A new beech and self-tapping screw composite dowel is proposed and studied,its performance being compared with that of beech dowels and self-tapping screws alone.The single shear performance of components connected by...A new beech and self-tapping screw composite dowel is proposed and studied,its performance being compared with that of beech dowels and self-tapping screws alone.The single shear performance of components connected by composite dowels was tested.Results show that the dowels are a good choice for components requiring high stiffness.Screws remain a good choice for components requiring excellent seismic performance.Combination group presents similar maximum load stiffness to those of composite dowels,but other ductility parameters are superior for composite dowels.The best connection mode was provided by two composite dowels.Based on connecting two points,structural elements with two composite dowels showed much better load bearing ability than when joined by two beech dowels or by two self-tapping screws separately.The structural element with two composite dowels not only presented better initial stiffness,but also exhibited a better ductility coeffi-cient and less energy consumption.So,the composite dowels can be used for beam column connection,dowel laminated timber,and restoration or enhancement of ancient buildings.展开更多
Screw connection is a type most commonly applied to timber structures.As important commercial tree species in China,Masson pine and Chinese fir have the potential to prepare wood structures.In this study,the effects o...Screw connection is a type most commonly applied to timber structures.As important commercial tree species in China,Masson pine and Chinese fir have the potential to prepare wood structures.In this study,the effects of the diameter of the self-tapping screw and the guiding bores on the nail holding performance on different sections of Masson pine and Chinese fir dimension lumbers were mainly explored.The results showed that:(1)The nail holding strength of the tangential section was the maximum,followed by that of the radial section,and that of the cross section was the minimum.(2)The nail holding strength of Masson pine was higher than that of Chinese fir.(3)The nail holding strength grew with the increase in the diameter of self-tapping screws,but a large diameter would lead to plastic cracking of the timber,thus further affecting the nail holding strength.Masson pine and Chinese fir reached the maximum nail holding strength when the diameter of self-tapping screws was 3.5 mm.(4)Under a large diameter of screws,prefabricated guiding bores could mitigate timber cracking and improve its nail holding strength.(5)Prefabricated guiding bores were more necessary for the screw connection of Masson pine.The results obtained could provide a scientific basis for the screw connection design of Masson pine and Chinese fir timber structures.展开更多
Introduction: An observation was made that when removing self-tapping cortical screws from patients bones, stripping or shearing of the head of the screw occurred more often in screws whose cutting flutes sat in corti...Introduction: An observation was made that when removing self-tapping cortical screws from patients bones, stripping or shearing of the head of the screw occurred more often in screws whose cutting flutes sat in cortical bone compared with screws that had penetrated the distal cortex with flutes exposed. Method: A model was designed to simulate screws with their cutting flutes either in contact with cortical bone or deep to cortical bone. Screws were grouped depending on the location of their cutting flutes and removal torque was measured. Results: Eighteen screws were included in final analysis. There was a statistically significant difference in average initial removal torque and average maximal removal torque with screws with their cutting flutes in substrate requiring significantly more torque to remove. Conclusion: We conclude that self-tapping cortical screws whose cutting flutes sit in cortical substrate require more torque to remove and are therefore more likely to fail. This finding may be used as a guide in pre-operative planning for removal of metalwork from patients.展开更多
经过40余年临床应用与不断发展,引导骨组织再生术(guided bone regeneration,GBR)已被证明是一种可靠的牙槽骨骨增量技术。GBR技术在应用过程中的核心要素是充足的血供和稳定的环境。但现有GBR技术都是在“以血供为核心”的理论体系下...经过40余年临床应用与不断发展,引导骨组织再生术(guided bone regeneration,GBR)已被证明是一种可靠的牙槽骨骨增量技术。GBR技术在应用过程中的核心要素是充足的血供和稳定的环境。但现有GBR技术都是在“以血供为核心”的理论体系下进行的,缺乏对稳定要素重要性的重视。我们通过文献阅读及系列临床试验,提出“以稳定为核心”的牙槽骨修复重建理念。基于新理念,创建了以单纯人工骨粉修复牙槽骨重度缺损的治疗新术式,革新了国际上必须用自体骨修复骨缺损的治疗理念。本文将从GBR技术的历史发展轨迹中寻找稳定的重要性,结合现有骨再生理论,详细阐述“以稳定为核心”的牙槽骨修复重建治疗新技术。展开更多
基金The authors are grateful for the support of the National Natural Science Foundation of China(Grant No.31901252)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20180276)+3 种基金Jiangsu Planned Projects for Postdoctoral Research Funds(Grant No.2020Z075)the Science and Technology Program of Jiangsu Housing and Construction Department(Grant Nos.2018ZD118 and 2020ZD29)Qing Lan Project of Jiangsu,the Yangzhou Science and Technology Project(Grant No.SGH2020010040)Yangzhou Polytechnic Institute Project(Grant No.2019xjzk007).
