This paper focuses on an estimation of light weighting opportunities for the frame structure of com- mercial road vehicles. This estimation is based on simpli- fied static load cases which play a predominant role for ...This paper focuses on an estimation of light weighting opportunities for the frame structure of com- mercial road vehicles. This estimation is based on simpli- fied static load cases which play a predominant role for the dimensioning of a frame structure and therefore these simplifications are not putting the general validity of the conclusions into question. A comparison of different ma- terials under this scenario shows that light metals do not show any weight reduction advantage in comparison to steel while a material-independent topology optimization has more weight reduction potential for the frame structure than a simple change of materials. Considering the con- straints of part complexity which is directly linked with production and assembly cost, the ladder frame structure has become the current state of the art design. Thus the paper also puts a spotlight on basic rules of node design and vertical load induction in order to keep the weight of such a design as low as possible. Practical examples from manufacturers show that the weight of a commercial vehicle could be reduced by 10%, and main parts of the frame structure could be reduced by 30% using high strength steel in combination with innovative production methods like roll forming.展开更多
A light?weight design method of integrated structural topology and size co?optimization for the force?performance?structure of complex structural parts is presented in this paper. Firstly, the supporting function of a...A light?weight design method of integrated structural topology and size co?optimization for the force?performance?structure of complex structural parts is presented in this paper. Firstly, the supporting function of a complex structural part is built to map the force transmission, where the force exerted areas and constraints are considered as connecting structure and the structural configuration, to determine the part performance as well as the force routines. Then the connecting structure design model, aiming to optimize the static and dynamic performances on connection configuration, is developed, and the optimum design of the characteristic parameters is carried out by means of the collaborative optimization method, namely, the integrated structural topology optimization and size optimization. In this design model, the objective is to maximize the connecting stiffness. Based on the relationship between the force and the structural configuration of a part, the optimal force transmission routine that can meet the performance requirements is obtained using the structural topology optimization technology. Accordingly, the light?weight design of conceptual configuration for complex parts under multi?objective and multi?condition can be realized. Finally, based on the proposed collaborative optimization design method, the optimal performance and optimal structure of the complex parts with light weight are realized, and the reasonable structural unit configuration and size charac?teristic parameters are obtained. A bed structure of gantry?type machining center is designed by using the proposed light?weight structure design method in this paper, as an illustrative example. The bed after the design optimization is lighter 8% than original one, and the rail deformation is reduced by 5%. Moreover, the lightweight design of the bed is achieved with enhanced performance to show the effectiveness of the proposed method.展开更多
Static strength finite element analysis was conducted to decrease the weight of a skeleton vehicle's frame. Results indicated that the maximum stress occurs on the front beam 's variable section area. Dynamic sensit...Static strength finite element analysis was conducted to decrease the weight of a skeleton vehicle's frame. Results indicated that the maximum stress occurs on the front beam 's variable section area. Dynamic sensitivity analysis elucidated the relationship between the maximum stress and the thickness of a particular beam,e. g.,top,middle,and bottom beam. Displacement was analyzed by the key part that influenced the maximum stress. Finally,the new plan using BS960 super-high-strength beam steel and the preferred beam thickness was compared with the original plan. New combinations of beam thickness were introduced on the basis of different purposes; the maximum responding light w eight ratio was 21%.展开更多
Surface metal matrix composites(MMCs)are a group of modern engineered materials where the surface of the material is modified by dispersing secondary phase in the form of particles or fibers and the core of the materi...Surface metal matrix composites(MMCs)are a group of modern engineered materials where the surface of the material is modified by dispersing secondary phase in the form of particles or fibers and the core of the material experience no change in chemical composition and structure.The potential applications of the surface MMCs can be found in automotive,aerospace,biomedical and power industries.Recently,friction stir processing(FSP)technique has been gaining wide popularity in producing surface composites in solid state itself.Magnesium and its alloys being difficult to process metals also have been successfully processed by FSP to fabricate surface MMCs.The aim of the present paper is to provide a comprehensive summary of state-of-the-art in fabricating magnesium based composites by FSP.Influence of the secondary phase particles and grain refinement resulted from FSP on the properties of these composites is also discussed.展开更多
A new type of hybrid welding method called resistance plug welding (RPW) was firstly adopted to achieve the connecting of dissimilar steel, mainly as for the poor welding characteristics of high strength stee...A new type of hybrid welding method called resistance plug welding (RPW) was firstly adopted to achieve the connecting of dissimilar steel, mainly as for the poor welding characteristics of high strength steel produced by increasing carbon, manganese, silicon, etc. Microstructures and mechanical properties of RPW joint were analyzed by optical microscope,micro-hardness test and shear tensile measurement. Experimental results indicate that the RPW joint has a rounded rectangle nugget ^ and the size is larger than elliptical nugget of resistance spot welding (RSW) jo in t; the hardness value of RPW joint is evenly distributed, accordingly there is no hard brittle phases ; the shear tensile strength o f RPW joint increases by 20% in comparison with RSW joint under the same welding conditions.展开更多
