Research on the optimization of China's foreign trade structure 并列题名:Research on the optimization of China's foreign trade structure Research on the optimization of local tax system Research on the systematization of remedies for trade secret Research on optimization of Chinese vegetable supply chain Research on the optimization of rural social endowment insurance system Research on asset securitization in the infrastructure Research on the change of China's export commodities structure Research on the structural optimization of China's multi-pillar pension system Research on system optimization of multi-regional technology adoption for new infrastructure