• Composites Research
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• 제33권4호
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• pp.198-204
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• 2020

본 연구에서는 탄소나노튜브 다발을 포함하는 나노복합재료의 열-기계적 특성을 정량적으로 예측하기 위하여 분자동역학 전산모사와 유한요소 기반 균질화 기법을 적용하였다. 응집된 탄소나노튜브의 수가 증가함에 따라 동일한 탄소나노튜브의 체적분율에도 불구하고, 면내 영률 및 면내 전단계수는 감소하였고, 면내 열팽창계수는 증가함을 확인할 수 있었다. 계면의 두께를 조사하기 위하여 밀도의 반경 방향 분포(Radial density distribution)을 조사하였으며, 계면의 두께는 탄소나노튜브의 수와는 거의 무관함을 확인할 수 있었다. 기지와 계면은 등방성 재료로 가정하였으며, 예측한 계면의 열-기계적 특성에 따르면, 응집된 탄소나노튜브의 수가 증가함에 따라 계면의 영률 및 전단계수는 감소하였으며, 열팽창계수는 반대로 증가하였다. 이를 토대로, 탄소나노튜브 다발을 포함하는 PLA 나노복합재료의 열-기계적 특성 예측을 위한 멀티스케일 균질화 모델을 개발하였다.

• Nuclear Engineering and Technology
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• 제55권3호
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• pp.1118-1124
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• 2023

Experimental study on the fluidelastic instability (FEI) of a curved tube bundle in single phase downward cross flow is investigated for the design qualification and analysis input preparation of helical coiled steam generator tubing. A 6×9 normal square curved tube array with equal and different vertical/horizontal pitch-to-diameter ratio was under-tested up to 6 m/s in term of gap flow velocity to measure the critical velocity for FEI. The critical velocity for FEI was measured at the turning point from the vibration amplitude plot along the gap flow velocity. Our test results were compared with straight tube results and published data in the design guideline. The applicability of the current design guidelines to a curved tube bundle is also assessed. We found that introducing frequency difference in a curved tube array increases the critical velocity for fluidelastic instability.

• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.2089-2097
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• 2014

Negative corona onset characteristics of the stranded conductors based on the ultra-high voltage (UHV) corona cage were studied in the paper. Based on the corona self-sustaining criterion in extreme uneven electric fields and the secondary emission process of the photoelectrons, the corona onset calculation model in the UHV corona cage is established and the corona current tests of the single LGJ900-75, 6 bundle LGJ900-75, 8 bundle LGJ400-35 conductors in dry and rain conditions were done in the UHV corona cage, and the rain rates are 2.4 mm/h, 20 mm/h and 30 mm/h. Corona onset electric field strength is gained by E-I tangent method, and the onset electric field strength in dry condition proves that the calculation model can be used to calculate the corona onset characteristics of the bundle conductors in the UHV corona cage. A further analysis proves that: the negative corona onset voltage of the conductor increases with the bundle number and the diameter of the sub conductor, but decreases with the bundle space in the corona cage. The onset electric field strength is influenced little by bundle space and bundle number, but decreases with the increase of the diameter of the sub-conductor. The surface irregularity coefficient decreases with the rain rate.

• Journal of Korean Biological Nursing Science
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• 제18권4호
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• pp.257-263
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• 2016

Background: This study purposed to examine how the incidence of the central line-associated bloodstream infection (CLABSI) in a operating room (OR) is affected by bundle application on central line insertion (CLI) practice. Methods: The study design was a pretest-posttest experimental trial. The subjects were 83 patients before the bundle application on CLI and 70 patients after. Results: The compliance(%) of bundle on CLI of among those who observed all of the five items increased from 7.2% before the intervention to 72.9% after. By items, compliance with the maximal barrier precaution was 100% for the use of a mask and cap before and after the intervention, but increased from 73.5% before the intervention to 88.6% after for the hand hygiene, from 73.5% to 88.6% for the use of a sterile gown, and from 9.6% to 75.7% for the use of a sterile large drape covering the whole body. CLABSI did not happen on CLI either before or after the application of the bundle intervention. Conclusion: Bundle application increased compliance with the use of a sterile gown and the use of a sterile large drape. However, its effect in the prevention of CLABSI was not clear probably due to the short period of intervention in a single hospital.

• 대한관절경학회지
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• 제13권2호
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• pp.111-114
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• 2009

단일 다발 십자인대 재건술의 임상적 결과를 보다 향상하고자 제안된 이중 다발 전방십자인대 재건술은 해부학적, 생역학적, 생물학적, 운동역학적으로 많은 이론적 장점이 있고 이에 따른 임상적 측면에서의 결과 향상이 기대되지만 이를 입증할 만한 충분한 관찰 기간을 가진 임상적 연구들이 매우 부족한 실정이다. 따라서 저자는 이중 다발 전방십자인대 재건술에 관련되어 최근까지 발표된 문헌을 통해 임상적 결과를 분석하고 이에 제기된 문제점을 살펴보고자 한다.

• International Journal of Air-Conditioning and Refrigeration
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• 제17권3호
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• pp.81-87
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• 2009

The effect of oil on convective boiling of R-123 in an enhanced tube bundle is experimentally investigated at $26.7^{\circ}C$ saturation temperature. The enhanced tube had pores (0.23 mm diameter) and connecting gaps (0.07 mm width), which had been optimized using pure R-123. The effects of oil concentration (0 to 5%), heat flux (10 to $40\;kW/m^2$), mass velocity (8 to $26\;kg/m2^s$) and vapor quality are investigated. The oil significantly reduces the bundle boiling heat transfer coefficient. With 1% oil, the reduction is approximately 35%. Further addition of oil further reduces the heat transfer coefficient. The data are also compared with the pool boiling counterpart. The reduction in the heat transfer coefficient is smaller in a bundle (convective boiling) than in a pool (single-tube pool boiling), with larger difference at a smaller heat flux. Similar to pure R-123 case, the effects of mass velocity and vapor quality are negligible for the convective boiling of R-123/oil mixture.

• 대한관절경학회지
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• 제12권3호
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• pp.167-171
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• 2008

• Nuclear Engineering and Technology
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• 제54권11호
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• pp.4296-4309
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• 2022

Mesh and turbulence model sensitivity analyses have been performed on computational fluid dynamics simulations executed with Hydra and ANSYS Fluent for a single CANadian Deuterium Uranium (CANDU) 37M nuclear fuel bundle placed within a standard pressure tube. The goal of this work was to perform a methodical analysis to objectively determine an appropriate mesh and to gauge the sensitivity of different turbulence models for CANDU subchannel flow under isothermal conditions. The boundary conditions and material properties are representative of normal operating conditions in a high-powered channel of the Darlington Nuclear Generating Station. Four meshes were generated with ANSYS Workbench Meshing, ranging from 22 to 84 million cells, and analyzed here to determine an appropriate level of mesh resolution and quality. Five turbulence models were compared in the turbulence model sensitivity analysis: standard k - ε, RNG k - ε, realizable k - ε, SST k - ω, and the Reynolds Stress Model. The intent of this work was to gain confidence in mesh generation and turbulence model selection of a single bundle to inform the decision making of subsequent investigations of an entire fuel channel containing a string of twelve bundles.

• 대한관절경학회:학술대회논문집
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• 대한관절경학회 2008년도 춘계 공동 학술대회
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• pp.14-14
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• 2008

• 대한관절경학회:학술대회논문집
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• 대한관절경학회 2008년도 춘계 공동 학술대회
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• pp.12-13
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• 2008