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Large-scale automated investigation of free-falling paper shapes via iterative physical experimentation
No full text© 2020, The Author(s), under exclusive licence to Springer Nature Limited. Free-falling paper shapes exhibit rich, complex and varied behaviours that are extremely challenging to model analytically. Physical experimentation aids in system understanding, but is time-consuming, sensitive to initial conditions and reliant on subjective visual behavioural classification. In this study, robotics, computer vision and machine learning are used to autonomously fabricate, drop, analyse and classify the behaviours of hundreds of shapes. The system is validated by reproducing results for falling discs, which exhibit four falling styles: tumbling, chaotic, steady and periodic. A previously determined mapping from a non-dimensional parameter space to behaviour groups is shown to be consistent with these new experiments for tumbling and chaotic behaviours. However, steady or periodic behaviours are observed in previously unseen areas of the parameter space. More complex hexagon, square and cross shapes are investigated, showing that the non-dimensional parameter space generalizes to these shapes. The system highlights the potential of robotics for the investigation of complex physical systems, of which falling paper is one example, and provides a template for future investigation of such systems
Digital Twin Assessments in Virtual Reality: An Explorational Study with Aeroengines
No full textWe present an immersive environment where Virtual Reality (VR) is used to visualize the performance of a fleet of aircraft engines. Our virtual environment uses 3D geometric computer-aided design (CAD) models of the engines paired with performance maps that characterize their nominal working condition. These maps plot pressure ratio and efficiency as a function of shaft speed and inlet flow capacity for the numerous engine sub-systems. Superimposed on these maps is the true performance of each engine, obtained through real-time sensors. In this bespoke virtual space, an engineer can rapidly analyze the health of different engine sub-systems across the fleet within seconds. One of the key elements of such a system is the selection of an appropriate interaction technique. In this paper we explore the potential of interaction methods supported by a combination of gaze-tracking and hand-tracking achieved via an additional sensor attached to the front of the VR headset, with no need for the user to hold a controller. We report on an observational study with a small number of domain-experts to identify usability problems, spot potential improvements, and gain insights into our design interaction capabilities. The study allows us to trim the design space and to guide further design efforts in this area. We also analyze qualitative feedback provided by the end-users and discuss the lessons learned during the design, implementation, verification and validation of the system
100 Gb/s (4 × 25 Gb/s) real-time coherent UDWDM-PON with a large power budget
No full textWe propose a 100-Gb/s coherent ultra-dense wavelength-division multiplexing passive optical network (UDWDM-PON) structure with a large power budget by placing an erbium-doped fiber amplifier at the optical line terminal side for amplification of optical signals in both the uplink and downlink. Then we experimentally demonstrate a real-time 4×25-Gb/s coherent UDWDM-PON at 12.5-GHz spacing over 50-km standard single-mode optical fiber. A high sampling rate analog-to-digital converter is designed for the 25-Gb/s real-time coherent optical module. Experimental results show that 100-Gb/s bidirectional transmission can be realized. The downlink power budget can be more than 44 dB, which can support more than 1000 users based on the proposed structure. The effects of several parameters have also been investigated in the experimental demonstration. The 24-h real-time performance evaluation for bidirectional transmission is conducted to prove the feasibility of real-time field-programmable gate array based transceivers in the proposed UDWDM-PON structure. An off-line experimental demonstration is also conducted to verify the feasibility of burst-mode operation in the uplink
PISA design model for monopiles for offshore wind turbines: Application to a marine sand
No full textThis paper describes a one-dimensional (1D) computational model for the analysis and design of laterally loaded monopile foundations for offshore wind turbine applications. The model represents the monopile as an embedded beam and specially formulated functions, referred to as soil reaction curves, are employed to represent the various components of soil reaction that are assumed to act on the pile. This design model was an outcome of a recently completed joint industry research project - known as PISA - on the development of new procedures for the design of monopile foundations for offshore wind applications. The overall framework of the model, and an application to a stiff glacial clay till soil, is described in a companion paper by Byrne and co-workers; the current paper describes an alternative formulation that has been developed for soil reaction curves that are applicable to monopiles installed at offshore homogeneous sand sites, for drained loading. The 1D model is calibrated using data from a set of three-dimensional finite-element analyses, conducted over a calibration space comprising pile geometries, loading configurations and soil relative densities that span typical design values. The performance of the model is demonstrated by the analysis of example design cases. The current form of the model is applicable to homogeneous soil and monotonic loading, although extensions to soil layering and cyclic loading are possible
Mass Tuning in Weakly Coupled Low-Q Piezoelectric MEMS Resonator Arrays for Particulate Sensing
