Runlin Chen, Jianlei Wang, XiaoYang Yuan, Longlong Li and Yahui Cui
To meet the high stiffness requirement of bearings used in high-precision spindles, this paper aims to propose a novel kind of bearing composited by hydrostatic cavities and…
Abstract
Purpose
To meet the high stiffness requirement of bearings used in high-precision spindles, this paper aims to propose a novel kind of bearing composited by hydrostatic cavities and tilting pads with preload.
Design/methodology/approach
Cavities are cut on the oil seal surface of a hybrid bearing, in which the tilting pads are set up. The load of the bearing is carried by the hydrostatic cavities and tilting pads. The structural features of this compound bearing and the controlling variables of the main stiffness coefficient are presented. Two basic design principles are proposed on the basis of equal machining clearance (EMC) and equal installation clearance (EIC).
Findings
The theoretical analysis indicates that the stiffness of compound bearings under the EMC condition increases to infinity monotonously when the preload coefficient of the tilting pad tends to 1, while the stiffness under the EIC condition has a peak value. Therefore, a synthetic design principle is proposed by synthetically using the above-mentioned two principles. The applicable range of the three principles is discussed through an example.
Originality/value
The study about technological combination of hydrostatic cavity and tilting pad in this paper can provide suggestions for the design of a high-stiffness bearing in a precision spindle.
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Zhiming Zhao, Rui Zhang, Feng Ji and Xiaoyang Yuan
High power and speed are new demands for rotating machinery which needs the journal bearings with high dynamic characteristics. The critical speed of the rotor-bearing system is…
Abstract
Purpose
High power and speed are new demands for rotating machinery which needs the journal bearings with high dynamic characteristics. The critical speed of the rotor-bearing system is one of the most significant parameters to evaluate the dynamic characteristics. This paper aims to investigate the theoretical and experimental analysis of a rotor system supported by large diameter elliptical bearings.
Design/methodology/approach
To obtain the theoretical and experimental support for rotor-bearing system design, dynamic characteristics theoretical analysis based on the finite difference method is given and an experiment focuses on critical speed identification is carried out.
Findings
The theoretical calculation results indicate that the critical speed is near to 800 rpm and there is no large vibration amplitude round working speed (1,500 rpm). Using the test bench in the factory unit, vibration data including three experimental processes are obtained. According to the vibration data, the critical speed is identified which also indicates that it is stable when working at 1,500 rpm.
Originality/value
The design method for the rotor system supported by large diameter elliptical bearing can be obtained by the theoretical and experimental results shown in this paper.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2020-0122/
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Zhiming Zhao, Feng Ji, Yongsheng Guan and Xiaoyang Yuan
High power rotating machinery requires large diameter bearings that can perform under extreme conditions. Vibrations and critical speeds of rotor supported by tilting pad journal…
Abstract
Purpose
High power rotating machinery requires large diameter bearings that can perform under extreme conditions. Vibrations and critical speeds of rotor supported by tilting pad journal bearing (TPJBs) exceeding their design limits may cause unit failure. This paper aims to investigate the experimental technique for large diameter bearings.
Design/methodology/approach
To obtain the experimental support for rotor-bearing system design, an experiment focusing on vibration monitoring is given. The sensors arrangement, monitoring system and critical speed identification method are provided.
Findings
By using test bench in factory unit, a large amount of vibrations data of different working situations is obtained. In addition, a method named non-excitation identification for critical speed is proposed. The critical speed of rotor identified through vibration data is given. The theoretical calculation results are also presented.
Originality/value
The basis for rotor-bearing system design can be obtained through comparisons between the experimental results and the theoretical calculation data.
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Ouyang Wu, Yuan Xiaoyang and Jia Qian
– The purpose of this paper is to analyze the problems of tilting-pad thrust bearing static instability and lubrication performance under static bistability.
Abstract
Purpose
The purpose of this paper is to analyze the problems of tilting-pad thrust bearing static instability and lubrication performance under static bistability.
Design/methodology/approach
The static equilibrium state of tilting-pad thrust bearing is analyzed, and key parameters are extracted from the general lubrication model. Then, a distribution area of bearing static equilibrium points is achieved by solving the model. The area is divided into three sub-areas which represent monostabillity, bistability and instability, and an unstable boundary of the area is discovered. By these findings, a reversible lubrication failure phenomenon is explained. A calculation method is proposed to obtain bearing lubrication performance under the bistability.
