• 한국산학기술학회논문지
• /
• 제19권9호
• /
• pp.146-155
• /
• 2018

본 연구는 허혈성심장질환으로 관상동맥우회술을 받은 환자에서 심폐바이패스 여부에 따른 임상성과를 확인하고자 시행하였다. 연구대상은 2008년 7월부터 2012년 6월까지 4년 동안 허혈성심장질환으로 관상동맥우회술을 받은 환자 전수이며, 총 10,981명이었다. 분석 자료는 건강보험심사평가원 청구명세서를 이용하여 후향적으로 수집하였다. 연구결과, 무심폐기 관상동맥우회술(Off Pump CABG, OPCAB) 환자 그룹이 고식적 관상동맥우회술(On Pump CABG, ONCAB) 환자 그룹에서보다 평균 수술소요시간(280분 vs 357분, p<.0001) 및 기관 내 삽관 후 발관까지 평균 소요시간이 짧았고(약 24시간 vs 40시간, p<.0001), 수술 후 출혈 및 혈종 등으로 인한 재수술률이 낮았다(2.7% vs 8.3%, p<.0001). 위험요인 통제 하에 심폐기 사용 여부에 따른 30일내 사망률과 재원일수를 분석한 결과, 고식적 관상동맥우회술(ONCAB) 대비 무심폐기 관상동맥우회술(OPCAB)의 사망 위험비는 0.339(0.266-0.434)이고, 재원일수는 -0.29229로 감소하였다(p<.0001). 이상의 결과 심폐기를 사용하지 않은 경우에서 30일내 사망률과 재수술률이 낮았고, 평균 수술소요시간, 기관 내 삽관 후 발관까지 소요시간, 재원일수가 짧았음을 확인하였다.

• Journal of Chest Surgery
• /
• 제20권1호
• /
• pp.187-190
• /
• 1987

The Saphenous vein is still the graft of choice for bypass of small calibered peripheral arteries, and many recent studies revealed that the "In Situ" technique had higher rate of long term patency than the conventional "reversed" one. A 71-year-old male who had atherosclerotic obstruction in the superficial femoral and popliteal trifurcation underwent In Situ saphenous vein arterial bypass. The saphenous vein is exposed by a long medial skin incision over the course of the vein. All branches of vein are ligated. A olive-tipped metal needle is introduced into the vein from above and everts the valves. The patient has been followed for 2 months after operation. The graft remained pulsatile and the gangrenous areas on the toe proceeded to heal. We think In situ vein bypass offers an excellent and safe method of revascularization of the arterial occlusion below the knee although it is technically demanding and the time consuming. time consuming.

• 한국전기전자재료학회논문지
• /
• 제21권1호
• /
• pp.12-17
• /
• 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
• /
• 제15권5호
• /
• pp.577-584
• /
• 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
• /
• 제49권6호
• /
• pp.485-488
• /
• 2016

Different suture techniques have been used for anastomosis in coronary artery bypass graft surgery. Bypass surgery may be difficult for patients who have small coronary arteries or marked size discrepancies between target coronary arteries and grafts. For proximal and distal anastomoses, three continuous stitches are first placed in the heel and toe of the small coronary arteries; for sequential anastomosis, an interrupted eight-stitch technique is used. We applied these anastomotic suture techniques in patients requiring coronary artery bypass graft surgery, achieving an early angiographic patency rate of 100%.

• Journal of Chest Surgery
• /
• 제26권12호
• /
• pp.926-933
• /
• 1993

We experienced 20 patients with Takayasu`s disease who required 22 surgical procedures for critical arterial stenoses, aneurym of descending thoracic aorta, and aortic regurgitation from 1986 to 1993.Five patients had type I arteritis, seven patients had type II , seven patients had type III, and one patients had type IV.15 patients were female and 5 patients were male.Patients` ages ranged from 17 to 47 years and mean age was 29.1 years. The surgical procedures were as follows;autotransplantations of kidney[3], aortic valve replacements[2], ascending aorta-bilateral internal carotid artery bypasses[2], unilateral renal artery bypasses[2], bilateral renal artery bypasses[3], replacement of descending thoracic aorta[1], ascending aorta-abdominal aorta bypass[1], ascending aorta-right internal carotid artery bypass[1], ascending aorta-right internal carotid artery and left subclavian artery bypass[1], left common carotid artery-left-subclavian artery bypass[1], pulmonary artery angioplasty[1], left femoro-bilateral axillary bypass[1] and others[2]. There was no hospital death.Mean duration of follow-up was 42.7 months[ranged from 3 to 96 months].There was one late death and late mortality rate is 5.9%.Two patients was underwent second vascular procedures, one after 5 years and the other after 5 months.The other patients have done well after surgery.

• 한국수소및신에너지학회논문집
• /
• 제23권4호
• /
• pp.293-299
• /
• 2012

The serpentine flow channel is widely used in polymer electrolyte membrane fuel cells (PEMFCs) to prevent flooding phenomena because it effectively removes liquid water in the flow channel. The pressure drop between inlet and outlet increases as compared with straight channels due to minor losses associated with the corners of the turning configurations. This results in a strong pressure gradient between adjacent channels in specific regions, where some amount of reactant gas can be delivered to catalyst layers by convection through a gas diffusion layer (GDL). The enhancement of the convective flow in the GDL, so-called bypass flow, affects fuel cell performance since the bypass flow influences the reactant transport and thus its concentration over the active area. In the present paper, for the bipolar plate design, a simple analytic model has been proposed to predict the bypass flow in the serpentine type flow channels and validated with three-dimensional numerical simulation results.

