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Performance analysis of the tight combination of GPS, BDS, GALILEO, and QzsS mixed frequencies signals
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作者 Yu Han Fangjun Qin +3 位作者 Xugang Lian Shengliang Wang Leiyuan Qian Wenhua Huang 《Geodesy and Geodynamics》 EI CSCD 2024年第4期366-378,共13页
With the gradual development and modernization of satellite navigation systems,using observation information from multi-GNss has become one of the hot-spot issues in recent years.Multi-system loose combinations form d... With the gradual development and modernization of satellite navigation systems,using observation information from multi-GNss has become one of the hot-spot issues in recent years.Multi-system loose combinations form double-difference observation equations within their respective systems,and the positioning effect is improved.However,the interchangeability and compatible interoperability between global navigation satellite systems(GNSS)cannot be truly realized.At the same time,when the number of visible satellites decreases abruptly,the positioning performance deteriorates sharply.This paper focuses on the GNsS multi-system tight combination relative positioning technique,gives a mathe-matical model of multi-system tight combination relative positioning considering differential inter-system bias(DISB),and analyzes the time-varying characteristics of DISB at overlapping and non-overlapping frequencies among GPS/Galileo,GPS/BDS,and GPS/QZSS in terms of receiver brand,tem-perature,and receiver restart.The GNsS tight combination relative positioning performance is verified by static data from Curtin University and dynamic data measured at Taiyuan University of Technology.The results show that compared with loose combination,the ambiguity-fixed rate increases from 62.18%to 97.60%for static data and from 74.97%to 99.53%for dynamic data when the elevation mask angle is 50°,resulting in a significant improvement in positioning performance. 展开更多
关键词 GNSS mix frequencies REDUNDANCY Tightcombination Differential inter-system bias
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Algebraic processing technique for extracting frequency-dependent shear-wave splitting parameters in an anisotropic medium 被引量:1
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作者 韩开锋 曾新吾 《Applied Geophysics》 SCIE CSCD 2011年第2期134-140,177,共8页
Based on the dual source cumulative rotation technique in the time-domain proposed by Zeng and MacBeth(1993),a new algebraic processing technique for extracting shear-wave splitting parameters from multi-component V... Based on the dual source cumulative rotation technique in the time-domain proposed by Zeng and MacBeth(1993),a new algebraic processing technique for extracting shear-wave splitting parameters from multi-component VSP data in frequency-dependent medium has been developed.By using this dual source cumulative rotation technique in the frequency-domain(DCTF),anisotropic parameters,including polarization direction of the shear-waves and timedelay between the fast and slow shear-waves,can be estimated for each frequency component in the frequency domain.It avoids the possible error which comes from using a narrow-band filter in the current commonly used method.By using synthetic seismograms,the feasibility and validity of the technique was tested and a comparison with the currently used method was also given.The results demonstrate that the shear-wave splitting parameters frequency dependence can be extracted directly from four-component seismic data using the DCTF.In the presence of larger scale fractures,substantial frequency dependence would be found in the seismic frequency range,which implies that dispersion would occur at seismic frequencies.Our study shows that shear-wave anisotropy decreases as frequency increases. 展开更多
关键词 Algebraic processing technique ANISOTROPY shear-wave splitting frequency dependence
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A Method in Mixed Frequency-time domain for Fatigue Life Estimation of Steel Girders of Cable-stayed Bridges Due to Buffeting 被引量:1
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作者 顾明 陈礼忠 项海帆 《应用基础与工程科学学报》 EI CSCD 1998年第4期70-79,共10页
