The thermal elasto-hydrodynamic lubrication characteristics of the internal meshing gears in a planetary gear train under vibrations were examined considering the influence of the modification coefficient and time-var...The thermal elasto-hydrodynamic lubrication characteristics of the internal meshing gears in a planetary gear train under vibrations were examined considering the influence of the modification coefficient and time-varying meshing stiffness.Based on dynamic theory of the gear system,a dynamic model of the planetary gear train was established.The lubrication performances of modified gear systems under vibrations and static loads were analyzed.Compared with other transmission types,the best lubrication effect could be produced by the positive transmission.A thicker lubricating oil film could be formed,and the friction coefficient and oil film flash temperature are the smallest.Increasing modification coefficient improves the lubrication performance continuously but intensifies the engage-in and tooth-change impact.For the planetary and inner gears,the increase in the modification coefficient also leads a decrease in the oil film stiffness.展开更多
目的探索股骨近端防旋髓内钉(proximal femoral nail anti-rotatio,PFNA)内固定术老年患者术后营养风险相关因素并建立营养不良预测模型。方法纳入2021年1月至2024年6月于我院接受PFNA内固定术老年患者574例,分为营养不良组(389例)和营...目的探索股骨近端防旋髓内钉(proximal femoral nail anti-rotatio,PFNA)内固定术老年患者术后营养风险相关因素并建立营养不良预测模型。方法纳入2021年1月至2024年6月于我院接受PFNA内固定术老年患者574例,分为营养不良组(389例)和营养良好组(185例),比较2组患者生理、心理、社会、经济、环境、医学等因素共39个指标的差异,采用Logistic分析筛选营养风险危险因素并构建列线图模型。结果年龄偏高、BMI指数偏低、术后SAS评分偏高、骨折前较少锻炼、农民、经济压力较高,及术前白蛋白、前蛋白、血红蛋白偏低,骨折前Barthel指数偏低是PFNA内固定术患者营养风险的独立危险因素(P<0.05)。纳入上述因素构建列线图预测模型,预测该类患者发生营养不良风险的AUC(95%CI)=0.995(0.987~1.000),在阈概率>0.02时采用本模型预测PFNA内固定术患者术后营养不良风险均可临床获益。结论基于年龄、BMI指数、经济压力、骨折前锻炼情况及术前白蛋白等指标构建老年患者PFNA内固定术术后营养风险预测模型,有较高的准确性和临床应用价值。展开更多
基金Projects(51575289,51705270)supported by the National Natural Science Foundation of China。
文摘The thermal elasto-hydrodynamic lubrication characteristics of the internal meshing gears in a planetary gear train under vibrations were examined considering the influence of the modification coefficient and time-varying meshing stiffness.Based on dynamic theory of the gear system,a dynamic model of the planetary gear train was established.The lubrication performances of modified gear systems under vibrations and static loads were analyzed.Compared with other transmission types,the best lubrication effect could be produced by the positive transmission.A thicker lubricating oil film could be formed,and the friction coefficient and oil film flash temperature are the smallest.Increasing modification coefficient improves the lubrication performance continuously but intensifies the engage-in and tooth-change impact.For the planetary and inner gears,the increase in the modification coefficient also leads a decrease in the oil film stiffness.
文摘目的探索股骨近端防旋髓内钉(proximal femoral nail anti-rotatio,PFNA)内固定术老年患者术后营养风险相关因素并建立营养不良预测模型。方法纳入2021年1月至2024年6月于我院接受PFNA内固定术老年患者574例,分为营养不良组(389例)和营养良好组(185例),比较2组患者生理、心理、社会、经济、环境、医学等因素共39个指标的差异,采用Logistic分析筛选营养风险危险因素并构建列线图模型。结果年龄偏高、BMI指数偏低、术后SAS评分偏高、骨折前较少锻炼、农民、经济压力较高,及术前白蛋白、前蛋白、血红蛋白偏低,骨折前Barthel指数偏低是PFNA内固定术患者营养风险的独立危险因素(P<0.05)。纳入上述因素构建列线图预测模型,预测该类患者发生营养不良风险的AUC(95%CI)=0.995(0.987~1.000),在阈概率>0.02时采用本模型预测PFNA内固定术患者术后营养不良风险均可临床获益。结论基于年龄、BMI指数、经济压力、骨折前锻炼情况及术前白蛋白等指标构建老年患者PFNA内固定术术后营养风险预测模型,有较高的准确性和临床应用价值。
文摘目的 比较使用螺钉或钢板进行内固定治疗骨折块≤3块的桡骨头颈骨折的中长期疗效。方法 回顾性分析2013年1月~2022年12月70例粉碎性桡骨头颈骨折资料,桡骨颈骨折合并桡骨头碎裂为2块44例,3块26例,其中31例无头加压螺钉内固定(螺钉组),39例解剖钢板内固定(钢板组)。比较2组梅奥肘关节功能评分(Mayo Elbow Performance Score, MEPS)、肘关节及前臂运动范围、并发症及再手术原因。结果 2组各1例因骨折不愈合(内固定失败)行桡骨头置换,其余68例均达到骨折愈合标准,随访时间20~135个月,平均66.7月,其中<36个月14例,36~60个月18例,>60个月36例。末次随访MEPS评分85~100分,中位数100分,2组差异无显著性(P=0.762)。螺钉组旋后优于钢板组(78.5°±5.0°vs.76.2°±4.6°,t=2.010,P=0.049),2组屈、伸、旋前差异无显著性(P>0.05)。螺钉组总并发症发生率低[12.9%(4/31) vs. 46.2%(18/39),P=0.003],二次手术率低[6.5%(2/31) vs. 30.8%(12/39),P=0.012],因硬件激惹症状引起的二次手术率低[3.3%(1/31) vs. 25.6%(10/39),P=0.026]。结论 对于骨折块≤3块的桡骨头颈骨折的内固定治疗,采用钢板及螺钉均可取得良好的长期疗效,螺钉内固定可降低术后二次手术率。
