Shanghai University

About: Shanghai University is a education organization based out in Shanghai, Shanghai, China. It is known for research contribution in the topics: Microstructure & Catalysis. The organization has 59583 authors who have published 56840 publications receiving 753549 citations. The organization is also known as: Shànghǎi Dàxué.

Symmetry-based text line detection in natural scenes

Abstract: Recently, a variety of real-world applications have triggered huge demand for techniques that can extract textual information from natural scenes. Therefore, scene text detection and recognition have become active research topics in computer vision. In this work, we investigate the problem of scene text detection from an alternative perspective and propose a novel algorithm for it. Different from traditional methods, which mainly make use of the properties of single characters or strokes, the proposed algorithm exploits the symmetry property of character groups and allows for direct extraction of text lines from natural images. The experiments on the latest ICDAR benchmarks demonstrate that the proposed algorithm achieves state-of-the-art performance. Moreover, compared to conventional approaches, the proposed algorithm shows stronger adaptability to texts in challenging scenarios.

Resilient Event-Triggering $H_{\infty }$ Load Frequency Control for Multi-Area Power Systems With Energy-Limited DoS Attacks

Abstract: This paper investigates a resilient event-triggering $H_{\infty }$ load frequency control (LFC) for multi-area power systems with energy-limited Denial-of-Service (DoS) attacks. The LFC design specifically takes the presence of DoS attacks into account. First, an area control error dependent time delay model is delicately constructed for multi-area closed-loop power systems. Second, a resilient event-triggering communication (RETC) scheme is well designed, which allows a degree of packet losses induced by DoS attacks and has the advantage of improving the transaction efficiency. Then, by using the Lyapunov theory, two stability and stabilization criteria for the multi-area power systems are derived under consideration of the energy-limited DoS attacks. In these criteria, the relationship between the allowable DoS attack duration and the resilient event-triggering communication parameters are clearly revealed. Moreover, an algorithm is also provided to obtain the RETC parameters and the LFC gains simultaneously. Finally, a case study shows the effectiveness of the proposed method.

Electromagnetic metasurfaces: physics and applications

Abstract: Metasurfaces are ultrathin metamaterials consisting of planar electromagnetic (EM) microstructures (e.g., meta-atoms) with pre-determined EM responses arranged in specific sequences. Based on careful structural designs on both meta-atoms and global sequences, one can realize homogenous and inhomogeneous metasurfaces that can possess exceptional capabilities to manipulate EM waves, serving as ideal candidates to realize ultracompact and highly efficient EM devices for next-generation integration-optics applications. In this paper, we present an overview on the development of metasurfaces, including both homogeneous and inhomogeneous ones, focusing particularly on their working principles, the fascinating wave-manipulation effects achieved both statically and dynamically, and the representative applications so far realized. Finally, we also present our own perspectives on possible future directions of this fast-developing research field in the conclusion.

Studies on alcohol sensing mechanism of ZnO based gas sensors

Abstract: Nanosized ZnO powder was synthesized by using a chemical precipitation method, and loaded with different dopants through impregnation. The as-prepared ZnO powder was characterized by XRD and TEM. The characterization results show that the as-prepared sample is wurtzite polycrystalline ZnO, the mean grain size is 30–40 nm, and there are three types of adsorbed oxygen (O 2 − , O 2 2− , and O 2− ) on the surface of the sample. The as-prepared ZnO powder shows excellent gas responses to alcohol and acetaldehyde, but no response to ethene. The sensing mechanism of ZnO was further studied with the help of gas chromatography (GC) associated with a fixed-bed reactor. The studies show that acetaldehyde, carbon dioxide and water are the only oxidation products of C 2 H 5 OH over ZnO. The gas response to C 2 H 5 OH is strongly dependent on the conversion ratio of C 2 H 5 OH to acetaldehyde. In addition, among all the dopants tested, Ru is the optimal dopant which can increase the response to C 2 H 5 OH, but cannot increase the conversion ratio of C 2 H 5 OH to acetaldehyde. Thus we suggest that the gas sensing mechanism of ZnO to C 2 H 5 OH is the mode controlled by chemisorption of negatively charged oxygen, and the sensitizing role of Ru in the ZnO sensor belongs to the electronic sensitization mechanism.