Vegetation Change in Great Lakes Coastal Wetlands: Deviation from the Historical Cycle

Water-level change is integral to the structure and function of Great Lakes coastal wetlands, and many studies document predictable relationships between vegetation and water level. However, anthropogenic stressors, such as invasive species, land-use change, and water-level stabilization, interact to shift the historical cycle (of native vegetation migration up- and down-slope) toward dominance by invasive Typha species. Knowing from earlier studies that water-level stabilization alters the historical vegetation cycle, we asked if similar shifts can occur where water levels are not stabilized. Using historical aerial photographs of three coastal wetlands (in Lake Michigan's Green Bay, Wisconsin), we determined that habitat dominated by Typha species has expanded to eliminate wet meadow habitat. Between 1974 and 1992, linear regressions showed strong, significant relationships of both meadow area (R² ≥ 0.894; p < 0.02) and marsh area (R² ≥ 0.784; p < 0.05) to water level in all three wetlands. In 2000, meadow area was below that predicted by the historical pattern due to the landward advance of marsh habitat during a year of decreasing water levels. In the same period, land use in the wetland watersheds converted from agriculture to urban. Urbanization and the replacement of native Typha latifolia by the invasive hybrid Typha xglauca may have overwhelmed the beneficial impact of water-level fluctuation. The documentation of vegetation shifts, as herein, is an essential step in the process of preserving and restoring ecological integrity.     

无人机光电载荷及其应用

简要介绍了无人机优势及应用范围,对目前世界上主要固定翼无人机及无人直升机的光电载荷进行了研究分析,在此基础上,对新型无人飞行器概念平台进行介绍。最后总结了无人机光电载荷发展趋势,即随着无人机平台技术及光电载荷技术的迅速发展,长航时、良好隐身性、多用途、具备主动光电干扰能力、高智能将是无人机光电载荷的发展趋势。     

无人机多假目标欺骗式干扰效能研究

无人机多假目标干扰是一种重要的欺骗干扰样式。分析了无人机多假目标干扰效果的评估指标,建立了多假目标数量计算和标准化模型,最后利用单目标突防被击中模型和突防成功目标数模型对无人机多假目标在不同干扰距离下的干扰效果进行了定量分析,并用仿真计算加以验证。     

Transferring human grasping synergies to a robot

In this paper, a system for transferring human grasping skills to a robot is presented. In order to reduce the dimensionality of the grasp postures, we extracted three synergies from data on human grasping experiments and trained a neural network with the features of the objects and the coefficients of the synergies. Then, the trained neural network was employed to control robot grasping via an individually optimized mapping between the human hand and the robot hand. As force control was unavailable on our robot hand, we designed a simple strategy for the robot to grasp and hold the objects by exploiting tactile feedback at the fingers. Experimental results demonstrated that the system can generalize the transferred skills to grasp new objects.     

基于超宽带的无人机通信链路设计

无人机组网作战是未来的发展趋势,无人机之间有效可靠的实时通信是实现其协同作战的前提和基础。由于超宽带通信技术具有良好的低检测概率和低截获概率特性、系统复杂度低和耗电量小等优点,将其应用在无人机通信链路上是一个很好的选择。文章紧密结合无人机通信的需求,设计了一个无人机超宽带通信链路,包括调制方式、中心频率、跳时序列、发射功率、帧长、每比特的脉冲数和信息速率等,为脉冲无线电技术在未来军事通信中的应用提供了参考。     

无人机装备自主式保障系统研究

目前我军无人机装备采用事后维修、定期维修、预防性维修等维修保障方式,存在故障诊断及修复能力差、维修资源繁多、保障费用急剧增长等问题。充分考虑我军无人机装备技术特点及现行维修保障体制,文中创新性地提出了构建适合我军无人机装备的自主式保障系统;并对系统组成、故障模式影响及危害性分析、测试性设计技术、机载故障快速诊断及自修复技术、预测与健康管理技术、分布式信息融合技术等关键技术进行重点研究。该系统为我军新型信息化装备提供了新的维修保障模式,并可提高我军无人机装备的一体化、精确化保障水平。     

光学系统设计中降低公差灵敏度的方法

基于初级像差理论提出了一种降低系统公差灵敏度的方法,即通过控制光学系统各元件表面的初级像差值以“小像差互补”达到像差平衡.首先阐明“小像差互补”含义,然后通过理论公式指出了初级像差与公差灵敏度的关系,最后举出一个航空相机光学系统的设计实例,通过对其“大像差互补”与“小像差互补”两种设计结果进行公差分析,结果表明利用“小...     

多无人机模糊多目标分布式地面目标协同追踪

针对城市环境中多约束条件下多无人机协同追踪地面目标问题,综合考虑具有不同重要性等级的多个优化目标,提出了一种基于分布式预测控制的模糊多目标航迹规划方法.首先,考虑城市环境中建筑物对无人机视线遮挡、无人机和传感器能量消耗等因素,分别采用目标覆盖度、控制输入代价和开关量形式传感器能耗等为目标函数,将多无人机协同追踪航迹规划转化为多目标优化问题;然后,基于分布式预测控制框架,利用每架无人机未来有限时域内的预测状态,构建多无人机之间的避碰约束,并结合最小转弯半径等约束,形成分布式协同航迹规划模型;最后,针对多个优化目标的不同重要性等级要求,利用模糊满意优化思想将目标模糊化,并根据更重要目标具有更重要满意度的原则,将优先等级表示为松弛满意度序,通过在线求解得到有限时域内每架无人机的局部航迹;与传统多目标加权算法仿真结果对比,验证了所提方法的有效性,充分说明了该方法能够获得同时满足目标优化和重要性等级要求的最优航迹.     

用于清洗绝缘子的四旋翼无人机抗回冲力控制

本文主要针对利用四旋翼无人机清洗绝缘子时受到的回冲力干扰及姿态控制问题,提出了一种用于清洗绝缘子的无人机抗回冲力控制方法.对于无人机系统,本文运用非线性控制方法中的反步法来设计姿态控制器,使其达到输入状态稳定,并对外部扰动具有鲁棒性.本文首先根据无人机运动模型建立了其动力学方程.之后,运用动量定理和流体力学中的伯努利方...     

全景航空相机性能检测系统设计

为实现全景航空相机对地面目标的检测要求,根据其工作原理设计出一套可完成高精度、多参数航空相机的室内检测系统。首先在分析其性能指标和工作原理的基础上,给出了该检测系统的总体方案。详细设计了系统的主要组成部分：远目标模拟系统即大视场平行光管,动态图形发生系统等结构。提出平行光管和动态图形发生器核心参数的测试方法后,对所设计的检测系统进行实际测试,结果显示其整体性能满足所提设计要求。