Unbalanced Crystal Mixer
A circuit consisting of a section of coaxial transmission line one-half wavelength long that is tuned to the difference frequency between the local oscillator and RF echo signals.
Unbalanced Line
Cable that consists of one conductor and a shield. Here the shield is also carrying the other half of the signal.
Unbalanced Seal
A mechanical seal arrangement wherein the full hydraulic pressure of the seal chamber acts to close the seal faces.
Having no bias.
Unbiased Annoyance
A combination of sharpness, fluctuation strength, N10 level, and includes a correction factor for time of day.
Unbounded Mathematical Program
Objective is not bounded on the feasible region.
UNF tapping sizes, pitch and OD.
Uncertainty Principle
The quantum principle, first formulated by Heisenberg, that states that is is not possible to know exactly both the position x and the momentum p of an object at the same time.
Unconstrained Mathematical Program
One with no constraints.
Uncontrolled Experiment
An experiment in which there is no control group.
Undamped Natural Frequency
The same as the natural frequency of a structure.
An eleven sided polygon.


A liquid alkane hydrocarbon that is used as a mild sex attractant for various types of moths and cockroaches.

Under Potential Deposition
The electrodeposition of a metal on a foreign metal at potentials less negative than the equilibrium potential of the deposition reaction.
An opaque cloud layer viewed from an observation point above the layer.
A coating applied prior to the paint finishing or top coat.
Cooling a material below the temperature of an equilibrium phase change fast enough to not allow the occurrence of the transformation.
A handling condition in which the slip angle of the front tyres is greater than the slip angle of the rears.
UNF tapping sizes, pitch and OD.
The symbol for Unnilhexium. An element with an atomic number of 106.
A standard of computer character set.
In one direction only.
Uniform Corrosion
Corrosion that is uniform across the surface of the object.
Uniform Motion
Motion at a constant velocity.
Uniform Resource Identifier
A string of characters that represents the location or address of a resource on the Internet and how that resource should be accessed.
Uniform Window
The uniform, or rectangular, window does not modify the signal amplitude at all.
Unijunction Transistor
A trigger device that has an emitter lead (e) and two bases B1 and B2.
Unilateral Surface
A surface with only one side, such as a Moebius strip.
A finite sequence is unimodal if it first increases and then decreases.
Unimodular Matrix
A square matrix is unimodular if its determinant is 1.
Unimolecular Reaction
A reaction that involves isomerization or decomposition of a single molecule.
Uninterruptible Power Supply
A type of power supply designed to support the load for specified periods when the line varies outside specified limits.
A plumbing fitting that joins pipes end-to-end so they can be dismantled.
Union of Sets
The union of two or more sets is the set of all the objects contained by at least one of the sets.
A standard for comparison in measurements. For example, the metre is a standard length which may be compared to any object to describe its length.
Unit Cell
The smallest repetitive volume that comprises the complete pattern of a crystal.
Unit Circle
A circle with radius 1.
Unit Cube
A cube with edge length 1.
Unit Fraction
A fraction whose numerator is 1.
Unit of Blood
Unit of volume for human blood and its components.
Unit Square
A square of side length 1.
Unit Vector
A vector with a length of 1.
Unitary Divisor
A divisor d of c is called unitary if gcd(d,c/d) = 1.
Unitary Matrix
A nonsingular matrix whose Hermitian adjoint equals its inverse.
Lists all Units topics in the Encyclopaedia
Units Books
Lists all Units Books in the Encyclopaedia
Units Calculations
Lists all Units Calculations in the Encyclopaedia
Units Conversions
Lists all Units Conversions in the Encyclopaedia
Units Weblinks
Lists all Units Weblinks in the Encyclopaedia
Unity Gain
A gain setting of one, or a device having a gain of one.
Univariate Optimisation
Mathematical program with a single variable.
Universal Asynchronous Receiver Transmitter
The device that performs the bidirectional parallel-to-serial data conversions necessary for the serial transmission of data into and out of a computer.
Universal Gas Constant
Also known as Molar Gas Constant.
Universal Grinder
A versatile grinding machine designed to perform both internal and external grinding operations.
Universal Indicator
A universal indicator is an indicator which undergoes several colour changes over a wide range of pH.
Universal Joint
A mechanical device which transmits torque and/or rotary motion between two shafts that are not in a straight line.
Universal Law of Gravitation
Every particle in the Universe attracts every other with a force which is proportional to the product of their masses and inversely proportional to the square of their seperation.
Universal Milling Machine
A milling machine with a worktable that can be swiveled for milling helical work.
Universal Output Transformer
An audio output transformer having a number of taps on the secondary winding which provide a variety of impedances for matching the speaker impedance to that of the recommended load resistance.
Universal Resource Locator
Address used to locate something on the internet, most often a web page.
Universal Serial Bus
An external bus standard that supports data transfer rates of 12 Mbps.
Universal Statement
A conditional that uses the words "all" or "everything".
Universal Terminal Post
A style of battery terminal, with a round post similar to the automotive post, but with a threaded stud in the center of the post.
Universal Time
Time defined by the rotational motion of the earth and determined from the apparent diurnal motions which reflect this rotation.
Universal Vice
A vice designed for holding work at a double or compound angle.
All the matter and space that exists.
Unladen Weight
The actual weight of a vehicle or combination with no payload.
Unmanned Aerial Vehicle
A machine which functions either by the remote control of a navigator, or pilot or autonomously.
A carrier signal without modulation.
Element with an atomic number of 106.
Element with an atomic number of 105.
An element with an atomic number of 104.
An element with an atomic number of 107.
The symbol for Unnilpentium. An element with an atomic number of 105.
Unpaired Electron
A single electron occupying an orbital.
The symbol for Unnilquadium. An element with an atomic number of 104.
The symbol for Unnilseptium. An element with an atomic number of 107.
Unsaturated Compounds
Organic compounds containing double or triple bonds capable of forming addition products.
Unsaturated Fat
A lipid containing one or more carbon-carbon double bonds.
Unsaturated Fatty Acid
A fatty acid containing one or more double bonds.
Unsaturated Solution
A solution with a concentration lower than its equilibrium solubility.
Unsigned Binary Number
A binary number in which all the bits are used to represent positive quantities.
Unsprung Weight
All parts of the vehicle that are not supported by the suspension system, wheels, tyres, brakes, etc
Characteristic of a structure that collapses or deforms under a realistic load or a chemical that decomposes.
Unstable Equilibrium
A body is in unstable equilibrium if it does not return to its equilibrium position and does not remain in the displaced position after it has been displaced slightly.