\documentclass[letterpaper,12pt,onecolumn,oneside]{article}
\setlength{\parindent}{0pt}
\setlength{\parskip}{1em}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%   Use the "geometry" package to set the page layout correctly and the			%
%		"titlesec"' package to set proper sectioning commands. If you do not 		%
%		have these packages, they can be downloaded from the web at: 						%
%	http://www.ctan.org/tex-archive/macros/latex/contrib/supported/geometry/	%
% http://www.ctan.org/tex-archive/macros/latex/contrib/supported/titlesec/	%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\usepackage{geometry}
\geometry{textheight=720pt,
          textwidth=462pt,
          top=36pt,
          left=54pt,
          noheadfoot}
\pagestyle{empty}
%
\usepackage[center]{titlesec}
\setcounter{secnumdepth}{0}
\titleformat{\section}[hang]{\normalfont\normalsize\bfseries} {\thesection}{1em}{\centering}
\titleformat{\subsection} {\normalfont\normalsize\bfseries} {\thesubsection}{1em}{\underline}
\titleformat{\subsubsection}[runin] {\normalfont\normalsize\bfseries} {\thesubsubsection}{1em}{\underline}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% New commands related to paper title and author affilications. %
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\newcommand{\PaperTitle}[1]{%
\begin{center}%
    \begin{large}%
        \textbf {#1} \\%
    \end{large}%
\end{center}%
}%
\newcommand{\AuthorList}[1]{%
\begin{center}%
    {#1} \\%
\end{center}%
}%
\newcommand{\AuthorAffiliation}[1]{%
\begin{center}%
    {#1}
\end{center}%
}%