• Journal of Chest Surgery
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• v.56 no.5
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• pp.359-361
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• 2023

Coronary ostium obstruction due to dislodgement of the prosthetic valve is a rare and life-threatening complication, and particular caution is required for sutureless aortic valve replacement (AVR) with concomitant valvular surgery. In general, coronary artery bypass surgery is performed when coronary ostium obstruction occurs after AVR, but other options may need to be considered in some cases. Herein, we present a case of coronary artery occlusion in an 82-year-old female patient who had undergone AVR and mitral valve replacement for aortic valve stenosis and mitral valve stenosis at the age of 77 years. A hybrid procedure involving redo AVR and percutaneous coronary intervention after left main coronary ostium endarterectomy was performed. To summarize, we present a case of hybrid AVR in a patient with coronary artery obstruction after AVR that was successfully managed using this method.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.145-145
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• 2021

Water distribution networks (WDNs) are designed to satisfy water requirement of an urban community. One of the central issues in human history is providing sufficient quality and quantity of water through WDNs. A WDN consists of a great number of pipelines with different ages, lengths, materials, and sizes in varying degrees of deterioration. The available annual budget for rehabilitation of these infrastructures only covers part of the network; thus it is important to manage the limited budget in the most cost-effective manner. In this study, a novel pipe replacement scheduling approach is proposed in order to smooth the annual investment time series based on a life cycle cost assessment. The proposed approach is applied to a real WDN currently operating in South Korea. The proposed scheduling plan considers both the annual budget limitation and the optimum investment on pipes' useful life. A non-dominated sorting genetic algorithm is used to solve a multi-objective optimization problem. Three decision-making objectives, including the minimum imposed LCC of the network, the minimum standard deviation of annual cost, and the minimum average age of the network, are considered to find optimal pipe replacement planning over long-term time period. The results indicate that the proposed scheduling structure provides efficient and cost-effective rehabilitation management of water network with consistent annual budget.

• Journal of Chest Surgery
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• v.31 no.11
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• pp.1031-1036
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• 1998

Background: Medtronic-Hall mechanical valve is a world widely using prosthesis. But, in Korea, the clinical result from Medtronic-Hall valve replacement is not frequenthy available. Materials and methods: From March 1986 to May 1990, 50 patients underwent valve replacement surgery with Medtronic-Hall valve at Pusan National University Hospital. Seventeen were male and thirty three were female and ra nging in age from 16 to 70 years of age(mean=35 years). Results: The causes of valvular lesion were rheumatic in 43 patients, bicuspid aortic valve in 3 patients, degenerative lesion in three patients and bacterial endocarditis in one patient. The operative procedures were mitral valve replacement(MVR) in 38, aortic valve replacement(AVR) in 5 and double valve replacement(DVR) in 7. The most commonly used valve size was 21mm in AVR, 29mm in MVR. Concomitant surgical procedures were performed in 15 patients; left atrial thrombectomy in 9, left atrial auricle obliteration in 6 and tricuspid annuloplasty in 5(Kay: 2, DeVega: 3). New York Heart Association functional class was mostly Class Ⅲ or Ⅳ(91.5%) preoperatively and ClassⅠor Ⅱ(87.2%) after operation. The findings of postoperative echocardiogram of LAD, LVESD, LVEDD were reduced compared with preoperative period and ejection fraction was increased compared with preoperative period. Postoperative complications were massive bleeding in three, low cardiac output syndrome in two, thromboembolism in one and fulminant hepatitis in one patient. There were three hospital deaths and their causes were low cardiac output syndrome in two and rupture of left ventricle in one patient. The 5 year survival rate was 93.65±0.71% and 10 year actuarial survival rate was 88.27±6.42%. Conclusions: Medtronic-Hall mechanical valve has low valve related complication rate. It's durability and hemodynamic performance is comparable to other mechanical valves.

