Recent publications

Fast estimation is a critical feature of the proposed modeling approach as a “forward” fast solver that has a key role in solving the “inverse” problem involved in crack sizing, especially for real‐time applications. To this end, two different inversion methods have been proposed to estimate the crack depth. The first one uses an interpolation model of the 3D direct model simulation data. The second approach is based on artificial neural networks (ANN). In this article, the rotating uniform eddy current (RUEC) probe is used to detect the normal magnetic component Bz which is defined as the characteristic signal for reconstructing the crack length and depth concurrently. Using the first approach, The Bz characteristic 3D surface is presented, and this can be modeled by a fitted polynomial interpolation equation. Thus, the crack depth can be inverted using this equation referring to the experimental or simulated Bz signal and the crack length. The ANN is outlined to determine the crack depth based on the simulated Bz signature. The move from the first inversion method to the second was flexible and useful, in which the interpolation model is used as a defect signal generator for fast building of a large and efficient database for ANN training. Both of the proposed methods proved the objectivity and accuracy of the inversion results and offered more robust engineering support for automated NDT, reducing production time and increasing productivity.

2023): First-principles calculations to investigate structural, mechanical, electronic, optical, and thermoelectric properties of novel cubic double Perovskites X2AgBiBr6 (X=Li, Na, K, Rb, Cs) for optoelectronic devices, Molecular Simulation, ABSTRACT Structural, elastic, electronic, optical, and thermoelectric properties of cubic double perovskites X 2 AgBiBr 6 (X = Li, Na, K, Rb, Cs) were investigated using the density functional theory (DFT) method. The DFT calculations were carried out with various exchange-correlation potentials, e.g. LDA, GGA-PBE, GGA-WC, and hybrid functionals (YS-PBE0). Structural and elastic properties of X 2 AgBiBr 6 demonstrate that these compounds are ionically bonded, elastically stable, ductile, and anisotropic. Calculations show that the compounds are semiconductors with indirect bandgap at the (X-L) point, with bandgap values of 2.124, 2.222, 2.198, 2.209, and 1.902 eV for X 2 AgBiBr 6 (X = Li, Na, K, Rb, and Cs), respectively. Due to their distinguishing optical characteristics and indirect wide bandgap, these compounds might be utilised as absorber layers in solar cells and other optoelectronic devices. Moreover, thermoelectric properties show that the Figure of Merit (ZT) has values of 0.713, 0.723, 0.721, 0.726, and 0.728 for X 2 AgBiBr 6 (X = Li, Na, K, Rb, Cs). The Figure of Merit shows a plateau in the temperature range of 500-900 K, which corresponds to the highest value of ZT. All investigated compounds have holes as the majority of charge carriers. Thermoelectric properties of X 2 AgBiBr 6 compounds reveal that these compounds can be employed in thermoelectric devices. ARTICLE HISTORY

This study presents a theoretical investigation of the 1,3-dipolar cycloaddition between cyclic nitrone a1 and substituted alkene b1. The mechanism, regioselectivity, and stereoselectivity of this 13DC reaction were analyzed using transition state theory and reactivity indices obtained from conceptual density functional theory (DFT) with DFT methods at B3LYP/6-31G(d) level of theory. The results indicate that this cycloaddition reaction proceeds via a synchronous one-step mechanism, exhibiting a non-polar nature and significant activation energies. These theoretical results are in agreement with the experimental observations. Moreover, topological analyses such as ESP, RDG-NCI, and ELF were employed to determine active sites, distinguish hydrogen bonds, van der Waals interactions, and steric repulsive interactions, and predict electron localization, respectively.

The diversity of bottom substrates is a primary driver of taxonomic richness and species abundance patterns of freshwater benthic insects in space and time. Here, we examine the influence of substrate composition on the seasonal patterns of benthic insect communities in streams of arid regions. Benthic insects were sampled monthly over a year at three sampling sites distributed along the Bouilef stream within the Belezma biosphere reserve (Algeria). Different substrate types (sand, gravel, pebbles, boulders, and emergent macrophytes) were sampled in the rainy and dry seasons. During the 2 studied seasons, a total of 8599 insects belonging to 6 orders, 26 families, and 39 genera/species were sampled and identified. Student's t-test analysis showed that season influences significantly the mean abundance of benthic insects, which increases in the rainy season. However, the season does not affect taxa richness. Substrate types influence taxa composition and variation of benthic insect communities. The results showed that pebbles and boulders are the most populated by gathering and filtering collectors in terms of taxa abundance. Emergent macrophytes are more favorable for herbivores shredders. Principal Coordinates Analysis ‘’PCoA’’ also showed that pebbles and boulders differed significantly from other substrates, whereas sand and gravel substrates exhibited similar taxa mean abundance. Such assessments can help propose conservation measures needed to successfully safeguard these fragile ecosystems.