In order to solve the problems of the traditional flame detection method, such as low detection accuracy, slow detection speed and lack of real-time detection ability. An improved high speed flame detection method bas...In order to solve the problems of the traditional flame detection method, such as low detection accuracy, slow detection speed and lack of real-time detection ability. An improved high speed flame detection method based on YOLOv7 is proposed. Based on YOLOv7 and combined with ConvNeXtBlock, CN-B network module was constructed, and YOLOv7-CN-B flame detection method was proposed. Compared with the YOLOv7 method, this flame detection method is lighter and has stronger flame feature extraction ability. 2059 open flame data sets labeled with single flame categories were used to avoid the enhancement effect brought by high-quality data sets, so that the comparative experimental effect completely depended on the performance of the flame detection method itself. The results show that the accuracy of YOLOv7-CN-B method is improved by 5% and mAP is improved by 2.1% compared with YOLOv7 method. The detection speed reached 149.25 FPS, and the single detection speed reached 11.9 ms. The experimental results show that the YOLOv7-CN-B method has better performance than the mainstream algorithm.展开更多
Since precise self-position estimation is required for autonomous flight of aerial robots, there has been some studies on self-position estimation of indoor aerial robots. In this study, we tackle the self-position es...Since precise self-position estimation is required for autonomous flight of aerial robots, there has been some studies on self-position estimation of indoor aerial robots. In this study, we tackle the self-position estimation problem by mounting a small downward-facing camera on the chassis of an aerial robot. We obtain robot position by sensing the features on the indoor floor.In this work, we used the vertex points(tile corners) where four tiles on a typical tiled floor connected, as an existing feature of the floor. Furthermore, a small lightweight microcontroller is mounted on the robot to perform image processing for the onboard camera. A lightweight image processing algorithm is developed. So, the real-time image processing could be performed by the microcontroller alone which leads to conduct on-board real time tile corner detection. Furthermore, same microcontroller performs control value calculation for flight commanding. The flight commands are implemented based on the detected tile corner information. The above mentioned all devices are mounted on an actual machine, and the effectiveness of the system was investigated.展开更多
The size effects of microstructure of lattice materials on structural analysis and minimum weight design are studied with extented multiscale finite element method(EMsFEM) in the paper. With the same volume of base ...The size effects of microstructure of lattice materials on structural analysis and minimum weight design are studied with extented multiscale finite element method(EMsFEM) in the paper. With the same volume of base material and configuration, the structural displacement and maximum axial stress of micro-rod of lattice structures with different sizes of microstructure are analyzed and compared.It is pointed out that different from the traditional mathematical homogenization method, EMsFEM is suitable for analyzing the structures which is constituted with lattice materials and composed of quantities of finite-sized micro-rods.The minimum weight design of structures composed of lattice material is studied with downscaling calculation of EMsFEM under stress constraints of micro-rods. The optimal design results show that the weight of the structure increases with the decrease of the size of basic sub-unit cells. The paper presents a new approach for analysis and optimization of lattice materials in complex engineering constructions.展开更多
In recent years,high-entropy alloys(HEAs)have become a research hotspot in materials community,and great progress has been made in exploring various high-performance HEAs.As a special class,the light-weight refractory...In recent years,high-entropy alloys(HEAs)have become a research hotspot in materials community,and great progress has been made in exploring various high-performance HEAs.As a special class,the light-weight refractory high-entropy alloys(RHEAs)own both excellent high-temperature comprehensive properties and low density and have accordingly attracted more and more attention.In this paper,we presented a comprehensive review of the recent progress and status in light-weight RHEAs.Based on an exhausting search of the literature reports,one strategy in terms of phase numbers after preparation was first proposed to classify the light-weight RHEAs into three categories.Then,the status on the fundamental thermodynamic and thermophysical data/databases,computational approaches for alloy designing,and preparation/fabrication techniques of light-weight RHEAs was introduced one after another.After that,the progress on mechanical properties and oxidation/corrosion/wear behaviors of light-weight RHEAs at room and high temperatures was summarized.Finally,the conclusions of this review were drawn.By pointing out the shortcomings of the current research,the follow-up development directions in the field of light-weight RHEAs were also given.展开更多
