interfaces lead to a measurable Casimir force, which is often assumed to be attractive. Our comprehensive computational analysis of atomic force microscopy and surface force apparatus measurements of the Casimir force between layered materials in solvents confirms that the Casimir interactions can give rise to a stable equilibrium. Given the excellent agreement with experiments for a range of materials, we extend the formalism to multiple-layer interfaces and investigate the effects of solvent and compositional changes on the Casimir equilibrium. We explain how the Casimir equilibrium can be tuned precisely and show that the scaling of the equilibrium distance with the thickness of the top layer is a controllable, solvent-dependent parameter. These findings have significant implications for the self-assembly of layered materials and design of future quantum entrapment experiments
Stokes' phenomenon in continuous limits of discrete Painlevé I
No full textWe use exponential asymptotic analysis to identify the relevance of Stokes' phenomenon to integrability in discrete systems. We study Stokes' phenomenon in two discrete problems with the same (leading-order) continuous limit, a finite-difference discretisation of the first continuous Painlevé equation and the first discrete Painlevé equation, as well as a family of differential equation associated with each discrete problem. This analysis reveals two important observations. Firstly, the orderly behaviour that characterises Stokes' phenomenon in discrete equations emerges naturally from corresponding continuous differential equations as the order of the latter increases, although this is not apparent at low orders. Secondly, Stokes' phenomenon vanishes in the continuum limit of the integrable discrete equation, but not the non-integrable discrete equation. This means that subdominant exponentials do not appear in the integrable equation, and therefore do not cause moveable singularities to form in the solution. The results are clarified further by consideration of one-parameter family of difference equations that interpolates between the two considered in detail
Here comes the sun: the central role of human and clinical physiology in the era of multi‐omics and inter‐organ crosstalk
No full text“Kind of Students… Kind of Staff” - Navigating Roles: A Thematic Exploration of PhD Demonstrators’ Experiences, Identity, and Career Implications
Get PDFWe examined the experiences of 16 PhD demonstrators from Russell and non-Russell universities, exploring teaching benefits and challenges, dual student-teacher identities, and opinions on the “demonstrator” title. Through interviews and reflexive thematic analysis, four themes were found: 1) ambiguity in the demonstrator label persists despite the GTA alternative, reflecting a disconnect between title and role, 2) the unpredictability, heavy workload, and lack of freedom in the role contribute to stress and diminish enjoyment for demonstrators, 3) feelings of being unsupported due to inadequate preparation, lack of recognition, poor treatment by staff, and the burdens of casualised contracts, 4) positive aspects including the unique demonstrator-student relationship, skill development, mentorship, supportive community, and flexible scheduling that provides a break from PhD work. The study highlights the importance of recognizing the dual identity, finding a label that reflects their responsibilities, addressing stress factors, and enhancing support and recognition for individuals within these roles
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