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Magnetic Field Fluctuations in the Solar Wind, Foreshock and Magnetosheath:Cluster Data Analysis

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空间科学学报 2005年第5期25卷 368-373页

作者： J. Du C. Wang x. x. zhang N. N. Shevyre G. N. Zastenker Key Laboratory of Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing 100080 China Graduate School Chinese Academy of Sciences Space Research Institute Russian Academy of Sciences Moscow Russia

46 magnetosheath crossing events from the two years (2001.2-2003.1) of Cluster magnetic field measurements are identified and used to investigate the characters of the magnetic field fluctuations in the regions of undisturbed solar wind, foreshock, magnetosheath. The preliminary results indicate the properties of the plasma turbulence in the magnetosheath are strongly controlled by IMF orientation with respect to the bow shock normal. The amplitude of the magnetic field magnitude and direction variations behind quasiparallel bow shock are larger than those behind quasi-perpendicular bow shock. Almost purely compressional waves are found in quasi-perpendicular magnetosheath.

关键词：太阳风磁场磁鞘行星

Static and dynamic snap-through behaviour of an elastic spherical shell

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Acta Mechanica Sinica 2012年第3期28卷 695-710页

作者： D. Karagiozova x.-W. zhang T.-x. Yu Department of Mechanical Engineering Hong Kong University of Science and TechnologyClear Water Bay Kowloon Hong Kong China Institute of Mechanics Bulgarian Academy of SciencesAcad. G. Bonchev Street Block 4Sofia 1113 Bulgaria School of Mechantronical Engineering Beijing Institute of Technology100081 Beijing China

The deformation and snap-through behaviour of a thin-walled elastic spherical shell statically compressed on a flat surface or impacted against a fiat surface are studied the- oretically and numerically in order to estimate the influence of the dynamic effects on the response. A table tennis ball is considered as an ex.mple of a thin-walled elastic shell. It is shown that the increase of the impact velocity leads to a variation of the deformed shape thus resulting in larger de- formation energy. The increase of the contact force is caused by both the increased contribution of the inertia forces and contribution of the increased deformation energy. The contact force resulted from deformation/inertia of the ball and the shape of the deformed region are calcu- lated by the proposed theoretical models and compared with the results from both the finite element analysis and some previously obtained ex.erimental data. Good agreement is demonstrated.

关键词： Elastic spherical shell Snap-through buckling.Static Dynamic

A Three-Dimensional Asymmetric Magnetopause Model

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A Three-Dimensional Asymmetric Magnetopause Model

Limit of Spectral Resolution in Terahertz Time—Domain Spectroscopy

第27届中国气象学会年会空间天气自主资料应用与模式集成分会场

作者： R. L. Lin1,2 x. x. zhang3 S. Q. Liu1 Y. L. Wang4 J. C. Gong1 1Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing, China 2Graduate University of Chinese Academy of Sciences, Beijing, China 3 National Center for Space Weather, China Meteorological Administration, Beijing, China 4 NASA/Goddard Space Flight Center, Greenbelt, Maryland, USA

A new three-dimensional asymmetric magnetopause model has been developed for corrected GSM coordinates and parameterized by the solar wind dynamic and magnetic pressures (Pd+Pm), the interplanetary magnetic field (IMF) Bz, and the dipole tilt angle. Based on the magnetopause crossings from Geotail, IMP8, Interball, TC1, THEMIS, Wind, Cluster, Polar, LANL, GOES and Hawkeye, and the corresponding upstream solar wind parameters from ACE, Wind or OMNI, this model is constructed by the Levenberg-Marquardt method for nonlinear multi-parameter fitting step by step over the divided regions. The asymmetries of the magnetopause and the indentations near the cusps are appropriately described in this new model. In addition, the saturation effect of IMF Bz on the subsolar distance and the ex.rapolation for the distant tail magnetopause are also considered. Based on this model, the power law index.for the subsolar distance versus Pd+Pm is a bit less than -1/6, the northward IMF Bz almost does not influence the magnetopause, and the dipole tilt angle is very important to the north-south asymmetry and the location of indentations. In comparison with the previous empirical magnetopause models based on our database, the new model improves prediction capability to describe the three-dimensional structure of the magnetopause. It isshown that this new model can be used to quantitatively study how Pd+Pm compresses the magnetopause, how the southward IMF Bz erodes the magnetopause, and how the dipole tilt angle influences the north-south asymmetry and the indentations.