This study suggests a new nature-inspired metaheuristic optimization algorithm called the red-tailed hawk algorithm (RTH). As a predator, the red-tailed hawk has a hunting strategy from detecting the prey until the swoop stage. There are three stages during the hunting process. In the high soaring stage, the red-tailed hawk explores the search space and determines the area with the prey location. In the low soaring stage, the red-tailed moves inside the selected area around the prey to choose the best position for the hunt. Then, the red-tailed swings and hits its target in the stooping and swooping stages. The proposed algorithm mimics the prey-hunting method of the red-tailed hawk for solving real-world optimization problems. The performance of the proposed RTH algorithm has been evaluated on three classes of problems. The first class includes three specific kinds of optimization problems: 22 standard benchmark functions, including unimodal, multimodal, and fixed-dimensional multimodal functions, IEEE Congress on Evolutionary Computation 2020 (CEC2020), and IEEE CEC2022. The proposed algorithm is compared with eight recent algorithms to confirm its contribution to solving these problems. The considered algorithms are Farmland Fertility Optimizer (FO), African Vultures Optimization Algorithm (AVOA), Mountain Gazelle Optimizer (MGO), Gorilla Troops Optimizer (GTO), COOT algorithm, Hunger Games Search (HGS), Aquila Optimizer (AO), and Harris Hawks optimization (HHO). The results are compared regarding the accuracy, robustness, and convergence speed. The second class includes seven real-world engineering problems that will be considered to investigate the RTH performance compared to other published results profoundly. Finally, the proton exchange membrane fuel cell (PEMFC) extraction parameters will be performed to evaluate the algorithm with a complex problem. The proposed algorithm will be compared with several published papers to approve its performance. The ultimate results for each class confirm the ability of the proposed RTH algorithm to provide higher performance for most cases. For the first class, the RTH mostly got the optimal solutions for most functions with faster convergence speed. The RTH provided better performance for the second and third classes when resolving the real word engineering problems or extracting the PEMFC parameters.

In this paper, we use the generalized notions of Riemann-Liouville (fractional calculus with respect to a regular function σ ) to extend the definitions of fractional integration and derivative from the functional sense to the distributional sense. First, we give some properties of fractional integral and derivative for the functions infinitely differentiable with compact support. Then, we define the weak derivative, as well as the integral and derivative of a distribution with compact support, the integral and derivative of a distribution using the convolution product. Then, we generalize those concepts from the unidimensional to the multidimensional case. Finally, we propose the definitions of some usual differential operators.

Water erosion is a serious challenge in Algeria, because it affects ecosystems, contributes to soil degradation, and leads to the silting of dams; moreover, this process is complex and needs costly field equipment and trip reconnaissance. The main objective of this paper is to evaluate the sensitivity of the Revised Universal Soil Loss Equation (RUSLE) model to rainfall erosivity in the Ksob watershed in Algeria, using six empirical formulas of rainfall erosivity. The RUSLE model with the Geographic Information System (GIS) produces highly variable specific soil loss ranging from 11.35 to 22.85 t ha−1 year−1 throughout the watershed, depending on the erosivity R factor. To validate the results, the soil loss is compared with the silting volume data of the Ksob dam, which is located at the outflow of the basin. The best result is obtained using the Diodato R factor formula with a relative error of 21% and a specific soil loss of 11.35 t ha−1 year−1. Moreover, over 81% of the watershed area is exposed to low erosion (50 t ha−1 year−1).
HIGHLIGHTS
The RUSLE model (using six empirical formulas of rainfall erosivity R factor) integrated with GIS has been successfully used for quantitative assessment and mapping of soil losses.;
The quality of the RUSLE results and the performance of the R factor were verified by the bathymetric measurements of the Ksob dam.;
The best result is obtained with Diodato (2004, 2005) R formula with a relative error of 21%.;

The equilibrium geometries, and electronic and magnetic properties of phosphorus, cobalt‐phosphorus, and nickel‐phosphorus ( P n+1 , CoP n , and NiP n , n = 1–24) clusters have been investigated by using first principle calculations. The doping with cobalt or nickel atom favors the endohedral structures in which the metal atom is encapsulated inside the phosphorus framework, while geometrical structures are metal‐dependent. The growth pattern behaviors and stabilities are examined from the binding energies, the second‐order energy differences, and the HOMO–LUMO gaps. The doping with Co or Ni atom contributes to strengthening the stability of the phosphorus frame with a marked improvement in the case of Ni atom. The total spin magnetic moment is enhanced with doping with Co atom. In contrast, the magnetic moment is quenched in the case of NiP n . Vertical electron affinities and ionization potentials are also reported and discussed.

