All articles starting with U
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Unit hydrograph
A unit hydrograph is the direct runoff hydrograph resulting from one unit depth of rainfall excess falling uniformly over a watershed, introduced by LeRoy Sherman in 1932.
Unit injector
A unit injector is a diesel fuel injection device combining the high-pressure pump and injection nozzle in one assembly, mounted directly in each cylinder head.
Unit load device
A unit load device (ULD), also called a ULD container, is a container or pallet with net that groups cargo, mail, and baggage for air transport.
Unit load method
The unit load method, or virtual work method, is a structural analysis technique for calculating the deflection or rotation at a chosen point of a structure.
Unit of account
A unit of account is the standard in which prices are quoted and debts are recorded, one of money's three classical functions alongside medium of exchange and store of value.
Unit of length
A unit of length, also called a unit of distance, is a chosen standard distance for measuring other distances; the SI unit is the meter.
Unit of measurement
A unit of measurement, also called a physical unit, is a definite quantity of a physical quantity adopted by convention, used to express quantities of the same kind as numbers.
Unit of time
A unit of time, also called a time unit, is a standardized interval for measuring durations; the SI base unit is the second, defined since 1967 by cesium-133.
Unit operation
Unit operation: the basic step of an industrial or food process (mixing, heating, drying, filtration), based on momentum, heat, or mass transfer, subject to mass and energy conservation laws, distinct from whole process design.
Unit prefix
A unit prefix, as in the SI prefixes, is a symbol placed before a unit to show multiplication by a power of ten, from kilo (10³) to quecto and quetta.
Unit price contract
A unit price contract, also called an admeasurement or re-measurement contract, is a construction contract where the contractor is paid fixed unit rates for actual quantities of work completed.
Unit protection
Unit protection is power system protection that operates only for faults inside a clearly defined zone, such as a transformer or busbar, never for faults outside it.
Unit root
A unit root, or unit root process, is a time-series property in which shocks have permanent effects on the level, tested by the Dickey–Fuller and related tests.
Unit root test
A unit root test is a statistical hypothesis test used in time series analysis to decide whether a series contains a stochastic trend rather than being stationary.
Unit testing
Unit testing, also called component or module testing, verifies that individual software components behave as intended in isolation, forming the base of the automated test pyramid.
Unit train
A unit train is a freight train that carries one commodity, such as coal or grain, between a single origin and destination without intermediate sorting.
Unit vector
A unit vector, also called a normalized or unit-norm vector, is a vector whose length equals 1, written with a hat as the standard way to express direction.
UNITA
UNITA (União Nacional para a Independência Total de Angola), Angolan movement founded by Jonas Savimbi on 13 March 1966 at Muangai; fought Portugal and then the MPLA in the 1975–2002 civil war; now Angola's main opposition party.
UNITA sanctions regime
The UNITA sanctions regime was a set of UN Security Council measures imposed from 1993 to 2002 against Angola's UNITA rebels, covering arms, petroleum, travel, finance, and diamonds.
Unitarian Church of Transylvania
The Unitarian Church of Transylvania (Erdélyi Unitárius Egyház) is a Protestant church founded in 1568 that rejects the Trinity, with Dávid Ferenc as its first bishop.
Unitarian Party
The Unitarian Party was, with the Federalists, one of Argentina's two main factions of the 1820s, favoring a strong national government in Buenos Aires; it dissolved after Rosas's persecution.
Unitarian Universalism
Unitarian Universalism is a liberal, non-creedal religious tradition whose Unitarian Universalist Association was formed in 1961 by merging the American Unitarian and Universalist churches, welcoming diverse beliefs.
Unitarian Universalist Association
The Unitarian Universalist Association (UUA), formally the Unitarian Universalist Association of Congregations, is the denominational body of Unitarian Universalist congregations, incorporated in 1961 as successor to the American Unitarian Association and the Universalist Church of America.
Unitarianism
Unitarianism, also called Christian Unitarianism, is a Christian theology that rejects the Trinity and Christ's divinity, holding God is one person and Jesus fully human.
Unitarity triangle
The unitarity triangle is a triangle in the complex plane representing a CKM matrix relation, used to test quark mixing and CP violation in the Standard Model.
Unitary authorities of England
Unitary authorities of England: single-tier councils providing all local government services, unlike two-tier county and district areas. 62 existed by 2023; the 2024-26 reorganisation programme replaces remaining two-tier areas, with Surrey first in 2027.
Unitary Bose gas
A unitary Bose gas is an ultracold bosonic gas with its scattering length tuned to infinity, where interactions reach the quantum-mechanical unitarity limit and properties become universal.
Unitary coupled cluster ansatz
The unitary coupled cluster ansatz is a parameterized quantum circuit for quantum chemistry that applies exp(T − T†) to a reference state, used in the variational quantum eigensolver.
Unitary dual
The unitary dual of a group G, written Ĝ, is the set of its irreducible unitary representations, identified with the spectrum of the group C-algebra.
Unitary executive theory
The unitary executive theory is a constitutional law doctrine holding that the President alone controls the executive branch, including at-will removal of officials, a view mainstreamed since the Reagan administration.