• Pediatric Infection and Vaccine
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• v.28 no.2
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• pp.66-81
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• 2021

The coronavirus disease 2019 pandemic has been continuously spreading throughout the world. As of July 15, 2021, there have been more than 188 million confirmed cases and more than 4.06 million deaths. Although the incidence of severe infections is relatively low in children and adolescents compared to adults, a complication called multisystem inflammatory syndrome in children (MIS-C) may occur in some cases at approximately 2-6 weeks after severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. MIS-C can be seen in patients of various ages, from young infants to adolescents, and may present with diverse clinical manifestations. While fever present in a great majority of patients, symptoms suggesting the involvement of the digestive or nervous system and the skin and mucous membranes (Kawasaki disease-like symptoms) also appear in many cases. Cardiac involvement may also be observed, including left ventricular dysfunction, myocarditis, coronary artery dilatation, and coronary aneurysm. In some cases, hypotension or shock can occur, and mechanical ventilation or treatment in the intensive care unit may be necessary. Fortunately, recovery is generally reported after appropriate treatment. MIS-C is a rare but important complication of SARS-CoV-2 infection in children and adolescents. As such, it is important to recognize the clinical symptoms and provide appropriate treatment at an early stage. In this review, the epidemiology, clinical symptoms, suggested pathophysiology, diagnostic approach, and treatment of MIS-C will be discussed.

• Journal of the Korean Institute of Gas
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• v.26 no.6
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• pp.9-15
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• 2022

In order to verify the durability of the high-pressure hydrogen tank in the operating pressure range, a hydraulic rupture test should be performed. However, if the bubbles generated by the initial injection process of water are attached to the inner wall of the tank and remain, a sudden pressure change of the bubbles during the rupture of the pressurized tank may cause shock and noise. Therefore, in this study, the flow velocity required to remove the bubbles remaining on the inner wall of the tank was predicted through simplified formulas, and the shape of the injection nozzle to maintain the flow velocity was determined based on the shape of the hydrogen tank for the hydrogen bus. In addition, a numerical model was developed to predict the change in flow velocity according to the inlet pressure, and an experiment was performed through a model tank to prove the validity of the prediction result. As a result of the experiment, the flow velocity near the tank wall was similar to the predicted value of the analysis model, and when the inlet pressure was 1.5 to 5.5 bar, the minimum size of the removable bubble was predicted to be about 2.2 to 4.6 mm.

• Korean Journal of Optics and Photonics
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• v.33 no.2
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• pp.74-83
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• 2022

The entire process, from the raw material to the final system qualification test, has been developed to fabricate a large-diameter, lightweight reflective-telescope system for a satellite observation. The telescope with 3 anastigmatic mirrors has an aperture of 700 mm and a total mass of 66 kg. We baked a silicon carbide substrate body from a carbon preform using a reaction sintering method, and tested the structural and chemical properties, surface conditions, and crystal structure of the body. We developed the polishing and coating methods considering the mechanical and chemical properties of the silicon carbide (SiC) body, and we utilized a chemical-vapor-deposition method to deposit a dense SiC thin film more than 170 ㎛ thick on the mirror's surface, to preserve a highly reflective surface with excellent optical performance. After we made the SiC mirrors, we measured the wave-front error for various optical fields by assembling and aligning three mirrors and support structures. We conducted major space-environment tests for the components and final assembly by temperature-cycling tests and vibration-shock tests, in accordance with the qualifications for the space and launch environment. We confirmed that the final telescope achieves all of the target performance criteria.

• Journal of Korean Society of Disaster and Security
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• v.16 no.1
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• pp.61-70
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• 2023

This study presents an analytical study of investigating the effect of shock waves generated by the hydrogen detonation and damage to structures for the safety evaluation of hydrogen storage facilities against detonation. Blast scenarios were established considering the volume of the hydrogen storage facility of 10 L to 50,000 L, states of charge (SOC) of 50% and 100%, and initial pressures of 50 MPa and 100 MPa. The equivalent TNT weight for hydrgen detonation was determined considering the mechanical and chemical energies of hydrogen. A hydrogen detonation model for the converted equivalent TNT weight was made using design equations that improved the Kingery-Bulmash design chart of UFC 3-340-02. The hydrogen detonation model was validated for overpressure and impulse in comparison to the past experimental results associated with the detonation of hydrogen tank. A parametric study based on the blast scenarios was performed using the validated hydrogen detonation model, and design charts for overpressure and impulse according to the standoff distance from the center of charge was provided. Further, design charts of the three-stage structural damage and standoff distance of adjacent structures according to the level of overpressure and impact were proposed using the overpressure and impulse charts and pressure-impulse diagrams.

