Approximate periodic time series means it has an approximate periodic trend.The so-called approximate periodicity refers that it looks like having periodicity,however the length of each period is not constant such as ...Approximate periodic time series means it has an approximate periodic trend.The so-called approximate periodicity refers that it looks like having periodicity,however the length of each period is not constant such as sunspot data.Approximate periodic time series has a wide application prospect in modelling social economic phenomenon.As for approximate periodic time series,the key problem is to depict its approximate periodic trend because it can be dealt as an ordinary time series only if its approximate periodic trend has been depicted.However,there is little study on depicting approximate periodic trend.In the paper,the authors first establish some necessary theories,especially bring forward the concept of shape-retention transformation with lengthwise compression and obtain necessary and sufficient condition for linear shape-retention transformation with lengthwise compression,then basing on the theories the authors present a method to estimate scale transformation,which can model approximate periodic trend very clearly.At last,a simulated example is analyzed by this presented method.The results show that the presented method is very effective and very powerful.展开更多
Laser-driven ramp compression was used to investigate iron characteristics along the isentropic path. The iterative Lagrangian analysis method was employed to analyze the free surface velocity profiles in iron stepped...Laser-driven ramp compression was used to investigate iron characteristics along the isentropic path. The iterative Lagrangian analysis method was employed to analyze the free surface velocity profiles in iron stepped target measured with two VISARs. The onset stress for the α to ε phase transformation was determined from the sudden change in the sound velocity and was found over-pressurized compared to the static and shock results. The derived stress（26 GPa） and strain rate（up to 10-8 s^-1） are consistent with our previous experimental results. The stress-density relations were compared with those from previous ramp experiments and good agreements were found, which experimentally confirms the simulations,showing that iterative Lagrangian analysis can be applied to the ramp-compression data with weak shock.展开更多
In this paper,a lifted Haar transform(LHT)image compression optical chip has been researched to achieve rapid image compression.The chip comprises 32 same image compression optical circuits,and each circuit contains a...In this paper,a lifted Haar transform(LHT)image compression optical chip has been researched to achieve rapid image compression.The chip comprises 32 same image compression optical circuits,and each circuit contains a 2×2 multimode interference(MMI)coupler and aπ/2 delay line phase shifter as the key components.The chip uses highly borosilicate glass as the substrate,Su8 negative photoresist as the core layer,and air as the cladding layer.Its horizontal and longitudinal dimensions are 8011μm×10000μm.Simulation results present that the designed optical circuit has a coupling ratio(CR)of 0:100 and an insertion loss(IL)of 0.001548 d B.Then the chip is fabricated by femtosecond laser and testing results illustrate that the chip has a CR of 6:94 and an IL of 0.518 d B.So,the prepared chip possesses good image compression performance.展开更多
Modularized circuit designs for chaotic systems are introduced in this paper.Especially,a typical improved modularized design strategy is proposed and applied to a new hyper-chaotic system circuit implementation.In th...Modularized circuit designs for chaotic systems are introduced in this paper.Especially,a typical improved modularized design strategy is proposed and applied to a new hyper-chaotic system circuit implementation.In this paper,the detailed design procedures are described.Multisim simulations and physical experiments are conducted,and the simulation results are compared with Matlab simulation results for different system parameter pairs.These results are consistent with each other and they verify the existence of the hyper-chaotic attractor for this new hyper-chaotic system.展开更多
Yule-Simon distribution has a wide range of practical applications, such as in networkscience, biology and humanities. A lot of work focuses on the study of how well the empirical datafits Yule-Simon distribution or h...Yule-Simon distribution has a wide range of practical applications, such as in networkscience, biology and humanities. A lot of work focuses on the study of how well the empirical datafits Yule-Simon distribution or how to estimate the parameter. There are still some open problems,such as the error analysis of parameter estimation, the theoretical proof of the convergence of theiterative algorithm for maximum likelihood estimation of parameters. The Yule-Simon distributionis a heavy-tailed distribution and the parameter is usually less than 2, so the variance does notexist. This makes it difficult to give an interval estimation of the parameter. Using the compressiontransformation, this paper proposes a method of interval estimation based on the centrallimit theorem. This method can be applied to many heavy-tailed distributions. The other twoasymptotic confidence intervals of the parameter are obtained based on the maximum likelihoodand the mode method. These estimation methods are compared in simulations and applications toempirical data.展开更多
A coding method of speech compression, which is based on Wavlet Transform and Vector Quantization (VQ), is developed and studied. The Wavlet Thansform or Wavlet Packet Thansform is used to process the speech signal, t...A coding method of speech compression, which is based on Wavlet Transform and Vector Quantization (VQ), is developed and studied. The Wavlet Thansform or Wavlet Packet Thansform is used to process the speech signal, then VQ is used to compress the coefficients of Wavlet Thansform, and the entropy coding is used to decrease the bit rate. The experimental results show that the speech signal, sampled by 8 kHz sampling rate and 8 bit quatisation,i.e., 64 kbit/s bit rate, can be compressed to 6 - 8 kbit/s, and still have high speech quality,and the low-delay, only 8 ms.展开更多
基金Supported by the National Natural Science Foundation of China(Grant No.11471120)the Science and Technology Commission of Shanghai Municipality(Grant No.19JC1420100)。
文摘Approximate periodic time series means it has an approximate periodic trend.The so-called approximate periodicity refers that it looks like having periodicity,however the length of each period is not constant such as sunspot data.Approximate periodic time series has a wide application prospect in modelling social economic phenomenon.As for approximate periodic time series,the key problem is to depict its approximate periodic trend because it can be dealt as an ordinary time series only if its approximate periodic trend has been depicted.However,there is little study on depicting approximate periodic trend.In the paper,the authors first establish some necessary theories,especially bring forward the concept of shape-retention transformation with lengthwise compression and obtain necessary and sufficient condition for linear shape-retention transformation with lengthwise compression,then basing on the theories the authors present a method to estimate scale transformation,which can model approximate periodic trend very clearly.At last,a simulated example is analyzed by this presented method.The results show that the presented method is very effective and very powerful.
