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Plasma flows and fluctuations with magnetic islands in the edge plasmas of J-TEXT tokamak

NUCLEAR FUSION 2015年第7期55卷 073022-073022页

作者： Zhao, K. J. Shi, Y. J. Hahn, S. H. Diamond, P. H. Sun, Y. Cheng, J. Liu, H. Lie, N. Chen, Z. P. Ding, Y. H. Chen, Z. Y. Rao, B. Leconte, M. Bak, J. G. Cheng, Z. F. Gao, L. Zhang, X. Q. Yang, Z. J. Wang, N. C. Wang, L. Jin, W. Yan, L. W. Dong, J. Q. Zhuang, G. NFRI WCI Ctr Fus Theory Taejon 305333 South Korea Southwestern Inst Phys Chengdu Peoples R China Natl Fus Res Inst Taejon 305806 South Korea Seoul Natl Univ Dept Nucl Engn Seoul South Korea Univ Calif San Diego Ctr Momentum Transport & Flow Org La Jolla CA 92093 USA Huazhong Univ Sci & Technol Coll Elect & Elect Engn Wuhan 430074 Hubei Peoples R China

The first comprehensive measurements of plasma flows and fluctuations nearby static magnetic islands driven by resonant magnetic perturbations are presented. These experiments were performed using multiple Langmuir probe arrays on the edge plasmas of the J-TEXT tokamak. Controlled variations of the island size and location are explored. This study aims to understand the interaction between turbulence and magnetic islands, and to elucidate magnetic island effects on edge turbulence and flow intensity profiles, edge electric fields, and thus confinement regime transitions. Turbulence and low frequency flows (LFFs) all drop inside the magnetic island, but increase at its boundary, as island width increases. The geodesic acoustic mode is damped in most of the edge area with magnetic islands. The sign of the radial electric field changes from negative to positive within the islands. The gradient of turbulent stresses vanishes at the island center, and becomes steeper at the boundaries of the islands. The particle transport induced by the turbulence is reduced inside the magnetic islands. The magnetic island effects on flows and turbulence can lead to an increase in LFFs and enhance Reynolds stresses near the last closed flux surface (LCFS). A stronger radial electric field layer can be formed near the LCFS when magnetic islands are present. The results suggest that magnetic islands can be used as a tool to enhance edge turbulence and flows, edge electric fields, and thus to trigger confinement regime transitions.

关键词： turbulence resonant magnetic perturbation flows

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A 3D-coupled field-circuit model for analyzing the internal short-circuit faults of power transformer

Lecture Notes in Electrical Engineering

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Lecture Notes in Electrical engineering 2015年 334卷 55-64页

作者： Hu, Guozhao Wu, Xixiu Long, Fei Wu, Shipu College of Automation Wuhan University of Technology Wuhan430070 China The 712 Research Institute China Shipbuilding Industry Corporation Wuhan430064 China Electric Power Research Institute of China Wuhan430074 China

To characterize the complex physical behavior of power transformer’s internal fault is very important for its protection and fault detection. Therefore, this chapter presents a complete three-dimensional-coupled field-circuit model to analyze the internal short-circuit faults of power transformer. The coupled mechanism and modeling which are used to evaluate the performance of transformer under internal short-circuit fault condition are introduced as well. A 500 kVA, three-phase, oil-immersed, core-type transformer is modeled by this field-circuit 3D-coupled method. Based on this, a deep analysis for turn-to-turn and internal phase-to-phase faults is made. The distribution of magnetic field and electrical characteristics which contribute to the development of reliable and sensitive fault detection methods are discussed in this study. © Springer International Publishing Switzerland 2015.

关键词： Power transformers

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Reconstruction in Reverse engineering Based on Geomagic

Reconstruction in Reverse Engineering Based on Geomagic

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2016 International Conference on Applied Mechanics, Mechanical and Materials engineering(AMMME 2016)

作者： Yan-qin LI Gui-zhong XIE Fan-nian MENG Chao WU De-hai ZHANG Mechanical and Electrical Engineering Institute Zhengzhou University of Light Industry State Key Laboratory for Manufacturing Systems Engineering (Xi’an Jiaotong University)

In the process of reverse engineering, the most important and most complex step is the reconstruction of the three-dimensional model, because the follow-up product design or manufacturing are based on this. The existing problems and advantages of Nurbs method are analyzed. A part is reconstructed using Geomagic and Pro/E softwaves. The proposed technique can provide a unique tool in reverse engineering, as well as in CAD and CAE and CAM research.

