Researchers are investigating the possibility of developing Eye drops that will dissolve protein clumps that cause cataracts,but this study is in its early stages.Our aim in this article is to think about geometric-ma...Researchers are investigating the possibility of developing Eye drops that will dissolve protein clumps that cause cataracts,but this study is in its early stages.Our aim in this article is to think about geometric-mathematical tools,that compare such Eye drops to a vector flux through a closed curved surface as an Eye lens,with the help of Gauss’s Theorem.展开更多
In this paper the transient two-phase flow equations and their eigenvalues are first introduced. The flux vector is then split into subvectors which just contain a specially signed eigenvalue. Using one-sided spatial ...In this paper the transient two-phase flow equations and their eigenvalues are first introduced. The flux vector is then split into subvectors which just contain a specially signed eigenvalue. Using one-sided spatial difference operators finite difference equations and their solutions are obtained. Finally comparison with experiment shows the predicted results produce good agreement with experimental data.展开更多
Our aim in this paper is to interest retinal eye specialists in preventing dry macula degeneration by a special flurry vector field through open or closed curved surfaces. The flux of vector fields through surfaces is...Our aim in this paper is to interest retinal eye specialists in preventing dry macula degeneration by a special flurry vector field through open or closed curved surfaces. The flux of vector fields through surfaces is based on vector element area and volume element. Therefore, we explain a few geometrical derivations of area and volume elements in curved orthogonal coordinate systems. We hope that by derivation of a spatial vector field flurry against drusen through open or closed surfaces due to the Gauss theorem might select drusen under eye retina cells without destroying the cells and prevent macula degeneration. A changed flurry of a magnetic or electric vector field through a closed line causes an electric or magnetic vector field on the surface closed by the line. We also hope that derivation by Stokes’ and Greens’ theorems, with the help of iron, might help eye cells to get in life.展开更多
The gas-liquid-solid three-phase mixed flow is the most general in multiphase mixed transportation. It is significant to exactly solve the coupling hydraulic transient problems of this type of multiphase mixed flow in...The gas-liquid-solid three-phase mixed flow is the most general in multiphase mixed transportation. It is significant to exactly solve the coupling hydraulic transient problems of this type of multiphase mixed flow in pipelines. Presently, the method of characteristics is widely used to solve classical hydraulic transient problems. However, when it is used to solve coupling hydraulic transient problems, excessive interpolation errors may be introduced into the results due to unavoidable multiwave interpolated calculations. To deal with the problem, a finite difference scheme based on the Steger- Warming flux vector splitting is proposed. A flux vector splitting scheme is established for the coupling hydraulic transient model of gas-liquid-solid three-phase mixed flow in the pipelines. The flux subvectors are then discretized by the Lax-Wendroff central difference scheme and the Warming-Beam upwind difference scheme with second-order precision in both time and space. Under the Rankine-Hugoniot conditions and the corresponding boundary conditions, an effective solution to those points located at the boundaries is developed, which can avoid the problem beyond the calculation region directly induced by the second-order discrete technique. Numerical and experimental verifications indicate that the proposed scheme has several desirable advantages including high calculation precision, excellent shock wave capture capability without false numerical oscillation, low sensitivity to the Courant number, and good stability.展开更多
To solve water hammer problems in pipeline systems,many numerical simulation approaches have been developed. This paper improves a flux vector splitting( FVS) scheme whose grid is the same as the fixedgrid MOC scheme....To solve water hammer problems in pipeline systems,many numerical simulation approaches have been developed. This paper improves a flux vector splitting( FVS) scheme whose grid is the same as the fixedgrid MOC scheme. The proposed FVS scheme is used to analyze water hammer problems caused by a pump abrupt shutdown in a pumping system with an air vessel. This paper also proposes a pump-valve-vessel model combining a pump-valve model with an air vessel model. The results show that the data obtained by the FVS scheme are similar to the ones obtained by the fixed-grid method of characteristics( MOC). And the results using the pump-valve-vessel model are almost the same as the ones using both the pump-valve model and the air vessel model. Therefore,it is effective that the proposed FVS scheme is used to solve water hammer problems and the pump-valve-vessel model replaces both the pump-valve model and the air vessel model to simulate water hammer flows in the pumping system with the air vessel.展开更多
