Excessive erosion caused by the continuous collision of sand-carrying annular flow with the gas well wellbore can lead to serious production accidents.This study combined the multifrequency response characteristics of...Excessive erosion caused by the continuous collision of sand-carrying annular flow with the gas well wellbore can lead to serious production accidents.This study combined the multifrequency response characteristics of sand particle-wall collision with a deep learning algorithm to improve the recognition accuracy of sand particle information in annular flow.The findings showed that sand-wall collision strength was closely related to the velocity,size,and number of sand particles and that the shielding effect generated by the collision behavior between multiple particles had a protective effect on the elbow.In addition,sand-wall collision strength increased with increases in gas velocity and particle size and decreased with an increase in liquid velocity.The shear effect,the secondary flow effect,and the liquid film buffering effect were shown to be key factors affecting the transportation behavior and spatial distribution of sand particles in annular flow.Furthermore,the fast Fourier transform(FFT)and short-time Fourier transform(STFT)analysis results showed that the multifrequency collision response characteristics of sand carrying annular flow were complex and that the main frequency response of sand-wall collision was concentrated in the high frequency range of 50e80 kHz.Moreover,the recognition accuracy results of convolutional neural network(CNN)models for particle size,gas velocity,and liquid velocity were 93.8%,91.7%,and 91%,respectively,which were significantly higher than the results for the long short-term memory(LSTM)model.The combination of multifrequency collision response and deep learning effectively characterized sand particle feature information in strong gas-liquid turbulence,providing a reference for the accurate monitoring of sand particle information in high-yield waterbearing gas wells.展开更多
The application of traditional synchronous measurement methods is limited by frequent fluctuations of electrical signals and complex frequency components in distribution networks.Therefore,it is critical to find solut...The application of traditional synchronous measurement methods is limited by frequent fluctuations of electrical signals and complex frequency components in distribution networks.Therefore,it is critical to find solutions to the issues of multifrequency parameter estimation and synchronous measurement estimation accuracy in the complex environment of distribution networks.By utilizing the multifrequency sensing capabilities of discrete Fourier transform signals and Taylor series for dynamic signal processing,a multifrequency signal estimation approach based on HT-IpDFT-STWLS(HIpST)for distribution networks is provided.First,by introducing the Hilbert transform(HT),the influence of noise on the estimation algorithm is reduced.Second,signal frequency components are obtained on the basis of the calculated signal envelope spectrum,and the interpolated discrete Fourier transform(IpDFT)frequency coarse estimation results are used as the initial values of symmetric Taylor weighted least squares(STWLS)to achieve high-precision parameter estimation under the dynamic changes of the signal,and the method increases the number of discrete Fourier.Third,the accuracy of this proposed method is verified by simulation analysis.Data show that this proposed method can accurately achieve the parameter estimation of multifrequency signals in distribution networks.This approach provides a solution for the application of phasor measurement units in distribution networks.展开更多
Multifrequency polarimetric SAR imagery provides a very convenient approach for signal processing and acquisition of radar image. However, the amount of information is scattered in several images, and redundancies exi...Multifrequency polarimetric SAR imagery provides a very convenient approach for signal processing and acquisition of radar image. However, the amount of information is scattered in several images, and redundancies exist between different bands and polarizations. Similar to signal-polarimetric SAR image, multifrequency polarimetric SAR image is corrupted with speckle noise at the same time. A method of information compression and speckle reduction for multifrequency polarimetric SAR imagery is presented based on kernel principal component analysis （KPCA）. KPCA is a nonlinear generalization of the linear principal component analysis using the kernel trick. The NASA/JPL polarimetric SAR imagery of P, L, and C bands quadpolarizations is used for illustration. The experimental results show that KPCA has better capability in information compression and speckle reduction as compared with linear PCA.展开更多
A numerical model which consists of the Korteweg-de Vries(KdV)equation,the action balance equation and the radar backscattering model is developed to simulate the frequency dependence of synthetic aperture radar(SAR)r...A numerical model which consists of the Korteweg-de Vries(KdV)equation,the action balance equation and the radar backscattering model is developed to simulate the frequency dependence of synthetic aperture radar(SAR)remote sensing of nonlinear ocean internal waves.Multifrequency data collected by NASA SIR-C SAR and NASA JPL AIRSAR are used as comparison.Case studies show that the results of simulation agree well with the results of SAR data.展开更多
Different ocean features usually appear in synthetic aperture radar(SAR)images simultaneously.This makes the image complicated and hard to understand.Because of lower signal-to-noise rate,it is much more difficult to ...Different ocean features usually appear in synthetic aperture radar(SAR)images simultaneously.This makes the image complicated and hard to understand.Because of lower signal-to-noise rate,it is much more difficult to separate different ocean features than to separate different land features.A completely novel method is presented to separate ocean features from multifrequency polarimetric SAR imagery.AIRSAR data from Jet Propulsion Laboratory(JPL),National Aeronautics and Space Administration(NASA)are used in the case studies and good results are achieved.展开更多
