The application of controlled external electric pulses increases cell membrane conductivity by generating pores that act as aqueous channels within the lipid bilayer able to facilitate drugs delivery into the cell, phenomenon known as electropermeabilization. In this study, optical properties extracted from phase images of cells of two malignancy stages were used to compare the pores density formed inside their membranes. Numerical simulations were performed on cells of elongated shapes, using bipolar electric pulses of two pulse durations, alongside multiple values of the pulse amplitude, extracellular medium conductivity, pore radius, and cell orientation relative to the electric field lines. As reference, simplified topologies (ellipses) were also evaluated under the same conditions. Our examination of the spatio-temporal distribution of pores density indicated higher values at cells poles, in lower-conductivity extracellular media and for higher electric pulse amplitude. Cells in higher malignant stage consistently showed an increased pores density, suggesting an enhanced capacity for an intracellular drug accumulation during membrane electropermeabilization. This simulation-derived information, incorporating experimental data at the cellular level, can be used to develop procedures applicable in clinical medicine.

Modeling density-driven hydrogeological dynamics in arid endorheic basins: A numerical analysis of variable-density groundwater flow systems.

This study aims to improve the numerical solution of the two-dimensional Eikonal equation, a fundamental partial differential equation in wave propagation and geometric optics, by creating highly efficient and precise recursive schemes. These schemes enhance computational performance, reduce numerical complexity, and increase solution accuracy for essential applications in seismic imaging, computer vision, and robotic path planning. We propose two innovative recursive schemes that enhance an advanced adaptation of the modified decomposition method. These schemes break down the nonlinear Eikonal equation into manageable components, enabling robust iterative solutions. The methodology is rigorously derived and confirmed through extensive numerical simulations across various examples, featuring multiple boundary conditions and domain complexities. Results indicate that the proposed schemes surpass existing methods in terms of accuracy, stability for complex geometries, and computational efficiency, as shown by faster convergence rates, making them suitable for large-scale challenges in applied mathematics and engineering. This work introduces two novel recursive schemes, specifically designed for the Eikonal equation, which extend the modified decomposition method with innovative adaptations. These schemes offer a unique blend of simplicity, scalability, and durability, addressing the limitations of traditional methods and providing novel numerical algorithms and insights that greatly enhance the computational toolkit for tackling nonlinear partial differential equations in scientific and industrial applications contexts.

An efficient chirp pulse-based mixing technique, Adiabatic Linearly FREquency Swept reCOupling (AL FRESCO), is introduced for establishing broadband two-dimensional (2D) 13C-13C dipolar correlations in uniformly 13C-labeled protein samples. AL FRESCO utilizes a single or a series of frequency-swept (chirped) pulses applied to homonuclear spin pairs (e.g., 13Cs, 15Ns, or 1Hs) to mediate homonuclear correlations under magic-angle spinning (MAS). Originally developed for ultrafast MAS, we demonstrate that AL FRESCO performs robustly across a wide range of MAS rates. The AL FRESCO method exhibits strong immunity to dipolar truncation, allowing efficient recoupling of long-range interactions even in the presence of dominant short-range dipolar couplings and regardless of the chemical shift difference between the recoupled sites. A distinctive feature of AL FRESCO is its use of weak radiofrequency (rf) fields (5-20kHz), independent of the MAS rate, significantly reducing sample heating and enabling extended mixing times (>1s). This facilitates the observation of long-range correlations that are often inaccessible using conventional recoupling techniques under ultrafast MAS rates. The effectiveness of the method is governed by key parameters such as rf amplitude and envelope shape, dwell time (Δt), and sweep bandwidth. Numerical simulations and average Hamiltonian theory offer insight into the recoupling mechanism. Experimental validation was carried out via 2D 13C-13C correlation spectroscopy at fast, moderate, and slow MAS rates using three different protein systems: uniformly 13C,15N-labeled transthyretin, selectively 13C-[T,W]-labeled CrgA, and uniformly 13C,15N-labeled GB1.

