Satellite ocean colour algorithm for Prochlorococcus, Synechococcus, and picoeukaryotes concentration retrieval in the South China Sea

An algorithm for retrieval of surface waters cell concentrations (in cell/ml) for three picophytoplankton components, Prochlorococcus (Pro), Synechococcus (Syn), and picoeukaryotes (Peuk) in the South China Sea (SCS), from ocean colour satellite data was developed and tested. Level 3 merged multisensor Ocean Colour Climate Change Initiative satellite data is used. Training is performed using in situ data on abundances of the three phytoplankton components. Several predictors derived from satellite reflectance data were tested. The regression form that assures the highest accuracy of the algorithm was chosen based on cross-validation (CV). According to the CV on test data subset, the algorithm performance is characterized by the r value 0.89, 0.72, and 0.73 and MAPD 38, 71 and 51% for Peuk, Pro, and Syn respectively. This is one of the few studies aimed at the Peuk, Pro, and Syn distribution research in the northern SCS using ocean colour satellite data. This is the only research providing algorithm with accuracy estimates of the Peuk, Pro, and Syn concentrations retrieval from the ocean colour data. Analysis of the developed algorithm allows us to conclude that both mechanisms (specific spectral features caused by pigments composition and spectrum features sensitive to general primary productivity, e.g. band ratios in 443–510?nm range and spectrum absolute values) are important for getting accurate information on the picophytoplankton composition.     

A longitudinal & longitudinal-torsional vibration actuator for rotary-percussive ultrasonic planetary drills

Ultrasonic drills, which can sample rocks using a lower weight on bit and lower power, are more suitable for sampling on a minor planet than conventional drills. To remove cutting chips and improve drilling efficiency, rotary-percussive ultrasonic drills (RPUD) drive drill tools for rotary-percussive motion. This paper proposes a novel longitudinal & longitudinal-torsional (L-LT) actuator, which is composed of a stepped horn, a piezoelectric stack, and a longitudinal-torsional (LT) coupler, for the RPUD. The horn magnifies the longitudinal vibration on the front surface of the piezoelectric stack, which is clamped between the horn and the LT coupler, and impacts the drill tool. The LT coupler transforms the longitudinal vibration on the back surface into longitudinal-torsional vibration, which generates elliptical movements that drive the rotor to rotate. Then, the rotor drives the drill tool to rotate. A method of adjusting the displacement amplitudes of the horn and the driving tips is discussed. The prototype achieved a maximum speed and torque of 193?r/min and 0.065?N$·$m, respectively. The maximum drilling speed through sandstone under a weight on bit of 5?N was 13?mm/min.     

大面质比空间碎片在太阳光压和引力作用下的轨道演化

分析了较高轨道(a > 10000km)大面质比空间碎片的轨道动力学演化问题. 重点讨论了位于地球同步轨道的空间碎片轨道演化问题, 并给出轨道偏心率 随时间演化的表达式. 通过进一步分析得出, 倾角大于63°26'的GTO轨 道空间碎片, 仅在J₂和第三体摄动影响下, 会出现轨道偏心率升高; 而对 于大面质比空间碎片, 在J₂项和太阳光压同时作用下, 当近地点指向的角 变率与太阳平黄经变化率接近时, 会出现长期共振现象, 导致轨道偏心率升 高, 近地点降低. 分析还得出, 轨道演化过程中, 偏心率的最大值与初始轨 道近地点的指向有关.     

航天器交会飞行设计方法研究

针对半自主飞行追踪星,阐述航天器交会总体设计方法。根据对接点的地理位置范围、共面轨道倾角以及目标星轨道周期与追踪星入轨点地理位置,确定交会飞行时间和两星初始相位差范围。考虑最小轨道机动动力要求与飞行轨迹安全性等因素,并兼顾地面测控条件,设计追踪星远程导引段与相对导航段的轨道机动与飞行轨迹,特别是选择与比较不同的初始轨道、调相轨道与漂移轨道以及保持点停泊时间与最终逼近段飞行时间等交会飞行要素,调整飞行时间、相位差与对接点位置,确定最佳交会飞行方案,完成空间交会任务。     

