University of Macau

About: University of Macau is a education organization based out in Macao, Macau, China. It is known for research contribution in the topics: Computer science & Population. The organization has 6636 authors who have published 18324 publications receiving 327384 citations. The organization is also known as: UM & UMAC.

A ZigBee-Based Wireless Sensor Network Node for Ultraviolet Detection of Flame

Abstract: This paper describes a ZigBee-based wireless sensor network node for the ultraviolet (UV) detection of flame. The sensor node is composed of a ZnSSe UV photodetector, a current-sensitive front end including a high-gain current-to-voltage amplifier with 120 dB and a logarithm converter, and a transceiver operated at a 2.4-GHz industrial, scientific, and medical band. A passive photodetector is designed to have a cutoff at 360 nm and convert the UV emission of flame into picoamperes. Including mixed signal processing and ZigBee transmission, the speed of flame detection is as fast as 70 ms. The sensor node consumes only an average of 2.3 mW from a 3.3-V supply. The performance of a prototype sensor node was verified when the luminous flame was imaged onto the sensor node with different angles ranging from -30° to 30° and distances of 0.1, 0.2, and 0.3 m enabling effective fire safety applications.

1 D Hierarchical MnCo2O4 Nanowire@MnO2 Sheet Core–Shell Arrays on Graphite Paper as Superior Electrodes for Asymmetric Supercapacitors

Abstract: Heterostructured metal oxide core–shell architectures have attracted considerable attention owing to their superior electrochemical performance in supercapacitors compared to a single structure. Here, we report a simple and effective synthesis of hierarchical MnCo2O4 nanowire@MnO2 sheet core–shell nanostructures anchored on graphite paper for use in supercapacitors. The proposed electrode exhibits a specific capacitance of 2262 F g−1 at 1 A g−1. In addition, good rate capability and excellent cycling performance are observed. An asymmetric supercapacitor with operating potential at 1.6 V is demonstrated using MnCo2O4@MnO2 as cathode and graphene/nickel foam (NF) as anode. The MnCo2O4@MnO2//graphene/NF asymmetric device shows a high energy density of 85.7 Wh kg−1 at a power density of 800 W kg−1 while maintaining a high energy density of 34.7 Wh kg−1 at 24 kW kg−1. Moreover, the device demonstrates a long-term cycling stability of 81.6 % retention of its initial specific capacitance.