• 대한인간공학회:학술대회논문집
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• 대한인간공학회 1995년도 춘계학술대회논문집
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• pp.155-164
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• 1995

For efficient operation, vital hand controls must be easily controlled by the operator from his normal working position. The primary working area based on operator's working comfort was developed to serve as a design guideline tothe control panel layout. Ten male subjects participated in the experiment in which working comfort was measured for two controls of a lever type control and a knob type control with respect to the frontal and sagittal distances from the body center and the slope of a workplace. The response surface methodolgy using a central composite design was employed to develop a prediction model for perceived working comfort of each control. Both controls have a similar pattern of comfortable working area, but the lever type control has slightly broader working area. The concept of the proposed working area is a significant extension to the conventional working area such as Farley's or Squires' curves. It is shown that the distance toa control device and the slope have a quadratic effect to working comfort. It is noticeable that comfortable working area exists outside the conventional working area. The result of the response surface analysis also indicated that a little slope of about 15 .deg. for a control panel improves working comfort.

• 대한수학회보
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• 제24권1호
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• pp.23-26
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• 1987

The aim of this note is to study some properties of Schrodinger operators, the magnetic case, $H_{0}$ (a)=1/2(-i.del.-a)$^{2}$; H(a)= $H_{0}$ (a)+V, where a=( $a_{1}$,.., $a_{n}$ ).mem. $L^{2}$$_{loc}$ and V is a potential energy. Also, we are interested in solutions, .psi., of H(a).psi.=E.psi. in the sense that (.psi., $e^{-tH}$(a).PSI.)= $e^{-tE}$(.psi.,.PSI.) for all .PSI..mem. $C_{0}$ $^{\infty}$( $R^{n}$ ) (see B. Simon [1]). In section 2, under some conditions, we find that a semibounded quadratic form of H9a) exists and that the Schrodinger operator H(a) with Re V.geq.0 is accretive on a form domain Q( $H_{0}$ (a)). But, it is well-known that the Schrodinger operator H=1/2.DELTA.+V with Re V.geq.0 is accretive on $C_{0}$ $^{\infty}$( $R^{n}$ ) in N Okazawa [4]. In section 3, we want to discuss $L^{p}$ estimates of Schrodinger semigroups.ups.

• 대한수학회보
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• 제58권1호
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• pp.205-215
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• 2021

In [1], Beznosova proved that the bound on the norm of the dyadic paraproduct with b ∈ BMO in the weighted Lebesgue space L2(w) depends linearly on the Ad2 characteristic of the weight w and extrapolated the result to the Lp(w) case. In this paper, we provide the weighted norm estimates of the dyadic paraproduct πb with b ∈ VMO and reduce the dependence of the Ad2 characteristic to 1/2 by using the property that for b ∈ VMO its mean oscillations are vanishing in certain cases. Using this result we also reduce the quadratic bound for the commutators of the Calderón-Zygmund operator [b, T] to 3/2.

• 한국지반공학회논문집
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• 제22권9호
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• pp.45-59
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• 2006

탄소성 구성방정식은 주로 미분방적식(rate equation)으로 이루어져 있기 때문에 유한요소법 등을 이용한 지반구조물 해석시 미분방정식들에 대한 수치적분을 수행할 수 있는 방법이 필요하다. 구조물의 거동을 해석할시 미분방정식들을 위한 적분방법은 해석결과의 정확성과 유한요소법 모델링의 안전성에 큰 영향을 미치고 있다. 본 논문에서는 최근에 개발되어 사용되고 있는 흙에 관한 구성모델인 "Two-surface soil plasticity model (Manzari and Dafalias 1997)"을 Implicit return-mapping 수치적분방법을 이용하여 실행하는 과정을 제시한다. 본 연구에서 사용된 수치적분방법은 Closest-Point-Projection Method(CPPM) 방법으로 탄성 예측자-소성 교정자(elastic predictor-plastic corrector) 개념을 Implicit Backward Euler방법으로 체계화 시킨 알고리듬이다. 본 연구에서 수행한 "Two-surface soil plasticity model"은 조립토의 비선형거동을 해석하며, Bounding surface 개념 및 비선형 등방경화와 이동경화법칙을 사용하는 모델이다. 본 연구는 CPPM 방법이 정확하고 안정되며 유용한 수치적분을 수행할 수 있는 알고리듬이라는 것을 제시한다. 또한, CPPM 알고리듬은 구성방정식의 해를 반복적으로 해석하는 동안 "Consistent tangent operator $d{\sigma}/d{\varepsilon}$"를 제공하므로, 비선형 유한요소 해석이 2차(quadratic convergence rate)의 수렴 조건을 만족하는데 기여한다는 것을 보여준다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.708-710
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• 2004

