Haichuan Zhang

University libraries are critical campus venues characterized by high-density occupancy, making comprehensive fire evacuation safety assessment essential for protecting lives and cultural assets. Conventional evaluation methods often suffer from either subjective bias or a lack of engineering realism, while standalone cloud models lack robust weight allocation mechanisms. To address these deficiencies, this study proposes a fire evacuation safety evaluation method integrating combined weighting and the cloud model. An evaluation framework consisting of 21 indicators is established across four dimensions: human factors, evacuation facilities, emergency management, and venue environment. For weight determination, the Analytic Hierarchy Process (AHP) and the entropy method are synthesized to balance expert experience with data-driven objectivity. The cloud model is then employed to handle the inherent fuzziness and randomness in safety assessment, utilizing the forward and backward cloud generators to map qualitative linguistic descriptions to quantitative values based on three digital characteristics: expectation (Ex), entropy (En), and hyper-entropy (He). A case study of a university library in Wuhan is conducted. The results demonstrate that the library’s overall fire evacuation safety level is "Excellent," with a comprehensive cloud parameter set of (83.577, 0.620, 0.116). The assessment reveals that while evacuation facilities perform optimally, the complex architectural layout represents a structural vulnerability, and personnel safety literacy requires further stabilization. This integrated framework effectively overcomes the limitations of single-weighting strategies and provides a reliable, fine-grained quantitative tool for fire safety management and targeted risk mitigation in high-density public buildings.

The selective catalytic reduction (SCR) system is a key component for addressing NOx emissions from internal combustion engines. To resolve the issues of modeling distortion in SCR systems and the difficulty in characterizing the local reaction mechanism, a multi-dimensional SCR reaction model based on the coupling of Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) dual mechanisms was established and conducted by experiment. The SCR catalytic characteristics and the dual-mechanism reaction process were systematically investigated. Additionally, based on the combined analysis of species concentration distribution coupled with temperature characteristics, a calculation method for the synergy of concentration-temperature fields was developed, and the synergistic characteristics of the concentration-temperature fields were explored. The results showed that high load accelerated the light-off speed, but this effect was counteracted by the negative impact of high flow rate. A strong negative correlation was maintained between temperature and NOx concentration across the full load range, and the axial consistency increased with load increasing. The results provide important theoretical support for the mechanism analysis of diesel engine SCR reactions and the optimization of thermal management.

In visible light communication (VLC) systems, lenses are typically used to collimate light at the transmitter. However, due to the wide light emission angle of mini-LEDs, capturing light at large angles using a lens at the transmitter can be challenging. This paper presents a design of a reflective cup at the mini-LED-based VLC transmitter. The redesigned reflective cup can collect most of the light and collimate it, achieving an efficiency of approximately 86% at a distance of 10 m in the simulation. In the experiment, error-free communication was achieved at a distance of 100 m with a data rate of 190 Mbps. To the best of our knowledge, a long-distance VLC system based on mini-LEDs is investigated for the first time. The reflective cup offers advantages, including high efficiency, low cost, and a simple structure. It holds reference value for addressing the issue of limited communication distance in underwater wireless optical communication (UWOC).

This paper investigates the fixed-time prescribed performance control problem for a class of axis-motion servo systems subject to the external disturbances and parameter uncertainties. To eliminate the requirement for velocity measurements in the control process, an auxiliary observer is first designed to reconstruct the velocity signal of the controlled plant. Subsequently, an error transformation procedure incorporating a prescribed performance index is integrated into the control system architecture. To overcome the limitations of periodic control design, a robust event-triggered controller is developed, ensuring that the dynamic error of the closed-loop system exhibits fixed-time convergence. Through rigorous theoretical analysis and proofs, it is demonstrated that the proposed event-triggered strategy guarantees Zeno-behavior-free operation. Finally, simulation results are presented to validate the effectiveness of the proposed control algorithm.