Existing blockwise empirical likelihood(BEL)method blocks the observations or their analogues,which is proven useful under some dependent data settings.In this paper,we introduce a new BEL(NBEL)method by blocking the ...Existing blockwise empirical likelihood(BEL)method blocks the observations or their analogues,which is proven useful under some dependent data settings.In this paper,we introduce a new BEL(NBEL)method by blocking the scoring functions under high dimensional cases.We study the construction of confidence regions for the parameters in spatial autoregressive models with spatial autoregressive disturbances(SARAR models)with high dimension of parameters by using the NBEL method.It is shown that the NBEL ratio statistics are asymptoticallyχ^(2)-type distributed,which are used to obtain the NBEL based confidence regions for the parameters in SARAR models.A simulation study is conducted to compare the performances of the NBEL and the usual EL methods.展开更多
Feature extraction is an important part of signal processing,which is significant for signal detection,classification,and recognition.The nonlinear dynamic analysis method can extract the nonlinear characteristics of ...Feature extraction is an important part of signal processing,which is significant for signal detection,classification,and recognition.The nonlinear dynamic analysis method can extract the nonlinear characteristics of signals and is widely used in different fields.Reverse dispersion entropy(RDE)proposed by us recently,as a nonlinear dynamic analysis method,has the advantages of fast computing speed and strong anti-noise ability,which is more suitable for measuring the complexity of signal than traditional permutation entropy(PE)and dispersion entropy(DE).Empirical wavelet transform(EWT),based on the theory of wavelet analysis,can decompose a complex non-stationary signal into a number of empirical wavelet functions(EWFs)with compact support set spectrum,which has better decomposition performance than empirical mode decomposition(EMD)and its improved algorithms.Considering the advantages of RDE and EWT,on the one hand,we introduce EWT into the field of underwater acoustic signal processing and fault diagnosis to improve the signal decomposition accuracy;on the other hand,we use RDE as the features of EWFs to improve the signal separability and stability.Finally,we propose a novel signal feature extraction technology based on EWT and RDE in this paper.Experimental results show that the proposed feature extraction technology can effectively extract the complexity features of actual signals.Moreover,it also has higher distinguishing ability for different types of signals than five latest feature extraction technologies.展开更多
Fetr6 is an underground mine using the stope-and-pillar mining method. As there was some evidence regarding pillar failure in this mine, improving works such as roof support and replacing existing pillars with concret...Fetr6 is an underground mine using the stope-and-pillar mining method. As there was some evidence regarding pillar failure in this mine, improving works such as roof support and replacing existing pillars with concrete pillars (CP) were carried out. During the construction of the second CP, in the space between the remaining pillars, one of the pillars failed leading to the progressive failure of other pillars until 4 000 m 2 of mine had collapsed within a few minutes. In this work, this phenomenon is described by applying both numerical and empirical methods and the respective results are compared. The results of numerical modelling are found to be closer to the actual condition than those of the empirical method. Also, a width-to-height (W/H) ratio less than 1, an inadequate support system and the absence of a detailed program for pillar recovery are shown to be the most important causes of the Domino failure in this mine.展开更多
The failure criterion of rocks is a critical factor involved in reliability design and stability analysis of geotechnical engineering.In order to accurately evaluate the triaxial compressive strength of rocks under di...The failure criterion of rocks is a critical factor involved in reliability design and stability analysis of geotechnical engineering.In order to accurately evaluate the triaxial compressive strength of rocks under different confining pressures,a nonlinear empirical strength criterion based on Mohr-Coulomb criterion was proposed in this paper.Through the analysis of triaxial test strength of 11 types of rock materials,the feasibility and validity of proposed criterion was discussed.For a further verification,six typical strength criteria were selected,and the prediction results of each criterion and test results were statistically analyzed.The comparative comparison results show that the prediction results obtained by applying this new criterion to 97 conventional triaxial compression tests of 11 different rock materials are highly consistent with the experimental data.Statistical analysis was executed to assess the application of the new criterion and other classical criteria in predicting the failure behavior of rock.This proposed empirical criterion provides a new reference and method for the determination of triaxial compressive strength of rock materials.展开更多
A novel satellite fault diagnosis scheme is presented based on the predictive filter and empirical mode composition（EMD）.First,the predictive filter is utilized to obtain the fault estimation,which is corrupted by n...A novel satellite fault diagnosis scheme is presented based on the predictive filter and empirical mode composition（EMD）.First,the predictive filter is utilized to obtain the fault estimation,which is corrupted by noise.Then the EMD method is introduced to decompose the fault estimation into a finite number of intrinsic mode functions and extract the trend of faults for fault diagnosis.The proposed scheme has the ability of diagnosing both abrupt and incipient faults of the actuator in a satellite attitude control subsystem.A mathematical simulation is given to illustrate the effectiveness of the proposed scheme.展开更多
