• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 하계학술대회 논문집
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• pp.32-34
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• 2007

전자산업 부문의 친환경 대응이 이슈화 되면서 전자기기의 대기전력 소비감소를 위한 연구가 지속적으로 수행되고 있다. 전자기기의 대표적인 전원공급장치인 Switched Mode Power Supply(SMPS)의 경우 부하기기의 대기모드 시 극도로 낮은 출력전력에서 고효율을 달성해야 하는 요구가 높다. 특히 많은 SMPS들이 부하기기의 요구에 의하여 다출력 컨버터로 설계되어 있는데, 이러한 다출력 구조에서 대기모드 시 불필요한 출력을 절체함과 동시에 저전력에서 고효율을 내기가 쉽지 않다. 또한 다출력 구조로 인한 Cross Regulation 문제를 극복해야 하는 과제가 있다. 따라서 본 논문에서는 단일 컨버터 혹은 복수의 컨버터로 구성되어 있는 다출력 컨버터에서 대기전력 개선을 위한 Secondary Side Post Regulator(SSPR), 전류모드, Power Sequence 제어기술을 제안하고, 대기전력과 더불어 SSPR의 Cross Regulation 특성 개선을 검토하였다. 그리고 제안한 기술이 구현된 다출력 구조의 110W와 270W급 SMPS를 제작하여 회로의 타당성 및 우수성을 검증하였다.

• Journal of Power Electronics
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• 제19권6호
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• pp.1554-1565
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• 2019

When grid voltage is unbalanced, the grid-connected output current and power of Virtual Synchronous Generators (VSGs) are distorted and quadratic. In order to improve the power quality of a grid connected to a VSG when the grid voltage is unbalanced, a comprehensive coordinated control strategy is proposed. The strategy uses the positive sequence current reference command obtained by a VSG in the balanced current control mode to establish a unified negative sequence current reference command analytical expression for the three objectives of current balance, active power constant and reactive power constant. In addition, based on the relative value of each target's volatility, a comprehensive wave function expression is established. By deriving the comprehensive wave function, the corresponding negative sequence current reference value is obtained. Therefore, the VSG can achieve the minimum comprehensive fluctuation under the premise that the three targets meet the requirements of grid connection, and the output power quality is improved. The effectiveness of the proposed control strategy is verified by simulation and experimental results.

• Composites Research
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• 제36권6호
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• pp.383-387
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• 2023

탄소섬유 복합재료는 우수한 물성을 바탕으로 산업 전반에 활용되고 있으나 취성이 강하다는 단점이 있다. 연신율이 높은 소재와의 하이브리드화를 통해 강도는 다소 감소되더라도 파괴인성을 향상시킬 수 있다. 이 연구에서는 탄소섬유와 아라미드섬유를 하이브리드한 적층 판재의 물성을 평가하되, 적층 순서를 다르게 하여 이종 재료와의 계면 형성 정도를 조절하였다. 그 결과 25%의 아라미드 섬유 포함 시 순수 탄소섬유 대비 최대 63%의 Izod 충격강도의 향상을 확인할 수 있었으며, 중간 정도의 복잡도를 가진 적층순서 [CF/CAF₂/CF]_s 에서 가장 우수하였다. 그러나 전체적인 복합화 효과는 부정적인 것으로 분석되었다.

• 한국통신학회논문지
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• 제21권4호
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• pp.984-995
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• 1996

Data errors according to the various noises caused in the satellite communication links are corrected by the Viterbi decoding algorithm which has extreme error correcting capability. In this paper, we designed and implemented a convolutional encoder and Viterbi decoder ASIC which is used to encode the input data at the transmit side and correct the errors of the received data at the receive side for use in the VSAT communication system. And this chip may be used in any BPSK, QPSK, or OQPSK transmission system. The ambiguity resolver corrects PSK modem ambiguities by delaying, interting, and/or exchanging code symbol to restore their original sequence and polarity. In case of previous decoding system, ambiguity state(AS) of data is resolved by external control logic and extra redundancy data are needed to resolve AS. But, by adopting decoder proposed in this paper, As of data is resolved automatically by internal logic of decoder in case of continuous mode, and by external As line withoug extra redudancy data in burst mode case. So, decoding parts are simple in continuous mode and transmission efficiency is increased in bust mode. The features of this chip are full duplex operation with independent transmit and receive control and clocks, start/stop inputs for use in burst mode systems, loopback function to verify encoder and decoder, and internal or external control to resolve ambinguity state. For verification of the function and performance of a fabricated ASIC chip, we equiped this chip in the Central and Remote Earth Station of VSAT system, and did the performance test using the commerical INTELSAT VII under the real satellite link environmens. The results of test were demonstrated the superiority of performance.

