Wide-band oscillations have become a significant issue limiting the development of wind power.Both large-signal and small-signal analyses require extensive model derivation.Moreover,the large number and high order of ...Wide-band oscillations have become a significant issue limiting the development of wind power.Both large-signal and small-signal analyses require extensive model derivation.Moreover,the large number and high order of wind turbines have driven the development of simplified models,whose applicability remains controversial.In this paper,a wide-band oscillation analysis method based on the average-value model(AVM)is proposed for wind farms(WFs).A novel linearization analysis framework is developed,leveraging the continuous-time characteristics of the AVM and MATLAB/Simulink’s built-in linearization tools.This significantly reduces modeling complexity and computational costs while maintaining model fidelity.Additionally,an object-based initial value estimation method of state variables is introduced,which,when combined with steady-state point-solving tools,greatly reduces the computational effort required for equilibrium point solving in batch linearization analysis.The proposed method is validated in both doubly fed induction generator(DFIG)-based and permanent magnet synchronous generator(PMSG)-based WFs.Furthermore,a comprehensive analysis is conducted for the first time to examine the impact of the machine-side system on the system stability of the nonfully controlled PMSG-based WF.展开更多
A novel elevator door driven by tubular permanent magnet linear synchronous motor (TPMLSM) is presented. This TPMLSM applies axial magnet array topology of the secondary rod, air-cored armature windings and slotless s...A novel elevator door driven by tubular permanent magnet linear synchronous motor (TPMLSM) is presented. This TPMLSM applies axial magnet array topology of the secondary rod, air-cored armature windings and slotless structure of the forcer to improve the stability of the thrust. The influence of two major dimensions, the pitch and radius of the permanent magnet (PM), on magnetic field was studied and the best values were given by the finite element analysis (FEA). The magnetic field, back EMF and thrust of the motor were analyzed and the PM size was optimized to reduce the harmonic components of the magnetic field and improve the performance of the motor. Predicted results are validated by the experiment. It is shown that the performance of the motor and the novel elevator door system is satisfying.展开更多
This paper gives performance analysis of a three phase Permanent Magnet Synchronous Generator (PMSG) connected to a Vertical Axis Wind Turbine (VAWT). Low speed wind condition (less than 5 m/s) is taken in considerati...This paper gives performance analysis of a three phase Permanent Magnet Synchronous Generator (PMSG) connected to a Vertical Axis Wind Turbine (VAWT). Low speed wind condition (less than 5 m/s) is taken in consideration and the entire simulation is carried in Matlab/Simulink environment. The rated power for the generator is fixed at 1.5 KW and number of pole at 20. It is observed under low wind speed of6 m/s, a turbine having approximately1 mof radius and2.6 mof height develops 150 Nm mechanical torque that can generate power up to 1.5 KW. The generator is designed using modeling tool and is fabricated. The fabricated generator is tested in the laboratory with the simulation result for the error analysis. The range of error is about 5%-27% for the same output power value. The limitations and possible causes for error are presented and discussed.展开更多
This paper presents an analytical method to design the high-efficiency surface permanent magnet synchronous motor(SPMSM)or generator(SPMSG).The air-gap and permanent magnet size can be approximately determined based o...This paper presents an analytical method to design the high-efficiency surface permanent magnet synchronous motor(SPMSM)or generator(SPMSG).The air-gap and permanent magnet size can be approximately determined based on our mathematics model,which is the most important part of SPMSM design.From our method,we can know that motor’s power out torque is related to the torque angle that we selected in our design and it affects the air-gap and permanent magnet size.If we choose a low torque angle,the motor or generator’s overload power handing capability will increase.The embrace value has a vital place in designing a motor or generator due to its effects on air gap flux density,cogging torque,efficiency and so on.In order to avoid the knee effect,the working point of the permanent magnet we selected in the design should be bigger than 0.5.The developed 36 slots,4 poles,surface mound permanent generator is proposed.The corresponding finite element analysis(FEA)model is built based on our design method.Structure optimization includes stator and rotor structure size,permanent magnet size,magnetic bridge and air gap length which are analyzed and simulated by ANSYS Maxwell 2D FEA.Thermal analysis is conducted,and the housing of the alternator is designed.The alternator prototype is fabricated and tested based on our design.展开更多
To improve the heat dissipation performance,this paper proposes a novel hybrid cooling method for high-speed high-power Permanent Magnet assisted Synchronous Reluctance Starter/Generator(PMa Syn R S/G)in aerospace app...To improve the heat dissipation performance,this paper proposes a novel hybrid cooling method for high-speed high-power Permanent Magnet assisted Synchronous Reluctance Starter/Generator(PMa Syn R S/G)in aerospace applications.The hybrid cooling structure with oil circulation in the housing,oil spray at winding ends and rotor end surface is firstly proposed for the PMa Syn R S/G.Then the accurate loss calculation of the PMa Syn R S/G is proposed,which includes air gap friction loss under oil spray cooling,copper loss,stator and rotor core loss,permanent magnet eddy current loss and bearing loss.The parameter sensitivity analysis of the hybrid cooling structure is proposed,while the equivalent thermal network model of the PMa Syn R S/G is established considering the uneven spraying at the winding ends.Finally,the effectiveness of the proposed hybrid cooling method is demonstrated on a 40 k W/24000 r/min PMa Syn R S/G experimental platform.展开更多
