Physiological repair of large-sized bone defects is great challenging in clinic due to a lack of ideal grafts suitable for bone regeneration.Decalcified bone matrix(DBM)is considered as an ideal bone regeneration scaf...Physiological repair of large-sized bone defects is great challenging in clinic due to a lack of ideal grafts suitable for bone regeneration.Decalcified bone matrix(DBM)is considered as an ideal bone regeneration scaffold,but low cell seeding efficiency and a poor osteoinductive microenvironment greatly restrict its application in large-sized bone regeneration.To address these problems,we proposed a novel strategy of bone regeneration units(BRUs)based on microgels produced by photo-crosslinkable and microfluidic techniques,containing both the osteogenic ingredient DBM and vascular endothelial growth factor(VEGF)for accurate biomimic of an osteoinductive microenvironment.The physicochemical properties of microgels could be precisely controlled and the microgels effectively promoted adhesion,proliferation,and osteogenic differentiation of bone marrow mesenchymal stem cells(BMSCs)in vitro.BRUs were successfully constructed by seeding BMSCs onto microgels,which achieved reliable bone regeneration in vivo.Finally,by integrating the advantages of BRUs in bone regeneration and the advantages of DBM scaffolds in 3D morphology and mechanical strength,a BRU-loaded DBM framework successfully regenerated bone tissue with the desired 3D morphology and effectively repaired a large-sized bone defect of rabbit tibia.The current study developed an ideal bone biomimetic microcarrier and provided a novel strategy for bone regeneration and large-sized bone defect repair.展开更多
This paper aims to address the problem of geometric state control of large-segment steel box girders in offshore hoisting during the construction of large-span bridges. First, the geometric state control indexes of a ...This paper aims to address the problem of geometric state control of large-segment steel box girders in offshore hoisting during the construction of large-span bridges. First, the geometric state control indexes of a large-segment steel box girder are determined, such as the manufacturing parameters of the top and bottom slabs, the width of the annular joint, and the support position. Second, the geometric state equations and state transfer matrixes of large-segment steel box girders under different conditions are deduced by taking the mileage and elevation of control points as basic state variables. In application of the geometric state transfer method in the construction control of the Hong Kong-Zhuhai-Macao Bridge, the width of the annular joint and the position parameters for the support of the large-segment steel box girder are predicted precisely. Moreover, the manufacturing parameters of the top and bottom slabs of the steel box girders are calculated reliably. The measured values show that the width of the annular joint is basically the same with the difference of less than 2 mm, the eccentricity of bridge support is less than 20 mm, and the elevation error of the bridge deck is within-10 mm to +15 mm, which meets the construction accuracy. Using the geometric state transfer method, the rapid and accurate installation of the Hong Kong-Zhuhai-Macao Bridge has been realized, demonstrating that the precise control of the geometric state of a steel box girder with ectopic installation and multi-state transition can be realized by using the geometric state transfer method.展开更多
A significant clinical challenge in large-to-massive rotator cuff tendon injuries is the need for sustaining high mechanical demands despite limited tissue regeneration,which often results in clinical repair failure w...A significant clinical challenge in large-to-massive rotator cuff tendon injuries is the need for sustaining high mechanical demands despite limited tissue regeneration,which often results in clinical repair failure with high retear rates and long-term functional deficiencies.To address this,an innovative tendon substitute named“BioTenoForce”is engineered,which uses(i)tendon extracellular matrix(tECM)’s rich biocomplexity for tendon-specific regeneration and(ii)a mechanically robust,slow degradation polyurethane elastomer to mimic native tendon’s physical attributes for sustaining long-term shoulder movement.Comprehensive assessments revealed outstanding performance of BioTenoForce,characterized by robust core-shell interfacial bonding,human rotator cuff tendon-like mechanical properties,excellent suture retention,biocompatibility,and tendon differentiation of human adipose-derived stem cells.Importantly,BioTenoForce,when used as an interpositional tendon substitute,demonstrated successful integration with regenerative tissue,exhibiting remarkable efficacy in repairing large-to-massive tendon injuries in two animal models.Noteworthy outcomes include durable repair and sustained functionality with no observed breakage/rupture,accelerated recovery of rat gait performance,and>1 cm rabbit tendon regeneration with native tendon-like biomechanical attributes.The regenerated tissues showed tendon-like,wavy,aligned matrix structure,which starkly contrasts with the typical disorganized scar tissue observed after tendon injury,and was strongly correlated with tissue stiffness.Our simple yet versatile approach offers a dual-pronged,broadly applicable strategy that overcomes the limitations of poor regeneration and stringent biomechanical requirements,particularly essential for substantial defects in tendon and other load-bearing tissues.展开更多
