• 한국분말재료학회지
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• 제21권3호
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• pp.196-201
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• 2014

In this study, nanocrystalline Cu-Ni bulk materials with various compositions were cold compacted by a shock compaction method using a single-stage gas gun system. Since the oxide layers on powder surface disturbs bonding between powder particles during the shock compaction process, each nanopowder was hydrogen-reduced to remove the oxide layers. X-ray peak analysis shows that hydrogen reduction successfully removed the oxide layers from the nano powders. For the shock compaction process, mixed powder samples with various compositions were prepared using a roller mixer. After the shock compaction process, the density of specimens increased up to 95% of the relative density. Longitudinal cross-sections of the shock compacted specimen demonstrates that a boundary between two powders are clearly distinguished and agglomerated powder particles remained in the compacted bulk. Internal crack tended to decrease with an increase in volumetric ratio of nano Cu powders in compacted bulk, showing that nano Cu powders has a higher coherency than nano Ni powders. On the other hand, hardness results are dominated by volume fraction of the nano Ni powder. The crystalline size of the shock compacted bulk materials was greatly reduced from the initial powder crystalline size since the shock wave severely deformed the powders.

• 대한기계학회논문집A
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• 제33권11호
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• pp.1274-1278
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• 2009

Fracture characteristics for plate and dome shapes of glass filled ceramics using shock tube were carried out. Glass filled ceramics have been considered as a promising candidate material for the dome port cover of air breathing engine. This part of the air breathing engine has an important role as separated membrane between combustion and external air, and needs the frangible characteristics that the particles of fractured glass filled ceramics should not affect the internal components of combustion. The objectives of this study are to evaluate the fracture pressures for various thicknesses and diameters of shock impact area. Also fracture phenomena of separated membrane using a shock tube compare with analytical method. The experimental apparatus consists of a driver, a driven section and a dump tank. The used material is glass filled ceramic made from Corning company. Specimens have the thickness of 3, 4.5 and 6mm. It is expected that the results obtained from this study can be used in the basic data for the dome port cover design of an air breathing engine.

• 한국연소학회지
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• 제22권1호
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• pp.8-13
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• 2017

Ignition delay time of methane/oxygen mixture is measured experimentally with the shock tube in order to obtain the data for high pressure conditions where gas turbines and internal combustion engines are operating. The shock tube experiment is validated first over the temperature range of 1400-2000 K at 10 bar and with the various equivalence ratios of 0.5, 1 and 2. The measured ignition delays are compared with the data from the literatures. And then, experiments are conducted for non-explored conditions, i.e., at 40 bar and with the equivalence ratio of 1.5. The present experimental data show a good agreement with the available ones from the literatures and reasonable dependence on pressure and equivalence ratio. In addition, the effects of the temperature and equivalence ratio on ignition delay time are analyzed.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.202-212
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• 2008

A three-dimensional computation was conducted to understand effects of the low Reynolds number on the loss characteristics in a transonic axial compressor, Rotor67. As a gas turbine becomes smaller in size and it is operated at high altitude, the operating condition frequently lies at low Reynolds number. It is generally known that wall boundary layers are thickened and a large separation occurs on the blade surface in axial turbomachinery as the Reynolds number decreases. In this study, it was found that the large viscosity did not affect on the bow shock at the leading edge but significantly did on the location and the intensity of the passage shock. The passage shock moved upstream towards leading edge and its intensity decreased at the low Reynolds number. This change had large effects on the performance as well as the internal flows such as the pressure distribution on the blade surface, tip leakage flow and separation. The total pressure rise and the adiabatic efficiency decreased about 3% individually at the same normalized mass flow rate at the low Reynolds number. In order to analyze this performance drop caused by the low Reynolds number, the total pressure loss was scrutinized through major loss categories such as profile loss, tip leakage loss, endwall loss and shock loss.

