To fully utilize the resources provided by optical fiber networks,a cross-band quantum light source generating photon pairs,where one photon in a pair is at C band and the other is at O band,is proposed in this work.T...To fully utilize the resources provided by optical fiber networks,a cross-band quantum light source generating photon pairs,where one photon in a pair is at C band and the other is at O band,is proposed in this work.This source is based on spontaneous four-wave mixing(SFWM)in a piece of shallow-ridge silicon waveguide.Theoretical analysis shows that the waveguide dispersion could be tailored by adjusting the ridge width,enabling broadband photon pair generation by SFWM across C band and O band.The spontaneous Raman scattering(SpRS)in silicon waveguides is also investigated experimentally.It shows that there are two regions in the spectrum of generated photons from SpRS,which could be used to achieve cross-band photon pair generation.A chip of shallow-ridge silicon waveguide samples with different ridge widths has been fabricated,through which cross-band photon pair generation is demonstrated experimentally.The experimental results show that the source can be achieved using dispersion-optimized shallow-ridge silicon waveguides.This cross-band quantum light source provides a way to develop new fiber-based quantum communication functions utilizing both C band and O band and extends applications of quantum networks.展开更多
With the increasingly complex and changeable electromagnetic environment,wireless communication systems are facing jamming and abnormal signal injection,which significantly affects the normal operation of a communicat...With the increasingly complex and changeable electromagnetic environment,wireless communication systems are facing jamming and abnormal signal injection,which significantly affects the normal operation of a communication system.In particular,the abnormal signals may emulate the normal signals,which makes it very challenging for abnormal signal recognition.In this paper,we propose a new abnormal signal recognition scheme,which combines time-frequency analysis with deep learning to effectively identify synthetic abnormal communication signals.Firstly,we emulate synthetic abnormal communication signals including seven jamming patterns.Then,we model an abnormal communication signals recognition system based on the communication protocol between the transmitter and the receiver.To improve the performance,we convert the original signal into the time-frequency spectrogram to develop an image classification algorithm.Simulation results demonstrate that the proposed method can effectively recognize the abnormal signals under various parameter configurations,even under low signal-to-noise ratio(SNR)and low jamming-to-signal ratio(JSR)conditions.展开更多
The Chinese Altai,a key component of the Central Asian Orogenic Belt(CAOB),represents a significant Phanerozoic accretionary orogenic belt.The oceanic-continental subduction processes spanning the Cambrian to Carbonif...The Chinese Altai,a key component of the Central Asian Orogenic Belt(CAOB),represents a significant Phanerozoic accretionary orogenic belt.The oceanic-continental subduction processes spanning the Cambrian to Carboniferous and subsequent intracontinental extension since the Triassic have been well documented in the Chinese Altai,the southwestern segment of the CAOB.Deciphering the petrogenetic evolution of this region during the Permian is thus crucial for advancing our understanding of its tectonic transitions.However,the Permian tectonic setting of the Chinese Altai remains contentious.To address this knowledge gap,this study presents new geochronological and geochemical data for the Jiangjunshan pluton in the southern Chinese Altai.Zircon U-Pb geochronology reveals that the gabbro and two-mica alkali feldspar granite—which collectively constitute the primary lithology of the Jiangjunshan pluton—were emplaced at∼272±3.5 and∼272±1.6 Ma,respectively.Geochemically,the gabbro exhibits pronounced light rare-earth element(LREE)depletion,low Nb/Yb(0.39–0.46)and Ti/V(23.7–25.3)ratios,and trace-element signatures akin to normal mid-ocean ridge basalts(N-MORB).However,its conspicuous Nb-Ta depletion parallels that of island arc basalts.Depleted Hf-Nd isotopic compositions(ε_(Hf)(t)=+0.60 to+4.63,ε_(Nd)(t)=+6.32 to+7.80)in the gabbro,coupled with negligible correlation betweenε_(Nd)(t)and SiO2 contents imply limited crustal assimilation during magma evolution.Petrological modeling,based on Sm/Yb and La concentrations,suggests the gabbroic melt derived from∼8%–20%spinel lherzolte mantle melting.Analogously depleted Hf-Nd isotopes(ε_(Hf)(t)=+6.81 to+9.10,ε_(Nd)(t)=+0.79 to+1.45)in the granite,together with petrographic evidence lacking mafic-ultramafic xenoliths,point to a juvenile lower-crustal source.Integrating the gabbro’s N-MORB-like affinity with arc-specific features,regional ultrahigh-temperature metamorphism in southern Chinese Altai,and Permian tectonics,we propose a ridge-subduction regime as the likely petrogenetic setting for the Jiangjunshan magmas.During ridge subduction,upwelling of asthenospheric mantle beneath the ridge induced partial melting of the lithospheric mantle,giving rise to the parental magma of the Jiangjunshan gabbro.This mafic magma underplating subsequently heated the juvenile lower crust,triggering its partial melting and generating the parental magma of the two-mica alkali feldspar granite.Our model indicates that ridge-subduction-related magmatism persisted in the Chinese Altai until the Middle Permian,followed by a tectonic shift from oceanic-continental subduction to intracontinental extension.展开更多
