• 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.

• Journal of Environmental Science International
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• v.26 no.4
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• pp.411-420
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• 2017

This research aims at comparing the accuracy of flood discharge estimation. For this, we focused on the Oedo watershed of Jeju Island and compared flood discharge by analyzing the values as follows: (1) the concentration of the lumped model (HEC-HMS) and distributed model (Vflo), and (2) the in-situ data using Fixed Surface Image Velocimetry (FSIV). The flood discharge estimation from the HEC-HMS model is slightly larger than the Vflo model results. This result shows that the estimations of the HEC-HMS are larger than the flood discharge data by 4.43 to 36.24% and that of the Vflo are larger by 8.49 to 11%. In terms of the error analysis at the peak discharge occurrence time of each mapping, HEC-HMS is one hour later than the measured data, but Vflo is almost the same as the measured data.

• Journal of Hydrogen and New Energy
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• v.26 no.2
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• pp.184-191
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• 2015

As the power electronics system increases the frequency, the power loss and thermal management are paid more attention. This research presents a real time model of dissipation power with junction temperature response for 120kw IGBT inverter which is applied to the thermal management of high power IGBT inverter. Since the computational time is critical for real time simulation, look-up tables of IGBT module characteristic curve are implemented. The power loss from IGBT provides a clue to calculate the temperature of each module of IGBT. In this study, temperature of each layer in IGBT is predicted by lumped capacitance analysis of layers with convective heat transfer. The power loss and temperature of layers in IGBT is then communicated due to mutual dependence. In the dynamic model, PWM pulses are employed to calculation real time IGBT and diode power loss. Under Matlab/Simulink$^{(R)}$ environment, the dynamic model is validated with experiment. Results showed that the dynamic response of power loss is closely coupled with effective thermal management. The convective heat transfer is enough to achieve proper thermal management under guideline temperature.

• 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.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.1
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• pp.130-136
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• 2009

A lumped parameter model of Li-ion battery in hybrid electric vehicle(HEV) is constructed and system parameters are identified by using recursive least square estimation for different C-rates, SOCs and temperatures. The system characteristics of pole and zero in frequency domain are analyzed with the parameters obtained from different conditions. The parameterized model of Li-ion battery indicates highly dependant of temperatures. The system pole and internal resistance changes 6.6 and 18 times at $-20^{\circ}C$, comparing with those at $25^{\circ}C$, respectively. These results will be utilized on constructing model-based state observer or an on-line identification and an adaptation of the model parameters in battery management systems for hybrid electric vehicle applications.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.1
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• pp.63-72
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• 2020

The purpose of this study is to investigate the effects of the application of various numerical models and frequency contents of earthquakes on the performances of the reactor containment building (RCB) in a nuclear power plant (NPP) equipped with an advanced power reactor 1400. Two kinds of numerical models are developed to perform time-history analyses: a lumped-mass stick model (LMSM) and a full three-dimensional finite element model (3D FEM). The LMSM is constructed in SAP2000 using conventional beam elements with concentrated masses, whereas the 3D FEM is built in ANSYS using solid elements. Two groups of ground motions considering low- and high-frequency contents are applied in time-history analyses. The low-frequency motions are created by matching their response spectra with the Nuclear Regulatory Commission 1.60 design spectrum, whereas the high-frequency motions are artificially generated with a high-frequency range from 10Hz to 100Hz. Seismic responses are measured in terms of floor response spectra (FRS) at the various elevations of the RCB. The numerical results show that the FRS of the structure under low-frequency motions for two numerical models are highly matched. However, under high-frequency motions, the FRS obtained by the LMSM at a high natural frequency range are significantly different from those of the 3D FEM, and the largest difference is found at the lower elevation of the RCB. By assuming that the 3D FEM approximates responses of the structure accurately, it can be concluded that the LMSM produces a moderate discrepancy at the high-frequency range of the FRS of the RCB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.5B
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• pp.985-991
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• 2000

In this paper, the optimum structure of 2GHz magnetic thin film planar inductor were designed and fabricated to reduce the inductor area and to maximize the inductance L and quality factor Q of the inductor. The optimum design was performed utilizing Co90Fe10 layer multilayered with SiO2 layers to avoid the eddy-current skin effect and considering new lumped element model. New magnetic thin film inductors operating at 2GHz were fabricated on a Si substrate utilizing photo-lithography and lift-off techniques. The frequency characteristics of L, Q, and impedance in more than fifty identical inductors were measured using an RF Impedance Analyzer(HP4291B with HP16193A test fixture). The self-resonant frequencies(SRF) of the inductors were measured by a Vector Network Analyzer(HP8510). The developed inductors have SRF of 1.8 to 2.3GHz, L of 47 to 68nH, and Q of 70 to 80 near 1GHz. Finally, high frequency, high performance, planar micro-inductor(area=30.8 x 30.8il$^2$) with maximized L and Q were fabricated succefully.

• 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.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.2
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• pp.59-68
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• 1997

Seismic responses of the Hualien large scale seismic test model on a layered soil site are estimated for three recorded earthquakes with different level of peak acceleration using two different approaches of soil-structure interaction analysis. The analysis results are then compared and evaluated with the recorded. The method adopted for the analysis is based on substructuring method using a lumped parameter model in both the frequency and time domain. The study results indicate that the proposed method can reasonably estimate the earthquake responses of a soil-structure interaction system of r engineering purposes if the techniques of defining input motion and modeling of the backfilled soil are prudently selected.

• Journal of Power Electronics
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• v.17 no.2
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• pp.398-410
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• 2017

This work presents the design of a dual extended Kalman filter (EKF) as a state/parameter estimator suitable for adaptive state-of-charge (SoC) estimation of an automotive lithium-iron-phosphate ($LiFePO_4$) cell. The design of both estimators is based on an experimentally identified, lumped-parameter equivalent battery electrical circuit model. In the proposed estimation scheme, the parameter estimator has been used to adapt the SoC EKF-based estimator, which may be sensitive to nonlinear map errors of battery parameters. A suitable weighting scheme has also been proposed to achieve a smooth transition between the parameter estimator-based adaptation and internal model within the SoC estimator. The effectiveness of the proposed SoC and parameter estimators, as well as the combined dual estimator, has been verified through computer simulations on the developed battery model subject to New European Driving Cycle (NEDC) related operating regimes.