The paper studies reachability problem of autonomous ai^ine systems on n-dimensional polytopes.Our goal is to obtain both the largest positive invariant set in the polytope and the backward reachable set(the attractio...The paper studies reachability problem of autonomous ai^ine systems on n-dimensional polytopes.Our goal is to obtain both the largest positive invariant set in the polytope and the backward reachable set(the attraction domain)of each facet.Special attention is paid to the largest stable invariant affine subspace.After presenting several useful properties of those sets,a partition procedure is given to determine the largest positive invariant set in the polytope and all the attraction domains of facets.展开更多
Robust adaptive control of nonholonomic systems in chained form with linearly parameterized and strongly nonlinear disturbance and drift terms is dicussed.The novelty of the proposed method is a combined use of the st...Robust adaptive control of nonholonomic systems in chained form with linearly parameterized and strongly nonlinear disturbance and drift terms is dicussed.The novelty of the proposed method is a combined use of the state-scaling and the back-stepping procedure.展开更多
Dear Editor,This letter studies the bipartite consensus tracking problem for heterogeneous multi-agent systems with actuator faults and a leader's unknown time-varying control input. To handle such a problem, the ...Dear Editor,This letter studies the bipartite consensus tracking problem for heterogeneous multi-agent systems with actuator faults and a leader's unknown time-varying control input. To handle such a problem, the continuous fault-tolerant control protocol via observer design is developed. In addition, it is strictly proved that the multi-agent system driven by the designed controllers can still achieve bipartite consensus tracking after faults occur.展开更多
A grey-box modelling framework was developed for the estimation of cut point temperature of a crude distillation unit(CDU)under uncertainty in crude composition and process conditions.First principle(FP)model of CDU w...A grey-box modelling framework was developed for the estimation of cut point temperature of a crude distillation unit(CDU)under uncertainty in crude composition and process conditions.First principle(FP)model of CDU was developed for Pakistani crudes from Zamzama and Kunnar fields.A hybrid methodology based on the integration of Taguchi method and genetic algorithm(GA)was employed to estimate the optimal cut point temperature for various sets of process variables.Optimised datasets were utilised to develop an artificial neural networks(ANN)model for the prediction of optimum values of cut points.The ANN model was then used to replace the hybrid framework of the Taguchi method and the GA.The integration of the ANN and FP model makes it a grey-box(GB)model.For the case of Zamama crude,the GB model helped in the decrease of up to 38.93%in energy required per kilo barrel of diesel and an 8.2%increase in diesel production compared to the stand-alone FP model under uncertainty.Similarly,for Kunnar crude,up to 18.87%decrease in energy required per kilo barrel of diesel and a 33.96%increase in diesel production was observed in comparison to the stand-alone FP model.展开更多
In this study,a Grey-box(GB)model was developed to predict the optimum mass flow rates of inlet streams of a Shell and Tube Heat Exchanger(STHE)under varying process conditions.Aspen Exchanger Design and Rating(Aspen-...In this study,a Grey-box(GB)model was developed to predict the optimum mass flow rates of inlet streams of a Shell and Tube Heat Exchanger(STHE)under varying process conditions.Aspen Exchanger Design and Rating(Aspen-EDR)was initially used to construct a first principle model(FP)of the STHE using industrial data.The Genetic Algorithm(GA)was incorporated into the FP model to attain the minimum exit temperature for the hot kerosene process stream under varying process conditions.A dataset comprised of optimum process conditions was generated through FP-GA integration and was utilised to develop an Artificial Neural Networks(ANN)model.Subsequently,the ANN model was merged with the FP model by substituting the GA,to form a GB model.The developed GB model,that is,ANN and FP integration,achieved higher effectiveness and lower outlet temperature than those derived through the standalone FP model.Performance of the GB framework was also comparable to the FP-GA approach but it significantly reduced the computation time required for estimating the optimum process conditions.The proposed GB-based method improved the STHE's ability to extract energy from the process stream and strengthened its resilience to cope with diverse process conditions.展开更多
This survey provides a brief overview on the control Lyapunov function(CLF)and control barrier function(CBF)for general nonlinear-affine control systems.The problem of control is formulated as an optimization problem ...This survey provides a brief overview on the control Lyapunov function(CLF)and control barrier function(CBF)for general nonlinear-affine control systems.The problem of control is formulated as an optimization problem where the optimal control policy is derived by solving a constrained quadratic programming(QP)problem.The CLF and CBF respectively characterize the stability objective and the safety objective for the nonlinear control systems.These objectives imply important properties including controllability,convergence,and robustness of control problems.Under this framework,optimal control corresponds to the minimal solution to a constrained QP problem.When uncertainties are explicitly considered,the setting of the CLF and CBF is proposed to study the input-to-state stability and input-to-state safety and to analyze the effect of disturbances.The recent theoretic progress and novel applications of CLF and CBF are systematically reviewed and discussed in this paper.Finally,we provide research directions that are significant for the advance of knowledge in this area.展开更多