Seismic time-frequency(TF)transforms are essential tools in reservoir interpretation and signal processing,particularly for characterizing frequency variations in non-stationary seismic data.Recently,sparse TF trans-f...Seismic time-frequency(TF)transforms are essential tools in reservoir interpretation and signal processing,particularly for characterizing frequency variations in non-stationary seismic data.Recently,sparse TF trans-forms,which leverage sparse coding(SC),have gained significant attention in the geosciences due to their ability to achieve high TF resolution.However,the iterative approaches typically employed in sparse TF transforms are computationally intensive,making them impractical for real seismic data analysis.To address this issue,we propose an interpretable convolutional sparse coding(CSC)network to achieve high TF resolution.The proposed model is generated based on the traditional short-time Fourier transform(STFT)transform and a modified UNet,named ULISTANet.In this design,we replace the conventional convolutional layers of the UNet with learnable iterative shrinkage thresholding algorithm(LISTA)blocks,a specialized form of CSC.The LISTA block,which evolves from the traditional iterative shrinkage thresholding algorithm(ISTA),is optimized for extracting sparse features more effectively.Furthermore,we create a synthetic dataset featuring complex frequency-modulated signals to train ULISTANet.Finally,the proposed method’s performance is subsequently validated using both synthetic and field data,demonstrating its potential for enhanced seismic data analysis.展开更多
Seismic fault rupture can extend to the surface,and the resulting surface deformation can cause severe damage to civil engineering structures crossing the fault zones.Coseismic Surface Rupture Prediction Models(CSRPMs...Seismic fault rupture can extend to the surface,and the resulting surface deformation can cause severe damage to civil engineering structures crossing the fault zones.Coseismic Surface Rupture Prediction Models(CSRPMs)play a crucial role in the structural design of fault-crossing engineering and in the hazard analysis of fault-intensive areas.In this study,a new global coseismic surface rupture database was constructed by compiling 171 earthquake events(Mw:5.5-7.9)that caused surface rupture.In contrast to the fault classification in traditional empirical relationships,this study categorizes earthquake events as strike-slip,dip-slip,and oblique-slip.CSRPMs utilizing Bayesian ridge regression(BRR)were developed to estimate parameters such as surface rupture length,average displacement,and maximum displacement.Based on Bayesian theory,BRR combines the benefits of both ridge regression and Bayesian linear regression.This approach effectively addresses the issue of overfitting while ensuring the strong model robustness.The reliability of the CSRPMs was validated by residual analysis and comparison with post-earthquake observations from the 2023 Türkiye earthquake doublet.The BRR-CSRPMs with new fault classification criteria are more suitable for the probabilistic hazard analysis of complex fault systems and dislocation design of fault-crossing engineering.展开更多
The Ninety-East Ridge(NER)is located in the semioceanic to oceanic region of the southern Bengal Fan in the Northeast Indian Ocean.The sedimentary environment,ocean currents,and scientific issues related to climate ch...The Ninety-East Ridge(NER)is located in the semioceanic to oceanic region of the southern Bengal Fan in the Northeast Indian Ocean.The sedimentary environment,ocean currents,and scientific issues related to climate change have always been the focus of scientists.To well understand the sedimentary environment of the sea area,we studied the modern sedimentary environment of the NER by analyzing the redox-sensitive trace elements(RSEs)and biomarkers in the surface sediments of the northern region and both sides of the NER and the mechanism of their formation.The ratios of Mo/U(average 2.22),(Cu+Mo)/Zn(average 1.51),and the results ofδCe<1 of the sediment samples,all indicate the reduction of the sedimentary environment.In addition,the ratio of pristane(Pr)to phytane(Ph),C30diahopane to C30 hopane,and diasterane to sterane were low in all samples,on average of 1.03,0.9,and 0.33,respectively.The analysis of RSE and biomarker data revealed that the sedimentary environment on seabed of the NER is generally a rare low-oxygen reduction environment.Through the analysis of sediment characteristics,material sources,and ocean currents,we preliminarily constructed a genetic model for the low-oxygen reducing environment of surface sediments in the NER.We believe that the low-oxygen reduction environment of surface sediment in the NER could be influenced by multiple factors,such as terrestrial input of materials,productivity at sea surface,and sediment particle size.展开更多
The hydrothermal signatures of mid-ocean ridge sediments are crucial geochemical data providing insights into investigating hydrothermal anomalies and locating seafloor massive sulfide deposits.This paper outlines the...The hydrothermal signatures of mid-ocean ridge sediments are crucial geochemical data providing insights into investigating hydrothermal anomalies and locating seafloor massive sulfide deposits.This paper outlines the geochemical features of 24 surface sediments and one sediment core(26 V-GC 01,294 cm)along the South Mid-Atlantic Ridge(SMAR)from 18°S to 22°S,an area where hydrothermal active fields have yet to be discovered.The surface sediments mainly consist of biogenic carbonates,aluminosilicates,and hydrothermal Fe-Mn(oxy)oxides.The core sediments primarily comprise organic matter,detrital materials,hydrothermal components,and substances scavenged from seawater.The rare Earth element(REE)patterns suggest the presence of hydrothermal contributions within the surface and core sediments.The enrichment factors for Fe,Mn,Cu,and Zn in surface sediments suggest these metals are concentrated at the 19°S,21°S,and 21.5°S segments,further indicating their potential as hydrothermal active fields.Downcore variations of Fe,Mn,P,Cu,Pb,V,and Co suggest at least six episodes of hydrothermal activity.The impact of hydrothermal processes on the sediments from SMAR 18°S to 22°S indicates that the study area has the potential to host a significant number of hydrothermal active fields.展开更多
