The mathematical model is developed that describes the periodic mode of softening of the ice surface during friction on the case of deformational defect of ice shear modulus. This case corresponds to formation of premelted film with thickness about 10 nm by mechanism of first-order phase transition. Such film is very affected by noise due to small thickness. The second-order differential equations are derived describing damped harmonic oscillations for boundary relations between the shear strain, stresses, and temperature relaxation times. In all cases, phase portraits and time series of friction force are constructed. It is shown that white noise influence leads to an undamped oscillation mode corresponding to a periodic intermittent (stick-slip) regime of friction that is basically responsible for destruction of rubbing parts. The conditions in which the periodic intermittent regime is manifested most clearly are determined, as well as parameters for which this mode does not set in the entire range of the friction surface temperature.
The development of eco-friendly nanomaterials is of increasing importance due to their potential applications in bioengineering, environmental protection, coupled with the need to reduce the use of toxic chemicals in synthesis. In this study, silver nanoparticles (AgNPs) were synthesized through a simple and sustainable green method mediated by a hydroalcoholic extract of wild garlic ( (Allium ursinum L., 1753) leaves. The obtained extract and the synthesized nanoparticles were characterized using different spectroscopic (UV-Vis; Fourier-Transform Infrared-FT-IR; Energy-Dispersive X-ray-EDX), chromatographic (High-Performance Liquid Chromatography with Diode-Array Detection-HPLC-DAD) and microscopic (Transmission Electron Microscopy-TEM) methods. The antimicrobial activity of both the hydroalcoholic extract of wild garlic (WG) and the synthesized nano-particles (AgNPs-WG) were evaluated against selected bacterial and fungal strains using the disk diffusion method. The AgNPs-WG demonstrated antimicrobial efficacy, with inhibition zones measuring 21.97 mm against Staphylococcus aureus and 21.53 mm against Candida albicans. In addition, the antioxidant activity of both the wild garlic extract and the AgNPs-WG were assessed.
Ionizing radiation with sufficient energy can eject electrons from atoms. This characteristic of ionizing radiation may lead to permanent adverse effects on biological systems. The half-value thickness-an essential parameter in radiation shielding-is used to quantify and manage exposure risks. This study investigates the half-value thickness of gamma rays at different energy levels across various absorbing materials and compares standard theoretical results with experimental findings. The analysis reveals a discrepancy between standard theoretical data and experimental findings. To resolve this inconsistency, the fractional attenuation equation d(alpha)I / dx(alpha) = -& micro;(alpha)x is employed. A constant derivative order of approximately alpha congruent to 0.316 provides the best agreement between the theoretical and experimental data is determined.
The Schrodinger equation with an infinitely negative potential at large distances cannot be solved using conventional methods. In previous studies by R.J. Lombard et al. [Rom J. Phys. 67, 104 (2022)] and S. Garidi et al. [Rom J. Phys. 68, 105 (2023); Phys. Scr. 99, 035229 (2024)] on potentials of the form-|x|(n), a method based on the properties of PT-symmetric complex potentials was developed to determine the energy levels of a few states for various values of n. In this work, we suggest a novel and more efficient numerical approach that allows for the computation of the entire spectrum of such potentials.
In this work, we develop an original and reliable technique for the approximate resolution of the coupled 2-dimensional Burgers' equation. It is a combination of Adomian decomposition method and finite elements which provides reliable results as shown by the numerical tests.
Pristine tri-s-triazine graphitic carbon nitride (g-C3N4) was synthesized by thermal polymerization of thiourea ranging from 500 to 600 degrees C to investigate the influence of calcination temperature on its physical properties. Increasing temperature induced progressive exfoliation, enhanced porosity, improved crystallinity, and reduced interlayer spacing. Optical studies revealed strengthened light absorption and a narrowed band gap at higher temperatures. The optimized g-C3N4 exhibited favorable structural ordering and electronic characteristics, indicating strong potential for efficient photocatalytic applications under both UV and visible light irradiation.