• Journal of Chest Surgery
• /
• 제30권2호
• /
• pp.195-199
• /
• 1997

복부대동맥과 그 이하 주요분지들의 동맥폐쇄에 의한 하지 만성허혈은 동맥경화증이 주원인이며 이 질환의 임상적 중요성은 혈관이 진행적으로 폐쇄됨에 따라 혈류장애가 발생하여 간헐적 파행, 휴식시 동통이 일어나며 더 진행되면 조직의 괴사가 발생,결국괴사된 조직의 절단을 초래하게된다. 본한국보 훈병원 흉부외과에서는 1992년 12월부터 1995년 12월까지 폐쇄성 하지동맥 경화증으로 입원한 20명의 환자를 대상으로 동맥간 우회술을 시 행하였다. 임상증상은 괴사및 괴저 9례(45B4), 파행 7례(35%), 안정 시 동통 4례(20%)순이었다. 사용한 혈관은 복부대동맥및 총대퇴동맥의 경우 Y-형및 I-형 인조혈관을 사 용하였고 대퇴동맥이하의 혈관에서는 주로 자가 대복재정 맥을 사용하였다. 술후 합병증은 4례로 20% 를 보였고 이식된 혈관내 혈전증 2례, 창상감염 2례 였다. 술후 혈관개존율은 복부대동맥과 양측 대퇴동 맥간 우회술의 경우 100%였고 대퇴동맥 이하에서는 6개월이 92.6%, 1년 84.2%, 2년 75.4%, 3년 69.4% 였다.

• Journal of Korean Neurosurgical Society
• /
• 제58권6호
• /
• pp.518-527
• /
• 2015

Objective : The treatment of complex intracranial aneurysms remains challenging. One approach is the application of surgical flow alteration to treat aneurysms that are neither clippable, trappable, or coilable. The efficacy and limitations of surgical flow alteration have not yet been established. Methods : Cases of complex aneurysms treated with surgical flow alteration (proximal occlusion with or without bypass, distal occlusion with or without bypass and bypass only) were included in this retrospective study. Results : Among a total of 16 cases, there were 7 giant aneurysms (${\geq}25mm$ diameter) and 9 large aneurysms (>10 mm diameter); 15 of 16 aneurysms were unruptured. There were 8 aneurysms located in the anterior circulation, while the other 8 were in the posterior circulation. Aneurysms were treated with proximal occlusion in 10 cases and distal occlusion in 5 cases; in 1 case, the aneurysm occluded spontaneously after bypass without parent artery occlusion. All but 2 cases underwent prior or concurrent bypass surgery. Complete obliteration of the aneurysm at the latest imaging follow-up was shown in 12 of 16 cases (75.0%). Bypass patency was confirmed in 13 of 15 cases (86.7%). Surgery-related morbidity developed in 3 cases (18.8%, Glasgow outcome scale of 4) and all were perforator infarctions. There were no mortalities. Conclusion : Surgical flow alteration resulted in a high rate of aneurysmal obliteration with acceptable morbidity. Although several limitations remained, it could represent an alternative method for treating complex aneurysms.

• Journal of Chest Surgery
• /
• 제22권6호
• /
• pp.1092-1100
• /
• 1989

Since May 1987 to April 1989, fifteen patients have been subjected to coronary artery bypass graft [CABG] including coronary thromboendarterectomy in 3 patients at Hanyang University Hospital. The correlation between the preoperative coronary angiography, electrocardiography, clinical status, operative finding and postoperative blood flow, complication and degree of clinical improvement were evaluated. 1. Ten patients [67 %] were male and five patients [33 %] were female, Ages ranged from 30 to 68 years. [average 52.2 years] 2. The angina by types of presentation was stable in 3 patients, unstable in 12 patients with resting, postinfarction and progressive angina as the criteria of unstability. 3. The number of involved vessels were single in 6 cases, double in 4 cases, triple in 5 cases including 1 case of left main coronary arterial disease. 4. The distribution of sites of distal anastomosis revealed predilection to left coronary arterial system [83 %], especially left anterior descending arterial system. 5. The author performed 4 cases of single bypass, 4 cases of double bypass, 5 cases of triple bypass and 2 cases of quadruple bypass. Of these 15 patients, 3 patients received coronary thromboendarterectomy, LAD in 2 patients and right coronary artery [RCA] in 1 patient. 6. The distal anastomosis were performed first with using saphenous vein grafts as conduits in all cases except 1 case using Gore-Tex conduit because of deficient in length and narrowed internal mammary artery and sequential bypass methods were employed in last 6 cases. 7. One operative death occurred and therefore, mortality rate was 6.7%. The perioperative myocardial infarction were occurred in 3 cases [20%] and its cause was supposed that they were triple vessel disease and therefore, aortic cross clamping times were relatively long. 8. All survivors were followed for 17.7 months on an average [range 5-28 months] and they have had symptomatic improvement except 1 case having mild degree of angina at 1.5 months after operation.