Traditional passive flexible protection systems often fail under high-energy rockfall impacts,leading to structural destruction and casualties.To address this critical limitation,this study develops a novel high-ducti...Traditional passive flexible protection systems often fail under high-energy rockfall impacts,leading to structural destruction and casualties.To address this critical limitation,this study develops a novel high-ductility energy-absorbing(HDEA)system incorporating negative Poisson's ratio(NPR)materials.The mechanical performance of the HDEA system was comprehensively evaluated through an integrated methodology comprising static/dynamic tests,finite element simulation,and field monitoring.Quasi-static tensile and drop hammer impact tests were conducted on conventional positive Poisson's ratio(PR)steel and NPR materials.The NPR material exhibits 54.4%-68.8%higher tensile strength and 1.04-1.31 times greater elongation at break than the PR material.Dynamic tests reveal the NPR cable achieves 44.29%lower single-impact deformation with 1.39 times higher cumulative impact deformation versus the PR counterpart.These results indicate that the NPR material breaks the strength-ductility trade-off,equipping the cable with both high impact resistance and exceptional energy absorption.The fastener transits from plastic deformation to fracture under extreme conditions while the NPR cables retain integrity.This contrasting behavior validates a deliberate failure hierarchy,where the fastener acts as a sacrificial component,thereby preserving the integrity and reusability of the NPR cable.Slip resistance tests verify an anti-slip capacity exceeding 350 kN.This confirms a robust interfacial bond between the cable and fastener,which is critical for ensuring the coordinated deformation of the entire interception net under rockfall impact.Field implementation demonstrates the HDEA system withstands daily average of 3 rockfall impacts with 2000 J mean impact energy while maintaining structural integrity.This study pioneers the application of NPR materials in rockfall protection systems,providing a groundbreaking solution for mitigating high-energy rockfall hazards.展开更多
Molecular chaperones are a family of proteins that were first noticed to exist about 45 years ago from their increased transcription under heat shock conditions.As a result,the regulation of their encoding genes has b...Molecular chaperones are a family of proteins that were first noticed to exist about 45 years ago from their increased transcription under heat shock conditions.As a result,the regulation of their encoding genes has been subject to extensive studies.Recent studies revealed that the biological activities of molecular chaperones can also be effectively modulated at the protein level.The ways of modulation so far elucidated include allosteric effect,covalent modification,protein-protein interaction,and con-formational alteration induced by such macro-environmental conditions as temperature and pH.These latter aspects were reviewed here.Emphasized here is the importance of such immediate structural alterations that lead to an immediate activity increase,providing the immediate protection needed for the cells to survive the stress conditions.展开更多
基金financial support from the National Natural Science Foundation of China-Railway Fundamental Research Joint Fund Project(U2468219)National Natural Science Foundation of China(Grant No.42377195)。
文摘Traditional passive flexible protection systems often fail under high-energy rockfall impacts,leading to structural destruction and casualties.To address this critical limitation,this study develops a novel high-ductility energy-absorbing(HDEA)system incorporating negative Poisson's ratio(NPR)materials.The mechanical performance of the HDEA system was comprehensively evaluated through an integrated methodology comprising static/dynamic tests,finite element simulation,and field monitoring.Quasi-static tensile and drop hammer impact tests were conducted on conventional positive Poisson's ratio(PR)steel and NPR materials.The NPR material exhibits 54.4%-68.8%higher tensile strength and 1.04-1.31 times greater elongation at break than the PR material.Dynamic tests reveal the NPR cable achieves 44.29%lower single-impact deformation with 1.39 times higher cumulative impact deformation versus the PR counterpart.These results indicate that the NPR material breaks the strength-ductility trade-off,equipping the cable with both high impact resistance and exceptional energy absorption.The fastener transits from plastic deformation to fracture under extreme conditions while the NPR cables retain integrity.This contrasting behavior validates a deliberate failure hierarchy,where the fastener acts as a sacrificial component,thereby preserving the integrity and reusability of the NPR cable.Slip resistance tests verify an anti-slip capacity exceeding 350 kN.This confirms a robust interfacial bond between the cable and fastener,which is critical for ensuring the coordinated deformation of the entire interception net under rockfall impact.Field implementation demonstrates the HDEA system withstands daily average of 3 rockfall impacts with 2000 J mean impact energy while maintaining structural integrity.This study pioneers the application of NPR materials in rockfall protection systems,providing a groundbreaking solution for mitigating high-energy rockfall hazards.
基金Supported by National Natural Science Foundation of China(Grant Nos.30570355 and 30670022)National Key Basic Research Foundation of China(Grant Nos.2006CB806508 and 2006CB910300)
文摘Molecular chaperones are a family of proteins that were first noticed to exist about 45 years ago from their increased transcription under heat shock conditions.As a result,the regulation of their encoding genes has been subject to extensive studies.Recent studies revealed that the biological activities of molecular chaperones can also be effectively modulated at the protein level.The ways of modulation so far elucidated include allosteric effect,covalent modification,protein-protein interaction,and con-formational alteration induced by such macro-environmental conditions as temperature and pH.These latter aspects were reviewed here.Emphasized here is the importance of such immediate structural alterations that lead to an immediate activity increase,providing the immediate protection needed for the cells to survive the stress conditions.
