We propose a novel method for seismic noise attenuation by applying nonstationary polynomial fitting （NPF）, which can estimate coherent components with amplitude variation along the event. The NPF with time-varying ...We propose a novel method for seismic noise attenuation by applying nonstationary polynomial fitting （NPF）, which can estimate coherent components with amplitude variation along the event. The NPF with time-varying coefficients can adaptively estimate the coherent components. The smoothness of the polynomial coefficients is controlled by shaping regularization. The signal is coherent along the offset axis in a common midpoint （CMP） gather after normal moveout （NMO）. We use NPF to estimate the effective signal and thereby to attenuate the random noise. For radial events-like noise such as ground roll, we first employ a radial trace （RT） transform to transform the data to the time-velocity domain. Then the NPF is used to estimate coherent noise in the RT domain. Finally, the coherent noise is adaptively subtracted from the noisy dataset. The proposed method can effectively estimate coherent noise with amplitude variations along the event and there is no need to propose that noise amplitude is constant. Results of synthetic and field data examples show that, compared with conventional methods such as stationary polynomial fitting and low cut filters, the proposed method can effectively suppress seismic noise and preserve the signals.展开更多
Robust Parameter Design(RPD) has been widely applied for improving quality and reliability of products.One of the key drawbacks of applying RPD using Taguchi method is that the stable factors may not be independent of...Robust Parameter Design(RPD) has been widely applied for improving quality and reliability of products.One of the key drawbacks of applying RPD using Taguchi method is that the stable factors may not be independent of the adjustment factors, resulting in unsatisfactory design.Moreover, the Taguchi method cannot guarantee global optimality since the levels set in the experiment are usually discrete to ensure orthogonal design.In this paper, robust solutions of the stable factors are obtained via a nonlinear model based on polynomial fitting;while the adjustment factors are obtained via interactions analysis so that they are independent of the stable factors.In particular, the values of the adjustment factors are determined by output offset compensation so as to achieve robustness of the design scheme.An example on the design of an aeronautical electrical apparatus is presented to illustrate the procedure.The results show that the proposed method can take full advantage of the nonlinearity in the response and achieve the desired outcome.展开更多
In order to</span></span><span><span><span style="font-family:""><span style="font-family:Verdana;"> reduce the influence of nonlinear </span><span...In order to</span></span><span><span><span style="font-family:""><span style="font-family:Verdana;"> reduce the influence of nonlinear </span><span style="font-family:Verdana;">characteristic</span><span style="font-family:Verdana;"> and temperature on the measuring accuracy of </span><span style="font-family:Verdana;">inclinometer</span><span style="font-family:Verdana;">, the application of </span><span style="font-family:Verdana;">polynomial</span><span style="font-family:Verdana;"> fitting principle to compensate </span><span style="font-family:Verdana;">the</span><span style="font-family:Verdana;"> measuring error of </span><span style="font-family:Verdana;">inclinometer</span><span style="font-family:Verdana;"> is studied. According to the analysis of the experimental data of inclinometer, a polynomial model of the nonlinear error and the measured value is constructed, and then the relation between the coefficient of the polynomial model and the temperature is obtained by fitting, and </span><span style="font-family:Verdana;">finally</span><span style="font-family:Verdana;"> the function of the measurement error of inclinometer on the measured inclination and temperature is obtained. The results show that this method is feasible and effective, which can not only reduce the influence of </span><span style="font-family:Verdana;">temperature,</span><span style="font-family:Verdana;"> but also correct its nonlinear error.展开更多
Segmentation of pulmonary nodules in chest radiographs is a particularly challenging task due to heavy noise and superposition of ribs,vessels,and other complicated anatomical structures in lung field. In this paper,a...Segmentation of pulmonary nodules in chest radiographs is a particularly challenging task due to heavy noise and superposition of ribs,vessels,and other complicated anatomical structures in lung field. In this paper,an adaptive order polynomial fitting based raycasting algorithm is proposed for pulmonary nodule segmentation in chest radiographs. Instead of detecting nodule edge points directly,the nodule intensity profiles are first fitted by using the polynomials with adaptively determined orders. Then,the edge positions are identified through analyzing the local minimum of the fitted curves.The performance of the proposed algorithm was evaluated over an image database with 148 nodule cases in chest radiographs that were collected from a variety of digital radiograph modalities. The preliminary results show the proposed algorithm can obtain a high rate of successful segmentations.展开更多
Wireless sensor network(WSN)positioning has a good effect on indoor positioning,so it has received extensive attention in the field of positioning.Non-line-of sight(NLOS)is a primary challenge in indoor complex enviro...Wireless sensor network(WSN)positioning has a good effect on indoor positioning,so it has received extensive attention in the field of positioning.Non-line-of sight(NLOS)is a primary challenge in indoor complex environment.In this paper,a robust localization algorithm based on Gaussian mixture model and fitting polynomial is proposed to solve the problem of NLOS error.Firstly,fitting polynomials are used to predict the measured values.The residuals of predicted and measured values are clustered by Gaussian mixture model(GMM).The LOS probability and NLOS probability are calculated according to the clustering centers.The measured values are filtered by Kalman filter(KF),variable parameter unscented Kalman filter(VPUKF)and variable parameter particle filter(VPPF)in turn.The distance value processed by KF and VPUKF and the distance value processed by KF,VPUKF and VPPF are combined according to probability.Finally,the maximum likelihood method is used to calculate the position coordinate estimation.Through simulation comparison,the proposed algorithm has better positioning accuracy than several comparison algorithms in this paper.And it shows strong robustness in strong NLOS environment.展开更多
