• Journal of Chest Surgery
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• v.39 no.8 s.265
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• pp.604-610
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• 2006

Background: Recent improvements in interventional procedure and medical therapy for congestive heart failure result in an increase of number of patients with ischemic cardiomyopathy considered for coronary artery bypass grafting. We retrospectively review the results of CABG in these patients with decreased LV function to know the early and mid-term follow-up results. Material and Method: Between January 2001 and June 2005, 1,143 patients underwent coronary artery bypass grafting and 144 of these patients had preoperative left ventricular function of equal to or less than 35% ${(LVEF{\leq}\;35%)}$. There were off-pump coronary artery bypass grafting (OPCAB) in 66 cases (45.8%), on-pump beating heart coronary artery bypass grafting in 34 cases (23.6%) and conventional coronary artery bypass grafting in 44 cases (30.6%). The combined operations including mitral annuloplasty were 48 cases in thirty five patients (24.3%). Result: The mean number of dstal anastomosis were $3.5{\pm}1.3$. The median postoperative duration of stay in intensive care unit and hospital was 2 days and 8 days, respectively. There were 6 early death (4.2%) and causes of deaths were ventricular tachycardia in 5 patients, small bowel infarction in one patient. Mean follow-up time was $21{\pm}14$ months $(4{\sim}54\;months)$. The 1-year was $95{\pm}2%$ and 3-year survival rate was $83{\pm}7%$, the 1-year and 3-year cardiac event-free survival were ${88{\pm}3%\;and\;69{\pm}7%}$, respectively. Conclusion: Based on satisfactory early and mid-term results in our study, CABG should be carried out as actively as possible in patients with ischemic cardiomyopathy. Postoperative aggressive management for ventricular arrhythmia would be helpful for better results.

• Journal of Chest Surgery
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• v.42 no.4
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• pp.528-531
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• 2009

Transesophageal echocardiography (TEE) is widely used to evaluate the heart function and the result of surgery during a cardiac operation. The incidence of complications associated with TEE is low, yet critical complications such as lower pharyngeal injury and esophageal perforation may happen. We report hereon a case of 77-year old male patient who suffered from injury to the pyriform sinus and concurrent deep neck infection after off pump coronary artery bypass surgery and intraoperative TEE.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.2
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• pp.111-119
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• 2011

Recently, the performances of speed and accuracy are enhanced in machine tools. The high speed of the machine tools usually causes harmful thermal displacements on the objects. To reduce the thermal displacements, machine tools generally adopt oil coolers with precise temperature control function. This study aims at precise control of oil outlet temperature in the oil coolers with hot-gas bypass manner based on PI control logic. The control system was designed for obtaining steady state error within ${\pm}0.1^{\circ}C$ and maximum overshoot with 0.8% even though abrupt disturbances are added to the system. We showed that the PI gains could be easily decided by numerical simulations using practical transfer function which got experiments. Also, transient characteristics could be improved significantly by reflecting the inlet temperature of an evaporator to the output of a controller feedforwardly considering periodic abrupt disturbances. Through some experiments, excellent control performances were established by the suggested control.

• The Korean Journal of Nuclear Medicine
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• v.19 no.1
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• pp.67-72
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• 1985

The development of paradoxical interventricular septal motion is a common consequence of cardiopulmonary bypass operation. The reason for this postoperative abnormal septal motion is not clear. 41 patients were studied preoperatively and postoperatively with radionuclide blood pool scan to evaluate the frequency of development of paradoxical septal motion with right ventricular volume overload before surgery and the frequency of development of paradoxical septal motion after cardiac surgery with cardiopulmonary bypass, and to evaluate the change of EF related to the development of paradoxical septal motion after cardiac surgery. The results were as follows; 1) 7 of 41 patients with right ventricular volume overload(that is 17%) showed paradoxical septal motion before surgery. But 13 of 34 patients(that is 42%) had paradoxical septal motion after cardiac surgery with cardiopulmonary bypass. So open heart surgery with cardiopulmonary bypass related the development of paradoxical septal motion after surgery. 2) EF significantly decreased in patients who developed paradoxical septal motion after surgery, whereas the EF did not change in the patients who retained normal interventricular septal motion after surgery. So paradoxical septal motion usually reflected some diminution of left ventricular function, immediately after cardiac surgery.

