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Understanding the ontogeny of diving behaviour in marine megafauna is crucial owing to its influence on foraging success, energy budgets, and mortality. We compared the ontogeny of diving behaviour in two closely related species-northern elephant seals (Mirounga angustirostris, n = 4) and southern elephant seals (Mirounga leonina, n = 9)-to shed light on the ecological processes underlying migration. Although both species have similar sizes and behaviours as adults, we discovered that juvenile northern elephant seals have superior diving development, reaching 260 m diving depth in just 30 days, while southern elephant seals require 160 days. Similarly, northern elephant seals achieve dive durations of approximately 11 min on their first day of migration, while southern elephant seals take 125 days. The faster physiological maturation of northern elephant seals could be related to longer offspring dependency and post-weaning fast durations, allowing them to develop their endogenous oxygen stores. Comparison across both species suggests that weaned seal pups face a trade-off between leaving early with higher energy stores but poorer physiological abilities or leaving later with improved physiology but reduced fat stores. This trade-off might be influenced by their evolutionary history, which shapes their migration behaviours in changing environments over time.

This paper investigates the Magnetohydrodynamics (MHD) convective flow over a cone with the influence of viscous dissipation, variable viscosity, chemical reaction and variable thermal conductivity effects. Related equations are tackled by the Homotopy analysis method (HAM). The impacts of physical variables on concentration, velocity and temperature are presented through numerical tables and graphs. It is noticed that the heat transfer rate (Nusselt number) increases against Prandtl number. Similarly, the mass transfer rate (Sherwood number) increases against Schmidt number. Also, it is seen that skin friction in tangential and azimuthal direction increases against the buoyancy forces ratio parameter. Current results are validated with previous literature work. [ABSTRACT FROM AUTHOR]

Hybrid nanofluids provide several advantages over conventional fluids, including improved thermal characteristics, increased stability, customizable features, multifunctionality, and environmental advantages. Hybrid nanofluids are an appealing alternative for a variety of applications due to these benefits. This study aims to compute the non-similar solution of single-multi wall carbon nanotubes (SWCNTs-MWCNTs)-based hybrid nanofluid flow over an inclined extending surface. Heat transmission and flow are observed under the effects of quadratic convection, Darcy-Forchheimer quadratic drag forces, viscous dissipation, and non-linear thermal radiative heat flux. The velocity and thermal slip constraints are imposed at the inclined surface. For the model-based comparison, Xue, and Modified Hamilton Crosser thermal conductivity models for carbon nanotubes (CNTs) are adopted. The irreversibility of the system is also investigated using the second law of thermodynamics for the distinct CNTs-based thermal conductivity models. Non-similarity variables are adopted to convert nonlinear partial differential equations into dimensionless PDEs. Analytical modeling of non-similar systems is done by adopting non-similarity transformations up to second-level truncation, and the bvp4c technique is then used to compute the results numerically. The research found that at 75° of plate inclination, the Modified Hamilton Crosser model for CNTs outperforms the Xue model in terms of heat transfer rate. Further, entropy generation is significantly larger for the Xue model than for the Modified Hamilton Crosser model for CNTs against higher values of viscous dissipation and porosity parameters. It is also revealed that for opposing buoyancy force GR < 0, the temperature of the fluid escalates. This study possesses multiple applications including petroleum engineering, heat exchangers, environmental remediation, and biomedical applications. [ABSTRACT FROM AUTHOR]

Seed dispersal distance is an important indicator of how well a plant species can cope with environmental changes. Seeds of wetland plants are primarily dispersed by hydrochory (floating on the water surface) or endozoochory (ingestion and egestion by animals). However, both mechanisms can also be combined (diplochory), which increases dispersal distances. In wetlands, seeds often float on the water surface before ingestion and transport by animals, such as waterbirds. Here, we consider what happens next after endozoochory and test whether seeds dispersed inside waterbirds can then continue to disperse by hydrochory. We experimentally assessed the buoyancy capacity of 41 wetland plant species for 14 weeks before and after simulated passage through avian digestive systems. This revealed that (1) seeds of plants previously assigned a hydrochory dispersal syndrome floated longer than those from other syndromes, but with considerable overlap; (2) fully aquatic and shoreline plant species had seeds with stronger buoyancy than terrestrial plants; and (3) digestive processes negatively affected seed buoyancy capacity for all plant species, which included wetland species with a typical hydrochory syndrome. The capacity for hydrochory is more limited after endozoochory than beforehand, with strong implications for the effectiveness of seed dispersal. [ABSTRACT FROM AUTHOR]

This study addresses the applications of non-uniform heat source/sink and viscous dissipation in the magnetohydrodynamic (MHD) flow of Casson nanoparticles toward a porous stretchable sheet. The free convective flow for the inclusion of thermal buoyancy along with dissipative heat encourages the flow phenomena. The governing equations of the flow model are presented in terms of partial differential equations and then transformed into a system of ordinary differential equations using similarity transformations. These systems of equations are solved numerically by using the Runge–Kutta fourth-order method with a very efficient shooting technique. The effects of various parameters such as the Casson parameter, elastic parameter, porosity parameter, Prandtl number, non-uniform heat source/sink constant, Eckert number, skin fraction and Nusselt number on the flow area are computed and represented graphically. The present results reflect that the velocity of nanoparticles declined effectively with the porosity parameter and nanoparticle volume fraction. The temperature profile is increased with the elastic parameter and heat source parameter while decreasing with the Eckert number and Casson fluid parameter. Moreover, it is observed that when the Hartmann number is maximum, a retardation in wall shear force against nanoparticles volume fraction is marked. [ABSTRACT FROM AUTHOR]

Kelps are resilient organisms, capable of thriving in high-energy wave environments. However, when hydrodynamic drag forces exerted by the wave environment exceed the kelps’ structural limits, individuals become dislodged. Floating kelps generally follow ocean currents, traveling long distances until air-filled structures fail or the epibiont load becomes too great, causing them to sink to the seafloor. The ability of kelp to disperse over vast offshore and nearshore systems makes them important for organic subsidy and as a dispersal vector for marine organisms. Previous research on dislodged macroalgae focused on context-specific rafts, limiting insights into the broader ecological role of floating kelp. This study employed a site-specific Lagrangian trajectory model to describe the spatial distribution of floating Ecklonia maxima along the South African coastline. The model incorporated buoyancy and sinking using site-specific morphological data. Findings revealed that the distribution of floating E. maxima is influenced by oceanographic conditions, and seasonal patterns were also evident. Mesoscale features played a vital role in kelp accumulation on the surface and seafloor and acted as barriers to dispersal. This study offers essential insights into kelp’s role as an organic subsidy and provides numerical evidence for kelp’s potential as a carbon sink, contributing to a better understanding of kelp ecosystems and their ecological functions. [ABSTRACT FROM AUTHOR]