Human motion prediction is a critical issue in human-robot collaboration(HRC)tasks.In order to reduce the local error caused by the limitation of the capture range and sampling frequency of the depth sensor,a hybrid h...Human motion prediction is a critical issue in human-robot collaboration(HRC)tasks.In order to reduce the local error caused by the limitation of the capture range and sampling frequency of the depth sensor,a hybrid human motion prediction algorithm,optimized sliding window polynomial fitting and recursive least squares(OSWPF-RLS)was proposed.The OSWPF-RLS algorithm uses the human body joint data obtained under the HRC task as input,and uses recursive least squares(RLS)to predict the human movement trajectories within the time window.Then,the optimized sliding window polynomial fitting(OSWPF)is used to calculate the multi-step prediction value,and the increment of multi-step prediction value was appropriately constrained.Experimental results show that compared with the existing benchmark algorithms,the OSWPF-RLS algorithm improved the multi-step prediction accuracy of human motion and enhanced the ability to respond to different human movements.展开更多
Raman spectrum, as a kind of scattering spectrum, has been widely used in many fields because it can characterize the special properties of materials. However, Raman signal is so weak that the noise distorts the real ...Raman spectrum, as a kind of scattering spectrum, has been widely used in many fields because it can characterize the special properties of materials. However, Raman signal is so weak that the noise distorts the real signals seriously. Polynomial fitting has been proved to be the most convenient and simplest method for baseline correction. It is hard to choose the order of polynomial because it may be so high that Runge phenomenon appears or so low that inaccuracy fitting happens. This paper proposes an improved approach for baseline correction, namely the piecewise polynomial fitting （PPF）. The spectral data are segmented, and then the proper orders are fitted, respectively. The iterative optimization method is used to eliminate discontinuities between piecewise points. The experimental results demonstrate that this approach improves the fitting accuracy.展开更多
Global warming has attracted much concern about the worldwide organization, civil society groups, researchers, and so forth because the worldwide surface temperature has been expanding. This investigation intends to a...Global warming has attracted much concern about the worldwide organization, civil society groups, researchers, and so forth because the worldwide surface temperature has been expanding. This investigation intends to assess and compare the ability of a combination of land cover indices to predict the future distribution of land surface temperatures in Freetown using the Polynomial model analysis. Landsat satellite images of 1988, 1998, 2000, 2010, and 2018 of the Freetown Metropolitan zone were utilized for analysis. The investigation had adopted two land covers indices, Modification of normalized difference water index and Urban Index (UI) (e.g., MNDWI and UI) and applied a multi regression equation for forecasting the future LST. The stimulation results propose that the development will be accompanied by surface temperature increases, especially in Freetown’s western urban area. The temperature prevailing in the west of the metropolitan area may increase in the city somewhere in the range </span></span><span><span><span>from</span></span></span><span><span><span> 1988 to 2018. Additionally, the results of the LST prediction show that the model is perfect. Our discoveries can be represented as a helpful device for policymakers and community awareness by giving a scientific basis for sustainable urban planning and management.展开更多
The change in interannual precipitation variability(P_(IAV)),especially the part driven by El Niño–Southern Oscillation over the Pacific,has sparked worldwide concern.However,it is plagued by substantial uncerta...The change in interannual precipitation variability(P_(IAV)),especially the part driven by El Niño–Southern Oscillation over the Pacific,has sparked worldwide concern.However,it is plagued by substantial uncertainty,such as model uncertainty,internal variability,and scenario uncertainty.Single-model initial-condition large ensembles(SMILEs)and a polynomial fitting method were suggested to separate these uncertainty sources.However,the applicability of a widely used polynomial fitting method in the uncertainty separation of P_(IAV)projection remains unknown.This study compares three sources of uncertainty estimated from five SMILEs and 28 models with one ensemble member in phase 6 of the Coupled Model Intercomparison Project(CMIP6).Results show that the internal uncertainty based on models with one ensemble member calculated using the polynomial fitting method is significantly underestimated compared to SMILEs.However,internal variability in CMIP6 as represented in the pre-industrial control run,aligns closely with SMILEs.At 1.5°C warming above the preindustrial level,internal variability dominates globally,masking the externally forced P_(IAV)signal.At 2.0°C warming,both internal and model uncertainties are significant over regions like Central Africa,the equatorial Indian Ocean,the Maritime Continent,and the Arctic,while internal variability still dominates elsewhere.In some regions,the forced signal becomes distinguishable from internal variability.This study reveals the limitations of the polynomial fitting method in separating P_(IAV)projection uncertainties and emphasizes the importance of SMILEs for accurately quantifying uncertainty sources.It also suggests that improving the intermodel agreement at warming levels of 1.5°C and 2.0°C will not substantially reduce uncertainty in most regions.展开更多
Land use sustainability is a pivotal concern in contemporary ecological protection efforts,necessitating a comprehensive understanding of the ramifications of changes in land use intensity(LUI)on ecosystem services(ES...Land use sustainability is a pivotal concern in contemporary ecological protection efforts,necessitating a comprehensive understanding of the ramifications of changes in land use intensity(LUI)on ecosystem services(ESs).Although ecological control zoning typically emphasizes ES outcomes,it tends to overlook the impacts of human activity intensity.This research focuses on the Yellow River Basin and integrates various data sources,encompassing land use,meteorological,soil,and socioeconomic data from 1980 to 2020.Using the InVEST model,quadratic polynomial fitting,and cluster analysis,this work evaluates the spatiotemporal changes and zoning characteristics of LUI and three ESs—water yield,soil conservation,and habitat quality—to explore the influence of LUI changes on ESs.The results indicate that from 1980 to 2020,LUI shows a sustained increase with considerable spatial heterogeneity,gradually intensifying from upstream to downstream areas.The interannual variability of ESs is minimal,with substantial local fluctuations but overall minor changes.LUI correlates positively with ESs.Based on regional ESs,the Yellow River Basin is categorized into four primary ecological function zones:ecological restoration,ecological pressure,ecological sustainability,and ecological conservation.Considering LUI characteristics,this categorization is further refined into six secondary function zones:ecological restoration,ecological transition,ecological overload,potential development,eco-economic carrying,and ecological conservation.This study provides a scientific foundation for land use planning and ecological conservation policy formulation within the watershed area.展开更多
