This work develops a systematic ansatz framework to construct and classify exact nonlinear wave structures of a recently proposed extended (4+1)-dimensional Fokas equation [Wazwaz et al., Rom. Rep. Phys. 78, 109 (2026)], a higher-dimensional integrable model that remains robust under additional linear couplings in the transverse directions. Building on a fully integrable Fokas-type extension, the new extended model preserves its Painlevé property while incorporating additional mixed-derivative and dispersive terms relevant to multidimensional wave propagation across various interdisciplinary fields, including fluids, plasmas, and optical media. Within this setting, a logarithmic ansatz formula combined with mixed derivatives Φ=R(lnf)mn is introduced to the extended (4+1)-dimensional Fokas equation, which yields seven distinct closed-form families of soliton-like solutions. These solutions explicitly link the amplitude and geometric localization of the waves to the extended dispersion relation, thereby exposing how the added linear terms reshape the propagation and interaction of coherent structures in higher dimensions. Complementing this construction, various forms of the ansatz in hyperbolic and trigonometric forms are employed to derive additional hyperbolic and trigonometric solutions, producing both regular and singular localized pulses as well as spatially periodic wave trains within a single unified framework. The resulting catalogue of solutions, supported by numerical visualization of their dynamics, demonstrates that the extended Fokas model can sustain a rich hierarchy of multidimensional solitons and periodic patterns, thereby providing a versatile prototype for describing nonlinear wave phenomena in complex dispersive media.
Large-core optical fibers typically offer the advantages of high input power and improved coupling efficiency at the expense of low nonlinearity and large transmission loss. In this work, we numerically verified that large-core photonic crystal fibers provide high nonlinearity and low confinement loss, enabling broadband mid-infrared supercontinuum generation with nanojoule input pulse energies. The designs use highly nonlinear refractive index Ge25Sb10S65 glass as the substrate material with seven rings of air hole in the cladding arranged in a regular octagonal pattern around the core. The nonlinear propagation in the two proposed fibers is well described by solving the generalized nonlinear Schrödinger equation. Using pump pulses at 3.6 μm with durations of 40 fs and 250 fs and peak powers of 12 kW and 18.5 kW, respectively, two fibers generate supercontinuum bandwidths covering the ranges of 1.921 ̶ 5.698 μm and 1.79 ̶ 9.0 μm under both all-normal and anomalous pump regimes. These compact and stable all-fiber supercontinuum sources, operating at relatively high peak powers, are potentially suitable for medical diagnostic applications due to their arsenic-free nature.
This study investigates the physical properties of short carbon fiber reinforced polylactic acid (SCFR-PLA) specimens produced by fused deposition modeling (FDM). The influence of fiber content, raster angle, and printing speed on mechanical, hygroscopic, and microstructural behavior is analyzed. Printing at a 0⚬ raster angle provides maximum stiffness and tensile strength, while higher speeds enhance strength and ductility but reduce stiffness. Carbon fiber addition improves stiffness, strength, and moisture resistance. SEM analysis reveals pore morphology, linking porosity to mechanical and hygroscopic variations. Correlations among fiber-matrix adhesion, voids, moisture uptake, and durability are also discussed.
Mathematical and neural network models of heat propagation in a solid under pulsed laser irradiation have been constructed. The proposed mathematical model takes into account the simultaneous existence of different phases, the boundaries of which may shift over time. Within the framework of the developed model, regularities of the spatiotemporal temperature distribution in polycrystals of copper and niobium under the influence of a pulsed laser with a pulse duration in the nanosecond range were established. An artificial neural network architecture has been developed that is capable of predicting the spatiotemporal temperature distribution in solids based on their given thermophysical parameters and laser irradiation characteristics. The obtained results within the framework of the neural network model demonstrate a high degree of generalization, which indicates the prospects for its use for the optimal selection of materials and their irradiation regimes in order to create predicted temperature fields.
The paper presents exact analytical solutions for stationary nonlinear surface waves propagating along the interface between a gradient-index medium and a generalized Kerr-type nonlinear medium. Four wave modes, classified by the signs of the nonlinearity coefficients in the bulk and boundary layer, demonstrate a fundamental physical dichotomy. When the boundary layer exhibits self-focusing nonlinearity, the wave peak is localized within the nonlinear medium, and the intensity strongly depends on the effective refractive index. In contrast, a defocusing boundary layer pushes the field maximum into the gradient-index region, resulting in wave properties that are primarily determined by the linear refractive index profile.
This study explores how scaffold geometry affects structural and mechanical performance in tissue engineering. Lattice-based designs ̶ including cross, diamond, honeycomb, octet, grid, vintiles, and X-type ̶ were modeled within a standardized 1728 mm3 volume. High-porosity structures (X, diamond) promoted cell adhesion and nutrient transport, while honeycomb architectures exhibited low porosity and high relative density, enhancing mechanical stability. Mechanical performance was evaluated via mesh analysis and finite element simulations, and manufacturing feasibility was assessed using FDM and SLA, with SLA showing superior fidelity for complex microstructures. Scaffold behavior is governed by the interplay of geometry, material properties, and fabrication constraints.
