Acoustic evaluation of modular greenery noise barriers

Green noise barriers have become an alternative means of reducing urban traffic noise. In this paper, the acoustic performance of a modular greenery noise barrier is evaluated. In situ measurements of noise reflection were performed using an experimental prototype to estimate the sound absorption coefficients. These coefficients were found to have values of approximately 0.7, higher than those previously found in laboratory measurements for a similar system with a lower vegetation density. The obtained values were input into software for predicting environmental noise to analyse the expected performance of such barriers, particularly in the case of a pair of parallel barriers. A comparison with the results for reflective barriers indicates a significant improvement in sound attenuation of up to 4 dBA. The values are similar and even superior to results reported by other authors regarding the effectiveness of absorptive treatments applied to parallel barriers, and furthermore, the proposed barriers offer an aesthetic element for environmental integration.Peer ReviewedPostprint (published version

The challenges and possibilities of reflective learning in higher education. Research focused from the perspective of university students on four different degree courses

Despite an increase in university teaching practices based on reflective learning methodology (RL), only very few studies are found in the context of higher education aimed at determining students? perception of this approach to teaching and learning. The aim of this research was to ascertain the opinions of students on different university degree courses regarding the challenges, difficulties and contributions arising from the application of reflective learning methodology in their learning process so as to propose strategies for improving education. The study was carried out on four Bachelor degree courses at the University of Girona: Social Education, Environmental Sciences, Nursing and Psychology. The research was conducted in two stages. In the first (2011-12 academic year), a questionnaire was administered to 162 students (43 from Social Education; 33 from Environmental Sciences; 31 from Nursing; and 55 from Psychology). One section of the questionnaire was specifically devoted to studying the perceptions of students participating in various RL experiences regarding the main difficulties they faced and the contributions of the RL to their learning process. Among the highlighted difficulties was the fact that RL requires a work process they are not used to and their lack of reflective writing skills. Among the contributions, the students felt that RL results in more complex and selfregulated knowledge, develops greater dynamic capabilities and increases the degree of reflection on learning processes and areas for improvement. In the second stage of the study (2012-13 academic year), four focus groups were held with students who had participated in the previous years? experience with the aim of gaining further insight into their perceptions regarding the challenges and contributions of RL. A total of 20 students participated, all of whom gave informed written consent. The sessions were recorded and transcribed in full and a thematic content analysis was performed. In all four groups the students stated that the experience had allowed them to improve their learning and become aware of their current situation and areas for improvement. As for the challenges, they cited difficulties in understanding the aims and purpose of RL, particularly at the beginning of the experience, together with problems experienced in writing about it, doubts about the level of openness required and uncertainty about how they would be assessed. The research conducted suggested that RL has significant potential to connect academic activity with professional action. It also provided working guidelines for improving experiences carried out on the basis of RL. These include the need to clarify the methodology and present arguments for its use, so that students understand the type of work it will mean for them and the objectives they pursued. Students should also be provided with sufficiently clear guidelines regarding how they will be assessed (in relation to both activities and level of reflection). There is a need to build a group climate based on mutual trust, continuous feedback and the establishment of a support process that maintains this trust throughout the learning process

Physics research on the TCV tokamak facility: from conventional to alternative scenarios and beyond

