The stability of two bubbles rising initially in line through a viscous liquid is revisited using a global linear stability analysis formulated within an arbitrary Lagrangian–Eulerian framework, complemented by fully resolved embedded boundary method simulations. Whereas previous studies attributed the promoted in-line stability of oblate bubbles to a deformation-enhanced wake entrainment, the present analysis demonstrates that the dominant stabilizing mechanism arises instead from an inclination-induced rotational feedback generated as the trailing bubble (TB) experiences the asymmetric shear of the leading bubble’s wake. This inclination–shear coupling, rather than deformation itself, governs the recovery of stability with increasing aspect ratio. Furthermore, the results reveal that the unstable drafting–kissing–tumbling mode originates from short-range, two-way coupling between the bubbles, whereas the asymmetric side-escape mode corresponds to a long-range, one-way interaction dominated by the TB response. In addition, a previously unreported oscillatory global mode emerges from the unsteady recirculation linking the two bubbles, acting as a hydrodynamic spring whose effective stiffness and damping govern the oscillation frequency and growth rate. Together, these findings identify inclination-induced lift as the primary mechanism controlling the stability of rising bubble pairs and provide a unified framework for interpreting their stationary and oscillatory transitions across a broad range of inertial and deformable regimes.

Current flying-car designs lack scalability for diverse missions. This paper presents a modular design platform for developing reconfigurable flying-cars, embedding modularity across structural, electrical, and flight control domains. A full-scale sightseeing prototype demonstrates the platform’s feasibility and flexibility. The work contributes to design methodology by illustrating how modular architectures improve cross-mission adaptability, scalability, and lifecycle efficiency in complex mechatronic systems. (project introduction video available at https://www.aidilab.ai/flying-car)

Direct numerical simulations are performed on compressible turbulent boundary layers with micro-blowing controls applied to the walls at a free stream Mach number of 2.0 to investigate the influences of wall-blowing mass flux and spatial arrangements on drag reduction. Using law-of-the-wall for uniform blowing control, an estimation of skin friction is proposed based on Reynolds number and wall-blowing mass flux. At a given Reynolds number, the drag reduction rate increases almost logarithmically with wall-blowing mass flux within the control region. Downstream of the interaction zone, the drag reduction rate increases linearly. The disparities of the drag reduction rate in the integral sense among cases with different spatial arrangements are attributed to the asymmetric pressure gradient associated with flow compression, and expansion at the commencement and termination of the micro-blowing region.

This study was conducted to explore the effects of organic trace elements on milk composition, serum trace element concentrations, antioxidant and immune function, and metabolites in dairy cows. Thirty Holstein cows with similar body condition scores (3.5 ± 0.25 points) and parity were randomly divided into a control group (C), a 50% organic group (O_50), and a 100% organic group (O_100), with 10 cows in each group. The C group was fed a basal diet supplemented with 3% inorganic trace element premix, the O_50 group received 1.5% inorganic and 1.5% organic trace element premix, and the O_100 group received 3% organic trace element premix. Organic trace elements were supplemented from 21 days postpartum for 90 days. The results showed that milk protein concentration showed a linear response to organic trace element supplementation, with the highest value in the O_50 group (P < 0.05). Lactose concentration showed an increased quadratic effect (P < 0.01), whereas total solids (TS) and solid-not-fat (SNF) concentrations decreased linearly and quadratically. Serum selenium (Se) concentration increased linearly with increasing organic trace element supplementation (P < 0.05). Malondialdehyde (MDA) concentration decreased linearly (P < 0.05), whereas serum immunoglobulin A (IgA), superoxide dismutase activity, and immunoglobulin G (IgG) concentration increased significantly (P < 0.05). Liquid chromatography–tandem mass spectrometry (LC–MS/MS) analysis identified 70 and 76 differential metabolites in the O_50 and O_100 groups, respectively, compared with the C group. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis indicated that these metabolites were mainly involved in inflammatory mediator regulation, lysine degradation, sphingolipid metabolism, cytochrome P450-mediated drug metabolism, and ABC transporters. In conclusion, dietary supplementation with organic trace elements improved milk composition, antioxidant capacity, immune function, and serum metabolic profiles in dairy cows.

