In the reliability designing procedure of the vehicle components, when the distribution styles of the random variables are unknown or non-normal distribution, the result evaluated contains great error or even is wrong...In the reliability designing procedure of the vehicle components, when the distribution styles of the random variables are unknown or non-normal distribution, the result evaluated contains great error or even is wrong if the reliability value R is larger than 1 by using the existent method, in which case the formula is necessary to be revised. This is obviously inconvenient for programming. Combining reliability-based optimization theory, robust designing method and reliability based sensitivity analysis, a new method for reliability robust designing is proposed. Therefore the influence level of the designing parameters’ changing to the reliability of vehicle components can be obtained. The reliability sensitivity with respect to design parameters is viewed as a sub-objective function in the multi-objective optimization problem satisfying reliability constraints. Given the first four moments of basic random variables, a fourth-moment technique and the proposed optimization procedure can obtain reliability-based robust design of automobile components with non-normal distribution parameters accurately and quickly. By using the proposed method, the distribution style of the random parameters is relaxed. Therefore it is much closer to the actual reliability problems. The numerical examples indicate the following: (1) The reliability value obtained by the robust method proposed increases (】0.04%) comparing to the value obtained by the ordinary optimization algorithm; (2) The absolute value of reliability-based sensitivity decreases (】0.01%), and the robustness of the products’ quality is improved accordingly. Utilizing the reliability-based optimization and robust design method in the reliability designing procedure reduces the manufacture cost and provides the theoretical basis for the reliability and robust design of the vehicle components.展开更多
With the help of today’s computers, it is always relatively easy to find maximum-likelihood estimators of one or more parameters of any specific statistical distribution, and use these to construct the corresponding ...With the help of today’s computers, it is always relatively easy to find maximum-likelihood estimators of one or more parameters of any specific statistical distribution, and use these to construct the corresponding approximate confidence interval/region, facilitated by the well-known asymptotic properties of the likelihood function. The purpose of this article is to make this approximation substantially more accurate by extending the Taylor expansion of the corresponding probability density function to include quadratic and cubic terms in several centralized sample means, and thus finding the corresponding -proportional correction to the original algorithm. We then demonstrate the new procedure’s usage, both for constructing confidence regions and for testing hypotheses, emphasizing that incorporating this correction carries minimal computational and programming cost. In our final chapter, we present two examples to indicate how significantly the new approximation improves the procedure’s accuracy.展开更多
Raindrop size distribution(DSD)is crucial in the study of precipitation microphysics,but the parameters that characterize the DSD is not easy to be derived accurately.Wind profile radar(WPR)provides rich data with hig...Raindrop size distribution(DSD)is crucial in the study of precipitation microphysics,but the parameters that characterize the DSD is not easy to be derived accurately.Wind profile radar(WPR)provides rich data with high spatiotemporal resolution and low attenuation,and the previous studies using WPR power spectral distribution to extract DSD parameters demonstrate certain limitations.In this study,a WPR-based Gamma DSD parameter estimation network(WPR-DSDnet)combined with a neural network(NN)and a long short-term memory(LSTM)network is designed,and then a WPR-DSDnet-based model is trained to retrieve the Gamma DSD parameters including normalized intercept parameter(N_(w))and mass-weighted average diameter(D_(m))by means of the high-resolution WPR reflectivity factor and velocity spectral width as the inputs,and the spatiotemporal matching disdrometer data collected from 2017 to 2021 in Beijing as labels.Two precipitation cases are used to validate the performance of the model,and the results demonstrate that the model can retrieve the Gamma DSD parameters effectively,in which the ratio between the estimated and measured values of both lg N_(w)and D_(m)exceeds 99%.The estimation accuracy of lg N_(w)is slightly better than that of D_(m)due to smaller relative deviation of lg N_(w)although the absolute deviation between the estimated and true values of lg N_(w)is larger than that of D_(m),which are probably caused by the larger distribution range of lg N_(w).The vertical distributions of lg N_(w)closely aligns with variations in precipitation intensity,which hints it is a useful indicator for precipitation intensity change.On the other hand,the distribution of D_(m)is closely associated with the degree of convection,which is valuable for precipitation recognition and classification.The two parameters extracted by the deep learning-based model can facilitate further in-depth analysis on precipitation characteristics and mechanisms with WPR data.展开更多
