• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.255-261
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• 2002

A four-degree of freedom model is suggested to understand the basic dynamical behaviors of the normal interaction between two masses of the friction induced normal vibration system. The two masses may be considered as the pad and the disk of the brake. The phase space analysis is performed to understand complicated in-plane dynamics of the non-linear model. Attractors in the phase space are examined for various conditions of the parameters. In certain conditions, the attractor becomes a limit cycle showing the stick-slip phenomena. In this paper, on the basis of the in-plane motion not only the existence of the limit cycle but also the size of the limit cycle is examined o demonstrate the non-linear dynamics that leads the unstable state and then the normal vibration is investigated as the state of the in-plane motion For only one case of the system frequency(two masses with same natural frequencies), the propensity of the normal vibration is discussed in detail. The results show an important fact that it may be not effective when too much damping is present in the only one part of the masses.

• Korean Journal of Mathematics
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• 제11권1호
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• pp.35-43
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• 2003

We study the weak convergence to Fractional Brownian motion and some examples with applications to traffic modeling. Finally, we get loss probability for queue-length distribution related to self-similar process.

• 한국컴퓨터산업학회논문지
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• 제3권7호
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• pp.927-936
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• 2002

본 논문은 비디오의 효율적인 내용기반 검색을 지원하기 위해 움직임벡터의 특징을 검출하였다. 이를 위해 비디오의 현재 프레임을 일정한 크기의 블록으로 나누고 시간 축상 기준이 되는 프레임에서 각 블록의 움직임을 추정하는 블록정합 알고리즘을 이용하였다. 하지만 블록 정합법의 경우 여러 가지 제약 조건과 함께 블록 정합법에 의해 얻어지는 벡터가 실제 움직임과 상이한 경우도 발생한다. 이러한 문제점을 해결하기 위해서 전역탐색방식을 응용했으나 이 방법은 계산량이 많다는 단점이 있다. 그 대안으로 본 논문에서는 탐색범위를 $\pm$15로 제안하고 탐색은 정수화소로 제한하였다. 결과 본 논문에서는 인접 블록의 움직임 벡터를 이용하여 좀 더 정확한 움직임 벡터의 예측을 행할 수 있었다. 하지만 참조되는 블록 벡터가 여러 개가 발생되기 때문에 이러한 부가 정보를 수신단에 전송해야 하는 부담을 안는다. 따라서, 각 블록의 움직임 특징을 예측하고 이에 알맞은 탐색 범위를 설정하는 문제도 고려하였다. 제시된 알고리즘을 바탕으로 움직임 보상을 위한 움직임 추정 기법을 고찰하고 이를 적용한 결과를 제시한다.

• 대한수학회논문집
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• 제26권4호
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• pp.649-660
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• 2011

S. M. Saperstone and M. Nishihama [6] had showed both continuity and stability of the orbital and limit set maps, K(x) and L(x), where K and L are considered as maps from X to $2^X$. The main purpose of this paper is to extend continuity and stability for dynamical systems to general dynamical systems.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.622-627
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• 2003

A numerical study is made of a flow in a cylinder with a rotating grooved endwall disk. The aim is to describe differences in the flow fields when there is concentrically-grooved obstacle characterized by amplitude(a) and wave number(N). The Reynolds number(Re) is varied from $10^{3}$ to $10^{4}$ and the aspect ratio(Ar) fixed to 1.0 for the most part of the simulation. For the various cases of amplitude(a) and wave number(N), numerical results are acquired. As the endwall groove roughness increases until certain limit, the interior azimuthal velocity component(v) increases drastically. But over the limit, the swirl motion chararcterized by velocity v decreases and finally it approaches much alike Ar=1.0-a case. The reason of activating swirl motion is based on increasing of torque transported by endwall disk. Torque coefficients($C_{T}$) are aquired for the various (a,N,Re) combinations and the limiting phenomena of swirl motion activation is explained.