We investigate theoretically the buoyancy-driven motion of a viscous drop in a yield-stress material, incorporating elastic effects represented by the Saramito–Herschel–Bulkley constitutive equation. We solve the governing equations using an open-source finite volume solver and utilizing the volume of fluid technique to accurately capture the interface between the two fluids. To validate our numerical approach, we compare our results with data from previous experimental and numerical studies. We find quantitative agreement in terms of terminal velocities and drop shapes, affirming the accuracy of our model and its numerical solution. Notably, we observe that incorporating elastic effects into the modeling of the continuous phase is essential for predicting phenomena reported in experiments, such as the inversion of the flow field behind the sedimenting drop (i.e., the negative wake) or the formation of a teardrop shape. Due to the elastoviscoplastic nature of the continuous phase, we observe that small drops remain entrapped because the buoyancy force is insufficient to fluidize the surrounding material. We investigate entrapment conditions using two different protocols, which yield different outcomes due to the interplay between capillarity and elastoplasticity. Finally, we conduct an extensive parametric analysis to evaluate the impact of rheological parameters (yield stress, elastic modulus, and interfacial tension) on the dynamics of sedimentation. [ABSTRACT FROM AUTHOR]

The current article has identified dual solutions and their stability for the Ti-alloy/water nanofluid over an exponentially shrinking sheet, while taking into consideration the presence of magnetic fields, radiation and thermal buoyancy forces. The Tiwari and Das model has been utilised to formulate mathematical equations, which have subsequently been transformed from partial differential equations to ordinary differential equations using suitable similarity transformations. The transformed equations have been solved using the shooting method incorporated with the Runge–Kutta technique. Through the application of these techniques, it has been ascertained that multiple solutions have emerged for this problem. To assess the stability of these solutions, the eigenvalue approach has been employed. The eigenvalue approach has revealed that only the first solution is physically viable in laboratory settings, while the second solution is not. The effects of radiation on temperature, skin friction, velocity and heat transfer rate have been elaborated upon in detail. Furthermore, flow separation points have been identified and the rationale behind the delay in flow separation has been expounded upon. Streamlined patterns have been drawn and explained to enhance our understanding of the fluid flow behaviour. Finally, it is worth noting that these types of studies have significant applications in the medical and aerospace industries. [ABSTRACT FROM AUTHOR]

Upwelling along the western boundary of the major ocean basin subtropical gyres has been diagnosed in a wide range of ocean models and state estimates. This vertical transport is O(5 × 106) m3 s−1, which is on the same order of magnitude as the downward Ekman pumping across the subtropical gyres and zonally integrated meridional overturning circulation. Two approaches are used here to understand the reason for this upwelling and how it depends on oceanic parameters. First, a kinematic model that imposes a density gradient along the western boundary demonstrates that there must be upwelling with a maximum vertical transport at middepths in order to maintain geostrophic balance in the western boundary current. The second approach considers the vorticity budget near the western boundary in an idealized primitive equation model of the wind- and buoyancy-forced subtropical and subpolar gyres. It is shown that a pressure gradient along the western boundary results in bottom pressure torque that injects vorticity into the fluid. This is balanced on the boundary by lateral viscous fluxes that redistribute this vorticity across the boundary current. The viscous fluxes in the interior are balanced primarily by the vertical stretching of planetary vorticity, giving rise to upwelling within the boundary current. This process is found to be nearly adiabatic. Nonlinear terms and advection of planetary vorticity are also important locally but are not the ultimate drivers of the upwelling. Additional numerical model calculations demonstrate that the upwelling is a nonlocal consequence of buoyancy loss at high latitudes and thus represents an integral component of the meridional overturning circulation in depth space but not in density space. Significance Statement: The purpose of this study is to better understand what is forcing water to upwell along the western boundary at midlatitudes of the major ocean basins. This is a potentially important process since upwelling can bring heat and nutrients closer to the surface, where they can be exchanged with the atmosphere. Also, since ocean currents vary with depth, pathways followed in the upper ocean are different from those found for the deeper ocean, so the amount and location of upwelling influence where these waters go. Idealized numerical models and theory are used to demonstrate that the upwelling is ultimately driven by density changes along the western boundary of the basin that result from heat loss at high latitudes. [ABSTRACT FROM AUTHOR]

We investigate the mechanism for eye formation in hurricane-like vortices, using a formulation adapted from Oruba, Davidson, and Dormy. Numerical simulations are performed using an axisymmetric model of dry rotating Rayleigh–Bénard convection under the Boussinesq approximation. The fluxes of heat and momentum at the sea surface are described using the bulk aerodynamic formula. A simplified model for radiative cooling is also implemented. We find that the mechanism for eye formation introduced in Oruba et al., relying on vorticity stripping from the boundary layer, is robust in dry hurricane-like vortices. Furthermore, with these boundary conditions, the structure of the flow is closer to the flow of actual tropical cyclones. The applicability of this mechanism to the moist case however remains uncertain and deserves further study. Finally, energy budgets, obtained either by a heat engine approach or by a direct estimation of the work of buoyancy forces, are investigated. They provide estimations of the surface wind speed as a function of the controlling parameters. Significance Statement: Tropical cyclones (also known as hurricanes or typhoons, depending on their location) are life-threatening and devastating atmospheric vortices. Their impact worsens with sea level rise and increasing coastal population. Here, we explore, using idealized models, the physics behind the formation of an eye (the quiet and typically clear region at the center of these storms). We then investigate the controlling parameters for the amplitude of the strongest winds in the model, using energy constraints, and compare them to what is observed in actual tropical cyclones. [ABSTRACT FROM AUTHOR]

The present study focuses on the MHD Radiative Casson fluid flow with the effect of triple diffusivity over a vertical porous wall along with convective boundary conditions. The governing equations for detecting the nature of the fluid under the influence of solutal diffusivity and thermal conductivity in triple diffusive boundary layer flow are derived. Non-linear partial differential equations are reduced to ordinary differential equations via similarity transformation. The BVP4C method in MATLAB software is then used to solve them. The outcomes of several physical dimensionless parameters like permeability, convective parameter, buoyancy ratio parameter, Casson parameter and chemical reaction parameter with source/sink impacts established by graphics. Also, the impression of the local skin friction coefficient, Nusselt number, and local Sherwood number are presented through the tables. [ABSTRACT FROM AUTHOR]

This study considers in depth the flow of the boundary layer of an incompressible, viscous, and steady Casson fluid through an expanding surface when thermal radiation, heat source, Soret, and Dufour effects are present. Using suitable similarity transformations, the governing non-linear partial differential equations are converted into coupled ordinary differential equations and then estimated using the MATLAB software bvp4c using a shooting process. Variable values of the parameters employed in the current inquiry are offered, together with solutions for the parameters of momentum, temperature, concentration, coefficient of local skin friction, and local Nusselt number. It is observed that the Casson fluid parameter improves fluid velocity and decreases the temperature. Also, it is found that thermal radiation and the presence of a heat source/sink increase the temperature of the fluid. We compared the present investigation with previously published papers and found them harmonious. [ABSTRACT FROM AUTHOR]

We explore the stability of floating objects at a two-fluid interface through mathematical modeling and experimentation. Our models are based on standard ideas of center of gravity, center of buoyancy, and Archimedes' Principle extended to the two-fluid scenario. We investigate floating shapes with uniform, two-dimensional cross sections and identify analytically and/or computationally a potential energy landscape that helps identify stable and unstable floating orientations. We compare our analyses and computations to experiments on floating objects designed and created through 3D printing. Additionally, the paper includes open problems for further study. [ABSTRACT FROM AUTHOR]

