In this paper, we study the flocking behavior of a thermodynamic Cucker–Smale model with local velocity interactions. Using the spectral gap of a connected stochastic matrix, together with an elaborate estimate on pe...In this paper, we study the flocking behavior of a thermodynamic Cucker–Smale model with local velocity interactions. Using the spectral gap of a connected stochastic matrix, together with an elaborate estimate on perturbations of a linearized system, we provide a sufficient framework in terms of initial data and model parameters to guarantee flocking. Moreover, it is shown that the system achieves a consensus at an exponential rate.展开更多
Realizing the uniform dispersion of nanocarbons such as carbon nanotube and graphene in metals, is an essential prerequisite to fully exhibit their enhancement effect in mechanical, thermal, and electrical properties ...Realizing the uniform dispersion of nanocarbons such as carbon nanotube and graphene in metals, is an essential prerequisite to fully exhibit their enhancement effect in mechanical, thermal, and electrical properties of metal matrix composites(MMCs). In this work, we propose an effective method to achieve uniform distribution of nanocarbons in various metal flakes through a slurry-based method. It relies on the electrostatic interactions between the negatively charged nanocarbons and the positively charged metal flakes when mixed in slurry. For case study, flake metal powders(Al, Mg, Ti,Fe, and Cu) were positively charged in aqueous suspension by spontaneous ionization or cationic surface modification. While nanocarbons, given examples as carboxylic multi-walled carbon nanotubes, pristine single-walled carbon nanotube, and carbon nanotube–graphene oxide hybrid were negatively charged by the ionization of oxygen-containing functional groups or anionic surfactant. It was found that through the electrostatic interaction mechanism, all kinds of nanocarbons can be spontaneously and efficiently adsorbed onto the surface of various metal flakes. The development of such a versatile method would provide us great opportunities to fabricate advanced MMCs with appealing properties.展开更多
Elastohydrodynamic lubrication characteristics of hydraulic reciprocating seals have significant effects on sealing and tribology performances of hydraulic actuators, especially in high parameter hydraulic systems. On...Elastohydrodynamic lubrication characteristics of hydraulic reciprocating seals have significant effects on sealing and tribology performances of hydraulic actuators, especially in high parameter hydraulic systems. Only elastic deformations of hydraulic reciprocating seals were discussed, and hydrodynamic effects were neglected in many studies. The physical process of the fluid-solid interaction effect did not be clearly presented in the existing fluid-solid interaction models for hydraulic reciprocating O-ring seals, and few of these models had been simultaneously validated through experiments. By exploring the physical process of the fluid-solid interaction effect of the hydraulic reciprocating O-ring seal, a numerical fluid-solid interaction model consisting of fluid lubrication, contact mechanics, asperity contact and elastic deformation analyses is constructed with an iterative procedure. With the SRV friction and wear tester, the experiments are performed to investigate the elastohydrodynamic lubrication characteristics of the O-ring seal. The regularity of the friction coefficient varying with the speed of reciprocating motion is obtained in the mixed lubrication condition. The experimental result is used to validate the fluid-solid interaction model. Based on the model, The elastohydrodynamic lubrication characteristics of the hydraulic reciprocating O-ring seal are presented respectively in the dry friction, mixed lubrication and full film lubrication conditions, including of the contact pressure, film thickness, friction coefficient, liquid film pressure and viscous shear stress in the sealing zone. The proposed numerical fluid-solid interaction model can be effectively used to analyze the operation characteristics of the hydraulic reciprocating O-ring seal, and can also be widely used to study other hydraulic reciprocating seals.展开更多
A brain tumor occurs when abnormal cells grow, sometimes very rapidly, into an abnormal mass of tissue. The tumor can infect normal tissue, so there is an interaction between healthy and infected cell. The aim of this...A brain tumor occurs when abnormal cells grow, sometimes very rapidly, into an abnormal mass of tissue. The tumor can infect normal tissue, so there is an interaction between healthy and infected cell. The aim of this paper is to propose some efficient and accurate numerical methods for the computational solution of one-dimensional continuous basic models for the growth and control of brain tumors. After computing the analytical solution, we construct approximations of the solution to the problem using a standard second order finite difference method for space discretization and the Crank-Nicolson method for time discretization. Then, we investigate the convergence behavior of Conjugate gradient and generalized minimum residual as Krylov subspace methods to solve the tridiagonal toeplitz matrix system derived.展开更多
