Non-intrusive,three-dimensional temperature and composition measurements inside fluid cells in microgravity using a confocal holography microscope

Application of a confocal scanning laser holography (CSLH) microscope to the study of fluid flow in a microgravity environment is described herein. This microscope offers a new, non-intrusive means to determine three-dimensional density gradients within solid objects, fluids, and plasmas, including flames. The index-of-refraction is determined from the phase measurements of the microscope, which is a function of the object temperature and composition. The object being studied is a fluid-cell chamber, which is heated and cooled on opposing walls to produce a steady-state fluid flow due to convection and heat transfer. The holograms are created from the interference of a “known” reference beam with an “unknown” object beam. A three-dimensional amplitude and phase image of the object is produced by the reconstruction of many holograms, where each hologram represents a scanned point inside the object.     

Nonlinear effects in the correlation of tracks and covariance propagation

Even though there are methods for the nonlinear propagation of the covariance the propagation of the covariance in current operational programs is based on the state transition matrix of the 1st variational equations, thus it is a linear propagation. If the measurement errors are zero mean Gaussian, the orbit errors, statistically represented by the covariance, are Gaussian. When the orbit errors become too large they are no longer Gaussian and not represented by the covariance. One use of the covariance is the association of uncorrelated tracks (UCTs). A UCT is an object tracked by a space surveillance system that does not correlate to another object in the space object data base. For an object to be entered into the data base three or more tracks must be correlated. Associating UCTs is a major challenge for a space surveillance system since every object entered into the space object catalog begins as a UCT. It has been proved that if the orbit errors are Gaussian, the error ellipsoid represented by the covariance is the optimum association volume. When the time between tracks becomes large, hours or even days, the orbit errors can become large and are no longer Gaussian, and this has a negative effect on the association of UCTs. This paper further investigates the nonlinear effects on the accuracy of the covariance for use in correlation. The use of the best coordinate system and the unscented Kalman Filter (UKF) for providing a more accurate covariance are investigated along with assessing how these approaches would result in the ability to correlate tracks that are further separated in time.     

非对称机动能力多无人机智能协同攻防对抗

协同攻防对抗是未来军用无人机的重要作战场景。针对不同机动能力无人机群体间的攻防对抗问题，建立了多无人机协同攻防演化模型，基于多智能体强化学习理论，研究了多无人机协同攻防的自主决策方法，提出了基于执行-评判（Actor-Critic）算法的集中式评判和分布式执行的算法结构，保证算法稳定收敛的同时，提升执行效率。无人机的评判模块使用全局信息评价决策优劣引导策略学习，而执行时只需要依赖局部感知信息进行自主决策，提高了多机攻防对抗的效能。仿真结果表明，所提的多无人机强化学习方法具备较强的自进化属性，赋予了无人机一定智能，即稳定的自主学习能力，通过不断演化，能自主学习提升协同对抗的决策效能。     

轻小型太阳能/氢能无人机发展综述

轻小型无人机（UAV）在军民领域都有着广泛的用途，电动无人机由于其振动低、无污染、无排放等优势，已经成为无人机领域的发展热点。为了提高轻小型电动无人机的航时，清洁、高能量密度的太阳能和氢能成为非常可行的技术途径之一。本文总结了轻小型太阳能、氢能无人机的发展历程；梳理了相关的关键技术，并对太阳能、氢能无人机的总体设计方法和能源动力系统的发展进行了较为深入的探讨；最后，展望了该类无人机的发展趋势，并对所面临的挑战进行了预测。     

空间高稳定碳/碳蜂窝夹层结构制备及性能

针对空间高稳定结构在极端环境下的灵敏度和稳定性需求，提出一种新型高稳定、高承载的轻质碳/碳(C/C)蜂窝夹层结构方案。碳/碳蜂窝夹层结构由化学气相渗透(CVI)致密化获得的整体碳/碳蜂窝和面板经胶粘剂粘接集成，通过评价蜂窝、面板以及夹层结构的内部质量、力学性能及热物理性能，展示了碳/碳蜂窝夹层结构在承载和尺度稳定性方面的优势。研究结果表明,典型特征碳/碳蜂窝承载性能稳定，平压强度＞10 MPa，L/W向剪切强度＞4 MPa，典型特征碳/碳蜂窝夹层结构热膨胀系数低，满足空间环境条件下面内热膨胀系数绝对值低于 1×10 -7 /℃的高稳定设计需求。     

Target berthing and base reorientation of free-floating space robotic system after capturing