空间Internet的安全体系结构

根据信息系统安全体系结构设计原则和方法,结合空间通信的特性,通过分析空间Internet的安全威胁、安全需求、安全等级、安全策略和安全机制,提出了空间Internet的安全体系结构模型。     

Selection of candidate salad vegetables for controlled ecological life support system

Higher plants, as one of the essential biological components of CELSS, can supply food, oxygen and water for human crews during future long-duration space missions and Lunar/Mars habitats. In order to select suitable leaf vegetable varieties for our CELSS Experimental Facility (CEF), five varieties of lettuce (“Nenlvnaiyou”, “Dasusheng”, “Naichoutai”, “Dongfangkaixuan” and “Siji”), two of spinach (“Daye” and “Quanneng”), one of rape (“Jingyou No. 1”) and one of common sowthistle were grown and compared on the basis of edible biomass, and nutrient content. In addition, two series of experiments were conducted to study single leaf photosynthetic rates and transpiration rates at 30 days after planting, one which used various concentrations of CO₂ (500, 1000, 1500 and 2000 μmol mol⁻¹) and another which used various light intensities (100, 300, 500 and 700 μmol m⁻² s⁻¹). Results showed that lettuce cvs. “Nenlvnaiyou”, “Siji” and “Dasusheng” produced higher yields of edible biomass; common sowthisle would be a good source of β-carotene for the diet. Based on the collective findings, we selected three varieties of lettuce (“Nenlvnaiyou”, “Dasusheng” and “Siji”) and one of common sowthistle as the candidate crops for further research in our CEF. In addition, elevated CO₂ concentration increased the rates of photosynthesis and transpiration, and elevated light intensity increased the rate of photosynthesis for these varieties. These results can be useful for determining optimal conditions for controlling CO₂ and water fluxes between the crops and the overall CELSS.     

民用飞机外翼中央翼对接肋腹板选型研究

典型民用飞机外翼中央翼是通过对接肋完成对接的,对接肋的腹板在其中起到重要的传递载荷和支持结构的作用。随着制造技术的发展,先进的民用飞机上出现了整体加筋式的腹板,这有别于传统的组合式加筋的腹板结构。利用商业有限元软件Hyperworks研究在压剪复合载荷并均匀油压载荷下,这两种加强筋类型腹板在变形、局部失稳、整体失稳和破坏下的承载能力,得出了较好的加强筋形式。最后分析针对两种类型腹板的压剪复合加载试验,验证了软件的仿真分析,为关键连接区的零件设计提供方法支持。     

倾斜射流撞壁实验研究及液膜几何参数建模

倾斜射流撞壁在液体火箭发动机液膜冷却、射流撞壁雾化等领域具有广泛的应用。为了研究倾斜射流撞击壁面后形成的液膜的关键特征,开展单股圆柱射流撞击壁面的实验研究。从实验中研究各射流参数对液膜外形的影响规律,继而开展理论建模,获取液膜外形的关键几何参数表达式。实验研究发现随着射流倾角增大,液膜长度减小而宽度增大,随着射流孔径和射流速度增大液膜长度和宽度均增大这一定性规律。理论分析得到了液膜最大宽度位置与液膜对称面的夹角近似等于射流倾角α,液膜的长宽比近似等于1+cot α。通过进一步分析得到液膜宽度、最大宽度距撞击点的距离、液膜长度这几个液膜关键参数的表达式。建立的液膜几何参数表达式预测结果与实验结果的误差均在20%以内。     

组合体航天器输入-状态稳定姿态接管控制

本文针对具有对抗性力矩输出能力的空间非合作目标,研究了基于输入-状态稳定理论的组合体航天器姿态接管控制方法。首先,建立了基于相互作用力矩实时计算的组合体姿态激励-响应映射关系,实现了对组合体航天器姿态运动的准确描述;然后,基于输入-状态稳定性理论设计了不依赖系统模型参数的姿态接管控制器并给出了参数选择范围,实现了对存在有界不确定对抗力矩非合作目标的姿态接管;最后通过数值仿真校验了控制方法的有效性。