一种推广的靶效应模型及其对剂量-存活率的拟合探讨

辐射生物物理模型对于准确、有效地评估空间辐射引起的生物损伤及风险具有重要意义。目前较为流行的基于地基模拟的“靶效应模型”和“非靶效应模型”，是进一步探索空间辐射生物物理模型的基础。在考虑了辐射的非靶效应和机体复杂的修复过程的基础上，将传统理论中“击中”即“失活”的线性关系进行了推广，提出了基于否定算子的靶效应模型。通过对辐射钝感和敏感的两类细胞辐射实验中剂量与细胞存活率数据进行拟合发现，对于正常皮肤成纤维细胞的存活率数据，经典的靶学说与基于否定算子的改进靶效应模型都有较好的拟合效果；而对于人类胚胎肝细胞的存活率数据，基于否定算子的改进靶效应模型的拟合结果明显优于传统的靶学说模型。拟合结果中的模型参数值在人成纤维细胞和胚胎肝细胞中明显不同，说明了本模型的参数与传能线密度，细胞的种类、以及修复能力等物理和生物因素有关。     

Occurrence features of simultaneous H+- and He+-band EMIC emissions in the outer radiation belt

As an important loss mechanism of radiation belt electrons, electromagnetic ion cyclotron (EMIC) waves show up as three distinct frequency bands below the hydrogen (H⁺), helium (He⁺), and oxygen (O⁺) ion gyrofrequencies. Compared to O⁺-band EMIC waves, H⁺- and He⁺-band emissions generally occur more frequently and result in more efficient scattering removal of <～5?MeV relativistic electrons. Therefore, knowledge about the occurrence of these two bands is important for understanding the evolution of the relativistic electron population. To evaluate the occurrence pattern and wave properties of H⁺- and He⁺-band EMIC waves when they occur concurrently, we investigate 64 events of multi-band EMIC emissions identified from high quality Van Allen Probes wave data. Our quantitative results demonstrate a strong occurrence dependence of the multi-band EMIC emissions on magnetic local time (MLT) and L-shell to mainly concentrate on the dayside region of L?=?～4–6. We also find that the average magnetic field amplitude of H⁺-band waves is larger than that of He⁺-band waves only when L?<?4.5 and AE¹?<?300?nT, and He⁺-band emissions are more intense under all other conditions. In contrast to 5 events that have average H⁺-band amplitude over 2 nT, 19 events exhibit >2 nT He⁺-band amplitude, indicating that the He⁺-band waves can be more easily amplified than the H⁺-band waves under the same circumstances. For simultaneous occurrences of the two EMIC wave bands, their frequencies vary with L-shell and geomagnetic activity: the peak wave frequency of H⁺-band emissions varies between 0.25 and 0.8 f_cp with the average between 0.25 and 0.6 f_cp, while that of He⁺-band emissions varies between 0.03 and 0.23 f_cp with the average between 0.05 and 0.15 f_cp. These newly observed occurrence features of simultaneous H⁺- and He⁺-band EMIC emissions provide improved information to quantify the overall contribution of multi-band EMIC waves to the loss processes of radiation belt electrons.     

电磁铆接放电过程仿真分析

目前,电磁铆接的放电回路主要有两种形式,一种是电容直接对线圈进行放电;另一种是电容对脉冲变压器放电,然后脉冲变压器作用于线圈.     

On the spatial extent of the proton radiation belt from solar cell output variation of the Akebono satellite

Output current of silicon solar cells of Akebono satellite orbiting in the inner magnetosphere decreased from 13 A in 1989 to about 7 A in 2009, due to accumulated damage by energetic particles. A fair correlation between the monthly decrease rate of solar cell output current and trapped proton flux was found between 1989 and 1992, indicating that trapped energetic protons are responsible for the solar cell degradation. Simple variation from month to month was dominated by a fluctuation with one-year period and the correlation was not discernible after 1993. On the other hand, during orbiting the earth, another kind of decrease of output current emerged at low altitude above the sub-solar point, i.e., in the midst of sunlit condition. The decrease was larger in later years. The fact indicates more prominent temperature effect in the later years because of progress of the degradation. By removing data affected by the orbit condition above, variation from the same month in the previous year shows a clear oscillation due to orbit precession correlated with trapped energetic proton flux up to 1996. The amplitude of the annual variation oscillation tends to be larger than that expected from a degradation model based on energetic proton distribution of the NASA’s AP8 model. The larger oscillation amplitude suggests that the proton radiation belt was more sharply localized than given by the AP8 model throughout the early half of 1990s.     

