\section{Detailed Intermittent Execution Model}

\subsection{System Description}
\label{sec:system_description}

\begin{figure}
    \centering
    \includegraphics[width=\linewidth]{figs/cropped/system.pdf}
    \caption{A typical hardware setup of intermittent systems.}
    % \label{fig:introduction}
\end{figure}

\subsection{Execution Model}

\begin{figure}
    \centering
    \begin{subfigure}{\linewidth}
        \includegraphics[width=\textwidth]{figs/plot_expr_8a_cropped.pdf}
        \caption{Trace of one power cycle.}
        % \label{fig:eval_voltage_trace}
    \end{subfigure}
    \begin{subfigure}{\linewidth}
        \includegraphics[width=\textwidth]{figs/plot_expr_8b_cropped.pdf}
        \caption{Detailed trace.}
        % \label{fig:eval_adaptivenss_finished_tasks}
    \end{subfigure}
    \caption{Voltage measurement of capacitor and Vdd (470uF, 1.5mA current supply).}
    % \label{fig:}
\end{figure}

Three key observations that affect software designer's decision.

\begin{itemize}
    \item \textbf{O1}: The capacitor voltage drops quickly to charge decoupling capacitor when system wakes-up ($t1$--$t2$).
    \item \textbf{O2}: The system executes at sub-voltage using the decoupling capacitor, even after power supply stops ($t4$--$t5$).
    \item \textbf{O3}: The decoupling capacitor discharges while the system is powered-off (after $t5$).
\end{itemize}

\begin{figure}
    \centering
    \includegraphics[width=\linewidth]{figs/cropped/detailed_execution_model.pdf}
    \caption{Detailed execution model of intermittent systems.}
    \label{fig:detailed_execution_model}
\end{figure}

\subsection{Impact on Power Efficiency}

\begin{figure}
    \centering
    \includegraphics[width=\linewidth]{figs/plot_expr_5_cropped.pdf}
    \caption{Distribution of energy consumed in a power cycle in different capacitor sizes (1mA current supply).}
    % \label{fig:introduction}
\end{figure}

\subsection{Impact on Predicting Power Failures}

\begin{figure}
    \centering
    \includegraphics[width=\linewidth]{figs/plot_expr_6_cropped.pdf}
    \caption{Ratio of sub-voltage operations in total execution time.}
    % \label{fig:introduction}
\end{figure}

Show percentage of execution time executed after power supply stops.

\subsection{Impact of Sub-normal Voltage Execution}

\begin{figure}
    \centering
    \begin{subfigure}{0.48\linewidth}
        \includegraphics[width=\textwidth]{figs/plot_expr_2_cropped.pdf}
        \caption{Trace of one power cycle.}
        % \label{fig:eval_voltage_trace}
    \end{subfigure}
    \hfill
    \begin{subfigure}{0.48\linewidth}
        \includegraphics[width=\textwidth]{figs/plot_expr_2_cropped.pdf}
        \caption{Detailed trace.}
        % \label{fig:eval_adaptivenss_finished_tasks}
    \end{subfigure}
    \caption{Voltage of the capacitor and Vdd, sampled 470uF and 1.5mA.}
    % \label{fig:}
\end{figure}