This study introduces a continuum medium approximation(CMA)and an empirical effective medium approxi-mation(EMA)-type formulation to estimate the transport properties,including electrical conductivity,thermal conducti...This study introduces a continuum medium approximation(CMA)and an empirical effective medium approxi-mation(EMA)-type formulation to estimate the transport properties,including electrical conductivity,thermal conductivity,Seebeck coefficient,and Hall mobility,of nanostructured composites.The CMA incorporates the interface parameters mediated by newly introduced distribution functions to resolve predictions that deviate from the inclusion properties at its volume fraction of 1 in current EMAs and yields predictions agreed well with both the empirical EMA and experimental data.The empirical EMA-type formulation resolves the differ-ences in CMA predictions for the media A_(1-x)B_(x)and B_(1-x)A_(x)and provides a unique prediction that agrees very well with experimental data at a given volume fraction ranging from 0 to 1.The effects of the interface param-eters on the transport properties were investigated.The results indicated that the efficiency of nanostructured composites could be further improved by optimizing the interface parameters.展开更多
Since the effectiveness of the flexible current arc suppression method heavily relies on the accurate measurement of the distribution line-to-ground parame-ters,the suppression of single line-to-ground(SLG)fault curre...Since the effectiveness of the flexible current arc suppression method heavily relies on the accurate measurement of the distribution line-to-ground parame-ters,the suppression of single line-to-ground(SLG)fault current may deteriorate due to factors such as line switching and other disturbances during SLG fault arc suppression.Additionally,during SLG fault arc suppres-sion,promptly identifying the fault type and rapidly de-activating the flexible arc suppression device(FASD)can reduce the overvoltage risk in non-faulted phase devices.To address these issues,this paper presents a parameter identification method based on recursive least squares(RLS)while a variable forgetting factor strategy is in-troduces to enhance the RLS algorithm’s disturbance rejection capability.Simulations verify that the variable forgetting factor recursive least squares(VFF-RLS)algo-rithm can accurately identify distribution line-to-ground parameters in real time and effectively suppress SLG fault current.The online identification of grounding transition conductance is simultaneously used to deter-mine the fault type and quickly detect when the SLG fault has been cleared.展开更多
Burden distribution is one of the most important operations, and also an important upper regulation in blast furnace(BF) iron-making process. Burden distribution output behaviors(BDOB) at the throat of BF is a 3-dimen...Burden distribution is one of the most important operations, and also an important upper regulation in blast furnace(BF) iron-making process. Burden distribution output behaviors(BDOB) at the throat of BF is a 3-dimensional spatial distribution produced by burden distribution matrix(BDM),including burden surface output shape(BSOS) and material layer initial thickness distribution(MLITD). Due to the lack of effective model to describe the complex input-output relations,BDM optimization and adjustment is carried out by experienced foremen. Focusing on this practical challenge, this work studies complex burden distribution input-output relations, and gives a description of expected MLITD under specific integral constraint on the basis of engineering practice. Furthermore, according to the decision variables in different number fields, this work studies optimization of BDM with expected MLITD, and proposes a multi-mode based particle swarm optimization(PSO) procedure for optimization of decision variables. Finally, experiments using industrial data show that the proposed model is effective, and optimized BDM calculated by this multi-model based PSO method can be used for expected distribution tracking.展开更多
Previous studies have shown that the fatigue life distribution of metal materials fabricated with Additive Manufacturing(AM) methods, such as Direct Energy Deposited(DED) Ti-6.5Al-2Zr-1Mo-1V alloys, exhibits two peaks...Previous studies have shown that the fatigue life distribution of metal materials fabricated with Additive Manufacturing(AM) methods, such as Direct Energy Deposited(DED) Ti-6.5Al-2Zr-1Mo-1V alloys, exhibits two peaks. To promote the application of AM in aerospace and other engineering fields, developing a fatigue strength evaluation method suitable for AM materials based on their unique fatigue behaviours and fatigue life distributions is necessary. In this paper, a novel Detail Fatigue Rating(DFR) method was developed to evaluate the fatigue strength of DED Ti-6.5Al-2Zr-1Mo-1V based on a bimodal Weibull distribution and the excessive restriction on the allowable stress of potential was improved. Meanwhile, a Bimodal Weibull distribution model for fatigue life and its parameter estimation method were established based on a twoparameter Weibull distribution. The fatigue life at a specific reliability level and confidence level was calculated by using the bootstrap method. The calculation results showed that fatigue life estimated by using the bimodal Weibull distribution at the high reliability level and high confidence level is higher than that estimated by using the two-parameter Weibull distribution. Furthermore,The S-N curve at the specified confidence level and reliability level was fitted.展开更多
The modelling of the distribution transformer winding is the starting point and serves as important basis for the transformer characteristics analysis and the lightning pulse response prediction.A distributed paramete...The modelling of the distribution transformer winding is the starting point and serves as important basis for the transformer characteristics analysis and the lightning pulse response prediction.A distributed parameters model can depict the winding characteristics accurately,but it requires complex calculations.Lumped parameter model requires less calculations,but its applicable frequency range is not wide.This paper studies the amplitude-frequency characteristics of the lightning wave,compares the transformer modelling methods and finally proposes a modified lumped parameter model,based on the above comparison.The proposed model minimizes the errors provoked by the lumped parameter approximation,and the hyperbolic functions of the distributed parameter model.By this modification it becomes possible to accurately describe the winding characteristics and rapidly obtain the node voltage response.The proposed model can provide theoretical and experimental support to lightning protection of the distribution transformer.展开更多