In this paper,a coupled CFD-CSD method based on N-S equations is described for static aeroelastic correction and jig-shape design of large airliners.The wing structural flexibility matrix is analyzed by a finite eleme...In this paper,a coupled CFD-CSD method based on N-S equations is described for static aeroelastic correction and jig-shape design of large airliners.The wing structural flexibility matrix is analyzed by a finite element method with a double-beam model.The viscous multi-block structured grid is used in aerodynamic calculations.Flexibility matrix interpolation is fulfilled by use of a surface spline method.The load distributions on wing surface are evaluated by solving N-S equations with a parallel algorithm.A flexibility approach is employed to calculate the structural deformations.By successive iterations between steady aerodynamic forces and structural deformations,a coupled CFD-CSD method is achieved for the static aeroelastic correction and jig-shape design of a large airliner.The present method is applied to the static aeroelastic analysis and jig-shape design for a typical large airliner with engine nacelle and winglet.The numerical results indicate that calculations of static aeroelastic correction should employ tightly coupled CFD-CSD iterations,and that on a given cruise shape only one round of iterative design is needed to obtain the jig-shape meeting design requirements.展开更多
The matrix catalytic function when cracking the feed oil with large molecular size was systematically studied using three different catalyst configurations, including staged bed, partly mixed bed and completely mixed ...The matrix catalytic function when cracking the feed oil with large molecular size was systematically studied using three different catalyst configurations, including staged bed, partly mixed bed and completely mixed bed. Results showed that molecules in the feed oil with large molecular size indeed preferred to be first precracked on the matrix surface and then entered into the zeolite pores during the practical reaction process. Furthermore, the matrix catalytic function exhibited a great matrix-precracking ability to large feed molecules, which considerably increased the catalyst activity and the light oil selectivity. Besides the much better accessibility, the matrix-precracking ability was also from the similar capability to crack large feed hydrocarbons into the moderate fragments with that of the zeolite component. More interestingly, the interactions between the matrix catalytic function and the zeolite catalytic function made the catalyst not only exhibit much more catalytic advantages of the zeolite component, but also retain the matrix-precracking ability. As a result, the interactions enhanced the catalyst activity and improved the product distribution at the same time. The matrix catalytic function is indispensable for the catalytic cracking of feed with large molecular size, although the matrix component itself presented an inferior catalytic performance than the zeolite component did. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.展开更多
Refined projection methods proposed by the author have received attention internationally. We are concerned with a conventional projection method and its refined counterpart for computing approximations to a simple ei...Refined projection methods proposed by the author have received attention internationally. We are concerned with a conventional projection method and its refined counterpart for computing approximations to a simple eigenpair (λ, x) of a large matrix A. Given a subspace ω that contains an approximation to x, these two methods compute approximations (μ,x) and μ,x) to (λ,x), respectively. We establish three results. First, the refined eigenvector approximation or simply the refined Ritz vector x is unique as the deviation of x from ω approaches zero if A is simple. Second, in terms of residual norm of the refined approximate eigenpair (μ, x), we derive lower and upper bounds for the sine of the angle between the Ritz vector x and the refined eigenvector approximation x, and we prove that x≠x unless x = x. Third, we establish relationships between the residual norm ||AX -μx|| of the conventional methods and the residual norm ||Ax -μx|| of the refined methods, and we show that the latter is always smaller than the former if (μ, x) is not an exact eigenpair of A, indicating that the refined projection method is superior to the corresponding conventional counterpart.展开更多
