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磁暴期间环电流离子中性原子成像的模拟与观测比较研究

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空间科学学报 2012年第2期32卷 182-190页

作者：陈志青沈超路立 s.mckenna-lawlor 刘振兴燕广庆中国科学院空间科学与应用研究中心空间天气学国家重点实验室北京100190 中国科学院研究生院北京100049 space Technology Ireland National University of IrelandMaynoothCounty KildareIreland

采用已经建立的环电流离子解析模型,结合Chamberlain地冕中性层模型,研究了2004年11月一次大磁暴期间的环电流区域中性原子(ENA)图像.结果表明,模拟的ENA图像与TC-2卫星搭载的中性原子成像仪(NUAUD)的观测图像在方位角或地方时分布、高... 详细信息

采用已经建立的环电流离子解析模型,结合Chamberlain地冕中性层模型,研究了2004年11月一次大磁暴期间的环电流区域中性原子(ENA)图像.结果表明,模拟的ENA图像与TC-2卫星搭载的中性原子成像仪(NUAUD)的观测图像在方位角或地方时分布、高度或纬度分布和能谱分布方面存在一定的差异.如果依据磁暴发展的不同阶段来选择环电流离子模型的方位角不对称因子和通量最大方向的方位角,增大地冕中性层在低高度区域的密度或者考虑氢(H)以外的其他中性成分,改进注入边界处的离子能谱分布函数,且考虑不同种类环电流离子的比例随磁暴发展可能发生的变化,该模型有望产生更符合观测的模拟ENA图像.

关键词：环电流中性原子成像磁暴环电流模拟地冕中性层

Ring current injections associated with eastward gradient-B drift at high latitudes during a major storm on 15 May, 2005 Running title: A possible ring current injection path

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Ring current injections associated with eastward gradient-B ...

TC-2/中性原子成像仪观测到等离子体片纵向振荡

第十四届全国日地空间物理学术研讨会

作者： s.mckenna-lawlor s.Barabash K.Kudela J.Balaz G.D.Reeves space Technology Ireland National University of Ireland Maynooth Co.Kildare Ireland swedish Institute of space Physics Kiruna Sweden

A complete record is available in ENA data of ring current activity recorded by the NUADU instrument aboard TC-2 on 15 May, 2005 during a major magnetic storm (including a substorm that occurred in the recovery phase) (. Comparisons of the ion fluxes derived from ENA data in the energy ranges 50-81 keV and 81-158 keV with in situ particle fluxes measured by the LANL-sOPA instruments aboard LANL-01, LANL-02, LANL-97 and LANL-84 (a series of geosynchronous satellites that encircle the equatorial plane at 6.6 RE near the outer radiation belt) are presented. It is shown that ion injections into the ring current began from the dayside. During the storm the pressure of the solar wind compressed the magnetopause Earthward so that ions spiraling around magnetic field lines in the magnetosphere were energized on the dayside and flowed poleward along the magnetic field lines. It was deduced that energetic ions could drift eastward into the night side from the dusk side along the magnetic field gradient beyond Bz stward flowing ring current (ERC) in the polar regions. During the rising phase of the ring current, the ERC acted to restrain the growth of the accompanying negative sYM-H index, even causing it to reduce. This effect provides a diagnostic signature of the ERC. During the recovery phase of the storm the magnetosphere on the dayside expanded anti-Earthward, and those energetic ions collected in the dusk-night sector during the main phase of the storm were impelled at low latitudes (Bz > 0) under the westward gradient-B drift to pass through the dusk side to the dayside.

关键词： Energetic neutral atoms Ring current Energetic particles magnetic field gradient drift

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科学通报 2007年第5期52卷 502-506页

作者：路立 s.mckenna-lawlor s.Barabash 刘振兴曹晋滨 J.Balaz K.Kudela T.L.Zhang C.M.Carr 中国科学院空间科学与应用研究中心北京100080 space Technology Ireland National University of Ireland Maynooth Co. Kildare Ireland swedish Institute of space Physics Kiruna Sweden Institute of Experimental Physics Kosice Slovakia space Research Institute Austrian Academy of Sciences Graz Austria Imperial College of science London United Kingdom

