Simultaneous fleet assignment and cargo routing using benders decomposition

In this paper, we incorporate the cargo routing problem into fleet assignment to model the fleet assignment more accurately. An integrated model and a Benders decomposition-based approach are developed to simultaneously obtain the optimal assignment of fleet to legs and the routing of forecasted cargo demand over the network. Computational experiments show that this integrated approach converges very fast for all different test scenarios.     

Integrated channel assignment and data aggregation routing problem in wireless sensor networks

In wireless sensor networks, data aggregation routing could reduce the number of data transmission so as to achieve efficient total energy consumption. However, this kind of data aggregation introduces data retransmission that is caused by co-channel interference from neighbouring sensor nodes. Hence, more data aggregation leads to more extra energy consumption and significant retransmission delay from retransmission. This could jeopardise the benefits of data aggregation. One possible solution to circumvent retransmission caused by co-channel interference is to assign different channel to every sensor node that is within each other's interference range on the data aggregation tree. As the number of non-overlapping channels is limited in wireless networks, it is unlikely that we could assign a different channel to every sensor node on the data aggregation tree. Then, an interesting problem is to perform data aggregation routing in conjunction with channel assignment to minimise total transmission power under limited number of non-overlapping channels. This problem is an NP-complete problem. We devise heuristic algorithm, Iterative Channel Adjustment Data Aggregation Routing algorithm (ICADAR), and other three heuristics, to tackle this problem. From the simulation results, the ICADAR algorithm outperforms the other three algorithms under all experimental cases.     

Multi-objective decision-making model based on CBM for an aircraft fleet with reliability constraint

Modern production management patterns, in which multi-unit (e.g. an aircraft fleet) are managed in a holistic manner, have brought new challenges for multi-unit maintenance decision-making. To schedule a good maintenance plan, not only does the individual aircraft maintenance have to be considered, but also the maintenance of the other aircraft in fleet have to be taken into account. Condition-based maintenance (CBM) is a maintenance scheme which recommends maintenance decisions according to equipment status collected by condition monitor over a period of time. Evaluating risk is necessary for scheduling appropriate maintenance, avoiding aircraft losses and maintaining the repairable components at a high-reliable state. In this paper, a novel two-models-fusion framework is proposed to predict the reliability of aircraft structures subjected to fatigue loads. Furthermore, we established a fleet maintenance decision-making model based on CBM for the maintenance of fatigue structures. The model concentrates on both minimising fleet maintenance cost and maximising fleet availability, overcoming the shortcomings of traditional fleet CBM research, which has simply focused on one or the other of these parameters. Finally, a case study regarding a fleet of 10 aircraft is conducted, and the results indicated that the proposed model efficiently generates outcomes that meet the schedule requirements.     

A comparison of techniques for solving the fleet size and mix vehicle routing problem

Summary In the fleet size and mix vehicle routing problem, one decides upon the composition and size of a possibly heterogeneous fleet of vehicles so as to minimize the sum of fixed vehicle acquisition costs and routing costs for customer deliveries. This paper reviews some existing heuristics for this problem as well as a lower bound procedure. Based on the latter, a new heuristic is presented. Computational results are provided for a number of benchmark problems in order to compare the performance of the different solution methods.

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Zusammenfassung Das Problem der Bestimmung einer optimalen Anzahl von möglicherweise verschiedenen Fahrzeugen in einem Fuhrpark sowie die bestmögliche Zusammensetzung verschiedener Fahrzeuge bei der Tourenplanung, wobei die Fixkosten der Beschaffung und die Kosten für die laufende Unterhaltung der Routen minimiert werden soll, wird diskutiert. Einige bekannte Heuristiken und ein Algorithmus zur Bestimmung einer unteren Schranke werden besprochen. Mit diesen Grundlagen wird eine neue Heuristik vorgeschlagen. Um die Leistungsfähigkeit der verschiedenen Lösungsmethoden zu vergleichen, werden anschließend Rechenergebnisse verschiedener benchmark Probleme vorgestellt.

     

Integrated order picking and vehicle routing with due dates

OR Spectrum - Supermarkets typically order their goods from a centrally located distribution center (warehouse). Each order that the warehouse receives is characterized by the requested...     

Integrated berth allocation and quay crane assignment with maintenance activities

With the rapid development of worldwide container trade, quay cranes and other resources in container terminals are suffering from increasing workloads. To reduce their failure probabilities, quay cranes usually require preventive maintenance. However, these important activities are often ignored during quay crane planning in literature. This work studies an integrated berth allocation, quay crane assignment and specific quay crane assignment problem where quay crane maintenance is involved, and establishes an integer linear programming with the objective of minimising the total turnaround time. Due to the NP-hardness of the problem, CPLEX only solves instances with up to 18 vessels. For solving larger instances, we propose Left-and-Right Vessel Move (LRVM) algorithm and improved Genetic Algorithm (GA). Experimental results reveal that GA slightly outperforms LRVM with respect to solution quality as the solution of LRVM serves as one of the initial chromosomes of GA. LRVM can output feasible solutions within seconds, even for instances with 50 vessels. We further present a sensitivity analysis of preferred berth segments, and make numerical comparison on algorithm performance for the relevant model without quay crane maintenance. Both the models and proposed heuristics in this work help in dealing with the operational management of container terminal resources in practice.     

