3D printing is widely adopted to quickly produce rock mass models with complex structures in batches,improving the consistency and repeatability of physical modeling.It is necessary to regulate the mechanical properti...3D printing is widely adopted to quickly produce rock mass models with complex structures in batches,improving the consistency and repeatability of physical modeling.It is necessary to regulate the mechanical properties of 3D-printed specimens to make them proportionally similar to natural rocks.This study investigates mechanical properties of 3D-printed rock analogues prepared by furan resin-bonded silica sand particles.The mechanical property regulation of 3D-printed specimens is realized through quantifying its similarity to sandstone,so that analogous deformation characteristics and failure mode are acquired.Considering similarity conversion,uniaxial compressive strength,cohesion and stress–strain relationship curve of 3D-printed specimen are similar to those of sandstone.In the study ranges,the strength of 3D-printed specimen is positively correlated with the additive content,negatively correlated with the sand particle size,and first increases then decreases with the increase of curing temperature.The regulation scheme with optimal similarity quantification index,that is the sand type of 70/140,additive content of 2.5‰and curing temperature of 81.6℃,is determined for preparing 3D-printed sandstone analogues and models.The effectiveness of mechanical property regulation is proved through uniaxial compression contrast tests.This study provides a reference for preparing rock-like specimens and engineering models using 3D printing technology.展开更多
A weld joint is composed of three principal zones viz., base metal, Heat Affected Zone (HAZ), and weld zone. Thus, the variation in mechanical behavior exists not only among these zones, but also from point to point i...A weld joint is composed of three principal zones viz., base metal, Heat Affected Zone (HAZ), and weld zone. Thus, the variation in mechanical behavior exists not only among these zones, but also from point to point in each individual zone. Being destructive in nature, the conventional method of mechanical testing cannot successfully used to estimate the variation in the mechanical behavior at different zones of the weld joint. Moreover, the conventional method of mechanical testing cannot characterize the material using small amount of material. In this respect, Ball Indentation (BI) methodology was considered to be useful approach, since it can characterize the mechanical properties of a material using very small amount of material in non destructive manner. The present work is an attempt to characterize the variation in the mechanical properties among each zone (global variation), and from point to point in each zone (local variation) of the similar weld joint used in nuclear application using BI approach. For this purpose, the similar weld joint of two SS-304 LN pipe lines was investigated using BI approach.展开更多
Three-dimensional(3D)printing technology has been widely used to create artificial rock samples in rock mechanics.While 3D printing can create complex fractures,the material still lacks sufficient similarity to natura...Three-dimensional(3D)printing technology has been widely used to create artificial rock samples in rock mechanics.While 3D printing can create complex fractures,the material still lacks sufficient similarity to natural rock.Extrusion free forming(EFF)is a 3D printing technique that uses clay as the printing material and cures the specimens through high-temperature sintering.In this study,we attempted to use the EFF technology to fabricate artificial rock specimens.The results show the physico-mechanical properties of the specimens are significantly affected by the sintering temperature,while the nozzle diameter and layer thickness also have a certain impact.The specimens are primarily composed of SiO_(2),with mineral compositions similar to that of natural rocks.The density,uniaxial compressive strength(UCS),elastic modulus,and tensile strength of the printed specimens fall in the range of 1.65–2.54 g/cm3,16.46–50.49 MPa,2.17–13.35 GPa,and 0.82–17.18 MPa,respectively.It is capable of simulating different types of rocks,especially mudstone,sandstone,limestone,and gneiss.However,the simulation of hard rocks with UCS exceeding 50 MPa still requires validation.展开更多
Refill friction stir spot welding(RFSSW)provides a novel method to join similar and/or dissimilar metallic materials without a key-hole in the center of the joint.Having the key-hole free characterization,the similar/...Refill friction stir spot welding(RFSSW)provides a novel method to join similar and/or dissimilar metallic materials without a key-hole in the center of the joint.Having the key-hole free characterization,the similar/dissimilar RFSSW joint exhibits remarkable and endurable characteristics,including high shear strength,long fatigue life,and strong corrosion resistance.In the meanwhile,as the key-hole free joint has different microstructures compared with conventional friction stir spot welding,thus the RFSSW joint shall possess different shear and fatigue fracture mechanisms,which needs further investigation.To explore the underlying failure mechanism,the similar/dissimilar metallic material joining parameters and pre-treatment,mechanical properties,as well as fracture mechanisms under this novel technology will be discussed.In details,the welding tool design,welding parameters setting,and the influence of processing on the lap shear and fatigue properties,as well as the corrosion resistance will be mainly discussed.Moreover,the roadmap of RFFSW is also discussed.展开更多
