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Head (hydraulic)

Hydraulic head is a specific measurement of water pressure or total energy per unit weight above a datum. It is usually measured as a water surface elevation, expressed in units of length, but represents the energy at the entrance or bottom of a ...

                                               

Hypersonic

In aerodynamics, hypersonic speeds are speeds that are highly supersonic. The word hypersonic came from a word used in the 1970s, Mach 5, or 5 times the speed of sound. Everything about the plane changes greatly when the airplane that is flying a ...

                                               

Nozzle

A nozzle is a device that takes incoming fluid and increases the speed. This is done by changing the size of the pipe that the fluid is flowing through.

                                               

Vorticity

Vorticity is a mathematical concept used in fluid dynamics. It can be related to the amount of "circulation" or "rotation" in a fluid. The average vorticity in a small region of fluid flow is equal to the circulation Γ {\displaystyle \Gamma } aro ...

                                               

Heat lamp

A heat lamp is a lamp with the main purpose of making heat. This is commonly infrared light but white light incandescent lightbulbs are also used. Sometimes the glass of the light bulb is colored to cut out yellow and even higher frequency light. ...

                                               

ITS 90

The ITS 90 is the international temperature scale, published in the year 1990. It mainly is a set of fixed temperatures and instructions how to realise a practical temperature scale, being as close to the thermodynamical temperature scale as curr ...

                                               

Room temperature

A comfortable room temperature depends on individual needs and other factors. According to the West Midlands Public Health Observatory UK, 21 °C 70 °F is the recommended living room temperature, and 18 °C 64 °F is a good bedroom temperature. Howe ...

                                               

Society for American City and Regional Planning History

The Society for American City and Regional Planning History is an American non-profit organization for the history of urban planning. It was established in 1986 in Ohio, United States. The organizations members includes urban planners, architects ...

                                               

Centre for Cities

The Centre for Cities is a non-partisan urban policy research unit in London, United Kingdom. The organization was established in 2005 as a part of the Institute for Public Policy Research. It became independent in 2007. The Centre for Cities was ...

                                               

Project for Public Spaces

The Project for Public Spaces is a non-profit organization dedicated to public participation in planning urban spaces in cities. The organization works in the subjects of architecture, landscape architecture, urban planning, urban design, urban g ...

                                               

Urban Land Institute

The Urban Land Institute is a non-profit research organization dedicated to urban planning and urban development. The institute is located in Washington D.C., United States, with branches in London and Hong Kong.

                                               

Favelas

A favela is the term for a shanty town in Brazil. They are mostly found on the outskirts of urban areas. The people living in the favelas are the poor, and the rich people live in the city. Most of the buildings in favelas are made out of cheap m ...

                                               

Kowloon Walled City

Kowloon Walled City was a tiny Chinese enclave in Hong Kong. It was a military fort for hundreds of years, but later became a very dense settlement. In 1980, the city had about 35.000 people on about 20.000 m² of land, making it one of the most d ...

                                               

Castle Vale Estate

Castle Vale is a housing estate near Erdington, 9 km northeast of Birmingham city centre, in England. The area has about 10.000 people. It has modern homes because a lot of new houses were built after World War II. It is known as a postwar oversp ...

                                               

Urban design

Urban design is a subject of urban planning focusing on design of cities or other urban areas. Whereas architecture focuses on individual buildings, urban design is about the design of whole neighbourhoods and entire cities. It is about making th ...

                                               

Urban morphology

Urban morphology is the field of research, study, study, and design of the form of human settlement and the process of their formation and change. This study seeks to understand the spatial structure and nature of: "metropolis, city, town, neighb ...

                                               

Boolean expression

In computer science, a Boolean expression is an expression used in programming languages that produces either true or false when evaluated. Boolean expressions are often used by conditionals in computer programs to decide which code to run. Most ...

                                               

Cross product

The cross product is a mathematical operation which can be done between two three-dimensional vectors. It is often represented by the symbol × {\displaystyle \times }. After performing the cross product, a new vector is formed. The cross product ...

                                               

Determinant

The determinant of a square matrix is a scalar that indicates how that matrix behaves. It can be calculated from the numbers in the matrix. The determinant of the matrix A {\displaystyle A} is written as det A {\displaystyle \detA} or | A | {\dis ...

                                               

Dot product

In mathematics, the dot product is an operation that takes two vectors as input, and that returns a scalar number as output. The number returned is dependent on the length of both vectors, and on the angle between them. The name is derived from t ...

                                               

Matrix (mathematics)

In mathematics, a matrix is a rectangle of numbers, arranged in rows and columns. The rows are each left-to-right lines, and the columns go top-to-bottom. The top-left cell is at row 1, column 1. Matrices are often represented by capital roman le ...

                                               

Positive-definite matrix

A positive-definite matrix is a matrix with special properties. The definition of the term is best understood for square matrices that are symmetrical, also known as Hermitian matrices.

                                               

Antiderivative

Antidifferentiation is the process of finding a certain function in calculus. It is the opposite of differentiation. It is a way of processing a function to give another function called an antiderivative. Antidifferentiation is like integration - ...

                                               

Contour integral

In complex analysis, contour integration is a way to calculate an integral around a contour on the complex plane. In other words, it is a way of integrating along the complex plane. More specifically, given a complex-valued function f {\displayst ...

                                               

Derivative (mathematics)

In mathematics, the derivative is a way to show instantaneous rate of change: that is, the amount by which a function is changing at one given point. For functions that act on the real numbers, it is the slope of the tangent line at a point on a ...

