Mechanisms and benefits of ultrasonic vibration-assisted laser trepanning drilling (UVLTD) for high-quality microhole fabrication.

Research on the relationship between periodic flow and heat input of inhomogeneous melting of laser cladding molten pool

ABSTRACT This paper assesses the extent to which country-specific uncertainty affects gross capital inflows and episodes of extreme capital inflows in the form of sudden stops and sudden surges in emerging market economies. The main findings indicate that an increase in country-specific uncertainty is associated with a decline in aggregate capital inflows and a decline in specific types of capital inflows including equity, portfolio, and direct investment. In addition, heightened uncertainty is also associated with a drop in net capital inflows. Furthermore, the results suggest that an increase in uncertainty could be associated with an increase in the probability of transitioning from a period of normal capital flows into a sudden stop episode, and that, heightened uncertainty could be negatively associated with the probability of exiting a tranquil period and experiencing a sudden surge.

Passive flow control in triangular arrangement of cylinders: Role of Reynolds number, role of gap spacing, role of splitter plate

Dual-platform metagenomic surveillance distinguishes pathogen and resistome hotspots across agricultural and mixed-use watersheds.

Uterine incision-to-delivery interval and neonatal outcomes among nonurgent, term, cesarean deliveries.

Urbanization alters riverine fluorescent dissolved organic matter characteristics in a forested city - metropolitan Atlanta, Georgia (USA).

In this study, building on the tet-to-hex paradigm—where a linear tetrahedron is split into four linear hexahedra—we propose a concise yet robust projection-relaxation framework to enhance the geometric adaptability of high-order discontinuous Galerkin spectral element methods (DGSEMs) for wall-modeled large-eddy simulations (WMLESs). This framework is specifically designed to enhance geometric fidelity on curved boundaries while meeting strict mesh-quality criteria. Since WMLES favors near-wall isotropic meshes, the tet-to-hex splitting produces hexahedra of minimal cell-volume distortion, with the projection-relaxation pipeline guaranteeing high geometric fidelity at curved walls. The small loss of geometric fidelity is further justified in the context of WMLES, where the near-wall region is intentionally under-resolved, and overall modeling accuracy is dominated by outer-layer physics. Additionally, for high-order DGSEM, numerical accuracy is governed primarily by the degree of cell-volume distortion—quantified by the Jacobian determinant—rather than by the cell angular distortion (e.g., loss of orthogonality) introduced during tet-to-hex conversion. Numerical experiments on two benchmark turbulent flows—turbulent channel flow and periodic hill flow—show that high-order DGSEM-based WMLES on the generated meshes achieves predictive accuracy comparable to that of structured meshes with similar grid counts. Finally, the observed WMLES accuracy for the NASA High-Lift Common Research Model further confirms that the proposed meshing method is ready for industrial applications.

This project presents the design and development of a hybrid solar-hydro power generation system aimed at providing a sustainable, efficient, and reliable source of electricity for remote and rural areas. The system integrates a floating hydropower unit with a solar photovoltaic (PV) setup to ensure continuous power generation under varying environmental conditions. The hydropower unit utilizes a water turbine coupled with a DC motor which will act as generator to convert the kinetic energy of flowing water into electrical energy, while the solar panel supplements power generation during periods of low water flow or dry seasons. The generated DC power from both sources is regulated and stored in a rechargeable battery, which supplies power through a DC to AC inverter for general household and community use. An ESP32 microcontroller with integrated Bluetooth is used as a monitoring unit, replacing separate Arduino and ESP8266 modules used in earlier designs. This reduces circuit complexity, enhances processing efficiency, and enables real-time monitoring through the Serial Bluetooth Terminal. Additionally, a water level sensor is employed to continuously monitor river or canal levels and provide early flood alerts when unsafe conditions are detected. Alert message is sent via GSM Module. The combination of renewable energy sources, smart monitoring, and storage ensures a stable and uninterrupted power supply with enhanced safety. The proposed hybrid system effectively overcomes the limitations of existing standalone hydropower systems by adding solar energy support and battery backup. It demonstrates the potential of combining multiple renewable energy technologies with Real-time monitoring to achieve reliable, clean, and self-sustained power generation suitable for off-grid applications

