Search results

The aim of this study is to investigate the horizontal displacement effects of foundation pit excavation on adjacent metro stations and shield tunnel composite structures. It seeks to develop a theoretical calculation method capable of accurately assessing these engineering impacts, aiming to provide practical assistance for engineering applications.

This study introduces a model for shield tunnel segments incorporating rotation and misalignment, considering the constraints of metro stations. It establishes a displacement model for tunnel-station combinations during foundation pit excavation, deriving a formula for calculating station-proximal tunnel horizontal displacements. The method's accuracy is validated against field data from three engineering cases. The research also explores variations in tunnel displacement, inter-ring shear force, misalignment and rotation angle under different spatial relationships between pits, tunnels and stations.

This study models uneven deformation between stations and tunnels due to bending stiffness and shear constraints. It enhances the misalignment model with station-induced shear effects and introduces coefficients for their mutual interaction. Results show varied responses based on pit-station-tunnel positioning: minimal displacement near pit edges (coefficients around 0.1) and significant effects near pit centers (coefficients from 0.4 to 0.5). “Whip effect” from station constraints affects tunnel displacement, shear force, misalignment and rotation, with fluctuations decreasing with distance from excavation areas.

This study demonstrates significant originality and value. It introduces a novel displacement model for tunnel-station combinations considering station constraints, addressing theoretical calculations of horizontal displacement effects from foundation pit excavation on metro stations and shield tunnel structures. Through validation with field data and parameter studies, the concept of influence coefficients is proposed, offering insights into variations in structural responses under different spatial relationships. This research provides crucial technical support and decision-making guidance for optimizing designs and facilitating practical construction in similar engineering projects.

The serious friction and wear problem occurs on the mechanical seal’s faces during the start-up stage of the high-speed turbopump for a liquid rocket engine. This paper aims to propose a kind of thick metal alloy coatings on the surface of the seal’s rotor so as reduce the friction and wear.

With the pin-disk (the graphite pin and the disk with the metal coating) tribology-tester, the tribological behaviors of four metal coatings are investigated. The special friction coefficients under the dry friction, boundary friction and different temperatures of water-lubricated conditions were obtained.

The test results show that the thick metal coating has a good performance of the wear resistance and friction reduction; and the friction coefficients of a Sn-Sb-Cu coating under the dry friction and water-lubricated conditions are 0.377 and 0.043, respectively, and the corresponding mass wear volumes are only 2.74 and 0.81 mg, respectively.

The thick metal coating scheme for the mechanical seal’s faces might lend itself to the harsh working conditions of the low-viscosity liquid rocket engine.

This work was focused upon the main factors that influence the formation of a hydroxypropyl-β-cyclodextrin (HP-β-CD) supramolecular complex with octadecylamine (ODA) and their optimal processing conditions. The anti-corrosion properties of the products in the simulated boiler water condensate of power plants also needed to be tested. The paper aims to discuss these issues.

A grinding method was applied to synthesize the supramolecular structures. Using Fourier transform infrared, X-ray diffraction and proton nuclear magnetic resonance spectroscopy (1H NMR), the specific structures of the complex were clarified. The anti-corrosion properties were obtained from gravimetric results, potentiodynamic polarization tests and electrochemical impedance spectroscopy measurements.

The results reveal the highly soluble supramolecular complex could be formed between two HP-β-CD molecules and one ODA molecule at 85°C with a processing period of 15 minutes. In the condensate, the corrosion inhibition efficiency of the complex was over 95 percent, much higher than the inhibition efficiency of the hydrophobic ODA compound.

The supramolecular corrosion inhibitor could be used as an anti-corrosion method for industrial boiler condensate to reduce the content of corrosive ions. In this way, it is easier to reuse the condensate without re-polishing.

The research introduces supramolecular chemistry into corrosion science for the first time. The results provide a new option to modify the traditional corrosion inhibitors.

To further understand the granular flow lubrication mechanism in metal contact pairs, the effect of sliding-rolling ratio on the force chain properties was investigated.

The parallel inter-plate model of the granular flow lubrication was established with discrete element method. Then, the correlation law between sliding-rolling ratio and force chain evolution properties was calculated and analyzed with PFC2D software platform.

