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  2. List of space groups - Wikipedia

    en.wikipedia.org/wiki/List_of_space_groups

    In Hermann–Mauguin notation, space groups are named by a symbol combining the point group identifier with the uppercase letters describing the lattice type. Translations within the lattice in the form of screw axes and glide planes are also noted, giving a complete crystallographic space group. These are the Bravais lattices in three dimensions:

  3. Principal component analysis - Wikipedia

    en.wikipedia.org/wiki/Principal_component_analysis

    Principal component analysis (PCA) is a linear dimensionality reduction technique with applications in exploratory data analysis, visualization and data preprocessing.. The data is linearly transformed onto a new coordinate system such that the directions (principal components) capturing the largest variation in the data can be easily identified.

  4. Category:Minerals in space group 21 - Wikipedia

    en.wikipedia.org/wiki/Category:Minerals_in_space...

    This category lists minerals that display the C222 (No. 21) space group symmetry of the orthorhombic crystal system. Pages in category "Minerals in space group 21" The following 2 pages are in this category, out of 2 total.

  5. Hermann–Mauguin notation - Wikipedia

    en.wikipedia.org/wiki/Hermann–Mauguin_notation

    For example, symbols P 6 m2 and P 6 2m denote two different space groups. This also applies to symbols of space groups with odd-order axes 3 and 3. The perpendicular symmetry elements can go along unit cell translations b and c or between them. Space groups P321 and P312 are examples of the former and the latter cases, respectively.

  6. Space group - Wikipedia

    en.wikipedia.org/wiki/Space_group

    A space group is called symmorphic (or split) if there is a point such that all symmetries are the product of a symmetry fixing this point and a translation. Equivalently, a space group is symmorphic if it is a semidirect product of its point group with its translation subgroup. There are 73 symmorphic space groups, with exactly one in each ...

  7. Layer group - Wikipedia

    en.wikipedia.org/wiki/Layer_group

    It is a space group with a two-dimensional lattice, ... 21 p2 1 2 1 2 22 c222 23 pmm2 24 pma2 25 pba2 26 cmm2 27 pm2m 28 pm2 1 b 29 pb2 1 m 30 pb2b 31

  8. NASA Astronaut Group 21 - Wikipedia

    en.wikipedia.org/wiki/NASA_Astronaut_Group_21

    All eight members of the group have completed their training and have flown or are currently flying. Five were assigned to Soyuz expeditions to the International Space Station (ISS), with Hague as the first of the class to be assigned to fly, aboard Expedition 57/58 in November 2018, his flight being aborted during launch. McClain was on 58/59 ...

  9. Space Delta 2 - Wikipedia

    en.wikipedia.org/wiki/21st_Fighter-Bomber_Group

    On 24 July 2020, the Space Force reorganized its wings and groups into deltas, inactivating the 21st Space Wing and redesignated the 21st Operations Group as Space Delta 2. Space Delta 2 transferred its space warning squadrons to Space Delta 4, retaining its space domain awareness and space battle management squadrons. On 21 October 2020, with ...