Carbon fiber is a kind of high-temperature fiber with high modulus and strength characteristics.Carbon fiber material is made of carbon fiber braid with carbon content>90%.Among them,resin-based carbon fiber reinfo...Carbon fiber is a kind of high-temperature fiber with high modulus and strength characteristics.Carbon fiber material is made of carbon fiber braid with carbon content>90%.Among them,resin-based carbon fiber reinforced composite material is often used as automotive structural material.Compared with the A36 steel commonly used in automobiles,the T300/5208 carbon fiber reinforced epoxy resin composite commonly used in automobiles has a higher tensile strength of 2500-3300 MPa and a lower density of 6.25 g/cm 3,showing great performance advantages.In this paper,by analyzing the trend of automobile lightweight,and exploring the development prospects of carbon fiber in the field of automobile lightweight,the literature in the Elsevier database is analyzed by scientific measurement analysis method,and the research hotspot in the field is listed.The relationship between the development of fiber materials and the promotion of policies is analyzed by comparing the number of carbon fiber automobile literature publications and key event nodes.This paper proposes a keyword-based influence calculation method.Through drawing analysis tools of information visualization scientific knowledge map and scientific measurement methods of keyword,it proposes the scientific measurement analysis literature of on-board carbon fiber,explores and discusses some frontier directions of automotive carbon fiber materials.The research provides reference for studying automobile lightweight carbon fiber material.展开更多
In this study,the authors present Buoycrete,a new material and work method invented by the company Boskalis.Buoycrete is a light-weight concrete that is able to float and does not dissolve in water.Buoycrete is based ...In this study,the authors present Buoycrete,a new material and work method invented by the company Boskalis.Buoycrete is a light-weight concrete that is able to float and does not dissolve in water.Buoycrete is based on a unique combination of different materials.This paper will start with an overview of concrete structures in combination with fabrics and will present the structural behavior,construction methods and applications of Buoycrete.It demonstrates that Buoycrete combined with fabric formwork creates new possibilities for a broad kind of applications,for instance,the realization of façade elements,shell structures and civil engineering.展开更多
An extensive experimental-mechanistic study was conducted to reveal the relationship between the light weight deflectometer(LWD)measured deflections and the degree of compaction of pavement base materials.Both laborat...An extensive experimental-mechanistic study was conducted to reveal the relationship between the light weight deflectometer(LWD)measured deflections and the degree of compaction of pavement base materials.Both laboratory experiments and test pits experiments were performed with different types of pavement base materials.The modulus based maximum allowable LWD deflections under different structural and compaction conditions were developed for the most commonly used pavement base aggregate in Indiana.The maximum allowable deflections are based on the equivalent subgrade modulus and the thickness of the layer to be compacted.It is emphasized that the LWD deflections must be measured as soon as the material is compacted or before the moisture content decreases beyond a specified range.Therefore,the maximum allowable deflections are specified in terms of the difference between the actual moisture content and the optimum moisture content.The maximum allowable deflection values provide a sound basis for compaction quality control using LWD devices.展开更多
Considering the challenge of aerodynamic heating,the development of high-performance insulating ce-ramic materials with lightweight and low thermal conductivity is crucially important for aerospace vehi-cles to achiev...Considering the challenge of aerodynamic heating,the development of high-performance insulating ce-ramic materials with lightweight and low thermal conductivity is crucially important for aerospace vehi-cles to achieve flight at high speed for a long time.In this work,macro-porous silicon oxycarbide(SiOC)ceramics with directional pores(DP-SiOC)(mean pore size of 88.1μm)were prepared using polysiloxane precursors via freeze casting and photocrosslinking,followed by pyrolysis.The DP-SiOC samples were lightweight(density∼0.135 g cm^(-3))with a porosity of 90.4%,which showed good shapability through the molding of polysiloxane precursors.The DP-SiOC samples also exhibited an ultra-low thermal con-ductivity of 0.048 W(m K)^(-1)at room temperature,which can also withstand heat treatment at 1200°C for 1 h.In addition,scaffolds with triply periodic minimal surfaces(TPMS)were fabricated using digital light processing(DLP)printing,which was further filled with polysiloxane precursors for increasing the strength of DP-SiOC.The TPMS scaffolds filled with macro-porous SiOC ceramics(TPMS-DP-SiOC)showed good integration between TPMS and macro-pore structures,which had a porosity∼75%and high specific strength of 9.73×10^(3)N m kg^(-1).The thermal conductivity of TPMS-DP-SiOC samples was 0.255 W(m K)^(-1)at room temperature.The biomimetic TPMS-DP-SiOC ceramics developed in this study are likely used for thermal protection systems.展开更多
Wood-derived carbon has a 3D porous framework composed of through channels along the growth direction,which is a suitable matrix for preparing electromagnetic wave(EMW)absorbing materials with low cost,light weight,an...Wood-derived carbon has a 3D porous framework composed of through channels along the growth direction,which is a suitable matrix for preparing electromagnetic wave(EMW)absorbing materials with low cost,light weight,and environmental friendliness.Herein,the carbonized wood decorated by short cone-like NiCo_(2)O_(4)(NiCo_(2)O_(4)@CW)with highly ordered straight-channel architecture was successfully manufactured through a facile calcination procedure.The horizontal arrangement of the through channels of NiCo_(2)O_(4)@CW(H-NiCo_(2)O_(4)@CW)exhibits a strong reflection loss value of-64.0 dB at 10.72 GHz with a thickness of 3.62 mm and a low filling ratio of 26 wt%(with the density of 0.98 g-cnf3),and the effective absorption bandwidth(EAB)is 8.08 GHz(9.92-18.0 GHz)at the thickness of 3.2 mm.The excellent microwave absorption(MA)property was ascribed to the ordered-channel structure with abundant interfaces and defects from NiCo_(2)O_(4)@CW,which could promote the interfacial polarization and dipole polarization.What is more,this advantageous structure increased the multiple reflections and scattering.Finite element analysis(FEA)simulation is carried out to detect the interaction between the prepared material and EMW when the ordered channels are arranged in different directions.This research provides a low-cost,sustainable,and environmentally friendly strategy for using carbonized wood to fabricate microwave absorbers with strong attenuation capabilities and light weight.展开更多
