Isotropic magnets were prepared from melt-spun powders at different hot pressing temperatures from 550 to 700 ℃, then upset into fully dense anisotropic magnets at the same die-upsetting temperature of 850 ℃. Die-up...Isotropic magnets were prepared from melt-spun powders at different hot pressing temperatures from 550 to 700 ℃, then upset into fully dense anisotropic magnets at the same die-upsetting temperature of 850 ℃. Die-upset magnets had the characteristics of inhomogeneous microstructure, including well-aligned grains structure and nonaligned grains layers transverse to press direction, which was quasi-periodic layer structure with a total length of 5-15 μm. Nonaligned grains layers were mainly made of large grains and had higher Nd content. To clearly understand the formation of layer structure, the microstructure of isotropic precursors with different hot pressing temperatures and their subsequent die-upset magnets was investigated. A new interpretation for the formation of layer structure was proposed in this paper： the layer structure was correlated to the original ribbon interface which was divided into three types based on the contact forms. Because of the incomplete contact of neighboring ribbons, concentration of stress occurred in the contacted points and the Nd-rich phase was squeezed into interspaces at high temperature under stress. Due to the release of interfacial energy and the fluidity of enough Nd-rich liquid phases, the nonaligned layers with large grains formed both in hot compaction and subsequent hot deformation process. The layer structure affected the magnetic properties of die-upset magnets. With increase of the hot pressing temperature, the nonaligned grains layers became thicker, and the magnetic performance of die-upset magnets decreased. It was necessary to reduce the thickness of large grains layers for the preparation of high-performance die-upset magnets.展开更多
多模态图像之间存在显著的非线性强度差异,并且图像会因为噪声而退化,因此,多模态图像自动配准是一项具有挑战性的任务。为了解决这两个问题,本文提出一种多模态图像自动配准方法,该方法分为预配准和精配准两个阶段。在预配准阶段,通过...多模态图像之间存在显著的非线性强度差异,并且图像会因为噪声而退化,因此,多模态图像自动配准是一项具有挑战性的任务。为了解决这两个问题,本文提出一种多模态图像自动配准方法,该方法分为预配准和精配准两个阶段。在预配准阶段,通过改进SIFT算法来大致对齐多模态图像。在精配准阶段,首先,利用块Harris检测器在预配准后的参考图上提取均匀分布的特征点。然后,通过各向异性结构张量捕捉多模态图像中的结构信息来构建特征描述符,该特征描述符对噪声具有稳健性。更进一步,本文结合张量方向平行度和梯度互信息提出了一种相似度准则(tensor orientation and mutual information,TOMI)。最后,本文用多种模态图像(包括Optical,LiDAR,SAR和Map)来评估提出的方法。试验结果表明,本文提出的方法对非线性强度变化和噪声具有较好的稳健性,并且匹配效果优越。展开更多
Biomimetic intelligent polymeric hydrogel actuators with cooperative fluorescence-color switchable behaviors are expected to find great potential applications in soft robotics,visual detection/display,and camouflage a...Biomimetic intelligent polymeric hydrogel actuators with cooperative fluorescence-color switchable behaviors are expected to find great potential applications in soft robotics,visual detection/display,and camouflage applications.However,it remains challenging to realize the spatial manipulation of synergistic shape/color-changing behaviors.Herein,we report an interfacial supramolecular assembly(ISA)approach that enables the construction of robust fluorescent polymeric hydrogel actuators with spatially anisotropic structures.On the basis of this ISA approach,diverse 2D/3D soft fluorescent hydrogel actuators,including chameleon-and octopi-shaped ones with spatially anisotropic structures,were facilely assembled from two different fluorescent hydrogel building blocks sharing the same physically cross-linked agar network.Spatially control over synergistic shape/color-changing behaviors was then realized in one single anisotropic hydrogel actuator.The proposed ISA approach is universal and expected to open promising avenues for developing powerful bioinspired intelligent soft actuators/robotics with selective spatial shape/color-changing behaviors.展开更多