Operational matrix methods used in time-fractional differential equations often suffer from limited accuracy. This is primarily due to the approximation of non-smooth fractional derivatives using operational matrices based on smooth basis functions. These errors can be reduced by using non-smooth basis functions. This study proposes a numerical method for the time-fractional GHS-C-KdV system using shifted Gegenbauer polynomials. A novel orthogonal shifted Gegenbauer function, time-nonsmooth and spatially smooth, is constructed to form the basis of the operational matrix for fractional derivatives. Combined with the spectral collocation approach, this method reduces the computational complexity. The numerical results demonstrate high accuracy and superiority over traditional shifted Gegenbauer polynomials.
In the context of students studying renewable energy sources, it is important to understand how the integration of renewable energy sources into isolated electrical systems is carried out. This aspect presents significant challenges related to voltage stability and power quality. The present study focuses on modeling a reactive power compensation system to stabilize a solar-powered network using MATLAB/Simulink. Two simulation models were developed: one employing capacitor banks and the other utilizing a Static VAR Compensator (SVC). The simulations incorporated both dynamic phasor and steady-state analysis methods. Results indicate that while capacitor banks offer a cost-effective solution for steady-state reactive power compensation, SVCs provide superior dynamic response and voltage regulation. The study concludes that a hybrid approach, combining both technologies, can enhance grid stability and ensure reliable integration of renewable energy sources in remote areas. This paper emphasizes the importance of managing reactive power in the transition to sustainable energy systems and the way to develop problem-solving skills for this type of issue among master's students in renewable energy studies.
We study the anticipatory reaction of bees preceding the earthquake that occurred at 16:28:17 on September 18, 2020 (UTC) with an epicenter 12 km south-southeast of the city of Arkalochori (Southern Crete, magnitude 5.9), at 01:17:35 February 6, 2023 with the epicenter in the area of Sehitkamil (Turkey, magnitude 7.8), as well as at 02:42:27 June 22, 2023 with the epicenter 50 km south of Sevastopol (Crimea, magnitude 4.7). Shows that statistical phenomena interpreted as precursors, in all the cases considered quite clearly “gravitate” to the moment of the onset of the corresponding earthquake. The effect of a significant increase in the concentration of statistical phenomena, considered as harbingers of an approaching earthquake, was revealed during a time interval of about one day before the start of the event. The study was made of the influence of a distant earthquake on the statistics of the noise of bees in a hive. The seismic processes influence the behavior of bees in the hive at least up to distances of the order of 1200 km from the epicenter. The effect of anticipatory reaction of bees to an upcoming remote event with a characteristic time of such a reaction of the order of several hours was found.
This paper aims to explore a variety of distinct physical solutions for a novel extended nonlinear (4+1)-dimensional Fokas equation (4D-FE). Using the simplified Hirota method (SHM) systematically, we showcase multiple soliton solutions for this model. The dispersion relations and phase shifts associated with the colliding solitons are determined. Additionally, for a (2+1)-dimensional model obtained from the 4D-FE, the lump solutions are derived. Moreover, some derived solutions are graphically simulated to provide context for the dynamics of wave propagation described by these solutions.
The paper is aiming to present a synthesis of results obtained in the period 2014-2025 for the activity concentration of indoor radon (Rn-222) and thoron (Rn-220) and their temporal variations in selected dwellings and public spaces in Galati, Ilfov, Suceava and Tulcea counties, Romania, including educational institutions (gymnasium and high schools), universities and research laboratories at Dunarea de Jos University of Galati and Horia Hulubei National Institute for Physics and Nuclear Engineering. For the active measurements, calibrated instruments of SARAD type have been used (Radon Scout, RTM1688-2, Thoron Scout). A disscussion is made for the factors which may influence the variability of radon/thoron levels, such as: building type, design and characteristics, location, building materials, floor level, ventilation type, season and measuring time. Radon activity concentration (RAC) is higher than the thoron (TAC) one in all the cases, except for brick residential buildings and educational premises located at higher floors, suggesting an influence of the building materials for radon/thoron exhalation rather than the soil/foundation. Repeated measurements performed in houses built with clay or waste slag bricks and in the vicinity of terracotta stoves show maximum radon levels in the range 379-1100 Bq m(-3) which exceed in a large extent the value legislated by the Romanian norms, of 300 Bq m(-3). Also, the lack of aeration or artificial/natural ventilation of underground laboratories or ground floor apartment rooms led to the fast accumulation of radon gas, reaching in 2-7 days levels of 490-657 Bq/m(3), while the meteorological data did not exhibit noticeable variations. The effect is even more pronounced for the kitchen room in a ground floor apartment, probably due to the proximity of domestic water and gas conducts, as well as the presence of ceramic tiles. The RAC values are lower in an adobe and wood house compared to an adobe and clay house, with similar construction age. The results of this work provide a reliable support for national radon monitoring program and a useful radon and thoron database for future screening plans.
