Using hyperspectral data collected in January and June 2022 from the Sha River,the concentrations of total nitrogen(TN)and total phosphorus(TP)were estimated using the differential method.The results indicate that the...Using hyperspectral data collected in January and June 2022 from the Sha River,the concentrations of total nitrogen(TN)and total phosphorus(TP)were estimated using the differential method.The results indicate that the optimal bands for estimation vary monthly due to temperature fluctuations.In the TN model,the power function model at 586 nm in January exhibited the strongest fit,yielding a fit coefficient(R2)of 0.95 and F-value of 164.57 at a significance level(p)of less than 0.01.Conversely,the exponential model at 477 nm in June provided the best fit,with R2=0.93 and F=80.95 at p<0.01.In the TP model,the exponential model fit of the differential values at 851 nm with TP in January produced the best results,with R2=0.78 and F=20.61.However,the overall fit in June outperformed that in January.Specifically,the quadratic and linear model fits of the differential values at 824 and 863 nm with TP achieved R2=0.96 and F-values of 34.42 and 203.34,respectively.展开更多
Source term identification is very important for the contaminant gas emission event. Thus, it is necessary to study the source parameter estimation method with high computation efficiency, high estimation accuracy and...Source term identification is very important for the contaminant gas emission event. Thus, it is necessary to study the source parameter estimation method with high computation efficiency, high estimation accuracy and reasonable confidence interval. Tikhonov regularization method is a potential good tool to identify the source parameters. However, it is invalid for nonlinear inverse problem like gas emission process. 2-step nonlinear and linear PSO （partial swarm optimization）-Tikhonov regularization method proposed previously have estimated the emission source parameters successfully. But there are still some problems in computation efficiency and confidence interval. Hence, a new 1-step nonlinear method combined Tikhonov regularizafion and PSO algorithm with nonlinear forward dispersion model was proposed. First, the method was tested with simulation and experiment cases. The test results showed that 1-step nonlinear hybrid method is able to estimate multiple source parameters with reasonable confidence interval. Then, the estimation performances of different methods were compared with different cases. The estimation values with 1-step nonlinear method were close to that with 2-step nonlinear and linear PSO-Tikhonov regularization method, 1-step nonlinear method even performs better than other two methods in some cases, especially for source strength and downwind distance estimation. Compared with 2-step nonlinear method, 1-step method has higher computation efficiency. On the other hand, the confidence intervals with the method proposed in this paper seem more reasonable than that with other two methods. Finally, single PSO algorithm was compared with 1-step nonlinear PSO-Tikhonov hybrid regularization method. The results showed that the skill scores of 1-step nonlinear hybrid method to estimate source parameters were close to that of single PSO method and even better in some cases. One more important property of 1-step nonlinear PSO-Tikhonov regularization method is its reasonable confidence interval, which is not obtained by single PSO algorithm. Therefore, 1-step nonlinear hybrid regularization method proposed in this paper is a potential good method to estimate contaminant gas emission source term.展开更多
The induced polarization relaxation time spectrum（RTS） reflects the distribution of rock pore size,which is a key factor in estimating the oil or water storage capacity of strata.However,as the data acquisition and ...The induced polarization relaxation time spectrum（RTS） reflects the distribution of rock pore size,which is a key factor in estimating the oil or water storage capacity of strata.However,as the data acquisition and transmission abilities of well logging instruments are much limited due to the underground environment,it is necessary to explore suitable sampling methods which can be used to obtain an accurate RST with less sampling data.This paper presents a uniform amplitude sampling method（UASM）,and compares it with the conventional uniform time sampling method（UTSM） and logarithm time sampling method（LTSM） in terms of the adaptability to different strata,RTS inversion accuracy,and stratum vertical resolution.Numerical simulation results show that the UASM can obtain high inversion accuracy of RTS with different kinds of pore size distribution formation,with high dynamic ranges of pore size,and with a small number of sampling points.The UASM,being able to adapt to the attenuation speed of polarization curve automatically,thus has the highest vertical resolution.The inversion results of rock samples also show that the UASM is superior to the UTSM and LTSM.展开更多
The transient heat flux was calculated using a model for inverse heat conduction problems based on temper- ature measurements. The unknown heat flux was taken as an optimization variable and solved by minimizing the d...The transient heat flux was calculated using a model for inverse heat conduction problems based on temper- ature measurements. The unknown heat flux was taken as an optimization variable and solved by minimizing the differences between the calculated temperatures and the measured ones. Several examples were given to show the ef- fectiveness and the accuracy of the inverse algorithm in estimating the transient heat flux to a slab surface. The re sults show that the inverse approach can be applied in the steel industry or in other areas where the target of investi- gation is inaccessible to direct measurements or difficult to be directly modeled.展开更多
