Search results for "interval"
showing 10 items of 1703 documents
Approximation of the Feasible Parameter Set in worst-case identification of Hammerstein models
2005
The estimation of the Feasible Parameter Set (FPS) for Hammerstein models in a worst-case setting is considered. A bounding procedure is determined both for polytopic and ellipsoidic uncertainties. It consists in the projection of the FPS of the extended parameter vector onto suitable subspaces and in the solution of convex optimization problems which provide Uncertainties Intervals of the model parameters. The bounds obtained are tighter than in the previous approaches. hes.
A fuzzy mathematical programming approach to the assessment of efficiency with DEA models
2003
In many real applications, the data of production processes cannot be precisely measured. This is particularly worrying when assessing efficiency with frontier-type models, such as data envelopment analysis (DEA) models, since they are very sensitive to possible data errors. For this reason, the possibility of having available a methodology that allows the analyst to deal with imprecise data becomes an issue of great interest in these contexts. To that end, we develop some fuzzy versions of the classical DEA models (in particular, the BCC model) by using some ranking methods based on the comparison of α-cuts. The resulting auxiliary crisp problems can be solved by the usual DEA software. We…
Optimal Switches in Multi–inventory Systems
2007
Given a switched multi-inventory system we wish to find the optimal schedule of the resets to maintain the system in a safe operating interval, while minimizing a function related to the cost of the resets. We discuss a family of instances that can be solved in polynomial time by linear programming. We do this by introducing a set-covering formulation with a totally unimodular constraint matrix.
A novel technique for stochastic root-finding: Enhancing the search with adaptive d-ary search
2017
The most fundamental problem encountered in the field of stochastic optimization, is the Stochastic Root Finding (SRF) problem where the task is to locate an unknown point x∗ for which g(x∗) = 0 for a given function g that can only be observed in the presence of noise [15]. The vast majority of the state-of-the-art solutions to the SRF problem involve the theory of stochastic approximation. The premise of the latter family of algorithms is to oper ate by means of so-called “small-step”processesthat explorethe search space in a conservative manner. Using this paradigm, the point investigated at any time instant is in the proximity of the point investigated at the previous time instant, render…
Solving the pentahedron problem
2015
Nowadays, all geometric modelers provide some tools for specifying geometric constraints. The 3D pentahedron problem is an example of a 3D Geometric Constraint Solving Problem (GCSP), composed of six vertices, nine edges, five faces (two triangles and three quadrilaterals), and defined by the lengths of its edges and the planarity of its quadrilateral faces. This problem seems to be the simplest non-trivial problem, as the methods used to solve the Stewart platform or octahedron problem fail to solve it. The naive algebraic formulation of the pentahedron yields an under-constrained system of twelve equations in eighteen unknowns. Even if the use of placement rules transforms the pentahedron…
Existence results for parametric boundary value problems involving the mean curvature operator
2014
In this note we propose a variational approach to a parametric differential problem where a prescribed mean curvature equation is considered. In particular, without asymptotic assumptions at zero and at infinity on the potential, we obtain an explicit positive interval of parameters for which the problem under examination has at least one nontrivial and nonnegative solution.
Some structural properties of a formal model of measurement procedure
1996
Three kinds of a model structure for a measurement procedure are analyzed, i.e. one-cyclic, tree-like and multicyclic. For a multicyclic structure a method of the choice of the optimal strategy for partitioning the uncertainty interval is constructed. An example of a measurement procedure using the suggested strategy is given. Some specific cases of the strategies under different initial conditions are discussed.
The Impact of Venous Thromboembolism In Critically Ill Patients: A Meta-Analysis of Major Clinical outcomes
2010
Abstract Abstract 3327 Background: Critically ill patients are at high risk of developing venous thromboembolism (VTE) during their stay in the intensive care unit (ICU) because of premorbid medical and surgical conditions. The clinical consequences of Deep Vein Thrombosis (DVT) have the potential to be serious yet are frequently unrecognized in the Intensive Care Unit (ICU). In contrast to the extensive documentation on the short and long–term outcomes of patients with DVT evaluated in other clinical settings, little is known about the clinical course of this disease in the ICU setting. We hypothesized that both undetected and clinically evident VTE would affect the prognosis of critically…
Predicting critical illness on initial diagnosis of COVID-19 based on easily-obtained clinical variables: Development and validation of the PRIORITY …
2020
ABSTRACTObjectivesCurrently available COVID-19 prognostic models have focused on laboratory and radiological data obtained following admission. However, these tests are not available on initial assessment or in resource-limited settings. We aim to develop and validate a prediction model, based on clinical history and examination findings on initial diagnosis of COVID-19, to identify patients at risk of critical outcomes.MethodsWe used data from the SEMI-COVID-19 Registry, a nationwide multicenter cohort of consecutive patients hospitalized for COVID-19 from 132 centers in Spain. Clinical signs and symptoms, demographic variables, and medical history ascertained at hospital admission were sc…
Electrocardiographic Abnormalities and Mortality in Epilepsy Patients
2021
Background and Objectives: People with epilepsy (PWE) have a 2–3 times higher mortality rate than the general population. Sudden unexpected death in epilepsy (SUDEP) comprises a significant proportion of premature deaths, whereas sudden cardiac death (SCD) is among the leading causes of sudden death in the general population. Cardiac pathologies are significantly more prevalent in PWE. Whether electrocardiographic (ECG) parameters are associated with remote death in PWE has yet to be elucidated. The study objective was to assess whether interictal ECG parameters are associated with mortality in the long-term. Materials and Methods: The study involved 471 epilepsy patients who were hospitali…