• Journal of Chest Surgery
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• v.56 no.2
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• pp.99-107
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• 2023

Background: The neutrophil-to-lymphocyte ratio (NLR) has been suggested as a novel predictive marker of cardiovascular disease. However, its prognostic role in patients under-going coronary artery bypass grafting (CABG) is unclear. This study aimed to determine the association between the preoperative NLR and early mortality in patients undergoing CABG. Methods: Cardiac surgery was performed in 2,504 patients at Seoul St. Mary's Hospital from January 2010 to December 2021. This study retrospectively reviewed 920 patients who underwent isolated CABG, excluding those for whom the preoperative NLR was unavailable. The primary endpoints were the 30- and 90-day mortality after isolated CABG. Risk factor analysis was performed using logistic regression analysis. Based on the optimal cut-off value of preoperative NLR on the receiver operating characteristic curve, high and low NLR groups were compared. Results: The 30- and 90-day mortality rates were 3.8% (n=35) and 7.0% (n=64), respectively. In the multivariable analysis, preoperative NLR was significantly associated with 30-day mortality (odds ratio [OR], 1.28; 95% confidence interval [CI], 1.17-1.39; p<0.001) and 90-day mortality (OR, 1.17; 95% CI, 1.07-1.28; p<0.001). The optimal cut-off value of the preoperative NLR was 3.4. Compared to the low NLR group (<3.4), the high NLR group (≥3.4) showed higher 30- and 90-day mortality rates (1.4% vs. 12.1%, p<0.001; 2.8% vs. 21.3%, p<0.001, respectively). Conclusion: Preoperative NLR was strongly associated with early mortality after isolated CABG, especially in patients with a high preoperative NLR (≥3.4). Further studies with larger cohorts are necessary to validate these results.

• IEMEK Journal of Embedded Systems and Applications
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• v.5 no.3
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• pp.157-167
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• 2010

One of the most famous proactive routing protocols, DSDV (Destination -Sequenced Distance-Vector), is based on the minimum hop count. This paper suggests BIMP(Bypass Information Multi-Path) DSDV routing protocol that this protocol could route reliably as it can take the information of the bypass for the solution of the problem on EHMP DSDV. In this paper, the protocol checks throughput, packet delivery delay, packet delivery ratio, number of management messages, packet transmit finish time, etc on the traffic compared to DSDV, HMP DSDV, and EHMP DSDV protocols.

• Journal of Chest Surgery
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• v.39 no.4 s.261
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• pp.298-303
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• 2006

Background: This study was performed to investigate the outcomes of vascular operations that were done in patients with atheroscerosis obliterans (ASO) of lower limb. Material and Method: Forty patients underwent vascular operations from December 1996 to June 2004. The patient's records were analyzed retrospectively. Mean age was $66{\pm}8$ years (range, $47{\sim}81$ years). Gender ratio was 37:3 (male:female). Result: The operations were done on 50 lower limbs of 40 patients. The names of operations were femoropopliteal bypass in 12 patients (30%), femorofemoral bypass in 12 (30%), femorofemoral bypass and femoropopliteal bypass in five (12.5%), aorta-lower limb artery bypass in five (12.5%), axillofemoral bypass in two (5%), iliopopliteal bypass in two (5%), and endarterectomy in two (5%). All bypass surgeries were done with prosthetic conduits. Mean follow up period was $33.2{\pm}23.2$ months (range, $3.8{\sim}90.2$ months). The cumulative patency rates of 1 and 5 years were 75.5 and 58.7% respectively. In six patients, amputation of the lower limb was done. In eight patients, 12 complications occurred. After the first operation, 10 patients underwent reoperations. Conclusion: Our lower limb arterial bypass surgery revealed acceptable patency rate, but not a few patients required reoperations. An epochal treatment modality that can inhibit the progress of ASO and improve long term patency should be established.

