钛合金蜂窝三层结构的扩散焊接研究

介绍了俄罗斯钛合金蜂窝三层结构扩散焊接的研究成果.详细介绍了铝合金、焊接规范选择、接头应力变形状态的分析、模拟计算等,有助于国内钛合金的焊接研究.     

一种负极性直流高压线性电源设计

本文提出了一种基于光耦反馈调整的负极性高压线性电源解决方案，使用NPN型三极管作为功率调整管的前提下，实现了负1200V直流电压输出。本文对提出的电源方案建立了小信号传递函数模型，在传递函数模型的基础上论证了所提出的电源系统具有稳定性高、噪声低等优点。     

Phasic-to-tonic shift in trunk muscle activity relative to walking during low-impact weight bearing exercise

The aim of this study was to investigate the influence of an exercise device, designed to improve the function of lumbopelvic muscles via low-impact weight-bearing exercise, on electromyographic (EMG) activity of lumbopelvic, including abdominal muscles. Surface EMG activity was collected from lumbar multifidus (LM), erector spinae (ES), internal oblique (IO), external oblique (EO) and rectus abdominis (RA) during overground walking (OW) and exercise device (EX) conditions. During walking, most muscles showed peaks in activity which were not seen during EX. Spinal extensors (LM, ES) were more active in EX. Internal oblique and RA were less active in EX. In EX, LM and ES were active for longer than during OW. Conversely, EO and RA were active for a shorter duration in EX than OW. The exercise device showed a phasic-to-tonic shift in activation of both local and global lumbopelvic muscles and promoted increased activation of spinal extensors in relation to walking. These features could make the exercise device a useful rehabilitative tool for populations with lumbopelvic muscle atrophy and dysfunction, including those recovering from deconditioning due to long-term bed rest and microgravity in astronauts.     

远程星际航行补篇

通过一系列变量置换推导出不同喷气速度和不同加速度条件下,计算恒星际飞船加速段的时间和距离的普遍公式及多级火箭加速情况下加速段的时间和距离的公式。最后以天狼星作为航行目标、计算了用5级和10级火箭加速飞行的时间和距离。结果表明,当火箭的级数很多,且各级加速度相等时,其飞行时间与距离非常接近匀加速飞行的情况。     

Lunar geophysical parameters inversion based on gravity/topography admittance and particle swarm optimization

This paper presents a FORTRAN computer program. The program as code will be used for lunar parameter inversions based on gravity/topography admittance. This will be done by assuming that the lunar lithosphere is modeled as a thin elastic spherical shell. The parameters discussed here include; load ratio, crustal thickness, subsurface load depth, crustal density and elastic lithosphere thickness. The admittance of the best-fitting model can be found through automatically adjusting misfits between one theoretical admittance and an observed one. The results in this paper indicate that this research’s theoretical model is reasonable for exploring the best-fitting parameters. In addition, this code is not only able to automatically and simultaneously calculate the global optimum solution of the parameters studied, but also performs well in computational speed. The code can be easily modified to include more parameter inversions; such as the inversion for subsurface density anomaly and the case of considering infilling material in some lunar mare basins.     

基于容栅技术数显力矩扳手无线通信系统的设计

随着无线通信技术的飞速发展，许多电气电子系统中的数据传输方式逐步使用无线通信方式替代原来的有线数据通信方式。目前我公司使用的基于容栅技术的数显力矩扳手广泛应用于航空航天、兵器、船舶、铁路等领域，对数据测量、数据存储都有严格的要求，而传统的有线数据传输方式，将对测量环境带来了极大的限制，而且传输距离短、接线方式复杂，由于计算机传输接口有限，将给大量的数据传输带来不便。本文则使用一种低功耗芯片设计了一款无线通信模块，将目前数显力矩扳手的通信方式通过有线数据传输改为无线通信技术传输。这将给客户应用带来了极大的便利，适应了不同的环境，挺高了产品的性能和市场竞争力，可以达到多组设备数据同时显示到计算机上，该产品已经过测试验证可以达到预期的效果。     

推进剂重定位过程仿真与分析

为了拓展低温上面级滑行时间，满足深空探测任务需求以及提升运载火箭任务适应性，中国未来型号研制将采用间歇沉底的方案，其主要难点是推进剂重定位过程的研究。本文针对目前重定位仿真多为二维CFD仿真且不能准确合理地预示气泡逸出过程的问题，提出一种基于Flow-3D的三维CFD仿真方法。该方法采用卷气体积与液体体积之比（卷气率）预示气泡逸出过程，比以往采用气泡粒子数预示气泡逸出过程的方法更为合理准确。重定位及气泡逸出过程的仿真结果与半人马座落塔试验的结果具有一致性，捕捉到了重定位过程所有特征流型，且对应时刻误差不超过10%。仿真结果表明间歇沉底推进剂管理方案的可行性，并确定了某低温上面级的相关设计参数。     