An efficient convolution neural network(CNN) plays a crucial role in various visual tasks like object classification or detection, etc. The most common way to construct a CNN is stacking the same convolution block or ...An efficient convolution neural network(CNN) plays a crucial role in various visual tasks like object classification or detection, etc. The most common way to construct a CNN is stacking the same convolution block or complex connection. These approaches may be efficient but the parameter size and computation(Comp) have explosive growth. So we present a novel architecture called"DLA+", which could obtain the feature from the different stages, and by the newly designed convolution block, could achieve better accuracy, while also dropping the computation six times compared to the baseline. We design some experiments about classification and object detection. On the CIFAR10 and VOC data-sets, we get better precision and faster speed than other architecture. The lightweight network even allows us to deploy to some low-performance device like drone, laptop, etc.展开更多
The growing demand for portable electronic devices means that lightweight power sources are increasingly sought after. Electric double layer capacitors (EDLCs) are promising candidates for use in lightweight power s...The growing demand for portable electronic devices means that lightweight power sources are increasingly sought after. Electric double layer capacitors (EDLCs) are promising candidates for use in lightweight power sources due to their high power densities and outstanding charge/discharge cycling stabilities. Three-dimensional (3D) self-supporting carbon-based materials have been extensively studied for use in lightweight EDLCs. Yet, a major challenge for 3D carbon electrodes is the limited ion diffusion rate in their internal spaces. To address this limitation, hierarchically porous 3D structures that provide additional channels for internal ion diffusion have been proposed. Herein, we report a new chemical method for the synthesis of an ultralight (9.92 mg/cm3) 3D porous carbon foam (PCF) involving carbonization of a glutaraldehyde- cross-linked chitosan aerogel in the presence of potassium carbonate. Electron microscopy images reveal that the carbon foam is an interconnected network of carbon sheets containing uniformly dispersed macropores. In addition, Brunauer-Emmett-Teller measurements confirm the hierarchically porous structure. Electrochemical data show that the PCF electrode can achieve an outstanding gravimetric capacitance of 246.5 F/g at a current density of 0.5 A/g, and a remarkable capacity retention of 67.5% was observed when the current density was increased from 0.5 to 100A/g. A quasi-solid-state symmetric supercapacitor was fabricated via assembly of two pieces of the new PCF and was found to deliver an ultra-high power density of 25 kW/kg at an energy density of 2.8 Wh/kg. This study demonstrates the synthesis of an ultralight and hierarchically porous carbon foam with high capacitive performance.展开更多
Unmanned aerial vehicles(UAV)based remote sensing is an emerging and important data source.Recently,the use of UAVs for remote sensing applications has been rapidly growing owing to their greater availability and the ...Unmanned aerial vehicles(UAV)based remote sensing is an emerging and important data source.Recently,the use of UAVs for remote sensing applications has been rapidly growing owing to their greater availability and the miniaturization of sensors.UAVs are surpassing satellites and aircraft in remote sensing data supply for many local requirements.In comparison with satellite remote sensing data,most UAV remote sensing data is characterized by high resolution,small coverage area,and heterogeneous multi-sources.However,UAVs lack a unified space–time framework and standardized data process.This paper describes a UAV remote sensing data carrier that can be used as an e-commerce platform for data sharing among registered members and a mission planner for new data acquisition.To the best of our knowledge,the data carriers described herein,are the first of their kind.Through seamless docking with UAVs,the data carrier will form a national UAV network,capable of dynamically obtaining very-high-resolution UAV remote sensing images.In practice,a pilot retrieval system of UAV meta data has been developed to provide a catalogue of data product services.展开更多
文摘This paper focuses on an estimation of light weighting opportunities for the frame structure of com- mercial road vehicles. This estimation is based on simpli- fied static load cases which play a predominant role for the dimensioning of a frame structure and therefore these simplifications are not putting the general validity of the conclusions into question. A comparison of different ma- terials under this scenario shows that light metals do not show any weight reduction advantage in comparison to steel while a material-independent topology optimization has more weight reduction potential for the frame structure than a simple change of materials. Considering the con- straints of part complexity which is directly linked with production and assembly cost, the ladder frame structure has become the current state of the art design. Thus the paper also puts a spotlight on basic rules of node design and vertical load induction in order to keep the weight of such a design as low as possible. Practical examples from manufacturers show that the weight of a commercial vehicle could be reduced by 10%, and main parts of the frame structure could be reduced by 30% using high strength steel in combination with innovative production methods like roll forming.