• Journal of Chest Surgery
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• v.20 no.2
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• pp.261-269
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• 1987

From 1976 through 1986, authors have experienced 127 cases of peripheral vascular surgery which had been done in this department. There were 29 cases of atherosclerosis obliterances including 7 Leriche syndrome, 32 Buerger`s diseases, 25 arterial thromboembolisms, 21 vascular injuries, 2 peripheral arterial aneurysms, 2 renovascular hypertensions, 1 congenital A-V malformation, 13 varicose vein of lower extremities, and 2 Jugular venous ectasia. Cases with vena caval disease and aortic disease were excluded. The mean age of ASO and Buerger`s disease was 56.1 yrs, 33.8 yrs respectively. The male to female ratio showed marked male preponderance [27:2, and 30:2], and almost every male patient was smoker. The indication of operation was similar in both disease entities. The method of operation for ASO were bypass procedure [17], thromboendarterectomy [6], and lumbar sympathectomy [5], and for Buerger`s disease were mainly sympathectomy and few bypass procedures and amputations. Seventeen patients with ASO were followed from 3 to 75 month and overall patency rate for bypass or endarterectomy in one and two months and 2 1/2 yr were 93%, 87%, and 31% respectively. Post operatively patient`s symptoms was relieved or alleviated in almost ASO patients, and about 60% of Buerger`s disease. We concluded that in patient with ischemic limb, we must revascularized aggressively for symptomatic relief. And choice of graft for bypass procedure was to be evaluated further.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.9
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• pp.146-155
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• 2018

This study was conducted to evaluate the clinical outcomes of coronary artery bypass surgery for ischemic heart disease according to use of a cardiopulmonary bypass machine. The subjects were 10,981 patients who underwent coronary artery bypass grafting for ischemic heart disease from July 2008 to June 2012. Analysis data were retrospectively collected using health insurance claims data. The results of the study showed that mean time to surgery (280 min vs 357 min, p<0.0001) and intubation time (about 24 hours vs 40 hours, p<0.0001) were significantly shorter in the Off-Pump CABG (OPCAB) group than in the On-Pump CABG (ONCAB) group. The rate of reoperation because of postoperative bleeding and hematoma was lower in the OPCAB group (2.7% vs 8.3%, p<.0001). The odds ratio of risk adjusted 30 days mortality rate was 0.339 (0.266-0.434) and the postoperative length of stay was decreased in the OPCAB (p<0.0001). Overall, the 30 days mortality and reoperation rates were lower in the OPCAB, as was the resources use.

• Journal of Chest Surgery
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• v.49 no.sup1
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• pp.60-67
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• 2016

Background: Coronary angioplasty has been replacing coronary artery bypass grafting (CABG) because of the relative advantage in terms of recovery time and noninvasiveness of the procedure. Compared to other Organization for Economic Cooperation and Development (OECD) countries, Korea has experienced a rapid increase in coronary angioplasty volumes. Methods: We analyzed changes in procedure volumes of CABG and of percutaneous coronary intervention (PCI) from three sources: the OECD Health Data, the National Health Insurance Service (NHIS) surgery statistics, and the National Health Insurance claims data. Results: We found the ratio of procedure volume of PCI to that of CABG per 100,000 population was 19.12 in 2014, which was more than triple the OECD average of 5.92 for the same year. According to data from NHIS statistics, this ratio was an increase from 11.4 to 19.3 between 2006 and 2013. Conclusion: We found that Korea has a higher ratio of total procedure volumes of PCI with respect to CABG and also a more rapid increase of volumes of PCI than other countries. Prospective studies are required to determine whether this increase in absolute volumes of PCI is a natural response to a real medical need or representative of medical overuse.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.5
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• pp.34-42
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• 2020

In modern air combat, infrared signals play an important role in the detection of opponents and must be reduced to improve survivability and stealth. In particular, IR signals generated in the wake of aircraft engines have high intensity and short wavelengths, so most heat-tracking missiles detect these signals. Accordingly, the measurement and characteristic analysis of Gas radiation signals from the engine's wake were carried out in this study. Micro turbojet engine has been configured to simulate a real aircraft turbofan engine, and the characteristics of IR signal reduction by adjusting the bypass ratio were identified. Through this, the IR signal characteristics for each wavelength are analyzed and verification of signal reduction technologies is performed.

