Pa
- Pa
- Protactinium is a radioactive element.
- Pa
- The SI derived unit of pressure is the pascal.
- Packing
- A material used to seal a joint against leakage or to displace one part relative to another.
- Packing Density
- The fractionof a volume filled by a given collection of solids.
- Packing Rings
- Rubber rings used to form a watertight joint at the bottom of the cylinder liner.
- Pagoda
- A temple or sacred building, typically in an Asian nation, usually pyramidal, forming a tower with upward curving roofs over the individual stories.
- PAH
- Abbreviation of Polynuclear Aromatic Hydrocarbons.
- Paint
- A generally opaque coating including resin, a solvent and additives.
- Paintbrush
- Brush used to apply paint.
- Pair Annihilation
- When a particle encounters its antiparticle, they annihilate each other, disappearing in a burst of photons.
- Pair Production
- The conversion of energy into matter in which a particle and its antiparticle are produced.
- Palaeocene
- The geological period covering about 65 million years ago to 56.5 million years ago.
- Paleozoic
- The geological era covering about 570 million years ago to 245 million years ago.
- Palindrome
- A positive integer whose digits read the same forward and backwards.
- Palindromic
- A positive integer is said to be palindromic with respect to a base b if its representation in base b reads the same from left to right as from right to left.
- Palladium
- A member of the platinum group of metals. It is silvery white in colour, is malleable and ductile, and is one of the most reactive in the group
- PAM
- Abbreviation of Pulse Amplitude Modulation
- Pandiagonal Magic Square
- A magic square in which all the broken diagonals as well as the main diagonals add up to the magic constant.
- Pandigital
- A decimal integer is called pandigital if it contains each of the digits from 0 to 9.
- Panel Hammer
- A special hammer for metalworking.
- Panel Saw
- Also known as a hand saw.
- Paper
- Made by pressing a pulp of rags, straw and wood into thin sheets.
- Paper Glue
- Many different forms of paper glue, the most common being the solid stick form.
- Parabolic Reflector
- An antenna reflector in the shape of a parabola.
- Paraboloid
- A paraboloid of revolution is a surface of revolution produced by rotating a parabola about its axis.
- Paracetamol
- Another name for Acetaminophen.
- Parachute
- Used to decelerate an object.
- Paradox
- A statement that appears to contradict itself, for example, suggesting a solution which is actually impossible.
- Paraffin Oil
- A term describing a whole series of saturated aliphatic hydrocarbons, also known as alkane hydrocarbons.
- Paraffin Wax
- Obtained as a residue from the distillation of petroleum.
- Paraheliotropism
- Movement of a plant in response to light.
- Parallax
- Change in the apparent position of objects when viewed from two widely separated positions.
- Parallel
- Two or more lines are said to be parallel if they are in the same plane, but never intersect. Two or more planes are parallel if the planes never intersect.
- Parallel Circuit
- Two or more electrical devices connected to the same pair of terminals so separate currents flow through each.
- Parallel Hybrid Vehicle
- The power may be provided by the internal combustion engine or the electric motor or a combination of the two.
- Parallel Limiter
- A resistor and diode, connected in series with the input signal, in which the output is taken across the diode.
- Parallel Negative Limiter
- A resistor and diode, connected in series with the input signal, in which the output is taken across the diode and the negative alternation is eliminated.
- Parallel Planes
- Planes that have no points in common.
- Parallel Port
- A special socket for plugging a printer into a computer.
- Parallel Positive Limiter
- A resistor and diode connected in series with the input signal, in which the output is taken across the diode and the positive alternation is eliminated.
- Parallel Resonant Circuit
- A resonant circuit in which the source voltage is connected across a parallel circuit to furnish a high impedance to the frequency at which the circuit is resonant.
- Parallel Transfer
- A transfer of multiple bits from one register to another simultaneously.
- Parallelepiped
- A prism whose bases are parallelograms.
- Parallelogram
- A quadrilateral in which opposite sides are parallel.
- Paramagnetic Material
- A material having a permeability slightly greater than 1.
- Paramagnetism
- A relatively weak form of magnetism that results from the independent alignment of atomic dipoles (magnetic) with an applied magnetic field.
- Parametric Amplifier
- A low-noise amplifier that uses a nonlinear variable reactance as the active element instead of a variable resistance.
- Parasitic Array
- An antenna array containing one or more elements not connected to the
transmission line.
- Parasitic Element
- The passive element of an antenna array that is connected to neither the
transmission line nor the driven element.
- Paraxial Optics
- Optical characteristics limited to infinitesimally small pencils of light.
