The European Physical Journal Plus

In the processes of preparation and application of nanomaterials, the thermal decomposition of nanoparticles is often involved. An improved general theory of thermal decomposition kinetics of nanoparticles, developed over the past 10 years, was presented in this paper where the relations between reaction kinetic parameters and particle size were derived. Experimentally, the thermal decomposition kinetics of nano-sized calcium oxalate (nano- CaC2O4 with different sizes was studied by means of Thermogravimetry Analysis (TGA) at different heating rates. The values of the apparent activation energy and the logarithm of pre-exponential factor were calculated using the equation of Iterative Kissinger-Akahira-Sunose (IKAS) and its deformations. The influence regularities of particle size on the apparent activation energy and the pre-exponential factor were summarized, which are consistent with the thermal decomposition kinetics theory of nanoparticles. Based on the theory, the method of obtaining the surface thermodynamic properties by the determination of kinetic parameters was presented. Theoretical and experimental results show that the particle size, through the effect on the surface thermodynamic properties, has notable effect on the thermal decomposition kinetics. With the particle size decreasing, the partial molar surface enthalpy and the partial molar surface entropy increases, leading to the decrease of the apparent activation energy and the pre-exponential factor, respectively. Furthermore, the apparent activation energy, the pre-exponential factor, the partial molar surface enthalpy and the partial molar surface entropy are linearly related to the reciprocal of particle diameter, respectively.

This paper investigates static wormhole solutions through Noether symmetry approach in the context of energy–momentum squared gravity. This newly developed proposal resolves the singularity of big bang and yields feasible cosmological results in the early times. We consider the particular model of this theory to establish symmetry generators and corresponding conserved quantities. For constant and variable red-shift functions, we examine the presence of viable traversable wormhole solutions for both dust and non-dust matter distributions and analyze the stable state of these solutions. We investigate the graphical interpretation of null and weak energy bounds for normal and effective energy–momentum tensors to examine the presence of physically viable wormhole geometry. It is found that realistic traversable and stable wormhole solutions are obtained for a particular model of this gravity.

Opinion dynamics have attracted the interest of researchers from different fields. Local interactions among individuals create interesting dynamics for the system as a whole. Such dynamics are important from a variety of perspectives. Group decision making, successful marketing, and constructing networks (in which consensus can be reached or prevented) are a few examples of existing or potential applications. The invention of the Internet has made the opinion fusion faster, unilateral, and on a whole different scale. Spread of fake news, propaganda, and election interferences have made it clear there is an essential need to know more about these dynamics. The emergence of new ideas in the field has accelerated over the last few years. In the first quarter of 2020, at least 50 research papers have emerged, either peer-reviewed and published or on preprint outlets such as arXiv. In this paper, we summarize these ground-breaking ideas and their fascinating extensions and introduce newly surfaced concepts.

Unconventional scenarios with hazardous radioactive levels are expected as consequences of accidents in the industrial sector of the nuclear energy production or following intentional releases of radioactive materials for terrorist purposes (dirty bombs, indoor contaminations, etc.). Nowadays, the need to balance the high standards of safety and security through an effective detection network is a matter of paramount importance. In this work, the authors’ challenge has been to design, realize and test a low-cost gamma detection and spectroscopy system which may be used in unmanned vehicles in general and/or drones with low payload capabilities. The designed platform may be used to carry out mapping or localization operations in order to reduce the risk factor for first responders or for the population affected by radiological and nuclear events. In this paper, the design process of a gamma ray detection and spectroscopy system based on affordable and commercially available technologies is presented along with the results of our ongoing characterization of the prototype.

 This paper aims to investigate the combined effect of AB-flux field and inverse square plus Yukawa potential (ISPYP) on the bound state energy levels of diatomic molecules placed at point-like global monopole. Asymptotic iteration method has been employed for numerical calculations. Same quantum system with Kratzer–Feus potential, a particular case of ISPYP, is also discussed here. Pekeris approximation scheme is used to deal with the terms $$\frac{1}{r^2}$$ and $$\frac{1}{r}$$ .

The Newtonian and general-relativistic position and velocity probability densities, which are calculated from the same initial Gaussian ensemble of trajectories using the same system parameters, are compared for a low-speed weak-gravity bouncing ball system. The Newtonian approximation to the general-relativistic probability densities does not always break down rapidly if the trajectories in the ensembles are chaotic -- the rapid breakdown occurs only if the initial position and velocity standard deviations are sufficiently small. This result is in contrast to the previously studied single-trajectory case where the Newtonian approximation to a general-relativistic trajectory will always break down rapidly if the two trajectories are chaotic. Similar rapid breakdown of the Newtonian approximation to the general-relativistic probability densities should also occur for other low-speed weak-gravity chaotic systems since it is due to sensitivity to the small difference between the two dynamical theories at low speed and weak gravity. For the bouncing ball system, the breakdown of the Newtonian approximation is transient because the Newtonian and general-relativistic probability densities eventually converge to invariant densities which are close in agreement.