• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.93-94
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• 2007

An essential step for SERGI is to show the TRANSFORMER PROTECTOR (TP) efficacy for all transformers and all types of rupture of insulation. Its research program philosophy is thus to maintain a strong connection between experiments and the theoretical developments. Up to now, two TP test campaigns have been performed, both under the worst conditions by creating low impedance faults leading to electrical arcs inside the transformer tank dielectric oil. In 2002, Electricite de France performed 28 TP tests. Then, in 2004, a second campaign of 34 TP tests was carried out by CEPEL, the Brazilian independent High Voltage Laboratory. For the 62 tests, each transformer was equipped with the TP, which reacts directly to the moving dynamic pressure peak, shock wave, caused by the low impedance fault. When an electrical arc occurs, only one pressure peak is generated. The initial energy transfer is almost instantaneous, and so is the phase change. Because of the oil inertia, the gas is very quickly pressurised. As it is more difficult to vaporise a liquid than to crack oil-vapour into smaller molecules, the arc location would mainly remain in the gaseous phase after and less gas will be produced. As a result, when comparing tests for which pressure peaks are respectively equal to 8 bar (116 psi) and 8.8 bar (127 psi), the corresponding arc energies vary by an order 10 of magnitude (0.1 MJ and 1 MJ respectively). The correlation of the results obtained between arc energy and dynamic pressure demonstrates that the arc energy is not the key parameter during transformer tank explosion, which is in opposition with the common electrical engineers belief.

• 식물조직배양학회지
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• 제25권4호
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• pp.231-236
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• 1998

배지상에 여과지를 덮어놓는 간단한 물리적 처리가 체세포배의 발생 및 발아에 미치는 영향을 밝히기 위하여 본 실험관찰을 수행하였다. 배지상에 덮어놓은 세장의 여과지위에서 일주일 동안 당근 자엽절편을 배양한 후 MS 기본배지에 계대배양을 하면 여과지 덮개 없는 배지에서의 체세포배발생 보다 2배에서 39배의 배발생을 나타내었고, 체세포배의 성숙 및 발아도 증진되었다. 배지상의 여과지에 배양액을 첨가한 다음 배양을 하면 여과지에 배양액을 첨가하지 않은 경우보다 배발생이 감소되었다. 그러므로 여과지덮개는 자엽절편을 치상한 배양환경의 습기를 변화시켜 체세포배의 발생을 증진시킨 것으로 생각된다.

• 식물조직배양학회지
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• 제21권5호
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• pp.315-318
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• 1994

CaMV35S promoter-$\beta$-glucuronidase (GUS) 유전자와 선발 표지로서 neomycin phosphotransferase 유전자를 가진 pBI121 binary 벡터를 도입한 Agrobacterium turmfaciens LAB4404와 더덕 유식물체의 자엽 절편을 1 mg/L BA가 첨가된 MS 배지에서 48시간 동안 공동배양한 후 1 mg/L BA, 250 mg/L carbenicillin 100 mg/L kanamycin sulfate을 첨가한 고체배지에 옮겨 명조건에서 배양하였다. 배양 2주 후 절편의 절단면 부근으로부터 수많은 부정아가 형성되기 시작하였다. 이들 부정아의 GUS 활성을 조사한 결과 15%가 양성반응을 나타내었다. 배양 6주 후 절편이 형성한 수많은 부정아로부터 56.7% 빈도로 shoot이 발달하였다. 이들 shoot은 기본배지에 옮겨서 4주 경과되었을 때 대부분 발근하였으며, 재분화된 개체는 토양에 이식하였다. Southem 분석결과 GUS양성을 보인 재분화 개체의 게놈 DNA에 GUS 유전자가 삽입되었음이 확인되었다.

• Journal of Plant Biotechnology
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• 제29권3호
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• pp.185-188
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• 2002

유자의 성숙종자를 MS 기본배지에 치상하여 종자의 내피에서 주심조직 유래의 희고 부서지기 쉬운 배발생캘러스가 1.2%의 빈도로 형성되었다. 이 캘러스는 1 mg/L 2,4-D를 첨가한 MS배지에서 증식되었다. 증식된 캘러스를 0.1 mg/L kinetin을 첨가한 MS 배지에 옮겼을 때 많은 수의 체세포배가 형성되었다. 배발생캘러스를 1 mg/L 2,4-D를 첨가한 액체 배지에 넣어 배발생 현탁배양계를 확립하였다. 배양된 현탁배양세포를 0.5 mg/L ABA를 첨가한 고체배지에 평판하였을 때 높은 빈도로 체세포배로 발달하였으며 MS 기본배지 혹은 1 mg/L kinetin 첨가배지에서 소식물체로 발달하였다. 소식물체는 성공적으로 토양으로 옮겨서 온실에서 육성되었다.

