Random Distribution Of Elements Research Articles

High Entropy Protected Sharp Magnetic Transitions in Highly Disordered Spinel Ferrites.

How disorder affects magnetic ordering is always an intriguing question, and it becomes even more interesting in the recently rising high entropy oxides due to the extremely high disorder density. However, due to the lack of high-quality single crystal samples, the strong compositional disorder effect on magnetic transition has not been deeply investigated. In this work, we have successfully synthesized high-quality single crystalline high entropy spinel ferrites (Mg0.2Mn0.2Fe0.2Co0.2Ni0.2)xFe3-xO4. Our findings from high-temperature magnetization and neutron diffraction experiments showed ferrimagnetic transitions at 748, 694, and 674 K for x values of 1, 1.5, and 1.8, respectively. Notably, the magnetic transition almost showed no broadening for x values of 1 and 1.5, compared to Fe3O4. Extended X-ray absorption fine structure measurements provided insights into the elemental distribution among the octahedral and tetrahedral sites. The random distribution of elements across these sites reduced the formation of local clusters and short-range orders, enhancing sample homogeneity and preserving the sharpness of the magnetic transition, despite bond length variation. Our study not only marks the first successful synthesis of an HEO bulk single crystal exhibiting long-range magnetic order but also sheds light on the interaction between high configurational entropy and magnetic orderings. This opens new avenues for future research and applications of magnetic high entropy oxides.

Convolution Operations on Coding Metasurface for RCS Reduction

In this paper, a polarization conversion unit is designed as the coding unit. The units are arranged in a regular cross-arrangement. Convolution operation is composed of the Dirac-delta function and the principle of scattering-pattern shift. The Dirac-delta is optimized by generalized Snell's law and addition theorem. According to the convolution operations, the cross-arrangement pattern is shifted to multiple directions to reduce the backscattering field. Compared with regularly arranged metasurface, this method can reduce the radar cross section (RCS) of single station by at least 10dB. Compared with the traditional intelligent optimization algorithm, this method provides a new route to reduce RCS by random distribution of elements.

Influence of chemical composition of the surface layer on the nucleation of plasticity in CoCrFeMnNi high-entropy alloys

The role of segregation of chemical elements upon free surfaces in the peculiarities of the plastic deformation mechanisms of thin films of the high-entropy CoCrFeMnNi alloy was clarified using a combined simulation of the Metropolis Monte Carlo and molecular dynamics. Irrespectively of surface orientation and stoichiometric composition of alloy Mn escapes to free surface and Fe goes to the bulk of the films. Ni also enriches the (111) surface while Co content is reduced. It is shown that for different compositions segregation reduces or decreases the elastic limit of the samples. In Co10Cr10Fe30Mn30Ni20 for all considered free surfaces, segregation equally influences the type and volume fraction of the formed defects. In Co30Cr30Fe10Mn10Ni20, they may remain the same or the mechanism of plastic deformation may change drastically in samples with segregation depending on the orientation of the free surface. Despite the redistribution of the volume fractions of various type defects, in general, the main mechanism for the development of plasticity in samples both before and after segregation is the growth of the hcp-bands. Change of defect structure in samples with surface segregation compared to samples with random distribution of elements is not necessary related to change of elastic limit.

A Revisit of Infinite Population Models for Evolutionary Algorithms on Continuous Optimization Problems

Infinite population models are important tools for studying population dynamics of evolutionary algorithms. They describe how the distributions of populations change between consecutive generations. In general, infinite population models are derived from Markov chains by exploiting symmetries between individuals in the population and analyzing the limit as the population size goes to infinity. In this article, we study the theoretical foundations of infinite population models of evolutionary algorithms on continuous optimization problems. First, we show that the convergence proofs in a widely cited study were in fact problematic and incomplete. We further show that the modeling assumption of exchangeability of individuals cannot yield the transition equation. Then, in order to analyze infinite population models, we build an analytical framework based on convergence in distribution of random elements which take values in the metric space of infinite sequences. The framework is concise and mathematically rigorous. It also provides an infrastructure for studying the convergence of the stacking of operators and of iterating the algorithm which previous studies failed to address. Finally, we use the framework to prove the convergence of infinite population models for the mutation operator and the -ary recombination operator. We show that these operators can provide accurate predictions for real population dynamics as the population size goes to infinity, provided that the initial population is identically and independently distributed.