A coupled tide-surge-wave model was established to analyze the impacts of radial sand ridges on storm surges in the South Yellow Sea.Numerical topography experiments were designed on the basis of multiple well-verifie...A coupled tide-surge-wave model was established to analyze the impacts of radial sand ridges on storm surges in the South Yellow Sea.Numerical topography experiments were designed on the basis of multiple well-verified types of extreme weather events.The findings demonstrated that the radial sand ridges(RSRs)generally enhanced tidal levels,current velocities,and significant wave heights in the affected area.The nonlinear effects of shallow water in the radial sand ridge area can induce large tide ranges.A unique seabed can cause an increase in current speed from the open sea to the nearshore.Another impact is that subaqueous ridges can result in shallow water conditions,and the degree of depth-induced wave breaking significantly varies.Compared with those in the northern and southern radial sand ridge areas,the tidal levels,current speeds,and wave heights in the middle radial sand ridge area were the highest,which can cause more severe storm surge disasters.Additionally,the wave radiation stress varied obviously under the action of fan-shaped sand ridges.Thus,it is necessary to consider wave-current interactions when modeling storm surges in sand ridges.展开更多
A time-frequency signal processing method for two-phase flow through a horizontal Venturi based on adaptive optimal-kernel （AOK） was presented in this paper.First,the collected dynamic differential pressure signal o...A time-frequency signal processing method for two-phase flow through a horizontal Venturi based on adaptive optimal-kernel （AOK） was presented in this paper.First,the collected dynamic differential pressure signal of gas-liquid two-phase flow was preprocessed,and then the AOK theory was used to analyze the dynamic differ-ential pressure signal.The mechanism of two-phase flow was discussed through the time-frequency spectrum.On the condition of steady water flow rate,with the increasing of gas flow rate,the flow pattern changes from bubbly flow to slug flow,then to plug flow,meanwhile,the energy distribution of signal fluctuations show significant change that energy transfer from 15-35 Hz band to 0-8 Hz band;moreover,when the flow pattern is slug flow,there are two wave peaks showed in the time-frequency spectrum.Finally,a number of characteristic variables were defined by using the time-frequency spectrum and the ridge of AOK.When the characteristic variables were visu-ally analyzed,the relationship between different combination of characteristic variables and flow patterns would be gotten.The results show that,this method can explain the law of flow in different flow patterns.And characteristic variables,defined by this method,can get a clear description of the flow information.This method provides a new way for the flow pattern identification,and the percentage of correct prediction is up to 91.11%.展开更多
The Gabor and S transforms are frequently used in time-frequency decomposition methods. Constrained by the uncertainty principle, both transforms produce low-resolution time-frequency decomposition results in the time...The Gabor and S transforms are frequently used in time-frequency decomposition methods. Constrained by the uncertainty principle, both transforms produce low-resolution time-frequency decomposition results in the time and frequency domains. To improve the resolution of the time-frequency decomposition results, we use the instantaneous frequency distribution function（IFDF） to express the seismic signal. When the instantaneous frequencies of the nonstationary signal satisfy the requirements of the uncertainty principle, the support of IFDF is just the support of the amplitude ridges in the signal obtained using the short-time Fourier transform. Based on this feature, we propose a new iteration algorithm to achieve the sparse time-frequency decomposition of the signal. The iteration algorithm uses the support of the amplitude ridges of the residual signal obtained with the short-time Fourier transform to update the time-frequency components of the signal. The summation of the updated time-frequency components in each iteration is the result of the sparse timefrequency decomposition. Numerical examples show that the proposed method improves the resolution of the time-frequency decomposition results and the accuracy of the analysis of the nonstationary signal. We also use the proposed method to attenuate the ground roll of field seismic data with good results.展开更多
Predicting the time-varying auto-spectral density of a spacecraft in high-altitude orbits requires an accurate model for the non-stationary random vibration signals with densely spaced modal frequency. The traditional...Predicting the time-varying auto-spectral density of a spacecraft in high-altitude orbits requires an accurate model for the non-stationary random vibration signals with densely spaced modal frequency. The traditional time-varying algorithm limits prediction accuracy, thus affecting a number of operational decisions. To solve this problem, a time-varying auto regressive （TVAR） model based on the process neural network （PNN） and the empirical mode decomposition （EMD） is proposed. The time-varying system is tracked on-line by establishing a time-varying parameter model, and then the relevant parameter spectrum is obtained. Firstly, the EMD method is utilized to decompose the signal into several intrinsic mode functions （IMFs）. Then for each IMF, the PNN is established and the time-varying auto-spectral density is obtained. Finally, the time-frequency distribution of the signals can be reconstructed by linear superposition. The simulation and the analytical results from an example demonstrate that this approach possesses simplicity, effectiveness, and feasibility, as well as higher frequency resolution.展开更多