发展了斜拉桥钢主梁抖振疲劳寿命的混合时-频域方法.在本方法中,首先建立了桥面处的风速风向概率密度函数,导出的应力谱因其包括背景分量而不再是窄带谱.据应力谱模拟出了疲劳应力的时间历程,并用雨流计数法统计了其幅值特性.基... 发展了斜拉桥钢主梁抖振疲劳寿命的混合时-频域方法.在本方法中,首先建立了桥面处的风速风向概率密度函数,导出的应力谱因其包括背景分量而不再是窄带谱.据应力谱模拟出了疲劳应力的时间历程,并用雨流计数法统计了其幅值特性.基于修正的Miner定理导出了考虑风速风向作用的桥梁主梁抖振疲劳寿命的估算公式,并用此分析了杨浦大桥钢主梁的抖振疲劳寿命.结果表明,风向对抖振疲劳寿命有很大影响;杨浦大桥主梁的疲劳寿命远大于设计寿命. 展开更多
关键词 斜拉桥 钢主梁 抖振 疲劳寿命 混合时-频域
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Fuzzy-Model-Based Finite Frequency Fault Detection Filtering Design for Two-Dimensional Nonlinear Systems
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作者 Meng Wang Huaicheng Yan +1 位作者 Jianbin Qiu Wenqiang Ji 《IEEE/CAA Journal of Automatica Sinica》 SCIE EI CSCD 2024年第10期2099-2110,共12页
This article studies the fault detection filtering design problem for Roesser type two-dimensional(2-D)nonlinear systems described by uncertain 2-D Takagi-Sugeno(T-S)fuzzy models.Firstly,fuzzy Lyapunov functions are c... This article studies the fault detection filtering design problem for Roesser type two-dimensional(2-D)nonlinear systems described by uncertain 2-D Takagi-Sugeno(T-S)fuzzy models.Firstly,fuzzy Lyapunov functions are constructed and the 2-D Fourier transform is exploited,based on which a finite frequency fault detection filtering design method is proposed such that a residual signal is generated with robustness to external disturbances and sensitivity to faults.It has been shown that the utilization of available frequency spectrum information of faults and disturbances makes the proposed filtering design method more general and less conservative compared with a conventional nonfrequency based filtering design approach.Then,with the proposed evaluation function and its threshold,a novel mixed finite frequency H_(∞)/H_(-)fault detection algorithm is developed,based on which the fault can be immediately detected once the evaluation function exceeds the threshold.Finally,it is verified with simulation studies that the proposed method is effective and less conservative than conventional non-frequency and/or common Lyapunov function based filtering design methods. 展开更多
关键词 Fault diagnosis finite frequency specifications mixed H_(∞)/H_(-)performance two-dimensional nonlinear systems
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Harmonic balance method with alternating frequency/time domain technique for nonlinear dynamical system with fractional exponential 被引量:10
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作者 张智勇 陈予恕 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2014年第4期423-436,共14页
Comparisons of the common methods for obtaining the periodic responses show that the harmonic balance method with alternating frequency/time (HB-AFT) do- main technique has some advantages in dealing with nonlinear ... Comparisons of the common methods for obtaining the periodic responses show that the harmonic balance method with alternating frequency/time (HB-AFT) do- main technique has some advantages in dealing with nonlinear problems of fractional exponential models. By the HB-AFT method, a rigid rotor supported by ball bearings with nonlinearity of Hertz contact and ball passage vibrations is considered. With the aid of the Floquet theory, the movement characteristics of interval stability are deeply studied. Besides, a simple strategy to determine the monodromy matrix is proposed for the stability analysis. 展开更多
关键词 fractional exponential nonlinearity harmonic balance method with alter-nating frequency/time (HB-AFT) domain technique global response stability
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Frequency measurement technique based on frequency conversion 被引量:2
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作者 宁泽洪 徐达旺 董占勇 《Journal of Measurement Science and Instrumentation》 CAS 2013年第2期146-149,共4页
To measure the signals with high freq u ency(>500 MHz),a sampling frequency down conversion method is introduced.This pa per analyzes the intermodulation signals and figures out the relationship betwee n the interm... To measure the signals with high freq u ency(>500 MHz),a sampling frequency down conversion method is introduced.This pa per analyzes the intermodulation signals and figures out the relationship betwee n the intermodulation signal and intermediate frequenc y signal.Based on the frequency conversion technology,an exclusion algorithm i s proposed a nd the actual implementation of the algorithm is given.The application resu lts show that the exclusion algorithm can identify the intermodulation signal exactly and eliminate the bad influence on the frequency measurement. 展开更多
