Xingwen Wu, Zhenxian Zhang, Wubin Cai, Ningrui Yang, Xuesong Jin, Ping Wang, Zefeng Wen, Maoru Chi, Shuling Liang and Yunhua Huang
This review aims to give a critical view of the wheel/rail high frequency vibration-induced vibration fatigue in railway bogie.
Abstract
Purpose
This review aims to give a critical view of the wheel/rail high frequency vibration-induced vibration fatigue in railway bogie.
Design/methodology/approach
Vibration fatigue of railway bogie arising from the wheel/rail high frequency vibration has become the main concern of railway operators. Previous reviews usually focused on the formation mechanism of wheel/rail high frequency vibration. This paper thus gives a critical review of the vibration fatigue of railway bogie owing to the short-pitch irregularities-induced high frequency vibration, including a brief introduction of short-pitch irregularities, associated high frequency vibration in railway bogie, typical vibration fatigue failure cases of railway bogie and methodologies used for the assessment of vibration fatigue and research gaps.
Findings
The results showed that the resulting excitation frequencies of short-pitch irregularity vary substantially due to different track types and formation mechanisms. The axle box-mounted components are much more vulnerable to vibration fatigue compared with other components. The wheel polygonal wear and rail corrugation-induced high frequency vibration is the main driving force of fatigue failure, and the fatigue crack usually initiates from the defect of the weld seam. Vibration spectrum for attachments of railway bogie defined in the standard underestimates the vibration level arising from the short-pitch irregularities. The current investigations on vibration fatigue mainly focus on the methods to improve the accuracy of fatigue damage assessment, and a systematical design method for vibration fatigue remains a huge gap to improve the survival probability when the rail vehicle is subjected to vibration fatigue.
Originality/value
The research can facilitate the development of a new methodology to improve the fatigue life of railway vehicles when subjected to wheel/rail high frequency vibration.
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Xiumei Cai, Xi Yang and Chengmao Wu
Multi-view fuzzy clustering algorithms are not widely used in image segmentation, and many of these algorithms are lacking in robustness. The purpose of this paper is to…
Abstract
Purpose
Multi-view fuzzy clustering algorithms are not widely used in image segmentation, and many of these algorithms are lacking in robustness. The purpose of this paper is to investigate a new algorithm that can segment the image better and retain as much detailed information about the image as possible when segmenting noisy images.
Design/methodology/approach
The authors present a novel multi-view fuzzy c-means (FCM) clustering algorithm that includes an automatic view-weight learning mechanism. Firstly, this algorithm introduces a view-weight factor that can automatically adjust the weight of different views, thereby allowing each view to obtain the best possible weight. Secondly, the algorithm incorporates a weighted fuzzy factor, which serves to obtain local spatial information and local grayscale information to preserve image details as much as possible. Finally, in order to weaken the effects of noise and outliers in image segmentation, this algorithm employs the kernel distance measure instead of the Euclidean distance.
Findings
The authors added different kinds of noise to images and conducted a large number of experimental tests. The results show that the proposed algorithm performs better and is more accurate than previous multi-view fuzzy clustering algorithms in solving the problem of noisy image segmentation.
Originality/value
Most of the existing multi-view clustering algorithms are for multi-view datasets, and the multi-view fuzzy clustering algorithms are unable to eliminate noise points and outliers when dealing with noisy images. The algorithm proposed in this paper has stronger noise immunity and can better preserve the details of the original image.
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Ruizhi Li, Fangzhou Wang, Siqi Liu, Ruiqi Xu, Minghao Yin and Shuli Hu
Maximum k vertex cover problem is a significant combinatorial optimization problem with various applications, such as transportation planning, social networks and sensor…
Abstract
Purpose
Maximum k vertex cover problem is a significant combinatorial optimization problem with various applications, such as transportation planning, social networks and sensor placement. Up to now, no practical algorithm has ever been proposed to solve this problem. Therefore, this paper aims to present an efficient local search algorithm LSKVC combining three methods for it.
Design/methodology/approach
First, the quick incremental evaluation method is proposed to update the related vertex scores following each addition or removal incrementally rather than recalculating them, which can speed up the algorithm. Second, the configuration checking method forbids vertices whose configuration has not changed since the last removal from being added into the candidate solution again, which can avoid the cycling problem effectively. Third, the two-stage exchange method swaps the pairs of inside and outside vertices separately rather than simultaneously, which can guarantee the tradeoff between the accuracy and complexity of the algorithm.
