Search Results (5,435)

Maintaining stable dissolved oxygen (DO) and pH conditions is critical for reliable operation of bioreactor systems used in cell culture and bioprocess manufacturing. However, accurate regulation of DO and pH remains challenging due to nonlinear process dynamics and variations in operating conditions. In particular, temperature fluctuations can affect gas solubility, gas–liquid mass transfer, and CO₂ buffering equilibrium, resulting in deviations in DO and pH. Existing control methods often rely on predefined mechanistic models or reactor-specific parameter identification, which may limit adaptability under changing operating conditions. This paper proposes a disturbance-compensated data-driven adaptive predictive control framework for DO and pH stabilization in bioreactor systems under dynamic temperature disturbances. Based on dynamic linearization, the proposed framework establishes an online input–output representation using measured gas composition, temperature disturbance, and environmental responses. An adaptive gain adjustment mechanism and pseudo-partial-derivative estimation method are developed to update the control relationship online without requiring an explicit process model or iterative optimization. Furthermore, temperature variations are incorporated as measurable disturbances to achieve real-time compensation of their effects on DO and pH dynamics. The proposed framework was evaluated through simulations and experiments using a 3 L bioreactor platform. Compared with a PID controller with temperature feedforward and conventional model-free adaptive predictive control, the proposed method reduced DO and pH tracking errors and improved recovery performance under temperature disturbances. The results demonstrate that the proposed data-driven adaptive predictive control strategy provides an effective approach for DO and pH stabilization in bioreactor systems under temperature-varying conditions. Full article

The premature degradation of aluminium extrusion dies remains one of the major challenges affecting process efficiency, product quality, and tooling costs. Although numerous studies have investigated wear mechanisms and proposed solutions such as surface treatments, coatings and lubrication, the absence of a generic and reproducible laboratory methodology for evaluating tribological performance under representative extrusion die contact conditions limits the objective and systematic comparison of alternative tribological solutions. This study proposes and experimentally validates a generic tribological methodology for laboratory simulation of aluminium extrusion die contacts. Rather than reproducing the complete extrusion process, the methodology isolates the dominant physical mechanisms governing die degradation and reproduces their essential characteristics under controlled laboratory conditions, providing a representative platform for systematic tribological investigations. The methodology was developed through the selection and scaling of representative contact parameters, including contact geometry, normal load, sliding velocity and operating temperature. The experimental programme incorporated physical similarity principles, a controlled run-in procedure and repeated use of the same hardened steel counterface to reproduce cumulative die exposure under successive aluminium contacts. Two aluminium alloys (AA6063 and AA6082) were evaluated using a small ring-on-disc configuration against a hardened GCr15 steel counterface. Experimental validation was carried out using two extrusion lubricant systems, complemented by three additional commercial lubricants to assess the robustness and general applicability of the proposed methodology. The experimental results demonstrate that the proposed methodology provides repeatable and sufficiently sensitive measurements of friction and wear, allowing clear differentiation between lubricant systems and aluminium alloy–lubricant combinations while maintaining representative contact conditions. The study also demonstrates that steady-state friction should be identified from the actual friction evolution rather than by applying a fixed averaging interval. Although lubricant evaluation is employed here as the experimental validation case, the proposed methodology is intended as a generic experimental framework applicable to the assessment of surface treatments, coatings, tool materials, lubrication systems, and other tribological strategies aimed at extending extrusion die service life. Full article