In consideration of the problem that the effect of conduit structure on water hammer has been ignored in the classical theory,the Poisson coupling between the fluid and the pipeline was studied and a fourteen-equation...In consideration of the problem that the effect of conduit structure on water hammer has been ignored in the classical theory,the Poisson coupling between the fluid and the pipeline was studied and a fourteen-equation mathematical model of fluid-structure interaction(FSI)was developed.Then,the transfer matrix method(TMM)was used to calculate the modal frequency,modal shape and frequency response.The results were compared with that in experiment to verify the correctness of the TMM and the results show that the fluid-structure coupling has a greater impact on the modal frequencies than the modal shape.Finally,the influence on the response spectrum of different damping ratios was studied and the results show that the natural frequency under different damping ratios has changed little but there is a big difference for the pressure spectrum.With the decreasing of damping ratio,the damping of the system on frequency spectrum is more and more significant and the dispersion and dissipation is more and more apparent.Therefore the appropriate damping ratio should be selected to minimize the effects of the vibration of the FSI.The results provide references for the theory research of FSI in the transient process.展开更多
An integrated fluid-thermal-structural analysis approach is presented. In this approach, the heat conduction in a solid is coupled with the heat convection in the viscous flow of the fluid resulting in the thermal str...An integrated fluid-thermal-structural analysis approach is presented. In this approach, the heat conduction in a solid is coupled with the heat convection in the viscous flow of the fluid resulting in the thermal stress in the solid. The fractional four-step finite element method and the streamline upwind Petrov-Galerkin (SUPG) method are used to analyze the viscous thermal flow in the fluid. Analyses of the heat transfer and the thermal stress in the solid axe performed by the Galerkin method. The second-order semi- implicit Crank-Nicolson scheme is used for the time integration. The resulting nonlinear equations are lineaxized to improve the computational efficiency. The integrated analysis method uses a three-node triangular element with equal-order interpolation functions for the fluid velocity components, the pressure, the temperature, and the solid displacements to simplify the overall finite element formulation. The main advantage of the present method is to consistently couple the heat transfer along the fluid-solid interface. Results of several tested problems show effectiveness of the present finite element method, which provides insight into the integrated fluid-thermal-structural interaction phenomena.展开更多
In order to extend the service life of torque converters, it is essential to predict the pressure condition and improve its weak areas. According to computational fluid dynamics and structural statics, a model of torq...In order to extend the service life of torque converters, it is essential to predict the pressure condition and improve its weak areas. According to computational fluid dynamics and structural statics, a model of torque converter is constructed using software ANSYS. Then, a fluid-solid interaction(FSI) analysis method is proposed to obtain its stress distribution, in which the fluid pressure is applied to the coupling surface to calculate the interaction between fluid and solid. The results show that the fluid pressure at the inlet of the impeller is maximum and decreases along the flow direction, the pressure at the inlet of the turbine blade is minimum and the outlet pressure is the largest, increasing along the flow direction gradually;the pressure distribution of the impeller is concentrated mainly at the corner, especially between the inner ring and the impeller blades;the pressure of the turbine is concentrated mainly on the connection between turbine and the outer edge of the blade.展开更多
The interaction of particles with a solid-liquid interface during solidification of metal matrix composites has been investigated theoretically in this paper.Owing to the presence of particles in the melt,the shape of...The interaction of particles with a solid-liquid interface during solidification of metal matrix composites has been investigated theoretically in this paper.Owing to the presence of particles in the melt,the shape of the solidification front and solute concentration field in front of solidification interface have been disturbed The thermodynamic method was employed,and a mathematical expression of the shape of the solidification interface and solute concentration field were deduced.Meanwhile,a theory is developed for evaluation of critical velocities of particles pushed by the solidification interface.A numerical simulation is done in which the critical velocity is evaluated as a function of particle size,thermal conductivity,diffusion coefficient,temperature gradient at the solidification front,the solid-liquid interfacial energy and the melt viscosity.The critical velocity is shown to be closely linked to the shape of the solidification interface and solute concentration field, and hence all the parameters also affect the shape of the solidification interface and solute concentration field of the front.展开更多