The high-speed winding spindle employs a flexible support system incorporating rubber O-rings.By precisely configuring the structural parameters and the number of the O-rings,the spindle can stably surpass its critica...The high-speed winding spindle employs a flexible support system incorporating rubber O-rings.By precisely configuring the structural parameters and the number of the O-rings,the spindle can stably surpass its critical speed points and maintain operational stability across the entire working speed range.However,the support stiffness and damping of rubber O-rings exhibit significant nonlinear frequency dependence.Conventional experimental methods for deriving equivalent stiffness and damping,based on the principle of the forced non-resonance method,require fabricating custom setups for each O-ring specification and conducting vibration tests at varying frequencies,resulting in low efficiency and high costs.This study proposes a hybrid simulation-experimental method for dynamic parameter identification.Firstly,the frequency-dependent dynamic parameters of a specific O-ring support system are experimentally obtained.Subsequently,a corresponding parametric finite element model is established to simulate and solve the equivalent elastic modulus and equivalent stiffness-damping coefficient of this O-ring support system.Ultimately,after iterative simulation,the simulated and experimental results achieve a 99.7%agreement.The parametric finite element model developed herein can directly simulate and inversely estimate frequency-dependent dynamic parameters for O-rings of different specifications but identical elastic modulus.展开更多
In present paper, we obtain the inverse moment estimations of parameters of the Birnbaum-Saunders fatigue life distribution based on Type-Ⅱ bilateral censored samples and multiply Type-Ⅱ censored sample. In this pap...In present paper, we obtain the inverse moment estimations of parameters of the Birnbaum-Saunders fatigue life distribution based on Type-Ⅱ bilateral censored samples and multiply Type-Ⅱ censored sample. In this paper, we also get the interval estimations of the scale parameters.展开更多
Computer vision(CV)methods for measurement of structural vibration are less expensive,and their application is more straightforward than methods based on sensors that measure physical quantities at particular points o...Computer vision(CV)methods for measurement of structural vibration are less expensive,and their application is more straightforward than methods based on sensors that measure physical quantities at particular points of a structure.However,CV methods produce significantly more measurement errors.Thus,computer vision-based structural health monitoring(CVSHM)requires appropriate methods of damage assessment that are robust with respect to highly contaminated measurement data.In this paper a complete CVSHM framework is proposed,and three damage assessment methods are tested.The first is the augmented inverse estimate(AIE),proposed by Peng et al.in 2021.This method is designed to work with highly contaminated measurement data,but it fails with a large noise provided by CV measurement.The second method,as proposed in this paper,is based on the AIE,but it introduces a weighting matrix that enhances the conditioning of the problem.The third method,also proposed in this paper,introduces additional constraints in the optimization process;these constraints ensure that the stiffness of structural elements can only decrease.Both proposed methods perform better than the original AIE.The latter of the two proposed methods gives the best results,and it is robust with respect to the selected coefficients,as required by the algorithm.展开更多
Accurate release rate of the source is a crucial parameter for the refined design of the exhaust system in the industrial buildings. For the heated pollutant sources emitted by strong convection (SCHP source), it is d...Accurate release rate of the source is a crucial parameter for the refined design of the exhaust system in the industrial buildings. For the heated pollutant sources emitted by strong convection (SCHP source), it is difficult to accurately measure the source release rate with instruments due to inconsistent emission parameters tested at different locations near the source. In this paper, the three-dimensional CFD (Computational Fluid Dynamics) simulation was used to obtain the hourly concentration of pollutants and to study the applicability of four different regularization methods in the inverse estimation of the release rate of the SCHP source. The influence of the denoising filter and the strong convection of the SCHP source on the accuracy of the inverse estimated source release rate (IESR) was analyzed, and an exhaust flow rate calculation method based on the IESR is proposed. The results show that, compared with the zero-order Tikhonov regularization (ZOTR) and the LSQR methods, the second-order Tikhonov regularization (SOTR) and the truncated SVD (TSVD) methods are more suitable for the inverse estimation of the SCHP source. And it is found that, the introduction of the denoising filter can effectively eliminate the high-frequency or the high-amplitude deviations caused by the regularization method, compared with the SOTR method, the RMSE can be reduced by a maximum of 37.04 %. It is also concluded that the strong convection and the measurement error both have the negative impact on the accuracy of the IESR. Finally, compared to the calculation methods in the existing design manuals, the local exhaust system designed by the IESR method can efficiently capture the pollutants with a 46 % reduction in the exhaust flow rate. This study is useful for the accurately determining the SCHP source release rate and the optimal design of the exhaust system.展开更多