Spectrum distribution of the second order generalized distributed parameter system was discussed via the functional analysis and operator theory in Hilbert space. The solutions of the problem and the constructive expr...Spectrum distribution of the second order generalized distributed parameter system was discussed via the functional analysis and operator theory in Hilbert space. The solutions of the problem and the constructive expression of the solutions are given by the generalized inverse one of bounded linear operator. This is theoretically important for studying the stabilization and asymptotic stability of the second order generalized distributed parameter system.展开更多
The dynamic performance of a nozzle-flapper servo valve can be affected by several factors such as the disturbance of the input signal,the motion of the armature assembly and the oscillation of the jet force.As the pa...The dynamic performance of a nozzle-flapper servo valve can be affected by several factors such as the disturbance of the input signal,the motion of the armature assembly and the oscillation of the jet force.As the part of vibrating at high frequency,the armature assembly plays a vital role during the operation of the servo valve.In order to accurately predict the transient response of the armature assembly during the vibration,a mathematical model of armature assembly is established based on the distributed parameters method(DPM)and Hamilton principle.The new mathematical model is composed of three main parts,the modal eigenfunction,modal mechanical response expressions of the spring tube and the motion equation of the other armature assembly.After programing,the purpose of using the DPM to predict the dynamic response of different positions located on the armature assembly is achieved.For verifying the validity of the mathematical model,the finite element method(FEM)and classic model(CM)of armature assembly are applicated by commercial software under the same condition.The comparison results prove that the DPM can effectively predict the axial and tangential deflection of the armature assembly different positions which the CM can’t duing to its over-simplification.A certain error is generated when predicting the axial deformation at different heights by DPM,which is caused by an approximate method to simulate the torsion of the spring tube.The comparison results of the spring tube deflection at different vibration frequencies shows that the adaptability of DPM is significantly higher than the classic model,which verify the model is more adaptable for predicting the dynamic response of the armature assembly.展开更多
In this paper, we devote to constructing the one-sided empirical Bayes(EB) test for the location parameter in the Gamma distribution by nonparametric method. Under some mild conditions, we prove that the EB test is as...In this paper, we devote to constructing the one-sided empirical Bayes(EB) test for the location parameter in the Gamma distribution by nonparametric method. Under some mild conditions, we prove that the EB test is asymptotically optimal with the rate of the order O(n^(-δs/(2s+1))), where 1/2 ≤ δ < 1 and s > 1 is a given natural number. An example is also given to illustrate that the conditions of the main theorems are easily satisfied.展开更多
Particle size distribution of coarse aggregates through mechanical sieving gives results in terms of cumu- lative mass percent. But digital image processing generated size distribution of particles, while being fast a...Particle size distribution of coarse aggregates through mechanical sieving gives results in terms of cumu- lative mass percent. But digital image processing generated size distribution of particles, while being fast and accurate, is often expressed in terms of area function or number of particles. In this paper, a mass model is developed which converts the image obtained size distribution to mass-wise distribution, mak- ing it readily comparable to mechanical sieving data. The concept of weight/particle ratio is introduced for mass reconstruction from 2D images of particle aggregates. Using this mass model, the effects of several particle shape parameters （such as major axis, minor axis, and equivalent diameter） on sieve-size of the particles is studied. It is shown that the sieve-size of a particle strongly depend upon the shape param- eters, 91% of its variation being explained by major axis, minor axis, bounding box length and equivalent diameter. Furthermore, minor axis gives an overall accurate estimate of particle sieve-size, error in mean size （D-50） being just 0.4%. However, sieve-size of smaller particles （〈20 ram） strongly depends upon the length of the smaller arm of the bounding box enclosing them and sieve-sizes of larger particles （〉20 mm） are highly correlated to their equivalent diameters. Multiple linear regression analysis has been used to generate overall mass-wise particle size distribution, considering the influences of all these shape parameters on particle sieve-size. Multiple linear regression generated overall mass-wise particle size distribution shows a strong correlation with sieve generated data. The adjusted R-square value of the regression analysis is found to be 99 percent （w.r,t cumulative frequency）. The method proposed in this paper provides a time-efficient way of producing accurate （up to 99%） mass-wise PSD using digital image processing and it can be used effectively to renlace the mechanical sieving.展开更多
