| 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. |
- Choi, Nuri, et al.
(författare)
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Influence of Manufacturing Conditions on Inclusion Characteristics and Mechanical Properties of FeCrNiMnCo Alloy
- 2020
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Ingår i: Metals. - : MDPI. - 2075-4701. ; 10:10
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Tidskriftsartikel (refereegranskat)abstract
- Three CoCrFeMnNi high-entropy alloys (HEAs) were produced by vacuum induction melting, induction melting under inert gas atmosphere, and melting under inert gas atmosphere followed by air exposure, respectively. The different manufacturing conditions for the three investigated alloys resulted in different levels and types of inclusions. The alloys melted under vacuum or inert gas contained Al2O3 inclusions formed by impurity Al, due to its high oxidation tendency. The molten alloy exposed in air showed an excessive oxidation. During oxidation of the molten alloy in air, impurity Al was initially oxidized, and fine MnCr2O4 inclusions were formed rather than pure Al2O3 inclusions. This difference was analyzed based on thermodynamic calculations. Specifically, the influence of impurity content on the inclusion characteristics was investigated for the three HEAs. Moreover, the inclusion characteristics were found to have an influence on mechanical properties of the alloys also. In air-exposed HEA, smaller inclusions were formed, resulting in a higher dislocation density at the matrix/inclusion interface and thus strengthening of the HEA. Thus, it is proposed that atmospheric conditions could be an important factor to control the inclusion characteristics and to form fine inclusion particles, which could improve the mechanical properties of HEAs.
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| 3. |
- Kim, Bokyeong, et al.
(författare)
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Decoupled Address Translation for Heterogeneous Memory Systems
- 2020
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Ingår i: PACT '20. - New York, NY, USA : ASSOC COMPUTING MACHINERY. - 9781450380751 ; , s. 155-156
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Konferensbidrag (refereegranskat)abstract
- The support for the heterogeneous memory in the conventional virtual memory has an inherent problem. For the efficient translation in the critical translation lookaside buffers (TLBs), the page size has been growing. However, the heterogeneous memory management requires a nimble fine-grained migration mechanism to quickly move necessary memory portions to the precious fast memory. To address the challenges posed by the conflicting goals in the heterogeneous memory support, this paper proposes to decouple the address translation into a two-step process. The decoupling resolves the conflict as the critical core-side TLBs perform the translation to an intermediate address space, and the memory-side translation provides the actual physical location of the memory devices.
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| 4. |
- Kim, Bokyeong, et al.
(författare)
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Supporting Dynamic Translation Granularity for Hybrid Memory Systems
- 2022
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Ingår i: 2022 IEEE 40th International Conference on Computer Design (ICCD). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781665461863 - 9781665461870 ; , s. 25-32
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Konferensbidrag (refereegranskat)abstract
- Hybrid memory has become a promising new solution for meeting ever growing memory capacity demands in a cost-effective way. In hybrid memory systems, the fast and high bandwidth memory is used to store performance-critical data, while the slow and low bandwidth memory provides capacity backup. In supporting such hybridization, virtual memory is the key mechanism, which can combine different memory components to a single memory view. For efficient translation for virtual memory, page size has been growing. However, the hybrid memory support requires fine-grained migration to quickly move only necessary memory portions to the precious fast memory. To address the challenges posed by the conflicting goals in the hybrid memory support based on virtual memory, this paper investigates decoupling of address translation into a two-step process. With the two-level translation, the critical core-side TLBs perform the translation to an intermediate address space, and the memory-side translation provides the actual physical location in memory devices. As the second-level translation handling page migration across different memory types, is decoupled from the first-level translation, it allows dynamic adjustment of its mapping granularity to improve the efficiency of translation and data reuse in the fast memory. This paper proposes a hardware architecture which identifies the memory access behavior of an application online and selects the best mapping granularity for the second-level translation.
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| 5. |
- Kim, D. H., et al.
