Papers by Keyword: Critical Time

Abstract: Hybrid TiO₂ nanowire–nanotube structure was synthesized by a facile anodization on Ti substrate. To study the origin and evolution of TiO₂ nanotubes, the morphology of TiO₂ nanotubes was investigated. It was found that nanotubes corrode gradually into nanowires, and the critical time was about 8.5 h after the beginning of anodization. Uniform nanotubes were obtained by ultrasonic cleaning. It was demonstrated experimentally that the inner diameter of TiO₂ nanotube increased with the extension of anodization time, but the outer diameter of TiO₂ nanotubes, which were fabricated under different anodization time, was almost the same.

Abstract: The induction motor (IM) is important equipment among industries. When voltage sag occurs, both the protective device like reclosure mounted in high voltage transmission and distribution lines and the terminal undervoltage tripping of contactor will make the IM disconnect away from the utility, with its terminal voltage changed from voltage sag to interruption. The IM will continue to operate because of inertia. The first-order dynamic model between slip, load torque and terminal voltage is set up based on IM steady-state equivalent circuit. And the universal analytic functions of slip and critical time are deduced from the model which can be used to evaluate the IM low voltage ride through (LVRT) capability, thus providing reference for the designation of IM.

Abstract: Stability of static liquid layer in mass transfer process accompanied by concentration-driven Marangoni effect was modeled and analyzed by utilizing the linear stability theory. The critical condition of the onset of the Marangoni convection was obtained. It is found that the liquid layer becomes more unstable with the increase of the Schmidt number, and it becomes the most volatile when the Biot number is about 0.85. The critical time to mark the onset of Marangoni convection can be predicted with the established model. The research results show that the concentration gradient is the main factor to initiate the Marangoni convection.

Abstract: In this paper, we make a detail analysis of some factors, which affects the electrostatic bonding process. According to the electrical properties of glass, combined with the principle of electrostatic bonding, we analysed the relationship of critical bonding time, voltage and temperature as well as the factors which affect electrostatic bonding. Then we come up with the mathematical model of the intensity and temperature of electrostatic bonding. In accordance with the above-mentioned formula and the experimental data, we can get the following conclusions: the intensity of electrostatic bonding is much greater between 280°C to 370°C; the best temperature for this bonding is about 350°C; however, when the temperature is below 280°C,the intensity of electrostatic bonding is lower due to the great impact of particles under low temperature; but when the temperature is higher than 370°C,the mismatch of coefficient of thermal expansion of silicon and glass gets larger, then as a result, the intensity of this bonding has a significant decrease with the increasing of temperature.

Abstract: The critical times of phosphorus segregation in low alloy steel 12Cr1MoV at different solution temperatures, 1050°C and 1300°C, are studied and the diffusion coefficient of complexes, Dc, and diffusion coefficient of phosphorus, Di, are calculated. Results show that the calculated result with the kinetic equations perfectly fits with the experimental observations. And that the higher the solution temperature, the higher is the segregation level of phosphorus, and also the longer is the critical time. It also shows that in the segregation process, the rate of phosphorus segregation at first is high due to a large diffusivity of the complex, Dc. Then the segregation rate decreases due to decreasing complex concentration gradient. In the de-segregation process, the level of phosphorus segregation decreases with increasing holding time t. But the rate of phosphorus desegregation from grain boundaries to centre is slower compared with that in segregation for the diffusion coefficient of phosphorus atoms, Di, is far lower than that of the complexes, Dc.