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.

Force Sensorless Admittance Control With Neural Learning for Robots With Actuator Saturation

Abstract: In this paper, we present a sensorless admittance control scheme for robotic manipulators to interact with unknown environments in the presence of actuator saturation. The external environment is defined as linear models with unknown dynamics. Using admittance control, the robotic manipulator is controlled to be compliant with external torque from the environment. The external torque acted on the end-effector is estimated by using a disturbance observer based on generalized momentum. The model uncertainties are solved by using radial basis neural networks (NNs). To guarantee the tracking performance and tackle the effect of actuator saturation, an adaptive NN controller integrating an auxiliary system is designed to handle the actuator saturation. By employing Lyapunov stability theory, the stability of the closed-loop system is achieved. The experiments on the Baxter robot are implemented to verify the effectiveness of the proposed method.

Information conservation principle determines electrophilicity, nucleophilicity, and regioselectivity

Abstract: Electrophilic and nucleophilic reactions are important chemical transformations involving charge acceptance and donation, so chemical intuition suggests that atomic charges should be a reliable descriptor to determine electrophilicity, nucleophilicity, and regioselectivity. Nevertheless, no such theoretical framework has been established as of yet. Herein, we report that the Hirshfeld charge can be used for such purposes. We justify this usage by showing that it results from the Information Conservation Principle. This principle not only decides where electrophilic and nucleophilic attacks will preferably occur but also dictates the amount of the Hirshfeld charge distribution, which, as we will show here, remarkably strongly correlates with experimental scales of both electrophilicity and nucleophilicity.

Carbon-Oxygen-Bridged Ladder-Type Building Blocks for Highly Efficient Nonfullerene Acceptors.

Abstract: Recently, acceptor-donor-acceptor (A-D-A) small molecules have emerged as promising nonfullerene acceptors (NFAs) for organic solar cells and have attracted great attention. The carbon-bridged (C-bridged) ladder-type D unit plays a crucial role in developing high-performance A-D-A NFAs. However, the medium electron-donating capability of C-bridged units is unfavorable for making NFAs with strong light-harvesting capability. In this regard, carbon-oxygen-bridged (CO-bridged) ladder-type units present advantages in developing strong light-absorbing NFAs. Here, recent progress in the newly emerging CO-bridged NFAs is highlighted. The synthetic methods for the polycyclic CO-bridged building blocks are introduced. The photovoltaic performance for CO-bridged NFAs is summarized and discussed. Perspectives on developing high-performance CO-bridged-NFA-based solar cells are made.