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Lateral magnetic stiffness under different parameters in a high-temperature superconductor levitation system

Chinese Physics B 2021年第7期30卷 515-525页

作者： Yong yang Yun-Yi Wu School of Mechano-Electronic Engineering Xidian UniversityXi'an 710071China China Three Gorges Science and Technology Research Institute Beijing 100036China Physikalisches Institute B RWTH AachenAachen 52056Germany

Magnetic stiffness determines the stability of a high-temperature superconductor(HTS)magnetic levitation *** quantitative properties of the physical and geometrical parameters that affect the stiffness of HTS levitation systems should be identified for improving the stiffness by some effective *** magnetic stiffness is directly related to the first-order derivative of the magnetic force with respect to the corresponding displacement,which indicates that the effects of the parameters on the stiffness should be different from the relationships between the forces and the same *** this paper,we study the influences of some physical and geometrical parameters,including the strength of the external magnetic field(B0)produced by a rectangular permanent magnet(PM),critical current density(Jc),the PM-to-HTS area ratio(α),and thickness ratio(β),on the lateral stiffness by using a numerical approach under zero-field cooling(ZFC)and field cooling(FC)*** the first and second passes of the PM,the lateral stiffness at most of lateral positions essentially increases with B0 increasing and decreases withβincreasing in ZFC and *** largest lateral stiffness at every lateral position is almost produced by the minimum value of Jc,which is obviously different from the lateral force–Jc ***α-dependent lateral stiffness changes with some parameters,which include the cooling conditions of the bulk HTS,lateral displacement,and movement history of the *** findings can provide some suggestions for improving the lateral stiffness of the HTS levitation system.

关键词： high-temperature superconductor magnetic levitation lateral stiffness lateral force

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Nanoparticles assembly-induced special wettability for bio-inspired materials

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Particuology 2013年第4期11卷 361-370页

作者： Shuai yang Xu Jin Kesong Liu Leijiang Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of the Ministry of Education School of Chemistry and EnvironmentBeihang University Research Institute of Petroleum Exploration and Development Beijing National Laboratory for Molecular Sciences(BNLMS) Key Laboratory of Organic SolidsInstitute of ChemistryChinese Academy of Sciences

Through billions of years of evolution, nature has optimized the programmed assembly of the nano- and micro-scale structures of biological materials. Nanoparticle assembly provides an avenue for mimick- ing these multiscale functional structures. Bio-inspired surfaces with special wettability have attracted much attention for both fundamental research and practical applications. In this review, we focus on recent progress in nanoparticle assembly-induced special wettability, including superhydrophilic surfaces, superhydrophobic surfaces, superamphiphobic surfaces, stimuli-responsive surfaces, and self- healing surfaces. A brief summary and an outlook of the future of this research field are also provided.

关键词： Nanoparticle assemblyBio-inspired materialsWettabilitySurface

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Two exact first-order k-space formulations for low-rank viscoacoustic wave propagation on staggered grids

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Petroleum Science 2023年第3期20卷 1521-1531页

作者： Hong-Yu Zhou yang Liu Jing Wang China Universityof Petroleum(Bejing) State Key Laboratory of Petroleum Resources and Prospecting and CNPC Key Laboratory of Geophysical ProspectingBeijing102249China China University of Petroleum(Bejing) Karamay CampusKaramayXinjiang834000China

Wave propagation in the viscoacoustic media is physically dispersive and *** excluding the numerical dispersion error from the physical dispersion in the viscoacoustic wave simu-lation is indispensable to understanding the intrinsic property of the wave propagation in attenuated media for the petroleum exploration *** recent years,a viscoacoustic wave equation char-acterized by fractional Laplacian gains wide attention in geophysical ***,the first-order form of the viscoacoustic wave equation,often solved by the conventional staggered-grid pseu-dospectral method,suffers from the numerical dispersion error in time due to the low-order finite-difference *** is challenging to completely eliminate the error because the viscoacoustic wave equation contains two temporal derivatives,which stem from the time stepping and the amplitude attenuation terms,*** tackle the issue,we derive two exact first-order k-space viscoacoustic formulations that can fully exclude the numerical error from the physical *** the homoge-neous case,two formulations agree with the viscoacoustic analytical solution very well and have the same *** the heterogeneous case,our second k-space formulation is more efficient than the first one because the second formulation significantly reduces the number of the wavenumber-space mixed-domain operators,which are the expensive part of the viscoacoustic k-space ***-merical cases validate that the two first-order k-space formulations are effective and efficient alternatives to the current staggered-grid pseudospectral formulation for the viscoacoustic wave simulation.