In this paper, we investigate the influences of wall temperature on compressible turbulent boundary layers at free-stream Mach number 6.0 and moderate Reynolds numbers. The findings demonstrate that turbulent statistics, including the logarithmic scaling of Reynolds stresses in the overlap region, the presence of very-large-scale motions in the outer layer, and their superposition on near-wall turbulence, exhibit qualitative invariance across varying wall temperatures. However, the reduced scale separation between near-wall small-scale motions and outer-layer large-scale motions leads to a contraction in the vertical extent of Reynolds stresses adhering to the logarithmic law. Very-large-scale motions are attenuated in viscous units but intensified in global scalings due to the lower free-stream Reynolds number, following approximately the power law. Their superposition effects on near-wall turbulence, when weighted by density, show only weak dependence on wall temperature. Conversely, the modulation of near-wall velocity and temperature fluctuations by very-large-scale motions diminishes with decreasing wall temperature. Through detailed analysis of spanwise spectra in the outer region, a distinct inertial subrange obeying the classical $-5/3$ scaling law is identified, alongside a universal scaling over the dissipative range. These observations suggest that the mechanisms governing energy cascade processes and the associated small-scale turbulent fluctuations remain independent of wall temperature variations.

Oil-based drilling fluids (OBDFs) are widely used in high-temperature ultra-deep wells, high-inclination wells, horizontal wells and various complex wellbores due to their excellent lubricity, high temperature stability, salt tolerance and contamination resistance. However, the intrusion of drill cuttings during drilling destabilizes water-in-oil (W/O) emulsion drilling fluids. Therefore, bentonite – a common component of drill cuttings – was selected to study the factors influencing its dispersion stability in W/O emulsions. The macroscopic stability of the system was evaluated via static observation, and the dispersion state was characterized using optical microscopy. Additionally, the viscosity, the contact angle of bentonite after adsorption of various surfactants, the interfacial tension and the charge of the bentonite particles were measured. The results indicate that various surfactants affect dispersion stability through distinct mechanisms. The system stabilized by a non-ionic surfactant exhibited low interfacial tension and the greatest stability. Furthermore, dispersion stability increased with surfactant concentration. Finally, binary surfactant systems were formulated with Span80. Calcium stearate demonstrated a significant synergistic effect with Span80, improving the stability of the bentonite dispersed in the emulsion, with an optimal ratio of 1:1. The mechanism of the stable dispersion of bentonite in oil was analysed, providing theoretical guidance for improving the stability of W/O emulsion drilling fluids during drilling operations.

Sexual dimorphism, a widespread phenomenon, has been extensively researched in extant and fossil crustaceans. However, identifying sexual dimorphism in phyllocarid fossils preserved as isolated parts is often challenging, except in cases where the specimens are exceptionally well preserved, including those with soft tissues. This study proposes a novel approach by introducing the use of geometric morphometric techniques to identify sexual dimorphism in phyllocarid fossils based on carapace morphology. It presents a comprehensive re-analysis of Soomicaris ordosensis Liu et al., 2023a, carapaces from the Upper Ordovician in North China and Tarim Plates. Elliptic Fourier analysis was applied to quantify the size and shape variation in nearly 100 specimens. The results demonstrate the presence of significant sexual dimorphism in the length and shape of the S. ordosensis carapace. The carapace shape exhibited variation between the sexes: the posterodorsal margin of one group of carapaces gradually extends backward to form a posterodorsal spine; the carapaces of the other group have a convex posterior margin and lack a posterodorsal spine. Additionally, both types manifest an overall allometric growth pattern, albeit with distinct growth coefficients. Furthermore, the observed approximately 1:1 ratio between the two forms suggests that the population of S. ordosensis may have exhibited a dioecious mating system. Geometric morphometrics are a highly effective method for elucidating the subtle variations in the carapace morphology of S. ordosensis, thereby underscoring the cryptic dimorphism characteristics of fossil animals. This finding offers the first indirect evidence for egg-brooding behavior within the extinct order Archaeostraca.