2005年8月24日磁暴期间(Dst=-219nT),TC-2卫星上的中性原子成像仪(NUADU)观测到了绕近地等离子体片区磁力线作螺旋运动的全空间4π立体角离子通量分布.在TC-2卫星历时34min的多次穿越等离子体片过程中,多个能量离子束事件均具有绕磁力... 详细信息

2005年8月24日磁暴期间(Dst=-219nT),TC-2卫星上的中性原子成像仪(NUADU)观测到了绕近地等离子体片区磁力线作螺旋运动的全空间4π立体角离子通量分布.在TC-2卫星历时34min的多次穿越等离子体片过程中,多个能量离子束事件均具有绕磁力线呈现两个对称环状离子通量分布特征.在每一次穿越等离子体片过程中低频波探测器(LFEW/TC-2)都探测到了频率略高于低混杂波摸的哨声波摸合声的增强.比较离子投掷角分布与磁场,我们发现场向能量离子通量增强总伴随有等离子体片磁力线的尾向拉伸;垂直磁力线方向的能量离子通量增强却伴随有等离子体片磁力线的地向压缩,并出现总磁场强度的峰值.由于平行和垂直磁力线的离子通量增强是间歇性地交替出现,探测数据揭示了一种近地等离子体片磁力线的纵向振荡(磁力线的尾向拉伸和地向收缩)过程,这有助于在近地等离子体片区域形成离子与场的相互作用区,从而触发磁暴期间的连续极光亚暴.

关键词：近地等离子体片投掷角分布能量离子通量哨声波摸合声

Acetabular cup size trends in total hip arthroplasty

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World Journal of Orthopedics 2024年第1期15卷 39-44页

作者： Daniel Patrick mckenna Alex Price Timothy McAleese Darren Dahly Paul mckenna May Cleary Department of Trauma and Orthopaedics University Hospital WaterfordWaterford X91 ER8EIreland Department of Epidemiology and Public Health University College CorkCork T12 XF62Ireland

BACKGROUND Total hip arthroplasty(THA)is a common procedure for end stage *** learning curve for THA is complex and *** of the most difficult skills to master is acetabular *** wish to identify if experience in arthroplasty leads to preservation of more bone *** To investigate if increasing surgeon experience will predict an ever decreasing acetabular cup *** A retrospective case series of four attending orthopaedic surgeons was *** uncemented elective total hip arthroplasties since appointment were selected for *** size of acetabular cup used was noted and logistic regression was used to identify if a trend to smaller cups *** A total of 1614 subjects were included with a mean age of 64 *** cups were on average 0.18mm smaller per year(95%confidence interval-0.25 to-0.11,Psurgeon trends showed cup sizes to decrease 0.27 mm/year for surgeon A,0.02 mm/year for surgeon B,0.15 mm/year for surgeon C and 0.29 mm/year for surgeon *** of the four surgeons had a more pronounced trend to smaller cups for male subjects than their female *** We found increasing surgeon experience to be associated with an ever-decreasing acetabular cup *** acetabular cup size may act as a surrogate marker of surgical proficiency by virtue of decreased acetabular reaming.

关键词： Hip Arthroplasty Acetabulum Cup Learning

Optimizing laser coupling,matter heating,and particle acceleration from solids using multiplexed ultraintense lasers

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Matter and Radiation at Extremes 2024年第4期9卷 16-28页