• 한국지열·수열에너지학회논문집
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• 제18권3호
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• pp.7-18
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• 2022

Secondary batteries used in electric vehicles have a potential risk of ignition and explosion. Various safety measures are being taken to prevent these risks. A numerical study was performed using a computational fluid dynamics code on the cases where pressure relief vents that can reduce the blast overpressures of batteries were installed in the through-compression test room, short-circuit drop test room, combustion test room, and immersion test room in facilities rleated to battery used in electric vehicles. This study was conducted using the weight of TNT equivalent to the energy release from the battery, where the the thermal runaway energy was set to 324,000 kJ for the capacity of the lithium-ion battery was 90 kWh and the state of charge (SOC) of the battery of 100%. The explosion energy of TNT (△H_TNT) generally has a range of 4,437 to 4,765 kJ/kg, and a value of 4,500 kJ/kg was thus used in this study. The dimensionless explosion efficiency coefficient was defined as 15% assuming the most unfavorable condition, and the TNT equivalent mass was calculated to be 11 kg. The internal explosion generated in a test room shows the very complex propagation behavior of blast waves. The shock wave generated after the explosion creates reflected shock waves on all inner surfaces. If the internally reflected shock waves are not effectively released to the outside, the overpressures inside are increased or maintained due to the continuous reflection and superposition from the inside for a long time. Blast simulations for internal explosion targeting four test rooms with pressure relief vents installed were herein conducted. It was found that that the maximum blast overpressure of 34.69 bar occurred on the rear wall of the immersion test room, and the smallest blast overpressure was calculated to be 3.58 bar on the side wall of the short-circuit drop test room.

• Journal of Electrical Engineering and Technology
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• 제12권5호
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• pp.2079-2087
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• 2017

As the number of tall buildings is increasing, the high-speed lift is necessary in the modern world. Therefore, the further considerations for associated safety devices of lifts were required by the International Standards. In order to stop the moving of cage and keep it, the lifts have to be provided with means that can detect the unintended car movement. Therefore, the International Standard Safety Rules for the construction and installation of lifts had been revised. This paper describes the operation principles of the Rope Brake to fit the Unintended Car Movement Protection (UCMP) means required by the International Standards. This paper confirmed that the performance of these devices was suitable in the scope of the safety standards. This paper also analyzed that the shocks on working of these devices in a car would be dangerous to each passenger differently. Thus, this paper proposes a new design that the circuit diagram of the Unintended Car Movement Protection systems should be improved from the existing design to solve these internal shock problems. So, it is expected to protect passengers from the internal shocks by working of Rope Brake due to irrelevant factors.

• Parasites, Hosts and Diseases
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• 제51권5호
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• pp.551-555
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• 2013

Complicated malaria is mainly caused by Plasmodium falciparum, but, increasingly, Plasmodium vivax is also being reported as a cause. Since the reemergence of indigenous vivax malaria in 1993, cases of severe malaria have been steadily reported in Korea. Herein, we report a case of vivax malaria complicated by adult respiratory distress syndrome (ARDS) that was successfully managed with extracorporeal membrane oxygenation (ECMO). A 59-year-old man presented at our hospital with fever and abdominal pain, which had persisted for 10 days. On admission, the patient had impaired consciousness, shock, hypoxia and haziness in both lungs, jaundice, thrombocytopenia and disseminated intravascular coagulation, metabolic acidosis, and acute kidney injury. A peripheral blood smear and a rapid diagnostic test verified P. vivax mono-infection. Ten hours after admission, hypoxia became more severe, despite providing maximal ventilatory support. The administration of antimalarial agents, ECMO, and continuous venovenous hemofiltration resulted in an improvement of his vital signs and laboratory findings. He was discharged from the hospital 7 weeks later, without any sequelae.

• Tuberculosis and Respiratory Diseases
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• 제44권6호
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• pp.1382-1389
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• 1997

저자들은 감기증상 후에 빠른 시간내에 급성호흡부전증에 이르렀던 환자에서 신증후성 출혈열과는 다르게 주로 호흡기와 순환기를 침범하는 한타바이러스 폐 증후군 1예률 경험하였기에 고하는 바이다.

