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Electrochemical gas evolution reactions are common but essential in many electrochemical processes including water electrolysis. During these processes, gas bubbles are constantly nucleating on reaction interfaces in electrolyte a...
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Electrochemical gas evolution reactions are common but essential in many electrochemical processes including water electrolysis. During these processes, gas bubbles are constantly nucleating on reaction interfaces in electrolyte and consequently exert an impact on catalysts and the performance. In the past few decades, extensive studies have been conducted to characterize bubbles with emerging advanced technologies, manage behaviors of bubbles, and apply bubbles to various domains. In this review, we summarize representative discoveries as well as recent advancements in electrochemical gas evolution reactions from the perspective of gas bubbles. Finally, we end up this review with a profound outlook on future research topics from the combination of experiments and theoretical techniques, non-negligible bubble effects, gravity-free situation, and reactions under practical industrial conditions.
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The demand for cost reduction in proton exchange membrane water electrolyzer (PEMWE) is driving it to increase the operating current density and higher current densities require better bubble management. In this work, we demonstra...
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The demand for cost reduction in proton exchange membrane water electrolyzer (PEMWE) is driving it to increase the operating current density and higher current densities require better bubble management. In this work, we demonstrate that introducing patterned grooves to the catalyst layer surface (CL) is able to enhance the bubble evolution and improve electrolyzer performance. The patterned grooves mi-crostructure on CL provides additional bubble nucleation sites and faster bubble evolution. Smaller average bubble size and higher bubble detachment frequency during water electrolysis are observed through a bubble evolution visualization system and further confirmed by a frequency analysis method. In addition, patterned grooves also improve the hydrophilicity and aerophobicity of CL surfaces. In the PEM water electrolyzer cell, the patterned grooves on CL boost the cell performance and reach high current densities up to 5.0 A cm~(-2). With better bubble management, patterned grooves significantly reduce the mass transport overpotential at each current density. At 5.0 A cm~(-2), the mass transport overpotential is reduced by 59%. This work provides a new idea of bubble management in PEMWE and is highly informative for designing CLs for PEMWE and other gas-evolving electrochemical energy conversion applications.
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Heat transfer in nucleate boiling relies on the detachment and rise of the boiling bubble, in which gravity plays the dominant role. Previous studies showed that in the absence of gravity, the bubble fails to rise, causing the dry...
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Heat transfer in nucleate boiling relies on the detachment and rise of the boiling bubble, in which gravity plays the dominant role. Previous studies showed that in the absence of gravity, the bubble fails to rise, causing the dryout of the heater and significantly reducing the thermal efficiency of nucleate boiling. Recently, a new boiling regime termed oscillate boiling was discovered. By localizing thermal energy as high as 50 mW into an area as small as 15x15 mu m(2), a boiling bubble is formed and oscillate at high frequency while remaining pinned at the heating spot. This regime was proposed to be independent of buoyancy as its operation does not involves the detachment and rise of the boiling bubble. To test this hypothesis, we compared experimental observations of oscillate boiling in low gravity, normal gravity and hyper gravity. The results support the hypothesis and promote its potential for outer-space heat transfer application.
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In project risk management many firms use bubble diagrams to get a graphical presentation of a project's most uncertain attributes. The bubble diagrams and procedures used to put attributes into these diagrams are seen to provide ...
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In project risk management many firms use bubble diagrams to get a graphical presentation of a project's most uncertain attributes. The bubble diagrams and procedures used to put attributes into these diagrams are seen to provide a rational framework for managing risks. In this paper we review and discuss the use of these diagrams and procedures. Special attention is given to the way safety is treated. We show that the standard use of bubble diagrams is not adequate for identification and follow up critical activities that affect safety. The main problem is that the present structure means that the uncertainty is not properly taken into account. In this paper a reformulated bubble diagram is suggested that better reflects safety related uncertainties. The offshore oil and gas industry is the starting point, but the discussion is to large extent general.
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Hydrogen, as a promising energy carrier to alleviate the global issues of energy crisis, has arisen a worldwide concern. However, the lack of management of the produced bubbles on electrode surface is one of the critical barriers ...
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Hydrogen, as a promising energy carrier to alleviate the global issues of energy crisis, has arisen a worldwide concern. However, the lack of management of the produced bubbles on electrode surface is one of the critical barriers for hydrogen evolution reaction (HER) since insufficient bubble removal causes the blockage of the active sites, increased ohmic resistance in the electrolyte and deficient ion transfer from the bulk solution to the electrode surface. In this study, an open-structured carbon fiber brush electrode (CFB) that can be produced by simply twisting a folded Ti wire fitted with carbon fibers was proposed. As a proof-of-concept demonstration, an earth-abundant electrocatalyst, MoS2 nanosheets was loaded on the CFB via solvothermal method to fabricate the HER electrode (MoS2 perpendicular to CFB). This structure not only ensures a uniform electrocatalyst distribution throughout the exterior and internal electrode surface but also ensures an improved exposure of active sites and a sufficient reaction ion supply by inducing oriented hydrogen bubble transport during the electrochemical process. Additionally, the open structure of CFB accelerates fluid flow around the electrode, which also guarantees a sufficient proton supply and hydrogen bubble removal. As a results, MoS2 perpendicular to CFB exhibits a 3.7 times higher current density at an overpotential of 400 mV and prominent durability as compared with the same catalyst growing on the common carbon cloth substrate.