• Tuberculosis and Respiratory Diseases
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• v.44 no.5
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• pp.1072-1082
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• 1997

Background : To characterize the clinical features and determine the prognostic factors of severe community-acquired pneumonia. This study is the first of its kind in Korea. Methods : Recruited were 40 patients diagnosed as severe community-acquired pneumonia in Hallym University Hospital from January 1, 1989 through July 31, 1996. Patients were analysed retrospectively for age, sex, underlying disease, respiration rate, hypoxemia, requirement of mechanical ventilation, involvement on chest radiograph, shock, and the serum concentration of BUN and albumin. All parameters were compared between survived and dead group. Results : Male to female ratio was 2.07 : 1. The mean age was $63.1{\pm}17.5$years(range 25~90years) with 65% of patients aged equal to or more than 60. The major underlying diseases were old pulmonary tuberculosis(12.5%), chronic obstructive pulmonary disease(7.5%), bronchial asthma(5%), bronchiectasis(2.5%), and diabetes mellitus(22.5%). Microbiologic diagnosis was made in 26 out of 40 patients(65%). The most common causative organism was S. pneumoniae(17.5%, 7/40) followed by S. aureus(15.0%, 6/40), K. Pneumoniae(12.5%, 5/40), M. tuberculosis(7.5%, 3/40), H. influenzae(2.5%, 1/40), coagulase negative staphylococcus(2.5%, 1/40), P. aeruginosa(2.5%. 1/40), E. cloaceae(2.5%, 1/40), and E. coli(2.5%, 1/40). M. pneumoniae was detected in no patient. The most frequent drugs administered in single or combination therapy were aminoglycosides(75%, 30/40), second- and third-generation cephalosporin(40%, 16/40 and 27.5%, 11/40), macrolides(27.5%, 11/40), and amoxicillin/clavulanic acid(22.5%, 9/40). Of the 40 patients, 14 died of severe community-acquired pneumonia(37.5%). Among them, seven patients (50%) expired within 72h of hospital arrival. According to multivariate analysis, mortality was significantly associated with requirement of mechanical ventilation, bilateral pulmonary involvement, and serum albumins$\leq$3.0g/dl. Conclusion : An understanding of the clinical characteristics and prognostic factors in severe community-acquired pneumonia identified in this study will optimize therapeutic approach in this disease and help decreasing its notorious mortality rate.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2000.04a
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• pp.9-10
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• 2000