基金Project supported by the National Basic Research Program of China(Grant No.2013CBA01503)the National Natural Science Foundation of China(Grant No.11103040)
文摘Laser-driven ramp compression was used to investigate iron characteristics along the isentropic path. The iterative Lagrangian analysis method was employed to analyze the free surface velocity profiles in iron stepped target measured with two VISARs. The onset stress for the α to ε phase transformation was determined from the sudden change in the sound velocity and was found over-pressurized compared to the static and shock results. The derived stress（26 GPa） and strain rate（up to 10-8 s^-1） are consistent with our previous experimental results. The stress-density relations were compared with those from previous ramp experiments and good agreements were found, which experimentally confirms the simulations,showing that iterative Lagrangian analysis can be applied to the ramp-compression data with weak shock.
基金the Natural Science Foundation of Hubei Province(No.2017CFB685)Hubei University of Technology"Advanced Manufacturing Technology and Equipment"Collaborative Innovation Center Open Research Fund(Nos.038/1201501 and 038/1201803)the College-level Project of Hubei University of Technology(Nos.4201/01758,4201/01802,4201/01889,and 4128/21025)。
文摘In this paper,a lifted Haar transform(LHT)image compression optical chip has been researched to achieve rapid image compression.The chip comprises 32 same image compression optical circuits,and each circuit contains a 2×2 multimode interference(MMI)coupler and aπ/2 delay line phase shifter as the key components.The chip uses highly borosilicate glass as the substrate,Su8 negative photoresist as the core layer,and air as the cladding layer.Its horizontal and longitudinal dimensions are 8011μm×10000μm.Simulation results present that the designed optical circuit has a coupling ratio(CR)of 0:100 and an insertion loss(IL)of 0.001548 d B.Then the chip is fabricated by femtosecond laser and testing results illustrate that the chip has a CR of 6:94 and an IL of 0.518 d B.So,the prepared chip possesses good image compression performance.
基金supported by the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.61403395)the Natural Science Foundation of Tianjin,China(Grant No.13JCYBJC39000)+3 种基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry of Chinathe Fund from the Tianjin Key Laboratory of Civil Aircraft Airworthiness and Maintenance in Civil Aviation of China(Grant No.104003020106)the National Basic Research Program of China(Grant No.2014CB744904)the Fund for the Scholars of Civil Aviation University of China(Grant No.2012QD21x)
文摘Modularized circuit designs for chaotic systems are introduced in this paper.Especially,a typical improved modularized design strategy is proposed and applied to a new hyper-chaotic system circuit implementation.In this paper,the detailed design procedures are described.Multisim simulations and physical experiments are conducted,and the simulation results are compared with Matlab simulation results for different system parameter pairs.These results are consistent with each other and they verify the existence of the hyper-chaotic attractor for this new hyper-chaotic system.
基金supported by the National Natural Science Foundation of China(Grant No.11961035)Jiangxi Provincial Natural Science Foundation(Grant No.20224BCD41001).
文摘Yule-Simon distribution has a wide range of practical applications, such as in networkscience, biology and humanities. A lot of work focuses on the study of how well the empirical datafits Yule-Simon distribution or how to estimate the parameter. There are still some open problems,such as the error analysis of parameter estimation, the theoretical proof of the convergence of theiterative algorithm for maximum likelihood estimation of parameters. The Yule-Simon distributionis a heavy-tailed distribution and the parameter is usually less than 2, so the variance does notexist. This makes it difficult to give an interval estimation of the parameter. Using the compressiontransformation, this paper proposes a method of interval estimation based on the centrallimit theorem. This method can be applied to many heavy-tailed distributions. The other twoasymptotic confidence intervals of the parameter are obtained based on the maximum likelihoodand the mode method. These estimation methods are compared in simulations and applications toempirical data.
文摘A coding method of speech compression, which is based on Wavlet Transform and Vector Quantization (VQ), is developed and studied. The Wavlet Thansform or Wavlet Packet Thansform is used to process the speech signal, then VQ is used to compress the coefficients of Wavlet Thansform, and the entropy coding is used to decrease the bit rate. The experimental results show that the speech signal, sampled by 8 kHz sampling rate and 8 bit quatisation,i.e., 64 kbit/s bit rate, can be compressed to 6 - 8 kbit/s, and still have high speech quality,and the low-delay, only 8 ms.