(författare)
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Improving the production efficiency of high-titania slag in Ti extraction process : fluxing effect on formation of pseudobrookite
- 2020
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Ingår i: Scientific Reports. - : Nature Research. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the carbothermic reduction process of ilmenite ore at 1873 K with flux addition. Without flux, the pseudobrookite phase with a high melting temperature was precipitated during ilmenite smelting. This could be the main reason for decreased reduction of iron in ilmenite. To accelerate reduction of ilmenite, two factors were considered. One is increasing the reduction driving force during smelting. Activity of FeO is the major factor to control reduction in driving force. The other factor is delay in formation of the pseudobrookite phase, a high-melting point precipitation phase. In this system, MgO in ilmenite could be used to form pseudobrookite. To control these factors, in this study, flux agent (i.e., Na2O or SiO2) addition was considered. The thermochemical simulation program, FactSageTM7.0 was used to calculate the viscosity of slag and the activity of components as fluxing agents were added. High-temperature experiments using an induction furnace were also conducted to confirm the computational results. To determine the composition of final products, i.e., titanium slag, X-ray fluorescence analysis was executed. As a result of Fe and Ti behaviours in slag, SiO2 addition showed no significant difference from the slag without flux. However, Fe reduction in ilmenite, i.e. TiO2-enrichment, was more accelerated when Na2O was added. X-ray diffraction, scanning electron microscopic and transmission electron microscopic analyses results also showed that even 1 wt% Na2O addition significantly influenced the titanium slag production compared to no flux addition.
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| 6. |
- Park, Sung Hyun, et al.
(författare)
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New paradigm of lean six sigma in the 4th industrial revolution era
- 2020
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Ingår i: Quality Innovation Prosperity. - 1335-1745. ; 24:1, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: In early 2000s Six Sigma and Lean were combined into Lean Six Sigma (LSS), which has been one of the major strategic quality initiatives all over the world. Now, we are in the era of the 4th Industrial Revolution (IR), which changes almost everything including LSS and quality management (QM) in the companies. We need new paradigm of LSS to boost LSS activities in this 4th IR era. In this paper, the typical characteristics of the 4th IR are investigated, and desirable new paradigm of LSS is presented. Methodology/Approach: The changing characteristics of production strategy, quality goal and quality strategy with regard to QM in the 4th IR are discussed and presented. Then the new and emerging paradigm of LSS in this 4th IR era is discussed in detail. Also 9 success factors for this new paradigm of LSS are shown for practitioners in the industry. Findings: The direction of the new paradigm of LSS will be ‘simple, speedy and smart’, which may be called ‘3S paradigm’. Simple open procedures and simple statistical modelling tools will be mainly used. Speedy on-site improvement based on Open Data, Big Data and artificial intelligence (AI) will be favoured. Also smart mass customized ‘Smart Factory’ method will be emphasized. Research Limitation/implication: Since we are in the beginning stage of the 4th IR, there are not many research papers which study the impact of this revolution to LSS and QM, which is the major research limitation. Originality/Value of paper: This paper suggests some new and emerging paradigm of LSS, which could be of high value.
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| 7. |
- Yang, J. G., et al.
(författare)
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Gold Solubility in CaO-SiO2-Al2O3-Fe2O3 Slags
- 2021
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Ingår i: JOM. - : Springer Nature. - 1047-4838 .- 1543-1851. ; 73:2, s. 688-693
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Tidskriftsartikel (refereegranskat)abstract
- Gold solubility in the CaO-SiO2-Al2O3-Fe2O3 slag system was measured at 1723 K under an oxidizing atmosphere. Gold solubility in the present slag system increased with increasing slag basicity, which was quantified by the Vee ratio (= CaO/SiO2), theoretical optical basicity, and activity of CaO. However, the effect of Fe2O3 and Al2O3 on gold solubility was negligible. From the thermodynamic assessment, it was found that gold was stabilized as the AuO− (aurate) complex ion, and thus the dissolution reaction into the slag was proposed. The aurate capacity was originally defined from the dissolution reaction. The iso-Au solubility contours were plotted in the CaO-Fe2O3-(SiO2 + Al2O3) pseudo-ternary diagram, from which the lower content of CaO can be proposed to be useful for higher recovery of gold (i.e., lower solubility) based on the thermodynamic view during pyrometallurgical processing of gold-containing E-waste materials. However, because the viscosity of the slag increases by decreasing the content of CaO, the operating window for best practice should be carefully proposed by considering the physicochemical properties of molten slag.
