The microstructure evolution of a new directionally solidified（DS） Ni-based superalloy used for gas turbine blades after long-term aging at 950 ℃ was investigated.The results show that the γ ＇ phase becomes more ...The microstructure evolution of a new directionally solidified（DS） Ni-based superalloy used for gas turbine blades after long-term aging at 950 ℃ was investigated.The results show that the γ ＇ phase becomes more regular in dendritic arm and interdendritic area,while both the mass fraction and the size of γ ＇ phase increase gradually with increasing aging time.During long-term aging,the MC carbide dissolves on the edge to provide the carbon for the formation of M23C6 carbide by the precipitation of Cr at the grain boundary.The rose-shaped γ ＇/γ eutectic partly dissolves into γ matrix and the aging promotes it transform into raft-shape γ ＇.The microstructure is generally stable and no needle-like topologically close-packed phase（TCP） can be found after aging for 1 000 h.展开更多
We theoretically investigate the evolutions of two-dimensional, third-order, nonlinear photon echo rephasing spectra with population time by using an exact numerical path integral method. It is shown that for the same...We theoretically investigate the evolutions of two-dimensional, third-order, nonlinear photon echo rephasing spectra with population time by using an exact numerical path integral method. It is shown that for the same system, the coherence time and relaxation time of excitonic states are short, however, if the couplings of electronic and intra-pigment vibrational modes are considered, the coherence time and relaxation time of this vibronic states are greatly extended. It means that the couplings between electronic and vibrational modes play important roles in keeping long-lived coherence in light-harvesting complexes. Particularly, by using the method we can fix the transition path of the energy transfer in bio-molecular systems.展开更多
The morphology and crystal structure of the precipitates in Mg-7Gd-3Y-1Nd-1Zn-0.5Zr(wt.%)alloy with fine plate-like 14H-LPSO structures aged at 240℃were investigated using transmission electron microscopy(TEM)and hig...The morphology and crystal structure of the precipitates in Mg-7Gd-3Y-1Nd-1Zn-0.5Zr(wt.%)alloy with fine plate-like 14H-LPSO structures aged at 240℃were investigated using transmission electron microscopy(TEM)and high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM).Fine plate-like 14H-LPSO structures precipitate after heat treatment at 500℃for 2 h,andβ-type phases precipitate after the alloy is aged at 240℃.The long-period atomic stacking sequence of 14H-LPSO structures along the[0001]αdirection is ABABCACACACBABA.After being aged at 240℃for 2 h,theβ-type phases are the ordered solution clusters,zig-zag GP zones,and a small number ofβ′phases.The peak hardness is obtained at 240℃for 18 h with a Brinell hardness of 112,theβ-type phases areβ’phases and local RE-rich structures.After being aged at 240℃for 100 h,theβ-type phases areβ’,β1 andβ’F phases.β′phases nucleate from the zig-zag GP zones directly withoutβ″phases,and then transform intoβ1 phase byβ’→β’F→β1 transformations.The Zn not only can form LPSO structure,but also is the constituent element ofβ1 phases.LPSO structures have a certain hindrance to the coarsening ofβ’andβ1 along<0001>α.展开更多
The morphology and crystal structure of the precipitates in Mg-7Gd-3Y-1Nd-1Zn-0.5Zr alloy during isothermal ageing at 240 ℃ were investigated using transmission electron microscopy (TEM) and high-angle annular dark- ...The morphology and crystal structure of the precipitates in Mg-7Gd-3Y-1Nd-1Zn-0.5Zr alloy during isothermal ageing at 240 ℃ were investigated using transmission electron microscopy (TEM) and high-angle annular dark- eld scanning transmission electron microscopy (HAADF-STEM). After under-ageing for 2 h, the precipitates in the alloy are ordered solute clusters with rare earth atomic columns exhibiting hexagonal ring structure, zigzag GP zones and β' in its early formation. After peak-ageing for 18 h, the precipitates are mainly β' and new rod-like β'p accompanied with β'. After over-ageing for 100 h, the precipitates are β',β1, long-period stacking ordered (LPSO) building block known as γ′ and 14H-LPSO.β' has the three-dimensional shape of convex lens with smaller length-to-width ratio viewed along <0001>α than that in the EW75 alloy. The excellent thermal stability of this alloy can be attributed to the γ' and 14H-LPSO retarding the growth of β' and β1, low diffusion rate of rare earth atoms and physical character of β' and β1.展开更多
