• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.441-452
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• 2004

Nowcast and forecast based on realtime data are quite essential for space weather monitoring. We have developed the web pages (http://sun.kao.re.kr) of the KAO Space Weather Monitoring system by using ION (IDL on the Net). They display latest solar and geomagnetic data, and present their expected effects on satellite, communications and ground power system. In addition, daily NOAA/SEC prediction reports on the probability of solar X-ray flares, proton events and geomagnetic storms are provided. To predict the arrival times of interplanetary shocks and CMEs, two different types of prediction models are also implemented. A work is in progress to develop web-based database of several solar and geomagnetic activities. These data are automatically downloaded to our data server in every minute, or every day using IDL and FTP programs. In this paper, we will introduce more details on the development of the KAO Space Weather Monitoring system.

• Journal of Astronomy and Space Sciences
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• v.28 no.2
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• pp.123-132
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• 2011

It is generally believed that the occurrence of a magnetic storm depends upon the solar wind conditions, particularly the southward interplanetary magnetic field (IMF) component. To understand the relationship between solar wind parameters and magnetic storms, variations in magnetic field polarity and solar wind parameters during magnetic storms are examined. A total of 156 storms during the period of 1997~2003 are used. According to the interplanetary driver, magnetic storms are divided into three types, which are coronal mass ejection (CME)-driven storms, co-rotating interaction region (CIR)-driven storms, and complicated type storms. Complicated types were not included in this study. For this purpose, the manner in which the direction change of IMF $B_y$ and $B_z$ components (in geocentric solar magnetospheric coordinate system coordinate) during the main phase is related with the development of the storm is examined. The time-integrated solar wind parameters are compared with the time-integrated disturbance storm time (Dst) index during the main phase of each magnetic storm. The time lag with the storm size is also investigated. Some results are worth noting: CME-driven storms, under steady conditions of $B_z$ < 0, represent more than half of the storms in number. That is, it is found that the average number of storms for negative sign of IMF $B_z$ (T1~T4) is high, at 56.4%, 53.0%, and 63.7% in each storm category, respectively. However, for the CIR-driven storms, the percentage of moderate storms is only 29.2%, while the number of intense storms is more than half (60.0%) under the $B_z$ < 0 condition. It is found that the correlation is highest between the time-integrated IMF $B_z$ and the time-integrated Dst index for the CME-driven storms. On the other hand, for the CIR-driven storms, a high correlation is found, with the correlation coefficient being 0.93, between time-integrated Dst index and time-integrated solar wind speed, while a low correlation, 0.51, is found between timeintegrated $B_z$ and time-integrated Dst index. The relationship between storm size and time lag in terms of hours from $B_z$ minimum to Dst minimum values is investigated. For the CME-driven storms, time lag of 26% of moderate storms is one hour, whereas time lag of 33% of moderate storms is two hours for the CIR-driven storms. The average values of solar wind parameters for the CME and CIR-driven storms are also examined. The average values of ${\mid}Dst_{min}{\mid}$ and ${\mid}B_{zmin}{\mid}$ for the CME-driven storms are higher than those of CIR-driven storms, while the average value of temperature is lower.

• Journal of the Korean Institute of Gas
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• v.24 no.3
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• pp.33-39
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• 2020

In general, in a batch reaction process in which products are made using flammable liquids, splash filling is used to clean the walls of the reactor by spraying flammable liquids, which are raw materials used for product, during cleaning of the reactor after work. During this process, mist of flammable liquid is generated, the lower limit of explosion is lowered, and fire·explosion may occur due to discharges caused by various types of complex charges, such as flow charge, collision charge, and ejection charge. Therefore, based on the recent accident case, to identify the risk when working in the form of splash filling with toluene in a batch process and perform an explosion impact analysis using the TNT equivalent method After that, we will analyze the accident results and suggest preventive measures such as constant purge system, improvement of cleaning method, and use of tantalum to prevent such accident.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.510-517
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• 2016

