星载二次电源的电磁兼容预设计

针对星载二次电源电磁兼容试验中辐射发射的超标问题,提出了电磁兼容预设计方法.分析二次电源电磁干扰产生的机理,利用SPICE仿真器建立传导干扰的电路等效模型,优化电路设计得到传导干扰源;应用修正的单线模型近似计算辐射干扰,根据计算结果,利用遗传算法优化等效偶极子的数目和分布位置建立场等效模型;基于场路结合的方法,以传导干...     

追踪及凝视状态下地气光对空间目标成像影响

为了分析不同探测方式下地气光辐射对空间目标成像特性的影响,利用卫星仿真工具包(satellite tool kit,STK)设计了一个以地球同步轨道(geosynchronous orbit,GEO)卫星与中轨道(medium orbit,MEO)卫星上搭载的可见光成像器为探测平台,以高椭圆轨道(highly elli...     

遮挡板参数对二元喷管气动和红外辐射影响

采用计算流体力学/红外辐射强度数值计算的方法,以宽高比3.33二元收敛喷管为研究对象,计算分析了二元喷管加双层遮挡板结构对喷管气动和红外辐射影响.结果表明:二元喷管加遮挡板后,总压恢复系数系数和推力系数并未降低,在98.81％和95.15％以上;单层遮挡结构的二元喷管在绝大多数角度都比基准二元喷管高,且增加的幅度较大;与基准二元喷管相比较,双层遮挡板结构的喷管在-90°至-10°探测方向上红外辐射强度降低38％-80％,但是由于上遮挡板的存在,喷管上方(30°-90°)的红外辐射增强;遮挡间距增加,引射气流流量增加,上、下遮挡板红外辐射减小,当遮挡间距增加到35mm时,上遮挡板的红外辐射峰值降低到800W/Sr,下遮挡板红外辐射强度仅为4W/Sr左右.这说明了双层遮挡结构的二元喷管(喷口后延)在某些方向上有较强的红外抑制效果.     

三维单室稳态火灾数值模拟

本文对单室火灾中流动，传热，燃烧过程进行数值模拟。采用PI辐射模型计算火焰传热，并将计算机结果与实验数据进行了比较。得出了较为合理的结论。     

远红外加热制备预浸带及其对复合材料性能的影响

以远红外加热方式制备了连续芳纶纤维浸胶带，并与工艺成熟的电加热方式制备的预浸带及相应的复合材料性能作比较，确定了远红外加热预浸胶工艺参数。研究结果表明，远红外加热所制备的预浸带性能及相应复合材料压力容器性能与现行工艺成熟的电加热制品性能相当。     

管道惯性测量系统散热仿真分析

基于FLUENT商用软件建立了在60℃高温油内使用的管道惯性测量系统的传热数值模型,模拟了系统在自然对流、不同风冷强制对流和不同热辐射系数下散热的温度分布,分析了风扇布置、空气流量及结构件表面热辐射系数对系统温度分布的影响.通过仿真分析取得了系统有效的散热配置,试验验证结果与仿真计算情况基本吻合,两者相差1.1％.     

一体化红外抑制器遮挡和出口修型对后机身表面温度和红外辐射特性的影响

针对与后机身融合的一体化红外抑制器模型,采用数值模拟的方法研究了内部遮挡和出口修型对后机身表面温度场和红外辐射特性的影响。在混合管外部采用遮挡套或曲面遮挡板可有效降低后机身侧壁面对应混合管后段的局部区域最高温度,两种方式均可有效降低水平探测面以及铅垂面上方3~5 μm波段和8~14 μm波段红外辐射强度峰值;然而,加装遮挡套方式会影响旋翼下洗气流的导入,使3~5 μm波段的红外辐射强度在铅垂面下方较基准模型有小幅的增加。对后机身排气口进行出口修型,虽然对降低后机身3~5 μm和8~14 μm波段红外辐射强度的作用效果并不显著,但可以有效消除排气出口下方壁面的高温区,其中采用狭窄流道引气冷却方式可以使得后机身侧壁仅高于环境温度10 K左右。     

Photo-alteration of hydantoins against UV light and its relevance to prebiotic chemistry

Aqueous solutions of 5-substituted hydantoins were irradiated with ultraviolet (UV) light, to investigate their structural stability against UV radiation as well as the possible photolysis products. The photolysis products were identified and the degree of photolysis was measured using reversed-phase and ion-exchange high-performance liquid chromatography. Hydantoin (2,4-imidazolidinedione) was dominantly detected as a photolysis product of 5-substituted hydantoins. With hydrolysis of UV-irradiated 5-substituted hydantoins, glycine and alanine were dominantly detected. These experimental results are important for the prebiotic photochemistry of 5-substituted hydantoins in the formation of hydantoin since they have been detected in Solar System materials.     

Pion and electromagnetic contribution to dose: Comparisons of HZETRN to Monte Carlo results and ISS data

Recent work has indicated that pion production and the associated electromagnetic (EM) cascade may be an important contribution to the total astronaut exposure in space. Recent extensions to the deterministic space radiation transport code, HZETRN, allow the production and transport of pions, muons, electrons, positrons, and photons. In this paper, the extended code is compared to the Monte Carlo codes, Geant4, PHITS, and FLUKA, in slab geometries exposed to galactic cosmic ray (GCR) boundary conditions. While improvements in the HZETRN transport formalism for the new particles are needed, it is shown that reasonable agreement on dose is found at larger shielding thicknesses commonly found on the International Space Station (ISS). Finally, the extended code is compared to ISS data on a minute-by-minute basis over a seven day period in 2001. The impact of pion/EM production on exposure estimates and validation results is clearly shown. The Badhwar–O’Neill (BO) 2004 and 2010 models are used to generate the GCR boundary condition at each time-step allowing the impact of environmental model improvements on validation results to be quantified as well. It is found that the updated BO2010 model noticeably reduces overall exposure estimates from the BO2004 model, and the additional production mechanisms in HZETRN provide some compensation. It is shown that the overestimates provided by the BO2004 GCR model in previous validation studies led to deflated uncertainty estimates for environmental, physics, and transport models, and allowed an important physical interaction (π/EM) to be overlooked in model development. Despite the additional π/EM production mechanisms in HZETRN, a systematic under-prediction of total dose is observed in comparison to Monte Carlo results and measured data.     

The extension of the INCL model for simulation of shielding in space

Radiation hazard for space missions is mainly due to cosmic ray protons, helium nuclei and light ions, whose energy spectrum is maximum around 1 GeV per nucleon but remains non-negligible for energies up to 15 GeV per nucleon. Nuclear reactions induced by high energy protons are often described by intranuclear cascade plus evaporation models. The attention is focused here on the Liège Intranuclear Cascade model (INCL), which has been shown to reproduce fairly well a great deal of experimental data for nucleon-induced reactions in the 200 MeV to 2 GeV range, when coupled with the ABLA evaporation-fission code. In order to extend the model to other conditions relevant for space radiation, three improvements of INCL are under development. They are reported on here. First, the reaction model has been extended to nucleon–nucleus reactions at incident energies up to 15 GeV, mainly by the inclusion of additional pion production channels in nucleon–nucleon collisions during the cascade. Second, a coalescence mechanism for the emission of light charged particles has been implemented recently. Finally, the model has been modified in order to accommodate light ions as projectiles. First results are shown and compared with illustrative experimental data. Implications for issues concerning radiation protection in space are discussed.