• Journal of Chest Surgery
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• v.14 no.1
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• pp.17-25
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• 1981

In 1980, 416 cases of open heart surgery were done in this Department with over all operative mortality of 12.3%. 1. There were 288 congenital anomalies consisting of 174 acyanotic and 114 cyanotic varieties, which showed operative mortality of 6.9% and 25.4% respectively. 2. There were 128 cases of acquired lesions, 124 valvular disease and 3 myxoma being the main lesions. 3. There were 128 cases of valve replacement with operative mortality of 7.8%. 4. The most frequently operated anomaly was VSD, 90 pure VSD and 21 cases were associated with one or 2 cardiac anomalies. Over all operative mortality in 111 VSD cases was 8.1% but in 90 pure VSD cases it was 6.7%. 5. Tetralogy of Fallot showed the highest incidence in cyanotic group with 88 cases, consisting of 68 pure and 20 with other cardiac anomalies. Over all mortality in 88 cases was 19.3% but in pure form 16.2%. 6. In 128 valve replacement cases over all mortality was 9.4%. There were 85 mitral, 11 aortic, 2 tricuspid, 21 mitral with aortic, 6 mitral with tricuspid, 3 mitral, aortic, and tricuspid valve replacement cases. For mitral valve replacement operative mortality was 5.9%. 7. Twenty-one cases of babies under 10kg body weight were operated on with over all operative mortality of 28.6%. Sixteen cases of VSD were found with operative mortality of 25%. 8. Among 128 cases of valve replacement 7 were under the age of 15 years and 12 were between 15 and 20 years old. Five pediatric cases underwent mitral valve replacement without mortality, 9 year old boy was the youngest among them. In this Department open heart surgery for infancy and complex anomalies showed still hip operative risk which should be improved in the coming years. For open heart surgery Shiley oxygenators and 2 sets of A-O de-lux 5 head roller pump were utilized exclusively. For valve replacement Ionescu-Shiley bovine pericardial xenografts were mainly used. In pediatric and rural patients Persantin with aspirin regimen was satisfactorily administered for anticoagulation after valve replacement. Routinely Coumadin was administered for one year after valve replacement* In patients who had thrombus on valve sites, chronic atrial fibrillation, and giant left atrium Persantin-Aspirin regimen was used when one year coumadin administration was discontinued.

• Journal of Chest Surgery
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• v.18 no.3
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• pp.446-455
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• 1985

A total and consecutive 156 patients have undergone cardiac valve surgery including 13 closed mitral commissurotomy, 13 open mitral commissurotomy, one mitral annuloplasty, 75 mitral valve replacement, one aortic annuloplasty, 24 aortic valve replacement, 3 tricuspid valve replacement, 25 double valve replacement and one triple valve replacement. 155 prosthetic valves were replaced in a period between September 1976 and August 1985. There were 68 males and 88 females with age range from 8 to 69 yrs [mean 36.5 yr]. Out of replaced valves, 61 was tissue valve including 54 Carpentier-Edwards, and 4 was mechanical valves including 74 St. Jude Medical, and the position replaced was 101 valves for mitral, 46 for aortic and 8 for tricuspid. Single valve replacement in 102 cases, double valve replacement in 25 cases [17 for AVR+MVR, and 8 for MVR+TVR], and only one case was noted in the triple valve replacement. Early mortality within 30 days after operation was noted in 11 cases [7%]; 7 after MVR, 2 after DVR, and each one after open mitral commissurotomy and mitral annuloplasty. Cause of death was valve thrombus, cerebral air embolism, low output syndrome, uncontrollable arrhythmia, parapneumonic sepsis, acute cardiac tamponade and left atrial rupture. 7 late deaths were noted during the follow-up period from 1 to 104 months [average 48 month]; three due to valve and left atrial thrombus formation, two due to CVA from overdose of warfarin, and each one due to congestive heart failure and chronic constrictive pericarditis, Anticoagulants after prosthetic valve replacement were maintained with warfarin, dipyridamole and aspirin to the level of around 50% of normal prothrombin time in 79 cases, and Ticlopidine with aspirin in 47 cases to compare the result of each group. There were 11 major thromboembolic episodes including 3 deaths in the warfarin group. Two cases of CVA due to overdose of warfarin was noted in the warfarin group. In the ticlopidine group, there was only one left atrial thrombus confirmed at the time of autopsy. Among the survived 138 cases, nearly all cases[136 cases] were included in NYHA functional class I and II during the follow-up period. In conclusion, surgical treatment of the cardiac valve disease in 156 clinical cases revealed excellent result with acceptable operative risk and late mortality. Prevention of thrombus formation with anti-platelet aggregator Ticlopidine has better result than warfarin group presently with no specific side effect such as bleeding or gastrointestinal trouble.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.237-240
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• 1999

