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Dynamic interactions of surface wear and tooth crack in gear transmission systems: An investigation of progressive-degradation mechanisms
No full textGear transmission systems are essential components in numerous industrial applications due to their efficient power transmission, precise ratios and smooth operation. However, under complex operating conditions and extended use, gear pairs, particularly those bearing the main load, are susceptible to faults that probably jeopardize the entire system. While extensive research has been conducted on gear faults, most studies focus on isolated fault types, overlooking the inevitable surface wear during the mid-to-late operation stages. Wear often interacts with other faults, leading to system instability and reducing the reliability of current analysis. Neglecting the interaction between wear and other failures can result in inaccurate evaluations of gear system performance and unreliable assessments of overall gear transmission health. To address these challenges, this paper proposes a framework for the dynamics analysis of gear systems over their lifespan, accounting for the coupling effects of surface wear and root crack. Specifically, an enhanced model based on the potential energy method is developed to calculate mesh stiffness as faults progress. During model construction, the variation in multi-tooth meshing is carefully considered, as it is influenced by factors such as tooth profile deviation, static transmission error, deformation and fluctuating meshing forces. Furthermore, the dynamic interactions between wear and crack are thoroughly examined. To predict system degradation, a new model updating scheme is introduced considering the coupled faults. Moreover, the vibration response is analyzed, with the results validated through finite element analysis and run-to-failure experiments, demonstrating the effectiveness of the developed scheme in predicting coupled fault progression.This research was supported by the National Natural Science Foundation of China (52025056, 52435003), SanQin Scholar Innovation Team, Shaanxi Science and Technology Innovation Team (2023-CX-TD-15) and Fundamental Research Funds for the Central Universities, China
Unlocking Business Success: How Networking and Branding Capabilities Drive Performance Through Product Innovativeness
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The data that support the findings of this study are available from the corresponding author upon reasonable request.In today's fast-paced market, developing innovative products with significant advantages over existing alternatives is essential for a strong market presence. This study, based on the resource-based and dynamic capability view, examines how market and technological innovativeness contribute to differentiation advantage and improved business performance. It also investigates the roles of complementary capabilities in enhancing these relationships. Primary data were collected through an on-site questionnaire survey of Iranian research and development-intensive manufacturing firms. Using 125 valid responses from senior managers, partial least squares structural equation modeling tested the proposed model. Findings indicate that networking and branding capabilities enhance technological and market innovativeness, respectively, thereby strengthening differentiation advantage. Moreover, differentiation advantage is a crucial mechanism for translating innovativeness into improved business performance. These results provide theoretical insights and practical guidance for developing effective product innovativeness strategies to augment international competitiveness and performance
Talent identification and management in the Ghana civil service: Evaluating perspective and practices
No full textThis thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonTalent management is perceived as any action plan instigated to attract, develop, engage and retain employees who are regarded as indispensable and highly valuable to the organisation. With the fierce competitiveness in the global world of international and national businesses, the implication of harnessing and nurturing talents has become a topical issue in organisation, work and management research and practice. While there exists a proliferation of research on talent management practices from western countries, little is known about similar studies from non-western contexts particularly in the African region. More specifically, there remains paucity of research on talent management evaluation and practices with the Civil Service necessitating a scholarly focus on understanding talent and talent management practices within the Ghana Civil Service.
Using human capital theory as a theoretical lens, this doctoral thesis explored the identification, effects and challenges of talent management as well as the nature of methods adopted in talent management research in an African context with the aim of showcasing the realities of talent management in an under-researched terrain (i.e. Ghana Civil Service). The study adopted a qualitative research design to retrieve data by conducting 30 interviews with senior management staff of the Ghanaian Civil Service which includes Chief Directors, Heads of Directorates, line managers and supervisors involved in implementing and assessing talent identification processes and programs. The thematic analysis revealed divergent context-specific definitions of talent identification and talent management which includes talents being conceptualised as managing scarce resource, human capital management and building personnel for a high-performance workplace. Furthermore, results relating to challenging factors affecting the processes of identification and employee differentiation when managing talents in Ghana are lack of specialised Civil Service structure and challenging work environment.
