National School of Built and Ground Works Engineering

This paper presents a comprehensive contribution to the design of doubly reinforced prestressed concrete I-beams by means of cost optimization. The objective function, which is the sum of the costs of the cross-section’s constituents (concrete, reinforcement steel, prestressing steel, and formwork), is subjected to design constraints according to Eurocode 2 provisions. These constraints involve serviceability and ultimate limit states, along with current rules of practice, and take into consideration long-term effects such as creep and shrinkage to accurately depict the structural behavior of the I-beam. A combination of gradient-based and metaheuristic optimization techniques is employed to solve the nonlinear optimization problem. An illustrative example demonstrates the efficacy of the optimal design model and its merited gain compared to the conventional design method. The results highlight the significance of certain constraints that are often overlooked in the literature, along with a study of sensitivity to cost fluctuations. An investigation of the results showed that the proposed model can provide practical guidelines for initial geometry selection to achieve more economical conventional designs. Moreover, the model’s simple and practical implementation holds potential for extension to other types of prestressed structures.

This work designs and implements a single-stage rectifier-based RF energy harvesting device. This device integrates a receiving antenna and a rectifying circuit to convert ambient electromagnetic energy into useful DC power efficiently. The rectenna is carefully engineered with an optimal matching circuit, achieving high efficiency with a return loss of less than −10 dB. The design uses a practical model of the Schottky diode, where both RF and DC characteristics are derived through extensive experimental measurements. The results from both experiments and simulations confirm the effectiveness of the design, showing its proficiency in efficient RF energy harvesting under low-power conditions. The antenna produced operates in the wifi band with a gain close to 4 dBi and a bandwidth of 100 MHz. With a load resistance of 1600 Ω, the proposed device achieves an impressive RF-to-DC conversion efficiency of approximately 52% at a low incident power of −5 dBm. These findings highlight the potential and reliability of rectenna systems for practical and efficient RF energy harvesting applications. The study significantly contributes to our understanding of rectenna-based energy harvesting, providing valuable insights for future design considerations and applications in low-power RF systems.

On 25th April 2012, a moderate Mw4.9 earthquake, followed by an aftershock sequence (0.6 ≤ ML ≤ 4.3), occurred in Beni Haoua, northern Algeria. To reveal the fault responsible for this earthquake and the likely associated subsurface deformation, a detailed study of the weak seismicity based on spectral modelling of source parameters has been performed. The earthquake affected the area located in the north-eastern extend of the El Asnam seismic zone and it appears likely related to the reactivation of a segment of the fault zone that caused the El Asnam Mw7.1 earthquake on 10th October 1980, one of the most destructive earthquakes recorded in northern Africa and western Mediterranean. The determination of the source parameters of these earthquakes is important because they are too small to be reported in a global catalogue. In this study, source parameters are determined for 35 associated aftershocks using spectral modelling of three components P and S waves, assuming the Madariaga 1976 model. This model is one of the most widely used for a singular crack, radially expanding at a constant rupture speed. In this study, we estimated the source parameters (seismic moment, size of the seismic source, source dislocation and stress drop) from data in the frequency domain and we show how the results depend on the model assumptions. The Q attenuation factors for P and S waves are estimated to be 97 (50–170) and 153 (73–242), respectively, with a ratio of Qs/Qp = 1.62. We analysed source spectra and stress drops of 35 micro-earthquakes and resolved significant variations in earthquake stress drop and apparent average source dimension Rp and Rs of about 17 and 75 m, respectively. From the local magnitude calculated for the studied aftershock sequence, we highlighted similar relationship between the moment magnitude and the local magnitude, Mwp = 0.62 ML + 0.86 and Mws = 0.63 ML + 0.81, for P and S waves, respectively. This type of study is very important since we have exploited low magnitude earthquakes to obtain information that can contribute to the seismotectonic analysis of active seismic zone.

Currently, the search for efficient materials with desirable optoelectronic and thermoelectric properties for power generation holds great importance. This study investigates the structural, optoelectronic, and thermoelectric properties of potassium tin halide vacancy-ordered double perovskites (K2SnX6) through first-principles computations. Our comprehensive analysis encompasses DFT method of calculation and Boltzmann transport theory. Generalized Gradient Approximation (GGA) with and without mBJ potential is applied, employing LAPW base-set. The electronic analysis reveals that all compounds are direct band gap semiconductors, with band gaps ranging from 1.70 eV to 4.126 eV (using PBESol-mBJGGA), making them promising for solar cells and optoelectronic applications. Optical calculations demonstrate excellent agreement with theoretical band gaps, highlighting their accurate prediction. K2SnI6 exhibits superior light absorption in the visible range compared to K2SnCl6 due to its narrower band gap, making it a suitable material for solar cells. The refractive index analysis confirms their viability for solar applications. Regarding thermoelectric properties, iodine substitution increases electric conductivity, while phonon heat transfer diminishes with temperature. The compounds display p-type conductivity, and the power factor values indicate their potential as effective thermoelectric materials. At 500 K, the compounds achieve maximum ZT values of 0.58, 0.69, and 0.50 for K2SnCl6, K2SnBr6, and K2SnI6, respectively. These findings suggest the materials suitability for high-temperature thermoelectric applications

