SAR卫星用能量功率兼顾型锂离子电池研究

未来大功率合成孔径雷达(SAR)卫星的发展对储能电池组提出了轻量化、倍率高及在轨寿命长等要求,而现有的SAR卫星用功率型锂离子电池产品已无法满足未来需求。通过优化正极材料和电池设计,加入功能电解液,在保证电池功率特性的同时,显著提升了电池的能量密度和循环稳定性。本文研制出的新一代能量功率兼顾型锂离子蓄电池,额定容量为25.0 Ah,初期放电比能量达到180.0 Wh·kg~(-1),2 C放电容量为0.2 C容量的91.0%,1 C-100%放电深度(DOD)和2 C-30%DOD循环性能优异,可以满足下一代大功率SAR卫星的供配电需求,且大幅降低了电源系统重量,提高了卫星储能系统的利用率和平台有效载荷能力。     

Multiple Coulomb scattering method to reconstruct low-energy gamma–ray direction in the GAMMA-400 space-based gamma–ray telescope

The GAMMA-400 currently developing space-based gamma-ray telescope is designed to measure the gamma-ray fluxes in the energy range from ～20?MeV to several TeV in the highly elliptic orbit (without shadowing the telescope by the Earth) continuously for a long time. The physical characteristics of the GAMMA-400 gamma-ray telescope, especially the angular and energy resolutions (at 100-GeV gamma rays they are ～0.01° and ～1%, respectively), allow us to consider this space-based experiment as the next step in the development of extraterrestrial high-energy gamma-ray astronomy. In this paper, a method to improve the reconstruction accuracy of incident angle for low-energy gamma rays in the GAMMA-400 space-based gamma-ray telescope is presented. The special analysis of topology of pair-conversion events in thin layers of converter was performed. Applying the energy dependence of multiple Coulomb scattering for pair components, it is possible to estimate the energies for each particle, and to use these energies as weight in the angle reconstruction procedure. To identify the unique track in each projection the imaginary curvature method is applied. It allows us to obtain significantly better angular resolution in comparison with other methods applied in current space-based experiments. When using this method for 50-MeV gamma rays the GAMMA-400 gamma-ray telescope angular resolution is about 4°.     

Inertial aided BDS triple-frequency integer ambiguity rounding method

The integer ambiguity resolution (AR) of carrier phase is significant for Global Navigation Satellite System (GNSS) precise positioning. However, in kinematic case, single-epoch AR methods based on alone GNSS are usually not reliable due to the instable pseudorange accuracy. Moreover, the computation of classical AR method Least Squares Ambiguity Decorrelation Adjustment (LAMBDA) is large. Thus, the inertial measurement unit (IMU) is introduced, a new inertial-aided AR method that directly rounds the float ambiguity of BeiDou triple-frequency combined observations, which is characterized by long wavelength, low carrier-phase noise and ionospheric delay, is proposed. The mathematical model of the new method is derived first. Then the impacts of the carrier-phase noise, ionospheric delay and inertial navigation system (INS) position error on the AR success ratio of combined observation are analyzed through probabilistic approach. Based on above investigation, the combinations (0, ?1, 1), (1, 4, ?5) and (4, ?2, ?3) are selected to resolve the original ambiguity. A vehicular integrated navigation test is performed to demonstrate the proposed method. The results show that the average AR success ratios of the three selected combinations, whose float ambiguity errors are 0.041, 0.146, 0.279 cycle respectively, are above 97.25% without regard to low-elevation C05. With respect to positioning accuracy based on our AR method when compared with IE software, the east, north, up error RMS of position are 0.042, 0.024, 0.069 m, respectively. In terms of the AR recover after the BeiDou signals outage, as long as 62 s BeiDou signal complete outage, all the ambiguities of all satellites could be re-fixed immediately. Besides, during the 90 s signals partial outage, the AR is not influenced by the position error, since the float ambiguity errors are all below half-cycle. The research of this contribution demonstrates the effectiveness of the proposed new method, which indicates it is applicable to kinematic positioning, even in BDS degraded and denied environments.     

榫连结构的高应力梯度及破坏分析

某燕尾形榫连结构的分析表明叶盘榫齿/榫槽接触区边缘存在较高的应力梯度,接触应力的有限元解同网格疏密程度密切相关.通过建立一系列不同密度网格的模型,对此问题展开有限元建模分析,以改善接触应力的求解精度,同时深入讨论材料弹塑性对接触应力的影响.在弹塑性接触应力分析的基础上,采用断裂力学方法建立了榫连结构高应力梯度位置的破坏分析模型,判断裂纹的萌生及扩展方向,以进行结构的强度及寿命分析.     