Based on the analogy to gas dynamics, the kinetic flux vector splitting (KFVS) method is used to stimulate the shallow water wave equations. The flux vectors of the equations are split on the basis of the local equili...Based on the analogy to gas dynamics, the kinetic flux vector splitting (KFVS) method is used to stimulate the shallow water wave equations. The flux vectors of the equations are split on the basis of the local equilibrium Maxwell-Boltzmann distribution. One dimensional examples including a dam breaking wave and flows over a ridge are calculated. The solutions exhibit second-order accuracy with no spurious oscillation.展开更多
Originally, the kinetic flux vector splitting (KFVS) scheme was developed as a numerical method to solve gas dynamic problems. The main idea in the approach is to construct the flux based on the microscopical descript...Originally, the kinetic flux vector splitting (KFVS) scheme was developed as a numerical method to solve gas dynamic problems. The main idea in the approach is to construct the flux based on the microscopical description of the gas. In this paper, based on the analogy between the shallow water wave equations and the gas dynamic equations, we develop an explicit KFVS method for simulating the shallow water wave equations. A 1D steady flow and a 2D unsteady flow are presented to show the robust and accuracy of the KFVS scheme.展开更多
Stem cell transplantation for the blind is a promising area of research, but it is still in the early stages of development. Our aim in this article is to think about geometric-mathematical tools so that by the flux o...Stem cell transplantation for the blind is a promising area of research, but it is still in the early stages of development. Our aim in this article is to think about geometric-mathematical tools so that by the flux of stem cells into open and curved spaces in the retina of recently blind people and macular degeneration patients, (AMD) patients, we will enable the growth of visual cells in their retinas.展开更多
The bearingless induction motor, which combines the inductionmotor and magnetic bearing is a strongly coupled complicatednonlinear system; the decoupling control of the electromag- net toqueand readial levitation forc...The bearingless induction motor, which combines the inductionmotor and magnetic bearing is a strongly coupled complicatednonlinear system; the decoupling control of the electromag- net toqueand readial levitation force is the base of the stable operation ofthe benaringless motor. In this paper, the air-gap motor fluxoriented vector control is proposed to realize the decoupling controlof this nonlinear system even in the transient case based on thelevitation principle. Simulations show the stable suspension and goodperformance of the proposed algorithm.展开更多
ZVS（zero voltage switching） PWM（pulse width modulation） inverters have attracted much attention recently. The basic idea is to use ZVS circuit as the main circuit of inverter resonance at the beginning of every ca...ZVS（zero voltage switching） PWM（pulse width modulation） inverters have attracted much attention recently. The basic idea is to use ZVS circuit as the main circuit of inverter resonance at the beginning of every carrier period so that each power device can commutate when voltage of the main circuit＇s DC bus line is zero. To ensure the resonant circuit to operate properly, sawtooth with alternate slope （positive or negative） is used as carrier. But the time of zero voltage vectors with such PWM pattern is greatly different from traditional hard-switching PWM pattern. This paper discusses the locus of flux linkage under soft-switching PWM pattern by using space voltage vector. It is pointed out that, under the hard-switching PWM pattern, speed of flux linkage is adjusted by zero space voltage vector. When soft-switching PWM pattern is used, however, effective time of space voltage vector varies considerably, sometimes even without zero space voltage vector. Therefore non-zero space voltage vector has been used to make the speed of flux linkage locus equal to that of hard-switching PWM pattern. The cause of current distortion in soft-switching PWM inverters is also discussed. Based on the flux linkage locus circle, corresponding compensation methods are proposed. Experimental results show that the described method can effectively improve output current waveform of inverter.展开更多
