| 1. |
- Fenstermacher, M.E., et al.
(författare)
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DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy
- 2022
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 62:4
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Tidskriftsartikel (refereegranskat)abstract
- DIII-D physics research addresses critical challenges for the operation of ITER and the next generation of fusion energy devices. This is done through a focus on innovations to provide solutions for high performance long pulse operation, coupled with fundamental plasma physics understanding and model validation, to drive scenario development by integrating high performance core and boundary plasmas. Substantial increases in off-axis current drive efficiency from an innovative top launch system for EC power, and in pressure broadening for Alfven eigenmode control from a co-/counter-I p steerable off-axis neutral beam, all improve the prospects for optimization of future long pulse/steady state high performance tokamak operation. Fundamental studies into the modes that drive the evolution of the pedestal pressure profile and electron vs ion heat flux validate predictive models of pedestal recovery after ELMs. Understanding the physics mechanisms of ELM control and density pumpout by 3D magnetic perturbation fields leads to confident predictions for ITER and future devices. Validated modeling of high-Z shattered pellet injection for disruption mitigation, runaway electron dissipation, and techniques for disruption prediction and avoidance including machine learning, give confidence in handling disruptivity for future devices. For the non-nuclear phase of ITER, two actuators are identified to lower the L-H threshold power in hydrogen plasmas. With this physics understanding and suite of capabilities, a high poloidal beta optimized-core scenario with an internal transport barrier that projects nearly to Q = 10 in ITER at ∼8 MA was coupled to a detached divertor, and a near super H-mode optimized-pedestal scenario with co-I p beam injection was coupled to a radiative divertor. The hybrid core scenario was achieved directly, without the need for anomalous current diffusion, using off-axis current drive actuators. Also, a controller to assess proximity to stability limits and regulate β N in the ITER baseline scenario, based on plasma response to probing 3D fields, was demonstrated. Finally, innovative tokamak operation using a negative triangularity shape showed many attractive features for future pilot plant operation.
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| 2. |
- Romanelli, F, et al.
(författare)
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Overview of the JET results
- 2011
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 51:9
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Tidskriftsartikel (refereegranskat)abstract
- Since the last IAEA Conference JET has been in operation for one year with a programmatic focus on the qualification of ITER operating scenarios, the consolidation of ITER design choices and preparation for plasma operation with the ITER-like wall presently being installed in JET. Good progress has been achieved, including stationary ELMy H-mode operation at 4.5 MA. The high confinement hybrid scenario has been extended to high triangularity, lower ρ*and to pulse lengths comparable to the resistive time. The steady-state scenario has also been extended to lower ρ*and ν*and optimized to simultaneously achieve, under stationary conditions, ITER-like values of all other relevant normalized parameters. A dedicated helium campaign has allowed key aspects of plasma control and H-mode operation for the ITER non-activated phase to be evaluated. Effective sawtooth control by fast ions has been demonstrated with3He minority ICRH, a scenario with negligible minority current drive. Edge localized mode (ELM) control studies using external n = 1 and n = 2 perturbation fields have found a resonance effect in ELM frequency for specific q95values. Complete ELM suppression has, however, not been observed, even with an edge Chirikov parameter larger than 1. Pellet ELM pacing has been demonstrated and the minimum pellet size needed to trigger an ELM has been estimated. For both natural and mitigated ELMs a broadening of the divertor ELM-wetted area with increasing ELM size has been found. In disruption studies with massive gas injection up to 50% of the thermal energy could be radiated before, and 20% during, the thermal quench. Halo currents could be reduced by 60% and, using argon/deuterium and neon/deuterium gas mixtures, runaway electron generation could be avoided. Most objectives of the ITER-like ICRH antenna have been demonstrated; matching with closely packed straps, ELM resilience, scattering matrix arc detection and operation at high power density (6.2 MW m-2) and antenna strap voltages (42 kV). Coupling measurements are in very good agreement with TOPICA modelling. © 2011 IAEA, Vienna.
