• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.4
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• pp.192-197
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• 2009

This paper presents the design and measurement of a 2.4/5.2-GHz dual band VCO with a balanced frequency doubler in $0.18\;{\mu}m$ CMOS process. The topology of a 2.4 GHz VCO is a cross-coupled VCO with a LC tank and the frequency of the VCO is doubled by a frequency balanced doubler for a 5.2 GHz VCO. The gate bias matching network for class B operation in the balanced doubler is adopted to obtain as much power at 2nd harmonic output as possible. The average output powers of the 2.4 GHz and 5.2 GHz VCOs are -12 dBm and -13 dBm, respectively, the doubled VCO has fundamental harmonic suppression of -25 dB. The measured phase noises at 5 MHz frequency offset are -123 dBc /Hz from 2.6 GHz and -118 dBc /Hz from 5.1 GHz. The total size of the dual band VCO is $1.0\;mm{\times}0.9\;mm$ including pads.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.13-14
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• 2011

The power conversion converter for driving the wireless power transfer system is can be into the two part of the DC power conversion rectifier and the high frequency dc-ac power conversion inverter. In this paper, The operating characteristics of the Class-${\Phi}_2$ resonant inverter have been investigated through by simulation and by experiment. It can be switched at a high frequency without the switching losses and the harmonics are reduced effectively due to the input LC filter. Its switching frequency is 1MHz and the input voltage is 96V which is the output voltage of LLC resonant converter. And its output peak voltage is 170V. The resonant inverter module operated at the commercial power source of 220V was built. And also the electromagnetic coupled resonance coils were designed for wireless power transfer with a 1MHz operating frequency. As a experimental result, the wireless power transmission was confirmed and it is varified the validity of the experiment.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.3
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• pp.267-274
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• 2016

In this study, a fast charger for electric vehicle with wide charging voltage range is proposed. To achieve high efficiency, three-level topologies are employed for the AC-DC and DC-DC converters. Given that the output range of the DC-DC converter in fast chargers is quite wide, the circulating current of conventional three-level converter will increase under low voltage condition. The proposed hybrid switching method mitigates this issue. When a coupled inductor is used on the output side, the circulating current is further reduced, and the switches $S_2$, $S_3$, $S_6$, and $S_7$ achieve turning-off under the ZCS condition. Experimental results from a 50 kW prototype are provided to validate the proposed charger, and a rated efficiency of 95.9% is obtained.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.376-381
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• 2009

The increasing needs for higher cargo capacity in the container vessels' fleet has led to ship builder's demand for higher power output rating engine to meet the propulsion requirement, thus, leading to the development of super large two stroke low speed diesel engines. This large sized bore engines with more than 12 cylinders are capable of delivering power output up to more than 100,000 bhp at maximum continuous rating. The thrust variation force due to axial vibration occurring in propulsion shafting of these ships are transmitted to ship structure via thrust bearing. This force may vibrate the super structure of ship in the fore-aft direction and the fatigue strength of crank shaft can be decreased by additional bending stress increase in crank shaft pin and journal. In this paper, the axial vibration of propulsion shafting system on the 14RT-flex96C super large diesel engine with 14 cylinders is identified by theoretical analysis and vibration measurement.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.481-487
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• 2010

The equivalent circuits intended to analyze the characteristics of IPT systems can be shown in structures similar to those of existing transformers. IPT systems are composed of combinations of the primary and secondary coils based on magnetic coupling, and the performances are determined by the lengths or the degrees of magnetic coupling of current collecting conductors(secondary) and feeding rails (primary) and system performances become the maximum when they are coupled under the optimum condition. To maximize the output currents of the secondary side, the shapes of iron cores and the structures of coils etc should be considered. To this end, three types of IPT system simulation models were selected and they were analyzed using an electromagnetic field analyzing program. To compare the types with each other, the sizes of the IPT systems and the primary side voltages etc were made to be the same. The electromagnetic fields were analyzed while changing the thicknesses of the cores and the lengths of the air gap etc and the results were analyzed in order to derive the optimum specifications.

• Journal of Korean Association for Spatial Structures
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• v.15 no.2
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• pp.105-112
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• 2015

A shared tuned mass damper (STMD) was proposed in previous research for reduction of dynamic responses of the adjacent buildings subjected to earthquake loads. A single STMD can provide similar control performance in comparison with two traditional TMDs. In previous research, a passive damper was used to connect the STMD with adjacent buildings. In this study, a smart magnetorheological (MR) damper was used instead of a passive damper to compose an adaptive smart STMD (ASTMD). Control performance of the ASTMD was investigated by numerical analyses. For this purpose, two 8-story buildings were used as example structures. Multi-input multi-output (MIMO) fuzzy logic controller (FLC) was used to control the command voltages sent to two MR dampers. The MIMO FLC was optimized by a multi-objective genetic algorithm. Numerical analyses showed that the ASTMD can effectively control dynamic responses of adjacent buildings subjected to earthquake excitations in comparison with a passive STMD.

