All units relating to specificaiton of angles.
The units of angular mass have dimensions of mass * area. They are used to measure the moment of inertia.
When the temperature of a substance changes, the energy that is stored in the intermolecular bonds between atoms changes. When the stored energy increases, so does the length of the molecular bonds. As a result, solids typically expand in response to heating and contract on cooling; this dimensional response to temperature change is expressed by its coefficient of thermal expansion. Different coefficients of thermal expansion can be defined for a substance depending on whether the expansion is measured by: * linear thermal expansion * area thermal expansion * volumetric thermal expansion These characteristics are closely related. The volumetric thermal expansion coefficient can be defined for both liquids and solids. The linear thermal expansion can only be defined for solids, and is common in engineering applications. Some substances expand when cooled, such as freezing water, so they have negative thermal expansion coefficients. For exactly isotropic materials, the area thermal expansion coefficient is very closely approximated as twice the linear coefficient.
The electric charge of an ion, equal to the number of electrons the atom has gained or lost in its ionization multiplied by the charge on one electron. This class contains the following instance(s): "atomic number".
A Base Unit is a unit adopted by convention for a base quantity.
Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. This class contains the following instance(s): "Abfarad", "Farad", "MicroFarad", "NanoFarad", "PicoFarad", "Statfarad".
Electrical conductance is the inverse of electrical resistance. It measures the ease with which electricity flows along a path through an electrical element. This class contains the following instance(s): "Abmho", "Mho", "Siemens", "Statmho".
All units about counts. Examples are Atomic Number, Number, Number per Year, Percent and Sample per Second.
The canonicall example of extrinsic curvature is that of a circle, which has curvature equal to the inverse of its radius everywhere. Smaller circles bend more sharply, and hence have higher curvature. The curvature of a smooth curve is defined as the curvature of its osculating circle at each point. The osculating circle of a sufficiently smooth plane curve at a given point on the curve is the circle whose center lies on the inner normal line and whose curvature is the same as that of the given curve at that point. This circle is tangent to the curve at the given point. That is, given a point P on a smooth curve C, the curvature of C at P is defined to be 1/R where R is the radius of the osculating circle of C at P. The magnitude of curvature at points on physical curves can be measured in diopters (also spelled dioptre) — this is the convention in optics. [Wikipedia]
A DerivedUnit is a type specification for units that are derived from other units.
A Dimensionless Unit is a quantity for which all the exponents of the factors corresponding to the base quantities in its quantity dimension are zero.
The linear, surface, or volume charge density is the amount of electric charge in a line, surface, or volume. It is measured in coulombs per metre (C/m), square metre (C/m^2), or cubic metre (C/m^3), respectively. Since there are positive as well as negative charges, the charge density can take on negative values. [Wikipedia]
The linear charge density is the amount of electric charge in a line. It is measured in coulombs per metre (C/m). Since there are positive as well as negative charges, the charge density can take on negative values. [Wikipedia]
Electric Charge Per Amount Of Substance Unit
Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. Electrically charged matter is influenced by, and produces, electromagnetic fields. The interaction between a moving charge and an electromagnetic field is the source of the electromagnetic force, which is one of the four fundamental forces.
The volume charge density is the amount of electric charge in a volume. It is measured in coulombs per cubic metre (C/m^3). Since there are positive as well as negative charges, the charge density can take on negative values. [Wikipedia]
Electric current density is a measure of the density of flow of a conserved charge. Usually the charge is the electric charge, in which case the associated current density is the electric current per unit area of cross section, but the term current density can also be applied to other conserved quantities. It is defined as a vector whose magnitude is the current per cross-sectional area. [Wikipedia] In SI units, the electric current density is measured in amperes per square metre. This class contains the following instance(s): "Ampere per square meter".
Electric current is the flow (movement) of electric charge. The SI unit of electric current is the ampere, and electric current is measured using an ammeter. This class contains the following instance(s): "Abampere", "Ampere", "Biot", "Statampere".
The electric dipole moment (or electric dipole for short) is a measure of the polarity of a system of electric charges. [Wikipedia] This class has the following instance(s): "Coulomb meter", "Debye".