ABSTRACT Adding syngas to diesel engines can significantly reduce emissions of nitrogen oxides and hydrocarbons. Previous research on Syngas-Diesel Dual Fuel (SDDF) engines mainly focused on the composition of syngas, syngas substitution rate (SSR), injection strategy, and EGR. However, it still faces challenges of low thermal efficiency and poor combustion performance. In order to further improve the performance of SDDF engines, the combustion strategies of a SDDF engine were studied numerically. The baseline engine is a four-cylinder diesel engine, which was modified a SDDF engine with an intake-port syngas injection and in-cylinder direct diesel injection combustion modes. Numerical simulations were performed using GT-Power software and validated against experimental results. Based on orthogonal experiments, key parameters such as intake pressure, diesel rail pressure, number of nozzle holes, and compression ratio (CR) were optimized under operating conditions of 2800 rpm, 50% load, and 40% SSR. The results demonstrated that the indicated thermal efficiency (ITE) increased by 4.2% when SDDF engine operates at intake pressure of 1.8 bar, rail pressure of 120 MPa, 8-hole nozzle, and CR of 19.

ABSTRACT Regenerative thermal oxidizer (RTO) is a widely used device for reducing volatile organic compounds (VOCs) generated in the industry. As an essential component of VOCs, o-xylene undergoes a complex multistep combustion process in RTO. A simplified combustion mechanism (SCM) containing 62 species and 296 elementary reactions is derived from the detailed combustion mechanism (DCM) of o-xylene. A comprehensive validation of the SCM is performed by comparing its predictions with experimental measurements of ignition delay times, laminar flame speeds, and species concentration distributions. Subsequently, an integrated RTO–SCM coupled combustion model is formulated and rigorously verified against experimental date. Simulation results reveal distinct distribution regions for o-xylene combustion intermediates within the RTO. The primary reaction zone is localized at the junction area connecting the regenerator and the combustion chamber. However, low concentrations of o-xylene cannot be completely oxidized to the final products in the RTO. During the initial operating cycle of the RTO, VOC emission peaks with o-xylene, C6H6, and C6H5CH3 as the dominant components. As combustion chamber temperature increases in subsequent cycles, the o-xylene concentration at the outlet gradually decreases to below 40% of the total emissions, with overall VOC levels maintained below 10 mg/m3.

ABSTRACT Recovery and reuse of waste heat has become an effective way to improve energy efficiency and reduce carbon emissions. In this paper, a set of dry anaerobic fermentation system with air-conditioner condensation heat recovery was designed to study the stability of constant temperature and temperature distribution by combining experimental and numerical simulation methods. The results show that: the system can maintain the reactor material temperature in the microbial activity zone of 30 ~ 35°C, but gravity causes the material stratification to form a vertical temperature gradient; the system operates for 29 days with a cumulative energy consumption of 25.19 kW·h, an average gas production of 116 L per day, a gas production rate of 0.97 L/(L·d) in the pool, and the methane content stabilized at 25%. The tube diameter of Helical coiled tubes affects the temperature field more strongly than the flow rate in the tubes, increasing the coil pitch reduces the inhomogeneity of the temperature field but weakens the rate of heat transfer; increasing the coil diameter increases the percentage of high-temperature region of the fermentation material, although the secondary flow effect is reduced. This study provides an innovative practical solution for waste heat utilization and energy saving.

Eliminating tool eccentricity is critical for longer tool-life and high-quality surface finish. This paper presents an on-machine eccentricity cancellation strategy using machine tool feed drives. Circular motion at the spindle frequency is commanded to the feed axes to introduce an artificial eccentricity vector in tool coordinates. Cutting forces are monitored to extract the components induced by eccentricity in frequency domain, and an extremum seeking controller (ESC) is designed to cancel the eccentricity component by automatically adjusting the magnitude and orientation of the circular motion. Effectiveness of the proposed strategy is demonstrated in numerical simulations and machining experiments.

Cutting tools with high length-to-diameter ratios used in internal turning often experience chatter due to increased compliance. To ensure stable machining, active damping methods using hydraulic-, piezoelectric-, magneto-strictive-, electromagnetic- actuators are explored earlier. Magnetic actuators stand out for their cost-effectiveness, manufacturability, and wide bandwidth. However, their bulky design limits industrial adaptability. This work proposes a hybrid approach that integrates numerical simulation with optimization to design compact and optimal magnetic actuators without sacrificing force/torque. The proposed approach resulted in an actuator having equivalent performance, enhancing suitability with dimensional reduction of (65.59%, 64.60%) for (Si-Fe, Ni-Fe) against Somaloy reported in literature.

