不管有无准备，我们都必须面对大变局。何谓大变局，是不是可以说， 大变局就是全球竞争格局发 生重大变化。 其中，比较根本的是美国的变化，因为美国的变化对全球有重要影响，对中国的发展 有特别重要的影响。中国走上和平发展、改革开放之路，离不开在冷战终结前后中美关系从对抗转趋 缓和，中国抓住了当时全球变局带来的历史机遇。 1978年10月，中美两国还没有建交，时任北京大学校长周培源受命带队中国科协代表团与美国国家 科学基金会达成关于派遣留学生的11项口头谅解。1978年年底，首批中国留美学生抵达美国。 1979年1月，这份口头谅解协议在邓小平访美时正式签署。1979年7月，中美在北京达成双方互享 贸易最惠国待遇协议，两国市场互相开放。虽然还需要年度审议，但不论经过多少风风雨雨，中美贸 易互惠协议一直延续，直到2000年，美国国会通过对中国的永久正常贸易关系议案，此后中国也正 式加入世贸组织。1992年10月，华晨中国（CBA）在纽交所挂牌，发行500万普通股，每股招股价 16美元，被超额认购85倍，募资7000多万美元，上市首日该股股价劲升25%。我翻看过那份招股 书，封面上用小字披露风险，包括公司所在国度曾发生过" ...

Investment Rating - The report maintains a "Positive" investment rating for the aerospace and defense industry [2]. Core Insights - The report emphasizes that the aerospace sector is experiencing short-term fluctuations in fundamentals, with expectations for demand to be released during the 14th Five-Year Plan, potentially leading to a new cycle of prosperity [7][24]. - The drone segment is becoming an indispensable force in modern warfare, driven by the rapid development of AI, which is facilitating intelligent and autonomous upgrades [7][3]. - The report highlights the importance of selecting companies that can enhance product capabilities, increase penetration rates, and improve average transaction values as the 14th Five-Year Plan concludes [7][4]. Summary by Sections Section 1: Tariff Friction and National Security - The report discusses the perspective of offensive realism in understanding tariff friction, asserting that great power competition necessitates safeguarding national security [9][18]. Section 2: Aerospace and Engine Sector - The aerospace sector's performance in 2024 is under pressure, with revenue and profit growth rates of -4.69% and -15.41%, respectively, indicating a further slowdown compared to 2023 [27][30]. - The main engine manufacturers showed slight revenue declines, while the intermediate and upstream segments experienced significant fluctuations [27][30]. - The report notes that the main engine manufacturers have maintained strong profitability, while the intermediate segment has faced notable volatility due to price reductions [30][34]. Section 3: Company-Specific Insights - **AVIC Shenyang Aircraft Corporation**: Achieved a record high in quarterly profitability, with a 50.99% year-on-year increase in Q4 revenue to 17.54 billion yuan, despite an overall annual revenue decline of 7.37% [39][43]. - **AVIC Xi'an Aircraft Industry Group**: Reported a 21.09% increase in Q4 revenue, with a 39.14% rise in net profit, although the gross margin decreased [59][63]. - **AVIC Optical-Electrical Technology**: Demonstrated strong growth in defense and civil sectors, with a focus on high-quality delivery and market expansion [69][73]. Section 4: Engine Sector Performance - The engine sector maintained stable revenue growth, with a 9.48% increase in revenue for AVIC Engine, although profitability was impacted by rising costs and increased R&D expenses [92][97]. - The report highlights the growth potential in the civil aviation engine market, with significant contracts signed at the Zhuhai Airshow [102][104]. Section 5: Material Supply Sector - The material supply sector showed steady revenue growth, with a focus on increasing R&D investments for future development [105].