• Journal of Power Electronics
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• v.18 no.5
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• pp.1470-1478
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• 2018

Recently, wireless power transfer (WPT) via coupled magnetic resonances has attracted a lot of attention owing to its long operation distance and high efficiency. However, the WPT systems is over-coupling and a frequency splitting phenomenon occurs when resonators are placed closely, which leads to a decrease in the transfer power. To solve this problem, an adaptive frequency tracking control (AFTC) was used based on a closed-loop control scheme. An improved particle swarm optimization (PSO) algorithm was proposed with the AFTC to track the maximum power point in real time. In addition, simulations were carried out. Finally, a WPT system with the AFTC was demonstrated to experimentally validate the improved PSO algorithm and its tracking performance in terms of optimal frequency.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.11a
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• pp.351-356
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• 1995

A optical switch which on the LiNbO$_3$substrate is fabricated by using proton exchange method and self-alignet method. The annealing at 400[$^{\circ}C$] was carried out to control waveguide width and depth. A self-aligned method, which doesn\`t need the additional mask precesses, was applied to simplify the fabrication processes and to maximize efficiency of electric field application. The depths of the two annealed optical waveguides, which were measured by using ${\alpha}$-step, ware 1.435[K${\AA}$] and 1,380[K${\AA}$]. Using ${\alpha}$-step facility, we examined that the width of waveguides is increased from 5[$\mu\textrm{m}$] to 6.45[$\mu\textrm{m}$] and 6.3[$\mu\textrm{m}$] due to the annealing effects. The process of proton exchange was done at 400[$^{\circ}C$] for 60[min] and annealing process was done at 400[$^{\circ}C$] for 60[min]. The high speed optical modulator has very good figures of merits: the measured voltage of the input waveguide power is 3.5[V], the voltage of the coupling waveguide power is 3.9[mV], and -29.5[dB] crosstalk and 8[V] switching voltage were achieved.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5A
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• pp.372-380
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• 2009

In this paper, we analyze the active RFID systems ISO/IEC 18000-7 and ISO/IEC 18000-4. In order to improve the coverage in sensor networks, which consist active RFID tag, we propose RFID multi-hop relay system using active RFID relay tag. To compare the performance between the existing ISO/IEC 18000-7 system and the proposed RFID multi-hop relay system, we introduce new system efficiency measure and sensitivity-based measure of achieved coverage. Also, we analyze the performance of the proposed system and compare it with that of the existing system through MCL (Minimum Coupling Loss) analysis and SLS (System Level Simulation) analysis.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.8
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• pp.73-80
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• 2020

The 3D printing of electronics has been a major application topics in additive manufacturing technology for a decade. In this paper, wireless power transfer (WPT) technology for 3D electronics is studied to supply electric power to its inner circuit. The principle of WPT is that electric power is induced at the recipient antenna coil under an alternating magnetic field. Importantly, the efficiency of WPT does rely on the design of the antenna coil shape. In 3D printed electronics, a flat antenna that can be placed on the printed plane within a layer of a 3D printed part is used, but provided a different antenna response compared to that of a conventional PCB antenna for NFC. This paper investigates the WPT response characteristics of a WPT antenna for 3D printed electronics associated with changes in its design elements. The effects of changing the antenna curvature and the gap between the wires were analyzed through experimental tests.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.3
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• pp.171-176
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• 2014

The polarization characteristics of ultracompact polarization-insensitive directional coupler (PIDC) based on double sandwiched rib-type waveguide are explored in detail by using longitudinal modal transmission-line theory (L-MTLT). To obtain the polarization-insensitive condition of ultracompact directional coupler, the coupling length and coupling efficiency as functions of the refractive index and thickness of sandwiched rib-type waveguide are analyzed for quasi-TE and quasi-TM modes. The numerical results show that the ultracompact polarization-insensitive coupler with hundreds of micrometer scales is realized by properly choosing structural and material parameters of double sandwiched layers. Furthermore, the influence of fundamental mode profile, which is distributed in lateral waveguide of coupler, on the coupler performance has been investigated.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.470-474
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• 2006

This dissertation discuses about a ferrite core plasma source using low operating frequency without sputtering problem by the stored electric field. Compared with the conventional RF power system with 13.56MHz switching frequency, the proposed plasma power system is only separated at 400kHz, so that it makes possible to use of low cost switching elements, PWM control and soft switching. Moreover, it could improve the coupling efficiency for plasma and antenna by using the ferrite core in order to transfer the energy of the load This dissertation tried to analyze new plasma generation method for the plasma generation system by modeling the plasma load and grafting the concept of impedance matching in order to interpret it with the formula This dissertation verified the ferrite core inductive coupling plasma source authorized for 400kHz of low frequency power by applying to the semi-conductor ash process thru the measurement of ash capacity and uniformed plasma distribution on the actual wafer.

