Search results for "Operations"
showing 10 items of 1692 documents
Congestion analysis to evaluate the efficiency and appropriateness of hospitals in Sicily
2015
Over the past twenty years, important changes in the Italian National Health System have been made in order to obtain significant improvements in the efficiency, appropriateness and quality of health care delivery, while reducing health expenditure. In this paper we proposed a multidimensional approach to assess the impact of organization inappropriateness on the efficiency evaluation of hospitals in Sicily for the year 2009. This study was based on cross-sectional data for 116 (out of 129) short-term, acute-care hospitals. The analysis considered beds, physicians, nurses and other personnel as inputs, ordinary discharges and day-hospital admissions as desirable outputs and inappropriate di…
Fitting random cash management models to data
2019
Abstract Organizations use cash management models to control balances to both avoid overdrafts and obtain a profit from short-term investments. Most management models are based on control bounds which are derived from the assumption of a particular cash flow probability distribution. In this paper, we relax this strong assumption to fit cash management models to data by means of stochastic and linear programming. We also introduce ensembles of random cash management models which are built by randomly selecting a subsequence of the original cash flow data set. We illustrate our approach by means of a real case study showing that a small random sample of data is enough to fit sufficiently goo…
An application of Matlab c on Dimensional Nonlinear Programming
2014
[EN] Nonlinear Programming (NLP) is a widely applicable tool in modeling real life problems applied to business, economics and engineering. Is to maximize or minimize a scalar field whose domain is given as a set of constraints given by equalities and/or inequalities not necessarily linear. In this paper we present a virtual laboratory to study the PNL graphically and numerically in the case of two variables
Determinants of elimination decisions in the activity scheduling process
2016
[EN] This paper presents an analysis on the determinants related to a particular rescheduling decision in the activity-travel scheduling process: elimination decisions, which consist in the non-execution of pre-planned activity-travel episodes. Data used come from an in-depth computer-assisted telephone interview (CATI) follow up survey carried out during the implementation of the first wave of an activity scheduling process panel survey. Open-ended answers related to the reasons associated to changes between pre-planned and executed agenda are studied. First, an interpretative qualitative method based on analytic induction (AI) is used to cope with the complex nature of the rescheduling de…
Changes in the Scheduling Process According to Observed Activity-travel Flexibility
2014
Abstract In this work we analyze the reasons for changing pre-planned activities and travels episodes considering the type of modification observed during the scheduling process. Specifically we selected a small sample from those pre-planned episodes that are no executed at all as a pilot study. The data analyzed was collected in the first wave of a weekly activity-travel panel survey carried out in Valencia (Spain) in 2010. Each survey wave consisted on a face-to-face interview to generate a pre-planned activity agenda for the following week, an activity-travel diary implemented on mobile phones to collect activities and travels as they are executed, and in-depth telephone interviews to in…
Minimizing weighted earliness-tardiness on parallel machines using hybrid metaheuristics
2015
We consider the problem of scheduling a set of jobs on a set of identical parallel machines where the objective is to minimize the total weighted earliness and tardiness penalties with respect to a common due date. We propose a hybrid heuristic algorithm for constructing good solutions, combining priority rules for assigning jobs to machines and a local search with exact procedures for solving the one-machine subproblems. These solutions are then used in two metaheuristic frameworks, Path Relinking and Scatter Search, to obtain high quality solutions for the problem. The algorithms are tested on a large number of test instances to assess the efficiency of the proposed strategies. The result…
ANOVA-MOP: ANOVA Decomposition for Multiobjective Optimization
2018
Real-world optimization problems may involve a number of computationally expensive functions with a large number of input variables. Metamodel-based optimization methods can reduce the computational costs of evaluating expensive functions, but this does not reduce the dimension of the search domain nor mitigate the curse of dimensionality effects. The dimension of the search domain can be reduced by functional anova decomposition involving Sobol' sensitivity indices. This approach allows one to rank decision variables according to their impact on the objective function values. On the basis of the sparsity of effects principle, typically only a small number of decision variables significantl…
NAUTILUS framework : towards trade-off-free interaction in multiobjective optimization
2016
In this paper, we present a framework of different interactive NAUTILUS methods for multiobjective optimization. In interactive methods, the decision maker iteratively sees solution alternatives and provides one’s preferences in order to find the most preferred solution. We question the widely used setting that the solutions shown to the decision maker should all be Pareto optimal which implies that improvement in any objective function necessitates allowing impairment in some others. Instead, in NAUTILUS we enable the decision maker to make a free search without having to trade-off by starting from an inferior solution and iteratively approaching the Pareto optimal set by allowing all obje…
Simultaneous optimization of harvest schedule and data quality
2015
In many recent studies, the value of forest inventory information in harvest scheduling has been examined. In a previous paper, we demonstrated that making measurement decisions for stands for which the harvest decision is uncertain simultaneously with the harvest decisions may be highly profitable. In that study, the quality of additional measurements was not a decision variable, and the only options were between making no measurements or measuring perfect information. In this study, we introduce data quality into the decision problem, i.e., the decisionmaker can select between making imperfect or perfect measurements. The imperfect information is obtained with a specific scenario tree fo…
Interactive Nonlinear Multiobjective Optimization Methods
2016
An overview of interactive methods for solving nonlinear multiobjective optimization problems is given. In interactive methods, the decision maker progressively provides preference information so that the most satisfactory Pareto optimal solution can be found for her or his. The basic features of several methods are introduced and some theoretical results are provided. In addition, references to modifications and applications as well as to other methods are indicated. As the role of the decision maker is very important in interactive methods, methods presented are classified according to the type of preference information that the decision maker is assumed to provide. peerReviewed