• Journal of Chest Surgery
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• v.8 no.2
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• pp.89-100
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• 1975

Sixteen cases of cardiac valve replacements have been done in this department since 1970. Twelve cases of mitral valve replacement were done with Beall valve, 2 cases of aortic valve replacement with Starr-Edwards and Magoven valve and 2 cases of double valve replacement using Beall valve for mitral and Magovern valve for aortic. Three patients [18.8%] died during operation. Two cases [12.5%] of hospital mortality occurred because of congestive heart failure and asphyxia due to tracheomalacia 3 months after operation. Follow-up studies from two to 27 months showed excellent results except three cases of late mortality [18.8 %]. Thromboembolism occurred in two double valve replacement patients[12.5%]who were fatal.

• Journal of Chest Surgery
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• v.22 no.6
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• pp.1036-1043
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• 1989

Seventy eight patients underwent operation for combined multiple valve disease, with an overall early mortality of 14.1 % from January, 1983 to September, 1988 in the department of thoracic and cardiovascular surgery of Pusan National University Hospital. All of the above cases had combined multiple valve procedures. There were 33 mitral valve replacements and tricuspid annuloplasties, 33 aortic and mitral valve replacements, 5 aortic and mitral valve replacements with tricuspid annuloplasties, 3 aortic valve replacements and mitral annuloplasties, 1 open mitral commissurotomy and tricuspid annuloplasty and, 1 mitral valve replacement and primary closure of tricuspid valve cleft, 1 mitral valve replacement and aortic commissurotomy, 1 mitral, aortic and tricuspid valve replacement were done. 44 were male and 34 were female and the age distribution was from 14 to 57 with mean 38 year old. According to NYHA[New York Heart Association] classification, 49 patients were class I, 19 patients were class Il and 10 were class IV. Average perfusion time was 205.3 minutes. The live patients perfusion time was 178.7 minutes while that of dead ones was 272.0 minutes. Early deaths within 30 days from operation were 11 cases, 6 of which were due to low cardiac output, 3 were acute renal failure and 2 were cardiac rupture. The 65 patients were followed up from 2 to 30 months for a total 20.6 patient years. 1 patient committed suicide because of postoperative depression 1 year after operation. All of the survivors were enjoying their daily life and their NYHA class was superior to the preoperative ones.

• Journal of Chest Surgery
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• v.24 no.10
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• pp.979-986
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• 1991

From October 1988 to November 1989, seven patients underwent valve replacement during the active phase of native valve endocarditis. There were 4 males and 3 females whose mean age was 41 years[range, 16 to 68 years]. Preoperative two-dimensional and Doppler echocardiography showed vegetations and severe valvular regurgitation in all patients. Blood cultures were positive in 4, and negative in 3 patients Organisms were alpha-hemolytic Streptococcus in 2, Staphylococcus epidermidis in 1, Erysipelothrix rhusiopathiae in 1 patient Valve tissue cultures were negative in all patients. Intravenous antibiotic therapy had been done for 3 to 18 days in 5 patients pre-operatively and was not done in 2 patients, Indications for operation were heart failure in h, and systemic emboli in 1 patient. The aortic valve was involved in 3, mitral in 1, and both aortic and mitral in 3 patients, One operative death[14.4%] occurred in patient with cardiogenic shock before operation. Late death occurred in one on 14 months after operation. The remaining 5 patients were followed up over a two year period in good condition. In conclusion, native valve endocarditis with severe heart failure must be considered for early operation.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.24 no.4
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• pp.172-179
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• 1988