In this study, the design, analysis and optimization of the performance of a concentrated solar power plant that is based on the parabolic trough technology with a capacity of 100 MW equipped with a thermal energy storage system were conducted, in two representative sites in Algeria (Tamanrasset and M’Sila). The System Advisor Model software is used to evaluate the technical and economic performances of the two proposed power plants, in addition to carrying out the process of optimizing the initial design of the two power plants by finding the optimal values of the solar multiple and full load hours of the thermal energy storage system, with the aim of increasing the annual energy production and reducing the levelized cost of electricity. The results of the performance analysis conducted on the optimized design showed that the optimum values of the solar multiple and full load hours of the thermal energy storage system for the proposed power plant at the Tamanrasset site were found to be 2.4 and 7 h, respectively, with an annual electricity production of 514.6 GWh, and a minimum value of the levelized cost of electricity of 6.3¢/kWh. While the optimum performance of the proposed plant at the M'Sila site can be achieved by selecting a solar multiple of 3 and 7 h for thermal energy storage system, with a high annual energy production of 451.84 GWh and a low value of the levelized cost of electricity of 7.8¢/kWh. The results demonstrate that CSP plants using parabolic trough technology can increase energy security in the country, while reducing environmental concerns associated with the use of fossil materials.

Metal foam (MF) and nano-sized particles (NSP) are regarded as patent tools for enhancing the thermal performance of phase change materials (PCM)-based latent thermal energy storage unit (LTES), but data on this issue for large-scale installations is very scarce. The current numerical study aimed at using Fluent 15.0 CFD platform to provide a large visualization on the use of MF and NSP for improving the sonification rate of paraffin RT82 in a big-scale shelland-tube built LTES. The developed 2D transient model was initially verified using available literature experimental data. The process performance was tested for 5% Al2O3 nanoparticles and various MFs [i.e. aluminum (Al), copper (Cu), nickel (Ni) and titanium (Ti)] with varied porosity (96-100%). The computed mean and spatial temperature and solidified degree of the PCM block showed a drastic acceleration of the solidification process with theb MF technique rather than with the nanoparticles system. The solidification performance increased in the direction of MFthermal conductivity increase, i.e. Cu>Al>Ni>Ti, and material porosity decrease. These conditions allow rapid HTF heat recovery and then stocking considerable thermal energy. However, the MF porosity could not decrease below 95% to avoid a huge loss of material storage (PCM), thereby diminishing the thermal storage capacity of the LTES unit.

This study employs density functional theory to investigate the structural, elastic, electronic, and magnetic properties of FeVScSb and FeVYSb Heusler compounds. FeVScSb exhibits ferromagnetic properties in its stable state, whereas FeVYSb displays ferrimagnetic behavior. The obtained elastic constants ( C ij ) indicate that FeVScSb and FeVYSb possess mechanical stability and ductility, while also displaying a significant degree of elastic anisotropy. The aggregate magnetic moment of said alloys is determined to be equivalent to 3 μ B , in accordance with the Slater–Pauling principle. The investigation of the impact of uniform strain on electronic and magnetic characteristics is conducted. The findings indicate that FeVScSb and FeVYSb exhibit semiconductivity within extensive lattice parameter intervals, ranging from 5.84 to 6.60 Å for FeVScSb and from 6.11 to 6.70 Å for FeVYSb. The Heusler compounds FeVScSb and FeVYSb exhibit half‐metallic behavior within a range of lattice parameters. Specifically, FeVScSb displays this behavior when the lattice parameter varies from 6.61 to 6.72 Å, while FeVYSb exhibits half‐metallicity within the range of 6.71–6.81 Å. Under the influence of strain, the magnetic moment retains a constant value of 3 μ B . Therefore, the potential for spintronics is promising.

