Search Results (25,425)

In networked control systems, power line communication technique is used to transfer data over existing energy cables. A soft fault degrades the integrity of the signal without impacting the system behaviour. This work develops a transferometry-based method for detecting, localising, and estimating the severity of two simultaneous soft faults in such cables. A soft fault is modelled as a series impedance, and the transmission coefficient (TC) is computed from the ABCD cascade model of the cable. We prove that, under unmatched terminations, the time-domain TC exhibits a five-pulse signature whose peak positions and amplitudes map directly to the two fault positions and their individual severities. A residual signal constructed from this signature yields closed-form estimators for the fault positions and their combined severities; individual fault severities require a bounded nonlinear least-square fit, valid for approximately symmetric, known terminations. We further show that the method extends to n simultaneous soft faults under a combined soft-fault condition, with the $(2n+1)$-pulse pattern verified in simulation for $n\in \{1,2,3,4\}$. A Monte Carlo study using correct localisation probability as the detection criterion establishes a practical SNR threshold of 25 dB; fault-separation resolvability shows intermittent, sidelobe-driven degradation rather than a single threshold. Simulations on a measured 24 AWG cable, extrapolated beyond its characterised band, confirm reliable two-fault diagnosis under additive noise, with reliable multi-fault performance demonstrated for $n=1,2$, presented as a numerical proof of concept on this extrapolated cable model rather than a characterisation confirmed by measurement over the full simulated band. Full article

This study focuses on a three-step iterative scheme, referred to as the NIP iteration, for the approximation of fixed points associated with nonexpansive mappings in uniformly convex Banach spaces. Weak convergence is established using Fejér monotonicity, asymptotic regularity and the demiclosedness principle. Strong convergence is proved under uniform convexity, compactness, and Condition (I) of Senter and Dotson. A numerical convergence and computational-cost comparison is developed numerically, showing that the NIP iteration performs better than the Ishikawa, S, Noor, Abbas–Nazir and SP schemes. Numerical experiments for nonlinear nonexpansive mappings validate the theoretical findings. An application to convex optimization via fixed point reformulation is also presented, illustrating the effectiveness of the method. Full article

Safety, profitability, as well as energy and resource efficiency of hydropower plants require, among others, appropriate operation of hydraulic turbines, which involves reliable estimation and monitoring of water flow rate. In this work, computer simulation is used for investigation of water flow through the spiral casing of a hydraulic turbine under real operating conditions. The wall pressure at the pre-defined monitoring points in a radial plane, such as used in the Winter–Kennedy measurement method, is calculated for a range of water flow rates. The choice of the boundary-condition type downstream of the stay vanes and sensitivity to adopted turbulent-flow approach are also investigated. The numerical results agree well with the reference measurements. A relation is established between the computed monitoring pressure difference and the corresponding incoming flow rate. Having measured the static pressure at the given points, it can be used for continuous estimation of the water flow rate in the turbine under actual operating conditions. Full article

This paper presents an observer-based strategy for controlling the horizontal trajectories of a hummingbird robot from on-board inertial measurements (MEMS). The centrifugal acceleration resulting from sharp turns is responsible for the dynamic coupling between the roll axis and the pitch and yaw axes. This coupling cannot be accounted for with independent control loops for the three axes; the problem can be solved with a modified state observer (MSO) introduced on the roll axis. Numerical simulations are presented to confirm the idea. The limited additional computational burden allows for real-time implementation. The MSO allows the robot to mimic the behavior of birds that lean towards the inside when turning. Under steady-state conditions (uniform longitudinal velocity and constant yaw rate), the pitch angle is such that the longitudinal component of the gravity vector balances the longitudinal drag force and the roll angle is such that the lateral component of the gravity vector balances the centrifugal acceleration. Full article

As urban mining plays an increasingly important role in resource security and sustainable development, insufficient coordination among reverse supply chain participants has become a major constraint on the efficient recovery of urban mineral resources. From the perspective of interfirm cooperative innovation, this study takes waste mobile phones as an application context and develops a four-party evolutionary game model involving the government, recyclers, remanufacturers, and consumers. The model incorporates opportunistic behavior in cooperative innovation, government subsidy intensity, and product pricing into a unified analytical framework. Replicator dynamics, Jacobian-based stability analysis, and numerical simulations are employed to examine the evolutionary mechanisms and stability conditions of multi-actor collaborative governance. The results identify four stable equilibrium configurations and show that: (1) excessive innovation spillovers and asymmetric interdependence between recyclers and remanufacturers may weaken incentive compatibility and induce opportunistic behavior; (2) the effects of government subsidies vary across evolutionary stages and depend on the strategic responses of other actors; and (3) interfirm transfer prices and final market prices promote stable cooperation only within specific ranges. These findings provide a theoretical basis and policy implications for improving collaborative governance in reverse supply chains for urban mineral resource recovery and supporting sustainable urban mining. Full article