In order to further study the damage and failure mechanism for rock similar materials,this study investigated the mechanical properties and failure characteristics,law of damage space development,and damage evolution ...In order to further study the damage and failure mechanism for rock similar materials,this study investigated the mechanical properties and failure characteristics,law of damage space development,and damage evolution characteristics for rock similar materials with pre-existing cracks of varying length under uniaxial compression load.The equipment used in this study is the self-developed YYW-Ⅱ strain controlled unconfined compression apparatus and the PCIE-8 acoustic emission monitoring system.Results show that,as the length of pre-existing crack increases:(1) the peak and residual strength reduces,and the peak axial strain and the strain during the initial compression phase increases;(2) the major failure mode is changed from shear failure to tensile failure along a vertical plane that passes the middle of the pre-existing crack;(3) The damage increases during the stable and accelerated development stage,and the effect of the pre-existing cracks is more during the accelerated development stage than the stable development stage.展开更多
Coarse graining of complex networks is an important method to study large-scale complex networks, and is also in the focus of network science today. This paper tries to develop a new coarse-graining method for complex...Coarse graining of complex networks is an important method to study large-scale complex networks, and is also in the focus of network science today. This paper tries to develop a new coarse-graining method for complex networks, which is based on the node similarity index. From the information structure of the network node similarity, the coarse-grained network is extracted by defining the local similarity and the global similarity index of nodes. A large number of simulation experiments show that the proposed method can effectively reduce the size of the network, while maintaining some statistical properties of the original network to some extent. Moreover, the proposed method has low computational complexity and allows people to freely choose the size of the reduced networks.展开更多
Objective:In this study,the property combinations(PCs)of single herbs,two-herb combinations,and multi-herb prescriptions were studied to determine that the propertycombination patterns will be associated with these th...Objective:In this study,the property combinations(PCs)of single herbs,two-herb combinations,and multi-herb prescriptions were studied to determine that the propertycombination patterns will be associated with these three levels.Method:By calculating the prescription PC weight,we analyzed the PCs of the single herb coptis rhizome,the two-herb combination of coptis rhizome and scutellaria root,and the classic prescriptions Coptis Decoction to Resolve Toxicity,White Tiger Decoction to Resolve Toxicity,and Peony Decoction,all three of which contain coptis and scutellaria.Results:Calculated results show that cold-bitter-lung,cold-bitter-heart,and cold-bitterstomach are present in both Coptis Decoction and White Tiger Decoction and have the highest PC weights.The weights of coptis and scutellaria in Peony Decoction differs from in their weights in Coptis Decoction and White Tiger Decoction,in that the PCs of highest weights in Peony Decoction are cold-bitter-spleen,cold-bitter-liver,cold-bitter-large intestine,coldsour-liver,and cold-sour-spleen.Conclusion:This novel method for exploring the properties and compatibilities of traditional Chinese herbs helps validate the combination theories of herbs.Application of this method may be valuable in designing new efficacious herbal prescriptions.展开更多
In this paper,for the regularized Hermitian and skew-Hermitian splitting(RHSS)preconditioner introduced by Bai and Benzi(BIT Numer Math 57:287–311,2017)for the solution of saddle-point linear systems,we analyze the s...In this paper,for the regularized Hermitian and skew-Hermitian splitting(RHSS)preconditioner introduced by Bai and Benzi(BIT Numer Math 57:287–311,2017)for the solution of saddle-point linear systems,we analyze the spectral properties of the preconditioned matrix when the regularization matrix is a special Hermitian positive semidefinite matrix which depends on certain parameters.We accurately describe the numbers of eigenvalues clustered at(0,0)and(2,0),if the iteration parameter is close to 0.An estimate about the condition number of the corresponding eigenvector matrix,which partly determines the convergence rate of the RHSS-preconditioned Krylov subspace method,is also studied in this work.展开更多
