广义数及其应用(Ⅰ)

本文在文献[2]的基础上引进广义数系统,定义了以广义数为基础的广义函数(本质不同于L.Schwartz的分布),研究了勒贝格积分的推广,将这理论应用于分布,便得到对σ函数等的自然理解,对广义数应用于量子场论中,也作了一些尝试性的工作。     

An extension and analysis of the Shu-Osher representation of Runge-Kutta methods

In the context of solving nonlinear partial differential equations, Shu and Osher introduced representations of explicit Runge-Kutta methods, which lead to stepsize conditions under which the numerical process is total-variation-diminishing (TVD). Much attention has been paid to these representations in the literature.

In general, a Shu-Osher representation of a given Runge-Kutta method is not unique. Therefore, of special importance are representations of a given method which are best possible with regard to the stepsize condition that can be derived from them.

Several basic questions are still open, notably regarding the following issues: (1) the formulation of a simple and general strategy for finding a best possible Shu-Osher representation for any given Runge-Kutta method; (2) the question of whether the TVD property of a given Runge-Kutta method can still be guaranteed when the stepsize condition, corresponding to a best possible Shu-Osher representation of the method, is violated; (3) the generalization of the Shu-Osher approach to general (possibly implicit) Runge-Kutta methods.

In this paper we give an extension and analysis of the original Shu-Osher representation, by means of which the above questions can be settled. Moreover, we clarify analogous questions regarding properties which are referred to, in the literature, by the terms monotonicity and strong-stability-preserving (SSP).

     

Automation of the manipulation of multivariate power series

This paper reports on the development of compact and remarkably general algorithms for the manipulation of multivariate power series. The problem of efficiently storing the coefficients of such series is solved in a way which admits weighted truncation and yields simple algorithms for (i) algebraic operations, (ii) composition of special functions with power series and (iii) composition and reversion of multivariate power series. The algorithms, which are expressed in a form that can readily be translated into any standard computer language, can manipulate power series in an arbitrary number of variables while retaining all terms up to an arbitrary weighted order with respect to an arbitrary set of weights. The size of the power series which can be manipulated is limited only by memory capacity. For most purposes, a conventional microcomputer is adequate.     

Semiconductor Equations for variable Mobilities Based on Boltzmann Statistics or Fermi-Dirac Statistics

The first aim of this paper is to characterize those limit spaces (X, τ) which can be valuated, i.e. for which a set E of valuations exists such that for each x ∈ X, τ(x) equals the set of filters on X which converge to x relative to E. It is shown further that a separated pretopological space is a URYSOHN -space iff it can be valuated by a set of subadditive valuations. In the second part of the paper a completion is constructed for the separated subadditively valuated limit spaces which can be considered as a generalization of the usual completion of a uniform space.     

Noise can create periodic behavior and stabilize nonlinear diffusions

It is shown that unlike nondegenerate (linear) diffusion processes, nonlinear diffusion processes can have a periodic law. We provide an example of a nonlinear diffusion for which periodic behavior is even created by the noise, i.e. no periodicity occurs when the noise is turned off. In the second part of the paper we give an example of a one-dimensional nonlinear diffusion which can be stabilized by noise. Finally we show also that the N-dimensional (N ≥ 2) ‘linear’ diffusion approximations of that system are stabilized by noise.     

MEPAR-miner: Multi-expression programming for classification rule mining

Classification and rule induction are two important tasks to extract knowledge from data. In rule induction, the representation of knowledge is defined as IF-THEN rules which are easily understandable and applicable by problem-domain experts. In this paper, a new chromosome representation and solution technique based on Multi-Expression Programming (MEP) which is named as MEPAR-miner (Multi-Expression Programming for Association Rule Mining) for rule induction is proposed. Multi-Expression Programming (MEP) is a relatively new technique in evolutionary programming that is first introduced in 2002 by Oltean and Dumitrescu. MEP uses linear chromosome structure. In MEP, multiple logical expressions which have different sizes are used to represent different logical rules. MEP expressions can be encoded and implemented in a flexible and efficient manner. MEP is generally applied to prediction problems; in this paper a new algorithm is presented which enables MEP to discover classification rules. The performance of the developed algorithm is tested on nine publicly available binary and n-ary classification data sets. Extensive experiments are performed to demonstrate that MEPAR-miner can discover effective classification rules that are as good as (or better than) the ones obtained by the traditional rule induction methods. It is also shown that effective gene encoding structure directly improves the predictive accuracy of logical IF-THEN rules.     

