With the rapid development of large megawatt wind turbines,the operation environment of wind turbine towers(WTTs)has become increasingly complex.In particular,seismic excitation can create a resonance response and cau...With the rapid development of large megawatt wind turbines,the operation environment of wind turbine towers(WTTs)has become increasingly complex.In particular,seismic excitation can create a resonance response and cause excessive vibration of the WTT.To investigate the vibration attenuation performance of the WTT under seismic excitations,a novel passive vibration control device,called a prestressed tuned mass damper(PS-TMD),is presented in this study.First,a mathematical model is established based on structural dynamics under seismic excitation.Then,the mathematical analytical expression of the dynamic coefficient is deduced,and the parameter design method is obtained by system tuning optimization.Next,based on a theoretical analysis and parameter design,the numerical results showed that the PS-TMD was able to effectively mitigate the resonance under the harmonic basal acceleration.Finally,the time-history analysis method is used to verify the effectiveness of the traditional pendulum tuned mass damper(PTMD)and the novel PS-TMD device,and the results indicate that the vibration attenuation performance of the PS-TMD is better than the PTMD.In addition,the PS-TMD avoids the nonlinear effect due to the large oscillation angle,and has the potential to dissipate hysteretic energy under seismic excitation.展开更多
BACKGROUND Paramyotonia congenita(PMC)stands as a rare sodium channelopaty of skeletal muscle,initially identified by Eulenburg.The identification of PMC often relies on electromyography(EMG),a diagnostic technique.Th...BACKGROUND Paramyotonia congenita(PMC)stands as a rare sodium channelopaty of skeletal muscle,initially identified by Eulenburg.The identification of PMC often relies on electromyography(EMG),a diagnostic technique.The child’s needle EMG unveiled trains of myotonic discharges with notably giant amplitudes,alongside irregular wave trains of myotonic discharges.This distinctive observation had not surfaced in earlier studies.CASE SUMMARY We report the case of a 3-year-old female child with PMC,who exhibited la-ryngeal stridor,muffled speech,myotonia from birth.Cold,exposure to cool water,crying,and physical activity exacerbated the myotonia,which was relieved in warmth,yet never normalized.Percussion myotonia was observable in bilateral biceps.Myotonia symptoms remained unchanged after potassium-rich food consumption like bananas.Hyperkalemic periodic paralysis was excluded.Cranial magnetic resonance imaging yielded normal results.Blood potassium remained within normal range,while creatine kinase showed slight elevation.Exome-wide genetic testing pinpointed a heterozygous mutation on chromosome SCN4A:c.3917G>A(p.G1306E).After a six-month mexiletine regimen,symptoms alleviated.CONCLUSION In this case revealed the two types of myotonic discharges,and had not been documented in other studies.We underscore two distinctive features:Giant-amplitude potentials and irregular waves.展开更多
基金Fundamental Research Funds for the National Natural Science Foundation of China under Grant No.52078084the Natural Science Foundation of Chongqing (cstc2021jcyj-msxmX0623)+2 种基金the 111 project of the Ministry of Educationthe Bureau of Foreign Experts of China under Grant No.B18062China Postdoctoral Science Foundation under Grant No.2021M690838。
文摘With the rapid development of large megawatt wind turbines,the operation environment of wind turbine towers(WTTs)has become increasingly complex.In particular,seismic excitation can create a resonance response and cause excessive vibration of the WTT.To investigate the vibration attenuation performance of the WTT under seismic excitations,a novel passive vibration control device,called a prestressed tuned mass damper(PS-TMD),is presented in this study.First,a mathematical model is established based on structural dynamics under seismic excitation.Then,the mathematical analytical expression of the dynamic coefficient is deduced,and the parameter design method is obtained by system tuning optimization.Next,based on a theoretical analysis and parameter design,the numerical results showed that the PS-TMD was able to effectively mitigate the resonance under the harmonic basal acceleration.Finally,the time-history analysis method is used to verify the effectiveness of the traditional pendulum tuned mass damper(PTMD)and the novel PS-TMD device,and the results indicate that the vibration attenuation performance of the PS-TMD is better than the PTMD.In addition,the PS-TMD avoids the nonlinear effect due to the large oscillation angle,and has the potential to dissipate hysteretic energy under seismic excitation.
基金The Scientific Research Foundation of Suzhou University of Science and Technology (No.332311106)the National Natural Science Foundation of China (No.52078087)111 Project of the Ministry of Education and the Bureau of Foreign Experts of China (No.B18062)。
文摘BACKGROUND Paramyotonia congenita(PMC)stands as a rare sodium channelopaty of skeletal muscle,initially identified by Eulenburg.The identification of PMC often relies on electromyography(EMG),a diagnostic technique.The child’s needle EMG unveiled trains of myotonic discharges with notably giant amplitudes,alongside irregular wave trains of myotonic discharges.This distinctive observation had not surfaced in earlier studies.CASE SUMMARY We report the case of a 3-year-old female child with PMC,who exhibited la-ryngeal stridor,muffled speech,myotonia from birth.Cold,exposure to cool water,crying,and physical activity exacerbated the myotonia,which was relieved in warmth,yet never normalized.Percussion myotonia was observable in bilateral biceps.Myotonia symptoms remained unchanged after potassium-rich food consumption like bananas.Hyperkalemic periodic paralysis was excluded.Cranial magnetic resonance imaging yielded normal results.Blood potassium remained within normal range,while creatine kinase showed slight elevation.Exome-wide genetic testing pinpointed a heterozygous mutation on chromosome SCN4A:c.3917G>A(p.G1306E).After a six-month mexiletine regimen,symptoms alleviated.CONCLUSION In this case revealed the two types of myotonic discharges,and had not been documented in other studies.We underscore two distinctive features:Giant-amplitude potentials and irregular waves.