Seismic oscillations of the “building-building” system which is interconnected buildings built close to each other, and “building-stack-like structure” system which is adjacent and connected in different ways to e...Seismic oscillations of the “building-building” system which is interconnected buildings built close to each other, and “building-stack-like structure” system which is adjacent and connected in different ways to existing building are considered in the paper. Different types of connections, such as dampers, including the ones suggested by the authors, are studied. Seismic impact is given as a harmonic function and various existing accelerograms, including synthesized ones. Distinctive feature of this paper from previously published ones [1] [2] is the fact that the emphasis falls on the influence of soil-foundation interaction properties, which are described using various models of load-displacement connections. Calculation results are compared in the case of representation of the building as concentrated masses and spatial systems. Ways to reduce seismic response of buildings during the earthquakes are pointed out. Results of experimental studies are given in the paper and are compared with calculations.展开更多
Nonlocal property is an important feature of natural images,which means that the patch matrix formed by similar image patches is low-rank.Meanwhile,learning good image priors is of great importance for image denoising...Nonlocal property is an important feature of natural images,which means that the patch matrix formed by similar image patches is low-rank.Meanwhile,learning good image priors is of great importance for image denoising.In this paper,we combine the image self-similarity with EPLL(Expected patch log likelihood)method,and propose an EPLL denoising model based on internal and external image similarity to improve the preservation of image details.The experiment results show that the validity of our method is proved from two aspects of visual and numerical results.展开更多
Increasing size of wind turbine and deep water deployment have raised the issue of appropriate selection of the most suitable support structure to make offshore wind energy cost competitive.The paper presents an optim...Increasing size of wind turbine and deep water deployment have raised the issue of appropriate selection of the most suitable support structure to make offshore wind energy cost competitive.The paper presents an optimization methodology for decision making process of bottom mounted supports of offshore wind turbines (OWTs) through reasonable engineering attributes derivation.Mathematic models of support structures are reduced by the generalized single-degree-of-freedom theory with relatively fewer structural parameters.Soft-stiff design optimization based on dynamic properties of OWTs is performed for monopile and lattice supports with different wind turbines,water depth and hub height.Attributes of support structures,wind turbines and environment conditions are applied in the multi-criteria decision making method——TOPSIS for benchmarking of those options.The results illustrate the effectiveness of the proposed optimazation methodology combined with economical and environmental attributes together.展开更多
基金the National Natural Science Foundation of China(Nos.51988101 and 42007262).
文摘3D printing is widely adopted to quickly produce rock mass models with complex structures in batches,improving the consistency and repeatability of physical modeling.It is necessary to regulate the mechanical properties of 3D-printed specimens to make them proportionally similar to natural rocks.This study investigates mechanical properties of 3D-printed rock analogues prepared by furan resin-bonded silica sand particles.The mechanical property regulation of 3D-printed specimens is realized through quantifying its similarity to sandstone,so that analogous deformation characteristics and failure mode are acquired.Considering similarity conversion,uniaxial compressive strength,cohesion and stress–strain relationship curve of 3D-printed specimen are similar to those of sandstone.In the study ranges,the strength of 3D-printed specimen is positively correlated with the additive content,negatively correlated with the sand particle size,and first increases then decreases with the increase of curing temperature.The regulation scheme with optimal similarity quantification index,that is the sand type of 70/140,additive content of 2.5‰and curing temperature of 81.6℃,is determined for preparing 3D-printed sandstone analogues and models.The effectiveness of mechanical property regulation is proved through uniaxial compression contrast tests.This study provides a reference for preparing rock-like specimens and engineering models using 3D printing technology.
文摘A weld joint is composed of three principal zones viz., base metal, Heat Affected Zone (HAZ), and weld zone. Thus, the variation in mechanical behavior exists not only among these zones, but also from point to point in each individual zone. Being destructive in nature, the conventional method of mechanical testing cannot successfully used to estimate the variation in the mechanical behavior at different zones of the weld joint. Moreover, the conventional method of mechanical testing cannot characterize the material using small amount of material. In this respect, Ball Indentation (BI) methodology was considered to be useful approach, since it can characterize the mechanical properties of a material using very small amount of material in non destructive manner. The present work is an attempt to characterize the variation in the mechanical properties among each zone (global variation), and from point to point in each zone (local variation) of the similar weld joint used in nuclear application using BI approach. For this purpose, the similar weld joint of two SS-304 LN pipe lines was investigated using BI approach.
