• 제목/요약/키워드: Performance conversion

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JPEG 영상 복원을 위한 다중 모드 채도 복원과 연산 재배열 기반의 시간 최적화된 컬러 변환 (Time-optimized Color Conversion based on Multi-mode Chrominance Reconstruction and Operation Rearrangement for JPEG Image Decoding)

  • 김영주
    • 한국컴퓨터정보학회논문지
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    • 제14권1호
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    • pp.135-143
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    • 2009
  • 최근 모바일 장치에서 고해상도 영상의 인코딩 및 디코딩에 대한 요구가 늘어남에 따라 효율적인 영상 코덱 개발의 필요성이 증대되고 있다. 본 논문은 JPEG 디코딩 과정에서 IDCT 변환과 컬러변환 배열간의 선형성을 바탕으로 이들 연산순서를 재배열함으로써 컬러변환 과정에서 요구되는 계산 횟수를 줄이고 재배열된 부동소수점 연산에 정수 맵핑을 적용하여 시간 복잡도를 줄임으로써 실행시간을 크게 단축하는 컬러변환 기법을 제안한다. 또한, 제안된 기법은 연산 재배열 및 정수 맵핑의 양자화오류로 인한 화질 저하를 다중 모드 채도 재구성 기법을 적용하여 보상하도록 한다. 임베디드 시스템 개발 플랫폼에서의 성능평가를 통해 제안 된 기법이 기존의 컬러변환 기법들과 비교하여 복원 영상의 화질 저하를 최소화하면서 실행시간을 크게 단축함을 알 수 있었다.

$M/Al_2O_3$ (M = Mn, Fe, Co, Ni, Cu) 촉매 상에서 에탄올 자열개질반응에 의한 수소 제조 (Hydrogen Production by Auto-thermal Reforming of Ethanol over $M/Al_2O_3$ (M = Mn, Fe, Co, Ni, Cu) Catalysts)

  • 윤민혜;서정길;조경민;박선영;김필;송인규
    • 청정기술
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    • 제13권4호
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    • pp.287-292
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    • 2007
  • 상용 알루미나($Al_2O_3$)에 담지된 $M/Al_2O_3$ (M = Mn, Fe, Co, Ni, Cu) 촉매를 함침법에 의해 제조하였으며, 이를 에탄을 자열개질반응에 의한 수소제조에 적용하였다. 각각의 촉매는 고유한 금속상을 가지는 것으로 나타났으며, 생성물의 분포는 활성금속의 종류에 크게 의존하였다. 제조된 촉매 중에서, $M/Al_2O_3$ 및 Co/$Co/Al_2O_3$는 에탄을 자열개질반응에서 매우 우수한 촉매활성을 보였다. 그러나 두 촉매상에서의 반응메커니즘은 서로 다른 것으로 나타났다. $Ni/Al_2O_3$ 촉매는 $500^{\circ}C$의 반응온도에서 100%의 에탄올 전환율을 보였으나, 수소 선택도에서는 시간에 따라 급격한 저하현상을 나타내었다. 한편 $Co/Al_2O_3$ 촉매는 수소 선택도 면에서 우수한 활성을 보였으나, 에탄올 전환율이 저조하여 수소 수율에는 큰 변화가 나타나지 않았다.

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Simple Neuro-Controllers for Field-Oriented Induction Motor Servo Drives

  • Fayez F. M.;Sousy, E-I;M. M. Salem
    • Journal of Power Electronics
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    • 제4권1호
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    • pp.28-38
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    • 2004
  • In this paper, the position control of a detuned indirect field oriented control (IFOC) induction motor drive is studied. A proposed Simple-Neuro-Controllers (SNCs) are designed and analyzed to achieve high-dynamic performance both in the position command tracking and load regulation characteristics for robotic applications. The proposed SNCs are trained on-line based on the back propagation algorithm with a modified error function. Four SNCs are developed for position, speed and d-q axes stator currents respectively. Also, a synchronous proportional plus integral-derivative (PI-D) two-degree-of-freedom (2DOF) position controller and PI-D speed controller are designed for an ideal IFOC induction motor drive with the desired dynamic response. The performance of the proposed SNCs and synchronous PI-D 2DOF position controllers for detuned field oriented induction motor servo drive is investigated. Simulation results show that the proposed SNCs controllers provide high-performance dynamic characteristics which are robust with regard to motor parameter variations and external load disturbance. Furthermore, comparing the SNC position controller with the synchronous PI-D 2DOF position controller demonstrates the superiority of the proposed SNCs controllers due to attain a robust control performance for IFOC induction motor servo drive system.