The two-dimensional hydrodynamic model, MIKE21, is applied to simulate the tidal currents and sediment concentration in the radial sand ridges of the South Yellow Sea. Results are in accordance with in situ observatio...The two-dimensional hydrodynamic model, MIKE21, is applied to simulate the tidal currents and sediment concentration in the radial sand ridges of the South Yellow Sea. Results are in accordance with in situ observations. Then the variations of tidal currents and suspended sediment concentration caused by reclamation and artificial islands projects are simulated. The results show that the impacts are limited around the project areas. After the projects, the fan-shaped, Jianggang centered tidal current pattern would be replaced by a pattern which is formed by two tidal paths. One locates at the Xiyang channel in north-south direction, and the other locates at the Huangshayang channel in east-west direction. The reclamation of Tiaozini separates the waters into south portion and north portion. The changes of sediment concentrations coincide with those of currents. Both the sediment concentrations and tidal currents increase at the northwest of Dongsha and the south of Gaoni, while both decrease at the north and south of Tiaozini, and the east and southwest of Dongsha.展开更多
A polymer electro optic modulator has been fabricated with the functional layer acting as a kind of corona poled crosslinkable polyurethane. The three optical layers, namely waveguide, photolithography and oxygen are...A polymer electro optic modulator has been fabricated with the functional layer acting as a kind of corona poled crosslinkable polyurethane. The three optical layers, namely waveguide, photolithography and oxygen are fabricated by spin coating. With the Reactive Ion Etching method, the ridge of the waveguide is constructed. With light at 1 31μm being fiber coupled to waveguide, the mode and the modulation properties of these devices are demonstrated in a micron control system.展开更多
Some factors influencing the intelligibility of the enhanced whisper in the joint time-frequency domain are evaluated. Specifically, both the spectrum density and different regions of the enhanced spectrum are analyze...Some factors influencing the intelligibility of the enhanced whisper in the joint time-frequency domain are evaluated. Specifically, both the spectrum density and different regions of the enhanced spectrum are analyzed. Experimental results show that for a spectrum of some density, the joint time-frequency gain-modification based speech enhancement algorithm achieves significant improvement in intelligibility. Additionally, the spectrum region where the estimated spectrum is smaller than the clean spectrum, is the most important region contributing to intelligibility improvement for the enhanced whisper. The spectrum region where the estimated spectrum is larger than twice the size of the clean spectrum is detrimental to speech intelligibility perception within the whisper context.展开更多
Two-line super hybrid rice （Oryza sativa L.） Guiliangyou 2 was taken as the experimental variety, the growth and physiological characteristics of rice under conventional tillage and smashing ridge tillage were compa...Two-line super hybrid rice （Oryza sativa L.） Guiliangyou 2 was taken as the experimental variety, the growth and physiological characteristics of rice under conventional tillage and smashing ridge tillage were compared based on field re- search. The results showed that smashing ridge tillage was beneficial to the tillering growth of rice plants in the the middle and later periods of tillering; under the tillage mode, the white root was more, the vigour was strong during the whole growing period, the SPAD was extremely significantly higher than that of conventional tillage, the net photosynthetic rate of the leaves was high and held green long, which were beneficial to the production and accumulation of photoassimilates; during mature pe- riod, the dry matter accumulation of the overground part under smashing ridge tillage was significantly higher than that of conventional tillage, and the number of productive ears under smashing ridge tillage was more than that of conventional tillage by 27.6×10^4/hm2, thus, the yield-increasing effect was significant and in- creased by 20.36%.展开更多
基金supported by the Quantum Science and Technology-National Science and Technology Major Project (Grant No.2024ZD0302502 for WZ)the National Natural Science Foundation of China(Grant No.92365210 for WZ)+1 种基金Tsinghua Initiative Scientific Research Program (for WZ)the project of Tsinghua University-Zhuhai Huafa Industrial Share Company Joint Institute for Architecture Optoelectronic Technologies (JIAOT,for YH)。
文摘To fully utilize the resources provided by optical fiber networks,a cross-band quantum light source generating photon pairs,where one photon in a pair is at C band and the other is at O band,is proposed in this work.This source is based on spontaneous four-wave mixing(SFWM)in a piece of shallow-ridge silicon waveguide.Theoretical analysis shows that the waveguide dispersion could be tailored by adjusting the ridge width,enabling broadband photon pair generation by SFWM across C band and O band.The spontaneous Raman scattering(SpRS)in silicon waveguides is also investigated experimentally.It shows that there are two regions in the spectrum of generated photons from SpRS,which could be used to achieve cross-band photon pair generation.A chip of shallow-ridge silicon waveguide samples with different ridge widths has been fabricated,through which cross-band photon pair generation is demonstrated experimentally.The experimental results show that the source can be achieved using dispersion-optimized shallow-ridge silicon waveguides.This cross-band quantum light source provides a way to develop new fiber-based quantum communication functions utilizing both C band and O band and extends applications of quantum networks.