The strength of the electric field at a given point is defined as the force that would be exerted on a positive test charge of +1 coulomb placed at that point; the direction of the field is given by the direction of that force. Electric fields contain electrical energy with energy density proportional to the square of the field intensity. The electric field is to charge as gravitational acceleration is to mass and force density is to volume.
The class of units used to measure the properties of electricity and magnetism.
Energy and work per mass amount of substance
Units that measure energy density, i.e. energy per unit volume.
Units that quantify energy per unit area.
The ratio of energy to electric charge arises repeatedly in electrodynamics. It is the dimensional equivalent to the electrostatic potential and electromotive force. In both cases, the SI unit is the volt, or newton meters per coulomb.
This class is for all enumerated and/or coded values. For example, it contains the dimension objects that are the basis elements in some abstract vector space associated with a quantity kind system. Another use is for the base dimensions for quantity systems. Each quantity kind system that defines a base set has a corresponding ordered enumeration whose elements are the dimension objects for the base quantity kinds. The order of the dimensions in the enumeration determines the canonical order of the basis elements in the corresponding abstract vector space.
This class is for describing the enumerations themselves. Having an enumerated value is one concept. Having a way to descrive the set of enumerated valies is a distinct need. An enumeration is a collection of enumeration elements. In some cases it is necesaary to refer to the enumeration as opposed to one of its values.
This class contains units that measure financial quantities, such as currency, transactions, rates of return, etc.
An electric current flowing around a circuit produces a magnetic field and hence a magnetic flux through the circuit. The ratio of the magnetic flux to the current is called the inductance, or more accurately self-inductance of the circuit. [Wikipedia] This class contains the following instance(s): "Abhenry", "Henry", "Micro Henry", "Milli Henry", "Stathenry".
When the temperature of a substance changes, the energy that is stored in the intermolecular bonds between atoms changes. When the stored energy increases, so does the length of the molecular bonds. As a result, solids typically expand in response to heating and contract on cooling; this dimensional response to temperature change is expressed by its coefficient of thermal expansion. Different coefficients of thermal expansion can be defined for a substance depending on whether the expansion is measured by: * linear thermal expansion * area thermal expansion * volumetric thermal expansion These characteristics are closely related. The volumetric thermal expansion coefficient can be defined for both liquids and solids. The linear thermal expansion can only be defined for solids, and is common in engineering applications. Some substances expand when cooled, such as freezing water, so they have negative thermal expansion coefficients. [Wikipedia]
Linear Velocity units measure change of length per unit time. Examples include meters per second, miles per hour, knots, etc.
Logarithmic units are abstract mathematical units that can be used to express any quantities (physical or mathematical) that are defined on a logarithmic scale, that is, as being proportional to the value of a logarithm function. Examples of logarithmic units include common units of information and entropy, such as the bit, and the byte, as well as units of relative signal strength magnitude such as the decibel.
A magnetic field is a vector field that permeates space and which can exert a magnetic force on moving electric charges and on magnetic dipoles (such as permanent magnets). [Wikipedia] The strength of a magnetic field at a point in space is the magnitude of the field vector at that point. This class contains the following instance(s): "Ampere per meter", "Ampere turn per inch", "Ampere turn per meter", "Oersted".
Magnetic flux is a measure of quantity of magnetism, taking into account the strength and the extent of a magnetic field. The SI unit of magnetic flux is the weber (in derived units: volt-seconds), and the unit of magnetic field is the weber per square meter, or tesla. [Wikipedia] This class contains the following instance(s): "Maxwell", "Unit pole", "Weber".
Magnetomotive force is any physical cause that produces magnetic flux. In other words, it is a field of magnetism (measured in tesla) that has area (measured in square meters), so that (Tesla)(Area)= Flux. It is analogous to electromotive force or voltage in electricity. MMF usually describes electric wire coils in a way so scientists can measure or predict the actual force a wire coil can generate. [Wikipedia] This class contains the following instance(s): "Ampere turn", "Gilbert", "Oersted centimeter", "Unit pole".
Mass Amount Of Substance Temperature Unit
A Non-SI unit. Typically an imperial measure.
A type specification for all units that are not used in the SI standard.
The ratio of power to electric charge is proportional to the rate of change of electric potential.
Electrical resistance is a ratio of the degree to which an object opposes an electric current through it, measured in ohms. Its reciprocal quantity is electrical conductance measured in siemens. This class contains the following instance(s): "Abohm", "Ohm", "Statohm".