We consider the new boundary value problem for the generalized Boussinesq model of heat transfer under the inhomogeneous Dirichlet boundary condition for the velocity and under mixed boundary conditions for the temperature. It is assumed that the viscosity, thermal conductivity and buoyancy force in the model equations, as well as the heat exchange boundary coefficient, depend on the temperature. The mathematical apparatus for studying the inhomogeneous boundary value problem under study based on the variational method is being developed. Using this apparatus, we prove the main theorem on the global existence of a weak solution of the mentioned boundary value problem and establish sufficient conditions for the problem data ensuring the local uniqueness of the weak solution that has the additional property of smoothness with respect to temperature. This article is part of the theme issue 'Non-smooth variational problems with applications in mechanics'. [ABSTRACT FROM AUTHOR]

Ocean color satellites require a procedure known as System Vicarious Calibration (SVC) after launch as the pre-launch and on-orbit calibration accuracy is insufficient. The current approach for determination of post-launch SVC uses a single fixed measurement location and may be susceptible to unexpected biases in satellite processing algorithms. Here we describe a novel SVC program which is based on a high resolution and high accuracy radiometric system integrated with an autonomous profiling float (providing a buoyancy engine, physical observations, and communication). This float + radiometer (HyperNav) system can be shipped via air, land, ocean and is deployable from small boats. This SVC program relies on multiple deployment sites with associated facilities to collect a significant amount of SVC quality data in a relatively short time. It has centralized logistics and command-and-control centers ensuring easy access to information regarding the status of each asset and to ensure floats stay within a certain ocean area. The development of the program has been associated with the launch of NASA's PACE satellite and has been executed by academic institutions in collaboration with an industrial partner. Other approaches for a future float-based operational SVC program are discussed. [ABSTRACT FROM AUTHOR]

Ocean waves have the potential to contribute to future renewable electricity production. A wave energy converter (WEC) is a technology developed to absorb the energy of the wave and convert it to another form of energy. The Uppsala University WEC (UU WEC) is a point absorber with a direct drive permanent magnet synchronous linear generator power take off. Among other parameters affecting the value of absorbed power for UU WEC are the buoy size, mass of the system consisting of the buoy and translator, and available wave energy at the site of interest. This study reviews the earlier static model that considered only static forces as the buoyancy and gravity forces and neglected all dynamic forces. The static model was proposed to simplify the early‐stage design decision. Although the static model was applied to two UU WECs of different dimensions, the present study shows that the static model is not held for certain buoy and translator dimensions. As an alternative, the dynamic model which accounts for the impact of hydrodynamic forces and various translator masses is proposed. The dynamic model is based on Cummins' equation and the linear potential flow theory, and the damping force is approximated as a viscous damper with the constant damping coefficient optimizing the absorbed mechanical power under a particular sea condition. The dynamic model is applied to four fixed buoy geometries of two shapes (cylinder and cylinder with a moonpool), each of two different dimensions, but the method can be extended to other buoy shapes and dimensions. In addition, the impact of translator mass was assessed for two sites located on the west coast of Sweden and near Gran Canaria, Spain. A translator of 10–11 t promotes 16.8% higher annual average power absorption for a cylindrical buoy compared to a translator of 6 t for the same buoy. However, heavier translators up to 15 t provide only 1.1% increase in average annual absorbed power. [ABSTRACT FROM AUTHOR]

Polymer matrix solid buoyancy materials (PSBMs) have the advantages of low density, high strength, low cost, and low water absorption, and they are widely used in marine engineering fields. How to improve the performance of PSBMs further and adapt them to harsh marine environments has become a hot topic in current research. This paper provides a comprehensive summary of PSBM, detailing both the preparation methodologies and properties of single-component and multi-component PSBM. In this paper, relevant research is systematically summarized from two dimensions of matrix and filler, and the application of thermosetting resin and thermoplastic resin as a matrix in PSBM is introduced in detail, and the corresponding research on fillers such as hollow glass microspheres, fly ash, hollow ceramic spheres and hollow polymer microspheres are expounded. This paper aims to summarize the latest advancements in PSBM research, thereby providing insights into the current state of the field and guiding future investigations. [ABSTRACT FROM AUTHOR]

The major aim of this work is to analyze the thermophysical properties of hybrid nanoliquid inside a square lid driven enclosure under the effect of applied magnetic field and mixed convection. The Hybrid nanofluid is considered a suspension of Iron-oxide (Fe3O4) and Copper (Cu) nanoparticles into water. The cavity walls have varying properties such as top adiabatic wall is moving continuously while the lower wall is maintained at a high constant temperature, in addition, the vertical walls are kept at a low fixed temperature. The magnetic field is applied to the right vertical wall in a horizontal direction. Additionally, the effects of buoyancy forces caused by temperature gradients and shear forces caused by continuous lid motion are considered. The mathematical modelling of problem with all assumptions yields the nonlinear partial differential system. First this system is transferred into non-dimensional form and then transformed system is solved by using Galerkin finite element method (GFEM) along with Gaussian elimination method. Results for isotherms, streamlines and average Nusselt number are obtained versus Richardson number (0.1 ≤ Ri ≤ 15), Grashof number (10 ≤ Gr ≤ 10000), Hartmann number (0 ≤ Ha ≤ 100), volume fractions of solid nanoparticles (0.005 ≤ ϕ1 ≤ 0.02) and (0.005 ≤ ϕ2 ≤ 0.02). It is observed that the Richardson number and Grashof number have significant impacts on both flow velocity and temperature. In addition, concentration of hybrid nanoparticles improves the heat transfer performance. The obtained results may be crucial for thermal management in the cooling of electronics, heat exchangers, solar thermal collectors, industrial operations, medical equipment, HVAC systems, food processing, and renewable energy systems. [ABSTRACT FROM AUTHOR]

There are several uses for bio-convection mechanisms, such as in sedimentary pools, fuel models, and microbially accelerated oil restoration. These are the basis of motile microorganisms which are applied to improve the mixability of fluid and tiny nanoparticles because they are accountable for biological transmission procedure. This work examines the bio-convective nanoparticles fluid flow and electrically conducting incompressible magneto-hydrodynamic flow of nanofluid towards a chemically reactive stretchable surface. Buongiorno model is considered here, which incorporates Brownian motion and thermophoretic diffusion, is employed in this study to explain how nanofluids improve heat transfer. The controlling boundary layer nonlinear PDEs are converted into ODEs by utilizing certain suitable similarity approaches. Numerical scheme is adopted to solve the transformed ordinary differential equations. The main findings of this research are that the magnetic field slows motion of the fluid when the thermal and mass buoyancy forces speed it up, and that thermophoretic diffusion increases the temperature and concentration of dimensionless fluids, resulting in stronger concentration and thermal boundary layers. The Brownian motion, concentration exponent, and chemical reaction parameters show an inverse relationship between temperature and concentration. Additionally, the first-order chemical reaction creates a lighter concentration boundary layer while the magnetic field's presence due to impact of thermal and mass buoyancies helps to lower the heat transfer rate and shear stress. The findings show that while the Nusselt number and wall shear stress values are declining, the microorganism number is increasing. [ABSTRACT FROM AUTHOR]

