Under Type-Ⅱ progressively hybrid censoring, this paper discusses statistical inference and optimal design on stepstress partially accelerated life test for hybrid system in presence of masked data. It is assumed tha...Under Type-Ⅱ progressively hybrid censoring, this paper discusses statistical inference and optimal design on stepstress partially accelerated life test for hybrid system in presence of masked data. It is assumed that the lifetime of the component in hybrid systems follows independent and identical modified Weibull distributions. The maximum likelihood estimations(MLEs)of the unknown parameters, acceleration factor and reliability indexes are derived by using the Newton-Raphson algorithm. The asymptotic variance-covariance matrix and the approximate confidence intervals are obtained based on normal approximation to the asymptotic distribution of MLEs of model parameters. Moreover,two bootstrap confidence intervals are constructed by using the parametric bootstrap method. The optimal time of changing stress levels is determined under D-optimality and A-optimality criteria.Finally, the Monte Carlo simulation study is carried out to illustrate the proposed procedures.展开更多
目的探讨成人骨型Ⅲ类患者矫治前后上下前牙区牙槽高度和宽度变化以及前牙区牙根位置变化。方法选取2020年5月—2022年11月在中山市小榄人民医院口腔科正畸掩饰治疗的成人骨型Ⅲ类患者50例,比较正畸治疗前后患者上下颌前牙牙槽骨厚度和...目的探讨成人骨型Ⅲ类患者矫治前后上下前牙区牙槽高度和宽度变化以及前牙区牙根位置变化。方法选取2020年5月—2022年11月在中山市小榄人民医院口腔科正畸掩饰治疗的成人骨型Ⅲ类患者50例,比较正畸治疗前后患者上下颌前牙牙槽骨厚度和高度,其中包括上前牙槽骨厚度(upper anterior alveolar bonethickness,UA)、上后牙槽骨厚度(upper posterior alveolar bone thickness,UP)、上牙槽骨总厚度(upper alveolar bone width,UW)、下前牙槽骨厚度(lower anterior alveolar bone thickness,LA)、下后牙槽骨厚度(lower posterior alveolar bone thickness,LP)、下牙槽骨总厚度(lower alveolar bone width,LW)、根中水平上前牙槽骨厚度(upper anterior alveolar bone thickness at the mid-root level,UA-m)、根中水平上后牙槽骨厚度(upper posterior alveolar bone thickness at the mid-root level,UP-m)、根中水平上牙槽骨总厚度(upper alveolar bone thickness at the mid-root level,UW-m)、根中水平下前牙槽骨厚度(lower anterior alveolar bone thickness at the mid-root level,LA-m)、根中水平下后牙槽骨厚度(lower posterior alveolar bone thickness at the mid-root level,LP-m)、根中水平下牙槽骨总厚度(lower alveolar bone thickness at the mid-root level,LW-m)以及上前牙槽骨高度(upper anterior alveolar bone height,UAH)和下前牙槽骨高度(lower anterior alveolarbone height,LAH)。结果正畸治疗前后患者UA、UP-m测量值比较,差异无统计学意义(P>0.05)。与正畸治疗前比较,正畸治疗后患者UP、UW、UA-m、UW-m测量值均显著降低(P<0.05)。正畸治疗后患者LP、LA-m测量值与正畸治疗前比较,差异无统计学意义(P>0.05)。与正畸治疗前比较,正畸治疗后患者LA、LW、LP-m、LW-m测量值均降低(P<0.05)。与正畸治疗前比较,正畸治疗后患者UAH、LAH测量值均显著降低(P<0.05)。正畸治疗后,患者上下颌前牙解剖牙根长度分别为(10.62±0.57)mm、(9.65±0.48)mm,正畸治疗前患者上下颌前牙解剖牙根长度分别为(11.01±0.58)mm、(10.37±0.48)mm,与正畸治疗前比较,患者上下颌前牙解剖牙根长度明显减小(P<0.05)。结论成人骨型Ⅲ类患者进行正畸掩饰治疗后,牙槽形态会发生相应改变,患者上下前牙牙槽骨厚度和高度会一定程度地减少。因此,在矫治过程中应当对患者牙槽形态的变化给予密切关注,尽量避免上下前牙发生代偿性移动,从而降低不良反应情况发生的风险。展开更多
基金supported by the National Natural Science Foundation of China(71401134 71571144+1 种基金 71171164)the Program of International Cooperation and Exchanges in Science and Technology Funded by Shaanxi Province(2016KW-033)
文摘Under Type-Ⅱ progressively hybrid censoring, this paper discusses statistical inference and optimal design on stepstress partially accelerated life test for hybrid system in presence of masked data. It is assumed that the lifetime of the component in hybrid systems follows independent and identical modified Weibull distributions. The maximum likelihood estimations(MLEs)of the unknown parameters, acceleration factor and reliability indexes are derived by using the Newton-Raphson algorithm. The asymptotic variance-covariance matrix and the approximate confidence intervals are obtained based on normal approximation to the asymptotic distribution of MLEs of model parameters. Moreover,two bootstrap confidence intervals are constructed by using the parametric bootstrap method. The optimal time of changing stress levels is determined under D-optimality and A-optimality criteria.Finally, the Monte Carlo simulation study is carried out to illustrate the proposed procedures.