We present the logistic growth model to study the stochastic resonance （SR） in a bacterium growth system under the simultaneous action of two external multiplicative cross-correlation noises and periodic external fo...We present the logistic growth model to study the stochastic resonance （SR） in a bacterium growth system under the simultaneous action of two external multiplicative cross-correlation noises and periodic external forcing. The expression of the signal-to-noise ratio （SNR） for a bacterium growth system is derived by using the theory of SNR in the adiabatic limit. Based on SNR, we discuss the effects of self-correlation time τ1 and τ2, cross-correlation time 3-3 and cross-correlation strength λ on the SNR. It is found that the self-correlation time τ1 and τ2, and cross-correlation strength λ enhance the SR of the bacterium growth system, while cross-correlation time τ3 weakens the SR of the bacterium growth system.展开更多
An incremental time-delay neural network based on synapse growth, which is suitable for dynamic control and learning of autonomous robots, is proposed to improve the learning and retrieving performance of dynamical re...An incremental time-delay neural network based on synapse growth, which is suitable for dynamic control and learning of autonomous robots, is proposed to improve the learning and retrieving performance of dynamical recurrent associative memory architecture. The model allows steady and continuous establishment of associative memory for spatio-temporal regularities and time series in discrete sequence of inputs. The inserted hidden units can be taken as the long-term memories that expand the capacity of network and sometimes may fade away under certain condition. Preliminary experiment has shown that this incremental network may be a promising approach to endow autonomous robots with the ability of adapting to new data without destroying the learned patterns. The system also benefits from its potential chaos character for emergence.展开更多
We simulated the temporal correlation of sound transmission using a two-dimensional advective frozen-ocean model with temperature data from a temperature sensor array on a propagation path in the South China Sea （SCS...We simulated the temporal correlation of sound transmission using a two-dimensional advective frozen-ocean model with temperature data from a temperature sensor array on a propagation path in the South China Sea （SCS） Experiment 2009, and investigated the relationships of temporal correlation length, source-receiver range, and maximal sound speed fluctuation mainly caused by the solitary internal waves. We found that the temporal correlation length is -h2-power dependent on source-receiver range and -0.9-power dependent on maximal sound speed fluctuation. The empirical relationship is deduced from one-day environmental measurements in a limited area, needing more works and verification in the future with more acoustic data. But the relationship is useful in many applications in the area of SCS Experiment 2009.展开更多
On the basis of the earthquake （gL I〉3.0） catalog in North China from 1970 to 2009, the pattern of temporal and spatial distribution of medium-small earthquakes in Datong and its surrounding areas is studied by cor...On the basis of the earthquake （gL I〉3.0） catalog in North China from 1970 to 2009, the pattern of temporal and spatial distribution of medium-small earthquakes in Datong and its surrounding areas is studied by correlation analysis with a focus on its anomaly before moderate and strong earthquakes. With different spatial scales, temporal scales and time steps, the spatial distribution of earthquakes is converted to a sequence, then the correlation coefficients between the spatial distribution of medium-small earthquakes in a long-term and a longer time are calculated for the analysis of anomalies before moderate and strong earthquakes. In the study region center on the epicenter of the 1989 Datong- Yanggao earthquake （Ms5. 9） within a radius of less than 0.8~, with the time length of 3600 days, the longer time length of 3700 days, and the time step of 100 days, the correlation coefficient from 1980 to 2009 is steady between 0.94 and 1.00, but there were anomalies with values less than 0. 94 in the 2 years before the 1989 Datong-Yanggao earthquake （Ms 5.9）, the 1991 Datong earthquake （ Ms 5.8） and 1999 Hunyuan earthquake （Ms 5. 6 ）, which indicates the spatial distribution of a medium-small earthquake is very different from steady background seismicity. The implication for earthquake prediction from the anomaly of the correlation coefficient is also discussed with the three conclusions： （1） Before moderate and strong earthquakes in Datong and its surrounding areas, the obvious change of spatial distribution patterns of medium-small earthquake can be a kind of seismic precursor of the 2-year time scale for the prediction of an earthquake＇s time. （2） As the study region is restricted within a radius of less than 0. 8~, the result of correlation analysis is also good for the prediction of an earthquake＇s location. （3） The method of correlation analysis in this paper helps recognize the anomaly of spatial distribution of medium-small earthquake.展开更多