An important business-field of world-wide steel-industry is the coating of thin metal-sheets with zinc, zinc-aluminum and aluminum based materials. These products mostly go into automotive industry. in particular for the car-body. into building and construction industry as well as household appliances. Due to mass-production, the processing is done in large continuously operating plants where the mostly cold-rolled metal-strip as the substrate is handled in coils up to 40 tons unwind before and rolled up again after passing the processing plant which includes cleaning, annealing, hot-dip galvanizing / aluminizing and chemical treatment. In the liquid Zn, Zn-AI, AI-Zn and AI-Si bathes a combined action of corrosion and wear under high temperature and high stress onto the transfer components (rolls) accounts for major economic losses. Most critical here are the bearing systems of these rolls operating in the liquid system. Rolls in liquid system can not be avoided as they are needed to transfer the steel-strip into and out of the crucible. Since several years, ceramic roller bearings are tested here [1.2], however, in particular due to uncontrollable Slag-impurities within the hot bath [3], slide bearings are still expected to be of a higher potential [4]. The today's state of the art is the application of slide bearings based on Stellite\ulcorneragainst Stellite which is in general a 50-60 wt% Co-matrix with incorporated Cr- and W-carbides and other composites. Indeed Stellite is used as the bearing-material as of it's chemical properties (does not go into solution), the physical properties in particular with poor lubricating properties are not satisfying at all. To increase the Sliding behavior in the bearing system, about 0.15-0.2 wt% of lead has been added into the hot-bath in the past. Due to environmental regulations. this had to be reduced dramatically_ This together with the heavily increasing production rates expressed by increased velocity of the substrate-steel-band up to 200 m/min and increased tractate power up to 10 tons in modern plants. leads to life times of the bearings of a few up to several days only. To improve this situation. the Mechanical Alloying (MA) TeChnique [5.6.7.8] is used to prOduce advanced Stellite-based bearing materials. A lubricating phase is introduced into Stellite-powder-material by MA, the composite-powder-particles are coated by High Energy Milling (HEM) in order to produce bearing-bushes of approximately 12 kg by Sintering, Liquid Phase Sintering (LPS) and Hot Isostatic Pressing (HIP). The chemical and physical behavior of samples as well as the bearing systems in the hot galvanizing / aluminizing plant are discussed. DependenCies like lubricant material and composite, LPS-binder and composite, particle shape and PM-route with respect to achievable density. (temperature--) shock-reSistibility and corrosive-wear behavior will be described. The materials are characterized by particle size analysis (laser diffraction), scanning electron microscopy and X-ray diffraction. corrosive-wear behavior is determined using a special cylinder-in-bush apparatus (CIBA) as well as field-test in real production condition. Part I of this work describes the initial testing phase where different sample materials are produced, characterized, consolidated and tested in the CIBA under a common AI-Zn-system. The results are discussed and the material-system for the large components to be produced for the field test in real production condition is decided. Outlook: Part II of this work will describe the field test in a hot-dip-galvanizing/aluminizing plant of the mechanically alloyed bearing bushes under aluminum-rich liquid metal. Alter testing, the bushes will be characterized and obtained results with respect to wear. expected lifetime, surface roughness and infiltration will be discussed. Part III of this project will describe a second initial testing phase where the won results of part 1+11 will be transferred to the AI-Si system. Part IV of this project will describe the field test in a hot-dip-aluminizing plant of the mechanically alloyed bearing bushes under aluminum liquid metal. After testing. the bushes will be characterized and obtained results with respect to wear. expected lifetime, surface roughness and infiltration will be discussed.

• Tuberculosis and Respiratory Diseases
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• v.60 no.5
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• pp.548-553
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• 2006

Background : Alcoholic ketoacidosis(AKA) is a metabolic disturbance that is caused by prolonged and excessive alcohol consumption. Though the prognosis is reportedly good, its outcome is unclear in some cases that are combined with multi-organ failure. There are few reports of an analysis of cases admitted to an intensive care unit(ICU) Method: Cases of AKA admitted to the ICU over the last 5 years were retrospectively analyzed. Severe AKA was characterized by multi-organ failure that required treatment in an ICU Results : All patients were males with a history of excessive alcohol consumption. Five of them (50%) mainly complained of gastrointestinal symptoms (nausea, vomiting, diarrhea), showing metabolic acidosis with an increased asmolar and anion gap. Rhabdomyolysis with acute renal failure was the most common combined organ failure. Mechanical ventilation was performed in 80%. Six patients died and 4 patients survived. In the surviving patients, the arterial blood gas analysis(ABGA) was normalized within 12 hours after admission. Conclusion : In severe AKA patients, rhabdomyolysis with acute renal failure was the most common complication. The mortality rate was high and death from shock occurred within 3 days.

• Pediatric Infection and Vaccine
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• v.10 no.2
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• pp.186-192
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• 2003

Purposes : Recently, acute gastroenteritis broke out among the neonates transferred from postpartum care centers located in Seoul, and Gyeounggi area. Thus, we researched the cause, progress and characters of the disease by analyzing the cases from 9 hospitals in Seoul and Gyeounggi area. Methods : We conducted retrospective study of 33 neonates transferred from postpartum care centers from October 2001 to July 2002 : we divided the neonates into 2 groups. The severe group had any of following 5 conditions : blood pH <7.20, respiratory difficulty, mechanical ventilation, shock, and disseminated intravascular coagulation. And the rest were classified into the moderate group. Results : The severe group was significantly more aged than the moderate group(P= 0.005). Weight loss was significantly severe in the severe group(P=0.0512). In blood gas analysis, bicarbonate was less in the severe group than the moderate group(P=0.032). In the virus examination, rotavirus was detected in 7 cases, and astrovirus was detected in 1 case. In the severe group, 4 neonates were dead. Conclusion : In acute gastroenteritis of neonates, early diagnosis and treatment are important. Thus, the legislation of postpartum care center is needed, and the medical specialists should be stationed in postpartum care center. We assume that the severe group had severe conditions because they were treated comparatively late. However, to find out the cause of the disease and to cope with it, the nationwide epidemiologic study on acute gastrenteritis of neonates is needed.