Reliable state-of-charge (SOC) estimation is essential for lithium-ion battery management, yet parameter drift, operating-profile variation, and sensor faults can compromise observer consistency. This study presents a reproducible constrained FFRLS-EKF framework in which online second-order RC parameter updates are subjected to resistance, capacitance, and time-constant feasibility constraints before being scheduled in the EKF. Estimator residuals and parameter variations are then reused for exploratory concurrent fault analysis. Because the dynamic driving-cycle datasets do not provide independently measured continuous reference SOC, SOC RMSE/MAE is not reported for DST, FUDS, UDDS, US06, or BJDST; Coulomb counting is treated only as a non-independent trajectory reference because it also contributes to the FFRLS regression target. A separate 21-checkpoint HPPC validation, with reference labels withheld from the estimator, yields SOC RMSE/MAE values of 2.24/1.76 percentage points for the constrained adaptive method, compared with 2.50/2.04 percentage points for the fixed EKF. A 270-run robustness study varies fault magnitude, onset time, voltage-noise level, and initial SOC. The results identify physical projection as the dominant stabilizing mechanism, with adaptive forgetting providing secondary transient-memory adjustment. An additional 243-run two-fault stress test shows that residual-sensitivity decoupling is not universally identifiable: exact-pair recovery degrades as noise increases and remains strongly dependent on the operating profile and fault pair. Accordingly, the concurrent fault module is presented as a transparent diagnostic baseline rather than a universally validated fault-isolation method. Full article

Stable circulation and limited mechanical loading are key requirements in the fluidized-bed coating of small vegetable seeds. For Chinese cabbage seeds, their small mass, irregular geometry, and mechanical sensitivity make it difficult to evaluate operating conditions using only global indicators, such as mean particle velocity and bed expansion height. In this study, a two-way coupled computational fluid dynamics–discrete element method (CFD-DEM) model was developed for a draft-tube fluidized-bed seed coater. Chinese cabbage seeds were represented by seven-sphere clumps, and an L9(3³) orthogonal array was used as a screening design to examine inlet air velocity, initial bed height, and bottom circulation inlet gap. The evaluation combined cycle time distribution (CTD), the global low-speed particle fraction R_s, the 95th-percentile normal contact force F_95,n, and the normalized high-percentile contact-load ratio η_c,95. Because the L9 array cannot resolve interactions or support a full quadratic model, factor effects were interpreted descriptively within the investigated range rather than as a confirmatory global optimization. Initial bed height produced the largest descriptive contribution to the circulation period, R_s, and F_95,n. Increasing inlet air velocity shortened the circulation period and reduced Rs but increased high-percentile contact loading. Across the nine cases, F_95,n ranged from 7.50 to 14.50 mN and η_c,95 from 0.18% to 0.35%; η_c,95 is used only as a normalized load ratio and not as a validated probability of seed damage. Case 4 ranked first under equal weighting and contact-load-priority weighting, whereas Case 7 ranked first under circulation-priority weighting. Case 4 is therefore described as a weight-dependent balanced candidate within the tested parameter range. Prototype experiments reproduced the ordering of circulation periods for three dry operating conditions, supporting qualitative consistency between simulated and observed circulation behavior. Visible breakage remained below 0.5%, but this observation provides only preliminary qualitative correspondence with the simulated contact-load trend. The proposed framework is intended for dry-stage screening and does not directly predict wet-coating quality, adhesion, agglomeration, or germination performance. Full article

In battery energy storage systems (BESSs) in microgrids, traditional proportional–integral (PI) controllers remain a popular choice for management. The PI-based system often fails during sharp transients and under sudden shifts in solar irradiance or load demands. PI-based systems typically exhibit sluggish recovery times and pronounced voltage overshoots. To overcome these limitations, this article develops a flatness-based control (FBC) framework designed to optimize the dynamic response and stability of an islanded hybrid microgrid powered by photovoltaic (PV) arrays and wind turbines. The core mechanism directly regulates the battery charging and discharging currents. This mechanism ensures that the DC-bus voltage strictly tracks its reference command regardless of fluctuations in load or weather profiles. Crucially, the structural resilience of this control architecture was rigorously assessed, with the simulation model subjected to severe 20% mismatches in physical parameters, specifically the main DC-bus capacitance and battery inductance, alongside continuous high-frequency Gaussian white noise injected into the measurement feedback channels. Three scenarios have been implemented in MATLAB/Simulink: variable weather conditions, realistic weather conditions, and parameter uncertainties with measurement noise. The comparison shows that the new FBC controller cuts the settling time down from 0.47 s with the regular PI controller to just 0.02 s, which is a 95.7% decrease. In addition, the proposed controller substantially mitigates transient voltage deviations and eliminates the 2.6% voltage overshoot observed with the PI controller. The rise time is also reduced by approximately 35%. These results demonstrate that the proposed FBC provides faster, overshoot-free, and more stable DC-bus voltage regulation under the investigated operating conditions. Full article

