• 한국정보처리학회논문지
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• 제7권7호
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• pp.2229-2237
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• 2000

본 논문은 고정 우선순위를 가지는 주기 태스크와 동적으로 발생하는 비주기 태스크를 스케줄링하는 슬렉 스틸링(slack stealing) 알고리즘의 문제점을 개선하다. 슬랙 스틸링 알고리즘은 비주기 태스크의 발생에 따라 슬랙 스틸링 서버가 적합한 우선순위를 비주기 태스크에 부어하여 즉시 서비스 가능하도록 함으로써 불필요한 대기시간을 최소화하고 있다. 하지만, 슬랙 스틸링을 수행하기 위해서는 임의의 시점가지 주기적 태스크의 수행 시간을 구해야 한다. 그리고 주기적 태스크의 수행 시간은 슬랙 알고리즘을 적용하는 동안 매 시간 마다 다디 구해지고 이싸다. 이때 사 되는 시간 복잡도는 계산에 적용되는 태스크의 수가 n이라면 O(n)으로 나타난다. 본 논문에서는 스케쥴링된 쥐적 태스크의 슬랙타임과 수행시간을 테이블에 저장하여 비주기 태스크가 사용하는 슬랙을 구함으로서 동적으로 발생하는 비주기적 태스크의 복잡도를 O(log n)으로 감소시키고 응답시간을 향상시킨다. 본 논문에서 제안한 알고리즘을 모의 실험을 통하여 증명한다.여 증명한다.

• 한국광학회지
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• 제31권3호
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• pp.148-154
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• 2020

본 논문에서는 주기적인 구멍배열(periodic hole array, PHA) 패턴을 가진 나노금속구조 컬러필터의 문제점인 입사광의 각도에 따른 컬러필터 중심파장의 이동을 해결하기 위해 새로운 구멍 패턴인 polyperiodic hole array (PPHA)를 제시한다. 먼저 녹색파장대역 컬러필터를 만들기 위해 구멍의 직경과 주기를 정했으며 propagation length와 skin depth를 고려해 단위셀의 크기, 금속과 유전체의 두께를 설정했다. PPHA 패턴을 만들기 위해 주기적인 구멍배열을 국부적으로 회전시켜 전체적으로는 비주기적이지만 부분적으로 주기적인 패턴을 만들었다. 그 결과 PHA 패턴과 대비하여 PPHA 패턴 나노금속구조 컬러필터는 입사광각이 0°에서 30°까지 증가하였을 때 파장의 이동도가 최대 40% 개선되었다. 본 연구를 통해 나노금속구조 컬러필터의 성능을 향상시킬 수 있으며 디스플레이, 이미지 센서 등 이미징 디바이스 분야에 접목시켜 산업적으로 활용할 수 있을 것으로 예상한다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권6호
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• pp.692-710
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• 2018

The Three-dimensional (3-D) dynamical behaviors of a fluid-conveying pipe subjected to vortex-induced vibration are investigated with different internal flow velocity ${\nu}$. The values of the internal flow velocity are considered in both subcritical and supercritical regimes. During the study, the 3-D nonlinear equations are discretized by the Galerkin method and solved by a fourth-order Runge-Kutta method. The results indicate that for a constant internal flow velocity ${\nu}$ in the subcritical regime, the peak Cross-flow (CF) amplitude increases firstly and then decrease accompanied by amplitude jumps with the increase of the external reduced velocity. While two response bands are observed in the In-line (IL) direction. For the dynamics in the lock-in condition, 3-D periodic, quasi-periodic and chaotic vibrations are observed. A variety of CF and IL responses can be detected for different modes with the increase of ${\nu}$. For the cases studied in the supercritical regime, the dynamics shows a great diversity with that in the subcritical regime. Various dynamical responses, which include 3-D periodic, quasi-periodic as well as chaotic motions, are found while both CF and IL responses are coupled while ${\nu}$ is beyond the critical value. Besides, the responses corresponding to different couples of ${\mu}_1$ and ${\mu}_2$ are obviously distinct from each other.

• Kyungpook Mathematical Journal
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• 제49권4호
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• pp.605-618
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• 2009

A stage-structured predator-prey system with time delay and Beddington-DeAngelis functional response is considered. By analyzing the corresponding characteristic equation, the local stability of a positive equilibrium is investigated. The existence of Hopf bifurcations is established. Formulae are derived to determine the direction of bifurcations and the stability of bifurcating periodic solutions by using the normal form theory and center manifold theorem. Numerical simulations are carried out to illustrate the theoretical results.