Findings
The proposed algorithm LSKVC is compared with the traditional GRASP algorithm and the well-known commercial solver CPLEX on DIMACS and BHOSLIB benchmarks. For the best solutions, the LSKVC algorithm is significantly superior to GRASP and CPLEX on DIMACS instances and the CPLEX solver fails, and the LSKVC algorithm slightly outperforms GRASP on the BHOSLIB instances. In addition, we undertake comparative studies of the offered methodologies and demonstrate their efficacy.
Originality/value
In previous research, the focus on the maximum k-vertex cover problem primarily centered around exact algorithms and approximation algorithms, with limited application of heuristic algorithms. While heuristic algorithms have been well-explored for the closely related Minimum Vertex Cover problem, they have seen limited application in the context of the maximum k-vertex cover problem. Consequently, existing algorithms designed for the Minimum Vertex Cover problem do not exhibit satisfactory performance when applied to the maximum k-vertex cover problem. In response to this challenge, we have undertaken algorithmic improvements specifically tailored to address this issue.
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Brad McKenna, Wenjie Cai and Hyunsun Yoon
Research into older adults' use of social media remains limited. Driven by increasing digitalisation in China, the authors focus on Chinese older adults (aged 60–75)’ use of…
Abstract
Purpose
Research into older adults' use of social media remains limited. Driven by increasing digitalisation in China, the authors focus on Chinese older adults (aged 60–75)’ use of WeChat.
Design/methodology/approach
This study used a qualitative interpretive approach and interviewed Chinese older adults to uncover their social practices of WeChat use in everyday life.
Findings
By using social practice theory (SPT), the paper unfolds Chinese older adults' social practices of WeChat use in everyday life and reveals how they adopt and resist the drastic changes in Chinese society.
Originality/value
The study contributes to new understandings of SPT from technology use by emphasising the dynamic characteristics of its three elements. The authors synthesise both adoptions and resistance in SPT and highlight the importance of understanding three elements interdependently within specific contexts, which are conditioned by structure and agency.
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Abstract
Purpose
This paper aims to verify the inhibition of the hydrogen permeation effect of the coating and to quantitatively and qualitatively characterize the coating-induced stress.
Design/methodology/approach
By means of slow strain rate tensile testing (SSRT) in humid air, thickness measurement, fracture morphology, cross-section morphology and surface morphology, hydrogen content measurements, flow stress difference method.
Findings
The results demonstrate that the mechanism of the inhibition of hydrogen embrittlement by the coating is mainly attributed to the repression of hydrogen permeation and the additional coating-induced compressive stress.
Originality/value
It is proven that the micro-arc oxidation (MAO) coating does inhibit hydrogen entry into the alloy, and the stress induced by the MAO coating is compressive stress, which can restrain the hydrogen embrittlement of the alloy. Therefore, the mechanism of the inhibition of hydrogen embrittlement is dominated by the mechanisms of both hydrogen permeation inhibition and coating-induced stress.
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Abstract
Purpose
This paper aims to investigate the effects of different electrolyte systems on the properties of micro-arc oxidation coating on 7050 high strength aluminum alloy.
Design/methodology/approach
The coatings were prepared in silicate system with Na2SiO3 as main component, borate system with Na2B4O7 as main component and aluminate solution with Na2AlO2 as main salt, respectively.
Findings
The results show that the 7050 high strength aluminum alloy shows the best properties in silicate system.
Originality/value
This manuscript studied the crucial influence of different electrolyte systems on the microstructure and properties of the aluminum alloy micro-arc oxidation layer.
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Di Yang, Weiwei Qu and Yinglin Ke
For the automatic drilling and riveting in panel assembly, gaps between the skin and strangers are inevitable and undesirable. At present, the determination of pre-joining schemes…
Abstract
Purpose
For the automatic drilling and riveting in panel assembly, gaps between the skin and strangers are inevitable and undesirable. At present, the determination of pre-joining schemes relies on workers’ experience, introducing excessive number and inappropriate locations of pre-joining. This paper aims to present a new method for the evaluation of residual clearances after pre-joining and the pre-joining scheme optimization, providing operation guidance for the workers in panel assembly workshop.
Design/methodology/approach
In this paper, an equivalent gap assembly model for pre-joining is proposed on the basis of the mechanism of variation. This model retains the essential elastic behavior of the key features during the pre-joining operation and calculates the residual clearances in the view of the potential energy. Subsequently, this method is embedded into a Pareto optimality-based genetic algorithm, and the optimal pre-joining schemes are achieved with the consideration of the total residual clearances and the permissive tolerances.
