针对柴油发动机推进特性下的中高负荷工况出现的NO_(x)排放峰值现象,以及燃油价格日益上涨带来降低油耗率的迫切需求,本研究通过调节柴油/甲醇组合燃烧(diesel/methanol compound combustion,DMCC)发动机多种控制参数,在保证动力性前提...针对柴油发动机推进特性下的中高负荷工况出现的NO_(x)排放峰值现象,以及燃油价格日益上涨带来降低油耗率的迫切需求,本研究通过调节柴油/甲醇组合燃烧(diesel/methanol compound combustion,DMCC)发动机多种控制参数,在保证动力性前提下,实现NO_(x)排放和有效燃油消耗率(brake specific fuel consumption,BSFC)的同步下降。为避免大规模试验带来的成本增加,首先基于高斯过程回归建立DMCC发动机排放的NO_(x)体积分数、BSFC和指示功率预测模型;然后将所建模型与第二代非支配排序遗传算法(non-dominated sorting genetic algorithm-Ⅱ,NSGA-Ⅱ)结合,对NO_(x)的体积分数和BSFC进行优化,并将Pareto前沿解集代入逼近理想解排序法(the technique for order preference by similarity to an ideal solution,TOPSIS)寻找最优控制参数组合;最后将最优控制参数组合标定至电子控制单元,与原机数据进行对比分析。结果表明:基于高斯过程回归建立的预测模型的拟合优度大于0.95,均方根误差小于1,具有良好的一致性和准确性;使用NSGA-Ⅱ获取的最佳控制参数与优化前(原机工况)的相比,NO_(x)的排放量下降74.5%,仅为3.47 g/(kW·h),BSFC平均下降6.7%,仅为203.5 g/(kW·h)。展开更多
为解决当前山区高速公路选线过程中存在的影响因素多、参建各方侧重点不同、无法定量描述比选方案等难题,在充分调研中外高速公路及铁路选线影响因素的基础上,系统分析和总结中国山区高速公路选线影响因素,并将其概括为经济、技术、安...为解决当前山区高速公路选线过程中存在的影响因素多、参建各方侧重点不同、无法定量描述比选方案等难题,在充分调研中外高速公路及铁路选线影响因素的基础上,系统分析和总结中国山区高速公路选线影响因素,并将其概括为经济、技术、安全和环境4个方面,共计16个具体影响因子;依托西和—宕昌高速公路工程,组织项目区域所在地方政府、行业主管部门、业主、设计、施工、监理、第三方检测单位及科研院所相关专家共计164人组成专家组,采用层次分析法(analytic hierarchy process,AHP)对16个选线影响因子重要度进行评价。结果表明:环境指标中3个影响因素的综合权重平均分值较高,反映了工程建设领域环保意识的进一步加强。为进一步建立方案比选的优选模型,以依托项目灯塔—蒿林村段路线的方案比选为例,在AHP的基础上运用逼近理想解的排序法(technique for order preference by similarity to idea solution,TOPSIS)对比选方案进行优选,4种比选方案的优越度分别为2.84、0.56、0.72、2.15,即方案1最优。研究成果在全面分析山区高速公路选线影响因素的前提下,采用AHP-TOPSIS综合评判指标体系模型,在充分利用专家经验的同时,又能客观、科学的对比选方案进行最优解排序,较好地解决了山区高速公路选线问题,可为类似线形工程方案的选择提供参考。展开更多
针对传统方法子指标的不确定性问题,提出了一种基于三角直觉模糊网络分析法(triangular intuitionistic fuzzy analytic network process,TIFANP)、优劣解距离法(technique for order preference by similarity to an ideal solution,TO...针对传统方法子指标的不确定性问题,提出了一种基于三角直觉模糊网络分析法(triangular intuitionistic fuzzy analytic network process,TIFANP)、优劣解距离法(technique for order preference by similarity to an ideal solution,TOPSIS)和三角直觉模糊综合评价(triangular intuitionistic fuzzy comprehensive evaluation,TIFCE)的大跨桥梁安全状态评估方法。首先,建立大跨桥梁安全状态分层指标体系,采用TIFANP法确定考虑指标相互影响后的权重;其次,引入TOPSIS法分配指标各截面权重,进而获得子指标取值;然后,将桥梁安全状态划分为5级,通过TIFCE法构建指标在不同等级的隶属度和非隶属度函数,据此建立对应判断矩阵,并进行桥梁安全状态指数综合计算;最后,以某大跨悬索桥监测数据为依托,验证了所提方法的有效性。结果表明:所提方法能够更合理地处理评价指标间的相互影响以及专家评分时的不确定,可为运营期大跨桥梁安全状态的准确评估提供新思路。展开更多
Adaptive broadband beamforraing is a key issue in array applications. The adaptive broadband beamformer with tapped delay line （TDL） structure for nonuniform linear array （NLA） is designed according to the rule of...Adaptive broadband beamforraing is a key issue in array applications. The adaptive broadband beamformer with tapped delay line （TDL） structure for nonuniform linear array （NLA） is designed according to the rule of minimizing the beamformer＇s output power while keeping the distortionless response （DR） in the direction of desired signal and keeping the constant beamwidth （CB） with the prescribed sidelobe level over the whole operating band. This kind of beamforming problem can be solved with the interior-point method after being converted to the form of standard second order cone programming （SOCP）. The computer simulations are presented which illustrate the effectiveness of our beamformer.展开更多
This paper presents a joint optimization policy of preventive maintenance(PM)and spare ordering for single-unit systems,which deteriorate subject to the delay-time concept with three deterioration stages.PM activities...This paper presents a joint optimization policy of preventive maintenance(PM)and spare ordering for single-unit systems,which deteriorate subject to the delay-time concept with three deterioration stages.PM activities that combine a non-periodic inspection scheme with age-replacement are implemented.When the system is detected to be in the minor defective stage by an inspection for the first time,place an order and shorten the inspection interval.If the system has deteriorated to a severe defective stage,it is either repaired imperfectly or replaced by a new spare.However,an immediate replacement is required once the system fails,the maximal number of imperfect maintenance(IPM)is satisfied or its age reaches to a pre-specified threshold.In consideration of the spare’s availability as needed,there are three types of decisions,i.e.,an immediate or a delayed