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The variation in the magnetic fluctuation anisotropy across the front boundaries of magnetic clouds and its geomagnetic response

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Chinese Science Bulletin 2002年第10期47卷 863-867页

作者： LIU Rui & WEI FengsiDepartment of Geophysics, Peking University, Beijing 100871, China lab for space Weather, Center for space Science and Applied Research, Chinese Academy of Sciences, Beijing 100080, China Department of Geophysics Peking University Beijing China lab for space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing China

A statistical study of magnetic fluctuations near the front boundaries of magnetic clouds is approached with the method of Minimum Variance Analysis, based on the data of ImpS and Wind spacecraft. New discoveries are that (1) fluctuation anisotropy tends to increase across the front boundaries of magnetic clouds; (2) there is a good correlation between the fluctuation anisotropy and the geomagnetic activity indices; and (3) in some cases, although there is southward field component immediately after the front boundary, Kp index descends (or Dst index ascends) with a corresponding decrease of the fluctuation anisotropy; in other cases with no distinct southward field component, Kp index ascends (or Dst index descends) with a corresponding increase of the fluctuation anisotropy. Thus we suggest that the fluctuation anisotropy might be a useful indicator in diagnosing the magnetic activities of magnetic clouds.

关键词： front boundary of magnetic clouds geomagnetic activity fluctuation anisotropy.

Effects of Staged Injection on Supersonic Mixing and Combustion

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Chinese Journal of Aeronautics 2011年第5期24卷 584-589页

作者： HOU Lingyun Bernhard WEIGAND Marius BANICA School of Aerospace Tsinghua University Beijing 100084 China lnstitut fiir Thermodynamik der Lufi- and Raumfahrt （ITLR） Universitaet Stuttgart Stuttgart 70569 Germany TEB42 Liquid propulsion Systems EADS Astrium Space Transportation Les MureauxCedex 78133 France

The three-dimensional （3D） reacting flow in a staged supersonic combustor is examined numerically. In order to obtain the optimum stream-wise vortices, a swept ramp injector is chosen as the second-stage wall injection combined with the first-stage central strut injection. The performance of the two-staged injection is compared with that of a one-staged injection, while the strut is kept installed in both cases. The two-staged injections can make full use of the residual oxygen near the wall and release more heat. The second-stage injection further downstream avoids the strong shock waves in the isolator and results in a rising wall pressure and good burning effects after the wall injection. Therefore, it allows more fuel to be injected into the supersonic combustor without causing thermal choking. Parallel injection from the second-stage swept ramp shows low total pressure loss and the best burning efficiency, compared with the other injection angles.

关键词： supersonic mixing stream-wise vortices staged injection swept ramp combustion

Thermoviscoelastic Modeling Approach for Predicting the Recovery Behaviors of Thermally Activated Amorphous Shape Memory Polymers

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Transactions of Nanjing University of Aeronautics and Astronautics 2019年第5期36卷 798-807页

作者： GU Jianping FANG Changqing SUN Huiyu ZHANG Xiaopeng Jiangsu Key laboratory of advanced Structural Materials and Application Technology School of Materials Science and EngineeringNanjing Institute of TechnologyNanjing 211167P.R.China Shanghai space propulsion Technology Research Institute Shanghai 201109P.R.China State Key laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016P.R.China

A thermoviscoelastic modeling approach is developed to predict the recovery behaviors of the thermally activated amorphous shape memory polymers(SMPs)based on the generalized finite deformation viscoelasticity *** this paper,a series of moduli and relaxation times of the generalized Maxwell model is estimated from the stress relaxation master curve by using the nonlinear regression(NLREG)*** that the amorphous SMPs are approximately incompressible isotropic elastomers in the rubbery state,the hyperelastic response of the materials is well modeled with a hyperelastic model in Ogden *** addition,the Williams-Landel-Ferry(WLF)equation is used to describe the horizontal shift factor obtained with time-temperature superposition principle(TTSP).The finite element simulations show good agreement with the experimental thermomechanical ***,the possibility of developing a temperature-responsive intravascular stent with the SMP studied here is investigated in terms of its thermomechanical ***,it can be concluded that the model has good prediction capabilities for the recovery behaviors of amorphous SMPs.

关键词： shape memory polymers(SMPs) thermoviscoelastic modeling approach finite deformation recovery behavior

Sample selection for models to represent ceramic cores fabricated by stereolithography three-dimensional printing

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Journal of Materials Science & Technology 2022年第26期121卷 117-123页

作者： X.L.An J.J.Liang J.G.Li J.W.Chen Y.Z.Zhou X.F.Sun School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China Shi-changxu Innovation Center for advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China space Manufacturing Technology(CAS Key lab) Beijing 100094China

Ceramic cores with good chemical stability and moderate mechanical properties near casting temperatures of 1550℃ for example are used for the manufacturing of internal structures of hollow blades,requiring complex structures and high precision[1–3].However,traditional preparation method based on investment casting is tedious,requiring not only long production cycles but also high cost[4].

