基于改进遗传算法的航空集装箱装载问题研究

针对标准遗传算法求解装载方案时存在收敛速度慢、易早熟、寻优结果欠佳的问题,基于拟人装载策略,提出了一种以集装箱空间利用率最大为目标,考虑货物装载顺序、体积、质量、重心、不重叠等多种实际约束的改进遗传算法。首先,采用与货物放置状态相结合的实数编码,随机产生初始种群;然后,在常规选择操作中加入最优解保存策略,并将稳定性、支撑限制、重心约束考虑到进行线性尺度变换后的适应度函数中,以此来计算每种装载方案的评估值;最后,输出评估值最高的方案作为最优装载方案。实验采用异构性不同的测试算例进行性能测试,结合3组具体货物装载数据证明算法的普适性与实用性。结果表明:所提算法在求解强异构货物装载过程中具有较好的优化效果,适用于求解集装箱装载问题。与标准遗传算法相比,收敛性与搜索速度有所提高,2种不同箱型的集装箱空间利用率分别提高了3.82%和3.66%,运行时间分别缩短了7.9 s和5.58 s,能快速找到最优装载方案,可有效解决规则、不规则集装箱的货物装箱问题。基于MATLAB软件实现装载方案的可视化,为集装箱的实时装载决策提供了理论基础。      

基于遗传模糊聚类的机群编队最优分配方法

针对当前机群的编队分配存在效率低、编队分配结果不可靠、智能性差等问题,提出了一种新的结合遗传算法和模糊聚类算法的机群编队最优分配方法.该混合算法通过模糊聚类算法解决了机群的编队分配不确定性问题,并且通过对传统遗传操作算子的改进,采用改进的遗传算法有效地克服了模糊聚类算法容易陷入局部极小值和对初始条件敏感的缺点,使机群的编队分配能快速收敛至全局最优解.3组不同分布类型的机群编队分配算例结果表明,该混合算法具有较好的通用性、有效性和智能性,适用于机群的编队最优分配.      

基于混合遗传算法的多箱型集装箱装载问题分析

航空多箱型集装箱装载是实现快速、高效、安全航空货物运输的重要环节。针对现实约束条件下多种货物和箱型的集装箱多箱装载优化问题,搭建数学优化模型,提出一种求解货物装载布局方案的混合遗传算法,以达到充分利用集装箱装载空间的目的。采用三段式编码确定货物装载顺序、货物放置状态及集装箱编号,随机产生初始种群;在常规选择操作中加入最佳个体保护策略,并将重心、不重叠、承重约束考虑到适应度函数中,以此来评价解的优劣;加入模拟退火算子,用其突跳性避免遗传陷入局部最优的情况,进一步提高优化效果。通过算例对比表明,所提算法在满足多种约束条件下仍能保持较高的体积利用率,能够很好地解决强弱异构货物的装载;采用具体货物数据进一步验证算法的可行性与适用性,4种航空集装箱的平均体积利用率高于82%,表明所提算法能够有效解决规则和不规则多箱型集装箱的货物装载问题,具有较好的工程应用价值。      

基于边际-人工蜂群算法的舰载机机群出动保障人员配置-调度联合优化方法

保障人员配置和保障作业调度是舰载机机群出动保障任务决策的2项核心内容。针对复杂甲板作业约束条件下保障人员配置-调度联合优化的实际问题，首先，系统分析舰载机机群出动保障流程约束、出动时限约束、保障人员约束、保障设备约束、工位空间约束和资源供给能力约束。其次，以保障人员数量和负载方差和最小化为优化目标，建立了混合整数规划模型，进而提出了基于边际-人工蜂群（ABC）算法的两层优化决策架构。上层决策模型基于边际优化算法对保障人员配置方案进行迭代优化，下层决策模型采用改进的双向人工蜂群算法对舰载机机群出动保障任务调度进行优化。最后，通过典型算例验证了所提模型和两层优化机制的可行性与有效性。      

基于动态四叉树搜索的民航行李车码放算法

民航行李智能化码放是未来行李处理的重要发展方向。为解决当前运输过程中劳动密集、效率低下等问题,提出了基于动态四叉树搜索的民航行李车码放算法。基于行李构型沿竖直方向动态规划组合成复合条,针对根节点空码放方案构造四叉树,设计动态最低利用率公式,在四叉树的每层生成复合层,4个分支为4种复合层放入后的新码放方案。设计了一种优化剩余空间的动态选择算法,在每层选择并保留n个最优码放方案继续搜索,当无法生成新码放方案时算法结束,取搜索过程中填充率最高者为最终码放方案。在现实算例的测试中,码放方案的平均空间利用率为91.63%,相对于选取的同类算法提升了16.83%,且算法稳定性更强,可多行李一次装载,并使用现实机械手码放平台验证码放结果。      