• Journal of Chest Surgery
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• v.33 no.1
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• pp.51-59
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• 2000

Background: Magnesium is one of the important intracellular cations. Hypomagnesemia is common after an open heart surgeryand may affect the development of posoperative arrhythmias. The aims of this study were to identify 1) the severity of the hypomagnesemia 2) the adequate dose of the magnesium replacement and 3) the effect of magnesium replacement on the postoperative arrhythmias. Material and Method: The serum magnesium level was measured in 20 patients in whom magnesium was replaced postopertively(6gm at the operative day 4gm at the 1st postoperative day and 2gm at the 2nd postoperative day) and compared with that of the 13 patients in whom magnesium was not replaced postopertively The serum magnesium level was normalized after magnesium replacement. We analyzed the development of arrhythmias in the patients groups who did not receive magnesium and were operated on between Oct. 1994 and Oct. 1995(Group I; n=206) and who received the magnesium postoperatively and were operated on between Nov. 1995 and Aug. 1996(Group II; n=133) Result: There were no differences in the preoperative risk factors and the rate of postoperative supraventricular or ventricular tachyarrhythmia occur-rences irrespectivel of the magnesium replacement. Magnesium replacement could prevent the aggrevation of the occurrence of postoperative arrhythmias in high risk groups of ventricular tachyarrhytnmia in old age but magnesium could not prevent postoperative arrhythmia in other high risk groups. Conclusion: The magnesium replacement after open heart surgery could prevent the development of ventricular tachyarrhythmias especially in old age groups but could not prevent atrial tachyarrhthmias.

• Journal of Internet Computing and Services
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• v.16 no.5
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• pp.19-27
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• 2015

Due to the advantages of fast read/write operation and low power consumption, SSD(Solid State Drive) is now widely adopted as storage device of smart phone, laptop computer, server, etc. However, the shortcomings of SSD such as limited number of write operations and asymmetric read/write operation lead to the problem of shortened life span of SSD. Therefore, the block replacement policy of SSD used as cache for HDD is very important. The existing solutions for improving the lifespan of SSD including the LARC scheme typically employ the LRU algorithm to manage the SSD blocks, which may increase the miss rate in SSD due to the replacement of frequently used block instead of rarely used block. In this paper we propose a novel block replacement scheme which considers the block reuse interval to effectively handle various data read/write patterns. The proposed scheme replaces the block in SSD based on the recency decided by reuse interval and age along with hit ratio. Computer simulation using workload trace files reveals that the proposed scheme consistently improves the performance and lifespan of SSD by increasing the hit ratio and decreasing the number of write operations compared to the existing schemes including LARC.

• Journal of Chest Surgery
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• v.20 no.1
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• pp.13-21
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• 1987

To clarify the difference between the outcome of warfarin anticoagulation and the antiplatelet [Aspirin, Dipyridamole] therapy after bioprosthetic heart valve replacement, we compared the following two groups. Group I [Warfarin group] consisted of 557 patients undergone lonescu - Shiley valve replacement between January, 1979 and December, 1985, and treated with scheduled warfarin therapy at Seoul National University Hospital. Group II [Antiplatelet group] consisted of 128 patients undergone lonescu - Shiley, Carpentier - Edwards or Wessex bioprosthetic valve replacement between March, 1983 and December, 1986, and treated primarily with antiplatelet therapy [Aspirin plus Dipyridamole] at SeJong General Hospital. The two groups were similar with respect to age, number of valves utilized per patient, type of operation and risk factors of thromboembolism. In group I, 522 patients excluding 35 hospital death [hospital mortality 6.3%], and in group II, 119 survivors excluding 9 hospital death [hospital mortality 7.0%] were followed. In group I, there were 13 fatal complications, of which seven were thromboembolic [0.6% / pt-yr] and six hemorrhagic [0.5%/pt-yr] during the period of four years. In group II, there were 3 fatal thromboembolic complications [2.3%/pt-yr] during the period of four years. This showed no statistically significant difference. Apart from fatal complications, there were lots of warfarin related minor complications in group I comparing with those of group II. The actuarial probability of the freedom from thromboembolism and of the freedom from fatal complications were very similar at each corresponding years postoperatively. As a result, warfarin anticoagulation in patients with bioprosthetic valve replacement did not reveal any significant advantages over antiplatelet therapy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.4031-4039
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• 2015

The problems related with blood supply shortage and the stability of blood transfusion are on the rise, as it is expected that the blood doners will decrease but the blood use amount for aged population will increase, owing to low birth and aged population increase. The purpose of this study is to analyze the hospital characteristics which affect patients receiving and non-receiving blood transfusion for the knee and hip total replacement arthroplasty. Data were collected from Health Insurance Review and Assessment Service's 2011 sample data, and 5,370 inpatients were abstracted from them. Logistic regression analysis was performed, using SPSS 20. Independent variables used are hospital characteristics variables and patient characteristics variables. Hospital characteristics variables are hospital type, ownership, residence and the number of usable beds, and patient characteristics variables are gender, age, severity, type of anesthesia, main diagnosis, whether or not of anemia and insurance class. At the result of this study, it was found that hospital type, region, gender, age, severity, main diagnosis and whether or not of anemia were the factors that mostly affected the blood transfusion for knee arthroplasty. And hospital type, residence, gender, age, severity, type of anesthesia and whether of not of anemia were the factors that mostly affected the blood transfusion for hip arthroplasty. In addition to that, it is expected that this research which analyzed the present state of blood transfusion and its influence factors are cost effective, and would make a good use of preliminary data for good quality of medical service.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.11
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• pp.6919-6924
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• 2013

