• Journal of Chest Surgery
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• v.17 no.2
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• pp.223-230
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• 1984

Since January 1977 to the end of September 1982, total 60 Ionescu-Shiley pericardial xenograft heart valves were implanted for valve replacement in 50 patients at the Han Yang University Hospital. The operative procedures were as follow: Mitral valve replacement [MVR] in 25 patients, Mitral valve replacement [MVR] and Tricuspid valve [TV] annuloplasty in 7 patients, Aortic valve replacement [AVR] in 8 patients, Aortic valve replacement [AVR] and Mitral valve replacement [MVR] in 8 patients. Aortic valve replacement [AVR] and Mitral valve replacement [MVR] and Tricuspid valve [TV] annuloplasty in 2 patients. To evaluate the immediate hemodynamic changes after valve replacements, the pressures of each cardiac chamber and ulmonary artery were checked before and after valve replacement on the operation table. Right ventricle [RV] pressure was decreased from 52.09\ulcorner6.71 to 45.57\ulcorner5.03 mmHg, Pulmonary artery [PA] pressure was decreased from 45.97\ulcorner2.69 to 41.00\ulcorner3.99 mmHg, and Left atrium [LA] pressure was decreased from 30.33\ulcorner13.02 to 22.76\ulcorner.97 mmHg before and after valve replacement. In MVR group, RV pressure was decreased from 49.17\ulcorner7.89 to 43.14\ulcorner4.14 mmHg, PA pressure was decreased from 44.67\ulcorner3.18 to 38.67\ulcorner2.85 mmHg, and LA pressure was decreased from 31.46\ulcorner13.47 to 21.91\ulcorner.17 mmHg. In AVR group, RV pressure was decreased from 53.0\ulcorner7.44 to 44.71 \ulcorner3.24 mmHg, PA pressure was decreased from 34.83\ulcorner0.73 to 31.86\ulcorner.36 mmHg, and LA pressure was not changed. In double valve replacement [MVR and AVR] group, RV pressure was decreased from 57.50\ulcorner3.82 to 42.50\ulcorner.80 mmHg, PA pressure was decreased from 51.17\ulcorner1.42 to 43.33\ulcorner4.53mmHig, and LA pressure was decreased from 34.33\ulcorner2.09 to 25.50\ulcorner0.21 mmHg. But in the group where MVR and TV annuloplasty were performed, preoperative RV and PA pressure were markedly increased and no pressure decrease in RV and PA noticed after valve replacement. This study shows good immediate postoperative hemodynamic results after valve replacement using Ionescu-Shiley xenograft valve except in the cases of MVR and TV annuloplasty and advanced disease with pulmonary hypertension.

• Journal of Chest Surgery
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• v.16 no.4
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• pp.602-614
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• 1983

Six hundred fourteen consecutive cases of bioprosthetic cardiac valve replacement performed during the period from March 1976 through December 1982 were reviewed. A total of 748 tissue valves [534 Ionescu-Shiley valves, 144 Hancock valves, 46 Angell-Shiley, and 24 Carpentier-Edwards] were implanted in 610 patients. Of these, 477 had single valve replacements [403 mitral, 60 aortic, and 14 tricuspid] including three REDO MVR and one REDO AVR. The remaining 129 had double valve replacements [95 AVR and MVR and 34 MVR and TVR] and 8 had triple valve replacement.592 cases were evaluated. Overall early mortality rate [within 30 days of operation] was 7.1% [6.2% in single valve replacement, 10.2% in double valve replacement, and 16.7% in triple valve replacement]. Leading causes of mortality were low cardiac output or myocardial failure and ventricular arrhythmias. The follow-up period was from one month to 7 years with a cumulative follow-up of 906.6 patient-years [mean 1.53 years]. The late mortality was 1.6%, 3.9%, 0%, 2.6%, 6.6% and 2.0% per patient-year for MVR, AVR, TVR or triple valve replacement, AVR+MVR, MVR+TVR and total, respectively. Actuarial analysis of late results including early mortalities indicates an expected survival rate of 87.6+1.8% at 3 years and 85.92.4% at 7 years for all cases. We also analyzed actuarial survival rate between groups of each valve replacement [AVR, TVR, Double valve, and Triple valve] and the tissue valve groups in MVR. We experienced 7 cases [0.77% per patient-year] of confirmed endocarditis, two of which were fatal. Valve failure-free rates calculated according to the confirmed cases were 97.5% at 4 years, 87.5% at 7 years, and 88.3% at 6 years for Ionescu-Shiley, Hancock and Angell-Shiley valves, respectively. The occurrence rate of thromboembolism was 2.0% per patient-year in total cases, although almost all the patients were given anticoagulant therapy for one year. The occurring rate in MVR was 1.5% and 2.7% per patient-year for Ionescu-Shiley and Hancock valve groups, respectively. The difference in actuarial rate free from thromboemboli between Ionescu-Shiley and Hancock groups was statistically significant [P value less than 0.001]. Thromboembolic events beyond the period of anticoagulation therapy mainly occurred in patients with atrial fibrillation. The actuarial thromboemboli free survival was 95.71.4% at 3 years and 80.17.3% at 7 years. The incidence of hemorrhagic complications was 1.2% per patient-year [fatality 0.55% per patient-year] for anticoagulated patients. Although our clinical data favorably compares with results from other reports, our results suggest that anticoagulant therapy be given on a short-term basis or not at all to hemodynamically stable patients. Long-term therapy with antiplatelet drugs is probably inevitable with patients who have thromboembolic risk factors [such as atrial fibrillation].