基于本体映射的产品概念设计方案生成新方法

将本体与本体映射引入产品概念设计方案生成领域,提出了一种基于本体映射的产品概念设计方案生成新方法,有助于解决传统概念设计方案生成算法中由于知识描述不一致而导致的产品设计知识重用困难,以及设计方案生成准确性低的问题.该方法使用本体知识表示方法建立产品设计知识库;使用本体映射算法自动地搜索产品设计知识库中符合设计需求的产品概念设计方案.通过起重机起升机构驱动装置设计实例,验证了基于本体映射的产品概念设计方案生成新方法的正确性和有效性.     

考虑外包的货运航空公司货流分配问题

针对货运航空公司大量、纷繁交错的航空货运需求,制定合理的路径规划和配流方案可以降低运输成本、提高运输效率。考虑货机运输和外包运输2种运输方式,建立了运力配置和货流分配一体化的混合整数规划模型。以中国国际货运航空有限公司为例进行算例求解,根据不同运输距离对货流进行预分配,根据OD对机场所在集合预先规定货流可以中转的机场,不仅缩小了搜索空间,比两者均不处理时节省了85.12%的计算时间,而且中转货流运输路径总长度和中转货流周转量与不处理相比也分别降低了17.19%和28.99%,减少了大量绕路。得到的结果与不考虑外包的模型相比节省了4.87%的成本。引入外包价格系数进行灵敏度分析,随着外包价格系数从1.2到0.8不断减小,货运航空公司通过外包运输的货物量增加,同时小型货机执飞的航段不断减少,而大型货机执飞的航段没有变化。对不同运输方式的单位运输成本随运输量变化的曲线进行分析,当货运航空公司在面临新增局部货运需求时,可以不改变全局方案,而根据曲线及剩余运力情况做出较优的决策。      

基于动态指标的飞机方案多目标优化方法

为提高飞机方案多目标优化过程中最优解的搜索效率,对多目标方案的比较评价方法及其在优化中的应用进行了研究.提出了可用于多目标方案对比评价的基准指标,并建立了利用新生成方案的目标值对基准指标进行动态更新的动态指标.通过采用动态指标构造适应度函数改进了多目标遗传算法,进行的双目标优化算例表明,改进的算法能够获得更优的Pareto前沿.采用改进的多目标优化方法对一种轻型战斗机概念方案进行了优化设计,设置了重量、气动、隐身等4个优化目标,优化结果验证了基于动态指标改进的多目标遗传算法在飞机概念方案设计优化中的有效性.      

时间触发CAN总线实时性分析及评估方法

针对目前时间触发控制器局域网(CAN,Controller Area Network)总线缺乏统一评估方法的现状,提出了一套系统建立与评估方案.采用均匀装载算法建立系统调度矩阵,实现了周期信息的实时传输.结合CAN总线的传输机制与时间触发的特点,改进了时间触发系统中非周期信息最坏延迟的计算方法.在此基础上针对不满足系统实时性要求的信息提出了计算其失效概率的方法,建立了时间触发CAN总线系统的设计与评估流程,提出了系统参数调整方案.评估方案能够提高设计效率,利用信息失效概率以及最坏延迟对系统实时性进行分析,使分析结果更加精确、实用.     

Learning in an immersive digital theater

The Houston Museum of Natural Science, in collaboration with Rice University has an outreach program taking portable digital theaters to schools and community sites for over five years and has conducted research on student learning in this immersive environment. By using an external independent evaluator, the effectiveness of NASA-funded Education and Public Outreach (EPO) projects can be assessed. This paper documents interactive techniques and learning strategies in full-dome digital theaters. The presentation is divided into Evaluation Strategies and Results and Interactivity Strategies and Results. All learners from grades 3–12 showed statistically significant short-term increase in knowledge of basic Earth science concepts after a single 22-min show. Improvements were more significant on items that were taught using more than one modality of instruction: hearing, seeing, discussion, and immersion. Thus immersive theater can be an effective as well as engaging teaching method for Earth and Space science concepts, particularly those that are intrinsically three-dimensional and thus most effectively taught in an immersive environment. The portable system allows taking the educational experience to rural and tribal sites where the underserved students could not afford the time or expense to travel to museums.     

