• Journal of Chest Surgery
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• v.32 no.1
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• pp.53-57
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• 1999

We describe a case of successful extracorporeal membrane oxygenation(ECMO) in a small infant with cardiopulmonary resuscitation(CPR) failure after an open heart surgery. A 35-day-old male infant weighing 4.4 kg who had congestive heart failure and pulmonary hypertension underwent patch closure of ventricular septal defect without any intraoperative event. Postoperative course was unremarkable in the intensive care uint for about 5 hours before the junctional ectopic tachycardia developed. Sudden cardiac decompensation with bradycardia occurred about 50 minutes after the development of junctional ectopic tachycardia. He was put on ECMO by arterial cannulation at the ascending aorta and by venous cannulation at the right atrial appendage after 4 hours' CPR. The hemodynamics were stable with enough urine output during ECMO. He was weaned from ECMO 38.5 hours after initiation. Delayed sternal closure was attempted. He was extubated on postoperative day 7 and discharged home on postoperative day 21 without any neurologic sequelae.

• 전자공학회논문지 IE
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• v.46 no.2
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• pp.33-45
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• 2009

In this paper, the implementation of the backward movement control of a truck-trailer type mobile robot using fuzzy model based control scheme considering the practical constraints, computing time-delay and quantization is presented. We propose the fuzzy feedback controller whose output is delayed with unit sampling period and predicted. The analysis and the design problem considering the computing time-delay become very easy because the proposed controller is syncronized with the sampling time. Also, the stability analysis is made when the quantization exists in the implementation of the fuzzy control architectures and it is shown that if the trivial solution of the fuzzy control system without quantization is asymptotically stable, then the solutions of the fuzzy control system with quantization are uniformly ultimately bounded. The experimental results are shown to verify the effectiveness of the proposed scheme.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.5
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• pp.1018-1024
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• 2011

For the driving of the sinusoidal type permanent magnet synchronous motor with a maximum continuous torque, the 1200 delayed three phase sinusoidal current inputs which matched with the absolute rotor position are needed at the stator coil. Therefore, the detection of a absolute rotor position is required inevitably. And the right angle relationship between stator magnetic field and rotor magnetic field has to be preserved at a stator by this commutation action. The detection of a absolute position for the commutation can be made generally by the output signal analysis of the encoder attached at a motor shaft. The purposes of this study are to design signal processing logic circuits which could detect the absolute position of motor with a modern encoder system and generate the three reference wave for making sinusoidal current input at a stator coil.

• Journal of Chest Surgery
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• v.22 no.3
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• pp.416-424
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• 1989

We have performed eight, single transplantations of right lung in dogs from September, 1988 to March 1989 at the Thoracic & Cardiovascular Surgical department, Yonsei University, College of Medicine, Seoul, Korea. We wrapped bronchial anastomosis site with great omentum and used cyclosporin in preoperative and postoperative periods in seven cases except one. The one without wrapping the bronchial anastomotic site with omentum and using cyclosporin died due to bronchial anastomotic site rupture in postoperative fourth day. If there is no reason to choose one side over the other, we would generally choose to do left-sided transplant as this is technically somewhat easier because of the long length of recipient bronchus and the ease of clamping the left atrium proximal to the pulmonary veins. The right atrium limits the amount of left atrium that can have incorporated into the clamp proximal to the pulmonary veins on the right side. But we had chosen to do right-sided transplant of lung because we must take variable technical experiences on right sided lung transplant in dogs. We have to anastomose one of pulmonary vein and left atrial wall on right-sided transplant easily only with double ligation of one pulmonary vein because right atrium limited the clamp of left atrium proximal to pulmonary veins with decreased venous return and cardiac output in some dogs. All seven dogs with right-sided lung transplant had survived more than one day with good condition except one. The one dog have to be sacrificed to evaluate the difference between the gas analysis in pulmonary venous and arterial blood in post-operative eight hours. We found hemorrhagic pulmonary edematous changes of contralateral left lung in this dog. And also all dogs have to be sacrificed for the evaluation of surgical problems, anytime in post-operative periods without any cardiopulmonary resuscitative efforts when the general condition would be worse progressively. We found no any surgical technical errors in seven dogs except one with thrombi in suture site of left atrium. There were hemorrhagic pulmonary edematous changes of transplanted right lung in one, of contralateral left lung in one, of contralateral left lung with double ligation of its pulmonary artery in one, thrombi around left atrial sutures sites in one, multiple air leakage in one bronchial rupture in one due to rejection or infection. There were accidental extubation and delayed intubation in one and unknown cause of death in one.