• 소음진동
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• 제5권1호
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• pp.59-65
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• 1995

In this study, we investigated the operational limit of magnetic bearing-rotor system due to the maximum force limit and slew rjate limit of the electromagnetic actuator as a function of the time dependent control characteristics. The feedback gain of the controller varies the current of the electromagnet coil with the motion of the rotor. The distorsion of magnetic force due to the slew rate limit is not occurred jup to 30, 000 rpm in the magnetic bearing that we have a close relation with the rotational speed and vibration level of the rotor and the proportional gain of the controller. Therefore the maximum force limit determines the maximum allowable orbit radius of the magnetic bearing-rotor system. The maximum allowable vibration levels are exponentially decreased according to the increment of rotational speed and proportional gain of the controller.

• Korean Journal of Mathematics
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• 제22권1호
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• pp.71-84
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• 2014

By using the multidimensional normal approximation of functionals of Gaussian fields, we prove that functionals of Gaussian fields, as functions of t, converge weakly to a standard Brownian motion. As an application, we consider the convergence of the Stratonovich-type Riemann sums, as a function of t, of fractional Brownian motion with Hurst parameter H = 1/4.

• 풍력에너지저널
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• 제14권2호
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• pp.26-33
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• 2023

In this study, the global response characteristics of floater and mooring for floating offshore wind turbine with a detachable mooring system are performed. Global motion and structural response result extracted from the coupled motion analysis of 10MW DTU floating offshore wind turbine with detachable mooring system modeled by high-order boundary element model and finite element mesh, were used to study the characteristics of tension on mooring lines subjected to three different types of ocean loads. Breaking limit of mooring line characterized by wind, current and wave load has a major effect on the distribution of mooring tension found in time domain analysis. Based on the numerical results of coupled motion analysis, governing equation for calculating the motion response of a floater under ocean loads, and excitation force and surge motion and tension respectively are presented using excursion curve. It is found that the response of floater is reliable and accurate for calculating the tension distributions along the mooring lines under complex loadings. This means that the minimun breaking limit of mooring system satisfied a design criteria at ultimate ocean environmental loading condtions.

• 한국전문물리치료학회지
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• 제29권2호
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• pp.87-93
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• 2022

To solve the pathological problems of the musculoskeletal system based on evidence, a sophisticated analysis of human motion is required. Traditional optical motion capture systems with high validity and reliability have been utilized in clinical practice for a long time. However, expensive equipment and professional technicians are required to construct optical motion capture systems, hence they are used at a limited capacity in clinical settings despite their advantages. The development of information technology has overcome the existing limit and paved the way for constructing a motion capture system that can be operated at a low cost. Recently, with the development of computer vision-based technology and optical markerless tracking technology, webcam-based 3D human motion analysis has become possible, in which the intuitive interface increases the user-friendliness to non-specialists. In addition, unlike conventional optical motion capture, with this approach, it is possible to analyze motions of multiple people at simultaneously. In a non-optical motion capture system, an inertial measurement unit is typically used, which is not significantly different from a conventional optical motion capture system in terms of its validity and reliability. With the development of markerless technology and advent of non-optical motion capture systems, it is a great advantage that human motion analysis is no longer limited to laboratories.

• 한국산업융합학회 논문집
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• 제25권4_2호
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• pp.707-714
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• 2022

Versatile Video Coding (VVC) is the most recent video coding standard, which had been developed by Joint Video Expert Team (JVET). It can improve significant coding performance compared to the previous standard, namely High Efficiency Video Coding (HEVC). Although VVC can achieve the powerful coding performance, it requires the tremendous computational complexity of VVC encoder. Especially, affine motion compensation (AMC) was adopted the block-based 4-parameter or 6-parameter affine prediction to overcome the limit of translational motion model while VVC require the cost of higher encoding complexity. In this paper, we proposed the early termination of AMC that determines whether the affine motion estimation for AMC is performed or not. Experimental results showed that the proposed method reduced the encoding complexity of affine motion estimation (AME) up to 16% compared to the VVC Test Model 17 (VTM17).