A Resource Unit is a unit for measuring the amount of various types of resources.
All SI units are derived from the SI Base units
The solid angle subtended by a surface S is defined as the surface area of a unit sphere covered by the surface S's projection onto the sphere. A solid angle is related to the surface of a sphere in the same way an ordinary angle is related to the circumference of a circle. Since the total surface area of the unit sphere is 4*pi, the measure of solid angle will always be between 0 and 4*pi.
Units which quantify specific energy, i.e. energy per unit mass.
This class contains units of measure for specific heat capacity at a constant pressure.
This class contains units of measure for specific heat capacity at a constant volume.
In physics, natural units are physical units of measurement based only on universal physical constants. For example the elementary charge e is a natural unit of electric charge, or the speed of light c is a natural unit of speed. A purely natural system of units is defined in such a way that some set of selected universal physical constants are normalized to unity; that is, their numerical values in terms of these units become exactly 1. Examples are Planck Units and Atomic Units. Atomic units (au or a.u.) form a system of natural units which is especially convenient for atomic physics calculations. There are two different kinds of atomic units, which one might name Hartree atomic units[1] and Rydberg atomic units, which differ in the choice of the unit of mass and charge. Planck units are unique among systems of natural units, because they are not defined in terms of properties of any prototype, physical object, or even elementary particle. [Wikipeda]
A system of units is a set of units which are chosen as the reference scales for some set of quantity kinds together with the definitions of each unit. Units may be defined by experimental observation or by proportion to another unit not included in the system. If the unit system is explicitly associated with a quantity kind system, then the unit system must define at least one unit for each quantity kind.
Thermodynamics units are units that provide reference scales for quantifying the conversion of energy into work, as well as heat and its relation to macroscopic variables such as temperature and pressure.
Turbidity is the cloudiness or haziness of a fluid caused by individual particles (suspended solids) that are generally invisible to the naked eye, similar to smoke in air.
A unit of measure, or unit, is a particular quantity value that has been chosen as a scale for measuring other quantities the same kind (more generally of equivalent dimension). For example, the meter is a quantity of length that has been rigorously defined and standardized by the BIPM (International Board of Weights and Measures). Any measurement of the length can be expressed as a number multiplied by the unit meter. More formally, the value of a physical quantity Q with respect to a unit (U) is expressed as the scalar multiple of a real number (n) and U, as Q = nU.
A type specification for all units that are used in the SI standard.
A "Space And Time" Unit with the following instance(s): "Cubic foot per minute", "Cubic foot per second", "Cubic inch per minute", "Cubic meter per second", "Cubic yard per minute", "Gallon per day", "Gallon per minute".
When the temperature of a substance changes, the energy that is stored in the intermolecular bonds between atoms changes. When the stored energy increases, so does the length of the molecular bonds. As a result, solids typically expand in response to heating and contract on cooling; this dimensional response to temperature change is expressed by its coefficient of thermal expansion. Different coefficients of thermal expansion can be defined for a substance depending on whether the expansion is measured by: * linear thermal expansion * area thermal expansion * volumetric thermal expansion These characteristics are closely related. The volumetric thermal expansion coefficient can be defined for both liquids and solids. The linear thermal expansion can only be defined for solids, and is common in engineering applications. Some substances expand when cooled, such as freezing water, so they have negative thermal expansion coefficients. For exactly isotropic materials, the volumetric thermal expansion coefficient is very closely approximated as three times the linear coefficient. [Wikipedia]
An abbreviation for a unit is a short (usually 5 characters or less) string that is used in place of the full name for the unit in contexts where space is limited, or where using the abbreviation will enhance readability.
This property relates a unit of measure with a unit system that does not define the unit, but allows its use within the system. An allowed unit must be convertible to some dimensionally eqiuvalent unit that is defined by the system.
This property associates a system of quantities with an enumeration that enumerates the base dimensions of the system in canonical order.
This property relates a unit of measure to the system of units in which it is defined as a base unit for the system. The base units of a system are used to define the derived units of the system by expressing the derived units as products of the base units raised to a rational power.
A unit code is a numeric string that uniquely identifies a unit
This property relates a unit of measure to the unit system in which the unit is derived from the system's base units with a proportionality constant of one.
