• Water for future
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• v.23 no.3
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• pp.319-328
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• 1990

The Parameter Identification of 2-demensional estuarine model was carried out using new output ADI-FDM numerical semi-implicit schem transformed in boundary fitted(BF) - coordinate. The hydrodynamic equations which is coupled with the transport equations were used as basic equations in the model. Thompson's equations were used to transform governing equations into rectangular plane equations and his elliptic grid generation scheme was used to generate curvilinear grid system. in BF - coordinates. The parameters to be identified are friction coefficient and disperse coefficient embedded in the governing equations. The numerical output scheme is tidally averaged salinity model in BF - coordinates. The algorithm to optimize norm of error between observations and calculations is the influence coefficinet algorithm associated with least square criterion. The lumped model is conssidered in identification. This paper was concetrated on checking whether the new output scheme might be useful to identify parameters in estuarine salinity model or not. The proposed method was tested through experimental application with hypothetical simple model. The result of the test shows that the proposed method can be used for parameter identification in estuarine model.

• Journal of the Korean Society of Propulsion Engineers
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• v.13 no.2
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• pp.42-53
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• 2009

Gas turbine engine simulation program has been developed. In compressor and turbine, 2-D NS implicit code is used with k-$\omega$ SST turbulent model. In combustor, 0-D lumped method chemical equilibrium code is adopted under the limitations, the products are only 10 species of molecular and air-fuel is perfectly mixed state with 100% combustion efficiency at constant pressure. Fluid properties are shared on interfaces between engine components. The outlet conditions of compressor have been used as the inlet condition of combustor. The inlet condition of turbine comes from the compressor The back pressure in compressor outlet is transferred by the inlet pressure of turbine. Unsteady phenomena at rotor-stator in compressor and turbine is covered by mixing-plane method. The state of engine can be determined only by given inlet condition of compressor, outlet condition of turbine, equivalence ratio and rotating speed.

• Korean Chemical Engineering Research
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• v.61 no.3
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• pp.446-455
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• 2023

A mathematical model for predicting the liquid circulation velocity in an airlift reactor was developed based on the mechanical energy balance of the fluid circulation loop. The model considered the energy loss due to a 90° turn, the energy loss due to friction, and the energy loss due to the change in cross-sectional area at each part of the reactor. The model that separately considered the loss coefficients related to friction, direction change, and cross-sectional area change was able to predict the liquid circulation velocity better than the previous model using lumped parameters. The liquid circulation velocity was measured by the tracer pulse method. Most of our experimental results obtained in external-loop airlift reactors, which had the top and bottom connecting pipes, as well as other investigators' results obtained in various types of airlift reactors, were well predicted by the developed model with an error within 20%. Useful empirical equations for the loss coefficient related to the 90° turn of the circulating fluid were obtained in external and internal-loop airlift reactors and used to predict the liquid circulation velocity.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.3
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• pp.10-17
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• 2003

In this paper, genetic algorithm (GA)-based Thin Film Bulk Acoustic Resonator (FBAR) RF filter design technique is proposed. Since the BVD(Butterworth-Van Dyke) lumped element model is valid only around the resonance, FBAR filter design technique based on BVD circuit has an approximate error. Instead of using BVD model, optimizing filter design method utilizes an analytical electrical impedance equation of FBAR. The geometry of FBAR such as thickness of the piezoelectric layer and area which significantly affect the filter response is optimized by GA. US-PCS Rx Bandpass filter obtained by the proposed technique shows a better response comparing with the typical and BVD-based filter.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.2
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• pp.458-466
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• 1998

In this work, a frequency domain method is tested numerically and experimentally to improve nonlinear model parameters using the frequency response function at the nonlinear element connected point of structure. This method extends the force-state mapping technique, which fits the nonlinear element forces with time domain response data, into frequency domain manipulations. The force-state mapping method in the time domain has limitations when applying to complex real structures because it needd a time domain lumped parameter model. On the other hand, the frequency domain method is relatively easily applicable to a complex real structure having nonlinear elements since it uses the frequency response function of each substurcture. Since this mehtod is performed in frequency domain, the number of equations required to identify the unknown parameters can be easily increased as many as it needed, just by not only varying excitation amplitude bot also selecting excitation frequency domain method has some advantages over the classical force-state mapping technique in the number of data points needed in curve fit and the sensitivity to response noise.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.262-264
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• 2009

