• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.1
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• pp.97-102
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• 2012

A hermetically sealed oil transformer is designed by applying expanding function of the tank due to the volume changes of the insulation oil according to the temperature rises. When the insulation oil expands, an increase in the volume of the corrugated fin prevents a pressure rise of the transformer. For a wind turbine transformer, a vegetable-oil-immersed transformer has the advantages of excellent biodegradation and fire-resistant properties like an exceptionally high fire point. When vegetable oil is substituted for mineral oil, however, the maximum winding temperature rises because of the decrease in the internal circulation flow rate resulting from the variations of the oil's physical characteristics, such as density and viscosity. The purpose of this study is to develop a hermetically sealed vegetable oil transformer that can be applied in a wind turbine and to analyze the thermal stability of the active part of the transformer to deal with pressure variations due to the temperature changes. In addition, thermal tests for the vegetable oil transformer have been performed, and the measured values are compared with the analysis results.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.186-186
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• 2000

After LeComber et al. reported the first amorphous hydrogenated silicon (a-Si: H) TFT, many laboratories started the development of an active matrix LCDs using a-Si:H TFTs formed on glass substrate. With increasing the display area and pixel density of TFT-LCD, however, high mobility TFTs are required for pixel driver of TF-LCD in order to shorten the charging time of the pixel electrodes. The most important of these drawbacks is a-Si's electron mobiliy, which is the speed at which electrons can move through each transistor. The problem of low carier mobility for the a-Si:H TFTs can be overcome by introducing polycrystalline silicon (poly-Si) thin film instead of a-Si:H as a semiconductor layer of TFTs. Therefore, poly-Si has gained increasing interest and has been investigated by many researchers. Recnetly, fabrication of such poly-Si TFT-LCD panels with VGA pixel size and monolithic drivers has been reported, . Especially, fabricating poly-Si TFTs at a temperature mach lower than the strain point of glass is needed in order to have high mobility TFTs on large-size glass substrate, and the monolithic drivers will reduce the cost of TFT-LCDs. The conventional methods to fabricate poly-Si films are low pressure chemical vapor deposition (LPCVD0 as well as solid phase crystallization (SPC), pulsed rapid thermal annealing(PRTA), and eximer laser annealing (ELA). However, these methods have some disadvantages such as high deposition temperature over $600^{\circ}C$, small grain size (<50nm), poor crystallinity, and high grain boundary states. Therefore the low temperature and large area processes using a cheap glass substrate are impossible because of high temperature process. In this study, therefore, we have deposited poly-Si thin films on si(100) and glass substrates at growth temperature of below 40$0^{\circ}C$ using newly developed high rate magnetron sputtering method. To improve the sputtering yield and the growth rate, a high power (10~30 W/cm2) sputtering source with unbalanced magnetron and Si ion extraction grid was designed and constructed based on the results of computer simulation. The maximum deposition rate could be reached to be 0.35$\mu$m/min due to a high ion bombardment. This is 5 times higher than that of conventional sputtering method, and the sputtering yield was also increased up to 80%. The best film was obtained on Si(100) using Si ion extraction grid under 9.0$\times$10-3Torr of working pressure and 11 W/cm2 of the target power density. The electron mobility of the poly-si film grown on Si(100) at 40$0^{\circ}C$ with ion extraction grid shows 96 cm2/V sec. During sputtering, moreover, the characteristics of si source were also analyzed with in situ Langmuir probe method and optical emission spectroscopy.

• Journal of Navigation and Port Research
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• v.32 no.6
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• pp.499-503
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• 2008

As the conference result of MEPC in IMO, development of ballast water management system corresponding to newly established ballast water management standard (D2 regulation) of shipping is being made an active progress over the whole world. The ballast water management system should treat particular material of more than $10{\mu}m$ in high capacity of more than 500t per hour in the event of filtration process. Also, it is very difficult to develop a practical management system since a limited element which a narrow space of the ship should be designed in the minimal volume is assumed. Therefore, the study promoted a study on the next generation auto back wash media filter to overcome such a limited element. Also, the study performed pressure and flux measurement test followed by thickness of each filter medium for filtration by each size to grasp a relation between absorption and pressure at the time of vacuum filtration and mechanical analysis and turbidity change observation of filtered water after vacuum filtration.