Periods of extreme flow (i.e., drought and flood) structure aquatic communities, but their effects in hydrologically stable, groundwater-dominated systems (e.g., karst springs) remain poorly understood. These spring systems are often viewed as refugia for endemic fishes. As such, the effects of drought and flooding are thought to be more pronounced than in hydrologically variable systems with the potential to lead to extirpations of endemic fishes. We analyzed a 9-year dataset (2014-2022) from three reaches of the San Marcos River and four reaches of the Comal River, Texas, to evaluate how a major flood and a severe drought influenced habitat structure and fish assemblages among wadeable and non-wadeable areas. Habitat variables were surveyed alongside standardized fish sampling, and fishes were grouped into habitat usage guilds for analysis. Effects of extreme flow periods were similar to the effects reported for hydrologically variable systems in wadeable areas but not in non-wadeable areas. Among wadeable areas, an increase in the amount of algae was detected during drought, but changes to substrates and vegetation coverage because of scouring were not detected following a flood. Also, abundances of pelagic generalist fishes (e.g., Lepomis sp., Herichthys cyanoguttatus) and one species of a pelagic specialist fish (i.e., Astyanax argentatus) decreased following a flood. Unexpectedly, abundances of benthic guild fishes (i.e., Etheostoma sp.) increased during drought and abundances of one species of pelagic specialist fish (Dionda nigrotaeniata) decreased following a flood. Effects of extreme flow periods on habitat structure and fish assemblages in hydrologically stable systems were similar to, or unexpectedly less pronounced, than the effects of flow periods on hydrologically variable systems. These patterns reveal vulnerabilities among generalist species during high flows and drought-associated increases for benthic taxa. These results support ecological theory that groundwater-dominated systems provide resistance to climatic extremes but remain susceptible to community restructuring, with implications for conservation under future climate variability and groundwater extraction.

Abstract While significant attention has been paid to the impact of land surface uncertainties on terrestrial forecasts, there has been little research on how land surface uncertainties impact predictability over the maritime environments. The Navy Global Environmental Model (NAVGEM) is used to better understand the impact of the land surface uncertainty on forecasts over maritime environments. We examine three ensemble simulations during a period of offshore flow over the U. S. East Coast. The first ensemble perturbs only the atmospheric initial conditions, the second ensemble perturbs only the soil moisture and temperature, and the third ensemble perturbs both the atmospheric initial conditions and the soil moisture and temperature. The impact of land perturbations on ensemble spread over land and ocean shows a slow increase in the spread at early lead times, then a rapid increase after the first week, which is consistent with the hypothesized impacts of the land surface on forecast skill between days 5 to 14. By the end of the 14-day forecast, the ensemble spread resulting from the land surface perturbations is similar in magnitude to that resulting from atmosphere-only perturbations over both the land and ocean, illustrating the importance of accounting for land uncertainty in maritime forecasts. We interpret the mechanisms through which initial land surface perturbations impact the maritime environment through an examination of surface fluxes and upper tropospheric fields. As the land surface perturbations also change the ensemble mean state, they result in increased upper-tropospheric baroclinic instability, which in turn results in enhanced ensemble spread.

Blade impact faults degrade power generation quality, if not detected in time, may lead to turbine malfunction or even complete failure. Moreover, the accuracy of blade impact fault detection in tidal current turbine (TCT) is significantly affected by variations in flow velocity and tidal flow period. To solve this problem, a self-adaptive detection method based on stator current signals and k-nearest neighbor-multiplicative score (KNN-MS) is proposed. The method first employs the KNN algorithm to characterize local feature distributions. Then, robustness under unstable flow conditions is improved through variance-based weighting. Finally, a cumulative multiplicative scoring mechanism is proposed to amplify and quantify fault-related anomaly indicators. The experimental results show that the proposed method achieves high diagnostic accuracy and stability across steady, periodic, and variable-period flow scenarios.

