scholarly journals Algorithm of reconstruction of a three-dimensional crystal structure from two-dimensional projections

2019 ◽  
Vol 43 (2) ◽  
pp. 324-331 ◽  
Author(s):  
D.V. Kirsh ◽  
A.S. Shirokanev ◽  
A.V. Kupriyanov
Keyword(s):  
Crystal Lattice ◽  
Three Dimensional ◽  
Analytical Calculation ◽  
Reconstruction Error ◽  
Identification Accuracy ◽  
Two Dimensional ◽  
Reconstruction Algorithms ◽  
Total Reconstruction ◽  
Dimensional Crystal

The article deals with a problem of three-dimensional crystal lattice reconstruction, which is an important stage in the X-ray structural analysis. The accuracy of parametric and structural identification of crystals directly depends on the quality of crystal lattice reconstruction. The proposed algorithm of reconstruction of a three-dimensional crystal lattice is based on minimizing the distances from each node to a line projected onto a specified plane. Three sets of two-dimensional node coordinates, obtained from three two-dimensional projections, are used as input data. We performed an analytical calculation of the reconstruction error, allowing the total reconstruction accuracy to be estimated. The results of computational experiments confirmed the high quality of the proposed reconstruction algorithms and its stability against the distortion of node coordinates. In addition, we revealed a problem of lattice system separability, with the identification accuracy for monoclinic, rhombic and tetragonal systems found to be 34%, 53% and 10%, respectively.

scholarly journals Composite hollow truss with multiple vierendeel panels

2013 ◽  
Vol 66 (4) ◽  
pp. 431-438
Author(s):  
Augusto Ottoni Bueno da Silva ◽  
Newton de Oliveira Pinto Júnior ◽  
João Alberto Venegas Requena
Keyword(s):  
Bearing Capacity ◽  
Failure Modes ◽  
Three Dimensional ◽  
Analytical Calculation ◽  
Two Dimensional ◽  
Shear Forces ◽  
Vertical Displacements ◽  
New System ◽  
The Ideal

The aim of this study was to evaluate through analytical calculation, two-dimensional elastic modeling, and three-dimensional plastic modeling, the bearing capacity and failure modes of composite hollow trusses bi-supported with a 15 meter span, varying the number of central Vierendeel panels. The study found the proportion span/3 - span/3 - span/3, as the ideal relationship for the truss - Vierendeel - truss lengths, because by increasing the proportion of the length occupied by the central Vierendeel panels, the new system loses stiffness and no longer supports the load stipulated in the project. Furthermore, they can start presenting excessive vertical displacements and insufficient resistance to external shear forces acting on the panels.

The Representation of Experience in Architectural Design

1995 ◽  
Vol 4 (3) ◽  
pp. 254-266 ◽  
Author(s):  
Richard W. Zobel
Keyword(s):  
Architectural Design ◽  
New Technology ◽  
Three Dimensional ◽  
Electronic Media ◽  
Physical Models ◽  
Two Dimensional ◽  
Immersive Environments ◽  
Architectural Space ◽  
Experiential Quality

Architecture, which is by its very nature a three-dimensional art, has in the last 500 years evolved to a stage where nearly all of the design exploration and visualization occur in any of a number of two-dimensional media. These media do not effectively portray the experiential quality of approaching, entering, and moving through an architectural space, an aspect which is primary to any design. In discussing this, James J. Gibson's concept of affordance will be used as a basis for the examination of a variety of media that are commonly used to describe the experiential quality of architecture, and how each of these media speaks to this frequently neglected characteristic. Particular attention will be given to the new technology of computer-generated immersive environments, which as a design medium promises to bring the issue of experiential quality in architecture to the forefront of design. Examples of each of the most common media, physical models, perspectives, noninteractive screen-based architectural walk throughs, interactive screen-based architectural walk throughs, and computer-generated immersive environments, will be examined as to their utility in experiential description. A discussion of the specific characteristics of each of the electronic media and the applications benefits and drawbacks will be included.

Structures of the ZrZn22 family: suprapolyhedral nanoclusters, methods of self-assembly and superstructural ordering

2009 ◽  
Vol 65 (3) ◽  
pp. 300-307 ◽  
Author(s):  
G. D. Ilyushin ◽  
V. A. Blatov
Keyword(s):  
Crystal Structures ◽  
Self Assembly ◽  
Topological Analysis ◽  
Three Dimensional ◽  
Topological Type ◽  
Point Symmetry ◽  
Two Dimensional ◽  
The Matrix ◽  
Nanocluster Precursor ◽  
Dimensional Crystal

