scholarly journals Review of Non-Classical Features of Deformation Twinning in hcp Metals and Their Description by Disconnection Mechanisms

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1134
Author(s):  
Andriy Ostapovets ◽  
Anna Serra
Keyword(s):  
Twin Boundary ◽  
Simple Shear ◽  
Scientific Literature ◽  
Deformation Twinning ◽  
Main Attention ◽  
New Findings ◽  
Interfacial Defects ◽  
Hcp Structure ◽  
Mechanisms Of Deformation

The study of deformation twinning has long history. However new, sometimes surprising, findings have shown that the phenomenon of deformation twinning still is not completely understood. During recent years, some debates are taking place in the scientific literature concerning deformation twinning mechanisms in metals with hcp structure. These debates deal with the importance of special twin boundary dislocations named disconnections, growth and nucleation of twins, non-Schmid behavior of twinning, difference of deformation produced by twins from simple shear. They invoked new propositions for atomistic mechanisms of deformation twinning. The purpose of this review is to compare the classical theories of interfacial defects with the new findings and prove that many of these findings can be understood in terms of these well-established theories. The main attention is paid to summarizing the explanations of different phenomena in terms of disconnection mechanisms in order to show that there is no contradiction between these mechanisms and the new findings.

Etiopathogenetic aspects of otosclerosis

2021 ◽  
Vol 20 (5) ◽  
pp. 68-74
Author(s):  
V. M. Svistushkin ◽  
◽  
E. V. Sin’kov ◽  
I. V. Stozhkova ◽  
◽  
...  
Keyword(s):  
Hearing Loss ◽  
Scientific Literature ◽  
Molecular Genetic ◽  
Surgical Techniques ◽  
Main Attention ◽  
Progressive Hearing Loss ◽  
Common Causes ◽  
Working Age ◽  
The Many ◽  
New Research

Otosclerosis is one of the most common causes of progressive hearing loss, in particular in people of working age. The effectiveness of stapedial surgery largely determines the interest in studying the problems and prospects for the development of technologies, namely, the improvement of prostheses, surgical techniques, and assistance during interventions. It is worth noting that the main attention in the scientific literature is paid to the description of the clinic, the diagnosis of otosclerosis, as well as the methods of stapedoplasty. However, the question of the etiology and pathogenesis of this disease remains relevant and open for discussion, despite the many domestic and foreign works in this field. The emergence of new research methods, including molecular-genetic ones, contributed to the transition of research to a new level and the development of several new theories. Modern understanding of the pathogenesis of otosclerosis considers this disease as a multifactorial condition, in which many processes are involved, for example, genetic, hormonal, biochemical, and immunological. Likely, further study of the theory and hypothesis of the development of otosclerosis will find their justification, which will help answer many questions. The purpose of this article is to analyze and systematize data concerning various theories of the etiopathogenesis of the otosclerosis process, based on the study of modern domestic and foreign literature.

scholarly journals Hard-sphere displacive model of deformation twinning in hexagonal close-packed metals. Revisiting the case of the (56°,a) contraction twins in magnesium

2017 ◽  
Vol 73 (4) ◽  
pp. 346-356 ◽  
Author(s):  
Cyril Cayron
Keyword(s):  
Simple Shear ◽  
Hard Spheres ◽  
Martensitic Transformations ◽  
Deformation Twinning ◽  
Angular Distortion ◽  
Interatomic Distances ◽  
Hexagonal Close Packed ◽  
Atomic Displacements ◽  
Shear Theory ◽  
Distortion Matrix

Contraction twinning in magnesium alloys leads to new grains that are misoriented from the parent grain by a rotation (56°,a). The classical shear theory of deformation twinning does not specify the atomic displacements and does not explain why contraction twinning is less frequent than extension twinning. The paper proposes a new displacive model in line with our previous work on martensitic transformations and extension twinning. A continuous angular distortion matrix that transforms the initial hexagonal close-packed (h.c.p.) crystal into a final h.c.p. crystal is determined such that the atoms move as hard spheres and reach the final positions expected by the orientation relationship. The calculations prove that the distortion is not a simple shear when it is considered in its continuity. The ({0{\overline 1}1}) plane is untilted and restored, but it is not fully invariant because some interatomic distances in this plane evolve during the distortion process; the unit volume also increases up to 5% before coming back to its initial value when the twinning distortion is complete. Then, the distortion takes the form of a simple shear on the ({0{\overline 1}1}) plane with a shear along the direction [{18,{\overline 5},{\overline 5}}] of amplitude 0.358. Experiments are proposed to validate or disprove the model.

scholarly journals Images of Relations between Nobility and Peasantry in Russian Liberal Literature in Late 19th — Early 20th Centuries

2021 ◽  
pp. 391-409
Author(s):  
M. A. Ponomareva
Keyword(s):  
Scientific Literature ◽  
Free Action ◽  
Local History ◽  
Main Attention ◽  
Main Research ◽  
Liberal Ideology ◽  
Methodological Approaches ◽  
Main Ideas ◽  
The Relationship ◽  
Liberal Thought