基金supported by Natural Science Foundation of China(No.62371231)Natural Science Foundation on Frontier Leading Technology Basic Research Project of Jiangsu under Grant BK20222001Jiangsu Provincial Key Research and Development Program(No.BE2023027).
文摘With the increasingly complex and changeable electromagnetic environment,wireless communication systems are facing jamming and abnormal signal injection,which significantly affects the normal operation of a communication system.In particular,the abnormal signals may emulate the normal signals,which makes it very challenging for abnormal signal recognition.In this paper,we propose a new abnormal signal recognition scheme,which combines time-frequency analysis with deep learning to effectively identify synthetic abnormal communication signals.Firstly,we emulate synthetic abnormal communication signals including seven jamming patterns.Then,we model an abnormal communication signals recognition system based on the communication protocol between the transmitter and the receiver.To improve the performance,we convert the original signal into the time-frequency spectrogram to develop an image classification algorithm.Simulation results demonstrate that the proposed method can effectively recognize the abnormal signals under various parameter configurations,even under low signal-to-noise ratio(SNR)and low jamming-to-signal ratio(JSR)conditions.
基金supported by the Xinjiang Key R&D Program(No.2022B03015-3)the National Natural Science Foundation of China(No.91962214)+1 种基金the Fundamental Research Funds for the Central Universities,Chang’an University(No.300102272201)the“Tianchi Talent”Plan to Chang-Zhi Wu.
文摘The Chinese Altai,a key component of the Central Asian Orogenic Belt(CAOB),represents a significant Phanerozoic accretionary orogenic belt.The oceanic-continental subduction processes spanning the Cambrian to Carboniferous and subsequent intracontinental extension since the Triassic have been well documented in the Chinese Altai,the southwestern segment of the CAOB.Deciphering the petrogenetic evolution of this region during the Permian is thus crucial for advancing our understanding of its tectonic transitions.However,the Permian tectonic setting of the Chinese Altai remains contentious.To address this knowledge gap,this study presents new geochronological and geochemical data for the Jiangjunshan pluton in the southern Chinese Altai.Zircon U-Pb geochronology reveals that the gabbro and two-mica alkali feldspar granite—which collectively constitute the primary lithology of the Jiangjunshan pluton—were emplaced at∼272±3.5 and∼272±1.6 Ma,respectively.Geochemically,the gabbro exhibits pronounced light rare-earth element(LREE)depletion,low Nb/Yb(0.39–0.46)and Ti/V(23.7–25.3)ratios,and trace-element signatures akin to normal mid-ocean ridge basalts(N-MORB).However,its conspicuous Nb-Ta depletion parallels that of island arc basalts.Depleted Hf-Nd isotopic compositions(ε_(Hf)(t)=+0.60 to+4.63,ε_(Nd)(t)=+6.32 to+7.80)in the gabbro,coupled with negligible correlation betweenε_(Nd)(t)and SiO2 contents imply limited crustal assimilation during magma evolution.Petrological modeling,based on Sm/Yb and La concentrations,suggests the gabbroic melt derived from∼8%–20%spinel lherzolte mantle melting.Analogously depleted Hf-Nd isotopes(ε_(Hf)(t)=+6.81 to+9.10,ε_(Nd)(t)=+0.79 to+1.45)in the granite,together with petrographic evidence lacking mafic-ultramafic xenoliths,point to a juvenile lower-crustal source.Integrating the gabbro’s N-MORB-like affinity with arc-specific features,regional ultrahigh-temperature metamorphism in southern Chinese Altai,and Permian tectonics,we propose a ridge-subduction regime as the likely petrogenetic setting for the Jiangjunshan magmas.During ridge subduction,upwelling of asthenospheric mantle beneath the ridge induced partial melting of the lithospheric mantle,giving rise to the parental magma of the Jiangjunshan gabbro.This mafic magma underplating subsequently heated the juvenile lower crust,triggering its partial melting and generating the parental magma of the two-mica alkali feldspar granite.Our model indicates that ridge-subduction-related magmatism persisted in the Chinese Altai until the Middle Permian,followed by a tectonic shift from oceanic-continental subduction to intracontinental extension.