关键词： Viscoacoustic K-space Staggered-grid Low-rank

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Oilfield analogy and productivity prediction based on machine learning: Field cases in PL oilfield, China

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Petroleum Science 2024年第4期21卷 2554-2570页

作者： Wen-Peng Bai Shi-Qing Cheng Xin-yang Guo yang Wang Qiao Guo Chao-Dong Tan State Key Laboratory of Petroleum Resources and Engineering China University of Petroleum(Beijing)Beijing102249China

In the early time of oilfield development, insufficient production data and unclear understanding of oil production presented a challenge to reservoir engineers in devising effective development plans. To address this challenge, this study proposes a method using data mining technology to search for similar oil fields and predict well productivity. A query system of 135 analogy parameters is established based on geological and reservoir engineering research, and the weight values of these parameters are calculated using a data algorithm to establish an analogy system. The fuzzy matter-element algorithm is then used to calculate the similarity between oil fields, with fields having similarity greater than 70% identified as similar oil fields. Using similar oil fields as sample data, 8 important factors affecting well productivity are identified using the Pearson coefficient and mean decrease impurity(MDI) method. To establish productivity prediction models, linear regression(LR), random forest regression(RF), support vector regression(SVR), backpropagation(BP), extreme gradient boosting(XGBoost), and light gradient boosting machine(Light GBM) algorithms are used. Their performance is evaluated using the coefficient of determination(R^(2)), explained variance score(EV), mean squared error(MSE), and mean absolute error(MAE) metrics. The Light GBM model is selected to predict the productivity of 30 wells in the PL field with an average error of only 6.31%, which significantly improves the accuracy of the productivity prediction and meets the application requirements in the field. Finally, a software platform integrating data query,oil field analogy, productivity prediction, and knowledge base is established to identify patterns in massive reservoir development data and provide valuable technical references for new reservoir development.

关键词： Data mining technique Analogy parameters Oilfield analogy Productivity prediction Software platform

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Risk Analysis in Action

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Biomedical and Environmental Sciences 2001年第1期14卷 30-31页

作者： KYU-HWAN yang Commissioner KoreaFoodandDrugAdministration

Risk analysis is a useful tool for making good decisions on the risks of certain potentially hazardous agents and suggests a safe margin through scientific processes using toxicological data , contaminant residue levels , statistical tools , exposure values and relevant variants. Risk managers consider scientific evidence and risk estimates , along with statutory , engineering , economic , social , and political factors , in evaluating alternative regulatory options and choosing among those options (NRC , 1983)

关键词： analysis making good decisions hazardous

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Tailoring Optical and Plasmon Resonances in Core-shell and Core-multishell Nanowires for Visible Range Negative Refraction and Plasmonic Light Harvesting:A Review

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Journal of Materials Science & Technology 2015年第6期31卷 533-541页

作者： Sarath Ramadurgam Tzu-Ging Lin Chen yang Department of Physics and Astronomy Purdue University Department of Chemistry Purdue University

