空间超高速撞击碎片云前端速度的预测模型

文章利用一组二级轻气炮发射2017-T4 铝质球形弹丸撞击6061-T6单层铝板的地面试验数据,通过选择适当的函数模型,采用多元函数拟合的方法,得到了碎片云前端速度与靶板厚度、弹丸直径和弹丸速度关系的三元二阶多项式模型。再用另外一组数据对该模型进行检验,验证了其对碎片云前端速度具有较好的预测效果。将以上两组数据同样用于建立“无量纲化”模型进行碎片云前端速度预测,并与前述多项式模型的预测结果进行比较发现,该多项式模型预测的方均根误差及平均相对误差均明显优于“无量纲化”模型。该多项式模型可用于预测空间碎片撞击航天器产生的碎片云的前端速度,有助于航天器的空间碎片防护设计。     

FY—1C卫星的资料处理及应用研究

介绍了FY－1C的轨道特征、对地观测能力、星上数据贮存能力和数据传输能力等，以及卫星仪器特性、光谱波段特征和应用能力。最后给出了卫星资料的应用情况。     

我校大学生心理健康状况不容乐观

本文用SCL－90症状自评量表方法，对我校三个年级的部分班级进行了测查。分析表明：我院大学生的心理健康状况不容乐观。本文还对学生管理现状提出了进一步改进建议。     

关于双向弯曲变形构件危险截面的讨论

本文通过具体例题，阐述了双向弯曲变形构件中危险截面的判定方法，论证了合成弯矩大的截面不一定是危险截面的结论。     

RDX/硬脂酸铅复合粒子的制备及其性能表征

为改善RDX-CMDB推进剂的燃烧性能和安全性能,以硬脂酸铅为包覆剂,采用化学沉淀法对RDX填料进行了表面包覆,制备了RDX/硬脂酸铅复合粒子。用SEM、XPS对包覆效果进行了表征;对包覆前后样品的机械感度进行了测试和对比;采用DSC对分别由包覆前后RDX制成的推进剂进行了热分解催化性能测试。结果表明,经过硬脂酸铅包覆,RDX的机械感度得到明显降低,撞击感度特性落高(H50)升高了17.6 cm,摩擦爆炸概率(P)降低了60%。与加有纯RDX的推进剂样品相比,添加RDX/硬脂酸铅复合粒子推进剂样品的硝化棉/硝化甘油放热峰峰温降低了约3.7℃,总放热量也得到了提高。     

Effects of in-track maneuver on Sun illumination conditions of near-circular low Earth orbits

By developing approximate analytical models considering the J₂ perturbation, the effects of an in-track maneuver on the orbital Sun illumination conditions of near-circular low Earth orbits are analyzed. First, two approximate models for the variations in orbital sunshine angles are developed, one for variations at a given time and the other for variations at a given argument of latitude. Next, two approximate models for variations in orbital arc in Earth shadow are developed, one considers the small eccentricity and the other uses the zero eccentricity. Finally, the developed approximate models are applied to analyzing the Sun illumination conditions of a typical in-track maneuver mission on a near-circular low Earth orbit. From the results obtained, three major conclusions can be drawn. First, the variations in orbital sunshine angles at a given time may reach tens of degrees when the drifting time reaches hundreds of orbital periods, and the approximate model for that situation cannot effectively approach the numerical results. Second, the variations in orbital sunshine angles for any given argument of latitude are only a couple of degrees even when the drifting time reaches 500 orbital periods, and the approximation model developed can effectively approach the numerical results. Third, for variations in orbital arc in Earth shadow, the approximate model considering the small eccentricity has simple expressions and can effectively approach the numerical results; in contrast, the approximate model using the zero eccentricity has relatively worse precision.     

Non-stationarity and cross-correlation effects in the MHD solar activity

The analysis of turbulent processes in sunspots and pores which are self-organizing long-lived magnetic structures is a complicated and not yet solved problem. The present work focuses on studying such magneto-hydrodynamic (MHD) formations on the basis of flicker-noise spectroscopy using a new method of multi-parametric analysis. The non-stationarity and cross-correlation effects taking place in solar activity dynamics are considered. The calculated maximum values of non-stationarity factor may become precursors of significant restructuring in solar magnetic activity. The introduced cross-correlation functions enable us to judge synchronization effects between the signals of various solar activity indicators registered simultaneously.     

Numerical investigation of flow mechanisms of tandem impeller inside a centrifugal compressor

This study numerically investigated a single stage centrifugal compressor ‘‘Radiver’’ with a wedge diffuser and several tandem-designed impellers to explore the flow phenomena within the tandem impeller and the potential to enhance compressor performance. The results demonstrate that tandem design and clocking fraction (λ_s) significantly affects the compressor performance. The compressor stage with tandem impellers of Series A of boundary layer growth interruption alone are observed to have a widely operating range but efficiency and total pressure ratio penalty compared with that of conventional impeller. The tandem impeller with at least the same impeller efficiency as the conventional design is considered as a critical design criteria so that further modification process based on the flow characteristic of tandem impeller is necessary. In order to restrain the inducer wake and exducer shock losses, parameters modification of blade angle and thickness distributions are necessary and the modified tandem impeller of Series B is obtained. The modified tandem impeller with 25% clocking arrangement shows an 8.45% stall margin increase and maintains the total pressure ratio and efficiency as the conventional design, which proves the potential of tandem impeller to improve compressor stage performance. It is noteworthy that the tandem impellers of Radiver have not shown obviously balanced exit flow field and the fundamental mechanism of stall margin extending of tandem impeller lies on the improved impeller/diffuser matching performance resulting from the incidence angle variation at diffuser inlet.     

某型飞机前起落架摆振性能研究

阐述了摆振分析基本思路,分析了轮胎充气压力对某型飞机前起落架摆振特性的影响,并进行了摆振响应分析和摆振试验验证。研究表明:当轮胎充气压力降低时,摆振临界阻尼减小,有利于防摆;当轮胎充气压力增大,摆振临界阻尼增大,不利于防摆;摆振响应分析试验表明前起落架满足摆振稳定性要求。