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Psychological approaches to symptom management are among the oldest and are anintrinsic part of medical practice in every culture. Hypnosis under various names hasbeen used for as long as records have been kept, and suggestive the...
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Psychological approaches to symptom management are among the oldest and are anintrinsic part of medical practice in every culture. Hypnosis under various names hasbeen used for as long as records have been kept, and suggestive therapy of all kinds isprobably the oldest of all therapeutic approaches. The acceptability and use of hypnosishas waxed and waned over the years, but recently a renewed interest has been sparkedin researchers and clinicians, with many exciting developments in the field. Many ofthese recent advances are succinctly summarized in the current special issue of Contem-porary Hypnosis on hypnotic analgesia.
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A novel method for removing CO2 from gas streams is described. The carbon dioxide continuous scrubber, CDOCS, takes advantage of the intimate liquid-gas contact afforded in a packed bubble column to both absorb the CO2 from a gas ...
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A novel method for removing CO2 from gas streams is described. The carbon dioxide continuous scrubber, CDOCS, takes advantage of the intimate liquid-gas contact afforded in a packed bubble column to both absorb the CO2 from a gas stream, and to regenerate the solution. The design relations and performance of a prototype CDOCS system using amine solution are presented. Over a 30-day trial, 20 m~3/h of air was continuously scrubbed to 60-80 ppm. The CDOCS footprint is less than 0.18 m~3 with power consumption around 300 W. Applications for air scrubbing include alkaline fuel cells, small scale processing, and industrial safety. A concept is proposed to sweeten biogas from dairy farm effluent for on-farm electricity generation. While industrial processes involving packed or plate trickle columns are well known for CO2 production and sweetening, these conventional methods are complex and expensive, and do not scale down to air scrubbing or to small scale biogas production.
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Abstract Background Fiberoptic bronchoscope?guided tracheal intubation is the gold standard for managing patients with supraglottic growths. In infants with a large and overhanging epiglottis, the success of fiberoptic-guided intu...
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Abstract Background Fiberoptic bronchoscope?guided tracheal intubation is the gold standard for managing patients with supraglottic growths. In infants with a large and overhanging epiglottis, the success of fiberoptic-guided intubation relies heavily on the available space between the inferior surface of the epiglottis and the posterior pharyngeal wall or, more specifically, the superior surface of the supraglottic growth. Case Report We describe the inability to negotiate the tip of the fiberscope between the epiglottis and the supraglottic growth and the successful use of direct laryngoscopy to improve the available space along with the usefulness of “bubbling of air” to locate the glottic opening in an infant. Why Should an Emergency Physician Be Aware of This? We emphasize the role of the emergency physician in managing such patients. Most of the time, the setting is not ideal in such emergency situations and the most qualified clinician to treat them is the emergency physician. The knowledge and skills of the emergency physician, along with awareness of the possible techniques for airway management, can be lifesaving.
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Many commentators and scholars blame a lack of regulation for the present economic crisis. They maintain that the crisis is mainly due to the alleged neoliberal deregulation of the socio-economic system. This article considers a d...
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Many commentators and scholars blame a lack of regulation for the present economic crisis. They maintain that the crisis is mainly due to the alleged neoliberal deregulation of the socio-economic system. This article considers a different possible explanation, attributing greater responsibility to interventionist public policies. In this perspective, and within a framework of general reform, the role of land and building regulations in particular will be critically discussed. To avoid any misunderstanding: the idea is not to put all' the blame on public intervention, but to also recognize its contribution.
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Inert gas bubbles frequently occur in SCUBA divers’ vascular systems, eventually leading to decompression accidents. Only in professional settings, dive profiles can be adjusted on individual basis depending on bubble grades dete...
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Inert gas bubbles frequently occur in SCUBA divers’ vascular systems, eventually leading to decompression accidents. Only in professional settings, dive profiles can be adjusted on individual basis depending on bubble grades detected through ultrasonography. A total of 342 open-circuit air dives following sports diving profiles were assessed using echocardiography. Subsequently, (Eftedal-Brubakk) bubble grades were correlated with dive and individual parameters. Post-dive cardiac bubbles were observed in 47% of all dives and bubble grades were significantly correlated with depth (r=0.46), air consumption (r=0.41), age (r=0.25), dive time (r=0.23), decompression diving (r=0.19), surface time (r=??0.12). Eftedal-Brubakk categorical bubble grades for sports diving with compressed air can be approximated by bubble grade = (age*50?1 – surface time*150?1+maximum depth*45?1+air consumption*4500?1)2 (units in years, hours, meter, and bar*liter; R2=0.31). Thus, simple dive and individual parameters allow reasonable estimation of especially relevant medium to higher bubble grades for information on relevant decompression stress after ascent. Echo bubble grade 0 is overestimated by the formula derived. However, echo might fail to detect minor bubbling only. The categorical prediction of individual decompression stress with simple bio and dive data should be evaluated further to be developed towards dive computer included automatic ex-post information for decision-making on individual safety measures.
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