During the operation of high-temperature subsea pipelines, marine sediments are subjected to complex thermo–hydro–mechanical (THM) interactions and high-frequency dynamic loading. Conventional THM models often fail to capture the full generality required to characterize these seabed responses, as they overlook microstructural size effects and soft clay rheology and assume idealized interfacial thermal contact. To address these limitations, this study proposes a unified non-local THM coupled dynamic model integrating non-local elasticity, fractional derivative viscoelasticity, and four distinct imperfect thermal contact conditions. Analytical solutions for temperature increment, excess pore water pressure and displacement in layered saturated porous media are rigorously derived. The framework assumes a one-dimensional, linear small-strain, fully saturated, and steady-state harmonic regime within homogeneous soil layers, and its validity is verified against an established analytical solution. Systematic parametric studies are performed to investigate the influences of the fractional order ratio (α⁽¹⁾/α⁽²⁾), constitutive parameters (τ_σ/τ_ε), and interfacial thermal resistance. The results indicate that when τ_σ/τ_ε < 1, the resonance frequency shifts toward lower frequencies as α⁽¹⁾/α⁽²⁾ increases. Conversely, when τ_σ/τ_ε > 1, the resonance frequency gradually increases, while the peak amplitude decreases. Moreover, interfacial thermal resistance significantly impedes heat transfer and induces pronounced localized temperature gradients. Neglecting these coupled effects may result in inaccurate predictions of the dynamic behavior of marine sediments. Full article

In this work, a methodology based on the finite element method is proposed for the design and simulation of optical modulators that exploit the magnetostrictive effect, aimed at enhancing the performance of magnetometers. The study focuses on a channel-type optical waveguide whose cross-section is carefully engineered to maximize opto-mechanical interaction while ensuring straightforward integration with magnetostrictive thin films. Fabrication follows the Induced Static Stress (ISS) technique: sputter deposition of a Terfenol-D (Tb_0.3Dy_0.7Fe_1.92) layer onto a bismuth germanium oxide (Bi₁₂GeO₄) substrate creates residual stresses because of mismatched thermal expansion coefficients. During operation, applied magnetic fields induce magnetostrictive deformation, which, together with the pre-existing thermal stresses, modifies the local refractive index via the elasto-optic effect, thereby enabling dynamic guiding and modulation of guided light. Numerical analysis is carried out in COMSOL Multiphysics 5.6, employing coupled structural and optical modules. A fine mesh is generated along the waveguide core, while material parameters such as Young’s modulus, Poisson’s ratio, magnetostriction constant, and refractive indices are specified for each layer. Full article

Grid-forming doubly fed induction generator (DFIG) systems integrated with flywheel energy storage systems (FESSs), hereafter referred to as FESS-DFIG systems, must be designed to provide rapid frequency support while maintaining DC-link voltage stiffness and respecting rotor-speed limits under finite kinetic-energy reserves. This study presents a model-based engineering design and verification framework that allocates these coupled requirements between the grid-side converter (GSC) and the rotor-side converter (RSC). For the GSC, stator–rotor coupling terms derived from the dq model are implemented as load-current feedforward signals to reduce the transient power imbalance across the DC link. For the RSC, virtual synchronous control is combined with a sigmoid-based rotor-energy constraint whose minimum-speed limit, transition width, and shape coefficient serve as physically interpretable design parameters for balancing frequency support against mechanical protection. The resulting architecture replaces abrupt support withdrawal with a continuous transition from inertial response to rotor-speed recovery. MATLAB/Simulink verification under load disturbances shows that compared with the conventional feedback-only dual-loop PI controller under the same 0.2 p.u. step-load disturbance, the proposed load-current-feedforward design reduces the maximum DC-link voltage deviation by approximately 33%, suppresses the secondary frequency dip and power oscillations caused by hard-switching logic, and maintains the rotor speed at the prescribed safety boundary of 0.8 p.u. Tests under low and high kinetic-energy conditions further demonstrate stable operation without changing the overall control architecture. The proposed framework therefore provides a systematic design basis for integrating DC-link regulation, grid-forming response, and rotor-energy management in converter-interfaced wind-energy systems. Full article

