具有屈服后硬化刚度减震结构的输入能计算中,等效速度谱一般通过改变结构阻尼比获得,这与实际不符,而不同的反应谱对输入能的计算精度影响较大。本文旨在构建综合考虑结构参数、场地类别和地震类型的等效速度谱,为相关减震结构能量设计...具有屈服后硬化刚度减震结构的输入能计算中,等效速度谱一般通过改变结构阻尼比获得,这与实际不符,而不同的反应谱对输入能的计算精度影响较大。本文旨在构建综合考虑结构参数、场地类别和地震类型的等效速度谱,为相关减震结构能量设计提供参考。基于此,首先,建立了考虑屈服后硬化刚度影响的能量平衡方程及其运动方程,并构建了具有屈服后硬化刚度单自由度(single degree of freedom,SDOF)体系等效速度谱计算程序;其次,选取了不同场地类别和地震类型的120条地震记录,利用上述程序分析了屈服后硬化刚度、阻尼比、延性系数、场地类别和地震类型等五种因素对等效速度的影响规律;最后,利用数据拟合工具提出了综合考虑多因素影响的等效速度谱计算公式并与程序计算结果对比。研究表明:等效速度随硬化刚度系数的增大呈减小趋势,但对等效速度谱的下降段影响较小,同时,等效速度随延性系数和阻尼比增大也有减小趋势,但阻尼比影响更为显著。展开更多
Nickel based single crystal superalloy is currently widely used as the material for turbine blades in aerospace engines.However,metallurgical defects during the manufacturing process and damage during harsh environmen...Nickel based single crystal superalloy is currently widely used as the material for turbine blades in aerospace engines.However,metallurgical defects during the manufacturing process and damage during harsh environmental service are inevitable challenges for turbine blades.Therefore,bonding techniques play a very important role in the manufacturing and repair of turbine blades.The transient liquid phase(TLP)bonding of DD5 Ni-based single crystal superalloy was performed using the designed H1 interlayer.A new third-generation Ni-based superalloy T1 powder was mixed with H1 powder as another interlayer to improve the mechanical properties of the bonded joints.The res-ults show that,such a designed H1 interlayer is beneficial to the improvement of shear strength of DD5 alloy bonded joints by adjusting the bonding temperature and the prolongation of holding time.The maximum shear strength at room temperature of the joint with H1 interlayer reached 681 MPa when bonded at 1260℃for 3 h.The addition of T1 powder can effectively reduce holding time or relatively lower bond-ing temperature,while maintaining relatively high shear strength.When 1 wt.%T1 powder was mixed into H1 interlayer,the maximum room temperature shear strength of the joint bonded at 1260℃reached 641 MPa,which could be obtained for only 1 h.Considering the bonding temperature and the efficiency,the acceptable process parameter of H1+5 wt.%T1 interlayer was 1240℃/2 h,and the room tem-perature shear strength reached 613 MPa.展开更多
为改善极端梯度提升(extreme gradient boosting,XGBoost)集成算法的信贷风险预测准确率,提出了一种改进的麻雀算法(improved sparrow search algorithm based on golden sine search,Cauchy mutation and oppositionbased learning,GCO...为改善极端梯度提升(extreme gradient boosting,XGBoost)集成算法的信贷风险预测准确率,提出了一种改进的麻雀算法(improved sparrow search algorithm based on golden sine search,Cauchy mutation and oppositionbased learning,GCOSSA)来优化XGBoost参数。采用黄金正弦搜索策略来更新发现者位置,既增强全局搜索能力又增强局部搜索能力;在算法中引入反向学习策略和柯西变异进行扰动来扩大搜索领域改善陷入局部最优,同时使用贪婪规则确定最优解;将改进的算法用6个基准函数进行测试,并对SSA和GCOSSA进行对比,评估GCOSSA寻优性能;用GCOSSA优化XGBoost参数。在数据集上测试,并与网格搜索寻优、SSA及其混合正余弦改进算法(improved sparrow search algorithm based on sine and cosine,ISSA)方法进行对比。结果表明改进后的GCOSSA优化XGBoost参数,在信贷风险预测中准确率更高。展开更多