For the linear crack skeleton of railway bridges with irregular strike,it is difficult to accurately express the crack contour feature by using a single smoothing fitting algorithm.In order to improve the measurement ...For the linear crack skeleton of railway bridges with irregular strike,it is difficult to accurately express the crack contour feature by using a single smoothing fitting algorithm.In order to improve the measurement accuracy,a polynomial curve fitting was proposed,which used the calibration point of crack contour as the boundary point,and then put them all together to produce a continuous contour curve to achieve the crack length measurement.The method was tested by measuring the linar cracks with different shapes.It is shown that this proposed algorithm can not only solve the jagged problem generated in the crack skeleton extraction process,but also improve the crack length measurement accuracy.The relative deviation is less than 0.15,and the measurement accuracy is over 98.05%,which provides a more effective means for the crack length measurement in railway bridges.展开更多
Comprehensive studies on CO_(2)breakthrough times and flooding effects are crucial for optimizing CO_(2)flooding strategies.This study utilized numerical simulations to investigate the effects of hydraulic fractures,p...Comprehensive studies on CO_(2)breakthrough times and flooding effects are crucial for optimizing CO_(2)flooding strategies.This study utilized numerical simulations to investigate the effects of hydraulic fractures,permeability,and CO_(2)injection rates on CO_(2)breakthrough times and cumulative oil production.Nonlinear relationships among the respective variables were established,with Sobol method analysis delineating the dominant control factors.The key findings indicate that although hydraulic fracturing shortens CO_(2)breakthrough time,it concurrently enhances cumulative oil production.The orientation of hydraulic fractures emerged as a pivotal factor influencing flooding effectiveness.Furthermore,lower permeability corresponds to lower initial oil production,while higher permeability corresponds to higher initial daily oil production.When reservoir permeability is 1 mD,oil production declines at 1000 days,and at 2 mD,it declines at 700 days.At a surface CO_(2)injection rate of 10,000 m^(3)/d,the daily oil production of a single well is approximately 7.5 m^(3),and this value remains relatively stable over time.The hierarchical order of influence on CO_(2)breakthrough and rapid rise times,from highest to lowest,is permeability,well spacing,CO_(2)injection rate,porosity,and hydraulic fracture conductivity.Similarly,the order of influence on cumulative oil production,from highest to lowest,is well spacing,porosity,permeability,CO_(2)injection rate,and hydraulic fracture conductivity.This paper analyzed the impact of geological and engineering parameters on CO_(2)flooding and oil production and provided insights to optimize CO_(2)injection strategies for enhanced oil recovery.展开更多
We propose a k-domain spline interpolation method with constrained polynomial fit based on spectral phase in swept-source optical coherence tomography(SS-OCT).A Mach-Zehnder interferometer(MZI)unit is connected to.the...We propose a k-domain spline interpolation method with constrained polynomial fit based on spectral phase in swept-source optical coherence tomography(SS-OCT).A Mach-Zehnder interferometer(MZI)unit is connected to.the swept-source of the SS-OCT system to generate calibration signal in sync with the fetching of interference spectra.The spectral phase of the calibration signal is extracted by Hilbert transformation.The fitted phase-time relationship is obtained by polynomial fitting with the constraint of passing through the central spectral phase.The fitting curve is then adopted for k-domain uniform interpolation based on evenly spaced phase.In comparison with conventional k-domain spline interpolation,the proposed method leads to improved axial resolution and peak response of the axial point spread function(PSF)of the SS-OCT system.Enhanced performance resulting from the proposed method is further verified by OCT imaging of a home-constructed microspheres-agar sample and a fresh lemon.Besides SS-OCT,the proposed method is believed to be applicable to spectral domain OCT as well.展开更多
High-vertical-resolution radiosonde wind data are highly valuable for describing the dynamics of the meso-and microscale atmosphere. However, the current algorithm used in China's L-band radar sounding system for ...High-vertical-resolution radiosonde wind data are highly valuable for describing the dynamics of the meso-and microscale atmosphere. However, the current algorithm used in China's L-band radar sounding system for calculating highvertical-resolution wind vectors excessively smooths the data, resulting in significant underestimation of the calculated kinetic energy of gravity waves compared to similar products from other countries, which greatly limits the effective utilization of the data. To address this issue, this study proposes a novel method to calculate high-vertical-resolution wind vectors that utilizes the elevation angle, azimuth angle, and slant range from L-band radar. In order to obtain wind data with a stable quality, a two-step automatic quality control procedure, including the RMSE-F(root-mean-square error F) test and elemental consistency test are first applied to the slant range data, to eliminate continuous erroneous data caused by unstable signals or radar malfunctions. Then, a wind calculation scheme based on a sliding second-order polynomial fitting is utilized to derive the high-vertical-resolution radiosonde wind vectors. The evaluation results demonstrate that the wind data obtained through the proposed method show a high level of consistency with the high-resolution wind data observed using the Vaisala Global Positioning System and the data observed by the new Beidou Navigation Sounding System. The calculation of the kinetic energy of gravity waves in the recalculated wind data also reaches a level comparable to the Vaisala observations.展开更多
In seismic data processing, random noise seriously affects the seismic data quality and subsequently the interpretation. This study aims to increase the signal-to-noise ratio by suppressing random noise and improve th...In seismic data processing, random noise seriously affects the seismic data quality and subsequently the interpretation. This study aims to increase the signal-to-noise ratio by suppressing random noise and improve the accuracy of seismic data interpretation without losing useful information. Hence, we propose a structure-oriented polynomial fitting filter. At the core of structure-oriented filtering is the characterization of the structural trend and the realization of nonstationary filtering. First, we analyze the relation of the frequency response between two-dimensional（2D） derivatives and the 2D Hilbert transform. Then, we derive the noniterative seismic local dip operator using the 2D Hilbert transform to obtain the structural trend. Second, we select polynomial fitting as the nonstationary filtering method and expand the application range of the nonstationary polynomial fitting. Finally, we apply variableamplitude polynomial fitting along the direction of the dip to improve the adaptive structureoriented filtering. Model and field seismic data show that the proposed method suppresses the seismic noise while protecting structural information.展开更多