On applying large eddy simulation (LES) to engineering interest, one of the keys is to obtain two-order low-dissipation shock-capturing schemes adapted to LES. Therefore, the preconditioning method for all speed flows...On applying large eddy simulation (LES) to engineering interest, one of the keys is to obtain two-order low-dissipation shock-capturing schemes adapted to LES. Therefore, the preconditioning method for all speed flows is adopted. However, the accuracy of preconditioned schemes is not satisfactory because of the poor per-formance of stability of preconditioning techniques especially in viscous flows. The reason of unstability is attributed to the unstability structure in the preconditioned eigenvalue matrix. Based on Roe scheme and two assumptions for low-Mach- Number flows, the new scheme named Low-Speed-Roe scheme is deduced for removing the unstability structure. Numerical experiments show that this scheme has the reasonable computational stability. For general-precision problems, Low-Speed-Roe scheme has similar behavior as the classical preconditioned Roe scheme. For simulations of high-accuracy requirement such as LES, Low-Speed- Roe scheme can obtain better results of complex flows, such as the laminar sepa-ration bubble on the suction surface of the high-loaded turbine blade T106.展开更多
The identification and analysis of spatiotemporal traffic patterns in road networks constitute a crucial process for sophisticated traffic management and control.Traditional methods based on mathematical equations and...The identification and analysis of spatiotemporal traffic patterns in road networks constitute a crucial process for sophisticated traffic management and control.Traditional methods based on mathematical equations and statistical models can hardly be applicable to large-scale urban road networks,where traffic states exhibit high degrees of dynamics and complexity.Recently,advances in data collection and processing have provided new opportunities to effectively understand spatiotemporal traffic patterns in large-scale road networks using data-driven methods.However,limited efforts have been exerted to explore the essential structure of the networks when conducting a spatiotemporal analysis of traffic characteristics.To this end,this study proposes a modified nonnegative matrix factorization algorithm that processes high-dimensional traffic data and provides an improved representation of the global traffic state.After matrix factorization,cluster analysis is conducted based on the obtained low-dimensional representative matrices,which contain different traffic patterns and serve as the basis for exploring the temporal dynamics and spatial structure of network congestion.The applicability and effectiveness of the proposed approach are examined in a road network of Beijing,China.Results show that the methods exhibit considerable potential for identifying and interpreting the spatiotemporal traffic patterns over the entire network and provide a systematic and efficient approach for analyzing the network-level traffic state.展开更多
The performance of analytical derivative and sparse matrix techniques applied to a traditional dense sequential quadratic programming (SQP) is studied, and the strategy utilizing those techniques is also presented.Com...The performance of analytical derivative and sparse matrix techniques applied to a traditional dense sequential quadratic programming (SQP) is studied, and the strategy utilizing those techniques is also presented.Computational results on two typical chemical optimization problems demonstrate significant enhancement in efficiency, which shows this strategy is promising and suitable for large-scale process optimization problems.展开更多
A method is presented in this work that integrates both emerging and mature data sources to estimate the operational travel demand in fine spatial and temporal resolutions.By analyzing individuals’mobility patterns r...A method is presented in this work that integrates both emerging and mature data sources to estimate the operational travel demand in fine spatial and temporal resolutions.By analyzing individuals’mobility patterns revealed from their mobile phones,researchers and practitioners are now equipped to derive the largest trip samples for a region.Because of its ubiquitous use,extensive coverage of telecommunication services and high penetration rates,travel demand can be studied continuously in fine spatial and temporal resolutions.The derived sample or seed trip matrices are coupled with surveyed commute flow data and prevalent travel demand modeling techniques to provide estimates of the total regional travel demand in the form of origindestination(OD)matrices.The methodology is evaluated in a series of real world transportation planning studies and proved its potentials in application areas such as dynamic traffic assignment modeling,integrated corridor management and online traffic simulations.展开更多