文摘具有屈服后硬化刚度减震结构的输入能计算中,等效速度谱一般通过改变结构阻尼比获得,这与实际不符,而不同的反应谱对输入能的计算精度影响较大。本文旨在构建综合考虑结构参数、场地类别和地震类型的等效速度谱,为相关减震结构能量设计提供参考。基于此,首先,建立了考虑屈服后硬化刚度影响的能量平衡方程及其运动方程,并构建了具有屈服后硬化刚度单自由度(single degree of freedom,SDOF)体系等效速度谱计算程序;其次,选取了不同场地类别和地震类型的120条地震记录,利用上述程序分析了屈服后硬化刚度、阻尼比、延性系数、场地类别和地震类型等五种因素对等效速度的影响规律;最后,利用数据拟合工具提出了综合考虑多因素影响的等效速度谱计算公式并与程序计算结果对比。研究表明:等效速度随硬化刚度系数的增大呈减小趋势,但对等效速度谱的下降段影响较小,同时,等效速度随延性系数和阻尼比增大也有减小趋势,但阻尼比影响更为显著。
基金supported by the National Science and Technology Major Project(2017-VI-0009-0080)the Key-Area Research and Development Program of Guangdong Province(2019B010935001)+1 种基金Shenzhen Science and Technology Plan(Project No.JSGG20210802093205015)Industry and Information Technology Bureau of Shenzhen Municipality(Project No.201806071354163490).
文摘Nickel based single crystal superalloy is currently widely used as the material for turbine blades in aerospace engines.However,metallurgical defects during the manufacturing process and damage during harsh environmental service are inevitable challenges for turbine blades.Therefore,bonding techniques play a very important role in the manufacturing and repair of turbine blades.The transient liquid phase(TLP)bonding of DD5 Ni-based single crystal superalloy was performed using the designed H1 interlayer.A new third-generation Ni-based superalloy T1 powder was mixed with H1 powder as another interlayer to improve the mechanical properties of the bonded joints.The res-ults show that,such a designed H1 interlayer is beneficial to the improvement of shear strength of DD5 alloy bonded joints by adjusting the bonding temperature and the prolongation of holding time.The maximum shear strength at room temperature of the joint with H1 interlayer reached 681 MPa when bonded at 1260℃for 3 h.The addition of T1 powder can effectively reduce holding time or relatively lower bond-ing temperature,while maintaining relatively high shear strength.When 1 wt.%T1 powder was mixed into H1 interlayer,the maximum room temperature shear strength of the joint bonded at 1260℃reached 641 MPa,which could be obtained for only 1 h.Considering the bonding temperature and the efficiency,the acceptable process parameter of H1+5 wt.%T1 interlayer was 1240℃/2 h,and the room tem-perature shear strength reached 613 MPa.
文摘为改善极端梯度提升(extreme gradient boosting,XGBoost)集成算法的信贷风险预测准确率,提出了一种改进的麻雀算法(improved sparrow search algorithm based on golden sine search,Cauchy mutation and oppositionbased learning,GCOSSA)来优化XGBoost参数。采用黄金正弦搜索策略来更新发现者位置,既增强全局搜索能力又增强局部搜索能力;在算法中引入反向学习策略和柯西变异进行扰动来扩大搜索领域改善陷入局部最优,同时使用贪婪规则确定最优解;将改进的算法用6个基准函数进行测试,并对SSA和GCOSSA进行对比,评估GCOSSA寻优性能;用GCOSSA优化XGBoost参数。在数据集上测试,并与网格搜索寻优、SSA及其混合正余弦改进算法(improved sparrow search algorithm based on sine and cosine,ISSA)方法进行对比。结果表明改进后的GCOSSA优化XGBoost参数,在信贷风险预测中准确率更高。
