A complementary covariant approach to gravito-electromagnetism

From a previous paper where we proposed a description of general relativity within the gravito-electromagnetic limit, we propose an alternative modified gravitational theory. As in the former version, we analyze the vector and tensor equations of motion, the gravitational continuity equation, the conservation of the energy, the energy-momentum tensor, the field tensor, and the constraints concerning these fields. The Lagrangian formulation is also exhibited as an unified and simple formulation that will be useful for future investigation.

Solitary Wave Solutions for Some Fractional Evolution Equations via New Kudryashov Approach

In this work, we construct solitary wave solutions of a nonlinear evolution equation in the physical phenomena of waves;namely the time-fractional fifth-order Sawada-Kotera equation and the (4+1)-dimensional space-time fractional Fokas equation by Kudryashov method with a new function. As a result, new types of exact analytical solutions are obtained. Here the fractional derivative is described in beta sense.

Monte Carlo simulation of the measurement by the 2E technique of the average prompt neutron multiplicity as a function of the mass of fragments from thermal neutron-induced fission of 239Pu

Using a Monte Carlo method, we simulate the measurement, by the 2E technique, of the average prompt neutron multiplicity as a function of the mass of fragments from the thermal neutron-induced fission of 239Pu. The input data for the simulation, associated with the primary fragment mass (A), consist of the yield (Y), the distribution of the total kinetic energy characterized by its average ((TKE) ̅) and its standard deviation (σ_TKE), the average prompt neutron multiplicity (ν ̅_s, a sawtooth approach of experimental data), and the slope of neutron multiplicity against total kinetic energy (dν_s/d<TKE>). The output data, associated with the simulated as the fragment mass measured by the 2E technique (µ), consist of the yield (y), the distribution of the total kinetic energy characterized by its average ((tke) ̅) and its standard deviation (σ_tke), and the average prompt neutron multiplicity (ν ̅_µ). In the mass regions A≈115 and A>150, ν ̅_µ is higher than ν ̅_s. This result suggests that, in those mass regions, the 2E experimental values associated with the average neutron multiplicity are overestimated, referred to the corresponding to the primary fragments.

Preparation, thermal analysis, and crystal structure refinement of the quaternary alloy (CuIn)2NbTe5

The quaternary alloy (CuIn)2NbTe5 was synthesized by solid-state reaction using the melt and annealing technique. The thermal analysis shows that this compound melts at 1026 K. The present alloy is isotypic with Cu2FeIn2Se5 and crystallizes in the space group P2c (Nº 112), with unit cell parameters a = 6.1964(2) Å, c = 12.4761(4) Å, c/a = 2.01, V = 479.02(3) Å3. (CuIn)2NbTe5, belonging to the system (CuInSe2)1-x(FeSe)x with x= ⅓, is a new adamantane compound with a P-chalcopyrite structure. This structure is characterized by a double alternation of anions-cations layers according to the Te-Te : Nb-In-Nb-In : Cu-In-Cu-In : Te-Te sequence, along the 010 direction.

Elastic constants, electronic properties and thermoelectric response of LiAlX (X=C, Si, Ge, And Sn) half-Heusler

Since they have become indispensable in various technological applications and a powerfulsource for generating energy in thermoelectric devices, Lithium-based alloys symbolize the topicof many experimental and theoretical reports. Hence, LiAlX(X = C, Si, Ge, Sn) materials representthe main research in this study. Different interesting properties such as the effect of pressure onthe band gap as well as the elastic parameters and the thermoelectric efficiency of these materialswere investigated using the full potential linearized augmented plane wave (FP-LAPW) method.LiAlX alloys were found to be semiconducting with indirect band gaps. When studying themechanical properties, we found that LiAlC alloy is stable against a wide range of pressurechanges (90 GPa), while the rest three systems preserve their mechanical stability in a moderaterespectively range of 40, 50 and 30 GPa, respectively. The semiconducting band gap for eachpossible transition have been calculated in a range of different pressures using both GGA andmBJ-GGA approximations. The results ended up revealing a decaying trend of the indirect gapalong Г-X direction with the increase of pressure. High values of the power factor were achievedand a large figure of merit (almost 0.7 for all systems) was calculated at 600K, which makesthese Li-based alloys very auspicious in the thermoelectric field applications.

A different approach for the fractional chemical model

This article analyzes and compares the two algorithms for the numerical solutions of the fractional isothermal chemical equations (FICEs) based on mass action kinetics for autocatalytic feedback, involving the conversion of a reactant in the Liouville-Caputo sense. The first method is based upon the spectral collocation method (SCM), where the properties of Legendre polynomials are utilized to reduce the FICEs to a set of algebraic equations. We then use the well-known method like Newton-Raphson method (NRM) to solve the set of algebraic equations. The second method is based upon the properties of Newton polynomial interpolation (NPI) and the fundamental theorem of fractional calculus. We utilize these methods to construct the numerical solutions of the FICEs. The accuracy and effectiveness of these methods is satisfied graphically by combining the numerical results and plotting the absolute error. Also, the absolute errors are tabulated, and a good agreementfound in all cases.

