• 한국직업건강간호학회지
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• 제9권1호
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• pp.30-38
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• 2000

This study was carried out to investigate what factors affect satisfaction of periodic health examination undertaken by employees. The purpose of the study was to improve quality of periodic health examination and to increase the rate of workers participation in the screening test. The content of questionnaire was designed with focus on the satisfaction and attitude on the periodic health examination. Data were analyzed with 212 males, 181 females among 393 samples who took periodic examination at a general hospital in Seoul. Korea. The results were as follows: 1. Respondents were mainly in the thirties(42.7%), married(58.5%), more than 3 years working experiences(66.7%) and employed in Sales & Customers service industry(60.1%). 2. There were significant differences in the scores of satisfaction by general characteristics among the respondents. The highly educated and the single showed higher satisfaction on the periodic health examination than other respondents. 3. The scores of satisfaction in periodic health examination showed highly influenced by level of age, work duration, level of knowledge to the health screening and income. Based on the results, this study concluded that the periodic health examination might be necessary to modify its items according to the clients characteristics and their individual demands for maintenance of healthy life.

• 대한수학회보
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• 제32권2호
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• pp.271-279
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• 1995

In 1986, Fabry, Mawhin and Nkashama [1] have considered periodic solutios for Lienard equation $$ (1_s) x" + f(x)x' + g(t,x) = s, $$ where s is a real parameter, f and g are continuous functions, and g is $2\pi$-periodic in t and have proved that if $$ (H) lim_{$\mid$x$\mid$\to\infty} g(t,x) = \infty uniformly in t \in [0,2\pi], $$ there exists $s_1 \in R$ such that $(1_s)$ has no $2\pi$periodic solution if $s< s_1$, and at least one $2\pi$-periodic solution if $s = s_1$, and at least two $2\pi$-periodic solutions if $s > s_1$.s_1$.

• 한국소음진동공학회논문집
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• 제15권12호
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• pp.1355-1360
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• 2005

Periodic structures can be applied as a MEMS(micro-electro-mechanical system) sensor or actuator due to low energy loss and wideband frequency response. The dynamic behavior of a mistuned periodic structure Is dramatically changed from that of a perfectly tuned periodic structure. The effects of mistuning, coupling stiffness, and driving point on the forced vibration responses of a simple periodic structure ate investigate4 through numerical simulations. On the basis of that, one can design effective and reliable MEMS components using periodic structures.

• 한국전자파학회논문지
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• 제14권11호
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• pp.1207-1215
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• 2003

본 논문에서는 대수주기 다이폴 안테나(LPDA: Log-Periodic Dipole Antennas)의 크기를 줄이기 위해 다이폴 소자를 벤트 다이폴 소자로 대체한 대수주기 벤트 다이폴 안테나(LPBDA: Log-Periodic Bent Dipole Antennas)를 제안하였다. 1 ㎓∼3 ㎓ 사이에서 동작하는 LPBDA를 설계하고 모멘트법을 이용하여 복사특성을 해석하여 LPDA의 특성과 비교 검토하였다. 그 결과 본 논문에서 제시한 LPBDA는 다이폴 소자의 길이를 약 20% 줄이면서도 복사특성이 LPDA와 비교하여 거의 차이가 없는 것으로 나타났으며, 제작 측정한 LPBDA의 특성도 계산 결과에 근접했다.

• 대한기계학회논문집B
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• 제25권3호
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• pp.433-441
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• 2001

Natural convection of a fluid with intermediate Prand시 number of Pr=0.2 in a horizontal annulus is considered, and the bifurcation phenomena and chaotic flows are numerically investigated. The unsteady two-dimensional streamfunction-vorticity equation is solved with finite difference method. The steady downward flow with two counter-rotating eddies bifurcates to a simple periodic flow with a fundamental frequency. And afterwards, second Hopf bifurcation occurs, and a quasi-periodic flow with two incommensurable frequencies appears. However, a new time-periodic flow is established after experiencing quasi-periodic states. As Rayleigh number is increased further, the chaotic flow regime is reached after a sequence of successive Hopf bifurcation to quasi-periodic and chaotic flow regimes. A scenario similar to the Ruelle-Takens-Newhouse scenario of the onset of chaos is observed.

• 대한수학회지
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• 제56권1호
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• pp.39-52
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• 2019

The aim of this paper is to introduce the notions of (quasi) weakly almost periodic point, measure center and minimal center of attraction of amenable group actions, explore the connections of levels of the orbit's topological structure of (quasi) weakly almost periodic points and study chaotic dynamics of transitive systems with full measure centers. Actually, we showed that weakly almost periodic points and quasiweakly almost periodic points have distinct orbit's topological structure and proved that there exists at least countable Li-Yorke pairs if the system contains a proper (quasi) weakly almost periodic point and that a transitive but not minimal system with a full measure center is strongly ergodically chaotic.

• 대한수학회논문집
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• 제13권1호
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• pp.123-129
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• 1998

In this paper, we study some dynamical properties of a weakly almost periodic flow. In particular we get, in a weakly almost periodic flow (X,T), the groups I and A(I) of all automorphisms of I are isomorphic, where E(X) is the enveloping semigroup of (X,T) and I is the minimal right ideal in E(X).

• 대한수학회논문집
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• 제33권3호
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• pp.1039-1048
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• 2018

In this paper we study the dynamics of a general ${\omega}-periodic$ model. Necessary and sufficient conditions for the global stability of zero steady state of the model are given. The conditions under which there exists a unique periodic solutions to the model are determined. We also show that the unique periodic solution is the global attractor of all other positive solutions. Some applications to mathematical models for cancer and tumor growth are given.

• Structural Engineering and Mechanics
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• 제38권5호
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• pp.619-631
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• 2011

This paper provides a complex variable BIE for solving the periodic notch problems in plane plasticity. There is no limitation for the configuration of notches. For the periodic notch problem, the remainder estimation technique is suggested. In the technique, the influences on the central notch from many neighboring notches are evaluated exactly. The influences on the central notch from many remote notches are approximated by one term with a multiplying factor. This technique provides an effective way to solve the problems of periodic structures. Several numerical examples are presented, and most of them have not been reported previously.

• 충청수학회지
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• 제24권4호
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• pp.735-743
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• 2011

Let f be a diffeomorphism of a closed n-dimensional smooth manifold. In this paper, we introduce the notion of $C^1$-stably periodic shadowing property for a closed f-invariant set, and prove that for a transitive set ${\Lambda}$, if f has the $C^1$-stably periodic shadowing property on ${\Lambda}$, then ${\Lambda}$ admits a dominated splitting.