We propose an analytical approximation for the modified Bessel function of the second kind K_ν. The approximation is derived from an exponential ansatz imposing global constrains. It yields local and global errors of less than one percent and a speed-up in the computing time of three orders in magnitude in comparison with traditional approaches. We demonstrate the validity of our approximation for the task of generating long-range correlated random fields.

The nonlinear Bratu’s boundary value problem arises in a large variety of application areas such as solid fuel ignition model of thermal combustion, radiative heat transfer, thermal reaction, electrospinning process for the manufacturing of nanofibers, the Chandrasekhar model of the expansion of the universe, chemical reactor theory and nanotechnology. In this study, our aim is to solve nonlinear Bratu’s problem via Kashuri Fundo decomposition method which is a hybrid form of the Kashuri Fundo transform method and the Adomian decomposition method.

We theoretically investigate the photoionization of H atom in twocolor laser fields synthesized by one circularly polarized laser pulse and one linearly polarized laser pulse. In this kind of two-color laser fields, the circularly polarized laser pulse is firstly turned on, and after a time delay τ the linearly polarized laser pulse will be turned on. Our results show the difference of the ionization rate becomes smaller and smaller with increasing the time delay τ. Due to the appearance of linearly polarized laser field, the rescattering ionization process happens and is dependent on its intensity and the time delay τ. If the intensity of the linearly polarized laser is lower than that of the circularly polarized laser, the rescattering ionization process is weak, and it becomes more weaker with increasing time delay. The characteristic plateau in the photoelectron energy spectra and the prominent spiderlike structures are reproduced by enhancing the linearly polarized laser intensity. Our results show that this kind of two-color laser field can be used to control the laser-induced rescattering ionization processes.

Collisions of photons and charged particles with molecules lead to their excitation, ionization, and dissociation into neutral and ionized fragments. Accurately determining thresholds of the formation of particular products plays a vital role in analyzing processes occurring during these interactions. Therefore, we present a computer program, “ThreSpect”, that allows calculating threshold energies of various species generated in these collisions irrespective of whether they are recorded with mass spectrometric or emission spectroscopic techniques.

The optical and structural properties of CdSe thin films with different thicknesses (0.02–0.73 µm) prepared by the high-frequency magnetron sputtering method are determined. The phase analysis and crystal structure refinement are performed using X-ray diffraction (XRD). All obtained CdSe thin films are crystallized in the cubic structure (ZnS – structure type) from XRD studies. The mean grain size of the films was determined using the Scherrer equation. The strain and the dislocation density are also calculated. The spectral dependence of the optical transmittance and reflectivity of the obtained sample in the visible and near-infrared regions is studied at room temperature. The normalized integral optical transmittance, reflectivity, optical band gap and the Urbach energy value of studied films are determined. The optical band gap values of CdSe thin films are changed between 1.57–2.32 eV (estimation from Tauc plot for CdSe with thicknesses 0.016–0.73 µm) and 1.62–1.66 eV (estimation from the dependence of dT/dλ versus wavelength λ for CdSe with thicknesses 0.242–0.73 µm). Optical properties (refractive index n(λ), absorption coefficient α(λ), extinction coefficient k(λ) and dielectric functions ε(λ)) of thin films and thickness d can be determined from the transmission spectrum. The dispersion of the refractive index was explained using a single oscillator model investigated. The material optical parameters such as static and high-frequency dielectric constant, the density of states effective mass ratio were also calculated. Dependence of the optical properties from the time of CdSe thin films deposition (thickness) is studied.

Solid State Nuclear Track Detectors (SSNTD) are wide used in nuclear track detection and analysis. After chemical etching in alkaline solution, the track spot in CR-39 detector can be assessed using optical microscope. In this paper it is presented the use of SSNTD type CR-39 for neutron field exposure estimation within a water tank using a PuBe neutron source. The paper presents the experimental calibration factor to convert gray level of the etched CR-39 detector to personal equivalent dose. In this work also is presented the track size analysis for small radius of the track related to incident energy. The calibration was performed with respect to calibrated TLD 8806 detectors.

Compounded by the current leaps in hardware acceleration, Neural Networks are becoming viable for high data-rate applications such as data acquisition trigger algorithms. Using data from a simulated assembly of eight Micromegas detector planes interacting with muons originating from p−p collisions, two neural network approaches are compared in terms of resource requirements and track reconstruction performance. Within our trigger use-case, the track’s slope is used as part of the discriminant variable for rejecting background muons that can’t be traced back to the interaction point. Convolutional and Recurrent Neural Networks are trained on the same dataset and the results are compared in terms of the angular resolution and the number of parameters. The Convolutional Neural Network is found to be more efficient in terms of the number of parameters, but the Recurrent Neural Network is more robust to noise and has a better angular resolution.