• Tuberculosis and Respiratory Diseases
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• 제52권4호
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• pp.355-366
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• 2002

연구배경: 열 전처치는 조직 내에 열충격단백질의 생성을 유도하며 이러한 열 전처치가 내독소로 유도된 쥐의 급성폐손상을 감소시키고 패혈증에 의한 사망률을 감소시킨다고 알려져 있다. 그러나, 폐손상을 유발하는 원인에 노출된 후 가해진 열처치가 폐손상에 미치는 효과에 대하여는 아직까지 잘 알려져 있지 않다. 따라서 본 연구는 내독소 투여 직후 시행한 열충격이 내독소에 의해 유발된 쥐의 급성폐손상에 미치는 영향과 그에 따른 염증성 및 항염증성 사이토카인에 미치는 영항을 알아보고자 하였다. 방 법: 대조군은 백서의 기관지 내로 생리식염수를 투여하였고 열처치 대조군은 생리식염수 투여 직후 열처치를 시행하였다. 내독소군은 열처치 없이 내독소를 기관지내로 투여하였다. 열 전처치군은 내독소 투여 18시간 전에 열 전처치를 시행하였고, 열 동시처치 군은 내독소 투여 직후 열처치를 시행하였다. 내독소 투여 후 6시간에 기관지폐포세척을 시행하여 기관지폐포세척액 내의 호중구 백분율을 측정하였고 폐를 적출하여 myeloperoxidase(MPO)의 활성도를 측정하였으며 기관지폐포세척액과 혈청에서 LDH(lactic dehydrogenase), 단백질, IL(interleukin)-$1{\beta}$, TNF(tumor necrosis factor)-${\alpha}$ 및 IL-10를 측정하였다. 또한 각군에서 폐 조직 내 HSP72의 표현정도를 관찰하였다. 결 과: 1) 내독소군, 열 전처치군 및 열 동시처치군 모두에서 기관지폐포세척액 내의 호중구 백분율, 폐조직이 MPO, 혈청 및 기관지폐포세척액내의 $IL-1{\beta}$, $TNF-{\alpha}$ 및 IL-10이 대조군에 비해 증가하였다(각 p<0.05). 2) 열 동시처치군은 폐조직의 MPO와 기관지폐포세척액 단백질의 농도가 내독소군과 차이가 없었고 기관지폐포세척액의 LDH가 내독소군에 비해 증가하였다(p<0.05). 3) 열 동시처치군의 혈청 $TNF-{\alpha}$의 농도는 내독소군과 비교 시 증가하였다(p=0.01). 결 론: 내독소 투여 직후 시행한 열충격은 내독소로 유도되는 폐손상을 감소시키지 못하며 염증성 사이토카인의 농도를 증가시켰다.

• Tuberculosis and Respiratory Diseases
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• 제69권6호
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• pp.469-473
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• 2010

Nocardia farcinia, an aerobic, gram-positive bacilli actinomycetes of the genus Nocardia, is an uncommon pathogen found in humans. The most common Nocardia infection sites are the lung, central nervous system, and skin. Even though hematogenous dissemination can occur, isolation of the organism from blood cultures is very rare. We report a case of Nocardia infection that was isolated on blood cultures. A 59-year-old male with a medical history that includes a liver transplantation 6-years prior due to hepatocellular carcinoma secondary to chronic hepatitis B, developed pneumonia and was transferred to Severance Hospital. At the time of admission, the patient's initial exam showed hypothermia, tachypnea, and hypotension. His chest radiograph showed severe pneumonia and a large abscess on left upper lobe. Under the presumptive diagnosis of bacterial pneumonia or other opportunistic infection, we started broad spectrum antibiotics. However, he developed Nocardia sepsis, rapidly deteriorated, and subsequently died.