In a passive ultra-high frequency(UHF)radio frequency identification(RFID)system,the recovery of collided tag signals on a physical layer can enhance identification efficiency.However,frequency drift is very common in...In a passive ultra-high frequency(UHF)radio frequency identification(RFID)system,the recovery of collided tag signals on a physical layer can enhance identification efficiency.However,frequency drift is very common in UHF RFID systems,and will have an influence on the recovery on the physical layer.To address the problem of recovery with the frequency drift,this paper adopts a radial basis function(RBF)network to separate the collision signals,and decode the signals via FM0 to recovery collided RFID tags.Numerical results show that the method in this paper has better performance of symbol error rate(SER)and separation efficiency compared to conventional methods when frequency drift occurs.展开更多
We report a clock transition spectrum approach,which is used to calibrate the zero-crossing temperature and frequency drift of an ultralow expansion(ULE)cavity with a Hertz level resolution.With this approach,the line...We report a clock transition spectrum approach,which is used to calibrate the zero-crossing temperature and frequency drift of an ultralow expansion(ULE)cavity with a Hertz level resolution.With this approach,the linear and nonlinear drifts of the ULE cavity along a variety of controlled temperatures are clearly presented.When the controlled temperature of ULE cavity is tuned away from the zero-crossing temperature of the ULE cavity,the cavity shows larger and larger nonlinear drift.According to our theoretical analysis and experimental results,we investigate more details of the drift property of the ULE cavity around the zero-crossing temperature,which has seldom been explored before.We can definitely conclude that the zero-crossing temperature of our ULE cavity used in an ytterbium(Yb)lattice clock is around 31.7℃.展开更多
Mooring system plays an important role in station keeping of floating offshore structures. Coupled analysis on mooring-buoy interactions has been increasingly studied in recent years. At present, chains and wire ropes...Mooring system plays an important role in station keeping of floating offshore structures. Coupled analysis on mooring-buoy interactions has been increasingly studied in recent years. At present, chains and wire ropes are widely used in offshore engineering practice. On the basis of mooring line statics, an explicit formulation of single mooring chain/wire rope stiffness coefficients and mooring stiffness matrix of the mooring system were derived in this article, taking into account the horizontal restoring force, vertical restoring force and their coupling terms. The nonlinearity of mooring stiffness was analyzed, and the influences of various parameters, such as material, displacement, pre-tension and water depth, were investigated. Finally some application cases of the mooring stiffness in hydrodynamic calculation were presented. Data shows that this kind of stiffness can reckon in linear and nonlinear forces of mooring system. Also, the stiffness can be used in hydrodynamic analysis to get the eieenfrequencv of slow drift motions.展开更多
Due to the increased penetration of multi-inverter distributed generation(DG)systems,different DG technologies,inverter control methods,and other inverter functions are challenging the capabilities of islanding detect...Due to the increased penetration of multi-inverter distributed generation(DG)systems,different DG technologies,inverter control methods,and other inverter functions are challenging the capabilities of islanding detection.In addition,multi-inverter networks connecting the distribution system point of common coupling(PCC)create islanding at paralleling inverters,which adds the vulnerability of islanding detection.Furthermore,available islanding detection must overcome more challenges from non-detection zones(NDZs)under reduced power mismatches.Therefore,in this study,a new method called parameter self-adapting active islanding detection was utilized to minimize the dilution effect and reduce NDZs in multi-inverter power systems.The method utilizes an active frequency drift(AFD)method and applies a positive feedback gain of adoption parameters,which significantly minimizes NDZs at parallel inverters.The simulation and experimental outcomes indicate that the proposed method can effectively weaken the dilution effect in multi-inverter networks connecting the distribution system PCC.展开更多
3 Summary and discussion In the generalized drift resonance theory[17],a characteristic signature of the ULF wave-particle interactions is the increasingly-tilted stripes in the particle energy spectrum.The phase diff...3 Summary and discussion In the generalized drift resonance theory[17],a characteristic signature of the ULF wave-particle interactions is the increasingly-tilted stripes in the particle energy spectrum.The phase difference across different energy channels is relatively small展开更多