There have been several developments in determining the spontaneous combustion liability of coal. Most of the methods of concern have purely been based on the internal properties of the coal itself. The relation betwe...There have been several developments in determining the spontaneous combustion liability of coal. Most of the methods of concern have purely been based on the internal properties of the coal itself. The relation between the crossing-point method and the electrical resistance of coal was examined here to outline the spontaneous combustion tendency of coal, The electrical resistance property of coal was looked into as a decision-making parameter of the interaction matrix concept for the final decision on the spontaneous combustion tendency.展开更多
Formulation/pharmaceutical excipients play a major role in formulating drug candidates,with the objectives of ease of administration,targeted delivery and complete availability.Many excipients used in pharmaceutical f...Formulation/pharmaceutical excipients play a major role in formulating drug candidates,with the objectives of ease of administration,targeted delivery and complete availability.Many excipients used in pharmaceutical formulations are orphanized in preclinical drug discovery.These orphan excipients could enhance formulatability of highly lipophilic compounds.Additionally,they are safe in preclinical species when used below the LD50 values.However,when the excipients are used in formulating compounds with diverse physico-chemical properties,they pose challenges by modulating study results through their bioanalytical matrix effects.Excipients invariably present in study samples and not in the calibration curve standards cause over-/under-estimation of exposures.Thus,the mechanism by which excipients cause matrix effects and strategies to nullify these effects needs to be revisited.Furthermore,formulation excipients cause drug interactions by moderating the pathways of drug metabolizing enzymes and drug transport proteins.Although it is not possible to get rid of excipient driven interactions,it is always advised to be aware of these interactions and apply the knowledge to draw meaningful conclusions from study results.In this review,we will comprehensively discuss a)orphan excipients that have wider applications in preclinical formulations,b)bioanalytical matrix effects and possible approaches to mitigating these effects,and c)excipient driven drug interactions and strategies to alleviate the impacts of drug interactions.展开更多
This paper is devoted to the two-dimensional nonlinear modeling of the fluid-solid interaction (FSI) between fabric and air flow, which is based on the Automatic Incremental Dynamic Nonlinear Analysis (AIDNA)-FSI prog...This paper is devoted to the two-dimensional nonlinear modeling of the fluid-solid interaction (FSI) between fabric and air flow, which is based on the Automatic Incremental Dynamic Nonlinear Analysis (AIDNA)-FSI program in order to study the dynamic bending features of fabrics in a specific air flow filed. The computational fluid dynamics (CFD) model for flow and the finite element model (FEM) for fabric was set up to constitute an FSI model in which the geometric nonlinear behavior and the dynamic stress-strain variation of the relatively soft fabric material were taken into account. Several FSI cases with different time-dependent wind load and the model frequency analysis for fabric were carried out. The dynamic response of fabric and the distribution of fluid variables were investigated. The results of numerical simulation and experiments fit quite well. Hence, this work contributes to the research of modeling the dynamic bending behavior of fabrics in air field.展开更多
Based on the transfer matrix method and the virtual source simulation technique, this paper proposes a novel semi-analytical and semi-numerical method for solving 2-D sound- structure interaction problems under a harm...Based on the transfer matrix method and the virtual source simulation technique, this paper proposes a novel semi-analytical and semi-numerical method for solving 2-D sound- structure interaction problems under a harmonic excitation.Within any integration segment, as long as its length is small enough,along the circumferential curvilinear coordinate,the non- homogeneous matrix differential equation of an elastic ring of complex geometrical shape can be rewritten in terms of the homogeneous one by the method of extended homogeneous capacity proposed in this paper.For the exterior fluid