Multi-fountional hollow structures have emerged as promising platforms for intelligent drug delivery due to their unique properties,such as high loading capacities and programmed drug release.In particular,hollow mult...Multi-fountional hollow structures have emerged as promising platforms for intelligent drug delivery due to their unique properties,such as high loading capacities and programmed drug release.In particular,hollow multishell structures(HoMSs)with multilevel shell and space can regulate the molecular-level interaction between drugs and materials,so as to achieve the temporal-spatial order and sequential release of drugs.The anisotropic hollow structures can control the drug diffusion process by inducing the macroscopic interface flow through autonomous movement,realizing the targeted drug transport and release.In this paper,a key focus will be HoMSs with their temporal-ordered architectures and anisotropic hollow carriers with directional movement.Their synthesis mechanisms,structure-property relationships,smartly programmed drug delivery and biomedical applications will be discussed,providing insights into designing next-generation intelligent drug carriers.展开更多
With the improvement of aero-engine performance,the preparation of hollow blades of single-crystal superalloys with complex inner cavity cooling structures is becoming increasingly urgent.The ceramic core is the key i...With the improvement of aero-engine performance,the preparation of hollow blades of single-crystal superalloys with complex inner cavity cooling structures is becoming increasingly urgent.The ceramic core is the key intermediate part of the preparation and has attracted wide attention.To meet this challenge,new technologies that can make up for the defects of long periods and high costs of fabricating complex structural cores by traditional hot injection technology are needed.Vat photopolymerization 3D printing ceramic technology has been applied to the core field to realize the rapid preparation of complex structural cores.However,the industrial application of this technology still needs further research and improvement.Herein,ceramic cores were prepared using traditional hot injection and vat photopolymerization 3D printing techniques using fused silica,nano-ZrO_(2),and Al_(2)O_(3) powders as starting materials.The 3D printed ceramic core has a typical layered structure with a small pore size and low porosity.Because of the layered structure,the pore area is larger than that of the hot injection ceramic core,the leaching performance has little effect(0.0277 g/min for 3D printing cores,0.298 g/min for hot injection cores).In the X and Y directions,the sintering shrinkage is low(2.7%),but in the Z direction,the shrinkage is large(4.7%).The fracture occurs when the inner layer crack expands and connects with the interlayer crack,forming a stepped fracture in the 3D-printed cores.The bending strength of the 3D printed core at high temperature(1500℃)is 17.3 MPa.These analyses show that the performance of vat photopolymerization 3D-printed ceramic cores can meet the casting requirements of single crystal superalloy blades,which is a potential technology for the preparation of complex structure ceramic cores.The research mode of 3D printing core technology based on the traditional hot injection process provides an effective new idea for promoting the industrial application of 3D printing core technology.展开更多
With high water content,excellent biocompatibility and lubricating properties,and a microstructure similar to that of the extracellular matrix,hydrogel is becoming one of the most promising materials as a substitute f...With high water content,excellent biocompatibility and lubricating properties,and a microstructure similar to that of the extracellular matrix,hydrogel is becoming one of the most promising materials as a substitute for articular cartilage.However,it is a challenge for hydrogel materials to simultaneously satisfy high loading and low friction.Most hydrogels are brittle,with fracture energies of around 10 J·m^(-2),as compared with∼1000 J·m^(-2) for cartilage.A great deal of effort has been devoted to the synthesis of hydrogels with improved mechanical properties,such as increasing the compactness of the polymer network,introducing dynamic non-covalent bonds,and increasing the hydrophobicity of the polymer,all at the expense of the lubricating properties of the hydrogel.Herein,we develop a hydrogel material with anisotropic tubular structures where the compactness gradually decreases and eventually disappears from the surface to the subsurface,achieving a balance between lubrication and load-bearing.The porous layer with hydrophilic carboxyl groups on the surface exhibits extremely low friction(coefficient of friction(COF)∼0.003,1 N;COF∼0.08,20 N)against the hard steel ball,while the bottom layer acts as an excellent load-bearing function.What is more,the gradual transition of the tubular structures between the surface and the subsurface ensures the uniform distribution of friction stress between a lubricating and bearing layers,which endows the material with long-lasting and smooth friction properties.The extraordinary lubricious performance of the hydrogels with anisotropic tubular structure has potential applications in tissue engineering and medical devices.展开更多