A cartridge type hydraulic logic valve consists of simple two port valve whose poppet is closed or opened by means of pressure signal of a pilot line. Accordingly, the logic valve can be used not only for direction, flow and pressure control purpose but also for versatile function valve which enables all above mentioned functions. In addition, the valve has little internal leakage and pressure loss, superior response characteristics and easiness in making small block type valve. The above mentioned good performances being recognized recently, the logic valve has been used widely in the large scale hydraulic system such as a hydraulic press system, for the performance requirements of high speed operation and precise control characteristics. However, there are scarce reports until now, except for a few ones from Aachen Institute of Technology in West Germany, so it is necessary to be studied on development and investigation for practical application. This paper showed that the static and dynamic characteristics of a logic valve when the logic valve is used for directional control, to investigate the relations between the valve operating characteristics and the valve design conditions. From the above mentioned procedure, it was ascertained that the valve operation characteristics obtained by numerical analysis showed good agreements with experimental results. The representative results obtained are as follows; 1. During the valve is closing, the poppet velocity is almost constant in the logic valve. 2. The pilot pressure P sub(3) and the resistance R in the pilot line have much influences on the valve operation time. 3. Spring strength have not such a severe influence on the valve operating time. 4. The operation characteristics of the logic valve can be estimated with good accuracy comparatively by numerical analysis with the equations describing poppet motion.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.6
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• pp.50-56
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• 2006

Residual gas fraction in a combustion process is very crucial to improve combustion and cyclic variations. Especially, the residual gas fraction is strongly affected by backflow of the residual gas during the valve overlap period in an idle operation. Therefore, it is one of the most interesting that valve timings can affect flow characteristics of gas exchange process, especially during idle operation. This analysis investigates residual gas fraction with respect to valve timing changes which is critical for combustion efficiency and engine performance. Flow characteristics of residual gas by changing intake and exhaust valve timing are calculated by CFD methodology during an idle operation in an SI engine. It is analyzed that retarded EVO and advanced IVO results in the increase of valve overlap period and consequently, residual gas fraction. Futhermore, changes in IVO have stronger effects on variation of residual gas fraction.

• Journal of Chest Surgery
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• v.45 no.3
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• pp.141-147
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• 2012

Background: Although the aortic valve-sparing procedure has gained popularity in recent years, it still remains challenging in patients with advanced aortic regurgitation (AR). We compared the long-term outcomes of the aortic valve-sparing procedure with the Bentall operation in patients with advanced aortic regurgitation secondary to aortic root dilatation. Materials and Methods: A retrospective review of 120 patients who underwent surgery for aortic root dilatation with moderate to severe AR between January 1999 and June 2009 was performed. Forty-eight patients underwent valve-sparing procedures (valve-sparing group), and 72 patients underwent the Bentall procedure (Bentall group). The two groups' overall survival, valve-related complications, and aortic valve function were compared. Results: The mean follow-up duration was $4.9{\pm}3.1$ years. After adjustment, the valve-sparing group had similar risks of death (hazard ratio [HR], 0.61; p=0.45), and valve related complications (HR, 1.27; p=0.66). However, a significant number of patients developed moderate to severe AR in the valve-sparing group at a mean of $4.4{\pm}2.5$ years of echocardiographic follow-up (p<0.001). Conclusion: Both the Bentall operation and aortic valve-sparing procedure showed comparable long-term clinical results in patients with advanced aortic regurgitation with aortic root dilatation. However, recurrent advanced aortic regurgitation was more frequently observed following valve-sparing procedures.

• Journal of Chest Surgery
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• v.41 no.3
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• pp.305-312
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• 2008

Background: Anatomic and functional abnormalities of the systemic atrioventricular (AV) valve are common in single ventricle. pathologies and continue to be associated with poor early and late outcomes in surgically palliated single. ventricle patients. We aggressively performed valvuloplasty for atrioventricular valve regurgitation (AVVR) during the course toward a Fontan operation. Material and Method: Between January 1995 and December 2004, 209 patients underwent a Fontan operation in our institution. We retrospectively evaluated the prevalence of AVVR and the influence of AV valve repair on outcome, and we analyzed the progression of AVVR after the Fontan operation for 168 patients where echocardiographic follow up results for more than 6 months after the Fontan operation were available. During the course toward a Fontan operation, 25 patients underwent 30 procedures for AVVR. These procedures. were. carried out during placement of a bidirectional cavopulmonary shunt (BCPS) for nine patients, between the time of placement of a BCPS and the Fontan operation for four patients, and during the Fontan operation for 17 patients. Five patients underwent procedures for AVVR twice. Result: The late mortality rate after the Fontan operation was 4.2% (n=7), with a median follow-up duration of 52 months (range, $6{\sim}123$ months). Seven patients (4%) had unfavorable outcomes such as significant (moderate or severe) AVVR in six patients, and significant AV valve stenosis in one patient was determined at the last follow up after the Fontan operation. Among the seven patients, four patients underwent AV valve repair after the Fontan operation, and one patient underwent subsequent AV valve replacement. Progression to AVVR of equal to or greater than grade 2 was noted in 30 patients (18%) at the last follow up after the Fontan operation, including 12 patients that underwent previous AV valve procedures. Initial grading of AVVR, a previous AV valve operation, and specific AV valve morphology such as a common AV valve or mitral atresia were significant risk factors for the progression of AVVR after the Fontan operation. Conclusion: In our surgical series, a small percentage of patients showed unfavorable outcomes. related to AVVR during the course toward a Fontan operation. However, a closer follow-up is required to evaluate the progression of the AVVR after a Fontan operation, especially for patients showing poor AV valve function at the first presentation and specific AV valve morphology.

