空域拥挤风险管理时间决策模型与方法

针对目前日益严重的空域拥挤现象,缺乏有效的空域拥挤风险管理机制,造成拥挤难以应对等问题,建立了空域拥挤风险预测模型、空域拥挤风险解决模型和风险损失成本模型。采用风险预测模型和解决模型预测可能产生空域拥挤的时段、提出不同时段的实施流量管理策略,基于风险损失成本模型给出了不同时段调整拥挤的运行成本,通过比较运行成本和空域拥挤风险管理决策方法确定出解决空域拥挤的最佳时间点。采用实际运行数据进行验证,结果表明:所建立的空域拥挤预测模型、空域拥挤风险解决模型、风险损失成本模型和空域拥挤风险管理时间决策方法能有效地预测未来空域发生拥挤的时段,迅速找到运行成本最小的调整拥挤的时间点,为空中交通流量动态管理提供了新途径。     

A novel signal processing approach for LEO space debris based on a fence-type space surveillance radar system

The increase in space debris can seriously threaten regular activities in the Low Earth Orbit (LEO) environment. Therefore, it is necessary to develop robust, efficient and reliable techniques to understand the potential motions of the LEO debris. In this paper, we propose a novel signal processing approach to detect and estimate the motions of LEO space debris that is based on a fence-type space surveillance radar system. Because of the sparse distribution of the orbiting debris through the fence in our observations, we formulate the signal detection and the motion parameter estimation as a sparse signal reconstruction problem with respect to an over-complete dictionary. Moreover, we propose a new scheme to reduce the size of the original over-complete dictionary without the loss of the important information. This new scheme is based on a careful analysis of the relations between the acceleration and the directions of arrival for the corresponding LEO space debris. Our simulation results show that the proposed approach can achieve extremely good performance in terms of the accuracy for detection and estimation. Furthermore, our simulation results demonstrate the robustness of the approach in scenarios with a low Signal-to-Noise Ratio (SNR) and the super-resolution properties. We hope our signal processing approach can stimulate further work on monitoring LEO space debris.     

基于ANCF的松弛绳索动力学建模与仿真

传统绝对节点坐标方法(ANCF)绳索模型是基于梁单元建立的,其不能反映纤维绳索的不可抗压和松弛特性。考虑纤维绳索初始松弛余量,给出了绳索非线性轴向应力-应变关系。绳索在松弛状态下轴向力接近于零,在张紧状态下表现出线弹性特性。在此基础上,采用绝对节点坐标方法推导了松弛绳索动力学模型。通过静力学和动力学仿真,将传统绳索模型和松弛绳索模型进行对比,结果表明:在重力及不同集中载荷作用下,松弛绳索相比于传统绳索都具有更大的变形;分析移除集中载荷后绳索的动力学响应可知,传统绳索在振动过程中始终处于张紧状态,且绳索上各点振动同步,而松弛绳索会在张紧和松弛状态之间不断转换,绳索上各点的振动存在相位差,能够更好地反映绳索在松弛状态下的动力学特性。     

Co-registration of Chang’E-1 stereo images and laser altimeter data with crossover adjustment and image sensor model refinement

Topographic information is of fundamental importance for various scientific investigations in lunar and planetary exploration. To provide high-precision, seamless mapping capability, it is critical to co-register image and altimetry data, the two major data sources for topographic modeling. This paper presents a method for co-registration of Chang’E-1 (CE-1) stereo images and laser altimeter (LAM) data with crossover adjustment and refinement of the image sensor model. The crossover adjustment is tested in a larger area (0–60°N, 50–0°W); the image refinement and co-registration with LAM data are tested in an area (46.2–50.0°N, 31.8–28.8°W) within the larger area. Experimental results demonstrate that this co-registration reduces the mean differences of inconsistency from more than 200 m to just 3.21 m in the Z direction of object space. In image space, the mean errors of homologous points both in the column and row directions are reduced to below 0.1 pixel. This indicates that the proposed crossover adjustment of LAM data and refinement of the CE-1 stereo image model can effectively improve co-registration of the two data sets.     

Nostoc sphaeroides Kützing,an excellent candidate producer for CELSS

Some phytoplankton can be regarded as possible candidates in the establishment of Controlled Ecological Life Support System (CELSS) for some intrinsic characteristics, the first characteristic is that they should grow rapidly, secondly, they should be able to endure some stress factors and develop some corresponding adaptive strategies; also it is very important that they could provide food rich in nutritious protein and vitamins for the crew; the last but not the least is they can also fulfill the other main functions of CELSS, including supplying oxygen, removing carbon dioxide and recycling the metabolic waste. According to these characteristics, Nostoc sphaeroides, a potential healthy food in China, was selected as the potential producer in CELSS. It was found that the oxygen average evolution rate of this algae is about 150 μmol O₂ mg⁻¹ h⁻¹, and the size of them are ranged from 2 to 20 mm. Also it can be cultured with high population density, which indicated that the potential productivity of Nostoc sphaeroides is higher than other algae in limited volume. We measured the nutrient contents of the cyanobacterium and concluded it was a good food for the crew. Based on above advantages, Nostoc sphaeroides was assumed to a suitable phytoplankton for the establishment of Controlled Ecological Life Support System. We plan to develop suitable bioreactor with the cyanobacterium for supplying oxygen and food in future space missions.     

大型数控成形磨齿机床装配误差–齿面误差研究

如何根据齿轮齿面精度要求,精准调整装配几何误差,是提升大型数控成形磨齿机床性能的关键技术之一.基于成形磨削系统的误差传递链,砂轮与工件之间的共轭运动关系,利用曲面族包络法建立了包含装配几何误差的成形磨削齿面模型;通过计算理论齿面和包络齿面的差值,进行成形磨削齿面的误差评价,并提出了实现磨削齿面误差评价的流程方法;在此基...     

Optimal parity vector sensitive to designated sensor fault

Based on the parity space construction and the orthogonal constraint condition of parity vector, the approach of fault detection and isolation using optimal parity vector is presented. Its main idea is to design a performance criterion similar to the criterion presented by Zhang and Patton (1993), but most sensitive to the designated sensor's fault and least sensitive to other sensor's fault and unknown inputs such as noise. Through the Monte-Carlo simulation, it is shown that the proposed approach of choosing optimal parity vector greatly increases the ability of fault detection and the effectiveness of fault isolation is better than the generalized likelihood test (GLT) approach     

液体火箭发动机汽蚀管堵塞仿真研究

建立了某泵压式液体火箭发动机系统组件数学模型,在此基础上进行了发生器氧化剂汽蚀管堵塞的动态仿真计算。仿真计算结果表明:发动机涡轮转速在堵塞初始快速下降,之后下降变缓。     

治理汽车排放污染的三大要素

概述了治理汽车排放污染的技术法规、汽车排放控制技术和车用燃油三大要素的内容和作用，以及它们相互依存的关系。最后提出了对我国治理汽车排放污染的４ 点建议。     

铝合金高速铣削温度的动态测量

用红外辐射测温技术对铝合金铣削温度进行了间接、近似、直观的测量,获得了高速铣削研究所必需的温度数据,并测出铣床主轴转速为7500r/min左右时切削温度达到最高临界值.