Synthesis of TiO2 nanoparticles induced by electron beam irradiation and their electrochemical performance as anode materials for Li-ion batteries

  • Ahn, Ja-Hwa;Eom, Ji-Yong;Kim, Jong-Huy;Kim, Hye Won;Lee, Byung Cheol;Kim, Sung-Soo
    • Journal of Electrochemical Science and Technology
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    • 제6권3호
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    • pp.75-80
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    • 2015
  • We introduce a new synthesis method to prepare small TiO2 nanoparticles with a narrow particle size distribution, which is achieved by electron beam (E-beam) irradiation. The effects of E-beam irradiation on the synthesis of TiO2 nanoparticles and the electrochemical performance of TiO2 nanoparticles as alternative anode materials for Li-ion batteries are investigated. The TiO2 nanoparticles induced by E-beam irradiation present better cycling performance and rate capability than the TiO2 nanoparticles synthesized by normal hydrolysis reaction. The better electrochemical performance is attributed to small particle size and narrow particle size distribution, resulting in the large surface area that provides innumerable reaction sites and short diffusion length for Li+ through TiO2 nanoparticles.

단일디스크 고장시 RAID 5의 성능개선을 위한 레벨 전환 기법 (Level Conversion Scheme for Improving Performance of RAID 5 on Single Disk Failure)

  • Jeon, Sang-Hoon;Chung, Hyun-Sik
    • 한국컴퓨터정보학회논문지
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    • 제4권2호
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    • pp.8-18
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    • 1999
  • 주문형 멀티미디어 시스템 등 사용자 요구에 실시간 응답을 하여야하는 저장시스템 구조에 있어, 단일 디스크 고장시 즉각적인 데이타 복구는 상당히 중요하다. 본 논문에서는 기존의 RAID5구조에 있어 단일디스크 고장시 새로운 디스크가 교체되기 전까지 유발되는 급격한 성능저하를 RAID 레벨 전환 기법을 이용하여 개선하고자 한다. 이 기법은 기존의 연구에서 제시된 예비 디스크 기법에 비해 추가의 디스크를 필요로 하지 않는 저가형 시스템에 적합하다. 제안된 기법과 기존의 RAID5구조는 시뮬레이션을 통하여 여러 모드에서 성능이 측정되었다. 측정 결과 제안된 기법은 실패모드에서는 20%, 재구성모드에서는 80%이상의 성능 개선을 보인다.

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Performance of Solid Oxide Fuel Cells with Direct Internal Reforming of Methane

  • Kim, Young Jin;Lim, Hyung-Tae
    • 한국세라믹학회지
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    • 제52권5호
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    • pp.325-330
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    • 2015
  • Performance of solid oxide fuel cells (SOFCs), in comparison with that under hydrogen fuel, were investigated under direct internal reforming conditions. Anode supported cells were fabricated with an Ni+YSZ anode, YSZ electrolyte, and LSM+YSZ cathode for the present work. Measurements of I-V curves and impedance were conducted with S/C (steam to carbon) ratio of ~ 2 at $800^{\circ}C$. The outlet gas was analyzed using gas chromatography under open circuit condition; the methane conversion rate was calculated and found to be ~ 90% in the case of low flow rate of methane and steam. Power density values were comparable for both cases (hydrogen fuel and internal steam reforming of methane), and in the latter case the cell performance was improved, with a decrease in the flow rate of methane with steam, because of the higher conversion rate. The present work indicates that the short-term performance of SOFCs with conventional Ni+YSZ anodes, in comparison with that under hydrogen fuel, is acceptable under internal reforming condition with the optimized fuel flow rate and S/C ratio.