The article is devoted to the peculiarities of the representation of relations between the nobility and the peasantry in Russian liberal thought at the cusp of XIX—XX centuries. A review of the existing historiography on the problem is carried out, the main attention is paid to the emerging from the middle 1980s the traditions of studying the liberal intelligentsia in Russia and the peculiarities of the relationship between the “educated minority and the peasant world”, an analysis of the latest scientific literature is presented. Special attention is paid to the main research approaches to the study of the topic, microhistorical, positional and other approaches, the concept of “new local history” is highlighted and the need for their complex use is declared. The results of a comparative analysis of various groups of sources are presented: reminiscence and memoirs, periodicals, statistical materials, correspondence. The question is raised about the differences in the self-identification of the Russian nobility, as well as in the mutual representations of the two most important estates of post-reform Russia. The novelty of the study is seen in the fact that, on the basis of new methodological approaches, several images of relations between the nobility and the peasantry have been identified at the cusp of XIX—XX centuries: the image of the “new entrepreneurial type”, “guardianship” and “preservation of traditions”, conventionally “lordly”, as well as the image of “free action”; their distinctive characteristics are given. The proposed classification is due to the main ideas of the Russian nobility about the peasants in the context of the institutionalization of liberal ideology.

scholarly journals A fast algorithm to find reduced hyperplane unit cells and solve N-dimensional Bézout's identities

2021 ◽  
Vol 77 (5) ◽  
Author(s):  
Cyril Cayron
Keyword(s):  
Simple Shear ◽  
Fast Algorithm ◽  
Mirror Symmetry ◽  
Deformation Twinning ◽  
Unit Cell ◽  
Unit Cells ◽  
Bézout’S Identity

Deformation twinning on a plane is a simple shear that transforms a unit cell attached to the plane into another unit cell equivalent by mirror symmetry or 180° rotation. Thus, crystallographic models of twinning require the determination of the short unit cells attached to the planes, or hyperplanes for dimensions higher than 3. Here, a method is presented to find them. Equivalently, it gives the solutions of the N-dimensional Bézout's identity associated with the Miller indices of the hyperplane.

ANALYSIS OF THE INNOVATIVE POTENTIAL OF A COMMUNICATION ENTERPRISE IN THE SYSTEM FOR EVALUATING ITS COMPETITIVENESS

2017 ◽  
Author(s):  
Kateryna Statirova ◽  
◽  
Volodymyr Granaturov ◽  
Keyword(s):  
Scientific Literature ◽  
Main Attention ◽  
Management Decisions ◽  
Scientific Methods ◽  
Minimum Number ◽  
Innovative Potential ◽  
Enterprise Competitiveness ◽  
Effective Use

The object of the research is the process of determining the level of enterprise competitiveness. It is shown that the existing methods for assessing the level of enterprise competitiveness use different criteria. It has been determined that among these methods the most suitable in modern conditions is the method based on the use of indicators of its competitive potential as criteria for the competitiveness of an enterprise. The main attention is paid to the possibility of using innovative potential as one of the criteria of competitiveness. The paper considered approaches to determining the composition of indicators, with the help of which the level of innovative potential of a communications enterprise, its assessment, and its application in the process of a generalized assessment of the level of enterprise competitiveness are determined. In the course of the research, the following scientific methods were used, such as a methodological analysis of scientific literature, a comparative, abstract-logical and systemic method. The analysis of existing approaches to assessing the innovative potential of an enterprise has shown that this problem remains unsolved. The reason for the uncertainty is, first of all, the fact that scientists put different meanings into this concept, distinguish different components of the innovative potential. As a result of the study, three requirements were stated - the minimum number of indicators, the availability of information and the avoidance of the influence of other potentials - which should become fundamental in identifying indicators for analyzing the innovative potential and using it in assessing the competitiveness of an enterprise. The studies performed will contribute to a more effective use of the method for assessing the competitiveness of an enterprise based on the use of its competitive potential, and to increase the efficiency of management decisions made on the basis of this assessment.

Deformation twinning in the diamond structure

1957 ◽  
Vol 241 (1227) ◽  
pp. 568-577 ◽  
Keyword(s):  
Twin Boundary ◽  
Deformation Twinning ◽  
Diamond Structure ◽  
Structure Deformation ◽  
Parallel Array ◽  
Twinning Plane

The theory of surface dislocations is used to calculate the most likely deformation twinning plane in the diamond structure. The surface dislocation representing the twin boundary is assumed to correspond to one parallel array of like, glissile dislocations; that is a ‘simple glissile surface dislocation’. The treatment indicates that, in the diamond structure, deformation twinning of the first kind ought to occur on the {123} planes.

scholarly journals Chinchilla lanigera (Molina 1782) and C. chinchilla (Lichtenstein 1830): review of their distribution and new findings

2014 ◽  
Vol 37 (1) ◽  
pp. 89-93
Author(s):  
P. Valladares ◽  
◽  
C. Zuleta ◽  
A. Spotorno ◽  
◽  
...  
Keyword(s):  
Twentieth Century ◽  
Current Distribution ◽  
Wild Species ◽  
Scientific Literature ◽  
Critically Endangered ◽  
Current Range ◽  
Early Twentieth Century ◽  
Live Trapping ◽  
New Findings ◽  
Trapping Methods