Background: Bicuspid aortic valve disease (BAVD) is the most frequent congenital heart disease, occurring either as an isolated lesion or in association with other congenital cardiovascular malformations, with variable patterns of progression and risk of valvular and vascular complications. Studies addressing pediatric bicuspid aortopathy are still in their infancy. This narrative review aims to provide a comprehensive perspective on the current scientific evidence regarding BAVD-associated aortopathy in pediatric patients, underscoring multiple challenges in initial diagnosis, long-term surveillance, and therapeutic decision-making, and focusing on the potential roles of circulating biomarkers and advanced multimodal imaging tools that may improve individualized risk stratification. Methods: Despite the narrative design of this review, a structured search of the current available literature was performed to identify studies addressing pediatric BAV, associated aortopathy, biomarkers, vascular remodeling, and multimodal imaging. Priority was given to pediatric cohorts, longitudinal studies, consensus documents, and contemporary guidelines. The search was conducted in the online databases PubMed/Medline and Web of Science for English-language original articles published in the last 10 years, up to May 2026. We used the following main terms: “Bicuspid Aortic Valve Disease” [MeSH], “Aorta” [MeSH], “Infant” [MeSH], “Child” [MeSH], “Adolescent” [MeSH], combined by Boolean operators with secondary keywords: “pathogenesis”, “mechanism”, “progression”, “multimodal imaging”, “echocardiography”, “cardiovascular magnetic resonance imaging”, “computed tomography”, “circulating biomarkers”. The retrieved studies were screened for eligibility using previously established inclusion and exclusion criteria. A total of 63 studies were included in the analysis for this narrative review. Results: Two main theories underpin the etiopathogenesis of aortopathy associated with the bicuspid aortic valve, positing that genetic factors predispose the aortic wall to remodeling in an abnormal hemodynamic environment. Embryological development and dysregulation of molecular and cellular structures are also intertwined during the formation and progression of the aortic valve with two semilunar cusps, resulting in consequent alterations in the aortic wall’s architectural organization. Advances in molecular studies have highlighted circulating biomarkers with potential utility in predicting aortopathy, as they are involved in extracellular matrix remodeling, endothelial dysfunction, and aortic valve calcification, including matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs), transforming growth factor-β (TGF-β), and microRNAs. In addition, multimodal imaging techniques have emerged as essential tools for assessing the morphology and function of cardiovascular structures, particularly aortic biomechanical properties and hemodynamic abnormalities, at the time of initial diagnosis and during regular monitoring. Taken together, blood biomarkers and imaging parameters of aortic remodeling and flow disturbances might gain increasing prognostic value in pediatric BAVD-associated aortopathy. However, larger longitudinal studies are required for clinical validation beyond research settings. Although guidelines on the management of BAVD are available for adults, they are not entirely applicable to children, who are undergoing continuous somatic growth that affects diagnostic possibilities and therapeutic options. Conclusions: Despite growing literature in the realm of BAVD and related conditions, the management of pediatric patients remains challenging in daily clinical practice, as adult guidelines cannot be completely applied to children. Given the heterogeneity and complexity of pathogenic mechanisms, clinical presentations, natural history, and outcomes, future research is warranted to explore the progression profiles of valvular and vascular disorders associated with BAV in children and to achieve an optimal approach to pediatric bicuspid aortopathy. Full article

Voltage spikes are particularly severe in low-voltage high-current inverters due to the influence of parasitic inductance during the turn-off process. A resistor-capacitor (RC) snubber circuit is commonly connected in parallel with the switching device to suppress excessive voltage overshoot. However, the snubber circuit inevitably introduces additional power losses, making the selection of snubber parameters critical for achieving low-loss operation. In this paper, the voltage spike suppression mechanism of the RC snubber circuit is first analyzed. Then, a comprehensive turn-off loss model is established by considering the MOSFET turn-off loss, the RC snubber loss, and the loss associated with the DC-bus parasitic inductance. Based on the proposed model, the influence of the snubber capacitance on the total turn-off loss is investigated. The results show that an optimal capacitance value exists, with which the total switching loss can be minimized. Finally, both simulation and experimental results are presented to validate the proposed loss model and demonstrate the effectiveness of the optimized snubber capacitance in minimizing inverter turn-off losses. Full article

