【多选题】关于分节制作沉井的要求,正确的有( )。
B.
设计无要求时,前节混凝土强度应达到设计强度75%,方可浇筑后节混凝土
D.
混凝土施工缝处理应采用凹凸缝或设置钢板止水带,施工缝应凿毛并清理干净
E.
分节制作、分次下沉的沉井严禁在接高施工过程中发生倾斜和突然下沉
【判断题】动植物细胞在进行有丝分裂时,它们的纺锤体内都有两个中心粒
【单选题】平面汇交力系平衡的充要条件是各力在两个互不平行的坐标轴上投影的代数和( )
【多选题】有关沉井干封底施工要求的表述,说法正确的有______。
A.
在井点降水条件下施工的沉井应继续降水,并稳定保持地下水位距坑底不小于0.5m在沉井封底前应用大石块将刃脚下垫实
C.
钢筋混凝土底板施工前,井内应无渗漏水,且新、老混凝土接触部位凿毛处理,并清理干净
E.
封底前应设置泄水井,底板混凝土强度达到设计强度等级且满足抗浮要求时,方可封填泄水井、停止降水
【单选题】接种疫苗后,疫苗中的抗原分子就会发挥( ),刺激机体免疫系统产生免疫保护物质。
【单选题】What does the professor mainly discuss in this lecture?
A.
Various types of helpful symbiotic relationships.
B.
Difficulties in classifying relationships between species.
C.
Different types of relationships between species.
D.
The erroneous popular understanding of symbiosis.
【单选题】What is the main purpose of the lecture?
A.
To discuss recent innovations in laboratory equipment
B.
To give an example of a practical use for a particular scientific technique
C.
To familiarize students with the chemical composition of paint pigments
D.
To show how researchers were able to restore a particular work of art
【单选题】What is the main purpose of this lecture?
A.
To discuss three types of authority
B.
To distinguish between power and authority
C.
To examine alternatives to Weber's model
D.
To argue in favor of a legal rational system
【多选题】沉井干封底施工应符合哪些规定?()
A.
沉井基底土面应全部挖至设计标高,待其下沉稳定后再将井内积水排干;
B.
清除浮土杂物,底板与井壁连接部位应凿毛、清洗干净或涂刷混凝土界面处理剂,及时浇筑防水混凝土封底;
D.
在封底混凝土施工过程中,应从底板上的集水井中不断地抽水;等地混凝土达到设计强度后,方可停止抽水,集水井的封堵应采用微膨胀混凝土填充捣实,并用法兰、焊接钢板等方法封平。