• Tuberculosis and Respiratory Diseases
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• v.67 no.3
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• pp.205-211
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• 2009

Background: Serum procalcitonin level has been considered prognostic during sepsis and septic shock. We investigated the significance of procalcitonin in critically ill patients with respiratory infections. Methods: The patients who had radiographically diagnosed diffuse lung infiltrations were enrolled on a prospective basis. Bronchoalveolar lavage (BAL) fluid for the purpose of quantitative cultures (${\geq}10^4$ cfu/mL) was obtained from all patients. Serum procalcitonin levels determined by PCT-Q kit were measured on BAL day and classified as follows; <0.5 ng/mL, 0.5~2.0 ng/mL, 2.0~10.0 ng/mL and >10.0 ng/mL. We analyzed the patient's characteristics according to outcome; favorable or unfavorable, defined as death. Results: Patients from the following categories were included: medical 17 (47.2%), surgical 9 (25%), and burned 10 (27.8%). APACHE II scores on admission to intensive care unit were 11.5${\pm}$6.89 and 11 (30.6%) had unfavorable outcomes. A procalcitonin level ${\geq}$0.5 ng/mL was in 17 (47.2%) of all. On univariate analysis, the frequencies of burn injury, mechanical ventilation, multiple organ failure, and a procalcitonin level ${\geq}$0.5 ng/mL were more often increased in patients with unfavorable outcomes than in those with favorable outcomes (p<.05). Also, a higher procalcitonin range and ventilator-associated pneumonia (VAP) were more closely associated with an unfavorable outcome (p<.05). However in multivariate analysis, a strong predictor of unfavorable outcome was burn injury (p<.05). A procalcitonin level ${\geq}$0.5 ng/mL was more sensitive in predicting VAP than unfavorable outcome. Conclusion: A higher procalcitonin level seems to be associated with VAP, but further study is required to know that procalcitonin would be a prognostic marker in critically ill patients with respiratory infections.

• Journal of Chest Surgery
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• v.29 no.11
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• pp.1218-1222
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• 1996

The reported incidence of postcardiotomy cardiogenic shock not responding to conventional therapy is still 0.1 to 0.8%. For this group of patients, more aggressive form of circulatory support must be employed. Centrifugal pumps are a ventricular assist device most commonly used on this purpose, due to low cost and easy availability. Currently, however, clinical experience of centrifugal pumps as a ventricular assist device is rarely reported in Korea. From January 1992 to January 1996, 2986 patients underwent cardiac operations on cardiopulmonary bypass at Seoul National University Hospital. Refractory postcardiotomy cardiac failure requring ventricular support with a Biomedicus centrifugal pump developed in ten of these patients. There were eight men and two women, ranged in age from nine years to 77 years with a mean of 50$\pm$20 years. The primary surgical procedures consisted of isolated coronary revascularization in four patients, combined coronary revascularization and aortic valve replacement in two, aortic dissection repair in two, pulmonary embolectomy in one, and heart transplantation in one. Of the ten patients, five had left ventricular assistance, one had right ventricular assistance, and four had biventricular assistance. Duration of ventricular assistance ranged from 24 to 175 hours, with a mean of 76$\pm$51 hours. Seven patients were weaned from ventricular assistance, and four of them discharged. The causes of death for nonsurvivors were progressive cardiac failure in two patients and multiorgan failure, intractable ventricular fibrillation, irreversible brain injury, and mechanical problem, respectively, in the other four. Survival was not predicted by time on cardiopulmonary bypass, aortic cross-clamp time, or duration of ventricular support. Major complications included bleeding(7), renal failure(6), infection(3) and neurologic complication(2). These results indicate that a centrifugal pump can provide reasonably satisfactory short-term circulatory support.