| 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. |
- Dong, B., et al.
(författare)
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Local surface plasmon resonance of single silver nanorice particles in the near-infrared
- 2014
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Ingår i: Mikrochimica Acta. - : Springer Science and Business Media LLC. - 1436-5073 .- 0026-3672. ; 181:7-8, s. 791-795
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Tidskriftsartikel (refereegranskat)abstract
- We report on the synthesis and optical spectra of silver nanorice particles. Two strong absorption bands are resolved in the near UV and near-IR region, and the dark field scattering spectra are consistent with the absorption spectra. Finite-difference time-domain simulations reveal that the peak in the IR region can be attributed to the E field that is parallel to the long axis, while the peak in the UV can be attributed to the E field perpendicular to the short axis of the silver nanorice particles.
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| 3. |
- Chen, H., et al.
(författare)
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Unprecedented non-hysteretic superelasticity of [001]-oriented NiCoFeGa single crystals
- 2020
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Ingår i: Nature Materials. - : Nature Research. - 1476-1122 .- 1476-4660.
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Tidskriftsartikel (refereegranskat)abstract
- Superelasticity associated with the martensitic transformation has found a broad range of engineering applications1,2. However, the intrinsic hysteresis3 and temperature sensitivity4 of the first-order phase transformation significantly hinder the usage of smart metallic components in many critical areas. Here, we report a large superelasticity up to 15.2% strain in [001]-oriented NiCoFeGa single crystals, exhibiting non-hysteretic mechanical responses, a small temperature dependence and high-energy-storage capability and cyclic stability over a wide temperature and composition range. In situ synchrotron X-ray diffraction measurements show that the superelasticity is correlated with a stress-induced continuous variation of lattice parameter accompanied by structural fluctuation. Neutron diffraction and electron microscopy observations reveal an unprecedented microstructure consisting of atomic-level entanglement of ordered and disordered crystal structures, which can be manipulated to tune the superelasticity. The discovery of the large elasticity related to the entangled structure paves the way for exploiting elastic strain engineering and development of related functional materials.
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| 4. |
- Wang, Shu Min, 1963, et al.
(författare)
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A novel semiconductor compatible path for nano-graphene synthesis using CBr4 precursor and Ga catalyst
- 2014
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- We propose a novel semiconductor compatible path for nano-graphene synthesis using precursors containing C-Br bonding and liquid catalyst. The unique combination of CBr4 as precursor and Ga as catalyst leads to efficient C precipitation at a synthesis temperature of 200 degrees C or lower. The non-wetting nature of liquid Ga on tested substrates limits nano-scale graphene to form on Ga droplets and substrate surfaces at low synthesis temperatures of T = 400 degrees C. Good quality interface nano-graphene is demonstrated and the quality can be further improved by optimization of synthesis conditions and proper selection of substrate type and orientation. The proposed method provides a scalable and transfer-free route to synthesize graphene/semiconductor heterostructures, graphene quantum dots as well as patterned graphene nano-structures at a medium temperature range of 400-700 degrees C suitable for most important elementary and compound semiconductors.
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| 5. |
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| 6. |
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| 7. |
- Chen, Xiangrong, 1982, et al.
(författare)
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Study on conducting characteristics of electrical trees in cross-linked polyethylene cable insulation
- 2012
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Ingår i: Wuli Xuebao/Acta Physica Sinica. - : Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences. - 1000-3290. ; 61:8, s. Art. no. 087701-
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Tidskriftsartikel (refereegranskat)abstract
- The conducting characteristics of two typical electrical trees in cross-linked polyethylene (XLPE) cable insulation are studied by a combination of optical microscopy observation, partial discharge measurement and con-focal Raman spectroscopy analysis. Although they are grown under similar conditions, these two trees display very different shapes. One is a typical branch-pine tree grown at 9 kV, and the other is a branch tree grown at 11 kV. The growth and the partial discharge regularities show obvious differences. The disordered graphitic carbon is condensed in the main tree channels of the branch-pine tree. From the relative intensity of the graphitic carbon G band to D band, the graphitic domain is estimated to be about 8 nm in size. The tree channel resistance per unit length is less than 10 Ω· μm-1, which is sufficient to prevent the partial discharge from developing within the tree structure. The branch-pine tree shows the features of the conducting tree. The fluorescence background is observed in the channels of branch tree, which shows the existence of the products of the material degradation, but no disordered graphitic carbon is observed in these tree channels. These tree channels display obvious non-conducting characteristics, which is not sufficient to prevent the continuous effect of the partial discharges. Finally, a single channel growth model is proposed for the conducting and non-conducting trees grown in XLPE cable insulation. Based on the equivalent circuit theory, the growth mechanisms of the two trees with different conducting characteristics in XLPE cable insulation are discussed.