In addressing these challenges, emerging themes such as fostering career development, encouraging coaching and mentoring as well as attenuating job dissatisfaction were identified as mitigating interventions. In addition, future talent management programs were evaluated that are necessary to improve talent management in Ghana’s civil service. In terms of research contribution, the study contributes to talent management research by exploring the concept and realities from a largely overlooked African region – Ghana. This study informs policy and practice in African countries, helping to develop effective strategies for attracting, retaining, and developing talented professionals. The study extends the notion that future research should examine the accounts of those in the private sector to report balanced views on non-governmental employees of different occupational groups in Ghana and beyond
Propeller tonal noise reductions through synchrophasing: Mechanisms and performance
No full textData availability:
The authors do not have permission to share data.This paper presents an analytical investigation into the mechanisms and effectiveness of propeller synchrophasing in which noise reductions from a number of co-planar identical propellers are obtained by setting their blade azimuthal positions at any instant in time to be separated by a fixed angle. In this paper we demonstrate that noise reductions obtained through propeller synchrophasing arises from the destructive interference between acoustic spinning modes that are locked to the propeller as it rotates. We demonstrate that the main factor in determining levels of noise reduction is the separation distance between the centres of rotation compared to the acoustic wavelength at the blade passing frequency of interest. Simple analytic expressions are developed to predict the azimuthal directivity and sound power reduction for two co-rotating and counter-rotating propellers, which will be shown to be in close agreement with measured data. The principles of propeller synchrophasing identified for the two propeller case are generalised to multiple propellers, and an iterative scheme for identifying the optimum synchro phase angles will be presented. This paper will demonstrate that propeller synchronising is only effective for relatively small propellers operating at low tip Mach numbers and is ineffective for contra-rotating propellers, as observed in previous studies.The authors Joseph and Paruchuri would like to acknowledge the funding of this work from the EPSRC grant EP/VO5614X/1
Liouville theorems and gradient estimates for positive solutions to a class of quasilinear elliptic equations
Get PDFAMS Subject Classification: 53C20.In this paper, we use the Nash-Moser iteration method to investigate the local and global gradient estimates of positive solutions to a class of quasi-linear elliptic equations [mathematical notation, see full text] on a complete Riemannian manifold [mathematical equation, see full text]. In particular, we provide the explicit expressions of global gradient estimates of entire positive solutions. As an application, we derive several Liouville theorems for these equations.This work is partly supported by the National Natural Science Foundation of China (12161095, 12361048), Yunnan Fundamental Research Projects (202401AT070130), Cross-integration Innovation team of modern Applied Mathematics and Life Sciences in Yunnan Province, China (202405AS350003) and the China Scholarship Council (202308530236)
The Use of Mindfulness in the Metaverse: A Scoping Review
No full textData Availability:
The data generated and analysed during the current study are available from the corresponding author on reasonable request.Objectives:
This scoping review aimed to address a significant research limitation concerning mindfulness practices within the metaverse. The primary aim was to examine whether metaverse-based mindfulness training programs incorporate fundamental elements of traditional mindfulness-based interventions (MBIs) and adhere to core mindfulness principles.
Methods:
The review followed the five-step framework for scoping reviews, with a comprehensive search strategy employed across six databases, covering scholarly articles published between January 2015 and August 2023.
Results:
The review identified 23 studies combining mindfulness practices with virtual reality (VR) technology. Key findings include the following: (1) research in this field is in its infancy, with a lack of consistency in defining and measuring mindfulness; (2) a wide variety of study designs and implementations were observed, presenting challenges for drawing meaningful conclusions; (3) high levels of engagement were reported, but may be influenced by the novelty effect of VR; (4) mixed results were found across studies regarding the effectiveness of VR-based mindfulness interventions; and (5) there was limited ethnic diversity in study populations.
Conclusions:
While VR-based mindfulness interventions show promise, there is a critical need for more rigorous, high-quality studies that adhere to standardized definitions of mindfulness, employ validated measurement tools, and explore long-term effects. Future research should focus on developing a core set of outcome measures, investigating the sustainability of engagement, and expanding studies to include more diverse populations.