• Journal of KSNVE
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• v.6 no.1
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• pp.71-82
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• 1996

The finite element analysis for rotor bearing systems has been an essential tool for design, identification, and diagnosis of rotating machinery. Among others, the unbalance response analysis is fundamental in the vibration analysis of rotor bearing systems because rotating unbalance is recognized as a common sourve of vibration in rotating machinery. However there still remains a problem in the aspect of computational efficiency for unbalance response analysis of large rotor bearing systems. Gyroscopic terms and local bearing parameters in rotor bearing systems often make matters worse in unbalance response computation due to the complicated dynamic properties such as rotational speed dependency and/or anisotropy. The present paper proposes an efficient method for unbalance responses of multi-span rotor bearing systems. An improved substructure synthesis scheme is introduced which makes it possible to compute unbalance responses of the system by coupling unbalance responses of substructures that are of self adjoint problem with small order matrices. The present paper also suggests a scheme to easily deal with gyroscopic tems and local, coupling or bearing parameters. The proposed method causes no errors even though the computational effort is reduced drastically. The present method is demonstrated through three test examples.

• Nuclear Engineering and Technology
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• v.46 no.5
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• pp.655-666
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• 2014

The CUPID code has been developed at KAERI for a transient, three-dimensional analysis of a two-phase flow in light water nuclear reactor components. It can provide both a component-scale and a CFD-scale simulation by using a porous media or an open media model for a two-phase flow. In this paper, recent advances in the CUPID code are presented in three sections. First, the domain decomposition parallel method implemented in the CUPID code is described with the parallel efficiency test for multiple processors. Then, the coupling of CUPID-MARS via heat structure is introduced, where CUPID has been coupled with a system-scale thermal-hydraulics code, MARS, through the heat structure. The coupled code has been applied to a multi-scale thermal-hydraulic analysis of a pool mixing test. Finally, CUPID-SG is developed for analyzing two-phase flows in PWR steam generators. Physical models and validation results of CUPID-SG are discussed.

• The Journal of the Acoustical Society of Korea
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• v.15 no.1
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• pp.17-22
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• 1996

Planar array of acoustic transducer is normally used in a sonar system. Acoustic radiation makes beam pattern in underwater uses. The main source of the beam pattern is due to the transducer array. Therefore, estimation of the acoustic radiated power is necessary to predict the performance and efficiency of the transducer. As an example of the acoustic radiation power, nine acoustic transducers mounted to a rigid infinite baffle are considered in a theoretical model. Each piston's acoustic radiation consists of self- and mutual-radiation impedances. Total radiation impedances and acoustic radiation power of the transducers are extracted using on the theory of an equivalent electric circuit. The theoretical results reveal that acoustic radiation power of the transducer depends on the mutual coupling effects.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.53-53
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• 2008

Piezoelectric transformers have been widely used such as DC-DC convertor, invertor, Ballast, etc. Because, the y have some merits compared with electro-magnetic transformers such as step-up ratio, high efficiency, small size and lg hit weight, etc. Piezoelectric transformer require high electromechanical coupling factor kp in order to induce a large out put power in proportional to applied electric field. And also, high mechanical quality factor Qm is required to prevent mechanical loss and heat generation. In general, PZT system ceramics should be sintered at high temperatures between 1200 and $1300^{\circ}C$ in order to obtain complete densification. Accordingly, environmental pollution due to its PbO evaporation. Hence, to reduce its sintering temperature, various kinds of material processing methods such as hot pressing, high energy mill, liquid phase sintering, and using ultra fine powder have been performed. Among these methods, liquid phase sintering is basically an effective method for aiding densification at low temperature. In this study, In order to comparis on low temperature sintering and solid state sintering piezoelectric transformers, rosen type transformers were fabricated u sing two PZT ceramics compositions and their electrical properties were investigated.