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.

Adaptive Robust Output Feedback Control for a Marine Dynamic Positioning System Based on a High-Gain Observer

Abstract: This paper develops an adaptive robust output feedback control scheme for dynamically positioned ships with unavailable velocities and unknown dynamic parameters in an unknown time-variant disturbance environment. The controller is designed by incorporating the high-gain observer and radial basis function (RBF) neural networks in vectorial backstepping method. The high-gain observer provides the estimations of the ship position and heading as well as velocities. The RBF neural networks are employed to compensate for the uncertainties of ship dynamics. The adaptive laws incorporating a leakage term are designed to estimate the weights of RBF neural networks and the bounds of unknown time-variant environmental disturbances. In contrast to the existing results of dynamic positioning (DP) controllers, the proposed control scheme relies only on the ship position and heading measurements and does not require a priori knowledge of the ship dynamics and external disturbances. By means of Lyapunov functions, it is theoretically proved that our output feedback controller can control a ship’s position and heading to the arbitrarily small neighborhood of the desired target values while guaranteeing that all signals in the closed-loop DP control system are uniformly ultimately bounded. Finally, simulations involving two ships are carried out, and simulation results demonstrate the effectiveness of the proposed control scheme.

A Low-Profile Aperture-Coupled Microstrip Antenna With Enhanced Bandwidth Under Dual Resonance

Abstract: A low-profile aperture-coupled microstrip patch antenna (MPA) using the TM10 and TM30 resonant modes to enhance the impedance bandwidth is proposed in this paper. Based on the cavity model for a square MPA, the TM10 and TM30 modes as well as both higher odd-order and even-order modes between them can be characterized. In order to combine the dual radiative resonant modes for a wide impedance bandwidth, a rectangular radiating patch with an aperture-coupled feeder is employed and theoretically investigated at first, aiming to demonstrate that all of the undesired modes between them can be removed effectively. After that, by loading the shorting pins properly underneath the patch, the resonant frequency of TM10 mode is shown to progressively turn up with slight effect on that of TM30 mode. As a result, these two radiative modes can be allocated in proximity to each other, resulting in a wide impedance bandwidth with a stable radiation pattern and the same far-field polarization. Moreover, the principal parameters of the MPA have been extensively studied in order to investigate the sensitivity in input impedance of the aperture-fed patch antenna. Finally, the proposed antenna is fabricated and measured. Simulated and measured results are found in good agreement with each other and illustrate that the antenna achieves a wide impedance bandwidth of about 15.2% in fraction or 2.32–2.70 GHz under $\vert \text{S}_{\mathrm {\mathbf {11}}}\vert dB, while keeping a low profile property with the height of 0.032 free-space wavelength. Besides, a stable gain varied from 3 to 6.8 dBi within the whole operating band is also obtained.

Luminescent chemosensors by using cyclometalated iridium(iii) complexes and their applications.

Abstract: Luminescent metal complexes have found increasing use in multiple areas of science and technology, including in chemosensing, light-emitting devices and photochemistry. In particular, the use of cyclometalated iridium(III) complexes as chemosensors has received increasing attention in the recent literature. Phosphorescent metal complexes enjoy a number of advantages (e.g., long-lived phosphorescence, high quantum efficiency and modular syntheses) that render them as suitable alternatives to organic dyes for sensing a variety of analytes. This review describes recent examples of cyclometalated iridium(III) complexes that act as luminescent chemosensors for cations, anions or small molecules.

Time-Dependent Phosphorescence Colors from Carbon Dots for Advanced Dynamic Information Encryption.

Abstract: The development of phosphorescent materials with time-dependent phosphorescence colors (TDPCs) is of considerable interest for application in advanced dynamic information encryption. In this study, TDPC is realized in carbon dots (CDs) synthesized by the one-pot hydrothermal treatment of levofloxacin. CD ink printed on paper (CD@paper) exhibits a change in phosphorescence color from orange to green, 1 s after irradiation with 395 nm light. However, when irradiated with wavelengths shorter or longer than 395 nm, the CD@paper exhibits only green or red phosphorescence, respectively. The red and green phosphorescence originates from the low-energy surface oxide triplet state and high-energy N-related triplet state, respectively. When irradiated with a suitable light energy (around 395 nm wavelength), the two phosphorescent centers can be simultaneously activated, emitting red and green phosphorescence with different decay rates. The red and green phosphorescence merge into an orange phosphorescence initially, exhibiting the TDPC phenomenon. Based on the unusual phosphorescent properties of the CDs, a kind of multilevel, dynamic phosphorescence colored 3D code is designed for advanced dynamic information encryption.

Technological Collaboration in Product Innovation: The Role of Market Competition and Sectoral Technological Intensity

Abstract: Drawing on the strategic alliances and innovation literature, this study proposes that the impact of technological collaboration on product innovation is contingent on market competition and sectoral technology characteristics. Specifically, it argues that the generally observed positive effect of technological collaboration on product innovation may be diluted in highly competitive markets, and the interactive effect of technological collaboration and market competition on product innovation will be further moderated by sectoral technological intensity. Data on the product innovation and technological collaboration of 944 Chinese firms across five manufacturing sectors provide robust support for the contingent effects of technological collaboration on product innovation.