Deterministic pion and muon transport in Earth’s atmosphere

An accurate understanding of the physical interactions and transport of space radiation is important for safe and efficient space operations. Secondary particles produced by primary particle interactions with intervening materials are an important contribution to radiation risk. Pions are copiously produced in the nuclear interactions typical of space radiations and can therefore be an important contribution to radiation exposure. Charged pions decay almost exclusively to muons. As a consequence, muons must also be considered in space radiation exposure studies. In this work, the NASA space radiation transport code HZETRN has been extended to include the transport of charged pions and muons. The relevant transport equation, solution method, and implemented cross sections are reviewed. Muon production in the Earth’s upper atmosphere is then investigated, and comparisons with recent balloon flight measurements of differential muon flux are presented. Muon production from the updated version of HZETRN is found to match the experimental data well.     

Hard X-ray continuum from lunar surface: Results from High Energy X-ray spectrometer (HEX) onboard Chandrayaan-1

The High Energy X-ray spectrometer (HEX) on Chandrayaan-1 was designed to study the photon emission in the range of 30–270 keV from naturally occurring radioactive decay of ²³⁸U and ²³²Th series nuclides from the lunar surface. The primary objective of HEX was to study the transport of volatiles on the lunar surface using radon as a tracer and mapping the 46.5 keV line from ²¹⁰Pb, a decay product of ²²²Rn. HEX was tested for two days during the commissioning phase of Chandrayaan-1 and performance of all sub systems was found to be as expected. HEX started collecting science data during the first non-prime imaging season (February–April, 2009) of Chandrayaan-1. Certain anomalies persisted in this data set and the early curtailment of Chandrayaan-1 mission in August, 2009, did not allow any further operation of HEX. Despite these issues, HEX provided the first data set for 30–270 keV continuum emission, averaged over a significant portion of the lunar surface, including the polar region.     

大型天线装配测量与实时反馈调整技术

针对大型天线在装配过程中共轴铰链空间位置难以准确定位和测量、传统测量方法容易受到天线杆件的干涉影响测量精度等问题,通过搭建大型天线装配测量与实时反馈调整系统,采用数字摄影测量技术对天线的面板、铰链和杆件的装配精度进行了测量,并将测量结果实时反馈给六自由度自动执行机构调整共轴铰链的空间位置,实现大型天线的柔性化、自动化和精准化装配。试验结果表明数字摄影测量相机的精度与激光跟踪仪的精度偏差不大于0.01 mm;六自由度自动执行机构对共轴铰链的位姿调整位移精度优于0.02 mm,角度精度优于0.01°,能够满足大型天线的装配和测量要求,该方法可以提高大型天线装配效率和自动化技术水平,为尺寸更大和结构更复杂的天线集成装配奠定技术基础。     

双超卫星平台柔性线缆构型设计与仿真

研究舱间线缆动力学模型及其扰动传递特性,是深入考察连接线缆刚柔耦合效应影响的重要依据。以绝对节点坐标方法(ANCF)三维缩减曲梁单元模型为背景,考虑线缆的大变形特性,构造新的大变形线缆单元弹性力模型。在此基础上,用数值方法对典型约束工况下线缆单元弹性力模型进行计算和分析,获得位移-扰动力线性关系下的两舱振幅范围。此外,结合有限元方法,获得了舱间线缆不同布线构型的等效结构刚度矩阵模型。结果表明:布线过程中合理排列不同材料性能线缆,可有效降低耦合效应的影响,为后续舱间线缆布线规划提供了理论依据。     

紧凑式强预冷换热器叉排管束的大涡模拟

采用大涡模拟方法对紧凑式强预冷换热器叉排管束的对流换热问题进行了研究,并运用动力模态分解(DMD)方法对流场的拟序结构及换热统计特性进行了分析.结果表明:在计算工况内(Re≤6000),前排管束的流动结构为有规律的剪切层运动和尾涡脱落.后排管束的流动结构为无规律的小尺度旋涡结构,同时其流场表现出无序性;前排管表面瞬时努...     

DBD等离子体非定常激励下的平板流场结构分布研究

文章采用DBD等离子体简化模型,基于大涡模拟方法,对DBD等离子体作用下的流场进行数值模拟研究,探讨等离子体非定常激励作用下平板流动的流场结构特点。结果表明:等离子体作用下,在近壁区形成了一系列的正负涡对结构,涡对的产生促进了近壁区内流体与主流流体的能量交换,时均结果表现为从等离子体作用点形成向下游发展的壁面射流;在等离子体作用点下游0.5b的位置,等离子体最大诱导速度UDBD随激励强度Dc呈指数形式增加。     

大型航天器与外热流模拟装置的数字化结构匹配方法

在航天器真空热试验中,常选用红外加热笼作为外热流模拟装置。为提高外热流模拟的准确性,红外加热笼需要对航天器进行全表面覆形。文章针对如何确认外热流模拟装置与航天器的结构匹配性这个难题,依托三维扫描技术,建立了一套数字化结构匹配方法,解决了多站测量拼接误差累积、三维扫描仪参数优化选择2个技术难点,使三维扫描和逆向建模过程引入的几何误差不超过10 mm。该数字化结构匹配方法的实际应用结果表明,外热流模拟装置与航天器的配装成功率达到100%,实际安装状态与仿真结果吻合度较好。     

1.2m×1.2m高速风洞大振幅动态试验系统及其初步应用

高速大迎角动态气动特性是衡量新一代高机动飞行器性能的重要参数之一.本文简要介绍了在CARDC的1.2m×1.2m高速风洞的大振幅动态试验系统.试验M=0.40,0.60,0.80;振幅为15°、30°;振动频率分别为0.84Hz、1.47Hz、2.84Hz和4.41Hz.初步分析试验研究所揭示的70°三角翼模型高速大迎角动态气动特性,结果表明:M数、迎角振荡的幅值和K值(振动减缩频率)是影响70°三角翼模型动态迟滞气动特性的主要参数.     

APPROXIMATE SOLUTION FOR THIN PLATES CONSTRAINED AT ARBITRARY POINTS

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