This paper describes the propagation of the action potentials (APs) along a neuron as well as the chain of interconnected neurons by means of chemical and electrical synapses. At the level of dendrites, soma, axon, and axonal ramifications, the AP propagation is of electric type, being mediated by ionic currents. The soma membrane depolarizations due to affluent signals sent by dendrites are summed up in space and time. If the depolarization at the level of axonal hillock, is over a threshold, a train of APs is generated and propagated along the axon reaching the presynaptic membranes and producing the fusion of neurotransmitter vesicles, with the presynaptic membrane. The liberated neurotransmitters are passively diffusing in the synaptic cleft reaching the specific receptors embedded in the postsynaptic membrane. Here, they interact specifically with receptors and opens or closes different ionic channels depolarizing the postsynaptic membrane (for excitatory synapses) or hyperpolarizing them (for inhibitory synapses). Also, in this case, if membrane depolarization is beyond a threshold, a train of APs is downstream delivered to the next neuron and so on. The chain of neurons assuring AP propagation could be affected by different anomalies engendering many neural disorders as it is described in the last part of the paper.
This investigation examines the dynamical characteristics of various soliton-type solutions of the (2+1)-dimensional non-autonomous perturbed Gardner-Kadomtsev-Petviashvili (NAPGKP) equation. Using its bilinear form, multi-soliton solutions are derived through Hirota's approach. Intensive study on soliton propagation, soliton interaction, and complex hybrid solutions are performed. Breathers are explored from a multi-soliton solution by selecting a suitable complex conjugate relation in the wave vector. The significant impact of different parameters on the characteristic line of the breather is examined. Along with the group velocity, the phase velocity of the breather is presented explicitly. Positon solution of higher order and the interaction of other waveforms are exhibited by selecting suitable values of parameters.
Given the continue desire to increase accuracy and precision in the delivery of radiotherapy treatments, new methods are needed to minimize the uncertainties that can arise throughout the treatment chain. One of the key elements in the accuracy of treatment delivery is the images acquired by CT scanner. Based on this information, the geometric localization of the volume to be irradiated, generically referred to as the target volume, as well as the virtual calculation of dose absorbed inside the patient are performed. With the technological evolution, it is necessary to update the procedures used for patient scanning, given the increased detection and processing capabilities, in order to obtain more qualitative and ultimately more clinically conclusive data. This issue becomes increasingly significant in short session treatments (1-5) fractions. Given the low number of fractions, relative to conventional treatments with around (20-25) fractions, the random element of error starts to become non-mediating and can produce significant deviations in treatment delivery if this aspect is not adequately compensated for. The aim of this work is to test and optimize the CT scanner acquisition and processing parameters so that the data series used to perform the entire chain of processes will ultimately produce a decrease in the uncertainty of treatment delivery. Specifically, the available reconstruction algorithms are tested as well as the modification of slice thickness, slice-to-slice thickness and scan diameter.
Ultra-high-energy cosmic rays are still some of the most mysterious phenomena in astroparticle physics. Boasting energy levels of above 1 EeV (1018 eV), far higher than other particles traveling the Universe, or energies reached in the laboratory, they incite significant unanswered questions concerning their actual origin and nature. Highly energetic cosmic particles are a window into the study of fundamental physics at its limits and beyond. The most comprehensive method of studying them is by observing their signatures resulted from the atmospheric interactions in the developing extensive air shower (EAS). An EAS consists of secondary elementary particles produced in a cascade reaction from a primary cosmic ray particle entering the Earth’s atmosphere. It can be traced on the ground using the powerful grid of radio detectors of the upgraded Pierre Auger Observatory (AugerPrime). The radio footprint of cosmic ray induced air shower events is fed to a convolutional neural network, alongside geometric characteristics extracted from CORSIKA 7 (with the CoREAS option) simulated air showers. Thus, modified ResNet and EfficientNet deep learning models are trained to classify the nuclear mass of the primary cosmic ray particle based on the observable parameters, with performances assessed by standard metrics such as Accuracy, F1 Score and MCC Score, which are shown to fluctuate, as expected, with the number and types of primary particles represented in the dataset, and the features included in the analysis, indicating the depth of the shower’s maximum aperture (Xmax) as the most valuable for the classification task, and the radio footprint image as a good replacement for the numerical simulation data. The classification metrics indicate an overall moderate positive rate, with accuracies of up to 83% reached for groups of particles with larger nuclear mass differences.
