The empirical Bayes test problem is considered for scale parameter of twoparameter exponential distribution under type-II censored data.By using wavelets estimation method,the EB test function is constructed,of which ...The empirical Bayes test problem is considered for scale parameter of twoparameter exponential distribution under type-II censored data.By using wavelets estimation method,the EB test function is constructed,of which the asymptotic optimality and convergence rates are obtained.Finally,an example concerning the main result is given.展开更多
The two-parameter exponential distribution is proposed to be an underlying model,and prediction bounds for future observations are obtained by using Bayesian approach.Prediction intervals are derived for unobserved li...The two-parameter exponential distribution is proposed to be an underlying model,and prediction bounds for future observations are obtained by using Bayesian approach.Prediction intervals are derived for unobserved lifetimes in one-sample prediction and two-sample prediction based on type Ⅱ doubly censored samples.A numerical example is given to illustrate the procedures,prediction intervals are investigated via Monte Carlo method,and the accuracy of prediction intervals is presented.展开更多
While log law is an equation theoretically derived for near-bed region, in most cases, power law has been researched by experimental methods. Thus, many consider it as an empirical equation and fixed power law exponen...While log law is an equation theoretically derived for near-bed region, in most cases, power law has been researched by experimental methods. Thus, many consider it as an empirical equation and fixed power law exponents such as 1/6 and 1/7 are generally applied. However, exponent of power law is an index representing bed resistance related with relative roughness and furthermore influences the shapes of vertical velocity distribution. The purpose of this study is to investigate characteristics of vertical velocity distribution of the natural rivers by testing and optimizing previous methods used for determination of power law exponent with vertical velocity distribution data collected with ADCPs during the years of 2005 to 2009 from rivers in South Korea. Roughness coefficient has been calculated from the equation of Limerinos. And using theoretical and empirical formulae, and representing relationships between bed resistance and power law exponent, it has been evaluated whether the exponents suggested by these equations appropriately reproduce vertical velocity distribution of actual rivers. As a result, it has been confirmed that there is an increasing trend of power law exponent as bed resistance increases. Therefore, in order to correctly predict vertical velocity distribution in the natural rivers, it is necessary to use an exponent that reflects flow conditions at the field.展开更多
To satisfy the mechanical and biological requirement of porous bone substitutes, porous Ti with two different pore sizes designed in advance was fabricated by the space-holder sintering process. Mechanical properties ...To satisfy the mechanical and biological requirement of porous bone substitutes, porous Ti with two different pore sizes designed in advance was fabricated by the space-holder sintering process. Mechanical properties of the porous Ti were explored via room temperature compressive tests. The pore sizes and shapes are uniform throughout the specimens with porosities ranging from 36% to 63%. The compression strength and the elastic modulus are in the range from 94.05 to 468.57 MPa and 2.662 to 18 GPa, respectively. It is worth noting that the relationship between the compressive strength and the porosities is completely linear relation beyond the effect of pore size distributions on the mechanical properties. The value of the constant C achieved from the Gibson-Ashby model suggests that the pore sizes affect the yield strength of the porous Ti and the values of density exponent （n） for porous Ti with two different pore sizes are higher than 2, which suggests that the deformation mode of the porous Ti with a porosity ranging from 36% to 63% is mainly buckling of the cell struts.展开更多
Nuclear charge density distribution plays an important role in both nuclear and atomic physics,for which the two-parameter Fermi(2pF)model has been widely applied as one of the most frequently used models.Currently,th...Nuclear charge density distribution plays an important role in both nuclear and atomic physics,for which the two-parameter Fermi(2pF)model has been widely applied as one of the most frequently used models.Currently,the feedforward neural network has been employed to study the available 2pF model parameters for 86 nuclei,and the accuracy and precision of the parameter-learning effect are improved by introducing A^(1∕3)into the input parameter of the neural network.Furthermore,the average result of multiple predictions is more reliable than the best result of a single prediction and there is no significant difference between the average result of the density and parameter values for the average charge density distribution.In addition,the 2pF parameters of 284(near)stable nuclei are predicted in this study,which provides a reference for the experiment.展开更多