In this article, we propose the design of a rectangular-shaped patch antenna suitable for ultra-wideband (UWB) applications and short and long–range Millimeter-Wave Communications. We begin with the design of a high-gain UWB rectangular patch antenna featuring a partial ground plane and operating within the 3.1–10.6 GHz bandwidth. Complementary Split Ring Resonators (CSRRs) are integrated on both sides of the structure to meet desired specifications. The resulting UWB antenna boasts an extended frequency bandwidth, covering 2.38–22.5 GHz (twice that of the original antenna), with a peak gain of 6.5 dBi and an 88% radiation efficiency. The grey wolf optimization technique (GWO) determines optimal structural dimensions. Validation of the antenna's performance is demonstrated through the strong agreement between measurement and simulation.

This paper focuses on the free vibration analysis of sandwich plates with variable stiffness composite laminated (VSCL) face sheets and a functionally graded (FG) porous core. The problem is solved using the hierarchical finite element method (FEM) based on the three-dimensional (3-D) elasticity theory. The use of an FG material core in a VSCL sandwich plate offers many advantages in terms of lightweight properties, high stiffness, as well as high strength and toughness. The sandwich plate is modeled by an assembly of 3-D p-elements, where each element or layer has an independent thickness and material properties. The layers of the sandwich plate are assumed to be perfectly bonded between the interfaces. The present 3-D solutions are validated through convergence and comparison studies with the published results of various sandwich plates that employ different theories and methods. A parametric study is performed to investigate the effects of several factors, including the volume fraction function index, porosity, core-to-face sheet thickness ratio, plate thickness, fiber orientation angles and boundary conditions on the vibrational frequencies. The results show that the incorporation of composite curvilinear fibers in the face sheets, combined with a porous FG core, significantly enhances the stiffness of the sandwich plate. These results can be used to establish benchmarks for future comparisons.

The synergy effect between adsorption and solar photocatalysis to remove Cr (VI) is a new approach which is environmentally friendly and sustainable development technology. the choice of photocatalyst is crucial for achieving better performance in adsorption and photocatalytic reactions. The CuFe 2 O 4 catalysts with a spinel structure was synthesized by co-precipitation and sol-gel methods, and characterized by X-ray diffraction (XRD), Brunauer, Emmett and Teller (BET) surface area, scanning electron microscopy (SEM), Raman and Fourier transform infrared spectroscopy (FTIR). The results of this study show that the CuFe 2 O 4 -co is an excellent adsorbent and photocatalyst simultaneously for Cr (VI) removal, this activity is correlated to it structural, textural properties and a relatively narrow band gap. The catalyst is mainly crystallized in cubic inverse spinel structure, and exhibit a large pore size facilitates the accessibility of active sites by chromium ions on the surface, and which can also improve absorbed light penetration. Moreover, UV–vis diffuse reflectance spectrum (UV–vis DRS) show that the catalyst has a low band gap energy (E g =1.2 eV), allowing a broader absorption spectrum, which enhances it capability to generate electron-hole pairs under visible light of solar irradiation.We investigated the effects of oxalic acid as a reducing agent, preparation technique, catalyst concentration, and initial dose of Cr (VI) in this research. The optimum catalyst and pollutant concentrations are 0.25g/L and 25 g/L, respectively, with a 100% reduction of Cr(VI) to Cr(III) accomplished within 1 hour.