A coherent unit of measurement for a unit system is a defined unit that may be expressed as a product of powers of the system's base units with the proportionality factor of one.
A system of units is coherent with respect to a system of quantities and equations if the system of units is chosen in such a way that the equations between numerical values have exactly the same form (including the numerical factors) as the corresponding equations between the quantities. In such a coherent system, no numerical factor other than the number 1 ever occurs in the expressions for the derived units in terms of the base units.
The currency exponent indicates the number of decimal places between a major currency unit and its minor currency unit. For example, the US dollar is the major currency unit of the United States, and the US cent is the minor currency unit. Since one cent is 1/100 of a dollar, the US dollar has a currency exponent of 2. However, the Japanese Yen has no minor currency units, so the yen has a currency exponent of 0.
This property relates a unit of measure with the unit system that defines the unit.
This property relates a unit of measure to the system of units in which it is defined as a derived unit. That is, the derived unit is defined as a product of the base units for the system raised to some rational power.
This property relates a quantity kind to its generalization. A quantity kind, PARENT, is a generalization of the quantity kind CHILD only if 1. PARENT and CHILD have the same dimensions in every system of quantities; 2. Every unit that is a measure of quantities of kind CHILD is also a valid measure of quantities of kind PARENT.
A negative change limit between consecutive sample values for a parameter. The Negative Delta may be the encoded value or engineering units value depending on whether or not a Calibrator is defined.
A positive change limit between consecutive sample values for a parameter. The Positive Delta may be the encoded value or engineering units value depending on whether or not a Calibrator is defined.
a property to relate an observable thing with a quantity (qud:Quantity)
The relative standard uncertainty of a measurement is the (absolute) standard uncertainty divided by the magnitude of the exact value.
This property relates a quantity kind to its specialization(s). For example, linear velocity and angular velocity are both specializations of velocity.
The standard uncertainty of a quantity is the estimated standard deviation of the mean taken from a series of measurements.
The symbol for a unit is a glyph that is used to represent the unit in a compact form. For example, the symbol for the US Dollar is $. This contrasts with unit:abbreviation, which gives a short alphanumeric abbreviation for the unit. (I.e. USD for US Dollar).
This property relates a unit system with a unit of measure that is not defined by or part of the system, but is allowed for use within the system. An allowed unit must be convertible to some dimensionally eqiuvalent unit that is defined by the system.
This property relates a system of units to a base unit defined within the system. The base units of a system are used to define the derived units of the system by expressing the derived units as products of the base units raised to a rational power.
This property relates a unit system with a unit of measure that is defined by the system.
This property relates a system of units to a unit of measure that is defined within the system in terms of the base units for the system. That is, the derived unit is defined as a product of the base units for the system raised to some rational power.
This property relates a system of units with a unit of measure that is either a) defined by the system, or b) accepted for use by the system and is convertible to a unit of equivalent dimension that is defined by the system. Systems of units may distinguish between base and derived units. Base units are the units which measure the base quantities for the corresponding system of quantities. The base units are used to define units for all other quantities as products of powers of the base units. Such units are called derived units for the system.
A reference to the unit of measure of a quantity (variable or constant) of interest.
This property relates a unit of measure with a system of units that either a) defines the unit or b) allows the unit to be used within the system.
A property to relate an observable thing with a quantity value (qud:QuantityValue)
The QUDT Ontologies are issued under a Creative Commons Attribution Share Alike 3.0 United States License. Attribution should be made to NASA Ames Research Center and TopQuadrant, Inc.
Quantities, Units, Dimensions and Types (QUDT) Ontology Version 1.1
The QUDT, or 'Quantity, Unit, Dimension and Type' collection of ontologies define the base classes properties, and restrictions used for modeling physical quantities, units of measure, and their dimensions in various measurement systems. The goal of the QUDT ontology is to provide a unified model of, measurable quantities, units for measuring different kinds of quantities, the numerical values of quantities in different units of measure and the data structures and data types used to store and manipulate these objects in software. This OWL schema is a foundation for a basic treatment of units.
Basic treatment of quantities and units. No dimensional treatment in this graph.
Provides a schema for describing Units of Measure
Quantities, Units, Dimensions and Types (QUDT) - Level 1