The deployment of floating offshore wind systems in deeper waters introduces additional challenges for subsea power cables due to complex mechanical, environmental and operational factors. Among these, ensuring the longevity of cables requires a reliable fatigue damage assessment, which this study addresses by applying a wave fatigue methodology that integrates global and local analyses. Central to this methodology is the Adaptive Hysteresis Model, which transforms global loads into local strain. To evaluate its effectiveness, the methodology is applied to a 400 kV direct current subsea power cable design. Strain parameters from a detailed local analysis are used to transform global loads into local strain, followed by a rainflow counting method to extract the ranges. The identified strain ranges are then evaluated against a fatigue curve to determine the number of cycles to failure and the cumulative damage is calculated using the Miner–Palmgren summation. The study demonstrates the efficiency of the Adaptive Hysteresis Model and highlights the differences between higher-order hysteresis-based and simplified strain transfer methodologies when predicting strain ranges and fatigue damage in higher-order helically laid elements. Full article

The large-scale integration of renewable energy causes grid strength to vary over a wide range, exposing grid-following (GFL) inverters to both mid- and high-frequency resonance and subsynchronous oscillation (SSO). Conventional fixed-parameter designs cannot simultaneously maintain stability and dynamic performance because the phase-locked loop (PLL) and grid-voltage feedforward (GVF) dominate different frequency bands. This paper therefore proposes a backpropagation-neural-network (BPNN)-based adaptive parameter control strategy with frequency-band-coordinated regulation. First, a q-axis small-signal output-admittance model incorporating the current loop, digital delay, PLL, and GVF is established. The model reveals that the GVF coefficient primarily shapes mid- and high-frequency admittance under strong and moderately weak grids, whereas the PLL bandwidth becomes the dominant factor in low-frequency and subsynchronous stability under ultra-weak grids. Based on this mechanism, a BPNN is constructed with the grid short-circuit ratio (SCR) as the input and the GVF coefficient and PLL bandwidth as the outputs. Training targets are generated offline using parameter sweeps and performance screening based on current total harmonic distortion, Point of Common Coupling (PCC) voltage error, and settling time. During operation, the GVF coefficient is adjusted first, and the PLL bandwidth is reduced only when the grid becomes ultra-weak. Simulation results over $\mathrm{SCR}=1.25$–10 demonstrate that the proposed strategy preserves stable operation while providing better transient and harmonic performance than fixed-parameter and single-parameter tuning schemes in the cases studied. Full article

Electrified mobility regulations and lifecycle emissions targets have increased the demand for lightweight structural materials in vehicle architectures. Bioinspired composite materials offer microstructural configurations that alter conventional trade-offs among specific stiffness, crash energy absorption, and manufacturing energy requirements. This review evaluates the translation of biological structural archetypes including nacre, bamboo, cortical bone, and lotus leaves into load-bearing and functional automotive components. Quantitative benchmarks of continuous natural-fiber laminates, bio-cellular lattices, and mycelium-based acoustic cores are compared against high-strength steel and aluminum alloys. Key mechanical and functional metrics, including specific energy absorption (ranging from 35 to 48 kJ kg⁻¹ for bioinspired crash structures), dynamic loss factors, and Cassie-Baxter superhydrophobic surface stability, are evaluated alongside high-throughput manufacturing routes such as high-pressure resin transfer molding (HP-RTM) and additive manufacturing. Methodological parameters for ISO 14040/14044-compliant Life Cycle Assessment (LCA) are synthesized, emphasizing component-level functional units over gravimetric mass equivalence. Furthermore, operational boundaries, specifically hygrothermal interfacial degradation, matrix glass transitions (T_g < 120 °C), and multi-axial loading sensitivity, are systematically outlined to define design limits for automotive deployment. Full article

