为了对半潜式风机水平向和竖向的振动进行控制,提出了多向多点位调谐质量阻尼器(tuned mass damper,TMD)的布设方式,即在机舱内布置H-TMD,平台内布置V-TMD。为研究这种TMD布设方式的减振效果,建立了半潜式风机-多向多点位TMD全耦合数值...为了对半潜式风机水平向和竖向的振动进行控制,提出了多向多点位调谐质量阻尼器(tuned mass damper,TMD)的布设方式,即在机舱内布置H-TMD,平台内布置V-TMD。为研究这种TMD布设方式的减振效果,建立了半潜式风机-多向多点位TMD全耦合数值模型,利用OpenFAST仿真分析风浪联合作用下半潜式风机的动力响应。结果表明:布置多向多点位TMD的减振效果要比单点位TMD的减振效果要好,且在机舱内布置低频H-TMD,平台内布置V-TMD为最优布置方案,能够使半潜式风机纵摇、横摇、垂荡、塔架纵向振动的平均标准差控制率分别达到13.97%、32.85%、15.21%、2.86%。展开更多
考虑到海上浮式风机(floating offshore wind turbine,FOWT)因存在整体晃动导致背景响应强烈,在频域上有时表现为激励频率,且随激励频率的变化而变化,在使用传统调谐质量阻尼器(tuned mass damper,TMD)对其进行振动控制时出现频率失调...考虑到海上浮式风机(floating offshore wind turbine,FOWT)因存在整体晃动导致背景响应强烈,在频域上有时表现为激励频率,且随激励频率的变化而变化,在使用传统调谐质量阻尼器(tuned mass damper,TMD)对其进行振动控制时出现频率失调和效果不佳等现象,该研究设计并提出了一种带碰撞的磁流变弹性体变刚度调谐质量阻尼器(magnetorheological elastomer-pounding tuned mass damper,MRE-PTMD)对FOWT实施半主动控制。在该控制装置中,利用MRE的刚度可调特性,通过半主动控制技术实现阻尼器频率的实时调节,保持对FOWT的最优控制,同时引入限位挡板对MRE材料加以保护并实现碰撞耗能。以驳船型FOWT为例,建立了包含控制装置的17自由度动力方程,对其在风浪联合作用下的减振性能及参数影响进行了研究,并与传统TMD进行了对比。结果表明,所提控制装置能通过对结构响应的实时追踪适时调节阻尼器的控制参数,相比传统TMD有更佳的减振性能和适应性。参数分析表明,增大阻尼器质量比是提升MRE-PTMD工作性能的有效途径,通过对阻尼器质量比及碰撞参数的合理设计可在不过多影响减振效果的情况下实现对MRE的保护及控制装置小型化。展开更多
The success of the tuned mass damper (TMD) in reducing wind-induced structural vibrations has been well established. However, from most of the recent numerical studies, it appears that for a structure situated on very...The success of the tuned mass damper (TMD) in reducing wind-induced structural vibrations has been well established. However, from most of the recent numerical studies, it appears that for a structure situated on very soft soil, soil-structure interaction (SSI) could render a damper on the structure totally ineffective. In order to experimentally verify the SSI effect on the seismic performance of TMD, a series of shaking table model tests have been conducted and the results are presented in this paper. It has been shown that the TMD is not as effective in controlling the seismic responses of structures built on soft soil sites due to the SSI effect. Some test results also show that a TMD device might have a negative impact if the SSI effect is neglected and the structure is built on a soft soil site. For structures constructed on a soil foundation, this research verifies that the SSI effect must be carefully understood before a TMD control system is designed to determine if the control is necessary and if the SSI effect must be considered when choosing the optimal parameters of the TMD device.展开更多
调谐质量阻尼器(tuned mass damper,TMD)的减振效率与结构和TMD的固有参数相关,准确从结构-TMD耦合系统响应中识别结构和TMD固有参数是对在役TMD减振性能评价的必要条件。提出了一种基于NSGA-Ⅱ(非支配排序遗传算法,nondominated sortin...调谐质量阻尼器(tuned mass damper,TMD)的减振效率与结构和TMD的固有参数相关,准确从结构-TMD耦合系统响应中识别结构和TMD固有参数是对在役TMD减振性能评价的必要条件。提出了一种基于NSGA-Ⅱ(非支配排序遗传算法,nondominated sorting genetic algorithm)的参数识别方法,从结构-TMD耦合运动响应中识别“裸结构”和“裸TMD”的固有参数,进而实现对在役状态TMD的减振性能评估。该方法构建了结构-TMD耦合运动方程,并将其减缩和转化为结构被控模态和TMD耦合的两自由度系统,借助系统状态空间矩阵搭建两个目标函数,通过遗传算法寻找理论值与试验值的最小误差所对应的最优解,从而识别结构和TMD的固有参数。开展了单自由度结构-TMD耦合系统和多自由度结构-TMD耦合系统参数识别数值仿真分析,结果表明:提出的方法可以从耦合系统动力响应中准确识别结构和TMD的固有参数。展开更多
为解决颤振控制TMD(tuned mass damper)设计时更准确地获取拟控制桥梁动力特性的问题,基于Sherman Morrison公式、拟控制桥梁的频响函数以及TMD参数,推导桥梁-TMD耦合系统的模态频率和阻尼。基于航空领域的颤振裕度法,推导两自由度弯扭...为解决颤振控制TMD(tuned mass damper)设计时更准确地获取拟控制桥梁动力特性的问题,基于Sherman Morrison公式、拟控制桥梁的频响函数以及TMD参数,推导桥梁-TMD耦合系统的模态频率和阻尼。基于航空领域的颤振裕度法,推导两自由度弯扭耦合气弹系统附加扭转TMD之后的颤振裕度随风速变化的表达式。提出了一种基于颤振裕度的TMD优化设计方法,以最大化颤振临界风速(颤振裕度等于0)为目标,得到TMD的优化参数。基于一个两自由度桥梁截面数值例子,对比分析了颤振裕度法和传统复特征值法所预测的耦合系统颤振临界风速和最优TMD参数,探讨了基于颤振裕度法的TMD优化设计方法的准确性,对比分析了控制前后4个风速下的时域响应,探讨了最优TMD的控制效果。研究结果表明:颤振裕度法和复特征值法两者计算得到的TMD最优参数一致,基于颤振裕度法预测的桥梁-最优TMD系统的颤振临界风速与基于复特征值法预测的结果仅存在2.2%的误差,且用最优TMD控制后桥梁颤振临界风速提高了50%。研究结果为桥梁颤振控制TMD的优化设计提供了一种新的方法。该方法所使用的频响函数包含了结构和气动力信息,依据应用场景不同,其可以是数值计算的频率响应函数,也可以是实测的频响函数。在实际应用中可通过大型激振器进行实验模态分析测试得到,其更加准确地表征了拟控制桥梁的动力特性,为TMD的精准设计奠定了基础。该方法的实际工程应用值得进一步发展和研究。展开更多
