%% 
%%  A DANTE-Edition example
%% 
%%  Example 36-00-3 on page 770.
%% 
%%  Copyright (C) 2011 Herbert Voss
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%% 
%%  See http://www.latex-project.org/lppl.txt for details.
%% 
%% 
%% ==== 
% Show page(s) 1
%% 
\documentclass[]{article}
\pagestyle{empty}
\setlength\textwidth{375.57637pt}
\setlength\parindent{0pt}

\usepackage{pst-node,amsmath}
\SpecialCoor
%___ POWER SCHEME ___
%
% \begin{PSpic_PowSch}{`width'}{`height'}{`label pow-in'}{`label pow-out'}
%   \PowLoss[`inter pow flux label']%
%         {`relative horizontal position'}%
%         {`loss relative amount'}{`label'}
%          ...
%  \end{PSpic_PowSch}
%
\makeatletter
\def\Mul#1#2#3{%
\pst@dima=#1 pt\pst@dimb=#2\pst@dima%
\edef\value{\pst@number\pst@dimb}%
\let#3=\value%
}
\newcommand{\PowLoss}[4][ ]{%
\Mul{#2}\Lrgh\DeltaX
\Mul{#3}\PW\DeltaY
\Mul\DeltaY{0.5}\HalfDeltaY
\Mul\DeltaY\rCur\SmallRadius
\Mul\DeltaY\rLarr\ArrowFly
\Mul\DeltaY\rHarr\ArrowPeak
%                               NODE DEFINITIONS
    \pnode(CurPoint){PrevPoint}
    \pnode(\DeltaX,0|PrevPoint){PointRelX}
    \pnode([nodesep=\DeltaY,angle=-90]PrevPoint){PointRelY}
    \pnode(PointRelX|PointRelY){CurPoint}
    \pnode([nodesep=\SmallRadius,angle=90]PointRelX){PointRadius}
    \pnode([nodesep=\SmallRadius,angle=0]PointRadius){PointOne}
    \pnode([nodesep=\ArrowFly,angle=180]PointOne){PointTwo}
    \pnode([nodesep=\DeltaY,angle=0]PointOne){PointThree}
    \pnode([nodesep=\ArrowFly,angle=0]PointThree){PointFour}
    \pnode([nodesep=\HalfDeltaY,angle=0]PointOne|[nodesep=\ArrowPeak,angle=90]PointOne){PointPeak}
%                               DRAWING ARROW
    \psline(PrevPoint)(PointRelX)
    \ncarc[arcangle=-45]{-}{PointRelX}{PointOne}
    \ncarc[arcangle=-45]{-}{CurPoint}{PointThree}
    \psline(PointOne)(PointTwo)(PointPeak)(PointFour)(PointThree)
    \nput[labelsep=.2]{90}{PointPeak}{#4}% loss label
%                               OPTIONAL POWER FLUX LABEL
    \ifx#1 \relax % if no label do nothing
    \else\ncline[linestyle=none]{-}{PrevPoint}{PointRelX}\ncput{\pnode{MPointUp}}
         \pnode(MPointUp|0,0){MPointDwn}
         \ncline[linestyle=solid,linewidth=.5pt,nodesep=.05]{<->}{MPointUp}{MPointDwn}\naput{#1}\fi
}
\newlength{\ObjWidth}
\newenvironment{PSpic_PowSch}[4]{% >>> OPENING ENVIRONMENT
    \psset{unit=1cm,linestyle=solid,linewidth=.035}
%                               DIMENSIONAL PARAMETERS DEFINITION
    \def\Lrgh{#1}\def\Altz{#2}% PSpicture dimensions
    \def\Hcoeff{.65}
\Mul\Hcoeff\Altz\PW% pow-in relative value (`fp.sty' needed)
    \def\rHarr{.8}\def\rLarr{.35}% loss arrows relative dimensions
    \def\rCur{1}% arrows curvature radius relative value
    \def\Punta{.5}% in-out peak dimension
%                               PICTURE
    \begin{pspicture}(\Lrgh,\Altz)
        \pnode(!0 \Hcoeff\space \Altz\space mul){StartPoint}
        \pnode(StartPoint){CurPoint}
        \pnode(!\Punta\space \Hcoeff\space \Altz\space mul 2 div){MiddleSx}
        \psline(0,0)(MiddleSx)(StartPoint)
        \nput[labelsep=.3]{0}{MiddleSx}{#3}% pow-in label
        \def\potUlabel{#4}}% pow-out label
                                {% >>> CLOSING ENVIRONMENT
        \pnode(\Lrgh,0){ExtPointDxDown}
        \pnode(ExtPointDxDown|CurPoint){ExtPointDxUp}
        \ncline[linestyle=none]{-}{ExtPointDxUp}{ExtPointDxDown}\ncput{\pnode{MiddleDx}}
        \psline(CurPoint)([nodesep=\Punta,angle=180]ExtPointDxUp)(MiddleDx)%
               ([nodesep=\Punta,angle=180]ExtPointDxDown)(0,0)
        \settowidth{\ObjWidth}{\potUlabel}
        \pnode([nodesep=\ObjWidth,angle=180]MiddleDx){LabelDx}
        \nput[labelsep=-.3]{0}{LabelDx}{\potUlabel}
    \end{pspicture}}
\makeatother


\begin{document}
\psset{linecolor=red}
\begin{PSpic_PowSch}{12}{6}{\(P_e\)}{\(P_u\)}
    \PowLoss{.18}{.12}{\(R_s \, I_s2\)} % Joule
    \PowLoss{.35}{.08}{\(G_{Fe} \, E_s^{\phantom{.}2}\)} % iron
    \PowLoss[\(P_{tr}=\dfrac{\omega}{n} C_e\)]{.62}{.13}{\(R_R \, I_r2\)} % Joule
    \PowLoss[\(\dfrac{\omega_m}{n} C_e\)]{.79}{.09}{\textit{attr}} % mec
\end{PSpic_PowSch}
\end{document}