A Relationship Among Gentzen's Proof-Reduction,Kirby-Paris' Hydra Game and Buchholz's Hydra Game

We first note that Gentzen's proof-reduction for his consistency proof of PA can be directly interpreted as moves of Kirby-Paris' Hydra Game, which implies a direct independence proof of the game (Section 1 and Appendix). Buchholz's Hydra Game for labeled hydras is known to be much stronger than PA. However, we show that the one-dimensional version of Buchholz's Game can be exactly identified to Kirby-Paris' Game (which is two-dimensional but without labels), by a simple and natural interpretation (Section 2). Jervell proposed another type of a combinatorial game, by abstracting Gentzen's proof-reductions and showed that his game is independent of PA. We show (Section 3) that this Jervell's game is actually much stronger than PA, by showing that the critical ordinal of Jervell's game is φ_ω (0) (while that of PA or of Kirby-Paris' Game is φ₁ (0) = ?₀) in the Veblen hierarchy of ordinals.     

A modified goal programming model for piecewise linear functions

Piecewise linear function (PLF) is an important technique for solving polynomial and/or posynomial programming problems since the problems can be approximately represented by the PLF. The PLF can also be solved using the goal programming (GP) technique by adding appropriate linearization constraints. This paper proposes a modified GP technique to solve PLF with n terms. The proposed method requires only one additional constraint, which is more efficient than some well-known methods such as those proposed by Charnes and Cooper's, and Li. Furthermore, the proposed model (PM) can easily be applied to general polynomial and/or posynomial programming problems.     

Mehar’s method for solving fully fuzzy linear programming problems with L-R fuzzy parameters

To the best of our knowledge, there is no method in literature for solving such fully fuzzy linear programming (FLP) problems in which some or all the parameters are represented by unrestricted L-R flat fuzzy numbers. Also, to propose such a method, there is need to find the product of unrestricted L-R flat fuzzy numbers. However, there is no method in the literature to find the product of unrestricted L-R flat fuzzy numbers.In this paper, firstly the product of unrestricted L-R flat fuzzy numbers is proposed and then with the help of proposed product, a new method (named as Mehar’s method) is proposed for solving fully FLP problems. It is also shown that the fully FLP problems which can be solved by the existing methods can also be solved by the Mehar’s method. However, such fully FLP problems in which some or all the parameters are represented by unrestricted L-R flat fuzzy numbers can be solved by Mehar’s method but can not be solved by any of the existing methods.     

On the number of subwords of everywhere growing DTOL languages

It is shown that the number of subwords of length k that can be found in an everywhere growing DTOL language (one which is generated by a DTOL system in which each letter derives at least two letters in every step) is bounded by a polynomial in k. Furthermore this polynomial bound is shown to be best.     

Compressive Sampling via Random Convolution

Several recent results in compressive sampling show that a sparse signal (i.e. a signal which can be compressed in a known orthobasis) can be efficiently acquired by taking linear measurements against random test functions. In this paper, we show that these results can be extended to measurements taken by convolving with a random pulse and then subsampling. The measurement scheme is universal in that it complements (with high probability) any fixed orthobasis we use to represent the signal. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

GENERALIZED CLIFFORD TORUS IN S~(n+1)AND PRESCRIBED MEAN CURVATURE FUNCTION

Given some function H(X),one can find a compact hypersurface in S~(n+1),which ishomeomorphic to S~m(1)×S~(n-m)(1)and whose mean curvature is given by H(X).     

Production of locomotive rosters for a multi-class single-locomotive problem

A multi-class single locomotive (MCSL) problem is defined in this paper as one involving the allocation of a single locomotive to each of a number of pre-timetabled trains, some of which can be pulled by more than one type (or class) of locomotive. This is typical of problems arising in many passenger train networks and an exact solution method exists for the general form of this problem (Forbes et al¹) This paper describes the analysis of a particular type of MCSL problem, as faced by the Public Transport Corporation (PTC) in the Australian State of Victoria, where all journeys either start or end at one location (Melbourne). Because of this feature, the problem can be solved in two separate stages. The first stage (an integer programming model) determines the type of locomotive that will hall each trip. The second stage, which can either be solved by the LP assignment algorithm or by computerised inspection, determines the locomotive rosters, (the sequence of round trips that each locomotive hauls).Splitting the problem into two stages achieves a significant reduction in problem size, resulting in greatly reduced computation time (4 seconds as opposed to a number of hours).     