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| 3. |
- Abel, I, et al.
(författare)
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Overview of the JET results with the ITER-like wall
- 2013
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:10, s. 104002-
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Tidskriftsartikel (refereegranskat)abstract
- Following the completion in May 2011 of the shutdown for the installation of the beryllium wall and the tungsten divertor, the first set of JET campaigns have addressed the investigation of the retention properties and the development of operational scenarios with the new plasma-facing materials. The large reduction in the carbon content (more than a factor ten) led to a much lower Z(eff) (1.2-1.4) during L- and H-mode plasmas, and radiation during the burn-through phase of the plasma initiation with the consequence that breakdown failures are almost absent. Gas balance experiments have shown that the fuel retention rate with the new wall is substantially reduced with respect to the C wall. The re-establishment of the baseline H-mode and hybrid scenarios compatible with the new wall has required an optimization of the control of metallic impurity sources and heat loads. Stable type-I ELMy H-mode regimes with H-98,H-y2 close to 1 and beta(N) similar to 1.6 have been achieved using gas injection. ELM frequency is a key factor for the control of the metallic impurity accumulation. Pedestal temperatures tend to be lower with the new wall, leading to reduced confinement, but nitrogen seeding restores high pedestal temperatures and confinement. Compared with the carbon wall, major disruptions with the new wall show a lower radiated power and a slower current quench. The higher heat loads on Be wall plasma-facing components due to lower radiation made the routine use of massive gas injection for disruption mitigation essential.
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| 4. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 5. |
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| 6. |
- Roberts, Jason D., et al.
(författare)
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Ankyrin-B dysfunction predisposes to arrhythmogenic cardiomyopathy and is amenable to therapy
- 2019
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Ingår i: Journal of Clinical Investigation. - : AMER SOC CLINICAL INVESTIGATION INC. - 0021-9738 .- 1558-8238. ; 129:8, s. 3171-3184
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Tidskriftsartikel (refereegranskat)abstract
- Arrhythmogenic cardiomyopathy (ACM) is an inherited arrhythmia syndrome characterized by severe structural and electrical cardiac phenotypes, including myocardial fibrofatty replacement and sudden cardiac death. Clinical management of ACM is largely palliative, owing to an absence of therapies that target its underlying pathophysiology, which stems partially from our limited insight into the condition. Following identification of deceased ACM probands possessing ANK2 rare variants and evidence of ankyrin-B loss of function on cardiac tissue analysis, an ANK2 mouse model was found to develop dramatic structural abnormalities reflective of human ACM, including biventricular dilation, reduced ejection fraction, cardiac fibrosis, and premature death. Desmosomal structure and function appeared preserved in diseased human and murine specimens in the presence of markedly abnormal beta-catenin expression and patterning, leading to identification of a previously unknown interaction between ankyrin-B and beta-catenin. A pharmacological activator of the WNT/beta-catenin pathway, SB-216763, successfully prevented and partially reversed the murine ACM phenotypes. Our findings introduce what we believe to be a new pathway for ACM, a role of ankyrin-B in cardiac structure and signaling, a molecular link between ankyrin-B and beta-catenin, and evidence for targeted activation of the WNT/beta-catenin pathway as a potential treatment for this disease.
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| 7. |
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| 8. |
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| 9. |
- Anderson, Johan, 1973, et al.
(författare)
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Elucidating plasma dynamics in Hasegawa-Wakatani turbulence by information geometry
- 2020
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 27:2
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Tidskriftsartikel (refereegranskat)abstract
- The impact of adiabatic electrons on drift-wave turbulence, modeled by the Hasegawa-Wakatani equations, is studied using information length. Information length is a novel theoretical method for measuring distances between statistical states represented by different probability distribution functions (PDFs) along the path of a system and represents the total number of statistically different states that a system evolves through in time. Specifically, the time-dependent PDFs of turbulent fluctuations for a given adiabatic index A are computed. The changes in fluctuation statistics are then quantified in time by using information length. The numerical results provide time traces exhibiting intermittent plasma dynamics, and such behavior is identified by a rapid change in the information length. The effects of A are discussed.
