In geometry, a Johnson solid is a strictly convex polyhedron each face of which is a regular polygon. There is no requirement that each face must be the same polygon, or that the same polygons join around each vertex. An example of a Johnson solid is the square-based pyramid with equilateral sides (J1); it has 1 square face and 4 triangular faces. Some authors require that the solid not be uniform (i.e., not Platonic solid, Archimedean solid, uniform prism, or uniform antiprism) before they refer to it as a “Johnson solid”. As in any strictly convex solid, at least three faces meet at every vertex, and the total of their angles is less than 360 degrees. Since a regular polygon has angles at least 60 degrees, it follows that at most five faces meet at any vertex. The pentagonal pyramid (J2) is an example that has a degree-5 vertex. Although there is no obvious restriction that any given regular polygon cannot be a face of a Johnson solid, it turns out that the faces of Johnson solids which are not uniform (i.e., not a Platonic solid, Archimedean solid, uniform prism, or uniform antiprism) always have 3, 4, 5, 6, 8, or 10 sides. In 1966, Norman Johnson published a list which included all 92 Johnson solids (excluding the 5 Platonic solids, the 13 Archimedean solids, the infinitely many uniform prisms, and the infinitely many uniform antiprisms), and gave them their names and numbers. He did not prove that there were only 92, but he did conjecture that there were no others. Victor Zalgaller in 1969 proved that Johnson's list was complete. Of the Johnson solids, the elongated square gyrobicupola (J37), also called the pseudorhombicuboctahedron, is unique in being locally vertex-uniform: there are 4 faces at each vertex, and their arrangement is always the same: 3 squares and 1 triangle. However, it is not vertex-transitive, as it has different isometry at different vertices, making it a Johnson solid rather than an Archimedean solid. (Wikipedia).
Chemistry - Liquids and Solids (44 of 59) Crystal Structure: Covalent: Metallic
Visit http://ilectureonline.com for more math and science lectures! In this video I explain the metallic crystal structure.
From playlist CHEMISTRY 16 LIQUIDS AND SOLIDS
Ionic Solids, Molecular Solids, Metallic Solids, Network Covalent Solids, & Atomic Solids
This chemistry video tutorial provides a basic introduction into solids. It explains how to classify a solid as ionic solids, molecular solids or atomic solids. There are 3 different types of atomic solids that you need to be familiary with - metallic solids, Group 8A solids, and network
From playlist New AP & General Chemistry Video Playlist
Chemistry - Liquids and Solids (25 of 59) Crystal Structure: The Unit Cell: Simple Cube
Visit http://ilectureonline.com for more math and science lectures! In this video I will explain how atoms are arranged in a simple crystal structure.
From playlist CHEMISTRY 16 LIQUIDS AND SOLIDS
Chemistry - Liquids and Solids (30 of 59) Crystal Structure: Two Types of Dense Packing
Visit http://ilectureonline.com for more math and science lectures! In this video I will explain the 2 types of dense packing in a crystal structure.
From playlist CHEMISTRY 16 LIQUIDS AND SOLIDS
How to Construct a Dodecahedron
How the greeks constructed the Dodecahedron. Euclids Elements Book 13, Proposition 17. In geometry, a dodecahedron is any polyhedron with twelve flat faces. The most familiar dodecahedron is the regular dodecahedron with regular pentagons as faces, which is a Platonic solid. A regular dode
From playlist Platonic Solids
Solid State Physics in a Nutshell: Topic 2-2: Crystal Structure Types
Today, we discuss different types of centering in cubic system. We also delve into the similarities between the fcc and the diamond structure. Finally, we compared two types of close packed structures.
From playlist CSM: Solid State Physics in a Nutshell | CosmoLearning.org Physics
This shows a 3d print of a mathematical sculpture I produced using shapeways.com. This model is available at http://shpws.me/L5R
From playlist 3D printing
What's the difference between concrete and cement? Concrete is the most important construction material on earth and foundation of our modern society. At first glance it seems rudimentary, but there is a tremendous amount of complexity involved in every part of designing and placing conc
From playlist Civil Engineering
Delta-Star is a polyhedral object which I invented in 1996. The type of Delta-Star corresponds to Deltahedrons. It expands and shrinks.