Tetrapod-shaped ZnO whiskers and microrods were synthesized in one crucible by thermal evaporation of Zn/C mixtures at 930 ℃ in air without any catalyst.The digital camera,optical microscopy,scanning electron microsc...Tetrapod-shaped ZnO whiskers and microrods were synthesized in one crucible by thermal evaporation of Zn/C mixtures at 930 ℃ in air without any catalyst.The digital camera,optical microscopy,scanning electron microscopy,energy dispersive X-ray spectroscopy,and X-ray diffraction techniques were used to study the morphologies and crystal structures of these tetrapod-shaped ZnO microcrystals.The results show that these two types of ZnO tetrapods are grown at different heights within the same crucible.The legs of these tetrapod-shaped ZnO crystals are hexagonally faceted.Some tetrapod-shaped ZnO whiskers show hierarchical structures.A short button-like hexagonal ZnO microcrystal is observed at the triple junctions of some tetrapod-shaped ZnO whiskers.The tetrapod-shaped ZnO microrods are capped by two sets of hexagonal pyramids with two different groups of crystal planes for the surfaces.These two types of tetrapod-shaped ZnO microcrystals have different side faces and aspect ratio,which are believed to be the result of their different growth behaviors.The octa-twin model was used to discuss the different growth behaviors of these two types of ZnO tetrapods.The crystal planes of the legs and the pyramids were determined.展开更多
In this investigation, the effect of time, percentage of copper and nickel on the hardness property of aluminum based powder metallurgy alloys were studied. A full factorial analysis with four levels for each factor w...In this investigation, the effect of time, percentage of copper and nickel on the hardness property of aluminum based powder metallurgy alloys were studied. A full factorial analysis with four levels for each factor was used. The samples were produced using powder metallurgy process, and then subjected to natural aging where heat treatment was conducted for all samples together at 550°C for 3 hours before quenching in water. Then, the samples were left at room temperature for 936 hours (39 days) to allow traces atoms to diffuse and form coherent phases which increase the hardness. It was found that the hardness was firstly increased with time for about 300 hours after the quenching time, and then it tends to remain constant after that. However, the hardness drop at overage stage was not observed until the end of 936 hours. To get a full analysis of the natural aging we used design of experiment tool to study the effect of %Cu, %Ni and aging time on the hardness. The results showed that the hardness was influenced significantly by all considered factors and interactions between them.展开更多
With income data from Chinese household income projects in 1998-2002, we study the functional form of Chinese income distribution. The fitting results suggest a log-normal distribution plus a power-law tail. This dist...With income data from Chinese household income projects in 1998-2002, we study the functional form of Chinese income distribution. The fitting results suggest a log-normal distribution plus a power-law tail. This distributional form has changed a lot from its appearance in the early stage of China＇s reform and turns out to be consistent with that of some complete market economies. The uncertainty and diversity of income growth rate aroused by marketing reform are the main causes of current Chinese income distribution.展开更多
Multi-objective robust state-feedback controller synthesis problems for linear discrete-time uncertain systems are addressed. Based on parameter-dependent Lyapunov functions, the Gl2 and GH2 norm expressed in terms of...Multi-objective robust state-feedback controller synthesis problems for linear discrete-time uncertain systems are addressed. Based on parameter-dependent Lyapunov functions, the Gl2 and GH2 norm expressed in terms of LMI (Linear Matrix Inequality) characterizations are further generalized to cope with the robust analysis for convex polytopic uncertain system. Robust state-feedback controller synthesis conditions are also derived for this class of uncertain systems. Using the above results, multi-objective state-feedback controller synthesis procedures which involve the LMI optimization technique are developed and less conservative than the existing one. An illustrative example verified the validity of the approach.展开更多
This paper studies the statistical characteristics of Chinese surnames, first names and full names based on a credible sample. The distribution of Chinese surnames, unlike that in any other countries, shows an exponen...This paper studies the statistical characteristics of Chinese surnames, first names and full names based on a credible sample. The distribution of Chinese surnames, unlike that in any other countries, shows an exponential pattern in the top part and a power-law pattern in the tail part. The distributions of Chinese first names and full names have the characteristics of a power law with different exponents. Finally, the interrelation of the first name and the surname is demonstrated by using a computer simulation and an exhibition of the name network. Chinese people take the surname into account when they choose a first name for somebody.展开更多
