We present a method for solving partial differential equations using artificial neural networks and an adaptive collocation strategy.In this procedure,a coarse grid of training points is used at the initial training s...We present a method for solving partial differential equations using artificial neural networks and an adaptive collocation strategy.In this procedure,a coarse grid of training points is used at the initial training stages,while more points are added at later stages based on the value of the residual at a larger set of evaluation points.This method increases the robustness of the neural network approximation and can result in significant computational savings,particularly when the solution is non-smooth.Numerical results are presented for benchmark problems for scalar-valued PDEs,namely Poisson and Helmholtz equations,as well as for an inverse acoustics problem.展开更多
Nanophotonics,the field that merges photonics and nanotechnology,has in recent years revolutionized the field of optics by enabling the manipulation of light–matter interactions with subwavelength structures.However,...Nanophotonics,the field that merges photonics and nanotechnology,has in recent years revolutionized the field of optics by enabling the manipulation of light–matter interactions with subwavelength structures.However,despite the many advances in this field,the design,fabrication and characterization has remained widely an iterative process in which the designer guesses a structure and solves the Maxwell’s equations for it.In contrast,the inverse problem,i.e.,obtaining a geometry for a desired electromagnetic response,remains a challenging and time-consuming task within the boundaries of very specific assumptions.Here,we experimentally demonstrate that a novel Deep Neural Network trained with thousands of synthetic experiments is not only able to retrieve subwavelength dimensions from solely farfield measurements but is also capable of directly addressing the inverse problem.Our approach allows the rapid design and characterization of metasurface-based optical elements as well as optimal nanostructures for targeted chemicals and biomolecules,which are critical for sensing,imaging and integrated spectroscopy applications.展开更多
This paper puts forward a design idea for blended wing body（BWB）.The idea is described as that cruise point,maximum lift to drag point and pitch trim point are in the same flight attitude.According to this design id...This paper puts forward a design idea for blended wing body（BWB）.The idea is described as that cruise point,maximum lift to drag point and pitch trim point are in the same flight attitude.According to this design idea,design objectives and constraints are defined.By applying low and high fidelity aerodynamic analysis tools,BWB aerodynamic design methodology is established by the combination of optimization design and inverse design methods.High lift to drag ratio,pitch trim and acceptable buffet margin can be achieved by this design methodology.For 300-passenger BWB configuration based on static stability design,as compared with initial configuration,the maximum lift to drag ratio and pitch trim are achieved at cruise condition,zero lift pitching moment is positive,and buffet characteristics is well.Fuel burn of 300-passenger BWB configuration is also significantly reduced as compared with conventional civil transports.Because aerodynamic design is carried out under the constraints of BWB design requirements,the design configuration fulfills the demands for interior layout and provides a solid foundation for continuous work.展开更多
The Moore-Penrose metric generalized inverse T+ of linear operator T in Banach space is systematically investigated in this paper. Unlike the case in Hilbert space, even T is a linear operator in Banach Space, the Moo...The Moore-Penrose metric generalized inverse T+ of linear operator T in Banach space is systematically investigated in this paper. Unlike the case in Hilbert space, even T is a linear operator in Banach Space, the Moore-Penrose metric generalized inverse T+ is usually homogeneous and nonlinear in general. By means of the methods of geometry of Banach Space, the necessary and sufficient conditions for existence, continuitv, linearity and minimum property of the Moore-Penrose metric generalized inverse T+ will be given, and some properties of T+ will be investigated in this paper.展开更多
In the paper,the characters of surface energy budget on Huayin(Gobi)and the desert surface during the period from 26 June to 31 August 1990 in the HEIFE have been analyzed,then have been compared with the observed res...In the paper,the characters of surface energy budget on Huayin(Gobi)and the desert surface during the period from 26 June to 31 August 1990 in the HEIFE have been analyzed,then have been compared with the observed results during 4—19 September 1988 in the Pilot Observation Period of the HEIFE.The results show that the atmosphere is in superadiabatic unstable state and there is a phenomenon of inverse humidity to form negative water vapour flux.The sensible heat flux on the surface energy budget is in majority,but the latent heat flux may be neglected over the Gobi and desert surface in the cloudless daytime in the summer.展开更多
