Behind the removal of tariffs lies a multiplication of benefits for both China and Africa A transformative policy is set to significantly reshape economic relations between China and Africa.China’s policy to grant ze...Behind the removal of tariffs lies a multiplication of benefits for both China and Africa A transformative policy is set to significantly reshape economic relations between China and Africa.China’s policy to grant zero-tariff treatment to imports from the 53 African nations with diplomatic ties will go into effect on 1 May this year.This initiative,which Chinese Foreign Minister Wang Yi likened to an arithmetic operation during this year’s Two Sessions,marks a further step in China’s efforts to boost imports from Africa.展开更多
In physics,our expectations for system behavior are often guided by intuitive arithmetic.For systems composed of identical units,we anticipate synergy of the contributions from these units,where 1+1=2.Conversely,for s...In physics,our expectations for system behavior are often guided by intuitive arithmetic.For systems composed of identical units,we anticipate synergy of the contributions from these units,where 1+1=2.Conversely,for systems built from opposing units,we expect cancellation of their contributions,where 1-1=0.This intuitive arithmetic has long underpinned our understanding of physical properties of materials,from electronic transport to optical responses.However,scientific breakthroughs often occur when nature reveals ways to circumvent these seemingly fundamental rules,opening new possibilities that challenge our deepest assumptions about material behavior.展开更多
The original online version of this article was revised:The layout update for Article 758 has impacted the page range in the published issue,but did not affect the scholarly content.To ensure consistency with the orig...The original online version of this article was revised:The layout update for Article 758 has impacted the page range in the published issue,but did not affect the scholarly content.To ensure consistency with the originally assigned pages(2595-2614),we will need to publish an erratum to correct the article and restore the original page range.The original article has been corrected.展开更多
Let a_(1),a_(2),a_(3)be nonzero integers with gcd(a_(1),a_(2),a_(3))=1,and let k be any positive integer,K=max[3,|a_(1)|,|a_(2)|,|a_(3)|,k].Suppose that l_(1),l_(2),l_(3)are integers each coprime to k.Suppose further ...Let a_(1),a_(2),a_(3)be nonzero integers with gcd(a_(1),a_(2),a_(3))=1,and let k be any positive integer,K=max[3,|a_(1)|,|a_(2)|,|a_(3)|,k].Suppose that l_(1),l_(2),l_(3)are integers each coprime to k.Suppose further that b is any integer satisfying some necessary congruent conditions.The solvability of linear equation a_(1)p_(1)+a_(2)p_(2)+a_(3)p_(3)=b(p_(j)=l_(j)(mod k),1≤j≤3)with prime variables pi,p_(2),ps is investigated.It is proved that if ai,a_(2),a_(3)are all positive,then the above equation is solvable whenever b≥K^(25);if a,a_(2),a_(3)are not all of the same sign,then the above equation has a solution p_(1),p_(2),p_(3)satisfying max(p_(1),p_(2),p_(3))≤3|b|+K^(25).展开更多
Reversible data hiding in encrypted images(RDH-EI)enables the concealment of secret data within ciphertext images while preserving the ability to fully recover both the original image and the hidden message.However,ex...Reversible data hiding in encrypted images(RDH-EI)enables the concealment of secret data within ciphertext images while preserving the ability to fully recover both the original image and the hidden message.However,existing RDH-EI schemes based on vacating room after encryption(VRAE)suffer from limited embedding capacity.To address this issue,we propose a method based on arithmetic coding and dual prediction for encrypted images.First,the original image is encrypted with a chunked modulus and permutation.Then,using the upper-left corner pixel of each subblock as a reference,adaptive MSB prediction and difference prediction are employed to predict the remaining pixels within the subblock.The resulting label map is then compressed via arithmetic coding to vacate the embedding space for the secret message.Finally,the separable operations of the original image restoration and secret message extraction can be performed on the basis of the type of key possessed.The experimental results demonstrate that the proposed algorithm not only successfully extracts the secret information but also recovers the original image without any loss.Furthermore,it effectively enhances the embedding capacity by fully utilizing the correlation between adjacent pixels while ensuring the security of the image.展开更多
