The MohroCoulomb criterion has been widely used to explain formation of fractures. However, it fails to explain large strain deformation that widely occurs in nature. There is presently a new theory, the MEMC, which i...The MohroCoulomb criterion has been widely used to explain formation of fractures. However, it fails to explain large strain deformation that widely occurs in nature. There is presently a new theory, the MEMC, which is mathematically expressed as Meff = （（σ1-σ3） L.sin 2α sin α）/2, where σ1-σ3 represents the yield strength of the related rock, L is a unit length and a is the angle between σ1 and deformation bands. This criterion demonstrates that the maximum value appears at angles of ±54.7° to σ1 and there is a slight difference in the moment in the range of 55°±10°. The range covers the whole observations available from nature and experiments. Its major implications include： （1） it can be used to determine the stress state when the related deformation features formed; （2） it provides a new approach to determine the Wk of the related ductile shear zone if only the ratio of the vorticity and strain rate remains fixed; （3） It can be used to explain （a） the obtuse angle in the contraction direction of conjugate kink-bands and extensional crenulation cleavages, （b） formation of low-angle normal faults and high-angle reverse faults, （c） lozenge ductile shear zones in basement terranes, （d） some crocodile structures in seismic profiles and （e） detachment folds in foreland basins.展开更多
Crocodiles,one of the oldest and most resilient species on Earth,have demonstrated remarkable locomotor abilities both on land and in water,evolving over millennia to adapt to diverse environ-ments.In this study,we dr...Crocodiles,one of the oldest and most resilient species on Earth,have demonstrated remarkable locomotor abilities both on land and in water,evolving over millennia to adapt to diverse environ-ments.In this study,we draw inspiration from crocodiles and design a highly biomimetic crocodile robot equipped with multiple degrees of freedom and articulated trunk joints.This design is based on comprehensive analysis of the structural and motion characteristics of real crocodiles.The bionic crocodile robot has a problem of limb-torso incoordination during movement.To solve this problem,we used the D-H method for both forward and inverse kinematics analysis of the robot's legs and spine.Through a series of simulation experiments,we investigated the robot's motion stability,fault tolerance,and adaptability to environments in two motor patterns:with and without spine and tail movements.The experimental results show that the bionic crocodile robot exhibits superior motion performance when the spine and tail cooperate with the extremities.This study not only demonstrates the potential of biomimicry in robotics but also underscores the significance of understanding how nature's designs can inform and enhance technological innovations.展开更多
Collagen is one of the most versatile tissues of living organisms that comes in many shapes and sizes,providing functions ranging from tissue matrix through,ligament formation up to enabling mineralization in teeth.Th...Collagen is one of the most versatile tissues of living organisms that comes in many shapes and sizes,providing functions ranging from tissue matrix through,ligament formation up to enabling mineralization in teeth.The detailed light microscopy and Scanning Electron Microscopy(SEM)observations conducted in this study,allowed us to investigate morphology,sizes and crimp patterns of collagen fibers observed in crocodile skin and teeth.Moreover,the microscopy study revealed that although two completely different tissues were investigated,many similarities in their structure based on collagen fibers were observed.Collagen type I is present in crocodile skin and teeth,showing the flexibility in naturally constructed tissues to obtain various functions.The crimp size investigation of collagen fibers confirmed experimentally the theoretical 67 nm D-periodicity expected for collagen type I.The collagen in teeth provides a matrix for crystal growth and in the skin provides flexibility and is a precursor for corneous scales.Importantly,these observations of the collagen in the skin and tooth structure in crocodiles play an important role in designing biomimetic materials with similar functions and properties.展开更多
The resistance between mud surface and ship-type paddy field machine hull accounts for a certain proportion of the total mechanical power consumption during the operation process.The special characteristic has been fo...The resistance between mud surface and ship-type paddy field machine hull accounts for a certain proportion of the total mechanical power consumption during the operation process.The special characteristic has been found via preliminary study,it showed that when starting or working at low velocity,the resistance is much greater than the machine working at the rated velocity.This characteristic affects the dynamic matching and structural design of the machine.The critical velocity of resistance distortion was around 0.025 m/s under the setting experimental conditions,and the mechanism of resistance distortion under multi-medium was analyzed.Based on water film drag reduction theory,a macroscopic structure of crocodile's abdominal armor biomimetic drag reduction method was proposed.Two kinds of bionic macroscopic structure ship board were fabricated.The macroscopic structure can introduce more water into the bottom surface of the hull;thicken the water film,which can reduce the travel resistance.Design and manufacture a ship-type paddy field experimental setup with velocity control,and compare the traditional smooth surface ship board with the two bionic macroscopic structure surfaces through orthogonal test.The experiment results demonstrated that the ship board with rectangle gully structure has better drag reduction effect than the hexagon one in the lower velocity.But when the travel velocity approach to the resistance distortion critical point,the hexagon gully structure become better than the other one.Through the orthogonal test,the best drag reduction combination is 2.5 kg load weight,0.025 m/s travel velocity with hexagon ship board,which decreases the drag by 6.3%.展开更多
基金This work is financed by the grants of the National Natural Science Foundation of China （Grant No 40272084, 40472101 and 40572123）.