This study was performed to analyze strength characteristics of concrete using FWS(foundry waste sand), as a way of study for reusing the FWS disused in the foundry as the fine aggregate for concrete. As the experimental results, the slump of concrete showed a decline with the increase of replacement ratio of FWS. The compressive strength of concrete made with FWS 25% replacement river sand showed higher value than that of concrete not containing FWS, but the flexural strength of concrete containing FWS was decreased 21% compared with that of concrete not containing FWS at age of 28days.

• Journal of Korean Society for Quality Management
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• v.28 no.1
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• pp.57-77
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• 2000

A two-dimensional warranty policy, two types of warranty criteria, such as the age and mileage of an automobile, are employed simultaneously to determine the eligibility of a warranty claim. We deal with the analysis of a variety of combined two-dimensional free replacement warranty(FRW) and pro-rata replacement warranty(PRW). In this paper we also propose the analysis of policies with item failures modelled using the one-dimensional and two-dimensional approach, respectively. We obtain expressions for the expected warranty costs and illustrate through numerical examples.

• Journal of Chest Surgery
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• v.28 no.3
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• pp.258-262
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• 1995

We have experienced 18 abdominal aortic aneurysms between March,1987 and June,1994.Unruptured patients were 11 cases and ruptured were 7.The fifth[33.4% ,sixth[27.7% and seventh[27.7% decades were most common age distributions.Sex ratio was 2.6:1[m:f .The most frequent symptoms were abdominal or back pain and palpable pulsating mass.Sixteen patients underwent resection and graft replacement.One patient refused operation.Atherosclerosis was the underlying pathology in 76%.Two ruptured patients died postoperative[28.5% .The frequency of postoperative complication was higher in the ruptured group.

• International Journal of Reliability and Applications
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• v.7 no.1
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• pp.13-25
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• 2006

A new class of life distributions is studied. This class is defined based on comparing the residual life time to the whole life in the moment generating function order giving 'the new better than used in the moment generating function order ageing class $(NBU_{mgf})$'. Fundamental properties of this class are given including some closure properties and characterizations. Finally, we consider new results about comparisons of age and block replacement policies when the underlying distribution belongs to $NBU_{mgf}$ aging classes.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.647-652
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• 2008

Railway signal system has been more complex, larger and required high reliability. So, maintenance by experience must be changed to optimize maintenance program or introduced systematic method for estabilish new maintenance program. In this paper, we introduced the maintenance period decision method which are Age based method and Block replacement method based on the failure distribution for the equipment. So, we allocated optimum maintenacne period for the railway signal equipment using block replacement method.

• Journal of Chest Surgery
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• v.13 no.4
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• pp.422-434
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• 1980