文摘A new beech and self-tapping screw composite dowel is proposed and studied,its performance being compared with that of beech dowels and self-tapping screws alone.The single shear performance of components connected by composite dowels was tested.Results show that the dowels are a good choice for components requiring high stiffness.Screws remain a good choice for components requiring excellent seismic performance.Combination group presents similar maximum load stiffness to those of composite dowels,but other ductility parameters are superior for composite dowels.The best connection mode was provided by two composite dowels.Based on connecting two points,structural elements with two composite dowels showed much better load bearing ability than when joined by two beech dowels or by two self-tapping screws separately.The structural element with two composite dowels not only presented better initial stiffness,but also exhibited a better ductility coeffi-cient and less energy consumption.So,the composite dowels can be used for beam column connection,dowel laminated timber,and restoration or enhancement of ancient buildings.
基金funded by the National Natural Science Foundation of China (32160348)Forestry Science and Technology Research Project of Guizhou Forestry Bureau (J[2022]21 and[2020]C14)+1 种基金Department Program of Guizhou Province ([2020]1Y128)the Cultivation Project of Guizhou University of China ([2019]37).
文摘Screw connection is a type most commonly applied to timber structures.As important commercial tree species in China,Masson pine and Chinese fir have the potential to prepare wood structures.In this study,the effects of the diameter of the self-tapping screw and the guiding bores on the nail holding performance on different sections of Masson pine and Chinese fir dimension lumbers were mainly explored.The results showed that:(1)The nail holding strength of the tangential section was the maximum,followed by that of the radial section,and that of the cross section was the minimum.(2)The nail holding strength of Masson pine was higher than that of Chinese fir.(3)The nail holding strength grew with the increase in the diameter of self-tapping screws,but a large diameter would lead to plastic cracking of the timber,thus further affecting the nail holding strength.Masson pine and Chinese fir reached the maximum nail holding strength when the diameter of self-tapping screws was 3.5 mm.(4)Under a large diameter of screws,prefabricated guiding bores could mitigate timber cracking and improve its nail holding strength.(5)Prefabricated guiding bores were more necessary for the screw connection of Masson pine.The results obtained could provide a scientific basis for the screw connection design of Masson pine and Chinese fir timber structures.
文摘Introduction: An observation was made that when removing self-tapping cortical screws from patients bones, stripping or shearing of the head of the screw occurred more often in screws whose cutting flutes sat in cortical bone compared with screws that had penetrated the distal cortex with flutes exposed. Method: A model was designed to simulate screws with their cutting flutes either in contact with cortical bone or deep to cortical bone. Screws were grouped depending on the location of their cutting flutes and removal torque was measured. Results: Eighteen screws were included in final analysis. There was a statistically significant difference in average initial removal torque and average maximal removal torque with screws with their cutting flutes in substrate requiring significantly more torque to remove. Conclusion: We conclude that self-tapping cortical screws whose cutting flutes sit in cortical substrate require more torque to remove and are therefore more likely to fail. This finding may be used as a guide in pre-operative planning for removal of metalwork from patients.
文摘经过40余年临床应用与不断发展,引导骨组织再生术(guided bone regeneration,GBR)已被证明是一种可靠的牙槽骨骨增量技术。GBR技术在应用过程中的核心要素是充足的血供和稳定的环境。但现有GBR技术都是在“以血供为核心”的理论体系下进行的,缺乏对稳定要素重要性的重视。我们通过文献阅读及系列临床试验,提出“以稳定为核心”的牙槽骨修复重建理念。基于新理念,创建了以单纯人工骨粉修复牙槽骨重度缺损的治疗新术式,革新了国际上必须用自体骨修复骨缺损的治疗理念。本文将从GBR技术的历史发展轨迹中寻找稳定的重要性,结合现有骨再生理论,详细阐述“以稳定为核心”的牙槽骨修复重建治疗新技术。