文摘The MohroCoulomb criterion has been widely used to explain formation of fractures. However, it fails to explain large strain deformation that widely occurs in nature. There is presently a new theory, the MEMC, which is mathematically expressed as Meff = （（σ1-σ3） L.sin 2α sin α）/2, where σ1-σ3 represents the yield strength of the related rock, L is a unit length and a is the angle between σ1 and deformation bands. This criterion demonstrates that the maximum value appears at angles of ±54.7° to σ1 and there is a slight difference in the moment in the range of 55°±10°. The range covers the whole observations available from nature and experiments. Its major implications include： （1） it can be used to determine the stress state when the related deformation features formed; （2） it provides a new approach to determine the Wk of the related ductile shear zone if only the ratio of the vorticity and strain rate remains fixed; （3） It can be used to explain （a） the obtuse angle in the contraction direction of conjugate kink-bands and extensional crenulation cleavages, （b） formation of low-angle normal faults and high-angle reverse faults, （c） lozenge ductile shear zones in basement terranes, （d） some crocodile structures in seismic profiles and （e） detachment folds in foreland basins.
基金supported by the Graduate Reaearch and Innovation Projects of Jiangsu Province(KYCX21_2251).
文摘Crocodiles,one of the oldest and most resilient species on Earth,have demonstrated remarkable locomotor abilities both on land and in water,evolving over millennia to adapt to diverse environ-ments.In this study,we draw inspiration from crocodiles and design a highly biomimetic crocodile robot equipped with multiple degrees of freedom and articulated trunk joints.This design is based on comprehensive analysis of the structural and motion characteristics of real crocodiles.The bionic crocodile robot has a problem of limb-torso incoordination during movement.To solve this problem,we used the D-H method for both forward and inverse kinematics analysis of the robot's legs and spine.Through a series of simulation experiments,we investigated the robot's motion stability,fault tolerance,and adaptability to environments in two motor patterns:with and without spine and tail movements.The experimental results show that the bionic crocodile robot exhibits superior motion performance when the spine and tail cooperate with the extremities.This study not only demonstrates the potential of biomimicry in robotics but also underscores the significance of understanding how nature's designs can inform and enhance technological innovations.
基金The authors thank Adam Hryniewicz from Warsaw Zoo for crocodile skin and teeth samples used in this study.This study was conducted as part of the“Nano-fiber-based sponges for atopic skin treatment"project,which is carried out within the First TEAM programme of the Foundation for Polish Science co-financed by the European Union under the European Regional Devel-opment Fund,Project No.POIR.04.04.00-00-4571/18-00.This study was supported by the infrastructure at the International Centre of Electron Microscopy for Materials Science(IC-EM)at AGH University of Science and Technology.
文摘Collagen is one of the most versatile tissues of living organisms that comes in many shapes and sizes,providing functions ranging from tissue matrix through,ligament formation up to enabling mineralization in teeth.The detailed light microscopy and Scanning Electron Microscopy(SEM)observations conducted in this study,allowed us to investigate morphology,sizes and crimp patterns of collagen fibers observed in crocodile skin and teeth.Moreover,the microscopy study revealed that although two completely different tissues were investigated,many similarities in their structure based on collagen fibers were observed.Collagen type I is present in crocodile skin and teeth,showing the flexibility in naturally constructed tissues to obtain various functions.The crimp size investigation of collagen fibers confirmed experimentally the theoretical 67 nm D-periodicity expected for collagen type I.The collagen in teeth provides a matrix for crystal growth and in the skin provides flexibility and is a precursor for corneous scales.Importantly,these observations of the collagen in the skin and tooth structure in crocodiles play an important role in designing biomimetic materials with similar functions and properties.
基金The authors gratefully acknowledge the financial support of Guangdong Provincial Special Fund for Modern Agriculture Industry Technology Innovation Teams under Grants No.2019KJ125the fund of Young Innovative Talents Project from Department of Education of Guangdong Province China(Grants No.2018KQNCX021).
文摘The resistance between mud surface and ship-type paddy field machine hull accounts for a certain proportion of the total mechanical power consumption during the operation process.The special characteristic has been found via preliminary study,it showed that when starting or working at low velocity,the resistance is much greater than the machine working at the rated velocity.This characteristic affects the dynamic matching and structural design of the machine.The critical velocity of resistance distortion was around 0.025 m/s under the setting experimental conditions,and the mechanism of resistance distortion under multi-medium was analyzed.Based on water film drag reduction theory,a macroscopic structure of crocodile's abdominal armor biomimetic drag reduction method was proposed.Two kinds of bionic macroscopic structure ship board were fabricated.The macroscopic structure can introduce more water into the bottom surface of the hull;thicken the water film,which can reduce the travel resistance.Design and manufacture a ship-type paddy field experimental setup with velocity control,and compare the traditional smooth surface ship board with the two bionic macroscopic structure surfaces through orthogonal test.The experiment results demonstrated that the ship board with rectangle gully structure has better drag reduction effect than the hexagon one in the lower velocity.But when the travel velocity approach to the resistance distortion critical point,the hexagon gully structure become better than the other one.Through the orthogonal test,the best drag reduction combination is 2.5 kg load weight,0.025 m/s travel velocity with hexagon ship board,which decreases the drag by 6.3%.
