• Journal of Chest Surgery
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• v.30 no.2
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• pp.195-199
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• 1997

From Dec. 1992 to Dec. 1995, 20 patients with atherosclerotic occlusive disease in the lower extremities underwent arter al bypass surgery. The age of the patients ranged between 46 and 77 years(mean .60.8 years) and the most prevalent incidence was in the 7th decades. The mean follow up period was 18.8 months ranging from 4 to 36 months. Associated diseases were diabetus mellitus(25%), hypertension (35%), cerebrovascular accident(25%), and acute myocardial infarction(5%). Disabling intermittent claudifcation(35%), resting pain(20%) or ischemic gangrene(or ulceration)(45%) were operative indications. Aorto-bifemoral bypass in 4 cases, aorto-single femoral bypass in 2 cases, Aorto-bifemoral bypass and femoropopliteal bypass in 3 cases, aorto-single femoral bypass and femoropopliteal bypass in 1 case, femoropopliteal bypass in 4 cases, femorotibial bypass in 1 case, popliteotibial bypass 4 cases and femorofemoral bypass in 1 case were the surgical approches. Early thrombosis(2 cases) and wound infection(2 case) were main complication. Postoperative complication rate was 20% . Postoperative patency rates re 92.6% at 6 months, 84.2% at 1 year, 75.4% at 2 years and 69.4% at 3 years.

• Journal of Chest Surgery
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• v.38 no.5 s.250
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• pp.377-381
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• 2005

Background: Extra-anatomic bypass was performed in the patient who could not use anatomic bypass due to many causes. The purpose of this study is to evaluate the efficacy of extra-anatomic bypass surgery. Material and Method: We reviewed 31 patients who underwent extra-anatomic bypass surgery at Pusan national university hospital. We analysed the combined diseases, etiologic diseases, symptoms, patency rate and the factors affecting patency rate retrospectively. Result: There were 26 cases of femoro-femoral bypass and 5 cases of axillo-bifemoral bypass among 31 patients. The mean age was 70.23 years. Combined disease were hypertension, hyperlipidemia, and ischemic heart disease in order of frequency. The indications for surgery were disabled claudication, tissue necrosis, rest pain, and a cute ischemia. We analysed the ages, smoking history, hypertension, ischemic heart disease, severity of limb ischemia, and hyperlipidemia as factors affecting patency rate. We could not find any statistical differences between these factors. The primary graft patency rates were $73.65\%$ one year, $73.65\%$ two year, and $65.46\%$ three year respectively according to the Kaplan-Meier method. Conclusion: Nevertheless extra-anatomic bypass has a relatively low patency rate, it has good merits that is less dangerous, simple and easy re-do surgery compared to anatomic bypass. We think that extra-anatomic bypass is one of the good treatment modalities for the high risk vascular patients.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.437-440
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• 2005

In the present work, characteristics of the flow in CAGE of a steam turbine LP/HP Bypass control valve for thermal power plant are investigated. The flow field is analyzed numerically by solving steady three-dimensional Reynolds-averaged Navier-Stokes equations. Shear stress transport (SST) model is used as turbulence closure.

• Journal of Chest Surgery
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• v.26 no.7
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• pp.552-556
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• 1993

Infection after reconstructive surgery is one of the most catastrophic postoperative complication in vascular surgery. Mortality rates reported from a world-wide experience range between 25 and 88 percent. The surgeon faced with such a complication must choose among many diagnostic and management options to maximize limb salvage and survival based on the presentation and site of the infectiota the degree of ischemia of the lower extremities, and the overall medical condition of the patient. We successfully managed with descending thoracic aorta-to-bifemoral arteries bypass after the entire removal of the infected axillo-bifemoral graft because of bypass graft infection.

• Journal of Chest Surgery
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• v.32 no.6
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• pp.495-503
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• 1999

Background: We tested the technical feasibility of fetal cardiac bypass and collected baseline data on the fetal hemodynamics and placental functions related to the cardiopulmonary bypass in the fetal lamb model. Material and Method: Eleven fetuses at 120 to 150 days of gestation were subjected to bypass via trans-sternal approach with a 12 G pulmonary arterial cannula and 14 to 18 F venous cannula for 30 minutes. All ewes received general anesthesia with ketamine. In all the fetuses, no anesthetic agents were used except muscle relaxant. Eight served as a group in which placenta was excluded from the extracorporeal circulation by clamping the umbilical cord during the bypass(the oxygenator group) and in the remaining three, the placenta worked as the only source of oxygen supply(the placenta group). Observations were made every 10 minute during a 30-minute bypass and 30-minute post bypass period. No prostaglandin inhibitors were used both in ewes and in fetuses. Result: Weights of the fetuses ranged from 1.9 to 5.2 kg. In the oxygenator group, means of arterial pressure, PaO2, atrial pressure, heart rate, and bypass flow rate ranged 69.8 to 82.6 mmHg, 201.7 to 220.9 mmHg, 4.1 to 4.3 mmHg, 169 to 182/min, and 140.3 to 164.0 ml/kg/min, respectively during bypass, but rapid deterioration of the fetal cardiac functions and the placental gas exchange was observed after the cessation of bypass. In the placenta group, means of arterial pressure decreased from 44.7 to 14.4 mmHg and means of PaCO2 increased from 61.9 to 129.6 mmHg during bypass. Flow rate was suboptimal(74.3 to 97.0 ml/kg/min) during bypass. All hearts fibrillated immediately after the discontinuation of bypass. Conclusion: In this study, the technical feasibility of fetal cardiopulmonary bypass was confirmed in the fetal lamb model. However, further studies with modifications of the bypass including an addition of prostaglandin inhibitor, an application of the total spinal anesthesia on the fetus, a creation of more concise bypass circuit, and a use of active pump are mandatory to improve the outcome.