Background: Surgical treatment of lumbar disc herniation is a widely debated topic, with several techniques available. Percutaneous endoscopic discectomy (PELD) has gained popularity due to its lower invasiveness comp...Background: Surgical treatment of lumbar disc herniation is a widely debated topic, with several techniques available. Percutaneous endoscopic discectomy (PELD) has gained popularity due to its lower invasiveness compared to conventional techniques such as microdiscectomy/open lumbar microdiscectomy (OLMD)/tubular microdiscectomy (TMD). However, evidence on the effectiveness, recovery time and complications of these techniques is not yet clearly established. This systematic review aims to compare the preoperative and postoperative outcomes of both techniques. Methods: A comprehensive search was performed in databases including PubMed and Cochrane, following strict inclusion and exclusion criteria. Comparative studies and narrative reviews on PELD and OLMD/TMD published between 2019 and 2024 were included. Key outcomes considered were pre- and postoperative Visual Analogue Scale (VAS), hospitalization time, time to return to work, and postoperative complications. Results: The reviewed studies indicated that PELD is associated with a greater reduction in postoperative pain compared to OLMD/TMD, with a significant decrease in VAS, according to the study by Priola et al. (2019). The hospital stay was also shorter for patients undergoing PELD, averaging 2 days compared to OLMD/TMD. Furthermore, PELD favored a faster return to work and had a lower rate of postoperative complications, such as dural tears and reoperations, compared to OLMD/TMD. Conclusions: PELD demonstrates clear advantages over OLMD/TMD in terms of pain reduction, shorter hospital stay, faster return to work, and fewer postoperative complications. However, the implementation of this technique requires a significant learning curve, suggesting that its effectiveness may vary depending on the surgeon’s experience. PELD should be considered a preferred option in the resection of lumbar disc herniations, especially in patients seeking a quick and less invasive recovery.展开更多
文摘为了对半潜式风机水平向和竖向的振动进行控制,提出了多向多点位调谐质量阻尼器(tuned mass damper,TMD)的布设方式,即在机舱内布置H-TMD,平台内布置V-TMD。为研究这种TMD布设方式的减振效果,建立了半潜式风机-多向多点位TMD全耦合数值模型,利用OpenFAST仿真分析风浪联合作用下半潜式风机的动力响应。结果表明:布置多向多点位TMD的减振效果要比单点位TMD的减振效果要好,且在机舱内布置低频H-TMD,平台内布置V-TMD为最优布置方案,能够使半潜式风机纵摇、横摇、垂荡、塔架纵向振动的平均标准差控制率分别达到13.97%、32.85%、15.21%、2.86%。
文摘考虑到海上浮式风机(floating offshore wind turbine,FOWT)因存在整体晃动导致背景响应强烈,在频域上有时表现为激励频率,且随激励频率的变化而变化,在使用传统调谐质量阻尼器(tuned mass damper,TMD)对其进行振动控制时出现频率失调和效果不佳等现象,该研究设计并提出了一种带碰撞的磁流变弹性体变刚度调谐质量阻尼器(magnetorheological elastomer-pounding tuned mass damper,MRE-PTMD)对FOWT实施半主动控制。在该控制装置中,利用MRE的刚度可调特性,通过半主动控制技术实现阻尼器频率的实时调节,保持对FOWT的最优控制,同时引入限位挡板对MRE材料加以保护并实现碰撞耗能。以驳船型FOWT为例,建立了包含控制装置的17自由度动力方程,对其在风浪联合作用下的减振性能及参数影响进行了研究,并与传统TMD进行了对比。结果表明,所提控制装置能通过对结构响应的实时追踪适时调节阻尼器的控制参数,相比传统TMD有更佳的减振性能和适应性。参数分析表明,增大阻尼器质量比是提升MRE-PTMD工作性能的有效途径,通过对阻尼器质量比及碰撞参数的合理设计可在不过多影响减振效果的情况下实现对MRE的保护及控制装置小型化。
基金National Natural Science Foundation of China Under Grant No.59778027State Key Laboratory of Coastal Offshore EngineeringDalian University of Technology Under Grant No.9702