In this paper, we consider the construction of the approximate profile-</span><span style="font-family:""> </span><span style="font-family:Verdana;">likelihood confiden...In this paper, we consider the construction of the approximate profile-</span><span style="font-family:""> </span><span style="font-family:Verdana;">likelihood confidence intervals for parameters of the 2-parameter Weibull distribution based on small type-2 censored samples. In previous research works, the traditional Wald method has been used to construct approximate confidence intervals for the 2-parameter Weibull distribution</span><span style="font-family:""> </span><span style="font-family:Verdana;">under type-2 censoring scheme. However, the Wald technique is based on normality assumption and thus may not produce accurate interval estimates for small samples. The profile-likelihood and Wald confidence intervals are constructed for the shape and scale parameters of the 2-parameter Weibull distribution based on simulated and real type-2 censored data, and are hence compared using confidence length and coverage probability.展开更多
The uniform distribution model of the surface donor states in AlGaN/GaN heterostructures has been widely used in the theoretical calculation.A common and a triple-channel AlGaN/GaN heterostructure Schottky barrier dio...The uniform distribution model of the surface donor states in AlGaN/GaN heterostructures has been widely used in the theoretical calculation.A common and a triple-channel AlGaN/GaN heterostructure Schottky barrier diodes have been fabricated to verify the models,but the calculation results show the uniform distribution model can not provide enough electrons to form three separate 2DEGs in the triple-channel Al GaN/GaN heterostructure.Our experiments indicate the uniform distribution model is not quite right,especially for the multiple-channel AlGaN/GaN heterostructures.Besides,it is found the exponential distribution model possibly matches the actual distribution of the surface donor states better,which allows the 2DEG to form in each channel structure during the calculation.The exponential distribution model would be helpful in the research field.展开更多
In this paper,the power law of particle size distributions (PSDs) in conventional water treatment processes is developed. After measuring the particle size distributions of raw-water,settled water and filtered water,a...In this paper,the power law of particle size distributions (PSDs) in conventional water treatment processes is developed. After measuring the particle size distributions of raw-water,settled water and filtered water,a mathematical model between particle diameter and the amount of particles was studied. The value of collision frequency factor β in the PSDs model can be used to represent the collision behavior of particles ,and can be used as foundation exponent to choose suitable coagulation to accelerate particles aggregation. At the same time,the relationship between the value of parameter K and the total particles volume V was deduced. K is defined as particle volume exponent,which can represent the total volume of particles. The degression degree of K shows the removal efficiency of potable water treatment units.展开更多
The question of the power-law exponent of exponential growth networks is studied here.In a discrete case,the degree distribution is defined as the probability distribution of the discrete variable.Based on this,the de...The question of the power-law exponent of exponential growth networks is studied here.In a discrete case,the degree distribution is defined as the probability distribution of the discrete variable.Based on this,the degree distribution of the pseudofractal scale-free web,an exponential growth network,is obtained.The power-law exponent ln3/ln2 is analyzed according to the maximum likelihood principle.It satisfies consistency and is good for small generations of the network.For many exponential growth networks,their power-law exponent needs to be tested.The work provides a new view on the power-law exponent of an exponential growth network.展开更多
The logarithmic moment estimations of parameters are proposed for two-parameter generalized Birnbaum-Saunders Logistic fatigue life distribution GBS-Logistic(α,β)under the full sample.The precisions of point estimat...The logarithmic moment estimations of parameters are proposed for two-parameter generalized Birnbaum-Saunders Logistic fatigue life distribution GBS-Logistic(α,β)under the full sample.The precisions of point estimations are investigated and compared with other point estimations by Monte-Carlo simulations.The approximate interval estimations of parameters are given by using Taylor expansion,and the precisions of approximate interval estimations are investigated by Monte-Carlo simulations.Finally,several examples show the feasibility of the methods.展开更多
