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Rapid Failure of Lubricated Contacts With Grease Under Zero Entraining Velocity Condition
No full textIn response to the rapid failure of grease lubrication under low surface speed with zero entraining velocity, a common occurrence in ball screws or cageless rolling element bearings, detailed observations were conducted through optical interferometric experiments. It was observed that despite a constant surface speed and load, the motion remained transient due to the transition between outlet cavitation and inlet starvation. The reciprocating motion of the cavitation zone rapidly depleted the contact area, leading to severe surface peeling. However, as the surface speed increased, this phenomenon was alleviated and eventually disappeared. To enhance lubrication performance, bilateral grooves were created using laser technology, proving to be advantageous for grease lubrication life under low surface speed conditions. Despite the occurrence of rapid surface failure, grease lubrication demonstrated clear benefits over oil lubrication when operating at low surface speeds.</p
Transition Metal Dichalcogenide‐Based Composites in Powder Bed Additive Manufacturing for Electrochemical Applications—A Review
Get PDFRobust electrochemical sustainability of tailored high-performance nanocomposites is integral to advanced electrochemical energy conversion and storage (EECS) systems. Functions, such as nanoscale ionic-diffusion distance, electrocatalytic reactions, electrical conductivity, and fluid distribution, of transition metal dichalcogenide (TMD)-based nanostructures have been extensively designed and studied. However, challenges in materials selection, operational scalability, and design flexibility of TMD-incorporated metal-matrix composites (MMCs) consisting of non-noble metallic nanostructures and their originating TMD materials have scarcely been studied. Highlighting the effectiveness of emerging additive manufacturing techniques in sustainable energy supply and storage, laser powder bed fusion (L-PBF) can offer a directly added dual-functionality to fabricated complex multimaterial and TMD-incorporated MMC electrocatalytic electrodes. In this review, the characteristics of composite powder feedstock and optimizing process parameters are critically emphasized from another perspective to maintain a balance between mechanical robustness and enhanced electrochemical response. It is demonstrated how factors such as surface roughness, particle shape, and rheological characteristics of TMDs can influence the flowability of composite powder feedstock and the electrochemical performance of L-PBF-processed electrodes. The review further aims to contribute compiled information for use in the rapidly growing global market for advanced energy storage systems, underscoring the transformative potential of L-PBF and TMD-incorporated MMCs in modernizing the EECS components
Experimental Study of the Effect of Thickener on the Film Thickness in the Contacts of a Grease-Lubricated Ball Bearing at Low Speed
Get PDFThe level of starvation in axially loaded grease lubricated ball bearings can be well described by the product of the base oil viscosity, the half contact width and the rotational speed (ηbu). This paper highlights the effect of the thickener as another parameter for estimating the film thickness in a ball bearing. Film thickness measurements were done with an optical simulator of the ball-on-disc configuration and a real ball bearing using the capacitance method. Three greases with the same base oil but different thickener types were selected for the experiments. Two greases followed the ηbu model but the grease with alicyclic di-urea thickener produced a higher thickness than the model prediction, which is most likely caused by the formation of residual layers on the contact surfaces. The layer formation occurs in the first few hours of operation reaching a thickness of about 500–550 nm. Other greases also form layers, but they are comparable to prior observations, and they follow the model. The evolution of the normalized film thickness versus ηbu in the case of alicyclic-di urea grease shows the same trend as the other grease types but with overall higher values.</p
Mens en Klimaat;:De kracht van sociale infrastructuur bij adaptatie
Get PDFNederlanders hebben te maken met een veranderend klimaat. Meer hitte, droogte, hevige neerslag en een stijgende zeespiegel kunnen de samenleving ontwrichten. De impact van een klimaatgebeurtenis reikt verder dan schade en slachtoffers. In het slechtste geval verliezen mensen hun vertrouwen in de overheid en elkaar, raken gemeenschappen onthecht en neemt armoede toe. Een klimaatgebeurtenis heeft dus fysieke én sociale gevolgen. Andersom bepaalt de sociale context voor een deel hoe goed mensen met klimaatgebeurtenissen om kunnen gaan. Wie een sterk netwerk heeft of over voldoende middelen beschikt, komt doorgaans minder snel in de problemen en herstelt sneller. Voor deze sociale factoren is in het Nederlandse adaptatiebeleid te weinig aandacht. De focus ligt op fysieke beschermingsmaatregelen. Die zijn essentieel, maar niet voldoende. In dit rapport betoogt de Wetenschappelijke Raad voor het Regeringsbeleid (wrr) dat Nederland beter klimaatbestendig wordt wanneer de overheid ook inzet op sociale infrastructuur die mensen naar elkaar laat omkijken, hun onderlinge vertrouwen verhoogt, en handelingsperspectief bied