By means of finite element analysis methods calculated the stress, strainand displacement of the belt teeth and analysisied the factors such as load distribution,specific property coefficient of material and tempe...By means of finite element analysis methods calculated the stress, strainand displacement of the belt teeth and analysisied the factors such as load distribution,specific property coefficient of material and temperature variation, which influence the fatigue strength of the belt teeth..展开更多
A novel text independent speaker identification system is proposed. In the proposed system, the 12-order perceptual linear predictive cepstrum and their delta coefficients in the span of five frames are extracted from...A novel text independent speaker identification system is proposed. In the proposed system, the 12-order perceptual linear predictive cepstrum and their delta coefficients in the span of five frames are extracted from the segmented speech based on the method of pitch synchronous analysis. The Fisher ratios of the original coefficients then be calculated, and the coefficients whose Fisher ratios are bigger are selected to form the 13-dimensional feature vectors of speaker. The Gaussian mixture model is used to model the speakers. The experimental results show that the identification accuracy of the proposed system is obviously better than that of the systems based on other conventional coefficients like the linear predictive cepstral coefficients and the Mel-frequency cepstral coefficients.展开更多
As a driving motor, surface mounted permanent magnet synchronous motor exhibits high efficiency and high power density. However, it is susceptible to suffer irreversible demagnetization and insulation failure of coils...As a driving motor, surface mounted permanent magnet synchronous motor exhibits high efficiency and high power density. However, it is susceptible to suffer irreversible demagnetization and insulation failure of coils under severe thermal load condition. Therefore, it is essential to predict temperattrre distribution in the driving motor. In this paper, a lumped parameter thermal mode/of surface mounted permanent magnet is investigated. By using finite element method, the iron loss distribution in various parts of the driving motor is achieved. Moreover, the influences of interface gap and flow rate on temperature distribution are discussed. Finally, the simulation of temperature distribution in different parts of the driving motor is achieved. The presented methodology contributes to verify the feasibility of the driving motor design.展开更多
Multi-phase machines are so attractive for electrical machine designers because of their valuable advantages such as high reliability and fault tolerant ability.Meanwhile,fractional slot concentrated windings(FSCW)are...Multi-phase machines are so attractive for electrical machine designers because of their valuable advantages such as high reliability and fault tolerant ability.Meanwhile,fractional slot concentrated windings(FSCW)are well known because of short end winding length,simple structure,field weakening sufficiency,fault tolerant capability and higher slot fill factor.The five-phase machines equipped with FSCW,are very good candidates for the purpose of designing motors for high reliable applications,like electric cars,major transporting buses,high speed trains and massive trucks.But,in comparison to the general distributed windings,the FSCWs contain high magnetomotive force(MMF)space harmonic contents,which cause unwanted effects on the machine ability,such as localized iron saturation and core losses.This manuscript introduces several new five-phase fractional slot winding layouts,by the means of slot shifting concept in order to design the new types of synchronous reluctance motors(SynRels).In order to examine the proposed winding’s performances,three sample machines are designed as case studies,and analytical study and finite element analysis(FEA)is used for validation.展开更多
This paper presents a new technique for measuring the bunch length of a high-energy electron beam at a bunch-by-bunch rate in storage rings.This technique uses the time–frequency-domain joint analysis of the bunch si...This paper presents a new technique for measuring the bunch length of a high-energy electron beam at a bunch-by-bunch rate in storage rings.This technique uses the time–frequency-domain joint analysis of the bunch signal to obtain bunch-by-bunch and turn-by-turn longitudinal parameters,such as bunch length and synchronous phase.The bunch signal is obtained using a button electrode with a bandwidth of several gigahertz.The data acquisition device was a high-speed digital oscilloscope with a sampling rate of more than 10 GS/s,and the single-shot sampling data buffer covered thousands of turns.The bunch-length and synchronous phase information were extracted via offline calculations using Python scripts.The calibration coefficient of the system was determined using a commercial streak camera.Moreover,this technique was tested on two different storage rings and successfully captured various longitudinal transient processes during the harmonic cavity debugging process at the Shanghai Synchrotron Radiation Facility(SSRF),and longitudinal instabilities were observed during the single-bunch accumulation process at Hefei Light Source(HLS).For Gaussian-distribution bunches,the uncertainty of the bunch phase obtained using this technique was better than 0.2 ps,and the bunch-length uncertainty was better than 1 ps.The dynamic range exceeded 10 ms.This technology is a powerful and versatile beam diagnostic tool that can be conveniently deployed in high-energy electron storage rings.展开更多