Millions of Chinchilla chinchilla and C. lanigera were killed during the early twentieth century and they were nearly hunted to extinction. In order to establish the current range of distribution of these two wild species and to localize possible new colonies, we used the available scientific literature, technical reports, information from residents, and live trapping methods. Both species are ‘critically endangered’ since their current distribution is highly fragmented and all recognized colonies are small and isolated. We report a small new wild colony of C. lanigera in the Atacama region, Chile.

scholarly journals ON THE QUESTION OF DEFINITION OF THE CONCEPT OF ADMINISTRATIVE ACTIVITY OF THE STATE MIGRATION SERVICE OF UKRAINE

2020 ◽  
pp. 230-236
Author(s):  
В. В. Репело
Keyword(s):  
Public Administration ◽  
Scientific Literature ◽  
Administrative Law ◽  
The State ◽  
Main Attention ◽  
Public Authorities ◽  
Administrative Functions ◽  
Characteristic Features ◽  
Definition Of ◽  
The Right

The study analyzes the categorical apparatus related to the concept of administrative activity of the State Migration Service in Ukraine, namely the categories «administration», «public administration», «public administration», «administrativeactivity»andothers.Thedefinitionoftheconceptof«administration» in the encyclopedic literature, in particular in the Legal Encyclopedia, highlights the main features of the administration, public administration. The term «public administration» is analyzed, the positions on definition of this definition by researchers O. Shatylo are given), it is indicated that this term is used in two meanings (narrow and wide), the definitions of public administration of V. Averyanov, R. Kravtsova, S. Chernov are also given. A. Zelentsov’s position on the characteristic features of public administration that distinguish it from private administration is highlighted. The main attention is paid to the disclosure of the term «administrative activity», the definition is defined in the reference literature, namely in the Great Ukrainian Encyclopedia, the Encyclopedia of Modern Ukraine. It is emphasized that the administrative activities of public authorities are implemented through the powers vested in the state, and from the state they receive the right to perform administrative functions, such powers are defined exclusively in regulations of the state and its authorities. Positions on the definition of «administrative activity» by M. Ishchenko, E. Mishchuk, A. Sorochynsky, S. Petkov and L. Spytska are given. Based on the analysis of legislation, bylaws and scientific literature on administrative law, the definition of the concept of administrative activity of the State Migration Service of Ukraine is proposed.

The Structure of Defects Formed by Absorption of Crystal Dislocations in Interfaces in the HCP Metals

1999 ◽  
Vol 578 ◽  
Author(s):  
D.J. Bacon ◽  
R.C. Pond ◽  
A. Serra
Keyword(s):  
Twin Boundary ◽  
Tilt Boundary ◽  
Interfacial Structure ◽  
Atomic Scale ◽  
Tilt Axis ◽  
Hexagonal Close Packed ◽  
The Core ◽  
Interaction Processes ◽  
Interfacial Defects

AbstractAtomic-scale computer simulation has been used to investigate the interaction of crystal dislocations with two interfaces in hexagonal-close-packed (HCP) metals, namely the {1012} twin boundary and a <1210>/90° tilt boundary that is incommensurate in the direction perpendicular to the tilt axis. Crystal dislocations are absorbed in the tilt boundary with concomitant reconstruction of their cores. In the twin boundary, a broader range of interactions is observed, including defect transmission from matrix to twin and decomposition in the interface into discrete defects. The role of crystallographic features and interfacial structure is elucidated by comparing interaction processes in the two interfaces. The core structure of interfacial defects can be complex and contributes significantly to total defect energy.

Influence of a Slip Plane Orientation with Respect to the Shear Plane of ECAP on Microstructure of Copper Single Crystal Subject to One Pressing at Room Temperature

2008 ◽  
Vol 584-586 ◽  
pp. 387-392 ◽  
Author(s):  
Soichi Katayama ◽  
Hiroyuki Miyamoto ◽  
Alexei Vinogradov ◽  
Satoshi Hashimoto
Keyword(s):  
Simple Shear ◽  
Crystallographic Orientation ◽  
Room Temperature ◽  
Electron Backscatter Diffraction ◽  
Pure Copper ◽  
Shear Bands ◽  
Large Angle ◽  
Shear Plane ◽  
Deformation Twinning ◽  
Shear Direction

This paper describes the influence of initial crystallographic orientation on the formation of dense shear bands in pure copper single crystals subjected to equal-channel angular pressing (ECAP) for one pass at room temperature. Local orientation change during simple shear by ECAP traced by electron backscatter diffraction (EBSD) indicated that the shear bands were formed when twinning plane and direction become parallel to the macroscopic shear plane and shear direction of simple shear strain, respectively. Orientation splitting associated with shear bands have a twinning relation. The shear bands were delineated by large-angle grain boundaries, having close relation to twinning relation with matrix, suggesting the role of deformation twinning as their nucleation sites. The activation of deformation twinning is suggested and can be rationalized by favorable crystallographic orientation and critical dislocation density as indicated elsewhere by the present authors.

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