Explore the people, places, events, achievements, struggles and stories that shaped our journey.
Movements, leaders, victories and the continuing fight for equality.
Innovation, patents, science, technology and world-changing contributions.
Pioneers, champions, Negro Leagues, records, activism and excellence.
Meet the people whose lives, choices and achievements shaped the journey.
Black towns, communities, institutions and places where history happened.
Moments that changed communities, movements, institutions and the nation.
In 1968 Shirley Chisholm became the first Black woman elected to the United States Congress. In 1972 she launched a campaign for the Democratic presidential nomination, breaking another political barrier.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
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A regular grid is a tessellation of n-dimensional Euclidean space by congruent parallelotopes (e.g. bricks).[1] Its opposite is irregular grid.
Grids of this type appear on graph paper and may be used in finite element analysis, finite volume methods, finite difference methods, and in general for discretization of parameter spaces. Since the derivatives of field variables can be conveniently expressed as finite differences,[2] structured grids mainly appear in finite difference methods. Unstructured grids offer more flexibility than structured grids and hence are very useful in finite element and finite volume methods.
Each cell in the grid can be addressed by index (i, j) in two dimensions or (i, j, k) in three dimensions, and each vertex has coordinates in 2D or in 3D for some real numbers dx, dy, and dz representing the grid spacing.
A Cartesian grid is a special case where the elements are unit squares or unit cubes, and the vertices are points on the integer lattice.
A rectilinear grid is a tessellation by rectangles or rectangular cuboids (also known as rectangular parallelepipeds) that are not, in general, all congruent to each other. The cells may still be indexed by integers as above, but the mapping from indexes to vertex coordinates is less uniform than in a regular grid. An example of a rectilinear grid that is not regular appears on logarithmic scale graph paper.
A skewed grid is a tessellation of parallelograms or parallelepipeds. (If the unit lengths are all equal, it is a tessellation of rhombi or rhombohedra.)
A curvilinear grid or structured grid is a grid with the same combinatorial structure as a regular grid, in which the cells are quadrilaterals or [general] cuboids, rather than rectangles or rectangular cuboids.
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A regular grid is a tessellation of n-dimensional Euclidean space by congruent parallelotopes (e.g. bricks). Its opposite is irregular grid. Grids of this type appear on graph paper and may be used in finite element analysis, finite volume methods, finite difference methods, and in general for discretization of parameter spaces. Since the derivatives of field variables can be conveniently expressed as finite differences, structured grids mainly appear in finite difference methods. Unstructured grids offer more flexibility than structured grids and hence are very useful in finite element and finite volume methods. Each cell in the grid can be addressed by index (i, j) in two dimensions or (i, j, k) in three dimensions, and each vertex has coordinates ( i ⋅ d x , j ⋅ d y ) {\displaystyle (i\cdot dx,j\cdot dy)} in 2D or ( i ⋅ d x , j ⋅ d y , k ⋅ d z ) {\displaystyle (i\cdot dx,j\cdot dy,k\cdot dz)} in 3D for some real numbers dx, dy, and dz representing the grid spacing.
A grid network is a computer network consisting of a number of computer systems connected in a grid topology. In a regular grid topology, each node in the network is connected with two neighbors along one or more dimensions. If the network is one-dimensional, and the chain of nodes is connected to form a circular loop, the resulting topology is known as a ring. Network systems such as FDDI use two counter-rotating token-passing rings to achieve high reliability and performance. In general, when an n-dimensional grid network is connected circularly in more than one dimension, the resulting network topology is a torus, and the network is called "toroidal". When the number of nodes along each dimension of a toroidal network is 2, the resulting network is called a hypercube. A parallel computing cluster or multi-core processor is often connected in regular interconnection network such as a de Bruijn graph, a hypercube graph, a hypertree network, a fat tree network, a torus, or cube-connected cycles. A grid network is not the same as a grid computer or a computational grid, although the nodes in a grid network are usually computers, and grid computing requires some kind of computer network or "universal coding" to interconnect the computers.
In mathematics the regular paperfolding sequence, also known as the dragon curve sequence, is an infinite sequence of 0s and 1s. It is obtained from the repeating partial sequence by filling in the question marks by another copy of the whole sequence. The first few terms of the resulting sequence are: If a strip of paper is folded repeatedly in half in the same direction, i {\displaystyle i} times, it will get 2 i − 1 {\displaystyle 2^{i}-1} folds, whose direction (left or right) is given by the pattern of 0's and 1's in the first 2 i − 1 {\displaystyle 2^{i}-1} terms of the regular paperfolding sequence. Opening out each fold to create a right-angled corner (or, equivalently, making a sequence of left and right turns through a regular grid, following the pattern of the paperfolding sequence) produces a sequence of polygonal chains that approaches the dragon curve fractal:
A monospaced font, also called a fixed-pitch, fixed-width, or non-proportional font, is a computer font whose letters and characters each occupy the same amount of horizontal space. This contrasts with variable-width fonts, where the letters and spacings have different widths. Monospaced fonts are customary on typewriters and for typesetting computer code. Monospaced fonts were widely used in early computers and computer terminals, which had limited graphical capabilities. Hardware implementation was simplified by using a text mode where the screen layout was addressed as a regular grid of tiles, each of which could be set to display a character by indexing into the hardware's character map. Some systems allowed colored text to be displayed by varying the foreground and background color for each tile. Other effects included reverse video and blinking text. Nevertheless, these early systems were typically limited to a single console font. Even though computers can now display a wide variety of fonts, the majority of IDEs and software text editors employ a monospaced font as the default typeface. This increases the readability of source code, which is often heavily reliant on distinctions involving individual symbols, and makes differences between letters more unambiguous in situations like password entry boxes where typing mistakes are unacceptable. Monospaced fonts are also used in terminal emulation and for laying out tabulated data in plain text documents. In technical manuals and resources for programming languages, a monospaced font is often used to distinguish code from natural-language text. Monospaced fonts are also used by disassembler output, causing the information to align in vertical columns. Optical character recognition has better accuracy with monospaced fonts. Examples are OCR-A and OCR-B. The term modern is sometimes used as a synonym for monospace generic font family. The term modern can be used for a fixed-pitch generic font family name, which is used in OpenDocument format (ISO/IEC 26300:2006) and Rich Text Format. Examples of monospaced fonts include Courier, Lucida Console, Menlo, Monaco, Consolas, Inconsolata, PragmataPro and Source Code Pro.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Shirley Chisholm, elected in 1968.
