超大型海上浮式结构物(Very Large Floating Structure, VLFS)是由若干个单模块通过连接器连接而成的海上结构物,连接器是整个结构中最薄弱而又最关键的部分,因此有必要对连接器基座进行静强度分析和极限强度分析。文章采用以包含连接...超大型海上浮式结构物(Very Large Floating Structure, VLFS)是由若干个单模块通过连接器连接而成的海上结构物,连接器是整个结构中最薄弱而又最关键的部分,因此有必要对连接器基座进行静强度分析和极限强度分析。文章采用以包含连接器基座的上箱体为研究对象,选取包含单个连接器基座和两个连接器基座的上箱体局部结构作为模型进行静强度分析,得到了两种模型连接器基座整体Von mises应力不大,但存在基座与连接器连接处、立柱与上箱体底甲板连接处两处明显的高应力区的相关结论。然后,采用非线性有限元准静态法对连接器基座进行极限强度分析,确定结构在危险工况下最先发生破坏的位置,得到基座连接器不同方向的极限承载力。结果表明,连接器基座在各个方向的极限承载力都远大于其载荷预报值,连接器基座具有较大的结构强度储备。文中的研究结果为超大浮体连接器基座的设计和安全可靠性分析提供了相关理论依据。展开更多
In the face of the corona virus disease 2019(COVID-19)pandemic,it is essential to stabilize the security of urban“shopping baskets”.Through a survey and interviews with 46 agricultural cooperatives in Shanghai,this ...In the face of the corona virus disease 2019(COVID-19)pandemic,it is essential to stabilize the security of urban“shopping baskets”.Through a survey and interviews with 46 agricultural cooperatives in Shanghai,this paper analyzes the impact of the pandemic on vegetable production and offers suggestions on agricultural insurance.The research results show that:(1)the pandemic has impacted almost all stages of the vegetable supply chain but has had a greater impact on the sales stage;(2)the market risks of vegetable production have increased significantly,and the gap between the field price and the market price has widened.The sales price difference between traditional channels and e-commerce is notable;(3)farmers’incomes have generally declined due to the COVID-19 pandemic,and traditional small-scale farmers have suffered more losses;and(4)agricultural insurance plays an important role in stabilizing the supply of vegetables to the city.To minimize the impact of the pandemic on vegetable production and to stabilize both urban“shopping baskets”and farmers’incomes,it is necessary to further improve agricultural insurance,especially to provide insurance against market risks.展开更多
基金This study was supported by the Humanity and Social Science Youth Fund of the Ministry of Education of China(18YJC790157)the National Social Science Fund of China(16ZDA019).
文摘In the face of the corona virus disease 2019(COVID-19)pandemic,it is essential to stabilize the security of urban“shopping baskets”.Through a survey and interviews with 46 agricultural cooperatives in Shanghai,this paper analyzes the impact of the pandemic on vegetable production and offers suggestions on agricultural insurance.The research results show that:(1)the pandemic has impacted almost all stages of the vegetable supply chain but has had a greater impact on the sales stage;(2)the market risks of vegetable production have increased significantly,and the gap between the field price and the market price has widened.The sales price difference between traditional channels and e-commerce is notable;(3)farmers’incomes have generally declined due to the COVID-19 pandemic,and traditional small-scale farmers have suffered more losses;and(4)agricultural insurance plays an important role in stabilizing the supply of vegetables to the city.To minimize the impact of the pandemic on vegetable production and to stabilize both urban“shopping baskets”and farmers’incomes,it is necessary to further improve agricultural insurance,especially to provide insurance against market risks.
