含激波的湍流流动高精度大涡数值模拟方法

针对采用亚格子模型进行含激波的湍流流动模拟时会面临激波附近的精度损失问题,考虑从通过亚格子模型以及数值模拟方法两方面的改进来实现湍流流动大涡模拟的精度提高.大涡模拟采用了Yee及Sj(o)green (2009)提出的高阶低耗散方法.该方法采用自适应的流场探测器以控制计算中所需区域的数值耗散,并考虑对动力学模型采用在激波位置使用Sagaut和Germano(2005)提出的单边亚格子过滤器和(或)直接禁用亚格子项等方法加以改进.对于标准的马赫数1.5和3条件下的激波-湍流干扰问题,上述新方法相较于全区域采用亚格子模型的方法均表现出了相似的精度提升.同时实现的数值精度改进方案采用了Harten的亚单元分辨过程来定位和锐化激波,并在精确激波位置附近的网格点处采用了单边测试滤波.     

Modelling of galactic Carbon in an asymmetrical heliosphere: Effects of asymmetrical modulation conditions

Observations of galactic cosmic rays (GCRs) from the two Voyager spacecraft inside the heliosheath indicate significant differences between them, suggesting that in addition to a possible global asymmetry in the north–south dimensions (meridional plane) of the heliosphere, it is also possible that different modulation (turbulence) conditions could exist between the two hemispheres of the heliosphere. We focus on illustrating the effects on GCR Carbon of asymmetrical modulation conditions combined with a heliosheath thickness that has a significant dependence on heliolatitude. To reflect different modulation conditions between the two heliospheric hemispheres in our numerical model, the enhancement of both polar and radial perpendicular diffusion off the ecliptic plane is assumed to differ from heliographic pole to pole. The computed radial GCR intensities at polar angles of 55° (approximating the Voyager 1 direction) and 125° (approximating the Voyager 2 direction) are compared at different energies and for both particle drift cycles. This is done in the context of illustrating how different values of the enhancement of both polar and radial perpendicular diffusion between the two hemispheres contribute to causing differences in radial intensities during solar minimum and moderate maximum conditions. We find that in the A > 0 cycle these differences between 55° and 125° change both quantitatively and qualitatively for the assumed asymmetrical modulation condition as reflected by polar diffusion, while in the A < 0 cycle, minute quantitative differences are obtained. However, when both polar and radial perpendicular diffusion have significant latitude dependences, major differences in radial intensities between the two polar angles are obtained in both polarity cycles. Furthermore, significant differences in radial intensity gradients obtained in the heliosheath at lower energies may suggest that the solar wind turbulence at and beyond the solar wind termination shock must have a larger latitudinal dependence.     

Comparison of ionosphere characteristic parameters obtained by ionosonde with IRI-2007 model over Southeast Asia

In this work, the foF2 and hmF2 parameters at the conjugate points near the magnetic equator of Southeast Asia are studied and compared with the International Reference Ionosphere (IRI) model. Three ionosondes are installed nearly along the magnetic meridian of 100°E; one at the magnetic equator, namely Chumphon (10.72°N, 99.37°E, dip angle 3.0°N), and the other two at the magnetic conjugate points, namely Chiang Mai (18.76°N, 98.93°E, dip angle 12.7°N) and Kototabang (0.2°S, 100.30°E, dip angle 10.1°S). The monthly hourly medians of the foF2 and hmF2 parameters are calculated and compared with the predictions obtained from the IRI-2007 model from January 2004 to February 2007. Our results show that: the variations of foF2 and hmF2 predicted by the IRI-2007 model generally show the similar feature to the observed data. Both parameters generally show better agreement with the IRI predictions during daytime than during nighttime. For foF2, most of the results show that the IRI model overestimates the observed foF2 at the magnetic equator (Chumphon), underestimates at the northern crest (Chiang Mai) and is close to the measured ones at the southern crest of the EIA (Kototabang). For hmF2, the predicted hmF2 values are close to the hmF2(M3000F2_OBS) during daytime. During nighttime, the IRI model gives the underestimation at the magnetic equator and the overestimation at both EIA crests. The results are important for the future improvements of the IRI model for foF2 and hmF2 over Southeast Asia region.     

