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基于灵敏度权重的双摆角铣头传动精度定量分配 被引量:1
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作者 吴凤和 李永欣 +1 位作者 李树枝 李少辉 《中国机械工程》 EI CAS CSCD 北大核心 2017年第22期2675-2680,2688,共7页
针对基于行星减速机构的双摆角铣头传动部分结构复杂,传动误差影响因素众多,导致传动精度分配困难的问题,提出了一种灵敏度计算与加权分配相结合的传动精度定量分配方法。首先建立双摆角铣头传动链的误差模型,根据其定位精度要求和传动... 针对基于行星减速机构的双摆角铣头传动部分结构复杂,传动误差影响因素众多,导致传动精度分配困难的问题,提出了一种灵敏度计算与加权分配相结合的传动精度定量分配方法。首先建立双摆角铣头传动链的误差模型,根据其定位精度要求和传动误差分析结果确定总传动误差允许值;然后根据各传动误差项对总传动误差影响的灵敏度值,筛选出对传动精度影响较大的误差项,并对其灵敏度值进行归一化处理;最后对较大误差项进行加权分配,得到符合精度设计要求的16种精度分配方案,进而选出满足经济性要求的方案。该方法推导过程物理意义明确,操作性强,可避免低灵敏度误差项对精度分配的干扰,提高了精度分配效率,对多误差复杂系统的精度优化分配具有指导意义。 展开更多
关键词 精度分配 双摆角铣头 灵敏度权重 比例加权方法
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Jackknifed random weighting for Cox proportional hazards model
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作者 LI Xiao 1 ,WU YaoHua 2,& TU DongSheng 1 1 Cancer Research Institute,Queen’s University,Kingston,Ontario K 7L 3N6,Canada 2 Department of Finance and Statistics,University of Science and Technology of China,Hefei 230026,China 《Science China Mathematics》 SCIE 2012年第4期775-786,共12页
The Cox proportional hazards model is the most used statistical model in the analysis of survival time data.Recently,a random weighting method was proposed to approximate the distribution of the maximum partial likeli... The Cox proportional hazards model is the most used statistical model in the analysis of survival time data.Recently,a random weighting method was proposed to approximate the distribution of the maximum partial likelihood estimate for the regression coefficient in the Cox model.This method was shown not as sensitive to heavy censoring as the bootstrap method in simulation studies but it may not be second-order accurate as was shown for the bootstrap approximation.In this paper,we propose an alternative random weighting method based on one-step linear jackknife pseudo values and prove the second accuracy of the proposed method.Monte Carlo simulations are also performed to evaluate the proposed method for fixed sample sizes. 展开更多
关键词 Cox proportional hazards model JACKKNIFE random weighting second-order accuracy simulations survival data
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