Supersonic jet technology using high pressures has been popularly utilized in diverse industrial and engineering areas related to working fluids. In this study, to consider the effects of a shock wave caused by supersonic jet flow from a high pressure pipe, the SST turbulent flow model provided in the ANSYS FLUENT v.16 was applied and the flow characteristics of the pressure ratio and Mach number were analyzed in accordance with the working fluids (air, oxygen, and hydrogen). Before carrying out CFD (Computational Fluid Dynamics) analysis, it was presumed that the inlet gas temperature was 300 K and pressure ratio was 5 : 1 as the boundary conditions. The density function was derived from the ideal gas law and the viscosity function was derived from Sutherland viscosity law. The pressure ratio along the ejection distance decreased more in the lower density working fluids. In the case of the higher density working fluids, however, the Mach number was lower. This shows that the density of the working fluids has a considerable effect on the shock wave. Therefore, the reliability of the analysis results were improved by experiments and CFD analysis showed that supersonic jet flow affects the shock wave by changing shape and diameter of the jet, pressure ratio, etc. according to working fluids.

• Journal of Chest Surgery
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• v.23 no.6
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• pp.1180-1190
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• 1990

96 patients underwent cardiac valve replacement for valvular heart diseases consecutively between February 1986 to February 1990 in the Department of Thoracic and Cardiovascular Surgery of Yeungnam University Hospital. The follow up period was between 6 months and 4.5 years postoperatively[mean 23.4$\pm$13.1 months]. 75 cases got mitral valve replacement, 6 cases, aortic valve replacement, 15 cases, double valve replacement. 30[31.2%] patients were male and 66[68.8%] were female and the age ranged from 14 to 66 years old. Early hospital death within 30 days postoperation were 5 patients[5.2%], consisting of by low cardiac output in 2, infective endocarditis in 1, multiple organ failure with sepsis in 1 patient. There was no late postoperative death. Most common early postoperative complication was wound disruption [8.7%] and then low cardiac output, pneumothorax, pleural effusion in order. Most common late postoperative complications were minor bleeding episodes[8.7%] related to anticoagulant therapy which were consisted of frequent epistaxis in 3, gum bleeding in 2, hemorrhagic gastritis in 1, hypermenorrhea in 1, hematoma in right arm in 1 patient. Valve-related complications included valve thrombosis [1.6%/ patient-year], valve failure due to pannus formation[1.1% /patient-year], prosthetic valve endocarditis[1, 1%o/patient-year] and minor anticoagulant hemorrhage[4.4% /patient-year]. 5 cases of reoperations were performed in 4 patients due to valve failure and all of them were in the mitral positions[2.7% /patient-year]. Cardiothoracic ratios in the chest X-ray decreased at the 6th month and 1st year postoperation in all patients. But in New York Heart Association[NYHA] functional class IV, no change in cardiothoracic ratio was found between 6 months and 1 year postoperation. In the echocardiogram, the size of the cardiac chambers decreased, but ejection fraction increased postoperatively in each functional class. In the electrocardiogram, decreases were found in the incidence of atrial fibrillation, left atrial enlargement, left ventricular hypertrophy with right bundle branch block increasing postoperatively in each functional class. The actuarial survival rate was 98.4% for all patients, 98.7% for mitral valve replacement, 83.8% for aortic valve replacement, and 80% for double valve replacement at the end of a 4.5 year follow up period. Meanwhile the actuarial freedom rate was 91.5% for prosthetic valve endocarditis, 91.6% for thromboembolism, 89.0% for prosthetic valve failure and 83.7% for minor anticoagulant hemorrhage. Preoperative NYHA class III and IV were 75% of all patients, but 95% of all patients were up graded to NYHA class I and II postoperatively.

• Journal of Chest Surgery
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• v.49 no.3
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• pp.165-170
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• 2016