文摘目的探讨成人骨型Ⅲ类患者矫治前后上下前牙区牙槽高度和宽度变化以及前牙区牙根位置变化。方法选取2020年5月—2022年11月在中山市小榄人民医院口腔科正畸掩饰治疗的成人骨型Ⅲ类患者50例,比较正畸治疗前后患者上下颌前牙牙槽骨厚度和高度,其中包括上前牙槽骨厚度(upper anterior alveolar bonethickness,UA)、上后牙槽骨厚度(upper posterior alveolar bone thickness,UP)、上牙槽骨总厚度(upper alveolar bone width,UW)、下前牙槽骨厚度(lower anterior alveolar bone thickness,LA)、下后牙槽骨厚度(lower posterior alveolar bone thickness,LP)、下牙槽骨总厚度(lower alveolar bone width,LW)、根中水平上前牙槽骨厚度(upper anterior alveolar bone thickness at the mid-root level,UA-m)、根中水平上后牙槽骨厚度(upper posterior alveolar bone thickness at the mid-root level,UP-m)、根中水平上牙槽骨总厚度(upper alveolar bone thickness at the mid-root level,UW-m)、根中水平下前牙槽骨厚度(lower anterior alveolar bone thickness at the mid-root level,LA-m)、根中水平下后牙槽骨厚度(lower posterior alveolar bone thickness at the mid-root level,LP-m)、根中水平下牙槽骨总厚度(lower alveolar bone thickness at the mid-root level,LW-m)以及上前牙槽骨高度(upper anterior alveolar bone height,UAH)和下前牙槽骨高度(lower anterior alveolarbone height,LAH)。结果正畸治疗前后患者UA、UP-m测量值比较,差异无统计学意义(P>0.05)。与正畸治疗前比较,正畸治疗后患者UP、UW、UA-m、UW-m测量值均显著降低(P<0.05)。正畸治疗后患者LP、LA-m测量值与正畸治疗前比较,差异无统计学意义(P>0.05)。与正畸治疗前比较,正畸治疗后患者LA、LW、LP-m、LW-m测量值均降低(P<0.05)。与正畸治疗前比较,正畸治疗后患者UAH、LAH测量值均显著降低(P<0.05)。正畸治疗后,患者上下颌前牙解剖牙根长度分别为(10.62±0.57)mm、(9.65±0.48)mm,正畸治疗前患者上下颌前牙解剖牙根长度分别为(11.01±0.58)mm、(10.37±0.48)mm,与正畸治疗前比较,患者上下颌前牙解剖牙根长度明显减小(P<0.05)。结论成人骨型Ⅲ类患者进行正畸掩饰治疗后,牙槽形态会发生相应改变,患者上下前牙牙槽骨厚度和高度会一定程度地减少。因此,在矫治过程中应当对患者牙槽形态的变化给予密切关注,尽量避免上下前牙发生代偿性移动,从而降低不良反应情况发生的风险。