LetE andF be Banach spaces, andB(E,F) all of bounded linear operators onE intoF. LetT 0 ∈B( E,F) with an outer inverseT 0 # ∈B( F,E). Then a characteristic condition ofS=(I + T0 # (T-T0)-1 T0 # with T∈B(E, F) and ...LetE andF be Banach spaces, andB(E,F) all of bounded linear operators onE intoF. LetT 0 ∈B( E,F) with an outer inverseT 0 # ∈B( F,E). Then a characteristic condition ofS=(I + T0 # (T-T0)-1 T0 # with T∈B(E, F) and ∥ T0 # (T - T0 ∥ < 1, being a generalized inverse ofT, is presented, and hence, a rank theorem of operators onE intoF is established (which generalizes the rank theorem of matrices to Banach spaces). Consequently, an improved finite rank theorem and a new rank theorem are deduced. These results will be very useful to nonlinear functional analysis.展开更多
文本分类是信息检索的关键问题之一.提取更多的可信反例和构造准确高效的分类器是PU(positive and unlabeled)文本分类的两个重要问题.然而,在现有的可信反例提取方法中,很多方法提取的可信反例数量较少,构建的分类器质量有待提高.分别...文本分类是信息检索的关键问题之一.提取更多的可信反例和构造准确高效的分类器是PU(positive and unlabeled)文本分类的两个重要问题.然而,在现有的可信反例提取方法中,很多方法提取的可信反例数量较少,构建的分类器质量有待提高.分别针对这两个重要步骤提供了一种基于聚类的半监督主动分类方法.与传统的反例提取方法不同,利用聚类技术和正例文档应与反例文档共享尽可能少的特征项这一特点,从未标识数据集中尽可能多地移除正例,从而可以获得更多的可信反例.结合SVM主动学习和改进的Rocchio构建分类器,并采用改进的TFIDF(term frequency inverse document frequency)进行特征提取,可以显著提高分类的准确度.分别在3个不同的数据集中测试了分类结果(RCV1,Reuters-21578,20 Newsgoups).实验结果表明,基于聚类寻找可信反例可以在保持较低错误率的情况下获取更多的可信反例,而且主动学习方法的引入也显著提升了分类精度.展开更多
Even though a large number of large-scale arch dams with height larger than 200 m have been built in the world, the transient groundwater flow behaviors and the seepage control effects in the dam foundations under dif...Even though a large number of large-scale arch dams with height larger than 200 m have been built in the world, the transient groundwater flow behaviors and the seepage control effects in the dam foundations under difficult geological conditions are rarely reported. This paper presents a case study on the transient groundwater flow behaviors in the rock foundation of Jinping I double-curvature arch dam, the world＇s highest dam of this type to date that has been completed. Taking into account the geological settings at the site, an inverse modeling technique utilizing the time series measurements of both hydraulic head and discharge was adopted to back-calculate the permeability of the foundation rocks,which effectively improves the uniqueness and reliability of the inverse modeling results. The transient seepage flow in the dam foundation during the reservoir impounding was then modeled with a parabolic variational inequality（PVI） method. The distribution of pore water pressure, the amount of leakage, and the performance of the seepage control system in the dam foundation during the entire impounding process were finally illustrated with the numerical results.展开更多
Shijiazhuang,the city with the worst air quality in China,is suffering from severe ozone pollution in summer.As the key precursors of ozone generation,it is necessary to control the Volatile Organic Compounds(VOCs)pol...Shijiazhuang,the city with the worst air quality in China,is suffering from severe ozone pollution in summer.As the key precursors of ozone generation,it is necessary to control the Volatile Organic Compounds(VOCs)pollution.To have a better understanding of the pollution status and source contribution,the concentrations of 117 ambient VOCs were analyzed from April to August 2018 in an urban site in Shijiazhuang.Results showed that the monthly average concentration of total VOCs was 66.27 ppbv,in which,the oxygenated VOCs(37.89%),alkanes(33.89%),and halogenated hydrocarbons(13.31%)were the main composite on.Eight major sources were identified using Positive Matrix Factorization modeling with an accurate VOCs emission inventory as inter-complementary methods revealed that the petrochemical industry(26.24%),other industrial sources(15.19%),and traffic source(12.24%)were the major sources for ambient VOCs in Shijiazhuang.The spatial distributions of major industrial activities emissions were identified by using geographic information statistics system,which illustrated the VOCs was mainly from the north and southeast of Shijiazhuang.The inverse trajectory analysis using Hybrid Single-Particle Lagrangian Integrated Trajectory(HYSPLIT)and Potential Source Contribution Function(PSCF)clearly demonstrated the features of pollutant transport to Shijiazhuang.These findings can provide references for local governments regarding control strategies to reduce VOCs emissions.展开更多
阐述了基于数字信号处理器TMS320F2812控制的单相光伏并网逆变系统的设计,该系统主要应用于小功率光伏并网发电系统。分析了系统的结构和控制原理,设计了最大功率跟踪MPPT(Maximum power point tracking)算法和锁相环的软件设计流程图,...阐述了基于数字信号处理器TMS320F2812控制的单相光伏并网逆变系统的设计,该系统主要应用于小功率光伏并网发电系统。分析了系统的结构和控制原理,设计了最大功率跟踪MPPT(Maximum power point tracking)算法和锁相环的软件设计流程图,构建了实验室样机。实验结果表明并网电流波形良好,但含有少量的高次谐波,逆变器输出的电流基本与电网电压同频同相,并网的功率因数近似为1。展开更多
文摘We present a method for solving partial differential equations using artificial neural networks and an adaptive collocation strategy.In this procedure,a coarse grid of training points is used at the initial training stages,while more points are added at later stages based on the value of the residual at a larger set of evaluation points.This method increases the robustness of the neural network approximation and can result in significant computational savings,particularly when the solution is non-smooth.Numerical results are presented for benchmark problems for scalar-valued PDEs,namely Poisson and Helmholtz equations,as well as for an inverse acoustics problem.
