Based on Newton ' s second law,the bend-torsion-shaft coupling nonlinear dynamic model and equations of power split gear transmission system are established.According to the principle of tooth profile modification...Based on Newton ' s second law,the bend-torsion-shaft coupling nonlinear dynamic model and equations of power split gear transmission system are established.According to the principle of tooth profile modification,the tooth profile modification is considered as time-varying gear backlash function acting along the line of action.Then the dynamic functions are solved by using Runge-Kutta numerical method.After analyzing the effect of tooth profile modification quantity( TPMQ) and relative tooth profile modification length( TPML) to the nonlinear dynamic characteristics of power split gear transmission,the following conclusions are drawn:1 The TPMQ of a certain stage transmission affects the vibration of its own stage more significantly than the other stage,and the coupling effect between two stages can be ignored usually in the modification design;2 If the first stage TPMLs are less than 0.3,the influence of the first stage TPMLs to the first stage transmission vibration is much more greatly than the influence of the second stage TPMLs to the first stage transmission vibration,or else both the first and second stage TPMLs affect the first stage transmission vibration largely.The same is true for the second stage TPMLs,and the cutoff value is 0.2;3 The TPMQ affects the vibration of power split gear transmission system more principally than the TPML,and should be top-priority in the modification design.展开更多
In order to implement the dynamic characteristic of a dual power-split transmission, a dynamic me- chanics model is built. Firstly, according to the method of theoretical analysis of the tooth contact analysis （TCA）...In order to implement the dynamic characteristic of a dual power-split transmission, a dynamic me- chanics model is built. Firstly, according to the method of theoretical analysis of the tooth contact analysis （TCA） and loaded tooth contact analysis （LTCA）, the actual meshing process of each gear pairs is simulated, and the time-varying mesh stiffness excitations are obtained, which can improve the numerical precision. Second- ly, by using the lumped mass method, the bending-torsional coupling three dimensional dynamic model of the dual power-split transmission is established, and the identical dimensionless equations are deduced by elimina- ting the effect of rigid displacement and the method of dimensional normalization. Finally, by the method of the fourth order Runge-Kutta algorithm with variable step lengths, the responses of this system in a frequency domain and time domain are obtained, and the dynamic load change characteristics of each gear pairs are analyzed. The results show that the establishment, solution and analysis of the system dynamics model could provide a basis for the dynamic design, and have an important significance for the dynamic efficiency analysis and dynamic perform- ance optimization design of the dual power-split transmission.展开更多
目的比较采用赤藓糖醇喷砂法和矽粒子旋转抛光法治疗儿童外源性牙面黑色素沉着(extrinsic black tooth stain,EBS)的临床疗效。方法筛选符合纳入标准的3~12岁儿童48名,通过改良Lobene色斑指数记录色素水平,采用自身半口对照,随机将左右...目的比较采用赤藓糖醇喷砂法和矽粒子旋转抛光法治疗儿童外源性牙面黑色素沉着(extrinsic black tooth stain,EBS)的临床疗效。方法筛选符合纳入标准的3~12岁儿童48名,通过改良Lobene色斑指数记录色素水平,采用自身半口对照,随机将左右侧分为试验组和对照组,试验组用赤藓糖醇喷砂法,对照组用矽粒子旋转抛光法清除牙齿唇颊面EBS,记录操作时间,进行治疗感受评分,评价治疗安全性,采用“色素积分(score)除以操作时间(second)”计算清洁效率(S/s),随访治疗后3个月和6个月色素再附着水平,通过SPSS23.0软件分析试验结果。结果治疗前唇颊面左右两侧色素得分差异无统计学意义,舌腭面色素得分大于唇颊面,牙面不同分区的色素得分有统计学差异。试验组的效率高于对照组[(0.06±0.05)S/s vs(0.04±0.02)S/s,P<0.001]。8例(16.7%)研究对象对喷砂治疗感到紧张,7例(14.6%)研究对象喷砂治疗过程中出现牙龈出血。治疗前、治疗后3个月、6个月试验组和对照组色素水平差异无统计学意义(P>0.05)。结论虽然赤藓糖醇喷砂更容易导致牙龈出血,使儿童紧张,但其清除色素效率更高,值得临床推广。展开更多
目的比较超声骨刀与横T形截冠法在下颌水平阻生智齿拔除的应用效果。方法选取2018年1月—2021年12月赤峰学院附属医院行下颌水平阻生智齿拔除的122例患者作为研究对象。将患者随机分为研究组和对照组,每组61例。对照组采用超声骨刀法拔...目的比较超声骨刀与横T形截冠法在下颌水平阻生智齿拔除的应用效果。方法选取2018年1月—2021年12月赤峰学院附属医院行下颌水平阻生智齿拔除的122例患者作为研究对象。将患者随机分为研究组和对照组,每组61例。对照组采用超声骨刀法拔除患牙,研究组采用横T形截冠法拔除患牙。统计两组患者手术时间、术中出血量,记录两组术中焦虑程度,对比两组术后疼痛情况,统计两组患者手术并发症发生情况。结果两组患者手术时间、术中出血量比较,差异无统计学意义(P>0.05)。研究组术中焦虑程度低于对照组(P<0.05)。两组术后1 d疼痛程度比较,差异无统计学意义(P>0.05)。两组患者术前与术后3 d PEG2、SP、5-TH的差值比较,差异无统计学意义(P>0.05)。两组患者术后并发症总发生率比较,差异无统计学意义(P>0.05)。结论超声骨刀与横T形截冠法用于下颌水平阻生智齿拔除均可获得满意手术效果,两种方案手术效果类似,但横T形截冠法更有助于缓解患者术中焦虑。展开更多
