It is identified that barely passing electrons are the drive of the e-fishbones, rather than the barely trapped electrons at low frequency. The frequency jump in e-fishbone experiments is reproduced and analyzed. It i...It is identified that barely passing electrons are the drive of the e-fishbones, rather than the barely trapped electrons at low frequency. The frequency jump in e-fishbone experiments is reproduced and analyzed. It is found that the e-fishbone frequency increases with the hot electron energy, which is consistent with the experiments. The growth rate of the mode （m= 2, n = 2） is greater than that of the mode （m = 1, n = 1）.展开更多
The arithmetic version of the frequency transition conjecture for the almost Mathieu operators was recently proved by Jitomirskaya and Liu[34].We give a new proof via reducibility theory and duality,which derives from...The arithmetic version of the frequency transition conjecture for the almost Mathieu operators was recently proved by Jitomirskaya and Liu[34].We give a new proof via reducibility theory and duality,which derives from the method developed in[22](in fact it is a simplified version).This new proof is applicable to more general quasiperiodic operators.展开更多
this paper discusses the frequency resolution of an acousto-optical spectrometer system under influences of deflector 's spectral resolution, coherent light-beam truncation ratio, and photodiode array's respon...this paper discusses the frequency resolution of an acousto-optical spectrometer system under influences of deflector 's spectral resolution, coherent light-beam truncation ratio, and photodiode array's response. The broadening of the resoluble line-pattern caused by the response of a photodiode pixel has been computed. According to this discussion the authors proposed the selecting principles for the design parameters of the acoustooptical spectrometer including light-beam truncation ratio, focal length of Fourier lens, and number of photodiode array elements, i.e. the quantitative criteria for specific observational necessities with an acousto-optical spectrometer considered with resolution, bandwidth, and sidelobes of instrumental profile comprehensively. An experimental measurement of the frequency resolution to verify the above theoretical computations has also been carried out.展开更多
A method to separate a harmonic signal from multiplicative and additive noises is proposed. The method is to square the signal x(t), which consists of a harmonic signal embedded in multiplicative and additive noises, ...A method to separate a harmonic signal from multiplicative and additive noises is proposed. The method is to square the signal x(t), which consists of a harmonic signal embedded in multiplicative and additive noises, to form another signal y(t) = x2(t)-E[x2(t)]. After y(t) having been gotten, the Fourier transform is imposed on it. Because the information of x(t) (especially about frequency) is included in y(t), the frequency of x(t) can be estimated from the power spectrum of y(t). According to the simulation, under the condition where frequencies divided by resolution dω are integer, the maximum relative error of estimated frequencies is less than 0.4% when the signal-to-noise ratio (SNR) is greater than -23 dB. If frequencies divided by resolution dω are not integer, the maximum relative error will be less than 2.9%. But it is still small in terms of engineering.展开更多
The mode-based damping torque analysis(M-DTA)method for studying the effect of an external controller on power system low-frequency oscillations is proposed in this paper.First,based on the interconnection model betwe...The mode-based damping torque analysis(M-DTA)method for studying the effect of an external controller on power system low-frequency oscillations is proposed in this paper.First,based on the interconnection model between the system and the controller in the frequency domain,the oscillation loop corresponding to the electromechanical oscillation mode is built,and then the mode-based damping torque of the controller can be calculated.Then,the application of the M-DTA method in the power system is illustrated.The derivation shows that in the single-machine infinite-bus power system,the M-DTA method is completely equivalent to the classical damping torque analysis(C-DTA)method.In the multi-machine power system,the mode-based damping torque directily reflects the effect of the controller on the oscillation mode,overcoming the shortcomings of the C-DTA method in which there is no direct correspondence between the damping torque and the oscillation mode.By deriving the relationship with the residue index,the M-DTA method shows higher accuracy than the residue method in applications,such as controller parameter adjustment.Finally,two example power systems are presented to demonstrate the application of the proposed M-DTA method.Index Terms-Electromechanical oscillation mode,FACTS,interconnection model in the frequency domain,mode-based damping torque analysis(M-DTA),power system low-frequency oscillation,PSS,residue method.展开更多
基金Supported by the Funds of the Youth Innovation Team of Science and Technology in Sichuan Province of China under Grant No2014TD0023the National Natural Science Foundation of China under Grant Nos 11447228,11261140327,11005035 and 11205053the Project-the Plasma Confinement in the Advanced Magnetic Mirror under Grant No WX-2015-01-01
文摘It is identified that barely passing electrons are the drive of the e-fishbones, rather than the barely trapped electrons at low frequency. The frequency jump in e-fishbone experiments is reproduced and analyzed. It is found that the e-fishbone frequency increases with the hot electron energy, which is consistent with the experiments. The growth rate of the mode （m= 2, n = 2） is greater than that of the mode （m = 1, n = 1）.
