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Pescador, E. Diaz,Schafer, F.,Kliem, S. Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.10
The implementation and validation of multi-dimensional (multi-D) features in thermal-hydraulic system codes aims to extend the application of these codes towards multi-scale simulations. The main goal is the simulation of large-scale three-dimensional effects inside large volumes such as piping or vessel. This novel approach becomes especially relevant during the simulation of accidents with strongly asymmetric flow conditions entailing density gradients. Under such conditions, coolant mixing is a key phenomenon on the eventual variation of the coolant temperature and/or boron concentration at the core inlet and on the extent of a local re-criticality based on the reactivity feedback effects. This approach presents several advantages compared to CFD calculations, mainly concerning the model size and computational efforts. However, the range of applicability and accuracy of the newly implemented physical models at this point is still limited and needs to be further extended. This paper aims at contributing to the validation of the multi-D features of the system code ATHLET based on the simulation of the Tests 1.1 and 2.1, conducted at the test facility ROCOM. Overall, the multi-D features of ATHLET predict reasonably well the evolution from both experiments, despite an observed overprediction of coolant mixing at the vessel during both experiments.
이찬주(C.J. Lee),김재영(J.Y. Kim),이상곤(S.K. Lee),고대철(D.C. Ko),H. Schafer,김병민(B.M. Kim) 한국소성가공학회 2009 한국소성가공학회 학술대회 논문집 Vol.2009 No.5
The purpose of this study is investigating the joint characteristics of advanced high strength steel DP780 and Al5052 alloy sheet in the clinching process. It is difficult to join the advanced high strength with light-weight materials like aluminum alloy, because of low formability of DP780. The defects of clinching joint such as necking of the upper sheet, cracks of the lower sheet and no interlocking were occurred by different ductility between advanced high strength steel and aluminum alloy. The clinching conditions should be optimized to interlock without andy defects. In this study, the effect of process parameters of clinching process on joinability of advanced high strength steel with Al5052 alloy was investigated by using FE-analysis. From the result of FE-analysis, the clearance between clinching punch and die, die depth and the shape of die cavity mainly affected the joinability of advanced high strength steel with Al5052 alloy.
Cohesive zone model을 이용한 접착 power steering cylinder 개발
손영기(Y.K. Son),이찬주(C.J. Lee),이상곤(S.K. Lee),고대철(D.C. Ko),H. Schafer,이종만(J.M. Lee),김병민(B.M. Kim) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5
Adhesively bonded power steering cylinder with steel tube and aluminum bracket was developed to reduce the weight of steering system. To achieve the joint strength between steel tube and aluminum bracket, the shape aluminum bracket re-designed by using FE-analysis. The fracture behavior of adhesive layer is considered by cohesive zone model(CZM), which is based on two-parameter fracture phenomenon with critical stress and fracture toughness. From the result of FE-analysis with CZM, re-designed power steering cylinder was satisfied desired joint strength for axial and torsion modes. And its joint strength was verified by fracture test for each mode.
Eck, T. F.,Holben, B. N.,Reid, J. S.,Xian, P.,Giles, D. M.,Sinyuk, A.,Smirnov, A.,Schafer, J. S.,Slutsker, I.,Kim, J.,Koo, J.-H.,Choi, M.,Kim, K. C.,Sano, I.,Arola, A.,Sayer, A. M.,Levy, R. C.,Munchak American Geophysical Union 2018 Journal of Geophysical Research: Atmospheres Vol.123 No.10
<P>Analysis of Sun photometer measured and satellite retrieved aerosol optical depth (AOD) data has shown that major aerosol pollution events with very high fine mode AOD (>1.0 in midvisible) in the China/Korea/Japan region are often observed to be associated with significant cloud cover. This makes remote sensing of these events difficult even for high temporal resolution Sun photometer measurements. Possible physical mechanisms for these events that have high AOD include a combination of aerosol humidification, cloud processing, and meteorological covariation with atmospheric stability and convergence. The new development of Aerosol Robotic Network Version 3 Level 2 AOD with improved cloud screening algorithms now allow for unprecedented ability to monitor these extreme fine mode pollution events. Further, the spectral deconvolution algorithm (SDA) applied to Level 1 data (L1; no cloud screening) provides an even more comprehensive assessment of fine mode AOD than L2 in current and previous data versions. Studying the 2012 winter-summer period, comparisons of Aerosol Robotic Network L1 SDA daily average fine mode AOD data showed that Moderate Resolution Imaging Spectroradiometer satellite remote sensing of AOD often did not retrieve and/or identify some of the highest fine mode AOD events in this region. Also, compared to models that include data assimilation of satellite retrieved AOD, the L1 SDA fine mode AOD was significantly higher in magnitude, particularly for the highest AOD events that were often associated with significant cloudiness.</P>
An overview of mesoscale aerosol processes, comparisons, and validation studies from DRAGON networks
Holben, Brent N.,Kim, Jhoon,Sano, Itaru,Mukai, Sonoyo,Eck, Thomas F.,Giles, David M.,Schafer, Joel S.,Sinyuk, Aliaksandr,Slutsker, Ilya,Smirnov, Alexander,Sorokin, Mikhail,Anderson, Bruce E.,Che, Huiz Copernicus GmbH 2018 Atmospheric Chemistry and Physics Vol.18 No.2
<P>Abstract. Over the past 24 years, the AErosol RObotic NETwork (AERONET) program has provided highly accurate remote-sensing characterization of aerosol optical and physical properties for an increasingly extensive geographic distribution including all continents and many oceanic island and coastal sites. The measurements and retrievals from the AERONET global network have addressed satellite and model validation needs very well, but there have been challenges in making comparisons to similar parameters from in situ surface and airborne measurements. Additionally, with improved spatial and temporal satellite remote sensing of aerosols, there is a need for higher spatial-resolution ground-based remote-sensing networks. An effort to address these needs resulted in a number of field campaign networks called Distributed Regional Aerosol Gridded Observation Networks (DRAGONs) that were designed to provide a database for in situ and remote-sensing comparison and analysis of local to mesoscale variability in aerosol properties. This paper describes the DRAGON deployments that will continue to contribute to the growing body of research related to meso- and microscale aerosol features and processes. The research presented in this special issue illustrates the diversity of topics that has resulted from the application of data from these networks. </P>