8 research outputs found
The impact of microbial biotechnology on the chemical industry
No full textvideo/mp4講演場所: バイオサイエンス研究科大講義室講演者所属: 京都大学大学院農学研究科教授vide
Simulation of Slump Test and Flow Test of Fresh Concrete
No full textapplication/pdfThe slump test and the flow test are simple and practical for evaluating the consistency of fresh concrete and fresh nortar, respectively. In recent years, many studies that examine the fluidity properties of fresh concrete based on rheology are reported, and its rheological characteristics are evaluated quantitatively with such rheological constants as yield stress and plastic viscosity of Bingham model. In earlier studies, however, there is considerable disagreement on the measurement of rheological constants of fresh concrete, and few studies show the possibilities and orientations of application of the rheological constants of fresh concrete to practical works. In the present paper, the slump test and the flow test are simulated by using the visco-plastic finite element method of fresh concrete, which has been proposed by the authors for simulating the deformation of fresh concrete in various conditions. The relationship between rheological constants and values obtained from the slump test and the flow test are clarified theoretically. Then some method for estimating rheological constants from slump value and flow value are proposed, and the adequacy of the analytical method and the estimating methods proposed are examined by comparison with experimental results.departmental bulletin pape
Early stage crack detection in mechanically joined steel/aluminum joints by condition monitoring
No full textComputational design of a high-efficiency accelerator grid for a miniature ion thruster by full-aperture ion optics simulations
Get PDFFull-aperture ion optics simulations have been conducted for the inhomogeneous plasma source of a miniature ion propulsion system (MIPS) to design a high-efficiency accelerator grid that provides high degree of the neutral confinement and absence of direct ion impingement. The designed accelerator grid has flat upstream and smoothly curved downstream surfaces with straight holes for easy low-cost manufacture. The diameter of the accelerator aperture was changed from the nominal value of 0.40 mm to 0.25 mm, which decreased neutral leakage and increased the propellant utilization efficiency from 31 to 50%. The direct impingement of ions caused by decreasing the accelerator aperture diameter was compensated by reducing the thickness of the accelerator grid while taking into account the inhomogeneous ion beam current density profile of the MIPS. An off-design performance simulation was conducted to validate the proposed grid design; the obtained results showed that the ion beam could be accelerated smoothly even during throttling the beam current between 75 and 150%. A grid wear simulation was also performed to compare the changes in the propellant utilization efficiency between the nominal and high-efficiency grids caused by erosion. It was found that the propellant utilization efficiency of the high-efficiency grid was greater than that of the nominal grid within the first 5,000 h of operation and that its lifetime exceeded 10,000 h of the accumulated operation time. By using the proposed high-efficiency accelerator grid and MIPS plasma source, the propellant utilization efficiency was increased, while the accelerator impingement current became negligible