A linear accelerator as a new injector for the Separated Sector Cyclotron at the Heavy Ion Research Facility of LAN Zhou is being designed. The Drift-Tube-Linac （DTL） has been designed to accelerate ^238U^34＋ from ...A linear accelerator as a new injector for the Separated Sector Cyclotron at the Heavy Ion Research Facility of LAN Zhou is being designed. The Drift-Tube-Linac （DTL） has been designed to accelerate ^238U^34＋ from 0.140 MeV/u to 0.97 MeV/u [1]. The 3D finite element analysis of thermal behavior is presented in this paper. During operation, the cavity will produce Joule heat. The cavity will not work normally due to the high temperature and thermal deformation will lead to frequency drift, So it is necessary to perform thermal analysis to ensure the correct working temperature is used. The result of the analysis shows that after the water cooling system is put into the cavity the temperature rise is about 20 degrees and the frequency drift is about 0.15%.展开更多
As a rule,stability calculation of atomic clock requires observations with equivalent sampling interval.Apart from atomic clocks in laboratory,orbital atomic clock stability calculations are impacted of raw data sampl...As a rule,stability calculation of atomic clock requires observations with equivalent sampling interval.Apart from atomic clocks in laboratory,orbital atomic clock stability calculations are impacted of raw data sampling intervals,noncontinuous time series,non-data segment,frequency drift,and other factors.So,the calculated stability results are not so exact.In this article,the impacts of kinds of error sources on Allan and Hadamard variances are analyzed using global positioning system satellite precise clock offset data.And the laws of variety are summarized.展开更多
Output voltage drifting was observed in MEMS gyroscopes. Other than the quadrature error, frequency mismatch and quality factor, the dielectric parasitic charge was thought to be a major determinant. We studied the me...Output voltage drifting was observed in MEMS gyroscopes. Other than the quadrature error, frequency mismatch and quality factor, the dielectric parasitic charge was thought to be a major determinant. We studied the mechanism and variation of the parasitic charge in the MEMS gyroscopes, and analyzed the effect of the parasitic charge on the output stability. This phenomenon was extremely obvious in the Pyrex encapsulated MEMS gyroscopes. Due to the DC voltage required for the electrostatic actuation, the parasitic charge in the dielectric layer would accumulate and induce a residual voltage. This voltage had an impact on the resonant frequency of the gyroscopes, so as to affect the output stability. The theoretical studies were also confirmed by our experimental results. It was shown that the parasitic charge was harmful to the output stability of MEMS gyroscopes.展开更多
基金supported by the National Natural Science Foundation of China(61762093)the 17th Batches of Young and Middle-aged Leaders in Academic and Technical Reserved Talents Project of Yunnan Province(2014HB019)+1 种基金the Key Applied and Basic Research Foundation of Yunnan Province(2018FA036)the Program for Innovative Research Team(in Science and Technology)in University of Yunnan Province。
文摘In a passive ultra-high frequency(UHF)radio frequency identification(RFID)system,the recovery of collided tag signals on a physical layer can enhance identification efficiency.However,frequency drift is very common in UHF RFID systems,and will have an influence on the recovery on the physical layer.To address the problem of recovery with the frequency drift,this paper adopts a radial basis function(RBF)network to separate the collision signals,and decode the signals via FM0 to recovery collided RFID tags.Numerical results show that the method in this paper has better performance of symbol error rate(SER)and separation efficiency compared to conventional methods when frequency drift occurs.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61227805,11574352,91536104,and 91636215)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB21030100)
文摘We report a clock transition spectrum approach,which is used to calibrate the zero-crossing temperature and frequency drift of an ultralow expansion(ULE)cavity with a Hertz level resolution.With this approach,the linear and nonlinear drifts of the ULE cavity along a variety of controlled temperatures are clearly presented.When the controlled temperature of ULE cavity is tuned away from the zero-crossing temperature of the ULE cavity,the cavity shows larger and larger nonlinear drift.According to our theoretical analysis and experimental results,we investigate more details of the drift property of the ULE cavity around the zero-crossing temperature,which has seldom been explored before.We can definitely conclude that the zero-crossing temperature of our ULE cavity used in an ytterbium(Yb)lattice clock is around 31.7℃.
基金Supported by the National Natural Science Foundation of China under Grant No.（51079034）.
