• 대한수학회보
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• 제60권1호
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• pp.75-81
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• 2023

If a multiplicative function f is commutable with a quadratic form x² + xy + y², i.e., f(x² + xy + y²) = f(x)² + f(x) f(y) + f(y)², then f is the identity function. In other hand, if f is commutable with a quadratic form x² - xy + y², then f is one of three kinds of functions: the identity function, the constant function, and an indicator function for ℕ ＼ pℕ with a prime p.

• 대한수학회보
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• 제51권2호
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• pp.531-538
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• 2014

Concentric hyperspheres in the n-dimensional Euclidean space $\mathbb{R}^n$ are the level hypersurfaces of a radial function f : $\mathbb{R}^n{\rightarrow}\mathbb{R}$. The magnitude $||{\nabla}f||$ of the gradient of such a radial function f : $\mathbb{R}^n{\rightarrow}\mathbb{R}$ is a function of the function f. We are interested in the converse problem. As a result, we show that if the magnitude of the gradient of a function f : $\mathbb{R}^n{\rightarrow}\mathbb{R}$ with isolated critical points is a function of f itself, then f is either a radial function or a function of a linear function. That is, the level hypersurfaces are either concentric hyperspheres or parallel hyperplanes. As a corollary, we see that if the magnitude of a conservative vector field with isolated singularities on $\mathbb{R}^n$ is a function of its scalar potential, then either it is a central vector field or it has constant direction.

• 충청수학회지
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• 제26권3호
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• pp.557-569
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• 2013

In this paper we shall introduce the $f$-function in a set, and give some properties of $f$-function of a set. In particular, we establish a relation between $f$-function of a set and fuzzy equivalence relation. We also introduce the notion of $f$-homomorphism on a semigroup S, and prove the generalized fundamental homomorphism theorem of semigroup.

• 호남수학학술지
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• 제32권3호
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• pp.389-397
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• 2010

Exton introduced 20 distinct triple hypergeometric functions whose names are Xi (i = 1,$\ldots$, 20) to investigate their twenty Laplace integral representations whose kernels include the confluent hypergeometric functions $_0F_1$, $_1F_1$, a Humbert function $\Psi_2$, a Humbert function $\Phi_2$. The object of this paper is to present 25 (presumably new) integral representations of Euler types for the Exton hypergeometric function $X_5$ among his twenty $X_i$ (i = 1,$\ldots$, 20), whose kernels include the Exton function X5 itself, the Exton function $X_6$, the Horn's functions $H_3$ and $H_4$, and the hypergeometric function F = $_2F_1$.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제17권4호
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• pp.347-354
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• 2010

Exton [Hypergeometric functions of three variables, J. Indian Acad. Math. 4 (1982), 113~119] introduced 20 distinct triple hypergeometric functions whose names are $X_i$ (i = 1, ..., 20) to investigate their twenty Laplace integral representations whose kernels include the confluent hypergeometric functions $_oF_1$, $_1F_1$, a Humbert function ${\Psi}_2$, a Humbert function ${\Phi}_2$. The object of this paper is to present 16 (presumably new) integral representations of Euler type for the Exton hypergeometric function $X_2$ among his twenty $X_i$ (i = 1, ..., 20), whose kernels include the Exton function $X_2$ itself, the Appell function $F_4$, and the Lauricella function $F_C$.

• 대한수학회보
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• 제52권6호
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• pp.1759-1776
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• 2015

We determine the general solution of the generalized additive-quartic functional equation f(x + 3y) + f(x - 3y) + f(x + 2y) + f(x - 2y) + 22f(x) - 13 [f(x + y) + f(x - y)] + 24f(y) - 12f(2y) = 0 without assuming any regularity conditions on the unknown function f : ${\mathbb{R}}{\rightarrow}{\mathbb{R}}$ and its stability is investigated.

• Korean Journal of Mathematics
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• 제30권2호
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• pp.249-261
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• 2022

Let f be a non-constant meromorphic function in the open complex plane ℂ. In this paper we prove under certain essential conditions that R(f) and P[f], rational function and differential polynomial of f respectively, share a small function of f and obtain a conclusion related to Brück conjecture. We give some examples in support to our result.

• 대한수학회보
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• 제53권2호
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• pp.365-371
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• 2016

Let f be a transcendental meromorphic function in the complex plane $\mathbb{C}$, and a be a nonzero constant. We give a quantitative estimate of the characteristic function T(r, f) in terms of $N(r,1/(f^2(f^{\prime})^n-a))$, which states as following inequality, for positive integers $n{\geq}2$, $$T(r,f){\leq}\(3+{\frac{6}{n-1}}\)N\(r,{\frac{1}{af^2(f^{\prime})^n-1}}\)+S(r,f)$$.

• 대한간호학회지
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• 제27권1호
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• pp.36-48
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• 1997

This survey was performed to evaluate and compare cognitive function, self-esteem and depression in the elderly related to aging. The data were collected from 200 elders in eight homes for the elderly in Taegu. Data collection was done from June 1 to 31, 1996. The scale used to measure cognitive function was the MMSE-K(Mini-Mental State Examination-Korea), Self-esteem was measmed using Rosenberg's self-esteem scale and depression using SDS(Self-rating Depression Scale). A comparison of cognitive function, self-esteem and depression by aging were summarised as follows : 1. There were significant differences on the cognitive function score in the elderly according to age group(F=24.81, P<.01). 2. There were significant differences on the self-esteem score in the elderly according to age group(F=3.84, P<.5). 3. There were significant differences on the depression score in the elderly according to age group (F=5.90, P<.1). 4. The general characteristics which affected the cognitive function scores of the elders were sex (F=8.45, P<.5), educational level(F=8.86, P<.5), spousing(F=34.59. P<.01), and the perception of health(F=4.63, P<.5). 5. The general characteristic which affected the self-esteem scores of the elders was the perception of health(F=3.81. P<.5). 6. The general characteristic which affected the depression scores was the educational level(F=3.96, P<.5).

• 논리연구
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• 제20권2호
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• pp.163-196
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• 2017

비트겐슈타인은 "논리-철학 논고"에서 러셀의 역설을 해결했다고 선언한다. 그에 따르면, 함수는 그 자신의 논항이 될 수 없다. 만일 함수 F(fx)가 자기 자신의 논항이 될 수 있다고 가정하면, "F(F(fx))"라는 명제가 주어지는데, 이 명제에서 외부 함수 F와 내부 함수 F는 상이한 의미를 갖는다. 그렇게 되면 "F(F(fx))"는 확정적인 뜻을 지닐 수 없다. 그러나 왜 비트겐슈타인은 함수 F(fx)와 "F(F(fx))"를 문제 삼고 있는가? 이 물음에 대답하기 위해서는 우리는 무엇보다도 러셀의 역설에 대해 러셀 자신이 어떻게 해결하려고 시도했는지를 면밀히 검토해야 한다. 오직 러셀의 해결책을 이해할 수 있을 때에만 우리는 비트겐슈타인이 러셀의 역설을 어떻게 해결하려고 했는지를 이해할 수 있다. 특히 비트겐슈타인이 1913년 노르웨이에서 러셀에게 보낸 편지는 우리에게 결정적인 실마리를 제공해 준다.