Underwater acoustic signal processing is one of the research hotspots in underwater acoustics.Noise reduction of underwater acoustic signals is the key to underwater acoustic signal processing.Owing to the complexity ...Underwater acoustic signal processing is one of the research hotspots in underwater acoustics.Noise reduction of underwater acoustic signals is the key to underwater acoustic signal processing.Owing to the complexity of marine environment and the particularity of underwater acoustic channel,noise reduction of underwater acoustic signals has always been a difficult challenge in the field of underwater acoustic signal processing.In order to solve the dilemma,we proposed a novel noise reduction technique for underwater acoustic signals based on complete ensemble empirical mode decomposition with adaptive noise(CEEMDAN),minimum mean square variance criterion(MMSVC) and least mean square adaptive filter(LMSAF).This noise reduction technique,named CEEMDAN-MMSVC-LMSAF,has three main advantages:(i) as an improved algorithm of empirical mode decomposition(EMD) and ensemble EMD(EEMD),CEEMDAN can better suppress mode mixing,and can avoid selecting the number of decomposition in variational mode decomposition(VMD);(ii) MMSVC can identify noisy intrinsic mode function(IMF),and can avoid selecting thresholds of different permutation entropies;(iii) for noise reduction of noisy IMFs,LMSAF overcomes the selection of deco mposition number and basis function for wavelet noise reduction.Firstly,CEEMDAN decomposes the original signal into IMFs,which can be divided into noisy IMFs and real IMFs.Then,MMSVC and LMSAF are used to detect identify noisy IMFs and remove noise components from noisy IMFs.Finally,both denoised noisy IMFs and real IMFs are reconstructed and the final denoised signal is obtained.Compared with other noise reduction techniques,the validity of CEEMDAN-MMSVC-LMSAF can be proved by the analysis of simulation signals and real underwater acoustic signals,which has the better noise reduction effect and has practical application value.CEEMDAN-MMSVC-LMSAF also provides a reliable basis for the detection,feature extraction,classification and recognition of underwater acoustic signals.展开更多
To improve the measurement performance, a method for diagnosing the state of vortex flowmeter under various flow conditions was presented. The raw sensor signal of the vortex flowmeter was adaptively decomposed into i...To improve the measurement performance, a method for diagnosing the state of vortex flowmeter under various flow conditions was presented. The raw sensor signal of the vortex flowmeter was adaptively decomposed into intrinsic mode functions using the empirical mode decomposition approach. Based on the empirical mode decomposition results, the energy of each intrinsic mode function was extracted, and the vortex energy ratio was proposed to analyze how the perturbation in the flow affected the measurement performance of the vortex flowmeter. The relationship between the vortex energy ratio of the signal and the flow condition was established. The results show that the vortex energy ratio is sensitive to the flow condition and ideal for the characterization of the vortex flowmeter signal. Moreover, the vortex energy ratio under normal flow condition is greater than 80%, which can be adopted as an indicator to diagnose the state of a vortex flowmeter.展开更多
A nonlinear data analysis algorithm, namely empirical data decomposition （EDD） is proposed, which can perform adaptive analysis of observed data. Analysis filter, which is not a linear constant coefficient filter, i...A nonlinear data analysis algorithm, namely empirical data decomposition （EDD） is proposed, which can perform adaptive analysis of observed data. Analysis filter, which is not a linear constant coefficient filter, is automatically determined by observed data, and is able to implement multi-resolution analysis as wavelet transform. The algorithm is suitable for analyzing non-stationary data and can effectively wipe off the relevance of observed data. Then through discussing the applications of EDD in image compression, the paper presents a 2-dimension data decomposition framework and makes some modifications of contexts used by Embedded Block Coding with Optimized Truncation （EBCOT） . Simulation results show that EDD is more suitable for non-stationary image data compression.展开更多
In order to eliminate noise interference of metal magnetic memory signal in early diagnosis of stress concentration zones and metal defects, the empirical mode decomposition method combined with the magnetic field gra...In order to eliminate noise interference of metal magnetic memory signal in early diagnosis of stress concentration zones and metal defects, the empirical mode decomposition method combined with the magnetic field gradient characteristic was proposed. A compressive force periodically acting upon a casing pipe led to appreciable deformation, and magnetic signals were measured by a magnetic indicator TSC-1M-4. The raw magnetic memory signal was first decomposed into different intrinsic mode functions and a residue, and the magnetic field gradient distribution of the subsequent reconstructed signal was obtained. The experimental results show that the gradient around 350 mm represents the maximum value ignoring the marginal effect, and there is a good correlation between the real maximum field gradient and the stress concentration zone. The wavelet transform associated with envelop analysis also exhibits this gradient characteristic, indicating that the proposed method is effective for early identifying critical zones.展开更多
Before-after study with the empirical Bayes(EB)method is the state-of-the-art approach for estimating crash modification factors(CMFs).The EB method not only addresses the regression-to-the-mean bias,but also improves...Before-after study with the empirical Bayes(EB)method is the state-of-the-art approach for estimating crash modification factors(CMFs).The EB method not only addresses the regression-to-the-mean bias,but also improves accuracy.However,the performance of the CMFs derived from the EB method has never been fully investigated.This study aims to examine the accuracy of CMFs estimated with the EB method.Artificial realistic data(ARD)and real crash data are used to evaluate the CMFs.The results indicate that:1)The CMFs derived from the EB before-after method are nearly the same as the true values.2)The estimated CMF standard errors do not reflect the true values.The estimation remains at the same level regardless of the pre-assumed CMF standard error.The EB before-after study is not sensitive to the variation of CMF among sites.3)The analyses with real-world traffic and crash data with a dummy treatment indicate that the EB method tends to underestimate the standard error of the CMF.Safety researchers should recognize that the CMF variance may be biased when evaluating safety effectiveness by the EB method.It is necessary to revisit the algorithm for estimating CMF variance with the EB method.展开更多
