等参化FVDAM在复合材料湿热应力分析中的应用

在等参化有限元体积直接平均法（FVDAM）中引入等效湿胀系数,建立了复合材料湿热耦合的细观应力场分析模型。计算了湿热环境中不同纤维体积含量和湿含量复合材料的细观应力场。结果表明：湿热环境中复合材料界面径向应力最大值发生于纤维密集区的相邻纤维间的界面处,最小值出现在基体富区;初始吸湿对热残余应力有释放作用,最终吸湿的影响将超过热残余应力,界面应力状态也随之改变。计算所得细观应力场与有限元（FEM）法有较好的一致性。     

Attempt to identify a source mechanism of Mercury’s sodium exosphere by a spectrometer using Fabry–Perot etalon

The Mercury’s Sodium Atmosphere Spectral Imager (MSASI) on BepiColombo (BC) will address a range of fundamental scientific questions pertaining to Mercury’s exosphere. The measurements will provide new information on regolith–exosphere–magnetosphere coupling as well as new understanding of the dynamics governing the exosphere bounded by the planetary surface, the solar wind and interplanetary space. MSASI is a high-dispersion visible spectrometer working in the spectral range around sodium D2 emission (589 nm). A tandem Fabry–Perot etalon is used to achieve a compact design. We presents a design of the spectral analyzer using Fabry–Perot interferometer. We conclude that: (1) The MSASI optical design is practical and can be implemented without new or critical technology developments; (2) The thermally-tuned etalon design is based on concepts, designs and materials that have good space heritage.     

MESSENGER and the Chemistry of Mercury’s Surface

The instrument suite on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft is well suited to address several of Mercury’s outstanding geochemical problems. A combination of data from the Gamma-Ray and Neutron Spectrometer (GRNS) and X-Ray Spectrometer (XRS) instruments will yield the surface abundances of both volatile (K) and refractory (Al, Ca, and Th) elements, which will test the three competing hypotheses for the origin of Mercury’s high bulk metal fraction: aerodynamic drag in the early solar nebula, preferential vaporization of silicates, or giant impact. These same elements, with the addition of Mg, Si, and Fe, will put significant constraints on geochemical processes that have formed the crust and produced any later volcanism. The Neutron Spectrometer sensor on the GRNS instrument will yield estimates of the amount of H in surface materials and may ascertain if the permanently shadowed polar craters have a significant excess of H due to water ice. A comparison of the FeO content of olivine and pyroxene determined by the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) instrument with the total Fe determined through both GRNS and XRS will permit an estimate of the amount of Fe present in other forms, including metal and sulfides.     

Study of the ionosphere during a magnetospheric storm using data on the ground and in space

For the magnetospheric storm of May 14–16, 1997 geophysical data of satellites DMSP and IMP-8 are compared with data of radio propagation on the high-latitude HF radio path of Heiss Island – St. Petersburg and data from European ionosondes. Peculiarities of variations of the operational frequencies range MOF–LOF (maximum and lowest observed frequencies) on the path were considered. The range has been determined by the method of oblique ionospheric sounding (OIS). The latter is more informative for observations during a magnetic storm compared to the vertical sounding method. Nevertheless, an analysis of variations of the critical frequency of the ionospheric F2 layer from the chain of European ionosondes was carried out. For interpretation of results, data of magnetospheric parameters, AE-indexes and riometer data were used. The variations of both frequency range on the path and critical frequencies of the F2 layer through the ionosondes chain during the disturbed period had certain regularities of behaviour. These regularities are being explained from the physical point of view. The analysis of the satellite DMSP data has showed that a magnetospheric disturbance causes displacement equatorward of precipitation and some growth of its width and energy.     

刍议军人婚姻保护

经济、社会的发展和多元化,使军人婚姻和家庭稳定面对越来越多的现实挑战,这直接关系和影响到部队日常训练和作战能力.因此,加强和完善必要的法律和措施,切实保护军人在婚姻家庭方面的合法权益对于稳定部队、提升部队作战能力有着重要的现实意义.本文主要从军婚概念的界定、军婚现状及保护军婚的意义、措施方面入手,对这一问题进行分析和探...     

Lightning strike to helicopters during winter thunderstorms over North Sea

Southerly winds over the Shetland Islands produce a wave flux which, in winter time, triggers convective clouds over the Atlantic Ocean. The clouds get electrified and produce isolated lightning flashes. In an attempt to describe the atmospheric electrical configuration produced by this meteorological situation, Méso-NH, a meso-scale non-hydrostatic model that delivers a 3D description of the convective cell was run. A microphysical and dynamical 1.5D model was then applied to simulate the vertical electrification within the cell. From the electrification study, the attachment model of ONERA was used to compute the zones on helicopters from which the lightning discharge can develop.     