Findings
The equivalent gap assembly model has the capability to predict an acceptable degree of accuracy of the residual clearances and achieve the optimized pre-joining schemes with less number of pre-joining at the same level of residual clearances.
Practical implications
The optimized pre-joining schemes are given in the form of Pareto optimality set, and workers can select suitable results according to their inclination to the quality and efficiency.
Originality/value
The paper is the first to propose the equivalent gap assembly model for the pre-joining operation, which provides for the simplification of the calculation of residual clearances based on the constrained variation principles.
Details
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Abstract
Purpose
This paper aims to study the effect of Micro-arc oxidation (MAO) coating on stress corrosion and electrochemical behavior of aluminum alloy.
Design/methodology/approach
The stress corrosion cracking behavior of 7050 aluminum alloy (AA7050) after MAO treatment was investigated in 3.5 Wt.% NaCl solution using the constant load ring. Electrochemical impedance spectroscopy (EIS) was used to evaluate the change of corrosion resistance of MAO specimens in 3.5 Wt.% NaCl solution, and appropriate equivalent circuits were established.
Findings
The results demonstrated that the MAO coating can improve the corrosion resistance of the AA7050 and avoid the reduction of mechanical properties caused by corrosion. In the initial stage of corrosion, the corrosion resistance of coated specimen decreased at first and then increased. In the middle and final stage of corrosion, the corrosion resistance of coated specimen decreased at first and then stabilized.
Originality/value
The long-term corrosion behavior of MAO specimens under stress was studied by constant load experiment and EIS. It has guiding significance for the application of MAO technology on aluminum alloy.
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Qing Ji, Yanfeng Xing, Xuexing Li and Sha Xu
The purpose of this paper is to present a novel assembly spring-back model which takes surface contact conditions between sheet metal parts into consideration so that the assembly…
Abstract
Purpose
The purpose of this paper is to present a novel assembly spring-back model which takes surface contact conditions between sheet metal parts into consideration so that the assembly dimensions and variations can be more precisely predicted than existing assembly simulation models.
Design/methodology/approach
Because an assembly process is composed of four essential steps, i.e. locating, clamping, joining and tool releasing, the mechanistic models associated with these steps are developed in the paper. In particular, the surface contact between the weld flanges (in folding joint configuration) and the overlapping surfaces (in lap joint configurations) is included in the models. Sensitivity models are developed.
Findings
Two cases studies are presented, i.e. the cantilever beams assembly and the Z-plates assembly. More precise prediction results are shown.
Research limitations/implications
The model developed in this paper is based upon analytical elastic beam theories. Therefore, the results and case studies are limited only to workpieces that can be approximately represented by beam geometries. However, the methods can be broadened to generic workpiece geometries by using finite element methods; thus, the developed method is highly valuable to a broad range of applications such as automotive body assembly and aerospace industries.
Originality/value
The novelty of this research lies in its inclusion of surface contact conditions in an assembly simulation model by using analytical beam mechanistic models to achieve more accurate assembly variation predictions.
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The 2006 General Assembly adoption of the United Nations (UN) Global Counter-terrorism strategy marked the first time all member states ratified a collective counter-terrorism…
Abstract
The 2006 General Assembly adoption of the United Nations (UN) Global Counter-terrorism strategy marked the first time all member states ratified a collective counter-terrorism (CT) agenda. Building on the 2000 Millennium Development Goals, the strategy incorporated Amartya Sen's capability-based approach to development. This promised human-oriented and holistic methods for countering terrorism and violent extremism, in contrast to the post-2001 ‘hard security’ context of the United States–led Global War on Terror (GWOT). Although the first pillar of the strategy emphasised human rights and social progress over isolated economic growth, poverty, violence and retrogression in conflict zones since 2006 have led to the deaths of millions. Combined with resource scarcity and environmental devastation, insurgency-related conflicts have resulted in 70 million people displaced worldwide in 2019, while the politically violent phenomena of extreme right-wing nationalism and neo-jihadism remain prevalent. Reflecting on the social and economic outcomes of the GWOT, this chapter evaluates development-related discourses and activity in UN-led initiatives to counter and prevent violent extremism and terrorism. In doing so, it accounts for the impacts of UN CT measures on contemporary patterns ‘in phenomena described in policy arenas as ‘violent extremism’ and ‘terrorism’, including ‘neo-jihadism’ and right-wing extremism, in Global North and Global South contexts.