In order to improve measurement accuracy of moving target signals, an automatic target recognition model of moving target signals was established based on empirical mode decomposition(EMD) and support vector machine(S...In order to improve measurement accuracy of moving target signals, an automatic target recognition model of moving target signals was established based on empirical mode decomposition(EMD) and support vector machine(SVM). Automatic target recognition process on the nonlinear and non-stationary of Doppler signals of military target by using automatic target recognition model can be expressed as follows. Firstly, the nonlinearity and non-stationary of Doppler signals were decomposed into a set of intrinsic mode functions(IMFs) using EMD. After the Hilbert transform of IMF, the energy ratio of each IMF to the total IMFs can be extracted as the features of military target. Then, the SVM was trained through using the energy ratio to classify the military targets, and genetic algorithm(GA) was used to optimize SVM parameters in the solution space. The experimental results show that this algorithm can achieve the recognition accuracies of 86.15%, 87.93%, and 82.28% for tank, vehicle and soldier, respectively.展开更多
A novel and efficient method for decomposing a signal into a set of intrinsic mode functions （IMFs） and a trend is proposed. Unlike the original empirical mode decomposition （EMD）, which uses spline fits to extrac...A novel and efficient method for decomposing a signal into a set of intrinsic mode functions （IMFs） and a trend is proposed. Unlike the original empirical mode decomposition （EMD）, which uses spline fits to extract variations from the signal by separating the local mean from the fluctuations in the decomposing process, this new method being proposed takes advantage of the theory of variable finite impulse response （FIR） filtering where filter coefficients and breakpoint frequencies can be adjusted to track any peak-to-peak time scale changes. The IMFs are results of a multiple variable frequency response FIR filtering when signals pass through the filters. Numerical examples validate that in contrast with the original EMD, the proposed method can fine-tune the frequency resolution and suppress the aliasing effectively.展开更多
The prediction equations formulated in the existing prediction methods toy using the empirical orthogonal function are generally based upon field resolution according to the statistical relation among the predictands....The prediction equations formulated in the existing prediction methods toy using the empirical orthogonal function are generally based upon field resolution according to the statistical relation among the predictands. The influence of external factors is seldom to be considered. The present paper attempts to introduce the influence factors into the empirical orthogonal prediction method. There are five different approaches to be proposed for this purpose, what the field prediction method with optimum factors is studied with emphasis. In this method we consider not only the internal correlation among the predictands but also the influence of external factors, and the optimal prediction equation which is suitable for predicting both values and grades that may he formulated by the selected optimum factors from the combinational factors.The conception of weighting correlation coefficient is suggested here. The obvious difference between it and other correlation coefficients is that the former has the field charactor. Several practical examples corresponding to the previous mentioned prediction methods are also presented in this paper.展开更多
How to define the value of the Right in Additional Al location of Stocks (RAAS) acts an important role in stock markets whether or not the shareholders execute the right. Moreover, the valuation defining of RAAS an d ...How to define the value of the Right in Additional Al location of Stocks (RAAS) acts an important role in stock markets whether or not the shareholders execute the right. Moreover, the valuation defining of RAAS an d the exercise price (K) are mutual cause and effect. Based on some literatures on this subject, this paper presents a model valuing the RAAS per-share. With t he opening information in ShenZheng Stock Markets, we make a simulation on the R AAS’s value of shenwuye, which is a shareholding corporation appearing in the ma rket. At last, we have a discussion on the simulation method.展开更多
The special columnar jointed structure endows rocks with significant anisotropy,accurately grasping the strength and deformation properties of a columnar jointed rock mass(CJRM)under complex geological conditions is c...The special columnar jointed structure endows rocks with significant anisotropy,accurately grasping the strength and deformation properties of a columnar jointed rock mass(CJRM)under complex geological conditions is crucial for related engineering safety.Combined with the irregular jointed networks observed in the field,artificial irregular CJRM(ICJRM)samples with various inclination angles were prepared for triaxial tests.The results showed that the increase in confining pressure can enhance the ability of the ICJRM to resist deformation and failure,and reduce the deformation and strength anisotropic degrees.Considering the field stress situation,the engineering parts with an inclination angle of 30°−45°need to be taken seriously.Four typical failure modes were identified,and the sample with an inclination angle of 15°showed the same failure behavior as the field CJRM.Traditional and improved joint factor methods were used to establish empirical relationships for predicting the strength and deformation of CJRM under triaxial stress.Since the improved joint factor method can reflect the unique structure of CJRM,the predictive ability of the empirical relationship based on the improved method is better than that based on the traditional joint factor method.展开更多