• Journal of Chest Surgery
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• v.19 no.4
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• pp.606-617
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• 1986

During the period from November 1981 through June 1986, 18 cases of coronary arterial bypass graft were performed at Department of Thoracic and Cardiovascular Surgery, Seoul National University Hospital. They consisted of 13 males and 5 females with the mean age of 49 [range: 28-69 years]. History of myocardial infarction was noted in 50% of the patients and cardiomegaly on chest PA in 2 patients with preserved LV function. On resting EKG, except the evidences of old myocardial infarction, the findings of LVH were noted in 7 cases, acute myocardial infarction in 2, diffuse myocardial ischemia in 1, and significant ventricular arrhythmia in 2 cases. The angina by type of presentation is stable in 3 patients, unstable in 15 patients with resting, postinfarction and progressive angina as the criteria of unstability. The patterns of involvement of significant disease were single vessel involvement [5 cases] double vessel involvement [8 cases], and triple vessel involvement [5 cases] including 5 cases of left main coronary arterial diseases. The pattern of coronary arterial disease in individual patient was one or more stenosis of the proximal left coronary arterial system with or without right coronary involvement, in every case. We performed 9 cases of double bypass and 9 cases of triple bypass with great saphenous vein using single anastomosis technique except in 4 cases, One of the 4 cases is our first case, sequential anastomosis between LAD and diagonal was performed due to shortage of the prepared vein graft. In the other 3 cases, our latest experience, we adopted the left internal mammary artery for the left anterior descending coronary revascularization. The distribution of sites of distal anastomosis revealed more striking predilection to LAD, showing our attention on the significance of the revascularization of LAD system. The ischemic time was 35 minutes per graft and mean number of grafts per patient was 2.5. Of the 18 patients, 13 [77.2%] had complete revascularization, and incomplete in 5 cases with the causes of incompleteness as presented. The early results of operation were as followed: surgical death in 2 [11%], perioperative infarction 2 [11%], need of inotropic support 5 [28%], arrhythmia 2 [11%], wound problem, bleeding, and emotional dysfunction. The actuarial anginal free survival during the period of 6 months through 2 years was 85.2% with excellent symptomatic control according to the angina classification of Canadian Cardiovascular Society.

• Current Optics and Photonics
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• v.1 no.2
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• pp.113-117
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• 2017

With the increasing use of high-power laser diode bars (LDBs) and stacked LDBs, the issue of thermal control has become critical, as temperature is related to device efficiency and lifetime, as well as to beam quality. To improve the thermal resistance of an LDB set, we propose and analyze a bypass heat sink with a top canopy structure for an LDB set, instead of adopting a thick submount. The thermal bypassing in the top-canopy structure is efficient, as it avoids the cross-sectional thermal saturation that may exist in a thick submount. The efficient thickness range of the submount in a typical LDB set is guided by the thermal resistance as a function of thickness, and the simulated bypassing efficiency of a canopy is higher than a simple analytical prediction, especially for thinner canopies.

• Journal of Chest Surgery
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• v.39 no.8 s.265
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• pp.611-618
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• 2006

Background: There have been controversies whether mitral valvular surgery is necessary in the patients with moderate ischemic mitral regurgitation undergoing coronary artery bypass grafting. The purpose of this study is to evaluate the long term clinical results of patients with moderate ischemic mitral regurgitation. Material and Method: Between January 1992 and February 2005, 44 patients with moderate ischemic mitral regurgitation underwent coronary artery bypass grafting. Concomitant mitral valvular procedure was performed in 20 patients (group 1) and isolated coronary artery bypass grafting was performed in 24 patients (group 2). There were no significant difference between groups except cardiopulmonary bypass time (p<0.01). Postoperative follow up duration was $30.1{\pm}29.6$ months and last follow up echocardiographic examination was performed at $21.2{\pm}28.0$ months. Result: There was no difference in operative mortality between groups (group 1 vs group 2, 15.0% vs 8.3%, p=0.493). Grade of mitral regurgitation ${(0.81{\pm}0.91\;vs\;1.50{\pm}0.05,\;p=0.046)}$ and reduction in regurgitation grade ${(1.75{\pm}0.93\;vs\;0.70{\pm}1.26,\;p=0.009)}$ were different between two groups. But there were no significant differences in left ventricular ejection fraction ${(34.1{\pm}11.4%\;vs\;41.6{\pm}12.9%)}$, left ventricular end systolic volume ${(118.2{\pm}63.9\;ml%\;vs\;85.6{\pm}281\;ml)}$, New York Heart Association functional class ${(2.1{\pm}0.2\;vs\;2.4{\pm}1.2)}$ and 5 year survival rate ${(85{\pm}8%\;vs\;82{\pm}8%)}$. There was no risk factor for operative mortality and the only risk factor for late death was preoperative atrial fibrillation (p=0.042). There was no significant correlation between mitral valvular surgery and late death. Conclusion: Concomitant mitral valvular procedure in patients with moderate ischemic mitral regurgitation undergoing coronary artery bypass grafting had no significant positive effect on survival and ventricular function compared with isolated coronary artery bypass grafting. Prospective randomized study may be needed to evaluate the necessity of concomitant mitral procedure and to find more effective method for the improvement of ventricular function.

