Qiang Li, Shuo Zhang, Yujun Wang, Wei-Wei Xu, Zengli Wang and Zhenbo Wang
Shear stresses have a considerable influence on the characteristics of lubricants and become significant at high rotating speeds. This study aims to investigate the influences of…
Abstract
Purpose
Shear stresses have a considerable influence on the characteristics of lubricants and become significant at high rotating speeds. This study aims to investigate the influences of shear cavitation (SC) on loading capacity of journal bearings.
Design/methodology/approach
A principal normal stress cavitation criterion based on the stress applied to flowing lubricant in journal bearings is developed and used to investigate SC in journal bearings. A computational fluid dynamic (CFD) model for calculating the loading capacity is established using this criterion. After validation with experimental results, the loading capacity is calculated under different conditions.
Findings
The calculation results indicate that SC intensifies when viscosity, speed and eccentricity increase. Angle of loading capacity with SC is larger than that without SC. The magnitude of loading capacity with SC is smaller than that without SC due to the decrease in the ultimate pressure. In addition, the magnitude difference between the loading capacity with and without SC increases when viscosity, speed and eccentricity increases.
Originality/value
Present research can provide some guidance for calculating the loading capacity when a journal bearing is operating at high speed or with a high viscosity lubricant.
Details
Keywords
Qiang Li, Yujun Wang, Shuo Zhang, Wei-Wei Xu, Zengli Wang and Zhenbo Wang
Surface texturing has been proven as an effective means of contact performance enhancement. However, limited work has been done to investigate the regular relationship to solve…
Abstract
Purpose
Surface texturing has been proven as an effective means of contact performance enhancement. However, limited work has been done to investigate the regular relationship to solve the multi-parameters problem of textures, and inertia effect and elastic deformation were seldom considered together in previous optimization work. This paper aims to quantitatively obtain the relationship between the textured depth and liquid film thickness and find the effect of deformation on the optimal textured height ratio in elastic parallel sliders.
Design/methodology/approach
Numerical models of hydrodynamic lubrication are established based on the computational fluid dynamic method. Elastic deformation is considered through fluid–structure interaction (FSI) method. Using response surface optimization method, textured parallel sliders are optimized with maximum loading capacity as the objective.
Findings
The results show that the optimal height ratios are all within the range of 0.60-0.65 when textured parallel sliders are considered as rigid. After considering the effect of elastic deformation, loading capacity drops and is reduced more obviously with a decrease in the elastic moduli. The optimal height ratios are within the range of 0.60-0.63, which shows that FSI has a considerable influence on loading capacity but has no significant influence on the optimal height ratio.
Originality/value
The present research provides a theoretical reference for engineering application of elastic textured parallel sliders.
Details
Keywords
Qiang Li, Yujun Wang, Shuo Zhang, Wei-Wei Xu, Lu Bai and Zhenbo Wang
Surface textures have been widely used in thrust bearings as a means of enhancing the tribological performance. The effect of textures with a spiral distribution on the…
Abstract
Purpose
Surface textures have been widely used in thrust bearings as a means of enhancing the tribological performance. The effect of textures with a spiral distribution on the lubrication characteristics of thrust bearings has not been fully covered. This paper aims to investigate and find the optimal structure and distribution parameters of textures with the maximum loading capacity and minimum friction force as goals.
Design/methodology/approach
Combining the multi-objective optimization method based on the non-dominated sorted genetic algorithm-II with response surface methodology, the key textured parameters are optimized. Local sensitivity analysis is used to evaluate the impact level of each parameter.
Findings
Spiral distribution of textures can effectively improve the lubrication performance of the thrust bearing compared with the linear distribution. The distribution with high amplitudes and high cycle numbers will weaken the spiral effect and destroy the high-pressure region. Through the multi-objective optimization of the textured structure and distribution parameters, the loading capacity demonstrates a 55.05per cent improvement compared to the basic model. Textured width is the most sensitive parameter for both loading capacity and friction force.
Originality/value
Present research provides a fundamental design guide for textured thrust bearings.
Details
Keywords
Qiang Li, Qinglei Liu, Yujun Wang, Shuo Zhang, Yujing Du, Bin Li and Wei-Wei Xu
The stringent requirements for environmental protection have induced the extensive applications of water-lubricated journal bearings in marine propulsion. The nonlinear dynamic…
Abstract
Purpose
The stringent requirements for environmental protection have induced the extensive applications of water-lubricated journal bearings in marine propulsion. The nonlinear dynamic analysis of multiple grooved water-lubricated bearings (MGWJBs) has not been fully covered so far in the literature. This study aims to conduct the nonlinear dynamic analysis of the instability for MGWJBs.