The research program of the TCV tokamak ranges from conventional to advanced-tokamak scenarios and alternative divertor configurations, to exploratory plasmas driven by theoretical insight, exploiting the device’s unique shaping capabilities. Disruption avoidance by real-time locked mode prevention or unlocking with electron-cyclotron resonance heating (ECRH) was thoroughly documented, using magnetic and radiation triggers. Runaway generation with high-Z noble-gas injection and runaway dissipation by subsequent Ne or Ar injection were studied for model validation. The new 1 MW neutral beam injector has expanded the parameter range, now encompassing ELMy H-modes in an ITER-like shape and nearly noninductive H-mode discharges sustained by electron cyclotron and neutral beam current drive. In the H-mode, the pedestal pressure increases modestly with nitrogen seeding while fueling moves the density pedestal outwards, but the plasma stored energy is largely uncorrelated to either seeding or fueling. High fueling at high triangularity is key to accessing the attractive small edge-localized mode (type-II) regime. Turbulence is reduced in the core at negative triangularity, consistent with increased confinement and in accord with global gyrokinetic simulations. The geodesic acoustic mode, possibly coupled with avalanche events, has Nucl. Fusion 59 (2019) 112023 S. Coda et al 4 been linked with particle flow to the wall in diverted plasmas. Detachment, scrape-off layer transport, and turbulence were studied in L- and H-modes in both standard and alternative configurations (snowflake, super-X, and beyond). The detachment process is caused by power ‘starvation’ reducing the ionization source, with volume recombination playing only a minor role. Partial detachment in the H-mode is obtained with impurity seeding and has shown little dependence on flux expansion in standard single-null geometry. In the attached L-mode phase, increasing the outer connection length reduces the in–out heat-flow asymmetry. A doublet plasma, featuring an internal X-point, was achieved successfully, and a transport barrier was observed in the mantle just outside the internal separatrix. In the near future variable configuration baffles and possibly divertor pumping will be introduced to investigate the effect of divertor closure on exhaust and performance, and 3.5 MW ECRH and 1 MW neutral beam injection heating will be added.EURATOM 63305

A fast model to resolve the velocity-space of fast-ion losses detected in ASDEX Upgrade and MAST Upgrade

A forward model to resolve the fast-ion loss velocity-space on a fast-ion loss detector (FILD) probe head (FILDSIM) has been extended, making it possible to perform real-time analysis of the FILD data ("real-time FILDSIM"). Parametric pre-processing with FILDSIM enables real-time mapping of the raw FILD measurements to the velocity-space of the fast-ion distribution reaching the FILD probe, which depends on the local magnetic field at the probe head. Such parametric pre-processing facilitates the study of fast-ion losses in stages of the discharge other than the flat-top, such as the ramp-up phase when changes in the local magnetic field at the probe head cannot be neglected. Real-time FILDSIM has been applied to the existing and newly installed FILDs in ASDEX Upgrade and will be used for the forthcoming FILD in MAST-Upgrade. Due to the larger size of the MAST-U FILD probe, the approximation used in FILDSIM of a uniform magnetic field in the FILD region has been generalised to the case of a non-uniform field, with gyro-orbits calculated numerically in this field.Universidad de Sevilla PP2016-7145Comunidad Europea de Energía Atómica (EURATOM) 633305

Electromagnetic VDE and Disruption Analysis in the SMART Tokamak

The SMall aspect ratio tokamak (SMART) is a new spherical device, that is, currently being constructed at the University of Seville. The operation of SMART will cover three phases reaching a maximum plasma current ( $I_{P}$ ) of 400 kA, a toroidal magnetic field ( $B_{T}$ ) of 1 T, and a pulse length of 500 ms. Such operating conditions present notable challenges to the design and verification of SMARTs structural integrity during normal and off-normal operations. In particular, vertical displacement events (VDEs) and disruptions (Boozer, 2012) are most important as they can cause severe damage to the components directly exposed to the plasma due to the significant electromagnetic (EM) and thermal loads delivered over ms timescales. As a consequence, a detailed evaluation of the EM loads during plasma disruptions is mandatory for the correct dimensioning of the machine, in particular the vacuum vessel. The EM loads are mainly produced by: the poloidal flux variation during the thermal and current quench, halo currents (Boozer, 2013) that flow into the vacuum vessel and interacts with the toroidal magnetic field; and toroidal flux variation during the thermal and current quench. We present, here, the EM and structural analysis performed for the design of SMART. The modeling has been carried out by combining equilibrium scenarios obtained through the FIESTA code (Cunningham, 2013), estimating VDE and disruption time-scales by comparing other machines (Chen et al. 2015), (Hender et al. 2007), and (Bachmann et al. 2011) and computing EM forces through a finite element model (FEM) taking into account the effects of both eddy and halo currents (Roccella et al. 2008), (Titus et al. 2011), and (Ortwein et al. 2020). Finally, the structural assessment of the vacuum vessel is performed in order to verify its integrity during normal and off-normal events in phase 3.10.13039/501100000780-Fondo Europeo de Desarollo Regional (FEDER) through the European Commission (Grant Number: IE17-5670 and US-15570

