[Objective] To study the correlation between the biomechanical properties of rape stalks and rape stem lodging. [Method] Through axial compression tests to the stalks of 4 different rape varieties, the change rules of...[Objective] To study the correlation between the biomechanical properties of rape stalks and rape stem lodging. [Method] Through axial compression tests to the stalks of 4 different rape varieties, the change rules of maximum stem bearing ca- pacity, maximum compressive strength, elastic modulus and moment of inertia along plant height were analyzed, as well as the effect of different varieties and water contents on the biomechanical property indices of rape stalks. [Result] The maximum loads of rape stalks presented liner decrease trend along with the increase of stem height, and all reached the maximums below the height of 50 cm. The maximum stem compressive strength and elastic modulus of the 4 varieties were increased with ascending height, but in a slow rate with small change, thus the modulus of e- lasticity could be considered as unchanged. The maximum bearing capacity, maxi- mum compressive strength and elastic modulus of dry rape stalks were higher than wet stalks, indicating that the water contents of rape stalks had significant effect on their mechanical properties. According to the actual lodging situations in filed, stalks of variety No. 1 owned the worst biomechanical properties and lodging degree, while the biomechanical properties of No. 6 and F5 were better than No. 1 and No. 9, and they also had stronger lodging-resistance. [Conclusion] The study provides parameters and bases for the design of mechanized production and mechanical deep processing of crops, and can better reveal the physical natures of organisms. The methods used in this study can also be used to screen excellent crop stalks.展开更多
Introduction:Runners from East Africa including Kenya,Ethiopia and Uganda have dominated middle-and longdistance running events,for almost six decades.This narrative review examines and updates current understanding o...Introduction:Runners from East Africa including Kenya,Ethiopia and Uganda have dominated middle-and longdistance running events,for almost six decades.This narrative review examines and updates current understanding of the factors explaining the dominance of East Africans in distance running from a holistic perspective.Content:The dominance of East African distance runners has puzzled researchers,with various factors proposed to explain their unparalleled success.Four key elements emerge:1)biomechanical and physiological attributes,2)training characteristics,3)psychological motivations,and 4)African diet.Runners from East Africa often exhibit ectomorphic somatotypes,characterized by lean body compositions which lead them to an extraordinary biomechanical and metabolic effciency.Their sociocultural lifestyle,training regimens beginning at a young age with aerobic activities,seem crucial,as well as moderate volume,high-intensity workouts at altitudes ranging from 2,000 to 3,000 m.Psychological factors,including a strong motivation to succeed driven by aspirations for socioeconomic improvement and a rich tradition of running excellence,also contribute significantly.A multifactorial explanation considering these factors,without a clear genetic influence,is nowadays the strongest argument to explain the East African phenomenon.Summary and outlook:To unravel the mystery behind the supremacy of East African runners,it is imperative to consider these multifaceted factors.The predominantly rural lifestyle of the East African population underscores the importance of aligning modern lifestyles with the evolutionary past of Homo sapiens,where physical activity was integral to daily life.Further research is required to explain this phenomenon,with a focus on genetics.展开更多
Anterior Cervical Discectomy and Fusion(ACDF)is the preferred surgical method for the treatment of severe cervical degenerative disc disease with radiculopathy or myelopathy,of which the objectives are to restore the ...Anterior Cervical Discectomy and Fusion(ACDF)is the preferred surgical method for the treatment of severe cervical degenerative disc disease with radiculopathy or myelopathy,of which the objectives are to restore the normal height of intervertebral space and cervical lordosis through the implantation of cervical interbody fusion cage.The biomechanical performance of a cervical interbody fusion cage,which plays a significant role in achieving the goals of ACDF,is influenced by multiple factors.In this paper,various studies focusing on the biomechanical performance of cervical interbody fusion cage are reviewed.Furthermore,the research methods,biomechanical evaluation parameters and data analysis methods of these research are analyzed in order to obtain a comprehensive understanding of the progress and limitations of research in this field.Although great progress has been made to clarify the biomechanical behaviors of cervical interbody fusion cage,there is still controversy regarding the issues such as the relative contribution of multiple factors to the performance of cage,the interactions among these factors,as well as whether the effects of factors change with the process of intervertebral osseointegration and so on.Thus,investigations are still needed to improve the comprehension of cervical interbody fusion cage biomechanically.展开更多
Total temporomandibular joint(TMJ)replacement is recommended only when there is irreversible damage to the joint and no conservative treatment can provide functional improvements.Several stock and custom-made TMJ impl...Total temporomandibular joint(TMJ)replacement is recommended only when there is irreversible damage to the joint and no conservative treatment can provide functional improvements.Several stock and custom-made TMJ implants have been made available;however,retrospective and comparative studies were unable to find significant differences between the two types of solutions.The introduction of additive manufacturing(AM)techniques in medical practice allows for a greater freedom of design and a higher degree of device customisation.The combination of AM with structural optimisation may streamline development and provide the key for fabricating biomechanic ally enhanced TMJ implants.In this study,structural optimis ation techniques were applied to develop and numerically validate a patient-specific TMJ implant.The biomechanical behaviour of each intermediate TMJ design was assessed under four different nominal and maximum biting tasks using finite element analyses.In addition,a new set of metrics were proposed to compare each design regarding biomechanical performance and implant safety.The results suggest that 55-82%of the natural/intact strain patterns can be recovered with the finally selected TMJ implant.This represents an increase of 15%in biomechanical performance for incisor biting,15%for right molar biting,17%for left molar biting and a decrease of 2%for left group biting compared with the initial design.The results also suggest that load transfer at the proximal ramus reduces the implant’s impact on the mandible’s strain patterns.Finally,structural optimisation allows for a volume reduction of up to 44%with a minimum loss of implant safety and biomechanical performance.展开更多