The unwanted vibrations resulting from man-made activities are very common and can cause damage to the surrounding buildings. Previous studies have suggested single barriers for vibration isolation that require unrealistic depth requirements. To effectively control the vibration-related hazards, a geotechnical seismic isolation strategy of dual shallow barriers has been explored in the present work. Geofoam has been used as a filling material in the barriers. Extensive field studies and numerical simulations have been performed to isolate the continuous harmonic vibrations. The Lazan-type mechanical oscillator has been utilized to generate continuous harmonic vibrations of frequencies ranging from 20 to 45 Hz. A comprehensive numerical investigation has been conducted to screen continuous harmonic vibrations. The barriers were found to eliminate vibrations of higher frequency more effectively compared to low-frequency excitations. The isolation efficiency of EPS15-infilled dual barriers of a normalized depth of 0.31 was noticed to be 45% higher than that of the EPS15-infilled single barrier of a similar depth (where EPS is expanded polystyrene). Furthermore, an optimum depth of 0.5 LR for EPS15-infilled dual barriers was noticed to be sufficient to reach the vibration-limiting criteria of isolation efficiency equal to or greater than 75% (where LR is Rayleigh wavelength).

Microfluidics is considered a revolutionary interdisciplinary technology with substantial interest in various biomedical applications. Many non-Newtonian fluids often used in microfluidics systems are notably influenced by the external active fields, such as acoustic, electric, and magnetic fields, leading to changes in rheological behavior. In this study, a numerical investigation is carried out to explore the rheological behavior of non-Newtonian fluids in a T-shaped microfluidics channel integrated with complex micropillar structures under the influence of acoustic, electric, and magnetic fields. For this purpose, COMSOL Multiphysics with laminar flow, pressure acoustic, electric current, and magnetic field physics is used to examine rheological characteristics of non-Newtonian fluids. Three polymer solutions, such as 2000 ppm xanthan gum (XG), 1000 ppm polyethylene oxide (PEO), and 1500 ppm polyacrylamide (PAM), are used as a non-Newtonian fluids with the Carreau–Yasuda fluid model to characterize the shear-thinning behavior. Moreover, numerical simulations are carried out with different input parameters, such as Reynolds numbers (0.1, 1, 10, and 50), acoustic pressure (5 Mpa, 6.5 Mpa, and 8 Mpa), electric voltage (200 V, 250 V, and 300 V), and magnetic flux (0.5 T, 0.7 T, and 0.9 T). The findings reveal that the incorporation of active fields and micropillar structures noticeably impacts fluid rheology. The acoustic field induces higher shear-thinning behavior, decreasing dynamic viscosity from 0.51 Pa·s to 0.34 Pa·s. Similarly, the electric field induces higher shear rates, reducing dynamic viscosities from 0.63 Pa·s to 0.42 Pa·s, while the magnetic field drops the dynamic viscosity from 0.44 Pa·s to 0.29 Pa·s. Additionally, as the Reynolds number increases, the shear rate also rises in the case of electric and magnetic fields, leading to more chaotic flow, while the acoustic field advances more smooth flow patterns and uniform fluid motion within the microchannel. Moreover, a proposed experimental framework is designed to study non-Newtonian fluid mixing in a T-shaped microfluidics channel under external active fields. Initially, the microchannel was fabricated using a high-resolution SLA printer with clear photopolymer resin material. Post-processing involved analyzing particle distribution, mixing quality, fluid rheology, and particle aggregation. Overall, the findings emphasize the significance of considering the fluid rheology in designing and optimizing microfluidics systems under active fields, especially when dealing with complex fluids with non-Newtonian characteristics.

This study examines the influence of low proportions ($<2.5\%$ by mass) of 40/63 mm gravel on the shear strength of hardfill used in the Mallegue-Amont Dam (Tunisia). To address the coarse nature of the material, a custom medium-scale direct shear apparatus was developed, despite its non-standard dimensions. Nine mixtures with varying sand-to-gravel ratios were prepared to evaluate the effect of fine content. Experimental testing was supported by statistical analysis and validated through numerical simulations using FLAC3D. Results indicate that the 40/63 mm fraction has a negligible effect on shear strength parameters. Instead, the mechanical response is predominantly controlled by cementation and particles smaller than 40 mm. Numerical modeling confirmed the reliability of the experimental findings and reinforced the validity of the adapted testing approach. The study demonstrates that representative shear strength parameters can be obtained using non-standard equipment, provided mixture preparation and mold dimensions are carefully controlled. These insights contribute to cost-effective hardfill design and improved durability of dam and infrastructure projects.