Based on the stability theory of the fractional order system, the dynamic behaviours of a new fractional order system are investigated theoretically. The lowest order we found to have chaos in the new three-dimensiona...Based on the stability theory of the fractional order system, the dynamic behaviours of a new fractional order system are investigated theoretically. The lowest order we found to have chaos in the new three-dimensional system is 2.46, and the period routes to chaos in the new fractional order system are also found. The effectiveness of our analysis results is further verified by numerical simulations and positive largest Lyapunov exponent. Furthermore, a nonlinear feedback controller is designed to achieve the generalized projective synchronization of the fractional order chaotic system, and its validity is proved by Laplace transformation theory.展开更多
Dissolved organic matter (DOM) can be originated from autochthonous or allochthonous sources, where allochthonous DOM can be from pedogenic sources (humic substances—HSs) or anthropogenicsources (wastewater). The ana...Dissolved organic matter (DOM) can be originated from autochthonous or allochthonous sources, where allochthonous DOM can be from pedogenic sources (humic substances—HSs) or anthropogenicsources (wastewater). The analysis of fluorescence emission, excitation, synchronous or excitation-emission matrix (EEM) have been used to identify the main source or probable contribution of dissolved compounds, such as humic acids (HA), fulvic acids (FA) and dissolved organic carbon (DOC) from sewage, but does not quantify. Fluorescence emission is a powerful technique to detect and qualify organic dissolved compounds but fails in quantitative aspects. In this work, we propose an in situ method for direct determination of DOC using synchronous fluorescence spectra with independent component analysis (ICA). Well known standard solutions were used for method development and validation. In this work, we show that it is possible to predict the number of independent contributions using an unsupervised method based on iterative Principal Component Analysis and Independent Component Analysis (PCA-ICA) approach over combined matrix results. Within these results it’s also possible to see that with a very small amount of independent components it is possible to describe environmental samples of HA, FA and primary productivity (PP).展开更多
In general, the seismic response analysis in earthquake engineering assumes that the vibration parameters of the target and the contact surface of the external media are identical,i. e., single point input. However, e...In general, the seismic response analysis in earthquake engineering assumes that the vibration parameters of the target and the contact surface of the external media are identical,i. e., single point input. However, earthquake energy has an attenuation phenomenon in wave propagation,so a wide range of soil slopes and the external medium contact surface of different input points on motion are not identical. If we consider single point input only, it may not correspond with reality, so it is necessary to carry out research on multi-point input methods. Based on the 2-D slope model,single-point input and multi-point input are performed respectively to analyze and compare their similarities and differences in the perspectives of the characteristics of seismic response of soil layer and plastic zone distribution to provide a reference for the seismic design of slopes. The results show that in the perspective of soil seismic response analysis,the peak acceleration output and peak velocity output under multi-point input are greater than the peak values under single point input at the same monitoring point,the peak appearing time is also earlier than that of the single point input; in terms of the plastic zone distribution,the multi-point effect is manifested as the presence of more obvious tensile shear failures; in the perspective of safety coefficient,the safety coefficient under each multi-point input is smaller than that of single point input,a difference of about 7 % or so. In summary,multi-point input is more reasonable and practical than single point input,so multi-point input should be considered in seismic design.展开更多
Pinning synchronization of a networked multi-agent system with a directed communication topology is investigated from a spectral analysis approach. Some new types of synchronized regions for networked systems with dif...Pinning synchronization of a networked multi-agent system with a directed communication topology is investigated from a spectral analysis approach. Some new types of synchronized regions for networked systems with different nonlinear agent dynamics and inner coupling structures are discovered. The eigenvalue distributions of the coupling and control matrices for different types of directed networks are obtained. The effects of the network topology, pinning density and pinning strength on the network synchronizability are examined through extensive numerical simulations. It is shown that the synchronizability of the pinned network can be effectively improved by increasing pinning density and pinning strength for some types of synchronized regions, whereas too large the pinning density and pinning strength will lead to desynchronization for other types. It is found that directed random networks are not always easier to synchronize than directed small-world networks, and a denser eigenvalue distribution may not always imply better synchronizability.展开更多