Background The correlation between anodization conditions and the ageing effect on TiO2 nanotubes (TNT) surface has been widely studied in different media and conditions (physiological solutions, mechanical stresses in water, etc.) for the prediction of their behaviour over a long period of time. In the present study, the synthesized TiO2 nanotubes (TNT) from Ti-6Al-4V alloy, which were left unattended and exposed to environmental conditions (i.e., humidity and ambient temperature) for more than 4 years, were investigated to underline any important alteration/changes and ageing effects, on the surface morphology, the surface composition, and the electrochemical behaviour. The nanotubes were made in 2018 by anodization in different potentials (20V, 40V, 50V, and 60V) for different times (30 min, 60 min, 90 min, 150 min and 180 min) in an Ethylene Glycol solution for other purposes. Methods For the surface morphology characterisation, electronic microscopy (SEM) was performed to depict any tendency with anodization conditions: potential and time. The comparison study between the obtained results and the SEM pictures taken on similar samples made and characterized under the same conditions in 2018, reveals a noticeable alteration in the morphology and a change in the TNT’s external diameter. Surface composition was checked using energy dispersive spectrometry (EDXS). The EDXS spectra analysis was realised to investigate the storage time impact on structure surface stability. A drastic decrease in the amount of oxygen was noticed on all of the surfaces where wettability measurements by contact angle were performed to confirm the latter. The verification of the hydrophobicity of TNT surfaces attested that all aged samples are hydrophobic in concordance with EDXS analysis and X-ray photoelectron spectroscopy (XPS). To affirm the surface modification during the storage duration and its impact on the electrical behaviour: cyclic voltammetry (CV), open circuit potential (OCP) measurements, and Tafel plots are undergone on the aged samples and compared with the freshly synthesised samples [1],[2]. The plotted CV curved as a function of the scan rate and the composition of the electrolyte showed a correlation between the different samples electrochemical behaviour and their surface morphologies as well as the existence of surface states for all samples. Results From the previous characterisation, it was obvious that the sample prepared at 40V over 3 hours showed a remarkable electrochemical behaviour. The ageing effect is closely related to the anodization conditions. It was also noticed that the amount of water in the electrolyte solution EG played a contributing factor in the onset of ageing. High water content causes the formation of nanograss which have a non-negligible influence on the morphology. Conclusion These results can open a new way for the optimization of the storage conditions according to anodization conditions (electrolyte, voltage, time, and temperature annealing) of this material as well as for the study of the life cycle of products made from TiO2 nanotubes. Exposing nanotube surfaces to ambient conditions without taking any precautionary measures and without knowing their historical anodization conditions can cause drastic changes in the electrochemical behaviour of TNT. These changes affect considerably their function for different applications.

In the chemical and water treatment industries, it is necessary to achieve maximum contact between the solid and liquid phase, thus promoting the mass and heat transfer, to obtain a homogeneous solution. Increasing stirring speed is the most recommended solution in different types of reactors: stirred tank, column, and tubular. However, this inadvertently increases the energy consumption of the industry. Determination of the minimum speed, labeled the just suspended speed (Njs) and crucial to attaining homogeneity, has been widely investigated. Numerous studies have been carried out to assess formulas for determining the solid particle speed in various reactor types. Given the limitations of the existing formulations based on a generalization of a unique equation for computing Njs for all soil classifications, it appears that most formulas can only approximate complex phenomena that depend on several parameters. A novel formula was developed, and the results given in this paper demonstrate the effectiveness of generating significant uncertainties for the estimation of Njs. The purpose of this study was the elaboration of experiment-based data-driven formulas to calculate Njs for different particle size classes. Nonlinear multiple regression (MNLR) models were used to generate the new formulas. The gradient descent optimization algorithm was employed to solve the hyperparameters of each novel equation, utilizing supervised learning. A comparison of the data indicated that the unique formulas presented in this study outperformed empirical formulas and provide a useful means for lowering energy consumption, while increasing the heat and mass transfer in torus type reactors.

The aim of this study was to determine the effect of deficit irrigation on evapotranspiration, crop water productivity, irrigation water productivity, yield response, yield components and quality characteristics of grain sorghum (Sorghum bicolor L.) grown in Antalya, Turkey. The experiment was carried out in a randomized block design with three replications at four different irrigation water levels (I100, I70, I35 and I0) in two growing seasons (2019 and 2020). Deficit irrigation levels significantly decreased plant height, chlorophyll content (SPAD), stomatal conductivity, average leaf area, leaf area index, leaf weight, stem weight, panicle weight, grains per panicle and grain yield in both growing seasons. Except for the ash content in the first year, quality components such as water, oil and protein content were not significantly affected by different irrigation levels. Also, fatty acid contents were not affected by irrigation levels in both growing seasons. The correlation test revealed a strong positive relationship between leaf weight, panicle weight, plant weight and sorghum grain yield in different irrigation applications. On the other hand, there was no correlation between grain yield and different fatty acid contents. When water is not limited, it is suggested that sorghum can be irrigated by bringing soil water to the field capacity when 40–45% of the water at the effective root depth of the sorghum plant is depleted. When water is limited, timing the irrigations when 40–45% depletion in the root zone has occurred, but refilling the profile to only 70% of available water capacity is recommended to limit significant yield loss.