The modelling of one kind of nonlinear parabolic distributed parameter control system with moving boundary, which had extensive applications was presented, Two methods were used to investigate the basic characteristic...The modelling of one kind of nonlinear parabolic distributed parameter control system with moving boundary, which had extensive applications was presented, Two methods were used to investigate the basic characteristics of the system: I) transforming the system it? the variable domain into that in the fixed domain; 2) transforming the distributed parameter system into the lumped parameter system. It is found that there are two critical values for the control variable : the larger one determines whether or not the boundary would move, while the smaller one determines whether or not the boundary, would atop automatically. For one-dimensional system of planar, cylindrical and spherical cases the definite solution problem can be expressed as a unified form. By means of the computer simulation the open-loop control system and close-cycle feedback control system have been investigated. Numerical results agree well with theoretical results. The computer simulation shows that the system is well posed, stable, measurable and controllable.展开更多
Based on the relationship between parameters of grain boundary internal friction peak (GBP) and grain boundary character distribution (GBCD), and the internal friction results of Al-Mg, Al-Ga, Al-Cu and Al-Zn alloys, ...Based on the relationship between parameters of grain boundary internal friction peak (GBP) and grain boundary character distribution (GBCD), and the internal friction results of Al-Mg, Al-Ga, Al-Cu and Al-Zn alloys, the addition of different kinds of solute atoms has different effects on GBCD. Among them, Mg atoms are able to concentrate and stabilize GBCD in Al-Mg alloys. The origin of these effects of solute atoms on GBCD is also discussed.展开更多
The (2+1)-dimensional Maxwell-Chern-Simons gravity with phantom dilaton field coupling is studied in this paper.It is shown that black hole solution to exist when electromagnetic coupled to dilaton field in the non-tr...The (2+1)-dimensional Maxwell-Chern-Simons gravity with phantom dilaton field coupling is studied in this paper.It is shown that black hole solution to exist when electromagnetic coupled to dilaton field in the non-trivial way.Moreover,asymptotic index and distribution parameter of current density are calculated by using black hole solution,some new features of this solution are briefly discussed.展开更多
An approach to design multi-channel cylinder dryer was proposed. The heat transfer performance and flow characteristic under various structural parameters were analyzed. First, an experiment was designed and set up to...An approach to design multi-channel cylinder dryer was proposed. The heat transfer performance and flow characteristic under various structural parameters were analyzed. First, an experiment was designed and set up to measure the condensing heat transfer coefficient and the pressure drop in order to ,~erify the applicability of the Cavallini＇s correlation. Then, the relationship among the count of channels, aspect ratio, spacing ratio, width, height and hydraulic diameter of a channel was given. Finally, the correlation of condensing heat transfer and the homogeneous model was introduced in order to observe the heat transfer performance and flow characteristic of the multi-channel cylinder dryer affected by different structures. The study reveals that the structural parameters including count of channels, aspect ratio, spacing ratio of a channel dramatically influence the condensation heat transfer coefficient and frictional resistance of the steam. Based on the selected paper machine, it is suggested that the overall performance of the multi-channel cylinder dryer is best if the count of channels is 150-200, the aspect ratio is 1 ： 3 and the spacing ratio is 1 ： 1-1 ： 3.展开更多
We develop a policy of observer-based dynamic event-triggered state feedback control for distributed parameter systems over a mobile sensor-plus-actuator network.It is assumed that the mobile sensing devices that prov...We develop a policy of observer-based dynamic event-triggered state feedback control for distributed parameter systems over a mobile sensor-plus-actuator network.It is assumed that the mobile sensing devices that provide spatially averaged state measurements can be used to improve state estimation in the network.For the purpose of decreasing the update frequency of controller and unnecessary sampled data transmission, an efficient dynamic event-triggered control policy is constructed.In an event-triggered system, when an error signal exceeds a specified time-varying threshold, it indicates the occurrence of a typical event.The global asymptotic stability of the event-triggered closed-loop system and the boundedness of the minimum inter-event time can be guaranteed.Based on the linear quadratic optimal regulator, the actuator selects the optimal displacement only when an event occurs.A simulation example is finally used to verify that the effectiveness of such a control strategy can enhance the system performance.展开更多
It was analyzed that the finite element-cellular automaton （CAFE） method was used to simulate 3D-microstructures in solidification processes. Based on this method, the 3D-microstructure of 9SMn28 free-cutting steel ...It was analyzed that the finite element-cellular automaton （CAFE） method was used to simulate 3D-microstructures in solidification processes. Based on this method, the 3D-microstructure of 9SMn28 free-cutting steel was simulated in solidification processes and the simulation results are consistent with the experimental ones. In addition, the effects of Gaussian distribution parameters were also studied. The simulation results show that the higher the mean undercooling, the larger the columnar dendrite zones, and the larger the maximum nucleation density, the smaller the size of grains. The larger the standard deviation, the less the number of minimum grains is. However, the uniformity degree decreases first, and then increases gradually.展开更多