Removing internal multiples remains an important but challenging problem in seismic processing.The generalized Estimation of Primaries by Sparsity Inversion(EPSI)method minimizes data residuals between the calculated ...Removing internal multiples remains an important but challenging problem in seismic processing.The generalized Estimation of Primaries by Sparsity Inversion(EPSI)method minimizes data residuals between the calculated and observed wave-form using the sparse constraint of primary impulse responses to predict multiples and remove them directly,instead of using the conventional adaptive subtraction method.Even though the generalized EPSI method provides a good estimate of the primaries and multiples when they overlap,it is limited by intensive computational cost.In this paper,we introduce two strategies to improve computational efficiency.First,the interface-controlled strategy is introduced by only selecting high-amplitude primary responses related to the interfaces with strong impedance contrasts to estimate multiples.The computational time is approximately proportional to the number of involved reflectors and usually,most of the internal multiple energy in the data is only related to a few strong reflectors.Therefore the modified method can remove most of the internal multiples in fewer computations than in the generalized EPSI,which loops through all the interfaces.Next,an approximate formula for estimating primary impulse responses is proposed by neglecting a computationally intensive term which corresponds to the primary responses estimated from internal multiples.According to our analyses and experiments,in most cases,the contribution of this term is negligible because the internal multiples are weak.Therefore,the computational efficiency can be improved without significantly losing quality when estimating most primaries and multiples.In order to demonstrate this,multiple elimination of a two-layered simple data and the Pluto data are implemented.We find that the modified method can yield reliable results that require fewer computations.The improvements of the modified method may encourage the use of the generalized EPSI method in industry.展开更多
基金funded by the Gansu Provincial Science and Technology Plan Project,Innovation Base and Talent Project(Project Number:21JR1RA284).
文摘Using hyperspectral data collected in January and June 2022 from the Sha River,the concentrations of total nitrogen(TN)and total phosphorus(TP)were estimated using the differential method.The results indicate that the optimal bands for estimation vary monthly due to temperature fluctuations.In the TN model,the power function model at 586 nm in January exhibited the strongest fit,yielding a fit coefficient(R2)of 0.95 and F-value of 164.57 at a significance level(p)of less than 0.01.Conversely,the exponential model at 477 nm in June provided the best fit,with R2=0.93 and F=80.95 at p<0.01.In the TP model,the exponential model fit of the differential values at 851 nm with TP in January produced the best results,with R2=0.78 and F=20.61.However,the overall fit in June outperformed that in January.Specifically,the quadratic and linear model fits of the differential values at 824 and 863 nm with TP achieved R2=0.96 and F-values of 34.42 and 203.34,respectively.
基金Supported by the National Natural Science Foundation of China(21676216)China Postdoctoral Science Foundation(2015M582667)+2 种基金Natural Science Basic Research Plan in Shaanxi Province of China(2016JQ5079)Key Research Project of Shaanxi Province(2015ZDXM-GY-115)the Fundamental Research Funds for the Central Universities(xjj2017124)
文摘Source term identification is very important for the contaminant gas emission event. Thus, it is necessary to study the source parameter estimation method with high computation efficiency, high estimation accuracy and reasonable confidence interval. Tikhonov regularization method is a potential good tool to identify the source parameters. However, it is invalid for nonlinear inverse problem like gas emission process. 2-step nonlinear and linear PSO （partial swarm optimization）-Tikhonov regularization method proposed previously have estimated the emission source parameters successfully. But there are still some problems in computation efficiency and confidence interval. Hence, a new 1-step nonlinear method combined Tikhonov regularizafion and PSO algorithm with nonlinear forward dispersion model was proposed. First, the method was tested with simulation and experiment cases. The test results showed that 1-step nonlinear hybrid method is able to estimate multiple source parameters with reasonable confidence interval. Then, the estimation performances of different methods were compared with different cases. The estimation values with 1-step nonlinear method were close to that with 2-step nonlinear and linear PSO-Tikhonov regularization method, 1-step nonlinear method even performs better than other two methods in some cases, especially for source strength and downwind distance estimation. Compared with 2-step nonlinear method, 1-step method has higher computation efficiency. On the other hand, the confidence intervals with the method proposed in this paper seem more reasonable than that with other two methods. Finally, single PSO algorithm was compared with 1-step nonlinear PSO-Tikhonov hybrid regularization method. The results showed that the skill scores of 1-step nonlinear hybrid method to estimate source parameters were close to that of single PSO method and even better in some cases. One more important property of 1-step nonlinear PSO-Tikhonov regularization method is its reasonable confidence interval, which is not obtained by single PSO algorithm. Therefore, 1-step nonlinear hybrid regularization method proposed in this paper is a potential good method to estimate contaminant gas emission source term.