• 대한병리학회지
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• 제52권6호
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• pp.404-410
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• 2018

Background: Fine-needle aspiration cytology serves as a safe, economical tool in evaluating thyroid nodules. However, about 30% of the samples are categorized as indeterminate. Hence, many immunocytochemistry markers have been studied, but there has not been a single outstanding marker. We studied the efficacy of CD56 with human bone marrow endothelial cell marker-1 (HBME-1) in diagnosis in the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) category III. Methods: We reviewed ThinPrep liquid-based cytology (LBC) samples with Papanicolaou stain from July 1 to December 31, 2016 (2,195 cases) and selected TBSRTC category III cases (n=363). Twenty-six cases were histologically confirmed as benign (six cases, 23%) or malignant (20 cases, 77%); we stained 26 LBC slides with HBME-1 and CD56 through the cell transfer method. For evaluation of reactivity of immunocytochemistry, we chose atypical follicular cell clusters. Results: CD56 was not reactive in 18 of 20 cases (90%) of malignant nodules and showed cytoplasmic positivity in five of six cases (83%) of benign nodules. CD56 showed high sensitivity (90.0%) and relatively low specificity (83.3%) in detecting malignancy (p=.004). HBME-1 was reactive in 17 of 20 cases (85%) of malignant nodules and was not reactive in five of six cases (83%) of benign nodules. HBME-1 showed slightly lower sensitivity (85.0%) than CD56. The specificity in detecting malignancy by HBME-1 was similar to that of CD56 (83.3%, p=.008). CD56 and HBME-1 tests combined showed lower sensitivity (75.0% vs 90%) and higher specificity (93.8% vs 83.3%) in detecting malignancy compared to using CD56 alone. Conclusions: Using CD56 alone showed relatively low specificity despite high sensitivity for detecting malignancy. Combining CD56 with HBME-1 could increase the specificity. Thus, we suggest that CD56 could be a useful preoperative marker for differential diagnosis of TBSRTC category III samples.

• 한국추진공학회지
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• 제20권4호
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• pp.94-103
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• 2016

액체로켓엔진에서의 재생냉각 채널은 높은 온도의 연소가스로부터 연소실 내벽을 효율적으로 냉각하기 위해 사용되며, 냉각채널 설계를 위해서는 열전달 특성과 압력손실 특성을 미리 예측하여야 한다. 본 연구에서는 서로 다른 형상을 갖는 5개의 냉각채널을 설계하고, 커터와 엔드밀로 채널을 제작하였다. 채널을 흐르는 유속과 후단 압력조건을 달리하여 가공방법, 채널 형상, 유동조건에 따른 압력손실을 실험적으로 측정하여 해석결과와 비교를 수행하였다. 동일 형상 및 유동조건에서 커터로 가공된 채널이 엔드밀로 가공된 채널보다 압력손실이 적었다. 또한 채널 형상, 유동조건에 따라 실험결과와 해석결과의 압력손실 비가 달라짐을 확인할 수 있었다.

• 설비공학논문집
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• 제18권11호
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• pp.915-922
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• 2006

Considering heat pipe design principles in fabrication and operational performances, water is one of the most recommended working fluids to make mid to low tempera lure heat pipes. But the conventional water heat pipes might encounter the failure in a cold start-up operation when socked at a chilling temperature lower than the freezing point. If they are subjected to a heat supply for start-up at a temperature around $-20^{\circ}C$, the rate of the vapor flow and the corresponding heat transfer from the evaporator to the condenser is so small that the vapor keeps to stick on the surface of the chilling condenser wall, forming an ice layer, resulting in a liquid deficiency in the evaporator. This kind of problems was resolved by Kang et al. in 2004 by adopting a gas loading heat pipe technology to the conventional water heat pipes. This study was conducted to examine a chilling start-up procedure of gas loading heat pipes by investigating the behaviors of heat pipe wall temperatures. And the thermal resistance of the gas loaded heat pipe that depends on the operating temperatures and heat loads was measured and examined. Two water heat pipes were designed and fabricated for the comparison of performances, one conventional and the other loaded with $N_2$ gas. They were put on start-up test at a heat supply of 30 W after having been socked at an initial temperature around $-20^{\circ}C$. It was observed that the gas loaded one had succeeded in chilling start-up operation.