Most of the existing studies on tunnel blast wave are based on spherical or grouped charges, however,conventional weapons are mostly cylindrical rather than spherical. In order to analyze the impact of cylindrical cha...Most of the existing studies on tunnel blast wave are based on spherical or grouped charges, however,conventional weapons are mostly cylindrical rather than spherical. In order to analyze the impact of cylindrical charges on the tunnel blast wave loads and to develop a quantitative calculation method, this study carried out experimental and numerical research. Initially, external explosion experiments were conducted using both 35 kg spherical charges and cylindrical charges with aspect ratio of 4.8 at two different distances from the tunnel entrance. Comparative analysis of the blast wave parameters in the tunnel revealed that the explosive equivalent of the cylindrical charges was significantly higher than that of the spherical charges. To address this, an equivalent coefficient κ based on the spherical charges was proposed for the cylindrical charges. Subsequently, numerical simulations were conducted for the experimental conditions, and the numerical simulation results match the experiments well. Through numerical calculations, the reliability of the equivalent coefficient κ under the experimental conditions was verified, and comparison analysis indicated that the explosion energy of cylindrical charges spreads more radially, resulting in more explosion energy entering the tunnel, which is the fundamental reason for the increase in tunnel blast wave loads. Additionally, analyzing the explosion energy ratio entering the tunnel is an effective method for calculating the equivalent coefficient κ. Finally, through more than one hundred sets of numerical calculation results, the impact of the proportional distance λ and the ratio of charge mass to the tunnel cross-section dimension φ on the equivalence coefficients κ was investigated. An empirical formula for the equivalence coefficient κ was derived through fitting, and the accuracy of the formula was validated through literature experimental results. The research findings of this paper will provide valuable guidance for the calculation of blast wave loads in tunnel.展开更多
The spin-exchange relaxation-free atomic gyroscope,with its exceptionally high theoretical precision,demonstrates immense potential to become the next-generation strategic-grade gyroscope.However,due to technological ...The spin-exchange relaxation-free atomic gyroscope,with its exceptionally high theoretical precision,demonstrates immense potential to become the next-generation strategic-grade gyroscope.However,due to technological noise,there is still a significant gap between its actual precision and theoretical precision.This study identifies the key factor limiting the precision of the SERF gyroscope as coupling noise.By optimizing the detection loop structure,a distinction between the dual-axis signals'response to optical and magnetic fields was achieved-where the optical errors responded similarly,while the response to magnetic noise was opposite.Based on the differences in the optical-magnetic response of the dual-axis signals,empirical mode decomposition was used to decompose the dual-axis gyroscope signals into multiple intrinsic mode functions,and Allan deviation analysis was applied to analyze the noise characteristics of the intrinsic mode functions over various periods.This study successfully reveals that optical errors caused by thermal-optical coupling and long-period magnetic noise induced by thermal-magnetic coupling are the dominant factors limiting the long-term stability of the SERF gyroscope.Based on these analyses,the study concludes that to achieve strategic-grade precision for the SERF gyroscope,it is essential to effectively address the noise issues caused by multi-physical field couplings.展开更多
Predictions of extreme near-field blast wave for cylindrical charge is crucial for designing sympathetic detonation protection structures,yet the quantitative analysis of detonation products and shock wave field are s...Predictions of extreme near-field blast wave for cylindrical charge is crucial for designing sympathetic detonation protection structures,yet the quantitative analysis of detonation products and shock wave field are still insufficient.The present work conducted experiments and numerical simulations of nearfield explosion for kilogram scale cylindrical charge,and investigated the propagation and spatial distribution characteristics of incident and reflected blast waves.The results show that near-field reflected overpressure exhibits multi-peak structures,which are primarily governed by reflections of detonation products and shock wave.The reflected peak overpressure dominated by detonation products shows higher sensitivity to scaled distance.Meanwhile,the Rayleigh-Taylor instability(RTI)effect induces the evolutions of detonation products and shock wave interface from smooth to random microjets,increasing dispersion of secondary re flected peak overpressure.In free-field explosion,the incident peak overpressure exhibits a dual-peak structure,governed by the shock wave front and detonation products flowing past the gauge points.The incident peak overpressure dominated by detonation products is sensitive to orientations due to the charge structures.As the aspect ratio of charge increases from 0.6 to 8,the dominant radial azimuth angle region expands from 60°-90°to 30°-90°.An empirical model was developed to predict the spatial distributions of incident peak loads at arbitrary orientations for cylindrical charge with 0.6≤L/D≤8.0 and 0.06 m·kg^(-1/3)展开更多
基金Supported by the National Natural Science Foundation of China(12061017,12361055)the Research Fund of Guangxi Key Lab of Multi-source Information Mining&Security(22-A-01-01)。
文摘Existing blockwise empirical likelihood(BEL)method blocks the observations or their analogues,which is proven useful under some dependent data settings.In this paper,we introduce a new BEL(NBEL)method by blocking the scoring functions under high dimensional cases.We study the construction of confidence regions for the parameters in spatial autoregressive models with spatial autoregressive disturbances(SARAR models)with high dimension of parameters by using the NBEL method.It is shown that the NBEL ratio statistics are asymptoticallyχ^(2)-type distributed,which are used to obtain the NBEL based confidence regions for the parameters in SARAR models.A simulation study is conducted to compare the performances of the NBEL and the usual EL methods.