The Control Of Terminal-Splay Sedimentation On Depositional Patterns and Stratigraphic Evolution In Avulsion-Dominated, Unconfined, Deep-Marine Basin-Floor Systems

Abstract Recent improvements in seismic resolution and more detailed outcrop mapping of basin-floor fans has shown that they are made up of a hierarchy of discrete building blocks. The most fundamental building block, made up of one or several event beds, is termed a stratal element. These elements stack to form lobes, which in turn stack to form lobe complexes and ultimately the fan. The arrangement of the building blocks on the fan is driven by channel avulsion, and the location of the avulsion defines the hierarchy. Basin-floor deposits of the Upper Kaza Group at Castle Creek comprise five stratal elements: scours fills, avulsion splays (interpreted to be genetically related with scours, and here combined into “avulsion complexes”), distributary channels, terminal splays, and fine-grained deposits. Using a Markov-chain statistical analysis the vertical stacking pattern of these elements was found to be non-random, which suggests an internal control or forcing on the system. Most notably, the results show that in spite of their thicker nature and high abundance in the studied section, sand-rich terminal splays are superimposed less frequently than expected in a random distribution of stratal elements. This reluctance of terminal splays to stack vertically suggests that it is not only deposition in the splay, but also the temporal stability of that deposition that drives upflow avulsions, and accordingly the observed stacking of the other associated stratal elements. This may be the result of the accumulated thickness of previous deposits forcing the system to episodically shift its depositional axis into bathymetrically lower areas. The consequence is that although the overall sedimentary pile contains abundant terminal splays with their characteristic high sandstone-to-mudstone ratio (∼ 75%), amalgamated terminal-splay deposits are thinner and the overall stratigraphic architecture more complex and heterogeneous than would otherwise be predicted in a random distribution of elements.

Binary phase masks on self-developing photopolymers: the technique for formation and testing in an optical correlator

Binary phase masks (PMs) of size 256×256 cells with a random distribution of elements, formed on the self-developing FPK-488 photopolymer, are studied. The masks were prepared by the projection method using amplitude transparencies. The phase shift between the mask elements corresponding to the regions of the amplitude transparency with the optical density D = 0 and 2 was (0.85±0.05)π at the wavelength of 0.633 μm. Holographic matched filters were recorded for PMs obtained. The diffraction efficiency of holographic matched PM filters was 40 %. The signal-to-noise ratio for recognition signals for PMs in the Vander Lugt correlator was 20 dB. The normalised power density of the recognition signal is studied as a function of the rotation angle of a PM in the input plane of the Vander Lugt correlator.

Asymptotic results on the product of random probability matrices

I study the product of independent identically distributed random probability matrices. Some exact asymptotic results are obtained. I find that both the left and the right products approach exponentially a probability matrix (asymptotic matrix) in which any two rows are the same. A parameter is introduced for the exponential coefficient which can be used to describe the convergent rate of the products. depends on the distribution of the individual random matrices. I find for D = 2 when each element of the individual random probability matrices is uniformly distributed in [0,1]. In this case, each element of the asymptotic matrix follows a parabolic distribution function. The distribution function of the asymptotic matrix elements can be shown numerically to be non-universal. Numerical tests are carried out for a set of random probability matrices with a particular distribution function. I find that increases monotonically from to as D increases from 3 to 99, and the distribution of random elements in the asymptotic products can be described by a Gaussian function with a mean of 1/D.

NMR study of minerals. III. The distribution of Mg2+and Fe2+around the OH groups in micas

For pt.II see Am. Mineral., vol.64, p.119 (1979). The proton NMR absorption lines of eleven micas have been examined. The crystalline samples (phlogopites and biotites with continuously variable amounts of fluorine and iron) are oriented in the applied magnetic field so that the different existing OH-Mg2+-Fe2+ associations (each giving rise to a shifted line) can easily be differentiated. The results are quantified by taking the integrated value of each line and comparing these with expectation values based on a random distribution of elements. It is found that the Fe2+ ions tend to cluster around the OH groups. A complete picture is obtained by taking into account the distribution in the lattice of the fluorine ions. These are found to be preferentially associated with Mg2+. The fluorine content therefore has a net influence on the OH-Fe2 associations which are detected. Infrared spectra run on the same samples tend to support these local fluctuations which exist in the chemical composition of the octahedral sheet of micas.