Robe's restricted problem of 2+2 bodies when the bigger primary is a Roche ellipsoid

In the problem of s="true">2s="true">+s="true">2" role="presentation" style="font-size: 90%; display: inline-block; position: relative;"><svg xmlns:xlink="http://www.w3.org/1999/xlink" width="5.165ex" height="2.086ex" viewBox="0 -747.2 2223.9 898.2" role="img" focusable="false" style="vertical-align: -0.351ex;" aria-hidden="true">stroke="currentColor" fill="currentColor" stroke-width="0" transform="matrix(1 0 0 -1 0 0)">s="true">se xlink:href="#MJMAIN-32">se>s="true" transform="translate(722,0)">se xlink:href="#MJMAIN-2B">se>s="true" transform="translate(1723,0)">se xlink:href="#MJMAIN-32">se>svg><script type="math/mml" id="MathJax-Element-1">script> bodies in Robe's setup, one of the primaries of mass m<sub>1sub> is a Roche ellipsoid filled with a homogeneous incompressible fluid of density sub is="true">s="true">s="true">&#x3C1;s="true">s="true">1sub>" role="presentation" style="font-size: 90%; display: inline-block; position: relative;"><svg xmlns:xlink="http://www.w3.org/1999/xlink" width="2.256ex" height="1.971ex" viewBox="0 -498.8 971.4 848.5" role="img" focusable="false" style="vertical-align: -0.812ex;" aria-hidden="true">stroke="currentColor" fill="currentColor" stroke-width="0" transform="matrix(1 0 0 -1 0 0)">s="true">s="true">s="true">se xlink:href="#MJMATHI-3C1">se>s="true" transform="translate(517,-253)">s="true">se transform="scale(0.707)" xlink:href="#MJMAIN-31">se>svg>s="true">s="true">s="true">ρs="true">s="true">1sub><script type="math/mml" id="MathJax-Element-2">s="true">s="true">s="true">ρs="true">s="true">1sub>script>. The smaller primary of mass m<sub>2sub> is a point mass outside the ellipsoid. The third and the fourth bodies (of mass m<sub>3sub> and m<sub>4sub>, respectively), supposed moving inside the ellipsoid, are small solid spheres of density sub is="true">s="true">s="true">&#x3C1;s="true">s="true">3sub>" role="presentation" style="font-size: 90%; display: inline-block; position: relative;"><svg xmlns:xlink="http://www.w3.org/1999/xlink" width="2.256ex" height="1.971ex" viewBox="0 -498.8 971.4 848.5" role="img" focusable="false" style="vertical-align: -0.812ex;" aria-hidden="true">stroke="currentColor" fill="currentColor" stroke-width="0" transform="matrix(1 0 0 -1 0 0)">s="true">s="true">s="true">se xlink:href="#MJMATHI-3C1">se>s="true" transform="translate(517,-253)">s="true">se transform="scale(0.707)" xlink:href="#MJMAIN-33">se>svg>s="true">s="true">s="true">ρs="true">s="true">3sub><script type="math/mml" id="MathJax-Element-3">s="true">s="true">s="true">ρs="true">s="true">3sub>script> and sub is="true">s="true">s="true">&#x3C1;s="true">s="true">4sub>" role="presentation" style="font-size: 90%; display: inline-block; position: relative;"><svg xmlns:xlink="http://www.w3.org/1999/xlink" width="2.256ex" height="1.971ex" viewBox="0 -498.8 971.4 848.5" role="img" focusable="false" style="vertical-align: -0.812ex;" aria-hidden="true">stroke="currentColor" fill="currentColor" stroke-width="0" transform="matrix(1 0 0 -1 0 0)">s="true">s="true">s="true">se xlink:href="#MJMATHI-3C1">se>s="true" transform="translate(517,-253)">s="true">se transform="scale(0.707)" xlink:href="#MJMAIN-34">se>svg>s="true">s="true">s="true">ρs="true">s="true">4sub><script type="math/mml" id="MathJax-Element-4">s="true">s="true">s="true">ρs="true">s="true">4sub>script>, respectively, with the assumption that the mass and the radius of the third and the fourth bodies are infinitesimal. We assume that m<sub>2sub> is describing a circle around m<sub>1sub>. The masses m<sub>3sub> and m<sub>4sub> mutually attract each other, do not influence the motions of m<sub>1sub> and m<sub>2sub> but are influenced by them. Robe's restricted three body problem is extended to s="true">2s="true">+s="true">2" role="presentation" style="font-size: 90%; display: inline-block; position: relative;"><svg xmlns:xlink="http://www.w3.org/1999/xlink" width="5.165ex" height="2.086ex" viewBox="0 -747.2 2223.9 898.2" role="img" focusable="false" style="vertical-align: -0.351ex;" aria-hidden="true">stroke="currentColor" fill="currentColor" stroke-width="0" transform="matrix(1 0 0 -1 0 0)">s="true">se xlink:href="#MJMAIN-32">se>s="true" transform="translate(722,0)">se xlink:href="#MJMAIN-2B">se>s="true" transform="translate(1723,0)">se xlink:href="#MJMAIN-32">se>svg><script type="math/mml" id="MathJax-Element-5">script> body problem under the assumption that the fluid body assumes the shape of the Roche ellipsoid (Chandrashekhar [2]). We take into consideration all the three components of the pressure field in deriving the expression for the buoyancy force viz (i) due to the own gravitational field of the fluid, (ii) that originating in the attraction of m<sub>2sub>, and (iii) that arising from the centrifugal force. In this paper, equilibrium solutions of m<sub>3sub> and m<sub>4sub> and their linear stability are analysed. We have proved that there exist only six equilibrium solutions of the system. In a system where the primaries are considered as earth–moon and sub is="true">s="true">s="true">ms="true">s="true">3sub>s="true">,sub is="true">s="true">s="true">ms="true">s="true">4sub>" role="presentation" style="font-size: 90%; display: inline-block; position: relative;"><svg xmlns:xlink="http://www.w3.org/1999/xlink" width="7.223ex" height="1.74ex" viewBox="0 -498.8 3110 749.2" role="img" focusable="false" style="vertical-align: -0.582ex;" aria-hidden="true">stroke="currentColor" fill="currentColor" stroke-width="0" transform="matrix(1 0 0 -1 0 0)">s="true">s="true">s="true">se xlink:href="#MJMATHI-6D">se>s="true" transform="translate(878,-150)">s="true">se transform="scale(0.707)" xlink:href="#MJMAIN-33">se>s="true" transform="translate(1332,0)">se xlink:href="#MJMAIN-2C">se>s="true" transform="translate(1777,0)">s="true">s="true">se xlink:href="#MJMATHI-6D">se>s="true" transform="translate(878,-150)">s="true">se transform="scale(0.707)" xlink:href="#MJMAIN-34">se>svg>s="true">s="true">s="true">ms="true">s="true">3sub>s="true">,sub is="true">s="true">s="true">ms="true">s="true">4sub><script type="math/mml" id="MathJax-Element-6">s="true">s="true">s="true">ms="true">s="true">3sub>s="true">,sub is="true">s="true">s="true">ms="true">s="true">4sub>script> as submarines, the equilibrium solutions thus obtained are unstable.     

