• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.1
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• pp.38-46
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• 2011

The hybrid defrost process combined with hot-gas bypass defrost and electric heater defrost was experimentally evaluated about its defrost performance in the fin-tube evaporators of household refrigerators. Also the hybrid defrost process was compared with only electric heater defrost process. The defrost efficiency of the hybrid defrost process was shown two times higher than electric heater defrost process. The defrost time of the hybrid defrost process was shorten about 10%~50% than electric heater defrost process. Thermal shock after defrost process was decreased about 50% for the case of the hybrid defrost. It was found that energy consumption ratio of defrost process was reduced up to 7.4% compared with 22.4% of electric heater defrost at the condition of $25^{\circ}C$ ambient temperature.

• Journal of Chest Surgery
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• v.26 no.5
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• pp.355-359
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• 1993

Ten consecutive patients with abdominal aortic aneurysm were treated in Chungnam National University Hospital from May of 1985 to June of 1993. Pulsating palable mass was the most common first sign [7 patients]. The ratio of male to female was 8:2. The age ranged from 53 to 73 years with mean age of 65 years. The etiology and location of the aneurysm was atherosclerosis and infrarenal aorta in all. Dacron graft interposition [straight graft-1, bifurcation graft-7] and wrapping with aneurysmal sac were performed in 8 patients. In one patient with infected abdominal aortic aneurysm, we performed aneurysmectomy and left axillo-bifemoral bypass with 8 mm PTFE graft. And in another patient with complete thrombotic obstruction of infrarenal aortic aneurysm, we performed the suturing of the proximal part of the abdominal aortic aneurysm and aorto-bifemoral bypass with 18 x 9 mm PTFE graft. There was one operative death with the mortality rate of 11 % and 8 complications in 4 patients; ARF[2], duodenal ulcer[1], mechanical ileus[1], genitourinary dysfunction[2] and wound infection with abdominal abscess[1]. Because of the high operative mortality after rupture of the aneurysm, we think it is better to operate on early at the diagnosis of abodominal aortic aneurysm is made.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.842-849
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• 2011

Open Rotor Engine is one of the several new technologies offering potential solution for the next generation aircraft. The coupling of ultra high bypass ratio and aerodynamically advanced fan blade design allow the open rotor engine to achieve and advantage in fuel consumption. The open rotor engine does have more thrust lapse than the general high bypass turbofan. The open rotor engine performance model was analyzed using a reference data based on the GE36 which was designed and tested data at which time a F404 turbojet was used as the core. The performance model of open rotor engine was verified by referred test data and was evaluated to be properly constructed, through the comparison of recent Next generation turboprop engine performance.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.38-39
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• 2019

Mechanical properties of concrete containing furnace slag according to the CBS Dust Replacement Ratio were analyzed. The experimental study found that the compressive strength was excellent in the early age when the CBS Dust was replaced, and the drying shrinkage was excellent, and the replacement of CBS Dust 5% on the concrete containing the furnace slag would have a positive effect.

• Journal of Chest Surgery
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• v.37 no.6
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• pp.511-516
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• 2004

Background: One of the theoretical advantages of skeletonized internal mammary artery harvesting in coronary artery bypass surgery is to minimize the interruption of the sternal blood flow inevitably accompanied by internal mammary harvesting. A study using bone scan is designed to determine the effects of internal mammary artery harvesting technique on the sternal blood flow. Material and Method: From April 2002 to March 2003, 27 patients out of 48 patients who underwent the isolated coronary bypass surgery were enrolled into the study. The enrolled patients underwent bone scan in the preoperative period and postoperative period respectively. Bilateral internal mammary artery was used in 8 patients (BIMA group) and single left internal mammary artery in 19 patients (LIMA group). The patients in LIMA group were divided into two groups: LlMA_skel group, in whom left internal mammary artery was harvested in skeletonized fashion (n=12), and LlMA_ped group, in whom left internal mammary artery was harvested in pedicled fashion (n=7). After the bone scan, the region of interest (ROI) was created on the left of the sternum and the mirror image with the same pixel numbers was placed on the right half of the sternum. The mean counts per pixel on the left side of the sternum was compared with those on the right side and expressed as left to right ratio (L/R ratio). Result: In LIMA group, the L/R ratio decreased from 94.6$\pm$4.1% to 87.9$\pm$6.9% (p=0.003) after the operation as compared to BIMA group, in which no change of the L/R ratio was observed. The changed of the L/R ratio in LlMA_skel group and LlMA_ped group were from 95.3$\pm$4.2% to 88.3$\pm$7.7% and from 93.4$\pm$3.9% to 87.4$\pm$5.8% respectively. The % changes in L/R ratio were -7.44 $\pm$7.08 in LIMA_skel group and -6.17$\pm$9.08 in LiMA_ped group, which did not reach the statistical difference. Conclusion: Ipsilateral sternal blood flow is interrupted by internal mammary artery harvesting as evidenced by the decrease in L/R ratio after left internal mammary artery harvesting irrespective of the harvesting techniques. Skeletonized harvesting did not show superiority in respect to sternal blood flow as compared to pedicled harvesting.