This paper describes the design and implementation of a three-axis acceleration control autopilot for an asymmetric tail-controlled,skid-to-turn tactical missile.In an earlier flight test,degraded autopilot performanc...This paper describes the design and implementation of a three-axis acceleration control autopilot for an asymmetric tail-controlled,skid-to-turn tactical missile.In an earlier flight test,degraded autopilot performance was attributed to multiple disturbances and uncertainties and the presence of hidden coupling terms,giving rise to a miss distance of greater than 20 m.To address these issues,the missile dynamics are decomposed into the angular rate dynamics as fast and the acceleration dynamics as slow subsystem using the singular perturbation theory to analyze a multi-time-scale property.Multifrequency extended state observers are then incorporated into the gain scheduling technique to attenuate disturbances,thus enhancing the control performance significantly.In the proposed engineering/practical design framework for missile autopilot,simple,conventional,and explicit tuning rules are provided.And the proposed control scheme can achieve input-to-state stability across the entire flight envelope under unknown but bounded disturbances.The advantages of the method over existing benchmark approaches are shown through nonlinear numerical simulations.This is supported by evidence from a new flight test result with a miss distance of only 2 m.展开更多
A novel method is proposed for the supervised classification of multifrequency polarimetric synthetic aperture radar （PolSAR） images. The coherency matrices in P-, L-, and C-bands are mapped onto a 9×9 matrix ...A novel method is proposed for the supervised classification of multifrequency polarimetric synthetic aperture radar （PolSAR） images. The coherency matrices in P-, L-, and C-bands are mapped onto a 9×9 matrix Ω based on the eigenvalue decomposition of the coherency matrix of each band. A boxcar filter is then performed on the matrix Ω. The filtered data are put into a complex Wishart classifier. Finally, the effectiveness of the proposed method is demonstrated with JPL/AIRSAR multifrequency PolSAR data acquired over the Flevoland area.展开更多
This paper introduces the characteristics of TD-SCDMA, and analyzes some networking schemes and methods of multifrequency. For the 5 MHz frequency bandwidth, a frequency planning scheme containing three frequencies is...This paper introduces the characteristics of TD-SCDMA, and analyzes some networking schemes and methods of multifrequency. For the 5 MHz frequency bandwidth, a frequency planning scheme containing three frequencies is examined, and a simulation model is built to validate the performance of this scheme. Finally, this paper analyzes the advantages and disadvantages of the scheme, and proposes some directions for the future study of networking planning.展开更多
A complex autonomous inventory coupled system is considered. It can take, for example, the form of a network of chemical or biochemical reactors, where the inventory interactions perform the recycling of by-products b...A complex autonomous inventory coupled system is considered. It can take, for example, the form of a network of chemical or biochemical reactors, where the inventory interactions perform the recycling of by-products between the subsystems. Because of the flexible subsystems interactions, each of them can be operated with their own periods utilizing advantageously their dynamic properties. A multifrequency second-order test generalizing the p-test for single systems is described. It can be used to decide which kind of the operation (the static one, the periodic one or the multiperiodic one) will intensify the productivity of a complex system. An illustrative example of the multiperiodic optimization of a complex chemical production system is presented.展开更多
Using partial electrodes and a multifrequency electrical source,we present a large-bandwidth,large-amplitude clamped–clamped microbeam resonator excited near the higher order modes of vibration.We analytically and ex...Using partial electrodes and a multifrequency electrical source,we present a large-bandwidth,large-amplitude clamped–clamped microbeam resonator excited near the higher order modes of vibration.We analytically and experimentally investigate the nonlinear dynamics of the microbeam under a two-source harmonic excitation.The first-frequency source is swept around the first three modes of vibration,whereas the second source frequency remains fixed.New additive and subtractive resonances are demonstrated.We illustrated that by properly tuning the frequency and amplitude of the excitation force,the frequency bandwidth of the resonator is controlled.The microbeam is fabricated using polyimide as a structural layer coated with nickel from the top and chromium and gold layers from the bottom.Using the Galerkin method,a reduced order model is derived to simulate the static and dynamic response of the device.A good agreement between the theoretical and experimental data are reported.展开更多
The Feynman diagram theory with the state-space formalism is adopted to study the multifrequency nonlinear acoustics effects. By establishing the relation between the strain magnitude corresponding to any final state ...The Feynman diagram theory with the state-space formalism is adopted to study the multifrequency nonlinear acoustics effects. By establishing the relation between the strain magnitude corresponding to any final state S(m1,…,mn; x) and the number of paths from the initial state of the interactingphonons to the final state, not only the complete perturbation solutions but also the corresponding analytical expressions of the acoustic harmonics and intermodulation products have been obtained. For a few special cases, results of our theory is consistent with those obtained by conventional methods. While the general solution for any number of frequencies can easily be obtained by our theory, this is impossible by using conventional methods.展开更多
