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As the infrastructure of the railway, the rail could sink or deform to different degrees due to the impact of train operation or the geological changing force for years, which will lead to the possibility that the facilities on both sides of the rail invade the rail clearance and bring hidden dangers to the safe operation of the train. The purpose of this paper is to design the gauge to measure the clearance parameters of rail.

Aiming at the problem, the gauge for clearance measurement was designed based on a combination measurement method in this paper. It consists of the measurement box and the rail measurement vehicle, which integrates a laser displacement sensor, inclination sensor, gauge sensor and mileage sensor. The measurement box was placed outside the rail vehicle. Through the design of a hardware circuit and software system, the movement measurement of the clearance parameters was realized.

In this paper, the measurement equations of horizontal distance and vertical height were established, the optimal solutions of the structural parameters in the equations were obtained by Levenberg–Marquardt method, then the parameter calibration problem was also solved.

The gauge has high precision; its measurement uncertainty reaches 1.27 mm. The gauge has manual and automatic working modes, which are convenient to operate and have practical popularization value.

The speed of internationalization is an important research topic in the process of internationalization. This paper aims to answer two questions: first, what is the relationship between the speed of internationalization of Chinese multinational firms and their performance? Second, how do potential slack and knowledge assets of firms affect this relationship?

The authors choose Chinese A-share listed manufacturing firms from 2009–2018 as the research sample and use the fixed-effect regression model to test the proposed hypotheses.

Firstly, there is an inverted U-shaped relationship between the speed of internationalization and firm performance (SI-P). Secondly, the potential slack and knowledge assets of firms moderate the inverted U-shaped relationship. Firms with a higher level of potential slack or knowledge assets have a flatter inverted U-shaped relationship between SI-P.

First, the authors develop and extend Penrose’s theory of firm growth to the research topic of speed of internationalization. Second, this paper incorporates the time dimension into the research on the internationalization process and locates the research context in emerging market firms (EMFs). This is a step forward in clarifying the complex relationship of SI-P. Third, the authors show that the SI-P relationship of EMFs is inverted U-shaped and integrate previous studies, which argue that rapid internationalization positively or negatively affects firm performance. Fourth, starting from inside the firm, the authors provide more contextual factors for better understanding and analysis of the SI-P relationship.