Secure transmission and storage of color images remain challenging tasks due to strong inter-pixel correlations and high data volume. This work proposes a one-dimensional sine-tent-logistic-exponential map (STLEM) equipped with numerical boundary correction rules to mitigate finite-precision numerical degradation so as to enhance the unpredictability of chaos-driven cryptosystems. We benchmark STLEM against classic logistic, tent, and sine maps via Lyapunov exponents, autocorrelation, approximate entropy, permutation entropy, Lempel-Ziv complexity, and Kolmogorov–Sinai entropy. Bifurcation diagrams, the 0–1 test, and NIST statistical tests are further adopted to characterize its chaotic dynamics and randomness. Comparative results verify that STLEM achieves improved dynamical complexity and randomness performance. Built upon the proposed STLEM, this paper constructs a color-image encryption scheme that employs a 256-bit master key and two groups of chaotic parameters to produce key-related chaotic sequences. The cryptosystem integrates dynamic edge expansion, chaotic permutation, position-dependent adaptive DNA encoding, DNA-domain chained diffusion, and two successive row-column permutation phases. HMAC-SHA-256 is utilized to generate plaintext-aware initial conditions and perform ciphertext authentication prior to decryption. Experimental validations demonstrate complete plaintext recovery under valid secret inputs, while authentication rejects invalid keys and tampered ciphertexts. Ciphered images exhibit high information entropy, negligible adjacent-pixel correlations, and satisfactory number of pixel change rate (NPCR) and unified average changing intensity (UACI) metrics. Benefiting from a sufficiently large key space and $O\left(MN\log \right(MN\left)\right)$ computational complexity, the proposed scheme is resilient against brute-force attacks and well suited for secure color-image communication scenarios, rather than acting as a general-purpose replacement for standard block ciphers. Full article

E-commerce platforms involve interactions among platform governance, manufacturer pricing, consumer perception, and managerial cognition. This study examines how platform overconfidence and consumer product-fit perception accuracy affect pricing, profitability, and operational mode selection. Product-fit perception accuracy denotes the probability that consumers correctly perceive the mismatch between their preferences and product attributes. We develop a two-period dynamic game involving two competing platforms and two manufacturers and compare resale and agency modes under simultaneous and sequential decisions. Equilibrium analysis shows that, under the agency mode, overconfidence increases promotional allowances and manufacturers’ first-period and switching-purchase prices, while its effect on repeat-purchase prices depends on a mismatch-cost threshold. Under the resale mode, overconfidence raises wholesale prices only within an intermediate range, and product-fit perception accuracy can have either a positive or negative effect depending on the level of overconfidence. Sequential decision-making further produces different pricing responses for leader and follower platforms due to differences in commitment and information conditions. Numerical analysis under the specified parameter settings indicates that resale tends to generate higher platform profits when consumers’ perceived product-quality level is high. When this level is low, the relative profitability of the two modes becomes more sensitive to overconfidence, product-fit perception accuracy, and decision position, with agency becoming more profitable in some parameter regions. These results characterize how governance mode and decision timing shape the economic consequences of managerial overconfidence and product-fit information within the modeled platform setting. Full article

This paper studies a coupled system of viscoelastic wave equations with frictional damping, cross-tempered fractional damping, viscoelastic memory, and logarithmic source nonlinearities. The fractional damping acts across the two components, so that the fractional feedback in each equation is generated by the velocity of the other component. To handle the memory and fractional terms, we introduce suitable history and diffusive variables and reformulate the problem as an evolution system in an extended energy space. Under appropriate assumptions on the relaxation kernels, fractional parameters, and nonlinear exponent, we establish the local well-posedness of mild and strong solutions using semigroup theory. We then use a potential-well argument to prove global existence for initial data in the stable set. Under an additional decay condition on the relaxation kernels, an appropriate Lyapunov functional is constructed to establish the exponential decay of the energy. Finally, numerical simulations based on a finite-difference scheme and a physics-informed neural network (PINN) are used to illustrate the predicted decay behavior. Full article

In molten salt reactors (MSRs), helium bubbling systems can be employed for the continuous removal of gaseous fission products. However, helium injection generates local gas–liquid two-phase flow in the fuel salt and may induce corresponding local perturbations in the calculated neutronic field. To investigate these bubble-scale interactions, this study developed a coupled multi-physics framework integrating the volume of fluid (VOF) method with a multigroup neutron diffusion model. The framework was applied to a localized 20 mm × 40 mm fuel-salt domain containing a single 1 mm helium injection nozzle. Planar 2D and axisymmetric calculations were performed to examine the influence of geometrical representation on bubble growth, detachment, transport, and the corresponding local power response. The axisymmetric formulation was further used to evaluate the sensitivity of the calculated response to the helium mass flow rate. Within this restricted numerical test problem, the coupled framework resolved the evolution of helium bubbles and the associated local changes in the power field under the prescribed boundary conditions. For the centered circular nozzle and symmetry-preserving near-inlet conditions considered, the axisymmetric formulation provided a more geometrically consistent representation of rotational volume weighting and interfacial curvature than the planar 2D formulation. Variations in helium mass flow rate also modified the calculated local bubble behavior and power-response metrics. These results constitute a numerical demonstration of local bubble-resolved multi-physics coupling and should not be interpreted as reactor-scale power predictions, core-wide safety metrics, or design criteria for an MSR helium bubbling system. Full article

