电磁探测卫星星上自主规划模型及优化算法

电磁探测卫星自治(AEDS)是一类对地观测卫星,其搜集的信息对工业、科研和军事等领域有着重要的意义。针对电磁探测卫星有效载荷特点,建立了基于动态拓扑结构无环路有向图的星上自主规划数学模型,提出了基于标记更新最短路径搜索的星上自主规划精确算法,对其完备性和时间复杂度进行了分析。并对精确算法时间复杂度较高的缺点,将近似支配概念引入到模型中,提出了标记更新最短路径搜索近似算法,分析了算法的近似程度和时间复杂度。最后,根据模拟的数据进行实验及分析,表明该方法能有效解决电磁探测卫星自主任务规划问题。     

Effects of long-term low atmospheric pressure on gas exchange and growth of lettuce

The objectives of this research were to determine photosynthesis, evapotranspiration and growth of lettuce at long-term low atmospheric pressure. Lettuce (Lactuca sativa L. cv. Youmaicai) plants were grown at 40 kPa total pressure (8.4 kPa _pO₂$p_{{\text{O}}_2}$) or 101 kPa total pressure (20.9 kPa _pO₂$p_{{\text{O}}_2}$) from seed to harvest for 35 days. Germination rate of lettuce seeds decreased by 7.6% at low pressure, although this was not significant. There was no significant difference in crop photosynthetic rate between hypobaria and ambient pressure during the 35-day study. The crop evapotranspiration rate was significantly lower at low pressure than that at ambient pressure from 20 to 30 days after planting (DAP), but it had no significant difference before 20 DAP or after 30 DAP. The growth cycle of lettuce plants at low pressure was delayed. At low pressure, lettuce leaves were curly at the seedling stage and this disappeared gradually as the plants grew. Ambient lettuce plants were yellow and had an epinastic growth at harvest. The shoot height, leaf number, leaf length and shoot/root ratio were lower at low pressure than those at ambient pressure, while leaf area and root growth increased. Total biomass of lettuce plants grown at two pressures had no significant difference. Ethylene production at low pressure decreased significantly by 38.8% compared with ambient pressure. There was no significant difference in microelements, nutritional phytochemicals and nitrate concentrations at the two treatments. This research shows that lettuce can be grown at long-term low pressure (40 kPa) without significant adverse effects on seed germination, gas exchange and plant growth. Furthermore, ethylene release was reduced in hypobaria.     

Initial ground experiments of silkworm cultures living on different feedstock for provision of high quality animal protein for human in space

Silkworm could be an alternative to provide edible animal protein in Controlled Ecological Life Support System (CELSS) for long-term manned space missions. Silkworms can consume non-edible plant residue and convert plant nutrients to high quality edible animal protein for astronauts. The preliminary investigation of silkworm culture was carried out in earth environment. The silkworms were fed with artificial silkworm diet and the leaves of stem lettuce (Lactuca sativa L. var. angustana Irish) separately and the nutritional structure of silkworm was investigated and compared, The culture experiments showed that: (1) Stem lettuce leaves could be used as food of silkworm. The protein content of silkworm fed with lettuce leaves can reach 70% of dry mass. (2) The protein content of silkworm powder produced by the fifth instar silkworm larvae was 70%, which was similar to the protein content of silkworm pupae. The powder of the fifth instar silkworm larvae can be utilized by astronaut. (3) The biotransformation rate of silkworm larvae between the third instar and the fifth instar could reach above 70%. The biotransformation cycle of silkworm was determined as 24 days. (4) Using the stem lettuce leaves to raise silkworm, the coarse fiber content of silkworm excrements reached about 33%. The requirements of space silkworm culture equipment, feeding approaches and feeding conditions were also preliminarily designed and calculated. It is estimated that 2.2 m³ of culture space could satisfy daily animal protein demand for seven astronauts.     