关键词 frequency mixing intermodulation signal intermediate frequency local oscillator harmonic order
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Nonparametric Spectral Estimation Technique to Estimate Dominant Frequency for Atrial Fibrillation Detection 被引量:2
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作者 Shafa-at Ali Sheikh Aftab Zafar Majoka +2 位作者 Khalil Ur Rehman Nauman Razzaq Tahir Zaidi 《Journal of Signal and Information Processing》 2015年第4期266-276,共11页
Atrial fibrillation (Afib) is related with heart failure, stroke, and high mortality rates. In frequency domain analysis, pre-requisite for Afib detection has been the estimation of reliable dominant frequency (DF) of... Atrial fibrillation (Afib) is related with heart failure, stroke, and high mortality rates. In frequency domain analysis, pre-requisite for Afib detection has been the estimation of reliable dominant frequency (DF) of atrial signals via different spectral estimation techniques. DF further characterizes Afib, and helps in its treatment. This paper aims at finding the most appropriate nonparametric FFT-based spectral estimation technique to estimate reliable DF for Afib detection. In this work, real-time intra-atrial electrograms have been acquired and pre-processed for frequency analysis. DF is estimated via Bartlett using Hanning window, and Welch methods. Regularity index (RI), a parameter to ensure reliability of DF, is calculated using Simpson 3/8 and Trapezoidal rules. The best method is declared based upon high accuracy of Afib detection using reliable DF. On comparison, Welch method is found to be more appropriate to estimate reliable DF for Afib detection with 98% accuracy. 展开更多
关键词 ATRIAL FIBRILLATION DOMINANT frequency REGULARITY Index NONPARAMETRIC Spectral Estimation techniques Welch Method
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Dynamic Output Feedback Control Synthesis with Mixed Frequency Small Gain Specifications 被引量:4
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作者 ZHANG Xiao-Ni YANG Guang-Hong 《自动化学报》 EI CSCD 北大核心 2008年第5期551-557,共7页
这篇论文与混合频率为线性连续时间的系统经由动态输出反馈涉及控制合成问题小获得说明。为设计动态产量反馈控制器的一个新方法被介绍以便结果靠近环的系统是 asymptotically 稳定的并且在两个有限频率范围和全部频率范围满足小获得说... 这篇论文与混合频率为线性连续时间的系统经由动态输出反馈涉及控制合成问题小获得说明。为设计动态产量反馈控制器的一个新方法被介绍以便结果靠近环的系统是 asymptotically 稳定的并且在两个有限频率范围和全部频率范围满足小获得说明的要求。设计条件以一套线性矩阵不平等(LMI ) 的答案被给。最后,一个数字例子被给与存在那个比较说明设计过程和建议方法的优点。 展开更多
关键词 动力输出反馈控制系统 小增益规格 FDIs 混合频率
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Research progress of traditional Chinese medicine nursing techniques for the management of postoperative complications in mixed hemorrhoids 被引量:2
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作者 Yu Leng Wei Xie Zhi Li 《TMR Integrative Nursing》 2018年第4期148-152,共5页
Mixed hemorrhoids,especially ring-shaped mixed hemorrhoid,is still a headache for anorectal surgeons due to its post-operative complications.In recent years,clinicians have been studying and exploring to avoid and all... Mixed hemorrhoids,especially ring-shaped mixed hemorrhoid,is still a headache for anorectal surgeons due to its post-operative complications.In recent years,clinicians have been studying and exploring to avoid and alleviate these complications.In the Chinese medicine industry,the application of traditional Chinese medicine nursing technology has good and unique effect in prevent local pain,perianal edema,promote wound healing,relieve urinary retention,improve constipation,relieve anxiety,and so on.This article summarized the evidences of investigated the role of traditional Chinese medicine nursing technique in preventing and treating mixed hemorrhoid so that practitioners can make decision based on the best available evidences. 展开更多
关键词 Traditional Chinese medicine nursing technique mixed hemorrhoid Postoperative complications Clinicalapplication
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Nonlinear mixed-effects height to crown base and crown length dynamic models using the branch mortality technique for a Korean larch( Larix olgensis ) plantations in northeast China 被引量:8
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作者 Weiwei Jia Dongsheng Chen 《Journal of Forestry Research》 SCIE CAS CSCD 2019年第6期2095-2109,共15页
