42,772 articles
Participatory modeling
Participatory modeling is a transdisciplinary approach in which stakeholders help build and use models of a system, clarifying the impacts of solutions for decision making and management.
Participatory rural appraisal
Participatory rural appraisal (PRA) is a family of qualitative research methods in which rural community members, facilitated by outsiders, map and analyze their own knowledge to plan and act.
Particle
A particle, in modern physics, is a localized quantity of energy and momentum that behaves as a discrete object, and is also a wave in an underlying field.
Particle acceleration in magnetic reconnection
Particle acceleration in magnetic reconnection is the conversion of magnetic energy into nonthermal, power-law particle energies in plasmas, invoked to explain high-energy astrophysical flares and jets.
Particle accelerator
A particle accelerator, also called an atom smasher or nuclear accelerator, is a machine using electric fields to boost charged particles, probing matter and treating cancer.
Particle beam mass spectrometry
Particle beam mass spectrometry (PB-MS) is an LC-MS interface technique that removes solvent and delivers analyte to a standard electron ionization source, giving library-searchable spectra.
Particle decay
Particle decay is the spontaneous process in which an unstable subatomic particle breaks down into two or more lighter particles, with excess energy carried away as kinetic energy.
Particle detector
A particle detector, also known as a radiation detector, is an instrument that records subatomic particles and measures their paths, momenta, energies, velocities, and charges, operating both at accelerators and beyond.
Particle filter
Particle filter, also known as Sequential Monte Carlo, is an algorithm that estimates the hidden state of a dynamic system using weighted random samples, introduced in 1993.
Particle filtering
Particle filtering is a sequential Monte Carlo method that estimates the hidden state of a nonlinear, non-Gaussian system from noisy observations, using weighted sample particles; the modern bootstrap filter dates to 1993.
Particle horizon
The particle horizon, also called the comoving horizon, is the maximum distance from which light could have reached us in the age of the universe.
Particle identification
Particle identification (PID) is the set of detector methods by which a particle physics experiment determines what kind of particle produced a track, usually by measuring mass from momentum and velocity.
Particle image velocimetry
Particle image velocimetry (PIV) is an optical, non-intrusive technique that measures a fluid flow's velocity field by imaging tracer particles between two closely spaced laser pulses.
Particle in a box
The particle in a box, also called the infinite square well, is a quantum model of a particle confined between impenetrable walls, with quantized energy levels and zero-point energy.
Particle MCMC
Particle MCMC (PMCMC) is a family of Monte Carlo algorithms combining particle filters with MCMC for Bayesian inference on non-linear state-space models, introduced by Andrieu, Doucet, and Holenstein in 2010.
Particle physics
Particle physics, also called high-energy physics, is the branch of science studying matter's fundamental constituents and forces through the Standard Model, tested in collider experiments at CERN.
Particle physics and representation theory
Particle physics and representation theory describe elementary particles as irreducible representations of the Poincaré group, classified by mass and spin, as Wigner showed in 1939.
Particle shower
A particle shower is a cascade of ever more numerous, lower-energy particles formed when a high-energy electron, photon, or hadron enters matter and repeatedly converts its energy.
Particle Size
Particle size: the measured dimension of solid particles, reported as equivalent spherical or circular diameters. Methods include sieving, sedimentation, microscopy, laser diffraction (ISO 13320), and DLS (ISO 22412); results differ by method.
Particle smoothing
Particle smoothing is a family of sequential Monte Carlo methods that approximates the distributions of a state-space model's past states conditioned on all observations, in nonlinear and non-Gaussian settings.
Particle tracking
Particle tracking, or the particle tracking method, detects particles in each frame of a microscopy video and links them into trajectories for measuring diffusion and motion.
Particle tracking velocimetry
Particle tracking velocimetry (PTV), also known as Lagrangian particle tracking, is an optical technique that measures 3D positions, velocities, and trajectories of tracer particles in flows.
Particle velocity
Particle velocity, symbol u, is the oscillatory velocity of the particles of a medium as a sound wave passes through, measured in meters per second.
Particle-in-cell simulation
Particle-in-cell (PIC) simulation is a numerical method that models plasmas by moving macroparticles through a fixed grid on which electromagnetic fields are solved self-consistently, developed at Los Alamos in the 1950s and 1960s.
Particle-induced X-ray emission
Particle-induced X-ray emission (PIXE) is an ion beam analysis technique in which MeV protons strike a sample, detecting elements from sodium to uranium at ppm sensitivity.
Particle-size distribution
Particle-size distribution, also known as grain size distribution, describes how the particles of a powder, spray, aerosol, suspension, or emulsion are divided among size classes, typically measured by laser diffraction.
Particular values of the Riemann zeta function
The particular values of the Riemann zeta function, also called zeta constants, are its values at integer arguments, such as ζ(2) = π²/6 and ζ(−1) = −1/12.
Partition (number theory)
In number theory, a partition of a nonnegative integer n is an unordered collection of positive integers summing to n, counted by the partition function p(n).
Partition chromatography
Partition chromatography is a chromatographic method that separates mixture components by distributing them between two liquid phases, introduced by Martin and Synge in 1941 and recognized with the 1952 Nobel Prize in Chemistry.
Partition coefficient
The partition coefficient, reported as log P, is the ratio of a dissolved substance's equilibrium concentrations in two largely immiscible solvents, such as octanol and water.