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| 10. |
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| 11. |
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| 12. |
- Kritz, A.H., et al.
(författare)
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PTRANSP: Predictive Integrated Tokamak Modeling
- 2009
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Ingår i: 36th European Physical Society Conference on Plasma Physics 2009, EPS 2009; Sofia; Bulgaria; 29 June 2009 through 3 July 2009. - 9781622763368 ; 33E, s. 905-908
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Konferensbidrag (refereegranskat)
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| 13. |
- Ma, J., et al.
(författare)
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Reversal of particle flux in collisional-finite beta tokamak discharges
- 2015
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 22:1, s. Art. no. 012304-
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Tidskriftsartikel (refereegranskat)abstract
- The mixed gradient method [Zhong et al. Phys. Rev. Lett. 111, 265001 (2013)] is adopted and effects of collisions and finite beta are included in the Weiland 9-equation fluid model. The particle flux and particle pinch, obtained using the Weiland anomalous transport fluid model, are compared with Tore Supra experimental results. Particle transport is also studied using predictive simulation data for an experimental advanced superconducting tokamak discharge in which neutral beam heating is utilized. The effects of collisions on particle transport are studied by turning collisions on and off in the Weiland model. It is found that the particle pinch region is related to the mode structure. The particle pinch region coincides with the region where the strong ballooning modes are present due to large gradients. The general properties of the fluid model are examined by finding regions where collisions can enhance the particle pinch.
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| 14. |
- Madsen, C. L., et al.
(författare)
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The left atrial appendage closure by surgery-2 (LAACS-2) trial protocol rationale and design of a randomized multicenter trial investigating if left atrial appendage closure prevents stroke in patients undergoing open-heart surgery irrespective of preoperative atrial fibrillation status and stroke risk
- 2023
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Ingår i: American Heart Journal. - 0002-8703. ; 264, s. 133-142
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Tidskriftsartikel (refereegranskat)abstract
- Background Current recommendations regarding the use of surgical left atrial appendage (IAA) closure to prevent thromboembolisms lack high-level evidence. Patients undergoing open-heart surgery often have several cardiovascular risk factors and a high occurrence of postoperative atrial fibrillation (AF)-with a high recurrence rate-and are thus at a high risk of stroke. Therefore, we hypothesized that concomitant IAA closure during open-heart surgery will reduce mid-term risk of stroke independently of preoperative AF status and CHA 2 DS 2 -VASc score. Methods This protocol describes a randomized multicenter trial. Consecutive participants & GE;18 years scheduled for first-time planned open-heart surgery from cardiac surgery centers in Denmark, Spain, and Sweden are included. Both patients with a previous diagnosis of paroxysmal or chronic AF, as well as those without AF, are eligible to participate, irrespective of their CHA 2 DS 2 -VASc score. Patients already planned for ablation or IAA closure during surgery, with current endocarditis, or where follow-up is not possible are considered noneligible. Patients are stratified by site, surgery type, and preoperative or planned oral anticoagulation treatment. Subsequently, patients are randomized 1:1 to either concomitant IAA closure or standard care (ie, open IAA). The primary outcome is stroke, including transient ischemic attack, as assigned by 2 independent neurologists blinded to the treatment allocation. To recognize a 60% relative risk reduction of the primary outcome with LAA closure, 1,500 patients are randomized and followed for 2 years (significance level of 0.05 and power of 90%). Conclusions The LAACS-2 trial is likely to impact the LAA closure approach in most patients undergoing open-heart surgery. Trial registration: NCT03724318. (Am HeartJ 2023;264:133-142.)
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| 15. |
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| 16. |
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| 17. |
- Ovaskainen, Otso, et al.
