• 조명전기설비학회논문지
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• 제19권8호
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• pp.102-108
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• 2005

본 논문에서는 소프트 스위칭에 의한 새로운 고역률 승압형 AC-DC 컨버터가 제안되고 입력전류의 파형 및 고조파분석에 대해 상세히 해석된다. 시비율 일정의 전류불연속 제어에 의해 동작되는 제안된 컨버터의 입력전류는 교류 입력전압의 크기에 비례한 불연속적인 펄스열의 정현파 형태로 되어 입력역률을 개선시킨다. 또한 제안된 컨버터는 소프트 스위칭을 위한 공진동작에 의해 무손실 스너버 커패시터의 입력측 에너지 유입에 따른 역률증대의 효과를 가지며, 기존의 고역률 승압형 AC-DC 컨버터와 비교되어 입력전류의 수학적 분석과 컴퓨터 시뮬레이션, 실험결과 등에 의해 그 우수성이 입증된다.

• Journal of Power Electronics
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• 제15권2호
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• pp.309-318
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• 2015

This study proposes a dual-output single-stage bridgeless single-ended primary-inductor converter (DOSSBS) that can completely remove the front-end full-bridge alternating current-direct current rectifier to accomplish power factor correction for universal line input. Without the need for bridge diodes, the proposed converter has the advantages of low component count and simple structure, and can thus significantly reduce power loss. DOSSBS has two uncommon output ports to provide different voltage levels to loads, instead of using two separate power factor correctors or multi-stage configurations in a single stage. Therefore, this proposed converter is cost-effective and compact. A magnetically coupled inductor is introduced in DOSSBS to replace two separate inductors to decrease volume and cost. Energy stored in the leakage inductance of the coupled inductor can be completely recycled. In each line cycle, the two active switches in DOSSBS are operated in either high-frequency pulse-width modulation pattern or low-frequency rectifying mode for switching loss reduction. A prototype for dealing with an $85-265V_{rms}$ universal line is designed, analyzed, and built. Practical measurements demonstrate the feasibility and functionality of the proposed converter.

• Journal of Electrical Engineering and Technology
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• 제11권4호
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• pp.905-914
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• 2016

This paper proposes a new phase current reconstruction technique for interleaved three-phase bidirectional dc-dc converters using a single current sensor. In the proposed current reconstruction algorithm, a single current sensor is employed at the dc-link, and the dc-link current information is sampled at either the peak or valley point of the pulse-width modulation (PWM) carriers regularly. From the obtained current information, all phase currents are reconstructed in a single PWM cycle. After that, the digital current controller is applied to achieve current balancing in each phase. Compare to the previous multiple current sensor method, the proposed strategy reduces the number of the current sensors in the interleaved three-phase bidirectional converter as well as reducing potential current sensing error caused by non-ideal characteristics of the multiple current sensors. The effectiveness of the proposed method is verified from the experiments based on a 3kW three-phase bidirectional converter prototype for the automotive battery charging application.

• 한국재료학회지
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• 제16권10호
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• pp.639-646
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• 2006

Over the last two decades, microbiologically influenced corrosion (MIC) of metallic materials has received considerable attention due to its serious effects on industrial field. In this context, it is important to devise control methods which inhibit biofilm formation on various metallic compounds and are compatible with environment. It was change of various conditions (duty cycle, current density, $AgNO_3$ concentration and pH) for injection of Ag particles in anodized Aluminum alloy pore using pulsed current. Optimal condition was obtained by means of FE-SEM, ICP analysis etc. The antibacterial metal's specimen were manufactured under optimal condition and this specimen were tested the antibacterial characterization and anticorrosion characterization. In result of test, we can confirmed that the antibacterial characterization and anticorrosion characterization of the specimens of injected Ag particles in anodized Aluminum alloy pore using pulsed current were better than the anodized Aluminum alloy specimens.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권12호
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• pp.3182-3196
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• 2012