Background: In elderly high-risk surgical patients, sutureless aortic valve replacement (AVR) should be an alternative to standard AVR. The potential advantages of sutureless aortic prostheses include reducing cross-clamping and cardiopulmonary bypass (CPB) time and facilitating minimally invasive surgery and complex cardiac interventions, while maintaining satisfactory hemodynamic outcomes and low rates of paravalvular leakage. The current study reports our single-center experience regarding the early outcomes of sutureless aortic valve implantation. Methods: Between October 2012 and June 2015, 65 patients scheduled for surgical valve replacement with symptomatic aortic valve disease and New York Heart Association function of class II or higher were included to this study. Perceval S (Sorin Biomedica Cardio Srl, Sallugia, Italy) and Edwards Intuity (Edwards Lifesciences, Irvine, CA, USA) valves were used. Results: The mean age of the patients was $71.15{\pm}8.60years$. Forty-four patients (67.7%) were female. The average preoperative left ventricular ejection fraction was $56.9{\pm}9.93$. The CPB time was $96.51{\pm}41.27minutes$ and the cross-clamping time was $60.85{\pm}27.08minutes$. The intubation time was $8.95{\pm}4.19hours$, and the intensive care unit and hospital stays were $2.89{\pm}1.42days$ and $7.86{\pm}1.42days$, respectively. The mean quantity of drainage from chest tubes was $407.69{\pm}149.28mL$. The hospital mortality rate was 3.1%. A total of five patients (7.69%) died during follow-up. The mean follow-up time was $687.24{\pm}24.76days$. The one-year survival rate was over 90%. Conclusion: In the last few years, several models of valvular sutureless bioprostheses have been developed. The present study evaluating the single-center early outcomes of sutureless aortic valve implantation presents the results of an innovative surgical technique, finding that it resulted in appropriate hemodynamic conditions with acceptable ischemic time.

• Journal of Chest Surgery
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• v.51 no.4
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• pp.266-272
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• 2018

Background: Limited comparative data are available on the efficacy of cryoablation versus radiofrequency ablation in patients with atrial fibrillation. This study aimed to compare radiofrequency ablation and cryoablation with regard to clinical outcomes and the restoration of sinus rhythm or atrial contractility. Methods: A total of 239 patients who underwent surgical ablation between August 2003 and December 2016 at our institution were included. The patients were divided into 2 groups according to the energy device that was used (group A: n=140, radiofrequency ablator; group B: n=99, cryoablator). Echocardiographic data, overall survival, and major cardiovascular and cerebrovascular event (MACCE)-free survival were compared between the 2 groups. Results: At 1 year of follow-up, the atrial contractility recovery rate was 32.2% (19 of 59) in group A and 48.8% (21 of 44) in group B. In addition, cryoablation was found to be a predictive factor for the recovery of atrial contractility (cryoablation vs. radiofrequency ablation: odds ratio, 2.540; 95% confidence interval, 1.063-6.071; p=0.036). The left ventricular ejection fraction was significantly higher in group B ($53.1%{\pm}11.5%$ vs. $59.1%{\pm}6.3%$, p=0.001). The median follow-up duration was 36 months. The 5-year overall survival rate was $80.1%{\pm}3.6%$ in group A and $92.1%{\pm}2.9%$ in group B (p=0.400). The 5-year MACCE-free survival rate was $70.3%{\pm}4.0%$ in group A and $70.9%{\pm}5.6%$ in group B (p=0.818). Conclusion: Cryoablation was associated with a higher atrial contractility restoration rate and better left ventricular function than radiofrequency ablation. However, no significant relationship was observed between the energy source and overall or MACCE-free survival.

• Journal of The Korean Society of Clinical Toxicology
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• v.13 no.2
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• pp.62-70
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• 2015

Purpose: Cardiac complications may occur in cases of organophosphate (OP) poisoning. However, a few studies regarding patterns of cardiac toxicity as determined by transthoracic echocardiography (TTE) after exposure to OP have been reported. In the current study, the authors examined cardiac functions using TTE in patients with myocardial injury caused by exposure to OP. Methods: A retrospective review was conducted on 16 consecutive cases of OP poisoning with myocardial injury (defined as elevated troponin I within 48 hours of arrival at the regional emergency center in South Korea and diagnosed and treated at the center from January 2012 to November 2014. Results: TTE was performed in 11 (69%) of the 16 patients with an elevated troponin I (TnI) level within 48 hours. Of these 11 patients, 5 patients (45.5%) exhibited reduced ejection fraction (EF), and 3 exhibited regional wall motion abnormality (RWMA). Two patients (18.2%) had both reduced systolic function and RWMA. Two of the 5 patients with reduced EF returned to normal systolic function, however two patients did not regain normal systolic function after admission. One patient expired due to multiple organ failure, and 4 patients were transferred with a moribund status. Twelve of 15 patients who survived to discharge (at 4 to 35 months) were followed. Five of these patients died during follow-up and 7 survived without further complications. Conclusion: OP can cause reversible cardiac dysfunction including reduced systolic function and RWMA. Serum TnI may be useful for initial assessment of cardiac function during the workup of patients suffering from OP poisoning. After the initial assessment of cardiac enzyme, further evaluation with TTE in patients with abnormal cardiac enzyme will be necessary to understand the cardiac toxicity.