Abstract. For the largest wind turbines currently being designed, operation close to cut-out conditions can lead to the tip airfoil experiencing transonic flow conditions. To date, this phenomenon has been explored primarily through numerical simulations, but modelling uncertainties limit the reliability of these predictions. In response to this challenge, our study marks the first experimental investigation of a wind turbine airfoil under transonic conditions, for which we selected the FFA-W3-211 airfoil. Measurements were carried out in the high-subsonic range (Mach 0.5 and 0.6), utilizing schlieren visualization and particle image velocimetry (PIV) to characterize the airfoil across a range of angles of attack (AoAs) expected to be close to the boundary of transonic flow occurrence. Unsteady shock wave formation was observed for the higher Mach number, with the shock oscillation range increasing with steeper angles of attack. In addition, it was confirmed that the presence of a local supersonic flow region does not necessarily result in a shock wave. For cases with shock waves and trailing-edge separation, a buffet cycle was identified that is similar to, but distinct from, those seen in aviation applications. Our findings highlight the need for unsteady analyses even in steady operating conditions and call for dedicated research on wind turbine tip airfoils in transonic flow.

In this paper, we study the local stability of an incommensurate fractional reaction–diffusion glycolysis model. The glycolysis process, fundamental to cellular metabolism, exhibits complex dynamical behaviors when formulated as a nonlinear reaction–diffusion system. To capture the heterogeneous memory effects often present in biochemical and chemical processes, we extend the classical model by introducing incommensurate fractional derivatives, where each species evolves with a distinct fractional order. We linearize the system around the positive steady state and derive sufficient conditions for local asymptotic stability by analyzing the eigenvalues of the associated Jacobian matrix under fractional-order dynamics. The results demonstrate how diffusion and non-uniform fractional orders jointly shape the stability domain of the system, highlighting scenarios where diffusion destabilizes homogeneous equilibria and others where incommensurate memory effects enhance stability. Numerical simulations are presented to illustrate and validate the theoretical findings.

Abstract The efficient mixing of fuel and oxidizer in a scramjet combustor is a critical issue for achieving future wide-speed-range flight. A numerical study is conducted using Reynolds-averaged Navier–Stokes equations coupled with shear stress transport k - ω turbulence model to investigate the mixing characteristics of hydrogen and air in a wide-speed-range supersonic combustor. Validation case using the numerical simulations shows remarkable consistency with experimental observations, confirming the reliability and accuracy of the computational approach. The results indicate that during a wide-speed-range flight, the enhancement effect of shock waves on the growth of the mixing region thickness within the combustor persists. This is attributed to the baroclinic torque and volumetric expansion effects caused by the interaction of shock waves and the turbulent shear layer, which enhance vorticity. When the combustor entrance Mach number is relatively low, this enhancement effect is more pronounced. As the combustor entrance Mach number increases, the enhancement effect gradually decreases. The area of the fuel–air mixing region decreases significantly as the combustor entrance Mach number increases, with this reduction being more pronounced at a low equivalence ratio compared to a higher one. The mixing efficiency of the fuel–air decreases with increasing combustor entrance Mach number. At a low equivalence ratio, a higher combustor entrance Mach number delays the location of full mixing. At a higher equivalence ratio, increasing the combustor entrance Mach number may result in the fuel and air remaining incompletely mixed by the time they reach the combustor exit.

Financial stability in interconnected markets is increasingly challenged by nonlinear interactions that amplify local disturbances into systemic crises. This study models a financial system as a complex network of coupled chaotic nodes, where each node represents a nonlinear macroeconomic subsystem governed by endogenous feedback dynamics. In contrast to traditional centralized interventions, a pinning control strategy is proposed to stabilize a network through selective control of a small subset of influential nodes. Numerical simulations show how local crises propagate through coupling links, generating systemic instability, and how the proposed impulsive control scheme effectively suppresses chaos and restores synchronization across an entire network. Results highlight the efficiency of localized interventions for achieving global stability, offering new theoretical insights into mechanisms of financial correlation and design of control-based resilience strategies for complex economic systems.

Large-scale renewable power supply system design for remote hydrogen production is a challenging task due to the 100% power electronics sending-end subsystem. The proper grid-forming strategy for a sending-end system to achieve large-scale remote hydrogen production still remains a research gap. This study first designs two grid-forming strategies for the concerned renewable power supply system, with one being based on virtual synchronous generator (VSG) and another one being based on V/f control. Then, the impedance analysis is carried out for ensuring the small-signal stable operation of the sending-end system including wind power plant and PV plant. Numerical simulation results implemented on PSCAD verify that the VSG-based grid-forming strategy configured on the sending-end modular multilevel converter (MMC) station of the MMC-based high-voltage direct-current (HVDC) link has a larger transient stability margin. Hence, the MMC-HVDC-based grid-forming strategy is a better choice for the power supply of large-scale remote hydrogen production. The enhanced stability margin ensures more robust operation under disturbances, which is critical for maintaining continuous power supply to large-scale electrolyzers.