基金supported by the National Natural Science Foundation of China under Grant 42474139the Key Research and Development Program of Shaanxi under Grant 2024GX-YBXM-067.
文摘Seismic time-frequency(TF)transforms are essential tools in reservoir interpretation and signal processing,particularly for characterizing frequency variations in non-stationary seismic data.Recently,sparse TF trans-forms,which leverage sparse coding(SC),have gained significant attention in the geosciences due to their ability to achieve high TF resolution.However,the iterative approaches typically employed in sparse TF transforms are computationally intensive,making them impractical for real seismic data analysis.To address this issue,we propose an interpretable convolutional sparse coding(CSC)network to achieve high TF resolution.The proposed model is generated based on the traditional short-time Fourier transform(STFT)transform and a modified UNet,named ULISTANet.In this design,we replace the conventional convolutional layers of the UNet with learnable iterative shrinkage thresholding algorithm(LISTA)blocks,a specialized form of CSC.The LISTA block,which evolves from the traditional iterative shrinkage thresholding algorithm(ISTA),is optimized for extracting sparse features more effectively.Furthermore,we create a synthetic dataset featuring complex frequency-modulated signals to train ULISTANet.Finally,the proposed method’s performance is subsequently validated using both synthetic and field data,demonstrating its potential for enhanced seismic data analysis.
基金Foundation of China under Grant Nos. U2139207 and 52378517the Natural Science Foundation of Hubei Province under Grant No. 2023AFB934
文摘Seismic fault rupture can extend to the surface,and the resulting surface deformation can cause severe damage to civil engineering structures crossing the fault zones.Coseismic Surface Rupture Prediction Models(CSRPMs)play a crucial role in the structural design of fault-crossing engineering and in the hazard analysis of fault-intensive areas.In this study,a new global coseismic surface rupture database was constructed by compiling 171 earthquake events(Mw:5.5-7.9)that caused surface rupture.In contrast to the fault classification in traditional empirical relationships,this study categorizes earthquake events as strike-slip,dip-slip,and oblique-slip.CSRPMs utilizing Bayesian ridge regression(BRR)were developed to estimate parameters such as surface rupture length,average displacement,and maximum displacement.Based on Bayesian theory,BRR combines the benefits of both ridge regression and Bayesian linear regression.This approach effectively addresses the issue of overfitting while ensuring the strong model robustness.The reliability of the CSRPMs was validated by residual analysis and comparison with post-earthquake observations from the 2023 Türkiye earthquake doublet.The BRR-CSRPMs with new fault classification criteria are more suitable for the probabilistic hazard analysis of complex fault systems and dislocation design of fault-crossing engineering.
基金Supported by the Science and Technology Development Foundation of South China Sea Bureau,Ministry of Natural Resources,China(No.230204)the National Program on Global Change and Air-Sea Interaction(No.GASI-02-IND-CJ04)+1 种基金the Natural Science Foundation of Guangdong Province,China(No.2021A1515012589)the Key Technologies Research and Development Program of Guangzhou,Guangdong Province,China(No.2023B03J1379)。
文摘The Ninety-East Ridge(NER)is located in the semioceanic to oceanic region of the southern Bengal Fan in the Northeast Indian Ocean.The sedimentary environment,ocean currents,and scientific issues related to climate change have always been the focus of scientists.To well understand the sedimentary environment of the sea area,we studied the modern sedimentary environment of the NER by analyzing the redox-sensitive trace elements(RSEs)and biomarkers in the surface sediments of the northern region and both sides of the NER and the mechanism of their formation.The ratios of Mo/U(average 2.22),(Cu+Mo)/Zn(average 1.51),and the results ofδCe<1 of the sediment samples,all indicate the reduction of the sedimentary environment.In addition,the ratio of pristane(Pr)to phytane(Ph),C30diahopane to C30 hopane,and diasterane to sterane were low in all samples,on average of 1.03,0.9,and 0.33,respectively.The analysis of RSE and biomarker data revealed that the sedimentary environment on seabed of the NER is generally a rare low-oxygen reduction environment.Through the analysis of sediment characteristics,material sources,and ocean currents,we preliminarily constructed a genetic model for the low-oxygen reducing environment of surface sediments in the NER.We believe that the low-oxygen reduction environment of surface sediment in the NER could be influenced by multiple factors,such as terrestrial input of materials,productivity at sea surface,and sediment particle size.
