与常规直流相比,永富直流逆变站存在功率全送和功率分送运行方式,而其处于分网接入方式时电网换相换流器高压直流输电(line commutated converter based high voltage directcurrent,LCC-HVDC)系统的交互振荡模式及特征尚不明确。针对...与常规直流相比,永富直流逆变站存在功率全送和功率分送运行方式,而其处于分网接入方式时电网换相换流器高压直流输电(line commutated converter based high voltage directcurrent,LCC-HVDC)系统的交互振荡模式及特征尚不明确。针对这一特殊运行方式,采用模块化建模的思路建立可以反映系统电气/控制回路间交互耦合路径的运动方程模型。在此基础上,依据系统整流侧-逆变侧、正极-负极间的交互耦合路径分解得到影响系统主导模式稳定性的3条扰动传递路径,即整流侧内部自稳性路径、逆变侧内部自稳性路径、双极交互作用致稳性路径。最后,设置不同工况下的案例,量化评估不同作用路径提供的阻尼大小,并通过仿真验证运动方程模型及扰动传递路径分析结果的正确性,为后续研究分网接入方式下LCC-HVDC系统交互振荡模式的阻尼特征提供模型基础。展开更多
In order to analyze the pavement stress caused by vehicle bumping at an approach slab, a simplified four-wheeled bi- axle vehicle-moving model is proposed. The effect of damping and vibration reduction in the process ...In order to analyze the pavement stress caused by vehicle bumping at an approach slab, a simplified four-wheeled bi- axle vehicle-moving model is proposed. The effect of damping and vibration reduction in the process of vehicle-moving is not considered. Based on the position change of vehicle wheels at the approach slab, the vehicle dynamic vibration equations are summarized. Meanwhile, the undetermined coefficients of the vibration equations are obtained using the boundary and initial conditions of the vehicle. The analytical motion solutions of rear and front wheels at different stages are concluded. Consequently, a four-wheeled vehicle model is developed and vibration equations are provided, which can be used to analyze the impact of complicated stress on pavement. The results show that the excessive stress and stress concentration will occur at the approach slab, and it needs to be strengthened.展开更多
The directed motion of a Brownian particle in a Bashing potential with various transition probabilities and waiting times in one of two states is studied. An expression for the average cycle period is proposed and the...The directed motion of a Brownian particle in a Bashing potential with various transition probabilities and waiting times in one of two states is studied. An expression for the average cycle period is proposed and the steady current J of the particle is calculated via Langevin simulation. The results show that the optimal cycle period (Tm), which takes the maximum of J, is shifted to a small value when the transition probability A from the potential on to the potential off decreases, the maximal current appears in the case of the average waiting time in the potential on being longer than in the potential off, and the direction of current depends on the ratio of the average times waiting in two states.展开更多
In this paper, a planar five-freedom model of whole vehicle is set up and its corresponding sport differential equation is founded. The square root of the driver＇ s acceleration is selected as the estimate index by t...In this paper, a planar five-freedom model of whole vehicle is set up and its corresponding sport differential equation is founded. The square root of the driver＇ s acceleration is selected as the estimate index by the estimate way of vehicle＇ s comfort. The estimate index is minimized by optimization of fore-and-aft suspension＇ s stiffness and written with corresponding program. In the end, a model of comfort simulation by soitware of Simulink is found, and a temporal simulation for the upper example is applied to guessing the comfort of vehicle.展开更多
The main purpose of this article is to present a mathematical model of ciliary motion in an annulus. In this analysis, the peristaltic motion of non-Newtonian Jeffrey six constant fluid is observed in an annulus with ...The main purpose of this article is to present a mathematical model of ciliary motion in an annulus. In this analysis, the peristaltic motion of non-Newtonian Jeffrey six constant fluid is observed in an annulus with ciliated tips in the presence of heat and mass transfer. The effects of viscous dissipation are also considered. The flow equations of non-Newtonian fluid for the two-dimensional tube in cylindrical coordinates are simplified using the low Reynolds number and long wave-length approximations. The main equations for Jeffrey six constant fluid are considered in cylindrical coordinates system. The resulting nonlinear problem is solved using the regular perturbation technique in terms of a variant of small dimensionless parameter α. The results of the solutions for velocity, temperature and concentration field are presented graphically. B_k is Brinkman number, ST is soret number, and SH is the Schmidth number. Outcome for the longitudinal velocity, pressure rise, pressure gradient and stream lines are represented through graphs. In the history, the viscous-dissipation effect is usually represented by the Brinkman number.展开更多