The increasing penetration of converter-interfaced renewable energy sources poses significant challenges to power quality in modern microgrids, especially under nonlinear and unbalanced load conditions. Conventional virtual-impedance strategies can improve converter-grid interaction; however, the use of fixed parameters or adaptation based on a single electrical variable may provide limited performance under dynamically changing power-quality conditions. This article proposes a multi-objective power-quality-index-based adaptive virtual impedance (PQI-AVI) strategy for grid-connected hybrid microgrids with high renewable-energy penetration. The supervisory PQI combines normalized voltage total harmonic distortion (THDv), the voltage unbalance factor (VUF), and voltage-magnitude deviation to continuously adjust the virtual resistance and reactance. To prevent excessive impedance adaptation, the setpoint generated by the PQI is further constrained by a grid-strength-dependent stability limit derived from a small-signal analysis that includes pulse-width modulation (PWM) delay dynamics. The proposed strategy is evaluated in MATLAB-Simulink^® using a modified IEEE 14-bus hybrid microgrid with an aggregate operating demand of 10 MW under nonlinear and unbalanced load conditions. Compared with the uncompensated condition, the proposed controller reduces THDv from 7.84% to 2.11%, THDi from 15.8% to 4.8%, and VUF from 2.50% to 0.80%, while simultaneously improving the power factor from 0.86 to 0.97. The stability analysis further demonstrates that the admissible virtual-impedance adaptation depends on grid strength when PWM dynamics are explicitly considered. These results show that the proposed stability-constrained PQI-AVI framework enables coordinated power-quality improvement while restricting the virtual-impedance command to the numerically identified small-signal stable adaptation region for the grid-strength conditions considered. Full article

Pipeline leakage acoustic signals are governed by the coupled effects of leakage excitation, acoustic–structural interaction, and propagation filtering, while the physical relationship between leakage conditions and measurable spectral characteristics remains insufficiently understood. In this study, a three-dimensional numerical framework combining leakage flow simulation, acoustic–structural coupling analysis, and dual-hydrophone experiments was developed to investigate the formation and propagation mechanisms of leak-induced acoustic signals in water pipelines. The investigated steel pipeline had an inner diameter of 50 mm, with leak hole diameters of 1–4 mm (d/D = 0.02–0.08). The leakage flow remained turbulent, with a Reynolds number of approximately 7.0 × 10³, and the dominant acoustic response corresponded to Strouhal numbers of 1.7 × 10⁻³–2.1 × 10⁻². The results show that supply pressure mainly controls leakage excitation intensity through hydraulic power, whereas the leak hole diameter primarily modifies the frequency-band distribution. A narrow-band pipe wall vibration enhancement was identified near 280 Hz, which was associated with the coupled pipe–water mode at 278.97 Hz. Experimental measurements further demonstrated strong propagation-induced frequency filtering, with more than 97% of far-field signal energy retained within the 20–250 Hz band. These findings establish a continuous relationship between hydraulic leakage input, local acoustic–structural response, and measurable leakage spectra, providing physical insights into acoustic-based pipeline leak detection. Full article

Multiphase pumps are key equipment for the efficient transport of multiphase fluids in the petroleum industry, and their transient stability under variable-speed conditions directly affects system reliability. By combining numerical simulation with experimental validation, this study systematically investigates the evolution of external characteristics, energy conversion mechanisms, and the dynamic response of the internal flow field during a 0.4 s variable-frequency speed regulation cycle at inlet gas volume fractions (IGVFs) of 10% and 20%. The numerical model was validated against experimental measurements of a four-stage multiphase pump under pure-water steady-state conditions, with deviations in head, efficiency, and power all within 5%. The results show that during acceleration, the increase in hydraulic efficiency at the lower IGVF is greater than that at the higher IGVF; once deceleration begins, IGVF has no significant effect on hydraulic efficiency. At the investigated IGVFs of 10% and 20%, a higher IGVF increases the transient sensitivity of the internal flow field to speed variation, and increasing IGVF suppresses energy conversion in the impeller. The principal novelty of this work lies in the temporal decomposition of impeller work into dynamic and static pressure components during transient speed variation, revealing that static pressure power consistently accounts for more than 50% of the total power throughout the speed regulation cycle. As rotational speed increases, dynamic pressure power rises because the circumferential velocity of the fluid increases with impeller peripheral speed, while static pressure power also increases continuously owing to the enhanced static pressure work of the blades. During deceleration, the impeller’s energy transfer capability weakens with decreasing rotational speed, and both dynamic and static pressure power decline. These findings elucidate the coupled evolution of gas–liquid two-phase flow under variable-speed conditions and provide a theoretical basis for the operational optimization and speed control of multiphase pumps. Full article