replacement by a regular ordered spare,an immediate replacement by an expedited ordered spare with a relative higher cost.Then,some mutually independent and exclusive renewal events at the end of a renewal cycle are discussed,and the optimization model of such a joint policy is further developed by minimizing the long-run expected cost rate to find the optimal inspection and age-replacement intervals,and the maximum number of IPM.A Monte-Carlo based integration method is also designed to solve the proposed model.Finally,a numerical example is given to illustrate the proposed joint optimization policy and the performance of the Monte-Carlo based integration method.展开更多
This paper proposes a joint inspection-based maintenance and spare ordering optimization policy that considers the problem of integrated inspection,preventive maintenance,spare ordering,and quality control for a four-...This paper proposes a joint inspection-based maintenance and spare ordering optimization policy that considers the problem of integrated inspection,preventive maintenance,spare ordering,and quality control for a four-state single-unit manufacturing system.When an inspection detects a minor defect,a second phase inspection is initiated and a regular order is placed.Product quality begins to deteriorate when the system undergoes a severe defect.To counter this,an advanced replacement of the minor defective system is carried out at the Jth second phase inspection.If a severe defect is recognized prior to the Jth inspection,or if system failure occurs,preventive or corrective replacement is executed.The timeliness of replacement depends on the availability of spare.We adopt two modes of ordering:a regular order and an emergency order.Meanwhile,a threshold level is introduced to determine whether an emergency order is preferred even when the regular order is already ordered but has not yet arrived.The optimal joint inspection-based maintenance and spare ordering policy is formulated by minimizing the expected cost per unit time.A simulation algorithm is proposed to obtain the optimal two-phase inspection interval,threshold level and advanced replacement interval.Results from several numerical examples demonstrate that,in terms of the expected cost per unit time,our proposed model is superior to some existing models.展开更多
文摘针对柴油发动机推进特性下的中高负荷工况出现的NO_(x)排放峰值现象,以及燃油价格日益上涨带来降低油耗率的迫切需求,本研究通过调节柴油/甲醇组合燃烧(diesel/methanol compound combustion,DMCC)发动机多种控制参数,在保证动力性前提下,实现NO_(x)排放和有效燃油消耗率(brake specific fuel consumption,BSFC)的同步下降。为避免大规模试验带来的成本增加,首先基于高斯过程回归建立DMCC发动机排放的NO_(x)体积分数、BSFC和指示功率预测模型;然后将所建模型与第二代非支配排序遗传算法(non-dominated sorting genetic algorithm-Ⅱ,NSGA-Ⅱ)结合,对NO_(x)的体积分数和BSFC进行优化,并将Pareto前沿解集代入逼近理想解排序法(the technique for order preference by similarity to an ideal solution,TOPSIS)寻找最优控制参数组合;最后将最优控制参数组合标定至电子控制单元,与原机数据进行对比分析。结果表明:基于高斯过程回归建立的预测模型的拟合优度大于0.95,均方根误差小于1,具有良好的一致性和准确性;使用NSGA-Ⅱ获取的最佳控制参数与优化前(原机工况)的相比,NO_(x)的排放量下降74.5%,仅为3.47 g/(kW·h),BSFC平均下降6.7%,仅为203.5 g/(kW·h)。
文摘为解决当前山区高速公路选线过程中存在的影响因素多、参建各方侧重点不同、无法定量描述比选方案等难题,在充分调研中外高速公路及铁路选线影响因素的基础上,系统分析和总结中国山区高速公路选线影响因素,并将其概括为经济、技术、安全和环境4个方面,共计16个具体影响因子;依托西和—宕昌高速公路工程,组织项目区域所在地方政府、行业主管部门、业主、设计、施工、监理、第三方检测单位及科研院所相关专家共计164人组成专家组,采用层次分析法(analytic hierarchy process,AHP)对16个选线影响因子重要度进行评价。结果表明:环境指标中3个影响因素的综合权重平均分值较高,反映了工程建设领域环保意识的进一步加强。为进一步建立方案比选的优选模型,以依托项目灯塔—蒿林村段路线的方案比选为例,在AHP的基础上运用逼近理想解的排序法(technique for order preference by similarity to idea solution,TOPSIS)对比选方案进行优选,4种比选方案的优越度分别为2.84、0.56、0.72、2.15,即方案1最优。研究成果在全面分析山区高速公路选线影响因素的前提下,采用AHP-TOPSIS综合评判指标体系模型,在充分利用专家经验的同时,又能客观、科学的对比选方案进行最优解排序,较好地解决了山区高速公路选线问题,可为类似线形工程方案的选择提供参考。
文摘针对传统方法子指标的不确定性问题,提出了一种基于三角直觉模糊网络分析法(triangular intuitionistic fuzzy analytic network process,TIFANP)、优劣解距离法(technique for order preference by similarity to an ideal solution,TOPSIS)和三角直觉模糊综合评价(triangular intuitionistic fuzzy comprehensive evaluation,TIFCE)的大跨桥梁安全状态评估方法。首先,建立大跨桥梁安全状态分层指标体系,采用TIFANP法确定考虑指标相互影响后的权重;其次,引入TOPSIS法分配指标各截面权重,进而获得子指标取值;然后,将桥梁安全状态划分为5级,通过TIFCE法构建指标在不同等级的隶属度和非隶属度函数,据此建立对应判断矩阵,并进行桥梁安全状态指数综合计算;最后,以某大跨悬索桥监测数据为依托,验证了所提方法的有效性。结果表明:所提方法能够更合理地处理评价指标间的相互影响以及专家评分时的不确定,可为运营期大跨桥梁安全状态的准确评估提供新思路。
基金supported by the National Nature Science Foundation of China (60472101)President Award of ChineseAcademy of Sciences(O729031511).
