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  2. Fick's laws of diffusion - Wikipedia

    en.wikipedia.org/wiki/Fick's_laws_of_diffusion

    J i is the diffusion flux vector of the i th species (for example in mol/m 2-s), M i is the molar mass of the i th species, and; ρ is the mixture density (for example in kg/m 3). The is outside the gradient operator. This is because: = where ρ si is the partial density of the i th species.

  3. Spectral flux density - Wikipedia

    en.wikipedia.org/wiki/Spectral_flux_density

    Spectral flux density. In spectroscopy, spectral flux density is the quantity that describes the rate at which energy is transferred by electromagnetic radiation through a real or virtual surface, per unit surface area and per unit wavelength (or, equivalently, per unit frequency). It is a radiometric rather than a photometric measure.

  4. Goldman–Hodgkin–Katz flux equation - Wikipedia

    en.wikipedia.org/wiki/Goldman–Hodgkin–Katz...

    The Goldman–Hodgkin–Katz flux equation (or GHK flux equation or GHK current density equation) describes the ionic flux across a cell membrane as a function of the transmembrane potential and the concentrations of the ion inside and outside of the cell. Since both the voltage and the concentration gradients influence the movement of ions ...

  5. Schwarzschild's equation for radiative transfer - Wikipedia

    en.wikipedia.org/wiki/Schwarzschild's_equation...

    Several sources [2] [12] [3] replace nσ λ with k λ r, where k λ is the absorption coefficient per unit density and r is the density of the gas. The absorption coefficient for spectral flux (a beam of radiation with a single wavelength, [W/m 2 /μm]) differs from the absorption coefficient for spectral intensity [W/sr/m 2 /μm] used in ...

  6. Darcy's law - Wikipedia

    en.wikipedia.org/wiki/Darcy's_law

    Darcy's law is an equation that describes the flow of a fluid through a porous medium. The law was formulated by Henry Darcy based on results of experiments [1] on the flow of water through beds of sand, forming the basis of hydrogeology, a branch of earth sciences. It is analogous to Ohm's law in electrostatics, linearly relating the volume ...

  7. Radiosity (radiometry) - Wikipedia

    en.wikipedia.org/wiki/Radiosity_(radiometry)

    M T−3. In radiometry, radiosity is the radiant flux leaving (emitted, reflected and transmitted by) a surface per unit area, and spectral radiosity is the radiosity of a surface per unit frequency or wavelength, depending on whether the spectrum is taken as a function of frequency or of wavelength. [1] The SI unit of radiosity is the watt per ...

  8. Maxwell stress tensor - Wikipedia

    en.wikipedia.org/wiki/Maxwell_stress_tensor

    The Maxwell stress tensor (named after James Clerk Maxwell) is a symmetric second-order tensor in three dimensions that is used in classical electromagnetism to represent the interaction between electromagnetic forces and mechanical momentum. In simple situations, such as a point charge moving freely in a homogeneous magnetic field, it is easy ...

  9. Radiative flux - Wikipedia

    en.wikipedia.org/wiki/Radiative_flux

    Radiative flux. Radiative flux, also known as radiative flux density or radiation flux (or sometimes power flux density[1]), is the amount of power radiated through a given area, in the form of photons or other elementary particles, typically measured in W/m 2. [2] It is used in astronomy to determine the magnitude and spectral class of a star ...