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11.
对1978年8月27至28日期间观测到的磁云与尾随高速流的相互作用进行数值模拟,基本拟合了1AU处的观测剖面。模拟结果表明,磁云-高速流系统将导致前向快,慢激波和后向快激波的形成。  相似文献   
12.
一种紧固孔细节原始疲劳质量评定方法   总被引:1,自引:1,他引:1  
 给出了一种由等幅载荷试验的断口金相数据反推得到的当量初始裂纹尺寸额定值(EIFSR)表征的紧固孔原始疲劳质量评定方法。并据此建立了原始疲劳质量符合性检查的EIF-SR判据和寿命判据。最后用上述判据对紧固孔细节进行了原始疲劳质量评定和符合性检查。  相似文献   
13.
采用遗传算法 ,对某机横航向操纵系统进行了等效系统拟配计算 ,并对遗传算法中控制参数和变量初始区间的设定进行了分析。结果表明 ,遗传算法在等效拟配计算中有效可用 ,并且在保证算法收敛和拟配结果合理方面有很强的优势。  相似文献   
14.
航空制件超声检测中的声场特性分析   总被引:2,自引:0,他引:2  
 针对航空制件超声检测中影响缺陷定量准确性的声场问题进行了深入讨论, 研究了脉冲波声场的计算方法, 设计了相应的计算软件并绘制出实用换能器声轴线上的声压分布曲线, 分析了不同材料和厚度的采样回波对频谱的影响, 比较了连续波声场和脉冲波声场的分布特性及异同点。研究结果为提高超声检测中缺陷定量的准确性和科学性提供了依据。  相似文献   
15.
结合数值Riemann不变量和通量限制器(FluxLimiter)的概念,将基于Chakravarthy和Osher半离散差分格式的等价差分格式应用于三维复杂流场计算,应用时间相关法和全流场捕捉技术,获得了Ma=10,a=10°状态下球头绕流结果,壁面压力分布与Rusanov的计算结果相符合,在此基础上细致地刻画了在Ma=7,a=20°状态下绕流带座能飞船的复杂流场。  相似文献   
16.
Eruptive prominences as sources of magnetic clouds in the solar wind   总被引:2,自引:0,他引:2  
Large amounts of coronal material are propelled outward into interplanetary space by Coronal Mass Ejections (CMEs). Thus one might expect to find evidence for expanding flux ropes in the solar wind as well. To prove this assumption magnetic clouds were analyzed and correlated with H-observations of disappearing filaments. When clouds were found to be directly associated with a disappearing filament, the magnetic structure of the cloud was compared with that of the associated filament. Additionally the expansion of magnetic clouds was examined over a wide range of the heliosphere and compared with the expansion observed for erupting prominences.  相似文献   
17.
大型挠性充液卫星的动力学模型   总被引:2,自引:0,他引:2  
研究了带有多个挠性附件和液体燃料贮箱的中继卫星系统的动力学建模问题。给出了微重力下小幅线性晃动等效模型基本参数,用混合坐标法描述中继卫星系统的构形,利用虚功原理推导出的矩阵形式的中继卫星动力学模型简洁且具有一般性,适用于许多开链飞行器系统。  相似文献   
18.
We review recent observations by the Yohkoh-SXT in collaboration with other spacecraft and ground-based observatories of coronal loops and prominences. These new results point to problems that SoHO will be able to address. With a unique combination of rapid-cadence digital imaging (32 s full-disk and 2 s partial-frame images), high spatial resolution (2.5 arcsec pixels), high sensitivity (EM 1042 cm–3), a low-scatter mirror, and large dynamic range, SXT can observe a vast range of targets on the Sun. Over the first 21 months of Yohkoh operations, SXT has taken over one million images of the corona and so is building up an invaluable long-term database on the large-scale corona and loop geometry. The most striking thing about the SXT images is the range of loop sizes and shapes. The active regions are a bright tangle of magnetic field lines, surrounded by a network of large-scale quiet-Sun loops stretching over distances in excess of 105 km. The cross-section of most loops seems to be constant. Loops displaying significant increase in the ratio of the footpoint to loop-top diameter () are the exception, not the rule, implying the presence of widespread currents in the corona.All magnetic structures show changes. Time scales range from seconds to months. The question of how these structures are formed, become filled with hot plasma, and are maintained is still open. While we see the propagation of brightenings along the length of active-region loops and in X-ray jets with velocities of several hundred km/s, much higher velocities are seen in the quiet Sun. In XBP flares, for example, velocities of over 1000 km/s are common. Active-region loops seem to be in constant motion, moving slowly outward, carrying plasma with them. During flares, loops often produce localized brightenings at the base and later at the apex of the loop. Quiescent filaments and prominences have been observed regularly. Their coronal manifestation seems to be an extended arcade of loops overlying the filament. Reliable alignment of the ground-based data with the X-ray images make it possible to make a detailed intercomparison of the hot and cold plasma structures over extended periods. Hence we are able to follow the long-term evolution of these structures and see how they become destabilized and erupt.  相似文献   
19.
Coronal mass ejections (CMEs) observed near the Sun via LASCO coronographic imaging are the most important solar drivers of geomagnetic storms. ICMEs, their interplanetary, near-Earth counterparts, can be detected in situ, for example, by the Wind and ACE spacecraft. An ICME usually exhibits a complex structure that very often includes a magnetic cloud (MC). They can be commonly modelled as magnetic flux ropes and there is observational evidence to expect that the orientation of a halo CME elongation corresponds to the orientation of the flux rope. In this study, we compare orientations of elongated CME halos and the corresponding MCs, measured by Wind and ACE spacecraft. We characterize the MC structures by using the Grad–Shafranov reconstruction technique and three MC fitting methods to obtain their axis directions. The CME tilt angles and MC fitted axis angles were compared without taking into account handedness of the underlying flux rope field and the polarity of its axial field. We report that for about 64% of CME–MC events, we found a good correspondence between the orientation angles implying that for the majority of interplanetary ejecta their orientations do not change significantly (less than 45 deg rotation) while travelling from the Sun to the near-Earth environment.  相似文献   
20.
为提高铯束管跃迁信号强度,在束光学参数设计中,用蒙特卡罗方法模拟计算铯原子通过率和未跃迁比例。通过改变模拟计算中的束光学参数,分析铯原子通过率、未跃迁比例和倍增器首极电流的变化趋势,得到了主要束光学参数的合理取值范围。在铯束管实际装配和试验中使用束光学参数设计结果,有效地增加了倍增器首极电流。  相似文献   
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