Korean larch(Larix olgensis)is one of the main tree species for aff orestation and timber production in northeast China.However,its timber quality and growth ability are largely infl uenced by crown size,structure and... Korean larch(Larix olgensis)is one of the main tree species for aff orestation and timber production in northeast China.However,its timber quality and growth ability are largely infl uenced by crown size,structure and shape.The majority of crown models are static models based on tree size and stand characteristics from temporary sample plots,but crown dynamic models has seldom been constructed.Therefore,this study aimed to develop height to crown base(HCB)and crown length(CL)dynamic models using the branch mortality technique for a Korean larch plantation.The nonlinear mixed-eff ects model with random eff ects,variance functions and correlation structures,was used to build HCB and CL dynamic models.The data were obtained from 95 sample trees of 19 plots in Meng JiaGang forest farm in Northeast China.The results showed that HCB progressively increases as tree age,tree height growth(HT growth)and diameter at breast height growth(DBH growth).The CL was increased with tree age in 20 years ago,and subsequently stabilized.HT growth,DBH growth stand basal area(BAS)and crown competition factor(CCF)signifi cantly infl uenced HCB and CL.The HCB was positively correlated with BAS,HT growth and DBH growth,but negatively correlated with CCF.The CL was positively correlated with BAS and CCF,but negatively correlated with DBH growth.Model fi tting and validation confi rmed that the mixed-eff ects model considering the stand and tree level random eff ects was accurate and reliable for predicting the HCB and CL dynamics.However,the models involving adding variance functions and time series correlation structure could not completely remove heterogeneity and autocorrelation,and the fi tting precision of the models was reduced.Therefore,from the point of view of application,we should take care to avoid setting up over-complex models.The HCB and CL dynamic models in our study may also be incorporated into stand growth and yield model systems in China. 展开更多
关键词 Larix olgensis plantation Height to CROWN BASE CROWN LENGTH Branch MORTALITY technique NONLINEAR mixed-eff ects models
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Micro-crack detection of nonlinear Lamb wave propagation in three-dimensional plates with mixed-frequency excitation 被引量:3
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作者 Wei-Guang Zhu Yi-Feng Li +3 位作者 Li-Qiang Guan Xi-Li Wan Hui-Yang Yu Xiao-Zhou Liu 《Chinese Physics B》 SCIE EI CAS CSCD 2020年第1期336-345,共10页
We propose a nonlinear ultrasonic technique by using the mixed-frequency signals excited Lamb waves to conduct micro-crack detection in thin plate structures.Simulation models of three-dimensional(3D)aluminum plates a... We propose a nonlinear ultrasonic technique by using the mixed-frequency signals excited Lamb waves to conduct micro-crack detection in thin plate structures.Simulation models of three-dimensional(3D)aluminum plates and composite laminates are established by ABAQUS software,where the aluminum plate contains buried crack and composite laminates comprises cohesive element whose thickness is zero to simulate delamination damage.The interactions between the S0 mode Lamb wave and the buried micro-cracks of various dimensions are simulated by using the finite element method.Fourier frequency spectrum analysis is applied to the received time domain signal and fundamental frequency amplitudes,and sum and difference frequencies are extracted and simulated.Simulation results indicate that nonlinear Lamb waves have different sensitivities to various crack sizes.There is a positive correlation among crack length,height,and sum and difference frequency amplitudes for an aluminum plate,with both amplitudes decreasing as crack thickness increased,i.e.,nonlinear effect weakens as the micro-crack becomes thicker.The amplitudes of sum and difference frequency are positively correlated with the length and width of the zero-thickness cohesive element in the composite laminates.Furthermore,amplitude ratio change is investigated and it can be used as an effective tool to detect inner defects in thin 3D plates. 展开更多
关键词 nonlinear Lamb wave mixed-frequency MICRO-CRACKS amplitude ratio