We analyze the dynamics of a bright soliton in atomic scattering length in an expulsive parabolic potential. Bose-Einstein condensates （BECs） with time-dependent Under a safe ravage of parameters in which the Gross...We analyze the dynamics of a bright soliton in atomic scattering length in an expulsive parabolic potential. Bose-Einstein condensates （BECs） with time-dependent Under a safe ravage of parameters in which the Gross-Pitaevskii （GP） equation is effective in one dimension, our results show that, the dynamics of the bright soliton can be classed into two phases, depending on the value of the scattering length. Meanwhile, there exists a critical value of the absolute value of the atomic scattering length, below which, the dynamics of the bright soliton is very regular. Those phenomena can be useful for developing concrete applications of the nonlinear matter waves. We also obtain the orbital equation of the bright soliton and get some interesting data which may be useful for the experimental observation of the bright soliton and the application of the atom laser with manipulated intensity.展开更多
In the paper, the generalized Riccati equation rational expansion method is presented. Making use of the method and symbolic computation, we present three families of exact analytical solutions of Bose-Einstein conden...In the paper, the generalized Riccati equation rational expansion method is presented. Making use of the method and symbolic computation, we present three families of exact analytical solutions of Bose-Einstein condensates with the time-dependent interatomic interaction in an expulsive parabolic potential. Then the dynamics of two anlytical solutions are demonstrated by computer simulations under some selectable parameters including the Feshbach-managed nonlinear coefficient and the hyperbolic secant function coefficient.展开更多
Contact detection between interacting blocks is of great importance to discontinuity-based numerical methods, such as DDA, DEM, and NMM. A rigorous contact theory is a prerequisite to describing the interactions of mu...Contact detection between interacting blocks is of great importance to discontinuity-based numerical methods, such as DDA, DEM, and NMM. A rigorous contact theory is a prerequisite to describing the interactions of multiple blocks. Currently, the penalty method, in which mathematical springs with high stiffness values are employed, is always used to calculate the contact forces. High stiffness values may cause numerical oscillations and limit the time step. Furthermore, their values are difficult to identify. The intention of this study is to present a two-scale contact model for the calculation of forces between colliding blocks. In this new model, a calculation step taken from the moment of contact will be divided into two time stages: the free motion time stage and the contact time stage. Actually, these two time stages correspond to two real physical processes. Based on this, we present a new numerical model that is intended to be more precise and useful in calculating the contact forces without mathematical springs. The propagation of the elastic wave during collision is of a characteristic length, which determines the volume of material involved in the contact force calculation. In conventional contact models, this range is always regarded as the length of one element, which may lead to an inaccurate calculation of contact forces. In fact, the real scale of this range is smaller than the length of a single element, and subdivided elements, which are refined according to the characteristic length and are presented in the new contact model.展开更多
The latest video coding standard High Efficiency Video Coding （HEVC） can achieve much higher coding efficiency than previous video coding standards. Particularly, by exploiting the hierarchical B-picture prediction ...The latest video coding standard High Efficiency Video Coding （HEVC） can achieve much higher coding efficiency than previous video coding standards. Particularly, by exploiting the hierarchical B-picture prediction structure, temporal redundancy among neighbor frarnes is eliminated remarkably well. In practice, videos available to consumers usually contain many repeated shots, such as TV series, movies, and talk shows. According to our observations, when these videos are encoded by HEVC with the hierarchical B-picture structure, the temporal correlation in each shot is well exploited. However, the long-term correlation between repeated shots has not been used. We propose a long-term prediction （LTP） scheme to use the long-term temporal correlation between correlated shots in a video. The long-term reference （LTR） frames of a source video are chosen by clustering similar shots and extracting the representative frames, and a modified hierarchical B-picture coding structure based on an LTR frame is introduced to support long-term temporal prediction. An adaptive quantization method is further designed for LTR frames to improve the overall video coding efficiency. Experimental results show that up to 22.86% coding gain can be achieved using the new coding scheme.展开更多