Preregistration:
This study is not preregistered.This research was supported by the University of Chichester
Thermodynamic Modeling of Metastable and Transition Carbides in the Fe-C System
Get PDFThe tempering of martensitic Fe-C steels involves the evolution of metastable and transition carbides, which play a crucial role in determining the mechanical properties of the material..
On the slit trailing edges for aerofoil self-noise reduction
Get PDFThis paper presents an experimental and analytical investigation into the use of trailing edge slits for the reduction of aerofoil trailing edge noise. The noise reduction mechanism is shown to be fundamentally different from conventional trailing edge serrations, relying on destructive interference from highly compact and coherent sources generated at either ends of the slit. This novel approach is the first to exploit the coherence intrinsic to the boundary layer turbulence. Furthermore, the study demonstrates that trailing edge slits not only achieve superior noise reductions compared with sawtooth serrations of the same amplitude at certain conditions, but also offer frequency-tuning capability for noise reduction. Noise reduction is driven by the destructive interference between acoustic sources at the root and tip of the slit, which radiate with a phase difference determined by the difference in times taken for the boundary layer flow to convect between the root and tip. Maximum noise reductions occur at frequencies where the phase difference between these sources is 180°. The paper also presents a detailed parametric study into the variation in noise reductions due to the slit length, slit wavelength and slit root width. Additionally, a simple two-source analytic model is proposed to explain the observed results. Wind tunnel measurements of the unsteady flow field around the trailing edge slits are also presented, providing insights into the underlying flow physics.This work is supported by the UK Engineering and Physical Sciences Research Council (EPSRC) research grant (EP/N018737/1) ‘Quiet aerofoils of the next-generation’. We would also like to express our appreciation for the PhD studentship funded by the EPSRC Doctoral Training Partnership (DTP) awarded to P.C.W
Pre-monsoon lightning in Bangladesh: Separating most from least active days with thermodynamic and synoptic composites
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GLD360 data were provided by Vaisala Inc. Researchers can request access to GLD360 data through the Vaisala Research Data Grant Program through the following link: https://www.vaisala.com/en/lp/request-vaisala-lightning-data-research-use.The pre-monsoon season (March–May) in Bangladesh is the most hazardous period for lightning-related human casualties, particularly during morning and afternoon hours. This heightened risk is primarily associated with labor-intensive manual agriculture on smallholder farms. This study investigates the atmospheric conditions corresponding to the 50 most active and 50 least active pre-monsoon lightning days between 2015 and 2020. Analysis of sounding and reanalysis data reveals distinct differences across nearly all dynamic, thermodynamic, surface, and upper-air composite parameters. On the most active lightning days, the environment typically features a SWEAT index exceeding 230, a mixed-layer mixing ratio above 15 g kg^−1, and high values of the most unstable convective available potential energy (≥1580 J kg^−1), along with elevated instability—all conducive to thunderstorms with heavy rainfall. Notably, on 20 % of these active days, storm-relative environmental helicity reaches between 300 and 485 m2 s^−2, indicating a high potential for supercell thunderstorms and intense lightning activity. In contrast, the least-active lightning days are characterized by weaker storm systems. These variations are primarily driven by strong, warm, moist southwesterly winds from the Bay of Bengal, which enhance horizontal temperature gradients and atmospheric instability. Regression models identified potential instability, cloud ice water content, and cloud liquid water content as strong synoptic-scale predictors of lightning activity. Principal component analysis (PCA) further highlighted the critical role of cloud-scale thermodynamic and kinematic variables in distinguishing lightning intensity. These findings provide a foundation for developing daily lightning forecast systems, with potential benefits for public safety and protection of lightning-sensitive infrastructure.Mohammed Sarfaraz Gani Adnan acknowledges the Leverhulme Trust for the Early Career Fellowship
The Migration Question: Politics, Economics and the Failure of Border Security
No full textThis authoritative book proposes a fresh perspective on international migration, offering decisive answers to the big questions, and dismantling the main myths surrounding one of the most salient issues of today's global politics
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