基金Project supported by National High-Tech R&D Program of China(2010AA03A401)the National Natural Science Foundation of China(50931001,51241009)
文摘Isotropic magnets were prepared from melt-spun powders at different hot pressing temperatures from 550 to 700 ℃, then upset into fully dense anisotropic magnets at the same die-upsetting temperature of 850 ℃. Die-upset magnets had the characteristics of inhomogeneous microstructure, including well-aligned grains structure and nonaligned grains layers transverse to press direction, which was quasi-periodic layer structure with a total length of 5-15 μm. Nonaligned grains layers were mainly made of large grains and had higher Nd content. To clearly understand the formation of layer structure, the microstructure of isotropic precursors with different hot pressing temperatures and their subsequent die-upset magnets was investigated. A new interpretation for the formation of layer structure was proposed in this paper： the layer structure was correlated to the original ribbon interface which was divided into three types based on the contact forms. Because of the incomplete contact of neighboring ribbons, concentration of stress occurred in the contacted points and the Nd-rich phase was squeezed into interspaces at high temperature under stress. Due to the release of interfacial energy and the fluidity of enough Nd-rich liquid phases, the nonaligned layers with large grains formed both in hot compaction and subsequent hot deformation process. The layer structure affected the magnetic properties of die-upset magnets. With increase of the hot pressing temperature, the nonaligned grains layers became thicker, and the magnetic performance of die-upset magnets decreased. It was necessary to reduce the thickness of large grains layers for the preparation of high-performance die-upset magnets.
文摘多模态图像之间存在显著的非线性强度差异,并且图像会因为噪声而退化,因此,多模态图像自动配准是一项具有挑战性的任务。为了解决这两个问题,本文提出一种多模态图像自动配准方法,该方法分为预配准和精配准两个阶段。在预配准阶段,通过改进SIFT算法来大致对齐多模态图像。在精配准阶段,首先,利用块Harris检测器在预配准后的参考图上提取均匀分布的特征点。然后,通过各向异性结构张量捕捉多模态图像中的结构信息来构建特征描述符,该特征描述符对噪声具有稳健性。更进一步,本文结合张量方向平行度和梯度互信息提出了一种相似度准则(tensor orientation and mutual information,TOMI)。最后,本文用多种模态图像(包括Optical,LiDAR,SAR和Map)来评估提出的方法。试验结果表明,本文提出的方法对非线性强度变化和噪声具有较好的稳健性,并且匹配效果优越。
基金supported financially by the National Natural Science Foundation of China (No.52073297)the Sino-German Mobility Programme (No.M-0424)+2 种基金Zhejiang Provincial Natural Science Foundation of China (No.LR23E030001)the Youth Innovation Promotion Association of Chinese Academy of Sciences (No.2019297)K.C.Wong Education Foundation (No.GJTD-2019-13).
文摘Biomimetic intelligent polymeric hydrogel actuators with cooperative fluorescence-color switchable behaviors are expected to find great potential applications in soft robotics,visual detection/display,and camouflage applications.However,it remains challenging to realize the spatial manipulation of synergistic shape/color-changing behaviors.Herein,we report an interfacial supramolecular assembly(ISA)approach that enables the construction of robust fluorescent polymeric hydrogel actuators with spatially anisotropic structures.On the basis of this ISA approach,diverse 2D/3D soft fluorescent hydrogel actuators,including chameleon-and octopi-shaped ones with spatially anisotropic structures,were facilely assembled from two different fluorescent hydrogel building blocks sharing the same physically cross-linked agar network.Spatially control over synergistic shape/color-changing behaviors was then realized in one single anisotropic hydrogel actuator.The proposed ISA approach is universal and expected to open promising avenues for developing powerful bioinspired intelligent soft actuators/robotics with selective spatial shape/color-changing behaviors.
基金This work was supported by the National Natural Science Foundation of China(Nos.92163209,21821005 and 51932001)the Beijing Natural Science Foundation,China(No.JQ22004).