基金the supported by National Natural Science Foundation of China(No.61871318 and 11574250)Scientific Research Plan Projects of Shaanxi Education Department(No.19JK0568).
文摘Feature extraction is an important part of signal processing,which is significant for signal detection,classification,and recognition.The nonlinear dynamic analysis method can extract the nonlinear characteristics of signals and is widely used in different fields.Reverse dispersion entropy(RDE)proposed by us recently,as a nonlinear dynamic analysis method,has the advantages of fast computing speed and strong anti-noise ability,which is more suitable for measuring the complexity of signal than traditional permutation entropy(PE)and dispersion entropy(DE).Empirical wavelet transform(EWT),based on the theory of wavelet analysis,can decompose a complex non-stationary signal into a number of empirical wavelet functions(EWFs)with compact support set spectrum,which has better decomposition performance than empirical mode decomposition(EMD)and its improved algorithms.Considering the advantages of RDE and EWT,on the one hand,we introduce EWT into the field of underwater acoustic signal processing and fault diagnosis to improve the signal decomposition accuracy;on the other hand,we use RDE as the features of EWFs to improve the signal separability and stability.Finally,we propose a novel signal feature extraction technology based on EWT and RDE in this paper.Experimental results show that the proposed feature extraction technology can effectively extract the complexity features of actual signals.Moreover,it also has higher distinguishing ability for different types of signals than five latest feature extraction technologies.
文摘Fetr6 is an underground mine using the stope-and-pillar mining method. As there was some evidence regarding pillar failure in this mine, improving works such as roof support and replacing existing pillars with concrete pillars (CP) were carried out. During the construction of the second CP, in the space between the remaining pillars, one of the pillars failed leading to the progressive failure of other pillars until 4 000 m 2 of mine had collapsed within a few minutes. In this work, this phenomenon is described by applying both numerical and empirical methods and the respective results are compared. The results of numerical modelling are found to be closer to the actual condition than those of the empirical method. Also, a width-to-height (W/H) ratio less than 1, an inadequate support system and the absence of a detailed program for pillar recovery are shown to be the most important causes of the Domino failure in this mine.
基金Project(51774322)supported by the National Natural Science Foundation of ChinaProject(2018JJ2500)supported by Natural Science Foundation of Hunan Province,China+1 种基金Project(2020JGB135)supported by Degree and Postgraduate Education Reform Project of Central South University,ChinaProject(2018zzts209)supported by the Fundamental Research Funds for the Central Universities,China。
文摘The failure criterion of rocks is a critical factor involved in reliability design and stability analysis of geotechnical engineering.In order to accurately evaluate the triaxial compressive strength of rocks under different confining pressures,a nonlinear empirical strength criterion based on Mohr-Coulomb criterion was proposed in this paper.Through the analysis of triaxial test strength of 11 types of rock materials,the feasibility and validity of proposed criterion was discussed.For a further verification,six typical strength criteria were selected,and the prediction results of each criterion and test results were statistically analyzed.The comparative comparison results show that the prediction results obtained by applying this new criterion to 97 conventional triaxial compression tests of 11 different rock materials are highly consistent with the experimental data.Statistical analysis was executed to assess the application of the new criterion and other classical criteria in predicting the failure behavior of rock.This proposed empirical criterion provides a new reference and method for the determination of triaxial compressive strength of rock materials.
基金supported by the National Natural Science Foundation of China (60874054)
文摘A novel satellite fault diagnosis scheme is presented based on the predictive filter and empirical mode composition（EMD）.First,the predictive filter is utilized to obtain the fault estimation,which is corrupted by noise.Then the EMD method is introduced to decompose the fault estimation into a finite number of intrinsic mode functions and extract the trend of faults for fault diagnosis.The proposed scheme has the ability of diagnosing both abrupt and incipient faults of the actuator in a satellite attitude control subsystem.A mathematical simulation is given to illustrate the effectiveness of the proposed scheme.