As seismic signals propagate underground,the subsurface media absorb high-frequency components,decreasing seismic resolution and limiting the identification and characterization of thin reservoirs.To address the limit...As seismic signals propagate underground,the subsurface media absorb high-frequency components,decreasing seismic resolution and limiting the identification and characterization of thin reservoirs.To address the limitation,this paper proposes a multichannel spectral fitting(MSF)method.The MSF method aims to enhance seismic resolution by considering the spectral characteristics and the correlations between adjacent seismic traces.The key to the MSF method involves utilizing the amplitude spectrum of the attenuated Ricker wavelet to construct an objective function for spectral fitting,leading to improved seismic resolution.Furthermore,the MSF method establishes the correlation between adjacent seismic traces as a constraint to stably solve the target parameters based on the entire seismic spectrum,which helps obtain horizontally consistent and more realistic seismic signals.Synthetic and field seismic examples demonstrate that the proposed method not only provides higher-resolution seismic signals but also reveals more fine details of thin reservoirs compared to the time-variant spectral whitening method.It is concluded that the MSF method is a promising tool for seismic signal processing.展开更多
In modern industrial applications,ensuring the reliability of mechanical fittings is critical for maintaining operational safety and efficiency,particularly in power grid systems where split pins serve a pivotal role ...In modern industrial applications,ensuring the reliability of mechanical fittings is critical for maintaining operational safety and efficiency,particularly in power grid systems where split pins serve a pivotal role despite being susceptible to environmental degradation and failure.Existing UAV-based inspection systems are hampered by a low representation of split pin elements and complex backgrounds,leading to challenges in accurate fault detection and timely maintenance.To address this pressing issue,our study proposes an innovative fault detection method for split pins.The approach employs a three-step process:first,cropping operations are used to accurately isolate the fittings containing split pins;second,super-resolution reconstruction is applied to enhance image clarity and detail;and finally,an improved YOLOv8 network,augmented with inner-shape IoU and local window attention mechanisms,is utilized to refine local feature extraction and annotation accuracy.Experimental evaluations on a split pin defect dataset demonstrate robust performance,achieving an accuracy rate of 72.1%and a mean average precision(mAP)of 67.7%,thereby validating the method’s effectiveness under challenging conditions.The proposed approach contributes to the field by specifically targeting the challenges associated with split pin detection in UAV-based inspections,offering a practically applicable and reliably precise method.展开更多
The ratio of the pressure drop force to the drag force,C_(P),is concerned for a non-closely fitting spherical particle settling along the central line in long rectangular tubes with different A_(r)(A_(r)is W/H,where W...The ratio of the pressure drop force to the drag force,C_(P),is concerned for a non-closely fitting spherical particle settling along the central line in long rectangular tubes with different A_(r)(A_(r)is W/H,where W,H is length of the longer and shorter side of the rectangle respectively).Under Stokes flow conditions,C_(P0)for an infinitely small sphere in long rectangular tubes and C_(P)for a sphere in a long channel between two parallel layered barriers are both calculated.Then C_(P)of a sphere settling in long rectangular tubes are conducted with the direct-forcing fictitious domain(DF/FD)method.At large Reynolds number,the sphere settles unstably with a fluctuating velocity and C_(P).The fluctuation of Cp is much stronger than that of velocity and both fluctuations are stronger for less confined sphere.The influences of the particle Reynolds number(Re_(p))on C_(P)is similar to the existing experimental results in long circular tubes.At low Re_(p),C_(P)is a determined value and is calculated.For a given d/H(d sphere diameter),Cp gets its maximum value at one A_(r)in the range of[1,1.5].For a given A_(r),C_(P)is a quadratic function of d/H similar to that in a circular tube,and parameters of the quadratic function are got by curve fitting from numerical data.The constant term coefficients got have almost no difference with C_(P0)and are furtherly replaced by the latter to get new quadratic coefficients C_(P1).Lastly,an algebraic correlation of C_(P1)to A_(r)is developed.The predictions of Cp are good with a maximum relative error about 1.5%for a sphere with d/H not greater than0.7,compared to numerical results.展开更多
In order to rationally select the welding current of stainless steel during metal inert gas(MIG)welding,its welding current under different plate thicknesses was taken as the object of study.The scatter function provi...In order to rationally select the welding current of stainless steel during metal inert gas(MIG)welding,its welding current under different plate thicknesses was taken as the object of study.The scatter function provided by the data fitting software was used to draw scatter plots for the welding current data from two different sources,the polynomial fit(polyfit)function and the curve fitting toolbox were used to fit polynomial curves and perform optimality analysis on the fitted equations.Scatter plots and first-,second-,and third-order curve fitting equations for welding currents at different plate thicknesses were obtained,as well as curve equations for the optimum order of welding current data from two different sources.The results show that the optimization effect of the third-order curve is superior to that of the first-order and second-order curves.Finally,through the experiment,it is verified that the curve equation has some guiding significance in determining the welding current range of stainless steel MIG welding.展开更多
The energy spectrum of energetic particles in space often shows a non-thermal spectral shape with two spectral transitions/breaks over a wide energy range, carrying crucial information about their acceleration, releas...The energy spectrum of energetic particles in space often shows a non-thermal spectral shape with two spectral transitions/breaks over a wide energy range, carrying crucial information about their acceleration, release and transportation process. To self-consistently characterize the spectral features of energetic particles, here we propose a novel extended pan-spectrum(EPS) formula to fit the particle energy-flux spectrum, which has the merit that can incorporate many commonly used spectrum functions with one spectral transition, including the pan-spectrum, double-power-law, Kappa, Ellison-Ramaty(ER) functions, etc. The formula can also determine the spectral shape with two spectral transitions, including the triple-power-law function, Kappa distribution(at low energy)plus power law(at high energy), power law(at low energy) plus ER function, etc. Considering the uncertainties in both J and E, we can fit this EPS formula well to the representative energy spectra of various particle phenomena in space, including solar energetic particles(electrons, protons, ~3He and heavier ions), anomalous cosmic rays, solar wind suprathermal particles(halo and superhalo electrons;pick-up ions and the suprathermal tail), etc. Therefore, the EPS fitting can help us self-consistently determine the spectral features of different particle phenomena, and improve our understanding of the physical nature of the origin, acceleration, and transportation of energetic particles in space.展开更多
文摘Behind the removal of tariffs lies a multiplication of benefits for both China and Africa A transformative policy is set to significantly reshape economic relations between China and Africa.China’s policy to grant zero-tariff treatment to imports from the 53 African nations with diplomatic ties will go into effect on 1 May this year.This initiative,which Chinese Foreign Minister Wang Yi likened to an arithmetic operation during this year’s Two Sessions,marks a further step in China’s efforts to boost imports from Africa.
基金supported by the National Natural Science Foundation of China (Grant No.12374109)the National Key Research and Development Program of China (Grant No.2023YFA1406600)。
文摘In physics,our expectations for system behavior are often guided by intuitive arithmetic.For systems composed of identical units,we anticipate synergy of the contributions from these units,where 1+1=2.Conversely,for systems built from opposing units,we expect cancellation of their contributions,where 1-1=0.This intuitive arithmetic has long underpinned our understanding of physical properties of materials,from electronic transport to optical responses.However,scientific breakthroughs often occur when nature reveals ways to circumvent these seemingly fundamental rules,opening new possibilities that challenge our deepest assumptions about material behavior.
文摘The original online version of this article was revised:The layout update for Article 758 has impacted the page range in the published issue,but did not affect the scholarly content.To ensure consistency with the originally assigned pages(2595-2614),we will need to publish an erratum to correct the article and restore the original page range.The original article has been corrected.
文摘Let a_(1),a_(2),a_(3)be nonzero integers with gcd(a_(1),a_(2),a_(3))=1,and let k be any positive integer,K=max[3,|a_(1)|,|a_(2)|,|a_(3)|,k].Suppose that l_(1),l_(2),l_(3)are integers each coprime to k.Suppose further that b is any integer satisfying some necessary congruent conditions.The solvability of linear equation a_(1)p_(1)+a_(2)p_(2)+a_(3)p_(3)=b(p_(j)=l_(j)(mod k),1≤j≤3)with prime variables pi,p_(2),ps is investigated.It is proved that if ai,a_(2),a_(3)are all positive,then the above equation is solvable whenever b≥K^(25);if a,a_(2),a_(3)are not all of the same sign,then the above equation has a solution p_(1),p_(2),p_(3)satisfying max(p_(1),p_(2),p_(3))≤3|b|+K^(25).
基金supported by the Provincial Colleges Quality Project of Anhui Prov-ince(2020xsxxkc047)the National Undergraduate Innovation and Entrepreneurship Training Program(2023103570289).
文摘Reversible data hiding in encrypted images(RDH-EI)enables the concealment of secret data within ciphertext images while preserving the ability to fully recover both the original image and the hidden message.However,existing RDH-EI schemes based on vacating room after encryption(VRAE)suffer from limited embedding capacity.To address this issue,we propose a method based on arithmetic coding and dual prediction for encrypted images.First,the original image is encrypted with a chunked modulus and permutation.Then,using the upper-left corner pixel of each subblock as a reference,adaptive MSB prediction and difference prediction are employed to predict the remaining pixels within the subblock.The resulting label map is then compressed via arithmetic coding to vacate the embedding space for the secret message.Finally,the separable operations of the original image restoration and secret message extraction can be performed on the basis of the type of key possessed.The experimental results demonstrate that the proposed algorithm not only successfully extracts the secret information but also recovers the original image without any loss.Furthermore,it effectively enhances the embedding capacity by fully utilizing the correlation between adjacent pixels while ensuring the security of the image.
基金supported in part by the National Natural Science Foundation of China under Grant 42174164 and Grant 41704132in part by the Key Program of the Joint Fund of the Science,Technology,and Education of Sichuan Province,China under Grant 2024NSFSC1955+4 种基金in part by the Natural Science Foundation of Sichuan Province,China under Grant 2024NSFSC0080in part by the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project under Grant SKLGP2022Z011in part by the Chengdu University of Technology Postgraduate Innovative Cultivation Program:Spatiotemporal Characterization of Seismic Signals for Tight Channel Sandstone Gas Reservoirs in the Synchro-Squeezing/Extracting Transform Domain under Grant CDUT2023BJCx002in part by the Creative Research Groups of the Natural Science Foundation of Sichuan under Grant 2023NSFSC198414th Five Year Plan Major Science and Technology Project of CNOOC under Grant KJGG2022-0903.
文摘As seismic signals propagate underground,the subsurface media absorb high-frequency components,decreasing seismic resolution and limiting the identification and characterization of thin reservoirs.To address the limitation,this paper proposes a multichannel spectral fitting(MSF)method.The MSF method aims to enhance seismic resolution by considering the spectral characteristics and the correlations between adjacent seismic traces.The key to the MSF method involves utilizing the amplitude spectrum of the attenuated Ricker wavelet to construct an objective function for spectral fitting,leading to improved seismic resolution.Furthermore,the MSF method establishes the correlation between adjacent seismic traces as a constraint to stably solve the target parameters based on the entire seismic spectrum,which helps obtain horizontally consistent and more realistic seismic signals.Synthetic and field seismic examples demonstrate that the proposed method not only provides higher-resolution seismic signals but also reveals more fine details of thin reservoirs compared to the time-variant spectral whitening method.It is concluded that the MSF method is a promising tool for seismic signal processing.
基金Fundamental Research Funds for the Central Universities(2023MS134)。
文摘In modern industrial applications,ensuring the reliability of mechanical fittings is critical for maintaining operational safety and efficiency,particularly in power grid systems where split pins serve a pivotal role despite being susceptible to environmental degradation and failure.Existing UAV-based inspection systems are hampered by a low representation of split pin elements and complex backgrounds,leading to challenges in accurate fault detection and timely maintenance.To address this pressing issue,our study proposes an innovative fault detection method for split pins.The approach employs a three-step process:first,cropping operations are used to accurately isolate the fittings containing split pins;second,super-resolution reconstruction is applied to enhance image clarity and detail;and finally,an improved YOLOv8 network,augmented with inner-shape IoU and local window attention mechanisms,is utilized to refine local feature extraction and annotation accuracy.Experimental evaluations on a split pin defect dataset demonstrate robust performance,achieving an accuracy rate of 72.1%and a mean average precision(mAP)of 67.7%,thereby validating the method’s effectiveness under challenging conditions.The proposed approach contributes to the field by specifically targeting the challenges associated with split pin detection in UAV-based inspections,offering a practically applicable and reliably precise method.
基金supported by the National Natural Science Foundation of China(12132015,12332015)。
文摘The ratio of the pressure drop force to the drag force,C_(P),is concerned for a non-closely fitting spherical particle settling along the central line in long rectangular tubes with different A_(r)(A_(r)is W/H,where W,H is length of the longer and shorter side of the rectangle respectively).Under Stokes flow conditions,C_(P0)for an infinitely small sphere in long rectangular tubes and C_(P)for a sphere in a long channel between two parallel layered barriers are both calculated.Then C_(P)of a sphere settling in long rectangular tubes are conducted with the direct-forcing fictitious domain(DF/FD)method.At large Reynolds number,the sphere settles unstably with a fluctuating velocity and C_(P).The fluctuation of Cp is much stronger than that of velocity and both fluctuations are stronger for less confined sphere.The influences of the particle Reynolds number(Re_(p))on C_(P)is similar to the existing experimental results in long circular tubes.At low Re_(p),C_(P)is a determined value and is calculated.For a given d/H(d sphere diameter),Cp gets its maximum value at one A_(r)in the range of[1,1.5].For a given A_(r),C_(P)is a quadratic function of d/H similar to that in a circular tube,and parameters of the quadratic function are got by curve fitting from numerical data.The constant term coefficients got have almost no difference with C_(P0)and are furtherly replaced by the latter to get new quadratic coefficients C_(P1).Lastly,an algebraic correlation of C_(P1)to A_(r)is developed.The predictions of Cp are good with a maximum relative error about 1.5%for a sphere with d/H not greater than0.7,compared to numerical results.
基金supported by the National Natural Science Foundation of China(52301098)。
文摘In order to rationally select the welding current of stainless steel during metal inert gas(MIG)welding,its welding current under different plate thicknesses was taken as the object of study.The scatter function provided by the data fitting software was used to draw scatter plots for the welding current data from two different sources,the polynomial fit(polyfit)function and the curve fitting toolbox were used to fit polynomial curves and perform optimality analysis on the fitted equations.Scatter plots and first-,second-,and third-order curve fitting equations for welding currents at different plate thicknesses were obtained,as well as curve equations for the optimum order of welding current data from two different sources.The results show that the optimization effect of the third-order curve is superior to that of the first-order and second-order curves.Finally,through the experiment,it is verified that the curve equation has some guiding significance in determining the welding current range of stainless steel MIG welding.
基金supported in part by NSFC under contracts 42225404, 42127803, 42150105by National Key R&D Program of China No. 2021YFA0718600by ISSI-BJ through the international teams Nos. 23-581 and 56。
文摘The energy spectrum of energetic particles in space often shows a non-thermal spectral shape with two spectral transitions/breaks over a wide energy range, carrying crucial information about their acceleration, release and transportation process. To self-consistently characterize the spectral features of energetic particles, here we propose a novel extended pan-spectrum(EPS) formula to fit the particle energy-flux spectrum, which has the merit that can incorporate many commonly used spectrum functions with one spectral transition, including the pan-spectrum, double-power-law, Kappa, Ellison-Ramaty(ER) functions, etc. The formula can also determine the spectral shape with two spectral transitions, including the triple-power-law function, Kappa distribution(at low energy)plus power law(at high energy), power law(at low energy) plus ER function, etc. Considering the uncertainties in both J and E, we can fit this EPS formula well to the representative energy spectra of various particle phenomena in space, including solar energetic particles(electrons, protons, ~3He and heavier ions), anomalous cosmic rays, solar wind suprathermal particles(halo and superhalo electrons;pick-up ions and the suprathermal tail), etc. Therefore, the EPS fitting can help us self-consistently determine the spectral features of different particle phenomena, and improve our understanding of the physical nature of the origin, acceleration, and transportation of energetic particles in space.
