• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1055-1059
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• 1992

Instantaneous Voltage Control of inverter for uninterruptible power supply(UPS) is presented. In order to improve the transient response, the authors propose a control scheme based on a double regulation loop with sinusoidal hysteresis band. And also, using 8097 single chip microprocessor, software synchronization and static switch control scheme is impremented with minimal hard ware structure.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.121-125
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• 1993

This paper proposes two kinds of novel switching method for a single phase current-controlled voltage-type ac-to-dc converter. Proposed are modifications of the conventional hysteresis current control, and are named by the half suppressing method and unipolar method, respectively. The first one suppresses an inactive half of the four switching signals and uses active another half for current control. The second method uses only one, a quarter of switching signals suppresed the others. Both the simulation and experimental results show that proposed methods are more efficient in switch utilization and have comparable or better performance when compared with conventional method.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2005.09a
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• pp.27-30
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• 2005

A nanoelectromechanical (NEM) switching device based on carbon nanotube (CNT) was investigated using atomistic simulations. The model schematics for a CNT based three-terminal NEM switching device fabrication were presented. for the CNT-based three-terminal NEM switch, the interactions between the CNT-lever and the drain electrode or the substrate were very important. When the electrostatic force applied to the CNT-lever was the critical point, the CNT-lever was rapidly bent because of the attractive foroe between the CNT-lever and the drain. The energy curves for the pull-in and the pull-out processes showed the hysteresis loop that was induced by the adhesion of the CNT on the copper, which was the interatomic interaction between the CNT and the copper.

• ETRI Journal
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• v.44 no.4
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• pp.560-572
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• 2022

H²RDC (heuristic handover based on RCC-DTSK-C), a heuristic algorithm based on a highly interpretable deep Takagi-Sugeno-Kang fuzzy classifier, is proposed for suppressing the mobile heterogeneous networks problem of frequent handover and handover ping-pong in the multibase-station scenario. This classifier uses a stack structure between subsystems to form a deep classifier before generating a base station (BS) priority sequence during the handover process, and adaptive handover hysteresis is calculated. Simulation results show that H²RDC allows user equipment to switch to the best antenna at the optimal time. In high-BS density load and mobility scenarios, the proposed algorithm's handover success rate is similar to those of classic algorithms such as best connection (BC), self tuning handover algorithm (STHA), and heuristic for handover based on AHP-TOPSIS-FUZZY (H²ATF). Moreover, the handover rate is 83% lower under H²RDC than under BC, whereas the handover ping-pong rate is 76% lower.

• Transactions on Electrical and Electronic Materials
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• v.6 no.4
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• pp.154-158
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• 2005

Organic molecules have many properties that make them attractive for electronic applications. We have been examining the progress of memory cell by using molecular-scale switch to give an example of the application using both nano scale components and Si-technology. In this study, molecular electronic devices were fabricated with amino style derivatives as redox-active component. This molecule is amphiphilic to allow monolayer formation by the Langmuir-Blodgett (LB) method and then this LB monolayer is inserted between two metal electrodes. According to the current-voltage (I-V) characteristics, it was found that the devices show remarkable hysteresis behavior and can be used as memory devices at ambient conditions, when aluminum oxide layer was existed on bottom electrode. The diode-like characteristics were measured only, when Pt layer was existed as bottom electrode. It was also found that this metal layer interacts with organic molecules and acts as a protecting layer, when thin Ti layer was inserted between the organic molecular layer and Al top electrode. These electrical properties of the devices may be applicable to active components for the memory and/or logic gates in the future.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.3
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• pp.149-155
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• 2006

This paper presents a torsional micromirror detached from PZT actuators (TMD), whose rotational motion is achieved by push bars in the PZT actuators detached from the micromirror. The push bar mechanism is intended to reduce the bending, tensile and torsional constraints generated by the conventional bending bar mechanism, where the torsional micromirror is attached to the PZT actuators (TMA). We have designed, fabricated and tested prototypes of TMDs for single-axis and dual-axis rotation, respectively. The single-axis TMD generates the static rotational angle of $6.1^{\circ}$ at 16 VDC, which is 6 times larger than that of single-axis TMA, $0.9^{\circ}$. However, the rotational response curve of TMD shows hysteresis due to the static friction between the cover and the push bar in the PZT actuator. We have shown that 63.2% of the hysteresis is due to the static friction caused by the initial contact force of the PZT actuaor. Without the initial contact force, the rotational response curve of TMD shows linear voltage-angle characteristics. The dual-axis TMD generates the static rotational angles of $5.5^{\circ}$ and $4.7^{\circ}$ in x-axis and y-axis, respectively at 16 VDC. The measured resonant frequencies of dual-axis TMD are $2.1\pm0.1$ kHz in x-axis and $1.7\pm0.1$ kHz in y-axis. The dual-axis TMD shows stable operation without severe wear for 21.6 million cycles driven by 16 Vp-p sinusoidal wave signal at room temperature.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.1
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• pp.46-52
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• 1999