The transient flow between matrix and natural fractures significantly impacts the exploitation of shale oil reservoirs. Existing characterization models, however, primarily target conventional fractured reservoirs, neglecting the specific mechanisms of shale, including nonlinear flow and stress sensitivity. A new characterization model for shale matrix-natural fracture flow is developed by incorporating these critical mechanisms. The shale reservoir flow equations were first constructed considering nonlinear flow and the stress sensitivity of the matrix. Then, the governing equations are solved numerically using a fully implicit scheme. Based on the equations, the dimensionless shape factor for matrix-fracture flow is derived via the material balance method. Our results demonstrate the time-dependent behavior of the shape factor in shale reservoirs, with values lower than in conventional fractured reservoirs except during initial flow periods. More pronounced nonlinear flow characteristics in the shale matrix result in smaller dimensionless shape factors. In addition, increased stress sensitivity in the shale matrix leads to more significant permeability reduction, yielding smaller dimensionless shape factors. An empirical correlation between dimensionless shape factor and dimensionless time is established through multiple numerical simulations and regression analysis. This model improves matrix-fracture flow characterization in shale systems and can be employed in reservoir numerical simulations to accurately predict the well-production performance, which is essential for the efficient exploitation of shale oil.

ABSTRACT Mathematical expressions for resistance and inductance that correspond to Womersley's well‐known solution for periodic unsteady flow in a cylindrical tube are rigorously formulated. A formal mathematical analysis is also formulated for periodic unsteady flow by assuming the paraboloid velocity profile. The volumetric flow rate given by such unsteady analysis is compared here with Womersley's solution; Womersley himself had compared his solution with Poiseuille's steady solution (without mathematical justification). Analytical expressions for the phase difference between the flow rate and pressure are derived, both for the paraboloid velocity profile and Womersley's solution. The formulations of the equivalent electrical circuits are mathematically exact. The equivalent electrical circuit corresponding to Womersley's solution and that for paraboloid velocity are shown to be different at an arbitrary Womersley number. When the Womersley number approaches zero, the resistances in the two analyses are the same, but the inductances are not. When the Womersley number approaches infinity, the inductances in the two analyses are the same, but the resistances are not. The validity (or inappropriateness) of the expressions for the resistance and the inductance that are routinely used, on a rather ad hoc basis, in the vast literature on the lumped parameter analysis of pulsatile physiological flows is thus rigorously assessed.

The study of turbulent Prandtl number is important for turbulent flows with heat transfer. Despite its importance, no universal model exists that is able to capture its behavior for a range of molecular Prandtl numbers. In this study, new turbulent Prandtl number models were developed using multi-gene gene expression programming (MGGEP) based on direct numerical simulation (DNS) data for heated periodic channel flows. DNS datasets covering both medium- and low-Prandtl-number fluids were employed to construct more universal closures suitable for Reynolds-averaged Navier–Stokes (RANS) simulations. Two case studies were conducted. In the first case study, turbulent Prandtl number models optimized for air (Pr = 0.71) were obtained using the friction Reynolds number and normalized wall distance as the physical inputs. In the second case study, generalized models applicable to both medium- and low-Prandtl-number fluids (down to Pr = 0.025) were developed. A novel Galilean-invariant local Reynolds number parameter was introduced to accurately capture the near-wall behavior and spatial variations in turbulent heat transfer. The resulting models demonstrated mean percent relative errors below 3% for the turbulent Prandtl number compared with the DNS data, while existing models in the literature show errors of up to 26.7%. In terms of root mean square error for the periodic channel flow, medium Prandtl number studies showed root mean square error reduction from 0.0596 to 0.0302, and low-Prandtl-number studies exhibited root mean square error reduction from 0.3128 to 0.0256 when MGGEP models and models from the literature are compared with respect to turbulent Prandtl number. The models were also validated using the turbulent periodic pipe flow problem, where the mean percent relative error for the turbulent Prandtl number decreased from 31.0% to 5.8%. The developed models were subsequently implemented in RANS simulations, showing that the proposed turbulent Prandtl number models lead to highly accurate temperature predictions for the periodic channel flow problem.