Foraging efficiency is key to animal fitness. Consequently, animals evolved a variety of kinematic, morphological, physiological, and behavioral adaptations for efficient locomotion to reduce energy expenditure while moving to find, capture, and consume prey. Often suited to specific habitat and prey types, these adaptations correspond to the terrain or substrate the animal moves through. In aquatic systems, adaptations focus on overcoming drag, buoyancy, and hydrostatic forces. Buoyancy both benefits and hinders diving animals; in particular, shallow divers constantly contend with the costs of overcoming buoyancy to dive and maintain position. Pacific Coast Feeding Group (PCFG) gray whales forage in shallow habitats where they work against buoyancy to dive and feed using various foraging tactics. Bubble blasts (underwater exhalations) have been observed during several foraging tactics performed by PCFG whales. As exhalations aid buoyancy regulation in other diving animals, we hypothesize that bubble blasts are performed by longer, more buoyant whales in shallower water and that bubble blasts increase dive duration while accounting for size and tactic. We test our hypotheses using Bayesian linear mixed effects models and a 7‐year dataset of drone footage containing concurrent individual morphological and behavioral data. We find that while headstanding – a stationary, head‐down tactic – bubble blasts are performed by longer, more buoyant whales and extend the dive duration, whereas whales using forward‐swimming tactics are less likely to bubble blast. Our results suggest that PCFG gray whales may use bubble blasts as a behavioral adaption to mitigate the cost of energetically expensive tactics in their shallow habitat foraging niche. [ABSTRACT FROM AUTHOR]

Innovative analytical instruments and development of new methods has provided a better understanding of protein particle formation in biopharmaceuticals but have also challenged the ability to obtain reproducible and reliable measurements. The need for protein-like particle standards mimicking the irregular shape, translucent nature and near-to-neutral buoyancy of protein particles remained one of the hot topics in the field of particle detection and characterization in biopharmaceutical formulations. An innovative protein-like particle model has been developed using two photo polymerization (2PP) printing allowing to fabricate irregularly shaped particles with similar properties as protein particles at precise size of 50 µm and 150 µm, representative of subvisible particles and visible particles, respectively. A study was conducted to compare the morphological, physical, and optical properties of artificially generated protein particles, polystyrene spheres, ETFE, and SU-8 particle standards, along with newly developed protein-like model particles manufactured using 2PP printing. Our results suggest that 2PP printing can be used to produce protein-like particle standards that might facilitate harmonization and standardization of subvisible and visible protein particle characterization across laboratories and organizations. [ABSTRACT FROM AUTHOR]

The flow of ethylene glycol-based titania nanoliquid passing through a vertical plate induced by significant buoyancy forces (nonlinear convection) is analyzed with quadratic thermal radiation and considering the aggregation kinematics of the nanoparticles. The nanoliquid is modeled accounting for thermo-migration, Brownian motion, and the effectual thermophysical properties. The realistic zero mass flux and thermal slip conditions are considered on the surface of the plate. In addition, the mechanisms of exponential space-related heat source (ESHS) and thermal-based heat source (THS) are incorporated. The finite-difference technique-based bvp5c routine is used to obtain the numerical solution of thenonlinear system of equations. The effects of the parameters are examined on the dimensionless profiles of velocity, temperature, heat transport rate, the volume fraction of nanoparticles, and streamlines. It was found that the aggregation of nanoparticles significantly advances the temperature field while the velocity field is reduced. The ESHS and THS modulations improve the thickness of the thermal boundary layer. The quadratic thermal convection aspect improves the velocity of nanoliquid. Furthermore, the effects of quadratic thermal radiation assist the growth of the thermal boundary layer. The present results are relevant to various thermal systems including flat plate solar collectors, heat exchangers, and nuclear reactors. [ABSTRACT FROM AUTHOR]

A low-cost, efficient and accurate structure from motion (SfM) photogrammetry is used to reconstruct the complex morphologies of unevenly deforming hydrogels during the drying process. The primary setups comprise a camera and rotary platform, which are low-cost and works stably for most drying conditions. The dynamic three-dimensional (3D) reconstruction of cylindrical hydrogel samples is achieved by SfM through the generation of point clouds, and the 3D morphologies are calculated by a Poisson reconstruction algorithm based on these point clouds. The accuracy of SfM in quantitatively measuring large-scale deformation is validated, and its applications in drying studies are explored. The results show that as drying proceeds, the maximum measurement deviation of the hydrogel volume between SfM and the traditional buoyancy force method is 1.93% at a volume shrinkage of 69%, confirming the accuracy of the current method for measuring large-scale drying shrinkage. Based on SfM, the temporal evolution of the cross section of the hydrogel is obtained. Comparing to conventional drying experiments that assess the dryness of deformed materials based on overall moisture content changes, SfM enables the evaluation of localized complete drying by quantitative analysis of deformation parameter variations. [ABSTRACT FROM AUTHOR]

'A lack of prior knowledge in the other discipline' is often given by geoscience instructors to explain why students struggle to apply knowledge from other disciplines to the Earth. We examine this assumption by considering the disciplinary crossing of buoyancy (physics) to isostasy (geoscience). We investigate the teachers' perspective through workshops, and use the theoretical framework of Interdisciplinary Reasoning and Communication to explore what geoscience textbooks ask of students. Most introductory textbooks rely on students applying pre-existing knowledge of hydrostatics in a geoscience context (forwards transfer), while intermediate and advanced textbooks develop the necessary physics explicitly in a geoscientific context (backwards transfer). Moreover, introductory textbooks frequently use analogies for concrete translation between physics and geoscience ideas, but the analogical relations and where they break down (relational translations), receive little attention. This places high demands on students' prior understanding of hydrostatics to successfully integrate and transfer knowledge from physics to geoscience. If students lack the relevant physics background, introductory textbooks may force them to rely on intuitive ideas of physics, potentially reinforcing old, and giving rise to new misconceptions. Our results move the focus from perceived shortcomings of students to the demands made on them in interdisciplinary learning. [ABSTRACT FROM AUTHOR]

We present experimental findings of Rayleigh–Taylor (RT) instability within porous materials, with a significant viscosity contrast of M ≈ 106, where M represents the ratio of the dynamic viscosity of heavy fluid to that of light fluid, M = μH/μL, and Ra = 6.62 × 104–6.67 × 105, and Rayleigh number (Ra) quantifies the relative significance of buoyancy forces compared to viscous forces. We observe that the lighter fluid diffuses into the denser one, creating a transient diffusive boundary layer that rapidly becomes unstable, transitioning into a convection-dominated regime. Initially, the instability manifests as small fingers protruding upward. However, these fingers coalesce and form fewer major fingers. Convection persists until fingers reach the upper boundary, transitioning into a shutdown regime. During the convection-dominated phase, the extracted solute concentration exhibits a linear relationship with time on a log –log scale, suggesting a constant mass flux. However, this flux diminishes upon entering the shutdown regime. The steady flux, quantified by the Sherwood number, correlates with the Rayleigh number as Sh = 0.046Ra, indicating independence from the height of the porous medium. We have also developed a simple conceptual model that effectively captures the dynamics of RT mixing. [ABSTRACT FROM AUTHOR]