关键词： Reverse modeling Curve Surface

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Direct Simulation of Drag Force on Fractal Flocs during Settling

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JOURNAL OF COASTAL RESEARCH 2015年第SP1期73卷 753-757页

作者： Zhang, Jinfeng Zhang, Qinghe Tianjin Univ State Key Lab Hydraul Engn Simulat & Safety Tianjin 300072 Peoples R China

The hydrodynamic drag force of fractal flocs during settling is examined by the Lattice Boltzmann method. Fractal flocs formed by Diffusion-Limited Aggregation (DLA) and diffusion-limited-cluster-cluster aggregation (DLCCA) models settle down in the quiescent water and drag forces are directly calculated. The numerical simulations are consistent with the analytical results. The ratio of drag force on fractal flocs and floc size shows a linear relationship with the floc settling velocity when the flow filed around the flocs is Stokes flow. The drag coefficient experienced by flocs is significantly different from the spheres. Moreover, drag forces on flocs formed by DLCCA are larger than flocs formed by DLA, when the flocs are composed of the same primary particles.

关键词： Drag force drag coefficient settling fractal flocs lattice boltzmann method

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Facile synthesis of hierarchical Ag₃PO₄/TiO₂ nanofiber heterostructures with highly enhanced visible light photocatalytic properties

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APPLIED SURFACE SCIENCE 2015年 355卷 921-929页

作者： Xie, Jinlei Yang, Yefeng He, Haiping Cheng, Ding Mao, Minmin Jiang, Qinxu Song, Lixin Xiong, Jie Zhejiang Sci Tech Univ Dept Mat Engn Coll Mat & Text Hangzhou 310018 Peoples R China Zhejiang Sci Tech Univ MOE Key Lab Adv Text Mat & Mfg Technol Hangzhou 310018 Peoples R China Zhejiang Sci Tech Univ Qixin Honors Coll Hangzhou 310018 Peoples R China Zhejiang Univ State Key Lab Silicon Mat Hangzhou 310027 Peoples R China Zhejiang Univ Sch Mat Sci & Engn Hangzhou 310027 Peoples R China

Heterostructured semiconductor nanostructures have provoked great interest in the areas of energy, environment and catalysis. Herein, we report a novel hierarchical Ag3PO4/TiO2 heterostructure consisting of nearly spherical Ag3PO4 particles firmly coupled on the surface of TiO2 nanofibers (NFs). The construction of Ag3PO4/TiO2 heterostructure with tailored morphologies, compositions and optical properties was simply achieved via a facile and green synthetic strategy involving the electrospinning and solution-based processes. Owing to the synergetic effects of the components, the resulting hybrid heterostructures exhibited much improved visible light photocatalytic performance, which could degrade the RhB dye completely in 7.5 min. In addition, the coupling of Ag3PO4 particles with UV-light-sensitive TiO2 NFs enabled full utilization of solar energy and less consumption of noble metals, significantly appealing for their practical use in new energy sources and environmental issues. The developed synthetic strategy was considered to be applicable for the rational design and construction of other heterostructured catalysts. (C) 2015 Elsevier B.V. All rights reserved.

