\documentclass{yathesis}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\laboratory[logo=,tel=, url=]{un laboratoire de recherche}{ et l'adresse du laboratoire de recherche}
\makeatletter
\renewcommand{\YAD@abstract@page}{
\bgroup
\enlargethispage{2cm}
\setlength{\parindent}{0pt}
\begin{minipage}{\linewidth}
\small
{
\bfseries
\YAD@ifemptyorundef{\printtitle}{
\YAD@generic@argument@translate{title}
}{
\textsc{\printtitle}
}
\ifundef{\printsubtitle}{
}{
\newline
\printsubtitle
}
\vspace{-.5em}
\vspace{\z@}
\begin{center}
\YAD@abstractname@mainlanguage
\end{center}
}
\par
\ifboolexpr{
bool {YAD@abstract@used}
and not bool {YAD@main@abstract@empty}
}{
\usebox{\YAD@abstract@mainlanguage}
}{
\YAD@generic@argument@translate{abstract}
}
