This article studies on Cauchy’s function f (z) and its integral, (2πi)J[ f (z)] ≡ ■C f (t)dt/(t z) taken along a closed simple contour C, in regard to their comprehensive properties over the entire z =...This article studies on Cauchy’s function f (z) and its integral, (2πi)J[ f (z)] ≡ ■C f (t)dt/(t z) taken along a closed simple contour C, in regard to their comprehensive properties over the entire z = x + iy plane consisted of the simply connected open domain D + bounded by C and the open domain D outside C. (1) With f (z) assumed to be C n (n ∞-times continuously differentiable) z ∈ D + and in a neighborhood of C, f (z) and its derivatives f (n) (z) are proved uniformly continuous in the closed domain D + = [D + + C]. (2) Cauchy’s integral formulas and their derivatives z ∈ D + (or z ∈ D ) are proved to converge uniformly in D + (or in D = [D +C]), respectively, thereby rendering the integral formulas valid over the entire z-plane. (3) The same claims (as for f (z) and J[ f (z)]) are shown extended to hold for the complement function F(z), defined to be C n z ∈ D and about C. (4) The uniform convergence theorems for f (z) and F(z) shown for arbitrary contour C are adapted to find special domains in the upper or lower half z-planes and those inside and outside the unit circle |z| = 1 such that the four general- ized Hilbert-type integral transforms are proved. (5) Further, the singularity distribution of f (z) in D is elucidated by considering the direct problem exemplified with several typ- ical singularities prescribed in D . (6) A comparative study is made between generalized integral formulas and Plemelj’s formulas on their differing basic properties. (7) Physical sig- nificances of these formulas are illustrated with applicationsto nonlinear airfoil theory. (8) Finally, an unsolved inverse problem to determine all the singularities of Cauchy function f (z) in domain D , based on the continuous numerical value of f (z) z ∈ D + = [D + + C], is presented for resolution as a conjecture.展开更多
This is a series of studies on Wu's conjecture and on its resolution to be presented herein. Both are devoted to expound all the comprehensive properties of Cauchy's function f(z) (z = x + iy) and its integral ...This is a series of studies on Wu's conjecture and on its resolution to be presented herein. Both are devoted to expound all the comprehensive properties of Cauchy's function f(z) (z = x + iy) and its integral J[f(z)]≡(2πi)-∮cf(t)(t-z)-1dt taken along the unit circle as contour C,inside which(the open domain D+) f(z) is regular but has singularities distributed in open domain Doutside C. Resolution is given to the inverse problem that the singularities of f(z) can be determined in analytical form in terms of the values f(t) of f(z) numerically prescribed on C(|t| = 1) ,as so enunciated by Wu's conjecture. The case of a single singularity is solved using complex algebra and analysis to acquire the solution structure for a standard reference. Multiple singularities are resolved by reducing them to a single one by elimination in principle,for which purpose a general asymptotic method is developed here for resolution to the conjecture by induction,and essential singularities are treated with employing the generalized Hilbert transforms. These new methods are applicable to relevant problems in mathematics,engineering and technology in analogy with resolving the inverse problem presented here.展开更多
The authors consider generalized statistically self-affine recursive fractals K with random numbers of subsets on each level. They obtain the Hausdorff dimensions of K without considering whether the subsets on each l...The authors consider generalized statistically self-affine recursive fractals K with random numbers of subsets on each level. They obtain the Hausdorff dimensions of K without considering whether the subsets on each level are non-overlapping or not. They also give some examples to show that many important sets are the special cases of their models.展开更多
This paper is concerned with the problem of designing robust H∞and H2static output feedback controllers for a class of discrete-time piecewise-affine singular systems with norm-bounded time-varying parameters uncerta...This paper is concerned with the problem of designing robust H∞and H2static output feedback controllers for a class of discrete-time piecewise-affine singular systems with norm-bounded time-varying parameters uncertainties. Based on a piecewise singular Lyapunov function combined with S-procedure,Projection lemma and some matrix inequality convexifying techniques,sufficient conditions in terms of linear matrix inequalities are given for the existence of an output-feedback controller for the discrete-time piecewiseaffine singular systems with a prescribed H∞disturbance attenuation level,and the H2norm is smaller than a given positive number. It is shown that the controller gains can be obtained by solving a family of LMIs parameterized by one or two scalar variables. The numerical examples are given to illustrate the effectiveness of the proposed design methods.展开更多