Automatic pavement crack detection plays an important role in ensuring road safety.In images of cracks,information about the cracks can be conveyed through high-frequency and low-fre-quency signals that focus on fine ...Automatic pavement crack detection plays an important role in ensuring road safety.In images of cracks,information about the cracks can be conveyed through high-frequency and low-fre-quency signals that focus on fine details and global structures,respectively.The output features obtained from different convolutional layers can be combined to represent information about both high-frequency and low-frequency signals.In this paper,we propose an encoder-decoder framework called octave hierarchical network(Octave-H),which is based on the U-Network(U-Net)architec-ture and utilizes an octave convolutional neural network and a hierarchical feature learning module for performing crack detection.The proposed octave convolution is capable of extracting multi-fre-quency feature maps,capturing both fine details and global cracks.We propose a hierarchical feature learning module that merges multi-frequency-scale feature maps with different levels(high and low)of octave convolutional layers.To verify the superiority of the proposed Octave-H,we employed the CrackForest dataset(CFD)and AigleRN databases to evaluate this method.The experimental results demonstrate that Octave-H outperforms other algorithms with satisfactory performance.展开更多
To make three-dimensional electromagnetic exploration achievable,the distributed wide field electromagnetic method(WFEM)based on the high-order 2^(n) sequence pseudo-random signal is proposed and realized.In this meth...To make three-dimensional electromagnetic exploration achievable,the distributed wide field electromagnetic method(WFEM)based on the high-order 2^(n) sequence pseudo-random signal is proposed and realized.In this method,only one set of high-order pseudo-random waveforms,which contains all target frequencies,is needed.Based on high-order sequence pseudo-random signal construction algorithm,the waveform can be customized according to different exploration tasks.And the receivers are independent with each other and dynamically adjust the acquisition parameters according to different requirements.A field test in the deep iron ore of Qihe−Yucheng showed that the distributed WFEM based on high-order pseudo-random signal realizes the high-efficiency acquisition of massive electromagnetic data in quite a short time.Compared with traditional controlled-source electromagnetic methods,the distributed WFEM is much more efficient.Distributed WFEM can be applied to the large scale and high-resolution exploration for deep resources and minerals.展开更多
AIM: In patients with liver cirrhosis, hypoalbuminemia causes edema and ascites, and a reduction in the quality of life. Since musculature is catabolized to supply amino acids for albumin synthesis in malnutritional c...AIM: In patients with liver cirrhosis, hypoalbuminemia causes edema and ascites, and a reduction in the quality of life. Since musculature is catabolized to supply amino acids for albumin synthesis in malnutritional cirrhotic patients, muscular volume is hypothesized to play an important role in albumin production. Therefore, we investigated the correlation between serum albumin levels and the fat-free mass (FFM) in cirrhotic patients.METHODS: Fifty-seven patients (26 males and 31 females)with compensated liver cirrhosis were evaluated. Patients with edema or ascites were excluded from the study.Healthy volunteers (n = 104; 48 males and 56 females)were also evaluated as controls. FFM was measured using 5-500 kHz multifrequency bioelectric impedance analysis.To minimize the difference in FFM distribution between males and females, we introduced a new marker, relative FFM (rFFM), which represents the ratio of FFM in a patient relative to that in a volunteer of the same height. Following FFM measurement, the serum albumin levels of patients were assayed monthly.RESULTS: In patients with active cirrhosis (alanine aminotransaminase [ALT] ＞50 U/L), both albumin (the difference between maximum and minimum levels) and the standard deviation of albumin levels (SD-albumin) during the observation period showed a significant correlation with rFFM. Multiple linear regression analysis using variables such as rFFM, platelet number, and serum cholesterol levels,choline esterase, albumin, bilirubin, and ALT revealed that rFFM and ALT were significant and independent factors that influenced albumin or SD-albumin in cirrhotic patients.CONCLUSION: Our results indicate that cirrhotic patients with high rFFM showed less of a decrease in albumin levels, and that the muscle volume is one of the most important factors for maintaining serum albumins level in active cirrhosis. Exercise and protein-rich nutrition at the early stage of liver cirrhosis may be advisable for maintaining or increasing muscular volume.展开更多
The study of energy transfer between coupled subsystems in a hybrid system is very important for applications. This paper presents an analytical analysis of energy transfer between plates of a visco-elastically connec...The study of energy transfer between coupled subsystems in a hybrid system is very important for applications. This paper presents an analytical analysis of energy transfer between plates of a visco-elastically connected double-plate system in free transversal vibrations. The analytical analysis shows that the visco-elastic connection between plates is responsible for the appearance of two-frequency regime in the time function, which corresponds to one eigen amplitude function of one mode, and also that time functions of different vibration modes are uncoupled, but energy transfer between plates in one eigen mode appears. It was shown for each shape of vibrations. Series of the two Lyapunov exponents corresponding to the one eigen amplitude mode are expressed by using the energy of the corresponding eigen amplitude time component.展开更多
