The dispersion curves of bulk waves propagating in both AlN and ZnO film bulk acoustic resonators(FBARs)are presented to illustrate the mode flip of the thickness-extensional(TE)and 2nd thickness-shear(TSh2)modes.The ...The dispersion curves of bulk waves propagating in both AlN and ZnO film bulk acoustic resonators(FBARs)are presented to illustrate the mode flip of the thickness-extensional(TE)and 2nd thickness-shear(TSh2)modes.The frequency spectrum quantitative prediction(FSQP)method is used to solve the frequency spectra for predicting the coupling strength among the eigen-modes in AlN and ZnO FBARs.The results elaborate that the flip of the TE and TSh2 branches results in novel self-coupling vibration between the small-wavenumber TE and large-wavenumber TE modes,which has never been observed in the ZnO FBAR.Besides,the mode flip leads to the change in the relative positions of the frequency spectral curves about the TE cut-off frequency.The obtained frequency spectra can be used to predict the mode-coupling behaviors of the vibration modes in the AlN FBAR.The conclusions drawn from the results can help to distinguish the desirable operation modes of the AlN FBAR with very weak coupling strength from all vibration modes.展开更多
A longitudinal accumulation scheme based on a triple-frequency RF system,in which the static radio frequency(RF)bucket is lengthened to be compatible with the realizable raise time of a fast pulse kicker,is proposed i...A longitudinal accumulation scheme based on a triple-frequency RF system,in which the static radio frequency(RF)bucket is lengthened to be compatible with the realizable raise time of a fast pulse kicker,is proposed in this paper.With this technique,the bunch from a booster can be captured by the longitudinal acceptance without any disturbance to the stored bunch,which remains at the center.This composite RF system consists of three different frequencies,which can be regarded as the conventional bunch lengthening RF system(usually containing fundamental and third harmonic cavities)extended by an additional second harmonic RF cavity.In this paper,we discuss the RF jitter and the transverse mode-coupling instability(TMCI)when using this special RF system.Considering several different bunch profiles,we discuss the beam stability with regard to the RF jitter.However,for the TMCI we assume an ideal bunch profile,where the bunch is exactly lengthened to the maximum extent.While macroparticle simulation is the main method used to study the impact of the RF jitter,numerical analysis and simulations for the TMCI while using a triple-frequency RF system are also presented in this paper.An approximation formula,based on the existing model,is also derived to estimate the impact of the TMCI on the single bunch current threshold when using harmonic cavities.展开更多
In this paper, derived from Maxwell and fluid equations of plasmas, unified nonlinear wave equations are used to describe the parametric decay instability (PDI) in magnetized plasmas, and in view of mode-coupling, w...In this paper, derived from Maxwell and fluid equations of plasmas, unified nonlinear wave equations are used to describe the parametric decay instability (PDI) in magnetized plasmas, and in view of mode-coupling, we can obtain all the possible PDI channels. By solving the nonlinear equations with a mode-coupling method, we obtain the growth rate of the PDI, of which all of the three waves are ordinary mode (O-mode) or extraordinary mode (X-mode) wave. Under the dipole approximation, an explicit formula of the growth rate of the X-mode and the condition of the equilibrium density scale are obtained. According to the existence conditions of three X-mode waves, this kind of instability might exist in ECRH with the second harmonic X-mode wave.展开更多
We investigate dynamics of Bose–Einstein condensates(BECs) in a single-well potential using the mode-coupling method. Symmetry is shown to play a key role in the coupling between modes. A proper mode-coupling theory ...We investigate dynamics of Bose–Einstein condensates(BECs) in a single-well potential using the mode-coupling method. Symmetry is shown to play a key role in the coupling between modes. A proper mode-coupling theory of the dynamics of BECs in a single-well potential should include at least four modes. In this context, the ideal BEC system can be decomposed into two independent subsystems when the coupling is caused by external potential perturbation and is linear. The mode dynamics of non-ideal BECs with interaction shows rich behavior. The combination of nonlinear coupling and initial condition leads to the different regimes of mode dynamics, from regularity to non-regularity, which also indicates a change of the dependence of coupling on the symmetry of modes.展开更多
Harmonic cavities(HCs)are widely used in electron storage rings,mainly to increase the Touschek lifetime by lengthening bunches.HCs have become critical components of almost all fourth-generation synchrotron light sou...Harmonic cavities(HCs)are widely used in electron storage rings,mainly to increase the Touschek lifetime by lengthening bunches.HCs have become critical components of almost all fourth-generation synchrotron light sources.In addition to the benefits of increasing the Touschek lifetime,they also affect the collective beam instabilities in electron storage rings.However,the influ-ence of HC settings on collective beam instabilities is still not well understood.HCs are typically designed to operate under so-called ideal lengthening conditions,which do not necessarily optimize the suppression of collective beam instabilities.We therefore extended earlier studies of col-lective beam instabilities to consider more general HC settings.We present preliminary studies and analyses of the influences of different HC settings on microwave and transverse mode-coupling instabilities.展开更多