飞行器新型碳基复合材料表面高温测量方法

本文针对飞行器新型碳基复合材料表面的高温测量问题,介绍了测量方法、传感器的安装方式、高温胶黏剂技术与工艺,传感器与热防护技术以及试验测试,并归纳了该方法的技术特点。     

改善高频宽压控晶振频率温度稳定性方法

高频宽压控晶体振荡器广泛应用于各种接收机和应答机中,工作温度范围通常为-40℃～+85℃。对于该类晶振,极易出现频率温度稳定性相对于其内部石英谐振器明显恶化的现象。对此,从理论上分析了引起恶化的原因,并提出通过合理控制振荡电路的压控范围和石英谐振器的激励功率,可以改善高频宽压控晶振的温频特性。最后,研制并测试了4只102.3MHz压控晶振,结果优于指标要求,充分验证了方法的有效性。     

A 3NM-64_He added to LARC for Solar Extreme Event studies during solar cycle 24

The Antarctic Laboratory for Cosmic Rays (LARC, acronym for Laboratorio Antartico per i Raggi Cosmici or Laboratorio Antártico para Rayos Cósmicos) operates on King George Island (South Shetlands). Since January 1991 a standard 6NM-64 detector has been recording continuous cosmic ray measurements and several Ground-Level Enhancements have been registered. Here we describe the different phases performed in Italy for the realization of a 3NM-64_³He detector, which started its measurements during the Italian XXII Antarctic Summer Campaign. Data recorded during solar activity cycle 24 will furnish an useful research tool for the next Solar Extreme Events.     

倾斜轨道小卫星太阳高度角分析与机动方案设计

针对倾斜轨道小卫星必然会面对的光学姿态敏感器受阳光干扰的问题,分析太阳高度角的变化规律,提出了计算太阳高度角的经验公式,并在此基础上提出了平台偏航姿态机动方案,可以使光学姿态敏感器规避阳光干扰,并可以简化整星热控和帆板驱动设计,提高了整星的可靠性.     

面向智能环境的活动模式迁移学习

针对智能环境中活动模式的学习和挖掘花销大、难以实际操作等问题,提出了能够有效地将已有活动模式迁移到新环境的整体框架。迁移学习框架将活动模式的迁移过程分解为轨迹的迁移和触发持续时间的迁移,首先对已有活动模式中的活动轨迹以及触发持续时间模糊化;然后采用备选轨迹生成(ATSG)算法在新环境中生成备选轨迹集;最后采用相似度计算(SC)算法进行活动模式中的轨迹与备选轨迹间的匹配,利用活动轨迹映射(TM)算法和触发持续时间迁移(TDT)算法对活动信息进行迁移,从而在新环境中得到活动模式。理论分析和实验结果表明,相比于基于频繁模式挖掘得到活动模式的方法,本文方法大幅度地降低了得到活动模式所需的时间开销,同时,利用本文方法获取的活动模式取得了较好的活动识别效果。      

高温材料光谱发射率测量技术研究

针对发射率测量技术现状及面临的问题,明确了建立高温材料光谱发射率测量装置的意义,对所研究的测量装置的技术路线和设计方案进行了介绍。     

同位素热源高温-冲击复合环境试验

为了考察深空探测器同位素热源模拟样品在高温–冲击复合环境下的环境可靠性,研制了一套高温–冲击复合环境试验装置。该装置由温度加载系统、冲击试验系统、带有热防护功能的夹具和控制系统等组成。该装置可完成室温约500℃热载荷加载。利用该试验装置对同位素热源模拟样品进行了500℃、5 000次的高温–冲击复合环境试验考核,获得了产品温升响应曲线、冲击波形图等相关试验信息。试验结果表明该试验装置能够进行高温–冲击复合环境试验。