• 항공우주시스템공학회지
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• 제17권5호
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• pp.11-18
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• 2023

The architecture of the Fuel Thermal Management System (FTMS) in a commercial aircraft engine was built to model and simulate the fuel system. The study shows the thermal interactions between the fuel and engine lubrication oil through the mission profile of a high bypass ratio, two-spool turbofan engine. Fuel temperature was monitored as it flowed through each sub-component of the fuel system during the mission. The heat load in the fuel system strongly depended on the fuel flow rate, and was significantly increased for the periods of cruise and descent with decrease of fuel flow rate, rather than for the periods of take-off. Due to the thermal interaction in the pump housing, the fuel temperature at the outlet of the low-pressure pump was increased (4.0, 9.2, and 30.0) % over the case without thermal interaction for take-off, cruise, and descent, respectively.

• 한국유체기계학회 논문집
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• 제7권2호
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• pp.21-26
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• 2004

In this study the effects of fluid viscosity on the pump performances for a conventional centrifugal pump were experimentally investigated. The study aimed to compare the pump characteristics between water and viscosity fluids. In order to measure the flow rate and pressure, v-notch welt and bourdon pressure gauges were used for the codes of KS B6301 and KS B6302. The working fluids were water, aqueous sugar and glycerin solutions. The results were summarized as follows : The experimental results were summarized as follows : the pump characteristics of the total head, shaft power, and efficiency with high viscosity fluids were different from those of water. When the viscosity of the applied fluid was increased, the total head and efficiency were more decreased than those of water. The decreasing gradients of the total head and the efficiency were larger than water due to the increased disk friction losses at the duty operation point. However, the shut-off head was almost constant regardless the viscosity of applied fluids. Each efficiency curves for the sugar $20w\%$ and glycerin $20w\%$ solutions was decreased up to $15.1\%$ and $34.4\%$ than that of water, respectively.

• 설비공학논문집
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• 제30권4호
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• pp.167-174
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• 2018

The geothermal heat pump systems were installed for heating and cooling of public buildings in Jincheon Eco-friendly Energy town. The heat pump system was operated at night to save on operational costs, and the cold heat was stored in thermal energy storage (TES). In this study, the performance of geothermal heat pump systems with the TES during the summer season was analyzed, and the operational costs with and without the TES were compared. The electric chiller model was used to simulate a heat pump applied without the TES system. Electric rates of each system were measured to calculate operational costs. When the TES is used in the air conditioning system, the electric load (30.4 MWh) calculated in the daytime can move to off-peak load time, and the operational cost is reduced by 36~54%.

• 대한흉부심장혈관외과학회:학술대회논문집
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• 대한흉부외과학회 1998년도 제30차 추계학술대회 대한흉부외과학회
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• pp.69-69
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• 1998

• Journal of Advanced Marine Engineering and Technology
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• 제25권4호
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• pp.797-808
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• 2001

Three-dimensional trajectory of fluid particle is simulated by a particle motion, which is able to examine the influences of changes in the several parameters. To calculate the trajectory of a particle, the Runge-Kutta method was utilized. The use of a projectile of particles for the trajectory of liquid jet has been shown to be useful to estimate the influence of different operating parameters such as best particle diameter, density of liquid body, initial take-off velocity, wind velocity, cross wind velocity, take-off angle, and base angle for a released flow from the nozzle. The results give the trajectories of various types of particle of body and at different elevations, base angles, wind velocities and densities of liquid body. The trajectories in a vacuum show that air resistances decreases both the distance and the maximum height of a projectile, and also explain that the termination time is also reduced in air. In addition, the maximum distance in the x direction was obtained with take-off angles from 30 degrees to 45 degrees in still air and the projectile of particles was highly effected by wind and cross wind. Clearly, a particle has to be so positioned as to take the optimum possible advantage of the wind if the maximum distances is requested. The wind astern increased the maximum distances of x direction compared with the wind ahead. Finally, it is possible to optimize the design of pump by using these results.

• Journal of Chest Surgery
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• 제47권4호
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• pp.350-357
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• 2014

Background: Conservation of blood during cardiac surgery is important because of the shortage of donor blood, risks associated with transfusion, and the costs of allogeneic blood products. This retrospective study explored the feasibility of off-pump coronary artery bypass (OPCAB) without transfusion. Methods: One hundred and two consecutive patients underwent OPCAB from January 2007 to June 2012 at Hallym University Sacred Heart Hospital. Excluding 10 chronic renal failures patients, 102 patients were enrolled. Their characteristics, clinical data, and laboratory data were analyzed. We investigated the success rate of OPCAB without transfusion according to preoperative hemoglobin (Hb), and the cutoff point of the Hb level and the risk factors for transfusion. We implemented multidisciplinary blood-saving protocols. Results: The overall operative mortality and the success rate of OPCAB without transfusion were 2.9% (3/102) and 73.5% (75/102). The success rates in patients with Hb<11, 11 70 years, diagnosis of acute myocardial infarction, preoperative Hb and creatinine levels, and operation time. The events precipitating the need for transfusion were low Hb level in 9 patients and hypotension or excessive bleeding in 18 patients. Conclusion: The preoperative Hb level of >11 facilitates OPCAB without transfusion. These results suggest that transfusion-free OPCAB can be performed by modifying the risk factors and correctable causes of transfusion and improving various blood salvage methods.