The use of Network Function Virtualization (NFV) is constantly increasing in Cloud environments, especially for next-generation networks such as 5G. In this context, the definition of a deployment scheme defining for each Virtual Network Function (VNF) the appropriate server in order to meet the quality of service (QoS) requirements. This problem is known in the literature as Virtual Network Function Placement. However, proper deployment of VNFs on servers can minimize the number of servers used, but may increase service latency. In this article, we propose a multi-objective integer linear programming model to solve the problem of network function placement. The objective is to find the best compromise between minimizing end-to-end total latency for users and reducing the number of servers used, while ensuring that the maximum number of VNFs is connected in the network. Our proposal to solve the NP-hard model is to develop an algorithm based on the Particle Swarm Optimization (PSO) metaheuristic to obtain a polynomial time resolution. By performing tests on a simple VNF deployment problem, we validated the relevance of our optimization model and demonstrated the effectiveness of our algorithm. The results obtained showed that our method provides feasible solutions very close to the exact optimal solutions.

The NaCeP 2 O 7 compound was successfully synthesized by a high-temperature reaction with the solid-state method. Analyzing the XRD pattern, of the studied compound, confirms the orthorhombic phase with the Pnma space group. The examination of SEM images reveals that the majority of grains are around 500 to 900 nm with a uniform distribution. As for the EDX analysis, all chemical elements were detected and found in their appropriate ratio. The curves of temperature-dependent imaginary modulus M" versus angular frequency reveal the presence of one peak at each temperature, proving that the dominant contribution is associated to the grains. The frequency dependence of the conductivity of alternating current is explained using Jonscher's law. The close values of the activation energies obtained from the jump frequency and extracted from the dielectric relaxation of the modulus spectra, as well from the continuous conductivity imply that the transport takes place by the Na ⁺ ions hopping mechanism. The charge carrier concentration in the title compound has been evaluated and shown to be independent of temperature. The exponent s increases with the increase in temperature, this behavior proves that the non-overlapping small polaron tunneling (NSPT) is the appropriate conduction mechanism model.

The structural, elastic, electronic, and magnetic properties of the CrCoSi, MnCoSi parent half-Heusler (HH) alloys, and their CrMnCo 2 Si 2 derivative double half-Heusler (DHH) compound are studied, utilizing the augmented plane wave method, which is based on density functional theory and implemented in the WIEN2k code. The stability of HH structure of the CrCoSi and MnCoSi alloys has been checked for their non-magnetic and ferromagnetic phases, leading to that the latter phase of the type I arrangement is the most stable. The CrMnCo 2 Si 2 DHH alloy, derivative from the found structural and magnetic ground states of CrCoSi and MnCoSi HH alloys, is constructed and investigated. This DDH as well as its CrCoSi parent HH are found to be resistant to deformation and can be classified as ductile materials, whereas the MnCoSi compound is brittle. By the gradient generalized approximation (GGA), the electronic structures of CrCoSi, MnCoSi, and CrMnCo 2 Si 2 compounds exhibit a metallic behavior in the spin-up channel and a semiconducting behavior in the spin-dn channel, with band gaps (half-metallic gaps) of 0.851(0.020), 0.852(0.021), and 0.531(0.002) eV, respectively. The half-metallicity of CrMnCo 2 Si 2 DHH is retained with smaller (larger) band gap (half-metallic gap) of 0.38(0.106) eV than that of GGA, using GGA + U approximation. In addition, the total magnetic moments are found to be 1, 2, and 3 µ B for CrCoSi, MnCoSi, and CrMnCo 2 Si 2 , respectively. Therefore, these alloys can be good candidates for spinitronic applications due to their half-metallicity.

In this work we propose to specify, describe and test a variant of a more powerful and flexible genetic algorithm that could be better suitable to tackle complex optimization problems such as in dynamic, stochastic or robust optimization. Our main goal is to give a new strong tool more efficient in terms of both solution quality and time processing for complex NP-hard optimization problems, which know great importance these past few decades in economy, management, manufacturing and many other fields. This algorithm gives a significant improvement to the basic genetic algorithm of J. Holland in order to imitate and simulate as close as possible the naturel selection phenomenal established in the theory of C. Darwin. Thus, in the evolution process of generations, the population should not keep a fixed size, but it should evolve over the generations. In the other hand, the population should contain several breeds of the species under study. Therefore, much kind of crossovers could be applied randomly such as crossover of pure or hybrid breeds. In addition, many types of mutation would be possible such as substitution, addition or deletion which could also happen randomly in the nature. The main idea is based on the maximal projection of the evolution theory on the optimization field to tackle complex problems. We aim to design flexible genetic algorithm by looking empirically for good compromise of adjusting the genetic parameters on sample cases.