In this work,the Lie point symmetries of the inhomogeneous Toda lattice equation are obtained by semi-discrete exterior calculus,which is a semi-discrete version of Harrison and Estabrook’s geometric approach.A four-...In this work,the Lie point symmetries of the inhomogeneous Toda lattice equation are obtained by semi-discrete exterior calculus,which is a semi-discrete version of Harrison and Estabrook’s geometric approach.A four-dimensional Lie algebra and its one-,two-and three-dimensional subalgebras are given.Two similarity reductions of the inhomogeneous Toda lattice equation are obtained by using the symmetry vectors.展开更多
Based on suitable choice of states, this paper studies the stability of the equilibrium state of the EZ model by regarding the evolution of the EZ model as a Markov chain and by showing that the Markov chain is ergodi...Based on suitable choice of states, this paper studies the stability of the equilibrium state of the EZ model by regarding the evolution of the EZ model as a Markov chain and by showing that the Markov chain is ergodic. The Markov analysis is applied to the EZ model with small number of agents, the exact equilibrium state for N = 5 and numerical results for N = 18 are obtained.展开更多
We systematically study the size dependency of income distributions,i.e.income distribution versus the population of a country.Using the generalized Lotka--Uolterra model to fit the empirical income data for 1996-2007...We systematically study the size dependency of income distributions,i.e.income distribution versus the population of a country.Using the generalized Lotka--Uolterra model to fit the empirical income data for 1996-2007 in the U.S.A,we find an important parameter A that can scale with aβpower of the size(population)of the U.S.A.in that year.We point out that the size dependency of income distributions,which is a very important property but seldom addressed in previous studies,has two non-trivial implications:(1)the allometric growth pattern,i.e.the power-law relationship between population and GDP in different years,can be mathematically derived from the size-dependent income distributions and also supported by the empirical data;(2)the connection with the anomalous scaling for the probability density function in critical phenomena,since the re-scaled form of the income distributions has asymptotically exactly the same mathematical expression for the limit distribution of the sum of many correlated random variables.展开更多
An experimental study investigated the characteristics of a stretched cylindrical diffusion flame, with a convex curvature with respect to the air stream, in response to periodic air flow velocity oscillation. The fue...An experimental study investigated the characteristics of a stretched cylindrical diffusion flame, with a convex curvature with respect to the air stream, in response to periodic air flow velocity oscillation. The fuel was methane diluted with nitrogen, and the oxidizer air. The oscillation frequency was varied from 5 to 250 Hz. The results are summarized as follows. Though the fluctuation amplitude of the air stream velocity gradient was constant with respect to the frequency, the amplitude of the fuel stream increased. The fluctuation amplitude of the flame radius changed quasi-steadily from 5 to 25 Hz, and decreased with increasing frequency in the frequency range greater than 50 Hz. The flame luminosity did not respond quasi-steadily at 5 Hz, and the oscillation amplitude of flame luminosity was less than that of a steady flame, over the same velocity fluctuation range. The oscillation amplitude of luminosity peaked at 50 Hz, and was greater than that of a steady flame. It is considered that this complex change in flame luminosity with respect to frequency was closely related to the phase difference in the respective time variations in the ratio of flame thickness to radius, the velocity gradients of the air and fuel streams, and the magnitude of these values, with the ratio of flame thickness to radius related to the flame curvature effect, the velocity gradient of the air stream correlated to the flame stretch effect, and the velocity gradient of the fuel stream impacting the fuel transportation.展开更多
Hardware-based sensing frameworks such as cooperative fuel research engines are conventionally used to monitor research octane number(RON)in the petroleum refining industry.Machine learning techniques are employed to ...Hardware-based sensing frameworks such as cooperative fuel research engines are conventionally used to monitor research octane number(RON)in the petroleum refining industry.Machine learning techniques are employed to predict the RON of integrated naphtha reforming and isomerisation processes.A dynamic Aspen HYSYS model was used to generate data by introducing artificial uncertainties in the range of±5%in process conditions,such as temperature,flow rates,etc.The generated data was used to train support vector machines(SVM),Gaussian process regression(GPR),artificial neural networks(ANN),regression trees(RT),and ensemble trees(ET).Hyperparameter tuning was performed to enhance the prediction capabilities of GPR,ANN,SVM,ET and RT models.Performance analysis of the models indicates that GPR,ANN,and SVM with R2 values of 0.99,0.978,and 0.979 and RMSE values of 0.108,0.262,and 0.258,respectively performed better than the remaining models and had the prediction capability to capture the RON dependence on predictor variables.ET and RT had an R2 value of 0.94 and 0.89,respectively.The GPR model was used as a surrogate model for fitness function evaluations in two optimisation frameworks based on genetic algorithm and particle swarm method.Optimal parameter values found by the optimisation methodology increased the RON value by 3.52%.The proposed methodology of surrogate-based optimisation will provide a platform for plant-level implementation to realise the concept of industry 4.0 in the refinery.展开更多