Malaria and typhoid fever co-infection produces severe illness affecting public health, especially in countries where both diseases coexist. A mathematical model that considers the critical factors influencing the transmission dynamics and control interventions of malaria and typhoid fever co-infection is developed. The essential epidemiological features of the model, such as the basic reproduction number and disease-free equilibrium, are determined and analysed. A dynamical systems analysis of the model reveals the conditions under which the disease can be eradicated or persists. Numerical simulations are conducted using real data from Nigeria as a case study. By fitting the model to the real data, essential parameter values are estimated and model prediction that reveals the possible long-term dynamics of the model is determined. The impact of the various control interventions are investigated. These findings are anticipated to aid in improving the management of malaria–typhoid co-infection in endemic regions for expeditious disease eradication. Full article

Green manuring may improve crop performance on acidic, low-fertility soils, although its effects depend on the incorporated species and mineral fertilization regime. This study evaluated the effects of five green manure crops and mineral fertilization on winter wheat during the 2021/2022 growing season at the Agricultural Research and Development Station Livada, northwestern Romania. A two-factor split-plot field experiment was conducted at a single location during one growing season (2021/2022) using three replicate blocks. Six main-plot treatments—wheat, triticale, pea, narrow-leafed lupine, oilseed rape, and a non-sown control with spontaneous vegetation—were combined with two subplot regimes: with and without combined N–P mineral fertilization. The green manure × mineral fertilization interaction was significant for grain yield (p = 0.008). Under mineral fertilization, pea produced the highest numerical grain yield (8018 ± 116 kg ha⁻¹; mean ± SE, n = 3), compared with 6730 ± 244 kg ha⁻¹ in the corresponding fertilized control. Without mineral fertilization, pea and lupine produced 5427 ± 187 and 5009 ± 237 kg ha⁻¹, respectively, compared with 3419 ± 108 kg ha⁻¹ in the corresponding non-fertilized control. Wheat and triticale green manures were associated with lower subsequent wheat yields than their corresponding controls under both fertilization regimes. Under the conditions of this single-site, single-season experiment, pea and narrow-leafed lupine were associated with favorable grain-yield responses, particularly relative to the corresponding non-sown controls. Further multi-year and multi-location experiments are required to determine the stability of these responses under contrasting soil and climatic conditions. Full article

Composite micromechanics is commonly divided between rapid mean-field estimates and computationally intensive full-field representative-volume-element (RVE) simulations. When these routes use different files, conventions and post-processing procedures, discrepancies can reflect bookkeeping rather than mechanics. This paper introduces HARVEST (Homogenisation and Representative Volume Element Simulation Tool; version 0.7.0.dev0), a general-purpose platform that coordinates mean-field homogenisation, three-dimensional RVE generation, finite-element model preparation, solver execution, homogenisation, parameter studies and post-processing through common project, service and provenance boundaries. The numerical framework is material-agnostic, whereas verification and validation are demonstrated using polymer-based nanocomposites. The Mori–Tanaka bulk response for spherical inclusions reproduces the Hashin composite-sphere result to machine precision, independent orientation procedures agree to a relative difference of $1.6\times {10}^{-14}$, and a sequential coated-particle approximation differs from an analytical composite-sphere reference by at most $0.417$% over 24 polymer-relevant configurations. An archived full-field epoxy/silica-type campaign using kinematic uniform boundary conditions and ${20}^3$ structured cells remains within the Hashin–Shtrikman interval at five inclusion fractions, with realisation scatter below $0.4$%. For published epoxy nanocomposites, aligned halloysite-nanotube predictions differ from measured flexural moduli by $-0.89$ and $+0.48$%, while spherical carboxyl-terminated butadiene–acrylonitrile-rubber predictions differ by $-7.03$ and $-2.25$%. The main conclusion is that a shared, traceable description of constituents, morphology, loading and outputs supports rapid mean-field screening followed by selective full-field analysis using the same material definition. The principal advantage over single-route or loosely coupled workflows is cross-route consistency and reproducibility. HARVEST is applicable to formulation screening, sensitivity studies and local-field assessment in particulate, tubular, rubber-modified, porous and mixed-matrix polymer systems, and can be extended through validated constitutive, geometry, solver and result adapters. Full article