In this article the authors have studied the stability analysis and chaos control of the fractional order Vallis and El-Nino systems. The chaos control of these systems is studied using nonlinear control method with t...In this article the authors have studied the stability analysis and chaos control of the fractional order Vallis and El-Nino systems. The chaos control of these systems is studied using nonlinear control method with the help of a new lemma for Caputo derivative and Lyapunov stability theory.The synchronization between the systems for different fractional order cases and numerical simulation through graphical plots for different particular cases clearly exhibit that the method is easy to implement and reliable for synchronization of fractional order chaotic systems. The comparison of time of synchronization when the systems pair approaches from standard order to fractional order is the key feature of the article.展开更多
Fast and accurate identification of unknown pollution sources plays a crucial role in the emergency response and source control of air pollution.In this work,the applicability of a previously proposed two-step inversi...Fast and accurate identification of unknown pollution sources plays a crucial role in the emergency response and source control of air pollution.In this work,the applicability of a previously proposed two-step inversion method is investigated with sensitivity experiments and real data from the first release of the European Tracer Experiment(ETEX-1).The two-step inversion method is based on the principle of least squares and carries out additional model correction through the residual iterative process.To evaluate its performance,its retrieval results are compared with those of two other existing algorithms.It is shown that for those cases with richer measurements,all three methods are less sensitive to errors,while for cases where measurements are sparse,their retrieval accuracy will rapidly decrease as errors increase.From the results of sensitivity experiments,the new method provides higher estimation accuracy and a more stable performance than the other two methods.The new method presents the smallest maximum location error of 18.20 km when the amplitude of the measurement error increases to 100%,and 22.67 km when errors in the wind fields increase to 200%.Moreover,when applied to ETEX-1 data,the new method also exhibits good performance,with a location error of 4.71 km,which is the best estimation with respect to source location.展开更多
We perform an analysis of brain-neuromuscular synchronization and coupling strength in muscular dystrophy before and after NPT treatment. In order to estimate with accuracy the level of brain synchronization, we intro...We perform an analysis of brain-neuromuscular synchronization and coupling strength in muscular dystrophy before and after NPT treatment. In order to estimate with accuracy the level of brain synchronization, we introduce and use the method of the cross GMI that was elaborated by Pompe. The finality is to account for the nonlinear chaotic dynamic contributions that regulate the dynamics. We find that this method is excellent and it may be applied in such case of sEMG and EEG study as well as at a general neurological level. By it we arrive to quantify the coupling strength and synchronization first between two muscular sections (left and right trapezes) and after between Brain activity, as recorded by the EEG, and the trapezes. We compare the results before and after the NPT treatment and we find that the improvement obtained following such treatment is very consistent. We have now in progress other studies relating in particular the application of such new methodologies to other more serious pathologies as the HSP (Hereditary Spastic Paraplegia).展开更多
The integration of converter-interfaced generators(CIGs)into power systems is rapidly replacing traditional synchronous machines.To ensure the security of power supply,modern power systems require the application of g...The integration of converter-interfaced generators(CIGs)into power systems is rapidly replacing traditional synchronous machines.To ensure the security of power supply,modern power systems require the application of grid-forming technologies.This study presents a systematic small-signal analysis procedure to assess the synchronization stability of gridforming virtual synchronous generators(VSGs)considering the power system characteristics.Specifically,this procedure offers guidance in tuning controller gains to enhance stability.It is applied to six different grid-forming VSGs and experimentally tested to validate the theoretical analysis.This study concludes with key findings and a discussion on the suitability of the analyzed grid-forming VSGs based on the power system characteristics.展开更多
An element coupling model (ECM) method was proposed to simulate the global behavior and local damage of a structure.In order to reflect the local damage and improve the computational efficiency,three-dimensional (3D) ...An element coupling model (ECM) method was proposed to simulate the global behavior and local damage of a structure.In order to reflect the local damage and improve the computational efficiency,three-dimensional (3D) solid elements and one-dimensional (1D) beam element were coupled by the multi-point constraint equations.A reduced scale 1?8 model test was simulated by the ECM and a full three dimensional model (3DM) contrastively.The results show that the global behavior and local damages of ECM agree well with the test and 3DM.It is indicated that the proposed method can be used in the structural nonlinear analysis accurately and efficiently.展开更多
基金supported by the National Natural Science Foundation of China under Grant 52277072.
