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The purpose of this study is to investigate the effects of nanoadditive lubricants on the vibration and noise characteristics of helical gears compared with conventional lubricants. The experiment aims to analyze whether nanoadditive lubricants can effectively reduce gear vibration and noise under different speeds and loads. It also analyzes the sensitivity of the vibration reduction to load and speed changes. In addition, it compares the axial and radial vibration reduction effects. The goal is to explore the application of nanolubricants for vibration damping and noise reduction in gear transmissions. The results provide a basis for further research on nanolubricant effects under high-speed conditions.

Helical gears of 20CrMnTi were lubricated with conventional oil and nanoadditive oils. An open helical gearbox with spray lubrication was tested under different speeds (200–500 rpm) and loads (20–100 N·m). Gear noise was measured by a sound level meter. Axial and radial vibrations were detected using an M+P VibRunner system and fast Fourier transform analysis. Vibration spectrums under conventional and nanolubrication were compared. Gear tooth surfaces were observed after testing. The experiment aimed to analyze the noise and vibration reduction effects of nanoadditive lubricants on helical gears and the sensitivity to load and speed.

The key findings are that nanoadditive lubricants significantly reduce the axial and radial vibrations of helical gears under low-speed conditions compared with conventional lubricants, with a more pronounced effect on axial vibrations. The vibration reduction is more sensitive to rotational speed than load. At the same load and speed, nanolubrication reduces noise by 2%–5% versus conventional lubrication. Nanoparticles change the friction from sliding to rolling and compensate for meshing errors, leading to smoother vibrations. The nanolubricants alter the gear tooth surfaces and optimize the microtopography. The results provide a basis for exploring nanolubricant effects under high speeds.

The originality and value of this work is the experimental analysis of the effects of nanoadditive lubricants on the vibration and noise characteristics of hard tooth surface helical gears, which has rarely been studied before. The comparative results under different speeds and loads provide new insights into the vibration damping capabilities of nanolubricants in gear transmissions. The findings reveal the higher sensitivity to rotational speed versus load and the differences in axial and radial vibration reduction. The exploration of nanolubricant effects on gear tribological performance and surface interactions provides a valuable reference for further research, especially under higher speed conditions closer to real applications.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2023-0220/

This study aims to identify the development, trends and research gaps related to start-ups during the COVID-19 pandemic. Furthermore, this research identified future research directions.

This research is a bibliometric study using 192 Scopus-indexed articles with the assistance of the VOSviewer. The selected articles discussed start-ups during the COVID-19 pandemic and were published between 2020 and 2022. The analyses included initial statistics on publication trend, distribution of research field, most productive journals, most productive authors, most cited article, geographic distribution, multinational collaboration and science.

Between 2020 and 2022, the literature on start-ups during the COVID-19 pandemic has increased. Most articles are in Business, Management and Accounting, Economics, Econometrics and Finance and Social Sciences. Regarding geographic distribution and multinational collaboration, the USA, India and the UK led the numbers. The UK was also the forerunner in research collaboration. Based on the science mapping results, COVID-19, fintech, entrepreneurship and innovation were the most simultaneously used keywords. Furthermore, this study also identified that there is a lack of study regarding consumer behavior, employee behavior and quality management of start-ups during the COVID-19 pandemic.

This research also has several limitations. First, this research only used the Scopus database. Even though Scopus has advantages compared to other databases, combining the Scopus database with other databases will be able to provide more comprehensive data. However, there is a risk associated with combining two or more databases, namely, duplication. When using more than one database, researchers must ensure no repetition of the articles used because it will affect the analysis results. Future research can consider combining the Scopus database with other databases. Second, this bibliometric study covered the publication of start-ups during the COVID-19 pandemic. The COVID-19 pandemic is still ongoing. This condition indicated that several research on start-ups during COVID-19 are still being performed and will be published. Thus, future bibliometric study start-ups during COVID-19 were needed to update the trend of the research on start-ups during COVID-19.

The bibliometric study provided at least two main practical implications that can be used to support the growth of start-ups during the COVID-19 pandemic. First, this research has mapped the existing literature on start-ups during the COVID-19 pandemic. This information can be used as input for start-up practitioners and policymakers when they need scientific reference and evidence in developing a policy and/or a management action/program needed during the COVID-19 pandemic. Second, this research highlighted several clusters of keywords that are attracted many researchers. These keywords can be viewed as important issues that are needed to be monitored by start-up practitioners and policymakers during the COVID-19 pandemic.

Start-ups have an important role in economic development. It is well known that start-ups can boost productivity and economic growth. As start-ups tend to use technology, it also has an important role in disrupting traditional economic practices. Start-ups may also offer a more convenient life. Furthermore, the availability of start-ups may also increase the quality of life of the people that are serviced by the start-ups.