According to the integral relationship between the vector magnetic flux density on a spatial point and that over a closed surface around magnetic sources,a technique for the extrapolation of vector magnetic field of a...According to the integral relationship between the vector magnetic flux density on a spatial point and that over a closed surface around magnetic sources,a technique for the extrapolation of vector magnetic field of a ferromagnetic object is given without computing scalar potential and its gradient. The vector magnetic flux density on a remote spatial point can be extrapolated by surface integral from the vector values over a closed measureed surface around the ferromagnetic object. The correctness of the technique testified by a special example and simulation. The experimented result shows that its accuracy is satisfying and the execution time is less than 1 second.展开更多
We study the controversy about the proper determination of the electromagnetic energy-flux field in anisotropic materials, which has been revived due to the relatively recent experiments on negative refraction in meta...We study the controversy about the proper determination of the electromagnetic energy-flux field in anisotropic materials, which has been revived due to the relatively recent experiments on negative refraction in metamaterials. Rather than analyzing energy-balance arguments, we use a pragmatic approach inspired by geometrical optics, and compare the predictions on angles of refraction at a flat interface of two possible choices on the energy flux: and . We carry out this comparison for a monochromatic Gaussian beam propagating in an anisotropic non-dissipative anisotropic metamaterial, in which the spatial localization of the electromagnetic field allows a more natural assignment of directions, in contrast to the usual study of plane waves. We compare our approach with the formalism of geometrical optics, which we generalize and analyze numerically the consequences of either choice.展开更多
Direct torque control (DTC) of Switched reluctance motor is known straightforward control structure with similar execution to that of field situated control strategies. In any case, the part of ideal determination of ...Direct torque control (DTC) of Switched reluctance motor is known straightforward control structure with similar execution to that of field situated control strategies. In any case, the part of ideal determination of the voltage space vector is one of the weakest focuses in a routine DTC drive because of adjustable switching frequency and high torque ripple. In this paper, ideal choice of voltage space vectors is accomplished utilizing ANFIS (Adaptive Neuro Fuzzy Inference System) with space vector Modulation. SVM-DTC gives consistent switching frequency and the proposed ANFIS controller’s structure manages the torque and stator flux error signals through the fuzzy deduction to get a yield that takes the type of space voltage vector. Simulation results accept the proposed evolutionary system with quick torque and flux reaction with minimized torque ripple and flux ripple.展开更多
A method of improving the stability of multiple-motor drive system fed by a 3-leg single inverter has been devised that employs the averages and differences of estimated parameters for field-oriented control. The para...A method of improving the stability of multiple-motor drive system fed by a 3-leg single inverter has been devised that employs the averages and differences of estimated parameters for field-oriented control. The parameters of each motor (stator current, rotor flux, and speed) are estimated using adaptive rotor flux observers to achieve sensorless control. The validity and effective of the proposed method have been demonstrated through simulations and experiments.展开更多
This paper deals with the vector control, including both the direct vector control(DVC) and the indirect vector control(Id VC),of induction motors. It is well known that the estimation of rotor flux plays a fundamenta...This paper deals with the vector control, including both the direct vector control(DVC) and the indirect vector control(Id VC),of induction motors. It is well known that the estimation of rotor flux plays a fundamental role in the DVC and the estimation of rotor resistance is vital in the slip compensation of the Id VC. In these estimations, the precision is significantly affected by the motor resistances. Therefore, online estimation of motor resistances is indispensable in practice.For a fast estimation of motor resistances, it is necessary to slow down the convergence rate of the current estimate. On the other hand, for a fast estimation of the rotor flux, it is necessary to speed up its convergence rate. It is very difficult to realize such a trade-off in convergence rates in a full order observer.In this paper, we propose to decouple the current observer from the flux observer so as to realize independent convergence rates. Then, the resistance estimation algorithm is applied to both DVC and Id VC. In particular, in the application to Id VC the flux observer needs not be used, which leads to a simpler structure. Meanwhile, independent convergence rates of current observer and flux observer yield an improved performance. A superior performance in the torque and flux responses in both cases is verified by numerous simulations.展开更多
