1,721,313 research outputs found
An Analytical Method for the Performance Evaluation of Flexible Manufacturing Systems with Deterministic Processing Times
No full textEnergy Saving Opportunities and Value of Information: A Trade-off in a Production Line
Full text linkAbstractA general framework for switching the machine off/on has been recently proposed in literature for single machines. However, the amount of information available along the production system is often limited and it might be not trivial to understand which information provides more benefits. This paper studies the performance of a production line when several control policies are applied at machine level. The amount of information at machine level varies and the trade-off with energy reduction is investigated. The considered performance measures are the energy consumed per part and the system throughput. Numerical results are based on discrete event simulation
Simulation optimization with mathematical programming representation of discrete event systems
No full textEnergy efficient control strategy for machine tools with stochastic arrivals and time dependent warm-up
Full text linkEnergy efficiency in manufacturing is becoming a challenging goal due to the demand of this sector in the worldwide scenario. One of the measures for saving energy is the implementation of control strategies that reduce machine energy consumption during the machine idle periods. This paper extends a threshold policy, that switches off the machine during interruptions of part flow, by modelling explicitly the warm-up time as dependent on the time period the machine stays in low power consumption state. The optimal policy parameter is provided numerically for general distributions of the part arrival time and general functions modelling the warm-up time. Numerical results are based on data acquired with dedicated experimental measurements on a real machining center
Analysis of a patient-nurse assignment policy in home care services
No full textThis paper deals with the problem of assigning a Home Care (HC) patient to an operator among a set
of possible ones, under the constraint of continuity of care. Starting from a previously proposed assignment
policy, we first compare the policy with that implemented in real organizations and then we derive some rules to
choose the reference operator that will be in charge to deliver the care service to a new admitted patient. The
proposed assignment rules take into account the variability of the patient needs, expressed in terms of the
number of visits requested along the time.
The comparison of the approach with the current practice of assigning the patient to the operator with the
highest expected free capacity shows that cost savings and workload balancing can be reached by including
patient and workload variabilities
Analysis of two-machine lines with finite buffer, operation-dependent and time-dependent failure modes
Full text linkAn analytical model for evaluating the throughput of two-machine lines, characterised by intermediate buffer with finite capacity, deterministic processing times and multiple failure modes for each machine is presented in this paper. Both operation-dependent failure and time-dependent failure are captured in a unique model as extension of the existing literature that was dealing with either one of them. Each machine has two failure modes, one is operation-dependent and the other is time-dependent. Time to failure and time to repair are assumed to be geometrically distributed. The presented method calculates the steady-state probabilities of the manufacturing system with a computational effort that depends only on the number of failure modes and not on the buffer capacity. A performance comparison of the proposed model with existing techniques is also reported, the aim is to show the error introduced by an analytical model that considers the operation-dependent failure mode as approximation of the time-dependent one
Value of perfect information in home care human resource planning with continuity of care
No full textEnergy-efficient control strategies for machine tools with stochastic arrivals
Full text linkEnergy saving in production plants is becoming more and more relevant due to the pressure from governments to contain the environmental impact of manufacturing and from companies to reduce costs. One of the measures for saving energy is the implementation of control strategies that reduce energy consumption during the machine idle periods. This paper proposes a framework that integrates different control policies for switching the machine off when production is not critical and on when the part flow has to be resumed. A general policy is formalized by modelling explicitly the energy consumed at each machine state. The policy parameters that minimize the requested machine expected energy are provided analytically for general distributions. Numerical results are based on data acquired with dedicated experimental measurements on a real machining centre, and a comparison with the most common practices in manufacturing is also reported.
Note to Practitioners-The paper analyzes the control problem of switching off-on a machine tool for energy saving during the idle times. Different control policies are investigated pointing out the most significant factors. A mapping of the optimal control policy as a function of warm-up time and mean part arrival time is also provided. An algorithm is described for identifying the optimal control parameters. The results of this research will be useful for a practical implementation of a switching policy for energy saving. This implementation requires the fitting of the distribution modelling the part arrival times, the estimation of the warm-up time, and the estimation of the power adsorbed by the machine in four different states
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