Teachers’ knowledge of the nature of definitions: The case of the zero exponent

This paper focuses on three junior high school mathematics teachers and their knowledge of the nature of definitions. The mathematical context of exponentiation is used as a springboard for discussing two aspects of definitions: their corresponding domains and the distinction and relationships between definitions, proofs, and theorems. Through interviews it was shown that some teachers are not aware that definitions and domains are intrinsically connected and some teachers believe that definitions may be proved. Findings also indicate that knowledge of the nature of definitions may be dependent on the context.     

Irreflexive and reflexive dimension

There are three equivalent definitions of dimension for partially ordered sets. When generating these three definitions to -dimension over an arbitrary class of orders , the three definitions diverge. We compare these three definitions and determine certain requirements under which they are equivalent.     

Toward a Unified Theory of Generalized Functions: Convergence

Generalized functions are usually treated as bounded linear functionals on spaces of test functions. Here they are considered as objects which ?convolute”? with test functions and satisfy a certain associativity condition. In this setting simple definitions are given for convergence of sequences of test functions and generalized functions, definitions which do not depend on particular properties of the space of test functions. It is shown that for the most commonly used spaces, these general definitions reduce to the standard ones.     

Topological approaches to generalized rough multisets

This paper proposes new definitions of lower and upper mset approximations, which are basic concepts of the rough mset theory. These definitions come naturally from the concepts of multiset topologies and of ambiguity introduced in this paper. The new definitions are compared to classical definitions and are shown to be more general. In the sense, they are the only ones which can be used for any type of indiscernibility or similarity mset relation.     

On Some Almost-Periodicity Problems in Various Metrics

The Bohr-type and the Bochner-type definitions for almost periodic functions are examined in various metrics (Stepanov, Weyl and Besicovitch). The correct definitions of Besicovitch-like multifunctions are given. Weak almost-periodic solutions are proved for differential equations and inclusions. This problem is also discussed as a fixed-point problem in function spaces.     

An analysis of the form and content of quadrilateral definitions composed by novice pre-service teachers

Mathematical definitions are an important mathematical construct which has been noted as a challenging topic for both teachers and students. This study provides an analysis of the form and content of a set of 308 definitions of quadrilateral types provided by 44 novice pre-service elementary teachers (NPSTs) who had not yet studied geometry or definitions on the college level. Analysis of definition structure including necessary, sufficient, and minimal conditions, as well as hierarchical and partitional structure, provides insight into what NPSTs may think about the form of mathematical definitions in general. Analysis of the properties used in definitions of each shape type and the frequency of those properties reveals the shape types with which NPSTs are most and least familiar. These results are presented alongside possible applications and implications for instruction.     

新的模糊数的模糊距离

文[1]中基于现有的模糊数的距离定义及模糊距离定义的缺陷进行分析并给出了改进的模糊数的距离定义。本文在此基础上给出新的模糊数的模糊距离定义,并给出相应的定理。     

On unified concepts of detectability and observability for continuous-time stochastic systems

This paper is concerned with detectability and observability of continuous-time stochastic linear systems. By adopting the idea used in defining these two concepts for time-varying systems and Markovian jump linear systems that have been studied in the literature, corresponding definitions for continuous-time stochastic linear systems are proposed. These two definitions are not only able to unify some recent definitions on these two concept reported in the literature, but also allow us to propose an efficient rank criterion to test observability of continuous-time stochastic linear systems. It seems that this rank criterion is quite analogous to the rank criterion for deterministic linear systems. With the help of these two concepts and the new criteria, the stochastic Lyapunov equation is revisited and some recent published work on this equation are generalized. Numerical examples are given to illustrate the effectiveness of the proposed approach.     

The Gergonne and Nagel centers of an n-dimensional simplex

In contrast with the analogous situation for a triangle, the cevians that join the vertices of a tetrahedron to the points where the faces touch the insphere (or the exspheres) are not concurrent in general. This observation led the present author and P. Walker in [4] to devise alternative definitions of the Gergonne and Nagel centers of a tetrahedron that do not assume the concurrence of such cevians and that coincide with the ordinary definitions in the case of a triangle. They then proved that the Gergonne center exists and is unique for all tetrahedra and that the Nagel center, though unique, exists only for tetrahedra that satisfy certain conditions. In this article, we extend these definitions to simplices of any dimension. By keeping the requirement that the Gergonne center be interior and relaxing such a condition for the Nagel center, we prove that both centers exist and are unique for all simplices, thus polishing the definitions and generalizing the results of the above-mentioned article.     