• The KSFM Journal of Fluid Machinery
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• v.15 no.5
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• pp.27-31
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• 2012

Turbine inlet temperature is steadily increasing to achieve high specific thrust and efficiency of gas turbine engines. Turbine cooling technology is essential to increase turbine inlet temperature. For this study, a small or medium sized aircraft engine of 10,000 lbf class with the turbine inlet temperature of $1,400^{\circ}C$, the engine overall pressure ratio of 32.2, and the bypass ratio of 5 was set as the baseline model and its performance analysis was performed at the design point. The engine has the performance of 10,013 lbf thrust and the specific fuel consumption of 0.362 lbm/hr/lbf. The thrust and the specific fuel consumption of the baseline model were compared with those of similar class engines. Based on these results, the turbine design requirements were assigned. In addition, the parametric analysis of the engine, related to aerodynamic and cooling design of the high pressure turbine, was performed. Based on the baseline model engine, the influence of turbine inlet temperature, cooling flow ratio, and high pressure turbine efficiency variations on the engine performance was analyzed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.1
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• pp.239-246
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• 2017

There are various transversal structures (small dams or drop structures) in median and small streams in Korea. Most of them are concrete structures and it is so hard to exclude low-level water. Unless drainage valves and/or gates would not be installed near bottom of bed, sediment from upstream should be deposited and also contaminants attached to the sediments would devastatingly threaten the water quality and ecosystem. One of countermeasures for such problem is the bypass pipe installed underneath the transversal structure. However, there is still issued whether it would be workable if the gravels and/or stones would roll into and be not excluded. Therefore, in this study, the conditions to exclude the rip stone which enter into the bypass pipe was reviewed. Based on sediment transport phenomenon, the behavior of stones was investigated with the concepts from the critical shear stress of sediment and d'Alembert principle. As final results, the basis condition (${\tau}_c{^*}$) was derived using the Lagrangian description since the stones are in the moving state, not in the stationary state. From hydraulic experiments the relative velocity could be obtained. In order to minimize the scale effect, the extra wide channel of 5.0 m wide and 1.0 m high was constructed and the experimental stones were fully spherical ones. Experimental results showed that the ratio of flow velocity to spherical particle velocity was measured between 0.5 and 0.7, and this result was substituted into the suggested equation to identify the critical condition wether the stones were excluded. Regimes about the exclusion of stone in bypass pipe were divided into three types according to particle Reynolds number ($Re_p$) and dimensionless critical shear force (${\tau}_c{^*}$) - exclusion section, probabilistic exclusion section, no exclusion section. Results from this study would be useful and essential information for bypass pipe design in transveral structures.

• Journal of Chest Surgery
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• v.25 no.12
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• pp.1570-1577
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• 1992

The vascular surgery is the field that has developed in early 20 century and is progressing nowadays. Recent advance in surgical technique accompanying with excellent medical diagnosis and treatment, prompt angiographic usage, development of variable prosthetic material, and concomitant use of anti-coagulant have made remarkable results of vascular surgery. 83 cases of vascular surgery have been performed at Thoracic and Cardiovascular Surgery Department of Pusan National Unversity Hosaital since 1971 till 1990, for 20 years and their results are followed. Patient ductus arteriosus and Buerger`s disease were omited in this study. 1. The age distribution shows that the fifth and sixth decades are most frequently affected and mean age was 56.1 years old. Male to female ratio is 1: 2.32. 2. Among the 83 cases of all, number of occlusive vascular disease is 46 and that of aneurysmal disease is 33. 3. In clinical manifestation, most common symptom of occlusive disease is pulselessness and pain was next. Mass sensation is most commonly complained by patients of aneurysmal disease. 4. CT scan was more important in diagnosis of aneurysmal diseases and angiogram was more commonly used in occlusive diseases. 5. The common site of arterial occlusion was common iliac artery, femoral artery, aortic bifurcation, and external iliac artery, as its frequency rate. The most commonly affecting portion of aortic aneurysm was abdminal aorta, and descending thoracic aorta and femoral artery were next 6. Preoperative associated diseases were atherosclerosis[41 cases], hypertension[21 cases], valvular heart disease[11 cases], and diabetes mellitus[9 cases], etc, 7. Operative methods in ocllusive diseases were thrombectomy[36.9%], endarterectomy [10.9%], and bypass graft insertion[52.7%]. Among the bypass graft, Y-graft was used in 7 case, straight graft was used in 17 cases, and saphenous venous graft was used in 2 cases. 8. Postoperative complications were developed in 17 cases, and morbidity rate was 36. 9. Eleven patient were died within 1 month after operation, so operative mortality rate was 13.3%. 10. Duration of patency was beteween 7 and 58 months[average 27.5 months] in occlusive diseases and their 5-year patency rate was 56.3%. Duration of patency of aneurysmal disease was 20 months in aveage and their 5-year patency rate was 51.3%. 11. Patients of eleven cases of occlusive disease and two cases of aneurysmal disease required reoperation for variable reason. 12. 35 cases of patient have used anticoagulants: coumadin, ticlid, and persanthin-ASA combination.