The inexact Rayleigh quotient iteration (RQI) is used for computing the smallest eigenpair of a large Hermitian matrix. Under certain condition, the method was proved to converge quadratically in literature. However, ...The inexact Rayleigh quotient iteration (RQI) is used for computing the smallest eigenpair of a large Hermitian matrix. Under certain condition, the method was proved to converge quadratically in literature. However, it is shown in this paper that under the original given condition the inexact RQI may not quadratically converge to the desired eigenpair and even may misconverge to some other undesired eigenpair. A new condition, called the uniform positiveness condition, is given that can fix misconvergence problem and ensure the quadratic convergence of the inexact RQI. An alternative to the inexact RQI is the Jacobi-Davidson (JD) method without subspace acceleration. A new proof of its linear convergence is presented and a sharper bound is established in the paper. All the results are verified and analyzed by numerical experiments.展开更多
We recently performed a series of improvement on evaluation of eigenvalues without complicated iterations. In this work we first discuss evaluation of the lowest eigenvalue for given systems,by which one conveniently ...We recently performed a series of improvement on evaluation of eigenvalues without complicated iterations. In this work we first discuss evaluation of the lowest eigenvalue for given systems,by which one conveniently obtains the value of the lowest eigenvalue based on the dimension and width of given matrix. We also discuss a strong correlation between eigenvalues and diagonal matrix elements for large matrices,by which one is able to predict eigenvalues approximately without iterations.展开更多
The conventional transfer matrix models of fluid elements were modified and a convenient method of dealing with junction boundary conditions was introduced. A large scale fluid network was modeled by standard procedur...The conventional transfer matrix models of fluid elements were modified and a convenient method of dealing with junction boundary conditions was introduced. A large scale fluid network was modeled by standard procedures, and a network was expressed with characteristic matrix and boundary condition matrix. By simple operation of matrix, the dynamic characteristics of a large scale fluid network was simulated in frequency domain. Validation test on a large scale pipeline network showed that the proposed method is accurate and practical.[展开更多
基金financially supported by the National Key Research and Development Program of China(2017YFC1103900)the National Natural Science Foundation of China(81871502,81701843,and 81671837)+3 种基金the Shanghai Excellent Technical Leader(18XD1421500)the Program of Shanghai Academic/Technology Research Leader(19XD1431100)the Shanghai Collaborative Innovation Program on Regenerative Medicine and Stem Cell Research(2019CXJQ01)the Clinical Research Plan of SHDC(No.SHDC2020CR2045B).
文摘Physiological repair of large-sized bone defects is great challenging in clinic due to a lack of ideal grafts suitable for bone regeneration.Decalcified bone matrix(DBM)is considered as an ideal bone regeneration scaffold,but low cell seeding efficiency and a poor osteoinductive microenvironment greatly restrict its application in large-sized bone regeneration.To address these problems,we proposed a novel strategy of bone regeneration units(BRUs)based on microgels produced by photo-crosslinkable and microfluidic techniques,containing both the osteogenic ingredient DBM and vascular endothelial growth factor(VEGF)for accurate biomimic of an osteoinductive microenvironment.The physicochemical properties of microgels could be precisely controlled and the microgels effectively promoted adhesion,proliferation,and osteogenic differentiation of bone marrow mesenchymal stem cells(BMSCs)in vitro.BRUs were successfully constructed by seeding BMSCs onto microgels,which achieved reliable bone regeneration in vivo.Finally,by integrating the advantages of BRUs in bone regeneration and the advantages of DBM scaffolds in 3D morphology and mechanical strength,a BRU-loaded DBM framework successfully regenerated bone tissue with the desired 3D morphology and effectively repaired a large-sized bone defect of rabbit tibia.The current study developed an ideal bone biomimetic microcarrier and provided a novel strategy for bone regeneration and large-sized bone defect repair.
