Various electromagnetic signals are excited by the beam in the acceleration and beam-diagnostic elements of a particle accelerator.It is important to obtain time-domain waveforms of these signals with high temporal re...Various electromagnetic signals are excited by the beam in the acceleration and beam-diagnostic elements of a particle accelerator.It is important to obtain time-domain waveforms of these signals with high temporal resolution for research,such as the study of beam–cavity interactions and bunch-by-bunch parameter measurements.Therefore,a signal reconstruction algorithm with ultrahigh spatiotemporal resolution and bunch phase compensation based on equivalent sampling is proposed in this paper.Compared with traditional equivalent sampling,the use of phase compensation and setting the bunch signal zero-crossing point as the time reference can construct a more accurate reconstructed signal.The basic principles of the method,simulation,and experimental comparison are also introduced.Based on the beam test platform of the Shanghai Synchrotron Radiation Facility(SSRF)and the method of experimental verification,the factors that affect the reconstructed signal quality are analyzed and discussed,including the depth of the sampled data,quantization noise of analog-to-digital converter,beam transverse oscillation,and longitudinal oscillation.The results of the beam experiments show that under the user operation conditions of the SSRF,a beam excitation signal with an amplitude uncertainty of 2%can be reconstructed.展开更多
The vacuum energy density of free scalar quantum field in a Rindler distributional space-time with distributional Levi-Cività connection is considered. It has been widely believed that, except in very extreme sit...The vacuum energy density of free scalar quantum field in a Rindler distributional space-time with distributional Levi-Cività connection is considered. It has been widely believed that, except in very extreme situations, the influence of acceleration on quantum fields should amount to just small, sub-dominant contributions. Here we argue that this belief is wrong by showing that in a Rindler distributional background space-time with distributional Levi-Cività connection the vacuum energy of free quantum fields is forced, by the very same background distributional space-time such a Rindler distributional background space-time, to become dominant over any classical energy density component. This semiclassical gravity effect finds its roots in the singular behavior of quantum fields on a Rindler distributional space-times with distributional Levi-Cività connection. In particular we obtain that the vacuum fluctuations have a singular behavior at a Rindler horizon . Therefore sufficiently strongly accelerated observer burns up near the Rindler horizon. Thus Polchinski’s account doesn’t violate the Einstein equivalence principle.展开更多
In order to deal with the special spatio-temporal environmental changes encountered in the process of open-cast mining,taking Huolinhe No.1 Open-cast Mine as the research object,this paper studied its typical problems...In order to deal with the special spatio-temporal environmental changes encountered in the process of open-cast mining,taking Huolinhe No.1 Open-cast Mine as the research object,this paper studied its typical problems in river reconstruction and cultural relics protection.The study focused on eight key core aspects,including the design optimization of the spatial layout of the mining area,the accurate estimation of the mineral resources reserves,the scientific theoretical demonstration of the mining scale,the fine analysis and calculation of the stripping ratio,the comprehensive consideration of the transport distance and efficiency,the accurate judgment of the best time for the implementation of the transformation,the analysis and evaluation of the slope stability,and the overall planning of the production system.The results show that the extracted problem-solving strategies and scheme system for special mining conditions can not only provide specific and practical guidance for Huolinhe No.1 Open-cast Mine,but also serve as a valuable reference and practical reference for other open-cast mine enterprises facing similar challenges.展开更多
The accuracy of distribution system state estimation(DDSE)is reduced when phasor measurement unit(PMU)measurements contain outliers because of cyber attacks or global positioning system spoofing attacks.Therefore,to e...The accuracy of distribution system state estimation(DDSE)is reduced when phasor measurement unit(PMU)measurements contain outliers because of cyber attacks or global positioning system spoofing attacks.Therefore,to enhance the robustness of DDSE to measurement outliers,approximate the target distribution of Metropolis-Hastings(MH)sampling,and judge the prediction of the long short-term memory(LSTM)network,this paper proposes an outlier reconstruction based state estimation method using the equivalent model of the LSTM network and MH sampling(E-LM model),motivated by the characteristics of the chronological correlations of PMU measurements.First,the target distribution of outlier reconstruction is derived using a kernel density estimation function.Subsequently,the reasons and advantages of the E-LM model are explained and analyzed from a mathematical point of view.The proposed LSTM-based MH sampling can approximate the target distribution of MH sampling to decrease the number of the futile iterations.Moreover,the proposed MH-based forecasting of the LSTM can judge each LSTM prediction,which is independent of its true value.Finally,simulations are conducted to evaluate the performance of the E-LM model by integrating the LSTM network and the MH sampling into the outlier reconstruction based DDSE.展开更多
