A new type of beam-to-column connection for steel moment flames, designated as a ＂self-centering connection,＂ is studied. In this connection, bolted top-and-seat angles, and post-tensioned （PT） high-strength steel...A new type of beam-to-column connection for steel moment flames, designated as a ＂self-centering connection,＂ is studied. In this connection, bolted top-and-seat angles, and post-tensioned （PT） high-strength steel strands running along the beam are used. The PT strands tie the beam flanges on the column flange to resist moment and provide self-centering force. After an earthquake, the connections have zero deformation, and can be restored to their original status by simply replacing the angles. Four full-scale connections were tested under cyclic loading. The strength, energy-dissipation capacity, hysteresis curve, as well as angles and PT strands behavior of the connections are investigated. A general FEM analysis program called ABAQUS 6.9 is adopted to model the four test specimens. The numerical and test results match very well. Both the test and analysis results suggest that： （1） the columns and beams remain elastic while the angles sustain plastic deformations for energy dissipation when the rotation of the beam related to the column equals 0.05 tad, （2） the energy dissipation capacity is enhanced when the thickness of the angle is increased, and （3） the number of PT strands has a significant influence on the behavior of the connections, whereas the distance between the strands is not as important to the performance of the connection.展开更多
This study numerically investigates the seismic response of a nine-story self-centering concentrically braced frame building incorporating force-limiting connections between the floor system and the lateral force-resi...This study numerically investigates the seismic response of a nine-story self-centering concentrically braced frame building incorporating force-limiting connections between the floor system and the lateral force-resisting system.Nonlinear earthquake simulations are conducted under design basis earthquake ground motions,and the results are compared against a baseline model with rigid-elastic connections.The study discusses connection design considerations and evaluates the effectiveness of force-limiting connections in mitigating higher-mode effects.The findings show that force-limiting connections significantly reduce the magnitude and variability of floor accelerations,brace forces,and connection forces,while maintaining comparable story drifts.limiting Force-connections primarily reduce the contribution of higher-mode responses,while the controlled rocking base mechanism modifies the first-mode response.Overall,the reduced dispersion in structural response improves the reliability of seismic design and enhances resilience by minimizing damage to both structural components and acceleration-sensitive nonstructural elements.展开更多
Background:Partial anomalous pulmonary venous connection(PAPVC)is frequently associated with atrial septal defect(ASD),especially sinus venosus defect(SVD).Although Waggstaffe described the pathology of SVDs in 1868,t...Background:Partial anomalous pulmonary venous connection(PAPVC)is frequently associated with atrial septal defect(ASD),especially sinus venosus defect(SVD).Although Waggstaffe described the pathology of SVDs in 1868,the exact anatomic features and the nature of SVD remains controversial.SVDs with no posterior atrial rim were observed in recent years.However,no studies suggested that absence of the residual posterior atrial septal tissue might be the key feature of SVD.The aims of this study were to investigate if absence of posterior rim of atrial septum played a crucial role in patients with SVD.Methods:From January 2011 to December 2019,256 children with PAPVC combined ASD and 878 children with isolated ASD who underwent corrective cardiac surgery were consecutively enrolled.Comprehensive review of preoperative transthoracic echocardiography,computed-tomography images and surgical findings were performed by experienced pediatric cardiologists.The subtypes of PAPVC,locations and types of ASD,and presence of posterior atrial rim of associated ASD were investigated.Results:PAPVC was right-sided in 244 children,left-sided in 6 children,and bilateral in 6 children.In PAPVC cases,ASD without posterior atrial rim existed in 226 SVD cases.ASD without posterior atrial septum only existed in cases with one or more right pulmonary veins returning to right atrium(RA)or to RA-superior vena cava junction.In cases with isolated ASD,there were 3 SVD,and the other 875 cases were secundum ASD.Conclusions:ASD without posterior atrial rims was associated with one or more right pulmonary veins returning to RA or RA-superior venous cava(SVC)junction.For SVD,the key feature is that the defect is in the posterior of the interatrial septum with no posterior septal rim,rather than adjacent to the SVC or to the inferior vena cava.展开更多