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| 8. |
- Wendt, Fabian, et al.
(författare)
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Ocean energy systemswave energy modelling task: Modelling, verification and validation ofwave energy converters
- 2019
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Ingår i: Journal of Marine Science and Engineering. - : MDPI AG. - 2077-1312. ; 7:11
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Tidskriftsartikel (refereegranskat)abstract
- The International Energy Agency Technology Collaboration Programme for Ocean Energy Systems (OES) initiated the OES Wave Energy Conversion Modelling Task, which focused on the verification and validation of numerical models for simulating wave energy converters (WECs). The long-term goal is to assess the accuracy of and establish confidence in the use of numerical models used in design as well as power performance assessment of WECs. To establish this confidence, the authors used different existing computational modelling tools to simulate given tasks to identify uncertainties related to simulation methodologies: (i) linear potential flow methods; (ii) weakly nonlinear Froude-Krylov methods; and (iii) fully nonlinear methods (fully nonlinear potential flow and Navier-Stokes models). This article summarizes the code-to-code task and code-to-experiment task that have been performed so far in this project, with a focus on investigating the impact of different levels of nonlinearities in the numerical models. Two different WECs were studied and simulated. The first was a heaving semi-submerged sphere, where free-decay tests and both regular and irregular wave cases were investigated in a code-to-code comparison. The second case was a heaving float corresponding to a physical model tested in a wave tank. We considered radiation, diffraction, and regular wave cases and compared quantities, such as the WEC motion, power output and hydrodynamic loading.
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| 9. |
- Subramanian, Arunprabaharan, et al.
(författare)
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Trade-off between Zr Passivation and Sn Doping on Hematite Nanorod Photoanodes for Efficient Solar Water Oxidation : Effects of a ZrO2 Underlayer and FTO Deformation
- 2016
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 8:30, s. 19428-19437
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Tidskriftsartikel (refereegranskat)abstract
- Herein we report the influence of a ZrO2 underlayer on the PEC (photoelectrochemical) behavior of hematite nanorod photoanodes for efficient solar water splitting. Particular attention was given to the cathodic shift in onset potential and photocurrent enhancement. Akaganite (beta-FeOOH) nanorods were grown on ZrO2-coated FTO (fluorine-doped tin oxide) substrates. Sintering at 800 degrees C transformed akaganite to the hematite (alpha-Fe2O3) phase and induced Sn diffusion into the crystal structure of hematite nanorods from the FTO substrates and surface migration, shallow doping of Zr atoms from the ZrO2 underlayer. The ZrO2 underlayer-treated photoanode showed better water oxidation performance compared to the pristine (alpha-Fe2O3) photoanode. A cathodic shift in the onset potential and photocurrent enhancement was achieved by surface passivation and shallow doping of Zr from the ZrO2 underlayer, along with Sn doping from the FTO substrate to the crystal lattice of hematite nanorods. The Zr based hematite nanorod photoanode achieved 1 mA/cm(2) at 1.23 V-RHE with a low turn-on voltage of 0.80 V-RHE. Sn doping and Zr passivation, as well as shallow doping, were confirmed by XPS, I-ph, and M-S plot analyses. Electrochemical impedance spectroscopy revealed that the presence of a ZrO2 underlayer decreased the deformation of FTO substrate, improved electron transfer at the hematite/FTO interface and increased charge-transfer resistance at the electrolyte/hematite interface. This is the first systematic investigation of the effects of Zr passivation, shallow doping, and Sn doping on hematite nanorod photoanodes through application of a ZrO2 underlayer on the FTO substrate.
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| 10. |
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