In this paper, a new pre-alignment approach based on Four-Quadrant-Photo-Detector （FQPD） for IC mask is presented. The voltage outputs from FQPDs are the functions of alignment mark＇s position offsets with respect ...In this paper, a new pre-alignment approach based on Four-Quadrant-Photo-Detector （FQPD） for IC mask is presented. The voltage outputs from FQPDs are the functions of alignment mark＇s position offsets with respect to FQPDs. The functions are obtained with least squares error （LSE）-based polynomial fitting after the normalization of experimental data. As the acquired functions are not monotonic about their variables, the alignment mark＇s position offset cannot be given by direct inverse operation on the obtained functions. However, the piecewise polynomial fitting gives the inverse function, with which the alignment mark＇s position offset can be predicted according to the voltage outputs of FQPDs. On the basis of prediction, a pre-alignment control strategy is proposed. The feasibility and robustness of the pre-alignment approach is shown by experiments. Furthermore, the results demonstrate that the maximum error of mask＇s position offset in the X- and Y- directions is less than 15μm after coarse pre-alignment. Keywords： Four-Quadrant-Photo-Detector （FQPD）, pre-alignment, IC mask, polynomial fitting展开更多
North China is a key region for studying geophysical progress. In this study, ground-based and Gravity Recovery and Climate Experiment（GRACE） gravity data from 2009 to 2013 are used to calculate the gravity change r...North China is a key region for studying geophysical progress. In this study, ground-based and Gravity Recovery and Climate Experiment（GRACE） gravity data from 2009 to 2013 are used to calculate the gravity change rate（GCR） using the polynomial fitting method. In general, the study area was divided into the Shanxi rift, Jing-Jin-Ji（Beijing-Tianjin-Hebei Province）, and Bohai Bay Basin（BBB） regions. Results of the distribution of the GCR determined from ground-based gravimetry show that the GCR appears to be ＂negativepositive-negative＂ from west to east, which indicates that different geophysical mechanisms are involved in the tectonic activities of these regions. However, GRACE solutions are conducted over a larger spatial scale and are able to show a difference between southern and northern areas and a mass redistribution of land water storage.展开更多
The constitutive relationship is the basis for studying the material processing technology and controlling the quality of products.Data and models of the plastic flow behavior of materials are often required during th...The constitutive relationship is the basis for studying the material processing technology and controlling the quality of products.Data and models of the plastic flow behavior of materials are often required during the manufacturing process.Therefore,establishing constitutive models with high precision and generalization and enriching material database is of great significance for optimizing processing technology and product quality of the material.Based on the Gleeble thermal compression test results,the essential relationship of 25 steel between the flow stress and thermal–mechanical state variables,such as temperature,strain rate,and strain,is quantitatively discussed for the first time.Combined with the Zener–Hollomon parameter and considering the influence of strain compensation,the constitutive model of 25 steel is built by the hyperbolic-sine equation over the full strain range.In the modeling process,the influence of strain on material constants is characterized by polynomial fitting.The selection basis of polynomial order is discussed in-depth,and the inconsistency between calculation accuracy and fitting effect is clarified.Finally,the accuracy of the model is analyzed,and the generalization and applicability are discussed.It is proved that the developed model can accurately predict the flow behavior of materials in the full strain range.展开更多
Distributed source coding （DSC） is applied to interferential multispectral image compression owing to strong correlation among the image frames. Many DSC systems in the literature use feedback channel （FC） to cont...Distributed source coding （DSC） is applied to interferential multispectral image compression owing to strong correlation among the image frames. Many DSC systems in the literature use feedback channel （FC） to control rate at the decoder, which limits the application of DSC. Upon an analysis of the image data, a rate control approach is proposed to avoid FC. Low-complexity motion compensation is applied first to estimate side information at the encoder. Using a polynomial fitting method, a new mathematical model is then derived to estimate rate based on the correlation between the source and side information. The experimental results show that our estimated rate is a good approximation to the actual rate required by FC while incurring a little bit-rate overhead. Our compression scheme performs comparable with the FC based DSC system and outperforms JPEG2000 significantly.展开更多
A method of MIMO channel tracking based on Kalman filter and MMSE-DFE is proposed. The Kalman filter tracks the time-varying channel by using the MMSE-DFE decision and the MMSE-DFE conducts the next decision by using ...A method of MIMO channel tracking based on Kalman filter and MMSE-DFE is proposed. The Kalman filter tracks the time-varying channel by using the MMSE-DFE decision and the MMSE-DFE conducts the next decision by using the channel estimates produced by the Kalman filter. Polynomial fitting is used to bridge the gap between the channel estimates produced by the Kalman filter and those needed for the DFE decision. Computer simulation demonstrates that this method can track the MIMO time-varying channel effectively.展开更多
基金supported by the National Basic Research Program of China (973 program, grant 2007CB209606) the National High Technology Research and Development Program of China (863 program, grant 2006AA09A102-09)
文摘We propose a novel method for seismic noise attenuation by applying nonstationary polynomial fitting （NPF）, which can estimate coherent components with amplitude variation along the event. The NPF with time-varying coefficients can adaptively estimate the coherent components. The smoothness of the polynomial coefficients is controlled by shaping regularization. The signal is coherent along the offset axis in a common midpoint （CMP） gather after normal moveout （NMO）. We use NPF to estimate the effective signal and thereby to attenuate the random noise. For radial events-like noise such as ground roll, we first employ a radial trace （RT） transform to transform the data to the time-velocity domain. Then the NPF is used to estimate coherent noise in the RT domain. Finally, the coherent noise is adaptively subtracted from the noisy dataset. The proposed method can effectively estimate coherent noise with amplitude variations along the event and there is no need to propose that noise amplitude is constant. Results of synthetic and field data examples show that, compared with conventional methods such as stationary polynomial fitting and low cut filters, the proposed method can effectively suppress seismic noise and preserve the signals.
