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.

G-Tree: An Efficient and Scalable Index for Spatial Search on Road Networks

Abstract: In the recent decades, we have witnessed the rapidly growing popularity of location-based systems. Three types of location-based queries on road networks, single-pair shortest path query, $k$ nearest neighbor ( $k$ NN) query, and keyword-based $k$ NN query, are widely used in location-based systems. Inspired by $\tt R$ - $\tt tree$ , we propose a height-balanced and scalable index, namely $\tt G$ - $\tt tree$ , to efficiently support these queries. The space complexity of $\tt G$ - $\tt tree$ is $\mathcal {O}(|\mathcal {V}|\log {|\mathcal {V}|})$ where ${|\mathcal {V}|}$ is the number of vertices in the road network. Unlike previous works that support these queries separately, $\tt G$ - $\tt tree$ supports all these queries within one framework. The basis for this framework is an assembly-based method to calculate the shortest-path distances between two vertices. Based on the assembly-based method, efficient search algorithms to answer $k$ NN queries and keyword-based $k$ NN queries are developed. Experiment results show $\tt G$ - $\tt tree$ ’s theoretical and practical superiority over existing methods.

How Careless Responding and Acquiescence Response Bias Can Influence Construct Dimensionality The Case of Job Satisfaction

Abstract: We investigated the effects that careless responding and acquiescence response bias have on analyses conducted to assess construct dimensionality. Using job satisfaction/dissatisfaction as the focal construct, we measured and controlled for careless responding and acquiescence bias in data obtained from an online survey of employees (N = 666) from different organizations and occupational groups. We found that the negative correlation between factors defined by job satisfaction and dissatisfaction items, respectively, was attenuated by careless responding and acquiescence bias, and was not significantly different from –1.0 when both were controlled. Moreover, the correlations between the two factors and measures of other constructs were similar when careless responding and acquiescence were controlled. These findings challenge recent research purporting to demonstrate that job satisfaction and dissatisfaction are distinct constructs. Recommendations for future investigations of construct dimensionality are...

Hyperspectral Image Classification Based on Three-Dimensional Scattering Wavelet Transform

Abstract: Recent research has shown that utilizing the spectral–spatial information can improve the performance of hyperspectral image (HSI) classification. Since HSI is a 3-D cube datum, 3-D spatial filtering becomes a simple and effective method for extracting the spectral–spatial information. In this paper, we propose a 3-D scattering wavelet transform, which filters the HSI cube data with a cascade of wavelet decompositions, complex modulus, and local weighted averaging. The scattering feature can adequately capture the spectral–spatial information for classification. In the classification step, a support vector machine based on Gaussian kernel is used as a classifier due to its capability to deal with high-dimensional data. Our method is fully evaluated on four classic HSIs, i.e., Indian Pines, Pavia University, Botswana, and Kennedy Space Center. The classification results show that our method achieves as high as 94.46 $\%$ , 99.30 $\%$ , 97.57 $\%$ , and 95.20 $\%$ accuracies, respectively, when only 5 $\%$ of the total samples per class is labeled.

Design, Analysis, and Test of a Novel 2-DOF Nanopositioning System Driven by Dual Mode

Abstract: Piezodriven flexure-based motion stages, with a large workspace and high positioning precision, are really attractive for the realization of high-performance atomic force microscope (AFM) scanning. In this paper, a modified lever displacement amplifier is proposed for the mechanism design of a novel compliant two-degree-of-freedom (2-DOF) nanopositioning stage, which can be selected to drive in dual modes. Besides, the modified double four-bar parallelogram, P (P denotes prismatic) joints are adopted in designing the flexure limbs. The established models for the mechanical performance evaluation of the stage, in terms of kinetostatics, dynamics, and workspace, are validated by the finite-element analysis. After a series of dimension optimizations carried out through the particle swarm optimization algorithm, a novel active disturbance rejection controller, including the nonlinearity tracking differentiator, the extended state observer, and the nonlinear state error feedback, is proposed to automatically estimate and suppress plant uncertainties arising from the hysteresis nonlinearity, creep effect, sensor noises, and unknown disturbances. The simulation and prototype test results indicate that the first natural frequency of the proposed stage is approximated to be 831 Hz, the amplification ratio in two axes is about 4.2, and the workspace is 119.7 μm × 121.4 μm, while the cross coupling between the two axes is kept within 2%. All the results prove that the developed stage possesses a good property for high-performance AFM scanning.