\documentclass{scrartcl}
\usepackage{color}
\usepackage{multicol}
\usepackage[final]{graphicx}
\usepackage{pst-plot,pstricks}
	\input{pstplot-logarithmic-axes}
\begin{document}
	\psset{xunit=1cm,yunit=1cm}
	\begin{pspicture}(-0.5,-0.5)(5,3)
		\psgrid[xunit=1,yunit=1,subgriddiv=0,griddots=5,gridlabels=0](0,0)(5,3)
		\psaxes[Dx=5,Dy=5]{->}(0,0)(-0.5,-0.5)(5,3)
		\psplot[plotstyle=curve]{0}{1}{x 2 mul}
		\psplot[plotstyle=curve]{1}{3}{2}
		\psplot[plotstyle=curve]{3}{4}{x 3 sub -2 mul 2 add}
		\rput(5,0.3){$t$}
		\rput(-0.4,2){$\frac{U_0T_2}{T_1}$}
		\rput(1,-0.5){$T_2$}
		\rput(3,-0.5){$T_1$}
		\rput(4,-0.5){$T_1+T_2$}
	\end{pspicture}
\end{document}
