Possible nutrient limiting factor in long term operation of closed aquatic ecosystem

To investigate nutrient limitation effect on the community metabolism of closed aquatic ecosystem and possible nutrient limiting factors in the experimental food chains, depletion of inorganic chemicals including carbon, nitrogen and phosphorous was tested. A closed aquatic ecosystem lab module consisting of Chlorella pyrenoidosa and Chlamydomonas reinhardtii, Daphnia magna and associated unidentified microbes was established. Closed ecological systems receive no carbon dioxide; therefore, we presumed carbon as a first limiting factor. The results showed that the algae population in the nutrient saturated group was statistically higher than that in the nutrient limited groups, and that the chlorophyll a content of algae in the phosphorus limited group was the highest among the limited groups. However, the nitrogen limited group supported the most Daphnia, followed by the carbon limited group, the nutrient saturated group and the phosphorus limited group. Redundancy analysis showed that the total phosphorus contents were correlated significantly with the population of algae, and that the amount of soluble carbohydrate as feedback of nutrient depletion was correlated with the number of Daphnia. Thus, these findings suggest that phosphorus is the limiting factor in the operation of closed aquatic ecosystem. The results presented herein have important indications for the future construction of long term closed ecological system.     

加表量化精度对惯导平台误差系数辨识的影响

通过采用加表的输出以及由离心机半径、角速度、角位置所确定的向心加速度输入作为观测量的辨识方法,结合惯导平台的误差模型,仿真分析了加表量化精度对惯导平台误差系数辨识结果的影响。结果表明,加表量化精度越高,惯导平台误差系数的辨识精度越高。     

气动执行器的全生命周期成本分析

分析了气动执行器的能耗特点,结合空气消耗量和比能量概念,提出了一种气动执行器的能耗计算方法.为解决公用气动设备的购置成本划分问题,提出了一种用气设备成本均分法.结合生命周期成本的概念,建立了气动执行器基于用户的全生命周期成本模型(LCCBOU,Life-Cycle Costing Based On Users),进行了实例验证.该模型不仅适用于气动执行器的全生命周期成本分析,也适用于其它用气设备的成本分析.结果表明:用气设备成本均分法实现了气动系统成本的合理划分;气动执行器的LCCBOU模型通过了实例验证,并发现通过空压机的实时监控和气动系统的泄漏测量,LCCBOU模型结果能够做到更精确.      

地形提示与告警系统试飞研究

对地形防撞系统的试飞技术和试飞风险规避进行研究。首先介绍了TAWS子模式功能。然后详细分析了各子模式的试飞技术。阐述了TAWS系统试飞的主要风险源,并分析相应风险源的规避措施。最后,通过实例论证了TAWS试飞技术的应用性,为新型号飞机TAWS试飞工作安全、有效的开展提供了参考。     

变深度水下发射系统内弹道实验研究

利用变深度水下发射模拟实验装置开展了变发射深度和发射速度条件下导弹发射系统内弹道研究。建立了描述缩比模型弹在发射筒内运动规律的简化模型,并提出了基于实验结果的运动方程求解方法。通过实验结果分析获得了模型弹的运动摩擦系数和发射速度,并利用高速摄影测量结果对获得的发射速度进行了验证。建立了运动摩擦系数和发射速度的数值拟合关系。结果表明,运动摩擦系数与发射速度呈反向变化规律,并且存在影响运动摩擦系数变化速率的临界发射速度,当发射速度小于临界值时运动摩擦系数变化剧烈,发射速度临界值为18～20 m/s。     

Coordinated control of tethered space robot using mobile tether attachment point in approaching phase

Tethered space robots (TSRs) have wide applications in future on-orbit service owing to its flexibility and great workspace. However, the control problem is quite complex and difficult in the phase of approaching target, and the fuel consumption must also be taken into account. Hence, we present a novel scheme of achieving coordinated orbit and attitude control simultaneously for the TSR. Space tether, which can provide greater force compared with the thruster force, is used in the design of the orbit and attitude coordinated controller. A coordinated control mechanism is designed to provide attitude control torques of the pitch and yaw motions by adjusting the position of the mobile tether attachment point, while the roll motion is stabilized by the thruster. In order to guarantee this mechanism to work properly, constant tether tension strategies are utilized to plan an optimal approaching trajectory which is tracked by the coordinated controller of tether force and thruster force. Numerical simulation validates the feasibility of our proposed coordinated control scheme for TSR in the approaching phase. Furthermore, fuel consumption of the orbit and attitude control are both significantly reduced compared with traditional thruster control.     

Cubature Kalman filtering for relative spacecraft attitude and position estimation

A novel relative spacecraft attitude and position estimation approach based on cubature Kalman filter is derived. The integrated sensor suit comprises the gyro sensors on each spacecraft and a vision-based navigation system on the deputy spacecraft. In the traditional algorithm, an assumption that the chief?s body frame coincides with its Local Vertical Local Horizontal (LVLH) frame is made to construct the line-of-sight observations for convenience. To solve this problem, two relative quaternions that map the chief?s LVLH frame to the deputy and chief body frames are involved. The general relative equations of motion for eccentric orbits are used to describe the positional dynamics. The implementation equations for the cubature Kalman filter are derived. Simulation results indicate that the proposed filter provides more accurate estimates of relative attitude and position over than the extended Kalman filter.     

基于可不断电维修的双机容错系统

对单个单片机控制系统可靠性不高的问题,提出了一种由双单片机构成容错系统的实现方法.在该系统中,用串行通讯技术,通过采集对方I/O输出,与自身的I/O输出值作比较,实现双单片机的故障互检;利用地址译码技术,设计仲裁切换模块,完成故障隔离;故障机修复后,通过回读对方执行程序的任务编号,达到双机同步控制,完成系统重构,实现对故障单元的不断电维修.通过对模拟机的实验表明,此控制系统能对运行中的错误实现实时的双机互检,且具有在线热插拔功能.     

载人航天器舱内辐射环境及剂量分析

构建载人航天器模型,利用Geant4软件计算了银河宇宙射线中的质子穿过载人航天器后在水模体中的总吸收剂量以及次级粒子吸收剂量,并且统计了不同种类的次级粒子在水模体中的总数量分布。计算结果表明,次级粒子引起的辐射剂量所占比例为50%,且二次电子总数量达到了10~7量级。