基金Project supported by the Zhejiang Provincial Natural Science Foundation of China(No.LZ16E080001)the National Natural Science Foundation of China(Nos.51578496 and 51878603)。
文摘This paper aims to address the problem of geometric state control of large-segment steel box girders in offshore hoisting during the construction of large-span bridges. First, the geometric state control indexes of a large-segment steel box girder are determined, such as the manufacturing parameters of the top and bottom slabs, the width of the annular joint, and the support position. Second, the geometric state equations and state transfer matrixes of large-segment steel box girders under different conditions are deduced by taking the mileage and elevation of control points as basic state variables. In application of the geometric state transfer method in the construction control of the Hong Kong-Zhuhai-Macao Bridge, the width of the annular joint and the position parameters for the support of the large-segment steel box girder are predicted precisely. Moreover, the manufacturing parameters of the top and bottom slabs of the steel box girders are calculated reliably. The measured values show that the width of the annular joint is basically the same with the difference of less than 2 mm, the eccentricity of bridge support is less than 20 mm, and the elevation error of the bridge deck is within-10 mm to +15 mm, which meets the construction accuracy. Using the geometric state transfer method, the rapid and accurate installation of the Hong Kong-Zhuhai-Macao Bridge has been realized, demonstrating that the precise control of the geometric state of a steel box girder with ectopic installation and multi-state transition can be realized by using the geometric state transfer method.
基金funding support,including The Research Grants Council of Hong Kong SAR(GRF 14121121,DMW,GRF 14118620,DMW,ECS24201720,DFEK)National Natural Science Foundation of China/Research Grants Council Joint Research Scheme(N_CUHK409/23,DMW)+1 种基金The Innovation and Technology Commission of Hong Kong SAR Innovation Tier 3 Support(ITS/090/18,DFEK)Health@InnoHK CNRM(DMW,AB,DFEK,RST).
文摘A significant clinical challenge in large-to-massive rotator cuff tendon injuries is the need for sustaining high mechanical demands despite limited tissue regeneration,which often results in clinical repair failure with high retear rates and long-term functional deficiencies.To address this,an innovative tendon substitute named“BioTenoForce”is engineered,which uses(i)tendon extracellular matrix(tECM)’s rich biocomplexity for tendon-specific regeneration and(ii)a mechanically robust,slow degradation polyurethane elastomer to mimic native tendon’s physical attributes for sustaining long-term shoulder movement.Comprehensive assessments revealed outstanding performance of BioTenoForce,characterized by robust core-shell interfacial bonding,human rotator cuff tendon-like mechanical properties,excellent suture retention,biocompatibility,and tendon differentiation of human adipose-derived stem cells.Importantly,BioTenoForce,when used as an interpositional tendon substitute,demonstrated successful integration with regenerative tissue,exhibiting remarkable efficacy in repairing large-to-massive tendon injuries in two animal models.Noteworthy outcomes include durable repair and sustained functionality with no observed breakage/rupture,accelerated recovery of rat gait performance,and>1 cm rabbit tendon regeneration with native tendon-like biomechanical attributes.The regenerated tissues showed tendon-like,wavy,aligned matrix structure,which starkly contrasts with the typical disorganized scar tissue observed after tendon injury,and was strongly correlated with tissue stiffness.Our simple yet versatile approach offers a dual-pronged,broadly applicable strategy that overcomes the limitations of poor regeneration and stringent biomechanical requirements,particularly essential for substantial defects in tendon and other load-bearing tissues.
基金supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘In this paper,a coupled CFD-CSD method based on N-S equations is described for static aeroelastic correction and jig-shape design of large airliners.The wing structural flexibility matrix is analyzed by a finite element method with a double-beam model.The viscous multi-block structured grid is used in aerodynamic calculations.Flexibility matrix interpolation is fulfilled by use of a surface spline method.The load distributions on wing surface are evaluated by solving N-S equations with a parallel algorithm.A flexibility approach is employed to calculate the structural deformations.By successive iterations between steady aerodynamic forces and structural deformations,a coupled CFD-CSD method is achieved for the static aeroelastic correction and jig-shape design of a large airliner.The present method is applied to the static aeroelastic analysis and jig-shape design for a typical large airliner with engine nacelle and winglet.The numerical results indicate that calculations of static aeroelastic correction should employ tightly coupled CFD-CSD iterations,and that on a given cruise shape only one round of iterative design is needed to obtain the jig-shape meeting design requirements.
