Purpose-Rail corrugation is still one of the unsolved challenges in the railway industry,and the abnormal vibration and high-frequency noise caused by it constitute serious adverse effects on the operating environment...Purpose-Rail corrugation is still one of the unsolved challenges in the railway industry,and the abnormal vibration and high-frequency noise caused by it constitute serious adverse effects on the operating environment.How to control corrugation has been an important research theme,and understanding corrugation evolution features is the necessary prerequisite.This study aims to investigate the specific evolution characteristics of corrugation from the contact stick-slip perspective.Design/methodology/approach-The formation and development processes of corrugation are analyzed by using a self-designed scale-down test device.Specifically,the contact stick-slip characteristics under different creepage conditions are analyzed and the formation mechanism of corrugation is summarized.On the basis of corrugation formation,the trend of corrugation development is further emphasized to completely describe the whole process of corrugation evolution.Findings-The results show that,under the determined vertical load condition,the contact interface appears the creep force-creepage negative slope phenomenon in the transverse direction.The cause of short-pitch corrugation on the rail wheel surface under the smaller angles of attack may be related to the inherent vibration frequency of the test device,and the cause of corrugation on the rail wheel surface under the larger angles of attack is mainly related to the stick-slip vibration induced by contact creep saturation.Originality/value-This research explores the evolution characteristics of corrugation by adopting a selfdesigned scale-down test device,and elucidates the mechanism of corrugation in detail.展开更多
Bioprocess scale-down simulators are used to investigate the phenomena occurring in industrial scale cultivations. The aim is to simulate the large-scale conditions, characterized by long mixing times introducing loca...Bioprocess scale-down simulators are used to investigate the phenomena occurring in industrial scale cultivations. The aim is to simulate the large-scale conditions, characterized by long mixing times introducing local gradients into the bioreactor, in laboratory scale bioreactor. We have expanded the current physiological knowledge about the consequences of such cultivation conditions from well-known mixed-acid fermentation to amino acid metabolism. Several interesting deviations were observed for amino acids derived from pyruvate when a STR-PFR scale-down simulator and a regular STR fed-batch cultivation were compared. In this article we show that the cultivation of Escherichia coli K-12 substrain W3110 in a scale-down two-compartment bioreactor has consequences on the free amino acid pools. Repeated occurrence of high glucose zones affects the biosynthesis of amino acids derived from pyruvate. This is interesting since the pyruvate based amino acids are precursors of the branched chain amino acid pathway, which is further disturbed by an unbalanced regulation caused by a frameshift mutation in the ilvG gene of E. coli K-12 strains. As a consequence the formation of non-typical amino acid norvaline was detected in the two compartment bioreactor cultivation.展开更多
脱丁烷塔聚合物结垢问题是制约乙烯装置长周期运行的主要因素之一。目前新建装置通过降低操作压力在防止脱丁烷塔聚合物结垢方面取得了显著效果。以脱丁烷塔为例,对降压过程的可行性、经济性以及风险点进行分析和总结,利用化工流程模拟...脱丁烷塔聚合物结垢问题是制约乙烯装置长周期运行的主要因素之一。目前新建装置通过降低操作压力在防止脱丁烷塔聚合物结垢方面取得了显著效果。以脱丁烷塔为例,对降压过程的可行性、经济性以及风险点进行分析和总结,利用化工流程模拟软件Aspen Plus对降压后各项工艺参数进行模拟优化,将优化结果应用于实际生产过程。结果表明,脱丁烷塔的降压极限为350 kPa,降压后全塔温度降低约4℃,塔釜粗裂解汽油中的C_(4)摩尔分数降低0.32百分点,节省低压蒸汽1.3 t h,装置能耗和C_(4)产品损失降低,循环水侧压降、循环水在换热器内的流速和对数传热温差均在合理范围之内。展开更多
在第2代加拿大地球系统模型(the second generation Canadian earth system model,CanESM2)中的3种典型浓度路径(representative concentration pathways,RCPs)情景(RCP2.6、RCP4.5和RCP8.5)下,基于统计降尺度模型(statistical down sca...在第2代加拿大地球系统模型(the second generation Canadian earth system model,CanESM2)中的3种典型浓度路径(representative concentration pathways,RCPs)情景(RCP2.6、RCP4.5和RCP8.5)下,基于统计降尺度模型(statistical down scaling model,SDSM)研究兰江流域未来年份温度和降水量的变化趋势。结果表明:1)SDSM在兰江流域具有较好的适用性,各站点最高温度、最低温度、降水量的解释方差分别为70.62%~79.74%、69.61%~78.76%、28.56%~41.45%;2)3种RCPs情景下温度均呈上升趋势,且上升幅度随辐射强迫度上升而同步增大,至21世纪末,RCP2.6、RCP4.5、RCP8.5情景下的最高温度分别较基准期上升0.06℃、1.22℃、2.76℃,最低温度分别较基准期上升0.35℃、1.15℃、3.01℃;3)RCP2.6情景下的降水量总体呈下降趋势,至2080—2100年下降0.98%,RCP4.5情景下的降水量呈先上升后下降趋势,至2050—2079年达到峰值,较基准期上升12.03%,RCP8.5情景下的降水量呈先下降后快速上升趋势,至2080—2100年上升38.08%。研究结果可为兰江流域内水资源管理、生态文明建设及社会经济可持续发展提供依据和理论支持。展开更多
基金funded by the Science and Technology Research Project of Universities in Hebei Province(No.QN2025314)Youth Specialization Fund for State Key Laboratory(No.50110010766)Shanghai Key Laboratory of Rail Infrastructure Durability and System Safety(No.R202405).