Superelastic shape memory alloys( SMAs) have the ability to recover their original shape after experiencing large strains. End-plate connection with using superelastic long shank SMA bolts is proposed in this paper. B...Superelastic shape memory alloys( SMAs) have the ability to recover their original shape after experiencing large strains. End-plate connection with using superelastic long shank SMA bolts is proposed in this paper. By using strong beam-weak bolt cluster design methodology and special configurations to strength beam ends,a superelastic hinge is expected to form in column flange. To validate the mechanical behavior of the proposed beam-to-column connection,both quasi-static tests and numerical analysis are conducted with cyclic transverse loads applied on the beam ends. The results indicate the connection deformations concentrate on the long shank SMA bolts upon loading and the bolt cluster rotates around the axis near beam flange. By using the super elastic effect,the SMA bolts recover most elongations and the connection recovers to its original shape after experiencing 0. 02 rad interstorey drift angle. The connection shows obvious self-centering properties.展开更多
Functional connectivity has emerged as a promising approach to study the functional organisation of the brain and to define features for prediction of brain state. The most widely used method for inferring functional ...Functional connectivity has emerged as a promising approach to study the functional organisation of the brain and to define features for prediction of brain state. The most widely used method for inferring functional connectivity is Pearson＇s correlation, but it cannot differentiate direct and indirect effects. This disadvantage is often avoided by computing the partial correlation between two regions controlling all other regions, but this method suffers from Berkson＇s paradox. Some advanced methods, such as regularised inverse covariance, have been applied. However, these methods usually depend on some parameters. Here we propose use of minimum partial correlation as a parameter-free measure for the skeleton of functional connectivity in functional magnetic resonance imaging （flVIRI）. The minimum partial correlation between two regions is the minimum of absolute values of partial correlations by controlling all possible subsets of other regions. Theoretically, there is a direct effect between two regions if and only if their minimum partial correlation is non-zero under faithfulness and Gaussian assumptions. The elastic PC-algorithm is designed to efficiently approximate minimum partial correlation within a computational time budget. The simulation study shows that the proposed method outperforms others in most cases and its application is illustrated using a resting-state fMRI dataset from the human connectome project.展开更多
Novel distributed parameter neural networks are proposed for solving partial differential equations, and their dynamic performances are studied in Hilbert space. The locally connected neural networks are obtained by s...Novel distributed parameter neural networks are proposed for solving partial differential equations, and their dynamic performances are studied in Hilbert space. The locally connected neural networks are obtained by separating distributed parameter neural networks. Two simulations are also given. Both theoretical and computed results illustrate that the distributed parameter neural networks are effective and efficient for solving partial differential equation problems.展开更多
The effects o f important parameters (beam reinforcing plates, initial post-tensioning, and material properties o f steel angles) on the behavior o f hexagonal castellated beams in post-tensioned self-centering (PTSC)...The effects o f important parameters (beam reinforcing plates, initial post-tensioning, and material properties o f steel angles) on the behavior o f hexagonal castellated beams in post-tensioned self-centering (PTSC) connections undergone cyclic loading up to 4% lateral drift have been investigated by finite element (FE) analysis using ABAQUS. The PTSC connection is comprised o f bolted top and bottom angles as energy dissipaters and steel strands to provide self-centering capacity. The FE analysis has also been validated against the experimental test. The new formulations derived from analytical method has been proposed to predict bending moment o f PTSC connections. The web-post buckling in hexagonal castellated beams has been identified as the dominant failure mode when excessive initial post-tensioning force is applied to reach greater bending moment resistance, so it is required to limit the highest initial post-tensioning force to prevent this failure. Furthermore, properties o f steel material has been simulated using bilinear elastoplastic modeling with 1.5% strain-hardening which has perfectly matched with the real material of steel angles. It is recommended to avoid using steel angles with high yielding strength since they lead to the yielding o f bolt shank. The necessity o f reinforcing plates to prevent beam flange from local buckling has been reaffirmed.展开更多
In the paper,the authors collect,discuss,and find out several connections,equivalences,closed-form formulas,and combinatorial identities concerning partial Bell polynomials,falling factorials,rising factorials,extende...In the paper,the authors collect,discuss,and find out several connections,equivalences,closed-form formulas,and combinatorial identities concerning partial Bell polynomials,falling factorials,rising factorials,extended binomial coefficients,and the Stirling numbers of the first and second kinds.These results are new,interesting,important,useful,and applicable in combinatorial number theory.展开更多
