• 지구물리와물리탐사
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• 제3권2호
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• pp.39-47
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• 2000

복잡한 지층구조에 대한 파동방정식의 해를 유한 차분법을 이용하여 구하는것은 많은 컴퓨터 계산시간과 기억 용량이 필요하다. 컴퓨터 계산시간과 기억용량은 최소 파장당 격자수를 줄이므로써 감소 시킬 수 있지만 수치분산으로 인해 정확도가 떨어지게 마련이다. 본 연구에서는 정확도를 유지하면서 파장당 격자수를 줄이는 방법으로 이용되고 있는 가중평균법을 최대 169점 까지 확장하여 주파수 영역에서 음향파동방정식의 해를 유한차분법으로 구할 때 최소 격자수를 구하기 위한 격자분석을 실시하였다. 지금까지 수치오차가 정확도 $1\%$내에 존재하기 위해서는 일반적인 5점을 이용하는 경우 파장당 격자수가 13개 이상이 필요하고, 9점의 경우 9개, 25점에서는 3개, 49점에서는 2.7개 이상이 필요하였다. 본 연구에서 정확도를 유지하기 위한 최소격자수를 결정하기 위해 실시된 격자분석 결과 81점에서는 2.5개 121점에서는 2.3개 그리고 169점에서는 오차 한계를 벗어나 가중평균 계수를 구할 수 없었으며 격자수를 2개까지 줄일 수 없음을 알 수 있었다. 또한 격자분석을 통해 가중평균에 적용되는 격자수가 증가할수록 정확도는 증가하지만 차분식 자체가 증가하여 매우 복잡하게 된다.

• 대한수학회보
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• 제60권5호
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• pp.1201-1219
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• 2023

We characterize the boundedness and compactness of differences of weighted composition operators acting from weighted Bergman spaces A^p_ω to Lebesgue spaces L^q(dµ) for all 0 < p, q < ∞, where ω is a radial weight on the unit disk admitting a two-sided doubling condition.

• 대한수학회보
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• 제53권4호
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• pp.1213-1235
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• 2016

We prove a uniqueness theorem of nonconstant meromorphic functions sharing three distinct values IM and a fourth value CM with their shifts, and prove a uniqueness theorem of nonconstant entire functions sharing two distinct small functions IM with their shifts, which respectively improve Corollary 3.3(a) and Corollary 2.2(a) from [12], where the meromorphic functions and the entire functions are of hyper order less than 1. An example is provided to show that the above results are the best possible. We also prove two uniqueness theorems of nonconstant meromorphic functions sharing four distinct values with their difference operators.

• 대한수학회논문집
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• 제26권4호
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• pp.591-601
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• 2011

In this paper, we deal with the discrete p-Laplacian operators with a potential term having the smallest nonnegative eigenvalue. Such operators are classified as its smallest eigenvalue is positive or zero. We discuss differences between them such as an existence of solutions of p-Laplacian equations on networks and properties of the energy functional. Also, we give some examples of Poisson equations which suggest a difference between linear types and nonlinear types. Finally, we study characteristics of the set of a potential those involving operator has the smallest positive eigenvalue.

• 대한인간공학회지
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• 제36권5호
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• pp.447-458
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• 2017

Objective: The purpose of this study is to present the basic guidelines for preventing human error by measuring and analyzing the risk of collision perceived by the ship operator in the collision risk situation by using Korea Coast Guard patrol ships. Background: In the last 5 years, 97.5% of the causes of ship collision occurred at the sea was caused by human factors. However, the rate of marine accidents due to human error has not been reduced yet. Experiments and researches on the ship operators using the ships in actual operation are rarely performed. Method: Using two K.C.G Ships on the sea, the ship measured by 30 persons who are the subject of the ship (ship operator) when both ships approach and the relative distance gradually decreases in four encounter situations, perceived ship collision risk (PSCR) data were analyzed by statistical analysis. Results: The age and boarding career of the ship operator in the situation of ship collision risks encountered a negative impact on perceived collision risk in all four opposing encounter situations S1 ($000^{\circ}$), S2 ($045^{\circ}$), S3 ($090^{\circ}$) and S4 ($135^{\circ}$) respectively. That is, the higher the age of the ship operator, the lower the perceived risk of collision and the lower the age, the higher the risk of collision. Also, there was a difference between the average of group A (20~30 years) and group B (40~50 years) according to age of the ship operators at $000^{\circ}$, $045^{\circ}$ and $090^{\circ}$ and there was no difference at $135^{\circ}$. The mean difference of the experience of boarding career was also significantly different between group A (less than 4 years) and group B (more than 5 years), but there was no significant difference at $135^{\circ}$. Conclusion: The results showed that age and boarding career of the ship operators had negative impact on perceived collision risk and there was a difference in perceived risk of collision according to age and abundance of boarding career. As a result, by focusing on the ship operators who are in the age group of 20~30 years old and have less than 4 years of experience in boarding the ship. It is expected that the effect of prevention of marine accidents can be expected by avoiding collision avoidance. Application: The results of this study can be used as policy data of related organizations to prevent human error of ship operators and as training data of training institutes.