Semiconductor nanowires(NWs) are sub-wavelength structures which exhibit strong optical(Mie)resonances in the visible *** addition to such optical resonances,the localized surface plasmon resonances(LSPRs) in metal-semiconductor core-shell(CS) and core-multishell(CMS) NWs can be tailored to achieve novel negative-index metamaterials(N1M),extreme absorbers,invisibility cloaks and ***,in this review,we focus on our recent theoretical studies which highlight the versatility of CS and CMS NWs for:1) the design of negative-index metamaterials in the visible range and2) plasmonic light harvesting in ultrathin photocatalyst layers for water *** the LSPR in the metal layer and the magnetic dipole(Mie) resonance in the semiconductor shell under transverse electric(TE) polarization,semiconductor-metal-semiconductor CMS NWs can be designed to exhibit spectrally overlapping electric and magnetic resonances in the visible *** exhibiting such double resonances can be considered as meta-atoms and arrayed to form polarization dependent,low-loss ***,by tuning the LSPR in the TE polarization and the optical resonance in the transverse magnetic(TM) polarization of metal-photocatalyst CS and semiconductor-metal-photocatalyst CMS NWs,the absorption within ultrathin(sub-50 nm) photocatalyst layers can be substantially ***,aluminum and copper based NWs provide absorption enhancement remarkably close to silver and gold based NWs,***,such absorption is polarization independent and remains high over a large range of incidence angles and permittivity of the ***,due to the tunability of their optical properties,CS and CMS NWs are expected to be vital components for the design of nanophotonic devices.

关键词： Nanowires Core-shell Core-multishell Negative refr

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Electrochemical DNA nano-biosensor for the detection of genotoxins in water samples

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Chinese Chemical Letters 2014年第1期25卷 29-34页

作者： Hong-Bo Xu Ran-Feng Ye Shang-Yue yang Rui Li Xu yang Wuhan No.11 High School Lab of Environmental Biomedicine Central China Normal University

In the present study, a disposable electrochemical DNA nano-biosensor is proposed for the rapid detection of genotoxic compounds and bio-analysis of water pollution. The DNA nano-biosensor is prepared by immobilizing DNA on Au nanoparticles and a self-assembled monolayer of cysteamine modified Au electrode. The assembly processes of cysteamine, Au nanoparticles and DNA were characterized by cyclic voltammetry （CV）. The Au nanoparticles enhanced DNA immobilization resulting in an increased guanine signal. The interaction of the analyte with the immobilized DNA was measured through the variation of the electrochemical signal of guanine by square wave voltammetry （SWV）. The biosensor was able to detect the known genotoxic compounds： 2-anthramine, acridine orange and 2- naphthylamine with detection limits of 2, 3 and 50 nmol/L, respectively. The biosensor was also used to test actual water samples to evaluate the contamination level. Additionally, the comparison of results from the classical genotoxiciw bioassay has confirmed the applicability of the method for real samoles.

关键词： Electrochemical DNA biosensor Au nanoparticles Genotoxic detection DNA damage

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A study on flow fields and performance of water wheel turbine using experimental and numerical analyses

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Science China(Technological Sciences) 2018年第3期61卷 464-474页

作者： NGUYEN Manh Hung JEONG Haechang yang Changjo Graduate School Division of Marine Engineering Mokpo National Maritime University Department of Marine Engineering Mokpo National Maritime University

In this paper, an analysis of the performance and flow fields of water wheel turbines for tidal energy extraction is carried out using experimental and numerical methods. The purpose of this work is to develop a water turbine suitable for sites, where fast and shallow surface flows are available, such as rivers or tidal currents. For both methods, the water wheel turbine is tested over a range of tip speed ratios with a differing number of rotor blades, ranging between three and twelve. The results indicate that the numerical simulation shows agreement with the experiment in most cases. Also, the water wheel turbine operates effectively at a range of small tip-speed ratios, where the highest turbine efficiency is produced. Under the same working conditions, the turbines using between six and nine blades generate a greater efficiency and cause lesser reverse flows than others when submerged in water. In contrast, the 3-bladed turbine is the least efficient design as it produces the lowest amount of energy and causes intense vibrations and noises. These noises are a result of a collision between the incoming flow of the channel and the wheel blades during the experimentation, especially at high load conditions. By adding more blades, the torque generated is improved considerably; however, the upstream and downstream depths of the turbine, in this case, are also elevated ***, in the inlet region, the 3-bladed and 6-bladed turbines have a smaller shock loss and a lower resistance to the main flow from the inlet than the others. Meanwhile, it is found that the flow in the outlet region on the turbines with between nine and twelve blades is in the opposite direction to the wheel's rotation, significantly obstructing the main flow from the inlet.

