军民合用机场结合军用机场与民用机场于一身,其发展有助于缓解机场项目建设地理位置稀缺、资源浪费及建设成本高等状况。机场航站楼屋架以其跨度大、采光好的建筑需求,多采用大跨度空间钢结构。然而,大跨度空间钢屋架涉及大量钢构件,造...军民合用机场结合军用机场与民用机场于一身,其发展有助于缓解机场项目建设地理位置稀缺、资源浪费及建设成本高等状况。机场航站楼屋架以其跨度大、采光好的建筑需求,多采用大跨度空间钢结构。然而,大跨度空间钢屋架涉及大量钢构件,造成施工管理困难。文章通过分析建筑信息模型(BuildingInformation Modeling, BIM)和射频识别(Radio Frequency Identification,RFID)技术的研究现状,基于两者具有数据记录效率高,交流及时和信息共享便捷等优势提出了大跨度空间钢屋架高精度定位方法。以某军民合用机场为例,验证了该方法能够精确定位钢构件位置,保证钢屋架的安装以及吊装精度。该方法丰富了大跨度钢屋架高精度定位方面的研究,为日后军民合用机场航站楼屋架工程的施工管理提供了参考。展开更多
SiC porous ceramics were prepared at 1 400 ℃ for4 h with crystalline silicon cutting waste and activated carbon as main starting materials and NH4HCO3 as the pore-forming agent. Effects of NH4HCO3 additions( 0,20%,30...SiC porous ceramics were prepared at 1 400 ℃ for4 h with crystalline silicon cutting waste and activated carbon as main starting materials and NH4HCO3 as the pore-forming agent. Effects of NH4HCO3 additions( 0,20%,30%,40%,by mass) on the phase composition,microstructure,sintering properties,cold compressive strength and thermal shock resistance of as-prepared Si C porous ceramics were investigated. The results show that:( 1) addition of NH4HCO3 remarkably influences the apparent porosity and cold compressive strength of specimens. The apparent porosity achieves its maximum value( 63. 40%) when 40% NH4HCO3 is added,while the minimum cold compressive strength is 4. 77 MPa;( 2) the specimen with 40% NH4HCO3 has the best thermal shock resistance. The thermal cycling times between1 000 ℃ to room temperature reach 62;( 3) the addition of NH4HCO3 does not remarkably affect the phase composition of the specimens;( 4) the specimens include a large number of SiC particles and a small amount of SiC whiskers.展开更多
In order to fabricate porous ceramics with good properties and proper production cost,SiC-Al2 O3 porous ceramics were prepared at 1 450 ℃ for 2 h from the powders of commercial silicon carbide and white fused corundu...In order to fabricate porous ceramics with good properties and proper production cost,SiC-Al2 O3 porous ceramics were prepared at 1 450 ℃ for 2 h from the powders of commercial silicon carbide and white fused corundum via a polymeric replication method. Effects of the mass ratio of SiC powder to white fused corundum powder（ 1 ∶ 3,1 ∶ 1 and 3 ∶ 1） on the appearance,phase composition,sintering properties and thermal shock resistance were investigated. The research results indicate that the as-prepared Si C-Al2 O3 porous ceramics have uniform pores,and their linear shrinkage ratio,apparent porosity and bulk density reach 4. 70%,67. 17%and 0. 83 g·cm-3,respectively. The thermal shock cycles from 1 400 ℃ to room temperature reach 23 including 15 cycles in air cooling condition and then 8 cycles in water cooling condition. Their main phases areα-Al2 O3 and Al6 Si2 O13 as well as a small amount of SiC and free SiO2. The as-prepared porous ceramic with the ratio of m（ SiC） ∶ m（ Al2 O3） = 1∶ 1 possesses prior comprehensive properties.展开更多
文摘军民合用机场结合军用机场与民用机场于一身,其发展有助于缓解机场项目建设地理位置稀缺、资源浪费及建设成本高等状况。机场航站楼屋架以其跨度大、采光好的建筑需求,多采用大跨度空间钢结构。然而,大跨度空间钢屋架涉及大量钢构件,造成施工管理困难。文章通过分析建筑信息模型(BuildingInformation Modeling, BIM)和射频识别(Radio Frequency Identification,RFID)技术的研究现状,基于两者具有数据记录效率高,交流及时和信息共享便捷等优势提出了大跨度空间钢屋架高精度定位方法。以某军民合用机场为例,验证了该方法能够精确定位钢构件位置,保证钢屋架的安装以及吊装精度。该方法丰富了大跨度钢屋架高精度定位方面的研究,为日后军民合用机场航站楼屋架工程的施工管理提供了参考。
文摘SiC porous ceramics were prepared at 1 400 ℃ for4 h with crystalline silicon cutting waste and activated carbon as main starting materials and NH4HCO3 as the pore-forming agent. Effects of NH4HCO3 additions( 0,20%,30%,40%,by mass) on the phase composition,microstructure,sintering properties,cold compressive strength and thermal shock resistance of as-prepared Si C porous ceramics were investigated. The results show that:( 1) addition of NH4HCO3 remarkably influences the apparent porosity and cold compressive strength of specimens. The apparent porosity achieves its maximum value( 63. 40%) when 40% NH4HCO3 is added,while the minimum cold compressive strength is 4. 77 MPa;( 2) the specimen with 40% NH4HCO3 has the best thermal shock resistance. The thermal cycling times between1 000 ℃ to room temperature reach 62;( 3) the addition of NH4HCO3 does not remarkably affect the phase composition of the specimens;( 4) the specimens include a large number of SiC particles and a small amount of SiC whiskers.
文摘In order to fabricate porous ceramics with good properties and proper production cost,SiC-Al2 O3 porous ceramics were prepared at 1 450 ℃ for 2 h from the powders of commercial silicon carbide and white fused corundum via a polymeric replication method. Effects of the mass ratio of SiC powder to white fused corundum powder（ 1 ∶ 3,1 ∶ 1 and 3 ∶ 1） on the appearance,phase composition,sintering properties and thermal shock resistance were investigated. The research results indicate that the as-prepared Si C-Al2 O3 porous ceramics have uniform pores,and their linear shrinkage ratio,apparent porosity and bulk density reach 4. 70%,67. 17%and 0. 83 g·cm-3,respectively. The thermal shock cycles from 1 400 ℃ to room temperature reach 23 including 15 cycles in air cooling condition and then 8 cycles in water cooling condition. Their main phases areα-Al2 O3 and Al6 Si2 O13 as well as a small amount of SiC and free SiO2. The as-prepared porous ceramic with the ratio of m（ SiC） ∶ m（ Al2 O3） = 1∶ 1 possesses prior comprehensive properties.