• Journal of the Korea Society of Computer and Information
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• v.17 no.12
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• pp.31-39
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• 2012

In this paper, we propose a microprocessor-based automatic voltage regulator(AVR) to reduce consumers' electric energy consumption and to help controlling peak demanding power. Hybrid Switching Automatic Voltage Regulator (HS-AVR) consist of a toroidal core, several tap control switches, display and command control parts. The coil forms an autotransformer which has a serial main winding and four parallel auxiliary windings. It controls the output voltage by changing the combination of the coils and the switches. Relays are adopted as the link switches of the coils to minimize the loss. To make connecting and disconnecting time accurate, relays of the circuit have parallel TRIACs. A software phase locked loop(PLL) has been used to synchronize the timings of the switches to the voltage waveform. The software PLL informs the input voltage zero-crossing and positive/negative peak timing. The traditional voltage transformers and AVRs have a disadvantage of having a large mandatory capacity to accommodate maximum inrush current to avoid the switch contact damage. But we propose a suitable AVR for every purpose in smart grid with reduced size and increased efficiency.

• Journal of Chest Surgery
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• v.54 no.5
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• pp.369-376
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• 2021

Background: Sutureless and rapid deployment valves for aortic valve replacement (AVR) were introduced in Korea in December 2016. This study evaluated changing trends in the prosthetic valves used for AVR in Korea after the introduction of sutureless and rapid deployment valves. Methods: From December 2016 to December 2018, 4,899 patients underwent AVR in Korea. After applying the exclusion criteria, 4,872 patients were analyzed to determine changes in the type of prosthetic valve used for AVR. The study period was divided into 5 groups corresponding to 5-month intervals. Results: The total number of AVR cases was 194.88±28.78 per month during the study period. Mechanical valves were used in approximately 27% to 33% of cases, and the proportion of mechanical valve use showed a tendency to decrease, with marginal significance overall (p=0.078) and significant decreases in patients less than 60 years of age and in men (p=0.013 and p=0.023, respectively). The use of sutureless valves increased from 13.4% to 25.8% of cases (p<0.001), especially in elderly patients (>70 years) and those requiring concomitant surgery. In a comparison between sutureless and rapid deployment valves, the use of Perceval S valves (a type of sutureless valve), gradually increased (p<0.001). Conclusion: After the introduction of sutureless and rapid deployment valves in Korea, the rate of use of these new valves remarkably increased, especially in elderly patients and those requiring concomitant surgery. Further studies should investigate the clinical outcomes of these new prostheses.

• NEWSLETTER 전기공업
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• no.5 s.5
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• pp.1-15
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• 1990

• 전기산업
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• v.1 no.2
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• pp.68-71
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• 1990

• NEWSLETTER 전기공업
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• no.99-10 s.227
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• pp.34-38
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• 1999

• 전기산업
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• v.5 no.3
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• pp.85-96
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• 1994

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.264-264
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• 2009

The sensitivity lighting of pendant type used Micro-controller AVR, embodiment method for Munsell chromaticity diagram system and adoption method for light source lens respectively. About a plan design of light fixture, LED circuit designed flow chart of circuits and LED driver of organizations in electron device. For used Solidworks soft ware program, LED light source must take a heat shink part and LED light fixture module for sensitivity lighting of pendant type into considerations

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2002.11a
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• pp.151-156
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• 2002

The output voltage of Synchronous Generator is regulated constantly by field current control in excitation system. A synchronous generator is equipped with an automatic voltage regulator(AVR), which is responsible for keeping the constant output voltage under normal operating conditions about various levels. High frequency PWM converter (Current Mode Control Buck converter) type excitation system for synchronous generator is able to sustain output voltage level properly when the fault condition happened. This paper deals with the design and evaluation of the excitation system controller for a synchronous generator to improve the steady state and transient stability. The simulation and experimental results show that the proposed excitation system is improve the respons time by the AVR(automatic voltage regulator) of 50kW synchronous generator that is applied the current mode control excitation system.