In this paper, the theory of signal singularity spectrum analysis(SSA) is proposed. Using SSA theory, a new method is presented to reduce truncation artifacts in magnetic resonance (MR) image due to truncated spectrum...In this paper, the theory of signal singularity spectrum analysis(SSA) is proposed. Using SSA theory, a new method is presented to reduce truncation artifacts in magnetic resonance (MR) image due to truncated spectrum data.In the scheme, after detecting signal singularity locations using wavelet analysis inspectrum domain, SSA mathematic model is constructed, where weight coefficientsare determined by known truncated spectrum data. Then, the remainder of thetruncated spectrum can be obtained using SSA. Experiment and simulation resultsshow that the SSA method will produce fewer artifacts in MR image from truncatedspectrum than existing methods.展开更多
We introduce a new type of modified Bernstein quasi-interpolants, which can be used to approximate functions with singularities. We establish direct, inverse, and equivalent theorems of the weighted approximation of t...We introduce a new type of modified Bernstein quasi-interpolants, which can be used to approximate functions with singularities. We establish direct, inverse, and equivalent theorems of the weighted approximation of this modified quasi-interpolants. Some classical results on approximation of continuous functions are generalized to the weighted approximation of functions with singularities.展开更多
This paper discusses all cases of second order linear singular defferential difference equations with delay and different coefficients, and prensents the conditionsfor existence and uniqueness of solutions nearly in a...This paper discusses all cases of second order linear singular defferential difference equations with delay and different coefficients, and prensents the conditionsfor existence and uniqueness of solutions nearly in all cases.展开更多
An improved interpolating complex variable element-frees Galerkin(IICVEFG)method for the two-dimensional elastic problems is developed.This method is based on the improved interpolating complex variable moving least-s...An improved interpolating complex variable element-frees Galerkin(IICVEFG)method for the two-dimensional elastic problems is developed.This method is based on the improved interpolating complex variable moving least-squares(IICVMLS)method and the integral form of the elastic problems.In the IICVEFG method,the proposed shape function has the interpolating feature.Therefore,the essential boundary conditions can be exerted directly.Additionally,the unnecessary t erms in the discrete mat rices are removed,which resul ts in a set of concise formulas.This method is verified by analyzing three elastic examples under different constraints and loads.The numerical results show that the IICVEFG method is superior in precision and efficiency to other non-interpolating meshless methods.展开更多
In this paper,we analyze the existence,multiplicity and nonexistence of nontrivial radial convex solutions to the following system coupled by singular Monge-Ampère equations{det D^(2)u_(1)=λh_(1)f_(1)(-u_(2))in...In this paper,we analyze the existence,multiplicity and nonexistence of nontrivial radial convex solutions to the following system coupled by singular Monge-Ampère equations{det D^(2)u_(1)=λh_(1)f_(1)(-u_(2))inΩ,det D^(2)u2=λh_(2)f_(2)(-u_(1)),u_(1)=u_(2)=0,onəΩinΩfor a certain range ofλ>0,hi are weight functions,f_(i)are continuous functions with possible singularity at 0 and satisfy a combined N-superlinear growth at∞,where i∈{1,2},Ωis the unit ball in N.We establish the existence of a nontrivial radial convex solution for smallλ,multiplicity results of nontrivial radial convex solutions for certain ranges ofλ,and nonexistence results of nontrivial radial solutions for the caseλ≥1.The asymptotic behavior of nontrivial radial convex solutions is also considered.展开更多
文摘This article studies on Cauchy’s function f (z) and its integral, (2πi)J[ f (z)] ≡ ■C f (t)dt/(t z) taken along a closed simple contour C, in regard to their comprehensive properties over the entire z = x + iy plane consisted of the simply connected open domain D + bounded by C and the open domain D outside C. (1) With f (z) assumed to be C n (n ∞-times continuously differentiable) z ∈ D + and in a neighborhood of C, f (z) and its derivatives f (n) (z) are proved uniformly continuous in the closed domain D + = [D + + C]. (2) Cauchy’s integral formulas and their derivatives z ∈ D + (or z ∈ D ) are proved to converge uniformly in D + (or in D = [D +C]), respectively, thereby rendering the integral formulas valid over the entire z-plane. (3) The same claims (as for f (z) and J[ f (z)]) are shown extended to hold for the complement function F(z), defined to be C n z ∈ D and about C. (4) The uniform convergence theorems for f (z) and F(z) shown for arbitrary contour C are adapted to find special domains in the upper or lower half z-planes and those inside and outside the unit circle |z| = 1 such that the four general- ized Hilbert-type integral transforms are proved. (5) Further, the singularity distribution of f (z) in D is elucidated by considering the direct problem exemplified with several typ- ical singularities prescribed in D . (6) A comparative study is made between generalized integral formulas and Plemelj’s formulas on their differing basic properties. (7) Physical sig- nificances of these formulas are illustrated with applicationsto nonlinear airfoil theory. (8) Finally, an unsolved inverse problem to determine all the singularities of Cauchy function f (z) in domain D , based on the continuous numerical value of f (z) z ∈ D + = [D + + C], is presented for resolution as a conjecture.