A distributed feedback(DFB) semiconductor laser with three phase shifts based on reconstruction equivalent chirp(REC) technology is proposed and investigated numerically.With the combination of multiple phase shifts a...A distributed feedback(DFB) semiconductor laser with three phase shifts based on reconstruction equivalent chirp(REC) technology is proposed and investigated numerically.With the combination of multiple phase shifts and corrugation pitch modulated(CPM) structure,we also propose a novel and more complex structure named dual CPM,which has a flatter light power distribution along the laser cavity compared with the true double phase shifts DFB laser diode(LD),while the P-I curves are nearly the same.The proposed dual CPM structure is also designed and analyzed based on REC technology.The simulation results show that,the DFB semiconductor laser with complex structure such as phase shifts,or even arbitrary variation of the grating period can be achieved equivalently and easily by changing the sampling structure.But its external characteristics are almost the same as those DFB lasers with true phase shifts,or true arbitrary variation of the grating period.The key advantage of the REC technology is that it varies only the sampling structure and keeps the seed grating(actual grating in sampling structure) period constant.So its fabrication needs only low-cost and standard holographic exposure technology.Therefore we believe this method can achieve the high-end and low-cost DFB LD for mass production.展开更多
近年来,单片集成的多波长激光器阵列作为波分复用(WDM)系统的理想光源而成为研究热点。通过重构-等效啁啾(REC)技术实现了一种低成本的分布反馈式(DFB)激光器阵列光源模块,采用掺铒光纤放大器(EDFA)对该激光器阵列的输出进行了光学放大...近年来,单片集成的多波长激光器阵列作为波分复用(WDM)系统的理想光源而成为研究热点。通过重构-等效啁啾(REC)技术实现了一种低成本的分布反馈式(DFB)激光器阵列光源模块,采用掺铒光纤放大器(EDFA)对该激光器阵列的输出进行了光学放大,并通过PID控制程序对光源输出进行稳定化调节。光源模块中各通道激光器的中心波长间隔均匀,平均间隔为1.64 nm,波长间隔的误差小于0.2 nm。光源所输出的总光功率大于50 m W,输出光功率变化小于0.02 d Bm。展开更多
基金supported by the National Key R&D Program of China(No.2022YFA1602201)the international partnership program of the Chinese Academy of Sciences(No.211134KYSB20200057).
文摘Various electromagnetic signals are excited by the beam in the acceleration and beam-diagnostic elements of a particle accelerator.It is important to obtain time-domain waveforms of these signals with high temporal resolution for research,such as the study of beam–cavity interactions and bunch-by-bunch parameter measurements.Therefore,a signal reconstruction algorithm with ultrahigh spatiotemporal resolution and bunch phase compensation based on equivalent sampling is proposed in this paper.Compared with traditional equivalent sampling,the use of phase compensation and setting the bunch signal zero-crossing point as the time reference can construct a more accurate reconstructed signal.The basic principles of the method,simulation,and experimental comparison are also introduced.Based on the beam test platform of the Shanghai Synchrotron Radiation Facility(SSRF)and the method of experimental verification,the factors that affect the reconstructed signal quality are analyzed and discussed,including the depth of the sampled data,quantization noise of analog-to-digital converter,beam transverse oscillation,and longitudinal oscillation.The results of the beam experiments show that under the user operation conditions of the SSRF,a beam excitation signal with an amplitude uncertainty of 2%can be reconstructed.
文摘The vacuum energy density of free scalar quantum field in a Rindler distributional space-time with distributional Levi-Cività connection is considered. It has been widely believed that, except in very extreme situations, the influence of acceleration on quantum fields should amount to just small, sub-dominant contributions. Here we argue that this belief is wrong by showing that in a Rindler distributional background space-time with distributional Levi-Cività connection the vacuum energy of free quantum fields is forced, by the very same background distributional space-time such a Rindler distributional background space-time, to become dominant over any classical energy density component. This semiclassical gravity effect finds its roots in the singular behavior of quantum fields on a Rindler distributional space-times with distributional Levi-Cività connection. In particular we obtain that the vacuum fluctuations have a singular behavior at a Rindler horizon . Therefore sufficiently strongly accelerated observer burns up near the Rindler horizon. Thus Polchinski’s account doesn’t violate the Einstein equivalence principle.