• Journal of Korean Neurosurgical Society
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• v.38 no.6
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• pp.431-434
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• 2005

Objective : Subarachnoid hemorrhage[SAH] is commonly associated with polyuria [solute diuresis or water diuresis]. The authors investigate the incidence and clinical characteristics of polyuria with special reference to the administration of osmotic diuretics. Methods : One hundred and forty eight patients with high urine output [>200ml/hr] after ruptured cerebral aneurysm operated early from Jan 1998 to Jun 2003 were selected. Water diuresis [diabetes insipidus, DI] was differentiated from solute diuresis by lower urine specific gravity [<1.005] and higher plasma osmolality. The incidence and mode of onset of polyuria were compared between two types of diuresis. Additionally, the relationships between development of polyuria and clinical features including aneurysm location, clinical grade, Fisher grade, and outcome were analyzed. Osmotic diuretics were not routinely used in patients with Hunt-Hess grade I-III since July 2001. Results : Annual incidence of polyuria decreased markedly since July 2001 : 45.2% in 1998, 34.5% in 2001, 11.9% in 2003. Postoperative DI occurred in $2.4{\sim}11.1%$. DI developed mainly from ruptured anterior communicating artery aneurysm. The mean interval between the last SAH and the onset of DI was 7.1 days [range $1{\sim}27$ days] and lasted mean 4.6 days. When compared with solute diuresis, the development of DI was significantly delayed. Other clinical features were not closely related to polyuria. Conclusion : Uncontrolled polyuria may lead to cerebral ischemia and electrolyte imbalance because SAH patients are already predisposed to hypovolemia, and will risk precipitating the opposite situation with overhydration. We can decrease the development of polyuria without routine use of osmotic diuretics, by avoiding the increased intracranial pressure such as the intraoperative ventriculostomy and gentle brain retraction in good grade patients.

• Nuclear Engineering and Technology
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• v.47 no.7
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• pp.838-848
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• 2015

One of the most important operations in nuclear power plants is load following, in which an imbalance of axial power distribution induces xenon oscillations. These oscillations must be maintained within acceptable limits otherwise the nuclear power plant could become unstable. Therefore, bounded xenon oscillation is considered to be a constraint for the load following operation. In this paper, the design of a sliding mode control (SMC), which is a robust nonlinear controller, is presented.SMCis ameansto control pressurized water nuclear reactor (PWR) power for the load following operation problem in a way that ensures xenon oscillations are kept bounded within acceptable limits. The proposed controller uses constant axial offset (AO) strategy to ensure xenon oscillations remain bounded. The constant AO is a robust state constraint for the load following problem. The reactor core is simulated based on the two-point nuclear reactor model with a three delayed neutron groups. The stability analysis is given by means of the Lyapunov approach, thus the control system is guaranteed to be stable within a large range. The employed method is easy to implement in practical applications and moreover, the SMC exhibits the desired dynamic properties during the entire output-tracking process independent of perturbations. Simulation results are presented to demonstrate the effectiveness of the proposed controller in terms of performance, robustness, and stability. Results show that the proposed controller for the load following operation is so effective that the xenon oscillations are kept bounded in the given region.

• Investigative and Clinical Urology
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• v.59 no.6
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• pp.410-415
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• 2018

Purpose: Despite meticulous techniques, surgical complications continue to be problematic in kidney transplant recipients. Role of routine stenting to reduce complications is controversial. In this study, we compare incidence of early urological complications, lymphoceles, urinary tract infections (UTI) and graft function; with or without double-J stenting. Materials and Methods: All patients who underwent live related donor renal transplantation from February 2014 to February 2016 were included. Transplants prior to February 2015 were without routine stenting; subsequent transplants were with routine stenting. Patients with neurogenic bladder, previously operated bladder and delayed or low urinary output were excluded. Followup was for at least three months. Descriptive statistics was performed for all parameters. Chi square test and Fisher's Exact test were used for qualitative variables. For quantitative variables, Mann-Whitney test was used to test median difference and independent samples t-test for mean difference. The p-value ${\leq}0.05$ was considered significant. Results: We analysed 74 patients (34 stented and 40 non-stented). There was no difference in the incidence of urinary leak, anastomotic obstruction, lymphoceles or UTI (p>0.4 for all comparisons). However, mean estimated glomerular filtration rate at sixth day, 14th day, one month and two months were 76.1 vs. 61.5 (p=0.025), 72.1 vs. 56.6 (p=0.005), 79.4 vs. 63.1 (p=0.002) and 82.0 vs. 63.3 (p=0.001) in the stented versus non-stented groups. Conclusions: Placement of ureteral stent in renal transplant does not significantly affect the incidence of early urinary complications or UTI. However, graft function is significantly better in stented recipients, at least in the short term.