基金supported by National Natural Science Foundation of China (Grant Nos. 51135003, U1234208, 51205050)New Teachers' Fund for Doctor Stations of Ministry of Education of China (Grant No.20110042120020)+1 种基金Fundamental Research Funds for the Central Universities, China (Grant No. N110303003)China Postdoctoral Science Foundation (Grant No. 2011M500564)
文摘In the reliability designing procedure of the vehicle components, when the distribution styles of the random variables are unknown or non-normal distribution, the result evaluated contains great error or even is wrong if the reliability value R is larger than 1 by using the existent method, in which case the formula is necessary to be revised. This is obviously inconvenient for programming. Combining reliability-based optimization theory, robust designing method and reliability based sensitivity analysis, a new method for reliability robust designing is proposed. Therefore the influence level of the designing parameters’ changing to the reliability of vehicle components can be obtained. The reliability sensitivity with respect to design parameters is viewed as a sub-objective function in the multi-objective optimization problem satisfying reliability constraints. Given the first four moments of basic random variables, a fourth-moment technique and the proposed optimization procedure can obtain reliability-based robust design of automobile components with non-normal distribution parameters accurately and quickly. By using the proposed method, the distribution style of the random parameters is relaxed. Therefore it is much closer to the actual reliability problems. The numerical examples indicate the following: (1) The reliability value obtained by the robust method proposed increases (】0.04%) comparing to the value obtained by the ordinary optimization algorithm; (2) The absolute value of reliability-based sensitivity decreases (】0.01%), and the robustness of the products’ quality is improved accordingly. Utilizing the reliability-based optimization and robust design method in the reliability designing procedure reduces the manufacture cost and provides the theoretical basis for the reliability and robust design of the vehicle components.
文摘With the help of today’s computers, it is always relatively easy to find maximum-likelihood estimators of one or more parameters of any specific statistical distribution, and use these to construct the corresponding approximate confidence interval/region, facilitated by the well-known asymptotic properties of the likelihood function. The purpose of this article is to make this approximation substantially more accurate by extending the Taylor expansion of the corresponding probability density function to include quadratic and cubic terms in several centralized sample means, and thus finding the corresponding -proportional correction to the original algorithm. We then demonstrate the new procedure’s usage, both for constructing confidence regions and for testing hypotheses, emphasizing that incorporating this correction carries minimal computational and programming cost. In our final chapter, we present two examples to indicate how significantly the new approximation improves the procedure’s accuracy.
基金Supported by the Beijing Natural Science Foundation(8242029)Beijing Municipal Science and Technology Commission(Z221100005222016)+1 种基金Science&Technology Plan Project of Fujian Province(2021L3019)Open Grants of the State Key Laboratory of Severe Weather(2023LASW-B02)。
文摘Raindrop size distribution(DSD)is crucial in the study of precipitation microphysics,but the parameters that characterize the DSD is not easy to be derived accurately.Wind profile radar(WPR)provides rich data with high spatiotemporal resolution and low attenuation,and the previous studies using WPR power spectral distribution to extract DSD parameters demonstrate certain limitations.In this study,a WPR-based Gamma DSD parameter estimation network(WPR-DSDnet)combined with a neural network(NN)and a long short-term memory(LSTM)network is designed,and then a WPR-DSDnet-based model is trained to retrieve the Gamma DSD parameters including normalized intercept parameter(N_(w))and mass-weighted average diameter(D_(m))by means of the high-resolution WPR reflectivity factor and velocity spectral width as the inputs,and the spatiotemporal matching disdrometer data collected from 2017 to 2021 in Beijing as labels.Two precipitation cases are used to validate the performance of the model,and the results demonstrate that the model can retrieve the Gamma DSD parameters effectively,in which the ratio between the estimated and measured values of both lg N_(w)and D_(m)exceeds 99%.The estimation accuracy of lg N_(w)is slightly better than that of D_(m)due to smaller relative deviation of lg N_(w)although the absolute deviation between the estimated and true values of lg N_(w)is larger than that of D_(m),which are probably caused by the larger distribution range of lg N_(w).The vertical distributions of lg N_(w)closely aligns with variations in precipitation intensity,which hints it is a useful indicator for precipitation intensity change.On the other hand,the distribution of D_(m)is closely associated with the degree of convection,which is valuable for precipitation recognition and classification.The two parameters extracted by the deep learning-based model can facilitate further in-depth analysis on precipitation characteristics and mechanisms with WPR data.