鸭翼/边条对融合体型机身大攻角气动特性影响

通过对融合体型机身进行表面测压和PIV(Particle Image Velocimetry)流动显示实验,研究了大攻角下鸭翼/边条对机身气动特性的影响规律.结果表明:加装鸭翼后攻角小于50°时机头区流动变化不大,超过50°攻角后,机头区法向力显著下降,并且随着攻角增加受影响区域向头部方向扩大;加装鸭翼致使鸭翼区截面法向力大幅增加.加装边条改善了边条区流动,边条涡对机头涡产生有利诱导,增大了边条区法向力.加装边条/鸭翼时,对机头区及鸭翼区流场的影响由鸭翼起主控作用,对边条区流场的影响由边条起主控作用.     

Cr对Nb-16Si-22Ti-2Al-2Hf合金显微组织与高低温力学性能的影响

 以Nb-16Si-22Ti-2Al-2Hf成分为基础,分别添加了2%和17%(原子分数,后同)的Cr元素替代Nb(分别称2Cr和17Cr合金),研究了Cr含量对Nb-16Si-22Ti-2Al-2Hf合金相组成、显微组织形貌、室温断裂韧性和高温强度的影响,分析了高低温失效机制。结果表明,铸态和1 375 ℃×100 h热处理后2Cr合金由Nbss和Nb₅Si₃两相组成;当Cr含量为17%时,出现了具有C15结构的Laves Cr₂Nb相,合金由Nbss、Nb₅Si₃和Cr₂Nb三相组成,热处理后在Nb₅Si₃中还析出了球状Cr₂Nb相。随着Cr含量由2%提高到17%,热处理合金的室温断裂韧性K_Q由14.32 MPa·m^1/2下降到10.30 MPa·m^1/2。合金强度与Cr含量的关系受温度影响,随Cr含量提高,室温和1 150 ℃时合金的硬度或强度增高,而1 250 ℃和1 350 ℃时合金强度降低。如1 150 ℃时2Cr和17Cr合金的屈服强度σ_0.2分别为349 MPa和387 MPa;1 350 ℃时分别为306 MPa和74 MPa。     

开花期高温胁迫对不同水稻品种花粉萌发和结实的影响

以5个籼稻品种为材料,通过抽穗期高温处理和离体花粉萌发等试验,研究了开花期高温对水稻花粉萌发和结实的影响.结果表明,不同品种水稻对高温处理的敏感度明显不同,其中品种黄华占在高温处理4 d后的花粉萌发率达到70%以上,在高温处理7 d后小穗结实率仍保持50%左右,其他4个品种的花粉萌发率和小穗结实率都明显低于黄华占,由此认为,黄华占是一个耐热性较强的品种.     

基于PCI接口的高速A/D采集电路设计

描述了一种基于PCI总线接口的高速A/D采样电路设计,提出了基本系统构型和硬件设计的开发思路,阐述了高速A/D芯片的选择、智能控制、PCI接口的电路设计,以及信号完整性设计的一般要求。     

低仰角射线对电离层CT成像的影响分析

电离层层析成像(Computerized Tomography, CT)是一个有限视角问题, 水平射线的缺失造成CT结果垂直分辨率的严重下降. 很多人直观地认为低仰角射线可以弥补水平射线的缺失, 然而本文的理论分析和数值模拟研究结果表明, 低仰角射线对CT结果的影响十分微小, 其无法弥补水平射线缺失所带来的垂直分辨率的下降. 模拟结果显示, 增加低仰角射线前后CT反演结果几乎没有变化; 而去掉680条低仰角射线和高仰角射线后, CT反演结果差别巨大; 去掉680条低仰角射线的CT结果与模型吻合很好; 去掉680条高仰角射线的CT反演结果失真严重, 几乎无法恢复模型的扰动特征.      

高空气球热力学模型与上升过程仿真分析

基于对高空气球热力学环境的分析,建立了热力学与动力学耦合的高空气球动力学模型;并采用该模型对某高空气球的上升与驻留过程进行仿真分析.结果表明:高空气球上升过程中内部氦气存在"超冷"现象,其中平流层区域"超冷"明显,氦气平均温差为-19 K;由于"超冷",其上升速度曲线呈双"V"形变化;强太阳辐射与弱对流环境使驻留过程中氦气呈现"超热"现象,平衡时氦气平均温度比环境温度高39 K,球内氦气超压648.8 Pa.数值仿真的速度、平均温度变化规律与相关飞行试验数据相吻合,说明该仿真模型是有效的.