\ProcessOptionsBeamer

\mode<presentation>

\useinnertheme{UMBC}
\useoutertheme{UMBC}
\usefonttheme{UMBC}
\usecolortheme{UMBC}

% Create a slide introducing new sections.
\AtBeginSection[]{
  \begin{frame}
    \frametitle{Part \thepart, Section \thesection}
    \vfill
    \begin{center}
      \usebeamerfont{title}\insertpart: \insertsectionhead\par%
    \end{center}
    \vfill
  \end{frame}
}

% Define a new ``partsecframe'' environment that uses a default frame
% title of ``<part>: <section>'' when no other frame title is given.
\newenvironment{partsecframe}[1][\insertpart: \insertsectionhead]
  {\begin{frame}{#1}}
  {\end{frame}}

\mode<all>