• Journal of KIISE:Computing Practices and Letters
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• v.15 no.7
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• pp.505-509
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• 2009

It is the most important object of real-time computing to make real-time tasks keep their given time conditions. In this paper, we implemented BCC(Basic Concurrency Constraint) scheduler which is provided as an essential element of TMO(Time-triggered Message-triggered Object) model, and TMO Supporting Library that supports object-oriented design for TMO. BCC scheduler is a means to design timeliness-guaranteed computing, and it predicts the start of SpMs first, and then it makes the execution of SvMs deferred when it is predicted that any SpM begins to run currently. In this way, BCC is able to prevent collisions between SpM and SvM, and it gives higher priority to SpMs than SvMs.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.510-510
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• 2013

탄소나노튜브를 발광층에 첨가하여 Alternating current (AC) 방식으로 구동되는 고분자유기물 소자를 제작하였다. 고분자유기물 소자는 ITO가 코팅된 유리기판을 사용하였으며, 전극으로는 ITO와Al을 사용하고 cyanoethyl pullulan (CRS)의 유전물질과 탄소나노튜브를 함유한 poly[2-methoxy-z5-(2-ethyl-hexyloxy)-1,4-phenylene-vinylene](MEH-PPV) 고분자유기발광물질을 이용하여 4개의 층(ITO/CRS/탄소나노튜브를 함유한 MEH-PPV/Al)으로 고분자유기물 소자를 구성하였다. 소자는 ITO가 코팅된 유리 기판 위에 CRS의 유전층과 탄소나노튜브를 함유한 MEH-PPV의 발광층은 스핀코우터를 이용하여 증착하였으며, Al은 thermal evaporator을 이용하여 증착하였다. 본 연구에서는 AC 방식 고분자유기물 소자에 탄소나노튜브의 함유량을 변경하면서 전압과 전류 특성을 관찰하여 탄소나노튜브가 함유된 소자가 저 전류 구동이 가능한 것을 확인하였으며, 탄소나노튜브를 통한 micro-capacitance 효과의 확인 및 percolation과의 상관관계를 알아보았다. AC 고분자유기물 소자는 가정에서 사용되는 AC전원을 바로 사용할 수 있는 범용성을 가지고 있으며, 탄소나노튜브를 발광층에 첨가함으로 낮은 소비전력으로 고분자유기물 소자를 구동 할 수 있는 장점으로 차세대 디스플레이나 조명으로 그 쓰임새를 기대해본다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.5
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• pp.119-123
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• 2015

This paper presents a theoretical study of transmission performance for an optical NRZ (nonreturn-to-zero) transmitter employed a Mach-Zehnder modulator. Especially, we have investigated the effects of the ${\alpha}$-parameters that represents the chirps and the driving voltage ratios(=driving voltage/switching voltage) of Mach-Zehnder modulators for transmitting 25Gbps optical NRZ signals at a wavelength of 1550nm without any dispersion compensation methods over single mode fiber. By optimizing the negative values of ${\alpha}$-parameters for the dispersion tolerance with the change of driving voltage ratios, it has been tested whether the transmission performance has improved. We have verified the improvement by the BERs and the optical eye diagrams.

• Journal of KIISE:Computing Practices and Letters
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• v.6 no.6
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• pp.628-634
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• 2000

We propose a data coding scheme for reducing' power consumption and ElVII in transmitting a sequence of data from LCD controller to LCD driver. The proposed coding scheme makes use of reducing data transitions in general text image of PC. It can be implemented with a little hardware and applied to the real-time applications of LCD driving system. We have executed computer simulations of the proposed coding scheme and compared the results of the proposed scheme with those produced by the existing coding schemes. The proposed coding scheme, compared to the existing ones, reduces the switching activity significantly in both of text and picture images.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.1
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• pp.13-18
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• 1999

This paper proposes a new overmodulation stategy to give a better voltage by the full utilization of the hexagon voltage range in the space vector PWM(SVPWM) inverter. This overmodulation strategy can apply to the vector control, leading to better output torque capability in the ac motor drive system. This strategy is that in the overmodulation range, the d-axis output current is given a priority to regulate the flux well, instead the q-axis output curent is sacrificed. Therefore, the vector control even in the overmodulation PWM operation can be achieved well. For this purpose, the d-axis output voltage of a current controller to control the flux is conserved. the q-axis output voltage to control the torque is controlled to place the reference voltage vector on the hexagon boundary in case of the overmodulation. The validity of the proposed overall scheme is confirmed by simulation and experiments for a 22[kW] induction motor drive system

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.11
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• pp.193-198
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• 2012

An LED converter used to operate an LED with high efficiency and long lifespan, activates an LED by keeping voltage and current constant. In spite of voltage drop by LED's overheating and over-voltage by damage of a power line and by circuit problem, most existing LED converters supply unchanged constant voltage and current to the LED. Eventually, LED is out of order because of over-voltage or over-current. To avoid the breakdown of an LED by over-voltage and over-current, we propose a new scheme which deactivate the PWM circuit in the event of over-current generating. The PWM circuit operates below the pre-determined level of current. While the over-voltage is generated in PWM circuit, the feedback circuit makes the PWM circuit stopped and therefore prevents LED from being damaged by over-voltage and over-current.