基金Sponsored by the National Natural Science Foundation of China(Grant No.2009AA04Z404)
文摘Based on Newton ' s second law,the bend-torsion-shaft coupling nonlinear dynamic model and equations of power split gear transmission system are established.According to the principle of tooth profile modification,the tooth profile modification is considered as time-varying gear backlash function acting along the line of action.Then the dynamic functions are solved by using Runge-Kutta numerical method.After analyzing the effect of tooth profile modification quantity( TPMQ) and relative tooth profile modification length( TPML) to the nonlinear dynamic characteristics of power split gear transmission,the following conclusions are drawn:1 The TPMQ of a certain stage transmission affects the vibration of its own stage more significantly than the other stage,and the coupling effect between two stages can be ignored usually in the modification design;2 If the first stage TPMLs are less than 0.3,the influence of the first stage TPMLs to the first stage transmission vibration is much more greatly than the influence of the second stage TPMLs to the first stage transmission vibration,or else both the first and second stage TPMLs affect the first stage transmission vibration largely.The same is true for the second stage TPMLs,and the cutoff value is 0.2;3 The TPMQ affects the vibration of power split gear transmission system more principally than the TPML,and should be top-priority in the modification design.
基金supported by the Natural Science Foundation of China under Grant No.51175423
文摘In order to implement the dynamic characteristic of a dual power-split transmission, a dynamic me- chanics model is built. Firstly, according to the method of theoretical analysis of the tooth contact analysis （TCA） and loaded tooth contact analysis （LTCA）, the actual meshing process of each gear pairs is simulated, and the time-varying mesh stiffness excitations are obtained, which can improve the numerical precision. Second- ly, by using the lumped mass method, the bending-torsional coupling three dimensional dynamic model of the dual power-split transmission is established, and the identical dimensionless equations are deduced by elimina- ting the effect of rigid displacement and the method of dimensional normalization. Finally, by the method of the fourth order Runge-Kutta algorithm with variable step lengths, the responses of this system in a frequency domain and time domain are obtained, and the dynamic load change characteristics of each gear pairs are analyzed. The results show that the establishment, solution and analysis of the system dynamics model could provide a basis for the dynamic design, and have an important significance for the dynamic efficiency analysis and dynamic perform- ance optimization design of the dual power-split transmission.
文摘目的比较采用赤藓糖醇喷砂法和矽粒子旋转抛光法治疗儿童外源性牙面黑色素沉着(extrinsic black tooth stain,EBS)的临床疗效。方法筛选符合纳入标准的3~12岁儿童48名,通过改良Lobene色斑指数记录色素水平,采用自身半口对照,随机将左右侧分为试验组和对照组,试验组用赤藓糖醇喷砂法,对照组用矽粒子旋转抛光法清除牙齿唇颊面EBS,记录操作时间,进行治疗感受评分,评价治疗安全性,采用“色素积分(score)除以操作时间(second)”计算清洁效率(S/s),随访治疗后3个月和6个月色素再附着水平,通过SPSS23.0软件分析试验结果。结果治疗前唇颊面左右两侧色素得分差异无统计学意义,舌腭面色素得分大于唇颊面,牙面不同分区的色素得分有统计学差异。试验组的效率高于对照组[(0.06±0.05)S/s vs(0.04±0.02)S/s,P<0.001]。8例(16.7%)研究对象对喷砂治疗感到紧张,7例(14.6%)研究对象喷砂治疗过程中出现牙龈出血。治疗前、治疗后3个月、6个月试验组和对照组色素水平差异无统计学意义(P>0.05)。结论虽然赤藓糖醇喷砂更容易导致牙龈出血,使儿童紧张,但其清除色素效率更高,值得临床推广。
文摘目的比较超声骨刀与横T形截冠法在下颌水平阻生智齿拔除的应用效果。方法选取2018年1月—2021年12月赤峰学院附属医院行下颌水平阻生智齿拔除的122例患者作为研究对象。将患者随机分为研究组和对照组,每组61例。对照组采用超声骨刀法拔除患牙,研究组采用横T形截冠法拔除患牙。统计两组患者手术时间、术中出血量,记录两组术中焦虑程度,对比两组术后疼痛情况,统计两组患者手术并发症发生情况。结果两组患者手术时间、术中出血量比较,差异无统计学意义(P>0.05)。研究组术中焦虑程度低于对照组(P<0.05)。两组术后1 d疼痛程度比较,差异无统计学意义(P>0.05)。两组患者术前与术后3 d PEG2、SP、5-TH的差值比较,差异无统计学意义(P>0.05)。两组患者术后并发症总发生率比较,差异无统计学意义(P>0.05)。结论超声骨刀与横T形截冠法用于下颌水平阻生智齿拔除均可获得满意手术效果,两种方案手术效果类似,但横T形截冠法更有助于缓解患者术中焦虑。