基金partially supported by a project from the National Natural Science Foundation of China (No.61401168)
文摘The induced polarization relaxation time spectrum（RTS） reflects the distribution of rock pore size,which is a key factor in estimating the oil or water storage capacity of strata.However,as the data acquisition and transmission abilities of well logging instruments are much limited due to the underground environment,it is necessary to explore suitable sampling methods which can be used to obtain an accurate RST with less sampling data.This paper presents a uniform amplitude sampling method（UASM）,and compares it with the conventional uniform time sampling method（UTSM） and logarithm time sampling method（LTSM） in terms of the adaptability to different strata,RTS inversion accuracy,and stratum vertical resolution.Numerical simulation results show that the UASM can obtain high inversion accuracy of RTS with different kinds of pore size distribution formation,with high dynamic ranges of pore size,and with a small number of sampling points.The UASM,being able to adapt to the attenuation speed of polarization curve automatically,thus has the highest vertical resolution.The inversion results of rock samples also show that the UASM is superior to the UTSM and LTSM.
基金Item Sponsored by National Natural Science Foundation of China(51206014,11172055)Fundamental Research Funds for Central Universities of China(DUT11LK09)
文摘The transient heat flux was calculated using a model for inverse heat conduction problems based on temper- ature measurements. The unknown heat flux was taken as an optimization variable and solved by minimizing the differences between the calculated temperatures and the measured ones. Several examples were given to show the ef- fectiveness and the accuracy of the inverse algorithm in estimating the transient heat flux to a slab surface. The re sults show that the inverse approach can be applied in the steel industry or in other areas where the target of investi- gation is inaccessible to direct measurements or difficult to be directly modeled.
基金National Key R&D Program of China(No.2017YFB1304000)Fundamental Research Funds for the Central Universities,China(No.2232023G-05-1)。
文摘The high-speed winding spindle employs a flexible support system incorporating rubber O-rings.By precisely configuring the structural parameters and the number of the O-rings,the spindle can stably surpass its critical speed points and maintain operational stability across the entire working speed range.However,the support stiffness and damping of rubber O-rings exhibit significant nonlinear frequency dependence.Conventional experimental methods for deriving equivalent stiffness and damping,based on the principle of the forced non-resonance method,require fabricating custom setups for each O-ring specification and conducting vibration tests at varying frequencies,resulting in low efficiency and high costs.This study proposes a hybrid simulation-experimental method for dynamic parameter identification.Firstly,the frequency-dependent dynamic parameters of a specific O-ring support system are experimentally obtained.Subsequently,a corresponding parametric finite element model is established to simulate and solve the equivalent elastic modulus and equivalent stiffness-damping coefficient of this O-ring support system.Ultimately,after iterative simulation,the simulated and experimental results achieve a 99.7%agreement.The parametric finite element model developed herein can directly simulate and inversely estimate frequency-dependent dynamic parameters for O-rings of different specifications but identical elastic modulus.
基金Supported by the NSF of China(69971016) Supported by the Shanghai Higher Learning Science Supported by the Technology Development Foundation(00JC14507)
文摘In present paper, we obtain the inverse moment estimations of parameters of the Birnbaum-Saunders fatigue life distribution based on Type-Ⅱ bilateral censored samples and multiply Type-Ⅱ censored sample. In this paper, we also get the interval estimations of the scale parameters.