일반적으로, 단위 배터리간의 직/병렬 연결을 통해 구성되는 팩은 이를 구성하는 각 배터리간의 상이한 전기화학적 특성으로 인해 전압 불균형이 존재한다. 이러한 전압 불균형은 팩의 노화 및 성능을 저하시키는 원인이 된다. 이러한 전압불균형을 없애기 위해 전압과 State of Charge(SOC)를 이용한 밸런싱 회로가 폭넓게 연구되고 있다. 하지만, 이러한 연구는 대체적으로, 다른 특성을 가지는 단위 배터리로 구성되는 팩의 밸런싱 방법이다. 따라서, 동일하고 균일한 특성을 갖는 배터리들을 미리 선별하여 팩을 구성한다면, 밸런싱의 전반적인 효율증대가 기대된다. 본 논문에서는 최적의 전압 밸런싱을 위한 스크리닝(Screening)의 새로운 방법을 연구하였다. 용량과 모델 파라미터(Lumped resistance;$R_{Diff}$)를 스크리닝의 척도로 고려하였고, 전압 불균형을 최대한 줄이기 위해 용량, 모델 파라미터의 순으로 스크리닝을 진행하였다. 또한, 전압패턴인식을 이용한 판별법을 통해 제안된 스크리닝 방법을 검증하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.11
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• pp.2049-2058
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• 1992

In this work, a 6 degree of freedom lumped mass model is constructed for an OHC-type cam valve train analysis, and the model is verified experimentally. Using the verified model, an optimum cam profile is designed to minimize the maximum contact force between cam and follower under the constraints such as cam lift and cam event angle. The designed cam was carefully machined and tested experimentally. As operating the designed cam shaft on the test rig, the valve motion was precisely measured with laser displacement meter and the contact force was indirectly monitored by measuring strain at a certain point of the finger follower. Judging from the model simulation and experiment results, the maximum contact force can be reduced as much as more than 16.7 percent under maintaining the original valve flow area by adopting the optimum cam profile.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.10
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• pp.209-216
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• 1999

일반적으로 힘 제어는 힘 센서의 사용 여부에 따라 능동적 힘 제어와 피동적 힘 제어로 분류시킬 수 있다. 능동적 힘 제어는 힘 세서를 이용하여 구속력을 목표한 힘에 근접하도록 제어한다. 유연 매니퓨레이터의 함수(위치, 속도, 가속도)를 이용하여 일정한 힘에 근접하도록 제어한다. 유연 매티퓨레이터에 있어서 링크 선단의 강성 증대는 힘 제어뿐만이 아니라, 링크의 진동을 크게 유발함으로서 위치 제어에 불리하게 작용한다. 주로 사용되고 있는 힘 센서는 많은 변형 게이지(strain gauge)로 구성되어 있다. 유연 매니퓨레이터 또한 링크 선단의 변형을 측정하기 위해 변형 게이지를 사용하고 있다. 본 논문에서는 이점에 착안하여, 유연 매니퓨레이터의 선단의 탄성 변형을 측정하기 위해 장착한 변형 게이지를 이용한 위치/힘 제어를 제안한다. 먼저, 유연 매니퓨레이터의 집중 정수 모델로부터 링크의 탄성 변형과 구속력 관계를 도출한 후 이 관계를 이용하여 3차원 실험 유연 매니퓨레이터를 실시간 위치/힘 제어 실험을 수행하였다. 또한 범용 동력학 해석 소프트웨어인 ADAMS FEM 을 이용하여 해석하였다. 마지막으로, 실험 결과와 해석 결과를 비교 분석하여 본 논문에서 제안한 유연 매니퓨레이터의 위치/힘 제어의 타당성을 입증시켰다.

• Computational Structural Engineering
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• v.8 no.3
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• pp.67-74
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• 1995

This study develops 2-D analysis method of a base-isolated pool structure, and verifies the method through shaking table test using a scaled model. A wall of the pool structure is modeled as lumped mass, and added mass of the fluid is imposed on the nodes of the structure to consider the hydrodynamic effect of contained fluid. The equation of motion of base-isolated pool structure is obtained by coupling of two equations for superstructure composed of wall and fluid, and for bottom slab and isolator. The scaled model for shaking table test is made with transparent acryle, and 4-high damping laminated rubber bearings are used. The responses of the scaled model by the test are generally good agreement with those by the analysis. It is shown that 2-D analysis method gives somewhat conservative results.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.18 no.1
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• pp.50-58
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• 2009

For precise tracking control of a servo system with nonlinear friction, a robust friction compensation scheme is presented in this paper. The nonlinear friction is difficult to identify the friction parameters exactly through experiments. Friction parameters can be also varied according to contact conditions such as the variation of temperature and lubrication. Thus, in order to overcome these problems and obtain the desired position tracking performance, a robust adaptive back-stepping control scheme with a dual friction observer is developed. In addition, to estimate lumped friction uncertainty due to modeling errors, a DEKF recurrent neural network and adaptive reconstructed error estimator are also developed. The feasibility of the proposed control scheme is verified through the experiment fur a ball-screw system.