An ensemble deep learning based shoreline segmentation approach (WaterNet) from Landsat 8 OLI images

Shorelines constantly vary due to natural, urbanization and anthropogenic effects such as global warming, population growth, and environmental pollution. Sustainable monitoring of coastal changes is vital in terms of coastal resource management, environmental preservation and planning. Publicly available Landsat 8 OLI (Operational Land Manager) images provide accurate, reliable, temporal and up-to-date information about coastal areas. Recently, the use of machine learning and deep learning algorithms have become widespread. In this study, we used our public Landsat 8 OLI satellite image dataset to create a majority voting method which is an ensemble automatic shoreline segmentation system (WaterNet) to obtain shorelines automatically. For this purpose, different deep learning architectures have been utilized namely as Standard U-Net, Dilated U-Net, Fractal U-Net, FC-DenseNet, and Pix2Pix. Also, we have suggested a novel framework to create labeling data from OpenStreetMap service to create a unique dataset called YTU-WaterNet. According to the results, IoU and F1 scores have been calculated as 99.59% and 99.79% for the WaterNet. The results indicate that the WaterNet method outperforms other methods in terms of shoreline extraction from Landsat 8 OLI satellite images.     

Detumbling strategy based on friction control of dual-arm space robot for capturing tumbling target

The rotational motion of a tumbling target brings great challenges to space robot on successfully capturing the tumbling target. Therefore, it is necessary to reduce the target’s rotation to a rate at which capture can be accomplished by the space robot. In this paper, a detumbling strategy based on friction control of dual-arm space robot for capturing tumbling target is proposed. This strategy can reduce the target’s rotational velocity while maintaining base attitude stability through the establishment of the rotation attenuation controller and base attitude adjustment controller. The rotation attenuation controller adopts the multi-space hybrid impedance control method to control the friction precisely. The base attitude adjustment controller applies the dual-arm extended Jacobian matrix to stabilize the base attitude. The main contributions of this paper are as follows: (1) The compliant control method is adopted to achieve a precise friction control, which can reduce the target angular velocity steadily; (2) The dual-arm extended Jacobian matrix is applied to stabilize the base attitude without affecting the target capture task; (3) The detumbling strategy of dual-arm space robot is designed considering base attitude stabilization, realizing coordinated planning of the base attitude and the arms. The strategy is verified by a dual-arm space robot with two 7-DOF (degrees of freedom) arms. Simulation results show that, target with a rotation velocity of 20 (°)/s can be effectively controlled to stop within 30 s, and the final deflection of the base attitude is less than 0.15° without affecting the target capture task, verifying the correctness and effectiveness of the strategy. Except to the tumbling target capture task, the control strategy can also be applied to other typical on-orbit operation tasks such as space debris removal and spacecraft maintenance.     

基于状态空间模型的无刷直流电机控制器设计

在无刷直流时机的位置伺服系统中，采用了基于状态空间模型的优化设计方法，综合出了次优控制器、建立了广义误差系统状态方程，并利用积分罚函数分段一经法处理伺服系统不等式约束的问题，得出了次优控制算法，经仿真证实，有杉该优化方法设计出的伺服系统的稳态跟踪误差为零；稳成输出不受阶跃干扰的影响；并具有期望的瞬态响应特性。     

应急救生系统逃逸动力装置的性能分析

载人航天中，应急救生分系统是火箭一飞船系统的重要组成部分，以联盟号应急救生系统为例介绍了其组成、工作程序并研究分析了逃逸动力装置──主逃逸发动机和控制发动机的性能参数与逃逸飞行弹道特性之间的相互关系；从逃逸弹道设计技术指标出发来选取动力装置的主要性能参数（推力大小及工作时间）。仿真计算得出了有益的结论。     

弱正则空间

本文给出了弱正则空间的定义,并研究了弱正则空间的性质,指出弱正则拓扑是一分离拓扑。     

GPS／SINS姿态组合系统空间一致性研究

在基于卡尔曼滤波器并引入了姿态观测量的GPS/SINS组合导航系统中,GPS天线体坐标系与IMU所在的载体坐标系由于安装误差或其他原因不能完全重合,两个坐标系间存在失准角,导致多天线GPS与SINS输出的姿态信息在空间不能同步,这将影响卡尔曼滤波的效果。本文针对这一问题进行了深入的研究,分析了两个坐标系空间不一致的机理,给出了静态和动基座情况下标定两个坐标系位置关系的方法并进行仿真分析验证了其可行性。     

航天飞机气动力辅助异面轨道变换

本文研究了以气动力作为辅助动力,实现异面圆轨道的最优变换。以目标轨道面倾角最大为优化性能指标,获得了升力和滚转角的最优控制规律。文中提出了优化问题的一种参数搜寻方法,有利于问题的求解。文末对结果作了分析,讨论,并就有关的多种变换模态作了分析、对比,表明在一定条件下,气动力辅助变换有明显的优越性。     

Menger PM-空间上复合映射不动点定理的推广

设（X，F，△）和（Y，－↑F，△）是两个完备的MengerPM－空间，△是连续的H型t－范数，函数Φ（t）满足条件（Φ1)，本文在映射T：X→Y和S：Y→X满意更一般的条件下给出了关于复合映射TS和ST的不动点定理。这一定量进一步推广了Fisher,Sehgal和Bharucha-Reid等的有关结果，也是作者“MengerPM－空间上复合映射的不动点定理”一文的一般推广，最后给出了几个有用的结果作为本文主要定理的推广论。     

加工钛合金大口径深盲孔的研究

钛合金属难加工材料,其深孔加工的难度更为突出,加工质量不易保证。本文通过实验对比,对加工钛合金大口径深盲孔中出现的偏孔、切屑堵塞、切削振动、刀具破损等主要问题进行了分析,提出了解决办法,得出了切削用量的优化参数。由于钛合金的化学亲和作用,深孔加工刀具的导向条表面易于粘附,结果拉伤已加工表面,造成表面粗糙度上升。加大导向条与孔壁的间隙虽可减少导向条表面的粘附,但同时会引起切削振动的加剧。针对这一矛盾,本文着重对加工刀具的导向条分布、导向条与孔壁的间隙以及导向条的选材方面进行了探讨,提出了以非金属导向条代替硬质合金导向条进行钛合金深孔精加工的方法,使得已加工表面的粗糙度大大降低。这些研究结果对实际加工具有一定的指导作用。     

Information space of sensor networks: Lagrangian,energy-momentum tensor,and applications

It is a challenge to investigate the interrelationship between the geometric structure and performance of sensor networks due to the increasingly complex and diverse architecture of them. This paper presents two new formulations for the information space of sensor networks, including Lagrangian and energy–momentum tensor, which are expected to integrate sensor networks target tracking and performance evaluation from a unified perspective. The proposed method presents two geometric objects to represent the dynamic state and manifold structure of the information space of sensor networks. Based on that, the authors conduct the property analysis and target tracking of sensor networks. To the best of our knowledge, it is the first time to investigate and analyze the information energy–momentum tensor of sensor networks and evaluate the performance of sensor networks in the context of target tracking. Simulations and examples confirm the competitive performance of the proposed method.