文摘Wide-band oscillations have become a significant issue limiting the development of wind power.Both large-signal and small-signal analyses require extensive model derivation.Moreover,the large number and high order of wind turbines have driven the development of simplified models,whose applicability remains controversial.In this paper,a wide-band oscillation analysis method based on the average-value model(AVM)is proposed for wind farms(WFs).A novel linearization analysis framework is developed,leveraging the continuous-time characteristics of the AVM and MATLAB/Simulink’s built-in linearization tools.This significantly reduces modeling complexity and computational costs while maintaining model fidelity.Additionally,an object-based initial value estimation method of state variables is introduced,which,when combined with steady-state point-solving tools,greatly reduces the computational effort required for equilibrium point solving in batch linearization analysis.The proposed method is validated in both doubly fed induction generator(DFIG)-based and permanent magnet synchronous generator(PMSG)-based WFs.Furthermore,a comprehensive analysis is conducted for the first time to examine the impact of the machine-side system on the system stability of the nonfully controlled PMSG-based WF.
基金Project (No. 50607016) supported by the National Natural ScienceFoundation of China
文摘A novel elevator door driven by tubular permanent magnet linear synchronous motor (TPMLSM) is presented. This TPMLSM applies axial magnet array topology of the secondary rod, air-cored armature windings and slotless structure of the forcer to improve the stability of the thrust. The influence of two major dimensions, the pitch and radius of the permanent magnet (PM), on magnetic field was studied and the best values were given by the finite element analysis (FEA). The magnetic field, back EMF and thrust of the motor were analyzed and the PM size was optimized to reduce the harmonic components of the magnetic field and improve the performance of the motor. Predicted results are validated by the experiment. It is shown that the performance of the motor and the novel elevator door system is satisfying.
文摘This paper gives performance analysis of a three phase Permanent Magnet Synchronous Generator (PMSG) connected to a Vertical Axis Wind Turbine (VAWT). Low speed wind condition (less than 5 m/s) is taken in consideration and the entire simulation is carried in Matlab/Simulink environment. The rated power for the generator is fixed at 1.5 KW and number of pole at 20. It is observed under low wind speed of6 m/s, a turbine having approximately1 mof radius and2.6 mof height develops 150 Nm mechanical torque that can generate power up to 1.5 KW. The generator is designed using modeling tool and is fabricated. The fabricated generator is tested in the laboratory with the simulation result for the error analysis. The range of error is about 5%-27% for the same output power value. The limitations and possible causes for error are presented and discussed.
文摘This paper presents an analytical method to design the high-efficiency surface permanent magnet synchronous motor(SPMSM)or generator(SPMSG).The air-gap and permanent magnet size can be approximately determined based on our mathematics model,which is the most important part of SPMSM design.From our method,we can know that motor’s power out torque is related to the torque angle that we selected in our design and it affects the air-gap and permanent magnet size.If we choose a low torque angle,the motor or generator’s overload power handing capability will increase.The embrace value has a vital place in designing a motor or generator due to its effects on air gap flux density,cogging torque,efficiency and so on.In order to avoid the knee effect,the working point of the permanent magnet we selected in the design should be bigger than 0.5.The developed 36 slots,4 poles,surface mound permanent generator is proposed.The corresponding finite element analysis(FEA)model is built based on our design method.Structure optimization includes stator and rotor structure size,permanent magnet size,magnetic bridge and air gap length which are analyzed and simulated by ANSYS Maxwell 2D FEA.Thermal analysis is conducted,and the housing of the alternator is designed.The alternator prototype is fabricated and tested based on our design.
