In this paper, standard accretion disk models of AGNs are tested using light curves of 26 objects well observed for reverberation mapping. Time scales of variations are estimated by the most common definition of the variability time scale and the zero-crossing time of the autocorrelation function of the optical light curves for each source. The measured time scales of variations by the two meth...

Identification of non-linear FIR-models is studied. In particular the selection of model structure, i.e., to find the contributing input time lags, has been examined. A common method, exhaustive search among models with all possible combinations of the input time lags, has some undesired drawbacks, as a tendency that the minimization algorithm gets stuck in local minima and heavy computations. ...

This paper presents a mathematical de nition of Left-Associative Grammar, and describes its formal properties. Conceptually, LA-grammar is based on the notion of possible continuations, in contrast to more traditional systems such as Phrase Structure Grammar and Categorial Grammar, which are linguistically motivated in terms of possible substitutions. It is shown that LA-grammar generates all a...