太阳电池在平流层中的工作性能分析

近年来,临近空间受到广泛关注,多种平流层飞行器被提出,它们大多以太阳电池为 主要的能源获取装置。研究平流层的太阳电池的性能,对平流层的开发和利用具有重要意义 。首先建立了平流层中太阳电池的热环境模型,并结合硅太阳电池的电学模型,得到了 平流层中硅太阳电池的热电耦合分析模型,进而用数值模拟方法对太阳能电池的热学、电学 性能进行了分析和讨论。研究结果表明,平流层热环境的变化对太阳能电池的温度、输出功 率以及电效率都有影响。讨论了风速对太阳电池性能的影响,结果表明随着风速的增 加,太阳电池温度降低、内部温差先增加后减小、发电效率和输出功率都增加。
     

武器系统小样本场合下的区间估计

介绍了区间估计的一般方法 ,针对武器系统试验次数少的特点 ,讨论了小样本条件下武器系统战术技术性能指标的置信区间估计的估计方法 ,并以示例进行了说明     

构架式可展天线机构自由度分析——拆杆等效法

针对四面体构架式可展天线机构的多环耦合特性,提出了一种空间多环耦合机构的自由度分析方法——拆杆等效法。首先拆除四面体基本可展单元机构的耦合约束链,将剩余部分视为一个并联机构,然后应用螺旋理论分析各输出节点的自由度数目及性质,进而构造各输出节点与定节点之间的等效串联运动链,最后复原拆除的耦合约束链得到四面体基本可展单元的等效机构,应用修正的G-K公式计算等效机构的自由度数目,并基于反螺旋理论分析等效机构的自由度性质,从而获得四面体基本可展单元的运动特性。根据四面体基本可展单元的等效机构及其组合方式对最小组合单元及大尺寸构架式可展天线机构的结构进行了化简,并根据其几何特征约束方程推导了最小组合单元及大尺寸构架式可展天线机构的自由度。建立了由27个四面体基本可展单元组成的构架式可展天线机构的仿真模型,对该机构的自由度进行了验证,结果表明提出的拆杆等效法求得的自由度正确,为进一步分析此类天线机构的运动学和动力学奠定了基础,同时为其他类型的空间多环耦合机构的自由度分析提供了一种新的思路。     

A systematic spatial bias in remembering eye positions

Categorical bias in location memory in geometric spaces is well established. The present study assessed the presence of the bias in locating eyes in images of human faces. Participants were presented with digital faces and indicated the position of one of the eyes in both upright and inverted orientations. Biases resulted from participants using multiple sources of accessible information. No differences were found for upright vs. inverted face images. Overall, the data were consistent with the retrieval category adjustment model. These distortions may be considered within the forensic context, when eyewitnesses work with a sketch artist or use a computer program to generate an image of the culprit.     

A boundary vector cell model of place field repetition

Hippocampal place cells are thought to form the neural substrate of a global cognitive map. However, in multicompartment mazes, these cells exhibit locally repeating representations, undermining the global cognitive map view of place cells. This phenomenon appears to be related to the repetitive layout of these mazes, but still no hypothesis adequately explains it. Here, we use a boundary vector cell (BVC) model of place cell firing to model the activity of place cells in numerous multicompartment environments. The activity of modeled place cells bears a striking resemblance to experimental data, replicating virtually every major experimental result. Our results support the BVC model and indicate that locally repeating place cell firing could result purely from local geometry.     

The adjusted optical properties for Galileo/BeiDou-2/QZS-1 satellites and initial results on BeiDou-3e and QZS-2 satellites