文摘In order to deal with the special spatio-temporal environmental changes encountered in the process of open-cast mining,taking Huolinhe No.1 Open-cast Mine as the research object,this paper studied its typical problems in river reconstruction and cultural relics protection.The study focused on eight key core aspects,including the design optimization of the spatial layout of the mining area,the accurate estimation of the mineral resources reserves,the scientific theoretical demonstration of the mining scale,the fine analysis and calculation of the stripping ratio,the comprehensive consideration of the transport distance and efficiency,the accurate judgment of the best time for the implementation of the transformation,the analysis and evaluation of the slope stability,and the overall planning of the production system.The results show that the extracted problem-solving strategies and scheme system for special mining conditions can not only provide specific and practical guidance for Huolinhe No.1 Open-cast Mine,but also serve as a valuable reference and practical reference for other open-cast mine enterprises facing similar challenges.
基金supported by the National Key Research and Development Program(No.2017YFB0902900).
文摘The accuracy of distribution system state estimation(DDSE)is reduced when phasor measurement unit(PMU)measurements contain outliers because of cyber attacks or global positioning system spoofing attacks.Therefore,to enhance the robustness of DDSE to measurement outliers,approximate the target distribution of Metropolis-Hastings(MH)sampling,and judge the prediction of the long short-term memory(LSTM)network,this paper proposes an outlier reconstruction based state estimation method using the equivalent model of the LSTM network and MH sampling(E-LM model),motivated by the characteristics of the chronological correlations of PMU measurements.First,the target distribution of outlier reconstruction is derived using a kernel density estimation function.Subsequently,the reasons and advantages of the E-LM model are explained and analyzed from a mathematical point of view.The proposed LSTM-based MH sampling can approximate the target distribution of MH sampling to decrease the number of the futile iterations.Moreover,the proposed MH-based forecasting of the LSTM can judge each LSTM prediction,which is independent of its true value.Finally,simulations are conducted to evaluate the performance of the E-LM model by integrating the LSTM network and the MH sampling into the outlier reconstruction based DDSE.
基金supported by the National Natural Science Foundation of China (60877043)the National High-Tech Research & Development Program of China (2007AA03Z417)the New-Century Excellent Talents Supporting Program of the Ministry of Education of China
文摘A distributed feedback(DFB) semiconductor laser with three phase shifts based on reconstruction equivalent chirp(REC) technology is proposed and investigated numerically.With the combination of multiple phase shifts and corrugation pitch modulated(CPM) structure,we also propose a novel and more complex structure named dual CPM,which has a flatter light power distribution along the laser cavity compared with the true double phase shifts DFB laser diode(LD),while the P-I curves are nearly the same.The proposed dual CPM structure is also designed and analyzed based on REC technology.The simulation results show that,the DFB semiconductor laser with complex structure such as phase shifts,or even arbitrary variation of the grating period can be achieved equivalently and easily by changing the sampling structure.But its external characteristics are almost the same as those DFB lasers with true phase shifts,or true arbitrary variation of the grating period.The key advantage of the REC technology is that it varies only the sampling structure and keeps the seed grating(actual grating in sampling structure) period constant.So its fabrication needs only low-cost and standard holographic exposure technology.Therefore we believe this method can achieve the high-end and low-cost DFB LD for mass production.
文摘近年来,单片集成的多波长激光器阵列作为波分复用(WDM)系统的理想光源而成为研究热点。通过重构-等效啁啾(REC)技术实现了一种低成本的分布反馈式(DFB)激光器阵列光源模块,采用掺铒光纤放大器(EDFA)对该激光器阵列的输出进行了光学放大,并通过PID控制程序对光源输出进行稳定化调节。光源模块中各通道激光器的中心波长间隔均匀,平均间隔为1.64 nm,波长间隔的误差小于0.2 nm。光源所输出的总光功率大于50 m W,输出光功率变化小于0.02 d Bm。