• 한국식품영양과학회지
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• 제26권3호
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• pp.514-520
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• 1997

The purpose of this study is to provide the reference data for estimating body composition and developing equations for prediction of percent body fat. This study was designed of two aspects: Comparison of percent body fat measurements between two operators. comparison of percent body fat measurements among four instruments. Percent body fat of college girls(n=71) aged 18-24 was measured by skinfold thickness, near-infratred interactance(Futrex-5000), and bioelectrical impedance analysis (TBF-105, Spectrum II). All measurements were duplicated & measured by two operators. The results are summarized as follows: Percent body fat observed from two operators had no significant difference. There was significant difference from four instruments. However, we found close relation between Skinfold thickness & TBF-105, Spectrum II & Near-infrared interactance. Four instruments have several assumptions and limitations. Therefore, many researches for developing new equations are required for Korean people.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제30권1호
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• pp.43-65
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• 2023

In this paper, by using the difference analogue of Nevanlinna's theory, the authors study the shared-value problem concerning two higher order difference operators of a transcendental entire function with finite order. The following conclusion is proved: Let f(z) be a finite order transcendental entire function such that λ(f - a(z)) < ρ(f), where a(z)(∈ S(f)) is an entire function and satisfies ρ(a(z)) < 1, and let 𝜂(∈ ℂ) be a constant such that ∆_𝜂ⁿ⁺¹ f(z) ≢ 0. If ∆_𝜂ⁿ⁺¹ f(z) and ∆_𝜂ⁿ f(z) share ∆_𝜂ⁿ a(z) CM, where ∆_𝜂ⁿ a(z) ∈ S ∆_𝜂ⁿ⁺¹ f(z), then f(z) has a specific expression f(z) = a(z) + Be^Az, where A and B are two non-zero constants and a(z) reduces to a constant.

• 대한인간공학회지
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• 제16권1호
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• pp.63-71
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• 1997

This paper presented an experiment which examined eye and hand movement characteristics of novice and experienced workers in the press operation. Continuous recordings of eye and hand movements were made on five novice operators and five experienced operators in press operation. Significant difference between the novice and the experienced operators was observed in eye fixation time, eye movement patterns, hand dwell time, and eye-hand coordination. Also, differences were observed in spatial distribution of eye fixations during the die-closing portion of a stroke. There were no significant differences between the novice and the experiencedoperators in the eye and the hand movement time. The results could be used to establish a guide determining the method and training period to train the novice operators.

• Korean Journal of Mathematics
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• 제27권2호
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• pp.505-514
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• 2019

In this paper we study the approximation properties of a continuous function by the sequence of (p, q)-Bernstein operators for q > p > 1. We obtain bounds of (p, q)-Bernstein operators. Further we prove that if a continuous function admits an analytic continuation into the disk $\{z:{\mid}z{\mid}{\leq}{\rho}\}$, then $B^n_{p,q}(g;z){\rightarrow}g(z)(n{\rightarrow}{\infty})$ uniformly on any compact set in the given disk $\{z:{\mid}z{\mid}{\leq}{\rho}\}$, ${\rho}>0$.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제20권1호
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• pp.1-15
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• 2016

The continuous analysis, such as smoothness and uniform convergence, for polynomials and polynomial-like functions using differential operators have been studied considerably, parallel to the study of discrete analysis for these functions, using difference operators. In this work, for the difference operator ${\nabla}_h$ with size h > 0, we verify that for an integer $m{\geq}0$ and a strictly decreasing sequence $h_n$ converging to zero, a continuous function f(x) satisfying $${\nabla}_{h_n}^{m+1}f(kh_n)=0,\text{ for every }n{\geq}1\text{ and }k{\in}{\mathbb{Z}}$$, turns to be a polynomial of degree ${\leq}m$. The proof used the polynomial convergence, and additionally, we investigated several conditions on convergence to polynomials.