Collective effects in breath figures
Get PDFBreath figures are the complex patterns that form when water vapor condenses into liquid droplets on a surface. The primary question concerning breath figures is how the condensing vapor is allocated between the growth of existing droplets and the nucleation of new ones. Although numerous theoretical studies have concentrated on scenarios resulting in highly polydisperse droplet ensembles, a companion paper [Bouillant, Phys. Rev. Lett. 134, 188204 (2025)10.1103/PhysRevLett.134.188204] demonstrates that nearly monodisperse patterns can be achieved on defect-free substrates in a diffusion-controlled regime. The objective of this work is to present a theoretical framework that elucidates the formation and evolution of nearly monodisperse patterns in breath figures. We discover that, following a short nucleation phase, the number of droplets remains constant over an extensive range of timescales due to collective effects mediated by the diffusion of vapor. The spatial extent of these diffusive interactions is identified through asymptotic matching, based on which we provide an accurate description of breath figures through a mean-field model. The model accounts for the subdiffusive growth of droplets as well as for the arrest of nucleating new droplets, and reveals the scaling laws for the droplet density observed in experiments. Finally, droplets expand and ultimately coalesce, which is shown to trigger a scale-free coarsening of the breath figures.</p
The influence of sacrocolporectopexy on pelvic anatomy assessed in an upright position using MRI
Get PDFAim: Rectopexy with concomitant sacrocolpopexy (sacrocolporectopexy) is the favoured technique for treating combined pelvic organ prolapse and internal or external rectal prolapse, despite limited functional improvement. Previous studies have assessed anatomical change after standalone rectopexy or sacrocolpopexy, based on supine MRI defaecography. Since a supine position can underestimate the extent of pelvic organ prolapse, it might also incorrectly assess the anatomical effect of sacrocolporectopexy. The aim of this study was to assess the effect of sacrocolporectopexy on the pelvic anatomy in an upright position. Method: Twenty one female patients undergoing sacrocolporectopexy from December 2022 to June 2024 were included. All patients underwent physical examination and MRI defaecography preoperatively and postoperatively. The descent of the bladder, vaginal vault and anorectal junction and the size of the rectocele and enterocele were assessed on the MRI defaecography images during maximum straining. Significance was tested using a paired t-test and an improvement of ≥10 mm was considered clinically relevant. The results were compared with previous studies, which used supine assessment. Results: Postoperative improvement was found for the bladder, vaginal vault, anorectal junction, rectocele and enterocele with 14, 44, 5, 16 and 54 mm respectively. The bladder, vaginal vault, rectocele and enterocele showed clinically relevant improvement. Compared with supine results, upright assessments revealed a larger organ lift for the vaginal vault as well as a higher, overall, position of the anorectal junction. Conclusion: Upright assessment of sacrocolporectopexy differs from supine assessment, with statistical and clinically relevant lift for the pelvic organs.</p
The State of the Art of eHealth Self-Management Interventions for People With Chronic Obstructive Pulmonary Disease:Scoping Review
Get PDFBackground: Chronic obstructive pulmonary disease (COPD) is a common chronic incurable disease. Treatment of COPD often focuses on symptom management and progression prevention using pharmacological and nonpharmacological therapies (eg, medication, inhaler use, and smoking cessation). Self-management is an important aspect of managing COPD. Self-management interventions are increasingly delivered through eHealth, which may help people with COPD engage in self-management. However, little is known about the actual content of these eHealth interventions.Objective: This literature review aimed to investigate the state-of-the-art eHealth self-management technologies for COPD. More specifically, we aimed to investigate the functionality, modality, technology readiness level, underlying theories of the technology, the positive health dimensions addressed, the target population characteristics (ie, the intended population, the included population, and the actual population), the self-management processes, and behavior change techniques.Methods: A scoping review was performed to answer the proposed research questions. The databases PubMed, Scopus, PsycINFO (via