• Journal of Biomedical Engineering Research
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• v.40 no.5
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• pp.197-205
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• 2019

The existing Extracorporeal membrane oxygenation(ECMO) and Cardiopulmonary bypass system(CPB) have been developed and applied to various devices according to their respective indications. However, due to the complicated configuration and difficult usage method, it causes inconvenience to users and there is a risk of an accident. Therefore, smart all-in-one cardiopulmonary circulation device is being developed recently. The smart all-in-one cardiopulmonary assist device consists of a blood pump for cardiopulmonary bypass, a blood oxidizer for cardiopulmonary bypass, a blood circuit for cardiopulmonary bypass, and an artificial cardiopulmonary device. It is an integrated cardiopulmonary bypass device that can be used for a variety of purposes such as emergency, intraoperative, post-operative intensive care, and long-term cardiopulmonary assist, combined with CPB used in open heart surgery and ECMO used when patient's cardiopulmonary function does not work normally. The smart all-in-one cardiopulmonary assist device does not exist as a standard and international standard applicable to advanced medical devices. Therefore, in this study, we will refer to the International Standard for Blood Components, the International Standard for Blood, the Guideline for Blood Products, and prepare applicable performance and safety guidelines to help quality control of medical devices, and contribute to the improvement of the health of people. The guideline, which is the result of conducted a survey of the method of safety and performance test, is based on the principle of all-in-one cardiopulmonary aiding device, related domestic foreign standards, the status of domestic and foreign patents, related literature, blood pump(ISO 18242), blood oxygenator (ISO 7199), and blood circuit (ISO 15676) for cardiopulmonary bypass.The items on blood safety are as follows: American Society for Testing and Materials ASTM F1841-97R17), and in the 2010 Food and Drug Administration's Safety Assessment Guidelines for Medical Assisted Circulatory Devices. In addition, after reviewing the guidelines drawn up through expert consultation bodies including manufacturers / importers, testing inspectors, academia, etc. the final guideline was established through revision and supplementation process. Therefore, we propose guidelines for evaluating the safety and performance of smart all-in-one cardiopulmonary assist devices in line with growing technology.

• Journal of Chest Surgery
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• v.38 no.2 s.247
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• pp.146-151
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• 2005

Background: Preoperative elevated serum creatinine values are associated with increased risk for both morbidity and mortality in patients undergoing on-pump coronary artery bypass surgery (CABG). We investigated the postoperative changes of renal function and proper management in the patients. Material and Method: Among 74 consecutive patients who underwent isolated on-pump CABG, 17 patients with increased serum creatinine level $(creatinine\;\geqq\;1.5\;mg/dL)$ within preoperative one week wereincluded in the study. Seven patients showed pre­operative serum creatinine level of 2.0 mg/dL or higher, and 3 of them had been undergoing hemodialysis. Preoperative hemodialysis was performed in the 3 patients due to end-stage renal failure (ESRD) the day before the operation. We started peritoneal dialysis immediately after the cardiopulmonary bypass in patients with ESRD or postoperative acute renal failure if it was necessary to remove intravascular volume and lower serum creatinine level. Result In most of the patients with CABG, postoperative serum creatinine level increased and recovered to the preoperative level at the discharge. In 2 of the 4 patients with serum creatinine level of 2.0 mg/dL or higher and 3 patients with ESRD, intravascular volume, serum creatinine level and serum electrolyte were controlled with peritoneal dialysis. Conclusion: Postoperative serum creatinine level increased transiently in most of CABG patients, and intravascular volume and serum creatinine level were controlled by peritoneal dialysis only in the patients with acute renal failure postoperatively and those depending on hemodialysis.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.7
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• pp.675-678
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• 2015

In this paper, we proposed a multi-function conversion block for microwave receiver. The proposed multi-function conversion block is composed of a broadband voltage controlled oscillator and a dual-mode mixer. Depending on whether the bias voltage is supplied, the first IF(Intermediate Frequency) output frequency(4,595 MHz/6,045 MHz) needed in microwave receiver is converted to 720 MHz and the another IF output frequency(720 MHz) for receiving Ku-band has the multi-functional operations of the dual mode that are bypass and attenuation without frequency conversion. Implementation and measurement results show that each intermediate frequency has conversion loss characteristic according to the LO power. The LO power conversion loss of 4,595 MHz at the LO levels from 2 dBm to 4 dBm is 13 dB, another of 6,035 MHz is 12 dB and the other of 720 MHz is 7.0 dB.