How persuaded are you? A typology of responses

Several recent studies have suggested that there are two different ways in which a person can proceed when assessing the persuasiveness of a mathematical argument: by evaluating whether it is personally convincing, or by evaluating whether it is publicly acceptable. In this paper, using Toulmin's (1958) argumentation scheme, we produce a more detailed theoretical classification of the ways in which participants can interpret a request to assess the persuasiveness of an argument. We suggest that there are (at least) five ways in which such a question can be interpreted. The classification is illustrated with data from a study that asked undergraduate students and research-active mathematicians to rate how persuasive they found a given argument. We conclude by arguing that researchers interested in mathematical conviction and proof validation need to be aware of the different ways in which participants can interpret questions about the persuasiveness of arguments, and that they must carefully control for these variations during their studies.     

Deriving amplitude equations for weakly-nonlinear oscillators and their generalizations

Results by physicists on renormalization group techniques have recently sparked interest in the singular perturbations community of applied mathematicians. The survey paper, [Phys. Rev. E 54(1) (1996) 376–394], by Chen et al. demonstrated that many problems which applied mathematicians solve using disparate methods can be solved using a single approach. Analysis of that renormalization group method by Mudavanhu and O’Malley [Stud. Appl. Math. 107(1) (2001) 63–79; SIAM J. Appl. Math. 63(2) (2002) 373–397], among others, indicates that the technique can be streamlined. This paper carries that analysis several steps further to present an amplitude equation technique which is both well adapted for use with a computer algebra system and easy to relate to the classical methods of averaging and multiple scales.     

Partial hyperbolicity far from homoclinic bifurcations

We prove that any diffeomorphism of a compact manifold can be C¹-approximated by a diffeomorphism which exhibits a homoclinic bifurcation (a homoclinic tangency or a heterodimensional cycle) or by a diffeomorphism which is partially hyperbolic (its chain-recurrent set splits into partially hyperbolic pieces whose centre bundles have dimensions less or equal to two). We also study in a more systematic way the central models introduced in Crovisier (in press) [10].     

The general a posteriori truncation method and its application to radiogenic source identification for the Helium production–diffusion equation

The purpose of the present paper is twofold: (i) to formulate the truncation method with a posteriori parameter choice rule in a uniform framework that can be adapted to solve a kind of linear inverse problems for which the solution can be represented by the eigensystem; (ii) to apply the a posteriori truncation method to the radiogenic source identification for the Helium production–diffusion equation, which is closely connected to the Helium isotopes dating as one method of the low temperature thermochronometry, the specific rate of convergence between the regularized solution and the exact solution is calculated, and numerical examples shed light on the efficiency and accuracy of the proposed method.     

Favard’s interpolation problem in one or more variables

Given scattered data on the real line, Favard [4] constructed an interpolant which depends linearly and locally on the data and whose nth derivative is locally bounded by the nth divided differences of the data times a constant depending only on n. It is shown that the (n —1)th derivative of Favard’s interpolant can be likewise bounded by divided differences, and that one can bound at best two consecutive derivatives of any interpolant by the corresponding divided differences. In this sense, Favard’s univariate interpolant is the best possible. Favard’s result has been extended [8] to a special case in several variables, and here the extent to which this can be repeated in a more general setting is proven exactly.     

Controlling jumps in correlated processes of Poisson counts

Processes of autocorrelated Poisson counts can often be modelled by a Poisson INAR(1) model, which proved to apply well to typical tasks of SPC. Statistical properties of this model are briefly reviewed. Based on these properties, we propose a new control chart: the combined jumps chart. It monitors the counts and jumps of a Poisson INAR(1) process simultaneously. As the bivariate process of counts and jumps is a homogeneous Markov chain, average run lengths (ARLs) can be computed exactly with the well‐known Markov chain approach. Based on an investigation of such ARLs, we derive design recommendations and show that a properly designed chart can be applied nearly universally. This is also demonstrated by a real‐data example from the insurance field. Copyright © 2008 John Wiley & Sons, Ltd.