| 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. |
- Yu, Xiaoran, et al.
(författare)
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Remaining-useful-lifetime prediction of proton exchange membrane fuel cell considering model uncertainty quantification on the full-time scale
- 2023
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Ingår i: IEEE Transactions on Transportation Electrification. - 2332-7782. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- A prognostics and health management (PHM) system with prediction at its core optimizes the durability of the proton exchange membrane fuel cell (PEMFC). However, the aging behavior model has some uncertainty due to limited knowledge, affecting the predictive performance in remaining useful life (RUL) prediction. To address this issue, an RUL prediction method based on the Bayesian framework considering uncertainty quantification on the full-time scale is proposed. Firstly, the state of health (SOH) of the PEMFC is estimated, and the behavior of uncertainty is quantified. Afterwards, a long short-term memory (LSTM) neural network is employed to make a prediction for its behavior. Finally, the RUL of PEMFC is predicted based on historical SOH and the predicted behavior of uncertainty. Validation indicates that the proposed method can make a long-term prediction and provide RUL prediction with high accuracy. Under the dynamic operating condition, in terms of long-term prediction, compared to unscented Kalman filter, adaptive unscented Kalman filter, double-input-echo-state-network and bidirectional LSTM, the proposed method decreases the error by 88.12%, 41.99%, 13.82% and 3.21%, respectively. And under the dynamic operating condition, the proposed method shows good stability. Moreover, the robustness of this method has also been verified.
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| 3. |
- Fan, Qunping, 1989, et al.
(författare)
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Mechanically Robust All-Polymer Solar Cells from Narrow Band Gap Acceptors with Hetero-Bridging Atoms
- 2020
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Ingår i: Joule. - : Elsevier BV. - 2542-4351. ; 4:3, s. 658-672
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Tidskriftsartikel (refereegranskat)abstract
- We developed three narrow band-gap polymer acceptors PF2-DTC, PF2-DTSi, and PF2-DTGe with different bridging atoms (i.e., C, Si, and Ge). Studies found that such different bridging atoms significantly affect the crystallinity, extinction coefficient, electron mobility of the polymer acceptors, and the morphology and mechanical robustness of related active layers. In all-polymer solar cells (all-PSCs), these polymer acceptors achieved high power conversion efficiencies (PCEs) over 8.0%, while PF2-DTSi obtained the highest PCE of 10.77% due to its improved exciton dissociation, charge transport, and optimized morphology. Moreover, the PF2-DTSi-based active layer showed excellent mechanical robustness with a high toughness value of 9.3 MJ m−3 and a large elongation at a break of 8.6%, which is a great advantage for the practical applications of flexible devices. As a result, the PF2-DTSi-based flexible all-PSC retained >90% of its initial PCE (6.37%) after bending and relaxing 1,200 times at a bending radius of ∼4 mm.
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| 4. |
- Yang, Xiaoyong, et al.
(författare)
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Structural, electronic, mechanical and thermodynamic properties of U-Si intermetallic compounds : A comprehensive first principles calculations
- 2022
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Ingår i: Progress in nuclear energy (New series). - : Elsevier BV. - 0149-1970 .- 1878-4224. ; 148, s. 104229-
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Tidskriftsartikel (refereegranskat)abstract
- Uranium silicides are proposed as the prominent accident tolerant fuels for the light water reactors (LWR) due to their high metal density and high thermal conductivity. Among the U-Si alloys, the alloy with high U:Si ratio is more favorable for nuclear fuel application due to the higher uranium density. Thus, the crystal structure, mechanical property, electronic structure, phonon band structure and thermodynamic property of U3Si, U3Si2 and USi compounds, along with the thermodynamic reaction between U-Si intermetallic compounds are systematically studied in our work. The optimized structural parameters of these U-Si alloys are comparable with previous results. Besides, all of them are metallic in nature. Since the calculated elastic constants satisfy the Born stability criteria, one can know U-Si alloys are mechanically stable. The phonon dispersion curves are obtained based on the density functional perturbation theory (DFPT). Accordingly, various thermophysical properties, such as Helmholtz free energy, heat capacity, internal energy and entropy are calculated. Furthermore, the reaction energies related to the formation of U3Si, U3Si2 and USi as well as transformation between them are calculated. It is revealed at the same chemical environment the reaction to form USi occurs more easily, whereas the high temperature and sufficient uranium environment are more in favor for fully silicification of uranium metal into U3Si. Theoretical investigation of this work is expected to provide some new insights for the application of uranium silicides as nuclear fuels and future exploration on the design and synthesis of new-type uranium silicides.
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| 5. |
- Chen, Zhi-Hui, et al.
(författare)
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Enhanced normal-direction excitation and emission of dual-emitting quantum dots on a cascaded photonic crystal surface
- 2014
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 6:24, s. 14708-14715
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Tidskriftsartikel (refereegranskat)abstract
- Large normal-direction excitation and emission of dual-emitting quantum dots (QDs) are essential for practical application of QD sensors based on the ratiometric fluorescence response. We have numerically demonstrated an all-dielectric four-layer cascaded photonic crystal (CPC) structure (alternating TiO2 and SiO2/SU8 layers with two dimensional nanoscale patterns in each layer) which is capable of providing normal-direction high Q-factor leaky modes at excitation wavelengths of QDs and two low Q-factor leaky modes coinciding with the two emission peaks of a dual-emitting QD. Normal-direction excitation and far-field emission of the dual-emitting QDs are enhanced significantly when QDs are distributed on/in the top TiO2 layer of the CPC structure, especially in the spatial distribution areas of the resonant leaky modes. QDs can be positioned differently depending on the applications. Positioning QDs on the top TiO2 layer will improve the signal-to-noise ratios of QD biomedical/chemical/temperature sensors, while embedding QDs in the top TiO2 layer will increase the light extraction from the QD light emitting device, making our CPC a versatile optical coupling structure. Our CPC-QD structure is experimentally feasible and robust against the parameter perturbation in real fabrication.