基金co-supported by the National Natural Science Foundation of China(Nos.51707044 and 61671172)the China Postdoctoral Science Foundation(No.2018M632377)。
文摘Robust Parameter Design(RPD) has been widely applied for improving quality and reliability of products.One of the key drawbacks of applying RPD using Taguchi method is that the stable factors may not be independent of the adjustment factors, resulting in unsatisfactory design.Moreover, the Taguchi method cannot guarantee global optimality since the levels set in the experiment are usually discrete to ensure orthogonal design.In this paper, robust solutions of the stable factors are obtained via a nonlinear model based on polynomial fitting;while the adjustment factors are obtained via interactions analysis so that they are independent of the stable factors.In particular, the values of the adjustment factors are determined by output offset compensation so as to achieve robustness of the design scheme.An example on the design of an aeronautical electrical apparatus is presented to illustrate the procedure.The results show that the proposed method can take full advantage of the nonlinearity in the response and achieve the desired outcome.
文摘In order to</span></span><span><span><span style="font-family:""><span style="font-family:Verdana;"> reduce the influence of nonlinear </span><span style="font-family:Verdana;">characteristic</span><span style="font-family:Verdana;"> and temperature on the measuring accuracy of </span><span style="font-family:Verdana;">inclinometer</span><span style="font-family:Verdana;">, the application of </span><span style="font-family:Verdana;">polynomial</span><span style="font-family:Verdana;"> fitting principle to compensate </span><span style="font-family:Verdana;">the</span><span style="font-family:Verdana;"> measuring error of </span><span style="font-family:Verdana;">inclinometer</span><span style="font-family:Verdana;"> is studied. According to the analysis of the experimental data of inclinometer, a polynomial model of the nonlinear error and the measured value is constructed, and then the relation between the coefficient of the polynomial model and the temperature is obtained by fitting, and </span><span style="font-family:Verdana;">finally</span><span style="font-family:Verdana;"> the function of the measurement error of inclinometer on the measured inclination and temperature is obtained. The results show that this method is feasible and effective, which can not only reduce the influence of </span><span style="font-family:Verdana;">temperature,</span><span style="font-family:Verdana;"> but also correct its nonlinear error.
基金Innovation Program of Shanghai Municipal Education Commission,China(No.13YZ136)
文摘Segmentation of pulmonary nodules in chest radiographs is a particularly challenging task due to heavy noise and superposition of ribs,vessels,and other complicated anatomical structures in lung field. In this paper,an adaptive order polynomial fitting based raycasting algorithm is proposed for pulmonary nodule segmentation in chest radiographs. Instead of detecting nodule edge points directly,the nodule intensity profiles are first fitted by using the polynomials with adaptively determined orders. Then,the edge positions are identified through analyzing the local minimum of the fitted curves.The performance of the proposed algorithm was evaluated over an image database with 148 nodule cases in chest radiographs that were collected from a variety of digital radiograph modalities. The preliminary results show the proposed algorithm can obtain a high rate of successful segmentations.
基金supported by the National Natural Science Foundation of China under Grant No.62273083 and No.61973069Natural Science Foundation of Hebei Province under Grant No.F2020501012。
文摘Wireless sensor network(WSN)positioning has a good effect on indoor positioning,so it has received extensive attention in the field of positioning.Non-line-of sight(NLOS)is a primary challenge in indoor complex environment.In this paper,a robust localization algorithm based on Gaussian mixture model and fitting polynomial is proposed to solve the problem of NLOS error.Firstly,fitting polynomials are used to predict the measured values.The residuals of predicted and measured values are clustered by Gaussian mixture model(GMM).The LOS probability and NLOS probability are calculated according to the clustering centers.The measured values are filtered by Kalman filter(KF),variable parameter unscented Kalman filter(VPUKF)and variable parameter particle filter(VPPF)in turn.The distance value processed by KF and VPUKF and the distance value processed by KF,VPUKF and VPPF are combined according to probability.Finally,the maximum likelihood method is used to calculate the position coordinate estimation.Through simulation comparison,the proposed algorithm has better positioning accuracy than several comparison algorithms in this paper.And it shows strong robustness in strong NLOS environment.