文摘This study introduces a continuum medium approximation(CMA)and an empirical effective medium approxi-mation(EMA)-type formulation to estimate the transport properties,including electrical conductivity,thermal conductivity,Seebeck coefficient,and Hall mobility,of nanostructured composites.The CMA incorporates the interface parameters mediated by newly introduced distribution functions to resolve predictions that deviate from the inclusion properties at its volume fraction of 1 in current EMAs and yields predictions agreed well with both the empirical EMA and experimental data.The empirical EMA-type formulation resolves the differ-ences in CMA predictions for the media A_(1-x)B_(x)and B_(1-x)A_(x)and provides a unique prediction that agrees very well with experimental data at a given volume fraction ranging from 0 to 1.The effects of the interface param-eters on the transport properties were investigated.The results indicated that the efficiency of nanostructured composites could be further improved by optimizing the interface parameters.
基金supported in part by the National Natural Science Foundation of China(No.51677030)in part by the Natural Science Foundation of Fujian Province,China(No.2023J05106).
文摘Since the effectiveness of the flexible current arc suppression method heavily relies on the accurate measurement of the distribution line-to-ground parame-ters,the suppression of single line-to-ground(SLG)fault current may deteriorate due to factors such as line switching and other disturbances during SLG fault arc suppression.Additionally,during SLG fault arc suppres-sion,promptly identifying the fault type and rapidly de-activating the flexible arc suppression device(FASD)can reduce the overvoltage risk in non-faulted phase devices.To address these issues,this paper presents a parameter identification method based on recursive least squares(RLS)while a variable forgetting factor strategy is in-troduces to enhance the RLS algorithm’s disturbance rejection capability.Simulations verify that the variable forgetting factor recursive least squares(VFF-RLS)algo-rithm can accurately identify distribution line-to-ground parameters in real time and effectively suppress SLG fault current.The online identification of grounding transition conductance is simultaneously used to deter-mine the fault type and quickly detect when the SLG fault has been cleared.
基金supported by the National Natural Science Foundation of China(61763038,61763039,61621004,61790572,61890934,61973137)the Fundamental Research Funds for the Central Universities(N180802003)
文摘Burden distribution is one of the most important operations, and also an important upper regulation in blast furnace(BF) iron-making process. Burden distribution output behaviors(BDOB) at the throat of BF is a 3-dimensional spatial distribution produced by burden distribution matrix(BDM),including burden surface output shape(BSOS) and material layer initial thickness distribution(MLITD). Due to the lack of effective model to describe the complex input-output relations,BDM optimization and adjustment is carried out by experienced foremen. Focusing on this practical challenge, this work studies complex burden distribution input-output relations, and gives a description of expected MLITD under specific integral constraint on the basis of engineering practice. Furthermore, according to the decision variables in different number fields, this work studies optimization of BDM with expected MLITD, and proposes a multi-mode based particle swarm optimization(PSO) procedure for optimization of decision variables. Finally, experiments using industrial data show that the proposed model is effective, and optimized BDM calculated by this multi-model based PSO method can be used for expected distribution tracking.
基金the support from the National Key Research and Development Program of China(No.2017YFB1104003)National Natural Science Foundation of China(No.11772027)Aeronautical Science Foundation of China(No.201909051002)。
文摘Previous studies have shown that the fatigue life distribution of metal materials fabricated with Additive Manufacturing(AM) methods, such as Direct Energy Deposited(DED) Ti-6.5Al-2Zr-1Mo-1V alloys, exhibits two peaks. To promote the application of AM in aerospace and other engineering fields, developing a fatigue strength evaluation method suitable for AM materials based on their unique fatigue behaviours and fatigue life distributions is necessary. In this paper, a novel Detail Fatigue Rating(DFR) method was developed to evaluate the fatigue strength of DED Ti-6.5Al-2Zr-1Mo-1V based on a bimodal Weibull distribution and the excessive restriction on the allowable stress of potential was improved. Meanwhile, a Bimodal Weibull distribution model for fatigue life and its parameter estimation method were established based on a twoparameter Weibull distribution. The fatigue life at a specific reliability level and confidence level was calculated by using the bootstrap method. The calculation results showed that fatigue life estimated by using the bimodal Weibull distribution at the high reliability level and high confidence level is higher than that estimated by using the two-parameter Weibull distribution. Furthermore,The S-N curve at the specified confidence level and reliability level was fitted.
