1,721,138 research outputs found
An integrated simulation-optimization framework for the operational planning of seaport container terminals
No full textIn this article the operational planning of seaport container terminals is considered by defining a suitable integrated framework in which simulation and optimization interact. The proposed tool is a simulation environment (implemented by using the Arena software) representing the dynamics of a container terminal. When the system faces some particular conditions (critical events), an optimization procedure integrated in the simulation tool is called. This means that the simulation is paused, an optimization problem is solved and the relative solution is an input for the simulation environment where some system parameters are modified (generally, the handling rates of some resources are changed). For this reason, in the present article we consider two modelling and planning levels about container terminals. The simulation framework, based on an appropriate discrete-event model, represents the dynamic behaviour of the terminal, thus it needs to be quite detailed and it is used as an operational planning tool. On the other hand, the optimization approach is devised in order to define some system parameters such as the resource handling rates; in this sense, it can be considered as a tool for tactical planning. The optimization procedure is based on an aggregate representation of the terminal where the dynamics is modelled by means of discrete-time equations
Modeling and Simulation of the Rail Port Cycle
No full textFor the undisputed degree of complexity that characterizes
the port system, it certainly belongs to the category of
systems of systems. In fact, the functioning of a port is made possible
due to the interaction of a certain number of subsystems, which
in turn depend on other subsystems. The goal of this paper is to
model and simulate, by adopting the System Dynamics methodology,
a subsystem of the port context: the rail port cycle. The model
has been applied to some important container terminals located in
Italy. “What-if” scenarios have been tested with the objective of
underlining system bottlenecks
Optimal shipment policies for distribution systems with a limited fleet of capacitated vehicles
No full textThis paper deals with a distribution system with one origin and one destination in which the shipments are realized with a limited fleet of capacitated vehicles. An optimization problem is defined to find the optimal shipment policies in order to satisfy the external demand, by minimizing holding costs of the customer and transportation costs. Note to Practitioners - A distribution system with one origin and one destination characterized by a Vendor-Managed Inventory policy is considered. In such a system the supplier plans the deliveries to the customer in order to minimize the customer's inventory and the transportation costs. Besides the definition of some solution methods based on mathematical programming techniques, an algorithmic approach for solving the considered optimization problem is also derived in this paper. Even though this approach is suboptimal, it provides very effective solutions and its major strength stands in the possibility of easily implementing it without the use of mathematical programming solvers
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