To address the inefficiencies of two-stage sweet potato harvesting in southern China, an integrated machine for synchronous haulm shredding and tuber excavation was developed. The equipment features a front-mounted, reverse-rotating crushing knife roller and a rear-mounted, adjustable grate-type digging shovel. The performance of the prototype was systematically evaluated through two-stage field trials in clay loam soil. First, an orthogonal test was employed to assess the haulm shredding quality. The results indicated that the knife roller speed significantly increased the qualified rate of crushed stems and leaves, whereas the forward speed exerted a negative effect. Additionally, the blade-to-ridge clearance primarily dictated the ridge-top stubble length. Second, a quadratic orthogonal rotational composite design was utilized to optimize the integrated harvesting parameters. The analysis demonstrated that shovel inclination significantly enhanced the tuber exposure rate, while both clearance and inclination exhibited quadratic nonlinear effects on the tuber damage rate. Multi-objective optimization established the optimal operational parameters as a blade-to-ridge clearance of 66.6 mm and a shovel inclination of 34.0°. Field validations under these settings achieved a tuber exposure rate of 83.7% and a damage rate of 4.3%, confirming the high reliability of the predictive models. The integrated equipment effectively shortens the harvesting cycle and demonstrates robust adaptability to clayey moist soils, thereby advancing the mechanization of sweet potato production. Full article

Background/Objectives: Acute hypercapnic respiratory failure is associated with significant morbidity and mortality despite advances in non-invasive mechanical ventilation (NIMV) therapy. The frontal QRS-T angle is a simple electrocardiographic marker reflecting ventricular depolarization–repolarization heterogeneity and has been associated with adverse cardiovascular outcomes. However, the relationship between dynamic changes in frontal QRS-T angle and NIMV treatment response in acute hypercapnic respiratory failure remains unclear. This study aimed to evaluate the association between frontal QRS-T angle changes after NIMV treatment and clinical outcomes in patients with acute hypercapnic respiratory failure. Methods: This retrospective observational cohort study included 186 adult patients hospitalized with acute hypercapnic respiratory failure and treated with bilevel positive airway pressure between January 2024 and December 2025. Frontal QRS-T angle values were obtained from standard 12-lead electrocardiograms recorded before NIMV initiation (T0) and at the 24th hour of treatment (T24). Clinical, laboratory, arterial blood gas, and electrocardiographic parameters were analyzed. Receiver operating characteristic (ROC) analysis, Kaplan–Meier survival analysis, correlation analysis, and multivariable logistic regression analysis were performed to evaluate the prognostic significance of frontal QRS-T angle. Results: Successful NIMV treatment was achieved in 143 patients (76.9%), whereas 43 patients (23.1%) experienced NIMV failure. Patients with failed NIMV treatment had significantly higher baseline frontal QRS-T angle values compared with the successful group [128° (94–156) vs. 71° (48–101), p < 0.001]. Frontal QRS-T angle significantly decreased after treatment in the successful NIMV group but not in the failed group. A significant positive correlation was observed between ΔPaCO₂ and Δfrontal QRS-T angle (r = 0.624, p < 0.001). ROC analysis demonstrated that baseline frontal QRS-T angle predicted NIMV failure with an AUC of 0.842 (95% CI: 0.773–0.898) and in-hospital mortality with an AUC of 0.811 (95% CI: 0.735–0.873). Kaplan–Meier analysis showed significantly lower survival rates in patients with frontal QRS-T angle >90° (log-rank p < 0.001). Multivariable logistic regression analysis identified frontal QRS-T angle >90° as an independent predictor of in-hospital mortality (OR: 3.617, 95% CI: 1.484–8.813, p = 0.005). Conclusions: Baseline frontal QRS-T angle was associated with NIMV failure and in-hospital mortality, while its 24-h change was associated with physiological response among patients with paired T0–T24 measurements. These findings are hypothesis-generating and do not establish the utility of frontal QRS-T angle monitoring for immediate escalation or intubation decisions. Full article