A new current controlled PWM t'||'&'||'pound;rlmique with NPC(Neutral Point Qarll)ed) structure is IrOIX>Sed in this paper. A current controlled PWM technique with neutral-JXlint-cIamped pulse-width modulation inverter composed of main switching devices which operates as switch for PWM and auxiliary switching devices to clamp the output terminal potential to the neutral point potential is described. The proposed current controller has a first and second current band The switching pattern will be made by the first current band. According to the second current band, the output state of the switching pattern is changed into positivee and negative state. This inverter output contains less hanronic content and lower switching frequency than that of conventional current controlled PWM technique at the same current limit. Thbe induction machine drive with proposed technique is investigated by commputer simulation.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.738-750
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• 2017

In this paper, carrier-based pulse width modulation (CBPWM), space vector PWM (SVPWM) and reduced switching losses PWM (RSLPWM) for the three-level neutral point clamped (NPC) inverter are introduced. In the case of the neutral point (NP) potential (NPP) offset, an asymmetric disposition PWM (ASPDPWM) strategy is proposed, which can output PWM sequences correctly and suppress the lower order harmonics of the inverter effectively. An NPP balance strategy based on carrier based PWM (CBPWM) is analyzed. A hybrid modulation strategy combining RSLPWM and the NPP balance based on CBPWM is proposed, and hysteresis control is adopted to switch between the two modulation strategies. An experimental prototype of the three-level NPC inverter is built. The effectiveness of the hybrid modulation is verified with a resistance-inductance load and a permanent magnetic synchronous motor (PMSM) load, respectively. The experimental results show that reduced switching losses and an acceptable NPP can be effectively achieved in the hybrid modulation strategy.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.55 no.1
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• pp.26-30
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• 2006

For the purpose of developing capacitive humidity sensor having interdigital electrodes, interdigital electrode was modeled and simulated to obtain capacitance and sensitivity as a function of geometric parameters like the structural gap and thickness. For the development of ASIC, switched capacitor signal processing circuits for capacitive humidity sensor were designed and simulated by Cadence using $0.25{\mu}m$ CMOS process parameters. The signal processing circuits are composed of amplifier for voltage gain control, and clock generator for sensor driving and switch control. The characteristics of the fabricated sensors are; 1) sensitivity is 9fF/%R.H., 2) temperature coefficient of offset(TCO) is $0.4%R.H./^{\circ}C$, 3) nonlinearity is 1.2%FS, 4) hysteresis is 1.5%FS in humidity range of $3%R.H.{\sim}98%R.H.$. The response time is 50 seconds in adsorption and 70 seconds in desorption. Fabricated process used in this capacitive humidity sensor having interdigital electrode are just as similar as conventional IC process technology. Therefore this can be easily mass produced with low cost, simple circuit and utilized in many applications for both industrial and environmental measurement and control system, such as monitoring system of environment, automobile, displayer, IC process room, and laboratory etc.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.8
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• pp.1125-1131
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• 2013

Wireless power transmission technology has been studied variety. Recently, wireless power transmission technology used by resonance and magnetic induction field is applied to various fields. However, magnetic resonance and inductive coupling are have drawbacks - power transmission distance is short. Microwave transmission and accept techniques have been developed to overcome short distance. However, improvement in efficiency is required. This paper, propose a high-efficiency microwave energy acceptor IC(EAIC). Suggested EAIC is consists of RF-DC converter and DC-DC converter. Wide Input power range is -15 dBm ~ 20 dBm. And output voltage is boosted up to 5.5 V by voltage boost-up circuit. EAIC can keep the output voltage constant. Available efficiency of RF-DC converter is 95.5 % at 4 dBm input. And DC-DC efficiency is 94.79 % at 1.1 mA load current. Fully EAIC efficiency is 90.5 %.