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此文介绍了超声振动在金属塑性加工领域的应用,讨论了超声塑性加工的理论机制和工艺特点,论述了超声场中的材料性能和粘塑性本构关系。 相似文献
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内凸筋口琴管,是汽车空调的一种新型散热管.具有散热效果好、单位面积小、重.量轻等优点.此文介绍了连续挤压内凸筋口琴管模具的设计方法及其模具芯头的冷挤压加工. 相似文献
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Although atrazine has been banned in the European Union since 2007 it still persists in soil from where it can enter the food chain. Milk-producing animals accumulate atrazine from contaminated feed and water and since large quantities of milk and milk products are consumed its quality should be constantly monitored. The objective of this investigation was to develop a simple tube ELISA procedure suitable for use in non-specialised laboratories and in the field. A polyclonal antibody raised in sheep and the hapten-gelatine conjugate was immobilised onto polystyrene tubes. This enables the colour produced to be read on a basic spectrophotometer. Milk samples were collected from three farms in different regions of Poland and diluted before immunoassay was performed. Samples were extracted with hexane-acetone for HPLC analysis. The amount of fat in the milk samples interferes with the dose response so it essential that the standards are prepared in the same samples matrix. A good correlation between 1% and 2% was found between the two methods in the analysis of real samples. However the ELISA procedure was more sensitive that the HPLC method since atrazine was detected in some samples by the ELISA but was not confirmed by the HPLC method. The study demonstrated that the simple antigen-coated tube assay provides a cost effective and valuable screening test that can be easily modified for direct use as a screening tool in the field. 相似文献
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Shell-tube type heat exchangers are often used to exchange heat between a high-pressure fluid and a low-pressure fluid, and the pressure difference between the two fluids could be significantly high. If the difference in the design pressure between the low-pressure (LP) and high-pressure sides is greater than that covered by American Petroleum Institute (API 520 and 521) 10/13th rule, dynamic analysis is required to ascertain that the maximum surge pressure that could be reached does not compromise the integrity of the LP side of the exchanger. API guidelines also notes that attention should also be given not only to the shell-side of the heat exchanger under evaluation, but also to the “upstream and downstream systems” This paper offers further insight into the importance of including the surrounding piping systems around the subject heat-exchanger where a tube-rupture scenario is considered, and also directs attention to the importance of correctly specifying the appropriate boundary conditions (B.C.) at the far ends of both the upstream and downstream piping systems. It demonstrates the effects of specifying different B.C. on the maximum pressure surge via a case study of a hot separator vapour condenser in a bitumen hydrotreating unit, where the process fluid on the tube-side is a vapour–liquid mixture at 9660 kPa(g). The vapour mass fraction of the process fluid is approximately 0.5, and is mostly hydrogen. The fluid on the LP side is cooling water connected to the plant supply and return cooling systems as well as another adjacent low pressure condenser. The design pressure for the cooling water piping system and the adjacent condenser is 1380 kPa(g). 相似文献
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针对某进口亚临界锅炉三级过热器T91炉管失效事件,通过对其进行硬度、金相组织和SEM扫描电镜分析找出导致爆管的原因,并根据高温氧化皮厚度对其进行蠕变剩余寿命评估,结果表明该段T91管材爆管类型为典型长期过热爆管,炉管长期处于较高温度运行导致组织老化严重,力学性能下降,引起材料蠕变损伤,导致长期过热爆管,经计算其蠕变剩余寿命已达到寿命极限。本文对该锅炉防止类似事故具有重要作用,并对国内其他同在二十世纪90年代开始服役的T9彳炉管具有重大的参考价值和借鉴意义。 相似文献