Findings
The variation of working conditions can lead to migration of unstable boundary and static instability. After resuming the working conditions, unstable boundary will resume in situ, and the bearing will operate steadily again. Moreover, there is a big difference between the two groups of lubrication performance solutions under the bistability.
Practical implications
The static stability acceptance test of tilting-pad thrust bearing should be implemented under start–stop, accidental excitation and other conditions before service to prevent such lubrication failure phenomenon. Moreover, fulcrum position of the bearing pad should be kept away from the bistable area.
Originality/value
This paper has preliminarily revealed a static instability mechanism of tilting-pad thrust bearing, analyzed bistability lubrication performance and proposed some suggestions to improve the bearing stability.
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Xudong Sang, Lijie Yang, Dongli Li, Wencai Xu, Yabo Fu and Jiazi Shi
Honey peaches are rich in a variety of vitamins and are well known in China as the queen of fruit. However, as highly climacteric fruit, peach is too easy to affect its economic…
Abstract
Purpose
Honey peaches are rich in a variety of vitamins and are well known in China as the queen of fruit. However, as highly climacteric fruit, peach is too easy to affect its economic value. In this paper, a new passive modified atmosphere packaging system was proposed to solve the lack of water vapour removal capacity – which is still the technical bottleneck of passive modified atmosphere packaging. This paper aims to address this issue.
Design/methodology/approach
Under the conditions of relative humidity 85−90% and temperature 28°C−38°C, the influence of new passive modified atmosphere packaging on the shelf life and quality of 70% ripe peaches was studied in the paper. The effect of the new passive modified atmosphere packaging (PMAP) on fruit appearance, colour, taste, flavour, soluble solids, Vitamin C and titratable acid was investigated.
Findings
Regardless of whether 1-Methylcyclopropene is added or not, the research results show that the new PMAP has a significant effect on extending the shelf life and maintaining the quality of peaches. Compared with the control group, the shelf life of peaches treated with modified atmosphere packaging and 1-Methylcyclopropene was prolonged by 7 and 11 days, increasing the retailer's revenue by 44 and 75%.
Originality/value
A new integrated structure, which is composed of two types of films with high oxygen and high water vapour permeability was designed for the retail of peaches at room temperature. The former was mainly responsible for regulating the concentration of O2 and CO2, while the latter was for removing water vapour and regulating the relative humidity in PMAP.
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Qian Li, Jingjing Wang, Xiaoyang Wang and Yubin Wang
This article examines the impact of different policy instruments on livestock farmers' willingness to recycle manure. The results shed light on the optimal policy combination.
Abstract
Purpose
This article examines the impact of different policy instruments on livestock farmers' willingness to recycle manure. The results shed light on the optimal policy combination.
Design/methodology/approach
A game theoretical framework is constructed to illustrate farmers' optimal strategies under different policies. Theoretical results are empirically tested by survey data from beef cattle farmers in Central China.
Findings
Empirical results show that penalties work better than subsidies if each type of policy is implemented separately. The authors also find a positive interaction between subsidy and penalty policies, suggesting that a combination of subsidy and penalty policies produces the best outcome in incentivizing livestock farmers to recycle manure. Furthermore, planting and breeding simultaneously have the strongest effect on increasing livestock farmers' willingness to recycle manure, suggesting that the combination of planting and breeding can be an optimal strategy for manure management.
Originality/value
This study is based on firsthand survey data and provides new evidence on the effectiveness of alternative environmental policies on manure recycling.
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Yun Zhan, Jia Liao and Xiaoyang Zhao
This study aims to investigate the effect of top management team (TMT) stability on outward foreign direct investment (OFDI) of Chinese firms and the moderating effects of state…
Abstract
Purpose
This study aims to investigate the effect of top management team (TMT) stability on outward foreign direct investment (OFDI) of Chinese firms and the moderating effects of state ownership and managerial ownership on this relationship.
Design/methodology/approach
An empirical analysis based on the ordinary least square regression model is conducted using Chinese A-share listed firms that engaged in OFDI from 2008 to 2021.
Findings
TMT stability has a positive effect on firms’ OFDI. Moreover, state ownership significantly strengthens the positive relationship between TMT stability and OFDI, while managerial ownership weakens this positive relationship.
Practical implications
The findings help firms to effectively retain TMT talents and promote the smooth internationalization of firms, thereby enhancing their long-term development capabilities and competitive advantages.