• Economic and Environmental Geology
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• v.52 no.5
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• pp.367-379
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• 2019

Pyeongan Supergroup (PS) in the Taebaeksan basin preserves key geological evidences to understand the tectonometamorphic evolution of the Songrim orogeny that affected the formation of the Korean Peninsula during the late Paleozoic to early Mesozoic. The aims of this paper therefore are to investigate the characteristics of the Songrim orogeny based on the previous results of metamorphism and deformations of the PS, and then to review geological significance and research necessity of the PS. Age distributions and Th/U ratio of detrital zircon in the PS indicate that sedimentary environment of the Taebaeksan basin during the late Paleozoic was arc-related foreland basin and retro-arc foreland basin at the active continental margin. In addition, the main magmatic activities occurred in the early Pennsylvanian and Middle Permian, thus sedimentation and magmatic activities occurred simultaneously. The PS was affected by lower temperature-medium pressure (M1) and medium temperature and pressure (M2) regional metamorphism during the Songrim orogeny. During M1, slate and phyllite containing chloritoid, andalusite, kyanite porphyroblasts intensively deformed by E-W bulk crustal shortening combined with folding and shearing. And garnet and staurolite porphyroblasts were formed during the N-S bulk crustal shortening accompained by M2. Such regional metamorphism of the PS is interpreted to occur in an area where high strain zone is localized during ca. 220-270 Ma. In order to elucidate the evolution of the Taebaeksan basin and tectonic features of the Songrim orogeny, it is expected that the study will be carried out such as the regional distribution of metamorphic zones developed in the PS, characteristics and timing of deformations, and late Paleozoic paleo-geography of the Taebaeksan basin.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.371-375
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• 2019

The role of resuscitative endovascular balloon occlusion of the aorta (REBOA) in hemodynamically unstable pancreatic trauma is unclear. We report here a case of traumatic pancreatic bleeding controlled with REBOA and angioembolization of the splenic artery before surgery. A 65-year old man experienced blunt trauma upon falling from a height of 20 m. Computed tomography (CT) revealed distal pancreatic trauma (grade III) and contrast extravasation around the splenic artery. Shortly after CT, his systolic blood pressure was 60 mmHg and REBOA was performed for hemodynamic stability. His systolic pressure increased to 130 mmHg after balloon inflation and angioembolization of the splenic artery was performed. On angiography, no further arterial bleeding was identified and the balloon was removed. Subsequently, the patient underwent emergent laparotomy with distal pancreatectomy. There was no active bleeding during surgery and distal main pancreatic duct injury was identified. After surgery, the patient recovered without complication. In this case, hemodynamically unstable hemorrhagic pancreatic trauma was treated effectively and safely with distal pancreatectomy after REBOA with angioembolization.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.1
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• pp.25-36
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• 2021

Hydrogen in hydrogen-electric vehicles has a wide range of combustion and explosion ranges, and is a combustible gas with a very fast flame propagation speed, so it has the risk of leakage, diffusion, ignition, and explosion. The fuel tank has a Thermally active Pressure Relief Device (TPRD) to reduce the risk of explosion and other explosions, and in the event of an accident, hydrogen inside the tank is released outside before an explosion or fire occurs. However, if an accident occurs in a semi-closed space such as an underground parking lot, the flow of air flow is smaller than the open space, which can cause the concentration of hydrogen gas emitted from the TPRD to accumulate above the explosion limit. Therefore, in this study, the leakage rate and concentration of hydrogen over time were analyzed according to the diameter of the nozzle of the TPRD. The diameter of the nozzle was considered to be 1 mm, 2.5 mm and 5 mm, and ccording to the diameter of the nozzle, the concentration of hydrogen in the underground parking lot increases in a faster time with the diameter of the nozzle, and the maximum value is also analyzed to be larger with the diameter of the nozzle. In underground parking lots where air currents are stagnant, hydrogen concentrations above LFL (Lowe Flammability Limit) were analyzed to be distributed around the nozzle, and it was analyzed that they did not exceed UFL (Upper Flammability Limit).

