Growth and Coalescence of γ’-Precipitates in Nickel-Based Alloy 115NC during Slow Cooling for Membrane Manufacturing

By coarsening of the γ’-precipitates and selective extraction of one of the two existing phases, porous structures can be produced from nickel-based superalloys. There are two basic approaches to achieve a bicontinuous γ/γ’-microstructure—directional and incoherent coarsening. Single crystalline superalloy membranes are produced by the so-called rafting of the microstructure, i.e., directional coarsening. Unlike this process, incoherently coarsened membranes lack a detailed understanding of the mechanisms leading to cross-linking of the precipitates. In this paper, the growth and coalescence of precipitates during initial slow cooling from above the γ’ solvus temperature was studied. In addition to the three-dimensional morphological changes of the precipitates, it is also shown that only little coalescence of the particles occurs despite the high γ’ content and, therefore, their very small distance. The loss of coherency that occurs during this part of coarsening must first advance through further aging before a bicontinuous microstructure is formed.

The misconception in graphene’s dispersion energy simulations

This study aims to find equations and simulations that satisfy the characteristics of graphene’s energy dispersion and identify misconceptions that may occur. Here we give students nine articles about graphene’s dispersion energy. They were asked to identify the equations, parameters, and software used in each of the articles. The assignment was then to make the distribution of the data in a spreadsheet. The parameters used were the lattice constant of 2.46 Å, the range of the k wave function for the x and y axes of -2πa to 2πa, and the interval for each range of 0.1. Each equation is divided into two parts, E(+) and E(-). The analysis was carried out by making a slice in the middle of the x and y axes, as well as the main and off-diagonals. Graphene has Dirac points where the band gap is zero. This means that there is no distance or very small distance between the valence and conduction bands. From this activity, it can be concluded that Rozhkov (2016) has the equations and simulations that best satisfy graphene’s dispersion energy. Misconceptions occur in almost all existing equations and simulations.

A Novel Macroscopic Traffic Model based on Distance Headway

A new model is proposed to characterize changes in traffic at transitions. These changes are affected by driver response. The distance headway between vehicles is considered as it affects driver behavior. Driver response is quick with a small distance headway and slow when the distance headway is large. The variations in traffic are greater with a slow driver while traffic is smooth with a quick driver. A model is developed which characterizes traffic based on driver response and distance headway. This model is compared with the well-known and widely employed Zhang and PW models. The Zhang model characterizes driver response at transitions using an equilibrium velocity distribution and ignores distance headway and driver response. Traffic flow in the PW model is characterized using only a velocity constant. Roe decomposition is employed to evaluate the Zhang, PW, and proposed models over a 270 m circular (ring) road. Results are presented which show that Zhang model provides unrealistic results. The corresponding behavior with the proposed model has large variations in flow with a slow driver but is smooth with a quick driver. The PW model provides smooth changes in flow according to the velocity constant, but the behavior is unrealistic because it is not based on traffic physics. Doi: 10.28991/CEJ-SP2021-07-03 Full Text: PDF

Double parton distributions out of bounds in colour space

We investigate the positivity of double parton distributions with a non-trivial dependence on the parton colour. It turns out that positivity is not preserved by leading-order evolution from lower to higher scales, in contrast to the case in which parton colour is summed over. We also study the positivity properties of the distributions at small distance between the two partons, where they can be computed in terms of perturbative splitting kernels and ordinary parton densities.

Specificfeatures of evolution of dense atomized superheated water plumes and peculiarities of its diagnostics

Experimental study of evolution of plumes of atomized metastable superheated water during its discharge through convergent-divergent nozzles is conducted. Dispersion characteristics of dense plumes in micron and submicron droplet diameter ranges are obtained. Theoretical and prediction analyses of different coagulation mechanisms in the considered two-phase flow are performed. The negligible effect of Brown-type coagulation is shown. It is also demonstrated that turbulent coagulation can change the fraction of micron-diameter droplets within 9%. In addition, for the first time, an “inertial” mechanism of coagulation is considered for the studied plumes under the conditions of plume baking in a cocurrent flow or in the ambient air. It can lead to a considerable decrease in the submicron-droplet mass fraction, which is observed in experiments even at a small distance from the nozzle cut. The predicted data are compared with experimental ones obtained at theexperimental setup.

Slow and Fast Lights in Metal/Dielectric Composite of Cylindrical Nanoinclusions in Passive and Active Linear Dielectric Host Matrices

This paper presents theoretical discussions and computational numerical results obtained from the study of extreme values of the speed of light in metal/dielectric composite, where the cylindrical nanoinclusions are uniformly distributed in the linear dielectric host matrix. The results testify that, within our approach, at the region of anomalous dispersion, light can travel with a group velocity greater than the speed of light in vacuum. In a composite with passive host matrix, the light pulse is absorbed within a very small distance. The problem of absorption can be reduced considerably by using an active host matrix.

Восстановление топографии поверхностных дефектов ферромагнетиков при нормальном намагничивающем поле

A technique for reconstructing the topography of defects in ferromagnetic materials in a normal magnetizing field is considered. It is shown that with such a magnetization, the surface of a soft magnetic ferromagnetic material is an equipotential surface. An approximation is proposed that makes it possible to obtain its topography from the results of measuring the three components of the magnetic field at a small distance from the defect. The reconstruction accuracy was estimated from the results of calculating the field from the defect by the finite element method and reconstructing the topography of the defect using the proposed approximation.