作者： Weipeng Yao Motoaki Nakatsutsumi sébastien Buffechoux Patrizio Antici Marco Borghesi Andrea Ciardi sophia N.Chen Emmanuel d’Humières Laurent Gremillet Robert Heathcote Vojtech Horny Paul mckenna Mark N.Quinn Lorenzo Romagnani Ryan Royle Gianluca sarri Yasuhiko sentoku Hans-Peter schlenvoigt Toma Toncian Olivier Tresca Laura Vassura Oswald Willi Julien Fuchs LULI-CNRs CEASorbonne UniversitéEcole PolytechniqueInstitut Polytechnique de ParisF-91128 Palaiseau CedexFrance sorbonne Université Observatoire de ParisUniversité PSLCNRSLERMAF-75005 ParisFrance INRs-EMT 1650 BoulLionel-BouletVarennesQuebec J3X 1S2Canada Center for Plasma Physics School of Mathematics and PhysicsQueen’s University BelfastBelfast BT71NNUnited Kingdom “Horia Hulubei”National Institute for Physics and Nuclear Engineering 30 Reactorului StreetRO-077125 Bucharest-MagureleRomania University of Bordeaux Centre Lasers Intenses et ApplicationsCNRSCEAUMR 5107F-33405 TalenceFrance CEA DAMDIFF-91297 ArpajonFrance Université Paris-saclay CEALMCE91680 Bruyères-le-ChatelFrance Central Laser Facility STFC Rutherford Appleton LaboratoryDidcotUnited Kingdom sUPA Department of PhysicsUniversity of StrathclydeGlasgow G40NGUnited Kingdom Department of Physics University of NevadaRenoNevada 89557USA Institute of Laser Engineering Osaka University2-6 YamadaokaSuitaOsaka 565-0871Japan Institut fur Laser und Plasmaphysik Heinrich Heine Universitat DusseldorfDusseldorfGermany

Realizing the full potential of ultrahigh-intensity lasers for particle and radiation generation will require multi-beam arrangements due to technology ***,we investigate how to optimize their coupling with solid ***,we show that overlapping two intense lasers in a mirror-like configuration onto a solid with a large preplasma can greatly improve the generation of hot electrons at the target front and ion acceleration at the target *** underlying mechanisms are analyzed through multidimensional particle-in-cell simulations,revealing that the self-induced magnetic fields driven by the two laser beams at the target front are susceptible to reconnection,which is one possible mechanism to boost electron *** addition,the resistive magnetic field generated during the transport of the hot electrons in the target bulk tends to improve their *** simulations also indicate that such effects can be further enhanced by overlapping more than two laser beams.

关键词： laser acceleration particle

Effect of Eu3+,Bi3+,and Li+ doping on luminescent property of GdNbO4

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Journal of Rare Earths 2024年第1期42卷 66-75页

作者： s.W.Wi Y.s.Lee Department of Physics and Integrative Institute of Basic sciences Soongsil University

We investigated the emission properties of Eu3+-doped GdNbO4-based oxide phosphors,aiming at improving the Eu3+emission by codoping of Bi3+and Li+.Eu3+singly doped,Eu3+and Bi3+doubly doped,and Eu3+,Bi3+,and Li+triply doped GdNbO4were prepared using a high-temperature solid-state reaction *** red-orange emissions from Eu3+in the singly doped samples are significantly improved by the codoping of Bi3+,mainly due to the energy transfer from Bi3+to Eu3+.The additional codoping of Li+is found to increase the Eu3+emission *** improvement might be attributed to the increase in the photoluminescent quantum yield originating from larger grain sizes and better crystallinity.A detailed analysis of the X-ray diffraction pattern and the asymmetric ratio estimated from the photoluminescence spectra show that the local lattice environment around Eu3+in GdNbO4does not change significantly with the codoping of Bi3+and Li+.Our results indicate that Li+doping is a promising way to improve the emission properties of rare-earth ion-doped GdNbO4phosphors.

关键词： Eu 3+ GdNbO 4 Codoping of Li + Photoluminescence sensitizer Rare earths

First evidence for chiral wobbling of triaxial nuclei

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Nuclear science and Techniques 2024年第7期35卷 4-7页

作者： s.Frauendorf Department of Physics and Astronomy University of Notre DameNotre DameIN 46556USA

Chirality(Greek“handiness”)is a property of many com-plex *** molecules exist in two forms,one being the mirror image of the *** for our hands,it is impossible to make the images identical by a suitable *** two forms are called left-handed and *** have the same binding energy,because the electro-magnetic interaction,which holds the molecule together,does not change under a *** properties that are insensitive to the geometry are also the *** different geometry is the reason why the left-handed form turns the polarization plane of transmitted light in one direction by some angle while the right-handed form turns it in the oppo-site direction by the same ***,the geometrical differences between the two species may have other *** two species of the carvon molecule shown in Fig.1 taste quite differently.