• Journal of Chest Surgery
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• v.55 no.3
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• pp.189-196
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• 2022

Background: This study investigated the predictive value of the frailty index calculated using laboratory data and vital signs (FI-L) in patients who underwent coronary artery bypass grafting (CABG). Methods: This study included 508 patients (age 67.3±9.7 years, male 78.0%) who underwent CABG between 2018 and 2021. The FI-L, which estimates patients' frailty based on laboratory data and vital signs, was calculated as the ratio of variables outside the normal range for 32 preoperative parameters. The primary endpoints were operative and medium-term all-cause mortality. The secondary endpoints were early postoperative complications and major adverse cardiac and cerebrovascular events (MACCEs). Results: The mean FI-L was 20.9%±10.9%. The early mortality rate was 1.6% (n=8). Postoperative complications were atrial fibrillation (n=148, 29.1%), respiratory complications (n=38, 7.5%), and acute kidney injury (n=15, 3.0%). The 1- and 3-year survival rates were 96.0% and 88.7%, and the 1- and 3-year cumulative incidence rates of MACCEs were 4.87% and 8.98%. In multivariable analyses, the FI-L showed statistically significant associations with medium-term all-cause mortality (hazard ratio [HR], 1.042; 95% confidence interval [CI], 1.010-1.076), MACCEs (subdistribution HR, 1.054; 95% CI, 1.030-1.078), atrial fibrillation (odds ratio [OR], 1.02; 95% CI, 1.002-1.039), acute kidney injury (OR, 1.06; 95% CI, 1.014-1.108), and re-operation for bleeding (OR, 1.09; 95% CI, 1.032-1.152). The minimal p-value approach showed that 32% was the best cutoff for the FI-L as a predictor of all-cause mortality post-CABG. Conclusion: The FI-L was a significant prognostic factor related to all-cause mortality and postoperative complications in patients who underwent CABG.

• 한국전산유체공학회:학술대회논문집
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• 1999.11a
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• pp.167-173
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• 1999

An Euler-based CFD tool has been developed for the performance evaluation of a thrust reverser mounted on a high bypass ratio turbofan engine. The computational domain surrounded by the ground and non-reflection boundary includes the whole nacelle configuration with a deployed thrust reverser. The numerical algorithm is based on the modified Godunovs scheme to allow the second order accuracy in both space and time. The grid system is generated by using eleven multi-blocks, of which the total cell number is 148,400. The thrust reverser is modeled as if it locates at the nacelle simply in all circumferential direction. The existence of a fan and an OGV(Outlet Guide Vane) is simulated by adopting the actuator disk concept, in which predetermined radial distributions of stagnation pressure ratio and adiabatic efficiency coefficient are used for the rotor type disk, and stagnation pressure losses and flow outlet angles for the stator type disk. All boundary conditions including the fan and OGV simulation are treated by Riemann solver. The developed solver is applied to a turbofan engine with a bypass ratio of about 5.7 and the diameter of the fan cowl of 83 inch. The computational results show that the Euler-based inviscid method is very useful and economical to evaluate the performance of thrust reversers.

• Journal of Korean Society of Disaster and Security
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• v.12 no.1
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• pp.57-66
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• 2019

One of the most serious problems with concrete small dams or barriers installed in small/median rivers is the deposit of sediments, especially, in Korea. An effective way to discharge such sediments to downstream is to construct a bypass pipe under the river bed. However, efficiency may become lowered if ripraps are entered into the bypass pipe. Therefore, in this study, we derived the threshold condition for the exclusion of ripraps from the bypass pipe using 3D numerical analysis. Upstream flow of the small dam was assumed to be stationary, and the energy concept was applied to the control volume containing the bypass pipe and its periphery. As a result, when the ratio of the water level difference between upstream and downstream to the diameter of the riprap was approximately equal to 1.2, the threshold condition for exclusion of the stones or riprap from the bypass pipe was affirmatively determined. If the characteristics of the adsorptive sediment adversely affecting the river environment in the future would be taken into account, results from this study are expected to put to practical use in the management of concrete small dam with bypass pipe system.