Dynamic multicast routing and wavelength assignment using generic graph model for wavelength-division-multiplexing networks

The problem of dynamic multicast routing and wavelength assignment (MC-RWA) in the wavelength-routed wavelength-division-multiplexing networks is addressed. Current solutions to this problem always rely on homogeneous network constructions. However, future backbone networks tend to be heterogeneous in nature. Thus, the dynamic MC-RWA problem should be studied in a more realistic situation by considering the heterogeneity of network structures. A new graph model is proposed for the MC-RWA problem. This model is based on layered auxiliary graph which is generic and able to support various node architectures and heterogeneous network structures. Based on this graph model, the dynamic MC-RWA problem can be simply solved by an efficient multicast tree algorithm on various light-splitting and wavelength-conversion scenarios. In general, this graph model provides a universal platform to study different aspects of the dynamic MC-RWA as well as related problems.     

Integrated multi-factory production and distribution scheduling applying vehicle routing approach

This paper introduces a new integrated multi-factory production and distribution scheduling problem in supply chain management. This supply chain consists of a number of factories joined together in a network configuration. The factories produce intermediate or finished products and supply them to other factories or to end customers that are distributed in various geographical zones. The problem consists of finding a production schedule together with a vehicle routing solution simultaneously to minimise the sum of tardiness cost and transportation cost. A mixed-integer programming model is developed to tackle the small-sized problems using CPLEX, optimally. Due to the NP-hardness, to deal with medium- and large-sized instances, this paper develops a novel Improved Imperialist Competitive Algorithm (IICA) employing a local search based on simulated annealing algorithm. Performance of the proposed IICA is compared with the optimal solution and also with four variants of population-based metaheuristics: Imperialist Competitive Algorithm, Genetic Algorithm, Particle Swarm Optimisation (PSO), and Improved PSO. Based on the computational results, it is statistically shown that quality of the IICA’s solutions is the same as optimal ones solving small problems. It also outperforms other algorithms in finding near-optimal solutions dealing with medium and large instances in a reasonably short running time.     

基于噪声抵消技术的时延估计

阐述了噪声抵消时延估计法(Time Delay Estimation based on Noise-canceling,TDENC)的基本原理,建立了TDENC分析的估计模型;并进行了大量仿真计算和初步海上试验。仿真结果表明:低信噪比且干扰噪声间相关性较强时,TDENC估计延时明显优于常规方法,但其主峰较宽;干扰噪声间彼此相关但信噪比高,估计时延精度则较差。海上试验结果和理论仿真一致。     

信息融合的飞机识别方法

以信息融合的理论为基础，利用从可见光图像序列和8-12μm长波红外图像序列中提取的信息对不同种类飞机进行识别。采用矩特征并结合BP神经网络的方法，分别在特征级和决策级两个不同层次上实现了信息融合。实验结果表明，通过信息融合进行飞机识别的准确率可达到90％以上。     

低时延能耗均衡的水声传感器网络簇间路由算法

针对水声传感器网络的簇间路由选择问题,提出了一种基于前向网关的低时延能耗均衡路由算法,该算法采用最优方向角原则和能耗均衡原则选择中继簇头和中继网关,以减小长延迟和高能耗对水声通信的影响。仿真结果表明该算法在网络平均能耗、端到端时延和网络生命周期等方面具有较好的性能。     

Dynamic operator assignment based on shifting machine loading

This study proposes a way to improve the efficiency of semiconductor wafer fabrications by better allocating operator resources. A semiconductor wafer fabrication facility produces multiple products using unreliable machines, and each product follows a different route. Random machine failures and demand fluctuations make machine loading change from time to time. Thus, the operator assignment needs adjustment accordingly to maintain a high factory throughput rate. We propose methods to make this dynamic adjustment. By using simulation models, we demonstrate that proportionally allocating operators among all work stations based on their utilization requirements can improve overall factory efficiency. We also show that frequent short term dynamic allocation of operators produces more output than conventional long term static allocation.     

基于模糊预测机制的QoS路由

由于有线网络的QoS选路算法不能直接用于自组网,基于预测机制,提出了一个时间约束的最小代价分布QoS路由协议.研究了模糊控制技术的使用,对每种度量,定义了相应的模糊隶属度函数用于预测一个更稳定的链路,实现了一个模糊推理规则库以产生每种链路的模糊代价.通过仿真,比较了基于最短路的QoS和基于洪泛机制的稳定路由QOS,结果表明,基于预测机制的QOS选路的平均呼叫有高的接收率.     