Black carbon(BC)is one of the short-lived air pollutants that contributes significantly to aerosol radiative forcing and global climate change.It is emitted by the incomplete combustion of fossil fuels,biofuels,and bi...Black carbon(BC)is one of the short-lived air pollutants that contributes significantly to aerosol radiative forcing and global climate change.It is emitted by the incomplete combustion of fossil fuels,biofuels,and biomass.Urban environments are quite complex and thus,the use of mobile jointly with fixed monitoring provides a better understanding of the dynamics of BC distribution in such areas.The present study addresses the measurement of BC concentration using real-time mobile and ambient monitoring in Barranquilla,an industrialized urban area of the Colombian Caribbean.A microaethalometer(MA200)and an aethalometer(AE33)were used for measuring the BC concentration.The absorption Ångström exponent(AAE)values were determined for the study area,for identifying the BC emission sources.The results of the ambient sampling show that vehicle traffic emissions prevail;however,the influence of biomass burning was also observed.The mean ambient BC concentration was found to be 1.04±1.03μg/m^(3) and varied between 0.5 and 4.0μg/m^(3).From the mobile measurements obtained in real traffic conditions on the road,a much higher average value of 16.1±16.5μg/m^(3) was measured.Many parts of the city showed BC concentrations higher than 20μg/m^(3).The spatial distribution of BC concentration shows that vehicle emissions and traffic jams,a consequence of road and transport infrastructure,are the factors that most affect the BC concentration.A comparison of results obtained from two aethalometers indicates that the concentrations measured by MA200 are 9%lower than those measured by AE33.The AAE obtained was found to vary between 1.1 and 1.6,indicating vehicular emissions as the most crucial source.In addition,it was observed that the BC concentration on working days was 2.5 times higher than on the weekends in the case of mobile monitoring and 1.5 times higher in the case of ambient monitoring.展开更多
In view of the non-Gaussian ocean ambient noise,the a stable distribution is applied to the statistical modeling.Firstly,the correspondence between the model characteristic exponent and the sample kurtosis is establis...In view of the non-Gaussian ocean ambient noise,the a stable distribution is applied to the statistical modeling.Firstly,the correspondence between the model characteristic exponent and the sample kurtosis is established based on the similarity in physical meaning of the two.And the kurtosis of the sum of two independent random variables is deduced,and this can be used to explain the kurtosis characteristic of interfered background noise.Secondly,some numerical simulations are made to model samples with higher and lower kurtosis than three,the results show good adaptability in leptokurtic distribution.Finally,three typical samples are taken under quiet environment,air gun interference and ship interference environment.Their Gaussianities are judged by the quantile-quantile plot.And then the four parameters of the model are estimated by the quantile based method and characteristic function based method jointly of the three categories.The statistical law of the characteristic exponent is emphatically analyzed:in the quiet environment,the characteristic exponent is close to 2.0,which is the value of Gaussian model;but for the air gun data,it is between 1.2 and 1.7,which means leptokurtic;and under the interference of the sailing ship,the value of a is related to the ship speed and the distance from the ship source to the receiving location,the more significant the ship impact is,the smaller the characteristic exponent is,which is consistent with the variation of kurtosis of disturbing noise in physical meaning.The results of the model verification show that the a stable distribution behaves well under the above three kinds of trial conditions,especially for the air gun environment which is far superior to the normal distribution.展开更多
This letter presents a new one-dimensional chaotic map with infinite collapses. Theoretical analyses show that the map has complicated dynamical behavior and ideal distribution.The map can be applied in chaotic spread...This letter presents a new one-dimensional chaotic map with infinite collapses. Theoretical analyses show that the map has complicated dynamical behavior and ideal distribution.The map can be applied in chaotic spreading spectrum communication and chaotic cipher.展开更多
This paper deals with a stochastic representation of the rainfall process. The analysis of a rainfall time series shows that cumulative representation of a rainfall time series can be modeled as a non-Gaussian random ...This paper deals with a stochastic representation of the rainfall process. The analysis of a rainfall time series shows that cumulative representation of a rainfall time series can be modeled as a non-Gaussian random walk with a log-normal jump distribution and a time-waiting distribution following a tempered a-stable probability law. Based on the random walk model, a fractional Fokker-Planck equation （FFPE） with tempered a-stable waiting times was obtained. Through the comparison of observed data and simulated results from the random walk model and FFPE model with tempered a-stable waiting times, it can be concluded that the behavior of the rainfall process is globally reproduced, and the FFPE model with tempered a-stable waiting times is more efficient in reproducing the observed behavior.展开更多
基金Supported by the NNSF of China（70471057）Supported by the Natural Science Foundation of the Education Department of Shannxi Province（03JK065）
文摘The empirical Bayes test problem is considered for scale parameter of twoparameter exponential distribution under type-II censored data.By using wavelets estimation method,the EB test function is constructed,of which the asymptotic optimality and convergence rates are obtained.Finally,an example concerning the main result is given.