Detecting coupling pattern between elements in a complex system is a basic task in data-driven analysis. The trajectory for each specific element is a cooperative result of its intrinsic dynamic, its couplings with ot...Detecting coupling pattern between elements in a complex system is a basic task in data-driven analysis. The trajectory for each specific element is a cooperative result of its intrinsic dynamic, its couplings with other elements, and the environment. It is subsequently composed of many components, only some of which take part in the couplings. In this paper we present a framework to detect the component correlation pattern. Firstly, the interested trajectories are decomposed into components by using decomposing methods such as the Fourier expansion and the Wavelet transformation. Secondly, the cross-correlations between the components are calculated, resulting into a component cross-correlation matrix(network).Finally, the dominant structure in the network is identified to characterize the coupling pattern in the system. Several deterministic dynamical models turn out to be characterized with rich structures such as the clustering of the components. The pattern of correlation between respiratory(RESP) and ECG signals is composed of five sub-clusters that are mainly formed by the components in ECG signal. Interestingly, only 7 components from RESP(scattered in four sub-clusters) take part in the realization of coupling between the two signals.展开更多
Along with the development of information technologies such as mobile Internet,information acquisition technology,cloud computing and big data technology,the traditional knowledge engineering and knowledge-based softw...Along with the development of information technologies such as mobile Internet,information acquisition technology,cloud computing and big data technology,the traditional knowledge engineering and knowledge-based software engineering have undergone fundamental changes where the network plays an increasingly important role.Within this context,it is required to develop new methodologies as well as technical tools for network-based knowledge representation,knowledge services and knowledge engineering.Obviously,the term“network”has different meanings in different scenarios.Meanwhile,some breakthroughs in several bottleneck problems of complex networks promote the developments of the new methodologies and technical tools for network-based knowledge representation,knowledge services and knowledge engineering.This paper first reviews some recent advances on complex networks,and then,in conjunction with knowledge graph,proposes a framework of networked knowledge which models knowledge and its relationships with the perspective of complex networks.For the unique advantages of deep learning in acquiring and processing knowledge,this paper reviews its development and emphasizes the role that it played in the development of knowledge engineering.Finally,some challenges and further trends are discussed.展开更多
We analyse the data from the recently published lists of the richest Chinese from the year 2003 to 2005. The results confirm that in these years the wealth is distributed according to a power law with exponents betwee...We analyse the data from the recently published lists of the richest Chinese from the year 2003 to 2005. The results confirm that in these years the wealth is distributed according to a power law with exponents between 1.758 and 2.285 in the high end. The power distribution is found to be quite robust although the persons in the list change drastically and the wealth increases rapidly. The relation between the wealth and the absolute change of wealth rejects the notion that the wealth evolution is a multiplicative stochastic process.展开更多
This article describes an Internet based laboratory (NETLAB) developed at Zhejiang University for electrical engi- neering education. A key feature of the project is the use of real experimental systems rather than si...This article describes an Internet based laboratory (NETLAB) developed at Zhejiang University for electrical engi- neering education. A key feature of the project is the use of real experimental systems rather than simulation or virtual reality. NELTAB provides remote access to a wide variety of experiments, including not only basic electrical and electronic experiments but also many innovative control experiments. Students can effectively use the laboratory at any time and from anywhere. NETLAB has been in operation since July 2003.展开更多
基金Supported by National Natural Science Foundation of China(60504024)Zhejiang Provincial Natural Science Foundation of China(Y106010)the Specialized Research Fund for the Doctoral Program of Higher Education of China(20060335022)
文摘The paper studies reachability problem of autonomous ai^ine systems on n-dimensional polytopes.Our goal is to obtain both the largest positive invariant set in the polytope and the backward reachable set(the attraction domain)of each facet.Special attention is paid to the largest stable invariant affine subspace.After presenting several useful properties of those sets,a partition procedure is given to determine the largest positive invariant set in the polytope and all the attraction domains of facets.