Background: Between 1998-2009 South Korea experienced significant progress in reducing the male smoking rate from 66.3% to 46.9%. As part of a significant government effort in the area of smoking cessation intervention, the Korean government implemented the national "Smoking Cessation Clinics (SCC)" program in 2004. Materials and Methods: Data covered 804,334 adult male smokers participating in SCC program at 253 public health centers between 2006-2009. We examined participant cessation rates with the SCC program, their characteristics and program intervention components using health insurance status as a socioeconomic status (SES) indicator. Multivariate logistic regression analyses were performed correcting for intra-class correlations within public health centers. Results: The overall 6-month quit rate was high (46.8%). Higher odds of smoking cessation were positively associated with higher levels of behavioral counseling sessions, but not nicotine replacement therapy (NRT). Cessation rates were lower for Medicaid participants than for regular health insurance participants. Disadvantaged younger smokers were less likely to participate in the program. Older smokers were more likely to quit regardless of SES. Stress was cited as major reason for failure. Conclusions: SES inequalities across different age groups exist in smoking cessation among Korean adult male smokers. There is a need for intervention programs specifically targeting sub-populations of SES by different age groups.

• Journal of Chest Surgery
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• v.25 no.12
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• pp.1404-1415
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• 1992

To understand the factors influencing Atrial fibrillation and embolism in mitral valve surgery and prevent their risk, we have reviewed our 324 patients who underwent mitral valve surgery from Fev. 1982 to May 1992. Age, disease duration, lesion type, left ventricular function and left atrial dimension were chosen as preoperative factors influencing the incidence of atrial fibrillation and embolism and their postoperative course, The number and type of replaced valve, site of atriotmy, LA obliteration, ACT and use of Defibrillator were chaser. as operative factors influencing postoperative rhythm change and postop emb-olization. The results of analyses were as follows 1. The incidence of preoperative atrial fibrillation, systemic embolism and LA throbmus was 63. 6%, 10.56% and 19.8% relatively. 2. The preoperative factors of atrial fibrillation onset was old age, prolonged symptom duration, stenotic lesion, lager LAD and lower ejection fraction. In the preoperative systemic embolism preoperative factors were old age, female, stenotic lesion. The left atrial thrombus found more commonly in patients with atrial fibrillation, old age, prolonged symptom duration, stenotic lesion and low ejection fraction. 3. The preoperative atrial fibriation persisted postoperatively in 165[50.9%] and converted to normal sinus rhythm in 50[15.4%]. The preoperative normal sinus rhythm per-eisted in 100[31%] and atrial fibrillation was occured postoperatively in 9[2.7%]. The prolonged symptom duration was the preoperative factor of persist atrial fibrillation. 4. Among 95 long term follow-up patients, atiral fibrillation was continued in 59[60%]. Conversion to normal sinus rhythm was more common significantly in left atriotomy and bileaflet valve replacement. 5. There were 12 patients who had postoperative embolism. Female, persist atrial fibrillation, no LA olbiteration and tilting disc monocusp valve were considered as possible factors influencing postoperative embolism but was impossible to analyse their statistical significance due to small sample size. So we have concluded that the patients with above risk factors need anticoagulant and early surgical intervention. Left atriotomy with minimal atrial injury, left auricular obliteration and bileaflet valve replacement may be needed to reduce postoperative atrial fibrillation persist and embolism.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.93-100
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• 2019

In this study, the mechanical properties of early-age concrete were evaluated by mixing the electric arc furnace oxidizing slag fine aggregate with 30% and 50% replacement ratio. Slump test, air content test and unit volume weight test were performed for fresh concrete, and compressive strength test and chloride penetration experiments were carried out in hardened concrete. The compressive strength increased up to 7 days of curing age with increasing replacement ratio of the electric furnace oxidizing slag, but the strength decreased to 90% level of OPC concrete at 28 days of age. Regarding the result of chloride penetration test, no significant differences from OPC concrete were evaluated, which shows a feasibility of application to concrete aggregate.