domain,the multi-circular virtual source simulation technique is adopted.The source density distributed on each virtual circular curve may be ex- panded as the Fourier's series.Combining with the inverse fast Fourier transformation,a higher accuracy and efficiency method for solving 2-D exterior Helmholtz's problems is presented in this paper.In the aspect of solution to the coupling equations,the state vectors of elastic ring induced by the given harmonic excitation and generalized forces of coefficients of the Fourier series can be obtained respectively by using a high precision integration scheme combined with the method of extended homogeneous capacity put forward in this paper.According to the superposition princi- ple and compatibility conditions at the interface between the elastic ring and fluid,the algebraic equation of system can be directly constructed by using the least square approximation.Examples of acoustic radiation from two typical fluid-loaded elastic rings under a harmonic concentrated force are presented.Numerical results show that the method proposed is more efficient than the mixed FE-BE method in common use.展开更多
In dealing with the square lattice model,we replace the traditionally needed Born-Von Karmann periodic boundary condition with additional Hamiltonian terms to make up a ring lattice.In doing so,the lattice Green's...In dealing with the square lattice model,we replace the traditionally needed Born-Von Karmann periodic boundary condition with additional Hamiltonian terms to make up a ring lattice.In doing so,the lattice Green's function of an infinite square lattice in the second nearest-neighbour interaction approximation can be derived by means of the matrix Green's function method.It is shown that the density of states may change when the second nearest-neighbour interaction is turned on.展开更多
Versican belongs to the family of the large aggregating chondroitin sulfate proteoglycans located primarily within theextracellular matrix (ECM). Versican, like other members of its family, has unique N- and C-termina...Versican belongs to the family of the large aggregating chondroitin sulfate proteoglycans located primarily within theextracellular matrix (ECM). Versican, like other members of its family, has unique N- and C-terminal globular regions,each with multiple motifs. A large glycosaminoglycan-binding region lies between them. This review will begin byoutlining these structures, in the context of ECM proteoglycans. The diverse binding partners afforded to versican byvirtue of its modular design will then be examined. These include ECM components, such as hyaluronan, type Icollagen, tenascin-R, fibulin-1, and -2, fibrillin-1, fibronectin, P- and L-selectins, and chemokines. Versican also binds tothe cell surface proteins CD44, integrin β1, epidermal growth factor receptor, and P-selectin glycoprotein ligand-1.These multiple interactors play important roles in cell behaviour, and the roles of versican in modulating such processesare discussed.展开更多
文摘In this paper, we study the flocking behavior of a thermodynamic Cucker–Smale model with local velocity interactions. Using the spectral gap of a connected stochastic matrix, together with an elaborate estimate on perturbations of a linearized system, we provide a sufficient framework in terms of initial data and model parameters to guarantee flocking. Moreover, it is shown that the system achieves a consensus at an exponential rate.
基金the financial support of the National Basic Research Program(973 Program)(No.2012CB619600)the National Natural Science Foundation(Nos.51131004,51071100,51001071,51511130038,51501111,51471190)+1 种基金the National High-Tech R&D Program(863 Program)(No.2012AA030311)the research grant(Nos.14DZ2261200,15JC1402100,13PJ1404000,14520710100)from Shanghai government
文摘Realizing the uniform dispersion of nanocarbons such as carbon nanotube and graphene in metals, is an essential prerequisite to fully exhibit their enhancement effect in mechanical, thermal, and electrical properties of metal matrix composites(MMCs). In this work, we propose an effective method to achieve uniform distribution of nanocarbons in various metal flakes through a slurry-based method. It relies on the electrostatic interactions between the negatively charged nanocarbons and the positively charged metal flakes when mixed in slurry. For case study, flake metal powders(Al, Mg, Ti,Fe, and Cu) were positively charged in aqueous suspension by spontaneous ionization or cationic surface modification. While nanocarbons, given examples as carboxylic multi-walled carbon nanotubes, pristine single-walled carbon nanotube, and carbon nanotube–graphene oxide hybrid were negatively charged by the ionization of oxygen-containing functional groups or anionic surfactant. It was found that through the electrostatic interaction mechanism, all kinds of nanocarbons can be spontaneously and efficiently adsorbed onto the surface of various metal flakes. The development of such a versatile method would provide us great opportunities to fabricate advanced MMCs with appealing properties.