Design/methodology/approach
An attenuation rate interpolation method is proposed for the determination of the critical instability speed. Based on a structured mesh movement algorithm, the transient hydrodynamic force model of MGWJBs is set up. Furthermore, the parameters’ analysis of nonlinear instability for MGWJBs is conducted. The minimum water film thickness, side leakage, friction torque and power loss of friction are fully analyzed.
Findings
With the increase of speed, the journal orbits come across the steady state equilibrium motion, sub-harmonic motion and limit circle motion successively. At the limit circle motion stage, the orbits are much larger than that of steady state equilibrium and sub-harmonic motion. The critical instability speed increases when the spiral angle decreases or the groove angle increases. The minimum water film thickness peak is at the rotor speed of 4,000 r/min for the MGWJB with Sa = 0°. As rotor speed increases, the side leakage decreases slightly while the friction torque and the power loss of friction increase gradually.
Originality/value
Present research provides a beneficial reference for the dynamic mechanism analysis and design of MGWJBs.
Details
Keywords
Qiang Li, Shuo Zhang, Yujun Wang, Wei-Wei Xu and Zhenbo Wang
The growing demand of efficiency and economy has led to a dramatic increase of the operating speed of the journal bearing, with a higher temperature distribution. This paper aims…
Abstract
Purpose
The growing demand of efficiency and economy has led to a dramatic increase of the operating speed of the journal bearing, with a higher temperature distribution. This paper aims to investigate the three-dimensional temperature distribution of journal bearings.
Design/methodology/approach
A thermo-hydrodynamic lubrication model of a journal bearing was established based on the full 3D CFD method. A two-sided wall was used to include the conjugate heat transfer effect. The temperature-dependent characteristics of lubrication and cavitation impact were also included. The simulation results well agreed with the experimental results. Based on this method, the three-dimensional temperature distribution was analyzed under different operating conditions.
Findings
The temperature distribution in the radial direction had a difference. An increase of speed and de-crease of inlet temperature promoted temperature differences in the higher temperature zone and the increasing temperature zone, respectively. However, the inlet pressure had less influence on these differences. The temperature distribution was basically the same at a lower bearing conductivity. As the conductivity increased, the radial temperature difference was increased.
Originality/value
The temperature distribution in the radial direction was found under different operating conditions, and the present research provides references to understand the three-dimensional temperature distribution of journal bearings.
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Wei Xu, Lingyu Liu and Wei Shang
Timely detection of emergency events and effective tracking of corresponding public opinions are critical in emergency management. As media are immediate sources of information on…
Abstract
Purpose
Timely detection of emergency events and effective tracking of corresponding public opinions are critical in emergency management. As media are immediate sources of information on emergencies, the purpose of this paper is to propose cross-media analytics to detect and track emergency events and provide decision support for government and emergency management departments.
Design/methodology/approach
In this paper, a novel emergency event detection and opinion mining method is proposed for emergency management using cross-media analytics. In the proposed approach, an event detection module is constructed to discover emergency events based on cross-media analytics, and after the detected event is confirmed as an emergency event, an opinion mining module is used to analyze public sentiments and then generate public sentiment time series for early warning via a semantic expansion technique.
Findings
Empirical results indicate that a specific emergency can be detected and that public opinion can be tracked effectively and efficiently using cross-media analytics. In addition, the proposed system can be used for decision support and real-time response for government and emergency management departments.
Research limitations/implications
This paper takes full advantage of cross-media information and proposes novel emergency event detection and opinion mining methods for emergency management using cross-media analytics. The empirical analysis results illustrate the efficiency of the proposed method.
Practical implications
The proposed method can be applied for detection of emergency events and tracking of public opinions for emergency decision support and governmental real-time response.
Originality/value
This research work contributes to the design of a decision support system for emergency event detection and opinion mining. In the proposed approaches, emergency events are detected by leveraging cross-media analytics, and public sentiments are measured using an auto-expansion of the domain dictionary in the field of emergency management to eliminate the misclassification of the general dictionary and to make the quantization more accurate.
Details
Keywords
Qian Li, Xunhua Guo, Xue Bai and Wei Xu
Considering the popularity and addictive attributes of microblogging, the purpose of this paper is to explore the key drivers of the microblogging addiction tendency, and to…
Abstract
Purpose
Considering the popularity and addictive attributes of microblogging, the purpose of this paper is to explore the key drivers of the microblogging addiction tendency, and to investigate the causal relationship between microblogging usage and addiction tendency through the lens of the uses and gratifications (U&G) theory.