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A PREDICTION TECHNIQUE FOR DYNAMIC ANALYSIS OF FLAT PLATES IN MID-FREQUENCY RANGE 被引量:5
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作者 Weicai Peng Zeng He Peng Li Jiaqiang Wang 《Acta Mechanica Solida Sinica》 SCIE EI 2007年第4期333-341,共9页
The wave-based method (WBM) has been applied for the prediction of mid-frequency vibrations of fiat plates. The scaling factors, Gauss point selection rule and truncation rule are introduced to insure the wave model... The wave-based method (WBM) has been applied for the prediction of mid-frequency vibrations of fiat plates. The scaling factors, Gauss point selection rule and truncation rule are introduced to insure the wave model to converge. Numerical results show that the prediction tech- nique based on WBM is with higher accuracy and smaller computational effort than the one on FEM, which implies that this new technique on WBM can be applied to higher-frequency range. 展开更多
关键词 mid-frequency range Trefftz method computational efficiency numerical prediction technique
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Mixed Monotone Iterative Technique and Boundary Value Problem for a Class of Impulsive Integro-Differential Equations
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作者 支妍妍 陈海波 吕晨辉 《Journal of Donghua University(English Edition)》 EI CAS 2016年第1期46-53,共8页
In this paper,the existence and uniqueness of iterative solutions to the boundary value problems for a class of first order impulsive integro-differential equations were studied. Under a new concept of upper and lower... In this paper,the existence and uniqueness of iterative solutions to the boundary value problems for a class of first order impulsive integro-differential equations were studied. Under a new concept of upper and lower solutions, a new monotone iterative technique on the boundary value problem of integro-differential equations was proposed. The existence and uniqueness of iterative solutions and the error estimation in certain interval were obtained.An example was also given to illustrate the results. 展开更多
关键词 impulsive integro-differential equations L-quasi-upper and lower solutions mixed monotone iterative technique boundary value problem
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Traffic Conflict Technique Development for Traffic Safety Evaluation under Mixed Traffic Conditions of Developing Countries
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作者 Tran Quang Vuong 《Journal of Traffic and Transportation Engineering》 2017年第4期228-235,共8页
In developing countries, the numbers of traffic accidents, injuries and fatalities are very high and tend to increase atsignalized intersections. For example, in Ho Chi Minh City (HCMC) of Vietnam, the number of acc... In developing countries, the numbers of traffic accidents, injuries and fatalities are very high and tend to increase atsignalized intersections. For example, in Ho Chi Minh City (HCMC) of Vietnam, the number of accidents at signalized intersectionsaccounted for 45% of the total accidents at all the intersections. This fact leads to strong necessity for analyzing traffic safety atsignalized intersections. Nevertheless, the historical accident data in HCMC is not available for deep analysis, this study uses videocameras to capture and analyze conflicts that potentially lead to accidents using TCT (traffic conflict technique). Conflict severityidentification is one of the most significant steps to evaluate traffic safety at signalized intersections using TCT. Six zones (seriousconflict, common conflict, non-conflict, highest potential serious conflict, potential serious conflict, and potential common conflict) areexplored in this study to clarify conflict severity. This result is based on being the cut off value between serious conflicts and commonconflicts, according to 85% cumulative frequency of TTC (time to collision) and CS (conflict speed) under 3,050 samples size whichwere observed at 10 signalized intersections during August-November, 2014. Such a deep understanding is a scientific basis to studyhow to apply TCT to evaluate traffic safety at signalized intersections under mixed traffic conditions. 展开更多
关键词 TRAFFIC CONFLICT technique TRAFFIC safety signalized intersections TRAFFIC CONFLICT severity mixed TRAFFIC condition.