基金The funding from the Israel Science Foundation(ISF)under grant number:1433/15 is acknowledged.
文摘Nanophotonics,the field that merges photonics and nanotechnology,has in recent years revolutionized the field of optics by enabling the manipulation of light–matter interactions with subwavelength structures.However,despite the many advances in this field,the design,fabrication and characterization has remained widely an iterative process in which the designer guesses a structure and solves the Maxwell’s equations for it.In contrast,the inverse problem,i.e.,obtaining a geometry for a desired electromagnetic response,remains a challenging and time-consuming task within the boundaries of very specific assumptions.Here,we experimentally demonstrate that a novel Deep Neural Network trained with thousands of synthetic experiments is not only able to retrieve subwavelength dimensions from solely farfield measurements but is also capable of directly addressing the inverse problem.Our approach allows the rapid design and characterization of metasurface-based optical elements as well as optimal nanostructures for targeted chemicals and biomolecules,which are critical for sensing,imaging and integrated spectroscopy applications.
文摘This paper puts forward a design idea for blended wing body（BWB）.The idea is described as that cruise point,maximum lift to drag point and pitch trim point are in the same flight attitude.According to this design idea,design objectives and constraints are defined.By applying low and high fidelity aerodynamic analysis tools,BWB aerodynamic design methodology is established by the combination of optimization design and inverse design methods.High lift to drag ratio,pitch trim and acceptable buffet margin can be achieved by this design methodology.For 300-passenger BWB configuration based on static stability design,as compared with initial configuration,the maximum lift to drag ratio and pitch trim are achieved at cruise condition,zero lift pitching moment is positive,and buffet characteristics is well.Fuel burn of 300-passenger BWB configuration is also significantly reduced as compared with conventional civil transports.Because aerodynamic design is carried out under the constraints of BWB design requirements,the design configuration fulfills the demands for interior layout and provides a solid foundation for continuous work.
基金the National Natural Science Foundation of China(No.19971023)the Heilongjiang Provincial Natural Science Foundation of China.
文摘The Moore-Penrose metric generalized inverse T+ of linear operator T in Banach space is systematically investigated in this paper. Unlike the case in Hilbert space, even T is a linear operator in Banach Space, the Moore-Penrose metric generalized inverse T+ is usually homogeneous and nonlinear in general. By means of the methods of geometry of Banach Space, the necessary and sufficient conditions for existence, continuitv, linearity and minimum property of the Moore-Penrose metric generalized inverse T+ will be given, and some properties of T+ will be investigated in this paper.
基金This paper is one of the results of HEIFE subject which is supported by the National Natural Science Foundation of China.
文摘In the paper,the characters of surface energy budget on Huayin(Gobi)and the desert surface during the period from 26 June to 31 August 1990 in the HEIFE have been analyzed,then have been compared with the observed results during 4—19 September 1988 in the Pilot Observation Period of the HEIFE.The results show that the atmosphere is in superadiabatic unstable state and there is a phenomenon of inverse humidity to form negative water vapour flux.The sensible heat flux on the surface energy budget is in majority,but the latent heat flux may be neglected over the Gobi and desert surface in the cloudless daytime in the summer.