The double plate system with a discontinuity in the elastic bonding layer of Winker type is studied in this paper. When the discontinuity is small, it can be taken as an interface crack between the bi-materials or two...The double plate system with a discontinuity in the elastic bonding layer of Winker type is studied in this paper. When the discontinuity is small, it can be taken as an interface crack between the bi-materials or two bodies （plates or beams）. By comparison between the number of multifrequencies of analytical solutions of the double plate system free transversal vibrations for the case when the system is with and without disconti- nuity in elastic layer we obtain a theory for experimental vibration method for identification of the presence of an interface crack in the double plate system. The analytical analysis of free transversal vibrations of an elastically connected double plate systems with discontinuity in the elastic layer of Winkler type is presented. The analytical solutions of the coupled partial differential equations for dynamical free and forced vibration processes are obtained by using method of Bernoulli＇s particular integral and Lagrange＇s method of variation constants. It is shown that one mode vibration corresponds an infinite or finite multi-frequency regime for free and forced vibrations induced by initial conditions and one- frequency or corresponding number of multi-frequency regime depending on external excitations. It is shown for every shape of vibrations. The analytical solutions show that the discontinuity affects the appearance of multi-frequency regime of time function corresponding to one eigen amplitude function of one mode, and also that time functions of different vibration basic modes are coupled. From final expression we can separate the newgeneralized eigen amplitude functions with correspon- ding time eigen functions of one frequency and multifrequency regime of vibrations.展开更多
We theoretically investigate the single-photon transport properties in an optical waveguide embedded with a V-type three-level atom(VTLA)based on symmetric and asymmetric couplings between the photon and the VTLA.Our ...We theoretically investigate the single-photon transport properties in an optical waveguide embedded with a V-type three-level atom(VTLA)based on symmetric and asymmetric couplings between the photon and the VTLA.Our numerical results show that the transmission spectrum of the incident photon can be well controlled by virtue of both symmetric and asymmetric coupling interactions.A multifrequency photon attenuator is realized by controlling the asymmetric coupling interactions.Furthermore,the influences of dissipation of the VTLA for the realistic physical system on single-photon transport properties are also analyzed.展开更多
The multifrequency voltage(MFV)stress,including switching impulses and harmonics,commonly appearing in the modern power system will stimulate the multifrequency impedance dynamics behaviours of electrical insulation.T...The multifrequency voltage(MFV)stress,including switching impulses and harmonics,commonly appearing in the modern power system will stimulate the multifrequency impedance dynamics behaviours of electrical insulation.Therefore,this article presents a novel concept of insulation resilience response(IRR)by employing polymer insulation materials,which may be extended to electrical insulation resilience(EIR).The focus is on understanding reversible recovery performance and supporting physics-informed condition assessment for electrical insulation exposed to MFV.The underlying physical mechanisms and modelling methodologies are integrated to characterise the IRR behaviours of polymer insulation systems.The multifrequency dielectric/impedance properties of different resin dielectrics under diverse temperatures are comparatively investigated as proofofconcept cases.Furthermore,multidimensional sensitivity indicators are developed to quantify the electrical insulation resilience behaviour.A radar plot representation integrating resilience sensitivity indicators qualitatively assesses the IRR behaviours of polymer insulation systems.Additionally,a quantification methodology,including the resilience index(RI)and time-varied RI(TVRI),is proposed for the reversible recovery performance analysis for electrical insulation,respectively.Ultimately,an application-oriented framework derived from TVRI is provided to analyse the recovery performance evolution behaviours of electrical insulation under complex operating conditions.This offers a key theoretical foundation for insulation performance characterisation and condition analysis for high-voltage power equipment.展开更多
Frequency engineering of whispering-gallery resonances is essential in microcavity nonlinear optics.The key is to control the frequencies of the cavity modes involved in the underlying nonlinear optical process to sat...Frequency engineering of whispering-gallery resonances is essential in microcavity nonlinear optics.The key is to control the frequencies of the cavity modes involved in the underlying nonlinear optical process to satisfy its energy conservation criterion.Compared to the conventional method that tailors dispersion by cross-sectional geometry,thereby impacting all cavity mode frequencies,grating-assisted microring cavities,often termed as photonic crystal microrings,provide more enabling capabilities through mode-selective frequency control.For example,a simple single period grating added to a microring has been used for single frequency engineering in Kerr optical parametric oscillation(OPO)and frequency combs.Recently,this approach has been extended to multifrequency engineering by using multi-period grating functions,but at the cost of increasingly complex grating profiles that require challenging fabrication.Here,we demonstrate a simple approach,which we term as shifted grating multiple mode splitting(SGMMS),where spatial displacement of a single period grating imprinted on the inner boundary of the microring creates a rotational asymmetry that frequency splits multiple adjacent cavity modes.This approach is easy to implement and presents no additional fabrication challenges compared to an unshifted grating,and yet is very powerful in providing multi-frequency engineering functionality for nonlinear optics.We showcase an example where SGMMS enables OPO across a wide range of pump wavelengths in a normal-dispersion device that otherwise would not support OPO.展开更多
基金supported by the National Natural Science Foundation of China(52104015)the Natural Science Foundation of Shandong Province(ZR2021ME001)the Innovation Fund Project for graduate students of China University of Petroleum(East China)supported by the Fundamental Research Funds for the Central Universities(24CX04040A).