基金financially supported by the Beijing Natural Science Foundation for Young Scientists(Grant No.8214052)the Talent Fund of Beijing Jiaotong University(Grant No.2021RC226)the State Key Laboratory for GeoMechanics and Deep Underground Engineering,China University of Mining and Technology(Grant No.SKLGDUEK2115).
文摘Three-dimensional(3D)printing technology has been widely used to create artificial rock samples in rock mechanics.While 3D printing can create complex fractures,the material still lacks sufficient similarity to natural rock.Extrusion free forming(EFF)is a 3D printing technique that uses clay as the printing material and cures the specimens through high-temperature sintering.In this study,we attempted to use the EFF technology to fabricate artificial rock specimens.The results show the physico-mechanical properties of the specimens are significantly affected by the sintering temperature,while the nozzle diameter and layer thickness also have a certain impact.The specimens are primarily composed of SiO_(2),with mineral compositions similar to that of natural rocks.The density,uniaxial compressive strength(UCS),elastic modulus,and tensile strength of the printed specimens fall in the range of 1.65–2.54 g/cm3,16.46–50.49 MPa,2.17–13.35 GPa,and 0.82–17.18 MPa,respectively.It is capable of simulating different types of rocks,especially mudstone,sandstone,limestone,and gneiss.However,the simulation of hard rocks with UCS exceeding 50 MPa still requires validation.
基金This work was supported by International Science and Technology Cooperation Project of Guangdong Province(Grant No.2022A0505050054)Innovation and Technology Fund(ITF)(Grant No.ITP/021/19AP)National Natural Science Foundation of China(Grant No.51905112).
文摘Refill friction stir spot welding(RFSSW)provides a novel method to join similar and/or dissimilar metallic materials without a key-hole in the center of the joint.Having the key-hole free characterization,the similar/dissimilar RFSSW joint exhibits remarkable and endurable characteristics,including high shear strength,long fatigue life,and strong corrosion resistance.In the meanwhile,as the key-hole free joint has different microstructures compared with conventional friction stir spot welding,thus the RFSSW joint shall possess different shear and fatigue fracture mechanisms,which needs further investigation.To explore the underlying failure mechanism,the similar/dissimilar metallic material joining parameters and pre-treatment,mechanical properties,as well as fracture mechanisms under this novel technology will be discussed.In details,the welding tool design,welding parameters setting,and the influence of processing on the lap shear and fatigue properties,as well as the corrosion resistance will be mainly discussed.Moreover,the roadmap of RFFSW is also discussed.
基金This paper is an extended version of a published conference paper Li et al.(2017)this paper gets its funding from Project(51734007)+1 种基金supported by National Natural Science Foundation of ChinaWe would also like to acknowledge the editor-in-chief,editors and the anonymous reviewers for their valuable comments,which have greatly improved this paper.
文摘In order to further study the damage and failure mechanism for rock similar materials,this study investigated the mechanical properties and failure characteristics,law of damage space development,and damage evolution characteristics for rock similar materials with pre-existing cracks of varying length under uniaxial compression load.The equipment used in this study is the self-developed YYW-Ⅱ strain controlled unconfined compression apparatus and the PCIE-8 acoustic emission monitoring system.Results show that,as the length of pre-existing crack increases:(1) the peak and residual strength reduces,and the peak axial strain and the strain during the initial compression phase increases;(2) the major failure mode is changed from shear failure to tensile failure along a vertical plane that passes the middle of the pre-existing crack;(3) The damage increases during the stable and accelerated development stage,and the effect of the pre-existing cracks is more during the accelerated development stage than the stable development stage.
文摘Coarse graining of complex networks is an important method to study large-scale complex networks, and is also in the focus of network science today. This paper tries to develop a new coarse-graining method for complex networks, which is based on the node similarity index. From the information structure of the network node similarity, the coarse-grained network is extracted by defining the local similarity and the global similarity index of nodes. A large number of simulation experiments show that the proposed method can effectively reduce the size of the network, while maintaining some statistical properties of the original network to some extent. Moreover, the proposed method has low computational complexity and allows people to freely choose the size of the reduced networks.