Abstract Achieving a uniform current distribution among parallel conductors is essential to prevent local heating and performance degradation in superconducting rotating machines that are used in aircraft to realize high-current operation. Although transposition methods are effective under single-phase excitation, their effectiveness under practical motor conditions remains unclear. This study investigates the current distribution characteristics of three parallel conductors transposed within an armature coil under realistic motor operating conditions involving three-phase excitation and rotor rotation. To this end, we conducted numerical simulations using finite element analysis for evaluating the effect of both the three-phase magnetic field and the rotating magnetic field of the rotor on current distribution. A previously developed transposition configuration for single-phase armature coils was applied to a three-stranded double-pancake winding, and an analysis was conducted. The results revealed that transposition significantly suppressed current imbalance even in the presence of rotor rotation, reducing the deviation from the ideal distribution to within a few percentages. Further, shielding currents induced by the magnetic field of the rotor were identified as a major factor. The effect of the shielding current on the current distribution was substantially mitigated by the transposition design. Experiments were performed in liquid nitrogen using a rotating test system for validating the method, and current distributions were measured using Rogowski coils under both static and rotating conditions. The measured results were in close agreement with the simulation results, confirming that the proposed transposition method was effective even under actual motor operating conditions. These findings confirm that transposition configurations developed under single-phase conditions can be extended to realistic motor environments, providing a robust approach for ensuring current uniformity in multistrand superconducting armature coils.

Abstract In this work, we consider the model of a mass transport problem through polymeric membranes which is important in many applications especially drug delivery. The aim of this paper is to present a more accurate mathematical model to describe this phenomenon. We propose adopting fractional diffusion modeling for the concentration by using spatial fractional-order Riesz derivative. The numerical simulations for studying this phenomenon were carried out using an approach of finite element method and finite difference method. The error analysis and stability condition for this technique are derived. For the order of the fractional derivative, we studied three cases: the constant-order case, the piecewise continuous case, and the time-varying-order case. The results obtained show that using time-varying Riesz fractional derivative yields a more accurate description of the considered problem than both the classical diffusion model reported in the literature and the other fractional derivatives considered.

Arteriovenous fistulas (AVF) are the preferred vascular access for maintenance haemodialysis. However, AVF non-maturation occurs in up to 60% of patients, frequently caused by inadequate vascular remodelling or stenosis development. This study explores the relationships between AVF anatomy, haemodynamics and AVF outcomes by combining, uniquely, high-fidelity numerical simulations and state-of-the-art ferumoxytol-enhanced magnetic resonance imaging (Fe-MRI) in patients. Patients underwent Fe-MRI 6 weeks after AVF creation. A novel computational fluid dynamics (CFD) methodology was employed to rigorously investigate haemodynamic metrics, including wall shear stress (WSS) and oscillatory shear index (OSI), and quantify changes in the AVF lumen at 1 cm intervals along the proximal artery, anastomosis and AVF vein. The primary outcome was AVF success, defined as AVF usage (assisted or unassisted) for dialysis for at least 3 months. ROC analysis was conducted to assess anatomical predictors of AVF flows of ⩾1000 ml/min. The analysis included 17 AVFs (13 successful, 4 failed). Compared to failed fistulas, successful AVFs had higher mean WSS and OSI. Failed AVFs exhibited different haemodynamics, including lower flow rates with less helical flow. On ROC analysis, the three metrics associated with the highest area under the curve (AUC) values were the feeding artery curvature (0.82) and diameter (0.76), and draining vein diameter (0.74), with a combined AUC value of 0.83. These data suggest that high WSS, OSI, larger feeding artery and draining vein diameters and lower feeding artery curvature are associated with successful AVF outcomes. Whilst venous parameters are important, this study highlights the critical role of feeding artery characteristics, particularly diameter and curvature. These findings provide significant insights into the role of haemodynamics and geometry in modulating AVF maturation, suggesting that incorporation of arterial metrics into preoperative assessments could enhance surgical decision-making for more reliable AVF maturation and better long-term outcomes in haemodialysis patients.