Spinal fracture is a serious problem impairing life quality,associating with low back pain and many other chronic diseases.Among all the spinal fractures,the rate of thoracolumbar fractures is the highest and accounts...Spinal fracture is a serious problem impairing life quality,associating with low back pain and many other chronic diseases.Among all the spinal fractures,the rate of thoracolumbar fractures is the highest and accounts for approximately 90%.Although surgical treatment is an effective approach,it is still unclear which treatment method performs the best.The aim of the present study was to investigate the biomechanical performance of three spinal implants for treating the thoracolumbar wedge-shaped burst fractures using the finite element(FE)method.FE model of the T12/L1/L2 spinal segment was created from CT images and the thoracolumbar wedge-shaped burst fractures were created by removing some elements in the anterior part of L1.The FE models of the traditional system,the universal spine system(USS)and the cortical bone trajectory(CBT)system were created and their biomechanical performances were evaluated.The results revealed that among the three fixation systems,the highest von-Mises stress occurred in the CBT system.Under all the loading scenarios except for the lateral bending,the maximal von-Mises stress was higher when the USS system rather than the traditional system was applied.The average displacement around the fracture site was the highest in the CBT system.Except for the lateral bending,the average displacement around the fracture site was higher when the USS system rather than the traditional system was applied.For all the fixation approaches,the highest von-Mises stress always occurred at the screw junctions.The present study provided important data for the treatment of thoracolumbar wedge-shaped burst fractures.For example,the traditional spinal system is preferentially selected for the thoracolumbar wedgeshaped burst fracture of L1.展开更多
基金Supported by the Special Fund for Crop Breeding of Sichuan Provincial Department of Education,China (2006LD006)the Rapeseed Breeding Research Program of Science & Technology Department of Sichuan Province,China (2006YZGG-5-5)~~
文摘[Objective] To study the correlation between the biomechanical properties of rape stalks and rape stem lodging. [Method] Through axial compression tests to the stalks of 4 different rape varieties, the change rules of maximum stem bearing ca- pacity, maximum compressive strength, elastic modulus and moment of inertia along plant height were analyzed, as well as the effect of different varieties and water contents on the biomechanical property indices of rape stalks. [Result] The maximum loads of rape stalks presented liner decrease trend along with the increase of stem height, and all reached the maximums below the height of 50 cm. The maximum stem compressive strength and elastic modulus of the 4 varieties were increased with ascending height, but in a slow rate with small change, thus the modulus of e- lasticity could be considered as unchanged. The maximum bearing capacity, maxi- mum compressive strength and elastic modulus of dry rape stalks were higher than wet stalks, indicating that the water contents of rape stalks had significant effect on their mechanical properties. According to the actual lodging situations in filed, stalks of variety No. 1 owned the worst biomechanical properties and lodging degree, while the biomechanical properties of No. 6 and F5 were better than No. 1 and No. 9, and they also had stronger lodging-resistance. [Conclusion] The study provides parameters and bases for the design of mechanized production and mechanical deep processing of crops, and can better reveal the physical natures of organisms. The methods used in this study can also be used to screen excellent crop stalks.
文摘Introduction:Runners from East Africa including Kenya,Ethiopia and Uganda have dominated middle-and longdistance running events,for almost six decades.This narrative review examines and updates current understanding of the factors explaining the dominance of East Africans in distance running from a holistic perspective.Content:The dominance of East African distance runners has puzzled researchers,with various factors proposed to explain their unparalleled success.Four key elements emerge:1)biomechanical and physiological attributes,2)training characteristics,3)psychological motivations,and 4)African diet.Runners from East Africa often exhibit ectomorphic somatotypes,characterized by lean body compositions which lead them to an extraordinary biomechanical and metabolic effciency.Their sociocultural lifestyle,training regimens beginning at a young age with aerobic activities,seem crucial,as well as moderate volume,high-intensity workouts at altitudes ranging from 2,000 to 3,000 m.Psychological factors,including a strong motivation to succeed driven by aspirations for socioeconomic improvement and a rich tradition of running excellence,also contribute significantly.A multifactorial explanation considering these factors,without a clear genetic influence,is nowadays the strongest argument to explain the East African phenomenon.Summary and outlook:To unravel the mystery behind the supremacy of East African runners,it is imperative to consider these multifaceted factors.The predominantly rural lifestyle of the East African population underscores the importance of aligning modern lifestyles with the evolutionary past of Homo sapiens,where physical activity was integral to daily life.Further research is required to explain this phenomenon,with a focus on genetics.