From playlist Handmade geometric toys
Data Science Jobs, Skills and Salary | Data Science Career | Data Science Training | Simplilearn
🔥 Enroll For Simplilearn's Data Science Job Guarantee Program: https://www.simplilearn.com/data-science-course-placement-guarantee?utm_campaign=DataScienceJobSkillsOct18&utm_medium=DescriptionFirstFold&utm_source=youtube Data Science as a field is expanding rapidly, with companies looking
History of the Democratic Party | American civics | US government and civics | Khan Academy
A quick overview of the history of the Democratic Party! 200+ years was hard to fit into 16 minutes, but we got most of the highlights, from Jefferson and Jackson through FDR and LBJ. View more lessons or practice this subject at https://www.khanacademy.org/humanities/us-government-and-ci
From playlist American civics | US government and civics | Khan Academy
Lec 1 | MIT 16.885J Aircraft Systems Engineering, Fall 2005
The Origins of the Space Shuttle View the complete course: http://ocw.mit.edu/16-885F05 License: Creative Commons BY-NC-SA More information at http://ocw.mit.edu/terms More courses at http://ocw.mit.edu
From playlist MIT 16.885J Aircraft Systems Engineering, Fall 2005
Three Great Minds Behind Apollo 11 | Compilation
Head to https://linode.com/scishow to get a $100 60-day credit on a new Linode account. Linode offers simple, affordable, and accessible Linux cloud solutions and services. It's the 53rd anniversary of the Apollo 11 launch, a monolith in mankind's journey to the stars. Celebrate with this
From playlist This Week on SciShow (July 9th - July 15th)
Hugo Gimbert: Two-player perfect-information shift-invariant submixing stochastic games are [...]
Find this video and other talks given by worldwide mathematicians on CIRM's Audiovisual Mathematics Library: http://library.cirm-math.fr. And discover all its functionalities: - Chapter markers and keywords to watch the parts of your choice in the video - Videos enriched with abstracts, b
From playlist Mathematical Aspects of Computer Science
(because you asked) Student Exemplar: Blood Brothers Analysis
Buy my revision guides in paperback on Amazon*: Mr Bruff’s Guide to GCSE English Language https://amzn.to/2GvPrTV Mr Bruff’s Guide to GCSE English Literature https://amzn.to/2POt3V7 AQA English Language Paper 1 Practice Papers https://amzn.to/2XJR4lD Mr Bruff’s Guide to ‘Macbeth’ htt
From playlist Student Exemplars
Lec 2 | MIT 16.885J Aircraft Systems Engineering, Fall 2005
Space Shuttle History View the complete course: http://ocw.mit.edu/16-885F05 License: Creative Commons BY-NC-SA More information at http://ocw.mit.edu/terms More courses at http://ocw.mit.edu
From playlist MIT 16.885J Aircraft Systems Engineering, Fall 2005
Adam Savage's New Machining Parallels!
Adam shows off his new set of steel machining parallels! These come courtesy of a fan, Lee Johnson, who machined them over 30 years ago while getting his start in aircraft manufacturing. Adam explains how these are used and marvels at how their surface dimensions are precise to within .000
From playlist Inside Adam's Cave
Ruby Conference 2008 - How I Learned to Love Javascript
By: John Barnette, Aaron Patterson Help us caption & translate this video! http://amara.org/v/GH3Q/
From playlist Ruby Conference 2008
Avid CNC's 4-Axis CNC Machines!
We check in with the team at Avid CNC--formerly CNC Router Parts--to see their new 4th rotary axis on their Pro line of CNC machine kits. Owner Ahren Johnson explains to us the capabilities of this machine, and digital fabrication producer Sami Woolhiser demonstrates their awesome ping pon
From playlist Maker Faire
Chemistry - Liquids and Solids (28 of 59) Crystal Structure: Density of the Unit Cell: Face Centered
Visit http://ilectureonline.com for more math and science lectures! In this video I will calculate the % volume of the molecules in a face centered cubic.
From playlist CHEMISTRY 16 LIQUIDS AND SOLIDS