| 1. |
- Murari, A., et al.
(författare)
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A control oriented strategy of disruption prediction to avoid the configuration collapse of tokamak reactors
- 2024
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Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- The objective of thermonuclear fusion consists of producing electricity from the coalescence of light nuclei in high temperature plasmas. The most promising route to fusion envisages the confinement of such plasmas with magnetic fields, whose most studied configuration is the tokamak. Disruptions are catastrophic collapses affecting all tokamak devices and one of the main potential showstoppers on the route to a commercial reactor. In this work we report how, deploying innovative analysis methods on thousands of JET experiments covering the isotopic compositions from hydrogen to full tritium and including the major D-T campaign, the nature of the various forms of collapse is investigated in all phases of the discharges. An original approach to proximity detection has been developed, which allows determining both the probability of and the time interval remaining before an incoming disruption, with adaptive, from scratch, real time compatible techniques. The results indicate that physics based prediction and control tools can be developed, to deploy realistic strategies of disruption avoidance and prevention, meeting the requirements of the next generation of devices.
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| 4. |
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| 5. |
- 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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| 6. |
- Renugopalakrishnan, V, et al.
(författare)
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Nanomaterials for energy conversion applications
- 2009
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Ingår i: Nanomaterials for Energy Conversion Applications. - : American Scientific Publishers. ; , s. 155-178
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 7. |
- Delsing, Per, 1959, et al.
(författare)
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The 2019 surface acoustic waves roadmap
- 2019
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Ingår i: Journal of Physics D: Applied Physics. - : IOP Publishing. - 1361-6463 .- 0022-3727. ; 52:35
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Forskningsöversikt (refereegranskat)abstract
- Today, surface acoustic waves (SAWs) and bulk acoustic waves are already two of the very few phononic technologies of industrial relevance and can been found in a myriad of devices employing these nanoscale earthquakes on a chip. Acoustic radio frequency filters, for instance, are integral parts of wireless devices. SAWs in particular find applications in life sciences and microfluidics for sensing and mixing of tiny amounts of liquids. In addition to this continuously growing number of applications, SAWs are ideally suited to probe and control elementary excitations in condensed matter at the limit of single quantum excitations. Even collective excitations, classical or quantum are nowadays coherently interfaced by SAWs. This wide, highly diverse, interdisciplinary and continuously expanding spectrum literally unites advanced sensing and manipulation applications. Remarkably, SAW technology is inherently multiscale and spans from single atomic or nanoscopic units up even to the millimeter scale. The aim of this Roadmap is to present a snapshot of the present state of surface acoustic wave science and technology in 2019 and provide an opinion on the challenges and opportunities that the future holds from a group of renown experts, covering the interdisciplinary key areas, ranging from fundamental quantum effects to practical applications of acoustic devices in life science.
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| 8. |
- Qiu, Min, et al.
(författare)
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Negative refraction in semiconductor photonic crystals
- 2005
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Ingår i: SEMICONDUCTOR AND ORGANIC OPTOELECTRONIC MATERIALS AND DEVICES. - : SPIE. ; , s. 345-352
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Konferensbidrag (refereegranskat)abstract
- The coupling efficiency between external plane waves and the Bloch waves in photonic crystals are investigated. It is found that the coupling coefficient is highly angular dependent even for an interface between air n=l and a photonic crystal with effective index -1. It is also shown that, for point imaging by a photonic crystal slab owing to the negative refraction, the influence of the surface termination to the transmission and the imaging quality is significant. Finally, we present results demonstrating experimentally negative refraction in a two-dimensional photonic crystal.
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| 9. |
- Billeter, J., et al.
(författare)
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On decoupling rate processes in chemical reaction systems – Methods and applications
- 2018
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Ingår i: Computers and Chemical Engineering. - : Elsevier BV. - 0098-1354 .- 1873-4375. ; 114, s. 296-305
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Tidskriftsartikel (refereegranskat)abstract
- Models of chemical reaction systems can be complex as they need to include information regarding the reactions and the mass and heat transfers. The commonly used state variables, namely, concentrations and temperatures, express the interplay between many phenomena. As a consequence, each state variable is affected by several rate processes. On the other hand, it is well known that it is possible to partition the state space into a reaction invariant subspace and its orthogonal complement using a linear transformation involving the reaction stoichiometry. This paper uses a more sophisticated linear transformation to partition the state space into various subspaces, each one linked to a single rate process such as a particular reaction, mass transfer or heat transfer. The implications of this partitioning are discussed with respect to several applications related to data reconciliation, state and rate estimation, modeling, identification, control and optimization of reaction systems.
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| 10. |
- Nanukuttan, Sree, 1990, et al.
(författare)
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Methodology for designing structures to withstand extreme environments: Performance based specifications
- 2010
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Ingår i: Research in Ireland, BCRI 2010, 2-3 Sept 2010, Cork, Ireland. - 9780954297336 ; , s. 663-670
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Konferensbidrag (refereegranskat)abstract
- Existing guidelines in BS 8500 allow the selection of concrete mix based on variables such as compressive strength, maximum water to binder ratio, minimum cement content and minimum cover thickness. This approach does not guarantee the durability and expected performance of the concrete structure in a given environment. One alternative is to develop performance- based specifications that supplement the existing guidelines in BS 8500, by specifying the required performance of concrete in terms of measurable properties such as resistance to environmental penetrations. This paper demonstrates one of such methodology for developing performance-based specifications for concretes exposed to marine environments. Chloride ingress related durability problem being critical in a marine environment, the reliability and repeatability of the different test methods for assessing the rate of chloride ingress is discussed first. Furthermore, a numerical simulation model is used to explore the test data to obtain long-term chloride ingress trends. Based on this, guidelines for selecting appropriate concrete mixes for a marine exposure is presented and discussed.
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