在清华大学的论文模板中找到了解决方案：

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        titleformat = \thu@stretch{3em},
        aftername  = \quad,
        beforeskip = 27bp,
        afterskip  = 27bp,
      },
      section = {
        format     = \sffamily\fontsize{14bp}{20bp}\selectfont,
        aftername  = \quad,
        beforeskip = 24bp,
        afterskip  = 6bp,
      },
      subsection = {
        format     = \sffamily\fontsize{13bp}{20bp}\selectfont,
        aftername  = \quad,
        beforeskip = 12bp,
        afterskip  = 6bp,
      },
      subsubsection = {
        format     = \sffamily\fontsize{12bp}{20bp}\selectfont,
        aftername  = \quad,
        beforeskip = 12bp,
        afterskip  = 6bp,
      },
    }%