Originality/value
This study expands the investigation of the factors influencing OFDI at the micro level of the TMT, providing valuable decision-making insights for firms.
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Jing Yang, Jie Zhong, Fang Xie, Xiaoyang He, Liwen Du, Yaqian Yan, Meiyu Li, Wuqian Ma, Wenxin Wang and Ning Wang
The purpose of this work is to controllably synthesize a carbon aerogel with programmable functionally graded performance via a simple and effective strategy.
Abstract
Purpose
The purpose of this work is to controllably synthesize a carbon aerogel with programmable functionally graded performance via a simple and effective strategy.
Design/methodology/approach
This work uses polyvinyl alcohol (PVA) via the controllable sol-gel, lyophilization, and carbonization approach to achieve a programmable carbon aerogel. This design has the advantages of low raw material and preparation cost, simple and controllable synthetic process and low carbonization temperature.
Findings
The thermal stability and microstructure of PVA aerogel can be controlled by the crosslinking agent content within a certain range. The crosslinking agent content and the carbonization temperature are the key factors for functionally graded programming of carbon aerogels, including microstructure, oxygen-containing functional groups and adsorption performance. The adsorption ratio and adsorption rate of uranium can be controlled by adjusting initial concentration and pH value of the uranium solution. The 2.5%25 carbon aerogel with carbonization temperature of 350 °C has excellent adsorption performance when the initial concentration of uranium solution is 32 ppm at pH 7.5.
Research limitations/implications
As a new type of lightweight nano-porous amorphous carbon material, this carbon aerogel has many excellent properties.
Originality/value
This work presents a simple, low cost and controllable strategy for functionally graded programming of novel carbon aerogel. This carbon aerogel has great potential for application in various fields such as uranium recovery, wastewater treatment, sound absorption and shock absorption.
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Yun Zhan, Jia Liao and Xiaoyang Zhao
According to the resource-based theory, a firm’s unique resources and capabilities are the key to its competitive advantage. This paper aims to investigate the effect of top…
Abstract
Purpose
According to the resource-based theory, a firm’s unique resources and capabilities are the key to its competitive advantage. This paper aims to investigate the effect of top management team (TMT) stability, an important intangible resource of the firm, on the maturity mismatch between investment and financing of companies. Additionally, we explore the moderating effects of state ownership and institutional ownership in this context.
Design/methodology/approach
This study conducts an empirical analysis based on the ordinary least squares (OLS) model with a sample of Chinese companies listed on the Shanghai and Shenzhen stock exchanges from 2010 to 2022.
Findings
The results show that TMT stability significantly mitigates the degree of maturity mismatch. Both state ownership and institutional ownership weaken the negative effect of TMT stability on maturity mismatch. Besides, alleviating financing constraints is a crucial pathway through which TMT stability influences maturity mismatch.
Practical implications
The findings help firms to effectively retain TMT talents and reduce the occurrence of maturity mismatch.
Originality/value
This paper not only helps to expand the research on the economic effects of TMT stability but also provides new ideas on how to alleviate the maturity mismatch of companies.
Details
Keywords
Heng (Emily) Wang and Xiaoyang Zhu
The dissemination of misleading and false information through media can jeopardize a company’s reputation, thus posing a threat to its stock and performance. Institutional…
Abstract
Purpose
The dissemination of misleading and false information through media can jeopardize a company’s reputation, thus posing a threat to its stock and performance. Institutional investors are known to influence capital markets. Therefore, this paper investigates whether institutional investors engage in shaping the media sentiment stock nexus, stabilize company stocks and enhance performance.
Design/methodology/approach
We first investigate the effect of media sentiment on market reactions by using panel regression models. To examine the role of institutional investors, we design a quasi-experiment by exploiting the Financial Crisis of 2008 and go further by examining the heterogeneity across levels of institutional ownership. Due to risk-averse, investors may respond asymmetrically to pessimistic and positive sentiment. Accordingly, we split the sample into two sub-types, good news and bad news, based on keywords representing positive or negative content.
Findings
We find supportive evidence that institutional investors have impacts on how the markets react to media news, and the impacts are heterogeneous in the face of bad and good news. We conjecture that institutional investors act as a stabilizer of stock prices through media sentiment management.
Originality/value
This paper confirms the distinctive effects of institutional investors on capital markets, and uncovers the behind-the-scenes intervention and possible causal link running from institutional investors to media sentiment management. It contributes to the broad field of institutional investors' behavior, media news involvement in capital markets and market efficiency.