基金The authors gratefully acknowledge the support of the National Natural Science Foundation of China(No.11574250).
文摘Underwater acoustic signal processing is one of the research hotspots in underwater acoustics.Noise reduction of underwater acoustic signals is the key to underwater acoustic signal processing.Owing to the complexity of marine environment and the particularity of underwater acoustic channel,noise reduction of underwater acoustic signals has always been a difficult challenge in the field of underwater acoustic signal processing.In order to solve the dilemma,we proposed a novel noise reduction technique for underwater acoustic signals based on complete ensemble empirical mode decomposition with adaptive noise(CEEMDAN),minimum mean square variance criterion(MMSVC) and least mean square adaptive filter(LMSAF).This noise reduction technique,named CEEMDAN-MMSVC-LMSAF,has three main advantages:(i) as an improved algorithm of empirical mode decomposition(EMD) and ensemble EMD(EEMD),CEEMDAN can better suppress mode mixing,and can avoid selecting the number of decomposition in variational mode decomposition(VMD);(ii) MMSVC can identify noisy intrinsic mode function(IMF),and can avoid selecting thresholds of different permutation entropies;(iii) for noise reduction of noisy IMFs,LMSAF overcomes the selection of deco mposition number and basis function for wavelet noise reduction.Firstly,CEEMDAN decomposes the original signal into IMFs,which can be divided into noisy IMFs and real IMFs.Then,MMSVC and LMSAF are used to detect identify noisy IMFs and remove noise components from noisy IMFs.Finally,both denoised noisy IMFs and real IMFs are reconstructed and the final denoised signal is obtained.Compared with other noise reduction techniques,the validity of CEEMDAN-MMSVC-LMSAF can be proved by the analysis of simulation signals and real underwater acoustic signals,which has the better noise reduction effect and has practical application value.CEEMDAN-MMSVC-LMSAF also provides a reliable basis for the detection,feature extraction,classification and recognition of underwater acoustic signals.
基金Project(200801346) supported by the China Postdoctoral Science FoundationProject(2008RS4022) supported by the Hunan Postdoctoral Scientific ProgramProject(2008) supported by the Postdoctoral Science Foundation of Central South University
文摘To improve the measurement performance, a method for diagnosing the state of vortex flowmeter under various flow conditions was presented. The raw sensor signal of the vortex flowmeter was adaptively decomposed into intrinsic mode functions using the empirical mode decomposition approach. Based on the empirical mode decomposition results, the energy of each intrinsic mode function was extracted, and the vortex energy ratio was proposed to analyze how the perturbation in the flow affected the measurement performance of the vortex flowmeter. The relationship between the vortex energy ratio of the signal and the flow condition was established. The results show that the vortex energy ratio is sensitive to the flow condition and ideal for the characterization of the vortex flowmeter signal. Moreover, the vortex energy ratio under normal flow condition is greater than 80%, which can be adopted as an indicator to diagnose the state of a vortex flowmeter.
基金This project was supported by the National Natural Science Foundation of China (60532060)Hainan Education Bureau Research Project (Hjkj200602)Hainan Natural Science Foundation (80551).
文摘A nonlinear data analysis algorithm, namely empirical data decomposition （EDD） is proposed, which can perform adaptive analysis of observed data. Analysis filter, which is not a linear constant coefficient filter, is automatically determined by observed data, and is able to implement multi-resolution analysis as wavelet transform. The algorithm is suitable for analyzing non-stationary data and can effectively wipe off the relevance of observed data. Then through discussing the applications of EDD in image compression, the paper presents a 2-dimension data decomposition framework and makes some modifications of contexts used by Embedded Block Coding with Optimized Truncation （EBCOT） . Simulation results show that EDD is more suitable for non-stationary image data compression.
基金Project(10772061) supported by the National Natural Science Foundation of ChinaProject(A200907) supported by the Natural Science Foundation of Heilongjiang Province, China Project(20092322120001) supported by the PhD Programs Foundations of Ministry of Education of China
文摘In order to eliminate noise interference of metal magnetic memory signal in early diagnosis of stress concentration zones and metal defects, the empirical mode decomposition method combined with the magnetic field gradient characteristic was proposed. A compressive force periodically acting upon a casing pipe led to appreciable deformation, and magnetic signals were measured by a magnetic indicator TSC-1M-4. The raw magnetic memory signal was first decomposed into different intrinsic mode functions and a residue, and the magnetic field gradient distribution of the subsequent reconstructed signal was obtained. The experimental results show that the gradient around 350 mm represents the maximum value ignoring the marginal effect, and there is a good correlation between the real maximum field gradient and the stress concentration zone. The wavelet transform associated with envelop analysis also exhibits this gradient characteristic, indicating that the proposed method is effective for early identifying critical zones.