• Journal of Korea Trade
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• v.24 no.4
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• pp.71-94
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• 2020

Purpose - Multi-National Enterprises (MNEs) tend to face a high level of institutional pressures in regions with high institutional development level. When complying with institutional pressures, firms try to make decisions to maximize profit while minimizing the risks to them. The purpose of this study is to investigate the influence of the institutional development level on institutional compliance timing by MNEs and the relationship between compliance speed and corporate performance. Design/methodology - The research focuses on three main variables, which are the institutional development level (as a determination of the institutional pressure level), the firm's compliance speed (as a determination of the compliance timing), and the firm's financial performance (as a determination of the corporate performance). We collected 19,869 firm-level data from CSMAR (the China Stock Market and Accounting Research), 6,922 CSR data from RKS (the Rankins CSR Ratings), and province and city-level data from the NERIM (National Economic Research Institute Index of Marketization) and NBSC (National Bureau of Statistics of China). The firms in China were chosen for analysis, and the analysis period was from 2008 to 2017. Random Effects GLS Regression was used to test the relationships among the variables. Findings - This study examined the effect of the institutional development level on the firm's compliance speed, together with the effect of compliance speed on the firm's financial performance of the MNEs in China. We found that the institutional development level positively influenced firms' financial performances, which means the firms' financial performances are better in the region with a high institutional development level. The compliance speed of institutional practice by firms was faster in the higher level of institutional development. However, the firm's delayed compliance led to better financial performance. Originality/value - Studies in the resource dependence view of Institutional Theory often fall short in understanding the theory by overlooking the firm's active decision-making. Thus, the findings do not present a full scope of corporate performance in this regard. This study not only found a way to test the role of a firm's independent decision-making (i.e., compliance timing) when facing the institutional pressure but also prove the significant role of the compliance timing on corporate performance. Also, we were able to test the effect of institutional development level, controlling location-specific variables because we used CSR performance data for MNEs operating in China. Lastly, by doing the above, the findings of this study suggest practical implications to the industry practitioners in MNEs.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.39 no.9
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• pp.41-51
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• 2010

건물의 배수 및 통기시스템에서 나타나는 현상중에 확실한 내용이 아직 밝혀지지 않은 부분이 몇 가지 남아 있다. 이것은 19세기 말엽의 근대 위생공학의 시작 단계에서부터 잘 알려진 사실이다. 건물의 배수 및 통기시스템 운용에 대한 내용은 일반 공학과 특정 유체역학의 범위 내에서 가장 잘 이해할 수 있다. 건물의 배수 및 통기시스템의 운영에 종사했던 초기의 기술진들은 이러한 점을 잘 알고 있었으며 유체역학에 적합하게 응용한 많은 사례를 확인할 수 있었다. 제2차 세계대전이 끝나고 이에 대한 많은 연구가 진행되어 왔으며 특히 유럽에서 시작된 전후 재건 붐을 통해 배수 및 통기시스템의 설계에 좀 더 효율적인 접근이 진척되게 되었다. 이러한 배수시스템의 중심에는 배수관 내부의 오염된 공기가 배수구 또는 위생기구를 통하여 주거 공간으로 유입되는 것을 방지하는 트랩(Water Trap)이 있다. 배수트랩의 주요 기능인 봉수는 일반적으로 깊이가 40 mm에서 50 mm 정도로 위생기구의 종류에 따라 봉수의 깊이는 다소 차이가 있다. 배수관내 공기의 흐름이 중요한 것처럼 트랩의 봉수 메커니즘이 중요하기 때문에 이 메커니즘을 소홀히 여긴다면 안전한 배수시스템의 운영을 기대하기는 어렵다. 배수관 내의 공기의 흐름은 배수에 의해 유입되거나 또는 배출된다. 배수관에서 내부 압력의 불규칙한 변화로 인하여 야기되는 불안정한 배수의 흐름은 트랩의 봉수를 파괴하고 나아가 주거공간으로 오염된 공기가 새어 나갈 수 있는 통로를 제공하게 된다. 관내압력의 천이는 이로 인한 문제가 발생할 가능성이 있는 위치에 그 압력을 완화할 수 있는 장치를 설계단계에 반영하여 적용함으로써 제어할 수 있다. 건물 내부에 상당한 길이의 통기배관을 설치하는 것은 배관의 마찰손실로 인하여 천이 현상을 효과적으로 제어할 수 있는 확실한 방법이 되지는 못한다. 그렇지만 통기밸브를 설치하는 것과 같이 배수관 내로 공기를 공급해주는 유입구를 건물 내부에 분산 설치하는 것이 효율적인 통기방식이 될 수 있고, 정압 천이로 인한 위험을 줄여줄 수 있다. 통기밸브는 정압 발생의 원인이 되지 않으며 단지 정압에 반응하여 더욱 기밀하게 닫히며, 약화된 압력파를 반사할 뿐이다. 고층 건물에서 배수입상관과 평행하게 설치된 통기입상관(Parallel Vent Pipe)의 경우 극히 일부분의 정압 천이 현상을 완화할 수 있다. (통기 배관의 직경이 배수 입상배관과 동일한 경우 대략 1/3 정도임), 그러므로 정압의 천이로 인한 압력 파동은 배수 시스템의 나머지 부분을 통해 전파되어 배수 트랩에 영향을 미치게 된다. 정압의 천이가 예상되는 위치에 정압천이 완화 장치(Positive Air Pressure Transient Alleviation Device)를 사용하면 배관 내부압력의 급격한 상승을 방지하여 연결된 트랩의 봉수를 보호할 수 있다. 이렇게 되면 순간적으로 발생하는 배관내 압력의 급등 현상을 90% 정도까지 완화 시킬 수 있다. 경험적으로 배수시스템에서 배관이 완전하게 막혀 과도한 정압이 발생하는 경우는 거의 없다. 이러한 경우에는 가장 낮은 위치에 있는 배수 트랩의 봉수가 깨지면서 자연스럽게 배수시스템의 압력이 해소되게 된다. 이러한 사례는 통기 방식과 상관없이 발생할 수 있다. 실제와 유사한 시뮬레이션을 통하여 통기 밸브(Air Admittance Valves)는 전면 통기 시스템 (Fully Vented System)에서 최소한 트랩의 봉수 보호용으로 적합한 것이 확인 되었다. 어떤 경우 에는 고층 건물에 더욱 적합하다는 것을 확인할 수 있었다. 부압 해소용으로 통기밸브를 이용하고 정압완화용으로 정압 완화장치(PAPAs: Positive Air Pressure Transient Attenuators)를 사용하는 전면적 능동 제어시스템(Fully Engineered Designed Active Control System)이 사용자에게 육안으로는 확인하지 못하는 기능을 보장하면서 배수 시스템의 안전과 효율성에 대한 효과적인 방법을 제공하고 있다.