基金supported by the National Natural Science Foundation of China(U146220521476263+3 种基金21406270)the Fundamental Research Funds for the Central Universities(15CX06036A)the China University of Petroleum for Postgraduate Technology Innovation Project(YCX2015028)the Qingdao People’s Livelihood Project(13-1-3-126-nsh)
文摘The matrix catalytic function when cracking the feed oil with large molecular size was systematically studied using three different catalyst configurations, including staged bed, partly mixed bed and completely mixed bed. Results showed that molecules in the feed oil with large molecular size indeed preferred to be first precracked on the matrix surface and then entered into the zeolite pores during the practical reaction process. Furthermore, the matrix catalytic function exhibited a great matrix-precracking ability to large feed molecules, which considerably increased the catalyst activity and the light oil selectivity. Besides the much better accessibility, the matrix-precracking ability was also from the similar capability to crack large feed hydrocarbons into the moderate fragments with that of the zeolite component. More interestingly, the interactions between the matrix catalytic function and the zeolite catalytic function made the catalyst not only exhibit much more catalytic advantages of the zeolite component, but also retain the matrix-precracking ability. As a result, the interactions enhanced the catalyst activity and improved the product distribution at the same time. The matrix catalytic function is indispensable for the catalytic cracking of feed with large molecular size, although the matrix component itself presented an inferior catalytic performance than the zeolite component did. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.
文摘Refined projection methods proposed by the author have received attention internationally. We are concerned with a conventional projection method and its refined counterpart for computing approximations to a simple eigenpair (λ, x) of a large matrix A. Given a subspace ω that contains an approximation to x, these two methods compute approximations (μ,x) and μ,x) to (λ,x), respectively. We establish three results. First, the refined eigenvector approximation or simply the refined Ritz vector x is unique as the deviation of x from ω approaches zero if A is simple. Second, in terms of residual norm of the refined approximate eigenpair (μ, x), we derive lower and upper bounds for the sine of the angle between the Ritz vector x and the refined eigenvector approximation x, and we prove that x≠x unless x = x. Third, we establish relationships between the residual norm ||AX -μx|| of the conventional methods and the residual norm ||Ax -μx|| of the refined methods, and we show that the latter is always smaller than the former if (μ, x) is not an exact eigenpair of A, indicating that the refined projection method is superior to the corresponding conventional counterpart.
基金Supported by the National Natural Science Foundation of China (Grant No. 50776051) the National Basic Research Program of China (973 Program) (Grant No. 2007CB210105)
文摘On applying large eddy simulation (LES) to engineering interest, one of the keys is to obtain two-order low-dissipation shock-capturing schemes adapted to LES. Therefore, the preconditioning method for all speed flows is adopted. However, the accuracy of preconditioned schemes is not satisfactory because of the poor per-formance of stability of preconditioning techniques especially in viscous flows. The reason of unstability is attributed to the unstability structure in the preconditioned eigenvalue matrix. Based on Roe scheme and two assumptions for low-Mach- Number flows, the new scheme named Low-Speed-Roe scheme is deduced for removing the unstability structure. Numerical experiments show that this scheme has the reasonable computational stability. For general-precision problems, Low-Speed-Roe scheme has similar behavior as the classical preconditioned Roe scheme. For simulations of high-accuracy requirement such as LES, Low-Speed- Roe scheme can obtain better results of complex flows, such as the laminar sepa-ration bubble on the suction surface of the high-loaded turbine blade T106.
