【判断题】大小和方向均随时间周期性变化的力称为交变应力;方向不变,大小周期变化的称为重复应力。二者统称为循环应力。
【判断题】随时间而循环变化的应力称为交变应力,交变应力随时间变化的历程称为应力谱或应力变化曲线。
【单选题】构件受到随时间作()性变化的应力作用,这种应力称为交变应力或重复应力。
【单选题】Which of the following statements about the statistics of pet ownership in the US is wrong?
A.
It's estimated that 78 million dogs & 85.8 million cats are owned in the United States. ~44% of all households in the United States have a dog, & 35% have a cat, according to American Pet Products Association (APPA).
B.
APPA reports that 64% of dogs are purchased from breeders, while 23% of dogs & 31% of cats are obtained from an animal shelter or humane society.
C.
~6.5 million companion animals enter US animal shelters nationwide every year. Of those, ~3.3 million are dogs and 3.2 million are cats.
D.
Each year, ~1.5 million shelter animals are euthanized (670,000 dogs & 860,000 cats). ~3.2 million shelter animals are adopted per year (1.6 million dogs & 1.6 million cats).
【判断题】打入桩没有明显的排挤土体作用,不用考虑对邻近结构(包括邻近基桩)的影响。
【判断题】2019年3月1日,中国航协全面停止了销售代理资质认可工作。
【单选题】Pet ownership can create feelings of being needed and a sense of purpose for those who may be feeling ____ aside.
【简答题】随时间作周期替变化的应力称为___,作用在构件上随时间作周期性变化的载荷称为___。