In this paper, we present a new LED (Light Emitting Diode) mood lighting system interacting with smartphones based on the generation of different light sequences. In the proposed system, one light sequence is considered to be one unit of the service contents, which is then transmitted through a network and played in an LED lighting system. To this end, we propose a novel generation scheme using a smartphone, and a decoding/playing mechanism in an LED lighting system. The lighting sequences have a fixed period divided into predefined time units. Two modes - basic and interpolation - are supported in each time unit when playing a color sequence. In the basic mode, the color is maintained for the entire time unit, whereas in the interpolation mode the color is interpolated. The sequence is decoded and played in the lighting circuit by changing the duty cycle of a PWM (Pulse Width Modulation) signal. A demonstration system of the overall proposed method was using smartphones, a server and an LED lighting system. The results from this experiment show the validity and applicability of the proposed scheme.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.326-329
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• 2008

DARPA가 계획 중인 대형 극초음속 추진 기관 개발 프로그램 VULCAN 프로그램은 듀얼모드 램제트/스크램제트 엔진과 연계되어 TBCC엔진을 이룰 수 있도록, 기존의 터보제트(또는 터보팬) 엔진과 CVC과 엔진을 결합하여 마하수 4이상에서 작동 가능한 엔진을 개발하는 것을 목표로 하고 있다. CVC 엔진은 데토네이션 연소 현상을 기본으로 하여 고마하수에서 고효율을 얻을 수 있는 PDE 이나 CDE와 같은 신개념의 엔진이다. 본 논문에서는 부산대학교 항공우주공학과 연소 추진 연구실에서 지난 수년간 국제공동 연구의 형태로 수행한 데토네이션 현상의 추진기관 응용에 연구에 대하여 소개한다.

• 반도체디스플레이기술학회지
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• 제20권3호
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• pp.22-26
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• 2021

Thin-film encapsulation (TFE) technology is most effective in preventing water vapor and oxygen permeation in the organic light emitting diodes (OLED). Of those, a laminated structure of Al₂O₃ and MgO were applied to provide efficient barrier performance for increasing the stability of devices in air. Atomic layer deposition (ALD) method is known as the most promising technology for making the laminated Al₂O₃/MgO and is used to realize a thin film encapsulation technology in organic light-emitting diodes. Atomic layer deposited inorganic films have superior barrier performance and have advantages of excellent uniformity over large scales at relatively low deposition temperatures. In this study, the control system of the MgCP₂ precursor for the atomic layer deposition of MgO was established in order to deposit the MgO layer stably by the injection time of second level and the stable heating temperature. The deposition rate was obtained stably to be from 4 to 10 Å/cycle using the injection pulse times ranging from 3 to 12 sec and a substrate temperature ranging from 80 to 150 ℃.

• 한국정밀공학회지
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• 제11권2호
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• pp.32-40
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• 1994

In this study by using EMAT(electro magnetic acoustic transducer)the artificial slit is installed on 12B-SUS pipe test piece. By making 4 cycle SH-burst (EMA) incidence to 45 .deg. angle, the signal data of pulse, received from EMAT are translated into digital-signal-processing- method SSP(Split Spectrum Processing) and Deconvolution method. The main conclusions obtained are as follows; (1) the signal data received from EMAT are translated with digital signal proc- essing of SSP-method and Deconvolution-method and this method shows exellent results more than Ultrasonic testing method does; (2) noise can well be removed by SSP with signal data, and resolution and S/N ratio are advanced; (3) when used with Ultrasonic wave general stainless steel has proporties of multiscattering and reflection phenomena, but resolution is progressed by using Deconvolution method;and (4) as addition-averaging-processing mumber is increasing, the resolution and S/N ratio are improved and the satisfactory signal is obtained.

• International Journal of Automotive Technology
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• 제8권4호
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• pp.437-444
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• 2007