The recently introduced multivariate multiscale sample entropy(MMSE)well evaluates the long correlations in multiple channels,so that it can reveal the complexity of multivariate biological signals.The existing MMSE a...The recently introduced multivariate multiscale sample entropy(MMSE)well evaluates the long correlations in multiple channels,so that it can reveal the complexity of multivariate biological signals.The existing MMSE algorithm deals with short time series statically whereas long time series are common for real-time computation in practical use.As a solution,we novelly proposed our dynamic MMSE(DMMSE)as an extension of MMSE.This helps us gain greater insight into the complexity of each section of time series,producing multifaceted and more robust estimates than the standard MMSE.The simulation results illustrated the feasibility and well performance in the brain death diagnosis.展开更多
Shoaling intensity in zebrafish Danio rerio is believed to vary throughout subjective day and night hours. This experiment examines long term variations in shoaling behavior. Adult zebrafish Dan io rerio were maintain...Shoaling intensity in zebrafish Danio rerio is believed to vary throughout subjective day and night hours. This experiment examines long term variations in shoaling behavior. Adult zebrafish Dan io rerio were maintained under a 12：12 LD cycle （with dim red light serving as reduced visibility during subjective dark hours）, and their shoaling behavior was monitored every hour for a three-day period of time. Our results show that zebrafish perform shoaling behavior throughout subjective day and under reduced visibility conditions, although mean shoaling times during the light phase were significantly higher than mean shoaling times during the dark phase. However, on the 3^rd day of the experiment, mean shoaling times during the subjective night had increased and mean shoaling times during the subjective day had decreased. This shift in intensity was not seen on the first two days of the study, and may represent the influence of experience on the behavior of the test fish. We believe this study shows that shoaling behavior changes with light/dark cycles and that fish shoal even during reduced visibility conditions.展开更多
基金Projects(2006CB605005,2010CB631203) supported by the National Basic Research Program of ChinaProject(IRT0713) supported by Changjiang Scholars and Innovative Research Team in University,China
文摘The microstructure evolution of a new directionally solidified（DS） Ni-based superalloy used for gas turbine blades after long-term aging at 950 ℃ was investigated.The results show that the γ ＇ phase becomes more regular in dendritic arm and interdendritic area,while both the mass fraction and the size of γ ＇ phase increase gradually with increasing aging time.During long-term aging,the MC carbide dissolves on the edge to provide the carbon for the formation of M23C6 carbide by the precipitation of Cr at the grain boundary.The rose-shaped γ ＇/γ eutectic partly dissolves into γ matrix and the aging promotes it transform into raft-shape γ ＇.The microstructure is generally stable and no needle-like topologically close-packed phase（TCP） can be found after aging for 1 000 h.
基金This work was supported by the Zhejiang Provincial Natural Science Foundation of China （No.LY13A040006）, and the K. C. Wong Magna Foundation in Ningbo University.
文摘We theoretically investigate the evolutions of two-dimensional, third-order, nonlinear photon echo rephasing spectra with population time by using an exact numerical path integral method. It is shown that for the same system, the coherence time and relaxation time of excitonic states are short, however, if the couplings of electronic and intra-pigment vibrational modes are considered, the coherence time and relaxation time of this vibronic states are greatly extended. It means that the couplings between electronic and vibrational modes play important roles in keeping long-lived coherence in light-harvesting complexes. Particularly, by using the method we can fix the transition path of the energy transfer in bio-molecular systems.
