• Journal of Institute of Control, Robotics and Systems
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• v.4 no.6
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• pp.772-779
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• 1998

본 논문에서는 강인한 비선형 예측제어기를 개발하여 연구용 원자로 벽면검사를 위한 수중로봇에 적용하여 보았다. 비선형 예측제어기는 먼저 적절한 함수 확장을 이용하여 시스템의 미래 출력 값을 예측하고, 예측값과 설정치와의 차이를 최소화시키는 제어입력을 구하여 시스템에 인가한다. 이러한 제어기에 의한 폐회로 동특성은 목적함수가 상태변수로 이루어진 경우는 항상 안정한 특성을 보이고 목적함수가 출력변수으로 이루어진 경우는 상대 계수가 4이하인 경우에 안정한 특성을 보인다. 이 제어기는 기존의 비선형 제어기가 적용 불가능한 시스템에도 적용 가능한 장점을 가지고 있다. 시스템의 불확실성이 큰 경우, 제어 안정도 및 제어 성능을 향상시키기 위하여 감독제어를 비선형 예측제어기에 포함시켰다. 이러한 제어기를 수중 벽면 주행로봇에 대한 모사실험에 적용한 결과 제어기의 강인함과 제어 성능 향상을 볼 수 있었다.

• 한국방재학회:학술대회논문집
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• 2009.02b
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• pp.56.2-56.2
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• 2009

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.2 s.54
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• pp.11-17
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• 2007

In current seismic design practice, the response modification factor (R-factor) is used as a factor to reduce the elastic base shear demand to the design force level. As is well-known, the R-factor is a committee-consensus factor and, as such, highly qualitative and empirical. The relationship between the R-factor and the connection rotation capacity available in a particular structural system has remained a missing link. In this paper, a rational procedure to evaluate the R-factor is proposed. To this end, the relationship between the available connection rotation capacity and the R-factor is defined and quantified using nonlinear pushover analysis. An RRS steel frame designed according to IBC 2000 was used to illustrate and verify the proposed procedure. Nonlinear time history analysis results indicated that the R-factor definition proposed in this study is generally conservative from design perspective.

• International Journal of Highway Engineering
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• v.12 no.4
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• pp.147-155
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• 2010

A prediction model of resilient modulus($E_R$) was developed for recycled crushed-rock-soil mixtures. The evaluation of $E_R$, using the "orthodox" repeated loading tri-axial test, is not feasible for such a large-size gravelly material. An alternative method was proposed hereby using the subtle different modulus called nonlinear dynamic modulus. The prediction model was developed by utilizing in-situ measured shear modulus($G_{max}$) and its reduction curves of modeled materials using the large free-free resonant column test. A pilot evaluation of the model parameters was carried out for recycled crushed-rock-soil-mixture at a highway construction site near Gimcheon, Korea. The values of the model parameters($A_E,\;n_E,\;{\varepsilon}_r\;and\;{\alpha}$) were proposed as 9618, 0.47, 0.0135, and 0.8, respectively.

• Proceedings of the Optical Society of Korea Conference
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• 1998.08a
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• pp.146-147
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• 1998

• Proceedings of the Optical Society of Korea Conference
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• 1990.07a
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• pp.101-105
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• 1990

• Journal of the Korean Geotechnical Society
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• v.19 no.2
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• pp.189-197
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• 2003

In this paper, deformation characteristics of fiber-mixed-soils were studied at small strain range(0.0001%～1%) using resonant column test and triaxial test, and reinforcement effect was evaluated by the measure of maximum shear moduli. The effects of the major parameters such as fiber content, aspect ratio and fiber type on reinforcement were comparatively assessed. The specimens were remolded from Jumunjin Sand randomly mixed with discrete polypropylene staple fibers. Maximum shear moduli of fiber-mixed-soils increased by up to 30% and modulus reduction was also restrained in nonlinear range. Shear moduli increased as the aspect ratio increases. The reinforcement was more effective with fibrillated fiber than with monofilament fiber. The most effective reinforcement was achieved with the specimen of 0.3 % fiber content.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.12
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• pp.2382-2390
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• 2007

A new polynomial-based predistortion method for linearizing nonlinear power amplifier is proposed. The proposed method finds the predistortion parameter directly without the help of postdistorter whereas most existing polynomial-based predistortion methods calculate the predistortion parameter indirectly from the prostdistorter. First, a new predistortion algorithm is derived based on the assumption that the characteristic of the amplifier is modeled by piecewise linear function. Then it is modified into a proposed method which does not require any assumption or prior knowledge of the amplifier. The proposed method is derived based on the RLS (recursive least squares) algorithm. The proposed technique is simpler to implement than the existing methods and the computer simulation demonstrates that the proposed method is more robust to the initial condition and the saturation region of the amplifier.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.2 s.54
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• pp.105-113
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• 2007

In the current research, an algorithm of performance-based seismic retrofit design of reinforced concrete columns using FRP jacket has been proposed. For exact prediction of the nonlinear flexural analysis or FRP composite RC members, multiaxial constitutive laws of concrete and composite materials have been presented. For seismic retrofit design, an algorithm of direct displacement-based design method (DDM) proposed by Chopra and Goel (2001) has been newly applied to determine the design thickness of FRP jacket in seismic retrofit of reinforced concrete columns. To compare with the displacement coefficient method (DCM), the DDM gives an accurate prediction of the target displacement in highly nonlinear region, since the DCM uses the elastic stiffness before reaching the yield load as the effective stiffness but the DDM uses the secant stiffness.

• Magazine of the Korea Concrete Institute
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• v.10 no.3
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• pp.219-226
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• 1998

본 연구에서는 경량콘크리트보의 거동을 연구하는데 적용될 수 있는 비선형해석이 나타나있다. 콘크리트에 대한 2축 실험 자료를 사용하여 경량콘크리트의 구성모델을 만들었다. 구성모델에서 콘크리트의 비선형성은 주응력비에 따른 강도증감계수와 탄성계수의 변화에 따른 비선형저감계수를 사용하여 나타내었다. 유한요소 모델해석에서 콘크리트는 8절점을 가진 사각형요소로 하고 철근은 1차원 선형요소로 가정하여 해석하였다. 유한요소해석으로부터 얻어진 수치해석결과와 실험실에서 행한 실험결과를 비교하였다.