(författare)
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Global Spore Sampling Project: A global, standardized dataset of airborne fungal DNA
- 2024
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Ingår i: Scientific Data. - 2052-4463. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Novel methods for sampling and characterizing biodiversity hold great promise for re-evaluating patterns of life across the planet. The sampling of airborne spores with a cyclone sampler, and the sequencing of their DNA, have been suggested as an efficient and well-calibrated tool for surveying fungal diversity across various environments. Here we present data originating from the Global Spore Sampling Project, comprising 2,768 samples collected during two years at 47 outdoor locations across the world. Each sample represents fungal DNA extracted from 24 m3 of air. We applied a conservative bioinformatics pipeline that filtered out sequences that did not show strong evidence of representing a fungal species. The pipeline yielded 27,954 species-level operational taxonomic units (OTUs). Each OTU is accompanied by a probabilistic taxonomic classification, validated through comparison with expert evaluations. To examine the potential of the data for ecological analyses, we partitioned the variation in species distributions into spatial and seasonal components, showing a strong effect of the annual mean temperature on community composition.
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| 18. |
- Pankin, A. Y., et al.
(författare)
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Extending the validation of multi-mode model for anomalous transport to high beta poloidal tokamak scenario in DIII-D
- 2018
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 25:5
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Tidskriftsartikel (refereegranskat)abstract
- The Multi-Mode Model (MMM7.1) for anomalous transport is tested in predictive modeling of temperature profiles of a high beta poloidal DIII-D discharge. This new H-mode plasma regime, with high beta poloidal and high bootstrap currents, has been studied in DIII-D tokamak discharges [A. Garofalo et al., Nucl. Fusion 55, 123025 (2015)]. The role of instabilities that can drive the anomalous transport described by MMM7.1 is investigated. The temperature profiles for a high beta poloidal DIII-D discharge are computed using the NCLASS model for the neoclassical transport and the Weiland and Electron Temperature Gradient (ETG) components of the MMM7.1 model for the anomalous transport. The neoclassical transport is found to be the main contributor to the ion thermal transport in the plasma core. The contributions from the ion temperature gradient driven modes are found to be important only outside of the internal transport barrier. The magnitudes of the predicted temperature profiles are found to be in a reasonable agreement with experimental profiles. The simulation results approximately reproduce the internal transport barrier in the ion temperature profile but not in the electron temperature profile due to a weak dependence of the ETG driven transport on the Shafranov shift in the ETG component of MMM7.1. Possible effects that can contribute to stabilization of these modes, for example, effects associated with the large beta poloidal such as the Shafranov shift stabilization in the MMM7.1 model, are discussed. It is demonstrated that the E x B flow shear has a relatively small effect in the formation of the internal transport barrier in the high beta poloidal DIII-D discharge 154406. The Shafranov shift (alpha stabilization) and small or reversed magnetic shear profiles are found to be the primary reasons for quenched anomalous transport in this discharge. Published by AIP Publishing.
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| 19. |
- Rafiq, T., et al.
(författare)
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Microtearing instabilities and electron thermal transport in low and high collisionality NSTX discharges
- 2021
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 28:2
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Tidskriftsartikel (refereegranskat)abstract
- Microtearing mode (MTM) real frequency, growth rate, magnetic fluctuation amplitude, and resulting electron thermal transport are studied in systematic NSTX scans of relevant plasma parameters. The dependency of the MTM real frequency and growth rate on plasma parameters, suitable for low and high collision NSTX discharges, is obtained by using the reduced MTM transport model [T. Rafiq et al., Phys. Plasmas 23, 062507 (2016)]. The plasma parameter dependencies are compared and found to be consistent with the results obtained from MTM using the gyrokinetic GYRO code. The scaling trend of collision frequency and plasma beta is found to be consistent with the global energy confinement trend observed in the NSTX experiment. The strength of the magnetic fluctuation is found to be consistent with the gyrokinetic estimate. In earlier studies, it was found that the version of the multi-mode (MM) anomalous transport model, which did not contain the effect of MTMs, provided an appropriate description of the electron temperature profiles in standard tokamak discharges and not in spherical tokamaks. When the MM model, which involves transport associated with MTMs, is incorporated in the TRANSP code and is used in the study of electron thermal transport in NSTX discharges, it is observed that the agreement with the experimental electron temperature profile is substantially improved.