基金the National Natural Science Foundation of China(U1564212,61773036,51508014)Beijing Natural Science Foundation(9172011)Young Elite Scientist Sponsorship Program of the China Association for Science and Technology(2016QNRC001)。
文摘The identification and analysis of spatiotemporal traffic patterns in road networks constitute a crucial process for sophisticated traffic management and control.Traditional methods based on mathematical equations and statistical models can hardly be applicable to large-scale urban road networks,where traffic states exhibit high degrees of dynamics and complexity.Recently,advances in data collection and processing have provided new opportunities to effectively understand spatiotemporal traffic patterns in large-scale road networks using data-driven methods.However,limited efforts have been exerted to explore the essential structure of the networks when conducting a spatiotemporal analysis of traffic characteristics.To this end,this study proposes a modified nonnegative matrix factorization algorithm that processes high-dimensional traffic data and provides an improved representation of the global traffic state.After matrix factorization,cluster analysis is conducted based on the obtained low-dimensional representative matrices,which contain different traffic patterns and serve as the basis for exploring the temporal dynamics and spatial structure of network congestion.The applicability and effectiveness of the proposed approach are examined in a road network of Beijing,China.Results show that the methods exhibit considerable potential for identifying and interpreting the spatiotemporal traffic patterns over the entire network and provide a systematic and efficient approach for analyzing the network-level traffic state.
基金Supported by the National Natural Science Foundation of China(No.29906010).
文摘The performance of analytical derivative and sparse matrix techniques applied to a traditional dense sequential quadratic programming (SQP) is studied, and the strategy utilizing those techniques is also presented.Computational results on two typical chemical optimization problems demonstrate significant enhancement in efficiency, which shows this strategy is promising and suitable for large-scale process optimization problems.
文摘A method is presented in this work that integrates both emerging and mature data sources to estimate the operational travel demand in fine spatial and temporal resolutions.By analyzing individuals’mobility patterns revealed from their mobile phones,researchers and practitioners are now equipped to derive the largest trip samples for a region.Because of its ubiquitous use,extensive coverage of telecommunication services and high penetration rates,travel demand can be studied continuously in fine spatial and temporal resolutions.The derived sample or seed trip matrices are coupled with surveyed commute flow data and prevalent travel demand modeling techniques to provide estimates of the total regional travel demand in the form of origindestination(OD)matrices.The methodology is evaluated in a series of real world transportation planning studies and proved its potentials in application areas such as dynamic traffic assignment modeling,integrated corridor management and online traffic simulations.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10471074, 10771116)the Doctoral Program of the Ministry of Education of China (Grant No. 20060003003)
文摘The inexact Rayleigh quotient iteration (RQI) is used for computing the smallest eigenpair of a large Hermitian matrix. Under certain condition, the method was proved to converge quadratically in literature. However, it is shown in this paper that under the original given condition the inexact RQI may not quadratically converge to the desired eigenpair and even may misconverge to some other undesired eigenpair. A new condition, called the uniform positiveness condition, is given that can fix misconvergence problem and ensure the quadratic convergence of the inexact RQI. An alternative to the inexact RQI is the Jacobi-Davidson (JD) method without subspace acceleration. A new proof of its linear convergence is presented and a sharper bound is established in the paper. All the results are verified and analyzed by numerical experiments.
基金National Natural Science Foundation of China(10575070,10675081)Research Foundation Doctoral Program of Higher Education of China(20060248050)+1 种基金Scientific Research Foundation of Ministry of Education in China for Returned Scholars(NCET-07-0557)Major State Basic Research Development Program of China(2007CB815000)
文摘We recently performed a series of improvement on evaluation of eigenvalues without complicated iterations. In this work we first discuss evaluation of the lowest eigenvalue for given systems,by which one conveniently obtains the value of the lowest eigenvalue based on the dimension and width of given matrix. We also discuss a strong correlation between eigenvalues and diagonal matrix elements for large matrices,by which one is able to predict eigenvalues approximately without iterations.
文摘The conventional transfer matrix models of fluid elements were modified and a convenient method of dealing with junction boundary conditions was introduced. A large scale fluid network was modeled by standard procedures, and a network was expressed with characteristic matrix and boundary condition matrix. By simple operation of matrix, the dynamic characteristics of a large scale fluid network was simulated in frequency domain. Validation test on a large scale pipeline network showed that the proposed method is accurate and practical.[