• Journal of Advanced Navigation Technology
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• v.23 no.1
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• pp.1-7
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• 2019

Thisstudy presentsthe development of a fast-time airport surface simulator. The simulator usesthe output from a first-come first-served (FCFS) scheduler and has adopted one-dimensional dynamic model to simulate the movement of the aircraft on the surface. Higher collision risks situations in the airport surface traffic are analyzed to classify those situations into six cases. A conflict detection and resolution algorithm is implemented to maintain separation distance and to prevent deadlock. The simulator was tested with a scenario at the Incheon International Airport that contains 72 aircraft. Without the conflict detection and resolution, various conflict situations are identified. When the conflict detection and resolution algorithm is managing the traffic, it is confirmed that the conflicts are removed at the price of additional delays. In the conflict resolution algorithm, three prioritization strategies are implemented, and delayed aircraft count and average additional delays are compared. Prioritization based on remaining time or distance showed smaller total additional delay compared to choosing minimum delay priority for each situation.

• Journal of Space Technology and Applications
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• v.3 no.2
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• pp.118-143
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• 2023

Space is becoming more commercialized. Despite of its delayed start-up, space activities in Korea are attracting more nation-wide supports from both investors and government. May 25, 2023, KSLV II, also called Nuri, successfully transported, and inserted seven satellites to a sun-synchronous orbit of 550 km altitude. However, Starlink has over 4,000 satellites around this altitude for its commercial activities. Hence, it is necessary for us to constantly monitor the collision risks of these satellites against resident space objects including Starlink. Here we report a quantitative research output regarding the conjunctions, particularly between the Nuri satellites and Starlink. Our calculation shows that, on average, three times everyday, the Nuri satellites encounter Starlink within 1 km distance with the probability of collision higher than 1.0E-5. A comparative study with KOMPSAT-5, also called Arirang-5, shows that its distance of closest approach distribution significantly differs from those of Nuri satellites. We also report a quantitative analysis of collision-avoiding maneuver cost of Starlink satellites and a strategy for Korea, being a delayed starter, to speed up to position itself in the space leading countries. We used the AstroOne program for analyses and compared its output with that of Socrates Plus of Celestrak. The two line element data was used for computation.

• Journal of International Area Studies (JIAS)
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• v.18 no.3
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• pp.109-144
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• 2014

In 2010, large areas of European airspace were closed by the volcanic ash generated by the eruption of Icelandic volcano and it disrupted global trade, business and travel which caused a huge economic damage on the air transport industry. This brought concerned about the economic impact by the eruption of Mt. Baekdu volcano. In this paper, we analyze the affected areas of the air transport industry were decided by calculating the PM10 density of volcanic ash changed over time and by determining the safe upper limit of ash density in their airspace. We separate the sales in the air transport industry according to each airline, airport, and month to estimate the direct losses when all flights inside a restricted zone were canceled. Also, we estimate the indirect losses in regional output, income, and value-added of the different major industries using interindustry (input-output) analysis. There is no direct damage from VEI 1 to VEI 5. But when VEI is 6, all flights to and from Yangyang airport will be canceled due to the No Fly Zone. And some flights to and from the airports Gimhae, Ulsan and Pohang will be restricted due to the Time Limited Zone. When VEI is 7, Yangyang, Gimhae, Ulsan, Pohang and Daegu airports will be closed and all flights will be canceled and delayed. During this time, the total economic losses on the air transport industry are estimated at 8.1 billion won(direct losses of about 3.55 billion won, indirect losses of about 4.57 billion won). Gimhae international airport accounted for 92% of the total loss and is the most affected area according to the volcanic ash scenario of Mt. Baekdu.