Tukey's halfspace median(HM), servicing as the multivariate counterpart of the univariate median,has been introduced and extensively studied in the literature. It is supposed and expected to preserve robustness pr...Tukey's halfspace median(HM), servicing as the multivariate counterpart of the univariate median,has been introduced and extensively studied in the literature. It is supposed and expected to preserve robustness property(the most outstanding property) of the univariate median. One of prevalent quantitative assessments of robustness is finite sample breakdown point(FSBP). Indeed, the FSBP of many multivariate medians have been identified, except for the most prevailing one—the Tukey's halfspace median. This paper presents a precise result on FSBP for Tukey's halfspace median. The result here depicts the complete prospect of the global robustness of HM in the finite sample practical scenario, revealing the dimension effect on the breakdown point robustness and complimenting the existing asymptotic breakdown point result.展开更多
增材制造由于加工速度快,精度高,无需模具成形常用于制备复杂的金属部件,成分梯度样品的制备更是金属增材制造中的热门,由于该技术目前尚未成熟,工件中往往存在较多缺陷,匹配的成分分布分析方法的研究对成品质量监测具有重要意义。宏观...增材制造由于加工速度快,精度高,无需模具成形常用于制备复杂的金属部件,成分梯度样品的制备更是金属增材制造中的热门,由于该技术目前尚未成熟,工件中往往存在较多缺陷,匹配的成分分布分析方法的研究对成品质量监测具有重要意义。宏观的成分分布表征手段主要有激光诱导击穿光谱原位统计分析技术(LIBS-OPA)和火花源原子发射光谱原位统计分布分析技术(Spark-OPA)两种, Spark-OPA由于激发斑点较大不适用于增材制造样品的逐层分析, LIBS-OPA具有多元素同步定位分析、空间分辨率高、分析尺度较大、样品损伤量小等诸多优势,可以实现金属块体材料的高精度成分分布表征。采用激光诱导击穿光谱法对增材制造成分梯度不锈钢样品的成分分布表征方法进行了研究。通过对仪器参数和分析条件进行优化,保证了分析的灵敏度以及信号的稳定性,确定最佳的测试条件为:激光灯电压1.32 kV,调Q延时280μs,样品室氩气气压6 300 Pa,光斑直径200μm, 0次预剥蚀,积分15次剥蚀,并在该条件下绘制Cr 298.9 nm, Ni 218.5 nm, Mn 293.3 nm, Mo 203.8 nm, Si 212.4 nm, P 178.3 nm, C 193.1 nm, Co 384.5 nm等元素的工作曲线,大部分元素判定系数超过0.99。使用LIBS-OPA对不同的多路送粉增材制造工艺制备出的两块成分梯度不锈钢样品进行了面扫描,得到样品沉积面上8种元素的成分分布信息,分析结果同火花源原子发射光谱原位统计分布分析技术(Spark-OPA)具有良好的一致性,其定量准确性也通过火花直读光谱仪进行了验证。该研究实现了增材制造样品的逐层分析,并通过成分分布结果对样品的制备工艺提供了指导,同时也对两种工艺制造出的样品中重复出现沿打印方向的裂纹带的成因进行了分析,该研究对于增材制造工艺的改进和完善具有指导意义。展开更多
基金supported by National Natural Science Foundation of China(Grant Nos.11601197,11461029,71463020,61263014 and 61563018),National Natural Science Foundation of China(Grant Nos.General program 11171331 and Key program 11331011)National Science Foundation of Jiangxi Province(Grant Nos.20161BAB201024,20142BAB211014,20143ACB21012 and 20151BAB211016)+3 种基金the Key Science Fund Project of Jiangxi Provincial Education Department(Grant Nos.GJJ150439,KJLD13033 and KJLD14034)the National Science Fund for Distinguished Young Scholars in China(Grant No.10725106)a grant from the Key Lab of Random Complex Structure and Data Science,Chinese Academy of SciencesNatural Science Foundation of Shenzhen University
文摘Tukey's halfspace median(HM), servicing as the multivariate counterpart of the univariate median,has been introduced and extensively studied in the literature. It is supposed and expected to preserve robustness property(the most outstanding property) of the univariate median. One of prevalent quantitative assessments of robustness is finite sample breakdown point(FSBP). Indeed, the FSBP of many multivariate medians have been identified, except for the most prevailing one—the Tukey's halfspace median. This paper presents a precise result on FSBP for Tukey's halfspace median. The result here depicts the complete prospect of the global robustness of HM in the finite sample practical scenario, revealing the dimension effect on the breakdown point robustness and complimenting the existing asymptotic breakdown point result.
文摘增材制造由于加工速度快,精度高,无需模具成形常用于制备复杂的金属部件,成分梯度样品的制备更是金属增材制造中的热门,由于该技术目前尚未成熟,工件中往往存在较多缺陷,匹配的成分分布分析方法的研究对成品质量监测具有重要意义。宏观的成分分布表征手段主要有激光诱导击穿光谱原位统计分析技术(LIBS-OPA)和火花源原子发射光谱原位统计分布分析技术(Spark-OPA)两种, Spark-OPA由于激发斑点较大不适用于增材制造样品的逐层分析, LIBS-OPA具有多元素同步定位分析、空间分辨率高、分析尺度较大、样品损伤量小等诸多优势,可以实现金属块体材料的高精度成分分布表征。采用激光诱导击穿光谱法对增材制造成分梯度不锈钢样品的成分分布表征方法进行了研究。通过对仪器参数和分析条件进行优化,保证了分析的灵敏度以及信号的稳定性,确定最佳的测试条件为:激光灯电压1.32 kV,调Q延时280μs,样品室氩气气压6 300 Pa,光斑直径200μm, 0次预剥蚀,积分15次剥蚀,并在该条件下绘制Cr 298.9 nm, Ni 218.5 nm, Mn 293.3 nm, Mo 203.8 nm, Si 212.4 nm, P 178.3 nm, C 193.1 nm, Co 384.5 nm等元素的工作曲线,大部分元素判定系数超过0.99。使用LIBS-OPA对不同的多路送粉增材制造工艺制备出的两块成分梯度不锈钢样品进行了面扫描,得到样品沉积面上8种元素的成分分布信息,分析结果同火花源原子发射光谱原位统计分布分析技术(Spark-OPA)具有良好的一致性,其定量准确性也通过火花直读光谱仪进行了验证。该研究实现了增材制造样品的逐层分析,并通过成分分布结果对样品的制备工艺提供了指导,同时也对两种工艺制造出的样品中重复出现沿打印方向的裂纹带的成因进行了分析,该研究对于增材制造工艺的改进和完善具有指导意义。
