• Proceedings of the KIEE Conference
• /
• 2000.07a
• /
• pp.165-168
• /
• 2000

This paper describes the guideline of design and tuning of practical Micro 5KVA machine's digital AVR/PSS control parameters by using the computer models and testing on-line AVR step test of laboratory simulator under the no-load or load conditions. The suggested procedures can be also applied to the large scaled machine's AVR/PSS control parameter tuning in KEPCO system.

• Journal of Chest Surgery
• /
• v.57 no.3
• /
• pp.242-251
• /
• 2024

Background: This study compared the outcomes of surgical aortic valve replacement (AVR) in patients aged 50 to 70 years based on the type of prosthetic valve used. Methods: We compared patients who underwent mechanical AVR to those who underwent bioprosthetic AVR at our institution between January 2000 and March 2019. Competing risk analysis and the inverse probability of treatment weighting (IPTW) method based on propensity score were employed for comparisons. Results: A total of 1,580 patients (984 patients with mechanical AVR; 596 patients with bioprosthetic AVR) were enrolled. There was no significant difference in early mortality between the mechanical AVR and bioprosthetic AVR groups (0.9% vs. 1.7%, p=0.177). After IPTW adjustment, the risk of all-cause mortality was significantly higher in the bioprosthetic AVR group than in the mechanical AVR group (hazard ratio [HR], 1.39; 95% confidence interval [CI], 1.07-1.80; p=0.014). Competing risk analysis revealed lower risks of stroke (sub-distributional hazard ratio [sHR], 0.44; 95% CI, 0.28-0.67; p<0.001) and anticoagulation-related bleeding (sHR, 0.35; 95% CI, 0.23-0.53; p<0.001) in the bioprosthetic AVR group. Conversely, the risk of aortic valve (AV) reintervention was higher in the bioprosthetic AVR group (sHR, 6.14; 95% CI, 3.17-11.93; p<0.001). Conclusion: Among patients aged 50 to 70 years who underwent surgical AVR, those receiving mechanical valves showed better survival than those with bioprosthetic valves. The mechanical AVR group exhibited a higher risk of stroke and anticoagulation-related bleeding, while the bioprosthetic AVR group showed a higher risk of AV reintervention.

• Journal of Microbiology and Biotechnology
• /
• v.21 no.7
• /
• pp.679-685
• /
• 2011

Xanthomonas oryzae pv. oryzae (Xoo) produces a putative effector, XoAvrBs2. We expressed XoAvrBs2 homologously in Xoo with a TAP-tag at the C-terminus to enable quantitative analysis of protein expression and secretion. Addition of rice leaf extracts from both Xoo-sensitive and Xoo-resistant rice cultivars to the Xoo cells induced expression of the XoAvrBs2 gene at the transcriptional and translational levels, and also stimulated a remarkable amount of XoAvrBs2 secretion into the medium. In a T3SS-defective Xoo mutant strain, secretion of the TAPtagged XoAvrBs2 was blocked. Thus, we elucidated the transcriptional and translational expressions of the XoAvrBs2 gene in Xoo was induced in vitro by the interaction with rice and the induced secretion of XoAvrBs2 was T3SSdependent. It is the first report to measure the homologous expression and secretion of XoAvrBs2 in vitro by rice leaf extract. Our system for the quantitative analysis of effector protein expression and secretion could be generally used for the study of host-pathogen interactions.

• Journal of Chest Surgery
• /
• v.45 no.5
• /
• pp.295-300
• /
• 2012

Background: With growing attention to the aortopathy associated with aortic valve diseases, the number of candidates for accompanying ascending aorta and/or root replacement is increasing among the patients who require aortic valve replacement (AVR). However, such procedures have been considered more risky than AVR alone. This study aimed to compare the surgical outcome of isolated AVR and AVR combined with aortic procedures. Materials and Methods: A total of 86 patients who underwent elective AVR between 2004 and June 2010 were divided into two groups: complex AVR (n=50, AVR with ascending aorta replacement in 24 and the Bentall procedure in 26) and simple AVR (n=36). Preoperative characteristics, surgical data, intra- and postoperative allogenic blood transfusion requirement, the postoperative clinical course, and major complications were retrospectively reviewed and compared. Results: The preoperative mean logistic European System for Cardiac Operative Risk Evaluation (%) did not differ between the groups: $11.0{\pm}7.8%$ in the complex AVR group and $12.3{\pm}8.0%$ in the simple AVR group. Although complex AVR required longer cardiopulmonary bypass ($152.4{\pm}52.6$ minutes vs. $109.7{\pm}22.7$ minutes, p=0.001), the quantity of allogenic blood products did not differ ($13.4{\pm}14.7$ units vs. $13.9{\pm}11.2$ units). There was no mortality, mechanical circulatory support, stroke, or renal failure requiring hemodialysis/filtration. No difference was found in the incidence of bleeding (40% vs. 33.3%) which was defined as red blood cell transfusion ${\geq}5$ units, reoperation, or intentional delayed closure. The incidence of mediastinitis (2.0% vs. 0%), ventilator ${\geq}24$ hours (4.0% vs. 2.8%), atrial fibrillation (18.0% vs. 25.0%), mean intensive care unit stay (34.5 hours vs. 38.8 hours), and median hospital stay (8 days vs. 7 days) did not differ, either. Conclusion: AVR combined with additional aortic or root replacement showed an excellent outcome and recovery course equivalent to that after isolated AVR.