• Defense and Technology
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• no.3 s.289
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• pp.58-65
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• 2003

접이식 방호부양장치체계 설계안은 전투장갑차의 부양장치로서 요구되는 부력, 방호성, 독자적 수상운행성을 위한 탑재운용성, 수상운행 준비시간을 최소화하는 구동장치의 최적화 및 수상안정성 극대화 등을 충족시키면서도 중량 증가 요인은 최소화하는 것이 가능할 것으로 검토된 바, 기존 방법으로는 기대할 수 없는 높은 수준의 수상운행성능 구현이 가능할 것으로 기대된다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.71.2-71.2
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• 2010

고체산화물연료전지는 청정에너지원으로써 기존의 발전방식을 대신할 차세대 에너지원으로 각광 받고 있다. 고체산화물 연료전지는 고온에서 작동하는 특성상 실험을 통하여 전극미세구조 및 구동조건을 최적화하는 것은 매우 어렵다. 본 연구는 전기화학식을 이용한 전산모사를 통해서 고체산화물 연료전지의 구동조건에 따른 성능 평가 및 전극의 미세구조 최적화 과정을 수행하였다. 전극 내 전달현상을 무시하고 오직 전기화학반응만을 고려한 전산모사는 단전지의 전극미세구조 및 구동조건에 따른 전지성능을 빠르게 예측할 수 있으며, 이를 기반으로 다양한 조건에서 얻은 전지 성능 데이터를 통해 전극미세구조를 최적화하였다. 개회로전압, 활성화분극, 저항분극, 물질수송손실을 표현하기 위하여 Nernst 식, Butler-Voler 식, 옴의 법칙, dusty-gas 모델을 각각 사용하였으며, 전극미세구조 및 구동조건의 변화는 물질확산계수 및 교환전류밀도를 통하여 그 영향이 전지성능에 반영된다. 온도, 압력, 주입 연료의 조성에 대한 성능평가가 수행되었으며, 1023K, 1 bar의 조건하에서 최적의 단전지 성능을 위한 기공도와 기공크기를 조사하였다. 더 향상된 단전지 성능 확보를 위해서 실험에서 쓰이는 기능층(functional layer)과 유사하게 넓은 반응 면적과 원활한 반응물 및 생성물의 이동을 보장하도록 기공도 및 기공크기를 그레이딩한 전극구조(graded-electrode)를 디자인하고 성능을 평가하였다. 그 결과 기존의 전지구조 대신에 그레이딩된 전극을 사용할 경우 50%이상 향상된 전지성능을 예측할 수 있었다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.6
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• pp.111-118
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• 2008

In this paper, novel latch-up prevention method that employs power-up sequential switches has been proposed to relieve latch-up problem in liquid crystal display (LCD) driver ICs. These sequential switches are inserted in the 2'nd and 3'rd boosting stages, and are used to short the emitter-base terminals of parasitic p-n-p-n circuit before relevant boosting stages are activated during power-up sequence. To verily the performance of the proposed method, test chips were designed and fabricated in a 0.13-um CMOS process technology. The measurement results indicated that, while the conventional LCD driver If entered latch-up mode at $50^{\circ}C$ accompanying a significant amount of excess current, the driver IC adopting the proposed method showed no latch-up phenomenon up to $100^{\circ}C$ and maintained normal current level of 0.9mA.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.1
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• pp.94-101
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• 1999

In this paper the problems associated with the switching surge of PWM inverter devices were analysed. As the application of ASD for efficient speed control of AC rmtors is increased, so is the rrntor and ASD-related failure increased. In the industrial rmtor awlications, the introduction of PWM drives can sometmes cause insulation breakdown between the phase windings due to high transient voltage peak. The motor cable length combined with the high switching frequency becomes more sensitive issue for proper drive operation. Effects of the cable length and high switching frequency influence both on rmtor and inverter. When the insulation level of rmtor winding is low, the failure probability caused by high peak voltage and fast voltage rise times(dv/dt) is high. Voltage refloctions are simulated far rmtor capacities, ASD and rise times and are presented graphically. The filtering techniques are discussed to reduce the rmtor terminal overvoltage and dv/dt in inverter fed AC rrntor drive systems. We confirmed that the lower motar capacity and rmtar insulation level, the shorter switching time and cable length and the higrer the probability of insulation breakdown .kdown .