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PISA2006天津试测的实施及其启示 被引量:2
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作者 孔祥娟 田园 李勇 《考试研究》 2007年第4期84-91,共8页
PISA是当前最知名的国际教育成效评价项目之一。本文结合2006年PISA天津测试的实践经验,从PISA测试的背景、实施流程、保密措施等方面介绍PISA的实施理念与操作规范,并在此基础上从测验实施角度,总结提出值得我国教育考试机构借鉴的有... PISA是当前最知名的国际教育成效评价项目之一。本文结合2006年PISA天津测试的实践经验,从PISA测试的背景、实施流程、保密措施等方面介绍PISA的实施理念与操作规范,并在此基础上从测验实施角度,总结提出值得我国教育考试机构借鉴的有关问题。 展开更多
关键词 PISA 测验实施 启示
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平原河道桥梁建设对附近水文站的影响分析 被引量:1
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作者 陈静 《中国水运(下半月)》 2012年第1期175-176,共2页
平原河道坡降小,水流较缓,如果在其上建桥,桥墩又必须设在河道内,由于桥墩的阻水作用,桥上游侧可能会产生壅水,下游侧则可能产生跌水,引起桥周围一定范围内水位、流速、流量及整个流场的改变。如果桥上、下游附近有水文站,则可能改变水... 平原河道坡降小,水流较缓,如果在其上建桥,桥墩又必须设在河道内,由于桥墩的阻水作用,桥上游侧可能会产生壅水,下游侧则可能产生跌水,引起桥周围一定范围内水位、流速、流量及整个流场的改变。如果桥上、下游附近有水文站,则可能改变水文站测量数据系列的一致性及已建立的水位、流量关系,降低测量数据的精度,甚至影响水文站正常测验工作的实施。因此,必须分析建桥对水文站的影响程度,判断在该河道位置建桥的可行性。 展开更多
关键词 平原河道 桥梁建设 阻水 水文站 测验数据 测验实施
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A new diamond bit for extra-hard, compact and nonabrasive rock formation 被引量:4
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作者 王佳亮 张绍和 《Journal of Central South University》 SCIE EI CAS CSCD 2015年第4期1456-1462,共7页
A new impregnated diamond bit was designed to solve the slipping problem when impregnated diamond bit was used for extra-hard, compact, and nonabrasive rock formation. Adding Si C grits into matrix, Si C grits can eas... A new impregnated diamond bit was designed to solve the slipping problem when impregnated diamond bit was used for extra-hard, compact, and nonabrasive rock formation. Adding Si C grits into matrix, Si C grits can easily be exfoliated from the surface of the matrix due to weak holding-force with matrix, which made the surface non-smooth. Three Ф36/24 mm laboratorial bits were manufactured to conduct a laboratory drilling test on zirconiacorundum refractory brick. The laboratory drilling test indicates that the abrasive resistance of the bit work layer is proportional to the Si C concentation. The higher the concentration, the weaker the abrasive resistance of matrix. The new impregnated diamond bit was applied to a mining area drilling construction in Jiangxi province, China. Field drilling application indicates that the ROP(rate of penetration) of the new bit is approximately two to three times that of the common bits. Compared with the common bits, the surface of the new bit has typical abrasive wear characteristics,and the metabolic rate of the diamond can be well matched to the wear rate of the matrix. 展开更多
关键词 SiC grits impregnated diamond bit non-smooth surface diamond rock fragmentation mechanism
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