由于动车组车轮受加工装配及工况载荷等不确定因素的影响,车轮退化过程复杂,存在显著的个体差异及多个性能退化特征量,且多个退化特征量间相互耦合,仅考虑单个性能特征量难以全面反映其退化过程。因此,以轮缘和轮径作为车轮退化特征量,...由于动车组车轮受加工装配及工况载荷等不确定因素的影响,车轮退化过程复杂,存在显著的个体差异及多个性能退化特征量,且多个退化特征量间相互耦合,仅考虑单个性能特征量难以全面反映其退化过程。因此,以轮缘和轮径作为车轮退化特征量,通过随机化尺度参数表征车轮个体差异,采用Gamma过程和Copula函数建立二元相关退化模型,并根据赤池信息准则(Akaike Information Criterion, AIC)筛选Copula函数,得到可靠度解析式。基于某型动车组车轮实测磨耗数据,对车轮进行可靠性分析,同时通过车辆动力学模型进行仿真验证。结果显示:考虑二元相关时的可靠性结果比仅考虑一元退化更贴近车辆实际运行情况;根据动力学仿真结果体现了考虑个体差异的必要性,表明所提模型能够更准确地表征车轮退化过程,可为可靠性分析以及维修决策优化提供理论支撑。展开更多
为探究城市轨道交通(简称:城轨)车辆轮对的轮径值退化规律,有效评估轮对可靠性,提出基于Wiener过程的城轨车辆轮对可靠性评估方法。选取轮径值作为性能退化指标,建立基于Wiener过程的城轨车辆轮对退化模型。通过计算轮对剩余寿命,选择...为探究城市轨道交通(简称:城轨)车辆轮对的轮径值退化规律,有效评估轮对可靠性,提出基于Wiener过程的城轨车辆轮对可靠性评估方法。选取轮径值作为性能退化指标,建立基于Wiener过程的城轨车辆轮对退化模型。通过计算轮对剩余寿命,选择精度最高的退化模型进行可靠性评估。针对退化模型参数后验分布计算公式较为复杂的问题,采用马尔可夫链蒙特卡洛(MCMC,Markov Chain Monte Carlo)方法进行求解。基于广州地铁8号线列车轮对实测数据进行实例验证,结果表明,城轨车辆应保证轮对可靠度不低于0.9,且在镟修后运行至27.51万km时,应检查轮对退化情况,以保障车辆的运行安全。展开更多
Nitric oxide （NO） removal and sulfur dioxide （SO2） removal by sodium persulfate （Na2S2O8） were studied in a Bubble Column Reactor. The proposed reaction pathways of NO and SO2 removal are discussed. The effects ...Nitric oxide （NO） removal and sulfur dioxide （SO2） removal by sodium persulfate （Na2S2O8） were studied in a Bubble Column Reactor. The proposed reaction pathways of NO and SO2 removal are discussed. The effects of temperatures （35-90℃）, Na25208 （0.05-0.5 mol·L-1）, FeSO4 （0.5-5.0 m mol·L-1） and H2O2 （0.25 mol·L-1） on NO and SO2 removal were investigated. The results indicated that increased persulfate concentration led to increase in NO removal at various temperatures. SO2 was almost completely removed in the temperature range of 55-85 ℃. Fe2 ＋ accelerated persulfate activation and enhanced NO removal efficiency. At 0.2 mol· L- 1 Na2S2O8 and 0.5-1.0 mmol· L-1Fe2 ＋, NO removal of 93.5%-99% was obtained at 75-90 ℃, SO2 removal was higher than 99% at all temperatures. The addition of 0.25 mol. L i H202 into 0.2 mol·L-1· Na2S2O8 solution promoted NO removal efficiency apparently until utterly decomposition of H2O2, the SO2 removal was as high as 98.4% separately at 35 ℃ and 80 ℃.展开更多
As the economy of China develops, an increasing number of key traffic projects have been undertaken in the west of China, where there are high, steep rock slopes. The collapse of dangerous rock masses, especially foll...As the economy of China develops, an increasing number of key traffic projects have been undertaken in the west of China, where there are high, steep rock slopes. The collapse of dangerous rock masses, especially following a strong earthquake, is one of common geological disasters known in rock slope engineering. Therefore, it is important to study the collapse mechanism of dangerous rock masses induced by an earthquake and the analysis approach of its stability. This study provides a simple and convenient method to determine the collapse mechanisms of two types of dangerous rock masses （i.e. cantilever and upright） associated with the definition and calculation of the safety factor, which is based on the flexure theory of a constant-section beam by combining with the maximum tensile-stress criterion to depict the process of crack propagation caused by seismic waves. The calculation results show that there are critical crack depths in each form of the dangerous rock masses. Once the accumulated depth of the crack growth during an earthquake exceeds the critical depth, the collapse will occur. It is also demonstrated that the crack extension amount of each step is not a constant value, and is closely associated with the current accumulated crack depth. The greater the cumulative crack depth, the more easily the crack propagates. Finally, the validity and applicability of the proposed method are verified through two actual engineering examples.展开更多