The objective of this study is to assess the effectiveness of Quantum Support Vector Regression in one-day-ahead river discharge forecasting, a critical task for water resources management and flood risk mitigation. By comparing its predictive performance with classical Support Vector Regression, the study examines whether quantum-enhanced learning techniques can better represent the complex, nonlinear behavior of river flow processes.
Leveraging data-driven prediction models in renewable energy systems (RES) is pivotal for boosting efficiency and optimizing power generation. This study investigates advanced machine learning (ML) techniques for accurate solar irradiance forecasting, a critical factor influencing photovoltaic (PV) system performance. Field measurements of solar irradiation, ambient temperature, and wind speed were collected in the Sahara Desert to develop and validate predictive models. Multiple nonlinear ML algorithms were implemented and rigorously compared in terms of accuracy and robustness. The Gradient Boosting Regressor (GBR) emerged as the most effective model, providing highly reliable solar irradiance predictions. These results demonstrate the potential of data-driven approaches to improve PV energy output assessment, support informed decision-making, and advance efficient management of large-scale renewable energy systems in challenging desert environments.
A dissipative dust ion-acoustic wave model in a multicomponent collisional dusty plasma is investigated to clarify how ionization processes and collisional damping reshape solitary, periodic, and shock structures supported by dust ion-acoustic modes. The plasma configuration consists of inertial negatively charged dust grains, inertial positively charged ions, and inertialess superthermal electrons and positrons embedded in a neutral background, so that both dispersive and dissipative effects arise naturally from charge separation and from ionization, ion-neutral, ion-dust, and dust-neutral collisions. Within this framework, a reductive perturbation technique (RPT) is employed to derive, first, a damped Korteweg-de Vries (dKdV) equation away from critical compositions and, second, a damped modified Korteweg-de Vries (dmKdV) equation at critical regimes where the quadratic nonlinearity vanishes, and the cubic nonlinearity becomes dominant. Semi-analytical dissipative periodic and solitary solutions to the dKdV equation are constructed by combining known cnoidal and solitary KdV profiles with a time-dependent amplitude-width ansatz, while weighted residual methods are applied systematically to obtain approximate solitary and shock solutions of the dmKdV equation, allowing the soliton or shock parameters to evolve under weak damping. The parametric analysis demonstrates that compressive and rarefactive dust ion-acoustic structures coexist in distinct regions of the space of superthermality, temperature ratios, and compositional parameters; in particular, increasing the spectral index and the electron-positron temperature ratio tends to favor compressive modes and suppress rarefactive ones. It is further shown that collisional damping (via ion-dust and ion-neutral frequencies) and ionization-loss parameters lead to a systematic reduction of the amplitudes of periodic, solitary, and shock waves. Overall, the study provides a unified analytical description of dissipative dust ion-acoustic solitons, cnoidal waves, and shocks governed by damped KdV-type equations, and delineates the parameter domains in which each structure can exist and remain dynamically robust in realistic collisional dusty plasmas with superthermal light species.
This paper presents a comprehensive investigation of the damped behavior of electron drift velocity in GaAs semiconductors with a p-i-n structure using the ensemble Monte Carlo (EMC) method under the influence of an external electric field. The simulation results show that, in the absence of an external electric field, the electron velocity in the device exhibits a damped oscillatory form if and only if the thickness of the intrinsic semiconductor layer is smaller than a threshold value. Additionally, when the thickness of the intrinsic semiconductor layer is below this critical threshold, an increase in the electric field changes the behavior of electron velocity from under-damped to critically damped and then to over-damped states. In particular, for the first time, we have plotted the phase diagram of electron velocity in phase space of the critical external electric field (E-c) and the thickness (S) of intrinsic semiconductor layer.
