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41.
戴琪  金台  罗坤  樊建人 《推进技术》2018,39(10):2357-2362
为了探究驻定斜爆轰波的起爆条件以及来流马赫数和楔面角对斜爆轰波形态结构的共同影响,基于二维欧拉方程和单步化学反应模型,对驻定斜爆轰波进行数值模拟研究。结果发现,斜爆轰波的起爆和结构受到来流马赫数和楔面角的显著影响,来流马赫数越小,形成斜爆轰波的楔面角条件越苛刻。随着来流马赫数和楔面角增加,波后混合气体温度升高,爆轰反应变得更加剧烈,使得斜激波诱导区域变短,未反应气团减少,接触间断面更靠近楔面,下游出现的涡结构也减少。  相似文献   
42.
A recent set of light ion experiments are analyzed using the Green's function method of solving the Boltzmann equation for ions of high charge and energy (the GRNTRN transport code) and the NUCFRG2 fragmentation database generator code. Although the NUCFRG2 code reasonably represents the fragmentation of heavy ions, the effects of light ion fragmentation requires a more detailed nuclear model including shell structure and short range correlations appearing as tightly bound clusters in the light ion nucleus. The most recent NUCFRG2 code is augmented with a quasielastic alpha knockout model and semiempirical adjustments (up to 30 percent in charge removal) in the fragmentation process allowing reasonable agreement with the experiments to be obtained. A final resolution of the appropriate cross sections must await the full development of a coupled channel reaction model in which shell structure and clustering can be accurately evaluated.  相似文献   
43.
挤压油膜阻尼器支承的转子系统的非线性振动   总被引:2,自引:0,他引:2  
分析了一个3质量转子一阻尼器系统的非线性振动特性。该系统是由一个带对中弹簧的挤压油膜阻尼器支承的。研究表明,当不平衡或供油压力或挤压油膜阻尼器的静偏心比增大时.由于油膜力的非线性特性,将引起施加在系统上的阻尼增大。相应地,阻尼的这一增大引起了系统共振位置的大幅值漂移。在设计阶段,必须等虑这一因素以适当地选择参数。实验结果验证了分析结果。  相似文献   
44.
产品成本计算是企业管理的重要部分。论文从产品BOM概念与层次出发,分析了构成产品成本的各个生要要素,并结合具体实例,利用基于BOM的标准成本计算模型对产品进行成本计算。该模型通过成本分解,计算底层零部件的标准本,由下至上逐层滚动累加,最终得出产品的标准成本。  相似文献   
45.
航天项目资源效用提升方法思考   总被引:1,自引:0,他引:1  
文章根据价值工程的管理思想,以提升我国航天项目价值为最终目标,在航天系统工程技术和项目管理的基础上,从资源配置和使用角度对项目最优价值的实现过程进行了项目资源管理实践的总结,得出通过资源效用提升可以更好地实现项目价值的结论,较为系统地提出了航天项目资源效用提升的有效实施方法。  相似文献   
46.
Beyond the Earth's atmosphere, galactic cosmic radiation (GCR) and solar energetic particles (SEPs) are a significant hazard to both manned and robotic missions. For long human missions on the lunar surface (months to a year) a radiation shelter is needed for dose mitigation and emergency protection in case of solar events. This paper investigates the interaction of source protons of solar events like those of February 1956 that emitted many fewer particles with energies up to 1000 MeV and of the October 1989 event of lower protons energy but higher fluence, with the lunar regolith and aluminum shielding of a lunar shelter. The shelter is 5 m in diameter and has a footprint of 5×8 m and a 10 cm thick aluminum support structure, however, actual thickness could be much smaller (~1–2 cm) depending on the weight of the regolith shielding piled on top. The regolith is shown to be slightly more effective than aluminum. Thus, the current results are still applicable for a thinner aluminum structure and increased equivalent (or same mass) thickness of the regolith. The shielding thicknesses to reduce the dose solely due to solar protons in the lunar shelter below those recommended by NASA to astronauts for 30 day-operation in space (250 mSv) and for radiation workers (50 mSv) are determined and compared. The relative attenuation of incident solar protons with regolith shielding and the dose estimates inside the shelter are calculated for center seeking, planar, and isotropic incidence of the source protons. With the center seeking incidence, the dose estimates are the highest, followed by those with isotropic incidence, and the lowest are those with the planar incidence.  相似文献   
47.
THEMIS was launched on February 17, 2007 to determine the trigger and large-scale evolution of substorms. During the first seven months of the mission the five satellites coasted near their injection orbit to avoid differential precession in anticipation of orbit placement, which started in September 2007 and led to a commencement of the baseline mission in December 2007. During the coast phase the probes were put into a string-of-pearls configuration at 100 s of km to 2 RE along-track separations, which provided a unique view of the magnetosphere and enabled an unprecedented dataset in anticipation of the first tail season. In this paper we describe the first THEMIS substorm observations, captured during instrument commissioning on March 23, 2007. THEMIS measured the rapid expansion of the plasma sheet at a speed that is commensurate with the simultaneous expansion of the auroras on the ground. These are the first unequivocal observations of the rapid westward expansion process in space and on the ground. Aided by the remote sensing technique at energetic particle boundaries and combined with ancillary measurements and MHD simulations, they allow determination and mapping of space currents. These measurements show the power of the THEMIS instrumentation in the tail and the radiation belts. We also present THEMIS Flux Transfer Events (FTE) observations at the magnetopause, which demonstrate the importance of multi-point observations there and the quality of the THEMIS instrumentation in that region of space.  相似文献   
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