Nuclear Adiabatic Effects of Electron-Positron Pairs on the Dynamical Instability of Very-Massive Stars

The adiabatic effects of electron-positron pair-production on the dynamical instability of very-massive stars is investigated from stellar progenitors of carbon-oxygen cores within the range of 64 M < MCO < 133 M both with and without rotation. At a very high temperature and relatively low density; the production of electron-positron pairs in the centres of massive stars leads the adiabatic index to below 4/3. The adiabatic quantities are evaluated by constructing a model into a thermodynamically consistent electron-positron equation of state (EoS) table. It is observed that the adiabatic indices in the instability regions of the rotating models are fundamentally positive with central temperature and density. Similarly, the mass of the oxygen core within the instability region has accelerated the adiabatic indices in order to compress the star, while the mass loss and adiabatic index in the non-rotating model exponentially decay. In the rotating models, a small amount of heat is required to increase the central temperature for the end fate of the massive stars. The dynamic of most of the adiabatic quantities show a similar pattern for all the rotating models. The non-rotating model may not be suitable for inducing the instability. Many adiabatic quantities have shown great effects on the dynamical instability of the massive stars due to electron-positron pair-production in their centres. The results of this work would be useful for better understanding of the end fate of very-massive stars.

Corrosion resistance evaluation of boron-carbon coating on ASTM A-36 steel

The ASTM A-36 steel is the main alloy, used in the metal-mechanical industry. In the present study, the effect of boron-carbon coating on the hardness and corrosion resistance of the steel ASTM A-36 was reported. Boronizing thermochemical treatment was carried out at 950 °C for 4 h followed by the carburizing process at 930 °C for 6 h. The corrosion study was conducted using the polarization technique (Tafel) and electrochemical impedance spectroscopy (EIS), which employed a fused deposition modeling-based 3D printing electrochemical cell made of polylactic acid (PLA). A commercial platinum foil and an Ag/AgCl (3.5 M KCl) electrode were used as the counter and reference electrode, respectively. The working electrode used an area of 1 cm2 of the sample. Optical microscopic analysis shown that borides formed on the surface of steels has a saw-tooth morphology and a uniform coating with a thickness of about 60 µm in both samples. The carburizing over boride promoted the formation of coatings on the outermost layer of the samples with a thickness of about 17 µm over the boride layer. Boride formation was verified by X-ray diffraction (XRD) analysis indicating only the formation of the Fe2B phase. Results showed that boride samples exhibited inferior corrosion resistance compared to original samples, but after carburizing, an outer layer was formed, with the hardness and corrosion resistance like that of the original sample.

Aberration patterns in the optical testing surfaces using transport of intensity equation

Classic phase retrieval techniques use intensity patterns to obtain typical aberrations such as coma or astigmatism. However, the patterns obtained with the Transport of Intensity Equation techniques have not been studied yet. In this work, we propose a method to obtain intensity distributions of some aberration wavefronts. It is expected that this characterization method may facilitate new testing strategies in optical workshops.

Effects of non-uniform nanoparticle concentration on entropy generation

The entropy generation analysis of a thermal process is capable of determining the efficiency of that process and is therefore helpful to optimize the thermal system operating under various conditions. There are several ingredients upon which the phenomenon of entropy generation can depend, such as the nature of flow and the fluid, the assumed conditions, and the material properties of the working fluid. However, the dependence of entropy generation phenomenon upon such properties has so far not been fully realized, in view of the existing literature. On the other hand, based upon the existing studies, it has been established that the non-uniform concentration of nanoparticles in the base fluid does cause to enhance the heat transfer rate. Therefore, it is logical to investigate the entropy production under the impact of non-homogenous distribution of nanoparticles. Based upon this fact the aim of current study is to explore a comprehensive detail about the influence of non-homogeneous nanoparticles concentration on entropy production phenomenon by considering a laminar viscous flow past a moving continuous flat plate. Non-uniform concentration is considered in the nanofluid modeling in which the Brownian and thermophoretic diffusions are considered which impart significant effects on velocity and temperature profiles. An exact self-similar solution to this problem is observed to be possible and is reported. The effects of various controlling physical parameters such as Brinkman number, Schmidt number, Prandtl number, diffusion parameter, and concentration parameter on both local as well as total entropy generation number and Bejan number are elaborated by several graphs and Tables. The obtained results reveal a significant impact of all aforementioned parameters on entropy generation characteristics. It is observed that by a 20% increase in nanoparticles concentration the total entropy generation is increased up to 67% for a set of fixed values of remaining parameters.