• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.4
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• pp.303-309
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• 2019

A hybrid control of a rectifier/regulator of wireless power transfer systems for electric vehicles is studied. A combined rectifier/regulator is used for charging control. The hybrid control comprises integral cycle control and pulse width modulation control to cope with the variations in the induced voltage due to clearance and alignment. The hybrid control has good control capability and does not cause severe switching loss. A 22 kW prototype of the Wireless Power Transfer class 4 charging system defined by the Society of Automotive Engineers is constructed and tested to verify the proposal.

• Korean Journal of Optics and Photonics
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• v.8 no.2
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• pp.161-164
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• 1997

A new hybrid, heterodyne, fiber-optic electric field sensor scheme is presented. In this scheme, a dual polarization, dual frequency, stabilized He-Ne laser is used for the light source of the interferometer, Probe beam is delivered to the sensor head using polarization maintaining fiber. In the sensor head, $LiTaO_3$ electro-optic crystal is used for sensing element. Phase retardation is induced on the dual frquency, dual polarization probe beam due to applied electric field across the crystal. Induced phase retardation is demodulated by in-phase and quadrature demodulation technique. In this way, we can obtain optimum sensitivity for electric field measurement regardless a quasi-static phase difference between two polarization components.

• Ocean Systems Engineering
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• v.3 no.1
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• pp.35-53
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• 2013

In this study, a hybrid floating structure with cylinder was introduced to reduce the hydrodynamic motions of the pontoon type. The hybrid floating structure is composed of cylinders and semi-opened side sections to penetrate the wave impact energy. In order to exactly investigate the hydrodynamic motions and structural behavior of the hybrid floating structure under the wave loadings, integrated analysis of hydrodynamic and structural behavior were carried out on the hybrid floating structure. Firstly, the hydrodynamic analyses were performed on the hybrid and pontoon models. Then, the wave-induced hydrodynamic pressures resulting from hydrodynamic analysis were directly mapped to the structural analysis model. And, finally, the structural analyses were carried out on the hybrid and pontoon models. As a result of this study, it was learned that the hybrid model of this study was showed to have more favorable hydrodynamic motions than the pontoon model. The surge motion was indicated even smaller motion at all over wave periods from 4.0 to 10.0 sec, and the heave and pitch motions indicated smaller motions beyond its wave period of 6.5 sec. However, the hybrid model was shown more unfavorable structural behavior than the pontoon model. High concentrated stress occurred at the bottom slab of the bow and stern part where the cylinder wall was connected to the bottom slab. Also, the hybrid model behaved with the elastic body motion due to weak stiffness of floating body and caused a large stress variation at the pure slab section between the cylinder walls. Hence, in order to overcome these problems, some alternatives which could be easily obtained from the simple modification of structural details were proposed.

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2489-2493
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• 2012

A new fluorescent system (acridine/RTIL hybrid gel) confined in the 3D micro-structure of a poly(lactic acid) membrane were prepared from 1-butyl-3-methylimidazolium-based ionic liquids ([bmim]X (X = $SbF_6$, $NTf_2$, Cl); RTILs), poly(lactic acid) (PLA), and acridine via the sol-gel route. SEM images showed that, in the presence of [bmim]$SbF_6$ and [bmim]$NTf_2$, 3D-ly paticulated structures were created inside the PLA membranes and acridine/RTIL hybrid gels were confined in gabs of particulates. However, the use of [bmim]Cl induced the formation of a 3D-ly porous structure containing the hybrid gel of acridine/[bmimCl in the micropores. The three fluorescent systems exhibited different fluorescence behaviors (fluorescence maximum and intensity) depending on the C2-H acidity scale of the RTILs (or their anion type). Acridine gels hybridized with [bmim]$SbF_6$ and [bmim]$NTf_2$ showed blue fluorescence with relative high intensity, whereas the hybrid gel with [bmim]Cl exhibited almost no fluorescence under dry conditions. However, the acridine/[bmim]Cl hybrid system in the micro-porous PLA membrane started to emit fluorescent light under humid conditions and showed a possible response, indicating that it could be applied as a humidity sensor.

