航班恢复问题的迭代局部搜索算法

在恶劣天气和机械故障等原因造成航班不能按照原计划执行时，航空公司需要采取相应的措施对航班进行恢复。本文基于经典的资源指派模型，综合考虑了调整时间、换机、联程拉直、取消航班和调机5种恢复策略，提出一种以最小化加权成本为优化目标的航班恢复模型，并设计一种迭代局部搜索算法。首先用构造-修复启发式方法构造可行解，然后从该初始解出发，在飞机路线对的邻域中进行局部搜索。当陷入局部最优后，对解进行扰动，然后从扰动后的解重新出发进行局部搜索。为了提高搜索效率，同时降低陷入局部最优解的概率，局部搜索过程采用模拟退火算法。实例结果表明，本文提出的模型及算法能够在短时间内对受到影响的大规模航班计划进行恢复。     

Improved non-maximum suppression for object detection using harmony search algorithm

Non-maximum suppression (NMS) plays a key role in many modern object detectors. It is responsible to remove detection boxes that cover the same object. NMS greedily selects the detection box with maximum score; other detection boxes are suppressed when the degree of overlap between these detection boxes and the selected box exceeds a predefined threshold. Such a strategy easily retain some false positives, and it limits the ability of NMS to perceive nearby objects in cluttered scenes. This paper proposes an effective method combining harmony search algorithm and NMS to alleviate this problem. This method regards the task of NMS as a combination optimization problem. It seeks final detection boxes under the guidance of an objective function. NMS is applied to each harmony to remove imprecise detection boxes, and the remaining boxes are used to calculate the fitness value. The remaining detection boxes in a harmony with highest fitness value are chosen as the final detection results. The standard Pattern Analysis, Statistical Modeling and Computational Learning Visual Object Classes dataset and the Microsoft Common Objects in Context dataset are used in all of the experiments. The proposed method is applied to two popular detection networks, namely Faster Region-based Convolutional Neural Networks and Region-based Fully Convolutional Networks. The experimental results show that the proposed method improves the average precision of these two detection networks. Moreover, the location performance and average recall of these two detectors are also improved.     

Backtracking search optimization heuristics for nonlinear Hammerstein controlled auto regressive auto regressive systems

In this work, novel application of evolutionary computational heuristics is presented for parameter identification problem of nonlinear Hammerstein controlled auto regressive auto regressive (NHCARAR) systems through global search competency of backtracking search algorithm (BSA), differential evolution (DE) and genetic algorithms (GAs). The mean squared error metric is used for the fitness function of NHCARAR system based on difference between actual and approximated design variables. Optimization of the cost function is conducted with BSA for NHCARAR model by varying degrees of freedom and noise variances. To verify and validate the worth of the presented scheme, comparative studies are carried out with its counterparts DE and GAs through statistical observations by means of weight deviation factor, root of mean squared error, and Thiel’s inequality coefficient as well as complexity measures.     

结合公钥加密和关键字可搜索加密的加密方案

带关键字搜索的公钥加密(PEKS)是一种有用的加密原语，它允许用户将在加密数据上搜索的功能委托给不可信的第三方服务器，而不影响原始数据的安全性和隐私性。但是，由于缺乏对于数据的加密以及解密能力，PEKS方案不能单独进行使用，必须与标准的公钥加密方案(PKE)相结合。因此，Baek等人在2006年引入了一种新的加密原语，称为结合PKE和PEKS的加密方案(PKE+PEKS)，它同时提供了PKE和PEKS的功能。目前，已有文献提出了几种PKE+PEKS方案。然而，他们都没有考虑关键字猜测攻击的问题。本文提出一个新的高效且能够抵抗关键字猜测攻击的PKE+PEKS方案，与已有方案相比，该方案在性能上有很大的提升，并且在生成关键字和数据密文时，不需要使用双线性对，极大地降低了计算和存储成本。安全性分析表明，本文中所提出的方案能够满足密文隐私安全性、陷门不可区分性和抗关键字猜测攻击的安全性。效率分析表明，本分提出的方案更加高效。     

Too big to surveil: the fourth amendment illuminated by ‘modern lights’ and shadowed by obsta principiis in a post-Carpenter world concerned with privacy

The Fourth Amendment to the U.S. Constitution functions as a shield against excess governmental or police power by prohibiting unreasonable searches and seizures. Since its ratification, legal challenges have tempered this shield by frequently disputing the application of investigative processes and tools, including those that bypass the traditional – and simpler – analysis that focused on physical trespass. But recent technological advancements have prompted novel challenges and have forced the U.S. Supreme Court to adopt a parallel inquiry that evaluates society’s expectations of privacy as an alternate path to invoke the Fourth Amendment’s protections apart from any physical trespass. As revolutionary technology continues to present unique issues, this 200-year-old shield manifests a reflective luster as if polished by years of legal discourse that reveals the priorities of those who would interpret its text. Viewing the Fourth Amendment’s shield as a mirror illustrates not only the thoughts of the drafters that revolved primarily around protecting property interests but also the expectations of modern society with its insistence on promoting privacy. And where the drafters channeled their outrage against the loathsome writs of assistance in colonial times, later Americans continued to denounce the similarly invasive general warrants and attempts by investigators to expand the tools in their arsenal beyond constitutional bounds, especially in the surveillance context. Yet, the problems posed by new technology upon privacy concerns are best resolved by relying on the core principles supporting the Fourth Amendment, previous U.S. Supreme Court precedent, and current societal perspectives regarding privacy as a top priority proven by recently enacted legislation both foreign and domestic.