关键词： Magnetopause model magnetopause size and shape solar wind dynamic pressure interplanetary magnetic field Bz indentation

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cnki会议

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Chinese Physics Letters 2003年第8期20卷 1266-1268页

作者： Jingzhoux. TaoYuan SamuelMickan x.-C.zhang CenterforTHzResearch RensselaerPolytechnicInstituteTroyNY12180USA

The pulsed nature of terahertz time-domain spectroscopy (THz-TDS) sets a fundamental limit on its spectral resolution. The spectral resolution of THz-TDS can be improved by increasing the duration of the temporal measurement, but is limited by the dynamic range of the system in the time domain. This paper presents calculations and ex.erimental results relating the temporal dynamic range of a THz-TDS system to its spectral resolution. We discuss three typical terahertz sources in terms of their dynamic range and hence achievable spectral resolution.

关键词： Terahertz spectroscopy

Landing gear noise control using perforated fairings

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维普期刊数据库

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Acta Mechanica Sinica 2010年第2期26卷 159-174页

作者： K. Boorsma x. zhang N. Molin University of Southampton Southampton SO171BJ UK Airbus Operations S.A.S 316 Route de Bayonne 31060 Toulouse Cedex 03 France

Landing gears of commercial aircraft make an important contribution to total aircraft noise in the approach configuration. Using fairings to shield components from high speed impingement reduces noise. Furthermore, perforating these fairings has been confirmed by flight tests to further enable noise reduction. Following an earlier fundamental study of the application of perforated fairings, a study has been performed to investigate and optimize the benefits of bleeding air through landing gear fairings. By means of wind tunnel tests, an aerodynamic and acoustic survey has been performed on a simplified generic main landing gear to ex.lore the influence of （perforated） fairings on the lower part of the gear. The results show that for this specific case, the application of impermeable fairings reduces noise in the mid- and high frequency range by shielding sharp edged components from high velocity impingement. However, below 1 kHz the noise is shown to increase significantly. Application of the perforations is shown to diminish this low frequency increase whilst maintaining the reduction in the mid- and high frequency range. The aerodynamic and acoustic measurements point in the direction of the separated flow of the fairings interacting with the downstream gear components responsible for the low frequency noise increase. Bleeding of the air through the fairings reduces the large scale turbulence in the prox.mity of these components and hence diminishes the low frequency noise increase.

关键词： Landing gear · Aerodynamics · Acoustics

First-Principles Study of the Influence of Lattice Misfit on the Behavior and the Ductility Effect of Hafnium in Ni-Ni3AI System

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Acta Metallurgica Sinica(English Letters) 2014年第1期27卷 87-94页

作者： Y. Wu J. Guo W. zhang x. Ma Q. zhang J. Hou R. Huang x. Liu Institute of Molecular Engineering and Applied Chemistry Anhui University of Technology Ma'anshan 243002 China Shenyang National Laboratory for Materials Science Instituteof Metal Research Chinese Academy of SciencesShenyang 110016 China College of Physics Science and Technology Shenyang NormalUniversity Huanghe Street 253 Shengyang 110034 China School of Materials Science and Engineering Anhui Universityof Technology Ma'anshan 243002 China

Two Ni/Ni3Al-interface-contained cluster models with/without lattice misfit are studied by first-principles method to clarify the debates about the segregation behaviors of Hafnium （Hf） and ex.lore the influence of lattice misfit on the ductility effect of Hr. It is found that though Hf prefers to substitute A1 rather than Ni in Ni3A1 phase within most of the investigated misfit range, its stronger preferring to Ni phase than NiaA1 phase makes it impossible to go into Ni3A1 phase to occupy A1 site in Ni-Ni3A1 alloys. Bond order analysis in Hf-free case shows that lattice misfit has different effects on the Griffith work of interfacial cleavage 27int/E and the max.mum theoretical shear stress Zmax.of Ni and Ni3A1, contributing to the ex.stence of anomalous strength-temperature phenomena in NiaA1 alloys. However, the addition of Hf will make the 27int/E （or Zmax. of both Ni3A1 and Ni decrease （or increase） with lattice misfit, indicating that the addition of Hf may make the anomalous strength-temperature relationship in Ni3A1 region disappear locally.