We report an experimental study on the effects of polymer additives in the dissipative-scale flow field properties in turbulent Rayleigh–Bénard convection. The experiments were conducted in a cylindrical convection cell with a minute amount of polyacrylamide long-chain polymer. The local velocity gradient tensor was measured using an integrated home-made measurement system (J. Fluid Mech., 2024, vol. 984, p. A8). Although the single-roll large-scale circulation persists (owing to the slight tilt of the convection cell), polymers induce an anisotropic suppression of the dissipative-scale flow properties. The normal velocity gradient components are suppressed more than the shear components. The mean energy dissipation rate in both centre and side regions decreases, then levels off with increasing polymer concentration and the final reduction ratio exceeds 50 % in each region. In the side region, adding polymers has a stronger stabilising effect on the strain rate than the rotation. The anisotropic suppression of the velocity gradient tensor affects dissipation-rotation co-occurrence probability, velocity gradient triple decomposition and local streamline topology. Adding polymers also induces a deceleration effect and increases the contribution of local buoyancy in driving the flow. These results reveal that the addition of polymers can non-trivially manipulate dissipative-scale turbulence fields and energy cascades.

One-degree-of-freedom flow-induced vibration (FIV) and energy harvesting through FIV of an elastically mounted circular cylinder with mechanically coupled rotation were investigated numerically for low Reynolds number 100, mass ratio 8 and a wide range of reduced velocities. The aims of this study are to investigate the effect of the flow direction angle $\beta$ on the vibration and energy harvesting through FIV. Two types of lock-in are found: vortex-induced vibration (VIV) and galloping. The response amplitude increases with the increase of $\beta$ in both regimes. Both VIV response and galloping regimes are found for $\beta$ = 45° to $\beta$ = 90°. For $\beta$ = −90° to $\beta$ = 0°, only VIV response regimes are found. The fluid force and fluid torque play different roles in exciting/damping the vibration. In the high-amplitude gallop regime, the fluid force excites the vibration, and the torque damps the vibration. Energy harvesting at flow direction angle 90° is investigated as this flow direction has the maximum galloping amplitude. The energy harvesting is achieved by a linear electric damping coefficient in the numerical model. The maximum harvestable power in the galloping regime is significantly greater than that in the VIV regime, and it increases with the increase of the reduced velocity. When the reduced velocity is 20, the harvested power is over 20 times that in the VIV regime, and can further increase if reduced velocity further increases. The maximum efficiency over all simulated parameters is 0.424, occurring when the reduced velocity is 20, and electric damping factor is 0.04.

This study employs a direct numerical simulation method to investigate the wake pattern evolutions of flows past an insulated spheroid and provides expressions of force and torque coefficients influenced by a streamwise magnetic field in an incompressible, conducting, viscous fluid. A total of 1150 cases are examined covering a parameter range of Reynolds number $50 \leqslant \textit{Re} \leqslant 250$, aspect ratio $1.5 \leqslant \beta \leqslant 6$, inclination angle $0^\circ \leqslant \theta \leqslant 90^\circ$, and interaction parameter $0 \leqslant N \leqslant 10$, where $\beta$ and $N$, respectively, reflect the anisotropy of the spheroid and the strength of magnetic field. Nine wake patterns are classified based on wake structure features and summarised in three maps of regimes according to the inclination angle. The transition mechanisms among these wake patterns are also investigated under the influence of a streamwise magnetic field. Furthermore, expressions for drag, lift and torque coefficients are derived with the help of three fundamental physical criteria. Results indicate that the force and torque expressions give a good prediction within the present parameter space $\{\textit{Re}, \beta , \theta , N\}$.

Some cadres receive promotions, whereas others do not. This study explores the Chinese Communist Party’s (CCP) personnel control over the central state-owned enterprise (SOE) leaders from the Hu era to the Xi era. An analysis of the résumés and careers of SOE leaders reveals that the CCP has established a dual-track system to manage enterprises with different functions. This system employs two types of incentives: promotion incentives for leaders of eldest-son enterprises associated with national security, and salary incentives for leaders of other enterprises. Through the dual-track system, the CCP aims to influence the career trajectories of SOE leaders and address conflicts of interest in the principal-agent relationship. This study also investigates the individual characteristics of SOE leaders, including their political qualifications, professional qualifications and ages. The results indicate a tendency towards specialization and institutionalization in central-enterprise leaders, even during the Xi era.