Scattering of oblique flexural-gravity waves by a submerged porous plate in a finite water depth is investigated under the assumptions of linearized surface waves and small-amplitude structural response. The study is ...Scattering of oblique flexural-gravity waves by a submerged porous plate in a finite water depth is investigated under the assumptions of linearized surface waves and small-amplitude structural response. The study is carried out using eigenfunction expansions and the corresponding orthogonal mode-coupling relations associated with flexural-gravity waves in uniform water depth. The characteristics of the roots of the complex dispersion relation are examined using the principle of counting argument and contour plot. Characteristics of the flexural-gravity waves are studied by assuming both the floating elastic plate and the submerged porous plate are infinitely extended in horizontal directions. The effectiveness of the submerged porous structure on the reflection, transmission, and dissipation coefficients is analyzed for various wave and structural parameters.展开更多
Titanium alloys are widely used in the aviation and aerospace industries due to their unique mechanical and physical properties.Specifically,thin-walled titanium(Ti)cylinders have received increasing attention for the...Titanium alloys are widely used in the aviation and aerospace industries due to their unique mechanical and physical properties.Specifically,thin-walled titanium(Ti)cylinders have received increasing attention for their applications as rocket engine casings,aircraft landing gear,and aero-engine hollow shaft due to their observed improvement in the thrust-to-weight ratio.However,the conventional cutting(CC)process is not appropriate for thin-walled Ti cylinders due to its low thermal conductivity,high strength,and low stiffness.Instead,high-speed ultrasonic vibration cutting(HUVC)assisted processing has recently proved highly effective for Ti-alloy machining.In this study,HUVC technology is employed to perform external turning of a thinwalled Ti cylinder,which represents a new application of HUVC.First,the kinematics,tool path,and dynamic cutting thickness of HUVC are evaluated.Second,the phenomenon of mode-coupling chatter is analyzed to determine the effects and mechanism of HUVC by establishing a critical cutting thickness model.HUVC can increase the critical cutting thickness and effectively reduce the average cutting force,thus reducing the energy intake of the system.Finally,comparison experiments are conducted between HUVC and CC processes.The results indicate that the diameter error rate is 10%or less for HUVC and 51%for the CC method due to a 40%reduction in the cutting force.In addition,higher machining precision and better surface roughness are achieved during thin-walled Ti cylinder manufacturing using HUVC.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.11872329,12192211,and 12072315)the Natural Science Foundation of Zhejiang Province of China(No.LD21A020001)+1 种基金the National Postdoctoral Program for Innovation Talents of China(No.BX2021261)the China Postdoctoral Science Foundation Funded Project(No.2022M722745)。
文摘The dispersion curves of bulk waves propagating in both AlN and ZnO film bulk acoustic resonators(FBARs)are presented to illustrate the mode flip of the thickness-extensional(TE)and 2nd thickness-shear(TSh2)modes.The frequency spectrum quantitative prediction(FSQP)method is used to solve the frequency spectra for predicting the coupling strength among the eigen-modes in AlN and ZnO FBARs.The results elaborate that the flip of the TE and TSh2 branches results in novel self-coupling vibration between the small-wavenumber TE and large-wavenumber TE modes,which has never been observed in the ZnO FBAR.Besides,the mode flip leads to the change in the relative positions of the frequency spectral curves about the TE cut-off frequency.The obtained frequency spectra can be used to predict the mode-coupling behaviors of the vibration modes in the AlN FBAR.The conclusions drawn from the results can help to distinguish the desirable operation modes of the AlN FBAR with very weak coupling strength from all vibration modes.
文摘A longitudinal accumulation scheme based on a triple-frequency RF system,in which the static radio frequency(RF)bucket is lengthened to be compatible with the realizable raise time of a fast pulse kicker,is proposed in this paper.With this technique,the bunch from a booster can be captured by the longitudinal acceptance without any disturbance to the stored bunch,which remains at the center.This composite RF system consists of three different frequencies,which can be regarded as the conventional bunch lengthening RF system(usually containing fundamental and third harmonic cavities)extended by an additional second harmonic RF cavity.In this paper,we discuss the RF jitter and the transverse mode-coupling instability(TMCI)when using this special RF system.Considering several different bunch profiles,we discuss the beam stability with regard to the RF jitter.However,for the TMCI we assume an ideal bunch profile,where the bunch is exactly lengthened to the maximum extent.While macroparticle simulation is the main method used to study the impact of the RF jitter,numerical analysis and simulations for the TMCI while using a triple-frequency RF system are also presented in this paper.An approximation formula,based on the existing model,is also derived to estimate the impact of the TMCI on the single bunch current threshold when using harmonic cavities.
