Tatsumi Tozawa

An efficient approach for large scale project planning based on fuzzy Delphi method

Abstract The goal of this paper is to replace probabilistic or deterministic considerations in the project network analysis by possibilistic ones and to reduce the difficulty arising from the inexact and insufficient information of activity times. The activity times are considered as fuzzy numbers (fuzzy intervals or time intervals) and the fuzzy Delphi method is used to estimate a reliable time interval of each activity. Based on these time estimates, we then propose an efficient methodology for calculating the fuzzy project completion time and the degree of criticality for each path in a project.

COMPUTER SIMULATION OF GRAIN GROWTH IN THREE DIMENSIONS

A Monte Carlo computer simulation has been carried out to study the kinetics of grain growth and the grain size distribution in three dimensions. The model employed is superimposed onto a fcc lattice, which has the least anisotropy among conceivable ones. The temporal evolution of the microstructure during normal grain growth is monitored for both the cross-section and the model itself to investigate the change in grain size distribution. The simulated results indicate the change in the distribution form of grain size during grain growth. Furthermore, it is found that the microstructural evolution including the change depends on the dimension in measurement and the temperature.

The Thickness of Liquid Phase during Superplastic Deformation in the Vicinity of Solidus Temperature for a 7475 Aluminum Alloy

The superplastic deformation has been studied in the temperature range including the solidus one for a 7475 aluminum alloy in order to investigate the relation to the thickness of a liquid phase. It is found that the superplastic elongation shows the maximum value in the vicinity of the solidus temperature at a comparatively-low strain rate. The thickness of a liquid phase during superplastic deformation is discussed from four aspects: flow stress, fracture surface, thermal analysis and composition analysis. The thickness of the liquid phase is estimated to be 10-60nm for the superplastically-deformed specimen.