To the best of the authors’ knowledge, this is the first bibliometric study that discussed start-ups during the pandemic. It provided a comprehensive literature review process to identify research gaps that allowed future researchers to develop studies related to start-ups.

The importance of modeling digital leadership in quickly digitizing countries, like the United Arab Emirates (UAE), is inevitable for building leadership capabilities to lead, engage and motivate remote employees in the digital environment. Using Blake and Mouton Grid, the current study examines the behavioral approach used by the leaders from both public and private sectors while managing their workforce digitally in the period of the pandemic, when 70% of the workforce worked remotely for the first-time in the region.

An online survey was conducted by the managerial employees working in different firms using self-administered questionnaires and adopting the snowball sampling technique. In total, 476 respondents participated in the study from both the Emirates of Abu Dhabi and Dubai.

The analysis using IBM SPSS and Smart PLS software reported that 9 out of 10 leaders positioned their digital leadership style well above the middle-of-the-road management style (5,5) oriented towards team management (9,9); with 7 out of 9 displaying high team management leadership style, while managing remote workers. However, millennials displayed higher task orientation when compared to generation-x leaders, who concentrated more on their relations with the workers.

The findings have implications for practitioners in technology driven regions. Also the results highlighting the task-oriented approach of millennials digital leaders have implication for owners and board of directors of the firms that seniority is not the only credible approach for leadership positions.

The study reveals the behavioral styles beneficial for digital leaders to develop their leadership capabilities and increase their effectiveness while managing the workforce digitally. Black Mountain Grid and its two-dimensional leadership matrix has been found to be a useful conceptual approach for understanding digital leadership behaviors, and based on study findings, recommendations have been provided to effectively improve its utilization for leading teams. The findings have implications for practitioners in technology driven regions as well as digital leadership field scholars.

Common availability of digital technologies encouraged companies in almost all industries to focus on exploring various ways of benefiting from their adoption and thus taking steps toward their digital transformation. This paper aims to describe the digital transformation of small and medium enterprises (SMEs) as a challenging opportunity and identify ways in which companies from the food industry address it.

The paper presents empirical evidence based on a case study of the Polish freeze-drying market and companies operating on it. This study adopted a single case study research method to describe the digital transformation journey of SMEs. The sample constitutes a single sectoral case study with more than one unit of analysis – sixteen companies. The undertaken approach follows an embedded case study design and allows for an extensive and multidimensional analysis of rich empirical data.

The results of this analysis allowed to identify four significant trends describing human resources involvement in the digital transformation of freeze-drying companies in Poland (i.e. visionary top-down, cooperative task-oriented, persuasive bottom-up, chaotic), a detailed catalog of outcomes of digital transformation from the perspective of food industry companies grouped in seven categories and a list of main barriers to digital transformation.

This paper contributes to expanding knowledge on the practices of food industry companies in addressing challenges posed by the development of information technology and the dynamically changing environment after the COVID-19 pandemic. It contributes further to the discussion related to context-, industry- and country-specific barriers to digital transformation, identifying time-related constraints as an essential barrier to digital transformation.

The electromechanical planetary transmission system has the advantages of high transmission power and fast running speed, which is one of the important development directions in the future. However, during the operation of the electromechanical planetary transmission system, friction and other factors will lead to an increase in gear temperature and thermal deformation, which will affect the transmission performance of the system, and it is of great significance to study the influence of the temperature effect on the nonlinear dynamics of the electromechanical planetary system.

The effects of temperature change, motor speed, time-varying meshing stiffness, meshing damping ratio and error amplitude on the nonlinear dynamic characteristics of electromechanical planetary systems are studied by using bifurcation diagrams, time-domain diagrams, phase diagrams, Poincaré cross-sectional diagrams, spectra, etc.

The results show that when the temperature rise is less than 70 °C, the system will exhibit chaotic motion. When the motor speed is greater than 900r/min, the system enters a chaotic state. The changes in time-varying meshing stiffness, meshing damping ratio, and error amplitude will also make the system exhibit abundant bifurcation characteristics.

Based on the principle of thermal deformation, taking into account the temperature effect and nonlinear parameters, including time-varying meshing stiffness and tooth side clearance as well as comprehensive errors, a dynamic model of the electromechanical planetary gear system was established.

This study aims to describe key elements that are critical to virtual qualitative research especially while working with practitioners as participants.

This paper takes a reflexive researcher approach using a case study to explore how researchers adopted a qualitative research approach using digital technology. We use five principles suggested by Boland et al. (2022) as a framework to consider and reflect on our experiences as researchers and those of our participants.

