摘要 

国家安全与国际安全密不可分。本研究分别搜集布什、奥巴马两位总统发表的美国国家安全战略报告76,992字符和72,453字符，自建两个小型标注语料库。并使用检索软件AntConc3.5.7w，对其模糊限制语的使用频率分别进行统计和比较分析，研究两届美国政府安全观的异同。研究发现：（1）布什与奥巴马在四类模糊限制语的使用上差异较大；（2）两位总统使用最多的模糊限制语均为直接型模糊限制语；（3）四类模糊限制语的使用帮助美国总统实现了不同的交际目的，帮助他们欺骗了世界人民，并为美国的外交政策披上了合法的外衣。

关键词：美国国家安全战略报告；语料库；模糊限制语；批评性话语分析

Contents       

Introduction 1

1. Theoretical Basis 2

1.1. Hedges 2

1.2. Classification of Hedges 2

2. Research Design 5

2.1. Research Subject 5

2.2. Research Questions 5

2.3. Research Tool 5

3. Research Procedures Based on BFSU Qualitative Coder1.1 6

4. Data Analysis Based on BFSU Qualitative Coder 1.1 10

4.1. A Contrastive Analysis of Frequencies within Four Hedges 10

4.2. Comparative Analysis Based on the Frequencies of the Four Hedegs Types Used in The US National Security Strategy Report 11

4.3. A Comparative Analysis Based on the Cross-results of Hedges Chi-square Test in The US National Security Strategy Report 13

4.4. Rounders Approximators 14

4.5. Adaptor Approximators 16

4.6. Plausibility Shields 19

4.7. Attribution Shields 21

4.8. Reasons for Differences in Hedges Used by US Presidents in The US National Security Strategy Report 23

5. Pragmatic Functions of Hedges in The US Reports of National Security Strategy 24

5.1. To Obscure the Source to Avoid Arbitrary Judgement 24

5.2. Follow the Principle of Politeness to Avoid Conflicts with Other Countries 25

5.3. Achieve Accuracy of the Language through Vaguenesses 26

5.4. Quote Others' Opinions and Euphemistically Express Their Own Views 26

Conclusion 27

References 29