GaAs太阳电池空间质子辐射损伤的分子动力学研究

GaAs太阳电池在空间辐射条件下的性能衰减与电池内部微观结构紧密相关。文章针对空间辐射带质子辐照GaAs材料,利用分子动力学方法研究由被辐射材料中产生的不同能量(0.1~10 ke V)初级离位原子(PKA)引起的级联碰撞过程,分析缺陷随辐照时间、入射PKA能量的演化规律,探讨点缺陷和缺陷簇的形成特征。研究发现,在GaAs材料的缺陷对数目随时间的演化曲线中,在"离位峰"和稳定状态时,缺陷对数目与PKA能量呈一定的线性关系;PKA能量越高,辐射损伤越严重、越不易恢复,但缺陷复合率随能量升高趋于饱和;点缺陷在GaAs中主要以缺陷簇的方式存在,且随着能量的升高,孤立缺陷倾向于缔合成缺陷簇。     

水下固体火箭发动机垂直气体射流结构和推力影响研究

为了探究高背压水介质条件下,固体火箭发动机垂直气体射流在浮力影响下的流场结构和发动机推力特点,建立了轴对称几何模型,在考虑有/无浮力的条件下,采用VOF(Volume of fluid)多相流模型进行气体-水两相耦合仿真计算,获取尾流气体射流流场结构,以及发动机尾部壁面受力和推力振荡曲线进行分析.研究结果表明,考虑浮力...     

太阳能模型飞机的设计方法研究

从太阳能模型飞机的发展状况,分析了太阳能电池应用在航模飞机上的技术难点,针对机载平台、太阳能电池应用、推进系统三方面提出了合理的解决优化方案。实践表明了在光照充足的情况下,能达到只依靠太阳能电池作为动力,实现滑跑起飞的要求。     

多尺度网格细胞路径综合方法

为实现无人作战飞机(UCAV,Unmanned Combat Aerial Vehicle)认知导航的空间方位自主推算,提出了一种基于多尺度网格细胞的路径整合方法.该方法模拟背侧内嗅皮层(dMEC,dorsal Medial Entorhinal Cortex)的相同区域网格细胞放电特征相同、不同区域放电特征递增变化的特点,构建尺度递增的仿生多尺度网格图组,在各层中引入突触样式(synaptic pattern)计算各细胞权值,通过细胞的活跃度变化表征各网格层中位置的变化,并在各层分别实现路径整合,进而利用低尺度整合结果调整高尺度整合,提高空间位置的推算精度.实验结果表明,所提方法在一定的速度误差与方向误差范围内能够精确推算方位,具有较高的空间位置推算精度,并且方向误差值随运动方向变化呈锯齿状分布.     

A method of determining effective elastic properties of honeycomb cores based on equal strain energy

A computational homogenization technique (CHT) based on the finite element method (FEM) is discussed to predict the effective elastic properties of honeycomb structures. The need of periodic boundary conditions (BCs) is revealed through the analysis for in-plane and out-of-plane shear moduli of models with different cell numbers. After applying periodic BCs on the represen-tative volume element (RVE), comparison between the volume-average stress method and the boundary stress method is performed, and a new method based on the equality of strain energy to obtain all non-zero components of the stiffness tensor is proposed. Results of finite element (FE) analysis show that the volume-average stress and the boundary stress keep a consistency over different cell geometries and forms. The strain energy method obtains values that differ from those of the volume-average method for non-diagonal terms in the stiffness matrix. Analysis has been done on numerical results for thin-wall honeycombs and different geometries of angles between oblique and vertical walls. The inaccuracy of the volume-average method in terms of the strain energy is shown by numerical benchmarks.     