• Journal of Chest Surgery
• /
• v.21 no.5
• /
• pp.899-904
• /
• 1988

In Behcet syndrome, cardiac involvements are rare and have been reported pericarditis, myocarditis, right heart endocardial fibrosis, right ventricle mural thrombus with pulmonary embolism, active endocarditis, granulomatous endocarditis, conduction disturbance, acute aortic insufficiency, mitral valve prolapse. Our three patients underwent AVR because of aortic insufficiency and ascending aorta enlargement combined with Behcet syndrome. Two patients had mitral regurgitation too. So one underwent MAP and the other underwent MVR concomitantly. One who underwent AVR have been well for 50 months. Another who underwent AVR+MAP and redo AVR due to aortic paravalvular leakage was died of congestive heart failure. The other who underwent AVR+MVR and repeated AVR three times because of aortic paravalvular leakage is in condition of aortic paravalvular leakage. Paravalvular leakage is considered to recur due to progressive dilatation and fragility of aortic root that is the result of pathologic change of Behcet syndrome in it. If Open heart surgery is needed in Behcet`s syndrome during inflammatory reaction is active, postoperative complications such as paravalvular leakage or suture line rupture may be prevented with pre- and postoperative anti-inflammatory management.

• Proceedings of the KIEE Conference
• /
• 2015.07a
• /
• pp.183-184
• /
• 2015

디지털 AVR은 동기발전기의 출력전압을 부하변동에 관계 없이 일정하게 제어하며 발전기 및 시스템 보호를 위한 각종 제어 알고리즘을 포함하고 있다. 종래의 아날로그 타입 AVR은 제어 설정이 불편하고 제어 신뢰성이 떨어지기 때문에 점차 디지털 타입으로 교체되고 있는 실정이다. 본 논문에서는 디지털 타입의 AVR에 익숙하지 않거나 심화 학습이 필요한 정비 기술자의 교육에 활용할 수 있도록 디지털 AVR 시뮬레이터를 개발하였으며 제어기와 HMI 간의 UDP 통신을 위해 프로토콜 하드웨어 컨버터, HMI, 및 EWS를 개발하였다. 추가로 스마트 단말기에서도 운전 상황을 확인할 수 있는 OIS 앱을 개발하였다.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.50 no.8
• /
• pp.351-358
• /
• 2001

This paper deals with the PSS modeling of Ulchin N/P #1 as well as the generator and excitation system modeling by utilizing the recorded data from AVR step test, which has been performed by entering small voltage signal into the AVR summing point. In addition to it. two recorded results obtained from the AVR step test with PSS sunning and without PSS running have not only been compared each other on the time domain, but also they heve been analyzed with FFT analysis on the frequency domain; thus, the desirable effects of running PSS in Ulchin N/P #1 on power system have been explicitly confirmed. Finally, the derived PSS model parameters lead to good matches between simulation results and recorded data.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.8
• /
• pp.1383-1391
• /
• 2016

This paper is concerned with applicability of a new type of controllers, called i-PID and GPI in which unknown parts of the plant are taken into account without any modeling procedure, to automatic voltage regulator (AVR) system. First, the procedure for applying i-PID and GPI algorithms to AVR system is proposed, which uses model reduction technique based on the given information of AVR. Second, simulations are given to verify their effectiveness comparing to various PID algorithms including PIDD2 which is four-term controller, that is, consisting of PID and second order derivative terms. Superior response performances of i-PID and GPI in comparison to conventional PID controllers are shown. Moreover, i-PID can highly improve the system robustness with respect to model uncertainties, especially to load variations.

• Journal of Advanced Marine Engineering and Technology
• /
• v.40 no.1
• /
• pp.39-44
• /
• 2016

Automated voltage regulators (AVRs) are used on ships and offshore to automatically adjust the voltage based on real-time output voltage readings of the generator engine. Analog-type AVR was previously more commonly used, but is slowly being replaced with digital-type AVR because of increased demands of response time. This study presents a new digital AVR system that contains appropriate features of the AVR with respect to offshore unstable load conditions and poor operating conditions. Furthermore, experiments of load and voltage change prove the excellence of stability and response of the proposed system compared to previous AVR systems. Additionally, an integrated control system for a monitoring the output voltage and field current was developed to easily set the gain value.

• Proceedings of the KIEE Conference
• /
• 1996.11a
• /
• pp.91-94
• /
• 1996

A simulation procedure was developed for identifying Yungnam unit 2 excitation model parameters to improve the accuracy of stability simulation of KEPCO. First, generator model parameters are derived by using modified load rejection technique from measured load rejection test. For identifying excitation model parameters, switch was changed from MVR mode to AVR mode in Yungnam unit 2 excitation system instead of applying to a small step to the voltage reference($V_{ref}$) because of saving time and efforts, assuming the test result would show coincided result with applying to a small step to the $V_{ref}$. However, it was found that the response of switching from MVR to AVR is greatly different from it of applying small signal to the $V_{ref}$. A simulation procedure was needed to take into accounts of real AVR component status before and after switching from MVR to AVR. This paper reports the procedure which duplicated the measured response and addresses the merits of this test on conventional AVR step test.