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| 20. |
- Rafiq, T., et al.
(författare)
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Physics basis of Multi-Mode anomalous transport module
- 2013
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 20:3
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Tidskriftsartikel (refereegranskat)abstract
- The derivation of Multi-Mode anomalous transport module version 8.1 (MMM8.1) is presented. The MMM8.1 module is advanced, relative to MMM7.1, by the inclusion of peeling modes, dependence of turbulence correlation length on flow shear, electromagnetic effects in the toroidal momentum diffusivity, and the option to compute poloidal momentum diffusivity. The MMM8.1 model includes a model for ion temperature gradient, trapped electron, kinetic ballooning, peeling, collisionless and collision dominated magnetohydrodynamics modes as well as model for electron temperature gradient modes, and a model for drift resistive inertial ballooning modes. In the derivation of the MMM8.1 module, effects of collisions, fast ion and impurity dilution, non-circular flux surfaces, finite beta, and Shafranov shift are included. The MMM8.1 is used to compute thermal, particle, toroidal, and poloidal angular momentum transports. The fluid approach which underlies the derivation of MMM8.1 is expected to reliably predict, on an energy transport time scale, the evolution of temperature, density, and momentum profiles in plasma discharges for a wide range of plasma conditions.
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| 21. |
- Rafiq, T, et al.
(författare)
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Predictive modeling of NSTX discharges with the updated multi-mode anomalous transport module
- 2024
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Ingår i: Nuclear Fusion. - 0029-5515 .- 1741-4326. ; 64:7
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study is twofold: firstly, to demonstrate the consistency between the anomalous transport results produced by updated Multi-Mode Model (MMM) version 9.0.4 and those obtained through gyrokinetic simulations; and secondly, to showcase MMM’s ability to predict electron and ion temperature profiles in low aspect ratio, high beta NSTX discharges. MMM encompasses a range of transport mechanisms driven by electron and ion temperature gradients, trapped electrons, kinetic ballooning, peeling, microtearing, and drift resistive inertial ballooning modes. These modes within MMM are being verified through corresponding gyrokinetic results. The modes that potentially contribute to ion thermal transport are stable in MMM, aligning with both experimental data and findings from linear CGYRO simulations. The isotope effects on these modes are also studied and higher mass is found to be stabilizing, consistent with the experimental trend. The electron thermal power across the flux surface is computed within MMM and compared to experimental measurements and nonlinear CGYRO simulation results. Specifically, the electron temperature gradient modes (ETGM) within MMM account for 2.0 MW of thermal power, consistent with experimental findings. It is noteworthy that the ETGM model requires approximately 5.0 ms of computation time on a standard desktop, while nonlinear CGYRO simulations necessitate 8.0 h on 8 K cores. MMM proves to be highly computationally efficient, a crucial attribute for various applications, including real-time control, tokamak scenario optimization, and uncertainty quantification of experimental data.
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| 22. |
- Rafiq, T, et al.
(författare)
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Study of the parametric dependence of linear and nonlinear microtearing modes in conventional tokamak discharges
- 2018
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 25:1
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Tidskriftsartikel (refereegranskat)abstract
- A reduced transport model for microtearing modes is developed for use in integrated predictive modeling studies, employing a unified fluid/kinetic approach to derive the nonlinear dispersion relation. This approach advances the kinetic description and allows the inclusion of nonlinear effects due to magnetic fluctuations. In this numerical study, the dependence of the microtearing mode real frequency and growth rate on plasma parameters and on DIII-D like L-mode and H-mode plasma profiles is examined. The magnetic fluctuation strength as well as electron thermal diffusivity due to microtearing modes is computed. The saturated amplitude of the magnetic fluctuations is calculated utilizing numerically determined microtearing mode eigenvalues in the nonlinear microtearing modes envelope equation. It is found that the electron temperature gradient in the presence of moderate collision frequency is required for the microtearing mode to become unstable. The effects of small and large collisionality and small and large wavenumbers on microtearing modes are found to be stabilizing, while the effects of density gradient, plasma beta, low current density, and large magnetic shear are found to be destabilizing. The microtearing mode growth rate, magnetic fluctuation strength, as well as electron thermal diffusivity is found to be larger in the H-mode plasma than in the L-mode plasma.