This paper deals with the mechanical behavior of variable stiffness composite laminated (VSCL) sandwich plates, for both static and dynamic analyses. The composite face sheets are made by curvilinear fibers. For static analysis, the VSCL sandwich plate is subjected to sinusoidal transversal load. The layer-wise (LW) theory and the p-version of the finite element method (FEM) are used to solve such problems. For the layer-wise model, each layer is modeled individually, while the displacement fields continuity is made by a linear zigzag variation in displacements through the thickness of the sandwich laminate. The principal of virtual work and the Lagrange’s method were applied to solve the static and dynamic problems of the VSCL sandwich plates. The efficiency and accuracy of the LW model coupled with the hierarchical FEM are demonstrated through convergence and comparison studies with the existing solutions for both static and dynamic analyses. A parametric study is performed to examine the effect of fiber orientation angles, plate thicknesses, core to face sheet thickness ratios, stacking sequences, and boundary conditions on the deflection and stresses values as well as the fundamental frequencies. New results concerning the static and dynamic analyses of VSCL sandwich plates are presented using layer-wise solutions, where they can be used to establish benchmarks for future comparisons.

In this paper, a frequency-adaptive neural network-based virtual flux (FANN-VF) estimator is developed for sensorless control of a pulse-width modulation converter under unbalanced and distorted grid conditions. This method exploits two parallel FANNs configured as quadrature signal generators. The VF fundamental positive and negative sequence components (PNSCs) are inherently separated in the estimator without employing any cascaded filters. A frequency-locked loop is introduced to accurately track the frequency variations. The estimated VF PNSCs are directly exploited to compute the power references in VF-based predictive direct power control scheme. The developed strategy ensures constant active power and sinusoidal current waveforms under nonideal grid conditions. Simulation and experimental tests are performed to verify the effectiveness of the proposed method.

This study highlights the alteration of refractory bricks for anode baking furnace for unused and used bricks after 96 baking cycles. The chemical composition of the unused bricks included silica (51.37wt.%) and alumina (34.05wt.%). A decrease of compressive strength from 48.45 MPa to 32 MPa respectively for unused and used bricks were observed. The bulk density obtained by mercury intrusion porosimeter method decreased from 2.48 to 2.38 g/cm ³ for unused and used bricks; while the bulk density by archimades method increased from 2.29 to 2.49 g/cm ³ . The water absorption by Archimedes method is decreased from 6.65wt.% to 5.05wt.%. While the total porosity obtained by mercury intrusion porosimeter increased from 15.41wt.% to 17.21wt.% for unused and used bricks. In the same way the total cumulative pore increased from 62.05 mm ³ /g to 72.35 mm ³ /g for unused and used brick. While the average pore radius decreased from 5.65 µm to 1.06 µm respectively for unused and used brick due to the deposition of C and particles inside the pores. The alteration of the hot side of brick is due by the decrease of Si and Ti with increase of Fe; while the alteration of anode side is due to the increase of Si and decrease of Al. The anode side of brick is deterioted rapidly than hot side of brick. Mullite peak seems to be not change, suggesting that a very compacted brick with high mullite content and high alumina content 75-90wt.% seems to be the best matrix for bricks in anode baking furnace.

This study analyses the alteration of refractory bricks after 96 baking cycles of anode baking furnace. A decrease of compressive strength from 48.45 MPa to 32 MPa respectively for unused and used bricks were observed. The bulk density obtained by mercury intrusion porosimeter method decreased from 2.48 to 2.38 g/cm ³ for unused and used bricks; while the bulk density by archimades method increased from 2.29 to 2.49 g/cm ³ . The water absorption by Archimedes method is decreased from 6.65wt.% to 5.05wt.%. While the total porosity obtained by mercury intrusion porosimeter increased from 15.41wt.% to 17.21wt.% for unused and used bricks. In the same way the total cumulative pore increased from 62.05 mm ³ /g to 72.35 mm ³ /g. While the average pore radius decreased from 5.65 µm to 1.06 µm respectively for unused and used brick. The anode side of brick is deterioted rapidly than hot side of brick. The instrusion porosimetry method seems to be the best method to characterize buld density and porosimetry of refractory bricks than Archimedes method. Mullite peak seems to be not change, suggesting that a very compacted brick with high mullite content seems to be the best matrix for bricks in anode baking furnace.

The bound state energy eigenvalues and eigenfunctions of the energy-dependent hyperbolic Pöschl–Teller II (HPT-II) potential with $l\ge 0$ are determined by means of quantum supersymmetry (SQM) and shape invariance using Pekeris approximation to the centrifugal term. On the one hand, SQM results are compared to the numerical ones to show the effectiveness of our calculation by SQM method. On the other hand, a comparison is made between energy-dependent and position-only-dependent cases of HPT-II potential to show the effects of energy dependence. An application to $\mathrm{H}_{2}$, HCl and LiH diatomic molecules is considered.