基金supported by the National Key Research and Development Plan of China under Grant(2016YFB0900600XXX)
文摘The modelling of the distribution transformer winding is the starting point and serves as important basis for the transformer characteristics analysis and the lightning pulse response prediction.A distributed parameters model can depict the winding characteristics accurately,but it requires complex calculations.Lumped parameter model requires less calculations,but its applicable frequency range is not wide.This paper studies the amplitude-frequency characteristics of the lightning wave,compares the transformer modelling methods and finally proposes a modified lumped parameter model,based on the above comparison.The proposed model minimizes the errors provoked by the lumped parameter approximation,and the hyperbolic functions of the distributed parameter model.By this modification it becomes possible to accurately describe the winding characteristics and rapidly obtain the node voltage response.The proposed model can provide theoretical and experimental support to lightning protection of the distribution transformer.
文摘Spectrum distribution of the second order generalized distributed parameter system was discussed via the functional analysis and operator theory in Hilbert space. The solutions of the problem and the constructive expression of the solutions are given by the generalized inverse one of bounded linear operator. This is theoretically important for studying the stabilization and asymptotic stability of the second order generalized distributed parameter system.
基金supported by National Natural Science Foundation of China(No.51675119)。
文摘The dynamic performance of a nozzle-flapper servo valve can be affected by several factors such as the disturbance of the input signal,the motion of the armature assembly and the oscillation of the jet force.As the part of vibrating at high frequency,the armature assembly plays a vital role during the operation of the servo valve.In order to accurately predict the transient response of the armature assembly during the vibration,a mathematical model of armature assembly is established based on the distributed parameters method(DPM)and Hamilton principle.The new mathematical model is composed of three main parts,the modal eigenfunction,modal mechanical response expressions of the spring tube and the motion equation of the other armature assembly.After programing,the purpose of using the DPM to predict the dynamic response of different positions located on the armature assembly is achieved.For verifying the validity of the mathematical model,the finite element method(FEM)and classic model(CM)of armature assembly are applicated by commercial software under the same condition.The comparison results prove that the DPM can effectively predict the axial and tangential deflection of the armature assembly different positions which the CM can’t duing to its over-simplification.A certain error is generated when predicting the axial deformation at different heights by DPM,which is caused by an approximate method to simulate the torsion of the spring tube.The comparison results of the spring tube deflection at different vibration frequencies shows that the adaptability of DPM is significantly higher than the classic model,which verify the model is more adaptable for predicting the dynamic response of the armature assembly.
基金Supported by the National Natural Science Foundation of China(11671375 and 11471303)Natural Science Foundation of Anhui Provincial Education Department(KJ2017A171)
文摘In this paper, we devote to constructing the one-sided empirical Bayes(EB) test for the location parameter in the Gamma distribution by nonparametric method. Under some mild conditions, we prove that the EB test is asymptotically optimal with the rate of the order O(n^(-δs/(2s+1))), where 1/2 ≤ δ < 1 and s > 1 is a given natural number. An example is also given to illustrate that the conditions of the main theorems are easily satisfied.
基金Indian Institute of Technology,Kharagpur in India for supporting this work
文摘Particle size distribution of coarse aggregates through mechanical sieving gives results in terms of cumu- lative mass percent. But digital image processing generated size distribution of particles, while being fast and accurate, is often expressed in terms of area function or number of particles. In this paper, a mass model is developed which converts the image obtained size distribution to mass-wise distribution, mak- ing it readily comparable to mechanical sieving data. The concept of weight/particle ratio is introduced for mass reconstruction from 2D images of particle aggregates. Using this mass model, the effects of several particle shape parameters （such as major axis, minor axis, and equivalent diameter） on sieve-size of the particles is studied. It is shown that the sieve-size of a particle strongly depend upon the shape param- eters, 91% of its variation being explained by major axis, minor axis, bounding box length and equivalent diameter. Furthermore, minor axis gives an overall accurate estimate of particle sieve-size, error in mean size （D-50） being just 0.4%. However, sieve-size of smaller particles （〈20 ram） strongly depends upon the length of the smaller arm of the bounding box enclosing them and sieve-sizes of larger particles （〉20 mm） are highly correlated to their equivalent diameters. Multiple linear regression analysis has been used to generate overall mass-wise particle size distribution, considering the influences of all these shape parameters on particle sieve-size. Multiple linear regression generated overall mass-wise particle size distribution shows a strong correlation with sieve generated data. The adjusted R-square value of the regression analysis is found to be 99 percent （w.r,t cumulative frequency）. The method proposed in this paper provides a time-efficient way of producing accurate （up to 99%） mass-wise PSD using digital image processing and it can be used effectively to renlace the mechanical sieving.
