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간문부 담관암 환자에서 경피경관 양측성 금속 배액관의 효과
김금래,김주형,박원규,장재천,조재호,김태년,김준화,장병익 영남대학교 의과대학 2005 Yeungnam University Journal of Medicine Vol.22 No.2
Background: The purpose of this study was to determine the effectiveness of percutaneously place self-expanding metallic stent for the relief of biliary obstruction in patients with hilar cholangiocarcinoma. Materials and Methods: From November 2001 to December 2004, 48 patients with hilar cholangiocarcinoma were prospectively studied. After percutaneous placement of bilateral self-expanding, uncovered metallic stents, follow-up evaluation was carried out until July 2005. Results: There were 4 cased of Bismuth type Ⅱ,21 cases of Bismuth typeⅢa 8 cases of Bismuth type Ⅲb and 15 cases of Bismuth type Ⅳ. Stent placement was technically successful in all patients All patients had satisfactory biliary drainage, resulting in one week drainage rate of 72.8% and final drainage of 91.9% There were 12 cases (21.3%) of abdominal pain requiring analgesics and 1 case (7.1%) of cholangitis; both were successfully managed with conservative treatments. Late complications occurred in four patient (8.3%), including two patients with cholangitis, one patient with liver abscess, and one patient with biloma; all were appropriately managed by percutaneous drainage. The average length and median durations of stent patency and median survival time were 303 days (range, 60~815) and 338 days (range, 60 ~1175), respectively. Conclusion: Placement of a percutaneous metallic stent is an effective and safe method of palliation of patients with hilar cholangiocarcinoma.
Single Pulse-Width-Modulation Strategy for Dual-Active Bridge Converters
Byeng-Joo Byen,Byong-Hwan Jeong,최규하 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1
This paper describes a single pulse-width modulation control strategy using the Single Pulse-Width Modulation (SPWM) method with a soft-switching technique for a wide range of output voltages from a bidirectional Dual-Active Bridge (DAB) converter. This method selects two typical inductor current waveforms for soft-switching, and proposes a rule that makes it possible to achieve soft-switching without any compensation algorithm from the waveforms. In addition, both the step-up and step-down conditions are analyzed. This paper verifies that the leakage inductance is independent from the rule, which makes it easier to apply in DAB converters. An integrated algorithm, which includes step-up and step-down techniques, is proposed. The results of experiments conducted on a 50-kW prototype are presented. The system efficiency is experimentally verified to be from 85.6% to 97.5% over the entire range.
Byeng-Joo Byen,Chung-Hwan Ban,Young-Bae Lim,Gyu-Ha Choe 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.6
In order to control the output voltage in a dual active bridge converter, this paper establishes a theoretical inductor current equation for a dual-pulse-width-modulation scheme that ensures low switching loss. It also proposes a modulation strategy that minimizes conduction loss. When compared to the conventional single-pulse-width-modulation strategy, the proposed approach can reduce the inductor current RMS and improve efficiency in the low power region, as verified through simulation and experimental results.
Byeng-Joo Byen,Kyung-Pil Kang,Younghoon Cho,Anno Yoo 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
This paper proposes a variable modulation strategy for a dual-active-bridge (DAB) converter with a wide operating range to achieve high efficiency. In the propose method, four voltage modulation strategies are automatically changed for efficiency optimization under the operating voltage and the output power. To do this, the boundary conditions of each modulation region are derived to minimize the power loss, and a seamless mode transition algorithm between each modulation strategy is introduced. A 3kW DAB converter whose primary voltage is 380V and the secondary voltage ranges from 100V to 500V has been built. The experimental results show that the DAB converter with the proposed modulation strategy achieves peak 98.9% peak efficiency under 400V output voltage condition.
Dual SRF based Torque Ripple Mitigation Strategy for a Fault Tolerant PMSM Drive System
Byeng-joo Byen,Seunghoon Baek,Younghoon Cho,Gyu-Ha Choe 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
This paper presents a torque ripple mitigation strategy for the fault tolerant permanent magnet synchronous motor (PMSM) drive system, in which an auxiliary phase is employed. It is shown that the torque ripple whose frequency is twice the fundamental frequency is induced in the PMSM undergoing an open circuit fault on a certain phase. In order to compensate the torque ripple, current controllers are implemented in the dual synchronous reference frame (SRF), in which the rotating frequencies of the two SRF are different. In more detail, one of the SRFs rotates in two times of the fundamental frequency to actively compensate the torque ripple in the steady state while another one is synchronized to the fundamental component. Compared to traditional methods, the proposed algorithm effectively extends the operating speed of the PMSM where the torque ripple can be compensated. Both the simulations and the experimental results confirm the usefulness of the proposed torque ripple mitigation strategy.
Byeng-Joo Byen,Jung-Muk Choe,Gyu-Ha Choe 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.4
This study proposes high-performance voltage controller design that employs a capacitor current control model for single-phase stand-alone inverters. The single-phase stand-alone inverter is analyzed via modeling, which is then used to design the controller. A design methodology is proposed to maximize the bandwidth of the feedback controller. Subsequently, to compensate for the problems caused by the bandwidth limitations of the controller, an error transfer function that includes the feedback controller is derived, and the stability of the repetitive control scheme is evaluated using the error transfer function. The digital repetitive controller is then implemented. The simulation and experimental results show that the performance of the proposed controller is high in a 1.5 kW singlephase stand-alone inverter prototype.
변병주(Byeng Joo Byen),한동화(DH Han),서현욱(HU Seo),반충환(CH Ban),김동진(DJ Kim),최규하(GH Choe) 전력전자학회 2011 전력전자학술대회 논문집 Vol.2011 No.7
본 논문에서는 계통 연계형 단상 인버터의 데드타임을 보상할 수 있는 방법을 제안한다. 인버터의 데드타임 영향을 수식적인 분석을 통하여 고조파의 함유량을 정량적으로 파악하여 인버터 지령치에 보상신호를 더함으로써 출력 파형이 개선되는 것을 시뮬레이션으로 검증하였다.
Byen, Byeng-Joo,Ban, Chung-Hwan,Lim, Young-Bae,Choe, Gyu-Ha The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.6
In order to control the output voltage in a dual active bridge converter, this paper establishes a theoretical inductor current equation for a dual-pulse-width-modulation scheme that ensures low switching loss. It also proposes a modulation strategy that minimizes conduction loss. When compared to the conventional single-pulse-width-modulation strategy, the proposed approach can reduce the inductor current RMS and improve efficiency in the low power region, as verified through simulation and experimental results.