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Electrolytic Bubble Coalescence on Hydrophobic Cavity Arrays Determines Departure Radius and Lowers Electrolyte Supersaturation
No full textBubble evolution on electrodes is a complex process that begins with the stochastic nucleation of bubbles on the electrode surface, followed by bubble growth due to diffusion and coalescence, and bubble departure. The stochasticity of bubble evolution on conventional electrodes is a significant challenge in efforts to study electrolytic bubbles. In this investigation, the growth of electrolytic hydrogen bubbles is studied on microfabricated silicon electrodes with arrays of hydrophobic cavities. These hydrophobic pits act as preferential nucleation sites for bubbles—thus lowering the degree of spatial-randomness in bubble nucleation and enabling the study of bubbles growing in the presence of coalescence with greater control. Substrates with different spacings between the hydrophobic pits were fabricated. It is shown that coalescence with neighboring bubbles strongly determines the departure radius of bubbles. Further analysis of the bubble growth rate and electrode coverage indicates that closer pits decrease the electrolyte supersaturation while increasing electrode coverage
Impact of different building roof types on hydrological processes at the urban community scale
No full textAs urbanization accelerates and urban hydrological cycles evolve, roof typology emerges as a pivotal role in water retention capacity and drainage efficiency. To systematically evaluate the influence of various roof types on urban hydrological processes, this study designed four distinct catchment scenarios: Thiessen Polygon Scenarios (TS), Roof Type Consideration Scenarios (RS), Full Flat-Roof Scenarios (FS), and Full Pitched-Roof Scenarios (PS). This study employed the Urban Flood Intelligent Model (UFIM) to simulate urban flooding scenarios, utilizing precipitation data from 21 August 2024 combined with four distinct return periods (1a, 5a, 10a, and 20a) as hydrological inputs. The results show that roof types significantly affected hydrological processes in urban communities. Flat roofs accumulate water and drain slowly, making it easy to form larger areas of accumulated water during peak rainfall periods, thereby increasing the risk of urban flooding. Pitched roofs drain quickly but experience a brief rise in water level during peak hours due to rapid drainage. Based on these insights, priority should be given to the use of sloped roof design in areas prone to accumulated water to accelerate drainage. In areas requiring runoff mitigation, the strategic integration of flat roofs with green roofs enhances rainwater retention capacity, thereby optimizing urban hydrological regulation and bolstering flood resilience.</p
Oxygen versus Hydrogen Bubble Dynamics during Water Electrolysis at Microelectrodes
No full textWhile the dynamics of hydrogen bubbles during water electrolysis have been intensively studied in recent years, adequate insights into the dynamics of oxygen bubbles are still lacking. Therefore, this study presents a comparative analysis of hydrogen and oxygen bubble dynamics during potentiostatic water electrolysis in an acidic electrolyte. Complementary optical techniques, such as high-speed shadowgraphy, particle tracking velocimetry, and schlieren imaging are applied to measure geometric features of the evolving bubbles and the microscale Marangoni convection, as well as the refractive index field around the growing bubbles. Distinct differences between oxygen and hydrogen bubbles are found in the average current, in the Marangoni convection pattern, and in the degree of refractive index reduction at the bubble foot, suggesting a synergetic action of both thermal and solutal effects at oxygen bubbles.</p
Spatiotemporal hotspots of potential microbial risk in shower systems
No full textShower systems create conditions conducive to the growth of opportunistic pathogens, but the timing and location of associated risks are poorly understood. In this study, we constructed 48 full size shower units with six incubation periods (4, 10, 16, 22, 30, and 40 weeks) and four water heater temperature (39, 45, 51, and 58 °C) to examine the dynamics of microbial growth and pathogen distribution. Results showed that during the initial stage (4 weeks), peak biomass was observed for all biofilms, ranked as shower hose (SHE) > cold-water pipe (CWP) > hot-water pipe (HWP), followed by a sharp decline by the 10th-week. At the 4th-week, the biofilm was loose and easily detached into the water, possibly promoted by leached organic carbon from plastic material, fostering the growth of specific microorganisms. The impacts of stagnation and temperature became more pronounced in CWP and HWP over time. Legionella pneumophila appeared in biofilms at the 4th-week, disappeared, and reappeared in large numbers since the 22nd-week. Differently, Mycobacterium spp. emerged in large numbers after 30 weeks. Both pathogens were notably enriched in showerheads and shower hoses. This study highlights critical periods of higher risk in shower systems, particularly in the early stages (4 weeks) and after 22 weeks, suggesting that risks can be mitigated by pre-soaking pipes or regularly cleaning (e.g., heat shock flushing) and replacing showerheads and hoses.</p
Model-Order Reduced Full-Wavefield Migration using Proper Orthogonal Decomposition
Get PDFAs seismic migration is increasingly applied to more and more complex media, more sophisticated imaging techniques are required to generate accurate images of the subsurface. Currently, the best results for imaging are achieved by Least-Squares Migration (LSM) methods, such as Least-Squares Reverse Time Migration (LS-RTM) and Full-Wavefield Migration (FWM). These methods iteratively update the image to minimize the misfit between the forward modelled wavefield and the recorded data at the surface. However, a key challenge for these techniques is the speed of convergence. To accelerate the speed of convergence, pre-conditioning is commonly applied. The most common preconditioner is the reciprocal of the Hessian operator. However, this operator is computationally expensive to calculate, making it difficult to apply directly. In this paper, we present a novel, alternative, preconditioner for FWM. This preconditioner is based on applying Galerkin projections to a linear system, which projects the system onto a set of known basis vectors. To find an appropriate set of basis vectors for this approach we apply Proper Orthogonal Decomposition (POD) to a set of partial solutions of the linear system. The resulting method gives an approximation to the pseudo-inverse based on these basis vectors. To test this technique, which we name Model-Order Reduced FWM (MOR-FWM), we apply it to the synthetic Marmousi model as well as to field data from the Vøring basin in Norway. For these examples, we show that MOR-FWM yields an improved data-misfit compared to the standard FWM approach. In addition, we show that the result for the field data case can be improved by normalizing the partial solutions before applying POD