• Journal of Chest Surgery
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• 제46권1호
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• pp.22-26
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• 2013

Background: Constrictive pericarditis after coronary artery bypass surgery has been known to affect cardiac output by limiting diastolic ventricular filling. We aimed to assess the influence of postoperative constrictive physiology on the early outcomes of patients undergoing off-pump coronary artery bypass grafting (OPCAB). Materials and Methods: Between January 2008 and July 2011, 903 patients underwent an isolated OPCAB and postoperative transthoracic-echocardiography. The patient cohort was classified into two groups: group A, constrictive physiology and group B, control group without constrictive physiology. Early outcomes were analyzed between the two groups. Results: Of the total 903 patients, group A consisted of 153 patients (16.9%). The amount of blood loss in group A during the postoperative 24 hours was greater than that of group B, but this was not statistically significant (p=0.20). No significant differences were found in the mortality rates (group A, 0.6%; group B, 1.4%; p=0.40) and 30-day major adverse cardiac and cerebrovascular events (MACCEs; group A, 3.3%; group B, 6.1%; p=0.42). Conclusion: Postoperative constrictive physiology does not affect 30-day MACCEs or other major complications after OPCAB. The results of this study suggest that patients with early postoperative constrictive physiology do not need medical or surgical treatment, and that conservative care is sufficient.

• Journal of Yeungnam Medical Science
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• 제28권2호
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• pp.124-132
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• 2011

Background: Antiplatelet agent administration is critical in managing coronary-artery disease, but there is a concern regarding operation-related bleeding and an increase in blood transfusion in such, especially when delivering combined antiplatelet agents. This study was conducted to evaluate the effect of the administration of antiplatelet agents on off-pump coronary-artery bypass surgery (OPCAB). Methods: From March 2003 to December 2009, 49 patients who had undergone OPCAB were collected retrospectively. The patients were divided into three groups according to the administration of antiplatelet agents before the OPCAB operation: 21 patients were given an aspirin agent (group 1), 19 patients were given combined agents (aspirin+clopidogrel) (group 2), and nine patients were not given any antiplatelet agent (group 3). The three groups' perioperative hematologic and coagulation profiles, including their platelet counts, hemoglobin levels, hematocrit, prothrombin times, and aPTTs (activated partial thromboplastin times), and their postoperative bleeding, related complications, transfusion requirements, and operation times, were compared. Results: The operation time in group 2 was 4.3 hours, longer than those in the two other groups, and urgent operation was significantly most frequent in group 2 (63%). The amount of blood loss and the number of patients who received blood transfusion were not different in the three groups. The perioperative hemoglobin level, hematocrit, platelet count, prothrombin time, and aPTT were also not significantly different among the three groups. Conclusion: The continuous administration of antiplatelet agents to the patients in this study did not increase their postoperative bleeding or operation-related complications. Therefore, OPCAB may well be considered even if combined antiplatelet agents are being administered.

• 대한의생명과학회지
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• 제15권3호
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• pp.207-215
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• 2009

We carried out this study to investigate differences of physiological variables between patients with (DM group) and without type II diabetes mellitus (Non-DM group) undergoing off-pump coronary artery bypass grafting (OPCABG). Postoperative $Mg^{++}$ and $Ca^{++}$ levels were lower, whereas $Na^+$ level was higher in DM group than those in Non-DM group. ICU (intensive care unit) stay time in DM group was longer than that of Non-DM group. Postoperative platelet counts tended to decrease, whereas C-reactive protein (CRP) and cardiac troponin-I (cTNI) levels tended to increase in DM group compared with Non-DM group. Postoperative albumin level was lower, while blood urea nitrogen (BUN) and creatinine levels were greater in DM group than those in Non-DM group. DM group had higher incidence of post-operative arrhythmias than Non-DM group. These results reveal that type II DM patients undergoing OPCAB may have higher incidences of postoperative hypomagnesemia, hypocalcemia and arrhythmias, and increases of CRP, cTNI, BUN, and creatinine levels than in Non-DM patients undergoing OPCAB. The perioperative check and control (supplement) of $Mg^{++}$ levels should be considered in cardiovascular surgery combined with DM.

• Journal of Chest Surgery
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• 제52권3호
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• pp.155-161
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• 2019

Background: Coronary artery bypass grafting (CABG) is being offered increasingly frequently to octogenarians. However, old age is known to be an independent risk factor in CABG. The aim of this study was to compare the outcomes of off-pump coronary artery bypass (OPCAB) between octogenarians and septuagenarians. Methods: We retrospectively reviewed the data of 1,289 consecutive patients aged ${\geq}70years$ who underwent OPCAB at a single institution between 2001 and 2016. We compared the outcomes of 115 octogenarians and 1,174 septuagenarians. Using propensity score matching, based on preoperative clinical characteristics, 114 octogenarians were matched with 338 septuagenarians. Results: Propensity score analysis revealed that the incidence of acute kidney injury (14.9% vs. 7.9%, p=0.028) and respiratory complications (8.8% vs. 4.2%, p=0.040) was significantly higher in octogenarians. The early mortality rate (2.6% vs. 1.0%, p=0.240) and 1-year survival rate (89.5% vs. 94.4%, p=0.097) were not statistically significant between the groups. However, the 5-year survival rate (67.3% vs. 79.9%, p<0.001) was significantly lower in octogenarians. Previous myocardial infarction and a left ventricular ejection fraction ${\leq}35%$ were associated with a poor 1-year survival rate. Conclusion: Early and 1-year outcomes of OPCAB in octogenarians were tolerable when compared with those in septuagenarians. OPCAB could be a suitable option for octogenarians.