Koma article class linespacing problems

Question

Now I have badbox warning with this table :

\documentclass[11pt,a4paper,twoside,twocolumn]{scrartcl}
\usepackage{ucs}
\usepackage[utf8x]{inputenc}
\usepackage[francais]{babel}
\usepackage[T1]{fontenc}
\usepackage{multicol}
\usepackage{textcomp}
\usepackage{multirow}
\usepackage{booktabs}
\usepackage{tabularx}
\usepackage{caption} 
\setlength{\columnsep}{30pt}
\usepackage[tracking=true]{microtype}
\usepackage{geometry}
\geometry{a4paper,left=2cm,right=2cm,top=2cm,bottom=2cm}
\captionsetup[table]{skip=10pt}
\raggedbottom
\begin{document}

\twocolumn[\begin{@twocolumnfalse} 

\begin{abstract}
some text here
\end{abstract}

\end{@twocolumnfalse}]  

\section*{title}
\subsection*{title}
some tex here

\begin{table}[ht!]
\small
\caption{Concentrations d'ADN mesurées par spectrophotométrie et rapports d'absorbance A$_{260\;\unit{nm}}$/A$_{280\;\unit{nm}}$.}
\label{tab:absorbance}
\begin{tabularx}{7,9cm}{X p{1,8cm} X}
\hline 
\textbf{Extrait de la souche N°} & \textbf{[ADN]* en ng/$\mu$L}  & \textbf{Rapport d'absorbance A$_{260\;\unit{nm}}$/A$_{280\;\unit{nm}}$} \\  
\hline
1 & 1178,13 & 2,23 \\  
2 & 957,52 & 1,68 \\  
6 & 1470,09 & 2,18 \\  
7 & 983,12 & 2,11 \\  
11 & 1003,30 & 1,15 \\  
12 & 536,17 & 1,88 \\  
14 & 1163,83 & 2,10 \\  
17 & 201,00 & 1,84 \\  
18 & 552,17 & 2,15 \\  
19 & 890,13 & 2,26 \\  
20 & 588,75 & 2,07 \\  
22 & 307,13 & 1,83 \\ 
\hline 
\end{tabularx} 
\caption*{\small\raggedright *[ADN] : Concentration d'ADN$_{\text{extrait}}$}
\end{table}

some text here

\end{document}

Answer 1

Both article and scrartcl use the same rubber lengths before and after the section heading. So I think the most likely cause of the problem stems from the fact that those two classes have different default text width and text heights. The page break is occurring at a different place resulting in an underfull vbox. In order to compensate, TeX is stretching the vertical glue on the page and that's what's causing the extra gap. Try using the geometry package to adjust the text body. Example:

\documentclass[twocolumn,a4paper,11pt]{scrartcl}

\usepackage[body={6.25in,8.25in}]{geometry}
\usepackage[T1]{fontenc}
\usepackage[onehalfspacing]{setspace}
\usepackage{lipsum}

\begin{document}

\section{Sample Section}

\lipsum[1-4]

\section{Another section}

\lipsum[5-10]

\end{document}

In the above, if you remove the line loading the geometry package, the vertical spacing increases around the section headings.