Kinds Of Physical Problems Research Articles

Prabhakar fractional simulations for hybrid nanofluid with aluminum oxide, titanium oxide and copper nanoparticles along with blood base fluid

This fractional model addresses the analytical simulations for the hybrid nanofluid problem with different nanoparticles with consideration of blood base fluid. The thermal increment of the hybrid nanofluid model is inspected with consideration of aluminum oxide , titanium oxide , and copper nanoparticles. The conducted thermal phenomenon is assumed due to the magnetized moving surface with porous space. Moreover, the velocity and thermal slip assumptions are also introduced to make the model versatile. The Prabhakar fractional derivative simulations with recent mathematical expressions are followed for the analytical simulations. The implementation of the Prabhakar model is due to motivations toward fractional calculus for various kinds of physical problems. The integral technique via Laplace transformations is used. The numerical simulations are accomplished to compare and validate the attained results. The graphical illustrations examine the empirical results and the physical impact of various pertinent parameters of velocity and heat transfer profiles.

Second-order two-scale analysis for heating effect of periodical composite structure

The multi-scale analysis method is presented for the heat transfer problems of periodical composite structures under irradiation heating. This kind of physical problem can be described as a class of parabolic equations with small periodical oscillating coefficients equipped with the mixed boundary conditions of both Dirichlet and Neumann type. It needs more expensive cost in both computer's memory and CPU time to solve these problems by the usual finite difference method or finite element method, since it is necessary to partition the considering geometrical region finer to capture the heat conduction behavior at small scale. To reduce the computational complexity, an approximate solution is derived by the asymptotic expansion technique. The convergence of asymptotic solution to exact solution is technically proved as the micro-scale parameter tends to zero. Based on the asymptotic expansion formula, a second-order two-scale finite element method is proposed to fully solve this problem in practice. Numerical results show convergent behavior of the proposed method.

Phase-Change Transpiration Cooling in a Porous Medium: Determination of the Liquid/Two-Phase/Vapor Interfaces as a Problem of Eigenvalues

In this work, we carry out a theoretical analysis of the transpiration cooling with a liquid coolant phase change in a porous medium. The evaporation of the liquid inside the porous medium causes the appearance of three regions: a liquid region, a two-phase region and a vapor region. This kind of physical problem has been widely studied in the specialized literature and the main contributions are based on the separated phase model or by using the two-phase mixture model. Here, we propose a new model that permits to numerically determine the thickness of the three regions that are formed inside of the porous medium. To analyze this phenomenon, the governing equations were appropriately nondimensionalized, where suitable Peclet numbers for each region appear such that these numbers represent eigenvalues for the mathematical model, and when they are obtained, the relative position of the interfaces between each region is found.

Particle-in-cell modeling of relativistic laser–plasma interaction with the adjustable-damping, direct implicit method

Implicit particle-in-cell codes offer advantages over their explicit counterparts in that they suffer weaker stability constraints on the need to resolve the higher frequency modes of the system. This feature may prove particularly valuable for modeling the interaction of high-intensity laser pulses with overcritical plasmas, in the case where the electrostatic modes in the denser regions are of negligible influence on the physical processes under study. To this goal, we have developed the new two-dimensional electromagnetic code ELIXIRS (standing for ELectromagnetic Implicit X-dimensional Iterative Relativistic Solver) based on the relativistic extension of the so-called Direct Implicit Method [D. Hewett, A.B. Langdon, Electromagnetic direct implicit plasma simulation, J. Comput. Phys. 72 (1987) 121–155]. Dissipation-free propagation of light waves into vacuum is achieved by an adjustable-damping electromagnetic solver. In the high-density case where the Debye length is not resolved, satisfactory energy conservation is ensured by the use of high-order weight factors. In this paper, we first derive the electromagnetic direct implicit method as a simplified Newton scheme. Its linear properties are then investigated through numerically solving the relation dispersions obtained for both light and plasma waves, accounting for finite space and time steps. Finally, our code is successfully benchmarked against explicit particle-in-cell simulations for two kinds of physical problems: plasma expansion into vacuum and relativistic laser–plasma interaction. In both cases, we will demonstrate the robustness of the implicit solver for crude discretizations, as well as the gains in efficiency which can be realized over standard explicit simulations.

Prevalence of Students With Symptoms of Depression Among High School Students in a District of Western Turkey: An Epidemiological Study

To determine the factors affecting the prevalence of depression and also to present some pertinent comments concerning prevention of depression among high school students. This study was deemed important and relevant due to the increasing importance of depression among high school students. A sample of students aged 14-19 years from the 6 high schools of 1 district of western Turkey were surveyed. The students selected were all attending the school during March and April 2006. The Beck Depression Inventory was used as a screening test. During the study, a total of 846 students completed the survey. Of the study group, 51.9% (439) were male and 48.1% (407) female, with an age average of 16.3 +/- 1.1 years. According to the scale, the prevalence of depression was 30.7% (n = 260), 22.6% for males (n = 99) and 39.6% for females (n = 161). The most depression was seen in males (22.6%), those with any kind of physical problem (37.3%), those with diseases necessitating the use of medication (51.1%), those with acne vulgaris (35.2%), and those having previously experienced any kind of problem (47.3%). These results highlight not only the need for students' parents and teachers to be well informed on the subject of depression in terms of students' health but also the need for more education programs to be aimed at students relating to the problems they may experience during the period of adolescence. Furthermore, these results show that students identified as depressed should be referred for an appropriate diagnosis to specialized psychiatry centers.

Thermo-mechanical analysis and application to depressurization and wave propagation

Pressure containing structures and their environment require investigations of phenomena resulting from a variety of hypothetical failure modes. Some of those lead to complex physical processes such as depressurization of subcooled fluids, wave propagation in gases, fluids and solids, vaporization of the fluid, two phase motion and dynamic deformation of the surrounding structures. In the first part of this paper (sections 1 to 5), the theoretical considerations and formulations used to establish the basic concept for the code system SAN (Structural Analysis) are outlined. A variational approach in Lagrangian and Eulerian or arbitrary description is used to simulate such kind of physical problems. The second part (section 6) presents practical applications, in particular to depressurization and wave propagation problems: (a) analysis of thermodynamic processes and structural response due to failure of a pressure vessel, (b) reflection and diffraction of shock waves in the vicinity of cylindrical reactor buildings, (c) nonlinear wave propagation including flow phenomena behind a step-shaped shock front.

Direct measurement of the Rayleigh scattering cross section in iron using selective excitation double Mössbauer techniques

Recent developments in selective excitation double M\ossbauer (SEDM) procedures and analysis have made this technique available for studying several kinds of physical problems. In this work we report the direct measurement of the Rayleigh scattering cross section in iron metal. The method consists of selectively exciting an absorption transition in $^{57}\mathrm{Fe}$ in iron metal which, owing to the magnetic dipole selection rules, results in two emission transitions of different energies. Since Rayleigh scattering is elastic, its only contribution is at the energy of the emission transition which corresponds to the absorption transition. By measuring the SEDM line shape of the two emission lines and comparing with SEDM theory, the Rayleigh differential scattering cross section can be determined. These experiments have been done using both enriched and natural $^{57}\mathrm{Fe}$ iron scatterers.