基金Supported by National Science and Technology Major Project(Grant No.2015ZX04014021)
文摘A light?weight design method of integrated structural topology and size co?optimization for the force?performance?structure of complex structural parts is presented in this paper. Firstly, the supporting function of a complex structural part is built to map the force transmission, where the force exerted areas and constraints are considered as connecting structure and the structural configuration, to determine the part performance as well as the force routines. Then the connecting structure design model, aiming to optimize the static and dynamic performances on connection configuration, is developed, and the optimum design of the characteristic parameters is carried out by means of the collaborative optimization method, namely, the integrated structural topology optimization and size optimization. In this design model, the objective is to maximize the connecting stiffness. Based on the relationship between the force and the structural configuration of a part, the optimal force transmission routine that can meet the performance requirements is obtained using the structural topology optimization technology. Accordingly, the light?weight design of conceptual configuration for complex parts under multi?objective and multi?condition can be realized. Finally, based on the proposed collaborative optimization design method, the optimal performance and optimal structure of the complex parts with light weight are realized, and the reasonable structural unit configuration and size charac?teristic parameters are obtained. A bed structure of gantry?type machining center is designed by using the proposed light?weight structure design method in this paper, as an illustrative example. The bed after the design optimization is lighter 8% than original one, and the rail deformation is reduced by 5%. Moreover, the lightweight design of the bed is achieved with enhanced performance to show the effectiveness of the proposed method.
文摘Static strength finite element analysis was conducted to decrease the weight of a skeleton vehicle's frame. Results indicated that the maximum stress occurs on the front beam 's variable section area. Dynamic sensitivity analysis elucidated the relationship between the maximum stress and the thickness of a particular beam,e. g.,top,middle,and bottom beam. Displacement was analyzed by the key part that influenced the maximum stress. Finally,the new plan using BS960 super-high-strength beam steel and the preferred beam thickness was compared with the original plan. New combinations of beam thickness were introduced on the basis of different purposes; the maximum responding light w eight ratio was 21%.
文摘Surface metal matrix composites(MMCs)are a group of modern engineered materials where the surface of the material is modified by dispersing secondary phase in the form of particles or fibers and the core of the material experience no change in chemical composition and structure.The potential applications of the surface MMCs can be found in automotive,aerospace,biomedical and power industries.Recently,friction stir processing(FSP)technique has been gaining wide popularity in producing surface composites in solid state itself.Magnesium and its alloys being difficult to process metals also have been successfully processed by FSP to fabricate surface MMCs.The aim of the present paper is to provide a comprehensive summary of state-of-the-art in fabricating magnesium based composites by FSP.Influence of the secondary phase particles and grain refinement resulted from FSP on the properties of these composites is also discussed.
文摘A new type of hybrid welding method called resistance plug welding (RPW) was firstly adopted to achieve the connecting of dissimilar steel, mainly as for the poor welding characteristics of high strength steel produced by increasing carbon, manganese, silicon, etc. Microstructures and mechanical properties of RPW joint were analyzed by optical microscope,micro-hardness test and shear tensile measurement. Experimental results indicate that the RPW joint has a rounded rectangle nugget ^ and the size is larger than elliptical nugget of resistance spot welding (RSW) jo in t; the hardness value of RPW joint is evenly distributed, accordingly there is no hard brittle phases ; the shear tensile strength o f RPW joint increases by 20% in comparison with RSW joint under the same welding conditions.
文摘In order to solve the problems of the traditional flame detection method, such as low detection accuracy, slow detection speed and lack of real-time detection ability. An improved high speed flame detection method based on YOLOv7 is proposed. Based on YOLOv7 and combined with ConvNeXtBlock, CN-B network module was constructed, and YOLOv7-CN-B flame detection method was proposed. Compared with the YOLOv7 method, this flame detection method is lighter and has stronger flame feature extraction ability. 2059 open flame data sets labeled with single flame categories were used to avoid the enhancement effect brought by high-quality data sets, so that the comparative experimental effect completely depended on the performance of the flame detection method itself. The results show that the accuracy of YOLOv7-CN-B method is improved by 5% and mAP is improved by 2.1% compared with YOLOv7 method. The detection speed reached 149.25 FPS, and the single detection speed reached 11.9 ms. The experimental results show that the YOLOv7-CN-B method has better performance than the mainstream algorithm.