文摘Excessive erosion caused by the continuous collision of sand-carrying annular flow with the gas well wellbore can lead to serious production accidents.This study combined the multifrequency response characteristics of sand particle-wall collision with a deep learning algorithm to improve the recognition accuracy of sand particle information in annular flow.The findings showed that sand-wall collision strength was closely related to the velocity,size,and number of sand particles and that the shielding effect generated by the collision behavior between multiple particles had a protective effect on the elbow.In addition,sand-wall collision strength increased with increases in gas velocity and particle size and decreased with an increase in liquid velocity.The shear effect,the secondary flow effect,and the liquid film buffering effect were shown to be key factors affecting the transportation behavior and spatial distribution of sand particles in annular flow.Furthermore,the fast Fourier transform(FFT)and short-time Fourier transform(STFT)analysis results showed that the multifrequency collision response characteristics of sand carrying annular flow were complex and that the main frequency response of sand-wall collision was concentrated in the high frequency range of 50e80 kHz.Moreover,the recognition accuracy results of convolutional neural network(CNN)models for particle size,gas velocity,and liquid velocity were 93.8%,91.7%,and 91%,respectively,which were significantly higher than the results for the long short-term memory(LSTM)model.The combination of multifrequency collision response and deep learning effectively characterized sand particle feature information in strong gas-liquid turbulence,providing a reference for the accurate monitoring of sand particle information in high-yield waterbearing gas wells.
基金supported by the State Grid Corporation of China Headquarters Management Science and Technology Project(No.526620200008).
文摘The application of traditional synchronous measurement methods is limited by frequent fluctuations of electrical signals and complex frequency components in distribution networks.Therefore,it is critical to find solutions to the issues of multifrequency parameter estimation and synchronous measurement estimation accuracy in the complex environment of distribution networks.By utilizing the multifrequency sensing capabilities of discrete Fourier transform signals and Taylor series for dynamic signal processing,a multifrequency signal estimation approach based on HT-IpDFT-STWLS(HIpST)for distribution networks is provided.First,by introducing the Hilbert transform(HT),the influence of noise on the estimation algorithm is reduced.Second,signal frequency components are obtained on the basis of the calculated signal envelope spectrum,and the interpolated discrete Fourier transform(IpDFT)frequency coarse estimation results are used as the initial values of symmetric Taylor weighted least squares(STWLS)to achieve high-precision parameter estimation under the dynamic changes of the signal,and the method increases the number of discrete Fourier.Third,the accuracy of this proposed method is verified by simulation analysis.Data show that this proposed method can accurately achieve the parameter estimation of multifrequency signals in distribution networks.This approach provides a solution for the application of phasor measurement units in distribution networks.
基金the Specialized Research Found for the Doctoral Program of Higher Education (20070699013)the Natural Science Foundation of Shaanxi Province (2006F05)the Aeronautical Science Foundation (05I53076).
文摘Multifrequency polarimetric SAR imagery provides a very convenient approach for signal processing and acquisition of radar image. However, the amount of information is scattered in several images, and redundancies exist between different bands and polarizations. Similar to signal-polarimetric SAR image, multifrequency polarimetric SAR image is corrupted with speckle noise at the same time. A method of information compression and speckle reduction for multifrequency polarimetric SAR imagery is presented based on kernel principal component analysis （KPCA）. KPCA is a nonlinear generalization of the linear principal component analysis using the kernel trick. The NASA/JPL polarimetric SAR imagery of P, L, and C bands quadpolarizations is used for illustration. The experimental results show that KPCA has better capability in information compression and speckle reduction as compared with linear PCA.
基金the National Natural Science Foundation of China under contract Nos 40206023 and 40776099.