关键词： water wheel tidal energy tip speed ratio the number of blades

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秋季巴伦支海海温异常对冬季我国渤海冰情的可能影响

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海洋学报 2016年第3期38卷 40-48页

作者：周群魏立新黄焕卿国家海洋环境预报中心北京100081

本文利用美国NCEP/NCAR逐月的再分析资料、HadISST海温、中国160台站气温和反映渤海冰情轻重的渤海冰情等级资料,研究了前秋巴伦支海海温异常对后期渤海冰情和东亚冬季风的影响,并对相关的物理过程进行分析。结果表明,前秋巴伦支海关键... 详细信息

本文利用美国NCEP/NCAR逐月的再分析资料、HadISST海温、中国160台站气温和反映渤海冰情轻重的渤海冰情等级资料,研究了前秋巴伦支海海温异常对后期渤海冰情和东亚冬季风的影响,并对相关的物理过程进行分析。结果表明,前秋巴伦支海关键区海温与该区域海冰密集度呈显著的负相关,且具有较好的持续性,通过调节随后冬季向大气释放的热通量,引起后期环流变化。偏高(偏低)年冬季亚洲纬向环流偏弱(偏强),东亚大槽加深(减弱),东亚冬季风加强(减弱),我国东北、华北及西北地区地区显著偏冷(偏暖),这与冬季渤海海冰异常的强度和范围都偏大(小)及与之相联系的环流异常相一致。进一步的分析揭示了联系上游关键区海温变化与后期东亚地区气候异常的重要途径,前秋巴伦支海海温偏高会导致200hPa高度场形成一个自西向东的波列形式,在东亚局地Hadley环流异常的作用下,加强了我国北方地区地表的北风异常。因此,前秋巴伦支海海温异常可以作为冬季渤海冰情的预报因子。

关键词：海温异常渤海海冰大气环流异常短期气候预测

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Investigating the co-evolution of massive black holes in dual active galactic nuclei and their host galaxies via galaxy merger simulations

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Science China(Physics,Mechanics & Astronomy) 2019年第12期62卷 96-109页

作者： Chao yang JunQiang Ge You Jun Lu National Astronomical Observatories Chinese Academy of SciencesBeijing 100012China School of Astronomy and Space Sciences University of Chinese Academy of SciencesBeijing 100049China CAS Key Laboratory for Computational Astrophysics National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100012China

Major galaxy mergers can trigger nuclear activities and are responsible for high-luminosity quasi-stellar objects/active galactic nuclei(QSOs/AGNs). In certain circumstances, such mergers may cause dual active galactic nuclei(dAGN) phenomenon. This study investigates dAGN triggering and evolution of massive black holes(MBHs) during the merging processes using hydrodynamic code GADGET-2 to simulate several gas-rich major mergers at redshift z = 2 and 3, respectively. Results reveal that gas-rich major mergers can trigger significant nuclear activities after the second and third pericentric passages and the formation of dAGN with significant time duration(~10-390 Myr). During the merging processes, galactic bulge evolves with time because of the rapid star formation in each(or both) galactic centers and initial mixing of stars in galactic disks due to violent *** grow substantially due to accretion and finally merge into a bigger black hole. The growth of galactic bulges and corresponding increases of its velocity dispersions predate the growth of MBHs in the d AGN stages. The MBHs in these stages deviate below the relation between MBH mass and bulge mass(or velocity dispersion), and they revert to the relation after the final mergers due to the significant accretion that occurs mostly at a separation less than a few kpc. Then, the two MBHs merge with each other.

关键词： galaxies quasars black hole numerical simulations

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