This study proposes a new post-tensioned precast bridge column(PT-PBC)with a socket connection.Compared to conventional PBCs connected by PT tendons,the combination of the PT tendons with the socket connection can avo...This study proposes a new post-tensioned precast bridge column(PT-PBC)with a socket connection.Compared to conventional PBCs connected by PT tendons,the combination of the PT tendons with the socket connection can avoid tensioning the PT tendons on site,which further accelerates construction speed while improving construction quality and safety.In addition,compared to conventional PBCs with a socket connection,a rocking interface can avoid the formation of a plastic hinge in a column,which greatly alleviates seismic damage to that area.One specimen for quasi-static testing is used to validate the feasibility of this connection type.Subsequently,finite element models(FEM)are established to systematically predict the responses of the proposed columns under lateral cyclic loading.The accuracy of the FEM is verified through quasistatic testing.Next,the influences of the key design parameters of the PT-PBC,including the area ratio and prestress level of the PT tendons,the area ratio of energy dissipation(ED)steel rebars,and the total axial compression ratio on the seismic performances of PT-PBC are systematically investigated.The use of shape memory alloy(SMA)rods as energy dissipation devices and their performances also are investigated.The results show that increasing the area ratio and prestress level of PT tendons has an overall positive impact on the self-centering capacity of the column.The prestress level of PT tendons should be kept between 35%and 55%,depending on different conditions.The total compression axial ratio of the columns should be maintained between 0.3 and 0.4.Both ED steel rebars and SMA rods can boost the column’s energy dissipation capacity,while SMA rods can reduce residual deformation due to their inherent mechanical properties.展开更多
基金National Natural Science Foundation of China under Nos.50808107,51178250 and 51261120377
文摘A new type of beam-to-column connection for steel moment flames, designated as a ＂self-centering connection,＂ is studied. In this connection, bolted top-and-seat angles, and post-tensioned （PT） high-strength steel strands running along the beam are used. The PT strands tie the beam flanges on the column flange to resist moment and provide self-centering force. After an earthquake, the connections have zero deformation, and can be restored to their original status by simply replacing the angles. Four full-scale connections were tested under cyclic loading. The strength, energy-dissipation capacity, hysteresis curve, as well as angles and PT strands behavior of the connections are investigated. A general FEM analysis program called ABAQUS 6.9 is adopted to model the four test specimens. The numerical and test results match very well. Both the test and analysis results suggest that： （1） the columns and beams remain elastic while the angles sustain plastic deformations for energy dissipation when the rotation of the beam related to the column equals 0.05 tad, （2） the energy dissipation capacity is enhanced when the thickness of the angle is increased, and （3） the number of PT strands has a significant influence on the behavior of the connections, whereas the distance between the strands is not as important to the performance of the connection.
基金financial support provided by Lehigh University,the Advanced Technology for Large Structural Systems(ATLSS)Engineering Research Center,and the Department of Structural Engineering at the University of California,San Diegolarge research team led by Professor Robert B.Fleischman under the project“NEESR:Inertial Force-Limiting Floor Anchorage Systems for Seismic Resistant Building Structures”with the support of grants from the National Science Foundation,award no.CMMI-1135033in the George E.Brown,Jr.Network for Earthquake gineering En-Simulation Research(NEESR)program and award no.CMMI-0402490 for the George E.Brown,Jr.Network for Earthquake ing Engineer-Simulation(NEES)consortium operations.
文摘This study numerically investigates the seismic response of a nine-story self-centering concentrically braced frame building incorporating force-limiting connections between the floor system and the lateral force-resisting system.Nonlinear earthquake simulations are conducted under design basis earthquake ground motions,and the results are compared against a baseline model with rigid-elastic connections.The study discusses connection design considerations and evaluates the effectiveness of force-limiting connections in mitigating higher-mode effects.The findings show that force-limiting connections significantly reduce the magnitude and variability of floor accelerations,brace forces,and connection forces,while maintaining comparable story drifts.limiting Force-connections primarily reduce the contribution of higher-mode responses,while the controlled rocking base mechanism modifies the first-mode response.Overall,the reduced dispersion in structural response improves the reliability of seismic design and enhances resilience by minimizing damage to both structural components and acceleration-sensitive nonstructural elements.