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| 6. |
- Cao, Xuan, et al.
(författare)
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Engineering yeast for high-level production of diterpenoid sclareol
- 2023
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Ingår i: Metabolic Engineering. - : Elsevier BV. - 1096-7176 .- 1096-7184. ; 75, s. 19-28
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Tidskriftsartikel (refereegranskat)abstract
- The diterpenoid sclareol is an industrially important precursor for alternative sustainable supply of ambergris. However, its current production from plant extraction is neither economical nor environmental-friendly, since it requires laborious and cost-intensive purification procedures and plants cultivation is susceptible to environmental factors. Engineering cell factories for bio-manufacturing can enable sustainable production of natural products. However, stringent metabolic regulation poses challenges to rewire cellular metabolism for overproduction of compounds of interest. Here we used a modular approach to globally rewire the cellular metabolism for improving sclareol production to 11.4 g/L in budding yeast Saccharomyces cerevisiae, the highest reported diterpenoid titer in microbes. Metabolic flux analysis showed that modular balanced metabolism drove the metabolic flux toward the biosynthesis of targeted molecules, and transcriptomic analysis revealed that the expression of central metabolism genes was shaped for a new balanced metabolism, which laid a foundation in extensive metabolic engineering of other microbial species for sustainable bio-production.
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| 7. |
- Fu, Keren, 1988, et al.
(författare)
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One-Class SVM Assisted Accurate Tracking
- 2012
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Ingår i: 6th ACM/IEEE Int'l Conf on Distributed Smart Cameras (ICDSC 12), Oct 30 - Nov.2, 2012, Hong Kong. ; , s. 6 pages-
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Konferensbidrag (refereegranskat)abstract
- Recently, tracking is regarded as a binary classification problem by discriminative tracking methods. However, such binary classification may not fully handle the outliers, which may cause drifting. In this paper, we argue that tracking may be regarded as one-class problem, which avoids gathering limited negative samples for background description. Inspired by the fact the positive feature space generated by One-Class SVM is bounded by a closed sphere, we propose a novel tracking method utilizing One-Class SVMs that adopt HOG and 2 bit-BP as features, called One-Class SVM Tracker (OCST). Simultaneously an efficient initialization and online updating scheme is alsoproposed. Extensive experimental results prove that OCST outperforms some state-of-the-art discriminative tracking methods on providing accurate tracking and alleviating serious drifting.
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| 8. |
- Jianfeng, Lin, 1994, et al.
(författare)
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Hydrodynamic simulation for evaluating Magnus anti-rolling devices with varying angles of attack
- 2022
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Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018. ; 260
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Tidskriftsartikel (refereegranskat)abstract
- The effective operation of anti-rolling devices is important for ensuring ship safety, comfort, combat capability, and performance. Stabilizers based on the principle of the Magnus effect were investigated in this study. The hydrodynamic performance of a three-dimensional Magnus anti-rolling device at different angles of attack was examined using the improved delayed detached eddy simulation method based on shear stress transport. Subsequently, a convergence analysis was performed to verify the accuracy of the method. Moreover, the effects of the rotational speed, angle of attack, and incoming flow speed on the lift–drag characteristics and wake flow field of the Magnus anti-rolling device were analyzed. The results indicated that the optimal spin ratio maximized the lift–drag ratio. However, in certain cases, the angle of attack and spin ratio significantly influenced the streamwise and crosswise vortex structures in the cylinder wake. These results would be useful for the practical application of Magnus anti-rolling devices.
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| 9. |
- Meng, Long, et al.
(författare)
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Dynamic Response of 6MW Spar Type Floating Offshore Wind Turbine by Experiment and Numerical Analyses
- 2020
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Ingår i: China Ocean Engineering. - : Springer Science and Business Media LLC. - 0890-5487 .- 2191-8945. ; 34:5, s. 608-620
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Tidskriftsartikel (refereegranskat)abstract
- The floating offshore wind turbine (FOWT) is widely used for harvesting marine wind energy. Its dynamic responses under offshore wind and wave environment provide essential reference for the design and installation. In this study, the dynamic responses of a 6MW Spar type FOWT designed for the water depth of 100 m are investigated by means of the wave tank experiment and numerical analysis. A scaled model is manufactured for the experiment at a ratio of 65.3, while the numerical model is constructed on the open-source platform FAST (Fatigue, Aerodynamics, Structures, and Turbulence). Still water tests, wind-induced only tests, wave-induced only tests and combined wind-wave-current tests are all conducted experimentally and numerically. The accuracy of the experimental set-up as well as the loading generation has been verified. Surge, pitch and heave motions are selected to analyze and the numerical results agree well with the experimental values. Even though results obtained by using the FOWT calculation model established in FAST software show some deviations from the test results, the trends are always consistent. Both experimental and numerical studies demonstrate that they are reliable for the designed 6MW Spar type FOWT.
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| 10. |
- Lyu, Zhidong, et al.
(författare)
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A Beam-Scannable Photonic THz-ISAC System Based on Risley Prisms
- 2023
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Ingår i: 2023 Asia Communications and Photonics Conference/2023 International Photonics and Optoelectronics Meetings, ACP/POEM 2023. - : Institute of Electrical and Electronics Engineers (IEEE).
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Konferensbidrag (refereegranskat)abstract
- We demonstrate a beam-scannable photonic terahertz-integrated sensing and communication (THz-ISAC) system using Risley prisms. 20 Gbps data rate and 1.5 cm resolution are simultaneously achieved at 300 GHz with 40 deg field of view (FoV).
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