基金supported by Branding Research Fund by Shibaura Institute of Technology(SIT)。
文摘Since precise self-position estimation is required for autonomous flight of aerial robots, there has been some studies on self-position estimation of indoor aerial robots. In this study, we tackle the self-position estimation problem by mounting a small downward-facing camera on the chassis of an aerial robot. We obtain robot position by sensing the features on the indoor floor.In this work, we used the vertex points(tile corners) where four tiles on a typical tiled floor connected, as an existing feature of the floor. Furthermore, a small lightweight microcontroller is mounted on the robot to perform image processing for the onboard camera. A lightweight image processing algorithm is developed. So, the real-time image processing could be performed by the microcontroller alone which leads to conduct on-board real time tile corner detection. Furthermore, same microcontroller performs control value calculation for flight commanding. The flight commands are implemented based on the detected tile corner information. The above mentioned all devices are mounted on an actual machine, and the effectiveness of the system was investigated.
基金supported by the National Natural Science Foundation of China(11372060,10902018,91216201,and 11326005)the National Basic Research Program of China(2011CB610304)the Major National Science and Technology Project(2011ZX02403-002)
文摘The size effects of microstructure of lattice materials on structural analysis and minimum weight design are studied with extented multiscale finite element method(EMsFEM) in the paper. With the same volume of base material and configuration, the structural displacement and maximum axial stress of micro-rod of lattice structures with different sizes of microstructure are analyzed and compared.It is pointed out that different from the traditional mathematical homogenization method, EMsFEM is suitable for analyzing the structures which is constituted with lattice materials and composed of quantities of finite-sized micro-rods.The minimum weight design of structures composed of lattice material is studied with downscaling calculation of EMsFEM under stress constraints of micro-rods. The optimal design results show that the weight of the structure increases with the decrease of the size of basic sub-unit cells. The paper presents a new approach for analysis and optimization of lattice materials in complex engineering constructions.
基金Q.Li acknowledges National Natural Science Foundation of China(No.U2102212)L.Zhang acknowledges the Natural Science Foundation of Hunan Province for Distinguished Young Scholars(No.2021JJ10062)+5 种基金S.Chen acknowledges the Fundamental Research Funds for the Central Universities of Central South University(No.2019zzts486)S.Yang acknowledges the financial support from the Fundamental Research Funds for the Central Universities of Central South University(No.2019zzts050)Postgraduate Scientific Research Innovation Project of Hunan Province(No.CX20190106)Q.Luo acknowledges the Shanghai Rising-Star Program(No.21QA1403200)W.Xie.acknowledges the financial support of National Science Foundation of China(No.52003150)Eastern Young Scholar at Shanghai Institutions of Higher Learning(No.QD2019006).
文摘In recent years,high-entropy alloys(HEAs)have become a research hotspot in materials community,and great progress has been made in exploring various high-performance HEAs.As a special class,the light-weight refractory high-entropy alloys(RHEAs)own both excellent high-temperature comprehensive properties and low density and have accordingly attracted more and more attention.In this paper,we presented a comprehensive review of the recent progress and status in light-weight RHEAs.Based on an exhausting search of the literature reports,one strategy in terms of phase numbers after preparation was first proposed to classify the light-weight RHEAs into three categories.Then,the status on the fundamental thermodynamic and thermophysical data/databases,computational approaches for alloy designing,and preparation/fabrication techniques of light-weight RHEAs was introduced one after another.After that,the progress on mechanical properties and oxidation/corrosion/wear behaviors of light-weight RHEAs at room and high temperatures was summarized.Finally,the conclusions of this review were drawn.By pointing out the shortcomings of the current research,the follow-up development directions in the field of light-weight RHEAs were also given.
基金Supported by the"Science and Technology Innovation Plan",Chinese Academy of Sciences(20194001882)National-level Entrepreneurship and Innovation Training for University Students in 2019(S201912649002).
文摘Carbon fiber is a kind of high-temperature fiber with high modulus and strength characteristics.Carbon fiber material is made of carbon fiber braid with carbon content>90%.Among them,resin-based carbon fiber reinforced composite material is often used as automotive structural material.Compared with the A36 steel commonly used in automobiles,the T300/5208 carbon fiber reinforced epoxy resin composite commonly used in automobiles has a higher tensile strength of 2500-3300 MPa and a lower density of 6.25 g/cm 3,showing great performance advantages.In this paper,by analyzing the trend of automobile lightweight,and exploring the development prospects of carbon fiber in the field of automobile lightweight,the literature in the Elsevier database is analyzed by scientific measurement analysis method,and the research hotspot in the field is listed.The relationship between the development of fiber materials and the promotion of policies is analyzed by comparing the number of carbon fiber automobile literature publications and key event nodes.This paper proposes a keyword-based influence calculation method.Through drawing analysis tools of information visualization scientific knowledge map and scientific measurement methods of keyword,it proposes the scientific measurement analysis literature of on-board carbon fiber,explores and discusses some frontier directions of automotive carbon fiber materials.The research provides reference for studying automobile lightweight carbon fiber material.