• Journal of Life Science
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• v.33 no.10
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• pp.791-796
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• 2023

It is well known that any kind of physical activity can be a useful nonpharmacological tool in the prevention and treatment of cardiovascular diseases, including antihypertension. There is also strong evidence that suggests that people with cardiovascular disease are less active than healthy people. Therefore, the aim of this study was to investigate the effect of a 12-week walking exercise intervention program on body composition, insulin resistance, and blood pressure in obese elderly women with stage 1 hypertension. The walking exercise program was performed for 50 min, three times per week. The intensity progressively increased: RPE 11 to 12, 40-50% HRR, for weeks 1-4; RPE 12 to 13, 50-60% HRR, for weeks 5-8; and RPE 13 to 14, 60-65% HRR, for weeks 9-12. The subjects were 20 obese elderly women with stage 1 hypertension (SBP: 140-159 mmHg or DBP: 90-99 mmHg). Half were placed in the walking exercise group (EX, n=10), and half were placed in the control group (CON, n=10). At the end of the program, the EX group members had significantly lower body fat, insulin resistance, and SBP compared to the CON group members. These results suggest that undertaking a 12-week walking exercise program improves body fat, insulin resistance, and SBP, which may improve the incidence of metabolic disease in elderly obese women with stage 1 hypertension.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.50 no.2
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• pp.103-110
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• 2024

Lipid nanoparticles (LNPs) are a stable and an effective system that protects cell-impermeable biologically active compounds such as nucleic acids, proteins, and peptides against degradation caused by subtle environmental changes. This study focuses on developing LNPs encapsulating gallic acid (GA), an antioxidant, to effectively prolong the half-life of tetrahexyldecyl ascorbate (THDC), a oil-soluble vitamin C derivative. These LNPs were synthesized in small, uniform sizes at room temperature and pressure conditions using a microfluidics chip. Compared to liposomes manufactured under high pressure and high temperature conditions through conventional microfluidizers, LNPs manufactured through microfluidics chips had excellent dispersion and temperature stability, and improved skin absorption as well as improved oxidative stability of fat-soluble vitamin C derivatives. Future studies will focus on ex vivo and in vivo evaluations to study skin improvement to further validate these results.