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Abstract: This study refers to minimization of quadratic functionals in infinite time. The coefficients of the quadratic form are quadratic matrix, function of the state variable. Dynamic constraints are represented by bilinear differential systems of the form . One selects an adequate factorization of A(x) such that the analyzed system should be controllable. Employing the Hamilton–Jacobi equation it results the matrix algebraic equation of Riccati associated to the optimum problem. The necessary extremum conditions determine the adjoint variables λ and the control variables u as functions of state variable, as well as the adjoint system corresponding to those functions. Thus one obtains a matrix differential equation where the solution representing the positive defined symmetric matrix P(x), verifies the Riccati algebraic equation. The stability analysis for the autonomous systems solution resulting for the determined feedback control is performed using the Liapunov function method. Finally we present certain significant cases. [ABSTRACT FROM AUTHOR]

Purpose: The present study aims to unveil the main predictors of perceived media influence (the third-person effect (TPE)) on people's opinions towards COVID-19 vaccination. While the TPE has been researched before in medical contexts, predictors of TPE on the topic of vaccination against COVID-19 are understudied. Design/methodology/approach: This study employs a national survey using an online panel (N = 945) representative for the online population of Romania aged 18 or higher; data were collected during 1–9 April 2021. Findings: Results indicate that people perceive both close and distant others to be more influenced by media information related to COVID-19 vaccination topics. TPE perception is correlated with belief in conspiracy theories about vaccines/vaccination, perceived incidence of fake news about COVID-19 vaccines/vaccination, perceived usefulness of social networking sites and critical thinking. Originality/value: Results from this study might explain the success rate of some communication strategies employed with the help of the media. Key findings could be used as starting points for understanding the profile of those who underestimate the media's impact on themselves with respect to COVID-19 immunization and for designing more successful media strategies. [ABSTRACT FROM AUTHOR]