文摘Robust adaptive control of nonholonomic systems in chained form with linearly parameterized and strongly nonlinear disturbance and drift terms is dicussed.The novelty of the proposed method is a combined use of the state-scaling and the back-stepping procedure.
基金supported by the National Natural Science Foundation of China(62325304,U22B2046,62073079,62376029)the Jiangsu Provincial Scientific Research Center of Applied Mathematics(BK20233002)the China Postdoctoral Science Foundation(2023M730255,2024T171123)
文摘Dear Editor,This letter studies the bipartite consensus tracking problem for heterogeneous multi-agent systems with actuator faults and a leader's unknown time-varying control input. To handle such a problem, the continuous fault-tolerant control protocol via observer design is developed. In addition, it is strictly proved that the multi-agent system driven by the designed controllers can still achieve bipartite consensus tracking after faults occur.
基金Higher Education Commission,Pakistan,under the National Research Program for Universities Project,Grant/Award Number:NBU-FPEJ-2024-1243-02。
文摘A grey-box modelling framework was developed for the estimation of cut point temperature of a crude distillation unit(CDU)under uncertainty in crude composition and process conditions.First principle(FP)model of CDU was developed for Pakistani crudes from Zamzama and Kunnar fields.A hybrid methodology based on the integration of Taguchi method and genetic algorithm(GA)was employed to estimate the optimal cut point temperature for various sets of process variables.Optimised datasets were utilised to develop an artificial neural networks(ANN)model for the prediction of optimum values of cut points.The ANN model was then used to replace the hybrid framework of the Taguchi method and the GA.The integration of the ANN and FP model makes it a grey-box(GB)model.For the case of Zamama crude,the GB model helped in the decrease of up to 38.93%in energy required per kilo barrel of diesel and an 8.2%increase in diesel production compared to the stand-alone FP model under uncertainty.Similarly,for Kunnar crude,up to 18.87%decrease in energy required per kilo barrel of diesel and a 33.96%increase in diesel production was observed in comparison to the stand-alone FP model.
基金National Research Program for Universities,Grant/Award Number:10215/FederalNorthern Border University,Arar,KSA,Grant/Award Number:NBU-FPEJ-2024-1243-01。
文摘In this study,a Grey-box(GB)model was developed to predict the optimum mass flow rates of inlet streams of a Shell and Tube Heat Exchanger(STHE)under varying process conditions.Aspen Exchanger Design and Rating(Aspen-EDR)was initially used to construct a first principle model(FP)of the STHE using industrial data.The Genetic Algorithm(GA)was incorporated into the FP model to attain the minimum exit temperature for the hot kerosene process stream under varying process conditions.A dataset comprised of optimum process conditions was generated through FP-GA integration and was utilised to develop an Artificial Neural Networks(ANN)model.Subsequently,the ANN model was merged with the FP model by substituting the GA,to form a GB model.The developed GB model,that is,ANN and FP integration,achieved higher effectiveness and lower outlet temperature than those derived through the standalone FP model.Performance of the GB framework was also comparable to the FP-GA approach but it significantly reduced the computation time required for estimating the optimum process conditions.The proposed GB-based method improved the STHE's ability to extract energy from the process stream and strengthened its resilience to cope with diverse process conditions.