By applying a similar method to address advancing communication technology and its use as a surveillance tool in Carpenter v. United States, the Court turned this shield-become-mirror upon society to conclude that cell phone location information deserves Fourth Amendment protection because of its untiring comprehensiveness and its uniquely detailed nature. Moreover, nearly every American adult carries a cell phone with them almost all the time, making it possible to create a time-stamped map of any cell-phone-carrying-individual’s movements reaching back years and years. Unfortunately, the Carpenter Court did not extend this crucial protection far enough to protect all cell phone location data, and the unmistakable gap in its holding leaves a potential privacy vulnerability the exploitation of which could cause greater harm than all previously disputed surveillance technology combined because of cell phone usage’s general – near universal – applicability. Allowing cell phone location information to be obtained without probable cause and a proper search warrant not only fails to meet the spirit of the Fourth Amendment, it also begins to tarnish that shield such that it no longer reflects historical or current societal values, reducing its goal of protecting Americans to a hollow incantation of words left to languish as time (and technology) marches on.     

YC12VC型高速柴油机发火顺序的分析研究

基于AVL-EXCITE软件搭建了YC12VC发电用高速柴油机轴系动力学模型,其模拟值与试验值吻合性较好,验证了该模型可以较好地模拟不同工况条件下轴系的运动情况。基于平衡性和均匀发火等原则,设计了8种不同的发火顺序,并针对轴承受力、轴承润滑、轴系扭振和转速不均匀性开展影响规律研究。结果表明:通过发火顺序的优化,在保证最大主轴承负荷和最小油膜厚度满足设计要求的前提下,标定工况下的曲轴扭振总振幅从0.465°降低到0.259°,转速不均匀系数从0.018降低到0.009。     

上游泵送机械密封多目标多工况优化研究

为了获得具有较强适应工况变化能力的上游泵送机械密封,以微间隙内流场的CFD计算为基础,建立涉及多工况的多目标优化数学模型,综合分析相关研究成果和密封特性确定了优化变量及其取值范围、工况参数取值范围和优化目标。应用模糊集理论确定不同工况下的液膜刚度和泄漏量的权重因子,并研究人工神经网络模型对优化结果的影响。基于穷尽搜索法和遗传算法对密封进行优化设计,对比分析2种优化方法得到的优化结果,并对优化前后的密封润滑膜流场特性进行BVF诊断分析。优化研究表明:人工神经网络模型很好地拟合了液膜刚度、泄漏量随槽型参数变化的函数关系;2种优化方法都能提高密封性能,但遗传算法优化比穷尽搜索法优化能获得更好的优化结果。     

柴油机喷油器结构参数与磨料流加工效果关联的研究

基于磨蚀模型和多相流离散相模型建立了柴油机喷油器磨料流加工过程的CFD计算模型。在验证基础模型的有效性后,分别针对喷孔直径、喷孔锥角和交点位置三种结构参数进行变参数模拟计算。通过对加工域颗粒流速、湍流强度和磨蚀率的分析,获得了喷油器主要结构参数对液力研磨加工的影响机理:喷孔直径和喷雾锥度的变化对喷孔壁面磨蚀量的影响较大,随着两者的增大,喷孔壁面的磨蚀量有所增加;交点位置由上至下的变化对喷孔壁面磨蚀量的影响较小,但是喷孔入口处磨蚀量有所增加。     

Simulation and experimental study of the NOx reduction by unburned H2 in TWC for a hydrogen engine

The unburned H₂ can be used to reduce NO emission in conventional TWC (three-way catalyst) for a hydrogen internal combustion engine when it works at equivalence ratio marginally higher than the stoichiometric ratio. To explore the effects and feasibility of this reaction, a Perfectly Stirred Reactor simulation model of TWC has been built with simplified mechanisms. Experiments on a 2.3 L turbocharged hydrogen engine are used to verify the conclusion. It shows that rising initial temperature accelerates the reduction of NO and the maximum reaction rate occurs at 400 °C temperature. The conversion efficiency of NO remains approximately 0 when temperatures below 300 °C. The efficiency reaches a peak value of approximately 98% with 400 °C and declines gradually. The unburned H₂ to NO mixing ratio greater than 1.5 in TWC guarantees 100% NO conversion efficiency. The experiments indicate that the NOx concentration decreases from 2056 ppm to 41 ppm at the stoichiometric ratio after the treatment of TWC and NOx reaches 0 ppm with a rich ratio. Results also demonstrate that the suitable reaction temperatures for TWC locate in the range of 400 °C–500 °C. Therefore, if the temperature and the mixing ratio are appropriate, it can achieve zero emissions with NOx reduction by unburned H₂ in conventional TWC for a hydrogen engine.     

基于实车状态的发动机均值模型研究

基于实车状态下发动机的测试运行参数，提出了一种改进发动机均值模型仿真精度的方法。首先基于五电机台架对实车搭载环境下的一款自然吸气发动机进行了性能测试，分别获得发动机水温、发动机转速、发动机缸内压力、进气道压力和温度、进气歧管压力和温度、燃油体积流量、发动机飞轮端扭矩、排气歧管压力和温度、排气歧管过量空气系数、三元催化后排气压力和温度等参数；然后运用Amesim/MATLAB软件联合仿真对发动机进行了基于实车搭载环境边界下的数值建模和模型标定。研究结果表明，标定后的发动机均值模型预测结果与实际测试结果最大差值可以控制在8%以内。