基金supported by National Basic Research Program of China(973 Program,Grant No. 2009CB724304)Key Research Program of the State Key Laboratory of Tribology of Tsinghua University,China (Grant No. SKLT08A06)National Natural Science Foundation of China(Grant No. 50975157)
文摘Elastohydrodynamic lubrication characteristics of hydraulic reciprocating seals have significant effects on sealing and tribology performances of hydraulic actuators, especially in high parameter hydraulic systems. Only elastic deformations of hydraulic reciprocating seals were discussed, and hydrodynamic effects were neglected in many studies. The physical process of the fluid-solid interaction effect did not be clearly presented in the existing fluid-solid interaction models for hydraulic reciprocating O-ring seals, and few of these models had been simultaneously validated through experiments. By exploring the physical process of the fluid-solid interaction effect of the hydraulic reciprocating O-ring seal, a numerical fluid-solid interaction model consisting of fluid lubrication, contact mechanics, asperity contact and elastic deformation analyses is constructed with an iterative procedure. With the SRV friction and wear tester, the experiments are performed to investigate the elastohydrodynamic lubrication characteristics of the O-ring seal. The regularity of the friction coefficient varying with the speed of reciprocating motion is obtained in the mixed lubrication condition. The experimental result is used to validate the fluid-solid interaction model. Based on the model, The elastohydrodynamic lubrication characteristics of the hydraulic reciprocating O-ring seal are presented respectively in the dry friction, mixed lubrication and full film lubrication conditions, including of the contact pressure, film thickness, friction coefficient, liquid film pressure and viscous shear stress in the sealing zone. The proposed numerical fluid-solid interaction model can be effectively used to analyze the operation characteristics of the hydraulic reciprocating O-ring seal, and can also be widely used to study other hydraulic reciprocating seals.
文摘A brain tumor occurs when abnormal cells grow, sometimes very rapidly, into an abnormal mass of tissue. The tumor can infect normal tissue, so there is an interaction between healthy and infected cell. The aim of this paper is to propose some efficient and accurate numerical methods for the computational solution of one-dimensional continuous basic models for the growth and control of brain tumors. After computing the analytical solution, we construct approximations of the solution to the problem using a standard second order finite difference method for space discretization and the Crank-Nicolson method for time discretization. Then, we investigate the convergence behavior of Conjugate gradient and generalized minimum residual as Krylov subspace methods to solve the tridiagonal toeplitz matrix system derived.
文摘In consideration of the problem that the effect of conduit structure on water hammer has been ignored in the classical theory,the Poisson coupling between the fluid and the pipeline was studied and a fourteen-equation mathematical model of fluid-structure interaction(FSI)was developed.Then,the transfer matrix method(TMM)was used to calculate the modal frequency,modal shape and frequency response.The results were compared with that in experiment to verify the correctness of the TMM and the results show that the fluid-structure coupling has a greater impact on the modal frequencies than the modal shape.Finally,the influence on the response spectrum of different damping ratios was studied and the results show that the natural frequency under different damping ratios has changed little but there is a big difference for the pressure spectrum.With the decreasing of damping ratio,the damping of the system on frequency spectrum is more and more significant and the dispersion and dissipation is more and more apparent.Therefore the appropriate damping ratio should be selected to minimize the effects of the vibration of the FSI.The results provide references for the theory research of FSI in the transient process.