基金supported in part by the National Natural Science Foundation of China(U22B2046,62073079,62088101)in part by the General Joint Fund of the Equipment Advance Research Program of Ministry of Education(8091B022114)in part by NPRP(NPRP 9-466-1-103)from Qatar National Research Fund。
文摘This survey provides a brief overview on the control Lyapunov function(CLF)and control barrier function(CBF)for general nonlinear-affine control systems.The problem of control is formulated as an optimization problem where the optimal control policy is derived by solving a constrained quadratic programming(QP)problem.The CLF and CBF respectively characterize the stability objective and the safety objective for the nonlinear control systems.These objectives imply important properties including controllability,convergence,and robustness of control problems.Under this framework,optimal control corresponds to the minimal solution to a constrained QP problem.When uncertainties are explicitly considered,the setting of the CLF and CBF is proposed to study the input-to-state stability and input-to-state safety and to analyze the effect of disturbances.The recent theoretic progress and novel applications of CLF and CBF are systematically reviewed and discussed in this paper.Finally,we provide research directions that are significant for the advance of knowledge in this area.
基金Project(0061)supported by the Doctorate Foundation of Nanchang University,ChinaProject(2006015)supported by the Center for Analysis and Testing,Nanchang University,China
文摘Tetrapod-shaped ZnO whiskers and microrods were synthesized in one crucible by thermal evaporation of Zn/C mixtures at 930 ℃ in air without any catalyst.The digital camera,optical microscopy,scanning electron microscopy,energy dispersive X-ray spectroscopy,and X-ray diffraction techniques were used to study the morphologies and crystal structures of these tetrapod-shaped ZnO microcrystals.The results show that these two types of ZnO tetrapods are grown at different heights within the same crucible.The legs of these tetrapod-shaped ZnO crystals are hexagonally faceted.Some tetrapod-shaped ZnO whiskers show hierarchical structures.A short button-like hexagonal ZnO microcrystal is observed at the triple junctions of some tetrapod-shaped ZnO whiskers.The tetrapod-shaped ZnO microrods are capped by two sets of hexagonal pyramids with two different groups of crystal planes for the surfaces.These two types of tetrapod-shaped ZnO microcrystals have different side faces and aspect ratio,which are believed to be the result of their different growth behaviors.The octa-twin model was used to discuss the different growth behaviors of these two types of ZnO tetrapods.The crystal planes of the legs and the pyramids were determined.
文摘In this investigation, the effect of time, percentage of copper and nickel on the hardness property of aluminum based powder metallurgy alloys were studied. A full factorial analysis with four levels for each factor was used. The samples were produced using powder metallurgy process, and then subjected to natural aging where heat treatment was conducted for all samples together at 550°C for 3 hours before quenching in water. Then, the samples were left at room temperature for 936 hours (39 days) to allow traces atoms to diffuse and form coherent phases which increase the hardness. It was found that the hardness was firstly increased with time for about 300 hours after the quenching time, and then it tends to remain constant after that. However, the hardness drop at overage stage was not observed until the end of 936 hours. To get a full analysis of the natural aging we used design of experiment tool to study the effect of %Cu, %Ni and aging time on the hardness. The results showed that the hardness was influenced significantly by all considered factors and interactions between them.
基金Supported by the National Natural Science Foundation of China under Grant No 70771012, and the National Soft Science Project under Grant No 2008GXS5B104.
文摘With income data from Chinese household income projects in 1998-2002, we study the functional form of Chinese income distribution. The fitting results suggest a log-normal distribution plus a power-law tail. This distributional form has changed a lot from its appearance in the early stage of China＇s reform and turns out to be consistent with that of some complete market economies. The uncertainty and diversity of income growth rate aroused by marketing reform are the main causes of current Chinese income distribution.