基金The current study was supported by the National Key R&D Program of China[2018YFC1002600]Science and Technology Planning Project of Guangdong Province[Nos.2018B090944002,2019B020230003 and 2018KJY2017]+1 种基金Guangdong Peak Project of Guangdong Province[DFJH201802]the Shenzhen San-Ming Project.
文摘Background:Partial anomalous pulmonary venous connection(PAPVC)is frequently associated with atrial septal defect(ASD),especially sinus venosus defect(SVD).Although Waggstaffe described the pathology of SVDs in 1868,the exact anatomic features and the nature of SVD remains controversial.SVDs with no posterior atrial rim were observed in recent years.However,no studies suggested that absence of the residual posterior atrial septal tissue might be the key feature of SVD.The aims of this study were to investigate if absence of posterior rim of atrial septum played a crucial role in patients with SVD.Methods:From January 2011 to December 2019,256 children with PAPVC combined ASD and 878 children with isolated ASD who underwent corrective cardiac surgery were consecutively enrolled.Comprehensive review of preoperative transthoracic echocardiography,computed-tomography images and surgical findings were performed by experienced pediatric cardiologists.The subtypes of PAPVC,locations and types of ASD,and presence of posterior atrial rim of associated ASD were investigated.Results:PAPVC was right-sided in 244 children,left-sided in 6 children,and bilateral in 6 children.In PAPVC cases,ASD without posterior atrial rim existed in 226 SVD cases.ASD without posterior atrial septum only existed in cases with one or more right pulmonary veins returning to right atrium(RA)or to RA-superior vena cava junction.In cases with isolated ASD,there were 3 SVD,and the other 875 cases were secundum ASD.Conclusions:ASD without posterior atrial rims was associated with one or more right pulmonary veins returning to RA or RA-superior venous cava(SVC)junction.For SVD,the key feature is that the defect is in the posterior of the interatrial septum with no posterior septal rim,rather than adjacent to the SVC or to the inferior vena cava.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50808084)
文摘Superelastic shape memory alloys( SMAs) have the ability to recover their original shape after experiencing large strains. End-plate connection with using superelastic long shank SMA bolts is proposed in this paper. By using strong beam-weak bolt cluster design methodology and special configurations to strength beam ends,a superelastic hinge is expected to form in column flange. To validate the mechanical behavior of the proposed beam-to-column connection,both quasi-static tests and numerical analysis are conducted with cyclic transverse loads applied on the beam ends. The results indicate the connection deformations concentrate on the long shank SMA bolts upon loading and the bolt cluster rotates around the axis near beam flange. By using the super elastic effect,the SMA bolts recover most elongations and the connection recovers to its original shape after experiencing 0. 02 rad interstorey drift angle. The connection shows obvious self-centering properties.
基金WU-Minn Consortium (Principal Investigators: David Van Essen and Kamil Ugurbil, 1U54MH091657) funded by the 16 NIH Institutes and Centers that support the NIH Blueprint for Neuroscience Researchby the Mc Donnell Center for Systems Neuroscience at Washington University+1 种基金support from the Imperial College NIHR Biomedical Research Centrepersonal support from the Edmond Safra Foundation and Lily Safra
文摘Functional connectivity has emerged as a promising approach to study the functional organisation of the brain and to define features for prediction of brain state. The most widely used method for inferring functional connectivity is Pearson＇s correlation, but it cannot differentiate direct and indirect effects. This disadvantage is often avoided by computing the partial correlation between two regions controlling all other regions, but this method suffers from Berkson＇s paradox. Some advanced methods, such as regularised inverse covariance, have been applied. However, these methods usually depend on some parameters. Here we propose use of minimum partial correlation as a parameter-free measure for the skeleton of functional connectivity in functional magnetic resonance imaging （flVIRI）. The minimum partial correlation between two regions is the minimum of absolute values of partial correlations by controlling all possible subsets of other regions. Theoretically, there is a direct effect between two regions if and only if their minimum partial correlation is non-zero under faithfulness and Gaussian assumptions. The elastic PC-algorithm is designed to efficiently approximate minimum partial correlation within a computational time budget. The simulation study shows that the proposed method outperforms others in most cases and its application is illustrated using a resting-state fMRI dataset from the human connectome project.
