Showing papers by "Wei Ji published in 2004"
TL;DR: In this paper, the structural evolution of pentacene thin films on Ag(110) crystal, during molecular deposition and during a subsequent change of substrate temperature, was investigated in situ by a molecular beam epitaxy low-energy electron diffraction technique.
Abstract: Structural evolution of pentacene thin films on Ag(110) crystal, during molecular deposition and during a subsequent change of substrate temperature, was investigated in situ by a molecular beam epitaxy low-energy electron diffraction technique. The pentacene molecules exhibit high mobility on the Ag(110) surface at room temperature and the adsorbate shows a structural evolution from disorder in the submonolayer to an ordered structure when it reaches one monolayer. Heating the substrate to $145\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ results in no further structural transition. The ordered monolayer structure on Ag(110) has two domains mirrored at the crystal axis of the silver substrate. Molecular mechanics calculations indicate that the pentacene molecules lie flat on the Ag(110) surface, which is in good agreement with the experimental results. The calculation also gives the favorable position; i.e., the orientation of pentacene on the Ag(110).
84 citations
Journal Article•
TL;DR: In this article, the authors present a comparison of heterogeneous and homogeneous representations of the microsphere and fuel compact cells, establishing the impact of heterogeneities on the overall VHTGR neutronics analysis.
Abstract: As part of an I-NERI project to develop safety analysis codes and experimental validation for a VeryHigh Temperature Gas-Cooled Reactor (VHTGR), we have developed MCNP5 [1] models to represent material heterogeneities inherent in the microsphere fuel particles and fuel compacts for a GT-MHR design [2]. We have also performed preliminary coupled nuclear-thermalhydraulic (NTH) analysis to obtain self-consistent global power and temperature distributions using a homogenized global model for MCNP5 and three-ring core model for the RELAP5-3D/ATHENA code [3]. We present a comparison of heterogeneous and homogeneous representations of the microsphere and fuel compact cells, establishing the impact of heterogeneities on the overall VHTGR neutronics analysis. We also discuss the importance of fuel temperature feedback on the global power distribution.
14 citations