基金National Science Centre,Poland Granted Through the Project 2020/39/B/ST8/02615。
文摘Computer vision(CV)methods for measurement of structural vibration are less expensive,and their application is more straightforward than methods based on sensors that measure physical quantities at particular points of a structure.However,CV methods produce significantly more measurement errors.Thus,computer vision-based structural health monitoring(CVSHM)requires appropriate methods of damage assessment that are robust with respect to highly contaminated measurement data.In this paper a complete CVSHM framework is proposed,and three damage assessment methods are tested.The first is the augmented inverse estimate(AIE),proposed by Peng et al.in 2021.This method is designed to work with highly contaminated measurement data,but it fails with a large noise provided by CV measurement.The second method,as proposed in this paper,is based on the AIE,but it introduces a weighting matrix that enhances the conditioning of the problem.The third method,also proposed in this paper,introduces additional constraints in the optimization process;these constraints ensure that the stiffness of structural elements can only decrease.Both proposed methods perform better than the original AIE.The latter of the two proposed methods gives the best results,and it is robust with respect to the selected coefficients,as required by the algorithm.
基金supported by the National Natural Science Foundation of China(Grant No.52178089)the Science and Technology Plan Project of Yulin(CXY-2021-139).
文摘Accurate release rate of the source is a crucial parameter for the refined design of the exhaust system in the industrial buildings. For the heated pollutant sources emitted by strong convection (SCHP source), it is difficult to accurately measure the source release rate with instruments due to inconsistent emission parameters tested at different locations near the source. In this paper, the three-dimensional CFD (Computational Fluid Dynamics) simulation was used to obtain the hourly concentration of pollutants and to study the applicability of four different regularization methods in the inverse estimation of the release rate of the SCHP source. The influence of the denoising filter and the strong convection of the SCHP source on the accuracy of the inverse estimated source release rate (IESR) was analyzed, and an exhaust flow rate calculation method based on the IESR is proposed. The results show that, compared with the zero-order Tikhonov regularization (ZOTR) and the LSQR methods, the second-order Tikhonov regularization (SOTR) and the truncated SVD (TSVD) methods are more suitable for the inverse estimation of the SCHP source. And it is found that, the introduction of the denoising filter can effectively eliminate the high-frequency or the high-amplitude deviations caused by the regularization method, compared with the SOTR method, the RMSE can be reduced by a maximum of 37.04 %. It is also concluded that the strong convection and the measurement error both have the negative impact on the accuracy of the IESR. Finally, compared to the calculation methods in the existing design manuals, the local exhaust system designed by the IESR method can efficiently capture the pollutants with a 46 % reduction in the exhaust flow rate. This study is useful for the accurately determining the SCHP source release rate and the optimal design of the exhaust system.
基金supported by the National Natural Science Foundation of China(Grant Nos.41704061,41730425)the National Major Project of China(Grant No.2017ZX05008-007)the Seismometry Talent Training Project of the China Earthquake Administration(Grant No.CEA-JC/QNCZ-18322).
文摘Removing internal multiples remains an important but challenging problem in seismic processing.The generalized Estimation of Primaries by Sparsity Inversion(EPSI)method minimizes data residuals between the calculated and observed wave-form using the sparse constraint of primary impulse responses to predict multiples and remove them directly,instead of using the conventional adaptive subtraction method.Even though the generalized EPSI method provides a good estimate of the primaries and multiples when they overlap,it is limited by intensive computational cost.In this paper,we introduce two strategies to improve computational efficiency.First,the interface-controlled strategy is introduced by only selecting high-amplitude primary responses related to the interfaces with strong impedance contrasts to estimate multiples.The computational time is approximately proportional to the number of involved reflectors and usually,most of the internal multiple energy in the data is only related to a few strong reflectors.Therefore the modified method can remove most of the internal multiples in fewer computations than in the generalized EPSI,which loops through all the interfaces.Next,an approximate formula for estimating primary impulse responses is proposed by neglecting a computationally intensive term which corresponds to the primary responses estimated from internal multiples.According to our analyses and experiments,in most cases,the contribution of this term is negligible because the internal multiples are weak.Therefore,the computational efficiency can be improved without significantly losing quality when estimating most primaries and multiples.In order to demonstrate this,multiple elimination of a two-layered simple data and the Pluto data are implemented.We find that the modified method can yield reliable results that require fewer computations.The improvements of the modified method may encourage the use of the generalized EPSI method in industry.