文摘The two-parameter exponential distribution is proposed to be an underlying model,and prediction bounds for future observations are obtained by using Bayesian approach.Prediction intervals are derived for unobserved lifetimes in one-sample prediction and two-sample prediction based on type Ⅱ doubly censored samples.A numerical example is given to illustrate the procedures,prediction intervals are investigated via Monte Carlo method,and the accuracy of prediction intervals is presented.
文摘While log law is an equation theoretically derived for near-bed region, in most cases, power law has been researched by experimental methods. Thus, many consider it as an empirical equation and fixed power law exponents such as 1/6 and 1/7 are generally applied. However, exponent of power law is an index representing bed resistance related with relative roughness and furthermore influences the shapes of vertical velocity distribution. The purpose of this study is to investigate characteristics of vertical velocity distribution of the natural rivers by testing and optimizing previous methods used for determination of power law exponent with vertical velocity distribution data collected with ADCPs during the years of 2005 to 2009 from rivers in South Korea. Roughness coefficient has been calculated from the equation of Limerinos. And using theoretical and empirical formulae, and representing relationships between bed resistance and power law exponent, it has been evaluated whether the exponents suggested by these equations appropriately reproduce vertical velocity distribution of actual rivers. As a result, it has been confirmed that there is an increasing trend of power law exponent as bed resistance increases. Therefore, in order to correctly predict vertical velocity distribution in the natural rivers, it is necessary to use an exponent that reflects flow conditions at the field.
基金Project （2012CB619100） supported by the National Basic Research Program of China
文摘To satisfy the mechanical and biological requirement of porous bone substitutes, porous Ti with two different pore sizes designed in advance was fabricated by the space-holder sintering process. Mechanical properties of the porous Ti were explored via room temperature compressive tests. The pore sizes and shapes are uniform throughout the specimens with porosities ranging from 36% to 63%. The compression strength and the elastic modulus are in the range from 94.05 to 468.57 MPa and 2.662 to 18 GPa, respectively. It is worth noting that the relationship between the compressive strength and the porosities is completely linear relation beyond the effect of pore size distributions on the mechanical properties. The value of the constant C achieved from the Gibson-Ashby model suggests that the pore sizes affect the yield strength of the porous Ti and the values of density exponent （n） for porous Ti with two different pore sizes are higher than 2, which suggests that the deformation mode of the porous Ti with a porosity ranging from 36% to 63% is mainly buckling of the cell struts.
基金supported by the Natural Science Foundation of Jilin Province (No. 20220101017JC)the National Natural Science Foundation of China (Nos. 11675063, 11875070, and 11935001)+1 种基金Key Laboratory of Nuclear Data foundation (JCKY2020201C157)the Anhui Project (Z010118169)
文摘Nuclear charge density distribution plays an important role in both nuclear and atomic physics,for which the two-parameter Fermi(2pF)model has been widely applied as one of the most frequently used models.Currently,the feedforward neural network has been employed to study the available 2pF model parameters for 86 nuclei,and the accuracy and precision of the parameter-learning effect are improved by introducing A^(1∕3)into the input parameter of the neural network.Furthermore,the average result of multiple predictions is more reliable than the best result of a single prediction and there is no significant difference between the average result of the density and parameter values for the average charge density distribution.In addition,the 2pF parameters of 284(near)stable nuclei are predicted in this study,which provides a reference for the experiment.