基金supported by National Natural Science Foundation of China(Nos.10990214 and 115450)
文摘In this paper, derived from Maxwell and fluid equations of plasmas, unified nonlinear wave equations are used to describe the parametric decay instability (PDI) in magnetized plasmas, and in view of mode-coupling, we can obtain all the possible PDI channels. By solving the nonlinear equations with a mode-coupling method, we obtain the growth rate of the PDI, of which all of the three waves are ordinary mode (O-mode) or extraordinary mode (X-mode) wave. Under the dipole approximation, an explicit formula of the growth rate of the X-mode and the condition of the equilibrium density scale are obtained. According to the existence conditions of three X-mode waves, this kind of instability might exist in ECRH with the second harmonic X-mode wave.
文摘We investigate dynamics of Bose–Einstein condensates(BECs) in a single-well potential using the mode-coupling method. Symmetry is shown to play a key role in the coupling between modes. A proper mode-coupling theory of the dynamics of BECs in a single-well potential should include at least four modes. In this context, the ideal BEC system can be decomposed into two independent subsystems when the coupling is caused by external potential perturbation and is linear. The mode dynamics of non-ideal BECs with interaction shows rich behavior. The combination of nonlinear coupling and initial condition leads to the different regimes of mode dynamics, from regularity to non-regularity, which also indicates a change of the dependence of coupling on the symmetry of modes.
基金supported by the National Natural Science Foundation of China(Nos.11805217 and 11775239)the Youth Innovation Promotion Association CAS,and NKPSTRD(No.2016YFA0402001).
文摘Harmonic cavities(HCs)are widely used in electron storage rings,mainly to increase the Touschek lifetime by lengthening bunches.HCs have become critical components of almost all fourth-generation synchrotron light sources.In addition to the benefits of increasing the Touschek lifetime,they also affect the collective beam instabilities in electron storage rings.However,the influ-ence of HC settings on collective beam instabilities is still not well understood.HCs are typically designed to operate under so-called ideal lengthening conditions,which do not necessarily optimize the suppression of collective beam instabilities.We therefore extended earlier studies of col-lective beam instabilities to consider more general HC settings.We present preliminary studies and analyses of the influences of different HC settings on microwave and transverse mode-coupling instabilities.
文摘Scattering of oblique flexural-gravity waves by a submerged porous plate in a finite water depth is investigated under the assumptions of linearized surface waves and small-amplitude structural response. The study is carried out using eigenfunction expansions and the corresponding orthogonal mode-coupling relations associated with flexural-gravity waves in uniform water depth. The characteristics of the roots of the complex dispersion relation are examined using the principle of counting argument and contour plot. Characteristics of the flexural-gravity waves are studied by assuming both the floating elastic plate and the submerged porous plate are infinitely extended in horizontal directions. The effectiveness of the submerged porous structure on the reflection, transmission, and dissipation coefficients is analyzed for various wave and structural parameters.
基金supported by the Defense Industrial Technology Development Program of China(No.JCKY2018601C209)。
文摘Titanium alloys are widely used in the aviation and aerospace industries due to their unique mechanical and physical properties.Specifically,thin-walled titanium(Ti)cylinders have received increasing attention for their applications as rocket engine casings,aircraft landing gear,and aero-engine hollow shaft due to their observed improvement in the thrust-to-weight ratio.However,the conventional cutting(CC)process is not appropriate for thin-walled Ti cylinders due to its low thermal conductivity,high strength,and low stiffness.Instead,high-speed ultrasonic vibration cutting(HUVC)assisted processing has recently proved highly effective for Ti-alloy machining.In this study,HUVC technology is employed to perform external turning of a thinwalled Ti cylinder,which represents a new application of HUVC.First,the kinematics,tool path,and dynamic cutting thickness of HUVC are evaluated.Second,the phenomenon of mode-coupling chatter is analyzed to determine the effects and mechanism of HUVC by establishing a critical cutting thickness model.HUVC can increase the critical cutting thickness and effectively reduce the average cutting force,thus reducing the energy intake of the system.Finally,comparison experiments are conducted between HUVC and CC processes.The results indicate that the diameter error rate is 10%or less for HUVC and 51%for the CC method due to a 40%reduction in the cutting force.In addition,higher machining precision and better surface roughness are achieved during thin-walled Ti cylinder manufacturing using HUVC.