基金supported by the National Natural Science Foundation of China(61701270)the Young Doctor Cooperation Foundation of Qilu University of Technology(Shandong Academy of Sciences)(2017BSHZ008)。
文摘Human motion prediction is a critical issue in human-robot collaboration(HRC)tasks.In order to reduce the local error caused by the limitation of the capture range and sampling frequency of the depth sensor,a hybrid human motion prediction algorithm,optimized sliding window polynomial fitting and recursive least squares(OSWPF-RLS)was proposed.The OSWPF-RLS algorithm uses the human body joint data obtained under the HRC task as input,and uses recursive least squares(RLS)to predict the human movement trajectories within the time window.Then,the optimized sliding window polynomial fitting(OSWPF)is used to calculate the multi-step prediction value,and the increment of multi-step prediction value was appropriately constrained.Experimental results show that compared with the existing benchmark algorithms,the OSWPF-RLS algorithm improved the multi-step prediction accuracy of human motion and enhanced the ability to respond to different human movements.
文摘Raman spectrum, as a kind of scattering spectrum, has been widely used in many fields because it can characterize the special properties of materials. However, Raman signal is so weak that the noise distorts the real signals seriously. Polynomial fitting has been proved to be the most convenient and simplest method for baseline correction. It is hard to choose the order of polynomial because it may be so high that Runge phenomenon appears or so low that inaccuracy fitting happens. This paper proposes an improved approach for baseline correction, namely the piecewise polynomial fitting （PPF）. The spectral data are segmented, and then the proper orders are fitted, respectively. The iterative optimization method is used to eliminate discontinuities between piecewise points. The experimental results demonstrate that this approach improves the fitting accuracy.
文摘Global warming has attracted much concern about the worldwide organization, civil society groups, researchers, and so forth because the worldwide surface temperature has been expanding. This investigation intends to assess and compare the ability of a combination of land cover indices to predict the future distribution of land surface temperatures in Freetown using the Polynomial model analysis. Landsat satellite images of 1988, 1998, 2000, 2010, and 2018 of the Freetown Metropolitan zone were utilized for analysis. The investigation had adopted two land covers indices, Modification of normalized difference water index and Urban Index (UI) (e.g., MNDWI and UI) and applied a multi regression equation for forecasting the future LST. The stimulation results propose that the development will be accompanied by surface temperature increases, especially in Freetown’s western urban area. The temperature prevailing in the west of the metropolitan area may increase in the city somewhere in the range </span></span><span><span><span>from</span></span></span><span><span><span> 1988 to 2018. Additionally, the results of the LST prediction show that the model is perfect. Our discoveries can be represented as a helpful device for policymakers and community awareness by giving a scientific basis for sustainable urban planning and management.
基金funded by the National Natural Science Foundation of China(Grant No.42425504).
文摘The change in interannual precipitation variability(P_(IAV)),especially the part driven by El Niño–Southern Oscillation over the Pacific,has sparked worldwide concern.However,it is plagued by substantial uncertainty,such as model uncertainty,internal variability,and scenario uncertainty.Single-model initial-condition large ensembles(SMILEs)and a polynomial fitting method were suggested to separate these uncertainty sources.However,the applicability of a widely used polynomial fitting method in the uncertainty separation of P_(IAV)projection remains unknown.This study compares three sources of uncertainty estimated from five SMILEs and 28 models with one ensemble member in phase 6 of the Coupled Model Intercomparison Project(CMIP6).Results show that the internal uncertainty based on models with one ensemble member calculated using the polynomial fitting method is significantly underestimated compared to SMILEs.However,internal variability in CMIP6 as represented in the pre-industrial control run,aligns closely with SMILEs.At 1.5°C warming above the preindustrial level,internal variability dominates globally,masking the externally forced P_(IAV)signal.At 2.0°C warming,both internal and model uncertainties are significant over regions like Central Africa,the equatorial Indian Ocean,the Maritime Continent,and the Arctic,while internal variability still dominates elsewhere.In some regions,the forced signal becomes distinguishable from internal variability.This study reveals the limitations of the polynomial fitting method in separating P_(IAV)projection uncertainties and emphasizes the importance of SMILEs for accurately quantifying uncertainty sources.It also suggests that improving the intermodel agreement at warming levels of 1.5°C and 2.0°C will not substantially reduce uncertainty in most regions.
基金National Natural Science Foundation of China,No.42101258Natural Science Foundation of Shandong Province,No.ZR2024MD073+1 种基金The Humanities and Social Sciences Youth FoundationMinistry of Education,No.19YJCZH144。
文摘Land use sustainability is a pivotal concern in contemporary ecological protection efforts,necessitating a comprehensive understanding of the ramifications of changes in land use intensity(LUI)on ecosystem services(ESs).Although ecological control zoning typically emphasizes ES outcomes,it tends to overlook the impacts of human activity intensity.This research focuses on the Yellow River Basin and integrates various data sources,encompassing land use,meteorological,soil,and socioeconomic data from 1980 to 2020.Using the InVEST model,quadratic polynomial fitting,and cluster analysis,this work evaluates the spatiotemporal changes and zoning characteristics of LUI and three ESs—water yield,soil conservation,and habitat quality—to explore the influence of LUI changes on ESs.The results indicate that from 1980 to 2020,LUI shows a sustained increase with considerable spatial heterogeneity,gradually intensifying from upstream to downstream areas.The interannual variability of ESs is minimal,with substantial local fluctuations but overall minor changes.LUI correlates positively with ESs.Based on regional ESs,the Yellow River Basin is categorized into four primary ecological function zones:ecological restoration,ecological pressure,ecological sustainability,and ecological conservation.Considering LUI characteristics,this categorization is further refined into six secondary function zones:ecological restoration,ecological transition,ecological overload,potential development,eco-economic carrying,and ecological conservation.This study provides a scientific foundation for land use planning and ecological conservation policy formulation within the watershed area.