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基于新权重函数的MIX-GARCH-L模型及其应用
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作者 杨炜明 刘涛 王琴 《统计与决策》 CSSCI 北大核心 2024年第8期22-27,共6页
文章引入一种新的权重函数,并构建新的波动率模型——MIX-GARCH-L模型,新模型能够充分利用高低频数据提炼出更有价值的信息。针对新模型参数估计问题,提出MIX-GARCH-L模型的参数估计方法来分析估计量的理论性质,证明了对应的中心极限定... 文章引入一种新的权重函数,并构建新的波动率模型——MIX-GARCH-L模型,新模型能够充分利用高低频数据提炼出更有价值的信息。针对新模型参数估计问题,提出MIX-GARCH-L模型的参数估计方法来分析估计量的理论性质,证明了对应的中心极限定理以及用Service-Boostrap方法模拟检验估计量的数据表现。所提模型具有以下优势:新权重函数能够更好地根据交易特征的变动来自动调整不同交易日的权重,从而使每个高频交易日所分配到的权重与未来波动率产生的冲击效果一致;能够利用同一交易过程中多种高频交易数据,信息利用更加充分,使得MIX-GARCH-L模型具有更好的预测精度和预测优势。实证结果显示:MIX-GARCH-L模型的MSPE值明显小于GARCH-RV模型和GARCH-M模型的MSPE值,说明MIX-GARCH-L模型不仅在模型预测上有更高的预测精度,而且在稳健性上的表现也更好。 展开更多
关键词 混频数据 新权重 波动率 参数估计 数值模拟
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Improvement of the Mirror Extending in Empirical Mode Decomposition Method and the Technology for Eliminating Frequency Mixing 被引量:32
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作者 赵进平 《High Technology Letters》 EI CAS 2002年第3期40-47,共8页
The mirror extending approach proposed by Zhao and Huang in EMD method is improved in this paper. Mirror extending manner of data is kept unchanged, but the approach for determining envelopes is changed. When the end ... The mirror extending approach proposed by Zhao and Huang in EMD method is improved in this paper. Mirror extending manner of data is kept unchanged, but the approach for determining envelopes is changed. When the end of data is obviously not extremum, the envelope is determined by the first inner extremum and the image value in the mirror, ignoring the value on the end. This improvement eliminates the frequency compression near the end and decreases the error. Meanwhile, tridiagonal equations are used and the calculation speed is much increased. The temporal process curve is more important in reflecting the real physical process and comparable with other phenomena. Frequency mixing in IMFs makes it impossible. A high frequency reconstruction (HFR) approach is proposed to eliminate common frequency mixing and reconstruct an IMF with all high frequency portions. By this approach, the IMFs without frequency mixing are obtained to express significative processes. The high frequency information restored in high frequency IMF can be extracted by general spectrum method. After obtaining IMFs by EMD method, some of the theoretical and technological issues still exist when using the IMFs. The consistency of IMFs with real physical process is discussed in detail. By virtue of the approach proposed in this paper, the EMD method can be widely used in various fields. 展开更多
关键词 empirical mode decomposition mirror extending intrinsic mode function high frequency reconstruction frequency mixing
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Application of Uniform Experimental Design in Optimizing Excitation Parameters for Magnetic Frequency Mixing Measurements 被引量:2
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作者 Yu Chang Jingpin Jiao +3 位作者 Xiucheng Liu Guanghai Li Cunfu He Bin Wu 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2020年第1期197-209,共13页
Excitation parameter preferences are key factors a ecting the performance of magnetic frequency mixing detection.A uniform experimental design method was used to analyze this influence.Using fuzzy theory,a comprehensi... Excitation parameter preferences are key factors a ecting the performance of magnetic frequency mixing detection.A uniform experimental design method was used to analyze this influence.Using fuzzy theory,a comprehensive model is established for evaluating the e ect of magnetic frequency mixing.A polynomial is selected as the regression function to express explicitly the correlation between the excitation parameters and the frequency-mixing e ect.The excitation parameters were then optimized using genetic algorithm.Magnetic frequency mixing experiments were conducted to measure the surface hardness of some ferromagnetic materials.Frequency mixing is further enhanced under the optimal settings,resulting in an improvement in the measurement sensitivity.The results of this study support the application of the magnetic frequency mixing technique in non-destructive testing. 展开更多
关键词 MAGNETIC frequency mixING technology EXCITATION parameters UNIFORM experimental design Regression STATISTICAL method Surface HARDNESS measurement
