42,772 articles
Health physics
Health physics, also called radiation protection, is the science of controlling ionizing radiation hazards. Born as a Manhattan Project code name under Herbert Parker, it spans dosimetry, dose limits, and the ALARA principle.
Health Physics Society
The Health Physics Society is an independent nonprofit organization of radiation safety specialists founded in 1956, headquartered in Herndon, Virginia, with about 4,400 members and 42 US chapters.
Heart Peaks
Heart Peaks: Pleistocene shield volcano with rhyolite lava domes in the Northern Cordilleran Volcanic Province, NW British Columbia, Canada; 2,012 m, no Holocene eruptions, low ash hazard, epithermal gold-silver prospect.
Heartbeat star
Heartbeat stars are eccentric binary stars whose light curves show a short brightening at each close approach, resembling an electrocardiogram, named from Kepler data in 2012.
Heat
Heat is energy transferred between a system and its surroundings because of a temperature difference, moving by conduction, convection, and radiation; its SI unit is the joule.
Heat capacity
Heat capacity, also called thermal capacity, is the amount of heat required to raise the temperature of an object or system by one degree. Per unit mass it is the specific heat.
Heat capacity ratio
The heat capacity ratio, also called the adiabatic index or ratio of specific heats, is the ratio of a gas's heat capacity at constant pressure to that at constant volume.
Heat death of the universe
The heat death of the universe, also called the Big Freeze, is the hypothetical final state of maximum entropy where no usable energy remains, proposed by Lord Kelvin in 1852.
Heat deflection temperature
Heat deflection temperature, or heat distortion temperature, is the temperature at which a loaded plastic test specimen bends a standard amount, measured by ASTM D648 or ISO 75.
Heat dome
A heat dome is an exceptionally warm air mass trapped beneath a high-pressure system aloft, suppressing clouds and precipitation; the term became widespread during the June 2021 Pacific Northwest heatwave.
Heat equation
The heat equation, also called the diffusion equation, is the partial differential equation describing how temperature or any diffusing quantity evolves in time, formulated by Joseph Fourier in 1807.
Heat flux
Heat flux, also called thermal flux, is the rate of thermal energy transfer through a surface per unit area, a vector quantity measured in watts per square meter and governed by Fourier's law.
Heat index
The heat index, also called the humiture or temperature-humidity index, combines air temperature and relative humidity to estimate how hot conditions feel to a resting person in the shade.
Heat lightning
Heat lightning, also called summer lightning, is the light from a distant thunderstorm too far away for thunder to be heard, often seen as silent flickers on hot summer nights.
Heat map
A heat map is a data visualization that encodes values in a two-dimensional matrix or table as colors, so patterns, clusters, and outliers can be read from shaded cells.
Heat pump and refrigeration cycle
The heat pump and refrigeration cycle is a thermodynamic loop in which a working fluid is compressed and expanded to move heat against its natural direction.
Heat transfer
Heat transfer, also known as heat flow or heat transport, is the movement of thermal energy from hotter to cooler regions, occurring by conduction, convection, and radiation.
Heat transfer coefficient
The heat transfer coefficient, or coefficient of heat transmission, relates the rate of heat transfer between a surface and a fluid to the temperature difference.
Heat wave
A heat wave is a period of unusually hot weather lasting several days, defined by local thresholds, and human-caused warming has made heat waves more frequent and intense.
Heat-bath configuration interaction
Heat-bath configuration interaction (HCI) is a selected configuration interaction method in quantum chemistry, introduced by Holmes, Tubman, and Umrigar in 2016, which grows a compact wavefunction by thresholding determinants.
Heather Couper
Heather Anita Couper (1949–2020) was a British astronomer and broadcaster who wrote more than 40 books and was the first woman to serve as President of the British Astronomical Association.
Heather D. Maynard
Heather D. Maynard is an American polymer chemist at UCLA, an endowed professor and founding member of the California NanoSystems Institute, known for protein–polymer conjugates for drug delivery.
Heather J. Kulik
Heather J. Kulik is an American computational chemist and chemical engineer who joined MIT in 2013 and uses machine learning with electronic structure calculations to discover new molecules and catalysts.
Heather M. Stapleton
Heather M. Stapleton is an American environmental chemist and exposure scientist at Duke University who studies flame retardants and PFAS in homes, products, and people, especially children.
Heather Wright
Heather Wright is an American volcanologist and Director of the Volcano Disaster Assistance Program at the Cascades Volcano Observatory. She received the Presidential Early Career Award in 2019.
Heave compensation
Heave compensation is the set of techniques that remove a vessel's wave-induced vertical motion from a suspended load or sensor, used in lifting and hydrographic surveying.
Heavenly stems
The heavenly stems (天干, tiangan) are ten Chinese characters paired with the twelve earthly branches to form the sixty-year cycle of the traditional Chinese calendar.
Heaviside step function
The Heaviside step function, also called the unit step function, is a discontinuous function taking the value 0 for negative input and 1 for positive input, named after Oliver Heaviside.
Heaviside–Lorentz units
Heaviside–Lorentz units, also called Lorentz–Heaviside units, are a rationalized system of electromagnetic units, derived from Gaussian units around 1900 by H. A. Lorentz following Oliver Heaviside.
Heavy fermion
A heavy fermion is a quasiparticle in rare-earth and actinide intermetallics whose effective mass can reach about 1000 times an electron's, a prototype of strongly correlated matter.