单选题
发布日期:2021-07-03
工程计量
法定计量
分析仪
检测仪
计量表一般指用来测量管路中在某一时间间隔内流体流过的总量(积累量)的仪表。
由法定计量部门或法定授权组织按照检定规程,通过实验,提供证明,来确定测量器具的示值误差满足规定要求的活动。
燃气是气体燃料的总称,它能燃烧而放出热量,供居民和工业企业使用。燃气的种类很多,主要有天然气、人工燃气、液化石油气和沼气、煤制气。
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Spanning-Tree Protocol is a link management protocol that provides path redundancy while preventing undesirable loops in the network. For an Ethernet network to function properly, only one active path can exist between two stations. Multiple active paths between stations cause loops in the network. If a loop exists in the network topology, the potential exists for duplication of messages. When loops occur, some switches see stations appear on both sides of the switch. This condition confuses the forwarding algorithm and allows duplicate frames to be forwarded. To provide path redundancy, Spanning-Tree Protocol defines a tree that spans all switches in an extended network. Spanning-Tree Protocol forces certain redundant data paths into a standby (blocked) state. If one network segment in the Spanning-Tree Protocol becomes unreachable, or if Spanning-Tree Protocol costs change, the spanning-tree algorithm reconfigures the spanning-tree topology and reestablishes the link by activating the standby path. Spanning-Tree Protocol operation is transparent to end stations, which are unaware whether they are connected to a single LAN segment or a switched LAN of multiple segments.There is a lab about STP in Cisco CCNP 642-812 / 642- 892 exam. Requirements: You will configure FastEthernet ports 0/12 through 0/24 for users who belong to VLAN 20. Also, all VLAN and VTP configurations are to be completed in global configuration mode as VLAN database mode is being deprecated by Cisco. You are required to accomplish the following tasks: 1. Ensure the switch does not participate in VTP but forwards VTP advertisements received on trunk ports. 2. Ensure all non-trunking interfaces (Fa0/1 to Fa0/24) transition immediately to the forwarding state of Spanning-Tree. 3. Ensure all FastEthernet interfaces are in a permanent non-trunking mode. 4. Place FastEthernet interfaces 0/12 through 0/24 in VLAN 20
______我来说,能考上重点大学是我的最大心愿。
一台换热器未设折流板和支持板,其管板间距为L,则换热管受压失稳的当量长度Lcr 为 () 。
机动车辆降低转速,增大输出扭矩和改变旋转方向的是()作用。
颌面部间隙感染最常见的病原菌是()
《打火匣》中士兵用火擦破打火匣,马上出现了()。
()的一般项目应该包括医疗机构名称,费别,患者姓名,年龄和病历号等
尿道膜部损伤时,尿生殖膈没损伤时,尿外渗至()
项目沟通有四个需求,其中不包括:()
肺性脑病发生机制主要是()
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燃气计量表必须经过()检定机构的检定,检定日期应在有效期限内。
管道燃气用户需移动燃气计量表及表前设施,以及安装、改装、拆迁用于经营的燃气设施,应向()
燃气灶具与燃气流量表保持的水平净距是()。
燃气用具与燃气流量表水平净距应大于()。
家用膜式燃气表属于()型计量表
燃气计量表的安装位置应满足()、()和安全使用的要求。
一般家用燃气计量表选用()。
大流量小于65m3/h的膜式燃气计量表,表后与墙净距不应小于()mm。
最大流量小于()m3/h的膜式燃气计量表,当采用高位安装时,表后距墙净距不宜小于30mm,并应加表托固定。
燃气计量表之间的净距应能满足安装管道、组对法兰、维修和换表的需要,并不宜小于()