文摘The modelling of one kind of nonlinear parabolic distributed parameter control system with moving boundary, which had extensive applications was presented, Two methods were used to investigate the basic characteristics of the system: I) transforming the system it? the variable domain into that in the fixed domain; 2) transforming the distributed parameter system into the lumped parameter system. It is found that there are two critical values for the control variable : the larger one determines whether or not the boundary would move, while the smaller one determines whether or not the boundary, would atop automatically. For one-dimensional system of planar, cylindrical and spherical cases the definite solution problem can be expressed as a unified form. By means of the computer simulation the open-loop control system and close-cycle feedback control system have been investigated. Numerical results agree well with theoretical results. The computer simulation shows that the system is well posed, stable, measurable and controllable.
文摘Based on the relationship between parameters of grain boundary internal friction peak (GBP) and grain boundary character distribution (GBCD), and the internal friction results of Al-Mg, Al-Ga, Al-Cu and Al-Zn alloys, the addition of different kinds of solute atoms has different effects on GBCD. Among them, Mg atoms are able to concentrate and stabilize GBCD in Al-Mg alloys. The origin of these effects of solute atoms on GBCD is also discussed.
基金Supported by Natural Science Foundation of Sichuan Education Committee under Grant No. 11ZA100Scientific Research Foundation for Graduate Student of Sichuan Normal University under Grant No. 20113
文摘The (2+1)-dimensional Maxwell-Chern-Simons gravity with phantom dilaton field coupling is studied in this paper.It is shown that black hole solution to exist when electromagnetic coupled to dilaton field in the non-trivial way.Moreover,asymptotic index and distribution parameter of current density are calculated by using black hole solution,some new features of this solution are briefly discussed.
基金Acknowledgements This project is supported by the National Natural Science Foundation of China （Grant No. 51375286）, Natural Science Basic Research Plan in Shaanxi Province of China （Program No. 2012JZ7002） and the key scientific and technological innovation team fund of Shaanxi Province of China （Program No. 2014KCT- 15）.
文摘An approach to design multi-channel cylinder dryer was proposed. The heat transfer performance and flow characteristic under various structural parameters were analyzed. First, an experiment was designed and set up to measure the condensing heat transfer coefficient and the pressure drop in order to ,~erify the applicability of the Cavallini＇s correlation. Then, the relationship among the count of channels, aspect ratio, spacing ratio, width, height and hydraulic diameter of a channel was given. Finally, the correlation of condensing heat transfer and the homogeneous model was introduced in order to observe the heat transfer performance and flow characteristic of the multi-channel cylinder dryer affected by different structures. The study reveals that the structural parameters including count of channels, aspect ratio, spacing ratio of a channel dramatically influence the condensation heat transfer coefficient and frictional resistance of the steam. Based on the selected paper machine, it is suggested that the overall performance of the multi-channel cylinder dryer is best if the count of channels is 150-200, the aspect ratio is 1 ： 3 and the spacing ratio is 1 ： 1-1 ： 3.
基金Project supported by the National Natural Science Foundation of China (Grant No.62073045)。
文摘We develop a policy of observer-based dynamic event-triggered state feedback control for distributed parameter systems over a mobile sensor-plus-actuator network.It is assumed that the mobile sensing devices that provide spatially averaged state measurements can be used to improve state estimation in the network.For the purpose of decreasing the update frequency of controller and unnecessary sampled data transmission, an efficient dynamic event-triggered control policy is constructed.In an event-triggered system, when an error signal exceeds a specified time-varying threshold, it indicates the occurrence of a typical event.The global asymptotic stability of the event-triggered closed-loop system and the boundedness of the minimum inter-event time can be guaranteed.Based on the linear quadratic optimal regulator, the actuator selects the optimal displacement only when an event occurs.A simulation example is finally used to verify that the effectiveness of such a control strategy can enhance the system performance.
基金supported by the National Natural Science Foundation of China (No.50874007, 50774109)
文摘It was analyzed that the finite element-cellular automaton （CAFE） method was used to simulate 3D-microstructures in solidification processes. Based on this method, the 3D-microstructure of 9SMn28 free-cutting steel was simulated in solidification processes and the simulation results are consistent with the experimental ones. In addition, the effects of Gaussian distribution parameters were also studied. The simulation results show that the higher the mean undercooling, the larger the columnar dendrite zones, and the larger the maximum nucleation density, the smaller the size of grains. The larger the standard deviation, the less the number of minimum grains is. However, the uniformity degree decreases first, and then increases gradually.