基金support of this work by the National Natural Science Foundation of China(No.81430094,81173568,81373985).
文摘Objective:In this study,the property combinations(PCs)of single herbs,two-herb combinations,and multi-herb prescriptions were studied to determine that the propertycombination patterns will be associated with these three levels.Method:By calculating the prescription PC weight,we analyzed the PCs of the single herb coptis rhizome,the two-herb combination of coptis rhizome and scutellaria root,and the classic prescriptions Coptis Decoction to Resolve Toxicity,White Tiger Decoction to Resolve Toxicity,and Peony Decoction,all three of which contain coptis and scutellaria.Results:Calculated results show that cold-bitter-lung,cold-bitter-heart,and cold-bitterstomach are present in both Coptis Decoction and White Tiger Decoction and have the highest PC weights.The weights of coptis and scutellaria in Peony Decoction differs from in their weights in Coptis Decoction and White Tiger Decoction,in that the PCs of highest weights in Peony Decoction are cold-bitter-spleen,cold-bitter-liver,cold-bitter-large intestine,coldsour-liver,and cold-sour-spleen.Conclusion:This novel method for exploring the properties and compatibilities of traditional Chinese herbs helps validate the combination theories of herbs.Application of this method may be valuable in designing new efficacious herbal prescriptions.
基金The work is partially supported by the National Natural Science Foundation of China (No. 11801362).
文摘In this paper,for the regularized Hermitian and skew-Hermitian splitting(RHSS)preconditioner introduced by Bai and Benzi(BIT Numer Math 57:287–311,2017)for the solution of saddle-point linear systems,we analyze the spectral properties of the preconditioned matrix when the regularization matrix is a special Hermitian positive semidefinite matrix which depends on certain parameters.We accurately describe the numbers of eigenvalues clustered at(0,0)and(2,0),if the iteration parameter is close to 0.An estimate about the condition number of the corresponding eigenvector matrix,which partly determines the convergence rate of the RHSS-preconditioned Krylov subspace method,is also studied in this work.
文摘Seismic oscillations of the “building-building” system which is interconnected buildings built close to each other, and “building-stack-like structure” system which is adjacent and connected in different ways to existing building are considered in the paper. Different types of connections, such as dampers, including the ones suggested by the authors, are studied. Seismic impact is given as a harmonic function and various existing accelerograms, including synthesized ones. Distinctive feature of this paper from previously published ones [1] [2] is the fact that the emphasis falls on the influence of soil-foundation interaction properties, which are described using various models of load-displacement connections. Calculation results are compared in the case of representation of the building as concentrated masses and spatial systems. Ways to reduce seismic response of buildings during the earthquakes are pointed out. Results of experimental studies are given in the paper and are compared with calculations.
基金This work was partly supported by the National Natural Science Foundation of China under Grants 61672293.
文摘Nonlocal property is an important feature of natural images,which means that the patch matrix formed by similar image patches is low-rank.Meanwhile,learning good image priors is of great importance for image denoising.In this paper,we combine the image self-similarity with EPLL(Expected patch log likelihood)method,and propose an EPLL denoising model based on internal and external image similarity to improve the preservation of image details.The experiment results show that the validity of our method is proved from two aspects of visual and numerical results.
基金Supported by the National Natural Science Foundation of China (No.51309209,51279186) and the National Basic Research Program of China (No.2011CB013704).
文摘Increasing size of wind turbine and deep water deployment have raised the issue of appropriate selection of the most suitable support structure to make offshore wind energy cost competitive.The paper presents an optimization methodology for decision making process of bottom mounted supports of offshore wind turbines (OWTs) through reasonable engineering attributes derivation.Mathematic models of support structures are reduced by the generalized single-degree-of-freedom theory with relatively fewer structural parameters.Soft-stiff design optimization based on dynamic properties of OWTs is performed for monopile and lattice supports with different wind turbines,water depth and hub height.Attributes of support structures,wind turbines and environment conditions are applied in the multi-criteria decision making method——TOPSIS for benchmarking of those options.The results illustrate the effectiveness of the proposed optimazation methodology combined with economical and environmental attributes together.