This paper experimentally investigates the effects of oxygen-enriched air (OEA) on the running behaviors of an LPG SI engine during both start/warm-up (SW) and hot idling (HI) stages. The experiments were performed on an air-cooled, single-cylinder, 4-stroke, LPG SI engine with an electronic fuel injection system and an electrically-heated oxygen sensor. OEA containing 23% and 25% oxygen (by volume) was supplied for the experiments. The throttle position was fixed at that of idle condition. A fueling strategy was used as following: the fuel injection pulse width (FIPW) in the first cycle of injection was set 5.05 ms, and 2.6 ms in the subsequent cycles till the achieving of closed-loop control. In closed-loop mode, the FIPW was adjusted by the ECU in terms of the oxygen sensor feedback. Instantaneous engine speed, cylinder pressure, engine-out time-resolved HC, CO and NOx emissions and excess air coefficient (EAC) were measured and compared to the intake air baseline (ambient air, 21% oxygen). The results show that during SW stage, with the increase in the oxygen concentration in the intake air, the EAC of the mixture is much closer to the stoichiometric one and more oxygen is made available for oxidation, which results in evidently-improved combustion. The ignition in the first firing cycle starts earlier and peak pressure and maximum heat release rate both notably increase. The maximum engine speed is elevated and HC and CO emissions are reduced considerably. The percent reductions in HC emissions are about 48% and 68% in CO emissions about 52% and 78%; with 23% and 25% OEA, respectively, compared to ambient air. During HI stage, with OEA, the fuel amount per cycle increases due to closed-loop control, the engine speed rises, and speed stability is improved. The HC emissions notably decrease: about 60% and 80% with 23% and 25% OEA, respectively, compared to ambient air. The CO emissions remain at the same low level as with ambient air. During both SW and HI stages, intake air oxygen enrichment causes the delay of spark timing and the increased NOx emissions.

• Tuberculosis and Respiratory Diseases
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• 제50권4호
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• pp.415-425
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• 2001

배 경 : 폐기종의 중증도 판정에 있어서 병리학적 기준은 기강(air space)의 확장 정도에 있으며, 이는 고해상도 전산화 촬영 (high resolution computed tomography, HRCT)에 의해 결정되는 폐기종 점수(emphysema scoring)와 좋은 상관성을 보인다는 것은 주지의 사실이다. 한편 폐기종의 주증상은 운동성 호흡곤란이므로 폐기종에 대한 임상적 평가는 운동능력의 감소를 측정하는 것이 타당하다고 알려져 있다. 그러나 대개의 경우 폐기종의 중증도 판정은 안정시 폐기능 검사에 의존하는 경우가 흔하며, 병리학적 중증도 판정과 상관성이 높다고 알려져 있는 고해상도 전산화 촬영에 의한 폐기종 점수와 운동부하 폐기능검사 지표들과의 상관성 여부에 대한 연구는 드문 실정이다. 이에 본 연구에서는 폐기종의 중증도 판정에 있어서 HRCT와 안정시 폐기능 검사 및 운동부하 폐기능 검사간에 상호 관련성을 확인하여 보았다. 방 법 : 평균 연령 $60.6{\pm}10.3$세인 14명의 폐기종 환자들을 대상으로 HRCT, 안정시 폐기능 검사(forced expiratory flow volume curve, lung volumes by He dilution method, DLco, ABGA), 그리고 점진적운동부하폐 기능검사(incremental cycle ergometer)를 시행하였으며 HRCT는 GE highlight를 이용하여 조영증강 없이 최대흡기시에 1.5mm collimation, 10mm 간격으로 폐전체를 스캔하였고, 환자마다 모든 스캔에서 density mask를 이용하여 -400 HU를 기준으로 한 총폐면적과 -900 HU를 기준으로 한 폐기종 면적을 각각 구하여 백분율로 환산하여 폐기종 점수를 구하였다. 결 과 : 평균 폐기종 점수는 $37.4{\pm}14.9%$ 이었다. 폐기종 점수와 안정시 폐기능 검사의 DLco(r=-0.75)와 $PaO_2$(r=-0.66) 사이에서만 유의한(p<0.05) 상관성이 관찰되었다. 반면 폐기종 점수와 운동부하폐기능 지표들간의 상관성은 최대 산소섭취량(r=-0.68), 혐기성 역치(V-slope method, r=-0.690), 최대운동부하(r=-0.74), 최대운동시 $O_2$ pulse(r=-0.73), 최대운동시의 생리적 사강비율 (r=0.80) 등과 높은 유의성 (p<0.01)을 나타내었다. 그러나 호흡예비율과 심박수 예비율간에서는 유의한 상관성이 없었고, pulse oxymeter로 측정한 산소포화도와의 상관성도 유의하지 않았다. 결 론 : 이상의 결과에서 폐기종의 병리학적 중증도를 잘반영한다고 알려진 HRCT 폐기종 접수는 폐기종에 의한 생리학적 장애를 잘 반영하는 운동부하 폐기능 검사의 주요 지표들과 유의한 상관성이 있음을 확인할 수 있었다.