基金Projects(51871195,51501015)supported by the National Natural Science Foundation of ChinaProject(TC170A5SU-1)supported by Ministry of Industry and Information Technology of China。
文摘The morphology and crystal structure of the precipitates in Mg-7Gd-3Y-1Nd-1Zn-0.5Zr(wt.%)alloy with fine plate-like 14H-LPSO structures aged at 240℃were investigated using transmission electron microscopy(TEM)and high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM).Fine plate-like 14H-LPSO structures precipitate after heat treatment at 500℃for 2 h,andβ-type phases precipitate after the alloy is aged at 240℃.The long-period atomic stacking sequence of 14H-LPSO structures along the[0001]αdirection is ABABCACACACBABA.After being aged at 240℃for 2 h,theβ-type phases are the ordered solution clusters,zig-zag GP zones,and a small number ofβ′phases.The peak hardness is obtained at 240℃for 18 h with a Brinell hardness of 112,theβ-type phases areβ’phases and local RE-rich structures.After being aged at 240℃for 100 h,theβ-type phases areβ’,β1 andβ’F phases.β′phases nucleate from the zig-zag GP zones directly withoutβ″phases,and then transform intoβ1 phase byβ’→β’F→β1 transformations.The Zn not only can form LPSO structure,but also is the constituent element ofβ1 phases.LPSO structures have a certain hindrance to the coarsening ofβ’andβ1 along<0001>α.
基金Projects(51871195,51501015) supported by the National Natural Science Foundation of ChinaProject(TC170A5SU-1) supported by Ministry of Industry and Information Technology,China
文摘The morphology and crystal structure of the precipitates in Mg-7Gd-3Y-1Nd-1Zn-0.5Zr alloy during isothermal ageing at 240 ℃ were investigated using transmission electron microscopy (TEM) and high-angle annular dark- eld scanning transmission electron microscopy (HAADF-STEM). After under-ageing for 2 h, the precipitates in the alloy are ordered solute clusters with rare earth atomic columns exhibiting hexagonal ring structure, zigzag GP zones and β' in its early formation. After peak-ageing for 18 h, the precipitates are mainly β' and new rod-like β'p accompanied with β'. After over-ageing for 100 h, the precipitates are β',β1, long-period stacking ordered (LPSO) building block known as γ′ and 14H-LPSO.β' has the three-dimensional shape of convex lens with smaller length-to-width ratio viewed along <0001>α than that in the EW75 alloy. The excellent thermal stability of this alloy can be attributed to the γ' and 14H-LPSO retarding the growth of β' and β1, low diffusion rate of rare earth atoms and physical character of β' and β1.
基金Supported by the Natural Science Foundation of Yunnan Province under Grant Nos.2005A0080m-2 and 08C0235the Key Subjects Fund for Condensed Physics of Qujing Normal University
文摘We present the logistic growth model to study the stochastic resonance （SR） in a bacterium growth system under the simultaneous action of two external multiplicative cross-correlation noises and periodic external forcing. The expression of the signal-to-noise ratio （SNR） for a bacterium growth system is derived by using the theory of SNR in the adiabatic limit. Based on SNR, we discuss the effects of self-correlation time τ1 and τ2, cross-correlation time 3-3 and cross-correlation strength λ on the SNR. It is found that the self-correlation time τ1 and τ2, and cross-correlation strength λ enhance the SR of the bacterium growth system, while cross-correlation time τ3 weakens the SR of the bacterium growth system.
文摘An incremental time-delay neural network based on synapse growth, which is suitable for dynamic control and learning of autonomous robots, is proposed to improve the learning and retrieving performance of dynamical recurrent associative memory architecture. The model allows steady and continuous establishment of associative memory for spatio-temporal regularities and time series in discrete sequence of inputs. The inserted hidden units can be taken as the long-term memories that expand the capacity of network and sometimes may fade away under certain condition. Preliminary experiment has shown that this incremental network may be a promising approach to endow autonomous robots with the ability of adapting to new data without destroying the learned patterns. The system also benefits from its potential chaos character for emergence.
