No abstract

Gearboxes are important transmission equipment for quay crane hoisting mechanisms. To accurately extract degradation features from vibration monitoring signals, a degradation feature extraction technique based on static divided symbol sequence entropy is proposed. Considering the uniformity of the symbolization standard, the technique takes the root mean square of the health condition signal as the basis and incorporates the scale coefficient to establish a uniform basic scale. Simultaneously, the symbol set is expanded to enhance the information content and the ability of the approach to characterize the complexity levels of signals in large-value regions. The logistic chaotic sequence and the lifetime signal of the hoisting mechanism gearbox are separately used for analysis. The results show that the proposed technique is able to characterize the complexity of the nonlinear time series and sensitively describe the performance degradation exhibited by the hoisting mechanism gearbox. The calculation speed is fast, which will lay a foundation for methods to further evaluate the health conditions of large-scale quay cranes in ports.

Based on the senior certified public accountants selected by the Chinese Institute of Certified Public Accountants and data drawn from China’s A-share listed companies from 2014 to 2019, this study studies the influence mechanism of signing auditors’ personal reputational promotion on corporate financing constraints. The results show that the improved reputation of signing auditors will help ease the financing constraints faced by companies. Moreover, compared with that of signing auditors from Big Four accounting firms, the improved reputation of signing auditors from non-Big Four firms has a more significant effect on alleviating the financing constraints of enterprises. In addition, private enterprises and small and medium-sized enterprises face more severe financing constraints than state-owned enterprises and large enterprises, and the reputational promotion of signing auditors can better alleviate the financing constraints of the former two types of enterprises. The research conclusions provide theoretical and data-driven support for constructing audit reputation mechanisms in China and improving the financing capabilities of enterprises.

The working environment of the quay crane is harsh and special. As an important transmission equipment of hoisting mechanism, health condition of gearbox is very important for reliable operation. In order to extract degradation features from complex vibration monitoring signals, an improved KW symbol entropy feature extraction technique is proposed. Considering the unity of symbol standard, the method takes the root mean square of the normal condition signal as the symbol standard and combines the symbol coefficient to construct a unified symbol scale. At the same time, symbols number variable is introduced to expand symbols set and improve the information expressing ability. On this basis, combining with information entropy theory, complexity of symbol sequence in symbol sequence and symbol distribution is calculated respectively, and two features named improved symbol sequence entropy (IKSE) and improved symbol distribution entropy (IKDE) are obtained. The Logistic chaotic sequence and the lifetime signal of the hoisting gearbox are used for analysis respectively. The result show that the proposed features are able to characterize the complexity of nonlinear time series, so as to describe the whole process of the performance degradation of the hoisting gearbox sensitively. The parameters have little influence and the technique have a good stability.