文摘Novel distributed parameter neural networks are proposed for solving partial differential equations, and their dynamic performances are studied in Hilbert space. The locally connected neural networks are obtained by separating distributed parameter neural networks. Two simulations are also given. Both theoretical and computed results illustrate that the distributed parameter neural networks are effective and efficient for solving partial differential equation problems.
文摘The effects o f important parameters (beam reinforcing plates, initial post-tensioning, and material properties o f steel angles) on the behavior o f hexagonal castellated beams in post-tensioned self-centering (PTSC) connections undergone cyclic loading up to 4% lateral drift have been investigated by finite element (FE) analysis using ABAQUS. The PTSC connection is comprised o f bolted top and bottom angles as energy dissipaters and steel strands to provide self-centering capacity. The FE analysis has also been validated against the experimental test. The new formulations derived from analytical method has been proposed to predict bending moment o f PTSC connections. The web-post buckling in hexagonal castellated beams has been identified as the dominant failure mode when excessive initial post-tensioning force is applied to reach greater bending moment resistance, so it is required to limit the highest initial post-tensioning force to prevent this failure. Furthermore, properties o f steel material has been simulated using bilinear elastoplastic modeling with 1.5% strain-hardening which has perfectly matched with the real material of steel angles. It is recommended to avoid using steel angles with high yielding strength since they lead to the yielding o f bolt shank. The necessity o f reinforcing plates to prevent beam flange from local buckling has been reaffirmed.
基金supported in part by the National Natural Science Foundation of China(Grant No.12061033)by the Research Program of Science and Technology at Universities of Inner Mongolia Autonomous Region(Grants No.NJZY20119)by the Natural Science Foundation of Inner Mongolia(Grant No.2019MS01007),China.
文摘In the paper,the authors collect,discuss,and find out several connections,equivalences,closed-form formulas,and combinatorial identities concerning partial Bell polynomials,falling factorials,rising factorials,extended binomial coefficients,and the Stirling numbers of the first and second kinds.These results are new,interesting,important,useful,and applicable in combinatorial number theory.
基金Natural Science Foundation of China under Grant No.52178449,the Beijing Natural Science Foundation under Grant No.8234060the Innovation Center of Beijing Association for Science and Technology。
文摘This study proposes a new post-tensioned precast bridge column(PT-PBC)with a socket connection.Compared to conventional PBCs connected by PT tendons,the combination of the PT tendons with the socket connection can avoid tensioning the PT tendons on site,which further accelerates construction speed while improving construction quality and safety.In addition,compared to conventional PBCs with a socket connection,a rocking interface can avoid the formation of a plastic hinge in a column,which greatly alleviates seismic damage to that area.One specimen for quasi-static testing is used to validate the feasibility of this connection type.Subsequently,finite element models(FEM)are established to systematically predict the responses of the proposed columns under lateral cyclic loading.The accuracy of the FEM is verified through quasistatic testing.Next,the influences of the key design parameters of the PT-PBC,including the area ratio and prestress level of the PT tendons,the area ratio of energy dissipation(ED)steel rebars,and the total axial compression ratio on the seismic performances of PT-PBC are systematically investigated.The use of shape memory alloy(SMA)rods as energy dissipation devices and their performances also are investigated.The results show that increasing the area ratio and prestress level of PT tendons has an overall positive impact on the self-centering capacity of the column.The prestress level of PT tendons should be kept between 35%and 55%,depending on different conditions.The total compression axial ratio of the columns should be maintained between 0.3 and 0.4.Both ED steel rebars and SMA rods can boost the column’s energy dissipation capacity,while SMA rods can reduce residual deformation due to their inherent mechanical properties.
文摘受到战争等特殊环境下部分节点导航拒止、节点移动性与环境干扰所带来的影响,快速进行测控网络拓扑重构是保证连续测控关键。为了解决上述问题,针对多体制无人集群测控网络的场景,提出一种基于多智能体深度确定性策略梯度(multi-agent deep deterministic policy gradient,MADDPG)的分布式多智能体测控网络群切换算法。该算法运用局部可观测马尔可夫决策模型,并考虑最小连通度、能耗与测控精度设计奖励函数,构建可靠的测控定位系统。仿真结果表明,该算法在不同的干扰环境下能有效抵抗外界干扰,保证测控定位的正常运行,与传统切换算法相比切换成功率提升12%以上。