基金This work was supported by the China National Key Research and Development Plan Project(grant number 2016YFB1101100)National Natural Science Foundation of China(grant number 11822201)the 111 Project(grant number B13003).
文摘Anterior Cervical Discectomy and Fusion(ACDF)is the preferred surgical method for the treatment of severe cervical degenerative disc disease with radiculopathy or myelopathy,of which the objectives are to restore the normal height of intervertebral space and cervical lordosis through the implantation of cervical interbody fusion cage.The biomechanical performance of a cervical interbody fusion cage,which plays a significant role in achieving the goals of ACDF,is influenced by multiple factors.In this paper,various studies focusing on the biomechanical performance of cervical interbody fusion cage are reviewed.Furthermore,the research methods,biomechanical evaluation parameters and data analysis methods of these research are analyzed in order to obtain a comprehensive understanding of the progress and limitations of research in this field.Although great progress has been made to clarify the biomechanical behaviors of cervical interbody fusion cage,there is still controversy regarding the issues such as the relative contribution of multiple factors to the performance of cage,the interactions among these factors,as well as whether the effects of factors change with the process of intervertebral osseointegration and so on.Thus,investigations are still needed to improve the comprehension of cervical interbody fusion cage biomechanically.
基金funding from the Interreg 2 Seas program 2014-2020 co-funded by the European Regional Development Fund under subsidy contract no.2S04-014。
文摘Total temporomandibular joint(TMJ)replacement is recommended only when there is irreversible damage to the joint and no conservative treatment can provide functional improvements.Several stock and custom-made TMJ implants have been made available;however,retrospective and comparative studies were unable to find significant differences between the two types of solutions.The introduction of additive manufacturing(AM)techniques in medical practice allows for a greater freedom of design and a higher degree of device customisation.The combination of AM with structural optimisation may streamline development and provide the key for fabricating biomechanic ally enhanced TMJ implants.In this study,structural optimis ation techniques were applied to develop and numerically validate a patient-specific TMJ implant.The biomechanical behaviour of each intermediate TMJ design was assessed under four different nominal and maximum biting tasks using finite element analyses.In addition,a new set of metrics were proposed to compare each design regarding biomechanical performance and implant safety.The results suggest that 55-82%of the natural/intact strain patterns can be recovered with the finally selected TMJ implant.This represents an increase of 15%in biomechanical performance for incisor biting,15%for right molar biting,17%for left molar biting and a decrease of 2%for left group biting compared with the initial design.The results also suggest that load transfer at the proximal ramus reduces the implant’s impact on the mandible’s strain patterns.Finally,structural optimisation allows for a volume reduction of up to 44%with a minimum loss of implant safety and biomechanical performance.
基金This study was supported by the National Natural Science Foundation of China(12072066)the DUT-BSU grant(ICR2103)the Chinese Fundamental Research Funds for the Central Universities(DUT21LK21).
文摘Spinal fracture is a serious problem impairing life quality,associating with low back pain and many other chronic diseases.Among all the spinal fractures,the rate of thoracolumbar fractures is the highest and accounts for approximately 90%.Although surgical treatment is an effective approach,it is still unclear which treatment method performs the best.The aim of the present study was to investigate the biomechanical performance of three spinal implants for treating the thoracolumbar wedge-shaped burst fractures using the finite element(FE)method.FE model of the T12/L1/L2 spinal segment was created from CT images and the thoracolumbar wedge-shaped burst fractures were created by removing some elements in the anterior part of L1.The FE models of the traditional system,the universal spine system(USS)and the cortical bone trajectory(CBT)system were created and their biomechanical performances were evaluated.The results revealed that among the three fixation systems,the highest von-Mises stress occurred in the CBT system.Under all the loading scenarios except for the lateral bending,the maximal von-Mises stress was higher when the USS system rather than the traditional system was applied.The average displacement around the fracture site was the highest in the CBT system.Except for the lateral bending,the average displacement around the fracture site was higher when the USS system rather than the traditional system was applied.For all the fixation approaches,the highest von-Mises stress always occurred at the screw junctions.The present study provided important data for the treatment of thoracolumbar wedge-shaped burst fractures.For example,the traditional spinal system is preferentially selected for the thoracolumbar wedgeshaped burst fracture of L1.