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| 8. |
- Feng, S. Z., et al.
(författare)
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Siloxane-Terminated Side Chain Engineering of Acceptor Polymers Leading to Over 7% Power Conversion Efficiencies in All-Polymer Solar Cells
- 2017
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Ingår i: ACS Macro Letters. - : American Chemical Society (ACS). - 2161-1653. ; 6:11, s. 1310-1314
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Tidskriftsartikel (refereegranskat)abstract
- To investigate the influence of functional pendent groups on acceptor polymers and photovoltaic properties of all-polymer solar cells (all-PSCs), two novel acceptor polymers containing siloxane-terminated side chains are synthesized and characterized. Increasing the content of siloxane-terminated side chains can reduce pi-pi stacking distance and improve crystalline behavior, yet lead to poorer solubility of the acceptor polymers. By modulating the proper loadings of siloxane-terminated side chains on the acceptor polymers, the PBDB-T:PNDI-Si25 all-PSC attains a maximal power conversion efficiency (PCE) of 7.4% with an outstanding fill factor of 0.68. The results provide, new insights for developing high-performance all-PSCs through functional group engineering on the acceptor polymers, to achieve good solubility, polymer miscibility, and blend morphology.
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| 9. |
- Zhang, Y., et al.
(författare)
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Enhanced variable reluctance energy harvesting for self-powered monitoring
- 2022
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 321
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Tidskriftsartikel (refereegranskat)abstract
- With the rapid development of microelectronic technology, wireless sensor nodes have been widely used in rotational equipment for health condition monitoring. However, for many low-frequency applications, there still remains an open issue of harvesting sufficient electrical energy to provide long-term service. Therefore, in this paper an enhanced variable reluctance energy harvester (EVREH) is proposed for self-powered health monitoring under low-frequency rotation conditions. A periodic arrangement of magnets and teeth is employed to achieve frequency up-conversion for performance enhancement under a specific space constraint. In addition, the permeance of the air gap is calculated by the combined magnetic field division and substituting angle method, and the output model of the EVREH is derived for parametric analysis based on the law of electromagnetic induction. Simulations and experimental evaluations under a range of structural parameters are then carried out to verify the effectiveness of the proposed model and investigate the output performance of the proposed harvester. The experimental results indicate that the proposed energy harvester could produce a voltage of 8.7 V and a power of 726 mW for a rotational speed of 200 rpm, with a power density of 0.545 mW/(cm3∙Hz2). Moreover, a self-powered wireless sensing system based on the proposed energy harvester is demonstrated, obtaining a vibration spectrum of the rotating motor and stator which can determine the health state of the system during low rotational speeds. Therefore, this autonomous self-sensing experiment verifies the potential of the EVREH for self-powered monitoring in low-frequency rotation applications.
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| 10. |
- Cao, B., et al.
(författare)
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A Multiobjective Intelligent Decision-Making Method for Multistage Placement of PMU in Power Grid Enterprises
- 2023
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Ingår i: IEEE Transactions on Industrial Informatics. - : Institute of Electrical and Electronics Engineers (IEEE). - 1551-3203 .- 1941-0050. ; 19:6, s. 7636-7644
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Tidskriftsartikel (refereegranskat)abstract
- The wide area measurement system (WAMS) based on synchronous phasor measurement technology plays an increasingly important role in dynamic monitoring and wide area protection of modern power systems. If the phasor measurement unit (PMU) is placed on all buses of the power system, the voltage and branch current of all buses can be directly observed. However, due to the high placement cost of PMU and its ability to measure the voltage phasor of the installed bus and the current of the associated branch, it is unrealistic and unnecessary to install PMU on all buses of the system. This paper discusses the incomplete observability under single PMU loss (N-1) contingencies and its effect on PMUs placement. An improved two-archive algorithm is proposed to solve the five-objective placement optimization model. In addition, a fuzzy decision-making method combining subjective and objective is proposed to help power grid enterprises select the most appropriate solution. The proposed method is tested on several IEEE bus systems and Polish 2383-bus system, and the test results verify its effectiveness.
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