Fire hazard is a crucial issue in urban arears. Fire plumes have large buoyancy forces and can significantly change the flow pattern around buildings. However, the interaction of these plumes with buildings under atmospheric boundary flow conditions has rarely been studied, and the effect on the wake characteristics of the buildings remains unclear. To investigate the interaction of fire with the wake flow around a building, the large-eddy simulation framework is used to simulate the flow and wake structures of an idealized cubic building. Fire is found to produce significant changes in the wake structures. In particular, fire leads to strong fire-swirl vortices near the trailing edges of the building and intense fire-plume vortices in the midair region downstream of the building. In the time-averaged results, a pair of tip vortices appears behind the top corners of the building and counter-rotating vortex pairs are observed downstream. [ABSTRACT FROM AUTHOR]

Ball-throwing temporary plugging fracturing is a new technology for achieving uniform-length fracture in a horizontal well. The migration and seating law of a temporary plugging ball (TPB) in the horizontal well is still not clear. Based on the computational fluid dynamics-discrete phase model coupling method, a three-cluster spiral perforated borehole model is established to analyze the effects of the density, diameter, and number of TPB, fracturing fluid injection rate, and viscosity on the migration and seating behaviors of TPB. The results show that the buoyancy ball and the gravity ball have better sealing effects on cluster 3, which is near the borehole heel, and cluster 1, which is near the borehole toe, respectively. When the diameter of TPB is 1–1.3 times the perforation diameter, the overall plugging effect is better. When the number of TPB is 5/6 times the total number of perforations, the plugging effect at cluster 3 and cluster 1 is better. When the injection rate of fracturing fluid ranges from 0.5 to 2.5 m3/min, the plugging efficiency at cluster 3 is higher with a low injection rate. When the viscosity of the fracturing fluid is 20–30 mPa s, cluster 3 and cluster 1 have better plugging effect. [ABSTRACT FROM AUTHOR]

In this work, we experimentally studied bubble formation on the superhydrophobic surface (SHS) under a constant gas flow rate and at quasi-static regime. SHS with a radius RSHS ranging from 4.2 to 19.0 mm was used. We observed two bubbling modes A and B, depending on RSHS. In mode A for small RSHS, contact line fixed at the rim of SHS, and contact angle (θ) initially reduced, then maintained as a constant, and finally increased. In mode B for large RSHS, contact line continuously expanded, and θ slowly reduced. For both modes, during necking, contact line retracts, and θ was close to the equilibrium contact angle. Moreover, the pinch-off of bubble at the early stage was similar to the pinch-off of bubble from a nozzle and followed a power-law relation Rneck ∼ τ0.54, where Rneck is the minimum neck radius and τ is the time to detaching. Furthermore, we calculated the forces acting on the bubble and found a balance between one lifting force (pressure force) and two retaining forces (surface tension force and buoyancy force). Last, we found a waiting time for a finite volume to be detected for large RSHS. The detached volume was well predicted by Tate volume, which was derived based on balance between buoyancy and surface tension and was a function of bubble base radius. [ABSTRACT FROM AUTHOR]

We computationally study the effects of inner cylinder rotation on the laminar displacement flow of two Newtonian fluids along a horizontal eccentric annulus. This flow arises in primary cementing operations in the oil and gas industry, used to seal wells and prevent leakage. We investigate how the rotational motion of the inner cylinder influences the displacement, affecting the interplay of viscosity and density differences, as well as eccentricity. We first simulate a series of experiments recently performed, in order to validate the computational approach. We then study the effects of the rotating inner cylinder in more detail. The rotation shears the fluid in the narrow annular gap and also drags fluid around the annulus, typically resulting in helical streamlines and a spiral pattern of the concentration. Over short timescales, the rotation tends to increase dispersion, but the redistribution of the fluids around the annulus can then improve the overall displacement, i.e., reducing slumping effects due to buoyancy. We also observe a new patterning instability at the inner cylinder, which was not visible in the previous experiments. This instability arises from destabilization of the wall film of displaced fluid, which forms naturally on the walls of the annular gap. We have studied the dimensional parameter space where this instability occurs. Strong buoyancy can suppress the instability, and a threshold value of dimensionless rotation velocity is required for onset of the instability. [ABSTRACT FROM AUTHOR]

This study investigates the dynamics of heat and mass transfer, focusing on the impact of nonlinear convection and thermophoresis in the flow of viscous nanofluid towards a shrinking sheet embedded with a porous matrix. To facilitate understanding of the flow behavior, the study employs similarity variables to simplify the resulting nonlinear partial differential equations. Numerical analysis utilizing the collocation method with Legendre polynomials as basis functions reveals distinct distributions of velocity, temperature, and concentration. The results demonstrate that the dimensionless suction coefficient amplifies nanoparticle volume fraction and momentum along the stretching surface. In addition, an increase in internal frictional force leads to heightened injection of heat energy, accelerates the temperature field, and impedes nanoparticle diffusion due to heat absorption. Elevation of convection terms augments momentum, reduces energy dispersion, and enhances nanoparticle diffusion. Moreover, an increase in the dimensionless Eckert number (Ec) correlates with intensified energy and diminished diffusion concentration of the nanoparticle volume fraction [ABSTRACT FROM AUTHOR]

Several barriers hinder students from producing clear and impactful written work. Writing assignments are often given on an individual basis, similar to homework, and without any assistance. Students in a classroom context have access to both their classmates and the teacher while they are working in groups or pairs as part of their assignments. The majority of students, however, are clueless about how to begin their homework assignments. The introduction of artificial intelligence in education may help solve this problem. The current research intended to demonstrate the effects of employing automated writing evaluation (AWE) in fostering learners’ writing skills, motivation to write, enjoyment of writing, and academic buoyancy in open and distributed English as a foreign language (EFL) learning. The participants were 86 intermediate EFL students from China. The participants in the experimental group (n = 44) received instruction and feedback from their teachers only; participants in the control group (n = 42) were exposed to their teachers’ instruction as well as AWE. The results of data analysis via one-way multivariate analysis of variance indicated that the participants in the experimental group outperformed their peers in the control group in motivation to write, enjoyment in writing, academic buoyancy, and academic success in writing. Further in-depth discussions proceed regarding the implications of the study. [ABSTRACT FROM AUTHOR]

To understand the stratification of the smoke layer in a road tunnel, numerical simulations are employed to model tunnel fires with varying heat release rates. The different simulations cases are carried out with FDS (Fire dynamic simulations). These simulations are conducted to examine the influence of tunnel slope and longitudinal airflow on the smoke stratification along the downstream side of tunnel. The aim is to explore the relationship between longitudinal airflow and temperature ratio taking into account the tunnel slope. As a result, a quantitative analysis, based on Newman's theory, is conducted to assess the clarity of the smoke layer stratification, a Froude number (Fr = 0.63) is obtained. The slopes in tunnels can have a substantial impact on smoke flow during a fire, primarily driven by thermal buoyancy and the stack effect. With a slope less than 1.5°, the stratification improves. Similarly, clear stratification occurs when the longitudinal airflow is less than 1 m/s. However, a balance between inertia force and buoyancy force is crucial for maintaining clear stratification. Increasing both the longitudinal airflow and the tunnel slope serves to disturb the stratification of the smoke layer. [ABSTRACT FROM AUTHOR]