文摘The success of the tuned mass damper (TMD) in reducing wind-induced structural vibrations has been well established. However, from most of the recent numerical studies, it appears that for a structure situated on very soft soil, soil-structure interaction (SSI) could render a damper on the structure totally ineffective. In order to experimentally verify the SSI effect on the seismic performance of TMD, a series of shaking table model tests have been conducted and the results are presented in this paper. It has been shown that the TMD is not as effective in controlling the seismic responses of structures built on soft soil sites due to the SSI effect. Some test results also show that a TMD device might have a negative impact if the SSI effect is neglected and the structure is built on a soft soil site. For structures constructed on a soil foundation, this research verifies that the SSI effect must be carefully understood before a TMD control system is designed to determine if the control is necessary and if the SSI effect must be considered when choosing the optimal parameters of the TMD device.
文摘为解决颤振控制TMD(tuned mass damper)设计时更准确地获取拟控制桥梁动力特性的问题,基于Sherman Morrison公式、拟控制桥梁的频响函数以及TMD参数,推导桥梁-TMD耦合系统的模态频率和阻尼。基于航空领域的颤振裕度法,推导两自由度弯扭耦合气弹系统附加扭转TMD之后的颤振裕度随风速变化的表达式。提出了一种基于颤振裕度的TMD优化设计方法,以最大化颤振临界风速(颤振裕度等于0)为目标,得到TMD的优化参数。基于一个两自由度桥梁截面数值例子,对比分析了颤振裕度法和传统复特征值法所预测的耦合系统颤振临界风速和最优TMD参数,探讨了基于颤振裕度法的TMD优化设计方法的准确性,对比分析了控制前后4个风速下的时域响应,探讨了最优TMD的控制效果。研究结果表明:颤振裕度法和复特征值法两者计算得到的TMD最优参数一致,基于颤振裕度法预测的桥梁-最优TMD系统的颤振临界风速与基于复特征值法预测的结果仅存在2.2%的误差,且用最优TMD控制后桥梁颤振临界风速提高了50%。研究结果为桥梁颤振控制TMD的优化设计提供了一种新的方法。该方法所使用的频响函数包含了结构和气动力信息,依据应用场景不同,其可以是数值计算的频率响应函数,也可以是实测的频响函数。在实际应用中可通过大型激振器进行实验模态分析测试得到,其更加准确地表征了拟控制桥梁的动力特性,为TMD的精准设计奠定了基础。该方法的实际工程应用值得进一步发展和研究。
文摘Background: Surgical treatment of lumbar disc herniation is a widely debated topic, with several techniques available. Percutaneous endoscopic discectomy (PELD) has gained popularity due to its lower invasiveness compared to conventional techniques such as microdiscectomy/open lumbar microdiscectomy (OLMD)/tubular microdiscectomy (TMD). However, evidence on the effectiveness, recovery time and complications of these techniques is not yet clearly established. This systematic review aims to compare the preoperative and postoperative outcomes of both techniques. Methods: A comprehensive search was performed in databases including PubMed and Cochrane, following strict inclusion and exclusion criteria. Comparative studies and narrative reviews on PELD and OLMD/TMD published between 2019 and 2024 were included. Key outcomes considered were pre- and postoperative Visual Analogue Scale (VAS), hospitalization time, time to return to work, and postoperative complications. Results: The reviewed studies indicated that PELD is associated with a greater reduction in postoperative pain compared to OLMD/TMD, with a significant decrease in VAS, according to the study by Priola et al. (2019). The hospital stay was also shorter for patients undergoing PELD, averaging 2 days compared to OLMD/TMD. Furthermore, PELD favored a faster return to work and had a lower rate of postoperative complications, such as dural tears and reoperations, compared to OLMD/TMD. Conclusions: PELD demonstrates clear advantages over OLMD/TMD in terms of pain reduction, shorter hospital stay, faster return to work, and fewer postoperative complications. However, the implementation of this technique requires a significant learning curve, suggesting that its effectiveness may vary depending on the surgeon’s experience. PELD should be considered a preferred option in the resection of lumbar disc herniations, especially in patients seeking a quick and less invasive recovery.
