Northeastern University (China)

About: Northeastern University (China) is a education organization based out in Shenyang, China. It is known for research contribution in the topics: Control theory & Microstructure. The organization has 36087 authors who have published 36125 publications receiving 426807 citations. The organization is also known as: Dōngběi Dàxué & Northeastern University (东北大学).

Hot deformation behavior of Ti-15-3 titanium alloy: a study using processing maps, activation energy map, and Zener–Hollomon parameter map

Abstract: The hot deformation behavior of Ti-15-3 titanium alloy was investigated by hot compression tests conducted in the temperature range 850–1150 °C and strain rate range 0.001–10 s−1. Using the flow stress data corrected for deformation heating, the activation energy map, processing maps and Zener–Hollomon parameter map were developed to determine the optimum hot-working parameters and to investigate the effects of strain rate and temperature on microstructural evolution of this material. The results show that the safe region for hot deformation occurs in the strain rate range 0.001–0.1 s−1 over the entire temperature range investigated. In this region, the activation energy is ~240 ± 5 kJ/mol and the ln Z values vary in range of 13.9–21 s−1. Stable flow is associated with dynamic recovery and dynamic recrystallization. Also, flow instabilities are observed in the form of localized slip bands and flow localization at strain rates higher than 0.1 s−1 over a wide temperature range. The corresponding ln Z values are larger than 21 s−1. The hot deformation characteristic of Ti-15-3 alloy predicted from the processing maps, activation energy map, and Zener–Hollomon parameter map agrees well with the results of microstructural observations.

Apatite formation on porous titanium by alkali and heat-treatment

Abstract: Hydroxyapatite coating on metal implants is an effective method to enhance bioactive properties of the metal surface. In the present study, the porous titanium with maximal pore size approximately 250 μm and 40% porosity was prepared by powder metallurgy process. All of samples were subjected to alkali and heat-treatments. The bone-like apatite coatings were formed on the surfaces of alkali- and heat-treated porous titanium while samples were soaked in simulated body fluid (SBF). Porous network structure was fabricated and sodium titanate and titanium oxide were formed on the surfaces after the porous titanium was subjected to NaOH aqueous solution. Apatite coatings were not induced in SBF when porous titanium was subjected to 0.5 or 1.0 M NaOH aqueous solutions because of the small porous network structure on the surfaces. The network structure was densified slightly and more uniform nucleation of apatite occurred on the surfaces of the alkali- and heat-treated porous titanium. It is expected that porous titanium with surface apatite coatings can be used in clinical orthopedics.

Adaptive Neural-Network-Based Dynamic Surface Control for Stochastic Interconnected Nonlinear Nonstrict-Feedback Systems With Dead Zone

Abstract: In this paper, an adaptive neural-network-based dynamic surface control (DSC) method is proposed for a class of stochastic interconnected nonlinear nonstrict-feedback systems with unmeasurable states and dead zone input First, an appropriate state observer is constructed to estimate the unmeasured state variables of the stochastic interconnected system Then radial basis function neural networks combined with adaptive backstepping technique are applied to model the unknown nonlinear system functions of the stochastic interconnected system; and the DSC method is adopted to ensure the computation burden is greatly reduced Furthermore, the proposed controllers guarantee that the closed-loop stochastic interconnected system is semi-globally bounded stable in probability In the end, two simulation examples are provided to show the effectiveness and practicability of the proposed control scheme