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A Posteriori Error Estimate of Two Grid Mixed Finite Element Methods for Semilinear Elliptic Equations
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作者 Yiming Wen Luoping Chen Jiajia Dai 《Journal of Applied Mathematics and Physics》 2023年第2期361-376,共16页
In this paper, we present the a posteriori error estimate of two-grid mixed finite element methods by averaging techniques for semilinear elliptic equations. We first propose the two-grid algorithms to linearize the m... In this paper, we present the a posteriori error estimate of two-grid mixed finite element methods by averaging techniques for semilinear elliptic equations. We first propose the two-grid algorithms to linearize the mixed method equations. Then, the averaging technique is used to construct the a posteriori error estimates of the two-grid mixed finite element method and theoretical analysis are given for the error estimators. Finally, we give some numerical examples to verify the reliability and efficiency of the a posteriori error estimator. 展开更多
关键词 Two-Grid mixed Finite Element Methods Posteriori Error Estimates Semilinear Elliptic Equations Averaging technique
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Determination of Natural Frequencies of Multilayered Plates by Mixed Finite Elements
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作者 Roberto S. Carnicer Braian A. Desia Rodolfo A. Schwarz 《Journal of Mechanics Engineering and Automation》 2014年第10期820-827,共8页
Natural frequencies for multilayer plates are calculated by mixed finite element method. The main object of this paper is to use the mixed model for multilayer plates, analyzing each layer as an isolated plate, where ... Natural frequencies for multilayer plates are calculated by mixed finite element method. The main object of this paper is to use the mixed model for multilayer plates, analyzing each layer as an isolated plate, where the continuity of displacements is achieved by Lagrange multipliers (representing static variables). This procedure allows us to work with any model for single plate (so as to ensure the proper behavior of each layer), and the complexity of the multilayer system is avoided by ensuring the condition of displacements by the Lagrange multipliers (static variables). The plate is discretized by finite element modeling based on a primary hybrid model, where the domain is divided by quadrilateral, both for the displacement field and static variables. This mixed element for plates was implemented and several examples of vibrations have been verified successfully by the results obtained by other methods in the literature. 展开更多
关键词 mixed finite element multilayer plate Lagrange multipliers natural frequencies free vibrations.
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Polarisation-sensitive four-wave mixing and soliton self-frequency shift effect in the highly birefringent photonic crystal fibre
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作者 苑金辉 桑新柱 +4 位作者 余重秀 忻向军 李曙光 周桂耀 侯蓝田 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第7期344-349,共6页
By adjusting the polarisation state of the pump at 805 nm parallel to slow (x) and fast (y) axes of the highly birefringent photonic crystal fibre with zero dispersion wavelengths 790 nm and 750 nm, this paper dem... By adjusting the polarisation state of the pump at 805 nm parallel to slow (x) and fast (y) axes of the highly birefringent photonic crystal fibre with zero dispersion wavelengths 790 nm and 750 nm, this paper demonstrates the efficient polarisation-sensitive four wave mixing involved in pump, anti-Stokes and Stokes signals and soliton self- frequency shift effects induced by the phase-matching between red-shifted solitons and blue-shifted dispersive waves. If the reduction of coupling efficiency to the circular pump laser mode or other circular fibres due to asymmetry of the core is neglected, more than 98% of the total input power is kept in a single linear polarisation. Controlled dispersion characteristic of the doublet of fundamental guided-modes results in achieving light field strongly confined in principal axes of photonic crystal fibre, and enhancing the corresponding nonlinear-optical process through the remarkable nonlinear birefringence. 展开更多
关键词 highly birefringent photonic crystal fibre four wave mixing soliton self-frequency shift PHASE-MATCHING
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