飞机供电系统自动化仿真技术

飞机供电系统是现代飞机核心组成部分之一,其性能和可靠性对飞机安全至关重要,仿真方法为高品质飞机供电系统设计提供了重要手段。传统的手动仿真方法需要耗费大量人力和时间资源,且无法完全考虑系统的复杂性和不确定性,因此无法满足飞机供电系统全面分析和评估的需求。文中提出了一种将虚拟仿真和实物系统相结合的飞机供电系统自动化仿真技术,能够提高仿真效率和准确性,且可快速、高效地评估飞机供电系统的性能,发现潜在问题,指导系统的优化与改进,对提高飞机供电系统的设计、分析和优化具有重要意义。     

压力、温度组合畸变对某发动机影响的数值研究

本文给出了组合畸变的描述参数,详细地计算和分析了组合畸变对某发动机稳定性的影响,讨论和分析了在不同组合相位和畸变强度下的影响情况。计算结果表明:当压力和温度畸变相位完全重合时,压缩系统中将产生最大的稳定裕度损失;如果适当调整压力与温度的组合畸变相位,一种畸变可能削弱另一种畸变,实际上可增加稳定裕度。     

Monitoring of maize lodging using multi-temporal Sentinel-1 SAR data

Lodging is a common phenomenon in maize production, which seriously affects its yield, quality, and mechanical harvesting capacity. With good penetrating power, satellite radar can monitor crop growth even under cloudy weather conditions. In this study, a method based on the change in plant height before and after lodging in maize is proposed to calculate the lodging angle and monitor the lodging degree by using dual-polarization Sentinel-1A data. The results show that the optimal sensitive polarization combinations of maize plant height before and after lodging are VH/VV and VV, respectively. The lodging angle is calculated using the plant height inversion results before and after lodging. The overall accuracy of classifying lodging grade of maize is 67%. The proposed model based on lodging angle could effectively mapped the maize lodging range on a regional scale and classify the lodging grades.     

Correction model of BDS satellite-induced code bias and its impact on precise point positioning

There are code biases on the pseudo-range observations of the Beidou Navigation Satellite System (BDS) that range in size from several decimeters to larger than one meter. These biases can be divided into two categories, which are the code biases in the pseudo-range observations of Inclined Geo-Synchronous Orbit (IGSO) satellites and Medium Earth Orbit (MEO) satellites and the code biases in the pseudo-range observations of Geosynchronous Earth Orbit (GEO) satellites. In view of the code bias of the IGSO/MEO satellites, the code bias correction model is established using the weighted least square curve fitting method. After the correction, the code biases of the IGSO and MEO satellites are clearly mitigated. A methodology of correcting GEO code bias is proposed based on the empirical mode decomposition (EMD)-wavelet transform (WT) coupled model. The accuracies of the GEO multipath combination of the B1, B2 and B3 frequencies are improved by 39.9%, 17.9%, and 29.4%, respectively. Based on the corrections above, the ten days observations of three Multi-GNSS Experiment (MGEX) stations are processed. The results indicate that the convergence time of the precise point positioning (PPP) can be improved remarkably by applying a code bias. The mean convergence time can be improved by 14.67% after the IGSO/MEO code bias correction. By applying the GEO code bias, the mean convergence time can be further improved by 17.42%.     

GOCE star tracker attitude quaternion calibration and combination

We analyse the inter-boresight angles (IBA) measured by the star trackers on board the GOCE satellite and find that they exhibit small offsets of 7–9″ with respect to the ones calculated from the rotation of the star tracker reference frames to the satellite reference frame. Further, we find small variations in the offsets with a peak-to-peak amplitude of up to 8″, which correlate with variations of the star trackers’ temperatures. Motivated by these findings, we present a method for combining the attitude quaternions measured by two or more star trackers that includes an estimation of relative attitude offsets between star trackers as a linear function of temperature. The method was used to correct and combine the star tracker attitude quaternions within the reprocessing of GOCE data performed in 2018. We demonstrate that the IBA calculated from the corrected star tracker attitude quaternions show no significant offsets with respect to the reference frame information. Finally, we show that neglecting the star tracker attitude offsets in the processing would result in perturbations in the gravity gradients that are visible at frequencies below 2?mHz and have a magnitude of up to 90?mE. The presented method avoids such perturbations to a large extent.     

基于蚁群改进 BP算法的组合预测模型在军械器材需求预测中的应用

针对在军械器材采购计划制定环节中的器材需求测算问题,提出基于蚁群改进BP算法的组合预测模型。先结合历史数据,利用多元线性回归预测法和自回归滑动平均模型（ARMA）进行初步预测,将初步预测的结果作为蚁群改进BP网络的输入,从而得到最终的预测结果。实验结果表明,基于蚁群改进BP算法的组合预测模型能够对积累的历史数据进行充分的应用,并且有较高的预测准确性。     

基于eN-数据库方法复杂构型飞机转捩预测

为探索边界层转捩对大型运输机在起降条件和有较大层流区的巡航条件下的气动力精确计算问题，通过在三维RANS求解器中引入eN-数据库方法来预测飞行器表面的转捩位置，并探索转捩对气动力的影响规律。方法与目前流行的基于间歇因子控制方程的转捩预测方法相比，具有计算效率高、易于工程应用、且考虑TS不稳定性转捩因素的特点。在此基础上，通过计算NASA梯形翼来分析起降构型条件下气动力受转捩影响的规律，并通过计算DLR－F6翼身组合体来探索三维构型在巡航条件下的气动力精度。使用eN-数据库转捩判断方法的计算结果与实验值吻合较好，验证了所构建的基于RANS求解器的eN-数据库转捩预测方法的有效性，并为大型运输机气动力精确计算提供了分析工具。     

结冰对翼型及翼身组合体气动特性影响研究

飞机结冰是影响飞机飞行安全的重要因素之一,研究结冰对飞机气动性能的影响具有重要意义。应用多块结构化网格生成方法,通过求解雷诺平均N-S方程分别对翼型及DLR-F4翼身组合体干净外形和三种不同带冰外形的流场进行计算,分析不同冰型对翼型及翼身组合体绕流流场及气动特性的影响。     

Combination methods of tropospheric time series

In this article we present two methods for combination of different Global Navigation Satellite Systems (GNSS) Zenith Total Delay (ZTD) time-series for the same GNSS site, but from different producers or different processing setups. One method has been setup at ASI/CGS, the other at KNMI. Using Near Real-Time (NRT) ZTD data covering 1 year from the E-GVAP project, the performance of the two methods is inter-compared and validation is made against a combined ZTD solution from EUREF, based on post-processed ZTDs. Further, validation of the ASI combined solutions is made against independent ZTDs derived from radiosonde, Numerical Weather Prediction (NWP) model and Very Long Baseline Interferometry (VLBI) ZTD.     

产融结合背景下我国金融业的三重抉择

世界各国金融业的制度、政策、组织形式和监管体制都有其各自的发展历程,混业经营也是我国今后发展的趋势.我国应当支持适度的产、融结合,构建银行控股集团、保险控股集团、产融结合型控股集团组织形式,推行伞型金融监管体制.