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31.
介绍了光时域反射仪检定装置的测量不确定度评定方法,此方法适用于建立计量标准的测量不确定度评定. 相似文献
32.
We present preliminary results from high resolution observations obtained with the Michelson Doppler Imager (MDI) instrument
on the SOHO of two large solar flares of 14 July 2000 and 24 November 2000. We show that rapid variations of the line-of-sight
magnetic field occured on a time scale of a few minutes during the flare explosions. The reversibility/irreversibility of
the magnetic field of both active regions is a very good tool for understanding how the magnetic energy is released in these
flares. The observed sharp increase of the magnetic energy density at the time of maximum of the solar flare could involve
an unknown component which deposited supplementary energy into the system.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
33.
张德荣 《沈阳航空工业学院学报》2005,22(3):65-69
太阳和木星的自转是不均匀的,纬度愈高,自转愈慢。据此,作者推测液态外地核的自转,也存在类似的不均匀性,而这种不均匀自转将对地壳板块运动产生影响。利用磁流体力学理论,阐明这类星球自转的不均匀性,是磁制动的不均匀性引起的。研究了磁制动对地壳板块运动影响的途径及表现方式,并举出实例证明这些表现方式的确存在,从而证明磁制动是影响地壳板块运动的一个极为重要的因素。 相似文献
34.
Alexeev Igor I. Belenkaya Elena S. Bobrovnikov Sergey Yu. Kalegaev Vladimir V. 《Space Science Reviews》2003,107(1-2):7-26
A magnetohydrodynamic model of the solar wind flow is constructed using a kinematic approach. It is shown that a phenomenological
conductivity of the solar wind plasma plays a key role in the forming of the interplanetary magnetic field (IMF) component
normal to the ecliptic plane. This component is mostly important for the magnetospheric dynamics which is controlled by the
solar wind electric field. A simple analytical solution for the problem of the solar wind flow past the magnetosphere is presented.
In this approach the magnetopause and the Earth's bow shock are approximated by the paraboloids of revolution. Superposition
of the effects of the bulk solar wind plasma motion and the magnetic field diffusion results in an incomplete screening of
the IMF by the magnetopause. It is shown that the normal to the magnetopause component of the solar wind magnetic field and
the tangential component of the electric field penetrated into the magnetosphere are determined by the quarter square of the
magnetic Reynolds number. In final, a dynamic model of the magnetospheric magnetic field is constructed. This model can describe
the magnetosphere in the course of the severe magnetic storm. The conditions under which the magnetospheric magnetic flux
structure is unstable and can drive the magnetospheric substorm are discussed. The model calculations are compared with the
observational data for September 24–26, 1998 magnetic storm (Dst
min=−205 nT) and substorm occurred at 02:30 UT on January 10, 1997.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
35.
A. G. Yahnin I. V. Despirak A. A. Lubchich B. V. Kozelov N. P. Dmitrieva M. A. Shukhtina H. K Biernat 《Space Science Reviews》2006,122(1-4):97-106
Although the auroral substorm has been long regarded as a manifestation of the magnetospheric substorm, a direct relation
of active auroras to certain magnetospheric processes is still debatable. To investigate the relationship, we combine the
data of the UV imager onboard the Polar satellite with plasma and magnetic field measurements by the Geotail spacecraft. The
poleward edge of the auroral bulge, as determined from the images obtained at the LHBL passband, is found to be conjugated
with the region where the oppositely directed fast plasma flows observed in the near-Earth plasma sheet during substorms are
generated. We conclude that the auroras forming the bulge are due to the near-Earth reconnection process. This implies that
the magnetic flux through the auroral bulge is equal to the flux dissipated in the magnetotail during the substorm. Comparison
of the magnetic flux through the auroral bulge with the magnetic flux accumulated in the tail lobe during the growth phase
shows that these parameters have the comparable values. This is a clear evidence of the loading–unloading scheme of substorm
development. It is shown that the area of the auroral bulge developing during substorm is proportional to the total (magnetic
plus plasma) pressure decrease in the magnetotail. These findings stress the importance of auroral bulge observations for
monitoring of substorm intensity in terms of the magnetic flux and energy dissipation. 相似文献
36.
37.
盘算尖响函数综合技术导出了用耦合频响函数和无有效载荷的运载火箭界面加速度响应表示的有效载荷/运载火箭耦合动力分析的频域方法,给出了以自由界面的运载火箭模态分数放自由界面或固定界面有效载荷模态参数构成的耦合频响函数表达式。 相似文献
38.
五自由度磁悬磨头电控系统研究 总被引:1,自引:0,他引:1
研究的高速磨床电磁悬浮磨头电控系统尽量采用最新技术,在保证系统 性能的前提下降低了系统造价。在该系统中采用TMS320F240 DSP芯片作为控制核心,同时控制磁悬浮轴承的悬浮和变频电机调速,采用运行效率很高的汇编语言编写控制软件,其中磁悬浮轴承是PID控制算法,电机调速为SPWM方式。磁悬浮轴承PWM功率放大器中采用能简化驱动的新型半桥电路,电机调速主电路中采用智能功率模块(IPM)。动态刚度测试和高速运转实验表明,该电控系统满足高速磨床电磁悬浮磨头的控制要求。 相似文献
39.
磁性磨料磁力研磨是近年发展起来的一种高效率、高质量的抛光方法,能够加工复杂外形工件和各种内壁、内腔表面,具有加工装置易于控制、工作环境清洁、加工成本低等优点,具有广阔的应用前景。本文设计、制造了加工装置并进行了一系列的试验,在研磨过程各主要参数对研磨的影响作了研究。试验结果表明,研磨初期加工效率较高,但随着研磨时间的延长,研磨效率降低,研磨质量提高不多;工件转速越高,研磨效率越高,而对研磨质量则没有影响;研磨存在最佳的加工间隙与电流强度值,在此条件下,研磨效率高,研磨质量也较好。本文最后对加工机理作了理论分析,认为磁极的设计与制造研磨能力好、磁性强的磁性磨料是非常重要的。 相似文献
40.