• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.163-165
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• 2020

본 논문에서는 전해 커패시터 없이 DC충전이 가능한 단상/3상 겸용 전기자동차용 탑재형 충전기를 제안한다. 제안하는 충전기는 전해커패시터를 제거하고 필름 커패시터를 사용하여 높은 수명 및 전력밀도를 기대할 수 있으며, 단일단(Single-stage) 구조로서 스위칭 개수가 적어 가격 절감에 유리하다. 제안하는 Single-stage OBC는 기존 Single-stage OBC의 단상동작에서 발생하는 배터리 측의 120Hz 전류 성분을 추가 스위칭 소자 없이 APD(Active Power Decoupling)회로로 제거하여 단상에서도 배터리에 DC충전이 가능하다. 본 논문에서는 제안하는 OBC와 APD 동작원리를 제시하고 11kW 시작품을 통해 타당성을 검증하였다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.10
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• pp.95-102
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• 2003

The buffering is a promising solution to resolve the contention problem in optical network. we study the packet loss probability and the dimensioning of optical buffer using a Fiber Delay Line for variable length packet. In this paper, we study the relation between the granularity and the loss of FDL buffer in Single-Stage FDL buffer and propose the Single-Bundle Multi-Stage FDL buffer. The Multi-Stage FDL buffer is too early yet to apply to the current backbone network, considering the current technology in view of costs. but we assume that the above restriction will be resolved in these days. The appropriate number of delay and pass line for a dimensioning is based on a amount of occupied time by packets. Once more another multi-stage FDL buffer is proposed, Split-Bundle multi-stage FDL buffer. The Split-Bundle ms-FDL buffer is more feasible for a FDL buffer structure, considering not only a size of switching matrix but also a bulk of switching element. its feasibility will be demonstrated from a loss probability.

• Archives of Plastic Surgery
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• v.34 no.3
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• pp.336-341
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• 2007

Purpose: The most accepted method for the reanimation of a paralyzed face is the two-stage method that combines cross-face nerve grafting with free-muscle transfer. Although the results of reconstruction with this method are satisfactory, there is an excessive delay between the stages, which prolongs the period of rehabilitation. In order to overcome this drawback, a one- stage, neurovascular free-flap reconstruction method using free neurovascular muscle flaps is introduced. Methods: From 1994 to 2004, 35 patients with longstanding facial palsy were treated. Fifteen patients underwent the single-stage reconstruction with the latissimus dorsi muscle, and 20 patients underwent the two-stage reconstruction method with the gracilis muscle. We compared the long-term results of the two methods of reconstruction. The mean follow-up period was 28.7 months for one-stage reconstruction, and 35.2 months for the two-stage, respectively. Results: In the patient group of the single stage reconstruction, both mouth corner excursion and animation grade were markedly improved at the final postoperative visit. Moreover, the first muscle contraction occurred earlier in this group, than in the two-stage reconstruction group. However, four patients in the single stage group never achieved a first muscle contraction or mouth corner excursion. Conclusion: Facial palsy is a very challenging condition for cosmetic surgeons to deal with. Traditional methods for treatment of chronic facial palsy use a two-stage muscle flap which is time-consuming and burdensome to patients, many of whom are averse to waiting 8 to 12 months to complete the two stages. The one-stage reconstruction method described herein uses a latissimus dorsi free-flap and has demonstrated consistent positive outcomes in clinical assessments.

• Journal of Power Electronics
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• v.13 no.2
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• pp.206-213
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• 2013

In this paper, an improved passive snubber is investigated in a single-phase single-stage full-bridge boost power factor correction (PFC) converter, by which the voltage spike across primary side of the power transformer can be suppressed and the absorbed energy can be transferred to the output side. When compared with the basic passive snubber, the two single-inductors are replaced by a coupled-inductor in the improved snubber. As a result, synchronous resonances in the snubber can be achieved, which can avoid the unbalance of the voltage and current in the snubber. The operational principle of the improved passive snubber is analyzed in detail based on a single-phase PFC converter, and the design considerations of both the snubber and the coupled-inductor are given. Finally, a laboratory-made prototype is built, and the experimental results verify the feasibility of the proposed method and the validity of the theoretical analysis and design method.

• International Journal of Fluid Machinery and Systems
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• v.9 no.4
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• pp.338-353
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• 2016

Information on the surge behaviors and stall stagnation boundaries for a nine-stage axial flow compressor are summarized on the basis of analytical data in comparison with those for a single-stage one, with attention to the pressure ratio effect. The general trends of the surge loop behaviors of the pressure-mass flow are similar for both compressors including the fact that the subharmonic surges tend to appear very near the stall stagnation boundaries. With respect to the nine-stage compressor, however, the mild loops in the subharmonic surges tend to be very small in size relative to the deep loops, and at the same time, insufficient surge recovery phenomenon, which is a kind of subharmonic surge, appears also far from the stagnation boundary for relatively short delivery flow-paths. The latter is found to be a rear-stage surge caused by unstalling and re-stalling of the rear stages with the front-stages kept in stall in the stalled condition of the whole compressor, which situation is caused by stage-wise mismatching in the bottom pressure levels of the in-stall multi-stage compressor. The fundamental information on the stall stagnation boundaries is given by a group of normalized geometrical parameters including relative delivery flow-path length, relative suction flow-path length, and sectional area-pressure ratio, and by another group of normalized frequency parameters including relative surge frequencies, modified reduced resonance frequencies, and modified reduced surge frequencies. Respective groups of the normalized parameters show very similar tendency of behaviors for the nine-stage compressor and the single-stage compressor. The modified reduced resonance frequency could be the more reasonable parameter suggesting the flow-induced oscillation nature of the surge phenomena. It could give the stall stagnation boundary in a more unified manner than the Greitzer's B parameter.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.351-354
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• 1996