关键词： investment printing ceramic

Ship recognition based on HRRP via multi-scale sparse preserving method

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Journal of Systems Engineering and Electronics 2024年第3期35卷 599-608页

作者： YANG Xueling ZHANG Gong SONG Hu College of Electronic and Information Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China Key lab of Radar Imaging and Microwave Photonics Ministry of EducationNanjing 210016China Nanjing Marine Radar Institute Nanjing 210016China

In order to extract the richer feature information of ship targets from sea clutter, and address the high dimensional data problem, a method termed as multi-scale fusion kernel sparse preserving projection(MSFKSPP) based on the maximum margin criterion(MMC) is proposed for recognizing the class of ship targets utilizing the high-resolution range profile(HRRP). Multi-scale fusion is introduced to capture the local and detailed information in small-scale features, and the global and contour information in large-scale features, offering help to extract the edge information from sea clutter and further improving the target recognition accuracy. The proposed method can maximally preserve the multi-scale fusion sparse of data and maximize the class separability in the reduced dimensionality by reproducing kernel Hilbert space. Experimental results on the measured radar data show that the proposed method can effectively extract the features of ship target from sea clutter, further reduce the feature dimensionality, and improve target recognition performance.

关键词： ship target recognition high-resolution range profile(HRRP) multi-scale fusion kernel sparse preserving projection(MSFKSPP) feature extraction dimensionality reduction

Dry sliding wear behavior of Ti-6Al-4V alloy in air

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Journal of Harbin Institute of Technology(New Series) 2002年第1期9卷 67-71页

作者：刘勇杨德庄武万良杨士勤 space Materials and Environment Engineering lab Harbin Institute of Technology Harbin 150001 China

The dry sliding wear properties of Ti-6Al-4V alloy sliding against GCr15 steel under different velocities(between 0.2 and 1.2 m/s)and applied loads(from 30 to 90 N)were tested using a pin on disk tester in air. The wear occurred on both surfaces of the tested couplings. The wear rate of the Ti-6Al-4V alloy ranged from 23.0 to 123.8 mg/km. The wear of Ti-6Al-4V samples was in severe wear. The wear rate of Ti-6Al-4V samples increased with the increasing of load and shows a minimum on the curves of wear rate versus sliding velocity. SEM morphologies of worn surfaces and debris were observed. Phases in the debris were analyzed by means of XRD spectra.

关键词： titanium alloy dry sliding wear oxidization delamination

Single self-leading suture technique for iridodialysis repairment

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International Journal of Ophthalmology(English edition) 2024年第9期17卷 1752-1754页

作者： Jing-Wen Hui Quan-Hong Han Yong Tang Ying Wang Tianjin Eye Hospital Tianjin 300020China Tianjin Key lab of Ophthalmology and Visual Science Tianjin 300020China Clinical College of Ophthalmology Tianjin Medical UniversityTianjin 300020China

Dear Editor,We described an innovative“single self-leading suture technique”for repairing *** of moving the needle forth and back,our method is easier to manipulate in the narrow surgical space between the cornea and lens,which will decrease the unnecessary complications related to iatrogenic *** provide an economical friendly and less time-taking method,which improves the suture accuracy.

关键词： dialysis needle suture

Determination of space Group Pncm of Prehnite Using Electron Diffraction Method

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Journal of Wuhan University of Technology(Materials Science) 2002年第4期17卷 17-20页

作者：赵文俞 State Key lab of advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan China

space symmetry of prehnite, which occurs in cavities and veins within Skarn from the Tieshan iron mineral deposit,Daye,Hubei province,Central China,has been determined using selected area electron diffraction (SAED) and convergent-beam electron diffraction (CBED) on the submicrometer *** results confirm that the natural prehnite may have the structure with symmetry *** unit-cell parameters of investigated prehnite (a=0.458nm,b=0.555nm,and c=1.853nm) have been calculated by using the multicrystal diffraction rings of gold,the internal standard.

关键词： prehnite Pncm selected area electron diffraction convergent-beam electron diffraction

Cluster of solar active regions and onset of coronal mass ejections

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Science China(Physics,Mechanics & Astronomy) 2015年第9期58卷 95-102页

作者： WANG JingXiu ZHANG YuZong HE Han CHEN AnQin JIN ChunLan ZHOU GuiPing Key lab of Solar Activity National Astronomical Observatories Chinese Academy of Sciences National Center for space Weather China Meteorological Administration

round-the-clock solar observations with full-disk coverage of vector magnetograms and multi-wavelength images demonstrate that solar active regions(ARs) are ultimately connected with magnetic field. Often two or more ARs are clustered, creating a favorable magnetic environment for the onset of coronal mass ejections(CMEs). In this work, we describe a new type of magnetic complex: cluster of solar ARs. An AR cluster is referred to as the close connection of two or more ARs which are located in nearly the same latitude and a narrow span of longitude. We illustrate three examples of AR clusters, each of which has two ARs connected and formed a common dome of magnetic flux system. They are clusters of NOAA(i.e., National Oceanic and Atmospheric Administration) ARs 11226 & 11227, 11429 & 11430, and 11525 & 11524. In these AR clusters, CME initiations were often tied to the instability of the magnetic structures connecting two partner ARs, in the form of inter-connecting loops and/or channeling filaments between the two ARs. We show the evidence that, at least, some of the flare/CMEs in an AR cluster are not a phenomenon of a single AR, but the result of magnetic interaction in the whole AR cluster. The observations shed new light on understanding the mechanism(s) of solar activity. Instead of the simple bipolar topology as suggested by the so-called standard flare model, a multi-bipolar magnetic topology is more common to host the violent solar activity in solar atmosphere.

关键词： activity coronal mass ejection magnetic fields