No full textThis paper reports the achievement of a mass balanced condition in a low-Q weakly coupled MEMS resonator array for ultrafine aerosol particulate sensing. The mass balancing technique enables the lifetime extension of such real-time particulate sensors without employing any wet or dry-cleaning techniques to remove particles from the resonators. This mass balancing is demonstrated for both the flexural and bulk modes of the same coupled resonator array occurring at ∼54kHz and ∼2.53MHz, respectively. This system also demonstrates for a degree of passive environment immunity to temperature effects by using an amplitude ratio output metric. The Q factor of the coupled MEMS resonator system do not degrade substantially with increased particulate loading
Erbium-Doped Nanoparticle-Polymer Composite Thin Films for Photonic Applications: Structural and Optical Properties
No full textErbium-doped nanocrystal (NC)-dispersed polymer thin films are attractive core materials for use in optical waveguides as they can provide high optical gain and enable the formation of compact waveguide amplifiers. Nonetheless, there are significant challenges associated with obtaining good dispersibility of NCs into a polymer matrix and favorable optical properties. Therefore, in this paper, we report the fabrication of Er3+-doped ceria (EGC) NCs employing the Leeds alginate process (LAP) and their incorporation into a siloxane polymer matrix. The surface morphology and compositional, structural, and optical properties of the fabricated films are evaluated to assess the NC dispersion and their suitability for the waveguide amplifier. The photoluminescence (PL) and lifetime measurements of the NCs-polymer nanocomposite thin film samples show intense, broadband PL emission of the Er3+ ions at 1534 nm (4I13/2 → 4I15/3 transition) with a full width at half-maximum (fwhm) of ∼64 nm and lifetime in the range of 2.6-3.0 ms. The inhomogeneously broadened PL spectra and improvement in lifetime of NCs in the polymer are important results that we report. The EGC NCs-polymer nanocomposite thin films also exhibit excellent transparency in the NIR wavelength range and a refractive index in the range of 1.53-1.58 in the visible wavelength. The work presented here clearly demonstrates the potential of using high-quality Er-doped nanocomposite polymer thin films for interesting applications such as compact low-cost waveguide amplifiers and lasers
Do vehicle efficiency improvements lead to energy savings? The rebound effect in Great Britain
No full textFuel efficiency improvements in vehicles reduce the cost of travel, which could stimulate drivers to travel further limiting energy savings. Estimates of this effect, known as the rebound effect, have varied widely, partly due to data constraints and a reliance upon highly aggregated government statistics. This paper instead uses a dataset of over 275 million vehicle roadworthiness tests. The high level of detail in our dataset can reveal, for the first time, how the response to changes in travel costs may differ across types of vehicles and socio-economic areas in Great Britain. We find that the rebound effect in Great Britain is just 4.6%, meaning efficiency improvements are unlikely to stimulate increased mileage in the short-run. We find that larger, less fuel efficient vehicles are more responsive to fuel price changes than smaller vehicles and that drivers in urban areas are more responsive to fuel price changes than drivers in rural areas. Our findings shed light on the effects that policies such as fuel taxation and fuel economy standards may have on vehicle mileage. This has implications for both CO2 emissions savings and social equity
Mechanisms of Asymmetrical Turn-On and Turn-Off and the Origin of Dynamic C<inf>GD</inf> Hysteresis for Hard-Switching Superjunction MOSFETs
No full textThe dV / dt in superjunction metal-oxide-semiconductor field-effect transistors (MOSFETs) during the turn-off transient has been shown to be higher than during the turn-on, which can be attributed to a shorter Miller plateau. In this article, we will show that these asymmetrical turn-on and turn-off characteristics are indirectly detected by the hysteresis of the dynamic gate-to-drain capacitance, {C}_{\text {GD}}. Moreover, this article reveals the mechanisms behind the asymmetrical switching and the origin of the hysteresis, which have been shown to be caused by the difference in the {C}_{\text {GD}} displacement current paths for the turn-off and the turn-on
Apparatus for measuring pipe-soil interaction behavior using shallow 'Pipe-like' penetrometers
No full textReliable characterization of surficial marine sediments is essential to ensure the safe and economical design of subsea infrastructure for offshore energy facilities (e.g., seabed cables, pipelines, and shallow foundations). Conventional in-situ testing methods (e.g., cone penetrometer test or T-bar) require careful interpretation to account for the effects of shallow embedment, whereas laboratory tests are affected by sampling-induced disturbances, the impact of which can be significant at the low stress levels relevant to the design of subsea infrastructure. This article describes two novel box-core-sized shallow penetrometers - the hemiball and toroid - which mimic the shape of subsea pipelines and have been designed to reliably measure the strength, consolidation, and frictional properties of surficial offshore sediments. The development and specification of the actuator used to operate these probes is also described. Another major benefit of these penetrometers, which are intended to be used offshore for on-deck testing aboard a survey vessel, is their capability to generate effective stress interpretations of the soil behavior, and this is made possible because pore pressure transducers are installed and monitored throughout testing. The results of a first laboratory proof test are presented to illustrate the potential of this novel sensor concept