• Nuclear Engineering and Technology
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• 제42권6호
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• pp.620-635
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• 2010

In this paper we describe current activities on the project Multi-Scale Modeling and Analysis of convective boiling (MSMA), conducted jointly by the Paul Scherrer Institute (PSI) and the Swiss Nuclear Utilities (Swissnuclear). The long-term aim of the MSMA project is to formulate improved closure laws for Computational Fluid Dynamics (CFD) simulations for prediction of convective boiling and eventually of the Critical Heat Flux (CHF). As boiling is controlled by the competition of numerous phenomena at various length and time scales, a multi-scale approach is employed to tackle the problem at different scales. In the MSMA project, the scales on which we focus range from the CFD scale (macro-scale), bubble size scale (meso-scale), liquid micro-layer and triple interline scale (micro-scale), and molecular scale (nano-scale). The current focus of the project is on micro- and meso-scales modeling. The numerical framework comprises a highly efficient, parallel DNS solver, the PSI-BOIL code. The code has incorporated an Immersed Boundary Method (IBM) to tackle complex geometries. For simulation of meso-scales (bubbles), we use the Constrained Interpolation Profile method: Conservative Semi-Lagrangian $2^{nd}$ order (CIP-CSL2). The phase change is described either by applying conventional jump conditions at the interface, or by using the Phase Field (PF) approach. In this work, we present selected results for flows in complex geometry using the IBM, selected bubbly flow simulations using the CIP-CSL2 method and results for phase change using the PF approach. In the subsequent stage of the project, the importance of effects of nano-scale processes on the global boiling heat transfer will be evaluated. To validate the models, more experimental information will be needed in the future, so it is expected that the MSMA project will become the seed for a long-term, combined theoretical and experimental program.

• Nuclear Engineering and Technology
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• 제54권5호
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• pp.1914-1928
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• 2022

To improve the heat transfer efficiency of the reactor fuel assembly, it is necessary to accurately calculate the two-phase flow boiling characteristics and the critical heat flux (CHF) in the fuel assembly. In this paper, a Eulerian two-fluid model combined with the extended wall boiling model was used to numerically simulate the 5 × 5 fuel rod bundle with spacer grids (four sets of mixing vane grids and four sets of simple support grids without mixing vanes). We calculated and analyzed 11 experimental conditions under different pressure, inlet temperature, and mass flux. After comparing the CHF and the location of departure from the nucleate boiling obtained by the numerical simulation with the experimental results, we confirmed the reliability of computational fluid dynamic analysis for the prediction of the CHF of the rod bundle and the boiling characteristics of the two-phase flow. Subsequently, we analyzed the influence of the spacer grid and mixing vanes on the void fraction, liquid temperature, and secondary flow distribution. The research in this article provides theoretical support for the design of fuel assemblies.

• 한국수소및신에너지학회논문집
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• 제33권4호
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• pp.391-399
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• 2022

Hydrogen is one of the energy carriers and has high energy efficiency relative to mass. It is an eco-friendly fuel that makes only water (H₂O) as a by-product after use. In order to use hydrogen conveniently and safely, development of production, storage and transfer technologies is required and attempts are being made to apply hydrogen as an energy source in various fields through the development of the technology. For transporting and storing hydrogen include high-pressure hydrogen gas storage, a type of storage technologies consist of cryogenic hydrogen liquid storage, hydrogen storage alloy, chemical storage by adsorbents and high-pressure hydrogen storage containers have been developed in a total of four stages. The biggest issue in charging high-pressure hydrogen gas which is a combustible gas is safety and the backfire prevention device is that prevents external flames from entering the tank and prevents explosion and is essential to use hydrogen safely. This study conducted a numerical analysis to analyze the performance of suppressing flame propagation of 2, 3 inch flame arrestor. As a result, it is determined that, where the flame arrestor is attached, the temperature would be lowered below the temperature of spontaneous combustion of hydrogen to suppress flame propagation.