Flame balls are stationary spherical flames known to exist in low-Lewis-number mixtures only under microgravity near-limit conditions. Whether such flame balls can form in NH₃ and NH₃/H₂ mixtures, and what characteristics they would exhibit, are questions of fundamental importance. In the present study, flame balls in NH₃/H₂/air mixtures are investigated numerically for the first time. Flame ball solutions are obtained for H2 molar ratios in the mixed fuel (aH2=XH2/(XH2+XNH3)) of 0.079 or more. When aH2< 0.079, no flame ball solution is obtained, indicating the critical aH2 for flame ball formation. With increasing aH2, the flammable range of flame ball expands toward that of the H2/air mixture. The flame radius exhibits an upward-convex variation with equivalence ratio, while the flame temperature exhibits a downward-convex variation. This inverse relationship arises because a smaller flame radius intensifies the Lewis number effect through increased curvature and simultaneously reduces total radiative heat loss. The boundary equivalence ratio for fuel-lean and fuel-rich combustion differs from 0.23 to 0.71 from aH2=1.00 to 0.079, rather than ϕ = 1. This shift arises from differences in the diffusivities of the fuel and oxidizer species. An extended formulation of the critical equivalence ratio for binary fuel spherical flames is proposed. The new formulation successfully captures the trend of fuel-lean and fuel-rich combustion boundary with different aH2. The non-equidiffusive characters of flame ball also affect NO formation: near the lean limit, NO at the flame ball center increases with decreasing equivalence ratio, in contrast to the equilibrium conditions. This is because the Lewis-number-driven flame temperature rise enhances NO production. The lean limit of flame ball for the aH2= 0.30 case (ϕ = 0.2374) is substantially lower than both counterflow flame (ϕ = 0.3206) and the standard limit (ϕ = 0.5280). The flame ball is expected to survive beyond the lean limit of propagating flames.
The better-than-average effect (BTAE), the tendency to evaluate oneself more favorably than the average other, has been linked to lower depressive symptoms. However, whether this association differs across evaluative domains remains unclear. This study investigated how BTAE in the moral and competence domains was associated with depressive symptoms. To further clarify these associations, we decomposed BTAE scores into self- and average-other evaluation components and examined their associations with depressive symptoms. A total of 285 adults rated themselves and the average person on moral and competence traits and reported depressive symptoms. Results showed that higher competence BTAE was associated with lower depressive symptoms, whereas moral BTAE was not, and these associations differed significantly. Component-level results suggested that depressive symptoms were associated more strongly with self-evaluation than with average-other evaluation in the competence domain. For morality, depressive symptoms were negatively associated with self-evaluation, but self- and average-other coefficients did not differ significantly. These findings indicate that BTAE is linked to depressive symptoms in a domain-specific manner. Competence BTAE may be more closely linked to depressive symptoms than moral BTAE, highlighting the need to distinguish evaluative domains when examining the psychological significance of BTAE.
The hazard posed by volcanic ballistic projectiles (VBPs) is commonly assessed using trajectory models that estimate impact locations and energies. Recent models simulate the one-way coupling between the erupting gas–ash mixture and particles by inserting the numerically obtained flow field into the equation of particle motion. Model testing typically relies on reproducing observed travel distances in the field, but this approach is hindered by poorly constrained pre-eruptive conditions such as vent overpressure. To overcome this limitation, this study applies a trajectory model based on the steady-state supersonic jet flow field to reproduce experimental trajectory data obtained from high-speed shadowgraph imaging of spherical glass beads initially at rest and accelerated by supersonic jets from an open-ended shock tube. The model successfully reproduces the observed velocity profiles, demonstrating the viability of the one-way coupling approach for dilute particle populations accelerated by supersonic jets. The reproduced trajectories yield particle Reynolds numbers between 103 and 2 × 105. In this range, drag coefficients for both spherical and irregular-shaped particles are largely independent of particle Reynolds number and depend primarily on particle Mach number. Furthermore, an equation for the duration of steady-state supersonic flow conditions is derived, validated, and then used. The equation shows that, in many explosive eruptions, VBPs are predominantly accelerated during the period in which the supersonic jet can be approximated as steady-state. Particle acceleration is strongest near the vent and decreases rapidly with distance, implying that early jet collapse has little influence on maximum VBP velocities.
Abstract Substandard reinforced concrete (RC) building stocks continue to pose a major seismic risk in earthquake-prone regions. While fiber-reinforced polymer (FRP) jacketing has been widely demonstrated as an effective retrofitting technique at the member level, its rational application at a large scale requires rapid yet reliable decision-making tools. In this study, the accuracy and applicability of a rapid FRP retrofitting framework integrated into the PERA2019 performance-based seismic assessment methodology are evaluated through a detailed investigation of five actual representative existing RC buildings. For each building, seismic performance before and after FRP retrofitting was evaluated using both the PERA2019 procedure and detailed nonlinear pushover analyses, which served as benchmark solutions. In addition, the framework was validated against the results of a full-scale experimental study reported in the literature. The results indicate that PERA2019 provides seismic safety ratio estimates that are in satisfactory agreement with detailed analysis outcomes. Buildings classified as A class by PERA2019 were consistently shown to satisfy the corresponding controlled damage performance target in detailed analyses, whereas buildings failing to reach A class did not meet this target. A comparison with the experimental results further demonstrated that the framework accurately captured the relative performance improvement achieved through FRP retrofitting and remained on the safe side of the observed structural response. Overall, the findings confirm that the proposed methodology can reliably distinguish buildings that can be effectively upgraded using FRP jacketing from those requiring alternative interventions. The framework provides a computationally efficient and practically applicable tool for large-scale seismic risk mitigation and prioritization of FRP retrofitting strategies.
During austenite reversion from martensite in steels, two distinct morphologies: acicular austenite (gamma A) and globular austenite (gamma G), form and play a significant role in mechanical performance. This study investigates the growth behaviors of gamma A and gamma G during intercritical annealing in an Fe-0.18C-8Mn (mass%) alloy. Experimental results reveal that gamma G can form but constitutes a negligible fraction compared with gamma A over the investigated temperature range. Surprisingly, both austenite types undergo Mn-partitioning growth from the earliest transformation stages, even at elevated temperatures, a finding that contradicts the negligible-partition growth predicted by the classical local equilibrium model. DICTRA simulations incorporating finite interface mobility successfully reproduce the growth mode and kinetics of gamma A. However, the experimentally observed Mn-partitioning behavior of gamma G cannot be captured, even when the presence of cementite is taken into account. Phase field simulations that explicitly consider the concurrent growth of gamma A and gamma G provide new insights: the concurrent growth strongly retards the development of gamma G, as the substantial amount of gamma A efficiently competes with gamma G for carbon in the matrix and drives the transition in gamma G growth mode from Mn-partitionless to Mn-partitioning. This effect highlights a previously unrecognized mechanism underlying microstructure evolution during intercritical annealing and, together with the effects of finite interface mobility and cementite presence, accounts for the distinctive lamellar microstructure in medium-Mn steels. (c) 2026 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.
