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Austenite Grain Growth Behavior of 30BF Steel Before Rough Rolling
Yong‑feng Chen,Jian‑bo Xie,Yan‑xin Wu,Jian‑xun Fu 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.4
To investigate the eff ect of heat treatment on the grain size of austenite in 30BF steel, the comparisons of the morphologiesand sizes of austenite grains between heating samples were made with a high-temperature electric resistance furnace, andthe austenite growth models were built with method of mathematics. The results show that most grains in original specimenwith the sizes below 70 μm uniformly distributed. At a heating rate ( v ) of 10 °C/s, the grain size ( d ) value under a certain time( t ) increased by 60–100 μm with raising temperature ( T ) from 850 to 1100 °C, whereas the d value under a certain T merelyincreased by 70–120 μm with raising time to 60 min. Under v = 0.1 °C/s, T = 850 °C, and t = 0 s, the occupied ratio of grainswith sizes of 40–50 μm was 0.165, whereas at 900 °C, the occupied ratio was 0.125. The evolutions of ln (d5.8− d5.80 ) with1/ T were in negative linear correlations, whereas the ln (d5.8− d5.80 ) with ln t were in positive linear correlations. To sum up,the grain growth behavior of steel was elucidated.
Train Students to Study Independently
Xie, Yong,Li, Ruheng,Ha, Jin-Cheol,Kim, Yun-Hae,Park, Se-Ho Korean Society for Engineering Education 2012 공학교육연구 Vol.15 No.5
Independent study is a major ability of engineering students. In independent study training practice, we need to use different instructional strategies and responds to individual student needs and learning styles. The purpose of this paper is to demonstrate a four-step student independent study training mode we applied to teaching the Biomedical Engineering students in Dali University, China. We developed this teaching mode to fulfill the goals of the first years' undergraduates training and improve the students learning skills. The four-step teaching mode includes both in-class and out-of-class activities. The emphasis is on how to train students to get information from the reading materials, understand the concept, develop critical thinking and eventually become independent learner.
Yong-Fang Xie,Wei-Hua Gui,Zhao-Hui Jiang 대한전기학회 2008 International Journal of Control, Automation, and Vol.6 No.4
In this paper, the problem of delay-dependent stabilization for singular systems with multiple internal and external incommensurate constant point delays is investigated. The condition when a singular system subject to point delays is regular independent of time delays is given and it can be easily test with numerical or algebraic methods. Based on Lyapunov-Krasovskii functional approach and the descriptor integral-inequality lemma, a sufficient condition for delay-dependent stability is obtained. The main idea is to design multiple memory less state feedback control laws such that the resulting closed-loop system is regular independent of time delays, impulse free, and asymptotically stable via solving a strict linear matrix inequality (LMI) problem. An explicit expression for the desired memory less state feedback control laws is also given. Finally, a numerical example illustrates the effectiveness and the availability for the proposed method.