Zinc sulfide (ZnS) is a promising material for optoelectronic and photocatalytic applications, yet its thermal stability and phase transformation behavior are crucial for optimizing performance. In this study, ZnS was synthesized hydrothermally and annealed between 20 and 700 degrees C. X-ray diffraction (XRD) confirmed cubic ZnS formation at room temperature, with peaks at 28.5 degrees, 47.5 degrees, and 56.3 degrees corresponding to the (111), (220), and (311) planes. Upon annealing, mixed ZnS/ZnO phases appeared at 445-550 degrees C, while complete transformation to hexagonal ZnO occurred above 600 degrees C, indicated by new peaks at 31.7 degrees, 34.4 degrees, and 36.2 degrees ((100), (002), and (101) planes). Energy-dispersive X-ray spectroscopy (EDX) revealed decreasing sulfur and increasing oxygen content with temperature, confirming oxidation and sulfur loss. Infrared spectroscopy showed the ZnS vibrational mode near 615 cm-1 red-shifted and disappeared at higher temperatures, consistent with the ZnS-ZnO transition. These results explain the temperature-dependent structural evolution of ZnS and highlight its potential for ZnS/ZnO heterostructure-based devices.
The variational Monte Carlo method is employed to conduct a comprehensive investigation of the beryllium atom, ions, and isoelectronic ions within three various plasma environments. Also, the study focuses on the low-lying excited singlet and triplet states (1s(2)2s2p, 1s(2)2p2, 1s(2)2s3s, and 1s(2)2s3p), utilizing plasma potentials such as the screened Coulomb (SCP), exponential cosine screened Coulomb (ECSCP), and Hulth & eacute;n potentials. Energy eigenvalues are determined using appropriate trial wave functions, which account for electron-electron repulsion and spin parts to adhere to the Pauli Exclusion Principle. Moreover, an effective-plasma factor related to the wave function of ECSCP model is considered. The results reveal an intriguing relative ordering for the electronic systems using the three plasma models, with many of the findings being novel contributions yet to be explored.
This paper presents a four-component integrable extension of the derivative nonlinear Schrodinger (DNLS) soliton hierarchy, providing a generalization of the Kaup-Newell hierarchy. Building on a general method for extending the Kaup-Newell spectral matrix, we propose a new eigenvalue problem with a 4 & times; 4 matrix incorporating four distinct potentials. We then derive the corresponding integrable Hamiltonian hierarchy using the zero-curvature approach. To demonstrate the Liouville integrability of this hierarchy, we construct a recursion operator and establish a bi-Hamiltonian formulation. As an application, we derive a coupled system of four DNLS equations, each featuring two linear dispersion terms, illustrating the integrability of the proposed system.
Rapid stabilization of quantum systems is of significant importance for quantum information technology. The exponential stabilization of stochastic quantum systems is investigated based on time-delay state feedback in this paper. In order to design time-delay state feedback, the result for noise-assisted feedback in our previous work is extended to the case of state feedback, and we obtain that the upper bound of delay time to ensure exponential stabilization still holds by using the same form of non-delay state feedback in time-delay state feedback.
Radiation hardness testing plays a vital role in ensuring the reliability of electronics and materials that will be used in high-radiation environments. In context, we designed and started implementing a low-energy proton irradiation multipurpose experimental platform for radiation hardness testing of microelectronic devices and integrated circuits. The platform will be integrated at the 3 MV TandetronTM facility of Horia Hulubei National Institute for Research & Development in Physics and Nuclear Engineering (IFIN-HH). Notably, this platform offers exceptional versatility and broad applicability across diverse ion irradiation facilities, enabling straightforward adoption beyond the present implementation.