• Journal of Chest Surgery
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• v.42 no.4
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• pp.532-536
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• 2009

Bypass surgery is performed for insuring continuity of a blood supply that is restricted due to obstruction of the native blood supply. Two types of surgery are commonly carried out: one is anatomic bypass and the other is extraanatomic bypass. Especially, extraanatomic bypass surgery is performed in patients who are a high risk for performing anatomical bypass surgery. The risk factors for anatomical bypass surgery are old age, infection, previous surgery and trauma. A 96-year-old patient underwent extraanatomic bypass surgery from the right femoral artery to the left femoral artery due to total occlusion of the left iliac artery, and 7 years after that operation, a pseudoaneurysm abruptly and spontaneously appeared from the bypass suture site without any predisposing factor. The lesion was revealed to be an organizing thrombus.

• Journal of Chest Surgery
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• v.50 no.5
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• pp.355-362
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• 2017

Background: Off-pump coronary artery bypass grafting (OPCABG) procedures can avoid the complications of an on-pump bypass. However, some cases unexpectedly require conversion to cardiopulmonary bypass during OPCABG. The risk factors associated with a sudden need for cardiopulmonary bypass were analyzed. Methods: This retrospective study included 283 subjects scheduled for OPCABG from 2001 to 2010. These were divided into an OPCABG group and an on-pump conversion group. Preoperative, operative, and postoperative variables were compared between the 2 groups. Results: Of the 283 patients scheduled for OPCABG, 47 (16%) were switched to on-pump coronary artery bypass grafting (CABG). The mortality of the both the OPCABG and on-pump conversion groups was not significantly different. The major risk factors for conversion to on-pump CABG were congestive heart failure (CHF) (odds ratio [OR], 3.5; p=0.029), ejection fraction (EF) <35% (OR, 4.4; p=0.012), and preoperative beta-blocker (BB) administration (OR, 0.3; p=0.007). The use of intraoperative (p=0.007) and postoperative (p=0.021) inotropics was significantly higher in the conversion group. The amount of postoperative drainage (p<0.001) and transfusion (p<0.001) also was significantly higher in the conversion group. There were no significant differences in stroke or cardiovascular complications between the groups over the course of short-term and long-term follow-up. Conclusion: Patients who undergo OPCABG and have CHF or a lower EF (<35%) are more likely to undergo on-pump conversion, while preoperative BB administration could help prevent conversions from OPCABG to on-pump CABG.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.1
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• pp.12-17
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• 2008

In this paper, an I-V characteristics of bypass diode has been studied by counting the shading effect in photovoltaic module. The shadow induces hot spot phenomenon in PV module due to the increase of resistance in the current path. Two different types of PV module with and without bypass diode were fabricated to expect maximum output power with an increasing shading rate of 5 % on the solar cell. Temperature distribution is also detected by shading the whole solar cell for the outdoor test. From the result, the bypass diode works properly over 60 % of shading per cell with constant output power. Maximum power generation in case of solar cell being totally shaded with bypass diode decreases 41.3 % compared with the one under STC(Standard Test Condition). On the other hand, the maximum output power of the module without bypass diode gradually decreases by showing hot spot phenomenon with the increase of shading ratio on the cell and finally indicates 95.5 % of power loss compared with the output under STC. Finally the module temperature measured increases around $10^{\circ}C$ higher than that under STC due to hot-spots which come from the condition without bypass diode. It has been therefore one of the main reasons for degrading the PV module and shortening the durability of the PV system.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.5
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• pp.577-584
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• 2015

A photovoltaic (PV) system generates electricity by installing a solar energy array; therefore, the photovoltaic system can be easily exposed to external factors, which include environmental factors such as temperature, humidity, and radiation. These factors-as well as shading, in particular-lead to power degradation. When there is an output loss in the solar cell of a PV module package, the output loss is partly controlled by the bypass diode. As solar cells become highly efficient, the characteristics of series resistance and parallel resistance improve, and the characteristics of reverse voltage change. A bypass diode is connected in parallel to the string that is connected in series to the PV module. Ideally, the bypass diode operates when the voltage is -0.6[V] around. This study examines the bypass diode operating time for different types of crystalline solar cells. It compares the reverse voltage characteristics between the single solar cell and polycrystalline solar cell. Special modules were produced for the experiment. The shading rate of the solar cell in the specially made solar energy module was raised by 5% each time to confirm that the bypass diode was operating. The operation of the bypass diode is affected not only by the reverse voltage but also by the forward bias. This tendency was verified as the number of strings increased.

• Journal of Chest Surgery
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• v.29 no.11
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• pp.1267-1269
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• 1996

Coronary artery bypass grafting without cardiopulmonary bypass is now one of accepted technique of myocardial revascularization. This technique is an alternative method for patients with lesions in the left anterior descending coronary artery and right coronary artery. We report a case of coronary artery bypass grafting without cardiopulmonary bypass or cardiac arrest.