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- Abel, I, et al.
(author)
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Overview of the JET results with the ITER-like wall
- 2013
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:10, s. 104002-
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Journal article (peer-reviewed)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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- Romanelli, F, et al.
(author)
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Overview of the JET results
- 2011
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 51:9
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Journal article (peer-reviewed)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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- Yazdi, Hossein S., et al.
(author)
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Mapping breast cancer blood flow index, composition, and metabolism in a human subject using combined diffuse optical spectroscopic imaging and diffuse correlation spectroscopy
- 2017
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In: Journal of Biomedical Optics. - : SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS. - 1083-3668 .- 1560-2281. ; 22:4
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Journal article (peer-reviewed)abstract
- Diffuse optical spectroscopic imaging (DOSI) and diffuse correlation spectroscopy (DCS) are modelbased near-infrared (NIR) methods that measure tissue optical properties (broadband absorption, mu(a), and reduced scattering, mu(s)) and blood flow (blood flow index, BFI), respectively. DOSI-derived mu(a) values are used to determine composition by calculating the tissue concentration of oxy- and deoxyhemoglobin(HbO2,HbR), water, and lipid. We developed and evaluated a combined, coregistered DOSI/ DCS handheld probe for mapping and imaging these parameters. We show that uncertainties of 0.3 mm(-1) (37%) in mu(s) and 0.003 mm(-1) (33%) in mu(a) lead to similar to 53% and 9% errors in BFI, respectively. DOSI/ DCS imaging of a solid tissue-simulating flow phantom and a breast cancer patient reveals well-defined spatial distributions of BFI and composition that clearly delineates both the flow channel and the tumor. BFI reconstructed with DOSI-corrected mu(a) and mu(s) values had a tumor/ normal contrast of 2.7, 50% higher than the contrast using commonly assumed fixed optical properties. In conclusion, spatially coregistered imaging of DOSI and DCS enhances intrinsic tumor contrast and information content. This is particularly important for imaging diseased tissues where there are significant spatial variations in mu(a) and mu(s) as well as potential uncoupling between flow and metabolism. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication,
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- Combs, Elizabeth K., et al.
(author)
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Physiological and Cognitive Performance in F-22 Pilots During Day and Night Flying
- 2021
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In: Aerospace Medicine and Human Performance. - : Aerospace Medical Association. - 2375-6314 .- 2375-6322. ; 92:5, s. 303-311
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Journal article (peer-reviewed)abstract
- BACKGROUND: Many workers routinely transition between day and night shifts—including pilots, where night flights are commonly considered more stressful. The physiological toll from this transition is not fully understood, though fatigue is a factor in many aviation accidents. This research investigated the changes in physiological markers of stress and cognitive performance as F-22 pilots transitioned from day flying to night flying. methods: There were 17 fully-qualified F-22 pilots who took part in a 2-wk data collection using salivary swabs, wrist-worn activity monitors, the National Aeronautics and Space Administration-Task Load Index (NASA-TLX) inventory, and a go/no-go (GNG) test. results: No differences were found in comparing day and night flying on the GNG reaction time/accuracy, NASA-TLX scores, or sleep quantity. Cortisol levels were significantly higher than civilian levels in all experimental conditions and control days. Participants had higher than predicted cortisol levels postflight in the day-flying condition and lower than predicted cortisol levels postflight in the night-flying condition, relative to levels from control day patterns. We also found smaller changes in cortisol (pre- to postflight) in the day-flying condition for those with more F-22 experience. Finally, we found a negative correlation between Perceived Stress Scale scores and age of pilots (r 5 -20.72). discussion: We hypothesized that the night-flying environment would be more stressful, but our results disputed this claim. Our results suggest day flying elicits more of a stress response; however, a larger sample size is required to verify results. Preliminary findings of potential stress adaptation may suggest stress adaptation in the F-22 community needs further investigation.
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