Iranian Journal of Science and Technology, Transactions A: Science最新文献

Perovskite phase bismuth ferrites substituted with nickel (BFNO) were fabricated using Sol Gel Method. The compositional formula being BiFe_1−xNi_xO₃ where x varies from 0.03 to 0.09 in steps of 0.02. The phase formation was assumed to be confirmed from X-Ray Diffraction (XRD) as no extra peak or impurity is observed. Fourier Transform Infrared Spectroscopy (FTIR) further confirmed the bond formation of Bi–O and Fe–O bond. MH loop was measured for all the samples and from the data, saturation magnetization and coercivity were studied. The saturation magnetization shows a maximum value for nickel concentration 0.07. PE loop analysis was also carried out, and the lowest in maximum polarization is found to be observed at nickel concentration 0.07. The above results obtained from the experiment was discussed based on the possible theoretical mechanism involved.

The investigation focused on the impact of porous activated carbon derived from Sapindus trifoliatus biomass (STAC) in conjunction with a conducting polymer, polyaniline (PA), aimed at achieving high specific capacitance supercapacitors. To create the PA@STAC composites with different weight ratios of STAC (PA@STAC5, PA@STAC10, PA@STAC15, PA@STAC30, PA@STAC50), a practical in situ chemical oxidative polymerization method was employed. The observed improvements in specific capacitance and long-term stability of PA@STAC composites can be attributed to the synergistic effects of both PA and STAC. Consequently, the inclusion of STAC in the composite led to a more than twofold increase in capacitance compared to the original polymers. Specifically, the maximum specific capacitance for the PA@STAC30 composite was 224 F g⁻¹ at a current density of 1 A g⁻¹. The rapid GCD characteristic of PA@STAC30 is attributed to the good porosity and well-organized architecture morphology with short-ion diffusion that allow for free access during the GCD cycles. This study underscores the notable increase in capacitance potential and the enhanced durability of pseudocapacitors achieved through the straightforward addition of a conductive porous carbon material.

Biodiesel occupies a prominent place as the alternative fuel to fossil diesel owing to socio-economic and environmental factors. In this present study, Podocarpus falcatus oil (PFO), having undergone a storage effect, was converted into biodiesel. PFO had a high fatty acid content (FFA = 8.19%). For this reason, a two-step transesterification procedure was developed to convert these high-free fatty acid (FFA) oils into their corresponding monoesters. In the initial step, an acid-catalyzed esterification was employed to lower the FFA content of the oil to below 2%. Subsequently, a second step involving an alkaline catalysis transesterification process was used to convert the product obtained in the first step into monoesters and glycerol. The methyl esters obtained were analyzed using nuclear magnetic resonance (¹H, ¹³C NMR), Fourier transform infrared spectroscopy (FT-IR), Thermal gravimetric analysis (TGA), carbon, hydrogen, nitrogen, and sulfur (CHNS), and Gas chromatography-mass spectrometry (GC–MS) analysis. The identity FAME were Hexadecanoic acid, methyl ester (C16:0), 9,11-Octadecadienoic acid, methyl ester, (E, E)- (C18:0), 6-Octadecenoic acid, methyl ester, (Z)- (C18:2), Methyl stearate (C18:1), Methyl (Z)-5,11,14,17-eicosatetraenoate (C20:5), 11,14-Eicosadienoic acid, methyl ester (C20:3), 11-Eicosenoic acid, methyl ester (C20:2). The study examined the thermal stability of synthesized biodiesel, revealing it remained stable up to 189 °C. Furthermore, the physicochemical properties of biodiesel were validated using ASTM6751 standards.

In this paper the Proca field equations for a massive gauge particle are obtained in the presence of a natural momentum cutoff “(p_{max })” based on a covariant generalization of a one-parameter extension of the Heisenberg algebra. The Yukawa potential for a static point source in the presence of (p_{max }) (generalized Yukawa potential) is obtained analytically and it is shown that in contrast with the Yukawa potential for a static point source in Proca electrodynamics, the generalized Yukawa potential has a finite value at the location of the static point source. Our calculations demonstrate that the Coulomb potential, the Yukawa potential, and the Coulomb potential in the presence of (p_{max }) can be derived from the generalized Yukawa poitential. We show that the free space solutions of Proca electrodynamics in the presence of (p_{max }) describe a massive gauge particle with the effective mass (m_{eff} = frac{m}{{sqrt {1 - left( {frac{mc}{{p_{max } }}} right)^{2} } }}), where (m) is the rest mass of the ordinary Proca particle. Numerical estimations in Sect. 5, show that the lower bound for (p_{max }) must take the value (left( {p_{max } } right)_{min } = (91.187 pm 0.007),,frac{GeV}{c}) in order to avoid complex values for the effective mass (m_{eff}). This lower bound for (p_{max }) is near to the momentum scale of the electroweak interactions. It should be mentioned that for the very large values of (p_{max }) the results of this work reduce to the well-known results of standard Proca electrodynamics.

