In the era of the digital economy, the exploration of useful knowledge from data streams has garnered significant attention due to its wide-ranging applications. However, the rapid and infinite nature of data streams poses challenges for efficiently mining high utility sequential patterns, including strong spatio-temporal constraints and the combinatorial explosion of sequence data search spaces. To address this and adapt to a variety of application scenarios, this paper delves into the investigation and design of an efficient algorithm for high utility sequential pattern mining over data streams based on the sliding window model (HUSP_DS). This algorithm utilizes a projection mechanism within a sliding window to recursively search for all interesting patterns. Additionally, it introduces a novel structure called the dynamic utility index table, which stores information such as the utility and index positions of data stream sequences. Notably, this structure proves highly effective in recursive search processes and utility updates. Comprehensive experimentation, conducted on both real-world and synthetic datasets, have shown that the superior performance of the HUSP_DS algorithm compared to state-of-the-art algorithms. This superiority is particularly evident in terms of temporal and spatial efficiency. Furthermore, the algorithm demonstrates suitability for mining sliding windows of arbitrary sizes, showcasing stable scalability.

The number of Brushless DC motor conduction mode is two, two-two conduction mode and three-three conduction mode. Aiming at the characteristics of large output power of brushless DC motor, good torque stability, high utilization rate of three-three conduction windings and low torque ripple, the two-two starting and three-three running strategy are studied. High-frequency link inverter technology has the characteristics of high power density, high reliability and electrical isolation. At the same time in order to overcome the traditional non-isolated three-phase inverter drive brushless DC motor, the problem of three-three conduction mode has the potential bridge through, studying high frequency link matrix converter driving brushless DC motor. For the bidirectional switch characteristics of the matrix converter, an HPWM modulation strategy for brushless DC motor load is applied based on the solution of decoupling. The simulation results of Matlab/Simulink verified the correctness and validity of the modulation strategy.

The virtual reality (VR) system has become popular in the last two decades and is being applied increasingly to navigation studies. This study developed a panorama manifestation (PM) VR system, with six monitors forming a circular display and an interactive chair equipped with rotation sensors and operating knobs. The advantages of the PM system include a large circular display, a body-centred design, body engagement and a low set-up cost. Based on navigation experimental tasks, this system's usability was compared with that of a typical desktop (DT) system. The results showed that participants using the PM system had a significantly higher success rate and required less completion time than participants using the DT system, indicating that the PM system outperforms the DT system in terms of effectiveness and efficiency in some navigation tasks, and also suggesting that the PM system may require lower spatial cognition workload in the navigation tasks. However, the participants’ subjective evaluations of task difficulty (TD) failed to reach significance although the PM group did report a lower mean value for TD. Additionally, in the PM system, the participants’ spatial ability was more predictive to their navigation performance than that in the DT system, indicating that the PM system offered greater usability for some spatial experiments and could provide more support for participants’ navigation tasks.