关键词： Ag3PO4 TiO2 nanofiber Heterostructure Visible light photocatalysis

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Poly (N-isopropylacrylamide)-co-(acrylic acid) microgel/Ag nanoparticle hybrids for the colorimetric sensing of H₂O₂

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NANOSCALE 2015年第6期7卷 2784-2789页

作者： Han, De-Man Zhang, Qiang Matthew Serpe, Michael J. Univ Alberta Dept Chem Edmonton AB T6G 2G2 Canada Taizhou Univ Dept Chem Taizhou 318000 Peoples R China

Poly (N-isopropylacrylamide)-co-(acrylic acid) (pNIPAm-co-AAc) microgels composed of Ag nanoparticles (Ag NPs) have been synthesized and employed for the colorimetric sensing of H2O2. Each pNIPAm-co- AAc microgel, which exhibited a diameter of similar to 800 nm, contained multiple Ag NPs (diameter of similar to 5 nm), and solutions of these hybrid materials showed a UV-vis absorption band at similar to 400 nm. This is due to the excitation of the Ag NP surface plasmon. We go on to show that the intensity of this absorption band is dependent on the concentration of H2O2 in solution. Specifically, in the presence of H2O2 the magnitude of the absorption peak dramatically decreases in a linear fashion over the concentration range of 0.30 to 3.00 mu M H2O2 (r(2) = 0.9918). We go on to show that the response is selective for H2O2 and can still function in complex mixtures, e.g., we showed that the response is still robust in milk samples. While Ag NPs themselves can exhibit similar responses, this system has many benefits including sample processing and long term stability - i.e., Ag NPs are destabilized in solutions of a certain pH, and aggregate readily. Our microgel/Ag NP hybrids have been shown to be extremely stable and are easily purified prior to use by simple centrifugation/washing protocols. This system is simple and straightforward to use, is low cost, and can be used in complex media, which makes it practical for analyzing complex biological and environmental samples.

关键词： Silver nanoparticles

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Growth of Ultrathin Mesoporous Ni-Mo Oxide Nanosheet Arrays on Ni Foam for High-performance Supercapacitor Electrodes

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ELECTROCHIMICA ACTA 2015年 176卷 1343-1351页

作者： Cheng, Ding Yang, Yefeng Luo, Yaobin Fang, Changjiang Xiong, Jie Zhejiang Sci Tech Univ Coll Mat & Text Dept Mat Engn Hangzhou 310018 Peoples R China Zhejiang Sci Tech Univ MOE Key Lab Adv Text Mat & Mfg Technol Hangzhou 310018 Peoples R China Zhejiang Sci Tech Univ Qixin Honors Coll Hangzhou 310018 Peoples R China Zhejiang Univ State Key Lab Silicon Mat Hangzhou 310027 Peoples R China

In this work, we present a simple two-step method to fabricate a series of three-dimensional (3D) interconnected networks of ultrathin mesoporous Ni-Mo oxide nanosheet arrays with enhanced electrochemical properties. The optimized Ni-Mo oxide nanosheets directly grown on Ni foam can deliver a high specific capacitance of 1189 F/g at a current density of 1 A/g, which is substantially higher than that of pure NiO nanosheets (191 F/g at 1 A/g). Moreover, the ternary Ni-Mo oxide nanosheets exhibit a good rate capability and remarkable long-term cycling stability (77.7%) over 5000 cycles at 5 A/g. Our work suggests that the resulting products prepared by this scalable and cost-effective fabrication process are very suitable and promising as advanced electrode materials for high-performance supercapacitors. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Ni-Mo oxide Nanosheet arrays Ni foam Supercapacitor

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A Novel Decomposition Analysis of Nonlinear Distortion in OFDM Transmitter Systems

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2015年第19期63卷 5264-5273页

作者： Lei Yiming O'Droma, Mairtin Peking Univ State Key Lab Adv Opt Commun Syst & Networks Beijing 100871 Peoples R China Peking Univ Beijing Key Lab Magnet Resonance Imaging Devices Beijing 100871 Peoples R China Univ Limerick Telecommun Res Ctr Limerick Ireland