• Elastomers and Composites
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• 제44권3호
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• pp.315-322
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• 2009

이피디엠/폴리프로필렌 열가소성 경화물을 오일의 배합 순서를 달리한 두 가지 방식(오일 블렌드 후 가교방식과 가교 후 오일 블렌드 방식)으로 제조하여 가교도(겔분율), 경도, 인장강도, 신율, 용융흐름지수 등을 조사, 오일의 블렌드 방식이 열가소성 경화물의 물성에 미치는 영향을 알아보았다. 오일의 블렌드 방식에 따른 두 경화물의 가교도와 기계적 물성의 차는 크지 않았으나, 가공성에 있어서는 가교 후 오일 블렌드 방식으로 제조한 경화물의 용융흐름지수가 현저히 증가한 결과를 보였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.58-60
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• 2007

Magnetic Resonance Imaging(MRI) has become a very widely used medical procedur e. Clo.sed and open systems are typically used with static magnetic fields at or below 2 Tesla. BWhole body SAR(specific absorbsion rate) is the value of SAR averaged over the entire body of the patient over any period of 15 minutes. Head SAR is the value of SAR averaged over the head of the patient for any period of 10 minutes. SAR is a measure of the absorption of electromagnetic energy in the body' (typically in watts per kilogram (W/kg)). The normal operating mode comprises values of head SAR not higher than 3 W/kg. The second level controlled operating mode comprises values higher than 3 W/kg. Current FDA guidance limits the SAR in the whole body. including the head to a range of 1.5 to 4.0 W/kg, depending on the patient's clinical condition. SAR, limit restrictions are incorporated in all MRI systems. and domestic' s guidance limits the SAR in a part body. including the head to 3.2w/kg and less. The purpose of this study is to evaluate on change of head SAR in using MRI pulse sequence and to check if exceed 3.2(w/kg) level in domestic a part exposure through measured head SAR. 23 patient's the average head SAR of pulse sequence is that T2WI sagittal is 0.5375. T2WI axial(FSE) is 0.4817, T1WI axial(SE) is, 0.8179. FLAIR axial is 0.4580. GRE axial is 0.0077, Diffusion is 0.0824w/kg. The head SAR exposed per patient was proved 2.3845w/kg less than the international standard. Coefficient of correlation for the relations body weight and SAR or for the relations ETL(echo train length) and SAR is 1 value. Coefficient of correlation for the relations between TR(time to repeat) and SAR is -0.602 value. so SAR increased relative to weight body and ETL. But the relations between TR and SAR is negative definite.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제24회 춘계학술대회논문집
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• pp.334-342
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• 2005

A numerical analysis is performed using two dimensional axisymmetric RANS (Reynolds Averaged Navier-Stokes) equations system on the transition sequence of the Integrated Rocket Ramjet and the unsteady reacting flow-field in a ramjet combustor during unstable combustion. The mode transition of an axisymmetric ramjet is numerically simulated starting from the initial condition of the boost end phase of the entire ramjet. The unsteady reacting flow-field within combustor is computed for varying injection area. In calculation results of the transition, the terminal normal shock is occurred at the downstream of diffuser throat section and no notable combustor pressure oscillation is observed after certain time of the inlet port cover open. For the case of a small injection area at the same equivalence ratio, periodic pressure oscillation in the combustor leads to the terminal shock expulsion from the inlet and hence the buzz instability occurred.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 연구회 합동 학술발표회 논문집
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• pp.39-43
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• 1998

A large number of soft switching topologies included a resonant circuit have been proposed. But these circuits increase number of switch in circuit and complicate sequence of switching operation. In this paper, the authors propose power conversion system, DC-AC inverter of high efficiency and high power factor with soft switching mode by partial resonant method. The switching devices in a proposed circuits are operated with soft switching by the partial resonant method, that is, PRS2MPC (Partial Resonant Soft Switching Mode Power Converter). The result is that the switching loss is very low and the efficiency of system is high. And the snubber condenser used in partial resonant circuit makes charging energy regenerated at input power source for resonant operation.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2010년 춘계학술발표회 논문집
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• pp.227-229
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• 2010

This study presents an application of the 3D patch extraction method which is based on gradient-driven properties to obtain 3D planar patches over the terrain and man-made objects from lidar data. The method which was exploited in this study is composed of a sequence of processes: segmentation by slope, initiation of triggering patches by mode selection, and expansion of the triggering patches. Since urban areas contain many planar regions over the terrain surface, application of the method has been experimented to extract 3D planar patches not only from non-terrain objects but also from the terrain. The experimental result shows that the method is efficient to acquire 3D planar patches.

• 한국통신학회논문지
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• 제23권7호
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• pp.1699-1706
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• 1998

This paper presents a threshold decision technique for direct sequence code acquistion employing Pseudo-Noise(PN) matched filter. The probabilities of detection and false alarm are derived as a measure of the system performance in both nonfading and nonselective Rician fading channels. For received PN codes with different SNR, the proposed acquisition scheme is able to detect a desired threshold in the search mode so that this value is utilized as a threshold for the verification mode. Thus, there is no need to determine a threshold by applying the Neyman-Person ciriteron. It is shown that this scheme achieves lower probability of false alarm than the acquisition scheme based on the Neyman-Person criterion, giving comparable performance in terms of the probability of detection.