ABSTRACT:To represent the solution of a differential equation by an artificial neural network (ANN) was an idea introduced by Lagaris. Sugawara applied this concept to solve Schrödinger's equation for select systems. We have submitted their method to a new kind of application. Here, for the first time, the approach is applied to the equations derived from density functional theory (DFT). At first, we have tested the procedure for two simple systems: the double harmonic oscillator and the hydrogen atom. The ANN solutions obtained for these simple systems reproduced the analytical results easily. Next, we have moved to the Tomas-Fermi theory and the Kohn-Sham formulation of DFT. In order to show the feasibility of the ANN representation of electronic density, we have solved the Hooke model-atom and two light atoms: helium and lithium. The ANN results match well with the analytical solution to the Hooke model-atom and with the numerical solutions for helium and lithium.
Ti-6Al-4V alloy has been considered in applications of aeronautical and aerospace industries, due to its properties such as high specific resistance, good creep resistance and metallurgical stability. However, its use in applications for high temperatures is restricted due to its great affinity with the oxygen, which results in the formation of oxide layers and limits its mechanical resistance at these conditions. Thus, specific treatments have been employed in the material to work as surface barriers to avoid the oxygen diffusion in the alloy under high temperature conditions. One surface treatment that can be used is laser nitriding. In the present work, the surface of Ti-6Al-4V alloy with Widmanstätten microstructure was nitrided by applying Nd:YAG laser focal with 0.6 mm diameter, at laser power of 700, 750 and 800 W, process speed of 100 mm/s and 20 L/min of N2 flow. Creep tests were performed at constant load at 600 °C and 125 MPa, to verify the influence of treatment on the Ti-6Al-4V alloy. Results have indicated a lower stationary creep rate for the titanium alloy with Widmanstätten laser-nitrided structure when compared to the non-nitriding material. Besides that, the surface hardness increased from 368 HV of base material to 1000 HV after laser nitriding.
The procedure to obtain gas temperature in plasmas is to fit the experimental rotational spectrum to a theoretical one based on the Boltzmann distribution. For many systems a single distribution fails to account for the occupation of the levels. Researchers have improved the fitting by coupling two distributions and obtaining two distinct temperatures. They assigned the lowest temperature to the gas. Here, we show that these systems should be described by Tsallis nonextensive statistics and its unique associated temperature. Experimental and simulated spectra are tested and excellent agreement is obtained.
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