updates the contents

Chapter12/chapter12.tex

@@ -21,6 +21,7 @@
 %	CHAPTER 12
 %----------------------------------------------------------------------------------------
 
+\part{机器翻译前沿}
 \chapter{神经机器翻译模型训练}
 
 %----------------------------------------------------------------------------------------

mt-book-xelatex.tex

@@ -148,6 +148,7 @@
 \include{Chapter15/chapter15}
 \include{Chapter16/chapter16}
 \include{Chapter17/chapter17}
+\include{Chapter18/chapter18}
 \include{ChapterAppend/chapterappend}