基金Supported by the Knowledge Innovation Program of Chinese Academy of Sciences (No.KZCX1-YW-12-02)the National Natural Science Foundation of China (Nos.10974218,10734100)
文摘We simulated the temporal correlation of sound transmission using a two-dimensional advective frozen-ocean model with temperature data from a temperature sensor array on a propagation path in the South China Sea （SCS） Experiment 2009, and investigated the relationships of temporal correlation length, source-receiver range, and maximal sound speed fluctuation mainly caused by the solitary internal waves. We found that the temporal correlation length is -h2-power dependent on source-receiver range and -0.9-power dependent on maximal sound speed fluctuation. The empirical relationship is deduced from one-day environmental measurements in a limited area, needing more works and verification in the future with more acoustic data. But the relationship is useful in many applications in the area of SCS Experiment 2009.
基金grant from Institute of Crustal Dynamics, China Earthquake Administration (No. ZDJ2011 - 01) and (No. ZDJ2010 - 26)
文摘On the basis of the earthquake （gL I〉3.0） catalog in North China from 1970 to 2009, the pattern of temporal and spatial distribution of medium-small earthquakes in Datong and its surrounding areas is studied by correlation analysis with a focus on its anomaly before moderate and strong earthquakes. With different spatial scales, temporal scales and time steps, the spatial distribution of earthquakes is converted to a sequence, then the correlation coefficients between the spatial distribution of medium-small earthquakes in a long-term and a longer time are calculated for the analysis of anomalies before moderate and strong earthquakes. In the study region center on the epicenter of the 1989 Datong- Yanggao earthquake （Ms5. 9） within a radius of less than 0.8~, with the time length of 3600 days, the longer time length of 3700 days, and the time step of 100 days, the correlation coefficient from 1980 to 2009 is steady between 0.94 and 1.00, but there were anomalies with values less than 0. 94 in the 2 years before the 1989 Datong-Yanggao earthquake （Ms 5.9）, the 1991 Datong earthquake （ Ms 5.8） and 1999 Hunyuan earthquake （Ms 5. 6 ）, which indicates the spatial distribution of a medium-small earthquake is very different from steady background seismicity. The implication for earthquake prediction from the anomaly of the correlation coefficient is also discussed with the three conclusions： （1） Before moderate and strong earthquakes in Datong and its surrounding areas, the obvious change of spatial distribution patterns of medium-small earthquake can be a kind of seismic precursor of the 2-year time scale for the prediction of an earthquake＇s time. （2） As the study region is restricted within a radius of less than 0. 8~, the result of correlation analysis is also good for the prediction of an earthquake＇s location. （3） The method of correlation analysis in this paper helps recognize the anomaly of spatial distribution of medium-small earthquake.
基金Supported by National Natural Science Foundation of China under Grant Nos.90406017 and 60525417the NKBRSF of China under Grant No.2006CB921400
文摘We analyze the dynamics of a bright soliton in atomic scattering length in an expulsive parabolic potential. Bose-Einstein condensates （BECs） with time-dependent Under a safe ravage of parameters in which the Gross-Pitaevskii （GP） equation is effective in one dimension, our results show that, the dynamics of the bright soliton can be classed into two phases, depending on the value of the scattering length. Meanwhile, there exists a critical value of the absolute value of the atomic scattering length, below which, the dynamics of the bright soliton is very regular. Those phenomena can be useful for developing concrete applications of the nonlinear matter waves. We also obtain the orbital equation of the bright soliton and get some interesting data which may be useful for the experimental observation of the bright soliton and the application of the atom laser with manipulated intensity.
基金The project supported by Natural Science Foundation of Zhejiang Province of China under Grant Nos. Y604056 and 605408 and the Doctoral Foundation of Ningbo City under Grant No, 2005A61030
文摘In the paper, the generalized Riccati equation rational expansion method is presented. Making use of the method and symbolic computation, we present three families of exact analytical solutions of Bose-Einstein condensates with the time-dependent interatomic interaction in an expulsive parabolic potential. Then the dynamics of two anlytical solutions are demonstrated by computer simulations under some selectable parameters including the Feshbach-managed nonlinear coefficient and the hyperbolic secant function coefficient.