文摘This is a series of studies on Wu's conjecture and on its resolution to be presented herein. Both are devoted to expound all the comprehensive properties of Cauchy's function f(z) (z = x + iy) and its integral J[f(z)]≡(2πi)-∮cf(t)(t-z)-1dt taken along the unit circle as contour C,inside which(the open domain D+) f(z) is regular but has singularities distributed in open domain Doutside C. Resolution is given to the inverse problem that the singularities of f(z) can be determined in analytical form in terms of the values f(t) of f(z) numerically prescribed on C(|t| = 1) ,as so enunciated by Wu's conjecture. The case of a single singularity is solved using complex algebra and analysis to acquire the solution structure for a standard reference. Multiple singularities are resolved by reducing them to a single one by elimination in principle,for which purpose a general asymptotic method is developed here for resolution to the conjecture by induction,and essential singularities are treated with employing the generalized Hilbert transforms. These new methods are applicable to relevant problems in mathematics,engineering and technology in analogy with resolving the inverse problem presented here.
基金This research is partly supported by NNSF of China (60204001) the Youth Chengguang Project of Science and Technology of Wuhan City (20025001002)
文摘The authors consider generalized statistically self-affine recursive fractals K with random numbers of subsets on each level. They obtain the Hausdorff dimensions of K without considering whether the subsets on each level are non-overlapping or not. They also give some examples to show that many important sets are the special cases of their models.
基金Sponsored by the National Natural Science Foundation of China(Grant No.61004038)
文摘This paper is concerned with the problem of designing robust H∞and H2static output feedback controllers for a class of discrete-time piecewise-affine singular systems with norm-bounded time-varying parameters uncertainties. Based on a piecewise singular Lyapunov function combined with S-procedure,Projection lemma and some matrix inequality convexifying techniques,sufficient conditions in terms of linear matrix inequalities are given for the existence of an output-feedback controller for the discrete-time piecewiseaffine singular systems with a prescribed H∞disturbance attenuation level,and the H2norm is smaller than a given positive number. It is shown that the controller gains can be obtained by solving a family of LMIs parameterized by one or two scalar variables. The numerical examples are given to illustrate the effectiveness of the proposed design methods.
文摘In this paper, the theory of signal singularity spectrum analysis(SSA) is proposed. Using SSA theory, a new method is presented to reduce truncation artifacts in magnetic resonance (MR) image due to truncated spectrum data.In the scheme, after detecting signal singularity locations using wavelet analysis inspectrum domain, SSA mathematic model is constructed, where weight coefficientsare determined by known truncated spectrum data. Then, the remainder of thetruncated spectrum can be obtained using SSA. Experiment and simulation resultsshow that the SSA method will produce fewer artifacts in MR image from truncatedspectrum than existing methods.
文摘We introduce a new type of modified Bernstein quasi-interpolants, which can be used to approximate functions with singularities. We establish direct, inverse, and equivalent theorems of the weighted approximation of this modified quasi-interpolants. Some classical results on approximation of continuous functions are generalized to the weighted approximation of functions with singularities.
文摘This paper discusses all cases of second order linear singular defferential difference equations with delay and different coefficients, and prensents the conditionsfor existence and uniqueness of solutions nearly in all cases.
基金The authors sincerely acknowledge the financial support from the National Science Foundation of China(No.12002240)the National Science and Technology Major Project(No.2017-IV-0003-0040).
文摘An improved interpolating complex variable element-frees Galerkin(IICVEFG)method for the two-dimensional elastic problems is developed.This method is based on the improved interpolating complex variable moving least-squares(IICVMLS)method and the integral form of the elastic problems.In the IICVEFG method,the proposed shape function has the interpolating feature.Therefore,the essential boundary conditions can be exerted directly.Additionally,the unnecessary t erms in the discrete mat rices are removed,which resul ts in a set of concise formulas.This method is verified by analyzing three elastic examples under different constraints and loads.The numerical results show that the IICVEFG method is superior in precision and efficiency to other non-interpolating meshless methods.
基金supported by Beijing Natural Science Foundation under Grant No.1212003the Promoting the Classified Development of Colleges and Universities-application and Cultivation of Scientific Research Awards of BISTU under Grant No.2021JLPY408。
文摘In this paper,we analyze the existence,multiplicity and nonexistence of nontrivial radial convex solutions to the following system coupled by singular Monge-Ampère equations{det D^(2)u_(1)=λh_(1)f_(1)(-u_(2))inΩ,det D^(2)u2=λh_(2)f_(2)(-u_(1)),u_(1)=u_(2)=0,onəΩinΩfor a certain range ofλ>0,hi are weight functions,f_(i)are continuous functions with possible singularity at 0 and satisfy a combined N-superlinear growth at∞,where i∈{1,2},Ωis the unit ball in N.We establish the existence of a nontrivial radial convex solution for smallλ,multiplicity results of nontrivial radial convex solutions for certain ranges ofλ,and nonexistence results of nontrivial radial solutions for the caseλ≥1.The asymptotic behavior of nontrivial radial convex solutions is also considered.