Coils and power supplies design for the SMART tokamak

Agredano-Torres, M., et al.A new spherical tokamak, the SMall Aspect Ratio Tokamak (SMART), is currently being designed at the University of Seville. The goal of the machine is to achieve a toroidal field of 1 T, a plasma current of 500 kA and a pulse length of 500 ms for a plasma with a major radius of 0.4 m and minor radius of 0.25 m. This contribution presents the design of the coils and power supplies of the machine. The design foresees a central solenoid, 12 toroidal field coils and 8 poloidal field coils. Taking the current waveforms for these set of coils as starting point, each of them has been designed to withstand the Joule heating during the tokamak operation time. An analytical thermal model is employed to obtain the cross sections of each coil and, finally, their dimensions and parameters. The design of flexible and modular power supplies, based on IGBTs and supercapacitors, is presented. The topologies and control strategy of the power supplies are explained, together with a model in MATLAB Simulink to simulate the power supplies performance, proving their feasibility before the construction of the system.This work received funding from the Fondo Europeo de Desarollo Regional (FEDER) by the European Commission under grant agreement numbers IE17-5670 and US-15570. Furthermore, it has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 and 2019–2020 under grant agreement no. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission

Magnetic equilibrium design for the SMART tokamak

The SMall Aspect Ratio Tokamak (SMART) device is a new compact (plasma major radius R≥0.40 m, minor radius a≥0.20 m, aspect ratio A≥1.7) spherical tokamak, currently in development at the University of Seville. The SMART device has been designed to achieve a magnetic field at the plasma center of up to B=1.0 T with plasma currents up to I=500 kA and a pulse length up to τ=500 ms. A wide range of plasma shaping configurations are envisaged, including triangularities between −0.50≤δ≤0.50 and elongations of κ≤2.25. Control of plasma shaping is achieved through four axially variable poloidal field coils (PF), and four fixed divertor (Div) coils, nominally allowing operation in lower-single null, upper-single null and double-null configurations. This work examines phase 2 of the SMART device, presenting a baseline reference equilibrium and two highly-shaped triangular equilibria. The relevant PF and Div coil current waveforms are also presented. Equilibria are obtained via an axisymmetric Grad-Shafranov force balance solver (Fiesta), in combination with a circuit equation rigid current displacement model (RZIp) to obtain time-resolved vessel and plasma currents.The authors would like to thank the VEST team for their technical and engineering support. This work received funding from the Fondo Europeo de Desarollo Regional (FEDER) by the European Commission under grant agreement numbers IE17-5670 and US-15570. In addition support from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 805162) is gratefully acknowledged

Mechanical and electromagnetic design of the vacuum vessel of the SMART tokamak

The SMall Aspect Ratio Tokamak (SMART) is a new spherical device that is currently being designed at the University of Seville. SMART is a compact machine with a plasma major radius (R) greater than 0.4 m, plasma minor radius (a) greater than 0.2 m, an aspect ratio (A) over than 1.7 and an elongation (k) of more than 2. It will be equipped with 4 poloidal field coils, 4 divertor field coils, 12 toroidal field coils and a central solenoid. The heating system comprises of a Neutral Beam Injector (NBI) of 600 kW and an Electron Cyclotron Resonance Heating (ECRH) of 6 kW for pre-ionization. SMART has been designed for a plasma current (I) of 500 kA, a toroidal magnetic field (B) of 1 T and a pulse length of 500 ms preserving the compactness of the machine. The free boundary equilibrium solver code FIESTA [1] coupled to the linear time independent, rigid plasma model RZIP [2] has been used to calculate the target equilibria taking into account the physics goals, the required plasma parameters, vacuum vessel structures and power supply requirements. We present here the final design of the SMART vacuum vessel together with the Finite Element Model (FEM) analysis carried out to ensure that the tokamak vessel provides high quality vacuum and plasma performance withstanding the electromagnetic j×B loads caused by the interaction between the eddy currents induced in the vessel itself and the surrounding magnetic fields. A parametric model has been set up for the topological optimization of the vessel where the thickness of the wall has been locally adapted to the expected forces. An overview of the new machine is presented here.This work received funding from the Fondo Europeo de Desarollo Regional (FEDER) by the European Commission under grant agreement numbers IE17-5670 and US-15570. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 and 2019-2020 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission