To address the issues of unknown target size,blurred edges,background interference and low contrast in infrared small target detection,this paper proposes a method based on density peaks searching and weighted multi-f...To address the issues of unknown target size,blurred edges,background interference and low contrast in infrared small target detection,this paper proposes a method based on density peaks searching and weighted multi-feature local difference.Firstly,an improved high-boost filter is used for preprocessing to eliminate background clutter and high-brightness interference,thereby increasing the probability of capturing real targets in the density peak search.Secondly,a triple-layer window is used to extract features from the area surrounding candidate targets,addressing the uncertainty of small target sizes.By calculating multi-feature local differences between the triple-layer windows,the problems of blurred target edges and low contrast are resolved.To balance the contribution of different features,intra-class distance is used to calculate weights,achieving weighted fusion of multi-feature local differences to obtain the weighted multi-feature local differences of candidate targets.The real targets are then extracted using the interquartile range.Experiments on datasets such as SIRST and IRSTD-IK show that the proposed method is suitable for various complex types and demonstrates good robustness and detection performance.展开更多
Detrital geochronology fundamentally involves the quantification of major age ranges and their weights winthin an age distribution.This study presents a streamlined approach,modeling the age distribution of detrital z...Detrital geochronology fundamentally involves the quantification of major age ranges and their weights winthin an age distribution.This study presents a streamlined approach,modeling the age distribution of detrital zircons using a normal mixture model,and employs the Expectation-Maximization(EM)algorithm for precise estimations.A method is introduced to automatically select appropriate initial mean values for EM algorithm,enhancing its efficacy in detrital geochronology.This process entails multiple trials with varying numbers of age components leading to diverse k-component models.The model with the lowest Bayesian Information Criterion(BIC)is identified as the most suitable.For accurate component number and weight determination,a substantial sample size(n>200)is advisable. Our findings based on both synthetic and empirical datasets confirm that the normal mixture model,refined by the EM algorithm,reliably identifies key age parameters with minimal error.As a kind of probability density estimator,the normal mixture model offers a novel visualization tool for detrital data and an alternative foundation for KDE in calculating existing similarity metrics.Another focus of this study is the critical examination of quantitative metrics for comparing detrital zircon age patterns.Through a case study,this study demonstrates that metrics based on empirical cumulative probability distribution(such as K-S and Kuiper statistics)may lead to erroneous conclusions.The employment of the Kullback-Leibler(KL)divergence,a metric grounded in probability density estimation,is proposed.Reference critical values,simulated via the Monte Carlo method,provide more objective benchmarks for these quantitative metrics. All methodologies discussed are encapsulated in a series of MATLAB scripts,available as open-source code and a standalone application,facilitating wider adoption and application in the field.展开更多
The navigation system plays a pivotal role in guiding aircraft along designated routes,ensuring precise and punctual arrival at destinations.The integration of scene matching with an inertial navigation system enhance...The navigation system plays a pivotal role in guiding aircraft along designated routes,ensuring precise and punctual arrival at destinations.The integration of scene matching with an inertial navigation system enhances the capability of providing a dependable guarantee for success-ful accomplishment of flight missions.Nonetheless,assuring reliability in scene matching encoun-ters significant challenges in areas characterized by repetitive or weak textures.To tackle these challenges,we propose a novel method to assess the reliability of scene matching based on the dis-tinctive characteristics of correlation peaks.The proposed method leverages the fact that the sim-ilarity of the optimal matching result is significantly higher than that of the surrounding area,and three novel indicators(e.g.,relative height,slope of a correlation peak,and ratio of a sub peak to the main peak)are determined to conjointly evaluate the reliability of scene matching.The pro-posed method entails matching a real-time image with a reference image to generate a correlation surface.A correlation peak is then obtained by extracting the portion of the correlation surface exhibiting a significant gradient.Additionally,the matching reliability is determined by considering the relative height,slope,and ratio of the peak collectively.Exhaustive experimental results with two sets of data demonstrate that the proposed method significantly outperforms traditional approaches in terms of precision,recall,and F1-score.These experiments also establish the efficacy of the proposed method in achieving reliable matching in challenging environments characterized by repetitive and weak textures.This enhancement holds the potential to significantly elevate scene-matching-based navigation.展开更多
A resolution method based on Gaussian-like distribution for overlapped linear sweep polarographic peaks was proposed to simultaneously detect the polymetallic components, such as Zn（Ⅱ） and Co（Ⅱ）, coexisting in t...A resolution method based on Gaussian-like distribution for overlapped linear sweep polarographic peaks was proposed to simultaneously detect the polymetallic components, such as Zn（Ⅱ） and Co（Ⅱ）, coexisting in the leaching solution of zinc hydrometallurgy. A Gaussian-like distribution was constructed as the sub-model of overlapped peaks by analyzing the characteristics of linear sweep polarographic curve. Then, the abscissas of each peak and trough were pinpointed through multi-resolution wavelet decomposition, the curve and its derivative curves were fitted by using nonlinear weighted least squares （NWLS）. Finally, overlapped peaks were resolved into independent sub-peaks based on fitted reconstruction parameters. The experimental results show that the relative error of half-wave potential pinpointed by multi-resolution wavelet decomposition is less than 1% and the accuracy of Ip fitted by NWLS is higher than 96%. The proposed resolution method is effective for overlapped linear sweep polarographic peaks of Zn（Ⅱ） and Co（Ⅱ）.展开更多
Different artificial two-stage ageing behaviors and their effect on stress corrosion cracking （SCC） susceptibility of AI-Zn-Mg alloy have been investigated. The experimental results show that two hardness peaks pres...Different artificial two-stage ageing behaviors and their effect on stress corrosion cracking （SCC） susceptibility of AI-Zn-Mg alloy have been investigated. The experimental results show that two hardness peaks present on the second-stage ageing-hardening curve when the first-stage ageing is dealt with comparatively lower temperature than the conventional one. The first peak is caused by dispersive and evenly distributed G.P. zones, while η ′phases and coarsened G.P. zones contribute to the second peak. Tensile strength of experimental alloy raises 9.6% （33.2 MPa） and SCC susceptibility decreases 38.9% by applying the second peak ageing regime instead of conventional T73. AI-Zn-Mg alloy obtains high strength and SCC resistance due to its finely dispersive matrix precipitates （MPts）, coarsened and discontinuous grain boundary precipitates （GBPs）, as well as the narrow precipitate free zone （PFZ） in the second peak ageing condition. 2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.展开更多
Modeling of energy consumption(EC) and effluent quality(EQ) are very essential problems that need to be solved for the multiobjective optimal control in the wastewater treatment process(WWTP). To address this issue, a...Modeling of energy consumption(EC) and effluent quality(EQ) are very essential problems that need to be solved for the multiobjective optimal control in the wastewater treatment process(WWTP). To address this issue, a density peaks-based adaptive fuzzy neural network(DP-AFNN) is proposed in this study. To obtain suitable fuzzy rules, a DP-based clustering method is applied to fit the cluster centers to process nonlinearity.The parameters of the extracted fuzzy rules are fine-tuned based on the improved Levenberg-Marquardt algorithm during the training process. Furthermore, the analysis of convergence is performed to guarantee the successful application of the DPAFNN. Finally, the proposed DP-AFNN is utilized to develop the models of EC and EQ in the WWTP. The experimental results show that the proposed DP-AFNN can achieve fast convergence speed and high prediction accuracy in comparison with some existing methods.展开更多
This article describes a hybrid simulation method to generate artificial ground motion time histories that are compatible with specified peak seismic acceleration, velocity and displacement as well as the target respo...This article describes a hybrid simulation method to generate artificial ground motion time histories that are compatible with specified peak seismic acceleration, velocity and displacement as well as the target response spectrum of absolute acceleration. First, based on traditional methods that match the target spectrum in the frequency domain, an initial acceleration time history was synthesized to satisfy the specified peak acceleration, target spectral acceleration and intensity envelope. Second, by using the inversion formula of the seismic input to a linear single-degree-of-freedom system and by superimposing a series of narrow-band time histories in the time domain, the initial time history is further modified to allow its peak velocity and displacement to approach the targets and improve its matching precision with the target spectrum. Numerical examples are provided to demonstrate that the proposed method achieves good agreement with the target values.展开更多
The ambiguity function of Chinese standard Digital Television Terrestrial Broadcasting (DTTB) signals for passive radar contains one main peak and many side peaks. The side peaks may cause the false alarms. The relati...The ambiguity function of Chinese standard Digital Television Terrestrial Broadcasting (DTTB) signals for passive radar contains one main peak and many side peaks. The side peaks may cause the false alarms. The relative positions and the reasons for the side peaks are analyzed and a new algorithm for side peaks suppression is proposed in this paper. The algorithm, in consideration of the characteristics of the structure of the frame, can eliminate the side peaks completely in the valid Doppler observation interval by setting the reference signals to zero at equal intervals. Both the simulative and experimental results show that this algorithm can improve the performance of target detection of the passive radar based on DTTB signal.展开更多
In this article,we consider the following coupled fractional nonlinear Schrödinger system in R^{(−Δ)su+P(x)u=μ1|u|^2p−2u+β|u|p|u|p−2u,x∈RN,(−Δ)sv+Q(x)v=μ2|v|^2p−2v+β|v|p|v|p−2v,x∈RN,u,v∈Hs(RN),where N≥2...In this article,we consider the following coupled fractional nonlinear Schrödinger system in R^{(−Δ)su+P(x)u=μ1|u|^2p−2u+β|u|p|u|p−2u,x∈RN,(−Δ)sv+Q(x)v=μ2|v|^2p−2v+β|v|p|v|p−2v,x∈RN,u,v∈Hs(RN),where N≥2,0<s<1,1<p<NN−2s,μ1>0,μ2>0 andβ∈R is a coupling constant.We prove that it has infinitely many non-radial positive solutions under some additional conditions on P(x),Q(x),p andβ.More precisely,we will show that for the attractive case,it has infinitely many non-radial positive synchronized vector solutions,and for the repulsive case,infinitely many non-radial positive segregated vector solutions can be found,where we assume that P(x)and Q(x)satisfy some algebraic decay at infinity.展开更多
The temperature dependence of internal friction （ T- tan φ curves） in pure aluminium （Al） is measured at sixteen different frequencies. Based on T- tan φ curves, the frequency dependence of internal friction （f...The temperature dependence of internal friction （ T- tan φ curves） in pure aluminium （Al） is measured at sixteen different frequencies. Based on T- tan φ curves, the frequency dependence of internal friction （f -tan φ curves） is also obtained by the interpolation method. An internal friction peak is observed in both the T - tan φ curves and the f - tan φ curves. The activation energy of the peak in the f - tan φ curves is found to be 2.08 ± 0.02 eV and compared to the value of 1.60 ± 0.04 eV in the T - tan φ curves. It is suggested that the change of relaxation strength with temperature should be considered when one calculates the activation energy of the peak in T- tan φ curves.展开更多
Performing cluster analysis on molecular conformation is an important way to find the representative conformation in the molecular dynamics trajectories.Usually,it is a critical step for interpreting complex conformat...Performing cluster analysis on molecular conformation is an important way to find the representative conformation in the molecular dynamics trajectories.Usually,it is a critical step for interpreting complex conformational changes or interaction mechanisms.As one of the density-based clustering algorithms,find density peaks(FDP)is an accurate and reasonable candidate for the molecular conformation clustering.However,facing the rapidly increasing simulation length due to the increase in computing power,the low computing efficiency of FDP limits its application potential.Here we propose a marginal extension to FDP named K-means find density peaks(KFDP)to solve the mass source consuming problem.In KFDP,the points are initially clustered by a high efficiency clustering algorithm,such as K-means.Cluster centers are defined as typical points with a weight which represents the cluster size.Then,the weighted typical points are clustered again by FDP,and then are refined as core,boundary,and redefined halo points.In this way,KFDP has comparable accuracy as FDP but its computational complexity is reduced from O(n^(2))to O(n).We apply and test our KFDP method to the trajectory data of multiple small proteins in terms of torsion angle,secondary structure or contact map.The comparing results with K-means and density-based spatial clustering of applications with noise show the validation of the proposed KFDP.展开更多
We present a novel method to analyze extreme events of flows over manifolds called Peaks Over Manifold (POM). Here we show that under general and realistic hypotheses, the distribution of affectation measures converge...We present a novel method to analyze extreme events of flows over manifolds called Peaks Over Manifold (POM). Here we show that under general and realistic hypotheses, the distribution of affectation measures converges to a Generalized Pareto Distribution (GPD). The method is applicable to floods, ice cover extent, extreme rainfall or marine heatwaves. We present an application to a synthetic data set on tide height and to real ice cover data in Antartica.展开更多
We present a novel unsupervised integrated score framework to generate generic extractive multi- document summaries by ranking sentences based on dynamic programming （DP） strategy. Considering that cluster-based met...We present a novel unsupervised integrated score framework to generate generic extractive multi- document summaries by ranking sentences based on dynamic programming （DP） strategy. Considering that cluster-based methods proposed by other researchers tend to ignore informativeness of words when they generate summaries, our proposed framework takes relevance, diversity, informativeness and length constraint of sentences into consideration comprehensively. We apply Density Peaks Clustering （DPC） to get relevance scores and diversity scores of sentences simultaneously. Our framework produces the best performance on DUC2004, 0.396 of ROUGE-1 score, 0.094 of ROUGE-2 score and 0.143 of ROUGE-SU4 which outperforms a series of popular baselines, such as DUC Best, FGB [7], and BSTM [10].展开更多
The PP intervals of pulse main peaks from healthy and unhealthy people(arrhythmia) have different nonlinear char-acteristics. In this paper,the extraction of PP intervals of pulse main peaks is achieved by picking up ...The PP intervals of pulse main peaks from healthy and unhealthy people(arrhythmia) have different nonlinear char-acteristics. In this paper,the extraction of PP intervals of pulse main peaks is achieved by picking up P peaks of pulse wave with wavelet transform. Furthermore,several nonlinear parameters(correlative dimensions,maximum Lyapunov exponents,com-plexity and approximate entropy) of the PP intervals of pulse main peaks extracted from normal and unhealthy pulse signals are calculated,with the results showing that these nonlinear parameters calculated from the main wave interval signals are helpful for analyzing human's health state and diagnosing heart diseases.展开更多
In this work,phase segregation and localization of PBSU have been investigated with the combination of SAXS and DSC in its blend with PVDF.After stepwise crystallization of PVDF and PBSU,there are double melting peaks...In this work,phase segregation and localization of PBSU have been investigated with the combination of SAXS and DSC in its blend with PVDF.After stepwise crystallization of PVDF and PBSU,there are double melting peaks of PBSU in DSC and double scattering peaks in SAXS.It has been demonstrated that double peaks can be attributed to the localization of PBSU in interlamellar/interfibrillar region in pre-formed PVDF crystal framework.In the case of low content of PBSU in blend,PBSU is trapped into the interlamellar region of PVDF crystals,resulting in the alternating lamellae crystal of them and the first peak(with low-q)in SAXS.The enhanced confinement effect produces thinner PBSU lamellae,corresponding to the lower melting temperature in DSC.Upon increasing its content in blend,some PBSU segregates in interfibrillar regions in addition to the enrichment in interlamellar regions of PVDF crystal framework.The larger space and higher concentration of PBSU in interfibrillarregions contribute to periodic lamellae structure of PBSU with higher thickness,which is the reason for the second peak(with high-q)in SAXS and DSC.Our results not only clarify the relationship between localization of PBSU in interlamellar/interfibrillar regions and double peaks in DSC/SAXS,but also provide a novel strategy to detect the interlamellar and interfibrillar segregation of low-T_(m) component in miscible crystalline/crystalline blend.展开更多
A new method called spline convolution (SC) for resolving overlapped peaks was proposed in this paper. The differential pulse voltammetric overlapped peaks of mixtures of Pb(II) and Tl(I) were investigated by this me...A new method called spline convolution (SC) for resolving overlapped peaks was proposed in this paper. The differential pulse voltammetric overlapped peaks of mixtures of Pb(II) and Tl(I) were investigated by this method, and satisfactory results were obtained. The results show excellent correlation between peak areas of the processed signals and the concentrations.展开更多
In this paper, we investigate a metamaterial formed by a planar array of a metallic L-shaped structure and a cut wire(CW), which behaves as an analogue of the electromagnetically induced transparency(EIT). The double ...In this paper, we investigate a metamaterial formed by a planar array of a metallic L-shaped structure and a cut wire(CW), which behaves as an analogue of the electromagnetically induced transparency(EIT). The double transmission peaks are formed by the destructive interference of two bright-modes and a quasi-dark mode. The two bright-modes are respectively excited by the L-shaped structure and CW. The unit structure itself performs a quasi-dark mode. The group refractive indexes are over 20 in the first transmission peak, and 117 in the second transmission peak, thus offering potential applications in slow light devices. Finally, all the above characteristics are achieved in just one simple unit cell.展开更多
Energy planning must anticipate the development and strengthening of power grids, power plants construction times, and the provision of energy resources with the aim of increasing security of supply and its quality. T...Energy planning must anticipate the development and strengthening of power grids, power plants construction times, and the provision of energy resources with the aim of increasing security of supply and its quality. This work presents a methodology for predicting power peaks in mainland Spain’s system in the decade 2011-2020. Forecasts of total electricity demand of Spanish energy authorities set the boundary conditions. The accuracy of the results has successfully been compared with records of demand (2000-2010) and with various predictions published. Three patterns have been observed: 1) efficiency in the winter peak;2) increasing trend in the summer peak;3) increasing trend in the annual valley of demand. By 2020, 58.1 GW and 53.0 GW are expected, respectively, as winter and summer peaks in a business-as-usual scenario. If the observed tendencies continue, former values can go down to 55.5 GW in winter and go up to 54.7 GW in summer. The annual minimum valley of demand will raise 5.5 GW, up to 23.4 GW. These detailed predictions can be very useful to identify the types of power plants needed to have an optimum structure in the electricity industry.展开更多
Liquid indium's structure was studied at 280, 390, 550, 650, and 750 deg Crespectively by using an elevated temperature X-ray diffractometer, and its radial distributionfunction (RDF) at different temperatures was...Liquid indium's structure was studied at 280, 390, 550, 650, and 750 deg Crespectively by using an elevated temperature X-ray diffractometer, and its radial distributionfunction (RDF) at different temperatures was decomposed into 4 Gaussian peaks in the range of0.2-0.6nm. Positions of the decomposed Gaussian peaks were compared with the nearest and the secondnearest neighbor atomic distances, respectively. It is shown that the position of the firstdecomposed Gaussian peak is similar to the nearest neighbor atomic distance in liquid In at thecorresponding temperature, and that of the third decomposed Gaussian peak is similar to the secondnearest neighbor atomic distance. Moreover, the first and the third Gaussian peaks correspond to thefirst and the second atom shells of liquid In at the corresponding temperatures, respectively.Therefore, the position and the area of Gaussian peaks can represent the position and atom number ofcorresponding shells. Based on this result, short-range structural changes in liquid In wasstudied. It was found that the first and the second shells are close to the referred atom, and theatom number at the shells decreases with the increasing temperature from 280 to 750 deg C. Indifferent ranges of temperature, structural changes in the first and the second shells showdifferent features.展开更多
基金supported by the National Natural Science Foundation of China (No.52205548)。
文摘To address the issues of unknown target size,blurred edges,background interference and low contrast in infrared small target detection,this paper proposes a method based on density peaks searching and weighted multi-feature local difference.Firstly,an improved high-boost filter is used for preprocessing to eliminate background clutter and high-brightness interference,thereby increasing the probability of capturing real targets in the density peak search.Secondly,a triple-layer window is used to extract features from the area surrounding candidate targets,addressing the uncertainty of small target sizes.By calculating multi-feature local differences between the triple-layer windows,the problems of blurred target edges and low contrast are resolved.To balance the contribution of different features,intra-class distance is used to calculate weights,achieving weighted fusion of multi-feature local differences to obtain the weighted multi-feature local differences of candidate targets.The real targets are then extracted using the interquartile range.Experiments on datasets such as SIRST and IRSTD-IK show that the proposed method is suitable for various complex types and demonstrates good robustness and detection performance.
文摘Detrital geochronology fundamentally involves the quantification of major age ranges and their weights winthin an age distribution.This study presents a streamlined approach,modeling the age distribution of detrital zircons using a normal mixture model,and employs the Expectation-Maximization(EM)algorithm for precise estimations.A method is introduced to automatically select appropriate initial mean values for EM algorithm,enhancing its efficacy in detrital geochronology.This process entails multiple trials with varying numbers of age components leading to diverse k-component models.The model with the lowest Bayesian Information Criterion(BIC)is identified as the most suitable.For accurate component number and weight determination,a substantial sample size(n>200)is advisable. Our findings based on both synthetic and empirical datasets confirm that the normal mixture model,refined by the EM algorithm,reliably identifies key age parameters with minimal error.As a kind of probability density estimator,the normal mixture model offers a novel visualization tool for detrital data and an alternative foundation for KDE in calculating existing similarity metrics.Another focus of this study is the critical examination of quantitative metrics for comparing detrital zircon age patterns.Through a case study,this study demonstrates that metrics based on empirical cumulative probability distribution(such as K-S and Kuiper statistics)may lead to erroneous conclusions.The employment of the Kullback-Leibler(KL)divergence,a metric grounded in probability density estimation,is proposed.Reference critical values,simulated via the Monte Carlo method,provide more objective benchmarks for these quantitative metrics. All methodologies discussed are encapsulated in a series of MATLAB scripts,available as open-source code and a standalone application,facilitating wider adoption and application in the field.
基金supported by the National Natural Science Foundation of China(No.42271446).
文摘The navigation system plays a pivotal role in guiding aircraft along designated routes,ensuring precise and punctual arrival at destinations.The integration of scene matching with an inertial navigation system enhances the capability of providing a dependable guarantee for success-ful accomplishment of flight missions.Nonetheless,assuring reliability in scene matching encoun-ters significant challenges in areas characterized by repetitive or weak textures.To tackle these challenges,we propose a novel method to assess the reliability of scene matching based on the dis-tinctive characteristics of correlation peaks.The proposed method leverages the fact that the sim-ilarity of the optimal matching result is significantly higher than that of the surrounding area,and three novel indicators(e.g.,relative height,slope of a correlation peak,and ratio of a sub peak to the main peak)are determined to conjointly evaluate the reliability of scene matching.The pro-posed method entails matching a real-time image with a reference image to generate a correlation surface.A correlation peak is then obtained by extracting the portion of the correlation surface exhibiting a significant gradient.Additionally,the matching reliability is determined by considering the relative height,slope,and ratio of the peak collectively.Exhaustive experimental results with two sets of data demonstrate that the proposed method significantly outperforms traditional approaches in terms of precision,recall,and F1-score.These experiments also establish the efficacy of the proposed method in achieving reliable matching in challenging environments characterized by repetitive and weak textures.This enhancement holds the potential to significantly elevate scene-matching-based navigation.
基金Project(2012BAF03B05)supported by the National Key Technology R&D Program of ChinaProject(61025015)supported by the National Natural Science Foundation for Distinguished Young Scholars of China+1 种基金Project(61273185)supported by the National Natural Science Foundation of ChinaProject(2012CK4018)supported by the Science and Technology Project of Hunan Province,China
文摘A resolution method based on Gaussian-like distribution for overlapped linear sweep polarographic peaks was proposed to simultaneously detect the polymetallic components, such as Zn（Ⅱ） and Co（Ⅱ）, coexisting in the leaching solution of zinc hydrometallurgy. A Gaussian-like distribution was constructed as the sub-model of overlapped peaks by analyzing the characteristics of linear sweep polarographic curve. Then, the abscissas of each peak and trough were pinpointed through multi-resolution wavelet decomposition, the curve and its derivative curves were fitted by using nonlinear weighted least squares （NWLS）. Finally, overlapped peaks were resolved into independent sub-peaks based on fitted reconstruction parameters. The experimental results show that the relative error of half-wave potential pinpointed by multi-resolution wavelet decomposition is less than 1% and the accuracy of Ip fitted by NWLS is higher than 96%. The proposed resolution method is effective for overlapped linear sweep polarographic peaks of Zn（Ⅱ） and Co（Ⅱ）.
基金financial supports by National Key R&D Program of China (No. 2016YFB1200600 and No. 2016YFB1200504)Strategic Priority Program of the Chinese Academy of Sciences (No. XDB22000000)
文摘Different artificial two-stage ageing behaviors and their effect on stress corrosion cracking （SCC） susceptibility of AI-Zn-Mg alloy have been investigated. The experimental results show that two hardness peaks present on the second-stage ageing-hardening curve when the first-stage ageing is dealt with comparatively lower temperature than the conventional one. The first peak is caused by dispersive and evenly distributed G.P. zones, while η ′phases and coarsened G.P. zones contribute to the second peak. Tensile strength of experimental alloy raises 9.6% （33.2 MPa） and SCC susceptibility decreases 38.9% by applying the second peak ageing regime instead of conventional T73. AI-Zn-Mg alloy obtains high strength and SCC resistance due to its finely dispersive matrix precipitates （MPts）, coarsened and discontinuous grain boundary precipitates （GBPs）, as well as the narrow precipitate free zone （PFZ） in the second peak ageing condition. 2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.
基金supported by the National Science Foundation for Distinguished Young Scholars of China(61225016)the State Key Program of National Natural Science of China(61533002)
文摘Modeling of energy consumption(EC) and effluent quality(EQ) are very essential problems that need to be solved for the multiobjective optimal control in the wastewater treatment process(WWTP). To address this issue, a density peaks-based adaptive fuzzy neural network(DP-AFNN) is proposed in this study. To obtain suitable fuzzy rules, a DP-based clustering method is applied to fit the cluster centers to process nonlinearity.The parameters of the extracted fuzzy rules are fine-tuned based on the improved Levenberg-Marquardt algorithm during the training process. Furthermore, the analysis of convergence is performed to guarantee the successful application of the DPAFNN. Finally, the proposed DP-AFNN is utilized to develop the models of EC and EQ in the WWTP. The experimental results show that the proposed DP-AFNN can achieve fast convergence speed and high prediction accuracy in comparison with some existing methods.
基金National Natural Science Foundation of ChinaUnder Grant No.50278090
文摘This article describes a hybrid simulation method to generate artificial ground motion time histories that are compatible with specified peak seismic acceleration, velocity and displacement as well as the target response spectrum of absolute acceleration. First, based on traditional methods that match the target spectrum in the frequency domain, an initial acceleration time history was synthesized to satisfy the specified peak acceleration, target spectral acceleration and intensity envelope. Second, by using the inversion formula of the seismic input to a linear single-degree-of-freedom system and by superimposing a series of narrow-band time histories in the time domain, the initial time history is further modified to allow its peak velocity and displacement to approach the targets and improve its matching precision with the target spectrum. Numerical examples are provided to demonstrate that the proposed method achieves good agreement with the target values.
文摘The ambiguity function of Chinese standard Digital Television Terrestrial Broadcasting (DTTB) signals for passive radar contains one main peak and many side peaks. The side peaks may cause the false alarms. The relative positions and the reasons for the side peaks are analyzed and a new algorithm for side peaks suppression is proposed in this paper. The algorithm, in consideration of the characteristics of the structure of the frame, can eliminate the side peaks completely in the valid Doppler observation interval by setting the reference signals to zero at equal intervals. Both the simulative and experimental results show that this algorithm can improve the performance of target detection of the passive radar based on DTTB signal.
基金supported by NSF of China(11701107)NSF of Guangxi Province (2017GXNSFBA198190)+1 种基金the second author is supported by NSF of China (11501143)the PhD launch scientific research projects of Guizhou Normal University (2014)
文摘In this article,we consider the following coupled fractional nonlinear Schrödinger system in R^{(−Δ)su+P(x)u=μ1|u|^2p−2u+β|u|p|u|p−2u,x∈RN,(−Δ)sv+Q(x)v=μ2|v|^2p−2v+β|v|p|v|p−2v,x∈RN,u,v∈Hs(RN),where N≥2,0<s<1,1<p<NN−2s,μ1>0,μ2>0 andβ∈R is a coupling constant.We prove that it has infinitely many non-radial positive solutions under some additional conditions on P(x),Q(x),p andβ.More precisely,we will show that for the attractive case,it has infinitely many non-radial positive synchronized vector solutions,and for the repulsive case,infinitely many non-radial positive segregated vector solutions can be found,where we assume that P(x)and Q(x)satisfy some algebraic decay at infinity.
基金Supported by the National Natural Science Foundation of China Grant Nos 10171067 and 10374089, and the Foundation of the Institute of Solid State Physics, Chinese Academy of Sciences.
文摘The temperature dependence of internal friction （ T- tan φ curves） in pure aluminium （Al） is measured at sixteen different frequencies. Based on T- tan φ curves, the frequency dependence of internal friction （f -tan φ curves） is also obtained by the interpolation method. An internal friction peak is observed in both the T - tan φ curves and the f - tan φ curves. The activation energy of the peak in the f - tan φ curves is found to be 2.08 ± 0.02 eV and compared to the value of 1.60 ± 0.04 eV in the T - tan φ curves. It is suggested that the change of relaxation strength with temperature should be considered when one calculates the activation energy of the peak in T- tan φ curves.
基金Professor Hong Yu at Intelligent Fishery Innovative Team(No.C202109)in School of Information Engineering of Dalian Ocean University for her support of this workfunded by the National Natural Science Foundation of China(No.31800615 and No.21933010)。
文摘Performing cluster analysis on molecular conformation is an important way to find the representative conformation in the molecular dynamics trajectories.Usually,it is a critical step for interpreting complex conformational changes or interaction mechanisms.As one of the density-based clustering algorithms,find density peaks(FDP)is an accurate and reasonable candidate for the molecular conformation clustering.However,facing the rapidly increasing simulation length due to the increase in computing power,the low computing efficiency of FDP limits its application potential.Here we propose a marginal extension to FDP named K-means find density peaks(KFDP)to solve the mass source consuming problem.In KFDP,the points are initially clustered by a high efficiency clustering algorithm,such as K-means.Cluster centers are defined as typical points with a weight which represents the cluster size.Then,the weighted typical points are clustered again by FDP,and then are refined as core,boundary,and redefined halo points.In this way,KFDP has comparable accuracy as FDP but its computational complexity is reduced from O(n^(2))to O(n).We apply and test our KFDP method to the trajectory data of multiple small proteins in terms of torsion angle,secondary structure or contact map.The comparing results with K-means and density-based spatial clustering of applications with noise show the validation of the proposed KFDP.
文摘We present a novel method to analyze extreme events of flows over manifolds called Peaks Over Manifold (POM). Here we show that under general and realistic hypotheses, the distribution of affectation measures converges to a Generalized Pareto Distribution (GPD). The method is applicable to floods, ice cover extent, extreme rainfall or marine heatwaves. We present an application to a synthetic data set on tide height and to real ice cover data in Antartica.
文摘We present a novel unsupervised integrated score framework to generate generic extractive multi- document summaries by ranking sentences based on dynamic programming （DP） strategy. Considering that cluster-based methods proposed by other researchers tend to ignore informativeness of words when they generate summaries, our proposed framework takes relevance, diversity, informativeness and length constraint of sentences into consideration comprehensively. We apply Density Peaks Clustering （DPC） to get relevance scores and diversity scores of sentences simultaneously. Our framework produces the best performance on DUC2004, 0.396 of ROUGE-1 score, 0.094 of ROUGE-2 score and 0.143 of ROUGE-SU4 which outperforms a series of popular baselines, such as DUC Best, FGB [7], and BSTM [10].
基金Project (No. 10402008) supported by the National Natural ScienceFoundation of China
文摘The PP intervals of pulse main peaks from healthy and unhealthy people(arrhythmia) have different nonlinear char-acteristics. In this paper,the extraction of PP intervals of pulse main peaks is achieved by picking up P peaks of pulse wave with wavelet transform. Furthermore,several nonlinear parameters(correlative dimensions,maximum Lyapunov exponents,com-plexity and approximate entropy) of the PP intervals of pulse main peaks extracted from normal and unhealthy pulse signals are calculated,with the results showing that these nonlinear parameters calculated from the main wave interval signals are helpful for analyzing human's health state and diagnosing heart diseases.
基金financially supported by National Key Research and Development Program of China(No.2018YFB0704200)the National Natural Science Foundation of China(Nos.51973048 and U1732123).
文摘In this work,phase segregation and localization of PBSU have been investigated with the combination of SAXS and DSC in its blend with PVDF.After stepwise crystallization of PVDF and PBSU,there are double melting peaks of PBSU in DSC and double scattering peaks in SAXS.It has been demonstrated that double peaks can be attributed to the localization of PBSU in interlamellar/interfibrillar region in pre-formed PVDF crystal framework.In the case of low content of PBSU in blend,PBSU is trapped into the interlamellar region of PVDF crystals,resulting in the alternating lamellae crystal of them and the first peak(with low-q)in SAXS.The enhanced confinement effect produces thinner PBSU lamellae,corresponding to the lower melting temperature in DSC.Upon increasing its content in blend,some PBSU segregates in interfibrillar regions in addition to the enrichment in interlamellar regions of PVDF crystal framework.The larger space and higher concentration of PBSU in interfibrillarregions contribute to periodic lamellae structure of PBSU with higher thickness,which is the reason for the second peak(with high-q)in SAXS and DSC.Our results not only clarify the relationship between localization of PBSU in interlamellar/interfibrillar regions and double peaks in DSC/SAXS,but also provide a novel strategy to detect the interlamellar and interfibrillar segregation of low-T_(m) component in miscible crystalline/crystalline blend.
基金We thank the National Natural Science Foundation of China(Project No.29975033)the NSF of Guangdong Province(Project No.980340)for financial support.
文摘A new method called spline convolution (SC) for resolving overlapped peaks was proposed in this paper. The differential pulse voltammetric overlapped peaks of mixtures of Pb(II) and Tl(I) were investigated by this method, and satisfactory results were obtained. The results show excellent correlation between peak areas of the processed signals and the concentrations.
基金supported by the Chinese Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20123218110017)the National Natural Science Foundation of China(Grant Nos.61307052 and 61471368)+1 种基金the Foundation of Aeronautical Science,China(Grant No.20121852030)the Fundamental Research Funds for the Central Universities(Grant No.kfjj20150407)
文摘In this paper, we investigate a metamaterial formed by a planar array of a metallic L-shaped structure and a cut wire(CW), which behaves as an analogue of the electromagnetically induced transparency(EIT). The double transmission peaks are formed by the destructive interference of two bright-modes and a quasi-dark mode. The two bright-modes are respectively excited by the L-shaped structure and CW. The unit structure itself performs a quasi-dark mode. The group refractive indexes are over 20 in the first transmission peak, and 117 in the second transmission peak, thus offering potential applications in slow light devices. Finally, all the above characteristics are achieved in just one simple unit cell.
文摘Energy planning must anticipate the development and strengthening of power grids, power plants construction times, and the provision of energy resources with the aim of increasing security of supply and its quality. This work presents a methodology for predicting power peaks in mainland Spain’s system in the decade 2011-2020. Forecasts of total electricity demand of Spanish energy authorities set the boundary conditions. The accuracy of the results has successfully been compared with records of demand (2000-2010) and with various predictions published. Three patterns have been observed: 1) efficiency in the winter peak;2) increasing trend in the summer peak;3) increasing trend in the annual valley of demand. By 2020, 58.1 GW and 53.0 GW are expected, respectively, as winter and summer peaks in a business-as-usual scenario. If the observed tendencies continue, former values can go down to 55.5 GW in winter and go up to 54.7 GW in summer. The annual minimum valley of demand will raise 5.5 GW, up to 23.4 GW. These detailed predictions can be very useful to identify the types of power plants needed to have an optimum structure in the electricity industry.
基金This work was financially supported by the National Natural Science Foundation of China(No. 50071028) and Shandong Natural Scien
文摘Liquid indium's structure was studied at 280, 390, 550, 650, and 750 deg Crespectively by using an elevated temperature X-ray diffractometer, and its radial distributionfunction (RDF) at different temperatures was decomposed into 4 Gaussian peaks in the range of0.2-0.6nm. Positions of the decomposed Gaussian peaks were compared with the nearest and the secondnearest neighbor atomic distances, respectively. It is shown that the position of the firstdecomposed Gaussian peak is similar to the nearest neighbor atomic distance in liquid In at thecorresponding temperature, and that of the third decomposed Gaussian peak is similar to the secondnearest neighbor atomic distance. Moreover, the first and the third Gaussian peaks correspond to thefirst and the second atom shells of liquid In at the corresponding temperatures, respectively.Therefore, the position and the area of Gaussian peaks can represent the position and atom number ofcorresponding shells. Based on this result, short-range structural changes in liquid In wasstudied. It was found that the first and the second shells are close to the referred atom, and theatom number at the shells decreases with the increasing temperature from 280 to 750 deg C. Indifferent ranges of temperature, structural changes in the first and the second shells showdifferent features.
