In this paper, the hot rolling batch scheduling problem is formulated as a multi-objective vehicle routing problem with double time windows model, in which the first time window deals with the surface grade constraint and the second one is for the linkage modes. In view of the complexity of the proposed model and the priority of considered objectives in practical production, a decomposition-based hierarchical optimization algorithm is proposed to solve the model. Firstly, the model is decomposed into two sub-problems: vehicle routing problem with time windows (VRPTW) and single vehicle routing problem with time windows (SVRPTW). Secondly, MACS-VRPTW is used to optimize the VRPTW sub-problem, in which the first objective is prior to the second one. Then, dynamic programming and genetic algorithm are used to optimize the SVRPTW sub-problem so as to reach a higher hot charge temperature. Experimental results based on the practical production instances have indicated that the proposed model and algorithm are effective and efficient.

Aimed at resolving the issues of the imbalance of resources and workloads at data centers and the overhead together with the high cost of virtual machine (VM) migrations, this paper proposes a new VM migration strategy which is based on the cloud model time series workload prediction algorithm. By setting the upper and lower workload bounds for host machines, forecasting the tendency of their subsequent workloads by creating a workload time series using the cloud model, and stipulating a general VM migration criterion workload-aware migration (WAM), the proposed strategy selects a source host machine, a destination host machine, and a VM on the source host machine carrying out the task of the VM migration. Experimental results and analyses show, through comparison with other peer research works, that the proposed method can effectively avoid VM migrations caused by momentary peak workload values, significantly lower the number of VM migrations, and dynamically reach and maintain a resource and workload balance for virtual machines promoting an improved utilization of resources in the entire data center.

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On the basis of research on charge design and cast scheduling methods and process rules of steelmaking-continuous casting production scheduling in melting factory, we establish a constrained 0-1 integer quadratic programming model for optimal charge design and cast scheduling, and then propose the structure of PSO algorithm and the solving method to this model. And the simulation computation with practical data shows that both the model and the solving method proposed are effective. INTRODUCTIONSteelmaking-continuous casting is the bottle neck process in melting production, and optimal production scheduling can greatly promote the production efficiency of large scale equipment, cut down the waiting time of processes, reduce the material and energy consumption, and consequently reduce production costs and enhance product competitiveness. Therefore, research on this problem involves much attention both at home and abroad [1-9]. Literature [2] studied the problem of charge design from the perspective of minimal steel type substitute costs, and settled the problem of minimal redundant output from charge design. Literature [3] established an integer programming model for charge design with a given number of cast plans, and studied the problem of minimal surplus under the restrictions of charge design. Literature [4] researched the cast problem based on the rules of cast scheduling, and established a quadratic programming model of cast scheduling. Literature [8] established a production planning model for twin strands continuous casting with the goal programming. All above studies on steelmaking-continuous casting scheduling mostly use a hierarchical division method, i.e. firstly settling the problem of charge scheduling, and secondary establishing the model of cast scheduling. Because of lack of consideration on restrictions of cast scheduling during cast design, the overall effect of the charge design-cast scheduling is not so satisfying. For the problem of steelmaking-continuous casting scheduling, this paper makes a deep research on modeling technique, solving