文摘Mooring system plays an important role in station keeping of floating offshore structures. Coupled analysis on mooring-buoy interactions has been increasingly studied in recent years. At present, chains and wire ropes are widely used in offshore engineering practice. On the basis of mooring line statics, an explicit formulation of single mooring chain/wire rope stiffness coefficients and mooring stiffness matrix of the mooring system were derived in this article, taking into account the horizontal restoring force, vertical restoring force and their coupling terms. The nonlinearity of mooring stiffness was analyzed, and the influences of various parameters, such as material, displacement, pre-tension and water depth, were investigated. Finally some application cases of the mooring stiffness in hydrodynamic calculation were presented. Data shows that this kind of stiffness can reckon in linear and nonlinear forces of mooring system. Also, the stiffness can be used in hydrodynamic analysis to get the eieenfrequencv of slow drift motions.
基金supported by the National Natural Science Foundation of China under Grant No.61671109.
文摘Due to the increased penetration of multi-inverter distributed generation(DG)systems,different DG technologies,inverter control methods,and other inverter functions are challenging the capabilities of islanding detection.In addition,multi-inverter networks connecting the distribution system point of common coupling(PCC)create islanding at paralleling inverters,which adds the vulnerability of islanding detection.Furthermore,available islanding detection must overcome more challenges from non-detection zones(NDZs)under reduced power mismatches.Therefore,in this study,a new method called parameter self-adapting active islanding detection was utilized to minimize the dilution effect and reduce NDZs in multi-inverter power systems.The method utilizes an active frequency drift(AFD)method and applies a positive feedback gain of adoption parameters,which significantly minimizes NDZs at parallel inverters.The simulation and experimental outcomes indicate that the proposed method can effectively weaken the dilution effect in multi-inverter networks connecting the distribution system PCC.
基金supported by the National Natural Science Foundation of China(Grant Nos.41421003&41474140)
文摘3 Summary and discussion In the generalized drift resonance theory[17],a characteristic signature of the ULF wave-particle interactions is the increasingly-tilted stripes in the particle energy spectrum.The phase difference across different energy channels is relatively small
基金Supported by National Natural Science Foundation of China (10635090)
文摘A linear accelerator as a new injector for the Separated Sector Cyclotron at the Heavy Ion Research Facility of LAN Zhou is being designed. The Drift-Tube-Linac （DTL） has been designed to accelerate ^238U^34＋ from 0.140 MeV/u to 0.97 MeV/u [1]. The 3D finite element analysis of thermal behavior is presented in this paper. During operation, the cavity will produce Joule heat. The cavity will not work normally due to the high temperature and thermal deformation will lead to frequency drift, So it is necessary to perform thermal analysis to ensure the correct working temperature is used. The result of the analysis shows that after the water cooling system is put into the cavity the temperature rise is about 20 degrees and the frequency drift is about 0.15%.
基金This work was supported by the National Natural Science Foundation of China(No.41074020).
文摘As a rule,stability calculation of atomic clock requires observations with equivalent sampling interval.Apart from atomic clocks in laboratory,orbital atomic clock stability calculations are impacted of raw data sampling intervals,noncontinuous time series,non-data segment,frequency drift,and other factors.So,the calculated stability results are not so exact.In this article,the impacts of kinds of error sources on Allan and Hadamard variances are analyzed using global positioning system satellite precise clock offset data.And the laws of variety are summarized.
基金supported by the National Natural Science Foundation of China(No.61504130)
文摘Output voltage drifting was observed in MEMS gyroscopes. Other than the quadrature error, frequency mismatch and quality factor, the dielectric parasitic charge was thought to be a major determinant. We studied the mechanism and variation of the parasitic charge in the MEMS gyroscopes, and analyzed the effect of the parasitic charge on the output stability. This phenomenon was extremely obvious in the Pyrex encapsulated MEMS gyroscopes. Due to the DC voltage required for the electrostatic actuation, the parasitic charge in the dielectric layer would accumulate and induce a residual voltage. This voltage had an impact on the resonant frequency of the gyroscopes, so as to affect the output stability. The theoretical studies were also confirmed by our experimental results. It was shown that the parasitic charge was harmful to the output stability of MEMS gyroscopes.