A combinatorial topological analysis is carried out by means of the program package TOPOS4.0 [Blatov (2006), IUCr Comput. Commun. Newsl. 7, 4–38] and the matrix self-assembly is modeled for crystal structures of the ZrZn22 family (space group Fd\bar 3m, Pearson code cF184), including the compounds with superstructural ordering. A number of strict rules are proposed to model the crystal structures of intermetallics as a network of cluster precursors. According to these rules the self-assembly of the ZrZn22-like structures was considered within the hierarchical scheme: primary polyhedral cluster → zero-dimensional nanocluster precursor → one-dimensional primary chain → two-dimensional microlayer → three-dimensional microframework (three-dimensional supraprecursor). The suprapolyhedral cluster precursor AB 2 X 37 of diameter ∼ 12 Å and volume ∼ 350 Å3 consists of three polyhedra (one AX 16 of the \bar 43m point symmetry and two regular icosahedra BX 12 of the \bar 3m point symmetry); the packing of the clusters determines the translations in the resulting crystal structure. A novel topological type of the two-dimensional crystal-forming 4,4-coordinated binodal net AB 2, with the Schläfli symbols 3636 and 3366 for nodes A and B, is discovered. It is shown that the ZrZn22 superstructures are formed by substituting some atoms in the cluster precursors. Computer analysis of the CRYSTMET and ICSD databases shows that the cluster AB 2 X 37 occurs in 111 intermetallics belonging to 28 structure types.

scholarly journals EXPOENTE DE AVRAMI PELA EQUAÇÃO DE JMAK PARA MÉTODO NÃO-ISOTÉRMICO DE ANÁLISE TÉRMICA

2018 ◽  
Vol 1 (2) ◽  
Author(s):  
Salmo Moreira Sidel ◽  
Elio Idalgo ◽  
Keizo Yukimitu ◽  
João Carlos Silos Moraes ◽  
Fabio Alencar Dos Santos
Keyword(s):  
Crystal Growth ◽  
General Theory ◽  
Isothermal Crystallization ◽  
Crystallization Process ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Nucleation Process ◽  
Vitreous System ◽  
Isothermal Measurements ◽  
Dimensional Crystal

This work reports a discussion about of the general theory for phase transformations of Melh-Johnson-Avrami-Kolmogorov in process involving non-isothermal crystallization. This model allows determine as occurs the mechanism of the nucleus formation and of growth of crystalline phases during the crystallization process. To demonstrate the validity this theory, the Avrami exponent (n) of the LiO2-TeO2-WO3 vitreous system was determined from DSC non-isothermal measurements. The obtained results indicate that the nucleation process is volumetric with two-dimensional or three-dimensional crystal growth. DOI: http://dx.doi.org/10.30609/JETI.2018-2.5566

scholarly journals MATHEMATICAL MODELLING OF MACROSEGREGATION IN INGOT CASTING

2018 ◽  
Vol 17 (2) ◽  
pp. 74
Author(s):  
M. O. Assunção Jr ◽  
M. Vynnycky
Keyword(s):  
Mathematical Model ◽  
Three Dimensional ◽  
Chemical Species ◽  
Ternary Alloys ◽  
Ingot Casting ◽  
Two Dimensional ◽  
Computational Simulations ◽  
Macroscopic Scale ◽  
Three Dimensional Models

The occurrence of macrosegregation in alloys produced by ingot casting can adversely affect the quality of the final product. Macrosegregation can be described as a severe variation on the macroscopic scale of the chemical species that compose the alloy, and the ability of computational simulations to predict such defects remains far from perfect. Therefore, this research focuses on the development of a two-dimensional mathematical model that - through computational simulations - could be applied to study and predict the formation of macrosegregation in the ingot casting of binary alloys. Once accomplished, this work can establish the framework to new studies that will tackle more advanced problems, e.g., for actual ingot geometries, three-dimensional models and industrially-important ternary alloys.

scholarly journals Kazantsev model in non-helical 2.5-dimensional flows

2016 ◽  
Vol 806 ◽  
pp. 627-648 ◽  
Author(s):  
K. Seshasayanan ◽  
A. Alexakis
Keyword(s):  
Turbulent Flows ◽  
Three Dimensional ◽  
Analytical Calculation ◽  
Reynolds Numbers ◽  
Two Dimensions ◽  
Two Dimensional ◽  
Control Parameters ◽  
Governing Equations ◽  
Field Correlation ◽  
Good Agreement

We study the dynamo instability for a Kazantsev–Kraichnan flow with three velocity components that depend only on two dimensions $\boldsymbol{u}=(u(x,y,t),v(x,y,t),w(x,y,t))$ often referred to as 2.5-dimensional (2.5-D) flow. Within the Kazantsev–Kraichnan framework we derive the governing equations for the second-order magnetic field correlation function and examine the growth rate of the dynamo instability as a function of the control parameters of the system. In particular we investigate the dynamo behaviour for large magnetic Reynolds numbers $Rm$ and flows close to being two-dimensional and show that these two limiting procedures do not commute. The energy spectra of the unstable modes are derived analytically and lead to power-law behaviour that differs from the three-dimensional and two-dimensional cases. The results of our analytical calculation are compared with the results of numerical simulations of dynamos driven by prescribed fluctuating flows as well as freely evolving turbulent flows, showing good agreement.

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