Virtual and Printed 3D Models for Teaching Crystal Symmetry and Point Groups

In this paper, the crystallographic relationships among all the NH4Cl crystallites in a zigzag aggregation pattern with local anisotropy, formed under low driving force, are analysed. It is found that all the crystallites in this aggregation are twinned with one another. The anisotropy of the zigzag pattern is controlled by the twin structure. The twin structure is of 6mmsymmetry. This twin structure is related to the crystal point groupm3m, so it is proposed that all crystals with point groupm3m(and even the similar point groups 432 andm3) have the possibility to form this zigzag pattern. It is illustrated that the crystal symmetry plays an important role in the crystallite aggregation pattern.

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Microstructure and crystal symmetry of Pb2Sr2(Y/Ca)Cu3O9−δ

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100173455 ◽

1990 ◽

Vol 48 (4) ◽

pp. 64-65

Author(s):

Y. P. Lin ◽

J. S. Xue ◽

J. E. Greedan

Keyword(s):

Electron Diffraction ◽

High Temperature Superconductors ◽

Carbon Film ◽

Basic Structure ◽

Crystal Symmetry ◽

X Ray Diffraction ◽

X Ray ◽

Space Groups ◽

New Family ◽

Convergent Beam

A new family of high temperature superconductors based on Pb2Sr2YCu3O9−δ has recently been reported. One method of improving Tc has been to replace Y partially with Ca. Although the basic structure of this type of superconductors is known, the detailed structure is still unclear, and various space groups has been proposed. In our work, crystals of Pb2Sr2YCu3O9−δ with dimensions up to 1 × 1 × 0.25.mm and with Tc of 84 K have been grown and their superconducting properties described. The defects and crystal symmetry have been investigated using electron microscopy performed on crushed crystals supported on a holey carbon film.Electron diffraction confirmed x-ray diffraction results which showed that the crystals are primitive orthorhombic with a=0.5383, b=0.5423 and c=1.5765 nm. Convergent Beam Electron Diffraction (CBED) patterns for the and axes are shown in Figs. 1 and 2 respectively.

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THE GENESIS OF TOOLS FOR TEACHING PUPILS TO DEVELOP FLOWCHARTS

Informatics in school ◽

10.32517/2221-1993-2020-19-1-11-15 ◽

2020 ◽

pp. 11-15

Author(s):

A. A. Zubrilin ◽

M. N. Makarov

Keyword(s):

Historical Perspective ◽

3D Models ◽

Computer Applications ◽

Internet Services

The historical perspective provides an overview of how to study flowcharts in a school informatics course. Computer applications and Internet services are considered that automate the development of flowcharts. It is shown how 3D technologies can help an informatics teacher in preparing 3D models for the study of flowcharts.

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