文摘In this paper, we consider the construction of the approximate profile-</span><span style="font-family:""> </span><span style="font-family:Verdana;">likelihood confidence intervals for parameters of the 2-parameter Weibull distribution based on small type-2 censored samples. In previous research works, the traditional Wald method has been used to construct approximate confidence intervals for the 2-parameter Weibull distribution</span><span style="font-family:""> </span><span style="font-family:Verdana;">under type-2 censoring scheme. However, the Wald technique is based on normality assumption and thus may not produce accurate interval estimates for small samples. The profile-likelihood and Wald confidence intervals are constructed for the shape and scale parameters of the 2-parameter Weibull distribution based on simulated and real type-2 censored data, and are hence compared using confidence length and coverage probability.
基金Project supported by the Science&Technology Plan of Guangdong Province,China(Grant Nos.2019B010132001 and 2019B010132003)the joint funding of the Nature Science Foundation of China(NSFC)&the Macao Science and Technology Development Fund(FDCT)of China(Grant No.62061160368)+1 种基金the National Key Research and Development Program of China(Grant Nos.2016YFB0400105 and 2017YFB0403001)the Zhuhai Key Technology Laboratory of Wide Bandgap Semiconductor Power Electronics,Sun Yat-sen University,China(Grant No.20167612042080001)。
文摘The uniform distribution model of the surface donor states in AlGaN/GaN heterostructures has been widely used in the theoretical calculation.A common and a triple-channel AlGaN/GaN heterostructure Schottky barrier diodes have been fabricated to verify the models,but the calculation results show the uniform distribution model can not provide enough electrons to form three separate 2DEGs in the triple-channel Al GaN/GaN heterostructure.Our experiments indicate the uniform distribution model is not quite right,especially for the multiple-channel AlGaN/GaN heterostructures.Besides,it is found the exponential distribution model possibly matches the actual distribution of the surface donor states better,which allows the 2DEG to form in each channel structure during the calculation.The exponential distribution model would be helpful in the research field.
基金Sponsored by the National Basic Research Program of China(973)(Grant No.2004CB41850)the Natural Science Foundation of Heilongjiang Prov-ince(Grant No.E200609)
文摘In this paper,the power law of particle size distributions (PSDs) in conventional water treatment processes is developed. After measuring the particle size distributions of raw-water,settled water and filtered water,a mathematical model between particle diameter and the amount of particles was studied. The value of collision frequency factor β in the PSDs model can be used to represent the collision behavior of particles ,and can be used as foundation exponent to choose suitable coagulation to accelerate particles aggregation. At the same time,the relationship between the value of parameter K and the total particles volume V was deduced. K is defined as particle volume exponent,which can represent the total volume of particles. The degression degree of K shows the removal efficiency of potable water treatment units.
基金Supported by the National Natural Science Foundation of China under Grant No 10774035the Foundation of Inner Mongolia University of Technology under Grant No X200937.
文摘The question of the power-law exponent of exponential growth networks is studied here.In a discrete case,the degree distribution is defined as the probability distribution of the discrete variable.Based on this,the degree distribution of the pseudofractal scale-free web,an exponential growth network,is obtained.The power-law exponent ln3/ln2 is analyzed according to the maximum likelihood principle.It satisfies consistency and is good for small generations of the network.For many exponential growth networks,their power-law exponent needs to be tested.The work provides a new view on the power-law exponent of an exponential growth network.
基金supported by the National Natural Science Foundation of China under Grant No.11671264
文摘The logarithmic moment estimations of parameters are proposed for two-parameter generalized Birnbaum-Saunders Logistic fatigue life distribution GBS-Logistic(α,β)under the full sample.The precisions of point estimations are investigated and compared with other point estimations by Monte-Carlo simulations.The approximate interval estimations of parameters are given by using Taylor expansion,and the precisions of approximate interval estimations are investigated by Monte-Carlo simulations.Finally,several examples show the feasibility of the methods.
