Abstract: The present disclosure relates to the technical field of fiber-optic gas sensing and laser photoacoustic spectroscopy, and reliability of a gas detection system is improved by actively selecting a working frequency of low noise interference combined with an optical fiber photoacoustic sensing probe capable of isolating high-frequency noise. A gas enters a photoacoustic microcavity through gaps on a sound-sensitive diaphragm after diffusing into a miniature air chamber through a plurality of micropores. Photoacoustic excitation light is incident into the photoacoustic microcavity through a fiber-optic collimator and then excited to generate a photoacoustic pressure wave to cause the sound-sensitive diaphragm to vibrate periodically. An end face of a single-mode optical fiber and the sound-sensitive diaphragm constitutes a fiber-optic Fabry-Perot interferometer. The interferometer measures a deflection of the diaphragm and inverts a concentration of the to-be-measured gas.

Abstract: A cable trench inspection robot. The cable trench inspection robot includes a base spreading system, and a camera lifting system disposed on the base spreading system, where the base spreading system includes a base plate, a linear action unit, a cantilever plate, a walking assembly, and a jacking assembly, and the camera lifting system includes a travel block, an imitated four-bar assembly, a support rod, and a camera assembly. Such inspection can realize a through-wall operation by using a cable trench, thereby avoiding many use problems caused by a firewall, and efficiently completing a predetermined inspection task.

Abstract: A method for evaluating the effectiveness of a transformer fire extinguishing system based on a natural language fuzzy analysis is provided, and a method and device for evaluating the fire extinguishing system are established. An expert fuzzy evaluation matrix is established by natural language fuzzifying and de-fuzzifying methods for the effectiveness of the fire extinguishing system. According to the relative influence of each index in the evaluation index system of the effectiveness of the fire extinguishing system, the weight comparison of each index is determined, and the index subjective weight is established based on the weight comparison of each index. A de-fuzzified matrix is obtained by de-fuzzifying an expert fuzzy evaluation matrix, and based on the de-fuzzified matrix, an objective weight is obtained by an entropy weight method. A comprehensive weight is obtained by combining the subjective and objective weights.

Abstract: The disclosure discloses a dynamic stability analysis method and device for a linear time-periodic (LTP) system. The method includes the following steps. Calculate the Q matrix corresponding to the LTP system, and use the eigenvalue of Q matrix whose real part is positive as an instability eigenvalue. Each instability eigenvalue is subjected to the following steps. (S1) the state space model is transformed into the infinite-order harmonic state space (HSS) model, and the truncation order m of HSS model is initialized to 1. (S2) after m-th order truncation of the HSS model, its eigenvalue thereof is calculated. If the real part of the eigenvalue of HSS model is not the same as the real part of the instability eigenvalue, m is updated, and step (S2) is performed again; otherwise, modal participation factor analysis is performed to obtain the state variables that dominate the system instability.