基金supported by the National Basic Research Program of China("973"Project)(Grant No.2015CB250903)the CAS Strategic Priority Research Program(B)(Grant No.XDB10030303)+1 种基金the National Key Technology Research and Development Program of the Ministry of Science and Technology of China(Grant No.2012BAK10B01)the Youth Science Fund of the National Natural Science Foundation of China(Grant No.11302230)
文摘Contact detection between interacting blocks is of great importance to discontinuity-based numerical methods, such as DDA, DEM, and NMM. A rigorous contact theory is a prerequisite to describing the interactions of multiple blocks. Currently, the penalty method, in which mathematical springs with high stiffness values are employed, is always used to calculate the contact forces. High stiffness values may cause numerical oscillations and limit the time step. Furthermore, their values are difficult to identify. The intention of this study is to present a two-scale contact model for the calculation of forces between colliding blocks. In this new model, a calculation step taken from the moment of contact will be divided into two time stages: the free motion time stage and the contact time stage. Actually, these two time stages correspond to two real physical processes. Based on this, we present a new numerical model that is intended to be more precise and useful in calculating the contact forces without mathematical springs. The propagation of the elastic wave during collision is of a characteristic length, which determines the volume of material involved in the contact force calculation. In conventional contact models, this range is always regarded as the length of one element, which may lead to an inaccurate calculation of contact forces. In fact, the real scale of this range is smaller than the length of a single element, and subdivided elements, which are refined according to the characteristic length and are presented in the new contact model.
基金Project supported by the National Natural Science Foundation of China(No.61371162)
文摘The latest video coding standard High Efficiency Video Coding （HEVC） can achieve much higher coding efficiency than previous video coding standards. Particularly, by exploiting the hierarchical B-picture prediction structure, temporal redundancy among neighbor frarnes is eliminated remarkably well. In practice, videos available to consumers usually contain many repeated shots, such as TV series, movies, and talk shows. According to our observations, when these videos are encoded by HEVC with the hierarchical B-picture structure, the temporal correlation in each shot is well exploited. However, the long-term correlation between repeated shots has not been used. We propose a long-term prediction （LTP） scheme to use the long-term temporal correlation between correlated shots in a video. The long-term reference （LTR） frames of a source video are chosen by clustering similar shots and extracting the representative frames, and a modified hierarchical B-picture coding structure based on an LTR frame is introduced to support long-term temporal prediction. An adaptive quantization method is further designed for LTR frames to improve the overall video coding efficiency. Experimental results show that up to 22.86% coding gain can be achieved using the new coding scheme.
基金supported by KAKENHI(Grant Nos.21360179,22560425)(JAPAN)supported by the Key Project of National Science Foundation of China(Grant Nos.11232005)The Ministry of Education Doctoral Foundation(Grant Nos.20120074110020)
文摘The recently introduced multivariate multiscale sample entropy(MMSE)well evaluates the long correlations in multiple channels,so that it can reveal the complexity of multivariate biological signals.The existing MMSE algorithm deals with short time series statically whereas long time series are common for real-time computation in practical use.As a solution,we novelly proposed our dynamic MMSE(DMMSE)as an extension of MMSE.This helps us gain greater insight into the complexity of each section of time series,producing multifaceted and more robust estimates than the standard MMSE.The simulation results illustrated the feasibility and well performance in the brain death diagnosis.
文摘Shoaling intensity in zebrafish Danio rerio is believed to vary throughout subjective day and night hours. This experiment examines long term variations in shoaling behavior. Adult zebrafish Dan io rerio were maintained under a 12：12 LD cycle （with dim red light serving as reduced visibility during subjective dark hours）, and their shoaling behavior was monitored every hour for a three-day period of time. Our results show that zebrafish perform shoaling behavior throughout subjective day and under reduced visibility conditions, although mean shoaling times during the light phase were significantly higher than mean shoaling times during the dark phase. However, on the 3^rd day of the experiment, mean shoaling times during the subjective night had increased and mean shoaling times during the subjective day had decreased. This shift in intensity was not seen on the first two days of the study, and may represent the influence of experience on the behavior of the test fish. We believe this study shows that shoaling behavior changes with light/dark cycles and that fish shoal even during reduced visibility conditions.