文摘Multi-fountional hollow structures have emerged as promising platforms for intelligent drug delivery due to their unique properties,such as high loading capacities and programmed drug release.In particular,hollow multishell structures(HoMSs)with multilevel shell and space can regulate the molecular-level interaction between drugs and materials,so as to achieve the temporal-spatial order and sequential release of drugs.The anisotropic hollow structures can control the drug diffusion process by inducing the macroscopic interface flow through autonomous movement,realizing the targeted drug transport and release.In this paper,a key focus will be HoMSs with their temporal-ordered architectures and anisotropic hollow carriers with directional movement.Their synthesis mechanisms,structure-property relationships,smartly programmed drug delivery and biomedical applications will be discussed,providing insights into designing next-generation intelligent drug carriers.
基金supported by the National Key Research and Development Program of China(Nos.2021YFB3702500,2018YFB1106600)the National Science and Technology Major Project(Nos.2019-VII-0019-0161 andY2019-VII-0011-0151)the Fundamental Research Funds for the Central Universities(No.WK5290000003).
文摘With the improvement of aero-engine performance,the preparation of hollow blades of single-crystal superalloys with complex inner cavity cooling structures is becoming increasingly urgent.The ceramic core is the key intermediate part of the preparation and has attracted wide attention.To meet this challenge,new technologies that can make up for the defects of long periods and high costs of fabricating complex structural cores by traditional hot injection technology are needed.Vat photopolymerization 3D printing ceramic technology has been applied to the core field to realize the rapid preparation of complex structural cores.However,the industrial application of this technology still needs further research and improvement.Herein,ceramic cores were prepared using traditional hot injection and vat photopolymerization 3D printing techniques using fused silica,nano-ZrO_(2),and Al_(2)O_(3) powders as starting materials.The 3D printed ceramic core has a typical layered structure with a small pore size and low porosity.Because of the layered structure,the pore area is larger than that of the hot injection ceramic core,the leaching performance has little effect(0.0277 g/min for 3D printing cores,0.298 g/min for hot injection cores).In the X and Y directions,the sintering shrinkage is low(2.7%),but in the Z direction,the shrinkage is large(4.7%).The fracture occurs when the inner layer crack expands and connects with the interlayer crack,forming a stepped fracture in the 3D-printed cores.The bending strength of the 3D printed core at high temperature(1500℃)is 17.3 MPa.These analyses show that the performance of vat photopolymerization 3D-printed ceramic cores can meet the casting requirements of single crystal superalloy blades,which is a potential technology for the preparation of complex structure ceramic cores.The research mode of 3D printing core technology based on the traditional hot injection process provides an effective new idea for promoting the industrial application of 3D printing core technology.
基金This research was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB 0470000)the National Natural Science Foundation of China(22032006,22072169 and 22102201)+3 种基金the National Key Research and Development Program of China(2021YFA0716304)the Key Research Project of Shandong Provincial Natural Science Foundation(ZR2021ZD27)the Gansu Province Basic Research Innovation Group Project(22JR5RA093)the Special Research Assistant Project of the Chinese Academy of Sciences。
文摘With high water content,excellent biocompatibility and lubricating properties,and a microstructure similar to that of the extracellular matrix,hydrogel is becoming one of the most promising materials as a substitute for articular cartilage.However,it is a challenge for hydrogel materials to simultaneously satisfy high loading and low friction.Most hydrogels are brittle,with fracture energies of around 10 J·m^(-2),as compared with∼1000 J·m^(-2) for cartilage.A great deal of effort has been devoted to the synthesis of hydrogels with improved mechanical properties,such as increasing the compactness of the polymer network,introducing dynamic non-covalent bonds,and increasing the hydrophobicity of the polymer,all at the expense of the lubricating properties of the hydrogel.Herein,we develop a hydrogel material with anisotropic tubular structures where the compactness gradually decreases and eventually disappears from the surface to the subsurface,achieving a balance between lubrication and load-bearing.The porous layer with hydrophilic carboxyl groups on the surface exhibits extremely low friction(coefficient of friction(COF)∼0.003,1 N;COF∼0.08,20 N)against the hard steel ball,while the bottom layer acts as an excellent load-bearing function.What is more,the gradual transition of the tubular structures between the surface and the subsurface ensures the uniform distribution of friction stress between a lubricating and bearing layers,which endows the material with long-lasting and smooth friction properties.The extraordinary lubricious performance of the hydrogels with anisotropic tubular structure has potential applications in tissue engineering and medical devices.