• Journal of Chest Surgery
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• v.18 no.4
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• pp.692-699
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• 1985

Fifty cases of Open Heart Surgery due to congenital and acquired heart disease were done using the cardiopulmonary bypass in the Department of Thoracic and Cardiovascular surgery, Chosun University Hospital from November, 1980 to June, 1985. 1. The age of the congenital heart disease was from 7 to 29 years, the mean age was 14.5 years. In the acquired heart disease, the age was from 14 to 48 years, and the mean age was 22.3 years. The ratio of male to female was about 1.8:1. 2. The number of congenital cyanotic heart disease were 7 patients, congenital acyanotic heart disease were 17 patients and acquired valvular heart disease were 26 patients. All of the acquired heart disease was one or more valve disease. 3. Preoperative symptoms of the congenital heart disease were exertional dyspnea [cyanotic 100%, acyanotic 70.6%] and palpitation [cyanotic 28.6%, acyanotic 76.1%], and the acquired heart diseases were exertional dyspnea [92.3%], palpitation [34.1 %], and chest discomfort [30.8%]. 4. The method of the myocardial protection during the cardiopulmonary bypass were mild or moderate hypothermia, intermittent coronary perfusion of the cardioplegic solution, topical myocardial hypothermia with 4oC Hartmann`s solution. 5. In the cases of the valve replacement, postoperative oral anticoagulant therapy was started at oral intake of food using the warfarin and persantin, and the prothrombin time was maintained 30-50% of control value during 3-6 months for tissue valve replacement and permanently for metal valve replacement. 6. The postoperative complications were appeared in 24 cases and the complications were wound infection, occipital alopecia, hemorrhage etc. 7. The mortality after open heart surgery was 8 percents and the cause of death was low cardiac output syndrome, right heart failure, DIC, and Left ventricle rupture.

• Journal of Preventive Medicine and Public Health
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• v.57 no.3
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• pp.260-268
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• 2024

Objectives: Regional disparities in cardiovascular care in Korea have led to uneven patient outcomes. Despite the growing need for and access to procedures, few studies have linked regional service availability to mortality rates. This study analyzed regional variation in the utilization of major cardiovascular procedures and their associations with short-term mortality to provide better evidence regarding the relationship between healthcare resource distribution and patient survival. Methods: A cross-sectional study was conducted using nationwide claims data for patients who underwent coronary artery bypass grafting (CABG), percutaneous coronary intervention (PCI), stent insertion, or aortic aneurysm resection in 2022. Regional variation was assessed by the relevance index (RI). The associations between the regional RI and 30-day mortality were analyzed. Results: The RI was lowest for aortic aneurysm resection (mean, 26.2; standard deviation, 26.1), indicating the most uneven regional distribution among the surgical procedures. Patients undergoing this procedure in regions with higher RIs showed significantly lower 30-day mortality (adjusted odds ratio [aOR], 0.73; 95% confidence interval, 0.55 to 0.96; p=0.026) versus those with lower RIs. This suggests that cardiovascular surgery regional availability, as measured by RI, has an impact on mortality rates for certain complex surgical procedures. The RI was not associated with significant mortality differences for more widely available procedures like CABG (aOR, 0.96), PCI (aOR, 1.00), or stent insertion (aOR, 0.91). Conclusions: Significant regional variation and underutilization of cardiovascular surgery were found, with reduced access linked to worse mortality for complex procedures. Disparities should be addressed through collaboration among hospitals and policy efforts to improve outcomes.