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管壳式换热器管束振动与防范 总被引:3,自引:0,他引:3
吴声鸧 《振动、测试与诊断》1992,12(4):28-33
在化工厂中,管壳式换热器使用十分普遍,换热器管束振动是经常发生的。本文根据有关文献以及从事换热器设计方面的经验,着重从理论上探讨了在换热器设计中做到防范管束振动。文中根据“振动是由壳程流体所引起”这一理论提出防范管束振动主要受控于两个比值(旋涡分离频率f_s和紊流抖振频率f_(tb)分别与管子固有频率f_n的比值K_s与K_(tb))范围的观点。希望这一观点对于从事换热器设计的工程技术人员有所裨益。 相似文献
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For an AB/BC countercurrent extraction separation using organic feed, the conditions to have minimum amount of ex- tracting solvent (Smin) and minimum amount of scrubbing agent solution (Wmin) were discussed, and the formulae of both Sroin and Wmin were deduced. It was shown that only when the ratio of flowrate of central component B leaving aqueous outlet to that leaving organic outlet took a certain optimal value, the AB/BC separation could have Smin as well as Wmin, and this optimal ratio was decided by the separation factors between the three components but independent of feed composition. Smin was only relative to the separation factor of A/C pair but regardless of the separation factors of other pairs as well as feed composition, whereas Wmin was determined by the separation factors between the components together with feed composition. Meanwhile it was also found that the organic stream out of feed stage was same composition as the initial organic feed when the separation system was given by the two minimum amounts and its steady state was achieved. Finally the results above were used to design a LuYb/YbTm separation case and the stage-wise compositions of each component in both the organic and the aqueous phase at steady state were given by computer simulation. 相似文献
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反射式液晶显示器因不需要背光源,有功耗小等优点.对于反射式彩色液晶显示器来说,其主要的问题是其反射的亮度低.光学干涉高反射膜有良好的反射特性.我们提出了采用光学高反射膜作彩色反射膜来制作彩色液晶显示器,并用计算机模拟的办法对其进行了研究.对膜的材料及视角优化也进行了讨论. 相似文献
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一场全民的“物理隔离”,也是一次突如其来的“心理疏离”,带来更加颗粒度的数字深化,也让实体行业更加发愁“找人”。变量其实自有脉络,突然提速或倒逼,是检阅也是警醒。未雨绸缪,该做的还是要晴天补瓦。市场对许多企业在这次疫情中展现出的主动创新的接受和包容度让人更确信——需求一直都在,只是要不断创新自己的场景。 相似文献
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Computer simulation of the preparation process loading rare earth(RE)directly from acidic extractant and RE chloride was established using MATLAB software.The mechanism of the extraction reaction was assumed,and then an experiment was conducted to confirm the mechanism and the apparent equilibrium constant of the reaction was determined as well.Owing to the involvement of H+ ion in the reaction between acidic extractant and RE chloride,the computer simulation of the process was more complicated than that of the extraction only between different rare earths.In the present work,MATLAB software was therefore introduced to handle the resolution of the complicated processing equation,and the simulation was performed by varying some key parameters including feed composition and phase ratio,etc.Consequently this work presented a simple method to simulate the H+ ion involved countercurrent extraction process of rare earths and also provided the practical references for the relative process designing. 相似文献
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灭蝇胺及其代谢物三聚氰胺在大棚黄瓜上的残留降解动态 总被引:4,自引:0,他引:4
[方法]采用亲水作用色谱-串联质谱法研究了灭蝇胺及其代谢物三聚氰胺在大棚黄瓜上的残留降解动态,为大棚黄瓜中灭蝇胺的安全使用提供科学依据。[结果]50%灭蝇胺SP以田间推荐用量150 g a.i./hm2(对水600 kg/hm2)喷施1次后,灭蝇胺在大棚黄瓜上的残留量于药后5 d达到最大值,为0.230 mg/kg。以0.230 mg/kg为原始沉积量,灭蝇胺在大棚黄瓜上的残留降解动态符合一级动力学方程,半衰期为14.3 d。处理后28 d内,黄瓜样品中三聚氰胺的残留量一直在增加,但其残留量均低于灭蝇胺的残留量。在最后1次采样时(药后28 d),三聚氰胺和灭蝇胺的残留量趋于相同。[结论]以0.2 mg/kg为灭蝇胺在黄瓜上的最高残留限量,建议灭蝇胺在大棚黄瓜上的安全间隔期为7 d。 相似文献
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农药毒死蜱和甲萘威对斑马鱼的联合毒性效应 总被引:2,自引:0,他引:2
[目的]探讨毒死蜱和甲萘威对斑马鱼的联合毒性效应以及斑马鱼体内对2种农药的敏感指标。[方法]采用半静态暴露法,测定2种农药对斑马鱼的单一及联合毒性;采用生化法测定2种农药单剂及复配剂对斑马鱼体内5种酶:ACh E、SOD、GST、CAT、AKP活性的毒性效应。[结果]急性毒性试验测得2种农药单剂对斑马鱼的毒性分别为高毒和低毒;2种农药复配剂的联合毒性试验结果显示在24、48、72、96 h相加指数均大于0;生化测定显示2种农药的单剂及复配剂对ACh E活性均表现出显著的抑制作用;对其他4种酶活性的影响无明显规律。[结论]2种农药对斑马鱼的联合毒性为协同作用;斑马鱼体内ACh E可作为评价2种农药污染水体环境的生物标志物。 相似文献
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本文提出了一种新型彩色反射式液晶显示器的设计方案。本文案采用微棱锥膜结构对环境光实行准直,用光学干涉膜实现高反射率。计算和分析表明,这种设计结构具有高反射率,较宽视角和良好的色度学性质。本文给出了这种结构的模拟计算及分析结果。 相似文献