基金supported by the Department of Civil and Environmental of the Universidad de la Costathe Center for Environmental Technology Research(Centro de Investigación de Tecnologías Ambientales–CITA)+1 种基金the Environmental Management and Sustainability Research Group(Grupo de Investigación de Gestión y Sostenibilidad Ambiental–GESSA)partial financial support from Colciencias Colombia(Project 141180764164,Contract 815-2018)。
文摘Black carbon(BC)is one of the short-lived air pollutants that contributes significantly to aerosol radiative forcing and global climate change.It is emitted by the incomplete combustion of fossil fuels,biofuels,and biomass.Urban environments are quite complex and thus,the use of mobile jointly with fixed monitoring provides a better understanding of the dynamics of BC distribution in such areas.The present study addresses the measurement of BC concentration using real-time mobile and ambient monitoring in Barranquilla,an industrialized urban area of the Colombian Caribbean.A microaethalometer(MA200)and an aethalometer(AE33)were used for measuring the BC concentration.The absorption Ångström exponent(AAE)values were determined for the study area,for identifying the BC emission sources.The results of the ambient sampling show that vehicle traffic emissions prevail;however,the influence of biomass burning was also observed.The mean ambient BC concentration was found to be 1.04±1.03μg/m^(3) and varied between 0.5 and 4.0μg/m^(3).From the mobile measurements obtained in real traffic conditions on the road,a much higher average value of 16.1±16.5μg/m^(3) was measured.Many parts of the city showed BC concentrations higher than 20μg/m^(3).The spatial distribution of BC concentration shows that vehicle emissions and traffic jams,a consequence of road and transport infrastructure,are the factors that most affect the BC concentration.A comparison of results obtained from two aethalometers indicates that the concentrations measured by MA200 are 9%lower than those measured by AE33.The AAE obtained was found to vary between 1.1 and 1.6,indicating vehicular emissions as the most crucial source.In addition,it was observed that the BC concentration on working days was 2.5 times higher than on the weekends in the case of mobile monitoring and 1.5 times higher in the case of ambient monitoring.
基金supported by the National Natural Science Foundation of China (11874384)。
文摘In view of the non-Gaussian ocean ambient noise,the a stable distribution is applied to the statistical modeling.Firstly,the correspondence between the model characteristic exponent and the sample kurtosis is established based on the similarity in physical meaning of the two.And the kurtosis of the sum of two independent random variables is deduced,and this can be used to explain the kurtosis characteristic of interfered background noise.Secondly,some numerical simulations are made to model samples with higher and lower kurtosis than three,the results show good adaptability in leptokurtic distribution.Finally,three typical samples are taken under quiet environment,air gun interference and ship interference environment.Their Gaussianities are judged by the quantile-quantile plot.And then the four parameters of the model are estimated by the quantile based method and characteristic function based method jointly of the three categories.The statistical law of the characteristic exponent is emphatically analyzed:in the quiet environment,the characteristic exponent is close to 2.0,which is the value of Gaussian model;but for the air gun data,it is between 1.2 and 1.7,which means leptokurtic;and under the interference of the sailing ship,the value of a is related to the ship speed and the distance from the ship source to the receiving location,the more significant the ship impact is,the smaller the characteristic exponent is,which is consistent with the variation of kurtosis of disturbing noise in physical meaning.The results of the model verification show that the a stable distribution behaves well under the above three kinds of trial conditions,especially for the air gun environment which is far superior to the normal distribution.
基金National Natural Science Fundation of China(Grant No. 69735101)
文摘This letter presents a new one-dimensional chaotic map with infinite collapses. Theoretical analyses show that the map has complicated dynamical behavior and ideal distribution.The map can be applied in chaotic spreading spectrum communication and chaotic cipher.
文摘This paper deals with a stochastic representation of the rainfall process. The analysis of a rainfall time series shows that cumulative representation of a rainfall time series can be modeled as a non-Gaussian random walk with a log-normal jump distribution and a time-waiting distribution following a tempered a-stable probability law. Based on the random walk model, a fractional Fokker-Planck equation （FFPE） with tempered a-stable waiting times was obtained. Through the comparison of observed data and simulated results from the random walk model and FFPE model with tempered a-stable waiting times, it can be concluded that the behavior of the rainfall process is globally reproduced, and the FFPE model with tempered a-stable waiting times is more efficient in reproducing the observed behavior.