文摘A numerical model which consists of the Korteweg-de Vries(KdV)equation,the action balance equation and the radar backscattering model is developed to simulate the frequency dependence of synthetic aperture radar(SAR)remote sensing of nonlinear ocean internal waves.Multifrequency data collected by NASA SIR-C SAR and NASA JPL AIRSAR are used as comparison.Case studies show that the results of simulation agree well with the results of SAR data.
基金National Natural Science Foundation of China under contract Nos 40206023 and 40776099.
文摘Different ocean features usually appear in synthetic aperture radar(SAR)images simultaneously.This makes the image complicated and hard to understand.Because of lower signal-to-noise rate,it is much more difficult to separate different ocean features than to separate different land features.A completely novel method is presented to separate ocean features from multifrequency polarimetric SAR imagery.AIRSAR data from Jet Propulsion Laboratory(JPL),National Aeronautics and Space Administration(NASA)are used in the case studies and good results are achieved.
基金the support of the National Natural Science Foundation of China(No.U21B6003)。
文摘This paper describes the design and implementation of a three-axis acceleration control autopilot for an asymmetric tail-controlled,skid-to-turn tactical missile.In an earlier flight test,degraded autopilot performance was attributed to multiple disturbances and uncertainties and the presence of hidden coupling terms,giving rise to a miss distance of greater than 20 m.To address these issues,the missile dynamics are decomposed into the angular rate dynamics as fast and the acceleration dynamics as slow subsystem using the singular perturbation theory to analyze a multi-time-scale property.Multifrequency extended state observers are then incorporated into the gain scheduling technique to attenuate disturbances,thus enhancing the control performance significantly.In the proposed engineering/practical design framework for missile autopilot,simple,conventional,and explicit tuning rules are provided.And the proposed control scheme can achieve input-to-state stability across the entire flight envelope under unknown but bounded disturbances.The advantages of the method over existing benchmark approaches are shown through nonlinear numerical simulations.This is supported by evidence from a new flight test result with a miss distance of only 2 m.
基金supported in part by the National Natural Science Fundation of China(4117131761132008+1 种基金61490693)Aeronautical Science Foundation of China(20132058003)
文摘A novel method is proposed for the supervised classification of multifrequency polarimetric synthetic aperture radar （PolSAR） images. The coherency matrices in P-, L-, and C-bands are mapped onto a 9×9 matrix Ω based on the eigenvalue decomposition of the coherency matrix of each band. A boxcar filter is then performed on the matrix Ω. The filtered data are put into a complex Wishart classifier. Finally, the effectiveness of the proposed method is demonstrated with JPL/AIRSAR multifrequency PolSAR data acquired over the Flevoland area.
文摘This paper introduces the characteristics of TD-SCDMA, and analyzes some networking schemes and methods of multifrequency. For the 5 MHz frequency bandwidth, a frequency planning scheme containing three frequencies is examined, and a simulation model is built to validate the performance of this scheme. Finally, this paper analyzes the advantages and disadvantages of the scheme, and proposes some directions for the future study of networking planning.
文摘A complex autonomous inventory coupled system is considered. It can take, for example, the form of a network of chemical or biochemical reactors, where the inventory interactions perform the recycling of by-products between the subsystems. Because of the flexible subsystems interactions, each of them can be operated with their own periods utilizing advantageously their dynamic properties. A multifrequency second-order test generalizing the p-test for single systems is described. It can be used to decide which kind of the operation (the static one, the periodic one or the multiperiodic one) will intensify the productivity of a complex system. An illustrative example of the multiperiodic optimization of a complex chemical production system is presented.
基金financial support from King Abdullah University of Science and Technology.
文摘Using partial electrodes and a multifrequency electrical source,we present a large-bandwidth,large-amplitude clamped–clamped microbeam resonator excited near the higher order modes of vibration.We analytically and experimentally investigate the nonlinear dynamics of the microbeam under a two-source harmonic excitation.The first-frequency source is swept around the first three modes of vibration,whereas the second source frequency remains fixed.New additive and subtractive resonances are demonstrated.We illustrated that by properly tuning the frequency and amplitude of the excitation force,the frequency bandwidth of the resonator is controlled.The microbeam is fabricated using polyimide as a structural layer coated with nickel from the top and chromium and gold layers from the bottom.Using the Galerkin method,a reduced order model is derived to simulate the static and dynamic response of the device.A good agreement between the theoretical and experimental data are reported.
基金The project was supported by National Natural Science Foundation of China
文摘The Feynman diagram theory with the state-space formalism is adopted to study the multifrequency nonlinear acoustics effects. By establishing the relation between the strain magnitude corresponding to any final state S(m1,…,mn; x) and the number of paths from the initial state of the interactingphonons to the final state, not only the complete perturbation solutions but also the corresponding analytical expressions of the acoustic harmonics and intermodulation products have been obtained. For a few special cases, results of our theory is consistent with those obtained by conventional methods. While the general solution for any number of frequencies can easily be obtained by our theory, this is impossible by using conventional methods.