Design/methodology/approach
By extending the U&G theory to accommodate the negative consequences of gratification, a research model that explains the relationships among microblogging use, gratification and addiction tendency was developed and empirically examined based on the data collected from 520 microblogging users in China.
Findings
The results showed that different types of microblogging use lead to different categories of gratification to different extents, while different categories of gratification play different roles in determining the level of addiction tendency. Specifically, the effect of content gratification on addiction is marginal, while social gratification has significant effects on all dimensions of addiction tendency.
Originality/value
The present study has both theoretical and practical implications. From a theoretical perspective, unlike many previous studies applied the U&G theory to explore the positive outcomes of media uses, this paper extends the U&G by including addiction tendency as a negative psychological outcome of U&G., resulting a research framework (use-gratification-addiction framework). Meanwhile, this paper contributes to the extending literature by examining the constructs of U&G at a granular level and investigated the causal relationship between “uses” and “gratifications.”
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Dinghao Xi, Wei Xu, Liumin Tang and Bingning Han
The boom in live streaming has intensified competition among streamers for viewers' gifts, which makes it meaningful to study the factors that affect the viewers’ gifting…
Abstract
Purpose
The boom in live streaming has intensified competition among streamers for viewers' gifts, which makes it meaningful to study the factors that affect the viewers’ gifting behavior. Given the emotional attachment between streamers and viewers, the authors set out to elucidate a new driver on viewer gifting: expressions of the streamer. This research aims to explore the impact of streamer emotions on the viewer gifting behaviors, including free and paid gifting. The loyalty level of the viewers is also introduced as a moderating factor to investigate the heterogeneous effect of streamer emotions on gifting behavior.
Design/methodology/approach
The dataset the authors collected consists of two parts, including 1809.69 h of live streaming videos and 358,002 gift giving records. Combined with deep learning methods and regression analysis, the authors performed empirical tests on the 81,110 valid samples. Several robustness checks were also conducted to ensure the reliability of main results.
Findings
The empirical results show that streamer emotions do have effects on viewers' free and paid gifting behavior. The authors’ findings show that positive streamer expressions, such as happiness and surprise, have a positive influence on viewer gifting behavior. However, some negative expressions, like sadness, can also have a positive impact. Moreover, the authors discovered that higher viewer loyalty amplifies the positive effect of streamer emotions and reduces the negative effect.
Originality/value
This research contributes to the study about streamer emotions and viewers' consumption behavior, which extends the application of emotion as social information model (EASI model) in the live streaming setting. The authors carefully divide the gifting behavior into two types: free and paid, and study how these two types are affected by streamer emotions. Besides, these effects are analyzed within viewers of different loyalty levels. This study offers practical emotion management strategies for streamers and live streaming platforms to gain more economic profits.
Details
Keywords
Jingfeng Yuan, Xuewei Li, Yongjian Ke, Wei Xu, Zhao Xu and M. Skibnewski
Effective performance management (PM) in public–private partnership (PPP) projects is critical to realizing value for money (VFM). This study aims to provide an in-depth…
Abstract
Purpose
Effective performance management (PM) in public–private partnership (PPP) projects is critical to realizing value for money (VFM). This study aims to provide an in-depth understanding of problems existing in PPP PM and possible avenues for improvement, presenting an experimental system to verify that building information modeling (BIM) and other information communication technologies can improve PPP PM.
Design/methodology/approach
The mixed research method adopted in this study combined empirical research with experimental research. Semistructured interviews were used to ascertain the current situation of PPP PM with the help of Nvivo software. A BIM-based performance management system (BPMS), which combines BIM with Web and Cloud technology, was then constructed to achieve performance monitoring, performance measurement, and performance-based payment. Finally, a case study was introduced to explain the function application of the proposed system.
Findings
The case demonstration verified is found to verify that the developed BIM-based execution framework for PPP PM can effectively guide stakeholders toward achieving mixed PM, promote effective PM, and improve work efficiency with the support of BIM and other information and communication technologies.
Originality/value
Through the development of a BPMS for PPP projects, the effectiveness and efficiency of PM are improved. Practical PM applications are also provided to different stakeholders, through which the key performance indicators and the behaviors of the government and private-sector partners can be monitored to form a more comprehensive and reasonable PM mechanism and promote the realization of VFM in PPP projects.