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| 23. |
- Sator, Lea, et al.
(författare)
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Overdiagnosis of COPD in Subjects With Unobstructed Spirometry A BOLD Analysis
- 2019
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Ingår i: Chest. - : Elsevier BV. - 0012-3692 .- 1931-3543. ; 156:2, s. 277-288
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: There are several reports on underdiagnosis of COPD, while little is known about COPD overdiagnosis and overtreatment. We describe the overdiagnosis and the prevalence of spirometrically defined false positive COPD, as well as their relationship with overtreatment across 23 population samples in 20 countries participating in the BOLD Study between 2003 and 2012.METHODS: A false positive diagnosis of COPD was considered when participants reported a doctor's diagnosis of COPD, but postbronchodilator spirometry was unobstructed (FEV1/FVC > LLN). Additional analyses were performed using the fixed ratio criterion (FEV1/FVC < 0.7).RESULTS: Among 16,177 participants, 919 (5.7%) reported a previous medical diagnosis of COPD. Postbronchodilator spirometry was unobstructed in 569 subjects (61.9%): false positive COPD. A similar rate of overdiagnosis was seen when using the fixed ratio criterion (55.3%). In a subgroup analysis excluding participants who reported a diagnosis of "chronic bronchitis" or "emphysema" (n = 220), 37.7% had no airflow limitation. The site-specific prevalence of false positive COPD varied greatly, from 1.9% in low- to middle-income countries to 4.9% in high-income countries. In multivariate analysis, overdiagnosis was more common among women, and was associated with higher education; former and current smoking; the presence of wheeze, cough, and phlegm; and concomitant medical diagnosis of asthma or heart disease. Among the subjects with false positive COPD, 45.7% reported current use of respiratory medication. Excluding patients with reported asthma, 34.4% of those with normal spirometry still used a respiratory medication.CONCLUSIONS: False positive COPD is frequent. This might expose nonobstructed subjects to possible adverse effects of respiratory medication.
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| 24. |
- Studnicka, Michael, et al.
(författare)
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COPD : Should Diagnosis Match Physiology?
- 2020
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Ingår i: Chest. - : Elsevier BV. - 0012-3692 .- 1931-3543. ; 157:2, s. 473-475
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 25. |
- Taheri, M., et al.
(författare)
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AdAM : Adaptive Fault-Tolerant Approximate Multiplier for Edge DNN Accelerators
- 2024
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Ingår i: Proceedings of the European Test Workshop. - : Institute of Electrical and Electronics Engineers (IEEE). - 9798350349320
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Konferensbidrag (refereegranskat)abstract
- Multiplication is the most resource-hungry operation in the neural network's processing elements. In this paper, we propose an architecture of a novel adaptive fault-tolerant approximate multiplier tailored for ASIC-based DNN accelerators. AdAM employs an adaptive adder relying on an unconventional use of the leading one position value of the inputs for fault detection through the optimization of unutilized adder resources. The proposed architecture uses a lightweight fault mitigation technique that sets the detected faulty bits to zero. The hardware resource utilization and the DNN accelerator's reliability metrics are used to compare the proposed solution against the triple modular redundancy (TMR) in multiplication, unprotected exact multiplication, and unprotected approximate multiplication. It is demonstrated that the proposed architecture enables a multiplication with a reliability level close to the multipliers protected by TMR utilizing 63.54% less area and having 39.06% lower power-delay product compared to the exact multiplier.
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