• Transactions on Control, Automation and Systems Engineering
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• 제2권2호
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• pp.130-135
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• 2000

A two parameter model of a single fictitious weak acid with unknown dissociation constant has been successfully applied to design a neutralization system for many multi-component acid streams. But there are some processes for which above two parameter model is not satisfactory due to poor approxmation of the nonlinearity of pH process. Here, for etter control of wide class of multi-component acid streams, a three parameter model of a strong acid and a weak acid with unknown dissociation constant is proposed. The model approximates effectively three types of largest gain variation nonlinearities. Based on this model a nonlinear pH control system is designed. Parameters can eeasily estimated since their combinations appear linearly in the model equations and nonlinear adaptive control system may also be constructed just as with the two parameter model.

• 대한전자공학회논문지SP
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• 제45권3호
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• pp.93-102
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• 2008

본 논문에서는 동영상의 화질을 일정하게 하기 위한 실시간 비트율 제어 기법을 제안한다. 일정 화질을 만족하기 위한 기존의 비트율 제어 알고리즘은 프레임의 부호화 복잡도를 잔여 신호인 MAD(mean absolute of difference)로 추정하여 비트 할당을 수행하였다. 그러나 MAD는 영상의 특성이나 부호화 파라미터에 따라 동일한 MAD라도 다른 비트를 생성하므로 영상의 부호화 복잡도를 적절히 나타내기 어렵다. 본 논문에서는 이 문제를 해결하기 위해 비트와 MAD사이의 기울기인 모델 파라미터를 프레임의 복잡도의 측도로 보고 이전 프레임과 현재 프레임의 모델 파라미터의 비율로 비트 할당을 수행한다. 또한 기존의 비트-복잡도 모델에서 구한 모델 파라미터는 양자화 파라미터가 변함에 따라 그 값이 크게 변하여 영상의 내재적 복잡도를 나타내기 어렵다. 따라서 본 논문에서는 비트-복잡도 모델에 양자화 파라미터를 추가하여 양자화 파라미터가 변하더라도 영상의 복잡도의 측도인 모델 파라미터는 변하지 않게 하였다. 광범위한 실험결과는 제안한 알고리즘이 기존의 알고리즘에 비해 비슷한 평균 화질을 유지하면서 화질의 변동을 큰 폭으로 줄였음을 보여준다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2009년도 학술발표회 초록집
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• pp.2215-2219
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• 2009

For model calibration in rainfall-runoff modeling, streamflow data at a specific outlet is obviously required but is not sufficient to identify parameters of a model since numerous parameter combinations can result in very similar model performance measures (i.e. objective functions) and indistinguishable simulated hydrographs. This phenomenon has been called 'equifinality' due to inherent parameter uncertainty involved in rainfall-runoff modeling. This study aims to investigate catchment responses in time and space to various uncertain parameter sets in distributed rainfall-runoff modeling. Seven plausible (or behavioral) parameter sets, which guarantee identically-good model performances, were sampled using deterministic and stochastic optimization methods entitled SCE and SCEM, respectively. Then, we applied them to a computational tracer method linked with a distributed rainfall-runoff model in order to trace and visualize potential origins of streamflow at a catchment outlet. The results showed that all hydrograph simulations based on the plausible parameter sets were performed equally well while internal catchment responses to them showed totally different aspects; different parameter values led to different distributions with respect to the streamflow origins in space and time despite identical simulated hydrographs. Additional information provided by the computational tracer method may be utilized as a complementary constraint for filtering out non-physical parameter set(s) (or reducing parameter uncertainty) in distributed rainfall-runoff modeling.

• 한국지반환경공학회 논문집
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• 제16권5호
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• pp.13-25
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• 2015

This paper proposes an extended model evaluation method that considers not only the model performance but also the model structure and parameter uncertainties in hydrologic modeling. A simple reservoir model (SFM) and distributed kinematic wave models (KWMSS1 and KWMSS2 using topography from 250-m, 500-m, and 1-km digital elevation models) were developed and assessed by three evaluative criteria for model performance, model structural stability, and parameter identifiability. All the models provided acceptable performance in terms of a global response, but the simpler SFM and KWMSS1 could not accurately represent the local behaviors of hydrographs. Moreover, SFM and KWMSS1 were structurally unstable; their performance was sensitive to the applied objective functions. On the other hand, the most sophisticated model, KWMSS2, performed well, satisfying both global and local behaviors. KMSS2 also showed good structural stability, reproducing hydrographs regardless of the applied objective functions; however, superior parameter identifiability was not guaranteed. A number of parameter sets could result in indistinguishable hydrographs. This result indicates that while making hydrologic models complex increases its performance accuracy and reduces its structural uncertainty, the model is likely to suffer from parameter uncertainty.