基金This research was done at the Baggermaatschappij Boskalis B.V.the Eindhoven University of Technology.
文摘In this study,the authors present Buoycrete,a new material and work method invented by the company Boskalis.Buoycrete is a light-weight concrete that is able to float and does not dissolve in water.Buoycrete is based on a unique combination of different materials.This paper will start with an overview of concrete structures in combination with fabrics and will present the structural behavior,construction methods and applications of Buoycrete.It demonstrates that Buoycrete combined with fabric formwork creates new possibilities for a broad kind of applications,for instance,the realization of façade elements,shell structures and civil engineering.
基金supported in part by the Joint Transportation Research Program administered by the Indiana Department of Transportation and Purdue University。
文摘An extensive experimental-mechanistic study was conducted to reveal the relationship between the light weight deflectometer(LWD)measured deflections and the degree of compaction of pavement base materials.Both laboratory experiments and test pits experiments were performed with different types of pavement base materials.The modulus based maximum allowable LWD deflections under different structural and compaction conditions were developed for the most commonly used pavement base aggregate in Indiana.The maximum allowable deflections are based on the equivalent subgrade modulus and the thickness of the layer to be compacted.It is emphasized that the LWD deflections must be measured as soon as the material is compacted or before the moisture content decreases beyond a specified range.Therefore,the maximum allowable deflections are specified in terms of the difference between the actual moisture content and the optimum moisture content.The maximum allowable deflection values provide a sound basis for compaction quality control using LWD devices.
基金supported by the CAS Interdisciplinary Innova-tion Team Project(No.JCTD-2020-10)of the Chinese Academy of SciencesChina and the Defense Industrial Technology Develop-ment Program(No.JCKY2021130B039).
文摘Considering the challenge of aerodynamic heating,the development of high-performance insulating ce-ramic materials with lightweight and low thermal conductivity is crucially important for aerospace vehi-cles to achieve flight at high speed for a long time.In this work,macro-porous silicon oxycarbide(SiOC)ceramics with directional pores(DP-SiOC)(mean pore size of 88.1μm)were prepared using polysiloxane precursors via freeze casting and photocrosslinking,followed by pyrolysis.The DP-SiOC samples were lightweight(density∼0.135 g cm^(-3))with a porosity of 90.4%,which showed good shapability through the molding of polysiloxane precursors.The DP-SiOC samples also exhibited an ultra-low thermal con-ductivity of 0.048 W(m K)^(-1)at room temperature,which can also withstand heat treatment at 1200°C for 1 h.In addition,scaffolds with triply periodic minimal surfaces(TPMS)were fabricated using digital light processing(DLP)printing,which was further filled with polysiloxane precursors for increasing the strength of DP-SiOC.The TPMS scaffolds filled with macro-porous SiOC ceramics(TPMS-DP-SiOC)showed good integration between TPMS and macro-pore structures,which had a porosity∼75%and high specific strength of 9.73×10^(3)N m kg^(-1).The thermal conductivity of TPMS-DP-SiOC samples was 0.255 W(m K)^(-1)at room temperature.The biomimetic TPMS-DP-SiOC ceramics developed in this study are likely used for thermal protection systems.
基金supported by the National Natural Science Foundation of China(NSFC,Grant Nos.51772060,51372052,and 51621091).
文摘Wood-derived carbon has a 3D porous framework composed of through channels along the growth direction,which is a suitable matrix for preparing electromagnetic wave(EMW)absorbing materials with low cost,light weight,and environmental friendliness.Herein,the carbonized wood decorated by short cone-like NiCo_(2)O_(4)(NiCo_(2)O_(4)@CW)with highly ordered straight-channel architecture was successfully manufactured through a facile calcination procedure.The horizontal arrangement of the through channels of NiCo_(2)O_(4)@CW(H-NiCo_(2)O_(4)@CW)exhibits a strong reflection loss value of-64.0 dB at 10.72 GHz with a thickness of 3.62 mm and a low filling ratio of 26 wt%(with the density of 0.98 g-cnf3),and the effective absorption bandwidth(EAB)is 8.08 GHz(9.92-18.0 GHz)at the thickness of 3.2 mm.The excellent microwave absorption(MA)property was ascribed to the ordered-channel structure with abundant interfaces and defects from NiCo_(2)O_(4)@CW,which could promote the interfacial polarization and dipole polarization.What is more,this advantageous structure increased the multiple reflections and scattering.Finite element analysis(FEA)simulation is carried out to detect the interaction between the prepared material and EMW when the ordered channels are arranged in different directions.This research provides a low-cost,sustainable,and environmentally friendly strategy for using carbonized wood to fabricate microwave absorbers with strong attenuation capabilities and light weight.