基金Project(51978082)supported by the National Natural Science Foundation of ChinaProject(19B022)supported by the Outstanding Youth Foundation of Hunan Education Department,ChinaProject(2019QJCZ056)supported by the Young Teacher Development Foundation of Changsha University of Science&Technology,China。
文摘Before-after study with the empirical Bayes(EB)method is the state-of-the-art approach for estimating crash modification factors(CMFs).The EB method not only addresses the regression-to-the-mean bias,but also improves accuracy.However,the performance of the CMFs derived from the EB method has never been fully investigated.This study aims to examine the accuracy of CMFs estimated with the EB method.Artificial realistic data(ARD)and real crash data are used to evaluate the CMFs.The results indicate that:1)The CMFs derived from the EB before-after method are nearly the same as the true values.2)The estimated CMF standard errors do not reflect the true values.The estimation remains at the same level regardless of the pre-assumed CMF standard error.The EB before-after study is not sensitive to the variation of CMF among sites.3)The analyses with real-world traffic and crash data with a dummy treatment indicate that the EB method tends to underestimate the standard error of the CMF.Safety researchers should recognize that the CMF variance may be biased when evaluating safety effectiveness by the EB method.It is necessary to revisit the algorithm for estimating CMF variance with the EB method.
基金Projects(61471370,61401479)supported by the National Natural Science Foundation of China
文摘In order to improve measurement accuracy of moving target signals, an automatic target recognition model of moving target signals was established based on empirical mode decomposition(EMD) and support vector machine(SVM). Automatic target recognition process on the nonlinear and non-stationary of Doppler signals of military target by using automatic target recognition model can be expressed as follows. Firstly, the nonlinearity and non-stationary of Doppler signals were decomposed into a set of intrinsic mode functions(IMFs) using EMD. After the Hilbert transform of IMF, the energy ratio of each IMF to the total IMFs can be extracted as the features of military target. Then, the SVM was trained through using the energy ratio to classify the military targets, and genetic algorithm(GA) was used to optimize SVM parameters in the solution space. The experimental results show that this algorithm can achieve the recognition accuracies of 86.15%, 87.93%, and 82.28% for tank, vehicle and soldier, respectively.
基金supported by the National Natural Science Foundation of China (60472021).
文摘A novel and efficient method for decomposing a signal into a set of intrinsic mode functions （IMFs） and a trend is proposed. Unlike the original empirical mode decomposition （EMD）, which uses spline fits to extract variations from the signal by separating the local mean from the fluctuations in the decomposing process, this new method being proposed takes advantage of the theory of variable finite impulse response （FIR） filtering where filter coefficients and breakpoint frequencies can be adjusted to track any peak-to-peak time scale changes. The IMFs are results of a multiple variable frequency response FIR filtering when signals pass through the filters. Numerical examples validate that in contrast with the original EMD, the proposed method can fine-tune the frequency resolution and suppress the aliasing effectively.
文摘The prediction equations formulated in the existing prediction methods toy using the empirical orthogonal function are generally based upon field resolution according to the statistical relation among the predictands. The influence of external factors is seldom to be considered. The present paper attempts to introduce the influence factors into the empirical orthogonal prediction method. There are five different approaches to be proposed for this purpose, what the field prediction method with optimum factors is studied with emphasis. In this method we consider not only the internal correlation among the predictands but also the influence of external factors, and the optimal prediction equation which is suitable for predicting both values and grades that may he formulated by the selected optimum factors from the combinational factors.The conception of weighting correlation coefficient is suggested here. The obvious difference between it and other correlation coefficients is that the former has the field charactor. Several practical examples corresponding to the previous mentioned prediction methods are also presented in this paper.
文摘How to define the value of the Right in Additional Al location of Stocks (RAAS) acts an important role in stock markets whether or not the shareholders execute the right. Moreover, the valuation defining of RAAS an d the exercise price (K) are mutual cause and effect. Based on some literatures on this subject, this paper presents a model valuing the RAAS per-share. With t he opening information in ShenZheng Stock Markets, we make a simulation on the R AAS’s value of shenwuye, which is a shareholding corporation appearing in the ma rket. At last, we have a discussion on the simulation method.
基金Projects(42307192,41831278)supported by the National Natural Science Foundation of ChinaProject(CKWV20231175/KY)supported by the CRSRI Open Research Program,China。
文摘The special columnar jointed structure endows rocks with significant anisotropy,accurately grasping the strength and deformation properties of a columnar jointed rock mass(CJRM)under complex geological conditions is crucial for related engineering safety.Combined with the irregular jointed networks observed in the field,artificial irregular CJRM(ICJRM)samples with various inclination angles were prepared for triaxial tests.The results showed that the increase in confining pressure can enhance the ability of the ICJRM to resist deformation and failure,and reduce the deformation and strength anisotropic degrees.Considering the field stress situation,the engineering parts with an inclination angle of 30°−45°need to be taken seriously.Four typical failure modes were identified,and the sample with an inclination angle of 15°showed the same failure behavior as the field CJRM.Traditional and improved joint factor methods were used to establish empirical relationships for predicting the strength and deformation of CJRM under triaxial stress.Since the improved joint factor method can reflect the unique structure of CJRM,the predictive ability of the empirical relationship based on the improved method is better than that based on the traditional joint factor method.