基金National Defense Pre-Research Fund Project(No.060601)Wanqiao Education Fund Project(No.06010023)。
文摘For the linear crack skeleton of railway bridges with irregular strike,it is difficult to accurately express the crack contour feature by using a single smoothing fitting algorithm.In order to improve the measurement accuracy,a polynomial curve fitting was proposed,which used the calibration point of crack contour as the boundary point,and then put them all together to produce a continuous contour curve to achieve the crack length measurement.The method was tested by measuring the linar cracks with different shapes.It is shown that this proposed algorithm can not only solve the jagged problem generated in the crack skeleton extraction process,but also improve the crack length measurement accuracy.The relative deviation is less than 0.15,and the measurement accuracy is over 98.05%,which provides a more effective means for the crack length measurement in railway bridges.
基金supported by the China Postdoctoral Science Foundation(No.2024M752803)the National Natural Science Foundation of China(No.52179112)+1 种基金the Open Fund of National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Southwest Petroleum University,China(No.PLN2023-02)the Open Fund of Key Laboratory of Deep Geothermal Resources,Ministry of Natural Resources of the People's Republic of China(No.KLDGR2024B01).
文摘Comprehensive studies on CO_(2)breakthrough times and flooding effects are crucial for optimizing CO_(2)flooding strategies.This study utilized numerical simulations to investigate the effects of hydraulic fractures,permeability,and CO_(2)injection rates on CO_(2)breakthrough times and cumulative oil production.Nonlinear relationships among the respective variables were established,with Sobol method analysis delineating the dominant control factors.The key findings indicate that although hydraulic fracturing shortens CO_(2)breakthrough time,it concurrently enhances cumulative oil production.The orientation of hydraulic fractures emerged as a pivotal factor influencing flooding effectiveness.Furthermore,lower permeability corresponds to lower initial oil production,while higher permeability corresponds to higher initial daily oil production.When reservoir permeability is 1 mD,oil production declines at 1000 days,and at 2 mD,it declines at 700 days.At a surface CO_(2)injection rate of 10,000 m^(3)/d,the daily oil production of a single well is approximately 7.5 m^(3),and this value remains relatively stable over time.The hierarchical order of influence on CO_(2)breakthrough and rapid rise times,from highest to lowest,is permeability,well spacing,CO_(2)injection rate,porosity,and hydraulic fracture conductivity.Similarly,the order of influence on cumulative oil production,from highest to lowest,is well spacing,porosity,permeability,CO_(2)injection rate,and hydraulic fracture conductivity.This paper analyzed the impact of geological and engineering parameters on CO_(2)flooding and oil production and provided insights to optimize CO_(2)injection strategies for enhanced oil recovery.
基金The authors acknowledge funding from National Key Research and Development Program of China(2017FA0700501)National Natural Science Foundation of China(62035011,11974310,31927801,61905214)+1 种基金Natural Science Foundation of Zhejiang Province(LR20F050001)Fundamental Research Funds for the Central Universities.
文摘We propose a k-domain spline interpolation method with constrained polynomial fit based on spectral phase in swept-source optical coherence tomography(SS-OCT).A Mach-Zehnder interferometer(MZI)unit is connected to.the swept-source of the SS-OCT system to generate calibration signal in sync with the fetching of interference spectra.The spectral phase of the calibration signal is extracted by Hilbert transformation.The fitted phase-time relationship is obtained by polynomial fitting with the constraint of passing through the central spectral phase.The fitting curve is then adopted for k-domain uniform interpolation based on evenly spaced phase.In comparison with conventional k-domain spline interpolation,the proposed method leads to improved axial resolution and peak response of the axial point spread function(PSF)of the SS-OCT system.Enhanced performance resulting from the proposed method is further verified by OCT imaging of a home-constructed microspheres-agar sample and a fresh lemon.Besides SS-OCT,the proposed method is believed to be applicable to spectral domain OCT as well.
基金funded by an NSFC Major Project (Grant No. 42090033)the China Meteorological Administration Youth Innovation Team “High-Value Climate Change Data Product Development and Application Services”(Grant No. CMA2023QN08)the National Meteorological Information Centre Surplus Funds Program (Grant NMICJY202310)。
文摘High-vertical-resolution radiosonde wind data are highly valuable for describing the dynamics of the meso-and microscale atmosphere. However, the current algorithm used in China's L-band radar sounding system for calculating highvertical-resolution wind vectors excessively smooths the data, resulting in significant underestimation of the calculated kinetic energy of gravity waves compared to similar products from other countries, which greatly limits the effective utilization of the data. To address this issue, this study proposes a novel method to calculate high-vertical-resolution wind vectors that utilizes the elevation angle, azimuth angle, and slant range from L-band radar. In order to obtain wind data with a stable quality, a two-step automatic quality control procedure, including the RMSE-F(root-mean-square error F) test and elemental consistency test are first applied to the slant range data, to eliminate continuous erroneous data caused by unstable signals or radar malfunctions. Then, a wind calculation scheme based on a sliding second-order polynomial fitting is utilized to derive the high-vertical-resolution radiosonde wind vectors. The evaluation results demonstrate that the wind data obtained through the proposed method show a high level of consistency with the high-resolution wind data observed using the Vaisala Global Positioning System and the data observed by the new Beidou Navigation Sounding System. The calculation of the kinetic energy of gravity waves in the recalculated wind data also reaches a level comparable to the Vaisala observations.
