A method of estimating GPS instrumental biases with a convolution algorithm

This paper presents a method of deriving the instrumental differential code biases (DCBs) of GPS satellites and dual frequency receivers. Considering that the total electron content (TEC) varies smoothly over a small area, one ionospheric pierce point (IPP) and four more nearby IPPs were selected to build an equation with a convolution algorithm. In addition, unknown DCB parameters were arranged into a set of equations with GPS observations in a day unit by assuming that DCBs do not vary within a day. Then, the DCBs of satellites and receivers were determined by solving the equation set with the least-squares fitting technique. The performance of this method is examined by applying it to 361?days in 2014 using the observation data from 1311 GPS Earth Observation Network (GEONET) receivers. The result was crosswise-compared with the DCB estimated by the mesh method and the IONEX products from the Center for Orbit Determination in Europe (CODE). The DCB values derived by this method agree with those of the mesh method and the CODE products, with biases of 0.091?ns and 0.321?ns, respectively. The convolution method's accuracy and stability were quite good and showed improvements over the mesh method.     

Simulation analysis for effects of bone loss on acceleration tolerance of human lumbar vertebra

The purpose of the present study was to analyze and predict the changes in acceleration tolerance of human vertebra as a result of bone loss caused by long-term space flight. A human L3–L4 vertebra FEM model was constructed, in which the cancellous bone was separated, and surrounding ligaments were also taken into account. The simulation results demonstrated that bone loss has more of an effect on the acceleration tolerance in x-direction. The results serve to aid in the creation of new acceleration tolerance standards, ensuring astronauts return home safely after long-term space flight. This study shows that more attention should be focused on the bone degradation of crew members and to create new protective designs for space capsules in the future.     

机翼结冰生命周期的数字孪生软件系统

飞机巡航中的机翼结冰情况是关系到飞行安全的重大实际问题之一,如果能够实时监测甚至根据环境提前预测机翼结冰过程和状况,对改进机翼防除冰设计、规避飞行危险都具有重大意义。数字孪生技术作为5G信息时代中新兴的技术,为物理过程的虚拟呈现提供了新的思路与解决方案、同时数字孪生技术结合人工智能等技术,同样可以应用于飞机巡航中机翼结冰物理过程,对实时监测与预测提供了新的技术保证。从数字孪生的角度出发,以机翼结冰神经网络模型为切入点,设计实现了一款基于数字孪生和人工智能技术的巡航中机翼结冰二维过程快速呈现软件系统。软件获取飞机巡航结冰参数与飞行参数,运行结果能够利用动态显示方式,呈现飞机巡航中机翼结冰全生命周期。     

待机状态下机翼结冰的快速计算方法

飞机在飞行过程中遭遇结冰气象,尤其是过冷大水滴结冰条件所导致的机翼结冰,将严重影响飞机的气动性能与操纵品质,从而导致飞行故障或飞行事故,是飞机飞行安全的重要影响因素,是飞机研制中必须重点解决的难题。虽然针对结冰已建立有多种计算仿真程序,但快速获得结冰模拟冰形,包括过冷大水滴条件下的结冰模型是工程师们一直追求的解决方案。利用前向多层神经网络,尝试建立了一种针对待机状态下的机翼结冰模型。此方法基于坐标转换原理,将获取的采用直角坐标表达的标准翼型的机翼结冰数据转换为对应的极坐标表达的数据,以飞行参数、气象参数和极坐标角度作为输入,极坐标模值作为输出训练构建出此种机翼结冰模型。使用所建立的模型,仿真预测结果表明该计算方法具备快速性和精确性,其计算精度可满足实际要求。     

综合飞行/推进控制(IFPC)技术综述

在分析国内外关于综合飞行／推进控制（ＩＦＰＣ）技术的研究资料的基础上,回顾了综合飞行／推进控制技术的问题来源及发展过程,总结了综合飞行／推进控制系统的总体方案,系统地介绍了在综合飞行／推进控制技术研究中采用的理论方法。     

不可压扰动方程高精度对称紧致差分数值解法及应用

从粘性不可压扰动方程一阶改型形式出发,对其实现了高精度对称紧致差分离散,就导出的扰动线性特征值问题给出了一个高铲双重迭代局部解法,以相同精度将特征值和特征函数同时得到。通过不可平面Ｐｏｉｓｅｕｉｌｌｅ流时间稳定性算例详细对比显示了算法良好的谱分辨能力和较弱的网格依赖性,并结合复矩阵广义特征隐式移ＱＺ算法获取了一个 扰动特征值谱计算结果。     

伸展柔性附件对简谐激励的响应分析

从Hamilton原理出发推导了柔性附件伸展过程的时变系数动力学方程。对附件在简谐激励下的响应进行了数值仿真,讨论了伸展柔性附件所具有的一些独特的现象：齐次解的非瞬态特性、特解的非稳态特性、瞬时共振的延续和加强。由于这些特性的存在,大大增加了由激励引发剧烈振动而导致结构破坏的可能性。     

开环FOG中PZT调制器的在线研究

从理论上分析了PZT(压电型)光纤相位调制器在开环FOG(光纤陀螺)中的应用特点,研究了它的调制系数和调制相位延迟变化对开环FOG性能的影响;并设计了两种独立的在线测试方法对它们进行了温度特性研究,利用所得数据,用最小二乘多项式拟合的方法分别得到了它们的温度模型.研究表明,在实验温度范围内,开环FOG的相位调制系数K_GP随温度呈线性变化,而调制相位延迟α随温度呈二次的变化.