In this paper,a CFD/CSD model coupling N-S equations and structural equations of motion in the time domain is described for aeroelastic analysis of large wind turbines.The structural modes of blades are analyzed with ...In this paper,a CFD/CSD model coupling N-S equations and structural equations of motion in the time domain is described for aeroelastic analysis of large wind turbines.The structural modes of blades are analyzed with one-dimensional beam models.By combining point matched sliding grid for wind turbine rotation and deforming grid for structural vibrations,a hybrid dynamic grid strategy is designed for the multi-block structured grid system of a wind turbine.The dual time-stepping approach and finite volume scheme are applied to the three-dimensional unsteady preconditioned N-S equations,and DES approach is employed to simulate the unsteady massively separated flows.A modal approach is adopted to calculate the structural response,and a predictor-corrector scheme is used to solve the structural equations of motion.CFD and CSD solvers are tightly coupled via successive iterations within each physical time step.As a result,a time-domain CFD/CSD model for aeroelastic analysis of a large wind turbine is achieved.The presented method is applied to the NH1500 large wind turbine under the rated condition,and the calculated aeroelastic characteristics agree well with those of the prescribed vortex wake method.展开更多
The stability of the rolling motion of near space hypersonic vehicles with rudder control is studied using method of qualitative analysis of nonlinear differential equations, and the stability criteria of the deflecte...The stability of the rolling motion of near space hypersonic vehicles with rudder control is studied using method of qualitative analysis of nonlinear differential equations, and the stability criteria of the deflected rolling motions are improved. The out- comes can serve as the basis for further study regarding the influence of pitching and lateral motion on the stability of rolling motion. To validate the theoretical results, numerical simulations were do^e for the rolling motion of two hypersonic vehicles with typical configurations. Also, wind tunnel experiments for four aircraft models with typical configurations have been done. The results show that： 1） there exist two dynamic patterns of the rolling motion under statically stable condition. The first one is point attractor, for which the motion of aircraft returns to the original state. The second is periodic attractor, for which the aircraft rolls periodically. 2） Under statically unstable condition, there exist three dynamic patterns of rolling motion, namely, the point attractor, periodic attractor around deflected state of rolling motion, and double periodic attractors or chaotic attrac- tors.展开更多
A mathematical theory of time-dependent dislocation mechanics of unrestricted geometric and material nonlinearity is reviewed. Within a "small deformation" setting, a suite of simplified and interesting mode...A mathematical theory of time-dependent dislocation mechanics of unrestricted geometric and material nonlinearity is reviewed. Within a "small deformation" setting, a suite of simplified and interesting models consisting of a nonlocal Ginzburg Landau equation, a nonlocal level set equation, and a nonlocal generalized Burgers equation is derived.In the finite deformation setting, it is shown that an additive decomposition of the total velocity gradient into elastic and plastic parts emerges naturally from a micromechanical starting point that involves no notion of plastic deformation but only the elastic distortion,material velocity, dislocation density and the dislocation velocity. Moreover, a plastic spin tensor emerges naturally as well.展开更多
In this paper, the analytical solutions of Schrodinger equation for Brownian motion in a double well potential are acquired by the homotopy analysis method and the Adomian decomposition method. Double well potential f...In this paper, the analytical solutions of Schrodinger equation for Brownian motion in a double well potential are acquired by the homotopy analysis method and the Adomian decomposition method. Double well potential for Brownian motion is always used to obtain the solutions of Fokker-P1anck equation known as the Klein-Kramers equation, which is suitable for separation and additive Hamiltonians. In essence, we could study the random motion of Brownian particles by solving Schr6dinger equation. The anaiytical results obtained from the two different methods agree with each other well The double well potentiai is affected by two parameters, which are analyzed and discussed in details with the aid of graphical illustrations. According to the final results, the shapes of the double well potential have significant influence on the probability density function.展开更多