基金Research supported by the 863 Program of China(No.2012AA09A20103)the National Natural Science Foundation of China(No.41274119,No.41174080,and No.41004041)
文摘In seismic data processing, random noise seriously affects the seismic data quality and subsequently the interpretation. This study aims to increase the signal-to-noise ratio by suppressing random noise and improve the accuracy of seismic data interpretation without losing useful information. Hence, we propose a structure-oriented polynomial fitting filter. At the core of structure-oriented filtering is the characterization of the structural trend and the realization of nonstationary filtering. First, we analyze the relation of the frequency response between two-dimensional（2D） derivatives and the 2D Hilbert transform. Then, we derive the noniterative seismic local dip operator using the 2D Hilbert transform to obtain the structural trend. Second, we select polynomial fitting as the nonstationary filtering method and expand the application range of the nonstationary polynomial fitting. Finally, we apply variableamplitude polynomial fitting along the direction of the dip to improve the adaptive structureoriented filtering. Model and field seismic data show that the proposed method suppresses the seismic noise while protecting structural information.
基金This work was supported by National High Technology Research and Development Program of PRC (No. 2002AA420040)National 973 Program of PRC (No. 2002CB312200).
文摘In this paper, a new pre-alignment approach based on Four-Quadrant-Photo-Detector （FQPD） for IC mask is presented. The voltage outputs from FQPDs are the functions of alignment mark＇s position offsets with respect to FQPDs. The functions are obtained with least squares error （LSE）-based polynomial fitting after the normalization of experimental data. As the acquired functions are not monotonic about their variables, the alignment mark＇s position offset cannot be given by direct inverse operation on the obtained functions. However, the piecewise polynomial fitting gives the inverse function, with which the alignment mark＇s position offset can be predicted according to the voltage outputs of FQPDs. On the basis of prediction, a pre-alignment control strategy is proposed. The feasibility and robustness of the pre-alignment approach is shown by experiments. Furthermore, the results demonstrate that the maximum error of mask＇s position offset in the X- and Y- directions is less than 15μm after coarse pre-alignment. Keywords： Four-Quadrant-Photo-Detector （FQPD）, pre-alignment, IC mask, polynomial fitting
基金supported by the National Natural Science Foundation of China(41304060)the national key basic research and development plan(2013CB733304)
文摘North China is a key region for studying geophysical progress. In this study, ground-based and Gravity Recovery and Climate Experiment（GRACE） gravity data from 2009 to 2013 are used to calculate the gravity change rate（GCR） using the polynomial fitting method. In general, the study area was divided into the Shanxi rift, Jing-Jin-Ji（Beijing-Tianjin-Hebei Province）, and Bohai Bay Basin（BBB） regions. Results of the distribution of the GCR determined from ground-based gravimetry show that the GCR appears to be ＂negativepositive-negative＂ from west to east, which indicates that different geophysical mechanisms are involved in the tectonic activities of these regions. However, GRACE solutions are conducted over a larger spatial scale and are able to show a difference between southern and northern areas and a mass redistribution of land water storage.
文摘The constitutive relationship is the basis for studying the material processing technology and controlling the quality of products.Data and models of the plastic flow behavior of materials are often required during the manufacturing process.Therefore,establishing constitutive models with high precision and generalization and enriching material database is of great significance for optimizing processing technology and product quality of the material.Based on the Gleeble thermal compression test results,the essential relationship of 25 steel between the flow stress and thermal–mechanical state variables,such as temperature,strain rate,and strain,is quantitatively discussed for the first time.Combined with the Zener–Hollomon parameter and considering the influence of strain compensation,the constitutive model of 25 steel is built by the hyperbolic-sine equation over the full strain range.In the modeling process,the influence of strain on material constants is characterized by polynomial fitting.The selection basis of polynomial order is discussed in-depth,and the inconsistency between calculation accuracy and fitting effect is clarified.Finally,the accuracy of the model is analyzed,and the generalization and applicability are discussed.It is proved that the developed model can accurately predict the flow behavior of materials in the full strain range.
基金Supported by the National Natural Science Foundation of China （No. 60532060 60672117）, the Program for Changjiang Scholars and Innovative Research Team in University （PCS1TR）.
文摘Distributed source coding （DSC） is applied to interferential multispectral image compression owing to strong correlation among the image frames. Many DSC systems in the literature use feedback channel （FC） to control rate at the decoder, which limits the application of DSC. Upon an analysis of the image data, a rate control approach is proposed to avoid FC. Low-complexity motion compensation is applied first to estimate side information at the encoder. Using a polynomial fitting method, a new mathematical model is then derived to estimate rate based on the correlation between the source and side information. The experimental results show that our estimated rate is a good approximation to the actual rate required by FC while incurring a little bit-rate overhead. Our compression scheme performs comparable with the FC based DSC system and outperforms JPEG2000 significantly.
文摘A method of MIMO channel tracking based on Kalman filter and MMSE-DFE is proposed. The Kalman filter tracks the time-varying channel by using the MMSE-DFE decision and the MMSE-DFE conducts the next decision by using the channel estimates produced by the Kalman filter. Polynomial fitting is used to bridge the gap between the channel estimates produced by the Kalman filter and those needed for the DFE decision. Computer simulation demonstrates that this method can track the MIMO time-varying channel effectively.
