排序方式： 共有5条查询结果，搜索用时 15 毫秒
1
3.
介绍房屋建筑工程存在的质量通病,针对存在的质量通病,在现场施工中采用了8种控制措施,以确保建筑工程的施工质量. 相似文献
4.
马金昌 《语文学刊:高等教育版》2012,(24)
作文综合地体现了一个人的思想、情操、个性、智慧等文化素养,展现了学生的生活积累、人生体验、语言表达和个性创造等方面的能力,是小考语文的半壁江山,教师和学生都投入了很多精力,但农村小学生的写作水平却不容乐观.本文针对农村小学生写作素养的培养提高提出了切实可行的途径和方法,希望能对农村小学生写作水平的提高有所帮助. 相似文献
5.
RH和RH-KTB精炼过程中钢液流动和混合特性的研究 总被引：7，自引：0，他引：7
The flow and mixing characteristics of molten steel during the vacuum circulation refining,including RH(Ruhrstahl-Heraeus) and RH-KTB(Ruhrastahl-Heraeus-Kawasaki top blowing) processes,were investigated on a 1/5 linear scale water model of a 90t multifunction RH degasser,The circulation rate was directly and more accurately determined,using a new method by which the more reliable results can be obtained.The fluid flow pattern and flow field in the ladle were demonstrated,observed and analyzed.The mixing time of liquid in the ladle was measured using electrical conductivity method.The residence time distribution in the RH model was obtained by tracer response technique.The influence of the main technological and geometric factors,including the gas top blowing*(KTB) operation,was examined.The results indicated that the circulation rate of molten steel in the RH degasser can be fairly precisely calculated by the formula:Q1p=0.0333Qg^0.26Du^0.69Dd^0.80(t/min),where Qg-the lifting gas flow rate(NL/min);Du and Dd-the inner diameters of the up and down-snorkels(cm),respectively.The maximum value of circulation rate of molten steel in the case of the 30cm diameters either of the up-and down-snorkels for the RH degasser(the “Saturated” rate) is approximately 31 t/min.the corresponding gas flow rate is 900NL/min.Blowing gas into the vacuum chamber through the top lance like KTB operation does not markedly influence the circulatory flow and mixing charateristics of the RH process under the conditions of the present work.There exist a major loop and a large number of small vortices and eddies in the ladle during the RH refining process.A liquidliquid two-phase flow is formed between the descnding stream from the down-snorkel and the liquid around the stream.All of these flow situation and pattern will strongly influence and determine the mixing and mass transfer in the ladle during the refining.The correlation between the mixing time and the stirring energy density is τmε^0.50 for the RH degasser.The mixing time rapidly shortens with an increase in the lifting gas flowrate.At a same gas flow rate,the mixing times with the up-and down-snorkel diameters either of 6 and 7cm are essentially same.The 30cm diameters either of the up-and down-snorkels for the RH degasser would be reasonalble.The concentration-time curve showed that three circulation cycles are at least needed for complete mixing of the liquid steel in the RH degasser. 相似文献
1