The basic types of composite structures with free damping and constrained damping, so what works derived free damping materials and constrained damping material.
复合结构的基本类型有自由阻尼和约束阻尼两种，因此派生出工程上所说的自由阻尼材料和约束阻尼材料。
2
The African Union's efforts to make peace are constrained by lack of human resources, material supplies and funding.