The structural parameters and elastic properties of rock-salt CaX (X = S, Se and Te) materials are explored employing the CASTEP code established on the density functional theory (DFT). The energy of exchange-correlation is calculated using the generalized gradient approximation (GGA). The convention between our outcomes related to the lattice parameter and experiment is 0.50%, 0% and 1% for CaS, CaSe and CaTe materials, respectively. The lattice constant augments when proceeding from CaS to CaSe to CaTe. This lowers also the modulus of compressibility. The studied materials present a weak elastic constants for C12 and C44. This signalizes that these materials are supplementary reluctant to the unidimensionelle compression than to the perversion of cisaillement. C11 increases very rapidly. However, C12 and C44 increase very slowly. The material stability of the structure for the results of interest is stable at zero pressure. A phase transition will happen at pressures of 25.20 GPa for CaSe and 20.10 GPa for CaTe. No phase transition has been detected for CaS up to 30 GPa. All studied materials have comported as fragile in the pressure range 0 to 4 GPa. The variation of energy under any little deformity is positive. The anisotropy indicates that all materials are anisotropic in the pressure range up to 30 GPa and they are more rigid along the axes 〈100〉.

We study the small vibrations of axially moving strings described by a wave equation in an interval with two endpoints moving in the same direction with a constant speed. The solution is expressed by a series formula where the coefficients are explicitly computed in function of the initial data. We also define an energy expression for the solution that is conserved in time. Then, we establish boundary observability inequalities with explicit constants.

This paper presents a numerical study of buoyancy‐driven double‐diffusive convection within an elliptical annulus enclosure filled with a saturated porous medium. An in‐house built FORTRAN code has been developed, and computations are carried out in a range of values of Darcy–Rayleigh number Ram (10 ≤ Ram ≤ 500), Lewis number Le (0.1 ≤ Le ≤ 10), and the ratio of buoyancy forces N (−5 ≤ N ≤ 5). In addition, three methods are used, namely the multi‐variable polynomial regression, the group method of data handling (GMDH), and the artificial neural network (ANN) for the predictions of heat and mass transfer rates. First, results are successfully validated with existing numerical and experimental data. Then, the results indicated that temperature and concentration distributions are sensitive to the Lewis number and thermal and mass plumes are developing in proportion to the Lewis number. Two particular values of Lewis number Le = 2.735 and Le = 2.75 captured the flow's transition toward an asymmetric structure with a bifurcation of convective cells. The average Nusselt number tends to have an almost asymptotic value for Le » 5. For the case of aiding buoyancies N > 1, the average Nusselt Number Nu¯ $\bar{{Nu}}$ decreased by 33% when the Lewis number increased to its maximum value. Then, it increased by 10% when the Lewis number increased to Le = 1 for the case of opposing buoyancies N < 1 and then decreased by 33% when the Lewis number increased to its maximum value., contrary to the behavior of the average Sherwood number Sh¯ $\bar{{Sh}}$ that increased by 700% for both cases N > 1 and N < 1. New correlations of Nu¯ $\bar{{Nu}}$, and Sh¯ $\bar{{Sh}}$ as a function of Ram, Le, and N are derived and compared with GMDH and ANN methods, and the ANN method showed higher performance for the prediction of Nu¯ $\bar{{Nu}}$ and Sh¯ $\bar{{Sh}}$ with R² exceeding 0.99.

this paper, we obtain analytical vibrational partition function with recent energy spectrum of the deformed hyperbolic barrier potential. We derive different thermodynamic properties for the RbH
, NaK
, KRb
, NI
, 7Li2
and N2
diatomic molecules. In addition, we obtain the total molar entropy for the two last molecules. Our results are in excellent agreement with the experimental data.

In this paper, the two-dimensional problem of irrotational flow past a wedge located in the center of the channel is considered. Assuming that the fluid is incompressible and non-viscous, the influence of gravity is ignored but the surface tension is considered. The problem which is characterized by the nonlinear boundary conditions on the free surface of the unknown equation is solved numerically by the series truncation technique. The results show that for all given wedge configurations, there is a critical value for the Weber number, for which there is no solution for every Weber number value smaller than this. In addition, the obtained results extend the work done by Gasmi and Mekias [2].

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