单相开路故障的五相永磁同步电机(permanent-magnet synchronous motor,PMSM)采用有限集模型预测转矩和磁链控制(finite-control-set model predictive torque and flux control,FCS-MPTFC)策略,存在转矩脉动大、价值函数的权重系数整...单相开路故障的五相永磁同步电机(permanent-magnet synchronous motor,PMSM)采用有限集模型预测转矩和磁链控制(finite-control-set model predictive torque and flux control,FCS-MPTFC)策略,存在转矩脉动大、价值函数的权重系数整定困难、迭代计算量大以及共模电压(commonmode voltage,CMV)高等问题。为此,该文提出一种简化FCS-MPTFC策略。首先,建立五相PMSM在单相开路故障情况下的数学模型,并分析CMV产生的机理。其次,以抑制3次谐波电流的原则合成等幅值虚拟电压矢量(virtual voltage vector,V^(3)),并将转矩和磁链价值函数等效转化为电压价值函数,同时采用无差拍控制思想计算出参考电压矢量,进而通过合理划分扇区,直接获得最优V^(3)。最后,选择方向相反的两个基电压矢量代替零矢量,以减小开路故障下的CMV。仿真和实验结果表明:所提控制策略不仅能抑制单相开路故障导致的转矩脉动、降低计算负荷和CMV、抑制电流谐波,而且具有优良的稳态和动态性能。展开更多
文摘Researchers are investigating the possibility of developing Eye drops that will dissolve protein clumps that cause cataracts,but this study is in its early stages.Our aim in this article is to think about geometric-mathematical tools,that compare such Eye drops to a vector flux through a closed curved surface as an Eye lens,with the help of Gauss’s Theorem.
文摘In this paper the transient two-phase flow equations and their eigenvalues are first introduced. The flux vector is then split into subvectors which just contain a specially signed eigenvalue. Using one-sided spatial difference operators finite difference equations and their solutions are obtained. Finally comparison with experiment shows the predicted results produce good agreement with experimental data.
文摘Our aim in this paper is to interest retinal eye specialists in preventing dry macula degeneration by a special flurry vector field through open or closed curved surfaces. The flux of vector fields through surfaces is based on vector element area and volume element. Therefore, we explain a few geometrical derivations of area and volume elements in curved orthogonal coordinate systems. We hope that by derivation of a spatial vector field flurry against drusen through open or closed surfaces due to the Gauss theorem might select drusen under eye retina cells without destroying the cells and prevent macula degeneration. A changed flurry of a magnetic or electric vector field through a closed line causes an electric or magnetic vector field on the surface closed by the line. We also hope that derivation by Stokes’ and Greens’ theorems, with the help of iron, might help eye cells to get in life.
基金supported by the Natural Science Foundation Project of CQ CSTC (No. 2010BB7421)
文摘The gas-liquid-solid three-phase mixed flow is the most general in multiphase mixed transportation. It is significant to exactly solve the coupling hydraulic transient problems of this type of multiphase mixed flow in pipelines. Presently, the method of characteristics is widely used to solve classical hydraulic transient problems. However, when it is used to solve coupling hydraulic transient problems, excessive interpolation errors may be introduced into the results due to unavoidable multiwave interpolated calculations. To deal with the problem, a finite difference scheme based on the Steger- Warming flux vector splitting is proposed. A flux vector splitting scheme is established for the coupling hydraulic transient model of gas-liquid-solid three-phase mixed flow in the pipelines. The flux subvectors are then discretized by the Lax-Wendroff central difference scheme and the Warming-Beam upwind difference scheme with second-order precision in both time and space. Under the Rankine-Hugoniot conditions and the corresponding boundary conditions, an effective solution to those points located at the boundaries is developed, which can avoid the problem beyond the calculation region directly induced by the second-order discrete technique. Numerical and experimental verifications indicate that the proposed scheme has several desirable advantages including high calculation precision, excellent shock wave capture capability without false numerical oscillation, low sensitivity to the Courant number, and good stability.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51208160)the Natural Science Foundation of Heilongjiang Province(Grant No.QC2012C056)
文摘To solve water hammer problems in pipeline systems,many numerical simulation approaches have been developed. This paper improves a flux vector splitting( FVS) scheme whose grid is the same as the fixedgrid MOC scheme. The proposed FVS scheme is used to analyze water hammer problems caused by a pump abrupt shutdown in a pumping system with an air vessel. This paper also proposes a pump-valve-vessel model combining a pump-valve model with an air vessel model. The results show that the data obtained by the FVS scheme are similar to the ones obtained by the fixed-grid method of characteristics( MOC). And the results using the pump-valve-vessel model are almost the same as the ones using both the pump-valve model and the air vessel model. Therefore,it is effective that the proposed FVS scheme is used to solve water hammer problems and the pump-valve-vessel model replaces both the pump-valve model and the air vessel model to simulate water hammer flows in the pumping system with the air vessel.
