University of Science and Technology Beijing

About: University of Science and Technology Beijing is a education organization based out in Beijing, China. It is known for research contribution in the topics: Microstructure & Alloy. The organization has 41558 authors who have published 44473 publications receiving 623229 citations. The organization is also known as: Beijing Steel and Iron Institute.

Estimating Remaining Useful Life With Three-Source Variability in Degradation Modeling

Abstract: The use of the observed degradation data of a system can help to estimate its remaining useful life (RUL). However, the degradation progression of the system is typically stochastic, and thus the RUL is also a random variable, resulting in the difficulty to estimate the RUL with certainty. In general, there are three sources of variability contributing to the uncertainty of the estimated RUL: 1) temporal variability, 2) unit-to-unit variability, and 3) measurement variability. In this paper, we present a relatively general degradation model based on a Wiener process. In the presented model, the above three-source variability is simultaneously characterized to incorporate the effect of three-source variability into RUL estimation. By constructing a state-space model, the posterior distributions of the underlying degradation state and random effect parameter, which are correlated, are estimated by employing the Kalman filtering technique. Further, the analytical forms of not only the probability distribution but also the mean and variance of the estimated RUL are derived, and can be real-time updated in line with the arrivals of new degradation observations. We also investigate the issues regarding the identifiability problem in parameter estimation of the presented model, and establish the according results. For verifying the presented approach, a case study for gyros in an inertial platform is provided, and the results indicate that considering three-source variability can improve the modeling fitting and the accuracy of the estimated RUL.

Tunable Fabrication of Molybdenum Disulfide Quantum Dots for Intracellular MicroRNA Detection and Multiphoton Bioimaging.

Abstract: Molybdenum disulfide (MoS2 ) quantum dots (QDs) (size <10 nm) possess attractive new properties due to the quantum confinement and edge effects as graphene QDs. However, the synthesis and application of MoS2 QDs has not been investigated in great detail. Here, a facile and efficient approach for synthesis of controllable-size MoS2 QDs with excellent photoluminescence (PL) by using a sulfuric acid-assisted ultrasonic route is developed for this investigation. Various MoS2 structures including monolayer MoS2 flake, nanoporous MoS2 , and MoS2 QDs can be yielded by simply controlling the ultrasonic durations. Comprehensive microscopic and spectroscopic tools demonstrate that the MoS2 QDs have uniform lateral size and possess excellent excitation-independent blue PL. The as-generated MoS2 QDs show high quantum yield of 9.65%, long fluorescence lifetime of 4.66 ns, and good fluorescent stability over broad pH values from 4 to 10. Given the good intrinsic optical properties and large surface area combined with excellent physiological stability and biocompatibility, a MoS2 QDs-based intracellular microRNA imaging analysis system is successfully constructed. Importantly, the MoS2 QDs show good performance as multiphoton bioimaging labeling. The proposed synthesis strategy paves a new way for facile and efficient preparing MoS2 QDs with tunable-size for biomedical imaging and optoelectronic devices application.

Controlled synthesis of monodispersed CuO nanocrystals

Abstract: Controlling the size, shape and structure of nanocrystals is technologically important because of the strong effect of size and shape on optical, electrical, and catalytic properties. Monodispersed nanocrystals of copper oxide were prepared by the precipitation?pyrolysis method. By controlling the starting materials, reactive concentration and annealing temperature, we can obtain spherical monodispersed CuO nanocrystals of different sizes or rodlike CuO nanocrystals. The particle sizes of CuO monodispersed nanocrystals can be tuned in the range between and 30?nm. The products have been characterized by x-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and the UV?visible absorption spectrum. The absorption spectra of CuO nanocrystals show clear evidence of the quantum size effect. The possible formation mechanism of monodispersed CuO nanocrystals is discussed.