• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.3
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• pp.225-233
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• 2004

In this study, the seismic safety of containment building is assessed using response surface method. The structural analyses considering random variables such as load, resistance and analysis by ABAQUS are performed to obtain the structural response. The structural response is represented by polynomial of random variables, and the reliability analysis is performed by Level II method. Drucker-Prager failure criterion is applied as limit state function to take bi-axial stress states into account in the concrete. The lifetime probability of failure is evaluated by considering the lifetime of containment building, the annual occurrence rate of earthquake and the conditional probability of failure. Also the sensitivity analysis on the selection of sampling points is performed to obtain the steady results from response surface method.

• Journal of Chest Surgery
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• v.20 no.2
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• pp.289-299
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• 1987

A total of 1,239 patients had cardiac valve replacement using 1,514 substitute valves at Seoul National University Hospital from 1968 to 1986. Of the total substitute vales, 84.9% were the glutaraldehyde-treated xenograft valves. Six hundred ninety-four patients who had 820 bioprosthetic tissue valves were studied for their clinical characteristics. They were a total and consecutive cases to the end of the study. Four hundred sixty-four patients had the lonescu-Shiley pericardial valves: MVR 291, AVR 66 and MVR+AVR 107; 163 had the Hancock porcine valves; 46 had the Angell-Shiley porcine valves; and 21 had the Carpentier-Edwards porcine valves. Five hundred forty patients underwent single valve replacement: MVR 460, AVR 76 and TVR 4; 154 had multiple valve replacement: MVR+AVR 141, MVR+TVR 12 and one triple valve replacement. Additional surgery was necessary in 22.3% of the cases. Operative mortality rate within 30 days of surgery was 6.77% for the total patients: 5.2% and 4.2% with MVR, 13.6% and 12.5% with AVR, and 7.5% and 7.4% with MVR+AVR using the lonescu and the Hancock valves respectively. A linealized annual late mortality rate was 2.56%/patient-year. Six hundred forty-three operative survivors were followed up for a total of 1482.7 patient-years [a mean 27.7 months], and the follow-up rate was 67.7%. The Idealized complication rates were: 2.02% emboli/patient-year, 0.94% bleeding/patient-year, 1.21% endocarditis/patient-year, and 3.84% overall valve failure/patient-year. A linealized rate of primary tissue failure was 0.87%/patient-year. Actuarial survival rates including the operative mortality were: 87.8*2.6%, 82.3*4.9% and 82.2*4.7% with MVR, AVR and MVR+AVR using the lonescu valves at 4 years after surgery respectively; and they were 88.0*4.1% with MVR at 8 years, 82.3*4.9% with AVR at 4 years and 84.9*7.0% with MVR+AVR at 6 years after surgery using the Hancock valves respectively. Probabilities of freedom from thromboembolism were 89.8*6.3% with MVR using the lonescu valves at postoperative 5 years and 89.2*3.8% with MVR using the Hancock valves at postoperative 7 years, and 93.3*3.9% with AVR using the lonescu valves at postoperative 5 years. None had embolic complication after AVR using the Hancock valves. Probabilities of freedom from valve failure [according to the Stanford criteria] were 81.0*7.1% with MVR using the lonescu valves at postoperative 4 years and 57.4*12.5% with MVR using the Hancock valves at postoperative 9 years. These clinical results prove the excellent antithrombogenicity of the glutaraldehyde-treated xenograft substitute valves and confirm the previously speculated rate of tissue failure. At the present situation, it may be concluded that there is a room for the further development of more durable bioprosthetic valves.

• The Journal of Advanced Prosthodontics
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• v.8 no.3
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• pp.194-200
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• 2016

PURPOSE. The prospective follow-up aimed to assess the performance of lithium disilicate crowns and clinical reasons of adverse events compromising survival and quality. MATERIALS AND METHODS. 58 patients were treated with 375 heat-pressed monolithic crowns, which were bonded with resin cement. Annual recalls up to five years included a complete dental examination as well as quality assessment using CDA-criteria. Any need for clinical intervention led to higher complication rate and any failure compromised the survival rate. Kaplan-Meier-method was applied to all crowns and a dataset containing one randomly selected crown from each patient. RESULTS. Due to drop-outs, 45 patients (31 females, 14 males) with the average age of 43 years (range = 17-73) who had 327 crowns (176 anterior, 151 posterior; 203 upper jaw, 124 lower jaw) were observed and evaluated for between 4 and 51 months (median = 28). Observation revealed 4 chippings, 3 losses of retention, 3 fractures, 3 secondary caries, 1 endodontic problem, and 1 tooth fracture. Four crowns had to be removed. Survival and complication rate was estimated 98.2% and 5.4% at 24 months, and 96.8% and 7.1% at 48 months. The complication rate was significantly higher for root canal treated teeth (12%, P<.01) at 24 months. At the last observation, over 90% of all crowns showed excellent ratings (CDA-rating Alfa) for color, marginal fit, and caries. CONCLUSION. Heat pressed lithium disilicate crowns showed an excellent performance. Besides a careful luting, dentists should be aware of patients' biological prerequisites (grade of caries, oral hygiene) to reach full success with these crowns.