Recent research has unveiled the critical roles of self-efficacy and buoyancy in teachers' work engagement. However, there has been limited research on the intricate links between teacher self-efficacy, buoyancy and engagement in the online English as a foreign language (EFL) teaching context. To address the underexplored relationships among these variables, the current study adopted a quantitative approach to verify the direct and indirect paths from online EFL teacher self-efficacy to engagement via the mediating effect of teacher buoyancy. We invited 978 Chinese high school EFL teachers to take part in the current study and answer questions about their self-efficacy, buoyancy and work engagement. The results of the structural equation modelling indicate that teacher self-efficacy could directly and indirectly predict online EFL teacher work engagement via the mediation of teacher buoyancy. The results of this study shed light on ways of improving EFL teachers' online teaching experience and educational outcomes. [ABSTRACT FROM AUTHOR]

It observers that an object is submerged in a liquid, more pressure is applied to its bottom surface than its top surface, as a result pressure rises within depth of fluids. A buoyancy force is generated due to the pressure difference. In the current investigation, the mathematical formulation of bio-convective stagnation point flow of a radiative Maxwell fluid with multiple slip effect on an exponentially porous stretching surface is analyzed thoroughly. The buoyancy assisting and opposing conditions with magnetic field are discussed in the current investigation. Moreover, the energy and concertation equations are formulated by the utilization of Cattaneo–Christov theory and non-uniform heat source/sink. The flow model is developed in the form of partial derivatives, then use the similarity variables to convert the physical system into nonlinear ordinary derivative. The nonlinear system is tackled numerically with the help of Bvp4c approach on the MATLAB. The graphical upshots for various emerging parameter are observed with two aspects: buoyancy assisting λ > 0 and buoyancy opposing λ < 0 . The observation shows that the greater values of mixed convection parameter improves the fluid velocity for assisting flow λ > 0 , while declining trend is noticing for opposing flow situation λ > 0 . Further, it is worth noticing that stronger inputs of thermal and concentration relaxation parameter yield lesser thermal and concentration diffusivity, which reduces the temperature and nanoparticles concentration. [ABSTRACT FROM AUTHOR]

Direct numerical simulation (DNS) has been employed with success in a variety of oceanographic applications, particularly for investigating the internal dynamics of Kelvin–Helmholtz (KH) billows. However, it is difficult to relate these results directly with observations of ocean turbulence due to the significant scale differences involved (ocean shear layers are typically on the order of tens to hundreds of meters in thickness, compared to DNS studies, with layers on the order of one to tens of centimeters). As efforts continue to inform our understanding of geophysical-scale turbulence by extrapolating DNS results, it is important to understand the impact of model setup and initial conditions on the resulting turbulent quantities. Given that geophysical-scale measurements, whether through microstructures or other techniques, can only provide estimates of averaged TKE quantities (e.g., TKE dissipation or buoyancy flux), it may be necessary to compare mean turbulent quantities derived from DNS (i.e., across one or more complete billow evolutions) with ocean measurements. In this study, we analyze the effect of domain length and initial velocity noise on resulting turbulent quantities. Domain length is important, as dimensions that are not integer multiples of the natural KH billow wavelength may compress or stretch the billows and impact their energetics. The addition of random noise in the initial velocity field is often used to trigger turbulence and suppress secondary instabilities; however, the impact of noise on the resulting turbulent energetics is largely unknown. In this study, we conclude that domain lengths on the order of 1.5 times the natural wavelength or less can affect the resulting turbulent energetics by a factor of two or more. We also conclude that increasing the amplitude of random initial velocity noise decreases the resulting turbulent energetics, but that different realizations of the random noise field may have an even greater impact than amplitude. These results should be considered when designing a DNS experiment. [ABSTRACT FROM AUTHOR]

As an component of hydrogen energy utilization, hydrogen‐refueling stations require considerable attention regarding their safety. In this study, the influence of wind conditions is analyzed, specifically no wind and 10 m s−1 wind speed, on hydrogen diffusion characteristics following a 70 MPa hydrogen‐filling machine leakage. In the results, it is suggested that, during the initial stage of leakage, hydrogen exists in the form of an under‐expanded jet, later transitioning to diffusion dominated by buoyancy and wind conditions after moving upward for a certain distance. When there is no wind, hydrogen is significantly affected by buoyancy and obstacles, which leads to the formation of flammable clouds. In windy conditions, the volume fraction of hydrogen in the station is smaller than that in the no‐wind condition at the same leakage time, but the flammable clouds still predominantly distribute in the direction of the hydrogen jet. In this study, risk mitigation measures based on the distribution of flammable clouds are proposed. In the results, it is shown that after implementing these measures, the volume of flammable clouds is reduced from0.135 to 0.014 m3, manifesting the effectiveness of risk mitigation measures and minimizing the risk of hydrogen explosion. [ABSTRACT FROM AUTHOR]

School burnout, defined as prolonged feelings of exhaustion, cynical attitude and inadequacy feelings towards schoolwork, can lead to mental problems during adolescence. To find effective ways to prevent burnout, this study examined the synergistic role of two positive personal resources, a stress-is-enhancing mindset and academic buoyancy in relation to school burnout dimensions. The participants were 932 Finnish middle-school 9th-grade (age = 14–15) students. The results of SEM revealed that academic buoyancy and stress-is-enhancing mindset were jointly negatively related to one dimension of school burnout, cynicism. However, the stress-is-enhancing mindset had an indirect effect on all dimensions (exhaustion, inadequacy and cynicism) via academic buoyancy. The findings highlight their joint effect and especially the role of academic buoyancy in relation to school burnout. The implications of the results to burnout prevention and stress theories are discussed. [ABSTRACT FROM AUTHOR]

The existence of temperature gradients within eukaryotic cells has been postulated as a source of natural convection in the cytoplasm, i.e. bulk fluid motion as a result of temperature-difference-induced density gradients. Recent computations have predicted that a temperature differential of ΔT ≈ 1 K between the cell nucleus and the cell membrane could be strong enough to drive significant intracellular material transport. We use numerical computations and theoretical calculations to revisit this problem in order to further understand the impact of temperature gradients on flow generation and advective transport within cells. Surprisingly, our computations yield flows that are an order of magnitude weaker than those obtained previously for the same relative size and position of the nucleus with respect to the cell membrane. To understand this discrepancy, we develop a semi-analytical solution of the convective flow inside a model cell using a bi-spherical coordinate framework, for the case of an axisymmetric cell geometry (i.e. when the displacement of the nucleus from the cell centre is aligned with gravity). We also calculate exact solutions for the flow when the nucleus is located concentrically inside the cell. The results from both theoretical analyses agree with our numerical results, thus providing a robust estimate of the strength of cytoplasmic natural convection and demonstrating that these are much weaker than previously predicted. Finally, we investigate the ability of the aforementioned flows to redistribute solute within a cell. Our calculations reveal that, in all but unrealistic cases, cytoplasmic convection has a negligible contribution toward enhancing the diffusion-dominated mass transfer of cellular material. [ABSTRACT FROM AUTHOR]