In this research paper, a novel numerical technique called Hermit-quasilinearization matrix technique (HQLMT) is proposed to acquire the approximate solutions of fourth-order multi-singular and nonlinear Emden–Fowler equations. Firstly, the quasilinearization procedure is utilized for the original model problem followed by the application of a collocation method based on the modified version of Hermite functions to the obtained subequations. After the application of the HQLMT, an algebraic system of linear equations is obtained and this system is solved. Hence, the coefficients of the solution form are determined and the approximate solution is obtained. In addition, the error and convergence analysis are studied for the present method. Finally, it is applied to test examples to explain the method and illustrate the efficiency and accuracy of the HQLMT. Simulation results and comparisons with other existing computational methods show that the presented combined technique is an effective approach.

This study aimed to determine the level of some brush border and pancreatic digestive enzymes through different stages of feeding and food shifts from hatching to 540 degree days post-hatching (ddph) in Stellate sturgeon (Acipenser stellatus). The evaluated brush border enzymes are alkaline phosphatase, aminopeptidase N, and leucine alanine peptidase, and the pancreatic ones are α-amylase, and bile salt-activated lipase. The results revealed that all these either brush border or pancreatic were present at hatching. Intercellular brush border enzymes including alkaline phosphatase and aminopeptidase N reached their highest levels at 234 and 288 ddph (2.93 ± 0.12 and 3.64 ± 0.14 U mg protein⁻¹ respectively) which were significantly different from hatching. Despite showing some fluctuations to the end, they remained high which can be suitable proof of the initiation of digestive activity in the intestine lumen. The highest specific activity of leucine alanine peptidase was observed at 234 ddph (0.15 ± 0.006 U mg protein⁻¹)and then started to decrease significantly to the end which indicates the transformation of digestion into intercellular form. Pancreatic enzymes including α-amylase and bile salt-activated lipase were high at hatching (7.39 ± 2 and 7.26 ± 0.8 U mg protein⁻¹) showing some fluctuations to the end. This high level at hatching can emphasize the necessity of the ability to consume the yolk sac composition right at hatching. The fluctuations at weaning stages can be due to the carbohydrate and lipid composition of diets.

The concentrations of radioisotopes (²³⁸U, ²³⁴U, ²³⁵U, ²¹⁰Po, ²³²Th, ⁴⁰K, and ²²⁶Ra) in naturally occurring radionuclide materials were determined through gamma and alpha spectrometry. The average activities of ²²⁶Ra, ²³²Th, and ⁴⁰K were matched with literature data from various countries. The radium equivalent value derived is 532.3 Bq kg⁻¹, which exceeds the recommended limit of 370 Bq kg⁻¹ for building materials without restrictions by 43.86%. The mean absorbed dose rate is 245.3 nGy h⁻¹, significantly superior than 57 nGy h⁻¹ reference value. The global annual effective dose, resulting from external radiation exposure and dust inhalation, is 0.3 mSv y⁻¹, below the 1 mSv y⁻¹ limit approved by the International Commission on Radiological Protection for public exposure.

The performance of pulsed laser radar systems in cloud media is severely affected by turbulence. These systems should then be able to identify targets in highly turbulent media. Here, the effects of turbulence on a laser beam reaching a target are investigated using ALTM software. The precise values of the beam parameters on the target (including the effective beam spot diameter, mean intensity, scintillation index, etc.) are also calculated for different states by changing the transmitter parameters (i.e., the divergence half-angle and power) and the separation distance between the target and the laser radar system. Accordingly, appropriate corrections can be applied to the laser radar system in order to efficiently perform in turbulent media such as cloud clutter. It is found that the transmitter beam divergence half-angle should be less than 500 μrad. Under this condition, it is possible to decrease the effective laser spot diameter and the scintillation index on the target, while also increasing the spatial coherence radius of the beam and the mean intensity. Alternatively, using PCModWin software, influences of absorption and scattering of cloud clutter on the beam intensity received by a target are simulated, followed by applying corrections to the intensity. As a result, the system performance can be improved for the desired detection distance in the presence of turbulence.

In spatially balanced sampling designs, joint inclusion probabilities for neighborhood units are often zero, or near to zero, because the sampling units tend to be spread across the sample space. In these cases it is difficult to use conventional estimators for the population variance. Alternative estimators, such as the neighborhood-based variance estimators have been introduced. The neighborhood-based variance estimator is recommended for use with Generalized Random Tessellation Stratified designs. In this paper, we review some of the currently available estimators, and introduce others, for use with spatially balanced sampling designs. In a simulation study, the efficiency of the introduced estimators are compared with different estimators under six spatially sampling designs (Balanced Acceptance Sampling, Halton Iterative Partitioning, Generalized Random Tessellation Stratified design, Spatially Correlated Poisson Sampling) and two local pivotal methods. In our simulation study the introduced estimators were more efficient than conventional ones.

After the outbreak of coronavirus disease, numerous models have been proposed for it. In this paper, a fractional mathematical model for COVID-19 is introduced. Applying generalized Bessel polynomials, each function in the model is approximated. For minimizing the norm-2 of residual functions, an optimization problem is obtained and this problem is solved using Lagrange multipliers. The numerical results shows that the proposed method has high accuracy and is suitable for solving nonlinear optimization problems and also can help specialists to cure and control Covid-19 disease.