1,721,127 research outputs found
Minimal positive realizations: A survey
Full text linkThis survey aims to present a comprehensive and systematic synthesis of concepts and results on the minimal state space realization problem for positive, linear, time-invariant systems. Positive systems are systems for which the state and the output are always non-negative for any non-negative initial state and input. They are used to model phenomena in which the variables must take non-negative values due to the nature of the underlying physical system. Restricting the state–space realization to positive systems makes the problem extremely different and much more difficult than that for ordinary systems. Indeed, a minimal positive realization may have a dimension even much greater than the order of the transfer function it realizes. Although the problem of finding a finite-dimensional positive state–space realization of a given transfer function has been solved, the characterization of minimality for positive systems is still an open problem. This survey introduces the reader to different aspects of the problem and presents the mathematical approaches used to tackle it as well as some relevant related problems. Moreover, some partial results are presented. Finally, a comprehensive bibliography on positive systems, organized by topics, is provided
The inverse eigenvalue problem for leslie matrices
Full text linkThe Nonnegative Inverse Eigenvalue Problem (NIEP) is the problem of determining necessary and sufficient conditions for a list of n complex numbers to be the spectrum of an entry-wise nonnegative matrix of dimension n. This is a very difficult and long standing problem and has been solved only for n <= 4. In this paper, the NIEP for a particular class of nonnegative matrices, namely Leslie matrices, is considered. Leslie matrices are nonnegative matrices, with a special zero-pattern, arising in the Leslie model, one of the best known and widely used models to describe the growth of populations. The lists of nonzero complex numbers that are subsets of the spectra of Leslie matrices are fully characterized. Moreover, the minimal dimension of a Leslie matrix having a given list of three numbers among its spectrum is provided. This result is partially extended to the case of lists of n > 2 real numbers
Evaluation of the technique of macerating alfalfa in a Parmigiano Reggiano producing area
No full text
Contributo metodologico per l'analisi delle interazioni meccanizzazione-ambiente agricolo nel territorio montano alpino
No full text
L'applicazione di tecnologie meccaniche nel sistema zootecnico-foraggero in aree montane: un caso di studio
No full text
Metodologia per la determinazione dell'umidità del foraggio in un centro consortile di essicazione
No full text- …