基金co-supported by the National Natural Science Foundation of China(No.52177028)in part by the Aeronautical Science Foundation of China(No.201907051002)。
文摘To improve the heat dissipation performance,this paper proposes a novel hybrid cooling method for high-speed high-power Permanent Magnet assisted Synchronous Reluctance Starter/Generator(PMa Syn R S/G)in aerospace applications.The hybrid cooling structure with oil circulation in the housing,oil spray at winding ends and rotor end surface is firstly proposed for the PMa Syn R S/G.Then the accurate loss calculation of the PMa Syn R S/G is proposed,which includes air gap friction loss under oil spray cooling,copper loss,stator and rotor core loss,permanent magnet eddy current loss and bearing loss.The parameter sensitivity analysis of the hybrid cooling structure is proposed,while the equivalent thermal network model of the PMa Syn R S/G is established considering the uneven spraying at the winding ends.Finally,the effectiveness of the proposed hybrid cooling method is demonstrated on a 40 k W/24000 r/min PMa Syn R S/G experimental platform.
文摘By means of finite element analysis methods calculated the stress, strainand displacement of the belt teeth and analysisied the factors such as load distribution,specific property coefficient of material and temperature variation, which influence the fatigue strength of the belt teeth..
文摘A novel text independent speaker identification system is proposed. In the proposed system, the 12-order perceptual linear predictive cepstrum and their delta coefficients in the span of five frames are extracted from the segmented speech based on the method of pitch synchronous analysis. The Fisher ratios of the original coefficients then be calculated, and the coefficients whose Fisher ratios are bigger are selected to form the 13-dimensional feature vectors of speaker. The Gaussian mixture model is used to model the speakers. The experimental results show that the identification accuracy of the proposed system is obviously better than that of the systems based on other conventional coefficients like the linear predictive cepstral coefficients and the Mel-frequency cepstral coefficients.
文摘As a driving motor, surface mounted permanent magnet synchronous motor exhibits high efficiency and high power density. However, it is susceptible to suffer irreversible demagnetization and insulation failure of coils under severe thermal load condition. Therefore, it is essential to predict temperattrre distribution in the driving motor. In this paper, a lumped parameter thermal mode/of surface mounted permanent magnet is investigated. By using finite element method, the iron loss distribution in various parts of the driving motor is achieved. Moreover, the influences of interface gap and flow rate on temperature distribution are discussed. Finally, the simulation of temperature distribution in different parts of the driving motor is achieved. The presented methodology contributes to verify the feasibility of the driving motor design.
文摘Multi-phase machines are so attractive for electrical machine designers because of their valuable advantages such as high reliability and fault tolerant ability.Meanwhile,fractional slot concentrated windings(FSCW)are well known because of short end winding length,simple structure,field weakening sufficiency,fault tolerant capability and higher slot fill factor.The five-phase machines equipped with FSCW,are very good candidates for the purpose of designing motors for high reliable applications,like electric cars,major transporting buses,high speed trains and massive trucks.But,in comparison to the general distributed windings,the FSCWs contain high magnetomotive force(MMF)space harmonic contents,which cause unwanted effects on the machine ability,such as localized iron saturation and core losses.This manuscript introduces several new five-phase fractional slot winding layouts,by the means of slot shifting concept in order to design the new types of synchronous reluctance motors(SynRels).In order to examine the proposed winding’s performances,three sample machines are designed as case studies,and analytical study and finite element analysis(FEA)is used for validation.