• Smart Structures and Systems
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• v.17 no.6
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• pp.1017-1030
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• 2016

This study focuses on the system identification of reinforced concrete bridges using vector autoregressive model (VAR). First, the time series output response from a bridge establishes the autoregressive (AR) models. AR models are one of the most accurate methods for stationary time series. Burg's algorithm estimates the autoregressive coefficients (ARCs) at p-lag by reducing the sum of the forward and the backward errors. The computed ARCs are assembled in the state system matrix and the eigen-system realization algorithm (ERA) computes: the eigenvector matrix that contains the vectors of the mode shapes, and the eigenvalue matrix that contains the associated natural frequencies. By taking advantage of the characteristic of the AR model with ERA (ARMERA), civil engineering can address problems related to damage detection. Operational modal analysis using ARMERA is applied to three experiments. One experiment is coupled with an artificial neural network algorithm and it can detect damage locations and extension. The neural network uses a specific number of ARCs as input and multiple submatrix scaling factors of the structural stiffness matrix as output to represent the damage.

• Coupled systems mechanics
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• v.1 no.3
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• pp.285-295
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• 2012

In this paper, two types of porous burners with radial and axial flow have been modeled numerically and compared. For this purpose, governing equations were solved one-dimensionally for methane-air premix gas. The mechanism used in simulating combustion phenomenon was 15 stage reduced mechanism based on GRI3.0. In order to compare the two burners, the inlet flow rate and fuel-air ratio have been assumed equal for the two burners. The results of the study indicated that reduction in speed and increase in cross-section area in the direction of flow have a considerable influence on the behavior of radial burner in comparison to axial burner. Regarding temperature distribution inside the burner, it was observed that the two above mentioned factors can be influential in temperature of flame propagation region. Also, regarding distribution of CO and NO emission, the results indicate that the porous radial burner has lower emissions in comparison to the axial once. The output radiative heat transfer efficiency of the two burners was also compared and in this case also even the radial porous burner was found to be preferable.

• Journal of the Korean Solar Energy Society
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• v.25 no.4
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• pp.69-76
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• 2005

The performance of water-to-water heat pump system coupled with the ground source vertical heat exchanger is presented in this paper. The CAP program of Florida Heat Pump Co. is used to predict the heat pump performances while the EED program calculates the borehole fluid temperature. It is shown that COPH increases with decreasing the temperature of output water for the operation of heating mode and COPR increases with increasing temperature of output water for the operation of cooling mode. The value of specific heat extraction rate must be moderate to insure the reasonable installation cost of borehole system. With $1^{\circ}C$decrease of $T_{wo}$ the average COPH increase is estimated as about $0.06/^{\circ}C$(for $T_{wo}\;=\;45{\sim}60^{\circ}C$ range) while with $1^{\circ}C$ increase of $T_{wo}$ the estimation of COPR increase is about $0.13/^{\circ}C$(for $T_{wo}\;= \;5{\sim}11^{\circ}C$ range) at the specific heat extraction rate of 30W/m.

• Journal of Power Electronics
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• v.18 no.1
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• pp.195-203
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• 2018

In the variable speed Wind Turbine based on ElectroMagnetic Coupler (WT-EMC), a synchronous generator is coupled directly to the grid. Therefore, like conventional power plants, WT-EMC is able to inherently support grid frequency. However, due to the reduced inertia of the synchronous generator, WT-EMC is expected to be controlled to increase its output power in response to a grid frequency drop to support grid frequency. Similar to the grid frequency support control of Type 3 or Type 4 wind turbine, inertial control and droop control can be used to calculate the WT-EMC additional output power reference according to the synchronous generator speed. In this paper, an experimental platform is built to study the grid frequency support from WT-EMC with inertial control and droop control. Two synchronous generators, driven by two induction motors controlled by two converters, are used to emulate the synchronous generators in conventional power plants and in WT-EMCs respectively. The effectiveness of the grid frequency support from WT-EMC with inertial control and droop control responding to a grid frequency drop is validated by experimental results. The selection of the grid frequency support controller and its gain for WT-EMC is analyzed briefly.