The laser pyrolysis technique was used in the synthesis of magnetic iron oxide nanopowders (NPs) in the presence of formic acid vapors as a sensitizer. This technique uses the energy from a continuous-wave CO2 laser operating at a 9.25 mu m wavelength, which is transferred to the reactive precursors via a resonant absorption of formic acid molecules. The iron precursor-Fe(CO)(5) and the sensitizer (H-COOH) vapors were obtained by bubbling an argon flow, through the liquid reservoirs. The laser irradiation of reactive gas mixture induces a rapid heating and followed by a decomposition of the Fe(CO)(5) vapors in the presence of oxygen. The synthesized samples were thermally treated at different temperatures between 150-550 degrees C for 2 hours and their morphostructural properties were investigated. Furthermore, a treatment at 400 degrees C in NH3 environment were also performed in order to induce a superficial nitridation of iron oxide NPs. XRD, TGA, XPS, EDX, DLS, TEM and magnetic analyses were performed on both the as synthesized and the treated ones. As a result, it was observed the consolidation of maghemite phase with increasing temperature up to 400 degrees C with a minimal increasing of crystalline dimension between (7.4-30.35 nm). The treatments at temperature higher than 450 degrees C suggest the solid phase transition from gamma Fe2O3 to alpha Fe(2)O(3 )crystalline structure followed by a significand increasing in crystalline dimension. Also, the aqueous NPs suspension having 0.5 g/l concentration were performed. It was observed in the DLS analysis that the suspensions show a spectacular high stability in time for those NPs treated at lower temperature. However, the suspensions become unstable when NPs treated at temperatures higher than 250 degrees C were used. TGA analysis performed in air shows different steps of mass decreasing associated with water desorption between 90-130 degrees C, followed by a sudden decrease in mass between 150-280 degrees C probably as a result of the functional groups disappearance for treatments above 250 degrees C. The XPS studies made for O 1s and C1s zones indicate the presence of Fe-OH, C=O and C-O bonds and with treatments at higher temperature such bonds attributed to functional bonds suffer a progressive attenuation.
A dynamic theory of coherent X-ray radiation of beams of relativistic electrons intersecting a single-crystal plate is developed, taking into account magnetic permeability. Expressions describing the spectral-angular and angular densities of parametric X-ray radiation are obtained and investigated, taking into account the divergence of the beam of relativistic electrons and the magnetic permeability of the single crystal.
Barium magnesium tantalate (BMT), a complex perovskite oxide, has garnered interest because of promising dielectric properties, making it a candidate for advanced electronic applications. In this study, BMT thin films were deposited on various substrates by pulsed laser deposition (PLD) using solid-state Nd: YAG laser (266 nm) on substrates of Si, Pt/Si and Al2O3 under various substrate temperatures and oxygen partial pressures to assess the impact of these conditions on film properties. The techniques employed for the analysis of the thin films are: Spectroscopic ellipsometry (SE), Scanning electron microscopy (SEM), Energy Dispersive X-Ray (EDX). The optical constants determined using SE exhibited dependence on deposition parameters higher temperatures of substrate during the deposition yielded thin films with higher refractive indices. Moreover, substrate type played a critical role in film-substrate interface quality, influencing film texture and optical response and bandgap. The BMT thin films deposited on Pt/Si have better uniformity and structure, making them more suitable than Si or Al2O3 for BMT growth, and have refractive indices (n) of 1.82-2.29 at a wavelength of 589 nm, direct transition bandgaps of 3.77-4.15 eV and relative permittivity between 25.6 up to 62.5. The findings highlight the tunability of BMT thin film optical properties through careful control of PLD parameters showcasing correlations between growth conditions and functional properties.
The transition process from fossil-fuel-based energy systems to renewable energy sources is a critical step toward achieving climate neutrality. However, the intermittent nature of renewables such as solar and wind energy presents significant challenges for grid stability and energy storage. Vanadium redox flow batteries (VRFBs) offer a promising solution due to their ability to reversibly store chemical energy. This paper presents a hands-on teaching module designed for Master's students in renewable energy programs, focusing on the fundamental redox processes in VRFBs. The module includes the preparation of vanadium-based electrolyte solutions, electrochemical characterization via cyclic voltammetry, and performance evaluation through polarization tests. Results demonstrate the reversible redox behavior of V4+ species and provide insights into the practical operation of VRFBs. This educational approach not only reinforces theoretical knowledge but also equips students with practical skills essential for advancing energy storage technologies.
The present paper presents significance of data digitizing and vectorization in decommissioning process of a radiological facility in view of decommissioning, outlines the key steps involved and provides references to relevant research and industry standards. An accurate representation of facility design was obtained by converting the relevant documents into digital format for the further use in planning and carrying out the decommissioning activities.