基金supported by the National Key R&D Program(No.2022YFA1602201)。
文摘This paper presents a new technique for measuring the bunch length of a high-energy electron beam at a bunch-by-bunch rate in storage rings.This technique uses the time–frequency-domain joint analysis of the bunch signal to obtain bunch-by-bunch and turn-by-turn longitudinal parameters,such as bunch length and synchronous phase.The bunch signal is obtained using a button electrode with a bandwidth of several gigahertz.The data acquisition device was a high-speed digital oscilloscope with a sampling rate of more than 10 GS/s,and the single-shot sampling data buffer covered thousands of turns.The bunch-length and synchronous phase information were extracted via offline calculations using Python scripts.The calibration coefficient of the system was determined using a commercial streak camera.Moreover,this technique was tested on two different storage rings and successfully captured various longitudinal transient processes during the harmonic cavity debugging process at the Shanghai Synchrotron Radiation Facility(SSRF),and longitudinal instabilities were observed during the single-bunch accumulation process at Hefei Light Source(HLS).For Gaussian-distribution bunches,the uncertainty of the bunch phase obtained using this technique was better than 0.2 ps,and the bunch-length uncertainty was better than 1 ps.The dynamic range exceeded 10 ms.This technology is a powerful and versatile beam diagnostic tool that can be conveniently deployed in high-energy electron storage rings.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60573172 and 60973152)the Doctoral Program Foundation of Institution of Higher Education of China (Grant No. 20070141014)the Natural Science Foundation of Liaoning Province,China (Grant No. 20082165)
文摘Based on the stability theory of the fractional order system, the dynamic behaviours of a new fractional order system are investigated theoretically. The lowest order we found to have chaos in the new three-dimensional system is 2.46, and the period routes to chaos in the new fractional order system are also found. The effectiveness of our analysis results is further verified by numerical simulations and positive largest Lyapunov exponent. Furthermore, a nonlinear feedback controller is designed to achieve the generalized projective synchronization of the fractional order chaotic system, and its validity is proved by Laplace transformation theory.
文摘Dissolved organic matter (DOM) can be originated from autochthonous or allochthonous sources, where allochthonous DOM can be from pedogenic sources (humic substances—HSs) or anthropogenicsources (wastewater). The analysis of fluorescence emission, excitation, synchronous or excitation-emission matrix (EEM) have been used to identify the main source or probable contribution of dissolved compounds, such as humic acids (HA), fulvic acids (FA) and dissolved organic carbon (DOC) from sewage, but does not quantify. Fluorescence emission is a powerful technique to detect and qualify organic dissolved compounds but fails in quantitative aspects. In this work, we propose an in situ method for direct determination of DOC using synchronous fluorescence spectra with independent component analysis (ICA). Well known standard solutions were used for method development and validation. In this work, we show that it is possible to predict the number of independent contributions using an unsupervised method based on iterative Principal Component Analysis and Independent Component Analysis (PCA-ICA) approach over combined matrix results. Within these results it’s also possible to see that with a very small amount of independent components it is possible to describe environmental samples of HA, FA and primary productivity (PP).
基金funded by the Program of China Earthquake Science Data Sharing Platform and the Youth Fund(17404031570521)
文摘In general, the seismic response analysis in earthquake engineering assumes that the vibration parameters of the target and the contact surface of the external media are identical,i. e., single point input. However, earthquake energy has an attenuation phenomenon in wave propagation,so a wide range of soil slopes and the external medium contact surface of different input points on motion are not identical. If we consider single point input only, it may not correspond with reality, so it is necessary to carry out research on multi-point input methods. Based on the 2-D slope model,single-point input and multi-point input are performed respectively to analyze and compare their similarities and differences in the perspectives of the characteristics of seismic response of soil layer and plastic zone distribution to provide a reference for the seismic design of slopes. The results show that in the perspective of soil seismic response analysis,the peak acceleration output and peak velocity output under multi-point input are greater than the peak values under single point input at the same monitoring point,the peak appearing time is also earlier than that of the single point input; in terms of the plastic zone distribution,the multi-point effect is manifested as the presence of more obvious tensile shear failures; in the perspective of safety coefficient,the safety coefficient under each multi-point input is smaller than that of single point input,a difference of about 7 % or so. In summary,multi-point input is more reasonable and practical than single point input,so multi-point input should be considered in seismic design.
基金supported by the National Natural Science Foundation of China(Nos.61104151,61104018,61473240)the Science Foundation of Fujian Province(No.2012J01289)the Hong Kong Research Grants Council under the GRF Grant CityU 1120/14
文摘Pinning synchronization of a networked multi-agent system with a directed communication topology is investigated from a spectral analysis approach. Some new types of synchronized regions for networked systems with different nonlinear agent dynamics and inner coupling structures are discovered. The eigenvalue distributions of the coupling and control matrices for different types of directed networks are obtained. The effects of the network topology, pinning density and pinning strength on the network synchronizability are examined through extensive numerical simulations. It is shown that the synchronizability of the pinned network can be effectively improved by increasing pinning density and pinning strength for some types of synchronized regions, whereas too large the pinning density and pinning strength will lead to desynchronization for other types. It is found that directed random networks are not always easier to synchronize than directed small-world networks, and a denser eigenvalue distribution may not always imply better synchronizability.