关键词： turns Chiral mirror

Tribological behavior of lubricant-impregnated porous polyimide

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Friction 2024年第4期12卷 711-725页

作者： Jinbang LI Ningning ZHOU Janet s.s.WONG school of Mechanical Engineering and Mechanics Ningbo UniversityNingbo 315211China Beijing Key Laboratory of Long-life Technology of Precise Rotation and Transmission Mechanisms Beijing Institute of Control EngineeringBeijing 100029China Department of Mechanical Engineering Imperial College LondonLondon SW72AZUK

Porous materials impregnated with lubricants can be used in conditions where limited lubricant is *** this work,three porous polyimides(PPI)with different densities were ***(PAO)impregnated PPI(iPPI)discs were rubbed against steel and sapphire *** operando observations of the iPPI-sapphire contacts show that oil is released under an applied load,forming a meniscus around *** at the outlet is created at high sliding *** amount of released oil increases with increasing PPI *** moduli,E*,estimated based on the actual contact size show that trapped oil in iPPIs contributes to load *** higher speeds,tribological rehydration of the contact occurs in low density iPPI,with that E*rises with *** high density PPIs,high speeds give a constantly high E*which is limited by the viscoelastic properties of the PPI network and possibly the rate of oil *** of iPPI-steel contacts is governed by the mechanical properties of the PPI,the flow of the lubricant,and the roughness of the PPI *** low-and medium-density(highly porous,high roughness)PPIs,large amount of oil is released,and lubrication is mainly via lubricant restricted in the contact in the pores and possibly tribological *** high density(low porosity)PPI,with lower roughness,hydrodynamic lubrication is achieved which gives the lowest *** results show that polymeric porous materials for effective lubrication require the optimization of its surface roughness,stiffness,oil flow,and oil retentions.

关键词： polyimide porous material friction mechanism polymer limited lubrication

Enhancing fatigue performance of AZ31 magnesium alloy components fabricated by cold metal transfer-based wire arc directed energy deposition through LPB

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Journal of Magnesium and Alloys 2024年第4期12卷 1638-1662页

作者： shambhu Kumar Manjhi srikanth Bontha A.s.s.Balan Department of Mechanical Engineering National Institute of Technology KarnatakaSurathkalSrinivasanagarMangaloreKarnataka 575025India

Cold Metal Transfer-Based Wire Arc Directed Energy Deposition(CMT-WA-DED)presents a promising avenue for the rapid fabrication of components crucial to automotive,shipbuilding,and aerospace ***,the susceptibility to fatigue of CMT-WA-DED-produced AZ31 Mg alloy components has impeded their widespread adoption for critical load-bearing *** this study,a comprehensive investigation into the fatigue behaviour of WA-DED-fabricated AZ31 Mg alloy has been carried out and compared to commercially available wrought AZ31 *** findings indicate that the as-deposited parts exhibit a lower fatigue life than wrought Mg alloy,primarily due to poor surface finish,tensile residual stress,porosity,and coarse grain microstructure inherent in the WA-DED *** Plasticity Burnishing(LPB)treatment is applied to mitigate these issues,which induce significant plastic deformation on the *** treatment resulted in a remarkable improvement of fatigue life by 42%,accompanied by a reduction in surface roughness,grain refinement and enhancement of compressive residual stress ***,during cyclic deformation,WA-DED specimens exhibited higher plasticity and dislocation density compared to both wrought and WA-DED+LPB specimens.A higher fraction of Low Angle Grain Boundaries(LAGBs)in WA-DED specimens contributed to multiple crack initiation sites and convoluted crack paths,ultimately leading to premature *** contrast,wrought and WA-DED+LPB specimens displayed a higher percentage of High Angle Grain Boundaries(HAGBs),which hindered dislocation movement and resulted in fewer crack initiation sites and less complex crack paths,thereby extending fatigue *** findings underscore the effectiveness of LPB as a post-processing technique to enhance the fatigue performance of WA-DED-fabricated AZ31 Mg alloy *** study highlights the importance of LPB surface treatment on AZ31 Mg components produced by CMT-WA-DED to remove surface d

关键词： Wire arc additive manufacturing AZ31 Mg alloy Low plasticity burnishing Low cycle fatigue test strain amplitude