A kinematical model （a parameterized deceleration parameter） and a dynamical model （a parameterized equation of state for dark energy） are constrained from the current observational data including the high-redshif...A kinematical model （a parameterized deceleration parameter） and a dynamical model （a parameterized equation of state for dark energy） are constrained from the current observational data including the high-redshift Gamma-Ray Bursts （GRBs） data with a redshift range from 1.4 to 9. We obtain the stringent constraint on the values of current deceleration parameter q0, current jerk parameter j0, current equation of state for dark energy Woae and transition redshift zT. In addition, we compare the difference of the constraint results between the kinematical and the dynamical scenarios.展开更多
文摘与常规直流相比,永富直流逆变站存在功率全送和功率分送运行方式,而其处于分网接入方式时电网换相换流器高压直流输电(line commutated converter based high voltage directcurrent,LCC-HVDC)系统的交互振荡模式及特征尚不明确。针对这一特殊运行方式,采用模块化建模的思路建立可以反映系统电气/控制回路间交互耦合路径的运动方程模型。在此基础上,依据系统整流侧-逆变侧、正极-负极间的交互耦合路径分解得到影响系统主导模式稳定性的3条扰动传递路径,即整流侧内部自稳性路径、逆变侧内部自稳性路径、双极交互作用致稳性路径。最后,设置不同工况下的案例,量化评估不同作用路径提供的阻尼大小,并通过仿真验证运动方程模型及扰动传递路径分析结果的正确性,为后续研究分网接入方式下LCC-HVDC系统交互振荡模式的阻尼特征提供模型基础。
基金The Doctoral Program of Central South University (No. 2010ybfz048)the National High Technology Research and Development Program of China (863 Program) (No. 2007AA021908)
文摘In order to analyze the pavement stress caused by vehicle bumping at an approach slab, a simplified four-wheeled bi- axle vehicle-moving model is proposed. The effect of damping and vibration reduction in the process of vehicle-moving is not considered. Based on the position change of vehicle wheels at the approach slab, the vehicle dynamic vibration equations are summarized. Meanwhile, the undetermined coefficients of the vibration equations are obtained using the boundary and initial conditions of the vehicle. The analytical motion solutions of rear and front wheels at different stages are concluded. Consequently, a four-wheeled vehicle model is developed and vibration equations are provided, which can be used to analyze the impact of complicated stress on pavement. The results show that the excessive stress and stress concentration will occur at the approach slab, and it needs to be strengthened.
文摘The directed motion of a Brownian particle in a Bashing potential with various transition probabilities and waiting times in one of two states is studied. An expression for the average cycle period is proposed and the steady current J of the particle is calculated via Langevin simulation. The results show that the optimal cycle period (Tm), which takes the maximum of J, is shifted to a small value when the transition probability A from the potential on to the potential off decreases, the maximal current appears in the case of the average waiting time in the potential on being longer than in the potential off, and the direction of current depends on the ratio of the average times waiting in two states.
文摘In this paper, a planar five-freedom model of whole vehicle is set up and its corresponding sport differential equation is founded. The square root of the driver＇ s acceleration is selected as the estimate index by the estimate way of vehicle＇ s comfort. The estimate index is minimized by optimization of fore-and-aft suspension＇ s stiffness and written with corresponding program. In the end, a model of comfort simulation by soitware of Simulink is found, and a temporal simulation for the upper example is applied to guessing the comfort of vehicle.
文摘The main purpose of this article is to present a mathematical model of ciliary motion in an annulus. In this analysis, the peristaltic motion of non-Newtonian Jeffrey six constant fluid is observed in an annulus with ciliated tips in the presence of heat and mass transfer. The effects of viscous dissipation are also considered. The flow equations of non-Newtonian fluid for the two-dimensional tube in cylindrical coordinates are simplified using the low Reynolds number and long wave-length approximations. The main equations for Jeffrey six constant fluid are considered in cylindrical coordinates system. The resulting nonlinear problem is solved using the regular perturbation technique in terms of a variant of small dimensionless parameter α. The results of the solutions for velocity, temperature and concentration field are presented graphically. B_k is Brinkman number, ST is soret number, and SH is the Schmidth number. Outcome for the longitudinal velocity, pressure rise, pressure gradient and stream lines are represented through graphs. In the history, the viscous-dissipation effect is usually represented by the Brinkman number.