基金the National Metal and Materials Technology Centerthe Thailand Research Fund+1 种基金the Office of Higher Education Commissionthe Chulalongkorn University for supporting the present research
文摘An integrated fluid-thermal-structural analysis approach is presented. In this approach, the heat conduction in a solid is coupled with the heat convection in the viscous flow of the fluid resulting in the thermal stress in the solid. The fractional four-step finite element method and the streamline upwind Petrov-Galerkin (SUPG) method are used to analyze the viscous thermal flow in the fluid. Analyses of the heat transfer and the thermal stress in the solid axe performed by the Galerkin method. The second-order semi- implicit Crank-Nicolson scheme is used for the time integration. The resulting nonlinear equations are lineaxized to improve the computational efficiency. The integrated analysis method uses a three-node triangular element with equal-order interpolation functions for the fluid velocity components, the pressure, the temperature, and the solid displacements to simplify the overall finite element formulation. The main advantage of the present method is to consistently couple the heat transfer along the fluid-solid interface. Results of several tested problems show effectiveness of the present finite element method, which provides insight into the integrated fluid-thermal-structural interaction phenomena.
基金Supported by the Natural Science Foundation of Shaanxi Province of China(No.2019JZ-10)
文摘In order to extend the service life of torque converters, it is essential to predict the pressure condition and improve its weak areas. According to computational fluid dynamics and structural statics, a model of torque converter is constructed using software ANSYS. Then, a fluid-solid interaction(FSI) analysis method is proposed to obtain its stress distribution, in which the fluid pressure is applied to the coupling surface to calculate the interaction between fluid and solid. The results show that the fluid pressure at the inlet of the impeller is maximum and decreases along the flow direction, the pressure at the inlet of the turbine blade is minimum and the outlet pressure is the largest, increasing along the flow direction gradually;the pressure distribution of the impeller is concentrated mainly at the corner, especially between the inner ring and the impeller blades;the pressure of the turbine is concentrated mainly on the connection between turbine and the outer edge of the blade.
文摘The interaction of particles with a solid-liquid interface during solidification of metal matrix composites has been investigated theoretically in this paper.Owing to the presence of particles in the melt,the shape of the solidification front and solute concentration field in front of solidification interface have been disturbed The thermodynamic method was employed,and a mathematical expression of the shape of the solidification interface and solute concentration field were deduced.Meanwhile,a theory is developed for evaluation of critical velocities of particles pushed by the solidification interface.A numerical simulation is done in which the critical velocity is evaluated as a function of particle size,thermal conductivity,diffusion coefficient,temperature gradient at the solidification front,the solid-liquid interfacial energy and the melt viscosity.The critical velocity is shown to be closely linked to the shape of the solidification interface and solute concentration field, and hence all the parameters also affect the shape of the solidification interface and solute concentration field of the front.
文摘There have been several developments in determining the spontaneous combustion liability of coal. Most of the methods of concern have purely been based on the internal properties of the coal itself. The relation between the crossing-point method and the electrical resistance of coal was examined here to outline the spontaneous combustion tendency of coal, The electrical resistance property of coal was looked into as a decision-making parameter of the interaction matrix concept for the final decision on the spontaneous combustion tendency.
文摘Formulation/pharmaceutical excipients play a major role in formulating drug candidates,with the objectives of ease of administration,targeted delivery and complete availability.Many excipients used in pharmaceutical formulations are orphanized in preclinical drug discovery.These orphan excipients could enhance formulatability of highly lipophilic compounds.Additionally,they are safe in preclinical species when used below the LD50 values.However,when the excipients are used in formulating compounds with diverse physico-chemical properties,they pose challenges by modulating study results through their bioanalytical matrix effects.Excipients invariably present in study samples and not in the calibration curve standards cause over-/under-estimation of exposures.Thus,the mechanism by which excipients cause matrix effects and strategies to nullify these effects needs to be revisited.Furthermore,formulation excipients cause drug interactions by moderating the pathways of drug metabolizing enzymes and drug transport proteins.Although it is not possible to get rid of excipient driven interactions,it is always advised to be aware of these interactions and apply the knowledge to draw meaningful conclusions from study results.In this review,we will comprehensively discuss a)orphan excipients that have wider applications in preclinical formulations,b)bioanalytical matrix effects and possible approaches to mitigating these effects,and c)excipient driven drug interactions and strategies to alleviate the impacts of drug interactions.
