• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.105-107
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• 1991

A chemical process model represented by partial differential equations was studied as one of nonlinear distributed parameter control problems. Using an optimal control theory in the form of maximum principles based on nonlinear integral equations, an algorithm to solve the problem was developed and coded into a computer program.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 하계종합학술대회 논문집
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• pp.651-654
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• 1989

A rate equation model describing the ultrashort pulse formation is presented. The temporal and energy behavior of the distributed feedback dye laser predicted by the model has been compared the earlier papers on DFDL's. The observed good agreement allows application of the theoretical model for picosecond laser.

• 한국수자원학회논문집
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• 제46권11호
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• pp.1041-1052
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• 2013

본 연구에서는 범용 매개변수 최적화 모형인 PEST를 이용하여 분포형 수문모형인 GRM(grid based rainfall-runoff model) 모형의 매개변수 및 불확실성 범위를 추정하였다. 특히, 레이더 강우 및 지상 관측 강우를 각각 적용하여, 입력자료 차이가 매개변수 추정에 미치는 영향을 분석하였다. 자동 보정 모형은 GUI (graphic user interface)에 대한 접근 없이 모형구동이 가능하도록 개선된 GRM-MP (multiple projects) 버전과 병렬 PEST 버전을 결합하여 매개변수 추정에 소요되는 시간을 단축시켰다. 이를 낙동강 수계 금호강 유역과 감천 유역에 대해 적용하여, 초기 포화도, 지표면 조도계수 및 토양 투수계수의 보정계수에 대해 매개변수 최적화 및 불확실성 추정을 수행하였다. 강우자료 분석 결과, 레이더와 지상 강우의 유역평균 누적시계열은 비슷하거나 지상 강우가 조금 큰 경향을 보였으나, 공간분포에 있어서는 지상 강우에 비해 레이더 강우에서 큰 변동성이 확인되었다. 보정된 수문모의 결과는 레이더 강우 적용 시, 지상 강우에 비해 비슷하거나 더 나은 정확도를 보였다. 추정된 매개변수는 레이더 강우 적용 시, 토양 투수계수의 보정계수가 일관되게 1보다 작은 경향을 보였으며, 이는 강우강도가 강한 격자가 상당수 존재하기 때문으로 판단되었다. 초기 포화도 및 지표면 조도계수의 보정계수는 레이더 및 지상 강우에서 일정한 경향성을 보이지 않았다. 본 연구의 대상 유역 및 호우사상에 대한 PEST의 최적화 모의 결과, 동일 유역 및 호우사상에 대해서도 강우 추정 방법에 따라 서로 다른 최적 매개변수 값을 갖는 것을 알 수 있었으며, 이는 향후 레이더 강우 자료의 수문 모의 활용 시 유의해야할 점으로 판단된다.

• Structural Engineering and Mechanics
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• 제75권3호
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• pp.327-337
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• 2020

The stability and dynamic performance of a flapper-nozzle servo valve depend on several factors, such as the motion of the armature component and the deformation of the spring tube. As the only connection between the armature component and the fixed end, the spring tube plays a decisive role in the dynamic response of the entire system. Aiming at predicting the vibration characteristics of the servo valves to combine them with the control algorithm, an innovative dynamic stiffness based on a distributed parameter model (DPM) is proposed that can reflect the dynamic deformation of the spring tube and a suitable discrete method is applied according to the working condition of the spring tube. With the motion equation derived by DPM, which includes the impact of inertia, damping, and stiffness force, the mathematical model of the spring tube dynamic stiffness is established. Subsequently, a suitable program for this model is confirmed that guarantees the simulation accuracy while controlling the time consumption. Ultimately, the transient response of the spring tube is also evaluated by a finite element method (FEM). The agreement between the simulation results of the two methods shows that dynamic stiffness based on DPM is suitable for predicting the transient response of the spring tube.

• 대한전자공학회논문지SD
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• 제42권5호
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• pp.1-8
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• 2005

본 연구에서는 MOSFET의 RF 성능에 영향을 미치는 게이트 분포효과를 고려하여 RC 병렬 게이트 모델을 사용하였으며, 측정된 S-파라미터로부터 모델 파라미터들을 직접 추출하기 위해 $Y_{11}$-파라미터를 기초로 한 추출 방정식들이 사용되었다. 이와 같이 추출된 RC 병렬 게이트 모델은 10GHz 이상의 고주파 영역에서 기존 Rg 모델보다 측정된 S-파라미터와 더 잘 일치하는 것을 확인하였으며, 이는 게이트 모델 및 추출방법의 정확도를 증명한다. 이러한 방법을 사용하여 RC 병렬 게이트 모델 파라미터들의 게이트 전압 종속 곡선을 새롭게 추출하였으며, 이러한 추출 데이터는 RF 비선형 게이트 모델 개발에 유용하게 사용될 것이다.

