Fully distributed time-varying formation tracking control for multiple quadrotor vehicles via finite-time convergent extended state observer

This paper investigates a time-varying anti-disturbance formation problem for a group of quadrotor aircrafts with time-varying uncertainties and a directed interaction topology. A novel Finite-Time Convergent Extended State Observer (FTCESO) based fully-distributed formation control scheme is proposed to enhance the disturbance rejection and the formation tracking performances for networked quadrotors. By adopting the hierarchical control strategy, the multi-quadrotor system is separated into two subsystems: the outer-loop cooperative subsystem and the inner-loop attitude subsystem. In the outer-loop subsystem, with the estimation of disturbing forces and uncertain dynamics from FTCESOs, an adaptive consensus theory based cooperative controller is exploited to ensure the multiple quadrotors form and maintain a time-varying pattern relying only on the positions of the neighboring aircrafts. In the inner-loop subsystem, the desired attitude generated by the cooperative control law is stably tracked under a FTCESO-based attitude controller in a finite time. Based on a detailed algorithm to specify the cooperative control protocol, the feasibility condition to achieve the time-varying anti-disturbance formation tracking is derived and the rigorous analysis of the whole closed-loop multi-quadrotor system is given. Some numerical examples are conducted to intuitively demonstrate the effectiveness and the improvements of the proposed control framework.     

Variation of dayside chorus waves associated with solar wind dynamic pressure based on MMS observations

The whistler-mode chorus waves are one of the most important plasma waves in the Earth’s magnetosphere. Generally, the amplitude of whistler-mode chorus waves prefers to strengthen when the energetic fluxes of anisotropic electrons increase outside the plasmapause. This characteristic is commonly associated with the geomagnetic storms or substorms. However, the relationship between the solar wind dynamic pressure (P_sw) and the long-time variation of chorus waves during the quiet period of the geomagnetic activity still needs more detailed investigations. In this paper, based on MMS observations, we present a chorus event just observed in the inner side of magnetopause without obvious geomagnetic storms or substroms. Interestingly, during this time interval, some P_sw fluctuations were recorded. Both the amplitudes and frequencies of chorus waves changed as a response to the variation in P_sw. It proved that the enhancement of P_sw increases the energetic electrons fluxes, which provides free energies for the chorus amplification. Furthermore, the wave growth rates calculated using linear theory increases and the central frequency of the chorus waves shifts to a higher frequency when the P_sw enhancement is greater, which are also consistent well with the observations. The results provide a direct evidence that the P_sw play an important role in the long-time variation of whistler-mode chorus waves inside the magnetopause.     

Manifold structure preservative for hyperspectral target detection

A nonparametric method termed as manifold structure preservative (MSP) is proposed in this paper for hyperspectral target detection. MSP transforms the feature space of data to maximize the separation between target and background signals. Moreover, it minimizes the reconstruction error of targets and preserves the topological structure of data in the projected feature space. MSP does not need to consider any distribution for target and background data. So, it can achieve accurate results in real scenarios due to avoiding unreliable assumptions. The proposed MSP detector is compared to several popular detectors and the experiments on a synthetic data and two real hyperspectral images indicate the superior ability of it in target detection.     

流动阻力及能量损失对注射成型制件的影响

本文分析了在塑料熔体充满型腔的过程中，流动阻力及能量损失产生的形式和物理原因，进而讨论了对塑料制件成型及凝固过程中的影响。并提出降低影响的措施。     

Calculation of the transonic dip of airfoils using viscous-inviscid aerodynamic interaction method

A numerical procedure for the calculation of the transonic dip of airfoils in the time domain is presented. A viscous-inviscid aerodynamic interaction method is taken to calculate the unsteady aerodynamic loads. In the present case the integral boundary layer equations are coupled with the Transonic Small Disturbance (TSD) Potential Equation. The coupling between structural motion and aerodynamic loads is carried out using State Space equation. It is solved by State Transition Matrix technique. Results are presented for NACA 64A010 and NLR 7301 airfoils with structural data from Isogai and DLR, respectively. Comparisons show good agreement with other numerical results. Certain deviations of experimental data taken from literature need more insight in the detailed test conditions.     

考虑胶层蠕变行为的胶接结构有限元分析

本文考虑胶层材料的蠕变行为，采用模拟岩层纹理单元的有限元法，分析工程中使用的典型胶接结构的应力场和位移场。数值结果表明，胶层蠕变行为对胶接结构位移和应力场均有较大影响     

等质量异形粒子超高速撞击侵蚀

用数值方法模拟双锥，圆柱，椭球、圆锥和倒圆锥五类等质量异形铝粒子五种高宽比共２５种粒子对半无限铝靶的超高速撞击侵蚀，撞击速度为４ｋｍ／ｓ，给出了坑深、坑径、坑形参数和坑体积随粒子形状及高宽比的变化曲线。结果与非圆球异形粒子超高速撞击侵蚀计算有重要参考价值。     

转变财政投资观念，促进经济发展

财政投资是政府运用国家财力调节宏观经济运行的重要手段，就如何重新确定财政投资范围，财政投资方式和财政投资产业的配置等方面进行了阐述。     

飞机超差结构疲劳寿命量化评定

依据美机实用手册介绍的疲劳寿命S-N方程,对超差结构疲劳寿命推导出了一个量化评定方程。并应用该方程对一些典型结构超差形式具体地进行了疲劳寿命量化评定。实践证明,用本文介绍的方法对超差结构疲劳寿命进行定量评定,不仅简捷明快,而且结果可靠。     

关于加大产业结构调整力度的思考

本文从我国产业结构调整的现状及存在的问题出发，针对一般加工产业生产能力过大，高水平的加工能力不足这一突出问题进行了原因分析，在此基础上，就我国加速优化产业结构的客观基础和可能，提出了关于加大产业结构调整力度的七点思考建议。