• 센서학회지
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• 제27권1호
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• pp.64-67
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• 2018

A new CMOS neuron circuit for implementing bistable synapses with spike-timing-dependent plasticity (STDP) properties has been proposed. In neuromorphic systems using STDP properties, the short-term dynamics of the synaptic efficacies are governed by the relative timing of the pre- and post-synaptic spikes, and the efficacies tend asymptotically to either a potentiated state or to a depressed one on long time scales. The proposed circuit consists of a negative shifter, a current starved inverter and a schmitt trigger designed using 0.18um CMOS technology. The simulation result shows that the proposed circuit can reduce the total size of neurons, and the spike energy of the proposed circuit is much less compared to the conventional circuits.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.I
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• pp.567-570
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• 2005

Most researches on monostable LCD and bistable LCD have separately been carried out. We introduce a novel liquid crystal display mode which can be operated as both memory mode and dynamic mode. The novel LCD mode has not only a long term memory time of memory mode but also a fast response time of dynamic mode. We describe switching characteristics of dual mode. Electro-optical characteristics of memory mode and dynamic mode are unique and show the possibility of device application.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.67.2-67.2
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• 2012

Graphene is expected to have a significant impact in various fields in the foreseeable future. For example, graphene is considered to be a promising candidate to replace indium tin oxide (ITO) as transparent conductive electrodes in optoelectronics applications. We report the tunability of the wavelength of localized surface plasmon resonance by varying the distance between graphene and Au nanoparticles [1]. It is estimated that every nanometer of change in the distance between graphene and the nanoparticles corresponds to a resonance wavelength shift of ~12 nm. The nanoparticle-graphene separation changes the coupling strength of the electromagnetic field of the excited plasmons in the nanoparticles and the antiparallel image dipoles in graphene. We also show a hysteresis in the conductance and capacitance can serve as a platform for graphene memory devices. We report the hysteresis in capacitance-voltage measurements on top gated bilayer graphene which provide a direct experimental evidence of the existence of charge traps as the cause for the hysteresis [2]. By applying a back gate bias to tune the Fermi level, an opposite sequence of switching with the different charge carriers, holes and electrons, is found [3]. The charging and discharging effect is proposed to explain this ambipolar bistable hysteretic switching.

• 제어로봇시스템학회논문지
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• 제18권3호
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• pp.168-174
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• 2012

This paper presents a bending propagating actuation using SMA (Shape Memory Alloy) spring for an effective shape transition of a flytrap-inspired soft morphing structure. The flytrap-inspired soft morphing structure is made from unsymmetric CFRP (Carbon Fiber Reinforced Prepreg) structure which shows bi-stability and snap-through phenomenon. For a thin and large curved bistable CFRP structure, SMA spring is more acceptable than SMA wire and piezoelectric actuator which used in previous investigations. A bending propagating actuation is proposed which can induce snap-through of the bi-stable CFRP structure effectively. From this research, effective shape transition of soft morphing structure is possible.

• 한국광학회지
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• 제9권5호
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• pp.348-352
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• 1998

Berreman에 의해 제시된 액정 유체 방정식을 이용하여 쌍안정 TN 액정 셀의 여러 가지 파라미터 광 스위칭특성에 미치는 효과를 시뮬레이션을 통하여 연구하였다. 이로부터 쌍안정 TN LCD의 rising time과 delay time을 줄이는 액정 물질 및 셀 제작조건을 제시하였다. 고속응답을 위한 탄성계수는 K11은 크고 K22, K33 는 작은 것이 유리하고, 유전율 이방성, 회전 점성계수, 두께, 프리틸트 각, d/p등은 모두 작은 것이 유리하다. 특히 d/p는 고속응답 뿐만 아니라 0$^{\circ}$스위칭에 필요한 selection 펄스의 폭에 가장 많은 영향을 주는 중요한 파라미터이다.

• 한국광학회지
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• 제4권3호
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• pp.317-322
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• 1993

본 논문에서는 특성행렬을 사용하여 비선형 집적거울 etalon의 입출력 특성을 해석하는 방법을 제시한다. 빛의 세기에 따른 매질의 굴절률 및 흡수율의 변화 특성을 알면, 관계식과 특성행렬식을 결합하여 집적거울 etalon의 비선형 특성을 해석할 수 있다. 이 방법은 파장에 따른 각 거울의 반사율(크기와 위상)을 일일이 구하지 않고, etalon의 구조가 주어지면 바로 임의의 파장에서의 etalon의 입출력 특성을 해석할 수 있다. 또한, 특성행렬식을 이용하여 비선형 집적거울 etalon에서의 쌍안정성을 보였다.