• Tribology and Lubricants
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• v.10 no.2
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• pp.43-50
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• 1994

The hydrodynamic bearing is accepted in many rotating systems because it has a large load carrying capacity. But the anisotropic pressure distribution of the bearing can arise the unstable vibration phenomenon over a certain speed. The magnetic bearing is an active element so that the unstable phenomenon of the hydrodynamic bearing, which is induced by the anisotropic support pressure of the oil film, can be controlled if the control algorithm and the controller gains are chosen appropriately. In this study, we investigate the stabilization method of the hydrodynamic bearing system composing the hybrid bearing which is the single unit of hydrodynamic bearing and magnetic bearing. The load carrying conditions of the hybrid bearing is modelled by the sum of the stiffness and damping coefficients of the hydrodynamic and the magnetic bearings in each direction. The dynamics of the rotor is analyzed by the Finite Element Method and the stability limit is determined by the eigenvalues of the hybrid bearings and shaft system. The eigenvalue study of the system shows that the stability limit of the hybrid bearing is increased compared to that of the hydrodynamic bearing. A Small increment of the stiffness and damping coefficient of the hybrid bearings by the magnetic actuators can increase the stability limit of the system. In this paper we tried to show the design references of the hybrid bearings by using the nondimensional bearing parameters. The analysis results show the possibilities of the stability limit increment of the hydrodynamic bearing system by combining the magnetic bearing.

• Membrane and Water Treatment
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• v.13 no.6
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• pp.291-301
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• 2022

In this study, cement/PVDF hollow-fiber hybrid membranes were prepared via a mixed process of diffusion-induced phase separation and hydration. The presence of X-ray diffraction peaks of Ca(OH)₂, an AFt phase, an AFm phase, and C-S-H phase confirmed the hydration reaction. Good hydrophilicity was obtained. The cross-sectional and surface morphologies of the hybrid membranes showed that an asymmetric pore structure was formed. Hydration products comprising parallel plates of Ca(OH)₂, fibrous ettringite AFt, and granulated particles AFm were obtained gradually. For the hybrid membranes cured for different time, the pore-size distribution was similar but the porosity decreased because of blocking of the hydration products. In addition, the water flux decreased with hydration time, and carbon retention was 90% after 5 h of rejection treatment. Almost all the Zn²⁺ ions were adsorbed by the hybrid membrane. The above results proved that the obtained membrane could be alternative as basement membrane for separation application.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.195-200
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• 2007

System identification of real-scale structure is performed using forced vibration test. There exist various techniques available for identifying the dynamic characteristis of structures using dynamic and static measurements. In this study, The finite element(FE) model of the structure is analytically constructed using ANSYS and the model was updated using the results experimentally measured by the forced vibration test. forced vibration tests showed that Hybrid Mass Damper induced floor responses coincided with the earthquake induced ones which was numerically calculated based on the updated FE model.

• Laser Solutions
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• v.5 no.3
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• pp.15-20
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• 2002

The principal obstacle to selection of a laser processing method in production is its relatively high equipment cost and the natural unwillingness of production supervision to try something new until it is thoroughly proven. The major objective of this work is focused on the combined features of gas tungsten arc and a low-power cold laser beam. In this work, the laser beam from a 7 watts carbon monoxide laser was combined with electrical discharges from a short-pulsed capacitive discharge GTA welding power supply. When the low power CO laser beam passes through a special composition shielding gas, the CO molecules in the gas absorbs the radiation, and ionizes through a process blown as non-equilibrium, vibration-vibration pumping. The resulting laser-induced plasma(LIP) was positioned between various configurations of electrodes. The high-voltage impulse applied to the electrodes forced rapid electrical breakdown between the electrodes. Electrical discharges between tungsten electrodes and aluminum sheet specimens followed the ionized path provided by LIP. The result was well-focused melted spots.

• Korean Journal of Crystallography
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• v.9 no.1
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• pp.44-47
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• 1998

A reduction/oxidation reaction between A1 metal powder and SiO2 powder was performed by Self-propagating High-temperature Synthesis (SHS) reaction induced by microwave energy to produce a composite of Al2O3 and Si powders by using a 2.45 GHz kitchen model microwave oven. A Microwave Hybrid Heating(MHH) method was applied by using SiC powders as a suscepting material to raise the temperature of the disk samples and the heat increase rate of over 100℃/min were obtained before the reaction. The reaction started around 850℃ and the heat increase rate jumped to over 200℃/min after the reaction took place.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.354-355
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• 2012