文摘由于动车组车轮受加工装配及工况载荷等不确定因素的影响,车轮退化过程复杂,存在显著的个体差异及多个性能退化特征量,且多个退化特征量间相互耦合,仅考虑单个性能特征量难以全面反映其退化过程。因此,以轮缘和轮径作为车轮退化特征量,通过随机化尺度参数表征车轮个体差异,采用Gamma过程和Copula函数建立二元相关退化模型,并根据赤池信息准则(Akaike Information Criterion, AIC)筛选Copula函数,得到可靠度解析式。基于某型动车组车轮实测磨耗数据,对车轮进行可靠性分析,同时通过车辆动力学模型进行仿真验证。结果显示:考虑二元相关时的可靠性结果比仅考虑一元退化更贴近车辆实际运行情况;根据动力学仿真结果体现了考虑个体差异的必要性,表明所提模型能够更准确地表征车轮退化过程,可为可靠性分析以及维修决策优化提供理论支撑。
文摘为探究城市轨道交通(简称:城轨)车辆轮对的轮径值退化规律,有效评估轮对可靠性,提出基于Wiener过程的城轨车辆轮对可靠性评估方法。选取轮径值作为性能退化指标,建立基于Wiener过程的城轨车辆轮对退化模型。通过计算轮对剩余寿命,选择精度最高的退化模型进行可靠性评估。针对退化模型参数后验分布计算公式较为复杂的问题,采用马尔可夫链蒙特卡洛(MCMC,Markov Chain Monte Carlo)方法进行求解。基于广州地铁8号线列车轮对实测数据进行实例验证,结果表明,城轨车辆应保证轮对可靠度不低于0.9,且在镟修后运行至27.51万km时,应检查轮对退化情况,以保障车辆的运行安全。
基金Supported by the National Natural Science Foundation of China(21536009)Science and Technology Plan Projects of Shaanxi Province(2017ZDCXL-GY-10-03)
文摘Nitric oxide （NO） removal and sulfur dioxide （SO2） removal by sodium persulfate （Na2S2O8） were studied in a Bubble Column Reactor. The proposed reaction pathways of NO and SO2 removal are discussed. The effects of temperatures （35-90℃）, Na25208 （0.05-0.5 mol·L-1）, FeSO4 （0.5-5.0 m mol·L-1） and H2O2 （0.25 mol·L-1） on NO and SO2 removal were investigated. The results indicated that increased persulfate concentration led to increase in NO removal at various temperatures. SO2 was almost completely removed in the temperature range of 55-85 ℃. Fe2 ＋ accelerated persulfate activation and enhanced NO removal efficiency. At 0.2 mol· L- 1 Na2S2O8 and 0.5-1.0 mmol· L-1Fe2 ＋, NO removal of 93.5%-99% was obtained at 75-90 ℃, SO2 removal was higher than 99% at all temperatures. The addition of 0.25 mol. L i H202 into 0.2 mol·L-1· Na2S2O8 solution promoted NO removal efficiency apparently until utterly decomposition of H2O2, the SO2 removal was as high as 98.4% separately at 35 ℃ and 80 ℃.
基金Scientific Research Fund of the Hebei Education Department under Grant No.QN2015166
文摘As the economy of China develops, an increasing number of key traffic projects have been undertaken in the west of China, where there are high, steep rock slopes. The collapse of dangerous rock masses, especially following a strong earthquake, is one of common geological disasters known in rock slope engineering. Therefore, it is important to study the collapse mechanism of dangerous rock masses induced by an earthquake and the analysis approach of its stability. This study provides a simple and convenient method to determine the collapse mechanisms of two types of dangerous rock masses （i.e. cantilever and upright） associated with the definition and calculation of the safety factor, which is based on the flexure theory of a constant-section beam by combining with the maximum tensile-stress criterion to depict the process of crack propagation caused by seismic waves. The calculation results show that there are critical crack depths in each form of the dangerous rock masses. Once the accumulated depth of the crack growth during an earthquake exceeds the critical depth, the collapse will occur. It is also demonstrated that the crack extension amount of each step is not a constant value, and is closely associated with the current accumulated crack depth. The greater the cumulative crack depth, the more easily the crack propagates. Finally, the validity and applicability of the proposed method are verified through two actual engineering examples.