基金supported in part by the National Natural Foundation of China(No.62176147)。
文摘Automatic pavement crack detection plays an important role in ensuring road safety.In images of cracks,information about the cracks can be conveyed through high-frequency and low-fre-quency signals that focus on fine details and global structures,respectively.The output features obtained from different convolutional layers can be combined to represent information about both high-frequency and low-frequency signals.In this paper,we propose an encoder-decoder framework called octave hierarchical network(Octave-H),which is based on the U-Network(U-Net)architec-ture and utilizes an octave convolutional neural network and a hierarchical feature learning module for performing crack detection.The proposed octave convolution is capable of extracting multi-fre-quency feature maps,capturing both fine details and global cracks.We propose a hierarchical feature learning module that merges multi-frequency-scale feature maps with different levels(high and low)of octave convolutional layers.To verify the superiority of the proposed Octave-H,we employed the CrackForest dataset(CFD)and AigleRN databases to evaluate this method.The experimental results demonstrate that Octave-H outperforms other algorithms with satisfactory performance.
基金funded by the National Natural Science Foundation of China(No.42004056)the Natural Science Foundation of Shangdong Province,China(No.ZR2020QD052)China Postdoctoral Science Foundation(No.2019M652386)。
文摘To make three-dimensional electromagnetic exploration achievable,the distributed wide field electromagnetic method(WFEM)based on the high-order 2^(n) sequence pseudo-random signal is proposed and realized.In this method,only one set of high-order pseudo-random waveforms,which contains all target frequencies,is needed.Based on high-order sequence pseudo-random signal construction algorithm,the waveform can be customized according to different exploration tasks.And the receivers are independent with each other and dynamically adjust the acquisition parameters according to different requirements.A field test in the deep iron ore of Qihe−Yucheng showed that the distributed WFEM based on high-order pseudo-random signal realizes the high-efficiency acquisition of massive electromagnetic data in quite a short time.Compared with traditional controlled-source electromagnetic methods,the distributed WFEM is much more efficient.Distributed WFEM can be applied to the large scale and high-resolution exploration for deep resources and minerals.
文摘AIM: In patients with liver cirrhosis, hypoalbuminemia causes edema and ascites, and a reduction in the quality of life. Since musculature is catabolized to supply amino acids for albumin synthesis in malnutritional cirrhotic patients, muscular volume is hypothesized to play an important role in albumin production. Therefore, we investigated the correlation between serum albumin levels and the fat-free mass (FFM) in cirrhotic patients.METHODS: Fifty-seven patients (26 males and 31 females)with compensated liver cirrhosis were evaluated. Patients with edema or ascites were excluded from the study.Healthy volunteers (n = 104; 48 males and 56 females)were also evaluated as controls. FFM was measured using 5-500 kHz multifrequency bioelectric impedance analysis.To minimize the difference in FFM distribution between males and females, we introduced a new marker, relative FFM (rFFM), which represents the ratio of FFM in a patient relative to that in a volunteer of the same height. Following FFM measurement, the serum albumin levels of patients were assayed monthly.RESULTS: In patients with active cirrhosis (alanine aminotransaminase [ALT] ＞50 U/L), both albumin (the difference between maximum and minimum levels) and the standard deviation of albumin levels (SD-albumin) during the observation period showed a significant correlation with rFFM. Multiple linear regression analysis using variables such as rFFM, platelet number, and serum cholesterol levels,choline esterase, albumin, bilirubin, and ALT revealed that rFFM and ALT were significant and independent factors that influenced albumin or SD-albumin in cirrhotic patients.CONCLUSION: Our results indicate that cirrhotic patients with high rFFM showed less of a decrease in albumin levels, and that the muscle volume is one of the most important factors for maintaining serum albumins level in active cirrhosis. Exercise and protein-rich nutrition at the early stage of liver cirrhosis may be advisable for maintaining or increasing muscular volume.
基金the Ministry of Sciences and Enviromental Protection of Republic Serbia through Mathematical Institute SANU Belgrade Grants No.ON144002
文摘The study of energy transfer between coupled subsystems in a hybrid system is very important for applications. This paper presents an analytical analysis of energy transfer between plates of a visco-elastically connected double-plate system in free transversal vibrations. The analytical analysis shows that the visco-elastic connection between plates is responsible for the appearance of two-frequency regime in the time function, which corresponds to one eigen amplitude function of one mode, and also that time functions of different vibration modes are uncoupled, but energy transfer between plates in one eigen mode appears. It was shown for each shape of vibrations. Series of the two Lyapunov exponents corresponding to the one eigen amplitude mode are expressed by using the energy of the corresponding eigen amplitude time component.
