1,721,024 research outputs found
A mathematical model for periodic scheduling problems
No full textA mathematical model is proposed for scheduling activities of periodic type. First a model is proposed for scheduling periodic events with particular time constraints. This problem, which could be considered the extension to periodic phenomena of ordinary scheduling with precedence constraints, is shown to be NP-complete. An algorithm for it of implicit enumeration type is designed based on network flow results, and its average complexity is discussed. Some extensions of the model are considered. The results of this first part serve as a basis in modelling periodic activities using resources. Several cases are considered. Finally some applications are presented for which the proposed model can be a useful tool
Smart Management of Electric Vehicles Charging Operations: the Vehicle-to-Charging Station Assignment Problem
No full textThe widespread diffusion of Electric Vehicles (EVs) gives a concrete answer to the growing environmental problems linked to the mobility in urban areas. This paper deals with a particular management problem related to the EVs charging operations: the integration of the EVs with the power distribution system. Possible electrical grid disruptions due to uncoordinated charging operations and the need of guaranteeing to drivers a certain level of confidence while travelling with an EV explain the efforts in the identification of a smart approach for the EVs charging management problem. In this work, a hierarchical mathematical programming approach is considered and a system made up of two interdependent optimization models is introduced in order to identify the optimum spatial and temporal scheduling of EVs charging operations in an urban area served by several charging stations. Moreover, a Mixed Integer Linear Programming (MILP) formulation for the Vehicle-to-Charging Station Assignment Problem is proposed and a preliminary example of application is presented
A Three Level Strategy for the Design and Performance Evaluation of Hospital Departments
No full textThe efficient management of hospital departments (HDs) has recently become an important issue. Indeed, the increased demand and design for hospital services have saturated the capacity of HD that requires suitable tools for the efficient use of resources and flow of patients, staff, and drugs. This paper proposes a model based on a three-level strategy to design at the tactical level in a concise and effective way the structure, the resources, and the dynamics of a critically congested HD. The design strategy is composed of three basic elements: the modeling module, the optimization module, and the simulation and decision module. The first module employs a Unified Modeling Language tool and a timed Petri net (PN) model to effectively capture the detailed flow and dynamics of patients, starting from their arrival to the HD until their discharge. The optimization module employs the fluid relaxation to concisely approximate in a continuous PN framework the HD model and optimize suitable performance indices. The simulation module verifies that the optimized parameters allow an effective workflow organization while maximizing the patient flow. In case of inconsistencies due to the fluid approximation between the continuous model used in the design phase by the optimization module and the discrete one used in the subsequent verification phase by the simulation module, the latter module revises the values of some HD model parameters. A real case study on the Emergency Cardiology Department of the General Hospital of Bari (Italy) shows the efficiency and accuracy of the proposed method
Operational research issues in transport analysis. A selection of the papers presented at the 41st Annual Conference of the Italian Operational Research Society (AIRO 2010)
No full textThis special issue of the European Transport/Trasporti Europei Journal on “Operational Research issues in transport analysis” publishes a selection of the papers presented at the 41st Annual Conference of the Italian Operational Research Society (AIRO 2010) held in Villa San Giovanni, Italy, September 7-10, 2010.
The papers are presented within the Workshop of the Euro Working Group on Transportation on “Models and algorithms for transport network management” organized by Maurizio Bielli within the AIRO2010 Conference.
The main target of the Workshop was exchange of knowledge and experiences in the field of transportation systems analysis and modeling.
The high standards of the conference have been ensured by a wide and competent scientific committee and by a selective review process. The reviewing of the manuscripts submitted for possible publication started in October 2010 with at least 2 reviewers per paper with further revision by the guest editors. The revision and selection process has been completed in December 2011. Among the 7 contributions selected for publication, advances in the state-of-the art related to several fields of transportation systems analysis are illustrated and discussed.
We would like to thank the participants to the EWGT Workshop for submitting high quality papers, allowing us to edit this special issue of the European Transport \Trasporti Europei Journal. A special thanks to all the reviewers for the professional work that they carried out
- …