• The Korean journal of internal medicine
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• v.39 no.2
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• pp.295-305
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• 2024

Background/Aims: The prognosis of patients with idiopathic pulmonary fibrosis (IPF) and respiratory failure requiring mechanical ventilation is poor. Therefore, mechanical ventilation is not recommended. Recently, outcomes of mechanical ventilation, including those for patients with IPF, have improved. The aim of this study was to investigate changes in the use of mechanical ventilation in patients with IPF and their outcomes over time. Methods: This retrospective, observational cohort study used data from the National Health Insurance Service database. Patients diagnosed with IPF between January 2011 and December 2019 who were placed on mechanical ventilation were included. We analyzed changes in the use of mechanical ventilation in patients with IPF and their mortality using the Cochran-Armitage trend test. Results: Between 2011 and 2019, 1,227 patients with IPF were placed on mechanical ventilation. The annual number of patients with IPF with and without mechanical ventilation increased over time. However, the ratio was relatively stable at approximately 3.5%. The overall hospital mortality rate was 69.4%. There was no improvement in annual hospital mortality rate. The overall 30-day mortality rate was 68.7%, which did not change significantly. The overall 90-day mortality rate was 85.3%. The annual 90-day mortality rate was decreased from 90.9% in 2011 to 83.1% in 2019 (p = 0.028). Conclusions: Despite improvements in intensive care and ventilator management, the prognosis of patients with IPF receiving mechanical ventilation has not improved significantly.

• Journal of Chest Surgery
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• v.17 no.3
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• pp.346-355
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• 1984

77 cases of Aortic Valve Replacement, which were composed of 64 rheumatic valvular heart disease and 13 combined congenital heart disease, were operated at Seoul National University Hospital for Aortic valvular disease during the period from June 1968 to December 1983. Among these 64 rheumatic aortic valvular heart disease cases, 8 patients were expired during and immediate after operation and overall mortality rate was 12.5%. For more precise remarks, these patients were divided into two periodic groups, 1st period [from 1968 to 1976] and 2nd [from 1977 to 1983] when annual open heart surgery were over 100 cases, and in 1st period three of four patients were died and in 2nd period five of sixty patients were died and its mortality rate was 8.3%. There were 12 cases of postoperative complication, which were 3 cases of remaining other valvular heart disease required MVR, 2 paravalvular leaks [one of them got Redo AVR], 4 thromboembolism or problem of anticoagulant therapy, 2 late death due to SBE with replaced valve failure and one functional AS with small sized valve. Operative death was affected by pump-time and aortic cross-clamping time, heart size, Ejection Fraction, LVEDP and symptom duration, and other many factors may influence the survival rate. Improved operative technique and myocardial protection and meticulous evaluation of the preoperative patient status will make the AVR safer.

• Journal of Chest Surgery
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• v.25 no.5
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• pp.494-503
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• 1992

The durability of the xenograft cardiac substitute valves is of a great concern on the clinical grounds. Four groups of tc tal and consecutive patients to the end of study operated on between 1976 and 1984 were Group ISM, 291 patients of MVR, ISA, 65 patients of AVR, and ISMA, 107 patients of MVR+AVR with the standard Ionescu-Shiley bovine pericardial valve, and H, 163 patients of valve replacement with the Hancock porcine aortic vlave. Operative mortality was 5.2%[ISM], 10.8%[ISA], 7.5%[ISMA] and 6.1%[H]. Early survivors were followed up for a total of 1148.3 patient-years[pt-yrs] [ISM], 271.2 pt-yrs [ISA], 488.1 pt-yrs[ISMA] and 822.9 pt-yrs[H]. Linearized late mortality was 2.1% /pt-yr [ISM], 1.l%/pt-yr[ISA], 1.8%/pt-yr[ISMA] and 1.8% /pt-yr[H]. Thromboembolic complication was experienced at the linearized rate of 1.045% /pt-yr [ISM], 1.475%/pt-yr[ISA], 0.615%/pt-yr[ISMA] and 1.822%/pt-yr[H], and bleeding complication at the rate of 0.871% /pt-yr[ISM], 0.63% /pt-yr[ISA], 0.205% /pt-yr [ISMA] and 0.729%a /pt-yr[H], respectively. Prosthetic valve endocarditis occurred at the rate of 0.610% /pt-yr[ISM], 1.475% /pt-yr[ISA], 1.639% /pt-yr[ISMA] and 0.972% /pt-yr[H]. The linearized annual incidence of primary tissue failure was 1.655%/pt-yr[ISM], l. 475%/pt-yr[ISA], 1.639% /pt-yr[ISMA], 2.187% /pt-yr[H] and 1.785% /pt-yr[Group HM : MVR with Hancock valve]. The incidence of tissue failure was significantly high in the patients younger than 30 years of age compared with the older patients. The actuarial survival was 87.7$\pm$2.5% at 10 years[ISM], 94.3$\pm$3.2% at 11 years[ISA], 89.6$\pm$3.4% at 10 years[ISMA] and 81.3$\pm$6.6% at 12 years[HM], The freedom from thromboembolism was 93.2$\pm$2.0% at 10 years[ISM], 90.6$\pm$4.6% at 11 years[ISA], 95.8$\pm$2.6% at 10 years[ISMA] and 80.9$\pm$11.1% at 12 years[HM], And, the freedom from primary tissue failure was 84.2$\pm$3.8% and 28.1$\pm$23.0% at 9 and 10 years[ISM], 60.4$\pm$16.9% at 11 years[ISA], 62.3$\pm$12.7 at 10 years[ISMA] and 65.6$\pm$9.8% at 12 years[HM]. In conclusion, the standard Ionescu-Shiley and the Hancock bioprosthetic valves are excellent in their antithrombogenicity and long-term survival. However, the features of the structural failure with the prolonged follow-up beyond 10 years appear to be guarding, and the clinical indications of these bioprostheses seem to be quite limited.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.360-362
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• 2003