In Orthogonal Frequency Division Multiplexing (OFDM) transmitter systems, nonlinear distortion is a major impairment caused by power amplifier (PA). The distortion is constituted by numerous noise-like inter-modulation products (IMPs). Although the overall behavior of nonlinear IMP distortion has been well studied, in large multi-carrier contexts, such as in OFDM, the knowledge of individual IMPs and their quantitative interrelationships, together with the derivation of behavioural knowledge and the predictability of consequences arising from such interrelationships, is a fairly unexplored topic. This is the subject of this paper. The powers of the very numerous individual IMPs generated are analytically derived based on a Bessel-Fourier PA behavioural model, and it is proven that these powers have only a small number of distinct powers. Proven also is that the ratios of these power values are constants, and that these constants are invariant with the particular PA's nonlinearity characteristics or operating point. Further, it is proven that specific types of IMPs dominate nonlinear distortion effects. Finally, it is shown that IMP power spectra can be derived from a simple product of two polynomials, which are quadrature functions of frequency and PA operating point, respectively. Application possibilities for findings presented in this paper, such as their potential to contribute efficiency improvements in OFDM system modulation fidelity calculations (over 1100 times faster than conventional methods), are also outlined in the conclusions.

关键词： Inter-modulation products nonlinear distortion OFDM power amplifier

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Influence of the deposition parameters on the properties of SnS2 films prepared by PECVD method combined with solid sources

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JOURNAL OF NANOPARTICLE RESEARCH 2014年第9期16卷 1-13页

作者： Wang, Shengming Wang, Shicai Chen, Junfeng Liu, Pei Chen, Ming Xiong, Hao Guo, Fu Liu, Minghai Huazhong Univ Sci & Technol Sch Elect & Elect Engn State Key Lab Adv Electromagnet Engn & Technol Wuhan 430074 Peoples R China Huazhong Univ Sci & Technol Sch Phys Wuhan 430074 Peoples R China

Hexagonal tin disulfide (SnS2) films were deposited by plasma-enhanced chemical vapor deposition (PECVD) method combined with solid sources, in which SnCl4 center dot 5H(2)O and Na2S2O3 were used as the tin and sulfur sources, respectively. Nano-sheet and nano-flower structure SnS2 films were obtained under different experimental conditions. The nano-sheet SnS2 films were built by irregular nanoplates with 400 +/- 100 nm in length and 10 nm in thickness. And the nano-flower SnS2 films consisted of uniform nano-flowers in size with the diameter being around 1 mu m. The influence of different substrates, the annealing treatment and the substrate temperature on the crystal structure, surface morphology, chemical composition, and optical properties of the SnS2 films were systemically discussed. The results show that the crystal structure and surface morphology have some differences in the films deposited on different substrates. After annealing treatment, the crystallinity of the SnS2 films increases, and at the same time, the internal stress reduces. However, there is no change in the stress direction. The surface morphology of the films turns into nano-flower from nano-sheet when the substrate temperature increases. The corresponding optical band gaps of the films are 2.68, 2.86, and 2.95 eV, which all show significant blue shift mainly due to the quantum confinement effect.

关键词： SnS2 PECVD Solid sources Nano-sheets Nano-flowers

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Preparation of Isotropic and Anisotropic Nanocrystalline NdFeB Magnets by High-Velocity Compaction and Hot Deformation

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IEEE TRANSACTIONS ON MAGNETICS 2015年第11期51卷

作者： Deng, X. X. Zhao, L. Z. Yu, H. Y. Liu, Z. W. Xiao, Z. Y. S China Univ Technol Sch Mat Sci & Engn Guangzhou 510640 Guangdong Peoples R China S China Univ Technol Sch Mech & Automot Engn Guangzhou 510640 Guangdong Peoples R China

NdFeB powders are consolidated into nanocrystalline bulk magnets by a near-net-shape process of high-velocity compaction (HVC) at room temperature with no binder employed. The magnets prepared under various conditions, including impact energy, filling weight, mold dimension, and plasticity and size of the starting powders, were investigated. The results showed that the density of as-compacted NdFeB magnets increased with the increasing impact energy and decreasing filling weight. The as-compacted magnets with relatively high density can inherit the coercivity and microstructure of the starting powders. The small flake powders with good plasticity and/or large mold diameter are beneficial to obtain high density. The relative green densities for the samples with low-Nd composition and high-Nd composition reach 92% and 87.5%, respectively. Using the HVCed magnet as the precursor, the anisotropic NdFeB magnets with enhanced magnetic properties have been prepared by hot deformation. This paper provides an alternative technique for preparing nanocrystalline NdFeB magnets.

关键词： Anisotropic high-velocity compaction (HVC) isotropic NdFeB magnets

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