• Journal of Electrical Engineering and Technology
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• 제4권2호
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• pp.149-158
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• 2009

It is important to derive reliable parameter values in the measurement-based load model development of electric power systems. However parameter estimation tasks, in practice, often face the parameter identifiability issue; whether or not the model parameters can be estimated with a given input-output data set in reliable manner. This paper introduces concepts and practical definitions of the local identifiability of model parameters. A posteriori local identifiability is defined in the sense of nonlinear least squares. As numerical examples, local identifiability of third-order induction motor (IM) model and a Z-induction motor (Z-IM) model is studied. It is shown that parameter ill-conditioning can significantly affect on reliable parameter estimation task. Numerical studies show that local identifiability can be quite sensitive to input data and a given local solution. Finally, several countermeasures are proposed to overcome ill-conditioning problem in measurement-based load modeling.

• 한국통신학회논문지
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• 제16권7호
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• pp.628-639
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• 1991

GaAs MESFET 모델의 정확한 매채변수 값을 구하기 위하여 바이어스 의존성을 바탕으로 3가지 바이어스 변화에 대한 S-,파라미터 측정만으로 모델 매개변수를 추출할 수 있는 새로운 계산 방법을 제시한다. Weighted Broyden update방법의 최적화 과정에서 얻어지는 오차 함수에 대한 매개 변수의 검토를 이용하여 전형 및 비전형 매개 변수의 유일해를 결정한다. 제안된 방법을 적용하기 위해 Marterka & Kacprzak 모델을 사용하였으며 추출한 매개변수 값의 정당성을 측정치와 비교함으로서 입증하였다.

• 전기학회논문지
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• 제58권9호
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• pp.1769-1774
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• 2009

An algorithm for extracting the BJT DC model parameter values for SPICE model is proposed. The nonlinear optimization method for analyzing the device I-V data using the Levenberg-Marquardt algorithm is proposed and the method for calculating initial conditions of model parameters to improve the convergence characteristics is proposed. The base current and collector current obtained from the proposed method shows the root mean square error of 6.04% compared with the measured data of the PNP BJT named 2SA1980.

• 한국산업정보학회논문지
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• 제6권3호
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• pp.123-127
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• 2001

CMOS 트랜지스터의 등가회로모델 파라미터 $C_{gs}$ 의 예측방법이 CMOS 트랜지스의 반전층내의 유동전하량 계산과 전하유도 특성에 의해 제안되었다. 이 $C_{gs}$ 파라미터는 MOS 트랜지스터의 RF대역의 차단주파수를 결정하고 또한 입력과 출력을 커플링 시키는 중요한 파라미터이다. 이 제안된 방법은 등가회로 모델에서 파라미터 값을 예측하고 파라미터 값을 추출하는 소프트웨어 개발에 기여할 것이다.

• 한국작물학회지
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• 제51권4호
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• pp.362-368
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• 2006

A pot experiment was conducted to investigate the effects of soil burial depth on seedling emergences of rice (Oryza sativa) and Echinochloa spp. and to model such effects for mathematical prediction of seedling emergences. When the Gompertz curve was fitted at each soil depth, the parameter C decreased in a logistic form with increasing soil depth, while the parameter M increased in an exponential form and the parameter B appeared to be constant. The Gompertz curve was combined by incorporating the logistic model for the parameter C, the exponential model for the parameter M, and the constant for the parameter B. This combined model well described seedling emergence of rice and Echinochloa species as influenced by soil burial depth and predicted seedling emergence at a given time after sowing and a soil burial depth. Thus, the combined model can be used to simulate seedling emergence of crop sown in different soil depths and weeds present in various soil depths.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.335-340
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• 2001

It is important to model the mechanical structure precisely and reasonably in predicting the dynamic characteristics, controlling the vibration, and designing the structure dynamics. In the finite element modeling, the errors can be contained from the physical parameters, the approximation of the boundary conditions, and the element modeling. From the dynamic test, more precise dynamic characteristics can be obtained. Model updating using parameter modification is appropriate when the design parameter is used to analyze the input parameter like finite element method. Finite element analysis for cantilever and simply supported beams with uniform area and shape change are carried out as model updating examples. Mass and stiffness matrices are updated by comparing test and analytical modal frequencies. The result shows that the updated frequencies become closer to the test frequencies.