In operation of distribution system, DGs(Distributed Generations) are installed as an alternative of extension and establishment of substations, transmission and distribution lines according to increasing power demand. Optimal capacity and allocation of DGs improve power quality and reliability. This paper proposes a method for determining the optimal number, size and allocation of DGs needed to minimize operation cost of distribution system. Capacity of DGs for economic operation of distribution system can be estimated by the load growth and line capacity during operation planning duration. DG allocations are determined to minimize total cost with failure rate and annual reliability cost of each load point using GA(Genetic Algorithm).

• International Journal of Internet, Broadcasting and Communication
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• v.16 no.3
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• pp.329-333
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• 2024

With increasing applications of technologies developed in the Fourth Industrial Revolution, data have come to replace important knowledge and experience in the agricultural field. Although data-based smart agriculture is growing at an average annual rate of 8.57%, research on ways to utilize data produced alongside is remains insufficient. Because such data may considerably help stakeholders involved in agricultural activities, we deployed the prosumer concept to revitalize agricultural data. We systematically structured and defined three relevant entities: the prosumer, which produces and consumes agricultural data; the database, which systematically processes and integrates agricultural data; and the consumer, which utilizes agricultural data in various ways. Our framework is designed to help stakeholders use agricultural data to improve the quality of crops, minimize the failure of agricultural activities, quickly adapt to new environments and methods of crop production, and find effective solutions to relevant issues.

• Earthquakes and Structures
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• v.13 no.2
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• pp.151-164
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• 2017

This article aims to investigate the possible retrofitting of a deficient building with soft story failure mode by connecting it to an adjacent building which is designed based on current code with friction dampers at all floors. Low cost and high performance reliability along with significant energy dissipation pertaining to stable hysteretic loops may be considered in order to choose the proper damper for connecting adjacent buildings. After connecting two neighbouring floors by friction dampers, the sliding forces of dampers at various stories are set in two arrangements: uniform sliding force and then variable sliding force. In order to account for the stochastic nature of the seismic events, incremental dynamic analyses are employed prior and after the installation of the friction dampers at the various floors. Based on these results, fragility curves and mean annual rate of exceedance of serviceability and ultimate limit states are obtained. The results of this study show that the collapse mode of the deficient building can affect the optimum arrangement of sliding forces of friction dampers at Collapse Prevention (CP) performance level. In particular, the Immediate Occupancy (IO) performance level is not tangible to the sliding force arrangement and it depends solely on sliding force value. Generally it can be claimed that this rehabilitation scheme can turn the challenge of pounding two adjacent buildings into the opportunity of dissipating a large amount of the seismic input energy by the friction dampers, thus improving significantly the poor seismic performance of the deficient structure.

• Journal of Arbitration Studies
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• v.17 no.1
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• pp.137-155
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• 2007

Since China joined the WTO, the trade between Korea and China has continued to grow by leaps and bounds, making both nations become mutually important trading partners to each other. The volume of trades with China showed a rapid upward trend with an average annual increase rate of 20% and the resultant dispute is also rising. Thus, this study was aimed to make some suggestions and come up with ways of responding claims by surveying Korean trading firms which have experience in making transactions with China to investigate the current status and the actual condition of their occurrence. As a result of this study, firstly, the main cause of such dispute was shown to be the failure to perform the agreement. Secondly, there were malty verbal agreements and due to a deterioration of trust in Chinese firms, the method of a letter of credit was adopted by many Korean firms. Thirdly, the payment and credit appeared to be most important in transactions with China. A credit inquiry is a must in future transactions with China. Fourthly, the indirect cause of the occurrence of trade claims was the difference in commercial practices and as for the way of settling disputes, the agreement through negotiations between the parties involved was the most. Fifthly, small and medium firms should make more of their credit and English proficiency than large ones do.