Enhancing Electrochemical Performance of Co(OH)2 Anode Materials by Introducing Graphene for Next-Generation Li-ion Batteries

  • Kim, Hyunwoo;Kim, Dong In;Yoon, Won-Sub
    • Journal of Electrochemical Science and Technology
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    • 제13권3호
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    • pp.398-406
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    • 2022
  • To satisfy the growing demand for high-performance batteries, diverse novel anode materials with high specific capacities have been developed to replace commercial graphite. Among them, cobalt hydroxides have received considerable attention as promising anode materials for lithium-ion batteries as they exhibit a high reversible capacity owing to the additional reaction of LiOH, followed by conversion reaction. In this study, we introduced graphene in the fabrication of Co(OH)2-based anode materials to further improve electrochemical performance. The resultant Co(OH)2/graphene composite exhibited a larger reversible capacity of ~1090 mAh g-1, compared with ~705 mAh g-1 for bare Co(OH)2. Synchrotron-based analyses were conducted to explore the beneficial effects of graphene on the composite material. The experimental results demonstrate that introducing graphene into Co(OH)2 facilitates both the conversion and reaction of the LiOH phase and provides additional lithium storage sites. In addition to insights into how the electrochemical performance of composite materials can be improved, this study also provides an effective strategy for designing composite materials.

동특성해석을 위한 계통연계 풍력발전 시스템의 모델링 (Modeling of a Grid-Connected Wind Energy Conversion System for Dynamic Performance Analysis)

  • 추연식;노경수
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2002년도 하계학술대회 논문집 B
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    • pp.1358-1360
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    • 2002
  • This paper presents a modeling and simulation of a utility-connected wind energy conversion system with a link of a rectifier and an inverter. It discusses the maximum power control algorithm for the wind turbine and presents the relationship of wind turbine output, rotor speed, power coefficient, tip-speed ratio and wind speed when the wind turbine is operated under the maximum power control algorithm. The control objective is to extract maximum power from wind and transfer the power to the utility. This is achieved by controlling the pitch angle of the wind turbine blades. Pitch control method is mechanically complicated, but the control performance is better than that of the stall regulation method. The simulation results performed on MATLAB will show the variation of generator's rotor speed, pitch angle, and generator output.

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Bi-Orthogonal 변조를 이용한 Multi-Code CDMA 시스템의 성능 개선 (Performance Improvement of Multi-Code CDMA Systems Using Bi-Orthogonal Modulation)

  • 한재광;신요안
    • 대한전자공학회:학술대회논문집
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    • 대한전자공학회 2000년도 하계종합학술대회 논문집(1)
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    • pp.29-32
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    • 2000
  • In this paper, we present an extension of the multi-code CDMA (code division multiple access) systems based on bi-orthogonal modulation by employing a convolutional encoder and an interleaver before serial-to-parallel conversion in the modulator. Bandwidth expansion by the convolutional encoder can be compensated for by the bi-orthogonal modulation, and the interleaver in the system scrambles the convolutionally encoded data bits so that, after serial-to-parallel conversion, each code channel conveys those bits far apart in time. The result is that the proposed system with several order of magnitude less implementational complexity, achieves quite close performance of the conventional systems comprised of Walsh modulation and multiple convolutional encoders and interleavers in all the code channels.

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고속, 고해상도 CMOS 샘플 앤 홀드 회로 (High Speed, High Resolution CMOS Sample and Hold Circuit)

  • 김원연;박공순;박상욱;윤광섭
    • 대한전자공학회:학술대회논문집
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    • 대한전자공학회 2004년도 하계종합학술대회 논문집(2)
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    • pp.545-548
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    • 2004
  • The paper describes the design of high-speed, high-resolution Sample-and-Hold circuit which shows the conversion rate 80MHz and the power supply of 3.3v with 0.35um CMOS 2-poly 4-metal process for high-speed, high resolution Analog-to-Digital Converter. For improving Dynamic performance of Sample-and-Hold, Two Double bootstrap switch and high performance operational amplifier with gain booster, which are used. and For physical stability of Sample and Hold circuit, reduces excess voltage of gate in bootstrap switch. Simulation results using HSPICE shows the SFDR of 71dB, 75dB in conversion rate of 80MHz result for two inputs(0.5Vpp, 10MHz and 1Vpp, 10MHz) and the power dissipation of 48mW at single 3.3V supply voltage.

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