Numerical calculation results show that the dynamic fluctuation property of force chain is existed, and the shock frequency of it is increased with the increase of sliding-rolling ratio. The same evolution law is also occurred for the bearing rate of strong force chain in the initial expansion and final compression phases, and the opposite phenomena is obtained for the overall expansion phase. Moreover, the directivity of strong force chain is changed by the sliding-rolling ratio. With the increase of sliding-rolling ratio, the directivity of strong force chain is first tended to y-axis, and then inclined to the x-axis in the whole phases. The basic reason is that a clamping up and downward movement impact for the neighbor particles are the essence of the above phenomenon.

The main contribution of this work is to lay a theory foundation of interfacial lubrication mechanism with granular flow.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2023-0133/

Using 3,994 observations of Chinese listed firms from 1995 to 2001, we find a significantly positive correlation between state ownership and cash dividend payment, and a significantly positive relation between private ownership and stock dividend payment. In particular, we find that the relation between dividend payment level and ownership structure is nonlinear. The higher the proportion of state ownership, the higher the cash dividend rate. The higher the proportion of private ownership, the higher the stock dividend rate. We conclude that the managers of Chinese listed companies are likely to cater for the preference of different shareholders.

The purpose of this paper is to increase understanding of the real situation of Enterprise's Sustainable Innovation (ESI) in China.

First, the paper analyzes the practice of Chinese ESI in the past 30 years, and then reviews research results of the topic in China, by the authors and by other Chinese scholars. Finally, it provides the future prospects for ESI in China.

The practice of Chinese ESI started in 1978 when this country began reform, and two stages of Chinese ESI practice has been summarized. Otherwise, six major characteristics have been highlighted. China is one of the earliest countries that began to research on ESI and has achieved significant results since 1995. The paper summarizes major research findings of ESI in China, which can be divided into two categories. Especially, it stresses that one of the distinguishing achievements is research on mechanisms of ESI in China.

The research on ESI in China is initially implemented based on Chinese practice. So, future research may explore whether the research results could be suitable for abroad, or not.

This original paper analyzes ESI practice and research findings in China, and may have value in helping people to understand ESI's real situation.

This paper seeks to investigate some current issues of ownership structure and corporate governance in China.

The methodology is a review, analysing issues of ownership structure and reviewing problems in corporate governance, followed by some suggestions for improvement.

It is found that the heavily concentrated equity ownership in the hands of large state‐owned shareholders mainly decides the status quo of the corporate governance system in China. In order to improve the effectiveness of corporate governance of Chinese‐listed companies, it is imperative to restructure roles of the government, restrict hands of controlling shareholders, enhance independence of the board of directors, reform the supervisory board, set up independent directors‐dominated sub‐committees and align the interests of managers with those of the shareholders.

This paper only investigates Chinese‐listed companies because of data availability.

It has implications for policy makers in China insofar as it offers evidence concerning ownership structure and corporate governance of Chinese‐listed companies. It also helps investors and trading partners (especially foreign ones) understand corporate governance and the investment environment in China.

This study contributes to the literature by extending the mainly US‐based board literature to China where there are important institutional differences in ownership structure and corporate governance system.

This case reviews the development of Dianping. After seeing Zagat's unique business model in the United States, founder Zhang Tao found that he could bring it to China and bring about local innovation. At the beginning of its establishment, the collection and promotion of comment content was the major challenge for Dianping. At the same time, Dianping faced legal issues. To solve these problems, the review mechanism of Dianping was designed to a certain extent to ensure the fairness of the review. With the advent of the mobile Internet era, Dianping began to develop a new business model. Relying on its high-quality “word-of-mouth” content and mass basis, Dianping launched group buying, online restaurant ordering, and other businesses. Dianping has always been open to strategic partners. Since 2015, Dianping has undergone historical changes, merging with Meituan. Since then, Dianping has continuously adjusted its business and organizational structure to maintain its competitiveness. Gradually, Dianping has changed from an independent business entity into a business unit of Meituan.

This paper aims to present ball bearings with a composite structure based on the bionics principle and shows the comparison between five types of different structures.

By means of the finite element method, the stress and other parameters between different structures are compared and verified. Finally, the comprehensive parameters of different structures are evaluated by the analytic hierarchy process method.

The evaluation of the comprehensive parameters of five types of structures is shown here.

The value of this paper is calculated and compared to the parameters of five types of different structures, and the parameter score evaluation of each structure is given. Different structures can be selected according to different parameter requirements, which to provide a theoretical basis for the design of ball bearings.

The peer review history for this article is available at: https://publons.com/publon10.1108/ILT-10-2019-0413