四阶微分方程两点边值问题解的存在唯一性

讨论了非线性四阶常微分方程y（4）=f（x,y,y’,y”,y”’）在混合两点边值条件y’（a）=0,y”（a）＋y”（6）=0,y（b）=0,y”’（b）=0或y’（a）=0,y”＇（a）＋y＇”（b）=0,y（b）=0,y”（6）=0下,解的存在唯一性。其中f在[a,b]×R4上连续且满足Lipschitz条件。并在推广后的Lipschitz条件与Banach压缩映射原理基础上,得到一些新的存在唯一性结果。     

On the possibility of existence of an additional source of anomalous cosmic rays outside the solar system

On the basis of experimental data obtained at exposure of solid-state track detectors in the magnetosphere of the Earth during solar flares and in quiet Sun periods, an estimate of possible contribution of singly charged oxygen ions to the flare particle fluxes is made. A possibility is considered of the appearance in the vicinity of the solar system of singly ionized oxygen ions generated on stars.     

ZrO2陶瓷切向超声辅助磨削表面及亚表面损伤机制

为进一步揭示切向超声辅助磨削过程中硬脆材料的表面及亚表面损伤机理,基于应变率模型对其磨削过程中材料的动态力学性能进行分析,并在此基础上建立了硬脆材料的脆-塑转变临界切削深度模型与微裂纹损伤深度模型。研究发现,脆-塑转变临界切削深度和微裂纹损伤深度均与应变率有关,其中临界切削深度随着应变率的增加而增加,而横向裂纹损伤深度与中位裂纹损伤深度均随应变率的增加而减小。通过ZrO<sub>2sub>陶瓷切向超声辅助磨削试验进行验证。试验结果表明：由于切向超声振动的引入提高了材料应变率,进而提高了材料的动态断裂应力以及动态断裂韧性,从而扩大了ZrO<sub>2sub>陶瓷的塑性域去除范围,降低了加工表面的横向裂纹与中位裂纹损伤深度,使得ZrO<sub>2sub>陶瓷的表面及亚表面质量得到明显改善。试验结果与理论分析相一致,为进一步揭示切向超声辅助磨削过程中硬脆材料的表面及亚表面微观损伤机理提供了理论参考。