太阳电池片间隙区域充电电场的数值计算

高压太阳电池阵在空间带电粒子环境中易发生静电放电,特别是太阳电池片间隙区域存在着诱发二次放电的风险。文章建立了太阳电池片间隙区域充电模型,基于静电理论研究了计算太阳电池片间隙区域充电电场的算法。数值计算结果表明:太阳电池片间隙区域两侧,充电电场呈对称分布;玻璃盖片与基底之间存在明显的电位差,且玻璃盖片的电位高于其他部位。     

Characterization of a novel gravitropic mutant of morning glory, weeping2

In higher plants, gravity is a major environmental cue that governs growth orientation, a phenomenon termed gravitropism. It has been suggested that gravity also affects other aspects of morphogenesis, such as circumnutation and winding movements. Previously, we showed that these aspects of plant growth morphology require amyloplast sedimentation inside gravisensing endodermal cells. However, the molecular mechanism of the graviresponse and its relationship to circumnutation and winding remains obscure. Here, we have characterized a novel shoot gravitropic mutant of morning glory, weeping2 (we2). In the we2 mutant, the gravitropic response of the stem was absent, and hypocotyls exhibited a severely reduced gravitropic response, whereas roots showed normal gravitropism. In agreement with our previous studies, we found that we2 mutant has defects in shoot circumnutation and winding. Histological analysis showed that we2 mutant forms abnormal endodermal cells. We identified a mutation in the morning glory homolog of SHORT-ROOT (PnSHR1) that was genetically linked to the agravitropic phenotype of we2 mutant, and which may underlie the abnormal differentiation of endodermal cells in this plant. These results suggest that the phenotype of we2 mutant is due to a mutation of PnSHR1, and that PnSHR1 regulates gravimorphogenesis, including circumnutation and winding movements, in morning glory.     

Strategies of developing advanced lunar power systems

Electric and thermal power have to be available at the base site on the lunar surface before the first lunar crew arrives. Unlimited solar energy is available during the lunar day, but this must be stored for use during the lunar night unless nuclear energy systems are available. State-of-the-art candidate systems are reviewed and the production of solar cells on the moon is discussed. Various options for developing a lunar power plant are proposed. These must be simulated and optimized in a real lifecycle systems scenario to provide operations and cost data essential for choosing a strategy.     

T cell regulation in microgravity – The current knowledge from in vitro experiments conducted in space,parabolic flights and ground-based facilities

Dating back to the Apollo and Skylab missions, it has been reported that astronauts suffered from bacterial and viral infections during space flight or after returning to Earth. Blood analyses revealed strongly reduced capability of human lymphocytes to become active upon mitogenic stimulation. Since then, a large number of in vitro studies on human immune cells have been conducted in space, in parabolic flights, and in ground-based facilities. It became obvious that microgravity affects cell morphology and important cellular functions. Observed changes include cell proliferation, the cytoskeleton, signal transduction and gene expression. This review gives an overview of the current knowledge of T cell regulation under altered gravity conditions obtained by in vitro studies with special emphasis on the cell culture conditions used. We propose that future in vitro experiments should follow rigorous standardized cell culture conditions, which allows better comparison of the results obtained in different flight- and ground-based experiment platforms.     

硫源种类对微波合成CZTS颗粒与薄膜性能的影响

研究不同硫源对微波液相合成的Cu２ＺｎＳｎＳ４（CZTS）纳米颗粒尺寸及形貌的影响。结果表明：当采用硫脲作为硫源时,所制备的CZTS纳米颗粒为平均尺寸500 nm的球状结构纳米颗粒;采用L 半胱氨酸作为硫源所制备的CZTS纳米颗粒为50 nm的空心球状纳米颗粒;而当使用硫代乙酰胺作为硫源制备CZTS纳米颗粒,其平均尺寸仅为3 nm。采用 平均尺寸为500 nm或50 nm的纳米颗粒制备墨水,将墨水旋涂到衬底上时,其致密性很差,明显存在许多孔洞。当采用平均尺寸为3 nm的纳米颗粒制作墨水,并将其制成薄膜时,薄膜致密性与均匀性都比较好。将最佳的预制薄膜进行硫化处理,其结晶性明显提高,并得到转化效率为2.1%的CZTS太阳电池。