• Kyungpook Mathematical Journal
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• 제56권3호
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• pp.831-844
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• 2016

In this paper, we consider a discrete predator-prey system with Watt-type functional response and impulsive controls. First, we find sufficient conditions for stability of a prey-free positive periodic solution of the system by using the Floquet theory and then prove the boundedness of the system. In addition, a condition for the permanence of the system is also obtained. Finally, we illustrate some numerical examples to substantiate our theoretical results, and display bifurcation diagrams and trajectories of some solutions of the system via numerical simulations, which show that impulsive controls can give rise to various kinds of dynamic behaviors.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.930-933
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• 2000

To understand the behavior of electron, ions and radicals on radio-frequency non-equilibrium plasma, it is necessary to know the basic information about its fundamental properties and reactions. Especially, the transient response of radio-frequency plasma has an important means of controlling selective etch rates and investigating the stability of a plasma chemical process. In this paper, we present the results of periodic steady-state behavior and transient behavior carbon Tetrafluoride(CF$_4$) discharge at 0.2 Torr in a 2 cm gap parallel-plate. After the number densities of charged particles became steady-state, the applied voltage was increased or decreased in an instant and the transient behavior of charged particles and radicals was investigated from one steady-state to the next steady state.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
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• pp.1264-1266
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• 2005

This paper analyzes static and transient response characteristics of a permanent magnet type stepping motor with claw poles using three-dimensional finite element method. The outer diameter of the stepping motor to be analyzed is approximately 6 mm. In this paper we analyzes only 2 poles of the stepping motor, which has 10 magnetic poles made up of NdFeB material, using periodic boundary condition. We clarify transient response and static torque charateristics using Maxwell 3D and Matlab Simulink.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1994년도 추계학술대회논문집; 한국종합전시장, 18 Nov. 1994
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• pp.35-39
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• 1994

One of the important characteristics of the response of nonlinear systems is the existence of subharmonic resonances. When some conditions in parameter space are satisfied. It is possible even in the presence of damping for a periodically excited nonlinear system to possess a response which is the combination of a contribution at the excitation frequency and a component at the system natural frequency. The system natural frequency being a submultiple of the excitation frequency implies that the resulting response is a subharmonic oscillation. In general, there also co-exists, for the system, a response at the excitation frequency, and initial conditions determine which of the steady-state responses is achieved in an experiment or a numerical simulation. In single-degree-of-freedom systems with harmonic excitation, depending on the type of the nonlinearity, e.g., cubic or quadratic the frequency of subharmonic response is respectively, one-third or one-half of that of the excitation frequency. Although subharmonic resonance is one of the principal characteristics of a nonlinear system the subharmonic responses of structures in the presence of internal resonances have been studied very rarely. In this work, we consider subharmonic responses in the two-mode approximation of the plate equations. It is assumed that the two modes are in one-to-one internal resonance. Constant and periodic steady-state solutions of the averaged equations are studied. Finally, the results of direct time integration of the original equations of motion are presented and compared with those obtained from the averaged equations.

• Advances in aircraft and spacecraft science
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• 제3권3호
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• pp.271-298
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• 2016

In this paper, we study a problem of passive suppression of helicopter Ground Resonance (GR) using a single degree freedom Nonlinear Energy Sink (NES), GR is a dynamic instability involving the coupling of the blades motion in the rotational plane (i.e. the lag motion) and the helicopter fuselage motion. A reduced linear system reproducing GR instability is used. It is obtained using successively Coleman transformation and binormal transformation. The analysis of the steadystate responses of this model is performed when a NES is attached on the helicopter fuselage. The NES involves an essential cubic restoring force and a linear damping force. The analysis is achieved applying complexification-averaging method. The resulting slow-flow model is finally analyzed using multiple scale approach. Four steady-state responses corresponding to complete suppression, partial suppression through strongly modulated response, partial suppression through periodic response and no suppression of the GR are highlighted. An algorithm based on simple criterions is developed to predict these steady-state response regimes. Numerical simulations of the complete system confirm this analysis of the slow-flow dynamics. A parametric analysis of the influence of the NES damping coefficient and the rotor speed on the response regime is finally proposed.

• Journal of the Korean Data and Information Science Society
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• 제22권5호
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• pp.961-966
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• 2011

Circular variables are those that have a period in its range. Their examples include direction of animal migration, and time of drug administration, just to mention a few. Statistical analysis of circular variables is quite different from that of linear variable due to its periodic nature. In this paper, the author proposes new circular regression models using geodesic lines on the surface of the sample space of the response and the predictor variables.