2,809 research outputs found
Numerical Studies of CO2 Leak Modeling in Sodium-CO2 Heat Exchanger in the SFR coupled with the S-CO2 Brayton Cycle
No full textFor applying the supercritical CO2 Brayton cycle to the Sodium-cooled Fast Reactor, several technical challenges should be resolved. One of the most significant issues is to comprehend the CO2 leak mechanism initiated from the pressure boundary failure in a sodium-CO2 heat exchanger. Since the chemical reaction between sodium and CO2 is followed, the modeling of CO2 leak process is essential to predict the system dynamics. So far, a few studies have been performed to understand the CO2 leak mechanism but some limitations could be found. Thus, to simulate the transient response of the sodium side and CO2 side during the leak process more realistically, a numerical study was conducted. Prior to fully investigating the CO2 leak and the reaction mechanism, an isentropic critical flow model as a reference model was developed while reflecting sodium-CO2 interaction with several assumptions in this study.
A numerical study was performed while varying the nozzle diameter and the cover gas space volume with a conceptually designed simple flow model. Mass flux was calculated by determining the flow state whether the flow is choked or not. Then, the change of system pressure was obtained while calculating the amount of reaction products and generated heat. Even though this model could generally simulate the leak process, it should be modified by adding frictional losses and other assumptions
Hepatocellular carcinoma with metastasis to the spleen in a Holstein cow
No full textHepatocellular carcinoma (HCC) with metastasis to the spleen in a Holstein cow was studied by histopathologic and immunohistochemical methods. The tumor was characterized by a pseudoglandular (acinar) pattern with an associated fibrous stroma. Individual cells often had a "hepatoid" appearance but were interspersed with scattered cells exhibiting a clear, periodic acid-Schiff (PAS)-positive cytoplasm and small eccentric nuclei. This pattern was present in nodules found in both liver and spleen. Moreover, hepatoid tumor cells were positive for alpha-fetoprotein. Immunohistochemical studies suggest that myofibroblasts were responsible for the production of fibrous septa surrounding the pseudoglandular structures of bovine HCC. In summary, our histologic and immunohistochemical findings support a diagnosis of primary HCC with splenic metastasis. Furthermore, the associated stromal response appears to be of a myofibroblast origin. The primary etiology of bovine HCC and the significance of the intralesional, PAS-positive clear cells remain undetermined
Buckled reconstruction of the alkali-metal (Na,K)-adsorbed Si(111)-(3x1) surfaces
No full textThe atomic and electronic structures of the alkali-metal (Na, K)-adsorbed Si(iii)-(3x1) surface are studied by the pseudopotential density-functional total-energy scheme for the structural models proposed to date: the missing-top-layer (MTL), pi-bonded chain, and overlayer models including their variations. From the extensive investigation of them, we propose the MTL model as the ground-state structure of this system based both on the energetics and on the comparison of the calculated electronic structures with recent angle-resolved ultra-violet photoemission data.open1134sciescopu
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