• Tuberculosis and Respiratory Diseases
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• v.68 no.5
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• pp.273-279
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• 2010

Background: Pulmonary hypertension is considered as a poor prognosis factor in patients with chronic obstructive pulmonary disease (COPD). There has been reported brain natriuretic peptide (pro-BNP) is related with increased right ventricular (RV) workloads. However, there are few studies that evaluate the relationship between BNP and pulmonary arterial pressure (PAP), RV function and St. George Respiratory Questionnaire (SGRQ) score in patients with COPD, and the effects of angiotensin converting enzyme inhibitor (ACEI) on these parameters. Methods: Pulmonary function test, echocardiography, blood BNP, and SGRQ score were evaluated in stabilized moderate degree COPD patients ($FEV_1$/FVC< 70%, $50%{\leq}FEV_1$ < 80%) aged 45 years and over, without worsening of symptoms within recent 3 months. After treating with ramipril 10 mg for 3 months, the same evaluation was repeated. Results: Twenty-two patients were included in this study. BNP was significantly correlated with PAP (Pearson coefficient ${\rho}=0.51$, p=0.02), but not with RV ejection fraction (EF) and predicted $FEV_1%$. The values for predicted $FEV_1%$ showed significant correlation with SGRQ total score and activity score, but not with BNP or PAP. After ramipril treatment, PAP showed significant decrease ($42.8{\pm}8.1$ vs. $34.5{\pm}4.5mm$ Hg p=0.0003), tricuspid annular plane systolic excursion significant increase ($21.5{\pm}3.3$ vs. $22.7{\pm}3.1mm$ p=0.009). BNP showed a tendency to decrease without statistical significance ($40.8{\pm}59.6$ vs. $18.0{\pm}9.1pg/mL$ p=0.55). SGRQ scores showed no significant change. Conclusion: BNP showed significant correlation with resting PAP, which means BNP could be used as markers for pulmonary hypertension. Treatment with ACEI didn't show significant change in the level of BNP, while pulmonary hypertension and RV function were improved.

• Journal of Life Science
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• v.20 no.10
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• pp.1458-1467
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• 2010

The present study was retrospectively designed to define whether preoperative levels of leukocytes and D-dimer are potentially useful factors in predicting perioperative outcomes of coronary heart disease (CHD). There was no relationship between preoperative leukocyte counts (Pre-OP leukocyte) and preoperative D-dimer levels (Pre-OP D-dimer). Pre-OP leukocyte counts each had positive correlation with cardiac troponin-I, creatine kinase-MB or C-reactive protein (cardiac markers) levels at preoperative and postoperative periods. Pre-OP D-dimer levels were positively associated with each cardiac marker at the same periods. Pre-OP leukocyte counts positively related with aspartate aminotransferase and alanine aminotransferase (liver markers), whereas Pre-OP D-dimer level positively or negatively correlated with bilirubin (liver marker), creatinine (renal marker) or glucose levels at preoperative and/or postoperative periods. Pre-OP leukocyte and Pre-OP D-dimer were inversely associated with Pre-OP high density lipoprotein cholesterol levels or left ventricular ejection fraction. Pre-OP leukocyte counts each had positive correlation operation duration and postoperative mechanical ventilation-time (PMVT), whereas Pre-OP D-dimer levels had positive relationship with PMVT, intensive care unit-staying period and hospitalization. The retrospective data suggest that Pre-OP leukocyte and Pre-OP D-dimer levels may be clinically useful factors for predicting perioperative outcomes in patients with CHD.