基于遗传算法的离场航班时刻优化

针对枢纽机场航班延误和放行正常率低的现象,对离场航班进行合理的调度,将航班延误降到最低,提高放行正常率.作者从机场运行角度出发,考虑了机场实际放行能力、航班调度难度和管制间隔、跑道容量等因素,建立了离场航班优化调度模型,引入遗传算法对该模型进行求解.并利用AirTop对优化结果仿真验证,以上海虹桥国际机场为例,利用所提...     

一种改进的多机场地面等待启发式算法

从满足航空公司关于航班公平性的需求出发,将航班时刻优先规则用于改进基于优先级的多机场地面等待启发式算法(ABG算法).采用被动优先级表,根据航班计划到达时刻的先后,依次分配降落时刻,分配后的降落时刻不再参与试图降低总延误时间的时刻交换处理.基于相同实验数据的计算结果对比表明,改进算法可降低最大延误时刻的50%和输出更为平滑的航班延误分布.     

一种改进的多机场地面等待启发式算法

从满足航空公司关于航班公平性的需求出发，将航班时刻优先规则用于改进基于优先级的多机场地面等待启发式算法（ABG算法）。采用被动优先级表，根据航班计划到达时刻的先后，依次分配降落时刻，分配后的降落时刻不再参与试图降低总延误时间的时刻交换处理。基于相同实验数据的计算结果对比表明，改进算法可降低最大延误时刻的50％和输出更为平滑的航班延误分布。     

基于时空特征的终端区多机场航班时刻优化北大核心

为更好的实施终端区协同决策(CDM),考虑大终端区下多机场的协同运行需要,对终端区内多机场离场航班时刻进行优化。同时考虑各机场的延误时间及航班的总延误成本,建立终端区多机场的协同放行模型;采用改进的多目标粒子群算法对所建模型进行求解。最后对大兴机场开航背景下的京津大终端区分别进行单目标及多目标的仿真验证,仿真结果表明,所提方法优于先到先服务策略(FCFS)且可以有效平衡终端区内各机场总延误成本与总延误时间,兼顾航班延误的均衡性及公平性。     

珠三角地区多机场系统航班时刻的仿真优化

珠三角地区机场分布稠密、空域紧张、航班延误率高。为降低该地区的航班延误,提出以延误分层模型为优化目标,采用空域机场仿真模型SIMMOD对珠三角地区多机场系统仿真建模和有约束限制的并行扰动随机近似（Simultaneous Perturbation Stochastic Approximation,SPSA）优化算法相结合的方法,对珠三角地区多机场系统的航班时刻进行仿真优化研究。采用非光滑反馈对SPSA算法进行了改进。仿真结果表明采用这种仿真优化方法生成的新航班时刻,可有效降低总延误时间。研究对从整体上减少珠三角地区多机场系统的延误成本具有重要价值。     

基于免疫进化算法的航班过站时间优化模型

针对当前航班延误在航班链中的波及的特性,通过研究航班过站时间对航班延误的影响的内在机理,在基于免疫进化算法基础上,没有增加过站时间的总数,调整过站时间来减少航班的延误波及的优化模型.在保持航班的飞行任务和机组安排不变的情况下,只对航班时刻做出了轻微的修改.根据国内某大型枢纽机场的数据进行仿真实验,调整后的计划可以很好的改善延误的情况.     

基于航班时刻优化的地面等待模型的建立与仿真

地面等待是指机场或者管制区内容量受限时，飞机通过地面等待的策略来缓解机场或者管制区拥挤的方法。为了优化航班的单机场地面等待问题，考虑不同机型，针对不同航空公司航班之间的排序，建立了基于航班时刻优化的地面等待模型。结果表明，当机场发生拥挤时，对航班进行排序，使航班有序进行起降，同时使所有航班的地面等待总体损失最小。     

多机场地面等待策略的建模与仿真

针对我国空中交通流量管理中出现的大规模航班延误情况,根据多个机场实际起飞和降落容量的约束,建立了一种考虑航班取消的多机场地面等待策略数学模型,并提出求解该模型的有效算法。在所提模型与算法的基础上,选择我国三大机场实际数据进行仿真。对比了取消航班与不取消航班两种情况结果,仿真结果验证了模型与方法的有效性与实用性,给出了最优排序的航班时刻表,从而支持了关键航班的运行,减少了航班总延误。     

