PWR-HYBRID-3/journal

Lab Journal

                        ___
                      ,'   `.
                     /  ___  \      n, C_i,
                    | ( UO2 ) |     T_f, T_c, T_cold
                     \  ‾‾‾  /         |
                      `.___,'          v
                       |||||  →→→→  [ controller ] →→→→ rods
                       |||||
                  ‾‾‾‾‾‾‾‾‾‾‾‾‾  primary loop
                  ___________
                 |   SG       |     Q_sg(t) ∈ [Q_min, Q_max]
                 |____________|

The HAHACS invention log for the pwr-hybrid-3-demo preliminary example. Each dated session gets an entry. The goal: a reader in 2030 should be able to rebuild the thesis work from this journal alone.

Structure

journal/
  preamble.tex         shared LaTeX setup (fonts, listings, callouts, macros)
  journal.tex          top-level aggregator (builds all entries into one PDF)
  entries/             dated session entries, one file per session
    YYYY-MM-DD-{topic-slug}.tex
  figures/             journal-specific figures (referenced from entries)
  README.md            this file

Conventions

Filename

entries/YYYY-MM-DD-{topic-slug}.tex. One file per session. If a day has multiple distinct sessions, use time-of-day in the slug (e.g., 2026-04-20-morning-predicates.tex and 2026-04-20-evening-mega-session.tex).

Entry skeleton

\session{2026-04-17}{duration}{one-line summary}

\section{Session: ... (YYYY-MM-DD)}
\label{sec:YYYYMMDD}

\subsection*{Goal}
What I set out to do and why.

\subsection*{What landed}
...

\subsection*{Key decisions}
...

\subsection*{Dead ends}
...

\subsection*{Derivations}
...

\subsection*{Results}
...

\subsection*{Limitations recorded}
...

\subsection*{Open at close}
...

Entries compile standalone (each starts with \input{../preamble.tex} wrapped in a conditional so it only pulls preamble when not already loaded by journal.tex), or together via journal.tex.

Two entry styles

• A-style (deep / invention-log): full derivations, code commentary, dead-ends, embedded figures, terminal output where useful. Used for retroactive entries and sessions that land meaningful artifacts.
• B-style (narrative + pointers): end-of-session notes. Uses \apass{...} callouts to flag spots that need a later A-pass.

Callout boxes

From preamble.tex:

Environment	Use
derivation	Math derivations
decision	Design choices with rationale + alternatives
deadend	Paths that didn't work
limitation	Soundness gaps, known-approximate behavior

Plus the inline \apass{text} marker for A-pass TODOs.

Code inclusion

• \juliafile[options]{path/to/file.jl} — includes a Julia source file as a numbered listing.
• \matlabfile[...]{...} — for MATLAB sources.
• Or inline with lstlisting environment and language=Julia for snippets.

Always include the path as the listing caption so readers can find the file.

Figures

Figures live in ../docs/figures/ (shared with the thesis) or figures/ (journal-only). The preamble sets \graphicspath to check both.

Always include:

1. A descriptive caption (what's on axes, what's being shown).
2. A discussion in the surrounding prose — what the figure proves or illustrates. Figures without discussion are noise.

Terminal output

For a numerical result or an error that drove a decision, include the actual terminal text in a lstlisting block with style=terminal:

\begin{lstlisting}[style=terminal]
TMJets: 10583 reach-sets
T_c envelope: [274.45, 295.0] C
FAILED: AssertionError: radius must be nonnegative
\end{lstlisting}

Don't include full logs — only the lines that changed what you did next.

Build

cd journal
latexmk -pdf journal.tex            # whole journal as one PDF
latexmk -pdf entries/2026-04-17-controllers-linear-reach.tex  # one entry

Requires TeX Live with tcolorbox, listings, inconsolata, siunitx, cleveref, hyperref, fancyhdr. All in the standard distribution.

Not a replacement for

• claude_memory/ — short AI-context notes, Markdown, different audience.
• reachability/WALKTHROUGH.md — standalone doc summarizing current state of reach analysis.
• Git commit messages — per-commit rationale for code changes.

The journal is the chronological narrative of the work. The others are snapshots, summaries, or pointers. They're all legitimate; they do different things.