• Journal of Electrical Engineering and Technology
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• 제7권4호
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• pp.589-595
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• 2012

When surges and electromagnetic pulses from lightning or power conversion devices are considered, it is desirable to evaluate grounding system performance as grounding impedance. In the case of large-sized grounding electrodes or long counterpoises, the grounding impedance is increased with increasing the frequency of injected current. The grounding impedance is increased by the inductance of grounding electrodes. This paper presents the measured results of frequency-dependent grounding impedance and impedance phase as a function of the length of counterpoises. In order to analyze the frequency-dependent grounding impedance of the counterpoises, the frequency-dependent current dissipation rates were measured and simulated by the distributed parameter circuit model reflecting the frequency-dependent relative resistivity and permittivity of soil. As a result, the ground current dissipation rate is proportional to the soil resistivity near the counterpoises in a low frequency. On the other hand, the ground current dissipation near the injection point is increased as the frequency of injected current increases. Since the high frequency ground current cannot reach the far end of long counterpoise, the grounding impedance of long counterpoise approaches that of the short one in the high frequency. The results obtained from this work could be applied in design of grounding systems.

• 조명전기설비학회논문지
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• 제26권2호
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• pp.99-105
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• 2012

This paper deals with the experimental results of the frequency-dependent resultant ground impedance of vertical ground electrodes installed with a regular n-polygon. In order to propose an effective method of installing the vertically-driven multiple ground electrodes used to obtain the low ground impedance, the resultant ground impedance of ground electrodes installed with a regular n-polygon were measured as functions of the number of ground electrodes and the frequency of test currents and the results were discussed based on the potential interferences among ground electrodes. As a consequence, the effect of potential interference on the resultant ground impedance of vertical ground electrodes is frequency-dependent and it is significant in the low frequency of a few hundreds [Hz]. The resultant ground impedance of multiple vertical ground electrodes is not decreased in linearly proportion to the number of ground electrodes due to the overlapped potential interferences. Also the distributed-parameter circuit model considering the potential interference, the frequency-dependent relative permittivity and resistivity of soil was proposed. The simulated results of the frequency-dependent resultant ground impedance of multiple vertical ground electrodes are in good agreement with the measured data.

• 조명전기설비학회논문지
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• 제26권3호
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• pp.73-79
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• 2012

A counterpoise is commonly employed in grounding systems installing near the ground surface of low resistivity soils and radial-type counterpoises are used in the limited space. Recently some studies on the evaluation of ground impedance of paralleling ground electrodes have carried out, but the data for providing the frequency-dependent ground impedances considering potential interferences are not yet sufficient. In order to provide the information about the design of grounding systems for surge protection, the simulations of the frequency-dependent ground impedance of various shaped counterpoises are carried out by using the distributed parameter circuit model including the effect of potential interferences. This paper presents the theoretical simulations and actual experiments of the frequency-dependent ground impedance of paralleling and 3 or 4-arms star counterpoises. The accuracy of the simulation methodology is examined by the comparison with the measured results, and the results show a good agreement between the simulation and the experiment.

• International Journal of Fluid Machinery and Systems
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• 제10권3호
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• pp.197-208
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• 2017

When Francis turbines operate at partial load, residual swirl in the draft tube causes low-frequency pulsation of pressure and power output. Scale effects and system response may bias the prediction of prototype behavior based on laboratory tests, but could be overcome by means of a 1D analytical model. This paper deals with the two most important features of such a model, the compliance and the source of excitation. In a distributed-parameter version, compliance should be represented as an exponential function of local pressure. Lack of similarity due to different Froude number can thus be compensated. The normally unknown gas content in the vortex cavity has significant influence on the pulsation, and should therefore be measured and considered as a test parameter.

• 제어로봇시스템학회논문지
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• 제6권12호
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• pp.1079-1085
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• 2000

In this paper, we propose a method of cooperative control (T-cell modeling) and selection of group behavior strategy (B-cell modeling) based on immune system in distributed autonomous robotic system (DARS). An immune system is the living bodys self-protection and self-maintenance system. these features can be applied to decision making of the optimal swarm behavior in a dynamically changing environment. For applying immune system to DARS, a robot is regarded as a B-cell, each environmental condition as an antigen, a behavior strategy as an antibody, and control parameter as a T-cell, respectively. When the environmental condition (antigen) changes, a robot selects an appropriate behavior strategy (antibody). And its behavior strategy is stimulated and suppressed by other robots using communication (immune network). Finally, much stimulated strategy is adopted as a swarm behavior strategy. This control scheme is based on clonal selection and immune network hypothesis, and it is used for decision making of the optimal swarm strategy. Adaptation ability of the robot is enhanced by adding T-cell model as a control parameter in dynamic environments.