基金Project (No. 60374028) supported by the National Natural ScienceFoundation of China
文摘Multi-objective robust state-feedback controller synthesis problems for linear discrete-time uncertain systems are addressed. Based on parameter-dependent Lyapunov functions, the Gl2 and GH2 norm expressed in terms of LMI (Linear Matrix Inequality) characterizations are further generalized to cope with the robust analysis for convex polytopic uncertain system. Robust state-feedback controller synthesis conditions are also derived for this class of uncertain systems. Using the above results, multi-objective state-feedback controller synthesis procedures which involve the LMI optimization technique are developed and less conservative than the existing one. An illustrative example verified the validity of the approach.
基金supported by the National Natural Science Foundation of China(Grant No.61174165)the Fundamental Research Funds for the Central Universities,China
文摘This paper studies the statistical characteristics of Chinese surnames, first names and full names based on a credible sample. The distribution of Chinese surnames, unlike that in any other countries, shows an exponential pattern in the top part and a power-law pattern in the tail part. The distributions of Chinese first names and full names have the characteristics of a power law with different exponents. Finally, the interrelation of the first name and the surname is demonstrated by using a computer simulation and an exhibition of the name network. Chinese people take the surname into account when they choose a first name for somebody.
基金Supported by National Natural Science Foundation of China under Grant Nos.11375030,11472315Department of Science and Technology of Henan Province under Grant No.162300410223Beijing Finance Funds of Natural Science Program for Excellent Talents under Grant No.2014000026833ZK19
文摘In this work,the Lie point symmetries of the inhomogeneous Toda lattice equation are obtained by semi-discrete exterior calculus,which is a semi-discrete version of Harrison and Estabrook’s geometric approach.A four-dimensional Lie algebra and its one-,two-and three-dimensional subalgebras are given.Two similarity reductions of the inhomogeneous Toda lattice equation are obtained by using the symmetry vectors.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 60534080, 60774085, and 70771012)
文摘Based on suitable choice of states, this paper studies the stability of the equilibrium state of the EZ model by regarding the evolution of the EZ model as a Markov chain and by showing that the Markov chain is ergodic. The Markov analysis is applied to the EZ model with small number of agents, the exact equilibrium state for N = 5 and numerical results for N = 18 are obtained.
基金Supported by National Natural Science Foundation of China under Grant Nos 61004107 and 70771012.
文摘We systematically study the size dependency of income distributions,i.e.income distribution versus the population of a country.Using the generalized Lotka--Uolterra model to fit the empirical income data for 1996-2007 in the U.S.A,we find an important parameter A that can scale with aβpower of the size(population)of the U.S.A.in that year.We point out that the size dependency of income distributions,which is a very important property but seldom addressed in previous studies,has two non-trivial implications:(1)the allometric growth pattern,i.e.the power-law relationship between population and GDP in different years,can be mathematically derived from the size-dependent income distributions and also supported by the empirical data;(2)the connection with the anomalous scaling for the probability density function in critical phenomena,since the re-scaled form of the income distributions has asymptotically exactly the same mathematical expression for the limit distribution of the sum of many correlated random variables.
文摘An experimental study investigated the characteristics of a stretched cylindrical diffusion flame, with a convex curvature with respect to the air stream, in response to periodic air flow velocity oscillation. The fuel was methane diluted with nitrogen, and the oxidizer air. The oscillation frequency was varied from 5 to 250 Hz. The results are summarized as follows. Though the fluctuation amplitude of the air stream velocity gradient was constant with respect to the frequency, the amplitude of the fuel stream increased. The fluctuation amplitude of the flame radius changed quasi-steadily from 5 to 25 Hz, and decreased with increasing frequency in the frequency range greater than 50 Hz. The flame luminosity did not respond quasi-steadily at 5 Hz, and the oscillation amplitude of flame luminosity was less than that of a steady flame, over the same velocity fluctuation range. The oscillation amplitude of luminosity peaked at 50 Hz, and was greater than that of a steady flame. It is considered that this complex change in flame luminosity with respect to frequency was closely related to the phase difference in the respective time variations in the ratio of flame thickness to radius, the velocity gradients of the air and fuel streams, and the magnitude of these values, with the ratio of flame thickness to radius related to the flame curvature effect, the velocity gradient of the air stream correlated to the flame stretch effect, and the velocity gradient of the fuel stream impacting the fuel transportation.
基金Higher Education Commission(HEC),Pakistan,under the National Research Program for Universities(NRPU)Project No.10,215/Federal.