文摘Adaptive broadband beamforraing is a key issue in array applications. The adaptive broadband beamformer with tapped delay line （TDL） structure for nonuniform linear array （NLA） is designed according to the rule of minimizing the beamformer＇s output power while keeping the distortionless response （DR） in the direction of desired signal and keeping the constant beamwidth （CB） with the prescribed sidelobe level over the whole operating band. This kind of beamforming problem can be solved with the interior-point method after being converted to the form of standard second order cone programming （SOCP）. The computer simulations are presented which illustrate the effectiveness of our beamformer.
基金supported by the Naitonal Natural Science Foundation of China(71701038)China Ministry of Education Humanities and Social Sciences Research Youth Fund Project(16YJC630174)+2 种基金the Natural Science Foundation of Hebei Province(G2019501074)the Fundamental Research Funds for the Central Universities(N2123019)the Postgraduate Funding Project of PLA(JY2020B085).
文摘This paper presents a joint optimization policy of preventive maintenance(PM)and spare ordering for single-unit systems,which deteriorate subject to the delay-time concept with three deterioration stages.PM activities that combine a non-periodic inspection scheme with age-replacement are implemented.When the system is detected to be in the minor defective stage by an inspection for the first time,place an order and shorten the inspection interval.If the system has deteriorated to a severe defective stage,it is either repaired imperfectly or replaced by a new spare.However,an immediate replacement is required once the system fails,the maximal number of imperfect maintenance(IPM)is satisfied or its age reaches to a pre-specified threshold.In consideration of the spare’s availability as needed,there are three types of decisions,i.e.,an immediate or a delayed replacement by a regular ordered spare,an immediate replacement by an expedited ordered spare with a relative higher cost.Then,some mutually independent and exclusive renewal events at the end of a renewal cycle are discussed,and the optimization model of such a joint policy is further developed by minimizing the long-run expected cost rate to find the optimal inspection and age-replacement intervals,and the maximum number of IPM.A Monte-Carlo based integration method is also designed to solve the proposed model.Finally,a numerical example is given to illustrate the proposed joint optimization policy and the performance of the Monte-Carlo based integration method.
基金This work was supported by the National Natural Science Foundation of China(71471015)the Social Science Fund Base Project of Beijing(19JDGLA001).
文摘This paper proposes a joint inspection-based maintenance and spare ordering optimization policy that considers the problem of integrated inspection,preventive maintenance,spare ordering,and quality control for a four-state single-unit manufacturing system.When an inspection detects a minor defect,a second phase inspection is initiated and a regular order is placed.Product quality begins to deteriorate when the system undergoes a severe defect.To counter this,an advanced replacement of the minor defective system is carried out at the Jth second phase inspection.If a severe defect is recognized prior to the Jth inspection,or if system failure occurs,preventive or corrective replacement is executed.The timeliness of replacement depends on the availability of spare.We adopt two modes of ordering:a regular order and an emergency order.Meanwhile,a threshold level is introduced to determine whether an emergency order is preferred even when the regular order is already ordered but has not yet arrived.The optimal joint inspection-based maintenance and spare ordering policy is formulated by minimizing the expected cost per unit time.A simulation algorithm is proposed to obtain the optimal two-phase inspection interval,threshold level and advanced replacement interval.Results from several numerical examples demonstrate that,in terms of the expected cost per unit time,our proposed model is superior to some existing models.