基金Subsidized by the Special Funds for Major State Basic Research Early Stage Project(2002CCA 01200)the Project-sponsored by SRF for ROCS,SME.
文摘Based on the analogy to gas dynamics, the kinetic flux vector splitting (KFVS) method is used to stimulate the shallow water wave equations. The flux vectors of the equations are split on the basis of the local equilibrium Maxwell-Boltzmann distribution. One dimensional examples including a dam breaking wave and flows over a ridge are calculated. The solutions exhibit second-order accuracy with no spurious oscillation.
基金Foundation item:Supported by the National Key Grant Program of Basic(2002CCA01200)original funding of Jilin Universitythe Project-sponsord by SRF for ROCS,SME
文摘Originally, the kinetic flux vector splitting (KFVS) scheme was developed as a numerical method to solve gas dynamic problems. The main idea in the approach is to construct the flux based on the microscopical description of the gas. In this paper, based on the analogy between the shallow water wave equations and the gas dynamic equations, we develop an explicit KFVS method for simulating the shallow water wave equations. A 1D steady flow and a 2D unsteady flow are presented to show the robust and accuracy of the KFVS scheme.
文摘Stem cell transplantation for the blind is a promising area of research, but it is still in the early stages of development. Our aim in this article is to think about geometric-mathematical tools so that by the flux of stem cells into open and curved spaces in the retina of recently blind people and macular degeneration patients, (AMD) patients, we will enable the growth of visual cells in their retinas.
文摘The bearingless induction motor, which combines the inductionmotor and magnetic bearing is a strongly coupled complicatednonlinear system; the decoupling control of the electromag- net toqueand readial levitation force is the base of the stable operation ofthe benaringless motor. In this paper, the air-gap motor fluxoriented vector control is proposed to realize the decoupling controlof this nonlinear system even in the transient case based on thelevitation principle. Simulations show the stable suspension and goodperformance of the proposed algorithm.
基金Project supported by Shanghai Leading AcademicDisciplineProject (Grant No .T0103) ,and Shanghai Post Doctoral ScientificResearch Project (Grant No .05R214122)
文摘ZVS（zero voltage switching） PWM（pulse width modulation） inverters have attracted much attention recently. The basic idea is to use ZVS circuit as the main circuit of inverter resonance at the beginning of every carrier period so that each power device can commutate when voltage of the main circuit＇s DC bus line is zero. To ensure the resonant circuit to operate properly, sawtooth with alternate slope （positive or negative） is used as carrier. But the time of zero voltage vectors with such PWM pattern is greatly different from traditional hard-switching PWM pattern. This paper discusses the locus of flux linkage under soft-switching PWM pattern by using space voltage vector. It is pointed out that, under the hard-switching PWM pattern, speed of flux linkage is adjusted by zero space voltage vector. When soft-switching PWM pattern is used, however, effective time of space voltage vector varies considerably, sometimes even without zero space voltage vector. Therefore non-zero space voltage vector has been used to make the speed of flux linkage locus equal to that of hard-switching PWM pattern. The cause of current distortion in soft-switching PWM inverters is also discussed. Based on the flux linkage locus circle, corresponding compensation methods are proposed. Experimental results show that the described method can effectively improve output current waveform of inverter.
文摘According to the integral relationship between the vector magnetic flux density on a spatial point and that over a closed surface around magnetic sources,a technique for the extrapolation of vector magnetic field of a ferromagnetic object is given without computing scalar potential and its gradient. The vector magnetic flux density on a remote spatial point can be extrapolated by surface integral from the vector values over a closed measureed surface around the ferromagnetic object. The correctness of the technique testified by a special example and simulation. The experimented result shows that its accuracy is satisfying and the execution time is less than 1 second.
