thesis-format.sty

\newcommand\partfontsize{12pt}
% redefine \part to not make a new page
%  Approach: create \@ambrosepart from \@part and remove formatting from both
%            (left \@spart alone, so \part* isn't changed)
\renewcommand\part{\cleardoublepage %\thispagestyle{empty}%
  %\null\vfil%
  \markboth{}{}
  \secdef\@ambrosepart\@spart}

\def\@ambrosepart[#1]#2{%
  \ifnum \c@secnumdepth >-2\relax \refstepcounter{part}%
    \addcontentsline{toc}{part}{\partname\ \thepart.
        \protect\enspace\protect\noindent#1}%
  \else
    \addcontentsline{toc}{part}{#1}\fi
  \begingroup\centering
  \ifnum \c@secnumdepth >-2\relax
       {\fontsize{\partfontsize}{\partfontsize}\bfseries
         \partname\ \thepart} \vskip 20\p@ \fi
  \fontsize{\partfontsize}{\partfontsize}\bfseries
      #1\vfil\vfil\endgroup%
      %\newpage\thispagestyle{empty}%
      % vertical space for chapter heading (doesn't seem to work very consistently)
      \vskip 20\p@
      }

% also provide a way to start a chapter without a page break so the first
% chapter of a part is on the same page as the part title
\newcommand\chapternobreak[1]{{\let\clearpage\relax \chapter{#1}}}