基金supported by National Key R&D Program of China(No.2020YFA0713300)and NSFC(No.11871286)supported by NSF DMS-1901462.L.Ge was partially supported by AMS-Simons Travel Grant 2020-2022supported by China Scholarship Council(No.201906190072)and NSFC(No.11771205).
文摘The arithmetic version of the frequency transition conjecture for the almost Mathieu operators was recently proved by Jitomirskaya and Liu[34].We give a new proof via reducibility theory and duality,which derives from the method developed in[22](in fact it is a simplified version).This new proof is applicable to more general quasiperiodic operators.
文摘this paper discusses the frequency resolution of an acousto-optical spectrometer system under influences of deflector 's spectral resolution, coherent light-beam truncation ratio, and photodiode array's response. The broadening of the resoluble line-pattern caused by the response of a photodiode pixel has been computed. According to this discussion the authors proposed the selecting principles for the design parameters of the acoustooptical spectrometer including light-beam truncation ratio, focal length of Fourier lens, and number of photodiode array elements, i.e. the quantitative criteria for specific observational necessities with an acousto-optical spectrometer considered with resolution, bandwidth, and sidelobes of instrumental profile comprehensively. An experimental measurement of the frequency resolution to verify the above theoretical computations has also been carried out.
基金the National Natural Foundation of China(No.59635140).
文摘A method to separate a harmonic signal from multiplicative and additive noises is proposed. The method is to square the signal x(t), which consists of a harmonic signal embedded in multiplicative and additive noises, to form another signal y(t) = x2(t)-E[x2(t)]. After y(t) having been gotten, the Fourier transform is imposed on it. Because the information of x(t) (especially about frequency) is included in y(t), the frequency of x(t) can be estimated from the power spectrum of y(t). According to the simulation, under the condition where frequencies divided by resolution dω are integer, the maximum relative error of estimated frequencies is less than 0.4% when the signal-to-noise ratio (SNR) is greater than -23 dB. If frequencies divided by resolution dω are not integer, the maximum relative error will be less than 2.9%. But it is still small in terms of engineering.
基金supported in part by the National Natural Science Foundation of China under Grant No.U1766202,51907179 and 51977197.
文摘The mode-based damping torque analysis(M-DTA)method for studying the effect of an external controller on power system low-frequency oscillations is proposed in this paper.First,based on the interconnection model between the system and the controller in the frequency domain,the oscillation loop corresponding to the electromechanical oscillation mode is built,and then the mode-based damping torque of the controller can be calculated.Then,the application of the M-DTA method in the power system is illustrated.The derivation shows that in the single-machine infinite-bus power system,the M-DTA method is completely equivalent to the classical damping torque analysis(C-DTA)method.In the multi-machine power system,the mode-based damping torque directily reflects the effect of the controller on the oscillation mode,overcoming the shortcomings of the C-DTA method in which there is no direct correspondence between the damping torque and the oscillation mode.By deriving the relationship with the residue index,the M-DTA method shows higher accuracy than the residue method in applications,such as controller parameter adjustment.Finally,two example power systems are presented to demonstrate the application of the proposed M-DTA method.Index Terms-Electromechanical oscillation mode,FACTS,interconnection model in the frequency domain,mode-based damping torque analysis(M-DTA),power system low-frequency oscillation,PSS,residue method.