Stochastic particle acceleration by the forced interaction of relativistic current sheets

We address the problem of interacting relativistic current sheets in self-consistent kinetic plasma simulations within the framework of the Particle-In-Cell model. The interaction is enforced in head-on collisions of up to 10 current sheets at relativistic bulk speeds. The simulations are motivated by the general problem of Poynting flux dissipation in ‘striped wind’ configurations presumably governing the relativistic outflows pervasive in pulsar winds and gamma-ray bursts. We identify the generation of non-thermal particles and formation of a stable power-law shape in the particle energy distributions f(γ) dγ ∝ γ^−s dγ. In 1D, a spectral index s ∼ 2 is observed and attributed to a stochastic Fermi-type acceleration mechanism. In 2D, the generic index of s ∼ 3–4 is retained as in previous simulations of individual current sheets. Whereas in 2D the high energy cut-off is constrained by the limited dissipation of magnetic energy, in 1D the process converts the bulk motion of current sheets towards directed particle momentum of an exclusive class of non-thermal particles.     

Concept options for the aerial survey of Titan

Various aerial platforms intended for long endurance survey of the Titan surface are presented. A few novel concepts are introduced, including a heated methane balloon and a balloon with a tethered wind turbine. All the concept options are predicted to have lower scientific payload fractions than the Huygens probe. It is concluded that the selection of the best aerial platform option depends on more accurate mass estimates and a clear decision on whether, or not, in situ surface composition measurements are required in conjunction with aerial remote sensing.     

Heterogeneous solid/gas chemistry of organic compounds related to comets,meteorites, Titan,and Mars: Laboratory and in lower Earth orbit experiments

To understand the evolution of organic molecules involved in extraterrestrial environments and with exobiological implications, many experimental programs in the laboratory are devoted to photochemical studies in the gaseous phase as well as in the solid state. The validity of such studies and their applications to extraterrestrial environments can be questioned as long as experiments conducted in space conditions, with the full solar spectrum, especially in the short wavelength domain, have not been implemented. The experiments that are described here will be carried out on a FOTON capsule, using the BIOPAN facility, and on the International Space Station, using the EXPOSE facility. Vented and sealed exposition cells will be used, which will allow us to study the chemical evolution in the gaseous phase as well as heterogeneous processes, such as the degradation of solid compounds and the release of gaseous fragments.     

基于LuGre模型的电液加载系统摩擦补偿

为了提高电液加载系统控制精度,针对摩擦问题提出了基于LuGre摩擦模型的前馈补偿方法.建立了用于摩擦仿真分析和补偿器设计的电液加载系统数学模型;通过实验获取并分析了相关的摩擦数据;基于实验数据进行LuGre模型参数辨识,把LuGre模型和辨识结果引入电液加载系统数学模型,并进行仿真结果与实际摩擦数据的对照,证明了LuGre摩擦模型的准确性.设计前馈补偿器,进行了实验对比,实验结果表明前馈补偿器可将摩擦产生的控制误差有效地降至未补偿时的30%左右.      

CoRoT and Kepler results: Solar-like oscillators

The space-borne observatories CoRoT (Convection Rotation and planetary Transits) and Kepler have provided photometric time series data of unprecedented precision for large numbers of stars. These data have revolutionized the fields of transiting exoplanets and asteroseismology. In this review some important asteroseismic results obtained using data from the CoRoT and Kepler space missions concerning stars that show solar-like oscillations are discussed. These results comprise, among others, measurements of the location of the base of the convection zone and helium second-ionization zone in main-sequence stars, the presence (or not) of core-helium burning in red-giant stars, as well as differential rotation in these stars.     

The ESA scientific programme

The ESA scientific programme has, so far, provided several significant astrophysics experiments and further important missions are scheduled for execution during the next decade. These missions are briefly summarised together with several astrophysics investigations presently under study.     

HELIO: The Heliophysics Integrated Observatory

Heliophysics is a new research field that explores the Sun–Solar System Connection; it requires the joint exploitation of solar, heliospheric, magnetospheric and ionospheric observations.     

Radioactivity of the Moon and planets

In this report the main results of the study of radioactivity of the solar sistem bodies are considered. The radioactivity of the Moon and planets was measured by means of vehicles in situ. The radioactivity of the lunar samples, brought to the Earth was studied with laboratory equipment.     

应用于毫米波反射计的多项式校准方法

为了在毫米波波段准确测量波导器件的反射系数,提出了一种应用在反射系数测试前端(反射计)中的校准方法.该校准方法采用基于多项式的误差模型,使得每一个误差项的求解都转化成一个求解轨迹圆圆心的问题,同时不影响求解精度.采用一个滑动负载、一个滑动短路和一个短路器,在毫米波波段降低了对标准件理想程度的要求.实验中搭建了一个Ka波段的反射计,图解误差项的求解过程,分析了误差项的物理意义.把校准后的测量结果与商用矢量网络分析仪(VNA,Vector Network Analyzer)进行比较,吻合较好.同样比较了一组W波段反射计对波纹喇叭的测量结果,进一步验证了方法的合理性.