基于模型定义的复合材料旁路挤压试验压缩夹具参数化设计

针对民用飞机复合材料许用值试验开展中需要设计大量构型类似而繁杂的试验夹具,为提高夹具设计的效率和准确性、促进设计的标准化,本文总结了 ASTM标准中复合材料旁路挤压试验的压缩试验夹具构型设计和制造等相关信息,采用包含基于模型的定义(Model Based Definition,MBD)信息的CATIA二次开发方法,提出...     

美国空军装备全寿命保障工作分析与思考

装备保障是装备有效发挥战斗力的基础，研究如何开展全寿命周期的保障工作具有重要的现实意义。本文系统梳理了美军装备全寿命周期保障工作，区分论证、研制、服役和退役四个阶段，分析了各阶段的工作内容和特点，并结合我军装备保障现状和存在的问题，从装备全寿命周期角度，提出了相应的对策建议，为推动和促进我军装备全寿命保障工作提供了理论支持。     

Land use and cover change (LUCC) impacts on Earth’s eco-environments: Research progress and prospects

Land use and cover change (LUCC) is one of the key variables dominating land–atmosphere interactions and strongly affects the Earth’s eco-environments by altering surface properties. Numerous studies have been carried out to assess the impact of LUCC. However, the Earth is a large, open and complex system characterized by complex interactions between its eco-environments and drivers. This study aimed to summarize previous studies of the impact of LUCC on the Earth’s eco-environments and discuss the progress and limitations in suggesting future directions. Previous studies have confirmed that LUCC has a wide range of impacts on the Earth’s eco-environments, which are represented by the alternation of climate (temperature, precipitation, wind, and humidity), hydrology (soil moisture, runoff, and evapotranspiration), ecology and environmental (air, water, and soil) pollution. Physically, the impacts were mainly attributed to the disturbance of the surface radiation budget and matter conservation caused by LUCC. Although great achievements have been made, several challenges remain because of the unavoidable uncertainties in data sources and methodologies and the complexity of eco-environmental evolution. Therefore, data assimilation, physical-based investigations, contribution isolation, and full-process analysis are required to overcome these challenges in future research. The results of this study helped to capture the impact of LUCC and its physical mechanisms, which provide useful clues for future research and support the relative land use management for sustainable development.