基金supported by the National Basic Research Program of China ("973" Project) (Grant No. 2007CB714600)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘In this paper,a CFD/CSD model coupling N-S equations and structural equations of motion in the time domain is described for aeroelastic analysis of large wind turbines.The structural modes of blades are analyzed with one-dimensional beam models.By combining point matched sliding grid for wind turbine rotation and deforming grid for structural vibrations,a hybrid dynamic grid strategy is designed for the multi-block structured grid system of a wind turbine.The dual time-stepping approach and finite volume scheme are applied to the three-dimensional unsteady preconditioned N-S equations,and DES approach is employed to simulate the unsteady massively separated flows.A modal approach is adopted to calculate the structural response,and a predictor-corrector scheme is used to solve the structural equations of motion.CFD and CSD solvers are tightly coupled via successive iterations within each physical time step.As a result,a time-domain CFD/CSD model for aeroelastic analysis of a large wind turbine is achieved.The presented method is applied to the NH1500 large wind turbine under the rated condition,and the calculated aeroelastic characteristics agree well with those of the prescribed vortex wake method.
基金supported by the National Natural Science Foundation of China(Grant Nos.91216203 and 91216304)
文摘The stability of the rolling motion of near space hypersonic vehicles with rudder control is studied using method of qualitative analysis of nonlinear differential equations, and the stability criteria of the deflected rolling motions are improved. The out- comes can serve as the basis for further study regarding the influence of pitching and lateral motion on the stability of rolling motion. To validate the theoretical results, numerical simulations were do^e for the rolling motion of two hypersonic vehicles with typical configurations. Also, wind tunnel experiments for four aircraft models with typical configurations have been done. The results show that： 1） there exist two dynamic patterns of the rolling motion under statically stable condition. The first one is point attractor, for which the motion of aircraft returns to the original state. The second is periodic attractor, for which the aircraft rolls periodically. 2） Under statically unstable condition, there exist three dynamic patterns of rolling motion, namely, the point attractor, periodic attractor around deflected state of rolling motion, and double periodic attractors or chaotic attrac- tors.
文摘A mathematical theory of time-dependent dislocation mechanics of unrestricted geometric and material nonlinearity is reviewed. Within a "small deformation" setting, a suite of simplified and interesting models consisting of a nonlocal Ginzburg Landau equation, a nonlocal level set equation, and a nonlocal generalized Burgers equation is derived.In the finite deformation setting, it is shown that an additive decomposition of the total velocity gradient into elastic and plastic parts emerges naturally from a micromechanical starting point that involves no notion of plastic deformation but only the elastic distortion,material velocity, dislocation density and the dislocation velocity. Moreover, a plastic spin tensor emerges naturally as well.
基金Supported by National Natural Science Foundation of China under Grant Nos.51276104,51476191
文摘In this paper, the analytical solutions of Schrodinger equation for Brownian motion in a double well potential are acquired by the homotopy analysis method and the Adomian decomposition method. Double well potential for Brownian motion is always used to obtain the solutions of Fokker-P1anck equation known as the Klein-Kramers equation, which is suitable for separation and additive Hamiltonians. In essence, we could study the random motion of Brownian particles by solving Schr6dinger equation. The anaiytical results obtained from the two different methods agree with each other well The double well potentiai is affected by two parameters, which are analyzed and discussed in details with the aid of graphical illustrations. According to the final results, the shapes of the double well potential have significant influence on the probability density function.
基金supported by the National Natural Science Foundation of China (Grant Nos.11147150,11175077 and 11005088)the Natural Science Foundation of Education Department of Liaoning Province (Grant No. L2011189)the Natural Science Foundation of Liaoning Province,China (Grant No.20102124)
文摘A kinematical model （a parameterized deceleration parameter） and a dynamical model （a parameterized equation of state for dark energy） are constrained from the current observational data including the high-redshift Gamma-Ray Bursts （GRBs） data with a redshift range from 1.4 to 9. We obtain the stringent constraint on the values of current deceleration parameter q0, current jerk parameter j0, current equation of state for dark energy Woae and transition redshift zT. In addition, we compare the difference of the constraint results between the kinematical and the dynamical scenarios.