基金supported by University Synergy Innovation Program of Anhui Province (No. GXXT-2019-007)Corporative Information Processing and Deep Mining for Intelligent Robot (No. JCYJ20170817155854115)+1 种基金Major Project for New Generation of AI (No.2018AAA0100400)Anhui Provincial Natural Science Foundation (No. 1908085MF206)。
文摘An efficient convolution neural network(CNN) plays a crucial role in various visual tasks like object classification or detection, etc. The most common way to construct a CNN is stacking the same convolution block or complex connection. These approaches may be efficient but the parameter size and computation(Comp) have explosive growth. So we present a novel architecture called"DLA+", which could obtain the feature from the different stages, and by the newly designed convolution block, could achieve better accuracy, while also dropping the computation six times compared to the baseline. We design some experiments about classification and object detection. On the CIFAR10 and VOC data-sets, we get better precision and faster speed than other architecture. The lightweight network even allows us to deploy to some low-performance device like drone, laptop, etc.
基金This work was supported by Jiangsu Government Scholarship for overseas studies, National Nature Science Foundation of China (Nos. 11204266 and 21276220), and Nature Science Foundation of Jiangsu Province (Nos. BK20141262 and BK20140463). The authors thank Dr. Tom Yuzvinsky from University of California, Santa Cruz for SEM images acquisition and acknowledge the W. M. Keck Center for Nanoscale Opto-fluidics for use of the FEI Quanta 3D Dual-beam scanning electron microscope. The authors also acknowledge Prof. Zhonghua Zhang from Shandong University for his help with BET characterization, Prof. Jin Z. Zhang from University of California, Santa Cruz, for offering the access to Reinshaw Raman spectrometer, Mr. Fuxin Wang from Sun Yat-sen University for TEM characterization, Prof. Xiaoxia Liu and Mr. Yu Song from Northeastern University for their generous help with AFM characterization.
文摘The growing demand for portable electronic devices means that lightweight power sources are increasingly sought after. Electric double layer capacitors (EDLCs) are promising candidates for use in lightweight power sources due to their high power densities and outstanding charge/discharge cycling stabilities. Three-dimensional (3D) self-supporting carbon-based materials have been extensively studied for use in lightweight EDLCs. Yet, a major challenge for 3D carbon electrodes is the limited ion diffusion rate in their internal spaces. To address this limitation, hierarchically porous 3D structures that provide additional channels for internal ion diffusion have been proposed. Herein, we report a new chemical method for the synthesis of an ultralight (9.92 mg/cm3) 3D porous carbon foam (PCF) involving carbonization of a glutaraldehyde- cross-linked chitosan aerogel in the presence of potassium carbonate. Electron microscopy images reveal that the carbon foam is an interconnected network of carbon sheets containing uniformly dispersed macropores. In addition, Brunauer-Emmett-Teller measurements confirm the hierarchically porous structure. Electrochemical data show that the PCF electrode can achieve an outstanding gravimetric capacitance of 246.5 F/g at a current density of 0.5 A/g, and a remarkable capacity retention of 67.5% was observed when the current density was increased from 0.5 to 100A/g. A quasi-solid-state symmetric supercapacitor was fabricated via assembly of two pieces of the new PCF and was found to deliver an ultra-high power density of 25 kW/kg at an energy density of 2.8 Wh/kg. This study demonstrates the synthesis of an ultralight and hierarchically porous carbon foam with high capacitive performance.
基金Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA19050501)the National Natural Science Foundation of China(grant number 41771388,41971359)。
文摘Unmanned aerial vehicles(UAV)based remote sensing is an emerging and important data source.Recently,the use of UAVs for remote sensing applications has been rapidly growing owing to their greater availability and the miniaturization of sensors.UAVs are surpassing satellites and aircraft in remote sensing data supply for many local requirements.In comparison with satellite remote sensing data,most UAV remote sensing data is characterized by high resolution,small coverage area,and heterogeneous multi-sources.However,UAVs lack a unified space–time framework and standardized data process.This paper describes a UAV remote sensing data carrier that can be used as an e-commerce platform for data sharing among registered members and a mission planner for new data acquisition.To the best of our knowledge,the data carriers described herein,are the first of their kind.Through seamless docking with UAVs,the data carrier will form a national UAV network,capable of dynamically obtaining very-high-resolution UAV remote sensing images.In practice,a pilot retrieval system of UAV meta data has been developed to provide a catalogue of data product services.