基于深度学习的飞机目标跟踪应用研究

本文针对飞机目标,提出了基于多域网络(MDNet)的改进网络用于飞机跟踪的快速深度学习(FDLAT)跟踪网络,使用迁移学习弥补目标跟踪的小样本集缺陷。卷积层作为特征提取层,全连接层作为目标和背景的分类层,采用特定的飞机数据集来更新网络参数。训练完成之后,结合回归模型,采用简单的线性更新对飞机进行跟踪,算法实现了飞机旋转、相似目标、模糊目标、复杂环境、尺度变换、目标遮挡以及形态变换等复杂状态的鲁棒跟踪,速度达到平均20.36 f/s,在ILSVRC2015飞机检测数据集上成功率均值达到0.592,基本满足飞机实时跟踪。     

Dragline operation modelling and task assignment based on mixed-integer linear programming

Draglines are among the largest earthmoving machines in surface mining, where they are used to remove the waste material (overburden) sitting above a target mineral or coal deposit. The effectiveness of their operation is highly dependent on decisions made by their operators, including the sequence of positions at which they operate and the bulk material movement (what to dig and where to dump) during excavation at each position. In this paper, we formulate a mixed-integer linear program that captures the operational constraints imposed in dragline excavation to determine the optimal material movement for a prescribed sequence of dragline positions. Through a simulation study, we show that the dragline productivity can be improved by more effective assignment of material movement tasks to individual dragline positions. We find that the improvement made compared to using a ‘greedy’digging and dumping strategy depends on the dragline positioning sequence and the terrain profile in the specific environment. The solutions in terms of what to dig and where to dump provide insights into the optimal digging and dumping patterns for different types of dragline positioning sequences, and contribute towards solving the overall dragline operation planning problem that includes the planning of the dragline positioning sequence.     

Curved crack propagation based on configurational forces

A numerical scheme is presented to predict crack trajectories in two-dimensional components. First a relation between the curvature in mixed-mode crack propagation and the corresponding configurational forces is derived, based on the principle of maximum dissipation. With the help of this, a numerical scheme is presented, which is based on a predictor–corrector method using the configurational forces acting on the crack together with their derivatives along real and test paths. With the help of this scheme it is possible to take bigger than usual propagation steps, represented by splines. Essential for this approach is the correct numerical determination of the configurational forces acting on the crack tip. The methods used by other authors are shortly reviewed and an approach that can be extended to arbitrary non-homogenous and non-linear materials with mixed-mode cracks is presented. Numerical examples show, that the method is a able to predict the crack paths in components with holes, stiffeners, etc. with good accuracy.     

基于历史数据的飞行器测试价值评估研究

飞行器测试过程中测试项目复杂,测试数据较为稳定,测试价值较低。该文针对飞行器测试价值评估方法进行研究,提出一种基于历史数据的飞行器测试价值评估方法,为简化测试项目提供理论依据。该方法对飞行器历年来测试数据进行归一化处理,分别利用标准差法和熵权法获得各项测试参数的客观权重,采用退化模型对测试参数进行二次修正,最后依据D-S证据理论,对各参数进行融合,获得测试项目的测试价值。将该方法应用于某型号飞行器测试中,结果表明对测试价值量化评估较为准确。     

基于时延估计的海底线阵阵形估计方法研究

阵形估计是水听器阵列应用中的关键问题,基于时延估计的阵形估计方法比基于传感器测量和基于匹配场处理的方法具有更强的适应性和较高的精度。针对浅海水听器阵列中水平长线阵存在的纵向相关振荡现象引起的不能简单以某一阵元为基准求相对时延的问题,充分利用了阵元信号的高相关性,提出了基于子阵时延的阵形估计方法,针对子阵间时延估计误差向阵端累积的问题,该方法以时延估计的克拉美罗界为依据提出了合理的子阵方式,在一定程度上减小了误差传递。对已有海试数据阵形估计处理的结果表明,相对于单源固定间距方法和未分子阵的双源时延估计方法,基于子阵时延的阵形估计方法满足阵元间距的约束,有较好的空间谱特性,减小了阵形估计误差,对长水听器阵列的应用及阵形估计具有较大应用价值。     

Integrated methodology for board assignment and component allocation in printed circuit board assembly

An approach to minimize makespan for assigning boards to production lines is described. Because of sequence-dependent set-up times, board assignment and component allocation have to be performed concurrently. An integrated methodology is developed to obtain a solution to these two problems. The methodology consists of seven phases: printed circuit board grouping, family decomposition, subfamily sequencing, Keep Tool Needed Soonest (KTNS) procedure, component set-up determination, component allocation and board assignment. Application of the methodology to industrial problems demonstrates that it can solve large-scale problems efficiently. In addition, the effect of two key parameters, feeder capacity and threshold value, on the performance of the solution procedure was examined. The results indicate that feeder capacity has an impact on total workload imbalance but not on the global makespan. Threshold value, a measure of effectiveness of joining a component type to a component group for a printed circuit board family, has a significant effect on the global makespan. The interactions of threshold value, and variations in printed circuit board requirement and component usage also affect global makespan.