面向正点率提升的华北机场群航班时刻优化

近年来,区域机场群协同发展逐渐成为了未来民航发展的基本导向。然而,相比国外关于机场群的研究水平,我国尚处于萌芽阶段,出现了机场群内发展不均衡、缺乏协同、功能定位不清晰、空管运行难度大、服务品质降低等问题。因此,以京津冀机场群为研究对象,借鉴国外先进发展经验,从协同发展的角度对机场群航线优化进行研究。构建了以提升航班正点率为目标的机场群现有航班时刻优化模型,运用粒子群迭代寻优算法求解最优解,将优化后的航班时刻表用SIMMOD进行仿真验证,实验结果表明,经航线优化后的京津冀机场群航班延误得到了缓解,且多机场群系统的航班冲突得到了明显的降低。     

基于PN和CNN-LSTM-ATT的航班延误预测

航班延误预测对提高机场地面保障效率具有重要参考意义。针对目前航班地面保障流程复杂多变以及航班过站延误预测精度不高的问题,提出了一种基于Petri Net和融合预测模型CNN-LSTM-ATT的航班延误预测模型。首先,根据机场航班实际地面保障流程抽象构建离港航班地面保障作业Petri Net模型,获取保障流程中的关键作业时长成为动态特征;其次,将动态特征、航班信息、延误信息和天气信息输入CNN-LSTM-ATT模型中进行特征提取和分类预测,模型中引入注意力机制,通过注意力权重突出关键数据信息的影响,进一步挖掘重要特征之间的内部规律。实验结果显示,该融合模型准确率相比独立模型提升了6%,达到98.1%。通过对不同模型的对比表明该模型能较好地应对场面流程变化并且具备较好的延误预测能力。     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

Enhancing a leaf radiative transfer model to estimate concentrations and in vivo specific absorption coefficients of total carotenoids and chlorophylls a and b from single-needle reflectance and transmittance

The relative concentrations of different pigments within a leaf have significant physiological and spectral consequences. Photosynthesis, light use efficiency, mass and energy exchange, and stress response are dependent on relationships among an ensemble of pigments. This ensemble also determines the visible characteristics of a leaf, which can be measured remotely and used to quantify leaf biochemistry and structure. But current remote sensing approaches are limited in their ability to resolve individual pigments. This paper focuses on the incorporation of three pigments—chlorophyll a, chlorophyll b, and total carotenoids—into the LIBERTY leaf radiative transfer model to better understand relationships between leaf biochemical, biophysical, and spectral properties.Pinus ponderosa and Pinus jeffreyi needles were collected from three sites in the California Sierra Nevada. Hemispheric single-leaf visible reflectance and transmittance and concentrations of chlorophylls a and b and total carotenoids of fresh needles were measured. These data were input to the enhanced LIBERTY model to estimate optical and biochemical properties of pine needles. The enhanced model successfully estimated reflectance (RMSE = 0.0255, BIAS = 0.00477, RMS%E = 16.7%), had variable success estimating transmittance (RMSE = 0.0442, BIAS = 0.0294, RMS%E = 181%), and generated very good estimates of carotenoid concentrations (RMSE = 2.48 µg/cm², BIAS = 0.143 µg/cm², RMS%E = 20.4%), good estimates of chlorophyll a concentrations (RMSE = 10.7 µg/cm², BIAS = − 0.992 µg/cm², RMS%E = 21.1%), and fair estimates of chlorophyll b concentrations (RMSE = 7.49 µg/cm², BIAS = − 2.12 µg/cm², RMS%E = 43.7%). Overall root mean squared errors of reflectance, transmittance, and pigment concentration estimates were lower for the three-pigment model than for the single-pigment model. The algorithm to estimate three in vivo specific absorption coefficients is robust, although estimated values are distorted by inconsistencies in model biophysics. The capacity to invert the model from single-leaf reflectance and transmittance was added to the model so it could be coupled with vegetation canopy models to estimate canopy biochemistry from remotely sensed data.     

Mr. Twinn’s bombes

This article discusses the history and design of the special versions of the bombe key-finding machines used by Britain’s Government Code & Cypher School (GC&CS) during World War II to attack the Enigma traffic of the Abwehr (the German military intelligence service). These special bombes were based on the design of their more numerous counterparts used against the traffic of the German armed services, but differed from them in important ways that highlight the adaptability of the British bombe design, and the power and flexibility of the diagonal board. Also discussed are the changes in the Abwehr indicating system that drove the development of these machines, the ingenious ways in which they were used, and some related developments involving the bombes used by the U.S. Navy’s cryptanalytic unit (OP-20-G).