Sailing at the brink – The no-limits of near-/now-term-technology solar sails and SEP spacecraft in (multiple) NEO rendezvous

Near-Earth object (NEO) in-situ exploration can provide invaluable information for science, possible future deflection actions and resource utilisation. This is only possible with space missions which approach the asteroid from its vicinity, i.e. rendezvous. This paper explores the use of solar sailing as means of propulsion for NEO rendezvous missions. Given the current state of sail technology, we search for multiple rendezvous missions of up to ten years and characteristic acceleration of up to 0.10 mm/s². Using a tree-search technique and subsequent trajectory optimisation, we find numerous options of up to three NEO encounters in the launch window 2019–2027. In addition, we explore steerable and throttleable low-thrust (e.g. solar-electric) rendezvous to a particular group of NEOs, the Taurid swarm. We show that an acceleration of 0.23 mm/s² would suffice for a rendezvous in approximately 2000 days, while shorter transfers are available as the acceleration increases. Finally, we show low-thrust options (0.3 mm/s²) to the fictitious asteroid 2019 PDC, as part of an asteroid deflection exercise.     

Accuracy analysis of GNSS-IR snow depth inversion algorithms

In recent years, with the continuous development of Global Navigation Satellite System (GNSS), it has been applied not only to navigation and positioning, but also to Earth surface environment monitoring. At present, when performing GNSS-IR (GNSS Interferometric Reflectometry) snow depth inversion, Lomb-Scargle Periodogram (LSP) spectrum analysis is mainly used to calculate the vertical height from the antenna phase center to the reflection surface. However, it has the problem of low identification of power spectrum analysis, which may lead to frequency leakage. Therefore, Fast Fourier Transform (FFT) spectrum analysis and Nonlinear Least Square Fitting (NLSF) are introduced to calculate the vertical height in this paper. The GNSS-IR snow depth inversion experiment is carried out by using the observation data of P351 station in PBO (Plate Boundary Observatory) network of the United States from 2013 to 2016. Three algorithms are used to invert the snow depth and compared with the actual snow depth provided by the station 490 in the SNOTEL network. The observations data of L1 and L2 bands are respectively used to find the optimal combination between different algorithms further to improve the accuracy of GNSS-IR snow depth inversion. For L1 band, different snow depths correspond to different optimal algorithms. When the snow depth is less than 0.8 m, the inversion accuracy of NLSF algorithm is the highest. When the snow depth is greater than 0.8 m, the inversion accuracy of FFT algorithm is higher. Therefore, according to the different snow depth, a combined algorithm of NLSF + FFT is proposed for GNSS-IR snow depth inversion. Compared with the traditional LSP algorithm, the inversion accuracy of the combined algorithm is improved by 10%. For L2 band data, the results show that the accuracy of snow depth inversion of various algorithms do not change with the variations of snow depth. Among the three single algorithms, the inversion accuracy of FFT algorithm is better than that of LSP and NLSF algorithms.     

复合材料MMB试件I-II混合型层间裂纹扩展分析

基于经典层合板理论及双线性黏聚区本构关系，建立了含一般分层裂纹层合板的理论模型，对I-Ⅱ混合型弯曲（MMB）断裂试件进行了裂纹扩展理论分析。提出了一种I-Ⅱ混合型断裂叠加模型，引入I型裂纹分量的刚体转动位移，同时考虑了裂纹长度超过试件半长后中部载荷分量对裂纹扩展的闭合效应，并根据黏聚区力学响应，分段获得了位移函数通解。结合叠加模型的边界条件与连续性条件，分析了MMB试件的裂纹扩展过程，求解获得了载荷-位移曲线。通过与梁模型预测以及试验结果进行对比，验证了本文模型对I-Ⅱ混合型裂纹扩展预测的有效性和准确性，并讨论了初始断裂模式混合比及闭合效应对裂纹扩展过程的影响。结果表明：初始Ⅱ型裂纹比重较大时，中部载荷的闭合效应更为明显，可能出现I型裂纹完全闭合的情况；裂纹扩展过程中，当裂纹长度小于试件半长时，断裂混合比基本保持常数；当裂纹扩展超过试件半长后，闭合效应明显，混合裂纹形式逐渐向单一型断裂模式退化。