Trust Violations due to Error or Choice:The Differential Effects on Trust Repair in Human–Human and Human–Robot Interaction
Get PDFMany decisions in life involve tradeoffs: To gain something, one often has to lose something in return. As robots become more autonomous, their decisions will extend beyond mere assessments (e.g., detecting a threat) to making choices (e.g., taking the faster or the safer route). The aim of the current research was to study perceived trustworthiness in scenarios involving adverse consequences due to (1) an assessment error versus (2) a choice. Perceived trustworthiness (ability, benevolence, integrity) was measured repeatedly during a computer task simulating a military mission. Participants teamed with either a virtual human or a robotic partner who led the way and warned for potential danger. After encountering a hazard, the partner explained that it (1) failed to detect the threat (error) or (2) prioritized the mission and chose the fastest route despite the risk (choice). Results showed that: (a) the error-explanation repaired all trustworthiness dimensions, (b) the choice-explanation only repaired perceptions of ability, not benevolence or integrity, (c) no differences were found between human and robotic partners. Our findings suggest that trust violations due to choices are harder to repair than those due to errors. Implications and future research directions are discussed
Vulnerability and resilience of older adults (65+) in the 2021 Ahr Valley flood
No full textFloods are known to cause immediate casualties and material damage, but they also have lasting impacts on the health of affected populations. According to the WHO Constitution, health encompasses not only physical but also mental and social dimensions[1]. While the physical health consequences of flooding among people have been extensively studied, the social and mental health impacts remain underexplored. Older adults represent a certain population group during disasters, and understanding the factors that exacerbate or mitigate their vulnerability is critical. This study examines the 2021 flood in Germany's Ahr Valley as a case study to investigate how such events affect the social and mental well-being of older individuals. Using a mixed-methods approach, comprising in-depth interviews, structured questionnaires, and group discussions, we explore the challenges, barriers, coping strategies, and sources of support that shaped their recovery experiences. Our findings highlight the need for more inclusive and socially responsive disaster preparedness and response that addresses the specific health dimensions of older adults in crisis contexts.REFERENCES1.WHO. (1946). Constitution. Retrieved from https://www.who.int/about/governance/constitution<br/
Gait kinematics at trot before and after repeated ridden exercise tests in young Friesian stallions during a fatiguing 10-week training program
Get PDFBackground: Appropriate training is essential for equine athletes to improve fitness and ensure welfare. Young Friesian stallions must complete a 10-week training program for acceptance as breeding stallions. Earlier, this training program was demonstrated to induce overtraining. Objectives: To evaluate how this training program affects stallions’ trot locomotion variables in relation to fatigue. Study design: Prospective analytical study. Methods: 3 or 4 years-old (n = 16) Friesian stallions performed three ridden indoor standardized exercise tests (SETs) in week-1 (SET-I; n = 15), week-6 (SET-II; n = 11) and week-10 (SET-III; n = 4), measuring heart rate (bpm) and lactate concentration (LA, mmol/L). Before and after each SET, stallions’ locomotion was measured with seven inertial sensors (EquiMoves, 200 Hz) during in-hand trot on a straight line. Stride characteristics, limb angular changes, and upper body kinematics were calculated. The within-measurement coefficient of variation (CV) was calculated for all parameters. Linear mixed models were used to analyze gait variables related to SET, pre-or post-SET and a peak LA ≥4 mmol/L during SETs. Results: Horses showed individual responses in gait kinematics to moderate fatigue. The range of motion of the withers (ROMwithers) increased post SET-II and SET-III compared to post SET-I. In horses reaching LA ≥ 4 mmol/L, CV increased post SETs for several stride characteristics and upper body asymmetry. Upper body vertical movement asymmetry was above the described reference ranges in 69% of the horses. Main limitations: Number of horses used and only four horses managed to complete the 10-week training program as breeding stallions. Conclusion: The young Friesian stallions showed individually different responses in absolute gait kinematics after exercise and during an intense training program. The increased ROMwithers and CV of stride characteristics after SETs suggest an acute effect of fatigue on the locomotion pattern. Further investigation is warranted for the pronounced upper body movement asymmetry related to published asymmetry reference values.</p
Secure addition of floating points
Get PDFSecure multi-party computation (MPC) and homomorphic encryption are very powerful tools to compute with secret numbers without revealing inputs or any intermediate values. To securely achieve high accuracy with varying number sizes, one needs to work with floating points in the secret (secret-shared or encrypted) domain. The main bottleneck of secure floating points is addition. We improve its efficiency by designing a protocol for multiple additions, using standard building blocks available in most MPC platforms. The more additions n were combined, the larger the relative gain, up to a factor 13 with n = 1,024. Additionally, we introduce a new protocol for securely computing the bitlength (given upper bound M), the first one with linear time complexity and constant round complexity. It reduces secure multiplications with a factor 4 (for the constant-round solution), or the number of communication rounds with a factor M/2 (for the logarithmic-round solution). We evaluate accuracy, execution time and communication complexity of our protocols, and release them open source, such that they can be used to improve the efficiency of secure floating-point arithmetic.</p