We highlight the gatekeeper’s support, trusted relationship with the organisations, interpersonal skills of interviewers, stringent measures of securing data and shared experiences of interviewee and interviewers helped complete virtual research. We recommend that four key factors such as digital competency, feasibility, flexibility and resilience should be considered while undertaking or commissioning virtual, qualitative research studies.

Social care practitioners and qualitative researchers increasingly negotiate with digital technologies to undertake their work. In this paper, we evidence how online qualitative approaches can be effective provided challenges are dealt with diligently in each stage of the research process.

Polymer laser powder bed fusion (PBF-LB/P) is an additive manufacturing technology that is sustainable due to the possibility of recycling the powder multiple times and allowing the fabrication of gears without the aid of support structures and subsequent assembly. However, there are constraints in the process that negatively affect its adoption compared to other additive technologies such as material extrusion to produce gears. This study aims to demonstrate that it is possible to overcome the problems due to the physics of the process to produce accurate mechanism.

Technological aspects such as orientation, wheel-shaft thicknesses and degree of powder recycling were examined. Furthermore, the evolving tooth profile was considered as a design parameter to provide a manufacturability map of gear-based mechanisms.

Results show that there are some differences in the functioning of the gear depending on the type of powder used, 100% virgin or 50% virgin and 50% recycled for five cycles. The application of a groove on a gear produced with 100% virgin powder allows the mechanism to be easily unlocked regardless of the orientation and wheel-shaft thicknesses. The application of a specific evolutionary profile independent of the diameter of the reference circle on vertically oriented gears guarantees rotation continuity while preserving the functionality of the assembled mechanism.

In the literature, there are various studies on material aging and reuse in the PBF-LB/P process, mainly focused on the powder deterioration mechanism, powder fluidity, microstructure and mechanical properties of the parts and process parameters. This study, instead, was focused on the functioning of gears, which represent one of the applications in which this technology can have great success, by analyzing the two main effects that can compromise it: recycled powder and vertical orientation during construction.

This review aims to give a critical view of the wheel/rail high frequency vibration-induced vibration fatigue in railway bogie.

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.

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.

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.

The safety and reliability of high-speed trains rely on the structural integrity of their components and the dynamic performance of the entire vehicle system. This paper aims to define and substantiate the assessment of the structural integrity and dynamical integrity of high-speed trains in both theory and practice. The key principles and approaches will be proposed, and their applications to high-speed trains in China will be presented.

First, the structural integrity and dynamical integrity of high-speed trains are defined, and their relationship is introduced. Then, the principles for assessing the structural integrity of structural and dynamical components are presented and practical examples of gearboxes and dampers are provided. Finally, the principles and approaches for assessing the dynamical integrity of high-speed trains are presented and a novel operational assessment method is further presented.

Vehicle system dynamics is the core of the proposed framework that provides the loads and vibrations on train components and the dynamic performance of the entire vehicle system. For assessing the structural integrity of structural components, an open-loop analysis considering both normal and abnormal vehicle conditions is needed. For assessing the structural integrity of dynamical components, a closed-loop analysis involving the influence of wear and degradation on vehicle system dynamics is needed. The analysis of vehicle system dynamics should follow the principles of complete objects, conditions and indices. Numerical, experimental and operational approaches should be combined to achieve effective assessments.

The practical applications demonstrate that assessing the structural integrity and dynamical integrity of high-speed trains can support better control of critical defects, better lifespan management of train components and better maintenance decision-making for high-speed trains.

Gears are prone to instantaneous failure when operating under extreme conditions, affecting the machinery’s service life. With numerous types of gear meshing and complex operating conditions, this study focuses on the gear–rack mechanism. This study aims to analyze the effects and optimization of biomimetic texture parameters on the line contact tribological behavior of gear–rack mechanisms under starvation lubrication conditions.

Inspired by the microstructure of shark skin surface, a diamond-shaped biomimetic texture was designed to improve the tribological performance of gear–rack mechanism under starved lubrication conditions. The line contact meshing process of gear–rack mechanisms under lubrication-deficient conditions was simulated by using a block-on-ring test. Using the response surface method, this paper analyzed the effects of bionic texture parameters (width, depth and spacing) on the tribological performance (friction coefficient and wear amount) of tested samples under line contact and starved lubrication conditions.

The experimental results show an optimal proportional relationship between the texture parameters, which made the tribological performance of the tested samples the best. The texture parameters were optimized by using the main objective function method, and the preferred combination of parameters was a width of 69 µm, depth of 24 µm and spacing of 1,162 µm.

The research results have practical guiding significance for designing line contact motion pairs surface texture and provide a theoretical basis for optimizing line contact motion pairs tribological performance under extreme working conditions.