• Current Optics and Photonics
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• 제6권1호
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• pp.10-14
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• 2022

Low-threshold optical bistability is essential for practical nonlinear optical applications. Many bistable optical devices based on high-quality-factor resonators have been proposed to reduce the threshold intensity. However, demonstrating high-quality-factor resonance requires complex fabrication techniques. In this work, we numerically demonstrate optical bistability with bound states in the continuum in a simple one-dimensional Si photonic crystal. The designed structure supports bound states in the continuum, producing an ultrahigh quality factor without tough fabrication conditions. The threshold intensity of the designed device is 150 MW/cm² at the optical communication wavelength. This scheme may lead to a new class of nonlinear photonics.

• 대한기계학회논문집A
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• 제34권8호
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• pp.1119-1127
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• 2010

본 논문에서는 작동 평면상의 네 위치에서 사중안정점을 가지는 신개념 전자기형 마이크로 액추에이터의 구조체와 전자기 로렌츠력을 이용하는 구동 방식을 제시하고, 이의 타당성을 비선형 구조해석 및 전기-열해석을 통하여 검증하였다. 사중안정성 액추에이터의 구현을 위해서 관련 분야에서 널리 연구되고 있는 쌍안정성 액추에 이터의 개념을 확장 응용하였다. 비선형 유한요소해석을 이용하여 사중안정성 미소 구조체의 정적 해석과 과도동 적 해석을 수행함으로써 액추에이터 구조체의 다중안정성 유무를 파악하고 이 결과를 분석하여 구조체 설계에 반영하였다. 사중안정성 미소 구조체를 도체화하여 자기장 내에서 구조체에 전류를 통할 때에 발생하는 로렌츠력으로 평면상의 네 안정점으로 구조체를 구동할 수 있도록 고안하고, 그 때 필요한 구동전류의 크기 및 전자기 구동에 의한 주울열에 의한 온도분포를 계산하여 전반적인 타당성을 검토하였다. 본 논문은 지금까지의 관심 대상인 쌍안정성의 이용이 아니라 더욱 확장된 다중안정성을 가진 미소 액추에이터의 구조체와 전자기 구동방법을 제안하여 향후에 다중안정성을 필요로 하는 마이크로 시스템에 활용될 수 있도록 하는데 그 의미가 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 심포지엄 논문집 정보 및 제어부문
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• pp.84-86
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• 2005

The digital systems such as PLC or DCS have been applied to non-safety systems of nuclear power plants because of many difficulties in using analog systems. Nowadays, digital systems have been applied to safety systems of the plants such as reactor protection system. One of the main advantages of digital systems is applicability of automatic testing methods to the systems. The protection system requires high-reliability and high-availability because it shall minimize the propagation of abnormal or accident conditions of nuclear power plants. The calculation of reliability and availability of systems depends on the maintenance period of the system. In general, the maintenance period of the protection system is one-month in case of the manual test. However, the cycle of test can be shortened in several hours by using automatic periodic testing. The reliability and availability of the system is better when test period is shortened because the reliability and availability is inverse proportion to the test period. In this research, we developed the automatic periodic testing method for KNICS Reactor Protection System, which can test the system automatically without an operator or a tester. The automatic testing contained all functions of reaction protection systems from analog-to-digital conversion function of the bistable Processor to the coincident trip function of the coincident processor. By applying the automatic periodic testing to reaction system, the maintenance cost can be cut down and the reliability can be increased.

• IEIE Transactions on Smart Processing and Computing
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• 제5권2호
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• pp.71-76
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• 2016

A controller area network (CAN) receiver measures differential voltage on a bus to determine the bus level. Since 3.3V transceivers generate the same differential voltage as 5V transceivers (usually ${\geq}1.5V$), all transceivers on the bus (regardless of supply voltage) can decipher the message. In fact, the other transceivers cannot even determine or show that there is anything different about the differential voltage levels. A new CMOS RC oscillator insensitive supply voltage for clock generation in a CAN transceiver was fabricated and tested to compensate for this drawback in CAN communication. The system consists of a symmetrical circuit for voltage and current switches, two capacitors, two comparators, and an RS flip-flop. The operational principle is similar to a bistable multivibrator but the oscillation frequency can also be controlled via a bias current and reference voltage. The chip test experimental results show that oscillation frequency and power dissipation are 500 kHz and 5.48 mW, respectively at a supply voltage of 3.3 V. The chip, chip area is $0.021mm^2$, is fabricated with $0.18{\mu}m$ CMOS technology from SK hynix.