Blood is a complex suspension of deformable red blood cells (RBCs), and its rheology plays a central role in physiology and pathology. While many computational studies have examined hemorheology under periodic or wall-confined flows, these approaches cannot capture the exchange of mass, momentum, and energy with the surroundings, a feature essential for the realistic simulation of non-equilibrium processes. Open-boundary methods provide this capability but remain largely underexplored. We present the first application of open-boundary molecular dynamics (OBMD) to RBC suspensions, with explicit control of flux exchange across the open boundary. The framework combines dissipative particle dynamics for the solvent and a coarse-grained RBC membrane model and introduces a novel, efficient membrane insertion algorithm capable of handling high hematocrits. It reproduces experimental bulk hemorheological properties, including shear-thinning and hematocrit-dependent viscosity. Our results validate OBMD for modeling blood rheology and establish a computational foundation for future studies of ultrasound-blood interactions and other phenomena where periodic boundaries constrain natural dynamics, such as pressure-driven flows, transient inflows, and cell-free layer formation.

In recent years, passive cell manipulation in microfluidic devices has emerged as a crucial tool for biomedical and biotechnological applications, allowing control over cell positioning and behavior without the need for chemical labels or complex external forces. However, achieving precise and tunable modulation of cell dynamics remains a challenge, particularly with low-cost and non-invasive methods. In this work, we present a novel approach that leverages controlled acousto-mechanical perturbations (AMPs) to modulate cell arrangement and behavior in microchannels. By coupling a smartphone-driven audio speaker with a microfluidic device, acoustic signals are converted into mechanical vibrations of the tubing, generating AMPs that interact with hydrodynamically driven flows. Experiments with yeast cells and silica beads under different flow conditions revealed that acoustic stimulation induced periodic flow dynamics, with yeast cells showing tunable, flow-dependent responses while inert particles exhibited weak and stable modulation. Frequency-domain analysis highlighted a dominant response synchronized with the applied acoustic protocol, accompanied by higher-frequency components characteristic of acoustic actuation. These results demonstrate that simple, low-cost acoustic actuation revealed distinct dynamical responses between rigid inert particles and deformable biological cells and enable label-free cellular manipulation. The proposed platform offers a versatile, non-invasive, and accessible approach for controlled cell manipulation in microfluidics.

Numerical simulation of periodic oscillatory Giesekus viscoelastic flow around a cylinder

The periodic electroosmotic flow of Jeffrey fluid with slip boundary conditions between parallel plates under high Zeta potential

Abstract The homoepitaxy of (100) β -Ga 2 O 3 via metal–organic chemical vapor deposition (MOCVD) was investigated using trimethylgallium (TMGa) as the gallium source. The study systematically examines how growth temperature and oxygen flow rate affect surface morphology and electrical properties. Growth temperature plays a crucial role in controlling gallium adatom diffusion length, while lower oxygen flow rates also promote gallium diffusion. At high temperatures, step bunching occurs, characterized by periodic mesas and local step flow. As the temperature increases, the density of mesas rises, and atomic steps merge, leading to a fully step-bunched morphology. At 895 °C, optimizing the oxygen flow produces an atomically smooth surface with a root-mean-square roughness of 0.71 nm. Hall effect and secondary ion mass spectrometry analyses reveal that higher growth temperatures and oxygen flow rates suppress carbon impurities, thereby enhancing electrical performance. However, excessive temperatures cause magnesium diffusion from the substrate, which compensates the n-type dopants, and excessive oxygen flow induces the formation of parasitic particles, both of which degrade electrical properties. The optimal conditions identified are 925 °C and 5000 sccm oxygen flow, achieving a room-temperature mobility of 103 cm 2 V·s −1 and an electron concentration of 1.17 × 10 18 cm −3 . A 4.8 μ m-thick film with excellent transport properties was successfully produced. This research offers valuable insights into the MOCVD growth process of (100) β -Ga 2 O 3 using TMGa, successfully achieving process optimization and precursor validation.