• Journal of Chest Surgery
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• v.17 no.1
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• pp.3-11
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• 1984

Prosthetic valve replacement has resulted in marked improvement in the functional status of many patients with valvular heart disease. But valve failure from various causes has necessitated re-replacement of prosthetic valve in some of these patients. This selective group of patients has many inherent problems. This report presents our experience with seven patients who received re-replacement of prosthetic valve in the Seoul National University Hospital from 1981, to 1983. The patients included one woman and six men in the range of 9 and 49 years old. As the first valve operations, there were five MVR using tissue valves, one DVR [Bjork-Shiley and Ionescu-Shiley valve] and one case of modified Bentall operation with composite graft [Ionescu-Shiley valve]. Reoperations on prosthetic valve failure were performed 17 to 54 months after the first operation [mean 34 months]. Amon8 seven patients, there were two cases of prosthetic valve endocarditis and five cases of primary tissue failure. Gross calcification of the xenograft was found in two children with Ionescu-Shiley valve. All except one had relatively successful operative results. The unsuccessful one died intraoperatively from low output syndrome.

• Journal of Chest Surgery
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• v.21 no.1
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• pp.164-168
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• 1988

Between November, 1984, and May, 1986, 93 patients underwent combined valvular and coronary artery operation. They were 70 male and 23 female, the age ranging from 29 to 82. From this population 89 patients underwent single valve replacement and 4 patients underwent double valve replacement. Patients with mitral valve disease were in the majority present in the age group between 50 till 70, where as in the group after 60 years, patients with aortic valve disease were dominant. The main indication for aortic valve replacement was aortic stenosis and the indication for mitral valve replacement was equal between mitral stenosis and mitral incompetence, the later was due to papillary dysfunction after myocardial infarction. Dyspnea was a very frequent symptom and it was found in nearly all patients. 28 patients had a previous myocardial infarction and severe left ventricular dysfunction. The grafts were placed prior to valve replacement and periods of myocardial ischemia were kept at a minimum by maintaining coronary perfusion throughout the operation. It is our opinion that simultaneous valve replacement and myocardial revascularization does not increase the risk of cardiac valve replacement substantially.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1450-1454
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• 1996

Even though digital control type high speed solenoid valve is a little inferior to analog control type servo valve and proportional control valve in performance, it is cheap and has secure performance against pollutant and simple control circuit. But high speed solenoid valve is hardly used for heavy machinery instead of servo valve or proportional control valve that is used in severe condition because the valve itself is small capacity and it shows wide dead zone during on-off control and chattering of hydraulic cylinder by chattering of pressure. It is desirable to use low-priced and strong pollutant resistant high speed solenoid valve for obtaining reliability of operation from severe working condition because it isn't necessary to acquire response characteristic of high frequency when we consider the characteristic of heavy machinery operation. In this study, PWM control algorithm for pilot pressure control of large capacity pilot operating valve will be used for precision position control of heavy machinery hydraulic cylinder. Not only cost reduction of main control valve but also high reliability of heavy machinery in severe condition can be obtained by using this pilot operating spool valve with high speed solenoid valve.