Nonequivalence of Various Definitions of Differentiability Directions for Vector Measures

It is proved that the definitions of differentiability directions for vector measures in various topologies, namely, the topology of convergence on a system measurable sets, the topology of convergence with respect to semivariation, and the topology of convergence in variation, are generally pairwise nonequivalent. It is also proved that, for measures with values in a Banach space with the Radon--Nikodym property, these definitions are equivalent.     

一类广义凸函数的充要条件

本文给出了广义梯度的广义单调性定义,借助这些定义给出了一类广义凸函数的充要条件。     

Local Baire classification of Lyapunov exponents

One considers two different definitions of the Baire class of a functional at a point. These definitions are in agreement with the common definition of the Baire class. The semicontinuity of a functional at a point is associated with its inclusion into the first Baire class at that point in the sense of the said definitions for Lyapunov exponents of a homogeneous nth-order system. In particular, it is shown that for the two smallest exponents, the inclusion into the first Baire class at a point is equivalent to semicontinuity in the sense of one of the two definitions and continuity in the sense of the other. __________ Translated from Trudy Seminara imeni I. G. Petrovskogo, No. 26, pp. 56–70, 2007.     

On the class of Skolem elementary functions

Under consideration are some equivalent definitions of the class of Skolemelementary functions (analogous to the known definitions of the class of Kalmar elementary functions) and some results for this class obtained by various mathematicians. The definitions of this class were studied independently of each other, and their equivalence is proved in this paper. The question is studied of the existence of finite superposition bases in this class. We prove that the problem of the existence of such a basis amounts to the well-known problem from the theory of computational complexity.     

A comparison of mathematical features of Turkish and American textbook definitions regarding special quadrilaterals

In this study, I analyzed and compared definitions of special quadrilaterals presented in the US and Turkish secondary school mathematics textbooks. To this end, seven textbooks from each country were examined based on the following features of mathematical definitions: form of presentation and mathematical correctness, minimality, the nature of definitions, and the reference sets and geometric properties used in definitions. The results showed that Turkish textbooks include both procedural and structural definitions of quadrilaterals, while procedural definitions are non-existent in the US mathematics textbooks. Meanwhile, all structural definitions and all procedural definitions excluding one are mathematically correct. Besides, in both country textbooks, there exists more number of minimal and inclusive definitions compared to the non-minimal and exclusive ones. Finally, textbooks from both countries mainly use quadrilaterals as reference sets and sides as geometric properties in definitions of special quadrilaterals. The results bring to light the varied opportunities provided to the students by the US and Turkish textbooks to experience and learn definitions of special quadrilaterals.     

函数两种凸性定义等价性的今惑前世之初探

通过研究中点凸函数和一般凸函数这两种凸性定义的早期发展历史和凸性性质来探索两种凸性定义的等价性.结果表明,两种凸性定义不等价;但是,当函数满足连续、可微、半连续和有界这四个条件中的任何一个条件时,两种凸性定义等价.     

Equivalence of two definitions of a chronological integral

A chronological integral is a generalization of the path integral when the values of the measure or integrated function do not commute with each other. Two definitions of a chronological integral over the space of functions with a real argument are formulated. Measures and integrated functions have not commuting matrix values. Sufficient conditions for the equivalence of these definitions are proved.     

Students Talk About Prime: What We Heard About Definitions

This study examines data from college students who worked in pairs to make decisions about a list of potential definitions of prime number. Analysis focused on the evidence each student pair cited when they decided whether or not a statement could be used as a definition for prime number. The purpose of this paper is to describe patterns in the ways students used the evidence they cited. Findings suggest that students attend to important features of mathematical definitions, with some students giving preference to usability and others giving preference to definitions that are unambiguous.     

A geometric approach for solving fuzzy linear programming problems

In this paper we first recall some definitions and results of fuzzy plane geometry, and then introduce some definitions in the geometry of two-dimensional fuzzy linear programming (FLP). After defining the optimal solution based on these definitions, we use the geometric approach for obtaining optimal solution(s) and show that the algebraic solutions obtained by Zimmermann method (ZM) and our geometric solutions are the same. Finally, numerical examples are solved by these two methods.     

"无穷小的比较"的定义及其改进

"无穷小的比较"的现有定义有多种表述形式,但其中不少表述尚不够准确,有失严谨,甚至会导致错误命题的出现.引入"基"概念可使无穷小及无穷小比较的定义更为严谨、简洁、一般化.将无穷小量按含O值点的不同情况分为2类,有利于找出"无穷小的比较"现有定义中存在的问题.通过调整大前提,解决了定义项与被定义项外延不一致的问题;通过转...     

Rectification of sets in Euclidean spaces

We criticize traditional definitions of the arc length which require semi-continuity from below. Symmetric definitions of lower and uppern-lengths (n-dimensional volumes) are introduced for a wide class of sets in Euclidean spaces, and the additivity of both functionals is proved.