Statistical validation of HZETRN as a function of vertical cutoff rigidity using ISS measurements

Measurements taken in Low Earth Orbit (LEO) onboard the International Space Station (ISS) and transit vehicles have been extensively used to validate radiation transport models. Primarily, such comparisons were done by integrating measured data over mission or trajectory segments so that individual comparisons to model results could be made. This approach has yielded considerable information but is limited in its ability to rigorously quantify and differentiate specific model errors or uncertainties. Further, as exploration moves beyond LEO and measured data become sparse, the uncertainty estimates derived from these validation cases will no longer be applicable. Recent improvements in the underlying numerical methods used in HZETRN have resulted in significant decreases in code run time. Therefore, the large number of comparisons required to express error as a function of a physical quantity, like cutoff rigidity, are now possible. Validation can be looked at in detail over any portion of a flight trajectory (e.g. minute by minute) such that a statistically significant number of comparisons can be made. This more rigorous approach to code validation will allow the errors caused by uncertainties in the geometry models, environmental models, and nuclear physics models to be differentiated and quantified. It will also give much better guidance for future model development. More importantly, it will allow a quantitative means of extrapolating uncertainties in LEO to free space. In this work, measured data taken onboard the ISS during solar maximum are compared to results obtained with the particle transport code HZETRN. Comparisons are made at a large number (∼77,000) of discrete time intervals, allowing error estimates to be given as a function of cutoff rigidity. It is shown that HZETRN systematically underestimates exposure quantities at high cutoff rigidity. The errors are likely associated with increased angular variation in the geomagnetic field near the equator, the lack of pion production in HZETRN, and errors in high energy nuclear physics models, and will be the focus of future work.     

Comparison of the transport codes HZETRN,HETC and FLUKA for galactic cosmic rays

The HZETRN deterministic radiation code is one of several tools developed to analyze the effects of harmful galactic cosmic rays (GCR) and solar particle events on mission planning and shielding for astronauts and instrumentation. This paper is a comparison study involving the two Monte Carlo transport codes, HETC–HEDS and FLUKA and the deterministic transport code, HZETRN. Each code is used to transport an ion from the 1977 solar minimum GCR spectrum impinging upon a 20 g/cm² aluminum slab followed by a 30 g/cm² water slab. This research is part of a systematic effort of verification and validation to quantify the accuracy of HZETRN and determine areas where it can be improved. Comparisons of dose and dose equivalent values at various depths in the water slab are presented in this report. This is followed by a comparison of the proton and forward, backward and total neutron flux at various depths in the water slab. Comparisons of the secondary light ion ²H, ³H, ³He and ⁴He fluxes are also examined.     

On-orbit verification of fuel-free attitude control system for spinning solar sail utilizing solar radiation pressure

This paper introduces a new attitude control system for a solar sail, which leverages solar radiation pressure. This novel system achieves completely fuel-free and oscillation-free attitude control of a flexible spinning solar sail. This system consists of thin-film-type devices that electrically control their optical parameters such as reflectivity to generate an imbalance in the solar radiation pressure applied to the edge of the sail. By using these devices, minute and continuous control torque can be applied to the sail to realize very stable and fuel-free attitude control of the large and flexible membrane. The control system was implemented as an optional attitude control system for small solar power sail demonstrator named IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun). In-orbit attitude control experiments were conducted, and the performance of the controller was successfully verified in comparison with the ground-based analytical performance estimation.     

基于浸入式边界方法的运动物体声辐射数值模拟

为了在声学计算中简化网格的处理,从而发展出适用于运动复杂边界问题模拟的计算格式,基于浸入式边界方法,提出了一种适用于无黏流动、无穿透边界条件的处理方法,并对一些简单的运动物体声辐射问题进行了数值模拟.数值结果与解析解得到了令人满意的对比,初步验证了所提出的研究方案的可行性.     

舰载导弹红外射频导引头电磁兼容设计

采用分层与综合设计法对舰载战术导弹导引头的有源器件选型,印制板、接地、屏蔽、滤波和瞬态骚扰抑制等电磁兼容（EMC）设计进行了研究。分析了各层次传导和辐射的电磁兼容性,给出了设计策略及某导引头壳体电子设计与仿真结果。研究对改善整个导引头的电磁兼容性设计有一定的参考价值。     

复杂目标红外辐射特性大数据知识表示及建模方法

为了提升复杂目标红外辐射特性建模效率及置信度问题，提出一种目标红外辐射特性的大数据知识表示及建模方法。首先利用机理分析法、主成分分析法确定目标红外辐射特性大数据维度;然后基于主成分分析的结果，进行目标红外辐射特性大数据知识表示，建立目标红外辐射特性仿真模型;最后进行模型的仿真应用，在应用过程中进一步完善目标红外辐射特性数据或知识表示。本文提供的大数据驱动的目标红外辐射特征建模方法，能够推广应用于复杂电磁环境的仿真。