Space robots are playing an increasingly important role in on-orbital servicing, including repairing, refueling, or de-orbiting the satellite. The target must be captured and berthed before the servicing task starts. However, the attitude of the base may lean much and needs re-orientating after capturing. In this paper, a method is proposed to berth the target, and re-orientate the base at the same time, using manipulator motion only. Firstly, the system state is formed of the attitude quaternion and joint variables, and the joint paths are parameterized by sinusoidal functions. Then, the trajectory planning is transformed to an optimization problem. The cost function, defined according to the accuracy requirements of system variables, is the function of the parameters to be determined. Finally, we solve the parameters using the particle swarm optimization algorithm. Two typical cases of the spacecraft with a 6-DOF manipulator are dynamically simulated, one is that the variation of base attitude is limited; the other is that both the base attitude and the joint rates are constrained. The simulation results verify the presented method.     

A new real-time guidance strategy for aerodynamic ascent flight

Reusable launch vehicles are conceived to constitute the future space transportation system. If these vehicles use air-breathing propulsion and lift taking-off horizontally, the optimal steering for these vehicles exhibits completely different behavior from that in conventional rockets flight. In this paper, the new guidance strategy is proposed. This method derives from the optimality condition as for steering and an analysis concludes that the steering function takes the form comprised of Linear and Logarithmic terms, which include only four parameters. The parameter optimization of this method shows the acquired terminal horizontal velocity is almost same with that obtained by the direct numerical optimization. This supports the parameterized Liner Logarithmic steering law. And here is shown that there exists a simple linear relation between the terminal states and the parameters to be corrected. The relation easily makes the parameters determined to satisfy the terminal boundary conditions in real-time. The paper presents the guidance results for the practical application cases. The results show the guidance is well performed and satisfies the terminal boundary conditions specified. The strategy built and presented here does guarantee the robust solution in real-time excluding any optimization process, and it is found quite practical.     

负荷条件下注意力分配策略对情境意识的影响

为探究负荷条件下不同注意力分配策略对情境意识（SA）的影响，招募22名被试开展了3种注意力分配策略（平均分配、主次分配、多级分配）×2种脑力负荷（低负荷、高负荷）条件下的被试内双因素设计的实验任务，记录情境意识全面测量技术（SAGAT）、行为绩效、眼动和脑电（EEG）指标为因变量。实验结果表明，在不同脑力负荷下，相较于多级注意力分配策略和主次注意力分配策略，平均注意力分配策略的SAGAT得分和绩效正确率均更低、最小近邻指数（NNI）更大；在高脑力负荷下，相较于多级注意力分配策略，主次注意力分配策略的SAGAT得分更高、绩效反应时间更短并且NNI值更低；SAGAT得分与平均注视时间、NNI、θ相对功率和α相对功率均存在显著低度相关。本研究结果提示，在不同脑力负荷条件下，采用平均注意力分配策略可能导致作业人员的注意力更为分散，从而产生更差的工作绩效和更低的SA水平；而在高脑力负荷条件下，相比于多级注意力分配策略，主次注意力分配策略更有助于作业人员提取关键信息并维持更好的SA水平，但同时可能存在SA丧失的风险；眼动的平均注视时间和NNI指标以及EEG的θ和α相对功率指标具有较好的表征SA的潜力。     

Nonlinear dynamics of a flapping rotary wing: Modeling and optimal wing kinematic analysis

The analysis of the passive rotation feature of a micro Flapping Rotary Wing(FRW)applicable for Micro Air Vehicle(MAV) design is presented in this paper. The dynamics of the wing and its influence on aerodynamic performance of FRW is studied at low Reynolds number(~10~3).The FRW is modeled as a simplified system of three rigid bodies: a rotary base with two flapping wings. The multibody dynamic theory is employed to derive the motion equations for FRW. A quasi-steady aerodynamic model is utilized for the calculation of the aerodynamic forces and moments. The dynamic motion process and the effects of the kinematics of wings on the dynamic rotational equilibrium of FWR and the aerodynamic performances are studied. The results show that the passive rotation motion of the wings is a continuous dynamic process which converges into an equilibrium rotary velocity due to the interaction between aerodynamic thrust, drag force and wing inertia. This causes a unique dynamic time-lag phenomena of lift generation for FRW, unlike the normal flapping wing flight vehicle driven by its own motor to actively rotate its wings. The analysis also shows that in order to acquire a high positive lift generation with high power efficiency and small dynamic time-lag, a relative high mid-up stroke angle within 7–15° and low mid-down stroke angle within -40° to -35° are necessary. The results provide a quantified guidance for design option of FRW together with the optimal kinematics of motion according to flight performance requirement.