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。     

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.     

Comparison of the transport codes HZETRN,HETC and FLUKA for a solar particle event

The protection of astronauts and instrumentation from galactic cosmic rays and solar particle events is one of the primary constraints associated with mission planning in low earth orbit or deep space. To help satisfy this constraint, several computational tools have been developed to analyze the effectiveness of various shielding materials and structures exposed to space radiation. These tools are now being carefully scrutinized through a systematic effort of verification, validation, and uncertainty quantification. In this benchmark study, the deterministic transport code HZETRN is compared to the Monte Carlo transport codes HETC-HEDS and FLUKA for a 30 g/cm² water target protected by a 20 g/cm² aluminum shield exposed to a parameterization of the February 1956 solar particle event. Neutron and proton fluences as well as dose and dose equivalent are compared at various depths in the water target. The regions of agreement and disagreement between the three codes are quantified and discussed, and recommendations for future work are given.     

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...     

Understanding solar streamers: The role of SOHO

Streamers have been observed since far back in time, but our knowledge of their morphology and of their physical characteristics is still very limited. As a consequence, the present streamer picture is largely incomplete: because individual features are poorly known, their role in more general phenomena (like the evolution of the global corona or the solar wind mass and flow pattern) is also poorly known. In this presentation, the more relevant open problems in the understanding of streamers will be illustrated and it will be shown how new data acquired by SOHO may help us to reach a better understanding of these structures.