Search results for "Operations Research"
showing 10 items of 1297 documents
Negotiation in Distributed Production Planning Environments
2006
Mass customization and global competition push enterprises to adopt proper business models able to capture all the opportunities arising from emerging competition rules. An increasing number of industrial enterprises distribute their production capacity world wide to achieve lower production costs, lower distribution costs (due to the closer proximity to customers), and deeper knowledge of customer needs. As a drawback, coordination of the different production plants and the balance among plants and enterprise goals represent a critical issue in the network management. In this context the paper looks at the production planning problem, adopting a traditional hierarchical time-based perspect…
An Object-Oriented Approach to Discrete-Event Simulation Applied to Underground Railway Systems
1999
This paper describes the implementation of an object-oriented simulator that supports the determination of timetables and the design of on-line control policies for underground rail way systems. The simulator has been developed on the basis of a new approach to object- oriented modelling. Such an approach has been used to design a development tool that supports the generation of simulation codes and is able to automatically define the skeleton of a code.
Risk Assessment of a compound feed process based on HAZOP analysis and linguistic terms
2016
[EN] The size and complexity of industrial plants, along with the characteristics of the products used, require a study, analysis and control of the existing risks in every industrial process. In this paper, a methodology for risk assessment in industrial plants, based on the combination of risks identification through the Hazard and Operability (HAZOP) analysis and the risks evaluation through linguistic variables and fuzzy numbers is applied to a case study consisting on a compound feed plant located in the town of Silla (Valencia, Spain). The results from this study show that the main risk in the compound feed production process is the formation of explosive atmospheres (ATEX). Therefore…
A feasibility study of some DSM enabling solutions in small islands: The case of Lampedusa
2017
Abstract The paper addresses the issue of the transition from a traditional electrical system without automation to a newer active and smart system allowing the possibility of implementing Demand Side Management policies, for little islands not supplied by the main grid. In particular, the paper focuses on two main topics related to the definition of: • an effective control, monitoring and communication system as a tool for the full exploitation of the opportunities given by Demand Response policies; • some solutions for the automation of the end-users’ electrical installations, in order to offer to the utility flexibility to be used for the improvement of the generation and distribution ef…
AGV-served assembly lines: influence of sequencing and launch policies on system performances
1990
SUMMARY The planning of an AGV-based flexible assembly line is studied. The conflicting objectives of the minimization of the AGVs wait along the line and of the maximization of the system productivity are investigated. To improve the system performances the late start policy to launch and transfer the AGVs is introduced and a heuristic sequencing algorithm is proposed. The developed computer-aided planning procedures make it possible to consider different AGV launch policies, buffer capacities and management goals; moreover, with the combined use of effective sequences a better utilization of the different resources is reached.
Assessment of methodologies and data used to calculate desalination costs
2017
Abstract In desalination, similarly with other industries, the cost of the final product is one of the most important criteria that define the commercial success of a specific technology. Therefore, when new projects are planned or new technologies are proposed, the analysis of the expected costs attracts a lot of attention and is compared to (perceived) costs of state-of-the-art desalination or costs of alternative fresh water supply options. This comparison only makes sense if the cost assessment methodologies are based on the same principles and use common assumptions. This paper assesses: (i) the methodologies used to calculate the water cost; (ii) the boundary conditions and (iii) the …
The cost of green roofs disposal in a life cycle perspective: covering the gap.
2012
Abstract This study is aimed at providing a contribution in overcoming the current gap, especially in Life Cycle Costing (LCC) and Benefit – Cost (BCA) analyses, due to the lack concerning the green roof disposal costs. Therefore, we have applied to an actual extensive green roof the LCC methodology suggested by D. G. Woodward (that appears like one of the most formalized and generalizable), but we have extended the analysis to the disposal phase. This will allow a complete and proper application of the LCC methodology in order of achieving an economic accounting of this component through its life cycle. In this way, it is possible to achieve the complete evaluation of the “green roof” perf…
A GRASP algorithm for the container stowage slot planning problem
2016
This work presents a generalization of the Slot Planning Problem which raises when the liner shipping industry needs to plan the placement of containers within a vessel (stowage planning). State-of-the-art stowage planning relies on a heuristic decomposition where containers are first distributed in clusters along the vessel. For each of those clusters a specific position for each container must be found. Compared to previous studies, we have introduced two new features: the explicit handling of rolled out containers and the inclusion of separations rules for dangerous cargo. We present a novel integer programming formulation and a Greedy Randomized Adaptive Search Procedure (GRASP) to solv…
Integrated Approach to Part Scheduling and Inspection Policies for a Job Shop Manufacturing System
2007
The quality of a product greatly depends on the quality of its components. This requires that manufacturing specifications have to be met in the manufacturing environment and as a consequence inspection stations are present in many manufacturing systems and inspection policies must be adopted. One problem, which has been widely investigated, concerns the detection of the inspection points in the hypothesis that the action to be taken is known when a defective part is detected. If different jobs are to be produced, then operation scheduling becomes yet another complex problem needing to be solved. And while the problem of scheduling has received a great amount of attention from researchers, …
Cloudy with a Chance of Fuzzy: Building a Multicriteria Uncertainty Model for Construction Project Delivery Selection
2017
AbstractThe process of choosing a project delivery method is infused with cognitive uncertainties associated with the decision maker. Fuzzy uncertainties arise because of imprecise understanding and subsequent representation of these uncertainties by the decision maker, whereas random uncertainties arise from variance of these imprecisions. Since there are no well-defined rules for spontaneous decisions, in order to be consistently confident in the appropriateness of the chosen delivery method, a structured approach incorporating uncertainty is required. Previously unanswered questions such as (1) what are the sources of uncertainty in project delivery decisions, (2) how do decision makers …