HEO倾角长期漂移与控制策略

考虑日月引力对卫星轨道的扰动影响,分析了大椭圆轨道(HEO)倾角漂移规律,推导了小倾角HEO轨道的倾角长期漂移解析公式。结合HEO轨道倾角保持要求,给出了相应倾角控制策略。以STK为比较验证软件平台,经仿真分析与比较可知:文中推导的小倾角HEO轨道的轨道倾角解析公式较STK计算偏差在5%以内,验证了解析公式正确性;基于推导的倾角长期漂移解析公式,进行了倾角控制仿真,仿真结果表明了控制策略的有效性,并同时体现了倾角长期漂移解析计算公式在工程中的作用。     

面向对象的虚拟组织集成建模方法

提出了一种适应虚拟组织业务过程动态变化的虚拟组织集成建模方法(VOIM,Virtual Organization Integrated modeling),该方法集标准化面向对象的建模语言(UML,Unified Modeling Language)、功能建模集成化定义方法(IDEF0,Integration Definition for Function Modeling)和事件驱动过程链(EPC,Event-driven Process Chain)为一体,以弥补单一方法的不足,适合复杂系统特别是虚拟组织的建模,其中:IDEF0对虚拟组织的功能建模,EPC对功能视图进行细化,UML通过实体映射关系把虚拟组织模型的各个视图有机结合起来,有利于实现系统的模块化和模型的重用;同时对建模过程中UML到EPC之间的转换方法进行了研究.最后对模型进行了形式化描述,从而使VOIM具备严格定义的抽象语法和语义,为模型的验证和仿真提供了良好的基础.     

超声速非平行边界层的非线性稳定性研究(英文)

用非线性抛物化稳定性方程(NPSE),研究超声速非平行边界层的扰动波的非线性演化过程。发展了高精度的数值方法,对NPSE进行有效求解和稳定推进。计算得到了各谐波的振幅增长曲线和不同的扰动剖面函数,特别是展示了谐波之间的非线性作用的物理特征,包括流向涡、展向涡和Λ结构的形成和演化等,以进行转捩过程的机理研究和分析。NPSE的计算结果显示了这个新方法是研究超声速边界层非线性稳定性的有效方法。     

需求信息共享供应链系统的稳定性分析

生产/库存系统的稳定性是供应链管理中的重要指标.需求信息共享(DIS, Demand Information Sharing)机制已在管理实践中得到广泛的应用.但对DIS供应链系统稳定性的研究仍然非常有限.使用控制工程理论建立了一个两级DIS供应链系统模型,定量分析了系统的稳定性条件,给出了系统参数的取值范围,并通过仿真实验进行了验证.研究结果表明合理调整系统参数能够提高供应链系统的稳定性.在此基础上针对阶跃需求输入研究了系统参数对供应链系统中订单、库存和在制品动态响应的影响.揭示了供应链系统的动态特性,提出了供应链成员决策的管理建议.     

基于系统可靠度的发动机组方案优化选择方法

某大型系统的动力装置由三台发动机构成,动力装置的设计方案有2种:两台以额定功率运行一台贮备,一台故障后切换贮备发动机的冷储备方案和三台同时降功率工作,一台故障后另两台以额定功率运行的降功率方案.假设每台发动机寿命服从威布尔分布的情况下,对这两种方案分别建立了可靠性模型,并依据额定功率和降功率下的发动机的寿命分布,分别给出在这两种设计方案下的动力装置的可靠度随时间变化的曲线.然后,根据这两种不同方案下可靠度随时间变化的曲线,选择此动力装置的发动机组的最佳优化方案.最后,给出实例说明此方法的可行性.     

基于信息公理的车间布局问题评价方法

车间布局评价问题属于典型多属性决策问题.为了使信息公理更适合于解决多属性决策问题,通过增加满意度项改进了原有的信息量计算方法.属性值被划分为精确型、不确定型和模糊型,同时针对效益性、成本性、定值性和区间性属性给出了这三种数值类型的信息量的计算办法.改进后的信息量同时反映系统的成功概率以及决策者满意程度,并能够对包含多种数值类型的多属性决策问题进行评价.最后,作为实例,对焊接装配车间的布局方案进行了评价,结果验证了所改进的信息公理对于解决多属性决策问题的可行性和有效性.     

一种统计意义下最优接近轨道快速搜索算法

设计空间监视卫星时,需要分析设计卫星与大量被监视空间飞行器的接近能力。通过具体仿真实例提出了一种基于摄动模型的快速最优接近轨道搜索方法,可以大大提高仿真速度,仿真结果证实了该方法的有效性,统计参数通过了精确模型的确认,也验证了算法的可信性。