Since 1968 up to the end of October 1980, 448 valves were replaced in 354 patients in Seoul National University Hospital. There were 238 mitral, 38 aortic, 7 tricuspid, 45 aortic with mitral, 23 tricuspid with mitral, and 3 triple valve replacement aortic mitral and tricuspid cases. Annual increase of mitral valve replacement cases and decrease of operative maortality were remarkable. Recently operative mortality of mitral valve replacement is about 5%. Sex ratio of mitral valve replacement is almost equal and there were 12 cases of pediatric patients (5%) among 238 cases, and patients under the age of 20 years were 34 (14.3%). Mitral valve replacement was done for 199 single mitral, 38 double valve and one triple valve lesions. Among 238 mitral valve replacement paients left atrial thrombus in 23(9.7%), atrial fibrillation in 132 (55.5%), and reoperation after blind mitral commissurotomy in 12(5%) cases were noted. In recent cases bioprosthetic valves, mainly lonescu-shiley valve were utilized to overcome the difficulties of postoperative late complications in anticoagnuation, especially for the rural patients and pediatric cases, in addition to the hemodynamic advantages of lonesocu valve. Among 354 patients 16 cases were congenital heart anomaly related, 5 ventricular septal defect related aortic and 4 Ebstein related tribuspid valve replacement cases. There were 2 congenital anomaly related mitral valve replacements, one for congenital mitral insufficiency of 7 years old boy and one for corrected transposition of the great vessels associated with mitral insufficiency. Among total 354 valve replacements 49 operative deaths (13.3%) were noted and in 238 mitral valve replacement 24 operative deaths occurred (10.1%). In 39 patients among 354 total valve replacements late complications were found. In 238 mitral valve replacement cases late complications were noted in 26 patients, among whom 16 cases expired. Main late complications were thrombe-embolism, subacute becteerial endocarditis, arrythmia cerebral hemorrhage due to unsatisfactory anticoagulation, and congestive heart failure in the incipient period of valve replacement were also noted. In mitral valve replacement cases long-term survival rate was 83.2% who showed marked clinical improvement. Ther were no evidences of calcification during the 2 years follow-up period for the lonescu-valve replacement cases among 19 pediatric patients. In conclusion 238 cases of mitral valve replacement were done with 24 operative deaths and 26 late complication cases among whom 16 expired. The long term survival was 83.2% of the cases. In pediatric cases in place of coumadin anticoagulation Persantin **** 75 and aspirin were administered after valve replacement. In adult cases who have difficulaties with coumadin anticoagulation and for those even with bioprosthetic heart valve replacement who needs long-term or permanent anticoagulation persantin 75 and aspirin combination regimen were administered with antisfactory results.

• Journal of Chest Surgery
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• v.12 no.4
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• pp.355-360
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• 1979

Mitral and aortic valve replacement with tricuspid annuloplasty was undertaken in 5 patients out of 38 valvular surgery between the period from Jan. 1977 to May 1979 in the Dept. of Thoracic and Cardiovascular Surgery in Korea University Hospital. All were male patients with age ranging from 18 to 42 years, and preoperative evaluation revealed one case in Class IV, and four cases in Class III according to the classification of NYHA. Preoperative diagnosis was confirmed by routine cardiac study including retrograde aorto- and left ventriculography, and there were two cases with MSi+ASi+Ti, two cases with MSi+Ai+Ti, and one case with Mi+Ai+Ti. Double valve replacement was performed under the hypothermic cardiopulmonary bypass with total pump time of 247 min. in average ranging from 206 min. to 268 min. During aortic valve replacement, left coronary perfusion was done in the first two cases, and cardiac arrest with cardioplegic solution proposed by Bretschneider was applied in the remained three cases. Starr-Edwards, Bjork-Shiley prosthetic valves and Carpentier-Edwards tissue valve were replaced in the aortic area, and Carpentier-Edwards and Angell-Shiley tissue valves were replaced in the mitral area with each individual combination [three prosthetic and two tissue valves in the aortic, and five tissue valves in the mitral area respectively]. Postoperative recovery was uneventful in all cases except one case with hemopericardium, which was managed with pericardiectomy on the postoperative 10th day in good result. Follow-up after double valve replacement of the all five cases for the period from 6 months to 33 months revealed satisfactory adaptation in social activity and occupation with cardiac function of Class I according to the classification of NYHA In all five cases.

• Advances in concrete construction
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• v.16 no.6
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• pp.317-325
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• 2023

Strength prediction and correlation of concrete is done using experimental and analytical methods. Main objective is to correlate the experimental and simulated values of compressive strength of concrete mix using Fly Ash (FA) and Silica Fume (SF) by partial replacement of cement in concrete. Mix proportion was determined using IS method for M40grade concrete. Hundred and forty-seven cubes were cast and tested using Universal Testing Machine (UTM). Genetic Algorithm (GA) model was developed using C++ program to simulate the compressive strength of concrete for various proportions of FA and SF replacements individually at 3% increments. Experiments reveal that 12 percent silica fume replacement produced maximum compressive strength of 35.5 N/mm², 44.5 N/mm² and 54.8 N/mm² moreover 9 percent fly ash replacement produced a maximum strength of 31.9 N/mm², 37.6 N/mm² and 51.8 N/mm² during individual material replacement of concrete mix. Correlation coefficient for each curing period of fly ash and silica fume replaced mix were acquired using trend lines. The correlation coefficient is found to be approximately 0.9 in FA and SF replaced mix irrespective of the mix proportion and age of concrete. A higher and positive correlation was found between the experimental and simulated values irrespective of the curing period in all the replacements.