文摘Hardware-based sensing frameworks such as cooperative fuel research engines are conventionally used to monitor research octane number(RON)in the petroleum refining industry.Machine learning techniques are employed to predict the RON of integrated naphtha reforming and isomerisation processes.A dynamic Aspen HYSYS model was used to generate data by introducing artificial uncertainties in the range of±5%in process conditions,such as temperature,flow rates,etc.The generated data was used to train support vector machines(SVM),Gaussian process regression(GPR),artificial neural networks(ANN),regression trees(RT),and ensemble trees(ET).Hyperparameter tuning was performed to enhance the prediction capabilities of GPR,ANN,SVM,ET and RT models.Performance analysis of the models indicates that GPR,ANN,and SVM with R2 values of 0.99,0.978,and 0.979 and RMSE values of 0.108,0.262,and 0.258,respectively performed better than the remaining models and had the prediction capability to capture the RON dependence on predictor variables.ET and RT had an R2 value of 0.94 and 0.89,respectively.The GPR model was used as a surrogate model for fitness function evaluations in two optimisation frameworks based on genetic algorithm and particle swarm method.Optimal parameter values found by the optimisation methodology increased the RON value by 3.52%.The proposed methodology of surrogate-based optimisation will provide a platform for plant-level implementation to realise the concept of industry 4.0 in the refinery.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11875042 and 11505114)the Shanghai Project for Construction of Top Disciplines (Grant No. USST-SYS-01)。
文摘Detecting coupling pattern between elements in a complex system is a basic task in data-driven analysis. The trajectory for each specific element is a cooperative result of its intrinsic dynamic, its couplings with other elements, and the environment. It is subsequently composed of many components, only some of which take part in the couplings. In this paper we present a framework to detect the component correlation pattern. Firstly, the interested trajectories are decomposed into components by using decomposing methods such as the Fourier expansion and the Wavelet transformation. Secondly, the cross-correlations between the components are calculated, resulting into a component cross-correlation matrix(network).Finally, the dominant structure in the network is identified to characterize the coupling pattern in the system. Several deterministic dynamical models turn out to be characterized with rich structures such as the clustering of the components. The pattern of correlation between respiratory(RESP) and ECG signals is composed of five sub-clusters that are mainly formed by the components in ECG signal. Interestingly, only 7 components from RESP(scattered in four sub-clusters) take part in the realization of coupling between the two signals.
基金supported in part by the National Natural Science Foundation of China(61621003,62073079,62088101,12025107,11871463,11688101)。
文摘Along with the development of information technologies such as mobile Internet,information acquisition technology,cloud computing and big data technology,the traditional knowledge engineering and knowledge-based software engineering have undergone fundamental changes where the network plays an increasingly important role.Within this context,it is required to develop new methodologies as well as technical tools for network-based knowledge representation,knowledge services and knowledge engineering.Obviously,the term“network”has different meanings in different scenarios.Meanwhile,some breakthroughs in several bottleneck problems of complex networks promote the developments of the new methodologies and technical tools for network-based knowledge representation,knowledge services and knowledge engineering.This paper first reviews some recent advances on complex networks,and then,in conjunction with knowledge graph,proposes a framework of networked knowledge which models knowledge and its relationships with the perspective of complex networks.For the unique advantages of deep learning in acquiring and processing knowledge,this paper reviews its development and emphasizes the role that it played in the development of knowledge engineering.Finally,some challenges and further trends are discussed.
文摘We analyse the data from the recently published lists of the richest Chinese from the year 2003 to 2005. The results confirm that in these years the wealth is distributed according to a power law with exponents between 1.758 and 2.285 in the high end. The power distribution is found to be quite robust although the persons in the list change drastically and the wealth increases rapidly. The relation between the wealth and the absolute change of wealth rejects the notion that the wealth evolution is a multiplicative stochastic process.
基金Project supported by the Promising Project Foundation of Zheji-ang University, China
文摘This article describes an Internet based laboratory (NETLAB) developed at Zhejiang University for electrical engi- neering education. A key feature of the project is the use of real experimental systems rather than simulation or virtual reality. NELTAB provides remote access to a wide variety of experiments, including not only basic electrical and electronic experiments but also many innovative control experiments. Students can effectively use the laboratory at any time and from anywhere. NETLAB has been in operation since July 2003.