基金the financial support from the UGC,New Delhi,India under the SRF scheme
文摘In this article the authors have studied the stability analysis and chaos control of the fractional order Vallis and El-Nino systems. The chaos control of these systems is studied using nonlinear control method with the help of a new lemma for Caputo derivative and Lyapunov stability theory.The synchronization between the systems for different fractional order cases and numerical simulation through graphical plots for different particular cases clearly exhibit that the method is easy to implement and reliable for synchronization of fractional order chaotic systems. The comparison of time of synchronization when the systems pair approaches from standard order to fractional order is the key feature of the article.
基金supported by the National Key R&D Program of China[grant numbers 2017YFC1501803 and 2017YFC1502102].
文摘Fast and accurate identification of unknown pollution sources plays a crucial role in the emergency response and source control of air pollution.In this work,the applicability of a previously proposed two-step inversion method is investigated with sensitivity experiments and real data from the first release of the European Tracer Experiment(ETEX-1).The two-step inversion method is based on the principle of least squares and carries out additional model correction through the residual iterative process.To evaluate its performance,its retrieval results are compared with those of two other existing algorithms.It is shown that for those cases with richer measurements,all three methods are less sensitive to errors,while for cases where measurements are sparse,their retrieval accuracy will rapidly decrease as errors increase.From the results of sensitivity experiments,the new method provides higher estimation accuracy and a more stable performance than the other two methods.The new method presents the smallest maximum location error of 18.20 km when the amplitude of the measurement error increases to 100%,and 22.67 km when errors in the wind fields increase to 200%.Moreover,when applied to ETEX-1 data,the new method also exhibits good performance,with a location error of 4.71 km,which is the best estimation with respect to source location.
文摘We perform an analysis of brain-neuromuscular synchronization and coupling strength in muscular dystrophy before and after NPT treatment. In order to estimate with accuracy the level of brain synchronization, we introduce and use the method of the cross GMI that was elaborated by Pompe. The finality is to account for the nonlinear chaotic dynamic contributions that regulate the dynamics. We find that this method is excellent and it may be applied in such case of sEMG and EEG study as well as at a general neurological level. By it we arrive to quantify the coupling strength and synchronization first between two muscular sections (left and right trapezes) and after between Brain activity, as recorded by the EEG, and the trapezes. We compare the results before and after the NPT treatment and we find that the improvement obtained following such treatment is very consistent. We have now in progress other studies relating in particular the application of such new methodologies to other more serious pathologies as the HSP (Hereditary Spastic Paraplegia).
基金supported by Grant PID2021-124571OB-I00 funded by MICIU/AEI/10.13039/501100011033FEDER,EU。
文摘The integration of converter-interfaced generators(CIGs)into power systems is rapidly replacing traditional synchronous machines.To ensure the security of power supply,modern power systems require the application of grid-forming technologies.This study presents a systematic small-signal analysis procedure to assess the synchronization stability of gridforming virtual synchronous generators(VSGs)considering the power system characteristics.Specifically,this procedure offers guidance in tuning controller gains to enhance stability.It is applied to six different grid-forming VSGs and experimentally tested to validate the theoretical analysis.This study concludes with key findings and a discussion on the suitability of the analyzed grid-forming VSGs based on the power system characteristics.
基金Project(2007CB714202) supported by the National Key Basic Research Program of ChinaProject(SLDRCE10-B-07) supported by theMinistry of Science and Technology of China
文摘An element coupling model (ECM) method was proposed to simulate the global behavior and local damage of a structure.In order to reflect the local damage and improve the computational efficiency,three-dimensional (3D) solid elements and one-dimensional (1D) beam element were coupled by the multi-point constraint equations.A reduced scale 1?8 model test was simulated by the ECM and a full three dimensional model (3DM) contrastively.The results show that the global behavior and local damages of ECM agree well with the test and 3DM.It is indicated that the proposed method can be used in the structural nonlinear analysis accurately and efficiently.