- Parent Isotope
- An element that undergoes nuclear decay.
- Parenthesis
- The symbols ( and ) used for grouping expressions.
- Pareto Distribution
- A distribution used for random variables which are constrained to be greater or equal to 0.
- Paris Bronze
- A term given to brass containing 88% copper, 10% zinc and 2% lead used to produce trinkets and souvenirs.
- Parquet Floor
- A floor covering laid out in a geometric design composed of small pieces of wood.
- Parsec
- 1 Parsec = 3.2615 Light Years
- Parsons, Charles Algernon
- English engineer, best known for his invention of the steam turbine.
- Partial Miscibility
- Two liquids are considered partially miscible if shaking equal volumes of the liquids together results in a meniscus visible between two layers of liquid, but the volumes of the layers are not identical to the volumes of the liquids originally added.
- Partial Pressures
- The pressure exerted by a certain gas in a mixture.
- Partial Vacuum
- A volume that contains traces of gas at very low pressure.
- Partial Zero Emission Vehicle
- A vehicle that meets SULEV tailpipe emissions and has zero fuel evaporative emissions.
- Particle Accelerator
- A device for accelerating charged particles to high velocities.
- Particle Beam
- A stream of particles guided into a defined direction by a particle accelerator.
- Particle Board
- A building panel composed of small particles of wood and resins bonded together under pressure.
- Particle Velocity
- A fluctuating velocity superimposed by the presence of sound on the other velocities with the particles of the medium may have.
- Particulate
- Composed of distinct particles.
- Parting
- When used in lathe or screw-machine operations, this process separates a completed part from chuck-held or collet-fed stock by means of a very narrow, flat-end cutting, or parting, tool.
- Parting-off Tool
- A tool used in a lathe to cut the workpiece from the main stock held in the chuck.
- Partition
- A division between two volumes.
- Partition Function
- A central construct in statistics and statistical mechanics, and it is a bridge between thermodynamics and quantum mechanics because it is formulated as a sum over the energies of states of a macroscopic system at a given temperature.
- Parts Per Million
- Used to describe the amount of a trace element or substance present in the main substance.
- Parts Per Million by Volume
- Used to describe the amount of a trace element or substance present in the main substance as measured by volume.
- Parts Per Million by Weight
- Used to describe the amount of a trace element or substance present in the main substance as measured by weight.
- Pascal
- The SI derived unit of pressure.
- Pascal, Blaise
- French philosopher and mathematician whose many achievements include the invention of an adding machine and the development of the modern theory of probability.
- Pascal′s Law
- When an external pressure is applied to any confined fluid at rest, the pressure is increased at every point in the fluid by the amount of external pressure applied.
- Pascal′s Triangle
- Each number is the sum of the two numbers above. The sum of each row is equal to a power of 2.
- Paschen Series
- The series which describes the emission spectrum of hydrogen when the electron is jumping to the third orbital.
- Passivation
- The process of rendering a metal surface chemically inactive, either by electrochemical polarization or by contact with a passivating agent.
- Passivator
- A type of corrosion inhibitor that appreciably changes the potential of a metal to a more positive value.
- Passive Absorber
- A sound absorber that dissipates sound energy as heat.
- Passive Satellite
- A satellite that reflects radio signals back to earth.
- Passive Transport
- Transport of a molecule across a membrane down a concentration gradient which does not require the input of energy.
- Password Authentification Protocol
- A protocol used for identifying and authenticating a user and his or her password.
- Pasteur, Louis
- Remembered for his remarkable breakthroughs in the causes and preventions of diseases. His discoveries reduced mortality from puerperal fever, and he created the first vaccine for rabies and anthrax.
- Patch Panel
- A panel used to tie electronics components together.
- Patent
- A document granting an inventor sole rights to an invention.
- Path Length
- In absorption spectroscopy, the length of a path taken by radiation through a sample.
- Pathogen
- Any microorganism or substance that causes disease.
- Patina
- A thin layer of corrosion products with a distinctive colouration that forms on a metal surface exposed to air and water.
- Pattern
- Recognizable regularities in situations such as in nature, shapes, events, sets of numbers.
- Pattern Recognition
- A computational technique used to find patterns and develop classification schemes for data in very large data sets.
- Pauli Exclusion Principle
- No two electrons can have the same set of quantum numbers.
- Pauling, Linus
- American chemist, biochemist, peace activist, author and educator. Among the first scientists to work in the fields of quantum chemistry and molecular biology.
- Payback Time
- The number of years an improved system must be operated to offset the increased cost of the technology.