关键词： Hafnium Lattice misfit Segregation Ductility

The Efficiency Analysis and A Market Decision Model on Equipment Maintenance

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Journal of Systems Engineering and Electronics 2001年第3期12卷 31-38页

作者： zhang, G. Cao, x. Wang, J. College of Economics and Management Guangdong University of Technology Guangzhou 510090 P. R. China

This paper presents and analyses the internal and ex.ernal efficiencies of equipment maintenance, and presents that the objective of maintenance is the max.mum ex.ernal efficiency. It defines generalized reliability degree of equipment and deduces the correspondent calculating method. It overcomes the defect that traditional calculating method of reliability degree has, which only considers the factor of time not function, therefore we establish a market decision model of equipment maintenance based on it. This model can determine the marginal efficiency of maintenance investment and critical value of generalized reliability degree when it reaches break-even point. After combining the equipment maintenance with economical benefit of enterprise and marketing situation of products, an optimal maintenance strategy will be got. It provides a new method for scientific and rational decisions of equipment maintenance.

关键词： Market decision model Equipment maintenance Generalized reliability degree.

MICROSTRUCTURE EVOLUTION AND MECHANICAL HARDENING OF HYPEREUTECTOID PEARLITIC STEEL DURING COLD ROLLING

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Acta Metallurgica Sinica(English Letters) 2007年第4期20卷 287-292页

作者： x. zhang C.x. Wang x.M. Liu Q.N. Shi Key Laboratory of Advanced Materials of Yunnan Province Kunming University of Science and Technology Kunming 650093 China Institute for Structural Materials Central Iron and Steel Research InstituteBeijing 100081 China

The microstructure evolution of different cold rolling reductions （from 0 to 81.6%） was studied by SEM （scanning electron microscopy） and TEM （transmission electron microscope）. The study showed that the orientation multiplicity of pearlitic lamellas resulted in inhomogeneous deformation of different pearlitic lamellas, and with the increase of reduction, the microstructure underwent a course of ＂homogeneity → inhomogeneity → homogeneity＂. The result of x.D （x.ray diffraction） analysis indicated that cementite did not decompose and dissolve into ferrite; the results of the mechanical property test suggested that the relationship between Rp0.2 （yield strength） and ε （true strain） was in good agreement with Hollomon relationship. With the equation Rp0.2 = 1465ε^0.18, the yield strength of the steel in different reductions could be well predicted.

关键词： cold rolling hypereutectoid pearlitic steel microstructure evolution mechanical hardening

Empirical models for predicting lateral spreading considering the effect of regional seismicity

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Earthquake Engineering and Engineering Vibration 2012年第1期11卷 121-131页

作者： zhang Jian Yang Changwei John x. Zhao Graeme H. Mcgerry Department of Civil Engineering Southwest Jiaotong University Chengdu 610031 China GNS Science Lower Hutt New Zealand

A revised empirical model has been developed for predicting liquefaction-induced lateral spreading displacement （LD） as a function of both response spectral acceleration derived from strong-motion attenuation models and geotechnical parameters from Youd＇s LD data set （Youd website）. This revised model is different from the model of zhang and Zhao, which overcame some drawbacks of earlier models for predicting lateral spreading and was primarily used in Japan and the western U.S. The revised model can potentially be applied anywhere if ground shaking （in terms of 5% damped acceleration or displacement response spectra） can be estimated using local strong-motion attenuation relationships. The revised model is ex.mined using data from Japan and the western U.S. and applied to Turkey and New Zealand, where the ground shaking is estimated using appropriate strong-motion attenuation relationships for each region. The accuracy of the revised model is evaluated by comparing its predicted lateral displacements with those measured in actual earthquakes. The results show that the revised model can account for the effects of local seismicity on lateral spreading displacements and is comparable with ex.sting prediction models.

关键词： lateral spreading liquefaction strong-motion attenuation