基金Supported by the China Ocean Mineral Resources R&D Association(No.DY135-S2-2)the Basic Scientific Fund for National Public Research Institutes of China(No.2021Q01)the National Natural Science Foundation of China(Nos.42106080,42006180,42276080)。
文摘The hydrothermal signatures of mid-ocean ridge sediments are crucial geochemical data providing insights into investigating hydrothermal anomalies and locating seafloor massive sulfide deposits.This paper outlines the geochemical features of 24 surface sediments and one sediment core(26 V-GC 01,294 cm)along the South Mid-Atlantic Ridge(SMAR)from 18°S to 22°S,an area where hydrothermal active fields have yet to be discovered.The surface sediments mainly consist of biogenic carbonates,aluminosilicates,and hydrothermal Fe-Mn(oxy)oxides.The core sediments primarily comprise organic matter,detrital materials,hydrothermal components,and substances scavenged from seawater.The rare Earth element(REE)patterns suggest the presence of hydrothermal contributions within the surface and core sediments.The enrichment factors for Fe,Mn,Cu,and Zn in surface sediments suggest these metals are concentrated at the 19°S,21°S,and 21.5°S segments,further indicating their potential as hydrothermal active fields.Downcore variations of Fe,Mn,P,Cu,Pb,V,and Co suggest at least six episodes of hydrothermal activity.The impact of hydrothermal processes on the sediments from SMAR 18°S to 22°S indicates that the study area has the potential to host a significant number of hydrothermal active fields.
基金financially supported by the Fundamental Research Funds for the Central Universities(Grant No.B210202031)the National Natural Science Foundation of China(Grant No.41606042)。
文摘A coupled tide-surge-wave model was established to analyze the impacts of radial sand ridges on storm surges in the South Yellow Sea.Numerical topography experiments were designed on the basis of multiple well-verified types of extreme weather events.The findings demonstrated that the radial sand ridges(RSRs)generally enhanced tidal levels,current velocities,and significant wave heights in the affected area.The nonlinear effects of shallow water in the radial sand ridge area can induce large tide ranges.A unique seabed can cause an increase in current speed from the open sea to the nearshore.Another impact is that subaqueous ridges can result in shallow water conditions,and the degree of depth-induced wave breaking significantly varies.Compared with those in the northern and southern radial sand ridge areas,the tidal levels,current speeds,and wave heights in the middle radial sand ridge area were the highest,which can cause more severe storm surge disasters.Additionally,the wave radiation stress varied obviously under the action of fan-shaped sand ridges.Thus,it is necessary to consider wave-current interactions when modeling storm surges in sand ridges.
基金Supported by the Natural Science Foundation of Zhejiang Province（Y1100842） the Planning Projects of General Administration of Quality Supervision Inspection and Quarantine of the People＇s Republic of China（2006QK23）
文摘A time-frequency signal processing method for two-phase flow through a horizontal Venturi based on adaptive optimal-kernel （AOK） was presented in this paper.First,the collected dynamic differential pressure signal of gas-liquid two-phase flow was preprocessed,and then the AOK theory was used to analyze the dynamic differ-ential pressure signal.The mechanism of two-phase flow was discussed through the time-frequency spectrum.On the condition of steady water flow rate,with the increasing of gas flow rate,the flow pattern changes from bubbly flow to slug flow,then to plug flow,meanwhile,the energy distribution of signal fluctuations show significant change that energy transfer from 15-35 Hz band to 0-8 Hz band;moreover,when the flow pattern is slug flow,there are two wave peaks showed in the time-frequency spectrum.Finally,a number of characteristic variables were defined by using the time-frequency spectrum and the ridge of AOK.When the characteristic variables were visu-ally analyzed,the relationship between different combination of characteristic variables and flow patterns would be gotten.The results show that,this method can explain the law of flow in different flow patterns.And characteristic variables,defined by this method,can get a clear description of the flow information.This method provides a new way for the flow pattern identification,and the percentage of correct prediction is up to 91.11%.
基金funded by the National Basic Research Program of China(973 Program)(No.2011 CB201002)the National Natural Science Foundation of China(No.41374117)the great and special projects(2011ZX05005–005-008HZ and 2011ZX05006-002)
文摘The Gabor and S transforms are frequently used in time-frequency decomposition methods. Constrained by the uncertainty principle, both transforms produce low-resolution time-frequency decomposition results in the time and frequency domains. To improve the resolution of the time-frequency decomposition results, we use the instantaneous frequency distribution function（IFDF） to express the seismic signal. When the instantaneous frequencies of the nonstationary signal satisfy the requirements of the uncertainty principle, the support of IFDF is just the support of the amplitude ridges in the signal obtained using the short-time Fourier transform. Based on this feature, we propose a new iteration algorithm to achieve the sparse time-frequency decomposition of the signal. The iteration algorithm uses the support of the amplitude ridges of the residual signal obtained with the short-time Fourier transform to update the time-frequency components of the signal. The summation of the updated time-frequency components in each iteration is the result of the sparse timefrequency decomposition. Numerical examples show that the proposed method improves the resolution of the time-frequency decomposition results and the accuracy of the analysis of the nonstationary signal. We also use the proposed method to attenuate the ground roll of field seismic data with good results.