The electron reconstruction efficiency in modern hadron collider experiments is often calibrated using known sources of electrons in the observed data, such as electroweak decays of short-lived particles. We recall the practical details of the tag-and-probe method used to perform such measurements in an unbiased way. We study the accuracy of the approximation used to estimate statistical uncertainties in published results of the ATLAS experiment. We conclude that the approximation is justified.

The mean field approximation has been used to study a ferrimagnetic hexagonal Ising nanotube consisting of a spin-1/2 core surrounded by a spin-1 shell with negative core-shell exchange coupling. More precisely, we have investigated the effects of the crystal field, the shell exchange coupling and the core-shell interfacial exchange coupling on the magnetic properties and phase diagrams of the system. The critical and compensation behaviors are highlighted for appropriate values of the Hamiltonian parameters, as well as the first-order phase transition in the ferrimagnetic ordered region at low temperatures.

DFT + U computations were performed to investigate the role of the used approach to study the adsorption and reaction of H₂S on the TiO₂ rutile (110) surface. We present new results using the GGA + PBE approach to clarify the interaction of H₂S molecule with rutile TiO₂ (110) surface, including their structural and electronic properties. Different adsorption configurations were obtained for the initial adsorption sites Ti_5c, O_2c, and O_3c with different H₂S-surface distances. The H₂S preferentially adsorbs dissociatively at the Ti_5c site, which is the most energetically favorable site, leaving a dissociated H atom bonded to another O_2c site. We have reported the results of the PBE + U calculation including geometrical structure, adsorption energy, electronic density of states, work function, and charge transfer. The inclusion of PBE + D2 interaction increases the adsorption energies. Upon the adsorption process, the calculated work function and band gap are reduced which enhanced the photocatalytic properties of the TiO₂, a stronger adsorption ability indicates a higher capability for H₂S as a detector and sensitive sensors.

In this work, the I–V characteristics and the coefficient of non-ideality of the rectifying contact are calculated taking into account the heating of charge carriers and phonons. It was shown that the heating of carriers by the internal field of the rectifying contact linearly depends on the current and leads to the deviation of the I–V characteristic from non-ideality, as a result of which the non-ideality coefficient will be different from unity even when I→0 . The nonideality I–V characteristic of the Schottky diode depends on the parameters of the semiconductor and the potential barrier.

In this work, we studied the dependence of the oscillations of the combined density of states on a strong magnetic field in heterostructures based on a rectangular quantum well. The influence of a quantizing magnetic field on the temperature dependence of the combined density of states in nanoscale direct-gap heterostructures has been studied. A new numerical method has been developed for calculating the temperature dependence of the two-dimensional combined density of states of a quantum well in quantizing magnetic fields. The proposed model explains the experimental results in nanoscale direct-gap semiconductors with a parabolic dispersion law.

The present study is focused on the understanding of the phenomenon and mechanism of phase transformations that were identified in Ti₅₀Ni_50-xCu_x materials after characterization of bulk materials realized from Ti, Ni and Cu powders using the spark plasma sintering technology between 800–900°C. The sintered materials with diameter of 20 mm and height of 4–5 mm were investigated by X-ray diffraction (XRD) and scanning electronic microscopy together with energy dispersive spectroscopy and nanoindentation measurements. The results of indentations are influenced by the existence of TiNiCu stable phases, Ti(Ni, Cu) phase precipitates, Ni or Ti unreacted observed in the microstructure of these materials, where the hardness value was about 350 HV and elastic modulus was about 75 GPa.

This paper reveals the ability of microbial communities isolated from a nuclear waste repository soil to withstand high radiation background, high concentrations of toxic heavy metals, and to reduce the concentration of certain heavy metals in the culture medium. After gamma irradiation, 12 resistant bacterial strains were isolated. These bacteria exhibited increased abilities in removing toxic concentrations of ⁶³Cu, ⁵⁹Co, and ¹³³Cs from the culture medium.

Characterization of radioactive waste involves establishing the list of radionuclides together with their activities. The estimated activity levels are compared with the limits given by the national authority in the field. Therefore, quantifying the uncertainty that affects the concentration of radionuclides is essential for estimating the acceptability of waste in the final repository, as well as for controlling the stages of segregation and radiological characterization. The approach proposed in this study aims to estimate the uncertainties involved in gamma-ray spectrometry, which is utilized for characterizing radioactive waste.

The conversion of waste and by-products into green building materials is gaining attention for a sustainable economy. Particularly, rice husk ash (RHA) is used as a precursor in self-compacting concrete due to its high pozzolanic activity. It also minimizes the use of conventional OPC as a primary binder during construction by exploiting its chemical features and characteristics as an alternative binding agent. Developing and mass-producing RHA as a cementitious material would lessen the carbon footprint that harms the environment. This study presents the compressive strength and microstructural characterizations of rice husk ash-based self-compacting concrete (RHA-SCC). The scanning electron microscope was utilized to determine the morphological images of RHA-SCC. The compressive strengths of 7, 28, and 90-day curing periods were also checked to relate how strength is developed from various sets of mixture proportions.