文摘We study the controversy about the proper determination of the electromagnetic energy-flux field in anisotropic materials, which has been revived due to the relatively recent experiments on negative refraction in metamaterials. Rather than analyzing energy-balance arguments, we use a pragmatic approach inspired by geometrical optics, and compare the predictions on angles of refraction at a flat interface of two possible choices on the energy flux: and . We carry out this comparison for a monochromatic Gaussian beam propagating in an anisotropic non-dissipative anisotropic metamaterial, in which the spatial localization of the electromagnetic field allows a more natural assignment of directions, in contrast to the usual study of plane waves. We compare our approach with the formalism of geometrical optics, which we generalize and analyze numerically the consequences of either choice.
文摘Direct torque control (DTC) of Switched reluctance motor is known straightforward control structure with similar execution to that of field situated control strategies. In any case, the part of ideal determination of the voltage space vector is one of the weakest focuses in a routine DTC drive because of adjustable switching frequency and high torque ripple. In this paper, ideal choice of voltage space vectors is accomplished utilizing ANFIS (Adaptive Neuro Fuzzy Inference System) with space vector Modulation. SVM-DTC gives consistent switching frequency and the proposed ANFIS controller’s structure manages the torque and stator flux error signals through the fuzzy deduction to get a yield that takes the type of space voltage vector. Simulation results accept the proposed evolutionary system with quick torque and flux reaction with minimized torque ripple and flux ripple.
文摘A method of improving the stability of multiple-motor drive system fed by a 3-leg single inverter has been devised that employs the averages and differences of estimated parameters for field-oriented control. The parameters of each motor (stator current, rotor flux, and speed) are estimated using adaptive rotor flux observers to achieve sensorless control. The validity and effective of the proposed method have been demonstrated through simulations and experiments.
文摘This paper deals with the vector control, including both the direct vector control(DVC) and the indirect vector control(Id VC),of induction motors. It is well known that the estimation of rotor flux plays a fundamental role in the DVC and the estimation of rotor resistance is vital in the slip compensation of the Id VC. In these estimations, the precision is significantly affected by the motor resistances. Therefore, online estimation of motor resistances is indispensable in practice.For a fast estimation of motor resistances, it is necessary to slow down the convergence rate of the current estimate. On the other hand, for a fast estimation of the rotor flux, it is necessary to speed up its convergence rate. It is very difficult to realize such a trade-off in convergence rates in a full order observer.In this paper, we propose to decouple the current observer from the flux observer so as to realize independent convergence rates. Then, the resistance estimation algorithm is applied to both DVC and Id VC. In particular, in the application to Id VC the flux observer needs not be used, which leads to a simpler structure. Meanwhile, independent convergence rates of current observer and flux observer yield an improved performance. A superior performance in the torque and flux responses in both cases is verified by numerous simulations.
文摘单相开路故障的五相永磁同步电机(permanent-magnet synchronous motor,PMSM)采用有限集模型预测转矩和磁链控制(finite-control-set model predictive torque and flux control,FCS-MPTFC)策略,存在转矩脉动大、价值函数的权重系数整定困难、迭代计算量大以及共模电压(commonmode voltage,CMV)高等问题。为此,该文提出一种简化FCS-MPTFC策略。首先,建立五相PMSM在单相开路故障情况下的数学模型,并分析CMV产生的机理。其次,以抑制3次谐波电流的原则合成等幅值虚拟电压矢量(virtual voltage vector,V^(3)),并将转矩和磁链价值函数等效转化为电压价值函数,同时采用无差拍控制思想计算出参考电压矢量,进而通过合理划分扇区,直接获得最优V^(3)。最后,选择方向相反的两个基电压矢量代替零矢量,以减小开路故障下的CMV。仿真和实验结果表明:所提控制策略不仅能抑制单相开路故障导致的转矩脉动、降低计算负荷和CMV、抑制电流谐波,而且具有优良的稳态和动态性能。