基金Aeronautical Science Foundation of China (20071551016)
文摘Predicting the time-varying auto-spectral density of a spacecraft in high-altitude orbits requires an accurate model for the non-stationary random vibration signals with densely spaced modal frequency. The traditional time-varying algorithm limits prediction accuracy, thus affecting a number of operational decisions. To solve this problem, a time-varying auto regressive （TVAR） model based on the process neural network （PNN） and the empirical mode decomposition （EMD） is proposed. The time-varying system is tracked on-line by establishing a time-varying parameter model, and then the relevant parameter spectrum is obtained. Firstly, the EMD method is utilized to decompose the signal into several intrinsic mode functions （IMFs）. Then for each IMF, the PNN is established and the time-varying auto-spectral density is obtained. Finally, the time-frequency distribution of the signals can be reconstructed by linear superposition. The simulation and the analytical results from an example demonstrate that this approach possesses simplicity, effectiveness, and feasibility, as well as higher frequency resolution.
文摘The two-dimensional hydrodynamic model, MIKE21, is applied to simulate the tidal currents and sediment concentration in the radial sand ridges of the South Yellow Sea. Results are in accordance with in situ observations. Then the variations of tidal currents and suspended sediment concentration caused by reclamation and artificial islands projects are simulated. The results show that the impacts are limited around the project areas. After the projects, the fan-shaped, Jianggang centered tidal current pattern would be replaced by a pattern which is formed by two tidal paths. One locates at the Xiyang channel in north-south direction, and the other locates at the Huangshayang channel in east-west direction. The reclamation of Tiaozini separates the waters into south portion and north portion. The changes of sediment concentrations coincide with those of currents. Both the sediment concentrations and tidal currents increase at the northwest of Dongsha and the south of Gaoni, while both decrease at the north and south of Tiaozini, and the east and southwest of Dongsha.
文摘A polymer electro optic modulator has been fabricated with the functional layer acting as a kind of corona poled crosslinkable polyurethane. The three optical layers, namely waveguide, photolithography and oxygen are fabricated by spin coating. With the Reactive Ion Etching method, the ridge of the waveguide is constructed. With light at 1 31μm being fiber coupled to waveguide, the mode and the modulation properties of these devices are demonstrated in a micron control system.
基金The National Natural Science Foundation of China(No.61301295,61273266,61301219,61201326,61003131)the Natural Science Foundation of Anhui Province(No.1308085QF100,1408085MF113)+2 种基金the Natural Science Foundation of Jiangsu Province(No.BK20130241)the Natural Science Foundation of Higher Education Institutions of Jiangsu Province(No.12KJB510021)the Doctoral Fund of Anhui University
文摘Some factors influencing the intelligibility of the enhanced whisper in the joint time-frequency domain are evaluated. Specifically, both the spectrum density and different regions of the enhanced spectrum are analyzed. Experimental results show that for a spectrum of some density, the joint time-frequency gain-modification based speech enhancement algorithm achieves significant improvement in intelligibility. Additionally, the spectrum region where the estimated spectrum is smaller than the clean spectrum, is the most important region contributing to intelligibility improvement for the enhanced whisper. The spectrum region where the estimated spectrum is larger than twice the size of the clean spectrum is detrimental to speech intelligibility perception within the whisper context.
基金Supported by the Special Project of Basic Scientific Research of Guangxi Academy of Agricultural Sciences(Gui Nong Ke 2013YM50)the Special Project of Basic Scientific Research of Guangxi Academy of Agricultural Sciences(Gui Nong Ke 2013YM43)the Planned Project of Guangxi Scientific Research and Technological Development(Gui Ke Neng 1346007-9)~~
文摘Two-line super hybrid rice （Oryza sativa L.） Guiliangyou 2 was taken as the experimental variety, the growth and physiological characteristics of rice under conventional tillage and smashing ridge tillage were compared based on field re- search. The results showed that smashing ridge tillage was beneficial to the tillering growth of rice plants in the the middle and later periods of tillering; under the tillage mode, the white root was more, the vigour was strong during the whole growing period, the SPAD was extremely significantly higher than that of conventional tillage, the net photosynthetic rate of the leaves was high and held green long, which were beneficial to the production and accumulation of photoassimilates; during mature pe- riod, the dry matter accumulation of the overground part under smashing ridge tillage was significantly higher than that of conventional tillage, and the number of productive ears under smashing ridge tillage was more than that of conventional tillage by 27.6×10^4/hm2, thus, the yield-increasing effect was significant and in- creased by 20.36%.