文摘Most of the existing studies on tunnel blast wave are based on spherical or grouped charges, however,conventional weapons are mostly cylindrical rather than spherical. In order to analyze the impact of cylindrical charges on the tunnel blast wave loads and to develop a quantitative calculation method, this study carried out experimental and numerical research. Initially, external explosion experiments were conducted using both 35 kg spherical charges and cylindrical charges with aspect ratio of 4.8 at two different distances from the tunnel entrance. Comparative analysis of the blast wave parameters in the tunnel revealed that the explosive equivalent of the cylindrical charges was significantly higher than that of the spherical charges. To address this, an equivalent coefficient κ based on the spherical charges was proposed for the cylindrical charges. Subsequently, numerical simulations were conducted for the experimental conditions, and the numerical simulation results match the experiments well. Through numerical calculations, the reliability of the equivalent coefficient κ under the experimental conditions was verified, and comparison analysis indicated that the explosion energy of cylindrical charges spreads more radially, resulting in more explosion energy entering the tunnel, which is the fundamental reason for the increase in tunnel blast wave loads. Additionally, analyzing the explosion energy ratio entering the tunnel is an effective method for calculating the equivalent coefficient κ. Finally, through more than one hundred sets of numerical calculation results, the impact of the proportional distance λ and the ratio of charge mass to the tunnel cross-section dimension φ on the equivalence coefficients κ was investigated. An empirical formula for the equivalence coefficient κ was derived through fitting, and the accuracy of the formula was validated through literature experimental results. The research findings of this paper will provide valuable guidance for the calculation of blast wave loads in tunnel.
基金supported by Hefei National Laboratory,Innovation Program for Quantum Science and Technology(2021ZD0300400/2021ZD0300402)the Beijing Natural Science Foundation(3252013)the China Postdoctoral Science Foundation(2024T171116).
文摘The spin-exchange relaxation-free atomic gyroscope,with its exceptionally high theoretical precision,demonstrates immense potential to become the next-generation strategic-grade gyroscope.However,due to technological noise,there is still a significant gap between its actual precision and theoretical precision.This study identifies the key factor limiting the precision of the SERF gyroscope as coupling noise.By optimizing the detection loop structure,a distinction between the dual-axis signals'response to optical and magnetic fields was achieved-where the optical errors responded similarly,while the response to magnetic noise was opposite.Based on the differences in the optical-magnetic response of the dual-axis signals,empirical mode decomposition was used to decompose the dual-axis gyroscope signals into multiple intrinsic mode functions,and Allan deviation analysis was applied to analyze the noise characteristics of the intrinsic mode functions over various periods.This study successfully reveals that optical errors caused by thermal-optical coupling and long-period magnetic noise induced by thermal-magnetic coupling are the dominant factors limiting the long-term stability of the SERF gyroscope.Based on these analyses,the study concludes that to achieve strategic-grade precision for the SERF gyroscope,it is essential to effectively address the noise issues caused by multi-physical field couplings.
基金supported by the National Natural Science Foundation of China(No.12172051,12172050,12141201,and 12221002)。
文摘Predictions of extreme near-field blast wave for cylindrical charge is crucial for designing sympathetic detonation protection structures,yet the quantitative analysis of detonation products and shock wave field are still insufficient.The present work conducted experiments and numerical simulations of nearfield explosion for kilogram scale cylindrical charge,and investigated the propagation and spatial distribution characteristics of incident and reflected blast waves.The results show that near-field reflected overpressure exhibits multi-peak structures,which are primarily governed by reflections of detonation products and shock wave.The reflected peak overpressure dominated by detonation products shows higher sensitivity to scaled distance.Meanwhile,the Rayleigh-Taylor instability(RTI)effect induces the evolutions of detonation products and shock wave interface from smooth to random microjets,increasing dispersion of secondary re flected peak overpressure.In free-field explosion,the incident peak overpressure exhibits a dual-peak structure,governed by the shock wave front and detonation products flowing past the gauge points.The incident peak overpressure dominated by detonation products is sensitive to orientations due to the charge structures.As the aspect ratio of charge increases from 0.6 to 8,the dominant radial azimuth angle region expands from 60°-90°to 30°-90°.An empirical model was developed to predict the spatial distributions of incident peak loads at arbitrary orientations for cylindrical charge with 0.6≤L/D≤8.0 and 0.06 m·kg^(-1/3)