文摘LetE andF be Banach spaces, andB(E,F) all of bounded linear operators onE intoF. LetT 0 ∈B( E,F) with an outer inverseT 0 # ∈B( F,E). Then a characteristic condition ofS=(I + T0 # (T-T0)-1 T0 # with T∈B(E, F) and ∥ T0 # (T - T0 ∥ < 1, being a generalized inverse ofT, is presented, and hence, a rank theorem of operators onE intoF is established (which generalizes the rank theorem of matrices to Banach spaces). Consequently, an improved finite rank theorem and a new rank theorem are deduced. These results will be very useful to nonlinear functional analysis.
文摘文本分类是信息检索的关键问题之一.提取更多的可信反例和构造准确高效的分类器是PU(positive and unlabeled)文本分类的两个重要问题.然而,在现有的可信反例提取方法中,很多方法提取的可信反例数量较少,构建的分类器质量有待提高.分别针对这两个重要步骤提供了一种基于聚类的半监督主动分类方法.与传统的反例提取方法不同,利用聚类技术和正例文档应与反例文档共享尽可能少的特征项这一特点,从未标识数据集中尽可能多地移除正例,从而可以获得更多的可信反例.结合SVM主动学习和改进的Rocchio构建分类器,并采用改进的TFIDF(term frequency inverse document frequency)进行特征提取,可以显著提高分类的准确度.分别在3个不同的数据集中测试了分类结果(RCV1,Reuters-21578,20 Newsgoups).实验结果表明,基于聚类寻找可信反例可以在保持较低错误率的情况下获取更多的可信反例,而且主动学习方法的引入也显著提升了分类精度.
基金financially supported through NSERC Discovery Grant(RGPIN/4994-2014)
文摘Even though a large number of large-scale arch dams with height larger than 200 m have been built in the world, the transient groundwater flow behaviors and the seepage control effects in the dam foundations under difficult geological conditions are rarely reported. This paper presents a case study on the transient groundwater flow behaviors in the rock foundation of Jinping I double-curvature arch dam, the world＇s highest dam of this type to date that has been completed. Taking into account the geological settings at the site, an inverse modeling technique utilizing the time series measurements of both hydraulic head and discharge was adopted to back-calculate the permeability of the foundation rocks,which effectively improves the uniqueness and reliability of the inverse modeling results. The transient seepage flow in the dam foundation during the reservoir impounding was then modeled with a parabolic variational inequality（PVI） method. The distribution of pore water pressure, the amount of leakage, and the performance of the seepage control system in the dam foundation during the entire impounding process were finally illustrated with the numerical results.
基金supported by the Hebei Provincial Depart-ment of Science and Technology(No.19273711D)the Min-istry of Education of the People’s Republic of China(No.CXZJHZ201717)+2 种基金the Shijiazhuang Science and Technology Bu-reau(No.191240273A,201240363A)the five fund platform projects of Hebei University of Science and Technology(No.1182210)the National Natural Science Foundation of China(No.21776059)。
文摘Shijiazhuang,the city with the worst air quality in China,is suffering from severe ozone pollution in summer.As the key precursors of ozone generation,it is necessary to control the Volatile Organic Compounds(VOCs)pollution.To have a better understanding of the pollution status and source contribution,the concentrations of 117 ambient VOCs were analyzed from April to August 2018 in an urban site in Shijiazhuang.Results showed that the monthly average concentration of total VOCs was 66.27 ppbv,in which,the oxygenated VOCs(37.89%),alkanes(33.89%),and halogenated hydrocarbons(13.31%)were the main composite on.Eight major sources were identified using Positive Matrix Factorization modeling with an accurate VOCs emission inventory as inter-complementary methods revealed that the petrochemical industry(26.24%),other industrial sources(15.19%),and traffic source(12.24%)were the major sources for ambient VOCs in Shijiazhuang.The spatial distributions of major industrial activities emissions were identified by using geographic information statistics system,which illustrated the VOCs was mainly from the north and southeast of Shijiazhuang.The inverse trajectory analysis using Hybrid Single-Particle Lagrangian Integrated Trajectory(HYSPLIT)and Potential Source Contribution Function(PSCF)clearly demonstrated the features of pollutant transport to Shijiazhuang.These findings can provide references for local governments regarding control strategies to reduce VOCs emissions.
文摘阐述了基于数字信号处理器TMS320F2812控制的单相光伏并网逆变系统的设计,该系统主要应用于小功率光伏并网发电系统。分析了系统的结构和控制原理,设计了最大功率跟踪MPPT(Maximum power point tracking)算法和锁相环的软件设计流程图,构建了实验室样机。实验结果表明并网电流波形良好,但含有少量的高次谐波,逆变器输出的电流基本与电网电压同频同相,并网的功率因数近似为1。
