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.     

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...     

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 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.     

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。     

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.     

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.     

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.     

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.     

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。     

非整数时延相位补偿的时域平均技术

从时域平均中误差的产生、相位累积误差原理等方面对已有的时域平均算法进行了深入的分析,在此背景下,提出了一种可以在理论上彻底避免相位累积误差的方法--非整数时延相位补偿.在提出该方法之初,对非整数时延在离散信号处理中的物理含义进行了详细的分析,进而给出了有限长序列的非整数时延的实现方法以及序列周期延拓带来的截断误差机理分析.然后,在已有时域平均算法的基础上,通过引入非整数时延相位补偿的方法避免了相位误差,得到了无相位误差的时域平均算法.最后,通过仿真对比实验,证明了这种有限长非整数时延的时域平均算法在理论上可以获得比现有时域平均更好的性能.     

基于自适应浸入与不变的VTOL飞行器跟踪控制

针对输入存在不确定干扰的垂直起降(VTOL)飞行器的跟踪控制问题,提出了一种基于自适应系统浸入与不变(II)的控制方案:对于不确定性输入干扰,采用自适应II方法对于扰进行实时估计补偿;为便于控制器设计,采用系统分解技术将原系统解耦成一个最小相位误差子系统和一个非最小相位子系统,将原系统的输出跟踪问题转换为两个误差子系统的镇定问题。基于自适应II估计律和滑模变结构控制方法分别设计了两个子系统的控制器,所设计的控制器能够保证两个闭环子系统指数稳定。仿真结果表明,上述控制方案在干扰估计精度和收敛速度方面明显优于传统自适应估计方法,能够实现飞行器对给定轨迹的准确跟踪,同时抑制输入干扰对系统性能的不良影响。     

Force sensors based on distortion in delay lines

The principle of operation of force sensors based on distortion in delay lines type of sensor is the distortion of an acoustic signal, in a pulse-excited magnetostrictive delay line due to a force applied at any point between the point where the pulse is generated and the receiving coil. A conductor orthogonal to the delay line is used for pulsed current transmission and its distance is fixed with respect to the delay line. The input and the output of the system are the applied force on the delay line support and the amplitude of the detected output V _o, respectively. Under fixed amplitude of the pulsed current, V_o has a maximum value under zero input and decreases as the applied force increases. Experimental results show that the response of the sensor is a monotonic, exponential function of the applied force. A method is also proposed, according to which an integrated sensor array could be made based on this principle     

Calibration of hydrophones based on reciprocity and time delay spectrometry

A brief survey is given of the calibration methods for hydrophones in the ultrasonic frequency range. The methods presently used in the Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, West Germany, for hydrophone calibrations in the frequency range from 1 to 15 MHz are the primary subject of concern. These methods are the two-transducer reciprocity method for the calibration at discrete frequencies, the time-delay-spectrometry substitution method for quasifrequency continuous calibrations, and the two-transducer reciprocity method with time-delay spectrometry, also for quasi-frequency continuous calibration. Compared with the calibration at discrete frequencies, the expenditure of time for a calibration is considerably reduced in the case of the last-mentioned method. The influencing parameters which affect the evaluation of the measurement uncertainty are briefly discussed for the calibration methods applied at the PTB.     

Ultraviolet light propagation under low visibility atmospheric conditions and its application to aircraft landing aid

Light scattering in the atmosphere by particles and molecules gives rise to an aureole surrounding the source image that tends to reduce the contrast of the source with respect to the background. However, UV scattering phase functions of the haze droplets present a very important forward peak. The spreading of a detected signal in the UV is not as important as in the case of a clear atmosphere where Rayleigh scattering predominates. This physical property has to be taken into account to evaluate the potential of UV radiation as an aircraft landing aid under low visibility conditions. Different results characterizing UV runway lights, simulations of UV radiation propagation in the atmosphere, and the use of a simple detection algorithm applied to one particular sensor are presented.     

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.