基金National Natural Science Foundations of China(No.50803010,No.60904056)
文摘This paper is devoted to the two-dimensional nonlinear modeling of the fluid-solid interaction (FSI) between fabric and air flow, which is based on the Automatic Incremental Dynamic Nonlinear Analysis (AIDNA)-FSI program in order to study the dynamic bending features of fabrics in a specific air flow filed. The computational fluid dynamics (CFD) model for flow and the finite element model (FEM) for fabric was set up to constitute an FSI model in which the geometric nonlinear behavior and the dynamic stress-strain variation of the relatively soft fabric material were taken into account. Several FSI cases with different time-dependent wind load and the model frequency analysis for fabric were carried out. The dynamic response of fabric and the distribution of fluid variables were investigated. The results of numerical simulation and experiments fit quite well. Hence, this work contributes to the research of modeling the dynamic bending behavior of fabrics in air field.
基金Project supported by the National Natural Science Foundation of China (No.10172038)
文摘Based on the transfer matrix method and the virtual source simulation technique, this paper proposes a novel semi-analytical and semi-numerical method for solving 2-D sound- structure interaction problems under a harmonic excitation.Within any integration segment, as long as its length is small enough,along the circumferential curvilinear coordinate,the non- homogeneous matrix differential equation of an elastic ring of complex geometrical shape can be rewritten in terms of the homogeneous one by the method of extended homogeneous capacity proposed in this paper.For the exterior fluid domain,the multi-circular virtual source simulation technique is adopted.The source density distributed on each virtual circular curve may be ex- panded as the Fourier's series.Combining with the inverse fast Fourier transformation,a higher accuracy and efficiency method for solving 2-D exterior Helmholtz's problems is presented in this paper.In the aspect of solution to the coupling equations,the state vectors of elastic ring induced by the given harmonic excitation and generalized forces of coefficients of the Fourier series can be obtained respectively by using a high precision integration scheme combined with the method of extended homogeneous capacity put forward in this paper.According to the superposition princi- ple and compatibility conditions at the interface between the elastic ring and fluid,the algebraic equation of system can be directly constructed by using the least square approximation.Examples of acoustic radiation from two typical fluid-loaded elastic rings under a harmonic concentrated force are presented.Numerical results show that the method proposed is more efficient than the mixed FE-BE method in common use.
文摘In dealing with the square lattice model,we replace the traditionally needed Born-Von Karmann periodic boundary condition with additional Hamiltonian terms to make up a ring lattice.In doing so,the lattice Green's function of an infinite square lattice in the second nearest-neighbour interaction approximation can be derived by means of the matrix Green's function method.It is shown that the density of states may change when the second nearest-neighbour interaction is turned on.
文摘Versican belongs to the family of the large aggregating chondroitin sulfate proteoglycans located primarily within theextracellular matrix (ECM). Versican, like other members of its family, has unique N- and C-terminal globular regions,each with multiple motifs. A large glycosaminoglycan-binding region lies between them. This review will begin byoutlining these structures, in the context of ECM proteoglycans. The diverse binding partners afforded to versican byvirtue of its modular design will then be examined. These include ECM components, such as hyaluronan, type Icollagen, tenascin-R, fibulin-1, and -2, fibrillin-1, fibronectin, P- and L-selectins, and chemokines. Versican also binds tothe cell surface proteins CD44, integrin β1, epidermal growth factor receptor, and P-selectin glycoprotein ligand-1.These multiple interactors play important roles in cell behaviour, and the roles of versican in modulating such processesare discussed.