Search results for "Markov chains"

Robust Assembly Assistance Using Informed Tree Search with Markov Chains

2022

Manual work accounts for one of the largest workgroups in the European manufacturing sector, and improving the training capacity, quality, and speed brings significant competitive benefits to companies. In this context, this paper presents an informed tree search on top of a Markov chain that suggests possible next assembly steps as a key component of an innovative assembly training station for manual operations. The goal of the next step suggestions is to provide support to inexperienced workers or to assist experienced workers by providing choices for the next assembly step in an automated manner without the involvement of a human trainer on site. Data stemming from 179 experiment partici…

Markov chain Monte Carlo importance samplers for Bayesian models with intractable likelihoods

2019

Markov chain Monte Carlo (MCMC) is an approach to parameter inference in Bayesian models that is based on computing ergodic averages formed from a Markov chain targeting the Bayesian posterior probability. We consider the efficient use of an approximation within the Markov chain, with subsequent importance sampling (IS) correction of the Markov chain inexact output, leading to asymptotically exact inference. We detail convergence and central limit theorems for the resulting MCMC-IS estimators. We also consider the case where the approximate Markov chain is pseudo-marginal, requiring unbiased estimators for its approximate marginal target. Convergence results with asymptotic variance formula…

Matemātika

2005

Temporal and spatial diversification of the African disjunct genus Androcymbium (Colchicaceae)

2009

Abstract The genus Androcymbium (Colchicaceae) includes 57 species that are distributed in the extreme northern and southern portions of Africa, mainly in regions with a Mediterranean climate. We present the first phylogeographic analysis of the genus with species from all five of its distribution areas (North Africa, Horn of Africa, Namibia, western South Africa, and eastern South Africa). We used sequence data from six chloroplast regions and one nuclear region. Phylogeographic reconstructions were conducted using both parsimony and Bayesian inference methods. Molecular dating estimates using a Bayesian approach suggest a middle Miocene (13.4 ± 1.5 mya) origin of the genus; this approach …

k-out-of-n systems: an exact formula for the stationary availability and multi-objective configuration design based on mathematical programming and T…

2018

[EN] Reliability and availability analyses are recognized as essential for guiding decision makers in the implementation of actions addressed to improve the technical and economical performance of complex systems. For industrial systems with reparable components, the most interesting parameter used to drive maintenance is the stationary availability. In this regard, the present paper proposes an exact formula for computing the system stationary availability of a k-out-of-n system. Such a formula is proved to be in agreement with the fundamental theorem of Markov chains. Then, a multi-objective mathematical model is formulated for choosing the optimal system configuration design. The Pareto …

Population pharmacokinetic model of lithium and drug compliance assessment.

2016

Population pharmacokinetic analysis of lithium during therapeutic drug monitoring and drug compliance assessment was performed in 54 patients and 246 plasma concentrations levels were included in this study. Patients received several treatment cycles (1-9) and one plasma concentration measurement for each patient was obtained always before starting next cycle (pre-dose) at steady state. Data were analysed using the population approach with NONMEM version 7.2. Lithium measurements were described using a two-compartment model (CL/F=0.41Lh-1, V1/F=15.3L, Q/F=0.61Lh-1, and V2/F = 15.8L) and the most significant covariate on lithium CL was found to be creatinine clearance (reference model). Lith…

Utility-based criteria for selecting patients with hepatocellular carcinoma for liver transplantation: A multicenter cohort study using the alpha-fet…

2015

The lifetime utility of liver transplantation (LT) in patients with hepatocellular carcinoma (HCC) is still controversial. The aim of this study was to ascertain when LT is cost-effective for HCC patients, with a view to proposing new transplant selection criteria. The study involved a real cohort of potentially transplantable Italian HCC patients (n = 2419 selected from the Italian Liver Cancer group database) who received nontransplant therapies. A non-LT survival analysis was conducted, the direct costs of therapies were calculated, and a Markov model was used to compute the cost utility of LT over non-LT therapies in Italian and US cost scenarios. Post-LT survival was calculated using t…

Osimertinib in first-line treatment of advanced EGFR-mutated non-small-cell lung cancer: a cost–effectiveness analysis

2019

Aim: Osimertinib improves progression-free survival in first-line EGFR mutation–positive non-small-cell lung cancer. Materials & methods: A Markov cohort model including costs, utilities and disutilities, was conducted to estimate quality-adjusted life-year (QALY) and incremental cost–effectiveness ratio when treating with osimertinib versus standard first-line tyrosine kinase inhibitors (TKIs). Results: Osimertinib presented higher QALYs (0.61) compared with standard EGFR–TKIs (0.42). Osimertinib costs were €83,258.99, in comparison with €29,209.45 for the standard EGFR–TKIs. An incremental cost–effectiveness ratio of €273,895.36/QALY was obtained for osimertinib. Conclusion: Osimerti…

Google matrix analysis of worldwide football mercato

2018

[EN] The worldwide football transfer market is analyzed as a directed complex network: the football clubs are the network nodes and the directed edges are weighted by the total amount of money transferred from a club to another. The Google matrix description allows to treat every club independently of their richness and allows to measure for a given club the efficiency of player sales and player acquisitions. The PageRank algorithm, developed initially for the World Wide Web, naturally characterizes the ability of a club to import players. The CheiRank algorithm, also developed to analyze large scale directed complex networks, characterizes the ability of a club to export players. The analy…

Hepatitis C virus prevalence and level of intervention required to achieve the WHO targets for elimination in the European Union by 2030: a modelling…

2017

Background Hepatitis C virus (HCV) is a leading cause of liver-related morbidity and mortality worldwide. In the European Union (EU), treatment and cure of HCV with direct-acting antiviral therapies began in 2014. WHO targets are to achieve a 65% reduction in liver-related deaths, a 90% reduction of new viral hepatitis infections, and 90% of patients with viral hepatitis infections being diagnosed by 2030. This study assessed the prevalence of HCV in the EU and the level of intervention required to achieve WHO targets for HCV elimination. Methods We populated country Markov models for the 28 EU countries through a literature search of PubMed and Embase between Jan 1, 2000, and March 31, 201…