文摘Purpose-Rail corrugation is still one of the unsolved challenges in the railway industry,and the abnormal vibration and high-frequency noise caused by it constitute serious adverse effects on the operating environment.How to control corrugation has been an important research theme,and understanding corrugation evolution features is the necessary prerequisite.This study aims to investigate the specific evolution characteristics of corrugation from the contact stick-slip perspective.Design/methodology/approach-The formation and development processes of corrugation are analyzed by using a self-designed scale-down test device.Specifically,the contact stick-slip characteristics under different creepage conditions are analyzed and the formation mechanism of corrugation is summarized.On the basis of corrugation formation,the trend of corrugation development is further emphasized to completely describe the whole process of corrugation evolution.Findings-The results show that,under the determined vertical load condition,the contact interface appears the creep force-creepage negative slope phenomenon in the transverse direction.The cause of short-pitch corrugation on the rail wheel surface under the smaller angles of attack may be related to the inherent vibration frequency of the test device,and the cause of corrugation on the rail wheel surface under the larger angles of attack is mainly related to the stick-slip vibration induced by contact creep saturation.Originality/value-This research explores the evolution characteristics of corrugation by adopting a selfdesigned scale-down test device,and elucidates the mechanism of corrugation in detail.
文摘Bioprocess scale-down simulators are used to investigate the phenomena occurring in industrial scale cultivations. The aim is to simulate the large-scale conditions, characterized by long mixing times introducing local gradients into the bioreactor, in laboratory scale bioreactor. We have expanded the current physiological knowledge about the consequences of such cultivation conditions from well-known mixed-acid fermentation to amino acid metabolism. Several interesting deviations were observed for amino acids derived from pyruvate when a STR-PFR scale-down simulator and a regular STR fed-batch cultivation were compared. In this article we show that the cultivation of Escherichia coli K-12 substrain W3110 in a scale-down two-compartment bioreactor has consequences on the free amino acid pools. Repeated occurrence of high glucose zones affects the biosynthesis of amino acids derived from pyruvate. This is interesting since the pyruvate based amino acids are precursors of the branched chain amino acid pathway, which is further disturbed by an unbalanced regulation caused by a frameshift mutation in the ilvG gene of E. coli K-12 strains. As a consequence the formation of non-typical amino acid norvaline was detected in the two compartment bioreactor cultivation.
文摘脱丁烷塔聚合物结垢问题是制约乙烯装置长周期运行的主要因素之一。目前新建装置通过降低操作压力在防止脱丁烷塔聚合物结垢方面取得了显著效果。以脱丁烷塔为例,对降压过程的可行性、经济性以及风险点进行分析和总结,利用化工流程模拟软件Aspen Plus对降压后各项工艺参数进行模拟优化,将优化结果应用于实际生产过程。结果表明,脱丁烷塔的降压极限为350 kPa,降压后全塔温度降低约4℃,塔釜粗裂解汽油中的C_(4)摩尔分数降低0.32百分点,节省低压蒸汽1.3 t h,装置能耗和C_(4)产品损失降低,循环水侧压降、循环水在换热器内的流速和对数传热温差均在合理范围之内。
文摘在第2代加拿大地球系统模型(the second generation Canadian earth system model,CanESM2)中的3种典型浓度路径(representative concentration pathways,RCPs)情景(RCP2.6、RCP4.5和RCP8.5)下,基于统计降尺度模型(statistical down scaling model,SDSM)研究兰江流域未来年份温度和降水量的变化趋势。结果表明:1)SDSM在兰江流域具有较好的适用性,各站点最高温度、最低温度、降水量的解释方差分别为70.62%~79.74%、69.61%~78.76%、28.56%~41.45%;2)3种RCPs情景下温度均呈上升趋势,且上升幅度随辐射强迫度上升而同步增大,至21世纪末,RCP2.6、RCP4.5、RCP8.5情景下的最高温度分别较基准期上升0.06℃、1.22℃、2.76℃,最低温度分别较基准期上升0.35℃、1.15℃、3.01℃;3)RCP2.6情景下的降水量总体呈下降趋势,至2080—2100年下降0.98%,RCP4.5情景下的降水量呈先上升后下降趋势,至2050—2079年达到峰值,较基准期上升12.03%,RCP8.5情景下的降水量呈先下降后快速上升趋势,至2080—2100年上升38.08%。研究结果可为兰江流域内水资源管理、生态文明建设及社会经济可持续发展提供依据和理论支持。