文摘The double plate system with a discontinuity in the elastic bonding layer of Winker type is studied in this paper. When the discontinuity is small, it can be taken as an interface crack between the bi-materials or two bodies （plates or beams）. By comparison between the number of multifrequencies of analytical solutions of the double plate system free transversal vibrations for the case when the system is with and without disconti- nuity in elastic layer we obtain a theory for experimental vibration method for identification of the presence of an interface crack in the double plate system. The analytical analysis of free transversal vibrations of an elastically connected double plate systems with discontinuity in the elastic layer of Winkler type is presented. The analytical solutions of the coupled partial differential equations for dynamical free and forced vibration processes are obtained by using method of Bernoulli＇s particular integral and Lagrange＇s method of variation constants. It is shown that one mode vibration corresponds an infinite or finite multi-frequency regime for free and forced vibrations induced by initial conditions and one- frequency or corresponding number of multi-frequency regime depending on external excitations. It is shown for every shape of vibrations. The analytical solutions show that the discontinuity affects the appearance of multi-frequency regime of time function corresponding to one eigen amplitude function of one mode, and also that time functions of different vibration basic modes are coupled. From final expression we can separate the newgeneralized eigen amplitude functions with correspon- ding time eigen functions of one frequency and multifrequency regime of vibrations.
基金Supported by the National Natural Science Foundation of China under Grant No 10774053。
文摘We theoretically investigate the single-photon transport properties in an optical waveguide embedded with a V-type three-level atom(VTLA)based on symmetric and asymmetric couplings between the photon and the VTLA.Our numerical results show that the transmission spectrum of the incident photon can be well controlled by virtue of both symmetric and asymmetric coupling interactions.A multifrequency photon attenuator is realized by controlling the asymmetric coupling interactions.Furthermore,the influences of dissipation of the VTLA for the realistic physical system on single-photon transport properties are also analyzed.
基金supported by the Science and Technology Project of State Grid Corporation of China(Grant 5500-202455120A-1-1-ZN).
文摘The multifrequency voltage(MFV)stress,including switching impulses and harmonics,commonly appearing in the modern power system will stimulate the multifrequency impedance dynamics behaviours of electrical insulation.Therefore,this article presents a novel concept of insulation resilience response(IRR)by employing polymer insulation materials,which may be extended to electrical insulation resilience(EIR).The focus is on understanding reversible recovery performance and supporting physics-informed condition assessment for electrical insulation exposed to MFV.The underlying physical mechanisms and modelling methodologies are integrated to characterise the IRR behaviours of polymer insulation systems.The multifrequency dielectric/impedance properties of different resin dielectrics under diverse temperatures are comparatively investigated as proofofconcept cases.Furthermore,multidimensional sensitivity indicators are developed to quantify the electrical insulation resilience behaviour.A radar plot representation integrating resilience sensitivity indicators qualitatively assesses the IRR behaviours of polymer insulation systems.Additionally,a quantification methodology,including the resilience index(RI)and time-varied RI(TVRI),is proposed for the reversible recovery performance analysis for electrical insulation,respectively.Ultimately,an application-oriented framework derived from TVRI is provided to analyse the recovery performance evolution behaviours of electrical insulation under complex operating conditions.This offers a key theoretical foundation for insulation performance characterisation and condition analysis for high-voltage power equipment.
基金Maryland Innovation InitiativeNational Institute of Standards and Technology(NIST-on-a-chip)Defense Advanced Research Projects Agency(LUMOS)。
文摘Frequency engineering of whispering-gallery resonances is essential in microcavity nonlinear optics.The key is to control the frequencies of the cavity modes involved in the underlying nonlinear optical process to satisfy its energy conservation criterion.Compared to the conventional method that tailors dispersion by cross-sectional geometry,thereby impacting all cavity mode frequencies,grating-assisted microring cavities,often termed as photonic crystal microrings,provide more enabling capabilities through mode-selective frequency control.For example,a simple single period grating added to a microring has been used for single frequency engineering in Kerr optical parametric oscillation(OPO)and frequency combs.Recently,this approach has been extended to multifrequency engineering by using multi-period grating functions,but at the cost of increasingly complex grating profiles that require challenging fabrication.Here,we demonstrate a simple approach,which we term as shifted grating multiple mode splitting(SGMMS),where spatial displacement of a single period grating imprinted on the inner boundary of the microring creates a rotational asymmetry that frequency splits multiple adjacent cavity modes.This approach is easy to implement and presents no additional fabrication challenges compared to an unshifted grating,and yet is very powerful in providing multi-frequency engineering functionality for nonlinear optics.We showcase an example where SGMMS enables OPO across a wide range of pump wavelengths in a normal-dispersion device that otherwise would not support OPO.