Low-mass planets migrating inwards in laminar protoplanetary discs (PPDs) experience a dynamical corotation torque (DCT), which is expected to slow down migration to a stall. However, baroclinic effects can reduce or even reverse this effect, leading to rapid inward migration. In the radiatively inefficient inner disc, one such mechanism is the buoyancy response of the disc to an embedded planet. Recent work has suggested that radiative cooling can quench this response, but for parameters that are not necessarily representative of the inner regions of PPDs. We perform global 3D inviscid radiation hydrodynamics simulations of planet–disc interaction to investigate the effect of radiative cooling on the buoyancy-driven torque in a more realistic disc model. We find that the buoyancy response exerts a negative DCT – albeit partially damped due to radiative cooling – resulting in sustained, rapid inward migration. Models that adopt a local cooling prescription significantly overestimate the impact of the buoyancy response, highlighting the importance of a realistic treatment of radiation transport that includes radiative diffusion. Our results suggest that low-mass planets should migrate inwards faster than has been previously expected in radiative discs, with implications for the formation and orbital distribution of super-Earths and sub-Neptunes at intermediate distances from their host stars, unless additional physical processes that can slow down migration are considered. [ABSTRACT FROM AUTHOR]

Thermal stratification improves coaxial pipe systems’ efficiency and stability. Thermal stratification enables accurate temperature maintenance, reduces thermal stress, optimizes heat transmission performance, and minimizes usage of energy to guarantee the system's long‐term performance. The main aim of the current study is to investigate the impacts of thermal stratification on buoyancy force flow and thermal transmission between coaxial fixed pipes. In the present research, the applications of thermally stratified medium on transient convective heat transfer between two coaxial fixed pipes are studied. A two‐dimensional mathematical formulation in terms of mutually nonlinear partial differential equations is used to analyze the unsteady flow and temperature field between the co‐axial pipes, when the internal pipe is uniformly heated and the outer wall of the external pipe is placed at infinity from the surface of the inner fixed pipe. Flow is assumed along the axial direction of the internal pipe and stationary boundary condition is assumed at the surface of the inner pipe. The coupled equations of the simulated model are solved numerically by applying the Implicit Finite Difference Technique. The computed outcomes in the form of geometrical interpretation are highlighted by using the technically advanced software TECHPLOT‐360. Comprehensive detail of the obtained results for the non‐dimensional parameters included in the flow formulation is predicted for steady state velocity, temperature distribution, time‐dependent surface shearness and time‐dependent energy shearness in results and discussion section of the manuscript. The emphasis is placed on the thermal stratification parameter in the above mentioned chief quantities. From the obtained results, it is predicted that the fluid flow pattern and thermal distribution are both reduced for rising values of the thermal stratification parameter S = 0.001, 0.03, 0.05, and 0.07. Minimum flow and thermal profile are observed at S = 0.07. Further, the amplitude of the time‐dependent surface shearness is uniformly distributed throughout the medium and the amplitude of the time‐dependent energy shearness is reduced effectively for S = 1.0, 5.0, and 10.0. [ABSTRACT FROM AUTHOR]

The work numerically investigated laminar natural convection heat transfer from the single sphere with a constant heat flux surface in air over the wide range of Grashof number ( 10 ≤ G r ≤ 10 7 ). The more efficient and precise numerical method based on Bejan et al. was employed here, the accuracy of which has been confirmed through validation against a single sphere case. The heat transfer characteristics were systemically analyzed in terms of isothermal contours and streamlines around the sphere, dimensionless temperature and velocity profiles. Additionally, local Nusselt number as well as local pressure and friction drag coefficients were studied with different Grashof number. In comparison to the sphere with uniform heat flux surface, the heat transfer from the isothermal sphere was found to be enhanced attributable to a more robust buoyancy force and a steeper temperature gradient. Moreover, the average Nusselt number for the sphere with a constant heat flux between 60.4 and 98.6% of the isothermal sphere's value, this range being contingent upon the specific Grashof number. What's more, the proposed correlation addresses a notable void in the predictive understanding of heat transfer from the sphere with uniform heat flux, which is scenario prevalent in various engineering applications, particularly for the cooling of electrical and nuclear systems, and offer values for academic research. [ABSTRACT FROM AUTHOR]

Interfacial floater possessing an open surface diversifies the functions of current systems in the field of solar evaporation, micro‐detector, multiphase catalysis, etc. However, most of the current floaters still face challenges such as the anti‐submersion, orientation adjusting, and multifunctional capabilities. Drawing inspiration from water striders and diving bell spiders, here a superhydrophobic cellular origami (SCO) is proposed with reliable stability, submerge resistance, switchable floatability, and multifunctional integration. The remarkable floating ability is achieved through the air storage ability of superhydrophobic air cells. SCO floats stably on the water surface and has a maximum load capacity that is 48% higher than the superhydrophobic sheet. Besides, SCO can resurface rapidly after complete submersion, even using titanium metal as substrate. To further enhance the universality of SCO, the Janus SCO with unbalanced structure can float with a specific orientation facing up and the origami structure is optimized to be switchable with hinge structure for adjustable buoyancy. To prove the concept in 3D structure, a cylindrical SCO is presented for cable locating on the water surface. This study presents an achievable strategy to extend superhydrophobic surfaces into anti‐sinking floaters, offering valuable insights into the development of multifunctional interface carriers. [ABSTRACT FROM AUTHOR]

Sharp structural variations induce specific signatures on stellar pulsations that can be studied to infer localised information on the stratification of the star. This information is key to improve our understanding of the physical processes that lead to the structural variations and how to model them. Here we revisit and extend the analysis of the signature of different types of buoyancy glitches in gravity-mode and mixed-mode pulsators presented in earlier works, including glitches with step-like, Gaussian-like, and Dirac-δ-like shapes. In particular, we provide analytical expressions for the perturbations to the periods and show that these can be reliably used in place of the expressions provided for the period spacings, with the advantage that the use of the new expressions does not require modes with consecutive radial orders to be observed. Based on a comparison with two limit cases and on simulated data, we further tested the accuracy of the expression for the Gaussian-like glitch signature whose derivation in an earlier work involved a significant approximation. We find that the least reliable glitch parameter inferred from fitting that expression is the amplitude, which can be up to a factor of two larger than the true amplitude, reaching this limit when the glitch is small. We further discuss the impact on the glitch signature of considering a glitch in the inner and outer half of the g-mode cavity, emphasising the break of symmetry that takes place in the case of mixed-mode pulsators. [ABSTRACT FROM AUTHOR]

The Embedded Discrete Fracture Model (EDFM) has emerged as a prominent piece of technology used for embedding the hydraulic behavior of rock joints in reservoir numerical models. This paper critically reviews its fundamentals, the latest developments, and opportunities for further research. The literature is extensive regarding novel algorithms attempting to reach more accurate and computationally effective estimates. While hydraulic fracture models seem suitable for their purposes, their assumptions might be excessively simplistic and unrealistic when assessing naturally fractured reservoirs. The paper begins by examining fractures as physical characteristics and the key mechanisms to be considered when integrating them into numerical flow simulators. The use of the EDFM technique shows promise for simulating capillary continuity and buoyancy effects in multiphase and multicomponent cases. However, there are significant limitations that hinder its widespread field-scale adoption for reservoir performance evaluation. In this regard, the lack of public-domain realistic benchmarks to validate and compare the potential of each method reinforces the difficulties of performing broader applications of the EDFM techniques in large-scale models. [ABSTRACT FROM AUTHOR]