EBSCO), and Wiley were searched for relevant articles. We identified articles published between January 1, 2012, and June 1, 2022, that described eHealth self-management interventions for COPD. Identified articles were screened for eligibility using the web-based software Rayyan.ai. Eligible articles were identified, assessed, and categorized by the reviewers, either directly or through a combination of methods, using Atlas.ti version 9.1.7.0. Thereafter, data were charted accordingly and presented with the purpose of giving an overview of currently available literature while highlighting existing gaps.Results: A total of 101 eligible articles were included. This review found that most eHealth technologies (91/101, 90.1%) enable patients to self-monitor their symptoms using (smart) measuring devices (39/91, 43%), smartphones (27/91, 30%), or tablets (25/91, 27%). The self-management process of “taking ownership of health needs” (94/101, 93.1%), the behavior change technique of “feedback and monitoring” (88/101, 87%), and the positive health dimension of “bodily functioning” (101/101, 100%) were most often addressed. The inclusion criteria of studies and the actual populations reached show that a subset of people with COPD participate in eHealth studies.Conclusions: The current body of literature related to eHealth interventions has a strong tendency toward managing the physical aspect of COPD self-management. The necessity to specify inclusion criteria to control variables, combined with the practical challenges of recruiting diverse participants, leads to people with COPD being included in eHealth studies that only represent a subgroup of the whole population. Therefore, future research should be aware of this unintentional blind spot, make efforts to reach the underrepresented population, and address multiple dimensions of the positive health paradigm.</p
Shared team mental models when using Building Information Models in construction projects
Get PDFThis study explores Team Mental Models in the context of inter-organizational use of Building Information Models in construction. Through a multiple case study of four construction projects, it is shown that most of the variations in sharedness of mental models can be explained by geographical, organizational, and technological proximity of parties to the core project team. It is also indicated that the level of consensus on the use of Building Information Models is positively related with the project's Building Information Model maturity and that parties with a central role in a project team score higher on the level of the sharedness of mental models for the use of this technology. This study emphasizes significant risks and challenges in collaboration based on Building Information Models among project participants arising from variations in sharedness of mental models. It is crucial for project management to engage in explicit and open discussions between project partners about risks and challenges related to the Team Mental Models, and implement measures to mitigate and resolve these issues.</p
Solid-liquid impact in thermal equilibrium
Get PDFDynamics of solid-liquid impact in thermal equilibrium differ significantly from those in ambient air, primarily due to phase change that can occur during the process. This is particularly relevant for the transport of cryogenic fuel, such as liquefied natural gas (LNG). Cryogenic fuels are usually transported at atmospheric or increased pressure, such that they are always close to thermodynamic equilibrium with their vapour phase in the containment tanks. Impact of the fuel on the containment wall during transportation, commonly known as sloshing, may induce a sudden high impact load and jeopardise the tank’s integrity. Despite its importance, the sloshing dynamics at thermal equilibrium remain poorly understood due to the lack of fundamental knowledge on the physics of impact phenomena with phase change.In this thesis, we experimentally investigated the solid-liquid impact dynamics in thermal equilibrium by impacting a circular flat disc onto a boiling liquid i.e., a liquid that is in thermal equilibrium with its vapour, to gain insight into the physics of impact involving phase change. Summarising the important findings obtained from our investigation: (1) Local over-pressure incurred upon solid-liquid impact causes the entrapped vapour under the disc to condense, which leads to its rapid collapse. This results in high local impact pressure on the solid that is significantly greater than what is expected for an impact in ambient air. (2) Unlike the dynamics of an entrapped air pocket that is typically influenced by the liquid inertia and/or surface tension, the dynamics of an entrapped vapour pocket upon impact is dominated by the effect of phase change. Condensation accelerates its collapse while vaporisation is effective in resisting the rapid collapse.Our study reveals the fundamental mechanism by which phase change can cause significant and often detrimental damage during solid-liquid impact in thermal equilibrium