Solar Radiation Pressure (SRP) is the dominant non-gravitational perturbation for GNSS (Global Navigation Satellite System) satellites. In the absence of precise surface models, the Empirical CODE Orbit Models (ECOM, ECOM2) are widely used in GNSS satellite orbit determination. Based on previous studies, the use of an a priori box-wing model enhances the ECOM model, especially if the spacecraft is a stretched body satellite. However, so far not all the GNSS system providers have published their metadata. To ensure a precise use of the a priori box-wing model, we estimate the optical parameters of all the Galileo, BeiDou-2, and QZS-1 (Quasi Zenith Satellite System) satellites based on the physical processes from SRP to acceleration. Validation using orbit prediction proves that the adjusted parameters of Galileo and QZS-1 satellites exhibit almost the same performance as the corresponding published and “best guess” values. Whereas, the estimated parameters of BeiDou-2 satellites demonstrate an improvement of more than 60% over the initial “guess” values. The resulting optical parameters of all the satellites are introduced into an a priori box-wing model, which is jointly used with ECOM and ECOM2 model in the orbit determination. Results show that the pure ECOM2 model exhibits better performance than the pure ECOM model for Galileo, BeiDou-2 GEO and QZS-1 orbits. Combined with the a priori box-wing model the ECOM model (ECOM+BW) results in the best Galileo, BeiDou-2 GEO and QZS-1 orbits. The standard deviation (STD) of satellite laser ranging residuals reduce by about 20% and 5% with respect to the pure ECOM2 model for Galileo and BeiDou-2 GEO orbits, while the reductions are about 40% and 60% for QZS-1 orbits in yaw-steering and orbit-normal mode respectively. BeiDou-2 IGSO and MEO satellite orbits do not benefit much from the a priori box-wing model. In summary, we suggest setting up a unified SRP model of ECOM+BW for Galileo, QZS-1, and BeiDou-2 orbits based on the adjusted metadata. In addition, we estimate the optical parameters of BeiDou-3e and QZS-2 satellites using a limited number of tracking stations. Results regarding the unified SRP model indicate the same advantages, the STD of satellite laser ranging residuals reduces by about 30% and 20% for QZS-2 and BeiDou-3e orbits respectively over orbit products without a priori model. The estimation procedure is effective and easy to apply to the new emerging satellites in the future.     

双向比对高精度物理时间同步方法

提出一种面向未来卫星在轨应用的闭环物理高精度时间同步方法。比较了所提方法与其他时间同步方法的区别与优势,建立了远程系统时间同步基本模型与误差传递模型,基于双向测距和时间传递技术分析了高精度钟差获取原理,给出了时钟调整环路的时域频域参数依赖关系。完成了高精度时间同步地面试验系统构建,测试了开环非调钟状态下钟差测量精度误差、闭环调钟状态下时间同步准确度误差以及长时运行情况下的时间同步监测结果。测试结果表明,该方法能够实现优于1 ns量级的时间同步,为高精度时间同步技术研究提供了新的途径。     

运载火箭主动段自适应增广控制

针对运载火箭上升段在复杂飞行环境、大不确定性干扰和振动等因素的影响下,传统PID控制方法难以满足高品质控制需求的问题,进行了自适应增广控制(AAC)方法研究,以实现对运载火箭姿态的精确控制。在深入分析自适应增广控制系统整体构架的基础上,通过标称PID控制器设计与基于粒子群优化(PSO)的数字滤波器设计实现了刚体控制及对弹性振动的抑制;继而针对大范围干扰、不确定性和由于滤波器切换产生的弹性振动影响,设计了在线调整算法自适应调节PID控制增益,并对其工作机理与参数设计原则进行研究;然后设计干扰补偿回路和主动减载回路以减小内外扰动、弹性振动和风载荷影响;最后在弹性振动、风干扰和参数不确定性等因素同时作用的状态下进行仿真分析,验证了自适应增广控制系统能够有效应对运载火箭主动段复杂飞行环境的影响,大幅度提升综合控制性能,具有理论研究意义与工程应用价值。     

离子液体推力器性能影响因素仿真研究

文章主要研究离子液体推力器发射阵列几何结构参数对推力器性能的影响。建立单个发射极粒子网格法仿真模型,模拟获得了单个发射极束流分布及推力、比冲等性能参数曲线;通过改变电极间距及引出极孔径获得了单个发射极平均推力和角向效率的变化曲线,分析了电极间距及引出极孔径对推力器性能的影响。研究表明：在离子被引出极拦截前,推力器角向效率与电极间距成正比,与引出极孔径成反比;在不考虑发射离子数量和比例改变情况下,推力器推力随电极间距的增加先增大后减小,一定范围内随引出极孔径的减小而增大,但过小的引出极孔径会造成严重的推力损失与栅极侵蚀。以上研究结果可为离子液体推力器的优化设计提供参考。     

用于荧光细胞观察的制冷CCD成像系统

细胞成像技术是研究细胞运动、分裂和凋亡的必要手段,所以荧光条件下的细胞成像技术显得尤为重要。为满足荧光细胞观察对微弱光信号的检测和成像的要求,文章通过结构和电路设计,研制了一种用于荧光细胞观察的制冷CCD成像系统。通过分析各组件的技术特点,设计了高效制冷结构,提高了细胞荧光观察输出图像质量。