The present research aim is the formulation and invitro evaluation of the floating tablets of Paliperidone with natural polymers. The Paliperidone tablets were prepared by physical direct compression method using guar gum and xanthan gum as natural polymers and Sodium bicarbonates. All the developed formulations were evaluated for physicochemical parameters, buoyancy, drug content, in vitro dissolution, Kinetic models and drug stability studies. The results were obtained within the limits for all formulations. Among all the formulations PF4 showed the better buoyancy and drug release profiles. The release of the drug follows Higuchi's kinetics and it was more stable under various storage conditions. [ABSTRACT FROM AUTHOR]

To enhance the heat-transfer performance of scramjet engines, a numerical simulation was conducted on the heat-transfer process of RP-3 aviation kerosene under supercritical pressure within a horizontal micro-fine circular tube. The intrinsic mechanism of the heat-transfer process was analyzed, summarizing the impacts of mass flux, inlet temperature, and gravitational acceleration. Furthermore, four commonly used buoyancy criterion numbers were compared and evaluated. The results indicate that the heat-transfer process can be divided into five phases: heating inlet phase, normal heat-transfer phase, heat-transfer deterioration phase, heat-transfer enhancement phase, and high-temperature normal heat-transfer phase. The heating inlet phase is significantly influenced by the inlet temperature, while the heat-transfer deterioration is affected both by the thermal property variations of the aviation kerosene and the buoyancy effects. Lower mass flux and hypergravity conditions all exacerbate heat-transfer deterioration. Inlet temperature, however, does not affect the heat-transfer pattern. Among the criteria, Grq/Grth provides the best prediction of buoyancy effects in horizontal circular tubes. [ABSTRACT FROM AUTHOR]

Natural ventilation is the most cost-effective environmental control method for protected horticulture. To overcome the issues associated with high temperatures in greenhouses, analyzing their ventilation characteristics and maximizing their natural ventilation performance are essential. Therefore, in this study, the natural ventilation performance of arched single-span plastic greenhouses with screened side openings was empirically investigated. Three identical single-span plastic greenhouses were used in this study, each with different side-opening heights. Temperature and wind-speed data were collected, and the ventilation-volume flow rate was calculated considering both buoyancy and wind forces. The natural ventilation performance of the greenhouses was strongly and positively correlated with the ventilation-area ratio and outdoor wind speed. The ventilation rate increased linearly with an increase in the ventilation-area ratio and high outdoor wind speeds. However, the association between ventilation performance and indoor–outdoor temperature differences was not strong. When the ratios of ventilation areas in the greenhouse were changed to 0.08, 0.19, and 0.29, the average indoor–outdoor temperature differences were 14.0, 10.1, and 7.7 °C, respectively, and the ventilation rates were 0.0081, 0.0196, and 0.0315 m3 s−1 m−2, respectively. The proportion of wind in the total ventilation performance was high with a low ratio of ventilation openings and high outdoor wind speeds. However, the proportion of the buoyancy was high, with a high ratio of ventilation openings and a large indoor–outdoor temperature difference. Overall, this study provides foundational insights for optimizing the design and evaluation of ventilation openings in greenhouses, considering the outdoor wind speed. [ABSTRACT FROM AUTHOR]

Flow circulation and heat removal through shield and reflector assemblies can have major impacts on safety in long transients for sodium fast reactors (SFRs). These transients are typically categorized by reduced flow rates and large-scale organized flow patterns, including potential intra-assembly circulation. Such low-flow cases can provide challenges for experiments because of complications in measuring the flow rates and temperatures with high accuracy in different areas. This consequently also raises the uncertainty of many modeling approaches for these phenomena. In an effort to address some of these issues, high-fidelity large eddy simulations are performed using the highly parallel solver NekRS. A 19-pin configuration of a tight-lattice wire-wrapped hexagonal bundle (pitch-to-diameter ratio = 1.07), representing a prototypical internal configuration of a shield assembly, was investigated. The sodium flow was set at a bundle Reynolds number of 2000, with simulations being performed for modified Richardson numbers of 0.0 (i.e., no buoyancy), 0.01, and 0.04, where mixed-convection effects are anticipated. The flow and temperature fields for these cases are discussed in detail. The high-fidelity data should prove useful as reference data for expanding and improving on various reduced-resolution approaches. A basic framework for combining subchannel and computational fluid dynamics methodologies in SFRs is also presented, with preliminary results from simulations of light water reactor bundles and a discussion of changes that need to be made for potential application to SFRs. [ABSTRACT FROM AUTHOR]

Stable density stratification in a large enclosure could significantly hamper the effectiveness of natural convection cooling in pool-type liquid metal or gas-cooled advanced reactors. In addition, accurate prediction of stratified front behavior remains to be a challenging task for turbulence modeling. With the rapid growth of high-performance-computing capabilities in recent years, conducting high-fidelity simulations for a large-timescale transient has become more affordable and hence a valuable data source to support turbulence modeling as well as to gain further physical insights. In this work, direct numerical simulation is performed at experiment-consistent conditions to simulate the density stratification transient High-Resolution Jet (HiRJET) facility. Specifically, we focus on the case where an injected aqueous sugar solution has 1.5% density higher than that in the enclosure. In the early stage of the transient, the impingement of the denser jet to the bottom surface of the enclosure promoted turbulent mixing locally. This rendered the establishment of the mixture layer, formation and swift upward propagation of the stratified front, and elevation with (locally) the highest vertical concentration gradient. As the front rose, the diminishing turbulent mass flux slowed down the propagation, and a larger vertical concentration gradient was established. In this stage, both the velocity and the concentration scalar showed large-timescale fluctuation behavior around the stratified front. For the concentration time signal, the characteristic frequency in the power spectral density was found to agree well with the Brunt-Väisällä frequency. The preliminary validation endeavor showed that the stratified front location and the corresponding concentration gradient magnitude in the simulation agreed well with the experiment data. Further validation will mainly revolve around benchmarking against high-resolution density measurement and high-order flow statistics. [ABSTRACT FROM AUTHOR]

Amphibious drone is an Unmanned Aerial Vehicle (UAV) capable of performing in both air and under water for application in various fields, such as marine, military, and underwater habitat research, but complexity in the design and provable mathematical model to withstand the arguably swift changes in the forces during the transition phase makes it difficult to build a sustainable UAV that can operate seamlessly in both media. Beginning with the mathematical principles and physical laws, the basic concept of operation is arrived at in the present study for both media (air and water) keeping the prime objective as developing a reliable drone design and mathematical model that will satisfactorily describe the behavior of the amphibious drone with accuracy by defining the coordinate system to describe the amphibious drone's kinematics. Basic forces and torques are considered to explicitly describe the drone dynamics using Newton–Euler equations, and the final equation derived is the matrix Newton's second law. Based on the mathematical model, the final design of the drone is arrived at considering the feasibility of withstanding forces, placement of commercial-off-the-shelf components, and the amount of thrust required to carry the seamless operation. A prototype is built with active buoyancy control technique to control the underwater depth of the drone, which clearly satisfies the design and mathematical model developed in this study. [ABSTRACT FROM AUTHOR]