Herein, we present the development of a controlled environment chamber system, designed for precisely regulating environmental parameters such as ambient temperature, relative humidity rate, and pressure within a well-controlled atmosphere. This system constitutes a versatile and essential tool for a wide range of applications, particularly for the evaluation and optimization of the performance of materials and devices such as gas sensors by ensuring reproducible experimental conditions and enabling the analysis of the impact of environmental variations on their production or operation. One of the main challenges was to achieve independent and accurate control of each parameter while maintaining optimal homogeneity within the chamber. To this end, the chamber incorporates a relay-controlled ON-OFF regulation system, combining sensors, actuators, and a control unit. Environmental parameters are measured using calibrated sensors (MS5611 and DHT22), while regulation is achieved through heating lamps, an ultrasonic humidifier and solenoid valves for ventilation control. The entire system is managed by an Arduino MEGA microcontroller board, coupled with a user interface that allows for adjustment of set-points and real-time display of measured and set-point parameters. Experimental tests demonstrated the system's ability to maintain stable and reproducible environmental conditions over a wide range of temperatures and relative humidity levels. Meanwhile, the pressure remains stabilized around 1 bar, regardless of the other parameters. The integration of fans significantly improved the internal homogeneity. This system offers precise control across a broad range of environmental conditions, serving as a flexible and reliable platform for applications requiring strictly controlled environments.
In this work, new exact implicit relations describing the stationary solutions of the Wadati-Konno-Ichikawa (WKI) system are established. Through a systematic sequence of transformations, the original coupled nonlinear equations are reduced to a canonical Abel-type ordinary differential equation, which admits an exact analytical solution. From this reduction, an implicit but closed-form expression is derived for the stationary states of the WKI system, revealing the underlying analytical structure of the model. The resulting expressions provide a direct link between the nonlinear coupling of the WKI system and the spatial dependence of its stationary fields. To assess their accuracy, the analytical solutions are compared with high-precision numerical integrations of the original coupled equations. The comparison demonstrates a very good correspondence between the two approaches, particularly in the central region where the fields exhibit localized behavior. This close agreement verifies the reliability of the analytical formulation and underscores its value as a benchmark for validating numerical schemes and investigating the nonlinear dynamics of the WKI system.
The simplified Hirota method is utilized to derive and study the lump and breather solutions of the Korteweg-de Vries-Calogero-Bogoyavlenskii-Schiff (KdV-CBS) equation. We will also derive other physical structures using various methods and techniques, including the Tanh and Coth methods for hyperbolic functions, the Tan and Cot methods for trigonometric functions, and many others. These methods will enable the generation of several physical solutions that may elucidate various nonlinear phenomena occurring in water waves, fluid mechanics, and plasma physics.
We propose a model for the refractive index variation that causes the self-focusing, for a laser beam in plasma and using a Vlasov approach. We derive the dynamics of the electrons in the laser region, under the action of the ponderomotive and charge separation forces and taking into account the constant influx of electrons the beam encounters during its propagation. The results show that the number density and the average Lorentz factor of the electrons in a given region both grow with the distance from the beam's center to its margins. Their cumulative contribution makes the refractive index decrease towards the edges, which is necessary for self-focusing, as verified for the numerical example we provide.
A new quaternary chalcogenide compound, AgCd2InSe4, belonging to the I-II2-III-VI4 family of diamond-like semiconductors, has been synthesized using the melt and annealing technique. The stoichiometric composition was confirmed by energy-dispersive X-ray spectroscopy (EDS), yielding elemental ratios consistent with the nominal 1:2:1:4 proportions. Powder X-ray diffraction (PXRD) data revealed a single-phase material with an orthorhombic crystal structure and successfully refined using the Rietveld method in the Pmn2(1) space group with unit cell parameters a = 8.5817(6) & Aring;, b = 7.4099(9) & Aring;, c = 6.9953(6) & Aring;, and V = 444.83(7)(5) & Aring;(3). This quaternary compound crystallizes in a wurtzite-stannite structure where tetrahedrally coordinated cations (Ag+, Cd2+, In3+) and anions (Se2-) form a three-dimensional honeycomb structure. Interatomic distances suggest enhanced ionic contributions to bonding, consistent with other related chalcogenides. A Hirshfeld surface analysis (HSA) indicates that the most important contributions to the crystal packing are from Cd-Se (39.4%), In-Se (31.93%), and Ag-Se (19.9%) interactions, suggesting that the Ag+ ion is the most labile species and making this material a promising candidate for applications requiring fast ion transport. Additionally, Debye temperature and heat capacity estimations point to soft lattice dynamics, indicating potential for use in thermoelectric and optoelectronic devices.