A zero-voltage-transition(ZVT) full bridge (FB) boost converter for single stage power factor correction (PFC) in distributed power system is proposed. A simple auxiliary circuit provides zero-voltage-switching(ZVS) condition to all semiconductor devices without imposing additional voltage and current stresses and loss of PWM capability. The proposed boost converter provides both input power factor correction and direct conversion from $110{\sim}220VAC$ line to 300VDC bus with single power stage. Operational principle, analysis of the proposed converter are described and verified by computer simulation and experimental results from a 1.5 kW, 80 kHz laboratory prototype.

• Journal of Korean Society of Water and Wastewater
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• v.12 no.2
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• pp.106-114
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• 1998

In this research, single-, two- and four-stage intermittently aerated activated sludge system were investigated for simultaneous removal of nitrogen and phosphorus with swine wastewater. For the comparison of removal efficiency, conventional activated sludge system was operated. Operational conditions of intermittently aerated activated sludge system were SRT 20day, HRT 24hr and aeration/nonaeration time 1hr/1hr, respectively. Nitrogen and phosphorus removal efficiency in Intermittently aerated activated sludge system was upgraded compare with conventional activated sludge system. In single-stage intermittently aerated activated sludge system, release-uptake of $PO_4^{3-}-P$ was observed very well but, phosphosrus removal in effluent was not effective. In single-stage intermittently aerated activated sludge system, release-uptake of $PO_4^{3-}-P$ in first reactor, was observed very well but, in following reactor, $PO_4^{3-}-P$ concentation showed almost no change. T-N removal efficiency in conventional activated sludge system, single-, two-, and four-stage intermittently aerated activated sludge system were 48, 87, 90.9 and 95.5%, respectively, and phosphorus removal efficiency were 48, 75, 97 and 95%, respectively. Intermittently aerated activated sludge system as a alternative processes of conventional system leads to meet satisfactory effleunt with only on/off aeration regulation and save energy for aeration.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.7
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• pp.60-66
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• 2005

This paper presents the single-stage TSFC(Two-Switch Forward Converter). Recently, due to growing concern about the harmonic pollution of power distribution systems and the adoption of standards such as ICE 61000-3-2 and IEEE 519, There is a need to reduce the harmonic contests of AC line currents of power supplies. This research proposed the single-stage two switch forward circuit for low voltage and high current output. The principle of operation, feature and design considerations is illustrated and verified through the experiment with a 200[W](5[V], 40[A]) 100[kHz] MOSFET based experimental circuit.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.2
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• pp.84-94
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• 2013

In case when the existing TRIAC phase controlled dimmer is drove for the LED lighting equipments, there are many problems such as the LED flicker in low phase-angles, the acoustic noise and elements damage by increase of the peak voltage in the input filter capacitor, mulfunction by insufficiency of the TRIAC holding current, and the abnormal oscillation by LC resonant. In this paper, we proposes the single-stage quasi-resonant PSR(Primary Side Regulation) PWM converter, and the design, the simulation and experiment are performed. As a result, it could confirm that the proposed PWM converter is the lighting equipments for LED drive which can alternate the existing 60W class incandescent bulbs and it has the high drive performance of the efficiency 80% and over, the power factor 0.95 and over under the normal voltage 220V. Finally, total harmonic distortion(THD) is gratified with a standard[1] of the lighting equipments and the durability is evaluated as the high reliablilty of 150,000 hours and over.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.541-543
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• 2008

현재 폭넓은 시장을 형성하고 있는 LED는 전 세계적으로 이슈화 되고 있는 친환경 조명기기로 각광받고 있으며, 향후 조명 산업의 50% 이상 시장 점유율을 차지할 것으로 예상된다. 본 논문에서는 Analog Dimming을 이용하여 Single-stage LED 구동 회로를 제안한다. 제안된 회로는 기존 방식과 달리 DC/DC단이 없으므로 가격 경쟁력 및 높은 전력 변환 효율을 확보할 수 있고, 고조파 규제 만족을 위한 역률 보정 기능이 있으며 휘도를 선형적으로 제어할 수 있는 Analog Dimming 기능을 가지고 있다. 최종적으로 제안된 Single-stage LED 구동 회로의 동작 및 Analog Dimming 제어 기법을 소개하고, 시뮬레이션 및 40W급 시작품을 제작, 동작 실험을 통하여 그 타당성을 검증한다.