This paper studies a multirate sampled-data control for LTI systems by using the digital redesign (DR) method. In this note, to well tackle the problem associated with both the state matching and the stabilization, our nobel strategy is to minimize the linear quadratic cost function. The main features of the proposed method are that i) the delta-operator-based descretization method is applied to improve the state-matching performance in the fast sampling limit and/or the large input multiplicity; ii) the proposed multirate control scheme can improve the state-matching performance in the long sampling limit; iii) some sufficient conditions that guarantee the stability of the closed-loop discrete-time system and provide a guarantee cost for the cost function can be formulated in the LMIs format; and iv) an optimal sampled-data controller in the sense of minimizing the upper bound of the cost function is also given by means of an LMI optimization procedure.

• Ocean Systems Engineering
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• 제12권1호
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• pp.23-38
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• 2022

In this paper, a pitch-type wave energy converter (WEC-rotor) is investigated in irregular wave conditions for the real sea testing at the west coast of Jeju Island, South Korea. The present research builds on and extends our previous work on regular waves to irregular waves. The hydrodynamic characteristics of the WEC-rotor are assessed by establishing a quasi-two-dimensional numerical wave tank using computational fluid dynamics by solving the Reynolds-averaged Navier-Stokes equation. The numerical solution is validated with physical experiments, and the comparison shows good agreement. Furthermore, the hydrodynamic performance of the WEC-rotor is explored by investigating the effect of the power take-off (PTO) loading torque by one-way and two-way systems, the wave height, the wave period, operational and high sea wave conditions. Irrespective of the sea wave conditions, the absorbed power is quadratic in nature with the one-way and two-way PTO loading systems. The power absorption increases with the wave height, and the increment is rapid and mild in the two-way and one-way PTO loading torques, respectively. The pitch response amplitude operator increases as the wave period increases until the maximum value and then decreases. For a fixed PTO loading, the power and efficiency are higher in the two-way PTO loading system than in the one-way PTO loading system at different wave periods.

• 한국컴퓨터그래픽스학회논문지
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• 제22권5호
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• pp.1-16
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• 2016

본 논문에서는 최소자승법에 기반한 효율적인 곡선 복구 기법을 제안한다. 구체적으로는, 법선 벡터를 포함한 평면상의 샘플포인트가 주어졌을 때 계층적인 ZP(Zwart-Powell)-스플라인의 레벨로 곡선을 복구하는데, 세밀한 부문을 복구하면서도 비교적 큰 구멍도 효율적으로 메꾸고 있다. 정규화를 위해서는, (1) 선형시스템의 특이성을 피하기 위한 티코노프 정규항과 (2) 아이소커브를 부드럽게 하기 위한 이산 라플라스 정규항 두 가지를 사용하고 있다. 정량적인 벤치마크 테스트를 통해 비교한 결과, 본 방법은 다항식에 기반한 기법들에 비해 훨씬 우수한 결과를 보여준다는 것을 확인할 수 있다. 구멍이 있는 데이터의 경우, 계층적인 B-스플라인과 비교해본 결과 엇비슷한 품질을 보이지만 약 90%의 계산량만을 필요로 한다.