                                               

Differential equation

A differential equation is a mathematical equation that involves variables like x or y, as well as the rate at which those variables change. Differential equations are special because the solution of a differential equation is itself a function i ...

                                               

Divergent series

In mathematics, a divergent series is an infinite series that is not convergent, meaning that the infinite sequence of the partial sums of the series does not have a finite limit. If a series converges, the individual terms of the series must app ...

                                               

Fourier series

Joseph Fourier said that it is possible to use sine waves to approximate another function. This is a series in the mathematical sense. This theory can be generalized to the Fourier transform. Mathematical analysis of these functions is called Fou ...

                                               

Integral

In calculus, an integral is the space under a graph of an equation. An integral is the reverse of a derivative, and integral calculus is the opposite of differential calculus. A derivative is the steepness, as the rate of change, of a curve. The ...

                                               

Mathematical analysis

Mathematical analysis is a part of mathematics. It is often shortened to analysis. It looks at functions, sequences and series. These have useful properties and characteristics that can be used in engineering. Mathematical analysis provides a rig ...

                                               

Taylors theorem

Taylors theorem is a theorem named after Brook Taylor, who first stated it in 1712: It is possible to approximate a function at a given point using polynomials. These polynomials are the result of a Taylor series.

                                               

Dijkstras algorithm

Dijkstras algorithm is a method to find the shortest paths between nodes in a graph. It is faster than many other ways to do this, but it needs all of the distances between nodes in the graph to be zero or more.

                                               

Divide and conquer algorithm

The Divide and Conquer algorithm is a basis for many popular sorting algorithms. An algorithm is simply a series of steps to solve a problem. The general idea of divide and conquer is to take a problem and break it apart into smaller problems tha ...

                                               

Hollands schema theorem

Hollands schema theorem, also called the fundamental theorem of genetic algorithms, is a theorem regarding genetic algorithms. It says that individuals with a fitness that is higher than average are more likely to prevail. John Holland proposed t ...

                                               

Kalman filter

The Kalman filter is an algorithm that helps people remove errors from numbers. It is named for Rudolf E. Kalman, a mathematician who helped to make it. Science can use the Kalman filter in many ways. One important use is steering airplanes and s ...

                                               

RSA algorithm

RSA is an algorithm used by modern computers to encrypt and decrypt messages. It is an asymmetric cryptographic algorithm. Asymmetric means that there are two different keys. This is also called public key cryptography, because one of the keys ca ...

                                               

Run-length encoding

Run-length encoding is a very simple form of lossless data compression. In RLE runs of data are stored as a single data value and count, rather than as the original run.

                                               

Advanced Encryption Standard

In cryptography, the Advanced Encryption Standard, is a symmetric-key, block cipher algorithm that was selected by the National Institute of Standards and Technology in 2001. It was selected for encrypting data. It is commonly used around the wor ...

                                               

Avalanche effect

The avalanche effect is a property of block ciphers and cryptographic hash function algorithms. It is often desired in cryptography. The effect says that a lot of the output must change, even when the input changes only a little. In good block ci ...

                                               

Blowfish (cipher)

In cryptography, Blowfish is a keyed, symmetric block cipher, made in 1993 by Bruce Schneier and since 1993 has been included in a large number of encryption products. Blowfish has a good encryption rate in software and until 2008 no cryptanalyti ...

                                               

Caesar cipher

To encrypt a message with a Caesar cipher, each letter in the message is changed using a simple rule: shift by three. Each letter is replaced by the letter three letters ahead in the alphabet. A becomes D, B becomes E, and so on. For the last let ...

                                               

Chosen-ciphertext attack

A chosen-ciphertext attack is an attack model for cryptanalysis in which the cryptanalyst gathers information, at least in part, by choosing a ciphertext and obtaining its decryption under an unknown key. When a cryptosystem is susceptible to cho ...

                                               

Cleartext

In telecommunications, cleartext is the form of a message or data which is in a form that is immediately understandable to a human being without additional processing. In particular, it implies that this message is sent or stored without cryptogr ...

                                               

Code

A code is a way of changing information into something else. Sometimes this is done as a way of keeping a message secret. This is called encryption or cryptography. One source gives this explanation: a code is "a word, number or some other symbol ...

                                               

Cryptographic hash function

A cryptographic hash function is a hash function which takes an input and returns a fixed-size string of bytes. The string is called the hash value, message digest, digital fingerprint, digest or checksum. The ideal hash function has three main p ...

                                               

Cryptographic protocol

A cryptographic protocol is an abstract or an existing protocol that performs a security-related function and applies cryptographic methods. A protocol describes how the cryptographic algorithms should be used to secure information. The descripti ...

                                               

Cypher

A cipher is an algorithm for performing encryption or decryption. It is a series of well-defined steps that can be followed as a procedure. To encipher or encode is to convert information from plain text into cipher or code. In non-technical usag ...

                                               

Diffie-Hellman key exchange

In 1976, Whitfield Diffie and Martin Hellman invented a way for people to encrypt data and send it over an open channel. The idea was based on a concept by Ralph Merkle. Diffie and Hellman wanted to make Transport Layer Security TLS, a secure way ...

                                               

Digital signature

A digital signature or digital signature scheme is a type of asymmetric cryptography. For messages sent through an insecure channel, a good implementation of digital signature algorithm is the one that makes the receiver believe that the message ...

                                               

Encryption

Encryption allows information to be hidden so that it cannot be read without special knowledge. This is done with a secret code or cypher. The hidden information is said to be encrypted. Decryption is a way to change encrypted information back in ...